JPH04115906A - Porous titania sintered body and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a sintered body which has uniform porous structure and is superior in mechanical strength, by a method wherein the present porous titania sintered body is constituted by gathering and sintering nonporous titania spherical bodies. CONSTITUTION:The present sintered body is constituted by gathering and sintering non porous titania spherical bodies. A mixture comprised of titania powder which is surface-treated with lipophilic agent, a polymerizable vinyl monomer and an organic solvent which is added at need and has compatibility with the above-mentioned monomer and no compatibility substantially with water is dispersed into an aqueous base and the above-mentioned monomer is polymerized. With this construction, a porous titania spherical body comprised of aggregate of titania powder coated with resin is obtained and then pressure molding is performed by gathering the resin-coated porous spherical bodies. Then the porous titania spherical bodies are heated and sintered under a temperature capable of converting the same into a nonporous state and porous titania sintered bodies having density of at least 2.5g/cm<2> can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a porous titania (titanium dioxide) sintered body and a method for producing the same. More details include sensors, catalysts, separation materials (filters), medical materials, insulation materials, fireproof materials,
The present invention relates to a porous titania sintered body as a porous ceramic body that is expected to be applied in many fields of application such as various functional materials such as adsorption/desorption materials, and a method for producing the same.

(B) Conventional technology The conventional method for producing the above ceramic porous bodies is to knead materials that disappear when fired at low temperatures (e.g. rubber, resin, rice husks, etc.) with raw ceramic powder as a binder. A common method is to mold and then fire at a high temperature to leave only the ceramic and sinter it. The above-mentioned kneading method includes, for example, (1) mixing water-soluble resin such as polyvinyl alcohol with water and ceramic powder, (2) mixing polystyrene, polyethylene,
Combinations such as heating and kneading thermoplastic resin such as polypropylene and ceramic powder, and mixing resin and its solvent with ceramic powder as described in (1) and (3) are known.

(c) Problems to be Solved by the Invention However, in all of the above conventional methods, since the mixture is mixed by kneading, the inside of the green body is inevitably in a non-uniform state with areas with a high resin content and areas with a low resin content. do not have. Therefore, the sintered body obtained by firing this will have only non-uniform pores. Furthermore, if the porosity is increased, the resin content will further increase, and the above problem will become even more serious.

Furthermore, even if the ceramic porous body obtained by kneading and firing in this manner has a desired porosity, its mechanical strength is sometimes insufficient and cannot be put to practical use.

The present invention was made under such circumstances, and specifically aims to provide a porous titania sintered body with a uniform porous structure and excellent mechanical strength, and a method for efficiently manufacturing the same. be.

(d) Means for Solving the Problems Thus, according to the present invention, a porous titania sintered body is provided in which non-porous titania spheres are aggregated and sintered. Furthermore, according to the present invention, the surface of the 1
Dispersing in an aqueous system a mixture consisting of this titania powder, a polymerizable vinyl monomer, and an organic solvent that is compatible with the monomer and is not substantially compatible with water, which is added as necessary, By polymerizing the above monomer, porous titania spheres coated with a resin and consisting of an aggregate of one titania powder are obtained, and then the resin-coated porous spheres are aggregated and pressure-molded, and then the porous titania spheres are There is provided a method for producing a porous titania sintered body, characterized in that the porous titania sintered body described above is obtained by heating and sintering titania spheres at a temperature that can convert them into a non-porous body.

This invention is a porous titania sintered product made by assembling resin-coated (composite) porous titania spheres made from titania (titanium dioxide) powder as constituent elements, and further pressurizing and sintering them. It's about the body. The sintered body of the present invention can be produced, for example, by the following method. That is, a mixture of titania powder surface-treated with a lipophilic agent and a polymerizable vinyl monomer is prepared, and in some cases, an organic solvent that is compatible with the monomer and substantially incompatible with water is prepared. is added to the above mixture to suppress the increase in viscosity due to an increase in the amount of titania powder in the above mixture, to expand the range of addition amount of titania powder, and to reduce the amount of individual oils in the oil droplet dispersion of the above mixture in an aqueous system. This enables the droplets to be dispersed and held in a spherical shape, and as a result, the titania powder (-order particles) dispersed within each oil droplet.
are assembled into a spherical shape to produce resin-coated (composite) porous titania spheres, which are further assembled into a predetermined shape and pressure molded, and then heated at a predetermined temperature to remove the coating resin. At the same time, the material is sintered to form a porous body.

