JPS591166A - Method of removing fatigued film coating - Google Patents

Abstract

PURPOSE:To effectively remove only a finishing film coating without damaging a primary film coating, by projecting ice particles together with carrier water toward a painted member so that impact and frictional force are applied to the finishing film coating. CONSTITUTION:Ice particles which are produced by a heat-exchange between liquid nitrogen and cold water, are transferred by high pressure water pumped out at a 50-300kg/cm<2> pressure or compressed air 2 at a 6-7kg/cm<2> pressure, and is jetted from a jet nozzle 3 to a painted body 6 coated with under coating 4 and a top-coating film 5. The ice particles 1 impinge on the fatigued top- coating 5 to exert a large impact and frictional force to the top-coating film 5, thereby the latter alone is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing a fatigued paint film, and more particularly to a method for removing a fatigued paint film that can remove only the top coat film without damaging the undercoat film by ice particle projection.

In general, metal surfaces are painted for the purpose of protection, rust prevention, and aesthetics, but in order to complete the purpose, it is not necessary to apply a single coat, but to apply an undercoat and a topcoat, or an intermediate coat to this Ijl. It is customary for two or more coats of paint to be applied. However, due to fatigue that occurs over time, deterioration, lifting, or damage to the coating film is unavoidable, and the undercoat coating film may be broken and rust may occur. In this case, conventionally, the undercoat film was completely removed by sandblasting or shot blasting, and then an undercoat and topcoat were applied again. I'Lij: In sandblasting and shotblasting, the projected particles, sand, or steel balls are highly hard and apply a larger impact force than necessary, which removes them without distinguishing between top coat and base coat. It is.

However, regardless of where rust occurs, it is not desirable to remove even a completely adhered undercoat film from the viewpoint of workability and cost, and it is desirable to remove only the paint film that is fatigued or damaged. Since it is usually the exposed topcoat that is fatigued and damaged, only this topcoat should be removed. As a method to achieve this, there are differences in hardness and adhesion of dust due to the difference in fatigue level, as well as in the top coat and undercoat paint films, as well as in the different coating methods and the different bases. It is conceivable to pay attention to the difference between the two and use granules with appropriate hardness. but,
It is difficult to find granules having such hardness because of the requirement to remove only the top coat without damaging the undercoat, and so far there have been no reports.

Incidentally, recently, the ice blasting method, which uses ice particles instead of sand in the sandblasting method, has been attracting attention because it does not produce waste. This ice blasting method is a method in which the surface of the object to be ground is polished using ice particles conveyed by a high-speed fluid. Because ice was generally believed to be hard, and in fact is quite hard, ice blasting was considered to be an alternative to sandblasting, and nothing more. It was thought that it could be used only in the field of interest, or in a relatively narrow range by expanding the field slightly since no waste is produced.

Since the field of application of this method is still under development, the present inventors have investigated the possibilities inherent in this method, and have determined that the ice blast method may be more widespread than previously thought. As a result of various experiments, it was discovered that this ice blasting method could be used effectively to remove just the fatigued top coat mentioned above, which was believed to be impossible due to the hardness of the ice grains. .

Therefore, in the present invention, by projecting ice particles together with a carrier fluid toward a painted body, the fatigued top coat is subjected to an impact.
To provide a method for removing a fatigued paint film that can effectively remove only the top coat film without applying frictional force and damaging the undercoat film.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

The drawings are schematic explanatory diagrams showing an example for explaining the present invention.

Ice grains 1 have a particle size of 2 to 8 cm, and are made into a spherical shape without bubbles by injecting ultra-low temperature liquid nitrogen from the bottom into a continuous ice production device, such as a cold water tank, and mixing it with cold water. Using a device configured to generate ice particles through heat exchange, the ice particles are heated with high-pressure water extruded at a pressure of 50 to 300 Kg/ca or 6 to 7 Kg/ct/l. It is conveyed by compressed air 2 and is projected from a spray nozzle 3 used in the existing sandblasting method toward a painted body 6 that has been coated with a base coat 4 and a top coat 5. .

By the above projection, the ice particles 1 collide with the top coat film 5, applying a large impact force and frictional force to the fatigued paint film, and removing only the top coat film 5. By removing the top coat 5, the base coat 4 is exposed, onto which the ice grains 1 are similarly projected, but they are neither removed nor damaged. This is thought to be because the surface of the ice grains 1, which is different from other grains such as sand, melts due to the frictional heat caused by the collision, and this melted water forms the protective layer of the undercoat film 4. Also, the reason why it is not removed is because the hardness of the undercoat 4 is sufficiently greater than the hardness of the ice grains 1 because the adhesion is strong unlike the tired topcoat 5 and the base material 7 backs it up. It is presumed that there is.

This is possible because of the ice blasting method that uses ice particles as particles, and is not possible with other particles.

In summary, the present invention exhibits the following excellent effects.

(g) Since only the tired top coat is removed by ice particle projection, unlike conventional methods that also remove the undercoat, repainting is only required once, and a large amount of painted body or painted area can be covered in a short period of time. processing becomes possible.

(2) Since the undercoat film is not damaged, the topcoat film applied thereon will adhere reliably and the surface finish will be good.

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view showing one embodiment of the method of the present invention. In addition, 1 is an ice particle, 2 is high pressure water or compressed air which is an example of a carrier fluid, 4 is an undercoat film, 5 is an overcoat film, and 6 is a painted body. Patent applicant: Patent attorney representing Ishikawajima-Harima Heavy Industries Co., Ltd.
Nobuo Kinuya

Claims (1)

[Claims] A method for removing a fatigued paint film, characterized by projecting ice grains together with a carrier fluid toward a painted body that has been coated with a top coat and a base coat, and removing the top coat film using the frictional force and impact force of the ice grains. .