JP2011194306A - Method for treating wet coating booth-circulating water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating wet coating booth-circulating water capable of effectively solid-liquid separating wet coating booth-circulating water.SOLUTION: In the water treatment method for the wet coating booth-circulating water system provided with a first circulating water system in which the circulating water is supplied from a circulating water tank 1 to a wet coating booth 2 and then returned to the circulating water tank 1 and a second circulating water system in which the circulating water is supplied from the circulating water tank 1 to a solid-liquid separation device 20 and the separated water is returned to the circulating water tank 1, a cationic polymer and/or an anionic polymer is added, or an amphoteric polymer is added to the circulating water, which is then filtered with a net 23. Further, a phenolic resin, and an organic coagulant and/or an inorganic coagulant is added to the first circulating water returned from the wet coating booth 2 to the circulating water tank 1.

Description

  The present invention relates to a method for treating circulating wet paint booth water, and more particularly, to a method for treating circulating wet paint booth water that efficiently recovers paint sludge from wet circulating booth circulating water.

  In the painting process in the automobile industry, the yield of paint (paint) sprayed on the vehicle body is generally 60 to 80%, and 40 to 20% of the paint used is excess paint to be removed in the next process. The excessively sprayed excess paint is usually collected in a wet painting booth by washing with water, and the washing water is recycled.

FIG. 2 is a system diagram showing a circulating water system in this wet painting booth. Water in the circulating water tank 1 is sent to the wet painting booth 2 through a pipe 11 having a pump P ₁ and sprinkled in the wet painting booth 2. Is done. Water sprinkled in the wet painting booth 2 and collected excess paint is returned to the circulating water tank 1 through the pipe 12 (hereinafter, the water is sent from the circulating water tank 1 to the wet painting booth 2 and returned to the circulating water tank 1. The circulating water system may be referred to as a “first circulating water system”). Water in the circulation water tank 1 is water from the pipe 13 having a pump P ₂ to the solid-liquid separation device of the centrifuge 3 and the like, paint sludge is separated and recovered. The treated water from which the paint sludge has been removed by the centrifugal separator 3 is returned to the circulating water tank 1 through the pipe 14 (hereinafter, the circulating water system which is sent from the circulating water tank 1 to the centrifugal separator 3 and returned to the circulating water tank 1). May be referred to as a “second circulating water system”). In some cases, a water-permeable partition plate 1 </ b> A is provided in the circulating water tank 1 to prevent contamination from being mixed into the washing water fed to the wet coating booth 2. Further, the circulating water tank 1 may be provided with a stirrer 1B to prevent sedimentation of the collected paint.

  Among the circulating water systems of such wet coating booths, the first circulating water system has a high adhesiveness of the excess paint collected in the washing water, so it can be used in spray booth water curtains, piping systems, spray nozzles, etc. Adhesion causes clogging of piping and nozzles, and the water washing efficiency is significantly reduced. Further, most of the surplus paint is deposited on the bottom of the booth pit and the circulation pit of the spray booth, and the deposited paint is solidified into a rubber-like shape over time, which requires much labor and labor for cleaning and removal.

  In the second circulating water system, surplus paint adheres in the same manner.

  As such a wet paint booth circulating water treatment method, JP 2001-170528 A (Patent Document 1) describes that clay minerals such as sepiolite are added to the first circulating water system and the second circulating water system, respectively. Has been.

  Japanese Patent Application Laid-Open No. 2004-337671 (Patent Document 2) describes that a phenolic resin and a cationic polymer are added to the first circulating water for aggregation treatment. In Patent Document 2, after the aggregation treatment, the floc is separated and collected by floating separation, rotary screen, bar screen, cyclone, centrifuge, filtration device, or the like (paragraph 0033).

  In JP-A-2005-95819 (Patent Document 3), anodic electrolysis of aluminum is performed in the first circulating water, and a cationic polymer and, if necessary, a nonionic or anionic polymer flocculant are added in the second circulating water. It is described to be added. In Patent Document 3, flotation separation or centrifugation is employed as the solid-liquid separation means in the second circulating water.

JP 2001-170528 A JP 2004-337671 A JP-A-2005-95819

  When solid-liquid separation is performed with the second circulating water, the sludge tends to adhere to solid-liquid separation means such as a centrifuge or a filter medium.

  An object of this invention is to provide the processing method of the wet coating booth circulating water which can perform solid-liquid separation of the wet coating booth circulating water efficiently.

  In the method for treating wet paint booth circulating water of the present invention (Claim 1), a cationic polymer and / or an anionic polymer is added to the paint-containing water from the wet paint booth, or an amphoteric polymer is added, Next, it is filtered by a net.

  The wet paint booth circulating water treatment method according to claim 2 is characterized in that, in claim 1, the diameter of the net is distributed in a range of 0.1 to 1 mm.

  The wet paint booth circulating water treatment method according to claim 3 is the first circulating water system according to claim 1 or 2, wherein the paint-containing water from the wet paint booth is received in the circulating water tank and is sent from the circulating water tank to the wet coating booth. A wet paint booth circulating water system having a second circulating water system that feeds water from the circulating water tank to a solid-liquid separator and returns the separated water to the circulating water tank. The water flowing into the solid-liquid separator is characterized by containing a cationic polymer and / or an anionic polymer or an amphoteric polymer.

  According to a fourth aspect of the present invention, there is provided a wet painting booth circulating water treatment method according to the third aspect, wherein water supplied from the circulating water tank to a solid-liquid separator is first introduced into a small tank, and the outflow water from the small tank is supplied to the net. It is characterized by filtering with.

  The wet paint booth circulating water treatment method according to claim 5 is characterized in that, in claim 3 or 4, the cationic polymer is added to the second circulating water system.

  The wet paint booth circulating water treatment method according to claim 6 is the method according to any one of claims 3 to 5, wherein phenolic resin and organic condensation are performed on water returning from the wet paint booth to the circulating water tank in the first circulating water system. An agent and / or an inorganic coagulant is added.

  In the present invention, both the cationic polymer and / or the anionic polymer are added to the paint-containing water from the wet coating booth, or the amphoteric polymer is added, and then filtered through a net, thereby efficiently containing the water content. Low paint sludge. Further, by adding both a cationic polymer and an anionic polymer or an amphoteric polymer to the second circulating water, a strong floc having a higher density and larger than when only a cationic polymer or an anionic polymer is added. Produces. By filtering the flocs with a net having a relatively large aperture, clogging of the net is prevented or suppressed, and the filtering is performed efficiently.

  When the circulating water to be filtered is first received in a small tank and then filtered through a net, flocs grow further in the small tank, and thus filtration is performed more efficiently.

  Stabilize and separate the paint components in the return water from the wet paint booth by adding phenolic resin and organic coagulant and / or inorganic coagulant to the water returning to the circulating water from the wet paint booth. Can do.

It is a flowchart of the processing method of the wet paint booth circulating water which concerns on embodiment. It is a flowchart of the conventional wet paint booth circulating water.

  Hereinafter, the present invention will be described in more detail.

  In the present invention, a cationic polymer and / or an anionic polymer is added to the paint-containing water from the wet coating booth, or an amphoteric polymer is added, and then filtered through a net to separate flocs.

  Here, when both the cationic polymer and the anionic polymer are added, the cationic polymer and the anionic polymer are firmly bonded, and a high density, large and strong floc is formed. The same applies when amphoteric polymers are used.

  The cationic polymer used in the treatment method of the present invention has a cationic structural unit derived from a quaternary ammonium salt of (meth) acrylic acid ester, and a benzyl group is present on the nitrogen atom of the quaternary ammonium salt. Preferred examples include a polymer formed by bonding.

