JPH022889A - Coating method - Google Patents

Abstract

PURPOSE:To prevent coating failure due to voltage drop by mixing a solvent for electrostatic coating having insulating properties in an atomization state into the gas fed to an electrostatic coating machine through a gas feed pipe and enhancing the electric resistance value of a catalyst stuck to the inside of the gas feed pipe. CONSTITUTION:Coating is performed by simultaneously ejecting both coating and gas incorporating a catalyst for promoting the curing reaction thereof from one electrostatic coating machine 1. A solvent for electrostatic coating having insulating properties is mixed in an atomization state into the above- mentioned gas fed to the electrostatic coating machine 1 through a gas feed pipe 11 and the electric resistance value of the catalyst stuck to the inside of the gas feed pipe 11 is enhanced. As a result, a leakage of the high voltage impressed to the electrostatic coating machine via the catalyst stuck to the inside of the gas feed pipe is prevented, therefore, the coating failure due to the voltage drop of the electrostatic coating machine is surely prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a coating method in which a coating material and a gas containing a catalyst that accelerates the curing reaction are ejected simultaneously from one electrostatic coating machine. .

[Conventional technology]

In order to uniformly cure a coating film of a catalytically cured paint such as a urethane paint in a short time, it is necessary to effectively mix a catalyst such as an amine catalyst into the paint ejected from a coating machine.

For this reason, in the past, paint supplied to an airless atomizing spray gun was atomized using its hydraulic pressure, and at the same time,
A gas containing a catalyst that accelerates the curing reaction of paint is ejected concentrically from the surrounding area (Patent Application Publication No. 60-50).
0324), the paint and the catalyst are combined into one by atomizing the paint supplied to an air atomizing spray gun with a gas containing a catalyst (see Japanese Patent Application Laid-open No. 170153/1983). They are being squirted together from a paint machine.

[The problem that the idea aims to solve]

However, when paint and catalyst are ejected from an electrostatic sprayer, the high voltage applied to the sprayer leaks through the gas supply pipe that supplies the gas containing the catalyst, resulting in paint failure due to voltage drop. There was a risk that this would occur.

In other words, if the mist-like catalyst carried by the gas adheres to the gas supply pipe while being fed to the electrostatic atomizer,
There was a problem in that the insulation of the gas supply pipe was impaired and a predetermined high voltage could no longer be applied to the electrostatic coating machine.

Therefore, the present invention aims to solve the technical problem of preventing the high voltage applied to the electrostatic coating machine from leaking through the gas supply pipe that supplies the gas containing the catalyst. The purpose is to prevent paint defects due to machine voltage drop.

[Means to solve the problem]

In order to achieve this object, the present invention provides a coating method in which a coating material and a gas containing a catalyst that accelerates the curing reaction are ejected simultaneously from one electrostatic coating machine.
An insulating electrostatic coating solvent is mixed in an atomized state into the gas being supplied to the electrostatic coating machine through the gas supply pipe, and the electrical resistance value of the catalyst attached to the gas supply pipe is adjusted. It is characterized by increasing

(Function) According to the present invention, since the insulating electrostatic coating solvent is mixed in the atomized state into the gas containing the catalyst that is supplied to the electrostatic coating machine through the gas supply pipe, the gas If some of the catalyst contained therein may adhere to the inside of the gas supply pipe, the electrostatic coating solvent will also adhere to the inside of the gas supply pipe.
The catalyst and the insulating electrostatic coating solvent mix with each other, increasing the electrical resistance of the catalyst, and preventing the high voltage applied to the electrostatic coating machine from leaking through the gas supply pipe.

In addition, if you do this, the solvent will be ejected from the electrostatic sprayer along with the catalyst, but since the solvent is originally mixed with the paint, there is a concern that it will have a negative effect on the paint film. There are few.

〔Example〕

Embodiments of the present invention will be specifically described below based on the drawings.

FIG. 1 is a flow sheet diagram showing an example of an electrostatic coating apparatus to which the method of the present invention is applied, and FIG. 2 is a time chart showing its operation.

In this example, a urethane paint that uses a mixture of two liquids, a base and a curing agent, and a gas containing an amine catalyst that accelerates the curing reaction are applied using an electrostatic coating machine to which a high voltage is applied. 1, and when the trigger (not shown) of the electrostatic coating machine 1 is pulled to start it, amine is pumped and supplied by the gear pump 3 from the catalyst tank 2, which is the catalyst supply source. Catalyst and gear pump 5 from solvent tank 4
The electrostatic coating solvent with insulating properties is pumped and supplied by
The gas is mixed in an atomized state into the gas supplied from the compressed gas supply source 6 to the electrostatic coating machine 1.

After a certain period of time has elapsed since the gas containing the catalyst and the electrostatic coating solvent began to be ejected from the electrostatic coating machine 1, the base material, which is pumped by the gear pump 8 from the base tank 7, and the hardening agent tank 9, Supply of the paint mixed with the curing agent pumped by the gear pump 10 is started.

That is, the gas supply pipe 11 that supplies gas from the compressed gas supply source 6 to the electrostatic atomizer 1 includes an on/off valve 12;
An air flow switch 13 that is automatically opened and closed in conjunction with the trigger of the electrostatic sprayer 1 is interposed, and a catalyst supply pipe 15 is connected to the catalyst tank 2 via an on/off valve 14, and an on/off valve. 16 through solvent tank 4
A branch connection is made to a solvent supply pipe 17 connected to the solvent supply pipe 17 .

Note that the on/off valves 14 and 16 interposed in the catalyst supply pipe 15 and the solvent supply pipe 17 are connected to the air flow switch 1.
The switch is opened two seconds after the switch signal No. 3 is output.

Further, a base supply pipe 18 for pumping the base in the base tank 7 with the gear pump 8 and a hardening agent supply pipe 19 for pumping the hardening agent in the hardening agent tank 9 with the gear pump 10 are connected to an on/off valve 20 and Static mixer 22 via 21
is connected to.

Then, 4 seconds after the air flow switch 13 is opened, the on/off valves 20 and 21 are opened (i.e., the on/off valves 4 and 6 are opened and the gas supply pipe
2 seconds after the start of supplying the catalyst and solvent into the gas flow in the tank), the base is pumped from the base tank 7 and the curing agent is pumped from the curing agent tank 9. The paint is mixed uniformly by the static mixer 22 and then supplied to the electrostatic coating machine 1 through the paint supply pipe 23.

Note that the gear pumps 8 and 10 each have a drive motor 2.
The rotational speeds of rotation speeds 4 and 25 are variably controlled by inverters 26 and 27 to adjust the mixing ratio of the base material and the curing agent. In addition, the gear pump 10 that pumps the high viscosity curing agent starts the drive motor 25 after 4 seconds have elapsed since the switch signal of the air flow switch 13 is output (that is, when the on/off pulp 21 is released). The rotational speed is increased by 2 seconds from the normal speed, so that the supply of the base material and curing agent can be started at the optimum mixing ratio from the beginning.

Therefore, before starting the electrostatic atomizer 1, the on-off pulp 12 installed in the gas supply pipe 11 is opened in advance to connect the electrostatic atomizer 1 to the compressed gas supply source 6.

When the trigger of the electrostatic atomizer 1 is pulled to start the atomizer I, compressed gas starts to be supplied from the compressed gas supply source 6 to the electrostatic atomizer 1 through the gas supply pipe 11, and at the same time, the compressed gas starts to be supplied to the electrostatic atomizer 1 through the gas supply pipe 11. The air flow switch 13 installed in the gas supply pipe 11 is opened by the flow of gas, and the switch 13 is opened.
A switch signal is output from (see T in FIG. 2).

As a result, first, only gas is ejected from the electrostatic coating machine 1, and the amine catalyst droplets that remained attached to the gas supply pipe 11 at the end of the previous coating are completely vaporized by the gas. Since it is wiped off, leakage of the high voltage applied to the electrostatic coating machine 1 is prevented.

Then, two seconds after the air flow switch 13 is opened, the on/off pulps 14 and 16 interposed in the catalyst supply pipe 15 and the solvent supply pipe 17 are opened and are pumped from the catalyst tank 2 by the gear pump 3. The amine catalyst is supplied in an atomized state into the gas supply pipe 11 through the catalyst supply pipe 15, mixed into the gas flowing through the gas supply pipe 11, and is pumped from the solvent tank 4 by the gear pump 5. The electrostatic coating solvent is supplied in an atomized state into the gas supply pipe 11 through the solvent supply pipe 17 and mixed into the gas containing the catalyst (see T2 in FIG. 2).

As a result, a gas flow containing a highly concentrated amine catalyst in an atomized state is ejected from the electrostatic coating machine 1.

Then, two seconds after the amine catalyst is mixed with the gas stream and started being supplied to the electrostatic coating machine 1, the on/off pulps 20 and 21 are opened, and the amine catalyst is mixed with the gas stream and fed through the base supply pipe 18 from the base tank 7. The base material being pumped and the curing agent being pumped from the curing agent tank 9 through the curing agent supply pipe 19 are mixed in a static mixer 22 and then supplied to the electrostatic coating machine 1 through the paint supply pipe 23 (first step). (See T in Figure 2).

In this way, the gas containing the amine catalyst that accelerates the curing reaction is ejected before the paint is ejected after the electrostatic coating machine 1 is started, so that the catalyst is ejected. By checking the condition in advance, it is possible to reliably prevent poor curing of the coating film. Therefore, since it is only necessary to check the spouting state of the paint, the paint can be instantly discarded and blown away to reduce wastage of the paint.

In addition, if the pre-collection gas is supplied to the electrostatic coating machine 1, the atomization of the amine catalyst mixed in the gas will be promoted and its concentration can be quickly increased, so that it can be supplied afterwards. It is possible to reliably prevent poor curing of paint films.

Furthermore, an insulating electrostatic coating solvent is mixed in the atomized state with the amine catalyst into the gas supplied to the electrostatic coating machine 1, so that the electricity of the amine catalyst attached to the gas supply pipe 11 is removed. Since we are trying to increase the resistance value, electrostatic coating machine 1
The high voltage applied to the gas supply pipe 11 is prevented from leaking through the droplets of the amine catalyst adhering to the inside of the gas supply pipe 11, and the voltage drop in the electrostatic atomizer 1 will not cause coating defects.

Note that the voltage generated when the high voltage applied to the electrodes of the electrostatic atomizer 1 leaks from the surface inside the gas supply pipe 11 wetted with amine catalyst droplets to the grounded trigger or grip of the electrostatic atomizer 1. Since an insulation resistance of several MΩ or more is sufficient to prevent the drop, the amount of electrostatic coating solvent mixed into the gas being supplied to the electrostatic coating machine l through the gas supply pipe 11 is: It is sufficient to select the amine catalyst to such an extent that the electrical resistance value of the amine catalyst mixed with the solvent and deposited inside the gas supply pipe 11 can be increased to several MΩ or more.

Furthermore, the electrostatic coating solvent may be placed in the catalyst tank 2 and mixed with the amine catalyst in advance, but in this case, it would be very difficult to control the concentration of the amine catalyst in accordance with the amount of paint ejected. At the same time, there is a risk that the coating film will become rough due to too much solvent.

On the other hand, as shown in Figure 1, if the amine catalyst and the solvent are supplied separately from the catalyst tank 2 and the solvent tank 4, the concentrations of both can be easily and precisely controlled, so that the coating due to lack of catalyst can be avoided. It is possible to reliably prevent poor curing of the film and roughness of the coating due to too much solvent.

〔Effect of the invention〕

As described above, according to the present invention, in the gas containing the catalyst being supplied to the electrostatic coating machine through the gas supply pipe,
By mixing insulating electrostatic coating solvent in atomized state,
Since the electrical resistance of the catalyst attached to the gas supply pipe is increased, the high voltage applied to the electrostatic atomizer leaks through the catalyst adhering to the gas supply pipe, resulting in a voltage drop in the electrostatic atomizer. This has the very valuable effect of reliably preventing coating defects.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet diagram showing an example of an electrostatic coating apparatus to which the method of the present invention is applied, and FIG. 2 is a time chart showing its operation. Explanation of symbols 1- Electrostatic coating machine, 2- Catalyst tank, 4- Solvent tank, 6- Compressed gas supply source, 11- Gas supply pipe, 15- Catalyst supply pipe, 17- Solvent supply pipe, 23- Paint supply tube.

Claims (1)

[Claims] In a coating method in which paint and a gas containing a catalyst that accelerates the curing reaction are ejected simultaneously from one electrostatic coating machine, the gas is supplied to the electrostatic coating machine through a gas supply pipe. . A coating method, characterized in that an insulating electrostatic coating solvent is mixed in atomized state to increase the electrical resistance value of the catalyst attached to the gas supply pipe.