JPH0576759B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus and method for uniformly plasma treating the inner surface of a plastic tube.

Plastic pipes are widely used for a variety of purposes, and various surface treatments are applied to improve their surface properties.The present invention particularly allows the inner surface of long, thin plastic pipes to be easily treated. The present invention relates to an apparatus and method for uniformly performing plasma processing at high speed.

[Prior Art] Various apparatuses and methods have been proposed for plasma treating the inner surface of plastic tubes.

The inventor of this application has also proposed a method of glow discharge with two rod-shaped electrodes inserted into a plastic tube. This method allows setting of discharge conditions, requires less energy for discharge, and uses low frequency (e.g.
Although it has the advantage of being possible even at 5KHz),
Since it is an internal electrode method, it has the disadvantage that the diameter of plastic tubes that can be treated and the length that can be treated are limited.

On the other hand, the external electrode method has drawbacks such as low energy conversion efficiency and high equipment costs;
It is reported in Publication No. 29505.

However, as a result of additional tests using these devices and methods, it was possible to obtain a discharge length of only 30 cm for a plastic tube with an inner diameter of 4 mm, and 7 cm for a plastic tube with an inner diameter of 1 mm. Furthermore, according to the specification of the publication, it is generally difficult to increase the discharge length of a thin tube, and in this method, the maximum discharge length is 50 to 60 cm under any conditions.

The processing time for a given length of plastic tube is inversely proportional to the length of the discharge. For example, if the discharge length is doubled, the processing time can be halved.

[Objective of the Invention] The present invention lengthens the discharge length on the inner surface of a plastic tube with a small diameter, which could not be obtained conventionally, shortens the processing time and reduces processing costs, while achieving uniform and stable processing and improving surface characteristics. For example, it is an object of the present invention to provide a simple plasma treatment apparatus and method for improving adhesion, water wettability, chargeability, plasticizer transferability, antithrombotic property, and the like.

[Structure of the Invention] In the present invention, the ground side electrode is cylindrical, has an insulating layer on the electrode, a plastic tube is wrapped around this, and both end openings of the plastic tube are connected to a vacuum exhaust system and a gas supply system. A plasma processing apparatus that is airtightly connected to a system box, and has a hollow truncated cone-shaped electrode on the voltage application side with a large diameter on the evacuation system side of a plastic tube and a small diameter on the gas supply system on the outer periphery of this ground side electrode. While moving at least one of the cylindrical ground side electrode, the treated plastic tube wrapped around it, and the hollow truncated cone-shaped voltage application electrode on its outer periphery, low-pressure gas is passed through the plastic tube and both sides are moved. A plasma processing apparatus and method characterized in that an electric field is formed with an electrode to perform plasma processing on the inner surface of a plastic tube.

This will be explained below based on the figures.

FIG. 1 schematically shows plasma treatment of the inner surface of a plastic tube using the apparatus of the present invention. The plastic tube 1 is airtightly connected to the vacuum evacuation system box 2 and the gas supply box 3, and is wrapped around the cylindrical ground electrode 4 via the insulating layer 5, and its outer periphery is 6 hollow truncated cone-shaped voltage application side electrodes are arranged on the side. 7 is a power source.

Figure 2 is a detailed view of the cylindrical ground side electrode and insulating layer part, 4 is an electrode made of a conductive layer, 5 is a thin insulating layer, and the part 8 is either hollow, insulating material, or conductive material. Alternatively, a device for cooling the cylindrical ground electrode 4, the insulating layer 5, etc. may be incorporated, and by cooling it, it is possible to suppress the heat applied to the plastic tube being processed.

FIG. 3 is a diagram showing details of the voltage application side electrode, in which 6a is set to be on the evacuation side, 6b is set to be on the gas supply side, and 6c is tapered. This taper is preferably within 30°, and particularly desirably about 10°; if it is larger than this, a uniform discharge state cannot be obtained and uniform processing becomes difficult.

A method of plasma treatment on the inner surface of a plastic tube using this apparatus will be explained.

First, the plastic tube 1 is wound around the ground side electrode cylinders 4 and 5, and the hollow truncated conical voltage application side electrode 6 is brought into contact with the outer periphery of the plastic tube 1.

The plastic tube 1 may be wound in a loose manner, in a diagonal manner, or in any other manner. The cylindrical ground side electrode and the hollow truncated conical voltage application side electrode can be installed in relative positions with high precision, and either one of them can be moved with high precision. (not shown).

Next, one end of the plastic tube, the larger diameter side of the hollow truncated conical voltage application side electrode, is connected to a vacuum evacuation system box, and the other end is connected to a gas supply system box.
In this state, high-frequency electromagnetic waves are oscillated from the power source 7 between each electrode while the gas to be treated is flowing through the plastic tube at low pressure in the same manner as in a normal plasma processing apparatus. Gas pressure is controlled by a vacuum pump box.
The range is 0.01 to 10 Torr, preferably about 0.1 Torr. As for the frequency of the power supply, a low frequency (for example, 10KHz or less) is not effective, and a high frequency (for example, 100KHz or more) is preferable. Glow discharge treatment is performed while moving at least one of the cylindrical ground side electrode and the hollow truncated conical voltage application side electrode.

