Aqueous solution for circulation water treatment

Abstract

To provide an aqueous solution for circulation water treatment that makes excess substances existing in circulation water used in a wet coating booth become simply and easily removed and a processing method of circulation water using the same.SOLUTION: In an aqueous solution for circulation water treatment that is a single-liquid to be included in circulation water used in a wet coating booth to make excess substances not deposited on a coated matter and existing in the circulation water become easily removed and comprises at least (1) a novolak having a weight-average molecular weight of 3000 or under, (2) sodium hydroxide or potassium hydroxide, (3) a cationic low molecular weight polymer, and (4) water, the aqueous solution for circulation water treatment is characterized by that, per 1 mole of phenolic hydroxyl group of the novolak (1) of the weight-average molecular weight of 3000 or under, in sum total of 0.40 mole or over and 1.5 mole or under of the sodium hydroxide or potassium hydroxide (2) are blended, and 0.14 mole or over and 1.18 mole or under of the polyethyleneimine (3) is blended.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an aqueous solution for treating circulating water that is added to circulating water used in a wet paint booth to facilitate the removal of excess substances and the like in the circulating water. More specifically, the present invention relates to a one-component aqueous solution for treating circulating water that facilitates the removal of unnecessary excess substances and the like in the circulating water, and a method for treating "circulating water used in the wet paint booth." [Background technology]

[0002] When painting automobiles and other vehicles, spray painting is carried out using a wet painting booth, as shown in Figure 1, and during this process, a large amount of surplus material (unapplied paint, overmist) is generated that is not used in the painting. In order to ensure that the coating process is carried out properly, the excess material must be removed frequently, as shown in FIG. There are various types of wet painting booths, such as the water curtain type, but in all of them, the excess substances in the circulating water are removed or recovered as appropriate (removal or recovery is unavoidable) (see Figures 1 and 2).

[0003] On the other hand, the paints used in wet painting booths are classified into solvent-based paints using organic solvents and water-based paints such as emulsion paints that use water as a medium. And, both solvent-based and water-based paints may be used in the same wet paint booth or in the same circulating water system.

[0004] Solvent-based paints are superior to water-based paints in terms of weather resistance and chipping resistance, and are widely used, for example, in clear topcoats. Furthermore, because water-based paints use water as a medium, they have the advantages of being non-flammable, safe, hygienic, and free from the pollution caused by organic solvents. Therefore, in a common wet painting booth or a common circulating water system, both solvent-based paints and water-based paints are used depending on the object to be painted, and as a result, excess material (unadhered paint) A caused by the solvent-based paint and excess material (unadhered paint) B caused by the water-based paint are mixed in the circulating water.

[0005] When solvent-based paint is used, excess substance A that is taken into the circulating water is highly adhesive and therefore tends to adhere to the surrounding area or to solidify into large clumps, easily causing clogging. On the other hand, when a water-based paint is used, excess substance B that is absorbed into the circulating water clouds the water, increases the COD (Chemical Oxygen Demand), which indicates the degree of water pollution by organic matter, and also causes foaming in the circulating water, which is likely to cause problems in the circulating system.

[0006] Therefore, Patent Document 1 describes an aqueous solution of tannin and alkali metal hydroxide or carbonate as a treatment agent for excess substance A mainly resulting from solvent-based paints.

[0007] Furthermore, Patent Document 2 describes a treatment agent having, as a unit, a "quaternary ammonium salt having a structure in which a benzyl group is bonded" of a (meth)acrylic acid ester.

[0008] Furthermore, Patent Document 3 describes an organic coagulant that contains a water-soluble (co)polymer having a specific water-soluble cationic monomer unit and has a specific intrinsic viscosity.

[0009] Furthermore, Patent Document 4 describes a circulating water treatment agent containing a phenol resin having a weight-average molecular weight of more than 3,000 and not more than 100,000.

[0010] Furthermore, Patent Document 5 describes a circulating water treatment agent containing basic aluminum chloride with a specific ratio of aluminum to chlorine.

[0011] Furthermore, Patent Document 6 describes a circulating water treatment agent containing a specific benzoylhydrazine compound, a specific benzoylurea compound, or a specific diphenyl ether compound.

[0012] However, the above-mentioned known techniques do not necessarily provide a sufficient effect of "facilitating the removal and recovery of excess substances from the circulating water in a wet coating booth."

[0013] Furthermore, it did not facilitate the removal and recovery of both excess substance A resulting from the solvent-based paint and excess substance B resulting from the water-based paint from the circulating water. In other words, it was not designed to treat both of the above-mentioned excess substances, and was not actually a treatment composition that could handle both.

[0014] Patent Document 4 describes a treatment method in which excess substance A, which is mainly caused by solvent-based paints, is treated by a phenolic resin having a weight-average molecular weight of more than 3,000 and not more than 100,000, as described above, and excess substance B, which is caused by water-based paints, is treated by adding a "substance other than the phenolic resin" to the circulating water somewhere in the circulating system.

[0015] However, the circulation system for circulating water is generally complicated, and adding two liquid treatment agents separately to the circulation system makes handling difficult and reduces workability, leaving room for improvement. Therefore, it was considered to simply mix a treatment substance for excess substance A resulting from solvent-based paint with a treatment substance for excess substance B resulting from water-based paint, but this would not be effective enough to treat both of the above-mentioned excess substances, and even before that, the stability of the treatment solution would be poor, such as the active ingredient precipitating when it was made into a one-component solution (a one-component solution could not be realized). [Prior art documents] [Patent documents]

[0016] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-174064 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-188846 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-005833 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-052639 [Patent Document 5] International Publication No. 2017 / 170234 [Patent Document 6] Japanese Patent Publication No. 2020-006336 Summary of the Invention [Problem to be solved by the invention]

[0017] The present invention has been made in view of the above-mentioned background art, and an object of the present invention is to solve the above-mentioned problems and to provide an aqueous solution for treating circulating water that makes it easy to simply remove excess substances present in "circulating water used in a wet paint booth." Another object of the present invention is to provide a "method for treating circulating water used in a wet paint booth" using the aqueous solution for treating circulating water. [Means for solving the problem]

[0018] Through intensive research to solve the above problems, the inventors have discovered that if the unadhered paint, i.e., excess material present in the "circulating water used in a wet painting booth" can be easily removed by adding a single liquid (using the water in a single liquid state), the treatment of the circulating water can be greatly simplified. Furthermore, after extensive research into additives that can facilitate the removal of "excess substance A contained in solvent-based paints and excess substance B contained in water-based paints" even in a single liquid, the inventors discovered a composition that can be stably obtained in the form of a uniform aqueous solution, leading to the completion of the present invention.

