JPH0232121B2 - SERAMITSUKUSENISHITSUSURIIBUNOSEIZOHOHO - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a ceramic fibrous sleeve comprising a combination of ceramic fibers, an inorganic filler, an inorganic binder, and a molding aid, and more specifically, a method for manufacturing a ceramic fiber sleeve comprising a combination of ceramic fibers, an inorganic filler, an inorganic binder, and a molding aid. After adding water and kneading,
This invention relates to a method for producing a ceramic fibrous sleeve, which is characterized in that it is continuously formed into a hollow pipe using an extrusion molding machine having a circular nozzle at its tip with circular balls arranged concentrically, and then dried. Ceramic fibrous sleeves are used for casting feeders,
It is widely used in combustion tubes, high-temperature duct linings, thermocouple protection tubes, etc., and is mainly used for insulation purposes. However, in recent years, there has been a demand for high-density products (approximately 0.6 to 0.9 g/cm ³ ) that have not only heat insulation properties but also strength and corrosion resistance. In particular, in the steel industry, high-density ceramic fiber sleeves (approximately 0.6 to 0.9 ) is required. When used as a protective sleeve for a sensor, strength and corrosion resistance are required due to the harsh conditions of use, and since the sensor is set inside the ceramic fiber sleeve, high precision is required. ing. Incidentally, as a conventional method for producing ceramic fibrous sleeves, a mold suction dehydration molding method has mainly been used. This manufacturing method is used not only for sleeve-shaped molded products but also for most of the generally known ceramic fibrous molded products. In the above manufacturing method, a mixture of ceramic fibers and organic and inorganic binders, etc. is made into a slurry solution of about 0.5 to 3%, stirred uniformly in a vat with a constant volume, and a mold directly connected to a vacuum pump is placed in the slurry solution. After the mixture is adsorbed onto the surface of the mold to a certain thickness, the mold is removed and dehydrated, followed by release and drying. However, in the above manufacturing method, the adhesion of inorganic and organic binders is poor, and it is difficult to internally add inorganic fillers. Therefore, the bulk density of the molded product formed by the above manufacturing method is limited to about 0.4 g/cm ³ . Moreover, the strength of the molded body is also low. When high bulk density and high strength are required, after molding using the above manufacturing method, it is dried once, and then an inorganic or organic binder solution (for example, silica gel, alumina sol, etc.) is used.
The method is to impregnate it with water and dry it again. However, in these manufacturing methods,
Continuous production is impossible, labor is required, and the yield of binders and the like is poor, resulting in extremely low productivity. In addition, in terms of quality, since the method involves depositing ceramic fibers on the surface of the mold, the dimensional accuracy of the molded product is poor, and there are many drawbacks such as uneven impregnation of the binder or uneven density. Therefore, in order to eliminate these drawbacks all at once, the present invention involves adding water to ceramic fibers, an inorganic filler, an inorganic binder, and a forming aid, kneading them, and then forming a circular ball with concentrically arranged circular balls. It is an object of the present invention to provide a method for manufacturing a ceramic fibrous sleeve, which is characterized in that it is continuously formed into a hollow pipe using an extrusion molding machine having a nozzle at its tip and dried. That is, the ceramic fiber is 70 to 90% by weight, the total of the inorganic filler and inorganic binder is 5 to 25% by weight as a solid content, and the solid content of the forming aid is 0.5 to 10%.
For 100 parts by weight of a blended composition consisting of % by weight,
Water is added and kneaded so that the total moisture content is 70 to 130 parts by weight, and then a hollow pipe is continuously formed using an extrusion molding machine having a solid nozzle with concentric circular balls arranged at the tip. and dry. Further, a far-infrared heater is disposed at the exit of the circular nozzle at the tip of the extrusion molding machine to continuously dry the surface layer of the hollow pipe extruded from the extrusion molding machine, and then main drying is performed. The ceramic fibrous sleeve thus obtained consists of 70 to 90% by weight of ceramic fibers, 5 to 25% by weight of an inorganic filler and an inorganic binder in total, and 0.5 to 10% by weight of a forming aid. The fibers are partially defibrated and uniformly dispersed in the fireproof composition mainly composed of the inorganic filler and the inorganic binder, and the remainder is granular material with a particle size of 5 mm or less. , has a structure in which the granules are covered with a refractory composition in which a part of the ceramic fibers are uniformly dispersed, and the bulk density thereof is 06 to 0.9 g/cm ³
It is. The ceramic fibrous sleeve according to the present invention has extremely high dimensional accuracy compared to ceramic fibrous sleeves obtained by conventional methods because it is molded by regulating the inside and outside of the sleeve with a mold. Because of its structure, it has a high bulk density, and has extremely excellent strength and corrosion resistance. Furthermore, in terms of productivity, the yield of materials is improved and process automation becomes possible, resulting in a significant improvement in productivity. Next, a method for manufacturing a ceramic fibrous sleeve according to the present invention will be specifically explained. The ceramic fibers used in the present invention are mainly alumina-silica ceramic fibers, but some of them may be replaced with crystalline alumina fibers, crystalline mullite fibers, or various highly heat-resistant ceramic fibers. As the inorganic filler used in the present invention, powders of alumina, mullite, and siyamoto are particularly effective.Other examples include generally known refractory materials such as zirconia, chromium oxide, cordierite, silicon carbide, magnesia, and silica. Powders of these can also be used, and any one type or two or more types selected from these can be used. The inorganic binders used in the present invention are particularly effective, such as alumina sol, silica sol, and clay. In addition, generally known inorganic binders such as monoammonium phosphate, basic aluminum lactate, and aluminum hydroxychloride can also be used. ,
Any one type or two or more types selected from these can be used. Particularly effective molding aids used in the present invention include methylcellulose, carboxymethylcellulose, and polyacrylamide. Other,
Commonly known ingredients include hydroxyethyl cellulose, starch, gum arabic, wax emulsion, lignin, dextrin, polyvinyl, polyvinyl alcohol, polyethylene oxide, sodium alginate, aluminum alginate, vinyl acetate, gelatin, natural stem fat, synthetic resin, stearic acid, etc. Molding aids such as thickeners, lubricants, and plasticizers can also be used, and one or more types selected from these can be used. The ceramic fibers mentioned above are cut in advance using a type of crusher such as a cutter mill or feather mill, a shear mill, or a roll crusher.
Cut into chips with a size of mm or less, and granulated as necessary with a rolling granulator such as a pan type, drum type, vibrating conveyor type, horizontal vibrating plate, etc.70~ 90% by weight, a total of 5-25% by weight of inorganic filler and inorganic binder (solid content equivalent), and molding aid
A blended composition consisting of 0.5 to 10% (solid content equivalent)
A predetermined amount of water is added to 100 parts by weight so that the total water content is 70 to 130 parts by weight, and the mixture is uniformly kneaded using a kneader such as a mortar mixer or a kneader to obtain a plastic composition. The composition is continuously formed into a hollow pipe using an extrusion molding machine having a circular nozzle at the tip with circular balls arranged concentrically, and is manufactured using commonly known methods such as electric heat dryers, microwave dryers, kerosene combustion dryers, etc. Dry in a dryer. In addition, bulk ceramic fibers, an inorganic filler, an inorganic binder, a forming aid, and water are blended within the above-mentioned ratio range, and then kneaded.
