JPH07149573A - Ceramic molding composition - Google Patents

Abstract

(57) [Abstract] [Purpose] Completely fill up to the tip of a molding die that has a narrow void without creating weld lines on the surface of the ceramic molding.
(EN) A low-pressure moldable ceramic molding composition that is excellent in mass production and does not cause cracking or deformation of a ceramic body after degreasing or firing. [Composition] A mixture of a ceramic raw material powder, a binder composed of an organic dispersant, a solvent, and a solidifying agent is heated to a temperature not lower than the melting point of the binder, and a fluidized plasticized product is injected under pressure into a molding die, followed by solidification by cooling. A ceramic molding composition for obtaining a molded product by containing 0.2 to 3% by weight of polyethylene glycol alkylamine as an organic dispersant in the plasticized product.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a ceramic molding composition.

[0002]

2. Description of the Related Art In recent years, ceramic members have been widely used not only for conventional electronic parts but also for structural parts of various chemical industrial devices, mechanical parts of internal combustion engines, and decorative parts such as watches and accessories due to their characteristics. It's starting to happen.

However, many of the chemical industry constituent members, mechanical parts for internal combustion engines, and decorative parts generally have a complicated three-dimensional structure, and ceramic materials are more heat-resistant and corrosion-resistant than metal materials. Although it has excellent properties such as excellent wear resistance, high strength and small specific gravity, it has a complicated three-dimensional structure due to its difficulty in workability such as cutting and grinding. It was difficult to mass-produce, and the product cost became extremely high, making it difficult to put various ceramic parts into practical use. Therefore, as a method for molding various ceramic parts with complicated shapes as described above, ceramic sludge prepared by conventionally mixing and mixing ceramic raw material powder and a water-soluble binder is poured into a molding die made of gypsum and molded. A slurry casting method has been used in which a ceramic molded body is obtained by utilizing water absorption of a mold and inking of a ceramic raw material to a molding mold.

However, the above-mentioned sludge casting molding method has a drawback that the reproducibility of molding is poor and it is unsuitable for mass production due to wear of the molding die due to repeated use and deterioration of water absorption and inking ability.

On the other hand, as a molding method capable of mass-producing various ceramic parts having complicated shapes with high accuracy and efficiency, a ceramic raw material powder and a binder made of a thermoplastic material represented by wax and various organic resins are kneaded while heating. Injecting the plasticized material into the mold under high pressure to form a ceramic molded body has been put into practical use, and various compositions for ceramic molding have been proposed. (See Japanese Patent Laid-Open No. 4-338158).

[0006]

However, in the injection molding method, a large amount of an organic binder is added to the ceramic raw material powder, and heating and cooling of the molding die are cycled and injected at a high pressure of 2.0 atm or higher. For molding, for example, in a ceramic molded body having a complicated three-dimensional structure represented by a turbo rotor or the like, when the plasticized mixture is injected into the molding die, the solidification temperature is as high as 60 ° C. or higher, and the surface temperature of the molding die is high. Due to the temperature difference between the inside of the molded body after filling and the molded body, a weld line is generated on the surface of the molded body, and the residual stress inside the molded body is large because it is injected into the mold at high pressure. May deteriorate the characteristics.

On the contrary, if it is attempted to reduce the residual stress inside the molded body by injecting it at a low pressure, the thickness thereof is about 0. Poor filling is likely to occur in thin parts of 7 mm or less,
There is a problem that a highly reliable ceramic compact cannot be mass-produced with high yield.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its object is to prevent the formation of weld lines on the surface of a ceramic molded body even if the molding material is injected at a low pressure for molding, and is narrow. It is an object of the present invention to provide a ceramic molding composition excellent in mass production effect in which the tip of a molding die having voids is completely filled and cracking or deformation does not occur in a ceramic body after degreasing or firing.

[0009]

The composition for molding ceramics of the present invention comprises a mixture of a ceramic raw material powder, an organic dispersant, a solvent, and a binder, which is heated to a temperature above the melting point of the binder to fluidize it. Which is used to obtain a molded product by cooling and solidifying the plasticized product into a molding die, wherein the organic dispersant is 0.2 to 10% of the binder contained in the plasticized product. It is characterized by being 3% by weight of polyethylene glycol alkylamine.

In the present invention, the organic dispersant uniformly disperses the ceramic raw material powder and the binder and lowers the solidification temperature of the plasticized mixture. The solidification temperature is 100 ° C. from the viewpoint of workability. The following is desirable, and from the viewpoint of eliminating weld lines on the surface of the molded product and filling in narrow voids, the solidification temperature must be 60 ° C. or less, and if the content is less than 0.2% by weight. The solidification temperature does not decrease, the viscosity of the plasticized product is high, and low-pressure molding cannot be performed. On the other hand, when it exceeds 3% by weight, the molding shrinkage is large and it becomes difficult to demold depending on the structure of the molded body. Since the tip of the molded body may be damaged,
It is specified to 0.2 to 3% by weight of polyethylene glycol alkylamine.

The solvent in the ceramic molding composition is preferably a linear or branched saturated hydrocarbon. If the number of carbon atoms is less than 9, the solvent volatilizes during the molding operation to change the solid content concentration. If the carbon number exceeds 16, it becomes easier
The change in viscosity of the plasticized product becomes large, and it becomes difficult to efficiently mold a molded product having no internal defects.

Therefore, a normal hydrocarbon having a carbon number of ₉ to ₁₆ (C _{9 to} C ₁₆ ) is desirable, for example, 9, 10, 12
_{(C 9, C 10, C} 12) of n- paraffins and 10 to 16
N- paraffin mixture (C ₁₀ ~C _16), and the like,
Particularly, 9 to 13 (C _{9 to} C ₁₃ ) normal hydrocarbons are preferable, and the amount of the solvent added is preferably in the range of 3 to 15% by weight.

On the other hand, the solidifying agent used in the present invention has an action of solidifying the plasticized product of the ceramic molding composition while containing the solvent to form a molded product. Since the temperature at which the compound solidifies is preferably 100 ° C. or lower as described in detail in the section of the organic dispersant, the solidifying agent is, for example, a fatty acid represented by 12-hydroxystearic acid or a fatty acid ester thereof. , Fatty acid methyl ester, or polyalkylene oxide derivative, fatty acid amide, higher alcohol, higher amine, mineral oil or paraffin wax, and the like, and fatty acid, fatty acid ester, polyalkylene oxide derivative or fatty acid amide are particularly preferable.

Further, the solidification temperature of the plasticized product is 10 ° C.
The rate of change between the viscosity at the start of measurement at high temperature and the viscosity in the steady state is because the residual stress inside the ceramic molded body is prevented and the ceramic body does not crack or deform after degreasing or firing. Is preferably 10% or less.

The water content of the ceramic raw material powder of the plasticized material is preferably 0.5% by weight or less in order to sufficiently fill the details of the molding die.

Further, in the ceramic molding composition according to the present invention, silicon nitride (Si ₃ N ₃₎ is used as the ceramic raw material powder.
₄ ), non-oxide ceramics such as silicon carbide (SiC), alumina (Al ₂ O ₃ ), zirconia (ZrO
₂ ) It can be applied to any of the oxide ceramics such as
A desired amount of various sintering aids can be added to the ceramic raw material powder, and the particle diameter of these ceramic raw material powder is preferably several microns to submicron.

[0017]

In the ceramic molding composition of the present invention, since the organic dispersant in the binder is 0.2 to 3% by weight of polyethylene glycol alkylamine, the plasticized material obtained by mixing the ceramic raw material powder and the binder is solidified. As the temperature decreases, the temperature difference between the surface of the mold and the inside of the molded body becomes smaller, and the fluidity of the plasticized product on the surface of the mold until it solidifies by cooling is improved so that the tip of the mold can be filled. become.

[0018]

EXAMPLES Hereinafter, the ceramic molding composition of the present invention will be described in detail based on examples.

Yttrium oxide (Y ₂ O ₃ ) and aluminum oxide (A) are added to silicon nitride (Si ₃ N ₄ ) as a sintering aid.
l ₂ O ₃ ) and mixed with α-alumina (Al
₂ O ₃ ) with silica (SiO ₂ ), calcia (CaO),
Organic dispersants such as those shown in Tables 1 and 2 as binders are obtained by adding and mixing a sintering aid containing magnesia (MgO) as a main component, respectively as non-oxide type and oxide type ceramic raw material powders. Then, a solvent and a solidifying agent were respectively added and mixed to prepare a ceramic molding composition for evaluation.
A comparative example was one using dodecylamine (DA) as the organic dispersant.

[0020]

[Table 1]

[0021]

[Table 2]

First, the ceramic molding composition for evaluation was heated and mixed to be plasticized, and the plasticized product was kept at a temperature 10 ° C. higher than the solidification temperature of the binder, and then 20 s ⁻ using an E-type viscometer. ^The viscosity was measured under the measurement condition of ¹ , and the temperature at which the viscosity of the plasticized product became 8.0 Pa · s or more was evaluated as the solidification temperature while being left to cool. The viscosity at the start of measurement was taken as the viscosity of the plasticized product.

Next, after degassing with a vacuum device or the like while keeping the plasticized material heated and maintained at a predetermined temperature, the radial type turbo rotor forming die having a minimum blade thickness of 0.5 mm is kept at 20 ° C. Then, the plasticized material was pressure-injected at a pressure of 1.5 atm and cooled and solidified to form a ceramic turbo rotor.

The ceramic turbo rotor molded body thus obtained was taken out of the molding die, and the presence or absence of a weld line on the surface of the molded body and the filling property up to the blade tip were visually inspected.
The one that was filled up to the tip of the blade was marked with ◯, and the one that was not filled was marked with x.

The radial type ceramic turbo rotor molded body is dried at a predetermined temperature and then debindered at a temperature of 500 ° C. for 4 hours, and then the non-oxide type molded body is subjected to a nitrogen gas atmosphere. Further, the oxide-based molded body was fired in the atmosphere to prepare a sintered body of the radial type ceramic turbo rotor, and the sintered body was inspected with a binocular microscope to confirm the presence or absence of cracks. No crack was observed in any of the sintered bodies using the ceramic molding composition. The above results are shown in Tables 3 and 4.

[0026]

[Table 3]

[0027]

[Table 4]

[0028]

As described above, according to the ceramic molding composition of the present invention, since the organic dispersant in the binder is 0.2 to 3% by weight of polyethylene glycol alkylamine, it is complicated. Molded products with a narrow void without forming weld lines on the surface of the ceramic molded product, as well as having high dimensional accuracy and high strength molded products without internal defects even if the product has a three-dimensional structure. It is possible to obtain a ceramic molding composition which is completely filled up to the tip of a mold and does not cause cracking or deformation of the ceramic body after degreasing or firing and which is excellent in mass production and can be molded at low pressure.

Claims (1)

[Claims] 1. A mixture of a ceramic powder and a binder consisting of an organic dispersant, a solvent and a solidifying agent is heated to a temperature above the melting point of the binder for plasticization, and the plasticized product is injected under pressure into a mold. A ceramic molding composition used for cooling and solidifying to obtain a molded body, wherein the organic dispersant comprises 0.2 to 3% by weight of polyethylene glycol alkylamine. object.