JPS6218516B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a high-temperature heat insulating composite material molded body composed of ceramic fibers, sintered and vitrified parts, and holes, and a method for manufacturing the same, and its purpose is to have relatively high strength.
Moreover, it is an object of the present invention to provide a composite material molded article for high-temperature insulation that can be used up to high temperatures without causing harmful behavior such as shrinkage or deformation. The ceramic fiber mentioned here is made by melting raw materials whose main ingredients are alumina, silica, etc. in an electric furnace, and then using high-speed airflow such as steam or air, or by using the centrifugal force of a rotating disk. It is a fireproof insulation material obtained by making fibers, etc., and the widely commercially available materials are Al ₂ O ₃ 40-60% and SiO ₂ 60-60%.
It is a glassy substance whose main component is 40%.
In addition, materials having a composition of 70% or more Al ₂ O ₃ that have been commercially available in recent years, or materials such as zirconia may also be used. Ceramic fiber is commercially available as bulk cotton, but it is more commonly marketed as molded products such as boards, blocks, tubes, and various molded products, and is used in various furnaces and other equipment, especially high-temperature ducts, boiler combustion chambers, It is widely used as a lining material, backup material, heat insulating material, etc. for high-temperature pipes, and there is a national requirement for energy conservation.
In recent years, its demand has been increasing rapidly. The present invention relates to ceramic fiber molded bodies. Currently, the following methods are generally used to mold ceramic fibers into various shapes. Ceramic fiber is poured into a relatively large amount of water, a deflocculant, a binder, and in some cases an antifoaming agent are added to it, stirred and mixed to prepare a slurry, and this slurry is poured into a mold. A molded article consisting of a stack of ceramic fibers is obtained by pouring the mixture into a mold and dehydrating it by suction from the surface of the mold. At this time, if necessary, pressure is applied from the top of the stack during suction or after suction. As binding materials, inorganic sols (silica sol, alumina sol, etc.) and cements based on silicates, aluminates, phosphates, etc. are generally used, and organic glues are also used at the same time. There is also. The molded body can be sold as a product just by drying. Commercially available heat-insulating ceramic fiber molded bodies manufactured by this method are used in furnaces and other high-temperature parts in various industrial sectors, exhibiting excellent heat-insulating properties and playing an important role in energy conservation. However, it has been pointed out that these products generally have the following serious drawbacks. 1. When used at temperatures above 1200°C, the molded product suddenly becomes brittle. 2. If used at temperatures above 1200℃, the molded product will undergo significant shrinkage and deformation. The following are the main causes of these phenomena. a. When a commercially available ceramic fiber molded product is used at the above temperatures, its bonding parts (inorganic hydrogel, organic glue) will be significantly altered, resulting in a significant decrease in bonding or significant shrinkage. thing. b. When a molded product made of vitreous ceramic fiber is used at the above temperatures,
The fateful drawback of this type of fiber is that the crystallization of the glass becomes active, and as a result, the fiber itself rapidly becomes brittle and deforms. The present inventors have been conducting research for many years with the aim of producing a new type of high-temperature insulation molded product that eliminates the above-mentioned drawbacks that commercially available ceramic fiber molded products exhibit during use. As a result, we developed a heat-insulating composite material molded body consisting of ceramic fibers, sintered and vitrified parts, and pores that can be safely used up to considerably high temperatures without causing the above-mentioned drawbacks, and we also developed a manufacturing method for it. successfully established. Next, the manufacturing method of the present invention will be described. Slurry () Preparation Step If the powdered material is made of one or more natural minerals or artificial minerals, which is one of the main materials of the composite material molded product, approximately 50% (weight) or more of its constituent components are Natural materials that have a chemical composition that remains after the described firing process and that also consist of fine particles (e.g., solubilizable or refractory clays,
Elutriated substances such as kaolin, crushed bauxite)
Or use artificial materials (e.g. alumina powder, pulverized powder). One type or a mixture of two or more of these powdery substances is dispersed in water to form a slurry. Needless to say, the peptization conditions necessary for dispersing the powdered material must be adapted to the particular properties of the powdered material. In addition, if higher dry strength is required after the molding, drying, and processes described in (2) and in handling of the molded object, this slurry (2) should be prepared during the preparation of this slurry (2), or the slurry (20) described in
It is effective to add an organic sizing agent during adjustment. Ceramic fiber pre-treatment step Ceramic fiber is treated with a solution or colloid solution having properties suitable for agglomerating the powdery substance dispersed in the slurry. The term "properties suitable for agglomeration" as used herein refers to properties suitable for agglomeration, taking into account the unique properties of the powdered material used.
Of course, it refers to properties that are compatible with this.
The ceramic fiber used is preferably in the form of bulk cotton, but this need not necessarily be the case.
In addition, when bulk cotton is used, it can be impregnated with a solution. Further, the flocculant (solution or colloidal solution) may be of a nature that completely disappears during the firing step described in (2), or it may be of such a nature that some or all of the solute remains even after the firing step. Slurry () Preparation Step Ceramic fiber bulk cotton, which has been pretreated as described in the above, is put into the slurry () to prepare the slurry (). Ceramic fiber bulk cotton input amount is slurry ()
The amount of powdery material dispersed in the material is 30-100%
(weight). Although it is necessary to stir thoroughly during and after charging, it is desirable to maintain the fibril length without breaking the ceramic fibers as much as possible. Molding, Drying, and Firing Steps The amount of water in the slurry () is adjusted to be suitable for the molding method by increasing or decreasing it, and then the slurry is molded, dried, and then fired.
