JPH09176921A - Tin oxide fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely decrease halogen ions in a tin oxide fiber having high aspect ratio and obtain a tin oxide fiber having excellent chemical stability by producing a gel fiber from a stringy solution and treating the fiber with a high-temperature steam. SOLUTION: A tin oxide gel fiber produced by the spinning of a stringy solution is treated with steam at 60-1,550 deg.C, preferably 150-1,500 deg.C before, during or after heat-treatment to decrease the halogen content of the tin oxide fiber to <=0.05wt.% and obtain an amorphous or polycrystalline tin oxide fiber having a diameter of >1μm or a length of >3mm and a nearly circular cross-section and useful as a component for a composite material.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to tin oxide fibers. Specifically, the diameter exceeds 1 μm or the major axis exceeds 3 mm, and the cross-sectional shape is circular or substantially circular,
The present invention also relates to an amorphous or polycrystalline tin oxide fiber having a halogen content of 0.05% by weight or less.

[0002]

2. Description of the Related Art Tin oxide has excellent chemical resistance and heat resistance.
Moreover, it is an excellent material whose conductivity can be controlled over a wide range, and is used for various purposes. Recently, studies have been made on third-order nonlinear optical materials.

On the other hand, carbon black, carbon fiber, etc. are currently added for the purpose of imparting conductivity to polymer materials. However, when carbon is used, the material itself is black, so that the material is black. There was a problem that it was not possible to achieve bright coloration, and it was very light and easily scattered. For this reason, powders of metals and conductive metal oxides have been added. Among the metal oxides, tin oxide has high conductivity, and further has excellent chemical resistance and heat resistance, so that addition as a powder has been attempted. By the way, it is known that the effect of imparting conductivity increases as the aspect ratio of the conductivity imparting material increases. For this reason, it has been required to make tin oxide into a fiber.

However, it has been difficult to produce fibers by the conventional solid-state reaction method. Therefore, JP-A-60-5997, JP-A-60-161337, and JP-A-60-158199 propose methods for producing tin oxide whiskers by a melt precipitation method. However, these methods require a high temperature of 1000 ° C. or more and a reaction time of many days, so that it is possible to produce a very small amount on a laboratory scale, but it has not yet reached industrial production. . Moreover, the shape of the tin oxide whiskers obtained is 1 μm or less in diameter and 3 in length.
When it is used as a composite material, its function is not fully exhibited and its use is limited because it has a small aspect ratio of less than mm and a rectangular cross section. Japanese Unexamined Patent Publication (Kokai) No. 06-163051 proposes a method for producing tin oxide whiskers having a diameter of 1 μm to 100 μm. In this case as well, the tin oxide whiskers obtained are single crystals and have a rectangular cross section. Further, since all of the above tin oxide whiskers have too small a major axis, it is difficult to produce a woven fabric, a non-woven fabric or the like. Further, in order to improve the reproducibility of physical properties such as conductivity of the obtained composite material, it is important to control the shape and size of the tin oxide whiskers to be added with good reproducibility. However, since it is actually difficult to control the shape of tin oxide whiskers, if the diameter and length of the tin oxide to be added were to be made uniform, it was only possible to classify what was accidentally produced. Therefore, whiskers made by such an inefficient method are extremely expensive,
I couldn't actually use it.

The present inventors surprisingly exhibited spinnability when a solution containing a tin halide compound and an alcohol as a main component was found. By spinning and heating the solution, the spinnability was easily and extremely inexpensive. It has been found that tin oxide fiber can be obtained, and it has already been proposed (JP-A-4-35287).
JP-A-5-117906, JP-A-5-17951
No. 2).

