JPH06212466A - Device for hydrophilization treatment of metallic pipe - Google Patents

Abstract

PURPOSE:To provide a device for hydrophilization treatment of metallic pipe capable of obtaining a metallic pipe which is excellent in surface hydrophilicity, has also extremely little degradation of the surface hydrophilicity with the lapse of time and is suitable for a heat exchanger tube for air-conditioning. CONSTITUTION:In the device for hydrophilization treatment of metallic pipes, high voltage with high frequency is applied between an electrode 5 and a metallic pipe 3 to be treated by a power source section composed of an AC power supply 8, an oscillator 7 and a transformer 6 and a plasma discharge or a corona discharge is generated. The electrode 5 is formed of a duplex tube composed of an inner tube made of an insulator and an outer tube made of a metal. Wall thickness of the insulator inner tube is 3 to 6mm, the ratio of inside diameter Di of the metallic outer tube to an outside diameter d0 of the metallic tube 3 (Di/d0) is set at 1.5 to 2. In such a manner, hydrophobic components on the metallic tube surface are removed and a stable oxidized film is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal tube hydrophilic treatment device for improving the surface hydrophilicity of a metal tube such as a heat transfer tube for air conditioning, and more particularly to a hydrophilic treatment on the surface of a metal tube by generating plasma discharge or corona discharge. The present invention relates to a hydrophilic treatment device for a metal tube that imparts properties.

[0002]

2. Description of the Related Art Conventionally, as a surface hydrophilic treatment method for improving the surface hydrophilicity of a heat transfer tube processed into a predetermined tube shape for a heat exchanger, there are the following methods.

(1) Mechanical Polishing Method The surface of the metal heat transfer tube is polished with a wire brush or sandpaper to remove carbon and the like adhering to the surface of the tube to improve the surface hydrophilicity.

(2) Surface chemical treatment method The surface hydrophilicity is improved by cleaning and activating the surface of the heat transfer tube with sulfuric acid and a surfactant.

(3) Heat treatment method A metal heat transfer tube is heat-treated to change the oil content and carbon adhering to the tube surface and to be subjected to an oxide film treatment to improve the surface hydrophilicity.

[0006]

However, all of the above-mentioned conventional methods for treating the surface hydrophilicity of the heat transfer tube can obtain a certain degree of hydrophilicity, but are not sufficient, and have the following problems.

In the mechanical polishing method, fine powder containing carbon and oil removed by polishing is redeposited on the surface of the heat transfer tube to hinder surface hydrophilicity. Also, although good hydrophilicity can be obtained immediately after the treatment, since the surface of the metal heat transfer tube exposed by polishing is easily affected by the surrounding atmosphere, stains and the like adhere to the surface to make it hydrophilic. Will be deteriorated.

The surface chemical treatment method requires facilities such as pickling and water treatment, and the maintenance cost for these facilities is high. Further, in general, the processing takes a long time, so that the productivity is low. Further, similar to the mechanical polishing method, although good surface hydrophilicity can be obtained immediately after the treatment, there is a drawback that the hydrophilicity deteriorates with time.

In the heat treatment method, it is necessary to raise the temperature of the metal tube surface to the decomposition temperature of the processing oil (usually 300 ° C. or higher). However, in the case of a copper tube generally used as a heat transfer tube, Since the temperature exceeds the softening temperature of copper (about 250 ° C), the mechanical strength decreases. In addition, in order to avoid softening due to temperature rise, there is also a flame treatment method in which only the surface of the metal pipe is locally heated with a flame, but the flame is uniformly applied to the entire circumference of the pipe, and treatment is performed so as not to soften the pipe. It is difficult to do so and uneven processing is likely to occur.

The present invention has been made in view of the above problems, and it is possible to obtain a metal tube having excellent surface hydrophilicity and little deterioration of surface hydrophilicity over time, and productivity. It is an object of the present invention to provide a hydrophilic treatment device for a metal tube, which is excellent in

[0011]

A hydrophilic treatment device for a metal pipe according to the present invention is a hydrophilic treatment device for a metal pipe, wherein the surface of the metal pipe is continuously subjected to a hydrophilic treatment. An electrode disposed, a carrying means for moving the metal tube relative to the electrode, and a discharge generating means for applying a voltage between the electrode and the metal tube to generate a discharge. , The electrode is composed of an insulator inner tube having a wall thickness of 3 to 6 mm and a metal outer tube fitted to the outer side of the inner tube. The inner diameter Di of the metal outer tube and the outer diameter d0 of the metal tube to be treated are The ratio (Di / d0) is set to 1.5 to 2.

[0012]

According to the present invention, while the metal tube is moved relative to the electrode by the conveying means, a voltage is applied between the electrode and the metal tube by the discharge generating means to generate a discharge (plasma discharge or corona discharge). ) Is generated. Then,
By applying a voltage, free electrons existing in the air are accelerated, and the free electrons repeatedly collide with molecules in the air, causing an electron avalanche phenomenon. Then, a large number of high-energy electrons collide with the surface of the metal tube. This collision of electrons causes a so-called sputtering action that removes carbon, oil and the like adhering to the surface of the metal tube. Although a part of oil remains on the surface of the metal tube, the remaining oil is also in a state in which molecular chains are broken by the collision of electrons.

Further, ultraviolet rays and ozone (O ₃ ) are generated along with the plasma discharge or the corona discharge. Ozone is
Following fluorine, it is a substance that is highly oxidative. The ozone oxidizes the organic molecule in which the chain of the above-mentioned molecule is broken, and the carbon having a hydrophobic group [-OH] is changed to a hydrophilic group [-
It changes to carbon having C = O].

Further, the metal surface from which the organic substances have been removed reacts with ozone to form a metal oxide film on the surface of the metal tube. This metal oxide is not active like a simple metal and is present in a stable state, so that it is not easily affected by the surrounding atmosphere.

In the present invention, as described above, the mechanical strength of the copper pipe is deteriorated because the metal pipe surface is rendered hydrophilic by effectively utilizing the sputtering action by the discharge and the oxidizing action of ozone generated by the discharge. There is no fear of causing
Workability is also good. Further, since the surface of the metal tube after the treatment is covered with the metal oxide film, deterioration of hydrophilicity with time is suppressed.

The effect of such discharge treatment is better when the discharge output per unit length of the electrode is larger. That is,
The higher the electron collision energy per unit length, the better the hydrophilic surface can be obtained. For example, when the clearance between the electrode and the object to be processed is small, 0.5 to 1 mm, the electron energy emitted by the discharge is small, and the above-mentioned discharge is required unless the electrode length is lengthened or the processing speed is slowed. The effect of the treatment cannot be obtained sufficiently.

In the present invention, the electrode is constituted by a double tube consisting of an in-insulator tube and a metal outer tube, which makes it possible to increase the discharge output per unit length of the electrode. In this case, the thinner the in-insulator tube, the higher the discharge output. However, if the thickness of the in-insulator tube is less than 3 mm, a short circuit is likely to occur due to local dielectric breakdown of the in-insulator tube. On the other hand, when the wall thickness of the in-insulator tube exceeds 6 mm, the discharge output is remarkably reduced, and good hydrophilicity cannot be obtained. Therefore, the wall thickness of the insulator tube is 3 to 6 mm
It is necessary to be.

In the present invention, the ratio of the inner diameter Di of the metal outer tube to the outer diameter d0 of the metal tube to be treated (Di /
d0) is 1.5 to 2. If Di / d0 is less than 1.5, the electron collision energy will be small, and if Di / d0 exceeds 2, it will be difficult for the discharge to reach the surface of the metal tube from the electrode, so good hydrophilicity can be obtained in any case. I can't. Therefore, it is necessary to set the ratio (Di / d0) of the inner diameter Di of the metal outer tube to the outer diameter d0 of the metal tube to be treated to 1.5 to 2.

[0019]

Embodiments of the present invention will now be described with reference to the accompanying drawings.

FIG. 1 is a schematic view showing a hydrophilic treatment apparatus for metal pipes according to an embodiment of the present invention.

This hydrophilic treatment apparatus comprises ground rolls 4a and 4b for transporting a metal tube (copper tube) 3 in its length direction, an electrode 5, and a power supply section for supplying a high frequency high voltage to the electrode 5. It is configured. In addition, the power supply unit is an AC power supply 8
And an oscillator 7 which is supplied with power from the AC power supply 8 to generate a high frequency signal, and a transformer 6 which boosts the signal output from the oscillator 7.

FIG. 2 is a sectional view showing the electrode 5. This electrode 5 is an in-insulator tube 1 made of high-density ceramics.
And an outer tube 2 made of a metal such as aluminum and arranged outside the in-insulator tube 1. The wall thickness of the in-insulator tube 1 is set to 3 to 6 mm, and the ratio (Di / d0) of the inner diameter Di of the metal outer tube 2 to the outer diameter d0 of the metal tube 3 is set to 1.5 to 2. There is.

Next, a method of hydrophilically treating the surface of a metal tube using the apparatus of this embodiment will be described.

The metal tube 3 is conveyed in the lengthwise direction by the grounding rolls 4a and 4b and passes through the electrode 5. In this case, since the metal tube 3 is supported on both sides of the electrode 5 by the grounding rolls 4a and 4b, vibrations and the like are prevented, and the distance between the inner surface of the electrode 5 and the outer peripheral surface of the metal tube 3 is reduced. Maintained constant. Then, a high frequency high voltage is applied from the transformer 6 between the electrode 5 and the metal tube 3.

