JPS63319248A - Production of sintered ceramic - Google Patents

Abstract

PURPOSE:To produce the title sintered body permitting defatting at relatively low temp. and having high strength by molding a slurry obtd. by mixing ceramic powder with a specified binder and a solvent contg. an alcohol. CONSTITUTION:A binder (B) is obtd. by mixing (a) 100pts.wt. poly(alpha-methyl styrene) having several thousands-several millions mol.wt. with (b) 0.01-10pts. wt. anhydride of unsatd. acid (e.g. maleic anhydride) and treating the mixture at <=200 deg.C for 30min-several hours in the presence of a radical initiator. Then, a slurry is obtd. by mixing (A) 100pts.wt. ceramic powder, (B) 550pts.wt. (a) and 0.001-5pts.wt. (b), and (C) a solvent (e.g. benzene) contg. 0.1-10 times weight (basing on the amt. of A) 1-20C alcohol (e.g. methanol). The slurry is then molded, defatted, and sintered thereafter.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a ceramic sintered body, and more specifically, it improves the strength of a molded body before sintering treatment and completely degreases the body at a relatively low temperature. The present invention relates to a method of manufacturing a ceramic sintered body in which the following steps are performed.

[Conventional technology]

To manufacture ceramic products with complex shapes or requiring high dimensional accuracy, it is industrially possible to use techniques such as the so-called pressureless sintering method, in which a pre-formed compact is fired, or the reaction sintering method. It is being done. Here, the means for forming the compact includes, for example, forming a composition of ceramic powder such as alumina or ferrite into a desired shape using a dry or wet method, in which a sintering accelerator is added in addition to a binder as necessary. That is, molding is performed by a wet press method, a doctor blade method, an extrusion molding method, an injection molding method, or the like.

The present inventors have already developed a method that uses polyalphamethylstyrene (Japanese Patent Application Laid-Open No. 56-51657) as a method that allows degreasing at a relatively low temperature, and a method that further improves the strength of the molded product before sintering ( JP-A No. 60-65762).

[Problem that the invention seeks to solve]

However, the above-mentioned method requires a special poly-α-methylstyrene and has the problem that the molded product before sintering is non-uniform, especially when molded by a wet method.

[Means for solving problems]

The present inventors have intensively studied methods for solving the above problems and have completed the present invention.

That is, the present invention is a method for producing a ceramic sintered body in which ceramic powder is mixed with a thermoplastic resin as a binder, molded into a desired shape, degreased, and sintered. This is a method for producing a ceramic molded body, which uses treated polyα-methylstyrene and is characterized in that it is mixed in a solvent containing at least an alcohol and molded into a slurry.

In the present invention, the polyα-methylstyrene used as the pie inder is not limited to a homopolymer of α-methylstyrene before being heat-treated with an unsaturated acid anhydride to the extent that it does not lose the decomposition properties of polyα-methylstyrene. Copolymers with other copolymerizable monomers can also be used. For example, a copolymer containing other copolymerizable monomers, styrene and derivatives, methacrylic esters, acrylic esters, etc. in several percent to several tens of gold can be used.

There is no particular restriction on the molecular weight of the polymer used, but it is usually in the range of several thousand to several million.
It may also be a mixture with a dimer to octamer as shown in Japanese Patent No. 51657.

In the present invention, what is important is that the polyα-methylstyrene used as the binder is previously heat-treated with an unsaturated acid anhydride.

Here, the unsaturated acid anhydride may be any acid anhydride containing an unsaturated group, and maleic anhydride, itaconic anhydride, etc. are preferably used.

The heat treatment is usually carried out by dissolving the unsaturated acid anhydride and polyα-methylstyrene in a solvent capable of dissolving them in order to disperse them well. The heating temperature is usually 100°C or higher when a radical initiator is not used in combination, or at a temperature higher than the decomposition temperature of the initiator when a radical initiator is used in combination, preferably 200°C.
Performed below C. The heating time varies depending on the temperature, but it is preferably kept to an extent that does not significantly reduce the molecular weight of polyα-methylstyrene, and is usually from 30 minutes to several hours. The proportion of the unsaturated acid anhydride used is preferably about 0.01 to 10 parts by weight per 100 parts by weight of polyα-methylstyrene. If it is less than 0.01 parts by weight, there is no effect, and if it is more than 10 parts by weight, it affects the decomposability of polyα-methylstyrene, which is not preferable.

In the present invention, the poly-alpha-methylstyrene treated in this way is then mixed with a ceramic and an alcohol. Mixing involves adding alcohol to the solution during heat treatment,
Furthermore, adding ceramic powder is easy and economical. Therefore, during the heat treatment, a hydrocarbon compound that is a good solvent for polyα-methylstyrene among the solvents in the final ceramic powder slurry may be used, and the ratio thereof may be the same as the ratio when mixed with the ceramic.

The alcohols are compounds containing one or more OH groups in the molecule, and may be polyhydric alcohols. As alcohols, those having about 1 to 20 carbon atoms can be used, such as methanol, ethanol, propatool,
Aliphatic alcohols such as butanol and hexanol are commonly used, but of course alicyclic alcohols such as cyclohexanol and terpineol, aromatic alcohols such as phenol and benzyl alcohol, etc. can also be used.

In the present invention, polyα-
The above-mentioned hydrocarbon compounds that are good solvents for methylstyrene include aromatic hydrocarbon compounds such as benzene, toluene, xylene, and ethylbenzene, and alicyclic hydrocarbon compounds such as cyclohexane and decalin, in combination with ethers such as tetrahydrofuran. You can also.・Although the amount of alcohol to be used varies depending on the type and type of ceramic, it is appropriate that the volume of alcohol be approximately 0.1 to 10 times the volume of the ceramic powder used, and a good solvent should be used. When used, the amount ratio varies depending on the type of solvent used, but it is preferable to use the above-mentioned solvent, which is a good solvent, to the extent that the polyα-methylstyrene is uniformly melted. Moreover, if necessary, the ceramic powder can be first dispersed in alcohol and then mixed with the above-mentioned solution of treated polyα-methylstyrene.

For mixing, it is preferable to use a device capable of relatively strong mixing, such as a ball mill or a homogenizer. There are no particular restrictions on the temperature during mixing, and room temperature is sufficient.

In the present invention, in addition to the above-mentioned polyα-methylstyrene, a plasticizer such as phthalic acid diester, liquid paraffin, styrene, or an oligomer of α-methylstyrene can be used in combination, if necessary. The ratio of these used is 5 to 50 parts by weight of polyα-methylstyrene and 0.001 to 5 parts by weight of unsaturated acid anhydride to 100 parts by weight of ceramic powder.
It is common to use 0 to 50 parts by weight of the plasticizer.

Although the method of the present invention can be applied to any molding method, it is particularly effective when applied to wet methods such as mixing ceramic powder, a binder, and an appropriate solvent, fluidizing it, and forming it into a sheet using a doctor blade method. It is true.

〔Example〕

The present invention will be further explained below with reference to Examples.

Example 1 Poly α-methylstyrene (number average molecular weight 150,000) 35w
Add 20 mg of benzoyl peroxide to 60 g of toluene solution containing 15 iyt%, 3.5 wt% of maleic anhydride, and stir well for 1 hour at 100°C. Thereafter, the slurry was cooled to room temperature, 30 d of 2-ethylhexanol was added, 100 g of ultrafine alumina for ceramic molding was added, and the well-mixed slurry was poured onto a Teflon sheet to form a sheet with a thickness of 1+ mm.

After drying, the sheet was cut and the cut surface was observed to find that the alumina was uniformly dispersed.

In addition, when the sheet was cut to 1010 x 10 and a hole with a diameter of 5 mm was made with a packing cutter and degreased at 400''C, there were no defects in the shape of the sheet or the hole.Furthermore, the sheet was sintered at 1400℃ and there was no defect. A sintered body of alumina was obtained.

Comparative Example 1 The same procedure as Example 1 was performed except that no heat treatment was performed with maleic anhydride and toluene was used instead of 2-ethylhexanol. Some parts were destroyed, and after degreasing, a total of three places were destroyed.

Example 2 The same procedure as Example 1 was carried out except that itaconic anhydride was used instead of maleic anhydride. The cross section of the sheet was uniform, there was no problem with the shape of the molded product after degreasing, and after sintering. There were no defects.

Example 3 A copolymer of α-methylstyrene and styrene (molecular weight 250,000, styrene content 52
When the procedure was the same as in Example 1 except that terpineol was used as the alcohol, there was no abnormality in the shape of the molded body after degreasing, and a uniform sintered body was obtained by sintering at 1400°C. I got it.

〔Effect of the invention〕

By implementing the method of the present invention, the molded product before degreasing is uniform, can be degreased at a relatively low temperature, and furthermore, processing, degreasing,
It is extremely valuable industrially because ceramic sintered bodies can be produced without breaking during sintering.

Claims (1)

[Claims] 1. A method for producing a ceramic sintered body in which ceramic powder is mixed with a thermoplastic resin as a binder, molded into a desired shape, degreased, and sintered, wherein an unsaturated acid anhydride is used as the thermoplastic resin. 1. A method for producing a ceramic molded body, which comprises using heat-treated polyα-methylstyrene and mixing the mixture in a solvent containing at least alcohol to form a slurry. 2. The method for producing a ceramic molded body according to claim 1, which comprises treating a thermoplastic resin with an unsaturated acid anhydride in the presence of a radical polymerization initiator.