  In the cationic hydrophobic polymer, a cationic structural unit derived from a quaternary ammonium salt of (meth) acrylic acid ester, in which a benzyl group is bonded to a nitrogen atom of a quaternary ammonium salt, has the following general formula ( The structural unit (A) represented by I) can be preferably exemplified.

In general formula (I), R < ¹ > shows a hydrogen atom or a methyl group, R < ² > and R < ³ > show a C1-C4 alkyl group each independently. Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, and tert-butyl group.

A ¹ represents a linear or branched alkylene group having 2 to 4 carbon atoms, and specific examples include an ethylene group, a propylene group, a trimethylene group, and various butylene groups. (X ¹ ) ^a− represents an anion having a valence of a. a is usually an integer of 1 to 3. Specific examples of the anion include halogen ions such as chlorine ion, fluorine ion, bromine ion and iodine ion, sulfate ion, nitrate ion, phosphate ion, methylsulfate ion and perchlorate ion. Of these, halogen ions are preferred.

  In the present invention, two or more different structural units (A) represented by the general formula (I) may be introduced into the polymer.

  Examples of the quaternary ammonium salt of the (meth) acrylic acid ester of the monomer that forms the structural unit (A) include (meth) acryloyloxyalkyl (benzyl) dialkylammonium salts. Specifically, [2- (acryloyloxy) ethyl] benzyldimethylammonium salt, [2- (acryloyloxy) ethyl] benzyldiethylammonium salt, [2- (acryloyloxy) ethyl] benzylethylmethylammonium salt, [2 -(Methacryloyloxy) ethyl] benzyldimethylammonium salt, [2- (methacryloyloxy) ethyl] benzyldiethylammonium salt, [2- (methacryloyloxy) ethyl] benzylethylmethylammonium salt, [3- (acryloyloxy) propyl] Benzyldimethylammonium salt, [3- (acryloyloxy) propyl] benzyldiethylammonium salt, [3- (acryloyloxy) propyl] benzylethylmethylammonium salt, [3- (methacrylo Yloxy) propyl] benzyl dimethyl ammonium salts, [3- (methacryloyloxy) propyl] benzyl diethyl ammonium salts, and the like [3- (methacryloyloxy) propyl] benzyl methyl ammonium salts.

  These monomers may be used individually by 1 type, and may be used in combination of 2 or more type.

  Thus, a polymer having a cationic structural unit derived from a quaternary ammonium salt of a (meth) acrylic acid ester in which a benzyl group is bonded to a nitrogen atom of a quaternary ammonium salt is a highly hydrophobic benzyl. The hydrophobic part of the surplus paint and the hydrophobic part of the surplus paint detackifying agent such as the above-mentioned phenolic resin are bonded to the base, and furthermore, since this hydrophobic polymer is cationic, the anion-charged paint particles It is easy to combine with an anionic phenolic resin, and as a result, a strong and coarse floc is formed. In addition, since the polymer is strongly hydrophobic, this floc is easily separated from water and has an effect of being easily floated.

  In the processing method of this invention, the copolymer which has a nonionic structural unit and / or another cationic structural unit with the said (A) structural unit can be used as a cationic polymer. Although there is no restriction | limiting in particular about the said nonionic structural unit and another cationic structural unit, The copolymer shown below can be used preferably.

  In the treatment method of the present invention, as a cationic hydrophobic polymer, a copolymer having a nonionic (B) structural unit represented by the following general formula (II) together with the (A) structural unit (hereinafter, (Referred to as copolymer I).

In the general formula (II), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a dimethylaminoalkyl group. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. Examples of the dimethylaminoalkyl group include 2-dimethylaminoethyl group and 3-dimethylaminopropyl group.

  In the present invention, two or more different types of structural units (B) represented by the general formula (II) may be introduced into the copolymer I.

  Examples of the monomer that forms the structural unit (B) include acrylamide, N-methylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, and N, N. -Diisopropylacrylamide, N-ethyl-N-methylacrylamide, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-isopropylmethacrylamide, N, N-dimethylmethacrylamide, N, N-diethylmethacrylamide, N, N-diisopropylmethacrylamide, N-ethyl-N-methylmethacrylamide, N- (2-dimethylaminoethyl) acrylamide, N- (2-dimethylaminoethyl) methacrylamide, N- (3-dimethylamido Propyl) acrylamide, (meth) acrylamides such as N- (3- dimethylaminopropyl) methacrylamide. These monomers may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content ratio of the structural unit (A) and the structural unit (B) in the copolymer I is preferably 2: 8 to 9: 1 in terms of molar ratio from the viewpoint of cohesive performance with respect to the surplus paint, and 3: 7 ~ 6: 4 is more preferred.

  In the treatment method of the present invention, as a cationic hydrophobic polymer, a copolymer having a cationic (C) structural unit represented by the following general formula (III) together with the (A) structural unit (hereinafter, (Referred to as copolymer II).

In general formula (III), R < ⁷ > shows a hydrogen atom or a methyl group, and R < ⁸ >, R < ⁹ > and R < ¹⁰ > show a C1-C4 alkyl group each independently. Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, and tert-butyl group.

A ² represents a linear or branched alkylene group having 2 to 4 carbon atoms, and specific examples include an ethylene group, a propylene group, a trimethylene group, and various butylene groups. (X ² ) ^b− represents an anion having a valence b. b is usually an integer of 1 to 3. Specific examples of the anion include halogen ions such as chlorine ion, fluorine ion, bromine ion and iodine ion, sulfate ion, nitrate ion, phosphate ion, methylsulfate ion and perchlorate ion. Of these, halogen ions are preferred.

  In the present invention, two or more different types of structural units (C) represented by the general formula (III) may be introduced into the copolymer (II).

  Examples of the monomer that forms the structural unit (C) include (meth) acryloyloxyalkyl (trialkyl) ammonium salts. Specifically, [2- (acryloyloxy) ethyl] trimethylammonium salt, [2- (acryloyloxy) ethyl] triethylammonium salt, [2- (acryloyloxy) ethyl] ethyldimethylammonium salt, [2- (methacryloyl) Oxy) ethyl] trimethylammonium salt, [2- (methacryloyloxy) ethyl] triethylammonium salt, [2- (methacryloyloxy) ethyl] ethyldimethylammonium salt, [3- (acryloyloxy) propyl] trimethylammonium salt, [3 -(Acryloyloxy) propyl] triethylammonium salt, [3- (acryloyloxy) propyl] ethyldimethylammonium salt, [3- (methacryloyloxy) propyl] trimethylammonium salt, [3- Methacryloyloxy) propyl] triethylammonium salts, and the like [3- (methacryloyloxy) propyl] dimethylammonium salt.

These monomers may be used individually by 1 type, and may be used in combination of 2 or more type.
The content ratio of the structural unit (A) and the structural unit (C) in the copolymer II is preferably 8: 2 to 2: 8 in terms of molar ratio from the viewpoint of aggregation performance with respect to surplus paint, and 6: 4. ~ 4: 6 is more preferable.

  In the treatment method of the present invention, as the cationic polymer, a copolymer having the nonionic (B) structural unit and the cationic (C) structural unit together with the (A) structural unit (hereinafter referred to as copolymer). (Referred to as polymer III) can be used particularly preferably. The content ratio of the structural unit (A), the structural unit (B), and the structural unit (C) in the copolymer III is 5 to 90% on a molar basis from the viewpoint of aggregation performance with respect to the excess paint, It is preferably 30 to 90% and 0 to 90%, more preferably 10 to 40%, 50 to 70%, and 10 to 40%.

  Representative examples of the copolymer III include acrylamide / [2- (acryloyloxy) ethyl] benzyldimethylammonium chloride / [2- (acryloyloxy) ethyl] trimethylammonium chloride, acrylamide / [3- (acryloyloxy) propyl. ] Benzyldimethylammonium chloride / [2- (acryloyloxy) ethyl] trimethylammonium chloride, acrylamide / [2- (acryloyloxy) ethyl] benzyldimethylammonium chloride / [3- (acryloyloxy) propyl] trimethylammonium chloride, acrylamide / [3- (acryloyloxy) propyl] benzyldimethylammonium chloride / [3- (acryloyloxy) propyl] trimethylammonium chloride Or the like can be mentioned de.

  The weight average molecular weight of the cationic polymer used in the treatment method of the present invention is 0.1 mol / L sodium chloride as an eluent by gel permeation chromatography method (GPC method) from the viewpoint of coagulation performance of excess paint. The value in terms of polyethylene glycol measured using an aqueous solution is preferably 6 million or more, more preferably 9 million to 11 million.

  There is no restriction | limiting in particular about the polymerization method of this cationic polymer, A general polymerization method is employable. For example, in the case of aqueous solution polymerization, potassium persulfate, ammonium persulfate, 2,2'-azobis (2-amidinopropane) dihydrochloride, a redox initiator, or the like can be used as a polymerization initiator. In the case of reverse phase suspension polymerization, the same polymerization initiator as described above can be used. On the other hand, in the case of reverse phase emulsion polymerization, in addition to the polymerization initiator, azobisisobutyro Polymerization may be performed using a water-insoluble initiator such as nitrile or benzoyl peroxide.

  The cationic polymer can be used in any form of an aqueous solution, a suspension, and an emulsion. The addition amount of the cationic polymer is preferably about 0.1 to 10%, particularly about 0.5 to 2% with respect to the surplus paint.

  As the anionic polymer, a copolymer of sodium acrylate or sodium methacrylate and acrylamide or methacrylamide (anionization degree of 22 to 28 mol%) is suitable. The weight average molecular weight of the anionic polymer is preferably about 8 million to 10 million. The addition amount of the anionic polymer is preferably about 0.1 to 10%, particularly about 0.5 to 2% with respect to the surplus paint.

  When the cationic polymer and the anionic polymer are used in combination, the ratio of the addition amount of the cationic polymer to the anionic polymer is preferably about 90:10 to 10:90, particularly about 80:20 to 20:80 by weight. is there.

  Any amphoteric polymer may be used, but a copolymer of sodium acrylate or sodium methacrylate and acrylamide or methacrylamide and an acrylate or quaternary ammonium salt of methacrylic acid (anion / cation molar ratio of 0.00). 2 to 2.0) and the like are preferable. The weight average molecular weight of the amphoteric polymer is preferably about 8 million to 10 million, and the addition amount is preferably 0.1 to 10%, particularly preferably about 0.5 to 2.0% with respect to the surplus paint.

  As the net, a thermoplastic synthetic resin yarn having a yarn diameter of 1 to 1000 μm, particularly about 10 to 100 μm, is braided not only vertically and horizontally but also diagonally and heated and pressed to fuse the yarns together. As this synthetic resin, polyolefins such as polyethylene and polypropylene are suitable. If the diameter of the net (the length of the longest part from the end of the hole) is too small, clogging tends to occur, and if it is too large, the floc will pass, so 0.1-1 mm, especially 0.2-0. About 8 mm is preferable. By using nets that are braided randomly, not only vertically and horizontally but also diagonally, the shape of the openings becomes various, and the holes with various diameters are randomly distributed within the range of the diameters. Clogging due to collected sludge is less likely to occur.

  In the present invention, as shown in FIG. 1, water is supplied from the circulating water tank 1 to the wet coating booth 2 and returned to the circulating water tank 1, and water is supplied from the circulating water tank 1 to the solid-liquid separator 20. It is suitable for applying to a processing method of a wet painting booth circulating water system having a second circulating water system for returning separated water to the circulating water tank.

  In this case, it is preferable to add a phenolic resin and an organic coagulant to the first circulating water system returning from the wet coating booth 2 to the circulating water tank 1. By adding the phenolic resin and the organic coagulant, the paint components in the return water from the wet coating booth can be stably aggregated and separated. The phenolic resin is more compatible with a paint made of petroleum-derived organic matter than an inorganic agent.

  Examples of the phenolic resin include a condensate of phenols such as phenol, cresol, and xylenol and an aldehyde such as formaldehyde, or a modified product thereof, and a phenolic resin before being crosslinked and cured. Specifically, a condensation product of phenol and formaldehyde, a condensation product of cresol and formaldehyde, a condensation product of xylenol and formaldehyde, an alkyl-modified phenol resin obtained by alkylating these phenol resins, polyvinyl phenol, etc. Can be mentioned. These phenolic resins may be novolak type or resol type. The molecular weight is 3,000 or less, preferably 2,000 or less. These may be used alone or in combination of two or more.

  Since these phenolic resins are hardly soluble in water, they are preferably used in the form of a solution or emulsion by dissolving or dispersing them in a solvent that is soluble in water. Solvents used include ketones such as acetone, esters such as methyl acetate, water-soluble organic solvents such as alcohols such as methanol, alkaline aqueous solutions, amines, etc., but alkalis such as sodium hydroxide aqueous solution and potassium hydroxide aqueous solution. It is preferable to use it dissolved in an aqueous solution.

  When using a phenolic resin as an alkaline aqueous solution, the alkaline aqueous solution is preferably in the range of an alkali agent concentration of 1 to 25% by mass and a phenolic resin concentration of 1 to 50% by mass.

  The addition amount of the phenolic resin is usually 1 mg / L or more, preferably 5 mg / L or more as an active ingredient amount (resin solid amount) with respect to the wet paint booth circulating water. ) Is usually 0.1% by mass or more, preferably 0.5% by mass or more. If the amount of phenolic resin added is less than these proportions, a sufficient detackifying effect cannot be obtained. However, even if the amount of phenolic resin added is excessively large, improvement in the tack-free effect corresponding to the amount added may not be obtained, and foaming may occur. The amount of resin added is preferably 1,000 mg / L or less, particularly preferably 5 to 200 mg / L, as the amount of active ingredient, and preferably 100% by mass or less, particularly as the amount of active ingredient with respect to the paint in the circulating water. Preferably it is 0.5-10 mass%.

  The organic coagulant is preferably a cationic one, for example, dimethyldiallylammonium chloride polymer, alkylamine-epichlorohydrin condensate, ethyleneimine polymer, alkylene dichloride-polyalkylene polyamine condensate, dimethylaminoethyl acrylate polymer, Mention may be made of cationic organic polymer compounds such as dimethylaminoethyl methacrylate polymer and polyvinylamidine. As the inorganic coagulant, for example, aluminum sulfate, polyaluminum chloride or the like can be used. These organic coagulants and inorganic coagulants may be used alone or in combination of two or more.

  The organic coagulant and the inorganic coagulant are used for the purpose of, for example, neutralizing the charge of the suspended material of the excess paint that has been detackified by the above-mentioned paint detackifier and forming fine flocs.

  The addition amount of the organic coagulant and inorganic coagulant is usually 5 mg / L or more, preferably 10 to 30 mg / L as an active ingredient amount (resin solid content) with respect to the wet coating booth circulating water, The amount of the active ingredient with respect to the paint (solid content) in the circulating water is usually about 0.5 to 10% by mass, preferably 0.8 to 1.5% by mass.

  There is no restriction | limiting in particular about the usage form of the said organic coagulant and an inorganic coagulant, Any of aqueous solution form, suspension form, and emulsified liquid form may be sufficient.

