JPH085729B2 - Method for manufacturing ceramic precursor compact - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a ceramics precursor molded body. More specifically, the present invention relates to a method for producing a ceramics precursor compact suitable for obtaining a ceramics compact with controlled pores suitable for a raw material of an optical fiber preform, a filter, a catalyst carrier and the like.

(Prior Art) There are many known methods for obtaining metal oxides and hydroxides by hydrolyzing various metal alkoxides (for example, industrial materials 29 , No. 5,85 to 89; 29 , No. 6,101). ~ 110; Electronics Ceramics, March 1986; JP-A-58-2205;
JP-A-56-9,427). Further, in order to produce a dense and transparent lump, it is also possible to hydrolyze a metal alkoxide with a catalyst such as an acid-based catalyst such as hydrochloric acid to produce a gel-like substance, and then gradually heat it. There is.

On the other hand, an example of applying the supercritical gas extraction technology to the degreasing process of the fine ceramics manufacturing process [Chemical Engineering 31 , No.5, 45 (1986)] is known, but ceramic precursors under supercritical conditions are known. The manufacturing method of the molded body is not known.

(Problems to be Solved by the Invention) However, attempts to obtain a molded product from a metal alkoxide as a raw material have been vigorously carried out centering on a glass-based composition because the shape can be easily given. The shrinkage during molding is large, and there are problems such as cracks accompanying it, which is a major problem. On the other hand, as a method for obtaining a porous molded body, a resin is mixed with a slurry of a metal oxide and dissolved, and after molding, the molded product is burned to burn the resin, thereby making it porous. However, it has been extremely difficult to obtain a molded product having high purity, a molded product having high uniformity and a porous molded product having a controlled pore size by such a method.

Therefore, an object of the present invention is to provide a method for producing a ceramics precursor compact. Another object of the present invention is to provide a precursor molded article suitable for obtaining a metal oxide-based porous molded article having high purity and uniformity and a controlled pore size.

(Means for Solving Problems) These various purposes include forming a sol from a metal compound, injecting the sol into a mold for molding, and then gelating the sol as it is, or by using a supercritical fluid under supercritical conditions. This is achieved by a method for producing a ceramics precursor molded body, which is characterized in that a molded body is obtained by performing solvent removal and dehydration.

Further, the present invention is a method for producing a ceramic precursor compact, wherein the sol obtained from the metal compound is preferably a sol comprising a metal alkoxide-based composition. Furthermore, the present invention is more preferably a ceramic precursor in which the sol obtained from the metal oxide is a sol comprising at least one compound selected from the group consisting of metal hydroxides and metal oxides and a metal alkoxide-based composition. It is a manufacturing method of a compact.

(Operation) The ceramic precursor molded body according to the present invention forms a sol from a metal compound, injects the gel into a molding die, and gels the gel as it is or after supercritical conditions in the molding die under supercritical conditions. It is manufactured by desolvating and dehydrating with a critical fluid to obtain a molded body.

The metal compound used in the present invention may be any as long as it forms a sol, and examples thereof include chloride, nitrate, sulfate, phosphate, organic acid salt, organic chelate compound, and alkoxide. Preferred are metal alkoxides.

Examples of the metal alkoxide compound include a single metal alkoxide represented by the general formula I and a composite metal alkoxide represented by the general formula II.

M _a (OR) _n X _mn (I) M _a [M _b (OR) _n ] _mn (II) (wherein M _a and M _b are metals capable of forming an alkoxide, m is a metal M _a or M _b is the maximum valence capable of forming an alkoxy group, n is an integer of 1 to m, X is an oxygen atom, a halogen atom, a hydroxyl group or an organic residue, and R is an alkyl group. Is. R is an alkyl group having 1 to 20 carbon atoms, preferably 1 to 7, more preferably 1 to 4 carbon atoms, X is an oxygen atom, a halogen atom,
Preferably a chlorine atom, a hydroxyl group or an organic residue, for example having 1 to 20 carbon atoms, preferably 1 to 7, more preferably 1
To 4 alkyl groups, 6 to 20 carbon atoms, preferably 6 to
8 aryl groups, more preferably phenyl groups, C 3-5 allyl groups, C 2 vinyl groups, C 2-10 β-diketones and chelates with aluminum such as organic carboxylic acids. And the residue of the organic compound.

Examples of M _a and M _b include tetravalent metals such as silicon, titanium, zirconium, tin, germanium and hafnium, preferably silicon, titanium and zirconium.
Tin, germanium and the like, most preferably silicon, titanium and zirconium, trivalent metals such as aluminum, yttrium, boron, iron, gallium, indium, thallium and scandium, etc., preferably aluminum and yttrium, and divalent metals such as magnesium and zinc. , Barium, beryllium, calcium lead, etc., preferably barium, magnesium, zinc, etc., and monovalent metals include sodium, lithium, etc. Divalent of the above metals,
Trivalent and tetravalent metals are more preferable. Most preferred are the general formulas M _a (OR) ₃ X, M _a (OR) ₂ X ₂ and M _b (OR) ₂ X, where M _a is a tetravalent metal and M _b is a trivalent metal. .) At least one compound.

Examples of silicon alkoxide compounds include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetrafunctional alkoxide compounds such as tetrabutoxysilanes, trimethoxymethylsilane, trimethoxyethylsilane, trimethoxyn- Propyl silane, trimethoxy isopropyl silane, trimethoxy n-butyl silane, trimethoxy isobutyl silane, trimethoxy t-butyl silane, trimethoxy allyl silane, trimethoxy vinyl silane,
Trimethoxyphenylsilane, trimethoxy (acetylacetonato) silane, triethoxymethylsilane, triethoxyethylsilane, triethoxyn-propylsilane, triethoxyisopropylsilane, triethoxybutylsilanes, triethoxyvinylsilane, triethoxyphenylsilane, triethoxy (Acetylacetonato) silane, tri-n-propoxymethylsilane, tri-n-propoxyethylsilane, tri-n-propoxyn-propylsilane, tri-n-propoxybutylsilanes, triisopropoxymethylsilane, triiso Propoxyethylsilane, triisopropoxyphenylsilanes, triisopropoxy (acetylacetonate)
Silane, tributoxymethylsilanes, tributoxyethylsilanes, tributoxy (ethylacetylacetate) silanes, tris (2-methoxyethoxy) vinylsilane, γ-chloropropyltrimethoxysilane, trimethoxychlorosilane, triethoxychlorosilane, triiso Trifunctional silane compounds such as propoxychlorosilane, trimethoxy (hydroxy) silane, dimethoxydimethylsilane, dimethoxydiethylsilane, dimethoxydiisopropylsilane, dimethoxydi-n-butylsilane, dimethoxydiisobutylsilane, dimethoxydi-t.
-Butylsilane, dimethoxydiphenylsilane, dimethoxydi (acetylacetonato) silane, diethoxydimethylsilane, diethoxydiethylsilane, diethoxydiisopropylsilane, diethoxydibutylsilanes,
Diethoxydi (acetylacetonato) silane, di-n
-Propoxydimethylsilane, di-n-propoxydiethylsilane, di-n-propoxydiphenylsilanes,
Di-n-propoxydi (acetylacetonato) silane, diisopropoxydimethylsilane, diisopropoxydiethylsilane, diisopropoxydipropylsilanes, diisopropoxydibutylsilanes, diisopropoxydiphenylsilanes, diisopropoxydisilane (Acetylacetonato) silane, dibutoxydimethylsilanes, dibutoxydiethylsilanes, dibutoxydipropylsilanes, dibutoxydibutylsilanes, dibutoxydiphenylsilanes, dimethoxydichlorosilane, diethoxydichlorosilane, diisopropoxy There are difunctional silane compounds such as dichlorosilane, dimethoxy (dihydroxy) silane, and diethoxy (dihydroxy) silane.

Titanium alkoxide compounds include tetramethoxy titanium, tetraethoxy titanium, tetra n-propoxy titanium, tetraisopropoxy titanium, tetrabutoxy titanium, trimethoxymethyl titanium, trimethoxyethyl titanium, trimethoxypropyl titanium, trimethoxyallyl titanium. , Trimethoxyphenyl titanium,
Trimethoxy (acetylacetate) titanium, triethoxymethyl titanium, triethoxyethyl titanium, triethoxypropyl titanium, trimethoxy vinyl titanium,
Triethoxyphenyl titanium, tripropoxymethyl titanium, tripropoxyethyl titanium, tripropoxybutyl titanium, tripropoxyphenyl titanium, tributoxymethyl titanium, tributoxy (acetylacetonate) titanium, dimethoxydimethyl titanium, dimethoxy Diethyl titanium, dimethoxydipropyl titanium, dimethoxydibutyl titanium, dimethoxydi (acetylacetonate) titanium, diethoxydimethyl titanium, diethoxydiethyl titanium, diethoxydipropyl titanium, dipropoxydimethyl titanium, dipropoxydiethyl titanium , Dibutoxydimethyl titanium, dibutoxy diethyl titanium, dibutoxydi (acetylacetonate) titanium, diisopropoxybis (acetylacetonate) Titanium, isopropoxy (2
-Ethylhexanediolate) titanium, di-n-butoxybis (triethanolaminato) titanium and the like.

Examples of zirconium-based alkoxide compounds include tetramethoxyzirconium, tetraethoxyzirconium,
Tetraisopropoxyzirconium, tetrabutoxyzirconium, trimethoxymethylzirconium, trimethoxyethylzirconium, trimethoxypropylzirconium, trimethoxybutylzirconium, trimethoxyallylzirconium, trimethoxyphenylzirconium, trimethoxy (acetylacetonato) zirconium, trimethoxyphenylzirconium Ethoxymethylzirconium, triethoxyethylzirconium, triethoxypropylzirconium, triethoxyvinylzirconium, triethoxyphenylzirconium, tripropoxymethylzirconium, tripropoxypropylzirconium, tributoxymethylzirconium, dimethoxydimethylzirconium, dimethoxydiethylzirconium , Dimethoxydipro Zirconium, dimethoxydiphenylzirconium, dimethoxydi (acetylacetonato) zirconium, diethoxydimethylzirconium, diethoxydiethylzirconium, diethoxydipropylzirconium, dipropoxydimethylzirconium, dipropoxydipropylzirconium, dibutoxydimethylzirconium , Dibutoxydibutylzirconium, and the like.

Tin-based alkoxide compounds include tetramethoxytin, tetraethoxytin, tetraisopropoxytin, tetrabutoxytins, trimethoxymethyltin, trimethoxyethyltin, trimethoxyisopropyltin, trimethoxybutyltins, triethoxymethyltin , Triethoxyisopropyltin, triisopropoxymethyltin, triisopropoxybutyltins, triisopropoxyphenyl tin,
Dimethoxydimethyltin, dimethoxydiisopropyltin,
Diethoxydiethyltin, diethoxydibutyltins and the like.

Examples of germanium-based alkoxide compounds include tetramethoxygermanium, tetraethoxygermanium,
Tetraisopropoxygermanium, tetrabutoxygermanium, trimethoxymethylgermanium, trimethoxyethylgermanium, trimethoxyisopropylgermanium, trimethoxybutyl sigeraniums,
Examples include triethoxymethyl germanium, triethoxyisopropyl germanium, triisopropoxymethylgermanium, dimethoxydimethylgermanium, dimethoxydiisopropylgermanium, diethoxydiethylgermanium, diethoxydibutylgermanium and the like.

Examples of aluminum alkoxide compounds include aluminum trimethoxide, aluminum triethoxide, aluminum tri-n-propoxide, aluminum triisopropoxide, aluminum tri-n-butoxide, monomethoxyaluminum diethoxide, and monoethoxyaluminum dioxide. Trifunctional alkoxide compounds such as isopropoxide, monoisopropoxyaluminum di-sec-butoxide, dimethoxyaluminum monoethoxide, diethoxyaluminum monoisopropoxide, aluminum ethylacetoacetate dimethoxide, aluminum ethylacetoacetate diethoxide, aluminum Ethyl acetoacetate diisopropoxide, acetoalkoxy aluminum diisopropoxide, methyl aluminum Methoxide, methyl aluminum diethoxide, methyl aluminum diisopropoxide, ethyl aluminum diisopropoxide, dimethoxy aluminum chloride, diethoxy aluminum chloride, diisopropoxy aluminum chloride, diisopropoxy aluminum bromide, dimethoxy aluminum hydroxide, diiso Bifunctional alkoxide compounds such as propoxyaluminum hydroxide, yttrium alkoxide compounds include trimethoxy yttrium, triethoxy yttrium, triisopropoxy yttrium, tributoxy yttrium, dimethoxymethyl yttrium, dimethoxyethyl yttrium, dimethoxyisopropyl yttrium, dimethoxyphenyl yttrium. , Dimethoxy (aceto Cetate) yttrium, diethoxymethyl yttrium, diethoxyethyl yttrium, diethoxyisopropyl yttrium, diethoxyphenyl yttrium, diethoxy (acetoacetate) yttrium, diisopropoxymethyl yttrium, diisopropoxyethyl yttrium, diisopropoxy (acetoacetate) ) Yttrium, dibutoxymethyl yttrium and the like.

