JPH04310586A - Production of zircon-based coating composition and zircon-based oxide-coated graphite compact - Google Patents

Abstract

PURPOSE:To obtain a zircon-based coating composition, capable of readily performing coating, providing films excellent in stability and preservable for a long period by blending a zirconium tetraalkoxide with an organoalkoxysilane, an amine compound, an organic solvent and water. CONSTITUTION:A zircon-based coating composition is obtained by blending (a) a zirconium tetraalkoxide (having 1-5C alkyl) with (b) an organoalkoxysilane expressed by formula 1, II or III (R<2> is 1-5C alkyl group; R<3>, R<4> and R<5> are organic group), (c) an amine compound selected from the group composed of compounds expressed by formula IV or V (R<6> is 1-5C alkyl group; R<7> is 1-5C alkyl group or hydrogen; R<8> is 2-5C alkylene group) and ethylenediamine derivatives, (d) an organic solvent and (e) water. The blending molar ratio of the components is 0.01-2.5 components (b/a), 0.5-6 components (c/a), 0.05-500 components [d/(a+b)] and 0.02-4 components [e/(a+b)].

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zircon-based coating composition that can be stored for a long period of time, can be coated easily, and provides a coating film with excellent stability. The present invention further relates to a method for easily producing a zircon-based oxide-coated graphite molded body having a coating film with excellent stability.

0002

[Prior art] Conventionally, metal, plastic, wood, paper,
Coatings are used to form coatings on materials such as cement and graphite in order to improve their corrosion resistance, heat resistance, abrasion resistance, and insulation properties. The material is useful as a coating composition for the above-mentioned materials because it has excellent corrosion resistance, heat resistance, abrasion resistance, insulation, etc., and also has a low coefficient of thermal expansion.

[0003] Zircon-based compositions are disclosed, for example, in JP-A-61
JP-A-250063 describes a composition formed by mixing a zircon compound, ethyl silicate and isopropyl alcohol, and JP-A-63-190175 describes a composition containing a zirconium oxyalt salt, silicon alkoxide or a derivative thereof. , a composition consisting of water and an organic solvent is described. However, the above composition has poor long-term storage stability, and the coating film obtained by coating it on the substrate is
It had the disadvantage of being prone to cracking and peeling.

On the other hand, among the above materials, graphite is particularly
Known as a material with low coefficient of thermal expansion and excellent thermal shock resistance,
It is used as a material for jigs for use at high temperatures. However, graphite has the disadvantage of poor oxidation resistance at high temperatures. In addition, when using graphite jigs for powder metallurgy, alumina powder is sprinkled on the graphite surface,
It is necessary to apply an alumina-based, silica-based, etc. binder to prevent the molten metal from wetting or reacting with graphite, but the former method is not only complicated, but also creates a working environment due to the fine alumina powder. In the latter method, the binder easily peels off from the graphite surface due to the difference in thermal expansion coefficient between the binder and graphite, and in a hydrogen atmosphere, the binder deteriorates at high temperatures. The silica in the binder reacts with hydrogen to generate water vapor, which has the disadvantage of interfering with the sintering of the metal.

[0005] In order to solve the above-mentioned drawbacks, it has been proposed to form a coating of a zircon-based composition on the surface of a graphite molded body. Known methods for forming this coating include vapor deposition, sputtering, CVD, thermal spraying, paste sintering, and coating thermal decomposition.
It was difficult to form such a thick film, and it was insufficient to prevent oxidative deterioration of graphite.

Furthermore, JP-A-1-122982 discloses that a solution of tetraalkoxysilane, its hydrolyzate and/or partial condensate, and zirconium tetraalkoxide, its hydrolyzate and/or partial condensate, etc., is mixed with graphite. A method of coating or impregnating a molded object and drying it is described, and the coating film obtained by the above method has a coefficient of thermal expansion that is almost the same as that of graphite. , the molten metal exhibits no wettability or reactivity, and the coating does not react with hydrogen. However, the above method has
There was a drawback that the coating solution could not be stored for a long time because it was easily hydrolyzed. Moreover, the stability of the resulting coating film is poor,
It has the drawback of being prone to cracking and peeling.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and its purpose is to provide a coating film that can be easily coated, has excellent stability, and can be stored for a long period of time. An object of the present invention is to provide a ZrO2-CaO based coating composition.

