JP2002114583A - Porous ceramic molded goods - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide porous ceramic molded goods whose transpiration performance is optionally adjusted for matching the kind of a transpiration device and the property of a liquid chemical, for example, and which are used suitably for a liquid sucking core of a suction type thermal transpiration device. SOLUTION: The porous ceramic molded goods are constituted of powder of a silica-based ceramic raw material as a principal component and have 5-30 volume % pipe-shaped pores having 3 or larger aspect ratio and 10-30 volume % almost square pores.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous ceramic molded product which is suitably used, for example, as a liquid absorption core of a wicking type heat evaporation device, and more particularly to a type of evaporation device and a property of a chemical solution. It relates to a device devised so that the transpiration performance can be arbitrarily adjusted.

[0002]

2. Description of the Related Art In recent years, for the purpose of insecticide and the like, a suction-type heating and evaporating apparatus in which a porous ceramic liquid absorbing core is immersed in a chemical and the upper part of the core is heated to evaporate the chemical is widely used.
The reason why porous ceramics are used as a liquid absorbent core is that
This is because there is almost no clogging due to dissolution of the substance constituting the absorbent core even with an aqueous chemical solution, and the mechanical strength can be maintained.

[0003] This kind of porous ceramics absorbent core is disclosed in, for example, Japanese Patent No. 2731789 and Japanese Patent Laid-Open No. 11-19 / 1999.
No. 6,747,674.

First, Japanese Patent No. 2731789 discloses that
It consists of inorganic powders such as alumina, silica, talc, mica, zirconia, diatomaceous earth, activated clay, wood powder, synthetic resin, organic substances such as starch and carboxymethylcellulose, and inorganic binders such as kaolin clay, bentonite and halloysite. After adding water to the mixture and kneading, molding,
A porous ceramic absorbent core obtained by drying and firing is disclosed. This porous ceramics liquid absorbent core has continuous pores formed by burning and burning of an organic substance in a firing process.

Japanese Patent Application Laid-Open No. 11-196747 discloses flammable powders such as graphite, carbon, coke, and wood powder, ceramic raw material powders such as alumina, silica, zirconia, talc, mica, kaolin clay, and phosphorus. Aluminum oxide, inorganic binders such as water glass, and a mixture of organic binders such as carboxymethyl cellulose, after adding water and kneading the mixture, molding, drying, and firing, a porous ceramic absorbent core is disclosed. I have. This porous ceramics absorbent core has continuous vents having an average diameter of 150 to 500 μm formed by burning and burning out the combustible powder in the firing process.

[0006]

In recent years, in a suction-type heating and evaporating apparatus, it has become popular to prepare various types of replacement days of a chemical solution container according to consumers' preference. In the case of chemicals, aqueous chemicals are widely used for 60 days in addition to 30 days. Along with this, the type of evaporator and the properties of the chemical have also changed.

[0007] In order for the porous ceramic liquid absorbent core to exhibit the vaporization performance suitable for the type of the vaporization apparatus and the properties of the chemical solution, it is extremely important that the water absorption rate and the porosity can be adjusted. In general, in a porous ceramics liquid absorbent core, a passage through which one unit of the active ingredient of the chemical solution evaporates as it is (mainly an index relating to water absorption) and a very fine passage through which only the solvent evaporates and evaporates (porosity) ), And if these two passages can be made properly, the water absorption and the porosity can be adjusted. However, in the conventional porous ceramics absorbent core, since there is no recognition about these two passages, the type of the compounding material, the compounding ratio, the firing conditions (temperature,
Time, etc.).
Therefore, many experiments and a great deal of time are required to find out suitable compounding materials and firing conditions, and there has been significant technical difficulty in achieving the desired transpiration performance.

The inventors of the present invention have conducted intensive studies in order to solve such problems of the prior art, and as a result, have found that a pipe-shaped pore having a specific aspect ratio and a substantially rectangular pore are formed. For example, it is possible to easily adjust the water absorption and porosity without having to set complicated conditions with a strong correlation such as the mixing ratio and firing conditions. It was found that the transpiration performance could be adjusted arbitrarily.

