JPH05238848A - Ceramic porous material - Google Patents

Abstract

PURPOSE:To make it possible to preferably use a ceramic porous material to a grease filter for kitchen, a support for catalyst, an air permeable heat- insulating material, a filtering agent for melted metal, because the above ceramic porous material is reduced in clogging and has low pressure loss, large strength and excellent chemical resistance. CONSTITUTION:The objective ceramic porous material is obtained by immersing a synthetic resin foam with a three-dimensional network skeleton structure having internally communicating space into ceramic slurry to attach a ceramic to the synthetic resin foam and drying and burning the foam. The ceramic porous material is characterized in that the ceramic component of the ceramic porous material contains 75-90wt.% alumina, 1-10wt.% oxide having eutectic point at <= burning temperature with the alumina and 0-15wt.% clay and 40-90wt.% electromelting alumina is contained in alumina.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic porous body having a low pressure loss, which is suitably used as a grease filter for kitchens, a catalyst carrier, a gas permeable heat insulating material, a molten metal filtering material and the like.

[0002]

2. Description of the Related Art Conventionally, a synthetic resin foam having a three-dimensional network skeleton structure having an internal communication space, for example, a soft polyurethane foam without a cell membrane, is immersed in a ceramic slurry to adhere the ceramic to the skeleton of the polyurethane foam. A ceramic porous body having a three-dimensional network skeleton obtained by drying and firing is known.

This ceramic porous body has features such as low bulk specific gravity, high heat resistance, inertness, and low ventilation resistance, that is, low pressure loss. Therefore, it is a grease filter for kitchen, catalyst carrier, and breathable heat insulating material. Although it is used as a molten metal filter material and the like, it is required that the pressure loss be as low as possible when used in these applications.

Conventionally, in order to reduce the pressure loss, the degree of adhesion of the ceramic slurry to the polyurethane foam has been reduced to almost eliminate clogging, but on the other hand, the apparent specific gravity is reduced, which causes a problem in strength. was there.

In addition, in terms of formulation, a method is adopted in which various organic surfactants, deflocculants, etc. are added to the ceramic slurry to adjust the sludge characteristics. According to this method, the skeleton Is thicker and stronger, but there is a problem that it causes some clogging and the pressure loss is not sufficiently reduced. In addition, since the ceramic raw material soil contains many organic components that are inflammable and disappear, the resulting ceramic porous body has many pores and has a porous structure. Therefore, for example, when used in a kitchen grease filter that collects oil mist in exhaust gas, the oil mist penetrates into the skeleton of the ceramic porous body and retains oil, which is a performance item of the grease filter. When the grease filter surface is exposed to a flame, the oil retained in the skeleton may cause flame propagation. Further, since it has a porous skeleton, there is a problem in strength.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a ceramic porous body having a three-dimensional network skeleton having a large porosity, a large strength and a low pressure loss. And

[0007]

Means for Solving the Problems and Actions The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, the synthetic resin foam having a three-dimensional net-like skeleton structure having an internal communication space was dipped in a ceramic slurry to obtain the above-mentioned material. When a ceramic is adhered to a synthetic resin foam, dried and fired to form a ceramic porous body having a three-dimensional network skeleton structure, the ceramic component of the ceramic porous body is alumina containing fused alumina and this alumina. It has been found that it is effective to use an oxide having an eutectic point below the firing temperature (hereinafter referred to as an alumina eutectic oxide).

That is, a part of normal alumina is converted to fused alumina, which is 40 to 90% by weight of the total alumina, and more preferably 5%.
A ceramic slurry is prepared by substituting 0 to 80% by weight, and by including 75 to 90% by weight of alumina including this fused alumina and 1 to 10% by weight of alumina eutectic oxide. In this case, the slurry characteristics are improved without using a large amount of various organic binders and surfactants, the ceramic is uniformly adhered to the skeleton of the synthetic resin foam, and a ceramic porous body free of clogging is obtained, and the firing is performed. It was found that the ceramics obtained in this way became dense, and they act synergistically to obtain a ceramic porous body having a three-dimensional network skeleton having a large porosity, a large strength and a low pressure loss.

