JPH06219722A - Silicon oxynitride fiber and its production - Google Patents

Abstract

PURPOSE:To provide the subject fiber useful as a reinforcing material for high performance composite materials by reacting a dihalosilane or its adduct with a Lewis base with ammonia and water or oxygen, spinning the produced polysiloxazane and subsequently baking the produced fiber. CONSTITUTION:A dihalosilane (e.g. dichlorosilane) or the adduct of the dihalosilane with a Lewis base is reacted with ammonia and water or oxygen to produce a polysiloxazane. The polysiloxazane contains -(SiH2)n(NH)r- and -(SiH2)mO- (n, m and r are 1-3) as main repeating units, and has a polymerization degree of 5-300 based on the repeating units. The polymer is dissolved in a suitable solvent (e.g. pentane) in a concentration of 5-90wt.% to prepare a spinning raw solution having a viscosity of 1-5000 poises. The spinning raw solution is spun by a dry-spinning method, etc., and subsequently baked at >=800 deg.C in an inert gas. The produced fiber contains >=5mol.% of nitrogen and >=5mol.% of oxygen and has a chemical formula of Si1+xN(4-y)/3Oy/2Cz (0<x<3, 0<4, 0<z<1.1).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel silicon oxynitride fiber and a method for producing the same. Silicon oxynitride fiber is very useful as a reinforcing material for high performance composite materials required in advanced fields in a wide range of industries such as transportation, energy, metal, and aerospace.

[0002]

2. Description of the Related Art In recent years, the research and development of ceramics have made great progress, and many researchers have synthesized ceramic materials such as silicon carbide and silicon nitride. On the other hand, silicon oxynitride is also a heat-resistant material like silicon carbide and silicon nitride, and is known to have higher oxidation resistance than silicon carbide and silicon nitride.

There are several prior art techniques for the synthesis of silicon oxynitride ceramic materials. (1) A mixture of metallic silicon and silicon dioxide is alkaline earth,
Or in the presence of alkali metal fluoride under a nitrogen atmosphere 1
Method of nitriding at 150 to 1350 ° C. (Tada, JP-A-47)
-42400). As a method of using silicon and silicon dioxide as a starting material, a method of adding a certain kind of metal to a mixture of these and heating it under a nitrogen atmosphere to generate and grow in a fibrous or whisker-like shape is disclosed. (Japanese Patent Application Laid-Open No. 50-29498; Japanese Patent Application Laid-Open No. 51-1)
29898; Japanese Patent Laid-Open No. 53-79799).

(2) Polycarbosilane is made into fibers, which are oxidatively infusible and then NH at a temperature of 800 to 1400 ° C.
Method for producing continuous fibers of silicon oxynitride having a structure of SiN _1.5 O _0.47 by treatment with ₃ (Okamura et al., Chemistry
Letters, PP. 2059-2060, 1984).

[0005]

The above method (1) does not provide a method for making silicon oxynitride into continuous fibers. It is known that not only silicon oxynitride but also each ceramic material is dramatically improved in mechanical strength when it is formed into a fibrous shape, and the degree of freedom in molding is increased. The properties that can be made into fibers are extremely important.

The method (2) via polycarbosilane provides a method for producing continuous silicon oxynitride fibers.
However, the process is complicated and there is room for improvement in this respect.

[0007]

Means for Solving the Problems In the process of studying a novel industrial process suitable for industrialization of continuous inorganic fibers of silicon oxynitride, the present inventors continuously added a novel polysiloxazane by an appropriate method. The present invention has been completed by discovering that if fiberized, an inorganic continuous fiber of silicon oxynitride having excellent properties can be produced by a relatively simple process.

That is, according to the present invention, first, a dihalosilane such as dichlorosilane (SiH ₂ Cl ₂ ) or an adduct of a dihalosilane and a Lewis base is added to NH ₃ and H _2.
Reaction with O or O ₂ produces a novel polysiloxazane. The polysiloxazane is - (SiH _{2) n} (N
H) _r − and − (SiH ₂ ) _m O − (wherein n, m,
Each r is 1, 2 or 3, preferably 1 or 2. ) As the main repeating unit, and based on these,
It has a degree of polymerization of 300. Furthermore, in the present invention, this polysiloxazane is spun and fired to produce a silicon oxynitride fiber. The resulting inorganic continuous fiber of silicon oxynitride consists essentially of silicon, nitrogen, oxygen and optionally carbon,
Containing 5 mol% or more of nitrogen and 5 mol% or more of oxygen, and having the formula Si _{1+ x} N _{(4-y) / 3} O _{y / 2} C _z (wherein 0 <x <3,
It is a novel silicon oxynitride fiber having a composition represented by 0 <y <4 and 0 ≦ z <1.1). The present invention relates to this novel inorganic continuous fiber.

The inorganic continuous fiber having the novel composition can be produced by treating the polysilazane fiber with a gas containing water or oxygen and firing the novel polysiloxazane fiber. It also relates to a method for producing an inorganic continuous fiber based on such polysiloxazane fiber (shaped body). The present invention will be described in more detail. The dihalosilane used in the present invention is particularly represented by the general formula SiH ₂ X.
₂ , it is preferable to use dihalomonosilane or dihalodisilane represented by Si ₂ H ₄ X ₂ (X = F, Cl, Br, I). In the present invention, dichlorosilane is particularly preferable among these dihalosilanes. Such a dihalosilane is preferably reacted with a base to form an adduct. The base that can be used in the present invention is a base that does not react other than the reaction that forms an adduct with dihalosilane, and examples of such a base include:
Lewis bases, that is, tertiary amines (trialkylamine, pyridine, picoline and their derivatives), secondary amines having a sterically hindering group, phosphine, stipine, arsine and their derivatives (eg trimethylphosphine). , Dimethylethylphosphine, methyldiethylphosphine, triethylphosphine, trimethylarsine, trimethylstibin, trimethylamine, triethylamine, thiophene, furan, dioxane, selenophene, 1-methylphosphor, etc., but especially low Bases that are less basic than ammonia at boiling points (eg pyridine, picoline, trimethylphosphine, dimethylethylphosphine, methyldiethylphosphine, triethylphosphine, thiophene, furan Dioxane, selenophene, 1-methyl phosphate fall) are preferred, in particular pyridine and picoline preferred handling and economic. The amount of base used does not have to be particularly precise, and it is sufficient if it is present in a stoichiometric amount with respect to the dihalosilane, including the base in the adduct, ie in excess of 2: 1 base: dihalosilane.

For example, adding dichlorosilane to pyridine
And SiHCl₂・ 2C_FiveH_FiveWhite solid represented by N
The adduct of is generated. NH for this product₃And
And H ₂Solvent-soluble perhydropolyshiro when reacted with O
Produced by Kizazan. In this way, dihalosilane
Rui is an NH with an adduct with the Lewis base₃And H₂O
Or O₂To produce solvent-soluble polysiloxazane.
To achieve. NH ₃And H₂O or O₂Are added at the same time
It is preferable to add either one first, and then
It is also possible to react each one in turn.

The polysiloxazane thus produced is-(SiH ₂ ) _n (NH) _r -and-(SiH)
It is a copolymer having _m O- as a main repeating unit. Briefly, it is a linear or cyclic polymer composed of these repeating units, but it is generally a composite of such linear or cyclic polymers. The chemical structure of the polysiloxazane is dependent on the starting material, for example, -SiH ₂ SiH ₂ NH if it contains a dichlorosilane as the starting material
- and -SiH ₂ would SiH ₂ O-are included.
Further, a unit of> SiHNH- or> SiHO- is present at the binding site of the cyclic substance and the linear substance, and -NH ₂ ,
There are OH or -SiH ₃ becomes units. Furthermore, in the present invention, 10% or less of a hydrocarbon group is contained in a part of the starting material,
A dihalosilane having an organic group such as an ether group, an ester group or a carbonyl group can be used, and in such a case, the polysiloxazane to be produced will partially contain such an organic group.

