JPS59141462A - Manufacture of ceramic 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 manufacturing a ceramic body.

Typical examples of new ceramics include highly pure oxides, silicides, carbides, and nitrides, their composite compounds, and cermets.

Manufacturing methods for these new ceramics include the doctor blade method, extrusion method, cast molding method, potter's wheel molding method,
Injection molding methods and the like are known.

In either method, the above-mentioned inorganic material is manufactured by adding an organic binder, water, a plasticizer, etc. to impart viscosity to the material, thereby improving and improving processability.

Among these, injection molding has attracted attention in recent years because it produces complex shapes and is suitable for mass production.

However, there is a problem in that injection molding is not possible unless an organic binder is added to the ceramic component in an amount of about 12 to 30% by weight to facilitate injection conditions. This organic binder is necessary during injection molding, but is unnecessary since the organic binder portion is ultimately removed by heating (hereinafter referred to as degreasing) and then fired.

In particular, as the amount of organic binder increases, it becomes disadvantageous in terms of its characteristics as a culm ceramic body.

It is advantageous to have as little as possible, or none at all. However, at this stage, it is not possible to perform injection molding on ceramic bodies alone.

Generally, a method of mixing an organic binder into ceramics to impart plasticity and lower viscosity, and C-injection is often used. In other words, organic binders, water, etc. are indispensable materials for improving processability. Since these binders must ultimately be degreased, this degreasing method is the most important technique in injection molding.

Generally, in order to degrease so-called binding materials such as organic binders in these ceramic bodies, it is more advantageous to gradually raise the temperature than to rapidly heat the body. However, if the temperature is raised slowly, a huge amount of energy and degreasing time are required.
It is also economically disadvantageous. At the same time, even if we spend a lot of energy and time, the resulting degreasing is not perfect.
The temperature is increased at a rate of O”c,/Dr to decompose and remove the binder)
This is a major problem in the industry, as it causes ``bulges'' and ``cracks'' in the appearance, and a solution is desired.

In order to solve such problems in the degreasing process of ceramic bodies, the present invention proposes a resin technology that does not cause "blistering" or "cracking" in the degreasing process of ceramic bodies containing organic binders. .

In the present invention, a molded product is formed from a mixture of fine ceramic powder and an organic binder as a binder, and the entire or most part of the molded product is made of fine particles that adsorb decomposed gas when the binder is thermally decomposed. The binder is heated and degreased while covered with an inorganic substance having pores.

In the present invention, particularly as inorganic substances belonging to these,
Examples include zeolite. There are two types of zeolite 1: natural products and synthetic products. Zeolite is a general term for a group of hydrous aluminosilicate minerals containing Na, Ca, etc., and is represented by the general formula Me'O.A620:3.m5i02.nH2O. For example, Anal Site, Chaba Site, Damelinite, Elionai 1, Na[ronite, Philip Sai! Examples of this are mordenite, faujasite, and clinopdilite. Among these, industrially useful ones are porgysite, mordenite, chabasite, and clinoptilite.

In Zeolite 1, part of the Si in the silica structure is A7! It is a type of aluminosilicate formed by electrically neutralizing a three-dimensionally developed condensed acid with a cation.
There are some differences depending on the condensed type and the ratio of Si and Al. The regularly arranged three-dimensional crystal structure has cavities (or pores) that serve as adsorption sites, and pores that connect these cavities and do not exhibit a sieving effect. The present inventors have discovered a new technological phenomenon in which decomposition gas is adsorbed into the pores when heating and degreasing the binding material of a ceramic body, which is highly effective in improving "blistering" and "cracking" after degreasing. be.

In general, adsorption has a strong effect on rm pores, which are formed by desorption of crystal water without destroying the crystal structure, and pores that connect them. The pores are said to have a uniform pore diameter of a human being (1/100 millionth of a billionth of a centimeter).

Materials used as binders in ceramics or decomposed molecules such as water, H2,02, N2, CO, C.

02 etc. have a molecular diameter of approximately 2 to 3 people, and include ammonia, methane, ethane, ethylene, propane, cyclopropane,
Propylene, n-butane, isobutane, ■-butene, n
-pentane, benzene, cyclohexane, methanol,
Ethylene oxide, Freon 12, di-n-propylamine,
Paraffins, olefins, etc. generally have a molecular diameter of 4 to 30 molecules.

When the decomposed gas of the binder containing these organic molecules comes into contact with an inorganic substance during the degreasing step when manufacturing a ceramic body, the decomposed gas molecules are adsorbed into the pores of the inorganic substance and are heated to be degreased. As a result, problems such as "blistering" and "cracking" are alleviated and excellent effects are achieved. Porous inorganic substances that exhibit such effects include silica gel, activated alumina, activated clay, and the like in addition to "zeolite."

In experiments conducted by the present inventors, it was found that a material with a high melting point and thermal deformation is more effective in degreasing a ceramic body.

