JPH10168666A - Production of tin oxide precursor solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject transparent and homogeneous solution in a short time by blowing oxygen or air into a liquid phase when a soluble tin compound and metal tin are dissolved in a solvent. SOLUTION: When a soluble tin compound and metal tin are dissolved in a solvent (e.g. an alcohol), oxygen or air is blown into the liquid phase to increase solubility of metal tin. The resultant tin oxide precursor solution is concentrated to provide a spinning solution for tin oxide fiber excellent in spinnability. The spinning solution is spun and subjected to heat treatment to provide tin oxide fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a tin oxide precursor solution.

[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 in a wide range, and is used for various applications. Recently, studies have been made on third-order nonlinear optical materials.

[0003] In gas sensors, it has been strongly desired to provide tin oxide in the form of a fiber from the viewpoint of improving sensitivity and response speed. Further, carbon fibers and the like are added for the purpose of imparting conductivity to the polymer material.
When carbon is used, there are problems in that the material itself cannot be colored because it is black, and that it is very light and easily scattered. For this reason, powders of metal fibers and metal oxides have been added. Although the metal fibers have high conductivity, there is a disadvantage that the surface is oxidized or corroded after a long time, and the conductivity is reduced. In addition, conventional metal oxide powders are not as high in conductivity as metal fibers, so they must be added in relatively large amounts in order to impart conductivity to polymer materials, lowering the intrinsic properties of polymer materials. There was a drawback to make it. Attempts have been made to add tin oxide having excellent chemical resistance and heat resistance in the form of a powder having conductivity. By the way, it is known that the effect of imparting conductivity increases as the aspect ratio of the material imparting conductivity increases. For this reason, there has been a demand for the formation of conductive tin oxide fibers.

However, it has been difficult to produce fibers by the conventional solid-state reaction method. For this reason, JP-A-60-5997, JP-A-60-161337 and JP-A-60-158199 propose methods for producing tin oxide fibers by a melt deposition 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 fiber is 1 μm or less in diameter and 3 μm in length.
mm or less, the aspect ratio is small, and the cross section is often rectangular. Therefore, when used as a composite material, its function cannot be sufficiently exerted, and its use is limited. Furthermore, it was difficult to produce a paper-like material or the like because the major axis was too small. 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 whisker to be added with good reproducibility. However, it is actually difficult to control the shape of the tin oxide whiskers. Therefore, if the diameter and length of the tin oxide to be added were to be made uniform, it was necessary to classify the tin oxide whiskers by accident. Therefore, whiskers made by such an inefficient method are extremely expensive and cannot be used in practice.

The inventors of the present invention have surprisingly found that the use of a solution containing a tin compound and an alcohol as a main component exhibits spinnability, which can be easily and very inexpensively oxidized by spinning and heating. It has been found that a tin fiber can be obtained and has already been proposed (JP-A-4-35287, JP-A-5-35287).
-117906, JP-A-5-179512).

[0006]

Although the above method is an excellent method, there has been a demand for a precursor solution which is excellent in spinnability and facilitates drying of the obtained tin oxide gel fiber. Therefore, it has been found that when metal tin is used as a raw material at the time of preparing the precursor solution, a precursor solution having excellent spinnability can be prepared and the obtained tin oxide gel fiber can be easily dried. It takes a long time for dissolution, which is problematic.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, when oxygen or air is blown in when dissolving the metal tin, the metal tin dissolves efficiently and becomes transparent in a short time. And a uniform tin oxide precursor solution is obtained, and when the solution is concentrated, a spinning solution for a tin oxide fiber having excellent spinnability is obtained. Further, when the spinning solution is spun and heat-treated, a tin oxide fiber is obtained. In addition, the inventors have found that a tin oxide film can be obtained by coating the precursor solution and then performing a heat treatment, thereby completing the present invention.

That is, the present invention is characterized in that, when a soluble tin compound and metallic tin are dissolved in a solvent to produce a tin oxide precursor solution, oxygen or air is blown into a liquid phase to dissolve metallic tin. This is a method for producing a precursor solution.

Another invention is characterized in that the precursor solution is concentrated, and a spinning solution for tin oxide fibers having improved spinnability is spun into tin oxide gel fibers, and the gel fibers are then heat-treated. This is a method for producing a tin oxide fiber.

