EP0045045A1

EP0045045A1 - Method of coating metallic material with resin

Info

Publication number: EP0045045A1
Application number: EP81105753A
Authority: EP
Inventors: Yoshinobu Yoshikawa
Original assignee: Kobunshi Giken Co Ltd
Current assignee: Kobunshi Giken Co Ltd
Priority date: 1980-07-25
Filing date: 1981-07-22
Publication date: 1982-02-03
Also published as: JPS5775173A

Abstract

A method of coating metallic materials (1) with resin, in which said metallic materials can be coated with synthetic resin uniformly and simultaneously all over the surfaces thereof by the action of Joule's heat developed by electrifying said metallic materials in an air containing fluidized synthetic resin powders or minute particulates (2).

Description

Summary of the Invention:

(a) Field of the Invention:

The present invention relates to a method of simultaneously coating the inside surface and the outside surface of metallic materials such as metallic pipes, nets, plates and the like with synthetic resin to form strong coating of the constant thickness without pinholes, cracks and the like.

(b) Descriptions of the prior arts:

In coating said metallic materials with synthetic resin such as polyethylene, polypropylene, polyvinyl chloride and the like by means of melt-dipping method, spraying method, adhering method and the like the defects such us poor uniformity in thickness, unstable peel strength, liability to develop pinholes, cracks and the like has made it very difficult to uniformly coat the special surface such as the inside surface of metallic pipes and the like with said synthetic resin.
It has, however, been desired to develop an industrial method of quite uniformly coating metallic materials with synthetic resin from a viewpoint of the required corrosion resistance, electric insulation and the like.
The present invention can eliminate said defects incidental to the prior arts and provide a method of simultaneously coating the inside surface and the outside surface of metallic materials with synthetic resin to form strong and quite uniform coating.
It is an object to provide a method of simultaneously coating the whole surface including the inside surface and the outside surface of metallic materials such as metallic pipes, nets, plates and the like with synthetic resin to form a strong coating of an uniform thickness without pinholes, cracks and the like.
This object can be attained by fixedly mounting metallic materials to be coated with synthetic resin in a vessel of the definite volume (hereinafter referred to as a fluidized-resin tank), in which resin powders or minute particulates are maintained in a fluidized condition by means of putting air therein through a lower bottom thereof under pressure and the like, or passing said metallic materials therethrough, said fluidized resin being uniformly coated on the inside surface and the outside surface of said metallic materials by the action of an electromagnetic force developed on the surface of said metallic materials and Joule's heat owing to the direct electrification of said metallic materials to form a strong coating of an uniform thickness without pinholes, cracks and the like. If necessary, a better coating can be obtained by electrifying a coating again to heat after leaving said fluidized-resin tank.
.Brief Description of the Drawings:

Fig. 1 is a flow chart showing an example of the preferred embodiments of a process of coating metallic materials such as metallic nets, plates and the like with synthetic resin according to the present invention, in which (a) is a side view and (b) is a plan; and
Fig. 2 is a flow chart showing an example of the preferred embodiments of aprocess of coating metallic pipes with synthetic resin according to the present invention; in which 1 is metallic materials, 2 being synthetic resin powders or particulates, 3 being a fluidized-resin tank, 3' being a finishing heating tank, 4, 4' being rolls, 5, 5' being electrode terminals, 6 beinga cooling tank, 7 being metallic materials to be coated with synthetic resin, 8 being a blower, 9 being metallic materials coated withsynthetic resin, and 10 being a supporter. Detail Description of the Invention:

