JPH09164363A - Coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently collect, separate and recover an undeposited spray paint. SOLUTION: A material to be coated is spray-coated with a water-base paint by using a wet coating booth, the paint not deposited on the material is collected in water, the collected liq. is filtered with a membrane and separated into the undeposited paint and permeated water, and the paint and water are recovered and reutilized. In this case, the solid paint content in the collected liq. to be treated is controlled to 10-30wt.%, and the solid paint content in the treated collected liq. is controlled to 31-40wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method for spray-coating a water-based paint with a wet coating boot and recovering and reusing uncoated spray paint which has not been applied to an object to be coated.

[0002]

2. Description of the Related Art Conventionally, in spray coating, a coating boot has been used for the purpose of improving environmental hygiene for workers and preventing contamination of the surrounding area due to spraying of sprayed paint.

The coating boot is a device used for collecting uncoated spray paint which has not been applied to an object by spray coating, and is a wet device for collecting in water. Paint boots are generally known.

In the wet coating boots, the uncoated paint is dissolved and dispersed in water by a water flow curtain provided behind the object to be coated and collected in a water tank. −
It is circulated and used as a ten. The uncoated paint collected in the water tank is mixed with a coagulant to separate and remove the paint, but since a large amount of water is used, it is difficult to separate and remove the paint and the water treatment load is large. There are drawbacks that it is difficult to collect and reuse the applied paint, and it takes time to replace water. In addition to the above, there is also a method of separating uncoated paint and water collected in a water tank by ultrafiltration or reverse osmosis to separate into a high solid content paint and permeated water.
No. 4 publication. However, this method has the drawbacks that it is necessary to carry out filtration for a long time in order to obtain a coating material having a high solid content by these filtration treatments, the treatment efficiency is poor, and the filtration treatment cannot be completed when the spray coating frequency increases.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a method for recovering and reusing uncoated spray paint that has not been applied to an object by spray coating by filtration treatment with a membrane, The purpose is to eliminate the drawbacks of
The feature is that in the coating method in which filtration treatment with a membrane is performed to separate into uncoated paint and permeated water and these are collected and reused, the solid content of the collected liquid before the filtration treatment with a membrane is performed. The filtration treatment is carried out under the conditions that the concentration is 10 to 30% by weight and the solid content of the uncoated paint after the treatment is 31 to 40% by weight.

That is, according to the present invention, a water-based paint is spray-coated on an object to be coated using a wet coating boot, and an uncoated paint which has not been applied to the object is collected in water. A coating method in which the collected liquid is filtered by a membrane to separate into uncoated paint and permeated water, and these are collected and reused, and the filtration by the membrane performs the treatment. The solid content concentration of the previous collection liquid is 10 to 30% by weight, and the solid content concentration of the uncoated paint after the treatment is 31 to 40% by weight.
The present invention relates to a coating method characterized in that the treatment is carried out under the concentration condition of.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As the water-based paint that can be spray-painted, conventionally known heat-drying type and room-temperature-drying type water-based coatings can be used without particular limitation, but particularly low-viscosity emulsion-type room-temperature-drying type water-based coatings. Is preferred.

As a wet coating boot, it is well known in the art that, for example, the uncoated coating material is dissolved and dispersed in water by a water flow curtain provided behind the article to be coated to form a lower portion of the water flow curtain. It is possible to cite a booth that collects in a water tank provided in the direction and then circulates the collected material as a water flow chart.

Spray coating on the article to be coated can be carried out by using a conventionally known spray coating means such as an air spray or an electrostatic spray. As the article to be coated, for example, any of metal, glass, plastic, wood, paper, and a laminated material in which these materials are combined can be used.

The membrane filtration treatment is carried out to separate a liquid obtained by collecting the uncoated coating material with water into an uncoated coating fluid and permeated water. A reverse osmosis filtration treatment and a treatment combining these treatments are preferable. The ultrafiltration and reverse osmosis filtration treatments are conventionally known methods, and in particular, those used in electrodeposition coating baths and those used in other fields can be used. The ultrafiltration method generally involves contacting a collecting liquid with one surface of a semipermeable membrane for ultrafiltration, and then applying pressure to the collecting liquid so that only water or a low molecular weight substance permeates through the membrane. It is a method of concentration and separation.
The reverse osmosis filtration treatment is a method performed by applying a large pressure equal to or higher than the osmotic pressure so that water flows in the opposite direction through the semipermeable membrane, and the shape of the membrane is a hollow fine fiber body, a spiral shape or a preform. It may have any shape such as a flat shape or a frame shape.

The solid content concentration of the collected liquid on which the filtration treatment is carried out is in the range of 10 to 30% by weight. When the solid content concentration is less than 10% by weight, the amount of treatment is large, and as a result, the time required for the treatment is long and the recovery efficiency of the paint is poor. On the other hand, when it exceeds 30% by weight, the load on the filtration membrane is large. Since the amount of treatment per unit area of the filtration membrane becomes small, there is a drawback that the recovery efficiency of the paint becomes extremely poor. Further, the viscosity of the collected liquid is preferably in the range of about 1 to 100 mPa · s from the viewpoint of filtration treatment capacity.

The uncoated paint obtained by separation by the above filtration treatment is preferably used as a paint for spray coating by mixing it with a stock solution paint having a solid content concentration of 60% by weight or more. As a result, the uncoated paint is completely recovered and reused. A high solid type coating material for spray coating can be obtained by using the high concentration solid content as the undiluted coating material. Further, the permeated water can be reused as it is or after being subjected to an ion exchange treatment, as circulating water of a wet coating booth.

In the filtration treatment equipment, the filtration treatment equipment may be directly connected to a water tank (for example, a circulating water tank in which water flow carts are dropped and stored) provided in the coating booth equipment, or the coating treatment equipment may be used. -It is possible to install a water tank for the filtration treatment apparatus separately from the filtration apparatus and connect the filtration treatment apparatus to this tank.

[0014]

The present invention will be described in detail. The present invention is not limited to this embodiment.

Example 1 Oxidation-curable emulsion paint having a solid content concentration of 65% by weight (oxidation-curable epoxy ester base resin "acid value 40, number average molecular weight about 8,000", drier, carbon and barita compound) Water was added to the stock solution to obtain a water-based paint for initial spray coating having a solid content of 40% by weight.

The water-based paint was over-painted until the solid content of the circulating water in the wet coating boot became 25% by weight.

Next, 1000 liters of the circulating water thus obtained was subjected to an ultrafiltration device (manufactured by Asahi Kasei Kogyo Co., Ltd., permeable membrane type Micro-the-KCV-3010E, membrane area 4.7 m ² ×).
2) with an inlet pressure of 2.5 Kg / cm ² and an outlet pressure of 0.5 Kg
It was circulated at a temperature of 25 ° C./cm ² and separated into a concentrate and a permeate.

Table 1 shows the results.

[0019]

[Table 1]

From the results shown in Table 1, 1000 liters of circulating water having a solid content of 25% by weight can be achieved in about 180 minutes to obtain a water having a solid content of 40% by weight, and the aqueous paint and the permeate can be efficiently separated. I was able to recover it.

Further, the obtained water-based paint and the undiluted solution of the water-based paint can be mixed and used as a paint for spray coating.

Comparative Example 1 Ultrafiltration treatment of circulating water was carried out in the same manner as in Example 1. As a result, it took about 400 minutes for 1000 liters of circulating water having a solid content of 25% by weight to reach a solid content of 45% by weight, and it was very inefficient to separate and collect the concentrated aqueous paint and permeate.

Comparative Example 2 Ultrafiltration treatment of circulating water was carried out in the same manner as in Example 1. The circulating water had a solid content of 8% by weight. As a result, it took about 220 minutes for 1000 liters of circulating water having a solid content of 8% by weight to reach the same solid content concentration (25% by weight) as that of the circulating water in Example 1, and the solid content was further adjusted to 40% by weight. The same processing time as in Example 1 was required for 180 minutes, and the total processing time was 400 minutes, which was very inefficient in separating and recovering the concentrated aqueous paint and permeate. .

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location B05D 7/24 301 B05D 7/24 301F C02F 1/44 C02F 1/44 K (72) Inventor Hiroshi Ichinose Kanagawa Kanagawa Paint Co., Ltd. 4-17-1, Higashi-Hachiman, Hiratsuka City (72) Inventor Toru Hayase 4-17-1 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd.

Claims (4)

[Claims] 1. A water-based coating composition is spray-coated on an article to be coated using a wet coating boot, and the uncoated coating composition that has not been applied to the article is collected in water. A coating method in which the collected liquid is filtered by a membrane to separate into uncoated paint and permeated water, and these are collected and reused, wherein the filtration liquid by the membrane performs the treatment. The coating method is characterized in that the filtration treatment is carried out under the conditions that the solid content concentration is 10 to 30% by weight and the solid content concentration of the uncoated coating after the treatment is 31 to 40% by weight. 2. The coating method according to claim 1, wherein the filtration treatment with a membrane is an ultrafiltration treatment, a reverse osmosis filtration treatment, or a combination of these treatments. 3. A water-based paint used for spray coating is a mixture of a stock solution paint having a solid content concentration of 60% by weight or more and an uncoated paint separated and recovered by a filtration treatment with the above membrane. The coating method according to claim 1. 4. The coating method according to claim 1, 2 or 3, wherein the water-based paint used for spray coating is a room-temperature-drying water-based paint.