Bulk ceramic fibers are chipped or granulated to a size of 10 mm or less using a blade-type kneading machine such as a paddle mixer, cutter mixer, or all-purpose mixer, and simultaneously kneaded uniformly to form a plastic composition. Form into a hollow pipe using an extruder and dry. Ceramic fiber and inorganic filler,
A plastic composition made by simply mixing an inorganic binder, a molding aid, and water lacks uniformity and fluidity compared to a composition based on ceramic powder that is generally subjected to extrusion molding. When continuously extruding hollow pipes in a molding machine, the hollow pipes tend to be bent and extruded. The fluidity and shape retention of the composition are improved by uniformly dispersing a portion of the ceramic fibers in a defibrated state in a composition consisting of an inorganic filler, an inorganic binder, a forming aid, and water. Therefore, bending of the hollow pipe during extrusion molding can be prevented. In addition, an inorganic filler in which a portion of the ceramic fibers described above is uniformly dispersed by forming the remainder of the ceramic fibers into granules with a size of 10 mm or less, preferably 5 mm or less;
Uniform dispersion in a composition consisting of an inorganic binder, a molding aid, and water further improves the overall fluidity, which is suitable for preventing hollow pipes from bending during molding. The reason why the blending ratio of ceramic fiber is limited to 70 to 90% by weight is that if it is less than 70% by weight, the bulk density of the ceramic fiber sleeve becomes too high, so the original purpose of blending ceramic fiber is to reduce the weight of the sleeve. On the other hand, if the amount exceeds 90% by weight, the amount of inorganic filler and inorganic binder blended is relatively too small, resulting in decreased fluidity and shape retention of the kneaded composition used for molding. It is difficult to extrude the hollow pipe continuously during molding, and the strength of the sleeve
This is because corrosion resistance will not be sufficient. The reason why the blending ratio of inorganic filler and inorganic binder is limited to 5 to 25% by weight in terms of solid content is as follows.
If it is less than 5% by weight, the fluidity and shape retention of the kneaded composition used for molding will decrease, making it difficult to extrude the hollow pipe continuously during molding, and the strength and corrosion resistance of the sleeve will not be sufficient, while if it exceeds 25% by weight. This is because the amount of ceramic fiber blended is relatively too small, making the sleeve insufficient in weight and heat insulation. The reason why the blending ratio of the molding aid is limited to the range of 0.5 to 10% by weight in terms of solid content is that if it is less than 0.5% by weight, the plasticity and maintenance of the kneaded composition used for molding, which is the original purpose of blending the molding aid, will be reduced. Effects such as formability and lubricity are not fully demonstrated, making it difficult to extrude hollow pipes continuously during forming.On the other hand, if the content exceeds 10% by weight, problems such as smoke generation or molten iron scattering occur when the sleeve is used. It is from. The water content in the plastic composition consisting of ceramic fibers, inorganic filler, inorganic binder, molding aid, and water is 70 to 70 parts by weight per 100 parts by weight of solid content.
The reason for limiting the amount to 130 parts by weight is that if it is less than 70 parts by weight, the fluidity of the kneaded composition used for molding will decrease and it will be difficult to continuously extrude the hollow pipe during molding, whereas if it exceeds 130 parts by weight, it will be difficult to extrude the hollow pipe. This is because the shape retention of the kneaded composition to be used deteriorates, making it difficult to extrude the hollow pipe continuously during molding, and causing problems such as only water being squeezed out from the circular nozzle outlet of the molding machine. As mentioned above, when a hollow pipe is continuously extruded using an extrusion molding machine, a plastic composition obtained by mixing and kneading ceramic fibers, an inorganic filler, an inorganic binder, a molding aid, and water within a predetermined range. By disposing a far-infrared heater at the exit of the circular nozzle at the tip of the extrusion molding machine to continuously dry the surface layer of the hollow pipe extruded from the molding machine, the strength of the hollow pipe is improved and the main drying process is improved. This is suitable because it prevents deformation when transporting the hollow pipe. Next, examples of the method for manufacturing a ceramic fibrous sleeve according to the present invention and comparative examples will be described. Example 1 Bulk alumina-silica fibers are cut into chips with a size of 10 mm or less using a cutter mill, and the chip-shaped alumina/silica fibers/crystalline alumina fibers, an inorganic filler, and an inorganic binder are molded. Auxiliary agents and water were mixed as shown in A, B, and C in Table 1 and kneaded using a mortar mixer. Next, inner diameter 60mm
Continuously extrude into a hollow pipe shape using an extrusion molding machine with an extrusion port in which a circular medium ball with an outer diameter of 50 mm is arranged concentrically inside a circular nozzle, and cut into a length of 300 mm. It was cut and then dried in an electric dryer. Outer diameter 60mmφ and inner diameter 50mm obtained in this way
Table 1 shows the quality of ceramic fibrous sleeves with a diameter of 300 mm and corresponding to formulations A, B, and C. Example 2 Bulk alumina-silica fibers, an inorganic filler, an inorganic binder, a forming aid, and water were mixed as shown in D and E in Table 1 and kneaded in a kneader.
