JPH08209454A - Production of silica-alumina fiber - Google Patents

Abstract

PURPOSE: To provide a process for giving silica-alumina fibers excellent in spinning stability, mechanical strength and heat resistance. CONSTITUTION: An alkylaluminum or a combination thereof with a silicon- containing compound and/or a β-diketone of the general formula: R1 COCH2 COR2 (R1 and R2 are each an alkyl or an alkoxy group) are mixed with an organic solvent containing 0.9-1.4 mole of water per mole of the alkylaluminum to effect bydrolysis. To the hydrolyzate, an alcohol of the general formula: R3 OH (R3 is an alkyl group) is added, and as necessary, a silicon-containing compound and/or a β-diketone are further added thereto and they are adjusted so that the amount of the β-diketone becomes 0.03-0.2 mole per mole of the aluminum in the mixture, the alcohol becomes more than 0.8 mole per mole of the aluminum, and the silicon-containing compound corresponds to less than 40wt.% in the silica-alumina fibers. Then, the adjusted mixture is subjected to the spinning process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing silica-alumina fiber, and more particularly, to the production of water in the presence of alkylaluminum or a compound containing alkylaluminum and silicon and / or a specific β-diketone compound. Hydrolyze by adding an organic solvent containing, and to the hydrolyzate, a specific alcohol and, if necessary, a compound containing silicon and / or a β-diketone compound are added and mixed to contain silicon in the mixture. The amount of the compound, the amount of the β-diketone compound, and the amount of the alcohol are adjusted to a specific range, the mixture is spun to obtain a precursor fiber, and the precursor fiber is fired to obtain spinnability and spinning stability. The present invention relates to a method for producing silica-alumina fiber having excellent mechanical strength and heat resistance.

[0002]

2. Description of the Related Art Conventionally, a precursor polymer method has been known as one of the methods for producing silica-alumina fibers. In the precursor polymer method, a compound containing silicon, for example, a silicate ester is mixed with polyaluminoxane to obtain a spinning dope. This method is characterized in that the spinning solution is highly uniform and the use of an organic polymer or a binder is not essential so that the mechanical strength of the obtained fiber is high. However, since the polyaluminoxane is easily hydrolyzed, there is a problem that the spinning stability is poor and the obtained fiber strength varies widely.

Various methods have been investigated in order to solve such problems. For example, in Japanese Examined Patent Publication No. 51-13768, polyaluminoxane and a compound containing silicon are mixed, and the concentration of polyaluminoxane is 50 to 60% by weight.
It has been shown that the spinnability is improved by adding an organic polymer or a higher carboxylic acid such as stearic acid or palmitic acid to the concentrated spinning solution. Japanese Patent Publication No. 62-49362 discloses that a polymetalloxane having a phenoxy group introduced therein has excellent spinnability and strength. JP-A-2
In Japanese Patent Publication No. 141417/1994, aluminum alkoxide is reacted with acetylacetone, water is then added, and then the mixture is polymerized in the presence of an acid to synthesize polyaluminoxane. The spinning dope is spun and baked for a short time. It shows that fibers are obtained. JP-A-3-
In Japanese Patent No. 104925, a silica-alumina is produced by reacting an aluminum alkoxide with a compound having active hydrogen, hydrolyzing a mixture of silicon alkoxide with this to form a sol, and spinning, steaming, and firing the sol. It shows that fibers are obtained. In particular, as compounds having active hydrogen, alkanolamine compounds, glycol compounds, organic acids, phenols, thiols, amines, etc., are in the range of 0.6 to 2.7 moles of active hydrogen per mole of aluminum alkoxide, β
It is shown that the use of the diketone compound in the range of 0.2 to 1.5 mol makes it possible to adjust the hydrolysis rate of the aluminum alkoxide and obtain a sol suitable for the spinning operation.

However, in JP-B-51-13768, although spinnability is improved by adding an organic polymer or a higher carboxylic acid such as stearic acid or palmitic acid to a spinning solution, the organic polymer is When added or when an organic residue having a large number of carbon atoms is introduced into the side chain of the polyaluminoxane, there is a problem that the denseness of the fiber after firing is lowered and the mechanical strength is difficult to develop. Japanese Patent Publication No. 62-4936
In JP-A-2, the polymetalloxane having a phenoxy group introduced is excellent in spinnability, but there is a problem that the denseness of the fiber is lowered and the mechanical strength is difficult to be expressed.

Further, in order to synthesize a sol having a viscosity suitable for spinning operation by hydrolyzing aluminum alkoxide, in JP-A-2-141417, acetylacetone is added in an amount of 0.4 to 1 mol of aluminum alkoxide. In the range of 1.5 mol, JP-A-3-10492
In JP-A No. 5, a compound having active hydrogen is used in an amount of 0.6 to 2.7 mol of an alkanolamine compound, a glycol compound, an organic acid, a phenol, a thiol, an amine, and the like. Is required in the range of 0.2 to 1.5 mol, and a large amount of organic residue is introduced into the side chain of the polyaluminoxane, so that there is a problem that the mechanical strength of the fired fiber is difficult to be expressed.

[0006]

In view of such a situation, the present inventors have used a hydrolyzate obtained by hydrolyzing alkylaluminum as a spinning stock solution, spinning it, and spinning it.
In obtaining the silica-alumina fiber, as a result of diligent study for the purpose of finding a method for producing the silica-alumina fiber having excellent physical properties such as spinnability, spinning stability, mechanical strength, heat resistance, etc. A compound containing a specific amount of silicon,
It has been found that silica alumina fibers satisfying all of the above objects can be produced when a specific amount of a specific β-diketone compound and alcohol is present, and the present invention has been completed.

[0007]

That is, the present invention provides an alkylaluminum or a compound containing alkylaluminum and silicon and / or a general formula R ₁ COCH ₂ COR ₂ (wherein R ₁ and R ₂ are an alkyl group or an alkoxy group). In the presence of a β-diketone compound represented by the formula 1), an organic solvent containing 0.9 to 1.4 mol of water is added to 1 mol of alkylaluminum for hydrolysis, and the hydrolyzate has the general formula R Alcohol represented by ₃ OH (wherein R ₃ is an alkyl group), and optionally a compound containing silicon and / or a β-diketone compound are added and mixed, and the β-diketone compound in the mixture is added. Amount of aluminum in the mixture 1
Silica-alumina fiber in which an amount of 0.03 mol to less than 0.2 mol per mol, an amount of alcohol of 0.8 mol or more per 1 mol of aluminum in the mixture, and an amount of a compound containing silicon are obtained. A method for producing a silica-alumina fiber, characterized in that the silica content is adjusted to an amount range of 40% by weight or less, the mixture is spun to obtain a precursor fiber, and the precursor fiber is fired. To provide.

The method of the present invention will be described in more detail below.
The alkylaluminum used in the method of the present invention is represented by the general formula AlX ₃ , wherein X is methyl, ethyl or n-.
It shows an alkyl group such as propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, among others,
Triethylaluminum, which consists of ethyl groups, is the prize.

In the present invention, the amount of water used for hydrolyzing the alkylaluminum should be in the range of 0.9 to 1.4 mol with respect to 1 mol of the alkylaluminum. If the amount added is less than 0.9 times the molar amount, only the polyaluminoxane having a low degree of polymerization can be obtained, so that the spinnability is low and the mechanical strength of the obtained fiber is low. If more than 1.4 times the mole of water is added, the polymerization solution will gel and the spinning stability will deteriorate. In the present invention, water used for hydrolysis of alkylaluminum is diluted with an organic solvent before use. As the organic solvent used for the dilution, organic solvents that do not react with hydrolyzable alkylaluminum such as aliphatic hydrocarbons, aromatic hydrocarbons and ether compounds can be used, but ether compounds relatively compatible with water are preferable. Particularly, tetrahydrofuran, diethyl ether and dioxane are preferable. The concentration of water in the organic solvent is 40% by weight or less, usually 3 to 30%.
Weight percent is preferred. When the concentration of water is more than 40% by weight, the mechanical strength of the obtained fiber is lowered. The hydrolysis reaction is preferably carried out in a dry inert gas. The alkylaluminum used in the reaction is used by diluting it with an organic solvent such as an aliphatic hydrocarbon, an aromatic hydrocarbon and an ether compound.

The compound containing silicon used in the present invention is Polysilicic acid ester having structural units of R ₄ and R
₅ is an organic atomic group) but R _n SiX _4-n
Organosilanes having a structure (X is OH, OR, etc., R is an organic atomic group, n is an integer of 4 or less), Si (O
It is possible to use a silicic acid ester having a structure of R) ₄ (R is an organic atomic group) and other compounds containing silicon. Further, the compound containing silicon is preferably dissolved and mixed in the polyaluminoxane uniformly because the spinnability is improved, but a compound that is not dissolved but dispersed can be used. The mixing amount of the compound containing silicon depends on the type of polyaluminoxane produced by the hydrolysis of alkylaluminum and the type of the compound containing silicon, but if the amount is too large, the heat resistance and mechanical strength of the obtained silica-alumina fiber will decrease. Therefore, the silica content in the silica-alumina fiber obtained after firing is mixed in the range of 40% by weight or less, preferably about 1% by weight to 30% by weight.

In carrying out the present invention, the β-diketone compound used in combination with the alkylaluminum or the compound containing alkylaluminum and silicon has the general formula R ₁ COCH.
₂ COR ₂ in the formula, R ₁ and R
₂ is an alkyl group or an alkoxy group, preferably R
₁ and R ₂ are an alkyl group or an alkoxy group having 4 or less carbon atoms. When the carbon number of R ₁ and R ₂ is more than 4, the obtained silica-alumina fiber is blackened or the mechanical strength is lowered. Specific examples of such β-diketone compounds include β-diketones such as acetylacetone, propionylacetone and butyrylacetone, methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, n-butyl acetoacetate and isoacetoacetate. Examples include β-ketone acid esters such as -butyl, tert-butyl acetoacetate, methyl propionyl acetate and ethyl propionyl acetate, and malonic acid diesters such as dimethyl malonate, diethyl malonate and methyl ethyl malonate. Above all, ethyl acetoacetate is more preferable because it is possible to obtain a fiber having excellent spinning stability and mechanical strength.

The amount of the β-diketone compound used in the present invention must be 0.03 mol or more and less than 0.2 mol, preferably 0.05 to 0.18 mol, per 1 mol of aluminum. The amount of β-diketone compound is 0.0
When the amount is less than 3 mol, the spinning stability of the spinning dope is poor and the mechanical strength of the obtained silica-alumina fiber varies greatly. Further, the amount of the β-diketone compound is 0.
When the amount is 2 mol or more, the obtained silica-alumina fiber is blackened or the mechanical strength is deteriorated.

In the practice of the present invention, the alcohol used in admixture with the hydrolyzate of an alkylaluminum containing a compound containing silicon and a β-diketone compound has the general formula R
_{The one represented by 3} OH is used. Wherein, R ₃ is an alkyl group, preferably, R ₃ is an alkyl group having 4 or less carbon atoms. When the carbon number of R ₃ is more than 4, the obtained silica-alumina fiber is blackened and the mechanical strength is deteriorated. Specific examples of such alcohols include methyl alcohol, ethyl alcohol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol and the like. Above all, iso-propyl alcohol is more preferable because it is possible to obtain a fiber having excellent spinning stability and mechanical strength.

In the present invention, it is essential that the alcohol is used in an amount of 0.8 mol or more, preferably 0.9 to 5.0 mol, per 1 mol of aluminum in the mixed solution. When the amount of alcohol is less than 0.8 mol, the spinning stability of the spinning dope is poor, and the mechanical strength of the obtained silica-alumina fiber varies greatly. The upper limit is not particularly limited, but 5.0 mol or less is preferable from the economical viewpoint.

The above-mentioned silicon-containing compound and β-diketone compound may be added to alkylaluminum before the hydrolysis of alkylaluminum, may be added after the hydrolysis, or may be added before and after the hydrolysis. You may add after dividing and adding. In the present invention, the above-mentioned hydrolyzate and alcohol are usually mixed by a known method and then heated and concentrated to be used as a spinning solution. For the purpose of improving the spinnability of the spinning solution, it is possible to add an organic polymer such as polyethylene glycol, polypropylene glycol or polymethylmethacrylate to the spinning solution.

The spinning temperature of the spinning solution is about 10 ° C. to 200 ° C., usually about 30 ° C., in view of the thermal stability of polyaluminoxane.
Temperatures of from 0 ° C to about 150 ° C are used. At the time of spinning, the viscosity of the spinning solution is not unique depending on the target fiber diameter, the spinning equipment used, the type of polymetalloxane, the degree of polymerization, etc., but is usually about 1 poise to about 3000 poise upon heating, preferably 10 poise. To about 2000 poise.

The spinning solution whose viscosity has been adjusted by heating is spun into a precursor fiber. As the spinning method, known spinning methods such as nozzle extrusion spinning, centrifugal spinning, blow-off spinning can be applied. As the spinning head, a spinning head having a heating mechanism in the spinning solution retention portion is preferably used from the viewpoint of spinning stability. During spinning, it is also possible to draw the precursor fiber with a rotating roller, a high-speed air stream, or the like. Further, in spinning, adjusting the spinning atmosphere and the temperature and humidity of blown air is a desirable method for obtaining stable and good fibers.

The precursor fiber spun in this manner is
Next, if necessary, steam treatment, hot water treatment, acid treatment, or a combination of these is pretreated and then fired.
The firing method is also not particularly limited, and for example, the precursor fiber may be fired in an air atmosphere, or may be fired in an inert atmosphere such as nitrogen or in a vacuum and then fired in an oxygen atmosphere. Further, the obtained silica-alumina fiber may be further fired in a reducing atmosphere such as hydrogen. Further, during the firing step, the precursor fiber or the silica-alumina fiber may be tensioned and fired. The firing temperature of the precursor fiber is not unique depending on the firing method, the composition of the precursor fiber, etc., but a temperature of about 900 ° C. to about 1500 ° C. is usually adopted. By such a method, it is possible to obtain continuous fibers having a calcined fiber diameter of about 5 μm to about 20 μm.

[0019]

As described in detail above, the method of the present invention is a simple operation method in which a specific amount of a compound containing silicon, a specific β-diketone compound and an alcohol are present in the spinning dope. , Spinning stability, mechanical strength,
This makes it possible to provide silica-alumina fibers having excellent heat resistance and the like, and its industrial value is extremely large.

[0020]

EXAMPLES The method of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The fiber diameter and tensile strength were measured by the following methods. Fiber diameter: The sample was observed with an optical microscope, 20 fibers existing in the visual field were randomly selected, the fiber diameter was measured, and the average value was calculated as the fiber diameter. Tensile strength; Fiber is measured with a tensile tester (Model UTM-ll-20R, Toyo Baldwin Co., Ltd.), and measurement length is 2
The tensile strength was defined as the strength at which the fiber was broken by pulling at 5 mm and a pulling speed of 1 mm / min.

Example 1 1 mol of triethylaluminum was dissolved in 350 ml of tetrahydrofuran, and 1.2 mol of water was added to this solution.
A solution dissolved in 0 ml of tetrahydrofuran was added and hydrolyzed at 45 ° C. to obtain a transparent solution containing polyethylaluminoxane. Next, 1.5 mol of isopropyl alcohol and 0.08 mol of ethyl acetoacetate were added to this liquid and heated to replace the ethyl group of polyethylaluminoxane.

Structural formula of this solution The polyethyl silicate (trade name: ethyl silicate 40, manufactured by Tama Chemical Industry Co., Ltd.) was mixed so that the silica content after firing would be 15% by weight.

