DE2064354A1 - Method and device for the continuous pretreatment of a metal foil strip used in particular for the production of lithographic planographic printing plates - Google Patents

Description

K 2OO4 / Gbm 4621 FP-Dr.E.-ur December 22, 1970

Description for registering the

KALLE AKTIENGESELLSCHAFT Wiesbaden-Biebrich

for a patent

Method and device for the continuous pretreatment of a, in particular for production of lithographic planographic printing plates

Metal foil tape

The invention relates to a method for the continuous pretreatment of a particularly for production of metal foil tape used for lithographic planographic printing plates, which is preferably made of aluminum or an aluminum alloy, by mechanical, chemical or electrochemical roughening and / or anodic oxidation. It also relates to a device suitable for this purpose.

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It is known that for use as lithographic planographic printing plates, certain metal foils generally have to be used be subjected to intensive pretreatment in order to make them suitable as a carrier for the printed image to be applied close. The metal foils almost always have to be subjected to a cleaning process, especially in order to remove the to remove grease or oil residues resulting from the rolling process, and those intended for recording the print image The surface must then be roughened. The film is cleaned by washing, e.g. B. with organic solvents, or by chemical or electrochemical treatment, and for roughening mechanical or chemical or electrochemical processes are used. As a roughening process come z. B. sandblasting or brushing the metal surface in question. In the chemical or electrochemical Roughening is generally used with acid, alkaline or neutral electrolytes, wherein in the electrochemical roughening in particular hydrochloric acid, which optionally also additives, such as Mercury ions and the like, 'is preferred. Can be used for electrochemical roughening Direct current or - often preferred - alternating current can be used; currents can also be superimposed be advantageous.

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The cleaned and roughened metal foils are then usually subjected to anodic oxidation subjected to produce a thin oxide or oxide hydrate layer on them, which for good Adhesion is responsible for the subsequently applied print image. As suitable electrolytes in the case of anodic oxidation, solutions of inorganic acids, e.g. B. nitric acid, Sulfuric acid, chromic acid, or organic acids such as oxalic acid, acetic acid, malonic acid, lactic acid, etc., used. Depending on the type and concentration of the electrolyte used as well as depending on the given temperature conditions and electrical parameters will generally have a different surface finish obtained, which when viewed microscopically appear to be crater-like to wildly fissured Appearance can be recognized, with the individual elevations still containing tiny pore-like openings which are presumably primarily responsible for anchoring the print image. It is as a result It is of great importance that these pore-like openings are kept as free from impurities as possible will.

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It is known that both the roughening and the subsequent anodic oxidation sludge-like deposits of reaction products between metal and treatment liquid, which fill the depressions in the metal surface and in particular also cover or clog the aforementioned pores. In addition, the The resulting sludge layer during the electrochemical treatments has an insulating effect that reduces the Roughening or oxidation process slowed down. It has been shown that the muddy deposits cannot be completely removed by a simple washing process, so you already have a number of them applied by supportive measures.

Removal of the sludge layer with mechanical Means such as brushing or rubbing with a sponge is difficult and also leads to an uneven finish Surface. The inevitable injuries to mechanical stress sensitive metal surfaces and their uneven cleaning cause an increase in the reject rate before especially in the production of presensitized printing plates.

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In the published documents of the German patent application K 9115/48 a, a method for anodic Oxidation of metals described, in which during anodic oxidation and, if necessary, in all Voroder After-treatments, the treatment liquid is converted into high-frequency vibrations by an ultrasound generator is moved. Although this process already largely removes the layers of sludge from the Metal surface is reached, it still does not represent a completely satisfactory solution to the upcoming Problem. The reason for this is mainly to be seen in the fact that the ultrasound treatment Metal foils are excited to natural oscillations, the nodal lines and thus by remaining unchanged Create line-shaped sound figures marked by mud parts *

The object of the present invention is now to create a continuous process in which by Ultrasonic treatment of the muddy debris flawlessly and completely from the surface of a Metal foil tape are detached and the formation of mud sound figures is prevented with certainty.

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It was found that there are no more sound figures on the Metal foil tape occur when the metal foil tape and the treatment liquid are exposed to ultrasound be moved relative to each other at a speed of 0.5 - 50 m / see.

The invention thus consists in a method for the continuous pretreatment of a particular for Production of metal foil tape used for lithographic planographic printing plates, which preferably consists of Aluminum or an aluminum alloy is made up of mechanical, chemical or electrochemical means Roughening and / or anodic oxidation, being used to avoid or eliminate sludge-like Deposits on the metal surfaces during and / or after the pretreatment stages with ultrasound thereon can act, and is characterized in that the metal foil strip during the action of ultrasound and the treatment liquid in contact with it at a speed of 0.5-50 m / sec relative are moved towards each other. A preferred range for the relative speed between treatment liquids and metal foil is 5-15 m / sec. Particularly good ones Results are achieved when the treatment liquid is passed through a relatively narrow gap

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along the uniformly moving metal foil strip. This can have an opening of about 0.1-50 mm, preferably 1-20 mm. In this way, not only is a relatively high relative speed achieved, but also, by maintaining a largely turbulent flow of liquid, the proper detachment of any sludge particles from the pile surface is additionally supported. The frequency of the ultrasound used must not be too low. Excellent results are achieved especially in the frequency range of 20 - HO kHz.

From the German patent specification 9 ^ 5 # 23 is already a method for anodic polishing of metals known in which the bath liquid with relatively treated with low-frequency ultrasound from 1000 to 3000 Hz and the workpieces to be polished be moved one after the other or at the same time through a large bathroom. However, this procedure is due the low frequency of the ultrasound used and the low speed of movement of the workpieces not suitable in the treatment bath for solving the problem on which the invention is based.

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In the German Auslegeschrift 1 108 536 is also already a process for the formation of ultra-hard surfaces on aluminum by anodic oxidation described, in which between the electrolyte and the anode a controlled relative movement in of the order of more than 10 cm / min for every centimeter of anode surface area is maintained. In this method, however, no ultrasound treatment is used on the one hand, and on the other hand the order of magnitude of the relative movement between the electrolyte flow and the anode surface increases again little than that, when used during an ultrasonic treatment, the formation of residual sludge deposits could prevent existing sound figures on the metal surface.

By using the method according to the invention on the other hand, a completely sludge-free, extremely evenly roughened and anodized metal foil is obtained, which by anodic oxidation and as a result of the complete exposure of those necessary for anchoring Surface microstructures, especially of the pore-like depressions, after the print image has been applied results in an offset printing plate that is ideally suited for long print runs.

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The technical port step inherent in the process according to the invention is not only based on the microfine removal of the sludge layers or in preventing their formation, but rather it is
also to be seen in an acceleration of the electrochemical processes themselves. The mud layers have an electrically insulating effect, what
to a severe obstruction of the passage of electricity
leads; Through the proper removal of the sludge layers, the electrochemical processes on the metal surface and in the pore-like depressions are therefore eliminated without increasing the electrical parameters
accelerated, the metal ions arising from the detachment of metal parts from the surface are quickly washed away from the vicinity of the surface, and prevents the sludge-like deposition of metal compounds, which
in turn, the action of ultrasound on the

Metal surface intensified. The ultrasonic effect consists primarily in the generation of small ones
Cavitation bubbles that generate a pulsating flow of electrolyte also near the surface and especially in the pore-like depressions of the metal surface or metal oxide layer that grow from the outside to the inside

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cause. This pulsating electrolyte flow is therefore primarily used to remove sludge particles from the pores and also supports the relatively high relative movement between the metal foil strip and the electrolyte solution in the surface area due to the floating effect.

For the electrochemical roughening and anodic oxidation are in a wide range, approximately between 5 and 500 A / dm lying current densities applicable, whereby the current density to be applied in the individual case from the other process parameters, such as type of electrolyte and -concentration, temperature and desired surface quality the metal foil. According to a preferred embodiment of the invention Process caused the electrolyte to flow through between a metal foil strip and electrodes lying narrow gap-shaped channel reduces the electrical resistance of the electrolyte and creates thus favorable conditions for the use of high current densities. The high one occurring in the narrow channel The relative speed between the metal foil strip and the electrolyte also causes the resulting electrolyte to be carried away quickly Warmth, d. H. the most extensive temperature constancy in the process.

