Method and apparatus for treating aqueous developing wastewater, and developing system.

Abstract

Provided is a method for treating an aqueous developer waste liquid that is generated due to development of a flexographic printing original plate using an aqueous developer liquid, the method including: a first filtration step in which an aqueous developer waste liquid at 5-48°C inclusive is filtered using a microfiltration membrane to obtain a recovered liquid and a concentrated waste liquid; and a re-use step in which the recovered liquid is re-used in development of a flexographic printing original plate.

Description

[Technical Field]

[0001] This invention relates to a method and apparatus for treating aqueous developing wastewater, as well as a developing system. [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 using 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 post-exposing it. Flexographic printing plates can be obtained, for example, by solvent development, in which the uncured areas are dissolved and developed with a solvent developer, or by aqueous development, in which the uncured areas are peeled and developed with an aqueous developer containing a surfactant. However, both solvent development and aqueous development generate waste solutions. CO2 is generated when manufacturing solvent or aqueous developers, and when these development waste solutions are disposed of by incineration. From an environmental perspective, it is desirable to reduce the amount of developer used during the development of printing plates and the amount of development waste generated.

[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] Aqueous developer wastewater contains not only developer components (e.g., surfactants) but also development residue, which is an impurity that gets mixed into the developer during development (e.g., unexposed resin removed from the developed flexographic printing plate). When reusing aqueous developer wastewater, it is necessary to remove the development residue. Here, it is expected that all of the developer components can be recovered by filtering the aqueous developer wastewater using a filtration membrane with a pore size larger than that of the developer components and smaller than that of the development residue. However, the inventors have found that in reality, the developer components are also removed (i.e., the concentration of the developer decreases).

[0007] Therefore, the present invention aims to improve the recovery rate of developer components when filtering aqueous developing wastewater and concentrated wastewater. [Means for solving the problem]

[0008] As a result of diligent research by the present inventors, it has been found that the recovery rate of developer components (e.g., surfactants) can be improved by filtering aqueous developer waste and concentrated waste under low-temperature conditions.

[0009] The present invention includes the following embodiments. [1] A method for treating aqueous developing waste liquid generated by developing flexographic printing plates using an aqueous developing solution, A first filtration step involves filtering the aqueous developing waste liquid, which is at a temperature of 5°C to 48°C, through a microfiltration membrane to obtain a recovered liquid and a concentrated waste liquid. The recovered liquid is reused in the development of flexographic printing plates in a reuse process, A processing method that includes this. [2] The processing method according to [1], further comprising a temperature control step of adjusting the temperature of the aqueous developing waste liquid to 5°C or more and 43°C or less before the first filtration step. [3] The treatment method according to [1] or [2], further comprising a second filtration step of repeatedly performing the first filtration step using the concentrated waste liquid as the aqueous developing waste liquid. [4] The treatment method according to [3], wherein during the second filtration step, the temperature of the concentrated waste liquid is controlled to be 5°C or higher and 48°C or lower. [5] The aqueous developing waste liquid contains a surfactant, The treatment method according to [3] or [4], wherein the permeation rate of the surfactant in the total of the recovered liquids obtained in the first filtration step and the second filtration step is 42% or higher and 95% or lower. [6] The treatment method according to [5], wherein the permeation rate of the surfactant is 55% or higher and 95% or lower. [(7)] The treatment method according to any one of [3] to [6], wherein when the amount of the concentrated waste liquid falls below a predetermined standard during the second filtration step, fresh aqueous developing waste liquid is added to the concentrated waste liquid. [8] When at least one of the following (A) to (F) satisfies a predetermined standard, the concentrated waste liquid is discarded, (A) The total amount of the recovered liquid, (B) The number of times of adding fresh aqueous developing waste liquid to the concentrated waste liquid, (C) The total amount of fresh aqueous developing waste liquid added to the concentrated waste liquid, (D) The supply pressure of the aqueous developing waste liquid or the concentrated waste liquid to the filtration membrane, (E) The outlet pressure of the aqueous developing waste liquid or the concentrated waste liquid from the filtration membrane, (F) The circulation flow rate of the aqueous developing waste liquid or the concentrated waste liquid to the filtration membrane, The treatment method according to any one of [1] to [7]. [9] The treatment method according to any one of [1] to [8], further comprising a cleaning step of cleaning the filtration membrane with an acidic aqueous solution having a pH of 3 or lower.

[10] The cleaning step is Immersing the filtration membrane in the acidic aqueous solution, and / or The acidic aqueous solution is circulated through the aforementioned filter membrane. The processing method described in [9], including the method described in [9].

[11] A device for processing aqueous developing waste liquid generated by developing flexographic printing plates using aqueous developing solution, A water-based developing waste liquid storage tank for storing the aforementioned water-based developing waste liquid, A filtration module having a microfiltration membrane for filtering the aqueous developing waste liquid, A recovered liquid storage tank for storing the recovered liquid produced by the filtration, A processing device that includes a processing device.

[12] The apparatus according to

[20] , further comprising a circulation tank for circulating the concentrated waste liquid generated by the filtration to the filtration module.

[13] The apparatus according to

[21] , wherein the circulation tank has a temperature controller.

[14] A processing apparatus as described in any of

[11] to

[13] , A developing apparatus that discharges aqueous developing waste liquid by developing a flexographic printing plate using an aqueous developing solution, A developing system, including a development system. [Effects of the Invention]

[0010] According to the present invention, the recovery rate of developer components when filtering aqueous developing wastewater and concentrated wastewater can be improved. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows a schematic diagram of a developing system according to one embodiment of the present invention. [Figure 2] Figure 2 shows the configuration for adjusting the filtration pressure (filtration rate). [Figure 3] This shows the temperature change of developing waste liquid over time, with and without temperature control. [Modes for carrying out the invention]

[0012] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these, and various modifications are possible without departing from the spirit of the invention.

[0013] <Disposal method for aqueous developer waste liquid> One embodiment of the present invention is a method for treating aqueous developing waste liquid generated by developing a flexographic printing plate using an aqueous developing solution, A first filtration step involves filtering the aqueous developing waste liquid, which is at a temperature of 5°C to 48°C, through a microfiltration membrane to obtain a recovered liquid and a concentrated waste liquid. The recovered liquid is reused in the development of flexographic printing plates in a reuse process, This concerns processing methods, including those mentioned above.

[0014] In the method according to this embodiment, filtering the aqueous developing waste liquid under low-temperature conditions reduces the amount of developer components removed during filtration. This allows the concentration of developer components in the recovered solution (filtrate) to be maintained, and by reusing the recovered solution for developing, the amount of new developer used can be reduced. Furthermore, by reusing the recovered solution, the amount of waste liquid that needs to be discarded can be reduced. Thus, the method according to this embodiment has significant economic and environmental advantages.

[0015] [Aqueous developing solution and aqueous developing waste solution] In this specification, "aqueous developer" means a developer that contains water as a solvent. In this specification, "aqueous developing waste liquid" means the aqueous developing liquid used for developing. In this specification, "concentrated waste liquid" means waste liquid obtained by filtering aqueous developing waste liquid.

[0016] The types of components contained in aqueous developer solutions (developer components) and aqueous developer waste or concentrated waste are not particularly limited, but examples include surfactants, additives, pH adjusters, and defoamers. In addition to the above components, aqueous developer waste or concentrated waste further contains development residue (for example, unexposed resin removed from the developed flexographic printing plate), which is an impurity that gets mixed into the developer solution during development.

[0017] (Surfactants) The type of surfactant is not particularly limited, but nonionic surfactants, anionic surfactants, or combinations thereof are preferred. The nonionic surfactant is more preferably a polyalkylene glycol represented 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.

[0018] 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.

[0019] The polyalkylene glycol represented by formula (B1) is preferably a polyoxyalkylene alkyl ether.

[0020] 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

[0021] In formula (B1-1), R 4 is an alkyl group having 1 to 20 carbon atoms, and p is an integer from 1 to 50.

[0022] In formula (B1-2), R[[ID=B12]] 4 is hydrogen or an alkyl group having 1 to 20 carbon atoms, and the sum of p1 and p2 is an integer from 1 to 50. -(CH2CH2O) p1 (CH(CH3)CH2O) p2 The - part may be a random polymer or a block polymer.

[0023] Commercially available products may be used as the polyoxyalkylene alkyl ether. Commercially available polyoxyalkylene alkyl ethers are not particularly limited. For example, 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. manufactured by Nippon Emulsion Co., Ltd. may be mentioned.

[0024] The polyalkylene glycol represented by formula (B1) is preferably a polyoxyalkylene polycyclic phenyl ether.

[0025] The polyoxyalkylene polycyclic phenyl ether is preferably a compound represented by the following formula (B1-3). Formula (B1-3): R 4O(CH2CH2O) p H

[0026] In formula (B1-3), R 4 It is a polycyclic phenyl compound, and p is an integer from 1 to 50.

[0027] 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.

[0028] Anionic surfactants are preferably alkyl ether sulfate salts, alkyl sulfate salts, fatty acid salts, linear alkylbenzene sulfonates, or combinations thereof. Examples of alkyl ether sulfate salts include sodium polyoxyethylene lauryl ether sulfate (e.g., Sanol LMT-1430 manufactured by Lion Corporation) and polyoxyethylene (C 13 ) Alkyl ether sulfate sodium (for example, Sanol TD-3130 manufactured by Lion Corporation) or alkyl ether sulfate salts with 8 to 18 carbon atoms in the alkyl group (for example, Teikapol NE1230 manufactured by Teika Corporation) may be used.

[0029] The amount of surfactant contained in aqueous developing wastewater is not particularly limited, but from the viewpoint of increasing the development speed, the lower limit is preferably 0.01% by mass, more preferably 0.1% by mass, even more preferably 1.0% by mass, and particularly preferably 1.5% by mass, and the upper limit is preferably 10% by mass, and more preferably 6.0% by mass. 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 0.1 to 10% by mass, more preferably 1.0 to 10% by mass, even more preferably 1.0 to 6.0% by mass, and particularly preferably 1.5 to 6.0% by mass.

[0030] (Additives) The type of additive is not particularly limited, but compounds represented by the following formula (A1) or formula (A2) are preferred.

[0031] 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, preferably an alkyl group having 2 to 6 carbon atoms, and more preferably an alkyl group having 4 carbon atoms (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.

[0032] 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.

[0033] The amount of the compound represented by formula (A1) contained in aqueous developing wastewater is not particularly limited, but from the viewpoint of increasing the development speed, 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 the compound represented by formula (A1) contained in aqueous developing wastewater is preferably 0.05% by mass or more and 0.40% by mass or less, more preferably 0.15% by mass or more and 0.30% by mass or less.

[0034] The amount of the compound represented by formula (A2) contained in aqueous developing wastewater is not particularly limited, but from the viewpoint of increasing the development speed, 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 the compound represented by formula (A2) contained in aqueous developing wastewater is preferably 0.20% by mass or more and 0.70% by mass or less, more preferably 0.25% by mass or more and 0.60% by mass or less.

[0035] (pH adjuster) The type of pH adjuster is not particularly limited, but inorganic bases are preferred. 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 pH adjuster included in aqueous developer wastewater is not particularly limited, but from the viewpoint of increasing the development speed, it is preferable that it be included in an amount such that the pH of the aqueous developer wastewater is between 9 and 12.

[0037] (Antifoaming agent) The type of defoaming agent is not particularly limited, but examples include silicone compounds, more specifically, compounds containing organically modified silicones, perfluoroalkyl group-containing silicones, or fluorine-modified silicones. From the viewpoint of improving dispersibility in aqueous developers, it is preferable to use emulsion-type defoaming agents. Examples of commercially available emulsion-type defoaming agents include 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, all manufactured by Shin-Etsu Chemical Co., Ltd.

[0038] (Developing residue) Examples of resins that make up the photosensitive resin layer of a 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.

[0039] (Other ingredients) The aqueous developer solution and the aqueous developer waste or concentrated waste may further contain other components such as viscosity modifiers, stabilizers, and fragrances.

[0040] [Each step in the processing method] The processing method according to this embodiment preferably includes a temperature control step, a first filtration step, a second filtration step, and a reuse step. Each step will be described below.

[0041] (Temperature adjustment process) The temperature control step is a process that takes place before the first filtration step, which will be described later, in which the temperature of the aqueous developing waste liquid is adjusted to between 5°C and 43°C.

[0042] Flexographic printing plates are typically developed with the developer heated to a higher temperature to increase the development speed, which also increases the temperature of the aqueous developer waste liquid produced. In the first filtration step, the aqueous developer waste liquid is filtered at a lower temperature, so it is preferable to lower the temperature of the aqueous developer waste liquid beforehand using a temperature control step.

[0043] Furthermore, while the aqueous developer waste liquid is actually filtered while circulating within a predetermined apparatus, the temperature of the aqueous developer waste liquid tends to rise during circulation due to heat sources, friction, etc., within the apparatus. Therefore, in the temperature control step, it is preferable to adjust the temperature of the aqueous developer waste liquid to a temperature lower than the temperature required in the first filtration step. Specifically, considering the rate of temperature rise of the aqueous developer waste liquid during circulation, it is preferable to lower the temperature of the aqueous developer waste liquid to a temperature at least 5°C lower than the upper temperature limit (48°C) required in the first filtration step. That is, in the temperature control step, the temperature of the aqueous developer waste liquid is adjusted to 5°C to 43°C, preferably 5°C to 35°C, and more preferably 5°C to 30°C. The reason why 5°C or higher is preferable is to prevent the aqueous developer waste liquid from freezing.

