JP3942904B2 - Water paint recovery method and recovery system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for recovering the non-volatile content of a water-based paint used for painting an object to be coated, such as an automobile body, and a coating method for coating the object to be coated with an aqueous paint. Furthermore, this invention relates to the collection | recovery system and coating system which are suitably utilized in order to implement such a collection | recovery method and a coating method, respectively.
[0002]
[Prior art]
In recent years, water-based paints have begun to be used in place of oil-based paints that have been conventionally used from the viewpoints of environmental considerations and economy. One advantage of water-based paints is the reuse of excess paint (also referred to herein as overspray paint) that was not applied to the object during painting and was not used for painting. Is relatively easy to reuse the non-volatile components contained in the overspray paint.
[0003]
For example, JP-A-6-142573 discloses a coating method and a coating system in which a dilute solution obtained by diluting an overspray paint is concentrated in a batch system, and the obtained concentrate is reused as a paint. . More specifically, first, during the coating, the overspray paint generated during the coating is collected with an aqueous medium and stored in a diluted liquid state. Then, the whole amount of the diluted solution stored while painting is stopped is transferred to another concentration tank. Then, the concentration of the diluent in the concentration tank is increased by a circulation operation in which the dilution liquid is taken out from the concentration tank, passed through an ultrafilter, the filtrate is removed, and the remainder is returned to the concentration tank. Concentrate to The concentrated solution thus obtained can be reused as a paint.
[0004]
[Problems to be solved by the invention]
Currently, painting of automobile bodies is attracting attention as one application of water-based paints. Under these circumstances, the overspray paint (more specifically, the non-volatile content contained in such paint) can be efficiently recovered in order to realize reuse of the overspray paint even when the automobile body is painted with water-based paint. Establishment of a painting method and a painting system that can be realized practically is desired.
[0005]
In order to respond to such demands, the conventional painting method and painting system as described above are applied to automobile body painting as they are, and the overspray paint generated during painting of the automobile body is collected in the booth tank, Concentrate and collect water-based paint (more specifically, non-volatile content in water-based paint) by transferring the entire amount of stored booth water to a concentration tank and circulating and concentrating in the same way as the conventional method. Can be conceived. However, in such a batch-type one-stage concentration operation, it is necessary to provide a large-capacity concentration tank that can accommodate the entire amount of booth water stored in the booth tank, and the entire coating system becomes very large. Not right.
[0006]
When coating the object to be coated on an industrial scale, especially when the object to be coated is relatively large, as in the case of the automobile body described above, the booth water to be treated is extremely large. It is very important to reduce the size of the entire system.
[0007]
An object of the present invention is to provide a method for recovering non-volatile components contained in a water-based paint and a coating method implemented in combination with the recovering method, which can reduce a necessary equipment space. . Moreover, the objective of this invention is providing the system (or apparatus) used suitably in order to implement such a collection | recovery method and / or a coating method.
[0008]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have completed the present invention based on the viewpoint that the concentration operation is performed in two stages and the two-stage concentration operation is performed using a single filter. It came to.
[0009]
According to one aspect of the present invention, a novel method for recovering non-volatile content contained in an aqueous paint is provided. In the recovery method of the present invention, first, a liquid material in which an aqueous paint containing a non-volatile content is diluted with an aqueous medium (hereinafter, the diluted liquid material is also referred to as a diluent) is used in a concentration tank. While supplying, the liquid in the concentration tank is passed through a filter to remove the filtrate, and the residue (concentrated liquid) is returned to the concentration tank to circulate and concentrate the liquid in the concentration tank. By such an operation, a primary concentrated solution in which the concentration of the non-volatile content in the liquid is increased can be obtained. And in the state which stopped supply of the liquid substance to the concentration tank containing the primary concentrated liquid, the primary concentrated liquid in the concentrated tank is passed through the same filter as above to remove the filtrate, and the remainder ( By returning the concentrate to the concentration tank, the primary concentration liquid in the concentration tank is circulated and concentrated. Thereby, the secondary concentrated liquid which further raised the density | concentration of the non volatile matter in a primary concentrated liquid is obtained. As described above, the non-volatile content contained in the water-based paint can be recovered in the form of a secondary concentrated liquid containing the non-volatile content.
[0010]
According to the recovery method of the present invention as described above, since the two-stage concentration operation is performed using only a single filter, compared with the case where the nonvolatile content is recovered by a batch-type one-stage concentration operation. And it is possible to reduce the necessary equipment space. Such an effect is suitable for treating booth water or the like generated when an object is painted on an industrial scale, as will be described later.
[0011]
Hereinafter, in the present specification, the operation of obtaining a primary concentrate by circulating and concentrating the liquid in the concentration tank while supplying the dilution liquid to the concentration tank is also referred to as a first-stage concentration operation (step (a)). Then, the operation of obtaining the secondary concentrated liquid by circulating and concentrating the primary concentrated liquid in the concentrated tank in a state where the supply of the liquid material to the concentrated tank containing the primary concentrated liquid is stopped is the second stage. It is also called a concentration operation (step (b)).
[0012]
In the present specification, the term “liquid material” simply refers to not only a dilute solution (that is, a liquid material in which an aqueous paint containing a non-volatile content is diluted with an aqueous medium), but also a residue obtained by removing the filtrate by filtration. Should be understood as referring to a generic concept including: a concentrate, a mixture of the concentrate and diluent, a primary concentrate and a secondary concentrate.
[0013]
The water-based paint generally contains a nonvolatile content and an aqueous medium. The aqueous medium that makes up the aqueous paint and the aqueous medium in which the aqueous paint is diluted with a liquid (or diluting solution) are generally volatile components with a relatively low molecular weight such as water, and are not distinguished from the non-volatile components. Can be done. The “nonvolatile content” that is a component of the water-based paint usually has a larger molecular weight than that of the aqueous medium. When a liquid material in which such a water-based paint is diluted is filtered, an aqueous medium having a small molecular weight can pass through the filter (filter medium) and move to the filtrate side, but the non-volatile content does not pass through the filter, Remains upstream. Therefore, the non-volatile content contained in the water-based paint can be concentrated by filtration with a filter in the method of the present invention.
[0014]
In the present invention, a general water-based paint can be used as the water-based paint. The water-based paint usually contains a resin for forming a coating film (that is, a binder resin), a pigment incorporated into the coating film, and the like as non-volatile components, and can contain other components as long as it can be concentrated. The nonvolatile content is not particularly limited, and may include, for example, a baked alkyd melamine resin. In addition to this, the non-volatile content may contain other components.
[0015]
In the present invention, the diluting solution is in a state in which a water-based paint containing a non-volatile content is diluted with an aqueous medium, but it should be noted that the operation of dilution is not necessarily required in the practice of the present invention. is there. The diluent may be, for example, booth water that accumulates in a so-called booth water tank. Generally in the present invention ,water The mixture containing the aqueous medium originally contained in the water-based paint and the aqueous medium diluted with the water-based paint is removed as a filtrate by the filter. Further, when the water-based paint contains a hydrophilic organic solvent, the hydrophilic organic solvent can also be included in the mixture and removed as a filtrate.
[0016]
Any appropriate aqueous medium can be used as the aqueous medium in which the aqueous paint is diluted, and preferably an aqueous medium having the same composition as the aqueous medium that is a constituent of the aqueous paint. However, the present invention is not limited to this, and the aqueous paint may be diluted with an aqueous medium having a composition different from that of the aqueous medium that is a component of the aqueous paint.
[0017]
The concentration of the non-volatile content in a liquid (including a diluted solution such as booth water and its concentrated liquid, for example, the primary concentrated liquid and the secondary concentrated liquid) is about 1.5 g of liquid containing non-volatile content and about pure water. The mixture with 3 g added was placed in a drying chamber at about 110 ° C. for about 60 minutes to evaporate the volatiles (including the aqueous medium and optionally the hydrophilic organic solvent), and the weight W2 of the material remaining without evaporation, It can be measured by determining the ratio (= W2 / W1 × 100 (%)) to the weight W1 (ie, 1.5 g) of the original liquid material. When recovering the overspray paint generated during painting, the non-volatile content in the booth water, primary concentrated liquid, and secondary concentrated liquid is determined based on the number of objects to be painted and the amount of aqueous paint used for painting. It is also possible to predict the concentration.
[0018]
As a filter used in the present invention in order to increase the non-volatile content concentration in the liquid material, a cross-flow type filter, preferably an ultrafilter can be generally used. By using such a filter, it is possible to efficiently remove the aqueous medium as a filtrate from a liquid material obtained by diluting the aqueous paint with an aqueous medium, and to concentrate the non-volatile content that is the purpose of recovery.
[0019]
In a preferred embodiment, separate concentration tanks are used for carrying out the first and second stage concentration operations. More specifically, the first concentration tank and the filter are used to carry out the concentration operation in the first stage to circulate and concentrate the diluted solution to obtain a primary concentrated solution. The obtained primary concentrate is transferred from the first concentration tank to the second concentration tank. The primary concentration operation and the transfer of the primary concentrate may be performed only once before the second concentration operation is performed, but preferably a plurality of times depending on the capacity of the second concentration tank. It is carried out repeatedly (in other words, it is transferred each time a primary concentrated liquid is obtained by the primary concentration operation). Next, using the second concentration tank storing the primary concentrated liquid and the same filter as before, the second stage concentration operation is performed except for the concentrated liquid returning from the filter to the second concentration tank. This is carried out without supplying the liquid (or in a state where neither the diluted solution nor the primary concentrated solution is supplied), whereby the primary concentrated solution is circulated and concentrated to obtain a secondary concentrated solution. Thus, the 1st concentration liquid is obtained in the 1st concentration tank by performing the concentration operation of the 1st stage and the 2nd stage using a single filter and a separate concentration tank, respectively. Since it can be transferred to the second concentration tank every time, the concentration operation with relatively low non-volatile content and high filtration efficiency (that is, the filtrate flow rate per unit time) is higher than when one concentration tank is used. Can be carried out selectively in the first concentration tank And thus The further effect that the burden to the filter at the time of implementing the concentration operation of the 1st step can be reduced effectively can be produced. Of course, such an embodiment can also provide an effect that a large amount of diluent (for example, booth water) can be processed in a smaller equipment space, compared to the case where the entire amount of the diluent is concentrated in a batch system. .
