WO2020008947A1

WO2020008947A1 - Method for treating wet paint booth circulating water

Info

Publication number: WO2020008947A1
Application number: PCT/JP2019/025109
Authority: WO
Inventors: 雄太有元; 努吉川; 恒行吉田
Original assignee: 栗田工業株式会社
Priority date: 2018-07-02
Filing date: 2019-06-25
Publication date: 2020-01-09
Also published as: CN112334416A; JP2020001027A; JP7206650B2

Abstract

A method for treating wet paint booth circulating water, the method including adding, to circulating water that includes water and excess paint: a phosphorous compound such as phosphoric acid; a nitrogen compound such as urea, or ammonium nitrate; and a phenol resin. Using this method makes it possible to effectively remove the excess paint caught in the wet paint booth and to reduce the chemical oxygen demand (COD) of the circulating water.

Description

Treatment method for circulating water in wet coating booth

The present invention relates to a method for treating circulating water in a wet coating booth. More specifically, the present invention relates to a method of forming a coating material such as surplus paint (dry oil, resin, etc., a film forming component such as a resin, a surfactant, a thickener, a pigment, a dye, etc.) in a wet painting booth. The present invention relates to a method for treating circulating water in a wet coating booth, which can efficiently remove components, viscosity adjusting components such as solvents, etc.) and can reduce the chemical oxygen demand of circulating water.

余 Excess paint that has not been applied to the painting target in the wet painting booth is collected by circulating water. Next, part or all of the surplus paint collected in the circulating water is removed, and the circulating water from which the surplus paint has been removed is reused in a wet coating booth. Here, various methods have been proposed for removing the excess paint collected in the circulating water of the wet coating booth.

For example, Patent Literature 1 discloses that in a circulating water of a wet coating booth, a solvent for degrading accumulated paint and a odorous component-decomposing bacterium are separated into a nitrogen source (eg, ammonium nitrate, urea, etc.), a phosphorus source (eg, potassium phosphate, etc.), and inorganic salts. (E.g., magnesium salts, iron salts, etc.), and a method for treating a wet coating booth, wherein the method is grown under the control of the amount of nutrients added, such as organic growth factors (e.g., yeast extract, peptone, etc.). I have.

Patent Literature 2 discloses a culture medium in which nitrogen and phosphorus are added to an aqueous glucose solution, in which microorganisms that decompose organic components contained in paint are cultured, and a culture solution in which the microorganisms are grown is added to circulating water in a painting booth. And a method for treating circulating water in a coating booth.

Patent Document 3 discloses a method in which a phenol resin and a cationic polymer are added to circulating water of a wet coating booth containing an aqueous coating and / or a solvent-type coating, and a coating treatment in the circulating water is performed.

Patent Document 4 discloses that sewage from a pulp paper mill or the like includes strains of Mucor racemosus, Paecitomyces lilacinus, Aspergillus ustus, or Trichoderma inhamatum treated with Trichoderma inhamatum. Disclosed are compositions and methods of treating sewage, including adding nutrients, if desired, to the sewage. Patent Document 4 discloses that as the nutrient, an inorganic phosphate compound, particularly a soluble phosphonate or orthophosphate, preferably phosphoric acid, monosodium phosphate, disodium phosphate or trisodium phosphate, or diammonium phosphate; ammonia (NH ₃ ) or ammonium salt (NH ₄ ⁺ ), preferably anhydrous ammonia, aqueous ammonia, ammonium nitrate or diammonium phosphate; trace elements, preferably aluminum, antimony, barium, boron, calcium, cobalt, copper, iron, lead , Magnesium, manganese, molybdenum, nickel, strontium, titanium, tin, zinc or zirconium.

JP 2001-286800 A JP 2011-110517 A JP-A-2004-337671 JP-A-2005-51432

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for treating wet paint booth circulating water, which is capable of efficiently removing excess paint collected by circulating water in a wet paint booth and reducing the chemical oxygen demand of the circulating water. It is to provide.