[0019] That is, the present invention provides an aqueous solution for treating circulating water used in a wet coating booth, which is contained in the circulating water to facilitate the removal of "excess substances that have not adhered to the object to be coated" present in the circulating water, and which comprises at least the following substances all blended in one solution: (1) Novolac with a weight-average molecular weight of 3,000 or less (2) Sodium hydroxide or potassium hydroxide (3) Cationic low molecular weight polymer (4)Water The present invention provides an aqueous solution for circulating water treatment, characterized in that the aqueous solution is obtained by blending a total of 0.40 mol to 1.5 mol of the sodium hydroxide or potassium hydroxide described in (2) above, and 0.14 mol to 1.18 mol of the cationic low-molecular-weight polymer described in (3) above, per mol of the phenolic hydroxyl group of the novolak having a weight-average molecular weight of 3,000 or less described in (1).

[0020] The present invention also provides the above-mentioned aqueous solution for treating circulating water, in which the circulating water contains an excess substance A that was contained in the solvent-based paint and an excess substance B that was contained in the water-based paint, and the excess substance A and the excess substance B are treated in a single solution.

[0021] The present invention also provides the aqueous solution for treating circulating water, in which the viscosity of the excess substance A is reduced to facilitate removal, and the excess substance B is flocculated to facilitate removal.

[0022] The present invention also provides the aqueous solution for circulating water treatment, wherein the cationic low-molecular-weight polymer (3) is polyethyleneimine.

[0023] The present invention also provides a method for producing the "aqueous solution for circulating water treatment," comprising: The present invention provides a method for producing an aqueous solution for circulating water treatment, characterized by comprising a step of dissolving the "novolak having a weight-average molecular weight of 3,000 or less" of (1) above in an aqueous solution in which the "sodium hydroxide or potassium hydroxide" of (2) above has been dissolved.

[0024] The present invention also provides a method for treating circulating water used in a wet paint booth, characterized in that the above-mentioned aqueous solution for treating circulating water is added in a single liquid state to the circulating water containing excess substance A that was contained in a solvent-based paint and excess substance B that was contained in a water-based paint, thereby reducing the viscosity of the excess substance A to make it easier to remove, and flocculating the excess substance B to make it easier to remove.

[0025] The present invention also provides a method for treating circulating water used in a wet paint booth, in which, after the excess substances A and B have been made easier to remove, a cationic high-molecular-weight polymer and / or an anionic high-molecular-weight polymer is added to the circulating water to coarsen the excess substances A and B into clumps, thereby making them easier to remove. [Effects of the Invention]

[0026] The aqueous solution for treating circulating water of the present invention solves the above-mentioned problems and issues, and can be added to the circulating water used in a wet coating booth to flocculate, gather, or aggregate the "excess substances that have not adhered to the object to be coated" contained therein, making them easier to remove and / or extract from the circulating water (see Figures 1 and 2). Here, "flocculation" refers to the process of collecting insoluble matter, colloids, etc. present in circulating water and forming them into agglomerates.

[0027] Specifically, the aqueous solution for circulating water treatment of the present invention can easily remove both "insoluble matter derived from solvent-based paints (excess substance A)" and "insoluble matter derived from water-based paints (excess substance B)" contained in the circulating water as insoluble matter or colloids from the circulating water by adding a single solution.

[0028] By removing solids and the like from the circulating water, clogging of pipes and the like can be prevented, making it easier to form a water curtain in a wet painting booth, for example, and maintaining the circulation system in a normal state.

[0029] Furthermore, by adding one solution, water-soluble substances such as humic substances contained as soluble matter in the circulating water can also be easily removed from the circulating water at the same time. Here, "at the same time" also means simultaneously with the removal of the insoluble matter. Circulating water containing excess substances tends to yellow over time due to humic substances, making it difficult to remove. However, the aqueous solution for treating circulating water of the present invention has excellent "yellowing removal properties."

[0030] More specifically, the stickiness of the surface of the excess material is suppressed (the surface is made non-sticky) and flocculation (solid-liquid separation) is promoted, thereby making it easier to remove the excess material from the circulating water.

[0031] As a result, the circulating water system can be operated and maintained normally, which makes it possible to improve the efficiency of maintenance work, extend the life of the circulating water, and maintain a stable circulating system.

[0032] In the past, excess material A resulting from solvent-based paints, excess material B resulting from water-based paints, soluble materials, etc. were treated by workers at the painting company by adding different treatment agents according to their chemical properties. The circulation system, which includes piping, water storage tanks, etc., is complex, and adding separate (two-liquid) treatment agents separately to the circulation system makes it difficult to handle and makes the work less efficient. However, by using the aqueous solution for circulating water treatment of the present invention, excess substance A, excess substance B, insoluble matter, and soluble matter can be treated simultaneously with one liquid, which not only improves the removal of unwanted substances but also significantly improves the workability. However, simply mixing two or more conventional treatment agents does not result in mutual compatibility and a homogeneous liquid. In other words, the "liquid stability (single-liquid characteristics)" of Evaluation Example 1 described below is inferior.

[0033] Furthermore, as described above, if a "cationic high-molecular-weight polymer and / or anionic high-molecular-weight polymer" is further added to circulating water obtained by adding (charging) the "aqueous solution for circulating water treatment of the present invention" to flocculate insoluble matter, suppress the stickiness of the surface (make the surface non-tacky), promote solid-liquid separation, and decolorize the circulating water, the flocs will become coarse, and furthermore, it will become easier to completely and easily remove unwanted insoluble matter from the circulating water.

