JP6533910B2 - Metal surface coating composition and metal material using the composition - Google Patents

Description

  The present invention relates to a heat resistant gas barrier coating composition on a metal surface, and more particularly to a heat resistant gas barrier coating composition on a metal surface using a smectite clay mineral and a metal material having the coating film.

  Various metal materials including stainless steel are widely used in industrial equipment of plants, precision machinery parts and electronic parts. However, the metal material is generally protected by a coating because the surface may be oxidized or discolored when exposed to high temperatures.

  In general, a paint containing resin or silicone is used to protect the surface of the metal material. Although these exhibit excellent anticorrosion performance, when used continuously in a temperature range of 200 ° C. to 400 ° C., the resin and silicone deteriorate and sufficient performance can not be obtained. Furthermore, in the high temperature range of about 600 ° C. or more, the organic matter is decomposed and burned, and is separated from the metal material. There is no resin-based paint or silicone-based paint that forms a protective film that can be used in such a high temperature range.

  As paints which can form a usable coating film in a high temperature range, glass paints and ceramic paints which have water glass as a main ingredient are known. Since these are coated with glass on the material surface, they have excellent heat resistance and corrosion resistance. For example, in JP 2007-314875 A and JP 2012-92207 A, it is proposed to form a coating film having heat resistance of 1000 ° C. or more by a paint obtained by blending glass frit and ceramic with water glass. ing.

  A film formed of glass paint or ceramic paint has high gas barrier properties, but since fine powder frit and ceramic powder are compounded, if it does not dry for a sufficiently long time, gas is generated during firing and the coating Sometimes it breaks. Moreover, when coating on a metal thin film or the like, flexibility in accordance with the flexibility of the thin film is required. However, a coating film which is not stretchable and is weak in impact resistance like a glass coating has a problem that it is easily cracked and can not exhibit sufficient performance.

  JP 2005-313604, JP 2006-077237, JP 2006-188408, JP 2006-188418, JP 2006-265088, JP 2007-277078, etc. It has been disclosed to form flexible films using layered clay minerals which are widely used as thickeners, which are easily dispersed and swollen in water to increase the viscosity of the liquid.

In the above-mentioned patent documents, a free standing film of layered clay mineral is obtained by applying the fact that layered clay minerals overlap each other to become a film when the dispersion of layered clay mineral dries.
According to the technique disclosed in the above-mentioned patent documents, a free standing film having excellent gas barrier properties can be produced by using a layered clay mineral. The self-standing film has high gas barrier performance, but since the polymer resin is blended in order to maintain the strength and flexibility of the film, the heat resistance is only up to about 350 ° C. Further, the form of the film is a self-supporting film or composite material of a layered clay mineral containing a resin, which can not form a coating film in close contact with a metal.

  Moreover, the manufacturing method of the film | membrane which has the heat resistance of 1000 degreeC formed of the layered clay mineral is disclosed by Unexamined-Japanese-Patent No. 2005-104133. According to the preparation method, it is possible to form a clay thin film consisting only of natural or synthetic layered clay mineral. However, it is not possible to form a coating film having peel resistance that is firmly in close contact with the metal surface.

  The present invention is a metal coating film which could not be achieved by the prior art, that is, a coating film having heat resistance and flexibility of 450 ° C. or higher, excellent peeling resistance, and gas barrier properties for preventing oxidation. It is an object of the present invention to provide a novel metal surface coating composition which can be easily formed, and a metal material having a coating film according to the composition.

  As a result of intensive studies to achieve the above object, the present inventors have found that a coating composition containing a low viscosity smectite clay mineral, a water soluble organic solvent and a surfactant has an interface with the water soluble organic solvent. Due to the presence of the activator, the low viscosity smectite clay mineral adheres firmly to the metal surface simply by coating, and forms a film having excellent peel resistance and flexibility and impact resistance. The present invention has been completed.

That is, the present invention is based on the above findings, and the metal surface coating composition of the present invention contains a low viscosity smectite clay mineral, a water-soluble organic solvent, and a surfactant.
And 80 mass% or more and less than 100 mass% of the above-mentioned inorganic material is contained in solid content,
The above inorganic material contains 70 mass% or more of low viscosity smectite clay mineral,
The low viscosity smectite clay mineral is a smectite clay mineral having a viscosity (25 ° C.) of 10 to 150 mPa · s when dispersed in water at 20% by mass .

