KR20170077262A - Aqueous two layer-coated metal plate - Google Patents

Abstract

A water-based two-layer coated metal sheet having good conductivity and excellent corrosion resistance with excellent adhesion, black degeneration, alkali-alkali deterioration and persistence is provided.
A metal plate having two layers of a thin film laminated on at least one surface of a metal sheet, comprising 60 to 80 parts of colloidal silica having an average particle diameter of 4 to 15 nm and 20 to 40 parts of a carboxyl group-containing polyurethane resin, Is contained in an amount of 7.5 to 20 parts based on 100 parts of the total of the colloidal silica and the carboxyl group-containing polyurethane resin, and the lithium-containing inorganic compound, the phosphoric acid compound and the metal component other than lithium An inorganic rich layer having a film thickness of 0.01 to 0.1 占 퐉 formed from the first water-based composition; and an organic rich layer having a film thickness of 0.2 to 0.5 占 퐉 formed on the inorganic rich layer with a second aqueous composition comprising an organic resin, Layer and the organic-rich layer is 0.25 to 0.6 m.

Description

{AQUEOUS TWO LAYER-COATED METAL PLATE}

TECHNICAL FIELD [0001] The present invention relates to an aqueous two-layer coated metal sheet excellent in conductivity for electromagnetic wave countermeasures used in household electric appliances and the like.

In the field of consumer electronics in recent years, there has been a strong demand for a metal material having good conductivity as an electromagnetic wave countermeasure for preventing electromagnetic wave leakage from a product. In the coated steel sheet, a conductive pigment such as Ni powder is added to the coating to impart conductivity to the coated film. However, in the case of a thin coating film having a thickness of about 1 탆, as in the case of a specially treated steel sheet, it is difficult to add a conductive pigment to the coating.

As such a specially treated thin film, there has been known a technique of securing corrosion resistance and adhesion with a two-layer structure. For example, Patent Document 1 discloses a method in which a mixed coating of lithium silicate having film-forming property and colloidal silica having no film-forming property is formed on the first layer (metal plate side) and a coating film composed mainly of an organic resin is formed on the second layer And the like. However, since lithium silicate has hygroscopic property, water or oxygen passing through the second layer oxidizes the zinc plated layer, causing a blackening phenomenon, and also corrosion resistance is lowered. Particularly, there is a problem that lithium silicate is eluted in an alkaline atmosphere at the time of alkali degreasing, and the corrosion resistance and the adhesion with the zinc plated layer are largely deteriorated.

Patent Document 2 discloses an organic coated steel sheet having a layer containing a phosphoric acid compound, oxide fine particles (colloidal silica) and a metal compound as a first layer and an organic resin coating film as a second layer. However, There is a problem that the coating film is discolored due to the deterioration of the corrosion resistance and the alkali resistance caused by the elution of the phosphoric acid based compound under the influence of the change of the metal element. Patent Document 3 discloses a surface treatment zinc-based coating film which is obtained by coating a layer containing Si, P, Al and an organic resin as a first layer with a zinc plating layer, washing the surface with water, and coating an organic resin layer thereon as a second layer, A coated steel sheet is disclosed. In this technique, since the unreacted components are removed by flushing, the adhesion of the film is improved, but the corrosion resistance and alkali-degreasing property of flaws are insufficient. Moreover, in order to solve the problems described in these patent documents, it is necessary to increase the film thickness of the second layer to about 1 mu m, and good conductivity can not be obtained.

On the other hand, a one-layer type surface-treated metal plate considering conductivity is also known. For example, Patent Document 4 discloses a surface-treated metal plate having a resin coating formed of an aqueous resin solution obtained by adding colloidal silica and a silane coupling agent to two kinds of organic resins. However, Therefore, the barrier property against water or oxygen was insufficient, and the corrosion resistance and black pigmentation were insufficient.

Japanese Patent Application Laid-Open No. 2001-26886 Japanese Patent Application Laid-Open No. 2001-11645 Japanese Patent Application Laid-Open No. 2005-26436 Japanese Patent Application Laid-Open No. 2006-269018

The present invention provides a surface-treated metal sheet (special-treated steel sheet) having good conductivity and excellent corrosion resistance (particularly, flaws) with excellent adhesion, black degeneration, alkali degreasing property and durability in consideration of the above- I set it up as a task.

The present invention, which has solved the above problems, is a metal plate in which two thin films are laminated on at least one surface of a metal sheet, wherein 60 to 80 parts by mass of colloidal silica having an average particle diameter of 4 to 15 nm and 60 to 80 parts by mass of a carboxyl group- And a silane coupling agent having a terminal glycidizing time in a range of 7.5 to 20 parts by mass based on 100 parts by mass of the total of the colloidal silica and the carboxyl group-containing polyurethane resin, An inorganic-rich layer having a film thickness of 0.01 to 0.1 mu m formed from a first water-based composition not containing a compound, a phosphate compound and a metal component other than lithium, and a film formed of a second water- Wherein the total thickness of the inorganic-rich layer and the organic-rich layer is 0.25 to 0.6 mu m.

