JPH09195127A - Production of tin-oxide fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a tin-oxide fiber having a high purity by discharging an alcoholic solution of a halogenated tin compound from a spinning nozzle to form a gel fiber and followed by a heat treatment and a steam treatment. SOLUTION: A spinning solution composed of a highly viscous sol is prepared by dissolving a halogenated tin compound such as stannous chloride or stannous bromide in methanol, etc., to obtain a clear homogeneous solution and then, condensing the obtained solution. A gel fiber is formed by extruding the spinning solution from a spinning nozzle under pressure and continuously winding up on a drum, and subsequently the alcohol and water are removed from the gel fiber. In order to strengthen the fiber skeleton, the fiber is subjected to a heat treatment at 250-1,550 deg.C, preferably 300-1,500 deg.C, and further the fiber is made to contact with steam at >=60 deg.C before, during or after the heat treatment to remove halogen ions in the fiber. Thus, the objective tin-oxide fiber having a high purity is obtained.

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to a method for producing tin oxide fiber.

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 becomes black, so that the material is brightened. There was a problem that it could not be achieved, and it was very light, so it was 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, conventional solid-phase reaction methods
Was difficult to manufacture. For this reason, Japanese Patent Application Laid-Open
-5997, JP-A-60-161337, JP-A-6
No. 0-158199 proposes a method 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 obtained tin oxide whiskers has a diameter of 1 μm or less, a length of 3 mm or less, a small aspect ratio, and a rectangular cross section, so that when it is used as a composite material, its function cannot be fully exhibited and its application There was a problem that was limited. 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. Furthermore,
Since all of the above tin oxide whiskers are too short, 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 and cannot be used in practice. The present inventors surprisingly exhibited spinnability when a solution containing a tin compound and an alcohol as a main component was used. By spinning and heating the solution, the tin oxide fiber was easily and extremely inexpensively produced. It has been found that the above-mentioned compounds can be obtained, and it has already been proposed (JP-A-4-35287, JP-A-5-117906, JP-A-5-179512).

However, in the above-mentioned method, a tin oxide fiber obtained by spinning using a spinnable solution containing tin halide as a main component in a tin compound and then subjecting it to heat treatment is used. In some cases, halogen ions such as chlorine ions, bromine ions, and iodine ions contained in tin halide compounds may remain, and tin oxide fibers were added because these halogen ions are eluted in an aqueous solution. It could lead to problems with the chemical stability of the material. In particular, when a large amount of fibers (hereinafter, also simply referred to as “gel fiber”) spun using a solution having the above spinnability are simultaneously heat treated,
The tendency was that halogen ions tend to remain in the tin oxide fiber. Therefore, intensive research was conducted on a method for surely and easily reducing the halogen ions in the tin oxide fiber.

As a result, it has been found that halogen ions in tin oxide fibers can be reliably removed by contacting with steam at a temperature of 60 ° C. or higher before, during or after heating the gel fibers, The present invention has been completed here. That is, the present invention relates to a method for producing tin oxide fibers by heating a fiber spun from a solution containing alcohol and a tin halide compound as main components, in which steam is added before or after heating at a temperature of 60 ° C. or higher. It is a method for producing tin oxide fibers, which is characterized by bringing them into contact with each other.

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described more specifically. In the present invention, a tin halide compound is dissolved in alcohol, and in some cases, a solution obtained by mixing and dissolving metal tin, an alcohol-soluble periodic table group V element compound, an alcohol-soluble silicon compound, and an alcohol-soluble polymer compound is concentrated. The method for producing a tin oxide fiber is characterized in that the spinning solution obtained is spun to obtain a gel fiber, and the gel fiber is then contacted with water vapor at a temperature of 60 ° C. or higher before or during 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 substituted alkyl group or substituted alkenyl group include a methoxy group, an alkoxy group such as an ethoxy group, a methoxymethoxy group, an alkoxyalkoxy group such as a methoxyethoxy group,
In addition to an aryl group such as a hydroxyl group and a phenyl group, an alkyl group such as a methyl group and an ethyl group, an amino group, a cyano group, a halogen atom such as a Cl atom, a Br atom, an I atom and an F atom can be given. When the group represented by ROH is specifically exemplified, R is an unsubstituted alkyl group such as methyl group, ethyl group, propyl group, butyl group, octyl group, 2-methoxyethyl group, 2-ethoxyethyl group, 2-hydroxyethyl group, 1 -Methoxy-2-propyl group, methoxyethoxyethyl group, 2-phenylethyl group, substituted alkyl group such as phenylmethyl group, unsubstituted alkenyl group such as allyl group,
Examples thereof include substituted alkenyl groups such as 2-methyl-2-propenyl group and 3-methyl-3-butenyl group. 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, Methoxyethoxy ethanol, 2-phenylethyl alcohol, benzyl alcohol
Ru, allyl alcohol, 2-methyl-2-propene-1
-Ol, 3-methyl-3-butene-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 halogens of the tin halide are Cl, Br, I, and F atoms. Specifically, Sn
Cl ₂ , SnCl ₂ .2H ₂ 0, SnBr ₂ , SnI ₂ , S
nF _{2 and the} like are mentioned, and in particular SnCl ₂ , SnBr ₂ , S
nCl ₂ .2H ₂ O is preferably used. Further, as the halogenated organotin compound, a compound in which a tin atom and an organic group are directly bonded, such as Sn (CH ₃ ) ₂ Cl ₂ can be used. Among these tin halide compounds, tin chloride,
Tin bromide is preferable in terms of price and stability. The mixing ratio of the tin halide compound and the 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 metallic tin because drying of the gel fiber is stopped and 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 may be plate-like, rod-like, sheet-like, granular, powder-like,
Examples thereof include sandy and flower-like ones, and granules, powdery and sandy ones are preferable from the viewpoint of easy dissolution. 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 addition amount of metallic tin is preferably in the range of 0.1 to 0.7 in terms of 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. Further, in the present invention, an alcohol-soluble periodic table group V element compound (hereinafter referred to as a group V compound) may be contained as necessary in order to obtain a highly conductive tin oxide fiber. This Group V compound finally becomes an oxide by the heat treatment described below and becomes a solid solution in tin oxide, but when the content is excessive, it does not form a solid solution in tin oxide and becomes a normal oxide. Exists in form. When it forms a solid solution in tin oxide,
Group V elements exist in place of tin atoms 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 Group V compounds 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. The compounding ratio of the group V compound is 0.1 to 25 m in terms of oxide contained in the tin oxide fiber when it is desired to impart conductivity to the tin oxide fiber.
ol% 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 may be added to the spinning solution in order to carry out spinning stably and to increase the mechanical strength of the obtained fiber. Such an alcohol-soluble silicon compound has the general formula Si (O
_A silicon alkoxide represented by R _A ) ₄ , R _B Si (OR _A ) ₃ , or R _B R _C Si (OR _A ) ₂ or a silicon halide is used. Here, R _A , R _B , and R _C are each a linear or branched alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group; an ethenyl group, a propenyl group, a butenyl group, and a pentenyl group. A linear or branched alkenyl group such as a group; an aryl group such as a phenyl group; Specific examples of the silicon alkoxide include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, propyltrimethoxysilane and n-butyltrisilane. Methoxysilane, isobutyltrimethoxysilane,
n-hexyltrimethoxysilane, n-octadecyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, amyltriethoxysilane, phenyltriethoxysilane, n-octyltriethoxysilane, n-octadecyltriethoxysilane, n- Dodecyltriethoxysilane, methyltributoxysilane,
Examples thereof include ethyltributoxysilane, ethyltripropoxysilane, vinyltriethoxysilane, allyltriethoxysilane, diphenyldimethoxysilane, dimethyldiethoxysilane, vinylmethyldiethoxysilane, diethyldimethoxysilane and ethylmethyldiethoxysilane. Examples of silicon halides include SiCl ₄ , Si
Examples include HCl ₃ and SiH ₂ Cl ₂ . By adding the 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,
Since the gel fiber immediately after spinning is less likely to be softened and crumbled, the handling becomes very easy. 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 preferably 2 to 80% by weight in the tin oxide fiber finally obtained, and further 2 to 50% by weight.
