TWI569956B - Water layer 2 coated metal plate - Google Patents

Description

Water system 2 layer coated metal sheet

The present invention relates to a water-based two-layer coating-treated metal sheet which is excellent in electrical conductivity for use in electromagnetic wave countermeasures for household electrical appliances and the like.

In recent years, in the field of home electric appliances, as a countermeasure against electromagnetic waves for preventing leakage of electromagnetic waves generated by products, the demand for metal materials having good electrical conductivity has become more intense. In the coated steel sheet, a conductive pigment such as Ni powder is added to the coating material to impart conductivity to the coating film. However, in a thin film having a thickness of about 1 μm as in the case of a special steel sheet, it is difficult to add a conductive pigment to the coating film. In the film.

As such a special processed film, a technique of forming a two-layer structure to ensure corrosion resistance or adhesion is known. For example, Patent Document 1 discloses that a mixed film of a film forming property of lithium niobate and a non-film forming colloidal ceria is formed on the first layer (metal plate side), and an organic resin is formed in the second layer. The technology of the main component of the membrane. However, since lithium niobate is hygroscopic, water or oxygen which is passed through the second layer oxidizes the galvanized layer to cause blackening, and the corrosion resistance is also lowered. In particular, in an alkaline environment in which alkali degreasing occurs, lithium niobate precipitates and corrosion resistance is obtained. Or the problem that the adhesion to the galvanized layer is greatly deteriorated.

Further, Patent Document 2 discloses an organic coated steel sheet having a layer containing a phosphate compound, oxide fine particles (colloidal cerium oxide) and a metal compound as a first layer, and an organic resin film as a second layer. There is a problem of deterioration of corrosion resistance or alkali resistance due to precipitation of a phosphate-based compound in a corrosive environment, or discoloration of a film due to a change in the valence of a metal element. Patent Document 3 discloses a surface treatment in which a layer containing Si and P and Al and an organic resin is coated as a first layer and reacted with a galvanized layer, followed by water washing, and an organic resin layer is coated thereon as a second layer. Galvanized steel plate. In this technique, since the unreacted component is removed by washing with water, the adhesion of the film is improved, but the corrosion resistance or alkali degreasing property of the crotch portion is not sufficient. Further, in order to solve the problem of the technique described in the above patent documents, it is necessary to increase the thickness of the second layer to about 1 μm, and thus it is not possible to obtain good conductivity.

On the other hand, a surface-treated metal sheet of a one-layer type in which conductivity is considered is also known. For example, Patent Document 4 discloses a surface-treated metal sheet having a resin film formed of an aqueous resin liquid in which a colloidal cerium oxide and a decane coupling agent are added to two kinds of organic resins, but Since the ratio of the components is low, the barrier property against water or oxygen is insufficient, and the corrosion resistance or blackening resistance is not sufficient.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-26886

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2001-11645

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2005-26436

[Patent Document 4] Japanese Laid-Open Patent Publication No. 2006-269018

The present invention is a surface-treated metal sheet which has good electrical conductivity and has excellent adhesion, blackening resistance, alkali degreasing resistance, and sustained corrosion resistance (especially crotch) in consideration of the above various circumstances. The provision of specialized steel sheets has been proposed as a problem.

The present invention which solves the above-mentioned problems is a water-based two-layer coated metal sheet which is a metal sheet in which two thin films are laminated on at least one surface of a metal sheet, and is characterized in that it has a first water-based composition. An inorganic-rich layer having a thickness of 0.01 to 0.1 μm formed thereon, and an organic layer having a thickness of 0.2 to 0.5 μm formed of a second aqueous component containing an organic resin on the inorganic-rich layer, and an inorganic substance-rich layer The total thickness of the layer and the organic-rich layer is 0.25-0.6 μm, and the first water-based composition contains 60 to 80 parts by mass of colloidal cerium oxide having an average particle diameter of 4 to 15 nm and a polyaminocarboxylic acid having a carboxyl group. 20 to 40 parts by mass of the ester resin, and 7.5 to 20 parts by mass of the decane having a glycidoxy group at the terminal with respect to 100 parts by mass of the total of the colloidal cerium oxide and the carboxyl group-containing urethane resin Coupling agent, and does not contain lithium-based inorganic compounds, phosphoric acid compounds and lithium Other than the metal components.

It is preferable that 50% by mass or more of the colloidal cerium oxide in the first water-based composition has an average particle diameter of 4 to 6 nm. Moreover, the water vapor permeability of the film obtained from the organic resin contained in the second water-based composition is preferably 100 g/m ² /day or less, which is also a preferred embodiment of the present invention.

According to the present invention, it is possible to provide good electrical conductivity (less than 0.5 Ω under the surface resistance meter/2 probe method) for electromagnetic wave countermeasures for home electric appliances and the like, and it is a film and has excellent adhesion and black resistance. Water-based 2-layer coated metal sheet with denaturation, alkali-resistant degreasing and long-term corrosion resistance.

[Fig. 1] is a schematic view showing the structure of a metal plate of the present invention.

[Fig. 2] A graph showing the relationship between the conductivity and the film thickness of the treatment film.

[Fig. 3] is a schematic view showing a method of measuring the surface resistance by a surface resistance measuring device.

[Fig. 4] is a schematic view showing a friction coefficient measuring device.

The inventors of the present invention have studied to solve the above problems. As a result, it has been found that the anti-corrosion property is ensured by an ultra-thin film (rich inorganic layer) rich in inorganic colloidal cerium oxide, and the barrier property of the organic resin as a main component (suppressing the dissolution of cerium oxide, etc.) is high. The organic-rich layer and the total film thickness of both of them are set to 0.6 μm or less, whereby good conductivity can be obtained, and the present invention has been completed. Hereinafter, the present invention will be described in detail.

