JP2848689B2 - Ceramic porous body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ceramic porous body suitable for use in filters, catalyst carriers, bioreactors, lightweight refractories, and the like.

(Prior Art) Porous ceramic fired bodies having continuous air holes are useful for filters for molten metals, exhaust gas filters, liquid filters, catalyst carriers, bioreactors, lightweight refractories, etc., and many of them have already been put to practical use.

The porous body used in these applications has a continuous resistance to passing gas or liquid, in other words, a pore having a porosity of 60% or more to reduce pressure loss. To prevent this, characteristics such as having a bending strength of 10 kg / cm ² or more are required.

Conventionally, these porous bodies are made of alumina, zirconia,
Using a cordierite, aluminum titanate, etc. as a ceramic raw material, fill the voids of the urethane foam with a slurry in which the ceramic raw material powder is dispersed, and then fire and bind the foamed synthetic resin spherical material. It has been manufactured by a method in which a slurry in which raw material powder is dispersed is filled and then fired. However, when using these ceramic raw materials, a high-strength porous body could not be obtained unless firing at a temperature of 1350 ° C. or higher. When the firing temperature is 1350 ° C. or higher, expensive equipment having high heat resistance is required, and the energy consumption cost required for firing is enormous, resulting in a high product cost.

(Problems to be Solved by the Invention) The inventor of the present invention has conducted intensive studies in view of the problems of the existing ceramic porous body, and as a result, by using specific ceramic raw materials, It has been found that a ceramic porous body having physical properties can be obtained, and the present invention has been completed.

An object of the present invention is to provide a high-strength ceramic porous body having heat resistance of about 1000 ° C. Another object of the present invention is to provide an inexpensive porous ceramic body that can be fired at a relatively low temperature. Still other objects and effects of the present invention will become apparent from the following description.

(Means for Solving the Problems) The object of the present invention is to provide a ceramic porous body made of a calcined product of alumina, cement and silica, which is 40 to 80% by weight.
Achieved by a ceramic porous body containing Al ₂ O ₃ , 30% by weight or less of SiO ₂ and 35% by weight or less of CaO, and the weight ratio of CaO to SiO ₂ is 0.5 to 2.1. Is done.

In the present invention, it is important to use a mixture of alumina, cement, and silica as a ceramic raw material.

Alumina is one of the most common ceramic raw materials, and stable quality is available at a low cost, and is therefore the most suitable base material of the present invention. The alumina applied to the present invention is not particularly limited, but calcined alumina obtained by calcining aluminum hydroxide, which is relatively easy to sinter, is preferable, and the average particle size is
When the thickness exceeds 10 μm, the reaction is delayed and the sintering becomes difficult.

Cement mainly serves as a supply source of CaO and SiO ₂ components, and is most suitable as a binder for obtaining the strength of the compact from the viewpoint of quality and price. The cement applied to the present invention is generally a cement made of Portland cement such as high-strength, ultra-high-strength, moderate heat, sulfate-resistant, low heat and white cement, blast furnace cement, silica cement and fly ash cement, and expanded cement. And special cements such as alumina cement. Of these, the most common and inexpensive ordinary Portland cement is preferred.

Further, silica reacts with alumina and cement to exhibit an effect as a flux, and has an effect of increasing the strength of the ceramic porous body even when fired at a low temperature. There are no particular limitations as the silica source to be applied to the present invention, it is preferably ground product of natural products in terms of price, as a main component such as SiO ₂ silica,
Pulverized silica sand and quartz, crushed porcelain limestone mainly composed of SiO ₂ and Al ₂ O ₃ , pulverized wollastonite mainly composed of CaO and SiO ₂ , or SiO ₂ , Al ₂ O ₃ and CaO Ground products of feldspars whose main component is

As described above, a mixture of alumina, cement and silica is used as a raw material of the ceramic porous body of the present invention, and the chemical composition in the mixture is specified as follows.

That is, Al ₂ O ₃ is 40 to 80% by weight, preferably 5 to 80% by weight.
0 to 70% by weight. If it exceeds 80% by weight, the amount of cement added as a raw material is limited, and a molded body cannot be obtained.
If it is less than 40% by weight, sufficient strength cannot be obtained even when firing at 1350 ° C.

SiO ₂ is at most 30% by weight, preferably at most 25% by weight. If it exceeds 30% by weight, sufficient strength cannot be obtained even when firing at 1350 ° C.

