JPS6186421A - Preparation of white electroconductive powder - Google Patents

Abstract

PURPOSE:To prepare the title powder having superior electroconductivity with a very simple method by calcining a deposited material obtd. by adding an alkali (carbonate) to a mixture of a water-soluble Zn compd. and a water-soluble metal compd. in a specified proportion in a reducing atmosphere. CONSTITUTION:A water-soluble Zn compd. (e.g. ZnCl2) and 0.05-5pts.wt. (expressed in terms of oxide in the calcined compsn.) at least one water-soluble metal compd. selected from Al2O3, SnO2, In2O3, and Ga2O3 [e.g. Al(NO33] are added to 100pts.wt. ZnO, and the mixture is mixed in water and stirred thoroughly. An amt. of caustic alkali (e.g. NaOH) or alkali carbonate (e.g. Na2CO3) corresponding to 99.9-50% for the theoretically equiv. amt. for neutralization is added to the soln. to cause deposition of precipitate, which is filtered, washed with water, dried, and if necessary, crushed to disintegrated to agglomerated particles, then calcined at 500-800 deg.C in a reducing atmosphere, such as H2 or CO.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a white conductive powder containing zinc oxide as a main component, which is mixed into plastics, rubber, etc. in order to impart conductivity.

In recent years, in the IC and electronic industries, it has been discovered that static electricity generated in plastic and rubber components causes functional problems in devices.As a countermeasure, conductive fillers such as carbon and zinc oxide are used in base materials such as plastic and rubber. It is proposed to add and mix.

In general, as a method for synthesizing conductive zinc oxide powder, activators A1, G
a. Supplying the raw material to which In oxide is added into the container,
Place this container under a reducing atmosphere or an oxidizing atmosphere,
A method of firing under a temperature condition of 600 to 1,100°C, and a so-called method of neutralizing a water-soluble zinc salt and a water-soluble metal salt such as AjL Ga, In, etc. with an alkali or alkali carbonate as seen in JP-A No. 56-69266. A method is known in which a precipitate obtained by coprecipitation by a wet production method is fired at a temperature of 600 to 1000° C. in a nitrogen atmosphere.

Although the wet production method has the advantage of being able to produce extremely fine powder particles compared to the solid mixing method described above, it has the disadvantage that the powder itself has poor electrical conductivity.

In view of these circumstances, the inventors of the present invention have diligently investigated the reason for the decrease in conductivity due to the wet production method, and have found that the cause of the decrease in the conductivity of the powder is Li and N, which do not reach the salt form in the powder.
The present invention was completed based on the discovery that the present invention lies in the presence of compounds such as a and .

That is, in the present invention, the composition after firing is such that at least one of aluminum oxide, tin oxide, indium oxide, and gallium oxide is added to 100 parts by weight of zinc oxide in terms of oxide.
05 to 5 parts by weight of a water-soluble zinc compound and at least one of aluminum, tin, indium and gallium.
Add a seed water-soluble metal compound, then add an alkali or alkali carbonate, stir to neutralize and coprecipitate, filter the obtained precipitate, wash with water, dehydrate if necessary, dry, and incubate for 500 minutes under a reducing atmosphere. A white conductive powder that is fired at a temperature of ~800℃! ! In the process, the amount of alkali or alkali carbonate relative to the water-soluble zinc compound is present in an amount less than the theoretical reaction equivalent for neutralization, and the white conductive powder is prepared by neutralization and co-precipitation. We are here to provide you with a method.

The method of the present invention will be explained in more detail below.

The water-soluble zinc compound that can be used in carrying out the present invention is not particularly limited as long as it forms zinc oxide after calcination, but examples include zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, and mixtures thereof. can be mentioned.

On the other hand, the water-soluble total bending compound may be any compound that forms aluminum oxide, tin oxide, indium oxide or gallium oxide after calcination, such as chlorides, nitrates, sulfates or acetates of aluminum, tin, indium and gallium, and alkalis. Metal salts and also mixtures thereof are applicable. More specifically, water-soluble closed aluminum compounds such as aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum acetate, sodium aluminate, alum, potassium alum, stannous chloride, tin chloride, tin sulfate, hexahydroxy Examples include water-soluble tin compounds such as sodium stannate and potassium hexachlorostannate, water-soluble indium compounds such as indium chloride and indium nitrate, and mixtures of gallium chloride, gallium nitrate, potassium sulfate, and soda and gallium oxide.

The mixing ratio of the water-soluble metal compound to the water-soluble zinc compound is 0.05 to 5 parts by weight, preferably 0.05 to 5 parts by weight in terms of oxide, per 100 parts by weight of zinc oxide in the form after firing.
It is used in a range of 1 to 2 parts by weight.