During firing, the original fiber structure of the ceramic fiber that can be seen with the naked eye changes to approximately 50%.
% (half) or more disappears, and if vitreous ceramic fiber bulk cotton is used, it crystallizes, and moreover, the shape of the molded product is generally maintained before and after firing (meaning that it retains a similar shape) (The shrinkage itself often occurs by about 10 to 20%) during firing within the temperature-time conditions. However, the lower limit of the firing temperature is 1000°C, especially 1200°C. The high-temperature heat insulating composite material molded article of the present invention is manufactured through the above four steps. The advantages of the composite material molded article for high temperature insulation of the present invention are as follows. (1) In the compact, a ceramic bond is formed between ceramic fibers, or between a ceramic fiber and a powdery substance deposited and sintered on its surface, and in some cases, a residual component of an aggregate. As a result, the strength of the molded product is high, and even when used at relatively high temperatures, the joints do not change in quality and are stable, and the molded product does not shrink or lose strength due to deterioration of the joints. do not have. (2) Ceramic fibers are mostly crystallized before use, so there is no embrittlement or deformation of the fiber itself that occurs due to crystallization of glassy ceramic fibers during use at high temperatures, and therefore molded products caused by these do not No embrittlement or deformation was observed. (3) Since many voids are formed in the molded body by the remaining relatively long fibers and partially melted glass, the molded body has extremely high heat insulation properties. In other words, it can be said that it is a high-performance high-temperature heat insulating composite material that eliminates the drawbacks of conventionally commercially available ceramic fiber molded bodies and can be safely used up to high temperatures. The powdered substance, which is one of the main materials here, may contain components that decompose and volatilize during the firing process as part of its composition, up to about 50% (by weight), but more than 50% (by weight) This is generally undesirable because it often shrinks too much during firing, causing cracks, making it difficult to maintain the shape, and making it difficult to maintain the precision of product dimensions. Within the range of commonly available particles, the finer the powder, the better the bond strength to ceramic fibers and the strength of the molded product.Experiments have shown that the average particle size is 30μ (50% passing particle size) or less, preferably 5μ.
Good results were obtained in the following cases. However, when two or more types of powdered substances are mixed and used, and one of them accounts for 30% or more of the total powdered substances, the average particle size of the particles other than that one may be larger than the above-mentioned average particle size. Therefore, when using a mixture of two or more types of powdered substances, it is also possible to use relatively coarse small particles containing pores (for example, alumina bubbles) as one of the types, thereby achieving higher It is also possible to produce a composite material molded body for high-temperature insulation with high performance. If the ratio of the powdery substance to the ceramic fiber is too small, the strength of the molded product will be insufficient, and if it is too large, the heat insulation properties of the molded product will be insufficient. As a result of various experiments, ceramic fiber 30~
It has been found practical to add powdered material corresponding to 100% (weight before firing). Additionally, if a substance that generates gas during firing is added to the powdered material, the powdered material portion of the compact will foam during firing, increasing the number of pores and further improving its insulation properties. . As mentioned above, the agglomerating material (solution or colloidal solution) must have properties suitable for agglomerating it depending on the type of powdery substance to be dispersed in the slurry (). Some types of solutes completely volatilize and disappear during the calcination process (e.g., many inorganic and organic acids), while others in which some or all of the solute components remain after the calcination process (e.g., many metal salt solutions). , inorganic hydrosol), but any of them may be used, and when the latter is used, it generally has the effect of assisting ceramic bond formation in the firing process. Firing is performed with the primary purpose of increasing the strength of the compact, generating and increasing pores, and obtaining stability during high-temperature use, but of course this purpose cannot be achieved if the firing conditions are too low. If the temperature is too high, it will be difficult to obtain a fired product that retains its shape during molding.
As a result of many repeated experiments, we have established a practical guideline under which conditions (temperature, time, ) It has been found that the above purpose can be achieved by firing it in The firing conditions selected depend on the chemical composition and dimensions (diameter, length) of the ceramic fiber, the chemistry and mineral composition of the powder material, the ratio of ceramic fiber to powder material, and the use of inorganic additives, if any. Needless to say, it varies depending on the properties and amount added, molding method, product size and shape, product quality goals, etc. In any case, the above conditions (temperature,
If the ceramic fiber is fired within a certain period of time, the powder material and the ceramic fiber whose fibril length is maintained as much as possible will be sintered or partially melted to form glass. Vacancies are generated. Further, when a vitreous ceramic fiber is used, the second purpose of firing the compact is to crystallize it and make it stable even at high temperatures. Although this objective can be achieved in most cases by firing within the above-mentioned conditions, the firing conditions must be set with due consideration given to this fact. Note that if the firing temperature is too low, defects may appear depending on the temperature used, so the lower limit of the firing temperature should be 1000°C and not lower than that.
A temperature of 1200°C or higher is desirable. Next, examples will be shown. Example 1 Slurry () Preparation Step Commercially available elutriated kaolin (A) and kaolin (B) used
The chemical composition and fineness of the powder are shown in Tables 1 and 2.

