JP2009234852A - Method of manufacturing ceramic molded boy and method of manufacturing ceramic sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of stably manufacturing a complicated shaped ceramic molded body by wet molding method. <P>SOLUTION: The method of manufacturing the ceramic molded body includes: a step of defoaming bubbles in a mixture containing ceramic powder, curable resin, a solvent, a dispersant and a curing agent; a step of injecting the defoamed mixture into a mold; a step of curing the injected mixture to form a solvent-containing ceramic molded body; a step of removing the mold; and a step of drying the resultant solvent-containing ceramic formed body. The mixture contains two or more kinds of the curing agents. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a ceramic molded body, particularly for manufacturing a molded body having a complicated shape.

  In recent years, ceramic parts having complicated shapes have been required, and studies have been made on injection molding, casting molding, extrusion molding, and the like. Among them, as for the casting molding method suitable for complex and large-size molding, resin binders and additives suitable for it have been studied, and various proposals have been made (Patent Documents 1, 2, 3, and 4).

However, in all cases, bubbles existing in the mixture, which is a problem of the wet forming method, may remain in the cured ceramic body, and there are bubbles in the sintered body obtained by sintering the ceramic body. It may become a starting point of destruction and cause a problem of strength reduction. However, at present, no manufacturing method has been found that can cope with complicated shapes and can maintain a stable strength.
Japanese Patent Publication No. 7-22931 Japanese Patent No. 3692682 JP 2005-53716 A JP 2007-136912 A

  An object of the present invention is to provide a method for producing a ceramic molded body in which the remaining of bubbles is reduced in view of the problems of the prior art.

  In order to achieve the above object, the present invention comprises the following arrangement. That is, a step of defoaming bubbles in a mixture containing ceramic powder, a curable resin, a solvent, a dispersant, and a curing agent, a step of injecting the mixture after defoaming into a mold, and the injected mixture In the method for producing a ceramic molded body comprising a step of curing to form a solvent-containing ceramic molded body, a step of removing the mold, and a step of drying the obtained solvent-containing ceramic molded body, the mixture comprises two or more curing agents It is a manufacturing method of the ceramic molded object characterized by including.

ADVANTAGE OF THE INVENTION According to this invention, the ceramic molded object which reduced the residual of a bubble can be manufactured, and the manufacturing method of the ceramic molded object excellent in the physical property when it is set as a sintered compact can be provided.

  In the present invention, first, a mixture containing ceramic powder, curable resin, solvent, dispersant, and curing agent is prepared, and bubbles in the mixture are degassed. For mixing, a ball mill or an attritor mill can be used. The method for defoaming bubbles in the mixture is not particularly limited, and may be a method of depressurizing and defoaming in a sealed container, a method of defoaming by centrifugation, or the like. Among them, the method of depressurizing and defoaming in an airtight container is preferable because air bubbles can be easily removed. The degree of vacuum in the container is preferably 5 to 50 kPa, and more preferably 5 to 30 kPa. When the degree of vacuum in the container exceeds 50 kPa, defoaming may be insufficient, and when it is less than 5 kPa, the viscosity of the solvent may increase. The decompression time is preferably 3 to 60 minutes, and more preferably 5 to 30 minutes. The decompression time needs to be completed before the viscosity increases due to curing, and can be appropriately selected depending on the composition of the mixture to be used. Further, the defoaming can be performed simultaneously with the mixing.

  In the present invention, the kind of ceramic powder is not limited, but for example, zirconium oxide, aluminum oxide, silicon oxide, titanium oxide, aluminum nitride, silicon nitride, silicon carbide, or a mixture thereof is used. be able to. As the zirconium oxide powder, a tetragonal partially stabilized zirconium oxide powder containing a stabilizer such as magnesium oxide, calcium oxide, yttrium oxide, cerium oxide or the like can be used. Those containing 2 to 25 mol% of these stabilizers are preferably used. 8 to 10 mol% for magnesium oxide, 6 to 12 mol% for calcium oxide, and 2 to 4 mol% for yttrium oxide. In the case of cerium oxide, 12 to 20 mol% is more preferable. Particularly preferred is a partially stabilized zirconium oxide powder containing yttrium oxide in the range of 2 to 4 mol% as a stabilizer.