If the mixing ratio of the water-soluble metal compound to zinc oxide is out of the above-mentioned range, filler powder with a low volume resistivity value cannot be obtained.

A water-soluble metal compound is added to a predetermined amount of a water-soluble zinc compound, and the solution is sufficiently stirred and mixed. Next, sodium hydroxide, potassium hydroxide, ammonium hydroxide,
An alkali such as lithium hydroxide or an alkali carbonate such as sodium carbonate or sodium bicarbonate is added and stirred to neutralize and precipitate. Among these, sodium hydroxide and sodium carbonate are recommended as the alkali or alkali carbonate used in the neutralization reaction because they are inexpensive.

The feature of the present invention is such a neutralization coprecipitation step, in which the amount of alkali or alkali carbonate used for neutralization is less than the theoretical reaction equivalent for neutralization with respect to the water-soluble zinc compound. Specifically, it is not unique depending on the reaction temperature or stirring conditions during neutralization, but the theoretical reaction equivalent of neutralization is 99.9 to 5.
0%, preferably within the range of 99 to 90%,
If it exceeds 99.9%, the conductivity of the resulting powder mainly composed of zinc oxide will deteriorate significantly, which is not preferable.
On the other hand, when it is less than 50%, the precipitation yield naturally decreases, which is not preferable, and it is recommended to carry out the reaction in the range of 99 to 90% from the viewpoint of ease of reaction adjustment and yield.

After completing the reaction through neutralization coprecipitation treatment, the precipitate and 78 liquid are filtered out by a known method, and the separated precipitate is washed with water, dried, and crushed or crushed as necessary. After being crushed to loosen agglomerated particles, it is fired at a temperature of 500 to 800° C. in a reducing atmosphere such as hydrogen or carbon oxide. When using a reducing gas, in order to prevent the risk of explosion, the inside of the firing furnace is replaced with nitrogen, etc., and then the reducing gas is introduced and fired, or a mixture of reducing gas and nitrogen gas is used. Although methods using gas may be mentioned, a method of firing in a hydrogen or hydrogen-nitrogen atmosphere is recommended because the volume resistivity after firing is excellent.

In the present invention, if the firing temperature of the powder is lower than 500°C, the volume resistivity will be high, while if it exceeds 800°C, the effect of imparting electrical conductivity per unit weight of the powder will be reduced, which is not preferred.

Furthermore, when carrying out the method of the present invention, the precipitate after neutralization and coprecipitation is washed with dilute acid such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, etc. prior to washing the precipitate with water, and furthermore, the precipitate is washed with 60% water before drying after washing with water.
Heat treatment in water or steam at a temperature of ~100°C does not impede the effectiveness of the method of the present invention.

As detailed above, the method of the present invention involves mixing a water-soluble zinc compound and a water-soluble metal compound as an activator, and neutralizing the mixture with an alkali.1. In the method of obtaining conductive zinc oxide powder by coprecipitation, washing with water, drying, and calcination of the coprecipitate, the amount of alkali or alkali carbonate relative to the water-soluble zinc compound at the time of neutralization is simply calculated as the neutralization theoretical reaction equivalent. By using an extremely simple method of making the filler exist in a range of less than 100%, we succeeded in significantly improving the conductivity of the filler, and its industrial value is enormous.

The method of the present invention will be explained in more detail by examples below.
The present invention is not limited to these examples.

In the text, the theoretical reaction equivalent is the amount necessary to just neutralize all the salts added, and the equivalent ratio is the value obtained by dividing the total equivalent of alkali by the total equivalent of acid.

Example 1 64.64 kg of zinc chloride, 1.65 kg of aluminum nitrate (nanahydrate) and 1.55 kg of tinnic chloride (pentahydrate)
Dissolve kg in 1.5 m of water and stir well.
Q, 11 kg, caustic soda 1.1 kg.

Aqueous solution o containing 48 kg of soda carbonate, 25rr
i, neutralized and co-precipitated (equivalence ratio: 0.95), and the precipitate obtained by filtration was washed with 3 m of water, and the slurry concentration was 300.
g/j? Place in a sealed container and heat at 80°C.
After heat treatment for 6 hours, the mixture was dried at 500° C. for 3 hours and then crushed into powder.

This powder was fired at a temperature of 700° C. for 3 hours in a hydrogen atmosphere to obtain a white conductive powder. The powder resistance of this white conductive powder was 1 Ωcm.

