JP5514436B2 - Method for producing white conductive powder having tin oxide layer - Google Patents

Description

  The present invention relates to a white conductive inorganic powder having excellent conductivity and causing no environmental pollution, and a method for producing the same. More specifically, the present invention is a white conductive inorganic powder having a conductive tin oxide layer on the surface of a carrier such as titanium oxide, has no risk of causing environmental pollution, has excellent conductivity, and is manufactured. The present invention relates to an easily white conductive inorganic powder and a method for producing the same.

  White conductive powder is currently widely used for antistatic, charge control, antistatic control, dustproof and other applications. Conventionally, conductive powder doped with antimony or the like has been used in order to enhance conductivity, but recently, an antimony-free conductive material is required from the viewpoint of preventing environmental pollution.

  Specifically, conventionally, as the white conductive powder, for example, white conductive powder in which a tin oxide film doped with antimony oxide is formed on the surface of zinc oxide doped with aluminum oxide, titanium dioxide powder or the like (patent) Literature 1, Patent Literature 2). Moreover, the white conductive fiber which formed the conductive film which consists of a tin oxide containing an antimony component in the potassium titanate fiber is known (patent documents 3 and patent documents 4).

Furthermore, a white conductive titanium dioxide powder is known in which a conductive layer containing tin oxide and phosphorus is formed on the surface of titanium dioxide particles (Patent Document 5). However, these powders do not have transparency. As the transparent conductive powder, antimony-doped tin oxide is known (Patent Document 6). However, although the conductive powder doped with antimony oxide has stable conductivity, antimony-free conductive powder is required from the viewpoint of preventing environmental pollution. As the antimony-free conductive powder, one doped with phosphorus is known, but this has unstable conductivity and has a problem of uneven distribution of phosphorus. Moreover, although the powder which reduced hydrogenation of stannic oxide is also known (patent document 7), in hydrogen reduction, it reduces to metal tin and control of reaction is difficult. There are transparent conductive tin oxide powders made of surface-modified non-doped tin oxide, but there are problems such as carbon remaining. Moreover, since it is not a white powder, there also exists a problem that it is not suitable for the use for which a white environment is requested | required from the point of an external appearance or functionality.
JP 58-209002 A Japanese Patent Laid-Open No. 62-180903 JP-A 61-136532 Japanese Patent Application Laid-Open No. 07-053217 International Publication WO2005 / 012449 JP 2006-59806 A JP 2005-108733-5 A

  The present invention is a solution of the above-mentioned problems in conventional conductive powder, and is a white conductive inorganic powder having a conductive tin oxide layer on the surface of a carrier such as titanium oxide, and there is no risk of causing environmental pollution or the like. Provided are a white conductive inorganic powder having excellent conductivity and easy production, and a method for producing the same.

The present invention relates to a method for producing a white conductive inorganic powder that solves the above-described problems with the following configuration.
[1] Using a white inorganic powder having a surface layer of stannic hydroxide on the powder surface, stannous ions ( stannous ions of fluoride are added to stannic hydroxide on the surface of the white inorganic powder in the liquid. The stannic hydroxide is reduced to form stannous hydroxide , and the white inorganic powder recovered by solid-liquid separation is recovered in an inert gas atmosphere and a stannous salt soluble vapor. A method for producing a white conductive inorganic powder containing no antimony, phosphorus and indium, characterized in that a surface layer of conductive tin oxide having oxygen defects is formed by heat treatment in the presence of oxygen.
[2] A white inorganic having a surface layer of stannic hydroxide by mixing a stannic salt solution and an alkali in the presence of the white inorganic powder to deposit stannic hydroxide on the surface of the white inorganic powder. The method for producing a white conductive inorganic powder according to the above [1], wherein the powder is recovered by solid-liquid separation and the white inorganic powder having the recovered stannic hydroxide surface layer is used.
[3] The method for producing a white conductive inorganic powder according to the above [1] or [2], wherein a white conductive inorganic powder having a powder volume resistance of 10 ⁴ Ω · cm or less is produced.
[4] The method for producing a white conductive inorganic powder according to any one of [1] to [3] above, wherein the amount ratio of stannous salt to stannic hydroxide is 10 mol% or less.
[5] The method for producing a white conductive inorganic powder according to any one of [1] to [4] above, wherein titanium oxide powder, potassium titanate powder, and white mica are used as the white inorganic powder.

The white conductive inorganic powder produced by the method of the present invention is a white conductive inorganic powder having high conductivity with a powder volume resistance of 10 ⁴ Ω · cm or less. It is suitable as a conductive material in applications requiring a white environment in terms of appearance and function, for example, interior materials or carpets in semiconductor clean rooms, computer rooms, hospitals, and the like.

In the production method of the present invention, a white inorganic powder having a surface layer of stannic hydroxide is used on the powder surface, and stannous ions (fluoride succinic acid) are added to stannic hydroxide on the surface of the white inorganic powder in a liquid . The stannous hydroxide is reduced to form stannous hydroxide , and the white inorganic powder recovered by solid-liquid separation is recovered in an inert gas atmosphere and stannous hydroxide. A white conductive inorganic powder containing no antimony, phosphorus, and indium, characterized in that a surface layer of conductive tin oxide having oxygen defects is formed by excluding oxygen in the presence of a soluble salt vapor and heat-treating. It is a manufacturing method, and white conductive inorganic powder having high conductivity can be easily manufactured. Moreover, according to the manufacturing method of this invention, control for obtaining desired electroconductivity can also be easily performed by changing the ratio of a stannic hydroxide and a stannous ion.

  Further, since the white conductive inorganic powder produced by the method of the present invention does not contain any of antimony, phosphorus, and indium, there is no concern of causing environmental pollution. Further, since it does not contain antimony, phosphorus, and indium, it is low cost. In the present invention, “antimony, phosphorus, and indium are not included” means that antimony, phosphorus, and indium sources are not used in the raw materials and processes, and therefore these elements are detected by a standard measuring device having a detection limit of 500 ppm. It is said that it is not detected.

  Since the white conductive inorganic powder produced by the method of the present invention has high conductivity without containing a doping component such as antimony, it is used in applications where a white environment is required in terms of appearance and function, such as a semiconductor clean room or a computer. It is suitable as a conductive material for interior materials or carpets in rooms and hospitals.

  Since the white conductive inorganic powder produced by the method of the present invention can be dispersed in water, it can be used as a conductive material such as a dispersion or an aqueous paint. Moreover, the electroconductive film composition containing the white electroconductive inorganic powder of this invention can be formed.

  Hereinafter, the present invention will be specifically described based on embodiments. Unless otherwise indicated, “%” means “% by mass” unless otherwise specified.

In the production method of the present invention, a white inorganic powder having a surface layer of stannic hydroxide is used on the powder surface, and stannous ions (fluoride succinic acid) are added to stannic hydroxide on the surface of the white inorganic powder in a liquid . The stannous hydroxide is reduced to form stannous hydroxide , and the white inorganic powder recovered by solid-liquid separation is recovered in an inert gas atmosphere and stannous hydroxide. A white conductive inorganic powder containing no antimony, phosphorus, and indium, characterized in that a surface layer of conductive tin oxide having oxygen defects is formed by excluding oxygen in the presence of a soluble salt vapor and heat-treating. It is a manufacturing method.

The white conductive inorganic powder produced by the method of the present invention is a white conductive inorganic powder having a powder volume resistance of 10 ⁴ Ω · cm or less. As the white inorganic powder supporting the conductive tin oxide layer, for example, powders such as titanium oxide, potassium titanate, and white mica can be used.

〔Production method〕
Specifically, the white conductive inorganic powder of the present invention is obtained by bringing stannous ions (excluding stannous ions of fluoride) into contact with stannic hydroxide on the surface of the white inorganic powder in a liquid. Stannous hydroxide is reduced to form stannous hydroxide , and solid-liquid separation is performed to recover a white inorganic powder, which is oxygenated in the presence of an inert gas atmosphere and a stannous salt soluble vapor. By eliminating and heat-treating, it is reduced by ionization of the stannous salt to produce oxygen defects, and it can be produced by becoming conductive tin oxide .

  The white inorganic powder having a stannic hydroxide layer on the powder surface reacts with a stannic salt solution and an alkali in the presence of the white inorganic powder to deposit stannic hydroxide on the white inorganic powder surface. Can be manufactured by. Specifically, for example, alkali may be added to a stannic salt solution to which white inorganic powder has been added to deposit stannic hydroxide on the surface of the white inorganic powder. Alternatively, a method in which a stannic salt solution is dropped into an alkaline solution charged with white inorganic powder with stirring, or an alkali solution and a stannous solution are simultaneously dropped into a container containing white inorganic powder with stirring. The stannic salt may be hydrolyzed by the method to deposit stannic hydroxide on the surface of the white inorganic powder. Heating may be used to promote the reaction.

  In order to reduce stannic hydroxide in the white inorganic powder surface layer with stannous ions, a stannous salt is continuously added after forming a stannic hydroxide layer on the white inorganic powder surface by the above reaction. Alternatively, the stannous salt may be added by washing with water after forming the stannic hydroxide layer by hydrolysis.

The amount (upper limit) of the stannous salt used for the reduction is suitably 10 mol% or less, preferably 5 mol% or less of stannous hydroxide with respect to stannic hydroxide on the surface of the white inorganic powder. 0.1 mol% or more of tin is appropriate. Even if the amount of stannous is more than 10 mol%, there is no great difference in conductivity, but rather the burden of cleaning treatment after the reduction reaction is increased. On the other hand, if the amount of stannous is less than 0.1 mol%, the powder volume resistance is larger than 10 ⁴ Ω · cm and the conductivity tends to be low, which is not preferable.

Reduction of stannic hydroxide on the surface of the inorganic powder is performed in a liquid. Therefore, a soluble salt is used as the stannous salt. For example, as stannous salts, inorganic soluble salts such as stannous chloride, stannous sulfate, stannous oxide, stannous nitrate, tin pyrophosphate, tin sulfamate, stannate and the like, alkanol Organic soluble salts such as stannous sulfonate, stannous sulfosuccinate and stannous aliphatic carboxylic acid can be used. As the soluble solvent for stannous salt, water, alcohol, ethyl acetate, glacial acetic acid and the like can be used, but water or alcohol is preferable because it is easy to handle and low in cost.

  In addition, as the stannic salt used for forming the stannic hydroxide layer on the surface of the white inorganic powder in the previous step, the respective stannic salts of the above-mentioned soluble stannous salt may be mentioned. In other words, liquid stannic chloride or an aqueous solution thereof may be used.

  In the presence of white inorganic powder having a stannic hydroxide layer on the powder surface, stannous hydroxide is reduced by contacting stannous ions with stannic hydroxide on the surface of the white inorganic powder in the liquid. Thus, stannous hydroxide is formed.

  After the stannous ions are brought into contact with stannic hydroxide on the surface of the white inorganic powder, if the residual salt does not become a problem, the white inorganic powder is usually recovered by washing with water and solid-liquid separation. The recovered white inorganic powder is heat-treated in an inert gas atmosphere and under a soluble solvent vapor of stannous salt, excluding oxygen.

  By this heat treatment, the stannous hydroxide on the surface of the inorganic powder is reduced by the ionization of the coexisting stannous salt in contact with the soluble vapor, and oxygen defects are generated to become conductive tin oxide.

  The heat treatment is preferably performed by excluding oxygen in an inert gas atmosphere with an adjusted atmosphere. For example, the heat treatment is adjusted to an inert gas atmosphere such as nitrogen gas or argon gas excluding oxygen.

  Further, the heat treatment is performed in the presence of a soluble solvent vapor of stannous ions together with an inert gas atmosphere. The production of stannous ions was recovered after, for example, reducing the stannous hydroxide on the powder surface by adding a stannous ion aqueous solution to a solution containing a white inorganic powder having a stannous hydroxide surface layer. The white inorganic powder may be put in a heating furnace in a slurry state or in a moderately wet state to exclude oxygen and form a state in which soluble stannous salt remaining on the powder surface is dissolved in water vapor.

  Alternatively, the dried white inorganic powder may be placed in a heating furnace and an inert gas saturated with water vapor may be introduced to form a state in which the soluble stannous salt remaining on the powder surface is dissolved in the water vapor. Or you may introduce | transduce the vapor | steam of the soluble solvent of a stannous ion at the time of heat processing. The introduction method is not limited. For example, the soluble solvent vapor may be introduced into the inert gas atmosphere of the heat treatment furnace, or the inert gas may be bubbled through the soluble solvent and introduced into the heat treatment furnace.

  The vapor pressure of the soluble solvent is preferably a saturated vapor pressure of 30% or more. In order to perform the heat treatment while maintaining the vapor pressure, it is preferable to use a closed heat treatment furnace. When the vapor pressure of stannous ion vapor is lower than 30%, reduction of tin oxide on the powder surface tends to be insufficient.

  The heat treatment is performed in an atmosphere excluding oxygen. When oxygen is contained in the atmosphere, a low-resistance powder cannot be obtained stably and the heat treatment becomes non-uniform. The heat treatment temperature is suitably 450 ° C to 650 ° C. When the treatment temperature is outside this range, the powder volume resistance of the obtained powder tends to increase.

[Conductive tin oxide]
The conductive inorganic powder of the present invention has a powder volume resistance of 10 ⁴ Ω · cm or less, preferably 1000 Ω · cm or less, more preferably 500 Ω · cm or less, and preferably a resin content of 2 parts by weight. And a white conductive inorganic powder having a conductivity of a surface resistance of 10 ⁶ Ω / □ or less in a transparent resin coating film having a content ratio of 8 parts by weight of white conductive tin oxide powder.

When the powder volume resistance of the white conductive inorganic powder is larger than 10 ⁴ Ω · cm, a conductivity of surface resistance of 10 ⁹ Ω / □ is obtained which exhibits an antistatic effect when added to a resin to form a coating film. For this reason, the amount of the resin mixed into the resin increases and the physical properties of the resin deteriorate. The conductivity of the inorganic powder of the present invention does not have such a problem because the powder volume resistance is small.

  The white conductive inorganic powder produced by the method of the present invention has an L value of 70 or more. Specifically, in Examples 1 to 4, an L value of 70 or more, preferably an L value of 80 or more. A white powder. Note that the more oxygen defects in the tin oxide layer, the higher the conductivity and the lower the L value. An L value lower than 70 is not preferable because the color becomes dark and cannot be used in a white environment.

Examples of the present invention are shown below together with comparative examples. In Examples and Comparative Examples, the powder volume resistance was measured with a digital multimeter (manufactured by Yokogawa Electric Corporation: Model 7561-02) after putting the sample powder in a pressure vessel and compressing it at 100 kgf / cm ² .
The L value was measured with a device manufactured by Suga Test Instruments Co., Ltd. (SM-7-IS-2B).

[Example 1]
150 g of titanium oxide powder (rutile type) was dispersed in 1 L of water and heated to 90 ° C. 100 g (0.19 mol) of 50% stannic chloride solution and 1N sodium hydroxide solution were added dropwise over 30 minutes while simultaneously maintaining pH 3-4 with stirring, and titanium oxide having a stannic hydroxide layer on the powder surface A powder was obtained.
An aqueous solution of 4.3 g (0.019 mol = 10 mol%) of stannous chloride dihydrate dissolved in 100 ml of ion-exchanged water was added dropwise over 10 minutes with stirring, washed thoroughly with water, filtered and dried at 90 ° C. This was put into a quartz tube furnace, and nitrogen gas saturated with water vapor through water was passed through the furnace at a rate of 0.3 L / min for 30 minutes to exclude oxygen and heat treatment was performed at 500 ° C. for 1 hour.
On the other hand, except that stannous chloride was changed to 2.1 g (5 mol%) and 1.1 g (2.5 mol%) respectively, precipitation, water washing, filtration, and heat treatment after drying were carried out under the above-mentioned conditions to obtain conductive tin oxide. A powder was obtained. The surface resistance of the transparent resin coating film having the powder volume resistance, 2 parts by weight of the resin content, and 8 parts by weight of the conductive tin oxide powder was measured. The results are shown in Table 1.

[Example 2]
150 g of titanium oxide powder (rutile type) was dispersed in 1 L of water and heated to 90 ° C. 100 g (0.19 mol) of 50% stannic chloride solution and 1N sodium hydroxide solution were added dropwise over 30 minutes while simultaneously maintaining pH 3-4 with stirring, and titanium oxide having a stannic hydroxide layer on the powder surface A powder was obtained.
To this, an aqueous solution of 4.1 g (0.019 mol = 10 mol%) stannous sulfate dissolved in 100 ml of ion-exchanged water was added dropwise over 10 minutes with stirring. The precipitate was sufficiently washed with water, filtered and dried at 90 ° C. This was put into a quartz tube furnace, and nitrogen gas saturated with water vapor through water was allowed to flow through the furnace at a rate of 0.3 L / min for 30 minutes to exclude oxygen and heat treatment was performed at 600 ° C.
On the other hand, except that stannous sulfate was changed to 2.0 g (5 mol%) and 1.0 g (2.5 mol%) respectively, precipitation, water washing, filtration, and heat treatment after drying were carried out under the above-mentioned conditions to obtain conductive tin oxide. A powder was obtained. The surface resistance of the transparent resin coating film having the powder volume resistance, 2 parts by weight of the resin content, and 8 parts by weight of the conductive tin oxide powder was measured. The results are shown in Table 2.

Claims (5)

Using a white inorganic powder having a surface layer of stannic hydroxide on the surface of the powder, stannous ions (excluding stannous ions of fluoride) are added to the stannic hydroxide on the surface of the white inorganic powder in the liquid. The stannic hydroxide is reduced by contact to form stannous hydroxide , and the white inorganic powder recovered by solid-liquid separation is recovered in the presence of an inert gas atmosphere and a stannous salt soluble vapor. A method for producing a white conductive inorganic powder containing no antimony, phosphorus and indium, characterized in that a surface layer of conductive tin oxide having oxygen defects is formed by heat treatment with exclusion of oxygen.
In the presence of the white inorganic powder, the stannic salt solution and alkali are reacted to deposit stannic hydroxide on the surface of the white inorganic powder, and the white inorganic powder having the surface layer of stannic hydroxide is solidified. The method for producing a white conductive inorganic powder according to claim 1, wherein the white inorganic powder having a recovered stannic hydroxide surface layer is collected by liquid separation and recovered.
The method for producing a white conductive inorganic powder according to claim 1 or 2, wherein a white conductive inorganic powder having a powder volume resistance of 10 ⁴ Ω · cm or less is produced.
The method for producing a white conductive inorganic powder according to any one of claims 1 to 3, wherein an amount ratio of stannous salt to stannic hydroxide is 10 mol% or less.
The manufacturing method of the white electroconductive inorganic powder in any one of Claims 1-4 which uses a titanium oxide powder, a potassium titanate powder, and a white mica as a white inorganic powder.