WO2016098629A1

WO2016098629A1 - Aqueous two layer-coated metal plate

Info

Publication number: WO2016098629A1
Application number: PCT/JP2015/084278
Authority: WO
Inventors: 忠繁中元; 航于
Original assignee: 株式会社神戸製鋼所
Priority date: 2014-12-18
Filing date: 2015-12-07
Publication date: 2016-06-23
Also published as: CN107000381B; KR101808495B1; TWI569956B; JP6396786B2; JP2016117171A; CN107000381A; TW201630722A; KR20170077262A; MY182210A

Abstract

Provided is an aqueous two layer-coated metal plate having good conductivity, excellent adhesiveness, blackening resistance, alkaline degreasing resistance, and long-lasting corrosion resistance. An aqueous two layer-coated metal plate having two layers of thin films layered on at least one surface of the metal plate, wherein the two thin films are: an inorganic material-rich layer having a film thickness of 0.01-0.1 µm and formed of a first aqueous composition containing 60-80 parts of colloidal silica having an average particle size of 4-15 nm, 20-40 parts of a carboxyl group-containing polyurethane resin, and 7.5-20 parts of a silane coupling agent having a glycidoxy group at a terminal end thereof with respect to a total of 100 parts of the colloidal silica and the carboxyl group-containing polyurethane resin, but not containing a lithium-based inorganic compound, a phosphoric acid compound, or a metal component other than lithium; and an organic material-rich layer provided on the inorganic material-rich layer, having a film thickness of 0.2-0.5 µm, and formed of a second aqueous composition containing an organic resin, wherein the total thickness of the inorganic material-rich layer and the organic material-rich layer is 0.25-0.6 µm.

Description

Aqueous two-layer coated metal plate

The present invention relates to a water-based two-layer coated metal plate having excellent conductivity for electromagnetic wave countermeasures used for household electric appliances and the like.

In recent years, in the field of home appliances, there is an increasing demand for a metal material with good conductivity as an electromagnetic wave countermeasure for preventing leakage of electromagnetic waves generated from products. In coated steel sheets, conductive pigments such as Ni powder have been added to the paint to impart conductivity to the coating film. However, in the case of thin films with a film thickness of about 1 μm, such as special chemical conversion treated steel sheets, the conductive pigment is contained in the film. It is difficult to add to.

As such a special chemical conversion treatment thin film, a technique for ensuring corrosion resistance and adhesion with a two-layer structure is known. For example, in Patent Document 1, a mixed film of lithium silicate having a film forming property and colloidal silica having no film forming property is formed on a first layer (metal plate side), and a film containing an organic resin as a main component on a second layer. Techniques for forming the are disclosed. However, since lithium silicate has a hygroscopic property, water and oxygen passing through the second layer oxidize the galvanized layer, thereby causing a blackening phenomenon and reducing corrosion resistance. In particular, in an alkaline atmosphere when alkali degreasing is performed, there is a problem that lithium silicate is eluted and the corrosion resistance and adhesion with the galvanized layer are greatly 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 film as a second layer. However, there are problems such as deterioration of corrosion resistance and alkali resistance due to elution of a phosphoric acid compound in a corrosive environment, and discoloration of the film due to a change in the valence of metal elements. In Patent Document 3, a layer containing Si, P, Al, and an organic resin is coated as a first layer, reacted with a galvanized layer, washed with water, and an organic resin layer is coated thereon as a second layer. A surface-treated galvanized steel sheet is disclosed. In this technique, since unreacted components are removed by washing with water, the adhesion of the film is improved, but the corrosion resistance and alkali degreasing resistance of the heel portion are insufficient. Furthermore, in order to solve the problems of the techniques described in these patent documents, it is necessary to increase the thickness of the second layer to about 1 μm, and good conductivity cannot be obtained.

On the other hand, a one-layer type surface-treated metal plate in consideration of conductivity is also known. For example, Patent Document 4 discloses a surface-treated metal plate having a resin film formed from an aqueous resin liquid in which colloidal silica and a silane coupling agent are added to two types of organic resins. Since it is low, the barrier property against water and oxygen is poor, and the corrosion resistance and blackening resistance are insufficient.

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

In consideration of the above circumstances, the present invention has a surface-treated metal plate having good conductivity and having excellent adhesion, blackening resistance, alkali degreasing resistance, and persistent corrosion resistance (particularly a buttock). Providing special chemical conversion steel sheets) was raised as an issue.

The present invention that has solved the above problems is a metal plate in which two thin films are laminated on at least one surface of a metal plate, wherein 60-80 parts by mass of colloidal silica having an average particle size of 4-15 nm and carboxyl Containing 20 to 40 parts by mass of a group-containing polyurethane resin and 7.5 to 20 parts by mass of a silane coupling agent having a glycidoxy group at the terminal with respect to a total of 100 parts by mass 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 μm formed from a first aqueous composition that does not contain a metal component other than an inorganic inorganic compound, a phosphoric acid compound, and lithium, and an organic layer on the inorganic rich layer The organic rich layer having a film thickness of 0.2 to 0.5 μm formed from the second aqueous composition containing a resin, and the total of the inorganic rich layer and the organic rich layer An aqueous two-layer coated metal sheet having a thickness of 0.25 to 0.6 μm.