Next, the present invention will be described more specifically. The tin oxide precursor solution of the present invention is applicable for coating or for spinning tin oxide fibers. In the case of coating, the precursor solution having a relatively low viscosity is coated on a substrate and then subjected to a heat treatment to obtain a tin oxide coating film. When a spinning solution of tin oxide fiber is used, the spinning solution is once concentrated to enhance spinnability, then spun as described later, and then subjected to heat treatment to obtain tin oxide fiber. Hereinafter, the present invention will be described for use in spinning tin oxide fibers, but is not limited thereto.

The solvent used in the present invention is not particularly limited as long as it can dissolve a tin compound and metal tin described below. In general, an organic solvent such as alcohol and acetone, or a mixed solution of an organic solvent such as alcohol and water is used. No.

When the alcohol is represented by the general formula ROH, R
Represents an unsubstituted alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, and an octyl group; a 2-methoxyethyl group;
-Ethoxyethyl group, 2-hydroxyethyl group, 1-methoxy-2-propyl group, methoxyethoxyethyl group,
Substituted alkyl groups such as 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.

Specific examples of the substituent in the above-mentioned substituted alkyl group, substituted alkenyl group or substituted aryl group include alkoxyl groups such as methoxy group and ethoxy group, hydroxyl group, phenyl group, etc. And an alkyl group such as an aryl group, a methyl group, and an ethyl group, and a halogen such as an amino group, a cyano group, a Cl atom, a Br atom, an I atom, and an F atom.

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. Particularly, methyl alcohol and ethyl alcohol are preferable because of high solubility. The above-mentioned alcohol is usually used alone, but a mixture of two or more alcohols can be used to control the reactivity with metal tin or the solubility.

The soluble tin compound used in the present invention (hereinafter referred to as "the tin compound")
Examples of the tin compound include tin halide and organotin. In particular, tin halide is preferred from the viewpoint of dissolving the metal tin used in combination. The halogens of the tin halide are Cl, Br, I, and F atoms. Among these tin halide compounds, tin chloride and tin bromide are preferred in view of price and stability. Specifically, SnC
l ₂ , SnCl ₂ · 2H ₂₀ , SnBr ₂ , SnI ₂ , Sn
F ₂ and the like preferably from lack of the halogen content, _{particularly, SnCl 2, SnBr 2, SnCl} 2 · 2H 2 O
Is preferably used. The tin halide compound modified with an organic compound, for example, Sn (CH ₃ )
₂ Cl ₂ or the like can also be used. As the organic tin compound, (C
H _{3) 2} Sn, can be used or added within a range that dissolves _{(C 2 H 5) 2 Sn} , is (C ₃ H _{7) 4} Sn or the like.

The shape of the metallic tin used in the present invention is not particularly limited, and may be plate, rod, sheet, granule, powder, sand, etc.
A flower-like thing is mentioned, and a granular thing, a powder-like thing, and a sand-like thing are preferable from the point of the ease of melt | dissolution. Higher purity is preferable, but it does not affect the manufacturing method and is not particularly limited as long as it does not affect the reproducibility of the specific resistance described later, but when the obtained tin oxide fiber is used as a battery material, Should not contain an element that causes a side reaction other than the battery reaction. For example, when the battery is a lead-acid battery, hydrogen such as iron or nickel or metal tin containing no element having a low oxygen overvoltage or the like is preferable.

The mixing ratio of the tin halide compound and the metal tin is preferably such that the atomic ratio [X / Sn] is 0.6 to 2.0, more preferably 0.6 to 2.0.
1.5. X and Sn represent the number of atoms of halogen and tin, respectively. The higher the atomic ratio [X / Sn], the easier the metal tin is to dissolve. However, if the atomic ratio is too high, the gel fiber obtained by spinning the spinning solution for a tin oxide fiber has high hygroscopicity and is difficult to dry. If it is smaller than the above range, it may take a long time to dissolve the metal tin, or precipitation may occur depending on the mixing ratio of the tin compound, the metal tin, and the solvent.

The mixing ratio of the tin compound, metallic tin and the solvent is not particularly limited as long as the tin compound and metallic tin are uniformly dissolved in the solvent. However, when the ratio of the tin compound to the metal tin is too low, the spinning property is not exhibited, so that it is necessary to considerably concentrate the solvent, and the solvent is wasted. On the other hand, if the concentrations of the tin compound and the metal tin are too high, they do not completely dissolve and insolubles remain, so that a uniform spinning solution cannot be obtained. Accordingly, the mixing ratio varies depending on the type of the tin compound, metal tin and the solvent used, but generally, the usage ratio of the tin compound and metal tin to the solvent is preferably 0.01 to 0.5 in a molar ratio. After blending in this ratio to form a transparent and uniform solution, the solvent is further evaporated and concentrated to obtain a spinning solution for tin oxide fibers having a desired viscosity.

In the present invention, when dissolving the metal tin, it is important to blow oxygen or air into the liquid phase. Japanese Patent Application Laid-Open No. 58-185436 proposes blowing air in dissolving stannous chloride. This is said to be effective for preventing the obtained solution from becoming cloudy for a long period of time and for dissolving stannous chloride in a short time. However, in the present invention, the dissolution time of stannous chloride is short and the stability of the precursor is high,
It doesn't matter at all.

The problem in the present invention was how to dissolve metallic tin. As a result of various studies, the present inventors have found that when a dissolving operation is performed while oxygen or air is actively blown into a liquid phase, metallic tin is dissolved in a short time. Although the present inventors cannot sufficiently explain the reason, since metal tin is a metal having a high hydrogen overvoltage, the remaining electrons generated when metal tin changes from zero valence to divalent or tetravalent are converted into protons or protons. It is also presumed that the reaction of receiving water to become hydrogen hardly proceeds on metal tin. In this case, it is considered that the metal tin becomes difficult to dissolve because no electrons are consumed. It may also be related that an organic solvent is a main component as a solvent. Therefore, if oxygen is present in the solution, a reaction in which oxygen is consumed by electrons generated when the metal tin is dissolved is likely to occur, and it is presumed that the reaction proceeds to facilitate the dissolution.

The method of absorbing oxygen or air into the solvent is not particularly limited, but the method of dispersing and absorbing oxygen or air in the form of droplets or a liquid film of the solvent in oxygen or air, or the method of absorbing oxygen or air from the solvent A method in which the solvent is blown into and dispersed and absorbed can be used, but the latter method is employed in the present invention because the metal tin is contained in the solvent.

The method and apparatus for blowing oxygen or air into the liquid phase composed of the solvent are not particularly limited, and known methods can be employed. It is preferable that the contact time is prolonged by blowing into the bottom, because the dissolving operation time can be shortened. When these methods are specifically exemplified, a method in which oxygen or air filled in a cylinder is blown into a solvent in the form of small bubbles through a tube having a glass filter or the like at the tip can be used in a laboratory. Industrially, a bubble tower, a bubble stirring tank, or the like can be used.

The amount of oxygen or air blown depends on the amount of the solvent,
The method of dissolving the metal tin varies depending on the amount of the metal tin and the like, and thus cannot be determined unconditionally. The blowing operation is generally performed continuously before and after the metal tin is introduced into the solvent until the metal tin is completely dissolved, but may be performed intermittently while observing the dissolved state. .

In the present invention, in order to stably perform spinning and to increase the mechanical strength and stability of the obtained fiber, silicon, aluminum, germanium,
Titanium, zirconium, magnesium, boron (hereinafter, referred to as
Alkoxides).
A soluble metal compound such as a halide, oxychloride, nitrate, or sulfate (hereinafter sometimes referred to as a soluble metal compound) may be added to the spinning solution for tin oxide fibers. Acetate can also be used if it is soluble.

The amount of the soluble metal compound to be added is determined by spinning,
What is necessary is just to calculate and determine in advance so that the oxide of the second element in the final form generated by the heat treatment has a composition ratio within the above range. Usually, the calculated value from the used raw material molar ratio matches the molar ratio of the oxide of the second element in the tin oxide fiber.

