JPS60258234A - Plasma treatment of plastic pipe on its inner surface and device therefor - Google Patents

Abstract

PURPOSE:A specific unit provided with a vacuum box and another gas-feeding box, both of which can be tightly connected to both openings of a plastic pipe at the ends, is used to apply a voltage to a rod electrode which has been inserted into the pipe under a reduced gas pressure to effect plasma treatment for the inner surface of the plastic pipe. CONSTITUTION:A couple of rod electrodes are inserted into a plastic pipe and one end-opening of the plastic pipe is connected to the vacuum box and the other, to the gas-feeding box. Then, high voltage is applied between the electrodes, as a low-pressure gas is fed in the plastic pipe to effect glow discharge all over the inner surface of the pipe.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for plasma treating the inner surface of a plastic tube;
and its apparatus.

Plastic pipes are widely used in a variety of applications, and are subjected to various surface treatments to further improve their surface properties.

The surface properties to be improved include adhesion, water wettability, charging properties, plasticizer migration properties, antithrombotic properties, etc. There are 11 methods for treating the inner surface of plastic tubes, and the present invention is a plasma treatment method among them. and its apparatus.

[Prior art]

Regarding the plasma treatment method for the inner surface of a plastic tube, there is a conventional method in which a plastic tube is placed inside an insulator tube, a predetermined amount of gas is passed through the insulator tube and the plastic tube, and discharge is caused by an external electrode. It is necessary to adjust the pressure inside the insulator pipe and the plastic pipe, and to adjust the difference between the inside diameter of the insulator pipe and the outside diameter of the plastic pipe, making setting the conditions very difficult.

In particular, plastic tubes have a relatively low modulus of elasticity, so the longer the tube is, the more it will sag, making adjustment even more difficult. (Japanese Unexamined Patent Publication No. 58-157829) Also, a method has been proposed for evacuation, gas introduction, and discharging by arranging electrodes at the openings at both ends of a plastic tube, but this method is limited by the length of the plastic tube. However, it was only possible to process up to approximately 50 meters. (Japanese Unexamined Patent Publication No. 59-40850) In this method, if the length of the plastic tube is 50 mm or more, the output will be 400 mm.
Even when a W power source is used, a good glow discharge does not occur, and this is presumed to be because the distance between the electrodes is too far apart, so that the energy required to start the discharge is high.

[Purpose of the invention]

An object of the present invention is to provide a method and an apparatus for the same, which are easy to set and can evenly plasma-treat the inner surface of a plastic tube even if the length of the tube is long.

[Structure of the invention]

In the present invention, a pair of rod-shaped electrodes approximately equal to the length of the plastic tube are inserted into a plastic tube, one opening of the plastic tube is connected to a vacuum exhaust system box, and the other opening is connected to a glass supply system box. A method for plasma treatment of the inner surface of a plastic tube, characterized in that a high voltage is applied between the rod-shaped electrodes while connecting the tube and supplying low-pressure gas into the inner surface of the plastic tube, thereby causing a glow discharge over the entire surface of the inner surface of the plastic tube. and its equipment.

In this device, the openings at both ends of the plastic tube are equipped with two vacuum boxes that can be closely connected, one box being a gas supply system and the other box being a vacuum exhaust system.

A pair of rod-shaped electrodes approximately equal to the length of the plastic tube to be processed is installed from one of the boxes, and after inserting the pair of rod-shaped electrodes into the plastic tube and bringing each box into airtight contact, the inside of the plastic tube is placed. The device utilizes a device that applies voltage to the rod-shaped electrode while flowing low-pressure gas through the tube to plasma-treat the inner surface of the plastic tube.

The present invention will be explained in detail below with reference to the drawings.

In Figs. 1 and 2, 1 is a plastic pipe to be processed;
2.2' is the airtight connection between the plastic tube and the vacuum box, 3, 3' is the gas supply system and vacuum exhaust system box, 41471 is the pulp, 5 and 6 are the gas supply and vacuum rod electrodes 7, 7' The mounting part is thick, and the plastic tube part that performs glow discharge may be thinner.