[0008]

[Means for Solving the Problems] The zirconium tetraalkoxide (a) used in the present invention has the general formula Zr (
It is a compound represented by OR1)4, in which R1
represents alkyl, but if the number of carbon atoms increases, the stability of the zircon-based coating composition decreases and the long-term storage stability deteriorates, so the number of carbon atoms is limited to 1 to 5.

The above zirconium tetraalkoxide (a
), for example, zirconium tetramethoxide, zirconium tetraethoxide, zirconium tetra-n-propoxide, zirconium tetra-iso-propoxide, zirconium tetra-n-butoxide, zirconium tetra-sec-butoxide, zirconium tetra-tert -butoxide, etc., and zirconium tetra-n-butoxide and zirconium tetra-iso-propoxide are particularly preferred. These may be used alone or in combination of two or more.

The organoalkoxysilane (b) used in the present invention is a compound represented by the following general formula I, II or III.

[0011]

[C3]

[0012] In the formula, R2 represents alkyl, but the number of carbon atoms is limited to 1 to 5 because as the number of carbon atoms increases, the stability of the zircon-based coating composition decreases and the long-term storage stability deteriorates. . R3, R4, R5 represent an organic group,
For example, saturated hydrocarbon groups (alkyl groups, substituted alkyl groups, etc.), unsaturated hydrocarbon groups (allyl groups, vinyl groups, etc.), aromatic hydrocarbon groups (phenyl groups, naphthyl groups, etc.), epoxy groups, amino groups, etc. can be given.

Examples of the compound represented by the general formula I include monomethyltrimethoxysilane, monomethyltriethoxysilane, monomethyltri-n-propoxysilane, monomethyltri-iso-propoxysilane,
Monomethyltri-n-butoxysilane, monomethyltri-sec-butoxysilane, monomethyltri-tert
-butoxysilane, ethyltriethoxysilane, vinyltriethoxysilane, phenyltriethoxysilane, epoxytriethoxysilane, etc., and have the general formula II
Examples of compounds represented by include dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiethoxysilane, and dimethyldimethoxysilane.
n-propoxysilane, dimethyldi-iso-propoxysilane, dimethyldi-n-butoxysilane, dimethyldi-sec-butoxysilane, dimethyldi-tert-
Examples include butoxysilane, diethyldiethoxysilane, ethylvinyldiethoxysilane, ethylphenyldiethoxysilane, methylepoxydiethoxysilane, etc. Compounds represented by the general formula III include, for example,
Trimethylmonomethoxysilane, trimethylmonoethoxysilane, trimethylmono-n-propoxysilane, trimethylmono-iso-propoxysilane, trimethylmono-n-butoxysilane, trimethylmono-sec-
Butoxysilane, trimethylmono-tert-butoxysilane, triethylethoxysilane, diethylvinylethoxysilane, diethylphenylethoxysilane, diethylphenylethoxysilane, methylethylepoxyethoxysilane, etc., especially monomethyltriethoxysilane, vinyltriethoxysilane. , dimethyldiethoxysilane and diethylphenylethoxysilane are preferred.

The above organoalkoxysilane (b) may be used alone or in combination of two or more. If the amount of the organoalkoxysilane (b) added to the zirconium tetraalkoxide (a) is too small, the stability of the zircon-based coating composition will decrease, resulting in poor long-term storage stability; if it is too large, the resulting coating will crack. organoalkoxysilane (b) / zirconium tetraalkoxide (a)
(molar ratio) is limited to 0.25 to 2.5.

Amine compound (b) used in the present invention
is one or more compounds selected from the group consisting of compounds represented by the following general formula IV or V and ethylenediamine derivatives.

