JPH06316815A - Fly ash fiber - Google Patents

Abstract

PURPOSE:To provide a novel inexpensive inorganic fiber excellent in profitability, having a high mechanical strength and heat resistance, and capable of being widely used as a fiber-reinforcing material, an heat-insulating material, a warm-keeping material, a sealing material, etc., for metals, for metals, resins, rubbers, woods, glass, etc. CONSTITUTION:This fly ash fiber is fly ash fiber containing 20-40% of Al2O3, 35-50% of SiO2, 15-35% of CaO, 3-12% of Fe2O3, and 2-5% of MgO, or a fly ash fiber containing 20-45% of Al2O3, 25-50% of SiO2, 15--35% of CaO, 3-12% of Fe2O3, 0-5% of MgO and 3-10% of ZrO2. When further containing a zirconium compound, the fiber is improved in alkali resistance, and is especially effective for cements, mortals and concretes. Coal ash which has been a broblem can be effectively utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new inorganic fiber, fly ash fiber.

[0002]

2. Description of the Related Art There is an inorganic fiber as a fiber containing an inorganic substance as a main component. They are asbestos, glass wool, fiberglass,
Rock wool, slag wool, silicon oxide fiber, alumina silicate fiber, ceramics fiber, silica fiber, zirconia fiber, carbon fiber, silicon carbide fiber, calcium titanate fiber, silicon carbide fiber, tyranno fiber, ceramic whisker and the like. Among these, asbestos is produced as a natural mineral, and other inorganic fibers are produced by heating and melting a natural material or another substance as a raw material and then fiberizing it.
Each fiber is roughly classified into two types, one that is mainly produced only in the form of cotton and one that is also produced in the form of continuous fibers.

Of these inorganic fibers, those produced mainly in the form of cotton are used as heat insulating materials and heat insulating materials. Glass wool has a maximum operating temperature of 250-350 ℃
Very low and limited applications. Glass fibers have problems in heat resistance and alkali resistance. Since asbestos has carcinogenicity, its use is beginning to be restricted in terms of working environment. Rockwool is used in large amounts because it is inexpensive, but it can only be used at 600 ° C or lower. Similarly, silicon oxide fibers can only be used below 750 ° C. 1000 ℃ for ceramic fiber and alumina fiber
Although it has the above heat resistance, it is expensive due to the large energy cost during manufacturing. Carbon fiber is excellent in specific strength and specific elastic modulus, but has a problem in oxidizing property. Silicon carbide fibers and Tyranno fibers are excellent in oxidation resistance, but they are expensive. From these facts, it is strongly desired to develop a new inorganic fiber having mechanical and thermal properties comparable to those of ceramic fibers and having a price comparable to that of rock wool.

Although the inorganic fiber may be used as a heat insulating material or a heat insulating material by itself, it is also used as a reinforcing material or a filling material of a composite material by compounding it with other materials. A composite material using fibers as a reinforcing material is made for the purpose of obtaining mechanical properties superior to the properties of a certain material alone. Composite materials using inorganic fibers as reinforcing materials include fiber reinforced plastic (FRP), fiber reinforced metal (FRM), fiber reinforced glass (meshed glass), carbon fiber reinforced carbon (C / C), fiber reinforced concrete, etc. is there. In addition to the above-mentioned various inorganic fibers, various organic fibers (polyamide, vinylon, cotton, hemp, wool, silk, acetate, nylon, tetron, cellulose, acrylic fiber, etc.), metal Textiles are also used. But,
When heat resistance is required, organic fibers cannot be used. In addition, it is often difficult to use a metal material because of its corrosiveness and density. From these points as well, the inorganic fibers are often used.

[0005]

As described above, various kinds of inorganic fibers are used in various fields as reinforcing fibers of composite materials, but with the progress of industrial technology, the present inorganic fibers have required functions. The reality is that we are no longer satisfied. Hereinafter, the manufacturing method, characteristics, problems, etc. of various inorganic fibers currently manufactured will be outlined.
Asbestos, a natural fiber, is roughly classified into serpentinites and amphiboles, but the former occupies 95% of world production,
Many are produced. Of these, three types that are industrially important are chrysotile asbestos, blue asbestos, and amosite asbestos. Table 1 shows these chemical components and characteristics.

[0006]

[Table 1]

Asbestos may be used alone,
Combined with other materials, cement products (asbestos slate, asbestos pipe, etc.), textile products (asbestos yarn, asbestos cloth, etc.), heat resistant products (boiler coating, joint sheets, packing, ship bulkheads, etc.), wear resistant products (Automotive brake linings, clutch facings, elevator and train control parts, etc.), electrical insulation, heat insulation, acid resistant products (asbestos threads, felts, heat insulation plates, tiles, paints, etc.), and other products (plastic reinforced, oil stove) Various asbestos products such as cores are produced and used in large quantities. Asbestos is important as a reinforcing material for cement, mortar and concrete because it has a particularly good dispersibility in cement. However, due to carcinogenic problems of asbestos, its use is being regulated and it is about to be discontinued.

[0008] Glass wool is a short glass fiber and has a length of several cm to several tens of cm depending on the manufacturing method. The manufacturing method includes steam blowing method (method of blowing molten glass flowing down from a nozzle with steam), flame blowing method or super fine method (drawing molten glass from a nozzle and solidifying and molding it into a thin rod, followed by high pressure There are three types: the method of blowing it into flames to make it into fibers), and the centrifugal method (the method of blowing molten glass from the rotating body by centrifugal force or the method of stretching molten glass from the nozzle of a rotating container by centrifugal force). . Plastics made by steam blowing method, flame blowing method or super fine method are suitable for heat insulation tubes, and centrifugal method is suitable for boards and mats.
The product is formed into a roll, a board, a mat, or the like using a phenol resin as a binder. Glass wool is classified into No. 1 (4 μm or less), No. 2 (8 μm or less) and No. 3 (20 μm or less) according to the average fiber diameter. The smaller the fiber diameter, the better the thermal conductivity. For example, the fiber diameter is 2.5
The thermal conductivity of μm is about 0.030 kcal / m · hr · ° C, but it greatly changes to 0.046 kcal / m · hr · ° C near 12.5 μm. The maximum operating temperature is about 250 ° C. Table 2 shows the chemical composition of glass wool.

[0009]

[Table 2]

[0010] In addition to glass wool, the fibrous material composed of glass includes glass fibers spun as long fibers. This glass fiber is widely used as a reinforcing material for resins. However, due to its poor alkali resistance, it cannot be used as a cement-based matrix reinforcement. Regarding the deterioration mechanism of glass fiber by cement,
(1) Chemical erosion by alkaline components of cement, (2) Physical damage by recrystallization of calcium hydroxide produced, and (3) Cement hydrate fills voids between glass fiber filaments, It is explained that the ability to absorb the fracture energy of a cured product is reduced by reducing the degree of freedom with respect to deformation.

