JP2007204297A - Method of preparing ceramic raw material and method of manufacturing ceramic formed body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a ceramic raw material in which ceramic particles and a resin component are uniformly dispersed with improved yield and a method of manufacturing a ceramic formed body. <P>SOLUTION: The method of manufacturing the ceramic raw material containing at least the ceramic particles and the resin component comprises a ceramic particle dispersing step for mixing the ceramic particles with water to prepare a ceramic particle dispersion, a resin component dispersing step for mixing the resin component with water to prepare a resin component dispersion, a mixing step for mixing the ceramic particle dispersion with the resin component dispersion to prepare mixed slurry, a freezing step for pressurizing the mixed slurry to atomize the pressurized mixed slurry under an atmosphere of a normal pressure or a reduced pressure to rapidly freeze to prepare a slurry freezed body and a drying step for drying the slurry freezed body under a reduced pressure to prepare the ceramic raw material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a ceramic raw material containing ceramic particles and a resin component, and a method for producing a ceramic molded body formed by molding the ceramic raw material.

Conventionally, sintered bodies of various ceramic materials have been used for various sensor elements such as ceramic capacitors, piezoelectric elements, honeycomb structures, and gas sensor elements.
Such a sintered body of ceramics is obtained by firing a ceramic formed body prepared by adding water and the like to a ceramic raw material containing ceramic particles and a binder (resin component) and then kneading and then forming. It is done.

As a method for producing a ceramic raw material to be a raw material of a ceramic molded body, there is a method of producing a ceramic raw material by spray drying a slurry obtained by adding and mixing a resin component, a dispersant, a sintering aid and the like to ceramic particles. It is disclosed (see Patent Document 1).
However, in the above manufacturing method, there is a possibility that the ceramic particles and the resin component cannot be uniformly dispersed in the slurry. As a result, there is a possibility that the obtained ceramic raw material does not become a material in which ceramic particles and a resin component are uniformly dispersed.
A ceramic molded body formed using such a ceramic raw material has a problem that the distribution of the resin component is uneven. When the ceramic molded body is sintered, voids such as voids and pores are formed in the sintered body. Therefore, the strength of the sintered body may be reduced, and the characteristics of various ceramics may vary depending on the portion of the sintered body.

  Moreover, as a method for producing a ceramic raw material, a method using freeze-drying that can be dried while maintaining the composition before drying is disclosed (Non-Patent Document 1). In this manufacturing method, a granular slurry frozen body is produced in a liquid refrigerant by spraying or dropping a slurry containing ceramic particles and a resin component onto a liquid refrigerant such as liquid nitrogen. Then, the process (separation process) which isolate | separates a liquid refrigerant and a slurry frozen body is performed, and a slurry frozen body is collect | recovered. Then, the frozen slurry is dried to obtain a ceramic raw material.

However, even in the above manufacturing method, if the ceramic particles and the resin component are not uniformly dispersed in the slurry, the obtained ceramic raw material is not evenly dispersed of the ceramic particles and the resin component.
Furthermore, in the manufacturing method described above, the slurry is frozen using a refrigerant, and the frozen slurry is produced in the refrigerant, so that the separation step described above is required. In the separation step, a physical separation method using a sieve is used, but due to the dimensional relationship between the sieve and the frozen slurry, a frozen slurry that cannot be recovered is generated. For this reason, the loss of the frozen slurry increases, and the recovery yield does not increase. This also leads to an increase in the yield of the ceramic raw material to be produced.

  For these reasons, there has been a demand for a method for producing a ceramic material in which the yield is good and the ceramic particles and the resin component are uniformly dispersed.

JP-A-6-144918 Toshiyuki Yokota (Yamagata Univ.), “Continuous Production Method of Frozen Particles in Freeze-Drying Using Wet Wall Tower”, Vol. 45, no. 1, page. 406-410, 2002

  The present invention has been made in view of such conventional problems, and can improve the yield, and a method for producing a ceramic raw material in which ceramic particles and a resin component are uniformly dispersed, and the ceramic. An object of the present invention is to provide a method for producing a ceramic molded body using raw materials.

1st invention is a manufacturing method of the ceramic raw material containing a ceramic particle and a resin component at least,
A ceramic particle dispersion step of preparing a ceramic particle dispersion by mixing the ceramic particles with water;
A resin component dispersion step of preparing a resin component dispersion by mixing the resin component with water;
A mixing step of preparing a mixed slurry by mixing the ceramic particle dispersion and the resin component dispersion;
Applying pressure to the mixed slurry, a freezing step for producing a frozen slurry by rapidly freezing the mixed slurry in a pressurized state by spraying it in an atmosphere under normal pressure or reduced pressure;
A method for producing a ceramic raw material comprising the step of producing the ceramic raw material by drying the frozen slurry under reduced pressure (claim 1).

  In the production method of the present invention, in the freezing step, slurry freezing is performed by applying pressure to the mixed slurry and spraying the mixed slurry in a pressurized state into an atmosphere under normal pressure or reduced pressure to rapidly freeze it. Create a body. That is, the mixed slurry that has been brought into a high pressure state by applying pressure is sprayed into an atmosphere in a lower pressure state than the mixed slurry. The sprayed mixed slurry is rapidly cooled and frozen by adiabatic cooling based on the adiabatic expansion principle due to a rapid pressure change from a high pressure state to a low pressure state. Thereby, the granular slurry frozen body is obtained.

That is, in the present invention, the mixed slurry is frozen without using a refrigerant such as liquid nitrogen as in the prior art, and the frozen slurry is produced. Therefore, there is no need to perform a separation step of separating the frozen slurry from the refrigerant, which has been a major cause of the yield loss of the frozen slurry, and the obtained granular frozen slurry is recovered as it is. Can do. Further, since the mixed slurry is sprayed and rapidly frozen at the same time, the recovery yield loss of the frozen slurry due to scattering of the mixed slurry can be suppressed.
As described above, the recovery yield of the slurry frozen body can be improved as compared with the related art. As a result, the yield of the ceramic raw material to be produced can be improved.

