JP2000119060A - Highly plastic alumina paste and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a highly plastic alumina paste useful as a ceramic stock by incorporating alumina particles with agar-agar. SOLUTION: This highly plastic alumina paste is obtained by melting agar powder under boiling followed by cooling to form agar gel which is then kneaded with alumina particles; alternatively, by adding alumina particles to an aqueous solution of agar powder which is melted under boiling in advance, followed by cooling the system to effect coating the alumina surface with agar-agar followed by dehydration; wherein it is preferable that the agar-agar to be used as a starting material is >=5 g/cm2 in jelly strength, and the agar content of the final alumina paste is 0.5-10 wt.%. This alumina paste obtained by mixing (kneading) process is capable of controlling its pore size depending on its gel size, therefore being advantageous for making porous forms; whereas another version of this alumina paste obtained by coating process is hard to produce pores because the agar-agar as binder uniformly and extremely thinly adheres to the alumina, therefore affording a dense sintered compact, dense/high- density molded form or molded form with controlled pore size. The above method for producing this alumina paste is effective in cost reduction and operability improvement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina kneaded clay having high plasticity and a method for producing the same, and more particularly to an alumina particle suitable as a molding material for ceramics.

[0002]

2. Description of the Related Art Alumina is widely used as a ceramic material. Alumina is produced by a Bayer method or the like, and the conventional alumina raw material is an alumina single phase. However, it is pointed out that the plasticity of alumina is lower than that of clay in rice fields, Shibazaki, Sakai, Katagiri, Fujimoto; Powder and Powder Metallurgy, Vol. 35, No. 7, (1988), p. 619.

[0003] Therefore, when producing alumina ceramics by plastic molding such as extrusion molding or injection molding, it is necessary to add an organic substance as a molding aid. However, in the case of the conventional organic additives, the addition increases the adhesive strength, and the use of an organic solvent as a dispersion medium deteriorates the workability due to volatilization of the organic solvent. In addition, most of the organic binders are chemically synthesized, and have an adverse effect on the environment during the synthesis.

[0004] Although there is an organic substance as an aqueous binder, the cost increases.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an alumina kneaded clay having high plasticity as a ceramic raw material and a method for producing the same. In particular, it is to improve the plasticity of the aqueous clay of alumina. Furthermore, by using agar which is inexpensive and easily available as a binder for molding in an aqueous system, cost reduction and improvement in workability are expected.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by adding agar to alumina particles to prepare a kneaded material, and have reached the present invention. That is, the present invention includes the following (1) to (7).

(1) A highly plastic alumina kneaded clay characterized by adding agar to alumina. (2) The highly plastic alumina kneaded clay according to the above (1), wherein the alumina surface is coated with agar. (3) The highly plastic alumina kneaded material according to the above (1) or (2), wherein the agar has a 1.5% jelly strength of 5 g / cm ² or more. (4) The highly plastic alumina kneaded clay according to any one of (1) to (3), wherein the content of agar to alumina is 0.5 to 10% by weight.

(5) After dissolving the agar powder, it is cooled,
A method for producing highly plasticized alumina kneaded clay, comprising preparing a swollen agar, pulverizing the agar, and mixing with alumina particles to form a kneaded clay. (6) A method for producing highly plastic alumina kneaded material, comprising dissolving agar powder, adding alumina particles to the powder, and cooling the resulting solution to coat the agar on the alumina surface. (7) The method for producing a highly plastic kneaded alumina according to any one of the above (5) to (6), wherein the amount of agar added to the alumina is 0.5 to 10% by weight.

The alumina kneaded material of the present invention is obtained by adding agar to alumina particles. There are the following two addition methods. That is, a method of obtaining a kneaded material by mixing and kneading the gel and alumina particles after preparing an agar gel by cooling after boiling the agar powder, adding alumina particles to an aqueous solution obtained by boiling the agar powder, and then cooling. This is a method in which agar is coated on the surface of the alumina particles, and the deaerated soil is obtained after dehydration. In the present invention, the shape of the alumina particles such as a sphere, a plate and a bar is not limited. The finer the particle size of the alumina particles, the better, but not particularly limited.

The type of agar is not particularly limited. Agar has different properties, such as jelly strength, depending on the raw material and method of preparation, but can be used as a binder if the jelly strength is 5 g / cm ² or more. Further, the amount of agar based on alumina is preferably 0.5 to 10% by weight. If the amount is less than 0.5% by weight, the effect as a binder is not sufficient and the plasticity as expected is not exhibited. If the amount exceeds 10% by weight, the clay becomes paste or gel, which is inconvenient.

