JP4952484B2 - Method for producing ceramic porous body and ceramic porous body and structure produced using the same - Google Patents

Description

  The present invention relates to a ceramic molded body made of a ceramic porous body.

  In recent years, ceramic porous bodies have characteristics such as high transmittance, large surface area, sound absorption, heat insulation, etc. in addition to being highly heat-resistant and lightweight as a functional material. It is applied to sensors, catalysts, building materials, etc., and is used properly depending on the type and shape of the product.

  The gel casting method considered as one of the methods for producing these ceramic porous bodies is a method of forming by a polymerization reaction of monomers dissolved in a slurry, and preparing a slurry containing ceramic powder and organic monomer in a dispersion medium. After mixing the initiator and the catalyst, it is poured into an impermeable mold.

  Then, the monomer undergoes radical polymerization in the mold to form a polymer network in the dispersion medium, and a gel wet molded body is obtained.

  This method has an advantage that the fluidization process and the solidification process of the slurry are completely separated and the particles are fixed in-situ, so that nonuniformity and defects in the molded body are hardly generated.

  In addition, slurry preparation is the same as cast molding and tape molding currently commonly used, and can be applied if a high-concentration slurry can be prepared, or near-net shaping using a complex-shaped mold is possible. There are also advantages.

  Further, in the gel casting method, it is possible to obtain a porous molded body by introducing bubbles into the slurry before polymerization and starting the polymerization.

  The gel casting procedure for making the pores is basically the same as that for forming a dense body, but a surfactant is added to the slurry to maintain the introduced bubbles until the slurry is solidified. .

  Bubbles are introduced by mechanical stirring. Porous forming using gel casting can provide a very high porosity as compared with other porous ceramic forming methods, and a porosity of 80% or more is also possible.

  Furthermore, the pore control in the production of a porous body using the gel casting method basically uses the change in the state of bubbles introduced into the slurry. The pore diameter and porosity can be controlled by changing the kind of surfactant, the amount of gelling agent added, the solidification time due to changes in slurry temperature, the slurry concentration, and the like.

  When the type of the surfactant is changed, the state of the bubbles changes and the pore diameter and porosity change. The gelling time varies depending on the addition amount of the gelling agent and the slurry temperature, and the pore diameter changes as a result of the coalescence, expansion, and contraction of the bubbles.

Therefore, the pore diameter and the porosity can be controlled by appropriately changing the type of surfactant and gelation time (see, for example, Non-Patent Document 1).
"Ceramic Engineering Research Center Annual Report (2005) Vol.5" P33-40, Hiroaki Takegami, Masanori Fujii, Minoru Takahashi "Porous Ceramics Molding by Gel Casting and its Applications"

  However, various problems occur in the manufacturing process of the above-mentioned conventional ceramic porous body. Especially, when the surfactant is added to the slurry and bubbles are introduced by mechanical stirring, condensation of the slurry occurs. Then, a phenomenon was observed in which the dispersion medium was dehydrated on the inner wall of the bubble introduction container used when the slurry was mechanically agitated, and the solid content was condensed and attached to grow.

  This is because, in order to efficiently introduce bubbles into the slurry for the purpose of obtaining a high porosity with a small pore diameter, the flow of the slurry can be reduced when a mechanical stirring device is used in combination with a two-axis rotating beater. When stagnation occurs, that is, not only does it cause condensation of the slurry on both sides of the inner wall of the bubble introduction container, which is the middle of the biaxial rotating beater, causing pores and density variations in the resulting bubble-containing slurry, but also when pouring into the mold In addition, when mixed, defective portions having a higher density than other portions may be formed.

  As such measures, a mechanical stirring device for introducing bubbles into the bubble introduction container and a rotating device having a rotating blade that scrapes off the condensation of the slurry on the inner wall of the bubble introduction container are used. For example, the use of fluororesin, which is difficult to adhere to the inner wall, was considered, but in the former, the device becomes complicated and maintenance such as cleaning becomes difficult, and the dead angle of the rotary blade in the bubble introduction container and the container There was a drawback that the clearance was uneven.

