JPH11180780A - Ceramic sheet and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat resistance, electric insulating property, chemical resistance and softness by incorporating an inorg. fiber containing an amorphous silica fiber and a binder as a reaction product of the inorg. fiber and a crystallization inhibitor powder which suppresses crystallization of the amorphous silica fiber. SOLUTION: A crystallization inhibitor and an inorg. fiber containing 10 to 90 wt.% amorphous silica fiber are dispersed in water and formed into a sheet, which is dried at 80 to 110 deg.C to obtain a sheet formed body. The crystallization inhibitor inhibits crystallization of the amorphous silica fiber and is selected from a boron nitride powder or nitrides, nitrates, carbonates and borides powder of zirconium, yttrium, chromium, vanadium and lanthanides. The sheet formed body is fired in an oxidative atmosphere at 1200 to 1400 deg.C for 10 to 60 min to bond the amorphous silica fiber with a binder produced by the reaction of the inorg. fiber and the crystallization inhibitor. Thus, a ceramic sheet having 60 to 97 vol.% porosity and <=0.15 g/cm<3> bulk density is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inorganic fibrous ceramic sheet having excellent heat resistance, electrical insulation, chemical resistance and flexibility, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a material which can be used as an electrical insulating material and a chemical resistant material which can be used at a high temperature of 300.degree. 60-137874) and have been used. Also, Japanese Patent Application Laid-Open No. Sho 62-30677
In Japanese Patent Application Publication No. 4-59271, there is proposed a sheet-like molded product containing inorganic fibers and having flexibility after high-temperature use.

[0003]

Problems to be Solved by the Invention JP-A-60-1378
No. 74, the ceramic sheet-like material containing inorganic fibers as a main component has a problem that the flexibility after use at a high temperature is inferior.

A method for producing an inorganic sheet material described in Japanese Patent Application Laid-Open No. Sho 62-30677 and a method for producing an inorganic molded product described in Japanese Patent Publication No. 4-59271 have been proposed to solve the above problems. However, these are still insufficient in flexibility after being manufactured or used at high temperatures.

For example, an inorganic molded product obtained by the production method described in Japanese Patent Publication No. 4-59271 has flexibility after being baked at 600 ° C. and has sintering at 1300 ° C. It is described as having a shape-retaining property.
(° C. or higher), it loses flexibility and does not have sufficient strength for handling.

Conventionally, no practical inorganic fibrous ceramic sheet having a thickness of 100 μm or less has been known.

[0007] The present invention solves the above-mentioned problems of the prior art and, together with heat resistance, electrical insulation and chemical resistance, sinters at a temperature higher than a predetermined temperature (for example, at a temperature of 600 ° C. or more, especially 1000 ° C. or more). It has flexibility even after being manufactured and manufactured, and has a higher temperature than a predetermined temperature (for example, 600
It is an object of the present invention to provide a ceramic sheet having flexibility even after use at a high temperature of 1000 ° C. or more, particularly 1000 ° C. or more, and having flexibility and sufficient strength for handling, and a method for producing the same. In another aspect of the present invention, when the thickness is reduced (for example, when the thickness is set to 100 μm or less).
However, it is an object of the present invention to provide a practicable ceramic sheet and a method for manufacturing the same.

[0008]

SUMMARY OF THE INVENTION The present inventors have developed an inorganic fiber containing substantially amorphous silica fiber and a powder of a crystallization inhibitor such as boron nitride powder for suppressing crystallization of the silica fiber. When baking the sheet-like molded article containing the crystallization inhibitor powder having a specific particle size, a reaction product of the crystallization inhibitor powder and the inorganic fiber is used as the inorganic fiber. The ceramic sheet obtained by bonding between them has heat resistance, electric insulation, chemical resistance, and also has excellent flexibility even after high temperature, and despite being excellent in flexibility The present inventors have found that they have sufficient strength for handling and that they can be manufactured with an extremely small thickness, and have completed the present invention.

That is, according to the present invention, there is provided a ceramic sheet comprising inorganic fibers containing substantially amorphous silica fibers and a binder for binding the inorganic fibers, wherein the binder is The above object can be achieved by a ceramic sheet containing a reaction product of a powder of a crystallization inhibitor that suppresses crystallization of substantially amorphous silica fibers and the inorganic fibers. This ceramic sheet can be made as follows.

The silica fiber may be an X-ray diffraction amorphous silica fiber. The crystallization inhibitor powder includes (a) boron nitride, (b) zirconium nitride, nitrate, carbonate, and boride; (c) chromium nitride, nitrate, carbonate, and boride; At least one of nitride, nitrate, carbonate and boride of yttrium; (e) nitride, nitrate, carbonate and boride of vanadium; and (f) nitride, nitrate, carbonate and boride of lanthanoid element It can be a powder containing one type.

The powder of the crystallization inhibitor can be a powder having a particle size that causes an oxidation reaction at a firing temperature or lower at the time of producing a ceramic sheet. The binder may include a sol containing inorganic particles or a fired body obtained from a solution for precipitating the inorganic particles. The ratio A / B of the tensile strength A in the in-plane direction to the tensile strength B in the direction perpendicular to the in-plane direction can be set to 3.5 or less. The thickness can be reduced to 100 μm or less.

Further, according to the present invention, there is provided a sheet-like molded article containing inorganic fibers containing substantially amorphous silica fibers and powder of a crystallization inhibitor for suppressing crystallization of the silica fibers. A first baking step of baking at 1200 to 1400 ° C., wherein a powder of the crystallization inhibitor is used as a powder of the crystallization inhibitor, and a reaction product with the inorganic fiber at the time of baking is formed as a binder for binding the inorganic fiber; The above object can be achieved by a method for producing a ceramic sheet using the above method. The method for manufacturing the ceramic sheet can be as follows.

The powder of the crystallization inhibitor includes (a) boron nitride, (b) zirconium nitride, nitrate, carbonate and boride, (c) chromium nitride, nitrate, carbonate and boride; (D) yttrium nitrides, nitrates, carbonates and borides; (e) vanadium nitrides, nitrates;
Powders of at least one of carbonates and borides and (f) nitrides, nitrates, carbonates and borides of lanthanoid elements can be used. As the crystallization inhibitor powder, a crystallization inhibitor powder having a particle size that oxidizes at or below the firing temperature in the first firing step can be used.
As the powder of the crystallization inhibitor, 3 to 50% by weight of boron nitride powder based on the total weight of the inorganic fibers can be used.

The method may further include a second firing step of firing the ceramic sheet to which the inorganic particles are attached, which is the ceramic sheet obtained in the first firing step. A process for applying or impregnating a sol containing inorganic particles or a solution for precipitating the inorganic particles to the ceramic sheet obtained in the first firing step, and drying the ceramic sheet to obtain the inorganic particle-attached ceramic sheet; Can be included. As the sol containing the inorganic particles, a sol containing one or more particles of silica, alumina, aluminosilicate, and aluminoborosilicate can be used.

In the present invention, the description of the numerical range includes not only the extreme values but also any arbitrary intermediate values included therein.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Ceramic Sheet] The inorganic fibers in the ceramic sheet of the present invention include substantially amorphous silica fibers. The term “substantially amorphous” means that it is composed of only an amorphous material by X-ray diffraction. That is, X
The crystal cannot be confirmed by the line diffraction method. For example, as shown in FIG.

[Inorganic Fiber] Preferably, 10 to 90% by weight of the total weight of the inorganic fiber in the ceramic sheet of the present invention can be made into substantially amorphous silica fiber. Inorganic fibers other than the substantially amorphous silica fibers in the ceramic sheet of the present invention are used in combination with substantially amorphous silica fibers such as alumina fibers, aluminosilicate fibers, and aluminoborosilicate fibers. In addition, at least one kind of inorganic fiber among the inorganic reinforcing fibers capable of reinforcing the amorphous silica fiber can be used. Further, all the silica fibers contained in the inorganic fibers in the ceramic sheet of the present invention can be made into substantially amorphous silica fibers.

[Binder] The binder in the ceramic sheet of the present invention contains a reaction product of a crystallization inhibitor powder for suppressing crystallization of substantially amorphous silica fibers and inorganic fibers. Preferably, the reaction product is a reaction product generated at the interface with the inorganic fiber by the reaction of the powder of the crystallization inhibitor with the inorganic fiber. The inorganic fibers are fused to each other through the reaction product. More preferably, the inorganic fiber and the binder are bonded in a three-dimensional knotted network, that is, they are bonded to each other via the binder at the intersection or contact point of the inorganic fiber and the inorganic fiber (at least, the contact point always has a knot. And a ceramic sheet forming a three-dimensional nodular network. Since the ceramic sheet can be fully utilized without impairing the flexibility inherent in the inorganic fiber, the ceramic sheet is more excellent in flexibility as well as shape retention.

The binder in the ceramic sheet of the present invention is more preferably the following (a), (b), (c),
It contains a reaction product of at least one powder of (d), (e) and (f) with inorganic fibers. That is,
(A) boron nitride powder, (b) zirconium nitride, nitrate, carbonate and boride powders, (c) chromium nitride, nitrate, carbonate and boride powders, (d)
Yttrium nitride, nitrate, carbonate and boride powders; (e) vanadium nitride, nitrate, carbonate and boride powders; (f) lanthanoid element nitrides;
It is a reaction product of at least one powder of nitrate, carbonate and boride powders with inorganic fibers. Here, the lanthanoid elements are lanthanum having an atomic number of 57 and 15 elements including cerium having an atomic number of 58 and lutetium having an atomic number of 71. The powder is preferably 1400 ° C. or less (more preferably 900 to 140 ° C.).
(At 0 ° C., more preferably 900 to 1200 ° C.).

The binder in the ceramic sheet of the present invention may be a dried product of a sol containing inorganic particles or a solution capable of precipitating the inorganic particles together with the reaction product of the powder of the crystallization inhibitor and the inorganic fibers. A fired body obtained by firing the dried body can be included.

