JPH0455335A - Production of inorganic fiber - Google Patents

Abstract

PURPOSE:To make a round cross section of fiber by bringing a fibrous sol during spinning from a viscous sol soln. or just after spinning into contact with a gas having constant humidity. CONSTITUTION:Water, catalyst and solvent are added to an org. metal compd. such as metal alkoxide, metal halide, metal org. acid salt, etc., to obtain a sol soln. of proper viscosity by hydrolysis and polymn. Then the sol soln. is drawn from a spinning nozzle under normal or high pressure to obtain a fibrous sol. This fibrous sol is brought into contact with gas maintained at 60 - 100 % relative humidity for >=0.5 sec to make a gel. The obtd. fibrous gel is sintered at 400 - 1200 deg.C to obtain inorg. fiber having a round cross section.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing inorganic fibers by a sol-gel method.

[Conventional technology]

A method for producing inorganic materials such as glasses and ceramics from metal alkoxides is generally called a sol-gel method. When attempting to produce fibers by this sol-gel method, the following steps are usually taken.

Water, a catalyst and, if necessary, a solvent are added to the metal alkoxide and mixed. Hydrolysis and polymerization reactions proceed in the solution,
A polymer is formed and becomes a sol solution. As this reaction progresses, the viscosity of the sol solution gradually increases. When the sol solution reaches an appropriate viscosity, it is spun using a conventional method to obtain a fibrous gel. When fibers are spun by this sol-gel method, the cross-sectional shape of the obtained fibers generally exhibits a non-circular shape such as an elliptical shape or a double shape. It is difficult to obtain a fiber with a substantially perfect circular cross-sectional shape as seen in E-glass fibers. For example, KAMIYA
stated that a circular cross section does not appear unless the raw materials are mixed in a limited molar ratio (K, KAMfYA an
d T, YOKO: Journal of Materi
al 5science, Vol, 21. (1986),
842-848). In addition, Ohta et al. also found that the cross-sectional shape of fibers produced by the sol-gel method was
(for example, Japanese Patent Laid-Open No. 61-24488) states that the shape is oval (including elliptical) with a minor axis of 15 to 7.5. Similarly, Mizuguchi et al. conducted spinning from a sol solution to obtain a fibrous gel having a substantially flat cross-sectional shape (for example, JP-A-62-230643).

[Problem to be solved by the invention]

In the case of fibers with such a non-circular cross-sectional shape, problems such as variations in the apparent outer diameter of the strands and finished thickness of the fabric, poor breathability of the fabric, and poor texture of the fabric may occur. .

An object of the present invention is to obtain inorganic fibers having a cross-sectional shape close to a circle using a sol-gel method.

[Means to solve the problem]

The present inventors discovered that in order to obtain fibers with a cross-sectional shape close to circular,
In a method for producing inorganic fibers by firing gel fibers spun from a viscous sol solution obtained by hydrolysis/polymerization of an organometallic compound, fibrous fibers are produced during or after spinning from the viscous sol solution. Sol, 60-100%R
, H was found to be effective in contacting with a gas having increased humidity.

The method for preparing the sol solution used in the spinning of the present invention is not particularly limited, and may be performed using well-known techniques.

The raw material used in the present invention may be any organometallic compound that forms metalloxane bonds through hydrolysis/polymerization reactions. For example, organometallic compounds such as metal alkoxides, metal halides, and metal organic acid salts are used. Water, a catalyst and, if necessary, a solvent are added to the organometallic compound to cause a hydrolysis/polymerization reaction to obtain a sol solution with an appropriate viscosity.

The method for spinning from a sol solution is not particularly limited, and conventional spinning methods applicable to glass fibers, polymer fibers, etc. can be used. Basically, a method is used in which a sol solution is made to flow out from a spinning nozzle under normal pressure or increased pressure to form fibers.

The fibrous sol flowing out from this nozzle has a humidity of 60 to 100.
%R, 11 gases are brought into contact.

The fibrous sol flowing out from the nozzle becomes a fibrous gel having a substantially circular cross-sectional shape by being exposed to high humidity gas.

When the humidity is less than 60%R,H, the effect is not significant and 5
．． It has a relatively flat cross-sectional shape. Preferably 80~
100% R, H.

The time period for which the sol is brought into contact with the highly humid gas is determined by the fiber diameter, the type of sol solution, humidity, temperature, etc., but is usually about 0.5 seconds or more. If exposed to high humidity gas for a long time, excess water may be incorporated into the sol and form a brittle fibrous gel with large pores, so please do not leave it in contact with high humidity gas for more than 24 hours. Good.

As a method of bringing the fibrous sol into contact with a highly humid gas,
Although not particularly limited, a method in which a pipe-like body is installed under the nozzle so that highly humid gas can stay and the fibrous sol passes through the vibrator, and a method in which high-humidity gas is sprayed onto the fibrous sol There are methods such as spinning in a room maintained at high humidity.

By sintering the fibrous gel thus obtained at 400 to 1200°C, an inorganic fiber having a roughly circular cross-sectional shape can be obtained without changing the cross-sectional shape.

[Effect]

The following may be the reason why the cross-sectional shape of the fiber does not become circular during spinning using the sol-gel method. When the spun fibrous sol solidifies into a fibrous gel, there are two types of solidification: solidification due to evaporation of the solvent and solidification due to progress of hydrolysis/polymerization reactions. Evaporation of the solvent from the spun fibrous sol occurs from the surface, causing solidification of the surface layer. Further, since the polymerization reaction is promoted by evaporation of the solvent at this time, the solidification of the surface layer further progresses.

The surface layer of the fibrous sol solidifies before the inside, resulting in a skin-like state on the surface. The subsequent internal hydrolysis/polymerization reaction and evaporation of the solvent cause shrinkage,
It becomes a fibrous gel with a flat cross-sectional shape.

Here, when the fibrous sol is exposed to a highly humid gas, water diffuses into the fibrous sol, and the hydrolysis reaction occurs relatively uniformly within the sol, and evaporation of the solvent from the surface is suppressed. . Therefore, fibers having a roughly circular cross-sectional shape can be obtained without the cross-sectional shape becoming flat.

〔Example〕

Hereinafter, the present invention will be described in detail based on Examples, but the present invention is not necessarily limited to these Examples.

5i (C2H50H)4, (CH3) at a given molar ratio
25i(C2H50H)2, water, IN-HCl and ethanol were mixed. The reaction was carried out at 30°C and 200cPo
Cool to 0℃ with ISE, and then cool to 600cPoise.
When the temperature reached -30°C, it was cooled. 1000c
When the poise was reached, spinning was performed by pressurizing with nitrogen gas using a nozzle with an inner diameter of 0.3 fins. Install a pipe (30c+e angle, length 5+n) under the nozzle, send steam into the pipe,
The humidity was %R,H.

The cross-sectional shape of the collected fibrous gel was observed under a microscope, and the oblateness was determined.

here, Oblateness (%) = 100X (longer axis - shorter axis)/longer axis.

Therefore, the larger the oblateness is, the flatter it is, and the smaller the oblateness is, the more perfectly round it is.

Table 1 shows the blending ratio, humidity, and aspect ratio. It can be seen that the flatness ratios are all 30% or less, and the cross-sectional shape is approximately circular.

[Comparative example]

A sol was prepared in the same manner as in the example, the humidity in the pipe was set to 30 to 55% R1H, and spinning was performed in the same manner as in the example. The oblateness of the cross section of the obtained fibrous gel was examined. Table 1 shows the blending ratio, humidity, and aspect ratio. The flatness ratio is 40%
It has a fairly flat cross section.

〔Effect of the invention〕

By contacting a fibrous sol during spinning or a fibrous sol after spinning produced by the sol-gel method with a gas having a humidity of 60 to 100% RH, a gel fiber having a roughly circular cross-sectional shape can be obtained. was completed.

Claims (1)

[Claims] (1) In a method for producing inorganic fibers by firing gel fibers spun from a viscous sol solution obtained by hydrolysis/polymerization of an organometallic compound, during or after spinning from the viscous sol solution. of fibrous sol at a humidity of 60
~100%R. H. A method for producing inorganic fibers, characterized by contacting with a gas maintained at