JP3256570B2 - Manufacturing method of conductive material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive material and its production. More specifically, the present invention is excellent in chemical resistance and stability over time, and is also suitable for electronic materials, electrode materials, antistatic materials,
The present invention relates to a novel method for producing a conductive material useful as a material for a composite material capable of imparting excellent current-carrying properties to a conductive material or the like.

[0002]

2. Description of the Related Art In recent years, a variety of composite materials as new materials have been researched and developed as advanced materials due to the sophistication and rapid progress of high-tech technologies. However, many problems remain in these materials. For example, in the case of conductive materials, development of higher quality, stable and inexpensive materials is desired.

[0003] As a conductive substance applied to a composite material, for example, as a conductive powder, a metal powder such as gold, silver, copper, nickel and the like and a carbon powder, etc., are known. It has poor oxidation stability and acid resistance.

Also, metal oxides as oxidation stable materials,
In particular, stannic oxide powder doped with antimony and indium has been studied for a long time, and various technological developments have been made at present, but antimony and indium are easily eluted in a strongly acidic atmosphere. It is currently restricted.

Further, technical development using fluorine-doped stannic oxide as a conductive material has been carried out for a long time, such as reaction between stannic chloride and ammonium fluoride, and fluorine-doped SnO ₂ -based conductive material. Films (all in 1967, Asakura Shoten, “Glass Industry Handbook”, Chapter 16 Conductive Glass), etc. These are fluorine-doped as a method of treating the surface of various insulating base materials with a conductive thin film. And a method for producing a stannic oxide thin film. In all of the above-described techniques relating to fluorine-doped stannic oxide, a solution of stannic chloride and ammonium fluoride is brought into contact on a heated substrate, and when the stannic chloride changes to stannic oxide, the oxygen site is changed. Is partially substituted with fluorine. However, although the above-described method gives a highly conductive fluorine-doped coating, it is necessary to use a large amount and wasteful use of ammonium fluoride as a raw material with respect to tin, and dangerous ammonium fluoride is vaporized to generate waste gas. In large quantities,
It is poorly applicable as industrial production technology.

In recent years, with the development of fluorine chemistry, research on organometallic compounds has been advanced, and organotins containing perfluoro groups have been developed, and a conductive film has been formed on a glass substrate by using an immobilized fluorine source. A method of forming the compound, and a method of manufacturing a fluorine-doped stannic oxide powder by directly pulverizing a product obtained by directly burning these compounds have been proposed (Heisei 1989, published by IPC, edited by Toshiaki Maruyama, "Thermal decomposition"). Coating of Transparent Conductive Thin Film by Method ", Chapter 11). According to the above-mentioned technology, although the utilization efficiency of fluorine is improved, the productivity is poor because the modifying group of the organotin is large and the tin content is small, and the cost is high due to the need for advanced technology and skill in raw material synthesis, and furthermore, It is difficult to obtain stable and high conductivity without using fluorine of 10 parts or more with respect to 20 parts of tin, and it is difficult to obtain homogeneous granular materials because pulverization is necessary for powdering,
Very poor industrial applicability.

The present inventor has developed various conductive materials. The method for producing a fluorine-doped conductive material is disclosed in Japanese Patent Application No. 2-235552, and the conductive material is disclosed in Japanese Patent Publication No. 61-26933. Ids 62-4328,
62-3767, 62-4029, Tokuhei 2-10
92, JP-A-60-9005 and 60-264326,
61-117119, 61-141618, 61
-167017, 61-197422, 62-59
828, 62-216105, 62-12758,
63-85171, 63-86205, JP-A-2-
As 149424, various proposals have been made for other functional powders and composite materials utilizing them. However, it is still insufficient from the viewpoint of a conductive material exhibiting acid resistance. In addition, from the viewpoint of manufacturing technology, powder processing using a fluorine-containing organotin solution has not been developed at the present stage because high-level technology is required in powder processing by the gas phase method. It is extremely difficult to uniformly coat the surface. In this case, the powder particles agglomerate, making it impossible to obtain a highly conductive powder, and the technical development is strongly desired.