CaO is 35% by weight or less, preferably 30% by weight or less. If it exceeds 35% by weight, sufficient strength cannot be obtained even when firing at 1350 ° C.

Still more from 0.5 to 2.1 weight ratio of CaO with respect to SiO _2, preferably 0.6 to 1.7. The weight ratio of CaO to SiO ₂ is
Sufficient strength cannot be obtained even when calcined at 1350 ° C. even if it is less than 0.5 or more than 2.1.

In the present invention, 5% or less of impurities such as MgO, TiO ₂ , Fe ₂ O ₃ , FeO, K ₂ O, and Ka ₂ O originally contained in cement and silica do not disturb the object of the present invention. It may be included in the range.

The ceramic porous body of the present invention is obtained by dispersing a ceramic raw material powder containing alumina, cement and silica in water to prepare a slurry, filling a mold filled with the slurry with a synthetic resin foam, compressing and fixing the same. After sufficiently filling the gap between the synthetic resin foams with the slurry, the mixture is cured and fired.

The preparation of the slurry is carried out according to a conventional method. For example, a ceramic raw material powder is dispersed in water by a mixer, disper or the like to prepare a slurry. The amount of water is preferably 15 to 30% by weight with respect to the powder 100. If the amount of water is too large, the setting and hardening action due to the hydration reaction of the cement is delayed, and the productivity is lowered and the strength of the compact is also lowered. Tend to
If the amount of water is too small, the viscosity of the slurry increases, and it becomes difficult to sufficiently fill the gaps between the synthetic resin foams with the slurry. At this time, it is effective to add a water reducing agent for cement such as lignin sulfonate or oxycarboxylate or a high-performance water reducing agent for cement such as melamine sulfonate or naphthalene sulfonate.

The slurry prepared as described above is poured into a mold, filled with a pre-foamed synthetic resin foam such as polyethylene spheres or polystyrene spheres and capped, and then compressed by a hydraulic press or a hydraulic jack. By fixing the slurry, the gap between the synthetic resin foams is sufficiently filled. At this time, the pore diameter and porosity of the obtained ceramic porous body can be arbitrarily changed depending on the diameter of the synthetic resin foam and the amount of compression at the time of compression. The cement is hydrated by standing at room temperature or by heat treatment to obtain a molded body that can be handled by its setting and hardening action. By subjecting the obtained molded body to a treatment such as wet curing, steam curing or autoclave curing, the strength of the molded body can be improved. Most of the components in the molded product thus obtained are incorporated into the cement as water of crystallization, so that it can be fired without drying. Firing at 1000 ° C
It is preferably carried out at 〜1350 ° C.

(Effects of the Invention) According to the present invention, even if fired at a relatively low temperature of about 1000 ° C to 1350 ° C, a high-strength ceramic porous body having heat resistance of about 1000 ° C can be obtained inexpensively and easily. The industrial value is great.

 Hereinafter, the present invention will be described specifically with reference to examples.

EXAMPLES The raw materials of alumina, cement and silica having the chemical compositions shown in Table 1 below are mixed at appropriate times so as to have the composition ratios shown in Table 2, and the mixed powder is mixed with an appropriate amount of water and a water reducing agent for cement. The mixture was dispersed to prepare a slurry. Slurry 10
Inject 0cc into a 100 × 100 × 50mm iron container and pre-diameter 2mm
Was filled with 400 cc of expanded polystyrene balls, compressed 20% in the height direction with a hydraulic jack, fixed, left standing all day and night, and sufficiently cured to obtain a molded body. The obtained molded body was cut to prepare a 100 × 30 × 10 mm test piece, which was fired at 1320 ° C. to obtain a ceramic porous body.

The porosity of the ceramic porous body thus obtained is all
More than 70%.

Flexural strength 40mm span, crosshead speed 0.5mm / m
The three-point bending strength was measured in. Table 2 shows the measurement results.

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 38/00 303 C04B 38/06 C04B 33/13

Claims (1)

(57) [Claims] 1. A ceramic porous body comprising a calcined product of alumina, cement and silica, comprising 40 to 80% by weight of Al
_A porous ceramic body comprising ₂ O ₃ , 30% by weight or less of SiO ₂ and 35% by weight or less of CaO, and a weight ratio of CaO to SiO ₂ is 0.5 to 2.1.