  Moreover, the said manufacturing method produces a ceramic particle dispersion by mixing the said ceramic particle with water in the said ceramic particle dispersion | distribution process. In the resin component dispersion step, the resin component dispersion is prepared by mixing the resin component with water. Thus, in the ceramic particle dispersion step and the resin component dispersion step, water having a large hydrogen bonding force is used as a solvent, and the ceramic particles and the resin component are separately dispersed in the solvent. Therefore, in the ceramic particle dispersion and the resin component dispersion, the ceramic particles and the resin component can be sufficiently uniformly dispersed, respectively.

  Next, in the mixing step, the mixed slurry is prepared by mixing the ceramic particle dispersion and the resin component dispersion. That is, the ceramic particles and the resin component dispersion are separately dispersed in the solvent to prepare the ceramic particle dispersion and the resin component dispersion, and then mixed to prepare the mixed slurry. is doing. Therefore, compared with the case where the ceramic particles and the resin component are dispersed in the same solvent at a time, the ceramic particles and the resin component can be dispersed sufficiently uniformly in the mixed slurry.

  Next, in the freezing step, as described above, the mixed slurry is sprayed and rapidly frozen by adiabatic cooling to produce the frozen slurry. As described above, by spraying the mixed slurry at the same time as it is rapidly cooled and frozen to accelerate the start of freezing of the mixed slurry, segregation of the composition of the obtained frozen slurry can be suppressed. That is, the frozen slurry can be produced while maintaining the composition of the mixed slurry in which the ceramic particles and the resin component are uniformly dispersed. Therefore, the frozen slurry body in which the ceramic particles and the resin component are uniformly dispersed can be obtained.

Thereafter, in the drying step, the frozen slurry is dried under reduced pressure. That is, the water in the frozen slurry is removed by sublimation. Therefore, the slurry frozen body can be dried with almost no deformation while maintaining the composition of the slurry frozen body, that is, with the ceramic particles and the resin component uniformly dispersed. The freeze-drying in the freezing step and the drying step can prevent aggregation of the resin component that occurs when the mixed slurry is directly heated and dried.
As a result, the ceramic raw material in which the ceramic particles and the resin component are uniformly dispersed can be obtained. Moreover, this ceramic raw material becomes a porous material that can be easily crushed, with voids formed in the portion from which moisture has been removed.

In the above manufacturing method, when the mixed slurry is frozen, the ceramic particles contained in the mixed slurry serve as a core substance necessary for freezing. Therefore, the start of freezing of the mixed slurry can be further accelerated, and segregation of the composition of the frozen slurry can be further suppressed.
Further, as described above, since the frozen slurry is produced without using a refrigerant, it is not necessary to perform a separation step of separating the frozen slurry from the refrigerant. Thereby, a manufacturing process can be shortened and manufacturing efficiency can be improved.

  Thus, according to the manufacturing method of the present invention, the yield of ceramic raw materials can be improved. In addition, the obtained ceramic raw material is obtained by uniformly dispersing ceramic particles and a resin component.

According to a second aspect of the present invention, there is provided a method for producing a ceramic molded body obtained by molding a ceramic raw material containing at least ceramic particles and a resin component.
A kneaded material containing the ceramic raw material obtained by the production method of the first invention is produced, and the ceramic molded body is produced by molding the kneaded material under a pressure of 1 to 50 MPa. In the method for producing a ceramic molded body according to claim 12 (claim 12).

In the manufacturing method of the present invention, molding is performed using the ceramic raw material of the first invention having a good yield. Therefore, the manufacturing efficiency of the ceramic molded body can be improved.
Moreover, in the said manufacturing method, it shape | molds using the ceramic raw material of the said 1st invention which has high crushability, and the said ceramic particle and the said resin component were disperse | distributed uniformly. Therefore, the ceramic molded body in which the ceramic particles and the resin component are uniformly dispersed can be obtained.

  Moreover, the said kneaded material containing the said ceramic raw material is produced, and the said kneaded material is shape | molded in the state which applied the pressure of 1-50 Mpa to this kneaded material. Specifically, the kneaded product can be molded in a state where a pressure of 1 to 50 MPa is applied to the kneaded product, for example, by extruding the kneaded product through a thin slit and performing extrusion molding. Therefore, at the time of shaping | molding, the high concentration part of the said resin component in the said kneaded material can be crushed, and the bias | inclination of the said resin component in the said ceramic molded object can be made small. As a result, the ceramic molded body in which the ceramic particles and the resin component are uniformly dispersed can be obtained.

  The kneaded product can be produced by adding water to the ceramic raw material and kneading. Further, in the drying step of the first invention, the ceramic raw material is produced in a state where moisture is left without completely drying the slurry frozen body, and the ceramic raw material containing a necessary amount of water is kneaded as it is. Thus, the kneaded product can be produced.

  Moreover, the said ceramic molded object can be used as a sintered compact by baking. As described above, in the ceramic molded body, since the resin component is uniformly dispersed, the generation of voids such as voids and pores on the surface and inside of the sintered body after firing is suppressed. Can do. Therefore, it is possible to obtain a high-quality sintered body with little variation in strength and various ceramic characteristics depending on the portion of the sintered body.

In the first invention, in the ceramic particle dispersion step, the ceramic particles and the ceramic particles are dispersed so that the content of water is 20 to 80 parts by weight with respect to 100 parts by weight of the total amount of the ceramic particles and water. It is preferable to mix with water.
If the water content is less than 20 parts by weight, it may be difficult to sufficiently disperse the ceramic particles in water as a solvent. On the other hand, when it exceeds 80 weight part, there exists a possibility that the said drying process which drys the said slurry frozen body may require a long time. Therefore, more preferably, the water content is 35 to 65 parts by weight, and even more preferably 45 to 55 parts by weight.