[Configuration of water-based 2-layer coated metal sheet]

In the water-based two-layer coating-treated metal sheet of the present invention, for example, as shown in Fig. 1, a galvanized layer is formed on the steel sheet main body, and an inorganic layer rich as the first layer is formed from the first water-based composition. The thickness of 0.01 to 0.1 μm further increases the thickness of the organic layer as the second layer from 0.2 to 0.5 μm from the second water-based composition. The metal plate is not particularly limited. For example, in addition to the galvanized steel sheet shown in Fig. 1, a galvanized steel sheet, an aluminum plate, an aluminum alloy plate, a titanium plate or the like can be used. The best is galvanized steel. From the viewpoint of environmental problems, it is preferred not to perform chromate treatment.

[rich inorganic layer] [colloidal cerium oxide]

In the present invention, it is necessary to include colloidal cerium oxide having an average particle diameter of 4 to 15 nm in the inorganic-rich layer. The colloidal cerium oxide has a high concentration at the interface with the galvanized layer, and is enhanced by the interaction of sterol groups (-SiOH) carried by cerium oxide (SiO ₂ ) with a galvanized surface (Zn-OH). The effect of the interface between the inorganic-rich layer and the galvanized surface. In addition, colloidal cerium oxide also has an effect of improving corrosion resistance. The colloidal ceria in the film is eluted when the pH rises in a corrosive environment to form a mixed corrosion product of zinc hydrate, and the mixed corrosion product exerts a barrier effect and improves corrosion resistance. In the present invention, since the organic-rich layer described later functions to slow the dissolution rate of the colloidal cerium oxide, it is possible to ensure excellent corrosion resistance (especially crotch), and also exhibit blackening resistance or resistance. Alkali degreasing.

In order to more effectively exert the effect of the colloidal cerium oxide, the average particle diameter of the cerium oxide used is set to 4 to 15 nm. The smaller the average particle diameter of cerium oxide, the more the corrosion resistance of the inorganic-rich layer is enhanced. It is presumed that the density of the inorganic-rich layer is further densified, and the interface adhesion to the galvanized layer is further improved, thereby further improving the corrosion resistance. From such a viewpoint, the particle size of the cerium oxide particles is preferably as small as possible. However, if the particles are extremely minute, the above effects are saturated. Therefore, the lower limit of the particle diameter is 4 nm. For the above-mentioned range of cerium oxide, for example, SNOWTEX (registered trademark) 30 (average particle diameter: 10 to 15 nm) and SNOWTEX (registered trademark) S (8 to 11 nm) manufactured by Nissan Chemical Industries Co., Ltd. can be used. SNOWTEX (registered trademark) XS (4~6nm), SNOWTEX (registered trademark) N (10~15nm), SNOWTEX (registered trademark) NXS (4~6nm), SNOWTEX (registered trademark) C (10~15nm), SNOWTEX (registered trademark) CXS (4~6nm), etc. In addition, the average particle size of the cerium oxide is preferably a nominal value of the catalogue, or a Sears method (4-6 nm) or a BET method (4~). 20 nm) measurement method.

As described above, the smaller the particle diameter of the cerium oxide, the more the corrosion resistance of the inorganic-rich layer is enhanced. It is presumed that the reason is that by increasing the surface area of the cerium oxide and increasing the degree of activity, it is advantageous for the elution of the cerium oxide or the formation of the mixed corrosion product in a corrosive environment. From this point of view, it is preferable that 50% by mass or more of the colloidal cerium oxide contained in the inorganic-rich layer is an average particle diameter of 4 to 6 nm. Further, if the colloidal cerium oxide having an average particle diameter of 4 to 6 nm contained in the inorganic-rich layer is gradually increased, there is no problem in the performance of the obtained water-based two-layer coated metal sheet, but in the first In the case where the carboxyl group-containing polyurethane resin in the aqueous composition is neutralized using an amine or the like, it is possible that the cerium oxide reacts with the amine to cause the equilibrium of the charge of the colloidal cerium oxide to disintegrate. 1 The viscosity of the water-based composition rises to cause gelation. Therefore, when it is necessary to increase the pot life of the first water-based composition, the above-mentioned "ST-30" (10 to 15 nm) or "ST-S" (8 to 11 nm) is used as a part of the colloidal cerium oxide. Just fine. However, the total of these is preferably 100% by mass of the colloidal cerium oxide, and is less than 50% by mass.

[Carboxyl group-containing polyurethane resin]

The inorganic-rich layer of the present invention contains a carboxyl group-containing polyurethane resin. This is due to the fact that only the colloidal cerium oxide is not formed. As the carboxyl group-containing polyurethane resin, a carboxyl group-containing polyurethane resin described in JP-A-2006-43913 can be suitably used. The carboxyl group-containing polyurethane resin must use a polyol having a carboxyl group. An aqueous dispersion of the synthesized polyurethane resin. As the raw material, a polyol component of a polyol having a carboxyl group such as 1,4-cyclohexanedimethanol, polytetramethylene glycol having an average molecular weight of about 400 to 4,000, or dimethylolpropionic acid can be used. An isocyanate component such as phenyl diisocyanate, diphenylmethane diisocyanate or dicyclohexane methane diisocyanate. The chain extender is preferably a polyamine such as ethylenediamine.

