JPH1147653A - Shower coat coating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a shower coat coating capable of recycling by using an oxidative polymerization type aqueous coating material by washing off and recovering a coating material which is not applied to a material to be coated by the shower coat coating with a washing liq. flowing down an inner wall surface of a coating chamber and reusing the coating material by filtering with an ultrafiltration device. SOLUTION: The shower coat coating is applied on the material 3 to be coated by spraying the oxidative polymerization type aqueous coating material from a coating material discharge port 2 provided at the coating chamber 1. The coating material which is not applied on the material 3 to be coated at this time falls to a bottom part of the coating chamber 1 or sticks to the inner wall surface of the coating chamber 1. Thereby, when the system is operated, a filtrate (washing liq.) in a filtrate tank 5 is sent with a liq. sending pump from an outlet 4 and allowed to fall on the inner wall surface of the coating chamber 1, and the coating material which is not applied to the material 3 to be coated is washed off with the washing liq. and collected to a storage tank 7. The washing liq. in the storage tank 7 is concentrated with the ultrafiltration device 8 and returned to the storage tank 7, and on the other hand, a part of a stored liq. is returned to the filtrate tank 5 through the storage tank 11 and the ultrafiltration device 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a shower coat coating system applicable to an oxidative polymerization type water-based paint.

[0002]

2. Description of the Related Art Shower coat coating is a coating method in which paint is discharged from a nozzle like a shower and passes through an object to be coated. This method is widely used as a coating method suitable for coating a metal product or an automobile part, for example, an automobile fuel tank or the like, since the coating amount is large and the application is completed in a short time.

[0003] In this coating method, paint that has not been applied to the object to be coated adheres to the inner surface of the coating chamber, so that periodic cleaning is required.

On the other hand, the oxidative polymerization type aqueous coating is useful as a low-temperature coating and has the advantage that energy saving in the curing process is possible. However, after adhesion, it tends to polymerize and harden due to air oxidation, and is easily applied to the inner surface of the coating chamber. Was difficult to apply.

By the way, in the field of spray coating, a recycling system has already been technically developed.
For example, Japanese Patent Application Laid-Open No. 5-228422 discloses a method of collecting spray splashes and reusing them as spray paint. In this method, only one stage of ultrafiltration concentration step is carried out, and the washing liquid is diluted with water after use for spray coating and has a concentration of 4 to 20% by weight.
Because of the features such as using a dilute aqueous solution of paint,
Even if such a method is applied to the shower coat coating method, it is difficult to apply the method to the shower coat coating method with a large discharge amount of the paint. It is difficult to apply to an oxidative polymerization type water-based coating material which tends to accumulate and adhere after being adhered and polymerized by air oxidation.

[0006] Japanese Patent Application Laid-Open No. 6-7718 discloses a method of collecting spray splashes and reusing them as spray paint. This method has a feature that the recovered washing water having a concentration of 1 to 1.5% by weight is concentrated through a two-stage ultrafiltration device and reused as a spray paint, and the filtrate is used as a washing liquid. Even if the above method is applied, it is practically impossible to apply and operate a shower coat coating method in which a large amount of paint is discharged and a high-concentration paint is stored at the bottom of a coating room.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to provide a shower coat coating system which can be applied to an oxidative polymerization type water-based paint and can be applied to a low temperature drying type paint. Is what you do.

[0008]

According to the present invention, a water-based paint recovered in a coating chamber after shower coating and a cleaning liquid after cleaning the coating chamber are collected in a first storage tank. To the ultrafiltration circulation path (I) to extract the filtrate, collect the filtrate in the filtrate tank, and maintain the solid content concentration of the aqueous paint in the first storage tank at a value lower than the concentration at the time of application, At the same time, a part of the liquid stored in the first storage tank is guided to a second storage tank, and the liquid stored in the second storage tank is guided to an ultrafiltration circuit (II) to perform the second filtration. The solid content concentration of the aqueous paint in the storage tank is adjusted to the application concentration, while the filtrate is collected in the filtrate tank, and the filtrate in the filtrate tank thus collected and the replenished filtrate component as necessary Is used as a washing liquid, and the second reservoir is used. A shower coating paint system and executes subjecting the new aqueous coating supplemented as necessary and recovered aqueous paint in the tank shower coating paint continuously. Hereinafter, the present invention will be described in detail.