In the above method, the surface-treated titania powder is
This means that it is only necessary that the titania (titanium dioxide) powder be surface-treated before polymerization of the polymerizable vinyl monomer used. Therefore, titania powder may be surface-treated in advance before being added to a polymerizable vinyl monomer or a mixture of the monomer and a predetermined organic solvent. The surface treatment may be carried out by adding titania powder to a mixture of the organic solvent and the lipophilic agent used for the surface treatment. The above-mentioned surface treatment refers to a treatment in which the titania powder is brought into contact with the above-mentioned lipophilic agent and the lipophilic agent is adsorbed or bonded to the surface of the powder. This treatment is accomplished by conventional mechanical methods and the like. That is, a mixture of a lipophilic agent and titania powder, or a mixture of a lipophilic agent, titania powder, and a polymerizable vinyl monomer is heated at room temperature or under cooling at high speed using, for example, a propeller blade or a homogenizer. This is achieved by stirring.

As the titania powder used in this invention, normal titanium dioxide powder can be used, and its particle size is 0. O1~
Preferably between 2.0 μm, 0.1 to 1.5
μ luster is preferred.

The lipophilic agent used in this invention is a hydrocarbon that has a functional group that strongly adsorbs or binds to the titania powder and has a high affinity with the polymerizable vinyl monomer, or a functional group that can bind to the monomer. Substances having groups 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, and polar Examples include coupling agents such as acrylic esters having groups, titanate coupling agents, and silane coupling agents. Among these, those having a functional group that strongly bonds with titania powder, such as titanate coupling agents and silane coupling agents, are preferred. For example, examples of titanate coupling agents include isopropyl tris(dioctyl pyrophosphate) and bis(dioctyl pyrophosphate) titanate, which have a pyrophosphate type lipophilic group, and tetraoctyl titanate has a phosphate type lipophilic group. Examples include bis(notridenylphosphate) titanate, and examples of silane coupling agents include those having a vinyl group, such as vinyl trichlornolane, vinyltrimethoquinonolane, and γ-methacryloxypropyltrimethoxinelan.

The polymerizable vinyl monomer used in this invention includes:
Any known monomer that exists as spherical oil droplets when dispersed in an aqueous system and can form a polymer under polymerization conditions can be used as is. Moreover, the above-mentioned monomers may be used alone or in combination of two or more kinds, and furthermore, they may be used in combination with a known crosslinking agent. Suitable monomers include acrylic esters such as methyl acrylate and ethyl acrylate, methacrylic esters such as methyl methacrylate and ethyl methacrylate, and aromatic vinyl compounds such as styrene. Suitable examples of the crosslinking agent include methacrylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate, divinylbenzene, and the like. The polymerization initiator may be any initiator as long as it is soluble in the polymerizable vinyl monomer used, such as commonly used peroxides such as benzoyl peroxide, lauroyl peroxide, and diacetyl peroxide; Examples include azo compounds such as isobutyronitrile and azobisdimethylvaleronitrile.

The organic solvent used in this invention is one that is compatible with the polymerizable vinyl monomer and substantially incompatible with water. "Substantially incompatible with water" means insoluble or slightly soluble in water. Further, this organic solvent is used to adjust the viscosity of a mixture consisting of titania powder and a polymerizable vinyl monomer as described below. Therefore, it is preferable that the organic solvent has a viscosity of 30 centipoise (CP) or less at room temperature. It is preferable that the polymerizable vinyl monomer has an affinity with the polymerizable vinyl monomer. Examples of such organic solvents include acetic acid esters such as methyl acetate and ethyl acetate, hydrocarbons such as hexane and heptane, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and aromatic hydrocarbons such as benzene and toluene.

In the present invention, a slurry-like mixture is prepared from titania powder surface-treated with the lipophilic agent described above, a polymerizable vinyl monomer, an organic solvent added as necessary, and the like. When preparing this slurry, the amount of titania powder is usually 150 parts by weight per 100 parts by weight of the polymerizable vinyl monomer.
-1300 parts by weight, and from the viewpoint of the porosity and sphericity of the titania particles obtained, the range is 230 to 100 parts by weight.
It is preferably used in a range of 0 parts by weight. The lipophilic agent is determined by the minimum coverage area of the lipophilic agent and the specific surface area of the titania powder used, but is usually used in an amount of 0.2 to 3.0 parts by weight based on the titania powder. .

