JPH01284367A - Continuous surface treatment of coated steel sheet - Google Patents

Abstract

PURPOSE:To accelerate surface modification and to efficiently mass-produce coated steel sheets having high function by continuously passing coated steel sheets through a vacuum reaction chamber and irradiating the surfaces of the steel sheets with plasma generated with high frequency waves or microwaves during passage. CONSTITUTION:Coated steel sheets 1 are continuously passed through a vacuum reaction chamber 10 for plasma treatment. Gas for plasma introduced into a glow discharge tube 7 from the gas inlet 4 is excited by high frequency discharge with a coil 6 to generate plasma and this plasma is accelerated by DC voltage and enters the chamber 10 from the plasma inlet 13. In the chamber 10, the surfaces of the steel sheets 1 are irradiated with the plasma. The adhesive strength and contamination resistance of the surfaces of the steel sheets 1 are considerably improved, coated steel sheets having high function can be efficiently mass-produced and the cost of production can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for continuously producing coated steel sheets having a highly functional surface.

(Prior Art) Surface treatment technology for steel plates has made significant progress in recent years, and not only conventional plated steel plates but also steel plates with various coatings are being manufactured. Typical painted steel sheets include galvanized sheets coated with polymers such as vinyl chloride, polyethylene, polyester, and fluororesin, and these are used as building materials and home appliances. There is.

By improving the properties of the organic film on the surface of painted steel sheets as described above, for example, increasing adhesion and stain resistance, or adding gloss to enhance decorative properties, it is possible to increase added value and expand applications. Attempts have also been made.

However, since coated steel sheets must be mass-produced at low cost, the method for modifying the surface film must be one that can be carried out continuously and quickly.In other words, the coated steel sheet is uncoiled and processed while running. Ideally, the coating should be modified in a continuous processing line where the treated steel sheet is wound up into a coil again.

Plasma treatment is already known as a method for modifying synthetic resin films (for example, in ``Polymer Surface Technology J'' edited by The Society of Polymer Science and Technology, 19879, Nikkan Kogyo Shimbunsha, p.

210-220), No practical method for modifying the coating film of painted steel sheets, especially in a continuous processing line, is known, and mass production of painted steel sheets with excellent surface properties has not been carried out. Not known.

(Issues to be Solved by the Invention 1i!!) The present invention relates to a method for modifying a coating film of a coated steel sheet, in particular, a continuous manufacturing process (coil
The purpose of the present invention is to provide a coating film modification method that improves the functionality of the surface of a coated steel plate through continuous treatment in coating lines.

A further object of the present invention is to provide a method for improving the efficiency of plasma treatment and obtaining a desired surface modification effect in a short time when a coated W4 temporary coil is subjected to continuous plasma treatment.

(Means for solving problems) The gist of the present invention is in (1) and (2) below.

(1) A continuous surface treatment method for a painted steel sheet, which comprises irradiating plasma generated using high frequency waves or microwaves onto the surface of a painted steel sheet that continuously passes through a reduced pressure reaction chamber equipped with a differential pressure sealing device.

(2) The continuous surface treatment method for a coated steel sheet according to the above (1), characterized in that plasma generated using high frequency waves or microwaves is accelerated and irradiated with a DC voltage.

As mentioned above, the coating film on painted steel sheets is a resin film made of vinyl chloride, polyethylene, etc., so by bringing the coating surface into contact with plasma, the chemical composition of the surface changes. Chemical etching causes porosity, etc., thereby making it possible to improve surface properties such as adhesion, stain resistance, and decorative properties.

Typical plasma generation methods include ■DC glow discharge■High frequency discharge■Microwave discharge, etc. Among these, high frequency discharge and microwave discharge are so-called plasma generation methods in which there are no electrodes in the discharge atmosphere. Since it is an electrodeless discharge and there is no need to supply electricity to the object to be treated, it is a suitable technique for surface modification of polymers, which are electrical insulators.

Generating plasma (strictly speaking, "low-temperature plasma") usually requires a reduced pressure atmosphere of 0.1 to 10 Torr. This degree of vacuum itself can be achieved quite easily. However, in order to carry out the continuous treatment aimed at in the present invention, the coil unwound in the atmosphere is sent into a vacuum chamber for plasma treatment, and the treated steel sheet is taken out into the atmosphere again and continuously wound. There must be. In other words, the degree of vacuum required for plasma processing cannot be maintained unless the entrance and exit of the steel plate running at high speed to the vacuum chamber are well sealed.Therefore, in the present invention, a differential pressure sealing device is installed at the entrance and exit of the steel plate before and after the vacuum chamber. We decided to use A differential pressure seal device is
This device has a mechanism that reduces the pressure in stages from atmospheric pressure to the target degree of vacuum through multiple decompression chambers separated by seal rolls.

Furthermore, when applying plasma treatment to the surface treatment of painted steel coils, the following points become serious problems. In other words, the activity of the plasma decreases at the time of contact with the coating surface compared to the time of generation, and the time required to achieve the desired surface modification effect becomes longer. Since the speed is fast, surface treatment must be done in an extremely short time.

Therefore, promoting plasma processing becomes an important issue.

