JPH04150913A - Wet treating method for coating spray mist - Google Patents

Abstract

PURPOSE:To separate the spray mist of a coating material into pigment and varnish for recovery thereof and permit a continuous, labor-saving treatment of a viscous coating mist by using an aq. solution of semi-etherified or semi- esterified product of polyhydric alcohol as an absorbing liq. to absorb the spray mist of the coating material. CONSTITUTION:An aq. solution of semi-etherified or semi-esterified product of a polyhydric alcohol is used as an absorbing liq. 2 to absorb the spray mist of a coating material 8. It is preferable to use, as the polyhydric alcohol, polyethylene glycol, polypropylene glycol or ethylene glycol-propylene glycol copolymer. The particles of the coating material 8 left uncoated and accumulated in a liq. reservoir part 1a are dissolved immediately by the coating dissolving power of the absorbing liq. 2 itself and the stirring action of a stirring machine 9 and a portion thereof is introduced into a settling and separating tank 11 in order for the coating material to be dissolved and dispersed in the absorbing liq. 2 and separated into varnish 8a and pigment 8b due to the difference in specific gravity, whereby the pigment 8b settles on the bottom part of the settling and separating tank 11 and the varnish 8a floats in an oily form on the liq. surface in this tank.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a wet treatment method for paint spray mist. Particles are captured by wet cleaning to prevent pollution near the workplace due to sprayed paint particles, and the paint captured by wet cleaning is quickly and energy-savingly extracted from the cleaning solution and separated into pigment and face for easy handling. The present invention relates to a wet treatment method for paint spray mist that can be recovered using

(Prior art) Conventionally, as a wet treatment method for paint spray mist, there is a wet booth method using a water curtain, venturi no-pump booth, etc. The substance is captured and treated with water.

(Problem to be Solved by the Invention) However, in the case of the wet booth method, paint particles captured in water generally have a higher specific gravity than water, so they not only settle to the bottom of the aquarium, but also have adhesive properties that prevent them from being submerged in the water. It aggregates into a sticky, sticky mass that accumulates at the bottom.
There are disadvantages such as the fact that this removal is a very difficult task.

In order to compensate for this drawback, attempts have been made to add a killer agent that makes paint particles insoluble to the absorbing liquid and to solidify and float the uncoated particles dispersed in water, but this method is incomplete as there is no perfect killer agent. Currently, they are used as they are, and it takes time to process and dispose of the collected paint residue.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wet treatment method for paint spraying mist that eliminates the drawbacks of the wet booth method.

(Another Means for Solving the Problem) The wet treatment method for paint spray mist of the present invention is characterized in that an aqueous solution of a semi-ether or semi-ester of polyhydric alcohol is used as an absorption liquid for paint spray mist.

The absorption liquid is preferably an aqueous solution of polyethylene glycol, polypropylene glycol, or a half-ether or half-ester of a copolymer of ethylene glycol and propylene glycol.

Further, the half-etherified product or half-esterified product preferably has a molecular weight of 400 or more and an alkyl chain length of 2 carbon atoms.
A concentration of about 10% to 10% is preferable, and the concentration of the solution as an absorption liquid can be used within a wide range of 3% to 50%.

The semi-etherified or half-esterified copolymer of ethylene glycol and propylene glycol is a water-soluble polyhydric alcohol with a molecular weight of 400 to 1500 obtained by random polymerization or block polymerization at a molar ratio of 20:80 to 90:10. It is preferable to use a polymer in which the terminal hydroxyl group is etherified or esterified with an alkyl group, alkylaryl group, or aryl group having 2 to 20 carbon atoms.

The semi-etherified or half-esterified compounds may be used alone or in combination of two or more.

The treatment method of the present invention can be applied to all wet type booths used as painting booths, such as water curtains and venturi no-pump booths, and can be used in combination with conventionally used killer agents, flocculants, etc. There is no problem.

(Function) The absorption liquid used in the present invention can temporarily dissolve paint particles, and then separate the dissolved paint particles into pigment and varnish.Due to the difference in specific gravity, the pigment moves downward and the varnish moves upward. move it.