In the resin component dispersion step, the resin component and water are mixed so that the water content is 50 to 99 parts by weight with respect to 100 parts by weight of the total amount of the resin component and water. It is preferable.
If the water content is less than 50 parts by weight, it may be difficult to sufficiently disperse the resin component in water as a solvent. On the other hand, when it exceeds 99 weight part, there exists a possibility that the said drying process which drys the said slurry frozen body may require a long time. Therefore, more preferably, the water content is 85 to 99 parts by weight, and even more preferably 97 to 99 parts by weight.

Moreover, in the said mixing process, it is preferable that the solid component ratio of the said mixing slurry shall be 70-99 wt%.
When the solid component ratio is less than 70 wt%, the drying process for drying the frozen slurry may take a long time. On the other hand, if it exceeds 99 wt%, it may be difficult to sufficiently disperse the ceramic particles and the resin component in the mixed slurry. Therefore, more preferably, the solid component ratio is 75 to 95 wt%, and even more preferably 80 to 90 wt%.
In addition, a solid component ratio represents the weight ratio of the solid component contained in the said mixed slurry in percentage.

Moreover, in the freezing step, a pressure of 0.2 to 1 MPa is applied to the mixed slurry, and air is applied and sprayed with a pressure of 0.2 to 1 MPa applied to the pressurized mixed slurry. (Claim 2).
When the pressure applied to the mixed slurry and the air is less than 0.2 MPa, the pressure difference between the mixed slurry and the air and the atmosphere necessary for operating the adiabatic expansion principle cannot be sufficiently secured. There is a fear. On the other hand, when it exceeds 1 MPa, the introduction cost of the equipment for realizing the high-pressure mixed slurry and the air and the operation cost thereof become expensive, and as a result, the production cost may increase. Moreover, there exists a possibility that the effect corresponding to cost cannot be acquired. Therefore, more preferably, the pressure is 0.3 to 0.7 MPa.

In the freezing step, the atmospheric pressure in the atmosphere is preferably 5 to 760 Torr.
When the atmospheric pressure is less than 5 Torr, the installation cost and the operation cost of equipment for realizing the low pressure state of the atmosphere become expensive, and as a result, the manufacturing cost may increase. Moreover, there exists a possibility that the effect corresponding to cost cannot be acquired. On the other hand, when it exceeds 760 Torr (normal pressure), there is a possibility that a sufficient pressure difference between the mixed slurry and the air and the atmosphere necessary for operating the adiabatic expansion principle cannot be secured. Therefore, more preferably, 50 to 760 Torr is good in the atmosphere.

In the freezing step, the temperature in the atmosphere is preferably 0 ° C. or lower (claim 4).
If the temperature exceeds 0 ° C., it may be difficult to sufficiently freeze the sprayed mixed slurry.

In the freezing step, the temperature in the atmosphere is more preferably −50 to −5 ° C. (Claim 5).
When the temperature is lower than −50 ° C., the introduction cost of the equipment itself and the operation cost for continuously maintaining the temperature in the atmosphere become expensive, and as a result, the production cost of the ceramic raw material may increase. There is. On the other hand, when it exceeds -5 degreeC, there exists a possibility that it may become difficult to freeze the sprayed said mixed slurry rapidly. Therefore, more preferably, the temperature is -30 to -10 ° C.

In the drying step, the frozen slurry is preferably dried in a vacuum with a degree of vacuum of 5 to 50 Torr.
When the degree of vacuum is less than 5 Torr, the introduction cost of the drying equipment itself for realizing the vacuum state and the operation cost thereof become expensive, and as a result, the production cost of the ceramic raw material may increase. On the other hand, if it exceeds 50 Torr, the water in the slurry frozen body cannot be sufficiently sublimated, and the slurry frozen body may melt during drying. Therefore, more preferably, the degree of vacuum is 5 to 20 Torr.

In the drying step, the frozen slurry is preferably dried under the conditions of a heating temperature of 20 to 70 ° C. and a heating time of 1 to 6 hours.
When the heating temperature is less than 20 ° C. or when the heating time is less than 1 hour, it may be difficult to sufficiently remove moisture from the frozen slurry and dry it. On the other hand, when it exceeds 70 degreeC, there exists a possibility that aggregation of the said resin component may arise. Moreover, even if it heats over 6 hours, while the effect commensurate with this will hardly be acquired, there exists a possibility that manufacturing time may become long and cost may increase. Therefore, more preferably, the heating temperature is 30 to 60 ° C. and the heating time is 1.5 to 5 hours.

The average particle size of the frozen slurry is preferably 5 to 500 μm.
When the average particle size is less than 5 μm, there is a possibility that a plurality of the frozen slurry bodies are aggregated. For this reason, the drying efficiency of the frozen slurry may be reduced, and the drying process may take time. On the other hand, when it exceeds 500 μm, there is a possibility that moisture in the frozen slurry is difficult to escape. Therefore, the drying efficiency of the slurry frozen body is lowered. The drying process may take time. Therefore, more preferably, the average particle size is 50 to 150 μm.
The particle diameter of the slurry frozen body is the particle diameter of the granular slurry frozen body.

The ceramic particles preferably have an average particle size of 0.3 to 1 μm.
When the average particle size is less than 0.3 μm, the ceramic particles have a small effect as a nucleus in freezing the mixed slurry, and there is a possibility that the mixed slurry cannot be efficiently frozen. On the other hand, when the thickness exceeds 1 μm, equipment such as a sprayer for spraying the mixed slurry containing the ceramic particles may be worn in a short period of time. Therefore, more preferably, the average particle size is 0.3 to 0.5 μm.

  The ceramic particles include aluminum titanate, mullite, potassium titanate, lithium aluminosilicate, cordierite, lead zirconate titanate (PZT), titanium oxide, tin oxide, gallium arsenide, silicon carbide, chromium oxide, zirconia. , Alumina, yttria, silicon nitride, carbonized fiber, calcium silicate, crystallized glass (FRC), amorphous carbon, tungsten carbide, titanium carbide, iron silicide, graphite, titania, carbon fiber, silica, aluminum nitride, titanic acid Ceramic particles comprising at least one selected from barium, zinc oxide, zinc sulfide, gallium phosphide, tungsten oxide, cadmium sulfide, indium tin oxide (ITO), and the like can be used.

