Disposal method for aqueous developer waste liquid

Abstract

To provide a method for recovering a recovery liquid containing a development accelerator from an aqueous development waste liquid.SOLUTION: Provided is a method for treating an aqueous development waste liquid generated by developing a flexographic printing original plate using an aqueous developer, the method including a step of recovering a recovery liquid containing a development accelerator and water from an aqueous development waste liquid containing a development residue, the development accelerator, and the water. The development accelerator contains a compound represented by the following formula (A1): R1O(A1O)nR2, wherein R1 and R2 are each independently an alkyl group having 2 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms, A1 is an alkylene group having 2 to 4 carbon atoms, and n is an integer of 1 to 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for treating aqueous developing waste liquid. [Background technology]

[0002] Printing plates with photosensitive resin can be manufactured using computer-aided printing (CTP) technology, which involves directly drawing information processed on a computer onto the printing plate to create a relief. Among these, flexographic printing, a type of letterpress printing, has the advantage of being applicable to various substrates because it uses soft materials such as rubber or synthetic resin for the printing plate.

[0003] Printing plates (especially flexographic printing plates) produced by CTP technology are obtained by following a procedure that involves laser drawing on an infrared absorption layer on a photosensitive resin, exposing and curing the photosensitive resin layer, developing the uncured areas, drying the resulting plate, and then exposing it to light again. Flexographic printing plates can be obtained by solvent development, which dissolves and develops the uncured areas with a solvent developer; aqueous development, which peels off and develops the uncured areas with an aqueous developer containing a surfactant; or thermal development, which heats the printing plate and wipes off the uncured areas with a nonwoven fabric. However, solvent development and aqueous development both generate waste solutions.

[0004] In solvent-based development, the developed solution is recovered and reused by distillation, and in aqueous development, a method for reusing water recovered by vacuum distillation has also been disclosed (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2003 / 005129 Pamphlet [Overview of the project] [Problems that the invention aims to solve]

[0006] Although the aqueous developing solution may contain a developing accelerator, the concentration of the developing accelerator gradually decreases by repeating the development. On the other hand, by adding unused aqueous developing solution, it is possible to maintain the concentration of the developing accelerator, but there is a problem that the amount of the aqueous developing solution used increases.

[0007] Therefore, the present invention provides a method for recovering a recovered liquid containing a developing accelerator from an aqueous developing waste liquid.

Means for Solving the Problems

[0008] As embodiments of the present invention, for example, the following can be mentioned. [1] A method for treating an aqueous developing waste liquid generated by developing a flexographic printing original plate using an aqueous developing solution, including a step of recovering a recovered liquid containing the developing accelerator and water from the aqueous developing waste liquid containing a developing residue, the developing accelerator, and water, where the developing accelerator is represented by the following formula (A1): Formula (A1): R 1 O(A 1 O) n R 2 (In the formula, R 1 and R 2 are each independently an alkyl group having 2 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms, A 1 is an alkylene group having 2 to 4 carbon atoms, n is an integer of 1 to 5) and contains a compound represented by, a method for treating an aqueous developing waste liquid. [2] The treatment method according to [1], wherein the recovery is recovery by distillation. [3] The treatment method according to [2], wherein the distillation is carried out at 100 hPa or less. [4] The treatment method according to any one of [1] to [3], wherein the recovery reduces the volume of the aqueous developing waste liquid to a range of 1 / 7 to 1 / 2 of the volume of the aqueous developing waste liquid before recovery. [5] The aforementioned aqueous developing waste liquid further contains a surfactant, The aforementioned surfactant is defined by the following formula (B1): Formula (B1):RO(AO) p H (In the formula, R is an alkyl group or aryl group having 10 to 20 carbon atoms. A is an alkylene group having 2 to 4 carbon atoms. p is an integer between 1 and 50. A processing method according to any one of [1] to [4], comprising a compound represented by . [6] In the above formula (B1), R is an alkyl group or aryl group having 10 to 18 carbon atoms. A is an alkylene group having 2 to 4 carbon atoms. The processing method described in [5], where p is an integer between 6 and 10. [7] The treatment method according to any one of [1] to [6], wherein the amount of the compound represented by formula (A1) contained in the recovered liquid is 25% by mass or more and 61% by mass or less, based on the amount of the compound represented by formula (A1) contained in the aqueous developing waste liquid. [8] The aforementioned aqueous developing waste liquid further contains an antifoaming agent, The treatment method according to any one of [1] to [7], wherein the recovered liquid further comprises the defoaming agent. [9] The treatment method according to [8], wherein the defoaming agent comprises a silicone compound.