In the present invention, the water-based paint collected in the coating chamber after the shower coat coating and the cleaning liquid after washing the coating chamber are collected in the first storage tank, and the storage liquid in the first storage tank is limited. After being led to the outer filtration circuit (I) and extracting the filtrate, the filtrate is returned to the first storage tank, and the solid content of the aqueous paint in the stored liquid in the first storage tank is set to be lower than the concentration at the time of application. The filtrate is maintained at a low value, while the filtrate is collected in a filtrate tank.

Water-based paint provided for shower coat coating,
For example, among the oxidative polymerization type water-based paints, those not applied to the object to be coated fall directly to the bottom of the coating chamber or scatter and adhere to the inner surface of the coating chamber. When left as it is, the paint that has adhered undergoes air oxidation and gradually polymerizes and hardens. Therefore, in order to quickly wash off the paint adhering to the interior of the coating chamber, the cleaning liquid is flown along the interior of the coating chamber. The paint that has been washed away with this washing liquid is also stored at the bottom of the coating room. In the present invention, the water-based paint and the cleaning liquid that have thus fallen to the bottom of the coating chamber and have been washed away with the cleaning liquid are once collected in the first storage tank. Since the solid content concentration of the aqueous paint in the first storage tank is diluted by the cleaning liquid,
Even when the amount of evaporation is taken into account, the concentration is generally lower than the coating concentration. In the case of an oxidative polymerization type water-based coating material, the coating concentration generally varies depending on the composition and use, but is usually 50% by weight or less, preferably 25 to 45% by weight.

In the present invention, the liquid stored in the first storage tank is led to the ultrafiltration circuit (I), and the filtrate is drawn out and returned to the first storage tank. This process is
The main purpose is to extract the filtrate from the stored liquid. Therefore, the solid content concentration of the aqueous paint in the first storage tank is:
It is not necessary to be raised by the above process,
By extracting at least an amount of the filtrate corresponding to the amount of the washing liquid flowing in, the concentration is maintained at a value lower than the concentration at the time of application. When an oxidative polymerization type water-based paint is used, this value is preferably maintained at a value about 5% by weight lower than the concentration at the time of application. And the filtrate extracted by this process is
Collected in the filtrate tank.

In the present invention, at the same time, a part of the liquid stored in the first storage tank is guided to the second storage tank, and the liquid stored in the second storage tank is ultrafiltered. II), the solid concentration of the water-based paint in the second storage tank is adjusted to the application concentration, and the filtrate is collected in the filtrate tank.

The main purpose of this process is to concentrate the solid content of the water-based paint in the second storage tank to a coating concentration. That is, in a state where the system of the present invention is continuously operated, the solid content concentration of the aqueous paint in the second storage tank has reached the application concentration. Therefore, in this process, an amount of filtrate corresponding to the amount diluted by the storage liquid led from the first storage tank is withdrawn from the ultrafiltration circuit (II), and the filtrate in the second storage tank is extracted. The solid content concentration of the water-based paint is set to the application concentration. In this case, the concentration of the circulating liquid guided to the ultrafiltration circuit (II) is higher than the concentration of the circulating liquid guided to the ultrafiltration circuit (I). Is usually higher than the ultrafiltration circuit (I). The filtrate drawn in this process is also collected in the filtrate tank.

When the system of the present invention is operated, the water-based paint applied by shower coating on the object to be coated is taken out of the system. Therefore, it is necessary to replenish the system with a new water-based paint in an amount corresponding to the amount taken out. In the present invention, this can be performed in the second storage tank. The solid content concentration of the replenishment paint may be the same as the application concentration, but may be higher.

