JP4261039B2 - Wet paint booth circulating water management method - Google Patents

Description

【００３１】
本発明の方法により、未塗着水性塗料を含む湿式塗装ブース循環水の電荷量を一定値内にコントロールすることによって、該循環水の安定で高い凝集性が得られることがわかる。
【００３２】
【発明の効果】
本発明の管理方法により、水性塗料を使用している湿式スプレーブース循環水中に捕集された水性塗料は効率良く凝集され、循環水のＣＯＤ、濁度の上昇や発泡性を抑えることができた。この結果、装置の安定した運転が可能となるばかりでなく、排水処理コストや凝集剤や消泡剤のコスト抑制など経済的にも非常に有効である。
【図面の簡単な説明】
【図１】 実施例に用いた試験用ブース装置。
【符号の説明】
１：ブース循環水ピット
２：循環ポンプ
３：ブース循環水配管
４：塗料捕集部
５：塗料用スプレーガン
６：ブース循環水保有ピット
７：薬品注入ポンプ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a management method for booth circulating water in a wet painting booth in a painting process for automobiles or household electrical appliances using water-based paint, and more specifically, agglomerates uncoated water-based paint collected in water. The present invention relates to a method for managing wet paint booth circulating water in which the amount of uncoated paint processing chemicals is appropriately maintained so that the solid-liquid separation between paint slag and water can be smoothly performed.
[0002]
[Prior art]
The painting of automobiles or household electric appliances is generally performed by spraying paint in a painting booth. At this time, surplus paint that has not been applied to the object is collected in water as uncoated paint and separated. However, some paints are not separated, but sticky particles or sticky lumps are floated, dispersed, and circulated in the booth water. Alternatively, the sticky blob is made non-tacky so that solid-liquid separation can be performed smoothly.
[0003]
By the way, due to recent environmental problems, there is a strong demand to reduce the amount of organic solvent scattered in the air or water, and water-based paints have been used instead of oil-based paints in the painting process. Since the water-based paint is obtained by dissolving or dispersing the paint resin in water, even if it is collected in water, the water-based paint is present in a state where it is simply diluted with water. When the paint is gradually accumulated in the booth circulating water, it cannot be properly treated by the property treatment method, and adheres to the wall surface or device in the booth circulating water path as an adhesive. The treatment of unpainted paints so far has been studied for oil-based paints, but the treatment of booth circulating water using water-based paints has to be studied from a completely different angle. .
[0004]
When the water-based paint enters the booth circulating water system, the resin component is dispersed with an anionic charge in the water, so that it is gradually concentrated unless appropriate removal treatment is performed. (1) COD, BOD of circulating water (2) Prone to spoilage due to deterioration of water quality, generating bad odor and worsening the work environment, (3) Prone to foaming, causing trouble in solid-liquid separation, and operation I was in trouble.
[0005]
As a method for avoiding the problems related to these water-based paints, a part of the circulating water is extracted or the circulating water is periodically replaced. However, there is a limit due to an increase in wastewater treatment cost. In addition, a method of aggregating and separating aqueous paints by adding an inorganic flocculant such as sulfuric acid band, polyaluminum chloride, iron chloride, etc. has been carried out. In addition to the increase in the concentration of salt, there is a problem that the corrosion of the apparatus increases, and further, the amount of sludge increases due to the generation of inorganic flocs. In addition, a method using a treating agent containing polyethyleneimine as an active ingredient (Japanese Patent Laid-Open No. 61-74607), a method of adding a cationic water-soluble organic polymer flocculant and an anionic organic polymer flocculant (special feature) No. 63-42706 has been proposed, and there have been some effects of reducing corrosion and reducing the amount of inorganic sludge. However, since the coagulation effect varies depending on the properties of the water-based paint, an appropriate amount of these coagulants is injected. There were administrative difficulties.
[0006]
[Problems to be solved by the present invention]
The purpose of the present invention is to evaluate the cohesiveness in order to properly maintain the coagulation treatment of the uncoated water-based paint in the wet booth circulating water in a short time, and facilitate solid-liquid separation of the non-coated water-based paint and water, And it is providing the management method of circulating water of a booth which can be performed economically.
[0007]
[Means for Solving the Problems]
As a result of intensive research on aggregation, precipitation, non-adhesion, etc. of the uncoated water-based paint collected in the booth circulating water, the present inventors have determined the charge amount of the booth circulating water containing the uncoated water-based paint. By measuring and managing, it was found that an economical and favorable agglomeration treatment can be performed, and the present invention has been completed.
[0008]
That is, the invention of claim 1 is a management method for wet painting booth circulating water using a water-based paint, and the charge amount of the booth circulating water is measured, and the value is from −100 μeq / liter to +1,000 μeq / liter. A cationic flocculant is added continuously or intermittently so that [wherein,-(minus) indicates an anionic charge and + (plus) indicates a cationic charge].
[0009]
The invention of claim 2 is the wet paint booth circulating water management method according to claim 1, wherein the cationic flocculant is polyacrylaminoethyltrimethylammonium chloride, acrylamide-acrylaminoethyltrimethylammonium chloride copolymer, dicyandiamide -Formaldehyde copolymer, diallyldimethylammonium chloride-sulfur dioxide copolymer, dimethylamine-epichlorohydrin condensate, dimethylamine-epichlorohydrin-ammonia condensate, diallyldimethylammonium chloride polymer, diallyldimethylammonium chloride-acrylamide copolymer and It is at least one selected from polyethyleneimine.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
Wet paint booth circulating water charge is the amount of water-soluble electrolyte component and water-dispersible charge component derived from uncoated water-based paint collected in water after spray coating, suspended substance in booth circulating water, and charge derived from electrolyte It is shown as the sum of When “minus (−)” is added to the anion charge and “plus (+)” is added to the cation charge, the charge of the booth water containing the collected uncoated paint generally has an anion charge and is minus several tens. It is 10,000 to minus several thousand μeq / liter and is dispersed in the booth circulating water.
[0011]
The method of the present invention measures the charge amount of booth circulating water including an unpainted paint of a water-based paint , and the value is from −100 μeq / liter to +1,000 μeq / liter, preferably from 0 μeq / liter to +500 μeq / liter. Preferably, the cationic flocculant is added continuously or intermittently so as to be 0 μeq / liter to +100 μeq / liter.
[0012]
If the amount of charge in the booth circulating water is lower than −100 μeq / liter, the cationic flocculant is insufficient and sufficient coagulation treatment cannot be performed, and it becomes difficult to separate the paint components from solid and liquid and to remove unpainted paint. , COD and BOD of the circulating water are increased, which may cause rot odor and foaming trouble. On the other hand, when the cationic charge amount exceeds +1,000 μeq / liter, the cationic flocculant is excessively added, and the uncoated water-based paint aggregated in the booth circulating water is re-dispersed, resulting in poor aggregation, and the subsequent aggregation uncoated Not only can the solid-liquid separation of the coating material and the booth water not be performed sufficiently, but foaming becomes violent, which is not preferable.
[0013]
In the method of the present invention, the booth circulating water containing a non-application paint collected in the pump or the like, the charge amount was measured, its value is set to be in -100Myueq / l ~ + 1,000μeq / liter. When the charge amount is lower than −100 μeq / liter (ie, the anion charge amount is high), the cationic flocculant is insufficient, and the uncoated water-based paint in water is in a dispersed state, and conversely, +1,000 μeq. > / Liter (i.e., high cationic charge) indicates that the cationic flocculant is excessive and the uncoated waterborne paint in water is in a dispersed state, and the addition of the cationic flocculant is stopped. Alternatively, an anionic flocculant is added if necessary.
[0014]
The cationic flocculant used in the present invention is a cationic inorganic substance or organic substance, and is selected in consideration of the aggregating performance and the cationic property according to the treatment degree of the target aqueous paint.
[0015]
Cationic inorganic flocculants include sulfated bands, polyaluminum chloride, iron chloride, bentonite, montmorillonite, pearlite, mica, cationized modified products of clay minerals such as silica. The cationized modified product of clay minerals is a product obtained by immersing a clay mineral in an amine compound aqueous solution or a cationic surfactant aqueous solution and adding it to the clay mineral. The amine compounds used here include aliphatic amines such as triethanolamine, diethylenehexanolamine and hexamethylenediamine, and aromatic amines such as aniline, paratoluidine, and α-naphthylamine, and the cationic surfactant used. Examples include aliphatic amine salts such as decyldimethylamine hydrochloride and dicoco alkylmethyl amine acetate, aliphatic quaternary ammonium salts such as coco alkyl trimethyl ammonium chloride, benzalkonium salts such as trimethyl benzyl ammonium chloride, methyl pyridinium There are pyridinium salts such as chloride.
[0016]
Cationic organic flocculants include natural product-based cationic organic polymer water-soluble chitosan and cationized starch. Synthetic cationic organic polymer polyacrylic acid-based quaternary ammonium salt, polyacrylamide-based quaternary Ammonium salts, copolymers with dicyandiamide, dialkylamine-epihalohydrin copolymers and dialkylamine-epihalohydrin-ammonia copolymers, copolymers with diallyldimethylammonium chloride (hereinafter abbreviated as DADMAC), polyalkylamines, etc. Polyacrylaminoethyltrimethylammonium chloride, acrylamide-acrylaminoethyltrimethylammonium chloride copolymer, dicyandiamide-formaldehyde copolymer, preferably cationic water-soluble polymer Diallyldimethylammonium chloride - sulfur dioxide copolymers, dimethylamine - epichlorohydrin copolymer and dimethylamine - epichlorohydrin - ammonia copolymer is poly DADMAC, DADMAC-acrylamide copolymer and polyethyleneimine.
[0017]
In the present invention, two or more cations from the group of these cationic inorganic flocculants, from the group of cationic organic flocculants, or from each group of the cationic inorganic flocculant and the cationic organic flocculant A combination of flocculating agents may be used. In addition, these cationic flocculants may be used in combination with acid colloids such as melamine / formaldehyde resin acid colloid, urea / melamine / formaldehyde resin acid colloid, fine clay minerals such as talc, clay, bentonite and montmorillonite.
[0018]
The charge amount of the booth circulating water is measured by a known method such as a colloid titration method, a particle charge measurement method (PCD method), or an electrophoresis method.
[0019]
Colloid titration method ["Colloid titration test method" by Seiichi Chite, 3-6, Nankodo, published in 1969] is used to measure the charge amount of electrolytes, colloidal particles, suspended substances, etc. in water with anionic and cationic water This is a method in which the charge is neutralized with a conductive polymer electrolyte and quantified by the change in color of the indicator. For example, to measure anion charge, add a few drops of toluidine blue (TB) as an indicator, and add an excessive amount of an aqueous methyl glycol chitosan aqueous solution (hereinafter abbreviated as “MGK”), which is a cationic aqueous electrolyte solution. The remaining MGK is titrated with an aqueous polyvinyl potassium sulfate (hereinafter abbreviated as “PVSK”) aqueous solution of an anionic water-soluble electrolyte, and the amount of cationic charge is measured. The anion charge is obtained by subtracting the measured cation charge from the amount of MGK added initially. On the other hand, the measurement of the amount of cationic charge is obtained by directly measuring with PVSK. Even in manual analysis, it is measured in a few minutes, and if a commercially available automated analyzer is used, the analysis is further shortened.
[0020]
The charge amount measurement by PCD can be easily performed by using, for example, a commercially available measuring apparatus that combines a PCD apparatus (manufactured by Muteck) and an automatic titration apparatus. In this PCD device, a cell having electrodes on the upper and lower sides of a cylindrical container and a rod-like piston slightly smaller than the inner diameter of the cell are placed in the cell. Put a predetermined amount of sample water in the cell, immerse a rod-shaped piston slightly smaller than the inner diameter of the cell, and move it up and down to generate an electric current due to the movement of the charged electrolyte and detect this as a potential difference Then, a cationic polymer electrolyte or an anionic polymer electrolyte is added until the potential difference becomes 0, and the charge amount of the sample water is measured. As the cationic polymer electrolyte used at this time, a polydiallyldimethylammonium chloride aqueous solution is generally used, and as the anionic polymer electrolyte, a sodium polystyrene sulfonate aqueous solution is generally used.
[0021]
In the measurement by electrophoresis, a small amount of sample water is collected and placed in a glass cylindrical cell, and the voltage of particles moving between the electrodes is observed by observing the inside of the cell with a microscope while applying voltage to both ends of the cell. This is a method of obtaining the charge amount by measuring.
[0022]
The place where the cationic flocculant is added is not particularly limited as long as the treatment agent is sufficiently dispersed in the circulating water including the unpainted paint. It is in front of the circulation pump.
[0023]
The addition method is not particularly limited, and is appropriately selected such that the cationic flocculant is made into an aqueous solution and is continuously added or intermittently added by a pump.
[0024]
Conversely, if the cationic charge becomes too high, the cationic charge may be neutralized with an anionic compound. Examples of the anionic compound include poly (meth) acrylate sodium, (meth) acrylamide- Examples include (meth) sodium acrylate copolymer, talc, clay, bentonite, colloidal silica, and the like.
[0025]
The paint cake coagulated in the booth circulating water by the method of the present invention can be easily separated into solid and liquid by floating separation or centrifugation, and the separated water can be circulated and reused.
[0026]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to this.
[0027]
[Processing chemicals]
(Cationic polymer flocculant)
A-1: Dimethylamine-epichlorohydrin-ammonia condensate;
[Average molecular weight 80,000, solid content 45%: manufactured by Asahi Denka Kogyo Co., Ltd.]
