JP3280994B2 - Atmospheric pressure glow plasma reaction method in tube - Google Patents

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. For more information,
The present invention relates to stationary inner and inner surfaces of an insulator tube such as a cylindrical tube,
The present invention relates to an in-tube atmospheric pressure glow plasma reaction method capable of treating or reacting a moving or flowing material under atmospheric pressure.

[0002]

2. Description of the Related Art Conventionally, film formation on an inner surface of an insulating tube made of plastic, glass, ceramics, or the like, or surface treatment such as hydrophilicity / hydrophobicity has been performed by chemical treatment or low-pressure plasma treatment. I have. However, the surface treatment by the conventional method has a drawback in that dangerous chemicals are generally used, and the treatment is very troublesome. Among them, the low-pressure plasma treatment has an advantage of realizing a good surface treatment, but usually has a problem that it must be performed under a low pressure of several Torr or less. This is because when the pressure inside the tube is increased, the discharge starts to concentrate at about 100 Torr, and at around atmospheric pressure, it shifts to spark discharge, and uniform treatment of the inside surface of the tube or the objects installed inside the tube is performed. It is impossible. For this reason, low-pressure plasma processing requires a vacuum evacuation system, which has the disadvantage of requiring a large-scale apparatus and increasing costs.

[0003] In the low-pressure plasma treatment, a long plastic thin tube or a porous thin tube having a large number of small holes formed in a tube wall is used to introduce a gas such as a reactive gas. The internal pressure rises due to the air passing through the pipe and the pipe wall, and it has been substantially impossible to perform a sufficient discharge treatment. On the other hand, the inventors of the present invention
Even if an atmospheric pressure plasma reaction method for generating a diffused glow discharge by using a rare gas mainly composed of He as a diluent gas, greatly diluting a reactive gas, and maintaining the total pressure near the atmospheric pressure has already been proposed. I have. In this method, since a stable glow discharge diffused under the atmospheric pressure can be generated, the evacuation system can be omitted, and the cost of the processing apparatus can be extremely reduced.

However, in this atmospheric pressure plasma reaction method, since the discharge electrode is a parallel plate electrode, processing on a sample having a flat surface is mainly performed, and processing on the inner surface of an insulator tube such as a cylindrical tube is performed. In addition, various improvements have been required in order to effectively obtain a gaseous reaction product flowing through the inside of the tube. By the way, as a discharge type for a cylindrical tube made of glass or the like in the conventional low-pressure plasma processing, for example, a capacitive coupling type or an inductive coupling type as shown in FIGS. 7 to 9 is widely known.

In the discharge type of capacitive coupling shown in FIG. 7, a pair of ring-shaped electrodes (a) and (b) are connected to a cylindrical tube (c).
Are arranged to face each other on the outer periphery. The discharge type shown in FIG. 8 is also a capacitive coupling type, in which a curved plate-shaped electrode (d) is arranged on the outer periphery of a cylindrical tube (c). In the case of the inductively coupled discharge type shown in FIG. 9, the coil-type electrode (e) is disposed on the outer periphery of the cylindrical tube (c).

It is conceivable to apply these discharge types to the plasma reaction method under atmospheric pressure proposed by the present inventors, however, it is practically impossible to apply them. It was a fact. That is, in the case of the discharge type using the ring-shaped electrodes (A) and (A) shown in FIG. 7, it is difficult to discharge under atmospheric pressure even if a mixed gas (F) diluted with He is used. In addition, the discharge does not spread and becomes local, which is unsuitable for the discharge treatment inside the cylindrical tube (c).

On the other hand, in the case of a discharge type using a curved plate-like electrode (D) shown in FIG. 8, the discharge is diffused in the tube axis direction by changing the axial length of the electrode (D). However, the distance between electrodes capable of discharging in a He mixed gas (f) at atmospheric pressure is at most 20 mm, and a large-diameter tube having a diameter of 20 mm or more cannot generate discharge. In addition, there is also a problem that the discharge density in the radial direction varies widely.

