JP2016164215A - Composition for coating metal surface and metal material using composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for coating a metal surface that is excellent in heat resistance and peel resistance and is excellent in coatability and to provide a metal material coated with the composition for coating a metal surface.SOLUTION: The composition for coating a metal surface contains a low-viscous smectite clay mineral, a water-soluble organic solvent and a surfactant. The metal material has a coating film containing a smectite clay mineral and the coating film is produced by drying or calcinating a coating film formed of the composition for coating a metal surface containing a low-viscous smectite clay mineral, a water-soluble organic solvent and a surfactant.SELECTED DRAWING: None

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 such as stainless steel are widely used from industrial equipment of plants to precision machine parts and electronic parts. However, since the surface of a metal material may be oxidized or discolored when exposed to high temperatures, it is generally protected by a coating.

  In general, a coating material containing a resin or silicone is used for protecting the surface of the metal material. These exhibit excellent anticorrosion performance, but if they are used continuously in the temperature range of 200 ° C. to 400 ° C., the resin and silicone deteriorate and sufficient performance cannot be obtained. Furthermore, in a high temperature range of about 600 ° C. or higher, the organic matter decomposes and burns and peels off 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 that can form a coating film that can be used in a high temperature range, glass paints and ceramic paints mainly composed of water glass are known. Since these materials coat the material surface with glass, they have excellent heat resistance and corrosion resistance. For example, Japanese Patent Application Laid-Open Nos. 2007-314875 and 2012-92207 propose forming a coating film having a heat resistance of 1000 ° C. or higher with a paint in which glass frit or ceramic is mixed with water glass. ing.

  Films made of glass paint or ceramic paint have high gas barrier properties, but fine powdered frit and ceramic powder are blended. It may break. Moreover, when coating on a metal thin film etc., the flexibility according to the softness | flexibility of a thin film is calculated | required. However, a coating film that is not stretchable and weak in impact resistance, such as glass paint, has a problem that it is liable to crack and cannot exhibit sufficient performance.

  JP-A-2005-313604, JP-A-2006-077237, JP-A-2006-188408, JP-A-2006-188418, JP-A-2006-265088, JP-A-2007-277078, etc. It is disclosed that a flexible film is formed using a layered clay mineral that is widely dispersed as a thickener that easily disperses and swells in water and increases the viscosity of the liquid.

The one described in the above-mentioned patent document is to obtain a self-supporting film of layered clay mineral by applying the layered clay mineral overlapping when the layered clay mineral dispersion is dried.
According to the technique disclosed in the above-mentioned patent document, a self-supporting film excellent in gas barrier properties can be produced by the layered clay mineral. The self-supporting film has a 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 about 350 ° C. The film is a self-supporting film or composite material of a layered clay mineral mixed with a resin, and a coating film in close contact with a metal cannot be formed.

  Japanese Patent Application Laid-Open No. 2005-104133 discloses a method for producing a film having heat resistance of 1000 ° C. formed of layered clay mineral. According to this production method, a clay thin film composed only of a natural or synthetic layered clay mineral can be formed. However, it is not possible to form a coating film having peel resistance that is firmly adhered to the metal surface.

  The present invention provides a metal coating film that cannot 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 and a metal material having a coating film made of 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 a water-soluble organic solvent and an interface. The presence of an activator allows low-viscosity smectite clay minerals to adhere firmly to the metal surface simply by coating, forming a film with excellent peeling resistance, flexibility, and impact resistance. As a result, the present invention has been completed.

  That is, the present invention is based on the above knowledge, and the metal surface coating composition of the present invention is characterized by containing a low-viscosity smectite clay mineral, a water-soluble organic solvent, and a surfactant. And

  The metal material of the present invention is characterized by having a coating film obtained by drying or baking a coating film of a metal surface coating composition containing a low-viscosity smectite clay mineral, a water-soluble organic solvent, and a surfactant. To do.

  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 the metal substrate and is resistant to peeling and resistance. It is possible to provide a metal surface coating composition that is capable of forming a protective film that is excellent in impact properties and that is excellent in heat resistance and gas barrier properties.

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

It is the schematic which shows the state by 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 including a low-viscosity smectite clay mineral, a water-soluble organic solvent, and a surfactant, and optionally contains other additives.

