JP2011068973A - Method for manufacturing aluminum substrate for lithographic printing plate and method for recycling lithographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an aluminum substrate for a lithographic printing plate, which can obtain the aluminum substrate for the lithographic printing plate that satisfies the quality in the purity of aluminum and the content of trace metals at a high yield with a decreased amount of aluminum oxide to be produced as a byproduct, when recycling a used lithographic printing plate, and greatly reduces the amount of CO<SB>2</SB>to be produced which causes global warming. <P>SOLUTION: The method for manufacturing the aluminum substrate for the lithographic printing plate includes: preparing a material to be regenerated for the aluminum substrate including the used lithographic printing plate provided with a support for the lithographic printing plate, which is an aluminum substrate that has been sequentially subjected to surface roughening treatment, anodizing treatment and hydrophilizing treatment using an aqueous solution containing polyvinyl phosphonic acid; obtaining a regenerated base metal by using the material to be regenerated; producing a new aluminum substrate by adding the necessary amount of a new aluminum base metal and mother alloys for the trace metals for the base metal of a regenerated material; and using the substrate as the support for the lithographic printing plate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing an aluminum substrate for a lithographic printing plate, in particular, a method for producing an aluminum substrate for a lithographic printing plate that efficiently recycles and reuses a used lithographic printing plate, and a lithographic printing plate using the method. Recycling method.

  A lithographic printing plate is produced by forming an image recording layer (for example, a photosensitive layer) on an aluminum lithographic printing plate support. This aluminum support requires a uniform and dense surface roughening treatment on the surface, specifically, a surface treatment such as an electrochemical surface roughening treatment. Therefore, as an aluminum raw material for an aluminum support, It is necessary that the raw material has a high purity and the content of trace metals is strictly adjusted.

On the other hand, in order to newly produce 1 kg of metallic aluminum, the energy of 140.9 MJ is theoretically required, and the CO ₂ generation amount at that time reaches 9.22 kg / kg. Therefore, in order to produce a lithographic printing plate with as little CO ₂ generation as possible, scrap materials such as used lithographic printing plates used for printing and cut pieces generated during the manufacturing process of the lithographic printing plate are used as recycled aluminum materials. Although the recycled aluminum material is considered to be recycled, the purity and alloy composition of the recycled aluminum material does not reach the required level as a raw material for producing a lithographic printing plate support. Is difficult to use as a base for lithographic printing plates, and is used as a raw material for window sashes, automobile engines, wheel wheels, etc. The current situation is not to recycle the plates.
However, the manufacturing energy of 1 kg of recycled bullion made from scrap materials such as the used lithographic printing plate and lithographic printing plate cut pieces is only about 4% of the 140.9 MJ, and such a material is used. If it can be recycled for lithographic printing plates, it is very effective in reducing CO ₂ generation. For that purpose, it is important to establish a recycling method for reducing energy while ensuring quality as an aluminum substrate for a lithographic printing plate.

In recent years, studies have been made to recycle used lithographic printing plates and scraps as recycled materials. For example, after removing impurities from a used lithographic printing plate, aluminum bullion and a mother alloy (with a desired metal) A method of reusing a used lithographic printing plate as a support by preparing a molten metal by directly adding it to a melting furnace before rolling and rolling it after filtration. Is disclosed (for example, see Patent Document 1). In addition, it has been proposed to reduce the production cost of an aluminum substrate for a lithographic printing plate by recycling it to an aluminum substrate for a lithographic printing plate produced with low-purity aluminum as a used aluminum can raw material (for example, Patent Documents). 2).
However, as in the latter case, when low-purity aluminum is used as the support substrate, it has sufficient adhesion to the image recording layer formed on the support surface and sufficient hydrophilicity to function as a non-image area. In order to achieve this, there is a problem that various other means are required.

  Further, in the method described in Patent Document 1, since a method in which a used lithographic printing plate is directly charged into a pre-rolling melting furnace for forming a support (hereinafter referred to as a direct charging method) is used, the used aluminum to be charged is used. It is unavoidable that the alloy composition of the aluminum sheet after rolling is greatly influenced by the composition. However, as described above, when the surface of a planographic printing plate is roughened, particularly when a roughening treatment using an electrolytic method is performed, the alloy composition of the aluminum plate has a decisive influence on the quality of the roughened shape. Therefore, when trying to obtain an aluminum substrate with a purity higher than that required for the roughening treatment by the electrolytic method, the amount of used lithographic printing plate is limited for quality assurance, and a large amount of high-purity aluminum is used. It is necessary to use it, the regeneration efficiency is poor, and it is not preferable from the viewpoint of carbon dioxide gas reduction. In addition, it is necessary to measure the impurity composition while carrying out the melting furnace charging and rolling processes, and it takes time for melting and component adjustment, which is also a factor of deterioration in yield.

Japanese Patent No. 3420817 JP 2002-331767 A

The present invention has been made in view of such circumstances, and the object of the present invention is to improve the purity of aluminum even when reusing a lithographic printing plate that has been used when producing an aluminum substrate for a lithographic printing plate. It is possible to obtain an aluminum substrate for a lithographic printing plate satisfying the quality of a trace metal content in a high yield, the amount of aluminum oxide formed as a by-product is reduced, and the amount of CO ₂ generation that causes global warming is greatly increased. Another object of the present invention is to provide a method for producing an aluminum substrate for a lithographic printing plate that is reduced in size.
Another object of the present invention is to apply the above-described method for producing an aluminum substrate for a lithographic printing plate of the present invention, so that an efficient lithographic printing plate recycling method in which the amount of CO ₂ generated in the process is greatly reduced. Is to provide.

