JPH0550465B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a method for manufacturing ceramic products,
In particular, ceramic products with excellent characteristics,
The present invention relates to a method that allows production with good degreasing properties at low temperatures.

(Prior art and its problems) Conventionally, one method for manufacturing ceramic products of desired shapes such as various structural parts and functional parts is to injection mold a predetermined ceramic powder and then mold the resulting injection molded product. A method of degreasing and then sintering is used, but when injection molding such ceramic powder, for example, "Industrial Materials" Vol. 33, No. 14, pp. 22-32 (1985)
As disclosed in the following, the main ingredients are polystyrene, polyethylene, polypropylene, cellulose acetate, atactic polypropylene, polyvinyl alcohol, polyacetal, acrylic resins, waxes, etc., which are solid at room temperature, and as needed. Using a resin composition for injection molding obtained by blending a plasticizer that is liquid at room temperature such as diethyl phthalate, dibutyl phthalate, dioctyl phthalate, etc., this resin composition and ceramic powder are uniformly blended to obtain the desired product. This is used as a kneaded material for injection molding, and this is injection molded to form an injection molded product in the desired shape.The resulting injection molded product is heated at a degreasing temperature of about 450 to 550°C. After that, a sintering operation is performed at a sintering temperature depending on each ceramic powder.

However, in such conventional methods, since the degreasing temperature is high as mentioned above, the temperature increase rate is about 1℃ to 10℃/Hr, so it takes a long time to reach the maximum temperature. It takes too much time and has inherent problems that are economically disadvantageous, and it is also difficult to use non-oxide ceramics, such as SiC,
Ceramic powders such as Si ₃ N ₄ and AlN have the problem of being oxidized by oxygen in the atmosphere, reducing the high-temperature strength of their sintered bodies.

Furthermore, even if the injection molded body is degreased, compounding agents such as resins and plasticizers in the molded body cannot be completely removed, and as a result, about 2 to 5% of carbon due to these compounding agents is removed by degreasing. This residual carbon may cause swelling (cavities) in the sintered body due to the CO gas generated by the reduction reaction of (oxide + C) during the sintering of the degreased body. Furthermore, the positions where carbon exists form holes, causing problems such as lowering the strength of the sintered body.

(Means for Solving the Problems) The present invention has been made to solve the problems of the conventional method as described above, and its gist is to injection mold ceramic powder. Then, the injection molded product is degreased and then sintered to produce a desired ceramic product.
The present invention uses a kneaded product obtained by blending a resin composition consisting of a methacrylic resin, a phthalic acid ester, and a terephthalic acid ester with the ceramic powder.

(Specific structure of the solution) By the way, the ceramic powder used in the present invention includes clays such as kaolin group, montmorillonite group, mica group, talc, pyrofluorite, diamonite, and daite group, silica, In addition to general ceramic base powder 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 base powders such as thoria, spinel, cordierite, lithia, olivine, steatite, titanium oxide, barium titanate, celsian, ferrite, and engineering such as carbon silicon, silicon nitride, aluminum nitride, and sialon. Examples include ceramic powder. However, it should be understood that these examples do not limit the present invention in any way, and that any of the various conventionally known ceramic powders, especially powders for producing injection molded bodies, can be used. It is.

Furthermore, the methacrylic resin constituting the resin composition used in the present invention and blended with the above-mentioned ceramic powder is an essential component in order to impart resin properties to the mixture with the ceramic powder. This combination allows the ceramic powder to be injection molded in the same way as general plastics. As this methacrylic resin, any known resin used in injection molding operations of ceramic powder can be used, but in particular, in the present invention, a polymer of methyl methacrylate, especially a polymer of methyl methacrylate, can be used. It is effective to use methyl methacrylate polymers having a degree of polymerization in the range of 10 to 150, particularly preferably 15 to 110. Incidentally, if the degree of polymerization of this methyl methacrylate polymer becomes too low, the shape of the injection molded product obtained will easily deform.
Furthermore, if the degree of polymerization is greater than 150, the degreasing temperature will rise above 350°C.

Furthermore, the phthalate ester that constitutes the resin composition together with the methacrylic resin has the role of lowering the viscosity of the prepared injection molding kneaded product, improving its fluidity, and reducing heat generated during degreasing. Terephthalic acid ester is sublimable and is added to create holes by sublimating at low temperatures during degreasing, and by creating the holes, This serves to improve the air permeability of subsequent liquid components, evaporated gas, or pyrolysis gas, and to prevent cracks in the molded product.

These phthalic acid esters and terephthalic acid esters are obtained by esterifying phthalic acid and terephthalic acid with a specified monohydric alcohol using a conventional method, but in particular, esters with a freezing point of 10°C or higher are used. Recommended to use.

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, and n-amyl 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. Also,
These phthalic esters and terephthalic esters used in the present invention may be those modified with polyhydric alcohols, and their specific compounds may be commercially available as solid plasticizers. Dicyclohexyl phthalate, which is used as a raw material for polyester resin, and dimethyl terephthalate, which is a raw material for polyester resin, are well known.

