JP3504094B2 - Method for producing tin oxide fiber - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing tin oxide fibers.

[0002]

2. Description of the Related Art Tin oxide has excellent chemical resistance and heat resistance,
Moreover, it is an excellent material capable of controlling conductivity in a wide range and is used for various purposes. Recently, research is also progressing as a third-order nonlinear optical material.

In a gas sensor, it has been strongly desired to provide tin oxide in a fiber shape from the viewpoint of improving sensitivity and response speed. Further, carbon fibers and the like have been added for the purpose of imparting conductivity to polymer materials,
When carbon is used, there are problems that the material itself cannot be brightened because it is black and that it is very light and easily scatters. For this reason, it has been practiced to add powders of metal fibers and metal oxides. Although metal fibers have high conductivity, they have the drawback that their surface is oxidized or corroded over a long period of time to lower their conductivity. In addition, the conductivity of conventional metal oxide powders is not as high as that of metal fibers, so in order to impart conductivity to polymer materials, a relatively large amount must be added, and the physical properties inherent in polymer materials deteriorate. There was a drawback that caused it. Even tin oxide, which has excellent chemical resistance and heat resistance, has been attempted to be added in the form of powder that imparts conductivity. 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 having conductivity into a fiber.

However, it has been difficult to manufacture fibers by the conventional solid-phase reaction method. Therefore, JP-A-60-5997, JP-A-60-161337, and JP-A-60-158199 propose methods for producing tin oxide fibers by a melt precipitation method. However, since these methods require a high temperature of 1000 ° C. or more and a reaction time of many days, it is possible to produce a very small amount on a laboratory scale, but it has not been industrially produced yet. . Moreover, the shape of the obtained tin oxide fiber is 1 μm or less in diameter and 3 in length.
When it is used as a composite material, there is a problem that its function cannot be sufficiently exerted and its application is limited because the aspect ratio is small when it is less than or equal to mm and the cross section is often rectangular. Furthermore, since the major axis is too small, it is difficult to produce a non-woven fabric, a paper-like material 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 fiber diameters and lengths of tin oxide were to be made uniform, there was no choice but to classify what was accidentally produced. Therefore, the whiskers produced by such an inefficient method are extremely expensive and practically unusable.

The present inventors surprisingly exhibited spinnability when a solvent containing a tin compound and an alcohol as a main component was used. By spinning and heating the spinnable compound, it was possible to oxidize it easily and at extremely low cost. It was found that a tin fiber can be obtained, and it has already been proposed (JP-A-4-35287, JP-A-5-35287).
-117906, JP-A-5-179512).

[0006]

Among them, when heat-treating a gel fiber spun from a spinning solution which employs tin halide as a tin compound, halogen or hydrogen halide is generated at a high temperature and a heat treatment furnace is used. There is a problem of damaging the material, and it was required to solve this problem in industrialization.

[0007]

Therefore, as a result of diligent studies, the inventors of the present invention have found that when the temperature is kept at 500 ° C. or lower for a certain period of time in a steam atmosphere, the amount of halogen in the tin oxide fiber is reduced, and subsequently at high temperature. It has been found that the amount of halogen generated even when the heat treatment is performed is small, so that the damage of the heat treatment furnace is reduced and the material of the heat treatment furnace can be selected in various ways, and the present invention has been completed here.

That is, according to the present invention, a tin oxide gel fiber spun from a spinning liquid for tin oxide fiber containing halogen is heat-treated at a temperature of 500 ° C. or lower in an atmosphere containing water vapor, and then heated at a temperature higher than 500 ° C. It is a method for producing tin oxide fiber, which is characterized in that it is treated.

Next, the present invention will be described more specifically.

