JPS6348358A - Sol for use in coating ceramic and coating method using same - Google Patents

Abstract

PURPOSE:To provide the title sol which gives a coating film having a thickness which can be easily controlled without causing cracking and forming any void or any pinhole, containing colloidal zirconia sol obtd. by hydrolyzing an aq. zirconium salt soln. CONSTITUTION:An aq. soln. of a water-soluble zirconium salt such as zirconyl chloride, zirconyl acetate, etc. is hydrolyzed. The solvent contg. anions and unreacted metal ions is removed by filtration, and the residue is washed with pure water. The pH thereof is adjusted to 5-9 by adding a basic matcrial (e.g., NaOH) and the resulting product is washed with pure water and dehydrated by adding an alcohol including polyhydric clcohol to obtain an org. solvent (A) contg. 0.01-20wt% (in terms of ZrO2 colloidal zirconia sol having an average particle size of 300-1,500Angstrom . If desired, 0.01-0.5wt% at least one sol (B) selected from the group consisting of alumina sol, silica sol and titania sol is added to the component A. The mixture is applied to a substrate and exposed to an atmosphere at a relative humidity of 70-95% and 30-70 deg.C for one hr or longer. The relative humidity is lowered to 10-40% and the substrate is heated to 100-500 deg.C at a heating rate of 0.2-5 deg.C/min to form a coating film having a thickness of 0.5-10mum.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a ceramic coating sol containing a colloidal zirconia sol having an average particle size in the range of 300 to 1500X, and a ceramic coating method using the same. It is.

Because Norphea has excellent properties not found in other materials, such as corrosion resistance, toughness, and oxygen ion conductivity, it is being applied to a variety of applications such as oxygen sensors, electronic components, various structural materials, and biomaterials, and will become increasingly important in the future. It is expected that it will be seen.

The colloidal zirconia sol provided by the present invention can also be found to have the following uses. That is, the ceramic coating sol of the present invention is coated by the method of the present invention on the surface of a base material such as metal, ceramics, glass, paper, plastic molded products, sheets, polymer films, organic polymer materials such as resins, etc. It is used to impart or improve functions such as heat resistance (9), anti-reflection, electrical conductivity, ultraviolet absorption, far-infrared radiation, hardness, chemical resistance, corrosion resistance, and durability (1). Especially coating voids and pin poles in printed circuits of electronic parts 2
It can be used as a ceramic piezoelectric thin film for surface acoustic wave devices, as a release film for molds, as a protective film for molds, as a coating on alumina fibers, etc., and has the advantage of being able to improve the above-mentioned functions.

Furthermore, it is naturally possible to disperse the coating sol of the present invention in metals or ceramics and use it for dispersion-strengthened alloys or reinforced ceramics.

<Prior art> Alkali metal silicates and metal acid phosphates are used as heat-resistant inorganic paints, and ZrO2 and 5i02 are used as heat-resistant base agents, wear-resistant coating agents, and chemical-resistant lining agents.
Some pastes containing k as the main component are used. Furthermore, polyfunctional silicone resin is used in organic polymer materials such as plastics to improve weather resistance and chemical resistance.

In these cases, application is done using a spray gun or brush, or by roll coating or screen printing, and the thickness of the coating film is generally 20 to 100 μm.
Cracks were formed in the film, and the film thickness was not uniform, making it unsuitable for thin film application to electronic parts such as those mentioned above.

On the other hand, the sol-kel method using a metal alkoxide solution has the advantage that the immersion method can be applied at room temperature, and that it can be processed at a temperature lower than the temperature at which oxidation of the metal of the substrate and softening of glass, plastic, etc. occur. 0.
Only a film thickness of about 1 to 0.5 μm could be obtained, and it was difficult to adjust the film thickness.O <Problems to be solved by the invention> Film thickness of ceramic coating is 20 to 100 μm.
If the coated surface becomes thicker, large cracks will appear on the coated surface due to differences in drying speed during the drying process, and even if the coated surface is vitrified, the surface will be uneven and cracks will form. It is not easy to prevent the generation of voids and pinholes of about 5 μm.

Furthermore, when a metal alkoxide solution is used, the alkoxide is expensive and it is necessary to coat the film multiple times to obtain a film thickness of 1 μm or more, which affects the cost.

Therefore, the purpose of the present invention is to reduce the film thickness to 0 with - times of coating.
．． To provide a sol for ceramic coating which can be freely adjusted from about 5 μm to about 10 μm, and a ceramic coating method in which a film coated using the sol is free from cracks, voids, and pinholes and a smooth coated surface is obtained.

Means for Solving Problems> The sol for ceramic coating of the present invention is a colloidal zirconia sol obtained by a hydrolysis method from an aqueous zirconium salt solution, and the sol has an average particle size of 300 to 1.
It is characterized by a range of 500X. Further, in the ceramic coating method of the present invention, after applying the above-mentioned ceramic coating sol to a base material,
After exposing the coated substrate to an atmosphere having a temperature of 0° C. and a relative humidity of 70 to 95% for at least one hour, a wet drying step is performed to reduce the relative humidity to 10 to 40%, followed by a wet drying step of 0.2 to 95%. It is characterized in that it includes a heat treatment step in which the coated substrate is heated to 100 to 500°C.

The present invention will be specifically explained below.

The colloidal zirconia sol used in the present invention is prepared from an aqueous solution of a zirconium salt such as water-soluble zirconyl chloride, norconyl nitrate, zirconyl sulfate, or organic acid diAzconyl such as zirconyl acetate, by peptizing with an acid, adding a base, or heating. It is adjusted by known methods such as hydrolysis.

The obtained colloidal sol contains anions and unreacted metal ions, and is introduced into a filtration device and washed. It is preferable to use a circulation type filtration device to avoid clogging of the membrane.The solvent containing anions and metal ions is discharged from the system, and the solvent is added to the concentrated colloidal sol solution. Clean thoroughly. At this time, it is particularly preferable to perform washing by adding a basic substance that does not cause aggregation of sol particles to the sol solution. Preferably, a method is adopted in which the sol is washed with pure water only, and after the sol has become a certain degree of consistency, a vaginal basic substance is added and washing is continued.

Basic substances include strong basic substances such as sodium hydroxide and potassium hydroxide, salts of strong bases and weak acids such as sodium carbonate and potassium carbonate, and alkali metals such as caldic acids such as formic acid, acetic acid, and tartaric acid. Salts and alkali metal salts of β-diketones such as acetylacetone and 2,4-hexadione are preferable, and the amount added is such that the - of the sol is from neutral to weakly alkaline, that is, from 5.0 to 9.0. The quantity is sufficient. Further, in order to make the effect of adding the basic substance more reliable, washing may be performed while adding the basic substance together with water continuously or twice or more. After washing, the sol concentration is adjusted to the required level to obtain highly pure colloidal norconiacil.

In addition, when pure water is used as a solvent for washing the sol, the washed sol and after concentration are added to various alcohols including polyhydric alcohols such as ethylene glycol, dehydrated by heating distillation, etc., or other organic A highly purified sol dispersed in an organic solvent can also be prepared by removing water with a solvent-based dehydrating agent.

The colloidal zirconia sol thus obtained was 3
With an average particle diameter of 00 to 1500X, in one wide area,
It is also stable for a long time even at high concentrations.

Furthermore, base materials such as metals, ceramics, glass, paper, and organic polymer materials, especially metals and ceramics.

It also has excellent adhesion to glass, and the sol concentration is -2
By optimally selecting the viscosity, etc., the thin thickness of the cycort layer, which is a good ceramic coating sol, can be reduced from 0.5 to 1.
It becomes possible to freely adjust the thickness to about 0 μm.

For example, when trying to obtain a thin film of 1 μm or less, the concentration of the sol is 0.01 to 20% as Z r O2 relative to the solvent.
Weight %, preferably in the range of 0.1 to 5 weight %, voice depending on the base material, but preferably in the range of 4 to 10, preferably 6 to 8, viscosity of 1
-50 centipoise, preferably 2-25 centipoise.

Magnesium in this colloidal zirconia sol.

It is also possible to use a sol of at least one metal selected from the group consisting of calcium, yttrium and cerium, or a sol of at least one metal selected from the group consisting of zirconium salt magnesium, calcium, yttrium and cerium. It is also possible to use it as a colloidal zirconia-based sol obtained by a hydrolysis method from an aqueous solution containing a metal salt.

Furthermore, alumina sol can be used as a binder if the adhesion to the substrate is weak due to contact angle issues.

At least one sol selected from the group consisting of silica sol and titania sol can be added to colloidal norconia sil and used as a sol for ceramic coating. In this case, the amount of each sol added is At20
5, S 402 and Z rO as T i O2
2 to 0.01 to 0.5 (weight ratio), especially 0
．． A range of 0.03 to 0.3 is preferable. Addition amount of each sol is 0
．． If it is less than 0.01 (weight ratio) or more than 0.5 (weight ratio), cracks will occur in the coating layer when applied, making it impossible to adjust the film thickness, and the characteristics of colloidal norconium sil It will no longer be effective.

As the alumina sol, a boehmite-based alumina hydrate solution is used, as the silica sol, a colloidal silica sol or ethyl silicate sol, and as the titania sol, a titania hydrate colloidal solution is used.

When applying the ceramic coating sol obtained in this way to each base material, dirt, dust, etc.
It is necessary to remove rust, etc., and degrease adhering oil using alkaline cleaning or surfactant.

The coating is applied to the degreased and cleaned substrate by dipping, brush coating, screen printing, I-spray gun, roll coating, etc., and the optimum method is selected depending on the shape of the substrate, etc.

Taking application by dipping as an example, after immersing it in a defoamed coating sol under vacuum,
The base material is pulled up from the sol at a constant speed of about 0 mm/min, and then undergoes a wet drying process using a constant temperature and humidity chamber, and a heat treatment process using a heating furnace, etc., to complete the ceramic coat layer.

In wet drying, after applying the sol to the substrate, the coated substrate is exposed to an atmosphere with a temperature range of 30 to 70°C and a relative humidity of 70 to 95% for at least 1 hour, but if the temperature exceeds 70°C,
When the relative humidity is less than 70%, the applied sol is rapidly dried and turned into a sol, which tends to cause cracks. If the temperature is lower than 30° C., a long drying time is required, and if the temperature is less than 1 hour, the drying will be insufficient and a satisfactory ceramic coating layer will not be obtained.

In the heat treatment step, the coated substrate is heated at 0.5 to 100 to 500'C. In this case, a speed of 2° C./min or higher is undesirable because cracks tend to occur. Depending on the conditions, the ceramic coat layer may be completed by further firing after the heat treatment.

Normally, when a coating film is made by dipping using the Zoldal method, the thickness of the film produced in one operation is 0.1~
The film thickness should be 0.2 μm or less, and it is possible to increase the thickness by repeating the operation, but it would be very complicated and the coating film should not be cracked, so the film thickness should be 2 to 3 μm or more. That was virtually impossible.

However, the zirconia sol of the present invention has an average particle diameter of 30
The range is 0 to 1500X, and the particle size distribution is 100 to 2
Since it is a colloidal sol that can be optimally adjusted to 0.000^, the thickness of the coated film can be freely adjusted from 0.5 μm to 10 μm depending on the sol concentration and viscosity. Metals, ceramics, and glass can be easily manipulated.

It has become possible to coat paper and organic polymer materials.

Furthermore, by the ceramic coating method of the present invention, it is possible to obtain a smooth surface in which cracks are not observed or are considerably prevented in the ceramic coating layer, and voids and pins of about 2 to 5 μm that occur in the base material can be obtained. This makes it possible to coat holes as well.

<Examples> Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Six volumes of norconyl nitrate aqueous solution (concentration 0.2 mol/l) were prepared and hydrolyzed by boiling under reflux for 100 hours to produce a milky white colloidal sol. - of the colloidal sol after this hydrolysis was 0.7.

Next, the colloidal sol is pumped into a filtration device equipped with a filtration membrane with a total filtration area of 8,000 crn2 and an average passing pore size of 100X, and filtration is performed. The F solution that has passed through the membrane is discharged, and the unfiltered colloidal particles The liquid containing the solution was returned to its original state and continuously filtered and concentrated. When the colloidal sol reached about 21, pure water was added to bring the total to 151. This was again filtered and concentrated to a concentration of about 21. This process is repeated until the NO=ion in the colloidal sol reaches 100
After dissolving acetylacetone in an aqueous IJ solution, the cooled and filtered solution was added to the colloidal sol to adjust the pH to 7.5. Thereafter, washing was repeated until the NO''5 ion in the sol became 1 ppm or less.

After washing, the colloidal solution was further filtered and concentrated to 1.51% to obtain a colloidal zirconia sol having a Z r O2 weight coefficient of 4.68. Na+ remaining in the sol is 0.
5 ppm, average particle size of zirconia is 700
The A% particle size distribution was 300-1200X.

Colloidal silica (20% by weight as SiO2) having a particle size of 10 to 20 μm was added to this sol, and pure water was added to adjust the viscosity to 4.2 centipoise.
2.75% by weight as r O2, 1 as S s O2
．． A zirconia-silica mixed sol for ceramic coating containing 25% by weight was obtained. - was 6.5.

After degassing this mixed sol under vacuum, a degreased and pickled stainless steel plate (5US-316) was dipped into the sol for 2 minutes, returned to atmospheric pressure, and pulled up at a constant speed of 45-7 minutes.

After that, it was placed in a constant temperature and humidity chamber at 50℃ and relative humidity of 90% for 10 hours, and then kept at a relative humidity of 60℃ for 3 hours.
Wet drying was carried out by holding at 0° C. and relative humidity of 30° C. for 3 hours.

Furthermore, this coated stainless steel plate was transferred to a heating furnace, and 1
The temperature was raised to 200° C. at a heating rate of ° C./min, and the temperature was maintained for 3 hours for heat treatment to obtain a ceramic coated stainless steel plate.

Example 2 Ethylene glycol was added to the colloidal zirconia sol obtained in Example 1, and water was distilled off by heating to obtain a colloidal zirconia sol having 10% by weight of Z r O2 dispersed in ethylene glycol. Ta.

Ethanol-dispersed titania sol was added to this sol, ethanol was further added to adjust the viscosity to 7.5 centipoise, and Z r O2 was 4.5% by weight T r 0
A ceramic coated zirconia-titania mixed sol containing 1.5% by weight of 2 was obtained. - was 6.

An alumina plate was immersed in this mixed sol, subjected to wet drying and heat treatment in the same manner as in Example 1, and then fired at 500° C. for 3 hours to obtain a ceramic coated alumina plate.

Example 3 Ceramic-coated quartz glass was obtained in the same manner as in Example 1 using the colloidal turconia sil obtained in Example 2 and using quartz glass as the base material.

Example 4 Triazol was added to the colloidal zirconia sol obtained in Example 1 to give 3.2% by weight of Y2O3 as ZrO2.
A ceramic-coated zirconia-yttoria mixed sol containing 0.2% by weight of 0.2% by weight was obtained.

This mixed sol was mixed with 5% 5102-containing alumina fiber (3
Ceramic coated alumina fibers were obtained in the same manner as in Example 1 by pouring .mu.mφ .gamma.-alumina specific surface area 135 m/jl).

Example 5 The ceramic coating substrates obtained in Examples 1 to 4 were observed using an optical microscope and an electron microscope to observe the state of the coated surface and the cross section of the coat layer, and the results are shown in Table 1.

As a result, almost no cracks were observed on the coated surfaces of the substrates of Examples 1 to 4, and ~
Only some cracks up to 5 μm were observed. Further, the cross section of the coating layer could be freely adjusted to 0.5 μm to 8 μm.

Claims (5)

[Claims] (1) A sol for ceramic coating, characterized in that it contains a colloidal zirconia sol obtained by a hydrolysis method from an aqueous zirconium salt solution. (2) The average particle diameter of the colloidal zirconia sol is 30
The sol according to claim (1), characterized in that the sol has a thickness in the range of 0 to 1500 Å. (3) The sol according to claim (1), to which at least one sol selected from the group consisting of alumina sol, silica sol, and titania sol is added. (4) After applying a ceramic coating sol containing a colloidal zirconia sol obtained from a zirconium salt aqueous solution by a hydrolysis method to a base material,
After exposing the coated substrate to an atmosphere in the temperature range of °C and the relative humidity range of 70 to 95% for at least 1 hour,
A wet drying step in which the relative humidity is lowered to 10-40%, followed by a heat treatment step in which the coated substrate is heated to 100-500°C at a heating rate of 0.2-5°C/min. Ceramic coating method. (5) The base material to be coated is metal, ceramics, glass,
The method according to claim (4), characterized in that the material is paper or an organic polymer material.