The methacrylic resin, phthalate ester, and terephthalate ester constituting the resin composition according to the present invention are added to a predetermined ceramic powder in accordance with a conventional method, either alone or after being mixed in advance. , added in the form of a solid powder or pellets, heated and mixed, or added and mixed as a solution in an organic solvent, or added in the form of an emulsion obtained by emulsifying in the presence of a suitable emulsifier. The mixture is uniformly blended and the desired kneaded material for injection molding is obtained.

In addition, in this compounding, the compounding ratio of the three components of methacrylic resin, phthalic acid ester, and terephthalic acid ester is determined as appropriate depending on the subsequent degreasing conditions and the shape of the intended injection molded product. When a resin composition containing a relatively large proportion of methacrylic resin is used, the shape of the injection molded product is difficult to deform, making it suitable for complex-shaped products; When using a resin composition with a small blending ratio of resin, such a resin composition may be
However, in general, methacrylic resin is about 20 to 75% by weight, phthalate is about 5 to 75% by weight, and terephthalate is about 3% by weight. It will be used in a resin composition composition in which the total amount is 100% by weight at a ratio of about 40% by weight.

In addition, the blending ratio of such resin composition to ceramic powder is generally about 17 to 33 parts by weight per 100 parts by weight of ceramic powder.
Preferably, a value within the range of about 19 to 22 parts by weight will be adopted.

Furthermore, as in the past, a mold release agent is added as a third substance to a kneaded product obtained by blending a resin composition consisting of a methacrylic resin, a phthalate ester, and a terephthalate ester with ceramic powder. , a lubricant, an antioxidant, a coloring agent, etc., are added and blended as necessary within known usage ranges.

The thus obtained kneaded ceramic powder obtained by blending the resin composition of the methacrylic resin, phthalic acid ester, and terephthalic acid ester according to the present invention is then molded by conventional injection molding. The operation is performed to form an injection molded body corresponding to the desired product shape, and then such injection molded body is subjected to a degreasing operation, but the degreasing temperature at that time is ,
Therefore, a temperature of 350°C or lower is preferably used. Such low-temperature degreasing operations effectively shorten the degreasing time and eliminate the effects of oxidation.
Moreover, the defatted body obtained in this way is
Each ceramic powder is sintered in accordance with a conventional method under sintering conditions appropriate for the powder, and is thereby made into a specified ceramic product (sintered body) and used as the intended structural component, functional component, etc. It becomes.

(Examples) Some examples of the present invention are shown below, but it should be understood that the present invention is not to be interpreted in any way limited by these illustrative examples. It goes without saying that the present invention includes many other embodiments in addition to these illustrative embodiments.

Note that all percentages and parts in the following examples are based on weight unless otherwise specified.

Example 1 98% β-SiC (product name: Beta Random Ultra Fine, manufactured by IBIDEN Corporation), 1% of carbon black (Diablack I, manufactured by Mitsubishi Chemical Industries, Ltd.) as a sintering aid, and amorphous 1% boron powder (manufactured by HC Schüttarch) was uniformly mixed in benzene and dried to obtain a powder containing 6 parts of polymethyl methacrylate, 1 part of dicyclohexyl phthalate, and 2.5 parts of dimethyl terephthalate. Add and blend the resin composition at a ratio of 17.4% (ceramic powder 82.6%),
The mixture was kneaded using a pressure kneader at a temperature of 140°C until the torque became stable. Next, the obtained kneaded product was heated to an injection temperature of 130°C, a diameter of 30 mm, and a length of 30 mm.
It was injection molded into a mm round bar. Thereafter, this injection molded body (round bar) was degreased by heating it in air at a temperature increase rate of 6 °C/Hr to 285 °C, and the obtained degreased body was further heated with Ar at a temperature of 2050 °C. Sintering was carried out in an atmosphere for 1 hour.

The density of the sintered body thus obtained is 3.06 g/cm ³
It was hot. Also, regarding the 3 x 4 x 30 mm ³ test piece cut out from this sintered round bar sample,
The top, bottom, and side surfaces were polished to a final mirror finish using 1/4 μm diamond abrasive grains, and a three-point bending test (span: 20 mm) was performed. As a result, the average value of 5 samples was 63 kg/mm ² . Obtained.

In addition, when the above injection molded round bar was degreased in nitrogen gas and similar tests were conducted, the performance of both density and strength was compared to the above degreasing in air. No significant difference was observed between the two.

Example 2 Si ₃ N ₄ (manufactured by Denki Kagaku Kogyo Co., Ltd.: product name SN-
9S) 96%, Al ₂ O ₃ (manufactured by Iwatani Chemical Co., Ltd.: trade name B type) 2% and Y ₂ O ₃ (manufactured by Mitsubishi Chemical Corporation: ceramic grade) 2% were uniformly mixed in ethanol with a ball mill. 16.2% of a resin composition consisting of 6 parts of polymethyl methacrylate, 3 parts of dicyclohexyl phthalate and 1.5 parts of dimethyl terephthalate was added to the mixed and dried powder.
(ceramic powder: 83.8%) and kneaded at a temperature of 130°C using a pressure kneader. Then, using this obtained kneaded material, injection molding was performed at an injection temperature of 120°C, and the maximum outer diameter was:
An injection molded body having the shape of a turbocharger impeller having a portion of 68 mm and a maximum wall thickness of 35 mm was manufactured. Incidentally, in the obtained injection molded article, no shape abnormality was observed in normal dimensional measurements.