The sol containing the inorganic particles (that is, the inorganic particles are usually dispersed in the liquid as colloid particles) is preferably one or more of silica, alumina, aluminosilicate, and aluminoborosilicate. Is a sol containing particles (colloidal particles).

In the present application, the sol containing the inorganic particles also includes a sol precursor such as a liquid containing the particles of the hydrated swellable mineral. The hydrated swellable mineral is
This will be described later. Examples of the solution capable of precipitating the inorganic particles include, for example, the following formula M (OR) _n
There is an alcohol solution of an alcoholate of a metal or submetal element represented by the following formula.

[Characteristics of Ceramic Sheet] The porosity of the ceramic sheet of the present invention can be 60 to 97% by volume (preferably 75 to 95% by volume), and the bulk density is preferably 0.15 g / cm ^3. Or less (more preferably 0.1
2 to 0.08 g / cm ³ , more preferably 0.11 to
0.09 g / cm ³ ). In addition, the diameter of the pores can be set to several μm or more, and can be set to 5 μm or more from a practical point of view, for example, 10 to 20 μm. The ceramic sheet of the present invention may have a uniform pore size distribution when measured by a pore size measuring method such as a mercury intrusion method.

When the ceramic sheet of the present invention is used as, for example, a sheet used in an alkaline battery, the pore size is 10 to 15 μm (preferably 10 and more μm) and the porosity is 30.
% By volume or more.

The tensile strength A in the in-plane direction and the tensile strength B in the direction perpendicular to the in-plane direction of the ceramic sheet of the present invention.
Is preferably 3.5 or less (more preferably 3 or less, further preferably 2.8 or less, particularly preferably 2.5 or less) in the thickness range of 50 to 100 mm.

The ceramic sheet of the present invention has a thickness of 50 to
In the range of 100 mm, the tensile strength A in the in-plane direction of the ceramic sheet is preferably 5.5 kgf / cm ^2.
(More preferably 6.0 kgf / cm ² or more, more preferably 6.5 kgf / cm ² or more), and the tensile strength B in the direction perpendicular to the in-plane direction is preferably 2.5 kgf / cm 2 ² or more (more preferably 3.0
kgf / cm ² or more, more preferably 3.5 kgf / cm ²
cm ² or more).

The degree of deformation in the thickness direction of the ceramic sheet of the present invention is preferably 100 μm or less (more preferably 50 μm or less) in the thickness range of 50 to 100 mm.
The thickness is preferably 10 μm or less (more preferably 5 μm or less) in the thickness range of 100 μm or less. For example, the degree of deformation in the thickness direction in the case of a sheet having a thickness of 40 μm is 2 to 3 μm.

The degree of deformation of the ceramic sheet in the thickness direction was determined as follows. That is, when the thickness of the ceramic sheet is measured using a micrometer, the ratchet of the micrometer is turned on, a few clicks are made, and the value is read after the value is stabilized, but the degree of deformation in the thickness direction is read. Was determined by reading the difference between the values immediately before and after a few sounds.

The thickness of the ceramic sheet of the present invention can be appropriately set according to the intended use. For example,
The minimum thickness is 20 μm or more (30 μm or more, 40 μm
Above or 50 μm or more), and a very thin ceramic sheet having a maximum thickness of 100 μm or less can be obtained. The maximum value of the thickness is, for example, 5 cm or less (or 3 cm or less, 1 cm or less, 5 m
m or less, 1 mm or less). Preferably, the thickness is such that the ceramic sheet has good flexibility, less than 1 mm (more preferably 0.5 m
m, preferably 0.2 mm or less, typically 100 μm or less).

[Method for Producing Ceramic Sheet] [First Firing Step] The method for producing a ceramic sheet of the present invention comprises an inorganic fiber containing substantially amorphous silica fiber and a crystal for suppressing crystallization of the silica fiber. A first baking step of baking the sheet-like formed body containing the powder of the chemical conversion inhibitor at 1200 to 1400 ° C. In the first baking step, as a powder of the crystallization inhibitor, a reaction product between the inorganic fibers and the inorganic fibers at the time of baking in the first baking step is generated as a binder that binds between the inorganic fibers ( Preferably, a crystallization inhibitor powder (produced at the interface with the inorganic fibers) is used as the binder.

The sheet-like molded product was prepared at 1200 to 1400
C. (preferably 1200-1300 ° C., more preferably 1250-1350 ° C.) to obtain the ceramic sheet of the present invention. The holding time at the highest temperature in the first firing step may be 10 to 60 minutes (more preferably 10 to 30 minutes). The atmosphere during firing is preferably an oxidizing atmosphere so that the oxidation reaction of a crystallization inhibitor such as boron nitride can easily proceed.

[0032] The sheet-like molded product is preferably made of an inorganic fiber containing substantially amorphous silica fiber, a crystallization inhibitor for suppressing crystallization of the amorphous silica fiber, and an organic fiber. Is dispersed in water and mixed, and the resulting dispersion is formed into a sheet and preferably further dried.

[Sheet-shaped molded body forming step] Before the first firing step, a forming step of obtaining the sheet-shaped molded body can be provided. This molding step is preferably an inorganic fiber containing substantially amorphous silica fiber, and a crystallization inhibitor for suppressing crystallization of the amorphous silica fiber,
The organic fiber is dispersed in water, and a mixing step is performed in which a dispersion obtained by mixing is formed into a sheet. Further, between the forming step and the first baking step, the sheet-like formed body obtained in the forming step is preferably dried at 80 to 110 ° C (more preferably 90 to 110 ° C) to obtain a dried sheet. A drying step for obtaining a shaped body can be provided. Less than,
The material and the forming method for obtaining the sheet-shaped molded body will be described in more detail.

<Inorganic Fiber> As part or all of the inorganic fiber used in the production method of the present invention, an amorphous silica fiber (substantially amorphous) is used in order to impart sufficient flexibility to the ceramic sheet after production. Silica fiber, the same applies hereinafter). In addition, since amorphous silica fiber has low strength, depending on the required strength, when used together with amorphous silica fiber such as alumina fiber, aluminosilicate fiber, aluminoborosilicate fiber, etc. It is preferable to select and use one or more kinds of inorganic fibers from the reinforcing fibers capable of reinforcing the fibers.

The ratio of the amorphous silica fiber and the other inorganic fiber (preferably, the inorganic fiber reinforcing the amorphous silica fiber) is determined by considering the flexibility of the ceramic sheet to be produced. Increase the amount of amorphous silica fiber,
When the strength is important, the proportion of the amorphous silica fiber may be reduced (that is, the proportion of the inorganic fiber for reinforcing the amorphous silica fiber may be increased), and the proportion of the amorphous silica fiber is 90%. It can be selected in the range of 10% by weight to 10% by weight.

In the case of producing a ceramic sheet having excellent flexibility, the total weight of the inorganic fibers used is preferably 5 to 5%.
0% by weight or more (more preferably 60% by weight or more, still more preferably 80% by weight or more) is made into amorphous silica fiber. On the other hand, when producing a ceramic sheet having excellent strength, preferably 50% by weight or more (more preferably 60% by weight or more, and still more preferably 80% by weight or more) of the total weight of the inorganic fibers used is made of amorphous silica fiber. Into inorganic fibers that can be reinforced.

The diameter of the inorganic fiber used in the production is preferably 0.65 to 10 μm (preferably 0.8 to 8 μm, more preferably 1 to 5 μm) in view of the strength and flexibility of the ceramic sheet obtained after the production. desirable. If the thickness is smaller than 0.65 μm, the strength of the ceramic sheet obtained after the production tends to decrease. If the thickness is larger than 10 μm, the flexibility tends to decrease.

The length of the inorganic fiber is preferably about 1 to 30 mm. If it is shorter than 1 mm, the entanglement between the inorganic fibers is reduced, and the strength of the ceramic sheet obtained after the production tends to decrease. If the length is longer than 30 mm, it is difficult to disperse the inorganic fibers in water, and it is difficult to obtain a sheet-like molded body having a uniform thickness before firing.

<Crystallization Inhibitor> The crystallization inhibitor used in the method for producing a ceramic sheet of the present invention is a crystallization inhibitor capable of suppressing crystallization of amorphous silica fibers. That is, the amorphous silica fiber crystallizes upon heating to become cristobalite, and the strength and flexibility of the fiber itself decrease. For this reason, a crystallization inhibitor that suppresses crystallization of the amorphous silica fiber during heating, such as during firing in the process of manufacturing the ceramic sheet or during heating after the ceramic sheet is manufactured, is added.

The powder of the crystallization inhibitor used in the method for producing a ceramic sheet of the present invention acts as a flux and reacts with the inorganic fibers during firing in the first firing step to produce a reaction product. . This reaction product is generated as a binder that bonds between the inorganic fibers (usually formed at the interface with the inorganic fibers).

Examples of the powder of the crystallization inhibitor include:
Preferably, the following (a), (b), (c), (d),
At least one powder of (e) and (f) is used. (A) boron nitride, (b) zirconium nitride, nitrate, carbonate and boride, (c) chromium nitride, nitrate, carbonate and boride, (d) yttrium nitride, nitrate, It is a powder of at least one of carbonate and boride, (e) nitride of vanadium, nitrate, carbonate and boride, (f) nitride of lanthanoid element, nitrate, carbonate and boride. Here, the lanthanoid elements are lanthanum of atomic number 57 and atomic number 58
15 including lutetium of atomic number 71 from cerium
It is an element.

The powder of the crystallization inhibitor is preferably at or below the firing temperature of the first firing step (more preferably 140 ° C.).
A powder of a crystallization inhibitor having a particle size that oxidizes at 0 ° C or lower, more preferably 900 to 1400 ° C, and still more preferably 900 to 1200 ° C is used.

When a powder of a boron compound is used as the powder of the crystallization inhibitor, the powder of the boron compound reacts with the amorphous silica fiber to form borosilicate and acts to fuse the inorganic fibers to each other. Also have.