As described above, the feature of the present invention is that a highly plastic alumina kneaded clay can be used as an inexpensive and easily available agar to convert alumina having poor plasticity into a kneaded clay exhibiting good plasticity. The porosity of the molded article differs depending on the method of adding agar. The kneaded mixture of alumina particles and agar gel can control the pore size by the gel size, which is advantageous for forming a porous body. Unlike these, in highly plasticized alumina kneaded clay in which the alumina surface is coated with agar, the binder is homogeneous and very thinly adhered on the alumina, so that it is difficult to form pores and a dense sintered body can be obtained. it can.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Evaluation of plasticity was carried out by a compression test using a universal testing machine (test piece size: φ33h4).
0). This evaluation shows the same tendency as the Peffer cone test which is known as a method for evaluating the plasticity of the clay. This method was used because it can be evaluated by an operation similar to the actual molding method of compression. The outline of the evaluation method is shown in FIGS. Displacement determined from compression test-Displacement from load curve-
A compression curve is determined, and the slope of the initial rise is evaluated as an index of shape retention, and the integral value of the latter half of the displacement-load curve is evaluated as an index of fluidity. Higher shape retention and better fluidity means better plasticity. That is, the evaluation is such that the gentler the slope in FIG. 3, the better the plasticity.

Example 1 As alumina particles, low soda alumina AE manufactured by Sumitomo Chemical Co., Ltd.
S11C (specific surface area 6.6 m ² / g, center particle diameter 0.36
μm α-alumina particles). T-1 (jelly strength 900 g / cm ² ) manufactured by Ina Food Industry Co., Ltd. was used as the agar powder. 3 parts of agar powder were added to and dissolved in 30 parts of boiling distilled water, and then cooled to prepare an agar gel. This gel was sifted using a sieve having a mesh size of 1 mm, and then mixed and kneaded with 100 parts of alumina to prepare a kneaded material. Evaluation of plasticity was performed by the above-mentioned compression test. FIG. 4 shows the plasticity evaluation results. The plasticity was improved as compared with the raw material low soda alumina.

Example 2 As alumina particles, low soda alumina AE manufactured by Sumitomo Chemical Co., Ltd.
S11C was used. Ina Food Industry Ultra Agar AX-30 (jelly strength 10 g / cm ² ) was used as the agar powder. 3 parts of agar powder were added to and dissolved in 30 parts of boiling distilled water, and then cooled to prepare an agar gel. This gel was sifted using a sieve having a mesh size of 1 mm, and then mixed and kneaded with 100 parts of alumina to prepare a kneaded material. Evaluation of plasticity was performed by the above-mentioned compression test. FIG. 4 shows the plasticity evaluation results. Although not comparable to Example 1, the plasticity is improved as compared with the starting material.

Example 3 Low Soda Alumina AE manufactured by Sumitomo Chemical Co., Ltd. as alumina particles
S11C was used. T- made by Ina Food Industry as agar powder
1 (jelly strength 900 g / cm ² ). 3 parts of agar powder is added to and dissolved in 1000 parts of boiling distilled water,
100 parts of alumina was added and mixed therein. Thereafter, the mixture was allowed to cool while stirring, and solid-liquid separation was performed by centrifugal separation. The cake was appropriately dried to obtain alumina clay. Evaluation of plasticity was performed by the above-mentioned compression test. FIG. 4 shows the plasticity evaluation results. The plasticity is higher than in Example 1.

Example 4 As alumina particles, low soda alumina AE manufactured by Sumitomo Chemical Co., Ltd.
S11C was used. Ina Food Industry Ultra Agar AX-30 (jelly strength 10 g / cm ² ) was used as the agar powder. 3 parts of agar powder were added to and dissolved in 1000 parts of boiling distilled water, and 100 parts of alumina was added thereto and mixed. Thereafter, the mixture was allowed to cool while stirring, and solid-liquid separation was performed by centrifugation. This cake was appropriately dried to obtain alumina kneaded material. Evaluation of plasticity was performed by the above-mentioned compression test. FIG. 4 shows the plasticity evaluation results. The plasticity is higher than in Example 2.

Example 5 As alumina particles, high-purity alumina AKP2 manufactured by Sumitomo Chemical Co., Ltd.
0 (α-alumina particles having a specific surface area of 4.7 m ² / g and a central particle diameter of 0.53 μm) were used. T-1 (jelly strength 900 g / cm ² ) manufactured by Ina Food Industry Co., Ltd. was used as the agar powder. 0.5, 1, 3, 5, and 10 parts of the agar powder were added and dissolved in 1000 parts of boiling distilled water, and 100 parts of alumina was added and mixed therein. Thereafter, the mixture was allowed to cool while stirring, and solid-liquid separation was performed by centrifugation. This cake was appropriately dried to obtain alumina kneaded material. Evaluation of plasticity was performed by the above-mentioned compression test. FIG. 5 shows the plasticity evaluation results.
The plasticity improved with each dose. Also, the plasticity improved as the amount of agar increased.

