JP2005314470A - Water-based coating easy in wastewater treatment and method for treating wastewater containing the coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based coating comprising a resin composition, and to provide a method for treating wastewater containing the coating. <P>SOLUTION: The water-based coating comprises an aminoformaldehyde resin introduced with carboxy group and/or carboxylate group, being easy in wastewater treatment. Specifically, in this coating, the total amount of the carboxy group and/or carboxylate group introduced into the aminoformaldehyde resin is 0.2-1.5 mol/kg. The method for treating wastewater containing the coating is also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an aqueous paint containing an aminoformaldehyde resin into which carboxyl groups and / or carboxylate groups have been introduced, and a method for treating waste water containing the same.

In recent years, demand for water-based paints having a low organic solvent content is increasing as paints having little influence on the environment. However, water-based paints are water-soluble in composition, and when used in a coating factory, the generation of paint wastewater with a high organic matter concentration is a problem. Therefore, wastewater treatment for reducing the TOC (total organic carbon) of paint wastewater is required.

    In water-based paints, paints using an aminoformaldehyde resin as a crosslinking agent are widely used as one of representative paints. The amino formaldehyde resin is a resin obtained by further reacting melamine and formaldehyde with water and / or alcohol as necessary. In this water-based paint using an aminoformaldehyde resin as a crosslinking agent, a polyol is used as a base resin component as necessary in addition to the aminoformaldehyde resin as a constituent component. Therefore, when this water-based paint is used, a large amount of aminoformaldehyde resin or Waste water containing polyol is produced. Among these, polyol-derived TOC can be significantly reduced by methods such as electrolytic treatment, agglomeration treatment, pH adjustment, and biological treatment, which are ordinary treatments.

    Regarding these wastewater treatment methods, for example, Patent Document 1 describes a wastewater treatment apparatus that performs treatment by electrolysis of wastewater generated in a painting process or a surface treatment process. Patent Document 2 describes a wastewater treatment method in which an electrolyte solution is added to wastewater obtained by washing a coating instrument using a water-based acrylic paint to precipitate an acrylic resin slurry and separate it. On the other hand, Patent Document 3 describes a method in which an acid is added to waste water containing components of a water-based paint to lower the pH to produce a solid content. Patent Document 4 describes a microbial treatment apparatus for coating waste liquid in which microorganisms effective for waste liquid treatment of coating waste liquid are immobilized on a carrier and accommodated in a treated water tank. However, since the aminoformaldehyde resin has a triazine ring having a chemically very stable structure, it has been extremely difficult to reduce the TOC derived from the aminoformaldehyde resin by the above-described method.

JP 2002-18444 A JP 2001-300548 A JP 2001-219176 A Japanese Patent Laid-Open No. 11-314095

An object of the present invention is to provide an aqueous paint containing a specific aminoformaldehyde resin composition that can be easily treated by an ordinary wastewater treatment method, and a method for treating wastewater containing the aqueous paint.

The present invention
1. A water-based paint having an aminoformaldehyde resin having a carboxyl group and / or a carboxylate group introduced therein and being easily treated with waste water;
2. The water-based paint according to 1, wherein the total amount of carboxyl groups and / or carboxylate groups introduced into the aminoformaldehyde resin is 0.2 to 1.5 mol based on a resin solid content of 1000 g;
3. Item 3. The water-based paint according to Item 1 or 2, wherein the number average molecular weight of the aminoformaldehyde resin into which the carboxyl group and / or carboxylate group is introduced is in the range of 500 to 5,000.
4). A wastewater treatment method for treating wastewater comprising an aqueous formaldehyde resin having a carboxyl group and / or a carboxylate group introduced therein, and comprising an aqueous paint that can be easily treated by PH adjustment and / or electrolytic treatment,
About.

ADVANTAGE OF THE INVENTION According to this invention, the water-based coating material which has an aminoformaldehyde resin by which the carboxyl group and / or the carboxylate group were introduce | transduced, and an easy waste water process can be obtained.

The amino formaldehyde resin is a resin obtained by further reacting melamine and formaldehyde with water and / or alcohol as necessary, and the resin can be used mainly as a crosslinking agent in an aqueous coating material. The specific amino formaldehyde resin contained in the water-based paint of the present invention is a resin in which carboxyl groups and / or carboxylate groups are introduced into the amino formaldehyde resin. Hereinafter, it may be referred to as a modified formaldehyde resin.