[0015] The second storage tank may be connected via a branch valve to a pipe returning to the first storage tank in the ultrafiltration circuit (I). In this case, the circulating liquid after the filtration in the ultrafiltration circuit (I) can be directly guided to the second storage tank by operating the branch valve, and the first storage tank and the second storage tank can be guided to the second storage tank. The amount and concentration of the liquid stored in the storage tank can be adjusted.

In the present invention, the filtrate thus collected in the filtrate tank and the filtrate component replenished as necessary are used as a washing liquid, and the recovered water-based paint in the second storage tank and The new water-based paint replenished as necessary is subjected to shower coating, and ultrafiltration is performed by the ultrafiltration circuit (I), storage from the first storage tank to the second storage tank. While simultaneously performing the transport of the liquid and the ultrafiltration by the ultrafiltration circuit (II), the filtrate in the filtrate tank is intermittently or continuously flown as a cleaning liquid onto the wall of the coating chamber. While performing the shower coat painting. The above-mentioned filtrate tank is used, if necessary, in order to balance the amount taken out of the system by spontaneous evaporation or coating on the object to be coated and the amount replenished by the newly replenished paint. It is replenished by injecting the filtrate components.

In order for the system of the present invention to operate smoothly and continuously, the material balance of the system needs to be balanced over a unit working period, for example, per day. That is, first, the amount of the cleaning liquid flowing on the wall surface of the coating chamber is determined by the ultrafiltration circuit (I).
The amount of the filtrate to be removed is adjusted so as to balance with the amount of the filtrate, and the amount of the aqueous paint discharged from the shower and the amount applied to the object to be coated, and the movement of the stored liquid from the first storage tank to the second storage tank. Adjust so that the liquid volume is balanced. Thus, it is preferable that the amount of liquid stored in the first storage tank is controlled so as not to substantially change per unit working period.

Thus, by operating the shower coat coating system of the present invention, the washing liquid is supplied to the outside of the system while replenishing the paint and the filtrate component in an amount corresponding to the amount of the substance to be applied to the object and taken out of the system. A water-based paint such as an oxidatively polymerizable paint can be continuously provided for shower coating without discharging water.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. The shower coat coating system of the present invention can be typically realized by the configuration shown in FIG. The coating chamber 1 is provided with a paint discharge port 2 from which an object to be coated 3 is subjected to shower coating with an oxidative polymerization type aqueous paint. The paint that has not been applied to the workpiece 3 falls to the bottom of the coating chamber 1 and partially adheres to the inner wall surface of the coating chamber 1. On the other hand, an outlet 4 for a cleaning liquid is provided in the coating chamber 1 and is connected to a filtrate tank 5 via a pipe 6 via a liquid feed pump (not shown).

The inner wall surface of the coating room 1 is made of plastic,
It is preferable to use a material such as a stainless steel plate or a metal plate whose surface is resin-processed with a fluororesin or the like. The coating object 3 is not particularly limited, and includes, for example, various metal products,
It can be suitably applied to automobile parts such as automobile fuel tanks.

When the system of the present invention is in operation, a filtrate of V ₄ liters per minute is sent from the washing liquid outlet 4 from the filtrate tank 5 by a liquid sending pump (not shown), and the coating chamber 1 is discharged.
While it is flowing on the inner wall surface of, for shower coating paint from the coating material discharge port 2 to the object to be coated 3 oxidation polymerization type aqueous coating having a solid concentration C ₁ at a rate per minute V ₁ 'liter. The above solid content concentration C
₁ can be, for example, 30% by weight. The article to be coated 3, oxidative polymerization type aqueous coating having a solid concentration C ₁ is V ₂ liters Nurigi per day, it is brought out of the system. A part of the paint that has not been applied to the object 3 is collected as it is in a first storage tank 7 provided at the lower part of the coating chamber 1,
The remaining part adheres to the inner wall surface of the coating room 1 as droplets or the like, and the paint adhered to the wall surface is washed away by the cleaning liquid and collected again in the first storage tank 7.