The solvent used in the spinning solution for tin oxide fiber used in the present invention is not particularly limited as long as it dissolves the tin compound and metallic tin which will be described later, but is generally an organic solvent such as alcohol or acetone, or an alcohol such as alcohol. Examples include a mixed solution of an organic solvent and water. When alcohol is represented by the general formula ROH, R is an unsubstituted alkyl group such as methyl group, ethyl group, propyl group, butyl group and octyl group, 2-methoxyethyl group, 2-ethoxyethyl group, 2-hydroxyethyl group, 1-methoxy-2-propyl group. Group, a methoxyethoxyethyl group, a 2-phenylethyl group, a substituted alkyl group such as a phenylmethyl group, an unsubstituted alkenyl group such as an allyl group, a substituted alkenyl group such as a 2-methyl-2-propenyl group, and a 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 alkoxy groups such as methoxy group and ethoxy group, hydroxyl group, phenyl group and the like which are found in the above-mentioned specific examples of R. In addition to the aryl group, the alkyl group such as a methyl group and an ethyl group, a halogen atom 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-butene-1-ol and the like. Methyl alcohol and ethyl alcohol are particularly preferred because of their high solubility. The above alcohols are usually used alone, but a mixture of two or more kinds of alcohols can be used in order to control the reactivity with metal tin, the solubility, or the like.

The soluble tin compound used in the present invention (hereinafter,
Examples of the tin compound) include tin halides. In particular, from the viewpoint of dissolving the metal tin used in combination,
Tin halide is preferred. The halogen of the tin halide is Cl, Br, I, F atoms. Among these tin halide compounds, tin chloride and tin bromide are preferable in terms of price and stability. Specifically, SnCl ₂ , SnC
l ₂ .2H ₂ 0, SnBr ₂ , SnI ₂ , SnF _{2 and the} like are preferred because of their low halogen content, and Sn is particularly preferred.
Cl ₂ , SnBr ₂ and SnCl ₂ .2H ₂ O are preferably used. Further, the tin halide compound modified with an organic compound such as Sn (CH ₃ ) ₂ Cl ₂ can also be used. Examples of the organic tin compound include (CH ₃ ) ₂ Sn,
It can be used or added within a range in which (C ₂ H ₅ ) ₂ Sn, (C ₃ H ₇ ) ₄ Sn and the like are dissolved.

In the present invention, metallic tin is used in combination to reduce the amount of halogen in the tin oxide fiber spinning solution, to improve the spinnability, and to improve the moisture resistance of the spun tin oxide gel fiber. can do.

The compounding ratio of the tin halide compound and metallic tin is preferably such that the atomic ratio [X / Sn] is 0.6 to 2.0, more preferably 0.6 to 2.0.
It is 1.5. X and Sn represent the numbers of atoms of halogen and tin, respectively. The larger the atomic ratio [X / Sn] is, the more easily the metallic tin is dissolved, but if the atomic ratio [X / Sn] is too large, the gel fiber obtained by spinning the obtained spinning solution has a high hygroscopic property and becomes difficult to dry. Further, if it is less than the above range, it may take a long time to dissolve the metal tin, and precipitation may occur depending on the mixing ratio of the tin compound and the metal tin to the solution.

The mixing ratio of the tin compound, metallic tin and solvent is not particularly limited as long as the tin compound and metallic tin are uniformly dissolved in the solvent. However, if the ratio of the tin compound and the metallic tin is too low, the spinnability is not exhibited, so it is necessary to concentrate the solvent considerably, and the solvent is wasted. Further, if the concentrations of the tin compound and metallic tin are too high, the tin compound is not completely dissolved and the insoluble matter remains, so that a uniform spinning solution cannot be obtained. Therefore, the compounding ratio varies depending on the type of tin compound, metallic tin and solvent used, but generally, the molar ratio of the tin compound and metallic tin to the solvent is preferably 0.01 to 0.5. After mixing at this ratio to form a transparent and uniform solution, the solvent is further evaporated to concentrate the solution to obtain a spinning solution having a desired viscosity.

The shape of metallic tin used in the present invention is not particularly limited, and may be plate-like, rod-like, sheet-like, granular, powder-like, sand-like,
Examples thereof include flower-like ones, and from the viewpoint of easy dissolution, granular, powdery, and sandy ones are preferable. The higher the purity, the better, but it may be appropriately determined depending on the use of the tin oxide fiber. Generally, it is not particularly limited as long as it does not affect the production method and does not affect the specific resistance and mechanical strength and chemical stability described later, but when the obtained tin oxide fiber is used as a battery material. It is better not to include an element that causes a side reaction other than the battery reaction. For example, when the battery is a lead storage battery, metal tin that does not contain hydrogen, such as iron and nickel, or an element having a low oxygen overvoltage is preferable.

In the present invention, it is preferable that oxygen or air be present in the solvent when dissolving the metal tin from the viewpoint of shortening the dissolving time.

The method of absorbing oxygen or air in the solvent is not particularly limited, but a method of forming the solvent in the form of droplets or a liquid film and dispersing it in oxygen or air to absorb it, or a liquid phase containing oxygen or air in the solvent It is possible to use a method in which the solvent is blown in to be dispersed and absorbed, but the latter method is preferable because metallic 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 ones can be adopted, but they are blown into the bottom of the liquid phase in the container by forming fine bubbles to increase the area in contact with the solvent. It is preferable to lengthen the contact time because the dissolution operation time can be shortened. To specifically exemplify these methods, 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 at the tip can be used in the laboratory. Industrially, a bubble column, a bubble stirring tank or the like can be used.

The amount of oxygen or air blown in varies greatly depending on the amount of metal tin to be dissolved and the amount of solvent, but cannot be determined uniquely, but usually it is 1 by volume ratio to the solvent.
The standard is to flow an amount of 1/2 to 1/200 per minute.
Further, the blowing operation is generally performed continuously before and after the metallic tin is put into the solvent until the metallic tin is completely dissolved, but it may be intermittently performed while observing the dissolved state. .

In the present invention, in order to carry out spinning stably and to enhance the mechanical strength and stability of the obtained fiber, silicon, aluminum, germanium,
Titanium, zirconium, magnesium, boron (hereinafter,
(Although sometimes collectively referred to as the second element) alkoxide,
A soluble metal compound such as a halide, an oxychloride, a nitrate, a sulfate, or a phosphate (hereinafter sometimes referred to as a soluble metal compound) may be added to the tin oxide fiber spinning solution. If the acetate salt is also soluble, it can be used.

The amount of the soluble metal compound added is determined by spinning,
The oxide of the second element in the final form produced by the heat treatment may be calculated and determined in advance so that the composition ratio falls within the above range. Usually, the calculated value from the used raw material molar ratio agrees with 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 and silicon halide. As the silicon alkoxide, the general formula Si (OR
Silicon alkoxides represented by _A ) ₄ , R _B Si (OR _A ) ₃ and R _B R _C Si (OR _A ) ₂ are used. Where 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; and a direct group such as an ethenyl group, a propenyl group, a butenyl group, and a pentenyl group. A chain or branched alkenyl group; an aryl group such as a phenyl group is shown. Specific examples of silicon alkoxides include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, propyltrimethoxysilane, and 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 silicon halides 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
Examples include aluminum alkoxides 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 tetraethoxy germanium, and the soluble metal compound of titanium includes TiC.
l ₄ , TiCl ₃ , TiCl ₂ , TiBr ₄ , TiBr ₄ ·
6H ₂ O, TiF ₄ , titanium alkoxides such as tetraisopropoxy titanium, and the like. Soluble metal compounds _{Jirukonimu, ZrCl 4, Zr (NO 3} ) 4 · 5
_{H 2 O, ZrOCl 2 · 8H} 2 O, ZrOI 2 · 8H 2 O,
Zirconium alkoxides such as tetrabutoxy zirconium may be mentioned, and as the soluble metal compound of magnesium, MgCl ₂ .6H ₂ O, MgBr ₂ .6H ₂ O, Mg
(NO ₃ ) ₂ · nH ₂ O, magnesium alkoxide and the like can be mentioned. As a soluble (metal) compound of boron,
Examples thereof include H ₂ B ₄ O ₇ , H ₃ BO ₃ , HBF ₄ , BBr ₂ , and boron alkoxides such as trimethoxyboron.

The soluble metal compound does not have to be the compound from the beginning, but may be the compound in the solution in the beginning. For example, in the case of aluminum halide, metallic aluminum may be added to the solution and tin halide may be blown into the solution to partially halogenate it.