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

According to the present invention, it is possible to provide a water-based two-layer (two-layer) film having good conductivity (less than 0.5? As a surface resistance meter / 2 probe method) useful for countermeasures against electromagnetic waves of household appliances and the like and having excellent adhesiveness, A coated metal plate could be provided.

1 is a schematic view showing a structure of a metal plate of the present invention.
2 is a graph showing the relationship between the conductivity and the film thickness of the treatment film.
3 is a schematic view showing a method of measuring the surface resistance with the surface resistance measuring apparatus.
4 is a schematic diagram showing a friction coefficient measuring apparatus.

The inventors of the present invention have conducted intensive studies to solve the above problems and have found that the present inventors have found that corrosion resistance is ensured with an inorganic rich polar thin film (inorganic rich layer) having a small amount of colloidal silica and a barrier property And the like), and that the good conductivity can be obtained by setting the total film thickness of both of them to 0.6 mu m or less. Thus, the present invention has been reached. Hereinafter, the present invention will be described in detail.

[Structure of metal plate coated with aqueous two-layer coating]

As shown in Fig. 1, for example, a zinc plated layer is formed on a steel sheet body, and an inorganic rich layer as a first layer is formed thereon in a thickness of 0.01 to 0.1 m 1 water-based composition, and an organic-rich layer as a second layer is further formed thereon to a thickness of 0.2 to 0.5 탆 by a second water-based composition. The metal plate is not particularly limited, and for example, a zinc plated steel plate, an aluminum plate, an aluminum alloy plate, a titanium plate, or the like can be used in addition to the zinc plated steel plate shown in Fig. Most preferred is a galvanized steel sheet. From the viewpoint of environmental problems, it is preferable not to perform the chromate treatment.

[Inorganic-rich layer]

[Colloidal silica]

In the present invention, the inorganic-rich layer needs to contain colloidal silica having an average particle diameter of 4 to 15 nm. The colloidal silica is concentrated at the interface with the zinc plating layer and the interaction between the silanol group (-SiOH) of the silica (SiO ₂ ) and the zinc plating surface (Zn-OH) It has an effect of improving the adhesion. In addition, the colloidal silica has an effect of improving the corrosion resistance. The colloidal silica in the coating film elutes when the surrounding pH rises in the corrosive environment to form a mixed corrosion product of zinc hydrate, and the mixed corrosion product exhibits a barrier effect to improve the corrosion resistance. In the present invention, since the later-described organic-rich layer exerts an effect of slowing the elution rate of the colloidal silica, it is possible to secure long-lasting excellent corrosion resistance (in particular, flaws), and to exhibit black weathering and alkali- have.

In order to more effectively exhibit the action and effect of the colloidal silica, the average particle size of the silica used is 4 to 15 nm. The smaller the average particle size of silica, the better the corrosion resistance of the inorganic-rich layer. It is considered that the inorganic-rich layer is densified to further improve the interfacial adhesion with the zinc plated layer, thereby further improving the corrosion resistance. From this point of view, the smaller the particle diameter of the silica particles is, the better, but the lower limit of the particle diameter is set to 4 nm because the effect is saturated when the particles are extremely small. Examples of the silica in the above range include Snotex (registered trademark) 30 (average particle diameter of 10 to 15 nm), SNOWTEX (registered trademark) S (8 to 11 nm), SNOWTEX (registered trademark) XS (10 to 15 nm), Snowtex (registered trademark) NXS (4 to 6 nm), Snowtex (registered trademark) C (10 to 15 nm), Snowtex (registered trademark) ) CXS (4 to 6 nm), and the like. On the other hand, it is preferable that the nominal value of the catalog is adopted for the average particle size of the silica, or the measurement method by the shear method (4 to 6 nm) or the BET method (4 to 20 nm) is employed.

As described above, the smaller the particle size of the silica, the better the corrosion resistance of the inorganic-rich layer. This is presumably because the surface area of the silica is increased and the activity is increased, which is advantageous for elution of the silica in the corrosive environment and formation of mixed corrosion products. From this viewpoint, it is preferable that 50 mass% or more of the colloidal silica contained in the inorganic-rich layer has an average particle size of 4 to 6 nm. On the other hand, if colloidal silica 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 resulting water-based two-layer coated metal plate. However, When an amine or the like is used for neutralization, the silica and the amine react with each other, and the balance of the charge dispersing the colloidal silica is destroyed, so that the viscosity of the first aqueous composition increases and gelation may occur. Therefore, when it is necessary to lengthen the pot life of the first water-based composition, if the above "ST-30" (10-15 nm) or "ST-S" (8-11 nm) is used as a part of the colloidal silica good. However, the total amount thereof is preferably less than 50% by mass in 100% by mass of the colloidal silica.

[Carboxyl group-containing polyurethane resin]

The inorganic-rich layer of the present invention includes a carboxyl group-containing polyurethane resin. This is because colloidal silica alone can not form a film. 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 is an aqueous dispersion of a polyurethane resin synthesized essentially by using a polyol having a carboxyl group. Examples of raw materials include polyol components such as 1,4-cyclohexane dimethanol, polytetramethylene glycol having an average molecular weight of about 400 to 4,000 and a polyol having a carboxyl group such as dimethylol propionic acid, and polyol components such as tolylene diisocyanate, Isocyanate components such as phenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and the like are used. The chain extender is preferably a polyamine such as ethylene diamine.

