JPH03113019A - Production of nitrogen-containing ceramic fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing oxynitride ceramic fibers, and in particular to fiber reinforced plastics (FR).
P), strength useful for fiber reinforced concrete (FRC),
The present invention relates to a method for producing reinforcing fibers with excellent elastic modulus and corrosion resistance, or ceramic fibers with excellent heat resistance and corrosion resistance, which can be used as chemical filters, heat-resistant heat insulating materials, etc.

[Conventional technology]

Fiber materials are important for reinforcing plastics and concrete, and various other fiber materials are also used in the field of high-temperature materials such as heat-insulating curtains, heat-insulating cushioning materials, catalyst carriers, and high-temperature filters.

Glass fibers, carbon fibers, alumina fibers, silicon carbide fibers, organic polymer fibers, etc. have traditionally been used as fiber materials, but the properties required of materials are diversifying, and fibers with new functions are being developed. is eagerly awaited.

Nitrogen-containing ceramic fiber is one of them, and when the nitrogen-containing ceramic is glass, oxynitride glass, it has a higher
Improves hardness, strength, elastic modulus, heat resistance, and corrosion resistance. or,
When the nitrogen-containing ceramic is a polycrystalline ceramic, such as Sialon, high-temperature strength, strength, thermal shock resistance, etc. are improved compared to oxide ceramics.

As a method for obtaining these nitrogen-containing ceramics or hybrid ceramics of oxide and nitride in the form of fibers, two types of methods have been studied.

(2) Method of spinning oxides and nitrides through melts High temperatures are required to melt oxides and nitrides. Further, undesirable crystal phases and metal phases are generated due to decomposition of nitrides or reduction of oxides. A special spinning device is required to stably produce oxynitride glass (Japanese Patent Application Laid-Open No. 63-3
10747).

■ Method of obtaining precursor fibers using metal alkoxides and inorganic polymers as starting materials and nitriding firing (1) Method of spinning and nitriding polycarbosilane is Che-s+1try
Letters 2059-2060 (1984), however, there are problems such as the complicated synthesis of polycarbosilane and the limitations on the composition of the oxynitride glass that can be obtained.

(2) TiN or T by nitriding T i O□ gel fiber or gel fiber containing Ti.
A method for producing TiO2 fibers coated with iN or infrared-transparent oxynitride glass containing Ti was published in Journal of Materials 5ci.
ence 22.937-9401987), JP-A No. 62-263322, JP-A No. 63-40742, etc., the composition of the ceramics obtained is limited to systems containing Ti, which is extremely reactive with nitrogen. There is a drawback.

(3) Journal of Non-Cr
ystallineSolids 83.208-22
2 (1986), JP-A-63-112437, JP-A-63
-242943 etc. However, in these cases, gel fibers produced solely from tetrafunctional alkoxides such as tetraethoxysilane contain almost no nitrogen even when nitrided under a stream of ammonia, so if monoalkyltrialkoxysilanes such as methyltriethoxysilane are used, Since the introduction of nitrogen is efficient, we are disclosing a technique for using it alone or in combination.

However, methyltriethoxysilane is expensive and has the problem of being limited to St-based acetic acid nitride compositions.

[Problem to be solved by the invention]

The present invention overcomes the drawbacks of the conventional methods mentioned above, namely, that a high temperature process is required, that the synthesis of precursors such as polycarbosilane is complicated, and that only those containing special elements such as Ti can be used. Eliminates disadvantages such as the need to use expensive starting materials such as methyltriethoxysilane, the need for complex and expensive equipment, the complicated manufacturing process, and the limited ceramic composition. The object of the present invention is to provide a method for obtaining nitrogen-containing ceramic fibers by a simple method with no restrictions on composition.

[Means to solve the problem]

The present invention provides a method for producing nitrogen-containing ceramic fibers using silicon alkoxide and aluminum alkoxide as main raw materials, in which a reaction mixture of a compound having active hydrogen other than alcohols and thiols and aluminum alkoxide and a mixture of silicon alkoxide are hydrated. The sol obtained by decomposition is spun at a viscosity range of 10 poise or higher, and the resulting gel fiber is heated with nitrogen and/or
Alternatively, there is a method for manufacturing a nitrogen-containing ceramic fiber characterized by firing under an ammonia stream, which can solve the above problems.

The present invention will be explained in detail below.

The aluminum alkoxide used in the present invention is represented by the general formula (RO)+Af (R: alkyl group), and specifically R is methyl, ethyl, n-propyl, 1so-propyl, n-butyl, 1so-butyl,
Examples include 5ec-butyl and tert-butyl.

In addition, compounds with active hydrogen that are reacted with aluminum alkoxide generally have a hydrogen atom in the compound bonded to a heteroatom other than a carbon atom such as oxygen, nitrogen, or sulfur, and the latter is better than the former. It is characterized by strong reactivity.

The compound having active hydrogen as used in the present invention is one that satisfies the above-mentioned conditions and has reactivity with aluminum alkoxide, which is a starting material, and includes D, C, Bra
dley, R.C., Mehrotra and D.P.
, Gaur, “Metal Alkoxides p.
Compounds listed in Nos. 149 to 298 correspond to this, but alcohols are excluded because no advantage can be found regarding the amount of nitrogen introduced during nitridation, and thiols are excluded because S is introduced.

Here, alcohol is alcohol in the narrow sense,
It is represented by the general formula ROH (R is an alkyl group), and the OH group represents an alcohol having only one monohydric alcohol and no other functional groups.

Specifically, compounds having active hydrogen include monoethanolamine, mono-n-purpanolamine, and mono-1so.
-propertoolamine, jetanolamine, di-1so
-Propertoolamine, triethanolamine, tri-1
Alkanolamine compounds represented by so-propaturamine; β-diketone compounds represented by acetylacetone and ethyl acetoacetate; glycol compounds represented by ethylene glycol and diethylene glycol; as well as organic acids, phenols, amines, etc. Although listed,
Alkanolamine compounds are particularly preferred from the viewpoint of introducing nitrogen into the ceramic fiber in the nitriding process described below.

The amount of the compound having active hydrogen used is 0.1 moles of active hydrogen per mole of aluminum alkoxide.
It is used in a range of 2.7 mol. Since β-diketone compounds such as acetylacetone and ethyl acetoacetate participate in the reaction in the enol form, the number of active hydrogens is counted as one per molecule. 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. count.

If the amount of the compound having active hydrogen used is less than 0.1 mole of active hydrogen, there will be no effect on the introduction of nitrogen in the nitriding process.
If the amount is more than 1 mol, these compounds with active hydrogen also have a stabilizing effect on the hydrolysis of aluminum alkoxide, so after removing the alcohol and organic solvent generated by hydrolysis from the system, a viscous sol can be obtained. Since it is stable against hydrolysis even after the spinning operation, the gelation rate is extremely slow, making it difficult to maintain the shape of the gel fiber, making it impractical.

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, but the reaction is preferably carried out in the presence of an organic solvent from the viewpoint of miscibility and uniformity of the reaction. It is preferable to do so.

However, the reaction is possible even in the absence of an organic solvent. The organic solvent used here is preferably one that dissolves the aluminum alkoxide, specifically methanol, ethanol, n-propanol, 1so-propanol, Alcohols such as 5ec-butanol,
Examples include aromatic hydrocarbons typified 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)4si (R: alkyl group), and specifically R is methyl, ethyl, n-propyl, n-butyl, iso-butyl, 5e
Examples include c-butyl and tert-butyl.

Further, this silicon alkoxide may be a derivative, such as a product obtained by partially hydrolyzing the above-mentioned silicon alkoxide with water in an amount of 4 times or less by mole relative to the silicon alkoxide, an oligomer that has undergone a polycondensation reaction in advance, etc. However, in order to stably and reproducibly produce a sol with particularly excellent spinnability, strong acids such as hydrochloric acid, nitric acid, hydrofluoric acid, sulfuric acid, and sulfonic acid compounds are added to 1 mole of silicon alkoxide. It is preferable to use a product that has been partially hydrolyzed with 4 times or less of water in the presence of a catalyst.

The composition of the present invention may further include Si,
//! Other metal elements may also be used. For example, in order to facilitate vitrification and obtain oxynitride glass, Li
, Na, alkali metals such as Cs, Be, Mg, Ca
, Sr, alkaline earth metals such as Ba, others, Ti, Z
r, Ge, Y, B.