Included in this polysiloxazane- (Si
_{H 2) n (NH) r} - and - (a optional SiH _{2) m} O-ratio, the sequences need not be regular, in fact irregular in. _{- (SiH 2) n (NH} )
_r - and _{- (SiH 2) NH 3 m} O- proportion of reacting
And H ₂ O or O ₂ can be changed and adjusted.

The degree of polymerization of this polysiloxazane is-(Si
_{H 2) n (NH) r} - or - (based on SiH _{2) m} O-units, such as is generally 5 to 300 or more. The degree of polymerization is the concentration of dihalosilane, the reaction temperature,
It can be adjusted by changing the solvent. If the degree of polymerization is higher, a crosslinking reaction occurs at room temperature, so that gelation of the polymer is easily promoted and handling becomes difficult.

Thus, the polysiloxazane according to the present invention generally has the following composition when a dihalosilane containing no organic group is used as the starting dihalosilane. Organic groups, when present, replace some of the hydrogen. H 50-60 mol% Si 20-25 mol% O 0-25 mol% (not including 0 mol%) N 0-20 mol% (not including 0 mol%) Polysilazane and poly starting from dichlorosilane The production of siloxanes dates back to the precursor work of Stock et al.
r.54 (1921) 740, Ber.52 (1919) 695). The researchers by reacting a dichlorosilane and ammonia dissolved in benzene _{- (SiH 2) n (NH} ) r - generates Origoshirazan to a repeating unit, which was hydrolyzed - (Si
H ₂₎ generated the oligosiloxane represented by _m O-.
On the other hand, Cyphers et al. Reacted a dichloromethane solution of dichlorosilane with ammonia gas or water,
Synthesized polysilazane or polysiloxane (Communic
ationof Am.Ceram.Sou.Jan.1983, C-13; Inorg.Chem., 198
3,22,2163-2167). The present inventors previously produced a high molecular weight polysilazane by decomposing a dichlorosilane base complex with ammonia (Japanese Patent Laid-Open No. 60-145903). The polysiloxazane in the present invention is remarkably different from the above polysiloxane in that it is a copolymer of silazane and siloxane.

The copolymer is-(SiH ₂ ) _n (NH)
It seems to be novel irrespective of the abundance ratios of _r − and − (SiH ₂ ) _m O—, but at least 1 mol% or more of silicon bonded to nitrogen and silicon bonded to oxygen based on the number of silicon atoms. The copolymer having 1 mol% or more is novel. In order to produce a silicon oxynitride fiber from polysiloxazane according to the present invention, first, polysiloxaxane is dissolved in a suitable solvent to prepare a spinning dope. Hydrocarbons, halogenated hydrocarbons, ethers, nitrogen compounds, sulfur compounds and the like can be used as the solvent. Preferred solvents are pentane, hexane, isohexane, methylpentane, heptane, isoheptane, octane, isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, hydrocarbons such as ethylbenzene, methylene chloride, chloroform,
Carbon tetrachloride, bromoform, ethylene chloride, ethylidene chloride, trichloroethane, tetrachloroethane, halogenated hydrocarbons such as chlorobenzene, ethyl ether, propyl ether, ethyl butyl ether, butyl ether, 1,2-dioxyethane, dioxane, dimethyloxane, tetrahydrofuran, Tetrahydropyran, ethers such as anisole, diethylamine, triethylamine, dipropylamine, diisopropylamine, butylamine, aniline, piperidine, pyridine, picoline, lutidine, ethylenediamine, nitrogen compounds such as propylenediamine, carbon disulfide, diethyl sulfide, thiophene, tetrahydro It is a sulfur compound such as thiophene.