Since the stored liquid in the first storage tank 7 contains the discharged oxidative polymerization type aqueous paint and the flowing cleaning liquid, even if the reduction of the filtrate due to spontaneous evaporation is taken into consideration,
Generally, the solid content concentration C ₂ is the concentration C ₁ at the time of application.
Lower than the concentration. The liquid stored in the first storage tank 7 is guided to the ultrafiltration device 8 at a rate of ₃ liters per minute, and the filtrate is extracted at a rate of ₄ liters per minute equal to the flow rate of the washing liquid. It is concentrated to the partial concentration C ₂ ′ and returned to the first storage tank 7 at a rate of V ₃ ′ = V ₃ −V ₄ liters per minute. In this case, the solid content concentration of the liquid stored in the first storage tank 7 is such that the amount of the stored liquid is sufficiently larger than the amount of V ₃ ′, and the diluted paint since entering the tank is maintained at a substantially C _2. The concentrated solid content concentration C ₂ ′ is controlled so as to satisfy such a condition. The first storage tank 7 is connected to the second storage tank 11 by a pipe 12. Part of the liquid stored in the first storage tank 7 is sent to the second storage tank 11 by a liquid feed pump (not shown) at a rate of ₁ liter per minute.

As described above, in the preferred embodiment of the present invention, the amount of filtrate withdrawn from the ultrafiltration circuit (I) and the amount of filtrate used as the washing liquid are balanced. From this, the ultrafiltration circuit (I)
It can be seen that the main purpose is to extract the filtrate from the recovered paint. The solids circulating in the ultrafiltration circuit (I) are returned to the first storage tank 7 again. Accordingly, the material balance for the coating room 1 is as follows. Amount of substances entering the coating room 1 : (a) Wash water (V ₄ liters per minute) (b) Paint (solid content concentration C ₁ , V ₁ 'liter per minute) to be used for shower coat coating Exit from the coating room 1 Material amount : (c) paint applied to substrate 3 (solid content C ₁ , V ₂ liters per day) (d) paint sent to second storage tank 11 (solid content C ₂ , (V) ₁ liter per minute) (e) Evaporation (V _X liter per minute)

In a preferred embodiment of the present invention,
The system is operated such that the material balance of the coating room 1 is balanced over a unit work period, for example, per day. For this purpose, first, it is necessary to control the inflow and outflow into the coating chamber 1 so that the amount of liquid stored in the first storage tank 7 does not substantially change when the system is operating. In particular, it is necessary to control so that V ₁ ′ and V ₁ having a large flow rate are substantially equal. Therefore, the solid content concentration of the aqueous paint in the first storage tank 7 can be maintained substantially constant. In a preferred embodiment of the present invention, a paint having a predetermined solid content concentration lower than the application concentration, for example, 25 to 30% by weight is previously stored in the first storage tank 7 at the start of operation of the system. The system is operated to maintain its concentration while the system is in operation. However, in order to balance the material balance with respect to the coating room 1, it is necessary to consider other factors, in particular, it is necessary to replenish the amount of the substance which is applied to the object 3 and taken out of the system, It is also necessary to replenish the filtrate corresponding to the amount of evaporation. For this purpose, in the present invention, a second storage tank 11 described below is provided to enable necessary control.

