JPS62128983A - Porous formed body and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a porous molded body whose skeleton is composed of two or more types of inorganic substances that have been integrally molded, and which has not been possible with a single material until now. The present invention relates to a porous molded body that combines the characteristics of various materials that were not available before, and a method for producing the same.

[Background of the Invention] Conventionally, as porous molded bodies, those described in the following (1) and (2) are known.

■ A viscoelastic material made of an inorganic substance or synthetic resin is extruded in a linear manner through a number of nozzle holes provided in an extrusion die and lowered in a vertical direction, and the extruded linear extrudate is stacked on the upper surface and the exit end of the extrusion die. A porous body obtained by stacking linear extrudates while keeping a substantially constant distance from each other while spirally winding them onto the top surface of the stack, which consists of a large number of linear extrudates made of an inorganic substance or synthetic resin. are spirally wound and laminated, and the spirally wound laminates are joined or intertwined with each other on adjacent surfaces (Japanese Patent Laid-Open No. 58-11
No. 6134).

■ A slurry-like inorganic substance is attached to the surface of polyurethane foam, then dried and fired! (Ceramic porous material (ceramic foam) has a shape and structure that is almost similar to polyurethane foam.

The porous materials mentioned above (■) and (■) each have excellent characteristics and are used as various filter materials, but depending on the atmosphere and environment in which they are applied, the material itself may become a problem, and the scope of application is naturally limited. It is.

The environment in which it is applied is usually a combination of adverse conditions.For example, it is often used in a combination of high temperature and alkaline atmosphere, high temperature and iron oxide atmosphere, or high temperature and strong oxidizing atmosphere. Currently, there is no single material that is durable even in such complex environments.

More specifically, the present inventor has developed a gas-permeable solid material suitable for an energy-saving method in which thermal energy in exhaust gas from a heating furnace or the like is converted into radiant heat using a simple gas-permeable solid material, and then recovered and converted to the heating side. Ceramic porous body)
No. 353), but it has been found that it is difficult to apply the porous bodies made of a single material to the above-mentioned complex atmosphere.

In general, breathable solids are held and fixed in the above-mentioned atmosphere with both ends supported, so one factor is their bending strength under high temperatures, and the other is that they can be raised or lowered depending on the operating pattern of the furnace. Two properties are basically required: thermal shock resistance associated with temperature.

Ceramics are generally superior to metals in terms of high-temperature strength, but the results of tests conducted by the present inventor show that even mullite or alumina, which are typical oxide-based materials, exhibit sway due to their own weight at high temperatures exceeding 1400°C. This has resulted in unsatisfactory results such as cracking and falling due to thermal shock.

On the other hand, S
Although it has been confirmed that iC satisfies this required performance, at high temperatures and in an alkali, iron oxide, or strong oxidizing atmosphere, SiC easily starts to react to form 5i02, and loses its original high-temperature strength. As a means to easily satisfy both conditions, for example, SiC
A possible solution is to coat the base product with an oxide ceramic, but as a result of various tests conducted by the present inventor, it was difficult to suppress the reaction of SiC due to the following points.

In other words, the only way to uniformly coat the skeleton of a porous body with intricate pores is by dipping the porous body into a ceramic slurry, and the coating obtained by this method is The layer can only be porous due to the composition of the slurry.
Further, the coating thickness is limited to several tens of micrometers and the film thickness is also non-uniform.

It may be possible with this technology to delay the oxidation reaction of SiC even slightly, but if there is even one point where the surrounding reactive gas permeates, the reaction from there will easily spread to other areas, or the reaction will be delayed. Even if the expansion of the porous material is delayed, the porous body itself will be destroyed as the location will become a starting point for cracking due to thermal shock or the like.

[Object of the invention] The object of the present invention is to provide a ceramic porous molded body that is sufficiently durable even under high temperature and adverse environments, which could not be achieved with the conventional techniques as described above, and a method for manufacturing the same. .

[Summary of the Invention] The first invention according to the present application is a porous molded body constructed by integrally molding a large number of linear objects made of an inorganic substance, which includes a center portion and an outer periphery of the linear objects. This porous molded body is characterized by having different parts made of different materials.

A second invention according to the present application is to linearly extrude a viscoelastic material made of an inorganic substance through a number of nozzle holes provided in an extrusion die to form a linear extrudate, and to accumulate the linear extrudate. In a method for producing a porous molded body, a first supply hole for a material constituting the center of a linear extrudate, and a donut-shaped second supply hole arranged so as to surround the first supply hole. The different materials are simultaneously extruded through a die equipped with This is a method for producing a porous molded body, which is characterized by integrally molding.

Examples of inorganic substances include mullite, corundum,
Examples include oxide ceramics such as zirconia and cordierite, and non-oxide ceramics such as silicon carbide and silicon nitride. These inorganic substances may be suitably combined in accordance with various uses. These inorganic substances are generally available in the form of powder or granules.

In order to make these inorganic substances into viscoelastic materials, for example, a binder is added to the inorganic substances and kneaded, and the viscosity is adjusted to form a slurry.

There are no particular restrictions on the binder, and any binder can be used as long as it exhibits a caking function for powder and granules. Typical binders include MC, CMC, starch, and CM3 (carboxymethyl starch), HEC (hydroxyethyl cellulose), HPC (hydroxypropyl cellulose), sodium lignin sulfonate, calcium lignin sulfonate, polyvinyl alcohol,
Examples include organic binders such as acrylic esters, methacrylic esters, phenol resins, and melamine resins, and inorganic binders such as water glass, colloidal silica, colloidal aluminan, bentonite, and shochu aluminum. They may be used together.

There are no restrictions on the mixing and kneading means, and any known equipment and equipment may be used. However, if a screw extrusion molding machine is used to extrude the linear material, the screw of the molding machine may be used. It can also be kneaded. The thus kneaded material is extruded into a linear product using the above-mentioned screw extruder or plunger extruder.

The linear object referred to in the present invention may have a circular or polygonal cross-sectional shape. It is also possible to have an irregular cross section such as a star shape.

By adjusting the grain size of the material constituting the outer peripheral part and extruding it under pressure, a stronger and denser outer peripheral part can be obtained.

According to the results of various studies conducted by the present inventor, the thickness d) of the outer periphery of the linear extrudate shown in FIG. 2 is 504 to 2.
, 0 mm range is desirable; below sog, the protective coating for the core material tends to be incomplete;
Even if the thickness was increased by mm or more, the effect did not change.

[Example] Examples of the present invention will be described below.

As shown in FIG. 1, through the first supply hole 2 for supplying the center material 6 and the second supply hole 4 for supplying the outer peripheral material arranged so as to surround the first supply hole 2. A dense composite linear extrudate 10 was easily obtained by pressurizing and extruding predetermined different materials, and a porous molded body was formed using the composite linear extrudate 10 in the same manner as in the conventional method.

More specifically, an evaluation test was conducted using a product manufactured under the following conditions, and the following results were obtained.

1.

A. Linear extrudate cross-sectional shape and material Center material: SiC Peripheral material: Alumina center grain system 30LL SiC powder and center grain system 4p Al2
Approximately 80 kg of O3 powder is kneaded with an organic binder.
A linear product having a two-layer structure was produced at an extrusion pressure of /cnn2, and further molded into a porous body.

This porous molded body was dried and then fired at about 1500°C to obtain a porous molded body.

In addition, as a result of analyzing the linear object obtained in this example in the cross-sectional direction, it was found that mullite (3A 120
3 Fist 2S i02) has been generated, and it has been confirmed that it has a three-layer structure.

2. For comparison, the following three types of porous bodies were manufactured.

B, porous body made of SiC mass material with linear cross-sectional diameter of 2.0 mmφ.

C,! A porous body made of alumina mass with an i-shaped cross-sectional diameter of 2.0 mmφ.

D. A porous body obtained by dipping the porous body of 2-H above with a reprinted alumina coating material and firing at 1500″C, with an average film thickness of about 60 tiles.

[Effects of the Invention] According to the first invention of the present application, a porous molded body having excellent bending strength at high temperatures and excellent thermal shock resistance can be obtained. According to invention No. 2,
Such a porous molded body can be easily produced. Further, according to the second invention of the present application, it is possible to arbitrarily adjust the film thickness, which was difficult with conventional coding methods, and thick-walled products can be easily produced.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the apparatus used in the examples, FIGS. 2 and 3 are sectional views of a linear extrudate, and FIG. 4 is a perspective view showing a high temperature bending test state. 2...First supply hole 4...Second supply hole 10...2
Layered linear extrudate

Claims (4)

[Claims] (1) A porous molded body constructed by integrally molding a large number of linear objects made of an inorganic substance, characterized in that the core and outer periphery of the linear objects are made of different materials. porous molded body. (2) The ceramic porous molded body according to claim 1, wherein the linear object is a linear object obtained by extrusion. (3) The porous molded article according to claim 1 or 2, wherein the center portion of the linear object is made of a non-oxide material and the outer peripheral portion is made of an oxide material. (4) A viscoelastic material made of an inorganic substance is linearly extruded through a number of nozzle holes provided in an extrusion die to form a linear extrudate, and the linear extrudate is assembled to produce a porous molded body. In the method of The method is characterized by extruding the materials at the same time, further integrating different materials at the exit ends of the first supply hole and the second supply hole to obtain a composite linear extrudate, and integrally molding the composite linear extrudate. A method for producing a porous molded body.