【table】

[Table] These were poured into water together with a commercially available dextrin and ethylamine in the following quantitative proportions, and stirred to fully decompose and glue, to prepare a slurry (). Elutriated kaolin (A) 2500g (B) 2500g Dextrin 50g Ethylamine 10g Water 70 Ceramic fiber pre-treatment process Table 3 shows the quality of the commercially available ceramic fiber bulk cotton used.

[Table] The above ceramic fiber bulk cotton is used as an acidic hydrosol, Cataloid SN (Catalyst Kasei Co., Ltd.).
(manufactured by). The quantitative proportions are as follows. Cataroid SN solution 70 Ceramic fiber bulk cotton 10Kg Slurry () Preparation process The ceramic fibers pretreated in the step are poured into the slurry () while stirring, and stirring is continued appropriately to mix the kaolin powder and the ceramic fibers. The stirring was stopped after the mixture was uniformly mixed and suspended in the water. During stirring, particular care was taken not to break the ceramic fibers as much as possible. Cataloid SN, a part of which is impregnated in the ceramic fiber, has the property of aggregating the two types of kaolin that are peptized in the slurry (), so the Kaolin aggregated on the surface of the ceramic fiber and adhered well. slurry()
And so. Forming, drying, and firing process The slurry () is poured into a wooden mold with a wire mesh on one side, suction is applied from the wire mesh side, and the other side is pressed to form a plate of approximately 200 x 200 x 50 mm. After drying this in a drying room at 105°C, it was fired in a firing oven at a maximum temperature of 1350°C (2 hours). In the sample product, more than half of the ceramic fiber fiber structure observed in the pre-fired molded body had disappeared to the naked eye, and although the dimensions had shrunk due to sintering, the external shape was maintained. kaolin and cataloids
The remaining component of SN (silica) surrounded and sintered the sufficiently crystallized ceramic fiber (mullite + corundum), forming a strong ceramic molded body. In addition, the ceramic fibers that still have their original shape are hardly broken, so the length of the fibrils is maintained, and the parts that have partially melted together with the surrounding kaolin and the remaining components (silica) of cataloid SN are Glass was produced by particularly reducing the volume, and many pores were generated or increased in the molded product due to the glass and these relatively long fibers. The quality of the composite material molded article for high-temperature heat insulation trial-produced in this way is as follows.

[Table] In other words, in terms of strength, this sample product far exceeds the values found in the catalogs of ceramic fiber molded products from various companies, and when heated, it already shrinks significantly at 1100℃ because the latter is an unfired product. However, the former showed no shrinkage even at 1400°C and its shape remained almost unchanged from before use. Moreover, the thermal conductivity was the same as, or even slightly smaller than, the values found in the catalogs of ceramic fiber molded products from various companies, and it can be said that this sample product has good high-temperature insulation properties. As described above, the high-temperature insulation composite material molded article of the present invention trial-produced by the method of the present invention has relatively high strength, is easy to handle, and can be used safely up to considerably high temperatures; It can be said that this is an excellent quality composite material molded product for high-temperature insulation that exhibits a high degree of heat insulation.

Claims (1)

[Claims] 1. (a) Dispersing a powdered substance made of one or more types of natural minerals or artificial minerals in water to prepare a slurry (b) Preparing ceramic fibers in the slurry. (2) treatment with a solution or colloidal solution having properties suitable for agglomerating the powdery substance dispersed therein; (c) ceramic fibers pretreated as described in (b) above; slurry (),
Add the above powdered substance to the slurry (2) in an amount equivalent to 30 to 100% (by weight) of the ceramic fiber, stir and make the slurry (2).
(d) The slurry () is molded after adjusting its moisture content to a value suitable for the molding method to be adopted,
After drying, the temperature and time are such that more than half of the fibrous structure visible to the naked eye disappears, and the shape of the molded product is maintained before and after firing, and at a temperature of 1000°C or higher. 1. A method for producing a composite material molded article for high-temperature insulation, comprising the following steps: