JP2008173562A - Method of treating booth circulation water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of treating painting booth circulation water by which uncoated paint in the booth circulation water is sufficiently rendered non-adhesive, even if aqueous paint and/or oily paint are contained in the booth circulation water in the wet painting booth, foams are little generated and uncoated paint can be easily and efficiently separated and recovered. <P>SOLUTION: When the aqueous paint and/or oily paint are contained in the booth circulation water of the wet painting booth, novolac type phenol resin expressed by general formula 1 (a methylol group may be bonded to a terminal benzene ring), a cation coagulant and a flocculant are added to the booth circulation water. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a booth circulating water treatment method for coagulating an aqueous paint and / or an oil paint contained in a booth circulating water of a wet painting 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 coating 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, and collected in contact with the booth circulating water at the contact portion. In this way, the uncoated paint that has settled or floated is collected and discarded.

  However, a portion of the unpainted paint floats and circulates in the booth circulating water without being separated, and adheres to the inner surface of the piping 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 alkali agents such as caustic soda, cationic polymers, inorganic flocculants, melamine-aldehyde resin acid colloids (Patent Document 1), and the like.

  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.

  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. However, in recent years, water-based paints are often used in consideration of the environmental impact of organic solvents in addition to oil-based paints that have been frequently used. For this reason, paint processing agents for oil-based paints and paint processing agents for water-based paints are often used in booth circulating water. However, when the paint treatment agents are used in this way, the paint treatment agents may interfere with each other and may not be fully effective.

  For example, alumina sol is effective for detackifying oil-based paints and cationic coagulant is effective for agglomeration of water-based paints. Therefore, alumina sol and cationic coagulant are used in combination with booth circulating water containing oil-based paints and water-based paints. Yes. 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.

Therefore, a treatment method using a cationic polymer and a phenolic resin is proposed as a treatment method suitable for booth circulating water in a paint booth where a paint treatment agent for oil paints and a paint treatment agent for water-based paints are used in combination. (Patent Document 4). According to this processing method, it is described that even if a water-based paint and an oil-based paint are used in combination at the painting booth, the uncoated paint can be separated and collected.
Japanese Patent Publication No. 6-2259 JP-A-61-74607 JP-A 63-42706 JP 2004-337671 A

  However, in the treatment method in which the cationic polymer and the phenolic resin described in Patent Document 4 are added to the paint booth circulating water, the defoaming time exceeds 60 seconds, as described in Examples in the same document. In such a case, it is difficult to separate and recover the uncoated paint due to the generation of bubbles. Moreover, according to the test results of the inventors, depending on the type of the phenolic resin, the uncoated paint does not aggregate and solid-liquid separation may not be possible.

  The present invention has been made in view of the above-described conventional situation, and even when a wet paint booth contains an aqueous paint and / or an oil paint in the booth circulating water, the non-coated paint in the booth circulating water becomes non-tacky. It is an object to be solved to provide a method for treating circulating water in a coating booth that can be sufficiently performed, that bubbles are not generated, and that an uncoated paint can be separated and recovered easily and efficiently.

  In order to solve the above problems, the inventors of the present invention have a method of adding a cationic polymer and a phenolic resin to the paint booth circulating water, how to suppress foaming and agglomeration of uncoated paint. We conducted intensive research. As a result, when a novolac type phenol resin is used as the phenolic resin and the degree of polymerization of the novolac type phenol resin is within a specific range, the present invention has been found to exhibit a particularly excellent defoaming effect, and the present invention is completed. It came to.

That is, the treatment method for circulating water in a painting booth according to the present invention is a treatment method for circulating water in a wet painting booth containing a water-based paint and / or an oil-based paint, and the following general formula (1) (however, A novolak type phenol resin represented by a methylol group may be bonded to the terminal benzene ring), a cationic coagulant and an aggregating agent are added.