In the device of the present invention, the insulating layer 5 serves to prevent spot discharge when a high voltage is applied between the hollow truncated conical voltage application side electrode and the cylindrical ground side electrode. When a spot discharge occurs, the corresponding part of the plastic tube is deformed, damaged, carbonized, etc., and the process is interrupted.

Next is the taper of the hollow truncated conical voltage application side electrode, which plays the role of increasing the glow discharge length. According to the inventor's experiments, glow discharge in a plastic tube generally occurs from the evacuation side. This is because when a plastic tube is evacuated, a pressure difference is created due to conductance. In this device, this pressure difference is offset by the diameter difference between the vacuum evacuation system side 6a and the gas supply system side 6b with the hollow truncated conical voltage application side electrode, so the hollow truncated conical voltage application side electrode is A glow discharge can be generated over a long period of time, and the discharge length can be increased. Another way to lengthen the discharge length is to increase the width of the voltage application side electrode, but the larger the width, the more power is required for discharge, and the heat loss that is unique to the external electrode method increases. It is not possible to increase the width too much because it will affect the plastic tube.

In order to suppress the heat generated by voltage application, it is effective to incorporate a cooling device into the cylindrical ground side electrode at part 8, or to take measures to blow cold air onto the hollow truncated conical voltage application side electrode. .

[Effects of the Invention] According to the apparatus and method of the present invention, plasma treatment can be performed uniformly and stably on a small-diameter plastic tube with a simple apparatus and with a discharge length longer than that of the prior art.

Furthermore, according to this device, the initial volume of evacuation is limited to the internal volume of a small-diameter plastic tube, which is small, so the capacity of the vacuum pump is also small, and the evacuation time is short.

When processing longer tubes, the cylindrical ground electrode does not require moving the electrode over the entire length (l) of the plastic tube;
It is sufficient to move by πD (D: outer diameter of the cylindrical ground side electrode), and the device can be made simple and compact.

[Example] In this device, a polyvinyl chloride pipe with a length of 50 cm and an outer diameter of 48 mm is wrapped in aluminum foil with a thickness of 100 μm, and one end is used as a connection terminal, and a ground side electrode is placed on top of this.
A 100μ polyether sulfone film was wound as an insulating layer.

Thickness as hollow truncated conical voltage application side electrode
It was made from 100μ aluminum foil with a width of 12mm and a taper of 8°.

The high frequency power source is a high frequency oscillator manufactured by JEOL Ltd.
JEH-005D (oscillation frequency 13.56MHz) and automatic matching device AST-08 were used.

The plastic tube has an outer diameter of 1.6 mm, an inner diameter of 1.0 mm, and a length
10 m long Teflon resin pipe made by Nichias Co., Ltd., 15 on each end.
It was wrapped around the cylindrical ground side electrode, leaving about a cm. Commercially available products were used for the vacuum exhaust and gas supply systems.

The gas was argon, the vacuum level was 0.1 Torr, the output was gradually increased, and the entire band of the hollow truncated conical electrode on the voltage application side was glow-discharged at 150 W, and plasma treatment was performed while moving the electrode. The length of the plastic tube covered by the hollow truncated conical ground electrode, that is, the discharge length, was 97 cm.

Comparative Example 1 When the voltage application side electrode was simply cylindrical without a taper and the same treatment as in the example was performed, glow discharge occurred only on the evacuation system side of the plastic tube among the voltage application side electrodes, and the discharge length was 30 cm. All I could get was that.

Comparative Example 2 When the cylindrical ground side electrode was treated in the same manner as in Example except that the polyether sulfone film as an insulating layer was removed, spot discharge occurred and holes formed in the Teflon resin tube, making treatment impossible. Summer.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a device according to the invention. FIG. 2 is a front view and a side view of the cylindrical ground side electrode part. FIG. 3 is a front view and a side view of a hollow truncated conical voltage application side electrode. In the figure, 1... plastic tube to be treated, 2... vacuum evacuation system box, 3... gas supply system box,
4...Cylindrical ground side electrode, 5...Insulating layer, 6...
Hollow truncated conical voltage application side electrode, 6a...Evacuation side diameter of the electrode, 6b...Gas supply side diameter of the electrode, 6c...Taper of the electrode, 7...Power source, 8
...Indicates the hollow part of the cylindrical ground side electrode.

Claims (1)

[Claims] 1. The ground side electrode is cylindrical, has an insulating layer on the electrode, and has a structure in which a plastic tube is wound around the electrode, and the voltage application side electrode on the outer periphery is cylindrical. Plasma processing characterized by comprising hollow truncated conical electrodes, one diameter of which is larger than the other, and the pair of electrodes is structured to be able to move parallel to each other with respect to each electrode. Device. 2. Wrap the plastic tube to be treated around a cylindrical ground electrode via an insulating layer, connect the ends of the plastic tube to a vacuum evacuation system box and a gas supply system box, and while flowing low pressure gas, wrap the plastic tube around the evacuation system box. A method of continuously plasma-treating the inner surface of a plastic tube by moving the grounding side electrode or the applying side electrode in a parallel direction while forming an electric field using a hollow truncated conical voltage applying side electrode with a large side diameter.