At the electrode 5, plasma discharge or corona discharge is generated by this high voltage, free electrons existing between the electrode 5 and the metal tube 3 are accelerated, and the molecules in the gas are ionized to avalanche. The phenomenon occurs. Then, a large number of high-energy electrons collide with the surface of the metal tube 3. By the collision of the electrons, the hydrophobic organic substance attached to the surface of the metal tube 3 is vaporized and separated from the tube surface. Also, some of the organic matter remains on the surface of the pipe, but this residual organic matter also
The molecular chains are broken by the collision of electrons. Further, the discharge causes the oxygen in the air to react and generate ozone. The ozone oxidizes the organic matter whose molecular chain has been cleaved, and changes the carbon having a hydrophobic group [-CH] to a hydrophilic carbon having a hydrophilic group [-C = O], so that the hydrophobic component on the tube surface is To be removed.

Further, the ozone generated by the discharge causes the electrode 5
The ozone is oxidized on the surface of the pipe that has stayed inside and has been cleaned, and an oxide film is formed on the surface of the pipe. Since this oxide film does not have the activity of a simple metal and exists in a stable state, it is less likely to be affected by the surrounding atmosphere.

In this embodiment, the metal tube can be continuously surface-treated. In addition, the metal tube treated according to this example has excellent surface hydrophilicity and can maintain the hydrophilicity in a good state for a long time. Furthermore, in this embodiment, compared with the conventional surface treatment method using a chemical method or the like, the treatment process is simple and can be easily put online with other equipment, so that the number of processes can be reduced and labor can be saved. Is. Furthermore, it is possible to eliminate the conventionally required cleaning step using CFCs and organic solvents.

Next, the results of actual surface treatment of copper pipes using the hydrophilic treatment apparatus according to the embodiment of the present invention will be described in comparison with the comparative example.

Using the device having the configuration shown in FIG.
Hydrophilic treatment was applied to a copper tube made of phosphorus deoxidized copper having a thickness of 0.6 mm and a thickness of 0.6 mm. That is, while passing the copper tube through the electrode having a length of 250 mm at a constant speed of 3 m / min, and between the electrode and the copper tube.
A high voltage of 14 kV was applied to generate discharge. The electrode is formed by a double tube including an inner tube made of high-density ceramics and an outer tube made of metal. Table 1 below shows the inner diameter and wall thickness of the in-insulator tube, the ratio of the inner diameter of the metal outer tube to the outer diameter of the copper tube as the material to be treated, and the output per unit length of the electrode.

Then, the wetting index of the metal tube after treated by the examples and comparative examples using these electrodes was measured by a wetting index reagent mainly composed of ethylene glycol. The results are also shown in Table 1.

[0031]

[Table 1]

As is clear from Tables 1 and 2, when the treatments according to Comparative Examples 1, 2 and 4 were performed, the output per unit length of the electrode was smaller than that of the Examples, so that the wetting index of the tube surface was determined. Is small and the hydrophilicity is not sufficient. Further, in the case of the treatment according to Comparative Example 3, although the output per unit length of the electrode was large and the wetting index of the tube surface was also large, a short circuit occurred in a short time after the start of discharge. On the other hand, in the case of the treatment according to the example, since the output per unit length of the electrode was large, the wetting index of the tube surface was large and good hydrophilicity could be obtained.
In addition, a short circuit did not occur even after long-term discharge, indicating a good discharge state.

[0033]

As described above, the apparatus for hydrophilically treating a metal tube according to the present invention has a metal tube to be treated disposed inside an electrode composed of a double tube consisting of an in-insulator inner tube and a metal outer tube, and discharges. By means of which discharge is generated between the metal tube and the electrode by means to impart hydrophilicity to the surface of the metal tube, the surface hydrophilicity is excellent and the hydrophilicity hardly changes with time, and the heat transfer tube for air conditioning It is possible to obtain a metal tube suitable as. Also,
INDUSTRIAL APPLICABILITY The hydrophilic treatment device according to the present invention is capable of continuously treating metal pipes and has excellent workability.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a hydrophilic treatment device for a metal tube according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the same electrode.

[Explanation of symbols]

 1; Insulator tube 2; Metal outer tube 3; Metal tubes 4a, 4b; Ground roll 5; Electrode 6; Transformer 7; Oscillator 8; AC power supply

Claims (1)

[Claims] 1. A hydrophilic treatment apparatus for a metal pipe, wherein a surface of the metal pipe is continuously subjected to a hydrophilic treatment, an electrode having a metal pipe to be treated therein, and the metal pipe with respect to the electrode. And a discharge generating means for generating a discharge by applying a voltage between the electrode and the metal tube, wherein the electrode has a wall thickness of 3 to 6 mm, and an in-insulator tube, It is composed of a metal outer tube fitted to the outside of the inner tube, and the ratio (Di / d0) of the inner diameter Di of the metal outer tube and the outer diameter d0 of the metal tube to be treated is set to 1.5 to 2. A hydrophilic treatment device for a metal tube, which is characterized in that