Next, the thus obtained impeller-shaped injection molded product was heated in air to 90°C at a rate of 20°C/Hr, then at a temperature increase rate of 4°C/Hr to 280°C, and then heated for 10 minutes. The product was fired by heating at 1760° C. for 2 hours in a nitrogen atmosphere at atmospheric pressure to produce 55 desired sintered bodies (turbine wheels). No surface or internal defects were detected in any of the obtained sintered bodies. In addition, after assembling a metal shaft to each sintered body, a spin test was conducted, and the results showed that the product had durability at an average speed of 184,000 rpm at a temperature of 900°C. Further, when a test piece of 3×4×30 mm ³ cut out from the sintered body was subjected to a three-point bending test (span: 20 mm), it showed a bending strength of 72 Kg/mm ² at a temperature of 900°C.

On the other hand, a similar impeller-shaped model was manufactured by using a commercially available acrylic injection molding resin in place of the above resin composition and injection molding the above ceramic powder at an injection temperature of 170°C. For injection molded products, the degreasing operation is carried out at 4°C/Hr.
At the heating rate of , the degreasing temperature required 580°C, and the degreasing took a long time. Moreover, cracks were observed on the surface of the degreased body.

Among these degreased bodies, an impeller-shaped degreased body with relatively small cracks was sintered in the same manner as above, and as a result, Si ₃ N ₄ was converted to SiO ₂ by oxidation.
The amount of linear shrinkage was about 0.3%, which was larger than in the above case, probably because of the generation of . In addition, when a test piece of 3 x 4 x 30 mm ³ cut out from the obtained sintered body was subjected to a similar three-point bending test, it was found that the bending temperature was 900℃.
It was low at 38Kg/ ^mm2 .

Example 3 1 part polymethyl methacrylate, 3 parts dicyclohexyl phthalate, and dimethyl terephthalate
Al ₂ O 3 was prepared in the same manner as in Example 1 using resin composition A consisting of 0.2 parts of polymethyl methacrylate, or resin composition B consisting of 9 parts of polymethyl methacrylate, 1 part of dicyclohexyl phthalate, and 2.5 parts of dimethyl _{terephthalate} . Injection molding was performed to obtain a round bar-shaped injection molded article. The amount of added resin is 16.8%.
It was hot.

Next, when the injection molded articles obtained using the respective resin compositions A and B were degreased in the air, the injection molded articles obtained using the resin composition A showed a degreasing treatment of 6°C/Hr. Degreasing can be carried out at a temperature of 250°C at a heating rate of 250°C, and at a temperature of 265°C at a heating rate of 8°C/Hr. Degreasing could be carried out at a temperature of 325°C at a heating rate of /Hr, and at a temperature of 338°C at a heating rate of 8°C/Hr.
In addition, as a result of surface observation using a stereomicroscope, no defects were observed in any of the molded bodies (degreased bodies) after such degreasing, and furthermore, non-destructive inspection using transmitted X-rays revealed no internal defects. No defects were detected.

(Effects of the Invention) As is clear from the above description, according to the present invention, a resin composition consisting of a methacrylic resin, a phthalic acid ester, and a terephthalic acid ester can be blended into a predetermined ceramic powder. By performing injection molding using the kneaded material and degreasing the injection molded product, it becomes possible to carry out the degreasing operation at a low temperature, particularly at a temperature of 350°C or less, This makes it possible to avoid the effects of oxidation on the injection molded product being degreased as much as possible, making it possible to degrease in air and significantly shortening the degreasing time. In addition, the resin etc. are easily removed from the injection molded product, so the residual carbon content is extremely low, and the degreased molded product has the following characteristics: there is almost no risk of defects such as cracks, surface layer peeling, and blistering. It is.

Furthermore, according to the present invention, by changing the ratio of the three components constituting the resin composition blended into the ceramic powder, it is possible to injection mold molded products from simple shapes to complex shapes. You can enjoy the following advantages.

Claims (1)

[Scope of Claims] 1. When manufacturing a desired ceramic product by injection molding ceramic powder, degreasing the obtained injection molded product, and then sintering it, the injection molding is performed using a methacrylic resin. A method for manufacturing a ceramic product, characterized in that the method is carried out using a kneaded product obtained by blending a resin composition comprising a resin, a phthalate ester, and a terephthalate ester with the ceramic powder. 2. The manufacturing method according to claim 1, wherein the injection molded article is degreased at a temperature of 350° C. or lower. 3 The degree of polymerization of the methacrylic resin: 10 to 150
The method according to claim 1 or 2, wherein the phthalate ester is dicyclohexyl phthalate, and the terephthalate ester is dimethyl terephthalate.