As a result of intensive studies, the present inventor has found that the above-mentioned object can be achieved by using a used lithographic printing plate having an aluminum support subjected to a specific surface treatment, thereby completing the present invention. .
That is, the method for producing an aluminum substrate for a lithographic printing plate according to the present invention is for a lithographic printing plate in which an aluminum substrate is successively subjected to a surface roughening treatment, an anodizing treatment, and a hydrophilic treatment with an aqueous solution containing polyvinylphosphonic acid. A recycled material preparing step for preparing a recycled material including a used lithographic printing plate provided with a support, and the recycled material obtained in the recycled material preparing step is put into a melting furnace, and a temperature range of 680 ° C. to 900 ° C. The recycled material manufacturing process to obtain the recycled ingot by forming the recycled material molten metal into a predetermined shape and weight after being melted in the above, and the regeneration obtained in the recycled ingot manufacturing process Analysis process for analyzing aluminum purity and trace metal content of bullion, analysis value of aluminum purity and trace metal content of recycled bullion obtained in said analysis process, and lithographic printing plate support About the predetermined desired aluminum purity and the desired trace metal content, the difference is obtained, and based on this difference, a new aluminum bullion and a trace metal master alloy having a predetermined purity with respect to the recycled metal The blending ratio determining step for determining the blending ratio, and the recycled ingot, the new aluminum ingot and the trace metal master alloy in the pre-rolling melting furnace in an amount corresponding to the blending ratio determined in the blending ratio determining step. A pre-rolling melt preparation step for charging and melting by heating to obtain a pre-rolling melt, and an aluminum base preparation step for producing a strip-shaped aluminum base by rolling using the pre-rolling melt obtained in the rolling melt preparation step; , In this order.

  The recycled material for an aluminum substrate including a used lithographic printing plate used in the production method of the present invention is not limited to a used lithographic printing plate, and further, the production of a lithographic printing plate production process A cut piece of an aluminum substrate or a cut piece of a lithographic printing plate generated during the processing may be included.

The lithographic printing plate recycling method of the present invention comprises a planographic printing method in which at least one surface of an aluminum substrate for a lithographic printing plate is subjected to a roughening treatment, an anodizing treatment, and a hydrophilization treatment with an aqueous solution containing polyvinylphosphonic acid in order. A support producing step for obtaining a plate support, a lithographic printing plate precursor producing step for producing a lithographic printing plate precursor by forming an image recording layer on the treated surface of the obtained lithographic printing plate support, and After making a lithographic printing plate precursor to obtain a lithographic printing plate, a printing process for performing desired printing, a collecting process for collecting a used lithographic printing plate generated after the completion of the printing process, and a collected use And a recycling step of providing the used lithographic printing plate as a recycled material for an aluminum substrate in the method for producing an aluminum substrate for a lithographic printing plate of the present invention.
Here, it is also a preferred aspect that the lithographic printing plate aluminum substrate is a recycled lithographic printing plate aluminum substrate obtained by the method for producing a lithographic printing plate aluminum substrate.

  Although the action in the method of the present invention is not clear, the support hydrophilized with polyvinylphosphonic acid used in the present invention is dissolved in the recycled metal manufacturing process compared to the aluminum support not subjected to the above treatment. Since the production of aluminum oxide, which is an oxidizing substance that is sometimes produced when aluminum comes into contact with air, is reduced, there is little loss of the aluminum raw material, and it is considered that regeneration with high yield is possible.

Furthermore, in the present invention, the aluminum purity and trace metal content in the recycled metal or recycled molten metal are analyzed, and the obtained analytical value and the desired aluminum purity and desired trace metal content as a predetermined lithographic printing plate are obtained. In order to have a blending ratio determining step for determining the blending ratio of the new aluminum ingot and the trace metal master alloy according to the difference by comparing the rate and determining the difference, The ratio is determined, and high yield recycling is achieved without loss of raw materials.
Here, the “desired aluminum purity and desired trace metal content in the lithographic printing plate support” refers to the “aluminum purity and trace metal content” required by the type of the lithographic printing plate to be produced. This optimum value is determined in advance depending on the required performance of the printing plate.

Therefore, according to the present invention, the amount of new aluminum bullion that consumes a lot of energy for manufacturing can be determined with high accuracy according to the set value for the maximum proportion of recycled bullion. This is useful for reducing the amount of carbon dioxide generated in the production process of an aluminum substrate for a lithographic printing plate.
For this reason, when manufacturing an aluminum substrate for a lithographic printing plate, energy loss and yield loss can be remarkably reduced even if the used lithographic printing plate is reused.

According to the present invention, the amount of aluminum oxide formed as a by-product is reduced even when the used lithographic printing plate is reused when producing an aluminum substrate for a lithographic printing plate, and the purity of aluminum and the content of trace metals are reduced. A method for producing an aluminum substrate for a lithographic printing plate, in which an aluminum support for a lithographic printing plate satisfying the quality of the lithographic printing plate can be obtained in a high yield and the amount of CO ₂ generation that causes global warming is greatly reduced. Can be provided.
In addition, according to the present invention, an efficient lithographic printing plate recycling method in which the amount of CO ₂ generated in the process is greatly reduced is provided by applying the method for producing an aluminum substrate for a lithographic printing plate of the present invention. can do.

It is the schematic which shows the flow of the closed loop recycling of the recycling method of a lithographic printing plate. It is the schematic diagram which showed an example of the reproduction | regeneration ingot manufacturing apparatus until it manufactures a reproduction | regeneration ingot from a used lithographic printing plate. FIG. 3A is a plan view showing a trapezoidal recycled metal bar shape obtained by the method of the present invention, and FIG. 3B is a side view thereof.

Hereinafter, preferred embodiments of a method for producing an aluminum substrate for a lithographic printing plate and a method for recycling the lithographic printing plate according to the present invention will be described in detail.
<Method for producing an aluminum substrate for a lithographic printing plate>
The method for producing an aluminum substrate for a lithographic printing plate according to the present invention comprises: a support for a lithographic printing plate in which an aluminum substrate is successively subjected to a surface roughening treatment, an anodizing treatment, and a hydrophilic treatment with an aqueous solution containing polyvinylphosphonic acid. A recycled material preparing step for preparing a recycled material including a used lithographic printing plate and a recycled material obtained in the recycled material preparing step are put into a melting furnace and melted in a temperature range of 680 ° C. to 900 ° C. After obtaining the recycled material molten metal, the recycled material manufacturing process of obtaining the recycled metal by forming the recycled material molten into a predetermined shape and weight, and the recycled metal obtained in the recycled metal manufacturing process Analysis process for analyzing aluminum purity and trace metal content, analytical value of aluminum purity and trace metal content of recycled metal obtained in the analysis process, and planographic printing plate support The desired aluminum purity and the desired trace metal content determined are determined and the difference is obtained. Based on this difference, a new aluminum bullion and a trace metal master alloy having a predetermined purity are added to the recycled metal. Mixing ratio determining step for determining the mixing ratio, and the recycled metal, aluminum new metal and trace metal master alloy are charged into the pre-rolling melting furnace in an amount corresponding to the mixing ratio determined in the mixing ratio determining process. A pre-rolling melt preparation step for obtaining a pre-rolling melt by heating and melting, an aluminum base preparation step for producing a strip-shaped aluminum base by rolling using the pre-rolling melt obtained in the rolling melt preparation step, In this order.

The present invention will be described in the order of steps.
[Support for lithographic printing plate]
The support used in the production method of the present invention is a lithographic printing plate support in which an aluminum substrate is successively subjected to a roughening treatment, an anodizing treatment, and a hydrophilic treatment with an aqueous solution containing polyvinylphosphonic acid. .
(Roughening treatment)
Aluminum substrate roughening methods include chemical etching, electrochemical surface roughening in hydrochloric acid or nitric acid electrolyte, and wire brush grain, ball grain, nylon brush and polishing. A mechanical surface roughening method such as brush grain for roughening the surface with an agent can be used, and the above surface roughening methods can be used alone or in combination. Methods useful inter alia roughening, hydrochloric or chemically electrochemical method for surface roughening include nitric acid electrolytic solution, a suitable anode time electricity is in the range of 50C / dm ² ~400C / dm ² It is. More specifically, in the electrolytic solution containing from 0.1 to 50% hydrochloric acid or nitric acid, the temperature 20 to 80 ° C., for 1 second to 30 minutes, alternating at a current density of 100C / dm ² ~400C / dm ² It is preferable to perform direct current electrolysis.

Further, the roughened aluminum substrate may be chemically etched with acid or alkali. Etching agents suitably used are caustic soda, sodium carbonate, sodium aluminate, sodium metasilicate, sodium phosphate, potassium hydroxide, lithium hydroxide, and the like. Preferred ranges of concentration and temperature are 1 to 50% and 20%, respectively. ~ 100 ° C. Pickling is performed to remove dirt (smut) remaining on the surface after etching. Nitric acid, sulfuric acid, phosphoric acid, chromic acid, hydrofluoric acid, borohydrofluoric acid and the like are used as the acid.
After the processing as described above, the method condition is not particularly limited as long as the center line average group Ra Ra of the processing surface is 0.2 to 0.55 μm.

(Anodizing treatment)
The roughened aluminum substrate is then subjected to an anodic oxidation treatment to form an oxide film. In the anodizing treatment, sulfuric acid, phosphoric acid, oxalic acid, or an aqueous solution of boric acid / sodium borate is used alone or in combination as a main component of an electrolytic bath. There are no particular limitations on the conditions for the anodizing treatment, but the treatment is preferably performed by direct current or alternating current electrolysis at a treatment liquid temperature of 10 to 70 ° C. and a current density of 0.1 to 40 A / m ² at 30 to 500 g / liter. . The thickness of the anodized film formed is preferably in the range of 0.5 to 1.5 μm, more preferably in the range of 0.5 to 1.0 μm.

(Hydrophilic treatment with aqueous solution containing polyvinylphosphonic acid)
In this invention, after providing an anodic oxide film as mentioned above, the support body which processed with the aqueous solution containing polyvinylphosphonic acid further is used.
As an example of the step of treating with an aqueous solution containing polyvinylphosphonic acid used in the present invention, a method of treating with polyvinylphosphonic acid described as a hydrophilization treatment in US Pat. No. 4,153,461 is preferable. It is done. For example, the treatment is performed by immersing the aluminum support in the following aqueous solution. Other than immersion, the aqueous solution may be applied with a brush, sponge, spray, wheel coater, or the like. After the treatment, if necessary, it may be washed with water and dried.

Polyvinylphosphonic acid is a vinyl polymer having a phosphonic group, and those having a number average molecular weight of 10,000 to 25,000 are preferably used. As content of the said polyvinyl phosphonic acid, it is preferable that it is 0.1-5.0 mass% aqueous solution. The treatment temperature is preferably 20 to 90 ° C., and the treatment time is preferably 10 to 30 seconds. The aqueous solution may further be an aqueous solution containing a volatile solvent such as ethyl alcohol, tetrahydrofuran, acetone, or methyl glycol acetate.
The amount of polyvinylphosphonic acid attached to the surface of the support subjected to the surface treatment with polyvinylphosphonic acid is preferably in the range of 8 to ²⁰ mg / m ² as the amount of phosphorus element, and if the amount of attached is small, the generation of aluminum oxide is suppressed. Is insufficient. The said adhesion amount can be calculated | required by the element amount measurement by a fluorescent X ray.

  As the surface roughness of the aluminum support thus prepared, those having a range of 0.2 to 0.55 μm in terms of Ra are preferably used. By setting the surface roughness Ra to 0.2 μm or more, imperfections in the formation of grain of the aluminum support can be further suppressed, and printing durability can be further ensured. In addition, by setting Ra to 0.55 μm or less, it is possible to further prevent a decrease in reproducibility of small points and fine lines due to the difficulty of photopolymerization in a deep grain portion. The more preferable range of the surface roughness Ra (grain roughness) is 0.25 μm to 0.5 μm, and the most preferable range is 0.3 μm to 0.45 μm.

Usually, an image recording layer made of a photosensitive composition according to the purpose is formed on the surface of such a support, and a lithographic printing plate precursor is obtained.
Examples of the photosensitive composition suitable for the present invention include a thermal positive photosensitive composition containing a photothermal conversion substance and an alkali-soluble polymer compound, and a thermal negative photosensitive composition containing a photothermal conversion substance and a thermosetting compound. , A conventional negative photosensitive composition containing a diazo resin and an alkali-soluble polymer compound, a conventional positive resin photosensitive composition containing an o-quinonediazide compound and an alkali-soluble polymer compound, developed on a printing press And the type of photosensitive composition.

The photosensitive layer of the thermal positive photosensitive composition contains an alkali-soluble polymer compound such as a novolak resin and a photothermal conversion substance such as a cyanine dye, and it is preferable to add a dissolution inhibitor. The photosensitive layer is not limited to a single layer, and may be provided as a two-layer structure.
The photosensitive layer of the thermal negative photosensitive composition contains a photothermal conversion substance and a thermosetting compound, and the portion irradiated with infrared rays is cured to form an image portion. An infrared absorber such as a cyanine dye, an onium salt There are a polymerization type containing a radical generator such as a radical polymerizable compound and a binder polymer, and an acid crosslinking type containing an infrared absorber, a thermal acid generator, an acid crosslinking agent and an alkali-soluble polymer compound.
The photopolymerization type photosensitive composition contains a compound having an ethylenically unsaturated bond, a photopolymerization initiator, and an alkali-soluble polymer binder. As a photoinitiator, it can select and use suitably according to the wavelength of the light source to be used, and it is preferable to provide an oxygen-blocking protective layer like polyvinyl alcohol on a photosensitive layer.
Examples of the photosensitive layer of the photosensitive composition that is developed on a printing machine include a thermosensitive thermoplastic fine particle polymer type and a microcapsule type.

