JPS5944910B2 - How to paint plastic extrusions - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of applying plastic to a continuous body having an outer surface of plastic, such as a plastic-coated wire rope.

Conventionally, methods for forming a plastic coating film on the surface of plastic materials include, in addition to the method of applying liquid paint,
Electrostatic spraying using powder, fluidized dipping, electrostatic dynamic dipping, and methods such as thermal spraying and plasma jetting in which powder is molten and injected are known.

However, in the above method, when using liquid paint, the adhesion of the coating film is insufficient, and there is a limit even if surface treatment is applied to improve adhesion. 2 of the melting temperature of the paint on the surface of the applied object
Because the material must be heated and cured at twice the high temperature, there is a problem of thermal deterioration of the material.Moreover, if the same material as the molded product is used as the coating material with emphasis on adhesion, the material to be coated may be damaged. There is a problem that the coating material is damaged by the heating during coating. Furthermore, the above method not only requires a coating process separate from molding, but also requires special equipment for that process. Another method is the hot stamping method, which uses a special machine to heat pigments or special inks and press them into the plastic surface, but this method has weak adhesive strength and does not require much thickness. Membrane cannot be formed. In view of these points, the present invention
It is an object of the present invention to provide a coating method that achieves good adhesion and does not cause problems such as thermal deterioration by coating at the same time as the extrusion molding of the plastic on the outer surface.

Hereinafter, the present invention will be explained with reference to drawings of embodiments. 1 is a plastic extruder, 2 is a head of the extruder, 3 is an extrusion molded product, 4 is a water cooling tank, 5 is a drawer 6 is a winding drum.

A thermal spray gun T is arranged at the molded product outlet section 20 of the extruder head to face the extruded product 3. In the drawing, the thermal spray gun T
Although only one is shown, in order to spray evenly onto the extruded product, three to four are arranged around the molded product.
8 is a plastic powder pumping machine, 9 is a gas pressure regulator, 1
1 is a pipe for oxygen gas, 12 is a pipe for fuel gas such as LP gas, and 13 is a pipe for compressed air.

Thermal spraying by the thermal spraying gun T has a mechanism as shown in FIG. That is, compressed air is injected from the outer circumferential hole of the nozzle 70 to form a compressed air band 16 on the outer periphery, and a mixing band 14 is formed in which powder and compressed air are mixed and injected from the central hole inside the nozzle 70. A flame zone 15 is formed between them by burning the fuel gas, thereby melting the powder in the mixing zone 14 and spraying it onto the coating surface 10. Next, a coating method using this device will be explained.

The molten plastic from the extruder 1 is coated on a core material (not shown) fed from the direction of the arrow in the head section 2 and extruded from the outlet 20 of the head section 2 to be sent out as a molded product 3. While the outer peripheral surface is in a semi-molten state, plastic powder is sprayed in a molten state from a thermal spray gun 7 to coat it. The coated molded article 3 then passes through a water-cooling tank 4 to solidify the coating film, and then passes from a drawer 5 to a winding drum 6. The plastic powder sprayed from the thermal spray gun 7 is the same as the plastic extruded from the extruder 1, or is compatible with the plastic powder. Therefore, the molten plastic powder sprayed onto the semi-molten outer surface chemically bonds with the surface to be coated, forming a strongly adherent coating film. If spraying is performed after the outer surface of the continuum 3 has solidified, no chemical bond will be formed.
It is desirable that the spray be applied within 0.5 seconds after the continuous body 3 is extruded from the head outlet 20. Alternatively, flame or high-temperature gas may be blown onto the continuum 3 at the outlet portion 20. The distance between the tip of the nozzle 70 of the injection gun 7 and the surface to be coated 10 varies depending on the type of powder, the type of thermal sprayer, the thickness of the coating film, etc., but is usually set to about 180 nm. Also, the injection conditions depend on the powder material, etc., but when using Nylon 12, the powder particle size is 70-80 mesh, and the compressed air is 0.5 kg/C! ! Good results were obtained at t. In this way, the present invention is designed to perform coating at the same time as extrusion molding of a molded product, and since the heat during molding is used as is, no extra heating is required, and therefore the heat resources are saved. Not only is it advantageous, but there is no problem of thermal deterioration.
Also, since it is applied in a semi-molten state to form a chemical bond, the adhesion of the coating film is extremely strong. In addition, since coating is performed simultaneously during extrusion molding, the process is simplified, and the coating thickness can be set to any value of 0.051 m or more by adjusting the powder pumping speed. It is also possible to perform marking by partial application by operating and stopping the actuator. The molded products to which the present invention is applicable include marine ropes with plastic coating on the outer periphery of wire ropes, wire ropes with plastic coating on the outer surface of pipes and rods, and wires made only of plastic. Of course, the present invention can also be applied to shaped objects and tubular objects. The need to form a plastic coating on the outer surface of such plastics is explained by, for example, spraying plastic powder mixed with foreign substances such as metal or glass after extrusion molding of the plastic to separate a foreign substance-contaminated layer and a non-contaminated layer. This occurs, for example, in the case of laminating plastics, thereby reducing the risk of fatigue failure due to the high notch sensitivity of the plastic.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of an apparatus implementing the present invention, and FIG. 2 is an explanatory diagram of an injection mechanism. 1...Extruder, 2...Head section, 3.
...Extrusion molded product, 4...Water cooling tank, 5...
...Drawer, 7...Injection gun, 8...
...Powder pressure feeder, 9...Gas pressure regulator.

Claims (1)

[Claims] 1 After extruding a continuous body whose outer surface is made of plastic from a plastic extrusion molding machine, while the outer surface is in a semi-molten state, a plastic powder that has a chemical affinity with the outer surface material is melted and injected. , a coating method for a plastic extrusion molded product.