JP2006043913A - Surface treated metal sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treated metal sheet excellent in corrosion resistance, coating properties, ablation resistance, alkali degreasing resistance and conductivity. <P>SOLUTION: The surface treated metal sheet has a resin film obtained from a resin aqueous liquid. The resin aqueous liquid contains 5-45 mass pts. of a carboxyl group-containing polyurethane resin aqueous liquid and an ethylene/unsaturated carboxylic acid copolymer aqueous liquid as a non-volatile resin component and 55-95 mass pts. of silica particles with an average particle size of 4-20 nm and a silane coupling agent is further added to 100 mass pts. in total of the non-volatile resin component and the silica particles in a ratio of 5-25 mass pts. The mixing ratio of the non-volatile resin component (PU) of the polyurethane resin aqueous liquid and the non-volatile resin component (EC) of the ethylene/unsaturated carboxylic acid copolymer aqueous liquid is PU:EC=9:1-2:1 in a mass ratio. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface-treated metal plate, and more specifically, corrosion resistance, abrasion resistance, paintability (coating film adhesion), conductivity, alkali degreasing resistance used for automobiles, home appliances, building materials and the like. The present invention relates to a surface-treated metal plate having excellent properties.

  Materials used for automobiles, home appliances, and building materials include zinc-plated steel sheets such as electrogalvanized steel sheets and hot-dip galvanized steel sheets, and chromate on the galvanized steel sheets for the purpose of further improving corrosion resistance and paintability. Many inorganic surface-treated steel sheets subjected to chemical conversion treatment such as treatment or phosphate treatment are used. In addition, for the purpose of further improving corrosion resistance, paintability, and workability, a resin-coated steel sheet in which an organic resin film is formed on a surface-treated steel sheet that has been subjected to chromate treatment has been proposed.

  However, when deep drawing is performed, such as motor case parts in home appliances, severe sliding friction occurs between the mold and the resin film on the sliding surface peels off and turns black. There was a problem that a blackening phenomenon occurred and the appearance of the product was remarkably deteriorated, and that the blackened material adhered to other equipment and caused another problem.

  In order to solve the above-mentioned problems of such resin-coated steel sheets, as the resin film, a lubricating steel sheet having a film having an inorganic polymer compound and a solid lubricant and a film having an aqueous resin were further formed. Lubricated steel sheets have been proposed (for example, Patent Documents 1 and 2). The film-treated steel sheets based on these inorganic polymers are found to have an improvement effect with respect to scratch resistance and the occurrence of film blackening during deep drawing. However, when applying a solution to a steel sheet, there are cases in which coating defects such as repellency may occur and the water permeability of the film is high, so black spot rust and white rust are likely to occur, and coating was performed. In some cases, the coating film had defects such as poor adhesion. That is, although the scratch resistance and deep drawability are improved, there are problems in terms of corrosion resistance and paintability.

  On the other hand, in some home appliances, there is a material that is required to have conductivity in order to prevent electrification. Regarding conductivity, when a film is applied on a galvanized steel sheet, the lower the resistance value of the film, the better the conductivity. Further, when the film is a resin film, the resistance value of the film becomes high, so it is necessary to reduce the adhesion amount of the film to ensure conductivity. However, if the adhesion amount of the resin film is low, the corrosion resistance and workability are inferior, so the advantages of the resin film described above cannot be obtained. Therefore, inorganic surface-treated steel sheets obtained by subjecting galvanized steel sheets to chemical conversion treatment such as chromate treatment and phosphoric acid treatment are often used for applications that require electrical conductivity.

  As a resin system applied to the organic resin film as described above, urethane resin is partially applied in that it has excellent hardness and elongation, but urethane resin has many polar groups. Therefore, there is a problem that many of them are inferior in corrosion resistance compared to other resin systems.

In addition, due to the recent increase in environmental awareness, the use of chromate treatment and steel plates that do not use hexavalent chromium, which have been used for the purpose of improving the corrosion resistance of galvanized steel sheets, has been increasing. Therefore, there is an increasing demand for coatings with better corrosion resistance.
JP-A-6-57441 JP-A-6-57442

  As described above, a resin film laminated on a chromium-free metal plate is required to have the same level of corrosion resistance as that of a resin film coated on a chromate-treated metal plate.

  However, the corrosion resistance of the conventional surface-treated metal sheet on which a urethane-based resin film is formed is still not sufficient, and paintability (adhesion with the coating film), conductivity, abrasion resistance, and alkali degreasing resistance Further improvements are also required in terms of sex.

  The present invention has been made in view of the above circumstances, and more specifically, a surface-treated metal plate, and more specifically, a metal plate having a polyurethane resin film formed on the surface thereof has corrosion resistance, paintability, alkali degreasing resistance, and abrasion resistance. And it aims at further improving electroconductivity.

  The surface-treated metal plate of the present invention that has solved the above problems is a surface-treated metal plate provided with a resin film obtained from a resin aqueous solution, and the resin aqueous solution is a carboxyl group-containing polyurethane resin aqueous solution and The ethylene-unsaturated carboxylic acid copolymer aqueous dispersion as a non-volatile resin component is 5 to 45 parts by mass, and the silica particles having an average particle diameter of 4 to 20 nm is 55 to 95 parts by mass, for a total of 100 parts by mass. The silane coupling agent is further contained in a ratio of 5 to 25 parts by mass with respect to the total of 100 parts by mass, and the non-volatile resin component (PU) of the polyurethane resin aqueous liquid and the ethylene-free component. The blending ratio of the saturated carboxylic acid copolymer aqueous dispersion to the nonvolatile resin component (EC) is PU: EC = 9: 1 to 2: 1 in terms of mass ratio.

  The carboxyl group-containing polyurethane resin is obtained by subjecting a urethane prepolymer to a chain extension reaction with a chain extender. The polyisocyanate component constituting the urethane prepolymer includes tolylene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane. At least one selected from the group consisting of diisocyanates is used, and all of 1,4-cyclohexanedimethanol, polyether polyol, and polyol having a carboxyl group are used as the polyol component constituting the urethane prepolymer. Those are preferred. Moreover, as said chain extension agent, ethylenediamine or hydrazine is suitable, for example. The mass ratio of the 1,4-cyclohexanedimethanol and the polyether polyol is preferably 1,4-cyclohexanedimethanol: polyether polyol = 1: 1 to 1:19. As the polyether polyol, for example, polyoxypropylene glycol or polytetramethylene ether glycol is suitable. The acid value of the carboxyl group-containing polyurethane resin is preferably 10 to 60 mgKOH / g.

  As the aqueous dispersion of ethylene-unsaturated carboxylic acid copolymer used in the present invention, in addition to the ethylene-unsaturated carboxylic acid copolymer, 1 mol of the carboxyl group of the ethylene-unsaturated carboxylic acid copolymer is used. 1 corresponding to 0.02 to 0.4 mol per 1 mol of amine having a boiling point of 100 ° C. or less corresponding to 0.2 to 0.8 mol and an ethylene-unsaturated carboxylic acid copolymer. Those containing a compound of a valent metal are preferred. The ethylene-unsaturated carboxylic acid copolymer is preferably a copolymer in which 10 to 40% by mass of an unsaturated carboxylic acid component is copolymerized. As the amine having a boiling point of 100 ° C. or lower, for example, triethylamine is preferable.

  The ethylene-unsaturated carboxylic acid copolymer aqueous dispersion further reacts with a carboxyl group when the nonvolatile resin component (EC) of the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion is 100 parts by mass. It is also a preferred embodiment of the present invention to contain a crosslinking agent having 2 or more functional groups that can be used at a ratio of 1 to 20 parts by mass. Furthermore, the aqueous ethylene-unsaturated carboxylic acid copolymer dispersion is preferably substantially free of amine and ammonia having a boiling point of more than 100 ° C.

  As the silane coupling agent used in the present invention, for example, a silane coupling agent represented by the following chemical formula (1) is suitable.

(In the chemical formula (1), R ¹ : glycidoxy group, R ² , R ³ : lower alkoxy group, R ⁴ : lower alkoxy group or lower alkyl group, X: lower alkylene group)

It is preferable that the adhesion amount of the resin film of the surface treatment metal plate of this invention is 0.05-1 g / m < ² >.

  According to the present invention, a surface-treated metal plate excellent in corrosion resistance, paintability, abrasion resistance, electrical conductivity, and alkali degreasing resistance can be obtained. In particular, the present invention can be suitably applied to improve the corrosion resistance of a non-chromated metal plate.

  The surface-treated metal plate of the present invention is a surface-treated metal plate provided with a resin film obtained from an aqueous resin solution, and the aqueous resin solution is a carboxyl group-containing polyurethane resin aqueous solution and an ethylene-unsaturated carboxylic acid copolymer. 5 to 45 parts by mass of the aqueous dispersion as a non-volatile resin component and 55 to 95 parts by mass of silica particles having an average particle diameter of 4 to 20 nm are contained in a total of 100 parts by mass, and the total amount is 100 parts by mass. Furthermore, it contains a silane coupling agent in a ratio of 5 to 25 parts by mass, and the nonvolatile resin component (PU) of the polyurethane resin aqueous liquid and the nonvolatile resin of the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion. The compounding ratio with the component (EC) is PU: EC = 9: 1 to 2: 1 in mass ratio. Hereinafter, the present invention will be described in detail.

(1) Resin component contained in resin aqueous liquid (1-1) First, the carboxyl group-containing polyurethane resin aqueous liquid used in the present invention will be described. As the carboxyl group-containing polyurethane resin aqueous liquid used in the present invention, either an aqueous dispersion in which a carboxyl group-containing polyurethane resin is dispersed in an aqueous medium or an aqueous solution in which the carboxyl group-containing polyurethane resin is dissolved in an aqueous medium is used. can do. The aqueous medium may contain a trace amount of a hydrophilic solvent such as alcohol, N-methylpyrrolidone and acetone in addition to water.

  The carboxyl group-containing polyurethane resin is preferably obtained by subjecting a urethane prepolymer to a chain extension reaction with a chain extender, and the urethane prepolymer reacts, for example, a polyisocyanate component and a polyol component described later. Obtained. As the polyisocyanate component constituting the urethane prepolymer, at least one polyisocyanate selected from the group consisting of tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and dicyclohexylmethane diisocyanate (hydrogenated MDI) is used. It is preferable. This is because by using such a polyisocyanate, a resin film having excellent corrosion resistance and reaction control stability can be obtained. In addition to the polyisocyanate, other polyisocyanates can be used as long as the corrosion resistance and the stability of reaction control are not lowered. The content of the polyisocyanate component is 70% by mass or more of the total polyisocyanate component. It is desirable to keep This is because when the content of the polyisocyanate component is less than 70% by mass, the corrosion resistance and reaction control stability tend to be lowered. Examples of the polyisocyanate other than the polyisocyanate component include tetramethylene diisocyanate, hexamethylene diisocyanate, dodecane methylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, and phenylene diisocyanate. The above polyisocyanates may be used alone or in admixture of at least two kinds.

  As the polyol component constituting the urethane prepolymer, all three types of polyols including 1,4-cyclohexanedimethanol, polyether polyol, and polyol having a carboxyl group are used, preferably all three types are diols. And This is because by using such a polyol component, a resin film having excellent corrosion resistance and slidability can be obtained. Moreover, the antirust effect of the polyurethane resin obtained can be heightened by using 1, 4- cyclohexane dimethanol as a polyol component.

  The polyether polyol is not particularly limited as long as it has at least two hydroxyl groups in the molecular chain and the main skeleton is composed of alkylene oxide units. For example, polyoxyethylene glycol (simply, Sometimes referred to as "polyethylene glycol"), polyoxypropylene glycol (sometimes simply referred to as "polypropylene glycol"), polyoxytetramethylene glycol (simply "polytetramethylene glycol" or "polytetramethylene") May be referred to as “ether glycol”), and commercially available ones may be used. Among the polyether polyols, it is preferable to use polyoxypropylene glycol or polytetramethylene ether glycol. The number of functional groups of the polyether polyol is not particularly limited as long as it is at least 2 or more, and may be, for example, trifunctional or tetrafunctional or more polyfunctional.

  The polyether polyol is obtained, for example, by adding an alkylene oxide such as ethylene oxide or propylene oxide using a compound having active hydrogen as an initiator. Examples of the compound having active hydrogen include diols such as propylene glycol and ethylene glycol, triols such as glycerin, trimethylolpropane, hexanetriol, and triethanolamine, tetraols such as diglycerin and pentaerythritol, and others, sorbitol, Examples thereof include sucrose and phosphoric acid. At this time, if a diol is used as an initiator to be used, a bifunctional polyether polyol can be obtained, and if a triol is used, a trifunctional polyether polyol can be obtained.

  Polyoxytetramethylene glycol is obtained, for example, by ring-opening polymerization of tetrahydrofuran.

  As the polyether polyol, it is preferable to use a commercially available one having an average molecular weight of about 400 to 4000, for example. This is because the resin film is hard when the average molecular weight is less than about 400, and too soft when it exceeds 4000. The average molecular weight can be determined by measuring the OH value (hydroxyl value).

  In the present invention, it is also a preferred embodiment that the mass ratio of 1,4-cyclohexanedimethanol and polyether polyol is 1,4-cyclohexanedimethanol: polyether polyol = 1: 1 to 1:19. It is because the rust prevention effect of the obtained polyurethane resin film can be further enhanced by using a fixed ratio of 1,4-cyclohexanedimethanol having a rust prevention effect.

  The polyol having a carboxyl group used in the present invention is not particularly limited as long as it has at least one carboxyl group and at least two hydroxyl groups. For example, dimethylolpropionic acid, dimethylolbutanoic acid, dihydroxy Examples include propionic acid and dihydroxysuccinic acid.

  In addition to the three types of polyol components, other polyols can be used as long as the corrosion resistance is not lowered. The content of the three types of polyol components is 70% by mass or more of the total polyol components. Is desirable. It is because there exists a tendency for corrosion resistance to fall that the content rate of the said 3 types of polyol component is less than 70 mass%. The polyol other than the three types of polyol components described above is not particularly limited as long as it has a plurality of hydroxyl groups, and examples thereof include a low molecular weight polyol and a high molecular weight polyol. The low molecular weight polyol is a polyol having an average molecular weight of about 500 or less. For example, ethylene glycol, diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6- Diols such as hexanediol; and triols such as glycerin, trimethylolpropane, and hexanetriol.

  The high molecular weight polyol is a polyol having an average molecular weight exceeding about 500. For example, a condensed polyester polyol such as polyethylene adipate (PEA), polybutylene adipate (PBA), polyhexamethylene adipate (PHMA); Examples include lactone polyester polyols such as ε-caprolactone (PCL); polycarbonate polyols such as polyhexamethylene carbonate; and acrylic polyols.