  In the treatment method for circulating water in the painting booth of the present invention, the novolak type phenolic resin added to the circulating water in the booth adheres to the surface of the water-based paint and / or oil-based paint that floats in the booth circulating water, and makes the booth non-tacky. The suspended state of the paint component suspended in the circulating water is made separable. In addition, there is an effect of suppressing a phenomenon of booth circulating water foaming caused by the water-based paint. According to the test results of the inventors, the effect of suppressing the foaming of the booth circulating water is remarkably different depending on the degree of polymerization of the novolak type phenol resin, and in the novolak type phenol resin represented by the general formula (1), n is 4 to In the case of 8, the defoaming effect is particularly high. In addition, the effect of making the suspended state separable is particularly excellent when n is in the range of 4 to 8, and solid-liquid separation of uncoated paint is facilitated. On the other hand, when n <4, the effect of making the aqueous paint and / or oil paint floating in the booth circulating water non-tacky and the effect of separating the suspended paint components become insufficient.

  The cationic coagulant used in the present invention refers to a water-soluble polymer having a cationic charge in water. Since the cationic coagulant has a positive surface charge in the booth circulating water, it is adsorbed by the Coulomb force to the aqueous paint that is negatively charged and dissolved or colloidally dispersed in a stable state. To sum up. By this action, the water-based paint is condensed and insolubilized as fine particles. On the other hand, since the phenolic resin also has a negative surface charge in the booth circulating water, the charge is neutralized by the cationic polymer, and is condensed and insolubilized. The water-insoluble paint thus insolubilized and the phenol-based resin insolubilized are combined with each other to form a slightly suspended floc having a certain size. In this way, the formed floc is likely to precipitate, so that solid-liquid separation can be easily performed by filtration or decantation.

  In addition, the flocculant has the effect of further solidifying the coating particles that have been solidified and separated by coagulation and non-adhesion to coarsen the particles. Furthermore, since finely dispersed paint particles that cause foaming are agglomerated and removed, there is also an effect of suppressing foaming.

  Therefore, according to the coating booth circulating water treatment method of the present invention, even when a wet paint booth contains a water-based paint and / or an oil-based paint in the booth circulating water, the uncoated paint in the booth circulating water can be made non-tacky. Sufficiently, there is little generation | occurrence | production of a bubble, and isolation | separation and collection | recovery of an uncoated paint can be performed easily and efficiently.

  The molecular weight of the cationic coagulant 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. More preferably, it is 2,000-200,000.

  Examples of the cationic coagulant include (meth) acrylic acid ester (ester of alcohol having 1 to 4 carbon atoms) / (meth) acrylaminoethyltrimethylammonium copolymer, (meth) acrylaminodialkyl (having 1 to 4 carbon atoms). Alkyl group) / (meth) acrylaminoethyltrimethylammonium copolymer, (meth) acrylaminoethyltrimethylammonium copolymer such as poly (meth) acrylaminoethyltrimethylammonium; dicyandiamide polymer, dicyandiamide-formaldehyde copolymer, Dicyandiamide copolymers such as dicyandiamide-diethylenetriamine copolymer; dimethylamine-epichlorohydrin copolymer, diethylamine-epichlorohydrin copolymer, dimethylamine-epichlorohydrin-a Monia copolymer, dialkylamine-epihalohydrin copolymer such as diethylamine-epichlorohydrin-ammonia copolymer, polydiallyldimethylammonium chloride, diallyldimethylammonium chloride-sulfur dioxide copolymer, diallyldimethylammonium chloride- (meth) acrylamide copolymer Polymers, diallyldimethylammonium chloride- (meth) acrylic acid copolymer, diallyldimethylammonium chloride- (meth) acrylic acid- (meth) acrylamide copolymer, etc. diallyldimethylammonium chloride (hereinafter referred to as DADMAC) Polymers: Polyalkylamines such as polyethyleneimine and polyallylamine.

  Among these, polyacrylaminoethyltrimethylammonium chloride, dicyandiamide-formaldehyde condensate, dicyandiamide-diethylenetriamine condensate, diallyldimethylammonium chloride-sulfur dioxide copolymer, dimethylamine-epichlorohydrin condensate, dimethylamine-epichlorohydrin-ammonia condensate , Diallyldimethylammonium chloride polymer, diallyldimethylammonium chloride-acrylamide copolymer and polyethyleneimine are preferred because of their high cation strength.

  Since the novolac type phenol resin in the present invention is hardly soluble in water, it is preferably used after being dissolved in an alkaline substance. Examples of the alkaline substance include alkali metal hydroxides, alkaline earth metal hydroxides, ammonia, and amines. Of these, sodium hydroxide and potassium hydroxide are preferably used.

  The flocculant used in the present invention is a water-soluble anionic, cationic or nonionic polymer having a molecular weight of 1,500,000 to 20,000,000, preferably 2,000,000 to 15,000. 1,000 water-soluble polymers. The flocculant is a novolac type phenolic resin and cationic coagulant that binds finely suspended flocs of water-based paint and oil-based paint that have been neutralized and condensed to form larger flocs for solid-liquid separation. make it easier. Specifically, polyacrylamide, acrylamide-acrylic acid copolymer, acrylamide-acrylaminoethyltrimethylammonium chloride copolymer, acrylamide-methacrylaminoethyltrimethylammonium chloride copolymer, acrylamide- [2- (acryloyloxy) ethyl And benzyldimethylammonium chloride / [2- (acryloyloxy) ethyl] trimethylammonium copolymer, acrylamide-vinyl sulfonic acid copolymer and salts thereof, polyvinyl imidazoline, and polyethylene oxide.

  Among these, polyacrylamide, acrylamide-acrylic acid copolymer, acrylamide-acrylaminoethyltrimethylammonium chloride copolymer, acrylamide-methacrylaminoethyltrimethylammonium chloride copolymer, acrylamide- [2- (acryloyloxy) ethyl] Benzyldimethylammonium chloride / [2- (acryloyloxy) ethyl] trimethylammonium copolymer is preferred.

  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 solid content, Preferably it is 0.5-30 weight%. Further, the addition amount of the novolac-type phenol resin is not particularly limited and may be appropriately determined in consideration of the degree of tack-free and suppression of foaming usually required for water-based paints and oil-based paints. However, it is usually 0.05 to 100% by weight, preferably 0.5 to 30% by weight, based on the coating resin solid content of the water-based paint and oil-based paint. The amount of the flocculant added is usually determined in consideration of the degree of agglomeration of the paint particles of the solid-liquid separated aqueous paint and oil paint, and is not particularly limited. The amount is 0.001 to 10% by weight, preferably 0.05 to 3% by weight, based on the solid content of the paint resin in the aqueous and oil-based paints separated into solid and liquid.

  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 the cationic coagulant added, and the amount of charge in the booth circulating water due to the addition of the novolak type phenol resin and the flocculant is negligible. is there. If the cationic coagulant is added so that the charge amount in the booth circulating water is −50 to +200 μeq / L, the coagulation effect of the water-soluble paint is enhanced, and the separation and recovery thereof becomes extremely easy.

  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. There is no particular limitation on the oil-based paint to be treated, for example, epoxy resin paint, polyester resin paint, urethane resin paint, alkyd resin paint, amino resin paint, vinyl resin paint, acrylic resin paint, phenol resin paint, cellulose Examples include derivative paints and alcoholic paints.

  Further, there are no particular limitations on the place where the cationic coagulant and the novolac type phenol resin are added, but it is preferable to add the booth circulating water to the booth circulating water before it comes into contact with the uncoated paint. 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 place where the flocculant is added is preferably after the cationic coagulant and the novolac type phenol resin are added, and at a place where the flocculant is easily mixed in the booth circulating water before collecting the paint sludge. The addition method is not particularly limited, and can be selected as appropriate, such as continuous addition with a metering pump or intermittent addition.

  In addition, when the amount of cationic coagulant added is controlled by the amount of charge in Booth circulating water, the amount of charge can be measured by a known method such as colloid titration method, particle charge measurement method (PCD method) or electrophoresis method. it can.

  The colloid titration method is a method in which the charge amount of electrolytes, colloidal particles, suspended substances, etc. in water is neutralized with anionic and cationic water-soluble polymer electrolytes and quantified by changing the color of the indicator (" Colloid titration test method ”by Shinichi Sente, 3-6, Nanedo, 1969)). For example, for the measurement of anion charge, a few drops of toluidine blue (TB) is added as an indicator, and an aqueous solution of methyl glycol chitosan (hereinafter abbreviated as “MGK”), which is a cationic aqueous electrolyte solution, is added in excess, 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.

  In addition, the PCD method can be easily measured by using a commercially available measuring apparatus that combines, for example, a PCD apparatus (manufactured by Mutek) 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. A predetermined amount of sample water is put into the cell, the piston is immersed and moved up and down to generate an electric current due to the movement of the charged electrolyte, and this is detected as a potential difference. A polyelectrolyte or an anionic polyelectrolyte is added to measure the charge amount of the sample water. 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 polyethylene sulfonate aqueous solution is generally used.

  Electrophoresis is a method in which a small amount of sample water is collected, placed in a glass cylindrical cell, and the voltage of the particles moving between the electrodes is observed with a microscope while applying voltage across the cell. Is a method for determining the charge amount.

  Examples in which the present invention is embodied will be described below in comparison with comparative examples.

(Example 1)
In Example 1, dimethylamine-epichlorohydrin-ammonia condensate (average molecular weight 30000, solid content 45%: “Wytex H-90” manufactured by Nagase Sangyo Co., Ltd.) was used as a cationic coagulant and sprayed at a coating booth. The added water-based paint was added in a proportion of 2.5% by weight. In addition, a novolac-type phenolic resin obtained by dissolving a resin in which n is 4 in sodium hydroxide in the general formula (1) (resin content: 20%) is applied to the paint sprayed in the coating booth. 10% by weight was added. Further, an acrylamide-acrylaminoethyltrimethylammonium chloride copolymer (molecular weight: 8 million: “Super Flock 3390” manufactured by Mitsui Cytec Co., Ltd.) as a flocculant is 0.5% by weight with respect to the paint sprayed at the coating booth. Added in proportions.

(Example 2)
In Example 2, the same cationic coagulant as in Example 1 was added in the same amount, and a novolak type phenol resin in which n is 6 in the general formula (1) was dissolved in sodium hydroxide (resin content) 20%) was added at a rate of 10% by weight with respect to the paint sprayed in the paint booth. Further, the same amount of the same flocculant as in Example 1 was added as the flocculant.

(Example 3)
In Example 3, the same cationic coagulant as in Example 1 was added in the same amount, and a novolac type phenol resin in which the resin having n of 8 in the general formula (1) was dissolved in sodium hydroxide (resin content) 20%) was added at a rate of 10% by weight with respect to the paint sprayed in the paint booth. Further, the same amount of the same flocculant as in Example 1 was added as the flocculant.

Example 4
In Example 4, the same cationic coagulant as in Example 2 was added in the same amount, and the same novolak type phenolic resin as in Example 2 was added in half the amount in Example 2. Further, as the flocculant, the same amount of the same flocculant as in Example 2 was added.

(Example 5)
In Example 5, 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 and sprayed at a coating booth. The same novolac type phenol and the flocculant as in Example 1 were added in the same amount.

(Example 6)
In Example 6, diallyldimethylammonium chloride (DADMAC) polymer (average molecular weight 200,000, solid content 40%, “PRP4440” manufactured by SNF) was used as a cationic coagulant, and this was applied to an aqueous paint sprayed at a coating booth. The same novolak type phenol and flocculant as in Example 1 were added in the same amount.

(Example 7)
In Example 7, diallyldimethylammonium chloride (DADMAC) -acrylamide polymer (average molecular weight 130,000, solid content 40%, “Sencafloc DC-7513” manufactured by SENKA) was used as a cationic coagulant at a coating booth. The same amount of the same novolak type phenol and flocculant as in Example 3 was added to the sprayed water-based paint at a ratio of 3% by weight.

(Example 8)
In Example 8, 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. The same novolak type phenolic resin and flocculant as in Example 1 were added in the same amount.

Example 9
In Example 9, the same cationic coagulant and novolac type phenol resin as in Example 1 were added in the same amount, and an acrylamide-acrylic acid copolymer (molecular weight: 17 million: “Super Flock 2360” manufactured by Mitsui Cytec Co., Ltd.) was used as a flocculant. )) Was added at a rate of 1% by weight with respect to the paint sprayed in the paint booth.

(Example 10)
In Example 10, the same cationic coagulant and novolak type phenol resin as in Example 3 were added in the same amount, and acrylamide- [2- (acryloyloxy) ethyl] benzyldimethylammonium chloride. [2- (acryloyloxy) was used as a flocculant. ) Ethyl] trimethylammonium copolymer (molecular weight: 4.5 million: “Ebagulose LDC-100” manufactured by Ebara Engineering Service Co., Ltd.) was added at a ratio of 0.5% by weight to the paint sprayed at the coating booth.

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

(Comparative Example 2)
In Comparative Example 2, dimethylamine-epichlorohydrin condensate (average molecular weight 5000, solid content 50%: “Wytex T-101-50” manufactured by Nagase Sangyo Co., Ltd.) was used as a cationic coagulant and sprayed at a coating booth. It was added at a ratio of 2% by weight based on the finished water-based paint. In addition, as a novolac type phenol resin, a resin in which n is 3 dissolved in sodium hydroxide (resin content: 20%) in the general formula (1) is used, and this is applied to the paint sprayed at the coating booth. 10% by weight was added. Also, no flocculant was added.

(Comparative Example 3)
In Comparative Example 3, the same cationic coagulant and novolac type phenol resin as in Comparative Example 2 were added in the same amount, and an acrylamide-acrylaminoethyltrimethylammonium chloride copolymer (molecular weight: 8 million, manufactured by Mitsui Cytec Co., Ltd.) as a flocculant. “Super Flock 3390”) was added at a ratio of 0.5% by weight to the paint sprayed in the paint booth.

(Comparative Example 4)
In Comparative Example 4, the same cationic coagulant as in Comparative Example 2 was added in the same amount, and a novolac type phenol resin in which n is 2 in the general formula (1) was dissolved in sodium hydroxide (resin This was added at a rate of 10% by weight to the paint sprayed in the paint booth. Further, as the flocculant, the same amount of the same flocculant as in Comparative Example 3 was added.

(Comparative Example 5)
In Comparative Example 5, the same cationic coagulant as in Comparative Example 2 was added in the same amount, and the same novolak type phenolic resin as in Comparative Example 2 was added in an amount three times that in Comparative Example 2. Further, as the flocculant, the same amount of the same flocculant as in Comparative Example 3 was added.

(Comparative Example 6)
In Comparative Example 6, a cationic coagulant was not added, and a novolak type phenol resin obtained by dissolving a resin having n of 4 in sodium hydroxide in the general formula (1) (resin content: 20%) was used. Was added at a ratio of 10% by weight to the paint sprayed in the painting booth. Further, as the flocculant, the same amount of the same flocculant as in Comparative Example 2 was added.

(Comparative Example 7)
In Comparative Example 7, dimethylamine-epichlorohydrin-ammonia condensate (average molecular weight 30000, solid content 45%: “Wastex H-90” manufactured by Nagase Sangyo Co., Ltd.) was used as a cationic coagulant and sprayed at a coating booth. The same amount of the same novolak phenol resin as that of Comparative Example 6 was added, and no flocculant was added.

<Treatment test of booth circulating water>
The treatment test of the booth circulating water was performed by the treatment methods of Examples 1 to 10 and Comparative Examples 1 to 7. As shown in FIG. 1, the wet painting booth used for the test surfaced in the painting booth body 1 for painting, the circulating water tank 2 receiving the booth circulating water flowing down the painting booth body 1, and the circulating water tank 2. A concentration collection tank 3 is provided for concentrating and collecting circulating water containing paint sludge. The paint sprayed in the painting booth body 1 is collected in the booth circulating water and floated and separated in the circulating water tank 2. The floating paint sludge is sent to the concentration recovery tank 3 by the pump 4. Further, the booth circulating water is sent from the bottom of the circulating water tank 2 to the painting booth main body 1 by the pump 5. The concentration recovery tank 3 is a pressurized floating tank, and the paint sludge that has floated is recovered and removed, and the treated booth circulating water is sent to the circulating water tank 2. The cationic coagulant is added to the addition site A between the pump 5 and the painting booth body 1, the novolac type phenol resin is added to the addition site B slightly upstream of the addition site A, and the coagulant is concentrated and recovered. The addition was made at the addition place C between 3 and the pump 4. The amount of water held in this wet painting booth was 500 L, the amount of booth circulating water by the pump 5 was 100 L / min, and the amount of water to the concentration recovery tank by the pump 4 was 30 L / min.

  Using the test wet paint booth configured as described above, while adding a predetermined amount of the above-mentioned chemicals shown in the examples or comparative examples, water paint and oil paint are directed toward the booth circulating water in the paint booth. Spraying was continued for 5 hours at 5 g / min. 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 +200 (μeq / L-booth circulating water). The amount of charge in the booth circulating water was measured by colloid titration.

<Evaluation>
After spraying, booth circulating water was collected and turbidity and foamability were measured. In addition, the tack-free property of the floating paint sludge was measured and evaluated. Turbidity was evaluated according to JIS K 0101. For foaming, 50 ml of circulating water was taken in a cylinder with a stopper, shaken up and down 20 times and allowed to stand, and the foam height after 15 seconds was measured and evaluated. 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。
（カチオン凝結剤）
Ａ−１：ジメチルアミン−エピクロルヒドリン−アンモニア縮合物
Ａ−２：ジメチルアミン−エピクロルヒドリン縮合物
Ａ−３：ジアリルジメチルアンモニウムクロライド(ＤＡＤＭＡＣ)重合体
Ａ−４：ジアリルジメチルアンモニウムクロライド(ＤＡＤＭＡＣ)-アクリルアミド重合体
Ａ−５：ポリエチレンイミン
（ノボラック型フェノール樹脂）
Ｂ−１：上記一般式（１）において、ｎ＝４のノボラック型フェノール樹脂
Ｂ−２：上記一般式（１）において、ｎ＝６のノボラック型フェノール樹脂
Ｂ−３：上記一般式（１）において、ｎ＝８のノボラック型フェノール樹脂
Ｂ−４：上記一般式（１）において、ｎ＝３のノボラック型フェノール樹脂
Ｂ−５：上記一般式（１）において、ｎ＝２のノボラック型フェノール樹脂
（凝集剤）
Ｃ−１：アクリルアミド−アクリルアミノエチルトリメチルアンモニウムクロライド共重
合体
Ｃ−２：アクリルアミド−アクリル酸共重合体
Ｃ−３：アクリルアミド−[２−（アクリロイルオキシ）エチル]ベンジルジメチルアンモ
ニウムクロライド・[２−（アクリロイルオキシ）エチル]トリメチルアンモニウ
ム共重合体

The symbols for treatment chemicals in Table 1 above indicate the following chemicals.
(Cationic coagulant)
A-1: Dimethylamine-epichlorohydrin-ammonia condensate A-2: Dimethylamine-epichlorohydrin condensate A-3: Diallyldimethylammonium chloride (DADMAC) polymer A-4: Diallyldimethylammonium chloride (DADMAC) -acrylamide polymer A-5: Polyethyleneimine (novolak type phenolic resin)
B-1: In the above general formula (1), n = 4 novolac type phenol resin B-2: In the above general formula (1), n = 6 novolac type phenol resin B-3: In the above general formula (1) N = 8 novolac type phenol resin B-4: in the above general formula (1), n = 3 novolac type phenol resin B-5: in the above general formula (1), n = 2 novolac type phenol resin (Flocculant)
C-1: Acrylamide-acrylaminoethyltrimethylammonium chloride copolymer C-2: Acrylamide-acrylic acid copolymer C-3: Acrylamide- [2- (acryloyloxy) ethyl] benzyldimethylammonium chloride [2- (Acryloyloxy) ethyl] trimethylammonium copolymer

