JP4920442B2 - Chrome-free surface-treated steel sheet with excellent performance balance - Google Patents

Description

  The present invention relates to a non-chromium surface-treated steel sheet using a zinc-based plated steel sheet as a base material. The surface-treated steel sheet of the present invention is excellent in corrosion resistance of the flat part, after alkaline degreasing and in the processed part, and has fingerprint resistance, electrical conductivity, paint adhesion, workability (sliding property), heat resistance and acid resistance. Excellent water resistance.

  Conventionally, zinc-based plated steel sheets including galvanized steel sheets and zinc alloy-plated steel sheets have been widely used for home appliances and building materials. Since the zinc-based plated steel sheet has insufficient corrosion resistance and paint adhesion as it is, products subjected to chemical conversion treatment such as chromate and zinc phosphate are manufactured. Among these products, chromate-treated products may be used without coating depending on the application. In that case, since fingerprints adhere to the surface of the steel sheet and the appearance is impaired, a product called an anti-fingerprint steel sheet coated with an organic resin has been put to practical use.

  This fingerprint-resistant steel sheet, that is, a surface-treated steel sheet obtained by subjecting a zinc-based plated steel sheet to chromate treatment and coating the upper layer of the formed chromate film with an organic resin, is flat surface corrosion resistance, corrosion resistance after alkaline degreasing, processed part corrosion resistance, Excellent performance balance of various required properties such as fingerprint, conductivity, paint adhesion, processability, heat resistance, acid resistance, water resistance, etc., and can be applied to various uses of home appliances and building materials. Or can be used without painting.

However, with the recent regulation of hexavalent chromium, there has been an increasing demand for chromium-free fingerprint-resistant steel plates that do not use chromate treatment, and several proposals have been made so far.
For example, in Patent Document 1 below, a zinc-based or aluminum-based plated steel sheet is prepared using a surface treatment solution containing a specific phenol resin, a cationic urethane resin, a silane coupling agent, a Ti compound, and a specific acid or salt thereof. A surface-treated steel sheet having a surface treated is disclosed. However, this surface-treated steel sheet has a performance balance of characteristics such as flat part corrosion resistance, corrosion resistance after alkaline degreasing, processed part corrosion resistance, fingerprint resistance, conductivity, paint adhesion, workability, heat resistance, acid resistance, and water resistance. Not necessarily good.

Patent Document 2 below discloses a technique using a water-soluble resin or water-based emulsion resin, a specific phenol resin, a specific metal compound, and optionally a metal surface treatment liquid containing an acid and a silane coupling agent. . Although the surface-treated steel sheet using this technique has a relatively good balance of performance, it may not always satisfy the user's request in terms of corrosion resistance (particularly corrosion resistance after alkaline degreasing) and workability.
JP 2003-105562 A JP 2003-13252 A

  Previously proposed chromium-free fingerprint-resistant steel plates have a flat surface corrosion resistance, corrosion resistance after alkaline degreasing, processed portion corrosion resistance, and fingerprint resistance compared to conventional fingerprint-resistant steel plates coated with an organic resin on a chromate film. Insufficient performance balance regarding properties such as conductivity, paint adhesion, processability, heat resistance, acid resistance, water resistance, etc., so it cannot be applied to some applications such as home appliances and building materials. Accordingly, fine adjustment of the film components and fine adjustment of the film adhesion amount were required.

  The present invention does not contain chromium, and balances in performance such as flat surface corrosion resistance, corrosion resistance after alkaline degreasing, processed portion corrosion resistance, fingerprint resistance, conductivity, paint adhesion, workability, heat resistance, acid resistance, and water resistance. An object of the present invention is to provide a surface-treated steel sheet having excellent resistance.

  As a result of studying to ensure various properties required for fingerprint-resistant steel sheets without performing chromate treatment, the present inventors have obtained a surface treatment liquid comprising a cationic phenol resin, a cationic urethane resin, and a silane coupling agent. In addition, by incorporating three kinds of metal compounds of manganese, zirconium, and vanadium and Fischer Tropus wax, the corrosion resistance of the flat part, corrosion resistance after alkaline degreasing, corrosion resistance of the processed part, fingerprint resistance, conductivity, paint adhesion As a result, it is possible to form a film with good properties, workability, heat resistance, acid resistance, and water resistance, thereby achieving the present invention.

The present invention provides an average degree of polymerization having a cationic polyurethane resin (A) containing a structural unit represented by the following general formula (1) and a repeating unit represented by the following general formula (2) on the surface of a galvanized steel sheet. Cationic phenol resin (B) composed of 2 to 50 polymer molecules, silane coupling agent (C), manganese compound (D), zirconium compound (E), vanadium compound (F), average particle An aqueous system containing Fischer-Tropsch wax (G) having a diameter of 0.1 to 0.5 μm, a number average molecular weight of 500 to 2000, a density of 0.85 to 0.95 and a melting point of 70 to 90 ° C. It has a surface treatment film formed by applying and drying the surface treatment liquid, and the solid content (components A, B, C, G) of each component in the surface treatment liquid or the solid content (components D, E) in metal conversion , F) is a mass ratio,
A / B = 7-120,
C / (A + B) = 0.2-0.75
D / (A + B) = 0.005 to 0.025,
E / (A + B) = 0.01-0.075,
F / (A + B) = 0.001 to 0.025,
G / (A + B) = 0.03-0.4,
It is the surface treatment steel plate characterized by being.

  In the formula, R is an aliphatic alkylene group having 4 to 9 carbon atoms, and n is an integer corresponding to a number average molecular weight in the range of 500 to 5000.

In the formula, Y ₁ and Y ₂ each independently represent hydrogen or a Z group represented by the following general formula (3) or (4), and the average number of substitutions of Z groups per benzene ring is 0.2 to 1.0.

In the formulas (3) and (4), R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or a hydroxyalkyl having 1 to 10 carbon atoms. Represents a group, and A ⁻ represents a hydroxide ion or an acid ion.

The adhesion amount of the surface treatment film is preferably in the range of 0.1 to 3 g / m ² .
According to the present invention, there is also provided a method for producing a surface-treated steel sheet, which comprises applying the surface-treated liquid and the surface-treated liquid to a zinc-based plated steel sheet and then drying by heating.

  The surface-treated steel sheet of the present invention does not contain chromium, and has a flat surface corrosion resistance, corrosion resistance after alkaline degreasing, processed portion corrosion resistance, fingerprint resistance, conductivity, paint adhesion, workability, heat resistance, acid resistance, and water resistance. Excellent performance balance with respect to these characteristics. Therefore, this surface-treated steel sheet can be used as it is for every application of home appliances and building materials, and fine-tuning of coating components and adhesion amount according to the application, like the known chromium-free fingerprint-resistant surface-treated steel sheet. do not need. This steel plate can be used without being painted or painted.

  The surface-treated steel sheet of the present invention does not contain any chromium, including hexavalent chromium harmful to the human body, and is manufactured using an aqueous surface treatment solution. Since it does not evaporate, the working environment is well maintained and waste liquid treatment is easy.

  As the base material of the surface-treated steel sheet of the present invention, a zinc-based plated steel sheet is used because of its excellent corrosion resistance. The zinc-based plated steel sheet includes a galvanized steel sheet and a zinc alloy plated steel sheet. Examples of zinc-based plating include zinc plating, Zn—Ni alloy plating, Zn—Fe alloy plating (electroplating, alloyed hot dip galvanizing), Zn—Co alloy plating, Zn—Al alloy plating (eg, Zn-5). % Al alloy plating, Zn-55% Al alloy plating), Zn-Mn alloy plating, Zn-Mg alloy plating, Zn-Al-Mg alloy plating, Zn-Sn alloy plating, and the like. These plated steel sheets are used in nickel plating, iron, aluminum, magnesium, tin, cobalt, molybdenum, tungsten, titanium, manganese, lead, antimony, copper, cadmium, arsenic, phosphorus, etc. 1 type or 2 or more types of elements may be contained. Further, it may contain an organic compound or an inorganic compound such as alumina, silica, and titania that can be co-deposited with plating. Further, it may be a multi-layer plated steel sheet in which two or more layers of plating are combined.

  The type of plating is not limited, and electroplating, hot dipping, vapor deposition plating, or the like may be applied depending on the plating type, and these plating methods may be combined. Usually, it is hot dipping or electroplating.

  Preferred as the substrate-plated steel sheet is a hot dip galvanized steel sheet, an electrogalvanized steel sheet, an electro Zn-Ni plated steel sheet, an alloyed hot dip galvanized steel sheet, a molten Zn-5% Al plated steel sheet, and a molten Zn-55% Al plated It is a steel plate.

  The surface treatment liquid used for the surface treatment of the base-plated steel sheet is a cationic polyurethane resin (A) containing a structural unit represented by the general formula (1) and a cationic having a repeating unit represented by the general formula (2). Phenol resin (B), silane coupling agent (C), manganese compound (D), zirconium compound (E), vanadium compound (F), and average particle size of 0.1 to 0.5 μm, number average molecular weight of 500 to 2000 A water-based treatment liquid containing Fischer-Tropsch wax (G) having a density of 0.85 to 0.95 and a melting point of 70 to 90 ° C. Each of the components (A) to (G) can be used alone or in combination of two or more, and when two or more are used, the total amount is the amount of that component. Each component will be described in more detail below.

