JP2575280B2 - Manufacturing method of silicon oxynitride fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel silicon oxynitride fiber.
Related to the manufacturing method . Silicon oxynitride fibers are very useful as reinforcement for high performance composites required in advanced fields in a wide range of industries such as transportation, energy, metals, aerospace, and the like.

[0002]

2. Description of the Related Art In recent years, research and development of ceramics have progressed dramatically, 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.

[0003] There are several prior arts relating to the synthesis of silicon oxynitride ceramic materials. (1) A mixture of metallic silicon and silicon dioxide is an alkaline earth,
Alternatively, in the presence of alkali metal fluoride in a nitrogen atmosphere
A method of nitriding at 150 to 1350 ° C. (Tada, JP 47
-42400). As a method using silicon and silicon dioxide as starting materials, there is also disclosed a method in which a certain metal is added to a mixture of these and heated under a nitrogen atmosphere to produce and grow into a fibrous or whisker state. (JP-A-50-29498; JP-A-51-1)
29898, JP-A-53-79799).

[0004] (2) Polycarbosilane is made into a fiber, oxidized and made infusible, and then NH3 is added at a temperature of 800 to 1400 ° C.
₃ to produce continuous fibers of silicon oxynitride having a structure of SiN _1.5 O _0.47 (Okamura et al., Chemistry
Letters, PP. 2059-2060, 1984).

[0005]

The method (1) does not provide a method for continuously making silicon oxynitride into long fibers. It is known that not only silicon oxynitride but also each ceramic material, when formed into a fibrous shape, has a remarkable improvement in mechanical strength and also has a greater degree of freedom in molding. The properties that can be made into fibers are extremely important.

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

[0007]

The inventors of the present invention have been studying a novel production method for continuous inorganic fibers of silicon oxynitride, which is more suitable for industrialization. It has been found that if the fibers are formed, inorganic continuous fibers of silicon oxynitride having excellent properties can be produced in a relatively simple process, and the present invention has been completed.

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 converted into NH ₃ and H _2.
O and O ₂ to react with the new polysiloxazan (positive
Surely it is perhydropolysiloxazan, but hereafter simply
It is called polysiloxazan. ) To manufacture. The polysiloxazane is _{- (SiH 2) n (NH} ) r - and - (S
iH ₂ ) _m O- (wherein, n, m, and r are each 1, 2 or 3, and preferably 1 or 2) as a main repeating unit, and have a polymerization degree of 5 to 300 based on these. doing. Further, in the present invention, the polysiloxazan is spun and fired to produce silicon oxynitride fibers. The resulting inorganic continuous fibers of silicon oxynitride are substantially silicon, nitrogen,
Composed of oxygen and optionally carbon, with at least 5 mol% of nitrogen,
Containing at least 5 mol% of oxygen and having the formula Si _{1 + x} N _{(4-y) / 3}
O _{y / 2} C _z (where 0 <x <3, 0 <y <4, 0 ≦ z <
A silicon oxynitride fiber having a composition represented by 1.1).
You.

Such an inorganic continuous fiber is a polysilazane.
(Actually, it is perhydropolysilazane, but hereafter simply
It is called polysilazane. ) It can also be produced by calcining a novel polysiloxazan fiber produced by treating the fiber with a gas containing water or oxygen, and the present invention is based on such a polysiloxazan fiber (shaped body). Also concerned with the production of inorganic continuous fibers. The present invention will be described in more detail. The dihalosilane used in the present invention has a general formula of SiH ₂ X ₂ , Si ₂ H ₄ X ₂ (X = F, Cl, B
It is preferable to use dihalomonosilane or dihalodisilane represented by r, I). In the present invention, dichlorosilane is particularly preferable among these dihalosilanes. A base is preferably acted on such dihalosilane 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 for forming an adduct with dihalosilane. Examples of such a base include Lewis bases, that is, tertiary amines (trialkylamine, pyridine , Picoline and derivatives thereof), secondary amines having a sterically hindered group, phosphine, stippin, arsine and derivatives thereof (eg, trimethylphosphine, dimethylethylphosphine, methyldiethylphosphine, triethylphosphine, Trimethylarsine, trimethylstibine, trimethylamine, triethylamine, thiophene, furan, dioxane, selenophene, 1-methylphosphor and the like, among which bases having a low boiling point and less basicity than ammonia (for example, pyridine, Choline, trimethylphosphine, dimethyl ethyl phosphine, methyl diethyl phosphine, triethyl phosphine, thiophene, furan, dioxane, selenophene, 1-methyl phosphate fall) are preferred, in particular pyridine and picoline preferred handling and economic.
The amount of the base to be used does not need to be particularly strict, and it is sufficient that the stoichiometric amount including the base in the adduct is more than the stoichiometric amount with respect to the dihalosilane, that is, base: dihalosilane = 2: 1.

