JPH0519453B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for joining metal plates, and more particularly to a method for joining pre-coated metal plates whose surfaces are coated with a thermoplastic resin. Conventional technology In recent years, various metal plates coated with synthetic resin have been developed as materials with beautiful colors and appearances and corrosion resistance, and have come to be widely used in architecture, automobiles, home appliances, furniture, etc. . When using these materials for the above purposes, joining techniques are essential. Conventional methods for joining metals include mechanical joining methods such as tightening with rivets or bolts, folding and wrapping, and bonding between metal atoms by melting metals into contact, such as gas welding, arc welding, and soldering. There are resistance welding methods such as metallurgical joining methods and spot welding methods that utilize force, but metal plates coated with synthetic resin have the following problems. Problems to be Solved by the Invention If a mechanical bonding method is applied to a synthetic resin-coated metal plate, processing such as drilling and bending is required, and the coating between the resin and metal may be partially damaged or the cut portion may be damaged. The metal plate may be exposed and corrosion resistance may deteriorate. Furthermore, the bending process for joining often involves multiple processes, which can cause the synthetic resin on the metal plates to crack or peel off, significantly reducing performance. Furthermore, if metallurgical bonding methods are to be applied, the resin coating must be removed by some means in advance to enable metal-to-metal bonding, which is not only complicated, but also requires high voltage and equipment. It is expensive, and if the welded part is not recoated with resin by painting or other means after joining, problems may arise in terms of appearance or corrosion resistance.Furthermore, the merits of using pre-coated metal plates are that they are difficult to work with. Due to this, it is lost. The present invention relates to a method for joining pre-coated metal plates, and provides a method for joining metal plates that does not have the above-mentioned problems. Means and Effects for Solving Problems The present invention is a metal plate joining method characterized in that metal plates whose surfaces are coated with thermoplastic resin are pressed against each other and the pressure-welded portions are heated. Since surface-coated metal plates are used for the above-mentioned purposes, the base metal is generally thin, and therefore the bonding strength does not necessarily have to be equal to that of the base metal. In many cases, it is sufficient that the parts do not peel off easily. In view of these circumstances, various methods of thermally bonding the coated resin were investigated. Thermal bonding has already been put into practical use for bonding thermoplastics together, and when the plastics are in the form of a film, a hot plate is applied to one side to melt the plastics and weld them together. However, this method is extremely inefficient for plastics coated with base metals that have low specific heat and high thermal conductivity. Also, due to the different coefficients of thermal expansion of metals and plastics, such heating methods may simply result in the metal and the coated plastic peeling off, especially if the coating is thin. The present inventor pressed metal plates whose surfaces were coated with thermoplastic resin to improve heat conduction as much as possible, and applied heat heated by, for example, electric heat, from both metal surfaces opposite to the contact surfaces. By applying heat to the plate and transmitting heat to the pressure-welding surface, the thermoplastic resin on the contact surface is melted, and the purpose of joining is fully achieved without damaging the covered surface other than the joint part due to pressure-welding. I got the knowledge that. The temperature of the pressure contact surface to achieve the purpose of joining varies depending on the type of thermoplastic resin coated, and is, for example, 120° C. or higher in the case of polyethylene. Further, as a heating method, if the thermoplastic resin has a polar group in its molecular structure, such as polyvinyl chloride resin or polyamide resin, heating by high frequency can also be employed. The method for joining thermoplastic resin coated metal plates is as follows:
For example, in the case of spot joining, as shown in Figure 1, 120
By pressing the top and bottom chips heated above ℃, the thermoplastic resin on the metal plate melts and adheres. In addition, in the case of continuous bonding, as shown in Figure 2, the thermoplastic resin-coated metal plate is heated to 120℃ or higher.
Easily adheres by crimping and threading between the lower rolls. The thermoplastic resin-coated metal plate joining method of the present invention requires only a simple heating device and a pressure bonding device, and has features such as simple operation, inexpensive equipment, and stable adhesive strength. The present applicant has conducted various studies on surface treatment of metal plates with thermoplastic resin, and found that the metal substrate is preheated to a temperature within the range of 50 to 170°C with a heating roll,
After that, it moves between the heating roll and the cooling roll,
The molten resin is extruded between a metal substrate heated by a heating roll and a cooling roll, and the resulting surface-treated metal plate is pressed onto the metal substrate by the cooling roll. It was disclosed that the adhesion was much better than colored steel plates coated with acrylic resin paints or thermosetting polyester resin paints, or laminated steel plates laminated with resin films (Figure 3 of JP-A-57-203545). Polyethylene has been shown to be excellent as a resin for coated metal plates by this method, considering its properties as a surface-treated metal plate other than adhesion, that is, corrosion resistance, weather resistance, and workability.
As shown in the Examples below, it was found that the bondability of the present invention was also good. The reason for this is thought to be that in addition to the good coating adhesion between the metal and the resin, the resin itself also has a high thermal conductivity. Therefore, it is most effective to apply this method to a surface-treated metal plate in which the metal plate is coated with polyethylene by the method described in the above-mentioned publication. Example A 0.4 mm galvanized steel plate treated with zinc phosphate or chromic acid was used as the metal substrate, and the resin shown in Table 1 was applied in a molten state from the T-die of an extruder. The metal plates obtained by direct coating were joined under the conditions shown in Table 1, and after cooling, both plates were peeled off in the vertical direction at a rate of 50 mm/min, and the peeled surfaces were observed. Similar observations were also made using a commercially available PVC-coated laminated steel plate. Similar observations were also made using a commercially available steel plate coated with PVC sol. The results are shown in Table 1.

[Table] Effects of the Invention According to the method of the present invention, a metal plate coated with a thermoplastic resin can be welded using a much safer and simpler operation than conventional welding operations, and the coating can be bonded to an adhesive without requiring advanced techniques. Therefore, it can be joined. Therefore, the present invention provides an extremely useful method for processing surface-treated metal plates such as colored steel plates.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of the method of the present invention. 1... Thermoplastic resin, 2... Metal plate, 3... Heating device, 4... Chip, 5... Roll.

Claims (1)

[Claims] 1. The metal substrate is preheated to a temperature within the range of 50 to 170℃ with a heating roll, and then passes between the heating roll and the cooling roll, and the molten polyethylene resin is heated between the metal substrate heated with the heating roll and the cooling roll. 〓
Pressing the resin surfaces of the surface-treated metal plates obtained by extruding them and pressing them onto the metal substrate with the cooling roll, and heating the pressed portion to 120°C or more from the metal surface side. A surface-treated metal plate joining method characterized by: