JPS5939765A - Manufacture of porous alumina sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention The present invention relates to a method for producing a porous alumina sintered body, which uses a novel fibrous basic aluminum sulfate or fibrous alumina as a raw material to produce a porous alumina sintered body with a small pore diameter and a large porosity. Provided is a method for producing a sintered alumina body.

Porous alumina sintered bodies are used in a wide range of fields such as filters, heat insulating materials, sound absorbing materials, adsorbents, and catalyst carriers. Conventionally, porous alumina sintered bodies are generally produced by molding a desired shape using spherical alumina particles of a predetermined size as a raw material.
,, it is manufactured by a method of sintering it.

In this case, the sintered spherical particles serve as a skeleton, and the voids between the particles form pores.

In this method of manufacturing a porous alumina sintered body, the diameter of the pores (
It has the advantage that the pore diameter (hereinafter referred to as "pore diameter") can be controlled over a wide range from about 1 micron to several hundred microns. However, because the proportion of the volume of the sintered body that is occupied by the skeleton is inevitably larger than that of pores, that is, the porosity is small, it has the disadvantage of poor fluid permeability and becoming a material. be.

Recently, a porous ceramic sintered body called a so-called ceramic foam, which is a porous body formed by forming a ceramic powder such as alumina powder into a spongy shape and sintering it, has been manufactured. Since the volume of the pores exceeds that of the skeleton, this material is lightweight with a high porosity and has excellent fluid permeability. However, on the other hand, it has the disadvantage that the pore diameter is several hundred microns or more, and it is difficult to obtain a pore diameter smaller than that.

As a result of studies to improve the drawbacks of the porous alumina sintered body produced by the above method, the inventors of the present invention discovered that by using the following novel fibrous basic aluminum sulfate or fibrous alumina as a raw material, , the average pore size is 0.1-5
The present invention was completed by discovering that it is possible to obtain a lightweight porous alumina sintered body having a large porosity of 50 to 90%, although it is as small as microns. That is, the present invention has a diameter of 0.1 to 1 micron and a length to diameter ratio of 20.
The present invention provides a method for producing a porous alumina sintered body, which is characterized by sintering a molded product made of fibrous basic aluminum sulfate or fibrous alumina as described above.

The fibrous basic aluminum sulfate and fibrous alumina used in the present invention are novel compounds with an extremely fine diameter of 0.1 to 1 micron and a length to diameter ratio (aspect ratio) of 20 or more. . The reason why such fine fibrous basic aluminum sulfate (hereinafter also abbreviated as FBA) or fibrous alumina (hereinafter also abbreviated as FA) is used as a raw material is as follows. In other words, when a porous sintered body is made, since the skeleton is composed of fine fibers, the volume occupied by the skeleton becomes smaller than that of the pores.
It has a large porosity.

Therefore, a porous alumina sintered body having a small diameter and fluid permeation resistance can be obtained. Moreover, since the voids formed between the fine fibers become pores, the diameter of the pores becomes minute. In this way, by using the fine FBA or FA used in the present invention as an aggregate, porous alumina sintering that is lightweight and has excellent fluid permeability despite having a minute pore size, which was previously unachievable. It is possible to obtain a body. However, the above FBA or F used in the present invention
Even if the fiber diameter meets the requirements of 0.1 to 1 micron, it has a smaller aspect ratio #! l! If fibers are used as raw materials, the pores tend to disappear during sintering, resulting in a decrease in porosity.On the other hand, if larger diameter fibers are used, the pore diameter increases and the uniformity of the pore diameter is significantly impaired. Shortcomings arise. Therefore, the object of the present invention cannot be manufactured using conventionally known alumina fibers as raw materials.

In the present invention, the shape of FBA or FA has a diameter of 0.1
~1 micron, and if the aspect ratio is 20 or more, the crystal structure seen by X-ray diffraction is α-alumina or γ-alumina.
-Alumina.

So-called transition aluminas such as δ-alumina, η-alumina, θ-alumina, etc., and even a mixture of these can be used as raw materials without particular restrictions.

FBA or FA that satisfies the above requirements used in the present invention
The manufacturing method is not particularly limited, but typical manufacturing methods are as follows. That is, the general formula LL
A sulfate soluble in a basic aluminum salt solution expressed as (OH) cxd (where X represents a monovalent anion, c+d=3, 0.5<c 1.9) was added to SO
Addition time T (unit: hours) until the molar ratio of 4/A4 reaches the value (3-c)/2 (where C is the general formula of basic aluminum salt At(OH), the sign in xd)
By adding at a rate that satisfies T<-14c+28, the average diameter is 0.05 microns or more.
less than a micron, usually around 0.1 to 0.5 micron,
General formula A having a length of 5 microns or more and 150 microns or less
t(OH)a(SO4)b-nH20 (however, a+2b=
5, 2.32<a<2.44, 0.28<b<0.
A fibrous basic aluminum sulfate (FBA) having the following formula (34°0<n≦10) is obtained.