  In the latter case, the phenomenon is originally caused by the stagnation of the slurry flow, so there is almost no effect, and the dispersion medium is dehydrated on the inner wall and the solid content condenses and adheres to grow.

  In view of the above-mentioned problems of the conventional technology, the problem to be solved by the present invention is to suppress the condensation of the solid content of the bubble-containing slurry generated during the mechanical stirring for introducing the bubbles and stabilize the pores and density variation. Thus, an object is to obtain a high-quality ceramic porous body.

In order to solve the above problems, a method for producing a ceramic porous body according to the present invention comprises preparing a slurry containing ceramic powder and an organic monomer, adding a surfactant to the slurry, and adding a monomer polymerization initiator and a catalyst. In a method for producing a porous ceramic body using a gel casting method in which a bubble-containing slurry produced by mechanical stirring is poured into a mold and dried and fired to produce a molded product, a cylindrical shape containing the slurry A foaming rotation device combining a two-axis rotating beater disposed so that its center is positioned at the approximate center of the bubble introduction container, and a container rotation device for mounting and rotating the bubble introduction container, and the container The rotating device includes a revolving means for rotating the center of the two-axis rotating beater at a predetermined distance from the center of the locus and the center of the bubble introduction container. Combining rotation means for rotating, mechanical agitation to perform the bubble introduction and simultaneously carried out by rotating the rotary beater in the foaming rotating device, said rotating beater bubbles introduced container by the container rotating device to a, It is designed to rotate in combination with rotation and revolution .

With the configuration described above, mechanical stirring for introducing bubbles is performed by rotating a rotating beater with the foaming rotation device. bubbles often incorporated, are efficiently bubbles in the slurry is introduced, it is possible to obtain a small high porosity and pore diameter.

At the same time, since the bubble introducing container is rotated by the container rotating device, the shearing flow of the slurry occurs near the inner wall of the bubble introducing container due to the inertia of the slurry, and it is difficult to stagnate and suppress the condensation of the attached slurry. At the same time, the middle position of the biaxial rotating beater is always moved by the rotation of the bubble introduction container, so that even if the slurry is condensed, it does not grow greatly.

  According to the present invention, the slurry in the vicinity of the inner wall of the bubble introduction container is less likely to stagnate and the condensation of the attached slurry is suppressed, and even if the slurry condenses, it can be prevented from growing greatly, resulting in high quality. The ceramic porous body can be obtained.

According to a first aspect of the present invention, there is provided a method for producing a ceramic porous body comprising preparing a slurry containing ceramic powder and an organic monomer, adding a surfactant to the slurry, and adding a monomer polymerization initiator and a catalyst. Introducing a cylindrical bubble into which the slurry is placed in a method for producing a porous ceramic body using a gel casting method in which a foam-containing slurry produced by agitation is poured into a mold and dried and fired. with a substantially central in the center was placed a foaming rotary device and the bubble introduction vessel that combines rotation beater 2 axes disposed so as to position providing a container rotating device for rotating the container, said container rotator Rotating around the center of the bubble introducing container and the revolution means for rotating the biaxial rotating beater at a predetermined distance from the center of the trajectory Combining rotation means for mechanical agitation to perform the bubble introduction and simultaneously carried out by rotating the rotary beater in the foaming rotary device relative to the rotating beater bubbles introduced container by the container rotating device, rotation and It is designed to rotate in combination with revolutions.

The mechanical agitation for introducing bubbles is performed by rotating the rotating beater with the foaming rotation device, so that many bubbles are generated in the slurry due to the collision of the rotating flow of the two-axis rotating beaters. The air bubbles are taken in and efficiently introduced into the slurry, and the pore diameter can be reduced and a high porosity can be obtained.
In addition, since the container rotation device rotates the bubble introduction container in combination with rotation and revolution with respect to the rotation beater, the portion near the rotation beater and the inner wall of the bubble introduction container moves.
Therefore, in addition to the effect of condensing the slurry and suppressing its growth according to the first invention, the effect of scraping off the condensation of the slurry on the inner wall of the bubble introduction container can be obtained. Growth can be suppressed, and a high-quality ceramic porous body can be obtained.