Further, in the case of the discharge type using the coil-type electrode (E) shown in FIG. 9, since the pulse-like discharge which is a necessary condition of the atmospheric pressure glow discharge does not occur, the discharge becomes essentially local. In addition, a high-temperature arc easily occurs, which is not suitable for low-temperature plasma. The present invention has been made in view of the above circumstances, and solves the drawbacks of the conventional plasma treatment inside an insulating tube, and makes the inner surface or the inside of an insulating tube such as a cylindrical tube stationary, moving or moving. An object of the present invention is to provide a new in-pipe atmospheric pressure glow plasma reaction method capable of treating or reacting a flow product under atmospheric pressure.

[0009]

According to the invention of the present application, as a solution to the above-mentioned problem, first , a pair of foil-shaped parallel electrode pairs are spirally attached to an outer peripheral portion. , A mixed gas of a reactive gas and a rare gas is introduced from one end of the insulator tube, and a glow discharge plasma is generated inside the insulator tube at atmospheric pressure, and a stationary or moving body inside the tube or inside the tube. Alternatively, there is provided an in-tube atmospheric pressure glow plasma reaction method characterized by performing glow plasma treatment on a flowing material. In addition, the invention of this application secondly provides an insulator tube
A pair of foil-shaped parallel electrode pairs are spirally stretched around
Reactive gas is supplied from one end of the insulator tube.
Insulation tube under atmospheric pressure by introducing a mixed gas of
Glow discharge plasma is generated inside, and inside the insulator tube
In which glow plasma processing is possible.
And an apparatus for glow plasma reaction in a tube.

For example, as shown in FIG. 1, in the method of the present invention, a pair of spiral parallel electrodes is provided on the outer peripheral portion of an insulating tube (1) such as a cylindrical tube, and one of the spiral parallel electrode pairs is provided. ) And the other is a ground electrode (3). The material of the insulator tube (1) is not particularly limited. For example, in addition to general-purpose plastics such as glass and vinyl tubes, PTF
T, FEP, PET, PPS, PEEK, ABS, general-purpose industrial plastic materials such as silicon tubes, ceramics, and any other materials. There is no particular limitation on the thickness of the insulator tube (1).
An arbitrary one such as a large-diameter tube exceeding 0 cm or an ultrafine tube having a diameter of 0.1 mm or less can be used. The cross-sectional shape may be a polygon other than the circle illustrated in FIG.

As the spiral parallel electrode pairs (2) and (3), for example, as shown in FIG. 1, a foil-like electrode is used, which is attached to the outer peripheral surface of the insulator tube (1). kill at. The material of the electrode pair (2) and (3) is copper,
Various conductive materials such as silver, nickel, aluminum, stainless steel, and carbon can be arbitrarily used. The distance (1) between the electrodes of such a spiral parallel electrode pair (2) (3) can be from 0.1 mm to about 30 mm. Preferably it is 5 mm to 20 mm. In the case of a foil-shaped electrode pair as exemplified in FIG. 1, the width (m) can be set to 0.1 mm to 30 mm, and can correspond to the diameter of the insulator tube (1). it can. Further, in order to prevent external creeping discharge, as shown in FIG. 2, for example, an insulating adhesive (4) such as an epoxy or silicone adhesive can be used to cover the entire outer peripheral surface.

Such a spiral parallel electrode (2)
There is no particular limitation on the power supply (5) connected to (3), and a low frequency of several kHz to a high frequency of several tens of kHz or 13.56 MHz can be used. Insulating tube (1)
As a reactive gas of the mixed gas (6) introduced from one end of the gas, an inorganic monomer such as oxygen or ammonia, C ₂ F ₄ ,
Functionality such as fluorinated ethylenes such as C ₃ F ₆ , fluorinated paraffin hydrocarbons such as CF ₄ and C ₂ F ₆ , or chain hydrocarbons with side chains containing fluorine atoms, or fluorinated aromatic hydrocarbons Any organic monomer, such as a hydrocarbon, with or without groups can be used. Such a reactive gas is greatly diluted with a diluent gas mainly composed of He to obtain a mixed gas (6). For stabilization of the glow discharge, it is preferable that the mixing ratio of He is large, but an inert gas such as Ar or N ₂ can be mixed if 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 the cost. In any case, the total pressure of the mixed gas (6) is set at around 1 atm.