The aqueous liquid of the carboxyl group-containing polyurethane resin used in the present invention can be prepared by a known method. For example, the carboxyl group of the carboxyl group-containing urethane prepolymer is neutralized with a base, A method in which a chain extension reaction is carried out by emulsification and dispersion, and a method in which a chain extension reaction is carried out by emulsifying and dispersing a carboxyl group-containing polyurethane resin in the presence of an emulsifier at a high shear force.

First, using the above-mentioned polyisocyanate and the above-mentioned polyol, an isocyanate group-containing isocyanate-terminated urethane prepolymer having a relatively low molecular weight is produced by 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 캜.

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

After the carboxyl group-containing isocyanate-terminated urethane prepolymer is emulsified and dispersed, a chain extender such as a polyamine or the like can be used to effect chain extension reaction. On the other hand, the chain extension reaction can be appropriately carried out before emulsion dispersion, simultaneous with emulsion dispersion, or after emulsion dispersion, depending on the reactivity of the chain extender used.

On the other hand, even if the carboxyl group-containing polyurethane resin is neutralized in the first water-based composition, since the amine used for neutralization is volatile after the formation of the inorganic rich layer, it is present as a carboxyl group-containing polyurethane resin.

[Silane coupling agent]

In the first water-based composition used in the present invention, a silane coupling agent containing a glycidoxy group is incorporated at the end. This silane coupling agent further improves the adhesion between the metal sheet surface and the inorganic rich layer. Further, since the silane coupling agent has a functional group that bonds an inorganic component and an organic component, and is more reactive than other silane coupling agents, the bonding strength between the colloidal silica and the polyurethane resin is enhanced, It is effective in enhancing the performance such as alkali resistance to degreasing.

Examples of the silane coupling agent having a glycidoxy group at the terminal thereof include? -Glycidoxypropyltrimethoxysilane,? -Glycidoxypropylmethyldiethoxysilane, and the like.

[First water-based composition]

In forming the inorganic rich layer, a first water-based composition prepared by mixing colloidal silica, a carboxyl group-containing polyurethane resin, and a silane coupling agent is used. This first water-based composition does not contain a lithium-based inorganic compound, a phosphate compound, and a metal component other than lithium. As the lithium-based inorganic compound, for example, lithium silicate used in Patent Document 1 can be mentioned, but lithium silicate is not preferable because it causes a black color (stain contamination, discoloration). In Patent Documents 2 and 3, the adhesion between the first layer and the plating layer is improved by etching the surface of the plating layer using a phosphate compound and a metal component. However, when the first layer is not washed after the formation, The residual metal compound or phosphoric acid component is eluted and deterioration of performance such as corrosion resistance and alkaline degreasing property occurs, and a black color or discoloration originating from the metal component occurs. Therefore, in the present invention, the lithium-based inorganic compound, the phosphoric acid compound and the metal component other than lithium are not added to the first water-based composition. However, since colloidal silica stabilized with sodium, such as Snowtex (registered trademark) XS described above, may be used, that is, a metal component may be contained, and therefore, strictly speaking, Means that the urethane resin and the silane coupling agent are not added with a lithium-based inorganic compound, a phosphoric acid compound and a metal component other than lithium.

The first water-based composition preferably contains 60 to 80 parts by mass (preferably 65 to 75 parts by mass) of the colloidal silica in the inorganic-rich layer, 20 to 40 parts by mass (preferably 25 to 40 parts by mass, 35 parts by mass), and a silane coupling agent having a glycidoxy group at the terminal is added in an amount of 7.5 to 20 mass parts. The aqueous solution of the colloidal silica and the carboxyl group-containing polyurethane resin is mixed with the silane coupling agent have. On the other hand, the description in this paragraph is the blending amount when the total amount of the two components of the colloidal silica and the carboxyl group-containing polyurethane resin is 100 parts by mass, that is, the amount of the silane coupling agent is the amount of the colloidal silica and the content of the carboxyl group And the total amount of the polyurethane resin is 100 parts by mass.

If the colloidal silica is too small, desired corrosion resistance can not be secured. If the amount of the carboxyl group-containing polyurethane resin is too small, the formation of the film becomes uneven. When the silane coupling agent is too small, the effect of improving the adhesion between the metal sheet surface and the inorganic rich layer becomes insufficient, and the reactivity of the colloidal silica and the polyurethane resin also deteriorates. Therefore, corrosion resistance, Alkaline degreasing property, black weathering and the like are deteriorated. On the other hand, if the amount of the silane coupling agent is too large, the stability of the first water-based composition with time is lowered, and the cost is also disadvantageous.

[Film thickness of inorganic rich layer]

The thickness of the inorganic rich layer as the first layer is set to 0.01 to 0.1 m. The inorganic rich layer of the present invention has an effect of improving the adhesion with the zinc plated layer even in the case of an extremely thin film having a thickness of 0.01 mu m. However, when it is thinner than 0.01 탆, the formation of the film becomes uneven, or the absolute amount of silica contributing to the adhesion is insufficient and the adhesion is lowered. On the other hand, when the thickness of the inorganic-enriched layer exceeds 0.1 mu m, cohesive failure occurs in the coating film, and as a result, the residual percentage of the film when the internal tape peeling test is conducted is greatly lowered. In order to secure conductivity, it is necessary to suppress the total film thickness to 0.6 占 퐉 or less (to be described later), but when the thickness of the inorganic rich layer exceeds 0.1 占 퐉, the total thickness of the organic rich layer (second layer) The film thickness can not be reduced, and corrosion resistance, black marking, and alkali alkali rusting resistance are lowered due to lowering of the barrier property. The film thickness of the inorganic rich layer is preferably 0.02 to 0.08 mu m, more preferably 0.03 to 0.06 mu m.

[Formation of inorganic rich layer]

The inorganic rich layer may be formed by applying the first aqueous composition onto one side or both sides of the metal plate surface by a known coating method, that is, a bar coater method, a roll coater method, a spraying method, a curtain flow coater method and the like. The heating temperature may be such that water is volatilized.

[Film thickness of organic-rich layer]

Next, the organic-rich layer that becomes the second layer will be described. The organic-rich layer is responsible for ensuring barrier properties and slowing the elution rate of silica to maintain the corrosion resistance. The present inventors examined the relationship between the total film thickness of the inorganic-rich layer and the organic-rich layer and the conductivity, and the results shown in FIG. 2 were obtained. This is a result obtained by changing the film thickness of the organic-rich layer while keeping the thickness of the inorganic-enriched layer constant at 0.06 mu m. What is required as a countermeasure against electromagnetic waves is that the conductivity when measured by a two-probe method using a surface resistance meter is less than 0.5 OMEGA, so that it has been found that the total film thickness needs to be 0.6 m or less.

Therefore, the organic-rich layer is 0.2 to 0.5 mu m. More preferably 0.3 to 0.5 m, and still more preferably 0.35 to 0.45 m. If the organic-enriched layer is thinner than 0.2 탆, the barrier property is lowered and the corrosion resistance and alkali-alkali degreasing property are lowered. Further, since the lubricity is lowered, problems arise in workability and the like. On the other hand, when the film thickness of the organic-enriched layer exceeds 0.5 탆, the conductivity is remarkably deteriorated.

[Organic resin of organic-rich layer]

The organic-rich layer is formed of a second aqueous composition comprising an organic resin. The organic resin is not particularly limited, but is preferably a resin capable of forming a film having a water vapor permeability of 100 g / m ² / day or less. On the other hand, the water vapor permeability was measured by applying the organic resin or the second aqueous composition on a copy paper so that the film thickness after drying with a bar coater was 18 μm, drying at 105 ° C. for 2 minutes, And measured by the cup method according to JIS Z0208.

If the resin is capable of producing a film having a water vapor transmission rate of 100 g / m ² / day or less, the barrier property of the organic-enriched layer can be ensured, and the dissolution rate of the colloidal silica can be further reduced. In the organic resin in which the film has a water vapor permeability exceeding 100 g / m ² / day, when colloidal silica is added in an amount exceeding 30 mass% in the second water-based composition in anticipation of improvement in corrosion resistance and the like, The permeability increases to 5000 g / m ² / day or more, and corrosion resistance and the like are considerably deteriorated. A more preferable water vapor permeability is 50 g / m ² / day or less.

For example, 20% by mass (in terms of solid content of the second water-based composition) of colloidal silica (average particle size of 4 to 6 nm) is added to a second water-based composition containing an organic resin having a water vapor transmission rate of 50 g / m ² / When added, the water vapor permeability of the organic-rich layer was about 1500 g / m ² / day, but the effect of improving the corrosion resistance and the like was recognized. Moreover, the water vapor permeability of the organic-enriched layer tends to be lowered by addition of a cross-linking agent to be described later or a silane coupling agent as described above, so that corrosion resistance, alkali-alkali rusting resistance, weathering resistance and the like can be improved.

It is preferable that the organic resin satisfies the above water vapor permeability, but specifically preferred is an ethylene-unsaturated carboxylic acid copolymer. As the ethylene-unsaturated carboxylic acid copolymer, those described in JP-A-2005-246953 and JP-A-2006-43913 can be used.

Examples of the unsaturated carboxylic acid include (meth) acrylic acid, crotonic acid, isocrotonic acid, maleic acid, fumaric acid, itaconic acid, etc., and by polymerizing at least one of these with ethylene by a known high- The merger can be obtained.