[0016]

[C4]

[0017] In the formula, R6 and R7 represent an alkyl group, but if the number of carbon atoms increases, the stability of the alumina-zirconia coating composition will decrease and long-term storage stability will deteriorate; Limited to 5. However, R7
may be hydrogen. In addition, in the formula, R8 represents an alkylene group, but if the number of carbon atoms decreases or increases, the stability of the zircon-based coating composition decreases and long-term storage property deteriorates, so the number of carbon atoms is 2. ~5.

Examples of the compound represented by the above formula IV include N-methylethanolamine, N-ethylethanolamine, N-methylpropanolamine, and N-methylethanolamine.
Ethylpropanolamine, N,N-dimethylethanol
N,N-diethylethanolamine, N,N
-dibutylethanolamine, N,N-dimethylpropanolamine, etc. Examples of the compound represented by the formula V include N-methyl-N,N-diethanol-
N-ethyl-N,N-diethanolamine,
Examples include N-methyl-N,N-diisopropanolamine.

Examples of the ethylenediamine derivatives include ethylenediamine, N-methylethylenediamine, N-ethylethylenediamine, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N-ethyl-N'-hydroxyethylethylenediamine, etc. can be given.

[0020] If the amount of the amine compound (c) added to the zirconium tetraalkoxide (a) is too small, the stability of the zircon-based coating composition will decrease, resulting in poor long-term storage stability; Since cracks are likely to occur in the amine compound (c) /
Zirconium tetraalkoxide (a) (molar ratio) is limited to 0.5-6.

The organic solvent (d) used in the present invention is:
It is not particularly limited as long as it is compatible with the zirconium tetraalkoxide (a) and organoalkoxysilane (b) (hereinafter referred to as total alkoxide), such as methyl alcohol, ethyl alcohol, isopropyl. Examples include alcohol, alcohols such as butyl alcohol, ketones such as acetone and methyl ethyl ketone, benzene, and toluene, and ethyl alcohol and isopropyl alcohol are particularly preferred. These may be used alone or in combination of two or more.

If the amount of the organic solvent (d) added to the total alkoxide is too small, the stability of the zircon-based coating composition will be reduced, resulting in poor long-term storage stability; if it is too large, pinholes will appear in the resulting coating film. is likely to occur, so the organic solvent (d)/total alkoxide (molar ratio) should be 0.
It is limited to 0.05 to 500, preferably 0.2 to 300.

[0023] When the amount of water (e) added to the total alkoxide used in the present invention is small, cracks are likely to occur in the resulting coating film, and when it is large, zircon-based coat
The water (e)/total alkoxide (molar ratio) should be set at 0.00 to reduce the stability of the tinging composition and impair its long-term storage.
It is limited to 02-4, preferably 0.1-2.

It is preferable that an acid or a base be added to the water (e) as a catalyst to promote hydrolysis of all alkoxides. Examples of the above acid include hydrochloric acid,
Examples of the base include inorganic acids such as hydrofluoric acid and nitric acid, and organic acids such as acetic acid and formic acid. Examples of the base include ammonia, sodium hydroxide, and potassium hydroxide, with hydrochloric acid being particularly preferred.

[0025] If the amount of the acid or base added is too small, it will not have the effect of promoting hydrolysis, and if it is too large, the stability of the zircon-based coating composition will decrease and the long-term storage property will deteriorate. It is preferably 0.01 to 15 mol.

The zircon-based coating composition of the present invention is obtained by mixing the above-mentioned constituent materials, and the mixing method is not particularly limited, but the zirconium tetraalkoxide (a), the amine compound After mixing (c) and the organic solvent (d), it is preferable to add the organoalkoxysilane (b) and water (e). Next, the zircon-based coating composition of the second invention will be explained.

In the composition of the second invention, a pyridine compound (c) is used in place of the amine compound (c). The above pyridine compound is one or more compounds selected from the group consisting of pyridyl alcohol derivatives and bipyridine.

The above pyridyl alcohol derivatives include:
For example, pyridyl alcohol, 2-pyridyl carbino
alcohol, α-(2-pyridyl)ethyl alcohol, β-(2-pyridyl)ethyl alcohol,
-pyridyl)ethyl alcohol and the like.