検討 As a result of studying to achieve the above object, the present invention including the following embodiments has been completed.

[1] A method for treating circulating water in a wet coating booth, comprising adding a phosphorus compound and a phenol resin to circulating water containing excess paint and water.
[2] The treatment method according to [1], further comprising adding a nitrogen compound to circulating water containing excess paint and water.

According to the treatment method of the present invention, of the excess paint collected by the circulating water in the wet coating booth, drying oil, film-forming components such as resins, surfactants, additives such as thickeners, pigments, dyes It can remove colored components such as flakes, remove viscosity adjusting components such as solvents by biodegradation, and reduce the chemical oxygen demand of circulating water.
Furthermore, the processing method of the present invention can also suppress foaming in pits and the like. Further, the treatment method of the present invention is excellent in clarifying the circulating water and has a high recycling rate of the circulating water. The amount of water discharged from the water pit to the wastewater treatment facility is also reduced.

It is a conceptual diagram showing the test equipment used in the example and the comparative example.

The method for treating circulating water in a wet coating booth of the present invention is a method including adding a phosphorus compound and a phenol resin to circulating water containing surplus paint and water, preferably a circulating water containing surplus paint and water. The method includes adding a nitrogen compound, a phosphorus compound and a phenol resin to water.

Examples of the wet coating booth to which the method for treating circulating water of the wet coating booth of the present invention are applicable include a water plate type (water film type) coating booth that collects excess paint with water film type circulating water, and a shower type circulation booth. Shower type painting booth that collects excess paint with water, water film / shower type painting booth that combines water film type and shower type, surplus paint separated by centrifugal force in the spiral chamber into water film-like circulating water A venturi-type painting booth to be collected can be mentioned.

フェノール The phenolic resin used in the present invention is a condensate of phenols and aldehydes or a modified product thereof before crosslinking and curing. Specific examples of the phenol resin include a condensate of phenol and formaldehyde, a condensate of cresol and formaldehyde, and a condensate of xylenol and formaldehyde. Examples of the modified product include an alkyl-modified phenol resin and polyvinyl phenol. These phenolic resins may be of novolak type or resol type. The phenol resins may be used alone or in combination of two or more. The phenol resin is not particularly limited by the molecular weight and other physical properties, and may be appropriately selected from those commonly used for treating circulating water in a wet coating booth. The phenol resin preferably used in the present invention has a weight average molecular weight of preferably 100 or more and 100,000 or less, more preferably 1,000 or more and 50,000 or less.

The phenol resin may be added by dissolving or dispersing (for example, suspending or emulsifying) the phenol resin in a solvent or a dispersion medium.
Examples of the solvent or dispersion medium for dissolving or dispersing the phenol resin include ketones such as acetone, esters such as methyl acetate, alcohols such as methanol, alkaline aqueous solutions, and amines. Among these solvents or dispersion media, aqueous alkali solutions are preferred. Examples of the aqueous alkali solution include an aqueous sodium hydroxide solution and an aqueous potassium hydroxide solution. In a product obtained by dissolving or dispersing a phenol resin in an aqueous alkali solution, the concentration of the alkali component is preferably 1 to 25% by mass, and the concentration of the phenol resin is preferably 1 to 50% by mass.

The amount of the phenol resin (solid content) is preferably 1 mg or more, more preferably 5 mg or more, per liter of circulating water, from the viewpoint of making the excess paint tack-free. From the viewpoint of suppressing excessive foaming and increase in operating cost, the upper limit of the amount of the phenol resin (solid content) to be added is preferably 1000 mg, more preferably 200 mg, per 1 L of circulating water. Further, the addition amount of the phenol resin (solid content) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, based on the surplus paint (solids). The upper limit of the amount of the phenol resin (solid content) is preferably 100% by mass, more preferably 10% by mass, based on the surplus paint (solid content).

(4) Phenol resin is suitable for water treatment in circulating water having a large amount of surface foam that has captured an aqueous paint or circulating water that has captured an organic solvent paint having a surface potential of almost zero. By adding the phenolic resin, it is possible to reduce the tackiness of the surplus paint in the circulating water (make it less tacky) and to suppress foaming.

The phosphorus compound used in the present invention is preferably an inorganic phosphorus compound, more preferably phosphoric acid or phosphate, and still more preferably orthophosphoric acid, monosodium phosphate, disodium phosphate, trisodium phosphate, dihydrogen phosphate. Ammonium or ammonium dihydrogen phosphate. Of these, orthophosphoric acid is preferred.

In the phosphorus compound, the phosphorus element derived from the phosphorus compound is preferably 0.5 to 8 parts by mass, more preferably 0.6 to 4 parts by mass, based on 100 parts by mass of BOD (biochemical oxygen demand). More preferably, it is added in an amount of 0.7 to 2 parts by mass.

The phosphorus compound may be added as it is to the circulating water, or may be added by dissolving or dispersing the phosphorus compound in a solvent or a dispersion medium.
The solvent or dispersion medium for dissolving or dispersing the phosphorus compound is not particularly limited, and examples thereof include ketones such as acetone, esters such as methyl acetate, alcohols such as methanol, and water. Of these, water is preferred in that it does not increase COD.

The nitrogen compound used as necessary in the present invention is preferably an inorganic nitrogen compound, more preferably urea, ammonia (NH ₃ ), ammonium salt (NH ₄ ⁺ ), nitrate (NO ₃ ⁻ ) or nitrite (NO ₂ ^2- ), more preferably anhydrous ammonia, aqueous ammonia solution, ammonium nitrate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, aluminum nitrate or urea. Note that diammonium hydrogen phosphate and ammonium dihydrogen phosphate are used as a phosphorus compound and a nitrogen compound. Aluminum nitrate is used as a nitrogen compound and an inorganic coagulant. Of these, urea, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium nitrate, and / or aluminum nitrate are preferred.

In the nitrogen compound, the nitrogen element derived from the nitrogen compound is preferably 2 to 20 parts by mass, more preferably 3 to 15 parts by mass, and still more preferably 4 to 10 parts by mass with respect to 1 part by mass of the phosphorus element derived from the phosphorus compound. It is added in an amount of 15 parts by mass. The addition of the nitrogen compound enhances the COD reduction effect.

The nitrogen compound may be added as it is to the circulating water, or may be added by dissolving or dispersing the nitrogen compound in a solvent or a dispersion medium.
The solvent or dispersion medium for dissolving or dispersing the nitrogen compound is not particularly limited, and examples thereof include ketones such as acetone, esters such as methyl acetate, alcohols such as methanol, and water. Of these, water is preferred because it does not increase COD (chemical oxygen demand).

Preferably, the treatment method of the present invention further comprises adding a coagulant to the circulating water. The coagulant has an action of neutralizing the charge of the fine fine particles in water to coagulate. Coagulants are broadly classified into organic coagulants and inorganic coagulants.
As organic coagulants, sodium alginate; chitin / chitosan coagulants; biocoagulants such as TKF04 strain, BF04; polyethyleneimine, cation-modified polyacrylamide, polyamine, polyamine sulfone, polyamide, polyalkylene polyamine, amine cross-linked polycondensate Dimethylaminoethyl polyacrylate, dimethyldiallylammonium chloride (DADMAC) polymer, polycondensate of alkylamine and epichlorohydrin, polycondensate of alkylene dichloride and polyalkylenepolyamine, polycondensate of dicyandiamide and formalin, DAM (Dimethylaminoethyl methacrylate) acid salt or quaternary ammonium salt homopolymer or copolymer, DAA (dimethylaminoethyl acrylate) acid salt or quaternary ammonium salt homopolymer Cationic polymers such as limmer or copolymer, polyvinylamidine, copolymer of diallyldimethylammonium chloride and acrylamide, polycondensate of melamine and aldehyde, polycondensate of dicyandiamide and aldehyde, and polycondensate of dicyandiamide and diethylenetriamine. Molecular coagulants and the like can be mentioned. Among these, a dimethyldiallylammonium chloride (DADMAC) polymer and a polycondensate of an alkylamine and epichlorohydrin are preferred. For example, the cationic polymer coagulant preferably has a weight average molecular weight of 1,000 or more and 1,000,000 or less, more preferably 5,000 or more and 300,000 or less.