The kind of ceramic component in the ceramic particles can be appropriately selected according to the application.
For example, when producing a ceramic raw material for a gas sensor, ceramic particles composed of one or more ceramic components selected from zirconia, alumina, yttria and the like can be used.

As the resin component, for example, a hydrophilic resin can be used.
Specifically, a resin component composed of one or more selected from methyl cellulose, hydroxylpropyl methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starch, polyvinyl alcohol, polyethylene oxide, sodium polyacrylate, polyacrylamide and the like can be used ( Claim 11).

In the second aspect of the invention, it is preferable to add water so that the content of water is 1 to 20 parts by weight with respect to 100 parts by weight of the total amount of the ceramic raw material and water.
When the water content is less than 1 part by weight, there is a possibility that water is too little to perform sufficient kneading. On the other hand, when the amount exceeds 20 parts by weight, there is a possibility that the resin component is dissolved again due to too much water. Therefore, the content of water is more preferably 2 to 8 parts by weight, and still more preferably 4 to 6 parts by weight.

Moreover, it is preferable that the pressure added to the said kneaded material at the time of shaping | molding is 1-50 Mpa.
In this case, even if the resin component bias remains in the kneaded product, the biased portion of the resin component can be crushed. Therefore, the resin component bias in the ceramic molded body is further reduced. It can be made even smaller.
Moreover, when the said pressure is less than 1 MPa, there exists a possibility that the bias | inclination of the said resin component which remained in the said ceramic raw material cannot fully be eliminated. On the other hand, it has been confirmed that the effect of reducing the bias of the resin component is saturated even when a pressure exceeding 50 MPa is applied. Therefore, more preferably, the pressure is 5 to 30 MPa, and more preferably 5 to 20 MPa.

The ceramic molded body is preferably used for a gas sensor.
In this case, it is possible to more remarkably exhibit the excellent characteristics of the ceramic molded body such that the resin component is less biased and there are few cavities (pores, voids).
That is, gas sensors are increasingly miniaturized in recent years and are used in higher temperature environments. Therefore, higher strength and heat resistance are required. On the other hand, when a gas sensor element (sintered body) is produced by sintering a ceramic molded body having a large resin component bias, voids such as pores and voids are generated on the surface and inside of the gas sensor element, and the strength and heat resistance are reduced. There is a fear. On the other hand, in the present invention, since the ceramic molded body is less biased in the resin component as described above, a sintered body having almost no voids such as pores and voids can be obtained even when sintered. Therefore, when applied to a gas sensor element, a gas sensor excellent in strength and heat resistance can be obtained, and the excellent characteristics of the ceramic molded body can be exhibited more remarkably.

Example 1
The manufacturing method of the ceramic raw material concerning the Example of this invention is demonstrated.
In this example, a ceramic raw material containing ceramic particles and a resin component is manufactured by performing a ceramic particle dispersion step, a resin component dispersion step, a mixing step, a freezing step, and a drying step.

The ceramic particle dispersion step is a step of preparing a ceramic particle dispersion by mixing ceramic particles with water.
The resin component dispersion step is a step of preparing a resin component dispersion by mixing the resin component with water.
The mixing step is a step of preparing a mixed slurry by mixing the ceramic dispersion and the resin component dispersion.
The freezing step is a step of producing a frozen slurry by applying pressure to the mixed slurry and spraying the pressurized mixed slurry into an atmosphere under normal pressure or reduced pressure to rapidly freeze it.
A drying process is a process of producing a ceramic raw material by drying a frozen slurry under reduced pressure.
This will be described in detail below.

  First, in the ceramic particle dispersion step and the resin component dispersion step, zirconia particles are prepared as ceramic particles, and 50 parts by weight of water is added to and mixed with 50 parts by weight of the zirconia particles, thereby producing a ceramic particle dispersion. did. On the other hand, methylcellulose was prepared as a resin component, and 95 parts by weight of water was added to and mixed with 5 parts by weight of this methylcellulose to prepare a resin component dispersion.

  Next, in the mixing step, a mixed slurry (test sample X) was prepared by mixing the ceramic particle dispersion and the resin component dispersion. The solid content ratio in this mixed slurry was about 80 wt%.

Next, in the freezing step, the slurry mixture was sprayed using the spray device 1 shown in FIGS. 1 and 2 to produce a frozen slurry.
As shown in FIG. 1, the spray device 1 includes a spray chamber 11, a fluid nozzle 12, and a slurry tank 14, and sprays mixed slurry 81 in the slurry tank 14 from the fluid nozzle 12 into the spray chamber 11. .

More specifically, as shown in FIG. 1, the spray device 1 has a spray chamber 11, a fluid nozzle 12 disposed in the spray chamber 11, and a slurry tank 14 disposed outside the spray chamber 11.
The spray chamber 11 is configured so that conditions such as atmospheric pressure and temperature in the spray chamber 11 can be adjusted.

  As shown in FIG. 2, the fluid nozzle 12 includes a slurry nozzle 121 that injects the mixed slurry 81 disposed at the nozzle tip 129 and two air nozzles that inject air 89 disposed on both sides of the slurry nozzle 121. The two-fluid nozzle type having the air nozzle 122. The fluid nozzle 12 can bring the air 89 sprayed from the air spray port 124 into contact with the mixed slurry 81 sprayed from the slurry spray port 123 at the contact position 125, and can squeeze and spray the mixed slurry 81 in a granular form. It is configured as follows.

  As shown in FIG. 1, the slurry nozzle 121 of the fluid nozzle 12 is connected to a slurry tank 14 that stores a mixed slurry 81 via a slurry supply pipe 141. A slurry regulator 149 that adjusts the pressure applied to the mixed slurry 81 is disposed in the middle of the slurry supply pipe 141. The slurry tank 14 is connected to an air supply device 13 that supplies air 89 via a first air supply pipe 131.