Tetrahydrofuran was removed from this solution by heating, and the solution was concentrated until the viscosity at 50 ° C. reached 5000 cp to prepare a spinning dope. This spinning stock solution was left standing for 10 hours to remove bubbles, then heated to 45 ° C. and extruded from a spinneret having a pore size of 50 μm and a number of pores of 6 to stably spin and obtain a homogeneous precursor fiber. After leaving the obtained transparent precursor fiber in an atmosphere of 70 ° C. and 70% relative humidity for 10 minutes,
When fired in air to 1200 ° C., colorless and transparent silica-alumina continuous fibers were obtained. This fiber had an average diameter of 15 μm and a tensile strength of 230 kg / mm ² .

Examples 2 to 11 To the polyethylaluminoxane solution obtained in the same manner as in Example 1, the β-diketone compound and alcohol shown in Table 1 were added and heated to replace the ethyl group of polyethylaluminoxane. This solution was mixed with polyethyl silicate described in Table 1, concentrated to a spinning stock solution until the viscosity at 50 ° C. reached 5000 cp, and further spinning, steam treatment and firing were carried out in the same manner as in Example 1, A silica-alumina continuous fiber was obtained. The physical properties of this fiber are shown in Table 2.

Comparative Examples 1 to 5 To the polyethylaluminoxane solution obtained by the same method as in Example 1, the β-diketone compound or higher carboxylic acid shown in Table 1 and an alcohol were added and heated to obtain ethyl ethyl polyethylaluminoxane. The group was replaced. This solution was mixed with the polyethyl silicate described in Table 1 and concentrated until the viscosity at 50 ° C. reached 5000 cp to prepare a spinning dope,
Further, spinning, steam treatment and firing were carried out in the same manner as in Example 1 to obtain silica-alumina continuous fibers. The physical properties of this fiber are shown in Table 2.

Example 12 1 mol of triethylaluminum was dissolved in 350 ml of tetrahydrofuran, and 0.08 mol of ethyl acetoacetate and the ethyl polysilicate shown in Example 1 were added to the silica content after calcination to be 15% by weight. After mixing as described above, hydrolysis was carried out in the same manner as in Example 1 to obtain a transparent liquid. Isopropyl alcohol was added to this solution in the same manner as in Example 1 and concentrated to obtain a spinning dope, which was then subjected to spinning, steam treatment and firing in the same manner as in Example 1 to obtain colorless transparent silica-alumina fibers. Was obtained. During spinning, there was no yarn breakage, and the obtained precursor had good stability. The obtained fibers had an average diameter of 15 μm and a tensile strength of 230 kg / mm ² .

Example 13 1 mol of triethylaluminum was dissolved in 350 ml of tetrahydrofuran, and 1.2 mol of water was added to this solution.
Hydrolysis was performed by adding a solution dissolved in ml of tetrahydrofuran to obtain a transparent solution containing polyethylaluminoxane. By the same operation as in Example 1, isopropyl alcohol, ethyl acetoacetate and polyethyl silicate were mixed and then concentrated to obtain a spinning dope. By spinning, steaming and firing in the same manner as in Example 1, colorless and transparent silica-alumina fibers were obtained. During spinning, there was no yarn breakage, and the obtained precursor had good stability. The obtained fiber had an average diameter of 15 μm and a tensile strength of 190 kg / mm ² .

Example 14 1 mol of triethylaluminum was dissolved in 350 ml of tetrahydrofuran, and 1.2 mol of water was added to this solution.
Hydrolysis was performed by adding a solution dissolved in ml of tetrahydrofuran to obtain a transparent solution containing polyethylaluminoxane. By the same operation as in Example 1, isopropyl alcohol, ethyl acetoacetate and polyethyl silicate were mixed and then concentrated to obtain a spinning dope. By spinning, steaming and firing in the same manner as in Example 1, colorless and transparent silica-alumina fibers were obtained. During spinning, there was no yarn breakage, and the obtained precursor had good stability. The obtained fibers had an average diameter of 15 μm and a tensile strength of 170 kg / mm ² .