The basic aluminum salt represented by the general formula AL(OH)cXd can be produced by various methods, but the most preferred method is the production of monovalent anionic aluminum salts, such as aluminum chloride, aluminum nitrate, and aluminum bromide. , aluminum iodide, aluminum citrate, aluminum acetate, etc., preferably aluminum chloride,
This method involves adding an alkali to an aqueous solution of aluminum nitrate, especially aluminum chloride. As the alkali, sodium hydroxide, potassium hydroxide, ammonia, etc. are used.

Soluble sulfates to be added to the basic aluminum salt solution include, for example, sodium sulfate, potassium sulfate,
Ammonium sulfate or the like may be used.

In this way, FBA can be used as a raw material for the present invention.

Furthermore, by firing this FBA, it is possible to obtain FA in which the above-described fiber shape is substantially maintained, and this FA is useful as a raw material for the present invention. For example, FBA is 1000
Fibrous r-alumina is obtained by firing at 1200C, and fibrous α-alumina is obtained by firing at 1200C.

The method for obtaining +M molded products with FBA or FA is not particularly limited, and includes slurry casting, vibration e1J
Known methods such as molding, wet or dry pressure molding, and extrusion molding can be used. In addition, the shape of the molded product is also pellet-like9.
spherical.

The shape may be appropriately selected depending on the purpose of use, such as a plate shape, a block shape, or a cylindrical shape. It is also effective to add a molding aid when obtaining a molded product. There are no special restrictions on molding aids.
Known materials used for molding powder and granular materials can be used.

For example, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone.

Alginate, methylcellulose, carboxymethylcellulose, starch, phenolic resin.

Organic molding aids such as melamine resin, sodium silicate, ethyl silicate, colloidal silica, colloidal alumina, basic aluminum chloride.

One or more types of inorganic molding aids such as aluminum phosphate can be used.

The obtained molded product is dried by an appropriate method, if necessary, and sintered to form a porous alumina sintered body. In the present invention, there are no restrictions on the sintering equipment or sintering conditions, and the shape of the molded product may vary.

Optimal conditions for the apparatus may be determined depending on the type of forming aid, the pore size, pore size, fluid permeability, mechanical strength, etc. of the sintered body. Regarding the sintering conditions, the sintering can be performed, for example, in an air atmosphere, and the temperature is preferably: 1200° C. or higher for 9 hours, preferably 1 hour or longer. Generally speaking, among the forming aids that can be used to obtain the above-mentioned molded products, inorganic ones in particular remain in the sintered body and act as binders, but they are also used to control glassy franks, viscosity, etc. It can also be added as a binder. Addition of a binder is effective in improving the mechanical strength of the sintered body when a porous alumina sintered body is obtained by sintering at a low temperature. When sintering at a high temperature, it is naturally possible that the components of the forming aid and binder form a solid solution in the alumina or react with the alumina to form a compound. For example, Sin,
A part of the porous alumina sintered body is obtained by adding a binder containing as a component and sintering at 1 sooc.
(3At20=.2SiO2) etc. may be observed.

This is permissible as long as requirements such as pore diameter, porosity, mechanical strength, heat resistance, and chemical resistance are satisfied depending on the intended use of the sintered body.

The obtained porous alumina sintered body has voids formed between fibers as pores. In the present invention, it is possible to obtain a porous alumina sintered body having fine pores with an average pore diameter of 0.1 to 5 microns and a porosity of 50 to 90%, although this varies depending on the molding method, sintering conditions, etc.

The porous alumina sintered body thus obtained can be used in the field of application of conventionally known porous ceramic sintered bodies. For example, it can be made into a plate-shaped or cylindrical sintered body and can be effectively used as a #f thermal radiation chemical resistant filter by taking advantage of its low fluid permeation resistance while having a narrow pore diameter. Moreover, it can be made into a lump-like sintered body and used as a heat insulating material or a sound absorbing material such as a fireproof insulation brick for high temperature use. The porous alumina sintered body produced by the present invention has great utility value, such as when it is made into a pellet-like or spherical sintered body, which can be used as a heat-resistant catalyst carrier or adsorbent that has fine pores inside. be.