Examples of the soluble metal compound of silicon include silicon alkoxide, silicon halide and the like. As the silicon alkoxide, the general formula Si (OR
_{A) 4, R B Si (} OR A) 3, R B R C Si ( silicon alkoxide represented by OR _{A) 2} 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 silicon alkoxide include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, propyltrimethoxysilane, n-butyltrimethoxy Silane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, n-octadecyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, amyltriethoxysilane, phenyltriethoxysilane,
n-octyltriethoxysilane, n-octadecyltriethoxysilane, n-dodecyltriethoxysilane,
Methyltributoxysilane, ethyltributoxysilane, ethyltripropoxysilane, vinyltriethoxysilane, allyltriethoxysilane, diphenyldimethoxysilane, dimethyldiethoxysilane, vinylmethyldiethoxysilane, diethyldimethoxysilane, ethylmethyldiethoxysilane, etc. Is mentioned. Examples of the silicon halide include SiCl ₄ , SiHCl ₃ , and SiH ₂ Cl ₂ .

Examples of soluble metal compounds of aluminum include AlCl ₃ , AlCl ₃ .6H ₂ O, and AlB
_{r 3, AlBr 3 · 6H 2} O, AlI 3, AlI 3 · 6H
_{2 O, Al (NO 3)} 3 · 9H 2 O, Al (NO 3) 3 · 6H
Alkoxides of aluminum such as ₂ O and aluminum isopropoxide.

Examples of the soluble metal compound of germanium include germanium alkoxides such as GeCl ₄ , GeBr ₂ , GeBr ₄ , and tetraethoxygermanium. Examples of the soluble metal compound of titanium include TiC
l ₄ , TiCl ₃ , TiCl ₂ , TiBr ₄ , TiBr _4.
Examples include titanium alkoxides such as 6H ₂ O, TiF ₄ , and tetraisopropoxy titanium. ZrCl ₄ , Zr (NO ₃ ) ₄ .5 include soluble metal compounds of zirconium.
_{H 2 O, ZrOCl 2 · 8H} 2 O, ZrOI 2 · 8H 2 O,
Zirconium alkoxides such as tetrabutoxy zirconium; and the soluble metal compounds of magnesium include MgCl ₂ .6H ₂ O, MgBr ₂ .6H ₂ O, Mg
(NO ₃ ) ₂ .nH ₂ O, magnesium alkoxide and the like. As a soluble metal compound of boron, H ₂
Boron alkoxides such as B ₄ O ₇ , H ₃ BO ₃ , HBF ₄ , BBr ₂ , and trimethoxyboron are exemplified.

The soluble metal compound does not need to be the compound from the beginning, and may be the compound in the solution at an early stage. For example, in the case of aluminum halide, metal aluminum may be added to the solution, and hydrogen halide may be blown into the solution to partially halogenate the solution.

When the soluble metal compound is a zirconium compound, the tetragonal or cubic crystal of zirconium oxide formed in the tin oxide fiber is stabilized or meta-stabilized to increase the strength or increase the oxygen ion conductivity. As the raw materials of the rare earth oxides such as calcium oxide, magnesium oxide and other alkaline earth oxides, yttrium oxide, cerium oxide, neodymium oxide, samarium oxide, gadolinium oxide, europium oxide, scandium oxide, etc. Soluble raw materials such as alkoxides, chlorides, oxychlorides, nitrates, sulfates, and acetates can be used.

By adding the above-mentioned soluble metal compound to the spinning solution for tin oxide fibers, fibers having a large diameter can be spun relatively stably even in a high humidity atmosphere. In addition, the gel fiber immediately after spinning is less likely to be softened and easily collapsed, so that handling becomes very easy. Further, the mechanical strength and stability of the finally obtained fiber are improved.

Depending on the heat treatment temperature, tin oxide exists in either amorphous or crystalline form. However, in order to obtain highly conductive one, crystalline is preferred. Further, the alcohol-soluble metal compound becomes an oxide of the second element by a heat treatment described later. It is presumed that tin oxide exists as a solid solution partially containing the oxide of the second element and mostly in the form of a mixture. In the case of solid solution, the second element replaces the tin atom in the tin oxide, or penetrates and exists in the crystal structure of the tin oxide. Sometimes.
In addition, even when the second element does not form a solid solution and exists in the form of a mixture, most of the second element subjected to heat treatment in an atmosphere in which oxygen is present becomes an oxide, but is partially contained without being oxidized. In some cases.

Components such as silica, aluminum oxide, zirconium oxide, magnesium oxide, and boron oxide, which are oxides of the second element, are mostly in the form of a mixture in tin oxide, except for a very small amount of solid solution in tin oxide. It is presumed that they exist in a dispersed manner. In the case of germanium oxide and titanium oxide, the range of solid solution is further widened. About 16 to about 82 mol%, or about 12 to about 86 mol%
In the case of adding titanium oxide (the range is slightly different depending on the reporter), tin oxide is separated into a solid solution rich in titanium oxide and a solid solution rich in titanium oxide by spinodal decomposition, and both phases are combined in a microstructure. It is considered to be present. As a result, besides improving mechanical strength,
It is promising as a new fibrous capacitor material and a semiconductor material such as a gas sensor element.

The oxides of the second element may be contained alone, or a plurality of them may be contained simultaneously. The content of the component is not particularly limited and may be appropriately determined according to the purpose. In particular, when it is desired to increase the tensile strength or the like, it is effective that the component is contained in a large amount. Usually, tin oxide is 20 to 98 mol% and oxide of the second element is 2 to 80 mol%. The composition ratio of the oxide of the second element in the tin oxide fiber can be confirmed by chemical analysis or X-ray fluorescence analysis. However, since there is usually no significant difference from that calculated by theoretical calculation from the raw material ratio, the production ratio When the raw material ratio is clear, it can be calculated from the raw material ratio.

In the present invention, a soluble polymer compound may be added to the spinning solution for tin oxide fibers to enable high-speed spinning. As such a polymer compound, any soluble polymer compound 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 soluble polymer compounds, spinning can be performed without being affected by the humidity in the atmosphere, and spinning can be performed with a low-viscosity spinning solution, so that spinning can be performed at higher speed. The addition amount of these soluble polymer compounds is preferably 0.01 to 20% by weight based on the metal tin. If the amount of the soluble polymer compound is less than 0.01% by weight, a sufficient effect cannot be obtained. On the other hand, even if the content exceeds 20% by weight, the effect is not only saturated, but also when the spun gel fiber is subjected to heat treatment, the amount of carbon and carbon dioxide gas generated increases, making it difficult to remove the gel fiber. It is not preferable because pores are generated.

In the present invention, in order to obtain a tin oxide fiber having high conductivity, a soluble Group V compound of the periodic table (hereinafter referred to as a Group V compound) is optionally contained in the spinning solution for the tin oxide fiber. Can be done. The Group V compound finally becomes an oxide by a heat treatment described later and is dissolved in tin oxide or exists as a mixture.

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. These compounds need to be soluble in alcohol, but when the above-mentioned hydrogen halide is dissolved in the solution, for example, a simple substance such as antimony may be dissolved. Can also be used.

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
Alkoxides of O and vanadium; NbCl ₅ , NbBr ₅ , NbF ₅ , NbOC as niobium compounds
l ₃ , an alkoxide of niobium, and TaBr ₅ , TaCl ₅ , and an alkoxide of tantalum as tantalum compounds; and SbCl ₃ and SbC as antimony compounds.
l ₅ , SbBr ₃ , antimony oxychloride, or alkoxides of antimony, and examples of bismuth compounds include BiCl ₃ , BiI ₃ , alkoxides of bismuth, and the like.

The compounding ratio of the group V compound is determined based on the amount of the oxide of the group V element in the tin oxide fiber in consideration of the desired conductivity, and based on the calculated amount.

The method of dissolving the soluble tin compound, metallic tin, soluble metal compound, soluble polymer compound, and soluble Group V compound in a solvent is not particularly limited. For example,
A method in which a soluble tin compound, metal tin, a soluble metal compound, a soluble polymer compound, and a soluble Group V compound are simultaneously or sequentially dissolved in a solvent such as an alcohol while blowing oxygen or air with stirring is employed. The temperature conditions during dissolution are not particularly limited, and the dissolution is usually carried out in a temperature range from room temperature to the boiling point of the solution. In order to promote the dissolution, it is also effective to reflux the solvent.

In order to further improve the stability of the spinning solution for tin oxide fibers of the present invention, acetylacetone is further added.
A compound having two or more carboxyl groups such as ethyl acetoacetate and diethyl malonate, or an organic acid such as tartaric acid, succinic acid, and lactic acid may be appropriately contained as a tin complexing agent. It is also possible to add compounds to increase.

