JPH0613413B2 - Method for producing silica-zirconia viscous sol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a method for easily and inexpensively producing a silica-zirconia-based viscous sol, which is an intermediate raw material for various materials including silica-zirconia-based glass fibers. Pertain.

[Conventional technology]

Silica-zirconia-based glass is known as a difficult-to-melt glass. Therefore, when the silica-zirconia glass fiber is produced by the melting method, the amount of zirconia added is naturally limited, and it is indispensable to add a melting point depressant such as an alkali metal oxide. For example, GemFIL, a commercially available melt-processed silica-zirconia fiber jointly developed by the British Institute of Architecture and the Pilkington Brothers (PB).
Contains 17 wt% zirconia, but at the same time contains about 15 wt% alkali component. This silica-zirconia-based glass is a glass called E glass used for ordinary glass fibers (eg, SiO ₂ 52.4 wt%, Al ₂ O ₃ 14.4 wt%).
%, Aluminoborosilicate glass containing 10.4 wt% of B ₂ O ₃ ) and about 10 times more alkaline corrosion resistance.

Such a melting method used for the production of glass and ceramics has drawbacks such as high temperature and inability to obtain a homogeneous composition. Recently, in order to solve this drawback, a sol-gel method has been developed. There is. Since this sol-gel method, especially the method by hydrolysis of alkoxide, is low-temperature synthesis from a liquid phase, it has the advantages of freedom in composition selection, high purification, and simple process.

Kamiya et al. Applied this sol-gel method to the production of silica-zirconia-based glass, exposing a mixed solution of silicon ethoxide and zirconium-n-propoxide to the air and gradually hydrolyzing it with water in the air. To obtain a spinnable solution, from which fibers are spun and fired at 500 to 700 ° C. to obtain silica-zirconia glass fibers.

[Problems to be Solved by the Invention]

Silica-zirconia fiber Ge produced by the above-mentioned melting method
mFIL has a low melting point because it contains an alkali, and there is a problem in heat resistance, and in the above-described method for producing a silica-zirconia glass fiber by the sol-gel method, since it is hydrolyzed by water in the atmosphere, it is considerably difficult to produce. It takes a few days, and is easily affected by the temperature and humidity of the atmosphere, resulting in poor reproducibility. Further, zirconium alkoxide used as a silica-zirconia source is expensive and has a drawback of high production cost.

An object of the present invention is to produce a silica-zirconia viscous sol which is inexpensive, has high performance, and can be a precursor of silica-zirconia fibers.

[Means for Solving the Problems]

The present inventor conducted research to solve the above problems, and conceived to use a compound other than zirconium alkoxide as a zirconia source, and a silica-zirconia-based composition-containing raw material containing a silicon alkoxide. The present invention has been completed by pursuing conditions under which reproducible hydrolysis can be performed.

That is, in the present invention, a mixture of a silicon alkoxide and a zirconium salt is mixed to form a mixture for a silica-zirconia composition, and the mixture is mixed with 1.2 to 1.7 times the molar amount of water with respect to the silicon alkoxide. A method for producing a silica-zirconia viscous sol, which comprises hydrolyzing and polycondensing.

Hereinafter, the present invention will be described in detail.

As the silicon alkoxide, silicon methoxide,
Silicon ethoxide, silicon-n-proxy, and the like can be used. Among them, silicon ethoxide has a slower rate of hydrolysis and polycondensation than silicon methoxide, and is easy to synthesize a spinnable sol.

As the zirconium salt, zirconium nitrate, zirconium chloride, zirconium oxychloride, etc. can be used. Acid radicals (nitrate, hydrochloric acid) forming these salts act as a catalyst for hydrolyzing silicon alkoxide (acid catalyst), and particularly act as a catalyst for expressing spinnability. Many of these salts exist as hydrated salts, but it is preferable to use those in the form of hydrated salts. The structural water in the hydrous salt is involved in hydrolysis, and the structural water causes slow hydrolysis to form a homogeneous sol. Among these salts, zirconium oxychloride is preferable in that the amount of hydrochloric acid radical is small. This is because the stability of the spinnable sol deteriorates when a large amount of hydrochloric acid radical is introduced from the salt. But,
Since zirconium oxychloride is a water-containing salt with 8 mol of structural water, it cannot be used in a large amount due to regulation of the amount of water added. Therefore, when it is desired to increase the content of zirconium, it is necessary to use an anhydrous salt, that is, zirconium chloride together with zirconium oxychloride. Among the salts, chloride is used because hydrochloric acid radical is the most preferable as a catalyst for the synthesis of spinnable sol.

The mixing ratio of the silicon alkoxide and the zirconium salt is determined by the desired composition of the silica-zirconia-based product in the final product. Silicon alkoxide is preferably used as a solution of an organic solvent such as alcohol. A more uniform mixture is obtained when mixed in the form of a solution. As the alcohol of the organic solvent, methanol, ethanol or the like can be used, but ethanol is preferably used. The other third component can be added in the form of alkoxide or salt.

In hydrolyzing the mixture, 1.2 to 1.7 times mol of water is used with respect to the silicon alkoxide in the mixture. If the amount of water used is less than this, spinnability is less likely to be exhibited, and if it is more than this, gelation tends to occur, and stability is lacking due to the narrow spinnability expression region. The amount of water used, when using the hydrated salt as the zirconium salt, includes the structural water, when using the hydrated salt, the amount of water subtracted from the hydrated salt Added. The water to be added can be added as a water-alcohol mixed solvent. When a hydrous salt is used as the zirconium salt, the hydrolysis starts immediately after mixing it with the silicon alkoxide.

In the present invention, since the zirconium salt has an acid radical,
When a large amount of this is used, a large amount of acid radicals (anions) are introduced with it, and the acid radicals act as a catalyst as described above. The homogeneity of the resulting sol,
Stabilization is reduced. Therefore, in order to remove anions, anion exchange treatment is performed to reduce acid radicals, but the timing of the treatment is when the silicon alkoxide and zirconium salt are mixed, that is, before desolvation is performed and spinnability is exhibited. Stages are preferred. On the contrary, if the number of residual acid radicals becomes extremely small by the anion exchange treatment, the spinnability may not be manifested. In that case, however, a spinnable sol can be obtained by adding an acid catalyst such as HCl afterwards. be able to. Further, the precursor from which such acid radicals are removed in a nearly complete form can be used as a precursor suitable for producing a silica-zirconia-based bulk gel, and eventually a bulk glass, by adding water and an alkali catalyst.

If necessary, the solvent is distilled off from the hydrolyzed product and polycondensation is performed to obtain a viscous sol having spinnability.

[Action]

In the present invention, a viscous sol having spinnability can be easily obtained in a short time by the hydrolysis. Since this viscous sol has no problem of precipitation due to single hydrolysis of zirconium as compared with the conventional method using zirconium alkoxide as a zirconium source, homogeneity on a molecular order is achieved and a large amount of zirconium can be added. Therefore, the glass fiber obtained by firing the gel fiber spun from the viscous sol of the present invention is of high quality in which zirconium is dispersed very uniformly, and may contain a large amount of zirconium that cannot be achieved by the melting method. it can.

〔Example〕

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

To Example _{1 Si (OC 2 H 5)} 4 100g, ZrOCl 2 · 8H 2 O15.5g, ethanol 80 g, was mixed with water 6 g, it was a homogeneous solution 20to
A viscous sol having a spinnability of 400 poise was synthesized in the process of distilling off the solvent ethanol at 80 ° C. under reduced pressure of rr. This was made into a continuous gel fiber by a spinning device,
By firing at 00 ° C., a transparent silica-zirconia fiber containing 21 wt% of ZrO ₂ was obtained.

Example 2 100 g of Si (OC ₂ H ₅ ) ₄ was mixed with 29.4 g of ZrOCl ₂ · 8H ₂ O and 66 g of ethanol at room temperature to form a homogeneous solution, and then 20 torr
In the process of distilling off the solvent ethanol at 80 ° C. under reduced pressure, a viscous sol having spinnability and a viscosity of about 500 poise was obtained. This was made into a continuous gel fiber using a spinning device, and 1050 ℃
A silica-zirconia glass fiber containing 37 wt% of ZrO ₂ was obtained by firing at.

Example 3 With respect to 100 g of Si (OC ₂ H ₅ ) ₄ , 29.4 g of ZrOCl ₂ · 8H ₂ O and ZrCl ₄ 2
2.4 g of ethanol and 70 zg of ethanol were mixed at room temperature to form a homogeneous solution, which was passed through the anion exchange resin once to reduce chlorine ions. In the process of distilling off the solvent ethanol at 80 ° C. under a reduced pressure of 20 torr, a spinnable viscosity of about 70 was obtained.
A viscous sol of 0 poise was obtained. Continuous gel fibers were spun from this viscous sol and fired at 1100 ° C to produce ZrO ₂
A silica-zirconia fiber containing 51 wt% of was obtained.

〔The invention's effect〕

According to the present invention, a silica-zirconia-based viscous sol having spinnability can be easily obtained in a short time. Also,
Since zirconium alkoxide is not used as the reaction raw material, there is no problem that zirconium alkoxide generated when it is used is more hydrolyzed than silicon alkoxide. Can contain a large amount of zirconium that cannot be achieved by. Further, since the zirconium salt is used as the zirconium source, the zirconium salt can be produced at a much lower cost than the case where the zirconium alkoxide produced using the zirconium salt as a raw material is used. This silica-zirconia-based viscous sol can be easily spun, and by firing the spun product, silica-zirconia-based glass fibers can be easily obtained. Further, a silica-zirconia-based product having a shape other than fibers such as a thin film can be produced from this silica-zirconia-based viscous sol.

Claims (3)

[Claims] 1. A silicon alkoxide and a zirconium salt are mixed to form a mixture for a silica-zirconia composition, and the mixture is added to the silicon alkoxide at 1.2.
A method for producing a silica-zirconia-based viscous sol, which comprises hydrolyzing and polycondensing using 1.7 to 1.7 times the molar amount of water. 2. The silica-zirconia-based viscosity according to claim 1, wherein the silicon alkoxide is silicon ethoxide, and the zirconium salt is zirconium oxychloride having structural water and / or zirconium chloride. Method of manufacturing sol. 3. The method according to claim 1, wherein in the process of hydrolyzing and polycondensing the mixture, the reaction solution is ion-exchanged to remove anions contained in the solution. 2) A method for producing the silica-zirconia-based viscous sol described above.