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

According to the present invention, it has good electrical conductivity (less than 0.5Ω by a surface resistance meter / 2 probe method) useful for electromagnetic wave countermeasures for home appliances, etc., and has excellent adhesion, blackening resistance, An aqueous two-layer coated metal plate having alkali degreasing properties and long-term corrosion resistance could be provided.

It is a schematic diagram which shows the structure of the metal plate of this invention. It is a graph which shows the relationship between electroconductivity and the film thickness of a process film. It is a schematic diagram which shows the method of measuring surface resistance with a surface resistance measuring apparatus. It is a schematic diagram which shows a friction coefficient measuring apparatus.

As a result of investigations to solve the above-mentioned problems, the present inventors have secured corrosion resistance with an inorganic-rich ultrathin film (inorganic-rich layer) having a fine colloidal silica, and the organic resin is mainly used therefor. The present invention has found that good conductivity can be obtained by providing an organic rich layer having a high barrier property (suppressing elution of silica and the like) and setting the total film thickness of both to 0.6 μm or less. Reached. Hereinafter, the present invention will be described in detail.

[Structure of aqueous two-layer coated metal sheet]
In the aqueous two-layer coated metal sheet of the present invention, for example, as shown in FIG. 1, a galvanized layer is formed on a steel plate body, and an inorganic rich layer is formed on the first layer as a first layer. A first aqueous composition is formed to a thickness of 0.1 μm, and an organic rich layer is formed as a second layer from the second aqueous composition to a thickness of 0.2 to 0.5 μm thereon. Yes. Although it does not specifically limit as a metal plate, For example, besides a galvanized steel plate shown in FIG. 1, a galvanized steel plate, an aluminum plate, an aluminum-type alloy plate, a titanium plate etc. can be used. Most preferred is a galvanized steel sheet. From the viewpoint of environmental problems, it is preferable not to perform chromate treatment.

[Inorganic rich layer]
[Colloidal silica]
In the present invention, the inorganic rich layer needs to contain colloidal silica having an average particle size of 4 to 15 nm. Colloidal silica is concentrated at the interface with the galvanized layer, and the interaction between the silanol group (—SiOH) of silica (SiO ₂ ) and the galvanized surface (Zn—OH) causes the inorganic rich layer and the galvanized surface. Has the effect of improving the interfacial adhesion. Colloidal silica also has an effect of improving corrosion resistance. The colloidal silica in the film is eluted when the ambient pH is increased in a corrosive environment, and forms a mixed corrosion product of zinc hydrate. This mixed corrosion product exhibits a barrier effect and improves the corrosion resistance. In the present invention, since the organic rich layer described later exerts an action of slowing the elution rate of colloidal silica, it ensures a durable and excellent corrosion resistance (particularly the heel part), and also has blackening resistance and alkali degreasing resistance. Can be expressed.

In order to more effectively demonstrate the effect of such colloidal silica, the average particle diameter of the silica used is 4 to 15 nm. The corrosion resistance of the inorganic rich layer improves as the average particle size of silica decreases. It is considered that the corrosion resistance is further improved by densifying the inorganic rich layer and further improving the interfacial adhesion with the galvanized layer. From this point of view, the smaller the particle diameter of the silica particles, the better. However, when the particles are extremely fine, the above effect is saturated, so the lower limit of the particle diameter is 4 nm. Examples of the silica in the above range include Snowtex (registered trademark) 30 (average particle size: 10 to 15 nm), Snowtex (registered trademark) S (8 to 11 nm), and Snowtex (registered trademark) XS manufactured by Nissan Chemical Industries, Ltd. (4 to 6 nm), Snowtex (registered trademark) N (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) or the like can be used alone or in combination. The average particle diameter of the silica is preferably a nominal value in the catalog or a measurement method based on the Sears method (4 to 6 nm) or the BET method (4 to 20 nm).

As described above, the corrosion resistance of the inorganic rich layer improves as the silica particle size decreases. This is presumably because the silica has a large surface area and high activity, which is advantageous for elution of silica in a corrosive environment and formation of mixed corrosion products. From this viewpoint, it is preferable that 50% by mass or more of the colloidal silica included in the inorganic rich layer has an average particle diameter of 4 to 6 nm. Note that when the amount of colloidal silica having an average particle size of 4 to 6 nm included in the inorganic rich layer is gradually increased, there is no problem in the performance of the obtained aqueous two-layer coated metal plate, but the carboxyl in the first aqueous composition When amine or the like is used for neutralization of the group-containing polyurethane resin, silica and amine react, the balance of the charge in which colloidal silica is dispersed is lost, the viscosity of the first aqueous composition is increased, and gelation occurs. May occur. Therefore, when it is necessary to lengthen the pot life of the first aqueous composition, the “ST-30” (10 to 15 nm) or “ST-S” (8 to 11 nm) is used as a part of the colloidal silica. It is good to use. However, the total of these is preferably less than 50% by mass in 100% by mass of colloidal silica.

[Carboxyl group-containing polyurethane resin]
The inorganic rich layer of the present invention contains a carboxyl group-containing polyurethane resin. This is because the film cannot be formed only with colloidal silica. As the carboxyl group-containing polyurethane resin, a carboxyl group-containing polyurethane resin described in JP-A-2006-43913 can be suitably used. This carboxyl group-containing polyurethane resin is an aqueous dispersion of a polyurethane resin synthesized by essentially using a polyol having a carboxyl group. The raw materials include 1,4-cyclohexanedimethanol, polyol components such as polytetramethylene glycol having an average molecular weight of about 400 to 4000, a polyol having a carboxyl group such as dimethylolpropionic acid, tolylene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane. Isocyanate components such as diisocyanate are used. The chain extender is preferably a polyamine such as ethylenediamine.

A known method can be used to prepare an aqueous liquid of the carboxyl group-containing polyurethane resin used in the present invention. For example, the carboxyl group of the carboxyl group-containing urethane prepolymer is neutralized with a base, There are a method of emulsifying and dispersing to chain extension reaction, a method of emulsifying and dispersing a carboxyl group-containing polyurethane resin with high shear force in the presence of an emulsifier, and the like.

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

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

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

In addition, even if the carboxyl group-containing polyurethane resin is neutralized in the first aqueous composition, the amine used for neutralization is volatilized after the formation of the inorganic rich layer. Present as a resin.

[Silane coupling agent]
In the first aqueous composition used in the present invention, a glycidoxy group-containing silane coupling agent is blended at the terminal. This silane coupling agent further improves the adhesion between the metal plate surface and the inorganic rich layer. In addition, the silane coupling agent has a functional group that binds an inorganic component and an organic component, and is more reactive than other silane coupling agents. Bonding strength is strengthened, and it is effective in improving performance such as corrosion resistance and alkali degreasing resistance.

Examples of the silane coupling agent having a glycidoxy group at the terminal include γ-glycidoxypropyltrimethoxysilane and γ-glycidoxypropylmethyldiethoxysilane.

[First aqueous composition]
When forming the inorganic rich layer, a first aqueous composition in which colloidal silica, a carboxyl group-containing polyurethane resin, and a silane coupling agent are mixed is used. The first aqueous composition does not include a metal component other than the lithium-based inorganic compound, the phosphate compound, and lithium. Examples of the lithium-based inorganic compound include lithium silicate used in Patent Document 1, but lithium silicate is not preferable because it causes blackening (stain stain, discoloration). Further, in Patent Documents 2 and 3, the adhesion between the first layer and the plating layer is improved by using the phosphoric acid compound and the metal component and etching the surface of the plating layer. When the treatment is not carried out, the metal compound and phosphoric acid component remaining in the corrosive environment are eluted, performance deterioration such as corrosion resistance and alkali degreasing resistance occurs, and blackening or discoloration derived from the metal component occurs. For this reason, in this invention, metal components other than a lithium-type inorganic compound, a phosphoric acid compound, and lithium are not added to a 1st aqueous composition. However, as the colloidal silica, colloidal silica stabilized with sodium like the above-mentioned Snowtex (registered trademark) XS may be used, that is, a metal component may be contained. It means that a metal component other than the lithium-based inorganic compound, the phosphate compound and lithium is not added to the carboxyl group-containing polyurethane resin and the silane coupling agent.

In the first aqueous composition, the colloidal silica in the inorganic rich layer is 60 to 80 parts by mass (preferably 65 to 75 parts by mass), and the carboxyl group-containing polyurethane resin is 20 to 40 parts by mass (preferably 25 to 35 parts by mass). It can be prepared by mixing colloidal silica, an aqueous solution of a carboxyl group-containing polyurethane resin, and the silane coupling agent so that the silane coupling agent having a glycidoxy group at the terminal is 7.5 to 20 parts by mass. The description in this paragraph is the blending amount when the total amount of the two components of colloidal silica and carboxyl group-containing polyurethane resin is 100 parts by mass, that is, the amount of the silane coupling agent is colloidal silica and carboxyl. This is the blending amount when the total amount of the group-containing polyurethane resin is 100 parts by mass.

If there is too little colloidal silica, the desired corrosion resistance cannot be ensured. When there is too little carboxyl group-containing polyurethane resin, the formation of the film becomes non-uniform. If the amount of the silane coupling agent is too small, the effect of improving the adhesion between the metal plate surface and the inorganic rich layer becomes insufficient, and the reactivity between the colloidal silica and the polyurethane resin also decreases, so that the corrosion resistance, tape peel resistance, Alkali degreasing resistance, blackening resistance, etc. deteriorate. On the other hand, when there are too many silane coupling agents, the time-dependent stability of a 1st aqueous composition will fall and it will become disadvantageous also in terms of cost.

[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 μm. Even when the inorganic rich layer of the present invention is an extremely thin film having a thickness of 0.01 μm, an effect of improving the adhesion with the galvanized layer is recognized. However, when it is thinner than 0.01 μm, the formation of the film becomes non-uniform, 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 rich layer exceeds 0.1 μm, cohesive failure occurs inside the film, and as a result, the film remaining rate when the tape peel resistance test is performed is significantly reduced. In order to ensure conductivity, it is necessary to suppress the total film thickness to 0.6 μm or less (described later), but when the thickness of the inorganic rich layer exceeds 0.1 μm, the organic rich layer with respect to the total film thickness The film thickness of the (second layer) must be reduced, and the corrosion resistance, blackening resistance, and alkali degreasing resistance are reduced due to a decrease in barrier properties. The film thickness of the inorganic rich layer is preferably 0.02 to 0.08 μm, more preferably 0.03 to 0.06 μm.

[Formation of inorganic rich layer]
The inorganic rich layer is heated by applying the first aqueous composition to one or both surfaces of the metal plate surface using a known coating method, that is, a bar coater method, a roll coater method, a spray method, a curtain flow coater method, or the like. What is necessary is just to dry. The heating temperature may be such that water is volatilized.

[Thickness of organic rich layer]
Next, the organic rich layer as the second layer will be described. The organic rich layer has a function of ensuring barrier properties, slowing the elution rate of silica, and maintaining corrosion resistance. When the present inventors investigated the relationship between the total film thickness of the inorganic rich layer and the organic rich layer and conductivity, 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 rich layer constant at 0.06 μm. What is required as an electromagnetic wave countermeasure is that the total film thickness must be 0.6 μm or less because the conductivity when measured by a two-probe method using a surface resistance meter is less than 0.5Ω. It was.

Therefore, the organic rich layer is 0.2 to 0.5 μm. 0.3 to 0.5 μm is preferable, and 0.35 to 0.45 μm is more preferable. When the organic rich layer is thinner than 0.2 μm, the barrier property is lowered, the corrosion resistance and the alkali degreasing resistance are lowered, and further, the lubricity is lowered. On the other hand, when the film thickness of the organic rich layer exceeds 0.5 μm, the conductivity is remarkably deteriorated.

[Organic resin of organic rich layer]
The organic rich layer is formed from a second aqueous composition containing an organic resin. Although it does not specifically limit as this organic resin, It is preferable that it is resin which can produce the film of water vapor permeability of 100 g / m < ² > / day or less. The water vapor permeability was obtained by applying an organic resin or a second aqueous composition on a copy paper so that the film thickness after drying with a bar coater was 18 μm, and drying at 105 ° C. for 2 minutes. Was measured by a cup method according to JIS Z0208 using a sample left standing for a whole day and night as a sample.

If the resin can produce a film having a water vapor permeability of 100 g / m ² / day or less, the barrier property of the organic rich layer can be secured, and the elution rate of colloidal silica can be further reduced. In the case of an organic resin that becomes a film having a water vapor permeability of more than 100 g / m ² / day, when colloidal silica is added to the second aqueous composition in an amount exceeding 30% by mass in anticipation of an improvement effect such as corrosion resistance, The water vapor permeability increases to 5000 g / m ² / day or more, which is not preferable because the corrosion resistance and the like are greatly deteriorated. A more preferable water vapor permeability is 50 g / m ² / day or less.

In addition, for example, colloidal silica (average particle diameter of 4 to 6 nm) is added to a second aqueous composition containing an organic resin having a water vapor permeability of 50 g / m ² / day, in terms of solid content of the second aqueous composition. ) When added, the water vapor permeability of the organic rich layer is about 1500 g / m ² / day, but an effect of improving corrosion resistance or the like was observed. Furthermore, the water vapor permeability of the organic rich layer tends to be reduced by the addition of a cross-linking agent described later, the above-described silane coupling agent, and the like, which can improve corrosion resistance, alkali degreasing resistance, blackening resistance, and the like. it can.

The organic resin preferably satisfies the water vapor permeability described above, but an ethylene-unsaturated carboxylic acid copolymer is particularly preferable. 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, and the like. A copolymer can be obtained by polymerization using a legal method or the like.

The copolymerization ratio of unsaturated carboxylic acid to ethylene is preferably 10 to 40% by mass of unsaturated carboxylic acid when the total amount of monomers is 100% by mass. When the amount of unsaturated carboxylic acid is less than 10% by mass, there are few carboxyl groups that serve as base points for intermolecular association by ion clusters or cross-linking points with cross-linking agents. The alkali degreasing resistance may be insufficient, and the emulsion stability of the emulsion composition is inferior. A more preferable lower limit of the unsaturated carboxylic acid is 15% by mass. On the other hand, when the unsaturated carboxylic acid exceeds 40% by mass, the organic rich layer is inferior in corrosion resistance and water resistance, and the alkali degreasing resistance is also deteriorated. A more preferred upper limit is 25% by mass.

Since the ethylene-unsaturated carboxylic acid copolymer has a carboxyl group, it can be emulsified (aqueous dispersion) by neutralization with an organic base or metal ion. In the present invention, it is preferable to use an amine as the organic base, and any of the above-described amines can be used, and triethylamine is particularly preferable. Monovalent metal ions are also preferably used in combination with amines. The amine is preferably used in an amount of 0.2 to 0.8 mol (20 to 80 mol%) based on 1 mol of the carboxyl group in the ethylene-unsaturated carboxylic acid copolymer. It can be seen that the amount of monovalent metal ions affects the water vapor permeability, and if the amount of monovalent metal compound used increases, the affinity between the resin and water increases, and the water vapor permeability increases. The amount is preferably 0.02 to 0.2 mol (2 to 20 mol%) based on 1 mol of the carboxyl group in the ethylene-unsaturated carboxylic acid copolymer. In addition, since excessive alkali content causes deterioration of corrosion resistance, the total amount of amines and metal ions used is 0.3 to 1 per mol of the carboxyl group in the ethylene-unsaturated carboxylic acid copolymer. It is good to set it as the range of 0 mol. The metal compound for imparting monovalent metal ions is preferably NaOH, KOH, LiOH or the like, and NaOH is most preferable because of its 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 by ion clusters (ionomerization), and has excellent corrosion resistance and tape peel resistance. An organic rich layer is formed. However, in order to form a tougher film, it is desirable to crosslink the polymer chains by chemical bonding utilizing a reaction between functional groups. As the crosslinking agent, a glycidyl group-containing crosslinking agent or an aziridinyl group-containing crosslinking agent is preferable.

Examples of glycidyl group-containing crosslinking agents include sorbitol polyglycidyl ether, (poly) glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether, (poly) ethylene glycol diglycidyl ether, etc. Glycidyl group-containing crosslinking agents such as polyglycidyl ethers and polyglycidylamines.

As the aziridinyl group-containing crosslinking agent, 4,4′-bis (ethyleneiminecarbonylamino) diphenylmethane, N, N′-hexamethylene-1,6-bis (1-aziridinecarboxamide), N, N′-diphenylmethane— Bifunctional aziridine compounds such as 4,4′-bis (1-aziridinecarboxamide) and toluenebisaziridinecarboxyamide; tri-1-aziridinylphosphine oxide, tris [1- (2-methyl) aziridinyl] phosphine oxide, 3 such as trimethylolpropane tris (β-aziridinylpropionate), tris-2,4,6- (1-aziridinyl) -1,3,5-triazine, tetramethylpropanetetraaziridinylpropionate, etc. More functional or more aziridine compounds or their derivatives It is below.

[wax]
Since the water-based two-layer coated metal plate of the present invention may be subjected to processing with the organic rich layer as the outermost surface, it is preferable that the organic rich layer contains a wax in order to improve processability. Industrially preferred are spherical polyethylene wax, polypropylene wax, modified wax, copolymer wax with ethylene and propylene, ethylene copolymer wax, oxides thereof, derivatives with carboxyl groups, etc. Examples thereof include paraffinic wax and carnauba wax provided with acid groups. As the wax, spherical polyethylene wax is most suitable. For example, “Daijet E-17” (manufactured by Kyoyo Chemical Co., Ltd.), “KUE-1”, “KUE-5”, “KUE-8” (Sanyo Chemical Industries) "W-100", "W-200", "W-300", "W-400", "W-500", "W-640" of "Chemipearl" series (Mitsui Chemicals) Commercial products such as “W-700” and “Elepon E-20” (manufactured by Nikka Chemical Co., Ltd.) can be preferably used.

[Second aqueous composition]
The second aqueous composition preferably contains colloidal silica having an average particle diameter of 4 to 6 nm. However, if the amount is too large, the water vapor permeability is inferior as described above. Therefore, in the second aqueous composition, the ethylene-unsaturated carboxylic acid copolymer (solid content) is 57 to 83% by mass, the colloidal silica having an average particle diameter of 4 to 6 nm is 10 to 30% by mass, and the aziridinyl group-containing crosslink It is preferable to add 5 to 8% by mass of the agent and 2 to 5% by mass of the spherical polyethylene wax. In addition, the sum total of these 4 components shall be 100 mass%.

If necessary, it is preferable to emulsify the components together or separately and mix them as an aqueous dispersion. The method for applying the second aqueous 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 flow coater method, or the like can be employed. After coating, it is preferable to heat and dry at about 80 to 130 ° C.

