JP6796390B2 - Alumina-based oxide continuous fiber and its manufacturing method - Google Patents

Description

The present invention relates to an alumina-based oxide continuous fiber having excellent heat resistance and a method for producing the same.

Alumina-based oxide continuous fibers containing alumina (Al ₂ O ₃ ) as a main component, which are generally called alumina long fibers, have many excellent properties such as high heat resistance, high tensile strength, and excellent electrical insulation. It is used in a wide range of fields, especially as a high-temperature heat-resistant material.

However, conventional alumina-based oxide continuous fibers tend to have a decrease in tensile strength when used for a long time in a high temperature atmosphere of 1200 ° C. or higher, and further improvement in heat resistance is required.

In order to improve the heat resistance of alumina-based oxide continuous fibers, silica (SiO ₂ ) is usually contained as a component in addition to alumina, but it has been proposed to further contain boron oxide as a third component (patented). Documents 1, 2, 3, and 4) have a problem that such fibers cannot be used in applications and fields where it is not preferable to contain boron.

On the other hand, in order to obtain an alumina-based oxide continuous fiber, it has also been proposed to contain a component other than boron oxide as a third component (Patent Document 5). In this proposal, alumina is the main component, and 3 to 12% by weight of silica is contained, and at least one of P, Ba, Sn, Y, Co, Sr, Cr, Zr or Fe oxide is contained as the third component. Alumina fibers are disclosed, which are made by firing in an inert gas atmosphere, and although the strength of the fibers is shown, they have been used for a long time in a high temperature atmosphere. Nothing is shown about the retention of tensile strength in the case.

Further, a ceramic fiber in which a compound of Ni, Fe, Co or Cu is added so as to be non-uniform has been proposed as a reducing metal compound (Patent Document 6), but this proposal is made by firing in a reducing atmosphere. The metal compound is reduced to obtain cermet fibers, and no retention of tensile strength is shown when the fibers are used for a long time in a high temperature atmosphere.

Special Publication No. 61-32405 Special Fair 1-1425 Japanese Unexamined Patent Publication No. 63-288217 JP-A-2007-277744 Japanese Unexamined Patent Publication No. 62-100457 Japanese Unexamined Patent Publication No. 62-199818

The present invention has been made in view of the above-mentioned problems in conventional alumina-based oxide continuous fibers, and alumina-based oxide continuous fibers containing alumina and silica as main components are produced in the process of firing during the production thereof. By investigating the effect of mullite crystals and firing precursor fibers containing a specific metal compound, a part of the crystal structure constituting the alumina-based oxide continuous fiber is stabilized in advance when the firing is completed. If it is transferred to a mullite crystal, it becomes difficult for newly formed mullite crystal to grow even if it is subsequently exposed to a high temperature atmosphere of 1200 ° C. or higher for a long time, and the fiber maintains a dense crystal structure. It has been found that the decrease in tensile strength with time is reduced, and the present invention has been reached.
An object of the present invention is a continuous alumina-based oxide having excellent heat resistance without any restrictions in the field of use, with little decrease in tensile strength over time when used for a long time in a high temperature atmosphere of 1200 ° C. or higher. To provide the fiber.

The gist of the present invention is as follows.
1. 1. Alumina is 70 to 75% by weight based on all components, silica is 20 to 29.7% by weight based on all components, and iron (Fe), magnesium (Mg), copper (Cu), yttrium (Y), zinc (Zr). , Nickel (Ni), Zinc (Zn) contains an oxide of a metal selected from the group of 0.3 to 5% by weight with respect to all components, and the ratio of mullite to the entire crystal structure in the fiber is 5 to 50%. A certain alumina-based oxide continuous fiber.
2. 2. The alumina-based oxide continuous fiber according to 1 above, wherein the tensile strength of the fiber is 60 N / 200 Tex or more, and the retention rate of the tensile strength of the fiber after heating at 1250 ° C. for 24 hours is 70% or more of the tensile strength before heating. ..
3. 3. The starting materials are all water-soluble or water-dispersible, and the starting materials are aluminum compounds, silicon compounds, and metal compounds selected from the group of Fe, Mg, Cu, Y, Zr, Ni, and Zn. The raw material is dissolved or suspended in water, and 70 to 75% by weight of the aluminum compound is converted to alumina, 20 to 29.7% by weight of the silicon compound is converted to silica, and the metal selected from the metal group. A precursor obtained by dry spinning using a spinning stock solution containing a compound in a weight ratio of 0.3 to 5% by weight in terms of the metal oxide and having a viscosity at 20 ° C. in the range of 10 to 2000 Pa · s. The method for producing an alumina-based oxide continuous fiber according to 1 above, wherein the body fiber is fired into a crystal structure having a mulliteization rate of 5 to 50% in an air atmosphere of 1000 to 1500 ° C.

The alumina-based oxide continuous fiber of the present invention has little decrease in tensile strength with time when used for a long time in a high temperature atmosphere of 1200 ° C. or higher, can withstand long-term use, and does not contain boron. Therefore, it has excellent heat resistance without restrictions in the field of use.
Further, according to the method for producing an alumina-based oxide continuous fiber of the present invention, by using a specific metal compound and including it as a third component, an alumina-based material having excellent heat resistance is excellent even if it does not depend on a special firing method. It is possible to obtain oxide continuous fibers.

Hereinafter, embodiments of the present invention will be described in detail.
The alumina-based oxide continuous fiber of the present invention is a fiber containing alumina as a main component, in which alumina is 70 to 75% by weight based on all components, silica is 20 to 29.7% by weight based on all components, and Fe. , Mg, Cu, Y, Zr, Ni, Zn, preferably a metal oxide selected from the group of Fe, Mg, Cu, Y is contained in the fiber in an amount of 0.3 to 5% by weight based on all the components. the ratio of mullite to total crystalline structure _{(3Al 2 O 3 · 2SiO 2} ~2Al 2 O 3 · SiO 2) is a fiber having a mullite crystal 5 to 50%.

The alumina-based oxide continuous fiber of the present invention preferably contains 70 to 74% by weight of alumina, 23 to 29.5% by weight of silica, and 0 oxides of Fe, Mg, Cu or Y as a third component. .. A fiber containing 5 to 3% by weight.

Further, the alumina-based oxide continuous fiber of the present invention is a fiber in which the ratio of mullite to the entire crystal structure in the fiber, that is, the mulliteization rate is 5 to 50%. Mullite formation is a crystal transition from crystalline γ-alumina / amorphous silica to mullite by alumina and silica. The higher the mulliteization rate, the more preferable in terms of retention of tensile strength, but the lower the tensile strength of the fired fiber. , It becomes easy to be restricted by the intended use. In the alumina-based oxide continuous fiber of the present invention, the mulliteization rate is preferably 10 to 45%, and it is necessary that mullite occupies a specific ratio in the crystal structure of the fiber.
The mulliteization rate is calculated from the measurement results by powder X-ray diffraction (XRD) before and after the crystal transition.

The alumina-based oxide continuous fiber of the present invention contains alumina as a main first component, silica as a second component, and an oxide of the metal as a third component, and a part of the crystal structure is made into a stable mulite. As a result, the tensile strength of the fiber is 60 N / 200 Tex or more, further 65 N / 200 Tex or more, and there is little decrease in the tensile strength with time in a high temperature atmosphere of 1200 ° C. or higher, and the tensile strength is maintained after heating at 1250 ° C. for 24 hours. The ratio is 70% or more of the tensile strength before heating, and further is 75% or more, which is excellent in heat resistance.

Alumina-based oxide continuous containing alumina as a main component of the present invention, silica, and one selected from oxides of the specific metal, and having a mulliteization rate of 5 to 50% in the entire crystal structure in the fiber. The fiber can be produced as follows.

That is, the alumina-based oxide continuous fiber of the present invention is a water-soluble or water-dispersible compound as a starting material, and is an aluminum compound, a silicon compound, and Fe, Mg, Cu, Y, Zr, Ni, Zn. As a starting material, a metal compound selected from the group of Fe, Mg, Cu, and Y is used as a starting material, the starting material is dissolved or suspended in water, and the aluminum compound is converted to alumina to be 70 to 70 to all the components. 75% by weight, 20 to 29.7% by weight of the silicon compound converted to silica, and Fe, Mg, Cu, Y, Zr, Ni, Zn groups, preferably Fe, Mg, Cu, Y. A spinning stock solution prepared by converting a metal compound selected from the group into the metal oxide and containing it in a weight ratio of 0.3 to 5% by weight with respect to all the components and preparing a viscosity at 20 ° C. in the range of 10 to 2000 Pa · s. It can be obtained by firing a precursor fiber obtained by dry spinning using a crystal structure having a mulliteization rate of 5 to 50% in an air atmosphere of 1000 to 1500 ° C.

The starting materials used in the production method of the present invention are all water-soluble or water-dispersible.
The aluminum compound as a starting material can form alumina, which is the main component of the alumina-based oxide continuous fiber, in the process of firing the precursor fiber. For example, organic acid aluminum such as basic aluminum acetate and basic aluminum lactate. Examples thereof include a basic salt of the above, a basic salt of inorganic acid aluminum such as basic aluminum chloride and basic aluminum nitrate, and an alumina sol.

Further, the silicon compound as a starting material can form silica in the process of firing the precursor fiber, and is, for example, a hydrolyzate such as methyl silicate or ethyl silicate, a silica sol, or a water-soluble compound modified to be soluble in water. Examples thereof include silicone compounds such as silicone. Further, the starting material Fe, Mg, Cu, Y, Zr, Ni or Zn compound, preferably the Fe, Mg, Cu or Y compound is the metal oxide as a third component in the process of firing the precursor fiber. Examples thereof include inorganic acid metal salts such as hydrochlorides, sulfates and nitrates of these metals, and organic acid metal salts such as acetates and formates.

When preparing a spinning stock solution by dissolving or suspending an aluminum compound, a silicon compound, and a compound of the metal as starting materials in water, it is necessary to add a water-soluble organic polymer as a spinning aid to improve the spinnability. It is preferable to enhance it. The water-soluble organic polymer may be any one having a spinnability improving function, and examples thereof include carboxymethyl cellulose, polymethacrylic acid ester, polyvinyl alcohol, and the like, and polyvinyl alcohol is particularly preferable.

When the spinning aid is added, the starting material and the spinning aid are preferably 95/5 to 70/30, more preferably 90/10 to 75 by weight in terms of the starting material in terms of total oxide. Dissolve or suspend in water so as to be in the range of / 25, and convert the aluminum compound to alumina to 70 to 75% by weight, the silicon compound to silica to 20 to 29.7% by weight, and the metal. A spinning stock solution containing the above compound in a weight ratio of 0.3 to 5% by weight in terms of the metal oxide is prepared.

In the preparation of the spinning stock solution, it is necessary to add 0.5 to 3% by weight of the metal compound contained in the spinning stock solution in terms of the metal oxide, and if the addition amount is less than 0.3% by weight. If the effect of the addition described later cannot be exhibited and exceeds 5% by weight, the viscosity of the spinning stock solution rapidly increases with time and the spinnability also decreases, making it difficult to stably obtain precursor fibers. Become.

Further, as the spinning stock solution, it is preferable to use a spinning stock solution prepared so that the viscosity at 20 ° C. is in the range of 10 to 2000 Pa · s in order to spin by the dry spinning method, and more preferably the viscosity is 20 to 500 Pa · s. A spinning stock solution in the range of s will further increase the stability of the spinning process. The viscosity of the undiluted spinning solution can be easily adjusted to a preferable viscosity range by the vacuum concentration method.

In the production method of the present invention, the prepared spinning stock solution is used for dry spinning to obtain long fibrous precursor fibers. When a long-fibrous precursor fiber is obtained by a dry spinning method, a spinning stock solution is discharged from a spinning nozzle into a heating atmosphere and wound up to a predetermined fiber diameter while being sufficiently dried.

The precursor fiber is fired by firing the obtained precursor fiber in an air atmosphere of 1000 to 1500 ° C., preferably 1000 to 1200 ° C., which is a firing method usually used in the production of alumina-based oxide continuous fiber. As a result, the alumina-based oxide continuous fiber of the present invention can be obtained.

In the production method of the present invention, the metal compound is particularly used, and a predetermined amount in terms of metal oxide is contained in the precursor fiber, so that when the precursor fiber is fired, the added metal compound becomes the first. Metal oxides as three components are produced. The metal oxide acts as a sintering aid, and a part of γ-alumina / amorphous silica generated from an aluminum compound / silicon compound is rapidly crystallized into a stable mullite crystal by firing in a short time, and the mullite is formed. Causes crystallization. According to the production method of the present invention, a crystal structure having a mulliteization rate of 5 to 50% can be obtained by rapid crystal transition in the presence of the metal oxide acting as a sintering aid.

That is, according to the present invention, in the alumina-based oxide continuous fiber containing the metal oxide as the third component, the mulliteization rate is already stable at a specific ratio of 5 to 50% when the firing is completed. Mullite is present in the crystal structure. Therefore, when the alumina-based oxide continuous fiber of the present invention is used as a heat-resistant material, the mulliteization rate becomes 50% or more by being exposed to a high temperature exceeding 1200 ° C. for a long time, and new mullite crystals are formed due to the progress of mulliteization. Is generated, but further crystal growth is inhibited or suppressed by the already existing mullite crystals. Therefore, there are few coarse mullite crystals in the fibers exposed to high temperature for a long time, and by maintaining a dense crystal structure, the fiber has a tensile strength of 60 N / 200 Tex or more and is in a high temperature atmosphere of 1200 ° C. or more. It is possible to obtain an alumina-based oxide continuous fiber in which the tensile strength is unlikely to decrease with time.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

(Example 1)
As a starting material, a basic aluminum chloride aqueous solution was used as the aluminum compound, silica sol was used as the silicon compound, iron sulfate was used as the metal compound to be the metal oxide of the third component, and polyvinyl alcohol (PVA) was used as the spinning aid. PVA and PVA are added to water at a weight ratio of 85/15 to convert the starting material into total oxides and suspended to obtain a mixed solution containing the starting material converted to the component ratio shown in Table 1, and further concentrated under reduced pressure. A spinning stock solution having a viscosity of 240 Pa · s at 20 ° C. was prepared. Using this undiluted spinning solution, a long fibrous precursor fiber was produced by discharging from a spinning nozzle into a heating atmosphere at 60 ° C. and drying and winding the filament by a dry spinning method. The obtained long fibrous precursor fiber was calcined in an air atmosphere at 1170 ° C. to obtain an alumina-based oxide continuous fiber having a fineness of 200 Tex.

The obtained alumina-based oxide continuous fiber contains iron oxide as a third component, has a tensile strength of 83.4 N / 200 Tex, and from the measurement result by XRD, the mulliteization rate of the crystal structure of the fiber is 25%. there were.
The obtained alumina-based oxide continuous fiber was heated at 1250 ° C. for 24 hours (hr), and the tensile strength was measured. As a result, the tensile strength was 70.6 N / 200 Tex, and the tensile strength retention rate was 85%. The resulting alumina-based oxide continuous fiber exhibited excellent heat resistance.
Further, when heated at 1250 ° C. for 24 hours, mulliteization progresses, and the mulliteization rate is approximately 10.
Although it was 0% , the dense crystal structure was maintained .

(Example 2)
In Example 1, dry spinning was carried out in the same manner as in Example 1 except that the component ratio of iron sulfate, which is the metal oxide of the third component, and the viscosity of the undiluted spinning solution were changed as shown in Table 1. Then, the produced long fibrous precursor fibers were fired to obtain alumina-based oxide continuous fibers.
The obtained alumina-based oxide continuous fiber contains iron oxide as a third component, has a tensile strength of 72.6 N / 200 Tex as shown in Table 2, and from the measurement results by XRD, mullite having a crystal structure of the fiber. The conversion rate was 30%.
The obtained alumina-based oxide continuous fiber was heated at 1250 ° C. for 24 hours, and the tensile strength was measured. As shown in Table 2, the tensile strength was 65.7 N / 200 Tex, and the tensile strength retention rate was 90%. The obtained alumina-based oxide continuous fiber exhibited excellent heat resistance. Further, when heated at 1250 ° C. for 24 hours, mulliteization proceeded and the mulliteization rate was almost 100%, but the dense crystal structure was maintained .

(Example 3)
In Example 1, dry spinning was carried out in the same manner as in Example 1 except that the starting material for the metal oxide of the third component was magnesium sulfate and the viscosity of the undiluted spinning solution was changed as shown in Table 1. The long fibrous precursor fibers were fired to obtain alumina-based oxide continuous fibers.
The obtained alumina-based oxide continuous fiber contains magnesium oxide as a third component, has a tensile strength of 78.5 N / 200 Tex as shown in Table 2, and from the measurement results by XRD, mullite having a crystal structure of the fiber. The conversion rate was 40%.
The obtained alumina-based oxide continuous fiber was heated at 1250 ° C. for 24 hours, and the tensile strength was measured. As shown in Table 2, the tensile strength was 63.8 N / 200 Tex, and the tensile strength retention rate was 81%. The obtained alumina-based oxide continuous fiber exhibited excellent heat resistance. Further, when heated at 1250 ° C. for 24 hours, mulliteization proceeded and the mulliteization rate was almost 100%, but the dense crystal structure was maintained .

(Example 4)
In Example 1, the starting material for the metal oxide of the third component was yttrium acetate, and the component ratio and the viscosity of the spinning stock solution were changed as shown in Table 1, except that the dry type was used in the same manner as in Example 1. The long fibrous precursor fibers produced by spinning were fired to obtain alumina-based oxide continuous fibers.
The obtained alumina-based oxide continuous fiber contains yttrium oxide as a third component, has a tensile strength of 68.5 N / 200 Tex as shown in Table 2, and from the measurement results by XRD, the mullite having a crystal structure of the fiber. The conversion rate was 33%.
The obtained alumina-based oxide continuous fiber was heated at 1250 ° C. for 24 hours, and the tensile strength was measured. As shown in Table 2, the tensile strength was 62.8 N / 200 Tex, and the tensile strength retention rate was 91%. The obtained alumina-based oxide continuous fiber exhibited excellent heat resistance. Further, when heated at 1250 ° C. for 24 hours, mulliteization proceeded and the mulliteization rate was almost 100%, but the dense crystal structure was maintained .

(Example 5)
In Example 1, dry spinning was carried out in the same manner as in Example 1 except that the starting material for the metal oxide of the third component was changed to copper chloride and the viscosity of the undiluted spinning solution was changed as shown in Table 1. The long fibrous precursor fibers were fired to obtain alumina-based oxide continuous fibers.
The obtained alumina-based oxide continuous fiber contains copper oxide as a third component, has a tensile strength of 80.4 N / 200 Tex as shown in Table 2, and from the measurement results by XRD, mullite having a crystal structure of the fiber. The conversion rate was 10%.
The obtained alumina-based oxide continuous fiber was heated at 1250 ° C. for 24 hours, and the tensile strength was measured. As shown in Table 2, the tensile strength was 64.7 N / 200 Tex, and the tensile strength retention rate was 80%. The obtained alumina-based oxide continuous fiber exhibited excellent heat resistance. Further, when heated at 1250 ° C. for 24 hours, mulliteization proceeded and the mulliteization rate was almost 100%, but the dense crystal structure was maintained .

(Comparative Example 1)
In Example 1, the component ratio and the viscosity of the undiluted spinning solution were changed as shown in Table 1 with a basic aluminum chloride aqueous solution and silica sol without using the starting metal compound as the metal oxide of the third component. , The precursor fiber produced by dry spinning was fired in the same manner as in Example 1 to obtain an alumina-based oxide filament.
The obtained alumina-based oxide continuous fiber does not contain the metal oxide of the third component, has a tensile strength of 89.2 N / 200 Tex as shown in Table 2, and has a crystal structure of the fiber based on the measurement results by XRD. The mulliteization rate was 0%, and there was no mullite in the crystal structure.
Further, the obtained alumina-based oxide continuous fiber was heated at 1250 ° C. for 24 hours, and the mulliteization rate of the crystal structure of the fiber was almost 100% from the measurement result by XRD. However, when the tensile strength was measured, it was found. As shown in Table 2, the tensile strength was 41.2 N / 200 Tex, the retention rate of the tensile strength was 46%, and the obtained alumina-based oxide continuous fiber was inferior in heat resistance.

The alumina-based oxide continuous fiber of the present invention has little decrease in tensile strength with time in a high temperature atmosphere of 1200 ° C. or higher, can withstand long-term use, and has excellent heat resistance, and is a heat insulating material, a refractory material, and a reinforcing material. It is useful for applications such as materials, furnace materials, heat-resistant sealing materials, and catalyst-supporting materials, and because it does not contain boron, it can be used in fields such as semiconductor manufacturing in which the presence of unintended boron is not preferable. Furthermore, since the method for producing an alumina-based oxide continuous fiber of the present invention includes firing in an air atmosphere, it is possible to obtain the fiber commercially.

Claims (2)

Alumina is 70 to 75% by weight with respect to all components, silica is 20 to 29.7% by weight with respect to all components, and oxides of metals selected from the group of iron, magnesium, copper and ittrum are 0.3 with respect to all components. It includes 5 wt%, alumina-based oxides, continuous fibers that mullite ratio according to some mullite of crystal γ alumina amorphous silica based on the main component is in the crystal structure Ru 5-50% der. The alumina-based oxide continuous according to claim 1, wherein the tensile strength of the fiber is 60 N / 200 Tex or more, and the retention rate of the tensile strength of the fiber after heating at 1250 ° C. for 24 hours is 70% or more of the tensile strength before heating. fiber.