If the processing time is long, there will be disadvantages such as a decrease in productivity due to a decrease in line speed, or an increase in equipment costs and operating costs due to an increase in the length of the plasma processing apparatus.

It has been found that acceleration of plasma processing can be achieved by the following method. That is, when introducing plasma generated using glow discharge using high frequency or microwave into the reaction chamber, there is a gap between the plasma source gas inlet and the reaction chamber, or between the plasma source gas inlet and the plasma inlet into the reaction chamber. It has become clear that by applying a DC voltage between the two, it is possible to irradiate the coating film surface with highly active plasma, and the efficiency of coating film surface modification can be dramatically improved.

The present invention utilizes plasma to modify the coating film of painted steel sheets, uses a differential pressure sealing device to enable continuous processing, and, if necessary, uses the above-mentioned DC voltage superimposition. This technology has made it possible to apply plasma treatment in the actual process of manufacturing continuously coated steel sheets.

(effect) The method of the invention is further explained by means of the attached figures.

Continuous surface treatment according to the present invention is carried out in a plasma treatment reaction chamber maintained at reduced pressure by a differential pressure sealing device, as shown in FIG. In Fig. 1, 1 is a painted steel plate;
2 is a differential pressure sealing device, 3 is a plasma processing reaction chamber, and P is a vacuum pump.

FIGS. 2 and 3 are detailed views of the plasma processing reaction chamber, both of which show the case where a high frequency induction coil is used.

The source gas introduced from the plasma source gas inlet 4 is excited and turned into plasma by the coil section 6 by high-frequency discharge.
DC voltage (between 9 and 10 in Figure 2, 9 and 12 in Figure 3)
) is applied between the plasma inlet 1 and
3 enters the reaction chamber 10 and is irradiated onto the surface of the coated steel plate 1 passing through the reaction chamber. In FIGS. 2 and 3, 5 is a high frequency power source, 7 is a glow discharge tube, 8 is an insulator, 9 and 12 are electrodes for applying a DC voltage, and 11 is a DC power source.

Although application of a DC voltage is not essential, it is desirable to employ it in order to improve processing efficiency and increase line speed.

(Example) Using a pilot line capable of continuous surface treatment of a 300 ff1s width coated steel plate coil, a high-performance coated steel plate was prototyped by plasma treatment.

i) Test material: Polyester coated steel plate (base material: 0.5 mm)
Thick steel plate, zinc plating thickness 11.4 μm, polyester film thickness 60 μm,) ii) Atmosphere inside the reaction tank: N, , 5 Torrii
i) Line speed: 50Il/ll1niv) Plasma generation conditions: High frequency discharge power and DC accelerating voltage are selected as shown in Table 1. Under these prototype conditions, the time that the painted steel plate is exposed to the plasma atmosphere is approximately 1.2 seconds.

Table 1 shows the evaluation results of the surface properties (adhesiveness, stain resistance) of the coated steel sheets subjected to the surface treatment of the present invention.

(Hereinafter, blank space) Table 1 The adhesive strength in Table 1 is determined by a tensile test using a 1-inch wide sample bonded with the epoxy thermosetting adhesive side with the painted surfaces facing each other as shown in Figure 4. It was measured by subjecting it to In addition, stain resistance was evaluated based on the extent to which lines drawn on the painted surface using commercially available red marker ink could be removed by wiping with an ethanol-impregnated cloth after being left for 2 hours. ◎ indicates that it is completely removed, ○ indicates that a slight trace remains, and × indicates that it is not removed.

As can be seen from the results of N113 and 4, when plasma treatment is performed by the method of the present invention that applies a DC voltage,
A dramatic increase in adhesive strength and a significant improvement in stain resistance were achieved. Furthermore, even when no DC voltage was superimposed, that is, when the plasma generated by high-frequency discharge was directly irradiated onto the surface of the painted steel sheet (Zui 2), an increase in adhesive strength and an improvement in contamination resistance were observed. is small.

(Effects of the Invention) According to the surface treatment method of the present invention, surface modification of a coated steel plate progresses rapidly, and a highly functional coated steel plate with excellent surface properties such as adhesiveness and stain resistance can be manufactured.

Furthermore, this method is suitable for efficiently mass-producing coiled coated steel sheets, and greatly contributes to the inexpensive manufacture of high-performance coated steel sheets and their widespread use.

[Brief explanation of the drawing]

Figure 1 is a schematic sectional view showing an overview of the equipment for implementing the continuous surface treatment method of the present invention, Figures 2 and 3 are schematic sectional views showing details of the plasma reaction chamber, and Figure 4 is a schematic sectional view showing the details of the plasma reaction chamber. FIG. 2 is a schematic cross-sectional view showing a steel plate adhesion test method.

Claims (2)

[Claims] (1) A continuous surface treatment method for a painted steel sheet, which comprises irradiating plasma generated using high frequency waves or microwaves onto the surface of a painted steel sheet that continuously passes through a reduced pressure reaction chamber equipped with a differential pressure sealing device. (2) The continuous surface treatment method for coated steel sheets according to claim 1, characterized in that plasma generated using high frequency waves or microwaves is accelerated and irradiated with a DC voltage.