JP2011157222A - Method for producing ceramic molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an alumina-zirconia composite ceramic molding in a wet molding method. <P>SOLUTION: The method for producing the ceramic molding includes: a mixing step of preparing composite slurry containing zirconia powder, alumina powder, a hardening resin, a solvent and a dispersant; a molding step of mixing a curing agent with the composite slurry, performing curing and molding in a mold and performing releasing from the mold to form a solvent-containing ceramic molding; and a drying step of drying the solvent-containing ceramic molding. The method further includes a step of previously preparing first slurry containing the zirconia powder, the hardening resin, the solvent and the dispersant and second slurry containing the alumina powder, the hardening resin, the solvent and the dispersant when the composite slurry is prepared in the mixing step and mixing the first slurry and the second slurry with each other. <P>COPYRIGHT: (C)2011,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.

  Ceramics are used in various structural parts for reasons such as excellent mechanical properties and corrosion resistance. In recent years, parts with complex shapes have been required, and studies have been made on extrusion molding, casting molding, injection molding, and the like, and various proposals have been made. Among them, as for the cast molding method suitable for complex and large-size molding, investigations on resin binders and additives suitable for it have been made, and various proposals have been made (Patent Documents 1, 2, 3, 4, 5).

  A method for preparing an alumina-zirconia composite slurry has been proposed (Patent Document 6).

  However, these methods are problematic in that when a high concentration slurry is prepared, the viscosity becomes high and it cannot be successfully cast into a mold having a complicated shape, and the strength of the sintered body obtained by sintering the obtained ceramic compact is reduced. was there.

Japanese Patent Publication No. 7-22931 Japanese Patent Publication No. 10-217212 Japanese Patent No. 3692682 JP 2005-53716 A JP 2007-136912 A Japanese Patent Publication No. 63-103859

  An object of the present invention is to provide a method for producing a ceramic molded body capable of reducing segregation when the viscosity of a slurry is reduced and a sintered body is obtained 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 mixing step of preparing a composite slurry containing zirconia powder, alumina powder, curable resin, solvent and dispersant, a curing agent is mixed with the composite slurry, cured in a mold, molded, demolded and contained. A method for producing a ceramic formed body comprising a forming step of forming a solvent ceramic formed body, and a drying step of drying the solvent-containing ceramic formed body, wherein the composite slurry is prepared in advance in the mixing step in the zirconia powder, curable resin Preparing a first slurry containing a solvent and a dispersant and a second slurry containing alumina powder, a curable resin, a solvent and a dispersant, and mixing the first slurry and the second slurry. Is a method for producing a ceramic molded body.

  ADVANTAGE OF THE INVENTION According to this invention, the alumina-zirconia ceramic molded object 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 order to achieve the above object, the present invention comprises the following arrangement. That is, a mixing step of preparing a composite slurry containing zirconia powder, alumina powder, curable resin, solvent and dispersant, a curing agent is mixed with the composite slurry, cured in a mold, molded, demolded and contained. A method for producing a ceramic formed body comprising a forming step of forming a solvent ceramic formed body, and a drying step of drying the solvent-containing ceramic formed body, wherein the composite slurry is prepared in advance in the mixing step when the zirconia powder and the curable resin are prepared. Preparing a first slurry containing a solvent and a dispersant and a second slurry containing alumina powder, a curable resin, a solvent and a dispersant, and mixing the first slurry and the second slurry. Is a method for producing a ceramic molded body.

  As the zirconia powder used in the present invention, tetragonal partially stabilized zirconia powder containing a stabilizer such as magnesia, calcia, yttria, and ceria can be used. These stabilizers are preferably used in an amount of 2 to 25 mol%, 8 to 10 mol% for magnesia, 6 to 12 mol% for calcia, 2 to 4 mol% for yttria, and ceria. If it exists, it is more preferable that 12-20 mol% is contained. Particularly preferred is a partially stabilized zirconia powder containing yttria in the range of 2 to 4 mol% as a stabilizer.

  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. . As for the affinity between the curable resin and the solvent, if the affinity is poor, it will separate and segregate inside the ceramic molded body, which may cause defects such as pores during sintering. It is desirable to select a curable resin. Examples of such curable resins include melamine resins, phenol resins, epoxy resins, acrylic resins, urethane resins, and the like. Among these, an epoxy resin is preferably used in order to improve the shape retention of the ceramic molded body. Examples of the epoxy resin include glycidyl such as 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 an aqueous solvent because of its influence on the environment. Therefore, the curable resin is also preferably a water-soluble epoxy resin. Of these, a glycidyl ether type epoxy resin is more preferable because it cures smoothly even at room temperature.

  When using an epoxy resin, the weight average molecular weight is preferably 20 to 30000, and the weight average molecular weight 50 to 3000 is more preferable because it can be easily mixed with the powder and a certain mechanical strength can be obtained. More preferably, it is 50-2500. Such epoxy resins can be used alone or in combination.

  Here, the curable resin contained in the composite slurry is preferably 5 to 15% by volume in the composite slurry. When the content of the curable resin is less than 5% by volume in the composite slurry, the strength of the solvent-containing ceramic formed body and the dried ceramic formed body may be insufficient. When the content exceeds 15% by volume, the drying process is in progress. Cracks may occur in the solvent-containing ceramic molded body, or problems such as cracking may occur in the process of removing the curable resin, such as a degreasing process or a sintering process for making the ceramic molded body into a sintered body. This is not preferable.

  The type of the solvent used in the present invention is not limited. For example, water, alcohols, organic solvents, and the like can be used as long as they do not remain in the sintered body after sintering. Among these, water is preferable from the viewpoints of environmental impact and good handleability. Examples of alcohols that can be used include methyl alcohol and ethyl alcohol. Moreover, as an organic solvent, benzene, toluene, xylene, etc. can be used, for example. The solvents in these slurries may be used alone or may be mixed as appropriate.

  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. Polymeric dispersants, inorganic dispersants such as phosphates such as sodium hexametaphosphate, and anionic, cationic, and nonionic organic surfactant dispersants can be used. Of these, the polycarboxylic acid type is preferable in that a wide range of powders can be dispersed.

  In this invention, the addition amount of a hardening | curing agent can be suitably determined with the combination with curable resin. That is, the preferred compounding ratio differs depending on the functional group equivalent of the curable resin and the active group equivalent of the curing agent. For example, when using an epoxy resin as the curable resin and a polyamine curing agent as the curing agent, The active hydrogen equivalent ratio of the amine curing agent is preferably about 0.8 to 1.5 from the viewpoint of curability.

  In the production method of the present invention, in the mixing step of preparing a composite slurry containing zirconia powder, alumina powder, curable resin, solvent and dispersant, a first slurry containing zirconia powder, curable resin, solvent and dispersant in advance It is necessary to prepare a second slurry containing alumina powder, a curable resin, a solvent and a dispersant, and to mix the first slurry and the second slurry. When preparing a slurry, it is desirable to prepare a slurry using an alumina-zirconia composite powder obtained by mixing and granulating alumina powder and zirconia powder with a spray dryer or the like, because the slurry is not highly dispersed and the fluidity of the slurry is poor. Absent.

  First, such a first slurry is prepared. Here, the content of the zirconia powder is preferably in the range of 40 to 45% by volume. When the zirconia powder is less than 40% by volume, the fluidity of the composite slurry is high and easy to cast, but it is not preferable because the solvent component in the composite slurry increases and cracks may occur during drying. Moreover, when exceeding 45 volume%, since the fluidity | liquidity of a composite slurry is inferior, it is unpreferable. The average particle size of the zirconia powder is preferably 0.1 to 0.3 μm.

  Next, such a second slurry is prepared. Here, the amount of the alumina powder is preferably in the range of 50 to 60% by volume. When the alumina powder is less than 50% by volume, the fluidity of the composite slurry is high and easy to cast, but this is not preferable because the solvent component in the slurry increases and cracking may occur during drying. On the other hand, when the volume exceeds 60% by volume, the fluidity of the composite slurry is inferior, and lumps remain in the slurry, causing segregation due to the lumps remaining when the sintered body is produced, resulting in a decrease in strength. The average particle diameter of the alumina powder is preferably 0.4 to 0.6 μm.

  A ball mill, an attritor mill, or the like can be used to prepare the first slurry and the second slurry, and to mix the obtained first slurry and second slurry.

  The composite slurry may have a viscosity of 5 Pa · s or less. The viscosity can be measured with a viscometer. Since the composite slurry is a non-Newtonian fluid and the viscosity changes depending on the shear rate, in the present invention, the value is set at a shear rate of 1.9 (1 / s). If it exceeds 5 Pa · s, the fluidity is poor, and it may not be cast well into a mold having a complicated shape, or large bubbles may be entrained in the composite slurry, resulting in defects. It is preferably 3 Pa · s or less, more preferably 1 Pa · s or less.

  A curing agent is mixed with the above composite slurry and injected into a mold, and then the mixed composite slurry is cured and molded to obtain a solvent-containing ceramic molded body. 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 solvent-containing ceramic molded body is degreased and sintered to form a sintered body. The degreasing conditions may be appropriately determined depending on the type and amount of the curable resin, the shape of the molded body and the like. In particular, a large molded body or a thick molded body is preferably heated to 600 ° C. at a rate of 30 ° C./hour or less to remove the binder so that cracking due to degreasing does not occur. Sintering conditions, i.e., sintering temperature and sintering time, are selected so that the density is at least 90% of the theoretical density so that the strength of the resulting sintered body is reduced and inconveniences such as breakage do not occur during use. To do. Preferably, it is at least 95%. In the case of this invention, sintering conditions are good to hold | maintain for 2 to 3 hours at 1500-1600 degreeC by an atmospheric condition.

  In addition, according to the present invention, when a sintered body is obtained, a sintered body with little segregation is obtained, so that the average bending strength of the sintered body is high. The average bending strength varies depending on the ratio of alumina and zirconia in the sintered body. For example, when the ratio of alumina is 70% by weight and zirconia is 30% by weight, it is 600 MPa or more, more preferably 700 MPa or more.

  Hereinafter, the present invention will be described in more detail with reference to examples.

  The physical properties of the examples were measured and evaluated as follows.

(1) Average particle diameter of powder The specific surface area s was calculated by the measurement method of the specific surface area by the gas adsorption BET method of JIS R1626 (1996) fine ceramic powder, and the average particle diameter was determined by applying the average particle diameter to the following equation.
d = 6 / (ρ · s)
Here, ρ is the theoretical density of the ceramic powder, and the following value was used.
Zirconia: 6.08 g / cm ³
Alumina: 3.98 g / cm ³
(2) Viscosity of composite slurry The viscosity of the prepared composite slurry before addition of the curing agent was measured with a viscometer. As the viscometer, an E-type viscometer DVU-EII type manufactured by Tokimec Co., Ltd. was used. The measurement conditions were such that the rotor was standard 1 ° 34′R24, the temperature was 20 ° C., and the rotation speed was 0.5 rpm (shear rate 1.9 (1 / s)).

(3) Cracking at the time of drying The produced 100 mm × 70 mm, 20 mm thick solvent-containing ceramic molded sample was kept at a temperature of 30 ° C. and a relative humidity of 90% for 48 hours using a constant temperature and humidity dryer, and then a temperature of 30 ° C. The number of samples with cracks was confirmed by observing the sample surface after being held at a relative humidity of 70% for 48 hours. The number of samples was 10, and was “excellent” when there was no sample that was cracked in 10 samples, and “good” when there were no more than 8 samples in 10 samples. When there were 3 or more cracks in 10 pieces, it was evaluated as “OK”.

