JP3138312B2 - Heat- and acid-resistant inorganic fibers and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inorganic fiber excellent in heat resistance and acid resistance and a method for producing the same, and particularly to a heat resistant acid resistant inorganic fiber suitable as a substrate for a denitration catalyst for flue gas containing acidic gas. And its manufacturing method.

[0002]

2. Description of the Related Art Woven fabrics made of inorganic fibers are used for heat-resistant products,
It is widely used for various catalyst base materials in addition to plastic and ceramic composite materials. Fibers used in these woven fabrics include glass fibers such as E glass, T glass and silica glass specified by JIS R 3414 and the like, as well as various ceramics such as ceramics made of mullite and fine ceramics such as silicon carbide. (Japanese Patent Application Laid-Open Nos. 50-104789 and 59-73)
No. 053).

[0003]

Among them, those containing alkali or aluminum oxide such as E glass and mullite are inexpensive, but react with oxidizing gas such as SOx in exhaust gas to reduce the strength. It cannot be used under corrosive conditions. On the other hand, silicon carbide fiber, silica fiber or glass fiber obtained by removing components other than the silica component with hydrochloric acid are excellent in acid resistance, but the production cost is about 10 to 100 times as compared with the glass woven cloth. In fact, there is no inexpensive and acid-resistant inorganic fiber suitable for applications requiring a woven fabric exceeding 10,000 m ² per plant, such as a flue gas denitration catalyst substrate. The invention of such an inorganic fiber is desired.

[0004] On the other hand, the present inventors have conducted research to solve the above-mentioned problem, and have studied a method of applying a catalyst into a mesh of an inorganic fiber woven fabric covered with a stabilizing oxide (JP-A-3-6524).
No. 6) and applied for a patent as a method for producing a large-sized, high-strength catalyst. However, when a general-purpose glass cloth (such as E glass) is used as the inorganic fiber,
Although the initial strength is high, there is a problem that the strength decreases with time when used at a high temperature in a gas containing SOx.

An object of the present invention is to provide a heat- and acid-resistant material which does not cause a decrease in strength even when used in a gas containing a corrosive gas such as a sulfur oxide or is used at a high temperature, or has a very small decrease in strength. And to provide a method for producing the same.

[0006]

The object of the present invention is to provide a coating made of titania particles having an average particle diameter of 0.01 μm or less on the surface of general-purpose glass fiber such as E glass.
It is formed with a thickness of 5 μm or less, and if necessary,
Forming a second layer film comprising mixed particles of oxide particles having an average particle diameter of 0.1 to 1.0 μm and titania particles or silica particles having an average particle diameter of 0.01 μm or less;
This is achieved by firing at a high temperature of 0 ° C. or more and 800 ° C. or less.

That is, in the first invention of the present application, the inorganic fiber containing alkali and / or aluminum oxide has titania particles having an average particle size of 0.01 μm or less on the surface thereof.
A film of not less than 05 μm and not more than 0.5 μm is formed,
The present invention relates to a heat-resistant and acid-resistant inorganic fiber which is fired at 0 ° C or more and 800 ° C or less. According to a second invention, in a method for producing a heat- and acid-resistant inorganic fiber, an inorganic fiber containing an alkali and / or an aluminum oxide is impregnated or applied with a colloidal titania solution, and then dried, and dried at 500 ° C or more and 800 ° C or less. And a method for producing heat- and acid-resistant inorganic fibers, characterized by firing.

A third invention is a method for producing a heat- and acid-resistant inorganic fiber, comprising impregnating or applying a colloidal titania solution to an inorganic fiber containing an alkali and / or aluminum oxide, and then drying it at 500 ° C. ° C
Calcined below, impregnated or coated with a mixed solution of colloidal titania or colloidal silica and oxide particles having a particle diameter of 0.1 to 1.0 μm, dried, and then calcined. The present invention relates to a method for producing a conductive inorganic fiber.

[0009]

According to the study of the present inventors, the main cause of the decrease in the strength of the inorganic fiber is CaO and Al contained in the glass fiber.
₂ O ₃ reacts with SOx in the atmosphere to produce CaSO ₄ , Al
₂ (SO ₄ ) is produced on the fiber surface,
(1) Adjacent fibers are bonded to each other and do not follow deformation due to bending or heat, and the fibers are easily cut;
(2) It has been found that the inorganic fibers are eroded and the strength of the single fibers themselves is reduced.

This reaction becomes more remarkable as the temperature becomes higher. Untreated fibers, even at about 400 ° C., fall to about １ ／ of the initial strength due to prolonged heating when contacted with SOx. That is, if a reaction between SOx and Ca or Al in the glass fiber can be prevented, a reduction in strength can be prevented. For that purpose, it is necessary to provide a dense layer on the glass fiber surface that does not react with SOx and does not allow SOx to enter the glass surface. Further, the diameter of the glass fiber is usually about 10 μm, and yarns obtained by combining several hundreds to several hundreds of yarns and further combining several yarns are woven in various shapes such as plain weave and twill weave. When used as a material, it is necessary that the catalyst has sufficient strength against bending deformation particularly generated during molding of the catalyst. Then, the present inventors searched for a suitable glass fiber coating method, and as a result, impregnated the fiber with colloidal titania composed of an aqueous solution of titania particles having an average particle diameter of 0.01 μm or less and an aqueous solution, or sprayed the fiber on the fiber surface and dried. By providing a titania layer having a thickness of 0.05 to 0.5 μm on the fiber surface by this, by firing at a high temperature of 500 to 800 ° C., it is favorable to the reaction with SOx even at a high temperature of 400 ° C. or more. It has been found that it exhibits excellent durability. With titania particles having an average particle size of 0.01 μm or more, it is difficult to form a thin titania layer having a uniform thickness as described above.

The surface of the glass fiber which has been treated according to the present invention is uniformly covered with a layer of titania having excellent heat resistance and good reaction with SOx. Even when used, the glass fibers containing CaO and Al ₂ O ₃ can prevent a decrease in strength due to the reaction between CaO or Al ₂ O ₃ and SOx without directly contacting the SOx gas. 1) Overall Configuration As the inorganic fiber used in the practice of the present invention, a yarn obtained by further combining several hundreds to several hundreds of single fibers of several to 10 μm of inorganic alkali glass such as E glass, and further combining several yarns is used. Those woven in various shapes such as plain weave and twill weave are used.

This fiber woven fabric (hereinafter referred to as a screen)
, Colloidal titania is supported by dipping or spraying, and then dried at 100 to 200 ° C. to provide a thin titania layer of 0.5 μm or less. Then 500-800
Heat for several hours at ° C. Also, if necessary, colloidal titania or colloidal silica and a stabilizing oxide (for example,
A mixed slurry of alumina, zirconia, titania, etc.) is formed on the surface of the titania layer by dipping or spraying.

Here, the characteristic feature is that the layer composed of titania particles having an average particle diameter of 0.01 μm or less, preferably 0.09 μm or less as the first layer is 0.05 to 0.5 μm (preferably 0.1 to 0 μm). 0.4 μm) on the surface of the glass fiber, and heat treatment at 500 to 800 ° C. Further, if necessary, after forming the titania layer, a mixture of colloidal titania or colloidal silica and a stabilizing oxide is provided outside the titania layer, and other methods for improving the rigidity of the screen, for example, polyvinyl alcohol, etc. An organic binder may be added to the mixture. 2) Interaction and relationship of each component FIG. 1 is a schematic cross-sectional view of the screen obtained by the above operation.
FIG. 2 is a fiber shape photograph showing the appearance of the inorganic fiber obtained by the above operation, and FIG. 3 is a fiber shape photograph showing an enlarged cross section thereof. As is clear from the figure, the surface of the inorganic fiber is covered with a dense titania particle layer. The titania layer covering the glass fiber surface is dense and has an effect of preventing the fiber from reacting with SOx gas. And then,
The inorganic fiber and the titania layer react by the heat treatment to be performed,
Titania penetrates the inorganic fiber surface to form a titania-rich reaction layer. The heat treatment temperature for obtaining such an effect is from 500 ° C. to 80 which is the softening temperature of the glass fiber.
Preferably it is between 0 ° C. FIG. 6 shows the firing temperature and the tensile test results of the screen before and after the acid resistance test.
If the firing temperature is lower than 500 ° C., the acid resistance is not improved.
On the other hand, when the temperature exceeds 800 ° C., the fibers are softened and restrained, so that the initial strength is significantly reduced. Further, in order to obtain the effect of the present invention at 500 ° C. or lower, it is necessary to perform firing for a long time. Further, as shown in FIG. 4, as the thickness of the titania film, as the thickness of the fiber increases, cracks or peels occur in the film as the thickness increases, so that the upper limit of the film thickness is 0.5 μm. It is necessary to On the other hand, if the film thickness is too thin, a portion where a film is not formed on the fiber appears, so the lower limit of the film thickness needs to be 0.05 μm. Table 1 shows the relationship between the film thickness and the occurrence of cracks. The film thickness can be controlled by setting the solid concentration and the impregnation time of the used colloidal titania to appropriate values.

[0014]

[Table 1] In addition, the improvement of heat resistance and acid resistance of the inorganic fiber is sufficiently achieved by the above treatment, but when used as a base material for a catalyst, the base material is not deformed when applying a catalyst paste other than the acid resistance. Some rigidity is required. For this purpose, after the above-mentioned film is formed on the surface of the inorganic fiber, a mixture of the outer colloidal titania (or colloidal silica) and oxide particles (particle diameter: 0.1 to 1.0 μm) of alumina, titania, zirconia, etc. By providing a coating layer consisting of, it contributes to improving the rigidity of the fiber. When the average diameter of the oxide particles is out of the above range, the rigidity of the fiber is reduced, and the coating layer is easily separated.

