JPH06219865A - Porous titania sintered compact and its production - Google Patents

Abstract

PURPOSE:To increase the hardness of a porous titania sintered compact by sintering a compact at >=1,300 deg.C and to obtain a porous titania sintered compact maintaining its porosity by using polymethyl methacrylate coated titania balls having 50-150mum average particle diameter. CONSTITUTION:Titania powder 1 is aggregated with polymethyl methacrylate resin 2 which vanishes at a sintering temp. to form polymethyl meth-acrylate coated titania balls 3 having 50-150mum average particle diameter. The balls 3 are then compacted and the resulting compact 4 is sintered at >=1,300 deg.C to obtain the objective porous titania sintered compact 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous titania sintered body which can be used in many fields of application as high-performance materials such as industrial medical materials, sensors, catalyst carriers, refractory materials, etc., and a method for producing the same. Is.

[0002]

2. Description of the Related Art Conventionally, it has been known that porous ceramics such as titania can be extremely increased in specific surface area and are therefore useful as sensors and catalysts.

As a method for producing such a porous ceramic body, as disclosed in Japanese Patent Laid-Open No. 2-239169, a binder such as a synthetic resin that disappears during firing is used to remove a ceramic powder from a ceramic powder. There is known a method of producing a resin-coated ceramic sphere, molding the resin-coated ceramic sphere, and firing the sphere to eliminate the binder, thereby producing a ceramic porous body.

By thus forming a porous body,
Since it is possible to increase its specific surface area, it is possible to control or improve the expression of functions of a sensor, a catalyst carrier, etc., and also to improve its operability as compared with ceramic powder. Has become.

By the way, it is desirable that the hardness of the porous ceramic body is high in order to enhance its strength.
When used in an environment where the temperature changes greatly, it is preferable that the coefficient of thermal expansion be low.

[0006]

However, in the above-mentioned conventional method, in order to improve the hardness and the like of the obtained porous ceramics sintered body, the sintering temperature may be raised to 1300 ° C. or higher. The sintered body obtained at such a sintering temperature has a problem that the porosity is lost due to crystal growth during sintering.

[0007]

[Means for Solving the Problems] In order to solve the above problems, a porous titania sintered body according to claim 1 is a titania body having a particle size of 50 to 150 μm, in which titania powder is aggregated,
It is characterized by being formed and sintered at 1300 ° C or higher.

In the method for producing a porous titania sintered body according to a second aspect of the present invention, the titania powder is aggregated by a binder that disappears at the temperature during sintering, and the titania body has an average particle size of 50 to 150 μm.
It is characterized in that a porous titania sintered body is obtained by molding the above-mentioned titania body to obtain a molded article, and then sintering the above-mentioned molded article at 1300 ° C. or higher.

In the method for producing a porous titania sintered body according to a third aspect of the present invention, the titania powder is aggregated by a binder that disappears at the temperature during sintering, and the titania body has an average particle size of 50 to 150 μm.
m, and then the above-mentioned titania body was fired to obtain a titania fired body, and then the above titania fired body was molded to obtain a fired body molded product, and the above-mentioned fired body molded product was heated at 1300 ° C or higher. It is characterized in that a porous titania sintered body is obtained by sintering.

The titania body is obtained by assembling titania powder with a binder that disappears at the temperature during sintering.
More specifically, a mixed solution prepared by mixing a polymerizable monomer such as acrylic acid that disappears at the temperature during sintering and a titania powder, and an organic solvent as necessary, a solution that is immiscible with the mixed solution, for example, The mixed solution having a substantially spherical shape is dispersed in an aqueous solution and suspended in the solution.

Then, the above-mentioned polymerizable monomer is polymerized to obtain a titania powder, that is, a titania body, which is bound and assembled by the polymer obtained by polymerizing the above-mentioned monomer.
At this time, the polymer has a function as a binder.

When the above-mentioned mixed solution is suspended in the solution, the particle size of the obtained titania body can be controlled by adjusting the viscosity of the mixed solution, the composition, the viscosity of the solution, the composition, the stirring speed during suspension, and the like. It can be adjusted and its particle size range is from 50 to
It is preferably adjusted to 150 μm.

As the above-mentioned titania powder, if the finally obtained sintered body can be suitably used as a high temperature functional material such as a sensor, a catalyst, a separating material, a medical material, a heat insulating material, a refractory material, etc. Good.

The particle size of the titania powder is such that, when particles having a large particle size are used, when the titania body is prepared, the mixed solution is suspended in an aqueous solution and polymerized, and dispersed in the form of oil droplets. This is inconvenient because the titania powder is easily released from the solution into the aqueous phase.