For example, adding dichlorosilane to pyridine
And SiHCl_Two・ 2C_FiveH_FiveWhite solid represented by N
Adduct is generated. NH 4_ThreeAnd
And H _TwoSolvent-soluble perhydropolysilo by reacting O
Kisazane is produced. In this way, the dihalosilane
Or NH to the adduct with the Lewis base_ThreeAnd H_TwoOma
Or O_TwoTo produce a solvent-soluble polysiloxazane.
To achieve. NH _ThreeAnd H_TwoO or O_TwoIs added at the same time
It is preferable to add either one first and then
It is also possible to make each react in order.

The polysiloxazan thus produced is-(SiH ₂ ) _n (NH) _r- and-(SiH)
_m O-which is a copolymer whose main recurring unit. Briefly, it is a linear or cyclic polymer composed of these repeating units, but in general, it is a composite of such a linear or cyclic polymer. 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.
In addition, a unit of> SiHNH— or> SiHO— is provided at the binding site between the cyclic substance and the linear substance, and —NH ₂ , −
There are OH or -SiH ₃ becomes units. Further, 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 resulting polysiloxazane will partially include such an organic group.

[0012] The-(Si) contained in this polysiloxazan
_{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
It can be adjusted by changing the ratio of H ₂ O or O ₂ .

The degree of polymerization of this polysiloxazan 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 depends on the concentration of dihalosilane, reaction temperature,
It can be adjusted by changing the solvent and the like. If the degree of polymerization is higher, a gelling of the polymer is easily promoted due to a cross-linking reaction at room temperature, which makes handling difficult.

Thus, the polysiloxazan according to the present invention generally has the following composition when a dihalosilane containing no organic group is used as a starting dihalosilane. Organic groups, when present, replace some of the hydrogens. H 50 to 60 mol% Si 20 to 25 mol% O 0 to 25 mol% (excluding 0 mol%) N 0 to 20 mol% (excluding 0 mol%) Polysilazane and poly starting from dichlorosilane The production of siloxane goes back to the precursors of Stock et al. (Be
r.54 (1921) 740, Ber.52 (1919) 695). The researchers reacted dichlorosilane dissolved in benzene with ammonia to produce oligosilazane having-(SiH ₂ ) _n (NH) _r -as a repeating unit, which was hydrolyzed to form-(Si
An oligosiloxane represented by H ₂ ) _m O- was produced.
Meanwhile, Cyphers and others reacted ammonia gas or water with dichloromethane solution of dichlorosilane, respectively,
Polysilazane or polysiloxane was synthesized (Communic
ationof Am. Ceram. Sou. Jan. 1983, C-13; Inorg. Chem., 198
3,22,2163-2167). The present inventors have previously produced a high molecular weight polysilazane by decomposing a dichlorosilane base complex with ammonia (Japanese Patent Application Laid-Open No. 60-145903). The polysiloxane of the present invention is significantly different from the above-mentioned polysiloxane in that it is a copolymer of silazane and siloxane.

This copolymer is-(SiH ₂ ) _n (NH)
_r - and - (SiH ₂₎ but are believed to be novel irrespective _m existing ratio of O-, at least, a silicon nitrogen based on the number of silicon atom is bonded to 1 mol% or more and silicon oxygen bound The copolymer having 1 mol% or more is novel. In order to produce silicon oxynitride fibers from polysiloxazan according to the present invention, first, polysiloxazan is dissolved in an appropriate solvent to prepare a spinning solution. As the solvent, hydrocarbons, halogenated hydrocarbons, ethers, nitrogen compounds, sulfur compounds and the like can be used. 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,
Halogenated hydrocarbons such as carbon tetrachloride, bromoform, ethylene chloride, ethylidene chloride, trichloroethane, tetrachloroethane, chlorobenzene, ethyl ether, propyl ether, ethyl butyl ether, butyl ether, 1,2-dioxyethane, dioxane, dimethyloxane, tetrahydrofuran, Ethers such as tetrahydropyran, anisole, diethylamine, triethylamine, dipropylamine, diisopropylamine, butylamine, aniline, piperidine, nitrogen compounds such as pyridine, picoline, lutidine, ethylenediamine, propylenediamine, carbon disulfide, diethylsulfide, thiophene, tetrahydro It is a sulfur compound such as thiophene.

The concentration of polysiloxazan in this spinning stock solution is adjusted so that the stock solution viscosity 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, etc., among which polyethylene oxide, polyisobutylene, polymethyl methacrylate , Polyisoprene and polystyrene are particularly desirable. For the concentration operation of the solution for adjusting the spinning solution having an appropriate viscosity, a normal method such as distillation under reduced pressure is used. The spinning solution obtained by such a concentration operation contains 5 to 90% by weight of polysiloxazan.

For spinning, dry spinning is convenient, but centrifugal spinning and blow spinning can also be used. Spinning is performed at room temperature under an inert gas atmosphere.
If necessary, the spinning solution can be heated. However, it should be noted that if the temperature exceeds 100 ° C., the thermal decomposition of polysiloxazan starts. After spinning, the fibers are sufficiently dried under heating and reduced pressure.

Thus, fibers of polysiloxazan, especially continuous fibers, are spun. This polysiloxazan fiber is white. Since the fibers have high strength even before firing, the fibers can be first processed into a yarn, woven fabric, or the like, and then fired to produce a silicon oxynitride product. It is desirable that the dried polysiloxan fiber be subjected to a heat treatment at about 100 ° C. in an inert gas atmosphere.
The purpose of this heat treatment is to minimize the generation of cracks, voids, and pores during the firing process by further ensuring solvent removal and promoting the cross-linking reaction between the molecular chains of polysiloxane. .

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

The inorganic fiber is substantially composed 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 the 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: 2 ７7 × 10 ¹⁰ Ω · cm, which is not much different from the high-purity silicon nitride fiber to which the present inventors previously applied for a patent (Japanese Patent Application No. 60-257,824), but has a considerable oxidation resistance. Improvement is seen. 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 above silicon nitride fiber was treated under the same conditions,
The weight gain was 4.8%.

The silicon oxynitride fiber having such a composition can be produced by a method other than the above. That is, Si
H ₂ X ₂ , Si ₂ H ₄ X ₂ (where X is F, C
l, Br or I), or a polysilazane obtained by forming an adduct with a Lewis base followed by ammonia decomposition to produce a polysilazane fiber, to which a gas of oxygen or water is added. By producing a polysiloxazan fiber by acting to a certain degree, and subjecting it to a heat treatment, the above-mentioned novel silicon oxynitride fiber of the present invention can be produced. That is, the polysilazane fiber (shaped body) reacts with gaseous water or oxygen at ordinary temperature, and the —NH— group and —O— group of polysilazane are substituted. Therefore, the polysilazane fibers can be converted into polysiloxazan fibers by exposing the polysilazane fibers to an atmosphere maintained at a constant temperature for a certain period of time. The polysiloxazanes shaped bodies also novel, main repeating unit is _{- (SiH 2) n (NH} ) r - and - (Si
H ₂ ) _m O—, the degree of polymerization of which is at least 4-1.
About 700 and more can be manufactured (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 - (Si
There is a distribution in the concentration of H ₂ ) _m O—, and depending on the treatment conditions of water or oxygen, polysilazane may be present in the center of the shaped body, and polysiloxane may be present on the surface. Also, as will be appreciated from this, according to the present invention,
Ammonia is first reacted with a dihalosilane or an adduct of a dihalosilane and a Lewis base to form polysilazane, and the resulting polysilazane is shaped or not shaped as necessary, and then reacted with water or oxygen to form a polysilazane. It is possible to produce siloxazan.

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

Example 1 A four-necked flask having an internal volume of 300 ml was equipped with a gas injection tube, a mechanical stirrer, and a Jewer condenser. 150 ml of dry pyridine was placed in a four-necked flask, and cooled with ice. Next, 15.8 g of dichlorosilane (0.1
(56 mol) was added over about 1 hour to form an adduct (SiH ₂ Cl ₂ .2C ₅ H ₅ N) as a white solid. The reaction mixture was cooled on ice 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 in over 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 liquid and the centrifuged liquid were combined and filtered under a nitrogen atmosphere. The filtrate contained 2.01 (g / ml) of polysiloxazan as shown below.
% Dissolved.

