JPH05277430A - Method for charging and applying liquid particles - Google Patents

Abstract

PURPOSE:To safely, inexpensively and effectively obtain charged particles of a liquid by mixing at least one of air, liquefied gas, a solvent, water and a super-critical fluid with the liquid in a liquid passage before the liquid is granulated and charging the formed liquid granules on the downstream side of the mixing part and/or after granulation. CONSTITUTION:A liquid is supplied from a liquid tank 10 by a pump 13 and the passage 7 sending the liquid under pressure is connected to the nozzle 3 of a spray gun 2 being a granulating device. A pin 5 is provided in the nozzle orifice 4 of the nozzle 3 as an internal charging electrode and connected to a high voltage generator 12 by a cable 9 to charge the liquid granules. A means mixing at least one fluid among air, liquefied gas, a solvent, water or a super- critical fluid with the liquid is provided in the liquid passage 7 to mix said fluid with the liquid and the liquid granules are charged with static electricity on the downstream side of the passage 7 and/or after the granulation of the liquid.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for charging liquid particles.

[0002]

2. Description of the Related Art Conventionally, when a conductive liquid is charged and applied, static electricity leaks through the liquid flow path from the liquid tank to the nozzle even if a high voltage is applied in the vicinity of the nozzle. Charging was difficult. This is because the electric resistance value of a conductive liquid, such as a coating agent or adhesive containing metal particles or conductive particles (carbon particles, fibers, etc.), an aqueous paint, an emulsion adhesive, a water-dispersed wax, etc. This is because static electricity easily leaks to the liquid supply side due to the low resistance value of 10 ⁸ Ω · cm or less. For this reason, various methods have been studied in which the liquid is made into particles by a spraying process, that is, a spray nozzle, a rotary atomizing cup, or the like, and then electrostatically charged. The static electricity flowed in the liquid channel, and a sufficient particle charging effect was not obtained.

For these reasons, at present, the method of insulating the entire liquid flow path to prevent the leakage of static electricity is taken. However, insulating all the liquid tanks, pumps, flow paths, nozzles, etc. Not only is such a large-scale facility required, but the insulated capacitance is also large because a high voltage of 15 to 100 KV is accumulated, and there is a concern that it may lead to personal injury.

[0004]

The charging effect of the liquid particles can be completely insulated by a simpler means without adopting the entire flow path insulating means including the increase in cost and the danger as described above. The motivation of the present invention was to provide a method of obtaining the same effect.

[0005]

Means for Solving the Problems The gist of the present invention is to supply gas from a liquid tank to particles, and in the flow path of the liquid, gas, liquefied gas, solvent, water, supercritical This is a method in which at least one of the sexual fluids is mixed and electrostatically charged at the downstream side of the mixed flow path or / and after the liquid is made into particles. That is, by increasing the resistance value in the liquid flow path, the leakage of static electricity is prevented and the charging effect is enhanced. Therefore, the range of the pressure of the liquid or the pressure of the gas is not limited.

The method of the present invention will be described with reference to the drawings. See FIG. From liquid tank (10) to pump (1
The flow path (7) for supplying the liquid by means of 3) or the like and for feeding the liquid under pressure is a particle-forming device, a spray gun (2) in the drawing.
To the nozzle (3). Also, the nozzle (3)
An electrode or pin (5) for internal charging is provided in the nozzle hole (4) of the device, and the pin is connected to the cable (9) from the high voltage generator (12) to charge the liquid particles. .. Alternatively, a colonna pin (9) for external charging, which is widely used outside the nozzle, may be provided. Here, means for mixing at least one of gas, liquefied gas, solvent, water and supercritical fluid is provided in the liquid flow path (7). The mixing method is as follows:
It is desirable to mix them intermittently (see FIG. 2). Then, as shown in FIG. 3, when gas is mixed, liquid (Li1), gas (G1), liquid (Li2),
It will flow with an array of gas (G2), .... In addition, the longer the flow path in which the gas is mixed, that is, the larger the amount of the mixed gas, the higher the electric resistance value in the flow path, and the static electricity leakage prevention at the time of charging the liquid or its particles. It goes without saying that the effect will be increased. In the present invention, the liquid and the gas are not strictly limited,
That is, it includes a liquid, a foam flow in which a gas is mixed into the liquid, a foam flow, and an arrangement of the gas.

Further, the liquid channel in the method of the present invention has a smaller cross-sectional area and a longer length, the higher the resistance value is, and the effective result of charging the particles can be obtained. Specifically, when the flow path has a circular cross section, the inner diameter is preferably 6 mm or less, specifically, the inner diameter is 2 mm or less and the length is preferably 3 m or more.
The diameter may be about 0.1 mm as long as a desired flow rate per unit time can be maintained depending on the type of liquid and processing accuracy. Further, the flow passage is not limited to the tubular shape as shown in FIG. 2 or FIG. 3, and may be processed into a desired shape, for example, an orifice shape, and two or more processed products, for example, a spiral groove in a cylinder. The flow path may be formed by combining a tube in which a fluid passage provided with is inserted or a tube. Furthermore, a method of mixing a liquid in the gas flow path is also included. The liquid may be pumped by any method such as a pressure tank or a pump.