[0006]

However, in the tin oxide fiber which has been spun with the above spinnability solution and subjected to the subsequent heat treatment, chlorine ions and bromine contained in the tin halide compound etc. There are cases where halogen ions such as ions and iodine ions remain, and these halogen ions are eluted in an aqueous solution or the like, which may cause a problem in the chemical stability of the material to which the tin oxide fiber is added. In particular, when a large amount of fibers (hereinafter, referred to as gel fibers) spun using the above spinnable solution were simultaneously heat-treated, halogen ions tended to remain in the tin oxide fibers. Therefore, earnest studies have been conducted on a method of reliably and easily reducing halogen ions in a tin oxide fiber having a large diameter or long diameter.

[0007]

As a result, as a result, water vapor and 60 ° C. are generated before and after the heat treatment of the gel fiber or during the heat treatment.
It was found that the halogen ions in the tin oxide fiber were surely removed by bringing them into contact with each other at the above temperature, and the present invention was completed here.

That is, according to the present invention, the diameter is more than 1 μm or the major axis is more than 3 mm, the cross-sectional shape is circular or substantially circular, and the halogen content is 0.05 wt% or less. It is a crystalline tin oxide fiber.

Next, the present invention will be described more specifically.

The tin oxide fiber of the present invention contains tin oxide as a main component, and the content of halogen contained in the tin oxide fiber is 0.05% by weight or less. From the viewpoint of chemical stability, that is, halogen solubility, the halogen content in the tin oxide fiber must be 0.05% by weight or less. More preferably, it is 0.03% by weight or less. The tin oxide fiber has a diameter of more than 1 μm, and the maximum value thereof can be a product having an arbitrary thickness depending on the spinning conditions described later, but a product having a diameter of 3 mm is usually possible. In addition, if the major axis exceeds 3 mm and continuous spinning is possible, even infinite length products can be manufactured. The cross-sectional shape of the tin oxide fiber of the present invention is circular or substantially circular. The ratio of the major axis to the minor axis of the cross section of the tin oxide fiber having a substantially circular cross section (major axis / minor axis) is preferably 1.0 to 3.0, and more preferably 1.0 to 2.0. The tin oxide fiber of the present invention is composed of amorphous or polycrystalline tin oxide depending on the conditions of the heat treatment described later. In this case, whether the tin oxide fiber is amorphous or polycrystalline can be confirmed by, for example, X-ray diffraction. When amorphous, the X-ray diffraction pattern becomes halo. On the other hand, in the case of polycrystallinity, an X-ray diffraction peak appears.

The tin oxide fiber of the present invention may be produced by any method, and a typical production method for producing the tin oxide fiber will be illustrated.

A tin halide compound is dissolved in alcohol, and if necessary, a solution in which metallic tin, an alcohol-soluble periodic table group V element compound, an alcohol-soluble silicon compound, and an alcohol-soluble polymer compound are mixed and dissolved is concentrated. The obtained spinning solution is spun to obtain a gel fiber, and the gel fiber is then contacted with steam at a temperature of 60 ° C. to 1550 ° C. before, after, or during the heating.

The alcohol used in the present invention is not limited as long as it dissolves the tin halide compound described below. The general formulas of these alcohols are as follows. It is represented by ROH (wherein R is an unsubstituted or substituted alkyl group, an unsubstituted or substituted alkenyl group).

Specific examples of the substituent in the above-mentioned substituted alkyl group or substituted alkenyl group include alkoxyl groups such as methoxy group and ethoxy group, alkoxyalkoxy groups such as methoxymethoxy group and methoxyethoxy group, hydroxyl group, phenyl group and the like. In addition to alkyl groups such as aryl groups, methyl groups and ethyl groups, amino groups, cyano groups, Cl
Examples thereof include halogen such as atom, Br atom, I atom and F atom.

When the group represented by ROH is specifically exemplified, R is a methyl group, an ethyl group, a propyl group, a butyl group,
Unsubstituted alkyl group such as octyl group, 2-methoxyethyl group, 2-ethoxyethyl group, 2-hydroxyethyl group,
Substituted alkyl groups such as 1-methoxy-2-propyl group, methoxyethoxyethyl group, 2-phenylethyl group and phenylmethyl group, unsubstituted alkenyl groups such as allyl group, substituted alkenyl groups such as 2-methyl-2-propenyl group and 3-methyl-3-butenyl group Is mentioned.

