JP5407706B2 - Wet paint booth circulating water treatment method - Google Patents

Description

  The present invention is a wet coating booth in which a phenolic resin, a coagulant, and a cationic hydrophobic polymer are added to circulating water, and then the surplus paint is separated by floating separation, and the separated surplus paint is further subjected to solid-liquid separation treatment. The present invention relates to a treatment method for circulating water in a painting booth, and in particular, relates to a method for improving the dewatering property of the surplus paint separated by floating separation and the compaction property of the surplus paint by removing bubbles from the surplus paint.

Conventionally, various paints are spray-painted in the painting process of the automobile industry, home appliances, metal product manufacturing industries, and the like. Industrially used paints are roughly classified into solvent-based paints and water-based paints, and each paint is used alone or in combination.
Of these, water-based paints are broadly classified into three types, water-soluble, dispersion-type, and emulsion-types, but since all use water as the main solvent, they are not flammable and are safe and hygienic. In recent years, its application range has been expanded because it has the advantage that there is no fear of pollution caused by solvents.

By the way, in the coating process in various industries, the yield of the paint sprayed on the object to be coated is not necessarily 100%. For example, in the automobile industry, it is about 60 to 80%, and 40 to 20% of the used paint is Excess paint to be removed in the next step. In order to collect the excessively sprayed excess paint, it is usually treated in a wet painting booth by washing with water, and the washing water is recycled.
In this case, since the water-based paint is soluble or dispersed in water and solid-liquid separation is difficult, it remains and accumulates in the circulating water of this wet paint booth, causing the following problems.

(A) Circulating water becomes highly viscous and highly viscous, increasing the load of the circulating pump, and if it is remarkable, the circulation becomes impossible and the operation stops.
(B) Paint deposited and insolubilized, dust other than paint, and SS components cause clogging troubles in nozzles and piping systems and troubles in adhesion to water film plates.
(C) A foaming obstacle is generated.
(D) Since the circulating water becomes high COD and high BOD, it rots and the working environment deteriorates due to the odor of rot. In addition, because of high COD and high BOD, wastewater treatment becomes difficult and the load on the treatment apparatus increases.

In order to solve such a problem, coagulation treatment of wet paint booth circulating water and solid-liquid separation of surplus paint are performed, and Patent Document 1 discloses a coagulation treatment method of wet paint booth circulating water. In the upstream of the wet paint booth circulating water line, a fine floc is formed by adding surplus paint detackifier such as phenolic resin and organic coagulant to the circulating water, and on the downstream side of the circulating water line, There has been proposed a wet booth circulating water treatment method for forming coarse flocs by adding a cationic hydrophobic polymer.
Further, Patent Document 2 has a cationic structural unit derived from a quaternary ammonium salt of (meth) acrylic acid ester as a treatment agent effective for the treatment of such wet paint booth circulating water, and A wet paint booth circulating water treatment agent containing a cationic polymer in which a benzyl group is bonded to a nitrogen atom of a quaternary ammonium salt has been proposed.

  Conventionally, the solid content (soot) floated by adding the treatment agent described in Patent Document 2 etc. to the wet paint booth circulating water and aggregating it is manually collected or circulated in the circulating water pit. The agglomerated treated water is fed from a water pit to a levitation device, preferably a pressure levitation device, and recovered by levitation separation. In any case, the recovered surplus paint is further concentrated by gravity filtration, pressure dehydration, or pressure dehydration after gravity filtration, and is subjected to incineration, landfill disposal, or the like.

JP 2008-149249 A JP 2008-149250 A

  By using the treatment agent proposed in Patent Documents 1 and 2, it is possible to improve the separation efficiency of the surplus paint of the wet paint booth circulating water, but the water content of the surplus paint that has been floated and separated is sufficiently low. In other words, there was a problem that the volume of water-containing solid content to be subjected to subsequent gravity filtration and pressure dehydration was large and the dehydration property was not sufficient, so that efficient concentration could not be performed.