The sticky varnish will float to the top of the absorbent, making it easier to collect the varnish. In addition, since the varnish adhering to the surface of the pigment that has settled downward is washed and removed by the absorption liquid, the settled pigment is recovered as smooth solid particles, making it easy to handle.

To explain this in detail, unlike ordinary aqueous solutions, the absorption liquid has good affinity with paint when it comes into contact with flying oily paint particles, so it easily envelops paint particles in the liquid and at the same time It has the property of instantly dissolving particles and separating them into pigment and varnish. The specific gravity of an aqueous solution of a semi-etherified or half-esterified polyhydric alcohol is slightly greater than 1.00, and the specific gravity of the pigment is 1.
．． Since it is much larger than 00, the pigment settles quickly. Paint varnishes are made of organic polymeric substances and have a specific gravity of 0.9 or less, so they do not settle.

This aqueous solution has the property of temporarily dissolving the paint.
Spraying is done because the paint contains a solvent to dilute the paint, and the varnish containing the solvent dissolves in this aqueous solution, and this aqueous solution also has a great ability to extract the solvent from the self-solvent varnish. - Since the solvent is extracted in a short time from the self-solvent varnish once dissolved, the varnish from which the solvent has been extracted becomes insoluble in this aqueous solution.

(Example) Next, a specific example of the wet treatment method for paint spraying mist of the present invention will be described with reference to the drawings.

In the figure, reference numeral 1 indicates a spray coating equipment (booth), which is equipped with a storage part 1a for absorbing liquid 2 and an exhaust pipe 1b above it, with one outer surface of the exhaust pipe b serving as a water film forming surface 1c. , liquid storage part 1a
The spout 3a of the circulation pipe 3 connected below faces the upper part of the water film forming surface 1C, and the absorption liquid 2 in the liquid storage part la is jetted out toward the water film forming surface 1c via the pump 4. membrane 5
The absorbent liquid 2 is circulated while forming the absorbent liquid. In this example, the absorption liquid 2 has a molecular weight of 800.
So 7=3 for ethylene oxide and propylene oxide
An aqueous solution containing a monobutyl ether compound as a solute in a molar ratio of was used.

When the paint 8 is sprayed from the paint spraying gun 6 toward the object 7 toward the water film 5, the paint 8 that has not been applied to the object 7 comes into contact with the water film 5 and is absorbed by the liquid stored below. This will lead you to part 1a. The absorbent liquid 2 stored in the liquid storage part 1a is stirred by a stirrer 9 provided at the bottom of the liquid storage part 1a, and the paint particles 8 entrained in the absorbent liquid 2 are quickly dissolved.

The stirrer 9 is constantly driven and also has the function of causing the dissolved pigment to settle at the bottom of the liquid storage portion 1a.

Further, an evacuation fan 10 is provided at the top of the exhaust pipe 1b, and the air on the front side of the water film forming surface IC is circulated through the slit l formed between the water film forming surface IC and the guide plate 1d of the liquid storage portion 1a.
The air is sucked in from e and discharged through the exhaust fan 10. This air also serves to strip the paint solvent dissolved in the absorption liquid 2, and serves to prevent the concentration of the solvent in the absorption liquid 2 from accumulating.

In this way, the absorbing liquid 2 circulates in the booth 1 while forming a water film 5, and on the surface of the water film 5, unpainted paint 8 is absorbed by this absorbing liquid 2 with affinity. , is dissolved and accumulated in the lower liquid storage portion 1al. This liquid storage part 1
The paint particles 8 accumulated in a are rapidly dissolved by the paint dissolving power of the absorbing liquid 2 and the stirring action of the stirrer 9, and are separated into the varnish containing the paint solvent and the pigment.

A portion of the absorption liquid 2 containing the dissolved paint components is led to the intravenous injection separation tank 11 and left there for a certain period of time. Then, the varnish 8a and the pigment 8b, which were dissolved and dispersed in the absorption liquid 2, are separated due to the difference in specific gravity. That is, since the pigment 8b in the absorption liquid 2 has a specific gravity larger than that of the absorption liquid 2, it settles to the bottom of the intravenous injection separation tank 11, and the varnish 8a remains in the upper liquid layer or is eventually absorbed by the solute in the absorption liquid 2. The solvent in the varnish 8a is extracted and becomes a varnish liquid, and since the varnish 8a is a polymeric substance, the varnish part 8a, which does not contain much solvent, is absorbed into the absorption liquid 21; since it becomes insoluble, it is transferred to the intravenous separation tank 1.
It floats to the top of No. 1 in the form of oil.

The varnish 8a separated into the absorption liquid 2 in this way overflows from the weir 12 at the top of the intravenous separation tank 11 and flows into the groove 1.
3 and led to the varnish extraction tank 14. On the other hand, the pigment 8b that has settled at the bottom of the intravenous injection separation tank 11 is removed by the scraper 1.
5 and is scraped out from the bottom and transferred to the fresh water dilution tank 16. The absorption liquid 2 containing a large amount of the pigment 8b led to the fresh water dilution tank 16 is diluted with fresh water here, and serves to wash away the solute components in the absorption liquid 2 that have adhered to the pigment 8b, and are taken out after adhering to the pigment 8b. Reduce loss of monobutyl etherified products of ethylene oxide and propylene oxide.

In some cases, this cleaning can be performed using two parts instead of one part to achieve a cleaning effect. Next, washed pigment 8b
In order to separate it from the absorption liquid 2 diluted with fresh water, it is passed through a filter or a continuous centrifuge 17 for solid-liquid separation. The separated pigment 8b is recovered as a powder containing almost no varnish component 8a. The separated liquid is mixed with the absorption liquid 2 containing a large amount of varnish 8b which has overflowed from the sedimentation separation tank 11 and is led to the varnish extraction tank 14. Here, the solubility of the varnish 8a is further reduced by the diluted absorption liquid 2, so that the solvent in the paint varnish 8a is extracted and the solute in the absorption liquid 2 dissolved in the varnish 8a is also transferred to the water side. The varnish component 8a becomes richer and floats to the top of the varnish extraction tank 14. This is varnish separator 1
8 and leave to stand, the varnish component 8a and the water layer are separated.
Completely separated. The absorbent liquid 2 separated into the lower layer and diluted with fresh water is returned to the liquid depositing section 1a of the booth 1 again. This returned dilution water is used as a water source to replenish the water that evaporates in the booth 1. In other words, since booth 1 always comes into intense gas-liquid contact with unsaturated air and evaporation occurs, up until now, fresh water has been replenished, or instead of replenishing this fresh water, pigments have been washed. By returning the obtained diluted and recovered absorption liquid, water can be automatically replenished, and the solute in the absorption liquid can also be recovered, reducing its loss.

When spraying mist of top coat melamine paint for household appliances was treated using the above-mentioned apparatus according to the method of the present invention, 34%
Recovery rate of pigment contained in unpainted paint is 99.5%
, the varnish recovery rate was 98%.

(Effect of the invention) According to the wet treatment ability of the paint spraying mist of the present invention, an aqueous solution of a half-ether or half-ester of a polyhydric alcohol is used, which was difficult to treat until now. It has the effect of separating the mist into pigment and varnish components, allowing continuous labor-saving treatment of sticky paint mist, and has a significant effect on improving the process of paint spraying.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of an example of an apparatus for carrying out the wet treatment method for paint spraying mist of the present invention. 1... Painting equipment (booth) for spraying 1a... Liquid storage section 2... Absorbing liquid 6... Paint spray gun 8... Paint 8b... Pigment 16... Hydrostatic dilution tank 18...Varnish separator 1b...Exhaust pipe 5...Water membrane 7...Object to be coated 8a...Varnish 11...Intravenous separation tank 17...Continuous centrifuge license applicant Nari Kin Hitomura

Claims (1)

[Scope of Claims] 1. A wet treatment method for paint spray mist, characterized in that an aqueous solution of a semi-ether or semi-ester of polyhydric alcohol is used as an absorption liquid for paint spray mist. 2. The treatment method according to claim 1, wherein the absorption liquid is an aqueous solution of polyethylene glycol, polypropylene glycol, or a half-ether or half-ester of a copolymer of ethylene glycol and propylene glycol.