JPH0448748B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a composition useful for manufacturing ceramic molded articles. (Prior art and its problems) Conventionally, in order to manufacture ceramic molded products, a mixture of ceramic base powder and synthetic resins and waxes as binders has been used as the main ingredient, and if necessary, plasticizers and lubricants have been added to the mixture. Compositions containing agents and the like are used. However, when producing ceramic molded articles using the above composition, it has been recognized that there are the following drawbacks. In other words, when waxes, polyethylene, polypropylene, acrylic resins, etc. are used as a binder, the degreasing process to remove the binder from the molded product requires a long process (about 1 week) at high temperatures (400-600°C). In particular, when heating in a non-oxidizing atmosphere, the processing conditions needed to be higher and for a longer period of time. On the other hand, in order to overcome this drawback, a method has been proposed that uses a synthetic resin binder that decomposes at a relatively low temperature, such as a methacrylic acid ester polymer. Due to the high melt viscosity, it is difficult to mix uniformly with the ceramic base powder during thermal mixing, and the release property from the mold after molding is poor, making continuous operation difficult in cases such as injection molding. It was hot. Therefore, the conventional method with the above defects has poor productivity and causes cracks in the molded product after degreasing, peeling of the surface layer,
It has many weaknesses, such as the tendency to cause defects such as blistering, and it has been extremely difficult to degrease molded products that are thick or have complex shapes. (Means for Solving the Problems) Here, the present invention has been made in order to solve the problems of the conventional method as described above, and its gist is that a predetermined ceramic base powder is The ceramic composition is constructed by using at least one ester selected from the group consisting of phthalic acid ester, isophthalic acid ester, and terephthalic acid ester, which has a freezing point of 10°C or higher, as a binder to be mixed. There is a particular thing. (Specific structure of the solution) By the way, the ceramic base powder used in the present invention includes clays such as kaolin group, montmorillonite group, mica group, talc, pyrofluorite, diamonite, and daite group, and silica. In addition to general ceramic materials such as non-plastic raw materials such as waxite, iron,
Metal powders such as aluminum, silicon, zirconium and their oxides, glass frit, alumina, magnesia, zirconia, beryllium,
Special ceramic bases such as thorium, spinel, cordierite, lithium, olivine, steatite, titanium oxide, barium titanate, celsian, ferrite, and engineering ceramics such as silicon carbide, silicon nitride, aluminum nitride, and sialon. Examples include base powders, but these examples do not limit the present invention in any way, and various conventionally known ceramic base powders, particularly base powders for producing molded bodies, can be used. It should be understood that In addition, the phthalic acid ester, isophthalic acid ester, and terephthalic acid ester having a freezing point of 10°C or higher used in the present invention are obtained by esterifying phthalic acid, isophthalic acid, or terephthalic acid with a monohydric alcohol by a conventional method. This refers to esters with a freezing point of 10°C or higher. The monohydric alcohol used in the above esterification includes methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tertiary-butyl alcohol, n-aluminum alcohol. , isoamyl alcohol, secondary amyl alcohol, tertiary amyl alcohol, fusel oil, 3-methoxybutyl alcohol, n-hexyl alcohol, 2-methylpentanol-1, secondary hexyl alcohol, 2
-Ethylbutyl alcohol, secondary heptyl alcohol, heptanol-3, n-octyl alcohol, 2-ethylhexyl alcohol, secondary octyl alcohol, nonyl alcohol, 2,6-dimethyl-4-heptanol, n-decanol, secondary undecyl Alcohol, trimethylnonyl alcohol, secondary tetradecyl alcohol, phenol, cresol, cyclohexanol, methylcyclohexanol, 3,3,5-trimethylcyclohexanol, dibenzyl alcohol, diacetone alcohol, methyl cellosolve, ethyl cellosolve, isopropyl cellosolve, Butyl cellosolve, hexyl cellosolve, methyl carbitol, ethyl carbitol, butyl carbitol,
There are benzyl cellosolve, phenylmethyl carbitol, etc., and it goes without saying that other monohydric alcohols other than these can also be used in the same way. Furthermore, when a polyhydric alcohol is added as a modifier during the esterification reaction between phthalic acid, isophthalic acid, or terephthalic acid and a monohydric alcohol, the freezing point, melt viscosity, and other physical properties of the resulting ester can be adjusted over a wide range. There are advantages. Such polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-
Butylene glycol, 2,3-butylene glycol, hexylene glycol, pentanediol-
2,4, hexanediol-2,5, heptanediol-2,4, 2-ethyl-1,3-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, glycerin, polyethylene glycol, polypropylene glycol , polyglycerin, and the like. The esters with a freezing point of 10°C or higher used in the present invention include dicyclohexyl phthalate (DCHP), dimethyl isophthalate (DMI), ethyl phthalylethyl glycolate, which is commercially available as a solid plasticizer, or dimethyl used as a raw material for polyester fibers. Terephthalate (DMT) is well known. Furthermore, the specific binder associated with the present invention, namely phthalate, isophthalate or terephthalate, is added to the ceramic base powder in the form of a solid powder or pellets and mixed with heat, or as a solution in an organic solvent. Alternatively, the binder is added in the form of an emulsion obtained by emulsifying the binder in the presence of a suitable emulsifier by a conventional method and mixed. The ceramic composition thus obtained using a predetermined binder is molded by a known appropriate method such as cast molding, injection molding, extrusion molding, compression molding, etc., and then heated to a temperature below the freezing point of the binder. It is cooled and the desired molded product is removed from the mold. Therefore, the freezing point of the binder needs to be at least room temperature, that is, at least 10°C, preferably at least 15°C. On the other hand, from the viewpoint of economic efficiency during thermoforming, it is desirable that the freezing point of the binder according to the present invention is 150°C or lower.
However, even if the binder has a freezing point of 150°C or higher, the freezing point of the binder can be adjusted to a low level by using ordinary liquid plasticizers such as DMP, DBP, DOP, etc. or other softeners. However, the upper limit is not uniquely defined. In addition, when the binder according to the present invention is used, the molded product obtained by molding the composition of the present invention has good mold releasability, but even if a mold release agent is separately added to the composition of the present invention, there is no effect. No problem. Furthermore, although the ceramic composition of the present invention using the above-mentioned binder usually has sufficient green strength before firing, in cases where it is necessary to further increase the green strength, flexibility, abrasion strength, etc. may be modified by adding a natural/synthetic resin or rubber to the above binder as a third substance. In this case, if the added resin or rubber is solid, it will have the effect of raising the freezing point of the ordinary binder.
If it is liquid, it has the effect of lowering the freezing point. The natural/synthetic resins and rubbers added to the binder include casein, tannin, shellac, damman, gelatin, blood powder, vinyl acetate resin, vinyl propionate resin, vinyl chloride resin, vinylidene chloride resin, Acrylic resin, methacrylic resin, styrene resin,
Butyral resin, polyvinyl ether resin,
Polyvinyl pyrrolidone, polybutene, polyisobutylene, polyethylene, polypropylene, silicone resin, fluororesin, polyester resin, polyamide resin, polyurethane resin, rosin and rosin derivatives, maleic acid resin, terpene resin, coumaron resin, petroleum resin , xylene resin,
PVA, EVA, cellulose derivatives, SBR, NBR,
Examples include CR, natural rubber, chlorinated rubber, cyclized rubber, butadiene rubber, butyl rubber, acrylic rubber, silicone rubber, fluorine rubber, IR, IIR, EPT, EPDM, etc., but other resins or It is also possible to blend using rubber. In addition, as third substances, sublimable substances such as naphthalene, anthracene, camphor, phenanthrene, anthraquinone, benzoic acid, phthalic anhydride, and salicylic acid, which help volatilize the binder in the degreasing process, paraffin, waxes and waxes, stearic acid, Ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, oleic acid,
There is no problem in adding lubricants such as rosin and rosin derivatives, antioxidants, colorants, etc. These third substances are either added to the binder and mixed in advance, or added and blended simultaneously when the ceramic base powder and the binder are mixed. By the way, in the ceramic composition according to the present invention as described above, the binder is usually contained in an amount of 0.1 to 150 parts by weight based on 100 parts by weight of the ceramic base powder.
It is added and blended in an amount of about 0.1 to 35 parts by weight, preferably about 0.1 to 35 parts by weight. In addition, in the composition of the present invention, the amount of the third substance added if necessary together with the ceramic base powder and the binder is arbitrary, but the amount of the plasticizer, natural/synthetic resin, and rubber added is usually determined by the binder. 50% by weight or less of the binder, or the amount of the release agent added is less than several weight% of the binder, and the proportion of third substances such as sublimable substances and lubricants is about 20% by weight or less of the binder. It will be used in Then, the composition as described above is molded into a predetermined shape by a method such as cast molding, injection molding, extrusion molding, compression molding, etc., and then baked.
It becomes a specified ceramic sintered body and is used as a desired constituent material, functional member, etc., and such a ceramic sintered body can be painted, powdered, etc.
It will be equipped with electronic circuits and the like, and will be applied to predetermined purposes. (Function/Effect) As is clear from the above explanation, since the binder used in the present invention is mainly composed of a pure single compound, the appearance of the freezing point is extremely sharp. , temperature control during thermal processing can be easily and strictly performed. In addition, the binder of the present invention has a lower freezing point and lower melt viscosity than conventional resin binders, so it can be easily mixed thermally with ceramic base powder, and can be used in cast molding, injection molding, extrusion molding, and compression molding. It is possible to set the molding temperature at a low temperature, making it extremely easy to inject into the mold, and making it possible to significantly reduce the extrusion pressure. Furthermore, using the binder according to the invention,
In the degreasing process, the binder tends to move within the molded product, and while it is easy to migrate to the surface of the molded product during heating, this is combined with the fact that the binder has a small molecular weight and is easily evaporated, sublimated, dispersed, and volatilized. Therefore, degreasing can be completed in a relatively short time by low-temperature treatment at 350 to 400°C even in a non-oxidizing atmosphere, the residual carbon content is extremely low, and defects such as cracks, surface layer peeling, and blistering do not occur in degreased molded products. It exhibits the characteristics that there is almost no risk. Therefore, in the present invention, the ceramic base powder and the binder can be uniformly mixed thermally, the necessary molding temperature and pressure can be reduced, and temperature control during processing becomes easy. In addition, accidents such as deformation, collapse, surface layer peeling, and cracking of the substrate due to insufficient thermal decomposition of the binder, residual ash, or sudden generation of gas can be prevented, even in the case of thick shapes. Ceramics with excellent appearance, performance, and strength can be obtained. Further, the composition has excellent moldability, and has the advantage that even delicate and complicated shapes can be molded with high precision. Therefore, the present invention can be applied not only to the production of relatively thin molded products such as ceramics and electronic parts, but also to the production of various thick-walled molded products such as turbocharger rotors and gas turbine rotors, resulting in high quality products. This enabled mass production with high performance and high yield. Some embodiments of the present invention are shown below, but it should be understood that the present invention is not to be construed as being limited by these illustrative embodiments. Furthermore, it goes without saying that the present invention includes many embodiments other than these illustrative embodiments. Note that all percentages and parts in the following examples are based on weight unless otherwise specified. (Example 1) 0.5 parts of dicyclohexyl phthalate (DCHP) was added to 100 parts of alumina powder, and the mixture was mixed with a kneader.
After kneading at 130° C. for 50 minutes to form a ceramic composition, this composition was compression molded at a pressure of 980 kg/cm ² to obtain a molded article with a diameter of 3 cm and a thickness of 5 cm. Then, the obtained molded product was 18
Degreasing was carried out by heating to 290°C at a heating rate of 0°C/min. The obtained results are shown in Section 1 below.
Shown in the table. In addition, as a comparative example, low molecular weight polyethylene,
The results using paraffin are also shown in the same table. After degreasing the molded product of the present invention, it was sintered in air at 1460°C for 1 hour, and the resulting sintered body showed no defects in non-destructive tests (transmission X-ray test, ultra-high frequency flaw detection test). I couldn't find it either.