The image forming mechanism of the image recording layer is arbitrary, and the solubility in a region to which energy such as exposure or heating is applied is improved or cured to change the solubility in the developer.
Examples of active light sources used for image exposure include mercury lamps, metal halide lamps, and xenon lamps. Examples of scanning exposure include helium / neon lasers, argon lasers, KrF excimer lasers, semiconductor lasers, and YAG lasers.
Then, in the development step, the uncured area or the solubilized area of the image recording layer is removed and the plate is made to obtain a lithographic printing plate.
The obtained lithographic printing plate is attached to a printing machine, supplied with ink and fountain solution, and subjected to a printing process.

In the present invention, the above-described support is used, and various aluminum materials to be regenerated are melted in a melting furnace different from the pre-rolling melting furnace to obtain a recycled metal bar having a predetermined shape and weight. It is a big thing to have a blending ratio determination process to determine the blending ratio of recycled metal, new metal, and trace metal master alloy to be introduced into the pre-rolling melting furnace using the analysis result of analyzing the metal (or recycled metal) It is a feature.
FIG. 1 is an explanatory diagram for explaining the flow of closed-loop recycling of the lithographic printing plate recycling method of the present invention, and an example of a lithographic printing plate having a photosensitive image recording layer will be described.
In addition, the manufacturing method of the aluminum base | substrate for lithographic printing plates of this invention is included as a part of the flow of closed loop recycling.

(Recycled material preparation process)
In this step, a recycled material is prepared. Usually, the used lithographic printing plate that has become unnecessary after being subjected to the printing is recovered and used as a recycled material.
The used lithographic printing plate may be used as a recycled material as it is, or may be subjected to a step of removing printing ink and the like adhering to the surface.
As shown in FIG. 1, the used lithographic printing plate 36 used for printing by the printing company 32 is collected from the printing company and sent to the next recycling factory 34 for processing.
Further, in the present invention, as the recycled material, in addition to the printed lithographic printing plate, an edge material such as a cut piece of the lithographic printing plate generated in the course of the manufacturing process of the lithographic printing plate may be included (see FIG. 1). The end material 33 generated in the processing step of the belt-shaped original plate is shown). In addition, when protective paper or wrapping paper is attached to the recycled material, it is desirable to remove these protective paper or wrapping paper. Further, it is also desirable to remove the adhering substances such as the image recording layer and the ink from the reproducing material before the dissolution, and the adhering substances such as the image recording layer and the ink may be removed so as to be 1% by mass or less. More desirable.
In order to improve the efficiency of subsequent melting, such a recycled material may be fragmented by a method as described in JP 2000-12718 A, for example.

(Recycled metal manufacturing process)
In FIG. 2, the recycled lithographic printing plate 36 generated at the printing company 32 and the recycled material 40 including the end material 33 having a side length of about 1 to 60 cm generated at the lithographic printing plate manufacturing factory 18 are processed into a recycled molten metal. Further, an example 38 of a reclaimed lump manufacturing apparatus for obtaining reclaimed metal is shown.
The recycled lump manufacturing apparatus 38 includes a melting furnace 42 that melts the recycled material 40 to form a molten metal 44, a mold that solidifies the molten metal 44 to form a recycled mass 74, and a cradle that receives the recycled mass 74 from below. .
The melting furnace 42 is shielded from the ceiling wall 46 at the top, and a partition wall hangs down from the ceiling wall 46 toward the bottom wall surface, and an inlet 48 is provided in the side wall. In addition, a burner 50 is provided on the other side wall facing the charging port 48 to heat and dissolve the recycled material 40 that has been charged.
When the melting furnace 42 is a dedicated melting furnace that exclusively melts the recycled material 40, fluctuations in the component purity (aluminum purity and trace metal content) of the resulting recycled molten metal 44 can be suppressed as much as possible. From the viewpoint of improving the purity of the recycled metal, the melting furnace 42 is subjected to a treatment for dissolving pure aluminum having an aluminum content of 99.5% or more before the recycled material 40 is melted, and the inside is cleaned. preferable. Further, it is preferable that the molten metal is filled in advance by about 1/3 to 1/2 of the melting furnace capacity before the recycled material 40 is charged into the melting furnace 42. Therefore, in the first stage of recycling, a molten amount of pure aluminum is previously present in the above amount.
In the melting step of the present invention, by melting the recycled material in the melting furnace 42 in the temperature range of 680 to 900 ° C., the melting rate is fast and the tact time until the recycled molten metal 44 is obtained can be shortened.

Usually, in the recycled molten metal manufacturing apparatus, the recycled material 40 and the molten metal 44 are in direct contact with air, so that aluminum oxide is inevitably generated when the metal aluminum is heated and melted, and the molten aluminum oxide is lighter than pure aluminum. It exists near the surface of the molten metal.
In the present invention, since the aluminum support of the lithographic printing plate used for the recycled material is surface-treated with polyvinylphosphonic acid, the generation of aluminum oxide when heated and melted in the recycled molten metal production apparatus is reduced. This is a major feature of the present invention.
When a predetermined amount of recycled material has been charged into the melting furnace 42 and melted, it is preferable to extract a small amount of molten metal from the molten metal 44 for analysis at this stage.
After the extraction for analysis is completed, the molten metal 44 flows through the pipe 52 and is poured into a trapezoidal mold 54. In this case, it is preferable not to pour the entire amount of the molten metal 44 but to leave about 1/3 to 1/2 in the melting furnace 42 and use it as a preliminary molten metal for the next batch of molten metal treatment.
The molten metal is cooled with water or air in the mold 54 and formed into a trapezoid-shaped recycled ingot 74 having a trapezoidal shape of 10 to 1200 kg per piece. The shape of the regenerated mass thus formed is, for example, as shown in FIG. FIG. 3 is a plan view showing an example of the shape of the trapezoidal recycled bullion, and FIG. 3B is a side view thereof.

(Analysis process)
In the aluminum reproduction factory 34, the components of the extracted recycled molten metal obtained in the recycled metal manufacturing process are analyzed. In some cases, the analysis sample may be extracted from the recycled metal 74 itself. The components to be analyzed are aluminum purity and the content of trace metals (for example, Si, Fe, Cu, Mn), and more preferably, Mg, Zn, Ti, Cr are also analyzed. This analysis data is attached when the recycled metal is delivered to the aluminum rolling factory 14. When the analysis is performed on the recycled metal 74, this analysis process may be performed at the aluminum rolling factory 14.

(Mixing ratio determination process)
Next, the recycled ingot 74 manufactured at the recycling factory 34 is transported to the aluminum rolling factory 14 where it is recycled. In the aluminum rolling factory 14, the analytical value of the aluminum purity and trace metal content obtained as a result of the analysis in the analysis step, and the desired desired aluminum purity and desired as the target lithographic printing plate aluminum substrate are obtained. The difference between the trace metal content and the difference is obtained, and according to the obtained difference, the new metal in which the aluminum purity is determined and the trace metal master alloy (alloy with aluminum) in which the trace metal content is determined, The blending ratio with respect to the recycled metal is determined. Through this process, the maximum blending ratio of recycled metal that can be blended to achieve the desired desired aluminum purity and the desired trace metal content in the target lithographic printing plate aluminum substrate can be known. The best recycling efficiency according to the gold composition is obtained.

(Pre-rolling melt preparation process)
In accordance with the blending ratio determined in the blending ratio determining step, the recycled ingot, the new aluminum ingot and the trace metal master alloy are put into a pre-rolling melting furnace and heated and melted to obtain a molten aluminum to be used for preparing a support. The melting furnace before rolling is generally much larger in capacity than the regenerative melting furnace 42 and has a scale of 100 t.
The aluminum purity of the molten metal before rolling obtained in this step is preferably 99.0% or more, and more preferably 99.5% or more. As will be described later, an aluminum plate having an aluminum purity of 99.5% or more is preferable for roughening the electrolytic system. If the aluminum purity is less than 99.0, cracks or the like may occur when rolling into an aluminum plate in the rolling process. This is because defects are likely to occur. The trace metal content is selected according to the intended physical properties of the aluminum base for a lithographic printing plate.
The melting conditions may be the same as the molten metal preparation conditions in the recycled metal manufacturing process, or may be appropriately adjusted according to the rolling conditions of the support.

(Aluminum substrate manufacturing process)
The molten aluminum produced in this manner is subjected to impurities, such as flux, gas, and filter, to remove non-metallic impurities, non-metallic impurity combustion gases, oxides, etc., and H ₂ gas dissolved in the molten metal. And Na are removed. In particular, the molten metal treatment may be performed in two stages, a method using a gas and a method using a filter. The molten aluminum melt is preferably cast by a DC casting method using a twin roll continuous casting machine or a fixed mold. A strip-shaped aluminum substrate that is rolled in the above process, rolled to a predetermined thickness, and annealed as necessary is produced. Usually, the manufactured aluminum substrate 16 is stored and transported in the state of an aluminum coil wound in a coil shape. The obtained aluminum substrate 16 is sent to a lithographic printing plate manufacturing factory 18 in the form of an aluminum coil. Then, the regenerated aluminum substrate 16 is used for the production of a lithographic printing plate precursor.
Thus, according to the present invention, an aluminum substrate for a lithographic printing plate can be efficiently regenerated and manufactured.

(Manufacture of lithographic printing plate precursors)
The obtained aluminum base for a lithographic printing plate is used for the production of a lithographic printing plate precursor. Thereby, the planographic printing plate of the present invention is recycled.
Hereinafter, a method for producing a lithographic printing plate precursor using the obtained lithographic printing plate aluminum substrate will be described.
(Production of support)
First, the aluminum substrate 16 obtained by the production method of the present invention is subjected to a roughening treatment necessary as a support for a lithographic printing plate. Here, one or both surfaces of the aluminum substrate 16 are roughened. The surface roughening treatment is not particularly limited, but an electrochemical surface roughening treatment is preferable. Electrochemical roughening is performed by etching an alternating current as an electrolytic current in an acidic aqueous solution such as hydrochloric acid or nitric acid. The acid concentration is preferably 3 to 150 g / L, and the aluminum ion concentration in the solution is preferably adjusted to 2 to 7 g / L. The amount of electricity is preferably applied so as to be ²⁰ to 500 C / dm ^{2. As} the alternating current, a rectangular wave current and a trapezoidal wave current are preferable, and a trapezoidal wave current is particularly preferable.
In the electrochemical surface roughening treatment using such an electrolytic method, the aluminum purity and the trace metal content of the aluminum substrate 16 affect the uniformity of the generated pits, and the printing durability, stain resistance, and exposure. Affects stability. Therefore, the aluminum purity of the aluminum plate is preferably 99.0% or more, and more preferably 99.5% or more. Moreover, among the trace metals contained in the aluminum plate 16, the Cu content is preferably 0.001 to 0.050% by mass, and more preferably 0.002 to 0.040% by mass. 0.008 to 0.035% by mass is particularly preferable. Furthermore, the Si content is 0.05 to 0.50 mass%, the Fe content is 0.15 to 0.7 mass%, the Mn content is 0.002 to 0.15 mass%, and the Mg content is 0.05 to 0.50 mass%. Is 0.001 to 1.5 mass%, the Zn content is 0.001 to 0.25 mass%, the Ti content is 0.001 to 0.10 mass%, and the Cr content is 0.001 to 0.001. It is preferably 0.10% by mass.

Since smut and intermetallic compounds exist on the surface of the aluminum substrate 16 roughened by the electrolytic method as described above, after the alkali treatment, it is possible to perform a washing treatment with an acidic solution mainly composed of sulfuric acid. preferable.
Next, the roughened aluminum substrate 16 is anodized to form an oxide film. In the anodizing treatment, sulfuric acid, phosphoric acid, oxalic acid, or an aqueous solution of boric acid / sodium borate is used alone or in combination as a main component of an electrolytic bath. The conditions for forming the oxide film are as described above, and the preferable thickness of the oxide film is 0.5 to 1.5 μm, and is appropriately selected within this range.
After that, the conditions for the hydrophilization treatment to be performed are variously selected as necessary. When the obtained lithographic printing plate precursor is used and then recycled again, the polyvinylphosphonic acid is used as the hydrophilization treatment. It can be said that the treatment is preferable from the viewpoint of recycling efficiency.
The hydrophilization treatment is not limited to this method. For example, a known hydrophilization treatment such as a hydrophilization treatment with a sodium silicate solution may be appropriately performed. In this way, a lithographic printing plate support 16A having a hydrophilic surface is obtained.

(Formation of image recording layer)
Next, a planographic printing plate precursor is produced by forming an image recording layer on the obtained support. In the image recording layer forming step 24, an image recording layer coating solution made of a photosensitive composition is applied to the surface of the support 16A that has been roughened, and in the drying step 26, the image recording layer is dried.
Examples of the photosensitive composition suitable for forming the image recording layer in the present invention include a thermal positive photosensitive composition containing a photothermal conversion substance and an alkali-soluble polymer compound, and a photothermal conversion substance and a thermosetting compound. Thermal negative photosensitive composition, photopolymerizable photosensitive composition, negative photosensitive composition using diazo resin or photocrosslinking resin, positive resin photosensitive composition using quinonediazide compound, special development process required And a photosensitive composition that does not.
As a result, a lithographic printing plate precursor 28 is produced, so that in the processing step, the strip-shaped interleaving paper is superposed on the strip-like master 28 and cut into a rectangular sheet of a predetermined size to provide a lithographic printing plate precursor with interleaving paper. 30 (see FIG. 1) is manufactured.
The manufactured sheet-like planographic printing plates 30 with slip sheets are stacked and then packed and sent to the printing company 32. When the lithographic printing plate precursors 30 are laminated, a slip sheet is sandwiched between the lithographic printing plate precursors 30, so that damage to the image recording layer surface of the lithographic printing plate precursor 30 during transportation and storage is effectively suppressed. The The slip sheet is removed before the image forming process on the image recording layer.
The lithographic printing plate precursor is subjected to a plate making process through a writing process (image forming process) by exposure or heating and a developing process performed as necessary to obtain a lithographic printing plate.
The resulting lithographic printing plate is supplied with printing ink and fountain solution and used for the printing process.

In the lithographic printing plate recycling method of the present invention, the “new bullion 100% route” 90 for sending the aluminum substrate 16 of 100% new bullion from the aluminum rolling factory 14 to the lithographic printing plate manufacturing factory 18 is performed only for the first time, and thereafter That is, from the second time onward, a “recycling route” for sending the aluminum substrate 88 containing recycled material obtained from the aluminum rolling factory 14 to the planographic printing plate manufacturing factory 18 by the method for manufacturing an aluminum substrate for a planographic printing plate of the present invention. 92 is performed.
According to the method of the present invention, a complete closed recycle flow for reusing aluminum scrap generated in the lithographic printing plate industry can be established. As a result, the amount of CO ₂ generated can be significantly reduced as compared with the case where an aluminum substrate for a lithographic printing plate is manufactured using only the new aluminum metal 12.
Therefore, according to the method of the present invention, energy loss and yield loss can be remarkably improved while ensuring the quality assurance of aluminum purity and trace metal content in the obtained lithographic printing plate aluminum support. In addition, the amount of CO ₂ generated in the lithographic printing plate precursor manufacturing process can be greatly reduced.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
(Examples 1 and 2 and Comparative Example 1)
1. Preparation of aluminum substrate Si: 0.073 mass%, Fe: 0.270 mass%, Cu: 0.028 mass%, Mn: 0.001 mass%, Cr: 0.001 mass%, Zn: 0.003 mass% %, Ti: 0.020% by mass, and the balance was prepared using an aluminum alloy composed of Al and inevitable impurities, and an aluminum substrate used in Example 1 was prepared as follows.
First, a molten aluminum treatment including degassing and filtration was performed on the molten aluminum alloy, and an ingot having a thickness of 500 mm was produced by a DC casting method. After chamfering the surface of the obtained ingot by 10 mm, the ingot was heated, hot rolling was started at 400 ° C. without performing a soaking treatment, and rolling was performed until the plate thickness reached 4 mm. Next, after cold rolling to a thickness of 1.5 mm and intermediate annealing, it was finished again by cold rolling to 0.24 mm and the flatness was corrected to obtain an aluminum plate (aluminum substrate).

2. Manufacture of lithographic printing plate support (surface treatment of aluminum substrate)
About the obtained aluminum plate, the surface treatment was performed in the procedure shown below. In addition, after each surface treatment and water washing, the liquid was removed with a nip roller. Water washing was performed by spraying water from a spray tube.
2-1. Mechanical surface roughening treatment First, while supplying a suspension of silica sand having a specific gravity of 1.12 (abrasive, average particle size 25 μm) and water as a polishing slurry liquid to the surface of the aluminum plate, 6,10-nylon A mechanical roughening treatment was performed using a brush roller on which a nylon brush having a material, a hair length of 50 mm, and a hair diameter of 0.48 mm was rotated.
2-2. Chemical Surface Roughening Treatment Next, an alkali etching treatment was performed by spraying an aqueous solution containing 27 mass% NaOH and 6.5 mass% aluminum ion at a liquid temperature of 70 ° C. on the aluminum plate. The dissolution amount of the aluminum plate was 8 g / m ² . Next, an aqueous nitric acid solution having a liquid temperature of 35 ° C. was sprayed onto the aluminum plate to perform desmutting treatment for 10 seconds.

2-3. Electrochemical roughening treatment Next, electricity was generated using a trapezoidal wave alternating current and a nitric acid aqueous solution containing 1% by mass of nitric acid (containing 0.5% by mass of aluminum ions and 0.007% by mass of ammonium ions, at a liquid temperature of 50 ° C.). Chemical roughening treatment was performed. The current density at the peak of the alternating current is 50 A / dm ² for both the anode and the cathode of the aluminum plate, and the ratio of the amount of electricity at the time of cathode and the amount of electricity at the time of the anode of the alternating current is 0.95. Was 0.50, the frequency was 60 Hz, and the total amount of electricity at the time of anode was 180 C / dm ² .
Then, it washed with water. Next, an alkali etching treatment was performed by spraying an aqueous solution having a liquid temperature of 45 ° C. containing 26% by mass of NaOH and 6.5% by mass of aluminum ions using a spray. The dissolution amount of the aluminum plate was 3 g / m ² . Next, sulfuric acid (sulfuric acid concentration 300 g / L, aluminum ion concentration 15 g / L) was sprayed from the spray tube to the aluminum plate at 80 ° C. for 7 seconds to perform acidic etching treatment. Then, it washed with water.

2-4. Thereafter, an aqueous solution (containing 0.5% by mass of aluminum ions) having a sulfuric acid concentration of 100 g / L was used as an anodizing solution, a direct current voltage was used, a current density of 25 A / dm ² , a temperature of 50 ° C., and 30 seconds. The aluminum plate was anodized under the above conditions to form an oxide film with a thickness of 1.5 μm, and then washed with water by spraying.
2-5. Hydrophilization treatment with aqueous solution of polyvinylphosphonic acid The aluminum substrate after the treatment was immersed for 30 seconds at a liquid temperature of 60 ° C. using a 0.6% aqueous solution of polyvinylphosphonic acid (an aqueous solution prepared using well water). . In this way, an aluminum support (1) for a lithographic printing plate was obtained. When this adhesion amount was determined by fluorescent X-ray, the phosphorus element amount was 18.8 mg / m ² .

3. Production of lithographic printing plate precursor (formation of image recording layer)
3-1. Undercoat A 3% methanol solution of a copolymer of p-vinylbenzoic acid and vinylbenzyltriethylammonium chloride (copolymerization molar ratio 85/15, Mw 28,000) is applied to the surface-treated surface of the support with a bar coater. The undercoat layer was provided so that the amount applied after drying was 18 mg / m ² .

3-2. Formation of Recording Layer (Multilayer) On the aluminum support on which the undercoat layer was formed, the following lower layer coating solution was applied with a bar coater so that the coating amount after drying was 0.85 g / m ² , and then 160 ° C. And dried for 44 seconds to form a lower layer. Thereafter, the following upper layer coating solution was applied with a bar coater so that the coating amount after drying was 0.22 g / m ^2, and dried at 148 ° C. for 25 seconds to prepare a lithographic printing plate precursor.
<Coating liquid for lower layer>
N- (4-aminosulfonylphenyl) methacrylamide / acrylonitrile /
1.73 g of methyl methacrylate (36/34/30: Mw 60,000)
・ M, p-cresol novolak (m / p ratio = 6/4, Mw 4,500) 0.192 g
・ Cyanine dye A (the following structure) 0.134 g
・ 3-methoxy-4-diazodiphenylamine hexafluorophosphate 0.032 g
・ Ethyl violet 0.0781g
・ Polymer 1 (the following structure) 0.035g
・ Methyl ethyl ketone 25.41g
・ 1-methoxy-2-propanol 12.97g
・ Γ-butyrolactone 13.18g

<Upper layer coating solution>
・ M, p-cresol novolak (m / p ratio = 6/4, Mw 4,500) 0.3479 g
・ Cyanine dye A (the above structure) 0.0192 g
・ Polymer 1 (the above structure) 0.015 g
・ Quaternary ammonium salt (the following structure) 0.0043g
・ Methyl ethyl ketone 6.79g
・ 1-methoxy-2-propanol 13.07 g

3. Preparation and printing of lithographic printing plate The above-described lithographic printing plate precursor was drawn with a test pattern in an image form using a Trend setter manufactured by Creo.
Thereafter, development was performed at a development temperature of 30 ° C. and a development time of 12 seconds using a PS processor LP940H manufactured by Fuji Photo Film Co., Ltd., which was charged with the developer DT-2 manufactured by Fuji Film Co., Ltd. After the development, it was continuously subjected to printing using a printing press Lithron manufactured by Komori Corporation.

4). Preparation of recycled material The printing ink adhering to the surface of the lithographic printing plate after the completion of the printing was removed with a petroleum cleanser and removed from the printing press. These used lithographic printing plates were cut using an electric shear so that the length of the longest part would be 5 to 50 mm, and fragmented. Foreign materials were separated from these small raw materials by a suction separation method and then by a magnetic separation method. Recycled materials obtained using the lithographic printing plate support are referred to as recycled materials (1).

5). Production of recycled metal bar In the recycling plant, a molten aluminum of 1.5 t having a purity of 100% is first melted in the melting furnace 42 of the recycled lump manufacturing apparatus 38 in FIG. Into this, 1.5 t of the recycled material (1) is charged and melted by heating at 720 ° C. to obtain a molten metal (1). Next, samples for analysis were drawn from each molten metal.
Thereafter, the molten metal was poured into the mold 54 through the pipe line 52 so as to have the size shown in FIG. 3, and then cooled and hardened to obtain a recycled metal (lump).
Separately, the aluminum oxide slab floated on the surface of the molten metal was scraped, the mass was measured, and the corresponding aluminum weight was subtracted from the ideal aluminum amount when hypothesizing that there was no oxidation, and the recycled metal yield was calculated. .
Next, the aluminum purity and trace metal content of the analytical sample were analyzed. As a result, the molten metal (1) was 0.070% Si, 0.300% Fe, 0.015% Cu, and 0.010% Mg.
The analysis result was attached to the recycled metal and transported to the aluminum rolling mill 14.

6). Preparation of aluminum substrate for lithographic printing plate In an aluminum rolling mill, a lithographic printing plate aluminum substrate is prepared according to an order received from a lithographic printing plate manufacturing plant. In this order, the thickness, size, Not only the amount but also the alloy composition is indicated.
Therefore, when the aluminum rolling factory 14 produces a lithographic printing plate substrate using the supplied recycled metal, the ordered alloy composition is set as a target value and compared with the analysis value attached to the recycled metal. The difference is calculated, and from that value, the amount of recycled metal, trace metal master alloy, and pure aluminum is calculated arithmetically with respect to the alloy composition target value and the predetermined amount of molten metal in the melting furnace before aluminum rolling. To do. By this step, the maximum blending ratio of the recycled bullion that can be blended can be known, and the best recycling efficiency according to the composition of the recycled bullion can be obtained.
For example, when the target values are 0.07% for Si, 0.25% for Fe, 0.025% for Cu, 0.01% for Mg, and the preparation amount of the melting furnace before rolling is 100 t, In the case of using recycled bullion of component composition, 83t of recycled bullion and 17t of pure aluminum bullion are mixed, and the contents of Si and Cu are adjusted by adding the respective master alloys, so that the alloy composition of the target value is obtained. Can be obtained.
Then, according to the blending ratio determined in the blending ratio determining step, a recycled metal, a new aluminum metal, and a trace metal master alloy were put into a melting furnace before rolling, and heated and melted to obtain a molten aluminum before rolling.
The molten aluminum was degassed and filtered to remove impurities, and then an aluminum substrate was cast by the same DC casting method as described above.

A lithographic printing plate support was produced in the same manner as in “2, Method for producing a lithographic printing plate support” using new aluminum, using the thus prepared aluminum substrate as a raw material.
The case where a new lithographic printing plate was produced by using a used lithographic printing plate (PS plate) obtained in accordance with the method for producing an aluminum substrate for a lithographic printing plate as a raw material, and the aluminum substrate initially used in Example 1 The amount of CO ₂ generated when a lithographic printing plate (PS plate) was manufactured with 100% of the raw material (new bullion) of 50 tons (control example 1), the aluminum refining process, the recycled bullion production process, the aluminum substrate production process The lithographic printing plate was examined for each manufacturing process. The results are shown in Table 1 below. Table 1 also shows the yield of the recycled metal.

(Example 2)
A lithographic printing plate as in Example 1 except that the polyvinylphosphonic acid aqueous solution treatment in Step 2-5 of Example 1 was immersed in a polyvinylphosphonic acid aqueous solution concentration of 0.5% and a liquid temperature of 40 ° C. for 30 seconds. An original plate was prepared. The amount of phosphorus element determined by fluorescent X-ray was 9.8 mg / m ² . After this was used for printing, it was similarly recycled to produce a new lithographic printing plate precursor, which was evaluated in the same manner as in Example 1.

(Comparative Example 1)
A lithographic printing plate precursor was prepared in the same manner as in Example 1 except that the polyvinylphosphonic acid aqueous solution treatment was not performed, and this was used for printing, and then recycled in the same manner to prepare a new lithographic printing plate precursor. This was evaluated in the same manner as in Example 1. The results are also shown in Table 1.

The amount of CO ₂ generated in the recycled metal manufacturing process was determined from the input energy and yield when each electrolytic product was dissolved. Moreover, the data of HP of Japan Aluminum Association was used for the amount of CO ₂ generation in the aluminum refining process and the rolling process.
As can be seen from the results in Table 1, in Example 1 and Example 2 in which a lithographic printing plate was produced by the production method of the present invention, the amount of CO ₂ generated was the same as when 100% of new bullion was used (Control Example 1). It can be reduced to about 1/4 (75% reduction) of the CO ₂ generation amount. On the other hand, in Comparative Example 1 using a support that was not treated with polyvinylphosphonic acid, the aluminum purity obtained after the weight of the recycled metal manufacturing process was lower than in the Examples.
As can be seen from the results in Table 1, in Example 1 and Example 2 in which a lithographic printing plate was produced by the production method of the present invention, the amount of CO ₂ generated was the same as when 100% of new bullion was used (Control Example 1). The CO ₂ generation amount can be reduced to 15% (85% reduction). On the other hand, in Comparative Example 1 using a support that was not treated with polyvinylphosphonic acid, the recycled metal yield was low compared to the Examples.

DESCRIPTION OF SYMBOLS 10 ... Aluminum refining factory 12 ... Aluminum new metal 14 ... Aluminum rolling factory 16 ... 100% new aluminum base 18 ... Planographic printing plate manufacturing factory 30 ... Lithographic printing plate 32 ... Printing company 33 ... End material 34 ... Recycle factory 36 ... used printing planographic printing plate 38 ... recycled metal manufacturing equipment 40 ... recycled material (printed used planographic printing plate and end material)
42 ... Melting furnace 44 ... Molten metal 52 ... Pipe line 74 ... Recycled metal

Claims (4)

Prepare a recycled material including a used lithographic printing plate comprising a support for a lithographic printing plate in which an aluminum substrate is successively subjected to roughening treatment, anodizing treatment, and hydrophilic treatment with an aqueous solution containing polyvinylphosphonic acid. A recycled material preparation process,
The recycled material obtained in the recycled material preparation step is put into a melting furnace and melted in a temperature range of 680 ° C. to 900 ° C. to obtain a recycled material melt, and then the recycled material melt is given a predetermined shape and weight. Recycled ingot manufacturing process to obtain recycled ingots by molding into
An analysis step of analyzing the aluminum purity and trace metal content of the recycled metal obtained in the recycled metal manufacturing process;
The analytical value of the aluminum purity and trace metal content of the recycled metal obtained in the analysis step is compared with the desired aluminum purity and desired trace metal content predetermined for the lithographic printing plate support, and the difference is determined. Obtaining, based on this difference, a blending ratio determining step for determining a ratio of blending a new pure aluminum and a trace metal master alloy with a determined purity with respect to the recycled metal,
Rolling in which the recycled metal, the new aluminum metal, and the trace metal master alloy are put into a melting furnace before rolling in an amount corresponding to the blending ratio determined in the blending ratio determining step, and are melted by heating to obtain a molten metal before rolling. Pre-melt preparation process,
Using the pre-rolled molten metal obtained in the rolled molten metal preparation step, an aluminum substrate manufacturing step of manufacturing a band-shaped aluminum substrate by rolling,
The manufacturing method of the aluminum base | substrate for lithographic printing plates which has these in this order.   The lithographic printing according to claim 1, wherein the recycled material in the recycled material preparation step further includes at least one of a cut piece of an aluminum substrate and a cut piece of a lithographic printing plate that are generated during the manufacturing process of the lithographic printing plate manufacturing step. A method for producing an aluminum substrate for printing plates. A support producing step for obtaining a lithographic printing plate support by sequentially subjecting at least one surface of an aluminum substrate for a lithographic printing plate to a surface roughening treatment, an anodizing treatment, and a hydrophilization treatment with an aqueous solution containing polyvinylphosphonic acid; ,
A lithographic printing plate precursor production process for producing a lithographic printing plate precursor by forming an image recording layer on the treated surface of the obtained lithographic printing plate support;
After making the lithographic printing plate precursor obtained to obtain a lithographic printing plate, a printing process for performing desired printing;
A recovery process for recovering used lithographic printing plates generated after completion of the printing process;
A recycling step of using the recovered used lithographic printing plate as a recycled material in the method for producing an aluminum substrate for a lithographic printing plate according to claim 1 or 2,
Recycling method of lithographic printing plates having in this order.   The planographic printing plate aluminum substrate according to claim 3, wherein the planographic printing plate aluminum substrate is a planographic printing plate aluminum substrate obtained by the method of producing a planographic printing plate aluminum substrate according to claim 1 or 2. Recycling method.

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