(A) Cationic Polyurethane Resin Cationic polyurethane resin (A) containing a structural unit represented by the above general formula (1), which is a water-based resin, has good adhesion and can form a dense film. In the present invention, it is used as a main component of the surface treatment liquid and the surface treatment film from the viewpoint that it is a resin that has an improvement effect of the above and has good alkali resistance, heat resistance and water resistance.

The cationic polyurethane resin (A) means a polyurethane resin having at least one cationic functional group selected from primary to tertiary amino groups and quaternary ammonium groups. This cationic functional group is the same group as the Z group represented by the formulas (3) and (4) with respect to the phenol resin (B). When the Z group is an ammonium group represented by the formula (4), the counter ion A ⁻ is a hydroxide ion or an acid ion. Specific examples of the acid ion include a sulfate ion, a nitrate ion, an acetate ion, and a phosphate. And ions and fluoride ions.
Examples of the cationic functional group include an amino group, a methylamino group, an ethylamino group, a dimethylamino group, a diethylamino group, a trimethylammonium group, and a triethylammonium group.

  The skeleton of the polyurethane resin is classified into a polyether type, a polyester type, a polycarbonate type, a polycaprolactone type, and the like depending on the polyol component to be used. By selecting the polycarbonate type, more excellent acid resistance can be obtained. .

  The number average molecular weight of the cationic polyurethane resin (A) is preferably 5,000 to 500,000, more preferably 10,000 to 300,000. The cationic polyurethane resin can be obtained by polycondensation of a polycarbonate polyol substituted at least in part with the amino group or ammonium group and an aliphatic, alicyclic or aromatic polyisocyanate.

  The number average molecular weight of the polycarbonate polyol is preferably 500 to 5,000, more preferably 500 to 3,000. If it is less than 500, the film becomes too hard, and if it exceeds 5000, it is difficult to produce.

  Polycarbonate polyol is a polyol having a hydroxyl group at the molecular end and an alkylene group bonded via a carbonate bond, and is obtained by reaction of ethylene carbonate, dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and the like with an alkylene diol. Examples of the alkylene diol include 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, and 1,9-nonanediol. Those having 4 to 9 carbon atoms are preferably used, and these are used alone or as a copolymer of two or more.

  Examples of polyisocyanates include tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate, cyclohexylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate and the like.

(B) Cationic phenol resin The cationic phenol resin (B) is blended in the surface treatment liquid in order to improve the corrosion resistance and solvent resistance of the film and improve the liquid stability of the surface treatment liquid. If the resin is only the above-mentioned cationic polyurethane resin (A), even if all the remaining components (C) to (G) are blended in a predetermined ratio, the corrosion resistance and solvent resistance of the film cannot be satisfied.

  The cationic phenol resin (B) is a water-soluble resin composed of a polymer molecule having a repeating unit represented by the general formula (2), and has an average degree of polymerization of 2-50. As can be seen from the general formula (2), this resin is a hydrogen on the benzene ring with a Z group, that is, a primary to tertiary amino group or a quaternary ammonium group represented by the formula (3) or the formula (4). Can be said to be substituted bisphenol A-formaldehyde resins. This resin is water-soluble, but water resistance improves when dried.

  If the average degree of polymerization of the cationic phenol resin (B) is lower than 2, the effect of imparting solvent resistance becomes insufficient. The stability of the agent is reduced.

The Z group represented by the formula (3) is a primary to tertiary alkyl and / or hydroxyalkylamino group, and the Z group represented by the formula (4) is a quaternary alkyl and / or hydroxyalkylammonium group. is there. This alkyl group or hydroxyalkyl group (indicated by R _{1 to} R ₅ ) has 1 to 10 carbon atoms. When the carbon number of the alkyl or hydroxyalkyl group is 11 or more, the water solubility of the resin (B) is remarkably lowered, the surface treatment liquid becomes unstable, and the film formability is lowered. This alkyl group or hydroxyalkyl group preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms. Specific examples include methyl, ethyl, propyl, butyl, hydroxyethyl, 2-hydroxypropyl, hydroxyisobutyl and the like. Particularly preferred is an alkyl group having 1 to 2 carbon atoms or a hydroxyalkyl group.

When the Z group is an ammonium group represented by the formula (4), the counter ion A ⁻ is a hydroxide ion or an acid ion. Specific examples of the acid ion include sulfate ion, nitrate ion, acetate ion, phosphorus ion. An acid ion, a fluoride ion, etc. can be mentioned.