The copolymerization ratio of the unsaturated carboxylic acid to ethylene is preferably 10 to 40% by mass of the unsaturated carboxylic acid when the total amount of the monomers is 100% by mass. When the content of the unsaturated carboxylic acid is less than 10% by mass, the effect of the film strength is not exhibited because the starting point of the intermolecular association by the ion clusters or the carboxyl group which is a crosslinking point with the crosslinking agent is small and the tape peeling resistance and alkali- And the emulsion composition of the emulsion composition is inferior in stability, which is not preferable. The lower limit of the more preferable unsaturated carboxylic acid is 15 mass%. On the other hand, when the content of the unsaturated carboxylic acid exceeds 40 mass%, the corrosion resistance and water resistance of the organic-rich layer are inferior and the alkali-alkali degreasing property is also deteriorated. A more preferable upper limit is 25 mass%.

Since the ethylene-unsaturated carboxylic acid copolymer has a carboxyl group, neutralization with an organic base or a metal ion enables emulsification (water dispersion). In the present invention, it is preferable to use an amine as an organic base, and all of the amines described above can be used, and triethylamine is particularly preferable. It is also preferable to use monovalent metal ions in addition to amines. The amines are preferably used in an amount of 0.2 to 0.8 mol (20 to 80 mol%) based on 1 mol of the carboxyl groups in the ethylene-unsaturated carboxylic acid copolymer. It can be seen that the amount of monovalent metal ion affects the water vapor permeability. When the amount of the monovalent metal compound used is increased, the affinity between the resin and water is increased and the water vapor permeability is increased. Therefore, the carboxyl group of the ethylenically unsaturated carboxylic acid copolymer It is preferably 0.02 to 0.2 mol (2 to 20 mol%) based on the molar amount. In addition, since the excessive alkali component causes deterioration in corrosion resistance, the total amount of the amine and metal ion to be used may be in the range of 0.3 to 1.0 mol based on 1 mol of the carboxyl group in the ethylene-unsaturated carboxylic acid copolymer. On the other hand, NaOH, KOH, LiOH and the like are preferable as metal compounds for imparting a monovalent metal ion, and NaOH is preferable because it has the best performance.

[Crosslinking agent]

The ethylene-unsaturated carboxylic acid copolymer having a carboxyl group neutralized with an amine and a monovalent metal ion forms an intermolecular association by ion clusters (ionomerization) to form an organic-rich layer excellent in corrosion resistance and internal tape peelability . However, in order to form a stronger film, it is preferable to cross-link the polymer chains by chemical bonding using a reaction between functional groups. As the crosslinking agent, a glycidyl group-containing crosslinking agent and an aziridine group-containing crosslinking agent are preferable.

Examples of the glycidyl group-containing crosslinking agent include sorbitol polyglycidyl ether, (poly) glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether Polyglycidyl ethers such as diallyl ether and (poly) ethylene glycol diglycidyl ether, and glycidyl group-containing crosslinking agents such as polyglycidyl amines.

Examples of the crosslinking agent containing an aziridine group include 4,4'-bis (ethyleneimine carbonylamino) diphenylmethane, N, N'-hexamethylene-1,6-bis (1-aziridine carboxamide) Bifunctional aziridine compounds such as diphenylmethane-4,4'-bis (1-aziridine carboxamide), toluene bisaziridine carboxamide; Tris (2-methyl) aziridinyl] phosphine oxide, trimethylol propane tris (? -Aziridyl propionate), tris-2,4,6- (1-aziridinyl) -1,3,5-triazine, and tetramethylpropane tetraaziridinyl propionate; and derivatives thereof.

[Wax]

Since the water-based two-layer coated metal sheet of the present invention may be provided for processing with the organic-rich layer as the outermost surface, it is preferable that wax is included in the organic-rich layer in order to improve workability. Preferable industrially preferable ones are spherical polyethylene waxes, polypropylene waxes, modified waxes, copolymer waxes with ethylene or propylene, and ethylenic copolymer waxes, and their oxides and derivatives imparted with carboxyl groups, and also paraffin waxes with acid groups , Carnauba wax, and the like. As the wax, a spherical polyethylene wax is most suitable. Examples of the wax include "Die Jet E-17" (product of Koya Chemical Co.), "KUE-1", "KUE-5", "KUE- , W-100, W-200, W-300, W-400, W-500, W-640, Quot; W-700 " and the like, and " Erefon E-20 " (manufactured by Nikka Chemical Co., Ltd.).

[Second water-based composition]

The second water-based composition preferably contains the above-mentioned colloidal silica having an average particle diameter of 4 to 6 nm. However, if it is excessively large, the water vapor permeability becomes poor as described above. Therefore, in the second water-based composition, it is preferable that 57 to 83 mass% of the ethylene-unsaturated carboxylic acid copolymer (solid content), 10 to 30 mass% of colloidal silica having an average particle diameter of 4 to 6 nm, By mass, and 2 to 5% by mass of spherical polyethylene wax. On the other hand, the total of these four components is 100% by mass.

If necessary, it is preferable to emulsify the components together or separately to prepare an aqueous dispersion. The method of applying the second waterborne composition to the metal plate on which the inorganic rich layer is formed is not particularly limited, and a bar coater method, a roll coater method, a spray method, a curtain floater method, or the like can be employed. After the application, it is preferable to carry out heating and drying at about 80 to 130 캜.

This application claims the benefit of priority based on Japanese Patent Application No. 2014-256631, filed on December 18, 2014. The entire contents of the specification of Japanese Patent Application No. 2014-256631 filed on December 18, 2014 are incorporated herein by reference.