As the iron alkoxide compound, trimethoxy iron,
Examples of boron alkoxide compounds such as triethoxy iron, triisopropoxy iron, dimethoxymethyl iron and diethoxyisopropyl iron include trimethoxyborane, triethoxyborane, triisopropoxyborane, dimethoxymethylborane, diethoxyisopropylborane, dimethoxyphenylborane. As the lead alkoxide compound, cimethoxy lead, diethoxy lead, diisopropoxy lead, etc., as the magnesium alkoxide compound, dimethoxy magnesium, diethoxy magnesium, diisopropoxy magnesium, etc., as the zinc alkoxide compound, dimethoxy zinc. , Barium alkoxide compounds such as diethoxyzinc, diisopropoxyzinc, etc. include dimethoxybarium, diethoxybarium, diisopropoxybarium There is.

These alkoxide compounds can be used alone or as a mixture, but it is preferable to compound them so as to be 1 to 4 functional, preferably 2 to 4 functional, and most preferably 2 to 3 functional to form a sol. .

More preferably, a more excellent effect can be obtained by using a sol in which a sol composed of the above metal alkoxide and at least one compound selected from the group consisting of metal hydroxides and metal oxides are used in combination.

As a method of forming a sol with a metal compound, for example, a metal alkoxide, there is a method of polymerizing under a hydrolysis condition.

The method of polymerizing under hydrolysis conditions is carried out in the presence of water and an acid or an alkali. As an acid,
Inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, carbonic acid, boric acid, etc.
Water-soluble acids such as organic acids such as formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, maleic acid, lactic acid, citric acid and malic acid can be used. As the alkali, sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia, methylamine, ethylamine, ethanolamine, etc. can be used.

The amount of water used for the hydrolysis is preferably 0.3 to 50 times mol, particularly preferably 0.5 to 40 times mol, based on the number of moles of alkoxy groups in the organometallic compound. The amount of acid is
It is preferably 0 to 0.5 times the molar number of water, particularly 0
It is preferably about 0.2 times by mole. When an alkali is used instead of the acid, the amount thereof is preferably 0 to 0.8 times, and more preferably 0 to 0.5 times the mole of water.

Polymerization under hydrolysis conditions is 0 to 100 ° C, preferably 2
It is carried out with stirring at a temperature of 0 to 80 ° C. The reaction can be carried out under reduced pressure, normal pressure or increased pressure. In this case, water may be added directly to the reaction mixture, but may also be used as a water-inert gas (for example, nitrogen, argon, helium, methane, ethane, propane, etc.) mixed gas, whereby water is added. Control of decomposition can be facilitated. In acid and alkali, for example, hydrogen chloride,
Carbon dioxide, ammonia and the like may be added in the form of an aqueous solution, but may be used by continuously blowing them in a gaseous state into the reaction medium. In this case, the above inert gas can be used as the inert gas. Control of hydrolysis can be facilitated. Further, the reaction can be carried out without a solvent, but it is preferably carried out in an organic solvent. In particular, an organic solvent capable of dissolving the metal alkoxide is more preferable. Examples of the organic solvent include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, hexanol and octanol, n-hexane, n-heptane,
Aliphatic hydrocarbons such as n-octane and isooctane, alicyclic hydrocarbons such as cyclohexane and cycloheptane,
Esters such as ethyl acetate and isopropyl acetate, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ethers such as diethyl ether and dioxane, cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, benzene, toluene and xylene. And other aromatic hydrocarbons.

When a metal hydroxide and / or a metal oxide is used in combination with these metal alkoxides, these compounds can be uniformly blended after the formation of the sol, but preferably the hydroxide and / or the oxide Performing the sol and / or gel forming reaction in the presence.

The sol and / or gel thus formed is poured into a molding die having a predetermined shape, and then, as it is or after gelation, desolvation and dehydration are carried out with a supercritical fluid under supercritical conditions. A ceramic precursor compact is thus obtained.

The supercritical state is a state in which the gas-liquid critical point (critical temperature, critical pressure) of a substance is exceeded. Here, the critical temperature is the highest temperature at which a gas can be liquefied, and the pressure above that Liquefaction does not occur even if raised. The medium used for forming supercritical conditions in the method of the present invention, that is, the supercritical fluid, is carbon dioxide, ammonia, ethane, propane, butane, pentane, toluene, freon, water, alcohol (for example, methanol, ethanol,
Isopropanol etc.) etc. There are various processes for performing the supercritical treatment, but one example is as follows.
For example, first, a mold for injection of the sol is put into an extraction tank, and a fluid pressurized to a supercritical state is supplied at a predetermined temperature to remove the solvent and water in the sol and / or gel. To do. Then, the extraction tank is depressurized at a constant temperature, the fluid containing the solvent and the water is discharged from the extraction tank and sent to the separation tank, and the density of the fluid decreases to lose the dissolving power for the solvent and the water. In, the supercritical fluid is separated into solvent and water, and the fluid is reused. In addition to the above, as a method for separating the supercritical fluid tank, there are a separation method using a temperature change, a separation method using an adsorbent, and the like.

The ceramic precursor compact thus obtained is fired at a temperature of 600 to 1,800 ° C., preferably 800 to 1,500 ° C. to obtain a ceramic compact.

(Example) Next, the method of the present invention will be described in more detail with reference to Examples.

Example 1 38 parts by weight of triethoxymethylsilane was dissolved in 39 parts by weight of ethanol, 10 parts by weight of water and 5 parts by weight of 28% ammonia water were added thereto, and the mixture was reacted at 60 ° C. for 3 hours to obtain a sol.
92 parts by weight were obtained. The obtained sol was poured into a cylindrical container made of cellulose, carbon dioxide was used as an extraction medium (supercritical fluid), and a temperature of 45 ° C. and a pressure of 200 kg / cm ² were applied under supercritical pressure conditions in the sol. When the solvent and water were removed for 2 hours, a porous molded body having a uniform pore size was obtained. This porous molded body was placed in an air atmosphere at 1,000 ° C.
Porosity with uniform pore size when fired for 5 hours
A 45% silica sintered compact was obtained.

Example 2 80 mol per mol of aluminum triisopropoxide
After adding 100 mol of water at 0 ° C and 0.07 mol of nitric acid, peptization treatment was carried out at 90 ° C for 3 days while stirring to obtain an almost transparent alumina sol (boehmite sol). This alumina sol was concentrated by heating to obtain a sol having a viscosity of 5 poise. This sol was poured into a square stainless steel container with an opening, placed in a supercritical gas extraction device, and treated with ethanol at a temperature of 300 ° C. and a pressure of 200 kg / cm ² for 5 hours to obtain almost perfection. Water and alcohol were extracted and removed. No cracks were observed in the obtained molded product. This molded product is gradually heated in an electric furnace to 1200
When kept at a temperature of ° C for 3 hours, an alumina sintered compact having a porosity of 50% was obtained.

Comparative Example 1 A sol was prepared in the same manner as in Example 1, poured into an open stainless steel rectangular container, the opening was covered with aluminum foil, several pinholes were opened, and dried at a temperature of 45 ° C. However, after 5 days, the gel was cracked and then cracked into gel pieces.

Comparative Example 2 An alumina precursor sol was prepared in the same manner as in Example 2, the sol was poured into a square stainless steel container having an opening, the opening was covered with an aluminum foil, and a few pinholes were formed at room temperature. The gel was cracked after 5 days, and after 10 days, it cracked and separated into several gel pieces.

Example 3 38 parts by weight of tetraethoxy titanium was dissolved in 39 parts by weight of ethanol, 8 parts by weight of water and 1 part by weight of 35% hydrochloric acid were added thereto, and the mixture was reacted at 60 ° C. for 3 hours to obtain 86 parts by weight of sol. It was The obtained sol was poured into a cylindrical container made of cellulose, carbon dioxide was used as an extraction medium (supercritical fluid), and the sol in the sol under the supercritical pressure conditions of a temperature of 45 ° C. and a pressure of 200 kg / cm ² was used. After removing the solvent and water for 5 hours, a porous molded body having a uniform pore size was obtained. When this porous compact was fired in an air atmosphere at 1,200 ° C. for 5 hours, a titania sintered compact having a porosity of 48% was obtained.

Example 4 38 parts by weight of triethoxymethylzirconium was dissolved in 39 parts by weight of ethanol, 6 parts by weight of water and 1 part by weight of 35% hydrochloric acid were added thereto, and the mixture was reacted at 60 ° C. for 5 hours to obtain sol 84.
Parts by weight were obtained. The obtained sol was poured into a cylindrical container made of cellulose, carbon dioxide was used as an extraction medium (supercritical fluid), and the sol in the sol under the supercritical pressure conditions of a temperature of 45 ° C. and a pressure of 200 kg / cm ² was used. After removing the solvent and water for 5 hours, a porous molded body having a uniform pore size was obtained. This porous compact was placed in an air atmosphere at 1,500 ° C.
When fired for 5 hours, it has a porosity of 45 with a uniform pore size.
% Zirconia sintered compact was obtained.

