JPH0463169A - Coating method with aerosol - Google Patents

Abstract

PURPOSE:To increase coating efficiency by heating an aerosol to a temp. above the temp. of a body to be coated during generation and/or transfer, condensing vapor of a solvent present in an atmosphere with particles of the aerosol in the atmosphere as nuclei, further condensing the vapor on the surface of the body to be coated and sticking the particles of the aerosol and the solvent on the body to be coated. CONSTITUTION:A soln. L to be sprayed to increase the amt. of vapor or a carrier gas CG and/or an aerosol generator 1 is heated or a generated aerosol is further heated during transfer. A body Oa to be coated is set at the lower part of a coating booth. Since vapor of a solvent in the aerosol is in a satd. state at a temp. above the temp. of the body Oa, the vapor is condensed by the temp. difference with particles of the aerosol as nuclei and further condensed on the surface of the body Oa. Fine particles R carried by the carrier gas collide against drops formed by the condensation, the kinetic energy of the particles is absorbed in the drops to reduce the bound of the particles and the particles stick on the drops. When a large number of such drops gather, a liq. film Sf is formed, covers the entire surface of the body Oa and can further reduce the bound of the fine particles.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to an aerosol application method.

[Prior art] A typical example of a conventional aerosol application method is the fifth method.
As shown in the figure, the liquid (L3) etc. was pressurized and ejected from the spray nozzle (54), and it was made to hit the hard plate (55) 82 to form finer particles, which were then introduced. It is carried on the airflow of carrier gas (CG3) to the surface of the object to be coated (Oc), and the surface of the object to be coated (Oc) is
) against a surface, or static electricity (electrostatic arrow added N58)
) was applied to the surface of the object to be coated (Oc).

[Problem to be solved] As shown in the upper figure, aerosol particles were hit on the surface of the object to be coated while being carried by a carrier gas, but at this time, these particles rebounded (bound). was unavoidable.

Originally, fine particles (around 1 micron) have a surface area of
Although they have a large weight, that is, a relatively large air resistance, they have a small inertial force, so they are easily affected by the movement of the gas around the particles. In other words, there is very little time for the velocity of the particles in the gas to reach the terminal velocity, and therefore,
The initial velocity of aerosol particles is almost unrelated to the gas flow velocity. Literature, William C. Hines Ao: "Aerosol Technology" Benjo Shoin (1980) Particle size (μm) Time to reach terminal velocity fms
)100' 9210
0.941
0.011 As mentioned above, the terminal velocity is reached almost instantaneously. That is, the aerosol particles almost instantaneously become equal to the gas flow velocity.

Therefore, aerosol particles hardly move in stationary gas, and the time required for them to reach the object to be coated becomes longer. On the other hand, when the flow rate of the carrier gas is increased, most of the aerosol particles become rfIJ particles and collide with the surface of the object to be coated, causing a rebound phenomenon and reducing the adhesion efficiency.

As mentioned above, the motivation of the present invention is to reduce bounce of aerosol particles during coating to increase coating efficiency, and at the same time, to implement a safe coating method by eliminating damage to the coated object or danger caused by electrical discharge. [Means for solving the problem] As mentioned above, very fine aerosol particles (for example, around 1 micron) are moved by a carrier gas, and with kinetic energy at a certain speed, w
1 Open on the painted surface. However, the force exerted by these fine particles is the Van der Saals force or the attractive force due to slightly charged static electricity, and has very small energy. On the other hand, due to the opening on the object to be coated, the converted rebound energy is larger and the aerosol particles are less likely to adhere.

For example, when the object to be coated is plastic and harder quartz, it is said that there is a three-fold difference in adhesion between them.

An object of the present invention is to efficiently apply aerosol dispersoids, that is, particles, to the surface of a workpiece by reducing bounce, and to more effectively increase the application efficiency by electrostatic charging in an aerosol application method. That's true.

The gist of the present invention is a method of guiding and coating an aerosol generated by an aerosol generation device onto the surface of a workpiece, in which solvent vapor is present in the aerosol, and the aerosol generation step and/or aerosol transfer step is performed. The material is heated to a temperature higher than the temperature of the object to be coated, and the temperature difference causes the solvent vapor present in the atmosphere above the object to be condensed with aerosol particles in the atmosphere as nuclei, and the surface of the object to be coated is heated. While condensing, the aerosol dispersoids (hereinafter referred to as particles) introduced above are allowed to adhere to the object to be coated, and then,
This aerosol coating method is characterized by evaporating the solvent and coating only the remaining aerosol particles.

Furthermore, the coating efficiency can be increased by charging the aerosol and/or the object to be coated with static electricity.

Next, the present invention will be explained in detail. The liquid used for aerosol generation is a solution containing a solvent,
I will explain the 13 bodies that are not included in two parts.

(1) In the case of solutions First, a conventional aerosol generation method will be briefly explained. Please refer to FIG. Pump up the liquid (L) and
Sprays in the chamber (2) and ejects from the nozzle (4),
The spray is applied to a hard plate (5) to obtain fine particles. At the same time, the solvent in the liquid (L) is also vaporized,
Aerosol (As) consisting of these gases and fine particles is generated. On the other hand, a necessary gas (G) is introduced from below the chamber (2), and this is a carrier gas (C
As G), the aerosol (As) is transported into the application section (22).

The gas in the aerosol contains vapors of the solvent as described above, and it is desirable that the amount of these vapors be as large as possible.

To do this, it is sufficient to heat the solution to be sprayed (L3, carrier gas (CG) and/or aerosol generator! (1), that is, to heat the aerosol generation step.
Furthermore, it is sufficient to heat the aerosol during the transfer process. In addition, below the coating part, there is a
), and the solvent vapor in the aerosol is saturated at a temperature higher than the temperature of the object to be coated, so due to the temperature difference, the solvent vapor condenses with the aerosol particles as nuclei, and Condensation (Sc) also occurs on the surface (second
In addition to the condensed dew (see figure), the fine particles fR) carried by the carrier gas are struck. However, the kinetic energy of the fine particles is absorbed by these n liquid drops, the bounce is reduced, and the fine particles are deposited on the same n1jI.

In addition, when a large number of these m droplets gather, as shown in Figure 3, they form a liquid film (Sf) that completely covers the surface of the object to be coated, making it possible to further reduce the bounce of fine particles. .

Although the above-mentioned aerosol generating material was used as a solution, it is known that it also includes suspensions, milk 1111W, and the like. Next, an experimental example using a suspension will be described.

Experiment example t! IL liquid water (pure) 9
2 parts by weight Zirconia powder (particle size 5 μm) 7 parts by weight Rosin water-soluble fat 1 part by weight Room temperature
25℃ Liquid pressure 40Kg/cm2 (with plunger pump) W! 60°C Aerosol Dispersoid Zirconia powder and rosin-based water-soluble resin dispersion medium Water carrier gas Dry air flow rate (in the aerosol transfer pipe 19) 8 m/min Heating temperature on the aerosol transfer pipe 80°C Object to be coated
Quartz glass 10cm x 10cm object temperature 2
0℃ Required time (for 1 piece of the above-mentioned object) 5 minutes Result
After 5 minutes, it was possible to obtain a coated surface on which about 2,000 pieces of zirconia powder were evenly distributed and adhered per 1 mm 2 of the glass surface.

There is no data regarding solutions and emulsions as they have not been tested.

Therefore, a suitable solvent vapor is introduced into the same chamber by the solvent vapor generator (47). As a result, in the same room, condensation with aerosol particles as a nucleus and the object to be coated (Ob)
Condensation occurs on the surface, forming dew droplets or a film of the solvent on the object to be coated. The fine particles in the aerosol are less likely to bounce and are efficiently coated on these surfaces, similar to the case with the top layer.

As mentioned above, the solid fine particles used as the dispersoid of the aerosol may have a single component or multiple components. Similarly, in the case of a liquid, there may be a single component or a plurality of components. Further, these may be a mixture of liquid fine particles and solid fine particles.

(2) In the case of a molten body This is a case where an aerosol of a molten body containing no solvent is generated. Please refer to Figure 4. The heated liquid melt (HM) is ejected from a spray nozzle (34), and is struck against a hard plate (35) to become fine particles. However, since no solvent is included as in the case of the liquid described above, an aerosol consisting of single solid particles of the melt is produced. It is placed on the carrier gas, coating chamber C42)
Reach within. As mentioned above, the object to be coated (Ob) is placed in the lower part of the same room, but since the aerosol in the same room does not contain solvent, the solvent vapor and the object to be coated are separated. Condensation due to temperature differences does not occur.

[Effect] According to the method of the present invention, the generated aerosol particles can be effectively applied onto the surface of the object to be coated without bouncing.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the aerosol application method of the present invention. Figure 2 is a diagram of dew condensation at the "A" section in the same figure as above. Figure 3 is a liquid film formed by the collection of dew condensation at the "A" section of the same figure. Figure 4 shows the aerosol application method when the aerosol dispersoid is a melt.
Figure 5 is an explanation of the main symbols of the conventional aerosol application method.

Claims (1)

[Claims] 1. A method of guiding and coating an aerosol generated from an aerosol generation device onto the surface of the object to be coated, in which solvent vapor is present in the aerosol, and the aerosol generation step and/or
Alternatively, in the aerosol transfer process, the object to be coated (Oa) is heated to a higher temperature than the object to be coated (Oa), and the temperature difference causes the solvent vapor present in the atmosphere above the object to be nucleated by aerosol particles (R) in the atmosphere. The aerosol particles (R) are deposited together with the solvent on the object to be coated while condensing on the surface of the object to be coated, and then the solvent is evaporated to form the remaining aerosol particles (R). An aerosol application method characterized by applying only R). 2. The method for applying an aerosol according to claim 1, which comprises charging the aerosol and/or the object to be coated with static electricity. 3. The method for applying an aerosol according to claim 1, wherein the dispersoid of the aerosol consists of solid particles of a single component or multiple components. 4. The method for applying an aerosol according to claim 1, wherein the dispersoid of the aerosol consists of liquid particles of a single component or a plurality of components. 5. Claims characterized in that the dispersoid of the aerosol is a mixed particle of solid and liquid consisting of solid particles consisting of a single component or multiple components and liquid particles consisting of a single component or multiple components. The method for applying an aerosol according to item 1.