JPH04263615A - Production of viscous aluminosilicate sol - Google Patents

Abstract

PURPOSE:To provide a process for easily producing a viscous sol of aluminosilicate having excellent spinnability in high reproducibility. CONSTITUTION:An aluminosilicate sol is produced by mixing a silicon alkoxide with a reaction product of an aluminum alkoxide and a compound having active hydrogen and hydrolyzing the mixture. The solvent in the sol is distilled off and the dried sol is dissolved again in a solvent to obtain a viscous aluminosilicate sol having extremely excellent spinnability and giving a spun fiber having fine denier.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for producing an aluminosilicate-based viscous sol that exhibits extremely good spinnability and is suitable for producing silica-alumina fibers. In the method of obtaining an aluminosilicate-based viscous sol by modifying and hydrolyzing silicon alkoxide or its derivatives, the organic solvent in the sol is removed, dried, and then redissolved, resulting in extremely good traction. Prepare a filamentous sol,
Furthermore, it is related to the production of silica-alumina fibers with fine fiber diameter and excellent strength.

0002

[Prior Art] Ceramic fibers are widely used in industry, for example, as heat insulating materials, vibration isolators, adsorbents, filtration materials, and reinforcing materials for composite materials. This will become important from now on.

[0003] Conventionally, reinforcing materials for the composite materials include metal fibers, carbon fibers, surface-treated composite fibers, polycrystalline fibers such as alumina and zirconia, and whiskers. Among these, polycrystalline fibers are superior to other fiber materials in that they can be used in high-temperature oxidizing atmospheres where carbon fibers and metal fibers cannot be used, and they do not lose their excellent mechanical properties even at high temperatures. , it becomes possible to achieve both heat resistance and brittleness mitigation, which are most expected of ceramic materials.

[0004] Methods for producing silica-alumina fibers having such characteristics include a method of melt-spinning silica-alumina minerals, or a method of spinning from a solution containing an aluminum compound or a silicon compound, and firing the filament to produce silica fibers. There are methods to obtain alumina fibers.

[0005] However, conventional production methods have problems such as limitations on the content of silicon compounds, only short fibers can be obtained, and special equipment is required for production. Therefore, it is desired to develop a manufacturing method for easily obtaining long-fiber silica-alumina fibers.

[0006] In order to solve this problem, the present inventors used aluminum alkoxide and silicon alkoxide as starting materials, took advantage of their advantages to the fullest, and created a material that could be spun into long fibers when fired. We have proposed a method for producing a silica-alumina precursor sol that can be obtained (Japanese Patent Application No. 63-254783, Japanese Patent Application No. 1-234623).
.

[0007] This method involves reacting aluminum alkoxide with a compound having active hydrogen, mixing the reaction product with silicon alkoxide and/or its derivatives, and
We proposed that when hydrolyzing the mixture, a silica-alumina precursor sol with sufficient stringiness could be obtained by adjusting the ratio of the compound with active hydrogen to the aluminum alkoxide and the ratio of water to a specific ratio. It is something.

[0008]

According to the above invention, it has become possible to easily obtain a precursor of silica alumina continuous filaments with good spinnability and with good reproducibility. However, in general, the strength of ceramic fibers increases as the fiber diameter becomes finer, and in order to obtain ceramic fibers with better mechanical properties, it is necessary to obtain fibers with finer diameters. There is a strong desire to develop a viscous sol that exhibits excellent stringiness.

The object of the present invention is to solve this problem and to produce an aluminosilicate-based viscous sol with good reproducibility and excellent spinnability using a simple method.

0010

[Means for Solving the Problems] The present invention provides a method for producing an aluminosilicate-based viscous sol by hydrolyzing a mixture of a reaction product of an aluminum alkoxide and a compound having active hydrogen, and a silicon alkoxide. After distilling off the solvent in the sol obtained by hydrolysis and drying the sol, one or two types that can dissolve the dried product are added.
The present invention is a method for producing an aluminosilicate-based viscous sol, which is characterized by preparing a sol by redissolving a dried product in at least one solvent, and thereby can solve the above-mentioned problems.

[0011] The present invention involves distilling off the solvent in a sol obtained by hydrolyzing a mixture of silicon alkoxide and a reaction product of an aluminum alkoxide and a compound having active hydrogen, that is, an aluminosilicate sol. By drying and then re-dissolving the dried substance with one or more solvents that can dissolve the dried substance, it is possible to create an extremely stringy yarn that is unprecedented compared to the aluminosilicate-based viscous sol before drying. It is characterized by being able to prepare aluminosilicate-based viscous sol with excellent properties.