Specific examples of these alcohols include methyl alcohol, ethyl alcohol, propyl alcohol,
Butyl alcohol, octyl alcohol, 2-methoxyethanol, 2-ethoxyethanol, ethylene glycol, 1-methoxy-2-propyl alcohol, methoxyethoxyethanol, 2-phenylethyl alcohol, benzyl alcohol, allyl alcohol, 2-methyl-2-propene-1 -Ol, 3-methyl-3-buten-1-ol, and the like. In particular, methyl alcohol and ethyl alcohol are preferable because of high solubility of the tin halide compound. The above alcohols are usually used alone, but a mixture of two or more kinds of alcohols may be used in order to control the reactivity with the tin halide compound, the solubility of the tin halide compound and the like.

Examples of the tin halide compound used in the present invention include tin halide and organotin halide. The halogen of tin halide is Cl, Br, I,
It is an F atom. Specifically, SnCl ₂ , SnCl ₂ · 2
_{H 2 0, SnBr 2, SnI} 2, SnF 2 , and the like, in _{particular, SnCl 2, SnBr 2, SnCl} 2 · 2H 2 O is preferably used. As the halogenated organotin compound, a compound in which a tin atom and an organic group are directly bonded, for example, Sn
(CH ₃ ) ₂ Cl ₂ can also be used. Among these tin halide compounds, tin chloride and tin bromide are preferred in view of price and stability.

The mixing ratio of the above tin halide compound and alcohol is not particularly limited as long as the tin halide compound is uniformly dissolved in the alcohol. The mixing ratio for completely dissolving the tin halide compound in alcohol and further reducing the amount of alcohol evaporated during concentration is as follows. The mixing ratio varies depending on the type of the tin halide compound and the alcohol used, but generally, the molar ratio of the tin halide compound to the alcohol is preferably 0.02 to 0.5.
After blending in this ratio to form a transparent and uniform solution, alcohol is further evaporated to concentrate the solution to obtain a spinning solution having a desired viscosity.

In the present invention, it is preferable to further add metal tin because the drying of the gel fiber is stopped and the handling becomes easy. It is also preferable in order to reduce the total amount of halogen ions to be removed and further to reduce the halogen content in the tin oxide fiber finally obtained. The shape of metallic tin is not particularly limited, and examples thereof include plate-like, rod-like, sheet-like, granular, powdery, sandy, flower-like ones, etc., in terms of ease of dissolution, granular, powdery, sandy. The shape is preferable. Higher purity is preferable, but it is not particularly limited as long as it does not affect the manufacturing method and does not affect the reproducibility of the specific resistance described later.

The metal tin is added in an amount of 0.1 to 0.7 in molar ratio with respect to the tin halide compound in order to uniformly dissolve it in alcohol and further improve the drying of the gel fiber.
It is preferable to add in the range.

The mixing ratio of the tin halide compound, metal tin and alcohol is not particularly limited as long as the tin halide compound and metal tin are uniformly dissolved in the alcohol. The compounding ratio for completely dissolving the tin halide compound and metallic tin in alcohol and further reducing the amount of alcohol evaporated during concentration is as follows. The compounding ratio of the tin halide compound, metal tin and alcohol to be used varies depending on the kind, but generally, the ratio of the tin halide compound and metal tin to the alcohol is 0.01 to 0.01.
0.5 is preferred. After blending in this ratio to form a transparent and uniform solution, alcohol is further evaporated to concentrate the solution to obtain a spinning solution having a desired viscosity.