Example 6 Plate-shaped alumina YFA006 made of YKK was used as the alumina particles.
10 (specific surface area: 7.6 m ² / g, center particle diameter: 0.60 μm
m, α-alumina particles having an aspect ratio of 10).
AX-100, ZR, M made by Ina Food Industry as agar powder
7, T1 (each jelly strength 100, 420, 73
0, 900 g / cm ² ). 3 parts of the agar powder were added to and dissolved in 1000 parts of boiling distilled water, and 100 parts of alumina was added thereto and mixed. Thereafter, the mixture was allowed to cool while stirring, and solid-liquid separation was performed by centrifugation. This cake was appropriately dried to obtain alumina kneaded material. Evaluation of plasticity was performed by the above-mentioned compression test. FIG. 6 shows the plasticity evaluation results. Plasticity improved with increasing jelly strength.

[0019]

According to the present invention, an alumina kneaded material having high plasticity can be obtained, and a compact having a high density and a compact having a controlled pore diameter can be obtained. Therefore, it can be widely applied to structural components, electronic components, porous materials, and other fields as materials having excellent heat resistance, electrical insulation, mechanical strength, and the like. In addition, since agar which is inexpensive and easily available is used as a binder, and good kneaded soil can be obtained only by kneading with water, it is effective in reducing costs and improving workability.

[Brief description of the drawings]

FIG. 1 is a graph showing how to determine fluidity.

FIG. 2 is a graph showing how to obtain shape retention.

FIG. 3 is an explanatory diagram of how to read a plasticity evaluation diagram.

FIG. 4 is a graph showing plasticity evaluation results of Examples.

FIG. 5 is a graph showing the results of plasticity evaluation of alumina kneaded clay according to the amount of agar added in Example 5.

FIG. 6 is a graph showing the results of evaluating the plasticity of the alumina kneaded material by adding agar in Example 6.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Ono 1-66, Koonji-cho, Kita-ku, Nagoya-shi, Aichi Prefecture, Estate String Fourth Road Room 306 (72) Inventor Yasuo Shibasaki 2-4 Daiho, Atsuta-ku, Nagoya-shi, Aichi Prefecture Shiratori Park Heights Daihodan 9 Building 601 (72) Inventor Kiichi Oda 5 Chiyogaoka, Chigusa-ku, Nagoya-shi, Aichi 5 Communitas S-715 (72) Inventor Saburo Sano 3-2-3, 15 −24 (72) Inventor Takumi Banno 2-109, Yachiyo Ryo 103, Yachiyo-cho, Kita-ku, Nagoya-shi, Aichi 103 (72) Inventor Kenta Oguri 3-2, 103-1206, Sunadabashi, Higashi-ku, Nagoya-shi, Aichi (72) Inventor Shuji Kawai 2-3-2-22 Mizuho-cho, Handa-shi, Aichi Prefecture, Room 206, East Town (72) Inventor Yuji Nomura 2-1-11 Kinjo, Kita-ku, Nagoya-shi, Aichi, Corp. No. F term (reference) 4G030 AA36 BA12 BA18 BA20 BA21 GA07 GA14 4G076 AA26 AB02 AB11 BF02 DA18 DA30

Claims (7)

[Claims] 1. A highly plasticized alumina kneaded clay characterized by adding agar to alumina. 2. The highly plasticized alumina kneaded clay according to claim 1, wherein the alumina surface is coated with agar. 3. The agar has a 1.5% jelly strength of 5 g / cm.
The highly plastic alumina kneaded clay according to claim 1 or 2, which is ² or more. 4. An agar content of 0.5 to alumina.
The highly plastic alumina clay according to any one of claims 1 to 3, which is 10 to 10% by weight. 5. A highly plasticized alumina kneaded clay characterized by dissolving agar powder, cooling and swelling agar to prepare a swollen agar, pulverizing the agar, and mixing it with alumina particles to form a kneaded soil. Method. 6. A method for producing a highly plasticized alumina kneaded material, comprising dissolving agar powder, adding alumina particles therein, and then cooling the agar on the alumina surface. 7. The amount of agar added to alumina is 0.5
The method for producing highly plasticized alumina kneaded material according to any one of claims 5 to 6, wherein the amount is from 10 to 10% by weight.