  As shown in Table 1, a novolak type phenol resin of n = 4, n = 6 or n = 8 and a cationic coagulant in the general formula (1) are added, and the charge of the booth circulating water is −50 to +200. In Examples 1 to 10 in which the addition amount of the cationic coagulant was adjusted so as to be (μeq / L-booth circulating water), the turbidity was 100 degrees or less and the foaming property was 10 mm or less. It can be seen that the separation of the paint and the suppression of foaming of the circulating water are efficiently performed. 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 4 using the novolak type phenol resin of n = 3 or n = 2 in the general formula (1), the turbidity is maintained even when the charge of the booth circulating water is adjusted to an appropriate range. The foaming property was as high as 420 to 610 degrees and 34 to 42 mm, and the separation of the paint in the booth circulating water was extremely insufficient, and the suppression of foaming of the circulating water was insufficient. Moreover, the tack-free property was also evaluated as x, and adhesion of the paint to the booth circulating water piping and the like was confirmed.
In Comparative Example 5, the amount of addition of the novolak type phenol resin of n = 3 in the general formula (1) is increased, but the foaming suppression effect is slightly increased, but is still insufficient, and the solid-liquid separation effect and It can be seen that the detackifying effect is also insufficient.
In Comparative Example 6, the specific novolak type phenol resin and the flocculant in the present invention were added and the cationic coagulant was not added. However, the solid-liquid separation of the water-based paint was insufficient, and foaming suppression was not effective. It was enough.
In Comparative Example 7, the cationic coagulant and the specific novolac type phenol resin in the present invention were added, and the flocculant was not added. However, the fine paint particles were dispersed in the circulating water to give high turbidity. It was. Dispersion of the paint particles reduced the amount of paint sludge collected, and also acted to stabilize the foam, increasing foamability.
In Comparative Example 5, the specific novolak type phenol resin and the flocculant in the present invention were added, and the cationic coagulant was not added. However, the solid-liquid separation of the water-based paint was insufficient, and foaming suppression was not effective. It was enough.
In Comparative Example 6, the cationic coagulant and the specific novolac type phenol resin in the present invention were added, and the flocculant was not added, but the fine paint particles were dispersed in the circulating water and became high turbidity. It was. Dispersion of the paint particles reduced the amount of paint sludge collected, and also acted to stabilize the foam, increasing foamability.
From the above results, it was found that the foam suppression effect is greatly influenced by the degree of polymerization of the novolak type phenol resin, and the foam suppression effect is excellent when n is in the range of 4-8.

  The present invention is not limited to the description of the embodiments of the invention. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used as a method for treating booth circulating water when a water-based paint and / or an oil-based paint are included 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 ... Painting booth body 2 ... Circulating water tank 3 ... Concentration collection tank 4 ... Concentration collection tank feed pump 5 ... Circulation pump A ... Location of addition of cationic coagulant B ... Location of addition of novolac type phenol resin C ... Location of addition of flocculant

Claims (6)

A method for treating circulating water in a wet paint booth containing a water-based paint and / or an oil-based paint,
Adding a novolak-type phenol resin represented by the following general formula (1) (wherein a methylol group may be bonded to the terminal benzene ring), a cationic coagulant, and an aggregating agent to the booth circulating water. A characteristic method for treating circulating water in a painting booth.

  Cationic coagulants include polyacrylaminoethyltrimethylammonium chloride, dicyandiamide-formaldehyde condensate, dicyandiamide-diethylenetriamine condensate, diallyldimethylammonium chloride-sulfur dioxide copolymer, dimethylamine-epichlorohydrin condensate, dimethylamine-epichlorohydrin-ammonia condensate. The processing method of the coating booth circulating water of Claim 1 characterized by being 1 or more types chosen from a product, diallyldimethylammonium chloride polymer, diallyldimethylammonium chloride-acrylamide copolymer, and polyethyleneimine.   The coating booth circulating water treatment method according to claim 2, wherein the cationic coagulant has a molecular weight of 2,000 to 500,000.   The flocculant is polyacrylamide, acrylamide-acrylic acid copolymer, acrylamide-acrylaminoethyltrimethylammonium chloride copolymer, acrylamide-methacrylaminoethyltrimethylammonium chloride copolymer, acrylamide- [2- (acryloyloxy) ethyl]. 4. The method for treating booth circulating water according to claim 1, wherein the booth circulating water is one or more selected from benzyldimethylammonium chloride / [2- (acryloyloxy) ethyl] trimethylammonium copolymer. 5. .   The booth circulating water treatment method according to claim 4, wherein the flocculant has a molecular weight of 2,000,000 to 20,000,000.   The method for treating booth circulating water according to any one of claims 1 to 5, wherein the addition amount of the cationic coagulant is adjusted so that the amount of charge in the booth circulating water becomes -50 to +200 µeq / L.

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