EXAMPLES Examples are shown below to specifically explain the present invention, but the present invention is not limited to these Examples.

Example 1 1000 d of V2N-Atct3 aqueous solution was placed in a beaker and stirred, and 466 d of 1/2N-kJHaOH aqueous solution was added thereto at a rate of 2.56 A/min. The resulting aqueous solution theoretically has the general formula At(OH) 1.4oc/,
It is an aqueous solution of basic aluminum chloride with a composition represented by +, 6o. While stirring the entire amount of this basic aluminum chloride aqueous solution, '/4N-Na2S04 aqueous solution 14
25all was added at a rate of 5.9 d/min to obtain a suspension of fibrous basic aluminum sulfate. All of the above reactions were performed at room temperature. Fibrous basic aluminum sulfate particles were filtered from the suspension, washed with water, and then dried at 60°C. The fibrous basic aluminum sulfate thus obtained has the general formula At(
OH12,5B(SO4)a, sl・0.98 H2O
It was expressed as

The fibrous basic aluminum sulfate obtained by the above method was fired at 1200° C. for 30 minutes in an electric furnace under an air atmosphere to obtain fibrous alumina.

The fibrous alumina particles have a diameter of about 0.1 to 0.5 microns, as observed using a scanning electron microscope.

It had a shape with a length of about 40 to 100 microns, and showed a diffraction pattern of only α-alumina in X-ray diffraction.

The above fibrous alumina 4f was suspended in 100 cr4 of a 2X polyvinyl alcohol aqueous solution for 1 li Jl, and the suspension was suction-filtered to produce a disk of fibrous alumina with a diameter of 50 mm and a thickness of 4 mm.

After drying this at 60℃, it was heated to 150℃ in an air atmosphere in an electric furnace.
After sintering at 0° C. for 3 hours, a disc of porous alumina sintered body having a diameter of 47 mr and a thickness of 3.6 mm was obtained. The apparent density of this sintered body was 0.64 t/-. When the structure of the sintered body was observed with a scanning electron microscope, the shape of the raw material fibrous alumina was somewhat broken, perhaps due to grain growth during sintering, but the sintered fibrous alumina particles formed a skeleton. Many fine pores were formed between them.

The pore size distribution and pore volume of this porous alumina sintered body were measured by mercury intrusion method. As a result, the pore diameter is 1.2~
The average pore size was 2.0 microns and the pore volume was 1.3 cI/I/f.

The porosity calculated from the apparent density and pore volume of the sintered body was 83N. The bending strength of the sintered body is 50Kf/d.
Met.

Example 2 Approximately 42 kg of the fibrous alumina obtained in Example 1 was filled into a mold,
Uniaxial pressure molding was performed at a pressure of 100 Ky/d and 2 DOKf/cd to form a disk with a diameter of 40 pieces and a thickness of 3 or 4 ropes (Sample A), and a disk with a diameter of 40 pieces and a thickness of 3 mm (Sample B).
) was created.

These disks were sintered at 1000° C. for 3 hours in the same manner as in Example 1. Apparent density of the obtained porous alumina sintered body,
The pore diameter, pore size, etc. are shown in Table 1.

Table 1 Example 3 To about 82 grams of the fibrous alumina obtained in Example 1, about 49 grams of a basic aluminum chloride aqueous solution (At205 content 20X) and about 61 grams of water were added and mixed well to prepare a slurry. This slurry was poured into a plastic mold and dried at 60°C for 12 hours to obtain a molded body. The molded body was prepared in the same manner as in Example 1.
Sintering was carried out at 00°C for 6 hours to obtain a porous alumina sintered body. In this sintered body, the pore diameters were distributed in the range of 1.2 to 4.0 microns, the average pore diameter was 2.2 microns, the pore volume was 0.96 ca/y, and the porosity was 76%. The bending strength was 44 h/cll.

Example 4 An ethanol solution of a hydrolyzed polymer of ethyl silicate (5i02 content 18
%) and about 41% of ethanol were added and mixed, and the entire amount was poured into a plastic mold and dried at room temperature for 24 hours to obtain a molded product. This compact was sintered in an electric furnace 1n''r1.200C and 1500C for 3 hours. From the results of X-ray diffraction measurements of these sintered compacts, it was found that the sample sintered at 1200℃ had a δ-alumina structure. However, the sample sintered at 1500°C showed a diffraction pattern of a partial mullite structure in addition to the α-alumina structure.The average pore diameter and porosity of the sintered body were 1.
4 microns, 86%, and 1.6 microns, 80% for the 1500° C. sintered sample.