Example 5 3 parts by weight of triethoxymethylsilane and 7 parts by weight of aluminum triisopropoxide were added to 10 parts of isopropanol.
After dissolving in 1 part by weight, 2 parts by weight of water and 1 part by weight of 35% hydrochloric acid were added, and the mixture was reacted at 60 ° C. for 3 hours to obtain 23 parts by weight of sol. The obtained sol was poured into a cylindrical container made of cellulose, carbon dioxide was used as an extraction medium (supercritical fluid), and the sol in the sol under the supercritical pressure conditions of a temperature of 45 ° C. and a pressure of 200 kg / cm ² was used. After removing the solvent and water for 5 hours, a porous molded body having a uniform pore size was obtained. This porous molded body is heated in an air atmosphere at 1,200 ° C for 5
Porosity of 35% with uniform pore size when fired for hours
Alumina-silica sintered compact of was obtained.

Example 6 5 parts by weight of trimethoxyethylsilane and 5 parts by weight of silica powder were dissolved in 10 parts by weight of methanol, 1 part by weight of water and 0.5 part by weight of 35% hydrochloric acid were added thereto, and the reaction was carried out at 60 ° C. for 5 hours. To obtain 21.5 parts by weight of sol. The obtained sol was poured into a cylindrical container made of cellulose and carbon dioxide was used as an extraction medium (supercritical fluid) at a temperature of 45 ° C and
When the solvent and water in the sol were removed for 2 hours under the supercritical pressure condition of 200 kg / cm ² , a porous molded body having a uniform pore size was obtained. When this porous compact was fired in an air atmosphere at 1,000 ° C. for 5 hours, a silica sintered compact having a uniform pore size and a porosity of 35% was obtained.

Example 7 5 mol of alumina powder and 100 mol of water at 80 ° C. were added to 1 mol of aluminum triethoxide, and nitric acid was further added.
After adding 0.07 mol, peptization treatment was performed at 90 ° C. for 3 days while stirring to obtain an alumina sol. This alumina sol was concentrated by heating to obtain a sol having a viscosity of 5 poise.
This sol was poured into an open stainless steel rectangular container, placed in a supercritical gas extraction apparatus, and treated with carbon dioxide gas at a temperature of 45 ° C. and a pressure of 200 kg / cm ² for 5 hours under supercritical pressure conditions. Water and alcohol were completely extracted and removed. No cracks were observed in the obtained molded product. When this molded product was gradually heated in an electric furnace and held at a temperature of 1,200 ° C. for 5 hours, an alumina sintered molded product having a porosity of 42% was obtained.

(Effects of the Invention) As described above, the method for producing a ceramics precursor molded body according to the present invention comprises forming a sol from a metal compound, injecting the sol into a molding die, and as-is or after gelling the supersol. Since a molded product is obtained by desolventizing and dehydrating with a supercritical fluid under critical conditions, the solvent, water, etc. are gradually diffused from the inside of the molded product into the supercritical fluid and uniformly removed. It As a result, compared to conventional drying methods, it is possible to obtain a porous material in which the pore size is controlled more uniformly. It is also possible to obtain various ceramics sintered bodies. Also,
As a result of desolvation and dehydration with a supercritical fluid, open pores are formed in the resulting ceramic precursor, and the hydroxyl groups and other functional groups that are harmful to the optical fibers, filters, etc. that are ultimately used as ceramics are sufficiently removed. Therefore, the performance is remarkably improved.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Makoto Hori 1-1, Higashihama-cho, Hachimansai-ku, Kitakyushu, Fukuoka Kurosaki Ceramics Co., Ltd. Technical Research Institute (72) Inventor Takao Kanai 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Shin Nippon Steel Co., Ltd.

Claims (3)

[Claims] 1. A sol is formed from a metal compound, the sol is injected into a molding die, and as it is or after gelation, a molded product is obtained by desolvation and dehydration with a supercritical fluid under supercritical conditions. A method for producing a ceramics precursor compact, which is obtained. 2. The production method according to claim 1, wherein the sol formed from the metal compound is a sol formed from a metal alkoxide composition. 3. A sol formed of a metal compound is a sol composed of at least one compound selected from the group consisting of metal hydroxides and metal oxides and a metal alkoxide-based composition. The manufacturing method according to item.