The aqueous solution of the carboxyl group-containing polyurethane resin used in the present invention can be produced by a known method, for example, the carboxyl group of the carboxyl group-containing urethane prepolymer is neutralized with an alkali, and the emulsion is dispersed. A method of performing a chain extension reaction in an aqueous medium, a method of performing a chain extension reaction by emulsifying and dispersing a carboxyl group-containing polyurethane resin in the presence of an emulsifier with high shear force.

First, a lower molecular weight carboxyl group-containing isocyanate-terminated urethane prepolymer is produced by using the above-mentioned polyisocyanate and the above-mentioned polyol so that the isocyanate group becomes excessive in the NCO/OH ratio. The temperature at which the urethane prepolymer is synthesized is not particularly limited, but it can be synthesized at a temperature of 50 to 200 °C.

After completion of the reaction of the urethane prepolymer, the obtained carboxyl group-containing isocyanate-terminated urethane prepolymer is emulsified and dispersed in water by neutralization with a base. The neutralizing agent is not particularly limited, but is preferably ammonia; a tertiary amine such as triethylamine or triethanolamine. More preferably, triethylamine is used.

After emulsifying and dispersing the carboxyl group-containing isocyanate-terminated urethane prepolymer, a chain extender such as polyamine can be used in water. The chain extends the reaction. Further, the chain extension reaction can be suitably carried out before emulsifying and dispersing, simultaneously with emulsifying and dispersing, or after emulsifying and dispersing depending on the reactivity of the chain extender to be used.

In addition, the carboxyl group-containing polyurethane resin is in a state after being neutralized in the first water-based composition, and after the formation of the inorganic-rich layer, since the amine used for neutralization volatilizes, it acts as a carboxyl group. The polyurethane resin is present.

[decane coupling agent]

In the first aqueous component used in the present invention, a decane coupling agent containing a glycidoxy group at the terminal can be blended. The decane coupling agent further enhances the adhesion between the surface of the metal sheet and the inorganic-rich layer. Further, the decane coupling agent has a functional group in which an inorganic component and an organic component are bonded, and is more reactive than other decane coupling agents, and therefore, a bond between a colloidal cerium oxide and a urethane resin The force is strengthened, and it is effective in improving the performance such as corrosion resistance or alkali degreasing.

The decane coupling agent having a glycidoxy group at the terminal is γ-glycidoxypropyltrimethoxydecane, γ-glycidoxypropylmethyldiethoxydecane, or the like.

[First water system composition]

In forming the inorganic-rich layer, a first aqueous composition in which a colloidal ceria, a carboxyl group-containing polyurethane resin, or a decane coupling agent is mixed is used. The first aqueous component does not contain a lithium-based inorganic compound or phosphorus. A compound and a metal component other than lithium. For example, lithium lithium niobate used in Patent Document 1 is used as the lithium-based inorganic compound, but lithium niobate may cause blackening (stain, discoloration), which is not preferable. Further, in Patent Document 2 or 3, the surface of the plating layer is etched by using a phosphoric acid compound and a metal component to improve the adhesion between the first layer and the plating layer, but the first layer is not formed after the formation of the first layer. In the case of the water washing treatment, the metal compound or the phosphoric acid component remaining in a corrosive environment is eluted, causing deterioration in performance such as corrosion resistance or alkali degreasing property, and causing blackening or discoloration from the metal component. Therefore, in the present invention, a lithium-based inorganic compound, a phosphorus-based compound, and a metal component other than lithium are not added to the first aqueous component. However, as the colloidal cerium oxide system, colloidal cerium oxide which utilizes sodium stabilization as in the above-mentioned SNOWTEX (registered trademark) XS can be used, that is, it can also contain a metal component, so strictly speaking, it means a carboxyl group. The lithium-based inorganic compound, the phosphoric acid compound, and the metal component other than lithium are not added to the polyurethane resin and the decane coupling agent.

The first aqueous system composition can be obtained by making the colloidal ceria in the inorganic-rich layer 60 to 80 parts by mass (preferably 65 to 75 parts by mass) and the carboxyl group-containing polyurethane resin 20~ 40 parts by mass (preferably 25 to 35 parts by mass) and a decane coupling agent having a glycidoxy group at the end are 7.5 to 20 parts by mass to form colloidal cerium oxide and a carboxyl group-containing polyurethane The aqueous liquid of the resin is mixed with the above decane coupling agent to prepare. In addition, in this paragraph, the total amount of the two components of the colloidal cerium oxide and the carboxyl group-containing polyurethane resin is 100 parts by mass, that is, the amount of the decane coupling agent. Colloidal II The blending amount of the cerium oxide and the carboxyl group-containing polyurethane resin is 100 parts by mass.

If the colloidal cerium oxide is too small, the desired corrosion resistance cannot be ensured. If the carboxyl group-containing polyurethane resin is too small, the formation of the film may become uneven. If the amount of the decane coupling agent is too small, the adhesion of the surface of the metal plate to the inorganic-rich layer may be insufficient, and the reactivity of the colloidal cerium oxide and the polyurethane resin may also be lowered, thereby preventing corrosion. Properties, tape peeling resistance, alkali degreasing resistance, blackening resistance, and the like are deteriorated. On the other hand, if the amount of the decane coupling agent is too large, the stability of the first water-based composition will be lowered with time, which is also disadvantageous in terms of cost.