[0009]

That is, a porous ceramic molded product according to claim 1 of the present invention is a porous ceramic molded product composed mainly of siliceous ceramic raw material powder, Means that 5 to 30% by volume of pipe-shaped pores having an aspect ratio of 3 or more and 1
It is characterized by being provided with 0 to 30% by volume. Also, the porous ceramic molded product according to claim 2 is
It is characterized in that 5 to 25 parts by weight of barium titanate is blended with 100 parts by weight of the above-mentioned siliceous ceramic raw material powder. Further, the porous ceramic molded article according to claim 3 is characterized in that glaze is blended in an amount of 5 to 30 parts by weight with respect to 100 parts by weight of the siliceous ceramic raw material powder. Further, the porous ceramic molded article according to the fourth aspect is characterized in that a film-forming material is baked in the vicinity of the surface.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the siliceous ceramic raw material powder used in the present invention include clay, talc, and mica. Although any of them may be used, it is most preferable to use a combination of clay and mica. In this case, it is more preferable that the mixing ratio of the clay is 50% by weight or more.

This is for the following reasons. That is, when the mixing ratio of the clay is less than 50% by weight, the kneading operation and the forming operation using only water as the kneading liquid are extremely difficult, so that a large amount of the organic binder (carboxymethylcellulose, polyvinyl alcohol, etc.) Must be blended. However, eccentricity, undulations, cracks, etc. are liable to occur in molded products manufactured with such compounding materials, so strict shape control over a long time is required in the drying process and firing process, and productivity is greatly reduced. Resulting in. This is a major factor in increasing the manufacturing cost. Therefore, as the siliceous ceramic raw material powder, those having a mixing ratio of clay of 50% by weight or more are preferable.

However, when a large amount of clay is blended, there is a concern that shrinkage due to sintering will increase and porosity will decrease. Therefore, in that case, shrinkage may be suppressed by adding a predetermined amount of barium titanate to prevent a decrease in porosity. Barium titanate having an average particle diameter of 1 to 50 μm is preferably used. The amount is not particularly limited, but is preferably 5 to 25 parts by weight with respect to 100 parts by weight of the above siliceous ceramic raw material powder. If the amount is less than 5 parts by weight, the effect of suppressing shrinkage may not be sufficiently exhibited, and the porosity may be reduced. On the other hand, if the amount exceeds 25 parts by weight, the effect of suppressing shrinkage may be saturated, and the firing may be insufficient, resulting in a decrease in mechanical strength.

The most significant feature of the porous ceramic molded article of the present invention is that it has two pores having another function of a pipe-shaped pore having an aspect ratio of 3 or more and a substantially rectangular pore. The pipe-shaped pores having an aspect ratio of 3 or more function as passages (mainly an index relating to water absorption) through which one unit of the active ingredient of the chemical solution evaporates as it is. In addition, the substantially rectangular pores function as passages (indicators for porosity) in which only the solvent evaporates and evaporates, and also contributes to lowering the thermal conductivity of the porous ceramic molded article. FIG. 2 is a cross-sectional view (a photograph as a substitute for a drawing) showing the structure of the pipe-shaped pores and the substantially rectangular pores. These pores can be formed by mixing a predetermined organic foaming substance with the above-mentioned siliceous ceramic raw material powder, and burning and burning them in a firing process.

Since the porous ceramic molded article of the present invention has these two pores, the water absorption rate can be reduced without the need for setting complicated conditions (compounding ratio, firing conditions) having a strong correlation as in the prior art. And porosity can be easily adjusted. Therefore, the transpiration performance can be arbitrarily adjusted according to the type of the transpiration device and the properties of the chemical solution.

Examples of the organic foaming material for forming pipe-shaped pores having an aspect ratio of 3 or more include natural fibers such as cotton and hemp, nylon, polyvinyl alcohol, polyethylene, polyester, polyurethane, polypropylene, and aramid. Organic short fibers such as fibers, semi-synthetic fibers such as acetate, and regenerated fibers such as viscose rayon. Among these, nylon short fibers that are most suitable for foaming after kneading and firing are not soluble in water even if they are hydrophilic, and have elasticity for kneading. Since hydrophobic fibers tend to stick to each other and have poor dispersibility, kneading requires skill. It is preferable to use nylon short fibers having a thickness of 17 to 72 T (decitex) and a length of 0.7 to 2.2 mm.
The compounding amount may be appropriately selected within a range where the volume ratio of the pipe-shaped pores is 5 to 30% by volume. When the volume ratio of the pipe-shaped pores is less than 5%, the water absorption is reduced, and a sufficient volatilization amount cannot be obtained. On the other hand, if it exceeds 30% by volume, the volatilization amount will be too large, and the chemical solution will be exhausted earlier than a predetermined number of days.