Smectite clay minerals are uniformly coated with a water-soluble organic solvent to improve the affinity with the metal surface, and by further improving the film formability with a surfactant, the smectite clay mineral adheres closely to the metal surface and has gas barrier properties and heat resistance. A coating film having properties is formed.
The smectite clay mineral is a layered clay mineral, and has a structure in which plate-like or disc-like particles (hereinafter simply referred to as “plate-like particles”) are layered. By drying the aqueous dispersion of the layered clay mineral, the plate-like particles are oriented and bonded to each other by van der Waals force and Coulomb force, and as shown in FIG. Thus, a coating film having a laminated structure is formed.
Therefore, since the gap between the plate-like particles becomes a winding path that sews between the plate-like particles and inhibits the movement of molecules and particles, the coating film containing smectite clay mineral has a high gas barrier property. is there.

  Moreover, since the thermal decomposition temperature of the smectite clay mineral is about 700 ° C., a coating film having excellent heat resistance as compared with 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.
Examples of the smectite-based clay mineral include saponite, hectorite, soconite, stevensite, swinholderite, montmorillonite, beidellite, nontronite, and bolconsite. Among these, hectorite, stevensite, and montmorillonite are excellent in film formability and can be preferably used. These may be either synthetic products or natural products, but are preferably synthetic products with a controlled primary particle size.

When the smectite clay mineral is dispersed in the aqueous phase, the plate surfaces of the plate-like particles are negatively charged, the ions between the plate-like primary particles are hydrated, and the interval between the primary particles is expanded. The layered smectite clay mineral is subdivided into plate-like primary particles. And since the plate-like particle | grains which approached repel electrostatically, a smectite clay mineral forms low-sol sol. However, it becomes a highly viscous gel over time, making 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 on the plate surface of the adjacent plate-like particle to form a card house structure by ionic bond and gel. End up.

The present invention is characterized by using a low-viscosity smectite clay mineral that does not gel even when dispersed in an aqueous phase and maintains a low-viscosity sol state.
As described above, smectite clay minerals form a guard house structure in water and gel. Since the above gel has thixotropy, it can be used as a coating solution by restoring fluidity by re-stirring, but it requires labor for re-stirring, or gels during coating and causes smears. For this reason, it is preferable to use a low-viscosity smectite clay mineral that can stably maintain a low-viscosity sol state for a long period of time even when dispersed in water.

  The low-viscosity smectite clay mineral is one in which gelation is suppressed, and the smectite clay mineral can be dispersed at a high concentration of 20% by mass or more. Specifically, the viscosity (25 ° C.) when dispersed in water by 20% by mass is 10 to 150 mPas.

  The low-viscosity smectite clay mineral is generally marketed, and Laponite S482, Laponite SL25 (both manufactured by ROCKWOOD) can be used.

  Examples of the low-viscosity smectite clay mineral include those modified with a modifier, and those modified with an anionic water-soluble polymer or a cationic water-soluble polymer. It is disclosed in JP-T-9-503480, US Pat. No. 5,015,334 and US Pat. No. 5,582,638.

  Examples of the modifier include those containing a low molecular weight amine salt, phosphate compounds, phosphonic acid and derivatives thereof.

  Examples of the anionic water-soluble polymer include polyacrylic acid and polymethacrylic acid. Examples of the cationic water-soluble polymer include polyethyleneimines and polyamidoamines. 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 phosphate compound include sodium salt and potassium salt of tripolyphosphoric acid, hexametaphosphoric acid, and pyrophosphoric acid. Examples of phosphonic acid and its derivatives include sodium salts, potassium salts, ammonium salts and amine salts of phosphonic acids and their derivatives.

As for the particle diameter of the smectite clay mineral, the primary particle diameter (median diameter) is generally 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.
The reason why the film-forming property / peeling resistance is improved when the particle size is in the above range is not clear, but the particle having the above particle size is coupled with the gelation inhibiting effect on the surface of the metal substrate. This is thought to be due to getting caught in fine irregularities.

  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 smectite clay mineral is prepared by vigorous stirring using a homodisper or an ultrasonic generator, and the particle diameter is measured by a dynamic light scattering method or a laser diffraction scattering type measuring device. The particle diameter 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 or more and 30% by mass or less, more preferably 5% by mass or more and 20% by mass or less, and further 10 It is preferable that it is at least 15% by mass.
Even a dispersion of less than 1% by mass can be uniformly coated on the metal surface, but a sufficient thickness cannot be obtained for coating, and gas barrier properties may be lowered. If it exceeds 30% by mass, it is difficult to completely wet the clay mineral, and it may precipitate without being sufficiently hydrated to form a low-viscosity sol.

The metal surface coating composition of the present invention can contain other layered clay minerals depending on the purpose as long as the coating property to the metal surface is not impaired.
Other layered clay minerals include natural smectite clay minerals with a high aspect ratio. By containing a high aspect ratio natural smectite clay mineral having 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 gives the metal surface coating composition an affinity with the surface of the metal substrate, prevents the occurrence of repellency and coating unevenness, and improves the drying property of the metal surface coating composition. .
Although the metal surface itself is hydrophilic, when the metal substrate is stored in the atmosphere, organic substances (hydrocarbon) or the like present in the atmosphere are adsorbed on the surface of the metal substrate and become hydrophobic. Therefore, the affinity with a metal surface improves by containing the water-soluble organic solvent which has an organic group, and coating property improves.
In addition, since the water-soluble organic solvent has volatility, the drying property is improved, and it is prevented that gas is generated inside the film when the coating film is baked and the film is peeled off. Adhesion is improved and gas barrier properties are 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. Examples include glycol ether solvents such as acetone, and ketone solvents such as acetone and methyl ethyl ketone. These may be used alone or in combination.
Among these, glycol ether solvents can be preferably used because they have a high flash point, are excellent in safety, and have a thinning effect. In particular, ethylene glycol monobutyl ether can be preferably used.

  The content of the water-soluble organic solvent in the metal surface coating composition is preferably 1% by mass to 30% by mass, preferably 3% by mass to 10% by mass, although it depends on the water-soluble organic solvent to be contained. Preferably there is. If it is less than 1% by mass, repelling may occur or the drying property may be reduced, and if it exceeds 30% by mass, the dispersibility of the low-viscosity smectite clay mineral may be reduced and sedimentation may occur.

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

  The surfactant is not particularly limited as long as it does not inhibit the gelation of the low-viscosity smectite clay mineral, but among them, the nonionic surfactant is most preferable. Nonionic surfactants are particularly preferable 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 any of an ester type, an ether type, or an ester / ether type having both an ester bond and an ether bond in the molecule, but has an HLB value of 4 to 16. preferable.

  Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, sucrose ester, glycerin ester polyoxyethylene ether, Examples include sorbitan ester polyoxyethylene ether, sorbitol ester polyoxyethylene ether, and the like. These may be used alone or in combination.

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 surface of the metal material is not sufficient and poor coating may occur. If the amount exceeds 5% by mass, the dispersibility of the low-viscosity smectite clay mineral may be lowered and settled. .

<Additives>
The metal surface coating composition of this invention can contain other additives, such as an inorganic binder and a rust preventive, as needed.

(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, alumina sol, alkali metal silicate, and phosphate are known, and silica sol and alumina sol are preferable.

  Examples of the silica sol include Nissan Chemical's colloidal silica "Snowtex", Nippon Chemical Industry's colloidal silica "Silica Doll" and the like. Examples of the alumina sol include Nissan Chemical's "Alumina sol" and the like. Can do.

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 a solid content, and 0.02% by mass or more and 0.6% by mass or less. Is preferred.
If it is less than 0.01% by mass, the effect of improving the peel resistance may not be sufficiently obtained, and if it exceeds 1% by mass, the dispersibility of the low-viscosity smectite clay mineral may be lowered.

(Rust inhibitor)
The metal surface coating composition of the present invention can contain a rust inhibitor. As rust inhibitors, nitrite, benzoate, molybdate, orthophosphate, orthosilicate, chromate, zinc, polyphosphate, polysilicate, polycarboxylate, phosphonate, amines, Mention may be made of thiazole, imidazole, benzotriazole.

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

  The low-viscosity smectite clay mineral sol is prepared by sufficiently stirring and defoaming a mixture of ion-exchanged water and low-viscosity smectite clay mineral using a planetary stirring and defoaming device that can simultaneously stir and degas. Can be made. By this method, a low-viscosity sol with a high concentration of a 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.
Moreover, it is preferable that it is 1 mPas-1500 mPas, and, as for the viscosity (25 degreeC) of a metal surface coating composition, it is more preferable that it is 1 mPas-1000 mPas or less. If it is less than 1 mPas, the content of the smectite clay mineral is small and the antioxidant property may be lowered, and if it exceeds 1500 mPas, coating may become difficult and unevenness may occur.
The viscosity of the metal surface coating composition can be measured, for example, by using a viscometer TVB-10M manufactured by Toki Sangyo Co., Ltd. and adjusting the rotational speed of the rotor according to the sample.

  In the metal surface coating composition, the content of the inorganic material in the solid content is preferably 80% by mass or more and less than 100% by mass, and more preferably 90% by 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 the organic substance 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% by mass or more of the low-viscosity smectite clay mineral 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 including a low-viscosity smectite clay mineral, and is obtained by applying the metal surface coating composition to the surface of a metal substrate and drying or baking it. The main component is an inorganic substance derived from an inorganic material such as clay mineral.