On the other hand, in the case of using particles having a small particle diameter, even if a large amount of an organic solvent is added as a viscosity reducing agent, at the time of suspension,
It is difficult to reduce the viscosity until the mixed solution can be dispersed in the aqueous solution as spherical oil droplets. From these, the particle size of titania powder is 0.01-2.0 μm.
It is preferably between 0.1 and 1.5 μm.

A lipophilic agent may be used in the mixed solution in order to increase the affinity between the titania powder and the polymerizable monomer. The lipophilic agent has a functional group capable of strongly adsorbing or binding to the titania powder, and a hydrocarbon having a high affinity for the polymerizable monomer, or a functional group capable of binding to the polymerizable monomer. A substance can be used.

Examples of such substances include higher fatty acids such as oleic acid, stearic acid and palmitic acid, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, aminoethyl acrylate and hydroxyethyl acrylate.
Examples thereof include acrylic acid esters having a polar group such as cyanoethyl acrylate, or titanate coupling agents or silane coupling agents.

Among the lipophilic agents as described above, those having a functional group capable of strongly binding to the titania powder, such as titanate coupling agents and silane coupling agents, are preferable. Examples include pyrophosphate-type titanate coupling agents such as isopropyl tris (dioctylpyrophosphate), bis (dioctylpyrophosphate) titanate, and phosphate-type titanate coupling agents tetraoctylbis (ditridecylphosphate) titanate. Examples of the silane coupling agent include vinyltrichlorosilane, vinyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane having a radically polymerizable functional group.

When the mixed solution is dispersed in the solution, a dispersant may be mixed with at least one of the mixed solution and the solution so that a suspension state can be maintained. As such a dispersant, a surfactant such as sodium dodecylbenzene sulfonate can be used.

[0020]

According to the structure described in claim 1, the average particle size is
Since a titania body of 50 to 150 μm is used, even if a titania crystal grows during firing at 1300 ° C. or higher, it is possible to leave pores between the titania bodies, which makes it a porous titania sintered body, and Since the sintering temperature is 1300 ° C. or higher, the crystal form can be changed from the anatase type to the rutile type, and the proportion of the rutile type can be increased, so that a porous titania sintered body having greater hardness can be obtained. And the coefficient of thermal expansion can be reduced.

According to the method described in claim 2, since the titania body having an average particle size of 50 to 150 μm is used, even if the titania crystals grow during firing at 1300 ° C. or higher, pores between the titania bodies are formed. By making it possible to leave a part, it is possible to obtain a porous titania sintered body and the sintering temperature is 1300
Since the temperature is not lower than 0 ° C, it is possible to obtain a porous titania sintered body having a hardness higher than that of the related art and a coefficient of thermal expansion lower than that of the related art.

According to the above method of claim 3, when a titania fired body is obtained by firing a titania body having an average particle size of 50 to 150 μm, the titania fired body loses the binder during firing, And since it binds between each titania powder,
The shape of the titania body can be almost maintained.

Since such a titania sintered body is molded and used, even if a crystal of titania grows during firing at 1300 ° C. or more, the pores between the titania sintered bodies can be left, so that the porous body is porous. A titania sintered body can be obtained.
At this time, since the sintering temperature is 1300 ° C. or higher, it is possible to obtain a porous titania sintered body having a hardness higher than that of the conventional one and a low coefficient of thermal expansion.

Furthermore, since the binder is removed in advance when sintering to obtain the porous titania sintered body, the inconvenience caused by the residual binder can be reduced.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS. In the method for producing a porous titania sintered body, first, a resin-coated titania sphere is prepared, the resin-coated titania sphere is pressure-molded into a predetermined shape to obtain a molded article, and then the molded article is baked. A porous titania fired body is obtained. At this time, after the resin-coated titania spheres are fired to obtain a porous titania sintered body, the porous titania sintered body is pressure-molded to obtain a porous molded article, and then the porous molded article is obtained. Can be further fired to obtain a porous titania fired body.

First, an example of a method for preparing the resin-coated titania sphere will be described. In the above preparation method example, first,
In a 1 liter beaker, 279 g of methyl methacrylate as a polymerizable monomer, 21.0 g of a silane coupling agent [γ-methacryloxypropyltrimethoxysilane, Toray Silicone Co., Ltd., SZ6030] as a lipophilic agent,
Azobisisobutyronitrile as polymerization initiator 0.60g
Was charged and mixed to obtain a completely dissolved mixed solution.

Then, titanium oxide (titania) [rutile type, average particle size 0.2 μm, manufactured by Teikoku Chemical Co., Ltd., JR-600A]
After adding 700 g to the above mixed solution to obtain a mixture, using a stirrer equipped with a propeller blade, insert the propeller blade into the mixture and rotate at 2000 rpm for 30 minutes to obtain the surface of the titania. Was subjected to a surface treatment for imparting lipophilicity to a slurry-like mixture.

Next, 2.6 kg of water was put into an autoclave having an internal volume of 5 liters, and subsequently 60 g of metathesis magnesium pyrophosphate as a dispersant and 2.6 g of sodium dodecylbenzenesulfonate were mixed with the above water. To obtain a mixed aqueous solution, and then the slurry-like mixture was added to and suspended in the mixed aqueous solution.

Then, the inside of the autoclave was replaced with nitrogen, and then the inside of the autoclave was stirred at a stirring speed of 500 rpm and at a liquid temperature.
The methyl methacrylate was polymerized at 60 ° C. After the completion of the polymerization, the liquid temperature in the autoclave was cooled to room temperature, and the dispersant was decomposed with hydrochloric acid to obtain a suspension.

Next, the above suspension was filtered to separate it into a particulate matter and a liquid. When the above particulate matter was observed using a scanning electron microscope (SEM), it was a substantially spherical particle having an average particle diameter of about 120 microns (hereinafter referred to as μm). As shown in FIG. 1 was a plurality of PMMA-coated titania spheres 3 coated with polymethylmethacrylate (PMMA) resin 2.

Example 1 P obtained as described above
1 g of the MMA-coated titania sphere 3 was taken, filled in a molding die (diameter 12 mm, depth 20 mm), and filled as described above.
The MMA-coated titania sphere 3 was pressed at a pressure of 3 ton / cm ² and molded to obtain a molded product 4.

Then, the molded product 4 is placed in an electric furnace and
By firing at 00 ° C. for 1 hour, a porous titania sintered body 5 having a density of 3.04 g / cm ³ was obtained. The porous titania sintered body 5 had a Mohs hardness of 6.5 to 7.0 and a coefficient of thermal expansion of 7.14 × 10 ⁻⁶ / ° C.

When the fracture surface of the porous titania sintered body 5 is observed by using SEM, as shown in the drawing-substitute photograph of FIG. 2, it is composed of dense titania spheres, and pores are formed between the titania spheres. A uniform porous titania sintered body was obtained in which the pores were well formed and the pore size distribution was narrow. The pore size was 20 μm to 50 μm.

Example 2 As shown in FIG. 3, the PMMA-coated titania spheres 3 obtained as described above were placed in an alumina crucible and fired at 1100 ° C. for 1 hour to give an average particle size of about 100 μm. A substantially spherical porous titania sintered body 6 was obtained.
1 g of the above-mentioned porous titania sintered body 6 was filled into a molding die (diameter 12 mm, depth 20 mm), and the porous titania sintered body 6 filled as described above was filled with 1 ton / cm ² . A sintered compact 4'was obtained by pressurizing with pressure.

Subsequently, the sintered compact 4'is put in an electric furnace and fired at 1400 ° C. for 1 hour to give a density of 3.34 g.
A porous titania sintered body 5'having a density of / cm ³ was obtained. The porous titania sintered body 5 ′ had a Mohs hardness of 6.5 to 7.0 and a coefficient of thermal expansion of 7.14 × 10 ⁻⁶ / ° C.

Further, observing the fracture surface of the porous titania sintered body 5'using an SEM, as shown in the drawing-substitute photograph of FIG. 4, it consists of dense titania spheres, and the pores are formed between the titania spheres. Was formed, and on top of that, a uniform porous titania sintered body was obtained in which the shapes of the pores were well aligned and the pore size distribution was narrow. The pore size was 10 μm to 40 μm.

As described above, in the method of each of the above-mentioned embodiments, by using the PMMA-coated titania spheres 3 having an average particle diameter of about 120 μm, a porous titania sintered body can be obtained at a firing temperature of 1400 ° C. In addition, the obtained porous titania sintered body 5.5 'has a conventional hardness (Mohs hardness of 5.
The hardness can be increased from 5 to 6.0), and the coefficient of thermal expansion can be made lower than the conventional coefficient of thermal expansion (10.2 × 10 ⁻⁶ / ° C.).

By the way, in the past, when the firing temperature was raised to 1300 ° or higher in order to increase the hardness of the porous titania sintered body and to lower the coefficient of thermal expansion, titania crystals grew during firing. However, the pores of the porous body are blocked, and the porosity for exhibiting excellent properties such as an increase in specific surface area is impaired.