[10] The processing method according to any one of [1] to [9], further comprising the step of reusing the recovered liquid for developing a flexographic printing plate.

[11] The processing method according to

[10] , wherein the recovered liquid is mixed with an aqueous developer.

[12] The treatment method according to

[11] , wherein the amount of the recovered liquid is adjusted so that the concentration of the compound represented by the formula (A1) in the mixed liquid of the recovered liquid and the aqueous developer is within the range of 0.15 to 0.30% by mass.

[13] The treatment method according to any one of [1] to

[12] , further comprising a step of reusing the recovered liquid for rinsing the developed flexographic printing plate.

Advantages of the Invention

[0009] According to the present invention, a method for recovering a recovered liquid containing a development accelerator from an aqueous development waste liquid can be provided.

Brief Description of the Drawings

[0010] [Figure 1] FIG. 1 shows a schematic view of an embodiment of an apparatus for carrying out the method of the present invention. [Figure 2] FIG. 2 shows the relationship (transition) between the number of developed flexographic printing plates and the DBDG concentration of the aqueous developer in the developer tank.

Embodiments of the Invention

[0011] Hereinafter, embodiments of the present invention will be specifically described, but the present invention is not limited to these, and various modifications are possible without departing from the gist thereof.

[0012] <Method for Treating Aqueous Development Waste Liquid> One embodiment of the present invention is a method for treating an aqueous development waste liquid generated by developing a flexographic printing plate using an aqueous developer, the method including a step of recovering a recovered liquid containing the development accelerator and water from the aqueous development waste liquid containing development residues, the development accelerator, and water (hereinafter referred to as the "recovery step"), wherein the development accelerator is represented by the following formula (A1): Formula (A1): R 1 O(A 1 O) n R 2 (In the formula, R 1 and R 2Each of these is independently an alkyl group having 2 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms. A 1 This is an alkylene group having 2 to 4 carbon atoms. n is an integer between 1 and 5. The present invention relates to a method for treating aqueous developing wastewater containing a compound represented by [the formula shown].

[0013] In the method according to this embodiment, the development accelerator, which decreases with repeated development, is recovered from the aqueous development waste solution. For example, by using a recovery solution containing the development accelerator instead of water as the solvent for the aqueous developer added to maintain the concentration of the development accelerator, it is possible to maintain the concentration of the development accelerator in the aqueous developer while reducing the amount of aqueous developer added.

[0014] The method according to this embodiment will be explained using an example of an apparatus for carrying out the method. Figure 1 shows the developing system 1. The developing system 1 is, A developing device 2 for developing the flexographic printing plate 4; A developer tank 21 for storing aqueous developer is located inside the developing apparatus 2; A brush 5 is placed inside the developing device 2 to rub the surface of the flexographic printing plate 4; A vacuum distillation apparatus 3 for distilling aqueous developing waste liquid; A concentration vessel 31 for storing and concentrating aqueous developing waste liquid is located inside the vacuum distillation apparatus 3; A developing solution supply pipe 61 that supplies the developing solution to the developing solution tank 21; A water supply pipe 62 that supplies water to the developing solution tank 21; A developer circulation pipe 63 supplies the aqueous developer stored in the developer tank 21 to the flexographic printing plate 4; A waste liquid discharge pipe 64 sends the aqueous developer stored in the developer tank 21 to the concentration kettle 31; A recovery liquid return pipe 65 returns the recovery liquid, which has been recovered from the aqueous developing waste liquid stored in the concentration kettle 31, to the developing liquid tank 21; A concentrated wastewater discharge pipe 66 for discharging the concentrated aqueous developing wastewater from the concentration kettle 31; It is equipped with. Furthermore, a developing waste tank (not shown) for storing aqueous developing waste liquid may be provided between the concentration kettle 31 and the developing tank 21. Alternatively, instead of directly sending the recovered liquid separated and recovered from the concentration kettle 31 to the developing apparatus 2, a further recovered liquid storage tank (not shown) may be provided.

[0015] In the developing system 1, the aqueous developer stored in the developer tank 21 is supplied to the flexographic printing plate 4 via the developer circulation pipe 63, while the surface of the flexographic printing plate 4 is rubbed by the brush 5. The developing residue removed from the flexographic printing plate 4 is returned to the developer tank 21 along with the aqueous developer. Each time a new flexographic printing plate is developed, developer concentrate and water are supplied to the developer tank 21 via the developer concentrate supply pipe 61 and the water supply pipe 62 as needed, and the aqueous developer (aqueous developing waste) is sent from the developer tank 21 to the concentration kettle 31 via the waste liquid discharge pipe 64. From the aqueous developing waste stored in the concentration kettle 31, a recovery solution containing a developing accelerator and water is recovered by vacuum distillation and returned to the developer tank 21 via the recovery solution return pipe 65. The aqueous developing waste concentrated by vacuum distillation is discharged via the concentrated waste discharge pipe 66.

[0016] In the method according to this embodiment, the aqueous developing waste liquid generated by developing a flexographic printing plate using an aqueous developing solution is treated. In this specification, "aqueous developer" means a developer that contains water as a solvent. In this specification, "aqueous developing waste" means aqueous developing solution that has been used for developing and then discarded. Here, "discarded" means, for example, in Figure 1, that it has been sent from the developing solution tank 21 to the concentration kettle 31.

[0017] (Recovery process) In the recovery step of the method according to this embodiment, a recovery solution is recovered from aqueous developing wastewater. The aqueous developing wastewater contains developing residue, a developing accelerator, and water. The recovery solution contains a developing accelerator and water.

[0018] In this specification, "development residue" refers to impurities that are mixed into the developer during development (for example, unexposed resin removed from the developed flexographic printing plate). Examples of resins constituting the photosensitive resin layer of the flexographic printing plate include hydrophobic resins, hydrophilic resins, and combinations thereof. When using a hydrophobic resin, it is preferable to impart hydrophilicity to the hydrophobic resin. By imparting hydrophilicity to the hydrophobic resin, it becomes easier to develop the hydrophobic resin with an aqueous developer. The main component of the resin constituting the photosensitive resin layer is preferably, A hydrophobic resin modified with a carboxylic acid or its salts; A mixture of a hydrophobic component mainly composed of a hydrophobic resin and a hydrophilic component mainly composed of a hydrophilic resin; A resin formed by chemically bonding a hydrophobic resin and a hydrophilic resin; A resin obtained by block copolymerizing hydrophobic monomers, which are raw materials for hydrophobic resins, with hydrophilic monomers, which are raw materials for hydrophilic resins; And so on.

[0019] The developing accelerator is given by the following formula (A1): Formula (A1):R 1 O(A 1 O) n R 2 (In the formula, R 1 and R 2 Each of these is independently a C2-C6 alkyl group or a C2-C6 alkenyl group, preferably a C2-C6 alkyl group, and more preferably a C4 alkyl group (butyl group). A 1 is an alkylene group having 2 to 4 carbon atoms, preferably an alkylene group having 2 or 3 carbon atoms, and more preferably an alkylene group having 2 carbon atoms (-CH2CH2-). n is an integer between 1 and 5, preferably between 1 and 3, and more preferably 2. It contains a compound represented by (hereinafter referred to as "compound (A1)").

[0020] The amount of compound (A1) contained in the aqueous developing wastewater is not particularly limited, but from the viewpoint of increasing the development speed of the developing apparatus, the lower limit is preferably 0.05% by mass, more preferably 0.15% by mass, and the upper limit is preferably 0.40% by mass, more preferably 0.30% by mass. The numerical range can be defined by appropriately combining the lower and upper limits. For example, the amount of compound (A1) contained in the aqueous developing wastewater is preferably 0.05 to 0.40% by mass, more preferably 0.15 to 0.30% by mass.

