JP2001220245A - Method for extrusion molding ceramic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for extrusion molding a ceramic material, not impairing moldability, capable of providing an excellent extrusion molding product even if the whole binder amount used is reduced by 40% at the maximum, being economic and improving the density of sintered compact after sintering due to a small amount of an organic binder required, by using both a water-soluble hydroxyalkyl alkyl cellulose and welan gum in comparison with the single use of the water-soluble hydroxyalkyl alkyl cellulose. SOLUTION: A ceramic material having 0.2-10 micron particle diameter on the average in an amount of 100 pts.wt. is mixed with 1-4 pts.wt. of water-soluble cellulose ether and 2-5% based on the water-soluble cellulose ether of welan gum as a binder, kneaded with water and molded by using a vacuum extrusion molding machine to give an excellent molding product.

Description

DETAILED DESCRIPTION OF THE INVENTION

INDUSTRIAL APPLICABILITY The present invention can significantly reduce the total amount of binder compared to the prior art, achieve economic effects, and improve the density of a ceramic material after sintering. It relates to a possible extrusion molding method.

2. Description of the Related Art Conventionally, sinterable ceramic materials such as alumina, zirconia and cordierite for oxides, and silicon carbide (α, β type) and silicon nitride for non-oxides Have been used for ceramic capacitors, IC packages, heating elements, catalyst carriers, filters, and industrial machine parts. In general, the molding method is extrusion molding into a sheet, plate, prism, column, or honeycomb shape, and cutting into an appropriate length and shape, followed by drying, degreasing, and sintering. It is manufactured through a process. As the binder for the extrusion molding, a water-soluble cellulose ether is used, and particularly preferably, a hydroxyalkylalkylcellulose is used. In this case, after the fine powder of the ceramic material and the binder are mixed in a dry state, water is added, the mixture is kneaded with a kneader or the like, and then molded through a suitable die using a vacuum extruder. In this case, polyhydric alcohols such as glycerin, glycol and derivatives thereof are often used in combination for the purpose of preventing cracks due to drying. As a ceramic material, generally considering moldability,
Fine powders having an average particle size of about 0.2 to 10 microns are used, but these are generally poor in plasticity and cannot be molded only by adding water. Therefore, the above-mentioned water-soluble hydroxyalkylalkylcellulose is added. In this case, the amount of addition varies depending on the properties of the ceramic material and its particle size, but the preferable range is generally 2 to 6 parts by weight. . The molded ceramic material is finally baked to produce a product, in which case the amount of binder is affected by the density after sintering. The smaller the amount of the binder, the better the results. When the density is high, the physical strength is improved, and it is also an important property that gives good results to the electrical characteristics and the like.

[Problems to be Solved by the Invention] Clays are sometimes added in order to impart plasticity to a ceramic material. In this case, however, physical properties after firing are often adversely affected. In the present situation, it has to be used in an amount, and it has to depend on hydroxyalkylalkylcellulose which is an organic binder. An object of the present invention is to significantly reduce the amount of added hydroxyalkylalkylcellulose, maintain moldability without impairing moldability, maintain excellent shape retention after molding, and furthermore, an important property of a ceramic material. An object of the present invention is to provide an extrusion molding method capable of improving the density of a sintered body.

[Means for Solving the Problems] For this reason, by using welan gum equivalent to only 2 to 5% of hydroxyalkylalkylcellulose as a binder, it is possible to reduce the total amount of binder added by up to 40%. And the density of the sintered body can be improved by 10% or more. Welan gum shows high viscosity at low concentration,
It has been found that the aqueous solution has a high non-Newtonian fluidity, or that it is in a kneaded state with inorganic fine particles, and has an effect of greatly improving moldability under a high shearing force. . The amount of welan gum added is generally better as much as possible, but if it exceeds 5% in the work process of the kneaded material before it is extruded by a kneader, the viscosity increases and it becomes a large lump. Feeding to the extruder becomes impossible. Also, the hydroxyalkylalkylcellulose is a ceramic material 1
If the amount is less than 1 part by weight relative to 00 parts by weight, the cohesive strength becomes poor, and welan gum cannot compensate for this.

The ceramic material used in the present invention is an oxide-based or non-oxide-based fine powder,
Both those that require and do not require caking aids are included, but as aids, silicates, such as feldspar,
Alternatively, a rare earth oxide such as yttrium oxide is used.

As the plasticizer and wetting agent used in the present invention, polyhydric alcohols such as glycerin, ethylene glycol, propylene glycol, polyethylene glycol or derivatives thereof are used. The purpose is to prevent the occurrence of the occurrence, or to plasticize the sheet-shaped product so that it can be wound up, but it is not always necessary for the purpose.

[Examples] Specific embodiments of the present invention will be described below with reference to examples and comparative examples.

Details of materials used; ceramic material; low-soda alumina as an oxide, having an average particle size of 0.9 μm (AES manufactured by Sumitomo Chemical Co., Ltd.)
-21), α-SiC, 2.0 μm average particle diameter (GP-6,000 manufactured by Shinano Electric Refining Co., Ltd.) was used as a non-oxide type. Hydroxyalkyl alkyl cellulose: 20 ° C, 2%
Hydroxypropyl methylcellulose having an aqueous solution viscosity of 4,000 cps (HPMC 65SH40 manufactured by Shin-Etsu Chemical Co., Ltd.)
00) was used. Welan gum: 20 ° C., viscosity of 1% aqueous solution is 2,500
Cps or more (KIA96 manufactured by Merck) was used. Plasticizer: Glycerin was used. After mixing and mixing the materials shown above in a 5-liter double-arm kneader with the composition shown in Tables 1 and 2, a water solution in which glycerin was previously dissolved in a predetermined amount of water was poured and kneaded, The molding speed was measured, and the observation and evaluation of the molding state and the density of the sintered body after firing were measured by the following method [0009]. The results are also shown in Tables 1 and 2.

Test method Extrusion speed: The length of the molded body extruded from the discharge port is 20
The time (sec) required to reach cm is measured. Motor current; measured by an ammeter attached to the main motor, the higher the extrusion resistance, the higher the current.
This is an indication of moldability, and the following relationship exists in the Y-22 type machine. State of molded body: Observed visually. Sintering density: A piece obtained by slicing an extruded molded body to a thickness of 2 mm in a direction perpendicular to the extrusion direction (length: 12 mm)
x width: 30 mm x thickness: 2 mm), and dried at 110 ° C. for 10 hours, and then left at 250 ° C. for 5 hours and further at 400 ° C. for 5 hours to evaporate or decompose the plasticizer and binder. . Next, firing is performed at 1,350 ° C. for silicon carbide and 1,600 ° C. for alumina for 5 hours. After cooling, the dimensions are measured to determine the volume, and the weight is further measured to determine the density (g / cm3). The average value of five sheets was calculated and recorded.

[0010] 1b: Very clean with a smooth surface. 2b: Smooth surface, but a little meandering can be seen inside.
Due to resistance, there is adhesion of metal powder on the inner surface. 3b: The surface is in a rippled state due to pulsation. Due to high resistance, much metal powder adheres to the inner surface. 1a; less meandering and better surface condition than 2b. For resistance,
Some metal powder adhered due to friction. 2a: Very clean with a smooth surface. There is no adhesion of metal powder. 3a; substantially the same as 2a. 4a: The surface is slightly rippled. Slightly large internal resistance, metal powder adheres due to friction. 5a: Very clean with a smooth surface.

[0011]

According to the present invention, the moldability can be maintained and the density of the ceramic sintered body can be improved even if the total amount of the binder is greatly reduced.

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[Procedure amendment]

[Submission date] March 21, 2000 (200.3.2
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005] As a ceramic material used in the present invention, oxide-based, or a fine powder of non-oxide baked
And those requiring sintering aid, but contains both do not require, as auxiliaries silicates, for example feldspar, or rare earth oxides, such as yttrium oxide is used.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008] Details of the materials used; ceramic materials; low-soda alumina as an oxide system having an average particle diameter of 0.9 micron (AES-A Sumitomo Chemical)
21) As the non-oxide type, α-SiC, average particle size 2.0 μm (GP-6,000 manufactured by Shinano Electric Refining Co., Ltd.) was used. Hydroxyalkyl alkyl cellulose: 20 ° C, 2%
Hydroxypropyl methylcellulose having an aqueous solution viscosity of 4,000 cps (HPMC65SH400 manufactured by Shin-Etsu Chemical Co., Ltd.)
0) was used. Welan gum: 20 ° C., viscosity of 1% aqueous solution is 2,500
A cps or more (KIA96 manufactured by Merck) was used. Plasticizer: Glycerin was used. After mixing and mixing the materials shown above in a 5-liter double-arm kneader with the composition shown in Tables 1 and 2, a water solution in which glycerin was previously dissolved in a predetermined amount of water was poured and kneaded, This is vacuum extruded
Thickness 12 using a molding machine (Y-22, manufactured by Ishikawa Toki Tekkosho)
mm, through a die with a width of 30 mm, vacuum degree -670 m
Perform molding at mHg, measure the molding speed, and

According to the above method, the observation and evaluation of the molding state and the density of the sintered body after firing were measured.
Also shown in Table 2.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B29K 105: 04 C04B 35/00 D 201: 00 108

Claims (3)

[Claims] 1. The viscosity of a 2% aqueous solution at 20 ° C. is 400 to 1
A water-soluble hydroxyalkylalkylcellulose having 5,000 cps and 20% corresponding to 2 to 5% thereof;
C., 1 to 4 parts by weight of welan gum having a 1% aqueous solution viscosity of 2,500 cps or more based on 100 parts by weight of a ceramic material having an average particle diameter of 0.2 to 10 microns, and kneading with water. And then extrusion molding under vacuum. 2. The water-soluble hydroxyalkylalkyl cellulose includes hydroxyethyl methylcellulose,
The method of claim 1, wherein the method is selected from the group consisting of hydroxyethylethylcellulose, hydroxyethylpropylmethylcellulose, hydroxypropylmethylcellulose, and the like. 3. The method of claim 1, wherein the welan gum is a heteropolysaccharide produced by fermentation of aerobic bacteria.