As discussed above, at present, there is a strong demand for the development of economical and efficient manufacturing techniques for conductive materials, especially fluorine-doped conductive powders.

[0009]

DISCLOSURE OF THE INVENTION The present invention is directed to a fluorine-doped material which is excellent in acid resistance, has a small fluorine content, is fine and well-shaped, and has a high suitability as a material for a composite material exhibiting excellent conductivity. It is another object of the present invention to provide a new method for producing a conductive powder .

[0010]

SUMMARY OF THE INVENTION In summary of the present invention,
The present invention provides a method for producing conductive particles, comprising the steps of: (1) reacting a stannous salt with an alkali substance in a homogeneous dispersion of particles having a major axis of 5 mm or less, and depositing an oxygen-containing tin compound on the surface of the particles. (2) a step of bringing a solution of a fluorine-containing compound into contact with the particles having an oxygen-containing tin compound deposited on the surface thereof; and (3) a step of bringing the particles obtained from the step (2) to 200 ° C. ~ 80
Baking at 0 ° C., the method for producing conductive particles.

Hereinafter, the technical structure of the present invention will be described in detail. In the present invention, the particles are those which show a good dispersion system in a solution having a major axis of 5 mm or less, preferably 1 mm or less.
Therefore, the particle shape is not particularly limited in the present invention, but is selected from fibrous particles, columnar particles, plate-like particles, and spherical particles for industrial use. Among the fibrous particles, those having an aspect ratio (fiber length / fiber diameter) of 1,000 or more are not preferred because the fibers are strongly entangled with each other and a uniform coating layer is hardly formed. However, recently developed whiskers having a fiber length of about 1 to 500 μm and an aspect ratio of about 5 to 500, or milled wool having an aspect ratio of 500 or less made of glass fiber powder can be dispersed in water and are included in the constitution of the present invention. .

Representative examples of the particles according to the present invention include glass powder having an aspect ratio of 500 or less, rock wool powder, titania whisker, titanate whisker, aluminum borate whisker, alumina whisker, magnesium borate whisker, silicate Whiskers, carbon whiskers, clay minerals, synthetic and natural mica powder, powdered glass,
Examples thereof include molten glass particles, silica particles, shirasu balloons, silicone particles, and the like, and one or a mixture of two or more of these may be used.

In the present invention, among the above-described various particles, various whiskers, plate-like particles, and spherical particles are suitable. However, in the present invention, since it is inappropriate for the alkali component to leach out of the base particles during the heat treatment when doping with fluorine, the alkali titanate and the alkaline earth titanate particles must be prepared in advance. It is desirable to reduce the leaching of the alkali component by acid extraction, or to stabilize it with an oxide such as alumina or silica, or with carbon, Ni or Cu, and the same treatment is required for alkali glass. These stabilization techniques are disclosed in the above-mentioned patent application proposed by the present inventors, or a part thereof is also disclosed in the above-mentioned reference.

In the present invention, the stannous salt is reactive,
Stannous chloride and its hydrates are preferred from the standpoint of availability, but can be arbitrarily selected from various stannous salts such as sulfates, nitrates, and oxalates.

In the present invention, the alkali substance to be reacted with the stannous salt can be arbitrarily selected from ammonia, ammonium carbonate, potassium carbonate, sodium carbonate, sodium hydroxide, potassium hydroxide and the like.

In the present invention, a part of the stannous salt or the alkali substance may be added to the aqueous dispersion of the particles according to the present invention or a dispersion to which a surface tension reducing agent such as a dispersant or alcohol is added as required. Alternatively, tin is added and dissolved, and the residue is added dropwise to the dispersion under stirring as a normal solution under stirring, or all the reactants are simultaneously added dropwise to the particle dispersion under stirring, so that oxygen is added to the particle surface. Precursor A is prepared by a first step of depositing a tin compound, filtering, washing and drying. The ratio of the stannous salt and the alkali substance used at this time varies depending on the raw material used and the purpose of use, but during the reaction, either an acidic or alkaline atmosphere may be used. The reaction temperature can be arbitrarily selected from room temperature to the boiling point of the solvent, but it is usually preferable to terminate the reaction at room temperature with a slight excess of alkali components.