[Table] (Example 2) 25 parts of dimethyl isophthalate (DMI) was added to 100 parts of silicon nitride powder containing a sintering aid, kneaded in a kneader at 130°C for 50 minutes, and then kneaded at 150°C and 550°C.
Table ² shows the results after degreasing a molded article having a diameter of 3 cm and a thickness of 6 cm at a heating rate of 4° C./hr to 340° C. in a nitrogen atmosphere at Kg/cm 2 . The same table also shows the results using low molecular weight polypropylene as a comparative example. In addition, after degreasing the above-mentioned molded product according to the present invention, 9.5
No defects were found on the surface or inside the sintered body, which was sintered at 1740°C for 2 hours in nitrogen at atmospheric pressure, in a non-destructive test.

[Table] (Example 3) 20 parts of dimethyl terephthalate (DMT) was added to 100 parts of zirconia powder containing 3 mol% yttrium oxide, and the mixture was heated at 145°C in a kneader at 50°C.
After kneading, the molded product was injection molded at 150°C and 550Kg/ ^cm2 into a shape of 3cm in diameter and 6cm in thickness, and heated to 320°C at a heating rate of 4°C/hr in a nitrogen atmosphere. I did some degreasing. The results obtained are shown in Table 3. Additionally, as a comparative example, the results using microcrystalline wax (MW) are also shown in the same table. It should be noted that, after degreasing the molded article according to the present invention, the sintered body was sintered in air at atmospheric pressure at 1450° C. for 2 hours, and no defects were found on the surface or inside the sintered body in a non-destructive test.

[Table] (Example 4) To 100 parts of alumina powder, 3 parts of a binder with a blending ratio shown in Table 4 was added, and after kneading in a kneader at 150°C for 50 minutes,
Compression molded with a pressure of Kg/ ^cm2 , diameter 3cm, thickness 6cm
The molded product was heated at a temperature increase rate of 18°C/min to 290°C.
The results after degreasing to ℃ are shown in Table 4. Furthermore, as comparative examples, the results of using polystyrene and polyvinyl acetate alone are also shown in the same table.

[Table] (Example 5) 30 parts of a binder with the mixing ratio shown in Table 5 was added to 100 parts of silicon nitride powder containing a sintering aid, and the mixture was kneaded in a kneader at 140°C for 50 minutes. ,
Diameter 3cm, thickness 6cm under the conditions of 150℃ and 550Kg/ ^cm2
A molded product injection molded in the shape of is heated to 340°C at a temperature increase rate of 4°C/hr in a nitrogen atmosphere.
I did some degreasing. The results obtained are shown in Table 5. Furthermore, as comparative examples, the results of using polymethyl methacrylate, isoprene, and ethylene-vinyl acetate copolymer alone are also shown in the same table.

【table】

Claims (1)

[Claims] 1. A ceramic composition mainly comprising a mixture of ceramic base powder and at least one ester selected from the group consisting of phthalate, isophthalate, and terephthalate having a freezing point of 10° C. or higher.