  As shown in the figure, the air nozzle 122 of the fluid nozzle 12 is connected to the middle of the first air supply pipe 131 via the second air supply pipe 132. An air regulator 139 that adjusts the pressure applied to the air 89 is disposed in the middle of the second air supply pipe 132.

  As shown in the figure, the air supply device 13 can supply air 89 to the slurry tank 14 via the first air supply pipe 131, and the first air supply pipe 131 and the second air supply pipe 132. The air 89 can be supplied directly to the fluid nozzle 12 via the.

Next, the process of spraying the mixed slurry 81 using the spray device 1 to produce a frozen slurry will be described.
In spraying the mixed slurry 81, first, the pressure in the spray chamber 11 is adjusted to 760 Torr (normal pressure) and the temperature is adjusted to 20 ° C. Next, pressurized air 89 is supplied from the air supply device 13 to the slurry tank 14. Thereby, the mixed slurry 81 is supplied from the slurry tank 14 to the fluid nozzle 12 through the slurry supply pipe 141 in a pressurized state. On the other hand, the air 89 supplied from the air supply device 13 is also supplied directly to the fluid nozzle 12. At this time, the slurry regulator 149 and the air regulator 139 are adjusted so that the mixed slurry 81 and the air 89 supplied to the fluid nozzle 12 are in an appropriate pressure state. The pressure applied to the mixed slurry 81 was 0.5 MPa, and the pressure applied to the air 89 was 0.5 MPa.

  The mixed slurry 81 in the slurry nozzle 121 supplied to the fluid nozzle 12 is ejected from the slurry ejection port 123. At the same time, the air 89 in the air nozzle 122 supplied to the fluid nozzle 12 is ejected from the air ejection port 124. The injected mixed slurry 81 is compressed by contacting with the air 89 at the contact position 125, and is sprayed into the spray chamber 11 in the form of granules. The sprayed mixed slurry 81 is rapidly cooled and frozen by adiabatic cooling based on the adiabatic expansion principle due to a rapid pressure change from a high pressure state to a low pressure state.

Thereby, the granular slurry frozen body was produced. The frozen slurry is in a state where the resin particles and ice (frozen water) are covered around the uniformly dispersed ceramic particles. Thereafter, the frozen slurry was collected from the spray chamber 11. The recovered frozen slurry is designated as test sample A.
The average particle size of the frozen slurry of this example was 10 μm. The particle size of the frozen slurry is the particle size of the granular frozen slurry.

Next, in the drying step, the frozen slurry was put in a vacuum dryer, depressurized to a vacuum degree of 10 Torr, and dried by heating at a temperature of 60 ° C. for 4 hours. That is, the water in the frozen slurry was removed by sublimation.
Thus, the ceramic raw material was produced. This is designated as Sample E1. The ceramic raw material is in a readily pulverizable porous state in which resin components cover the uniformly dispersed ceramic particles, and voids are formed in portions where moisture has been removed.

In this example, in order to examine the recovery yield of the frozen slurry, a frozen slurry was prepared using a refrigerant for comparison with the sample E1, and was collected to prepare a ceramic raw material (sample C1).
Specifically, in the freezing step, the mixed slurry was sprayed and dropped in liquid nitrogen as a liquid refrigerant in the spray chamber to freeze the slurry. Next, liquid nitrogen was passed through a sieve (# 400), and the frozen slurry was recovered from the liquid nitrogen. The recovered frozen slurry is designated as test sample B. The other steps were the same as in the case of sample E1, and a ceramic raw material was produced. This is designated as Sample C1.

Next, in order to investigate the recovery yield of the frozen slurry in the preparation of Sample E1 and Sample C1, the recovery yield loss of Test Sample A and Test Sample B was examined.
Here, the recovery yield loss is the ratio of the slurry frozen body that could not be recovered to the prepared slurry frozen body, and the difference between the weight of the sprayed mixed slurry and the weight of the recovered slurry frozen body was sprayed. It was obtained by dividing by the weight of the mixed slurry. The result is shown in FIG. In FIG. 3, the vertical axis represents the recovery yield loss (%).

  The breakdown of the recovery yield loss in FIG. 3 will be described. The passage through the sieve (# 400) is a frozen slurry that has not been collected through the sieve (# 400), and the liquid that has passed through the sieve. The weight of the frozen slurry that could not be recovered was estimated from the weight of the ceramic particles and resin components remaining after drying nitrogen, and the weight was determined by dividing the weight by the weight of the sprayed mixed slurry. Further, the wall surface adhesion is a frozen slurry body that has adhered to the wall surface of the spray chamber and has not been recovered, and the slurry frozen body that has adhered to the wall surface is recovered and its weight is divided by the weight of the sprayed mixed slurry. Was determined by In addition, “others” refers to unknown matters.

As can be seen from FIG. 3, the test sample A has a smaller recovery yield loss than the test sample B. That is, many test samples B cannot be recovered by passing through the sieve (# 400) or adhering to the wall surface of the spray chamber, whereas test sample A can be recovered with almost no loss. It can be seen that the recovery yield is high.
As a result, the yield of the ceramic raw material (sample E1) obtained by drying the test sample A is higher than that of the ceramic raw material (sample C1) obtained by drying the test sample B.
As described above, according to this example, the recovery yield of the frozen slurry can be greatly improved, and the yield of the ceramic raw material to be produced can be improved.

Furthermore, in this example, in order to investigate the dispersion state of the ceramic particles and the resin component, a slurry prepared by dispersing the ceramic particles and the resin component in one solvent (water) at a time as a comparison for the sample E1. A ceramic raw material (sample C2) was prepared.
Specifically, first, zirconia particles are prepared as ceramic particles, methyl cellulose is prepared as a resin component, and water is added to a mixture of 14.5 parts by weight of these ceramic particles and 0.5 part by weight of a resin component. A slurry (test sample Y2) containing ceramic particles and a resin component was prepared by adding and mixing 85 parts by weight. Next, using this slurry, a ceramic raw material was produced by performing a freezing step and a drying step in the same manner as in the case of the sample E1. This is designated as Sample C2.