[0020]
However, the recovery method of the present invention is not limited to this, and the first-stage concentration operation and the second-stage concentration operation may be performed using a single concentration tank. More specifically, each of the single concentration tank and the filter is used to carry out the first stage of the concentration operation, whereby the diluent is circulated and concentrated to the primary concentrate, and then the second stage of the concentration operation is performed. The primary concentrated solution may be circulated and concentrated into a secondary concentrated solution by carrying out the supply of the diluted solution to the concentration tank in a stopped state. Even in such a case, a large amount of diluent (for example, booth water) can be processed in a smaller facility space than when the entire amount of the diluent is concentrated batchwise.
[0021]
In a preferred embodiment, after the concentration operation of the second step is performed, the concentration operation of the first step is performed again. By carrying out the second stage concentration operation to obtain a secondary concentrated liquid containing a relatively high concentration of non-volatile content, non-volatile content may remain on the filter (particularly the filter). After the operation, the concentration operation in the first stage is performed again, and a liquid material having a low non-volatile content (a liquid material substantially equal to the diluent at the beginning of the concentration operation in the first step) is passed through the filter. The liquid substance having a low non-volatile content concentration performs the same function as the cleaning liquid, and the filter can be cleaned. For this reason, it is not necessary to provide a washing tank for washing the filter and a line connected thereto, and the equipment space can be further reduced.
[0022]
In a preferred embodiment, at least a part of the filtrate obtained by the concentration operation in the first step and / or the filtrate obtained by the concentration operation in the second step is used as a diluted solution in which the aqueous paint is diluted. An aqueous medium, such as an overspray paint, is utilized as an aqueous medium for collecting and diluting. By recycling the filtrate in this way, waste can be reduced and the efficiency of the recovery method can be improved.
[0023]
The secondary concentrated liquid obtained by the recovery method of the present invention can be reused as it is, or mixed with a new water-based paint and / or other appropriate material. For example, the secondary concentrate can be reused as an aqueous paint, supplemented with an aqueous medium, a suitable organic solvent, and / or non-volatile content.
[0024]
The recovery method of the present invention as described above can be carried out in combination with a coating method for coating an object to be coated with a water-based paint. Therefore, according to another aspect of the present invention, there is also provided a coating method for coating an object to be coated with an aqueous paint, which is carried out in combination with the method for recovering the non-volatile content contained in the aqueous paint of the present invention as described above. Is done. In the coating method of the present invention, first, a water-based paint is sprayed on the object to be coated to coat the object to be coated with the water-based paint, and the overspray paint is collected with an aqueous medium to contain a non-volatile content. To obtain a diluted solution (so-called booth water) diluted with an aqueous medium. Using the diluted solution, the above-described first-stage concentration operation is performed. Then, the concentration operation in the second stage is performed while the coating of the object to be coated is stopped. The period during which the article is coated (in other words, the period during which the diluted solution is obtained) and the period during which the first concentration operation is performed may overlap in time or in whole or in part. May be. On the other hand, the period during which the first stage concentration operation is performed and the period during which the second stage concentration operation is performed use a single filter in the first stage concentration operation and the second stage concentration operation. It is necessary to have separate periods (ie, avoid overlapping).
[0025]
According to the coating method of the present invention as described above, since a single filter is used, similarly to the above-described recovery method of the present invention. , Obedience The required equipment space can be reduced as compared with the case of painting using a conventional painting system. Such a coating method of the present invention is applied when an object is coated on an industrial scale, particularly when a relatively large object such as an automobile body is coated on an industrial scale by, for example, a line production method. There is a significant benefit in treating the large amount of booth water that is generated.
[0026]
For example, while applying the object to be coated (for example, while applying a plurality of objects to be coated in the line production system), the overspray paint is collected and diluted to obtain the booth water ( While the first stage of concentration operation is carried out while obtaining the diluted solution, and the coating of the coated object is stopped (for example, the continuous production of a plurality of coated objects in the line production method is stopped) The second stage concentration operation can be carried out.
[0027]
In particular, when separate concentration tanks are used to perform the first-stage concentration operation and the second-stage concentration operation, the overspray paint is collected and diluted to obtain booth water during the former. Repeat the operation of carrying out the first stage concentration operation and transferring the total amount of the primary concentrate obtained from the first concentration tank to the second concentration tank every time the primary concentrate is obtained, and During the latter, the second stage of the concentration operation can be carried out. During the transfer of the primary concentrated liquid from the first concentration tank to the second concentration tank, the booth water supply to the first concentration tank must be stopped. In addition, the coating of the object to be coated may or may not be temporarily stopped, and those skilled in the art will be able to select as necessary.
[0028]
However, the coating method of the present invention is not limited to this, and depending on the time balance between the period during which the coating of the object is being performed and the period during which the coating is stopped, Concentration operation and second-stage concentration operation are single (Or the same) It is also possible to carry out using a concentration tank. In such a case, only one concentration tank may be used, but two concentration tanks may be used. For example, the first-stage concentration operation and the second-stage concentration operation are performed using the first concentration tank, and then the first-stage concentration operation and the second-stage concentration operation are performed using the second concentration tank. For example, the first and second concentration tanks may be alternately used in accordance with the coating period and the coating stop period of the object to be coated.
[0029]
Further, for example, during the coating of the object to be coated, the first concentration tank is used to perform the first concentration operation, and when the primary concentrated liquid is obtained, the dilution liquid is supplied. Is switched from the first concentration tank to the second concentration tank, and subsequently the first concentration operation is performed again using the second concentration tank. While the coating is stopped, the primary concentrated liquid in the first concentration tank is subjected to the second stage concentration operation to obtain a secondary concentrated liquid, and the liquid in the second concentration tank is also obtained. A secondary concentrate can be obtained by concentrating the product (which preferably has a non-volatile concentration comparable to that of the primary concentrate).
[0030]
In a preferred embodiment, at least a portion of the filtrate obtained by the first and / or second stage concentration operations can be used as an aqueous medium for collecting and diluting the overspray paint. At this time, it is more preferable to adjust the amount of the filtrate to be reused so that the amount of the booth water becomes constant (for example, the liquid level of the booth water becomes a predetermined height).
[0031]
In a preferred embodiment, the obtained secondary concentrated liquid is used as it is, as described above in the recovery method of the present invention, or a new water-based paint (for example, an initial water-based paint before being used for painting) and / or a suitable one. After being mixed with other materials, it is reused as a water-based paint for coating the object to be coated. Thereby, efficiency improvement of the coating method can be achieved.
[0032]
According to still another aspect of the present invention, a first concentrating tank to which a liquid material (for example, booth water) in which an aqueous paint containing a non-volatile content is diluted with an aqueous medium is supplied; The second concentrating tank connected to the first concentrating tank so that the liquid substance is supplied, and the filtrate is removed from the liquid substance in the first or second concentrating tank, and the residue is removed from the first or second concentrating tank. A recovery system is provided that includes a first concentrating tank and a filter switchably connected to the second concentrating tank so as to return to the two concentrating tanks, respectively.
[0033]
Such a recovery system can be suitably used for carrying out the above-described recovery method of the present invention when the first-stage concentration operation and the second-stage concentration operation are performed using separate concentration tanks. .
[0034]
According to still another aspect of the present invention, there is provided a coating system including the recovery system of the present invention, wherein the coating is for spraying a water-based paint toward the object to be coated and coating the object with the water-based paint. A booth water tank further comprising a booth and a booth water tank for storing the booth water in which the water-based paint that has not been applied to the object is diluted as a diluent, and supplying the liquid material to the first concentration tank A coating system is also provided in which the first concentrator is connected.
[0035]
Such a coating system is implemented in combination with the above-described recovery method of the present invention when the first stage concentration operation and the second stage concentration operation are performed using separate concentration tanks. It can utilize suitably in order to implement the coating method of this.
[0036]
The above-described collection system and / or coating system of the present invention reduces the necessary equipment space as compared with the conventional system, so that space saving is realized. Such an effect is particularly advantageous for treating a large amount of booth water in which a water-based paint is diluted. The recovery system and / or coating system of the present invention can also be configured to reuse the filtrate and / or secondary concentrate removed by the filter. Preferably, the amount of filtrate and / or secondary concentrate to be recycled can be adjusted by any suitable means.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, as one embodiment of the present invention, a coating system and a non-volatile content coating method of a water-based paint performed using the coating system (recovery system and non-volatile content of a water-based paint performed using the coating system) (Including the recovery method) will be described with reference to the drawings. It should be noted that the coating system of this embodiment can also be recognized as a recycling system for aqueous paint and / or filtrate (or an aqueous medium for collecting and diluting overspray paint).
[0038]
As shown in FIG. 1, the painting system 40 of this embodiment schematically includes a painting booth 2 for painting an automobile body 1 that is an object to be coated, a paint tank 3 in which a water-based paint is stored, Booth water tank 5 for storing booth water obtained by diluting water-based paint not applied to automobile body 1, concentration tanks 13a and 13b, ultrafilter 25 which is a kind of filter, and concentration tank 13a 13b and a recovery tank 33 for recovering a concentrated liquid (secondary concentrated liquid) obtained through a two-stage concentration operation using the ultrafilter 25 and a filtrate separated by the ultrafilter 25 are stored. A filtrate tank 31 is provided. Here, the concentration tanks 13a and 13b respectively correspond to the first and second concentration tanks referred to in the system of the present invention.
[0039]
The ultrafilter 25 removes the liquid from the concentration tank 13a or 13b and passes it through the ultrafilter 25 to remove the filtrate, and returns the remaining concentrate to the concentration tank 13a or 13b, respectively. With the line (or piping) configuration as shown in FIG. 1, it is connected to the concentration tanks 13a and 13b in a switchable manner.
[0040]
In the booth tank 5, the concentration tanks 13a and 13b, and the recovery tank 33, the booth water in the booth tank 5 is transferred to the concentration tank 13a, and the liquid (more specifically, the primary concentrated liquid) in the concentration tank 13a is concentrated. It is transferred to the tank 13b and connected by a line configuration as shown in FIG. 1 so that the liquid material (more specifically, the secondary concentrated liquid) in the concentration tank 13b is recovered in the recovery tank 33.