  Details of the flow of FIG. 1 will be described next. This detailed flow is an example of the present invention, and the present invention is not limited to this.

As in the case of FIG. 2, the water in the circulating water tank 1 is sent to the wet painting booth 2 through the pipe 11 having the pump P ₁ and sprinkled into the wet painting booth 2. Water sprayed in the wet coating booth 2 and collected excess paint is returned to the circulating water tank 1 through the pipe 12 (first circulating water system). It is to be noted that a water-permeable partition plate similar to that shown in FIG. 2 may be provided in the circulating water tank 1 to prevent contamination from being contained in the washing water sent to the wet coating booth 2. May be provided to prevent sedimentation of the collected paint.

In this embodiment, the pipe 14 branches from the pipe 11 on the discharge side of the pump P ₁ , a cationic polymer is added in the middle of the pipe 14, and water is sprinkled into the circulating water tank 1 from the sprinkler 15 at the end of the pipe 14. To do.

Water in the circulation water tank 1 is water in the solid-liquid separator 20 by the pump P ₂ pipe 18, the paint sludge is separated and recovered. The treated water from which the paint sludge has been removed by the solid-liquid separator 20 is returned to the circulating water tank 1 through the pipe 19 (second circulating water system).

The pump P <b> ₂ is a submersible pump and is suspended by a plurality of floats 16 and 16 that float on the water surface in the circulating water tank 1. In the upper part of the pump P _2, anionic polymer is added to water in the circulation water tank 1.

  The solid-liquid separation device 20 includes a main tank 21, a basket body 22 disposed in the main tank 21, and a net 23 as a filter medium disposed in the basket body 22. The net 23 has a bag shape along the inner surface of the cage body 22 and is disposed in the cage body 22 so as to open upward. A small tank 24 is disposed in the upper region of the bag-like net 23, and water from the pipe 18 is introduced into the small tank 24 and overflows the small tank 24 and falls into the bag-like net 23. Has been. The water that has passed through the net 23 flows out from the lower outlet of the main tank 21 to the circulating water tank 1 through the pipe 19. Since the floc grows in the small tank 24, the floc collecting efficiency by the net 23 is improved.

  In this embodiment, a phenolic resin and an organic coagulant are added to the pipe 12 that returns the circulating water tank 1 water from the wet coating booth 2. Thereby, the paint component in the return water from the wet coating booth 2 aggregates to form a primary aggregated floc. This primary agglomerated floc grows to a secondary agglomerated floc by the cationic polymer and the anionic polymer. The phenolic resin, the organic coagulant, the cationic polymer, and the anionic polymer are preferably appropriately selected according to the characteristics and properties of the wastewater from the wet coating booth 2 and selected.

  In addition, when the collection sludge in the net 23 increases, it is preferable that the tub 24 is shifted, the net 23 is taken out, and a new net 23 is attached.

  In the present invention, the sediment in the circulating water tank 1 may be sucked and discharged into the small tank 24 or the net 23, and the sediment may be collected by the net 23.

[Example 1]
In the system of FIG. 1 in which the wet paint booth is an automobile bumper paint booth, a phenolic resin and an organic coagulant are added to the return water pipe 12 from the booth 2, and a cationic polymer is added to the pipe 14. , 16 was added to the region surrounded by the anionic polymer. The main conditions are as follows.
<Conditions>
Paint used for bumper paint: Acrylic water-based topcoat paint Retained water: 50 m ³
Circulating water volume of pipes 11 and 12: 10 m ³ / min
Bypass circulation water volume of piping 14: 30 L / min
Phenol resin: Phenol / formaldehyde condensate (liquid), novolak type, molecular weight of about 1700, solid content 32% by mass
Amount of phenolic resin added: 20 mL / min
Organic coagulant: dimethyl / epichlorohydrin condensate (liquid), weight average molecular weight 100,000, solid content 50% by mass
Organic coagulant addition amount: 1 mL / min
Cationic polymer: acrylamide / [2- (acryloyloxy) ethyl] benzyldimethylammonium chloride / [2- (acryloyloxy) ethyl] trimethylammonium chloride copolymer (liquid), copolymerization molar ratio 66/17/17, weight Average molecular weight 10 million, solid content 24% by mass
Cationic polymer addition amount: 3 mL / min
Anionic polymer: emulsion of sodium acrylate and acrylamide copolymer (anionic degree 22-28) (evaporation residue 40-45%)
Anionic polymer addition amount: 3 mL / min
Capacity of tub 24: 70L
The volume of the bag-like net 23: 1000L
Net 23: Polyethylene yarn braided at random, the shape of the opening of the net is random, and the aperture diameter is randomly distributed from 0.1 to 1 mm. Water supply amount of the pump P ₂ : 30 L / min