Next, in order to investigate the dispersion state of the ceramic particles and the resin component in Sample E1 and Sample C2, the particle size distribution was examined for Test Sample X and Test Sample Y2.
The particle size distribution was measured using a particle size distribution measuring device (“Microtrack” manufactured by Nikkiso Co., Ltd.). The results are shown in FIGS. FIG. 4 shows the measurement result of the particle size distribution for the test sample X, and FIG. 5 shows the measurement result of the particle size distribution for the test sample Y2. 4 and 5, the particle size distribution is shown as a bar graph, particles having a certain range of particle diameters are grouped together, and the frequency (%) of particles belonging to the same group is represented by the same bar (bar graph). It is shown.

Further, in this example, the dispersion state of the ceramic particles and the resin component in the test sample X is compared with the dispersion state of the ceramic particles in the comparative slurry (test sample Y3) in which only the ceramic particles are dispersed in water. It was.
Test sample Y3 was prepared by adding 50 parts by weight of water to 50 parts by weight of zirconia particles and mixing them. Subsequently, the particle size distribution of the test sample X and the test sample Y3 was measured using the above-mentioned particle size distribution measuring apparatus. The result is shown in FIG. In FIG. 6, the measurement result of the particle size distribution for the test sample X is indicated by a solid line, and the measurement result of the particle size distribution for the test sample Y3 is indicated by a dotted line. In FIG. 6, the horizontal axis indicates the particle size (μm), and the vertical axis indicates the frequency (%).

  As can be seen from FIGS. 4 and 5, the test sample X has a smaller variation in particle size distribution than the test sample Y2. That is, in the mixed slurry (test sample X) prepared by dispersing the ceramic particles and the resin component in separate solvents (water) and then mixing both, the ceramic particles and the resin component are used as a solvent at a time. It can be seen that the ceramic particles and the resin component are more uniformly dispersed as compared with the slurry (test sample Y2) prepared by dispersing. Therefore, in the sample E1 obtained by freeze-drying the test sample X, the ceramic particles and the resin component are more uniformly dispersed in a highly dispersed state than the sample C2 obtained by freeze-drying the test sample Y2. Yes.

Further, as can be seen from FIG. 6, the test sample X showed a particle size distribution almost the same as that of a slurry (test sample Y3) in which only ceramic particles were dispersed in water. Therefore, it can be seen that in the test sample X, the ceramic particles and the resin component are dispersed in a highly dispersed state similar to the case where only the ceramic particles are dispersed.
The ceramic raw material (sample E1) obtained by freeze-drying the test sample X can be dried while maintaining a highly dispersed state in the mixed slurry (test sample X), so that the ceramic particles and the resin component are uniformly dispersed. Has been.
As described above, according to this example, a ceramic raw material in which ceramic particles and a resin component are uniformly dispersed can be manufactured.

(Example 2)
This example is an example in which a ceramic compact is produced using the ceramic raw material (sample E1) produced in Example 1, and the ceramic compact is fired to produce a sintered compact.
First, a kneaded material is prepared by adding water to a ceramic raw material, and the kneaded material is molded by an extrusion molding method to produce a sheet-shaped ceramic molded body.

In the molding of this example, molding is performed using the extrusion molding apparatus 10 shown in FIGS.
As shown in FIG. 7, the extrusion molding apparatus 10 includes screw-type extruders 2 and 3 and a molding die 41 disposed at the tip of the extruder 2, and a kneaded product 80 introduced into the extruder 2. This is an apparatus for extruding the forming die 41 into a sheet shape and forming it into a sheet-like ceramic molded body 8.
The molding die 41 has temperature adjusting means 5 for adjusting the temperature of each of the regions obtained by dividing the kneaded material 80 passing through the molding die 41 in the width direction.
This will be described in detail below.

As shown in FIG. 7, the extrusion molding apparatus 10 of the present example is formed by connecting two stages of screw extruders 2 and 3, and the molding die 41 is disposed at the tip of the lower stage extruder 2.
As shown in FIGS. 7 and 8, the molding die 41 has a shape in which one of the circular tubes is crushed, and the size in the vertical direction is narrowed toward the tip, and the size in the width direction is widened. . As shown in FIG. 7, a pair of caps 421 and 422 for regulating the thickness of the ceramic molded body 8 to be extruded are disposed at the tip. The upper base 421 is disposed so as to be able to advance and retreat by adjusting the screwing amount of the adjustment screw 125, and the gap with the lower base 422 can be adjusted.

As shown in FIGS. 7 to 9, the molding die 41 has, as the temperature adjusting means 5, a chamber 51 provided for each region obtained by dividing the molding die 41 in the width direction, and the chamber 51. A heat medium circulating means 60 for circulating the heat medium 6 for cooling.
As shown in FIGS. 8 and 9, the chamber 51 of this example was provided in each of the regions formed by dividing the upper and lower portions into three in the width direction. Each chamber was provided with an inlet 511 and an outlet 512 for the heat medium, and circulation pipes 621 and 622 of the heat medium circulation means 6 were connected to these chambers.

  The heat medium circulating means 60 is configured so that the heat medium 6 can be appropriately circulated from the heat medium tank to each chamber 51 via a pump, an electromagnetic valve, or the like. Various configurations can be adopted as a control method and detailed structure of the heat medium circulating means 60. For example, automatic control can be performed by feedback control as in an embodiment described later. In this example, automatic control is not adopted, and the temperature and flow rate of the cooling heat medium 6 to each chamber 51 are manually adjusted.

  Further, as shown in FIG. 7, each of the screw type extruders 2 and 3 has extrusion screws 22 and 32 formed by spirally winding lead portions 222 and 322 around shaft bodies 221 and 321. It is built in the housings 21 and 31. In this example, as the extrusion screws 22 and 23, those having an outer diameter (outer diameter of the lead portion) d of 30 mm are employed. A vacuum chamber 29 is disposed between the two. In addition, a material introduction portion 39 for introducing the kneaded material 80 was disposed above the rear end of the upper extruder 3.

As shown in the figure, the material introduction part 39 has an opening part 390 formed in an inverted quadrangular pyramid shape, and a pair of left and right push rollers 392 disposed below the opening part 390. The pair of push rollers 392 is configured to bite the kneaded material 80 put between them and send it to the inside of the lower extruder 3.
The vacuum chamber 29 is configured such that the inside of the vacuum chamber 29 can be evacuated by a pump 55 in order to deaerate the kneaded material 80 extruded from the upper extruder 3. Further, the vacuum chamber 29 is provided with a pair of left and right push rollers 292 similar to those in the material introducing portion 39.

  Next, in this example, a drying device 7 for drying the molded body 8 formed by the extrusion molding device 10 and winding it up in a coil shape was prepared (see FIG. 10). The drying device 7 includes a belt conveyor 71 including a pair of pulleys 711 and 712 and a belt 713 driven by them. The belt conveyor 71 is provided with a heater chamber 73 through which the belt 713 passes. The heater chamber 73 includes a heater 731 and a temperature sensor 732 in the case 730, and the heater controller 735 controls the heater 731 based on the measured value of the temperature sensor 732 so as to maintain a constant temperature. Be controlled.

Further, on the entrance side of the belt conveyor 71, a displacement sensor 741 for measuring the deflection amount of the extruded ceramic molded body 8, and the belt conveyor 71 so that the deflection amount is constant based on the measured value. A speed controller 74 is provided for controlling the speed.
A coiler 75 is provided on the exit side of the belt conveyor 71 to wind the dried sheet-like ceramic molded body 8 in a coil shape.

Next, the sheet-shaped ceramic molded body 8 was actually molded using the extrusion molding apparatus 10.
The kneaded material 80 was produced by adding water to the ceramic raw material (sample E1) produced in Example 1 and kneading. Specifically, a kneaded product 80 was prepared by adding 5 parts by weight of water to 95 parts by weight of the ceramic raw material and kneading.
The size of the sheet-like ceramic molded body 8 to be molded was set such that the width W (FIG. 8) was 150 mm and the thickness T (FIG. 7) was 200 μm. And the said shaping | molding die 41 was comprised in the shape corresponding to the size of this ceramic molded object 8. FIG. Therefore, the relationship between the outer diameter d (FIG. 8) of the extrusion screw 22 of the screw extruder 2 and the width dimension W of the ceramic molded body 8 is W ≧ 3d.

  In forming the ceramic molded body 8, first, the kneaded material 80 is charged from the material introducing portion 39. The introduced kneaded material 80 is fed into the lower extruder 3 by a pair of pushing rollers 392. The kneaded material 80 in the extruder 3 advances while being kneaded by the rotation of the extrusion screw 32 and is extruded into the vacuum chamber 29. The kneaded material 80 that has entered the vacuum chamber 29 is sent to the lower extruder 2 by a pair of push rollers 292 in a deaerated state. The kneaded product 80 in the extruder 2 advances while being further kneaded by the rotation of the extrusion screw 22, enters the forming die 41, and is then formed into a sheet from between the caps 421 and 422 and extruded. At this time, the kneaded product 80 is molded in a state where a pressure of about 10 MPa is applied. The extruded sheet-like ceramic molded body 8 is dried by the drying device 7 and wound into a coil shape.

And in this example, in order to correct the shape of the ceramic molded body 8 to be extruded, by using the temperature adjusting means 5, the kneaded material 80 passing through the forming die 41 is divided into a plurality in the width direction. Extrusion was performed while adjusting the temperature in each divided region.
Specifically, first, at the start of molding, the heat medium 6 having a temperature of 10 ° C. is similarly circulated through all the chambers 51 by the heat medium circulation means 60. Then, the shape of the ceramic molded body 8 to be molded is observed, and the temperature of the heat medium 6 to be circulated in the chamber 51 in the region corresponding to the wrinkled portion is reduced, or the chambers in other regions are observed. The temperature of the heat medium 6 to be circulated in 51 is increased, or both. Thereby, the fluidity | liquidity of the kneaded material 80 which passes the inside of the shaping | molding die 41 is adjusted for every area | region, and the speed of the kneaded material 80 which passes the nozzle | cap | die 421,422 can be made substantially constant in the width direction.

Next, the 200-μm-thick sheet-like ceramic molded body produced as described above is fired to produce a sintered body.
Specifically, first, a ceramic molded body having a thickness of 200 μm was cut into a size of 150 mm × 150 mm. This ceramic molded body was fired at a temperature of about 1500 ° C. for 50 hours to obtain a sintered body. This is designated as Sample E2.

Next, the presence or absence of voids such as voids and pores in the sintered body of sample E2 was observed with a scanning electron microscope (SEM). The observation with the scanning electron microscope was performed on the polished surface by polishing the sample E2 to a depth of 0.05 mm from the surface. In addition, the number of cavities (hazardous defects) per fixed area was counted by SEM observation of sample E2, and the number of harmful defects per unit area (pieces / mm ² ) was calculated.
As a result, in the sample E2, cavities such as voids and pores were hardly observed. Further, the number of harmful defects in the sample E2 was less than 0.001 / mm ² . Thereby, it turned out that the sample E2 is a sintered compact with few defects.

(Example 3)
In this example, the sheet-like ceramic molded body of Example 2 is molded by the doctor blade method.
In the molding of this example, molding is performed using a doctor blade molding apparatus 9 shown in FIG.
As shown in FIG. 11, the doctor blade forming device 9 includes a material introduction unit 91, a dam 92 disposed in the material introduction unit 91, a discharge port 94 disposed in a lower portion of the dam 92, and a discharge port 94. A blade 93 for adjusting the height and a drying furnace 95 are provided.

Next, the sheet-shaped ceramic molded body 8 was actually molded using the doctor blade molding apparatus 9.
The kneaded material 80 was produced by adding a solvent to the ceramic raw material (sample E1) produced in Example 2 and kneading. Specifically, a kneaded product 80 was prepared by adding 100 parts by weight of a solvent to 100 parts by weight of the ceramic raw material and kneading.
The size of the sheet-like ceramic molded body 8 to be molded was 200 μm in thickness. Then, the position of the blade 93 was adjusted to correspond to the size of the ceramic molded body 8.