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.

Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are not intended to limit the present invention, and modifications that do not depart from the spirit of the present invention are included in the present invention. Hereinafter, “part” indicates “part by mass”, and “%” indicates “% by mass”. Moreover, the evaluation method used in the Example is as follows.

[Evaluation methods]
(1) Corrosion resistance 1: Salt spray test (SST flat plate, SST cross cut)
For the specimen with the back and edge seals, make a flat plate and a crosscut with a cutter knife, and perform a 5% salt spray test in an atmosphere of 35 ° C according to JIS Z2371. The time until the white rust occurrence rate reached 5% (area) was measured.

Evaluation of SST plate ◎: 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 crosscut ◎: 120 hours or more ○: 96 hours or more, 120 hours Less than △: 72 hours or more, less than 96 hours ×: Less than 72 hours

(2) Corrosion resistance 2: Salt spray cycle test (SST cycle)
The edge-sealed specimen (flat plate) was subjected to a salt spray cycle test in accordance with JIS Z2371, and the number of cycles at which the white rust generation rate reached 5% was measured. In one cycle, salt spray was performed for 8 hours (35 ° C.) and salt spray was stopped for 16 hours (35 ° C.).

Evaluation of SST cycle ◎: 10 cycles or more ○: 7 cycles or more, less than 10 cycles △: 5 cycles or more, less than 7 cycles ×: Less than 5 cycles

(3) Corrosion resistance 3: Neutral salt spray cycle test (JASO)
The edge-sealed specimen (flat plate) was subjected to a neutral salt spray cycle test in accordance with JIS H8502, and the number of cycles in which the white rust generation rate reached 5% was measured. In one cycle, salt spray was performed for 2 hours, drying (60 ° C., humidity 30% or higher) for 4 hours, and wet (50 ° C., humidity 95% or higher) for 2 hours.

JASO evaluation ◎: 21 cycles or more ○: 15 cycles or more, less than 21 cycles △: 9 cycles or more, less than 15 cycles ×: less than 9 cycles

(4) Conductivity The surface resistance of each test material is measured directly using a surface resistance measuring device (LorestaEP; Dia Instruments (currently Mitsubishi Chemical Analytech)) without a copper plate (2-probe AP probe type A). The pin spacing was 10 mm, the spring pressure was 240 g / piece, the pin tip diameter was 2 mmφ, and a schematic diagram of the surface resistance measuring device is shown in FIG. .

Evaluation of conductivity ◎: Less than 0.05Ω ○: 0.05Ω or more, less than 0.50Ω △: 0.50Ω or more, less than 1.00Ω ×: 1.00Ω or more

(5) Tape peeling resistance Adhesive tape (filament tape No. 9510 manufactured by Sliontec Co., Ltd .; rubber adhesive) was affixed to the test material, and 120 hours in an atmosphere of 40 ° C. and 98% humidity using a constant temperature and humidity test device. After storage, the tape was subjected to a peel test according to JIS K5400, and the residual rate (area) of the film was measured.

Evaluation of film remaining ratio ◎: 95% or more ○: 90% or more, less than 95% △: 80% or more, less than 90% ×: less than 80%

(6) Blackening resistance After the test material was stored for 168 hours in a constant temperature and humidity test apparatus at 50 ° C. and humidity of 98% or more, the appearance (black / stained / stained / not stained) was observed before and after the test, and the color change was measured. The color difference (ΔE) was calculated.

Appearance evaluation before and after the test ◎: No change before and after the test ○: Slightly blackened, no stain stain △: Slightly blackened, stain stain ×: Black change / stained stain Color difference (ΔE) evaluation ◎ : ΔE is less than 1 ○: ΔE is 1 or more and less than 2 Δ: ΔE is 2 or more and less than 3 ×: ΔE is 3 or more

(7) Lubricity (dynamic friction coefficient)
The dynamic friction coefficient of each test material was measured using the friction coefficient measuring apparatus shown in FIG. The size of the test material was 40 mm × 300 mm, the applied pressure was 4.5 MPa, the drawing speed was 300 mm / min, and no oil was applied. The material of the flat plate die was SKD11. The dynamic friction coefficient μ is F / 2P.

Evaluation of lubricity ◎: μ = 0.09 or less ○: 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 degreasing resistance The test material was immersed in an alkaline degreasing agent (CL-N364S) 20 g / liter (liquid temperature 65 ° C.) manufactured by Nihon Parkerizing Co., Ltd. for 2 minutes, pulled up, washed with water, dried, Edge sealing was performed, a salt spray cycle test (SST cycle flat plate) according to JIS Z2371 was performed, and the number of cycles until the white rust generation rate reached 5% was measured. One cycle was 5% salt spray 8 hours (35 ° C.) and salt spray rest 16 hours (35 ° C.).

◎: 7 cycles or more ○: 5 cycles or more, less than 7 cycles △: 3 cycles or more, less than 5 cycles ×: Less than 3 cycles

Synthesis example 1
Synthesis of carboxyl group-containing polyurethane resin aqueous dispersion 60 parts of polytetramethylene ether glycol (average molecular weight 1000; manufactured by Hodogaya Chemical Co., Ltd.) as a polyol component was added to a synthesizer equipped with a stirrer, thermometer and temperature controller. 1,4-cyclohexanedimethanol and 20 parts of dimethylolpropionic acid were added, and 30 parts of N-methylpyrrolidone was added as a reaction solvent. 104 parts of tolylene diisocyanate (TDI) was added as an isocyanate component, heated to 80 ° C. to 85 ° C., and reacted for 5 hours. The obtained prepolymer had an NCO content of 8.9%. Further, 16 parts of triethylamine was added for neutralization, a mixed aqueous solution of 16 parts of ethylenediamine and 480 parts of water was added, and a chain extension reaction was carried out while emulsifying at 50 ° C. for 4 hours to obtain an aqueous polyurethane resin dispersion (nonvolatile). Resin component 29.1%, acid value 41.4). This is designated as resin A. The water vapor permeability of Resin A was 1500 g / m ² / day.

Synthesis example 2
Synthesis of ethylene-unsaturated carboxylic acid copolymer aqueous dispersion 1
To an autoclave having an emulsification facility 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. Add 40 mol% of triethylamine and 15 mol% of sodium hydroxide to 1 mol of carboxyl group of the acrylic acid copolymer, stir at 150 ° C and 5 Pa at high speed, cool to 40 ° C, and then add ethylene-acrylic acid A copolymer emulsion was obtained. Here, 4,4′-bis (ethyleneiminocarbonylamino) diphenylmethane (manufactured by Nippon Shokubai Co., Ltd., “Chemite (registered trademark) DZ-22E”) was added to a solid content of 100 parts of ethylene-acrylic acid copolymer by 5 parts. The resin added was partly added. The water vapor permeability of this resin B was 50 g / m ² / day.

Synthesis Examples 3 and 4
Synthesis of aqueous dispersions of ethylene-unsaturated carboxylic acid copolymer, part 2 and part 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% with respect to 1 mol of the carboxyl group of the ethylene-acrylic acid copolymer in Synthesis Example 2. Resin D was obtained by adding 30 mol% of sodium hydroxide. 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
Colloidal silica having an average particle size of 4 to 6 nm (manufactured by Nissan Chemical Industries, Ltd., “Snowtex (registered trademark) XS”) 55 to 85 parts, a carboxyl group-containing polyurethane resin aqueous dispersion prepared in Synthesis Example 1 (resin A ) In the range of 15 to 45 parts, and 15 parts by mass of silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., KBM403 (glycidoxy group-containing silane coupling agent)) is added to 100 parts by mass of the total solid content. A first aqueous composition was prepared.

As the metal plate, an electrogalvanized steel plate (zinc adhesion amount 20 g / m ² , plate thickness 0.8 mm) was used. The first aqueous composition was applied to one side with a bar coater and dried at a plate temperature of 90 ° C. An inorganic rich layer having a thickness of 0.06 μm was formed. The film thickness was calculated by quantitatively measuring the Si element of colloidal silica (SiO ₂ ) in the film with a fluorescent X-ray analyzer. At this time, the specific gravity of SiO ₂ was calculated as 2.2 and the specific gravity of the resin as 1.

30 parts of colloidal silica having an average particle size of 4 to 6 nm with respect to 59 parts of the solid content of the resin B prepared in Synthesis Example 2, and a glycidyl group-containing crosslinking agent (“Epiclon (registered trademark)” manufactured by DIC) CR5L ") and 7.5 parts of spherical polyethylene wax (Mitsui Chemicals," Chemical (registered trademark) W640 ") were added to prepare a second aqueous composition. This is coated on the inorganic rich layer on the galvanized steel sheet with a bar coater in the same manner as the inorganic rich layer, and coated and dried so that the film thickness after drying is 0.4 μm to form an organic rich layer. Thus, an aqueous two-layer coated metal plate was obtained. The evaluation results are shown in Table 1.

In addition, RunNo. 6 and 7 are examples in which the amount of colloidal silica is outside the scope of the present invention. In addition, RunNo. 8 and 9 are 45 parts of an aqueous solution of aluminum biphosphate (manufactured by Nippon Chemical Industry Co., Ltd., solid content 50%) and acidic colloidal silica (Snowtex (registered trademark) ST-O; average particle size 10 to 15 nm) as an inorganic rich layer. A surface treatment agent mixed with 55 parts was applied with a spray ringer apparatus, then washed with water and dried to give a base treatment (about 10 nm). On top of that, an organic rich layer was formed in the same manner as described above. RunNo. No. 8 has a total film thickness of 0.46 μm, Run No. The total film thickness of 9 was 1.0 μm. The evaluation results are shown in Table 1.