It is desirable that the electrode mounting portion be insulated or shielded to prevent glow discharge.

Furthermore, the rod-shaped electrodes 7, 7' may be installed in pairs on only one side of the vacuum box as shown in FIG. 1, or one pair may be installed on both sides of the vacuum box as shown in FIG. That's fine, as long as the pair of rod-shaped electrodes covers the length of the plastic tube to be processed.

Further, it is preferable that a pair of two electrodes contact each other and short-circuit, and that part or all of the rod-shaped electrodes are electrically insulated with an organic or inorganic insulator.

After connecting the plastic tube 1 into which the rod-shaped electrodes 7, 7' have been inserted and arranged in this way to each box, the power source 8 is connected between the rod-shaped electrodes 7, 7' while supplying low-pressure gas by operating the pulp 4゜4'. When high voltage is applied using this method, it is possible to easily generate a good glow discharge over the entire inside of the plastic tube.

According to the present invention, since the distance between the electrodes is smaller than the inner diameter of the plus-nuc tube, the energy required to start the discharge is sufficient by using a normal power source, and the discharge conditions can be easily set.

Further, in the present invention, by appropriately changing the length of the rod-shaped electrode, it is possible to correspond to the length of the plastic pipe to be treated.

If the plastic pipe deforms due to its low internal pressure, it is also possible to prevent the plastic pipe from deforming by installing a container on the outside with approximately the same pressure.

The gas used in the present invention may be a non-polymerizable gas or a polymerizable gas.

Furthermore, the present invention can also be applied to a method in which the inner surface of a plastic tube is subjected to plasma treatment and then brought into contact with a monomer in a gas or liquid phase to form a graft polymerized film on the inner surface of a plastic tube.

The frequency of the power source used in the present invention is not particularly limited.

The specific device may be other than those shown in FIGS. 1 and 2 as long as it has the mechanism of the present invention.

Further, a large number of this device may be arranged in parallel to the power source 8 for processing.

〔Example〕

Made of low density polyethylene, outer diameter 6m, inner diameter 4mm, length 150
Glow discharge was performed on a No. 11II11 plastic tube for 20 seconds using the apparatus shown in FIG. 2 at a frequency of 5 kHz for the power source, air as the gas, a degree of vacuum of 0.07), and an output of 20 W.

This treatment showed good glow discharge over the entire surface of the plastic tube.

After the plasma treatment was completed, the plastic tube was cut and the water wettability of the inner surface was examined, and it was found that all parts of the plastic tube had better water wettability than untreated plastic tubes.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a plasma processing apparatus in which a pair of two rod-shaped electrodes are installed through a vacuum evacuation system box. Figure 2 is a diagram of a plasma processing apparatus in which two electrodes are installed, one through each of the vacuum evacuation system box (and the gas supply system box). 1.・Glasstic tube to be processed 2
．． 2'... Airtight joint between plastic tube and box 3.3'... Vacuum exhaust system and gas supply system box 4.4'... ... Pulp 5.6 ... Gas supply and vacuum exhaust pipe 7.7' ... Rod-shaped electrode 8 ...... Power supply Applicant: Sumitomo Bakelite Co., Ltd. 1. 1

Claims (1)

[Claims] A device that has a vacuum box for an evacuation system and a gas supply system that can airtightly connect the openings at both ends of a plastic tube, and a pair of two rod-shaped electrodes with the same length as the length of the plastic tube to be processed are installed through the vacuum box. Plasma on the inner surface of a plastic tube, characterized in that the pair of rod-shaped electrodes are inserted into the plastic tube and a voltage is applied to the rod-shaped electrodes under low pressure gas to generate a glow discharge over the entire inner surface of the plastic tube. Processing methods and sheep equipment.