In addition, the metal material of the present invention has a coating film obtained by drying or baking a coating film of a metal surface coating composition containing an inorganic material, a water-soluble organic solvent, and a surfactant .
And the said metal surface coating composition contains 80 mass% or more and less than 100 mass% of said inorganic materials in solid content,
The above inorganic material contains 70 mass% or more of low viscosity smectite clay mineral,
The low viscosity smectite clay mineral is a smectite clay mineral having a viscosity (25 ° C.) of 10 to 150 mPa · s when dispersed in water at 20% by mass .

  According to the metal surface coating composition of the present invention, since it contains a water-soluble organic solvent, a surfactant, and a low viscosity smectite clay mineral, it adheres firmly to the surface of a metal substrate to be resistant to peeling and resistance. The metal surface coating composition which can form the protective film which is excellent in impact property and is further excellent in heat resistance and gas-barrier property can be provided.

  Moreover, according to the metal material of this invention, the metal material protected by the coating film which is excellent in heat resistance and gas-barrier property can be provided.

It is the schematic which shows the state in which the smectite clay mineral was laminated | stacked.

The metal surface coating composition of the present invention will be described in detail.
The metal surface coating composition of the present invention contains a smectite clay mineral containing a low viscosity smectite clay mineral, a water-soluble organic solvent, and a surfactant, and optionally contains other additives.

The smectite clay mineral is coated uniformly by improving the affinity to the metal surface with a water-soluble organic solvent, and further improving the film formability with a surfactant to make it adhere to the metal surface to have gas barrier properties and heat resistance. To form a coating film having conductivity.
The smectite clay mineral is a layered clay mineral, and has a plate-like or disc-like particle (hereinafter, simply referred to as "plate-like particle") layered structure. The plate-like particles are oriented by drying the aqueous dispersion of the layered clay mineral, and they are bonded to each other by van der Waals force and coulomb force, and the plate-like particles 2 are formed on the metal substrate 1 as shown in FIG. Forms a coating film of a laminated structure.
Therefore, the gap between the plate-like particles forms a winding path so as to stitch between the plate-like particles and inhibits the movement of molecules and particles, so that the coating film containing smectite clay mineral has high gas barrier properties. is there.

  In addition, since the thermal decomposition temperature of the smectite clay mineral is about 700 ° C., a coating film which is more excellent in heat resistance than a coating film containing a resin is formed.

The smectite clay mineral has a layered structure in which primary particles having a thickness of about 1 nm are stacked.
As smectite clay minerals, for example, saponite, hectorite, sauconite, Stephenite, Swin hordeite, montmorillonite, beidellite, nontronite, and volconstite can be mentioned. Among them, hectorite, Stevensite, and montmorillonite have excellent film forming properties and can be preferably used. These may be either synthetic or natural products, but are preferably synthetic products with controlled primary particle size.

When the smectite clay mineral is dispersed in the aqueous phase, the plate surface of the plate-like particles bears a negative charge, the ions between the plate-like primary particles are hydrated, and the distance between the primary particles is broadened. Electrostatic repulsion occurs, and the layered smectite clay mineral is subdivided into plate-like primary particles. And, since the plate-like particles which approach each other electrostatically repel each other, the smectite clay mineral forms a low viscosity sol. However, it becomes a gel of high viscosity with the passage of time, which makes coating difficult.
That is, the plate-like particle has a weak positive charge at the edge, and this positive charge interacts with the negative charge of the plate face of the adjacent plate-like particle to form a cardhouse structure by ion bonding and gelation. I will.

The present invention is characterized by using a low viscosity smectite clay mineral which is not gelled and maintained in a low viscosity sol state even when dispersed in an aqueous phase.
Smectite clay minerals, resulting in gelation to form a mosquito Dohausu structure in water as described above. The above-mentioned gel is thixotropic and can be used as a coating solution by restoring fluidity by re-stirring, but it takes labor for re-stirring or gelation during coating to cause smears. It is preferable to use a low viscosity smectite clay mineral which is stable in the low viscosity sol state over a long period of time even when dispersed in water.