The use of sb etc. is exemplified.

When adding these metal elements, there are no particular restrictions on the type of compound; metal alkoxides, acetates, chlorides,
Examples include the use of nitrates and the like.

In addition, for alkoxides that are easily synthesized from metals such as alkali metals and alkaline earth metals,
It can also be added as a metal to a reaction system using alcohol as a medium.

The amount of water used when hydrolyzing a mixture of a reaction mixture of aluminum alkoxide and a compound having active hydrogen mixed with silicon alkoxide is based on the total amount of water used, including aluminum alkoxide, silicon alkoxide, and the other metal alkoxides mentioned above. It is used in an amount of 0.5 to 2.0 mol per mol of alkoxide. 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. Water is added so that the amount of hydrolyzed water is within the above range per mole of all alkoxides such as aluminum alkoxide and silicon alkoxide as a starting material.

If the amount of water used is less than 0.5 mol, a viscous sol is obtained after the removal of the hydrolyzed alcohol and, if an organic solvent is used in the system, but the spinning After the operation, it becomes difficult to maintain the shape of the gel fiber, 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 a powdery precipitate will be deposited, or even if a viscous sol is obtained, gelation will be rapid. The spinnable state and time are extremely short (unsuitable for synthesizing a sol with a viscosity suitable for spinning operations).

Moreover, from the above viewpoint, the amount of water used for hydrolysis is more preferably in the range of 0.5 to 1.5 mol per 1 mol of the total alkoxide.

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, hydrolysis using moisture in the air, Examples include hydrolysis using blowing gas containing water vapor, and there are no particular limitations.

The sol obtained by the above hydrolysis has a certain degree of viscosity and threadability, but the concentration is low and insufficient for spinning, so it can be spun by performing an appropriate concentration operation. A viscous sol is obtained. This concentration operation may be either normal pressure distillation or reduced pressure distillation.

The sol is spun at a viscosity of 10 poise or higher to obtain gel fibers.

In the case of 10 voids without grooves, it is possible to form the sol into a fiber shape, but it takes time to maintain the shape through gelation, making it extremely difficult to obtain gel fibers.

Further, known methods can be applied to the spinning, and gel fibers can be easily obtained by extrusion from a nozzle or the like.

The obtained gel fiber is fired under a nitrogen and/or ammonia stream to obtain an oxynitride ceramic fiber. Firing conditions vary depending on the composition of the gel fiber and whether nitrogen or ammonia is used as the gas, but -600° for ammonia for boat fishing.
For example, the temperature range is 800° C. or higher in the case of nitrogen gas.

In the present invention, by using aluminum alkoxide as a reactant with a compound having active hydrogen, nitrogen is easily introduced into the ceramic fiber during the nitriding firing process. The nitriding process in ammonia is significantly better than the nitriding process in N2, and it is particularly preferable to use ammonia as the nitriding gas.

[For production]

The reason why nitridation in nitrogen and/or ammonia tends to proceed when aluminum alkoxide is used as a reaction mixture with a compound having active hydrogen is unknown, but the following possibilities are considered.

■ Direct introduction of coordinating nitrogen when using compounds with nitrogen atoms such as alkanolamines and amines.

■ Changes in the microstructure of the gel due to added compounds.

■ Chemical bonds in gel fibers are cleaved at relatively high temperatures, and reactions with nitrogen in the active state tend to proceed.

Possibilities other than the above are possible, and although the mechanism is currently unknown, it is presumed that the above effects act synergistically to advance nitriding.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

Example 1 1 mole of aluminum tri-5ec-butoxide was converted into 5ec-
It was dissolved in 4 moles of butanol. 1 mole of monoethanolamine was dissolved in 4 moles of 5ec-butanol and reacted with an aluminum tri-5ec-butoxide solution.

Dissolve 1 mole of tetraethoxysilane in 4 moles of ethanol, and add 1 mole of water acidified with 1N hydrochloric acid to 2 moles of ethanol.
A solution of the tetraethoxysilane in molar ethanol was added to partially hydrolyze the tetraethoxysilane. Partially hydrolyzed at room temperature for 30 minutes, the above aluminum tri-5ec-
It was added to a solution containing butoxide, mixed, and reacted. A mixed solution of 1 mol of water and 1 mol of ethanol was added to this mixture to carry out hydrolysis and polycondensation.

