JPH02254106A - Production of inorganic cellular body - Google Patents

Abstract

PURPOSE:To produce the inorg. cellular body free of cracking and buldging by coating the skeleton of a cellular org. polymeric material with inorg. fine powder with the use of an adhesive and then heating the product to degrease the product. CONSTITUTION:The skeleton of a cellular org. polymeric material such as polyurethane foam and an org. three-dimensional fabric with inorg. fine powder with the use of an adhesive such as CMC. The inorg. fine powder is preferably composed of the grains in which the diameter of the >=80% of the grains is controlled to 1-50mu. One or more kinds of metallic powders or the mixture with nonmetals, iron oxide powder or its mixture with carbon powder, the mixture further added with alloy element powder, etc., are used as the inorg. fine powder. Ceramic fine powder can also be used. The coated inorg. fine powder is charged into an induction heating furnace, heated and degreased. In this case, the heating rate is controlled to 30-200 deg.C/min between the liquefaction starting temp. of the org. polymeric material and the liquefaction starting temp. plus 100 deg.C. The product of the inorg. cellular body is easily obtained in a short time without causing cracking and buldging.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a two-dimensional or three-dimensional inorganic porous body. Ceramic-based inorganic porous bodies are used, for example, as filters for removing non-metallic inclusions from molten metal, and metal-based inorganic porous bodies are used as catalyst carrier elements.

[Prior art] Fine inorganic powder is kneaded with, for example, an organic adhesive and applied to the skeleton of a porous organic polymer material such as urethane foam, and when this is heated, the skeleton of the organic polymer material decomposes or evaporates. The inorganic fine powder is removed by, for example, sintering to obtain an inorganic porous body.

FIG. 3 is a schematic diagram showing an example of a conventional heat treatment temperature in heating in the method of manufacturing this inorganic porous body. The organic polymer material is removed (degreased) between 1 and 2 in the figure, but if the temperature rise rate during this period is high, cracks and blisters occur frequently in the inorganic porous material, so for example, 1°C /hr~5
The temperature was raised extremely slowly at a temperature increase rate of 0°C/hr.

The period between 2 and 3 in the figure is an example of the temperature increase rate after degreasing, during which the inorganic fine powder is sintered or reduced and sintered. 4 in the figure is an example of this reduction period.

[Problems to be Solved by the Invention] As already mentioned, in the conventional method, the heating rate between 1 and 2 in FIG. 3 is extremely slow, so the heating time is long.
Therefore, productivity is low.

In Figure 3, the heat treatment between 1 and 2 and the heat treatment between 2 and 3 may be performed continuously in a continuous furnace or in separate furnaces, but the heat treatment between 1 and 2 is If it is too long, it is unfavorable in terms of equipment or process, whether in a continuous furnace or in a separate furnace.

According to the present invention, the inorganic porous material does not crack or blister, and the heat treatment between 1 and 2 in FIG. 3 can be performed in a short time. A method for producing an inorganic porous body is provided.

[Means and effects for solving the problem] The present invention involves coating the framework of a porous organic polymer material with inorganic fine powder using an adhesive, and then heating the powder to degrease the organic polymer material. This invention relates to a method for sintering inorganic fine powder.

In the present invention, the porous organic polymer material is, for example, a net formed of urethane foam or chemical fiber, or an organic three-dimensional fabric (
manufactured by Arisawa Seisakusho Co., Ltd.), etc.

In the present invention, inorganic fine powder is applied to the skeleton of these porous organic polymer materials. The inorganic fine powder is, for example, CMC.
It is applied to the skeleton of an organic polymer material using an aqueous solution such as phosphoric acid bond, water glass, or other suitable adhesive. Particle size is 5
Inorganic fine powder consisting of particles of 0 μm or less can be easily applied to the skeleton of an organic polymer material. However, particles with a particle size of 1 μm or less have small gaps between the particles when applied, making it difficult to dissipate gaseous decomposition products of the organic polymer material, which will be described later. The inorganic fine powder may be a metal powder such as iron powder or stainless steel powder, or it may be a mixed powder of two or more metals such as iron powder, metallic chromium powder, and ferronickel powder. Alternatively, it may be a mixed powder of metal powder and non-metal powder, such as iron powder mixed with carbon powder.

Further, the inorganic fine powder may be iron oxide powder or a mixed powder of iron oxide powder and carbon powder,
Alternatively, it may be a mixed powder in which alloying element powder such as metal chromium powder is added to iron oxide powder or a mixed powder of iron oxide powder and carbon powder.

For example, in the case of an inorganic fine powder made of a mixed powder of iron oxide powder and carbon powder, the iron oxide powder is reduced by the carbon powder during the heating process of sintering, which will be described later, and becomes an inorganic porous body with components equivalent to steel. However, the inorganic powder of the present invention also includes this mixed powder.

The inorganic fine powder of the present invention may also be a ceramic composition fine powder or mixed fine powder.

As the fine powder of ceramic composition, for example, AQ zO
Examples include fine powders such as Z + Zr2O3, mullite, SiC, and SiN, and mixed powders of these. Also, FeO and MnO are used as fine powder for ceramic ferrite porous bodies.