However, in the above-described structure, the crystal form of TiO ₂ can be changed from the anatase type (low temperature type) to the rutile type (high temperature type) by firing at a high temperature, and thus the rutile type Since the ratio can be increased, the hardness can be increased and the coefficient of thermal expansion can be decreased.

In addition, the above structure can maintain the porosity of increasing the specific surface area while avoiding the difficulty of handling the conventionally used ceramic powder, even if the ceramic powder is fired at a higher temperature than before. Since the hardness and the coefficient of thermal expansion can be improved, it can be suitably used even in places where the operating conditions are severe, such as places where there are many vibrations or changes in the temperature environment, and the application range of the above configuration can be improved. It can be expanded.

In addition, the above-mentioned manufacturing method can easily manufacture the porous titania sintered body having the above-mentioned excellent characteristics with good reproducibility. Therefore, the above method
It is possible to stably supply a porous ceramic body that can be further used in many application fields as a highly functional material such as an industrial medical material, a sensor, a catalyst carrier, and a refractory material.

In particular, the above structure has NO _{x in} the titania.
Since it has high selectivity as a reduction catalyst, and has vibration resistance and thermal shock resistance, it can be used very effectively as a catalyst for reducing NO _x from exhaust gas from automobiles and the like.

[0043]

As described above, the porous titania sintered body according to claim 1 of the present invention is obtained by molding a titania body having a particle size of 50 to 150 μm, which is an aggregate of titania powder, at 1300 ° C. or higher. It is a structure formed by sintering.

Therefore, the above-mentioned constitution can improve the hardness and the like while maintaining the porosity for increasing the specific surface area and exhibiting excellent characteristics, so that the range of application can be expanded. Produce an effect.

According to the second aspect of the present invention, the porous titania sintered body and the method for producing the same have a structure in which the titania powder is aggregated by a binder that disappears at the temperature during sintering, and the titania body has an average particle size of 50 to 150 μm. Then, the titania body is molded to obtain a molded product, and then the molded product is sintered at 1300 ° C. or higher to obtain a porous titania sintered body.

Therefore, the above method can stably obtain a porous titania sintered body whose hardness and the like are improved while maintaining the porosity, so that the applicable range can be expanded. This has the effect that the body can be manufactured stably.

As described above, the method for producing a porous titania sintered body according to claim 3 of the present invention is such that the titania powder is aggregated by the binder that disappears at the temperature during sintering to obtain an average particle size of the titania body. 50 to 150 μm, and then the above titania body is fired to obtain a titania fired body, and then the above titania fired body is molded to obtain a fired body molded product, and the above fired body molded product is 1300 It is a method of obtaining a porous titania sintered body by sintering at a temperature of ℃ or more.

Therefore, the above method is further effective in that it is possible to obtain the porous titania sintered body in which the residual amount of the binder can be reduced and the adverse effect of the binder can be reduced.

[Brief description of drawings]

FIG. 1 is a process drawing of a method for manufacturing a porous titania sintered body in Example 1 of the present invention.

FIG. 2 is a drawing-substituting photograph showing a particle structure of the above porous titania sintered body.

FIG. 3 is a process drawing of a method for manufacturing a porous titania sintered body in Example 2 of the present invention.

FIG. 4 is a drawing-substituting photograph showing a particle structure of the above porous titania sintered body.

[Explanation of symbols]

 1 Titania 2 PMMA resin (bonding material) 3 PMMA-coated titania spheres (titania body) 4 Molded product 5 Sintered body (porous titania sintered body)

Claims (3)

[Claims] 1. A particle size of aggregated titania powder of 50 to 150 μm.
A porous titania sintered body, which is obtained by molding a titania body of m and sintering it at 1300 ° C. or higher. 2. A titania powder is aggregated by a binder that disappears at the temperature during sintering to obtain a titania body having an average particle size of 50 to 150.
The porous titania is characterized in that it is made to have a size of μm, and then the above titania body is molded to obtain a molded product, and then the above molded product is sintered at 1300 ° C. or higher to obtain a porous titania sintered body. Manufacturing method of sintered body. 3. The titania powder is aggregated by a binder that disappears at the temperature during sintering to obtain a titania body having an average particle size of 50 to 150.
μm, then, the above titania body is fired to obtain a titania fired body, and then the above titania fired body is molded to obtain a fired body molded product, and subsequently, the above fired body molded product is heated to 1300 ° C. or higher. A method for producing a porous titania sintered body, characterized in that the porous titania sintered body is obtained by sintering.