Example

EXAMPLES The present invention is further described in the following examples. However, the following examples do not limit the present invention, but the scope of the present invention encompasses modifications that do not depart from the spirit of the present invention. Hereinafter, " part " means " part by mass " and "% " The evaluation method used in the examples is as follows.

[Assessment Methods]

(1) Corrosion resistance 1: Salt spray test (SST flat plate, SST cross cut)

The back side and edge sealing materials were subjected to a 5% salt spray test under an atmosphere of 35 ° C in accordance with JIS Z2371 with a flat cut and a cross cut with a cutter knife. The time to reach the% (area) was measured.

Evaluation of SST reputation

◎: 240 hours or more

○: 168 hours or more and less than 240 hours

B: 120 hours or more and less than 168 hours

×: less than 120 hours

Evaluation of SST crosscut

◎: 120 hours or more

○: 96 hours or more and less than 120 hours

?: 72 hours or more and less than 96 hours

×: less than 72 hours

(2) Corrosion resistance 2: Salt water spray cycle test (SST cycle)

The edge sealing material (flat plate) was subjected to a cycle test of salt spray according to JIS Z2371 to measure the number of cycles at which the incidence of white rust reached 5%. In one cycle, the salt water spray was performed for 8 hours (35 ° C) and the salt water spray was stopped for 16 hours (35 ° C).

Evaluation of SST Cycle

◎: 10 cycles or more

○: 7 cycles or more and less than 10 cycles

DELTA: 5 cycles or more and less than 7 cycles

×: less than 5 cycles

(3) Corrosion resistance 3: Neutral saline spray cycle test (JASO)

The edge sealings (flat plates) were subjected to a neutral salt spray cycle test in accordance with JIS H8502, and the number of cycles for which the incidence of white rust reached 5% was measured. In one cycle, salt water spraying was carried out for 2 hours, drying (60 ° C., humidity 30% or more) for 4 hours and wetting (50 ° C., humidity 95% or more) for 2 hours.

Evaluation of JASO

◎: 21 cycles or more

○: 15 cycles or more and less than 21 cycles

?: 9 cycles or more and less than 15 cycles

×: Less than 9 cycles

(4) Conductivity

The surface resistance value of each of the specimens was measured by using a surface resistance measuring device (Loresta EP; manufactured by Mitsubishi Chemical Corporation) (Dai Instruments Co., Ltd.) 2, the pin spacing was 10 mm, the spring pressure was 240 g / mm, and the pin end diameter was 2 mmφ. A schematic diagram of the surface resistance measuring apparatus is shown in FIG.

Evaluation of conductivity

?: Less than 0.05?

○: 0.05Ω or more and less than 0.50Ω

?: 0.50? Or more and less than 1.00?

×: 1.00Ω or more

(5) Tape peelability

(Filament tape No. 9510, rubber-based adhesive agent, manufactured by Sliontec Co., Ltd.) was stuck to the sealing material and stored in a constant-temperature and constant-humidity testing apparatus under an atmosphere at 40 ° C and a humidity of 98% for 120 hours. Then, the tape was peeled off according to JIS K5400 The test was conducted to measure the remaining ratio (area) of the film.

Evaluation of Film Remaining Rate

◎: 95% or more

○: 90% or more and less than 95%

?: 80% or more and less than 90%

×: less than 80%

(6) Black degeneration

After the specimens were stored for 168 hours in a constant temperature and humidity test apparatus at 50 占 폚 and at a humidity of 98% or more, the appearance (presence or absence of black stain and stain contamination) before and after the test and the change in color tone were measured to calculate the color difference? E.

Appearance evaluation before and after the test

◎: No change before and after test

○: Very little shade, no contamination

△: A little shade, stain contamination

×: Pollution with stain

Evaluation of color difference (? E)

&Amp; cir &: DELTA E is less than 1

?: ΔE is 1 or more and less than 2

DELTA: DELTA E is 2 or more and less than 3

X: When? E is 3 or more

(7) Lubrication (dynamic friction coefficient)

The coefficient of dynamic friction of each of the specimens was measured using the friction coefficient measuring apparatus shown in Fig. The size of the sealing material was 40 mm x 300 mm, the pressing force was 4.5 MPa, and the drawing speed was 300 mm / min. On the other hand, the material of the flat plate dice was SKD11. On the other hand, the dynamic friction coefficient mu is F / 2P.

Evaluation of lubricity

?: Less than 0.09

?: Mu = 0.09 or more and less than 0.15

?: Mu = 0.15 or more and less than 0.20

X: mu = 0.20 or more

(8) Alkali deterioration resistance

The sealing material was immersed in an alkali degreasing agent (CL-N364S) manufactured by Nihon Parkerizing Co., Ltd. (20 g / liter, liquid temperature: 65 占 폚) for 2 minutes and then pulled up, washed with water and dried, and then subjected to backside and edge sealing. Spray cycle test (SST cycle flat plate) was carried out to measure the number of cycles until the incidence of white rust became 5%. One cycle consisted of 5% salt water spray for 8 hours (35 ° C) and salt water spray for 16 hours (35 ° C).

◎: 7 cycles or more

○: 5 cycles or more and less than 7 cycles

DELTA: 3 cycles or more and less than 5 cycles

X: Less than 3 cycles

Synthesis Example 1

Synthesis of Dispersion of Polyurethane Resin Containing Carboxyl Group

60 parts of polytetramethylene ether glycol (average molecular weight: 1000; manufactured by Hodogaya Chemical Co., Ltd.) as a polyol component, 14 parts of 1,4-cyclohexanedimethanol, 1 part of dimethyl 20 parts of propionic acid was added, and 30 parts of N-methylpyrrolidone was further added as a reaction solvent. 104 parts of tolylene diisocyanate (TDI) as an isocyanate component was added, the temperature was raised to 80 to 85 캜, and the reaction was carried out for 5 hours. The NCO content of the obtained prepolymer was 8.9%. Then, 16 parts of triethylamine was added to neutralize, and a mixed aqueous solution of 16 parts of ethylenediamine and 480 parts of water was added and subjected to chain extension reaction while being emulsified at 50 DEG C for 4 hours to obtain a polyurethane resin aqueous dispersion (nonvolatile Resin component 29.1%, acid value 41.4). This is referred to as resin A. On the other hand, the water vapor permeability of the resin A was 1500 g / m ² / day.

Synthesis Example 2

Synthesis of Ethylene-Unsaturated Carboxylic Acid Copolymer Aqueous Dispersion 1

626 parts of water and 160 parts of an ethylene-acrylic acid copolymer (acrylic acid unit: 20 mass%, melt index: 300) were added to an autoclave equipped with a stirrer, a thermometer and a temperature controller. 40 mol% of triethylamine and 15 mol% of sodium hydroxide were added to 1 mol of the base, and the mixture was stirred at 150 DEG C and 5 Pa at high speed and cooled to 40 DEG C to obtain an ethylene-acrylic acid copolymer emulsion. To 100 parts of the solid content of the ethylene-acrylic acid copolymer was added 4,4'-bis (ethyleneiminocarbonylamino) diphenylmethane ("Chemitite (registered trademark) DZ-22E" The resin B was added with 5 parts. The water vapor permeability of the resin B was 50 g / m ² / day.

Synthesis Examples 3 and 4

Synthesis of Ethylene-Unsaturated Carboxylic Acid Copolymer Aqueous Dispersion 2 and 3

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

Experimental Example 1

(Resin A) prepared in Synthesis Example 1 was added to 55 to 85 parts of colloidal silica having an average particle size of 4 to 6 nm (Nissan Chemical Industries, "SNOWTEX (registered trademark) XS" And 15 parts by mass of a silane coupling agent (KBM403 (glycidoxime-containing silane coupling agent) manufactured by Shin-Etsu Chemical Co., Ltd.) was added in an amount of 15 parts by mass based on 100 parts by mass of the total solid content, .

The metal sheet used as the electro-galvanized steel sheet (zinc coating weight 20g / m ^2, thickness 0.8mm), and applying a first aqueous composition in its one surface with a bar coater and dried at plate temperature of 90 ℃, a film having a thickness of 0.06μm An inorganic rich layer was formed. On the other hand, the film thickness was calculated by quantitatively measuring the Si element of the colloidal silica (SiO ₂ ) in the film with a fluorescent X-ray analyzer. At this time, the specific gravity of SiO ₂ was calculated to be 2.2 and the specific gravity of the resin to be 1.

30 parts of colloidal silica having an average particle diameter of 4 to 6 nm and 7.5 parts of a glycidyl group-containing crosslinking agent ("Epiclon (registered trademark) CR5L") manufactured by DIC Co., Ltd. were added to 59 parts of the solid content of the resin B prepared in Synthesis Example 2 And 3.5 parts of a spherical polyethylene wax ("Chemipear (registered trademark) W640" manufactured by Mitsui Chemicals, Inc.) were added to prepare a second water-based composition. This was coated on the inorganic-rich layer on the zinc-plated steel sheet in the same manner as in the inorganic-rich layer with a bar coater, followed by coating and drying so as to have a thickness of 0.4 탆 after drying to form an organic rich layer, . The evaluation results are shown in Table 1.

On the other hand, 6 and 7 are examples in which the amount of colloidal silica exceeds the range of the present invention. In addition, 8 and 9 were prepared by mixing 45 parts of an aluminum acid aqueous solution (solid content 50%, manufactured by Nippon Chemical Industry Co., Ltd.) as an inorganic rich layer and 55 parts of an acidic colloidal silica (SNOWTEX (registered trademark) ST-O; average particle size of 10 to 15 nm) The surface treatment agent was applied by a sprayer apparatus and then washed and dried (about 10 nm). On this, an organic-rich layer was formed in the same manner as described above. Run No. 8 had a total film thickness of 0.46 m, 9 was 1.0 mu m. The evaluation results are shown in Table 1.

