JP2009102202A - Method for producing ceramic porous article, ceramic porous article produced by the method, and structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high quality ceramic porous article which is minimized in the damage of a molding during demolding and is suppressed in the fracture and the internal crack, by pushing out the molding from a mold without placing any unnecessary load on the molding to be used as a ceramic porous article 1. <P>SOLUTION: A method for producing a ceramic porous article using a gel casting method comprises the steps of pouring a ceramic slurry into a die 7, gelling it for curing, and demolding the produced molding, wherein, during the demolding, the molding is demolded into water by passing a water stream from one side of the die 7 to the other side, and thus, the water stream flows through the pore portion of the molding; a force which generally pushes out the molding works thereto, and the force is not greatly applied to a local area of the molding. The molding can be pushed out from the mold without placing any unnecessary load on the molding, and the damage to the molding can be minimized. <P>COPYRIGHT: (C)2009,JPO&INPIT

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 catalyst, pour into an impermeable mold.

  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 similar to casting molding and tape molding that are currently commonly used, and can be applied if a high-concentration slurry can be prepared, and near net shaping using a complex-shaped mold There is also an advantage that it is possible.

  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 (for example, see Non-Patent Document 1).
"Ceramic Engineering Research Center Annual Report (2005) Vol.5" P33-40, Hiroaki Takegami, Masanori Fujii, Minoru Takahashi "Porous Ceramic Molding by Gel Casting and its Application"

  However, various problems occur in the manufacturing process of the above-mentioned conventional ceramic porous body, and particularly when the molded product cast and solidified in the mold is removed, the molded product is deposited on the surface of the mold. When the mold is released, the solidified ceramic porous body before drying / firing which has insufficient strength may break or internal cracks may occur.

  In particular, when the porosity of the ceramic porous body is high and the porosity is 70% or more, a part of the molded product remains in the mold at the time of demolding or is easily broken at the center of the mold, Even if there is no crack, internal cracks are likely to occur, and when a cylindrical molded product is created and sliced thinly into a disk shape, etc., if there are internal cracks, etc. There was a concern that the ceramic porous body could not be maintained easily because it was difficult to handle because it would break.

  In view of the problems of the above-described conventional technology, the present invention reduces the damage of the molded product at the time of demolding by suppressing the crack and the internal crack by extruding from the mold without applying a load as much as possible to the molded product. The 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. A ceramic porous body using a gel casting method in which a mechanically stirred bubble-containing ceramic slurry is poured into a cylindrical mold, gelled and cured, and the produced ceramic molding is demolded, dried and fired. In the manufacturing method, when the molded product is poured into the mold, gelled and cured, and the molded product is demolded, it is demolded into water by flowing a water stream from one of the molds to the other. .

  Pour into a cylindrical mold by the method described above, gel and cure, and when removing the molded product, the mold is removed from the mold by flowing water from one side to the other. Therefore, the water flow flows through the pores of the molded product, and the force that pushes the molded product as a whole works, and the force is not applied locally on the molded product. It is possible to reduce the damage of the molded product.

  According to the present invention, it is possible to reduce the damage of the molded product at the time of demolding by reducing the damage of the molded product by extruding it entirely from the mold without applying a load as much as possible so as not to apply a large force to the molded product. Cracks can be suppressed and a high-quality 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, adding a monomer polymerization initiator and a catalyst, and mechanically adding the slurry. A method for producing a porous ceramic body using a gel casting method, in which a stirred ceramic slurry containing bubble-containing material is poured into a cylindrical mold, gelled and cured, and the produced ceramic molding is demolded, dried and fired. The mold is poured into the mold, gelled and cured, and when the produced molding is demolded, it is demolded into water by flowing a water stream from one of the molds to the other.

And when poured into a cylindrical mold, gelled and cured, and when the produced molded product is demolded, it is demolded into water by flowing a water stream from one of the molds to the other. Therefore, water flows through the pores of the molded product, and the force that pushes the molded product as a whole works, and the molded product does not apply a large force locally, so the molded product is extruded from the mold without applying as much load as possible. And damage to the molded product can be reduced.

  Therefore, it is possible to reduce damage to the molded product during demolding and suppress cracks and internal cracks by extruding the molded product as a whole without applying a load as much as possible so as not to apply a large force to the molded product. A high-quality ceramic porous body can be obtained.

  The method for producing a ceramic porous body according to the second aspect of the invention is particularly characterized in that when the mold is released into water by flowing a water flow from one of the molds of the first aspect of the invention to the other, a boundary layer between the molded article and the mold. The water flow is made to flow from a nozzle having an opening on the outer periphery so that the water flow mainly flows.

  Then, when demolding into the water by flowing a water flow from one side of the mold to the other, a water flow is flowed from a nozzle having an opening on the outer periphery so that the water flow mainly flows in the boundary layer between the molded product and the mold. Therefore, the water flow layer is quickly formed in the boundary layer between the molded product and the mold, making it easier to separate the mold, reducing the time for demolding, and reducing the flow of water flowing through the center of the molded product. Since it can reduce, formation of the communicating hole etc. which arise when a water flow flows can be suppressed.

  In the method for producing a ceramic porous body according to the third invention, in particular, in any one of the first and second inventions, the diameter of the mold gradually increases from the upstream side to the downstream side of the water flow during demolding. A gradient is provided.

  Since the mold has a gradient so that the diameter gradually increases from the upstream side to the downstream side of the water flow at the time of demolding, a water flow layer is formed at the boundary layer between the molded product and the mold even slightly. When the mold is separated, a gap is formed between the mold and the mold, so that the mold is completely separated from the mold, and the time for demolding can be shortened and unnecessary water flow is not required. It is possible to suppress the formation of communication holes caused by the flow of water.

  4th invention is the ceramic porous body obtained by the manufacturing method of any one of 1st-3rd invention, an effect is obtained, damage to a molded object at the time of demolding is reduced, a crack and Internal cracks are suppressed, and the fifth invention is a structure using the ceramic porous body of the fourth invention.

  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 manufacturing method of the ceramic molded body 1 according to the present embodiment includes a bubble-containing slurry preparation step for preparing a bubble-containing slurry, and a molded product after the bubble-containing slurry is injected into a mold and molded. A molding step for removing the molded product and taking out 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 adjustment step will be described.

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

  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 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.

  In addition, a known lubricant and thickener may be added to the slurry. Further, it is preferable to perform degassing under reduced pressure after the slurry adjustment or during the slurry adjustment step.

  Next, a bubble introduction step for adding bubbles to the slurry and introducing bubbles will be described.

  The bubble introduction step is performed by adding a foaming agent such as a surfactant or a protein foaming agent to the slurry and stirring. As the surfactant, an anionic surfactant such as an alkylbenzene sulfonic acid, a cationic surfactant such as a higher alkyl amino acid, or the like is used.

  Then, by adding a surfactant and stirring vigorously, bubbles are formed in the slurry. This stirring is preferably performed in a nitrogen atmosphere.

  Specifically, the slurry is put into a beaker, a predetermined amount of an initiator, a catalyst, and a surfactant are added, and the number of introduced bubbles is 20 to 70% by a double roll mixer in a nitrogen atmosphere. Stir for minutes.

  The air bubbles introduced into the slurry by the air bubble introducing step become a plurality of pores 4 as shown in FIG. 2 after the forming step, the drying step, and the firing step.

  In the bubble introduction step, a gelation accelerator is added.

  Moreover, an initiator is added when an initiator is required for polymerization of an organic monomer or the like. As the gelation accelerator, tetramethylethyldiamine, hydrogen peroxide compound, azo or diazo compound, etc., especially tetramethylethyldiamine can be used, and as initiator, sodium persulfate, ammonium persulfate, etc., especially ammonium persulfate Can be used.

  Although depending on the gelling agent, the gelation accelerator and initiator are added to the slurry when the surfactant is added.

  The bubble introduction step is not limited to being performed by adding a surfactant to the slurry and stirring. For example, bubbles may be introduced into the slurry by feeding an inert gas such as nitrogen gas into the slurry.

  Here, the introduction amount of the bubbles 5 and the diameter of the bubbles 5 formed in the slurry in the bubble introduction step can be adjusted by the addition amount of the surfactant, the viscosity of the slurry, the strength of stirring, and the like.

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

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

  At this time, the larger the amount of introduced bubbles, the weaker the strength of the molded product that becomes the ceramic porous body 1 to be taken out, and the more easily broken, for example, a cylindrical shape combining two semicircular molding dies. When the mold is broken and removed, a part or the whole of the molded product that becomes the ceramic porous body 1 is broken into a half circle from the center, a part of the surface is chipped, Prone to occur.

  Moreover, when it tries to mechanically extrude from one side of the cylindrical shaping | molding die 7 to the other with an extrusion rod etc., the molded object used as the ceramic porous body 1 will buckle from the part which an extrusion rod contacts, and it will break. May end up.

  This is particularly likely to occur with a thin and long material, and the strength of the molded product that becomes the ceramic porous body 1 increases the amount of bubbles introduced relative to the adhesion between the molded product that becomes the ceramic porous body 1 and the mold 7. , To come down.

Therefore, in the present embodiment, as shown in FIG. 3, the ceramic porous body is poured into the cylindrical molding die 7, gelled and cured, and the molded product that becomes the produced ceramic porous body 1 is demolded. By utilizing the fact that the pores of the molding to be 1 are continuous pores, the molding die 7 is buried in water together, and a water flow is made to flow from one side of the molding die 7 to the other, thereby allowing the molding to become the ceramic porous body 1. It is pushed out as a whole by the force of the water flow flowing through the pores 4 and demolded into the water.

  As a result, a water flow flows through the pores 4 of the molded product, and a force that pushes the molded product as a whole works, and the force is not applied locally on the molded product. It is possible to extrude from the mold 7 without damaging, and damage to the molded product can be reduced.

  Further, when demolding into the water by flowing a water flow from one side of the mold 7 to the other, the nozzle 8 having an opening 9 in a circumferential shape so that the water flow mainly flows in the boundary layer between the molded product and the mold 7. It is made to demold by flowing a water flow more.

  As a result, a water flow layer is quickly formed in the boundary layer between the molded product and the mold 7 so that the mold can be easily separated, and the time required for demolding can be shortened, and the water flow flowing through the center of the molded product can be reduced. It is possible to suppress the formation of communication holes caused by the flow of water.

  It should be noted that the water flow is adjusted so that a predetermined flow rate flows from the nozzle 8 in an open state so that the water flow flows in a state where the water flow is balanced around and around the molded body that becomes the ceramic porous body 1. The water flow is made to flow from the nozzle 8 having the opening 9 in a circumferential shape so that the water flow flows in the boundary layer between the molded product 1 and the mold 7. If the water flow is strong, it tends to flow only around the molded product that becomes the ceramic porous body 1 with vigor, so adjustment is made so that the mold can be effectively removed.

  Further, the mold 7 is provided with a gradient so that the diameter gradually increases from the upstream side to the downstream side of the water flow at the time of demolding.

  As a result, a water flow layer is formed at the boundary layer between the molded product and the mold 7 even if a slight gap is formed between the molded product and the mold 7 once the mold is separated, so that the molded product is completely removed from the mold 7. It is possible to reduce the time required for demolding, and it is possible to suppress the formation of communication holes and the like caused by the flow of water without flowing unnecessary water flow.

   Therefore, it is possible to reduce damage to the molded product at the time of demolding and suppress cracks and internal cracks by extruding from the mold 7 as a whole without applying a load as much as possible so as not to apply a large force to the molded product. In addition, a high-quality ceramic porous body can be obtained.

  Next, the drying process for drying the molding used as the ceramic porous body 1 is performed. In the drying process, the size of the molded product that becomes the ceramic porous body 1 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 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 molded product was cylindrical, this may be cylindrical, and the ceramic molded body 1 was sliced into a disk after processing the outer diameter after firing, This may be processed after drying, can be used as it is without further processing, and the configuration of each other part is within the scope of achieving the object of the present invention. It may be.

  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 view of the ceramic molded object in Embodiment 1 of this invention The block diagram when removing the ceramic molded body in Embodiment 1 of this invention from a shaping | molding die

Explanation of symbols

1 Ceramic molded body 7 Mold 8 Nozzle 9 Opening

Claims (5)

A slurry containing ceramic powder and an organic monomer is prepared, a surfactant is added to the slurry, a monomer polymerization initiator and a catalyst are added, and a mechanically stirred bubble-containing ceramic slurry is formed into a cylindrical mold. In the method for producing a ceramic porous body using a gel casting method in which the formed molded product is demolded, dried and fired, and poured into the molding die, gelled and cured, A method for producing a ceramic porous body, wherein when a produced molded product is demolded, the mold is demolded into water by flowing a water flow from one of the molds to the other. When demolding into the water by flowing a water flow from one of the molds to the other, a water stream is flowed from a nozzle having an opening on the outer periphery so that the water flow mainly flows in the boundary layer between the molded product and the mold. 2. The method for producing a ceramic porous body according to claim 1, wherein the ceramic porous body is demolded. The method for producing a ceramic porous body according to claim 1 or 2, wherein the forming die is provided with a gradient so that the diameter gradually increases from the upstream side to the downstream side of the water flow at the time of demolding. The ceramic porous body produced with the manufacturing method of the ceramic porous body of any one of Claims 1-3. A structure using the ceramic porous body according to claim 4.