The low viscosity smectite clay mineral is for gelation is inhibited, Der as it can disperse the smectite clay mineral with a high concentration of more than 20 wt% is, when dispersed 20 weight% in water The viscosity (25 ° C) of is 10 to 150 mPa · s.

  The low viscosity smectite clay mineral is generally marketed, and Laponite S482, Laponite SL25 (all manufactured by ROCKWOOD Co., Ltd.), etc. can be used.

  Examples of low viscosity smectite clay minerals include those modified with a modifier and those modified with an anionic water-soluble polymer or a cationic water-soluble polymer, for example, It is disclosed in Japanese Patent Application Publication No. 9-503480, U.S. Patent No. 5015334, and U.S. Patent No. 5582638.

  Examples of the modifier include those containing salts of low molecular weight amines, phosphate compounds, phosphonic acids and derivatives thereof.

  Examples of the anionic water-soluble polymer include polyacrylic acid and polymethacrylic acid, and examples of the cationic water-soluble polymer include polyethylene imines and polyamide amines. Moreover, as an organic acid which is a compound with said amine, a formic acid, an acetic acid, etc. can be mentioned, for example.

  Examples of the above-mentioned phosphate compounds include tripolyphosphoric acid, hexametaphosphoric acid, sodium salts and potassium salts of pyrophosphoric acid. As phosphonic acid and its derivative, sodium salt, potassium salt, ammonium salt, amine salt of phosphonic acid and its derivative can be mentioned.

The particle diameter of the smectite clay mineral generally has a primary particle diameter (median diameter) of 10 nm to 500 nm, but the primary particle diameter (median diameter) of the low viscosity smectite clay mineral of the present invention is 10 nm to 150 nm. preferable. When the primary particle diameter (median diameter) is within the above range, film formability and peel resistance are improved.
It is not clear why the film forming property and the peel resistance are improved if the particle size is within the above range, but the particles having the above particle size are combined with the above-mentioned gelation suppressing effect, It is thought that this is because the fine unevenness is caught and caught.

  The particle size of the smectite clay mineral can be measured by a dynamic light scattering method or a laser diffraction scattering method. An aqueous dispersion of a smectite clay mineral is prepared by strong stirring using a homodisper or an ultrasonic generator or the like, and the particle diameter is measured by a dynamic light scattering method or a laser diffraction scattering type measuring device. The particle size measurement results are displayed on a volume basis.

The content of the low viscosity smectite clay mineral in the metal surface coating composition of the present invention is preferably 1% by mass to 30% by mass, more preferably 5% by mass to 20% by mass, and further preferably 10 It is preferable that it is mass% or more and 15 mass% or less.
Even a dispersion of less than 1% by mass can be uniformly coated on a metal surface, but there is a risk that a sufficient thickness can not be obtained for the coating and the gas barrier properties may be reduced. If it exceeds 30% by mass, it is difficult to completely wet the clay mineral, and it may precipitate without fully hydrating, and it may not be a low viscosity sol.

The metal surface coating composition of the present invention can contain other layered clay minerals according to the purpose as long as the coatability to the metal surface is not impaired.
Other layered clay minerals include high aspect ratio natural smectite clay minerals and the like. By containing a natural smectite clay mineral having a high aspect ratio and a primary particle diameter (median diameter) of 100 nm to 500 nm, the flexibility of the coating film can be improved, and cracking can be prevented.

<Water-soluble organic solvent>
The water-soluble organic solvent imparts affinity to the metal surface coating composition to the metal base surface, prevents repelling and occurrence of coating unevenness, and improves the drying property of the metal surface coating composition. .
The metal surface itself is hydrophilic, but by storing the metal base in the air, organic substances (hydrocarbons) and the like present in the air are adsorbed on the metal base surface and become hydrophobic. Therefore, by containing the water-soluble organic solvent having an organic group, the affinity to the metal surface is improved, and the coating property is improved.
In addition, since the water-soluble organic solvent has volatility, the drying property is improved, and generation of gas inside the film at the time of baking of the coating film is prevented, and peeling of the film is prevented. The adhesion is improved and the gas barrier property is improved.

Examples of the water-soluble solvent include alcohol solvents such as methyl alcohol, ethyl alcohol, isopropanol, butanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether And glycol ether solvents such as acetone and ketone solvents such as acetone and methyl ethyl ketone. These may be used alone or in combination of two or more.
Among them, glycol ether solvents can be preferably used because they have a high flash point and excellent safety and have a viscosity reducing effect, and particularly, ethylene glycol monobutyl ether can be preferably used.

  Although the content of the water-soluble organic solvent in the metal surface coating composition depends on the water-soluble organic solvent to be contained, it is preferably 1% by mass to 30% by mass, and 3% by mass to 10% by mass Is preferred. If the amount is less than 1% by mass, repelling may occur or the drying property may be reduced. If the amount is more than 30% by mass, the dispersibility of the low viscosity smectite clay mineral may be reduced to precipitate.

<Surfactant>
The surfactant reduces the surface energy of the metal surface coating solution, improves the wettability to the metal material surface, and improves the adhesion and film forming property of the coating film. By containing the surfactant, a uniform and thin coating film can be formed.

  The surfactant is not particularly limited as long as it does not inhibit the inhibition of gelation of the low viscosity smectite clay mineral, and among them, nonionic surfactants are most preferable. Nonionic surfactants are particularly preferred because they do not become ions and do not affect the dispersion state of the low viscosity smectite clay mineral.

  The nonionic surfactant may be an ester type, an ether type, or an ester / ether type having both an ester bond and an ether bond in the molecule, but having an HLB value of 4 to 16 preferable.

  Examples of the nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, sucrose ester, polyoxyethylene ether of glycerin ester, The polyoxyethylene ether of sorbitan ester, the polyoxyethylene ether of sorbitol ester, etc. are mentioned, You may mix and use these 1 type, or 2 or more types.

The content of the surfactant in the metal surface coating composition is preferably 0.1% by mass to 5% by mass, and more preferably 0.2% by mass to 3% by mass.
If the amount is less than 0.1% by mass, the wettability to the metal material surface may not be sufficient and coating defects may occur. If the amount exceeds 5% by mass, the dispersibility of the low viscosity smectite clay mineral may decrease to precipitate. .

<Additives>
The metal surface coating composition of the present invention can optionally contain other additives such as an inorganic binder and a rust inhibitor.

(Inorganic binder)
The inorganic binder strengthens the bond between the smectite mineral and the metal substrate and improves the peel resistance.
As the inorganic binder, silica sol type, alumina sol type, alkali metal silicate type and phosphate type are known, but it is preferable to be silica sol type and alumina sol type.

  Examples of the silica sol include colloidal silica "Snowtex" manufactured by Nissan Chemical Industries, and colloidal silica "Silica doll" manufactured by Nippon Chemical Industries, Ltd., and examples of the alumina sol include "alumina sol" manufactured by Nissan Chemical Industries, etc. Can.

The content of the inorganic binder in the metal surface coating composition is preferably 0.01% by mass or more and 1% by mass or less as solid content, and is 0.02% by mass or more and 0.6% by mass or less Is preferred.
If the amount is less than 0.01% by mass, the effect of improving peel resistance may not be obtained sufficiently, and if it exceeds 1% by mass, the dispersibility of the low viscosity smectite clay mineral may be reduced.

(Rust inhibitor)
The metal surface coating composition of the present invention can contain a rust inhibitor. Antirust agents include nitrite, benzoate, molybdate, orthophosphate, orthosilicate, chromate, zinc, polyphosphate, polysilicate, polycarboxylate, phosphonate, amines, Thiazole, imidazole, benzotriazole can be mentioned.

<Metal surface coating composition>
The metal surface coating composition of the present invention can be prepared by preparing in advance a sol of a low viscosity smectite clay mineral in which a low viscosity smectite clay mineral is dispersed in an aqueous phase, and adding other components to the sol.

  The low viscosity smectite clay mineral sol can be prepared by sufficiently stirring and defoaming a mixture of ion-exchanged water and low viscosity smectite clay mineral with a planetary stirring / defoaming device capable of stirring and defoaming simultaneously. It can be made. By this method, a high viscosity, low viscosity sol of low viscosity smectite clay mineral in which gelation is suppressed can be produced.