The present invention relates to a method of simultaneously coating the whole surface, including the inside surface and the outside surface, of metallic materials such as metallic pipes, nets, plates and the like with synthetic resin to form a strong coating of an uniform thickness without pinholes, cracks and the like.
According to the present invention, metallic materials to be coated with synthetic resin are fixedly mounted in a vessel of the definite volume, in which resin : powders or minute particulates are maintained in a fluidized condition by means of putting air therein through a lower bottom thereof under pressure and the like, or passing said metallic materials therethrough, said fluidized resin being uniformly coated on the inside surface and the outside surface of said metallic materials by the action of an electromagnetic force developed on the surface of said metallic materials and Joule's heat owing to the direct electrification of said metallic materials to form a strong coating of an uniform thickness without pinholes, cracks and the like. If necessary, a better coating can be obtained by elecrifying a coating again after leaving said fluidized-resin tank.
The construction of the present invention will be in greater detail described below by reference to the drawings.
Fig. 1 is a flow chart showing an example of the preferred embodiments of a process of coating metallic nets made of iron (alias "lath") with synthetic resin according to the present invention.
Referring now to Fig. 1, iron nets are unwound from an iron net roll 7 and electrified by means of electrode terminals 5, 5' while they pass through a fluidized-resin tank 3 through a roll 4.
For example, polyethylene minute particulates 2 fluidized in said fluidized resin tank are coated on the whole inside and outside surface of said iron nets 1 by the action of the electromagnetic force developed on the surface thereof and Joule's heat developed in themselves to form a quite uniform coating thereon.
For example, an electrification of lath of 1,000 mm wide for 1 min. by an electric current (10 V, 1,000 A) can provide polyethylene coating of 0.5 mm thick all over the wires constructing said iron nets. In addition, the better coating can be provided by electrifying to heat the resulting polyethylene coating in a finishing heating tank 3' in which there are no fluidized-polyethylene minute particulates.
The resulting metallic nets coated with polyethylene are wound by a winding apparatus 9 through a cooling tank 6.
Furthermore, iron plates of 0.25 mm thick and 1,000 mm long could be electrified for 1 min, by an electric current (5 V, 3,000 A) in the similar apparatus to form a quite uniform polyethylene costing of 0.1 mm thick on the whele inside and outside surface thereof simultaneously.
It was found from test results that no pinholes were generated in both cases of metallic nets and iron plates.
The fluidized condition of resin was obtained by blowing air into the lower portion of said fluidized-resin tank by means of a blower 8.
Referring now to Fig. 2, there is shown an example of both of the inside surface and the outside surface of iron pipes 1 surface and the outside surface of iron pipes 1 with.synthetic resin according to the present invention.
For example, the inside surface and the outside surface of said iron pipes 1 can be simultaneously coated with polyethylene to form a quite uniform coating thereon by standing erect said iron pipes 1 by means of said supporter 10 in said fluidized-resin tank 3, in which polyethylene minute particulates are fluidized, and electrifying said iron pipes 1 through said lower electrode terminal 5 and said upper electrode terminal 5'.
A quite uniform polyethylene coating having an average thickness of 0.45 mm could be provided simultaneously on the inside surface and the outside surface of cast iron pipes having a diameter of 50 mm, a thickness of 3 mm and a length of 4 mm by standing erect them in said fluidized-resin tank and electrifying them for 1 min. by an electric current of 50 V, 3,000 A per a piece of cast iron pipe. This has been very difficult to attain by the conventional methods.
As described above, the present invention can easily coat simultaneously the whole surfaces of metallic materials, which have been difficulty coated with synthetic resin or have been coated with synthetic resin only by means of the complicated process, with synthetic resin to form a quite uniform coating showing excellent corrosion resistance, insulation and the like without pinholes and the like thereon.

Claims

1. A method of coating simultaneously the inside surface and the outside surface of metallic materials (1) with resin (2), characterized in that said metallic materials (1) are electrified while held in air containing fluidized synthetic resin powders or minute particulates (particles).

2. Method as claimed in claim 1, characterized in that said metallic materials (1) are fixed within said fluidized synthetic resin powders or minute particulates (2).

3. Method as claimed in claim 1, characterized in that said metallic materials (1) are passed through said fluidized synthetic resin powders or minute particulates (2).

4. Method as claimed in anyone of claims 1 to 3, characterised in that said synthetic powders or minute particulates (2) are fluidized within a vessel (3) of definite volume.

5. Method as claimed in anyone of claims 1 to 4, characterized in that said metallic materials (1) are coated with said resin (2) by the action of an electromagnetic force acting on the surface of said material (1) and Joule's heat developed by direct electrification of said metallic material (1).

6. Method as claimed in anyone of claims 1 to 5, characterized in that said metallic material (1) is further electrified after leaving said vessel (3) containing said fluidized resin (2).

7. Method as claimed in anyone of claims 1 to 6, characterized in that said metallic material (1) is cooled after electrically heating and coating with resin (2).

8. Device for practizing the method of anyone of claims 1 to 7, characterized in that it comprises a tank (3) containing fluidized powderous or particulate resin (2), a finish-heating tank (3') and a cooling tank (6), which are arranged in line one after the other.

9. Device as claimed in claim 8, characterized in that said fluidized-resin tank (3) and said finish-heating tank (3') arc provided with electric electrodes (5; 5'; 5").