  For example, surplus paint that has been floated and separated by the flotation device is collected in a flexible container bag (hereinafter referred to as a “flexible bag”), gravity filtered here, and further, the surplus paint after gravity filtration is pressure dehydrated by a press. In this case, since the water content and the foam content of the surplus paint that has been floated and separated are high, the capacity is large, and the dehydrating property (water draining) and the foaming property are poor, so that the flexible container bag is filled quickly. Also, the time required for gravity filtration in the flexible container bag is long. For this reason, the replacement frequency of the flexible container bag that receives the recovered surplus paint is high, and the number of flexible container bags and the space for mounting the flexible container bag are widely required. When replacing the flexible container bag, it is necessary to stop the operation of the pressure levitation device, and the efficiency of the levitation separation is also poor. In addition, the moisture content after gravity dehydration in the flexible container bag, and also the moisture content after pressure dehydration by the press machine are not sufficiently reduced, and the subsequent disposal amount is large, which also affects the transportation cost, etc. .

  The present invention solves the above-mentioned conventional problems, and after adding a phenolic resin, a coagulant, and a cationic hydrophobic polymer to the wet paint booth circulating water, the excess paint is separated by floating separation, and the separated excess paint In the method for further solid-liquid separation treatment, a wet coating booth that can obtain surplus paint with low water content and foam content and excellent dehydration properties by flotation separation, and can improve the subsequent solid-liquid separation treatment efficiency It aims at providing the processing method of circulating water.

  As a result of intensive studies to solve the above problems, the present inventors have found that when a phenolic resin, a coagulant, and a cationic hydrophobic polymer are added to the wet coating booth circulating water and separated by floating, the cationic hydrophobic By adding an anionic polymer after the addition of the water-soluble polymer, it is possible to reduce the water content and the foam content of the surplus paint separated by the floating separation, and to improve the dehydration and foaming properties. I found.

  The present invention has been achieved based on such knowledge, and the gist thereof is as follows.

[1] Wet coating booth Wet coating is performed by adding phenolic resin, coagulant, and cationic hydrophobic polymer to the circulating water, separating the surplus paint by flotation separation, and then separating the surplus paint further by solid-liquid separation. In the booth circulating water treatment method, the method further comprises the step of adding an anionic polymer after adding the cationic hydrophobic polymer, wherein the cationic hydrophobic polymer is a quaternary (meth) acrylate ester. A cationic polymer having a cationic structural unit derived from an ammonium salt and having a benzyl group bonded to the nitrogen atom of the quaternary ammonium salt, the anionic polymer comprising sodium (meth) acrylate and ( meth) Ri copolymer der acrylamide were added phenolic resin and coagulant in the wet paint spray booth circulating water system, the phenolic The cationic hydrophobic polymer is added in the circulating water system downstream from the addition position of the system resin and the coagulant, and the anionic polymer is added in the circulating water system downstream from the addition position of the cationic hydrophobic polymer. added, followed by flotation a process for separating the excess coating material, processing method of a wet spray booth circulating water characterized that you added the anionic polymer該浮on the device.

[ 2 ] In the method [ 1 ], the anionic polymer has a degree of anionization of 15 to 35 mol%, and the wet painting booth circulating water is treated.

[3] [1] or Oite in [2], the processing method of the wet paint spray booth circulating water, wherein the anionic polymer is an emulsion polymer of the colloid equivalent -2.0~-3.6meq / L .

[ 4 ] In any one of [1] to [ 3 ], the amount of the anionic polymer added is 0.1 to 10% by weight with respect to the excess paint, and the wet paint booth circulating water treatment Method.

According to the present invention, when a phenolic resin, a coagulant, and a cationic hydrophobic polymer are added to a wet coating booth circulating water and separated by floating, an anionic polymer is added after the addition of the cationic hydrophobic polymer. As a result, flocs with excellent cohesiveness can be formed, thereby reducing the water content and foam content of the surplus paint separated by floating separation, and having good dewaterability and foam breakage. It can be.
For this reason, while performing the further solid-liquid separation process of the surplus coating material floated and separated, the amount of waste can be reduced significantly and the disposal cost can be reduced.

  That is, for example, when surplus paint that has been levitated and separated by the levitation device is collected in a flexible container bag and gravity filtered here, and when the surplus paint after gravity filtration is pressure dehydrated by a press machine, the flexible container bag is filled up. Since the amount of processing (time) can be increased, and water can be drained and bubbles can be drained in a short time, the frequency of replacement of the flexible container bags is reduced, and the number of flexible container bags and the storage space thereof can be reduced. Further, when the flexible container bag is replaced, the frequency of stopping the operation of the levitation device is reduced, and the operation efficiency of the levitation device is increased. Furthermore, the moisture content after gravity dehydration in the flexible container bag and the moisture content after pressure dehydration by the press machine are sufficiently reduced, and the subsequent disposal capacity and weight are also reduced, so the transportation cost etc. are reduced. be able to.

It is a systematic diagram which shows the processing equipment of the wet paint booth circulating water used in the Example.

Below, embodiment of the processing method of the wet paint booth circulating water of this invention is described in detail.
In the present specification, “(meth) acryl” means “acryl and / or methacryl”. The same applies to “(meth) acryloyl”.

[Additives]
First, a phenolic resin, a coagulant, a cationic hydrophobic polymer, and an anionic polymer, which are agents added to the wet coating booth circulating water in the wet coating booth circulating water treatment method of the present invention, will be described.

<Phenolic resin>
Examples of the phenolic resin used in the present invention include a condensate of phenols such as phenol, cresol, xylenol and aldehydes 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, but the weight average molecular weight is preferably 3,000 or less, more 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 the phenolic resin is used as an alkaline aqueous solution, the alkaline aqueous solution is preferably in the range of an alkali agent concentration of 1 to 25% by weight and a phenolic resin concentration of 1 to 50% by weight.

Although it is not necessarily clear about the effect | action of a phenol-type resin, it estimates as follows.
When the phenolic resin is dissolved in an alkaline aqueous solution and injected into the wet coating booth circulating water, the phenolic resin is dispersed in a dissolved state or in a colloidal state. At this time, if a cationic hydrophobic polymer is present, the phenolic resin is charged and neutralized to be condensed and insolubilized. On the other hand, paint that is dissolved or colloidally dispersed in circulating water is also charged and neutralized by the cationic hydrophobic polymer to coagulate and insolubilize, but when the phenolic resin is insolubilized with the cationic hydrophobic polymer, The condensed paint is flocculated and aggregated. The flocs of phenolic resin agglomerated in the form of entraining paint become particles of a certain size, so they are easily separated and removed from the circulating water, and can be easily separated and removed by methods such as floating separation, centrifugation, and filtration. Can do.

<Coagulant>
The coagulant may be an inorganic coagulant or an organic coagulant, or a combination thereof.

  Examples of the organic coagulant include dimethyldiallylammonium chloride polymer, alkylamine-epichlorohydrin condensate, ethyleneimine polymer, alkylene dichloride-polyalkylene polyamine condensate, dimethylaminoethyl acrylate polymer, dimethylaminoethyl methacrylate polymer. And cationic organic polymer compounds such as polyvinylamidine. These organic coagulants may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the inorganic coagulant include polyaluminum chloride, aluminum sulfate, ferric chloride, ferrous sulfate, polyiron sulfate, and other polyvalent metal salts used in general water treatment. These inorganic coagulants may be used individually by 1 type, and may be used in combination of 2 or more type.

  These coagulants are used for the purpose of forming floc particles by coagulation of the non-adhesive paint. From the viewpoints of coagulation performance, corrosion inhibition, and foam suppression, organic coagulants are used rather than inorganic coagulants. Is preferred. The organic coagulant is preferably used as an aqueous solution of about 0.1 to 50% by weight.

<Cationic hydrophobic polymer>
The cationic hydrophobic polymer has a cationic structural unit derived from a quaternary ammonium salt of (meth) acrylic acid ester, and a cation formed by binding a benzyl group to the nitrogen atom of the quaternary ammonium salt. A functional polymer is used .

  Preferred examples of the cationic structural unit of the cationic polymer include a structural unit represented by the following general formula (I) (hereinafter sometimes referred to as “structural unit (I)”).

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.

  As the structural unit (I), two or more different structural units may be introduced into the cationic hydrophobic polymer.