In forming the ceramic molded body 8, first, the kneaded material 80 is charged into the material introducing portion 91. The kneaded material 80 dammed to the dam 92 flows out from the discharge port 94 between the blade 93 and the carrier film 97 sent out by the sending roller 961, and is continuously applied onto the carrier film 97. Then, the applied kneaded product 80 is dried in the drying furnace 95 and peeled off from the carrier film 97 wound around the winding roller 962, and the long sheet-shaped ceramic molded body 8 is obtained. This is cut according to the use, and a sheet-shaped ceramic molded body 8 having an arbitrary size is obtained.
Others are the same as Example 2, and have the same effect.

FIG. 3 is an explanatory diagram illustrating a configuration of a spray device in the first embodiment. FIG. 3 is an explanatory diagram illustrating a configuration of a fluid nozzle in the first embodiment. FIG. 3 is an explanatory diagram showing a recovery yield loss of a frozen slurry in Example 1. FIG. 3 is an explanatory diagram showing a particle size distribution of a mixed slurry (test sample X) in Example 1. FIG. 3 is an explanatory diagram showing a particle size distribution of a slurry (test sample Y2) in Example 1. FIG. 3 is an explanatory diagram showing particle size distributions of two types of slurry (test sample X and test sample Y3) in Example 1. Explanatory drawing which shows the structure of the extrusion molding apparatus in Example 2. FIG. Explanatory drawing which shows the structure of the upper part of the cross section of a shaping | molding die in Example 2. FIG. Explanatory drawing which shows the structure of the longitudinal cross-section orthogonal to the extrusion direction of a shaping | molding die in Example 2. FIG. Explanatory drawing which shows the structure of the drying apparatus in Example 2. FIG. Explanatory drawing which shows the structure of the doctor blade shaping | molding apparatus in Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spraying device 10 Extrusion molding device 11 Spraying chamber 12 Fluid nozzle 2, 3 Extruder 22, 32 Extrusion screw 29 Vacuum chamber 41 Mold 421, 422 Base 5 Temperature adjustment means 51 Chamber 6 Heat medium 60 Heat medium circulation means 7 Drying device
8 Ceramic molded body 80 Kneaded material 81 Mixed slurry 9 Doctor blade molding device

Claims (13)

In a method for producing a ceramic raw material containing at least ceramic particles and a resin component,
A ceramic particle dispersion step of preparing a ceramic particle dispersion by mixing the ceramic particles with water;
A resin component dispersion step of preparing a resin component dispersion by mixing the resin component with water;
A mixing step of preparing a mixed slurry by mixing the ceramic particle dispersion and the resin component dispersion;
Applying pressure to the mixed slurry, a freezing step for producing a frozen slurry by rapidly freezing the mixed slurry in a pressurized state by spraying it in an atmosphere under normal pressure or reduced pressure;
A method for producing a ceramic raw material, comprising: drying the slurry frozen body under reduced pressure to produce the ceramic raw material.   In Claim 1, the said freezing process WHEREIN: The air which added the pressure of 0.2-1 Mpa to the said mixed slurry, and added the pressure of 0.2-1 Mpa to the said mixed slurry of a pressurization state is supplied. A method for producing a ceramic raw material, characterized by spraying.   3. The method for producing a ceramic material according to claim 1, wherein in the freezing step, the atmospheric pressure in the atmosphere is 5 to 760 Torr.   The method for producing a ceramic raw material according to any one of claims 1 to 3, wherein in the freezing step, the temperature in the atmosphere is 0 ° C or lower.   5. The method for producing a ceramic raw material according to claim 1, wherein, in the freezing step, a temperature in the atmosphere is −50 to −5 ° C. 5.   6. The method for producing a ceramic material according to claim 1, wherein in the drying step, the frozen slurry is dried in a vacuum at a degree of vacuum of 5 to 50 Torr.   The ceramic raw material according to any one of claims 1 to 6, wherein in the drying step, the frozen slurry is dried under conditions of a heating temperature of 20 to 70 ° C and a heating time of 1 to 6 hours. Manufacturing method.   The method for producing a ceramic raw material according to any one of claims 1 to 7, wherein an average particle size of the frozen slurry is 5 to 500 µm.   9. The method for producing a ceramic raw material according to claim 1, wherein the ceramic particles have an average particle size of 0.3 to 1 μm.   10. The ceramic particles according to claim 1, wherein the ceramic particles are aluminum titanate, mullite, potassium titanate, lithium aluminosilicate, cordierite, lead zirconate titanate (PZT), titanium oxide, tin oxide, gallium. Arsenic, silicon carbide, chromium oxide, zirconia, alumina, yttria, silicon nitride, carbonized fiber, calcium silicate, crystallized glass (FRC), amorphous carbon, tungsten carbide, titanium carbide, iron silicide, graphite, titania, carbon A ceramic raw material comprising at least one selected from fiber, silica, aluminum nitride, barium titanate, zinc oxide, zinc sulfide, gallium phosphorus, tungsten oxide, cadmium sulfide, and indium tin oxide (ITO) Manufacturing method.   The resin component according to any one of claims 1 to 10, wherein the resin component is selected from methyl cellulose, hydroxylpropyl methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starch, polyvinyl alcohol, polyethylene oxide, sodium polyacrylate, and polyacrylamide. It consists of the above, The manufacturing method of the ceramic raw material characterized by the above-mentioned. In a method for producing a ceramic molded body formed by molding a ceramic raw material containing at least ceramic particles and a resin component,
A ceramic kneaded material containing the ceramic raw material obtained by the production method according to any one of claims 1 to 11 is prepared, and the ceramic molding is performed by molding the kneaded material under a pressure of 1 to 50 MPa. A method for producing a ceramic molded body comprising producing a body.   13. The method for manufacturing a ceramic molded body according to claim 12, wherein the ceramic molded body is used for a gas sensor.

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