In the present invention, the second storage tank 11
The ultrafiltration device 13 connected to the tube forms an ultrafiltration circuit (II) together with the lines 14 and 15. The main purpose of the ultrafiltration device 13 is to concentrate the liquid stored in the second storage tank 11 so that the solid content concentration of the oxidative polymerization type water-based paint becomes the application concentration. To this end, the stored liquid of V ₅ liters per minute is led to the ultrafiltration device 13, and the circulating liquid concentrated to the concentration C ₄ is returned to the second storage tank 11 at the rate of V ₅ ′ liters per minute. The filtrate is sent to the filtrate tank 5 at a rate of ₆ liters per minute. This concentration C ₄ is generally higher than the application concentration C ₁ , and the circulating liquid mixes with the liquid stored in the second storage tank 11 during operation of the system of the present invention, and the solid content of the aqueous coating in the tank is controlled to be substantially coating concentration C _1. In a preferred embodiment of the present invention, a predetermined application concentration, for example, 30% by weight of paint is stored in advance in the second storage tank 11 at the start of operation of the system, and the system is maintained at that concentration. Is operated. The circulating liquid circulating in the ultrafiltration circuit (II) is the ultrafiltration circuit (I)
The ultrafiltration device 13 needs to have better characteristics in the high concentration region than the ultrafiltration device 8 because it has a higher concentration than the circulating liquid that circulates. The recovered paint concentrated to the application concentration is transported to the paint discharge port 2 at a rate of V ₁ ′ per minute through a pipe 17. It is also possible that the circulating liquid concentrated in the ultrafiltration device 8 is directly sent from the line 7 of the ultrafiltration circuit (I) to the second storage tank 11 via the branch valve 18. The amount of liquid stored in the first storage tank 7 and the second storage tank can be adjusted.

In the second storage tank 11, an amount of oxidative polymerization corresponding to the total solid content of the oxidative polymerization type aqueous paint applied to the object within a unit working period, for example, one day, The mold waterborne paint is replenished from a replenishment paint tank (not shown). The solids concentration of the replenished paint may be equal to the application concentration, but may generally be replenished as a higher concentration.

In the present invention, the system is continuously operated for a unit working period while the recovered paint solution is washed with the filtrate extracted by the ultrafiltration circulation paths (I) and (II). It is possible to replenish the filtrate component composed of an aqueous solvent to the filtrate tank 5 as necessary in consideration of the evaporation amount, the amount taken out of the system due to application to the object to be coated, and the like. Can be. Further, the washing with the filtrate can be carried out continuously or intermittently as long as the above condition of the material balance is satisfied.

In this case, it is preferable to use a material having excellent wettability on the wall surface of the coating chamber 1 in order to efficiently exert a cleaning effect using a relatively small amount of cleaning liquid. Further, the outlet of the washing water preferably has a structure capable of uniformly guiding the filtrate to the wall surface, and may have, for example, a horizontally long shape with a brush-like structure.

The ultrafiltration devices 8 and 13 for constituting the system of the present invention can be selected from known ones in consideration of the required amount of filtrate and the like. For example, ACV3010 or Asahi Kasei Co., Ltd. Those having the same performance, manufactured by DESARINATION SYSTEMS CO., LTD.
(SYSTEMS) EW4026 or those having equivalent performance can be suitably used.

The water-based paint used in the present invention is not particularly limited, and a commonly used oxidation-polymerized water-based paint can be suitably used.

In the present invention, the solid content concentration of the water-based paint is adjusted by mixing demineralized water and a hydrophilic organic solvent such as butyldiglycol and butyrocellosolve with demineralized water / hydrophilic organic solvent.
98/2 to 80/20, preferably 95/5 to 90/1
It can be carried out with a mixture of 0.

The above-mentioned oxidative polymerization type aqueous paint can be cured by drying the object to be coated at a low temperature of about 60 to 100 ° C. after coating.

The shower coat coating system of the present invention comprises:
An ultrafiltration circuit (I) for extracting the filtrate from the diluted recovered paint solution in the first storage tank, and in a second storage tank maintained at a higher concentration than in the first storage tank. The provision of the ultrafiltration circulation path (II) for making the coating concentration of the coating material enables the collection of the filtrate and the concentration of the recovered coating material to be performed without imposing an excessive burden on the ultrafiltration device. As a result, it is possible to construct a recycling system that performs shower coat coating of the oxidative polymerization type aqueous paint while securing a necessary amount of filtrate.

Further, it is possible to efficiently maintain the material balance, and it is possible to continuously apply the oxidative polymerization type water-based paint to the shower coat throughout the unit operation period.