Examples of inorganic coagulants include aluminum coagulants such as aluminum sulfate (sulfuric acid band), polyaluminum chloride (PAC), polyaluminum hydroxychloride, pseudoboehmite alumina sol (AlO (OH)); ferrous hydroxide, sulfuric acid Iron salt-based coagulants such as iron, ferric chloride, ferric polysulfate, and iron-silica inorganic polymer coagulants; zinc-based coagulants such as zinc chloride; activated silicic acid and polysilica iron coagulants Can be. Of these, polyaluminum chloride (PAC) and polyaluminum hydroxychloride are preferred.

The amount of the coagulant added to the circulating water can be appropriately adjusted according to the state of formation of coagulated flocs of the surplus paint. The amount of the coagulant added to the circulating water is preferably 0.01 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, based on 100 parts by mass of the phenol resin.
When a cationic polymer coagulant is used, its addition amount is, for example, preferably 0.01 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the phenol resin. The amount of the cationic polymer coagulant added is, for example, preferably 0.001 to 1 meq / L, more preferably 0.002 to 0.5 meq / L, as a colloid equivalent value with respect to circulating water.
When an inorganic coagulant is used, its addition amount is preferably from 0.01 to 100 parts by mass, more preferably from 1 to 50 parts by mass, in terms of metal oxide, based on 100 parts by mass of the phenol resin.

The coagulant may be added as it is to the circulating water, or may be added by dissolving or dispersing the coagulant in a solvent or a dispersion medium. The solvent or dispersion medium for dissolving or dispersing the coagulant is not particularly limited, and examples thereof include ketones such as acetone, esters such as methyl acetate, alcohols such as methanol, and water. Of these, water is preferred because it does not increase COD (chemical oxygen demand).

It is preferable from the viewpoint of facilitating sedimentation and centrifugal separation that flocculated floc obtained by the action of the coagulant is aggregated to form coarse flocs.
In the treatment method of the present invention, a polymer flocculant can be added to the circulating water to form coarse flocs. The polymer flocculant comprises an anionic, cationic or amphoteric polymer. Such polymers usually have a weight average molecular weight of more than 1,000,000, preferably 5,000,000 or more.

Examples of the polymer flocculant comprising an anionic polymer include sodium polyacrylate, sodium polyacrylate / amide derivative, partially hydrolyzed polyacrylamide, partially sulfomethylated polyacrylamide, and poly (2-acrylamide) -2-methylpropane sulfate. And the like.

Examples of the polymer flocculant comprising a cationic polymer include polyaminoalkyl acrylate, polyaminoalkyl methacrylate, polyethyleneimine, polydiallylammonium halide, chitosan, urea-formalin resin, acrylamide / [2- (acryloyloxy) ethyl] benzyldimethylammonium chloride Copolymer of / [2- (acryloyloxy) ethyl] trimethylammonium chloride, copolymer of acrylamide / [3- (acryloyloxy) propyl] benzyldimethylammonium chloride / [2- (acryloyloxy) ethyl] trimethylammonium chloride Acrylamide / [2- (acryloyloxy) ethyl] benzyldimethylammonium chloride / [3- (acryloyloxy) propyl A copolymer of trimethyl ammonium chloride, acrylamide / [3- (acryloyloxy) propyl] benzyl dimethyl ammonium chloride / [3- (acryloyloxy) propyl] and the like trimethyl ammonium chloride copolymer.

Examples of the polymer aggregating agent comprising an amphoteric polymer include a copolymer of (meth) acrylamide, quaternary ammonium alkyl (meth) acrylate, and sodium (meth) acrylate; a copolymer of acrylamide, aminoalkyl methacrylate, and sodium acrylate; Can be mentioned.

液状 It is preferable to use a liquid product as the polymer flocculant from the viewpoint of handling properties. As the liquid product of the polymer flocculant, a W / O emulsion and a dispersion can be used. The dispersion is obtained by dispersing polymer flocculant particles in an aqueous medium having a high salt concentration. Therefore, it is preferable to use a dispersion from the viewpoint of reducing COD. However, there are many types of W / O emulsions, and therefore, W / O emulsions are more preferable in terms of aggregation effect.

添加 The amount of the polymer flocculant can be appropriately adjusted according to the formation state of the coarse flocs. The amount of the polymer flocculant to be added is, for example, preferably 0.01 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the phenol resin. The amount of the polymer coagulant added is, for example, preferably from 0.001 to 1 meq / L, more preferably from 0.002 to 0.5 meq / L, as a colloid equivalent value with respect to circulating water. The amount of the polymer flocculant (solid content) to be added is preferably 0.1 to 10% by mass, more preferably 0.2 to 3% by mass, based on the excess paint (solids).

処理 In the treatment method of the present invention, a tackifier, a pH adjuster, an aerobic microorganism, oxygen (air), and the like can be further added to the circulating water.

Examples of the tackifier include alumina sol, sepiolite, carboxylic acid-based polymer, tannin alkaline solution, tannin-based polymer, melamine formaldehyde resin, melamine dicyandiamide resin, bentonite, hectorite, linear cationic polyamine, sodium zincate, etc. Can be mentioned.

Examples of the pH adjuster include water-soluble alkali metal compounds such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate; hydrochloric acid, sulfuric acid, and nitric acid. The pH of the circulating water is adjusted to preferably 5 to 9, more preferably 6 to 8.5, and even more preferably 7 to 8.

Aerobic microorganisms include bacteria such as zooglare, pseudomonas, and bacillus; protozoa such as trichomes and rotifers.
Oxygen or air can be added using an aerator, a bubble generator, or the like. The addition of oxygen or air enhances the COD lowering effect. The oxygen concentration of the circulating water is not particularly limited, but is preferably adjusted to 1.2 to 10 mg-O ₂ / L, more preferably to 1.5 to 8 mg-O ₂ / L.

The position at which a phosphorus compound, a nitrogen compound, a phenol resin, a coagulant, a coagulant, a tackifier, a pH adjuster, an aerobic microorganism, oxygen (air), and the like are added to the circulating water is not particularly limited. For example, a coating booth, a transfer pipe from the coating booth to the circulating water pit, a circulating water pit, a transfer pipe from the circulating water pit to the coating booth, and the like can be given. Further, the temperature of the circulating water is preferably adjusted to 0 to 70 ° C., more preferably 0 to 60 ° C., and still more preferably 0 to 40 ° C.

凝固 The coagulated floc or coarse floc generated by the above method is separated and removed from the circulating water by a known method. In this way, it is possible to reduce turbidity and COD of water circulating in the wet coating booth.

Next, the present invention will be described more specifically with reference to examples. However, the following examples merely show one embodiment of the present invention, and the present invention is not limited to the following examples. The drugs used are as follows, and the amount of drug added in the examples is not the amount added as an active ingredient, but the amount added as a product (aqueous solution).

Phenolic resin alkaline solution: 20 parts by mass of a novolak type phenolic resin (weight average molecular weight = about 2000) and 10 parts by mass of 48% caustic soda were added to 70 parts by mass of pure water, and heated to dissolve. The obtained liquid was returned to room temperature to obtain a phenol resin alkaline solution.
PAC: polyaluminum chloride aqueous solution (10% by mass in terms of Al ₂ O ₃ )
Organic coagulant: aqueous solution of alkylamine epichlorohydrin condensate (active ingredient concentration: 50% by mass)
Phosphorus compound: 75% by mass aqueous solution of orthophosphoric acid Nitrogen compound: A mixture of 30 parts by mass of urea, 10 parts by mass of ammonium hydrogen phosphate, 0.5 parts by mass of ammonium nitrate and 59.5 parts by mass of water

Example 1
500 ml of the coating booth circulating water was collected from the circulating water pit and placed in a 1 L polybin. A test liquid was obtained by adding 5000 mg of the aqueous base paint for automobiles to this. The water quality of the test solution was 6600 mg / L for soluble CODMn, 3900 mg / L for BOD, 390 mg / L for Kjeldahl nitrogen, and 18 mg / L for total phosphorus.
To the test solution, 245 mg of a phenol resin alkaline solution, 250 mg of PAC, and 25 mg of an organic coagulant were added. The pH was adjusted to 7 using sulfuric acid or caustic soda. To this, a phosphorus compound was added at a ratio of 1 part by mass of a phosphorus element to 100 parts by mass of BOD. As shown in FIG. 1, air was supplied to the polybin at a rate of 1 L / min and aerated at room temperature for 7 days. The water quality of the liquid after the aeration was 3600 mg / L in soluble CODMn. There was some foaming during the aeration, but when the aeration was terminated, the foam disappeared within 2 minutes.

Example 2
After the addition of the phosphorus compound, the mixture was aerated for 7 days in the same manner as in Example 1 except that the nitrogen compound was added at a ratio of 5 parts by mass of the nitrogen element to 100 parts by mass of the BOD.
The water quality of the liquid after aeration was such that the soluble CODMn was 2200 mg / L. There was some foaming during the aeration, but when the aeration was terminated, the foam disappeared within 2 minutes.

Comparative Example 1
Aeration was performed for 7 days in the same manner as in Example 1 except that the phosphorus compound was not added.
The water quality of the liquid after the aeration was 3800 mg / L in soluble CODMn. There was some foaming during the aeration, but when the aeration was terminated, the foam disappeared within 2 minutes.

Comparative Example 2
Aeration was performed for 7 days in the same manner as in Example 1 except that 245 mg of phenol resin alkaline solution, 250 mg of PAC, and 25 mg of organic coagulant were changed to 300 mg of PAC and 25 mg of organic coagulant.
The water quality of the liquid after the aeration was 3700 mg / L in soluble CODMn. There was a lot of foaming during the aeration. Even after 2 minutes from the end of the aeration, about 50% of the foam amount at the end of the aeration remained.

The above results are summarized in Table 1.
As shown in Table 1, the treatment method of the present invention (Examples 1 and 2) can efficiently remove excess paints collected by the circulating water, particularly, organic substances that increase the chemical oxygen demand. The chemical oxygen demand of the circulating water can be reduced.

1: Polyvin 2: Tube for air supply 3: Mixture 4: Foam

Claims

(4) A method for treating circulating water in a wet coating booth, comprising adding a phosphorus compound and a phenol resin to circulating water containing excess paint and water.
The method according to claim 1, wherein the phosphorus compound is phosphoric acid.
The method according to claim 1, wherein the phenol resin is a novolak type phenol resin, and is added in a state of being dissolved or dispersed in an aqueous alkaline solution.
The treatment method according to claim 1, further comprising: adding a nitrogen compound to circulating water containing surplus paint and water.
The method according to claim 4, wherein the nitrogen compound is at least one selected from the group consisting of urea, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium nitrate and aluminum nitrate.
The processing method according to claim 1 or 4, further comprising: adding an inorganic coagulant and an organic coagulant to circulating water containing surplus paint and water.