  Examples of the quaternary ammonium salt of the (meth) acrylic acid ester that forms the structural unit (I) include (meth) acryloyloxyalkylbenzyldialkylammonium 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, the cationic 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 the nitrogen atom of the quaternary ammonium salt is a highly hydrophobic polymer. Since the hydrophobic part of the surplus paint, the hydrophobic part of the above-mentioned phenolic resin and the hydrophobic part of the antifoaming agent used as necessary are bonded to the benzyl group, and the polymer is cationic, It easily binds to highly charged paint particles and anionic phenolic resins, resulting in the formation of strong flocs. In addition, since the polymer is strongly hydrophobic, the floc is easily separated from water and has an effect of being easily floated.

  As the cationic hydrophobic polymer, a copolymer having a nonionic structural unit and / or another cationic structural unit together with the structural unit (I) can be used. Although there is no restriction | limiting in particular about the said nonionic structural unit and another cationic structural unit, The copolymer containing the structural unit shown below can be used preferably.

  A copolymer having a nonionic structural unit (hereinafter sometimes referred to as “structural unit (II)”) represented by the following general formula (II) together with the structural unit (I) (hereinafter referred to as copolymer ( I-II) may be preferably used.

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 structural units (II) may be introduced into the copolymer (I-II).

  Examples of the monomer that forms the structural unit (II) 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-dimethylaminopropyl) Pills) 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 (I) and the structural unit (II) in the copolymer (I-II) is preferably from 2: 8 to 9: 1 in terms of molar ratio, from the viewpoint of aggregation performance with respect to the excess paint, 3: 7-6: 4 is more preferable.

  As a cationic hydrophobic polymer, together with the structural unit (I), a cationic structural unit represented by the following general formula (III) (hereinafter sometimes referred to as “structural unit (III)”). A copolymer having the same (hereinafter sometimes referred to as copolymer (I-III)) can be preferably used.

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 structural units (III) may be introduced into the copolymer (I-III).

  Examples of the monomer that forms the structural unit (III) 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 (I) and the structural unit (III) in the copolymer (I-III) is preferably 8: 2 to 2: 8 in terms of molar ratio from the viewpoint of the aggregation performance with respect to the excess paint, 6: 4 to 4: 6 is more preferable.

  In the present invention, as a cationic hydrophobic polymer, a copolymer having a nonionic structural unit (II) and a cationic structural unit (III) together with the structural unit (I) (hereinafter referred to as copolymer ( I-II-III))) can be used particularly preferably.

  The content ratios of the structural unit (I), the structural unit (II), and the structural unit (III) in the copolymer (I-II-III) are respectively on a molar basis from the viewpoint of coagulation performance with respect to the excess paint. 5 to 90%, 30 to 90%, and 0 to 90% are preferable, and 10 to 40%, 50 to 70%, and 10 to 40% are more preferable.

  Representative examples of the copolymer (I-II-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] trimethyl Ammonium chloride, acrylamide / [3- (acryloyloxy) propyl] benzyldimethylammonium chloride / [3- (acryloyloxy) propyl] trimethylammoni Or the like can be mentioned Mukurorido.

  The weight average molecular weight of the cationic hydrophobic polymer used in 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 hydrophobic 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 hydrophobic polymer can be used in any form of an aqueous solution, a suspension, and an emulsion.

<Anionic polymer>
Anionic polymers are those which do not contain strong acid groups such as a sulfonic group or a phosphonic group, Ru include (meth) acrylamide and (meth) copolymer of sodium acrylate.

Since the coating booth circulating water is neutral to weakly alkaline and has a high effect of further aggregating and dewatering the primary agglomerated paint, a copolymer of sodium ( meth) acrylate and (meth) acrylamide is used. Since the degree of anionization of this copolymer of sodium (meth) acrylate and (meth) acrylamide is too high or too low, aggregation is poor, and it is preferably 15 to 35 mol%.

  The molecular weight of an anionic polymer such as a copolymer of sodium (meth) acrylate and (meth) acrylamide is preferably 5 to 15 million, particularly about 8 million in terms of viscosity average molecular weight. When the molecular weight of the anionic polymer is out of this range, the cohesiveness is deteriorated.

  The anionic polymer is preferably used as an emulsion polymer having a colloid equivalent value of -2.0 to -3.6 meq / L. Here, if the colloidal equivalent is out of this range, the cohesiveness deteriorates.

<Other drugs>
In the method for treating the circulating water of the wet paint booth of the present invention, in addition to the phenolic resin, the coagulant, the cationic hydrophobic polymer and the anionic polymer, in addition to the usual wet paint booth circulating water such as an antifoaming agent. Various drugs used can be used in combination.

  There is no restriction | limiting in particular as an antifoamer, Arbitrary things can be suitably selected and used out of the antifoamers conventionally used for wet coating booth circulating water use. As the antifoaming agent, for example, a hydrophobic organic solvent, a fatty acid polyvalent metal salt, a hydrophobic inorganic powder, an antifoaming nonionic surfactant, or the like can be used.

  Examples of the hydrophobic organic solvent include paraffinic hydrocarbons, naphthenic hydrocarbons, and petroleum solvents. Examples of the fatty acid polyvalent metal salt include lauric acid, palmitic acid, stearic acid, oleic acid, erucic acid, and the like. And metal salts of fatty acids such as magnesium, aluminum, calcium, iron, zinc, nickel and barium.

  Examples of the hydrophobic inorganic powder include hydrophobic silica, alumina, and magnesium oxide. Examples of the nonionic surfactant include fatty acid esters such as glycerin fatty acid ester, sorbitan fatty acid ester, polyethylene glycol fatty acid ester, and polyethylene. Examples thereof include ether types such as glycol, polyoxyethylene polyoxypropylene (pluronic type / tetronic type), and polyoxyethylene alkyl ether.

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

  The antifoaming agent is used in order to stably perform solid-liquid separation, surfacing and discharging of surplus paint.

[Order of drug addition]
In the present invention, the phenolic resin and the coagulant are first added to the wet paint booth circulating water, and then the cationic hydrophobic polymer is added, and then the anionic polymer is added.
When other agents such as an antifoaming agent are used in combination, there are no particular restrictions on the addition location.

  In the wet paint booth circulating water treatment, there are a case where the surplus paint floating in the circulating water pit is directly collected and a case where a collecting device (floating device, preferably a pressure floating device) is separately provided. Removes part of the circulating water from the circulating water pit and floats and separates it with a recovery device.

  Therefore, specifically, the phenolic resin and the coagulant are added at any point in the wet painting booth circulating water system, and the cationic hydrophobicity is added in the circulating water system downstream from the addition position of the phenolic resin and coagulant. It is preferable to add a polymer, add an anionic polymer in the circulating water system further downstream from the addition position of the cationic hydrophobic polymer, and then separate the solids by flotation separation. The phenolic resin and the coagulant may be added at the same time or either one may be added first.

  When a cationic hydrophobic polymer is injected into the pipe, the anionic polymer may be injected downstream from the position where the cationic hydrophobic polymer is injected, but the cationic hydrophobic polymer is sufficiently reacted. It is preferable to add an anionic polymer after the removal to float and separate surplus paint (cohesive floc with good tightness) having a low water content and excellent dewaterability. It is preferable to add a functional polymer.

  That is, for example, as shown in the examples described later, in the case where the circulating water is extracted from the circulating water pit and subjected to floating separation by the floating device, the phenolic resin and the wet coating booth circulating water are added to the circulating water pit. After adding the coagulant, it is preferable to inject a cationic hydrophobic polymer into a transfer pipe from the circulating water pit to the levitation apparatus, and then add the anionic polymer in the levitation apparatus.

[Amount of drug added]
In the present invention, the phenolic resin, the coagulant, the cationic hydrophobic polymer, the anionic polymer, and the defoaming agent added as necessary are the type of wet coating booth circulating water to be treated and the agent used. Depending on the type of the material, the following addition amount is preferable. In the following, the amount of surplus paint is defined by the following formula: surplus paint = used paint-paint paint-equipment paint

  The addition amount of the phenolic resin is usually 1 mg / L or more, preferably 5 mg / L or more as the active ingredient amount (resin solid content) with respect to the wet paint booth circulating water, and is the active ingredient for the surplus paint. The amount is usually 0.1% by weight or more, preferably 0.5% by weight or more. If the addition amount of the phenolic resin is less than the above lower limit, a sufficient tack-free 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 the resin added is preferably 1,000 mg / L or less, particularly preferably 5 to 200 mg / L as the amount of the active ingredient, and preferably 100% by weight or less, particularly preferably as the amount of the active ingredient with respect to the surplus paint. 0.5 to 10% by weight.

  The addition amount of the coagulant is usually 5 mg / L or more, preferably 10 to 30 mg / L as the active ingredient amount with respect to the wet paint booth circulating water, and is usually 10 to 30 mg / L as the active ingredient amount with respect to the surplus paint. It is about 0.5 to 2% by weight, preferably 0.8 to 1.5% by weight. If the addition amount of the coagulant is out of this range, the cohesiveness deteriorates.

  The addition amount of the cationic hydrophobic polymer is usually 1.0 mg / L or more, preferably 1.0 to 10 mg / L or more as an active ingredient amount with respect to the wet paint booth circulating water, and is added to the surplus paint. On the other hand, the amount of the active ingredient is usually about 0.1 to 20% by weight, preferably 0.2 to 1.0% by weight. When the addition amount of the cationic hydrophobic polymer is out of this range, the cohesion is deteriorated.

In addition, as a use ratio of the cationic hydrophobic polymer and the phenolic resin, the phenolic resin is usually used in a ratio of 5 to 20 times by weight, preferably 10 to 15 times by weight with respect to the cationic hydrophobic polymer. Is advantageous.
The ratio of the cationic hydrophobic polymer to the coagulant is such that the coagulant is usually 0.1 to 2 times by weight, preferably 1 to 1.5 times by weight of the cationic hydrophobic polymer. Is advantageously used.

The addition amount of the anionic polymer is usually 1.0 mg / L or more, preferably 1.0 to 10 mg / L as the active ingredient with respect to the wet paint booth circulating water, and the active ingredient for the surplus paint. The amount is usually about 0.1 to 2.0% by weight, preferably 0.2% by weight.
The anionic polymer is preferably used in a proportion of 0.1 to 2.0 times by weight, particularly 0.5 to 1 times by weight with respect to the cationic polymer.

  If the addition amount of the anionic polymer is out of this range, it is not possible to sufficiently obtain the effect of reducing the water content and improving the dewaterability of the floating separated solids due to the addition of the anionic polymer.

  When using an antifoaming agent, the amount added is usually 1.0 mg / L or more, preferably 1.0 to 10 mg / L as an active ingredient amount with respect to the wet paint booth circulating water. The amount of the active ingredient is usually about 0.1 to 10% by weight, preferably 0.2 to 1.0% by weight.

[Processing of separated solids]
As described above, the solid content floated and separated according to the present invention is usually subjected to gravity filtration, pressure dehydration, or pressure dehydration after gravity filtration and then incineration and landfill treatment.

  EXAMPLES The present invention will be described more specifically with reference to the following examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

In addition, the chemical | medical agent used by the Example and the comparative example is as follows.
Phenol resin: Kurita Kogyo Co., Ltd. phenolic resin “Chrystuck (registered trademark) B310”
(Phenol / formaldehyde condensate, novolak type, molecular weight about 1700)
Coagulant: Organic coagulant “Kuristack (registered trademark) B450” manufactured by Kurita Kogyo Co., Ltd.
(Dimethylamine-epichlorohydrin condensate, weight average molecular weight 100,000)
Cationic hydrophobic polymer: manufactured by Kurita Kogyo Co., Ltd.
Cationic hydrophobic polymer containing benzyl group
“Chrystuck (registered trademark) B302”
(Acrylamide / [2- (acryloyloxy) ethyl] benzyl
Dimethylammonium chloride / [2- (acryloyloxy) ethyl]
Trimethylammonium chloride copolymer, copolymer molar ratio 66/17/17,
(Weight average molecular weight 10 million)
Anionic polymer: Anionic polymer manufactured by Kurita Kogyo Co., Ltd.
“Cliff Rock (registered trademark) EA342”
(Sodium acrylate-acrylamide copolymer,
Anionization degree 25 mol%, viscosity average molecular weight 8 million,
(Emulsion polymer of colloidal equivalent -2.5 meq / L)

[Example 1]
The processing equipment shown in FIG. 1 was used to treat circulating water in an automobile painting booth (using base paint (water-based) and clear paint (solvent-based). Production volume 1000 units / day).
A phenolic resin and a coagulant are placed in the circulating water pit 1, and a cationic hydrophobic polymer serially diluted with industrial water is added to the inlet pipe of the pressure levitation device 2, and an anionic polymer serially diluted with industrial water is further added. The liquid was dropped from the upper part of the pressure levitation device 2 onto the liquid surface.
The water quality at the inlet of the pressurized flotation device was SS: 4500 mg / L, soluble COD: 500 mg / L, and total evaporation residue: 7500 mg / L.