Example 5 10ooy of a '/2N-AACt3 aqueous solution was placed in a beaker and stirred, and 466d of a 1/2N-NH40H aqueous solution was added thereto at a rate of 2.5 ffl/min. The resulting aqueous solution theoretically has the general formula ht(o () +, 4o
It is an aqueous solution of basic aluminum chloride with a composition represented by CL1, +so. While stirring this basic aluminum chloride aqueous solution, 1423 d of a 1/4N-Na2S04 aqueous solution was added at a rate of 5.9 m/min to obtain a suspension of fibrous basic aluminum sulfate particles. All of the above reactions were performed at room temperature. Fibrous basic aluminum sulfate particles were filtered out from a portion of the suspension, washed with water, and then dried at 60°C. The fibrous basic aluminum sulfate thus obtained is
General formula Az-(on)2.3a(804)o, x+ ・
0.98 H2O, and the particles have a diameter of 0.1 to 0.98 H2O, as observed with a scanning electron microscope.
It had a shape of 5 microns and a length of 40-100 microns.

The above suspension of fibrous basic aluminum sulfate particles was filtered with suction, and the precipitate was filtered off. After washing the filter cake with ion-exchanged water, dry it in a dryer without changing the shape of the filter cake.
When dried at 0'c, a disk was obtained that was strong enough to be handled. The disc is approximately 90B in diameter.

It was in the shape of 6 to 4 inches thick and weighed about 9 yards.

As described above, the particles of the fibrous basic aluminum sulfate used in the present invention have no fiber shape, and can be formed into molded products by easy operations such as suction filtration.

A disk-shaped molded product of fibrous basic aluminum sulfate was placed in an electric furnace and sintered at 1300° C. for 1 hour in an air atmosphere to produce a porous alumina sintered body. By sintering, the sample showed a linear shrinkage rate of about 25%, and the amount of i decreased by about 56%. This sintered body is designated as sample C.

In the same manner as above, a disc-shaped molded product of ffl & fU basic aluminum sulfate was heated at 1500°C for 1 hour (Sample D
) and 1700'C for 1 hour (Sample E).

The weight loss rate of these samples was the same as sample C, but
The linear shrinkage rate was about 27% for Sample 1, and about OX for Sample E. The properties of the porous alumina sintered sample are shown in Table 2.

(Table 2) Example 6 A disk of fibrous basic aluminum sulfate was prepared in the same manner as in Example 5 (shape: approx. 40% diameter).

A thickness of approximately 15 m and a weight of 9 tons was manufactured. A basic aluminum chloride aqueous solution (AL20s content 10
X) was impregnated under reduced pressure.

After impregnation, the discs were air-dried at room temperature for 5 hours and weighed, and the weight had increased to about 17 r. Next, this sample was placed in a cylindrical mold with an inner diameter of 40 mm and uniaxially pressed at 200 kg/cd to form a disc-shaped molded product. The molded product made of the fibrous basic aluminum sulfate thus obtained was heated to 1°C using an electric furnace.
It was baked at 000°C for 1 hour. The molded product after firing is
According to line diffraction, it was composed of r-alumina. Next, the molded product was placed in an electric furnace at 1500°C in an air atmosphere.
A disc-shaped porous alumina sintered body was produced by sintering for 6 hours. The sintered body has an apparent density of 1.46 g/d and a diameter of 27
It had a shape with a diameter of 5 cm and a thickness of 5 cm. The pore diameters of the porous alumina sintered body thus obtained were distributed in the range of 0.9 to 1.8 microns, the average pore diameter was 1.4 microns, and the pore volume was 0.437/f. The porosity calculated from the apparent density and pore volume is 66X. Furthermore, the bending strength was measured and found to be 390 Kg/cyJ.

Patent Applicant: Tokuyama Soda Co., Ltd. Procedure Amendment: June 2, 1939 Director-General of the Patent Office Mr. Kazuo Wakasugi/Case List Patent Application: 1982/Gua 0g S No. 6 Invention Famous Porous Alumina Relationship between molded products and their manufacturing method 3, person making amendment 9'4 Patent applicant address Mikage-cho, Tokuyama City, Yamaro Prefecture/No. Date of order to correct sleeves Voluntary Number of inventions increased by voluntary amendment 7. Contents of the amendment ■ 8. Name of the invention in the title of the invention column of the old publication 1 subject to amendment has been deleted to ``Porous alumina molded product and method for manufacturing the same.'' Correct.