  At the same time, since the bubble introduction container is rotated by the container rotation device, the vicinity of the inner wall of the bubble introduction container causes a shear flow of the slurry due to the inertia of the slurry, and it becomes difficult to stagnate and adheres. Since the position of the middle of the rotating beater is constantly moved by the rotation of the bubble introduction container, even if slurry condensation occurs, it can be prevented from growing large, and a high-quality ceramic porous body is obtained. be able to.

  In the method for producing a ceramic porous body according to the second invention, in particular, the mechanical agitation for introducing bubbles in the first invention is performed at the start with the rotation of the two-axis rotating beater of the rotating device at least at a low first rotational speed. After holding for a predetermined time, bubbles are introduced at a second rotational speed higher than the first rotational speed.

  And the surfactant is less than about half the specific gravity of the slurry, it is difficult to mix and floats, and when the bubbles are scattered at the start of bubble introduction and the surfactant adheres to the inner wall of the bubble introduction container, that part becomes the nucleus and the slurry is condensed. However, the surfactant does not scatter because the surfactant is added to the prepared slurry and the rotation of the rotating beater is kept at a low first rotation speed for a predetermined time to start introducing bubbles. In addition to being suppressed from adhering to the inner wall of the bubble introducing container, bubbles are introduced while slowly mixing with the slurry, and the condensation of the slurry due to poor dispersion of the slurry and the surfactant is suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the present embodiment.

(Embodiment 1)
1 to 3, the method for manufacturing the ceramic molded body 1 according to the present embodiment includes a bubble-containing slurry 7 preparation step for preparing the bubble-containing slurry 7, and the bubble-containing slurry 7 is injected into a mold and molded. Thereafter, a molding step for removing the molded product by removing the molded product, a drying step for drying the molded product, and a firing step for oxidizing and firing the molded product are performed.

  First, the bubble-containing slurry 7 adjustment step will be described.

  The bubble-containing slurry 7 adjustment step of this embodiment is a slurry adjustment step of adjusting the slurry 7 using an inorganic powder, water or an organic solvent, or both, and a gelling agent, and a foaming agent is added to the slurry 7 And a bubble introduction step for introducing bubbles.

  Said slurry adjustment process is performed by mixing silicon carbide powder, an oxide type ceramic material, water, and a gelatinizer.

  This mixing is performed until the average particle size of the silicon carbide becomes about 1 to 20 μm while pulverizing the silicon carbide powder or the like with a pot mill, a ball mill or the like.

  Moreover, 65 wt%-85 wt% of silicon carbide is mixed with the inorganic powder.

  Next, a mixture of alumina and Kibushi clay is used as the oxide-forming material, and alumina is mixed by 5 to 20% by weight, and clay mineral is mixed by 5 to 20% by weight.

  The oxide-based ceramic material is not limited to these, and any oxide-based ceramic material may be used as long as it has a property of being baked with each other while being contracted under oxidation firing.

  Next, as a medium for turbidity of silicon carbide powder and oxide-based ceramic material powder, water or an organic solvent or both are used, and environmentally preferable is water, but organic solvents include methanol, ethanol. Use alcohols.

  Further, a dispersing agent may be added to the ceramic slurry 7 in order to uniformly contain the ceramic powder.

  Water and / or an organic solvent is added in an amount of 25 to 40 parts by weight, particularly 30 to 35 parts by weight, based on 100 parts by weight of the silicon carbide powder and the oxide ceramic material powder.

  As the gelling agent, a synthetic resin or a natural polymer can be used, and as the synthetic resin, either a thermosetting resin or a thermoplastic resin can be used. Particularly, a polyurethane resin, an epoxy resin, etc. It is preferable to use methacrylamide (organic monomer) and methylenebisacrylamide (crosslinking agent).

  The gelling agent may be any gelling agent as long as it can be dispersed and gelated with silicon carbide powder and oxide ceramic material powder, and decomposes and vaporizes in the firing step.

  The gelling agent is added in an amount of 5 to 20 parts by weight, particularly 10 to 15 parts by weight, based on 100 parts by weight of the silicon carbide powder and the oxide ceramic material powder. Further, a known lubricant and thickener may be added to the slurry 7.

