JPS6259071B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a ceramic extrusion molding composition for manufacturing various ceramic products, and particularly to a new binder used in the composition. Ceramic electronic materials, typified by ceramic capacitors, insulators, permanent magnets, etc., are generally produced in large quantities through a molding-drying-firing process using extrusion molding. What is the ceramic extrusion molding method?Water, an organic binder, and a plasticizer are added to the raw material powder of the ceramics used, and these are sufficiently kneaded using a mixer.The composition is then molded into the desired shape using an extrusion molding machine. This method allows ceramics to be produced easily and efficiently in large quantities. The above-mentioned organic binder improves the extrudability by improving the fluidity of the kneaded product, and at the same time improves the shape retention and mechanical strength of the molded product, and has the effect of preventing the molded product from being damaged or deformed. Conventionally, water-soluble polymers such as starch, polyvinyl alcohol, and hydroxypropyl methylcellulose have been used for this purpose. However, such conventional organic binders have several drawbacks, and the development of binders with even better performance is expected. For example, when starch is used as a binder, the extrudability of the kneaded material for molding is not sufficiently improved, and it is also susceptible to spoilage, which poses a problem in its preservation. In the case of hydroxypropyl methylcellulose and polyvinyl alcohol, extrudability is good, but the molded products obtained by extrusion molding are highly adhesive, which makes it easy for the molded products to block each other, and the shape retention of the molded products is poor. However, there are drawbacks such as insufficient mechanical strength. The present inventors investigated the development of new binders to replace these conventional binders, and found that alkali metal salts or ammonium salts of sulfoethyl cellulose with a degree of etherification of 0.2 or higher were excellent as binders for ceramic extrusion molding compositions. The present invention was completed after confirming that the invention was true. According to the present invention, due to the unique action of the binder component, (1) the fluidity of the extrusion molding composition is improved and molding can be performed at low extrusion pressure. (2) The molded products obtained by extrusion molding are not sticky, and therefore, blocking between these molded products is not observed. (3) The molded product after molding has excellent shape retention and mechanical strength, and is unlikely to be deformed or damaged before being transferred to the firing process. This remarkable effect can be obtained. The alkali metal salt of sulfoethylcellulose used in the present invention can be easily synthesized by reacting alkali cellulose with an alkali metal salt of β-chloroethanesulfonic acid in a water-soluble organic solvent such as isopropyl alcohol or acetone. . Further, the ammonium salt of sulfoethylcellulose can be easily synthesized by reacting the alkali metal salt (for example, sodium salt) of sulfoethylcellulose with ammonium chloride salt in a mixed solvent of methyl alcohol and water. The degree of etherification of either the alkali metal salt or ammonium salt is required to be 0.2 or more. This is because if the degree of etherification is lower than this, the solubility in water will be poor and it will not function effectively as a binder. The alkali metal salt and ammonium salt of sulfoethyl cellulose have almost similar properties, but when fired at high temperatures, the alkali metal in the former remains in the ceramic product in the form of oxides or other inorganic salts. In contrast, the latter ammonium salt burns out completely without leaving any residue. Therefore, it is desirable to use ammonium salts of sulfoethyl cellulose for ceramic products that cannot fully exhibit their functions if even a trace amount of metal salts are present. As raw material powder for ceramics, conventionally used powders may be used, including oxides and carbides such as alumina, barium titanate, zirconium oxide, ferrite, titanium oxide, titanium carbide, silicon oxide, and silicon nitride, Nitride is exemplified. Plasticizers typified by polyethylene glycol, glycerin, propylene glycol, ethylene glycol, 1,4-butanediol, etc. are usually used in ceramic extrusion molding compositions, but these are also used in the present invention. No problem. The ceramic extrusion molding composition is obtained by blending and kneading water, an alkali metal salt or ammonium salt of sulfoethylcellulose, and a plasticizer with the raw material powder described above. The optimum amount is determined depending on the degree of polymerization of the material itself, the type of raw material powder, etc., but it is preferably approximately 0.5 to 20 parts by weight, preferably 1 to 10 parts by weight, per 100 parts by weight of raw material powder. If this amount is too small, the effect as a binder cannot be obtained, and if it is too large, the binding force of the binder becomes too large, which worsens extrusion moldability, and the extruded molded product has a sticky surface. It is disadvantageous because it becomes tinged with Next, specific examples will be given. Example 1 A molding composition prepared by thoroughly kneading alumina powder, a binder, glycerin as a plasticizer, and water in the proportions shown in Table 1 using a milk drum was tested for extrudability using a Koka type flow tester. Upon investigation, the results shown in Table 2 were obtained.

【table】

[Table] ×: Bad Example 2 A molding composition prepared by thoroughly kneading barium titanate powder, a binder, propylene glycol, and water in the proportions shown in Table 3 using a milk drum was prepared in the same manner as in the previous example. When the extrudability was examined, the results shown in Table 4 were obtained.

【table】

[Table] Example 3 A molding composition prepared by thoroughly kneading ferrite powder, the binder used in Example 1, propylene glycol, and water in the proportions shown in Table 5 using a milk wasp was extruded using a 16 mm extruder. Created Rod. Using this rod as a sample, the surface condition and bending strength of the rod were measured, and the results were as shown in Table 6. Bending strength measurement method: Dry the rod at 20℃ for 20 minutes, and then
The bending strength was measured using the following formula, with the maximum load being P (Kg), by supporting between two fulcrums and applying a load with a string at the center between the fulcrums. Bending strength (Kg/cm ² ) = 8・P・/πd ³ P: Maximum load (Kg) : Span (cm) d: Rod diameter (cm)

【table】

【table】

Claims (1)

[Claims] 1. A ceramic extrusion molding composition containing, as a binder, an alkali metal salt or ammonium salt of sulfoethyl cellulose having a degree of etherification of 0.2 or more.