  The ceramic powder preferably contains 30 to 65% by volume of the ceramic powder, and more preferably 35 to 60% by volume. When the ceramic powder in the mixture is less than 30% by volume, a dense ceramic sintered body may not be obtained. Moreover, when it exceeds 65 volume%, since there are too few solvent amounts in a mixture, it may become difficult to obtain the mixture with the fluidity | liquidity which can be shape | molded.

The curable resin used in the present invention is not particularly limited as long as it forms a three-dimensional network structure by a polymerization reaction. However, it is desirable that the curable resin is liquid in terms of improving the fluidity of the mixture and improving the injection into the mold. As for the affinity between the curable resin and the solvent, if the affinity is poor, it separates and segregates inside the molded body, which may cause pores and other defects during sintering. It is desirable to select a functional resin. Examples of such curable resins include melamine resins, phenol resins, epoxy resins, acrylic resins, urethane resins, and the like. Among them, an epoxy resin can be preferably used in order to increase the strength of the molded body. Examples of the epoxy resin include diglycidyl ether type epoxy resins of bisphenols such as bisphenol A type and bisphenol F type, phenol novolac type epoxy resins, cresol novolac type epoxy resins, glycidyl amine type epoxy resins, aliphatic epoxy resins and the like. Examples include ether type epoxy resins, glycidyl ester type epoxy resins, methyl glycidyl ether type epoxy resins, cyclohexene oxide type epoxy resins, and rubber-modified epoxy resins. The solvent is preferably aqueous based on the influence on the environment. Therefore, the curable resin is preferably water-soluble, and glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, methyl glycidyl ether type epoxy resin, and cyclohexene oxide type epoxy resin are preferable. An ether type epoxy resin is more preferable because it cures smoothly even at room temperature.
The average molecular weight of the epoxy resin is preferably 20 to 30000, and the average molecular weight of 50 to 3000 is more preferable because it can be easily mixed with the powder and a certain strength can be obtained. More preferably, it is 50-2500. Such epoxy resins can be used alone or in combination.

In the manufacturing method of this invention, it is preferable that 5-20 volume% of curable resin is contained in the said mixture, 5-15 volume% is more preferable, and 8-15 volume% is further more preferable. If the content of the curable resin is less than 5% by volume in the mixture, the strength of the molded body may be insufficient, and if it exceeds 20% by volume, a dense ceramic sintered body may not be obtained. .
The type of the dispersant used in the present invention is not limited, and the type of the dispersant is not limited as long as it does not hinder the curing of the curable resin. Polymer type dispersants, inorganic type dispersants such as phosphates such as sodium hexametaphosphate, anionic, cationic and nonionic organic surfactant type dispersants can be used. Of these, the polycarboxylic acid type is preferable in that a wide range of powders can be dispersed.

  In the production method of the present invention, it is necessary to contain two or more curing agents in the mixture. When the curing agent is mixed in this manner, the preferred compounding ratio varies depending on the functional group equivalent of the curable resin and the active group equivalent of the curing agent. For example, an epoxy resin is used as the curable resin, and a polyamine curing agent is used as the curing agent. Is preferably about 0.9 to 1.5 in terms of curability, the ratio of the active hydrogen equivalent of the amine curing agent to the epoxy equivalent is about 0.9 to 1.5.

  As the curing agent, for example, an amine curing agent, an acid anhydride curing agent, a polyamide curing agent, or the like can be used. In particular, amine-based curing agents are preferable in that the reaction is rapid. Examples of amine-based curing agents include aliphatic amines, alicyclic amines, aromatic amines, polyether polyamines, and the like. Examples of alicyclic amines such as polyalkylene polyamines (for example, ethylenediamine, 1,6-hexamethylenediamine), diethyltriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, etc. include 1-amino-3,3, 5-trimethyl-5-aminomethylcyclohexane, 1,4-diaminocyclohexane, bis- (4-aminocyclohexyl) -methane, piperazines (piperazine, N-aminoethylpiperazine, N-aminopropylpiperazine, etc.), aromatic, etc. As the amine, metaphenylene diene Min, diaminodiphenylmethane, diaminodiphenylsulfone and the like, as the polyether polyamine, can be used polyoxypropylene diamine. Among them, alicyclic amines are preferred to contain at least one alicyclic amine because of their rapid reaction and excellent shape retention. It is preferable to mix at least one alicyclic amine, and excellent shape retention because the defoaming operation can be easily performed. It is more preferable to include at least an alicyclic amine and a polyether polyamine because the curing time can be selected in a wide range. For example, when the epoxy resin is used as the curable resin and the polyamine curing agent is used as the curing agent, the ratio of the active hydrogen equivalent of the amine curing agent to the epoxy equivalent is 0.2 to 0.8. Is preferable from the viewpoint of curability, and more preferably 0.4 to 0.8. If it is less than 0.2, the solvent-containing ceramic molded body may be deformed because the shape retention is reduced. If it exceeds 0.8, the curing progresses too quickly and degassed under reduced pressure. Bubbles may remain because sufficient time cannot be obtained. Polyether polyamine, for example, when using an epoxy resin as the curable resin and a polyamine curing agent as the curing agent, the ratio of the active hydrogen equivalent of the amine curing agent to the epoxy equivalent is 0.2 to 0.8. It is preferable from the viewpoint of curability, and more preferably 0.4 to 0.8. If it is less than 0.2, the solvent-containing ceramic molded body may be deformed because the shape retention is reduced. If it exceeds 0.8, the curing progresses too quickly and degassed under reduced pressure. Bubbles may remain because sufficient time cannot be obtained.

  In the production method of the present invention, the solvent is preferably contained in the mixture in an amount of 20 to 60% by volume, more preferably 20 to 55% by volume, and more preferably 25 to 55% by volume. More preferably. When the solvent is less than 20% by volume, the fluidity is low and may not be suitable for molding. When it exceeds 60% by volume, a dense ceramic sintered body may not be obtained. Although the kind in the solvent in a mixture is not limited, For example, water, alcohol, other organic solvents, etc. can be used. Among these, water and alcohols are preferable from the viewpoint of easy handling. The solvent in these mixtures may be used independently and may be mixed suitably. It is preferable that it is a water system from the influence on an environment.

  Next, after the defoamed mixture is injected into a mold, the injected mixture is cured and molded, and the mold is removed to obtain a solvent-containing ceramic molded body. In order to produce a molded body having a complicated shape, the mold must be a collapsible mold. Examples of the demolding step for removing the mold include a method of melting and removing by heating using lost wax or the like, and a method of dissolving and removing with a solvent using a mold soluble in a solvent such as foamable resin.

  The obtained solvent-containing ceramic molded body can be dried in the air, in a hot air dryer, or in a constant temperature and humidity dryer.

  The dried ceramic molded body is then sintered to form a ceramic sintered body. The sintering conditions, that is, the sintering temperature and the sintering time, are set so that the density is at least 95% of the theoretical density so that the strength of the ceramic sintered body to be obtained does not decrease and inconvenience such as breakage does not occur during use. Select. Preferably, it is at least 97%. Sintering conditions vary depending on the type of ceramic powder used. For example, when zirconium oxide powder is used, the temperature is preferably set to 1,300 to 1,500 ° C. for 1 to 5 hours. Moreover, when using aluminum oxide powder, it is preferable to set it as 1500-1700 degreeC and 1 to 5 hours. As a matter of course, when obtaining an oxide-based ceramic sintered body such as a zirconium oxide sintered body or an aluminum oxide sintered body, the sintering atmosphere should be an oxidizing atmosphere such as air, and the silicon nitride sintered body or carbonized body. When obtaining a non-oxide ceramic sintered body such as a silicon sintered body, a reduced pressure (vacuum) atmosphere or an inert (reducing) atmosphere such as nitrogen or argon is used.

  In addition, according to the present invention, the ceramic product obtained by sintering the ceramic molded body in which the remaining bubbles are reduced to obtain a ceramic sintered body has a high average bending strength. For example, if it is an aluminum oxide sintered body, it is 300 MPa or more, more preferably 350 MPa or more, and in the partially stabilized zirconium oxide sintered body containing 2-4 mol% of yttrium oxide as a stabilizer, 1000 MPa or more, more The high strength is preferably 1100 MPa or more.

  The obtained ceramic sintered body has a stable quality with a minimum bending strength / average bending strength of 0.5 or more, more preferably 0.7 or more. As described above, since the minimum bending strength / average bending strength is high, damage during use is extremely reduced.

<Measuring method of elastic modulus of solvent-containing ceramic compact>
The produced solvent-containing ceramic molded body was subjected to a three-point bending test, the displacement amount and the bending load were continuously measured, and the elastic modulus at a bending stress of 7 MPa was obtained from the equation (1). The number of measurements was n = 10, and the average value was the elastic modulus of the solvent-containing ceramic molded body. The apparatus used was a universal testing machine CATY2000 manufactured by Yonekura Seisakusho. The measurement conditions are as follows. In the measurement of the solvent-containing ceramic molded body, it was measured immediately after demolding from the mold.
Measurement atmosphere: 20 ± 5 ° C, relative humidity 40 ± 10%
Distance between fulcrums: 20mm
Upper indenter radius of curvature: 5mm
Lower indenter radius of curvature: 5mm
Crosshead speed: 0.5 mm / second Test piece: cylinder E = 4 × 9.8 × P × L ³ / (3 × π × D ⁴ × Y) (9.5 mm in diameter × 40 mm in length) (1)
E: Elastic modulus (MPa)
P: Bending load (kg)
L: Distance between fulcrums (mm)
D: Sample diameter (mm)
Y: Displacement amount (mm).

<Measuring method of average bending strength and minimum bending strength / average bending strength of sintered ceramics>
As for the bending strength of the ceramic sintered body, ten test pieces having a size of 4 × 3 × 40 mm were cut out according to the method of JISR1601, and the three-point bending strength was measured with a universal testing machine manufactured by Yonekura Seisakusho (model CATY2000). The average bending strength is a simple average value of 10 measurement results.

  The lowest bending strength is the lowest of the ten three-point bending strengths.

<Method for measuring relative density of ceramic sintered body>
The sintered density of the ceramic sintered body was measured by the Archimedes method. As is well known, the theoretical density is calculated from a perfect crystal lattice. For example, it is 6.1 g / cm ^{3 for} tetragonal zirconium oxide and 4.0 g for aluminum oxide. / m ^3, if silicon nitride 3.2 g / m ^3, a long silicon carbide 3.2 g / m ^3. For those containing different types of ceramics, calculation may be made according to the weight ratio of each ceramic. For example, when the ceramics of theoretical density D1 and D2 are 60% by weight and 40% by weight, respectively, it can be obtained as D1 × (60/100) + D2 × (40/100).
Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
In the mixture, the following raw materials were used, mixed for 24 hours by a ball mill, and after mixing, a curing agent:
1- (2-Aminoethyl) piperazine and polyoxypropylenediamine were mixed and further mixed for 0.5 hours to obtain a mixture.
Ceramic powder: Aluminum oxide powder Curable resin: Water-soluble epoxy resin (EX-313 manufactured by Nagase ChemteX)
Solvent: ion-exchange water dispersant: polycarboxylate (Chukyo oil-based D-305)
Curing Agent 1: 1- (2-Aminoethyl) piperazine Curing Agent 2: Polyoxypropylenediamine Next, the mixture was put into a 500 ml container, degassed for 20 minutes at a vacuum degree of 30 kPa, and then the mixture was washed with a long side of 100 mm. X Short side 60 mm x Height 10 mm polyethylene mold and 9.5 mm diameter x 40 mm length silicone rubber mold Dried and left at 20 ° C for 24 hours for water retention with moderate shape retention A zirconium oxide molded body was obtained. The elastic modulus was measured using a sample containing hydrous aluminum oxide having a diameter of 9.5 mm and a length of 40 mm. Next, the hydrous aluminum compact was humidified and dried at 30 ° C. and 90% relative humidity for 5 days, then dried with hot air at 100 ° C. for 24 hours to obtain a dry compact, and further sintered in air at 1600 ° C. for 2 hours As a result, an aluminum oxide sintered body was obtained. The specifications of this aluminum oxide sintered body were as follows.

Average bending strength: 400 MPa
Minimum bending strength / average bending strength: 0.85
Density: 3.9 g / cm ³ (98% of theoretical density).

Example 2
The same procedure as in Example 1 was performed except that the curing agent 2 was phthalic anhydride and the mixing ratio of raw materials shown in Table 1 was used. The specifications of the obtained aluminum oxide sintered body were as follows.

Average bending strength: 390 MPa
Minimum bending strength / average bending strength: 0.7
Density: 3.9 g / cm ³ (98% of theoretical density).

Example 3
The curing agent 1 is diethylenetriamine, the curing agent 2 is polyoxypropylenediamine, and Table 1
The same procedure as in Example 1 was performed except that the mixing ratio of the raw materials shown in FIG. The specifications of the obtained aluminum oxide sintered body were as follows.

Average bending strength: 390 MPa
Minimum bending strength / average bending strength: 0.8
Density: 3.9 g / cm ³ (98% of theoretical density).

Example 4
Ceramic powder is partially stabilized zirconium oxide powder containing 2.7 mol% yttrium oxide, curable resin is urethane resin (manufactured by Sumitomo Bayer Urethane: Bihydrol A145), curing agent 1 is diethylenetriamine, and curing agent 2 is manufactured by Sumitomo Bayer Urethane. : Bihijoule 3100, except that the mixing ratio of raw materials shown in Table 1 was used. The specifications of the obtained aluminum oxide sintered body were as follows.

Average bending strength: 1250 MPa
Minimum bending strength / average bending strength: 0.8
Density: 6 g / cm ³ (98% of theoretical density).

Comparative Example 1
The same procedure as in Example 1 was performed except that the curing agent 2 was not mixed. When the mixture was degassed under reduced pressure, the fluidity deteriorated during the defoaming, and the mold could not be filled, and the desired hydrous aluminum-containing molded product could not be obtained.

Comparative Example 2
The procedure was the same as in Example 1 except that the curing agent 2 was not mixed and the vacuum time was 5 minutes. The specifications of the obtained aluminum oxide sintered body were as follows.

Average bending strength: 370 MPa
Minimum bending strength / average bending strength: 0.4
Density: 3.9 g / cm ³ (98% of theoretical density).

  The results are shown in Table 1. In Examples 1-4, since it was set as the mixture containing ceramic powder, curable resin, a solvent, a dispersing agent, and 2 or more types of hardening | curing agents, it became a desired ceramic sintered compact, and in Comparative Examples 1 and 2, 2 or more types were used. It can be seen that the desired ceramic sintered body could not be obtained because it did not contain a curing agent.

Claims (7)

A step of defoaming bubbles in a mixture containing ceramic powder, a curable resin, a solvent, a dispersant, and a curing agent; a step of injecting the mixture after defoaming into a mold; and curing the injected mixture. In the method for producing a ceramic molded body, which includes a step of forming a solvent-containing ceramic molded body, a step of removing the mold, and a step of drying the obtained solvent-containing ceramic molded body, the mixture contains two or more curing agents. A method for producing a ceramic molded body, comprising: The method for producing a ceramic molded body according to claim 1, wherein the curable resin is a water-soluble epoxy resin. The method for producing a ceramic molded body according to claim 2, wherein the water-soluble epoxy resin is a glycidyl ether type water-soluble epoxy resin. The method for producing a ceramic molded body according to any one of claims 1 to 3, wherein the curing agent is two or more selected from aliphatic amines, alicyclic amines, aromatic amines and polyether polyamines. The manufacturing method of the ceramic molded body in any one of Claims 1-4 in which the said hardening | curing agent contains an alicyclic amine at least. The method for producing a ceramic molded body according to claim 5, wherein the curing agent contains an alicyclic amine and a polyether polyamine. A method for manufacturing a ceramic sintered body, comprising sintering a ceramic molded body obtained by the method for manufacturing a ceramic molded body according to any one of claims 1 to 6.