JP3259186B2 - Plasma treatment method for powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atmospheric plasma processing method for a powder which continuously performs a plasma processing on a large amount of powder.

[0002]

2. Description of the Related Art Conventionally, powders such as pigments and dyes such as alumina oxide and titanium dioxide have been subjected to plasma treatment to increase the hydrophilicity of their surfaces, thereby improving their wettability, and being used in aqueous or oily solvents. It is easily dispersed. In particular, recently, powders having a fine particle size have been obtained, and it is a very important problem to disperse these powders well. The present inventor has previously found an invention in which these powders are subjected to an atmospheric pressure plasma treatment to improve dispersibility (Japanese Patent Application No. 2-195018). However, in this method, an electrode is attached to the outside of a cylinder, and the inside of the cylinder is passed between the electrodes together with a powder and an insoluble gas for generating an atmospheric pressure plasma such as helium or argon.
Therefore, the plasma processing time is extremely short because it is proportional to the gas flow rate, so that the plasma cannot be completely applied to the powder, and the powder is processed in a limited space within the cylinder by the batch method. Therefore, there is a disadvantage that a large amount of powder cannot be processed.

[0003]

SUMMARY OF THE INVENTION The present inventor has made various studies to improve the above-mentioned drawbacks and to perform a more complete plasma treatment of a large amount of powder. As a result, the present invention has been completed. It is an object of the present invention to provide an atmospheric pressure plasma processing method for a powder which continuously and for a longer time processes a large amount of powder.

[0004]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a lining made of a dielectric material on at least one of the outer side of a metal inner cylinder and the inner side of a coaxial metal outer cylinder. And the outer cylinder is coaxially supported to provide a certain gap between the two,
These inner and outer cylinders are tilted and rotatably installed, and 2500 to 3500 V at 3000 to 5000 Hz between the inner and outer cylinders.
Large powder which of the該間gap with applying a voltage to generate atmospheric pressure plasma in the gap between them to move the powder which is an object to be treated is characterized by continuously performing the plasma treatment
This is a pressure plasma processing method.

That is, according to the present invention, the atmospheric pressure plasma is generated in the gap between the outer side of the inner cylinder and the inner side of the outer cylinder, and the powder is moved through the gap by tilting and rotation of the inner and outer cylinders. The processing is performed, and therefore, the plasma processing can be continuously performed, and the processing time can be adjusted by the moving speed.

FIG. 1 shows an apparatus for carrying out the plasma processing method of the present invention. In FIG. 1, an outer cylinder 2 is coaxially arranged with an inner cylinder 1 by about 5 mm to 10 mm outside an inner cylinder 1 made of metal.
It is held by the bolts 3 so as to keep an interval of about mm. At this time, at least one of the inner surface of the outer cylinder and the outer surface of the inner cylinder was lined with a dielectric. However, when processing a conductive powder such as carbon black powder, both surfaces are lined with a dielectric. As the dielectric, a heat-resistant plastic such as Kapton, glass, ceramics, aluminum oxide, or the like is used.

[0007] A screw conveyor 13 is connected to one end of the inner cylinder 1 by extension. The inner cylinder 1 is rotatably supported by a deceleration motor 6 and a flange 14 by a shaft.
The bearing is supported by bearings 4 and 5 made of an insulator so as to be able to rotate together with the rotating shaft. At one end of the outer cylinder, a hopper 11 serving as a raw material supply port is provided, and at the other end, an outlet 15 for treated powder is provided, and an inert gas inlet for generating atmospheric pressure plasma is provided at the outlet, The gas is caused to flow in the gap between the outer cylinder and the inner cylinder so as to flow in the counterflow with the raw material. Further, a brush made of phosphor bronze is provided so as to contact the inner cylinder and the outer cylinder so that a glow discharge is generated between the outer cylinder and the inner cylinder. The entire apparatus is installed at an angle so that the raw material supply port side is high and the raw material discharge port is low by bolts and nuts 12.