Examples of the organic foaming substance for forming substantially rectangular pores include organic powders such as wood powder and various synthetic resin powders. Among them, nylon powder which is hydrophilic but does not dissolve in water is particularly preferable.
It is preferable to use nylon powder having an average particle diameter of 40 to 250 μm. The mixing amount may be appropriately selected within a range where the volume ratio of the substantially rectangular pores is 10 to 30% by volume. If the volume ratio of the substantially rectangular pores is less than 10%, the porosity decreases, and a sufficient volatilization amount cannot be obtained. On the other hand, if it exceeds 30% by volume, the mechanical strength will decrease.

In the present invention, the above-mentioned compounding materials are
After kneading by adding an appropriate amount of a kneading liquid appropriately selected from water, alcohol, an organic solvent, and the like, forming the mixture into a predetermined shape by a method such as an extrusion molding method, and then drying the mixture.
000-1300 ° C, more preferably 1150-12
By firing at 00 ° C., a porous ceramic molded product is manufactured. If the firing temperature is lower than 1000 ° C., the firing is insufficient and the mechanical strength is reduced. On the other hand, 130
If the temperature exceeds 0 ° C., the sintering proceeds excessively and the porosity decreases.

In the porous ceramic molded article of the present invention, the water absorption and the porosity can be adjusted by forming two pores within the above-mentioned specific volume ratio range. While keeping their volume ratio constant,
Water absorption and porosity can also be adjusted at finer levels. As one of the means, for example, it is conceivable to further add a glaze to the siliceous ceramic raw material powder. By blending the glaze, the water absorption can be significantly reduced after firing without significantly reducing the porosity. The amount is not particularly limited, but is preferably 5 to 3 parts by weight based on 100 parts by weight of the above siliceous ceramic raw material powder.
0 parts by weight. If the amount is less than 5 parts by weight, the effect of lowering the water absorption will not be sufficiently exhibited, and if the amount exceeds 30 parts by weight, the water absorption will be too low.

As another means, for example, it is conceivable to bake a film-forming material near the surface of the obtained porous ceramic molded product. By doing this, the "porosity" which is an index relating to a very fine passage in which only the solvent evaporates and evaporates without significantly reducing the "water absorption rate", which is an index relating to a passage in which one unit of the active ingredient of the chemical solution evaporates as it is, is not greatly reduced. Can be adjusted. As the film-forming material, general silicone resin, low melting point glass, and the like are preferable.

The porous ceramic molded article thus obtained is subjected to a wicking heating method in which chemicals such as various insecticides, bactericides, deodorants, and fragrances are heated and dispersed for the purpose of insecticide, sterilization, aroma and the like. It can be suitably used as a liquid absorption core of a transpiration device.

FIG. 1 shows an example of a suction-type heating and evaporating apparatus suitable for using the porous ceramic molded article according to the present invention. In FIG. 1, reference numeral 2 denotes a drug solution container containing a drug solution 4, which is detachably housed and held in the instrument body 1. A liquid absorbent core (porous ceramic molded product) 3 is mounted in the chemical liquid container 2, and an annular heating element 5 is disposed around the upper part of the liquid absorbent core 3, and electricity is supplied through a power cord 7. The heating element 5 heats the upper part of the liquid absorbing core 3 so that the chemical solution 4 sucked up by the capillary phenomenon evaporates from the top opening 6 provided in the upper part of the instrument body 1.

[0022]

Embodiments of the present invention will be described below. The details of the compounding materials used in this example are as shown in Table 2.

First, after the ingredients shown in Table 1 were sufficiently mixed, water was added as a kneading liquid and kneaded with a kneader. Next, the kneaded product was extruded into a round bar shape by a vacuum extruder having a nozzle having a diameter of 8.1 mmφ. The obtained round bar-shaped molded product was cut into a length of 80 mm, air-dried for 1 hour, and further dried with an infrared lamp for 15 minutes. Then, the rod-shaped molded product was placed in a firing furnace in a horizontal state and fired. In the firing, first, the solvent was removed at 450 ° C. for 2 hours, kept at 900 ° C. for 2 hours, and further kept at 1200 ° C. for 2 hours to lower the temperature. The rate of temperature rise / fall is 360 ° C. per hour, and the firing atmosphere is all in the air. still,
For Example 5, the obtained molded article was dipped in a silicone resin as a film-forming material, air-dried,
It was baked by heating at 150 ° C. for 15 minutes.

Here, among the porous ceramic molded articles thus obtained, the shrinkage ratios of Examples 1 to 4
When the water absorption and the porosity were measured, the results shown in Table 1 were obtained. Although not shown in Table 1, the water absorption of a conventional example (Japanese Patent Laid-Open No. 11-196747) is 4%.
The porosity was 3.9% and the porosity was 50.1%.

[0025]

[Table 1]

[0026]

[Table 2]

As is clear from Table 1, all of the examples according to the present embodiment depend on the volume ratio of pipe-shaped pores having an aspect ratio of 3 or more formed by organic short fibers.
The water absorption can be adjusted, and the porosity can be adjusted by the volume ratio of the substantially rectangular pores formed by the organic powder. These indicate that the correlation is thin and can be realized with high independence. Further, Example 4 in which a glaze was further blended shows that the water absorption can be significantly reduced without significantly reducing the porosity, and this can also be realized with high independence.

In the case of Example 5, the obtained porous ceramic molded article was mounted on a 60-day chemical liquid bottle (see chemical liquid container 2 in FIG. 1) containing a commercially available insecticide liquid, and heated by the manufacturer. It was incorporated into a transpiration device (see the apparatus main body 1 in FIG. 1) and the number of days of transpiration was measured. The number of samples was 10, and the energization time was 12 hours per day.

As a result, the maximum transpiration days were 64 days, the minimum was 59 days, and the average was 62 days. According to this, the water absorption rate of the conventional example (JP-A-11-196747) is 43.9.
% And porosity of 50.1%, but the same number of days of volatilization was obtained by baking the film-forming material. This indicates that even if there are variations in the characteristics of the structure, there is an action of flexibly and finely adjusting them. Therefore, when applied to variations in mass production lots at the time of manufacturing, the yield can be improved,
Economic efficiency can be improved.

[0030]

As described above in detail, according to the present invention, by forming a pipe-shaped pore having a specific aspect ratio and a substantially rectangular pore, the correlation of the mixing ratio, the firing conditions, and the like can be reduced. Without having to set strong and complicated conditions,
The water absorption and the porosity can be easily adjusted, and the pressure applied to the liquid absorbent core can be changed. Therefore, it is possible to arbitrarily adjust the evaporation performance such as the amount of evaporation and the evaporation distance in accordance with the type of evaporation device and the properties of the chemical solution. Since the porous ceramic molded article obtained in this manner exhibits stable evaporation performance for a long period of time, it is suitable as, for example, a liquid absorption core of a wicking heating evaporation apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a suction type heating and evaporating apparatus to which a porous ceramic molded article of the present invention can be applied.

FIG. 2 is a cross-sectional view (a photograph as a substitute for a drawing) showing the structure of pipe-shaped pores and substantially rectangular pores formed in the porous ceramic molded article of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Instrument main body 2 Chemical liquid container 3 Liquid absorption core 4 Chemical liquid 5 Heating element 6 Top opening 7 Power cord

Claims (4)

[Claims] 1. A porous ceramic molded article comprising a siliceous ceramic raw material powder as a main component,
The molded article has 5 pipe-shaped pores having an aspect ratio of 3 or more.
A porous ceramic molded article characterized by having approximately 30% by volume and approximately 30% by volume of substantially rectangular pores. 2. The porous ceramic molded article according to claim 1, wherein said siliceous ceramic raw material powder
A porous ceramic molded product comprising 5 to 25 parts by weight of barium titanate with respect to parts by weight. 3. The porous ceramic molded article according to claim 1, wherein glaze is mixed in an amount of 5 to 30 parts by weight with respect to 100 parts by weight of the siliceous ceramic raw material powder. Porous ceramic molded products. 4. The porous ceramic molded article according to claim 1, wherein a film-forming material is baked in the vicinity of the surface of the molded article. .