After 150 mg of the filtrate was dissolved by adding 30 mg of polyethylene oxide (molecular weight: 5,000,000), the solvent was distilled off under reduced pressure and concentrated, and a spinning solution containing about 30 (g / ml)% of polysiloxazan was obtained. Stock solution (viscosity 250 poise)
Was prepared. After the spinning solution was filtered and defoamed, dry spinning was performed under a nitrogen atmosphere to obtain white polysiloxazan fibers. This was dried under reduced pressure at 50 ° C. for 4 hours, and then dried under nitrogen atmosphere for 10 hours.
After heat treatment at 0 ° C for 3 hours, 1000 ° C in a nitrogen atmosphere
For 5 hours to obtain black fibers.

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

Table 1 Element 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
R and CP / MAS ²⁹ Si-NMR are shown in FIGS. 1 to 3, and the powder X-ray diffraction spectrum of the black fiber is shown in FIG. However, regarding the ¹ H-NMR spectrum, after isolating the polysiloxazan, only the products soluble in the measurement solvent (CDCl ₃ ) were measured.

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

The tensile strength of the black fiber having a fiber diameter of 5 to 50 μm is 30 to 280 kg / mm ² , and the elastic modulus is 8 to 20 t / mm ^2.
Met.

Example 2 The polysiloxazan fiber obtained in Example 1 was treated under the same conditions except for the drying temperature at a firing temperature of 1300 ° C., and the elemental composition (mol%) of the black fiber was as follows: Si: 44.4,
N: 48.6, O: 7.4. Black fiber powder X
Line diffraction revealed that 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, 1.00 g (0.056 mol) of water was used.
An adduct was prepared using 150 ml of pyridine to which polysiloxazan was added, and polysiloxazan and black fibers were prepared in the same manner as in Examples 1 and 2. The elemental compositions of the obtained polysiloxazan and black fibers were as shown in Table 2.

Table 2 Element 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 After an adduct was prepared under the same conditions as in Example 1, 16.0 g (0.94 mol) of dry ammonia was mixed with nitrogen gas and blown in over about 1.5 hours. After completion of the reaction, a filtrate containing 1.95 (g / mol)% of polysilazane was obtained by the same operation as in Example 1. This was spun into a polysilazane fiber by the same operation as in Example 1, then kept in an atmosphere at a humidity of 47% for 5 hours, and dried under reduced pressure, heat-treated and fired by the same operation as in Example 1 to obtain a black fiber. .

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

Example 5 The polysiloxazan fiber obtained in Example 1 was kept in an atmosphere of a humidity of 47% for 15 hours, and then treated in the same manner as in Example 1 to obtain a chemical composition (mol%) of black fiber. ) Is Si: 4
8.5, N: 7.5, and O: 44.0.

[0035]

According to the present invention, a novel silicon oxynitride fiber
A process is provided in which the silicon oxynitride fibers are particularly easy to produce in their continuous fibers, and the resulting silicon oxynitride fibers are very useful as reinforcement in high performance composites.

[Brief description of the drawings]

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

FIG. 2 is a ¹ H-NMR spectrum of polysiloxazan.

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

FIG. 4 is a powder X-ray spectrum diagram of a black fiber (Si—NO) inorganic fiber.

FIG. 5 is a GPC chromatogram of polysiloxazan.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-295273 (JP, A) JP-A-61-12915 (JP, A)

Claims (2)

(57) [Claims] 1. The main repeating unit is-(SiH ₂ ) _n
(NH) _r- and-(SiH) _m O- (where n,
m and r are 1, 2 or 3, respectively. ), And and Peruhi polymerization degree based on the repeating unit is 5 to 300
Mud polysiloxazanes spun, a method of manufacturing a silicon oxynitride fibers by firing the resulting fibers. Wherein pels obtained by reacting ammonia adduct of dihalosilane or dihalosilane with a Lewis base
After spinning hydropolysilazane and treating the resulting fiber with water or oxygen to form perhydropolysiloxazan ,
A method for producing silicon oxynitride fibers by firing.