Next, it is continuously extruded into a hollow pipe shape using an extrusion molding machine having an extrusion port in which a circular medium ball with an outside diameter of 50 mm is arranged concentrically inside a circular nozzle with an inside diameter of 61 mm. After continuously drying the surface layer of the hollow pipe by installing an infrared heater,
It was cut to a length of 300 mm and then dried in a microwave dryer. Outline 60mm obtained in this way
Table 1 shows the quality of ceramic fibrous sleeves with a diameter of 50 mm and a length of 300 mm, corresponding to the formulations D and E. Comparative Example Bulk alumina/silica fibers, an inorganic binder, a molding aid, and water were mixed as shown in F, G, and H in Table 2, defibrated with a pulper to form a slurry, and the slurry was made into a slurry. A suction mold with an outer diameter of 50 mmφ connected to a vacuum pump was put into the mold, and the material was adsorbed and deposited on its surface, and then the mold was taken out, dehydrated, released from the mold, and dried. The outer diameter 60mmφ, inner diameter 50mmφ, and length obtained in this way
The quality of the 300mm ceramic fiber sleeve is second to none.
The table shows the corresponding formulations F, G, and H.

【table】

【table】

[Table] As described above, according to the present invention, a plastic composition consisting of ceramic fibers, an inorganic filler, an inorganic binder, a molding aid, and water is continuously extruded into a hollow pipe using an extrusion molding machine, and then By drying, a ceramic fibrous sleeve with very good dimensional accuracy, high bulk density, and excellent strength and corrosion resistance can be manufactured with high productivity.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the nozzle at the tip of the extrusion molding machine. FIG. 2 is a sectional view taken along the line AA of the nozzle in FIG. 1. 3 and 4 are cross-sectional views showing other shapes of the nozzle portion at the tip of the extrusion molding machine. Explanation of symbols, 1... Nozzle, 2... Medium ball, 3...
...Strut, 4...Far-infrared heater, 5...Kneaded material,
10...Extrusion molding machine.

Claims (1)

[Scope of Claims] 1 Comprising 70 to 90% by weight of ceramic fibers, 5 to 25% by weight of the total solid content of inorganic filler and inorganic binder, and 0.5 to 10% by weight of molding aids as solid content. Water is added and kneaded to 100 parts by weight of the blended composition so that the total water content is 70 to 130 parts by weight, and then extrusion is carried out using a nozzle with a circular ball arranged in a circular shape at the tip. A method for manufacturing a ceramic fibrous sleeve, which comprises continuously forming a hollow pipe using a molding machine and drying it. 2. The method according to claim 1, characterized in that a far-infrared heater is disposed at the exit of the circular nozzle to continuously dry the surface layer of the hollow pipe extruded from the extrusion molding machine, and then to perform main drying. Production method. 3. The manufacturing method according to claim 1 or 2, wherein the inorganic filler is one or more selected from alumina, mullite, and syamoto powder. 4 The inorganic binder is alumina sol, silica sol,
The manufacturing method according to claims 1 to 3, wherein the clay is one or more selected from clays. 5. The manufacturing method according to claims 1 to 4, wherein the molding aid is one or more selected from methylcellulose, carboxymethylcellulose, and polyacrylamide.