[0029] As the above bipyridine, for example, 2,2
Examples include '-bipyridine, 2,3'-bipyridine, 2,4'-bipyridine, 3,3'-bipyridine, 3,4'-bipyridine, 4,4'-bipyridine, and the like.

If the amount of the amine compound (c) added to the zirconium tetraalkoxide (a) is too small, the stability of the zircon-based coating composition will decrease, resulting in poor long-term storage stability; Since cracks are likely to occur in the amine compound (c) /
Zirconium tetraalkoxide (a) (molar ratio) is 0. Limited to 5-6.

The composition of the zircon-based coating composition of the present invention and the present invention 2 is as described above, but in order to further improve the stability (crack resistance, peeling resistance, etc.) of the resulting coating film, Zircon powder may also be added.

[0032] The average particle size of the zircon powder is 0.01 to 100 μm, because if it becomes small, it becomes difficult to disperse it in the zircon-based coating composition, and if it becomes large, cracks are likely to occur in the resulting coating film. is preferable, and 0.
Particularly preferred is 02 to 10 μm.

[0033] When the amount of the above-mentioned zircon powder added to the zircon-based coating composition is small, the degree of improvement in the stability of the resulting coating film is decreased, and when it is increased, the stability of the zircon-based coating composition is Since this decreases the long-term storage properties, we recommend using all zircon-based oxides (zirconium tetraalkoxide (a) and organoalkoxysilane (
The total amount of oxide formed from b) and zircon powder is preferably 1 to 60% by weight. Incidentally, it is preferable that the zircon powder is added after mixing and stirring the constituent materials of the zircon-based coating composition.

In the method for producing a zircon-based oxide-coated graphite molded body according to the third aspect of the present invention, the above-mentioned zircon-based coating composition is applied or impregnated onto a graphite molded body, and the graphite molded body is dried to be coated with a zircon-based oxide. Ru.

[0035] Any method may be adopted for producing the graphite molded body, for example, after forming it by extrusion molding, cast molding, etc. using natural graphite, artificial graphite, etc. as a starting material,
Method of firing, anthracite, coal coke, petroleum coke,
Examples include a method in which an amorphous carbonaceous material such as pitch coke or carbon black is formed as a starting material by extrusion molding, cast molding, etc., followed by firing and graphitization. Note that the graphite molded body may contain other materials such as clay and metal.

The shape of the graphite molded body is not particularly limited, and may be, for example, rod-shaped, plate-shaped, block-shaped,
Examples include roll shape and crucible shape. The above-mentioned coating method is not particularly limited, and examples thereof include coating methods such as brush coating, spray coating, dip coating, spin coating, and roll coating.

The above-mentioned impregnation method is not particularly limited, and includes, for example, a method of impregnation by immersion under normal pressure, a method of impregnation by immersion under reduced pressure, etc. It is preferable to impregnate by immersion under reduced pressure. When the temperature is low, it becomes difficult for the zircon-based coating composition to be impregnated into the pores of the graphite molded body, and when it is high, the zircon-based coating composition volatilizes rapidly and the solution viscosity increases, resulting in a graphite molded body. The zircon-based coating composition is less likely to be impregnated inside the pores, so it is preferably 1×10 −3 to 100 Torr.

The above-mentioned drying method is not particularly limited, and includes, for example, natural drying at room temperature, natural drying at room temperature and then heat drying, and high temperature heat treatment after natural drying at room temperature. Examples include a method of naturally drying at room temperature, drying by heating, and then further heating at a high temperature.

[0039] The conditions at each stage in the above drying method are as follows:
Although it is determined appropriately depending on the type of zircon-based coating composition and graphite molded object, natural drying at room temperature is 2 to 4
It is preferable to perform 8 hours, heat drying is preferably performed at 60 to 300°C for 30 minutes to 48 hours, and high temperature heat treatment is preferably performed at 450 to 1700°C for 30 minutes to 10 hours in a non-oxidizing atmosphere.

[0040]

[Examples] Examples of the present invention will be described below. The methods for evaluating each physical property of the zircon-based coating composition and the zircon-based oxide-coated graphite molded article shown in the results are as follows.

1. Physical properties of zircon-based coating compositions (1) Initial adhesion A slide glass (manufactured by Matsunami Co., Ltd.) that had been ultrasonically cleaned with acetone was immersed in the obtained zircon-based coating composition at a speed of 300 mm/min. After pulling it up, an evaluation sample was prepared by drying under the following conditions to form a zircon-based oxide coating layer, and a cross-cut tape peeling test was conducted according to JISD 0202, and 100 pieces of zircon-based oxide were removed. The ratio of the squares of the remaining zircon-based oxide layer to the squares of the coating layer (adhesion rate) was measured and evaluated. (Drying conditions) Initial drying: 25°C, 24 hours Final drying: 500°C (temperature raised from 25°C at 50°C/hr), 2 hours

(2) Pencil hardness Using the obtained zircon-based coating composition, an evaluation sample prepared in the same manner as in the above evaluation of initial adhesion was used, and the surface hardness was determined according to JIS K 5400. It was measured and evaluated according to the same method.

(3) Boiling water resistance (crack resistance and adhesion durability) Using the obtained zircon-based coating composition, an evaluation sample prepared in the same manner as in the above initial adhesion evaluation was boiled. After being immersed in water for 8 hours, the state of the surface was subjected to a sensory test and the crack resistance was evaluated according to the following criteria. (Judgment criteria) ○: No cracks on the surface ×: Cracks on the surface After performing the above sensory test, a cross-cut tape peeling test was performed in the same manner as in the above initial adhesion evaluation, and the adhesion was determined by the adhesion rate. Durability was evaluated.

(4) Acid resistance (crack resistance and adhesion durability) Using the obtained zircon-based coating composition, an evaluation sample was prepared in the same manner as in the above initial adhesion evaluation. After being immersed in hydrochloric acid for 75 hours, the state of the surface was subjected to a sensory test and the crack resistance was evaluated according to the following criteria. (Judgment criteria) ○: No cracks on the surface ×: Cracks on the surface After performing the above sensory test, a cross-cut tape peeling test was performed in the same manner as in the above initial adhesion evaluation, and the adhesion was determined by the adhesion rate. Durability was evaluated.

(5) Long-term storage The sealed container containing the obtained zircon-based coating composition was left in an atmosphere of 50° C. and 65% RH for 6 months, and then the initial adhesion was evaluated. A cross-cut tape peeling test was conducted in the same manner as above, and long-term storage stability was evaluated according to the following criteria. (Judgment criteria) ○: Adhesion rate exceeds 80% ×:
Adhesion rate is less than 80%

2. Physical properties of the zircon-based oxide-coated graphite molded body [Heat resistance] After the obtained zircon-based oxide-coated graphite molded body was left at 600°C for 10 hours in the air, the initial weight of the zircon-based oxide-coated graphite molded body was determined. The heat resistance was evaluated by measuring the weight loss rate.

(Examples 1 to 14) Predetermined amounts of zirconium tetraalkoxide shown in Table 1, an amine compound (compound represented by formula IV or formula V), and isopropyl alcohol (hereinafter referred to as IPA) were separated. Feeded into a bull flask and stirred at room temperature for 15 hours at a stirring speed of 80
A stabilized alcoholic solution of zirconium tetraalkoxide was obtained by stirring at 0 rpm.

A predetermined amount of organoalkoxysilane shown in Table 1 was added to the alcohol solution obtained, and the mixture was heated at room temperature for 1 hour.
After stirring at a stirring speed of 800 rpm, a predetermined amount of hydrochloric acid aqueous solution shown in Table 1 (hydrochloric acid concentration: 0.003 mol/
l) and stirred at room temperature for 1 hour at a stirring speed of 800 rpm.
A zircon-based coating composition was obtained. Using the obtained zircon-based coating composition, various physical properties were measured based on the measurement method described above, and the results are shown in Table 1.