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 for tin oxide fiber 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 heat treatment of the gel fiber, an organic solvent such as alcohol or water is removed from the gel fiber to strengthen the fiber skeleton.
The crystallization is performed at a temperature for further crystallization. The gel fiber as spun from the spinning solution for tin oxide fiber does not show sufficient mechanical strength as it is. The mechanical strength is developed by heating the gel fiber. The heat treatment temperature is not particularly limited as long as it is within a temperature range where mechanical strength can be imparted to the obtained fiber. When the heat treatment temperature is low, a solvent such as alcohol, water, and the like remain in the fiber, so that sufficient mechanical strength is not generated. If the heat treatment temperature is too high, the decomposition of tin oxide proceeds,
Alternatively, there arises a problem that crystal grains in the fiber grow too much and the strength is reduced. For the above reasons, the heat treatment temperature is preferably in the range of 250 to 1550 ° C. More preferably, the heat treatment is performed at a temperature of 300 to 1500 ° C.

When it is desired to improve the conductivity of the resulting fiber by adding a Group V compound, a heat treatment is also required. The gel fiber as spun from the spinning solution for tin oxide fiber is an insulator as it is, and the conductivity is developed by heating the gel fiber. The heat treatment temperature is not particularly limited as long as it is within a temperature range in which conductivity can be imparted to the obtained fiber. In general, when the heat treatment temperature is low, organic substances such as alcohol, water, etc. remain in the fiber, and the Group V compound does not form an oxide and does not form a solid solution with tin oxide, so that the conductivity is low. Does not occur. If the heat treatment temperature is too high, the Group V compound in the fiber will volatilize and the conductivity will decrease, the decomposition of tin oxide will proceed, and the crystal grains in the fiber will grow too much and the strength will decrease. Occurs. For this reason, the temperature range of 250 ° C. to 1550 ° C. is preferable as the heat treatment temperature. More preferably, the heat treatment is preferably performed at a temperature of 300 ° C to 1500 ° C.

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

Further, it is desirable to remove solvent volatile components such as water and alcohol present in the gel fiber by drying during the heat treatment in order to obtain a good tin oxide fiber. Such drying may be performed simultaneously with the heat treatment, but it is more preferable to perform the drying before the heat treatment in order to obtain a good fiber. In these cases, the drying temperature is preferably performed at a temperature as low as possible in order to prevent occurrence of cracks in the obtained fiber.However, when a solvent having a high boiling point is used as the 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 specific resistance of the tin oxide fiber obtained from the spinning solution for a tin oxide fiber containing a group V compound varies greatly depending on the type and amount of the group V compound, the firing atmosphere and the firing temperature. , 10 ³ -10 ^-1
It can take a value of Ω · cm. When firing in a reducing atmosphere, a value of 10 ⁻⁴ Ω · cm can be obtained.

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

[0049]

According to the method of the present invention, a spinning solution excellent in spinnability can be efficiently obtained by using inexpensive metal tin, and a method for producing an industrially excellent tin oxide precursor solution. Was established.

[0050]

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

Example 1 In a container provided with a tube having a glass filter at the tip,
379.23 g (2.0 mol) of stannous chloride (SnCl ₂ ) and 237.42 g (2.0 mol) of metal tin (Sn) were added to 1,920 g of methanol, and oxygen gas was added to 20 g of methanol.
The mixture was stirred while blowing at a flow rate of 0 ml / min. 24
After an hour, the metallic tin had completely dissolved. This solution was concentrated to prepare a highly viscous spinning solution. The spinning solution was extruded from the nozzle by applying pressure, and was continuously wound on a drum. After leaving the obtained gel fiber at room temperature for 1 day, 1 ° C
/ Min at a rate of 400 ° C / min and then 2 ° C / mi
The temperature was raised to 800 ° C. at a speed of n and held at that temperature for 120 minutes to perform a heat treatment. The obtained fiber had an average diameter of 30 μm, and as a result of X-ray diffraction, it was confirmed that the fiber was tin oxide. The specific resistance of the obtained fiber was 8 × 10 ⁴ Ω · cm on average. The fiber had an average tensile strength of 11 MPa.

