JPH0455334A - 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 sol soln. or just after spinning into contact with an atmosphere containing an org. solvent. 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 fibrous sol. This fibrous sol is brought into contact with the atmosphere prepared by vaporizing an org. solvent or a mixture solvent selected from methanol, ethanol, propanol, butanol, etc., to 0.1 - 80 vol.% concn., or further with an org. solvent atmosphere mixed with water vapor or basic atmosphere, for several seconds or longer 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 manufacture 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 using this sol-gel method, the cross-sectional shape of the resulting fibers generally has a non-circular shape such as an ellipse or a cocoon shape, and has an almost perfect circular cross-sectional shape like that seen in E-glass fibers. It is difficult to obtain fibers with a high temperature. For example, KAMIYA
state that a circular cross section will not appear unless the raw materials are mixed in a limited molar ratio (l(, KAMIYA a
nd T, YOKO: Journal of Mater
ial 5science, Vol, 21. (1986
), 842-848). Therefore, it has the disadvantage that the formulation must be strictly carried out and the operation is difficult.

In addition, Ohta et al. reported that the cross-sectional shape of fibers produced by the blue gel method was 1.5 to 7.5 in aspect ratio (major axis/minor axis).
(For example, Japanese Patent Application Laid-Open No. 61-24488) states that the shape is oval (including elliptical). Similarly, Mizuguchi et al. performed spinning from a sol solution to obtain a fibrous gel with a nearly flat cross-sectional shape (for example, in Japanese Patent Application Laid-Open No. 62-2306
43).

[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. .

The present invention relates to inorganic fibers produced by a sol-gel method, and an object of the present invention is to easily obtain fibers with a cross-sectional shape close to circular using various sols without limiting the blending conditions.

[Means to solve the problem]

The present inventors have developed a method for producing inorganic fibers by firing gel fibers spun from a viscous sol solution obtained by hydrolysis/polymerization of organometallic compounds. found that it is effective to bring the fibrous sol during spinning from the viscous sol solution or the fibrous sol immediately after spinning into contact with an atmosphere containing an organic solvent.

In the present invention, a gas containing methanol, ethanol, propanol, butanol, etc. in a vaporized state is suitable as the organic solvent atmosphere used. At this time, the greatest effect can be obtained if the organic solvent used when preparing the sol and the organic solvent generated by the hydrolysis reaction of the organometallic compound are the same as the organic solvent in the organic solvent atmosphere, but they are not necessarily the same. There's no need. One type of organic solvent may be used,
Two or more types may be mixed. In addition, along with this organic solvent,
Water vapor may be mixed in to prevent ignition. There is no problem even if other gaseous substances are mixed into the organic solvent atmosphere as long as they do not react with the organic solvent.

The appropriate concentration of the organic solvent in the spinning atmosphere in a vaporized state is 0.1 to 1 iovol%. 0
．． If it is less than 1 vol%, the effect is small and a flat cross-sectional shape is exhibited. When the content is 80 vol% or more, depending on the type of sol solution, solidification of the fibrous sol may be delayed and adhesion may occur when the fibrous sol is wound up. Preferably it is 1 to 50 vol%.

The time for which the sol is brought into contact with an atmosphere containing an organic solvent is determined by the fiber diameter, type of sol solution, type of solvent, solvent concentration, temperature, etc., but the fibrous sol becomes a fibrous gel and deforms when rolled up. It is sufficient that the contact is maintained until the state is such that no contact occurs. Normally, a few seconds or more is sufficient. At this time, the contact time may be short if the atmosphere promotes gelation of the sol, such as a basic atmosphere or an organic solvent atmosphere mixed with water vapor.

The fibrous sol flowing out from the nozzle solidifies in an atmosphere containing an organic solvent, thereby becoming a fibrous gel having a substantially circular cross-sectional shape.

The method for producing the sol solution used in the spinning of the present invention is not particularly limited, and it can be produced 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 a solvent are added to this 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 for example, a spinning method applicable to conventional 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 gel thus obtained was heated to 400°C to 1200°C.
When sintered, an inorganic fiber with a substantially 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, and the surface layer solidifies first. Further, since the polymerization reaction is promoted by evaporation of the solvent at this time, the solidification of the surface layer further progresses.

In this way, the surface layer of the fibrous sol solidifies before the inside, resulting in a skin-like state on the surface. Then, due to the subsequent internal hydrolysis/polymerization reaction and evaporation of the solvent, it shrinks and becomes a fibrous gel with a flat cross-sectional shape.

Here, when the fibrous sol is exposed to an organic solvent atmosphere, evaporation of the solvent from the surface is suppressed. Therefore, the phenomenon in which only the surface of the fibrous gel becomes hard is suppressed. Therefore, fibers having a substantially circular cross-sectional shape can be obtained without the cross-sectional shape being flat. This effect is achieved regardless of the compositional conditions of the sol, so it can be applied to any sol.

〔Example〕

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

Tetraethoxyorthosilane (Si
(C2H50H)4), dimethyljethoxysilane (
(CH3)2Si(C2H501)2), titanium isopropoxide (Ti(0-iC3H7)4), water, hydrochloric acid and ethanol were mixed. Proceed the reaction at 30°C,
Cooled to 0℃ with 00cPoise and further 600℃
When the temperature reached cPoise, it was cooled to 30°C.

When the viscosity of the solution reaches 1000 cPoise,
Spinning was carried out by using a nozzle with an inner diameter of 0.3 mm and pressurizing with nitrogen gas. A pipe (30c+n square, length 5m) was installed under the nozzle, and an organic solvent was vaporized and sent into the pipe to create an organic solvent atmosphere with a concentration of 2 to 50 vol%.

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 closer it is to a circle. It is a perfect circle with an oblateness of 0%.

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 produced in the same manner as in the example, an air atmosphere was created in the pipe, and spinning was performed in the same manner as in the example. The oblateness of the cross section of the obtained fibrous gel was also investigated. Table Y shows the blending ratio, humidity, and aspect ratio.

The aspect ratio exceeds 40%, and the cross section is quite flat.

〔Effect of the invention〕

By contacting a fibrous sol during spinning or a fibrous sol after spinning produced by the sol-gel method with an organic solvent atmosphere, gel fibers having an almost circular cross-sectional shape can be easily produced from sol with various composition ratios. I was able to get it.

By sintering this gel fiber with a circular cross-section, an inorganic fiber with a circular cross-section was obtained.

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Claims (3)

[Claims] (1) A method for producing inorganic fibers by firing gel fibers spun from a viscous sol solution obtained by hydrolysis/polymerization of organometallic compounds, during or immediately after spinning from the viscous sol solution. A method for producing inorganic fibers, which comprises bringing a fibrous sol into contact with an atmosphere containing an organic solvent. (2) The method for producing inorganic fibers according to claim 1, wherein the organic solvent is one of methanol, ethanol, propanol, butanol, or a mixture of two or more selected from these. . (3) The method for producing inorganic fibers according to claim 1, wherein the concentration of the organic solvent is 0.1 to 80 vol%.