[0034] Finally, there are various methods for removing and extracting insoluble matters from the "circulating water treated with the aqueous solution for treating circulating water of the present invention," as shown in FIG. As shown in Evaluation Examples 2 to 5 of the Examples, the aqueous solution for circulating water treatment of the present invention is excellent in various performances, and furthermore, it is excellent in almost all of the performances required for removing unwanted substances such as insoluble matter from water, and therefore can be applied to all removal methods such as A floating flocculation type, B submerged dispersion type, and C floating dispersion type shown in Figure 2. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a schematic diagram showing an example of the flow of circulating water in a water curtain type wet painting booth. [Figure 2] FIG. 1 is a schematic diagram showing an example of a method for finally removing and recovering "excess substances derived from paint" from circulating water that has been treated with the circulating water treatment aqueous solution of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] The present invention will be described below, but the present invention is not limited to the specific embodiments below and can be modified as desired within the scope of the technical concept.

[0037] [Aqueous solution for circulating water treatment] The aqueous solution for treating circulating water of the present invention is contained in circulating water used in a wet coating booth to facilitate the removal of "excess substances that have not adhered to the object to be coated" present in the circulating water, and is a circulating water treatment aqueous solution comprising at least the following substances all blended in one solution: (1) Novolac with a weight-average molecular weight of 3,000 or less (2) Sodium hydroxide or potassium hydroxide (3) Cationic low molecular weight polymer (4)Water The composition is characterized in that the composition is prepared by blending a total of 0.40 mol to 1.5 mol of the "sodium hydroxide or potassium hydroxide" of the above (2) with 1 mol of the phenolic hydroxyl group of the "novolak having a weight-average molecular weight of 3,000 or less" of the above (1), and blending 0.14 mol to 1.18 mol of the cationic low-molecular-weight polymer of the above (3).

[0038] The circulating water treatment solution of the present invention can be applied to circulating water used in all kinds of wet paint booths, including the method and apparatus illustrated in Figure 2, and in any method, it makes it easy to remove "excess material that did not adhere to the original object to be coated." Here, "excess material that did not adhere to the substrate" means material that was applied to the substrate but did not form a coating film, such as over-mist, unadhered material, uncoated material, etc. (or what is called such) that is captured in the circulating water that forms a water curtain, etc.

[0039] The excess material may contain both excess material A that was contained in the solvent-based paint and excess material B that was contained in the water-based paint. However, the aqueous solution for treating circulating water of the present invention can treat circulating water containing both excess material A and excess material B with a single solution. Excess material A includes, for example, coating film (forming) components, solvents, paint compounding agents, etc. of solvent-based paints, and excess material B includes, for example, coating film (forming) components, dispersion media in emulsion paints, water-soluble media such as water, dispersants such as surfactants, etc. of water-based paints. The aqueous solution for treating circulating water of the present invention can facilitate the removal of these excess substances by adding a single solution to circulating water containing these substances.

[0040] Therefore, the present invention also relates to the aqueous solution for treating circulating water, in which the circulating water contains an excess substance A that was contained in the solvent-based paint and an excess substance B that was contained in the water-based paint, and the excess substance A and the excess substance B are treated in one solution.

[0041] As described above and also as shown in the Examples, the aqueous solution for treating circulating water of the present invention flocculates insoluble substances in the circulating water, suppresses stickiness of the surfaces of the flocs (makes them non-sticky), and promotes solid-liquid separation, thereby facilitating the removal of excess substances from the circulating water, and, when excess substances are dissolved in the circulating water, removes or makes easy the removal of water-soluble substances from the circulating water. The target of removal is not particularly limited, but the aqueous solution for circulating water treatment of the present invention reduces the viscosity of the excess substance A, making it easier to remove, and also flocculates the excess substance B, making it easier to remove.

[0042] The aqueous solution for circulating water treatment of the present invention contains at least all of the substances (1) to (4). (1) Novolac with a weight-average molecular weight of 3,000 or less (2) Sodium hydroxide or potassium hydroxide (3) Cationic low molecular weight polymer (4)Water

[0043] <(1) Novolac with a weight-average molecular weight of 3,000 or less> The "novolak" in "(1) novolak having a weight-average molecular weight of 3,000 or less" contained in the aqueous solution for circulating water treatment of the present invention is obtained by condensing "phenols having a phenolic hydroxyl group" and "aldehydes or ketones" in the presence of an acid catalyst, and also includes those obtained by modifying the obtained product.

[0044] Here, examples of the "phenols" include monofunctional phenols such as phenol (carbolic acid), o-cresol, m-cresol, p-cresol, chlorophenol, xylenol (dimethylphenol), ethylphenol, and vinylphenol; difunctional phenols such as catechol, resorcinol, hydroquinone, and "bisphenols such as bisphenol A, F, or S"; trifunctional phenols such as pyrogallol; and naphthols such as 1-naphthol and 2-naphthol. These may be used alone or in the form of co-condensation of two or more kinds.

[0045] Furthermore, examples of the above-mentioned "aldehydes or ketones" include aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde (propanal), and butylaldehyde (butanal); aromatic aldehydes such as benzaldehyde; and ketones such as acetone. These may be used alone or in combination of two or more.

[0046] Although not limited thereto, specific examples of particularly preferred compounds include condensation products of phenol (carbolic acid) and formaldehyde, condensation products of cresol and formaldehyde, and condensation products of xylenol and formaldehyde.

[0047] The weight average molecular weight of the novolak in the present invention must be 3,000 or less, but is preferably 1,000 or more and 2,800 or less, more preferably 1,200 or more and 2,600 or less, and particularly preferably 1,400 or more and 2,500 or less.

[0048] If the weight-average molecular weight of the novolac is too small, the evaluation results in Evaluation Examples 2 to 5 described below may be poor. Specifically, the effects of suppressing floc formation during use and stickiness of the surface of excess substance A (making the surface non-sticky), promoting solid-liquid separation of excess substance B, and removing yellowing of circulating water may not be sufficiently obtained.

[0049] Conversely, if the weight-average molecular weight of the novolak is too large, it may be difficult to dissolve in the aqueous solution containing (2) "sodium hydroxide or potassium hydroxide," and the results of Evaluation Example 1 (liquid stability (single-liquid characteristics)) described below may be poor. Furthermore, if a large amount of (2) "sodium hydroxide or potassium hydroxide" is not added, it may be difficult to dissolve in the aqueous solvent of the circulating water treatment solution, and adding a large amount of (2) in an attempt to dissolve it may result in the adverse effects described below.

[0050] The novolak may be dissolved or dispersed in the aqueous solution for circulating water treatment, but is preferably dissolved. It is preferable to use a sufficient amount of "(2) sodium hydroxide or potassium hydroxide" to dissolve the novolak. The essential or preferred content of (2) relative to (1) will be described later.

[0051] Since the novolak is easily dissolved in alkaline water, it is preferable to prepare an aqueous solution for circulating water treatment by blending it with "(4) water in which (2) sodium hydroxide or potassium hydroxide has been dissolved," although this is not a limitation.

[0052] The cause of yellowing of circulating water is thought to be humic substances, and the combination of "(1) novolac with a weight-average molecular weight of 3000 or less" and an appropriate amount of "(2) sodium hydroxide or potassium hydroxide" (described later) reduces the salinity (Na) of the phenolic OH of the novolac. + , K. + The aqueous solution for circulating water treatment of the present invention, in which the above-mentioned HCl is prepared, can effectively remove this yellowing.

[0053] <(2) Sodium hydroxide or potassium hydroxide> The aqueous solution for circulating water treatment of the present invention must contain "(2) sodium hydroxide or potassium hydroxide," and it is preferable to dissolve these in "(4) water," and then add and dissolve (1) and / or (3) to prepare the aqueous solution for circulating water treatment. Either "sodium hydroxide or potassium hydroxide" may be used alone or both may be used in combination.

[0054] It is essential that the "sodium hydroxide or potassium hydroxide" in (2) be blended in a total amount of 0.40 mol to 1.5 mol, preferably 0.45 mol to 1.30 mol, more preferably 0.50 mol to 1.10 mol, even more preferably 0.55 mol to 1.00 mol, and particularly preferably 0.60 mol to 0.92 mol, per mol of phenolic hydroxyl group in the "novolak having a weight-average molecular weight of 3,000 or less" in (1).

[0055] If the total number of moles of the (2) "sodium hydroxide or potassium hydroxide" relative to 1 mole of the phenolic hydroxyl groups of the (1) "novolac having a weight-average molecular weight of 3,000 or less," i.e., the molar ratio of (2) to the phenolic hydroxyl groups, is too small, the (1) novolac may be difficult to dissolve in water, the ionization of the phenolic hydroxyl groups may be suppressed, and the liquid stability (single-liquid characteristics) may be poor, making it difficult to achieve the effects of the present invention.

[0056] Conversely, if the number of moles of (2) is too large relative to the number of moles of phenolic hydroxyl groups in (1), excess "OH - " makes the aqueous solution for circulating water treatment more alkaline (higher pH), which may result in failure to form flocs during use, preventing excess substance A from becoming non-sticky, and preventing excess substance B from being solid-liquid separated.

[0057] It is known that alkaline water can be used as a solvent to dissolve novolak, but in the present invention, it was discovered that the above-mentioned problems occur when there is an excess of NaOH or KOH relative to the phenolic hydroxyl groups. Therefore, the above-mentioned "number of moles of '(2)' per mole of phenolic hydroxyl groups of novolak (molar ratio)" is extremely important.

[0058] When the "above-mentioned range" of the number of moles of phenolic hydroxyl groups in "(1) novolak having a weight-average molecular weight of 3,000 or less" is "(2) 'sodium hydroxide and / or potassium hydroxide'" and dissolved in water as a salt with the sodium cation and / or potassium cation, adding this to "circulating water containing excess substances" can, as described in the examples, satisfactorily form flocs during use, which is effective in preventing the adhesion of excess substance A and in the solid-liquid separation of excess substance B, and further has the effect of removing yellowing from the circulating water, etc.

[0059] <(3) Cationic low molecular weight polymer> The aqueous solution for circulating water treatment of the present invention must contain, in one solution, "(1) novolak having a weight-average molecular weight of 3,000 or less" and "(2) sodium hydroxide or potassium hydroxide" as well as "(3) a cationic low-molecular-weight polymer." Here, the term "cationic polymer" refers to a polymer having a group that can be a "+" such as a primary, secondary, or tertiary amino group, and in the case of an amino group, it is referred to as "N + " means a polymer that can be Furthermore, the term "low molecular weight polymer" refers to a polymer having a weight average molecular weight of 500,000 or less.

[0060] The "(3) cationic low-molecular-weight polymer" is not particularly limited, but specific examples thereof include polyethyleneimine; polyacrylamide (co)polymers; amino group-containing (meth)acrylic acid ester (co)polymers such as poly(dialkylaminoethyl (meth)acrylate; polyamine sulfones; polyamides; polyalkylene polyamines; amine crosslinked polycondensates; amino group-containing polycondensates such as alkylammonium chloride (DADMAC) polymers, polycondensates of alkylamines and epichlorohydrin, polycondensates of alkylene dichlorides and polyalkylene polyamines, and polycondensates of dicyandiamide and formalin; polyvinylamidine; polycondensates of melamine and aldehydes; polycondensates of dicyandiamide and aldehydes; and dicyandiamide derivatives such as polycondensates of dicyandiamide and diethylenetriamine. These may be blended either individually or in combination of two or more.

[0061] The preferred molecular weight of the "(3) cationic low-molecular-weight polymer" having a weight-average molecular weight of 500,000 or less is, in order to obtain the above-described effects of the present invention, preferably 300,000 or less, more preferably 200,000 or less, and particularly preferably 100,000 or less, in terms of weight-average molecular weight. The lower limit of the weight average molecular weight is preferably 2,000 or more, more preferably 5,000 or more, even more preferably 10,000 or more, particularly preferably 20,000 or more, and most preferably 40,000 or more. If the weight average molecular weight is too large, the "floc formation during use" may be poor.

[0062] The "(3) cationic low-molecular-weight polymer" must be contained (blended) in an amount of 0.14 mol to 1.18 mol per mol of phenolic hydroxyl group in the "novolak having a weight-average molecular weight of 3,000 or less" in (1) above, but is preferably contained in an amount of 0.20 mol to 1.02 mol, more preferably 0.25 mol to 0.85 mol, and particularly preferably 0.35 mol to 0.65 mol.

[0063] If the amount of "(3) cationic low-molecular-weight polymer" is too small relative to the phenolic hydroxyl groups of the novolac, the evaluation items evaluated in the examples may be inferior, and in particular, floc formation during use may not be achieved, and the non-adhesiveness of excess substance A and the solid-liquid separation properties of excess substance B may not be achieved. Conversely, if the amount of "(3) cationic low molecular weight polymer" is too high, the evaluation items evaluated in the examples may be inferior, and in particular, the ability to remove yellowing from circulating water may not be achieved.

[0064] <<Polyethyleneimine>> Among these, "(3) cationic low-molecular-weight polymer" is preferably polyethyleneimine, since it is particularly excellent in the effects of the present invention and in the evaluation items evaluated in the examples. For the reasons mentioned above, the polyethyleneimine has a branched structure, and is particularly preferably a polymer having a primary amine, a secondary amine, and a tertiary amine.

[0065] The preferred molecular weight of polyethyleneimine is the same as the preferred molecular weight of the above-mentioned "(3) cationic low-molecular-weight polymer" in order to obtain the above-mentioned effects of the present invention. Furthermore, it is most preferable that the polyethyleneimine has a branched structure, is a polymer having a primary amine, a secondary amine, and a tertiary amine, and has a weight-average molecular weight of 10,000 or more and 200,000 or less, and more preferably, is within the above-mentioned range.

[0066] The essential or (particularly) preferred content (ratio) of polyethyleneimine is also as described above, and although it is essential in the case of polyethyleneimine that it be contained (blended) in an amount of 0.14 mol to 1.18 mol per mol of phenolic hydroxyl groups in the "novolac having a weight-average molecular weight of 3,000 or less" described in (1) above, more specifically, it is desirable for the above-mentioned reasons to contain it in an amount of preferably 0.20 mol to 1.02 mol, more preferably 0.25 mol to 0.85 mol, even more preferably 0.30 mol to 0.75 mol, particularly preferably 0.35 mol to 0.65 mol, and most preferably 0.37 mol to 0.60 mol.

[0067] <(4)Wed> The aqueous solution for circulating water treatment of the present invention contains "(4) water" as an essential component.

[0068] There are no particular limitations on the concentration of each of the essential components (1), (2), and (3) relative to the total aqueous solution for circulating water treatment. However, the concentration of "(1) novolak having a weight-average molecular weight of 3,000 or less" is preferably 5 parts by mass or more and 40 parts by mass or less, and particularly preferably 10 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the aqueous solution for circulating water treatment.

[0069] The content of "(2) sodium hydroxide or potassium hydroxide" relative to "(1) novolak having a weight-average molecular weight of 3,000 or less" is as described above, but is preferably 1.2 parts by mass or more and 30.7 parts by mass or less, and particularly preferably 2.4 parts by mass or more and 15.4 parts by mass or less, relative to 100 parts by mass of the aqueous solution for circulating water treatment.

[0070] The content of "(3) cationic low-molecular-weight polymer" relative to "(1) novolac having a weight-average molecular weight of 3,000 or less" is as described above, but is preferably 0.3 parts by mass or more and 18.8 parts by mass or less, and particularly preferably 0.6 parts by mass or more and 9.4 parts by mass or less, relative to 100 parts by mass of the aqueous solution for circulating water treatment.

[0071] Within the above range, the composition is easy to add to the circulating water, has good handling properties, and is easily mixed into the circulating water. If the concentration is too low, the volume of the aqueous solution for circulating water treatment will be unnecessarily large, which may make transportation, sale, and storage difficult. On the other hand, if the concentration is too high, the solubility and liquid stability (single liquid characteristics) may be poor, and the material may not be easily mixed or dispersed throughout the circulating water.

[0072] <Method of manufacturing aqueous solution for circulating water treatment> The present invention provides a method for producing the aqueous solution for circulating water treatment, comprising: The present invention is also a method for producing an aqueous solution for circulating water treatment, characterized by comprising a step of dissolving the "novolac having a weight-average molecular weight of 3,000 or less" of (1) in an aqueous solution in which the "sodium hydroxide or potassium hydroxide" of (2) is dissolved.

[0073] Novolak is difficult to dissolve in pure water, so it can be easily dissolved by adding it to an alkaline aqueous solution containing "(2) sodium hydroxide or potassium hydroxide." It is particularly preferable to dissolve "(3) cationic low-molecular-weight polymer" in an aqueous solution of "(2) sodium hydroxide or potassium hydroxide" and then add the (1) novolak.

[0074] <Method for treating circulating water used in wet paint booths> The present invention also relates to a method for treating circulating water used in a wet paint booth, characterized in that the aqueous solution for treating circulating water is added in a single liquid state to circulating water containing excess substance A that was contained in a solvent-based paint and excess substance B that was contained in a water-based paint, thereby reducing the viscosity of excess substance A to make it easier to remove, and flocculating excess substance B to make it easier to remove. The aqueous solution for treating circulating water of the present invention is suitably used, for example, in any of the excess substance removal and extraction methods shown in Figure 2.

[0075] By using the one-component aqueous solution for treating circulating water of the present invention, not only is it a single-component solution, but excess substances A and B can be treated simultaneously, resulting in significantly improved handling properties and work efficiency.

[0076] <High-molecular-weight polymer to be added to circulating water after adding aqueous solution for circulating water treatment to the circulating water> Furthermore, the present invention also relates to the above-mentioned method for treating circulating water used in a wet paint booth, in which the excess substances A and B are made easy to remove by using the above-mentioned one-component aqueous solution for treating circulating water, and then a "cationic high-molecular-weight polymer and / or anionic high-molecular-weight polymer" is added to the circulating water to coarsen and form agglomerates of the excess substances A and B, thereby making the flocs larger and making them easier to remove.

[0077] Here, the term "high molecular weight" in "cationic high molecular weight polymer" and "anionic high molecular weight polymer" means a weight average molecular weight of 500,000 or more, and it is preferable that the polymer is supplied in the form of an aqueous solution.

[0078] As described above, by using the aqueous solution for treating circulating water of the present invention, it is possible to flocculate unnecessary insoluble substances in the circulating water, suppress stickiness of the surface (make the surface non-tacky), promote solid-liquid separation, and eliminate coloration such as yellowing. Furthermore, by subsequently adding a "cationic high-molecular-weight polymer and / or anionic high-molecular-weight polymer" to the treated circulating water, the flocs can be coarsened, and further coarsened into large agglomerates, making it easier to remove unnecessary substances from the circulating water.

[0079] The weight-average molecular weight of the high-molecular-weight polymer, "a cationic high-molecular-weight polymer and / or anionic high-molecular-weight polymer having a weight-average molecular weight of 500,000 or more," is preferably 700,000 or more, more preferably 1,000,000 or more, even more preferably 2,000,000 or more, particularly preferably 3,000,000 or more, and most preferably 5,000,000 or more. Furthermore, the weight-average molecular weight of the anionic high-molecular-weight polymer is most preferably 8,000,000 or more. There is no particular upper limit to the weight average molecular weight of the "cationic high molecular weight polymer and / or anionic high molecular weight polymer", but it is preferably 15 million or less, and particularly preferably 14 million or less. Furthermore, it is preferable that the upper and lower limits of the weight average molecular weight of both the cationic high molecular weight polymer and the anionic high molecular weight polymer are within the above ranges.

[0080] If the weight average molecular weight is less than 500,000 or is too lower than the lower limit, the flocs may not be coarsened. Moreover, if the weight average molecular weight is too large, the flocs may not be coarsened.

[0081] Specific examples of "cationic high molecular weight polymers and / or anionic high molecular weight polymers having a weight average molecular weight of 500,000 or more" include poly(meth)acrylic acid (co)polymers (salts), (partial) hydrolysates (salts) of poly(meth)acrylic acid amide (co)polymers, (partially) sulfomethylated poly(meth)acrylamide (salts), poly(meth)acrylamidomethylpropane sulfate (salts), N-vinylformamide (co)polymers, polyvinylamine, etc. [Example]

[0082] The present invention will be explained in more detail below by way of examples and comparative examples, but the present invention is not limited to these examples as long as it does not depart from the gist of the invention.

[0083] Preparation Example 1 <Preparation of aqueous treatment solutions for Examples 1 to 13 and Comparative Examples 1 to 4> The aqueous treatment solutions of Examples 1 to 13 and Comparative Examples 1 to 4 were prepared as follows. Note that some of the comparative examples were suspensions or gels and did not become homogeneous one-component aqueous solutions, but the term "aqueous treatment solution" also includes those in such states (see "Method for evaluating solution stability (one-component characteristics)" below).

[0084] Potassium hydroxide (KOH) was dissolved in an amount (molar number) shown in Tables 1 and 2 to prepare an aqueous potassium hydroxide solution.

[0085] Polyethyleneimine (weight average molecular weight 70,000, having a branched structure, and containing primary amines, secondary amines, and tertiary amines) was added as a cationic low molecular weight polymer in the amount (molar number) shown in Tables 1 and 2, and the whole was thoroughly stirred.

[0086] Next, 10 g of solid novolak was added to the above aqueous solution under stirring at room temperature, as shown in Tables 1 and 2, and dissolved, or in some comparative examples, dissolution was attempted. Regarding water, (1), (2), and (3) were added and the remainder was water. The novolak used was a phenol novolak with a weight-average molecular weight (Mw) of 1600. The weight-average molecular weight (Mw) was measured as a THF solution by gel permeation chromatography (GPC) calibrated with a polystyrene standard molecular weight sample.

[0087] The aqueous treatment solutions of Examples 1 to 13 and Comparative Examples 1 to 4 (see Tables 1 and 2) obtained above were evaluated as follows.

[0088] Evaluation example 1 <Evaluation method for "liquid stability (single-component properties)"> The "aqueous solution for treatment" prepared in Preparation Example 1 above was stirred at room temperature and then allowed to stand at room temperature. The state of the solution was visually observed from immediately after preparation until one day later, and evaluated according to the following criteria.

[0089] <Criteria for liquid stability (single liquid characteristics)> ○: It was in a transparent aqueous solution state. ○△: Some turbidity was observed in the aqueous solution, but within the acceptable range △: Suspension was observed in the aqueous solution, but within the acceptable range ×: Gelation occurred and the aqueous solution separated.

[0090] Evaluation example 2 <Evaluation method for "floc formation during use"> 5.0 g (equivalent to 0.5% by mass) of the "treatment aqueous solution" prepared in Preparation Example 1 above was added to 1 L of city water, and the mixture was stirred thoroughly at room temperature, and the presence or absence of flocs formed in the city water was visually observed. If flocs are not formed when added to city water, the "de-tackiness of excess substance A in solvent-based paint" and the "solid-liquid separation properties of excess substance B in water-based paint" described below tend to be poor or not observed. Conversely, if flocs are formed when added to city water, the "de-tackiness of excess substance A in solvent-based paint" and the "solid-liquid separation properties of excess substance B in water-based paint" described below tend to be good.

[0091] <Criteria for "floc formation during use"> ○: Strong flocs were formed △: Flocs were formed △×: Some flocs were formed, but within the acceptable range ×: No flocs were formed

[0092] Evaluation example 3 <Evaluation method for "detackifying properties of excess substance A in solvent-based paints"> (1) 400g of city water was prepared as test water in a 500mL plastic bottle. (2) 1 g (equivalent to 0.25% by mass of the total test water) of the "treatment aqueous solution" prepared in Preparation Example 1 above was added thereto, and the PET bottle was capped and shaken well to uniformly disperse the treatment aqueous solution. (3) 1 g (equivalent to 0.25% by mass of the total test water) of solvent paint for painting automobile parts was added to the water. (4) After adding the solvent paint, the mixture was shaken vigorously up and down for 30 seconds at 4 times per second. (5) After shaking, the mixture was left to stand for 10 minutes, and the non-stickiness of the floc was evaluated by touching with a finger.

[0093] <Criteria for determining "detackifying ability of excess substance A in solvent-based paints"> ○: Flock is non-adhesive and good △: It is possible to make flocks non-sticky, but some flocks remain sticky. ×: The adhesiveness of the flock was not completely removed, and the performance was poor.