[0008] This device is operated as follows. First, a gas-impermeable bag is attached to the material outlet so that gas introduced into the apparatus is not scattered from the outlet. Subsequently, a mixed gas of helium and argon is introduced from the gas inlet 9. This gas passes through the gap between the inner cylinder and the outer cylinder, and flows out to the hopper 11 while expelling air. After the inside of the gap becomes a mixed gas atmosphere of argon and helium, the hopper-1
Raw material is supplied into the apparatus from 1 and the inner and outer cylinders are motored.
Rotate slowly with 6. At the same time brushes 7 and 8
When a high frequency voltage of 3 KHz and 3000 V is applied to the device, a glow discharge occurs in the gap between the outer cylinder and the inner cylinder to excite the plasma. Conveyor belt 1 supplied from hopper 11 to powder
3 through the gap between the inner cylinder and the outer cylinder, which is slowly treated while passing through this gap, the powder surface of which is provided with significant hydrophilicity and is stored in the bag 10.

The total length of the apparatus used in the present invention is different from the laboratory scale and the industrial scale specification, but is from 0.5 m to about 10 m, and the moving distance of the powder is the same as that of the inner electrode, that is, 0.4 m. From 9m. In this method,
Since the surface treatment of the powder can be performed continuously, the powder can be processed in a large amount, and the moving speed of the powder can be adjusted by changing the inclination angle and the rotation speed. Next, the present invention will be specifically described with reference to examples.

[0010]

【Example】

Example 1 100 dielectrics were placed outside the inner cylinder of the device described in this specification.
A Kapton of micron thickness was laminated with an epoxy resin, and the gap between the inner and outer cylinders was set to 8 mm. As a gas, a mixed gas of helium gas and argon gas was fed from the inlet to replace the air in the cylinder and rotated at 10 revolutions per minute. The mixing ratio of the gas at this time is 40 parts of helium gas and 60 parts of argon gas. A voltage of 3000 Hz and 2500 V was applied with the outer cylinder of both cylinders on the + side and the inner cylinder on the ground side. Immediately, a glow discharge was generated in a gap of 8 mm between the two cylinders, and plasma was excited. The powder which entered the gap between the cylinders with the screw reached the outlet in 5 seconds and was discharged from the outlet into the bag. This treated powder had extremely high hydrophilicity and dispersibility, and when placed in water, the untreated one sank as it was in water, but the treated one was immediately dispersed and turned into an emulsion.

Embodiment 2 50 of the present specification is applied to both the outside of the inner cylinder and the inside of the outer cylinder.
Argon gas containing 10 ppm of acetone was supplied from a gas inlet as a gas to which Kapton having a thickness of micron was attached, and the air inside the cylinder was replaced.
A voltage of 5000 Hz and 3500 V was applied to the outer cylinder to cause glow discharge, and fine graphite powder was sent from a hopper. The powder entering the gap between the cylinders by the screw was discharged from the outlet continuously in 15 seconds because it was extremely light. This powder was highly hydrophilic and fine untreated graphite floated on the water, whereas the plasma-treated powder immediately sank and dispersed in water. It resulted in significantly higher hydrophilicity.

[0012]

As described above, according to the present invention, the powder is moved while slowly rotating in the gap between the inner cylinder and the outer cylinder which are plasma-excited. The resulting powder is subjected to a plasma treatment for a long time, and as a result, the surface of the obtained powder becomes highly hydrophilic, so that a powder having much better dispersibility than conventional ones is obtained.

[0013]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an apparatus for performing a method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner cylinder made of metal 2 Outer cylinder whose inner surface was lined with a derivative 3 Bolt 4 Bearing 5 〃 6 Reduction motor 7 Brush 8 ９ 9 Gas inlet 10 Bag 11 Hopper 12 Nut 13 Screw conveyor 14 Flange 15 Powder outlet

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-145038 (JP, A) JP-A-61-31319 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01J 19/00-19/32

Claims (1)

(57) [Claims] 1. A lining is made of a dielectric material on at least one of an inner side of a metallic outer cylinder and an inner side of a metallic outer cylinder which is coaxial with the outer peripheral of the metallic inner cylinder. A constant gap is provided between them, and these inner and outer cylinders are tilted and rotatably installed, and between the inner and outer cylinders at 3000 to 5000 Hz.
Applying a voltage of 2500 to 3500 V to generate atmospheric pressure plasma in a gap between the two, and continuously performing a plasma treatment by moving the powder to be processed through the gap; Atmospheric pressure plasma processing method.