    As a method for introducing a carboxyl group and / or carboxylate group into an aminoformaldehyde resin, (1) a compound containing one or more carboxyl groups or carboxylate groups and hydroxyl groups in one molecule, and (2) one molecule A compound containing at least one carboxyl group or carboxylate group and at least one aldehyde group, (3) a compound containing at least one carboxyl group, carboxylate group and ketone group in one molecule, (4) One or more of acrylic acid ester or acrylic acid having a carboxyl group or carboxylate group, (5) methacrylic acid ester or methacrylic acid having a carboxyl group or carboxylate group, and (6) cyclic acid anhydride. Select this Reacting a compound with an amino-formaldehyde resin, or by reacting such with melamine and formaldehyde and / or alcohol, it is possible to obtain the amino-formaldehyde resin obtained by introducing a carboxyl group and / or carboxylate groups. For the purpose of promoting the reaction, various acid catalysts or base catalysts can be used, and heating can be performed within a range of 30 to 200 ° C. In this reaction step, alcohol and / or moisture can be removed out of the system.

The above (1) to (6) are specifically hydroxyalkanoic acids such as hydroxypivalic acid, dimethylolpropanoic acid, dimethylolbutanoic acid, dimethyloloctanoic acid, malic acid, and ricinoleic acid. , And known acrylic resins, polyester resins, polyurethane resins, polycarbonate resins containing both carboxyl groups or carboxylate groups and hydroxyl groups, (2) as oxocarboxylic acids having an aldehyde group such as glyoxylic acid, As an example, an oxocarboxylic acid having a keto group such as pyruvic acid, (4) as acrylic acid, a reaction product of acrylic acid and a lactone compound, and (5) as an example reaction product of methacrylic acid, methacrylic acid and a lactone compound ,
(6) includes maleic anhydride, succinic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and the like.

    The total amount of carboxyl groups and / or carboxylate groups introduced into the amino formaldehyde resin is 0.2 to 1.5 mol based on the resin solid content of 1000 g from the viewpoint of wastewater treatment property of paint and water resistance of the coating film. Preferably, it is 0.25 to 1.3 mol. Specifically, the total amount herein can be calculated based on the numerical value obtained by measuring the acid value of the modified aminoformaldehyde resin. The acid value can be measured by neutralization titration and / or potentiometric titration using an indicator such as phenolphthalein or bromothymol blue.

    The number average molecular weight of the formaldehyde resin introduced with the carboxyl group and / or carboxylate group contained in the aqueous paint of the present invention is preferably in the range of 500 to 5000 from the viewpoint of wastewater treatment property and crosslinkability, more Preferably it is 600-4000. First, the number average molecular weight is measured by gel permeation chromatography and converted on the basis of polystyrene.

    The water-based paint of the present invention contains the modified aminoformaldehyde resin, and may further contain a polyol as necessary. Known polyols can be used as the polyol. A polyol is mainly used as a base resin and a reactive diluent in water-based paints, and usually has two or more hydroxyl groups in one molecule, and has a number average molecular weight of 60. The above can be preferably used.

    Specifically, for example, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, butanediol, polytetramethylene glycol, methylpropanediol, pentanediol, methylpentanediol, hexanediol, neopentylglycol, 2-butyl-2 -Ethyl-1,3-propanediol, 2,2'-diethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, 2-ethyl-1,3-hexanediol, 2 , 2,4-trimethyl-1,3-pentanediol, hydroxypivalic acid-neopentyl glycol ester, dimethylolpropanoic acid, dimethylolbutanoic acid, trimethylolethane, trimethylolpropane, trimethylolpropane Tyrolol butane, glycerin, pentaerythritol, a compound having two or more hydroxyl groups in one molecule and a ring-opening adduct of ethylene oxide and / or propylene oxide and / or tetrahydrofuran and / or lactone and / or cyclocarbonate, amino in one molecule Reaction product of compound having both group and hydroxyl group and epoxy group-containing compound, reaction product of compound having both amino group and hydroxyl group in molecule and polyisocyanate; hydroxyl group-containing polyester, hydroxyl group-containing polyurethane, hydroxyl group-containing Examples thereof include a vinyl copolymer, an epoxy resin, a hydroxyl group-containing carbonate, and polyvinyl alcohol. Furthermore, these polyols modified with other organic compounds and / or inorganic compounds can be used as polyols. In addition to these, one or two or more kinds can be selected from known polyols. Can be used. The polyol can be used in a state dissolved in water or in a dispersed state.