Example 2 Using the same container as in Example 1, stannous chloride (SnC
l ₂ ) 318.71 g (1.68 mol) and 275.41 g (2.32 mol) of metal tin (Sn) were added to 1,920 g of methanol, and the mixture was stirred while blowing oxygen gas at a flow rate of 200 ml / min. After 24 hours, the metal tin had completely dissolved. Then, antimony trichloride (S
48.1 g (0.211 mol) of bCl ₃ were added and dissolved. This solution was concentrated to prepare a highly viscous spinning solution. The spinning solution was extruded from the nozzle by applying pressure, and was continuously wound on a drum. The obtained gel fiber was subjected to a heat treatment under the same conditions as in Example 1. The resulting fiber had an average diameter of 30 μm, and fluorescent X-ray analysis confirmed that antimony was present in the fiber as charged. 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. The specific resistance of the obtained fiber is 8 * 10 on average.
^-1 Ω · cm. The tensile strength of the fiber was 6 MPa on average.

Example 3 Using the same container as in Example 1, stannous chloride (SnC
l ₂ ) 318.71 g (1.68 mol) and 275.41 g (2.32 mol) of metal tin (Sn) were added to 1,920 g of methanol, and the mixture was stirred while blowing oxygen gas at a flow rate of 200 ml / min. After 24 hours, the metal tin had completely dissolved. Then, antimony trichloride (S
48.1 g (0.211 mol) of bCl ₃ and 92.5 g (0.444 mol) of tetraethoxysilane were added and dissolved. This solution was concentrated to prepare a highly viscous spinning solution. The spinning solution was extruded from the nozzle by applying pressure, and was continuously wound on a drum. The obtained gel fiber was subjected to a heat treatment under the same conditions as in Example 1. The obtained fiber had an average diameter of 30 μm, and it was confirmed by fluorescent X-ray analysis that antimony and silica were present in the fiber as charged. 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. The specific resistance of the obtained fiber was 1 Ω · cm on average. The fiber had an average tensile strength of 40 MPa.

Example 4 Using the same container as in Example 1, stannous chloride (SnC
l ₂ ) 318.71 g (1.68 mol) and 275.41 g (2.32 mol) of metal tin (Sn) were added to 1,920 g of methanol, and the mixture was stirred while blowing air at a flow rate of 200 ml / min. After 5 days, the metallic tin had completely dissolved. Then, antimony trichloride (SbC
l ₃₎ 48.1 g of (0.211 mol) tetraethoxysilane 92.5 g (0.444 mol) was added dissolved. This solution was concentrated to prepare a highly viscous spinning solution. The spinning solution was extruded from the nozzle by applying pressure, and was continuously wound on a drum. The obtained gel fiber was used in Example 1.
The heat treatment was performed under the same conditions as described above. The resulting fibers have an average diameter of 30 μm and are obtained 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. The specific resistance of the obtained fiber is 1Ω on average.
Cm. The fiber had an average tensile strength of 40 MPa.

Comparative Example 1 The procedure of Example 1 was repeated, except that stirring was carried out without blowing oxygen and air. As a result, the metal tin was dissolved after 20 days. This solution was concentrated to prepare a highly viscous spinning solution.
The spinning solution was extruded from the nozzle by applying pressure, and was continuously wound on a drum. The obtained gel fiber was subjected to a heat treatment under the same conditions as in Example 1. The obtained fiber had an average diameter of 30 μm, and as a result of X-ray diffraction, it was confirmed that the fiber was tin oxide. The specific resistance of the obtained fiber was 8 × 10 ⁴ Ω · cm on average. The fiber had an average tensile strength of 11 MPa.

Claims (3)

[Claims] When producing a tin oxide precursor solution by dissolving a soluble tin compound and metallic tin in a solvent, oxygen or air is blown into a liquid phase to dissolve metallic tin. A method for producing a precursor solution. 2. A method for producing a spinning solution for tin oxide fibers, comprising concentrating the tin oxide precursor solution obtained by the production method according to claim 1. 3. A method for producing a tin oxide fiber, comprising spinning a spinning solution for a tin oxide fiber obtained by the production method according to claim 2 into a tin oxide gel fiber, and then subjecting the gel fiber to a heat treatment. .