The metal surface coating composition is preferably a sol or a gel having thixotropy, and is preferably a sol from the viewpoint of coatability.
The viscosity of the metal surface coating composition (25 ° C.) is preferably from 1mPa · s~1500mPa · s, and more preferably less 1mPas~1000mPa · s. If it is less than 1 mPa · s, the content of the smectite clay mineral may be small and the antioxidative properties may be lowered. If it is more than 1500 mPas, coating may be difficult and unevenness may occur.
The viscosity of the metal surface coating composition can be measured, for example, using a viscometer TVB-10M manufactured by Toki Sangyo Co., Ltd., and adjusting the number of rotations of the rotor according to the sample.

  It is preferable that content of the inorganic material in solid content is 80 to 100 mass%, and, as for the said metal surface coating composition, it is more preferable that it is 90 mass% or more. In the present invention, the solid content is a dry solid portion excluding volatile components such as water and solvent. When the amount of organic matter in the solid content is small, a coating film having excellent heat resistance can be formed.

  Moreover, it is preferable that content of the low viscosity smectite clay mineral in an inorganic material is 70 mass% or more. By containing 70 mass% or more of low viscosity smectite clay minerals in the inorganic material, gelation of the metal surface coating composition is suppressed, and a thin and uniform coating film can be formed.

<Metal material>
The metal material of the present invention has a coating film containing a smectite clay mineral containing a low viscosity smectite clay mineral, and can be obtained by applying the above-mentioned metal surface coating composition to the surface of a metal substrate and drying or firing it. The main component is an inorganic substance derived from an inorganic material such as a clay mineral.

  The coating film of the metal material of the present invention is excellent in heat resistance because it hardly contains an organic substance. Specifically, it has a heat resistance of 450 ° C. or higher, and has a heat resistance up to about 700 ° C. where decomposition of the smectite clay mineral starts. In the present invention, the "heat-resistant temperature" is a temperature that can be used continuously, and means a commonly used temperature that can maintain gas barrier properties without peeling even when heated continuously, and withstands a moment if it is a moment It does not mean the maximum operating temperature that can be used only for a short time.

In general, a flexible clay film containing a resin has a low heat resistance temperature, and when fired at 400 ° C. or more, the resin acting as a binder can not be maintained to form a film.
In the case of a freestanding film of heat-resistant layered clay mineral that does not contain resin, adhesion to the stainless steel surface is poor if it is deposited on the stainless steel surface and dried to form a film even if it is fired at 400 ° C or higher. As a result, the gas barrier properties can not be obtained, and the stainless steel surface is discolored.

  The metal material is not particularly limited, and examples thereof include stainless steel, iron, copper, zinc, titanium and the like.

The application to the metal material can be carried out by a conventionally known method, and examples thereof include a gap coater coating method, a dip coating method, a bead coating method, a ring coating method and the like.
The drying method may be standing at room temperature or hot air drying, the firing method may be firing in a firing furnace or an oven, and the firing temperature is preferably 400 ° C to 650 ° C.

  Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to the following examples.

Example 1
3% by mass of low viscosity synthetic hectorite (manufactured by Rockwood, UK: Laponite S 482: primary particle diameter (median diameter) 60 nm) is added to 91.1 mass% of ion exchange water, and a planetary stirrer (Kurashiki spinning Mazerustar KK- The mixture was stirred and defoamed until the solution became clear at 400 W) to obtain a low viscosity sol.
4.0 mass% of ethylene glycol monobutyl ether and 1.5 mass% of ethanol are mixed, and 0.4 mass% of polyoxyethylene lauryl ether (DKS NL40, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., HLB value 9) is added thereto and dissolved, A water soluble organic solvent solution was prepared.
The above water-soluble organic solvent solution was added while stirring the above low viscosity sol with a disper (manufactured by Primix, Inc .: Homodisper MODEL 2.5) at a rate of 500 rpm, followed by stirring for 10 minutes to obtain a metal surface coating composition.

[Examples 2 to 4]
In the same manner as in Example 1, Examples 2 to 4 formulated to the compositions shown in Table 1 below were produced.

