JP3365883B2 - Needle-like conductive tin oxide fine powder and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a needle-shaped conductive tin oxide fine powder and a method for producing the same, which are excellent in high functionality capable of expanding the applicability and increasing the added value in various fields of application. Regarding sexual material.

[0002]

BACKGROUND OF THE INVENTION It is used as a conductivity-imparting agent or antistatic agent for plastics, rubber, fibers, etc., and also as a conductivity-imparting agent for a support of recording materials such as electrophotographic copying paper and electrostatic recording paper. It Various needle-like or fibrous conductive tin oxides have been proposed. (For example, JP-A-56
-120519, JP 62-158199, JP 5-117906
issue).

[0003]

By the way, since the above-mentioned tin oxide-based conductive powder exhibits a so-called electron-conducting conductive function, it has a higher humidity and temperature than a so-called ion-conducting one such as a polymer electrolyte. Highly stable in conductivity to, for example, as a conductivity-imparting agent for antistatic treatment of materials and products in various fields such as paints, inks, plastics and fibers, and as a reinforcing filler, its functional material. Its use is being noticed, and its application is being rapidly pursued.

Generally, the conductivity-imparting agent is filled in rubber, plastics, paper or the like, or dispersed in a solution containing a binder to prepare a coating solution, which is used in various films, sheets,
It is used by coating it on a support, or even on an object to be treated such as a housing, but in order to obtain good conductivity, the powder content should be set so that at least adjacent powders come into close contact with each other. It is advantageous that the needle-like or fibrous conductivity-providing agent can effectively form the conductive path even with a small amount of the conductivity-providing agent per unit area or unit volume.

However, in the conventional conductive stannic oxide fiber, tin oxalate is heated at a very slow temperature (Japanese Patent Laid-Open No. 56-120519), and tin oxide is vaporized using copper as a solvent to lower the temperature. Introduced into the part to cause precipitation (JP-A-62-158199)
No.), a spinning solution is prepared from a tin compound, and spinning is performed (Japanese Patent Laid-Open No. H5-
It is known that the products obtained by these methods are thick with a short axis of about 0.5 μm, or have an extremely poor industrial production. There was a problem.

However, in the application of the conductive powder as described above, recently, for example, an OHP film or a CRT is used.
Antistatic treatment for avoiding electrostatic damage on windows, IC packages and housings of electronic devices, transparent electrodes of liquid crystal displays and other EL bodies, and the desired conductivity imparting ability, as well as treatment target. It is strongly desired that an ultrathin conductive film can be formed without substantially absorbing light on the surface of the body material.

The object of the present invention is to solve the above-mentioned problems of the prior art, and to provide suitable conductivity and transparency for imparting the above-mentioned desired characteristics to objects to be processed in various fields of application. An object is to provide an excellent acicular conductive tin oxide fine powder, a method for producing the same, and a method for using the same.

[0008]

The inventors of the present invention have made various investigations in order to solve the above-mentioned problems and provide a conductivity-imparting agent satisfying the above-mentioned performance in advance. The present inventors proceeded with the study by making the particle shape of the powder acicular and making the particles easily continuous in the medium of the application system, and efficiently adding conductivity by adding a small amount. as a result,
(1) The needle-shaped tin oxide fine powder having a specific long-axis average particle diameter, the specific short-axis average particle diameter, and the aspect ratio being a specific value or more, It can be an optimum highly functional material capable of imparting extremely excellent conductivity and transparency, and further surface smoothness. (2) In order to produce a tin oxide fine powder, a tin component is an alkali metal halogen. When firing in the presence of compounds,
Surprisingly, it can be acicularized only by the presence of a silicon component, and can form a needle-shaped tin oxide fine powder having the optimum particle diameter of the above (1) with great industrial advantage. Those that have undergone the removal treatment have the desired conductivity, transparency, and surface smoothness in various application systems.
It is also excellent in performance such as adhesion, and also becomes excellent in dispersibility in water by leaving a predetermined amount of the silicon component, and it is possible to easily form an aqueous dispersion suitable for various uses, In addition, coloring and carcinogenicity induction by using carbon black as a conductivity-imparting component, and further obtained the knowledge that it is possible to avoid any of the problems such as bluish tone and safety aspect due to the use of antimony, Completed the invention.