  The coating film of the metal material of the present invention is excellent in heat resistance because it contains almost no organic matter. Specifically, it has a heat resistance of 450 ° C. or higher, and has a heat resistance of up to about 700 ° C. at which the smectite clay mineral begins to decompose. In the present invention, the “heat-resistant temperature” is a temperature at which continuous use is possible, and refers to a normal use temperature at which gas barrier properties can be maintained without being peeled even if continuously heated, and it can withstand for a moment. It does not mean the maximum operating temperature that can be used only for a short time.

Usually, a flexible clay film containing a resin has a low heat-resistant temperature, so that when it is baked at 400 ° C. or higher, the resin acting as a binder is broken and the film formation state cannot be maintained.
In addition, a heat-resistant layered clay mineral free-standing film that does not contain a resin has poor adhesion to the stainless steel surface when fired at 400 ° C. or higher even if it is formed on a stainless steel surface and dried to form a film. Therefore, the gas barrier property cannot be obtained, and the stainless steel surface is discolored.

  Although there is no restriction | limiting in particular as said metal material, For example, stainless steel, iron, copper, zinc, titanium etc. are mentioned.

Application to the metal material can be performed by a conventionally known method, and examples thereof include a gap coater coating method, a dip coating method, a bead coating method, and a ring coating method.
Examples of the drying method include standing at room temperature and hot-air drying. Examples of the firing method include firing in a firing furnace or oven. The firing temperature is preferably 400 ° C to 650 ° C.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to the following Example.

[Example 1]
3% by mass of low-viscosity synthetic hectorite (manufactured by Rockwood, Inc .: Laponite S482: primary particle diameter (median diameter) 60 nm) is added to 91.1% by mass of ion-exchanged water, and a planetary agitator (Mazerustar KK-manufactured by Kurashiki Boseki). The mixture was stirred and degassed until the liquid became transparent at 400 W) to obtain a low-viscosity sol.
4.0% by mass of ethylene glycol monobutyl ether and 1.5% by mass of ethanol were mixed, and 0.4% by mass of polyoxyethylene lauryl ether (DKS NL40, HLB value 9 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added and dissolved therein. A water-soluble organic solvent solution was prepared.
While stirring the low-viscosity sol with a disper (manufactured by Primics: Homodisper MODEL 2.5) at 500 rpm, the water-soluble organic solvent solution was added and stirred 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 prepared to the compositions described in Table 1 below were prepared.

[Example 5]
14.99% by mass of low-viscosity synthetic hectorite (manufactured by Rockwood, Inc .: Laponite S482: primary particle diameter (median diameter) 60 nm) is added to 79.01% by mass of ion-exchanged water, and a planetary agitator (Mazerustar, Kurashiki Boseki Co., Ltd.) is added. KK-400W) until the liquid becomes transparent, the mixture is defoamed, and silica sol (silica doll 20: manufactured by Nippon Chemical Industry Co., Ltd., solid content 20% by mass) is further added so that the silica solid content becomes 0.02% by mass. 0.1 wt% was added and stirred to obtain a low viscosity sol. To this was added a water-soluble organic solvent solution prepared in the same procedure as in Example 1, and the mixture was stirred for 10 minutes at 500 rpm with a disper (manufactured by Primics: Homo Disper MODEL 2.5) to obtain a metal surface coating composition.

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

[Example 8]
Low-viscosity synthetic hectorite (manufactured by Rockwood, UK: Laponite S482: primary particle diameter (median diameter 60 nm)) is 11.25 mass%, natural layered clay mineral (bentonite: Kunipia M: Kunimine Kogyo Co., Ltd., 3.75% by mass of primary particle size (median diameter) is added, and a low-viscosity sol is obtained by stirring and defoaming with a planetary stirrer (Mazerustar KK-400W, Kurashiki Boseki) until the liquid becomes transparent. Obtained.
A water-soluble organic solvent solution prepared in the same procedure as in Example 1 was added, and the mixture was stirred with a disper (Primics Co., Ltd .: Homo Disper MODEL 2.5) at 2000 rpm for 10 minutes to obtain a metal surface coating composition.