Further, in order to obtain a tin oxide fiber having high conductivity in the present invention, an alcohol-soluble Periodic Table Group V element compound (hereinafter referred to as Group V compound) can be contained as necessary. This Group V compound is
By the heat treatment described later, it finally becomes an oxide and forms a solid solution in tin oxide, but when the content is excessive, it does not form a solid solution in tin oxide and exists in the form of a mixture as a normal oxide. When it forms a solid solution in tin oxide, the Group V element is present in place of the tin atom in tin oxide. Further, when it is present in the form of a mixture as an oxide without forming a solid solution, the Group V element is mostly an oxide in an atmosphere in which oxygen is present, but it may be present without being partially oxidized.

Examples of the Group V compound include compounds of Group V elements such as vanadium compounds, niobium compounds, tantalum compounds, antimony compounds, and bismuth compounds. Specifically, as the vanadium compound, V
Br ₃ , VCl ₂ , VCl ₃ , VCl ₄ , VOBr ₂ , VO
_{Br 3, VOCl 3, VF 3} , VF 4, VF 5, VI 3 · 6H
₂ O, vanadium alkoxide, and niobium compounds such as NbCl ₅ , NbBr ₅ , NbF ₅ , and NbO.
Cl ₃ and alkoxides of niobium can be cited. As a tantalum compound, TaBr ₅ , TaCl ₅ , and an alkoxide of tantalum, and as an antimony compound, SbCl ₃ and Sb.
Cl ₅ , SbBr ₃ , antimony oxychloride, or an alkoxide of antimony, and examples of the bismuth compound include BiCl ₃ , BiI ₂ , and bismuth alkoxide.

When it is desired to impart conductivity to the tin oxide fiber, the compounding ratio of the Group V compound is 0.1 to 25 mo in terms of the oxide contained in the tin oxide fiber.
1% is preferred. The above ratio is preferable for increasing the conductivity of the tin oxide fiber.

In the present invention, an alcohol-soluble silicon compound can be added to the spinning solution in order to carry out spinning stably and to increase the mechanical strength of the obtained fiber.

Such alcohol-soluble silicon compounds include those represented by the general formulas Si (OR _A ) ₄ and R _B Si (O
_A silicon alkoxide represented by R _A ) ₃ or R _B R _C Si (OR _A ) ₂ or a silicon halide is used. Where R
_A , R _B and R _C each represent a straight-chain or branched alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group and a pentyl group; and a straight-chain alkyl group such as an ethenyl group, a propenyl group, a butenyl group and a pentenyl group. A chain or branched alkenyl group; and an aryl group such as a phenyl group.

Specific examples of the silicon alkoxide include tetramethoxysilane, tetraethoxysilane,
Tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, propyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, n-
Octadecyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, amyltriethoxysilane, phenyltriethoxysilane, n-octyltriethoxysilane, n-octadecyltriethoxysilane, n-dodecyltriethoxysilane, methyltributoxysilane And ethyltributoxysilane, ethyltripropoxysilane, vinyltriethoxysilane, allyltriethoxysilane, diphenyldimethoxysilane, dimethyldiethoxysilane, vinylmethyldiethoxysilane, diethyldimethoxysilane, ethylmethyldiethoxysilane and the like. As the silicon halide, S
Examples thereof include iCl ₄ , SiHCl ₃ , and SiH ₂ Cl ₂ .

By adding the above alcohol-soluble silicon compound to the spinning solution, it is possible to spin a fiber having a large major axis relatively stably even in an atmosphere of high humidity, and further, the gel fiber immediately after spinning is softened. It is easy to handle because it is less likely to collapse. Furthermore, the mechanical strength of the finally obtained fiber is improved. In order to maintain conductivity and further increase mechanical strength, the compounding ratio of the above silicon compound is 2 to 80% by weight in the finally obtained tin oxide fiber.
The following is preferable, and further 2 to 50% by weight is preferable.

