JP2006061776A - Method for treating booth circulation water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating booth circulation water in which uncoated paint in the booth circulation water is sufficiently made tack-free, and flocculation/separation and recovery of the uncoated paint can be performed simply and efficiently even if both water base paint and oil paint are present in the booth circulation water in a wet coating booth. <P>SOLUTION: The method for treating the booth circulation water comprises loading a cationic coagulant and amino resin acid colloid in the booth circulation water in the wet coating booth. The loadings of the cationic coagulant is prepared so that an electric charges of the booth circulation water become -50 to +100 μeq/L. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a booth circulating water treatment method in the case where a water-based paint and an oil-based paint are mixed in the booth circulating water of a wet coating booth.

  2. Description of the Related Art Conventionally, there is a spray coating method in which paint is sprayed on an object to be coated as a kind of coating method for automobiles, electrical products and the like. In the spray painting method, paint is sprayed in a wet painting booth in order to maintain the quality of the paint and preserve the work environment.

  This wet painting booth has a painting chamber for spraying paint on an object to be coated, a duct having a fan for sucking air in the painting chamber, and a contact portion for bringing the sucked air and the booth circulating water into contact with each other. And a pit capable of storing booth circulating water.

  In this wet painting booth, uncoated paint that has not been applied to the object to be coated is sucked into the duct together with air by the fan. At this time, the uncoated paint is collected in contact with the booth circulating water at the contact portion, and separated by settling or floating the uncoated paint. The uncoated paint thus separated is collected and discarded.

  However, a part of the unpainted paint floats and circulates in the booth circulating water without being separated, adheres to the inner surface of the piping, etc., and reduces the circulating water volume of the booth circulating water. Furthermore, if the amount of circulating water is drastically reduced, the painting operation may even have to be stopped. In order to prevent such problems, a paint treatment agent is added to the booth circulating water in advance to detack the unpainted paint floating in the booth circulating water and facilitate solid-liquid separation. Yes.

Examples of such paint treating agents include alkaline agents such as caustic soda, cationic polymers, inorganic flocculants, melamine-aldehyde resin acid colloids (Patent Document 1), and the like.
Japanese Patent Publication No. 6-2259

  The alkaline agent saponifies the surface of the uncoated oil-based paint to make it non-tacky, thereby preventing the non-coated oil-based paint from adhering to the pipe. Further, the cationic polymer, the inorganic flocculant and the melamine-aldehyde resin acid colloid adhere to the surface of the uncoated paint and become non-tacky to facilitate solid-liquid separation.

For uncoated water-based paints, there are paint treatment agents containing polyethyleneimine as a component (Patent Document 2), paint treatment agents containing a cationic organic compound and an anionic organic compound (Patent Document 3), and the like. It is used. These paint treatment agents facilitate solid-liquid separation of uncoated water-based paints that are uniformly dispersed or dissolved in Booth circulating water.
JP-A-61-74607 JP-A 63-42706

  In the above conventional booth circulating water treatment method, solid-liquid separation of uncoated paint can be easily performed by selecting an appropriate paint treatment agent according to the type of uncoated paint in the booth circulating water. it can. In recent years, however, water-based paints have been widely used in consideration of the environmental impact of organic solvents in addition to oil paints that have been frequently used. For this reason, oil paints and water-based paints often coexist in the booth circulating water. In such a case, a paint treatment agent for oil paints and a paint treatment agent for water-based paints are used in combination. However, when the paint treatment agents are used in combination, the effects of those paint treatment agents may not be sufficiently exhibited.

  For example, alumina sol is effective for detackifying oil-based paints, and cationic coagulants are effective for agglomeration of water-based paints, so alumina sol and cationic coagulants are used in combination with booth circulating water containing oil-based paints and water-based paints. Has been. However, in this method, the detackifying action of the alumina sol is hindered by the cationic coagulant, and separation and recovery of the uncoated paint may be insufficient.

