JP2554166B2 - Resin coating gun - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention is a method of electrostatically charging a molten resin powder and electrostatically adhering it to the surface of a material to be coated (hereinafter referred to as “melt electrostatic coating method”). The present invention relates to a resin coating gun applied to.

<Prior art> Conventionally, for example, a method for forming an anticorrosion coating on flues, collisions, electrostatic precipitators, chemical plants, ships, offshore structures, piping, machine tool sliding parts, non-lubricated bearings, electronic parts. A method of forming a low-adhesion coating that adds corrosion resistance and abrasion resistance to parts, irons, frying pans, etc., is to use a molten electrostatic coating that heats and melts a resin, then electrostatically charges it and electrostatically adheres it to the surface of the material to be coated. Method is used.

This melt electrostatic coating method is generally performed through the following steps (see Japanese Patent Application Laid-Open No. 63-194771).

The first step is to heat and melt the powdery resin to form a droplet resin.

 Second step of charging the droplet resin.

A third step of forming a coating film by electrostatically attaching the charged droplet resin to the surface of the material to be coated.

The seventh specific example of carrying out this molten electrostatic coating method
Shown in the figure. As shown in the figure, the powdery resin 11 (for example, tetrafluoroethylene perfluoroalkyl ether copolymer) held in the hopper 10 is supplied by the gas 13 (especially air, nitrogen) supplied from the powder supply device 12. Etc.) from the resin transportation line 14 to the resin heating device 15. The average particle diameter of the powdery resin 11 supplied at this time is 10 to 100 μm.
It is about m, preferably about 30 μm.

The powdery resin 11 supplied to the resin heating device 15 is heated to a temperature equal to or higher than the melting point temperature (350 ° C. to 500 ° C.) and the droplet resin 16
Then, it is sprayed by the resin coating gun 18 provided in the spray nozzle 17. This sprayed droplet resin
Reference numeral 16 denotes an electrostatic charging electrode 19 (20 denotes a charging high-voltage generating power source, and 21 denotes a high-voltage cable I), which is charged with a positive or negative electrostatic charge and which is grounded to a grounded material 23 to be coated. Electrodeposition is performed to form the coating film 24.

Resins used in this method include olefin resins such as polyethylene and polypropylene, polyamide resins, polyimide, amide resins, thermoplastic resins such as fluorine resins, and epoxy resins crushed in a semi-cured state. well known.

By the way, as means for heating and melting the powdery resin,
There is a method of using a combustion gas (hereinafter referred to as a heating gas) such as oxygen (including air) -propane or oxygen-acetylene. That is, the resin coating gun has a double structure, and the powdered resin is blown out from the central portion and the heating gas is blown from the periphery thereof.

<Problems to be Solved by the Invention> As described above, when the heated gas is blown out together with the powdery resin, the temperature thereof needs to be properly adjusted. That is, when the temperature of the heating gas is too high, the powdery resin is heated to a temperature above its thermal decomposition temperature, and the resin is thermally decomposed before adhering to the surface of the material to be coated, resulting in a coating film formed. In addition to the poor properties, the melt viscosity of the resin adhering to the material to be coated becomes too low, causing sagging in the coating on the vertical part or the ceiling surface, and it is difficult to obtain a uniform film thickness. It will be difficult. On the other hand, when the heating temperature is too low, there arises a problem that powder having a particularly large particle size cannot be melted among the powdery resins.

Therefore, in this case, the temperature of the heating gas needs to be appropriately adjusted according to the type of resin, the particle size distribution of the powder, and the blowing amount. Specifically, for example, the temperature of the heating gas is lower than the thermal decomposition temperature in the vicinity of the blowout port that first comes into contact with the powdered resin, and the temperature at the time of reaching the material to be coated is lower than the melting temperature of the resin. It is preferable to adjust so as to be higher.

However, it is difficult to control the temperature of combustion gas such as oxygen-propane or oxygen-acetylene easily and accurately.

Further, the jet of the powdered resin and the heating gas blown from the gun in this manner passes through the gap between the electrode installed between the gas and the material to be coated to be charged, and then the material to be coated is charged. To reach. The jet area is appropriately determined according to the type of resin (melting temperature), particle size, flow velocity and temperature of heating gas. For example, when using resin powder having a wide particle size distribution, the maximum particle size is A length is needed that has the residence time required to completely melt. Alternatively, it is necessary to completely melt even a large particle size during a short residence time.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a resin coating gun that solves the above problems.

<Means for Solving the Problems> A resin coating gun of the present invention that achieves the above-mentioned object is a resin powder outlet for blowing resin powder to the center of the gun.
A resin coating gun having a heated gas outlet for blowing heated gas around it, comprising a temperature adjusting means for adjusting the temperature of the heated gas, and the diameter of the inner surface and outer surface of the innermost heated gas outlet is resin powder. 1.5 times the outlet diameter ~
5 times, the diameter of the inner surface of the outer wall is 3 to 20 times the diameter of the resin powder outlet
It is characterized by being doubled.

<Operation> Since the heating gas for heating and melting the resin powder is adjusted to an appropriate temperature by the temperature adjusting means included in the gun,
The resin powder is mixed with a heating gas under appropriate conditions and melted.

<Examples> Hereinafter, the present invention will be described based on Examples.

FIG. 1 is a longitudinal sectional view of a resin coating gun according to an embodiment, and FIGS. 2 and 3 are views II-II and III of the gun.
-III shows the arrow view. As shown in these drawings, at the tip of the resin coating gun 100, a resin powder outlet 101 is provided in the center, and a cooling air outlet 102, a first heating gas outlet 103 and a second outlet 103 are provided around the resin powder outlet 101. Each heating gas outlet 104 is provided.

Here, the resin powder outlet 101 communicates with a resin powder outlet pipe 105 penetrating the central portion of the gun 100, and the cooling air outlet 102 supplies air for cooling the resin powder outlet pipe covering the periphery of the resin powder outlet pipe 105. It communicates with the pipe 106. The resin powder blow-out pipe cooling air inlet pipe 106 is for preventing the resin powder from melting in the resin powder blow-out pipe 105, and the resin powder outlet pipe cooling air inlet pipe 106 is provided around the resin powder blow-out pipe cooling air inlet pipe 106. A heat insulating material layer 107 is provided.

On the other hand, the first heated gas outlet 103 and the second heated gas outlet 104 are respectively provided in the first heated gas temperature adjusting chamber 1
08 and the second heating gas temperature control chamber 109 for communication,
Both adjusting chambers 108 and 109 communicate with the combustion tubes 110a and 110b, respectively. Burners 111a, 111b and flame detectors 112a, 112b are installed on the upstream sides of these combustion cylinders 110a, 110b, respectively, and air blowing pipes 113a, 113a, near the adjustment chambers 108, 109 on the downstream side.
113b is connected. Here, the combustion cylinders 110a and 110b are
The mixed gas of oxygen and propane, which is sent from the burners 111a and 111b and ignited, is set to have a length sufficient for complete combustion on the upstream side by the connection point with the air suction pipes 113a and 113b. The first and second heating gas temperature adjusting control chambers 108 and 109 play a role of completely mixing the combustion gas from the combustion tubes 110a and 110b and the air from the air blowing pipes 113a and 113b, respectively. , Thermocouple 114a, 114b respectively
Is provided.

In the resin coating gun 100 having such a structure, the combustion gas passes through the combustion tubes 110a and 110b, and the first and second adjustment chambers 1
After being sent to 08,109 and mixed there with the air introduced from the air blowing pipes 113a, 113b and adjusted to predetermined temperatures respectively, they are blown out from the air outlets 103, 104. The thermocouples 114a and 114b detect the gas temperature in the adjustment chambers 108 and 109, and accordingly adjust the amount of air blown from the air blowing pipes 113a and 113b, and the heated gas blown out from the air outlets 103 and 104. The temperature of each is maintained properly. In addition,
The heated gas from the outer outlet 104 mainly acts to shut off the outside air.

In this way, by blowing out the resin powder together with air from the resin powder outlet 101 together with the heating gas whose temperature is properly adjusted, the blown out resin powder is mixed with the heating gas,
After being heated and melted into a droplet resin, it is charged by the electrostatic charging electrode and electrostatically adhered to the material to be coated.

In this embodiment, adjusting chambers 108 and 109 and air blowing pipes 113a and 113b are provided as heating gas temperature adjusting means on the upstream side of the heating gas outlets 103 and 104, and the temperature is adjusted by mixing the combustion gas with an appropriate amount of air. Therefore, the temperature of the heating gas can be easily adjusted depending on the type of resin, the particle size distribution of the resin powder, the blown amount, and the like. Further, at that time, the heating gas temperature can be set accurately by adjusting the amount of air blown, and the heating gas temperature from each is separately adjusted by duplicating the heating gas outlet,
More appropriate temperature setting is possible.

FIG. 4 shows a vertical section of a resin coating gun according to another embodiment. As shown in the figure, the resin coating gun 100A has basically the same configuration as the resin coating gun 100 of the above-described embodiment, and the same members are designated by the same reference numerals and duplicate description will be omitted. However, in this embodiment, the innermost first heating gas outlet 103A has a large diameter, and the second heating gas outlet 104A also has a large diameter, so that the gas blown from the heating gas outlet is large. The flow can be maintained in the potential core region which is less likely to be affected by the outside, and the potential core region can be kept as long as possible.

The length of such a potential core region formed is generally said to be 6 to 7 times the blowout pipe diameter, but since this general principle cannot be applied to the gun as in this embodiment, various investigations have made it the innermost one. It has been found that the diameter of the heating gas outlet 103A is 1.5 to 5 times the diameter of the resin powder outlet 101, and the diameter of the outer wall inner surface is 3 to 20 times the diameter of the resin powder outlet 101. It was When the dimension of the heated gas outlet 103A is set in this range, the formation of the potential core region is properly maintained without being affected by the shape of the resin powder outlet in the central portion, and the length thereof is sufficiently long. You can The diameter of the inner surface of the outer wall of the heating gas outlet 103A does not affect the formation of the potential core region even if it is 20 times or more the diameter of the resin powder outlet 101, but even if it is 20 times or more, the heating gas source The amount of combustion gas becomes
Problems such as the need for a large burner occur and are not practical. Further, the diameter of the outer surface of the inner wall of the heating gas outlet 103A is preferably as small as possible, but since the cooling air outlet 102 and the like must be provided around the resin powder outlet 101, a practical shape ratio As 1.5 times.

Table 1 shows the results of an experimental study on the potential core formation state by variously changing the diameter of the outer surface of the heated gas outlet and the diameter of the inner surface of the outer wall and the diameter of the resin powder outlet. From this result, it is recognized that the above range is more preferable.

According to such a resin coating gun 100A, after blowing, the temperature of the heating gas is adjusted to be lower than the thermal decomposition temperature of the resin near the tip of the gun 100A and higher than the melting temperature of the resin near the surface to be coated, Moreover, since the potential core region is formed long, a good coating film can be formed even by using resin powder having a wide particle size distribution or resin having a small difference between the melting temperature and the thermal decomposition temperature.

FIG. 5 shows a longitudinal section of a resin coating gun according to still another embodiment. As shown in the figure, this resin coating gun 100B is basically the same as that shown in FIG. 4, but for giving a swirl flow to the resin powder blown out in the resin powder outlet 101. The difference is that the vanes 115 are provided. The same members as those in FIG. 4 are designated by the same reference numerals, and duplicate description will be omitted.

6 (a) and 6 (b) show a front view and a sectional view of the vane mounting portion. As shown in both figures, the vane 115 has a shape twisted around the axis, and is fixed to the inner surface of the tip of the resin powder outlet pipe 105.

In the resin coating gun 100B of such an embodiment, the resin powder blown out from the resin powder outlet 101 becomes a swirl flow due to the action of the vane 115, and the first position is obtained near the gun tip.
Is mixed with the heating gas from the heating gas outlet 103A. That is, since the mixed state of the heating gas and the resin powder can be maintained for a long time, it is advantageous to dissolve the resin powder at a low temperature at which thermal decomposition is difficult.

Further, if the vane 115 is not provided, the blown resin powder will be mixed with the heating gas at a position far away from the tip of the gun. Although it is necessary to increase the amount, there is a problem that the gas burner and the gun main body must be made large, but the gun of this embodiment also solves such problems, downsizing the gun main body, fuel Economical effects such as reduced consumption can be obtained.

<Effects of the Invention> As described above, since the resin coating gun of the present invention has the temperature adjusting means, the temperature of the heated gas blown out can be easily and accurately controlled, and various resin powders can be used. A good coating film can be formed.

In addition, since the potential core region is kept long when the diameter of the heated gas outlet is within a specific range, good coating is possible even for resins with a small temperature range between melting temperature and thermal decomposition temperature or resin powder with a large particle size distribution. It can be a membrane.

Furthermore, by providing a vane in which the blowing of the resin powder is used as a swirling flow, the resin powder and the heating gas can be mixed in a short time, the gas main body can be downsized, and the fuel consumption for producing the heating gas can be reduced. It has effects such as reduction.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a resin coating gun according to an embodiment of the present invention, FIGS. 2 and 3 are views taken along arrows II-II and III-III, and FIG. FIG. 5 is a vertical sectional view of a resin coating gun according to an embodiment, FIG. 5 is a vertical sectional view of a resin coating gun according to still another embodiment, and FIGS. 6 (a) and 6 (b) are front views of essential parts thereof. FIG. 7 is a schematic view of a resin coating method according to the prior art. In the drawing, 100, 100A, 100B are resin coating guns, 101 is a resin powder outlet, 102 is an air outlet for cooling, 103, 104 are heated gas outlets, 105 is a resin powder outlet pipe, 106 is a resin powder outlet pipe for cooling Air inlet pipe, 107 heat insulating layer, 108 and 109 heating gas temperature adjusting chamber, 110a and 110b combustion cylinder, 111a and 111b burner, 112a and 112b flame detector, 113a and 113b air blowing pipe, 114a and 114b are thermocouples and 115 is a vane.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Miaki Aoki Iwa ▲ Tsuka ▼ Nakamura-cho, Nakamura-ku, Aichi Pref. 1st highway, Mitsubishi Heavy Industries, Ltd. Nagoya Research Center (72) Inventor Fumio Kondo Nakamura, Aichi Pref. Iwa-Tsuka-cho, Takadō No. 1, Mitsubishi Heavy Industries, Ltd., Nagoya Research Center (56) References JP-A-53-88046 (JP, A)

Claims (2)

(57) [Claims] 1. A resin coating gun having a resin powder outlet for blowing resin powder in the center of the gun and a heating gas outlet around the resin powder outlet, comprising temperature adjusting means for adjusting the temperature of the heating gas, Resin coating characterized in that the diameter of the inner wall outer surface of the innermost heated gas outlet is 1.5 to 5 times the diameter of the resin powder outlet, and the diameter of the inner surface of the outer wall is 3 to 20 times the diameter of the resin powder outlet. Gun. 2. The resin coating gun according to claim 1, further comprising a vane inside the resin powder outlet, the vane having a swirling flow of the blown resin powder.