The organic solvent is used in an amount necessary to adjust the slurry mixture to a viscosity that can maintain spherical oil droplets during dispersion in an aqueous system as described below.

This amount is suitably used in the range of 1 to 200 parts by weight, and preferably in the range of 1 to 150 parts by weight, based on 100 parts by weight of the polymerizable vinyl monomer. If the above amount is 200 parts by weight or more, it is not preferable because it becomes difficult to obtain substantial strength of the polymer that binds the titania powder together.

In addition, the polymerization initiator is 0.1 to 2 of the polymerizable vinyl monomer.
．． It is preferable to use it in a range of 0% by weight. The above-mentioned slurry-like mixture is prepared into a uniform slurry by a mechanical method similar to the above-mentioned surface treatment.

In this invention, the slurry mixture prepared as described above is dispersed in an aqueous system and subjected to polymerization conditions for the polymerizable vinyl monomer in the mixture. The dispersion is accomplished by mechanical methods similar to those described above. At this time, the dispersion conditions are set so that the oil droplets are dispersed in a size that yields resin-coated titania spheres having a particle size range described below. The above polymerization is achieved by adjusting the polymerization according to the type of polymerizable vinyl monomer used, but ordinary suspension polymerization conditions can be applied as they are.

Through the above dispersion and polymerization, spherical resin-coated titania, which is an aggregate of titania powder coated and composited with a resin made of a polymer of a polymerizable vinyl monomer in an aqueous system, has a particle size of 1 μm to 1 jlj+. A sphere is obtained. The titania spheres are dried in a conventional manner. Among these, it is more preferable to select and use spheres with a particle size of 15 um to 50 um from the viewpoint of mechanical strength of the sintered body.

In this invention, the resin-coated porous titania sphere obtained as described above is pressure-molded into a predetermined shape. Pressurizing conditions at this time vary depending on the size of the resin-coated porous titania sphere used, but a pressure sufficient to maintain the desired molded shape is applied.

The aggregate of resin-coated titania spheres held in the desired shape by the pressure molding is then subjected to heat treatment. This heat treatment is carried out under conditions in which the resin of the titania spheres is smoothly removed without being carbonized, and the titania powders in the titania spheres are fused together, that is, the porous titania spheres constituting the aggregate are It is carried out under conditions that convert it into substantially non-porous titania spheres. The heating temperature in this heat treatment is set to about 1150 to 1550°C. If the temperature is below 1150°C, the density of the sintered body is too low and it is not suitable, and if it exceeds 1550°C, not only the titania spheres but also the titania spheres will fuse together, making it impossible to secure the desired porosity of the sintered body, which is undesirable. .

A particularly preferred heating temperature is 1250 to 1400°C.

However, the temperature raised to the above heating temperature is 1000°C.
It may take a long time (for example, 5 hours) to raise the temperature to
This is necessary to avoid carbonization of the resin. On the other hand, the heating and holding time is usually about 1 to 6 hours.

Through such treatment, a porous titania sintered body having a density of 2.59/cm' or more can be obtained. Such a porous titania sintered body is a non-porous titania sphere (usually 1 to
It is made of a porous body in which 50μ-1 (preferably 15 to 50μ11) are aggregated and integrated, and has a uniform pore distribution and excellent mechanical strength.

The porosity of the pores and the density of the sintered body can be easily controlled within a range that does not impair the above characteristics by adjusting the titania powder content, the particle size of the titania spheres, etc.

(E) Effect According to the present invention, in a mixture consisting of titania powder surface-treated with a lipophilic agent, a polymerizable vinyl monomer, and an organic solvent added as necessary, titania powder A thin layer of polymerizable vinyl monomer is formed on the treated surface. When the mixture in this state is dispersed as oil droplets in an aqueous system, the oil droplets are held in a spherical shape, and in this state, the polymerizable vinyl monomer in each oil droplet is polymerized, resulting in titania powder. is composited and coated with a polymer, and the titania powders are bonded together by the polymer at the contact points of the powders, and as a result, porous and spherical resin-coated titania spheres are obtained. Become.

