JPS63147823A - Production of zinc oxide fine particle - Google Patents

Abstract

PURPOSE:To enlarge a specific surface area of the titled particle and to reduce the contained excess Zn by oxidizing and combusting a vapor of metallic Zn together with a jet gas contg. a combustible gas of a specified proportion in an oxidizing atmosphere. CONSTITUTION:The jet gas is obtained by allowing at inert gas as a carrier gas to contain 3-30vol% combustible gas (to the inert gas). The vapor of metallic Zn is allowed to blow out together with the jet gas into the atmosphere contg. O2. Then the above-mentioned metallic Zn is oxidized and combusted and the obtained oxidized Zn is rapidly cooled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improvement in a method for producing zinc oxide fine particles having a large specific surface area and a small amount of excess zinc.

(Prior Art) Zinc oxide particles are industrial products with a wide range of uses, such as rubber vulcanization accelerators, paints, catalysts, pharmaceuticals, electrophotographic materials, foundations, cosmetics such as creams, varistors, and ferrites. It is used in electronic component materials such as

Zinc oxide used for such purposes needs to be as fine as possible, that is, the particles need to have a large specific surface area and have high purity.

Conventionally, the following dry method is known as a method for producing zinc oxide. That is, in this method, metallic zinc vapor is jetted and introduced together with an inert gas as a carrier gas into an oxygen-containing atmosphere to oxidize and burn metallic zinc, and the obtained zinc oxide is rapidly cooled. .

[Problem that the invention seeks to solve]

However, the zinc oxide particles obtained by the above method are
Since the specific surface area was less than 15 m/g and the excess zinc contained was greater than 100 ppm by weight, the particle size and purity were not fully satisfactory.

The purpose of the present invention is to improve such conventional methods, solve the problems of this method, and produce zinc oxide having a specific surface area of 15 m/g or more and containing excess zinc of 100 ppm or less by weight. The object of the present invention is to provide a method for producing fine particles.

[Means for solving problems]

The present invention solves the above-mentioned problems by oxidizing and burning metal zinc by spouting metal zinc vapor together with an inert gas as a carrier gas into an oxygen-containing atmosphere.
The method for rapidly cooling the obtained zinc oxide is characterized in that the ejected gas contains combustible gas in an amount of 3 to 30% by volume based on the amount of inert gas.

[For production]

Metal zinc vapor obtained by heating and evaporating metal zinc is ejected from a nozzle into a combustion chamber as a carrier gas together with an inert gas such as nitrogen or argon.

The atmosphere in the combustion chamber contains oxygen, and air or oxygen is supplied from a nozzle different from the above-mentioned nozzle. The metallic zinc vapor ejected into such an atmosphere is immediately oxidized and burned to produce zinc oxide. The generated zinc oxide is rapidly cooled to prevent it from sintering into nodular particles before being cooled, and then collected.

In the present invention, the metal zinc vapor and inert gas ejected into the combustion chamber further contain 3 to 30% by volume of combustible gas based on the amount of inert gas.

Examples of the combustible gas include well-known hydrogen, carbon oxide, propane, and the like. If this inert gas is not included,
There are many cases where at most only one of the specific surface area and excess zinc conditions, which are the objectives of the present invention, can be achieved. If the amount to be contained is less than 3% by volume of the inert gas amount, the effect of containing the above-mentioned flammable gas will be diluted, and
If it exceeds 0% by volume, the combustion temperature when zinc oxide is produced is too high, and the specific surface area of the particles produced becomes small.

The reason why both the specific surface area and excess zinc conditions can be satisfied by containing a flammable gas is as follows.
The combustion temperature when zinc oxide is generated and the time that the generated zinc oxide stays in the combustion zone are higher and shorter, respectively, than when no flammable gas is included. It is assumed that this is due to the following.

In addition, the amount of metal zinc vapor and inert gas other than combustible gas among the ejected gases is 7 to 25%, respectively.
g/min, 8-20! ! /minute is preferable.

Fine and highly pure zinc oxide particles obtained by such a dry method are suitable as a light-sensitive material for electrophotography. Also,
It is also ideal as a raw material for cosmetics such as foundations and sunscreen creams because of its good elasticity and its ability to protect the skin from UV rays.

〔Example〕

Hereinafter, the present invention will be specifically explained using Examples and Comparative Examples.

Example 1 FIG. 1 is a schematic diagram of an apparatus used to carry out the method of the present invention. In the figure, a combustion chamber 1 was formed in the shape of a cube with a side of 50 cm using insulating bricks on an electric furnace 2 equipped with a resistance heating element. A graphite crucible 4 is placed in the electric furnace 2 and has a nozzle 3 at the top for spouting metallic zinc vapor. Metal zinc (purity 99
．． 99% by weight) is heated and melted in the electric furnace 2. The graphite crucible 4 is provided with an inlet pipe 5 through which nitrogen as a carrier gas or nitrogen and a combustible gas (hydrogen, -carbon oxide and propane) can be introduced onto the surface of the melted metal zinc bath. Around the nozzle 3,
A wind box 6 for blowing a swirling flow of oxygen in order to maintain an oxygen-containing atmosphere inside the combustion chamber 1 is also connected to a nozzle 3.
A cooling air blowing pipe 7 for rapidly cooling the produced zinc oxide is installed directly above the flame that is ignited nearby.

The outlet 8 of the combustion chamber 1 is connected to a suction fan via a gas flue 9, a classification box 10, and a collection device (
(Collection device and suction fan not shown).

Using the apparatus shown in Figure 1, 10 kg of metallic zinc is melted, and 507 kg of oxygen is added from the wind box 6! An experiment was conducted to produce zinc oxide by blowing air at 167 n/min from the cooling air blowing pipe 7.

Other zinc oxide production conditions and quality characteristics of zinc oxide obtained through experiments are shown in Table 1.

〔Effect of the invention〕

As is clear from the above, according to the method of the present invention, zinc fertilized fine particles having a specific surface area of 15 m/g or more and containing 100 ppm or less of excess zinc by weight can be produced by a dry method. The method has high industrial practicality.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an experimental apparatus used in an example of the present invention.

Claims (1)

[Claims] (1) In a method in which metal zinc vapor is ejected together with an inert gas as a carrier gas into an oxygen-containing atmosphere to oxidize and burn the metal zinc, and the resulting zinc oxide is rapidly cooled, the ejected gas is mixed with an inert gas. A method for producing zinc oxide fine particles, which comprises containing combustible gas in an amount of 3 to 30% by volume.