(4) Strength of sintered body The strength of the prepared sintered body sample was measured by three-point bending strength. The three-point bending strength was measured by the method specified in JIS R1601 (2008). A universal testing machine CATY2000 manufactured by Yonekura Seisakusho was used as the apparatus. The measurement conditions are as follows. The ratio of alumina and zirconia in the ceramic sintered body was 70% by weight of alumina and 30% by weight of zirconia, and the number of samples was 10 to obtain the average strength.
Measurement atmosphere: 20 ± 5 ° C., relative humidity 40 ± 10% RH
Distance between fulcrums: 30mm
Upper indenter radius of curvature: 5mm
Lower indenter radius of curvature: 5mm
Crosshead speed: 0.5 mm / second Test piece dimensions: 3 mm × 4 mm × 40 mm
(5) Relative density of sintered body The measured density of the sintered body was divided by the theoretical density, and the value expressed as a percentage was taken as the relative density. Here, the measured density of the composite ceramic sintered body was measured by the Archimedes method. The theoretical density of the composite ceramic sintered body was determined from the respective contents using the following values as the density of the single component of zirconia and alumina.
Zirconia: 6.08 g / cm ³
Alumina: 3.98 g / cm ³
Example 1
A slurry was prepared with the following raw materials. The first slurry and the second slurry were obtained by mixing with a ball mill for 24 hours. The formulation is shown in Example 1 of Table 1.
First slurry powder: zirconia powder (containing 2.5 mol yttrium oxide) (average particle size 0.2 μm)
Curable resin: Water-soluble epoxy resin (EX-313 manufactured by Nagase ChemteX)
Solvent: Ion-exchange water dispersant: Polycarboxylate (Pois 530 manufactured by Kao)
Second slurry powder: Alumina powder (purity 99.8%) (average particle size 0.5 μm)
Curable resin: Water-soluble epoxy resin (EX-313 manufactured by Nagase ChemteX)
Solvent: ion-exchange water dispersant: polycarboxylate (Seruna D305 manufactured by Chukyo Yushi)
Composite slurry curing agent: 1- (2-aminoethyl) piperazine Next, the first slurry and the second slurry were mixed with a ball mill for 4 hours so as to have the volume ratio shown in Table 1, and a composite slurry was prepared to obtain a viscosity. Was measured. Take out the composite slurry from the ball mill, mix the curing agent with a rotary evaporator, pour it into a mold (100 mm x 70 mm, polyethylene 20 mm in height), let it stand at 20 ° C for 24 hours to cure, and obtain a solvent-containing ceramic molded body It was. After demolding, it was immersed in ion-exchanged water, and the solvent-containing ceramic compact was kept for 48 hours at a temperature of 30 ° C. and a relative humidity of 90%, and then kept for 48 hours at 30 ° C. and a relative humidity of 70%. . Thereafter, it was dried with hot air at 100 ° C. for 24 hours to obtain a ceramic molded body, further heated to 600 ° C. at 25 ° C./hour in an electric furnace, further heated and sintered at 1550 ° C. for 3 hours to obtain a sintered body. It was. The obtained sintered body was measured for strength after density measurement. As a result, as shown in Table 1, the viscosity of the composite slurry was low, and dry cracking did not occur. The relative density of the sintered body was 95.3% and the strength was 720 MPa.

Example 2
It was produced and evaluated in the same manner as in Example 1 except that the formulation shown in Example 2 of Table 1 was used. As a result, as shown in Table 1, the viscosity of the composite slurry was low, and 8 out of 10 samples were “good” with no dry cracking. The relative density of the sintered body was 95.1% and the strength was 710 MPa.

Example 3
It was produced and evaluated in the same manner as in Example 1 except that the formulation shown in Example 3 in Table 1 was used. As a result, as shown in Table 1, the viscosity of the composite slurry was slightly high, and dry cracking did not occur and was “excellent”. The relative density of the sintered body was 95.2% and the strength was 710 MPa.

Example 4
It was produced and evaluated in the same manner as in Example 1 except that the formulation shown in Example 4 in Table 1 was used. As a result, as shown in Table 1, the viscosity of the composite slurry was slightly high, and dry cracking did not occur and was “excellent”. The relative density of the sintered body was 95.1% and the strength was 710 MPa.

Example 5
It was produced and evaluated in the same manner as in Example 1 except that the formulation shown in Example 5 in Table 1 was used. As a result, as shown in Table 1, the viscosity of the composite slurry was low, and 8 out of 10 samples were “good” with no dry cracking. The relative density of the sintered body was 95.2% and the strength was 680 MPa.

Example 6
It was produced and evaluated in the same manner as in Example 1 except that the formulation shown in Example 6 in Table 1 was used. As a result, as shown in Table 1, the viscosity of the composite slurry was low, and 8 out of 10 samples were “good” with no dry cracking. The relative density of the sintered body was 95.2% and the strength was 620 MPa.

Example 7
It was produced and evaluated in the same manner as in Example 1 except that the formulation shown in Example 7 in Table 1 was used. As shown in Table 1, the viscosity of the composite slurry was low and 9 out of 10 samples were “good” with no dry cracking. The relative density of the sintered body was 95.2% and the strength was 700 MPa.

Example 8
A slurry was prepared with the following raw materials and prepared and evaluated in the same manner as in Example 1 except that the formulation shown in Example 8 in Table 1 was used.
First slurry powder: zirconia powder (containing 2.5 mol yttrium oxide)
Curable resin: Urethane resin (Baihydrol A145 made by Sumitomo Bayer Urethane)
Solvent: Ion-exchange water dispersant: Polycarboxylate (Pois 530 manufactured by Kao)
Second slurry powder: Alumina powder (purity 99.8%)
Curable resin: Urethane resin (Baihydrol A145 made by Sumitomo Bayer Urethane)
Solvent: ion-exchange water dispersant: polycarboxylate (Seruna D305 manufactured by Chukyo Yushi)
Composite slurry curing agent: Sumitomo Bayer Urethane Bihijoule 3100
As a result, as shown in Table 1, the viscosity of the composite slurry was slightly high, and dry cracking did not occur and was “excellent”. The relative density of the sintered compact was 95.2% and the strength was 710 MPa.

Example 9
It was produced and evaluated in the same manner as in Example 8 except that the formulation shown in Example 9 in Table 1 was used. As a result, as shown in Table 1, the viscosity of the composite slurry was slightly high, and 8 samples out of 10 were “good” with no dry cracking. The relative density of the sintered body was 95.1% and the strength was 700 MPa.

Comparative Example 1
Using the alumina-zirconia composite powder mixed and granulated with a spray dryer, it was mixed for 24 hours with a ball mill to prepare a composite slurry, and the viscosity was measured. The results are as shown in Table 2. However, since the composite slurry had a high viscosity and could not be cast into a mold, cracks during drying could not be observed, and the density and strength of the sintered body could not be measured.

  As shown in the columns of Examples 1 to 9 in Table 1, according to the method for producing a ceramic molded body of the present invention, the viscosity of the composite slurry is low, there is no dry cracking, and the characteristics when the sintered body is obtained are excellent. A molded body can be obtained.

  The method for producing a molded body according to the present invention can be suitably applied to large-sized structural parts, semiconductor parts, various precision parts, etc., because it can suitably provide complicated shaped objects, large-sized complicated shaped objects, etc. However, it is not limited to these.

Claims (3)

  Mixing step of preparing a composite slurry containing zirconia powder, alumina powder, curable resin, solvent and dispersant, mixing a curing agent with the composite slurry, curing in a mold, molding, demolding, and solvent-containing ceramics A method for producing a ceramic formed body comprising a forming step for forming a formed body, and a drying step for drying the solvent-containing ceramic formed body, wherein the composite slurry is prepared in advance in the mixing step, zirconia powder, curable resin, solvent And a first slurry containing a dispersing agent and a second slurry containing alumina powder, a curable resin, a solvent and a dispersing agent, and a step of mixing the first slurry and the second slurry. A method for producing a ceramic molded body.   2. The method for producing a ceramic molded body according to claim 1, wherein the first slurry contains 40 to 45% by volume of zirconia powder, and the second slurry contains 50 to 60% by volume of alumina powder.   The method for producing a ceramic molded body according to claim 1, wherein the curable resin is a water-soluble epoxy resin.