The resin-coated porous titania spheres are then pressure-molded into a predetermined shape and aggregated, and then subjected to heat treatment, where the coating resin is incinerated and removed, and titania powder aggregated into a spherical shape is formed within one sphere. The bodies are closely fused together to form a non-porous sintered sphere, and these non-porous sintered spheres are fused together at the contact area of the spheres to obtain a porous titania sintered body. Become.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited thereby.

(f) Example [Preparation of resin composite titanium dioxide spherical particles] Example 1 In a 2Q beaker, 279 g of methyl methacrylate, Nran coupling agent [γ-methacryloxypropyltrimethoxynran, 5Z-603 manufactured by Toshin Ricoh Co., Ltd.]
0] 21.09, azobisisobutyronitrile 0.6
After adding 09 and dissolving it, titanium dioxide (rutile type, particle size 0.2 μm, JR-60OA manufactured by Teikoku Kako Co., Ltd.) 7
00g and heated to 200O using a stirrer equipped with propeller blades.
The surface was treated for 2 hours at rpm.

5g autoclave metathesized magnesium birophosphate 6
Add 9 to 2.6 of water containing 09 and 2.69 of sodium dodenlebenzenesulfonate, then add the above slurry to emulsify, replace with nitrogen, set the stirring speed to 50 rpm, and polymerize at 60 ° C. did. After the polymerization was completed, the mixture was cooled to room temperature, the dispersant was decomposed with hydrochloric acid, and then separated by filtration. When the obtained particles were observed with a scanning electron microscope (SEM), they were found to be spherical particles with a center diameter of approximately 8 μm, and were coated with polymethyl methacrylate (PMMA) resin to form monotitanium dioxide spherical particles. Ta.

Example 2 21! Methyl methacrylate 2799, Nran coupling agent [γ-methacryloquine propyltrimethoxysilane, Toshinricorn Co., Ltd. 5Z-60] were placed in a beaker.
30] 21.09, azobisisobutyronitrile 0.
After adding 609 and dissolving it, add titanium dioxide (rutile type, particle size 0.2 μm, Jl'l-600A manufactured by Teikoku Kako Co., Ltd.)
Add 7009 and mix with a stirrer equipped with propeller blades.
The surface was treated at 0 rpm for 2 hours.

Put 2.6 kg of water containing 0 g of metathesized magnesium pyrophosphate and 269 g of sodium dodenlebenzene sulfonate into a 5 g autoclave, then add the above slurry to emulsify it, replace the air with nitrogen, set the stirring speed to 40 Orpm, and heat at 60°C. Polymerized with After polymerization, cool to room temperature,
After the dispersant was decomposed with hydrochloric acid, it was separated by filtration. When the obtained particles were observed with a scanning electron microscope (SEM), they were spherical particles with a center diameter of about 20 μm, forming composite titanium dioxide spherical particles coated with polymethyl methacrylate (PMMA) resin. was.

Example 3 249g of methyl methacrylate and 30f of ethylene darecol dimethacrylate in a 212 beaker! , butyl acetate 300g, titanate coupling agent [his(dioctylpyrophosphate) oquinacetate titanate,
Blenact KR-138S (manufactured by Ajinomoto Co., Inc.) 210g
, 014 g of azobisisobutyronitrile was added and dissolved, and then titanium dioxide (rutile type, particle size 0.2 μm, JR-60OA manufactured by Teikoku Kako Co., Ltd.) 7009 was added and stirred at 200 rpm using a stirring device equipped with propeller blades. The surface was treated for 2 hours.

Magnesium pyrophosphate metathesis in 5Q autoclave 5
2.5 kg of water containing 0 g of sodium dodenlebenzene sulfonate and 075 g of sodium dodenlebenzene sulfonate were added thereto, and then the above slurry was added and emulsified. After purging with nitrogen, the stirring speed was set to 40 Orpm, and polymerization was carried out at 60°C. After the polymerization was completed, the mixture was cooled to room temperature, the dispersant was decomposed with hydrochloric acid, and then separated by filtration. When the obtained particles were observed using a scanning electron microscope (SEM), they were found to be spherical titanium dioxide spherical particles coated with polymethyl methacrylate (PMMA) resin and having a center diameter of approximately 50 μm.