  The average number of substitution per benzene ring of the Z group is in the range of 0.2 to 1.0. Here, the average number of substitution of Z groups is a numerical value obtained by dividing the total number of introduced Z groups by the total number of benzene rings (that is, average degree of polymerization × 2). When this average substitution number is lower than 0.2, the adhesion of the resin to the substrate surface becomes insufficient and the corrosion resistance is lowered. If this average number of substitutions exceeds 1.0 (that is, on average, more than one Z group is substituted on each benzene ring), the hydrophilicity of the resin becomes too large, and the corrosion resistance also decreases. The average number of substitutions of the Z group is preferably 0.3 to 0.7. When the Z group is only the ammonium group represented by the formula (4), the hydrophilicity imparting effect is great, and therefore the average substitution number of the Z group is preferably less than 0.5. Therefore, when the Z group is only the ammonium group represented by the formula (4), the particularly preferred average number of substitution of the Z group is 0.3 or more and less than 0.5.

  This cationic phenol resin is synthesized by reacting bisphenol A with an amine (or ammonia) that generates formaldehyde and a Z group in the presence of an alkali catalyst in accordance with a general method for synthesizing a phenol-formaldehyde resin. can do. The amine can be allowed to act on bisphenol A in advance before the condensation polymerization, or conversely on the polymer after the condensation polymerization.

(C) Silane coupling agent The silane coupling agent (C) is effective in improving the solvent resistance, corrosion resistance and adhesion of the coating.

  A commercially available product can be used as the silane coupling agent (C). Preferred silane coupling agents are those having at least one functional group selected from an amino group containing active hydrogen, an epoxy group, a vinyl group, a mercapto group, and a methacryloxy group. Specific examples include N- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2 -(3,4 Epoxycyclohexyl) ethyltrimethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and the like can be used.

(D) Manganese Compound The manganese compound (D) is effective in improving adhesion to the substrate and improving corrosion resistance.
Examples of the manganese compound (D) include inorganic compounds such as manganese nitrate, manganese sulfate, manganese phosphate, manganese oxide, manganese carbonate, manganese fluoride, manganese chloride; and manganese acetate, manganese lactate, manganese propionate, manganese acetyl. Organic compounds such as acetonate, tetrapropoxy manganese, tetrabutoxy manganese and the like can be mentioned. Preferred manganese compounds are manganese nitrate, manganese phosphate, manganese acetate, manganese lactate, and manganese acetylacetonate.

(E) Zirconium Compound Zirconium compound (E) is effective in improving the corrosion resistance of the film, and is particularly effective in improving alkali resistance. In Patent Document 1 described above, a titanium compound is used as the metal compound. However, since the titanium compound develops color when it coexists with the cationic phenol resin (B), the coating is discolored. On the other hand, zirconium is an element belonging to the same group as titanium. However, it has been found that when a zirconium compound is used, color development when coexisting with the cationic phenol resin (B) can be suppressed.

  Examples of the zirconium compound (E) include inorganic compounds such as zirconium nitrate, zirconium sulfate, zirconium oxide, zircon hydrofluoric acid, zircon sodium fluoride, zircon ammonium fluoride, zirconium ammonium carbonate; and zirconium acetate, zirconium lactate, zirconium stearate. And organic compounds such as zirconium octylate, zircon acetylacetonate, tetrapropoxyzirconium, tetrabutoxyzirconium, zirconium tributoxy systemate. Preferred zirconium compounds are zirconium sulfate, zircon hydrofluoric acid, sodium zircon fluoride, ammonium zircon fluoride, zirconium lactate and zirconium stearate.

(F) Vanadium compound The vanadium compound (F) is effective in improving the corrosion resistance of the film, and is particularly effective in improving the corrosion resistance of the processed part.

  Examples of vanadium compounds (F) include inorganic substances such as vanadium pentoxide, metavanadate, ammonium metavanadate, sodium metavanadate, vanadium oxytrichloride, vanadium trioxide, vanadium dioxide, vanadium trichloride, vanadyl phosphate, vanadyl sulfate, etc. Compounds; and organic compounds such as vanadium oxyacetylacetonate, vanadium acetylacetonate, tetrapropoxyvanadium, tetrabutoxyvanadium, vanadium tributoxy systemate. Preferred vanadium compounds are vanadium pentoxide, metavanadate, ammonium metavanadate, sodium metavanadate, vanadyl sulfate, vanadium acetylacetonate, and tetrabutoxy vanadium.

  Even if one of the above-mentioned manganese compound (D), zirconium compound (E) and vanadium compound (F) is missing, the corrosion resistance of the film is lowered. Therefore, in the present invention, in order to ensure a good performance balance of the surface-treated steel sheet, it is necessary to contain at least one of these three kinds of metal compounds in the film.

