JPH02189159A - Coating method for aerosol - Google Patents

Abstract

PURPOSE:To improve coating efficiency by reducing the occurrence of bound of aerosol particles by a method wherein solvent steam is present in aerosol, a substance to be coated is cooled, aerosol particles are adhered on dewdrops, generated resulting from formation of dew of steam, e.g. a solvent, on the surface of the substance to be coated, or a liquid film by means of a line of electric force, and thereafter, the solvent is vaporized. CONSTITUTION:Steam generated through gasification of a solvent is contained in aerosol. A cooling board 25 connected to a cooling device 23 is situated below a coating part, a substance Oa to be coated is placed thereon through an earthed plate 27 to cool the substance to be coated, and the temperature of the substance to be coated is by means of the temperature of solvent steam at the coating part. Reduction of the temperature causes solvent steam to produce dew Sc formed on the surface to be coated. Particles R carried by carrier gas are adhered on the dewdrops generated resulting from formation of the dew and accelerated by a line of electric force emitted toward the substance Oa to be coated from an electrode 26 for application of static electricity, and the line of electric force is collided with the surface of the substance to be coated. Movement energy of the particles is absorbed by liquid of the dewdrops, the occurrence of bound is reduced, and the particles are effectively adhered on the dewdrops by means of electrostatic attractive force. When a number of dewdrops are gathered, they form a liquid filmform substance Sf with which the whole surface of the substance to be coated is covered, and the occurrence of bound of the particles can be further reduced.

Description

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

[Conventional technology 1 To give a typical example of the conventional aerosol application method, the fifth
As shown in the figure, pressurized liquid is ejected from the spray nozzle 54 and collided with the hard plate 55.
The particles are made into finer particles and transported to the surface of the object to be coated on the airflow of the introduced carrier gas CG3.

At that speed, it was attached to or coated on the surface of the object to be coated 00 by shining a light onto the surface of the object to be coated, or by the force of static electricity (static electricity applying device!58).

[Problems to be Solved] As described above, aerosol particles have been applied to the surface of the object to be coated by carrying them on a carrier gas, that is, a conveying air flow, or by a force such as electric lines of force due to the application of static electricity.

Originally, fine particles (around 1 micron) have a surface area of
Although their weight is large, which means relatively large air resistance, their inertial force is small, so they are easily affected by the movement of the gas around them.In other words, the speed of movement of particles in the gas is influenced by the movement of the gas around them. There is therefore little time to reach terminal velocity.

The initial velocity of aerosol particles is almost unrelated to the flow velocity of the gas.0 Literature: "Aerosol Technology" by William C. Hines, Benjo Shoin (1980): Particle size (μm) Time to reach terminal velocity (ms) )1
0 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, in a stationary gas, aerosol particles hardly move, and the time it takes 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, the secondary arosol particles reach almost the same speed as the flow rate of the carrier gas 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 for the present invention was to increase the coating efficiency by reducing the bounce of aerosol particles during coating, and to further increase the efficiency by using electrostatic electric lines of force.

[Means for solving the problem] As mentioned above, very fine aerosol particles (for example, around 1 micron) are moved by a carrier gas and have kinetic energy with a certain degree of speed.

Collisions onto the surface of the workpiece. However, the force with which these fine particles adhere is the Van der Waals force or the attractive force due to slightly charged static electricity, and has very small energy. On the other hand, upon collision with the object to be coated, the converted rebound energy is larger, making it difficult for the aerosol particles to adhere. It is said that there is a difference of three times.

An object of the present invention is to form a liquid film of a solvent on the surface of an object to be coated by cooling the object in an aerosol coating method, thereby reducing bounce of aerosol particles on several sides, and furthermore, to reduce static electricity. The goal is to more effectively increase coating efficiency by using electric lines of force.

The gist of the present invention is to provide a method in which an aerosol generated by an aerosol generating device is guided onto the surface of a workpiece to be coated, in which solvent vapor is present in the gas, and the workpiece placed in the aerosol is The solvent vapor contained in the aerosol is cooled to below the saturation point, thereby condensing the solvent vapor contained in the aerosol onto the surface of the object to be coated, and further condensing the vapor onto the surface of the mist droplets or around them by the lines of electric force caused by the application of static electricity. The dispersoids (hereinafter referred to as particles) of the guided aerosol are more efficiently deposited on the surface of the liquid film formed by the aggregation of the particles, and then the solvent in the form of a liquid film is evaporated. , is an aerosol coating method characterized by coating only remaining aerosol particles.

Next, one aspect of the present invention will be explained in detail. The liquid used for aerosol generation will be divided into two types: a solution containing a solvent, and a melt that does not contain a solvent.

(1) In the case of ill liquid First, a conventional aerosol generation method will be briefly explained.

Refer to FIG. 1, the liquid is pumped up and ejected from the spray nozzle 4 in the chamber 2, and the spray is applied to the hard plate 5 to obtain fine particles. At the same time, the solvent in the liquid is also vaporized, and an 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 carries the aerosol As into the application section 22 as a carrier gas CG.

The gas in the aerosol contains vaporized solvent as described above, and the amount of this vapor is 50% of the saturated vapor amount.
% or more is desirable, because if it is less than that, the condensation phenomenon described in the first section becomes less likely to occur.