Now, Table 1 shows the trade name of "1 Zeolite", Table 2 shows the general properties of silica gel, Table 3 shows the general properties of activated alumina, and Table 4 shows the name of activated clay.

(Margin below) Next, embodiments of the present invention will be described.

(Practice f9111) To 100 parts of Δ1203 powder with an average particle size of 3/7, 17 parts of 65% active polypropylene (APP) and 35% polyethylene were added to make 100%, and kneaded with a Posoto blender at 180"C for 30 minutes. After that, the sample was made into a pellet shape using a twin-screw presser (outer diameter 3
01m, inner diameter 101I11. A bobbin-shaped molded article with a height of 20 cm was obtained by injection molding. The fifth section compares the molded product that has been heated and degreased so that the entire or almost the entire part is covered, and the conventional degreasing method of degreasing the molded product as it is in a heating furnace.
Shown in the table.

Regarding the degreasing conditions and temperature increase speed, the molded articles were left to cool from 1 to b, and then the molded articles were checked for degreased condition and fired at 1750°C. The same applies to Examples (2) to (4) below.

(Example 2) Microwax,
A sample was prepared by combining an organic binder of paraffin, α-olefin, and polyethylene, adjusted to have a viscosity of 70 to 7,000 poise at 180'C, and formed into a pellet using a twin-screw extruder. A bobbin-shaped molded product having an inner diameter of 10 mm and a height of 20 mm was obtained by injection molding. Furthermore, for the molded product, the above Table 1, Table 2, Table 3,
and a conventional degreasing method in which the molded article is heated and degreased so that the entire or almost the entire molded article is covered with the porous inorganic substance shown in Table 4, and the molded article is directly degreased in a furnace. A comparison is shown in Table 6.

(Leaving space below) (Example 3) Using the molded product obtained in Example (2) as a sample, activated alumina obtained good results without being particularly affected by the temperature increase conditions in the comparison results of the degreased state in Table 6 of C1. Tables 7 and 8 show the results of the combination with other inorganic materials based on the above.

(Leaving space below) (Example 4) Using the molded product obtained in Example (2) as a sample, the ratio V results in the degreased state in Table 6 show that good results were obtained especially under elevated temperature conditions (this effect was 71゛). Using the obtained activated alumina as a base, the particle size was increased and the effect of the increase was confirmed.The results are shown in Table 9.At this time, the +IJris particle size of the activated alumina was 2 to 6.
μ, the pore volume is 0.3-0.67 m ff/g
(7) Use Mo (7), this is 0.5 mm-12
up to m (71 grains, that is, the individual grain size is 0)
．． 2~6μ, but collect them to 0.5~12mm
The grain of the dog is G-tone T& and the ship (sai~jikoshitachino).

(Margin below) Table 9 Particle size and degreasing condition 1 Note) Explanation of the symbols ○△× used in the examples 0 mark - 20
Items with 19 or more cracks and no cracks or swelling marked with △
Out of 20 items, 10 or more had no cracks or bulges. - Out of 20 items, 3 or less were non-defective or all had cracks or bulges. As explained above, the present invention combines an organic binder with fine ceramic powder. Forming a molded article with the mixture as an agent,
Covering the entire or most part of the molded product with an inorganic substance and heating it,
In the process of degreasing, the structure of the inorganic substance is characterized by having pores that adsorb decomposition gas of the binder.

As a result, H2.02, N2.1 (20), and hydrocarbon substances such as paraffins and olefins are generated by thermal decomposition of the binder when the negative binder, which is the binder in the ceramic body molded product, is heated and degreased. classes, naphthenes, alcohols, aromatics, amines, ethylenes,
Substances such as propylene and butanes are adsorbed in the pores and pores of the inorganic material having pores. Therefore, it has a large effect on the effects of "blistering" and "cracking" after degreasing, and forms excellent degreased molded products and fired products. This means that the degreasing process, which conventionally took a long time, can be reduced to one time.
Not only is the time reduced by more than 0 times, but the rate of good products after firing of molded products is greatly improved, making a tremendous contribution to related industries.

Claims (3)

[Claims] (1) A molded article is formed from a mixture of ceramic fine powder and an organic binder as a binder, and in the process of heating and degreasing the binder in the molded article, pores are created to adsorb decomposition gas of the binder. A method for producing a ceramic body, comprising: heating and degreasing the binder in a state where the entire or most of the molded article is covered with an inorganic substance, and then firing the binder. (2) The method for producing a ceramic body according to item 1 of the scope of Patent No. 811, wherein the size of the pores of the inorganic substance is approximately equal to or larger than the molecular diameter of the decomposed gas of the binder phase. (3) The method for producing a ceramic body according to claim 2, wherein the inorganic substance is a fine powder or granule of zeolite, silica gel, activated alumina, or activated clay.