Although the coating layer of the oxygen-containing tin compound obtained by the method of the present invention varies depending on the reaction conditions, SnO, SnO.
aH ₂ O (0 <a <10), Sn (OH) ₂ , Sn (OH)
_{It is} composed of stannous oxide, stannous hydroxide represented by ₂ · bH ₂ O (0 <b <10), or a mixture of two or more kinds of compounds called stannic acid compounds. Depending on the reaction conditions, trace amounts of stannic oxide and hydrates thereof may be contained in the coating layer. In the present invention, a dark gray conductive material is obtained from a coating layer composed of stannous oxide. On the other hand, from the stannic acid compound , a white conductive material having excellent brightness can be obtained. The proportion of the particles of the present invention and the oxygen-containing tin compound constituting the coating layer varies depending on the purpose of use and the type of raw material, but is usually 10 to 200 parts, preferably 20 per 100 parts by weight of the particles (hereinafter the same). If the amount is too small, the coating is insufficient and a suitable conductivity cannot be obtained. On the other hand, if the amount is too large, the coating becomes excessively coated, the surface smoothness is deteriorated, and when used as a composite material, it tends to cause an increase in the amount of lubrication and poor dispersion.

In the present invention, as the fluorine-containing compound, any one of an organic compound and an inorganic compound can be used as long as it can be decomposed into fluorine by heating and firing.

Among such fluorine-containing compounds, inorganic compounds include hydrogen fluoride and derivatives thereof. Typical examples are hydrogen fluoride, ammonium fluoride, hydrofluoric acid, ammonium hydrofluoride, antimony fluoride, tin fluoride, stannic fluoride, boron fluoride, indium fluoride, and carbon fluoride. , Uranium fluoride, osmium fluoride, bromine fluoride, nitrosyl fluoride and the like. Further, inorganic compounds such as fluorosulfuric acids such as nitrosyl fluorosulfate are also exemplified. Among these fluorine-containing compounds, ammonium fluoride, ammonium hydrofluorate, tin fluoride and the like are preferable from the viewpoint of availability, toxicity and safety.

On the other hand, as the organic compound, a fluorine compound containing a fluoroalkyl group, that is, a fluoroalkane,
There are fluoroalcohols, fluoroethers, fluoroesters and derivatives thereof. As a typical example, C _n F _{2n + l} X _(2-l) (4 ≦ n ≦ 20, 0 ≦ l ≦ 2, X:
H, halogen and monovalent hydrocarbon groups), Rf · R ₁ · O
H (Rf is a fluoroalkyl group, R ₁ is a divalent hydrocarbon group), R ₂ · COOR ₆ · R ₃ (R ₂ and R ₃ are at least one of a fluoroalkyl group, and the remainder is a monovalent hydrocarbon group; R ₆ is a divalent hydrocarbon group), and the like. Further, compounds with these metals, for example, tin, antimony, boron and silicon are exemplified. In the present invention, the above-mentioned fluorine-containing compound can be used as one kind or a mixture of two or more kinds, and the precursor A obtained in the first step can be used.
Should be contacted.

In the present invention, the mode of contact between the fluorine-containing compound and the precursor A according to the present invention may be such that both components are simply mixed and contacted. However, as a most preferred embodiment, after dispersing the powder of the precursor A according to the present invention in a solution or dispersion of water or an organic solvent of the fluorine-containing compound, the dispersion medium or the solvent is volatilized to form a powder of the precursor A. It is desirable that the fluorine-containing compound be uniformly attached to the body surface. By heating and firing the mixture of the tin precursor powder according to the present invention and the fluorine-containing compound obtained by the above-described method, the tin compound in the precursor is oxidized and changes to stannic oxide, and the state changes. Active fluorine released from the fluorine-containing compound is doped into the oxygen site of stannic oxide to obtain conductive tin oxide powder.

In the present invention, the tin compound is limited to stannous tin for the following reasons. Conventionally, fluorine-doped stannic oxide is generally produced by a gas phase reaction. Now, considering a reaction system in which stannic chloride is used as a starting material and oxidized at high temperature to change to stannic oxide, active fluorine existing in the atmosphere is doped into the oxygen site of stannic oxide. Is considered to be changed to a conductive substance. However, as shown in a comparative example described below,
Even if the stannic oxide powder and the fluorine-containing compound are heated and fired in contact with each other, good conductivity cannot be obtained. This is what has been changed to stannic oxide (the one in the state of stannic oxide)
It is thought that the bond between tin and oxygen is stable and that fluorine doping is difficult. From this, in the present invention, a stannous compound is used as a starting material, and in the intermediate stage where the stannous compound changes to stannic oxide, the probability that active fluorine is doped into the oxygen site is low. It is based on the idea that stannic oxide doped with fluorine can be obtained more efficiently and efficiently.

With respect to the above points, the characteristics of the oxygen-containing stannous compound forming the precursor A of the present invention will be described.
When the precursor A obtained in the first step is boiled in an aqueous alkaline solution, the entire coating layer or the surface layer changes to stannous oxide, and the color tone becomes black or gray. Therefore, (a) those that have been boiled as described above, (b) those that have undergone the fluorine treatment of (b) above, and (c) those that have the first step performed at room temperature and are not boiled (this is white The change is remarkable especially when stannous chloride is used.), And (d) the first reagent
Thermal analysis by TG / DTA was performed on tin oxide and tin oxide. According to this, an exothermic peak was observed at 600 ° C. for the boiled product (a) and the stannous oxide reagent (d), and the weight change was also consistent with SnO → SnO ₂ . On the other hand, for the non-boiled white one (c), various exothermic peaks were observed,
In addition, the weight change is extremely small, and the hydrate of stannous acid, SnO.aH ₂ O, Sn (OH) ₂ .bH ₂ O (a,
It is considered that dehydration and oxidation in b) proceed simultaneously, and fluorine is easily taken into the structure.

In the present invention, stannous chloride or a hydrate thereof is used as a starting material, an aqueous solution of ammonium fluoride is used as a fluorine doping material, and the pH at the end of the first step is adjusted.
Was made alkaline to prepare a whole precursor A. Then, when this is redispersed in water, it shows an acidity of pH 4 to 5, and the whole precursor A shows the property of stannic acid. Further, when an aqueous solution of ammonium fluoride was added thereto for treatment, an ammonia odor was recognized, and the dry weight was equal to the amount of fluorine used. From the above, before the fluorine-dove treatment step (before firing), it becomes a substance in which fluorine reacts with the stannic compound in some form, and in the subsequent fluorine doping step (firing step), the volatilization of fluorine is suppressed, and fluorine is efficiently produced. It is considered to be doped to form a good conductive layer. In the present invention, the amount of the fluorine compound used for the fluorine treatment is 0.1 to 1 mol% (preferably 0.3 to 0.5 mol%) based on Sn in the precursor A, and (F) is 0.1 to 5% (preferably 1 to 2%). If the amount is too small, it is difficult to obtain conductivity, and if it is excessive, good results may not be obtained.