  Further, it is preferable to perform degassing under reduced pressure after the slurry adjustment or during the slurry adjustment step.

  Next, a bubble introduction process for adding a foaming agent to the slurry 7 and introducing bubbles is described.

  The bubble introduction step is performed by adding a foaming agent such as a surfactant and a protein foaming agent to the slurry 7 and mechanically stirring.

  As shown in FIG. 3, this mechanical agitation is performed by combining two-axis rotating beaters 9a arranged so that the center thereof is positioned at the approximate center of a cylindrical bubble introduction container 8 into which slurry 7 is put. While providing the rotating device 9 and the container rotating device 10 for placing and rotating the bubble introduction container 8, mechanical stirring for introducing the bubbles is performed by rotating the rotating beater 9a with the foaming rotation device 9, and at the same time, The bubble introducing container 8 is rotated by the container rotating device 10.

  Further, the container rotating device 10 is coaxial with the center 8a of the bubble introduction container 8 and the revolution means 11 for rotating around the revolution center 11a provided at a predetermined distance with the center of the biaxial rotating beater 9a as the center of the locus. The rotation means 12 that rotates as the center 12a is combined, and the bubble introduction container 8 is rotated by combining rotation and revolution with respect to the rotating beater 9a.

  The bubble introduction will be described in detail. First, the slurry 7 is put in the bubble introduction container 8 up to a predetermined amount 7a, and then a foaming agent such as a surfactant and a protein foaming agent is added. Placed on.

  Next, when the bubble introduction container 8 placed on the container rotation device 10 is rotated, the rotation of the biaxial rotating beater 9a is held at a low first rotation speed for a predetermined time almost at the same time, and then a second higher than the first rotation speed. Bubbles are introduced at the rotational speed.

  As a result, atmospheric gas is taken into the slurry 7 and becomes fine bubbles in the slurry 7 to increase the volume of the slurry 7. Finally, the slurry 7 is completely covered up to the upper surface of the biaxial rotating beater 9a. By holding the rotation of the biaxial rotating beater 9a for a predetermined time so as to reach the upper position 7b of the rotating shaft beater 9a. 7 is produced.

The porosity and density of the final ceramic porous body 1 are determined by the amount of bubbles introduced into the bubble-containing slurry 7. This is the amount of slurry 7 put into the bubble introduction container 8, the viscosity of the slurry 7, and the biaxial rotating beater. The position of 9a, the rotation speed and time of the biaxial rotating beater 9a, and the amount of foaming agent such as a surfactant and a protein-based foaming agent are adjusted by the addition amount.

Here, since the mechanical stirring for introducing bubbles is performed by rotating the rotating beater 9a with the foaming rotation device 9, the slurry is caused by the collision of the overlapping rotational flow of the biaxial rotating beater 9a. A large number of bubbles are taken into 7 and the bubbles are efficiently introduced into the slurry 7 so that the pore diameter can be reduced and a high porosity can be obtained.

  At the same time, since the bubble introducing container 8 is rotated by the container rotating device 10, the shear flow of the slurry 7 occurs due to the inertia of the slurry 7 near the inner wall of the bubble introducing container 8, and it becomes difficult to stagnate and adhere. At the same time, since the middle position of the biaxial rotating beater 9a is always moved by the rotation of the bubble introduction container 8, even if the slurry 7 is condensed, it can be prevented from growing greatly. A high-quality ceramic porous body can be obtained.

  Further, since the container rotation device 10 rotates the bubble introduction container 8 in combination with rotation and revolution with respect to the rotation beater 9a, a portion where the rotation beater 9a and the inner wall of the bubble introduction container 8 are close is moving. Since it rotates, in addition to the effect of condensing the slurry 7 and suppressing its growth, the effect of scraping off the condensation of the slurry 7 on the inner wall of the bubble introduction container 8 can be obtained. This can be suppressed, and a high-quality ceramic porous body can be obtained.

  If a rotating device having a rotating blade that scrapes off the condensation of the slurry 7 on the inner wall of the bubble introduction container 8 is used, the structure becomes complicated and maintenance such as cleaning becomes difficult. However, when the container rotating device 10 is used, the bubble introducing container 8 is simply placed on the tray portion of the container rotating device 10. In the bubble introduction container 8, since there is only a rotating beater 9 a in the bubble introduction container 8, there is no narrow portion and no blind spot, so there is no portion that is likely to generate an uneven portion of the slurry 7, and the rotating beater 9 a is raised upward. This makes it easy to separate and facilitate maintenance such as cleaning.

  Further, the surfactant is less than about half the specific gravity of the slurry 7 and hardly mixes and floats. When the surfactant is scattered at the start of bubble introduction and adheres to the inner wall of the bubble introduction container 8, that portion becomes the core and becomes slurry. 7 is likely to be condensed, but since a surfactant is added to the prepared slurry 7 and the rotation of the rotating beater 9a is held at a low first rotation number for a predetermined time to start introduction of bubbles, It is suppressed that the activator does not scatter and adhere to the inner wall of the bubble introduction container 8, and bubbles are introduced while slowly mixing with the slurry 7, and condensation of the slurry 7 due to poor dispersion of the slurry 7 and the surfactant is suppressed. Become so.

  This stirring is preferably performed in a nitrogen atmosphere. Specifically, a predetermined amount of an initiator, a catalyst, and a surfactant are added to the slurry 7, and in a nitrogen atmosphere, by a biaxial rotating beater 9a, Stirring is adjusted for several minutes so that the final bubble introduction amount is 20 to 70%.

  The air bubbles introduced into the slurry 7 by the air bubble introduction process become a plurality of pores 4 as shown in FIG. 2 after the molding process, the drying process, and the firing process.

  Next, a molding process performed by a gel casting method in which the bubble-containing slurry 7 is injected into a mold and molded will be described.

First, the bubble-containing slurry 7 prepared in the bubble introduction step is poured into a mold, and after a predetermined time has passed, the slurry 7 is gelled (solidified), and then a molded product that becomes the gelled ceramic porous body 1 is molded. Remove from 7.

  In this way, when the slurry 7 is solidified, the bubbles present in the slurry 7 are also stored in the gel-like body.

  As a result, the solidified body becomes porous, and a gel-like porous molded body is obtained. This is demolded and then dried, degreased and fired.

  Next, the drying process for drying the molding used as the ceramic porous body 1 is performed. A drying process is performed so that the water and the solvent which are contained in the gel-like porous molded object may be evaporated.

  Drying conditions (temperature, humidity, time, etc.) are appropriately adjusted according to the type of solvent used in the preparation of the slurry 7 and the components (gelling agent or polymer) constituting the skeleton of the gel-like porous molded body. In addition, the size of the molded product that becomes the ceramic porous body 1 in the drying process shrinks from the size of the molded product that becomes the ceramic porous body 1 before drying (the size of the molding die 7).

  The molded product to be the ceramic porous body 1 taken out from the mold 7 is dried for 40 to 100 hours while adjusting the humidity. The drying temperature is preferably 15 to 50 ° C., particularly 25 to 40 ° C., and the humidity in the drying step is particularly preferably 40 to 95%.

  Next, a firing process for oxidizing and firing the molded product that becomes the dried ceramic porous body 1 will be described.

  The firing temperature is a temperature lower than the melting point of silicon carbide or oxide-based ceramic material. Specifically, the firing temperature is preferably 1000 ° C to 1600 ° C, particularly 1200 ° C to 1400 ° C.

  The firing time is preferably 1.5 to 2.5 hr. By firing, the above-described gelling agent, gelation accelerator, catalyst, and water are decomposed or vaporized, and the ceramic molded body 1 shown in FIG. 1 is produced.

  The ceramic molded body 1 produced in this manner has fine pores 5 formed between ceramic particles forming a ceramic matrix.

  Further, as shown in FIG. 2, the ceramic matrix has medium pores 6 formed at portions where the pores 4 are adjacent to each other.

  The fine pores 5 are pores formed between particles of silicon carbide 2 and oxide ceramic material particles 3 whose surfaces are oxidized and covered with a silicon oxide film. The fine pores 5 are formed as open pores having an average pore diameter of 0.1 to 5 μm communicating with the pores 4 or the outside, or isolated closed pores.

  The ceramic matrix is mainly filled with silicon carbide particles 3 whose surfaces are oxidized and covered with a silicon oxide film, and oxide ceramic material particles 3 made of alumina particles and clay particles around the periphery. Are dispersed and fine pores (voids) 6 exist between the particles.

  The pores 4 are formed in the ceramic matrix and are formed as closed pores formed in the ceramic matrix that do not communicate with the outside or open pores that communicate with the outside.

  The pore 4 has a substantially spherical shape, a substantially elliptical spherical shape, or the like in order to form a shape from bubbles.

  Further, as shown in FIG. 2, the medium pores 6 are formed on the inner walls of the matrix constituting the pores 4 and are formed as channels that connect adjacent pores, and the medium pores 6 are formed. The plurality of pores 4 communicate with each other.

  Here, the strength of the ceramic molded body 1 is desirably as uniform as possible in the structure forming the ceramic matrix, and the plurality of pores 4 formed by the ceramic matrix are introduced by introducing the bubbles uniformly and finely when the bubbles are introduced. However, the pore diameter distribution can be narrowed and the structure can be configured to have high bending strength.

  Therefore, the ceramic molded body 1 can be configured to have a high bending strength by maintaining a high porosity and narrowing the pore size distribution and the pore size distribution.

  Thus, since the produced ceramic molded body 1 has a high bending strength while maintaining a high porosity, it can be sliced into a disk shape after processing the outer diameter, and has a high porosity. It will be used for a part of structures such as sensors and filters.

  In addition, although the container rotation apparatus 10 of this Embodiment demonstrated it as what rotated the bubble introduction container 8 combining rotation and revolution, this may be either rotation or revolution, and stirring is carried out. In the above description, after the rotation of the biaxial rotating beater 9a of the rotating device is held at a low first rotation speed for a predetermined time at the start, bubbles are introduced at a second rotation speed higher than the first rotation speed. May start up the rotation of the biaxial rotating beater 9a of the rotator at the start, and the slurry 7 is premixed with a foaming agent such as a surfactant or a protein foaming agent by another means. The configuration of each part may be any configuration as long as the object of the present invention is achieved.

  As described above, the method for producing a ceramic porous body according to the present invention and the ceramic porous body produced using the ceramic porous body have high strength while maintaining a high porosity, and can be sliced into a disk shape. Since it can be processed, it can be applied to applications of structures such as sensors and filters.

Structure diagram of ceramic molded body in Embodiment 1 of the present invention The principal part expanded sectional enlarged view of the ceramic molded object in Embodiment 1 of this invention Configuration diagram when introducing bubbles into the slurry in Embodiment 1 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic molded object 8 Bubble introduction container 9 Foaming rotation apparatus 9a Biaxial rotation beater 10 Container rotation apparatus 11 Revolving means 12 Rotating means

Claims (2)

A slurry containing ceramic powder and organic monomer is prepared, and a surfactant is added to the slurry, and a monomer polymerization initiator and a catalyst are added to form a bubble-containing slurry created by mechanical stirring. In a method for producing a ceramic porous body using a gel casting method in which a molded product poured into a mold is dried and fired,
A foaming rotation device combining a biaxial rotating beater arranged so that the center is positioned at the approximate center of the cylindrical bubble introduction container for containing the slurry, and a container rotation device for placing and rotating the bubble introduction container, And providing
The container rotating device combines a revolving means for rotating around a center of the biaxial rotating beater by a predetermined distance and a rotating means for rotating around the center of the bubble introducing container,
The mechanical stirring for introducing the bubbles is performed by rotating a rotating beater with the foaming rotation device, and at the same time, the bubble rotation container rotates the bubble introduction container with respect to the rotating beater by combining rotation and revolution . A method for producing a ceramic porous body. Mechanical agitation to perform the bubble introduction, said after holding a predetermined time at least a lower first rotation speed rotation of the rotary beater of two axes, performs bubbles introduced at higher than the first rotational speed second rotational speed at the start The method for producing a porous ceramic body according to claim 1.