Comparative Example 6 1 mol of triethylaluminum was dissolved in 350 ml of tetrahydrofuran, and 0.7 mol of water was added to this solution.
Hydrolysis was performed by adding a solution dissolved in 0 ml of tetrahydrofuran to obtain a transparent solution containing polyethylaluminoxane. By the same operation as in Example 1, isopropyl alcohol, ethyl acetoacetate and polyethyl silicate were mixed and then concentrated to obtain a spinning dope. When spinning, steam treatment and firing were carried out in the same manner as in Example 1,
A colorless and transparent silica-alumina fiber was obtained. During spinning, the yarn was often broken and the spinnability was poor. Further, the obtained precursor had many fluffs and had a large shrinkage. The obtained fibers had an average diameter of 15 μm and a tensile strength of 120 kg / mm ² .

Comparative Example 7 1 mol of triethylaluminum was dissolved in 350 ml of tetrahydrofuran, and 1.6 mol of water was added to this solution.
When hydrolysis was carried out by adding a solution dissolved in 0 ml of tetrahydrofuran, the solution containing the hydrolyzate became cloudy. By the same operation as in Example 1, isopropyl alcohol, ethyl acetoacetate and polyethyl silicate were mixed and then concentrated to obtain a spinning dope. In the same manner as in Example 1, spinning, steam treatment and firing were carried out to obtain silica-alumina fiber. There were many yarn breaks during spinning. The obtained fibers had an average diameter of 15 μm and a tensile strength of 100 kg / mm ² .

[0031]

[Table 1]

[0032]

[Table 2]

Claims (9)

[Claims] 1. An alkylaluminum or a compound containing an alkylaluminum and silicon and / or a general formula R ₁ CO
In the presence of a β-diketone compound represented by CH ₂ COR ₂ (wherein R ₁ and R ₂ represent an alkyl group or an alkoxy group), 0.9 mol per 1 mol of alkylaluminum
Hydrolyze by adding an organic solvent containing ~ 1.4 mol of water,
An alcohol represented by the general formula R ₃ OH (wherein R ₃ is an alkyl group), and optionally a compound containing silicon and / or a β-diketone compound are added to and mixed with the hydrolyzate. The amount of the β-diketone compound in the mixture is 0.03 mol to 0.
An amount of less than 2 moles, an amount of alcohol of 0.8 moles or more with respect to 1 mole of aluminum in the mixture, and an amount of a compound containing silicon, the silica content of silica-alumina fibers is 40% by weight or less A method for producing a silica-alumina fiber, which comprises adjusting the amount range as described above, spinning the mixture to obtain a precursor fiber, and firing the precursor fiber. 2. The silica content in the resulting silica-alumina fiber is 1 in the amount of the compound containing silicon in the mixture.
The method for producing a silica-alumina fiber according to claim 1, wherein the content is from 30% by weight to 30% by weight. 3. The method for producing a silica-alumina fiber according to claim 1, wherein R ₁ and R ₂ of the β-diketone compound are an alkyl group or an alkoxy group having 4 or less carbon atoms. 4. The method for producing a silica-alumina fiber according to claim 1, wherein the β-diketone compound is mixed in an amount of 0.05 mol to 0.18 mol with respect to 1 mol of aluminum. 5. The method for producing a silica-alumina fiber according to claim 1, wherein R _{3 of the} alcohol is an alkyl group having 4 or less carbon atoms. 6. An alcohol is mixed in an amount of 0.9 to 5.0 mol with respect to 1 mol of aluminum.
6. The method for producing a silica-alumina fiber according to any one of 5 to 6. 7. The method for producing silica-alumina fiber according to claim 1, wherein the concentration of water in the organic solvent used for hydrolysis is 40% by weight or less. 8. The method for producing a silica-alumina fiber according to claim 1, wherein the concentration of water in the organic solvent used for hydrolysis is 3 to 30% by weight. 9. The method for producing a silica-alumina fiber according to claim 1, wherein the organic solvent used for hydrolysis is an ether compound.