[Thickness of rich inorganic layer]

The thickness of the inorganic layer rich in the first layer is set to 0.01 to 0.1 μm. The inorganic-rich layer of the present invention can confirm the adhesion improving effect with the galvanized layer even in the case of a film having a thickness of 0.01 μm. However, when it is thinner than 0.01 μm, the formation of the film may become uneven, and the absolute amount of the cerium oxide contributing to the adhesion may be insufficient to lower the adhesion. On the other hand, when the thickness of the inorganic-rich layer exceeds 0.1 μm, aggregation failure occurs in the inside of the film, and as a result, the film residual ratio at the time of performing the tape peeling test is largely lowered. In addition, in order to ensure conductivity, it is necessary to suppress the total film thickness to 0.6 μm or less (described later). However, if the thickness of the inorganic-rich layer exceeds 0.1 μm, the organic layer must be formed with respect to the full film thickness (second layer). The film thickness is reduced, and the corrosion resistance, blackening resistance, and alkali degreasing resistance are lowered due to a decrease in barrier properties. The film thickness of the inorganic-rich layer is preferably 0.02~ 0.08 μm, more preferably 0.03 to 0.06 μm.

[Formation of rich inorganic layer]

The inorganic-rich layer system is applied to a metal plate by using a well-known coating method, that is, a bar coating method, a roll coating method, a spray coating method, a curtain coating method, or the like. One side or both sides of the surface can be heated and dried. The heating temperature is such that the water will volatilize.

[Thickness of the organic layer]

Next, the rich layer of the second layer will be described. The organic-rich layer serves as a function to ensure barrier properties, slow down the dissolution rate of cerium oxide, and maintain corrosion resistance. The inventors investigated the relationship between the total film thickness of the inorganic-rich layer and the organic-rich layer and the conductivity, and obtained the results shown in Fig. 2 . This is a result obtained by fixing the thickness of the inorganic-rich layer to 0.06 μm and changing the film thickness of the organic-rich layer. As a countermeasure against electromagnetic wave countermeasures, since the conductivity when measured by the 2-probe method using a surface resistance meter is less than 0.5 Ω, the total film thickness must be 0.6 μm or less.

Therefore, the organic-rich layer is set to 0.2 to 0.5 μm. It is preferably 0.3 to 0.5 μm, more preferably 0.35 to 0.45 μm. When the organic layer is thinner than 0.2 μm, the barrier property is lowered, the corrosion resistance or the alkali degreasing property is lowered, and the lubricity is lowered, which causes problems in workability and the like. On the other hand, if the film thickness of the organic-rich layer exceeds 0.5 μm and becomes thick, the conductivity is remarkably deteriorated.

[organic resin rich in organic layers]

The organic-rich layer is formed of a second water-based composition containing an organic resin. The organic resin is not particularly limited, but is preferably a resin which can produce a film having a water vapor permeability of 100 g/m ² /day or less. In addition, the water vapor permeability was applied to a copying paper by a bar coater to apply an organic resin or a second water-based composition so that the film thickness after drying became 18 μm, and dried at 105 ° C for 2 minutes. The film was allowed to stand for one night and the latter was used as a sample, and was measured in accordance with the cup method of JIS Z0208.

In the case of a resin which can produce a film having a water vapor permeability of 100 g/m ² /day or less, the barrier property of the organic layer can be ensured, and the dissolution rate of the colloidal cerium oxide can be further slowed down. When an organic resin having a film having a water vapor transmission degree of more than 100 g/m ² /day is used, when a coating effect of corrosion resistance or the like is desired, and more than 30% by mass of colloidal cerium oxide is added to the second aqueous component, a result is caused. The water vapor transmission degree of the organic-rich layer is increased to 5,000 g/m ² /day or more, and the corrosion resistance and the like are greatly deteriorated, which is not preferable. More preferably, the water vapor transmission rate is 50 g/m ² /day or less.

In addition, for example, in the second water-based composition containing an organic resin having a water vapor permeability of 50 g/m ² /day, 20% by mass (as a solid content of the second aqueous component) is added as a colloidal cerium oxide ( When the average particle diameter is 4 to 6 nm, the water vapor transmission rate of the organic-rich layer is about 1500 g/m ² /day, but the effect of improving corrosion resistance and the like can be confirmed. Further, even if the crosslinking agent described later or the above-described decane coupling agent is added, the water vapor permeability of the organic-rich layer tends to decrease, and corrosion resistance, alkali degreasing resistance, blackening resistance, and the like can be improved.

The organic resin preferably satisfies the above water vapor permeability, but is preferably an ethylene-unsaturated carboxylic acid copolymer. As the ethylene-unsaturated carboxylic acid copolymer, those described in JP-A-2005-246953 or JP-A-2006-43913 can be used.

Examples of the unsaturated carboxylic acid system include (meth)acrylic acid, crotonic acid, isocrotonic acid, maleic acid, fumaric acid, itaconic acid, and the like, and one or more of these may be known as ethylene. The copolymer is obtained by polymerization by a high temperature high pressure polymerization method or the like.

The copolymerization ratio of the unsaturated carboxylic acid to ethylene is preferably 10 to 40% by mass in the case where the total amount of the monomers is 100% by mass. When the amount of the unsaturated carboxylic acid is less than 10% by mass, the base point of the intermolecular association of the ion cluster or the carboxyl group at the crosslinking point of the crosslinking agent is small, so that the film strength effect does not occur and the tape peeling resistance may occur. Sexual or alkali-resistant degreasing property may be insufficient, and the emulsion stability of the emulsion composition may be poor, which is not preferable. The lower limit of the more preferable unsaturated carboxylic acid is 15% by mass. On the other hand, when the amount of the unsaturated carboxylic acid exceeds 40% by mass, the corrosion resistance or the water resistance of the organic-rich layer is poor, and the alkali-resistant degreasing property is still lowered, which is not preferable. A more preferable upper limit is 25% by mass.

Since the ethylene-unsaturated carboxylic acid copolymer has a carboxyl group, it is emulsifiable (aqueous dispersion) by neutralization with an organic base or a metal ion. In the present invention, an amine is preferably used as the organic base, and any of the above-mentioned amines can be used, and particularly preferably triethylamine. Further, it is preferred that the monovalent metal ion is also used together with the amine. Amine It is preferably 0.2 to 0.8 mol (20 to 80 mol%) based on the carboxyl group 1 molar in the ethylene-unsaturated carboxylic acid copolymer. It is understood that the amount of the monovalent metal ion affects the water vapor permeability. When the amount of the monovalent metal compound is increased, the affinity between the resin and water increases, and the water vapor permeability increases. The ratio is 0.02 to 0.2 mol (2 to 20 mol%) based on the carboxyl group 1 molar in the ethylene-unsaturated carboxylic acid copolymer. Further, since the amount of excess alkali is a cause of deterioration of corrosion resistance, the total amount of the amine and the metal ion used is 0.30 with respect to the carboxyl group 1 mole in the ethylene-unsaturated carboxylic acid copolymer. The 1.0 molar range is better. Further, the metal compound for imparting a monovalent metal ion is preferably NaOH, KOH, LiOH or the like, and the NaOH system has the best performance.

[crosslinking agent]

An ethylene-unsaturated carboxylic acid copolymer having a carboxyl group neutralized with an amine and a monovalent metal ion forms an intermolecular association (ionic polymerization) of an ion cluster to form an excellent corrosion resistance/resistance to tape. Rich in machine layers. However, in order to form a stronger film, it is preferred to crosslink the polymers with each other by chemical bonding using a reaction between functional groups. The crosslinking agent is preferably a crosslinking agent containing a glycidyl group or a crosslinking agent containing aziridinyl.

Examples of the crosslinking group containing a propylene group include sorbitol polyepoxypropyl ether, (poly)glycerol polyepoxypropyl ether, pentaerythritol polyepoxypropyl ether, and trimethylolpropane polycyclic ring. Polyepoxypropyl ethers such as oxypropyl ether, neopentyl glycol diepoxypropyl ether, (poly)ethylene glycol diepoxypropyl ether A crosslinking agent containing a propylene group such as a polyepoxypropylamine or the like.

As the crosslinking agent of the aziridine group, 4,4'-bis(ethyleneiminecarbonylamino)diphenylmethane, N,N'-hexamethylene-1,6-bis ( 2-functional nitrogen such as 1-aziridinecarboxamide, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarbamidine) or toluidine diaziridine carbenamide Propionate compound; tri-1-aziridine phosphine oxide, ginseng [1-(2-methyl)aziridine]phosphine oxide, trimethylolpropane ginseng (β-aziridine propionic acid) Trifunctional or higher aziridines such as esters, ginseng-2,4,6-(1-aziridine)-1,3,5-triazine, tetramethylpropane tetraaziridine propionate a compound or a derivative thereof.

[wax]

Since the water-based two-layer coating-treated metal sheet of the present invention is processed by using the organic-rich layer as the outermost surface, it is preferable to contain the wax in the organic-rich layer in order to improve the workability. Industrially preferred are spherical polyethylene wax, polypropylene wax, denatured wax, copolymerized wax with ethylene or propylene, vinyl copolymer wax, oxides such as these, and derivatives imparted to carboxyl groups. Acid-based paraffin wax, palm wax, and the like. The wax-based spherical polyethylene wax is most suitable, and for example, "DIJET E-17" (manufactured by Mutual Chemical Co., Ltd.), "KUE-1", "KUE-5", "KUE-8" (Sanyo) can be suitably used. "W-100", "W-200", "W-300", "W-400", "W-500", "W-" of the "CHEMIPEARL" series (manufactured by Mitsui Chemicals Co., Ltd.) 640", "W-700", etc., or "ELEPON E-20" (made by Rihua Chemical Co., Ltd.) and other commercial products.

[Second water system composition]

Preferably, the second aqueous component contains the above-mentioned colloidal cerium oxide having an average particle diameter of 4 to 6 nm. However, if it is too much, the water vapor transmission rate will be inferior as described above. Therefore, it is preferable that the second aqueous component is blended with an ethylene-unsaturated carboxylic acid copolymer (solid content) of 57 to 83% by mass and a colloidal cerium oxide having an average particle diameter of 4 to 6 nm of 10 to 30% by mass. The aziridine-containing crosslinking agent is 5 to 8 mass%, and the spherical polyethylene wax is 2 to 5 mass%. In addition, the total of these four components is 100% by mass.

It is preferred to emulsifie the components together or separately as needed, and to mix them as a water dispersion. The method of applying the second aqueous component to the metal plate on which the inorganic-rich layer is formed is not particularly limited, and a bar coating method, a roll coating method, a spray coating method, a curtain coating method, or the like can be employed. After coating, it is preferably dried by heating at about 80 to 130 °C.

The present invention claims the benefit of priority from Japanese Patent Application No. 2014-256631, filed on Dec. The entire contents of the specification of Japanese Patent Application No. 2014-256631, filed on Dec.

[Examples]

In the following, the present invention will be described in detail by way of examples. However, the following examples are not intended to limit the scope of the invention. Hereinafter, "parts" means "mass parts" and "%" means "mass%". Also, implementation The evaluation methods used in the examples are as follows.

[evaluation method]

(1) Corrosion resistance 1: salt spray test (SST plate, SST cross score)

For the test material to seal the back surface and the edge, the person who made the flat state and the cross-scratch with the cutting blade, according to JIS Z2371, performed a 5% salt spray test at 35 ° C to measure the white rust generation. The rate reaches 5% (area).

