JPH076092B2 - Method for producing nitrogen-containing ceramic fiber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an oxynitride ceramic fiber, and particularly to a fiber reinforced plastic (FR
P), Reinforced fiber with excellent strength, elastic modulus and corrosion resistance useful for fiber reinforced concrete (FRC), or ceramic fiber with excellent heat resistance and corrosion resistance, which can be used for chemical filters, heat resistant heat insulating materials, etc. It is about.

[Conventional technology]

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

Conventionally, glass fibers, carbon fibers, alumina fibers, silicon carbide fibers, organic polymer fibers, etc. have been used as fiber materials, but the characteristics required as materials have diversified, and fibers with new functions Is long-awaited.

Nitrogen-containing ceramic fiber is one of them, and when the nitrogen-containing ceramic is glass, that is, when it is oxynitride glass, hardness, strength, elastic modulus, heat resistance and corrosion resistance are improved as compared with oxide glass. To do.
When the nitrogen-containing ceramic is polycrystalline ceramic, for example, sialon, the high temperature strength, strength, thermal shock resistance, etc. are improved as compared with oxide ceramics.

As methods for obtaining these nitrogen-containing ceramics or mixed ceramics of oxides and nitrides in the form of fibers, two types of methods have been roughly studied from the past.

I. Method of spinning oxides and nitrides through a melt A high temperature is required to melt oxides and nitrides. In addition, an undesired crystal phase or metal phase is generated by decomposition of the nitride or reduction of the oxide. A special spinning device is required for stable production of oxynitride glass (Japanese Patent Laid-Open No. 63-63242).
-310747).

II. Method of obtaining precursor fiber using metal alkoxide and inorganic polymer as starting materials and nitriding and firing (1) Polycarbosilane spinning and nitriding is Chem
Although it is disclosed in istry Letters 2059-2060 (1984), there are problems such that the synthesis system of polycarbosilane is complicated and the composition system of the obtained oxylite glass is limited.

(2) TiN or TiN-coated TiO ₂ by nitriding TiO ₂ gel fiber or Ti-containing gel fiber
A method for producing an infrared transmissive oxynitride glass containing fibers or Ti is described in Journal of Materials Sci.
ence 22, 937-941 (1987), JP-A-62-263322, 63-4
However, there is a drawback in that the composition of the obtained ceramics is limited to a system containing Ti, which has extremely high reactivity with nitrogen.

(3) Journal of Non-Crystalline Solids 8
3 , 208-222 (1986), JP-A-63-112437, JP-A-63-242943 and the like. However, in these, since the gel fiber produced from tetrafunctional alkoxide alone such as tetraethoxysilane hardly introduces nitrogen even in the nitriding under the ammonia stream, when a monoalkyltrialkoxysilane such as methyltriethoxysilane is adopted. Since the introduction of nitrogen becomes efficient, a technique of using nitrogen alone or in combination is disclosed. However, there is a problem that methyltriethoxysilane is expensive and is limited to the composition component of Si-based oxynitride.

[Problems to be Solved by the Invention]

The present invention has the above-mentioned drawbacks of the conventional method, that is, a high temperature process is required, the synthesis of a precursor such as polycarbosilane is complicated, and only those containing a special element such as Ti are possible, Since expensive starting materials such as methyltriethoxysilane must be used, complex and expensive equipment is required, the manufacturing process is complicated, and the ceramic composition is limited. It is an object of the present invention to provide a method for obtaining a nitrogen-containing ceramic fiber by an easy method with no limitation on the composition.

[Means for Solving the Problems] The present invention is a method for producing a nitrogen-containing ceramic fiber containing silicon alkoxide and aluminum alkoxide as main raw materials, and mixing an alkanolamine compound and / or a β-diketone compound with an aluminum alkoxide. Reacting to form a reaction mixture, forming a mixture of the reaction mixture and a silicon alkoxide, hydrolyzing the mixture to obtain a sol, spinning the sol in a viscosity range of 10 poise or more, obtaining A method for producing a nitrogen-containing ceramic fiber, which comprises a step of producing a nitrogen-containing ceramic fiber by firing the obtained gel fiber in a nitrogen and / or ammonia stream, thereby solving the above-mentioned problems. it can.

Hereinafter, the present invention will be described in detail.

Aluminum alkoxide used in the present invention is represented by the general formula (RO) ₃ Al (R: alkyl group),
Specifically, R is methyl, ethyl, n-propyl, iso-
Propyl, n-butyl, iso-butyl, sec-butyl, te
rt-butyl and the like.