It is generally known that the tensile strength of ceramic fibers strongly depends on the fiber diameter, and that the finer the fiber diameter, the higher the strength. Therefore, the present invention provides an excellent spinnable sol that can be made into continuous long fibers and can provide fine fiber diameters.

[0013] The mixture contains at least both metal alkoxides, which are the constituent metals of the aluminosilicate sol produced from aluminum alkoxide and silicon alkoxide, and the compound having the active hydrogen, and any other optional components, such as organic Solvent, water, optional additives, catalysts such as inorganic acids, other sol composition metal materials,
It may contain a crystal control agent and the like.

By hydrolyzing this mixture, at least the metal alkoxide is hydrolyzed and an aluminosilicate-based viscous sol is produced. At this time, alcohol is also produced.

Therefore, the solvent in the sol obtained by hydrolyzing the mixture in the present invention, that is, the solvent to be distilled off, is
It is meant to include volatile compounds such as organic solvents, water, and hydrolyzed alcohols that can be added to the mixture in advance.

[0016] The method of distilling off the solvent in the sol to dry the sol can be carried out either under normal pressure or under reduced pressure. In order to exhibit better stringability, it is preferable to distill off the solvent and dry the sol completely by a combination of appropriate drying, such as drying under normal pressure and drying under reduced pressure. In these solvent distillation and drying processes, it is necessary to suppress the progress of gelation due to moisture in the air as much as possible, and it is necessary to perform the operations under reduced pressure in a dry atmosphere that does not contain moisture. be. The temperature during solvent distillation and drying is appropriately set depending on the type of solvent used for sol preparation and the degree of vacuum, but a temperature of 35° C. or higher is usually used.

The solvent for re-dissolving the dried sol is not particularly limited as long as it dissolves it, and alcohols such as methanol, ethanol and butanol, ketones such as acetone and methyl ethyl ketone, benzene and toluene can be used. , aromatic hydrocarbons such as xylene, and tetrahydrofuran, which may be used alone or in combination of two or more. In addition, several types are appropriately selected from them in order to adjust the drying rate during spinning.

Depending on the amount of solvent used during redissolution,
The viscosity of the stringable sol can be easily changed. The viscosity of the sol preferred for spinning varies depending on the spinning method employed, but for example, when spinning continuous filaments by extrusion, it is 10 to 10,000 poise, more preferably 100,000 poise.
Adjusted to ~10,000 poise. When spinning short fibers by a centrifugal method or the like, it is possible to spin the fibers at a lower viscosity, although it depends on the conditions. Using this viscous sol with excellent spinnability, spinning can be carried out by an appropriate known method.

[0019] The fibrous sol absorbs moisture in the air,
Alternatively, gel fibers can be obtained by increasing the amount of water vapor or rapidly gelling in the presence of a gaseous catalyst that promotes gelling. The viscous sol obtained by the present invention has excellent stringability, and gel fibers with a finer fiber diameter than ever before can be obtained. High-strength silica-alumina fibers can be obtained by subjecting the obtained gel fibers to heat treatment, steam treatment, etc., and then firing them on an appropriate schedule.

The aluminum alkoxide used in the present invention has the general formula (RO) 3 Al (R: alkyl group)
Specifically, R is methyl, ethyl, n-propyl, iso-propyl, n-butyl,
Examples include iso-butyl, sec-butyl, and tert-butyl.

[0021] Compounds with active hydrogen to be reacted with aluminum alkoxide generally have hydrogen atoms in organic compounds bonded to heteroatoms such as oxygen, nitrogen, sulfur, etc., and are more reactive than ordinary hydrogen-carbon bonds. It is characterized by strong The active hydrogen-containing compound referred to in the present invention is one that satisfies the above-mentioned conditions and is reactive with aluminum alkoxide, which is a starting material.D. C. Bradley, R. C. Meh
rotra and D. P. “Matal” by Gaur
Compounds listed in "Alkoxides" p. 149-298 correspond.

Specifically, alkanolamine compounds represented by monoethanolamine, mono-n-propanolamine, mono-iso-propanolamine, diethanolamine, di-iso-propanolamine, triethanolamine, and tri-iso-propanolamine; β represented by acetylacetone and ethyl acetoacetate
- Diketone compounds; glycol compounds represented by ethylene glycol and diethylene glycol; other examples include organic acids, phenols, thiols, amines, etc.
From the viewpoint of adjusting the hydrolysis rate, alkanolamine compounds and β-diketone compounds are particularly preferred. Furthermore, among these, triethanolamine is particularly preferred as the alkanolamine compound, and β-ketonic acid esters such as ethyl acetoacetate are particularly preferred as the β-diketone compound.