The solvent was distilled off under reduced pressure to obtain a viscous solution with a viscosity of 480 voids. Continuous gel fibers were obtained by extruding and spinning this viscous solution.

This gel fiber was used at an ammonia flow rate of 0.51.7si.
n, nitriding was performed at a temperature of 1200°C for 3 hours.

The nitrogen content in the obtained fiber was 5.9% and
The crystal phase determined in step 1 was microcrystalline mullite.

Comparative Example 1 A viscous solution with a viscosity of 650 voids was obtained in the same manner as in Example 1 without adding monoethanolamine, and this was extruded and spun to obtain continuous gel fibers.

This gel fiber was nitrided and fired under the same conditions as in Example 1. The nitrogen content in the obtained fiber was 0.01%
Below, little nitrogen was introduced and the crystalline phase was mullite.

Example 2 1 mole of aluminum tri-5ec-butoxide was converted into 5ec-
It was dissolved in 4 moles of butanol. 1 mole of monoethanolamine was dissolved in 4 moles of 5ec-butanol and reacted with a solution of aluminum tri5ec-butoxide.

Dissolve 1 mole of tetraethoxysilane in 4 moles of ethanol, and add 1 mole of water acidified with 1N hydrochloric acid to 2 moles of ethanol.
A solution of the tetraethoxysilane in molar ethanol was added to partially hydrolyze the tetraethoxysilane. Partially hydrolyzed at room temperature for 30 minutes, the above aluminum tri-5ee-
It was added to a solution containing butoxide, mixed, and reacted.

To this, 0.167 mol of magnesium acetate tetrahydrate was added and completely dissolved.

A mixed solution of 0.33 mol of water and 1 mol of ethanol was added to this reaction mixture to carry out hydrolysis and polycondensation.

The solvent was distilled off under reduced pressure to obtain a viscous solution with a viscosity of 330 voids. Continuous gel fibers were obtained by extruding and spinning this viscous solution.

This gel fiber was mixed with ammonia at a flow rate of 0. FM! /1l
In, nitriding firing was carried out at a temperature of 1200°C for 3 hours.

The nitrogen content in the obtained fiber was 7.6%, and the crystal phase determined by X-rays was mullite, MgA f□04, and an unknown phase of microcrystals.

Example 3 The gel fiber of Example 2 was subjected to an ammonia flow I0°5ff.
Nitriding firing was carried out at i/111in and a temperature of 1200°C for 6 hours.

The nitrogen content in the obtained fiber was 12.5%,
The crystal phase determined by the line is unknown phase, mullite, MgAl
It was a microcrystal of zOa.

Comparative Example 2 A viscous solution with a viscosity of 350 poise was obtained in the same manner as in Example 2 without adding monoethanolamine, and this was extruded and spun to obtain continuous gel fibers.

This gel fiber was nitrided and fired under the same conditions as in Example 2. The nitrogen content in the obtained fiber was 1.2%, only a small amount of nitrogen was introduced, and the crystal phase was mullite, Mg
A 1 zo4, unknown sum. Comparative Example 3 The gel fiber of Comparative Example 2 was nitrided and fired under the same conditions as in Example 3. The nitrogen content in the obtained fiber was 1.
At 9%, the crystalline phase was mullite, an unknown sum.

(Effects of the Invention) According to the present invention, oxynitride ceramic fibers with expected properties such as hardness, strength, elastic modulus, heat resistance, and corrosion resistance can be manufactured by a simple method and without using special equipment. This is an industrially useful manufacturing method.

(3 idiots)

Claims (1)

[Claims] (1) In a method for producing nitrogen-containing ceramic fibers using silicon alkoxide and aluminum alkoxide as main raw materials, a mixture of silicon alkoxide and a reaction mixture of aluminum alkoxide and a compound having active hydrogen other than alcohols and thiols is hydrolyzed. A method for producing nitrogen-containing ceramic fibers, which comprises spinning the resulting sol at a viscosity of 10 poise or higher, and firing the resulting gel fibers in a nitrogen and/or ammonia stream.