The polysiloxazane concentration in this spinning dope is adjusted so that the viscosity of the dope is in the range of 1 to 5000 poise. In order to improve the spinnability of this polysiloxazane, a small amount of a spinning aid may be added to the spinning dope, if necessary. Examples of such auxiliaries include polyethers, polyamides, polyesters, vinyl polymers, polythioethers, polypeptides, and the like. Among these, polyethylene oxide, polyisobutylene, polymethylmethacrylate. , Polyisoprene and polystyrene are particularly desirable. A common method such as vacuum distillation is used for the concentration operation of the solution for adjusting the spinning solution having an appropriate viscosity. The spinning solution obtained by such a concentration operation contains 5 to 90% by weight of polysiloxazane.

Dry spinning is convenient for spinning, but centrifugal spinning and blow-off spinning can also be used. Although spinning is performed at room temperature under an inert gas atmosphere,
If necessary, the spinning solution can be heated to carry out. However, it should be noted that heating above 100 ° C. will cause thermal decomposition of polysiloxazane. After spinning, the fibers are dried sufficiently under reduced pressure with heating.

Fibers of polysiloxazane, in particular continuous fibers, are thus spun. The polysiloxazane fiber is white. Since the fibers have high strength even before firing, it is also possible to produce silicon oxynitride products by first processing the fibers into the form of yarn, woven fabric, etc. and then firing. The dried polysiloxazane fiber is preferably heat-treated at around 100 ° C. in an inert gas atmosphere.
The purpose of this heat treatment is to further ensure solvent removal and to promote cross-linking reactions between the polysiloxazane molecular chains to minimize the formation of cracks, voids, and porosity during the firing process. .

Since the polysiloxazane fiber produced by the present invention is infusible to heat, it can be fired as it is under atmospheric gas. Nitrogen is convenient as the atmosphere gas, but it is also possible to use ammonia or a mixed gas of nitrogen, ammonia, argon, hydrogen or the like. When the white fibers are fired at a temperature of 800 ° C. or higher in such an inert gas atmosphere, white or black inorganic fibers are obtained.

This inorganic fiber consists essentially of silicon, nitrogen and oxygen, contains 5 mol% of nitrogen and 5 mol% or more of oxygen, and has a novel composition represented by the above formula (1). Contains. The properties of this novel silicon oxynitride fiber are not limited, but typically, fiber diameter: 5 to 50 μm tensile strength: 30 to 300 kg / mm ² elastic modulus: 7 to 30 t / mm ² specific resistance value : 2 to 7 × 10 ¹⁰ Ω · cm, which is not so different from the high-purity silicon nitride fiber (Japanese Patent Application No. 60-257,824) filed by the present inventors before, but with respect to oxidation resistance Has seen a considerable improvement. For example, when the fiber obtained in Example 1 was heated in air at 700 ° C. for 5 hours, the weight increase was 2.6%. For comparison, when the silicon nitride fiber was treated under the same conditions,
The weight increase was 4.8%.