The amount of each drug added (active ingredient amount) was as follows, and the operation was performed for about 21 hours.
Phenol-based resin: 80 ml / min, 2.0 mg / L-circulating water, 10% by weight of excess paint Coagulant: 20 ml / min, 0.5 mg / L-circulating water, 2.5% by weight of excess paint Cationic Hydrophobic polymer: 5 ml / min, 0.1 mg / L-circulating water, 0.6% by weight of excess paint Anionic polymer: 5 ml / min, 0.1 mg / L-circulating water, 0.6% by weight of excess paint

  The surplus paint (soot) floated and separated by the pressure flotation device was collected in the flexible container bag (capacity 500 L) 3 and allowed to stand for 8 hours for gravity filtration, and then pressure dehydrated by a press machine (not shown).

[Comparative Example 1]
In Example 1, the circulating water was treated under the same conditions except that the anionic polymer was not added.

[Comparative Example 2]
In Comparative Example 1, the circulating water was treated under the same conditions except that the gravity filtration time in the flexible container bag was 24 hours.

[Comparative Example 3]
In Comparative Example 1, the circulating water was treated under the same conditions except that the gravity filtration time in the flexible container bag was set to 48 hours.

  In Example 1 and Comparative Examples 1 to 3, the moisture content of the excess paint immediately after being collected in the flexible container bag, the moisture content of the excess paint after gravity filtration in the flexible container bag, and the moisture content of the excess paint after subsequent pressure dehydration Is shown in Table 1. Table 1 also shows the time when the flexible container bag with a capacity of 500 L was full and the amount of dewatering (draining speed) per unit time in the flexible container bag.

  From Table 1, the use of an anionic polymer can reduce the water content of the surplus paint that has been levitated and significantly improve the dehydration property, extend the full time of the flexible container bag, reduce the replacement frequency, It can be seen that shortening, subsequent improvement of pressure dehydration efficiency, and reduction of waste amount can be achieved.

1 Circulating water pit 2 Pressurized levitation device 3 Flexible container bag

Claims (4)

Wet paint booth circulating water which adds phenolic resin, coagulant and cationic hydrophobic polymer to wet paint booth circulating water, then separates surplus paint by floating separation, and further separates the separated surplus paint by solid-liquid separation treatment In the processing method of
Adding the anionic polymer after adding the cationic hydrophobic polymer,
A cation in which the cationic hydrophobic polymer has a cationic structural unit derived from a quaternary ammonium salt of (meth) acrylic acid ester and a benzyl group is bonded to a nitrogen atom of the quaternary ammonium salt. A functional polymer,
The anionic polymer, Ri copolymer der of (meth) sodium acrylate and (meth) acrylamide,
A phenolic resin and a coagulant are added to the wet painting booth circulating water system, and the cationic hydrophobic polymer is added in the circulating water system downstream from the addition position of the phenolic resin and the coagulant. A method of adding the anionic polymer in a circulating water system downstream from the addition position of the hydrophobic polymer, and then separating the surplus paint by floating separation,
Processing method of the wet spray booth circulating water characterized that you added the anionic polymer該浮on the device.   The method of treating wet paint booth circulating water according to claim 1, wherein the anionic polymer has an anionization degree of 15 to 35 mol%.   3. The method of treating wet paint booth circulating water according to claim 1, wherein the anionic polymer is an emulsion polymer having a colloid equivalent of -2.0 to -3.6 meq / L. The method for treating wet paint booth circulating water according to any one of claims 1 to 3 , wherein the addition amount of the anionic polymer is 0.1 to 10% by weight with respect to the surplus paint.

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