Therefore, various attempts have been made to coat the surface of the glass fiber with an alkali-resistant substance in order to increase the alkali resistance of the glass fiber. As an example of coating with an inorganic substance, glass fibers are immersed in a zirconium compound solution such as zirconium oxychloride and then heat-treated to form Z.
Method for forming rO ₂ microcrystals, contacting with vaporized organotitanium compound and then contacting with water containing gas
₂ There is a method of forming a film. Examples of the organic film include a method of applying a furan resin, a method of applying a rubber resin, a method of applying an alkali impermeable impregnating agent such as wax, and a method of applying polyvinyl alcohol. However, none of the methods has achieved good results.

Further, in order to increase the alkali resistance of the glass fiber, a substance that weakens the alkalinity of the cement or a substance that delays hydration of the cement on the surface of the glass fiber (for example, a delay of polyoxy aromatic compound, sugar, dihydroxybenzoic acid, etc.) Agent). However, these methods have not yet achieved sufficient results.

In addition to these ideas, a glass fiber containing about 20 wt% of zirconium oxide has been developed in order to impart alkali resistance to the glass fiber. It was found that this glass fiber did not dissolve even when immersed in cement paste and could maintain its strength. A glass fiber containing zirconium oxide is called an alkali resistant glass fiber and is called ARG (Nippon Electric Glass Co., Ltd.).
Manufactured) and Semfil (manufactured by Nippon Sheet Glass Co., Ltd.) are manufactured.

Of these, ARG contains 20% zirconium oxide and is manufactured by the all-electrofusion DM method. The all-electrofusion DM method is a method in which glass melted by Joule heat in an all-electric melting furnace is directly spun. Marble once in a conventional heavy oil combustion furnace (glass with a diameter of about 20 mm)
Compared with the method of making and remelting and spinning it, the vitrification reaction progresses uniformly, energy efficiency is high, glass volatilization loss is small, pollution control such as desulfurization equipment is not required, etc. Therefore, it is suitable for producing high-quality glass fiber at a relatively low cost.

ZrO that is difficult to dissolve during the production of ARG
_Since about 20% of the _two components are added, great care must be taken when preparing and dissolving the raw materials. The molten glass dough is drawn out from a large number of nozzles at the bottom of the platinum bushing and spun into filaments with a diameter of about 13 μm. A sizing agent is coated on the surface of hundreds of filaments according to the application, then they are bundled into a strand and wound with a winder rotating at high speed. The fiber diameter is adjusted by controlling the bushing temperature and the speed of rotation of the winder. The wound glass fiber is processed into rovings, chopped strands, etc. through a drying process. Table 3 shows the properties of ARG.

[0016]

[Table 3]

Attempts have also been made to modify the cement on the matrix side in order to further increase the alkali resistance of the alkali resistant glass fibers. In these, admixtures such as vinyl polymer, calcium sulfaluminate, and silica fume are added to cement, and low alkaline cement was developed from these. GR using alkali resistant glass fiber and low alkali cement
C-Cement (produced by Chichibu Cement Co., Ltd.) has been created and used for curtain walls and the like.

Rockwool is an artificial mineral fiber. The raw material for rock wool is basalt or andesite, which is exposed as lava flows, dikes or rock beds throughout the country. These rocks (igneous rocks)
Is a component similar to the glass raw material and is used in large quantities because the raw material is inexpensive. However, since it is difficult to obtain stable quality, metal refining slag, especially blast furnace slag, has recently been used as the main raw material, and silica stone, dolomite, limestone, etc. have been added to this to adjust the chemical composition. . These raw materials are melted in a cupola or electric furnace at a temperature of around 1500 ° C., and this hot water is poured from the furnace,
The fibers are formed by a blowing method or a centrifugal method in which high-pressure steam or compressed air is wiped to form fibers. The fiberized loose wool is collected into a product as it is, or it is adjusted to have a constant density and thickness and subjected to a continuous forming process, or is sent to a granulating device to be made into a granular cotton. Table 4 shows the typical chemical composition of rock wool chemical components.
Shown in.

[0019]

[Table 4]

Rock wool usually has a fiber diameter of 2 to 20 μm (average of 7 μm or less) and a length of 10 to 100 mm.
The tensile strength of rock wool is 50 kgf / mm ² (fiber diameter 5.
1 μm) and the thermal conductivity is 0.0348 kcal / m · hr · ° C.
Various industrial products have been produced using rock wool. Since they have a maximum use temperature of 600 ° C. and are higher than that of glass fiber, they are used not only as heat insulating materials and heat insulating materials but also as non-combustible building materials. Since rock wool has been certified as a non-combustible building material, it has attracted attention as a building material and is used as a fireproof coating for steel columns and as a heat insulating material for houses.
The demand areas are wide-ranging.

Although rock wool is cheaper than glass fiber in terms of price, it is inferior in terms of performance, is colored, has fibers that are dull and sticks to the body, and has problems in alkali resistance. There is a defect that strength can be maintained for a long period of time or it is unsolved. In fact, when rockwool is dipped in cement paste and heated at 80 ° C. for 20 hours, the fiber morphology cannot be retained and it becomes powdery. When observing those fiber surfaces with a scanning electron microscope,
Unlike the smooth surface state before the treatment, the multi-layered c had cracks and was violently etched.

Inorganic fibers having a higher heat resistance temperature than rock wool include silicon oxide fibers, and PMF (Process Minera
Fiber) and CMF are manufactured. The chemical composition and properties of this fiber are shown in Table-5.

[0023]

[Table 5]

The former PMF is developed and manufactured by Jim Walter, Inc. of the United States. Rock wool or slag wool manufactured by the same company is mechanically treated to make the fiber length uniform and the shot is removed. Is. Therefore, the chemical composition is exactly the same as rock wool. This PMF is used as a filler or a reinforcing material for various resins (for example, nylon, PBT, polypropylene, phenol resin, etc.) after being surface-treated with an organic silane compound. However, since this PMF has a problem in chemical resistance, particularly alkali resistance, from the viewpoint of chemical composition, it has not been used as a filler or a reinforcing material for cement-based substances.

The latter CMF was developed and manufactured by Nippon Cement KK. This fiber is an amorphous artificial inorganic fiber obtained by melting four types of natural ores at a high heat of about 1500 ° C. and blowing them with a centrifugal force or compressed air to form a fiber, which is carefully selected. This CMF has as high heat resistance as asbestos and a relatively high tensile strength with an average of 50 kgf / mm ² . However, the problem of CMF is that the chemical resistance, especially alkali resistance, is much worse than that of asbestos, and it is how to make this approach asbestos. In particular, there is a problem regarding whether strength can be maintained for a long period of time when added to a cement material, and it is not suitable for use as a reinforcing material for cement, mortar, concrete and the like. Moreover, the silicon oxide fiber is developed only as a substitute for asbestos, and has not been used for applications beyond the range of asbestos products. CMF applications include resin composite materials (thermoplastic resins, thermosetting resins), paint fillers, rubber fillers, non-combustible paper (cushion floors, wallpaper, interior building materials, etc.), non-combustible felts, non-combustible boards. Raw materials, plaster, friction materials (brake pads, brake disks, clutch facings, etc.).

Ceramic fiber is an inorganic fiber that is more heat resistant than rock wool. This fiber is mainly produced by amorphous silica-alumina fiber.
Ceramicus fiber was studied 60 years ago in the United States for the effective utilization of kaolin minerals. Since ceramic fibers have excellent properties as industrial materials, their commercialization was promoted around 1950 to 1955 after the Second World War.

As a raw material for the alumina-silica fiber, many natural minerals such as kaolin and kyanite were used at the beginning of development.
₍₂ O ₃ , TiO ₂ , Na ₂ O, etc.) affect heat resistance, so it is necessary to mix silica raw materials such as silica and silica with alumina raw materials such as buyer alumina and fused alumina. Depending on the requirement, borate glass, zirconia, chromium oxide, titanium oxide, etc. are added. Since the melting temperature of the raw material mixture is 2000 ° C. or higher, it is melted in an electric furnace of arc type, resistance type or induction type. Then, after lowering the viscosity of the melt to about several hundreds of cps, the melt is allowed to flow out to form fibers. Fiberizing methods include a blowing process in which compressed air or a steam jet is blown to a narrow stream of a melt, and a spinning process in which centrifugal force of a rotor rotating at high speed is used. The blowing process is: (Raw material mixing)-(Melting)-(Spraying)-
Made in the order of (fiber). In the spinning process, (melting material)-(melting) melt is flowed through a distributor and added dropwise onto one or two or several rotors rotating at high speed to be spun into fibers. It is a thing. The resulting fibers are collected in layers by a cotton collecting device and processed into various secondary products.

The characteristics of the ceramic fiber depend on the material (alumina / silica) and the morphology of the fiber. Properties based on the former material are fire resistance, chemical resistance, chemical neutrality, electrical insulation, and the like. In addition, the properties affected by the latter form are heat insulation, elasticity (compressibility, restoration), sheet property,
It has filterability and sound absorption. Ceramic fibers currently on the market (alumina silicate fiber)
1260 depends on its chemical composition, maximum temperature of use, etc.
It can be divided into two types, the ℃ class and the 1400 ℃ class. Their characteristics are shown in Table-6. For comparison,
The case of alumina fiber described later is also shown.

[0029]

[Table 6]

Table 7 shows the chemical composition and characteristics of various ceramic fibers produced. Also in this case, the maximum operating temperature is classified into a standard product having a temperature of 1260 to 1300 ° C and a high temperature product having a maximum operating temperature of 1400 to 1480 ° C.

[0031]

[Table 7]

The standard product having a heat resistance of 1260 to 1300 ° C. has an Al ₂ O ₃ / SiO ₂ weight ratio of 1.2 to 0.8.
Range, but CaO, MgO, TiO ₂ , Fe ₂ O ₃
It contains impurities such as. On the other hand, the high temperature products are Al ₂ O ₃ /
The weight ratio of SiO ₂ is 1.3 to 1.6 and the alumina component is large, and other impurities are very small. It is unavoidable that the ceramic fibers are mixed with glassy particles called “shots” which are not fiberized due to the manufacturing method. Since this adversely affects the performance of the product, it is desirable to minimize it. JIS
Then, in the case of a blanket, particles of 212 μm or more are 2
It is regulated to be 5% or less.

The maximum operating temperature of the ceramic fiber is
It is mainly determined by the heat shrinkage of the fiber. Alumina-silica fiber is mullite (3A
(l ₂ O ₃ · 2SiO ₂ ) crystals are deposited and transition from vitreous to crystalline. Along with this, the fiber contracts.
The amount of shrinkage increases as the temperature rises, and the flexibility is lost. In order to deal with these points, Cr ₂ O ₃ and ZrO
A component with a maximum operating temperature of about 1400 ° C is manufactured by adding ingredients such as ₂ . It is necessary to consider the maximum operating temperature in practice, because it varies depending on the construction method and operating conditions. Generally, fibrous materials have a low bulk density and a high porosity, so they have excellent heat insulating properties, but the thermal conductivity at high temperatures is strongly affected by radiation, so it is better to increase the density slightly. Tends to become. In addition, it has excellent sound absorption characteristics,
High sound absorption coefficient in the middle and high frequency range above MHz. Further, the electric insulating property is excellent because the amount of the alkaline component is small, but it tends to decrease at high temperatures.

Ceramic fibers include bulk fibers, felts, boards, blankets,
There are various products such as block insulation and molded products. In addition, textile products, casting materials, etc. are manufactured. On-site construction of thermal insulation by spraying is also performed. Ceramic fibers are widely used in various applications such as heat insulating materials, sealing materials, packing materials, and sound absorbing materials, but the greatest drawback of alumina-silica ceramic fibers is deterioration of quality due to recrystallization during heating. .
Since fibers of this type are originally formed into fibers in an extremely short time, they become amorphous in a supercooled state.

Alumina fibers were developed to withstand higher temperatures in order to compensate for the above drawbacks. Alumina fiber is, for example, a precursor inorganic material obtained by using an aqueous solution of aluminum chloride salt as a starting material, fibrating the aqueous solution under extremely strict control, and heating it to remove hydrochloric acid, acetic acid, and the like to obtain a polycrystalline fiber. It is produced by the salt method (salt decomposition method). Since this method makes it easy to control the fiberizing conditions,
The characteristic is that the generation of non-fibrous particles (shots) is extremely low. The characteristics of the alumina fiber are shown in Table-8.

[0036]

[Table 8]

Fused quartz fiber is superior to water vapor and weather resistance in comparison with glass fiber, and is not affected by long-term exposure to acid or alkali. The melting point is 1500 ° C. or higher. In this fiber manufacturing method, a quartz rod having a diameter of 0.12 to 0.15 mm is put into a high temperature flame at a constant low speed, and the tip of the softened rod is stretched and wound on a wind drum rotating at a high speed. As described above, fibers made of 99.95% of quartz are expensive, so that demand is low in Japan. The tensile strength of fused silica is about 600 kgf / cm ^2, which is about twice that of E glass fiber. Other properties are shown in Table-9.
Shown in. The molten glass fiber is produced in a fibrous form, yarn, tape, cloth and the like. Applications of this fiber are precision instrument parts, heat insulation materials, filtration materials, plastic reinforcement materials, electrical insulation materials and the like.

[0038]

[Table 9]

The high silicic acid fiber is obtained by treating glass fiber with sulfuric acid and converting it into a fiber having 96% or more of silica to improve heat resistance. This fiber has a diameter of 10.2-12.7 μm and is not affected by thermal or mechanical properties even when exposed to neutrons or γ rays. 9
Safe at continuous use at 00 ° C, but 1 at 1150 ° C
After being used for 00 hours, it becomes extremely brittle. From this fiber, various forms such as fiber, yarn, tape, cloth, putt, and rope are made. The fibers are used for general heat insulating materials, heat resistant coating materials for electric wires, high temperature gaskets, plastic reinforcing materials, petroleum stove cores, catalyst carriers and the like.

Zirconia fibers are fibers that have the potential to be used at high temperatures. The UCC fiber is made of organic fiber as a precursor, into which an aqueous solution of zirconium salt is pressed and uniformly dispersed in its fine structure, which is thermally decomposed in a special atmosphere furnace and then heat-treated again. Is made. This method produces an inorganic fiber that maintains the fine structure of the precursor. Further, the zirconia fiber manufactured by ICI is a polycrystalline body having fine pores, has a silky feel, and has excellent flexibility and elasticity.
This manufacturing method is a method called a blow-off spinning method in which a liquid containing zirconium is blown out from a nozzle and blown off with a high-pressure gas to form fibers. This fiber is also a polycrystallin fiber and has a stabilizer added thereto.

As other fibers, calcium titanate fibers and various whiskers have been developed, but since they are expensive, they are used only in special fields.

Carbon fibers have been developed mainly for aerospace, sports and leisure because of their excellent specific strength and specific elastic modulus, but they have the drawback of being oxidized and cannot be used in a high temperature oxidizing atmosphere. Fibers that can be used at high temperatures include various ceramic fibers such as the above-mentioned alumina fibers and silica fibers. These are excellent in oxidation resistance, but their use range must be limited because they are expensive. Also, metal fibers such as steel fibers
Although excellent in economical efficiency, it has a problem in specific strength and specific elastic modulus as compared with carbon fiber and the like due to its high density. In addition, since it is a metal, it has the drawback that it is easily corroded. Organic fibers such as nylon and vinylon are also used as reinforcing fibers. However, there is a problem in heat resistance.

As described above, various inorganic fibers are used as a heat insulating material, a heat insulating material, and a reinforcing fiber for a composite material, but each has various problems, and the development of new fibers is strongly desired. The reality is that Therefore, the object of the present invention is to
In view of such a social situation, it is an object of the present invention to provide a new inorganic fiber satisfying the above various conditions.

[0044]

The above object of the present invention is to provide, as a novel inorganic fiber, 20 to 40% Al ₂ O ₃ , 35 to 5%.
0% SiO _2, 15 to 35 percent of CaO, be achieved has been found by the fly ash fiber, characterized in that it contains 3 to 12% of the Fe ₂ O ₃ and 2-5% of MgO. Further, in addition to the above composition, further containing a zirconium compound, 20 to 45% of Al ₂ O ₃ , 25
˜50% SiO ₂ , 15-35% CaO, 3-12
% Fe ₂ O ₃ , 0-5% MgO and 3-10% Zr
With the fly ash fiber characterized by containing O ₂ , the alkali resistance is further improved, and an inorganic fiber suitable for use in a cement-based material can be obtained.

The present invention is an attempt to develop a fly ash fiber (FA fiber) obtained by melt spinning unutilized coal ash at a high temperature. In particular, it defines the raw material composition for producing new inorganic fibers, and also defines the properties, functions, structures, etc. of the new fibers that are industrially effective.

The coal ash is generated when the coal is burned for power generation. For example, in 1989, the amount of coal used for power generation was 24.5 million tons, and the amount of by-produced coal ash was about 40.
It has reached to 100,000 tons. Only 1.9 million tons (49%) are effectively used, and the remaining 51% is treated as landfill or sea surface landfill. In addition, about 1.5 million tons of coal ash is generated from general industries. Since the amount of coal ash generated is expected to increase in the future, it is strongly desired to develop technology for effectively utilizing coal ash. The present invention provides valuable inorganic fibers,
It is very effective in that the effective use of coal ash can be realized.

However, the composition of the coal ash discharged from the thermal power plant depends on the coal used. The metal content in coal differs between domestic coal and foreign coal, and also depends on the place of coal production. Table-10 shows the representative chemical composition of domestic coal and foreign coal and the chemical composition by origin.

[0048]

[Table 10]

As described above, although the chemical composition of coal ash differs depending on the place of production, various characteristics such as mechanical strength and thermal properties of the produced fly ash fiber are
Must be constant. Establishing a manufacturing technology for fly ash fibers having certain characteristics is extremely important industrially. Moreover, in addition to coal ash, the manufacturing technology of inorganic fibers or ceramic fibers having a function equivalent to fly ash fiber by using other raw materials (for example, natural ore, industrial by-products, etc.) should be established. That is extremely significant. In view of these points, the inventors of the present invention, as a result of diligent research, have found that the fly ash fiber having the above composition has excellent mechanical strength and thermal properties, and arrived at the present invention.

The greatest feature of the fly ash fiber of the present invention is that it has excellent heat resistance and mechanical properties.
The fly ash fiber having certain characteristics of the present invention is realized by determining the chemical composition of the raw materials for production and the blending of each raw material, and establishing the production technology for guaranteeing the quality of the fly ash fiber. Further, in the present invention, the mechanical and thermal characteristics, the structure, and the like of the inorganic fiber produced by using coal ash as the main raw material and, if necessary, other auxiliary raw materials can be specified.

The mechanical and thermal properties of the fly ash fibers of the present invention are determined by their chemical composition. Among them, alumina (Al ₂ O ₃ ) affects the thermal characteristics of the fiber. Increasing the alumina content increases the melting temperature, maximum temperature of use, and alkali resistance. In addition, the melting temperature of the raw material (raw material mixture) is increased and the chemical resistance is improved. However, the energy cost required for fiberizing increases, and the fiberizing technology becomes difficult, such as increasing the temperature of the furnace structural material. Therefore, in the fly ash fiber of the present invention, 2
It is desirable to contain 0 to 40%. When the amount of Al ₂ O ₃ is 20% or less, the heat resistance is insufficient, and when it is 40% or more, the spinning temperature becomes high, the energy cost rises, and the viscosity becomes high, making spinning difficult.

If the silica (SiO ₂ ) content is high, the melting temperature will be low, the viscosity of the melt will be low, and fiber formation will be easy. Naturally, the manufacturing cost will be low. However, the heat resistance becomes low and it cannot be used in high temperature range. Furthermore, it has low alkali resistance and cannot be used for cement / concrete composite materials. Therefore, in the fly ash fiber of the present invention, 35 to 50% is desirable. When the SiO ₂ content is 35% or less, the viscosity is low and spinning becomes difficult, and the melting temperature must be increased. On the other hand, if it is 50% or more, spinning is facilitated, but alkali resistance is deteriorated and it cannot be used as a reinforcing material for cement-based materials.

In addition, calcium oxide is also contained in a large amount in the case of glass wool or rock wool. In most cases, this is already contained in the raw material, but other than that, it may be added as a viscosity modifier to the raw material so as to obtain the composition of the present invention. The amount of calcium oxide is
In the case of the fly ash fiber of the present invention, 15 to 35
% Is desired. If it is 15% or less, it is difficult to melt and spinning is difficult. However, if it is 35% or more, when it is used as a cement-based material, there is a concern that neutralization will occur and the long-term strength will decrease.

The Fe ₂ O ₃ content contained in the coal ash and also contained in the fly ash fiber is 3 to 12%. It is desirable that this content be as low as possible,
Since coal ash is used, mixing of about 3% is unavoidable. In addition, it has been confirmed from experimental facts that the heat resistance of the produced fly ash fiber is improved when the Fe ₂ O ₃ content is decreased, and it is desirable to consider the reduction as much as possible. When the Fe ₂ O ₃ content increases,
The degree of coloring of the fly ash fiber increases, which is not preferable. For these reasons, a Fe ₂ O ₃ content of 12% or more causes many problems and must be avoided.

Further, 3 to 10% of zirconium oxide can be added in order to improve alkali resistance and to be used as a cement material. If it is 3% or less, the effect of improving alkali resistance is not observed. On the other hand, if it is 10% or more, the melting temperature is high and the spinning temperature is high.

The fiber diameter of fly ash fiber is 5
˜20 μm (average fiber diameter 5 to 10 μm) and fiber length 5 to 30 mm. It has been found that the mechanical properties of fly ash fiber depend on the fiber diameter. For example,
When the diameter is 6 μm, the tensile strength is 4120 MPa and the tensile elastic modulus is 200 GPa. These characteristics can be compared with other inorganic fibers such as alumina fiber (strength 1400 MPa,
Elastic modulus 385 GPa), glass fiber (strength 2400 MPa, elastic modulus 70 GPa), carbon fiber (strength 3000 MPa, elastic modulus 2)
It can be seen that the fly ash fiber has extremely excellent characteristics as compared with 20 GPa). Further, the fly ash fiber having a fiber diameter of 15 μm has a tensile strength of 290 MPa and a tensile elastic modulus of 17.5 GPa, and the mechanical properties are significantly affected by the fiber diameter. However, it is far superior to rock wool fiber and general glass fiber in terms of heat resistance and mechanical strength. Generally, the mechanical properties of the fly ash fiber of the present invention differ depending on the fiber, but the tensile strength is 2
The tensile elastic modulus is 10 to 250 GPa.

The melting temperature and crystallization temperature of the fiber can be determined by thermal analysis (differential thermal analysis). When the manufactured fly ash fiber is heated in the air with a thermal analysis device, an exothermic peak appears from around 940 ° C to 1150 ° C.
Endothermic peaks were seen in the vicinity. The former exothermic peak indicates the onset of crystallization of fly ash fiber.

Crystallization of fly ash fiber means
It indicates that the following phenomenon has occurred. That is, the produced fly ash fiber is made into a fiber from a state of being melted at a high temperature. Fiberizing is performed in an extremely short time of 0.1 seconds or less. At the same time as it is made into fibers, it is rapidly cooled from high temperature to room temperature, so it is supercooled and becomes amorphous. When such a supercooled fly ash fiber is heated to a high temperature again, crystals are precipitated (crystallized) in the fly ash fiber. However, when the heating temperature is low, the amount of precipitated crystals is small and the growth of crystals is not remarkable, but stress is generated in the fiber, and the fiber is bent or the rigidity is increased.
When the heating temperature is further increased, the precipitated crystal grows to affect the fiber diameter, and the rigidity increases and the fiber easily breaks, which deteriorates the quality of the fiber. Therefore, it is desirable that the crystallization temperature and the crystallization start temperature are as high as possible.

In the present invention, the temperature at which the exothermic peak rises in the differential thermal analysis is taken as the crystallization start temperature. At the same time, above this temperature, the performance is expected to deteriorate, so this temperature was defined as the maximum operating temperature. Also,
The melting start temperature was determined from the temperature at which the endothermic peak rises, and the melting temperature was determined from the temperature exhibited by the endothermic peak. The thermal characteristics of the fly ash fiber according to the present invention, which are affected by its chemical characteristics, are very high. The crystallization temperature is 950 to 1050 ° C and the melting temperature is 1150 to 130.
The temperature is 0 ° C and the maximum temperature is 910 to 950 ° C. As a result of comprehensively examining the chemical composition and producing fly ash fibers, the present inventor has established a very effective technique for producing inorganic fibers having a maximum service temperature of 910 ° C. or higher.

The components of the coal ash, which is the raw material of the fly ash fiber, differ depending on the origin of coal as shown in Table 11 above, but the main ones are silicon dioxide (silica; SiO ₂ ) and aluminum oxide (alumina). ;
Al ₂ O ₃ ), and these two minerals make up a total of 60 to 8
It accounts for 0%. In addition, it contains a small amount of ferric oxide, calcium oxide, magnesium oxide and the like. In order to maintain the quality of coal ash, it is preferable that the ingredients of the raw material coal are stable. In addition, fly ash fibers having a high crystallization temperature, a high melting temperature, and a maximum use temperature can be produced from coal ash having a low silica content and a high alumina content. However, when the content of alumina is high, the viscosity at high temperature becomes low. Therefore, when spinning fly ash fiber, it is preferable to add an auxiliary material such as limestone as a viscosity modifier.

The chemical composition of the fly ash fiber according to the present invention has the Al ₂ O ₃ content of 20 according to claim 1.
-40%, SiO ₂ content 35-50%, CaO content 15-35%, Fe ₂ O ₃ content 3-12%, MgO content 2-5%. The raw coal ash from which the fly ash fiber of this composition is obtained has a chemical composition of Al ₂ O ₃ of 10
To 40%, particularly 15~30%, SiO ₂ is 30 to 65
%, In particular 40 to 50%, CaO 0.5 to 15%, particularly 1 to 5%, Fe ₂ O ₃ is 1-20%, in particular 5 to 15%, M
It is preferable that gO is 0 to 10%, particularly 0 to 2%. As an example of the chemical composition of the raw material coal ash having this component composition, Al ₂ O ₃ is 18.9%, SiO ₂ is 56.6%,
The coal ash of China Datong Coal, which has 2.5% CaO, 12.8% Fe ₂ O ₃ and 1.0% MgO, can be mentioned.

Here, the composition of each component constituting the fly ash fiber according to the present invention and the raw material coal ash thereof is in a stable form based on the results obtained by elemental analysis by an X-ray microanalyzer. It is expressed in the form of an oxide. Therefore, they are not necessarily present in the fly ash fiber or coal ash of the present invention in the form of the above oxides.

When the fly ash fiber of the present invention is produced by using the coal ash in the above preferable composition, the coal ash may be melted as it is to be fiberized. However, if the chemical composition is not within these chemical compositions, it is preferable to add another auxiliary material as needed. Further, even with coal ash having the above chemical composition, various auxiliary raw materials can be added as necessary.

As the auxiliary material, the same materials as those used for the conventionally known inorganic fibers can be used in the present invention. For example, limestone, various silicas, various aluminas, clay minerals such as mullite or sillimanite, magnesium phosphate, etc. Examples thereof include fused phosphate, fused alumina, iron oxide, magnesium oxide, various natural minerals, and the like. In addition, a melting accelerator, a viscosity modifier, etc. may be added. More specifically, akermanite (2CaO ・ MgO ・ 2Si
O ₂ ), Andalusite (Al ₂ O ₃ · SiO ₂ ), Anorthite (CaO · Al ₂ O ₃ · 2SiO ₂ ), Nepheline (CaC
O _3), berlinite _{(Al 2 O 3 · P 2} O 5), boehmite _{(Al 2 O 3 · H 2} O), calcite (CaCO _3), diaspore _{(Al 2 O 3 · H 2} O), diopside ( CaO / MgO
・ 2SiO ₂ ), dolomite (MgCO ₃・ CaC
O ₃ ), iron olivine (2FeO · SiO ₂ ), forsterite (2MgO · SiO ₂ ), gerenites (2CaO)
・ Al ₂ O ₃・ SiO ₂ ), ash agate aragonite (3CaO ・ Al ₂
O ₃ · 3SiO _2), Hedenbergite (CaO · FeO · 2Si
O ₂ ), hirugen stockite (4CaO · P ₂ O ₅ ),
Water van stone _{(Al 2 O 3 · 3H 2} O), kyanite (Al ₂
O ₃ · SiO ₂ ), Ralunite (2CaO · SiO ₂ ),
Melwinite (MgO · 3CaO · 2SiO ₂ ), Monticellite (CaO · MgO · SiO ₂ ), Nagelschmitite (7CaO · P ₂ O ₅ · 2SiO ₂ ), Red Tartite (3MgO · Al ₂ O ₃ · 3SiO _2). ), Rankinite (3CaO · 2SiO ₂ ), Sapphirine (4MgO)
_{· 5Al 2 O 3 · 2SiO 2} ), talc (3MgO · 4Si
O ₂ · H ₂ O), Whitlocite (3CaO · P
₂ O ₅ ), wollastonite (CaO · SiO ₂ ), zirconia (Z
rO ₂ ), zircon (ZrO ₂ · SiO ₂ ), various zirconia compounds, and the like.

The fly ash fiber of the present invention can be manufactured by a conventional method for manufacturing an inorganic fiber such as a ceramic fiber. For example, in melting coal ash as a raw material, a batch system method (cupola method) using a cupola that solidifies and inputs a powdery raw material, an electric furnace method that uses an electric furnace that directly inputs a raw material in powder form, etc. To be Of these, the electric furnace method is preferable in terms of low power consumption rate, high yield, and the like. The coal ash melted by these methods, like the ceramic fiber,
Fiberized by blowing process or spinning process. Also in this case, a long fiber length with a low shot mixing ratio can be secured, which is preferable.

Fiberizing of the high-temperature melt requires melting at a temperature at which an appropriate viscosity is obtained, and depending on the composition of the raw material coal ash, it is 1100 to 1900 ° C., especially 1400 to 17 ° C.
A temperature of 00 ° C is suitable.

Since the fly ash fiber according to the present invention contains silica in an amount of 35 to 50%, the fly ash fiber is dissolved when immersed in cement paste, and there is a fear of a decrease in strength. To examine this point, 10 g of fly ash fiber was immersed in a paste of ordinary Portland cement, heated to 80 ° C., and taken out after 200 hours.
No weight reduction rate was observed with this treatment. In the case of rock wool, it was found that the alkali resistance of fly ash fiber was far superior to that of powdered rock wool which could not retain the fiber form. In addition, when the surface of the fly ash fiber was observed with a scanning electron microscope, it did not appear to be violently etched. Therefore, it can be said that the alkali resistance is not a problem from the weight reduction rate and the surface condition.

However, since SiO ₂ is contained in the chemical composition of fly ash fiber, it is doubtful whether the cement Matrix can maintain its properties for a long period of time. Therefore, the production of fly ash fiber having alkali resistance was further examined. In order to impart alkali resistance to the glassy fly ash fiber, it can be effectively achieved by adopting the addition method of zirconium oxide which has already been applied to the glass fiber (ARG) and has obtained favorable results. Zirconium oxide is added as a raw material, zirconium oxide (zirconia),
Zirconium silicate (zircon, ZrO ₂ · Si
O ₂ ), halides such as zirconium chloride, Zr
_{(NO 3) 4 · 5H 2} O, ZrO · (NO 3) 2, Zr (S
O ₄ ) ₂ , Zr (SO ₄ ) .4H ₂ O, ZrO (SO ₄ ),
Oxygen acid salts such as Zr (H ₂ PO ₄ ), ZrP ₂ O ₇ and various organic acid salts were used.

A predetermined amount (5 to 20% of coal ash) of these substances was added to the same raw material coal ash as described above, and 1500
After being heated to ˜1600 ° C. and dissolved, it was spun in the same manner as above. The appearance, fiber diameter, fiber length, etc. of the obtained fly ash fiber were almost the same as those of the general-purpose fly ash fiber containing no zirconium. The surface condition was observed with a scanning electron microscope, but no difference was observed depending on the presence or absence of zirconia.

When the composition of the fly ash fiber containing this zirconium compound was analyzed by using an X-ray microanalyzer, as described in claim 2, Al ₂ O ₃ ; 20 to 45%, SiO ₂ 25-50
%, CaO; 15 to 35%, Fe ₂ O ₃ ; 3 to 12%, M
It goes; 0~5%, ZrO _2; was 3-10%. Add 5 parts of this fly ash fiber to a saturated solution of cement.
After soaking for 0 hour, no weight loss was observed. The surface condition was observed with a scanning electron microscope, but it was not corroded. From these, it was found that by containing zirconium oxide, an alkali resistant fly ash fiber can be obtained.

Fly ash fibers according to the present invention can be used to develop a variety of excellent building materials. One of them is a fly ash fiber reinforced cement composite that uses fly ash fiber as a reinforcement. When a composite material is produced from fly ash fiber according to the present invention and ordinary Portland cement, its mechanical strength is affected by the production conditions. For example, the bending strength of a cement composite material containing fly ash fiber at 25% of the cement weight is 80kgf / cm ² ,
The compressive strength was 690 kgf / cm ² . In this case, the strength reinforcement of 2.5 times in bending strength and 20% in compressive strength was observed as compared with the cement hardened body to which fly ash fiber was not added.

Furthermore, it has been possible to develop a high-strength, high-fireproof building material using fly ash fiber. In that case, using alumina cement as the matrix, a fly ash fiber reinforced alumina cement composite material was produced. For example, the density was 2.2 g / cm ³ , the maximum bending strength was 190 kgf / cm ² , and the maximum compression strength was Is 14
A product of 50 kgf / cm ² was obtained. These strengths are 2.5 times more flexible than the alumina cement alone,
The compressive strength was 1.8 times higher. This fly ash fiber reinforced alumina cement composite had high fire resistance and thermal shock resistance, did not change its shape even after heat treatment at 900 ° C., and had practically high mechanical strength.

The above fly ash fiber reinforced concrete is effective as a heat insulating material and a heat insulating material reinforcing material, which are far superior to those of conventional ceramic fibers such as glass wool and rock wool.

In addition, the fly ash fiber of the present invention is prepared by using a material other than cement or concrete (plastic,
It has been found that when combined with metal, rubber, glass, wood, etc.), the respective properties are improved. For example, in the reinforcement material of fly ash fiber and plastic,
The impact strength was improved. Further, in the case of the composite material with metal (aluminum), the hardness was not improved, and the mechanical strength was not decreased even if 20% was added as an extender.

The fiber characteristics and chemical composition of the fly ash fiber of the present invention can be adjusted appropriately according to the type and characteristics of the matrix in which it is composited. For example, in the case of fly ash fiber for cement-based matrix, it must have alkali resistance. For metal reinforcement (FRM) and resin reinforcement (FRP)
For rubber, rubber, glass, wood, etc., mechanical strength, heat resistance, suppleness, etc. are required. The difference between the two is preferably controlled by the presence and amount of the zirconium oxide component contained in the fly ash fiber. The fly ash fiber according to claim 1 containing no zirconium oxide is suitable for metals, resins, glass, wood, rubber, etc., and the alkali resistant fly ash fiber according to claim 2 containing zirconium oxide comprises Suitable for cement, mortar and concrete.

Further specific applications of the fly ash fiber according to the present invention are not particularly limited, but in addition to the reinforcing materials as described above, heat insulating materials (lining materials for various industrial furnaces, heat insulating materials for automobile exhaust systems, induction coils). Part insulation, molten aluminum ladle and runner, glass tank kiln thermal storage chamber external insulation, unit sintering unit heater, heat insulation metal parts cooling induction furnace peripheral insulation, heat treatment furnace backup insulation, large diameter pipe welding Part slow cooling material, precision casting shell heat insulating material, casting hot top material, riser sleep material, electronic copying equipment heat insulating material, ladle lining material, etc., sealing material (coil annealing furnace inner cover gas sealing material, soaking furnace furnace) Gas sealing material for lids, sealing material for joints of various industrial kilns and ducts, tap cone for molten aluminum, vacuum steel degassing equipment gas Parts, gaskets for hot water boilers, small industrial kiln furnace materials, etc., packing materials (filling materials for furnace wall expansion material, burner tile surroundings, peephole blocks, temperature measuring pipes and other metal fittings surrounding packing materials) , Household combustion equipment packing materials, automobile engine parts, boilers, high temperature and high pressure container packing materials, etc.), sound absorbing materials (high temperature (around burner) sound absorbing materials, small hot water boiler combustion sound absorbing materials, etc.), composite materials Reinforcement materials (reinforcement materials in refractories, spacecraft outer wall reinforcement materials, etc.), catalyst carriers (raw materials for catalyst carrier production, gas reforming, catalyst heads for converters, catalytic combustion gas stoves, etc.), filtration materials (platinum) In addition to furnace dust recovery filters, etc., infrared burner surface heating elements, fireproof coating materials, heat resistant jigs, heat exchange elements, radiation materials, machinable ceramics, etc. It is possible.

[0077]

EXAMPLES The present invention will be illustrated below with reference to examples, but the present invention is not limited to these examples.

Example 1 Fly ash fiber was produced by burning Daido Coal of China and using the produced coal ash as a raw material. The chemical composition of this Daido coal ash is Al ₂ O ₃ ; 18.9%, SiO ₂ ; 56.6%.
, CaO; 2.5%, Fe ₂ O ₃ ; 12.8%, Mg
O: 1.0%. As it is difficult to melt as it is,
Limestone was added as a melting accelerator in an amount of 30% of the amount of coal ash used. In addition, minerals (such as magnesium phosphate compounds) as viscosity modifiers were added. These mixtures were placed in an electric furnace heated to about 1600 ° C., melted, and fiberized by a blowing process or a spinning process to produce fly ash fiber (fly ash fiber (1)).

The fiber obtained was in the form of white glass.
The fiber length was 5 to 30 mm and included shots. When the cross section is observed with a scanning electron microscope, the diameter is 5 to 2
It was about 0 μm. The obtained fly ash fiber was subjected to thermogravimetric analysis and differential thermal analysis with a thermal analyzer (Rigaku Denki Co., Ltd., Thermoflex). In the air 1
Weight analysis was performed up to 300 ° C., but there was no increase or decrease in weight. On the other hand, in the differential thermal analysis, an exothermic peak was observed at around 910 ° C and an endothermic peak was observed at around 1140 ° C.
The former was the onset of crystallization of fly ash fiber and the latter was melting. The crystallization temperature of this fly ash fiber was 995 ° C, the melting temperature was 1205 ° C, and the maximum use temperature was 910 ° C.

The mechanical properties of fly ash fiber were measured with a universal testing machine. Mechanical properties differed with fiber diameter. For example, when the diameter was 6 μm, the tensile strength was 4120 MPa and the tensile elastic modulus was 200 GPa.
The fly ash fiber having a fiber diameter of 15 μm had a tensile strength of 290 MPa and a tensile elastic modulus of 17.5 GPa. In both cases, rock wool and general glass fiber were far superior in heat resistance and mechanical strength.

Using an X-ray microanalyzer, each element contained in the fly ash fiber was qualitatively and quantitatively analyzed. The chemical composition of the produced fly ash fiber is Al ₂ O ₃ ; 24.7%,
SiO ₂ ; 40.5%, CaO; 26.5%, Fe
₂ O ₃ ; 8.3%.

Table 11 shows the chemical composition, crystallization temperature, melting temperature, maximum use temperature, etc. of the produced fly ash fiber. For comparison, glass wool, rock wool, silicon oxide fiber, ceramic fiber and raw coal ash are also shown. The maximum operating temperature of fly ash fiber was 910 ° C., which was much higher than that of silicon oxide fiber (750 ° C.) and slightly lower than that of ceramic fiber (1000 ° C.). Also,
The alumina content that affects heat resistance is 24.7%,
It was higher than the silicon oxide fiber and lower than the ceramic fiber. Therefore, it was revealed that the fly ash fiber is close in performance to the ceramic fiber.

[0083]

[Table 11]

Example 2 In order to further improve the maximum temperature of use of fly ash fiber, a fly ash fiber was produced in a composition different from that of Example 1. As the raw material coal ash, the coal ash produced by burning the same Chinese Daido coal as in Example 1 was used. The chemical composition of this Daido coal ash is Al ₂ O ₃ ; 18.9%, SiO
₂ ; 56.6%, CaO; 2.5%, Fe ₂ O ₃ ;
8% and MgO 1.0%. The amount of limestone added as a melting accelerator was set lower than in Example 1. The amount was two kinds, that of 25% of coal ash (fly ash fiber (2)) and that of 20% (fly ash fiber (3)). In addition, a viscosity modifier such as a magnesium phosphate-based compound was added as in the case of Example 1. These mixtures were placed in an electric furnace heated to about 1600 ° C., melted, and fiberized by a blowing process or a spinning process to produce each fly ash fiber.

The appearance, mechanical strength, diameter, etc. of the obtained fly ash fiber were almost the same as in Example 1. The texture of fly ash fiber increased as the amount of added limestone increased. Thermal analyzer for the produced fly ash fiber (Rigaku Denki Co., Ltd.)
Thermogravimetric analysis and differential thermal analysis. We performed gravimetric analysis up to 1300 ° C in air,
There was no increase or decrease in weight. On the other hand, in the differential thermal analysis, 940
An exothermic peak was observed at around 150 ° C. and an endothermic peak was observed at around 1,150 ° C. The former is the onset of crystallization of fly ash fiber and the latter is melting. Further, from the position of each peak, the crystallization temperature of the fly ash fiber was 975 ° C and the melting temperature was 1180 ° C. further,
The lower the limestone content, the higher the melting temperature is 1225
It has reached ℃.

Using an X-ray microanalyzer, qualitative and quantitative analyzes of each element contained in the fly ash fiber were performed. Table 12 shows the chemical composition, crystallization temperature, melting temperature, maximum safe use temperature, etc. of fly ash fiber produced by variously changing the composition of the main raw material coal ash and the auxiliary raw material limestone. The chemical composition of the produced fly ash fiber is such that the content of Al ₂ O ₃ is 24.7% by reducing the amount of limestone.
To 32.0%. The amount of CaO is 26.
It decreased from 5% to 20.7%. The SiO ₂ content was almost constant at 40%.

By decreasing the amount of limestone as compared with the case of Example 1, the crystallization start temperature increased from 910 ° C to 945 ° C. Also, the melting start temperature is 114
The temperature rose from 0 ° C to 1185 ° C. from these things,
It can be said that the amount of CaO in the fly ash fiber is preferably as small as possible if fiberization is possible.

[0088]

[Table 12]

Example 3 The fly ash fiber (3) prepared in Example 2 was examined for alkali resistance. 10.0 g of fly ash fiber (3) in a saturated solution of cement paste (pH
= 13) Immersed in 300 ml and heated at 80 ° C. for 200 hours. After washing with water and drying, the weight was measured, but no weight change was observed. When the surface of the fly ash fiber after immersion was observed with a scanning electron microscope, the smoothness was slightly lost as compared with that before the treatment. Therefore, when immersed in an alkaline matrix such as cement for an extremely long period of time, there remains a problem as to whether or not the fiber strength can be maintained. However, it is clear that the strength of the reinforcing material can be maintained with other matrices (for example, metal, resin, wood, rubber, glass, etc.).

It was examined whether fly ash fiber can be used as a FRM (fiber reinforced metal) reinforcing material. Fly ash fiber (1.5 g) was added to pure aluminum powder (13.5 g), and both were thoroughly mixed. This is a hot press graphite mold (inner diameter 40
mm) and reduced the pressure with a vacuum pump. A pressure of 280 kg / cm ² was applied to this mixture. Next, the vacuum pump was stopped from reducing the pressure, and the argon gas was heated to 665 ° C. at a rate of 3.3 ° C./min while flowing 1 liter / min. After holding at the same temperature for 30 minutes, the temperature was lowered at the same rate as when the temperature was raised.

The obtained fly ash fiber reinforced aluminum composite material was a disc having a diameter of 40 mm and a thickness of 6 mm. The tensile strength of the composite material was 96 MPa, which was about the same as the case of no addition (103 MPa). However, FR
The surface strength of M is 60 with Knoop hardness (3 with no addition).
3), the Rockwell hardness was as large as 81 (55 without addition). In fact, the ease with which abrasive paper can be sharpened is
As the amount of fly ash fiber increased, it became hard and difficult to scrape.

Example 4 In order to improve the alkali resistance of fly ash fiber, a fly ash fiber was produced with a composition different from those in Examples 1 and 2. As the raw material coal ash, the coal ash produced by burning the same Chinese Daido coal as in Example 1 was used. The chemical composition of this Daido coal ash is Al ₂ O ₃ ; 18.9.
%, SiO ₂ ; 56.6%, CaO; 2.5%, Fe ₂ O
₃ ; 12.8%, MgO; 1.0%. In this
Limestone as a melting accelerator was added in an amount corresponding to 20% by weight of coal ash. In addition, zirconium oxide or zircon or other zirconium compound was added. The amount was 10% of the coal ash in terms of ZrO ₂ .
In addition, as in the case of Example 1, a viscosity modifier such as a magnesium phosphate compound was added. These mixtures were placed in an electric furnace heated to about 1600 ° C., melted, and fiberized by a blowing process or a spinning process to produce fly ash fiber (4).

The appearance, mechanical strength, diameter, etc. of the obtained fly ash fiber were almost the same as in Example 2. Qualitative and quantitative analysis of each element contained in the fly ash fiber was performed using an X-ray microanalyzer device. Al ₂ O ₃ ; 35%, S
iO ₂ ; 30%, CaO; 20%, Fe ₂ O ₃ ; 8%, M
It was gO; 2% and ZrO ₂ ; 5%.

Next, this fly ash fiber (4)
Was immersed in a saturated solution of cement paste (pH = 13) and heated at 80 ° C. for 50 hours. After washing with water and drying, the weight was measured, but no weight reduction was observed. The surface of the fly ash fiber after immersion was observed with a scanning electron microscope, but it did not appear to be etched.
Therefore, it was found that the fly ash fiber containing zirconium has excellent alkali resistance.

[0095]

From the above, the fly ash fiber of the present invention is a low-cost novel inorganic fiber having excellent mechanical strength and heat resistance, for metals, resins, rubber,
It can be widely used as a fiber reinforcing material for wood and glass, a heat insulating material, a heat insulating material, and a sealing material. Further, by containing a zirconium compound, alkali resistance is further improved, and it is particularly effective for cement, mortar and concrete.

Claims (2)

[Claims] 1. Al ₂ O ₃ , 20 to 40%, 35 to 50%
SiO ₂ , 15-35% CaO, 3-12% Fe ₂
A fly ash fiber containing O ₃ and 2 to 5% of MgO. 2. Al ₂ O _{3 of 20 to} 45%, 25 to 50%
SiO ₂ , 15-35% CaO, 3-12% Fe ₂
A fly ash fiber comprising O ₃ , 0-5% MgO and 3-10% ZrO ₂ .