That is, according to the present invention, the acicular conductive particles having a short axis average particle size of 0.005 to 0.05 μm, a long axis average particle size of 0.1 to 3 μm, and an aspect ratio of 5 or more. Tin oxide fine powder. The average particle size referred to here is 5 after observing an electron micrograph (magnification: 100,000 times).
The 0% weight average diameter was obtained. Further, the needle-shaped conductive tin oxide fine powder of the present invention comprises 70% or more of the total weight,
The minor axis particle diameter is 0.003 to 0.1 μm, the major axis particle diameter is 0.05 to 5 μm, and the aspect ratio is 5 or more. Silicon component amount is 0.1% to 10% by weight of SnO ₂ as SiO _2, is preferably from 0.3 to 6%. Further, in the present invention, the "needle-like" includes not only needle-like ones within the range of the physical property values but also fibrous, columnar, rod-like and other similar shapes.

The acicular conductive tin oxide fine powder of the present invention is obtained by firing a substance to be fired containing a tin component, a silicon component and an alkali metal halide, and then removing soluble salts of the obtained fired product. Can be obtained by In the present invention, the material to be fired refers to a material containing a tin component, a silicon component and a halide of an alkali metal. Among them, a precursor not containing any one or more components other than the tin component is a precursor. It is called a substance.

To prepare the precursor with the tin compound and the silicon compound, powder of each compound is used, or
It can be carried out by various methods using a solution of each compound. For example, (a) a tin compound aqueous solution, a silicon compound aqueous solution and an alkaline aqueous solution are added in parallel to hot water of 70 to 90 ° C. for neutralization. (B) An alkaline aqueous solution is added to the tin compound aqueous solution for neutralization, and then a silicon compound aqueous solution is added to adjust the pH to a predetermined value or colloidal silica is added, (c) The tin compound aqueous solution is added to the alkaline aqueous solution. Is added to neutralize, and then a silicon compound aqueous solution is added to adjust the pH to a predetermined level or colloidal silica is added, and the like.Among such methods, the method (a) is particularly industrial. In this case, the pH of the neutralization reaction solution should be kept at 3 or higher, preferably 5 to 10. In the present invention, the system for producing tin oxide hydroxide means the step of neutralizing or hydrolyzing the aqueous tin compound solution to produce tin oxide hydroxide in the methods (a) to (c).

Examples of the tin compound used as the tin component used here include tin halides such as tin chloride, tin oxide, tin hydroxide, or tin inorganic salts such as tin sulfate and tin nitrate (stannous tin). Salt, stannic salt) and the like, and these may be used alone or in combination of two or more kinds. Above all, it is industrially desirable to use an aqueous solution of tin chloride in hydrochloric acid.

As the silicon compound as the silicon component, various silane coupling agents, silicone oil, colloidal silica and the like are used in addition to sodium silicate.

The mixing ratio of the silicon compound and the tin compound is
0.3 to 2 relative to the weight of SnO ₂ in terms of SiO ₂
It is desirable to add 0%, preferably 0.5 to 15%. If it is less than 0.3%, needle-like properties cannot be obtained. . In addition, it is desirable to add a large amount of silicon compound to some extent in order to obtain better acicularity, but if a large amount of silicon compound remains in the product after firing, it will adversely affect the conductivity. Since it is undesirable, it is desirable to remove unwanted amounts of silicon compounds by soluble salt removal treatments. In the product after the removal of soluble salts, if the silicon compound is left in an amount of 0.1 to 10%, preferably 0.3 to 6% based on the weight standard of SnO ₂ in terms of SiO ₂ , the product can be It has excellent dispersibility in water without adversely affecting the conductivity, and can easily form an aqueous dispersion suitable for various uses.

