JPH0365825B2 - - Google Patents

Description

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

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

Surface properties to be improved include adhesion, water wettability, chargeability, plasticizer migration, and antithrombotic properties.

There are various methods for treating the inner surface of plastic tubes.
The present invention particularly relates to a plasma processing method and an apparatus therefor.

[Prior art]

Regarding the plasma treatment method for the inner surface of a plastic tube, conventionally the plastic tube is placed inside an insulator tube.
There is a method that allows a predetermined amount of gas to flow through the insulator tube and the plastic tube and discharges it using an external electrode, but this method involves adjusting the pressure inside the insulator tube and the plastic tube and adjusting the difference between the inside diameter of the insulator tube and the outside diameter of the plastic tube. It is very troublesome to set the conditions.

In particular, plastic tubes have a relatively low modulus of elasticity, so as the tube becomes longer, it tends to sag, making adjustment difficult. (Japanese Unexamined Patent Publication No. 58-157829) Also, the openings at both ends of the plastic tube are evacuated and
A method has been proposed that involves introducing a gas and arranging electrodes to generate a discharge, but this method limits the length of the plastic tube and can only process plastic tubes up to approximately 50 mm. (Japanese Unexamined Patent Publication No. 59-40850) In this method, if the length of the plastic tube is 50 mm or more, a good glow discharge will not occur even if a power source with an output of 400 W is used, and this is because the distance between the electrodes is too far apart. It is presumed that this is because the energy required to start the discharge is higher due to the lower temperature.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus and method that are easy to set and that can uniformly plasma-treat the inner surface of a plastic tube even if the tube is long.

[Structure of the invention]

The present invention 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 having the same length as the length of the plastic tube to be processed are installed through the vacuum box. A plasma treatment device for the inner surface of a plastic tube, which is characterized by the following: using the device, inserting a pair of two rod-shaped electrodes into the plastic tube,
This plasma treatment method for the inner surface of a plastic tube is characterized in that a voltage is applied to the rod-shaped electrode under low-pressure gas supply in an airtight connection to generate a glow discharge over the entire inner surface of the plastic tube.

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 is a gas supply system, and the other box is a vacuum exhaust system.

A pair of rod-shaped electrodes approximately equal to the length of the plastic tube to be treated is installed from one of the boxes, and the pair of rod-shaped electrodes is inserted into the plastic tube and each box is brought into airtight contact, after which the tube is inserted into the plastic tube. This method utilizes a device that applies voltage to the rod-shaped electrode while flowing low-pressure gas 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 Figures 1 and 2, 1 is the plastic tube to be processed, 2 and 2' are airtight connections between the plastic tube and the vacuum box, 3 and 3' are the gas supply system and vacuum exhaust system box, and 4 and 4' are the valves. , 5 and 6 are gas supply and vacuum exhaust pipes, 7 and 7' are rod-shaped electrodes,
8 is a power supply.

The rod-shaped electrodes 7, 7' may be thick at their mounting portions and may be thinner at the plastic tube portion where glow discharge is performed.

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 part or all of the rod-shaped electrodes be electrically insulated with an organic or inorganic insulator so that the pair of two electrodes do not come into contact with each other and cause a short circuit.

After connecting the plastic tube 1 into which the rod-shaped electrodes 7, 7' are 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 valves 4, 4'. When a high voltage is applied using a plastic tube, a good glow discharge can be easily generated throughout the inside of the plastic tube.

According to the present invention, since the distance between the electrodes is smaller than the inner diameter of the plastic 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 tube to be treated.

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

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 polymer film on the inner surface of the 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 6mm inner diameter 4mm length
Glow discharge was performed in a 150 mm plastic tube using the apparatus shown in Figure 2 for 20 seconds at a frequency of 5 kHz, a vacuum of 0.07 Torr, and an output of 20 W using air as the gas.

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 drawings]

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. FIG. 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...Plastic 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'... Valve, 5, 6... Gas supply and vacuum exhaust pipe, 7, 7'... Rod electrode, 8... Power source.

Claims (1)

[Scope of Claims] 1. It 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 having the same length as the length of the plastic tube to be processed are used to connect the openings at both ends of the plastic tube. A plasma treatment device for the inner surface of a plastic tube, characterized in that it is installed through a box. 2 Using the device according to claim 1, a pair of two rod-shaped electrodes are inserted into a plastic tube, and a voltage is applied to the rod-shaped electrodes under a low-pressure gas supply in an airtight connection state to cause glow to glow over the entire inner surface of the plastic tube. A method for plasma treatment of the inner surface of a plastic tube, which is characterized by generating an electric discharge.