Next, the obtained zircon-based coating composition was supplied into a vacuum container, and a cylindrical graphite molded body (diameter: 20 mm, height: 20 mm) was ultrasonically cleaned with acetone.
) was immersed in the zircon-based coating composition, the pressure inside the vacuum container was reduced to 5 Torr, and the zircon-based coating composition was impregnated into the graphite molded body. Next, the pressure inside the vacuum container was returned to normal pressure, and the graphite molded body was taken out to obtain a graphite molded body impregnated with a zircon-based coating composition.

The obtained graphite molded body impregnated with the zircon-based coating composition was naturally dried at room temperature for 24 hours, then dried in a heating container at 100°C for 24 hours, and further dried at 1500°C for 1 hour in a nitrogen atmosphere. A zircon-based oxide-coated graphite molded body was obtained by time treatment.

[0051] Using the obtained zircon-based oxide-coated graphite molded body, the weight loss rate was measured based on the measurement method described above,
The results are shown in Table 1.

(Example 15) As shown in Table 1, IPA
A zircon-based coating composition was obtained in the same manner as in Example 1 except that the amount added was changed.

[0053] The obtained zircon-based coating composition is coated with a total zircon-based oxide (an oxide formed from zirconium tetraalkoxide and organoalkoxysilane,
A zircon-based coating composition containing zircon powder was prepared by adding zircon powder (average particle size 1 μm) in an amount equivalent to 40% by weight in the total amount of zircon powder and zircon powder, and stirring at room temperature for 1 hour at a stirring speed of 1000 rpm. I got it. Using the obtained zircon powder-containing zircon-based coating composition, each physical property was measured based on the measurement method described above, and the results are shown in Table 1.

A zircon-based oxide-coated graphite molded body was obtained in the same manner as in Example 1 using the above-mentioned zircon-based coating composition containing zircon powder. Using the obtained zircon-based oxide-coated graphite molded body, the weight loss rate was measured based on the measurement method described above, and the results are shown in Table 1.

[0055]

[Table 1]

(Comparative Examples 1 to 9) Predetermined amounts of zirconium tetraalkoxide, diketone compound, and IP shown in Table 2
A zircon-based coating composition was obtained in the same manner as in Example 1 using A and organoalkoxysilane. Using the obtained zircon-based coating composition, various physical properties were measured based on the measurement method described above, and the results are shown in Table 2.

Using the above zircon-based coating composition, a zircon-based oxide-coated graphite molded body was obtained in the same manner as in Example 1. Using the obtained zircon-based oxide-coated graphite molded body, the weight loss rate was measured based on the measurement method described above, and the results are shown in Table 2. (Comparative Example 10) A zircon-based coating composition containing zircon powder was obtained in the same manner as in Example 15, except that the amount of zircon powder added was 70% by weight. Using the obtained zircon powder-containing zircon-based coating composition, each physical property was measured based on the measurement method described above,
The results are shown in Table 2.

A zircon-based oxide-coated graphite molded body was obtained in the same manner as in Example 1 using the above-mentioned zircon-based coating composition containing zircon powder. Using the obtained zircon-based oxide-coated graphite molded body, the weight loss rate was measured based on the measurement method described above, and the results are shown in Table 2.

[0059]

[Table 2]

(Examples 16-26, Comparative Examples 11-16)
Predetermined amounts of zirconium tetraalkoxide, amine compound (ethylenediamine derivative) and IP shown in Table 3
A was supplied to a separable flask and stirred at room temperature for 15 hours at a stirring speed of 800 rpm to obtain a stabilized alcoholic solution of zirconium tetraalkoxide.

A predetermined amount of organoalkoxysilane shown in Table 3 was added to the alcohol solution obtained, and the mixture was heated at room temperature for 1 hour.
After stirring at a stirring speed of 800 rpm, a predetermined amount of hydrochloric acid aqueous solution shown in Table 3 (hydrochloric acid concentration: 0.003 mol/
l) and stirred at room temperature for 1 hour at a stirring speed of 800 rpm.
A zircon-based coating composition was obtained. Using the obtained zircon-based coating composition, various physical properties were measured based on the measurement method described above, and the results are shown in Table 3.