  In addition, a polyolefin that promotes detackification of an oil-based paint and a cationic coagulant that promotes the setting of an aqueous paint are also added. However, even in this method, the coagulation effect is lowered compared with the case where booth circulating water containing an aqueous paint or oil paint alone is treated, and the separation and recovery of the aqueous paint may be insufficient.

For this reason, the processing method of the booth circulating water which can process the booth circulating water in which an oil-based paint and a water-based paint are mixed is also proposed (patent document 5).
JP-A-5-84492

  According to the description of Patent Document 5, the melamine-aldehyde resin acid colloid is added while adjusting the alkalinity of the booth circulating water in which the oil-based paint and the water-based paint are mixed, and further the flocculant is added, so that the booth circulating water is added. Both oil-based paints and water-based paints mixed in can be efficiently separated and recovered.

  However, this method has to use a large amount of melamine-aldehyde resin acid colloid. That is, in this method, the melamine-aldehyde resin plays a role of neutralizing and condensing the aqueous paint having an anionic charge. However, since the cationic charge of the melamine-aldehyde resin is not so high as to be used as a cationic coagulant, even if the alkalinity is adjusted, it does not coagulate unless added in a large amount. For this reason, the processing cost of booth circulating water will rise. In addition, in order to effectively cause aggregation of the water-based paint, it is necessary to manage the alkalinity, which makes it difficult to manage.

  The present invention has been made in view of the above-described conventional situation, and even when both a water-based paint and an oil-based paint are present in the booth circulating water in the wet painting booth, the uncoated paint in the booth circulating water is present. Solved the problem of providing a booth circulating water treatment method that is sufficiently tack-free, allows easy and efficient separation and recovery of unpainted paint, is easy to manage and has low treatment costs It is an issue that should be done.

  In order to solve the above-mentioned problems, the inventors conducted tests on many paint treatment agents and combinations thereof against booth circulating water in which a water-based paint and an oil-based paint are mixed. And it discovered that if the combination of a cationic coagulant and an amino resin acid colloid was added to the booth circulating water as a paint treating agent, the above problems could be solved, and the present invention was made.

  That is, the booth circulating water treatment method of the present invention is a booth circulating water treatment method in the case where a water-based paint and an oil-based paint are mixed in the booth circulating water of the wet coating booth. It is characterized by adding both a coagulant and an amino resin acid colloid.

  In the booth circulating water treatment method of the present invention, the cationic coagulant added to the booth circulating water has the effect of facilitating solid-liquid separation by coagulating an aqueous paint uniformly dispersed or dissolved in the booth circulating water. Play. Unlike the cationic flocculant, the cationic coagulant does not entangle the water-based paint molecules to cause aggregation, but neutralizes and condenses the surface charge of the water-based paint. That is, this cationic coagulant has a cationic surface charge in the booth circulating water, and is negatively charged in the booth circulating water to neutralize the surface charge of the aqueous paint floating in a stable state. be able to. For this reason, the water-based paint in the booth circulating water can be coagulated by adding a cationic coagulant. Compared with the case where charge neutralization is performed by a combination of a cationic coagulant and an amino resin acid colloid, the amino resin acid colloid The amount added can be reduced. Furthermore, the coagulation effect can be achieved without carefully controlling the alkalinity.

On the other hand, the amino resin acid colloid added to the booth circulating water has the effect of adhering to the surface of the oil-based paint floating in the booth circulating water and making it non-tacky. Furthermore, the amino resin acid colloid adheres to the surface of the water-based paint that could not be sufficiently set by the cationic coagulant, promotes aggregation and exhibits a tack-free effect, and the water-based paint adheres to the piping wall and the like. There is also an effect of preventing the above. According to the test results of the inventors, the amino resin acid colloid does not inhibit the setting action of the cationic setting agent. Therefore, the cationic coagulant and the amino resin acid colloid can synergistically exert their effects, and as a result, the paint in the booth circulating water can be easily aggregated, separated and recovered.

  Therefore, according to the booth circulating water treatment method of the present invention, even when the water-based paint and the oil-based paint are mixed in the booth circulating water of the wet-painting booth, the water-based paint and the oil-based paint are sufficiently non-tacky. Therefore, the separation and recovery can be easily and efficiently performed, the management is easy, and the processing cost is low.

  In the booth circulating water treatment method of the present invention, the aqueous paint to be treated is not particularly limited, and examples thereof include an aqueous alkyd resin paint, an aqueous polyester resin paint, an aqueous acrylic resin paint, and an aqueous polyurethane resin paint.

  In the booth circulating water treatment method of the present invention, the oil-based paint to be treated is not particularly limited. For example, epoxy resin paint, polyester resin paint, urethane resin paint, alkyd resin paint, amino resin paint, vinyl resin Examples thereof include paints, acrylic resin paints, phenol resin paints, cellulose derivative paints and alcoholic paints.

  In the booth circulating water treatment method of the present invention, the place where the cationic coagulant and the amino resin acid colloid are added is not particularly limited, but these paint treating agents are placed in the booth circulating water before the circulation pump. It is preferable to add at a place where it is easily mixed. The addition method is not particularly limited, and can be selected as appropriate, such as continuous addition with a metering pump or intermittent addition.

  The cationic coagulant used in the present invention means a substance that is cationic in water, neutralizes the surface charge of the water-soluble paint in booth circulating water, and promotes coagulation with a small amount of addition. Examples of such a cationic coagulant include a water-soluble synthetic cationic coagulant and a water-soluble natural cationic coagulant.

  Examples of the water-soluble synthetic cationic coagulant include (meth) acrylic acid ester (ester of alcohol having 1 to 4 carbon atoms) / (meth) acrylaminoethyltrimethylammonium copolymer, (meth) acrylamide / (meta ) Acrylaminoethyltrimethylammonium copolymer, (meth) acrylaminodialkyl (alkyl group having 1 to 4 carbon atoms) / (meth) acrylaminoethyltrimethylammonium copolymer, poly (meth) acrylaminoethyltrimethylammonium (Meth) acrylaminoethyltrimethylammonium copolymer; dicyandiamide polymer, dicyandiamide-formaldehyde copolymer and other dicyandiamide copolymers; dimethylamine-epichlorohydrin copolymer, diethylamine-epichlorohydride Copolymer, dimethylamine-epichlorohydrin-ammonia copolymer, dialkylamine-epihalohydrin copolymer such as diethylamine-epichlorohydrin-ammonia copolymer; polydiallyldimethylammonium chloride, diallyldimethylammonium chloride-sulfur dioxide copolymer, Diallyldimethylammonium chloride- (meth) acrylamide copolymer, diallyldimethylammonium chloride- (meth) acrylic acid copolymer, diallyldimethylammonium chloride- (meth) acrylic acid- (meth) acrylamide copolymer, etc. Chloride (hereinafter referred to as DADMAC) copolymer; and polyalkylamines such as polyethyleneimine and polyallylamine.

  Among these, polyacrylaminoethyltrimethylammonium chloride, acrylamide-acrylaminoethyltrimethylammonium chloride copolymer, dicyandiamide-formaldehyde copolymer, diallyldimethylammonium chloride-sulfur dioxide copolymer, dimethylamine-epichlorohydrin copolymer and Dimethylamine-epichlorohydrin-ammonia copolymer, polyDADMAC, DADMAC-acrylamide copolymer and polyethyleneimine are preferred because of their high cation strength.

  On the other hand, examples of natural cationic coagulants include water-soluble chitosan and cationized starch.

  In the compound usable as the cationic coagulant, the molecular weight is preferably in the range of 2,000 to 500,000. This is because if the molecular weight is within this range, the setting effect of the aqueous paint is particularly excellent.

  In the present invention, as the amino resin acid colloid, an acid colloid of methylolated product, which is an adduct of melamine and / or urea and an aldehyde, can be used. Also, alkyl etherified methylol melamine acid colloid, alkyl etherified methylol melamine / urea acid colloid, alkyl etherified methylol urea acid colloid, etc. obtained by etherification of this methylolated product with lower alcohol such as methanol, ethanol, propanol, etc. It can be used as an amino resin acid colloid in the invention.

  More specific examples of amino resin acid colloids include melamine resin acid colloids and melamine / urea resin acid colloids. In the melamine / urea resin acid colloid, the ratio of melamine in the melamine / urea resin is preferably 10 mol% or more, more preferably 50 mol% or more, and most preferably 75 mol% or more. Further, in the amino resin acid colloid, the ratio of the sum of melamine and urea in the amino resin to the aldehyde in the amino resin is preferably 1: 1 to 1:10, more preferably 1: 2.5 to 1: 5. The aldehyde is preferably an aldehyde having 1 to 3 carbon atoms, specifically, paraformaldehyde which is a trimer of formaldehyde, acetaldehyde, propionaldehyde and formaldehyde, preferably formaldehyde and paraformaldehyde.

  Acids used for the amino resin acid colloid include mineral acids such as hydrochloric acid, sulfuric acid, nitric acid; formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, glycolic acid, malic acid, lactic acid, citric acid, etc. There are organic acids. Of these, monobasic acids are preferred, and specific examples include hydrochloric acid and lactic acid. The ratio of amino resin to acid in the amino resin acid colloid is such that (total number of moles of melamine and urea in amino resin: number of moles of acid) is 1: 0.3 to 1: 1.5. Is more preferable, and 1: 0.5 to 1: 1.3 is more preferable. When the ratio of the number of moles of acid to the total number of moles of melamine and urea in the amino resin is lower than this range, the efficiency of aggregation / separation of the water-based paint and the oil-based paint may be reduced. Moreover, when the ratio is higher than this range, the stability of the amino resin acid colloid is lowered. The molecular weight of the amino resin is not particularly limited, but is usually 400 to 50,000, preferably 500 to 5,000.

  Moreover, the melamine resin acid colloid and the melamine-urea resin acid colloid can be obtained by a commonly used method for preparing a melamine resin acid colloid or a melamine-urea resin acid colloid. For example, a method for producing a melamine resin acid colloid will be specifically described as follows. That is, a predetermined amount of melamine, paraformaldehyde and water are put into a reaction vessel, pH is adjusted to 10 with sodium hydroxide, heated to 70 ° C., stirred for about 80 minutes, and reacted to be suspended in methylolmelamine. Obtain a liquid. A predetermined amount of hydrochloric acid is gradually added to the obtained methylol melamine suspension with stirring to obtain a translucent to transparent melamine resin acid colloid solution, which is left to stand for 2 days at room temperature for aging, and then a melamine acid colloid solution. Is obtained. Also, since alkyl etherified methylol melamine is water-soluble, if it is dissolved in a predetermined amount of water and a predetermined amount of hydrochloric acid is gradually added with stirring, hydrolysis occurs and the alkyl etherified methylol melamine becomes methylol melamine. Further, a methylol melamine suspension is formed, and at the same time, a semitransparent to transparent melamic acid colloidal solution is obtained. In the melamine-urea resin acid colloid stock solution added to the booth circulating water in the present invention, the melamine-urea resin content is usually 0.1 to 20%, preferably 1 to 15%, more preferably 4 to 10%. Further, the aging period of the produced melamine-urea resin acid colloid varies depending on the solid content concentration of the melamine-urea resin acid colloid liquid, the composition of the melamine-urea resin, and the type of acid used, but cannot be determined uniformly. If it is normal temperature, it will become a standard for 2 to 5 hours if it is 2-30 days, and 50 degreeC. The melamine / urea resin acid colloid can be prepared in the same manner by using a mixture of melamine and urea instead of melamine in the method for preparing a melamine resin acid colloid.

  In the booth circulating water treatment method of the present invention, the addition amount of the cationic coagulant may be appropriately determined in consideration of the charge of the aqueous paint, and is not particularly limited. It is 0.05-100 weight% with respect to resin solid content, Preferably it is 0.5-30 weight%. The amount of the amino resin acid colloid added is not particularly limited as long as it is appropriately determined in consideration of the use state of the oil paint and the degree of tackiness required for the oil paint. However, it is usually 0.05 to 100% by weight, preferably 0.5 to 30% by weight, based on the solid content of the paint resin of the oil-based paint.

  It is also preferable to control the amount of cationic coagulant added based on the amount of charge in the booth circulating water. According to the test results of the inventors, the amount of charge in the booth circulating water varies greatly depending on the amount of cationic coagulant added, and the amount of charge in the booth circulating water due to the addition of the amino resin acid colloid is negligible. If the cationic coagulant is added so that the charge amount in the booth circulating water is −50 to +100 μeq / L, the coagulation effect of the water-soluble paint is enhanced, and the separation and recovery thereof becomes extremely easy. The amount of charge in the booth circulating water can be measured by a known method such as a colloid titration method, a particle charge measurement method (PCD method), or an electrophoresis method.

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 a change in the 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 cation charge amount 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.

The charge measurement by the PCD can be easily performed by using a commercially available measuring device that combines, for example, a PCD device (manufactured by Muteck) and an automatic titration device. 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.

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.

  Hereinafter, Examples 1 to 8 and Comparative Examples 1 to 12 embodying the present invention will be described with reference to the drawings.

Example 1
In Example 1, dimethylamine-epichlorohydrin condensate (average molecular weight 5000, solid content 50%: “Wastex T-101-50” manufactured by Nagase Sangyo Co., Ltd.) was used as a cationic coagulant at a coating booth. It added in the ratio of 0.7 mass% with respect to the sprayed coating material. Further, as amino resin acid colloid, 100 g of methylolated melamine of melamine: formaldehyde = 1: 2.19 (weight ratio) was added to 1 liter of 1.35% hydrochloric acid aqueous solution and stirred, and this was used. Was added at a ratio of 18% by mass with respect to the paint sprayed in the painting booth.

(Example 2)
In Example 2, the same cationic coagulant as in Example 1 was added in the same amount, and the same amino resin acid colloid as in Example 1 was added so as to be half the amount in Example 1.

(Example 3)
In Example 3, the same amount of the same cationic coagulant as in Example 1 was added. Also, 62.5 g of urea-melamine-formaldehyde resin (solid content 80%, “Milben Resin SM-615” manufactured by Showa Polymer Co., Ltd.) was added as an amino resin acid colloid to 1 liter of a 3.8% lactic acid aqueous solution. The mixture prepared by stirring was added at a ratio of 27% by mass with respect to the paint sprayed in the coating booth.

Example 4
In Example 4, the same cationic coagulant as in Example 3 was added in the same amount, and the same amino resin acid colloid as in Example 3 was added in half the amount of Example 3.

(Example 5)
In Example 5, diallyldimethylammonium chloride (DADMAC) polymer (average molecular weight 200,000, solid content 40%, “SRP” “PRP4440”)) was used as the cationic coagulant, and this was sprayed at the coating booth. It added in the ratio of 1.0 mass% with respect to the coating material. Moreover, the same amino resin acid colloid as Example 3 was added as an amino resin acid colloid in the ratio of 13.5 mass% with respect to the coating material sprayed by the coating booth.

(Example 6)
In Example 6, the same cationic coagulant as in Example 5 was added in the same amount, and the same amino resin acid colloid as in Example 3 was added at a ratio of 18.0% by mass with respect to the paint sprayed in the coating booth. did.

(Example 7)
In Example 7, polyethyleneimine (average molecular weight 70,000, solid content 30%, “Epomin P-1000” manufactured by Nippon Shokubai Co., Ltd.) was used as the cationic coagulant, and this was applied to the paint sprayed at the coating booth. 1.0% by mass. Moreover, the same amino resin acid colloid as Example 1 was added as an amino resin acid colloid in the ratio of 18.0 mass% with respect to the coating material sprayed by the coating booth.

(Example 8)
In Example 8, the same cationic coagulant as in Example 7 was added in the same amount, and the same amino resin acid colloid as in Example 3 was added at a ratio of 27.0% by mass with respect to the paint sprayed in the coating booth. did.

(Comparative Example 1)
In Comparative Example 1, nothing was added to the booth circulating water.

(Comparative Example 2)
In Comparative Example 2, polyethylene imine (average molecular weight 70,000, solid content 30%, “Epomin P-1000” manufactured by Nippon Shokubai Co., Ltd.) was used as a cationic coagulant added to the booth circulating water, and this was applied at the paint booth. It added in the ratio of 1.0 mass% with respect to the sprayed coating material, and the amino resin acid colloid was not added.

(Comparative Example 3)
In Comparative Example 3, the same cationic coagulant as in Comparative Example 2 was added in an amount 5 times that in Comparative Example 2, and the amino resin acid colloid was not added.

(Comparative Example 4)
In Comparative Example 4, 3.8 g of urea-melamine-formaldehyde resin (solid content 80%, “Milben Resin SM-615” manufactured by Showa Polymer Co., Ltd.) as 3.8 is added as the amino resin acid colloid added to the booth circulating water. A solution prepared by adding and stirring in 1 liter of a 1% aqueous lactic acid solution was added at a ratio of 27% by mass to the paint sprayed in the coating booth. No cationic coagulant was added.

(Comparative Example 5)
In Comparative Example 5, the same amino acid resin colloid as in Example 4 was added at a ratio of 54.0% by mass with respect to the paint sprayed at the coating booth, and no cationic coagulant was added.

(Comparative Example 6)
In Comparative Example 6, alumina sol was added at a ratio of 30% by mass with respect to the paint sprayed at the coating booth. Alumina sol was prepared as follows. That is, 134 g of dry aluminum hydroxide gel (“KYOWARD 200S” manufactured by Kyowa Chemical Industry Co., Ltd.), 820 g of water and 16 g of nitric acid (concentration 67.5%) are placed in an autoclave with stirring of 1.5 liter and sealed. Heat to 130 ° C. with stirring. After 2 hours, the mixture was cooled and 30 g of glycine was added to obtain an alumina sol.

(Comparative Example 7)
In Comparative Example 7, the polyethylene wax emulsion was added at a ratio of 30% by mass with respect to the paint sprayed at the painting booth. The polyethylene wax emulsion was prepared as follows. That is, 90 g of polyethylene wax (“Epolene E-10” manufactured by Nagase Sangyo Co., Ltd.), 363 g of water, 27 g of hexamethylenediamine (65% product) and 15 g of lauric acid were added to an autoclave with stirring of 1.5 liters in volume and sealed And warm to 120 ° C. with stirring. After 1 hour, it was cooled and 505 g of water was added to make a polyethylene wax emulsion.

(Comparative Example 8)
In Comparative Example 8, polyaluminum chloride (“PAC for water” manufactured by Asahi Chemical Industry Co., Ltd.) was added at a ratio of 30% by mass with respect to the paint contained in the booth circulating water.

(Comparative Example 9)
In Comparative Example 9, dimethylamine-epichlorohydrin condensate (average molecular weight 5000, solid content 50%: “Wastex T-101-50” manufactured by Nagase Sangyo Co., Ltd.) was used as a cationic coagulant added to the booth circulating water. It was used and added in a proportion of 0.7% by weight with respect to the paint sprayed in the painting booth. Further, the alumina sol used in Comparative Example 6 was added at a ratio of 30% by mass with respect to the paint sprayed at the coating booth.

(Comparative Example 10)
In Comparative Example 10, the same cationic coagulant as in Comparative Example 9 was added in the same amount, and the polyethylene wax emulsion used in Comparative Example 7 was added at a ratio of 30% by mass with respect to the paint sprayed in the coating booth. .

(Comparative Example 11)
In Comparative Example 11, 100 g of methylolated melamine of melamine: formaldehyde = 1: 2.19 (weight ratio) was added to 1 liter of a 1.35% hydrochloric acid aqueous solution as an amino resin acid colloid, and the mixture was prepared by stirring. This was added at a rate of 30% by weight based on the paint sprayed in the painting booth. Further, the same polyaluminum chloride as in Comparative Example 8 was added at a ratio of 30% by mass with respect to the paint sprayed at the coating booth.

(Comparative Example 12)
In Comparative Example 12, the same amount of the same amino resin acid colloid as in Comparative Example 11 was added, and polyacrylamide (“Super Flock 2300S” manufactured by Mitsui Cytec Co., Ltd.) was further added to the paint sprayed at the coating booth in an amount of 0.00. 4% by mass was added.

<Treatment test of booth circulating water>
By the booth circulating water processing method of the said Examples 1-8 and Comparative Examples 1-12, the processing test of the booth circulating water was done. As shown in FIG. 1, the wet painting booth used for the test is a painting booth main body 1 for painting, a storage tank 2 for receiving the booth circulating water flowing down in the painting booth main body 1, and a paint in the booth circulating water. And a separation tank 3 for separating the water. The painting booth main body 1, the storage tank 2, and the separation tank 3 are connected by a pipe 4, and the booth circulating water can be circulated by a circulation pump 5 installed in the middle of the pipe 4. Metering pumps 6a and 6b for adding chemicals to the booth circulating water are connected in the middle of the pipe 4, and these are connected to the chemical tanks 7a and 7b. The amount of water held in this wet painting booth is 120 liters, and the amount of booth circulating water by the circulation pump 5 is 50 liters / minute.

  Using the wet test booth for testing constructed as described above, the metering pumps 6a and 6b are driven to add a predetermined amount of the above chemicals, while water paint and oil paint are directed toward the booth circulating water in the paint booth. Was sprayed continuously at 2 g / min for 3 hours. As the water-based paint, a water-based top coat for automobiles (manufactured by Nippon Paint Co., Ltd.) was used, and as the oil-based paint, a solvent clear paint for automobiles (manufactured by Nippon Paint Co., Ltd.) was used. Moreover, while spraying the paint, the charge of the booth circulating water was measured, and the addition amount of the cationic coagulant was adjusted so that the charge was −50 to +100 (μeq / L-booth circulating water). The charge of the booth circulating water was measured by colloid titration. After spraying, the booth circulating water was collected, and after waiting for the paint to float or settle, the turbidity and COD of the intermediate layer were measured. In addition, the tack-free property of the floating paint sludge was measured and evaluated. Turbidity was evaluated by transmitted light turbidity according to JIS K 0101. The COD was evaluated by the oxygen consumption by potassium permanganate at 100 ° C. according to JIS K 0101. Furthermore, the non-tackiness of the paint sludge is determined by touch, and “◎” indicates that there is no stickiness even when pressed hard, “○” indicates that it is slightly sticky when pressed hard, and lightly presses to stick. “△” indicates that the material is sticky, and “×” indicates that the material has strong tackiness simply by touching. The results are shown in Table 1.

上記表１における処理薬品の記号は以下の薬品を示す。
（カチオン性凝結剤）
Ａ−１：ジメチルアミン−エピクロルヒドリン縮合物（カチオン電荷７．４ｍｅｑ／ｇ）
Ａ−２：ジアリルジメチルアンモニウムクロライド（ＤＡＤＭＡＣ）重合体（カチオン電荷６．１ｍｅｑ／ｇ）
Ａ−３：ポリエチレンイミン（カチオン電荷１８．１ｍｅｑ／ｇ）
（アミノ樹脂酸コロイド）
Ｂ−１：メラミン−ホルムアルデヒド樹脂塩酸コロイド
Ｂ−２：尿素−メラミン−ホルムアルデヒド樹脂乳酸コロイド
（その他）
Ｃ−１：アルミナゾル
Ｃ−２：ポリエチレンワックスエマルション
Ｃ−３：ポリ塩化アルミニウム
Ｃ−４：ポリアクリルアミド

The symbols for treatment chemicals in Table 1 above indicate the following chemicals.
(Cationic coagulant)
A-1: Dimethylamine-epichlorohydrin condensate (cation charge 7.4 meq / g)
A-2: diallyldimethylammonium chloride (DADMAC) polymer (cation charge 6.1 meq / g)
A-3: Polyethyleneimine (cation charge 18.1 meq / g)
(Amino resin acid colloid)
B-1: Melamine-formaldehyde resin hydrochloric acid colloid B-2: Urea-melamine-formaldehyde resin lactic acid colloid (others)
C-1: Alumina sol C-2: Polyethylene wax emulsion C-3: Polyaluminum chloride C-4: Polyacrylamide

  As shown in Table 1, a cationic coagulant and an amino resin acid colloid are added to the booth circulating water so that the charge of the booth circulating water becomes −50 to +100 (μeq / L-booth circulating water). In Examples 1 to 8 in which the addition amount of the coagulant was adjusted, the turbidity was 30 degrees or less and the COD was 480 (mg-O2 / L-booth circulating water) or less, both of which showed that the paint in the booth circulating water was separated. You can see that it is done efficiently. Further, the tack-free property was evaluated as “Good” or “Excellent”, and it was found that the paint could be sufficiently prevented from adhering to the booth circulating water piping. On the other hand, in Comparative Examples 2 to 8 in which various chemicals were added alone and the charge of the booth circulating water was not adjusted, the turbidity was 740 degrees or more and the COD was 640 (mg-O2 / L-booth circulating water). Thus, the separation of the paint in the booth circulating water was extremely insufficient. Further, Comparative Example 10 in which a cationic coagulant and polyethylene polyethylene wax emulsion are combined, Comparative Example 11 in which melamine-formaldehyde resin hydrochloride colloid and polyaluminum chloride are combined, and comparison in which melamine-formaldehyde resin hydrochloride colloid and polyacrylamide are combined In Example 11, although the turbidity is 100 degrees or more and the COD is 610 (mg-O2 / L-booth circulating water) or more and the separation of the paint in the booth circulating water is improved as compared with the addition of a single chemical, Is still inadequate. In Comparative Example 9 in which the cationic coagulant and alumina sol were combined, the turbidity was 37 degrees, the COD was 510 (mg-O2 / L-Booth circulating water), and the paint in the Booth circulating water was separated relatively well. However, it was found to be in a state in which it is inferior in non-tackiness and easily adheres to the booth circulating water piping even if separated.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used as a booth circulating water treatment method when both a water-based paint and an oil-based paint are present in the booth circulating water of a wet painting booth.

It is a schematic diagram of the coating booth apparatus for a test used by the Example and the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Paint booth body 2 ... Storage tank 3 ... Separation tank 4 ... Booth water circulation line 5 ... Booth water circulation pump 6a, 6b ... Metering pump 7a, 7b ... Chemical tank

Claims (5)

A booth circulating water treatment method when water-based paint and oil-based paint are mixed in the booth circulating water of the wet paint booth,
A processing method for booth circulating water, wherein both a cationic coagulant and an amino resin acid colloid are added to the booth circulating water.   Cationic coagulants are polyacrylaminoethyltrimethylammonium chloride, acrylamide-acrylaminoethyltrimethylammonium chloride copolymer, dicyandiamide-formaldehyde copolymer, diallyldimethylammonium chloride-sulfur dioxide copolymer, dimethylamine-epichlorohydrin condensate. The booth circulating water according to claim 1, wherein the booth circulating water is at least one selected from the group consisting of dimethylamine-epichlorohydrin-ammonia condensate, diallyldimethylammonium chloride polymer, diallyldimethylammonium chloride-acrylamide copolymer, and polyethyleneimine. Processing method. The method of treating booth circulating water according to claim 2, wherein the cationic coagulant has a molecular weight of 2,000 to 500,000. The method for treating booth circulating water according to any one of claims 1 to 3, wherein the addition amount of the cationic coagulant is adjusted so that the amount of charge in the booth circulating water is -50 to +100 µeq / L. .   The method for treating booth circulating water according to any one of claims 1 to 4, wherein the amino resin acid colloid is a melamine resin acid colloid or a melamine / urea resin acid colloid.

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