In the present invention, it is effective to add an alcohol-soluble polymer compound to the spinning solution in order to enable high speed spinning. As such a polymer compound, any polymer compound soluble in alcohol can be used without any limitation. Specific examples include celluloses such as ethyl cellulose, cellulose acetate, cellulose nitrate, cellulose propionate, cellulose triacetate, acetylbutyl cellulose, hydroxylpropyl cellulose, polyvinyl butyral, polymethylene oxide, polyethylene oxide, polypropylene oxide, and polyacetic acid. Vinyl and the like. By adding these alcohol-soluble polymer compounds, spinning can be performed without being much influenced by the humidity in the atmosphere, and spinning can be performed at a higher speed. That is, for example, when a method of extruding a spinning solution from a nozzle is adopted, in order to spin stably without adding an alcohol-soluble polymer compound, the alcohol is evaporated and concentrated,
The viscosity of the spinning solution should be about 500 to 1000 poise or higher. Generally, the spinning speed tends to decrease as the viscosity of the spinning solution increases. When the alcohol-soluble polymer compound is added to the spinning solution, it is about 50 to 500.
Spinning is possible even with a viscosity as low as poise, and higher speeds are possible. Further, when the viscosity is low, the pressure applied to the solution tends to be uniform, and therefore, when spinning is performed using a plurality of spinning nozzles, spinning can be performed from almost all nozzles. The amount of the alcohol-soluble polymer compound added is preferably 0.01 to 25 parts by weight with respect to 100 parts by weight of the tin halide compound. The amount is preferably 0.01 to 25 parts by weight in order to obtain a sufficient addition effect of the alcohol-soluble polymer compound and to easily remove the alcohol-soluble polymer compound during the heat treatment.

The method for dissolving the tin halide compound and the alcohol, and the metal tin, the alcohol-soluble silicon compound, the alcohol-soluble polymer compound, and the alcohol-soluble Group V compound, which are optionally added, are not particularly limited. A method in which alcohol is added dropwise to a mixture of a tin halide compound, and optionally tin metal, an alcohol-soluble silicon compound, an alcohol-soluble polymer compound, and an alcohol-soluble Group V compound under stirring, or an alcohol under stirring A tin halide compound, and optionally tin metal, an alcohol-soluble silicon compound, an alcohol-soluble polymer compound, and an alcohol-soluble Group V compound,
Alternatively, a method of sequentially dissolving can be used. Further, in order to promote dissolution of metallic tin, it is also effective to reflux alcohol solution to dissolve metallic tin.

In order to further improve the stability of the spinning solution of the present invention, a compound having two or more carboxyl groups such as acetylacetone, ethyl acetoacetate, diethyl malonate, etc. may be appropriately contained as a tin complexing agent. It is also possible to add a compound for further enhancing the spinnability.

The spinning method is not particularly limited, and a conventional spinning method can be used. For example, there is a method of extruding a spinning solution from a spinning nozzle. The major diameter and diameter of the obtained fiber can be arbitrarily controlled by adjusting the viscosity of the spinning solution, the nozzle diameter, the speed of extruding the spinning solution from the spinning nozzle, and the like.

In the present invention, it is important to subject the gel fiber obtained by the above spinning to steam treatment in order to remove halogen ions in the tin oxide fiber. still,
Steam treatment refers to a treatment method in which the gel fiber is contacted with steam at a temperature of 60 ° C. or higher.

The temperature for steam treatment is 60 ° C. to 1550.
C. is preferred. Furthermore, it is preferable to carry out at 150 ° C to 1500 ° C. The steam treatment may be performed in a separate step before and after the heat treatment, or may be performed simultaneously during the temperature increase or the heat treatment at a constant temperature. Since gel fibers spun from a spinning solution having a large halogen content have low moisture resistance, it is preferable to perform steam treatment at a temperature of 150 ° C. or higher after partially performing heat treatment or drying treatment described below. Gel fibers having high moisture resistance can be subjected to steam treatment immediately after spinning without performing drying treatment or heat treatment. The steam treatment time is preferably 10 minutes to 10 hours, and more preferably 30 minutes to 8 hours. The pressure of the atmosphere containing steam can be set to 1 atmospheric pressure or more, but it is usually atmospheric pressure. It The proportion of water vapor in the atmosphere including the water vapor treatment is preferably 20% by volume or more, and water vapor mixed with air and other gas described later may be used. Although the mechanism of the steam treatment is currently unknown, it is considered that chlorine existing in the gel fiber is replaced with a hydroxyl group, and the halogen ion contained in the gel fiber is easily desorbed.

The heat treatment is carried out at a temperature at which an organic solvent such as alcohol or water is removed from the gel fiber to strengthen the skeleton of the fiber, and in some cases, further crystallization is performed. The gel fiber as spun from the spinning solution does not show sufficient mechanical strength as it is. The mechanical strength is developed by heating the gel fiber. The heat treatment is performed before or after the steam treatment or simultaneously with the steam treatment. The heat treatment temperature is not particularly limited as long as it is within a temperature range capable of imparting mechanical strength to the obtained fiber. When the heat treatment temperature is low, alcohol, water, etc. remain in the fiber, so that sufficient mechanical strength may not occur. Further, if the heat treatment temperature is too high, the decomposition of tin oxide may proceed, or the crystal grains in the fiber may grow too much and the strength may decrease. For the above reason, the heat treatment temperature is 250 to 1550.
C. is preferred. More preferably 300 to 1500 ° C
It is preferable to perform heat treatment at the temperature of.

The heat treatment is usually carried out in air, but when it is desired to obtain a fiber having particularly high conductivity, it is heated in a reducing atmosphere such as nitrogen, argon, hydrogen or a mixed gas of argon and hydrogen, or in vacuum. Processing can be performed.

When the Group V compound is added, the specific resistance value of the tin oxide fiber of the present invention varies greatly depending on the type of the Group V compound, the addition amount, the firing atmosphere, the firing temperature, etc. It can take a value of ³ to 10 ⁻² Ω · cm. 10 ^-4 Ω · cm when fired in a reducing atmosphere
The value of can also be obtained.

Further, in the steam treatment and the heat treatment, it is desirable to remove the volatile components such as water and alcohol present in the gel fiber by drying in order to obtain a good tin oxide fiber. Such drying is
It may be performed at the same time as the heat treatment, but it is preferable to perform it before the heat treatment in order to obtain a good fiber. In this case, the steam treatment can be performed simultaneously with the drying treatment or before and after the drying treatment. The drying temperature of the drying treatment is preferably as low as possible in order to prevent generation of cracks in the obtained fiber, but when an alcohol having a high boiling point is used as a solvent, it is too low. It takes a long time to dry and is not effective. A general drying temperature is preferably in the range of room temperature to 300 ° C.

The tin oxide fiber obtained by the present invention may be crystalline or amorphous.
From the viewpoint of conductivity, crystalline is preferable.

[0040]

INDUSTRIAL APPLICABILITY The tin oxide fiber of the present invention is one in which the halogen ions remaining therein are greatly reduced.
As a result, it has become possible to provide tin oxide fibers having excellent chemical stability.

[0041]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 3 Tin halide, metallic tin and methyl alcohol were mixed and dissolved in the proportions shown in Table 1 to obtain a uniform and transparent solution.
This solution was concentrated to give a spinning solution composed of a highly viscous sol.
A pressure was applied to this spinning solution, which was extruded from a spinning nozzle and continuously wound around a drum in an atmosphere with a relative humidity of 55%.
The obtained gel fiber was 500 at a rate of 5 ° C./min.
The temperature was raised to 0 ° C., and at this temperature, 50 vol% of water vapor was heated by a heater and introduced into a heating container for treatment for 1 hour. As a result, continuous fibers having an average diameter of 50 μm were obtained. A fiber having a length of 10 cm was obtained by cutting. The cross-sectional shape of the obtained fiber was circular, and partly contained an oval shape. As a result of X-ray diffraction, it was confirmed to be crystalline tin oxide. When the residual chlorine content of the fiber was measured by the fluorescent X-ray method, it was 0.02-0.03.
% By weight.

Examples 4 to 7 Stannous chloride, metallic tin, antimony trichloride, tetramethoxysilane, polyethylene glycol and methanol were mixed and dissolved in the proportions shown in Table 1 to obtain a uniform and transparent solution. The above solution was concentrated to give a spinning solution composed of a highly viscous sol. Spinning was performed in the same manner as in Example 1, and steam treatment was performed in the same manner as in Example 1 except that saturated steam was introduced instead of 50 vol% steam. As a result, average diameter 3
A continuous fiber of 0 to 50 μm was obtained. A fiber having a length of 10 cm was obtained by cutting. Keiko X
Line analysis confirmed that antimony and silica were present in the fiber according to the feed composition. Also,
As a result of X-ray diffraction, it was confirmed that tin oxide had a peak, and antimony did not show a peak such as an oxide thereof and was dissolved in tin oxide. The residual chlorine in the fiber was 0.03% by weight or less.

Example 8 A gel fiber was prepared in the same manner as in Example 7. The gel fiber obtained is 300 ° C at a rate of 5 ° C / min.
Up to 5 ℃ /
The temperature was raised to 500 ° C. for min and the treatment was performed for 30 minutes. As a result, continuous fibers having an average diameter of 30 μm were obtained. A fiber having a length of 10 cm was obtained by cutting. The cross-sectional shape of the fiber was circular. By fluorescent X-ray analysis, it was confirmed that antimony and silica were present in the fiber according to the charged composition. Also, X
As a result of the line diffraction, it was confirmed that tin oxide had a peak, and antimony did not show a peak of its oxide or the like but was dissolved in tin oxide. No residual chlorine was detected in the fiber.

Example 9 A gel fiber was prepared in the same manner as in Example 7. The obtained fiber was heated to 700 ° C. at a rate of 5 ° C./min, saturated water vapor was introduced at that temperature, and treatment was performed for 1 hour. As a result, continuous fibers having an average diameter of 30 μm were obtained. A fiber having a length of 10 cm was obtained by cutting. The cross-sectional shape of the fiber was circular. By fluorescent X-ray analysis, it was confirmed that antimony and silica were present in the fiber according to the charged composition. In addition, as a result of X-ray diffraction, it was confirmed that tin oxide had a peak, and that antimony did not show a peak such as an oxide thereof and was dissolved in tin oxide. No residual chlorine was detected in the fiber.

Example 10 Example 7 except that the viscosity of the spinning solution was set to about 200 poise.
Preparation of gel fiber and heat treatment accompanied by steam treatment were performed in the same manner as in. As a result, continuous fibers having an average diameter of 15 μm were obtained. It was cut to obtain a fiber having a length of 10 cm. By fluorescent X-ray analysis, it was confirmed that antimony and silica were present in the fiber according to the charged composition. In addition, as a result of X-ray diffraction, it was confirmed that tin oxide had a peak, and that antimony did not show a peak such as an oxide thereof and was dissolved in tin oxide.
No residual chlorine was detected in the fiber.

[0047]

[Table 1]

Comparative Examples 1-2 Stannous chloride, antimony trichloride, tetraethoxysilane and methanol were mixed and dissolved at the ratios shown in Table 2 to obtain a uniform and transparent solution. Then, spinning was carried out in the same manner as in Example 1, and heat treatment was carried out in the same manner except that no steam was introduced. Continuous fibers with an average diameter of 50 μm were obtained. It was cut to obtain a fiber having a length of 10 cm. Further, the cross-sectional shape was circular, and partly included an elliptical shape. As a result of X-ray diffraction of the fiber, it was confirmed to be crystalline tin oxide. The residual chlorine content of the fiber showed a distribution in the heating device, and an average of 0.30 to 0.40% by weight of chlorine remained.

[0049]

[Table 2]

Claims (1)

[Claims] 1. The diameter exceeds 1 μm or the major axis is 3 mm.
Amorphous or polycrystalline tin oxide fiber having a cross section of a circular shape or a substantially circular shape and having a halogen content of 0.05% by weight or less.