[0008] Next, examples of use of each by mixing gas, liquefied gas, solvent, water and supercritical fluid will be described. First,
Gas, especially air, is the cheapest and most convenient method. However, if a high pressure is applied to the inside of the flow path when increasing the discharge flow rate, the gas is compressed and the resistance value per unit length becomes low. In such a case, liquefied gas can be used. The same applies to the case of supercritical fluids. When the liquid is an aqueous paint or the like, pure water or an organic solvent having a high specific resistance value may be mixed as a solvent.

Incidentally, the mixing point (8) of these gases is
In the drawing, it is located upstream of the gun (2) provided with an opening / closing valve, but it may be located upstream or downstream of the opening / closing valve, that is, it may be located upstream of the charging points (4) and (5). is there.

The liquid particles charged by the above method are applied to the article to be coated. Alternatively, it can be provided for various uses such as drying during flight and granulating for medicines, toners and the like.

Next, the data will be described for an example of the experiment. 1) Experimental equipment The sequence is shown in Fig. 1. There is no high voltage device. 2) Liquid supply tube Teflon tube, inner diameter 1.5mm
¢, outer diameter 9 mm ¢ length 8 m 3) Target liquid tap water 4) Liquid pressure 1.5 kg / cm ² 5) Gas used Compressor dry air 6) Gas blowing time ON 10 msec. OFF
20 msec. 7) Opening and closing of valve from gun nozzle 8) Atomizing air 1.5kg / cm ² 9) Pattern air 1.0kg / cm ² 10) Distance between nozzle and work piece 250mm 11) Conveyor speed of work piece 2.0m / Min. 12) Electric measurement value (measured with the gun valve closed)

[0012]

[Table 1]

Discussion As can be seen from the 12th item, the voltage at the EPU, which is the power source, is 30 kv when only water is used.
And 90 kv, the voltage at the tadashi corona pin was 0 in all cases, that is, most leaked and the liquid particles were not charged. On the contrary, when air is mixed, the voltage at the corona pin is high at 22 kv and 60 kv, which shows that static electricity is unlikely to leak. With respect to the state of the coated product by both, when it was only water, only the surface was coated. When air was mixed with the water, it was applied to the back side of the water.

[0014]

According to the method of the present invention, it is possible to prevent static electricity from leaking and to charge liquid particles by a simple method, which not only eliminates the need for a large-scale facility as in the prior art but also requires a large insulation capacity. It is possible to obtain effective charged particles of liquid at a low cost with safety without the danger of.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a basic method of the method of the present invention.

FIG. 2 is an enlarged view of “A” part in FIG. 1 above, showing a state in which gases are mixed in the liquid flow path.

FIG. 3 is an enlarged view of “A” part in FIG. 1 above, showing a state in which gases are mixed in the liquid flow path.

FIG. 4 is a timing chart of liquid channel gas mixture.

[Fig. 5] Timing chart of opening / closing of gun valve and gas valve

[Explanation of symbols]

1 Internal charging type liquid spray gun 4 Nozzle hole 5 Internal charging pin 8 Gas mixture joint G, G ₁ , G ₂ gas Li, Li ₁ , Li ₂ liquid

Claims (14)

[Claims] 1. A method of charging liquid particles, wherein at least one of a gas, a liquefied gas, a solvent, water and a supercritical fluid is provided in a flow path of the liquid until the liquid is made into particles. And charging static electricity at the downstream side of the mixed flow path or / and after the liquid is made into particles, a method for charging liquid particles. 2. A gas, a liquefied gas, a solvent,
The method for charging liquid particles according to claim 1, wherein mixing at least one of water and a supercritical fluid is performed intermittently. 3. The method for charging liquid particles according to claim 1, wherein the liquid is electrically conductive. 4. The method for charging liquid particles according to claim 1, wherein the liquid or melt is an aqueous paint or a water-based adhesive. 5. The method for charging liquid particles according to claim 1, wherein the liquid particles are formed by an airless spray method or a two-fluid spray method. 6. The method for charging liquid particles according to claim 1, wherein the liquid particles are formed by a rotary atomization method. 7. The method for charging liquid particles according to claim 1, wherein the liquid is mixed into a flow path formed of at least one of a gas, a liquefied gas, a solvent, water and a supercritical fluid. .. 8. A method of charging liquid particles, wherein at least one of a gas, a liquefied gas, a solvent, water and a supercritical fluid is contained in a flow path of the liquid until the liquid is made into particles. After being mixed and charged with static electricity on the downstream side of the mixed channel or / and after the liquid particles are formed into particles,
A method for applying liquid particles, which comprises applying the particles to an object to be coated. 9. A gas, a liquefied gas, a solvent,
9. The method of applying liquid particles according to claim 8, wherein mixing of at least one of water and a supercritical fluid is intermittently performed. 10. The method for applying liquid particles according to claim 8, wherein the liquid is electrically conductive. 11. The method for applying liquid particles according to claim 8, wherein the liquid or the melt is an aqueous paint or a water-based adhesive. 12. The liquid particle coating method according to claim 8, wherein the liquid particles are formed by an airless spray method or a two-fluid spray method. 13. The method of applying liquid particles according to claim 8, wherein the liquid particles are formed by a rotary atomization method. 14. The method for applying liquid particles according to claim 8, wherein the liquid is mixed into a flow path formed of at least one of a gas, a liquefied gas, a solvent, water and a supercritical fluid. ..