As the powder of the crystallization inhibitor, a powder of boron nitride is preferably used. The boron nitride powder works effectively as a flux at the interface between the inorganic fibers and the inorganic fibers, and the reaction time is short. Further, a ceramic sheet having higher strength can be manufactured without crystallizing the substantially amorphous silica fiber. There are also the following reasons.

Although there are various kinds of boron compounds, metal borides are not only undesirable because they may not only crystallize amorphous silica fibers but also inhibit fusion between inorganic fibers. For this reason, as nonmetallic borides,
There are boron oxide (B ₂ O ₃ ), boron nitride (BN), boron carbide (B ₄ C), and silicon boride (SiB ₄ , SiB ₆ ). Since boron oxide is water-soluble, it is dispersed in water. It is not suitable for a method of manufacturing a ceramic sheet that requires mixing. Boron carbide and silicon boride can each be used as a crystallization inhibitor for silica amorphous fibers, but it is difficult to obtain them, so it is preferable to use boron nitride.

Boron nitride added as a crystallization inhibitor is preferably oxidized during firing at 1200 to 1400 ° C. to form borosilicate and aluminoborosilicate, and it is particularly preferable to fuse the interface between inorganic fibers. ,
900 to 1200 ° C (more preferably 1000 to 120 ° C)
Boron nitride (crystalline (tetragonal)) having a particle size sufficient to cause an oxidation reaction at around 0 ° C, more preferably 1100 to 1200 ° C, is desirable.

Boron nitride which causes an oxidation reaction at a temperature lower than 900 ° C. is oxidized before reacting with the inorganic fiber, and the boron oxide generated by oxidizing the boron nitride is sublimated to reduce the amount of boron. The effect of suppressing crystallization is reduced, and the strength of the manufactured ceramic sheet tends to be reduced. Further, in the case of boron nitride oxidized at a temperature higher than 1200 ° C., crystallization of the amorphous silica fiber occurs first. Most preferably around 1000C (preferably 950-1050C, more preferably 980-1020)
C., more preferably 990 to 1010.degree. C.). Since boron nitride has a flat shape and the average particle size varies greatly depending on the measurement method, the particle size of boron nitride to be used should be determined from the temperature at which the oxidation reaction occurs.

The boron nitride is preferably added in an amount of 3 to 50% by weight (more preferably 5 to 30% by weight, more preferably 5 to 10% by weight) based on the total weight of the inorganic fibers. 3
When the amount is less than the weight percentage, crystallization of the amorphous silica fiber cannot be suppressed in the production process of the ceramic sheet, and the number and strength of the fused portions (strength of the ceramic sheet) tend to decrease. If it exceeds 50% by weight, the fused portion increases and the strength (strength of the ceramic sheet) increases, but the flexibility of the ceramic sheet obtained after production tends to decrease.

<Organic Fiber> Further, in order to maintain the strength of the sheet-like molded product after molding and before firing, organic fiber can be contained in the sheet-like molded product at the time of molding. Organic fibers include pulp obtained from conifers and hardwoods, long fibers for Japanese paper such as mitsumata and kozo, natural fibers such as hemp and cotton, vinylon, nylon, acrylic, polyester, P
It is an artificial fiber such as VA (polyvinyl alcohol), and preferably 5 to 40% by weight (more preferably 5 to 20% by weight, more preferably 5 to 20% by weight) based on the total weight of the inorganic fiber and the crystallization inhibitor (for example, boron nitride). Is 5 to 10% by weight). When the amount is less than 5% by weight, the strength before firing is not sufficiently obtained, so that the firing operation tends to be difficult.
On the other hand, if it is more than 40% by weight, the porosity of the ceramic sheet obtained after firing tends to be too high, and the strength of the ceramic sheet tends to be low.

The average diameter of the organic fibers is preferably smaller than the average diameter of the inorganic fibers, more preferably １ ／ or less of the average diameter of the inorganic fibers, and further preferably １ ／ or less of the average diameter of the inorganic fibers. I do. When two or more inorganic fibers having different average diameters are included, the average diameter of the organic fibers is preferably smaller than the average diameter of the inorganic fibers having the smallest average diameter, and more preferably the average diameter of the inorganic fibers having the smallest average diameter. 1/2 or less of the diameter (more preferably 1/4 or less)
To

The above-mentioned inorganic fiber, crystallization inhibitor and organic fiber are dispersed in water to obtain a dispersion, and the dispersion is used for molding, preferably by a wet papermaking method or a method similar thereto. Thus, a sheet-shaped molded body can be obtained. More preferably, molding is performed by a molding method (eg, dehydration molding, non-press molding, or the like) in which the molded article has as little steric anisotropy as possible. The sheet-shaped molded product is preferably a dried (preferably dried at 80 to 110 ° C.) sheet-shaped molded product.

The wet papermaking method or a method similar thereto refers to a method in which the dispersion liquid is applied to a filter medium such as a belt-like, circular or square filter net, a filter cloth or a filter plate so as to have a uniform thickness. This is a method of obtaining a sheet-like molded body by filtering after flowing or by sandwiching these filtration media (preferably by natural filtration or filtration under reduced pressure).

[Second firing step] The method for producing a ceramic sheet according to the present invention is directed to a second firing step in which the ceramic sheet obtained in the first firing step and having the inorganic particles deposited thereon is fired. The process as the first
It can be provided after the firing step.

The ceramic sheet with the inorganic particles attached thereto is
A sol containing inorganic particles or a solution capable of precipitating the inorganic particles is applied to or impregnated on the ceramic sheet obtained in the first firing step, and an applied body or impregnated body of the sol or the solution of the ceramic sheet is formed. The obtained coated body or impregnated body can be obtained by drying.

The method for producing a ceramic sheet according to the present invention comprises:
The inorganic particle-adhered ceramic sheet manufacturing step for obtaining the inorganic particle-adhered ceramic sheet may be provided after the first firing step and before the second firing step.

<Sol Containing Inorganic Particles> As the sol containing the above-mentioned inorganic particles (that is, the inorganic particles are usually dispersed as colloidal particles in a liquid), silica, alumina, aluminosilicate, alumino A sol containing one or more particles of a borosilicate is used.

The sol containing the inorganic particles also includes a precursor of the sol containing the particles of the hydrated swellable mineral. That is, a hydrated swellable mineral is an inorganic compound having a crystal structure in which a crystal unit cell is repeated in the thickness direction, and has a property of attracting water molecules between crystal layers and swelling. It is a general term for minerals that break down into ultrafine particles at the stage of development and form a stable sol in water.
For example, natural products such as hydrated swellable bentonites (eg, colloidal bentonite, colloidal sodium montmorillonite, etc.) or hydrated swellable mountain skins (eg, sebiolite, attabalgit, valigorskite, etc.), hydration There are compounds such as swellable mica groups (eg, sodium tetralithic mica, sodium or lithium teniolite, sodium or lithium hectorite).

Preferably, particles (colloidal particles) such as silica, alumina, aluminosilicate and aluminoborosilicate are dispersed in order to control the pore diameter and porosity of the ceramic sheet obtained in the first firing step to desired values. The sol is impregnated, dried after drying (preferably at 50 to 90 ° C.), and fired at 700 to 1000 ° C. (preferably 800 to 900 ° C.). More preferably, it is as follows.

The ceramic sheet obtained by firing in the first firing step preferably includes silica, alumina,
One of the sols of aluminosilicate and aluminoborosilicate is selected and impregnated. The concentration of the impregnating solution and the number of times of impregnation during the impregnation are appropriately selected according to the required pore diameter and porosity. However, when a high-concentration material is used as the impregnating liquid, the surface is cracked after drying and firing, and the coating may not be uniform.Therefore, it is preferable that the low-concentration material is impregnated in several times and dried repeatedly. . Then, it is dried (preferably dried at 50 to 90 ° C.) and fired at 700 to 1000 ° C.

<Solution capable of depositing inorganic particles> Examples of the solution capable of depositing inorganic particles include an alcohol solution of an alcoholate of a metal or submetal element represented by the formula M (OR) _n . In the above formula, M is preferably Ti, Zr, B, Al, Si or the like. R is an alkyl group, such as methyl, ethyl, propyl, iso-propyl, and butyl. n is a natural number determined by the valence of the metal M, and is usually 1 to 4.

The alcoholate of the metal or submetallic element is generally methyl alcohol, ethyl alcohol,
It is soluble in propyl alcohol, iso-propyl alcohol, butyl alcohol, iso-butyl alcohol and the like.

The amount of the metal alcoholate to be applied or impregnated on the ceramic sheet can be appropriately set depending on the type of the metal alcoholate and the use of the ceramic sheet. For example, 5 to 100% by weight based on the total weight of the ceramic sheet
Degree. In addition, the method of application or impregnation can be applied the method that is usually performed, for example,
Examples of the method include immersion in an alcohol solution containing 5 to 50% by weight of a metal alcoholate, spraying of this solution, and a roll transfer method.

The ceramic sheet coated or impregnated with a predetermined amount of the metal alcoholate as described above is heated to a temperature between room temperature and 20 ° C.
The ceramic sheet of the present invention can be obtained by drying at 0 ° C. to obtain a ceramic sheet to which the inorganic particles are attached, and firing it at 300 to 700 ° C.

[0064]

EXAMPLES Example 1 Amorphous silica fibers (average diameter 1.
2.12 g, alumina fiber (average diameter 3.5 μm)
m) 0.53 g, boron nitride 0.08 g, and pulp (average diameter 0.05 μm) 1.18 g were dispersed in 50 g of ion-exchanged water.
mm and dried at 100 ° C. 1300 ° C after drying
For 30 minutes to obtain an inorganic fibrous ceramic sheet.
The obtained ceramic sheet has a diameter of 185 mm and a thickness of 42 mm.
μm, it was restored to its original shape without being broken even when bent 180 degrees along a pipe with a radius of 2 mm, had sufficient flexibility, and had sufficient strength for handling the sheet.
The pore size and porosity of the ceramic sheet at this time are
They were 16 μm and 92%, respectively.

FIG. 1 shows an XRD (X-ray diffraction) pattern of the obtained ceramic sheet. In this XRD pattern, although a corundum peak of alumina was observed, a peak of cristobalite was not confirmed, and only an amorphous pattern of silica amorphous fibers was observed.

Reference Example 1 Amorphous silica fiber (average diameter 1.3 μm) 2.12 g, alumina fiber (average diameter 3.5)
μm) 0.53 g, boron nitride 0.02 g, and pulp (average diameter 0.05 μm) 1.18 g were dispersed in 50 g of ion-exchanged water.
It was molded to 5 mm and dried at 100 ° C. 1300 after drying
Calcination was performed at 30 ° C. for 30 minutes to obtain an inorganic fibrous ceramic sheet. The obtained ceramic sheet had a diameter of 190 mm and a thickness of 50 μm, and was broken when bent at 30 degrees along a pipe having a radius of 2 mm. Further, the sheet could be handled, but the strength was not sufficient. The XRD pattern of the obtained ceramic sheet is shown in FIG. 2, and a corundum peak of alumina and a cristobalite peak were confirmed.

Example 2 The inorganic fibrous ceramic sheet obtained in Example 1 was coated with silica sol (SiO ₂ amount 10%).
Wt%) and dried at 100 ° C. Again impregnated with silica sol in the same manner as described above, and dried at 100 ° C,
It was baked at 700 ° C. for 30 minutes. As a result, the obtained inorganic fibrous ceramic sheet had a pore size and a porosity of 1 respectively.
0 μm, 68%. The XRD pattern of the obtained ceramic sheet is the same as that shown in FIG. 1. Although a corundum peak of alumina is seen, a peak of cristobalite cannot be confirmed, and only an amorphous pattern of silica amorphous fiber is observed. .

FIG. 3 shows an SEM (scanning electron microscope) photograph of a product produced without impregnation with silica sol (Example 1), and FIG. 4 shows an SEM photograph of the ceramic sheet obtained in Example 2. The ceramic sheet of Example 2 was manufactured by incorporating silica sol in the portion where the inorganic fibers overlapped with each other, and thus were integrated. For this reason, the strength required for handling was further increased.

[0069]

The ceramic sheet according to any one of claims 1 to 7, wherein the ceramic sheet comprises inorganic fibers containing substantially amorphous silica fibers and a binder for bonding the inorganic fibers. Since the agent contains a reaction product of the powder of the crystallization inhibitor which suppresses the crystallization of the substantially amorphous silica fiber and the inorganic fiber, the following basic effects can be obtained.

In addition to heat resistance, electrical insulation and chemical resistance,
It can be manufactured by baking at a high temperature of up to about 300 ° C. and further up to about 1400 ° C., and does not produce crystals even when used at a high temperature of up to about 1300 ° C. and further up to about 1400 ° C. Despite having excellent flexibility, it has sufficient strength for handling and does not break during handling. By having flexibility, for example, a ceramic sheet can be spirally wound and used, for example, as a lining material. Further, the thickness is constant and thin (for example, 100 μm
Below), and it is practical even when thinned. Therefore, it can be used for various applications such as heat-resistant filter materials, catalyst carriers, separators, heat-resistant seal materials, high-temperature insulation materials, heat-resistant structural materials, and non-combustible building materials, and is extremely useful.

The ceramic sheets according to claims 2 to 7 further have the respective structures specified in the claims.
The above basic effects are remarkable. In particular, when the binder includes, in addition to the reaction product of the powder of the crystallization inhibitor and the inorganic fibers, a sol containing inorganic particles or a fired body obtained from a solution that precipitates the inorganic particles, Since the ceramic sheet has an effect of further increasing the bonding between the inorganic fibers, the strength of the ceramic sheet is further increased, and the handling is further facilitated.

The method for producing a ceramic sheet according to claims 8 to 13 comprises inorganic fibers containing substantially amorphous silica fibers and powder of a crystallization inhibitor for suppressing crystallization of the silica fibers. The sheet-like molded body is 1200 to 1400
Since the method includes a first baking step of baking at ℃, and a powder of the crystallization inhibitor is used as a powder of the crystallization inhibitor, a reaction product with the inorganic fiber during the baking is generated as a binder for binding the inorganic fiber. The following basic effects can be obtained.

The ceramic sheet of the present invention, which can exhibit the above-mentioned excellent effects, can be easily produced, and has a narrow pore size distribution as measured by a pore size measuring method such as a mercury intrusion method. A range of ceramic sheets can be produced.

The method for manufacturing a ceramic sheet according to any one of claims 9 to 13 further includes the respective structures specified in each claim, so that the above-described basic effects are remarkable. In particular, the second firing step of firing the ceramic sheet obtained by the first firing step and firing the inorganic particle-adhered ceramic sheet to which the inorganic particles are adhered is provided after the first firing step, so that the inorganic fibers are separated from each other. Since the bonding can be further enhanced, the strength of the ceramic sheet can be further increased, the handling of the ceramic sheet can be further facilitated, and the pore size of the ceramic sheet obtained in the first firing step can be improved. In addition, it is possible to produce a ceramic sheet in which the porosity is controlled to a desired value (particularly, the pore size is reduced to make fine pores (furthermore, the pore size is reduced to a more uniform diameter) and the porosity is reduced). it can. Therefore, it is particularly suitably used for applications in which an optimum pore size and porosity need to be selected (for example, a heat-resistant filter material, a catalyst carrier, a separator, a heat-resistant seal material, a high-temperature insulation material, a heat-resistant structure material, a non-combustible building material, and the like). Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a view showing an XRD (X-ray diffraction method) pattern of a ceramic sheet obtained in Example 1 of the present invention.

FIG. 2 is an XRD of the ceramic sheet obtained in Reference Example 1.
It is a figure which shows a pattern (X-ray-diffraction method) pattern.

FIG. 3 is a scanning electron micrograph (photograph of the structure of the ceramic material) of the structure of the ceramic sheet as the ceramic material obtained in Example 1 of the present invention.

FIG. 4 is a scanning electron micrograph (photograph of the structure of the ceramic material) of the structure of the ceramic sheet as the ceramic material obtained in Example 2 of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Misao Iwata 3-36 Noritake Shinmachi, Nishi-ku, Nagoya-shi, Aichi Prefecture Noritake Co., Ltd. (72) Inventor Hirokazu Matsunaga 3-chome Noritake Shinmachi, Nishi-ku, Nagoya City, Aichi Prefecture No. 1-36 Noritake Company Limited

Claims (14)

[Claims] 1. A ceramic sheet comprising: inorganic fibers containing substantially amorphous silica fibers; and a binder for binding the inorganic fibers, wherein the binder comprises the substantially amorphous silica fibers. A ceramic sheet comprising a reaction product of a powder of a crystallization inhibitor for suppressing crystallization of silica fibers and the inorganic fibers. 2. The ceramic sheet according to claim 1, wherein said silica fiber is an X-ray diffraction amorphous silica fiber. 3. The powder of the crystallization inhibitor comprises (a) boron nitride, (b) zirconium nitride, nitrate, carbonate and boride; and (c) chromium nitride, nitrate, carbonate and boron. (D) yttrium nitride, nitrate, carbonate and boride; (e) vanadium nitride, nitrate, carbonate and boride; (f) lanthanoid-based nitride, nitrate, carbonate and boron The ceramic sheet according to any one of claims 1 to 2, wherein the ceramic sheet is a powder containing at least one of the oxides. 4. The ceramic sheet according to claim 1, wherein the powder of the crystallization inhibitor has a particle size that causes an oxidation reaction at a firing temperature or lower at the time of producing the ceramic sheet. 5. The ceramic sheet according to claim 1, wherein the binder comprises a sol containing inorganic particles or a fired body obtained from a solution for precipitating the inorganic particles. 6. A method according to claim 1, wherein the ratio A / B of the tensile strength A in the in-plane direction to the tensile strength B in the direction perpendicular to the in-plane direction is 3.5 or less. The ceramic sheet according to any one of the above. 7. The ceramic sheet according to claim 1, having a thickness of 100 μm or less. 8. A sheet-like molded product comprising inorganic fibers containing substantially amorphous silica fibers and powder of a crystallization inhibitor which suppresses crystallization of said silica fibers is produced in the form of 1200-14.
A first baking step of baking at 00 ° C., wherein as a powder of the crystallization inhibitor, a powder of a crystallization inhibitor generated by a reaction product of the inorganic fiber at the time of baking as a binder for binding the inorganic fiber is used. A method for producing a ceramic sheet. 9. Powders of the crystallization inhibitor include (a) boron nitride, (b) zirconium nitride, nitrate, carbonate and boride, and (c) chromium nitride, nitrate, carbonate and boron. (D) yttrium nitride, nitrate, carbonate and boride; (e) vanadium nitride, nitrate;
9. The method for producing a ceramic sheet according to claim 8, wherein at least one powder selected from the group consisting of carbonates and borides, and (f) nitrides, nitrates, carbonates and borides of lanthanoid elements is used. 10. A crystallization inhibitor powder having a particle size that oxidizes at a temperature not higher than the firing temperature in said first firing step as said crystallization inhibitor powder.
The method for producing a ceramic sheet according to any one of the above. 11. The method according to claim 8, wherein 3-50% by weight of boron nitride powder is used as the crystallization inhibitor powder based on the total weight of the inorganic fibers. Manufacturing method of ceramic sheet. 12. The method according to claim 8, further comprising the step of firing the ceramic sheet obtained in the first firing step, wherein the ceramic sheet has inorganic particles attached thereto. A method for producing a ceramic sheet according to any one of the above. 13. A method for applying or impregnating a sol containing inorganic particles or a solution for precipitating inorganic particles to the ceramic sheet obtained in the first firing step, followed by drying to obtain the inorganic particle-adhered ceramic sheet. 2. The method according to claim 1, further comprising the step of manufacturing an attached ceramic sheet.
3. The method for producing a ceramic sheet according to item 2. 14. A sol containing the inorganic particles,
14. The method for producing a ceramic sheet according to claim 13, wherein a sol containing at least one particle of silica, alumina, aluminosilicate, and aluminoborosilicate is used.