From Table 1, it can be seen that when the amount of colloidal silica in the inorganic-enriched layer is small, the peelability of the inner tape, which is an index of adhesion to the plating layer, is poor (Run No. 6). On the other hand, when the amount of the colloidal silica is excessively large, the polyurethane resin is relatively decreased and the formation of the film is incomplete, so that various performances have deteriorated (Run No. 7).

Experimental Example 2

30 parts of the resin A was added to 70 parts of Snowtex XS which preceded the average particle size of 4 to 6 nm and 100 parts of the resin A was added in the range of 5 to 25 parts of KBM403, . An inorganic rich layer having a thickness of 0.06 mu m was formed on the surface of the electrogalvanized steel sheet in the same manner as in Experimental Example 1. [

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

As can be seen from Table 2, if the amount of the silane coupling agent in the inorganic-enriched layer is small, the effect of improving the adhesion to the plating layer becomes insufficient and the reactivity of the silica and the polyurethane resin also deteriorates. , And alkaline degreasing resistance (Run No. 14). On the other hand, if the amount of the silane coupling agent is excessively large, various performances are lowered (Run No. 15).

Experimental Example 3

To 70 parts of Snowtex XS which preceded the average particle diameter of 4 to 6 nm, 30 parts of resin A was added as solid content, and 15 parts of KBM403 was added to a total of 100 parts thereof to prepare a first water-based composition. An inorganic rich layer was formed on the surface of the electrodeposited steel sheet in the same manner as in Experimental Example 1, except that the film thickness was changed to 0.005 to 0.2 mu m.

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

From Table 3, if the film thickness of the inorganic enriched layer is too thin, the film formation of the inorganic enriched layer becomes uneven, or the absolute amount of silica contributing to the adhesion is insufficient, resulting in poor adhesion (Run No. 21). On the other hand, if the thickness of the inorganic-rich layer was too thick, various performances were degraded (Run No. 22).

Experimental Example 4

Snowtex ST-S (manufactured by Nissan Chemical Industries, Ltd.) having an average particle size of 8 to 11 nm and / or Snowtex ST-30 having an average particle size of 10 to 15 nm (manufactured by Nissan Chemical Industries, Ltd.) having an average particle size of 8 to 11 nm were added to 70 parts of Snowtex XS, Ltd.) was added in the ratio shown in Table 4. 30 parts of the resin A was added to 70 parts of the total amount of the silica, and 15 parts of KBM403 as the above was added to 100 parts of the total amount of the resin A, . Thereafter, in the same manner as in Experimental Example 1, an inorganic-rich layer and an organic-rich layer were formed in this order on the surface of an electrogalvanized steel sheet. The evaluation results are shown in Table 4.

From Table 4, the use of colloidal silica having a large average particle diameter tended to slightly deteriorate the performance.

Experimental Example 5

To 70 parts of Snowtex XS which preceded the average particle diameter of 4 to 6 nm, 30 parts of resin A was added as solid content, and 15 parts of KBM403 was added to a total of 100 parts thereof to prepare a first water-based composition. An inorganic rich layer having a thickness of 0.06 mu m was formed on the galvanized steel sheet in the same manner as in Experimental Example 1. [

An 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 varied between 0.1 and 0.6 m. The evaluation results are shown in Table 5.

If the thickness of the organic-enriched layer is small, the effect of suppressing the elution of the colloidal silica is not exhibited, and various performances are lowered (Run No. 37). When the thickness of the organic-rich layer was thick, only the conductivity was 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 forming the organic-rich layer was changed as shown in Table 6. [ The evaluation results are shown in Table 6.

When resin A having a high water vapor permeability was used, the corrosion resistance tended to be poor (Run No. 42).

According to the present invention, it is possible to provide a water-based two-layer coated metal sheet having good conductivity and excellent corrosion resistance (particularly, scratches) with excellent adhesion, black marking, alkali alkali rusting resistance and durability.

Therefore, the water-based two-layer coated metal sheet of the present invention is useful for household electric appliances that require electromagnetic wave countermeasures.

Claims (3)

A metal plate having two thin films laminated on at least one surface of a metal plate,
60 to 80 parts by mass of colloidal silica having an average particle size of 4 to 15 nm and 20 to 40 parts by mass of a carboxyl group-containing polyurethane resin, and a silane coupling agent having a glycidoxy termination at the terminal are mixed with the colloidal silica and the carboxyl group Containing polyurethane resin having a thickness of 0.01 to 0.1 mu m formed by a first aqueous composition containing 7.5 to 20 parts by mass based on 100 parts by mass of the total of the lithium-based inorganic compound, phosphoric acid compound and lithium, And an organic-rich layer having a film thickness of 0.2 to 0.5 占 퐉 formed from a second aqueous composition containing an organic resin on the inorganic-rich layer, wherein the total thickness of the inorganic-rich layer and the organic- Wherein the water-based two-layer coated metal sheet is 0.6 占 퐉. The method according to claim 1,
A water-based two-layer coated metal sheet wherein at least 50 mass% of the colloidal silica in the first water-based composition has an average particle size of 4 to 6 nm. 3. The method 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 transmission rate of 100 g / m ² / day or less.

Images