The amount of this active hydrogen-containing compound used is:
For other than β-diketone compounds, the number of moles of active hydrogen per mole of aluminum alkoxide is 0.6 ~
Use in a range of 2.7 moles. β-diketone compounds such as acetylacetone and ethyl acetoacetate are enol-type and participate in the reaction, so the number of active hydrogens is counted as one per molecule; however, β-diketone compounds, especially β-ketone acids such as ethyl acetoacetate, In the case of esters, they have an excellent ability to stabilize aluminum alkoxides, and the number of moles of active hydrogen,
That is, a sufficient effect can be obtained in an amount of 0.2 to 1.5 moles of molecules.

Since the hydrogen atom of the hydroxyl group of alkanolamines participates in the reaction with aluminum alkoxide,
The number of active hydrogens in one molecule is 1 for monoalkanolamines, 2 for dialkanolamines, and 3 for trialkanolamines. When the amount of the compound having active hydrogen is within the above range, the hydrolysis rate of aluminum alkoxide can be sufficiently adjusted during hydrolysis, and a sol having a viscosity suitable for spinning operations can be obtained.

[0025] If the amount of the compound having active hydrogen used is less than the above range, the hydrolysis rate of aluminum alkoxide will not be sufficiently adjusted, and the reaction will proceed rapidly during hydrolysis, resulting in the precipitation of powdery precipitates. However, it is impossible to synthesize a sol with a viscosity suitable for spinning operations. On the other hand, if the amount used is larger than the above range, a viscous sol will be obtained after removing the hydrolyzed alcohol and organic solvent from the system, but the gelation rate will be low because it is stable against hydrolysis even after the spinning operation. This is extremely slow and makes it difficult to maintain the shape of the gel fiber, making it impractical.

[0026] The reaction between aluminum alkoxide and a compound having active hydrogen can be carried out by mixing the two at room temperature or under heating. Preferably, it is carried out in the presence of However, the reaction is possible even in the absence of an organic solvent. The organic solvent used here is preferably one that dissolves aluminum alkoxide, specifically alcohols represented by iso-propanol, sec-butanol, etc., aromatic hydrocarbons represented by toluene, benzene, xylene, etc. , tetrahydrofuran, dimethylformamide, carbon tetrachloride, etc., but alcohols are preferred from the viewpoint of solubility.

On the other hand, the silicon alkoxide to be mixed with the above reaction mixture is represented by the general formula (RO) 4 Si (R: alkyl group) or a derivative thereof; specifically, R is methyl, ethyl, n-propyl,
n-butyl, iso-butyl, sec-butyl, t
Examples include ert-butyl and derivatives thereof. Derivatives of silicon alkoxide include those obtained by partially hydrolyzing the above-mentioned silicon alkoxide with water in an amount less than 4 times the mole of silicon alkoxide, and oligomers that have undergone a polycondensation reaction in advance. The use of oligomers is not preferred in order to prevent subsequent distillation of the organic solvent in the sol and gelation during drying of the sol.

The amount of silicon alkoxide and/or its derivative used is preferably such that the silica content in the fired ceramic is 40% by weight or less. If the amount of silica used exceeds 40% by weight in the ceramic after firing, the heat resistance of the resulting silica-alumina fibers will decrease significantly, making it difficult to use as a reinforcing material for heat-resistant and composite materials. is severely limited.

[0029] The amount of water used when hydrolyzing a mixture of a reaction mixture of aluminum alkoxide and a compound having active hydrogen with silicon alkoxide and/or its derivatives is as follows:
Silicon alkoxide, as described below, including other metal alkoxides, is 0.0% per mole of all alkoxides.
It is used in a range of 5 to 2.0 moles. Even when using an oligomer that has undergone a polycondensation reaction as a silicon alkoxide derivative, the oligomer is treated as one molecule and water within the above range is used. In addition, when using a derivative of silicon alkoxide that has been partially hydrolyzed with water that is less than 4 times the mole of silicon alkoxide, calculate the amount of water used for this partial hydrolysis. aluminum alkoxide,
Water is additionally added so that the amount of hydrolyzed water is within the above range based on 1 mole of all alkoxides such as silicon alkoxide as a starting material.

When the amount of water used is less than 0.5 mol, a viscous sol is obtained after removal of the hydrolyzed alcohol and, if organic solvents are used in the system, after removal of these solvents. However, it becomes difficult to maintain the shape of the gel fiber after the spinning operation, making it impractical. On the other hand, if the amount of water used is more than 2.0 mol, the reaction will proceed rapidly during hydrolysis, and even if a powdery precipitate is deposited or a viscous sol is obtained, the organic Gelation tends to occur during distillation of the solvent and drying of the sol, making it unsuitable for the synthesis of a sol having a viscosity suitable for spinning operations according to the present invention. Further, from the above viewpoint, the more preferable amount of water used for hydrolysis is 0.5 to 1 per mole of total alkoxide.
．． It is in the range of 5 moles.

Methods for hydrolyzing the mixture include hydrolysis by adding a mixture of water and an organic solvent that has an appropriate solubility in water or dissolves water, and using moisture in the air. Examples include hydrolysis, hydrolysis using blowing gas containing water vapor, and the like. Monoethanolamine as a compound with active hydrogen,
When acetylacetone is used, it is preferable to use a hydrolysis method using moisture in the air or a hydrolysis method using blowing gas containing water vapor. In this case, when hydrolysis is performed by adding a mixture of water and an organic solvent that has a suitable solubility in water or dissolves water, the concentration of water must be kept at an extremely low concentration. A precipitate forms, making it unsuitable for industrial synthesis of a sol with a viscosity suitable for spinning operations. When triethanolamine or ethyl acetoacetate is used as a compound having active hydrogen, there are no particular limitations on the hydrolysis method. From this point of view, these two compounds can be said to be particularly preferable compounds. Further, this hydrolysis is preferably carried out in the presence of an organic solvent for the same reason as described in the reaction of aluminum alkoxide and a compound having active hydrogen. An organic solvent for this purpose may be added during this hydrolysis step, but aluminum alkoxide and a compound having active hydrogen must be already mixed and reacted in the presence of an organic solvent, or silicon alkoxide must be partially hydrated. When decomposition is carried out in the presence of an organic solvent, a mixture of silicon alkoxide and/or its derivatives containing the organic solvent may be directly subjected to the hydrolysis reaction.

[0032] The order in which the aluminum alkoxide, the compound having active hydrogen, the silicon alkoxide and/or its derivatives, and water used in the present invention are mixed is that the aluminum alkoxide and the compound having active hydrogen are mixed before the addition of water. There are no particular limitations as long as the conditions are right for the reaction and for silicon alkoxide and/or its derivatives to coexist in the reaction mixture.

In addition, in the present invention, for the purpose of controlling crystal transition, suppressing abnormal grain growth, and progressing sintering during gel fiber firing, B2 O3, MgO, P2 O5
, CaO, Cr2O3, CuO, Fe2O3,
Additives such as TiO2 and ZrO2 can be added. These compounds can be added as oxides, inorganic salts, organic salts, metal alkoxides, etc. before or after the formation of the aluminosilicate-based viscous sol and before spinning. One or more of these additives may be added.

[0034]

[Operation] According to the present invention, volatile compounds such as organic solvents in the sol obtained by hydrolyzing a metal alkoxide are distilled off, and the sol is once dried and then an organic solvent is added to dry it. By redissolving the sol, a viscous sol with excellent stringiness was obtained.

Although the exact mechanism is unclear, it is thought to be as follows. The sol obtained by hydrolyzing a mixture of aluminum alkoxide, a compound having active hydrogen, and silicon alkoxide exhibits stringiness, but
It is thought that this stringiness is basically developed by the formation of inorganic polymers through polymetalloxane bonds. It is thought that the molecular weight of polymetalloxane in a sol obtained by drying the sol is improved compared to the molecular weight of polymetalloxane in a viscous sol obtained only by hydrolysis and concentration. It is presumed that this is the reason for the excellent stringability.

[0036]

[Examples] The present invention will be specifically explained below with reference to Examples. However, the present invention is not limited only to these examples.

Example 1 Se per mole of aluminum sec-butoxide
6.6 mol of c-butanol and 0.33 mol of triethanolamine were mixed at room temperature for 2 hours to obtain a reaction product. Partial hydrolysis of 0.15 mol of silicon ethoxide with 0.15 mol (2.7 g) of water acidified with 1N HCl was mixed with the above reaction product of aluminum alkoxide. A mixture of 1 mol of water and 3 mol of sec-butanol was added to this mixture and stirred for 12 hours to obtain a sol. This sol was distilled under reduced pressure at 60° C. and 100 mmHg to remove almost all of the sec-butanol to obtain a dry sol. Further, this dried product was vacuum-dried at 70° C. for 24 hours to thoroughly dry it. After adding 200 ml of methanol to this dry solid and completely dissolving the dry solid, 60°C.
Concentration was performed under the condition of 100 mmHg to obtain a 540 poise viscous sol with excellent stringiness. When a glass rod was immersed in this sol and pulled up, extremely fine gel fibers with a length of 130 cm or more were obtained. Actually diameter 1
When gel fibers were obtained by extrusion spinning from a 60 μm nozzle, continuous gel fibers with a fiber diameter of 18 μm were obtained.

Comparative Example 1 In Example 1, the sol obtained after hydrolysis was heated to 60°C.
The sol was concentrated to a viscous sol by vacuum distillation of sec-butanol at 100 mmHg. When a glass rod was soaked in the sol at 580 poise and pulled up, only gel fibers with a length of about 20 cm were obtained, and the stringability was inferior to that of the viscous sol of Example 1. Actually, when a continuous gel fiber is obtained by extrusion spinning from a noise with a diameter of 160 μm, the fiber diameter is 55 μm.
Met.

Example 2 The dried sol obtained in Example 1 was dissolved in a mixed solvent of methanol/toluene=1/1 (volume ratio) to obtain a solution with a viscosity of 630.
A poise viscous sol was obtained.

By pulling up the glass rod, gel fibers with a fine diameter of 150 cm or more were obtained. Gel fibers with a fiber diameter of 21 μm were obtained by extrusion spinning from a nozzle with a diameter of 160 μm.

Example 3 Se per mole of aluminum sec-butoxide
c-butanol 6.6 mol, ethyl acetoacetate 0.5
The moles were mixed for 2 hours at room temperature to obtain the reaction product. 0.36 mol of silicon methoxide, 0.72 mol of silicon sec-butoxide, and 0.36 mol of water acidified with 1N hydrochloric acid were mixed at 50°C for 2 hours to obtain a partial hydrolyzate of silicon alkoxide. . The reaction product and the partial hydrolyzate of silicon alkoxide were mixed, and a mixed solution of 1.0 mol of water and 3.3 mol of sec-butanol was added to perform a hydrolysis operation. After the addition, the mixture was stirred for 12 hours to obtain a sol. This sol was heated to 60℃ and 100mmHg.
The sec-butanol was almost completely removed by distillation under reduced pressure to obtain a dried sol, which was further vacuum-dried at 70°C for 24 hours.

Sec-butanol was added to the dried sol to redissolve it to obtain a viscous sol of 850 poise. Gel fibers with a fine diameter of 150 cm or more were obtained by pulling up the glass rod. Continuous gel fibers with a fiber diameter of 18 μm were obtained by extrusion spinning from a nozzle with a diameter of 160 μm.

Comparative Example 2 The sol obtained by hydrolysis in Example 3 was heated at 60°C.
The sol was concentrated by distilling sec-butanol under reduced pressure at 100 mmHg to obtain a viscous sol with a viscosity of 700 poise. When this sol was soaked with a glass rod and pulled up, gel fibers with a length of only about 15 cm were obtained, and the stringability was inferior to that of the viscous sol of Example 3. When a continuous gel fiber was actually obtained by extrusion spinning from a nozzle with a diameter of 160 μm, the fiber diameter was 60 μm.

[0044]

Effects of the Invention According to the present invention, chemically modified aluminum alkoxide, silicon alkoxide and/or
By drying a sol obtained by hydrolyzing or a derivative thereof and then redissolving it, a viscous sol with extremely excellent spinnability can be obtained. By performing a spinning operation using this sol, fine gel fibers are obtained, and by firing the gel fibers, aluminosilicate fibers with a fine diameter are obtained. This is a method for producing a viscous sol that is extremely useful for obtaining aluminosilicate fibers with excellent strength.

Claims (1)

[Claims] 1. A method for producing an aluminosilicate-based viscous sol by hydrolyzing a mixture of a reaction product of an aluminum alkoxide and a compound having active hydrogen, and a silicon alkoxide, comprising: a sol obtained by hydrolyzing the mixture; An alumino product characterized in that the sol is prepared by distilling off the solvent in the sol to dryness, and then redissolving the dried product in one or more solvents that can dissolve the dried product. A method for producing a silicate-based viscous sol.