Using the above zircon-based coating composition, a zircon-based oxide-coated graphite molded body was obtained in the same manner as in Example 1. Using the obtained zircon-based oxide-coated graphite molded body, the weight loss rate was measured based on the measurement method described above, and the results are shown in Table 3.

[0063]

[Table 3]

(Examples 27-36, Comparative Examples 17-20)
The predetermined amounts of zirconium tetraalkoxide, pyridine compound, and IPA shown in Table 4 were supplied to a separable flask, and stirred at room temperature for 15 hours at a stirring speed of 800 rpm to obtain a stabilized alcoholic solution of zirconium tetraalkoxide. Ta.

A predetermined amount of organoalkoxysilane shown in Table 4 was added to the alcohol solution obtained, and the mixture was heated at room temperature for 1 hour.
After stirring at a stirring speed of 800 rpm, a predetermined amount of hydrochloric acid aqueous solution shown in Table 3 (hydrochloric acid concentration: 0.003 mol/
l) and stirred at room temperature for 1 hour at a stirring speed of 800 rpm.
A zircon-based coating composition was obtained. Using the obtained zircon-based coating composition, various physical properties were measured based on the measurement method described above, and the results are shown in Table 3.

[0066] Using the above zircon-based coating composition, a zircon-based oxide-coated graphite molded body was obtained in the same manner as in Example 1. Using the obtained zircon-based oxide-coated graphite molded body, the weight loss rate was measured based on the measurement method described above, and the results are shown in Table 4.

[0067]

[Table 4]

[0068]

Effect of the invention: Zircon-based coat of the present invention and present invention 2
The composition of the coating composition is as described above, and contains a specific amount of zirconium tetraalkoxide stabilized with a specific amine compound or pyridine compound, organoalkoxysilane, an organic solvent, and water.
The coating film obtained from the above-mentioned zircon-based coating composition, which can be easily coated and can be stored for a long period of time, has excellent initial adhesion, hardness, boiling water resistance, and acid resistance.

The above-mentioned zircon-based coating composition is suitably used for coating metals, plastics, wood, paper, cement, graphite, and the like. In the method for producing a zircon-based oxide-coated graphite molded body according to the third aspect of the invention, the zircon-based oxide coated
Since the coating composition is used, a graphite molded body coated with a zircon-based oxide can be easily obtained, and the obtained graphite molded body coated with a zircon-based oxide has excellent heat resistance.

The above-mentioned zircon-based oxide-coated graphite molded body is
Suitable for use in metal melting crucibles, firing jigs, etc.

Claims (3)

[Claims] Claim 1: (a) a zirconium tetraalkoxide represented by the general formula Zr(OR1)4 (wherein R1 is an alkyl group having 1 to 5 carbon atoms), (b) a zirconium tetraalkoxide represented by the following general formula I, II or III Organoalkoxysilane represented by: [Formula 1] (wherein, R2 is an alkyl group having 1 to 5 carbon atoms, R3 is
R4 and R5 are organic groups) (c) An amine compound selected from the group consisting of compounds represented by the following general formula IV or V and ethylenediamine derivatives, [Formula 2] (wherein R6 is an alkyl group having 1 to 5 carbon atoms) group, R7 represents an alkyl group having 1 to 5 carbon atoms or hydrogen, and R8 represents an alkylene group having 2 to 5 carbon atoms) (d) an organic solvent, and (e) water, and the molar ratio of each of the above components is as follows: (b) /(a) =0. 01～
2. 5, (c) / (a) = 0. 5-6, ((d)
/(a)+(b))=0. 05-500 and ((e)/(a)+(b))=0. 02-4. A zircon-based coating composition. 2. In the zircon-based coating composition according to claim 1, a pyridine compound (c) selected from the group consisting of pyridyl alcohol derivatives and bipyridine is used in place of the amine compound (c). Characteristic zircon-based coating composition. 3. A method for producing a zircon-based oxide-coated graphite molded body, which comprises applying or impregnating a graphite molded body with the zircon-based coating composition according to claim 1 or 2, and drying the graphite molded body.