  The chain extender for chain extending reaction of the urethane prepolymer described above is not particularly limited, and examples thereof include polyamines, low molecular weight polyols, and alkanolamines. As the low molecular weight polyol, the same ones as described above can be used. Examples of the polyamine include aliphatic polyamines such as ethylenediamine, propylenediamine, and hexamethylenediamine; tolylenediamine, xylylenediamine, diaminodiphenylmethane. And alicyclic polyamines such as diaminocyclohexylmethane, piperazine and isophoronediamine; and hydrazines such as hydrazine, succinic dihydrazide, adipic dihydrazide and phthalic dihydrazide. Among these, it is preferable to use ethylenediamine and / or hydrazine as a chain extender component. Examples of the alkanolamine include diethanolamine and monoethanolamine.

  A known method can be used to prepare an aqueous liquid of the carboxyl group-containing polyurethane resin used in the present invention. For example, the carboxyl group of the carboxyl group-containing urethane prepolymer is neutralized with a base, There are a method of emulsifying and dispersing to chain extension reaction, and a method of emulsifying and dispersing a carboxyl group-containing polyurethane resin in the presence of an emulsifier with a high shear force to cause a chain extension reaction. Hereinafter, based on a method of neutralizing the carboxyl group of the carboxyl group-containing urethane prepolymer with a base and emulsifying and dispersing it in water, a method for preparing an aqueous liquid of a polyurethane resin will be described, but the present invention is limited to such a method. It is not something.

  First, a relatively low molecular weight carboxyl group-containing isocyanate group-terminated urethane prepolymer is prepared by using the above-described polyisocyanate and the above-described polyol so that the isocyanate group becomes excessive in the NCO / OH ratio. Although the temperature which synthesize | combines a urethane prepolymer is not specifically limited, It can synthesize | combine at the temperature of 50-200 degreeC. Moreover, a well-known catalyst can be used for the synthesis | combination of a urethane prepolymer. Examples of the catalyst include monoamines such as triethylamine and N, N-dimethylcyclohexylamine; N, N, N ′, N′-tetramethylethylenediamine, N, N, N ′, N ″, N ″ — Polyamines such as pentamethyldiethylenetriamine; 1,8-diazabicyclo [5,4,0] -7-undecene (DBU), cyclic diamines such as triethylenediamine; tin-based catalysts such as dibutyltin dilaurate and dibutyltin diacetate Is mentioned.

  In synthesizing the urethane prepolymer, a one-shot method may be adopted, or a prepolymer method may be adopted. The one-shot method is a method in which polyisocyanate and polyol are reacted together, and the prepolymer method is a method in which polyisocyanate and polyol are reacted in multiple stages. For example, once a low to medium molecular weight urethane prepolymer is reacted. This is a method of further increasing the molecular weight after synthesizing the polymer.

  In the present invention, for example, an embodiment in which polyisocyanate and all of the above three types of polyol are reacted together; first, polyisocyanate and the above three types of polyol components are first reacted with polyether polyol, and then 1 , 4-cyclohexanedimethanol, and a mode of further reacting a polyol having a carboxyl group, or, among the essential polyol components, first, after reacting polyether polyol and 1,4-cyclohexanedimethanol, Next, a urethane prepolymer may be synthesized by appropriately selecting an aspect in which a polyol having a carboxyl group is reacted.

  In preparing the carboxyl group-containing isocyanate group-terminated urethane prepolymer, it is also a preferred embodiment to use a solvent from the viewpoint of adjusting the viscosity and improving the emulsifying dispersibility of the prepolymer. As the solvent, it is preferable to use a solvent that is inert to the isocyanate group and has a relatively high hydrophilicity. For example, N-methylpyrrolidone, acetone, ethyl acetate, methyl ethyl ketone, N, N-dimethylformamide Etc., preferably N-methylpyrrolidone is used. This is because N-methylpyrrolidone is highly soluble in a polyol having a carboxyl group and can uniformly carry out a reaction for preparing an isocyanate group-terminated urethane prepolymer. In addition, reaction of a urethane prepolymer can obtain | require a reaction rate by calculating | requiring an isocyanate group density | concentration by the dibutylamine titration method, for example.

  After completion of the urethane prepolymer reaction, the obtained carboxyl group-containing isocyanate group-terminated urethane prepolymer can be emulsified and dispersed in water by neutralization with a base. The neutralizing agent is not particularly limited, and ammonia; tertiary amines such as triethylamine and triethanolamine; alkali metal hydroxides such as sodium hydroxide and potassium hydroxide can be used. Preferably, triethylamine is used.

  After emulsifying and dispersing the carboxyl group-containing isocyanate group-terminated urethane prepolymer, a chain extension reaction can be carried out in water using a chain extender such as polymian. The chain extension reaction can be appropriately performed before emulsification dispersion, simultaneously with emulsification dispersion, or after emulsification dispersion, depending on the reactivity of the chain extender used.

  The acid value of the carboxyl group-containing polyurethane resin used in the present invention is preferably 10 mgKOH / g or more and 60 mgKOH / g or less. This is because when the acid value is less than 10 mgKOH / g, the stability of the aqueous polyurethane resin dispersion is lowered. Moreover, when an acid value exceeds 60 mgKOH / g, there exists a tendency for the corrosion resistance of the resin film obtained to fall. The acid value is measured according to JIS-K0070.

  (1-2) Next, the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion used in the present invention will be described. The ethylene-unsaturated carboxylic acid copolymer aqueous dispersion used in the present invention is not particularly limited as long as it is a liquid in which an ethylene-unsaturated carboxylic acid copolymer is dispersed in an aqueous medium. The carboxylic acid copolymer is a copolymer of ethylene and an ethylenically unsaturated carboxylic acid. Examples of the unsaturated carboxylic acid include (meth) acrylic acid, crotonic acid, isocrotonic acid, maleic acid, fumaric acid, itaconic acid, and the like. A copolymer can be obtained by polymerization using a legal method or the like. The copolymer is most preferably random, but may be a block copolymer or a copolymer grafted with an unsaturated carboxylic acid moiety. In addition, (meth) acrylic acid is suitable as the unsaturated carboxylic acid. Further, an olefin monomer such as propylene or 1-butene may be used instead of a part of ethylene, and other known vinyl monomers are partially copolymerized as long as the object of the present invention is not impaired. (About 10 mass% or less).

  The ethylene-unsaturated carboxylic acid copolymer is preferably one in which 10 to 40% by mass of an unsaturated carboxylic acid component is copolymerized when the total amount of monomers is 100% by mass. When the amount of unsaturated carboxylic acid is less than 10% by mass, there are few carboxyl groups that serve as a base point for intermolecular association by ion clusters or a cross-linking point with a cross-linking agent, so that the film strength effect is not exhibited and the corrosion resistance after the degreasing process. May be insufficient, and the emulsion stability of the aqueous dispersion is inferior. A more preferable lower limit of the unsaturated carboxylic acid is 15% by mass. On the other hand, if the unsaturated carboxylic acid exceeds 40% by mass, the corrosion resistance and water resistance of the resin film are inferior, and the corrosion resistance after the alkaline degreasing step is also lowered, which is not preferable. A more preferred upper limit is 25% by mass.

  The ethylene-unsaturated carboxylic acid copolymer used in the present invention has a carboxyl group, and an aqueous dispersion can be obtained by neutralizing the carboxyl group with an organic base or metal ion.

  It is preferable to use an amine having a boiling point of 100 ° C. or lower as the organic base. Amines having a boiling point exceeding 100 ° C. tend to remain in the resin film on the metal plate when the resin aqueous solution is dried, and the water absorption of the resin film increases, resulting in a decrease in corrosion resistance. Therefore, it is preferable that the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion used in the present invention does not contain amines having a boiling point of more than 100 ° C. Moreover, since the addition effect of ammonia was not recognized, it is preferable that ammonia is not contained. As the boiling point, a boiling point under atmospheric pressure is adopted.

  The ethylene-unsaturated carboxylic acid copolymer aqueous dispersion corresponds to 0.2 to 0.8 mol (20 to 80 mol%) with respect to 1 mol of the carboxyl group of the ethylene-unsaturated carboxylic acid copolymer. Of a monovalent metal corresponding to 0.02 to 0.4 mol (2 to 40 mol%) with respect to 1 mol of an amine having a boiling point of 100 ° C. or less and a carboxyl group of the ethylene-unsaturated carboxylic acid copolymer. It is preferable that a compound is included.

  Specific examples of the amine having a boiling point of 100 ° C. or lower include tertiary amines such as triethylamine, N, N-dimethylbutylamine, N, N-dimethylallylamine, N-methylpyrrolidine, tetramethyldiaminomethane, and trimethylamine; N-methylethylamine Secondary amines such as diisopropylamine and diethylamine; primary amines such as propylamine, t-butylamine, sec-butylamine, isobutylamine, 1,2-dibutylpropylamine, and 3-pentylamine. Two or more kinds can be mixed and used. Of these, tertiary amines are preferred, and triethylamine is the most preferred.

  The amount of the amine having a boiling point of 100 ° C. or less may be in the range of 0.2 to 0.8 mol (20 to 80 mol%) with respect to 1 mol of the carboxyl group in the ethylene-unsaturated carboxylic acid copolymer. preferable. This is because the corrosion resistance is good within this range. If the amine having a boiling point of 100 ° C. or less is less than 0.2 mol, the particle size of the resin particles in the aqueous dispersion becomes large, and it is considered that the above effect is not exhibited. In addition, use of an amine having a boiling point of more than 0.8 mol and a boiling point of 100 ° C. or less is not preferable because the aqueous dispersion may thicken and gel. The upper limit of the amount of the amine is more preferably 0.6 mol, still more preferably 0.5 mol, and the lower limit of the amount of the amine is more preferably 0.3 mol.

  In the present invention, it is preferable to use a monovalent metal ion for neutralization in addition to the amine having a boiling point of 100 ° C. or less. Effective for improving solvent resistance and film hardness. The monovalent metal compound preferably contains one or more metals selected from sodium, potassium, and lithium, and a hydroxide, carbonate, or oxide of these metals is preferable. Among these, NaOH, KOH, LiOH and the like are preferable, and NaOH has the best performance and is preferable.

  The amount of the monovalent metal compound should be in the range of 0.02 to 0.4 mol (2 to 40 mol%) with respect to 1 mol of the carboxyl group in the ethylene-unsaturated carboxylic acid copolymer. Is preferred. When the amount of the metal compound is less than 0.02 mol, the emulsion stability becomes insufficient. However, when the amount exceeds 0.4 mol, the hygroscopicity (particularly with respect to the alkaline solution) of the resulting resin film increases, and degreasing Since corrosion resistance after a process deteriorates, it is not preferable. The lower limit of the more preferable amount of the metal compound is 0.03 mol, and the more preferable lower limit is 0.1 mol. The upper limit of the more preferable amount of the metal compound is 0.5 mol, and the more preferable upper limit is 0.2 mol.

  The preferred ranges of the respective amounts of the amine having a boiling point of 100 ° C. or less and the monovalent metal compound are as described above, and these all neutralize the carboxyl group in the ethylene-unsaturated carboxylic acid copolymer. And used to make it aqueous. Accordingly, if the total amount (neutralization amount) of these is too large, the viscosity of the aqueous dispersion may rapidly increase and solidify, and excessive alkali will cause corrosion resistance deterioration and volatilize. For this reason, a large amount of energy is required, which is not preferable. However, if the amount of neutralization is too small, the emulsifiability is poor, which is not preferable. Therefore, the total amount of the amine having a boiling point of 100 ° C. or less and the monovalent metal compound is in the range of 0.3 to 1.0 mol with respect to 1 mol of the carboxyl group in the ethylene-unsaturated carboxylic acid copolymer. It is preferable to do.

  The aqueous dispersion of ethylene-unsaturated carboxylic acid copolymer used in the present invention has an average particle diameter of 5 to 50 nm by emulsifying an amine having a boiling point of 100 ° C. or less and a monovalent metal ion in combination. What is dispersed in an aqueous medium in the form of small fine particles (oil droplets) is obtained. For this reason, it is presumed that the film forming property of the obtained resin film, the adhesion to the metal plate, the densification of the film are achieved, and the corrosion resistance is improved. The aqueous medium may contain a hydrophilic solvent such as alcohol or ether in addition to water. The particle diameter of the resin particles in the aqueous dispersion can be measured by a laser diffraction method using, for example, a light scattering photometer (manufactured by Otsuka Electronics Co., Ltd.).

  In the neutralization step (aqueous step) of the ethylene-unsaturated carboxylic acid copolymer with an amine having a boiling point of 100 ° C. or less and a monovalent metal ion, an amine having a boiling point of 100 ° C. or less and a monovalent metal compound are substantially simultaneously mixed. It is desirable to add to the copolymer or to add an amine having a boiling point of 100 ° C. or lower first. The reason is not clear, but if an amine having a boiling point of 100 ° C. or lower is added later, the effect of improving the corrosion resistance may be insufficient.

  As a method for preparing an aqueous dispersion of an ethylene-unsaturated carboxylic acid copolymer used in the present invention, an ethylene-unsaturated carboxylic acid copolymer is put together with an aqueous medium into, for example, a homogenizer device and the like. Under heating at ˜250 ° C., an amine having a boiling point of 100 ° C. or less and a monovalent metal compound is appropriately added in the form of an aqueous solution or the like (an amine having a boiling point of 100 ° C. or less is added first, or a boiling point of 100 ° C. or less is added) The amine and the monovalent metal compound are added almost simultaneously) and stirred with high shearing force.

(1-3) Compounding amount of resin component The aqueous resin liquid used in the present invention is 5 as a non-volatile resin component using the above-described aqueous carboxyl group-containing polyurethane resin liquid and ethylene-unsaturated carboxylic acid copolymer aqueous dispersion. -45 mass parts and 55-95 mass parts of silica particles are contained in a total of 100 mass parts, and the silane coupling agent is further contained in a ratio of 5-25 mass parts with respect to the total 100 mass parts. In the present invention, a surface-treated metal plate excellent in paintability, corrosion resistance, abrasion resistance, and alkali degreasing resistance is obtained by using a carboxyl group-containing polyurethane resin and an ethylene-unsaturated carboxylic acid copolymer in combination. It is done. Moreover, when the amount of the non-volatile resin component is too small, corrosion resistance, alkali degreasing resistance, and paintability tend to deteriorate. On the other hand, if the amount of the non-volatile resin component is too large, abrasion resistance and conductivity tend to decrease. From such a viewpoint, the resin aqueous liquid is 20 parts by mass or more, more preferably 25 parts by mass, using a carboxyl group-containing polyurethane resin aqueous liquid and an ethylene-unsaturated carboxylic acid copolymer aqueous dispersion as a nonvolatile resin component. It is desirable that it is contained in an amount of 40 parts by mass or less, more preferably 35 parts by mass or less. Here, the nonvolatile resin component of the polyurethane aqueous liquid is the above-described carboxyl group-containing polyurethane resin, and the nonvolatile resin component of the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion is the above-described ethylene-unsaturated resin. Carboxylic acid copolymer. The non-volatile resin component can be measured by a method known in the technical field of aqueous liquids or aqueous dispersions. For example, when the aqueous liquid or aqueous dispersion is heated and dried at 100 ° C. to 130 ° C. for 1 to 3 hours. The evaporation residue.