[0015]

The present invention will be described below in more detail with reference to specific examples. Example 1 54% SiO ₂ , 19% CaO, ₂ % Al ₂ O ₃ , B in colloidal titania (content of titania 5 wt%) solution
An inorganic fiber woven fabric obtained by plain weaving a yarn obtained by twisting 1400 E glass fibers having a diameter of 9 microns and consisting of 5% of ₂ O ₃ and other 2% at a rate of 10 stitches per inch is impregnated for about 1 minute and then at 130 ° C. for 30 minutes. Dried. After that, 55
Heat treatment was performed at 0 ° C. for 2 hours to obtain a sample. Example 2 An inorganic fiber woven fabric obtained in Example 1 was impregnated with a liquid mixture obtained by mixing titania particles having an average particle diameter of 0.5 μm and colloidal titania (titania content: 5 wt%) at a weight ratio of 1: 1. Dried at 130 ° C. for 30 minutes. Thereafter, heat treatment was performed at 550 ° C. for 2 hours to obtain a sample. Example 3 An inorganic fiber woven fabric obtained in Example 1 was impregnated with a liquid mixture obtained by mixing titania particles having an average particle diameter of 0.5 μm and colloidal silica (silica content: 5 wt%) at a weight ratio of 1: 1.
Dried at 130 ° C. for 30 minutes. Thereafter, heat treatment was performed at 550 ° C. for 2 hours to obtain a sample. Comparative Example 1 SiO solution was added to colloidal silica (silica content 5%) solution.
_{2 54%, CaO19%, Al} 2 O 3 2%, B 2 O 3 5
%, And 2%, other yarns of 1,400 E-glass fibers having a diameter of 9 microns are woven in 10 inches per inch.
Impregnated with plain woven inorganic fiber woven fabric,
And dried. Thereafter, heat treatment was performed at 550 ° C. for 2 hours to obtain a sample. Comparative Example 2 Untreated SiO ₂ 54%, CaO 19%, Al ₂ O ₃ 2
%, B ₂ O ₃ 5%, and other 2%, and a yarn obtained by combining 1,400 E-glass fibers having a diameter of 9 microns and having a diameter of 1400, was plain woven at 10 stitches per inch, and was used as a sample.

In the above Examples and Comparative Examples, the tensile strength (A) of one yarn extracted from the screen as it was was measured at 500 ° C. in a titania powder containing a sulfate group.
After contact for 00 hours, the tensile strength (B) per yarn was measured. The tensile test conditions are as follows. Jig distance: 20 mm Pulling speed: 2 mm / min Temperature: room temperature Number of repetitions: 5 FIG. 5 shows the average value of the measurement results. As is clear from this figure, each of the samples of Examples 1 to 3 has the same initial strength as the comparative example, but the strength after being brought into contact with the SOx gas-containing gas has a significantly higher value than the comparative example. This shows that the method of the present invention is excellent in obtaining heat-resistant and acid-resistant inorganic fibers.

[0017]

According to the present invention, inexpensive general-purpose glass fibers such as E glass can be used at a high temperature under a corrosive environment containing an acidic gas. As a result, high-cost ceramic fibers such as silica glass and silicon carbide can be replaced by the heat-resistant and acid-resistant fibers of the present invention, and the cost of various corrosion-resistant and heat-resistant products can be greatly reduced.

Further, by using as a catalyst base material such as a catalyst for denitration of boiler exhaust gas using a large amount of a base material excellent in corrosion resistance and heat resistance, the effect of improving durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an inorganic fiber according to the present invention.

FIG. 2 is a photograph of fiber shape showing the surface of an inorganic fiber in the present invention.

FIG. 3 is a photograph of a fiber shape showing an enlarged cross section of an inorganic fiber in the present invention.

FIG. 4 is a photograph of fiber shape showing the surface of inorganic fiber when the thickness of titania is large.

FIG. 5 is a diagram comparing the strengths of inorganic fibers of an example and a comparative example.

FIG. 6 is a diagram showing a relationship between a firing temperature and a tensile strength of a fiber in the present invention.

[Explanation of symbols]

 1 ... inorganic fiber, 2 ... titania layer.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C03C 25/42 B01D 53/86 B01J 21/16 B01J 35/06

Claims (3)

(57) [Claims] 1. A film of titania particles having an average particle size of 0.01 μm or less and a thickness of 0.05 μm or more and 0.5 μm or less is formed on the surface of an inorganic fiber containing an alkali and / or aluminum oxide. A heat- and acid-resistant inorganic fiber which is fired at a temperature of not more than ℃. 2. A method for producing a heat- and acid-resistant inorganic fiber, comprising impregnating or applying a colloidal titania solution to an inorganic fiber containing an alkali and / or aluminum oxide, drying, and then drying at 500 to 800 ° C. A method for producing a heat- and acid-resistant inorganic fiber, characterized by firing. 3. A method for producing a heat- and acid-resistant inorganic fiber, comprising impregnating or applying a colloidal titania solution to an inorganic fiber containing an alkali and / or aluminum oxide, followed by drying and firing at 500 ° C. or more and 800 ° C. or less. And heat- and acid-resistant inorganic fibers characterized by being impregnated or coated with a mixed solution of colloidal titania or colloidal silica and oxide particles having a particle size of 0.1 to 1.0 μm, dried and fired. Manufacturing method.