At this time, clay may be blended in order to increase the stability of the ceramic slurry. However, if too much clay is present, the bending strength of the ceramic porous body will decrease the strength retention rate under alkaline conditions, so that the clay content is 0-. The inventors have found that it is necessary to contain 15% by weight, and have completed the present invention.

Therefore, the present invention is obtained by immersing a synthetic resin foam having a three-dimensional net-like skeleton structure having internal communication spaces in a ceramic slurry to adhere the ceramic to the synthetic resin foam, and then drying and firing. In the ceramic porous body having a three-dimensional network structure, the ceramic component of the ceramic porous body is 75 to 90% by weight of alumina, 1 to 10% by weight of oxide having an eutectic point with alumina at a firing temperature or lower, and 0 to clay. 15% by weight, and 40% to 90% by weight of fused alumina in alumina.

The present invention will be described in more detail below. As described above, the ceramic porous body of the present invention is made of a synthetic resin foam having a three-dimensional network skeleton structure having an internal communication space as a base material. ..

As such a synthetic resin foam, any one can be used as long as it has a three-dimensional network skeleton structure having an internal communication space, but a flexible polyurethane foam, particularly a flexible polyurethane foam without a cell membrane is suitable. Can be used. As the polyurethane foam having no cell membrane, those having the cell membrane removed by control at the time of foaming or those having the cell membrane removed by alkali treatment, heat treatment, hydraulic treatment, etc. can be used. The physical properties can be selected according to the application.

The ceramic porous body of the present invention is obtained by immersing the above-mentioned synthetic resin foam in a ceramic slurry, adhering the ceramic slurry to the synthetic resin foam, and then drying,
It is obtained by firing and thermally decomposing or incinerating the synthetic resin foam, but in the present invention, the ceramic component of the slurry contains alumina and an alumina eutectic oxide, and as a part of alumina, It is characterized by using fused alumina.

In this case, alumina has a strong chemical resistance because it is neutral, and by using alumina as a main component, for example, when it is used as a grease filter for the kitchen, alkali is used to remove oil adhering to the surface. Although cleaning with acid or acid is performed, resistance to such cleaning is improved.

Further, a part of the alumina is placed on the fused alumina.
By replacing it, a large amount of surfactant or peptizer is used.
Slurry properties are improved without using and low pressure without clogging
A ceramic porous body having a force loss is obtained. Immediately
Then, with ordinary alumina alone, the rotation speed measured by the B-type viscometer
Large thixotropic index of viscosity ratio measured by changing
When removing excess slurry, the skeleton of synthetic resin foam
As the slurry does not adhere evenly to the
The remaining pressure loss is high. On the other hand, al
By replacing a part of the mina with fused alumina, particles
The interaction between them is reduced, which results in thixotropic fingers
The number becomes smaller and the skeletons are evenly attached, causing clogging.
It is presumed that it will be difficult to strain. Thixot like this
There is a correlation between the lopy index and clogging, and it is too small
Also, clogging easily occurs, and the thixotropy index (B
Type viscometer rotor No. Measured at 6 and 12 rpm using 4
Η_{6 rpm}/ η_{12 rpm}Ratio, the same below) is 1.2 to 2
Is preferred. To get such a thixotropic index
Therefore, the proportion of fused alumina is 40 to 90% of the total alumina.
(Wt%, same below), but if it exceeds 80%, it will settle
Therefore, the preferable range is 50 to 80%,
The preferable range is 60 to 75%.

The remaining alumina is normal alumina,
For example, Bayer method alumina or the like is used.

The total amount of alumina including the fused alumina is 75 to 90% with respect to the total ceramic components.

The alumina eutectic oxide is for promoting the sintering of the alumina particles by having a eutectic point with alumina, and this composition makes the skeleton surface of the ceramic porous body dense by sintering. The number of pores can be reduced, and the strength for practical use can be provided.

Examples of the alumina eutectic oxide include alkali metal oxides such as lithium oxide, sodium oxide and potassium oxide; alkaline earth metal oxides such as calcium oxide. One of these is used alone. Or 2
One or more species can be used in combination. Alternatively, it can be eutecticized by forming three components using silicon oxide, and examples thereof include silicon oxide / calcium oxide / alumina and silicon oxide / lithium oxide / alumina.

The content of the alumina eutectic oxide is 1 to 10%, preferably 3 to 7%, based on all the ceramic components. If the compounding amount is less than 1 part, the compounding effect is not obtained, and 10
If it exceeds%, the dimensional stability due to firing is lacking.

In addition to the above-described alumina (including fused alumina) and alumina eutectic oxide, the ceramic slurry according to the present invention may be mixed with clay to increase the stability of the ceramic slurry. As this clay, for example, Kibushi clay, frog clay can be used. Further, the blending amount is preferably 0 to 15% with respect to all the ceramic components. If the content is more than 15%, the thixotropy index changes and causes clogging.

In addition, the thixotropy can be adjusted by adding a binder such as polyvinyl alcohol or carboxymethyl cellulose to the ceramic slurry, if necessary.

The viscosity of the ceramic slurry can be adjusted by adjusting the amount of water added depending on the size of the cell of the intended ceramic porous body.

Next, a synthetic resin foam having a three-dimensional net-like skeleton structure is immersed in the above-mentioned ceramic slurry to remove excess sludge, dried and fired at a temperature of about 1250 to 1450 ° C. in a firing furnace. It is possible to obtain a ceramic porous body having a three-dimensional network skeleton structure having an internal communication space having a cell structure corresponding to a synthetic resin foam.

[0025]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Buyer method alumina (AL1 manufactured by Showa Denko KK
60SG4) and fused alumina (LA manufactured by Taiheiyo Random Co., Ltd.)
800) and the ceramic raw material soil 100 shown in Table 1
4 parts by weight of polyvinyl alcohol and an appropriate amount of water were added to parts by weight to prepare a highly viscous ceramic slurry (thixotropic index 1.2 to 1.8).

This slurry has 9 cells per inch.
A piece of flexible polyurethane foam having a three-dimensional network skeleton structure without a cell membrane having a shape of 50 cm × 25 cm × 2.5 cm was immersed. Excessive slurry was removed by a roll, sufficiently dried, and then fired at 1300 ° C. for 10 minutes to obtain a ceramic porous body.

A rectangular parallelepiped having a side of 5 cm was cut out from this fired product, and the pressure loss was measured at a tube diameter of 39 mm and a wind speed of 10 m / s. Also, from the baked product, 15 cm × 3.5 cm × 2.
A 5 cm rectangular parallelepiped was cut out and the bending strength was measured at a span of 12 cm and a crosshead speed of 1 cm / min. Further, a plate body of 5 cm × 14 cm × 2.5 cm was cut out from the fired product and immersed in a 10% NaOH solution at 60 ° C. for 120 hours, and then the bending strength was measured to measure the retention rate with respect to the bending strength before immersion. The results are also shown in Table 1.

[0029]

[Table 1]

[0030]

As described above, the ceramic porous body of the present invention has low pressure loss with little clogging, high strength, and excellent chemical resistance. Therefore, the grease filter for the kitchen, the catalyst carrier, and the ventilation are provided. It can be suitably used as a heat insulating material, a molten metal filter, and the like.

Claims (1)

[Claims] 1. A three-dimensional network obtained by immersing a synthetic resin foam having a three-dimensional net-like skeleton structure having an internal communication space in a ceramic slurry to adhere the ceramic to the synthetic resin foam, and then drying and firing. In the ceramic porous body having a skeletal structure, the ceramic component of the ceramic porous body is 75 to 90% by weight of alumina, 1 to 10% by weight of oxide having an eutectic point with alumina at a firing temperature or lower, and 0 to clay.
15% by weight, and the fused alumina contains 40 to 90% by weight of fused alumina in the alumina.