Examples of the alkali in the aqueous alkali solution include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, carbonates and ammonia. These may be used alone or in admixture of two or more. You may use it. The neutralization reaction can be carried out in water, hot water or alcohol, and is preferably carried out in hot water.

The precursor thus obtained is then subjected to usual treatments such as washing, drying and crushing, and is calcined at 700 to 1200 ° C. in the presence of an alkali metal halide.

When the precursor and the alkali metal halide are mixed, various methods can be used. For example, the treated product of the precursor and the alkali metal halide are mixed and stirred by a Henschel mixer or the like. If mixed and pulverized with a dry pulverizer after mixing, a more preferable one is obtained in terms of needle-like property. At this time, various regulators can be added to control the properties of the final product. For example, a phosphoric acid compound such as potassium phosphate is added for the purpose of controlling the acicularity of the acicular fine powder. You can also do it.

The firing can be carried out at 700 to 1200 ° C., preferably 800 to 1100 ° C., and the firing temperature is 7.
If it is lower than 00 ° C, the needle-like property becomes insufficient, and if it exceeds 1200 ° C, the short axis becomes thick and the transparency is apt to be impaired. A firing time of 30 minutes to 5 hours is suitable.

Various kinds of alkali metal halides may be used, and examples thereof include sodium chloride, potassium chloride and lithium chloride, which may be used alone or in combination. The amount of alkali metal halide used is SnO ₂ or SiO ₂ as precursors.
1% or more, preferably 10 to 100% based on the total weight of the above, and if the amount is less than the above range, the needle-like property becomes insufficient, and if it is too much, it is not economically advantageous and productivity is high. Is not good and is not preferable. It should be noted that some degree of acicularization can be achieved by using a halide of an alkaline earth metal such as BaCl _{2 in place} of the halide of an alkali metal, but this is sufficient compared with the case of using a halide of an alkali metal. Not a thing.

The calcined product is then treated with an aqueous medium of water or acid to remove soluble salts. As the acid used here, various acids can be used, but for example, there are inorganic acids and organic acids, and among these, inorganic acids such as hydrochloric acid, sulfuric acid, hydrofluoric acid are desirable.

The treated product obtained by removing the soluble salts as described above is, if necessary, for example, subjected to centrifugal sedimentation treatment or various classification means to remove those having insufficient needle-like properties, and then subjected to ordinary filtration. By carrying out washing, drying, finish pulverization, etc., the short-axis average particle size is 0.005 to 0.05 μm, the long-axis average particle size is 0.1 to 3 μm, and preferably 70% or more of the total weight. , Short axis particle size 0.003-0.1μ
m, the major axis particle diameter is 0.05 to 10 μm, and the acicular conductive tin oxide fine powder having a shape with an aspect ratio of 5 or more can be obtained. When the silicon compound is added as SiO _{2 in an} amount of more than 10% by weight, it is preferable to use hydrofluoric acid or the like and perform the dipping treatment so that the SiO ₂ content is 10% by weight or less. From the viewpoint of obtaining

The needle-like conductive tin oxide fine powder of the present invention is blended with plastics, rubber, fibers and the like as a conductivity-imparting material or a base material to obtain conductive plastics, conductive paints, magnetic paints, conductive rubbers, It can be used as a conductive composition such as a conductive fiber. When used as the conductive plastics, so-called general-purpose plastics, various engineering plastics can be used, as the general-purpose plastics, for example, polyethylene, vinyl chloride resin, polystyrene, polypropylene,
Methacrylic resin and urea-melamine resin are general-purpose engineering plastics such as phenol resin, unsaturated polyester resin, hard vinyl chloride resin, ABS resin and AS resin, and engineering plastics are, for example, epoxy resin, polyacetal, Polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyphenylene ether, polyphenylene sulfide, polysulfone, fluororesin, and as super engineering plastic, for example, diallyl phthalate resin,
Silicon resin, polyimide resin, polyamide imide, bismaleimide triazine, polyamino bismaleimide,
Olefin vinyl alcohol copolymer, polyoxybenzylene, polymethylpentene, polyether sulfone,
Polyether imide, polyarylate, polyether ether ketone, etc. are mentioned, and are compounded in these resins. The compounding amount of the acicular conductive tin oxide fine powder in the molding resin is 3 to 200 parts by weight, preferably 10 to 100 parts by weight, based on 100 parts by weight of the resin.

When the acicular conductive tin oxide fine powder of the present invention is used as a conductive paint or a magnetic paint, various binders such as polyvinyl alcohol resin, vinyl chloride-vinyl acetate resin, acrylic resin, epoxy resin, urethane are used. resin,
Natural system such as alkyd resin, polyester resin, ethylene vinyl acetate copolymer, acrylic-styrene copolymer, fibrin resin, phenol resin, amino resin, fluororesin, silicone resin, petroleum resin, shellac, rosin derivative, rubber derivative It is mixed with a resin or the like and dispersed in water or a solvent. The amount of the acicular conductive tin oxide fine powder blended in the binder resin is 3 to 200 parts by weight, preferably 10 to 100 parts by weight, based on 100 parts by weight of the binder solid content. In the case of a conductive paint, by applying the paint to an insulating substrate such as paper or a polymer film, a conductive coating that is light and has excellent transparency, surface smoothness, and adhesiveness can be applied to the substrate. The film can be formed into various antistatic coatings, electrostatic recording papers, electrophotographic copying papers, and the like. In addition,
When the needle-shaped conductive tin oxide fine powder of the present invention is applied to an aqueous paint, a treated cake after removing treatment of the tin oxide fine powder or soluble salts obtained from the production process of the tin oxide fine powder is used. When preparing an aqueous dispersion prepared by dispersing in an aqueous medium and using the aqueous dispersion for coating, reduction of dispersion energy at the time of coating and dehydration and drying energy in the tin oxide fine powder manufacturing process are aimed at. The above is preferable. The solid content concentration of the aqueous dispersion is 1 to 70% by weight, preferably 10 to 50% by weight, and the pH is 4 to 12, preferably 5 to 10.

On the other hand, in the case of a paint used for producing a magnetic recording medium, the adhesive force between the non-magnetic support and the magnetic layer is improved, the magnetic recording medium is prevented from being charged, the film strength is enhanced, and the magnetic layer is thin. It is useful for improving dispersibility and surface smoothness of the lower non-magnetic layer due to layering and surface smoothing. In particular, with the recent trend toward higher recording density in magnetic recording, there is a marked tendency for the recording wavelength to become shorter,
Along with this, there is a further demand for thinner magnetic layers in magnetic recording media. However, when the magnetic layer is made thinner, the influence of the support is likely to appear on the magnetic surface, and deterioration of the electromagnetic conversion characteristics cannot be avoided. For this reason, for example, by providing a non-magnetic undercoat layer on the surface of the non-magnetic support and then providing the magnetic layer as an upper layer, the influence of the surface roughness of the support can be eliminated, and the magnetic layer can be thinned to a high level. A method for achieving output is being used. The acicular conductive tin oxide fine powder of the present invention is packed in the lower nonmagnetic layer in a volume packing ratio of 20 to 80.
%.

When used as a conductive rubber, for example, silicone rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, butyl rubber, butadiene-
Acrylonitrile rubber, ethylene-propylene-diethane polymer, ethylene-propylene rubber, fluororubber,
Ethylene-vinyl acetate copolymer, chlorinated polyethylene,
It is mixed with conventionally known ones such as acrylic rubber, chloroprene rubber, urethane rubber, polysulfide rubber, chlorosulfonated polyethylene rubber, and epichlorohydrin rubber.

When it is used as a conductive fiber, it is blended with a fusible fiber such as a polyamide resin, a polyester resin, a polyolefin resin, a polyvinyl resin or a polyether resin.

The conductive composition thus obtained is
Compared with a conventional spherical conductive powder-containing conductive composition, a high conductivity can be obtained with a smaller amount of the resin binder, and the transparency is excellent, which is economically advantageous. . Since such a small amount is required, the binder can be used without lowering its strength. When a high-concentration conductive paint is used, desired conductivity can be obtained even with a thin coating film.