[Preparation of sintered titanate dioxide spherical particles] Example 4 0.59 of the PMMA composite titanium dioxide spherical particles obtained as in Example 1 were weighed, and this was placed in a mold for molding [12
, 5xxφx27.5*xh]. Molding pressure I
Pressure molded at ton/am' for 15 seconds, with an apparent density of 1
．． A molded article of 879/cI113 was obtained. Next, the above P
Five MMA composite titanium dioxide spherical particle molded bodies were stacked and placed in an electric furnace, and fired at 1300° C. for 3 hours to obtain a sintered body. The apparent density of this sintered body is 3.819/c+a
”And attu f2.

In addition, when observing this sintered body with a scanning electron microscope (SEM), it was observed that the sintered body was composed of titanium dioxide spherical particles that had lost their original shape as shown in Figure 1. It was done.

Example 5 0.59 of the PMMA composite titanium dioxide spherical particles obtained as in Example 2 were weighed and placed in a mold for molding [12
, 5xyφX 27.5■h. Molding pressure l
Pressure molded at ton/cm' for 15 seconds, with an apparent density of 1
A molded article having a particle size of 849/cm3 was obtained. Then, the above PMMA
Five composite titanium dioxide spherical particle molded bodies were stacked and placed in an electric furnace, and fired at 1300° C. for 3 hours to obtain a sintered body. The apparent density of this sintered body was 3.019/cm3.

Furthermore, when this sintered body was observed with a scanning electron microscope (SEM), as shown in Figure 2, the titanium dioxide spherical particles had shrunk by approximately 22% while maintaining their original shape, forming a T2 sintered body. It was observed that 'Example 6 0.5 g of PMMA composite titanium dioxide spherical particles obtained as in Example 3 was weighed and placed in a mold for molding [1].
Fill 2,5xxφX27.5zxh and T2. Pressure molding was carried out for 15 seconds at a molding pressure of 1 ton/cm' to obtain one molded product with an apparent density of 1929/cm3. Next, the above P
Five MMA composite titanium dioxide spherical particle molded bodies were stacked and placed in an electric furnace, and fired at 1300° C. for 3 hours to obtain a sintered body. The apparent density of this sintered body is 3.20 g/am3
There was.

Furthermore, when this sintered body was observed using a scanning electron microscope (SEM), it was found that the sintered body had shrunk by approximately 20% while maintaining the original shape of the titanium dioxide spherical particles, as shown in Figure 3. observed.

Example 7 Each titania sintered body obtained in Examples 4.5 and 6 was subjected to JI
SR-1601 was then subjected to a three-point bending strength test to evaluate its mechanical strength. The results are shown in the table below.

Thus, the titania sintered bodies of Examples 4 to 6 had excellent mechanical strength.

(g) Effects of the invention The porous titania sintered body of this invention is a collection and integration of non-porous titania spheres, and has both a uniform pore distribution and excellent mechanical strength. . According to the manufacturing method of the present invention, such a porous titania sintered body can be efficiently manufactured, and its porosity and mechanical strength can be easily controlled with good reproducibility.

Therefore, according to the present invention, a porous ceramic material with practical strength that can be used in many application fields as a highly functional material such as industrial medical materials, filters, cosmetics, etc., as well as sensor elements, catalysts, and fire-resistant materials, etc. Is it possible to provide materials easily?

[Brief explanation of the drawing]

1 to 3 are enlarged photographs showing the particles and pore structures of porous titania sintered bodies obtained in Examples 4 to 6 of the present invention, respectively. , Regitogu* 9C;

Claims (1)

[Claims] 1. A porous titania sintered body formed by aggregating and sintering non-porous titania spheres. 2. The porous titania sintered body according to claim 1, which has a density of 2.5 g/cm^3 or more. 3. Titania powder surface-treated with a lipophilic agent, a polymerizable vinyl monomer, and an organic solvent that is compatible with the above monomer and is substantially incompatible with water, which is added as necessary. A mixture consisting of the above is dispersed in an aqueous system and the monomers are polymerized to obtain porous titania spheres consisting of aggregates of resin-coated titania powder, and then the resin-coated porous spheres are aggregated and processed. A porous titania sintered body characterized in that the porous titania sintered body according to claim 1 is obtained by press-forming and then heating and sintering the porous titania spheres at a temperature that allows the porous titania spheres to become non-porous. Method for producing solids.