Developer recovery device and recovery method and developer device

Abstract

The present invention provides a developer recovery device for flexible printing plates that does not have clogging, is difficult to set processing conditions, and has a high separation and removal rate of resin agglomerates, as well as a developer recovery method using the device and a developing device for flexible printing plates. A device for recovering used aqueous developer after developing a flexible printing plate, wherein the flexible printing plate has a photosensitive resin layer containing a water-dispersible synthetic rubber polymer; the recovery device is characterized in that the device contains a centrifuge having a rotating body, and the rotating body is used to separate resin agglomerates from the used aqueous developer; the cross-sectional shape of the rotating body in the vertical direction including the rotating axis has a roughly cylindrical or roughly truncated cone-shaped profile; the rotating body has a slit on its side surface for allowing the used aqueous developer separated by centrifugation to flow out from the inside of the rotating body to the outside. When the total opening area of ​​the slit opening to the inside of the rotating body is set to Acm 2 , let the internal volume of the above rotating body be Bcm 3 When the slit opening area ratio (B / A) is 2.5×10 Å, the value of the slit opening area ratio (B / A) is preferably in the range of 30,000 to 140,000.

Description

Technical Field

[0001] The present invention relates to a developer recovery device for a flexible printing original plate capable of efficiently separating and removing resin agglomerates, a developer recovery method using the device, and a developer device for the flexible printing original plate. Background Art

[0002] The flexographic printing plate generally has a structure in which a photosensitive resin layer formed of a photosensitive resin composition is provided on a support. The platemaking of such a flexographic printing plate is carried out, for example, by selectively exposing the photosensitive resin layer with ultraviolet rays and developing the exposed photosensitive resin layer with an aqueous developer. Through development, the photosensitive resin composition in the photosensitive resin layer of the unexposed portion is removed from the printing plate and dispersed or dissolved in the developer. If the photosensitive resin layer is repeatedly developed using the same developer, the concentration of the photosensitive resin composition dispersed in the developer increases, the development speed decreases, or the dispersed photosensitive resin composition aggregates to form floating resin aggregates. The resin aggregates reattach to the surface of the printing plate and reduce the quality of the plate. Therefore, it is necessary to discard the developer with a higher concentration of the photosensitive resin composition and replace it with a new developer to re-plate. However, from the perspective of environmental load and manufacturing cost, it is not preferred to repeatedly discard the used developer and replace it with a new developer.

[0003] Patent Document 1 discloses a method of adding a coagulant to a developer to actively generate resin coagulations and removing the resin coagulations from the developer. However, the addition of the coagulant is costly and the developer to which the coagulant is added cannot be directly recovered as a developer.

[0004] As a developer processing method for recycling the developer, a filtration separation method using a filter material such as a membrane filter has been proposed. Patent document 2 discloses a method for filtering resin coagulation by circulating between a concentration tank and a filter. However, in the filtration separation method, there is a problem of resin coagulation clogging the filter. For example, in the case of a membrane filter, it is necessary to perform backwashing treatment (processing to make the filtrate flow in the opposite direction to the filtering direction) regularly to remove the clogging operation.

[0005] On the other hand, as a separation method without using filter material, a centrifugal separation method has been studied. Patent documents 3 and 4 disclose a method of separating and removing resin agglomerates using a centrifugal sedimentation type centrifuge with an inner disk. In this method, there is no clogging problem like the separation method using filter material, and the developer can be continuously processed until the volume limit of the resin agglomerates that can be accumulated in the centrifuge. However, in the centrifugal sedimentation type centrifuges of patent documents 3 and 4, in order to prevent the dispersed solids with a smaller specific gravity than the developer from flowing out from the inside to the outside of the rotating part of the centrifuge, it is necessary to set an inner disk in the centrifuge. The inner disk used in patent document 3 is fixed with locking bolts, etc., which is troublesome to load and unload. Although patent document 4 discloses an inner disk that does not need to be fixed, it is troublesome to set the raw material of the inner disk used and the relationship between the centrifugal separation conditions and the developer to the optimal conditions. In addition, the centrifugal separation method using an inner disk such as patent documents 3 and 4 is difficult to improve the separation and removal ratio of resin agglomerates. In view of the above-mentioned problems, there is a need for a developer recovery device and a developer recovery method which are free from clogging, difficult to set processing conditions, and have a high separation and removal rate of resin aggregates.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 6-194824

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 10-34147

[0010] Patent Document 3: Japanese Patent Application Laid-Open No. 7-328620

[0011] Patent Document 4: Japanese Patent Application Laid-Open No. 11-047638 Summary of the invention

[0012] Problems to be solved by the invention

[0013] The present invention is first created in view of the current status of the above-mentioned prior art, and its purpose is to provide a developer recovery device for flexible printing originals that does not have clogging, difficulty in setting processing conditions, and has a high separation and removal rate of resin agglomerates, a developer recovery method using the device, and a developer device for flexible printing originals.

[0014] Means for solving problems

[0015] As a result of intensive research to solve the above-mentioned problems, the inventors of the present invention have found that the above-mentioned problems can be solved by providing a slit on the side of the rotating body of the centrifuge instead of the inner disk as in Patent Documents 3 and 4, and using the slit to efficiently remove the developer free of resin aggregates, thereby achieving the present invention. That is, the present invention is composed of the following structures (1) to (8).

[0016] (1) A recovery device for recovering a used aqueous developer after developing a flexible printing plate, wherein the flexible printing plate has a photosensitive resin layer containing a water-dispersible synthetic rubber polymer; the device comprises a centrifuge having a rotating body, wherein the rotating body is used to separate resin agglomerates from the used aqueous developer; the cross-sectional shape of the rotating body in a direction perpendicular to the axis of rotation has a generally cylindrical or truncated cone-shaped profile; and the rotating body has a slit on its side surface for allowing the used aqueous developer separated by centrifugation to flow out from the inside to the outside of the rotating body.

[0017] (2) The recovery device according to (1), wherein the total opening area of ​​the slits in the interior of the rotating body is Acm 2 , let the internal volume of the rotating body be Bcm 3 When the slit opening area ratio (B / A) is within the range of 30,000 to 140,000.

[0018] (3) The recovery device according to (1) or (2), wherein the rotating body is divided into upper and lower parts, and the slit is formed between the upper and lower divided parts.

[0019] (4) The recovery device according to any one of (1) to (3), wherein the opening of the slit is provided at a position higher than the center height of the inner wall of the rotating body.

[0020] (5) The recovery device according to any one of (1) to (4), wherein a bag made of a nonwoven fabric or a resin sheet for collecting the resin aggregate is provided so as to cover the inner wall of the rotating body.

[0021] (6) The recovery device according to any one of (1) to (5), wherein the water-dispersible synthetic rubber polymer has a butadiene skeleton and / or a styrene skeleton.

[0022] (7) A method for recovering a used aqueous developer after developing a flexible printing plate having a photosensitive resin layer containing a water-dispersible synthetic rubber polymer, characterized in that the method includes a step of separating resin agglomerates from the used aqueous developer by a recovery device described in any one of (1) to (6).

[0023] (8) A developing device for a flexible printing plate, which is a developing device for a flexible printing plate used to develop the flexible printing plate using an aqueous developer containing a recovered aqueous developer, wherein the flexible printing plate has a photosensitive resin layer containing a water-dispersible synthetic rubber polymer, and is characterized in that the developing device includes a recovery device as described in any one of (1) to (6) for recovering the used aqueous developer after development.

[0024] Effects of the Invention

[0025] According to the present invention, even without using an inner disk, resin aggregates can be efficiently separated and removed from a used developer with a simple configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] [ Figure 1 ] is a cross-sectional view showing an embodiment of the recovery device of the present invention.

[0027] [ Figure 2 ] is seen from above Figure 1 A diagram of a portion of the rotating body of a centrifuge of a recovery device.

[0028] [ Figure 3 ] is seen from obliquely above Figure 1 A diagram of a portion of the rotating body of a centrifuge of a recovery device.

[0029] [ Figure 4 ] to display Figure 1 A diagram showing the operating status of the centrifuge of the recovery device.

[0030] [ Figure 5 ] to display Figure 1 A diagram showing the overflow condition of the centrifuge of the recovery device.

[0031] [ Figure 6 ] is a diagram showing the connection path adopted by the embodiment.

[0032] [ Figure 7 ] is a diagram showing the cross-sectional shape of the rotating body of the centrifuge used in Examples 1 to 4, 6 to 8, and Comparative Examples 1 and 2, and the position and shape of the slits.

[0033] [ Figure 8] is a diagram showing the cross-sectional shape of the rotating body of the centrifuge used in Example 5, and the position and shape of the slits.

[0034] [ Fig. 9 ] is a diagram showing the cross-sectional shape of the rotating body of the centrifuge used in Example 9, and the position and shape of the slits.

[0035] [ Fig.10 ] is a diagram showing the cross-sectional shape of the rotating body of the centrifuge used in Example 10, and the position and shape of the slits.

[0036] [ Fig.11 ] is a diagram showing the cross-sectional shape of the rotating body of the centrifuge used in Example 11, and the position and shape of the slits.

[0037] [ Fig.12 ](a) is a diagram showing the cross-sectional shape of the rotating body of the centrifuge used in Example 12, and the position and shape of the slits, and (b) is a diagram showing the number of slits.

[0038] [ Fig.13 ](a) is a diagram showing the cross-sectional shape of the rotating body of the centrifuge used in Example 13, and the position and shape of the slits, and (b) is a diagram showing the number of slits.

[0039] [ Fig.14 ] is a diagram showing the cross-sectional shape of the rotating body of the centrifuge used in Comparative Example 3.

[0040] [ Fig.15 ] is a diagram showing the cross-sectional shape of the rotating body of the centrifuge used in Comparative Example 4.

[0041] Explanation of symbols

[0042] 1: Shell

[0043] 2: Rotating body (main body)

[0044] 3: Cover of the rotating body

[0045] 4: Slit

[0046] 5: Rotating axis (driving axis)

[0047] 6: Supply port for used developer

[0048] 7: The outlet for the processed developer

[0049] 8: Non-woven fabric

[0050] 9: Processed developer

[0051] 10: Floating components (resin agglomerates)

[0052] 11: The processed developer

[0053] 11′: Overflow of processed developer

[0054] 12: Circulation pump

[0055] 13: Circulation pipeline

[0056] 14: Developer tank

[0057] 15: Flow control valve

[0058] 16: Inlet pipeline

[0059] 17: Switch valve

[0060] 18: Centrifuge (recovery device)

[0061] 19: Processing liquid line

[0062] 20: Treatment tank

[0063] 21: Internal disk DETAILED DESCRIPTION

[0064] The present invention is a device for recovering a used aqueous developer after developing a flexographic printing plate having a photosensitive resin layer by a centrifugal separator, and is particularly characterized in that a slit is provided on the side of a rotating body of the centrifugal separator for allowing the used aqueous developer separated by centrifugation to flow out from the inside to the outside of the rotating body. Hereinafter, the characteristic structure of the centrifugal separator of the recovery device of the present invention is first described, and then the developer to be processed by the recovery device of the present invention is described.

[0065] The recovery device of the present invention includes a centrifuge, and the resin aggregates are separated from the used aqueous developer by the rotating body of the centrifuge. The cross-sectional shape of the rotating body of the centrifuge in the vertical direction including the rotating axis has a substantially cylindrical or truncated cone-shaped profile, but the substantially cylindrical shape that has been used is preferred from the perspective of processing efficiency. The resin aggregates with a light specific gravity contained in the used aqueous developer are centrifugally separated by being supplied to the inside of the rotating body of the centrifuge, thereby becoming floating components and gathering on one side close to the rotating axis of the rotating body, and are separated from the residual aqueous developer.

[0066] The recovery device of the present invention is characterized in that the rotating body has a slit on its side surface for allowing the used aqueous developer that has been centrifugally separated to flow out from the inside to the outside of the rotating body. The slit has the function of separating resin aggregates by centrifugal separation and allowing the residual aqueous developer that does not substantially contain resin aggregates to flow out from the inside to the outside of the rotating body. In the present invention, the developer that does not substantially contain resin aggregates can be efficiently extracted through the slit even if an inner disk is not provided, which can greatly improve the maintainability of the centrifuge.

[0067] There is no particular limitation on the shape of the slit. As long as the flow of the liquid is not greatly reduced, it does not need to be set continuously (overall), and it can also be a divided slit. As a divided slit, there are slits formed by arranging rectangular or circular slits, etc. From the perspective of ease of manufacture and the flow of treated water, the slits are preferably arranged parallel to the direction of rotation. The number of slits only needs to be at least one, but when multiple slits are set, it is preferably arranged in a rotationally symmetrical and evenly distributed manner on the side of the rotating body of the centrifuge. The method of setting the slit on the side of the rotating body is not particularly limited. For example, the rotating body is divided into a cover-like cover and a main body from top to bottom, and a continuous slit can be formed between these upper and lower divided bodies. Specifically, a cover-like cover can be set on the upper part of the main body of the rotating body, and a gasket with a thickness equivalent to the width of the slit is partially placed and fixed with a locking bolt, so that the gap between the cover and the main body of the rotating body becomes a continuous slit. As another method, a plurality of divided slits can be provided by making slit-shaped cuts of a desired width on the side of the rotating body, but from the perspective of manufacturing difficulty, a method of forming continuous slits by installing a lid-like cover is preferred.

[0068] In the present invention, in order to prevent the slit from being clogged by the resin aggregate, it is preferred that the ratio of the opening area of ​​the slit to the internal volume of the rotating body is within a specific range. Specifically, the total opening area of ​​the slit opening in the interior of the rotating body is set to Acm 2 , let the internal volume of the above rotating body be Bcm 3 When the slit opening area ratio (B / A) is less than the lower limit, the removal rate of the resin aggregate may be poor; when it exceeds the upper limit, the treatment efficiency may be poor. In addition, the internal volume of the rotating body can be calculated based on the diameter and height of the rotating body.

[0069] In order to allow the resin coagulates to be discharged smoothly from the inside to the outside of the rotating body, the number of slits is not a problem. What is important is the ratio of the opening area of ​​the slit to the internal volume of the rotating body. Even if many small-area slits or a small number of large-area slits are formed in a rotating body with the same internal volume, the same effect will be exerted as long as the total opening area is the same. In addition, the direction of the slit is not particularly limited. Whether it is horizontal, oblique, stepped, or a shape in which the slit open area changes, the same effect is exerted. If it is a rotating body of the same shape, when the value of the slit opening area ratio obtained by dividing the internal volume of the rotating body by the opening area of ​​the slit increases, the maximum processing liquid flow rate increases, and the removal rate of the resin coagulates tends to decrease, but when the shape is different, the correlation changes. For example, when the diameter of the rotating body increases, the centrifugal force increases, the maximum processing liquid flow rate increases, and the removal rate of the resin coagulates also tends to increase. Among them, the opening area of ​​the slit facing the inside of the rotating body is preferably the same as the opening area facing the outside of the rotating body, or smaller than it.

[0070] The used developer before treatment is supplied from the supply port to the rotating body for centrifugal separation treatment. As the location for arranging the supply port, the bottom of the rotating body is preferred. Therefore, the opening of the slit is preferably arranged at a position above the central height of the inner wall of the rotating body. When the opening position of the slit is arranged at a position away from the developer supply port of the rotating body, the separation performance is excellent. The reason is that by arranging the opening position of the slit at a position away from the developer supply port of the rotating body, the centrifugal separation treatment can be performed without being affected by the lateral diffusion flow of the used developer before treatment put into the rotating body.

[0071] The centrifuge used in the recovery device of the present invention is a device that generates centrifugal force to separate solids from liquids or to separate substances with different specific gravities. The centrifuge used in the present invention preferably performs centrifugal separation in the range of centripetal acceleration of 200 to 4000G. The processing volume of the developer that the centrifuge can handle is determined by the volume in the centrifuge. When the developer is directly processed by connecting to a developer, it is sufficient to prepare a centrifuge with the optimal processing volume relative to the amount of developer in the developer. When the amount of developer is 60L, the processing volume is preferably more than 0.3L per minute; when the amount of developer is 200L, the processing volume is preferably more than 1L per minute. In addition, in the present invention, in order to improve the centrifugal separation effect, a coagulant may be added to the developer, but in order to reuse the developer, it is preferably not to use a coagulant.

[0072] In order to easily remove the resin aggregates, the recovery device of the present invention can be provided with a bag made of non-woven fabric or resin sheet along the inner wall of the rotating body of the centrifuge. By providing the bag made of non-woven fabric or resin sheet along the inner wall of the rotating body, the resin aggregates accumulated inside the rotating body can be removed outside the rotating body together with the bag made of non-woven fabric or resin sheet. From the perspective of removal efficiency, non-woven fabric is more preferred. In the case of the bag made of resin sheet, it is necessary to perform a fixing operation along the inner wall surface of the rotating body.

[0073] As the nonwoven fabric, commercially available nonwoven fabrics can be used. In the present invention, it is speculated that by configuring the nonwoven fabric in a manner that covers the inner wall of the rotating body, the developer separated from the resin condensate by centrifugal force can easily pass through the nonwoven fabric to move to the liquid flow path. The nonwoven fabric used is a material that is independent on the side of the rotating body of the centrifuge, and any nonwoven fabric can be used as long as it does not hinder the flow of the developer that has been processed or does not cause clogging due to the resin condensate. Although centrifugal separation can be performed even without a nonwoven fabric, it is preferably used to make the removal of the floating component simple. As the raw material of the nonwoven fabric, polyester, polyamide, polyurethane, polyethylene, polypropylene, polyolefin, vinyl chloride, cellulose, etc. can be considered, but it is not limited to this. In addition, in order to improve the independence of the nonwoven fabric, hot melt bonding fibers can be mixed within a range that does not hinder the flow of the developer that has been processed. As the thickness of the nonwoven fabric, since it is difficult to be independent when it is too thin, it is preferably 5 mm or more, and more preferably 10 mm or more. On the other hand, since the space for the floating components to accumulate is reduced when the thickness is too thick, it is preferably 80 mm or less, and more preferably 40 mm or less. As for the unit area weight (Japanese: basis weight) of the nonwoven fabric, since the strength of the nonwoven fabric becomes weak when it is too small, it is preferably 100 g / m 2 More preferably 200 g / m 2 On the other hand, since too much weight per unit area will hinder the flow of liquid, it is preferably 800g / m 2 Below, more preferably 400g / m 2 As particularly preferred examples of nonwoven fabrics, there are those made of polyethylene, polypropylene, polyester, cellulose, etc., with a unit weight of 200 to 500 g / m 2 , a nonwoven fabric with a thickness of 10 to 30 mm. As the bag made of a resin sheet, a bag made of a resin such as polyethylene can be used. The bag made of a resin sheet preferably has fine holes, as long as it is arranged in a manner that does not hinder the flow path of the treated water of the slit. The thickness of the resin sheet can be 0.02 to 0.5 mm.

[0074] Next, the developer to be processed by the recovery device of the present invention is described. The developer is a used aqueous developer obtained after developing a flexible printing plate having a photosensitive resin layer containing a water-dispersible synthetic rubber polymer. Such a used developer contains resin agglomerates of constituent components of the photosensitive resin layer originating from the unexposed portion of the flexible printing plate. In the present invention, a water-dispersible material is used as the synthetic rubber polymer as the main constituent component of the photosensitive resin layer. Therefore, the resin agglomerates of the used developer contain a lot of water-dispersible synthetic rubber polymers. The specific gravity of these water-dispersible synthetic rubber polymers is lighter than that of water, so they become floating components by centrifugal separation and can be easily separated from the residual aqueous developer.

[0075] The water-dispersible synthetic rubber polymer is a material used to impart appropriate elasticity to the photosensitive resin layer, and a rubber component known in the past can be used. As a water-dispersible synthetic rubber polymer, in order to impart rubber elasticity, it is preferably solid at room temperature. As a specific example of the water-dispersible synthetic rubber polymer, polybutadiene, polychloroprene, polyacrylonitrile-butadiene, polyacrylic acid, epichlorohydrin, polyurethane, polyisoprene, polystyrene-isoprene copolymer, polystyrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, ethylene-propylene copolymer, butyl polymer, chlorinated polyethylene, etc., can be cited, and polymers obtained by copolymerizing other components such as acrylic acid and methacrylic acid in these polymers, etc.

[0076] Among these, from the perspective of developability and physical properties, water-dispersible synthetic rubber polymers having a butadiene skeleton and / or a styrene skeleton are preferred, and water-dispersible latex is more preferred. As a water-dispersible latex, it can be a latex having a cross-linked structure represented by a gelation degree in the molecule. As a latex having a cross-linked structure in the molecule, a hydrophobic polymer obtained from a water-dispersible latex having a weight-average gelation degree of 20 to 80% is preferred. These can be used alone or in combination of two or more. In addition, the so-called water-dispersible latex refers to a latex in which rubber polymer particles are dispersed in water to form a stable suspension. The polymer is obtained by removing water from the water-dispersible latex.

[0077] In order to improve physical properties and water resistance, the photosensitive resin layer of the flexographic printing plate may contain a water-insoluble synthetic rubber polymer within a range that does not adversely affect the performance. Examples of the water-insoluble synthetic rubber polymer include polybutadiene, polychloroprene, polyacrylonitrile-butadiene, polyurethane, polyisoprene, polystyrene-isoprene copolymer, polystyrene-butadiene copolymer, and the like.

[0078] The photosensitive resin layer of the flexographic printing plate may contain a water-soluble or water-dispersible polymer other than a water-dispersible synthetic rubber polymer. Examples of the water-soluble or water-dispersible polymer include water-soluble or water-dispersible polyamides into which hydrophilic groups are introduced, partially saponified polyvinyl acetate or its derivatives, and anionic acrylic polymers.

[0079] In the used developer after developing the flexographic printing plate having such a photosensitive resin layer, the water-dispersible synthetic rubber polymer is dispersed in the developer, so the polymer concentration in the developer does not increase sharply. In addition, since the synthetic rubber polymer is water-dispersible, it is suitable for waste liquid treatment by centrifugation.

[0080] The photosensitive resin composition of the flexographic printing plate contains, in addition to the water-dispersible synthetic rubber polymer, a photopolymerizable unsaturated monomer compound, a photopolymerization initiator, etc. These additional components are well known to those skilled in the art and will not be described in detail here.

[0081] The flexographic printing plate may have a support in addition to the photosensitive resin layer, and the photosensitive resin layer may be disposed on the support. In addition, a protective layer and an infrared photosensitive layer may be disposed on the photosensitive resin layer. These elements are well known to those skilled in the art, and therefore will not be described in detail here.

[0082] The developer to be processed by the recovery device of the present invention is an aqueous developer with water as the main component. As an aqueous developer, it can be water alone or an aqueous solution to which a water-soluble development accelerator is added. As development accelerators, surfactants, acids, bases, salts, etc. can be mentioned. As surface accelerators, cationic surfactants, anionic surfactants, and nonionic surfactants can be mentioned. As acids, inorganic acids such as sulfuric acid, nitric acid, and phosphoric acid, or organic acids such as formic acid, acetic acid, oxalic acid, succinic acid, citric acid, maleic acid, and p-toluenesulfonic acid can be mentioned. As bases, lithium hydroxide, sodium hydroxide, potassium hydroxide, and calcium hydroxide can be mentioned. As salts, sodium carbonate, sodium silicate, etc. can be mentioned. From the perspective of development speed, a water-soluble development accelerator is preferred. As development accelerators, commercially available soaps and detergents can be used. The development accelerator can use surfactants, acids, bases, and salts in combination, as long as the best combination of development accelerators is determined according to the components of the photosensitive resin composition.

[0083] The aqueous developer may contain a water-soluble organic solvent in addition to water. Examples of such an organic solvent include methanol, ethanol, isopropyl alcohol, cellosolve, glycerin, ethylene glycol, and polyethylene glycol.

[0084] In addition, in order to suppress the generation of bubbles, a defoamer may be added to the aqueous developer. The defoamer may be any water-soluble defoamer. As components of the defoamer, higher alcohols, fatty acid derivatives, silicon dioxide, alum stone, silicone, etc. may be cited.

[0085] Next, the recovery device of the present invention will be described in detail using the drawings.

[0086] Figure 1 This is a schematic diagram of one embodiment of the recovery device of the present invention. Figure 1 In the figure, 1 is a shell, 2 is a rotating body, 3 is a cover of the rotating body, 4 is a slit formed between the rotating body 2 and the cover 3, 5 is a rotating shaft (driving shaft) of the rotating body, 6 is a supply port for used developer to be processed, 7 is a discharge port for processed developer, and 8 is a non-woven fabric arranged in a manner of covering the inner wall of the rotating body 2.

[0087] Figure 1 In the embodiment shown, the cross-sectional shape of the rotating body 2 in the vertical direction including the rotating shaft 5 of the rotating body has a substantially cylindrical profile. In the present invention, the used developer supplied from the supply port 6 is separated into the resin aggregates with a small specific gravity and the treated developer with a large specific gravity from which the resin aggregates are removed in the rotating body 2 of the centrifuge. Figure 2 and 3 As shown, it has a basketball-shaped body, on which a donut-shaped cover 3 is installed. In order to open a gap (slit 4) between the body and the cover, a gasket is inserted and fixed with screws at 4 locations. The rotating body is connected to the motor through a rotating shaft (driving shaft), and the centrifugal force generated by the centripetal acceleration during rotation is generated. The used developer is supplied to the rotating body from the supply port. When it is supplied to the rotating body, it immediately becomes attached to the side of the rotating body, as shown in FIG. Figure 4 As shown, by centrifugal force, it is separated into a floating component 10 formed by resin agglomerates with a small specific gravity and a processed developer 9 with a large specific gravity. Specifically, the water-dispersible synthetic rubber polymer derived from the photosensitive resin layer of the unexposed part of the printing original plate is lighter in specific gravity than water, so it becomes the floating component 10 and separates to the inner side (center side) of the rotating body, and the processed developer 9 with a large specific gravity separates to the outer side (inner wall side) of the rotating body. Water pressure is applied to the inner wall of the rotating body by centrifugal force, and the processed developer 9 with a large specific gravity on the inner wall side of the rotating body flows out from the slit 4. Since the outflowing liquid passes through the slit by the force of the water pressure, it is sprayed out in the form of a spray. The sprayed processed developer is recovered in Figure 1 In the housing 1 shown, the developer is guided to the discharge port 7. The developer discharged from the discharge port can be used as a recovered developer because the resin aggregates are removed.

[0088] In addition, when the nonwoven fabric 8 is provided along the inner wall of the rotating body in advance, the resin aggregates 10 gradually accumulate on the nonwoven fabric. When the rotating body is filled with the resin aggregates, as shown in FIG. Figure 5 As shown, the developer 11' after processing exceeds the cover 3 on the upper part of the rotating body and overflows (overflow). Before the overflow occurs, the developer supply is stopped, and after the dehydration operation is temporarily performed, the rotation of the centrifuge is stopped and the non-woven fabric is taken out to discharge the resin agglomerate. After removing the resin agglomerate, it is sufficient to configure a new non-woven fabric and restart the centrifugal separation.

[0089] In the above embodiment, as a method for forming the slit, bolting of the rotating body and the lid-like cover of the rotating body is used in the example, but a method other than bolting may be used. For example, even if the rotating body and the lid-like cover are integrated and the slit is cut, there is no problem. In addition, even if a plurality of holes are provided instead of the slit, the same effect can be achieved.

[0090] In the above-mentioned embodiment, the centrifugal separator has been described as having a vertical structure as an example, but the same effect can be achieved even if the centrifugal separator has a horizontal structure.

[0091] The recovery device of the present invention can be suitably used as an effective substitute for the conventional recovery device in a conventionally known flexographic printing plate developing device provided with a developer recovery device.

[0092] Example

[0093] Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

[0094] <Production of photosensitive resin printing plates>

[0095] (1) Preparation of photosensitive resin composition

[0096] Photosensitive resin composition A:

[0097] 91 parts by mass of butadiene latex (LX111NF manufactured by Nippon Zeon, solid content concentration 55%) as a water-dispersible synthetic rubber-based polymer, 15 parts by mass of oligomeric butadiene acrylate (ABU-3 manufactured by Kyoeisha Chemical: molecular weight 2700) as a photopolymerizable unsaturated monomer compound, 10 parts by mass of lauryl methacrylate, 10 parts by mass of trimethylolpropane trimethacrylate, 1 part by mass of benzyl dimethyl ketal as a photopolymerization initiator, 20 parts by mass of PFT-3 manufactured by Kyoeisha Chemical (a polymer having a molecular weight of about 20,000 and a urethane urea structure, solid content concentration 25%) as a hydrophilic polymer, 0.1 parts by mass of hydroquinone monomethyl ether as a polymerization inhibitor, 9 parts by mass of liquid butadiene as a plasticizer, and 5 parts by mass of toluene were mixed in a container, and then kneaded at 105° C. using a pressure kneader, and then toluene and water were distilled off under reduced pressure to obtain a photosensitive resin composition A.

[0098] Photosensitive resin composition B:

[0099] 56.4 parts by mass of butadiene latex (LX111NF, 55% solid content concentration, manufactured by Japan Zeon) as a water-dispersible synthetic rubber polymer, 10 parts by mass of polybutadiene terminal diacrylate (BAC-45, manufactured by Osaka Organic Chemical) as a photopolymerizable unsaturated monomer compound, and 10 parts by mass of acrylic monomer (1,9-nonanediol dimethacrylate) were mixed, and the water was evaporated for 2 hours in a dryer heated to 120° C. to obtain a mixture. The mixture was kneaded in a kneader for 45 minutes with 6 parts by mass of butadiene rubber (Nipol BR1220, manufactured by Japan Zeon), 7 parts by mass of a surfactant (Nonion TA-405, manufactured by NOF) (4 parts by mass as solid content), and 10 parts by mass of liquid butadiene as a plasticizer. Then, 0.2 parts by mass of hydroquinone monomethyl ether as a polymerization inhibitor and 1 part by mass of benzyl dimethyl ketal as a photopolymerization initiator were put into a kneader and kneaded for 5 minutes to obtain a photosensitive resin composition B.

[0100] Photosensitive resin composition C:

[0101] 100 parts by weight of carboxyl-modified methyl methacrylate-butadiene latex (MR174 manufactured by Japan A&L, solid content concentration 50%) as a water-dispersible synthetic rubber polymer, 15 parts by weight of oligomeric butadiene acrylate (ABU-3 manufactured by Kyoeisha Chemical: molecular weight 2700) as a photopolymerizable unsaturated monomer compound, 10 parts by weight of lauryl methacrylate, 10 parts by weight of trimethylolpropane trimethacrylate, 1 part by weight of benzyl alcohol as a photopolymerization initiator, A photosensitive resin composition C was prepared by mixing 20 parts by mass of PFT-3 (a polymer having a molecular weight of about 20,000 and a carbamate urea structure and a solid content of 25%) produced by Kyoeisha Chemical Co., Ltd. as a hydrophilic polymer, 0.1 parts by mass of hydroquinone monomethyl ether as a polymerization inhibitor, 9 parts by mass of liquid butadiene as a plasticizer, and 5 parts by mass of toluene in a container, and then kneading was performed at 105° C. using a pressure kneader, and then toluene and water were removed by distillation under reduced pressure to obtain a photosensitive resin composition C.

[0102] Photosensitive resin composition D:

[0103] 71 parts by mass of styrene-butadiene latex (C4850 manufactured by Nippon Zeon, solid content concentration 70%) as a water-dispersible synthetic rubber-based polymer, 15 parts by mass of oligomeric butadiene acrylate (ABU-3 manufactured by Kyoeisha Chemical: molecular weight 2700) as a photopolymerizable unsaturated monomer compound, 10 parts by mass of lauryl methacrylate, 10 parts by mass of trimethylolpropane trimethacrylate, 1 part by mass of benzyl dimethyl ketal as a photopolymerization initiator, 20 parts by mass of PFT-3 manufactured by Kyoeisha Chemical (a polymer having a molecular weight of about 20,000 and a urethane urea structure, solid content concentration 25%) as a hydrophilic polymer, 0.1 parts by mass of hydroquinone monomethyl ether as a polymerization inhibitor, 9 parts by mass of liquid butadiene as a plasticizer, and 5 parts by mass of toluene were mixed in a container, and then kneaded at 105° C. using a pressure kneader, and then toluene and water were distilled off under reduced pressure to obtain a photosensitive resin composition D.

[0104] (2) Preparation of protective layer coating liquid

[0105] A low-saponification polyvinyl alcohol (PVA405, manufactured by KURARAY Co., Ltd.), a plasticizer (SANFLEX SE270, manufactured by Sanyo Chemical Industries, Ltd., aliphatic polyol-based polyether polyol, solid content concentration 85%) and NBR latex (SX1503A, manufactured by Nippon Zeon Co., Ltd., solid content concentration 42%) were dissolved in a water / isopropyl alcohol mixture in a solid content weight ratio of 35 / 35 / 30 to prepare a protective layer coating solution.

[0106] (3) Preparation of infrared photosensitive layer coating liquid

[0107] A carbon black dispersion (AMBK-8, manufactured by Orient Chemical Industry Co., Ltd.) and a copolymerized polyamide (PA223, manufactured by Toyobo Co., Ltd.) were dissolved in a mixed solution of methanol / ethanol / isopropanol at a solid content weight ratio of 63 / 37 to prepare an infrared photosensitive layer coating solution.

[0108] (4) Fabrication of laminated films

[0109] The infrared photosensitive layer coating liquid prepared in (3) was applied to a 100 μm PET film with a demolding treatment applied to both sides using a suitable type of rod coater, and dried at 120°C for 5 minutes to laminate an infrared photosensitive layer with a thickness of 1.5 μm on the PET film. The optical density at this time was 2.3. The optical density was measured by a black and white transmission densitometer DM-520 (Dainippon Screen Manufacturing Co., Ltd.). Then, the protective layer coating liquid prepared in (2) was applied to the above infrared photosensitive layer using a suitable type of rod coater, and dried at 120°C for 5 minutes to obtain a laminated film in which an infrared photosensitive layer with a thickness of 1.5 μm and a protective layer with a thickness of 0.5 μm were laminated in sequence on the PET film.

[0110] (5) Preparation of photosensitive resin printing plates A, B, C, D formed from photosensitive resin compositions A, B, C, D and laminated films

[0111] The photosensitive resin composition A prepared in (1) is arranged on a 100 μm PET film coated with a copolyester-based adhesive, and the laminated film prepared in (4) is overlapped thereon. Lamination is performed at 100° C. using a hot press to obtain a flexible printing plate composed of a PET support, an adhesive layer, a photosensitive resin layer, a protective layer, an infrared photosensitive layer and a release-treated PET protective film (cover film). The total thickness of the plate is 1.14 mm. Photosensitive resin printing plates B to D are prepared in the same manner as photosensitive resin printing plate A, except that the photosensitive resin composition A is changed to B, C or D.

[0112] <Preparation of used aqueous developer after developing the flexographic printing plate>

[0113] Sodium oleate as a development accelerator was dissolved in tap water in an amount of 1% by mass of the total developer to prepare an aqueous developer. In the aqueous developer, the above-mentioned flexographic printing original plate from which the cover film was peeled off was developed by a developer in a manner of rubbing with a brush made of nylon filaments with a diameter of 200 μm as a brush material, to prepare a used aqueous developer after the flexographic printing original plate was developed. At this time, the concentration of the photosensitive resin composition in the aqueous developer was set to 5% by mass.

[0114] <How to connect the centrifuge to the developer tank and the treatment tank>

[0115] A developer tank 14 storing 50 L of the aqueous developer, a circulation tank 12 for circulating the developer in the tank, a flow control valve 15, a centrifugal separator 18, and a treatment liquid tank 20 are provided. Figure 6 Connect as shown.

[0116] <Method for measuring the NV value indicating the non-volatile content>

[0117] Connect the centrifuge to the developer tank and the treatment liquid tank according to the above-mentioned connection method, and treat the developer prepared by the above-mentioned method for making the used aqueous developer in the centrifuge by centrifugal separation at a rotation speed that becomes a specified centripetal acceleration. The treated developer is stored in the treatment liquid tank. The liquid sampled therefrom is taken as the post-treatment sample, and the liquid sampled from the developer tank before treatment is taken as the pre-treatment sample. Take 2g of the pre-treatment sample and the post-treatment sample respectively in an aluminum foil cup, dry them at 80°C for 2 hours in a vacuum dryer, and measure the NV value [%] representing the non-volatile component. The mass is measured using an electronic precision balance. The calculation formula is shown below.

[0118] NV value [%] = (mass after drying - mass of aluminum foil cup) ÷ (mass before drying - mass of aluminum foil cup) × 100

[0119] <Evaluation of resin aggregate removal rate>

[0120] The theoretical resin concentration is calculated from the measured NV value. The calculation formula is as follows.

[0121] Resin concentration [%] = NV value - amount of sodium oleate added (1 mass %)

[0122] The resin agglomerate removal rate is calculated based on the resin concentration of the sample before and after treatment. The calculation formula is as follows.

[0123] Resin agglomerate removal rate [%] = (resin concentration of sample before treatment - resin concentration of sample after treatment) ÷ (resin concentration of sample before treatment) × 100

[0124] <Flow Evaluation>

[0125] Connect the centrifuge to the developer tank and the treatment tank according to the above connection method, open the flow control valve, and let the treated developer flow out from the outlet of the centrifuge. Use a cup to collect the outflowing treated developer for 10 seconds, and use a measuring cylinder to measure the volume [L] collected by the cup. Six times the volume measurement value is taken as the flow rate per minute [L / min].

[0126] Example 1

[0127] Using the photosensitive resin printing original plate A, a used aqueous developer was prepared according to the method for preparing a used aqueous developer. Figure 7 The inside of the rotating body of the centrifuge shown in the figure [cylindrical rotating body inner diameter R = 30 cm, cylindrical rotating body height H = 20 cm, bottom closed type] is provided with a nonwoven fabric (polyester, thickness 20 mm, unit area weight 380 g / m 2 )( Figure 1 , Figure 2 ). A 0.03 mm thick gasket is placed between the cover-shaped cover of the rotating body and the main body of the rotating body, and the cover-shaped cover of the rotating body is locked with a screw to adjust the total opening area A of the slit. The centrifuge is connected to the developer tank and the processing liquid tank by the above-mentioned connection method, and the flow rate is measured. Then, the centrifuge is operated, and when the developer solution of twice the capacity of the rotating body is passed through, no overflow occurs ( Figure 5 ) was taken as the maximum processing volume. The developer was passed through the rotating body at the maximum processing volume in an amount twice the capacity of the rotating body and then stopped, and the resin agglomerate removal rate was evaluated by the above method. The results are shown in Table 1.

[0128] Examples 2 to 13 and Comparative Examples 1 to 4

[0129] The experiment was conducted in the same manner as in Example 1 except that the structure of the centrifuge and the centrifugal separation conditions were changed as shown in Table 1. The results are shown in Table 1.

[0130] [Table 1]

[0131]

[0132] Embodiments 14 to 16

[0133] The centrifugal separation treatment was carried out in the same manner as in Example 1 except that the photosensitive resin printing original plate B, C or D was used instead of the photosensitive resin printing original plate A. The results are shown in Table 2.

[0134] [Table 2]

[0135]

[0136] As can be seen from Tables 1 and 2, Examples 1 to 16 satisfying the constituent requirements of the present invention all have both a high resin aggregate removal rate and a high maximum throughput.

[0137] Specifically, Examples 1 and 2 are examples in which the slit opening area ratio is in a particularly preferred range, and the resin aggregate recovery rate and the maximum processing capacity are good.

[0138] Since the diameter of the cylindrical rotating body of Example 3 is larger than that of Example 1, the centrifugal force applied to the treatment liquid becomes larger, and the resin aggregate removal rate becomes better.

[0139] In Example 4, the slit opening area ratio is smaller than that in Example 3, so the resin aggregate removal rate is reduced, but the maximum treatment flow rate is increased.

[0140] As can be seen from Example 5, even if the slit is not located above the cylindrical rotating body but in the center, a good centrifugal separation process can be performed.

[0141] It can be seen from Examples 6 to 7 that even if the centripetal acceleration is increased or decreased compared with Example 1, sufficient centrifugal separation can be performed as long as it is within the acceleration range of a normal centrifuge.

[0142] Example 8 is an example in which the nonwoven fabric is not used, but similarly to Example 1, a good result is obtained, and it is understood that even without using a nonwoven fabric (although it is inconvenient in removing the resin aggregate), a good centrifugal separation process can be performed.

[0143] like Fig. 9 As shown, the slit opening of Example 9 is below the cylindrical rotating body, so the resin removal rate is slightly lower than that of Example 1, but good centrifugal separation can still be performed through the slit.

[0144] like Fig.10 As shown, Example 10 is an example in which a truncated cone-shaped rotating body is used instead of a cylindrical rotating body. Compared with Example 1, the resin aggregate removal rate is slightly lower, but this shape also has good results.

[0145] like Fig.11 As shown, Example 11 is an example in which the cross section of the slit is inclined and the upper part of the cylindrical rotating body is mortar-shaped. The inclination angle of the mortar is set to 30 degrees from the horizontal direction. Even with such a shape, good results are obtained as in Example 1.

[0146] like Fig.12 As shown, Example 12 is a structure having slits at four locations. Instead of adopting the method of Example 1 and the like (i.e., a method of inserting a gasket to form a continuous gap between the cover of the cylindrical rotating body and the main body of the cylindrical rotating body), a gasket is not inserted, and grooves of 0.7 mm in depth and 10 mm in width are inserted in advance at four locations on the upper part of the cylindrical rotating body to form an opening between the cover of the cylindrical rotating body. Even if the number of slits is changed in this way, since the diameter of the cylindrical rotating body and the value of the slit opening area ratio are not changed compared with Example 1, the same evaluation results are obtained.

[0147] like Fig.13As shown in the figure, Example 13 has a structure with 18 slit openings. The number of openings is changed in the same manner as in Example 12. Specifically, grooves with a depth of 0.4 mm and a width of 4 mm are placed in 18 locations on the upper part of the cylindrical rotating body in advance, so that an opening is formed between the cover of the cylindrical rotating body. Even if the number of slits is changed in this way, since the diameter of the cylindrical rotating body and the value of the slit opening area ratio are not changed compared with Example 1, the same evaluation results are obtained.

[0148] Furthermore, as shown in Table 2, in Examples 14 to 16 in which the type of the photosensitive resin printing original plate (photosensitive resin layer) was changed, good treatment results similar to those of Example 1 were obtained.

[0149] On the other hand, in Comparative Example 1, since the slit opening area ratio is too large compared with the preferred range, the maximum processing amount is small.

[0150] In Comparative Example 2, since the slit opening area ratio was too small compared to the preferred range, the resin removal rate was small.

[0151] like Fig.14 As shown in FIG. 3 , the inner disk 21 is arranged inside the cylindrical rotating body to perform centrifugal separation. The inner disk is made of a 0.3 mm thick polypropylene plate and is fixed to the inner side of the cylindrical rotating body by an upper cover and four bolts. Fig.14 In this method, since convection occurs in the rotating drum, the resin agglomerate removal rate is low and the separation efficiency is poor.

[0152] like Fig.15 As shown, in Comparative Example 4, no gasket was inserted and centrifugal separation was performed without providing any slits. In this case, the treated developer was centrifuged as shown in FIG. Figure 5 In the overflow removal shown, the resin aggregates accumulated on the inside float up due to the centrifugal force and flow out together with the processed developer, and the resin aggregates can hardly be separated.

[0153] Industrial Applicability

[0154] According to the present invention, even without using an inner disk, resin aggregates can be efficiently separated and removed from a used developer with a simple structure. Therefore, the present invention is extremely useful in this field.

Claims

1. A recovery device for recovering a used aqueous developer after developing a flexographic printing plate having a photosensitive resin layer containing a water-dispersible synthetic rubber polymer, characterized in that: The device includes a centrifugal separator having a rotating body, the rotating body being used to separate resin aggregates from a used aqueous developer; the cross-sectional shape of the rotating body in a direction perpendicular to the rotating axis having a substantially cylindrical or truncated cone-shaped profile; the rotating body having a slit on its side surface for allowing the used aqueous developer separated by centrifugation to flow out from the inside to the outside of the rotating body, The total opening area of ​​the slits opening inside the rotating body is defined as Acm 2 , the internal volume of the rotating body is set to Bcm 3 When , the value of the slit opening area ratio B / A is in the range of 30,000 to 140,000.

2. The recovery device according to claim 1, characterized in that: The rotating body is divided into upper and lower parts, and the slit is formed between the upper and lower parts.

3. The recovery device according to claim 1, characterized in that: The opening of the slit is provided at a position higher than the center height of the inner wall of the rotating body.

4. The recovery device according to any one of claims 1 to 3, characterized in that: A bag made of nonwoven fabric or a resin sheet for collecting resin aggregates is provided so as to cover the inner wall of the rotating body.

5. The recovery device according to any one of claims 1 to 3, characterized in that: The water-dispersible synthetic rubber-based polymer has a butadiene skeleton and / or a styrene skeleton.

6. A method for recovering an aqueous developer, which is a method for recovering a used aqueous developer after developing a flexographic printing plate having a photosensitive resin layer containing a water-dispersible synthetic rubber polymer, characterized in that: The method comprises the step of separating resin aggregates from the used aqueous developer by using the recovery device according to any one of claims 1 to 5.

7. A developing device for a flexographic printing plate, the developing device being for developing a flexographic printing plate using an aqueous developer containing a recovered aqueous developer, the flexographic printing plate having a photosensitive resin layer containing a water-dispersible synthetic rubber polymer, characterized in that: The developing device includes the recovery device according to any one of claims 1 to 5 in order to recover the used aqueous developer after development.

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