This operation was performed for 20 hours, and the average filtered water amount for 20 hours, the sludge amount collected (collected) by the net 23, and the moisture content thereof were measured. The results are shown in Table 1. Incidentally, the pump P ₂ stops when it becomes a bag-shaped net 23 likely overflow water, after the water level in the bag-shaped net 23 is lowered, and so as to re-operate the pump P _2.

[Example 2]
The operation was performed in the same manner as in Example 1 except that the anionic polymer was not added. Table 1 shows the measurement results of the average filtered water amount, the recovered sludge amount and the sludge moisture content for 20 hours.

[Comparative Example 1]
The same procedure as in Example 1 was used except that a commercially available flexible container bag made of polypropylene woven fabric (diameter of thread: about 2 mm, opening shape: square, opening diameter: about 0.5 mm) was used instead of net 23. Drove. Table 1 shows the measurement results of the average filtered water amount, the recovered sludge amount and the sludge moisture content for 20 hours.

[Example 3]
The operation was performed in the same manner as in Example 1 except that the tub 24 was not installed. Table 1 shows the measurement results of the average filtered water amount, the recovered sludge amount and the sludge moisture content for 20 hours.

  As shown in Table 1, according to Examples 1 to 3, paint sludge can be collected efficiently, and the moisture content of the collected sludge is low. In particular, Example 1 has a larger amount of filtered water and higher treatment efficiency than Examples 2 and 3.

DESCRIPTION OF SYMBOLS 1 Circulating water tank 2 Wet coating booth 16 Float 20 Solid-liquid separator 21 Main tank 22 Basket body 23 Net 24 Small tank

Claims (6)

  A method for treating circulating water in a wet paint booth, comprising adding a cationic polymer and / or an anionic polymer to the paint-containing water from the wet paint booth, or adding an amphoteric polymer and then filtering through a net .   In Claim 1, the aperture diameter of a net is distributed to 0.1-1 mm, The processing method of the wet paint booth circulating water characterized by the above-mentioned. In claim 1 or 2, a first circulating water system that receives paint-containing water from a wet painting booth in a circulating water tank and feeds water from the circulating water tank to the wet painting booth;
A process for treating a wet paint booth circulating water system having a second circulating water system for sending water from the circulating water tank to a solid-liquid separator and returning the separated water to the circulating water tank,
A treatment method for circulating water in a wet paint booth, characterized in that a cationic polymer and / or an anionic polymer are contained in the inflow water to the solid-liquid separator of the second circulating water system or an amphoteric polymer is contained.   4. The wet paint booth circulating water according to claim 3, wherein water supplied to the solid-liquid separator from the circulating water tank is first introduced into the small tank, and the outflow water from the small tank is filtered through the net. Processing method.   5. The wet paint booth circulating water treatment method according to claim 3, wherein the cationic polymer is added to the second circulating water system.   6. The phenol resin and the organic coagulant and / or the inorganic coagulant are added to water returning from the wet painting booth to the circulating water tank in the first circulating water system according to claim 3. Wet painting booth circulating water treatment method.

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