Below the application section, there is a cooling plate 2 connected to the cooling bag M23.
5 is provided, and the object to be coated Oa is placed on the board via a grounded board 27. The object to be coated Oa is cooled down to a temperature lower than that of the solvent vapor at the coating area. It is desirable that the temperature difference be larger than 10° C., because if it is smaller than that, it becomes difficult for dew condensation to occur as described in the first section. As a result, the solvent vapor easily condenses on the surface of the object to be coated (see Fig. 2). On top of these condensed mist droplets, the fine particles R riding on the carrier gas are exposed to the electrostatic charge applying electrode 26. It is accelerated by the electric lines of force emitted toward the object Oa and strikes the surface of the object to be coated. However, the liquid in these droplets absorbs the kinetic energy of the particles, reducing their bounce and allowing them to more effectively adhere to the droplets due to electrostatic attraction.

In addition, when a large number of the above-mentioned mist droplets gather, as shown in No. 31i1, they become a liquid film Sf that completely covers the surface of the object to be coated,
This makes it possible to further reduce the bounce of fine particles.

In addition, the aerosol is heated to an appropriate temperature during the spraying solution, carrier gas, or moving process.

Increasing the amount of steam increases the speed and area of liquid film formation due to cooling.

The above-mentioned aerosol generating material was made into a solution, but it was
As is known, it also includes Il suspensions, emulsions, and the like.

Next, an experimental example using an S suspension will be described.

Experimental Example 1 Suspension Water (pure water) 92 parts by weight Zirconia powder (particle size 5 μm) 7 parts by weight Rosin water-soluble resin 1 part by weight Room temperature 25°C Liquid pressure 40 kg/ff1 (by plunger pump) Liquid temperature 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 F0 sol transfer pipe 80°C Electrostatic applied voltage 10 KV Object to be coated
Quartz glass 10cn x 10cm Cooled object to be coated Humidity 20℃ Required time (for one object to be coated) 30 seconds Result Approximately 2,000 zirconia powders per glass surface are uniformly distributed and adhered after 30 seconds I was able to get

Experimental Example 2 Suspension Trichlorotrifluoroethane 97 parts by weight Vinyl resin 1.5 parts by weight Cyanine pigment (particle size 0.5 μm) 1.5 parts by weight Room 1Ilt25℃ Liquid pressure 40kg/aJ Liquid film 25℃ Aerosol Molecule Quality Vinyl resin and cyanine pigment dispersion medium Trichlorotrifluoroethane carrier gas
Nitrogen gas flow rate (in the aerosol transfer pipe 39) 5 m / min in Heating temperature on the aerosol transfer pipe 40°C Static electricity applied voltage 10 KV Object to be coated Rusted aluminum plate 1 oll! lXl0Q
I Cooled object temperature 15℃ Required time (for one object to be coated above) 20 seconds Result
After 20 seconds, a uniform blue coating of 0.7 microns was obtained.

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

(2) In the case of a molten body This is a case where an aerosol of a molten body containing no solvent is generated. Referring to FIG. 4, the heated liquid melt HM is ejected from the spray nozzle 34, hits the hard plate 35, and becomes 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. that is.

It is carried by the carrier gas and reaches the inside of the coating chamber 42. The cooling plate 45 is provided in the lower part of the same room as described above, but since the aerosol in the same room does not contain a solvent, no dew condensation phenomenon occurs due to cooling.

Therefore, a suitable solvent vapor is introduced into the same chamber by the solvent vapor generator 47. As a result, in the same room.

As dew condenses, mist droplets or a liquid film of the solvent are formed on the screen of the object to be coated. The fine particles in the aerosol are accelerated by the lines of electric force EF caused by static electricity and strike the liquid film. However, as in the main item, it is buffered by the liquid film and is less likely to bounce due to electrostatic attraction, resulting in more efficient coating.

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 are cases in which it has a single component and cases in which it has multiple components. Further, these may be a mixture of liquid fine particles and solid fine particles.

[Effects of the Invention] According to the method of the present invention, the generated aerosol particles are less likely to bounce and can be effectively applied onto the surface of the object to be coated.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the aerosol application method of the present invention. Fig. 2 is a diagram of dew condensation at the "A" section in the same figure as above. An explanatory diagram of the state in which fine particles adhere. Fig. 4 shows an aerosol application method when the aerosol dispersoid is a melt. Fig. 5 shows a conventional aerosol application method.
Aerosol generator! 4,34...Spray nozzle 5.35...Hard board 21,4
1... Application section 23.43... Cooling device 25.45... Cooling plate 26.44
-...Electrode for applying static electricity 47...Solvent evaporator 31 As...Aerosol CG・
−・・・Carrier gas EF, EF□・・・・・・
Electric force lines HM...Melted body Oa, Ob, Oc
・・・・・・Object to be coated Sc・・・・Condensation Sf・・・・Liquid film

Claims (1)

[Scope of Claims] 1. A method in which an aerosol generated by an aerosol generator is guided onto the surface of the object to be coated, in which solvent vapor is made to exist in the aerosol, the object to be coated is cooled by a cooling device, etc. The electric force of static electricity is applied to the fog droplets formed by condensing the vapor of the solvent, etc. present in the atmosphere above the workpiece on the workpiece surface, or to the liquid film formed by the collection of fog droplets. A method for applying an aerosol, which comprises making the particles of the aerosol adhere more effectively by using a line, and then evaporating the liquid solvent to apply only the aerosol particles. 2. The object to be coated is cooled by at least 10°C below the temperature of the vapor and/or aerosol of a solvent discharged from an outlet led from an aerosol generator. How to apply an aerosol. 3. The amount of vapor of the solvent that exists in the atmosphere above the object to be coated and which should cause dew condensation on the object to be coated is 50% of the saturated vapor amount of the solvent.
The method for applying an aerosol according to claim 1, characterized in that the method is as follows. 4. 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. 5. 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 multiple components. 6. 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.