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

By adding the soluble metal compound to the tin oxide fiber spinning solution, it is possible to spin a fiber having a large major axis relatively stably even in a high humidity atmosphere. Further, the gel fiber immediately after spinning is less likely to be softened and crumbled, which makes the handling very easy. Further, the finally obtained fiber has improved chemical stability such as mechanical strength and corrosion resistance.

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

The components of the oxides of the second element such as silica, aluminum oxide, zirconium oxide, magnesium oxide and boron oxide are mostly in the form of a mixture in tin oxide, except for a very small amount which forms a solid solution in tin oxide. It is presumed that they exist dispersedly in. In the case of germanium oxide and titanium oxide, the range of solid solution becomes wider. Also, about 16 to about 82 mol%, or about 12 to about 86 mol%.
When titanium oxide (the range is slightly different depending on the reporter) was added, spinodal decomposition separated tin oxide-rich solid solution and titanium oxide-rich solid solution, and both phases were complexed with a microstructure. Presumed to exist. As a result, besides improving the mechanical strength,
It is promising as a novel fibrous capacitor material and a semiconductor material such as a gas sensor element.

The above-mentioned second element oxides may be contained individually, 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. Particularly when it is desired to increase the tensile strength and the like, it is effective to contain a large amount of the component. Usually, tin oxide is 20 to 98 mol%, and the 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, but it usually does not differ greatly from that calculated by theoretical calculation from the raw material 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 tin oxide fiber spinning solution in order to enable high-speed spinning. As such a high molecular compound, any soluble high molecular compound can be used without any limitation. Specific examples include celluloses such as ethyl cellulose, cellulose acetate, cellulose nitrate, cellulose propionate, cellulose triacetate, acetyl butyl cellulose and hydroxyl propyl cellulose, polyvinyl butyral, polymethylene oxide, polyethylene oxide, polypropylene oxide, polyacetic acid. Vinyl etc. are mentioned. The addition amount of these soluble polymer compounds is 0.0 with respect to the metal tin.
1 to 20% by weight is preferable. If the amount of the soluble polymer compound added is less than 0.01% by weight, a sufficient effect cannot be obtained. On the other hand, if the amount exceeds 20% by weight, the effect is not only saturated, but also when the spun gel fiber is heat-treated, the amount of carbon and carbon dioxide gas generated increases and it is difficult to remove it. Porosity is generated, which is not preferable.

In the present invention, in order to obtain a tin oxide fiber having high conductivity, a soluble group V compound (hereinafter referred to as a group V compound) of the periodic table is contained in the tin oxide fiber spinning solution, if necessary. Can be made. The Group V compound is finally converted into an oxide by the heat treatment described later and is dissolved as a solid solution 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 are required to be soluble, but when the above-mentioned hydrogen halide is dissolved in the solution, a simple substance such as antimony may also be dissolved. Therefore, such a simple substance is also used. be able to.

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
Examples of the niobium compound include NbCl ₅ , NbBr ₅ , NbF ₅ , and NbOC.
l ₃ , alkoxides of niobium, tantalum compounds such as TaBr ₅ , TaCl ₅ and tantalum alkoxides, and antimony compounds such as SbCl ₃ and SbC.
Examples include l ₅ , SbBr ₃ , antimony oxychloride, or antimony alkoxide, and examples of the bismuth compound include BiCl ₃ , BiI ₃ , and bismuth alkoxide.

The blending ratio of the group V compound is determined based on the calculated amount of the oxide of the group V element in the tin oxide fiber in consideration of the intended conductivity.