[0094] Evaluation example 4 <Evaluation method for "Solid-liquid separation of excess substance B in water-based paint"> (1) 10 g (equivalent to 1% by mass) of water-based automotive paint was added to 1 L of city water and dispersed uniformly to prepare an "aqueous paint dispersion." (2) 100 mL of the above "aqueous paint dispersion" was placed in a 200 mL measuring cylinder. (3) 0.3 mL (equivalent to 0.3% by mass of the entire aqueous paint dispersion) of the "aqueous treatment solution" prepared in Preparation Example 1 above was added thereto, and the mixture was shaken vigorously up and down at 4 times per second for 30 seconds. (4) After shaking, the mixture was left to stand for 10 minutes, and the solid-liquid separation (state of solid-liquid separation) was visually evaluated and confirmed.

[0095] <Criteria for "Solid-liquid separation of excess substance B in water-based paint"> ○: Complete solid-liquid separation and easy to use △: Solid-liquid separation occurs and it can be used △×: Slight solid-liquid separation, within the acceptable range ×: No solid-liquid separation at all, outside the allowable range (unusable)

[0096] Evaluation example 5 <Evaluation method for "removal of yellowing in circulating water"> (1) 400g of yellowed circulating water actually used at a painting site was collected and placed in a 500mL plastic bottle. (2) 1 g (equivalent to 0.25% by mass of the total test water) of the "treatment aqueous solution" prepared in Preparation Example 1 above was added thereto, and the PET bottle was capped and vigorously shaken up and down 4 times per second for 30 seconds. (3) After shaking, the mixture was left to stand for 10 minutes, and the presence or absence of clarification was visually observed.

[0097] <Criteria for "Removal of yellowing from circulating water"> ○: The yellowing was completely removed and the product was clarified. ○△: Yellowing is almost completely removed and the product is clarified. △: Yellowing has been slightly removed and the product has been clarified (usable) ×: The yellowing is not completely removed and clarification is not achieved (unusable)

[0098] <Result> Tables 1 and 2 show the compositions of the aqueous treatment solutions of Examples 1 to 13 and Comparative Examples 1 to 4, and the results of Evaluation Examples 1 to 5 for these solutions. The aqueous treatment solutions of Examples 1 to 13 were excellent or within acceptable ranges in all evaluated performances and were usable. Furthermore, Examples 2 to 5 and Examples 9 to 13 were excellent in performance and were usable. In particular, Examples 3 to 5 and 10 to 13 were extremely excellent in all evaluation items and were usable with exceptionally good results.

[0099] [Table 1]

[0100] [Table 2]

[0101] Reference examples 1 and 2 <No cationic low molecular weight polymers> Aqueous solutions for treating circulating water that do not contain cationic low molecular weight polymers such as polyethyleneimine require the user, the painting company, to take some kind of measure, such as adding a separate treatment solution to the circulating water, and in that respect they are clearly inferior in terms of workability and ease of use. However, aqueous solutions for circulating water treatment that did not contain a cationic low-molecular-weight polymer such as polyethyleneimine were used as Reference Examples 1 and 2 and evaluated in the same manner as in Evaluation Examples 2 to 5 (see Table 3).

[0102] In addition, since Reference Examples 1 and 2 did not contain a cationic low molecular weight polymer such as polyethyleneimine, the "liquid stability (single-component characteristics)" in Evaluation Example 1 was not evaluated.

[0103] As shown in Table 3, the aqueous solution for circulating water treatment that did not contain a cationic low-molecular-weight polymer such as polyethyleneimine exhibited poor performance in all evaluation items.

[0104] Reference example 3 <Novolac and potassium hydroxide free> Aqueous solutions for treating circulating water that do not contain novolac require the user, such as a painting company, to take some kind of measure, such as adding a separate treatment solution to the circulating water, and in that respect they are clearly inferior in terms of workability and ease of use. However, an aqueous solution for circulating water treatment containing neither novolak nor "potassium hydroxide or sodium hydroxide" was used as Reference Example 3 and evaluated in the same manner as in Evaluation Examples 2 to 5 (see Table 3).

[0105] In addition, since Reference Example 3 did not contain novolak and potassium hydroxide, the "liquid stability (single-liquid characteristics)" in Evaluation Example 1 was not evaluated.

[0106] As shown in Table 3, the aqueous solution for circulating water treatment that did not contain novolac and potassium hydroxide performed poorly in all evaluation items except for "solid-liquid separation of excess substance B from water-based paint" (see Table 3).

[0107] [Table 3]

[0108] Example 21 <Changing the molecular weight of novolac> Aqueous solutions for circulating water treatment were prepared in the same manner as in Example 3, except that phenol novolac having a weight-average molecular weight Mw=2500 and phenol novolac having a weight-average molecular weight Mw=1000 were used instead of the novolac in Production Example 1, Examples 3, 5, and 10, and Tables 1 and 2 (phenol novolac having a weight-average molecular weight Mw=1600), and were evaluated in the same manner as in Evaluation Examples 1 to 5.

[0109] As in Example 3, good results of "◯" were obtained in all of Evaluation Examples 1 to 5.

[0110] Example 22 <Uses cresol novolac> Aqueous solutions for circulating water treatment were prepared in the same manner as in Production Example 1, and evaluated in the same manner as in Evaluation Examples 1 to 5, except that cresol novolac having a weight-average molecular weight Mw=1600 was used instead of the novolac (phenol novolac having a weight-average molecular weight Mw=1600) in Production Example 1, Examples 3, 5, and 10, and Tables 1 and 2, taking into consideration the number of moles of phenolic hydroxyl groups (combining the number of moles).

[0111] As in Examples 3, 5, and 10, in all of Evaluation Examples 1 to 5, good results of "◯" were obtained, similar to the phenol novolak.

[0112] Example 23 <Cationic low molecular weight polymer> Aqueous solutions for circulating water treatment were prepared in the same manner as in Production Example 1, Examples 3, 5, and 10, and Tables 1 and 2, except that, instead of polyethyleneimine (weight average molecular weight 70,000), an alkylammonium chloride (DADMAC) polymer or a polycondensate of alkylamine and epichlorohydrin was used in a manner that matched (corresponded to) the blending mass as the cationic low-molecular-weight polymer, and evaluated in the same manner as in Evaluation Examples 1 to 5.

[0113] As in Examples 3, 5, and 10, in all of Evaluation Examples 1 to 5, although it was inferior to polyethyleneimine (particularly in the one-component properties), almost the same results of "Good" were obtained.

[0114] Example 24 <Sodium hydroxide is used> Aqueous solutions for circulating water treatment were prepared in the same manner as in Production Example 1, Examples 3, 5, and 10, and Tables 1 and 2, except that sodium hydroxide (NaOH) was used instead of potassium hydroxide (KOH) with the same (corresponding) molar ratio, and evaluated in the same manner as in Evaluation Examples 1 to 5.

[0115] As in Examples 3, 5, and 10, good results of "◯" were obtained in all of Evaluation Examples 1 to 5 (not shown).

[0116] Preparation Example 2 and Evaluation Example 6 <Preparation of "High Molecular Weight Polymers" in Examples 31 to 40 and Comparative Example 31, and Evaluation of Floc Coarsening> In Examples 31 to 40 and Comparative Example 31, the "cationic high molecular weight polymer and / or anionic high molecular weight polymer" (compositions are shown in Table 4) was prepared, and the "floc coarsening" was evaluated as follows.

[0117] (1) 400g of city water was collected in a 500mL plastic bottle. (2) 1 g of the test agent (0.25% by mass relative to the amount of test water) was added thereto, and the mixture was shaken to uniformly disperse the test agent. (3) 1 g (0.25% by mass relative to the amount of test water) of solvent paint for painting automobile parts was added. (4) After adding the test paint, shake it vigorously up and down 4 times per second for 30 seconds.

[0118] <<Addition of cationic high molecular weight polymer (Examples 31 to 36)>> (5) 0.04 g (0.01% by mass based on the amount of test water) of a cationic high molecular weight polymer was added, and the mixture was shaken vigorously up and down 4 times per second for an additional 30 seconds. (6) After shaking, the mixture was allowed to stand and the coarsening of flocs was visually confirmed.

[0119] <<Addition of anionic high molecular weight polymer (Examples 37 to 40 and Comparative Example 31)>> (7) 0.04 g (0.01% by mass based on the amount of test water) of an anionic high-molecular-weight polymer was added, and the mixture was shaken vigorously up and down at 4 times per second for an additional 30 seconds. (8) After shaking, the mixture was allowed to stand and the coarsening of flocs was visually confirmed.

[0120] The "coarsening of flocs" of the obtained products was judged according to the following criteria.

[0121] <<Criteria for determining "coarsening of flocs">> ◎: Flocs are coarsened ○: Flocs are coarsened △: Flocs are somewhat dispersed, but coarsening is observed ×: Flocs are dispersed and no coarsening is observed

[0122] [Table 4]

[0123] <Result> As shown in Table 4, the evaluation results suggest that when circulating water is treated with the aqueous solution for circulating water treatment of the present invention and then treated with (added to) "a cationic high-molecular-weight polymer and / or a cationic high-molecular-weight polymer," the flocs become coarse. In particular, it was suggested that the flocs treated with both the cationic high molecular weight polymer and the anionic high molecular weight polymer were coarsened particularly effectively (Examples 37 to 40). [Industrial Applicability]

[0124] The aqueous solution for treating circulating water of the present invention can be contained (added) as a single liquid in the circulating water used in a wet painting booth, making it easy to remove excess substances from the circulating water. Therefore, it is suitable for use in companies that have a painting process, and is therefore widely used in fields such as the painting industry and the manufacturing industry of "products that require painting," such as the automobile manufacturing industry.

Claims

1. An aqueous solution for treating circulating water used in a wet coating booth is contained in the circulating water to facilitate the removal of "excess material that has not adhered to the object to be coated" present in the circulating water, the aqueous solution comprising at least the following substances all blended in one solution: (1) Novolak with a weight average molecular weight of 3,000 or less (2) Sodium hydroxide or potassium hydroxide (3) Cationic low molecular weight polymer (4) Water 1. A circulating water treatment aqueous solution characterized by comprising: (1) the "novolak having a weight-average molecular weight of 3,000 or less"; (2) the "sodium hydroxide or potassium hydroxide"; and (3) the cationic low-molecular-weight polymer; in a total amount of 0.40 mol to 1.5 mol per mol of phenolic hydroxyl group of the "novolak having a weight-average molecular weight of 3,000 or less."

2. 2. The aqueous solution for treating circulating water according to claim 1, wherein the circulating water contains an excess substance A that was contained in the solvent-based paint and an excess substance B that was contained in the water-based paint, and the excess substance A and the excess substance B are treated in a single solution.

3. 3. The aqueous solution for circulating water treatment according to claim 2, wherein the adhesiveness of said excess material A is reduced to facilitate removal, and said excess material B is flocculated to facilitate removal.

4. 2. The aqueous solution for circulating water treatment according to claim 1, wherein the cationic low-molecular-weight polymer (3) is polyethyleneimine.

5. 5. The aqueous solution for circulating water treatment according to claim 4, wherein the polyethyleneimine has a branched structure and is a polymer having a primary amine, a secondary amine, and a tertiary amine.

6. 2. The aqueous solution for circulating water treatment according to claim 1, wherein the cationic low-molecular-weight polymer (3) has a weight-average molecular weight of 10,000 or more and 200,000 or less.

7. A method for producing an aqueous solution for circulating water treatment according to any one of claims 1 to 6, comprising: A method for producing an aqueous solution for circulating water treatment, comprising a step of dissolving the "novolak having a weight average molecular weight of 3,000 or less" of (1) in an aqueous solution in which the "sodium hydroxide or potassium hydroxide" of (2) is dissolved.

8. A method for treating circulating water used in a wet paint booth, comprising adding the circulating water treatment aqueous solution according to any one of claims 1 to 6 in a single liquid state to the circulating water containing an excess substance A that was contained in a solvent-based paint and an excess substance B that was contained in a water-based paint, thereby reducing the viscosity of the excess substance A to make it easier to remove, and flocculating the excess substance B to make it easier to remove.

9. 9. The method for treating circulating water used in a wet paint booth according to claim 8, wherein after the excess material A and the excess material B have been made easier to remove, a cationic high molecular weight polymer and / or an anionic high molecular weight polymer is added to the circulating water to coarsen the excess material A and the excess material B into clumps, thereby making them easier to remove.

10. 10. The method for treating circulating water used in a wet paint booth according to claim 9, wherein the cationic high-molecular-weight polymer and / or the anionic high-molecular-weight polymer has a weight-average molecular weight of 500,000 or more.

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