A-2: diallyldimethylammonium chloride (DADMAC) polymer;
[Average molecular weight: 700,000, solid content 20%, manufactured by SNF, “PRP4520” (trade name)]
A-3: Polyethyleneimine;
[Average molecular weight: 70,000, solid content: 30%, manufactured by Nippon Shokubai Co., Ltd., “Epomin P-1000” (trade name)]
A-4: DADMAC-AM (acrylamide) copolymer;
DADMAC: AM = 30: 70 (molar ratio) copolymer [average molecular weight: 1 million, solid content 8%, manufactured by SNF, “D6030” (trade name)]
A-5: Cationized modified bentonite;
390 g of water and 10 g of coconut alkyltrimethylammonium chloride (“Cation FB” (trade name) manufactured by Nippon Oil & Fats Co., Ltd.) were stirred and homogenized in a vessel equipped with a stirrer. Bentonite Hotaka ”(trade name) 100 g was added and stirred to obtain a 20% slurry of cationized modified bentonite as a uniform slurry.
[0028]
(Other)
C-1: Melamine-formaldehyde resin acid colloid;
Prepared by adding 100 g of methylolated melamine of melamine: formaldehyde = 1: 2.19 (weight ratio) to 1 liter of 1.35% hydrochloric acid aqueous solution and stirring.
C-2: bentonite;
["Bentonite Hotakain" (product name) manufactured by Toyoshun Yoko Co., Ltd.]
[0029]
[Test equipment and test method]
The test was performed using the test booth apparatus shown in FIG. 1 [retained water volume: 1,000 liters, circulating water volume: 150 liters / min]. Water is circulated in the booth, and a predetermined amount of cationic flocculating agent is continuously added with a circulation pump 2 while water-based topcoat paint for automobiles (manufactured by Kansai Paint Co., Ltd., acrylic-polyester-melamine resin-based aqueous). The paint was sprayed continuously at 40 g / min for 3 hours. The charge amount of the booth circulating water in the circulating water holding pit 6 is measured by colloidal titration every hour with the start of spraying, and 5% by weight so that the charge amount of the booth circulating water is -500 μeq / liter to +1,000 μeq / liter. The amount of cationic flocculant aqueous solution added was adjusted. Booth circulating water was collected 1 hour after the start of spraying and immediately after the end of spraying (after 3 hours), and turbidity, COD, foamability and cohesiveness were measured and evaluated. Turbidity is transmitted light turbidity of JIS K 0101, COD is oxygen consumption by potassium permanganate at 100 ° C. [method of JIS K 0101], and foaming properties are accumulated from the liquid level at the pit wall in the circulating water test equipment. The height of the foam is measured, and the agglomeration is visually judged as “◎” if the agglomerate is large, “○” if the agglomerate is slightly small but good in agglomeration, and the agglomerate is fine and poorly agglomerated Was marked “x”. The results are shown in Table 1.
[0030]
[Table 1]

[0031]
According to the method of the present invention, it is understood that the stable and high cohesiveness of the circulating water can be obtained by controlling the charge amount of the wet coating booth circulating water containing the uncoated water-based paint within a certain value.
[0032]
【The invention's effect】
By the management method of the present invention, the water-based paint collected in the circulating water in the wet spray booth using the water-based paint is efficiently aggregated, and the COD of the circulating water, the increase in turbidity, and the foamability can be suppressed. . As a result, it is possible not only to stably operate the apparatus, but also from the economical viewpoint, such as wastewater treatment costs and cost control of the flocculant and antifoaming agent.
[Brief description of the drawings]
FIG. 1 is a test booth apparatus used in Examples.
[Explanation of symbols]
1: Booth circulating water pit 2: Circulating pump 3: Booth circulating water piping 4: Paint collecting part 5: Paint spray gun 6: Booth circulating water holding pit 7: Chemical injection pump

Claims (2)

In the wet painting booth using water-based paint, the charge amount of the circulating water of the booth is measured, and the value is -100 μeq / liter to +1,000 μeq / liter [where-(minus) is an anionic charge, + A method for controlling circulating water in a wet paint booth , wherein a cationic flocculant is added continuously or intermittently so that (plus) indicates a cationic charge.   Cationic flocculants are polyacrylaminoethyltrimethylammonium chloride, acrylamide-acrylaminoethyltrimethylammonium chloride copolymer, dicyandiamide-formaldehyde copolymer, diallyldimethylammonium chloride-sulfur dioxide copolymer, dimethylamine-epichlorohydrin condensate. The wet paint booth circulating water management method according to claim 1, which is at least one selected from the group consisting of dimethylamine-epichlorohydrin-ammonia condensate, diallyldimethylammonium chloride polymer, diallyldimethylammonium chloride-acrylamide copolymer and polyethyleneimine. .

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