    The weight ratio between the polyol and the modified aminoformaldehyde resin in the water-based paint of the present invention is preferably 0/100 to 95/5, more preferably 5/95 to 90/10 as a solid content from the viewpoint of curability. is there.

    The water-based paint of the present invention further comprises extender pigments, color pigments, solvents such as water or organic solvents, rheology control agents, pigment dispersants, anti-settling agents, acid / base catalysts, antifoaming agents, and antioxidants. Various additives such as ultraviolet absorbers, extender pigments and the like can be appropriately blended.

    Waste water containing water-based paints is produced as paint booth water in the paint factory using the water-based paint obtained as described above, coating booth water in the plating factory, and industrial waste water in the paint factory producing the water-based paint.

    In the present invention, pH treatment and / or electrolytic treatment can be performed as a treatment method for waste water containing the water-based paint. The modified amino formaldehyde resin of the present invention can easily reduce the TOC (total organic carbon) derived from the resin, particularly the waste water containing the water-based paint blended with the resin, by pH adjustment and / or electrolytic treatment. It is possible.

    The pH adjustment in the present invention is carried out in order to promote the precipitation, precipitation, and aggregation of pollutants by adjusting the pH of the wastewater and to improve the wastewater treatability. The pH range of the wastewater is preferably 5 or less. Although there is no restriction | limiting in particular in the acid to be used, In view of the quality of treated water, it is more preferable to use an inorganic acid than to use an organic acid. Examples of inorganic acids include hydrochloric acid and sulfuric acid.

    The electrolytic treatment in the present invention is one of the methods for removing the solid content. The electrode is put into waste water, an electric current is passed, and the pigment in the waste water is formed by using fine bubbles of oxygen and hydrogen generated by electrolysis of water. This is a method of adsorbing resin or resin and collecting these substances on the surface of wastewater by the buoyancy of bubbles. For example, the electrolyte can be charged and dissolved in the supplied waste water, and a plurality of electrodes can be arranged in the water tank at appropriate intervals, and the electrodes can be energized to perform electrolysis. It is preferable to use an aluminum electrode as the electrode and sodium nitrate, sodium chloride or the like as the electrolyte.

    In the present invention, a flocculant can be further added as a wastewater treatment for water-based paints. When adding a flocculant, examples of the flocculant include inorganic flocculants represented by aluminum sulfate, polyaluminum chloride, ferric chloride, low molecular flocculants such as surfactants, anionic and nonionic Or a cationic polymer flocculant can be mentioned. These flocculants can be used alone or in combination of two or more.

    In the present invention, biological treatment, ozone decomposition treatment, UV decomposition treatment, visible light decomposition treatment, activated carbon treatment, general activated sludge treatment, and membrane separation activated sludge treatment are performed as necessary as wastewater treatment of water-based paints. I can do it. These may be performed alone, but can be used in combination with the above-described pH adjustment, electrolytic treatment, and the like.

    In the method of the present invention, the precipitate produced by the wastewater treatment is excellent in filterability and can be easily filtered with various filters. It is also possible to remove the precipitate by gravity sedimentation separation or centrifugation according to the amount of waste water, the concentration of the melamine derivative, the composition of other components, and the like.

Next, an Example is given and this invention is demonstrated more concretely.

Production Example 1
In a three-necked 500 ml flask equipped with a stirrer, 306 g of Cymel 300 (trade name, manufactured by Mitsui Cytec Co., Ltd., methyl ether type aminoformaldehyde resin, number average molecular weight of about 400) and 71 g of hydroxypivalic acid were added and stirred. The temperature was raised to 120 ° C. Then, it heated up to 150 degreeC over 4 hours, and was made to react, and the methanol generated with time was distilled out of the system. The carboxyl group content of the reaction product was 0.66 mol / kg.

    This was neutralized by adding 21 g (about 1 equivalent) of N, N-dimethylethanolamine, and 64 g of methoxypropanol was further added to obtain an about 80% solution of aminoformaldehyde resin (A-1) containing a carboxyl group. It was. The number average molecular weight of this resin was about 900.

Production Example 2
In a three-necked 500 ml flask equipped with a stirrer, 255 g of Cymel 300 and 71 g of hydroxypivalic acid were placed, and the temperature was raised to 120 ° C. while stirring. Then, it heated up to 150 degreeC over 4 hours, and was made to react, and the methanol generated with time was distilled out of the system. The carboxyl group content of the reaction product was 0.66 mol / kg.

    18 g (about 1 equivalent) of dimethylethanolamine was added thereto for neutralization, and 53 g of methoxypropanol was further added to obtain an about 80% solution of aminoformaldehyde resin (A-2) containing a carboxyl group. The number average molecular weight of this resin was about 1000.

Production Example 3
In a three-necked 500 ml flask equipped with a stirrer, 255 g of Cymel 300, 35 g of hydroxypivalic acid, and 21 g of 2,2-dimethyl-1,3-propanediol were added, and the temperature was raised to 120 ° C. while stirring. Then, it heated up to 150 degreeC over 2 hours, was made to react, and the methanol generated with time was distilled out of the system. The carboxyl group content of the reaction product was 0.48 mol / kg.

    This was neutralized by adding dimethylethanolamine in the same manner as in Production Example 1, and further methoxypropanol was added to obtain an approximately 80% solution of aminoformaldehyde resin (A-3) containing a carboxyl group. The number average molecular weight of this resin was about 900.

Production Example 4
In a 3 L 2 L flask equipped with a stirrer, 38 g of deionized water, 740 g of 1-butanol and 205 g of 95% paraformaldehyde were added and heated to 90 ° C. with stirring to dissolve uniformly. Thereafter, 126 g of melamine was added to 80 ° C., and 0.4 g of formic acid was added. Thereafter, the temperature was raised to about 110 ° C. over about 1 hour, and the distillate was distilled out of the system. Then, it cooled to 100 degreeC and 93 g of 40% glyoxylic acid aqueous solution was added. Thereafter, the temperature was raised to 120 ° C. over about 4.5 hours, during which time the distillate was distilled out of the system. The carboxyl group content of the reaction product was 0.53 mol / kg.

    This was neutralized by adding dimethylethanolamine in the same manner as in Production Example 1, and further methoxypropanol was added to obtain an approximately 80% solution of aminoformaldehyde resin (A-4) containing a carboxyl group. The number average molecular weight of this resin was about 1500.

Production Example 5
A flask was charged with 1000 g of deionized water and 8 g of New Coal 562SF (trade name, manufactured by Nippon Emulsifier Co., Ltd., emulsifier), heated to 85 ° C. under a nitrogen atmosphere and stirred well. Separately, 486 g of methyl methacrylate, 754 g of butyl acrylate, 5 g of allyl methacrylate, 30 g of hydroxy acrylate, 20 g of methacrylic acid, 1200 g of deionized water, 17 g of New Coal 562SF and 10 g of ammonium persulfate were added dropwise and added dropwise over 3 hours. did. Thereafter, the mixture was aged for 2 hours, and a mixture of 200 g of deionized water and 20 g of dimethylethanolamine was added to obtain an approximately 35% emulsion dispersion of polyol (PO-1).
(Production and evaluation of water-based paint)
The amino formaldehyde resin containing the carboxyl group obtained in Production Examples 1 to 4 and the polyol obtained in Production Example 5 are mixed so that the weight ratio is 7/3 as a resin solid content, and the amino formaldehyde resin is mixed. A cross-linked water-based paint was obtained.

    These water-based paints were coated with a clear PTFE plate doctor blade to a thickness of 20 μm based on the dry film thickness, left at room temperature for 15 minutes, and then heated at 140 ° C. for 30 minutes using a hot air drying oven. A cured coating film was obtained by heating. When the gel fraction was measured for each, it was 80% or more, and it was confirmed that these were water-based paints excellent in curability. The gel fraction was calculated by measuring the solvent-free weight after immersion for 5 hours under acetone reflux conditions.

    Next, model wastewater containing a water-based paint was prepared in Production Examples 6 to 10. The model wastewater was adjusted so that the solid content weight ratio of the aminoformaldehyde resin and the polyol was 9/1 in order to examine the removability of the total carbon content (TOC) derived from the aminoformaldehyde resin.

Production Example 6: Wastewater containing aminoformaldehyde resin and polyol (B-1)
1.75 g of an aminoformaldehyde resin (A-1) containing carboxyl group and 1.75 g of an approximately 35% emulsion dispersion of polyol (PO-1) are added to 1000 g of deionized water while stirring. Then, the pH was adjusted to 8.5, and waste water (B-1) having an aminoformaldehyde resin concentration of about 0.14% was obtained. The TOC of this wastewater was 906 ppm.

Production Example 7: Wastewater containing aminoformaldehyde resin and polyol (B-2)
Add 1.75 g of about 80% solution of aminoformaldehyde resin (A-2) containing carboxyl group and 0.4 g of about 35% emulsified dispersion of polyol (PO-1) to 1000 g of deionized water while stirring. Then, the pH was adjusted to 8.5, and waste water (B-2) having an aminoformaldehyde resin concentration of about 0.14% was obtained. The TOC of this waste water was 897 ppm.

Production Example 8: Wastewater containing aminoformaldehyde resin and polyol (B-3)
Add 1.75 g of about 80% solution of aminoformaldehyde resin (A-3) containing carboxyl group and 0.4 g of about 35% emulsified dispersion of polyol (PO-1) to 1000 g of deionized water while stirring. Then, the pH was adjusted to 8.5, and waste water (B-3) having an aminoformaldehyde resin concentration of about 0.14% was obtained. The TOC of this wastewater was 873 ppm.

Production Example 9: Wastewater containing aminoformaldehyde (B-4)
While stirring, 1000 g of deionized water, 1.4 g of Cymel 300, which is an aminoformaldehyde resin, and 0.4 g of an approximately 35% emulsion dispersion of polyol (PO-1) are added, and the pH is adjusted to 8.5. Waste water (B-4) having an aminoformaldehyde resin concentration of about 0.14% was obtained. The wastewater TOC was 847 ppm.

Production Example 10: Wastewater containing aminoformaldehyde resin and polyol (B-5)
Emulsified dispersion of 1.75 g of aminoformaldehyde resin 80% Cymel 325 (trade name, Mitsui Cyanamide Co., Ltd., imino aminoformaldehyde resin) and polyol (PO-1) with stirring in 1000 g of deionized water. 0.4 g of body was added, pH was adjusted to 8.5, and waste water (B-5) having an aminoformaldehyde resin concentration of about 0.14% was obtained. The TOC of this wastewater was 1050 ppm.

Examples 1 to 3 and Comparative Examples 1 and 2
The wastewater prepared in Production Examples 6 to 10 was subjected to electrolytic treatment, and the TOC before and after treatment was measured. The results are shown in Table 1. Specifically, it was electrolyzed at a load voltage of 5 V for 30 minutes with an electrolytic treatment apparatus equipped with an aluminum electrode, and then filtered. The TOC removal rate here is
Removal rate (%) = (1- (TOC after treatment [mg / L]) / (initial TOC [mg / L]))) × 100
It is.
Moreover, the evaluation of processability was performed according to the following criteria.
○: Removal rate ≧ 20%
Δ: 20%> removal rate ≧ 10%
×: 10%> removal rate

Examples 4 and 5 and Comparative Examples 3 and 4
The waste water adjusted in Production Examples 6, 7, 9, and 10 was pH adjusted, and the TOC before and after the treatment was measured. The results are shown in Table 2. 1N HCl was used for pH adjustment, and the pH of the wastewater was adjusted to 4.5.

Examples 6 to 8 and Comparative Examples 5 and 6
The waste water prepared in Production Examples 6 to 10 was subjected to electrolytic treatment in the same manner as in Examples 1 to 3 and Comparative Examples 1 and 2, and further subjected to treatment by pH adjustment in the same manner as in Examples 4 and 5 and Comparative Examples 3 and 4. The TOC before and after the treatment was measured. The results are shown in Table 3.

Examples 9 to 11 and Comparative Examples 7 and 8
The wastewater prepared in Production Examples 6 to 10 was treated by pH adjustment in the same manner as in Examples 4 and 5 and Comparative Examples 3 and 4, and further subjected to electrolytic treatment in the same manner as in Examples 1 to 3 and Comparative Examples 1 and 2. The TOC before and after the treatment was measured. The results are shown in Table 4.

The present invention can be applied to water-based paints that require wastewater treatment, including aminoformaldehyde resins.

Claims (4)

A water-based paint having an aminoformaldehyde resin having a carboxyl group and / or a carboxylate group introduced therein, and which can be easily treated with waste water. The water-based paint according to claim 1, wherein the total amount of carboxyl groups and / or carboxylate groups introduced into the aminoformaldehyde resin is 0.2 to 1.5 mol based on 1000 g of resin solids. The water-based paint according to claim 1 or 2, wherein the number average molecular weight of the aminoformaldehyde resin into which the carboxyl group and / or carboxylate group is introduced is in the range of 500 to 5,000. A wastewater treatment method for treating wastewater containing an aqueous formaldehyde resin having a carboxyl group and / or a carboxylate group introduced therein and easily treating wastewater by pH adjustment and / or electrolytic treatment.