On the other hand, the glow discharge generated is such that the electrodes, which are the counter electrodes of the electrode pairs (2) and (3), are slightly displaced in the tube axis direction and the circumferential direction, so that they adhere to the inner surface of the insulator tube (1). In this way, it spreads along the tube axis direction, and the discharge density is also averaged. Various chemical treatments such as various surface treatments, thin film formation, synthesis, and decomposition can be caused by the glow discharge plasma thus diffused, and the efficiency can be significantly improved.

The object to be treated or reacted is, in addition to the inner surface of the insulator tube (1), an object placed inside the insulator tube (1) or a moving body such as a powder which is carried by floating or vibrating in the tube. Any material such as a surface, a flowable substance such as a gas, a liquid surface partially leaving a gas phase, or the like can be used. The surface that can be surface-treated is also not particularly limited, and may be any surface, such as an untreated surface, or a surface that has been formed of cellulose, a biomaterial, or has been surface-treated.

[0015]

The present invention will be described in more detail with reference to the following examples. Example 1 As shown in FIG. 3, a 190 μm thick pipe having a thickness of 190 μm was formed inside a Pyrex glass tube (7) having an outer diameter of 10 mm and a thickness of 1 mm.
A polyimide film (8) (manufactured by Kapton H / Dupon) having a length of 240 mm and a length of 240 mm was attached uniformly and unitarily in the tube axis direction. In addition, a pair of spiral copper foil electrodes (9) and (10) were disposed outside the glass tube (7) at positions from 2 cm to 18 cm from the left end of the polyimide film (8). Mixed gas (O ₂ and He and O ₂ at 1 atm into the tube from one end of the glass tube (7) (approximately 760 Torr) is 10
%) Is introduced at a total flow rate of 2000 ml / min, and a high-frequency high voltage is applied at a frequency of 3 kHz and 3 mA to the copper foil electrodes (9) and (10) disposed on the outer peripheral surface of the glass tube (7) to generate discharge. I let it.

A pale He discharge emission was observed over 16 cm of the copper foil electrodes (9) and (10). After the discharge, the polyimide film (8) attached to the inside of the glass tube (7) was extracted, and the change in hydrophilicity / hydrophobicity of the inner surface of the film (8) before and after the discharge was evaluated by the contact angle of a water droplet. Table 1 shows the results.

[0017]

[Table 1]

The contact angle of the film (8) before discharging was 70 degrees. As is clear from Table 1, the electrodes (9) (1
0) The hydrophilicity of the inner surface of the film (8) immediately below increased after discharge. In addition, it was confirmed that before and after the discharge region, particularly in the downstream region, the region was hydrophilized by the discharge over a considerably long distance. Such a surface treatment effect was also confirmed when the polyimide film (8) was cut into a width smaller than the inner diameter of the glass tube (7), cut into a strip, and inserted into the glass tube (7).

Example 2 In the same manner as in Example 1, an apparatus as shown in FIG. 3 was assembled, and He and C ₂ F ₄ (tetrafluoroethylene, TF
E) mixed gas at 1 atm, He flow rate 2000ml / min
And TFE at a flow rate of 4 ml / min.
During 0), a voltage was applied at 3 kHz and 2 to 4.5 mA to generate a discharge. A transparent film was formed on the inner surface of the polyimide film (8).

FIG. 4 is a correlation diagram showing the relationship between the atom density ratio of fluorine and carbon measured by ESCA (X-ray photoelectron spectroscopy) of the deposited film in relation to the discharge current. FIG. 5 is a correlation diagram showing the relationship between the discharge current and the film forming speed. As is clear from FIGS. 4 and 5, it was confirmed that a polytetrafluoroethylene (PTFE) -like film was formed at a sufficient speed on the polyimide film (8) used as the substrate. The measured contact angle of water droplets on the plasma polymerized film was about 110 ° to 115 °. It showed strong hydrophobicity comparable to Teflon.

Example 3 In a device similar to that of Example 1, NH as a model exhaust gas was used.
₃ and NO ₂ were each largely diluted with He and Ar, and refluxed to the discharge region through a circulation pump under the following conditions. Mixed gas flow rate: NH ₃ (NO ₂ ) 1 ml / min He 1000 ml / min Ar 1000 ml / min Pressure: Atmospheric pressure Discharge frequency: 13.56 MHz Output: 100 W A part of the gas that passed through the discharge area was taken out and analyzed by gas chromatography. did.

FIG. 6 shows NH ₃ and N versus discharge time.
FIG. 4 is a correlation diagram showing the decomposition rate of O ₂ . As is clear from FIG. 6, it was confirmed that NH ₃ and NO ₂ were decomposed in a short time. In particular, NH ₃ was completely decomposed within 1 minute. In the case of NH ₃ as a product, N ₂ H ₄ was detected in addition to N ₂ and H ₂ . The products in the case of NO ₂ were N ₂ and O ₂ .

It is considered that such a decomposition reaction occurs when He and Ar of the diluent gas are raised to metastable atoms in a highly excited state by electric discharge, and this energy is transferred to the sample gas. Of course, the present invention is not limited by the above examples. It goes without saying that various aspects are possible with respect to details such as the form and material of the electrode, the types of the reactive gas and the rare gas to be introduced, the applied power and the frequency thereof.

[0024]

As described above in detail, according to the present invention, the plasma treatment of the inner surface of an insulating tube such as a cylindrical tube made of glass, plastic, ceramics, or the like, or the stationary, moving, or circulating material is performed under atmospheric pressure. It is possible to do with.

[Brief description of the drawings]

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

FIG. 2 is a side view showing another example of the device.

FIGS. 3A and 3B are a cross-sectional view and a vertical cross-sectional view, respectively, showing an apparatus used for hydrophilizing a polyimide film on the inner surface of a cylindrical tube.

FIG. 4 is a correlation diagram showing a relationship between a discharge current and an atomic density ratio between fluorine and carbon by ESCA measurement of a plasma polymerized film.

FIG. 5 is a correlation diagram showing a relationship between a deposition rate and a discharge current.

FIG. 6 is a correlation diagram showing a decomposition rate of NH ₃ and NO _{2 with} respect to a discharge time.

FIG. 7 is a perspective view showing a conventional type of discharge to an insulator cylindrical tube.

FIG. 8 is a perspective view showing a conventional type of discharge to an insulator cylindrical tube.

FIG. 9 is a perspective view showing a conventional discharge type to an insulator cylindrical tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulator tube 2 High voltage electrode 3 Earth electrode 4 Insulating adhesive 5 Power supply 6 Mixed gas 7 Glass tube 8 Polyimide film 9,10 Spiral copper foil electrode

Claims (2)

(57) [Claims] 1. A pair of foil-shaped parallel electrode pairs are formed on an outer peripheral portion by a spa
A mixed gas of a reactive gas and a rare gas is introduced from one end of an insulator tube attached in a peripheral shape, and a glow discharge plasma is generated inside the insulator tube under atmospheric pressure.
Alternatively, an in-pipe atmospheric pressure glow plasma reaction method, wherein glow plasma processing is performed on a stationary body, a moving body, or a flowing material inside the pipe. 2. A pair of foil-shaped parallel electric wires are provided on the outer peripheral portion of the insulator tube.
The pole pairs are spirally attached and installed around the insulator.
Introduce mixed gas of reactive gas and rare gas from one end of tube
Glow discharge plasma inside the insulator tube under atmospheric pressure
Glow plasma treatment inside the insulator tube.
Atmospheric pressure glow plasma reaction tube
Applied equipment.