As described above, in the present invention, by contacting the precursor A according to the present invention with the fluorine-containing compound and then heating, the tin compound changes to stannic oxide in a fluorine-doped state and becomes conductive. Powder is obtained. The heating conditions at this time vary depending on the type and combination of the raw materials, but usually 2 hours.
The temperature is at least 00 ° C, preferably at least 300 ° C. At lower temperatures, it takes a long time to change to stannic oxide, and furthermore, the decomposition of the fluorine compound is insufficient, the doping effect is poor and a good conductor is obtained. It is difficult to obtain. Conversely, at higher temperatures, fluorine compounds are rapidly decomposed and discharged together with exhaust gas, and a large amount of fluorine-containing compounds must be used to dope the required amount of fluorine, which is likely to cause environmental pollution, Further, when the tin compound changes to stannic oxide, the particles coagulate and fuse to each other, making it difficult to adjust the design particle diameter. Therefore, the upper limit is preferably about 800 ° C. In the present invention, the heat treatment time is 10 minutes to 5 hours, usually 30 minutes to 3 hours.
It takes about an hour. In the present invention, as the heating means,
Any heater that is normally available can be used,
A rotary continuous kiln such as a rotary kiln is preferable from the viewpoint of contact with a uniform heating atmosphere gas and from the viewpoint of mass production. The heating may be performed in the air or in a partially reducing atmosphere.

The present invention relates to a conductive substance whose particles are coated with fluorine-doped tin oxide, particularly to a conductive powder. The present invention relates to the use of a surfactant which is usually used during production as a powder dispersant. Needless to say, a dopant for a commonly used tin-based compound such as zinc, antimony, and indium may be used together with fluorine.

In the present invention, the commercially available oxidized primary
Tin powder can be used as a starting material in the component of the precursor A. However, these are generally black or dark brown and have poor whiteness although there is no difference in conductivity after firing. As a method to improve this point,
A precursor A obtained from a reaction product of a tin solution and an alkaline solution may be used. In this case, when baked in contact with a fluorine compound, a material having high whiteness can be obtained, and when used as a conductive composite material, it can be colored, and a material having high industrial utility can be obtained. Here, as the stannous chloride solution, any solution such as an aqueous solution and an organic solvent solution can be used, but an aqueous solution is preferable from the viewpoint of drainage management, and a 10 to 50% aqueous solution is usually used. Also,
As the alkaline solution, those which hydrolyze stannous chloride, that is, any of the above-mentioned ammonia, ammonium carbonate, potassium carbonate, sodium carbonate, sodium hydroxide, potassium hydroxide, etc., can be used. Ammonia and its derivatives are preferred from the viewpoint of preventing alkali metals from being mixed.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Example 1 Aluminum borate whiskers (average fiber length 22 μm,
25 g of an average fiber diameter of 0.8 μm (manufactured by Otsuka Chemical Co., Ltd.) and 58 g of a stannous chloride aqueous solution having a tin content of 23.0 wt% were charged into a glass container, and 60 ml of 4N ammonia water was stirred at room temperature under stirring for about 1 hour. Then, the mixture was stirred for 30 minutes, aged, filtered, washed with water and dried to give a white powder.
4 g were obtained. The amount of tin in the reaction filtrate determined by atomic absorption spectrometry was 0.1 ppm or less, confirming that almost all of the stannous chloride used in the reaction had disappeared. Further, by observation with a scanning electron microscope, no foreign matter (powder) other than the raw material aluminum borate whiskers was observed, and a uniform adhesion state was confirmed. Furthermore, after treating this product with 10% sulfuric acid, the amount of tin determined by atomic absorption spectrometry was 32.3%, and the consumption of potassium permanganate was 5.3.
m.eq / g, and the stannous compound accounted for 95% or more of the total tin amount of the coating layer.

Using 10 g of the above reaction product, kneading 10 g of methanol and 4 g of a 10% aqueous solution of ammonium fluoride (Morita Chemical Co., Ltd.) in a polyethylene beaker for 30 minutes at room temperature, followed by drying at 70 ° C. for 2 hours to obtain a white color. 10.2 g of powder was obtained. Transfer this to a platinum crucible.
By heating and baking in a muffle furnace at 00 ° C. for 1 hour, 10.1 g of a white powder was obtained. In addition, the said powder is diameter 1
A 0 mm cylindrical ring was filled, and the volume resistivity measured under a pressure of 100 kgf / cm was 1.8 Ωcm. (Note that the volume resistivity shown below is a value measured by the same method as in Example 1.)