[0044] There are no particular limitations on the method for adjusting the temperature of aqueous developer wastewater, but examples include leaving the aqueous developer wastewater to dissipate heat naturally, performing heat exchange, and direct cooling. From the viewpoint of reducing power consumption and CO2 emissions, leaving the aqueous developer wastewater to dissipate heat naturally is preferred. When leaving the aqueous developer wastewater to dissipate heat naturally, it is preferable to provide an aqueous developer wastewater storage tank for temporarily storing the developer wastewater to avoid contamination of the circulation tank in the membrane filtration system.

[0045] (First filtration step) The first filtration step involves filtering aqueous developing waste liquid at temperatures between 5°C and 48°C using a microfiltration membrane (MF membrane) to obtain a recovered solution and concentrated waste liquid.

[0046] Filtering aqueous developer waste liquid under low-temperature conditions can improve the recovery rate of developer components. Therefore, the temperature of the aqueous developer waste liquid in the first filtration step is 5°C to 48°C, preferably 5°C to 43°C, and more preferably 5°C to 40°C. Filtering the aqueous developer waste liquid within the above temperature range can improve the recovery rate of surfactants. The lower temperature limit is to prevent the aqueous developer waste liquid from freezing.

[0047] The first filtration step is preferably carried out using a cross-flow method with a hollow fiber membrane as the filtration membrane. Examples of commercially available hollow fiber membranes include Asahi Kasei's Microza® MF Module USW-543 (nominal pore size: 0.1 μm), UMW-553 (nominal pore size: 0.2 μm), USP-343 (nominal pore size: 0.1 μm), UMP-353 (nominal pore size: 0.2 μm), ULW-348 (nominal pore size: 0.45 μm), and UTP-6443 (nominal pore size: 0.2 μm), and Kuraray's Puria® ML MLE-7101 (1210) (nominal pore diameter: 0.1 μm), MLE-7101H (1210) (nominal pore diameter: 0.1 μm), Sumitomo Electric POREFLON (registered trademark) module -01B25 (nominal pore diameter: 0.08 μm), -11B50 (nominal pore diameter: 0.08 μm), -11 B70 (nominal pore size: 0.08 μm), -11B110 (nominal pore size: 0.08 μm), -02B25 (nominal pore size: 0.1 μm), -12 Examples include B50 (nominal pore size: 0.1 μm), -12B70 (nominal pore size: 0.1 μm), and -12B100 (nominal pore size: 0.1 μm). By employing a cross-flow system, clogging of the membrane during filtration can be suppressed, allowing for the maintenance of a high filtration rate (amount of recovered liquid obtained per unit time).

[0048] From the viewpoint of obtaining a large amount of recovered liquid, it is preferable to make the pressure at the inlet side of the filtration membrane higher than the pressure at the outlet side. Furthermore, from the viewpoint of exhibiting a cross-flow effect and suppressing membrane clogging during filtration, thereby maintaining a high filtration rate (amount of recovered liquid obtained per unit time), it is preferable that the circulation flow velocity of the aqueous developing waste liquid to the membrane module during filtration be 1.3 m / second or higher.

[0049] (Second filtration step) The second filtration step is a process in which the concentrated waste liquid obtained in the first filtration step is used as aqueous developing waste liquid, and the first filtration step is repeated. For example, in the developing system shown in Figure 1, where aqueous developing waste liquid is circulated between the circulation tank 32 and the filtration module 33, the first filtration step is defined as the period until the same amount of aqueous developing waste liquid as the amount initially contained in the circulation tank 32 is filtered by the filtration module 33, and the subsequent filtration until the concentrated waste liquid is discarded is defined as the second filtration step.

[0050] In the second filtration step, by repeatedly filtering the concentrated waste liquid, it is possible to obtain a larger amount of recovered liquid while reducing the amount of concentrated waste liquid.

[0051] As described above, the temperature of the concentrated waste liquid tends to rise as it circulates within the apparatus due to heat sources, friction, etc. Therefore, from the viewpoint of improving the recovery rate of developer components, it is preferable to control the temperature of the concentrated waste liquid to 5°C or higher and 48°C or lower (preferably 5°C or higher and 43°C or lower, more preferably 5°C or higher and 40°C or lower) during the second filtration step.

[0052] The method of temperature control is not particularly limited, but for example, the temperature of the concentrated waste liquid can be directly checked and lowered as needed. The method of lowering the temperature is not particularly limited, but examples include letting the concentrated waste liquid stand to dissipate heat naturally (temporarily suspending filtration), performing heat exchange, and direct cooling. Heat exchange and direct cooling can also be performed in parallel with the filtration process. In addition, the temperature of the concentrated waste liquid can be lowered by adding new aqueous developing waste liquid whose temperature has been lowered in the above temperature control process. Alternatively, instead of directly checking the temperature of the concentrated wastewater, temperature control may be performed using the amount of concentrated wastewater as an indirect indicator. That is, if the amount of concentrated wastewater falls below a predetermined standard, the temperature of the circulating concentrated wastewater may be lowered, assuming that the temperature of the circulating concentrated wastewater has exceeded a certain level. Furthermore, as the amount of concentrated wastewater decreases, its viscosity increases, slowing down the flow rate of the concentrated wastewater supplied to the filtration membrane. Therefore, temperature control may be performed using the supply flow rate of the concentrated wastewater as an indirect indicator. Furthermore, as the amount of concentrated wastewater decreases, its viscosity increases, and the supply pressure of the concentrated wastewater to the filtration membrane rises. Therefore, temperature control may be performed using the supply pressure of the concentrated wastewater as an indirect indicator.

[0053] Furthermore, the "temperature control" of the present invention includes a method of completing filtration before the temperature of the concentrated waste liquid exceeds the range of the present invention by increasing the filtration rate (amount of recovered liquid obtained per unit time). In other words, since the rise in temperature of the concentrated waste liquid is approximately proportional to the filtration time, it is possible to suppress the rise in temperature of the concentrated waste liquid by shortening the filtration time. Furthermore, "temperature control" in this specification also includes, for example, sufficiently cooling the waste liquid before filtration in the temperature adjustment process, increasing the filtration rate, or a combination of both, to complete filtration before the waste liquid temperature exceeds the upper limit. In such cases, it is not necessarily required to interrupt filtration and implement temperature control such as natural heat dissipation, heat exchange, or direct cooling. Methods for increasing the filtration rate will be described later, but the filtration rate may be adjusted to a sufficient rate before filtration, or it may be adjusted as appropriate during filtration according to the situation. Furthermore, all of the above-mentioned "temperature control" methods can be used individually or in any combination.

[0054] The permeability of the surfactant contained in the aqueous developing waste liquid is preferably 34% or higher, more preferably 42% or higher, and even more preferably 55% or higher. A permeability of 34% or higher results in a reduction in the amount of developing solution used, and a permeability of 55% or higher results in a reduction in CO2 emissions. CO2 reduction refers to a state in which the amount of CO2 reduction achieved by reusing the recovered solution (i.e., reduction in the amount of developing solution used and reduction in the amount of developing waste liquid discharged) exceeds the amount of CO2 emissions related to the amount of electricity consumed in implementing the method according to this embodiment (CO2 emissions generated during power generation). The permeability of the surfactant is preferably 95% or less, and more preferably 90% or less. When the permeability is 95% or less, the concentrated waste liquid obtained after filtration will also contain a sufficient amount of surfactant, which suppresses the aggregation of resin in the concentrated waste liquid and prevents malfunction of the membrane filtration device. The permeability of the surfactant is preferably 42% to 95%, more preferably 55% to 95%, and even more preferably 55% to 90%.

[0055] The permeability of surfactants can be calculated using the following formula. Transmittance = [Concentration of surfactant in recovered solution / Concentration of surfactant in developing waste solution] × 100

[0056] The transmittance is calculated based on the total recovered liquid obtained from the start of the first filtration process to the end of the second filtration process (i.e., the sum of the multiple recovered liquids obtained in the first and second filtration processes). In this case, the transmittance is the ratio of the concentration of surfactant in the total recovered liquid obtained from the start of the first filtration process to the end of the second filtration process to the concentration of surfactant in the developing waste liquid before filtration in the first filtration process.

[0057] The transmittance is affected not only by the temperature of the developing waste liquid but also by factors such as clogging of the filter membrane. In other words, as the filter membrane becomes more clogged, the transmittance tends to decrease. Therefore, if the transmittance falls below the lower limit mentioned above, it is preferable to maintain the transmittance within the desired range by performing a washing process as described later.

[0058] On the other hand, it is not common to increase the filtration rate in membrane filtration. This is because, even when using a cross-flow system, if the filtration rate is too high, the membrane will become clogged with developer residue, resulting in a significant decrease in the filtration rate over time, making repeated use impossible. Furthermore, as the membrane becomes clogged, the clogged developer residue traps developer components such as surfactants, reducing the permeability of the developer components in the filtration process. As a result, when reusing the recovered solution, it becomes necessary to add a large amount of developer to adjust the concentration. In other words, there is a trade-off between a high filtration rate, the lifespan of the hollow fiber membrane, and the permeability of the developer components. Therefore, it is common practice to restrict the filtration rate by restricting the piping of the recovered solution with a valve (filtration valve).

[0059] The inventors have invented a cleaning technique for hollow fiber membranes to achieve both high filtration speed, long lifespan of the hollow fiber membrane (suppression of clogging), and permeability of developer components. By implementing the cleaning method according to the present invention, even when filtering aqueous developer waste and concentrated waste at high filtration speeds, the hollow fiber membrane will not clog, and it will be possible to repeatedly use it while maintaining high filtration speed and permeability of developer components. This suppresses the temperature rise of the concentrated waste during filtration and improves the recovery efficiency of developer components.

[0060] One way to increase the filtration rate is to increase the pressure (filtration pressure) of the aqueous developing waste or concentrated waste liquid applied to the hollow fiber membrane (specific adjustment methods will be described later). In reality, since the material and shape of the membrane module used impose mechanical upper limits on the filtration pressure and related pressure values, the pressures must be adjusted to be below these upper limits. In addition to the cleaning method for the hollow fiber membrane described later, methods to suppress clogging and maintain a high filtration rate can also be used to improve the operational methods in the filtration process.

[0061] As the concentrated waste liquid is repeatedly filtered in the second filtration step, the concentration of developing residue in the concentrated waste liquid gradually increases, making the filter membrane more prone to clogging. Therefore, it is preferable to discard the concentrated waste liquid (end the filtration step) at a predetermined timing. For example, the concentrated waste liquid may be discarded if at least one of the following (A) to (F) meets a predetermined criterion. (A) Total volume of recovered liquid (B) Number of times new aqueous developing waste liquid is added to concentrated waste liquid, (C) Total amount of new aqueous developing waste liquid added to concentrated waste liquid, (D) Supply pressure of aqueous developing waste liquid or concentrated waste liquid to the filtration membrane, (E) The outlet pressure of the aqueous developing waste liquid or the concentrated waste liquid discharged from the filtration membrane, (F) Circulation flow rate (L / min) of aqueous developing waste or concentrated waste to the filtration membrane For example, by using the values ​​of (A) and (B) or (C), the concentration ratio achieved can be calculated, allowing the filtration process to be terminated at the desired concentration ratio. Furthermore, if the viscosity of the concentrated waste liquid increases significantly more than expected due to some factor, the supply pressure (D) of the concentrated waste liquid to the filtration membrane will rise, the outlet pressure (E) of the filtration membrane will fall, and the circulation flow rate (F) will fall before the desired concentration ratio is reached. By monitoring these factors and terminating the filtration process when predetermined criteria are met, the filtration process can be terminated without placing excessive load on the filtration membrane, thereby suppressing clogging. When implementing such an operation, it is preferable to use a system that monitors at least one of the above (A) to (F) (for example, A only, A+B, A+C, D only, E only, F only, or any combination of D to F) to determine whether or not a predetermined standard is met.

[0062] According to the present invention, by filtering aqueous developing waste or concentrated waste at a low temperature, the recovery efficiency (transmittance) of developing solution components (e.g., surfactants) can be increased. Since aqueous developing waste discharged from the developing apparatus is at a high temperature, the filtration process can be started after cooling. As a method for controlling the temperature during filtration, at least one of the above methods can be adopted, or multiple methods can be combined. By increasing the filtration rate, the filtration time can be shortened, and the temperature rise of the concentrated waste can be suppressed. As the filtration rate is increased and the filtration membrane is used repeatedly, clogging from developing residue occurs, reducing the filtration rate. However, by adopting the cleaning method for the filtration membrane according to the present invention and the method for stopping the filtration process described above, the progression of clogging can be prevented, and the filtration membrane can be used repeatedly at a high filtration rate. The filtration rate is not particularly limited, but is preferably 8.5 L / hr·m 2 The above is preferable, and more preferably 10 L / hr·m 2 The above, and more preferably 11.5 L / hr·m 2 That concludes the explanation. Furthermore, from the perspective of monitoring the achieved concentration ratio, the pressure gauges, and the circulation flow rate of the concentrated waste liquid to complete the concentration at the appropriate time, the upper limit of the filtration rate is 50 L / hr·m. 2 Preferably, it is 45 L / hr·m 2 The following is more preferable: L / hr·m 2 This is defined by the unit area of ​​the hollow fiber membrane and the amount of recovered liquid obtained per unit time of filtration.

[0063] (Reuse process) The reuse process involves reusing the recovered liquid obtained in the first filtration process and / or the second filtration process for developing flexographic printing plates.

[0064] Since the concentration of developer components in the recovered solution is lower compared to aqueous developers, it is preferable to add developer components (for example, at least one component selected from the group consisting of water, surfactants, additives, and pH adjusters) when reusing the recovered solution for development.

[0065] The developer component to be added (for example, at least one component selected from the group consisting of water, surfactants, additives, and pH adjusters) may be added directly to the recovered solution or to an aqueous developer mixed with the recovered solution.

[0066] (Washing process) The washing process involves washing the filtration membrane with an acidic aqueous solution with a pH of 3 or lower.

[0067] After the first and second filtration steps, developing residue adheres to the filter membrane, causing clogging and a decrease in the filtration speed. Therefore, it is preferable to wash the filter membrane. The washing step is preferably performed after the completion of the second filtration step, if necessary. However, the frequency and interval of washing are not particularly limited; for example, the washing step may be performed when a decrease in the filtration speed is observed.

[0068] The pH of the acidic aqueous solution is 3 or less, preferably 2.5 or less, and more preferably 2 or less, from the viewpoint of removing developing residue. When the pH is 3 or less, the absolute value of the zeta potential of the developing residue particles attached to the filter membrane increases, causing the particles to repel each other and reduce their size, thereby removing the particles and resolving clogging.

[0069] The types of acids contained in an acidic aqueous solution are not particularly limited, but examples include inorganic acids (e.g., phosphoric acid, nitric acid, hydrochloric acid, sulfuric acid) and organic acids (e.g., acetic acid, formic acid, citric acid, oxalic acid), or mixtures thereof.

[0070] The cleaning method is not particularly limited, but examples include immersing the filter membrane in an acidic aqueous solution and circulating the acidic aqueous solution through the filter membrane.

[0071] In the washing process, the filtration membrane may be backwashed using the recovered solution. Backwashing means flowing the recovered solution in the opposite direction to the flow direction of the aqueous developing waste or concentrated waste in the first and second filtration processes to remove developing residue attached to the filtration membrane. Backwashing may also be performed during filtration; for example, backwashing can be performed using the recovered solution after temporarily stopping the circulation of the concentrated waste (stopping the first and second filtration processes). In this case, the time interval between filtration and backwashing can be freely determined; for example, 10 minutes of filtration followed by 10 seconds of backwashing can be considered one cycle, and this cycle can be repeated.

[0072] <Aqueous developing wastewater treatment device and developing system> One embodiment of the present invention is a treatment device for aqueous developing waste liquid generated by developing a flexographic printing plate using an aqueous developing solution, A water-based developing waste liquid storage tank for storing the aforementioned water-based developing waste liquid, A filtration module having a microfiltration membrane for filtering the aqueous developing waste liquid, A recovered liquid storage tank for storing the recovered liquid produced by the filtration, This relates to a processing apparatus, including the processing apparatus.

[0073] The processing apparatus may further include a circulation tank for circulating the concentrated waste liquid produced by filtration back to the filtration module. The circulation tank may have a temperature controller.

[0074] The water-based developer waste storage tank may have a temperature controller. If the water-based developer waste storage tank does not have a temperature controller, the water-based developer waste may be left in the storage tank to allow it to dissipate heat naturally and lower its temperature.

[0075] One embodiment of the present invention relates to a developing system that includes the processing apparatus and a developing apparatus that discharges aqueous developing waste liquid by developing a flexographic printing plate using an aqueous developing solution.

[0076] The following description will refer to the drawings and explain the processing apparatus and developing system according to embodiments of the present invention, but the configuration of the processing apparatus and developing system is not limited thereto.

[0077] Figure 1 shows the developing system 1. The developing system 1 includes a developing device 2 and a processing device 3.

[0078] The developing apparatus 2 includes a developing solution tank 21 for storing an aqueous developing solution, and a brush 5 for rubbing the surface of the flexographic printing plate 4.

[0079] In the developing apparatus 2, the aqueous developer stored in the developer tank 21 is supplied to the flexographic printing plate 4 via the return pipe 210, 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, the aqueous developer is supplied to the developer tank 21 via the discharge pipe 6 as needed, and any aqueous developer exceeding a predetermined amount (aqueous developer waste) is sent from the developer tank 21 to the aqueous developer waste storage tank 31 via the discharge pipe 221.

[0080] The processing apparatus 3 includes: an aqueous developer waste storage tank 31 for storing aqueous developer waste; a filtration module 33 having a microfiltration membrane for filtering the aqueous developer waste; and a recovery liquid storage tank 35 for storing the recovery liquid produced by filtration. Details of the filtration membrane are as described in the section above (First Filtration Step).

[0081] The processing device 3 may further include a circulation tank 32 for circulating concentrated waste liquid to a filtration module 33.

[0082] The processing apparatus 3 may further include a filtrate tank 34 that returns the recovered liquid produced by filtration to the filtration module 33 or sends it to the recovered liquid storage tank 35.

[0083] The processing apparatus 3 may further include a concentrated waste liquid storage tank 36 for storing the concentrated waste liquid to be discarded.

[0084] The processing apparatus 3 may further include a temperature controller 37 for adjusting (lowering) the temperature of the aqueous developing waste liquid stored in the aqueous developing waste liquid storage tank 31. The processing apparatus 3 may further include a temperature controller 38 for adjusting (lowering) the temperature of the concentrated waste liquid stored in the circulation tank 32. The type of temperature controller is not particularly limited, but examples include a heat exchanger, a direct cooling chiller, and a heat pump.

[0085] In the processing apparatus 3, the aqueous developer waste liquid stored in the aqueous developer waste liquid storage tank 31 is temperature-controlled as needed and then sent to the circulation tank 32 via the discharge pipe 311. The aqueous developer waste liquid stored in the circulation tank 32 is sent to the filtration module 33 via the discharge pipe 321 and filtered.

[0086] In the filtration module 33, recovered liquid and concentrated waste liquid are obtained, and the concentrated waste liquid is returned to the circulation tank 32 via the return pipe 330. The concentrated waste liquid returned to the circulation tank 32 is sent back to the filtration module 33 via the discharge pipe 321 and circulates between the circulation tank 32 and the filtration module 33. After repeated circulation of the concentrated waste liquid between the circulation tank 32 and the filtration module 33, the concentrated waste liquid is sent to the concentrated waste liquid storage tank 36 via the discharge pipe 322.

[0087] By having an aqueous developer waste storage tank 31 in the processing apparatus 3, the storage of aqueous developer waste for extended periods throughout the entire processing apparatus 3 is avoided, thereby preventing contamination within the processing apparatus 3. The processing apparatus 3 may have two or more (preferably two) aqueous developer waste storage tanks 31. With this configuration, while the temperature-controlled aqueous developer waste stored in one aqueous developer waste storage tank 31 is being filtered, the temperature of the aqueous developer waste in the other aqueous developer waste storage tank 31 can be adjusted, enabling efficient operation.

[0088] The circulation tank 32 may have a liquid level gauge (not shown). The amount of concentrated waste liquid in the circulation tank 32 can be measured with the liquid level gauge, and if it falls below a predetermined standard, new aqueous developer waste liquid can be supplied from the aqueous developer waste liquid storage tank 31 to the circulation tank 32 to lower the temperature of the concentrated waste liquid. For example, when filtering 200 L of aqueous developer waste liquid to concentrate it to 50 L (4x concentration), only 100 L of aqueous developer waste liquid can be supplied to the circulation tank 32 at the start of filtration, and the remaining 100 L of aqueous developer waste liquid can be supplied to the circulation tank 32 in one or more batches when the liquid volume in the circulation tank 32 falls below a predetermined standard.

[0089] The discharge pipe 321 and / or return pipe 330 may have a pressure gauge (not shown). The pressure of the concentrated waste liquid passing through the discharge pipe 321 and / or return pipe 330 is measured, and if it meets a predetermined standard, the filtration process may be completed and the concentrated waste liquid sent to the concentrated waste liquid storage tank 36, assuming that the concentrated waste liquid has been sufficiently concentrated (or the waste liquid viscosity has exceeded the standard). Alternatively, the discharge pipe 321 and / or return pipe 330 may have a flow meter (not shown). The flow rate [L / min] of the concentrated waste liquid passing through the discharge pipe 321 and / or return pipe 330 is measured, and if it meets (or falls below) a predetermined standard, the filtration process may be completed and the concentrated waste liquid sent to the concentrated waste liquid storage tank 36, assuming that the concentrated waste liquid has been sufficiently concentrated (or the waste liquid viscosity has exceeded the standard).

[0090] The recovered liquid obtained from the filtration module 33 is sent to the filtrate tank 34 via the discharge pipe 331. The recovered liquid stored in the filtrate tank 34 is returned to the filtration module 33 via the return pipe 340 as needed to clean (backwash) the filtration module 33. The recovered liquid stored in the filtrate tank 34 is also sent to the recovered liquid storage tank 35 via the discharge pipe 341.

[0091] As shown in Figure 2, the discharge pipe 321 may have a pressure gauge 8A and a valve 9A. The return pipe 330 may have a pressure gauge 8B and a valve 9B. The discharge pipe 331 may have a pressure gauge 8C and a valve 9C. Here, if the supply pressure of concentrated waste liquid to the filtration module 33 is Pi (pressure measured by pressure gauge 8A), the outlet pressure is Po (pressure measured by pressure gauge 8B), and the discharge pressure of the recovered liquid is Pf (pressure measured by pressure gauge 8C), then the filtration pressure is described as {(Pi+Po) / 2}-Pf. For example, opening valve 9C lowers Pf, increasing the filtration pressure and thus the filtration rate. Similarly, opening valve 9A increases Pi, increasing the filtration pressure and thus the filtration rate. Furthermore, closing valve 9B increases Po, increasing the filtration pressure and thus the filtration rate. A preferred filtration pressure is 0.03 MPa or higher, and more preferably 0.04 MPa or higher. In addition, from the viewpoint of reducing physical stress on the membrane and avoiding malfunctions, the filtration pressure is preferably 0.5 MPa or lower, and more preferably 0.4 MPa or lower. As described above, increasing the filtration rate allows filtration to be completed before the temperature of the concentrated waste liquid exceeds a predetermined standard.

[0092] The recovered liquid stored in the recovered liquid storage tank 35 is sent to the developing device 2 via the discharge pipe 351 for reuse after developer components are added as needed. [Examples]

[0093] 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.

[0094] The apparatus used in the examples and comparative examples is as follows: • Developing equipment: Asahi Kasei AWP TM -DEW 4260 PLF • Filtration module: Asahi Kasei Microza MF module UMP-153 (nominal pore size: 0.2 μm) or UMP-353 (nominal pore size: 0.2 μm)

[0095] The aqueous developer used in the examples and comparative examples contains the following components. Developer A • Solvent (water) • Surfactant (Product name: Newcol NT-7, manufactured by Nippon Emulsifier Co., Ltd.) • Surfactant (Product name: Newcol NT-9, manufactured by Nippon Emulsifier Co., Ltd.) • Additive (Diethylene glycol dibutyl ether (DBDG)) • Additive (Diethylene glycol monohexyl ether (HeDG)) • pH adjuster (potassium carbonate) Developer B • Solvent (water) • Surfactant (Product name: Sanol LMT-1430, manufactured by Lion Corporation)

[0096] The cleaning agents (products) used in the examples and comparative examples are as follows: • Ecolab ULTRASIL 75 • Ecolab ULTRASIL MP • Ecolab ULTRASIL 115

[0097] <Recovery Test 1> The aqueous developing waste liquid used in the examples and comparative examples was processed using a developing apparatus containing aqueous developing solution A to create a flexographic printing plate (AWP TМ -Obtained by developing a total of 119 plates of DEW (1.14mm, BL size). The concentrations of components contained in the aqueous developing wastewater are shown in Table 1.

[0098] [Example 1] The aqueous developer waste liquid was adjusted to 20°C, and cross-flow filtration was repeatedly performed using the UMP-153 filtration module (performing the first and second filtration steps described above) to obtain 80% of the aqueous developer waste liquid as a recovered solution (16 L of recovered solution and 4 L of concentrated waste liquid were obtained from 20 L of aqueous developer waste liquid). At this time, the supply pressure Pi of the aqueous developer waste liquid was 0.06 MPa, the outlet pressure Po was 0.04 MPa, the back pressure Pf was 0.01 MPa, and the circulation flow rate of the aqueous developer waste liquid was 2 m / sec. The concentrations, recovery rates, and transmittances of the components contained in the recovered solution are shown in Tables 1 to 3. The recovery rate refers to the ratio of the mass of each component contained in the recovered solution to the mass of each component contained in the aqueous developer waste liquid. The transmittance refers to the ratio of the concentration of each component contained in the recovered solution to the concentration of each component contained in the aqueous developer waste liquid. The concentration of each component was measured by sampling the wastewater from the aqueous developer wastewater before the start of filtration, and by sampling the recovered solution from a mixture of all the solutions obtained after the filtration described above (first filtration step and second filtration step). The measurement method is as follows. First, for the additives DBDG and HeDG, the concentration was determined by quantitative analysis using gas chromatography after removing developing residue and other contaminants using a 0.8 μm pore size membrane filter (Advantec Toyo Co., Ltd. 25CS080AN) to obtain a clarified solution. For the surfactant, the mass percentage concentration was measured by weighing the non-volatile content before and after drying the developing waste liquid. Specifically, a certain amount of developing waste liquid was first collected, filtered through a 0.8 μm pore size membrane filter (Advantec Toyo Co., Ltd. 25CS080AN) to remove developing residue, and then its weight W1 was measured. Next, the developing waste liquid was dried in a 40°C constant temperature bath, and the weight W2 of the non-volatile components was measured. (W2 / W1) × 100 was then calculated. For the developing waste liquid and recovered solution obtained using developer B, this value was used as the surfactant concentration. For the developing waste liquid and recovered solution obtained using developer A, the value obtained by subtracting the DBDG and HeDG concentrations measured using the above method was used as the surfactant concentration.

[0099] [Example 2] The aqueous developer waste solution was adjusted to 40°C, and other filtration conditions were set in the same manner as in Example 1. The solution was filtered using a filtration module to obtain a recovered solution representing 80% by volume of the aqueous developer waste solution. The concentrations, recovery rates, and transmittances of the components contained in the recovered solution are shown in Tables 1 to 3.

[0100] [Comparative Example 1] The aqueous developer waste liquid was adjusted to 50°C and filtered using a filtration module to obtain a recovered solution representing 80% by volume of the aqueous developer waste liquid. The concentrations, recovery rates, and transmittances of the components contained in the recovered solution are shown in Tables 1-3.

[0101] [Table 1]

[0102] [Table 2]

[0103] [Table 3]

[0104] From the results in Table 2, we found that the relationship between temperature and recovery rate can be treated as a linear model. Using the temperature of the aqueous developing waste liquid as the explanatory variable X and the recovery rate as the dependent variable Y, we obtained the following linear regression equation.

[0105] Surfactant: Y = -0.6131X + 56.676 HeDG: Y = -0.5595X + 65.92 DBDG: Y=-0.6755X+64.175

[0106] From the resulting formula, it can be seen that the recovery rate of all surfactants and additives (HeDG, DBDG) is 27% or higher when the temperature of the aqueous developing wastewater is 48°C or below. Furthermore, a desirable recovery rate of 30% or higher is achieved at 43°C or below, and a more desirable recovery rate of 32% or higher is achieved at 40°C or below.

[0107] <Recovery Test 2> The aqueous developing waste liquid used in the examples and comparative examples was processed using a developing apparatus containing aqueous developing solution B to create a flexographic printing plate (AWP TМ -Obtained by developing a total of 34 plates of DEW (1.14mm, BL size). The concentrations of components contained in the aqueous developing wastewater are shown in Table 4.

[0108] [Example 3] The aqueous developer waste liquid was adjusted to 15°C, and cross-flow filtration was repeatedly performed using a filtration module (UMP-153) (performing the first and second filtration steps described above) to obtain 80% of the aqueous developer waste liquid as a recovered solution (16 L of recovered solution and 4 L of concentrated waste liquid were obtained from 20 L of aqueous developer waste liquid). At this time, the supply pressure Pi of the aqueous developer waste liquid was 0.06 MPa, the outlet pressure Po was 0.04 MPa, the back pressure Pf was 0.01 MPa, and the circulation flow rate of the aqueous developer waste liquid was 2 m / sec. The concentrations, recovery rates, and transmittances of the components contained in the recovered solution are shown in Tables 4 to 6.

[0109] [Example 4] The aqueous developer waste solution was adjusted to 28°C, and other filtration conditions were set in the same manner as in Example 3. The solution was filtered using a filtration module to obtain a recovered solution representing 80% by volume of the aqueous developer waste solution. The concentrations, recovery rates, and transmittances of the components contained in the recovered solution are shown in Tables 4 to 6.

[0110] [Example 5] The aqueous developer waste liquid was adjusted to 48°C and filtered using a filtration module to obtain a recovered solution representing 80% by volume of the aqueous developer waste liquid. The concentrations, recovery rates, and transmittances of the components contained in the recovered solution are shown in Tables 4-6.

[0111] [Table 4]

[0112] [Table 5]

[0113] [Table 6]

[0114] <Temperature control of developing waste liquid> Next, in the developing apparatus tank, the temperature of developer A is adjusted within the range of 40-45°C while the flexographic printing plate (AWP) is processed. TМ The following conditions were used to examine the temperature change of the aqueous waste liquid A obtained by developing a total of 125 plates of DEW (1.14 mm, BL size) when the developer waste liquid (120 L) was cross-flow filtered using a filtration module (UMP-353 (nominal pore size: 0.2 μm)) under the following conditions. At this time, the supply pressure Pi of the aqueous developer waste liquid was 0.09 MPa, the outlet pressure Po was 0.01 MPa, the back pressure Pf was 0.03 MPa, and the circulation flow rate of the aqueous developer waste liquid was 2 m / sec. The results are shown in Figure 3. As shown in Figure 3, without temperature control of the developer waste liquid, the temperature rose over time and exceeded 48°C. (Condition A) No temperature control was used (the aqueous developing waste liquid A discharged from the developing unit was immediately cross-flow filtered). (Condition B) The aqueous developing waste liquid A discharged from the developing apparatus was immediately subjected to cross-flow filtration. Filtration was interrupted when the waste liquid temperature reached 46°C, and resumed after the temperature dropped to 43°C. (Condition C) The waste liquid temperature was lowered before filtration began. (Condition D) Before starting the filtration process, the waste liquid temperature was reduced, and for every 20 L of recovered liquid obtained, a new 20 L of waste liquid with a reduced temperature was added.

[0115] <Reuse of developing waste liquid> Tables 7 and 8 show the evaluation results when the recovered liquid (75% of the waste liquid recovered) obtained by cross-flow filtration of the same developer waste liquids A and B used in the above-described recovery experiments 1 and 2, using a filtration module UMP-353 (nominal pore size: 0.2 μm) while varying the temperature, was reused. During filtration, the supply pressure Pi of the aqueous developer waste liquid was 0.09 MPa, the outlet pressure Po was 0.01 MPa, the back pressure Pf was 0.03 MPa, and the circulation flow rate of the aqueous developer waste liquid was 2 m / sec. In the examples where "Temperature control" is "Yes" in the table, it indicates that one or more of the following were performed before the start of filtration: natural cooling of the waste liquid, adjustment of the filtration rate, topping up of waste liquid during the filtration process, or use of a temperature control device (installed in the circulation tank 32). In the examples where "Temperature control" is "No", the high-temperature waste liquid discharged from the developer was immediately cross-flow filtered, and the above temperature control was not performed during filtration. Before filtration began, the developer waste liquid was collected from the circulation tank 32, and after filtration was completed, the recovered liquid was collected from the liquid tank 34. The surfactant concentration was measured and the transmittance was calculated. To avoid clogging of the filtration module due to overconcentration, the amount of developer waste liquid supplied to the circulation tank 32 and the total amount of recovered liquid were monitored during filtration. The filtration process was terminated and the concentrated waste liquid was discharged when the concentration ratio reached 4 times (75% of the waste liquid was recovered). In addition, the supply pressure Pi of the concentrated waste liquid to the filtration module was monitored during filtration and operated so as not to exceed 0.15 MPa (an interlock was provided to terminate filtration if it exceeded this limit). After adjusting the concentration of the obtained recovered liquid by adding surfactant and water, it was returned to the developer and a development test was performed.

[0116] "Development Residue Separation" indicates whether or not the developer waste solution could be filtered. "A" indicates that the developer waste solution could be filtered. "B" indicates that the developer waste solution could not be filtered.

[0117] "Additional developer amount" indicates the amount of surfactant that needed to be added to the recovered solution in order to perform development with the recovered solution. It is defined as the ratio of the amount of surfactant added to the recovered solution to the amount of surfactant contained in a new developer solution that is normally used (a new solution that has not yet been used for development and has not been used for development; this refers to new developers A and B before development was performed in recovery experiments 1 and 2). For example, if the amount of surfactant (total of NT-7 and NT-9, ratio 1:1) in 200L of new developer solution A before development was 8kg (concentration: 4%), and 2kg of surfactant (total of NT-7 and NT-9, ratio 1:1) is added to the obtained recovered solution of 160L, it is expressed as 2 × 100 / 8 = 25%. After adding the surfactant, water was added to the recovered solution so that its volume was 200L before the development test was performed. In the development test, the flexographic printing plate was first back-exposed to harden the base layer, and the thickness of the resin in the unhardened areas was set to 0.6mm (relief depth). Subsequently, a development test was conducted using the new developer solution at the appropriate development time (development time to achieve a relief depth of 0.6 mm), and the surface of the plate was visually inspected to check for any irregularities (undeveloped areas). The amount of surfactant added was tested in the order of 25%, 35%, and 45%. If there were no irregularities at 25% or more, it was classified as "25%", if there were no irregularities at 35% or more, it was classified as "35%", if there were no irregularities at 45%, it was classified as "45%", and if irregularities were observed even with a surfactant added at 45%, it was classified as "B", and it was determined that no reduction in developer usage was achieved.

[0118] "CFP" indicates whether or not there was a CO2 reduction effect. "A" indicates that there was a CO2 reduction effect. "B" indicates that there was no CO2 reduction effect. The presence or absence of a CO2 reduction effect was estimated by considering the electricity consumed by the operation of the filtration device, the amount of developer used, and the reduction in developer waste. Electricity consumption and developer use were calculated based on the CO2 emission factors in the IDEA database provided by the National Institute of Advanced Industrial Science and Technology. Furthermore, for the disposal of developer waste, the CO2 emissions were calculated assuming that the substances contained in the developer waste were completely combusted.

[0119] It is evident that by suppressing clogging of the membrane module and controlling the wastewater temperature of the first and second filtration processes between 5°C and 48°C, it is possible to separate the developing residue and reuse the recovered solution (reducing the amount of developing solution used). In particular, when the transmittance is between 42% and 95%, the amount of developing solution used can be reduced by 65%, which is preferable. Furthermore, when the transmittance is 55% or higher, the amount of developing solution used can be reduced by 75%, and a CO2 reduction effect can also be obtained, making it even more preferable. [Table 7] [Table 8]

[0120] <Washing Test 1> Washing solutions were prepared by progressively diluting ULTRASIL 75 and ULTRASIL MP. The washing solution was filled into a filtration module (UMP-153) that had undergone 26 filtrations of aqueous developer waste (a total of approximately 520 L of filtration), and after being left for 3 days, the inner surface of the hollow fiber membrane was observed using a SEM. This was performed using a VHX-D510 manufactured by Keyence Corporation, and the secondary electron image (magnification: 5000x) was observed with the acceleration voltage set to 5kV. As shown in Table 9, the washing results depended on the pH of the washing solution; at pH 2.9 or below, the developer residue could be removed and the filtration rate recovered, while at pH 3.7, the developer residue could not be removed. Furthermore, even when using alkaline ULTRASIL 115, the developing residue could not be removed regardless of its concentration.

[0121] [Table 9]

[0122] <Washing Experiment 2> A flexographic printing plate (AWP) is processed in a developing apparatus containing aqueous developer A. TМCross-flow filtration was performed a total of 20 times (approximately 400L total) on the developer waste liquid A obtained during the development of DEW (1.14mm, BL size) on 50-125 plates using a filtration module (UMP-153). In one filtration experiment, 80% of the volume of the aqueous developer waste liquid was recovered (16L of recovered liquid and 4L of concentrated waste liquid were obtained from 20L of aqueous developer waste liquid). At this time, the supply pressure Pi of the aqueous developer waste liquid was 0.06Mpa, the outlet pressure Po was 0.04Mpa, the back pressure Pf was 0.01Mpa, and the circulation flow rate of the aqueous developer waste liquid was 2m / sec. Compared to the first time (new condition), when the appearance of the membrane of the filtration module was observed after the 20th filtration, a black discoloration was seen, so it was determined that it was clogged, and immersion cleaning was performed for 3 days in ULTRASIL 75 1% solution. The permeability of the surfactant in the new, clogged, and cleaned state was investigated (Table 10). The method for evaluating permeability was the same as in the developing waste liquid reuse experiment described above. [Table 10]

[0123] Table 10 shows that resolving the clogging issue is desirable because it allows for a higher transmittance. [Explanation of Symbols]

[0124] 1…Developing system 2… Developing equipment 3… Processing Unit 4… Flexographic printing plates 5…brush 21… Developer tank 31…Aqueous developing waste liquid storage tank 32... Circulation tank 33… Filtration module 34... filtrate tank 35…Recovered liquid storage tank 36…Concentrated waste liquid storage tank 37,38…Temperature controller 6,211,311,321,322,331,341,351…Delivery pipe 210, 330, 340… Return tube 8A, 8B, 8C… Pressure gauges 9A, 9B, 9C… valves

Claims

1. A method for treating aqueous developing waste liquid generated by developing flexographic printing plates using an aqueous developing solution, A first filtration step involves filtering the aqueous developing waste liquid, which is at a temperature of 5°C to 48°C, through a microfiltration membrane to obtain a recovered liquid and a concentrated waste liquid. A second filtration step is performed by repeatedly carrying out the first filtration step using the concentrated waste liquid as the aqueous developing waste liquid, The recovered liquid is reused in the development of flexographic printing plates in a reuse process, Includes, The process further includes a temperature control step, in which the temperature of the aqueous developing waste liquid is adjusted to 5°C or more and 43°C or less before the first filtration step, and / or a temperature control step, in which the temperature of the concentrated waste liquid is controlled to 5°C or more and 48°C or less during the second filtration step. The aforementioned aqueous developing waste liquid contains a surfactant, The permeability of the surfactant in the total recovered liquid obtained in the first filtration step and the second filtration step is 42% or more and 95% or less. Processing method.

2. The permeability of the surfactant is 55% or more and 95% or less. The processing method according to claim 1.

3. If the amount of concentrated waste liquid falls below a predetermined standard during the second filtration step, new aqueous developing waste liquid is added to the concentrated waste liquid. The processing method according to claim 1.

4. The concentrated waste liquid shall be disposed of if at least one of the following (A) to (F) meets the prescribed criteria. (A) Total amount of the recovered liquid, (B) Number of times new aqueous developing waste liquid is added to the concentrated waste liquid, (C) Total amount of new aqueous developing waste liquid added to the concentrated waste liquid, (D) Supply pressure of the aqueous developing waste liquid or concentrated waste liquid to the filtration membrane, (E) The outlet pressure of the aqueous developing waste liquid or concentrated waste liquid coming out of the filtration membrane, (F) The circulation flow rate of the aqueous developing waste liquid or the concentrated waste liquid to the filtration membrane, The processing method according to claim 1.

5. The process further includes a washing step of washing the aforementioned filter membrane with an acidic aqueous solution with a pH of 3 or less. The processing method according to claim 1.

6. The aforementioned cleaning step, Immersing the filtration membrane in the acidic aqueous solution, and / or The acidic aqueous solution is circulated through the aforementioned filter membrane. including, The processing method according to claim 5.

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