(G) Fischer Toro push wax:
The Fischer-Tropsch wax according to the present invention has a melting point of 70 ° C to 90 ° C. The melting point is correlated with the number average molecular weight and density, and the number average molecular weight and density tend to increase as the melting point increases. By setting the melting point to 70 to 90 ° C., the Fischer-Tropsch wax is partially softened during sliding and processing, and a film excellent in lubricity and workability that balances liquid lubricity and solid lubricity. Can be realized. Here, since the surface treatment liquid is water-based, it is preferable to use a water-based wax having excellent dispersibility in the water-based treatment liquid as the Fischer-Tropsch wax. It is preferable to use those having an average particle diameter in the range of 0.1 to 0.5 μm. If the average particle size is smaller than 0.1 μm, the workability tends to be lowered, and if it is larger than 0.5 μm, the dispersion in the surface treatment liquid becomes insufficient and the possibility of separation occurs. However, even when the average particle size of the wax is larger than 0.5 μm, a small amount does not cause a significant decrease in dispersibility. It is preferable to use a Fischer-Tropsch wax having a number average molecular weight in the range of 500 to 2,000. When the number average molecular weight is 500 or less, it is difficult to produce the wax itself. When the number average molecular weight exceeds 2000, the dispersion in the surface treatment liquid becomes insufficient and the separation may occur. It is preferable to use a Fischer-Tropsch wax having a density in the range of 0.85 to 0.95. If the density is less than 0.85, the workability tends to decrease, and if it is greater than 0.95, the water resistance and acid resistance tend to decrease.

The blending ratio of each component in the surface treatment solution should satisfy the following formula:
A / B = 7-120
C / (A + B) = 0.2-0.75
D / (A + B) = 0.005 to 0.025,
E / (A + B) = 0.01-0.075,
F / (A + B) = 0.001 to 0.025,
G / (A + B) = 0.03-0.4.

In said formula, AG is the mass as a solid content of component (A)-(G), respectively. However, metal compounds (D), (E), and (F) are solid contents in terms of metals of each compound.
When the mass ratio of A / B is smaller than 7, the cationic phenol resin (B) is too much, and the heat resistance and water resistance of the film are lowered. On the other hand, when the mass ratio of A / B is larger than 120, the amount of the cationic phenol resin (B) is too small, and the general corrosion resistance and solvent resistance are lowered.

  About component (C)-(G), a compounding quantity is prescribed | regulated as mass ratio with respect to the total amount of resin component (A) and (B), ie, (A + B). If each of the components (C) to (G) is less than the specified amount, the effect of each component described above will be insufficient. In particular, if the amount of the component (E) is too small, the corrosion resistance after alkaline degreasing decreases, and if the amount of the component (F) is too small, the corrosion resistance of the processed portion decreases. On the other hand, if the amount is too large, the silane coupling agent (C) decreases the corrosion resistance of the processed part, the manganese compound (D) and the zirconium compound (E) decrease in liquid stability, and the vanadium compound (F) exhibits heat resistance. With the Fischer Trop push wax (G), problems such as coil collapse due to a decrease in the coefficient of static friction appear.

  The surface treatment liquid used in the present invention is aqueous. An aqueous system means that the solvent is mainly composed of water. The solvent may be water alone, but one or more water-soluble organic solvents such as monohydric or polyhydric alcohols, ketones and cellosolves are used for the purpose of adjusting the drying property of the film and the viscosity of the treatment agent. You may use together.

  The surface treatment liquid may contain components other than the above components as desired. Such components include pH adjusters (acids or bases), fillers, surfactants, antifoaming agents, leveling agents, antibacterial agents, colorants, etc., and should be added within a range that does not impair the performance of the film. Can do.

The surface-treated steel sheet of the present invention has a surface-treated film formed on the surface of a galvanized steel sheet as a base material by applying the above-described surface treatment liquid and drying.
The surface treatment liquid can be applied using, for example, a roll coater (3-roll method, 2-roll method, etc.), a squeeze coater, a die coater, or the like. Alternatively, a method of adjusting the coating amount by an air knife or roll squeezing after dip coating or spray coating can be employed.

  Prior to this coating, the surface of the plated steel plate can be adjusted by one or more of degreasing, pickling, hot water washing, detergent washing, etc., and in either case, the surface can be thoroughly washed with water at the end. preferable. The liquid temperature of the treatment agent at the time of application may be room temperature, but it may be cooled or heated as desired.

  It is appropriate that the drying after applying the surface treatment liquid is performed at a maximum plate temperature (PMT) in the range of 50 to 250 ° C., preferably 60 to 220 ° C. If this heating temperature is less than 50 ° C., drying takes a long time, and corrosion resistance may be insufficient due to residual moisture in the film or insufficient curing. On the other hand, a drying temperature exceeding 250 ° C. is not only uneconomical but also may cause defects in the film and reduce the corrosion resistance. As the heating means, for example, a dryer, a hot air furnace, a high frequency induction heating furnace, an infrared furnace, or the like can be used.

  During this coating and drying, it is estimated that the cationic urethane resin (A) and the phenol resin (B) form a film on the base material to form a surface treatment film having an excellent shielding effect against the outside air. The Furthermore, the silane coupling agent (C) reacts with the metal surface of the base material to build a dense three-dimensional cross-linked structure, and three kinds of metal compounds (D) to (F) are also added to improve corrosion resistance and water resistance. Excellent film. In addition, the film is excellent in lubricity and workability due to the effect of the Fischer Trop push wax (G).

The adhesion amount of the surface treatment film thus formed is preferably in the range of 0.1 to 3 g / m ² . When the coating amount is thinner than 0.1 g / m ² , the corrosion resistance becomes insufficient. When corrosion resistance is required, 0.5 g / m ² or more is preferable. On the other hand, when the adhesion amount exceeds 3 g / m ² , conductivity and workability deteriorate. More preferably, it is 2.5 g / m ² or less.

  On the surface treatment film thus formed, an organic resin film can be formed as the second layer film. The organic resin film of the second layer is, for example, epoxy resin, polyhydroxy polyether resin, acrylic copolymer resin, ethylene-acrylic acid copolymer resin, alkyd resin, polybutadiene resin, phenol resin, polyurethane resin, polyamine resin, A resin film selected from polyphenylene resins, a mixture of two or more of these resins, or an addition polymer can be used.

The adhesion amount of the second layer film may be the same as the adhesion amount of the surface treatment film as the first layer. However, the total adhesion amount of the first layer and the second layer is preferably 5 g / m ² or less, more preferably 3 g / m ² or less.

  In addition, you may form the surface treatment film | membrane mentioned above on either the single side | surface of a base-plated steel plate, or both surfaces. When forming on one side, the back surface of the plated steel sheet may be left untreated or another surface treatment film may be formed.

[Adjustment of surface treatment solution]
A surface treatment solution having the composition shown in Tables 1 to 4 was prepared by mixing materials selected from the following for each of the components (A) to (G). For the silane coupling agent (C), two kinds of materials were used in combination in some cases. For other components, it is possible to use two or more materials. For comparison, a surface treatment solution not using some components was also prepared. In Tables 1 to 4, the types of components used for the preparation of the surface treatment liquid and the amounts of components (A) and (B) (parts = parts by mass), A / B mass ratios, and components (C) to ( The mass ratio of G) to (A + B) is shown.

(A) Polycarbonate-based cationic polyurethane resin A1: Polycarbonate-based cationic urethane resin, number average molecular weight 100,000
Polycarbonate polyol, R carbon number = 6, number average molecular weight 3000
Dicyclohexylmethane diisocyanate A2: Polycarbonate-based cationic urethane resin, number average molecular weight 200000
Polycarbonate polyol, R carbon number = 4, number average molecular weight 1000
Dicyclohexylmethane diisocyanate A3: polyether-based cationic urethane resin, number average molecular weight 100,000
Polyether, R carbon number = 6, number average molecular weight 2500
Dicyclohexylmethane diisocyanate A4: polyester-based cationic urethane resin, number average molecular weight 300,000
Polyester polyol, R carbon number = 4, molecular weight 1500
Dicyclohexylmethane diisocyanate A5: Polycarbonate-based cationic urethane resin, number average molecular weight 10,000
Polycarbonate polyol, R carbon number = 3, molecular weight 300
Dicyclohexylmethane diisocyanate

(B) Cationic phenol resin B1: n = 5, Y ₁ = —CH ₂ N (CH ₃ ) _2, Y ₂ = H, Z substitution degree = 0.5
B2: n = 10, Y ₁ = —CH ₂ N (CH ₃ ) (C ₂ H ₄ OH), Y ₂ = H, Z substitution degree = 1.0

(C) Silane coupling agent C1: 3-aminopropyltriethoxysilane C2: 3-glycidoxypropyltrimethoxysilane C3: 3-mercaptopropyltrimethoxysilane C4: vinyltriethoxysilane C5: 3-methacryloxypropyltri Methoxysilane

(D) Manganese compound D1: Manganese acetate D2: Manganese nitrate D3: Manganese lactate D4: Manganese acetylacetonate D5: Manganese phosphate

(E) Zirconium compound E1: Zirconium nitrate E2: Zircon hydrofluoric acid E3: Zirconium stearate E4: Zirconium lactate E5: Zirconium sulfate

(F) Vanadium compound F1: vanadium pentoxide F2: tetrabutoxyvanadium F3: vanadium acetylacetonate F4: ammonium metavanadate F5: vanadyl sulfate

(G) Fisher Tro Push Wax G1: Fisher Tro Push Wax
Average particle size 0.2 μm, number average molecular weight 900, density 0.95, melting point 90 ° C.
G2: Fischer Toro push wax
Average particle size 0.5 μm, number average molecular weight 600, density 0.90, melting point 70 ° C.
G3: Fischer Toro push wax
Average particle size 0.3 μm, number average molecular weight 400, density 0.80, melting point 60 ° C.
G4: Fischer Toro push wax
Average particle size 0.2 μm, number average molecular weight 2500, density 1.0, melting point 110 ° C.
G5: Fischer Toro push wax
Average particle size 0.05 μm, number average molecular weight 1000, density 0.95, melting point 90 ° C.
G6: Polyethylene wax
Average particle size 0.2 μm, number average molecular weight 3500, density 0.98, melting point 120 ° C.
G7: Polypropylene wax
Average particle size 0.2 μm, number average molecular weight 5000, density 1.0, melting point 150 ° C.

[Production of surface-treated steel sheet]
An electrogalvanized steel sheet having a thickness of 0.8 mm (adhesion amount per side of 20 g / m ² ) was used as a base material, and this was subjected to alkaline degreasing and water washing. It was applied on one side by a bar coater and dried by heating (baking) to form a surface treatment film. The film thickness and heating temperature (PMT, maximum plate temperature) of the formed film were as shown in Tables 1 to 4.

  The surface treatment film of the surface-treated steel sheet thus produced was evaluated for performance as follows. As a reference, performance evaluation was also performed on a surface-treated steel sheet in which a zirconium compound was replaced with a titanium compound as a metal compound. Those test results are also shown in Tables 1-4.

[Evaluation methods]
(1) Corrosion resistance (Flat part)-Using a test piece of an unprocessed surface-treated steel sheet, the surface rust generation surface rate after 120 hours of salt spraying based on JIS-Z-2371 was evaluated as follows.

A: Less than 5%, O: 5% or more, less than 10%, Δ: 10% or more, less than 30%, X: 30% or more, less than 50%, XX: 50% or more.
(Alkali = Corrosion resistance after alkaline degreasing)-Using an unprocessed surface-treated steel sheet test piece, an alkaline degreasing agent CL-364S (Nippon Parkerizing Co., Ltd., 20 g / L, 60 ° C, 10 seconds spray, spray pressure 0. After degreasing at 5 kg / cm ² ), spray water washing was performed for 10 seconds, and then the white rust generation surface rate after 120 hours of salt water spraying based on JIS-Z-2371 was evaluated as follows.

A: Less than 5%, O: 5% or more, less than 10%, Δ: 10% or more, less than 30%, X: 30% or more, less than 50%, XX: 50% or more.
(Processing part)-White rust generation surface rate after 120 hours of salt spraying based on JIS-Z-2371 using a test piece of a surface-treated steel sheet extruded by 7 mm with an Eriksen tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) Was evaluated as follows.

A: Less than 5%, O: 5% or more, less than 10%, Δ: 10% or more, less than 30%, X: 30% or more, less than 50%, XX: 50% or more.
(2) Ethanol resistance (solvent resistance)
The surface treatment film of the test piece of the surface-treated steel sheet was evaluated as follows according to the appearance after rubbing 5 times with gauze soaked with ethanol.

A: The rubbing trace is inconspicuous, O: The rubbing trace is slightly conspicuous, Δ: The rubbing trace is conspicuous, x: The rubbing trace is very conspicuous.
(3) Mold galling resistance (workability or slidability)
A test piece of an appropriate size is molded into a U-shape using a crank press (dies and punch shoulder R = 5 mm, clearance: −10% of the plate thickness), and the molded product (sliding with a mold) Evaluation was made on the appearance of the part.

○: No discoloration, Δ: Partially discolored black, ×: Discolored all over black (4) Heat resistance The surface treated steel sheet was heated at 180 ° C. for 20 minutes, and the color difference before and after heating Δb (hunter color system) The difference in b value) was measured and evaluated according to the following criteria.

A: Δb is 1 or less, ○: 1 <Δb ≦ 2, Δ: 2 <Δb <3, X: Δb is 3 or more (5) Water resistance The specimen of the surface-treated steel sheet immediately after baking (heat drying) is water-cooled. The elution component from the film was measured by XRF (fluorescence X-ray analysis) and evaluated according to the following criteria.

○: No elution, x: Elution.
(6) Fingerprint resistance After measuring the color tone (L1, a1, b1 in the Hunter color system) of a predetermined part of the test piece, petrolatum was applied to the specimen and wiped off with Kimwipe (Tech Jam). The color tone (L2, a2, b2) was measured again, and the color difference (ΔE = √ {(L2-L1) ² + (a2-a1) ² + (b2-b1) ² } at that time was evaluated.

○: ΔE is 2 or less, x: ΔE exceeds 2.
(7) Film color tone The b value (b value in the Hunter color system) of the test piece of the surface-treated steel sheet was measured and evaluated according to the following criteria.

○: b is 0.5 or less, x: b exceeds 0.5.
(8) Acid resistance Drop a drop of artificial fingerprint liquid (JIS-K-2246) on a test piece of surface-treated steel sheet, leave it for 2 minutes, wipe it off with Kimwipe (manufactured by Techjam), and visually check the appearance at that time It was evaluated with.

  ○: No change, △: Part of film disappeared, ×: All film disappeared

  As can be seen from Tables 1 to 4, in Examples 1 to 106 in which a film was formed from the surface treatment liquid according to the present invention, all the corrosion resistances of the flat part, the alkali (after alkali degreasing) and the processed part were good. Furthermore, solvent resistance (ethanol resistance), workability (mold galling resistance), heat resistance, water resistance, film color tone, fingerprint resistance and acid resistance were all good. That is, the surface-treated steel sheet of the present invention is excellent in performance balance, and various properties required for the surface-treated steel sheet are all good.

  Further, when the examples are compared, the corrosion resistance after alkaline degreasing is C / (A + B) ≦ 0.3 and E / (A + B) ≦ 0.02, the white rust generation area The rate reached 5% or more and less than 10%. When the corrosion resistance of the processed part is C / (A + B) ≧ 0.7 and F / (A + B) ≦ 0.01, the white rust generation area ratio reaches 5% or more and less than 10%. did. When the ethanol resistance was B ≦ 2 and C / (A + B) ≦ 0.3, rubbing marks were slightly noticeable. The heat resistance was 1 <Δb ≦ 2 when B ≧ 5 and F / (A + B) ≧ 0.5.

  Furthermore, about the component (G), when it deviated from the optimal area | region, it has confirmed that a slight performance fall was brought about. When the density was 0.8, the workability was slightly lowered and a part of the molded product was discolored to black, but it was a mild one that was not determined to have failed. Further, when the density was 1.0, the water resistance was slightly lowered, the acid resistance was lowered, and a part of the film disappeared although it was slightly. Further, even when the grain size was 0.05 μm, a part of the molded product was discolored black, and a slight decrease in workability was observed. In addition, although it was in this favorable range, the thing in which the characteristic fall was slight was described as "(circle) (triangle | delta)" in the table | surface.

  On the other hand, acid resistance fell in the comparative example that component (A) was polyether polyurethane resin or polyester polyurethane resin other than polycarbonate polyurethane resin. In addition, when any one of the components (B) to (F) is not present or the amount thereof is too small, the corrosion resistance and the solvent resistance are remarkably lowered, and the workability of the component (G) is lowered. On the other hand, when the component (B) is too much, the heat resistance and water resistance are remarkably lowered. When the component (C) is too much, the corrosion resistance of the processed part is lowered.

Claims (3)

A cationic polyurethane resin (A) containing a structural unit represented by the following general formula (1) on the surface of a galvanized steel sheet and an average degree of polymerization of 2 to 50 having a repeating unit represented by the following general formula (2) Cationic phenolic resin (B) composed of polymer molecules, silane coupling agent (C), manganese compound (D), zirconium compound (E), vanadium compound (F), Fischer-Tropsch wax (G ) Containing a surface treatment film formed by application and drying of an aqueous surface treatment liquid, and solid content (components A, B, C, G) of each component in the surface treatment liquid or solid in metal conversion The mixing ratio of the components (components D, E, F) is a mass ratio,
A / B = 7-120,
C / (A + B) = 0.2-0.75
D / (A + B) = 0.005 to 0.025,
E / (A + B) = 0.01-0.075,
F / (A + B) = 0.001 to 0.025,
G / (A + B) = 0.03-0.4,
A surface-treated steel sheet, characterized in that

In the formula, R is an aliphatic alkylene group having 4 to 9 carbon atoms, and n is an integer corresponding to a number average molecular weight in the range of 500 to 5000.

In the formula, Y ₁ and Y ₂ each independently represent hydrogen or a Z group represented by the following general formula (3) or (4), and the average number of substitutions of Z groups per benzene ring is 0.2 to 1.0.

In the formulas (3) and (4), R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or a hydroxyalkyl having 1 to 10 carbon atoms. Represents a group, and A ⁻ represents a hydroxide ion or an acid ion.   The Fischer-Tropsch wax (G) has an average particle size of 0.1 to 0.5 μm, a number average molecular weight of 500 to 2000, a density of 0.85 to 0.95, and a melting point of 70 to 90 ° C. The surface-treated steel sheet according to claim 1. The surface-treated steel sheet according to claim 1 or ² , wherein an adhesion amount of the surface-treated film is 0.1 to 3 g / m2.