Table 1 shows that when the amount of colloidal silica in the inorganic rich layer is small, the tape peel resistance, which is an index of adhesion to the plating layer, is inferior (Run No. 6). On the other hand, when the amount of colloidal silica was too large, the polyurethane resin was relatively decreased and the formation of the film was incomplete, and various performances were reduced (Run No. 7).

Experimental example 2
Add 30 parts of resin A in solids to 70 parts of Snowtex XS with an average particle size of 4 to 6 nm, and add KBM403 to 5 to 25 parts of the total 100 parts. Thus, a first aqueous composition was prepared. In the same manner as in Experimental Example 1, an inorganic rich layer having a 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, an organic rich layer having a thickness of 0.4 μm was formed on the inorganic rich layer. The evaluation results are shown in Table 2.

From Table 2, if the amount of the silane coupling agent in the inorganic rich layer is small, the effect of improving the adhesion to the plating layer becomes insufficient, and the reactivity between the silica and the polyurethane resin also decreases. And alkali degreasing resistance deteriorated (Run No. 14). On the other hand, when the amount of the silane coupling agent was too large, various performances were reduced (Run No. 15).

Experimental example 3
30 parts of Resin A was added as solids to 70 parts of the above-mentioned Snowtex XS having an average particle size of 4 to 6 nm, and 15 parts of the above KBM403 was added to the total of 100 parts. A 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, an organic rich layer having a thickness of 0.4 μm was formed on the inorganic rich layer. The evaluation results are shown in Table 3.

From Table 3, when the film thickness of the inorganic rich layer is too thin, the film formation of the inorganic rich layer becomes non-uniform or the absolute amount of silica that contributes to the adhesiveness is insufficient, so that the adhesiveness deteriorates (Run No. 21). On the other hand, when the film thickness of the inorganic rich layer was too thick, various performances decreased (Run No. 22).

Experimental Example 4
To the above-mentioned 70 parts of Snowtex XS having an average particle diameter of 4 to 6 nm, Snowtex ST-S (manufactured by Nissan Chemical Industries, Ltd.) having an average particle diameter of 8 to 11 nm and / or Snowtex ST-30 having an average particle diameter of 10 to 15 nm is used. (Nissan Chemical Industry Co., Ltd.) was added at the ratio shown in Table 4, and 30 parts of Resin A was added as a solid content to a total of 70 parts of this silica. A first aqueous composition was prepared by adding 15 parts of KBM403. Thereafter, in the same manner as in Experimental Example 1, an inorganic rich layer and an organic rich layer were formed on the surface of the electrogalvanized steel sheet in this order. The evaluation results are shown in Table 4.

From Table 4, when colloidal silica having a large average particle diameter was used, there was a tendency for the performance to slightly decrease.

Experimental Example 5
30 parts of Resin A was added as solids to 70 parts of the above-mentioned Snowtex XS having an average particle size of 4 to 6 nm, and 15 parts of the above KBM403 was added to the total of 100 parts. A composition was prepared. In the same manner as in Experimental Example 1, an inorganic rich layer having a thickness of 0.06 μm was formed on the electrogalvanized steel sheet.

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 changed between 0.1 and 0.6 μm. The evaluation results are shown in Table 5.

When the thickness of the organic rich layer was thin, the effect of suppressing the elution of colloidal silica was not exhibited, and various performances were reduced (Run No. 37). When the organic rich layer was thick, only the conductivity decreased (Run No. 38).

Experimental Example 6
In the same manner as in Experimental Example 1, an inorganic rich layer was formed. 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 the resin A having a high water vapor permeability was used, the corrosion resistance tended to be inferior (Run No. 42).

According to the present invention, it is possible to provide an aqueous two-layer coated metal sheet having good conductivity, excellent adhesion, blackening resistance, alkali degreasing resistance, and persistent corrosion resistance (particularly a buttock). did it.

Therefore, the aqueous two-layer coated metal plate of the present invention is useful for home appliances and the like that require countermeasures against electromagnetic waves.

Claims

A metal plate in which two layers of thin films are laminated on at least one surface of the 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 group at the terminal are used as the colloidal silica and carboxyl group-containing polyurethane resin. The film thickness formed from the first aqueous composition containing 7.5 to 20 parts by mass with respect to a total of 100 parts by mass and containing no metal component other than lithium-based inorganic compound, phosphate compound and lithium is 0.01 to 0 An inorganic rich layer having a thickness of 0.2 to 0.5 μm formed from a second aqueous composition containing an organic resin on the inorganic rich layer, An aqueous two-layer coated metal sheet characterized in that the total film thickness with the organic rich layer is 0.25 to 0.6 μm.
The aqueous two-layer coated metal plate according to claim 1, wherein 50% by mass or more of the colloidal silica in the first aqueous composition 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 a water vapor permeability of a film obtained from the organic resin contained in the second water-based composition is 100 g / m 2 / day or less.