[0021] The development accelerator is given by the following formula (A2): Formula (A2):R 3 O(A 2 O) m H (In the formula, R 3 This is an alkyl group having 3 to 8 carbon atoms, or an alkenyl group having 3 to 8 carbon atoms, preferably an alkyl group having 3 to 8 carbon atoms, and more preferably an alkyl group having 6 carbon atoms (hexyl group). A 2 is an alkylene group having 2 to 4 carbon atoms, preferably an alkylene group having 2 or 3 carbon atoms, and more preferably an alkylene group having 2 carbon atoms (-CH2CH2-). m is an integer between 1 and 5, preferably between 1 and 3, and more preferably 2. The material may further contain a compound represented by (hereinafter referred to as "compound (A2)").

[0022] The amount of compound (A2) contained in the aqueous developing wastewater is not particularly limited, but from the viewpoint of increasing the development speed of the developing apparatus, the lower limit is preferably 0.20% by mass, more preferably 0.25% by mass, and the upper limit is preferably 0.70% by mass, more preferably 0.60% by mass. The numerical range can be defined by appropriately combining the lower and upper limits. For example, the amount of compound (A2) contained in the aqueous developing wastewater is preferably 0.20 to 0.70% by mass, more preferably 0.25 to 0.60% by mass.

[0023] The aqueous developing waste liquid preferably further contains a surfactant. The surfactant facilitates bonding with the developing residue and inhibits bonding between the developing residue and the developing accelerator, thereby improving the recovery rate of the developing accelerator in the recovery process.

[0024] From the viewpoint of improving the recovery rate of the development accelerator, a nonionic surfactant is preferred, and a polyalkylene glycol represented by the following formula (B1) is more preferred. Formula (B1):RO(AO) p H (In the formula, R is an alkyl group or aryl group having 10 to 20 carbon atoms. A is an alkylene group having 2 to 4 carbon atoms. p is an integer between 1 and 50.

[0025] In equation (B1), R is preferably an alkyl group or aryl group having 10 to 18 carbon atoms. A is preferably an alkylene group having 2 to 4 carbon atoms. p is preferably an integer between 6 and 10.

[0026] The polyalkylene glycol represented by formula (B1) is preferably a polyoxyalkylene alkyl ether.

[0027] The polyoxyalkylene alkyl ether is preferably a compound represented by the following formula (B1-1) or (B1-2). Formula (B1-1):R 4 O(CH2CH2O) p H Formula (B1-2):R 4 O(CH2CH2O) p1 (CH(CH3)CH2O) p2 H

[0028] In formula (B1-1), R 4 p is an alkyl group having 1 to 20 carbon atoms, and p is an integer from 1 to 50. In formula (B1-2), R4 (CH2CH2O) is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and the sum of p1 and p2 is an integer between 1 and 50. p1 (CH(CH3)CH2O) p2 -The portion may be either a random polymer or a block polymer.

[0029] Commercially available polyoxyalkylene alkyl ethers may be used. Commercially available polyoxyalkylene alkyl ethers are not particularly limited, but examples include Newcol (registered trademark) NT-3, Newcol NT-5, Newcol NT-7, Newcol NT-9, Newcol NT-12, Newcol 2302, Newcol 2303, Newcol 1203, Newcol 1204, Newcol 2303-Y, Newcol 2304-YM, Newcol 2304-Y, polyoxyethylene 2-ethylhexyl ether (Newcol 1004, Newcol 1006, Newcol 1008), polyoxyethylene tridecyl ether (Newcol 1305), Newcol 2306-Y, Newcol 2306-HY, Newcol 2308-Y, Newcol 2308-LY, Newcol 708, Newcol 709, Newcol 82, Newcol 85, Newcol 1210, Newcol 1902-Y, etc., all manufactured by Nippon Emulsifier Co., Ltd.

[0030] The polyalkylene glycol represented by formula (B1) is preferably a polyoxyalkylene polycyclic phenyl ether.

[0031] The polyoxyalkylene polycyclic phenyl ether is preferably a compound represented by the following formula (B1-3). Formula (B1-3):R 4 O(CH2CH2O) p H

[0032] In formula (B1-3), R 4 It is a polycyclic phenyl compound, and p is an integer from 1 to 50.

[0033] Commercially available polyoxyalkylene polycyclic phenyl ethers may be used. There are no particular restrictions on the commercially available polyoxyalkylene polycyclic phenyl ethers, but examples include Newcol 703, Newcol 704, and Newcol 2604.

[0034] The amount of surfactant contained in aqueous developing wastewater is not particularly limited, but the lower limit is preferably 1.0% by mass and more preferably 1.5% by mass from the viewpoint of improving the recovery efficiency of the developing accelerator, and the upper limit is preferably 10% by mass and more preferably 6.0% by mass from the viewpoint of improving the development speed in the developing process. The numerical range can be defined by appropriately combining the lower and upper limits. For example, the amount of surfactant contained in aqueous developing wastewater is preferably 1.0 to 10% by mass and more preferably 1.5 to 6.0% by mass.

[0035] Aqueous developing waste liquid may further contain inorganic bases. Inorganic bases can function as pH adjusters. Examples of inorganic bases include lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, cesium bicarbonate, potassium fluoride, sodium fluoride, cesium fluoride, lithium chloride, and lithium bromide.

[0036] The amount of inorganic base contained in aqueous developing wastewater is not particularly limited, but from the viewpoint of increasing the particle size of the dispersed developing residue and suppressing its mixing into the recovery solution, it is preferable to add it so that the pH of the aqueous developing wastewater becomes 9 or higher, and from the viewpoint of economic efficiency, it is preferable to adjust the amount added so that the pH becomes 12 or lower.

[0037] The aqueous developing waste liquid may also contain an antifoaming agent. If the antifoaming agent is recovered together with the waste liquid during the recovery process, it is possible to suppress problems caused by foaming when the recovered liquid is returned for reuse.

[0038] Examples of defoaming agents include silicone compounds, and compounds containing organically modified silicones, perfluoroalkyl group-containing silicones, and fluorine-modified silicones can be used. From the viewpoint of improving dispersibility in aqueous developers, it is preferable to use emulsion-type defoaming agents. Commercially available products can be used, such as KM-73, KM-73A, KM-73E, KM-70, KM-71, KM-75, KM-7750D, KM-85, KM-89, KM-90, KM-98, KM7752, KM-72, KM-72S, KM-72GS, KM-72F, and KM-72FS from Shin-Etsu Chemical Co., Ltd.

[0039] The recovery process is preferably carried out by distillation, and more preferably by vacuum distillation. The vacuum conditions are preferably 120 hPa or less, more preferably 100 hPa or less, and even more preferably 80 hPa or less. By performing distillation under vacuum conditions, the boiling point of water is lowered, making it possible to recover the recovered liquid with less energy. The lower limit of the pressure is not particularly limited, but may be, for example, 10 Pa. The vacuum conditions are preferably 10 to 120 hPa, more preferably 10 to 100 hPa, and even more preferably 10 to 80 hPa.

[0040] The distillation temperature can be appropriately changed according to the boiling point of water under predetermined pressure conditions. While not particularly limited, the distillation temperature is preferably 65°C or lower, more preferably 50°C or lower, and even more preferably 40°C or lower. The lower limit of the distillation temperature is not particularly limited, but may be, for example, 20°C or 30°C. The numerical range can be defined by appropriately combining the lower and upper limits. For example, the distillation temperature is preferably 20 to 65°C, more preferably 20 to 50°C, and even more preferably 30 to 40°C. By setting the distillation temperature within the above range, it is possible to control the recovery efficiency of the developing accelerator while suppressing power consumption during distillation recovery.

[0041] In the recovery process, the lower limit of the amount of compound (A1) contained in the recovered solution is preferably 25% by mass, more preferably 30% by mass, and the upper limit of the amount of compound (A1) contained in the recovered solution is preferably 61% by mass, more preferably 60% by mass, based on the amount of compound (A1) contained in the aqueous developing wastewater. The numerical range can be defined by appropriately combining the lower and upper limits. For example, the amount of compound (A1) contained in the recovered solution is preferably 25% or more and 61% or less by mass, more preferably 30% or more and 60% or less by mass. By recovering in such amounts, it becomes easier to control the concentration of compound (A1) in the aqueous developing solution within a certain range when the recovered solution is reused.

[0042] Since the evaporation ratio of water to compound (A1) changes depending on the distillation temperature, the recovery rate of compound (A1) from aqueous developing waste can be adjusted by changing the distillation temperature.

[0043] There are no particular limitations on when the recovery process is completed, but for example, it may be completed when the volume of the aqueous developer waste liquid has decreased to 1 / 7 to 1 / 2 or 1 / 5 to 1 / 3 of its original volume before recovery.

[0044] (Reuse process) The method according to this embodiment includes, in addition to the recovery step, A process of reusing the recovered liquid for developing flexographic printing plates, and / or The process involves reusing the recovered liquid to rinse the developed flexographic printing plates. It may also include the following.

[0045] When the recovered solution is to be reused for developing, it is preferable to mix the recovered solution with an aqueous developer. In this context, "aqueous developer" includes both unused aqueous developer and used aqueous developer.

[0046] "Unused aqueous developer" refers to aqueous developer that has not been used for development (this term also includes developer stock). For example, in Figure 1, "unused aqueous developer" refers to the developer stock supplied from the developer stock supply pipe 61 and the water (or developer stock only) supplied from the water supply pipe 62.

[0047] "Used aqueous developer" refers to aqueous developer that has been used for developing but has not been discarded (in other words, aqueous developer that will be used again for developing). For example, in Figure 1, "used aqueous developer" is the aqueous developer stored in the developer tank 21.

[0048] The method by which the recovery solution is mixed with the aqueous developer is not particularly limited. For example, the recovery solution may be mixed with unused aqueous developer and then mixed with used aqueous developer, or the recovery solution and unused aqueous developer may be mixed separately with the used aqueous developer. Alternatively, the unused aqueous developer may be supplied to a flexographic printing plate, used once for development, and then mixed with the used aqueous developer.

[0049] The amount of recovered solution to be reused is preferably adjusted so that the concentration of compound (A1) in the mixture of the recovered solution and the aqueous developer falls within a predetermined range. In this context, "aqueous developer" includes unused aqueous developer and used aqueous developer. Therefore, the concentration of compound (A1) is, for example in Figure 1, the concentration in the aqueous developer stored in the developer tank 21 after the recovered solution, unused aqueous developer, and used aqueous developer have been mixed. The predetermined range is preferably within the range of 0.15 to 0.30 mass%.

[0050] In the method according to this embodiment, it is preferable to repeatedly perform the recovery step and the reuse step. This makes it possible to maintain the concentration of compound (A1) within a certain range even when development is repeated. [Examples]

[0051] The present invention will be described in more detail below using examples and comparative examples, but the technical scope of the present invention is not limited thereto.

[0052] The apparatus used in the examples and comparative examples is as follows: • Developing equipment: Asahi Kasei AWP TM -DEW 4260 PLF • Vacuum distillation apparatus: Veolia R-150

[0053] The aqueous developer used in the examples and comparative examples (stored in the developer tank of the developing apparatus) contains the following components. • Solvent (water, or a mixture of water and the recovery solution described below) • Surfactant (product name: Newcol NT-7, manufactured by Nippon Emulsifier Co., Ltd.) (1.0% by mass) • Surfactant (product name: Newcol NT-9, manufactured by Nippon Emulsifier Co., Ltd.) (1.0% by mass) • Development accelerator (diethylene glycol dibutyl ether (DBDG)) (0.2% by mass) • Development accelerator (diethylene glycol monohexyl ether (HeDG)) (0.3% by mass) • pH adjuster (potassium carbonate) (0.5% by mass) The photosensitive resin plates used are as follows: AWP T M-DEW (1.14mm, BL size)

[0054] [Example 1] Flexographic printing plates were developed using a developing apparatus with 400L of aqueous developer (solvent: water) in the developer tank. Specifically, after developing each plate, 15L of new aqueous developer (solvent: water) was added to the developer tank, and the same amount of aqueous developer was discarded from the tank. This procedure was performed for five plates. The discarded aqueous developer (waste liquid) was then subjected to vacuum distillation under conditions of a distillation temperature of 30-40°C and an internal pressure of 30-80 hPa, concentrating one batch of 64L to 16L (4-fold concentration) to obtain the recovered solution (distillate). Before vacuum distillation, Shin-Etsu Chemical Co., Ltd.'s KM-7750D was added to the aqueous developer waste liquid as an antifoaming agent. This suppressed foaming (due to surfactant) of the aqueous developer waste liquid during vacuum distillation. For the development of the originals after the above, the solvent of the new aqueous developer added to the developer tank after development was changed from water to a mixture of the recovery solution and water (mass ratio 3:1), and the development was repeated in the same manner. That is, the operation of developing 5 originals → distillation recovery → developing 5 originals → distillation recovery was repeated. In this example, distillation was performed on multiple batches of waste liquid, and the DBDG recovery rate for each batch was in the range of 38-51%. DBDG recovery rate (%) = {[Amount of DBDG in recovered liquid (g)] / [Amount of DBDG in waste liquid (g)]} × 100 The DBDG concentration in aqueous developing waste liquid and recovered liquid was determined by quantitative analysis using gas chromatography. Table 1 and Figure 2 show the relationship (overlapping) between the number of developed negatives and the DBDG concentration of the aqueous developer in the developer tank.

[0055] [Comparative Example 1] Except for not using the recovery solution, the development process was repeated in the same manner as in Example 1. The relationship (overlapping) between the number of developed originals and the DBDG concentration of the aqueous developer in the developer tank is shown in Table 1 and Figure 2.

[0056] [Table 1]

[0057] As is clear from the results in Table 1 and Figure 2, by reusing the recovered solution, the DBDG concentration could be maintained within a certain range even after repeated development. [Explanation of symbols]

[0058] 1…Developing system 2… Developing equipment 21… Developer tank 3. Vacuum distillation apparatus 31... Concentration kettle 4… Flexographic printing plates 5…brush 61...Development stock solution supply pipe 62…Water supply pipe 63...Developer circulation tube 64...Waste liquid discharge pipe 65...Recovered liquid return tube 66... ​​Concentrated wastewater discharge pipe

Claims

1. A method for treating aqueous developing waste liquid generated by developing flexographic printing plates using an aqueous developing solution, A step of recovering a recovered solution containing the developing accelerator and water from an aqueous developing waste liquid containing developing residue, a developing accelerator and water, by distillation carried out at 100 hPa or less, The process involves mixing the recovered liquid with an aqueous developer to reuse it for developing flexographic printing plates, Includes, The aforementioned developing accelerator is given by the following formula (A1): Formula (A1): R 1 O(A 1 O) n R 2 (In the formula, R 1 and R 2 Each of these is independently an alkyl group having 2 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms. A 1 This is an alkylene group having 2 to 4 carbon atoms. n is an integer between 1 and 5. It contains a compound represented by, The amount of the compound represented by formula (A1) contained in the recovered liquid is 25% by mass or more and 61% by mass or less, based on the amount of the compound represented by formula (A1) contained in the aqueous developing waste liquid. Method for disposing of aqueous developer waste liquid.

2. The aforementioned recovery reduces the volume of the aqueous developing waste liquid to a range of 1 / 7 to 1 / 2 of the volume of the aqueous developing waste liquid before recovery. The processing method according to claim 1.

3. The aforementioned aqueous developing waste liquid further contains a surfactant, The aforementioned surfactant is defined by the following formula (B1): Formula (B1): RO(AO) p H (In the formula, R is an alkyl group or aryl group having 10 to 20 carbon atoms. A is an alkylene group having 2 to 4 carbon atoms. p is an integer between 1 and 50. A compound represented by The processing method according to claim 1 or 2.

4. In the above formula (B1), R is an alkyl group or aryl group having 10 to 18 carbon atoms. A is an alkylene group having 2 to 4 carbon atoms. p is an integer between 6 and 10. The processing method according to claim 3.

5. The aforementioned aqueous developing waste liquid further contains an antifoaming agent, The recovered liquid further comprises the defoaming agent. The processing method according to claim 1 or 2.

6. The aforementioned defoaming agent contains a silicone compound. The processing method according to claim 5.

7. The amount of the recovered solution is adjusted so that the concentration of the compound represented by formula (A1) in the mixture of the recovered solution and the aqueous developer is within the range of 0.15 to 0.30% by mass. The processing method according to claim 1 or 2.

8. The process further includes reusing the recovered liquid to rinse the developed flexographic printing plate. The processing method according to claim 1 or 2.

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