The method of dissolving the tin metal, the soluble metal compound, the soluble polymer compound, the soluble group V compound and the solvent such as alcohol is not particularly limited. For example, a method of dissolving metal tin, a soluble metal compound, a soluble polymer compound, and a soluble Group V compound in a solvent such as alcohol under stirring simultaneously or sequentially can be used. The temperature condition at the time of dissolution is not particularly limited, and is usually room temperature to
Although it is carried out within the boiling temperature range of the solvent, it is also effective to reflux the solvent in order to promote the dissolution.
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, or an organic acid such as tartaric acid, succinic acid, or lactic acid is added to tin It may be optionally contained as a complexing agent, and it is also 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, a method of extruding a spinning solution from a spinning nozzle can be used. The major axis, the diameter, etc. of the obtained fiber can be arbitrarily controlled by adjusting the viscosity of the spinning solution, the nozzle diameter, the speed at which the spinning solution is extruded from the spinning nozzle, and the like.

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 may be performed at the same time as the heat treatment described below, but it is preferable to perform the drying before the heat treatment in order to obtain a good fiber. In these cases, the drying temperature is preferably as low as possible in order to prevent the occurrence of cracks in the obtained fiber, but when an alcohol 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. Typical drying temperature is room temperature ~
It is preferably in the range of 200 ° C.

The heat treatment of the gel fiber removes an organic solvent such as alcohol, water, halogen or the like from the gel fiber to form a Sn—O—Sn bond or the like to strengthen the skeleton of the fiber and further crystallize it. Done at temperature. The gel fiber as-spun from the spinning solution does not have sufficient Sn—O—Sn bond formed as it is, and does not exhibit sufficient mechanical strength or chemical stability such as corrosion resistance. Further, when the Group V compound is added to improve the conductivity of the obtained fiber, the heat treatment is necessary. The gel fiber as spun from the spinning solution does not show sufficient conductivity as it is. As for conductivity, Sn gel is obtained by heating gel fiber to remove organic solvent such as alcohol, water, or halogen from gel fiber.
-O-Sn bond and the like are formed, and the group V element is expressed by solid solution in tin oxide. From this perspective,
The heat treatment is preferably performed at a temperature higher than 500 ° C. It can be confirmed that crystallization has started by X-ray diffraction even with heat treatment at 300 ° C, but crystallization is not sufficient,
Further, chemical stability such as corrosion resistance against acids and alkalis is not yet sufficient. On the other hand, if the heat treatment temperature is too high, decomposition of tin oxide proceeds, crystal grains in the fiber grow too much, the fiber strength decreases, and energy is wasted. For the above reason, the heat treatment temperature exceeds 500 ° C and 1550 ° C.
The range of ℃ or less is preferable. More preferably 600 to 120
It is preferable to perform heat treatment at a temperature of 0 ° C.

What is important in the present invention is 500
That is, the heat treatment is carried out at a temperature of ℃ or less to remove the hydrogen halide in the gel fiber or the halogen bonded to the element constituting the gel fiber. If heat treatment is directly performed at a temperature exceeding 500 ° C to remove halogen, a large amount of hydrogen halide and halogen will be 500 ° C.
Direct contact with the constituent materials of the electric furnace at a temperature of over 100 ° C. damages the electric furnace in a short time. At present, as a material having high corrosion resistance against hydrogen halide and halogen at a high temperature of more than 500 ° C., it is difficult to find any materials other than ceramics and quartz glass. Quartz glass etc. are expensive,
Since it is not possible to manufacture a large one, tin oxide fibers cannot be industrially produced in large quantities.

As a result of various studies to solve the above problems, the higher the heat treatment temperature, the easier it is to remove hydrogen halide and halogen. However, even at a low temperature of 500 ° C. or less, a certain period of time is maintained in a steam atmosphere. Then, it was found that the halogen in the gel fiber was reduced. In this case, since the amount of hydrogen halide and the amount of halogen generated will be small even if the subsequent heat treatment at a temperature exceeding 500 ° C.,
The damage to the constituent materials of the electric furnace is reduced, and the method is suitable for industrialization.

In the present invention, the heat treatment atmosphere is preferably an air or oxygen atmosphere in order to remove the carbon component existing in the gel fiber or to turn tin or a Group V element into an oxide. .

Furthermore, when heat treatment is performed at a temperature of 500 ° C. or lower, it is preferable to use an atmosphere containing water vapor in order to remove hydrogen halide in the gel fiber and halogen combined with the elements constituting the gel fiber. is necessary. If the atmosphere containing water vapor is not used, it takes a long time to remove the hydrogen halide and the halogen, resulting in very poor efficiency. Introducing water vapor into the heat treatment atmosphere reduces the amount of halogen in the fiber. Further, from the viewpoint of reducing the amount of halogen in the fiber, the sulfur-containing compound may be introduced into the heat treatment atmosphere, or the compound may be contained in the tin oxide fiber spinning solution in advance.

The method of making the atmosphere of water vapor is not limited at all, and a known method can be adopted. For example, water vapor obtained by heating water in a boiler or the like to vaporize it under atmospheric pressure or under pressure is introduced into the heat treatment atmosphere. After the introduction, the heat treatment atmosphere may be kept in a water vapor atmosphere by forming a sealed system, but it is preferable to continuously flow a gas such as air containing water vapor into the heat treatment atmosphere in order to improve the halogen removal efficiency. When heat treatment is performed in a normal air or oxygen atmosphere, the amount of water vapor present in the atmosphere is small. In the present invention, it is important to positively adopt a water vapor atmosphere, and the amount of water vapor in the atmosphere may be at least 10% by volume.

Further, it is preferable to use a steam atmosphere also in the heat treatment at a temperature exceeding 500 ° C.,
In particular, treatment at a temperature of 500 ° C. or lower in an atmosphere containing water vapor has an advantage that polycondensation is promoted in the gel fiber and the bond is strengthened. However, if the gel fiber is treated in an atmosphere containing water vapor at an excessively low temperature, the shape of the gel fiber may collapse. Therefore, the temperature in the atmosphere containing water vapor is preferably 150 ° C. or higher, more preferably 200 ° C. or higher. is there. However, since the fiber once treated at a temperature of 150 ° C. or 200 ° C. or higher has a skeleton formed to some extent, the shape of the fiber does not collapse even if treated at room temperature to an atmosphere containing water vapor.

The holding time at a heat treatment temperature of 500 ° C. or lower is the amount of halogen in the spinning solution used, the type of additive, the heating rate of the electric furnace, the holding temperature, the steam partial pressure, the oxygen partial pressure, the flow rate, etc. Since it depends on, it cannot be decided uniquely. It is only necessary to change the holding time at a certain temperature of 500 ° C. or lower, measure the halogen content in the fiber, and determine the optimum conditions in advance. The important point is to reduce the amount of halogen in the fiber at a low temperature of 500 ° C. or lower, and then heat-treat at a temperature higher than 500 ° C.

The specific resistance value of the tin oxide fiber obtained from the spinning solution for tin oxide fiber containing the Group V compound of the present invention is large depending on the kind of the Group V compound, the addition amount, the firing atmosphere and the firing temperature. Usually 10
It can take values of ³ to 10 ^-1 Ω · cm. A value of 10 ⁻⁴ Ω · cm can be obtained by firing in a reducing atmosphere.

[0049]

According to the method of the present invention, a method for producing tin oxide fiber, which has less damage to an electric furnace and is suitable for industrialization, can be established.

[0050]

EXAMPLES The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 318.71 g (1.68) of stannous chloride (SnCl ₂ ).
Mole) and metallic tin (Sn) 275.41 g (2.3
(2 mol) was added to 1,920 g of methanol and dissolved with stirring. After dissolution, antimony trichloride (SbC
l ₃ ) 48.1 g (0.211 mol) and tetraethoxysilane 92.5 g (0.444 mol) 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 continuously wound on a drum. The gel fiber thus obtained was allowed to stand at room temperature for 1 day, then heated to 400 ° C. at a rate of 1 ° C./min, and kept at that temperature for 4 hours. Also, the temperature is 200 ℃
Then, a mixed gas of steam and air having a steam concentration of 50 vol% was introduced into the heating container. The amount of residual chlorine in the fiber taken out after the temperature was separately lowered was 0.6% by weight. This fiber is 800 ℃ at a speed of 2 ℃ / min
The temperature was raised to, and the temperature was maintained for 2 hours for heat treatment. The obtained fiber had an average diameter of 30 μm, and it was confirmed by fluorescence X-ray analysis that antimony and silica were present in the fiber according to the charged composition.
No chlorine was detected. Further, as a result of X-ray diffraction, it was confirmed that it had a peak of tin oxide, and that the peak of antimony was not found in the oxide thereof and was dissolved in tin oxide. The specific resistance of the obtained fiber is 1Ω on average.
It was cm. The tensile strength of the fiber was 40 MPa on average.

Example 2 Gel fibers were spun in the same manner as in Example 1. After leaving the obtained gel fiber at room temperature for 1 day, 1 ° C / min
The temperature was raised to 300 ° C. at the rate of and the temperature was maintained for 7 hours. Further, after the temperature reached 200 ° C., a mixed gas of steam and air having a steam concentration of 50 vol% was introduced into the heating container. The residual chlorine content in the fiber taken out after the temperature was separately lowered was 1.0% by weight. This fiber is 2 ℃ /
The temperature was raised to 800 ° C. at a rate of min and the temperature was maintained for 2 hours for heat treatment. The obtained fiber had an average diameter of 30 μm, and it was confirmed by fluorescence X-ray analysis that antimony and silica were present in the fiber according to the charged composition, and chlorine was not detected. Also, X
As a result of the line diffraction, it was confirmed that it had a tin oxide peak and that antimony was not dissolved in tin oxide without a peak of its oxide or the like. The specific resistance of the obtained fiber was 1 Ω · cm on average. The tensile strength of the fiber was 40 MPa on average.

Example 3 Gel fibers were spun in the same manner as in Example 1. After leaving the obtained gel fiber at room temperature for 1 day, 1 ° C / min
The temperature was raised to 500 ° C. at the rate of and the temperature was maintained for 1 hour. At this time, 50vol% after the temperature reached 200 ℃
A mixed gas of water vapor and air having a water vapor concentration of was introduced into a heating container. The residual chlorine content of the sample taken out after the temperature was separately lowered was 0.03% by weight. This fiber is 2 ℃ / mi
The temperature was raised to 800 ° C. at a rate of n, and the temperature was maintained for 2 hours for heat treatment. 30 fibers on average
It had a diameter of μm, and it was confirmed by fluorescence X-ray analysis that antimony and silica were present in the fiber according to the charged composition, and chlorine was not detected. Further, as a result of X-ray diffraction, it was confirmed that it had a peak of tin oxide, and that the peak of antimony was not found in the oxide thereof and was dissolved in tin oxide. The specific resistance of the obtained fiber was 1 Ω · cm on average. The tensile strength of the fiber was 40 MPa on average.

Comparative Example 1 A gel fiber produced in the same manner as in Example 1 was heated to 400 ° C. at a rate of 1 ° C./min in air (water vapor concentration 1.2 vol%) without introducing water vapor. The temperature was lowered without being held at that temperature. The residual chlorine content in the fiber taken out after the temperature was lowered was 4.6% by weight.

Comparative Example 2 A gel fiber produced in the same manner as in Example 1 was heated to 300 ° C. at a rate of 1 ° C./min in air (water vapor concentration 1.2 vol%) without introducing water vapor. The temperature was lowered without being kept at that temperature. The residual chlorine content of the sample taken out after cooling was 8.8% by weight.

Comparative Example 3 The gel fiber produced in the same manner as in Example 1 was heated to 800 ° C. at a rate of 1 ° C./min in air (water vapor concentration 1.2 vol%) without introducing water vapor. But 50
A large amount of hydrogen halide or halogen was generated at a temperature exceeding 0 ° C., which damaged the electric furnace.

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Claims (2)

(57) [Claims] 1. A tin oxide gel fiber spun from a tin oxide fiber spinning solution containing halogen is heat-treated at 500 ° C. or lower in an atmosphere containing water vapor, and then 50
A method for producing a tin oxide fiber, which comprises heat-treating at a temperature exceeding 0 ° C. 2. A water vapor concentration in an atmosphere containing water vapor is 1
The method for producing a tin oxide fiber according to claim 1, wherein the content is 0% by volume or more.