A fine powder having a ferrite composition mixed with ZnO, MgO, etc. may also be used.

As described later, in the present invention, the temperature increase rate from the liquefaction start temperature of the organic polymer material to the liquefaction start temperature +100°C is set to 3.
Even in the case of using a 0-b quality fine powder, heating at this temperature increase rate will not cause cracking or blistering in the inorganic porous body.

In the present invention, an organic polymer material coated with an inorganic fine powder is heated in order to remove the organic polymer material and sinter the inorganic fine powder. The temperature increase rate between +100° C. is 30 to b. The present inventors have studied the temperature increase rate in this heating and have arrived at the present invention. Figure 1-1 is a diagram showing an example of the results of this research.

Surface oxidized iron powder (C: 4, 5%, Sj,: 0.05
%, Mn: 0.35%.

Cr: 0, 50%, P: 0.01%, S: 0
．． 01%, 0near%) fine powder with an average particle size of 10μ is CM
Knead with an aqueous solution of C to make a slurry, which is then made into urethane foam (pore diameter: 3 mm, dimensions: ], 000 mm
100mm x 20mm, liquefaction start temperature = 250°
The skeleton of C) was applied to a thickness of about 1 mm by dipping method, and 10
The sample material was dried at 0°C.

In Figure 1, 5 is the liquefaction start temperature, and 6 is the liquefaction start temperature +100.
℃, 7 is the sintering start temperature, and 8 is the sintering end temperature.

Note that the dotted line 9 in the figure is the upper limit of the temperature increase rate in the conventional heating method.

The present inventors have determined that within a temperature increase rate of 250°C/min or less,
We investigated the effects of heating rates at various temperatures on cracking and blistering of sintered inorganic porous products.

In the first region of FIG. 1, a healthy inorganic porous material without cracks or blisters was obtained regardless of the temperature increase rate. Conventionally, the temperature in this region also rose slowly, but even if the temperature rise rate in this first region is high, there is no particular problem in the quality of the inorganic porous body after sintering. The reason for this is that unlike the IIIP rA and SIP methods, the manufacturing method of the present invention does not press and mold the inorganic fine powder, but rather coats it on urethane foam and molds it, so the bond between particles is loose. This is thought to be because there is a lot of room for thermal expansion to escape, and because the test material is porous, the test material is uniformly heated by the gas flow flowing through the through-holes of the porous material, resulting in small thermal stress.

In the second region of FIG. 1, the inorganic porous body is healthy without cracks or blisters when the temperature increase rate is extremely slow at 1° C./min or less, and after 30 b. However, at a temperature increase rate of more than 1° C./min to less than 30° C./min, cracks and blisters are observed in the inorganic porous body after sintering. Furthermore, if the temperature is increased at an extremely high rate of 201° C./min or more, the porous body will partially or completely disintegrate.

In the second region of FIG. 1, liquefaction and thermal decomposition of the skeleton of the organic polymer material occur, and gaseous thermal decomposition products escape through the gaps between the particles of the inorganic fine powder.

It is not always clear why cracks and blisters occur when the heating rate is 30°C/min or less, but when the heating rate is 30°C/min or less, liquefied organic polymers form inside the outer shell formed of fine inorganic powder. It is thought that cracks and blisters occur because the molecular material is trapped and pressurizes the outer shell. Also, it is not clear why cracks and blisters do not occur when the heating rate is 30°C/min or higher, but when the heating rate is 30°C/min or higher,
The gaseous pyrolysis products tend to dissipate through the gaps between the particles of the inorganic fine powder, so the pyrolyzed organic polymer material gradually dissipates and pressurizes the outer shell formed of the inorganic fine powder. No problem, no cracking or blistering.

The reason why a part of the porous body disintegrates at a heating rate of 201° C./min or more is considered to be because the organic polymer material is generated explosively.

In the third region of FIG. 1, O and C in the sample material react and iron oxide is reduced. However, in the third region, cracks and blisters do not occur regardless of whether the temperature increase rate is high or low. That is, even if the temperature rise rate in the second region is set at 30 to 30b, for example, even if the temperature is raised slowly in order to sufficiently perform degreasing and reduction of iron oxide, the product will not crack or blister. Therefore, the temperature in the third region can be raised under conditions suitable for degreasing and reducing iron oxide.

The reason why cracks and blisters are less likely to occur in the third region is that, as mentioned in the explanation of the first region, the inorganic fine powder of the present invention has loose bonds between particles and has many places for thermal expansion to escape, and also has through-holes. This is thought to be due to the fact that it is heated uniformly and has low thermal stress.

In the fourth region of FIG. 1, the inorganic fine powder is sintered. Fourth
Even in this area, cracks and blisters do not occur due to the rate of temperature rise. That is, by raising the temperature in the second region at a rate of 30 to 200° C./min, the temperature in the fourth region can be raised under conditions suitable for sintering.

The reason why cracks and blisters do not occur in the fourth area is believed to be the same as that described in the third area.

As described above, in the present invention, by performing this rapid heating rate from the liquefaction start temperature of the organic polymer material to the liquefaction start temperature +100°C, the inorganic porous material after sintering is Although it is possible to prevent cracking and blistering of the body, it is difficult to uniformly and rapidly raise the temperature of each skeleton of a porous organic polymer material coated with fine inorganic powder using conventional electrical heating type heat treatment furnaces or gas sintering. This is not easy with a type of heat treatment furnace.

The present inventors performed this rapid temperature increase using an induction heating furnace, and were able to achieve a rapid temperature increase with good controllability evenly over all skeletons.

[Example 1 Three-dimensional urethane foam (pore diameter: 1 mm, dimension: 100
mm x 100+nn+
The composition was applied to the urethane foam skeleton by a spray method using aluminum phosphate solution as an adhesive, and
After drying at 0°C for 30 minutes, high-speed heating at 100°C/min from room temperature to 350°C in the air in a 10KHz induction furnace, degreasing at 350°C for 15 minutes, and then at 150°C.
After sintering at 800°C for 3 hours with high-speed heating at a rate of 1/2 min, a healthy ceramic filter for filtration of molten iron was produced.

The conventional method took two days to manufacture, but now it can be manufactured in one hour.

[Example 2] Three-dimensional knitted fabric coated with epoxy resin (pore size:
15mm, '300mmX300+nmX20mm
Iron powder (C: 4.0%) obtained by wet-pulverizing granular pig iron to a temperature at which liquefaction starts: 100°C.

Si: 0.10%, Mn: 0.50%, Cr: 0.50
%, P: 0.01%, S: 0.005%, oxygen: 6.5
%) Powder composed of 90% of 5μ to 15μ was applied onto the skeleton of the three-dimensional knitted fabric by an impregnation method using a CMC aqueous solution as an adhesive, dried at 100°C for 60 minutes, and then heated with N2 in a 20KHz high-frequency induction furnace. 50℃ from room temperature to 200℃ in atmosphere
After high-speed heating for 1 minute at ℃, degreasing at 200℃ for 10 minutes, and self-reducing sintering at 1200℃ for about 60 minutes at a heating rate of 200℃/min, the result was a strong material that could be used as a composite material skeleton. A healthy bar body was obtained.

The manufacturing process, which previously took three days, can now be shortened to two hours.

(Example 3) A high frequency induction heating furnace consisting of two furnaces (degreasing furnace and sintering furnace) shown in FIG. :Heat up to 200℃ at 100℃/min, degrease for about 60 minutes, then move to a sintering furnace,
By continuously repeating heating to 1200° C. at 200° C./min and sintering for about 60 minutes, it was possible to continuously and economically manufacture barbed wire bodies.

[Effects of the Invention] According to the present invention, the heat treatment time can be significantly shortened in the production of inorganic porous bodies, and the occurrence of cracking and blistering in products made of inorganic porous bodies can be effectively prevented.

[Brief explanation of drawings]

FIG. 1 shows an example of the heat treatment temperature range and allowable temperature increase rate. FIG. 2 shows an example of the heat treatment apparatus used in the example. FIG. 3 shows an example of conventional heat treatment temperature. 5: Liquefaction start temperature, 6: Liquefaction start temperature +100°C, 7
: Sintering start temperature, 8: Sintering end temperature, 9: Temperature rise curve (conventional method), ■0: Material to be heat treated (organic polymer material coated with inorganic fine powder - inorganic porous body), 11: For degreasing High frequency furnace, 12: High frequency furnace for sintering, 13: Cooling chamber, 14:
N2 gas, 15: Conveyance direction of heat-treated material, 16: Seal cover

Claims (6)

[Claims] (1) When heating after applying an inorganic fine powder to the framework of a porous organic polymer material using an adhesive, the rate of temperature increase from the liquefaction start temperature of the organic polymer material to the liquefaction start temperature +100°C A method for producing an inorganic porous body, the method comprising degreasing at a rate of 30 to 200°C/min. (2) More than 80% of the inorganic fine powder has a particle size of 1 μm or more
Claim (1), which is an inorganic fine powder consisting of particles of 50μ
) The method for producing an inorganic porous body. (3) The method for producing an inorganic porous body according to claim (1) or (2), wherein the inorganic fine powder is a metal powder, a mixed powder of two or more metals, or a mixed powder of these and a nonmetal. (4) The inorganic fine powder according to claim (1) or (2), wherein the inorganic fine powder is an iron oxide powder, a mixed powder of iron oxide powder and carbon powder, or a mixed powder in which alloying element powder is added to these powders. Method for producing porous body. (5) The method for producing an inorganic porous body according to claim (1) or (2), wherein the inorganic fine powder is a ceramic composition fine powder or a mixed fine powder. (6) Claim (1) characterized in that the device for heating the organic polymer material at a heating rate of 30 to 200°C/min from the liquefaction start temperature to the liquefaction start temperature +100°C is an induction heating furnace. The method for producing an inorganic porous body according to 1) or (2) or (3) or (4) or (5).