Next, the obtained powder was filled in a commercially available urethane resin at a ratio of 50% by weight, and after kneading with rolls, it was formed into a 50 μm thick urethane film. The volume resistivity value of this film was 5×1 (fQcm).

The mixture was filled in a proportion of 50% by weight based on the polypropylene resin, kneaded with rolls, and then molded into a 70μ sheet. The volume resistivity value of the sheet was 8×10 5 Ωcm.

Example 2 64.64 kg of zinc chloride and 1.65 kg of aluminum nitrate (nonahydrate) were dissolved in 1.6 m of water, and while thoroughly stirring, an aqueous solution containing 48 kg of soda carbonate was added. ．． 25
m was added, neutralized and coprecipitated (equivalence ratio 20.94), and the precipitate obtained by filtration was washed with 3 m of water, and the slurry concentration was 300.
g/l, put it in a sealed container, and heat it at 80°C for 16
After being subjected to heat treatment for a period of time, it was dried at 500° C. for 3 hours and then crushed to form a powder.

This powder was fired at a temperature of 700° C. for 3 hours in a hydrogen atmosphere to obtain a white conductive powder. The powder resistance of this white conductive powder was 20Ωcn+.

Next, the obtained powder was filled in a commercially available urethane resin at a ratio of 50% by weight, and after kneading with rolls, it was formed into a 50 μm thick urethane film. The volume resistivity value of this film was 5×10 Ωcm.

The mixture was filled in a proportion of 50% by weight based on the polypropylene resin, kneaded with rolls, and then molded into a 70μ sheet. The volume resistivity value of the sheet was I x 107 Ωcm.

Example 3 6.464 kg of zinc chloride, 165 g of aluminum nitrate (nonahydrate) and 105 g of indium chloride were dissolved in 1601 water, and while stirring thoroughly, an aqueous solution 252 in which 4.9 g of soda carbonate was dissolved was added. Neutralized and coprecipitated (equivalent ratio:
0.95), the precipitate obtained by filtration was washed with 300β water, dried at 400° C. for 3 hours, and then crushed into powder.

This powder was fired at a temperature of 700° C. for 3 hours in a hydrogen atmosphere to obtain a white conductive powder. The powder resistance of this white conductive powder was 7 Ωcm.

Next, the obtained powder was filled in a commercially available urethane resin at a ratio of 50% by weight, and after kneading with rolls, it was formed into a 50 μm thick urethane film. The volume resistivity value of this Fidalum was 8×10 Ωcm.

The mixture was filled in a proportion of 50% by weight based on the polypropylene resin, kneaded with rolls, and then molded into a 70μ sheet. The volume resistivity value of the sheet was 2×10 6 Ωcm.

Comparative Example 1 A white conductive powder was obtained in exactly the same manner as in Example 1 except that the amount of soda carbonate was changed to 53 kg (equivalent ratio: 1.
05). The powder resistance value of this powder is 300Ωcm,
The ureboripropylene sheet obtained in the same manner as in the example had a resistance of 3×10 Ωcm.

Comparative Example 2 A white conductive powder was obtained in exactly the same manner as in Example 2 except that the amount of soda carbonate was changed to 56 kg (equivalent ratio: 1.
10). The powder resistance value of this powder is 500Ωcm,
The volume resistivity of the urethane film obtained in the same manner as in the example was 6 x 10 Ωcm, and that of the polypropylene sheet was 3 x 10 Ωcm.

Comparative Example 3 All samples were prepared in Example 3 except that the amount of soda carbonate was changed to 5.3 kg (white conductive powder was obtained in the same manner (equivalent ratio: 1).
．． 03). The powder resistance value of this powder is 80Ωcm,
The volume resistivity of the urethane film obtained in the same manner as in the example was 2 x 10 Ωcm, and that of the polypropylene sheet was 6 x 10 7 Ω.

Ta.

Claims (1)

[Claims] A water-soluble zinc compound, aluminum, and tin are mixed so that the composition after firing is 0.05 to 5 parts by weight of at least one of aluminum oxide, tin oxide, indium oxide, and gallium oxide per 100 parts by weight of zinc oxide. , adding at least one water-soluble metal compound of indium and gallium, and then adding an alkali or alkali carbonate,
Stir to neutralize and coprecipitate, filter the obtained precipitate, wash with water, dehydrate and dry if necessary, and heat to 500 ~
A method for producing a white conductive powder which is fired at a temperature of 800°C, characterized in that the amount of alkali or alkali carbonate relative to the water-soluble zinc compound is present in an amount less than the theoretical reaction equivalent for neutralization, thereby causing neutralization coprecipitation. A method for producing a white conductive powder.