JPS581981B2 - Method for forming resin coating on containers by spray coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a resin coating layer exclusively on the outer peripheral surface of a container such as an aluminum tube, particularly on the mouth peripheral surface, by spray coating.

Conventionally, there have been many products in which a synthetic resin outer layer is provided on the outer circumferential surface of the mouth of a metal tube such as aluminum. Many methods are used in which a synthetic resin outer layer is molded on the surface by injection molding, or a synthetic resin outer layer is molded separately from the tube and this is fitted into the tubular part.

There is also known a method of forming a synthetic resin coating on the outer peripheral surface of a tube by spraying synthetic resin from a nozzle under appropriate temperature conditions, but this method has the following problems.

In other words, there is no problem when forming a synthetic resin coating over the entire circumference of the tube, but if you want to form a synthetic resin coating only from the mouth or shoulder of the tube upwards, it is necessary to clearly form the boundary line of the coating. There are some serious drawbacks.

In other words, when spray coating synthetic resin with only the outer circumferential surface of the tube to be sprayed, such as the mouth or shoulder of the tube, exposed from a suitable jig, the jig must be held in close contact with the outer circumferential surface of the tube or the spray may not be produced. The synthetic resin flows down through the gap between the jig and the circumferential surface of the tube, making it impossible to form a clear boundary line between the coating layers.

By the way, tubes made of materials such as aluminum are very soft and easily deformed by even slight external pressure, so it is very difficult to bring the jig into complete contact with the outer circumferential surface of the tube.

Furthermore, since the molten synthetic resin adheres to the surface of the jig, there are problems such as the synthetic resin adhering to the jig adhering to the surface of the tube that does not require coating during the next spray coating and staining the tube surface.

Therefore, the main object of the present invention is to solve the above-mentioned problems and provide a method for forming a resin film on a container by spray coating, which can form a clear and clean boundary line.

The method of the present invention will be described below based on an embodiment shown in the drawings.

In the figure, number 1 is a tube made of a light metal material such as aluminum, and in this embodiment, a shoulder portion 2 is shown in FIG.
A synthetic resin coating layer 3 is formed on the upper outer peripheral surface by spray coating.

Reference number 4 is an annular shielding member disposed on the outer peripheral surface of the tube 1, and only the portion of the tube 1 to be coated, that is, the portion above the shoulder portion 2 protrudes from the shielding member.

The shielding member 4 has an air reservoir 5 inside thereof, and a high-pressure air supply source 7 such as a compressor is connected to this air reservoir via a duct 6.

Further, the shielding member 4 is formed with a slight gap 8 at least in a portion adjacent to the shoulder portion 2, and is formed so that the high pressure air supplied to the air reservoir is blown out from this gap.

Then, while spraying air at an appropriate pressure from the gap 8, the synthetic resin material is sprayed onto the upper surface of the tube from the shoulder part of the tube from the vertically moving spray nozzle 9 to coat the tube. This prevents the molten synthetic resin from flowing down from the gap, and also minimizes the adhesion of the synthetic resin material to the portion of the shielding member 4 adjacent to the tube shoulder. Even if it sticks, there is a gap 8 between it and the tube, so it will not stick to the tube during the next operation.

Therefore, the boundary line A of the coating layer 3 (FIG. 2) to be molded can be clearly and neatly formed, and continuous work can be performed at high speed.

It is of course important to adjust the air pressure and the injection pressure from the nozzle so that the resin material injected from the nozzle during spray coating by the nozzle 9 is not blown up by the pressure of the air ejected from the gap 8. The inventors have demonstrated that such adjustment can be easily achieved.

Furthermore, in the present invention, by changing the position of the shielding member 4, for example, if the shielding pitch 4 in FIG. 1 is lowered slightly, the lower limit of the coating layer can be formed at a location slightly below the shoulder. It is possible.

Further, in the present invention, the shape of the container to be spray coated is not limited to the tube as shown in the embodiments, but can be applied to all containers made of various other materials.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view showing an embodiment of the method of the present invention;
FIG. 2 is a partially sectional front view of the completed tube. 1...Tube, 2...Shoulder, 3...
... Synthetic resin coating layer, 4 ... Shielding member, 5
...Air reservoir, 6...Duct, 8.
...Gap, 9...Nozzle.

Claims (1)

[Claims] 1. An annular shielding member is arranged on the outer peripheral surface of the container to be coated, a slight gap is formed between the shielding member and the outer peripheral surface of the container, and air is continuously injected from this gap. A method for forming a resin film on a container by spray coating, the method comprising spray coating a synthetic resin on the outer peripheral surface of the container facing the air injection side. 2. In the method described in item 1, the shielding member has an air reservoir therein, and air supplied from a high-pressure air supply source such as a compressor to the air reservoir through a duct is continuously injected from the gap. A method for forming a resin film by spray coating, characterized in that the outer peripheral surface of the container facing the air injection side is coated by spraying synthetic resin from a nozzle.