[Example 5]
Low viscosity synthetic hectorite (manufactured by Rockwood, UK: Laponite S 482: primary particle diameter (median diameter) 60 nm) is added to 79.01 mass% of ion-exchanged water, 14.99 mass%, and a planetary stirrer (Kurashiki spinning Mazerustar) Stir and degas the solution until it becomes clear with KK-400 W), and further add silica sol (Silica Doll 20: Nippon Chemical Industrial Co., Ltd., 20 mass% solid content) to a silica solid content of 0.02 mass%, 0.1 mass% was added and stirred to obtain a low viscosity sol. A water-soluble organic solvent solution prepared in the same manner as in Example 1 was added thereto, and the mixture was stirred at 500 rpm for 10 minutes with Disper (manufactured by Primix, Inc .: Homodisper MODEL 2.5) to obtain a metal surface coating composition.

[Examples 6 to 7]
The inorganic binder was changed to an alumina sol (alumina sol: manufactured by Nissan Chemical Industries, 20% by mass solid content) by the same method as in Example 5 to obtain the composition shown in Table 1 Example 7 was produced.

[Example 8]
Low viscosity synthetic hectorite (manufactured by Rockwood, UK: Laponite S 482: primary particle diameter (median diameter) 60 nm) to 79.1 mass% of ion exchange water 11.25 mass%, natural layered clay mineral (bentonite: Kunipia M: 3.75% by mass of a primary particle diameter (median diameter) of 300 nm, made by Kuninin Kogyo Co., Ltd., stirred and defoamed with a planetary stirring device (Karashiki spinning Mazerustar KK-400W) until the liquid becomes transparent to form a low viscosity sol Obtained.
A water-soluble organic solvent solution prepared in the same manner as in Example 1 was added, and stirred at 2000 rpm for 10 minutes with a disper (manufactured by Primix, Inc .: Homodisper MODEL 2.5) to obtain a metal surface coating composition.

[Example 9]
Low viscosity synthetic hectorite (manufactured by Rockwood, UK: Laponite S 482: primary particle diameter (median diameter) 60 nm) to 79.1 mass% of ion-exchanged water, 9.75 mass%, natural layered clay mineral (bentonite: Kunipia M: 3.25% by mass of a primary particle diameter (median diameter) 300 nm, manufactured by Kunimin Kogyo Co., Ltd., stirred and defoamed with a planetary stirrer (Karashiki spinning Mazerustar KK-400W) until the liquid becomes transparent, and alumina sol (alumina sol (alumina sol) 2% by mass of Nissan Chemical Industries, 20% by mass of solid content) was added and stirred so that the alumina solid content was 0.4% by mass, to obtain a low viscosity sol. A water-soluble organic solvent solution prepared in the same manner as in Example 1 was added thereto, and the mixture was stirred at 500 rpm for 10 minutes with a disper (manufactured by Primix, Inc .: Homodisper MODEL 2.5) to obtain a metal surface coating composition.

Comparative Example 1
6.0% by mass of natural layered clay mineral (bentonite: Kunipia M: manufactured by Kunimine Industries) is added to 88.10% by mass of ion-exchanged water, and Disper (manufactured by Primix: Homodisper MODEL 2.5) is used for 30 minutes at 2500 rpm. Stir and disperse well.
The hydrophilic organic solvent solution produced similarly to Example 1 was added to this, and it stirred for 10 minutes, and obtained the metal surface coating composition.

Comparative Example 2
15% by mass of low viscosity synthetic hectorite (manufactured by Rockwood, UK: Laponite S 482: primary particle diameter (median diameter) 60 nm) is added to 85% by mass of ion exchange water, and a planetary stirrer (Kurashiki spinning Mazerustar KK-400W) The mixture was stirred and defoamed until the solution became clear to obtain a metal surface coating composition.

Comparative Example 3
15% by mass of low viscosity synthetic hectorite (manufactured by Rockwood, UK: Laponite S 482: primary particle diameter (median diameter) 60 nm) is added to 79.5 mass% of ion-exchanged water to make a planetary stirrer (Kurashiki spinning Mazerustar KK- The mixture was stirred and defoamed until the solution became transparent at 400 W) to prepare a low viscosity sol. To this was added a water-soluble organic solvent solution in which 4.0% by mass of ethylene glycol monobutyl ether and 1.5% by mass of ethanol were mixed, and stirred at 500 rpm for 10 minutes using a disper to obtain a metal surface coating composition .

The metal surface coating compositions of Examples 1 to 9 and Comparative Examples 1 to 3 were coated on the surface of a stainless steel material (SUS 304) using a gap coater.
The metal surface coating composition of Comparative Example 2 was repelled and could not be applied.

The formed coating was allowed to stand at room temperature for 8 hours and dried to obtain a metal material having a coating film.
In Comparative Example 1, application was possible by brush coating or an applicator, but when dried, the film was not adhered and peeled off.

The metal material having the dried coating film was heated at 150 ° C./1 hour in a muffle furnace FO-310 manufactured by Yamato Scientific Co., Ltd. and baked at 600 ° C. for 1 hour.
In the coating film of Comparative Example 3, cracking and peeling occurred partially in the firing, and the heat resistance was not sufficient.

<Evaluation>
The coating film of each metal material was evaluated by the following method. The evaluation results are shown in Table 2.

(Coating property)
○: non-uniform coating possible 可能: coating possible but non-uniformity occurs ×: non-coating possible (repelled to form a coating film)

(Film forming property)
○: uniform, uniform coating film △: partial cracking or peeling ×: no adhesion

(Testing of cross-cut tape)
Based on JIS (K5600-4-6), a test knife was used on the test surface, and cuts reaching the metal substrate were made 11 each at intervals of 1 mm in the longitudinal and transverse directions, to prepare 100 grids. Next, a pressure-sensitive adhesive tape was strongly pressed onto the cross-hatched portion, the end of the tape was pulled off at a 45 ° angle, and the number of points peeled off from the metal substrate was counted.

(Dupont type drop impact test)
A metal material is held between the shooting type and the pedestal of a Dupont type drop impact tester (made by Ueshima Seisakusho), and a weight of 500 g is dropped from a height of 1 m, and the presence or absence of cracking or peeling of the coating film due to impact deformation It evaluated based on JIS (K5600-5-3).
:: no cracking of the film :: slight cracking

(Pencil hardness test)
The hardness of the coating film was evaluated by a pencil hardness test (JIS K5600-4-4).

(Temper color)
The burnt color after firing was evaluated visually.

1 Metal base 2 Plate-like clay particles

JP 2007-314875 A JP 2012-92207 A JP 2005-313604 A JP, 2006-077237, A JP, 2006-188408, A JP, 2006-188418, A JP, 2006-265088, A JP 2007-277078 A JP, 2005-104133, A

Claims (8)

A metal surface coating composition comprising an inorganic material, a water soluble organic solvent, and a surfactant ,
80% by mass or more and less than 100% by mass of the above-mentioned inorganic material in solid content,
The above inorganic material contains 70 mass% or more of low viscosity smectite clay mineral,
A metal surface coating composition characterized in that the low viscosity smectite clay mineral is a smectite clay mineral having a viscosity (25 ° C.) of 10 to 150 mPa · s when dispersed in water at 20% by mass . The metal surface coating composition according to claim 1 , wherein the low viscosity smectite clay mineral is contained in an amount of 1% by mass to 30% by mass. The metal surface coating composition according to claim 1 or 2 , wherein the primary particle diameter (median diameter) of the low viscosity smectite clay mineral is 10 to 150 nm. The metal surface coating composition according to any one of claims 1 to 3 , wherein the inorganic material further contains an inorganic binder. The metal surface coating composition according to claim 4 , wherein the inorganic binder comprises silica sol and / or alumina sol. Content of the said inorganic binder is 1 mass% or less as solid content, The metal surface coating composition of Claim 4 or 5 characterized by the above-mentioned. A metal material having a coating film obtained by drying or baking a coating film of a metal surface coating composition containing an inorganic material, a water-soluble organic solvent, and a surfactant ,
The metal surface coating composition contains the inorganic material in a solid content of 80% by mass or more and less than 100% by mass,
The above inorganic material contains 70 mass% or more of low viscosity smectite clay mineral,
A metal material characterized in that the low viscosity smectite clay mineral is a smectite clay mineral having a viscosity (25 ° C.) of 10 to 150 mPa · s when dispersed in water at 20% by mass . The heat resistance temperature of the said coating film is 450 degreeC or more and 700 degrees C or less, The metal material of Claim 7 characterized by the above-mentioned.

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