[Example 9]
Low-viscosity synthetic hectorite (manufactured by Rockwood, UK: Laponite S482: primary particle diameter (median diameter 60 nm)) is 9.75% by mass, natural layered clay mineral (bentonite: Kunipia M: Add 3.25% by mass of the primary particle size (median diameter 300 nm) manufactured by Kunimine Kogyo Co., Ltd., and stir and degas it with a planetary stirrer (Mazerustar KK-400W, Kurashiki Boseki Co., Ltd.). : Nissan Chemical Industries, Ltd., solid content of 20% by mass) was added and stirred so that the alumina solid content was 0.4% by mass, and a low-viscosity sol was obtained. To this was added a water-soluble organic solvent solution prepared in the same procedure as in Example 1, and the mixture was stirred for 10 minutes at 500 rpm with a disper (manufactured by Primics: Homo Disper 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 Kogyo Co., Ltd.) is added to 88.10% by mass of ion-exchanged water, and 30 minutes at 2500 rpm using a disper (Primics Co., Ltd .: Homodisper MODEL 2.5). Stir and disperse well.
To this, a hydrophilic organic solvent solution prepared in the same manner as in Example 1 was added and stirred for 10 minutes to obtain a metal surface coating composition.

[Comparative Example 2]
Low-viscosity synthetic hectorite (manufactured by Rockwood, UK: Laponite S482: primary particle size (median diameter) 60 nm) is added to 85% by mass of ion-exchanged water, and a planetary stirrer (Mazerustar KK-400W, Kurashiki Boseki) is added. The mixture was stirred and degassed until the liquid became transparent to obtain a metal surface coating composition.

[Comparative Example 3]
Low-viscosity synthetic hectorite (manufactured by Rockwood, UK: Laponite S482: primary particle diameter (median diameter) 60 nm) is added to 79.5% by mass of ion-exchanged water, and a planetary agitator (Mazerustar KK- manufactured by Kurashiki Boseki Co., Ltd.) is added. The mixture was stirred and degassed until the liquid became transparent at 400 W) to prepare a low-viscosity sol. To this was added a water-soluble organic solvent liquid obtained by mixing 4.0% by mass of ethylene glycol monobutyl ether and 1.5% by mass of ethanol, and the mixture was stirred for 10 minutes at 500 rpm 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 respectively applied to the surface of a stainless steel material (SUS304) using a gap coater.
The metal surface coating composition of Comparative Example 2 was repelled and could not be applied.

The formed coating film was allowed to stand at room temperature for 8 hours and dried to obtain a metal material having a coating film.
Comparative Example 1 could be applied by brushing or applicator, but when dried, the film had no adhesion and was 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, and baked at 600 ° C. for 1 hour.
The coating film of Comparative Example 3 was partially cracked or peeled off by firing, and the heat resistance was not sufficient.

<Evaluation>
The coating films of the above metal materials were evaluated by the following methods. The evaluation results are shown in Table 2.

(Coating property)
○: Coating is possible without unevenness △: Coating is possible but unevenness occurs ×: Coating is impossible (the film cannot be formed by repelling)

(Film formability)
○: Adherent uniform coating film △: Some cracks and peeling ×: Not adhered

(Cross cut tape test)
Based on JIS (K5600-4-6), using a cutter knife on the test surface, 11 cuts reaching the metal substrate were made at a 1 mm interval in each of the vertical and horizontal directions to produce 100 grids. Next, the adhesive tape was strongly pressure-bonded to the grid area, the ends of the tape were peeled off at an angle of 45 °, and the number of places peeled off from the metal substrate was counted.

(DuPont drop impact test)
A metal material is sandwiched between a shooting type of a DuPont drop impact tester (manufactured by Ueshima Seisakusho) and a cradle, and a weight of 500 g is dropped from a height of 1 m to check whether the coating film is cracked or peeled off due to impact deformation. Evaluation was made based on JIS (K5600-5-3).
○: No cracking of the film △: Slight cracking ×: The film is torn

(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 visually evaluated.

1 Metal substrate 2 Plated 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 (10)

  A metal surface coating composition comprising an inorganic material, a water-soluble organic solvent, and a surfactant, wherein the inorganic material contains a low-viscosity smectite clay mineral.   2. The metal surface coating composition according to claim 1, wherein the inorganic material is contained in a solid content of 80% by mass or more and less than 100% by mass.   The metal surface coating composition according to claim 1 or 2, wherein the content of the low-viscosity smectite clay mineral in the inorganic material is 70% by mass or more.   The metal surface coating composition according to any one of claims 1 to 3, 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 any one of claims 1 to 4, wherein a 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 5, wherein the inorganic material further contains an inorganic binder.   The metal surface coating composition according to claim 6, wherein the inorganic binder contains 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 6 or 7 characterized by the above-mentioned.   A metal material comprising a coating film obtained by drying or baking a coating film of a metal surface coating composition containing a smectite clay mineral containing a low-viscosity smectite clay mineral, a water-soluble organic solvent, and a surfactant.   The metal material according to claim 9, wherein the heat resistance temperature of the coating film is 450 ° C or higher and 700 ° C or lower.

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