[0041]
As the ultrafilter 25, a commercially available ultrafilter can be used. For example, it is particularly preferable to use a filter having a spiral filter. However, the present invention is not limited to this, and any other suitable filter, such as a flat membrane type or a hollow fiber membrane type filter, may be used depending on the molecular weight of the non-volatile content of the aqueous paint to be recovered. An equipped ultrafilter can be used.
[0042]
Moreover, as the water-based paint for coating stored in the paint tank 3, for example, a so-called alkyd melamine resin paint containing an alkyd melamine resin as one kind of non-volatile content can be used. However, the present invention is not limited to this, and other water-based paints may be used.
[0043]
In such a coating system 40 of the present embodiment, first, an aqueous paint containing a non-volatile content at a predetermined concentration is transferred from the paint tank 3 through the line 4 and sprayed toward the automobile body 1 inside the paint booth 2. The car body 1 is painted with water-based paint. At this time, the overspray paint that has not been applied to the automobile body 1 is caused by the booth water circulated from the booth tank 5 through the lines 6 and 7 and / or the filtrate supplied from the filtrate tank 31 through the lines 35 and 7. It is collected and diluted and stored in the booth tank 5 as booth water.
[0044]
Here, the amount of the filtrate flowing into the booth tank 5 from the filtrate tank 31 through the lines 35 and 7 is adjusted by any appropriate method / means so that the level of the booth water in the booth tank 5 becomes substantially constant. It is preferable. In addition to the filtrate, an aqueous medium such as water may be used supplementarily.
[0045]
The concentration of the non-volatile content in the booth water in the booth water tank 5 is preferably about 5% by weight or less (naturally greater than 0% by weight), preferably about 0.5 to 1.0% by weight. If the concentration of the non-volatile content in the booth water is too large, it is not preferable because the cleaning property of the liquid contact part on the inner wall surface of the booth is deteriorated. Conversely, if the concentration of the nonvolatile content in the booth water is too small, it is not preferable because the capacity of the booth water tank 5 needs to be considerably increased. For this reason, it is preferable to set it as the above concentration ranges.
[0046]
Subsequently, while transferring the obtained booth water from the booth water tank 5 to the concentration tank 13a through the line 11, the liquid matter in the concentration tank 13a has a predetermined nonvolatile content concentration using the concentration tank 13a and the ultrafilter 25. It is circulated and concentrated until it becomes a primary concentrated solution.
[0047]
More specifically, the booth water transferred to the concentration tank 13a is transferred to the ultrafilter 25 through the lines 14a, 15a, and 16, and is filtered by the ultrafilter 25. It separates into a filtrate that does not contain and a concentrate in which the non-volatile content is concentrated. The resulting concentrate is returned to the concentration tank 13a through lines 26 and 28a, while the filtrate is transferred to the filtrate tank 31 through line 27. By continuously performing such an operation while supplying the booth water from the booth water tank 5 to the concentration tank 13a, the concentration of non-volatile components in the liquid material in the concentration tank 13a gradually increases. Eventually, the concentration of the nonvolatile content will rise sufficiently, and a primary concentrated liquid having a predetermined nonvolatile content concentration will be obtained.
[0048]
The concentration of the non-volatile content in the primary concentrated liquid can be preferably about 10 to 20% by weight. If the concentration of the non-volatile content in the primary concentrated liquid is too large, the flow rate (or filtration efficiency) of the filtrate filtered by the ultrafilter 25 decreases, and the booth water supplied from the booth water tank 5 to the concentration tank 13a is reduced. Since it becomes impossible to process sufficiently and the non-volatile content concentration of the booth water in the booth water tank 5 increases, it is not preferable. Conversely, if the concentration of the nonvolatile content in the primary concentrated liquid is too small, it is not preferable because the capacity of the concentration tanks 13a and / or 13b needs to be increased. For this reason, it is preferable to set it as the above concentration ranges.
[0049]
When the primary concentrated liquid is obtained in this way (in other words, when the non-volatile content in the liquid in the concentration tank 13a becomes a predetermined concentration), the supply of booth water to the concentration tank 13a and the concentration tank 13a The supply of the liquid material to the filter 25 is stopped, and the liquid material having a predetermined non-volatile content in the concentration tank 13a is used as the primary concentrated liquid, and the entire amount thereof is, for example, through the lines 14a, 21 and 22b ( (Through lines 15a, 16, 26 and 28b) to the concentration tank 13b. During the transfer of the primary concentrate from the concentration tank 13a to the concentration tank 13b, the supply of booth water to the concentration tank 13a is stopped when the change in the non-volatile concentration of the primary concentrate does not cause a problem. However, when it is desired to strictly control the nonvolatile concentration of the primary concentrated solution, it is preferable to stop. During this time, the painting of the automobile body 1, more specifically, the spraying of the paint may not be stopped if the booth water tank 5 has a sufficient capacity, but may be temporarily stopped.
[0050]
In the concentration operation of the first stage as described above and the transfer of the obtained primary concentrated liquid from the concentration tank 13a to the concentration tank 13b, the automobile body 1 is continuously coated by, for example, a line production method. It is preferable to carry out repeatedly throughout the period (specifically, for example, from Monday to Friday of the week or during the day). However, the present invention is not limited to this, and the painting of the automobile body 1 may be stopped when the primary concentrated liquid is obtained. In the former case, the liquid is circulated through, for example, the lines 14b, 21 and 22b until the primary concentrated liquid is subjected to the concentration operation in the second stage, and stirred in the concentration tank 13b. It is preferable to keep it.
[0051]
Thereafter, using the concentration tank 13b and the ultrafilter 25, the liquid in the concentration tank 13b is circulated and concentrated until it becomes a secondary concentrated liquid having a predetermined nonvolatile content concentration.
[0052]
More specifically, the liquid (primary concentrate) transferred to the concentration tank 13b is transferred to the ultrafilter 25 through the lines 14b, 15b and 16, and is filtered by the ultrafilter 25. The filtrate is separated into a filtrate that is substantially free of non-volatile content and a concentrated liquid in which the non-volatile content is concentrated. The resulting concentrate is returned to the concentration tank 13b through lines 26 and 28b, while the filtrate is transferred to the filtrate tank 31 through line 27. By continuously performing such an operation in a state where supply of the liquid material to the concentration tank 13b is stopped, the concentration of the nonvolatile content in the liquid material in the concentration tank 13b gradually increases. Eventually, the concentration of the nonvolatile content further increases sufficiently, and a secondary concentrated liquid having a predetermined nonvolatile content concentration is obtained.
[0053]
The concentration of the non-volatile content in the secondary concentrated liquid can be approximately the same as the concentration of the non-volatile content in the initial aqueous paint. If the concentration of non-volatile components in the secondary concentrate is too large, the viscosity of the secondary concentrate increases as the concentration of non-volatile components increases, resulting in increased pressure loss when transferring the secondary concentrate to the line. Depending on the case, the line may be clogged. On the other hand, if the concentration of the non-volatile content in the secondary concentrated liquid is too small, so-called “sagging” may occur in the coating film when reused as it is as a water-based paint for coating an object to be coated. It is not preferable. For this reason, it is preferable to set it as the above concentration ranges.
[0054]
The non-volatile content concentration of the secondary concentrated liquid can be predicted using the viscosity as an index. In particular, as will be described later, when the secondary concentrated liquid is reused and reused for coating, the viscosity is important.
[0055]
When the secondary concentrated liquid is obtained in this way (in other words, the non-volatile content concentration in the liquid material in the concentration tank 13b becomes a predetermined concentration, or the liquid material has a predetermined viscosity. Then, the supply of the liquid material from the concentration tank 13b to the filter 25 is stopped, and the liquid material having a predetermined nonvolatile concentration or viscosity in the concentration tank 13b is used as the secondary concentrated liquid, and the entire amount is collected through the line 19 It is transferred to the tank 33 and stored.
[0056]
The second-stage concentration operation as described above and the transfer of the obtained secondary concentrated liquid from the concentration tank 13b to the recovery tank 33 stop, for example, the coating of the automobile body 1 continuously by the line production method. It is carried out in batch mode during or regularly (specifically, for example, on Saturdays and Sundays or at night in a week).
[0057]
As a result, the non-volatile content in the overspray paint is recovered in the recovery tank 33 in the form of a secondary concentrated liquid. The recovered secondary concentrated liquid is supplied to the paint tank 3 alone, for example, through the line 37 alone or after adding an appropriate amount of water or filtrate for adjusting the viscosity (not shown). Then, it is mixed with the initial water-based paint (in other words, fresh water-based paint) and reused in the paint system 40 for painting the automobile body 61. The amount of the secondary concentrated liquid to be reused and the amount (or ratio) of the component to be added to the secondary concentrated liquid to be reused when adjusting the viscosity are adjusted by any appropriate method / means. It is preferable.
[0058]
Such a two-stage concentration operation using a single filter can be repeated. For example, the first stage concentration operation and the primary concentrated solution obtained thereby are transferred to the concentration tanks 13a to 13b. Preferably, the primary concentration operation and the transfer of the primary concentrated solution are repeated several times, and then Such a cycle can be repeated with a series of operations of carrying out the second-stage concentration operation and transferring and collecting the secondary concentrated liquid obtained thereby to the collection tank as one cycle.
[0059]
In particular, after the concentration operation of at least the second stage is performed, the second concentration liquid is obtained by further performing the concentration operation of the first stage, and then the liquid substance having a low nonvolatile content concentration is filtered from the concentration tank 13a. 25, the liquid material performs the same function as the cleaning liquid, and the filter can be cleaned without the need for additional members.
[0060]
Although one embodiment of the present invention has been described above, the present invention is not limited to this, and it will be easily understood by those skilled in the art that various modifications can be made.
[0061]
For example, in the above-described embodiment, the recovered secondary concentrated liquid is reused (or recycled) in the coating system 40, but may be used for another coating system and / or other applications. is there.
[0062]
Further, for example, in the above-described embodiment, of the two concentration tanks 13a and 13b, the concentration tank 13a is used for the first-stage concentration operation, and the concentration tank 13b is used for the second-stage concentration operation. However, it may be connected in a line so that it is possible to arbitrarily select which concentration tank is used to perform the concentration operation of the first stage and the second stage.
[0063]
More specifically, for example, as shown in FIG. 2, a line 41 is added between the booth water tank 5 and the concentration tank 13b, and a line 42 is added between the concentration tank 13a and the recovery tank 33. Thereby, the booth water of the booth water tank 5 can be selectively supplied to either the concentration tanks 13a and 13b.
[0064]
For example, As shown in FIG. If the coating system 50 is used, the following operations are possible depending on the time balance between the period during which the coating of the object is being performed and the period during which the coating is stopped. . While supplying the booth water to the concentration tank 13b, the first stage concentration operation is performed in the concentration tank 13b using the ultrafilter 25, and then the obtained primary concentrated solution is supplied to the ultrafilter 25. Concentration operation of the second stage in the concentration tank 13b as it is using Attached to Then, the secondary concentrated liquid obtained in this way can be collected in the collection tank 33 through the line 19. In the subsequent cycle, while the booth water is now supplied to the concentration tank 13a, the first concentration operation is performed in the concentration tank 13a using the ultrafilter 25, and then the obtained primary concentration liquid is obtained. Is concentrated in the second stage in the concentration tank 13a using the ultrafilter 25 as it is. Attached to Then, the secondary concentrated liquid obtained in this way can be collected in the collection tank 33 through the line 42.
[0065]
Moreover, if the coating system 50 is used, the following operation is also possible. While the automobile body 1 is being painted, the first-stage concentration operation is performed in the concentration tank 13a using the ultrafilter 25 while supplying booth water to the concentration tank 13a. When the concentration of the non-volatile content of the liquid in the concentration tank 13a increases and a primary concentrated liquid is obtained, the booth water is switched from the line 12 to the line 41, thereby supplying the booth water to the concentration tank 13b. Subsequently, the first-stage concentration operation is performed again in the concentration tank 13b using the ultrafilter 25 until the painting of the automobile body 1 is stopped. During this time, it is preferable to stir the primary concentrated liquid stored in the concentration tank 13a. Note that when the coating is stopped, the liquid in the concentration tank 13b may or may not be the primary concentrated liquid, but is concentrated to a predetermined non-volatile concentration close to the primary concentrated liquid. Preferably it is. Eventually, when the painting of the automobile body 1 is stopped, if the liquid in the concentration tank 13b has reached a predetermined non-volatile content, preferably about 10 to 20% by weight, an ultrafilter is used as necessary. 25 is used as a secondary concentrated liquid by subjecting it to a second stage concentration operation, and the obtained secondary concentrated liquid can be collected in the collection tank 33 through the line 19. Further, while the painting of the automobile body 1 is stopped, the primary concentrated liquid stored in the concentration tank 13a is subjected to a second-stage concentration operation using the ultrafilter 25, and the concentration in the concentration tank 13a. The primary concentrated liquid can be circulated and concentrated to obtain a secondary concentrated liquid, and the obtained secondary concentrated liquid can be collected in the collection tank 33 through the line 42. Here, the second-stage concentration operation for obtaining the secondary concentrated solution performed while the painting of the automobile body 1 is stopped may be performed on either side of the concentration tanks 13a and 13b. Good.
[0066]
As described above, according to the coating system 50 and the above-described coating method using the same, after the concentration operation in the first stage is performed, the liquid material is concentrated in the concentration tank 13a and before the concentration operation in the second stage. It is not necessary to transfer between 13b, and the concentration operation in the first stage can be performed using either of the concentration tanks 13a and 13b, and the concentration operation in the second stage can be performed as it is.
[0067]
In the above-described embodiment, two concentration tanks are used. However, a two-stage concentration operation can be performed using a single concentration tank. For example, while supplying booth water to a single concentration tank, a first concentrated liquid is obtained by carrying out the first concentration operation in the concentration tank using a single ultrafilter, and the concentration The supply of booth water to the tank may be stopped, and the secondary concentrated solution may be obtained by performing the second-stage concentration operation in the concentration tank using the ultrafilter.
[0068]
Of course, the automobile body in the above-described embodiment is merely an example of a workpiece, and it can be easily understood by those skilled in the art that the present invention can be used to coat any appropriate other workpiece. Will.
[0069]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the novel collection | recovery method of the non volatile matter contained in an aqueous coating material is provided. According to the recovery method of the present invention, since the two-stage concentration operation is performed using only a single filter, it is necessary as compared with the case where the nonvolatile content is recovered by the batch-type one-stage concentration operation. Equipment space can be reduced. Moreover, since the filtrate produced when recovering the nonvolatile content can be reused, it is efficient.
[0070]
In addition, according to the present invention, there is also provided a coating method carried out in combination with the recovery method of the present invention as described above. According to the coating method of the present invention, since the recovery method capable of producing the above-described effects is used, the necessary equipment space is reduced as compared with the conventional coating method in which a batch type one-stage concentration operation is performed. It becomes possible to do. Such a coating method of the present invention is applied when an object is coated on an industrial scale, particularly when a relatively large object such as an automobile body is coated on an industrial scale by, for example, a line production method. There is a significant benefit in treating the large amount of booth water that is generated. Moreover, since the non-volatile content recovered in the form of a filtrate and a secondary concentrated liquid generated when recovering the non-volatile content can be reused, it is efficient.
[0071]
Furthermore, according to this invention, the collection | recovery system and / or coating system which are utilized suitably in order to implement the collection | recovery method and / or coating method of this invention mentioned above are also provided. According to the collection system and / or the coating system of the present invention, the same effect as that of the collection method and / or the coating method of the present invention can be obtained, so that space saving can be realized and more efficient painting can be achieved. Is possible.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram schematically showing a coating system in one embodiment of the present invention.
FIG. 2 is a conceptual diagram schematically showing a coating system in a modification of one embodiment of the present invention.
[Explanation of symbols]
1 Auto Body (Coating)
2 Painting booth
3 Paint tank
5 Booth tank
13a, 13b Concentration tank (concentration tank)
25 Ultrafilter (filter)
31 Filtrate tank
33 Collection tank
40, 50 painting system
4, 6, 7, 11, 12, 14a, 14b, 15a, 15b, 16, 19, 21, 22a, 22b, 26, 27, 28a, 28b, 35, 37, 41, 42 lines (piping)

Claims (14)

A method for recovering non-volatile content contained in a water-based paint,
(A) While an aqueous paint containing a non-volatile content supplying liquid material that is diluted with an aqueous medium to a first condensation tank, the filtrate was removed through a liquid material in a first concentration tank to filter, by returning to the first concentration tank, circulating concentrated liquid of the first in the concentration tank, a primary concentrated solution was increased the concentration of non-volatile component, the primary concentrate thereby obtained first Transferred from the concentration tank to the second concentration tank,
(B) The filtration using the primary concentrated liquid in the second concentrated tank in the step (a) with the supply of the liquid material to the second concentrated tank containing the primary concentrated liquid stopped. the filtrate was removed through a vessel and same filter, by returning to the second concentration tank, a primary concentrated solution in the second condensation tank circulating concentrated further increasing concentrations of non-volatile content A recovery method comprising recovering a non-volatile content contained in an aqueous paint in the form of a secondary concentrated liquid, including a secondary concentrated liquid. The recovery method according to claim 1, wherein the step (a) is repeatedly performed, and then the step (b) is performed. The recovery method according to claim 1 or 2, wherein step (a) is performed again after performing step (b). The recovery method according to any one of claims 1 to 3, wherein the concentration of the non-volatile component in the liquid material in which the aqueous paint containing the non-volatile component is diluted with an aqueous medium is 5 wt% or less. The collection | recovery method in any one of Claims 1-4 whose density | concentration of the non volatile matter in a primary concentrated liquid is 10 to 20 weight%. The recovery method according to claim 1, wherein the filter is an ultrafilter. Further utilizing at least a part of the filtrate obtained by the steps (a) and (b) as an aqueous medium for forming the liquid material in which an aqueous coating material containing a nonvolatile content is diluted with an aqueous medium. The collection method according to any one of claims 1 to 6. A coating method for coating an object to be coated with a water-based paint, which is carried out in combination with the method for recovering the nonvolatile content contained in the water-based paint according to claim 1,
  While the water-based paint is sprayed on the object to be coated and the object to be coated is coated with the water-based paint, the water-based paint that has not been applied to the object to be coated is collected with an aqueous medium at the time of painting. To obtain a liquid material in which the aqueous paint is diluted with an aqueous medium,
  Step (a) is performed using the liquid,
  Step (b) is carried out while the coating of the object is stopped
Including painting methods. The coating method according to claim 8, further comprising utilizing the secondary concentrated liquid as at least a part of a water-based paint for coating an object to be coated. A non-volatile content recovery system contained in a water-based paint,
  A first concentration tank to which a liquid material in which a water-based paint containing a nonvolatile content is diluted with an aqueous medium is supplied;
  A second concentrating tank connected to the first concentrating tank so that the liquid in the first concentrating tank is supplied;
  The first and second concentration tanks are switchably connected so that the filtrate is removed from the liquid in the first or second concentration tank and returned to the first or second concentration tank, respectively. A collection system including a filter. The collection system according to claim 10, wherein the filter is an ultrafilter. A coating system comprising the recovery system according to claim 10 or 11,
  A painting booth for spraying water-based paint onto the object to be coated and coating the object with the water-based paint,
  Stores a liquid material in which a water-based paint that has not been applied to an object during painting is diluted with an aqueous medium. A booth tank that is connected to the first concentration tank so as to supply the liquid material to the first concentration tank;
Further including a coating system. The coating system according to claim 12, wherein at least a part of the filtrate removed from the liquid in the first or second concentration tank by the filter is supplied to the booth water tank. The coating system of Claim 12 or 13 comprised so that the liquid substance in a 2nd concentration tank may be utilized as a water-based coating material for coating a to-be-coated article in a painting booth.

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