Evaluation of SST Tablet

◎: 240 hours or more

○: 168 hours or more, less than 240 hours

Δ: 120 hours or more, less than 168 hours

×: less than 120 hours

Evaluation of SST Cross Scoring

◎: 120 hours or more

○: 96 hours or more, less than 120 hours

Δ: 72 hours or more, less than 96 hours

×: less than 72 hours

(2) Corrosion resistance 2: salt spray cycle test (SST cycle)

For the test material (flat plate) after edge sealing, follow the implementation The salt spray test of JIS Z2371 measures the number of cycles in which the white rust generation rate reaches 5%. The 1 cycle system set the salt water spray to 8 hours (35 ° C), and the salt water spray suspension to 16 hours (35 ° C).

Evaluation of the SST cycle

◎: 10 cycles or more

○: 7 cycles or more, less than 10 cycles

Δ: 5 cycles or more, less than 7 cycles

×: less than 5 cycles

(3) Corrosion resistance 3: Neutral salt water spray cycle test (JASO)

For the test material (plate) after edge sealing, a neutral salt spray cycle test was carried out in accordance with JIS H8502, and the number of cycles in which the white rust generation rate reached 5% was measured. In the first cycle, the salt water spray was set to 2 hours, the drying (60 ° C, humidity 30% or more) was set to 4 hours, and the wetness (50 ° C, humidity 95% or more) was set to 2 hours.

JASO assessment

◎: 21 cycles or more

○: 15 cycles or more, less than 21 cycles

Δ: 9 cycles or more, less than 15 cycles

×: less than 9 cycles

(4) Conductivity

The surface resistance value of each test material used was a surface resistance measuring device (Loresta EP; DIA INSTRUMENTS (now Mitsubishi Chemical Analytech)), and there was no copper plate and the terminal was directly contacted (2 probe AP probe type A) to 2 terminals. 2 probe method for measurement. The needle spacing is 10mm, the spring pressure is set to 240g/root, and the tip diameter is 2mm. . A schematic view of the surface resistance measuring device is shown in Fig. 3.

Conductivity assessment

◎: Less than 0.05Ω

○: 0.05 Ω or more and less than 0.50 Ω

Δ: 0.50 Ω or more, less than 1.00 Ω

×: 1.00 Ω or more

(5) Tape peeling resistance

Adhesive tape (FILAMENT TAPE No. 9510, rubber adhesive) manufactured by Sliontec Co., Ltd. was attached to the test material, and stored in a constant temperature and humidity test apparatus at 40 ° C and 98% humidity for 120 hours, in accordance with JIS K5400. The tape peeling test was carried out, and the residual ratio (area) of the film was measured.

Evaluation of film residual rate

◎: 95% or more

○: 90% or more and less than 95%

Δ: 80% or more, less than 90%

×: less than 80%

(6) Resistance to blackening

After the test material was stored in a constant temperature and humidity test apparatus at 50 ° C and a humidity of 98% or more for 168 hours, the appearance (black and stain) was observed before and after the test, and the color difference (ΔE) was calculated by measuring the change in color tone.

Appearance evaluation before and after the test

◎: no change before and after the test

○: slightly dark, no stains

Δ: a little black, stained

×: There is blackening/staining

Evaluation of color difference (ΔE)

◎: ΔE is less than 1

○: ΔE is 1 or more and less than 2

Δ: ΔE is 2 or more, less than 3

×: ΔE is 3 or more

(7) Lubricity (dynamic friction coefficient)

The coefficient of dynamic friction of each test material was measured using the friction coefficient measuring device shown in Fig. 4. The material for testing is 40mm×300mm, the pressing force is 4.5MPa, and the drawing speed is 300mm/min. It is carried out without oiling. In addition, the material of the flat mold is set to SKD11. In addition, the dynamic friction coefficient μ is F/2P.

Lubricity assessment

◎: μ = less than 0.09

○: μ=0.09 or more, less than 0.15

Δ: μ = 0.15 or more, less than 0.20

×: μ = 0.20 or more

(8) Alkali-resistant degreasing

The test material was immersed in an alkali degreasing agent (CL-N364S) manufactured by NIHON PARKERIZING Co., Ltd. at 20 g/liter (liquid temperature: 65 ° C) for 2 minutes, and then pulled up, washed with water and dried, and the back surface and the edge were sealed, and the JIS was sealed in accordance with JIS. The brine spray cycle test of Z2371 (SST cycle plate) was carried out, and the number of cycles in which the white rust generation rate became 5% was measured. 1 cycle was set to 5% saline spray for 8 hours (35 ° C), and saline spray was stopped for 16 hours (35 ° C).

◎: 7 cycles or more

○: 5 cycles or more, less than 7 cycles

Δ: 3 cycles or more, less than 5 cycles

×: less than 3 cycles

Synthesis Example 1

Synthesis of aqueous dispersion of carboxyl group-containing polyurethane resin

In a synthesis apparatus equipped with a stirrer, a thermometer, and a temperature controller, 60 parts of polytetramethylene ether glycol (average molecular weight: 1000; manufactured by Hodogaya Chemical Co., Ltd.) as a polyol component, 1,4-cyclohexane 14 parts of alkyl dimethanol and 20 parts of dimethylolpropionic acid were further added, and 30 parts of N-methylpyrrolidone as a reaction solvent was further added. 104 parts of methyl phenyl diisocyanate (TDI) as an isocyanate component was charged, and the temperature was raised to 80 to 85 ° C, and the reaction was carried out for 5 hours. The obtained prepolymer had an NCO content of 8.9%. Further, 16 parts of triethylamine was added for neutralization, and a mixed aqueous solution of 16 parts of ethylenediamine and 480 parts of water was added, and the chain extension reaction was carried out by emulsification at 50 ° C for 4 hours to obtain a polyurethane resin. Aqueous dispersion (non-volatile resin component 29.1%, acid value 41.4). This was taken as the resin A. Further, the water vapor permeability of the resin A was 1,500 g/m ² /day.

Synthesis Example 2

Synthesis of aqueous dispersion of ethylene-unsaturated carboxylic acid copolymer (1)

In an autoclave having an emulsification apparatus equipped with a stirrer, a thermometer, and a temperature controller, 626 parts of water and 160 parts of an ethylene-acrylic acid copolymer (acrylic acid unit: 20% by mass, melt index: 300) were added, and ethylene was added thereto. The carboxyl group of the acrylic copolymer is 40 mol% of triethylamine and 15 mol% of sodium hydroxide, and is stirred at a high speed of 150 ° C and 5 Pa, and cooled to 40 ° C to obtain ethylene-acrylic acid copolymerization. The emulsion of the substance. Here, 5 parts of 4,4'-bis(ethyleneiminecarbonylamino)diphenylmethane (manufactured by Nippon Shokubai Co., Ltd.) is added in an amount of 5 parts based on 100 parts by weight of the solid component of the ethylene-acrylic acid copolymer. CHEMITITE (registered trademark) DZ-22E") is used as resin B. The resin B had a water vapor permeability of 50 g/m ² /day.

Synthesis Examples 3 and 4

Synthesis of an aqueous dispersion of ethylene-unsaturated carboxylic acid copolymer (2 and 3)

In the above-mentioned Synthesis Example 2, the resin C was obtained in the same manner as in the above Synthesis Example 2 except that the amount of sodium hydroxide added was 20 mol% based on the carboxyl group 1 mol of the ethylene-acrylic acid copolymer. Further, as the resin D, the amount of sodium hydroxide added was set to 30 mol%. The water vapor permeability of the resin C was 100 g/m ² /day, and the water vapor permeability of the resin D was 1000 g/m ² /day.

Experimental example 1

In the case of 55 to 85 parts of "SNOWTEX" (registered trademark) XS manufactured by Nissan Chemical Industries Co., Ltd., which is prepared by the synthesis of the first embodiment, it is added in the range of 15 to 45 parts. A carboxyl group-containing polyurethane dispersion aqueous resin (Resin A) is added with 15 parts by mass of a decane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., KBM403 (containing epoxy propylene oxide), based on 100 parts by mass of the total solid content. The base water-based composition was prepared by the base decane coupling agent)).

As the metal plate, an electrogalvanized steel sheet (zinc adhesion amount: 20 g/m ² , thickness: 0.8 mm) was used, and the first water-based composition was applied on one surface thereof by a bar coater, and dried at a plate temperature of 90° C. An inorganic-rich layer having a film thickness of 0.06 μm was formed. Further, the film thickness was calculated by quantitatively measuring the Si element of the colloidal cerium oxide (SiO ₂ ) in the film by a fluorescent X-ray analyzer. At this time, the specific gravity of SiO ₂ was set to 2.2, and the specific gravity of the resin was made into 1.

30 parts of the colloidal ceria having an average particle diameter of 4 to 6 nm and 7.5 parts of the epoxy group-containing crosslinking agent as a crosslinking agent were added to 59 parts of the solid content of the resin B prepared in Synthesis Example 2. (EPICLON (registered trademark) CR5L) manufactured by DIC Corporation, and a spherical polyethylene wax ("CHEMIPEARL (registered trademark) W640" manufactured by Mitsui Chemicals Co., Ltd.) was added to prepare a second water-based composition. This was applied to the inorganic-rich layer on the galvanized steel sheet by a bar coater in the same manner as the inorganic-rich layer, and coating/drying was performed so that the film thickness after drying became 0.4 μm to form an organic-rich layer. And a water-based two-layer coated metal sheet was obtained. The evaluation results are shown in Table 1.

Further, Run No. 6 and the 7-series colloidal cerium oxide amount are examples outside the scope of the present invention. In addition, Run No. 8 and 9 are mixed with an aluminum phosphate aqueous solution (manufactured by Nippon Chemical Industry Co., Ltd., solid content: 50%) in an amount of 45 parts and an acidic colloidal cerium oxide (SNOWTEX (registered trademark) ST-O; The surface treatment agent having an average particle diameter of 10 to 15 nm) of 55 parts was applied by a spray drying apparatus, followed by water washing/drying, and subjected to a bottom treatment (about 10 nm). On top of this, an organic-rich layer is formed in the same manner as described above. The total film thickness of Run No. 8 was 0.46 μm, and the total film thickness of Run No. 9 was 1.0 μm. The evaluation results are shown in Table 1.

As is clear from Table 1, when the amount of the colloidal cerium oxide in the inorganic-rich layer is small, the tape peeling resistance as an index of the adhesion to the plating layer is poor (Run No. 6). On the other hand, if the amount of the colloidal cerium oxide is too large, the formation of the film is incomplete due to the relative decrease in the polyurethane resin, and thus various properties are lowered (Run No. 7).

Experimental example 2

With respect to the 70 parts of the SNOWTEX XS having an average particle diameter of 4 to 6 nm, 30 parts of the resin A is added in terms of solid content, and the range of 5 to 25 parts is added to the total of 100 parts. KBM403, and the first water system composition was prepared. In the same manner as in Experimental Example 1, an inorganic-rich layer having a film thickness of 0.06 μm was formed on the surface of the electrogalvanized steel sheet.