[0035]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 An apparatus having the structure shown in FIG. 1 was used. In a first storage tank having a capacity of 1000 L, about 1000 kg of an aqueous acrylic-modified epoxy resin paint (Aude Recycle F-1000, manufactured by Nippon Paint Co., Ltd.) adjusted to a solid content concentration of about 25% by weight was placed, and a second 1000 L capacity was also prepared. About 1000 kg of an aqueous acrylic-modified epoxy resin paint (Aude Recycle F-1000, manufactured by Nippon Paint Co., Ltd.) adjusted to a solid content concentration of about 30% by weight was put into the storage tank. The solid content concentration was adjusted using a mixture of demineralized water / butyl diglycol = 95/5. ACV3010 (permeation: 4 m ³ / day, manufactured by Asahi Kasei Corporation) was used as the first ultrafiltration device.
EW402 used for this and the second ultrafiltration device
6 (transmission amount: 4 m ³ / day, manufactured by DESARINATION SYSTEMS) were used. The parameters in the various parts of the shower coat coating system were set to the following values, and shower coat coating of the fuel tank for an automobile was performed. C ₁ = 30% V ₁ = 150 L / min C ₂ = 25% V ₂ = 400 L / day V ₃ = 400 L / min V ₄ = 10 L / min V ₅ = 400 L / min V ₆ = 2.5 L / min

The system of the present invention was able to operate continuously for one day. The amount of the water-based acrylic-modified epoxy resin paint applied to the object to be coated in one day operation is about 400 L, and 200 L of the 50% by weight water-based acrylic-modified epoxy resin replenishment paint and the replenishment filtrate component are removed. A mixture of salt water / butyl diglycol = 95/5 was mixed with 20
0 L was used.

[0038]

According to the present invention having the above-described structure, it is possible to carry out a shower coat coating that can be recycled by using an oxidative polymerization type aqueous coating.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a shower coat coating system of the present invention.

[Description of sign]

 1. Painting room 2. Paint outlet 3. Coated object 4. Washing liquid outlet 5. Filtrate tank 6, 9, 10, 12, 14, 15, 17, 19. Pipe line 7. First storage tank 8,13. Ultrafiltration device 11. Second storage tank 18. Branch valve

Claims (6)

[Claims] 1. A water-based paint collected in a coating room after shower coating and a cleaning liquid after washing the coating room,
The filtrate is collected in a first storage tank, guided to the ultrafiltration circuit (I) from the first storage tank, and the filtrate is withdrawn. The collected filtrate is collected in the filtrate tank, and the solid content of the water-based paint in the first storage tank is reduced. Keep the concentration lower than the concentration at the time of application,
At the same time, a part of the liquid stored in the first storage tank is guided to a second storage tank, and the liquid stored in the second storage tank is guided to an ultrafiltration circuit (II) to perform the second filtration. The solid content concentration of the aqueous paint in the storage tank of the application concentration,
On the other hand, the filtrate is collected in the filtrate tank, and the filtrate in the filtrate tank thus collected and the replenished filtrate component as necessary are used as a washing liquid, and collected in the second storage tank. A shower coat coating system for continuously performing the shower coat coating with the used water paint and new water paint replenished as necessary. 2. The shower coat coating system according to claim 1, wherein the aqueous paint is an oxidative polymerization type aqueous paint. 3. The shower coat coating system according to claim 1, wherein the amount of liquid stored in the first storage tank does not substantially change per unit working period. 4. The second storage tank while intermittently or continuously flowing a filtrate in the filtrate tank and a replenished filtrate component as a cleaning liquid to a wall surface of a coating chamber. The shower coat coating system according to claim 1, 2 or 3, wherein the recovered water paint and the new water paint replenished as necessary are supplied to the shower coat coating. 5. The wall of the coating room is made of a material selected from the group consisting of a plastic, a stainless steel plate, and a metal plate whose surface is processed with a resin.
Shower coat painting system as described. 6. The shower coat coating system according to claim 1, wherein the object to be coated with the shower coat is an automobile fuel tank.