■, Paulownia in the scope of patent claims Correct as shown in the attached sheet.

111, column for detailed description of the invention + I + 6th line from the bottom of the first R of the specification evening and λ from the bottom of In'l
In each line, correct the alumina "sintered body" to the alumina 1゛ molded body.

(2) In the 1st line of the 2nd R, "sinter" is 1' fired and sintered" and the pressure is 61.

(3) On the second page, line λ from the bottom, ``sintered'' was corrected to ``1 firing.''

tJJ 3rd line / 3rd line ~ /< line, "furnace, Ki body"
is defined as a "fired product".

(5) From the bottom of page 3, line A to end of episode M, ``This departure Moe is...
・・・・・・・・・It is provided. ” as follows.

``The present invention is a porous alumina molded product having an average pore diameter of θ, /~S micro/, and a porosity of 5θφ or more. Fiber glue having a ratio of diameter to diameter of 20 or more 1) Porous alumina molded product formed by RI kneading at a temperature of 200C or higher (61, page 21 Jig, line 9, "When made into a porous sintered body" is "") When the FBA or FA described in 1 is sintered in the firing steps 1 to 1, Corrected to 11.

(7) Same gtt <z 7th line from the bottom, "alumina sintered body" is corrected to "alumina molded product".

(Page 5/line 81, “sintered body” is corrected to “molded product”.

(9) Same page 9, line 7, ``Subject to sintering'' by 1゛ firing and j K correction.

(11th, 9th, lines 3 to 5, "sintered body" is corrected to "molded product".

aD, page 7, lines G to S, [Sintering device, sintering strip (1
2. On page 7, line 2, after "or" is corrected to "obtained by firing."

Correct the "sintering conditions" on the 9th page, line g to line 9 of the θ interval, to the "firing conditions".

C4) Insert "obtained by firing" between "monoha" and "sintered body" on page 7, line 73.

0!9 Page 1/Line 2 and 3~ from the bottom. The second line “
"sintering" should be corrected to "firing".

4th line from the bottom, ``sintered body'' is corrected to ``molded product.'' 15゜annnn.

08 Same page 0th line G, O line, 7th line, /G line 7/
In lines B, 777 and 799, "sintered body" is corrected to "molded product".

α1 1st page) line, S line, and 2 line, respectively.
Correct "sintered body" to "1 molded product".

(b) On page 13, line 1, "sintering" is corrected to "firing".

C11l, page 73, lines 2-3, line 3, line G, /θ
"Sintered body" in the 0th line and the /2nd line respectively.
Corrected to "molded object".

C2 same page 1, line 5, "sintering" has been corrected to "firing".

OQ Dodo 1st Wataru correct.

C41 14th/. Negative: The apparent density of "sintered body" in column 3 of Table 1 is corrected to the apparent density of "molded product."

Q9 On page 75 and line 1, correct "sintering" to "F# formation".

(1) ``1 sintered body'' in the moss area on the first left page of the same page is corrected to ``molded product.''

(Foundation) Correct "sintering" to "firing" in lines λ, 3, and G of page 1 of the same page.

(2) Correct "sintered body" in the first row of the same document to "molded product".

Usido page 1g, line 3, hiroki, and line 700, respectively.
Correct "sintering" to "firing".

01 DI/g Page 3, line 2, and line 733 [Correct sintered body-1 to "molded object."

6D Same page 19, column 2 of λ table, "Sintering temperature: 7 degrees" is corrected to V firing temperature J.

ζ3z Do 1, page 19, Table 34 (P0, correct the apparent density of "sintered body" to the apparent density of "molded product".

Q On page 2θ, line 7, "sintering" is corrected to "firing".

Apply pressure to the ``sintered body'' on page 20 of the same publication, lines 7, 6, and lines 70-//, respectively.

Claims after the above correction +2+ A porous structure composed of fibrous basic aluminum sulfate or fibrous alumina with a m diameter of 0.7 to 1 micron and a length-to-diameter ratio of 20 or more. A method for producing alumina molded product.

(2) A method according to claim 1, wherein the aluminum sulfate is composed of fiber-based aluminum sulfate and is then phosphoricated at a temperature of /2θOC or higher. ”

Claims (2)

[Claims] (1) Porous material characterized by sintering a molded product made of fibrous basic aluminum sulfate or fibrous alumina with a diameter of 0.1 to 1 micron and a length-to-diameter ratio of 20 or more. A method for producing an alumina sintered body. (2) The method according to claim (1), wherein a molded product made of fibrous basic aluminum sulfate is fired and then sintered.