The silicon oxynitride fiber having such a novel composition can be produced by a method other than the above. That is, SiH ₂ X ₂ and Si ₂ H ₄ X ₂ (in these formulas, X
Is F, Cl, Br or I) or the like, or a polysilazane fiber obtained by spinning a polysilazane obtained by decomposing ammonia with a Lewis base directly or by forming an adduct with a Lewis base to form a polysilazane fiber. To produce a polysiloxazane fiber by subjecting it to an appropriate degree and subjecting it to a heat treatment, the novel silicon oxynitride fiber, which is the product of the present invention, can be produced. That is,
The polysilazane fiber (shaped object) reacts with gaseous water or oxygen at room temperature to replace the -NH- group and the -O- group of polysilazane. Therefore, the polysilazane fiber can be converted into the polysiloxazane fiber by exposing the polysilazane fiber for a certain period of time in an atmosphere in which the temperature is kept constant. The polysiloxazanes shaped bodies also novel, main repeating unit is _{- (SiH 2) n (NH} ) r - and -
It is composed of (SiH ₂ ) _m O-, and its degree of polymerization is at least about 4 to 1700 and can be produced (see Japanese Patent Application No. 60-257824). Incidentally, the polysiloxazanes shaped bodies are within the shaped bodies surface by treatment conditions _{- (SiH 2) n (NH} ) r - and - (S
There is a distribution in the concentration of iH ₂ ) _m O-, and depending on the treatment conditions of water or oxygen, polysilazane may be present in the central part of the shaped body and polysiloxane may be present in the surface part. Further, as can be seen from this, according to the present invention,
The dihalosilane or dihalosilane and Lewis base adduct are first reacted with ammonia to form polysilazane, and the resulting polysilazane is optionally shaped or unshaped, and then reacted with water or oxygen to form a polysilazane. It is possible to produce siloxazane.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1 A four-necked flask having an inner volume of 300 ml was equipped with a gas blowing tube, a mechanical stirrer, and a dewar condenser. A four-necked flask was charged with 150 ml of dry pyridine and cooled with ice. Next, 15.8 g of dichlorosilane (0.1
(56 mol) was added over about 1 hour to produce a white solid adduct (SiH ₂ Cl ₂ .2C ₅ H ₅ N). The reaction mixture was ice-cooled, and with stirring, 15.7 g of ammonia
(0.92 mol) and 0.33 g (0.018 mol) of water were mixed with nitrogen gas and blown thereinto for about 1.5 hours. After completion of the reaction, the reaction mixture was centrifuged under a nitrogen atmosphere, the residue was washed with dry methylene chloride, and the washing solution and the centrifugal separation solution were combined and filtered under a nitrogen atmosphere. The filtrate contains 2.01 (g / ml) of polysiloxazane as shown below.
% Was dissolved.

After 30 mg of polyethylene oxide (molecular weight 5,000,000) was added to 150 ml of the filtrate and dissolved, the solvent was distilled off under reduced pressure and concentrated to give a spinning solution containing about 30 (g / ml)% polysiloxazane. Undiluted solution (viscosity 250 poise)
Was prepared. The spinning solution was filtered, defoamed, and then dry-spun in a nitrogen atmosphere to obtain white polysiloxazane fiber. This was dried under reduced pressure at 50 ° C. for 4 hours and then, under a nitrogen atmosphere, 10
After heat treatment at 0 ℃ for 3 hours, 1000 ℃ under nitrogen atmosphere
After heating for 5 hours, a black fiber was obtained.

The elemental composition (mol%) of the obtained polysiloxazane and the black fiber by chemical analysis was as shown in Table 1.

Table 1 Elemental composition (mol%) Si N O H polysiloxazanes 20.8 18.2 2.3 58.9 Black color textiles 49.3 44.0 6.0 0.0 polysiloxazanes infrared absorption spectrum, ¹ H-NM
1 to 3 show R and CP / MAS ²⁹ Si-NMR, and FIG. 4 shows a powder X-ray diffraction spectrum of black fiber. However, for the ¹ H-NMR spectrum, only the product soluble in the measurement solvent (CDCl ₃ ) was measured after isolation of polysiloxazane.

Further, the number average molecular weight measured by the vapor pressure drop method was 1100 ^* . Further, when gel permeation chromatography (GPC) was measured, as shown in FIG. 5, the polystyrene-reduced molecular weight was 250 to 4000, mainly 300 to 3400, and the number average molecular weight (polystyrene equivalent) was 78.
It was 5. The degree of polymerization of polysiloxazane in which the polystyrene reduced molecular weight is corrected to the molecular weight by the vapor pressure drop method is 7.
It is distributed from 8 to 125, mainly from 9.4 to 106.5.

Black fibers having a fiber diameter of 5 to 50 μm have a tensile strength of 30 to 280 kg / mm ² and an elastic modulus of 8 to 20 t / mm ^2.
Met.

Example 2 The elemental composition (mol%) of the black fiber obtained by treating the polysiloxazane fiber obtained in Example 1 under the same conditions except the drying temperature and treating the firing temperature at 1300 ° C. Si: 44.4,
It was N: 48.6 and O: 7.4. Black fiber powder X
When subjected to line diffraction, Si, α-Si ₃ H ₄ , β-Si ₃
An H ₄ peak was observed.

Example 3 Under the same conditions as in Example 1, water 1.00 g (0.056 mol)
After preparing an adduct using 150 ml of pyridine to which was added, polysiloxazane and black fiber were prepared in the same manner as in Examples 1 and 2. The elemental compositions of the obtained polysiloxazane and the black fiber are as shown in Table 2.

Table 2 Elemental composition (mol%) Si N O H polysiloxazanes 21.5 14.3 7.7 57.2 1000 ℃ fired black fibers 48.4 30.4 21.2 0.0 1300 ℃ fired black fibers 46.7 41.6 11.7 0.0

Example 4 An adduct was prepared under the same conditions as in Example 1, and then 16.0 g (0.94 mol) of dry ammonia was mixed with nitrogen gas and blown therein for about 1.5 hours. After completion of the reaction, the same operation as in Example 1 was carried out to obtain a filtrate containing 1.95 (g / mol)% polysilazane. This was spun into a polysilazane fiber by the same operation as in Example 1, held in an atmosphere having a humidity of 47% for 5 hours, and then dried under reduced pressure, heat-treated and fired by the same operation as in Example 1 to obtain a black fiber. .

The elemental composition (mol%) of the obtained black fiber is S
It was i: 54.0, N: 26.0, O: 20.0.

Example 5 The chemical composition (mol%) of the black fiber obtained by keeping the polysiloxazane fiber obtained in Example 1 for 15 hours in an atmosphere of 47% humidity and then treating it in the same manner as in Example ) Is Si: 4
It was 8.5, N: 7.5, and O: 44.0.

[0035]

According to the present invention, a novel silicon oxynitride fiber and a method for producing the same are provided. The silicon oxynitride fiber is particularly easy to produce its continuous fiber, and the obtained silicon oxynitride fiber has a high yield. Very useful as a reinforcement for performance composites.

[Brief description of drawings]

FIG. 1 is an infrared absorption spectrum diagram of polysiloxazane obtained in the present invention by a KBr method.

FIG. 2 is a ¹ H-NMR spectrum diagram of polysiloxazane.

FIG. 3 CP / MAS ²⁹ SiNM of polysiloxazane
It is an R spectrum figure.

FIG. 4 is a powder X-ray spectrum diagram of a black fiber (Si—N—O) inorganic fiber.

FIG. 5 is a GPC chromatogram of polysiloxazane.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Isoda No.5, 1-1-11 Tohoku, Niiza City, Saitama Prefecture

Claims (4)

[Claims] 1. An inorganic fiber essentially consisting of silicon, nitrogen and oxygen, containing 5 mol% or more of nitrogen and 5 mol% or more of oxygen, and having a chemical formula of Si _{1 + x} N _{(4-y) / 3} O
_A silicon oxynitride fiber represented by _{y / 2} (0 <x <3, 0 <y <4). 2. Substantially silicon, nitrogen, oxygen and carbon
An inorganic fiber consisting of 5 mol% or more of nitrogen and oxygen
Contains 5 mol% or more and has the chemical formula Si_{1 + x}N _{(4-y) / 3}O
_{y / 2}C_z(0 <x <3, 0 <y <4, 0 <z <1.1)
A silicon oxynitride fiber represented by. 3. The main repeating unit is-(SiH ₂ ) _n.
(NH) _r - and - (SiH _{2) m} O- (wherein, n,
m and r are 1, 2 and 3, respectively. And a polymerization degree of 5 to 300 based on repeating units is spun, and the obtained fiber is fired to produce a silicon oxynitride fiber. 4. A method for producing a silicon oxynitride fiber by spinning polysilazane obtained by reacting dihalosilane or an adduct of dihalosilane and a Lewis base with ammonia, treating the obtained fiber with water or oxygen, and then firing.