JPH04334543A - Method and apparatus for atmospheric in-pipe pressure glow plasma reaction - Google Patents

Abstract

PURPOSE:To perform uniform treatment on the inner surface of a pipe by a method wherein a plurality of ring-shaped electrode pairs are provided to an insulator pipe in the longitudinal direction of the outer peripheral part thereof to be connected each other and a gaseous mixture of reactive gas and rare gas is introduced into the insulator pipe to generate glow discharge plasma in the pipe under atmospheric pressure. CONSTITUTION:A pair of ring-shaped electrodes 2, 3 are provided to the outer peripheral part of an insulator pipe 1 such as a cylindrical pipe and a plurality of the combinations of those electrodes 2, 3 are provided in the longitudinal direction of the pipe and these electrode pairs 2, 3 are connected in parallel or in series. A gaseous mixture 5 of reactive gas of an inorg. monomer such as oxygen or ammonia or an org. monomer such as hydrocarbon and dilution gas based on He is introduced into the insulator pipe 1 thus constituted from one end part thereof. A current is supplied under atmospheric pressure from a power supply to generate glow discharge plasma in the pipe not only to form the film to the inner surface of the pipe but also to stop and move the mixture in the pipe or the treatment of flowing matter. By this method, plasma treatment can be performed under atmospheric pressure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-tube atmospheric pressure glow plasma reaction method and apparatus. More specifically, the present invention provides an atmospheric-pressure glow inside the tube that can treat or react stationary, moving, or flowing objects on the inner surface or inside of an insulating tube such as a long-distance cylindrical tube under atmospheric pressure. This invention relates to a plasma reaction method and an apparatus for the same.

0002

[Prior art and its problems] Conventionally, coating the inner surface of insulator tubes made of plastic, glass, ceramics, etc., or surface treatments such as making them hydrophilic or hydrophobic, have been carried out by chemical treatment or low-pressure plasma treatment. There is. However, conventional chemical surface treatments generally have the disadvantage that dangerous chemicals are used and the operations and treatments are very troublesome. Furthermore, although a relatively good treated surface can be obtained in the low-pressure plasma treatment method, there is a problem in that the treatment must be performed under a low pressure of several Torr or less. This becomes 10 as the pressure inside the pipe increases.
This is because the discharge begins to concentrate at one point at around 0 Torr and shifts to spark discharge near atmospheric pressure, making it impossible to uniformly treat the inner surface of the tube or objects installed inside the tube. For this reason, low-pressure plasma processing requires a vacuum evacuation system, which has the drawback of making the apparatus bulky and increasing costs.

In addition, in low-pressure plasma treatment, in order to introduce gas such as a reactive gas into a long plastic thin tube or a porous thin tube with many small holes formed in the tube wall, a conduit or a tube of such a thin tube is used. The internal pressure rose due to the air passing through the tube wall, making it virtually impossible to perform sufficient discharge treatment. On the other hand, the inventors of this invention used a rare gas mainly composed of He as a diluent gas, greatly diluted the reactive gas, and maintained the total pressure near atmospheric pressure, which was easily stabilized at conventional atmospheric pressure. We have already proposed an atmospheric pressure plasma reaction method that generates a glow discharge, which was previously thought not to occur. This method can generate a stable glow discharge under atmospheric pressure that is suitable for uniform surface treatment without concentrating in a narrow discharge path, so a vacuum exhaust system can be omitted, and the treatment equipment This is an epoch-making method that can significantly reduce costs.

[0004] However, in this atmospheric pressure plasma reaction method, since the discharge electrode used in the previous method was a parallel plate electrode, the treatment was mainly performed on a sample having a flat surface. Various improvements were required in order to treat the inner surface of the body tube and to effectively obtain reaction products of the gas flowing inside the tube. Incidentally, as a discharge type for a cylindrical tube made of glass or the like in conventional low-pressure plasma processing, for example, a capacitive coupling type or an inductive coupling type is widely known.