Next, in the same manner as in Experimental Example 1, a rich organic layer having a film thickness of 0.4 μm was formed on the above-mentioned inorganic-rich layer. The evaluation results are shown in Table 2.

As is clear from Table 2, if the amount of the decane coupling agent in the inorganic-rich layer is small, the adhesion improving effect on the plating layer is insufficient, and the reactivity of the cerium oxide and the polyurethane is also lowered. Therefore, corrosion resistance, tape peeling resistance, alkali degreasing resistance, and the like are deteriorated (Run No. 14). On the other hand, if the amount of the decane coupling agent is too large, various properties are lowered (Run No. 15).

Experimental example 3

With respect to 70 parts of the SNOWTEX XS having an average particle diameter of 4 to 6 nm, 30 parts of the resin A was added in terms of solid content, and 15 parts of the previous KBM403 was added to the total of 100 parts. The first water system composition was prepared. An inorganic-rich layer was formed on the surface of the electrogalvanized steel sheet in the same manner as in Experimental Example 1, except that the film thickness was changed to 0.005 to 0.2 μm.

Next, in the same manner as in Experimental Example 1, a rich organic layer having a film thickness of 0.4 μm was formed on the above-mentioned inorganic-rich layer. The evaluation results are shown in Table 3.

As is clear from Table 3, if the film thickness of the inorganic-rich layer is too thin, the formation of the film of the inorganic-rich layer becomes uneven, and the absolute amount of the cerium oxide which contributes to the adhesion is insufficient, so that the adhesion is deteriorated ( RunNo.21). On the other hand, if the film thickness of the inorganic-rich layer is too thick, various properties are lowered (Run No. 22).

Experimental example 4

SNOWTEX ST-S (manufactured by Nissan Chemical Industries, Ltd.) having an average particle diameter of 8 to 11 nm and/or an average particle diameter of 10 to 15 nm is added to 70 parts of the SNOWTEX XS having an average particle diameter of 4 to 6 nm. SNOWTEX ST-30 (manufactured by Nissan Chemical Industry Co., Ltd.), adding 70 parts of the resin A in terms of solid content to 70 parts of the total of the cerium oxide, and adding 100 parts of the total amount of the SNOWTEX ST-30 15 parts of the previous KBM403 were used to prepare the first water system composition. Thereafter, in the same manner as in Experimental Example 1, an inorganic-rich layer and an organic-rich layer were sequentially formed on the surface of the electrogalvanized steel sheet. The evaluation results are shown in Table 4.

As is clear from Table 4, when colloidal cerium oxide having a large average particle diameter is used, a tendency to deteriorate in performance can be observed.

Experimental example 5

With respect to 70 parts of the SNOWTEX XS having an average particle diameter of 4 to 6 nm, 30 parts of the resin A was added in terms of solid content, and 15 parts of the previous KBM403 was added to the total of 100 parts. The first water system composition was prepared. In the same manner as in Experimental Example 1, an inorganic-rich layer having a film thickness of 0.06 μm was formed on an electrogalvanized steel sheet.

The organic-rich layer was formed on the inorganic-rich layer in the same manner as in Experimental Example 1, except that the film thickness of the organic-rich layer was changed between 0.1 and 0.6 μm. The evaluation results are shown in Table 5.

If the film thickness of the organic-rich layer is too thin, the effect of suppressing the dissolution of the colloidal ceria is not exhibited, and various properties are lowered (Run No. 37). When the film thickness of the organic-rich layer is thick, only the conductivity is lowered (Run No. 38).

Experimental example 6

An inorganic-rich layer was formed in the same manner as in Experimental Example 1. An organic-rich layer was formed in the same manner as in Experimental Example 1, except that the resin used for the formation of the organic-rich layer was changed in the manner shown in Table 6. The evaluation results are shown in Table 6.

When the resin A having a large water vapor permeability is used, the corrosion resistance tends to be poor (Run No. 42).

[Industrial Applicability]

According to the present invention, it is possible to provide a water-based 2-layer coating metal having good electrical conductivity and excellent adhesion, blackening resistance, alkali degreasing resistance, and sustained corrosion resistance (especially crotch) board.

Therefore, the water-based two-layer coating-treated metal sheet of the present invention is a home electric appliance or the like which is necessary for electromagnetic wave countermeasures.

Claims (3)

A water-based two-layer coated metal sheet obtained by laminating a metal sheet having two thin films on at least one surface of a metal sheet, characterized in that the film thickness formed by the first water-based composition is 0.01 to 0.1 The inorganic-rich layer of μm and the organic-rich layer having a thickness of 0.2 to 0.5 μm formed of the second aqueous component containing the organic resin on the inorganic-rich layer, and the total of the inorganic-rich layer and the organic-rich layer The thickness of the first water system composition is 60 to 80 parts by mass of colloidal cerium oxide having an average particle diameter of 4 to 15 nm, and 20 to 40 parts by mass of a carboxyl group-containing polyurethane resin. 7.5 to 20 parts by mass of a decane coupling agent having a glycidoxy group at the terminal end, and containing no lithium compound, in an amount of 7.5 to 20 parts by mass based on 100 parts by mass of the total of the colloidal cerium oxide and the carboxyl group-containing urethane resin. Inorganic compounds, phosphoric acid compounds, and metal components other than lithium. The water-based two-layer coated metal sheet according to claim 1, wherein the colloidal cerium oxide in the first aqueous component has an average particle diameter of 4 to 6 nm. The water-based two-layer coated metal sheet according to claim 1 or 2, wherein the film obtained from the organic resin contained in the second water-based composition has a water vapor permeability of 100 g/m ² /day or less.