Further, 2.0 g of the above powder was mixed with 40% sulfuric acid 1
After being kept in contact with 00 ml and kept at 50 ° C. for 1 week, it was separated by filtration, and the elution amount of Sn and F in the filtrate was 15 ppm and 0.1 ppm or less, respectively, and the volume resistivity after filtration was 1.7 Ω.
cm, and showed excellent sulfuric acid resistance.

Examples 2 to 9 Table 1 shows the results obtained by changing the stannous chloride solution and the amount of alkali in Example 1 and changing the ratio of the base material and the coating layer. According to Table 1, when the coating layer is less than 20 wt% with respect to the base material, the conductivity is insufficient, and when it is more than 200 wt%, the coating layer is excessively coated as observed by a scanning electron microscope (SEM).

[0032]

[Table 1]

Comparative Examples 1 to 4 In Example 1, the conductivity and sulfuric acid resistance of the unfired product without fluorine treatment, the fired product thereof, and the unfired product after fluorine treatment were examined. Table 2 shows the results.

[0034]

[Table 2]

Comparative Examples 5 to 8 In Example 1, chlorinated chloride was used in place of the stannous chloride aqueous solution.
The same method was used except that 58 g of a tin aqueous solution (same at 23.0% tin content) and 60 ml of 8N aqueous ammonia were used, and 43.6.
g of a white powder were obtained. Fluorine treatment and calcination treatment were performed using the powder in the same manner as in Example 1. However, as shown in Table 3, before and after fluorination treatment, both the baked and unbaked products had neither conductivity nor sulfuric acid resistance. It was enough.

[0036]

[Table 3]

Examples 10 to 17 Table 4 shows the results of Examples using various substrates. In addition,
In the table, BK300, Rio Veil Ni and Super Dentol are carbon and titanium, respectively, on potassium whisker titanate.
i, Ag, and the coating amount indicates the ratio of the coating layer in the conductive material.

Comparative Examples 10 to 12 For comparison with Example 1, the results obtained when an alkali-containing substrate was used as a substrate are also shown in Table 4. Because these things ooze out the alkali into the coating layer during firing,
This indicates that good conductivity cannot be obtained.

[0039]

[Table 4]

Comparative Example 13 In Example 1, when 4N ammonia water was dropped, 10 g of 20% antimony trichloride was dropped in parallel, filtered, washed with water, and baked at 500 ° C. for 1 hour to obtain a conductive material of 2.1 Ω. I got However, in the sulfuric acid resistance test of this, 15
0 ppm of tin and 196 ppm of antimony were detected, and the elution amount almost equal to the total amount of antimony used was recognized.

[0041]

The conductive substance of the present invention has the following excellent effects. 1) The manufacturing method is simple, and a homogeneous good conductor can be efficiently and economically manufactured. 2) Since a conductive powder in which the shape of the starting material is maintained can be obtained, conductive particles suitable for the intended use can be obtained by selecting the starting material. For example, conductive particles having excellent applicability to coating materials, inks, and the like can be obtained by utilizing the shape characteristics of a raw material having a fine particle diameter. 3) It is excellent in acid resistance, especially in anti-sulfuric acid, so that it can be applied to electrode materials. 4) It has high whiteness and can be colored, so there is no restriction on whiteness or coloring in various application fields.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-216105 (JP, A) JP-A-63-11519 (JP, A) JP-A-55-58363 (JP, A) European Patent Application 441426 (EP, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01G 19/02 H01B 5/00 H01B 5/14 CA (STN)

Claims (2)

(57) [Claims] The method for producing conductive particles includes the steps of: (1) reacting a stannous salt with an alkali substance in a homogeneous dispersion of particles having a major axis of 5 mm or less, and adding an oxygen-containing tin compound to the surface of the particles. (2) a step of bringing a solution of a fluorine-containing compound into contact with the particles having an oxygen-containing tin compound deposited on the surface thereof; and (3) a step of preparing the particles obtained from the step (2) by 200. ° C to 80
Baking at 0 ° C. 2. The stannous salt is stannous chloride.
3. The method for producing conductive particles according to 1.).