In addition, with a compound having active hydrogen to be reacted with an aluminum alkoxide, the hydrogen atom in the compound is generally bonded to a heteroatom such as oxygen, nitrogen, or sulfur other than carbon atom, and the latter is more reactive than the former. It is characterized by its strong nature.

The compound having active hydrogen referred to in the present invention is one which satisfies the above-mentioned conditions and has reactivity with an aluminum alkoxide as a starting material, DC Bradley, R.
C. Mehrotra and DP Gaur "Metal Alkoxides" p149-2
The compounds listed in 98 correspond, but alcohols are excluded from the fact that no advantage can be found regarding the amount of nitrogen introduced during nitriding, and thiols are excluded from the introduction of S.

Here, alcohols are alcohols in a narrow sense,
Is represented by the general formula ROH (R is an alkyl group), O
The H group represents only one monohydric alcohol having no other functional group.

In the present invention, as a compound having active hydrogen, monoethanolamine, mono-n-propanolamine, monoiso-
Propanolamine, diethanolamine, diiso-propanolamine, triethanolamine, triiso-
Alkanolamine compounds represented by propanolamine; β-diketone compounds represented by acetylacetone and ethyl acetoacetate are used, and alkanolamine compounds are particularly preferable from the viewpoint of introducing nitrogen into the ceramic fiber in the nitriding process described later. .

The amount of the compound having active hydrogen used is 0.1 to 1 mol of active hydrogen per mol of aluminum alkoxide.
Use in the range of 2.7 moles. Since β-diketone compounds such as acetylacetone and ethyl acetoacetate are involved in the reaction with the enol type, the number of active hydrogen is counted as one in one molecule.
In alkanolamines, the hydrogen atom of the hydroxyl group participates in the reaction with aluminum alkoxide, so the number of active hydrogen in one molecule is 1 for monoalkanolamine, 2 for dialkanolamine, and 3 for trialkanolamine. count.

When the amount of the compound having active hydrogen used is less than 0.1 mol in terms of the number of active hydrogen, there is no effect on the introduction of nitrogen in the nitriding process. On the other hand, when the amount used is more than 2.7 mol, the compounds having these active hydrogens also have a stabilizing effect on the hydrolysis of the aluminum alkoxide, so the alcohol produced by hydrolysis and the viscosity after removal from the organic solvent are removed from the system. Although the obtained sol is obtained, the gelation rate is extremely slow because it is stable against hydrolysis even after the spinning operation, and it becomes difficult to maintain the shape of the gel fiber, which is not practical.

The reaction between the aluminum alkoxide and the compound having active hydrogen can be carried out by mixing both at room temperature or under heating, but the reaction is carried out in the presence of an organic solvent from the viewpoint of miscibility and uniformity of the reaction. It is preferable to carry out.
However, the reaction is possible without the presence of an organic solvent. As the organic solvent used here, it is preferable to dissolve aluminum alkoxide, and specifically, alcohols represented by methanol, ethanol, n-propanol, iso-propanol, sec-butanol, etc., toluene, benzene, xylene, etc. Representative aromatic hydrocarbons, tetrahydrofuran, dimethylformamide,
Carbon tetrachloride and the like are exemplified, but alcohols are preferable from the viewpoint of solubility.

On the other hand, the silicon alkoxide mixed with the above-mentioned reaction mixture is represented by the general formula (RO) ₄ Si (R; alkyl group), and specifically, R is methyl, ethyl, n-propyl, n-butyl. , Iso-butyl, sec-butyl, tert-
Butyl etc. Further, this silicon alkoxide may be a derivative, and the above-mentioned silicon alkoxide is
Examples include those that have been partially hydrolyzed with 4 mol times or less water of silicon alkoxide, oligomers that have undergone a polycondensation reaction in advance, and a sol with particularly excellent spinnability can be stably reproduced. In order to manufacture with good properties, one mol of silicon alkoxide is partially hydrolyzed with 4 mol times or less of water in the presence of strong acid catalyst such as hydrochloric acid, nitric acid, hydrofluoric acid, sulfuric acid, and sulfonic acid compound. Is preferably used.

The composition of the present invention further comprises Si, Al according to various purposes.
Other metal elements are also used. For example, in order to facilitate vitrification and form oxynitride glass, Li, Na, K, Cs
Examples thereof include alkali metals such as Al, alkaline earth metals such as Be, Mg, Ca, Sr, and Ba, and Ti, Zr, Ge, Y, B, Sb, and the like.

When adding these metal elements, the species of the compound is not particularly limited, metal alkoxide, acetate, chloride,
The use of nitrate and the like is exemplified.

In addition, for those in which an alkoxide is easily synthesized from a metal, such as alkali metal and alkaline earth metal,
It can also be added as a metal in the reaction system using alcohol as a medium.

The amount of water used when hydrolyzing the mixture obtained by mixing the reaction mixture of the aluminum alkoxide and the compound having active hydrogen with the silicon alkoxide is not limited to the total amount of aluminum alkoxide, silicon alkoxide, and other metal alkoxides described above. It is used in the range of 0.5 to 2.0 mol per mol of alkoxide. Even when an oligomer having undergone a polycondensation reaction is used as a derivative of a silicon alkoxide, the oligomer is treated as one molecule and water in the above range is used. In addition, when a silicon alkoxide derivative that is partially hydrolyzed with 4 mole times or less water of silicon alkoxide is used, the amount of water used for this partial hydrolysis is also calculated. Put in aluminum alkoxide,
Water is additionally added so that the amount of hydrolyzed water is within the above range with respect to 1 mol of all alkoxides such as silicon alkoxide as a starting material.

If the amount of water used is less than 0.5 mol, a viscous sol is obtained after removal of the hydrolysis product alcohol and after removal of the organic solvent used in the system, but after spinning operation. It becomes difficult to maintain the shape of the gel fiber, making it impractical. On the other hand, when the amount of water used is more than 2.0 mol, the reaction proceeds rapidly during hydrolysis, and even if a powdery precipitate is deposited or a viscous sol is obtained,
Gelation is fast, spinnable state and time are extremely short,
Not suitable for synthesizing sols with viscosities suitable for spinning operations.

From the above viewpoint, the more preferable amount of water used for hydrolysis is in the range of 0.5 to 1.5 mol with respect to 1 mol of all alkoxides.

As a method of hydrolyzing the mixture, having appropriate solubility in water, or by adding a mixture of water and an organic solvent that dissolves water, hydrolysis using water in the air, There is no particular limitation, such as hydrolysis utilizing the blowing of a gas containing water vapor.

The sol obtained by the above-mentioned hydrolysis has a certain degree of viscosity and spinnability, but since this is low in concentration and insufficient for spinning, it can be spun by performing an appropriate concentration operation. A viscous sol of different types is obtained. This concentration operation may be either atmospheric distillation or vacuum distillation.

The sol is spun in a viscosity range of 10 poise or more to obtain a gel fiber.

If it is less than 10 poise, it is possible to form the sol into a fibrous shape, but it takes time to maintain the shape due to gelation, and it is extremely difficult to obtain a gel fiber.

A known method can be applied to the spinning, and the gel fiber can be easily obtained by extrusion from a nozzle or the like.

An oxynitride ceramic fiber is obtained by firing the obtained gel fiber in a nitrogen and / or ammonia stream. The firing conditions differ depending on the composition of the gel fiber and whether nitrogen or ammonia is used as a gas, but in the case of ammonia, it is generally 600 ° C.
As described above, in the case of nitrogen gas, a temperature range of 800 ° C. or higher is exemplified.

In the present invention, by using aluminum alkoxide as a reaction product with a compound having active hydrogen, nitrogen is easily introduced into the ceramic fiber in the nitriding firing process, but the effect of using the compound having active hydrogen Is more remarkable when nitriding and firing in ammonia than when nitriding and firing in N ₂ , and it is particularly preferable to use ammonia as the gas for nitriding and firing.

[Action]

Although the reason why the nitriding in nitrogen and / or ammonia is likely to proceed by using the aluminum alkoxide as a reaction mixture with the compound having active hydrogen is not clear, the following possibilities are considered.

When using a compound having a nitrogen atom such as alkanolamines and amines, direct introduction of coordinated nitrogen.

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

The chemical bond in the gel fiber is cleaved at a relatively high temperature,
The reaction with the active nitrogen is likely to proceed.

Other than the above possibilities, the function thereof is currently unknown, but it is presumed that the above-mentioned effects act synergistically to promote nitriding.

〔Example〕

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

Example 1 Aluminum trisec-butoxide 1 mol sec-Butanol 4 mol was dissolved. 1 mol of monoethanolamine
sec-dissolved in 4 mol of butanol, aluminum tri sec
-Reacted with butoxide solution. The reaction proceeded exothermically and was reacted for 30 minutes without heating.

Dissolve 1 mol of tetraethoxysilane in 4 mol of ethanol, and add 1 mol of water adjusted to 1N hydrochloric acid to 2 mol of ethanol.
A solution dissolved in molar ethanol was added to partially hydrolyze the tetraethoxysilane. What was partially hydrolyzed at room temperature for 30 minutes was added to the above solution containing aluminum trisec-butoxide and mixed and reacted. A mixed solution of 1 mol of water and 1 mol of ethanol was added to this mixed solution for hydrolysis and polycondensation.

The solvent was distilled off under reduced pressure to obtain a viscous solution having a viscosity of 480 poise. The viscous solution was extruded and spun to obtain a continuous gel fiber.

Ammonia flow rate 0.5 l / min, temperature 12
Nitrided and baked at 00 ° C. for 3 hours.

The nitrogen content in the obtained fiber was 5.9%, and the crystal phase determined by X-ray was mullite microcrystal.

Comparative Example 1 In the same manner as in Example 1, a viscous solution having a viscosity of 650 poise was obtained without adding monoethanolamine, and this was extruded and spun to obtain a continuous gel fiber.

Nitriding and firing were performed under the same conditions as this gel fiber and Example 1. The nitrogen content in the obtained fiber was 0.01% or less, almost no nitrogen was introduced, and the crystal phase was mullite.

Example 2 1 mol of aluminum trisec-butoxide was dissolved in 4 mol of sec-butanol. Dissolve 1 mol of monoethanolamine in 4 mol of sec-butanol, and add aluminum tris
Reacted with ec-butoxide solution. The reaction proceeded exothermically and was reacted for 30 minutes without heating.

Dissolve 1 mol of tetraethoxysilane in 4 mol of ethanol, and add 1 mol of water adjusted to 1N hydrochloric acid to 2 mol of ethanol.
A solution dissolved in molar ethanol was added to partially hydrolyze the tetraethoxysilane. What was partially hydrolyzed at room temperature for 30 minutes was added to the above solution containing aluminum trisec-butoxide and mixed and reacted.

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

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

The solvent was distilled off under reduced pressure to obtain a viscous solution having a viscosity of 330 poise. The viscous solution was extruded and spun to obtain a continuous gel fiber.

Ammonia flow rate 0.5 l / min, temperature 12
Nitrided and baked at 00 ° C. for 3 hours.

The nitrogen content in the obtained fiber was 7.6%, and the crystal phase determined by X-ray was mullite, MgAl ₂ O ₄ , and microcrystals of unknown phase.

Example 3 The gel fiber of Example 2 was applied with an ammonia flow rate of 0.5 l / min.
Nitriding and firing were performed at a temperature of 1200 ° C. for 6 hours.

The nitrogen content in the obtained fiber was 12.5%, and the crystal phase determined by X-ray was an unknown phase, mullite, and MgAl ₂ O ₄ microcrystals.

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

Nitriding and firing were performed under the same conditions as this gel fiber and Example 2. The nitrogen content in the obtained fiber is 1.2%,
Only a small amount of nitrogen was introduced, and the crystal phase was mullite, MgAl ₂ O.
₄ , unknown phase.

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 is 1.9.
%, The crystalline phase was mullite, an unknown phase.

(Effect of the Invention) According to the present invention, oxynitride ceramic fibers expected to have hardness, strength, elastic modulus, heat resistance, corrosion resistance, etc. can be manufactured by an easy method without using a special device. This is a manufacturing method that is possible and industrially useful.

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Claims (1)

[Claims] 1. A method for producing a nitrogen-containing ceramic fiber containing silicon alkoxide and aluminum alkoxide as main raw materials, a step of mixing an alkanolamine compound and / or a β-diketone compound with an aluminum alkoxide to cause a reaction to form a reaction mixture. ,
A step of forming a mixture of the reaction mixture and a silicon alkoxide, a step of hydrolyzing the mixture to obtain a sol, a step of spinning the sol in a viscosity region of 10 poises or more, nitrogen and / or the obtained gel fiber A method for producing a nitrogen-containing ceramic fiber, comprising a step of producing a nitrogen-containing ceramic fiber by firing in an ammonia stream.