  The blending ratio of the carboxyl group-containing polyurethane resin (PU) and the ethylene-unsaturated carboxylic acid copolymer (EC) is PU: EC = 9: 1 to 2: 1 by mass ratio, preferably 6. 5: 1 to 3.3: 1, more preferably 5: 1. As a blending ratio of the non-volatile component (PU) of the polyurethane resin aqueous liquid and the non-volatile component (EC) of the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion, when the PU ratio is larger than 9: 1, the corrosion resistance, Alkali resistance deteriorates. On the other hand, if the PU ratio is less than 2: 1, the abrasion resistance decreases.

(2) Silica particles The aqueous resin liquid used in the present invention contains 5 to 45 parts by mass of a nonvolatile resin component of the above-described aqueous carboxyl group-containing polyurethane and aqueous ethylenic-unsaturated carboxylic acid copolymer dispersion. To 55 parts by mass or more, preferably 60 parts by mass or more, and 95 parts by mass or less, preferably 80 parts by mass or less, more preferably 75 parts by mass or less of silica particles (however, a nonvolatile resin) The total amount with the components is 100 parts by mass).

  The silica particles impart conductivity, corrosion resistance, and paintability to the resulting resin film, and increase the hardness of the film to improve abrasion resistance. When the content of silica particles is less than 55 parts by mass, conductivity and abrasion resistance tend to be lowered. Moreover, when content of a silica exceeds 95 mass parts, there exists a tendency for the film forming property of a resin film to fall and for corrosion resistance to fall. In order to maximize the effect of the silica particles, the average particle size of the silica particles is preferably in the range of 4 to 20 nm. The smaller the average particle size of the silica particles, the better the corrosion resistance of the resin film. However, when the average particle size is less than about 4 nm, the effect of improving the corrosion resistance tends to be saturated, and the stability of the aqueous resin liquid decreases. This is because it becomes easy to gel. On the other hand, when the average particle diameter of the silica particles exceeds 20 nm, the film forming property of the resin film is lowered, and the corrosion resistance, paintability, and alkali degreasing property may be lowered.

  As a method for measuring the average particle diameter of the silica particles, it is preferable to employ a Sears method (4 to 6 nm) or a BET method (4 to 20 nm). In the case of chain silica, it is preferable to employ a dynamic light scattering method. Such silica particles are generally known as colloidal silica. In the present invention, for example, “XS”, “SS”, “40” of “Snowtex” series (colloidal silica manufactured by Nissan Chemical Industries, Ltd.) are used. ”,“ N ”,“ UP ”and the like can be preferably used.

(3) Silane coupling agent The aqueous resin liquid used in the present invention contains a silane coupling agent. The silane coupling agent is used for improving abrasion resistance, paintability, corrosion resistance, and the like, and improving adhesion between the metal plate and the resin film formed on the metal plate.

  The content of the silane coupling agent in the resin aqueous liquid is the total mass part of the nonvolatile resin component and the silica particles of the carboxyl group-containing polyurethane aqueous liquid and the ethylenic-unsaturated carboxylic acid copolymer aqueous dispersion described above. Is 100 parts by mass, 5 parts by mass or more, preferably 7 parts by mass or more, and 25 parts by mass or less, preferably 15 parts by mass or less. If the content of the silane coupling agent is too small, the reactivity between the silica particles, the above-mentioned carboxyl group-containing polyurethane resin and the ethylenic-unsaturated carboxylic acid copolymer, etc. is lowered, resulting in abrasion resistance, paintability, and corrosion resistance. And so on. On the other hand, if the content of the silane coupling agent is too large, the stability of the aqueous resin liquid may decrease and gelation may occur, and the amount of the silane coupling agent that does not contribute to the reaction increases. Adhesion between the plate and the resin film formed on the metal plate may be reduced.

  As the silane coupling agent, it is preferable to use a silane coupling agent represented by the following chemical formula (1).

(In the chemical formula (1), R ¹ : glycidoxy group, R ² , R ³ : lower alkoxy group, R ⁴ : lower alkoxy group or lower alkyl group, X: lower alkylene group) 1 to 5, more preferably 1 to 3 carbon atoms.

  By containing the silane coupling agent, the paintability and corrosion resistance of the formed resin film can be improved. Examples of the silane coupling agent having a glycidoxy group at the terminal represented by the chemical formula (1) include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, vinyltris (β-methoxy). And ethoxy) silane. The use of a silane coupling agent having a glycidoxy group is rich in crosslinking reactivity with respect to a carboxyl group-containing polyurethane resin and an ethylene-unsaturated carboxylic acid copolymer. This is because the lubricity is improved.

(4) Other additives The above-described ethylene-unsaturated carboxylic acid copolymer having a carboxyl group neutralized by an amine having a boiling point of 100 ° C. or less and a monovalent metal ion forms an intermolecular association by an ion cluster. (Ionomerization), forming a resin film with excellent corrosion resistance. However, in order to form a tougher film, it is desirable to crosslink the polymer chains by chemical bonding utilizing a reaction between functional groups.

  Therefore, the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion used in the present invention preferably includes a crosslinking agent having two or more functional groups capable of reacting with a carboxyl group. The content ratio is 1 part by mass or more, more preferably 5 parts by mass or more when the nonvolatile resin component (EC) in the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion is 100 parts by mass, It is desirable to contain 20 parts by mass or less, more preferably 10 parts by mass or less.

  When the amount is less than 1 part by mass, the effect of crosslinking by chemical bonding becomes insufficient, and the effect of improving corrosion resistance is difficult to be exhibited. On the other hand, when the amount exceeds 20 parts by mass, the crosslink density of the resin film becomes excessively high, the hardness increases, and it becomes impossible to follow the deformation at the time of press working, resulting in cracks, resulting in corrosion resistance and paintability. Is not preferable.

  Although it does not specifically limit as a crosslinking agent which has two or more functional groups which can react with a carboxyl group in 1 molecule, Sorbitol polyglycidyl ether, (poly) glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, trimethylolpropane polyglycidyl Glycidyl group-containing crosslinking agents such as ether, neopentyl glycol diglycidyl ether, (poly) ethylene glycol diglycidyl ether, and polyglycidyl amines; 4,4′-bis (ethyleneiminecarbonylamino) diphenylmethane N, N′-hexamethylene-1,6-bis (1-aziridinecarboxamide), N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxamide), toluenebisua Bifunctional aziridine compounds such as lysine carboxamide; tri-1-aziridinylphosphine oxide, tris [1- (2-methyl) aziridinyl] phosphine oxide, trimethylolpropane tris (β-aziridinylpropionate), tris An aziridinyl group-containing crosslinking agent such as a tri- or higher functional aziridine compound such as 2,4,6- (1-aziridinyl) -1,3,5-triazine, tetramethylpropanetetraaziridinylpropionate, or a derivative thereof. Are mentioned as preferred examples, and one or more of them can be used. Of these, aziridinyl group-containing crosslinking agents are preferred. In addition, you may use together polyfunctional aziridine and monofunctional aziridine (ethyleneimine etc.).

(5) Preparation method of resin aqueous liquid and formation method of resin film The resin aqueous liquid used in the present invention is within a range that does not impair the object of the present invention, a dilution solvent, a skin anti-skinning agent, a leveling agent, an antifoaming agent, It can contain penetrants, emulsifiers, film-forming aids, color pigments, thickeners, lubricants and the like. The method for preparing the resin aqueous liquid is not particularly limited, but the carboxyl group-containing polyurethane aqueous liquid, ethylene-unsaturated carboxylic acid copolymer aqueous dispersion, silica particles, silane coupling agent, and necessary Depending on the case, it can be obtained by blending a predetermined amount of wax, a crosslinking agent or the like. Silica particles, silane coupling agent, wax, cross-linking agent, etc. may be added at any stage, but after adding the cross-linking agent and silane coupling agent, heat is applied so that the cross-linking reaction will not proceed and gel. It is desirable not to multiply.

  In order to form a resin film on a metal plate, the resin aqueous liquid is applied to one or both surfaces of the metal plate surface using a known coating method, that is, a roll coater method, a spray method, a curtain flow coater method, or the like. And heat drying. The heating and drying temperature is preferably a temperature at which the crosslinking reaction of the used crosslinking agent and the carboxyl group proceeds. In addition, when spherical polyethylene wax is used as the lubricant, it is preferable to perform drying in the range of 70 to 130 ° C. because maintaining the spherical shape improves the workability in the subsequent processing step. . The metal plate used in the present invention is not particularly limited, but is preferably a zinc-based plated steel plate, for example, a hot-dip galvanized steel plate (GI), an alloyed molten Zn-Fe plated steel plate (GA), or an alloyed molten steel. A Zn-5% Al-plated steel plate (GF), an electric pure galvanized steel plate (EG), an electric Zn-Ni plated steel plate, an aluminum plate, a Ti plate and the like can be suitably used. Before forming the resin film, the surface of the metal plate may be treated with Co or Ni, treated with an inhibitor, or treated with various non-chromates.

Amount of adhesion to the metal plate of resin film (thickness), after drying, 0.05 g / m ² or more, more preferably be at 0.2 g / m ² or more, 1 g / m ² or less, more preferably 0 It is desirable that it is not more than 5 g / m ² . When the adhesion amount is too small, abrasion resistance, corrosion resistance, and alkali degreasing resistance decrease. On the other hand, if the amount of adhesion is too large, the conductivity and weldability tend to decrease. This surface-treated metal plate can be used as it is after being processed according to the application, or it can be used after electrodeposition coating, powder coating, silk printing (about 130 to 160 ° C, about 20 to 30 minutes) under conventional conditions. May be.

[Evaluation methods]
(1) Corrosion resistance The obtained surface-treated metal plate (resin-coated steel plate) was subjected to a salt spray test on an edge-sealed flat plate according to JIS-Z2371, and evaluated in the time until 1% of white rust was generated. did.
(Evaluation criteria)
◎: White rust generation 240 hours or more ○: White rust generation 120 hours to less than 240 hours Δ: White rust generation 72 hours to less than 120 hours ×: White rust generation less than 72 hours

(2) Ablation resistance The surface-treated metal plate (resin-coated steel plate) obtained was subjected to a vibration test in accordance with the packaging cargo-vibration test (JIS-Z0232). Evaluation was based on the following criteria. In addition, the brand name "BF-500UC" by IDEC company was used for the vibration test apparatus.
(Evaluation criteria)
◎: No damage to the film ○: Damage to the film but no damage to the galvanized surface △: Damage to the galvanized surface that can be visually confirmed ×: Significant damage to the galvanized surface

(3) Paintability Spray coating was applied to the obtained surface-treated metal plate (resin-coated steel plate) so that the coating thickness after drying melamine alkyd paint (Amirac # 1000 manufactured by Kansai Paint Co., Ltd.) was about 20 μm. The film was baked at 130 ° C. for 20 minutes and then painted. Subsequently, after immersing this test material in boiling water for 1 hour, taking it out and allowing it to stand for 1 hour, 100 mm of 1 mm square grids were cut with a cutter knife, and a tape peeling test was performed on this to leave the coating film remaining. The coating film adhesion was evaluated in four stages according to the number of cells.
(Evaluation criteria)
A: Residual rate: 100%
○: Residual rate: 90% to less than 100% Δ: Residual rate: 80% to less than 90% ×: Residual rate: 70% to less than 80%

(4) Conductivity The surface resistance of the obtained surface-treated metal plate (resin-coated steel plate) was measured at 10 points with a surface resistance meter (Loresta-EP manufactured by Dia Instruments Co., Ltd.) / 4 probe type.
(Evaluation criteria)
◎: 1 mΩ or less overload 0 times / 10 locations ○: 1 mΩ or less overload 1 times / 10 locations Δ: 1 mΩ or less overload 2 times / 10 locations x: 1 mΩ or more overload 5 times / 10 locations

(5) Alkali degreasing resistance After immersing the specimen in an alkaline degreasing agent (CL-N364S, manufactured by Nihon Parker Rising Co., Ltd.) 20 g / l adjusted to a liquid temperature of 60 ° C. for 2 minutes, lifting, washing and drying, The test material was subjected to a salt spray test according to JISZ2371, and evaluated in terms of time until 1% white rust was generated.
(Evaluation criteria)
◎: 168 hours or more ○: 96 hours or more and less than 168 hours Δ: 48 hours or more and less than 96 hours ×: less than 48 hours

[Preparation of carboxyl group-containing polyurethane resin aqueous solution]
60 g of polytetramethylene ether glycol (average molecular weight 1000) manufactured by Hodogaya Chemical Co., Ltd. as a polyol component in a 0.8 L internal synthesizer equipped with a stirrer, thermometer and temperature controller, 1,4-cyclohexanedimethanol 14 g and 20 g of dimethylolpropionic acid were charged, and 30.0 g of N-methylpyrrolidone was added as a reaction solvent. 104 g of tolylene diisocyanate (hereinafter sometimes simply referred to as “TDI”) was added as an isocyanate component, and the temperature was raised from 80 to 85 ° C. and reacted for 5 hours. The obtained prepolymer had an NCO content of 8.9%. Further, 16 g of triethylamine was added for neutralization, a mixed aqueous solution of 16 g of ethylenediamine and 480 g of water was added, emulsified at 50 ° C. for 4 hours, and subjected to chain extension reaction to obtain an aqueous polyurethane resin dispersion (nonvolatile resin component 29 0.1%, acid value 41.4).

[Preparation of aqueous dispersion of ethylene-unsaturated carboxylic acid copolymer]
In an autoclave of an emulsification facility having an internal capacity of 0.8 L equipped with a stirrer, a thermometer, and a temperature controller, 626 parts by mass of water, ethylene-acrylic acid copolymer (acrylic acid 20% by mass, melt index (MI) 300) Add 160 parts by mass, add 40 mol% of triethylamine and 15 mol% of sodium hydroxide to 1 mol of carboxyl group of ethylene-acrylic acid copolymer, and stir at high speed under an atmosphere of 150 ° C and 5 Pa. And cooled to 40 ° C. to obtain an aqueous dispersion of an ethylene-acrylic acid copolymer. Subsequently, 4,4′-bis (ethyleneiminocarbonylamino) diphenylmethane (manufactured by Nippon Shokubai, Chemite DZ-22E, “Chemite” is a registered trademark), ethylene-acrylic acid copolymer as a crosslinking agent in the aqueous dispersion. It added so that it might become a ratio of 5 mass parts with respect to 100 mass parts of united non-volatile resin components.

[Preparation of aqueous resin liquid and preparation of surface-treated metal sheet]
(Experimental example 1)
Carboxyl group-containing polyurethane resin aqueous liquid obtained above, ethylene-acrylic acid copolymer aqueous dispersion, silica particles (Nissan Chemical Snowtex XS, average particle diameter 4-6 nm) and the blending ratio shown in Table 1 In total, 100 parts by mass in terms of non-volatile components are blended, and 15 parts by mass of γ-glycidoxypropyltrimethoxysilane (KBM403 manufactured by Shin-Etsu Chemical Co., Ltd.) is further added as a silane coupling agent to the total of 100 parts by mass. The aqueous resin solution was prepared by adding.

This aqueous resin solution is applied to the surface of an electropure galvanized steel sheet with a drawing roll, and heated and dried at a plate temperature of 90 ° C. to form a surface-treated metal plate on which a resin film having an adhesion amount of 0.4 g / m ² is formed ( A resin-coated steel sheet was obtained. Table 1 also shows the results of evaluating the corrosion resistance, conductivity, abrasion resistance, alkali degreasing resistance, paintability, etc. of the obtained resin-coated steel sheet.

In addition, as the said electropure galvanized steel plate, the electrogalvanized steel plate which does not perform a chromate process (Zn adhesion amount 20g / m < ² >, plate thickness 0.8mm) was used.

  Steel plate No. 1 to steel plate No. 1 14 is a surface-treated metal plate provided with a resin film obtained from an aqueous resin solution, and the aqueous resin solution is a non-volatile solution of a carboxyl group-containing polyurethane resin aqueous solution and an ethylene-unsaturated carboxylic acid copolymer aqueous dispersion. 5 to 45 parts by mass as a functional resin component and 100 parts by mass of 55 to 95 parts by mass of silica particles, and a ratio of 5 to 25 parts by mass of a silane coupling agent with respect to the total of 100 parts by mass The blending ratio of the nonvolatile resin component (PU) of the polyurethane resin aqueous liquid and the nonvolatile resin component (EC) of the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion is PU by mass ratio. EC = 9: 1 to 2: 1. It can be seen that all the steel plates are excellent in corrosion resistance, conductivity, abrasion resistance, alkali degreasing resistance, and paintability. Steel plate No. 15 and no. 16 is a case where the ratio of the non-volatile resin component is less than 5 parts by mass, and the corrosion resistance, alkali degreasing resistance, and paintability deteriorated. Steel plate No. 17 and no. 18 is a case where the ratio of the nonvolatile resin component exceeds 45 parts by mass, and the conductivity and the abrasion resistance were lowered. Steel plate No. 19 and No. 20 is a case where the ratio of the carboxyl group-containing polyurethane resin is too high compared with the ethylene-unsaturated carboxylic acid copolymer in the nonvolatile resin component, and the corrosion resistance, abrasion resistance, alkali degreasing resistance, and paintability are Declined. Steel plate No. 21 is a case where the ratio of the carboxyl group-containing polyurethane resin is too low as compared with the ethylene-unsaturated carboxylic acid copolymer in the nonvolatile resin component. Similarly, the corrosion resistance, abrasion resistance, alkali degreasing resistance, coating Decreased.

(Experimental example 2)
The carboxyl group-containing polyurethane resin aqueous solution obtained above, the ethylene-acrylic acid copolymer aqueous dispersion, and the silica particles are 30 parts by mass of the nonvolatile resin component and 70 parts by mass of the silica particles, for a total of 100 parts by mass. In addition, 0 to 30 parts by mass of γ-glycidoxypropyltrimethoxysilane (KBM403 manufactured by Shin-Etsu Chemical Co., Ltd.) is further added as a silane coupling agent to 100 parts by mass of the total resin aqueous liquid. Was prepared. In addition, as a silica particle, the Nissan Chemical Snowtex XS (average particle diameter of 4-6 nm) was used, and the carboxyl group-containing polyurethane resin (PC) in the non-volatile resin component and the ethylene-unsaturated carboxylic acid copolymer (EC). ) Is a mass ratio of PC: EC = 5: 1.

This aqueous resin solution is applied to the surface of an electropure galvanized steel sheet with a drawing roll, and heated and dried at a plate temperature of 90 ° C. to form a surface-treated metal plate on which a resin film having an adhesion amount of 0.4 g / m ² is formed ( A resin-coated steel sheet was obtained. The obtained resin-coated steel sheet was evaluated for the resin film composition, corrosion resistance, conductivity, abrasion resistance, alkali degreasing resistance, paintability, and the like.

In addition, as the said electropure galvanized steel plate, the electrogalvanized steel plate which does not perform a chromate process (Zn adhesion amount 20g / m < ² >, plate thickness 0.8mm) was used.

  As is apparent from Table 2, the resin aqueous liquid used in the present invention is added to a total of 5 to 45 as a nonvolatile resin component of a carboxyl group-containing polyurethane resin aqueous liquid and an ethylene-unsaturated carboxylic acid copolymer aqueous dispersion. By containing 100 parts by mass in total of 55 parts by mass and 95 parts by mass of silica particles, and by adding a silane coupling agent in a ratio of 5 to 25 parts by mass with respect to 100 parts by mass in total, A surface-treated metal plate excellent in corrosion resistance, conductivity, abrasion resistance, alkali degreasing resistance and paintability was obtained.

(Experimental example 3)
The polyurethane resin aqueous solution obtained above, the ethylene-acrylic acid copolymer aqueous dispersion, silica particles having an average particle diameter of 4 to 100 nm (Nissan Chemical Snowtex series), and a nonvolatile resin component of 30 masses. Part and silica particles are mixed in a total of 100 parts by mass, and 15 parts by mass of γ-glycidoxypropyltrimethoxysilane (KBM403 manufactured by Shin-Etsu Chemical Co., Ltd.) is further added as a silane coupling agent with respect to the total of 100 parts by mass. A resin aqueous solution was prepared by adding a part thereof. The mixing ratio of the carboxyl group-containing polyurethane resin (PC) and the ethylene-unsaturated carboxylic acid copolymer (EC) in the nonvolatile resin component is PC: EC = 5: 1 in mass ratio.

This aqueous resin solution is applied to the surface of an electropure galvanized steel sheet with a drawing roll, and heated and dried at a plate temperature of 90 ° C. to form a surface-treated metal plate on which a resin film having an adhesion amount of 0.4 g / m ² is formed ( A resin-coated steel sheet was obtained. The obtained resin-coated steel sheet was evaluated for the resin film composition, corrosion resistance, conductivity, abrasion resistance, alkali degreasing resistance, paintability, and the like, as shown in Table 3.

In addition, as the said electropure galvanized steel plate, the electrogalvanized steel plate which does not perform a chromate process (Zn adhesion amount 20g / m < ² >, plate thickness 0.8mm) was used.

  From the results of Table 3, by using silica particles having an average particle diameter of 4 to 20 nm, a surface-treated metal plate excellent in corrosion resistance, conductivity, abrasion resistance, alkali degreasing resistance, and paintability can be obtained. I understand.

(Experimental example 4)
The polyurethane resin aqueous liquid obtained above, the ethylene-acrylic acid copolymer aqueous dispersion, silica particles (Nissan Chemical Snowtex XS, average particle diameter 4-6 nm), and 30 parts by mass of a nonvolatile resin component A total of 100 parts by mass of 70 parts by mass of silica particles was blended, and 15 parts by mass of a silane coupling agent shown in Table 4 was further added to the total of 100 parts by mass to prepare an aqueous resin liquid. The mixing ratio of the carboxyl group-containing polyurethane resin (PC) and the ethylene-unsaturated carboxylic acid copolymer (EC) in the nonvolatile resin component is PC: EC = 5: 1 in mass ratio.

This aqueous resin solution is applied to the surface of an electropure galvanized steel sheet with a drawing roll, and heated and dried at a plate temperature of 90 ° C. to form a surface-treated metal plate on which a resin film having an adhesion amount of 0.4 g / m ² is formed ( A resin-coated steel sheet was obtained. The obtained resin-coated steel sheet was evaluated for the resin film composition, corrosion resistance, conductivity, abrasion resistance, alkali degreasing resistance, paintability, and the like.

In addition, as the said electropure galvanized steel plate, the electrogalvanized steel plate which does not perform a chromate process (Zn adhesion amount 20g / m < ² >, plate thickness 0.8mm) was used.

  From the results shown in Table 4, the use of a silane coupling agent having a glycidyl group at the terminal as the silane coupling agent results in excellent stability of the aqueous resin liquid for film formation, corrosion resistance, abrasion resistance, and paintability. A surface-treated metal plate having excellent resistance was obtained.

(Experimental example 5)
The polyurethane resin aqueous solution obtained above, the ethylene-acrylic acid copolymer aqueous dispersion, and the silica particles (Nissan Chemical Snowtex XS), the nonvolatile resin component being 30 parts by mass and the silica particles being 70 parts by mass. 15 parts by mass of γ-glycidoxypropyltrimethoxysilane (KBM403 manufactured by Shin-Etsu Chemical Co., Ltd.) was further added as a silane coupling agent to the total of 100 parts by mass. An aqueous resin solution was prepared. In addition, the mixing ratio of the carboxyl group-containing polyurethane resin (PC) and the ethylene-unsaturated carboxylic acid copolymer (EC) in the nonvolatile resin component was a mass ratio of PC: EC = 5: 1.

This resin aqueous liquid is applied to the surface of an electropure galvanized steel sheet with a squeeze roll, dried by heating at a plate temperature of 90 ° C., and by changing the squeeze pressure of the roll, the adhesion amount is 0.05 to 2.0 g / m. A surface-treated metal plate (resin-coated steel plate) on which a resin film ² was formed was obtained. The obtained resin-coated steel sheet was evaluated for the resin film composition, corrosion resistance, conductivity, abrasion resistance, alkali degreasing resistance, paintability, and the like.

In addition, as the said electropure galvanized steel plate, the electrogalvanized steel plate which does not perform a chromate process (Zn adhesion amount 20g / m < ² >, plate thickness 0.8mm) was used.

From Table 5, the surface-treated metal plate excellent in corrosion resistance, conductivity, abrasion resistance, and paintability can be obtained by setting the amount of the resin film on the metal plate in the range of 0.05 to 1 g / m ^2. I was able to get it.

Claims (13)

  A surface-treated metal plate provided with a resin film obtained from a resin aqueous liquid, wherein the resin aqueous liquid comprises a carboxyl group-containing polyurethane resin aqueous liquid and an ethylene-unsaturated carboxylic acid copolymer aqueous dispersion as a nonvolatile resin component. 5 to 45 parts by mass and 55 to 95 parts by mass of silica particles having an average particle diameter of 4 to 20 nm are contained to a total of 100 parts by mass, and further silane coupling with respect to 100 parts by mass in total. And a non-volatile resin component (PU) of the polyurethane resin aqueous liquid and a non-volatile resin component (EC) of the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion. The surface-treated metal plate, wherein the blending ratio of is PU: EC = 9: 1 to 2: 1 by mass ratio. The carboxyl group-containing polyurethane resin is obtained by chain extension reaction of a urethane prepolymer with a chain extender,
As the polyisocyanate component constituting the urethane prepolymer, at least one selected from the group consisting of tolylene diisocyanate, diphenylmethane diisocyanate and dicyclohexylmethane diisocyanate is used,
2. The surface according to claim 1, wherein all of 1,4-cyclohexanedimethanol, polyether polyol, and polyol having a carboxyl group are used as a polyol component constituting the urethane prepolymer. Processing metal plate.   The surface-treated metal sheet according to claim 1 or 2, wherein ethylenediamine or hydrazine is used as the chain extender.   The surface ratio according to claim 1, wherein a mass ratio of the 1,4-cyclohexanedimethanol and the polyether polyol is 1,4-cyclohexanedimethanol: polyether polyol = 1: 1 to 1:19. Processing metal plate.   The surface-treated metal plate according to claim 1, wherein the polyether polyol is polyoxypropylene glycol or polytetramethylene ether glycol.   The surface-treated metal plate according to any one of claims 1 to 5, wherein the carboxyl group-containing polyurethane resin has an acid value of 10 to 60 mgKOH / g.   In addition to the ethylene-unsaturated carboxylic acid copolymer, the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion may have an amount of 0.2 to 1 mol of the carboxyl group of the ethylene-unsaturated carboxylic acid copolymer. An amine having a boiling point of 100 ° C. or less corresponding to 0.8 mol and a monovalent metal compound corresponding to 0.02 to 0.4 mol with respect to 1 mol of the carboxyl group of the ethylene-unsaturated carboxylic acid copolymer The surface-treated metal plate according to any one of claims 1 to 6.   The surface-treated metal plate according to any one of claims 1 to 7, wherein the ethylene-unsaturated carboxylic acid copolymer is obtained by copolymerizing an unsaturated carboxylic acid component in an amount of 10 to 40% by mass.   The surface-treated metal sheet according to any one of claims 1 to 8, wherein the amine having a boiling point of 100 ° C or lower is triethylamine.   The ethylene-unsaturated carboxylic acid copolymer aqueous dispersion further reacts with a carboxyl group when the nonvolatile resin component (EC) of the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion is 100 parts by mass. The surface-treated metal plate according to any one of claims 1 to 9, wherein the surface-treated metal plate contains a crosslinking agent having two or more functional groups capable of being used in a ratio of 1 to 20 parts by mass.   The surface-treated metal sheet according to any one of claims 1 to 10, wherein the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion is substantially free of amine and ammonia having a boiling point exceeding 100 ° C. The surface-treated metal plate according to claim 1, wherein the silane coupling agent is a silane coupling agent represented by the following chemical formula (1).

(In the chemical formula (1), R ¹ : glycidoxy group, R ² , R ³ : lower alkoxy group, R ⁴ : lower alkoxy group or lower alkyl group, X: lower alkylene group) The adhesion amount of the resin film is surface-treated metal sheet according to any one of claims 1 to 12 is 0.05 to 1 g / m ^2.