Among these, for example, in the capacitively coupled discharge format shown in FIG. 2, a pair of ring-shaped electrodes (A) (
(a) are arranged opposite to the outer circumference of the cylindrical tube (c). The discharge type shown in FIG. 3 is also a capacitive coupling type, and a curved plate-shaped electrode (d) is arranged around the outer periphery of a cylindrical tube (c). In addition, in the case of the inductively coupled discharge format shown in Fig. 3, a coil-type electrode (
(e) is placed on the outer periphery of the cylindrical tube (c).

Although it has been considered to apply these discharge types to the plasma reaction method under atmospheric pressure proposed by the present inventors, such application has been extremely difficult. That is, in the case of a discharge format using a curved plate-shaped electrode (D) shown in Figure 3, the discharge can be diffused in the tube axis direction by changing the axial length of the electrode (D). However, there is a natural limit to changing the axial length in terms of plasma stability, and the distance between the electrodes that can be discharged in He mixed gas (F) at atmospheric pressure is at most 25 mm. In the case of a large-diameter tube with a diameter of 25 mm or more, discharge cannot be generated. Moreover, since the distance between the electrodes in the radial direction has a large distribution, there is also the problem that the discharge density is extremely non-uniform.

[0007] Furthermore, in the case of the discharge type using the coiled electrode (O) shown in Fig. 4, the discharge is essentially localized because it does not produce a pulsed discharge, which is a necessary condition for atmospheric pressure glow discharge. Moreover, it is prone to high-temperature arcing and is unsuitable for low-temperature plasma. On the other hand, in the case of the discharge method using ring-shaped electrodes (A) and (B) shown in Fig. 2, the discharge in the tube radial direction is stable, and the device configuration allows for expansion of the discharge range in the tube axis direction. There is a large degree of freedom above. However, in reality, the pressure is extremely high compared to low-pressure glow discharge, so the discharge impedance is high, and the distance between the electrodes cannot be made sufficiently large. At a normally used discharge voltage of several kilovolts, the dischargeable distance is limited to about 25 mm, and beyond that the discharge becomes unstable.

[0008] Such restrictions on the distance between the poles have the drawback that the objects to be processed placed inside and the shapes of the objects are limited. Therefore, this invention aims to stabilize the plasma in the tube radial direction and improve the device configuration in the longitudinal direction of the tube axis as a basic technology for actively utilizing atmospheric pressure glow discharge plasma inside the tube. Focusing on the capacitively coupled discharge method shown in Fig. 2, which has a large degree of freedom, it eliminates the drawbacks of conventional plasma treatment inside insulated tubes, and allows for static and moving inside and inside of insulating tubes such as cylindrical tubes. Another object of the present invention is to provide a new in-tube atmospheric pressure glow plasma reaction method and an apparatus therefor, which can process or react a circulating material under atmospheric pressure.

[0009]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a plurality of pairs of ring-shaped electrodes in the length direction of the outer periphery, and connects each pair of multiple electrodes in parallel or in series. A mixed gas of a reactive gas and a rare gas is introduced from one end of the connected insulator tube, and a glow discharge plasma is generated inside the tube under atmospheric pressure to control static, moving, or circulating inside or inside the tube. Provided is an in-tube atmospheric pressure glow plasma reaction method for treating a substance.

[0010] Furthermore, the present invention provides a device for this method in which a plurality of pairs of ring-shaped electrodes are arranged in the length direction on the outer periphery of an insulator tube, and each pair of multiple electrodes is arranged in parallel or in series. To provide an in-tube atmospheric-pressure glow discharge plasma reactor in which the electrodes are connected to each other, and the distance between the multiple electrodes is at most about 25 mm or less. For example, as shown in FIG. 1, in the method of the present invention, an insulator tube (1
) A pair of ring-shaped electrodes (2) and (3) are provided on the outer periphery of the electrode. A plurality of combinations of these electrodes (2) and (3) are provided in the longitudinal direction of the tube. There are no particular restrictions on the material of the insulator tube (1), and examples include general-purpose plastics such as glass and vinyl tubes, as well as PTFT, FEP, PET, PPS, and PE.
It can be made of any material such as industrial general-purpose plastic materials such as EK, ABS, and silicone tubes, and ceramics. In addition, there is no particular limitation on the thickness of the insulator tube (1), and there are large diameter tubes exceeding 10 cm in diameter and 0.1 m diameter tubes.
It can be of any type, such as an ultrathin tube with a diameter of mφ or less. Its cross-sectional shape can also be polygonal in addition to circular.

As the pair of ring-shaped electrodes (2) and (3), for example, foil-shaped electrodes can be used and attached to the outer peripheral surface of the insulator tube (1). In addition, it is also possible to use a rectangular plate-shaped electrode or a coil that can stand on its own with a thickness of 1 mm or more. In addition, since the electrodes (2) and (3) can be separated from the surface to be treated, the insulator tube can be placed between the electrodes (2) and (3).
(3) It can be moved in the axial direction, allowing continuous processing of long objects. The materials of electrodes (2) and (3) are as follows:
Various conductive materials such as copper, silver, nickel, aluminum, stainless steel, and carbon can be used as desired. The interelectrode distance (L
) can have a maximum length of about 25 mm. Preferably it is 5 mm to 20 mm. In addition, in the case of a foil-like or plate-like electrode pair as illustrated in Fig. 1, the width (
m) is preferably from about 0.1 mm to about 20 mm, and can be made to correspond to the diameter of the insulator tube (1). Furthermore, in order to prevent external creeping discharge, the entire outer peripheral surface can be covered with an insulating adhesive such as epoxy or silicone adhesive.

[0012] Regarding the connection of such ring-shaped electrodes (2) and (3), each pair of electrodes can be connected in parallel or in series, for example, as illustrated in FIG. Due to the multiple arrangement of such combinations of electrodes (2) and (3) in the lengthwise direction of the tube and their connections, the discharge is sufficiently stable even under atmospheric pressure, where long-distance discharge has been difficult until now. Uniform glow plasma can be obtained.

Regarding the method of connecting the electrodes, it is preferable to connect them in parallel from the viewpoint of reducing the applied voltage. In addition, there is no particular limit on the power source (4), and there are several k
From low frequency of Hz to several 10kHz or 13.56MHz
It can be a high frequency up to z. In addition, insulator tube (
The reactive gas of the mixed gas (5) introduced from one end of 1) includes oxygen, inorganic monomers such as ammonia, and C2.
Fluorinated ethylene such as F4, C3 F6, CF4
, C2F6, etc., chain hydrocarbons with side chains containing fluorine atoms, or hydrocarbons with or without functional groups such as fluorinated aromatic hydrocarbons. Monomers can be used. Such a reactive gas is highly diluted with a diluent gas mainly composed of He to obtain a mixed gas (5). In order to stabilize the glow discharge, it is preferable that the mixing ratio of He is large, but an inert gas such as Ar or N2 may be mixed as necessary. For example, the mixing ratio of Ar to He can be about 90%. This makes it possible to reduce the amount of expensive He used and reduce costs. In either case, the total pressure of the mixed gas (5) is approximately 1 atmosphere.

[0014] The generated glow discharge plasma can cause various surface treatments and arbitrary chemical reactions such as thin film formation, synthesis, and decomposition, and the efficiency thereof can be significantly improved. The objects of treatment or reaction include the inner surface of the insulator tube (1), objects installed inside the insulator tube (1), the surface of moving objects such as powders floating or vibrating inside the tube, and gases. It can be any object such as a liquid surface with a gas phase remaining in a part of it. There are no particular limitations on the surface that can be surface-treated, and any surfaces including untreated surfaces, surfaces made of cellulose, biomaterials, etc., or surfaces that have been surface-treated can be used.

[0015]

EXAMPLES The in-tube atmospheric pressure glow plasma reaction method of the present invention will be explained in more detail with reference to Examples below. Example 1 In the configuration shown in Fig. 1, the outer diameter was 15 mm and the thickness was 2 mm.
, 1 on the outside of a 500 mm long Pyrex glass tube.
The width of each electrode (m) is 10 mm, and the distance between each electrode (L) is 20 mm.
mm, a plurality of electrode pairs were arranged, and the length of the entire electrode group was 310 mm.

A PET (polyethylene terephthalate) film having a thickness of 0.1 mm and a length of 400 mm was pasted along the inner periphery of the glass tube as a sample to be treated. Note that the electrode material was a copper plate. The discharge conditions were as follows.・Discharge power frequency: 13.56MHz・output
Power: 20W ・Gas used: He/O2 (90/10) ・Flow rate: 100sccm ・Total pressure
: 1 atm/processing time: He and O2 are introduced into the glass tube from one end for 10 minutes or more.
A glow discharge was generated by introducing a mixed gas with

[0017] After discharge, PET pasted on the inside of the glass tube
The film was removed, and the contact angle of water droplets on the surface of each location on the film before and after discharge was evaluated. Table 1 shows the results.

[0018]

[Table 1]

The contact angle of the film before discharge was 70 degrees. As is clear from Table 1, it was confirmed that hydrophilicity was achieved by discharge over a considerable distance. Such a surface treatment effect was also confirmed when the film was cut into strips with a width smaller than the inner diameter of the glass tube and inserted into the glass tube. Furthermore, similar effects were confirmed for solid samples and powders of various shapes. Example 2 In the same manner as in Example 1, a gas mixture of He and C2F4 (tetrafluoroethylene, TFE) was introduced under 1 atm to generate electric discharge. A polyimide film was inserted into the glass tube, but a transparent film was formed on its inner surface.

It was confirmed that a polytetrafluoroethylene (PTFE)-like film was formed on the polyimide film used as a substrate. When the water drop contact angle of this plasma polymerized film was measured, it was approximately 110 degrees to 115 degrees. It showed strong hydrophobicity comparable to Teflon. Of course, the invention is not limited to the above examples. It goes without saying that various embodiments are possible with respect to details such as the form and material of the electrode, the types of reactive gas and rare gas to be introduced, the applied voltage and its frequency, etc.

[0021]

[Effects of the Invention] As explained in detail above, the method using the multi-structured capacitive electrode of the present invention facilitates long-distance discharge, which could not be achieved with conventional methods, and enables It becomes possible to perform plasma treatment on the inner surface of an insulator tube, or on stationary, moving, or flowing objects inside an insulator tube under atmospheric pressure.

[Brief explanation of drawings]

FIG. 1 is a perspective view illustrating an apparatus that can be used in the in-tube atmospheric pressure glow plasma reaction method of the present invention.

FIG. 2 is a perspective view showing a conventional discharge type to an insulating cylindrical tube.

FIG. 3 is a perspective view showing a conventional discharge type to an insulating cylindrical tube.

FIG. 4 is a perspective view showing a conventional discharge type to an insulating cylindrical tube.

[Explanation of symbols]

1 Insulator tube 2 Electric pole 3 Electric pole 4 Power source 5 Mixed gas

Claims (3)

[Claims] Claim 1: A plurality of ring-shaped electrode pairs are provided in the length direction of the outer periphery, and a reactive gas and a rare gas are connected from one end of an insulator tube in which each pair of multiple electrodes is connected in parallel or in series. By introducing a mixed gas and generating a glow discharge plasma inside the tube under atmospheric pressure, the inner surface of the tube or the inside of the tube remains stationary.
An in-tube atmospheric pressure glow plasma reaction method characterized by treating moving or circulating materials. [Claim 2] The distance between multiple electrodes is approximately 25 m at maximum.
2. The in-tube atmospheric pressure glow plasma reaction method according to claim 1, wherein the in-tube atmospheric pressure is less than m. 3. A plurality of pairs of ring-shaped electrodes are arranged in the length direction on the outer periphery of an insulator tube, each pair of multiple electrodes is connected in parallel or in series, and the multiple electrodes are connected between each other. An atmospheric-pressure glow plasma reactor in a tube, in which a mixed gas of a reactive gas and a rare gas is circulated in a tube at a distance of about 25 mm or less.