[0028]

【Example】

Example 1 500 g of stannic chloride pentahydrate was added to 5 l of pure water at 90 ° C.
Solution dissolved in 500 ml of 3N hydrochloric acid aqueous solution, and sodium silicate aqueous solution (SiO ₂ 308 g / l) 17.4 m
1 and sodium hydroxide were added in parallel over 20 minutes to maintain the pH of the system at 7-7.5 to form a co-precipitate. Next, hydrochloric acid was added thereto to adjust the pH of the system to 3, the precipitate was filtered, and then washed with water until the specific resistance of the filtrate became 15000 Ωcm. After drying the obtained cake at 110 ° C. for 12 hours, the dried product 100
20 parts by weight of sodium chloride was added to parts by weight, and both were uniformly mixed and ground. This mixture was baked in an electric furnace at 900 ° C. for 1 hour. Then, the obtained baked product was immersed in an aqueous solution of hydrofluoric acid to remove soluble salts, dried and pulverized to obtain the target needle-shaped conductive tin oxide fine powder.

Example 2 In Example 1, the sodium silicate aqueous solution 34.
The same process as in the case of the same example except that 9 ml was used to obtain the desired needle-shaped electroconductive tin oxide fine powder.

Example 3 In the same manner as in Example 1, except that potassium chloride was used instead of sodium chloride, the same treatment as in the case of the same example was carried out to obtain the desired needle-like conductive tin oxide fine powder.

Example 4 The same procedure as in Example 1 was carried out except that the firing temperature was set to 1000 ° C. to obtain the desired needle-shaped electroconductive tin oxide fine powder. An electron micrograph of this product is shown in FIG.

Example 5 300 g of stannic chloride pentahydrate was added to 5 l of pure water at 90 ° C.
A solution dissolved in 300 ml of N hydrochloric acid aqueous solution and 200 g /
sodium hydroxide solution having a concentration of 1
Was added in parallel over 20 minutes to maintain 7.0-8.0 to form a co-precipitate. Next, hydrochloric acid was added thereto to adjust the pH of the system to 3, and then the precipitate was filtered,
Thereafter, the filtrate was washed with water until the specific resistance reached 20000 Ωcm. The obtained cake was dried at 120 ° C. for 12 hours and then pulverized with a perparizer. 2.5 parts by weight of colloidal silica and 2 parts by weight based on 100 parts by weight of the pulverized product.
0 parts by weight of sodium chloride was added and mixed to homogeneity. This mixture was baked in an electric furnace at 900 ° C. for 1 hour. Then, the obtained baked product was immersed in an aqueous solution of hydrofluoric acid to remove soluble salts, dried and pulverized to obtain the target needle-shaped conductive tin oxide fine powder.

Example 6 The same procedure as in Example 1 was carried out except that the amount of sodium chloride was changed to 60 parts by weight to obtain the desired needle-shaped conductive tin oxide fine powder. .

Comparative Example 1 A conductive fine powder was obtained in the same manner as in Example 1 except that sodium chloride was not used.

Comparative Example 2 A conductive fine powder was obtained in the same manner as in Example 1 except that sodium silicate was not used. An electron micrograph of this product is shown in FIG.

Comparative Example 3 A conductive fine powder was obtained in the same manner as in Example 1 except that the firing temperature was 600 ° C.

Test Example 1 With respect to the conductive fine powder of each sample obtained in each of the above Examples and Comparative Examples, (1) an electron micrograph (magnification: 100,000 times) was observed to obtain a weight average particle diameter, and The aspect ratio was calculated based on it. Furthermore, (2) 1 of each sample powder
The specific resistance (Ωcm) under a pressure of 00 Kg / cm ² was measured (digital multimeter: Model 2502A, manufactured by Yokogawa Hokushin Electric Co., Ltd.). The results are shown in Table 1.

[0038]

[Table 1]

Test Example 2 Two conductive fine powders of each of the samples obtained in Example 1 and Comparative Example 2
0 g of acrylic resin (Acridic A-165-45,
Solid content 45% by weight, manufactured by Dainippon Ink and Chemicals, Inc.) 30.6
g, toluene-butanol mixed solution (mixing weight ratio 1:
1) After mixing with 26.4 g and 50 g of glass beads, paint shaker (Reddevil,
# 5110) and shaken for 20 minutes to prepare each mill base. Next, a predetermined amount of the acrylic resin and the toluene-butanol mixed solution were added to each mill base, and the mixture was stirred and mixed to obtain each pigment concentration (% by weight) in Table 2.
A paint was prepared. This paint was applied to a polyester film so that the dry film thickness was 4 μm, and naturally dried for 40 hours to prepare a test sheet. The surface resistivity (Ω / □) of this sheet was measured (digital ohm meter: R-506 type, manufactured by Kawaguchi Denki Seisakusho). Moreover, the haze degree (%) was measured (haze meter: NDH-300.
A type, manufactured by Nippon Denshoku Industries). These results are shown in Table 2 and Table 3.
Shown in.

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

INDUSTRIAL APPLICABILITY The present invention is a needle-shaped conductive material which requires less compounding amount as compared with the conventional conductive fine powder when the same conductivity is obtained without using a special device or expensive raw material. Provide fine tin oxide powder and a method for producing the same,
Moreover, the acicular conductive tin oxide fine powder of the present invention has a short axis of 0.005 to 0.05 μm, which is finer than that of the conventional one, and is excellent in transparency, and its manufacturing method is also extremely excellent in productivity. It is a thing.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing the particle structure of the acicular conductive tin oxide fine powder of the present invention obtained in Example 4 (magnification 100,
000 times).

FIG. 2 is an electron micrograph (magnification: 100,000 times) showing the particle structure of the conductive fine powder obtained in Comparative Example 2.

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-3-62433 (JP, A) JP-A-5-19525 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C01G 1/00-23/08 C30B 1/00-35/00 WPI (DIALOG) EUROPAT (QUESTEL)

Claims (8)

(57) [Claims] 1. The short axis average particle size is 0.005 to 0.05.
μm, the long axis average particle size is 0.1 to 3 μm,
In addition, the aspect ratio is 5 or more, and the silicon component is SiO ₂
Needle-like conductive tin oxide fine powder containing 0.1 to 10% by weight based on SnO ₂ . 2. 70% or more of the total weight has a short axis particle size of 0.
003 to 0.1 μm, and major axis particle diameter is 0.05 to 5
2. The aspect ratio is 5 μm and the aspect ratio is 5 or more.
The needle-shaped conductive tin oxide fine powder described. 3. A material to be fired containing a tin component, a silicon component and a halide of an alkali metal is 700 to 1200 ° C.
And the soluble salts of the obtained fired product are removed. The short-axis average particle size is 0.005 to 0.05 μm, the long-axis average particle size is 0.1 to 3 μm, and the aspect ratio is A method for producing a needle-shaped conductive tin oxide fine powder having a ratio of 5 or more. 4. The acicular conductive tin oxide fine powder according to claim 1,
An aqueous dispersion prepared by dispersing in an aqueous medium. 5. An aqueous dispersion obtained by dispersing the tin oxide cake after removing the soluble salts according to claim 3 in an aqueous medium. 6. The acicular conductive tin oxide fine powder according to claim 1,
A conductive coating composition prepared by mixing 3 to 200 parts with respect to 100 parts by weight of a binder solid content. 7. An aqueous dispersion according to claim 4 or 5 is obtained by applying the resin 1
An electroconductive coating composition obtained by blending 3 to 200 parts by weight of the aqueous dispersion with respect to 00 parts by weight (based on the solid content). 8. The needle-shaped conductive tin oxide fine powder according to claim 1,
An electrically conductive resin composition prepared by mixing 3 to 200 parts by weight with respect to 100 parts by weight of a molding resin.