JPH0811212B2 - Coating method for thermoplastic powder coatings - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a generally cylindrical pipe material having a surface with hot dip galvanizing with a thermoplastic powder coating material.

[0002]

2. Description of the Related Art A thermoplastic powder in which the surface of a pipe is pretreated by cleaning or polishing to keep it clean, the paint is baked in a heating furnace at a desired temperature, and then water cooling is performed. A method of applying paint is known. (See, for example, JP-A-63-1484)

[0003]

By the way, in baking the above-mentioned thermoplastic powder coating on the surface of a hot dip galvanized pipe, roughening of the surface of the pipe is important in order to increase its adhesion. However, in the conventional example, the surface roughening was carried out as a pretreatment, and the surface roughening was not particularly considered.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to maintain a hot-dip galvanized pipe material at a high temperature and heat it. The present invention intends to provide a method for coating a thermoplastic powder coating material having good adhesion by sufficiently polishing the surface to a desired degree of roughening.

[0005]

In order to achieve the above object, a method for coating a thermoplastic powder coating material according to the present invention is a method in which a substantially cylindrical pipe material having a surface subjected to hot dip galvanization is manufactured by a high frequency furnace. C. to 370.degree. C., the surface of the material is roughened by hot polishing, and the material having the roughened surface is baked in a state where the material is further heated to the above temperature range by a high frequency furnace, The feature is that the material on which the paint is baked is cooled with water.

[0006]

[Operation] The material of the substantially cylindrical pipe is 320 ° C in the high frequency furnace.
Since it is heated to ~ 370 ° C and hot-polished immediately after that by a grinder, the galvanized surface is in a state where it is easily roughened, and the polishing is extremely easy and the desired roughening is achieved. Can be done easily. Since the roughened material has a slightly lowered temperature, it is further heated in a high-frequency furnace to raise the temperature to the above temperature range, and the thermoplastic powder is removed by the electrostatic powder spraying device or the like. It is baked on the roughened part. Since the paint is thermoplastic, the paint is firmly adhered to the surface of the pipe material by cooling the baked material with water.

[0007]

EXAMPLE FIG. 1 is a schematic view of a coating line for carrying out the method for coating a thermoplastic powder coating material according to the present invention, in which 1 is a heating process by a high frequency heating furnace, and 2 is a brush. A polishing process using a polishing machine, 3 is a heating process using a high-frequency heating furnace, 4 is a paint baking process using an electrostatic coating device, and 5 is a cooling process using a water tank.

A pipe material having a substantially cylindrical shape (with some taper) formed in advance and having its surface plated with hot dip galvanized material is first subjected to a heating step 1 in a high frequency heating furnace by a heating step 1320.
By heating to 370C to 370C, the galvanized surface is easily roughened sufficiently.

The galvanized surface of the heated pipe material is sufficiently roughened in the polishing step 2 using a polishing machine composed of a brush. The zinc plating surface temperature is lowered by about 30 ° C. by this step.

The material whose zinc-plated surface has been roughened and whose temperature has been lowered is sequentially heated in a heating step 3 using a high-frequency heating furnace to 320 ° C. to 370 ° C. which is suitable for the baking temperature of the coating material in the next step.

In this state, the galvanized surface of the pipe material is sufficiently roughened and has a temperature suitable for baking the paint. Therefore, this is sequentially sent to the paint baking step 4 by the electrostatic coating device and heated. Perform electrostatic coating of plastic powder paint.

The material on which the paint has been baked is water-cooled in the cooling step 5 in the water tank so that the paint is hardened and firmly adheres to the surface of the pipe material.

[0013]

In the method for coating the thermoplastic powder coating material according to the present invention, the pipe material is first heated in the high frequency furnace at 320 ° C to 37 ° C.
Since it is heated to 0 ° C. and hot-polished immediately after that, the galvanized surface is in a state where it is easily roughened, and the polishing is extremely easy and the desired roughening is achieved. Easy to do. Therefore, the thermoplastic powder coating material is surely baked onto the roughened portion by an electrostatic powder spraying device or the like.

Further, the temperature drop on the galvanized surface due to the polishing is slight, and the temperature can be returned to the temperature suitable for the baking temperature again by a simple high-frequency furnace, so that the thermal efficiency is good and the work can be done quickly.

[Brief description of drawings]

FIG. 1 is a schematic view of a coating line when a method for coating a thermoplastic powder coating material according to the present invention is carried out.

[Explanation of symbols]

 1 Heating process by high frequency heating furnace 2 Polishing process by polishing machine 3 Heating process by high frequency heating furnace 4 Baking process of paint 5 Cooling process by water tank

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B05D 7/24 301 A 7415-4F C23C 2/26

Claims (1)

[Claims] 1. A substantially cylindrical pipe material having a hot-dip galvanized surface is heated to 320 ° C. to 370 ° C. in a high frequency furnace, and the surface of the material is roughened by hot polishing to roughen the surface. A method for coating a thermoplastic powder coating material, comprising: baking a coating material in a state in which the surface-treated material is further heated in the above-mentioned temperature range by a high-frequency furnace, and cooling the material on which the coating material is baked with water.