% By weight is preferred. If it is desired to maintain particularly high conductivity, the amount is preferably 2 to 30% by weight. Further, 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 the spinning solution from a nozzle is adopted, in order to perform stable spinning without adding the alcohol-soluble polymer compound, the viscosity of the spinning solution is about 30 by evaporating and concentrating the alcohol.
It must be 0 to 1000 poise or more. Generally, the spinning speed tends to decrease as the viscosity of the spinning solution increases. When the above alcohol-soluble polymer compound is added to the spinning solution, spinning can be performed even at a low viscosity of about 50 to 500 poise, and higher speed can be achieved. Also, if the viscosity is low, the pressure applied to the solution tends to be uniform,
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, is 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 The method of dissolving the tin halide compound, the metal tin optionally added, the alcohol-soluble silicon compound, the alcohol-soluble polymer compound, and the alcohol-soluble Group V compound simultaneously or sequentially can be used. Further, in order to promote dissolution of metallic tin, it is also effective to reflux alcohol solution to dissolve metallic tin. Further, in order to improve the stability of the spinning solution of the present invention, a compound having two or more carboxyl groups such as acetylacetone, ethyl acetoacetate and diethyl malonate may be appropriately contained as a tin complexing agent, Furthermore, it is possible to add a compound for increasing 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. The gel fiber obtained by such spinning becomes a tin oxide fiber when heated. The heating is performed 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. Mechanical strength is developed by heating the gel fiber. The heating temperature is not particularly limited as long as it is within a temperature range capable of imparting mechanical strength to the obtained fiber. If the heating temperature is low, alcohol, water, etc. may remain in the fiber, resulting in insufficient mechanical strength. Further, if the heating 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 heating temperature is 250 to 1550.
C. is preferred. More preferably 300 to 1500 ° C
It is preferable to heat at the temperature of. The heating time is not particularly limited, but is generally in the range of 10 minutes to 10 hours. Further, the heating is usually performed in air, but when it is desired to obtain a fiber having particularly high conductivity, heat treatment is performed in a reducing atmosphere such as nitrogen, argon, hydrogen, a mixed gas of argon and hydrogen, or in vacuum. You can also In the present invention, the gel fiber obtained by the above spinning is used at 60 ° C. to remove halogen ions in the tin oxide fiber.
It is important to contact with steam at the above temperature (hereinafter, simply referred to as “steam treatment”). The steam treatment can be performed at any time after spinning the gel fiber, and can be performed before or after the heating or during the heating. That is, after the gel fiber is steam-treated, the above heating can be carried out continuously or separately, or after the gel fiber is heated as described above, the steam treatment can be carried out subsequently or separately. Further, when the heating temperature is 60 ° C. or higher, steam may be supplied during heating to bring the gel fiber and steam under heating into contact with each other. Gel fiber spun from a spinning solution containing a large amount of halogen that does not contain metallic tin or silicon compounds has low moisture resistance, so after a part of the drying treatment described below, the temperature is 150 ° C.
As described above, it is preferable to perform steam treatment. The highly moisture-resistant gel fiber spun from a spinning solution containing metal tin or a silicon compound may be subjected to steam treatment immediately after spinning without performing drying treatment or heat treatment. The temperature for performing the steam treatment is not particularly limited as long as it is a temperature of 60 ° C or higher, but a temperature of 60 ° C to 1550 ° C is preferable. In order to perform the steam treatment efficiently, 150 ° C to 1500
It is preferable to carry out at a temperature of 350 ° C to 1500 ° C.
It is preferred to treat with. The steam treatment time is 10
It is preferably from 10 minutes to 10 hours, more preferably from 30 minutes to 8 hours. The pressure of the atmosphere containing water vapor can be set to a pressure of 1 atm or higher, but the atmospheric pressure is usually used for processing. The proportion of water vapor in the atmosphere including the water vapor treatment is preferably 20% by volume or more, and air or water vapor mixed with a gas such as nitrogen, argon, hydrogen or the like which can be used at the time of heating may be used. The mechanism of the steam treatment is currently unknown, but it is considered that chlorine present in the gel fiber or tin oxide fiber is replaced with a hydroxyl group, and the halogen ion contained in these fibers is easily desorbed. Further, during the steam treatment and the heating, it is desirable to remove 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 may be performed at the same time as the above heating, but it is preferable to perform it before heating 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, but crystalline is preferable from the viewpoint of conductivity. 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 0 ³ to 10 ⁻² Ω · cm. When firing in a reducing atmosphere, a value of 10 ⁻⁴ Ω · cm can be obtained.

By the method of the present invention, the amount of halogen ions remaining in the tin oxide fiber is greatly reduced. As a result, it has become possible to provide tin oxide fibers having excellent chemical stability.

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 5 and Comparative Examples 1 to 5 Stannous chloride or stannous bromide and methyl alcohol were mixed and dissolved at a ratio 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 gel fiber obtained was heated to 450 to 500 ° C. at a rate of 5 ° C./min and heated to 30 to 50 vo at this temperature.
A mixed gas of water vapor and air having a water vapor concentration of 1% was introduced into the heating container and treated for 0.5 to 1 hour. As a result of X-ray diffraction, the obtained fiber was confirmed to be crystalline tin oxide. When the residual halogen content (X1) of the fiber was measured by the fluorescent X-ray method, it was 0.02 to 0.3% by weight. In addition, in Examples 1 to 5, 30 to 50 vo
A tin oxide fiber was produced in exactly the same manner except that a mixed gas of water vapor and air with a water vapor concentration of 1% was not introduced into the heating container, and the residual chlorine amount (X2) of the fiber of the obtained fiber was measured by the fluorescent X-ray method. (Comparative Examples 1 to 5), the result was 0.45 to 1.0% by weight. The amount of residual halogen in the tin oxide fiber of each example (X1), the amount of residual halogen in the tin oxide fiber obtained in the corresponding comparative example (X2), and the residual halogen removal rate by steam treatment (10
0 (X2-X1) / X2 (%)) is shown in Table 1. Examples 6 to 10 and Comparative Examples 6 to 10 Stannous chloride and methanol were mixed with at least one selected from metallic tin, antimony trichloride, tetramethoxysilane and polyethylene glycol at a ratio shown in Table 1, dissolved and uniformly mixed. It became a clear solution. The above solution was concentrated to give a spinning solution composed of a highly viscous sol. Example 1 except that the spinning was performed in the same manner as in Example 1 and the conditions shown in Table 1 were used.
Steam treatment was carried out in the same manner as in (5). When the obtained tin oxide fiber was subjected to fluorescent X-ray analysis, the residual chlorine in the fiber was 0.03% by weight or less. Incidentally, it was confirmed by fluorescent X-ray analysis that antimony and silica were present in the fiber according to the charged composition. Also, as a result of X-ray diffraction, having a peak of tin oxide,
It was confirmed that antimony did not show peaks such as its oxide and was dissolved in tin oxide. Example 6
In Nos. 10 to 10, tin oxide fibers were produced in exactly the same manner except that water vapor was not introduced into the heating container, and the residual chlorine content (X2) of the fibers of the obtained fibers was measured by the fluorescent X-ray method (Comparative Example 6 -10) Where, 0.25
It was 0.40% by weight. The amount of residual halogen in the tin oxide fiber of each example (X1), the amount of residual halogen in the tin oxide fiber obtained in the corresponding comparative example (X2), and the residual halogen removal rate by steam treatment (100 (X2-X1) / X2
(%)) Is shown in Table 1.

[Table 1] Example 11 A gel fiber was prepared in the same manner as in Example 10. The obtained gel fiber was 300 at a rate of 5 ° C / min.
The temperature is raised to ℃ and saturated steam is introduced at that temperature, then 5 ℃
The temperature was raised to 500 ° C. at a speed of / min for 30 minutes. By fluorescent X-ray analysis, it was confirmed that antimony and silica were present in the fiber according to the charged composition. Also, as a result of X-ray diffraction, having a peak of tin oxide,
It was confirmed that antimony did not show peaks such as its oxide and was dissolved in tin oxide. No residual chlorine was detected in the fiber. In addition, Comparative Example 1 shown below
The residual chlorine removal rate calculated from the amount of chlorine remaining in the tin oxide fiber of No. 1 is greater than 98.3%. Comparative Example 11 A tin oxide fiber was produced in the same manner as in Example 11 except that saturated water vapor was not introduced. The residual chlorine content in the obtained fiber was 0.98% by weight. Example 12 A gel fiber was prepared in the same manner as in Example 10. 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. 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. The residual chlorine removal rate calculated from the amount of chlorine remaining in the tin oxide fiber of Comparative Example 12 shown below is higher than 91.6%. Comparative Example 12 A tin oxide fiber was produced in the same manner as in Example 12 except that saturated steam was not introduced. The amount of residual chlorine in the obtained fiber was 0.12% by weight. Example 13 A gel fiber was prepared in the same manner as in Example 10. The obtained fiber was heated to 300 ° C. at a rate of 5 ° C./min, 100 vol.% Of steam was introduced at that temperature, and further heated at a rate of 5 ° C./min to reach 500 ° C. Continued to be introduced. Then, stop introducing steam 50
Heated at 0 ° C. for 0.5 hours. Fluorescence X-ray analysis of the obtained fiber confirmed that antimony and silica were present in the fiber according to the charged 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. No residual chlorine was detected in the fiber. The residual chlorine removal rate calculated from the amount of chlorine remaining in the tin oxide fiber of Comparative Example 13 shown below is 83.3%. Comparative Example 13 A tin oxide fiber was produced in the same manner as in Example 13 except that saturated steam was not introduced. The residual chlorine content in the obtained fiber was 0.60% by weight. Example 14 A gel fiber was prepared in the same manner as in Example 10. The obtained fiber was heated to 500 ° C. at a rate of 5 ° C./min, held at that temperature for 1 hour, and then cooled. The heat-treated fiber was heated to 450 ° C. at a rate of 10 ° C./min, 100 vol.% Steam was introduced, and the fiber was treated for 0.5 hour. Fluorescence X-ray analysis of the obtained fiber 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. Residual chlorine in the fiber is 0.0
It was 6% by weight. The residual chlorine removal rate calculated from the amount of chlorine remaining in the tin oxide fiber of Comparative Example 14 shown below is 86.7%. Comparative Example 14 A tin oxide fiber was produced in the same manner as in Example 14 except that saturated water vapor was not introduced. The residual chlorine content in the obtained fiber was 0.45% by weight.

Claims (1)

[Claims] 1. A method for producing a tin oxide fiber by heating a fiber spun from a solution containing an alcohol and a tin halide compound as main components, which is contacted with steam at a temperature of 60 ° C. or higher before or after heating. A method for producing a tin oxide fiber, which comprises: