JPH05156476A - Surface treatment of aluminum base for printing plate - Google Patents

Abstract

PURPOSE:To recycle the waste water discharged in a large volume from surface treating stages for an aluminum plate for planographic printing plates as indus trial water effective for the surface treating stages. CONSTITUTION:The alkaline waste liquids or acidic waste liquids discharged from the respective surface treating stages and washing stage are neutralized by a pH adjustment and thereafter, insoluble components are removed therefrom in a flocculating and settling chamber. The supernatant liquids thereof are passed through a filter by which the fine insoluble components are further removed therefrom. The liquids are then sent to a reverse osmosis membrane device and are treated. The treated water from which impurities are removed by the treatment in the reverse osmosis membrane device has preferably <=200mus/cm electric conductivity. The concn. of the sulfate ions contained in the treated water is preferably <10mg/liter and the concn. of the nitrate ions therein is <10mg/liter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for an aluminum plate for a printing plate, and more particularly to recovering and reusing water from wastewater discharged from the surface treatment step.

[0002]

2. Description of the Related Art Various processing liquids are used for the surface treatment method of an aluminum plate for a printing plate. For example, nitric acid and hydrochloric acid are generally used in the process of electrochemically roughening, sulfuric acid is used in the process of anodizing, and sodium hydroxide is generally used in the process of chemically etching aluminum. ..

On the other hand, as a support for a lithographic printing plate, an aluminum plate or an aluminum alloy plate is used, and the surface shape after the treatment largely varies depending on the aluminum ion concentration in the above-mentioned treatment liquid. Has a great influence on the quality of the aluminum support for printing plates.

Therefore, it is important to keep the aluminum ion concentration in the treatment liquid constant at a predetermined concentration. In order to keep the aluminum concentration constant, the treatment liquid in the treatment system is discharged outside the system to perform waste liquid treatment, the waste liquid is neutralized, and the neutralized water is discharged outside the factory.

In Japanese Patent Laid-Open No. 1-29992, an aluminum dialyzer in an treating solution is separated by using an electrodialysis tank composed of an ion exchange membrane and discharged out of the system so that the aluminum ion concentration in the treating solution is kept constant. I suggest a way to keep it. In addition, if a part of the treatment liquid adheres to the aluminum support after each surface treatment, quality defects such as uneven treatment will occur. The treatment liquid adhering to the aluminum support is washed off with water. The waste water of the washing water generated at this time is also subjected to waste liquid treatment, and the neutralized water is discharged to the outside of the factory.

[0006] In recent years, industrial water is in short supply due to restrictions such as pumping of groundwater, but since the wastewater discharged to the outside of the factory contains sulfate ions, nitrate ions, etc., it can be directly used for the surface treatment process. Cannot be reused as industrial water.

[0007]

It is an important subject from the viewpoint of cost reduction and environmental conservation to reuse waste water discharged in large amounts from the surface treatment process of an aluminum plate for a lithographic printing plate as industrial water effective in the surface treatment process. Is.

[0008]

Means for Solving the Problems The inventors of the present invention have found the following inventions as a result of earnest research efforts for solving the above problems.

That is, the alkaline waste liquid or acidic waste liquid discharged from each surface treatment step and water washing step is pH-adjusted to be neutralized, then insoluble components are removed in a coagulation sedimentation tank, and then the supernatant is filtered. After removing the fine insoluble components, the surface treatment method is to reuse in the surface treatment step of the aluminum support for lithographic printing plates, such as washing water in a washing tank.

Here, (1) neutralization is carried out in a pH adjusting tank, insoluble components are removed in a coagulating sedimentation tank, and then the supernatant is passed through a filter to remove finer insoluble components, and then the reverse osmosis membrane device is used. And the treated water has an electric conductivity of 200 μs.
The surface treatment method is preferably such that the aluminum support for a lithographic printing plate is reused in the surface treatment step such as washing water in a washing tank after the treatment so that it becomes less than or equal to / cm. Further, (2) impurities such as sulfate ions and nitrate ions are removed by the reverse osmosis membrane device, and the sulfate ion concentration of the treated water becomes less than 10 mg / liter and the nitrate ion concentration becomes less than 10 mg / liter. It is a more preferable surface treatment method that the water from which the water has been removed can be reused in the surface treatment step of the aluminum support for a lithographic printing plate.

FIG. 1 is a schematic diagram showing the construction of an apparatus for surface-treating an aluminum plate by the surface-treating method described in (1) above in the surface-treating step for an aluminum support for a lithographic printing plate according to the present invention. A specific example of the surface treatment method described in (1) above will be described with reference to FIG. However, the present invention is not limited to this embodiment.

In the etching treatment, the treatment liquid is prepared in the preparation tank (5), and the prepared treatment liquid is supplied to the etching treatment tank (11) through the liquid supply pipe (12) using the liquid supply pump (4). Sent to the spray (3). The etching treatment liquid from the liquid preparation tank further passes through the liquid supply pipe (13) branched from the liquid supply pipe (12) to dissolve the tank (34).
Can also be delivered to. The amount of liquid supplied and the timing of liquid supply can be adjusted by operating a valve (not shown) provided in the middle of the pipe.

Liquid preparation tank (5) and etching treatment tank (1
1) is connected to a liquid supply pipe (12) and a return liquid pipe (14), and the etching treatment liquid is circulated between them. Sodium hydroxide component in the treatment liquid reacts during the etching treatment. , The aluminum ion content increases, and the water evaporates and decreases. For this reason, the sodium hydroxide solution and water are replenished to the treatment liquid in the liquid preparation tank (5) from the replenishment pipes (21) and (22), respectively. It is wasteful to keep the aluminum ions in the processing liquid at a predetermined concentration.

For this reason, a part of the processing liquid which is being circulated in the liquid preparation tank (5) is sent to the dissolution tank (34) through the liquid supply pipe (13) in a timely manner, and aluminum ions are removed from the system. To be removed. On the other hand, waste alkali (30), waste acid (31), (32), (33) discharged from each surface treatment process.
Is neutralized in the pH adjusting tank (27), and the coagulating sedimentation tank (28)
Is coagulated and precipitated as aluminum sludge (16), and further, aluminum sludge (16) is subjected to solid-liquid separation by a filter press (29) and sent to a dissolution tank at appropriate times.

In the dissolution tank (34), the etching treatment liquid and the aluminum sludge (16) are mixed to prepare a supersaturated sodium aluminate solution, and the solution is supplied to the precipitation tank (7) at a suitable time. In the precipitation tank (7), aluminum hydroxide is crystallized using seeds of aluminum hydroxide in a supersaturated sodium aluminate solution as nuclei.

Therefore, the mixture of the treatment liquid mainly containing sodium hydroxide solution in which the aluminum ion concentration is reduced and the crystals of aluminum hydroxide is sent to the thickener (8) by the liquid sending pipe (17) and crystallized. The formed aluminum hydroxide passes through the pipe (18), is separated by the drum filter (9), and is collected in the hopper (10). On the other hand, the treatment liquid mainly containing sodium hydroxide liquid is returned as a recovery liquid to the liquid preparation tank through the recovery pipe (20).

The supernatant liquid separated in the coagulating sedimentation tank (28) is sent to the filter (35) by the waste water pump (36) to remove fine insoluble components, and then to the reverse osmosis membrane device (37). Thus, impurities such as sulfate ions and nitrate ions are removed. The water from which the impurities have been removed is reused for washing water in a washing tank, etc., and the wastewater in which the impurities have been concentrated is treated as factory wastewater and discharged.

[0018]

EXAMPLE A surface treatment of an aluminum plate was carried out by collecting waste water under the following conditions with the apparatus arranged as shown in FIG. Amount of supernatant water discharged from coagulation tank 8.6 m ³ / min Same conductivity 1800 μs / cm Same nitrate ion concentration 400 mg / l Same sulfate ion concentration 600 mg / l Wastewater recovered water volume 7.2 m ³ / min Same conductivity 114 μs / cm Same nitrate ion Concentration 43 mg / liter Same sulfate ion concentration less than 5.0 mg / liter

As a result, the wastewater, which has been conventionally discharged as wastewater, is transformed into industrially usable water and can be reused, which greatly contributes to environmental protection and cost reduction of products.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for performing a surface treatment of an aluminum plate by the treatment method of the present invention.

FIG. 2 is a block diagram showing a flow of the device of the present invention.

[Explanation of symbols]

1 Nip roll 4 Liquid feed pump 2 Pass roll 5 Adjustment tank 3 Spray 6 Water washing tank 7 Precipitation tank 23 Aluminum plate 8 Thickener 24 Anodizing power supply tank 9 Drum filter 25 Anodizing tank 10 Aluminum hydroxide hopper 26 Electrode 11 Etching tank 27 pH Adjustment tank 12 Etching treatment liquid circulation pipe 28 Coagulation sedimentation tank 13 Etching treatment liquid circulation pipe 29 Filter press 14 Return liquid pipe 30 Washing water waste alkaline liquid 15 Electrolysis treatment tank 31 Electrolysis treatment liquid overflow pipe 16 Aluminum hydroxide sludge 32 Washing water waste Acid solution 17 Liquid supply pipe 33 Rinsing water Waste acid solution 18 Piping 34 Dissolution tank 19 Dissolution tank water supply pipe 35 Filter 20 Recovery piping 36 Waste water pump 21 Sodium hydroxide supply pipe 37 Reverse osmosis membrane device 22 Water supply pipe

[Procedure amendment]

[Submission date] October 14, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction content]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for an aluminum plate for a printing plate, and more particularly to recovering and reusing water from waste water discharged from the surface treatment step.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

Here, (1) neutralization is carried out in a pH adjusting tank, insoluble components are removed in a coagulating sedimentation tank, and then the supernatant is passed through a filter to remove finer insoluble components, and then the reverse osmosis membrane device is used. And the treated water has an electric conductivity of 200 μs.
The surface treatment method is preferably such that the aluminum support for a lithographic printing plate is reused in the surface treatment step such as washing water in a washing tank after the treatment so that it becomes less than or equal to / cm. Furthermore, (2) impurities such as sulfate ions and nitrate ions are removed by a reverse osmosis membrane device to reduce the sulfate ion concentration of the treated water to less than 10 mg / liter, and the nitrate ion concentration of 60 mg / liter. It is a more preferable surface treatment method that the water becomes less than this, and the water from which the impurities are removed can be reused in the surface treatment step of the lithographic printing plate aluminum support.

Claims (3)

[Claims] 1. An electric conductivity of water separated from a waste liquid generated during the neutralization of waste acid and waste alkali discharged from the surface treatment step of an aluminum support for a printing plate is 200 μs / cm.
A surface treatment method for an aluminum support for a printing plate, which comprises separating water and impurities as described below and reusing the water in the surface treatment step. 2. The waste liquid generated during the neutralization of waste acid and waste alkali discharged from the surface treatment step of the aluminum support for printing plates is treated with water so that the sulfate ion concentration of the separated water becomes less than 10 mg / liter. And a water, and water is reused in the surface treatment step. 3. The waste liquid generated during the neutralization of waste acid and waste alkali discharged from the surface treatment step of the aluminum support for printing plates is treated with water so that the concentration of nitrate ions in the separated water is less than 60 mg / liter. And a water, and water is reused in the surface treatment step.