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The inventive method can for example be carried out so that in the course of the electrochemical Roughening or anodic oxidation of the metal foil tape at the same time electrolytically and is treated with ultrasound, which results in a particularly favorable spatial utilization of the treatment zone results. In another variant, electrolytic processes alternate in the respective treatment stage and exposure to ultrasound, preferably multiple times. This is done during an electrolytic Process on the metal surface formed sludge in the subsequent ultrasound with support completely removed by the relative movement between the metal foil strip and the electrolyte, see above that the next subsequent electrolytic process can again act optimally on a clean metal or metal oxide surface. Under the electrolytic With each variant of the method according to the invention, roughening becomes an extremely uniform surface etch achieved and the risk of hole formation in the metal foil completely avoided. As a result of the strong Acceleration of the electrolytic process can be achieved by the roughening time, which is necessary with the conventional bathing method

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the order of magnitude of a few minutes, with particularly favorable coordination of the process parameters down to a few seconds. This enables the use of fast-working treatment systems that can also be kept compact.

Each variant of the method according to the invention also has a similarly beneficial effect in the context of anodic oxidation the end. The roughened surface oxidizes from the outside to the inside, although those already mentioned several times pore-like depressions allow electricity to be transported to the underlying metal. The one from the Interaction of electrolyte, the action of ultrasound and relative movement between the metal foil strip and The lively exchange of substances resulting from the electrolyte and the associated price maintenance of the pores increase the anodizing speed and uniformity are considerable.

Further possible variations of the method according to the invention also lie in whether the respective electro-lytic Process and the action of ultrasound on the same or different surfaces of the Metal foil tape. It was actually

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Surprisingly found that even with ultrasound the back of the electrochemically treated metal foil strip with the support of the relative movement between the foil and the electrolyte a perfect and complete removal of the sludge layer is guaranteed.

The invention also relates to an advantageous device for carrying out the process according to the invention 'Procedure. The device according to the invention consists essentially of one or more guide rollers for the metal foil strip, of which at least one connected to a drive element, means for conveying treatment liquid from one Storage container in the free space surrounding the metal foil strip as well as electrodes and ultrasonic transducers; it is characterized in that the electrodes and Ultrasonic transducers delimit the surrounding open space with the formation of a gap-shaped treatment channel. In a special embodiment the electrodes and ultrasonic transducers are arranged in multiple alternating rows of the same ones

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Metal foil face opposite. In another embodiment, which is particularly useful when using Direct current, d. H. is particularly advantageous in the case of anodic oxidation, the electrodes are simultaneous designed as an ultrasonic transducer. Since in this case the plant components are both electrochemical as well as - are exposed to cavitation attacks resulting from the effects of ultrasound, it is advantageous to To use titanium as a material. In a further embodiment, the electrodes and the ultrasonic vibrators in multiple alternating sequences opposite the same metal foil surface. It it is obvious that these different embodiments for the device according to the invention the individual described variants of the method according to the invention are particularly adapted.

Since it is useful to determine the duration of the ultrasound exposure from case to case as a function of current density as well To vary the type and concentration of electrolytes or to adapt them to the respective electrolytic treatment stage, the device according to the invention is preferably provided with diaphragms through which the ultrasonic oscillator can be partially or completely dimmed so that

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the effective number and width of which can be changed. The same applies to the electrodes, which also are variable in number and effective range through insulating panels.

Further details of the invention are given below with reference to the schematic drawing reproducing the embodiments explained. In this drawing mean

Figure 1 is a side view of a cut-open embodiment of the invention

Contraption;

FIG. 2 shows a section in the plane AB of FIG. 1; FIG. 3 shows the side view of a further cut open Embodiment of the invention Device and FIG. 4 shows a partially broken section along the plane CD from FIG.

According to FIGS. 1 and 2, the one entering the treatment device via the deflecting roller 2a wraps around it Metal foil tape 1, the driven drum 3 over an angle of about 340 ° and leaves the

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Treatment device then over the deflection roller 2b. The drum 3 is alternately surrounded by electrodes 9 and ultrasonic oscillators 10 at a roughly parallel distance, those on the insulating and liquid-sealing against leakage currents Wall 15 a, b sit, creating a gap-shaped treatment channel 8, the side is limited by the walls 16 a, b. The electrodes 9 can be fed with direct or alternating current, whereby the treatment device can be adapted to the respective pretreatment stage. The single ones Electrodes 9 and ultrasonic oscillators 10 can be partially or completely covered with the help of the diaphragms 20 .be, whereby they can be adjusted to the width of the metal foil strip 1 or the intensity electrolytic and ultrasonic treatment by fully covering one or the other electrode or one or the other ultrasonic transducer can be varied. The drum 3 is through the electric Insulation layer 19 »made of an electrolyte-proof and cavitation-resistant lacquer or an adhesive film with these properties is insulated from the metal foil strip 1 and the electrolyte 5. These when using the central conductor method in which the electrodes 9 a, b are insulated on all sides so that

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only their active surface facing the metal foil surface to be treated free for the passage of current is, required insulation layer 19 is omitted when using the contact method.

The one corresponding to the respective pretreatment stage Electrolyte 5 is pressed by the feed pump 6 through a filter 7 into the treatment channel 8, after Its flow through it via the overflows 11 a, b and lines 17 a, b into the storage container 12 flows back. In the storage container 12, a cooling system 13 is attached to the temperature control of the Electrolyte 5 is used, which is refreshed if necessary by additives from the regeneration system 14 will.

After exiting the treatment channel 8, the metal foil strip 1 is removed by means of the air brush blown dry.

The device according to Figures 1 and 2 can also be modified in such a way that the electrodes 9 are designed as ultrasonic transducers 10 at the same time.

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The device according to FIGS. 3 and 4 corresponds to that above with regard to a number of components described device. However, the metal foil strip 1 is guided around two drums 3 a, b, of which a drum or synchronously both are provided with a drive. The main difference is there but in the fact that the electrodes 9 a, b on the one hand and the ultrasonic oscillators 10 a, b on the other hand different Faces of the freely guided metal foil strip 1 between the two drums 3 a, b face parallel, which enables simultaneous electrolytic and ultrasonic treatment of the Metal foil tape is given. The gap-shaped treatment channel 8 is thereby converted into an electrode-side Part 4 and a part 4 'facing the ultrasonic transducers.

The construction principle of the device according to FIGS. 3 and 3 can also be transferred to an elongated system, whereby it is expedient to arrange the electrodes 9 above and the ultrasonic transducers 10 below the horizontally guided metal foil strip 1. The inlet pressure to the partial treatment channels 4, 4 ¹ can be regulated, for example, by a level vessel above the electrodes.

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The invention is further illustrated by the examples below.

example 1

A 0.3 mm thick aluminum foil strip 150 mm wide, which had previously been degreased in an alkali bath, was passed through a device according to FIG. 1 at a speed of 20 m / min. The device was charged with 1 ml of nitric acid which still contained 0.25% by weight of aluminum nitrate. This electrolyte, which was kept at a temperature of 15 ° C. by cooling, was pumped through the treatment channel 8 at such a speed that the speed relative to the foil strip was about 7 m / sec. The electrodes 9 fed with alternating current (50 Hz) had a distance of about 5 mm from the film strip; the voltage was chosen so that a current density of about 80 A / dm resulted. The ultrasonic transducer 10 generated an ultrasound of approximately 20 kHz. The foil tape parts leaving the device after a dwell time of about 11 seconds were rinsed with water and dried. The foil tape was great on the treatment side

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evenly roughened and the treated surface completely free of sludge deposits, especially of mud sound figures.

Example 2

The foil strip roughened according to Example 1 was anodized in 12% sulfuric acid using direct current at such a voltage that a current density of about 120 A / dm ² resulted. The other test conditions were those given in Example 1.

It became an extremely evenly anodized foil tape that was completely free of mud deposits and mud sound figures. That Foil tape was ideal for coating with photosensitive layers and for producing offset printing plates for long print runs.

Comparative experiment;

Formats of a length of 25 cm were cut off from the foil tape roughened according to Example 1 and combined in one usual electrolyser anodized. It was

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analogous to example 2 as electrolyte 12% sulfuric acid of 15 ° G and direct current of such a voltage that with an electrode spacing of about 10 cm a current density of about 17 A / dm resulted. At the same time, the foil surfaces were treated with ultrasound of about 20 kHz. After a treatment time of 5 minutes, the Pormate removed from the electrolysis vessel, rinsed and dried. Your surface was at usable anodizing covered with clearly visible mud lines, allowing them to be used for manufacture of quality printing plates were unsuitable.

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Claims (13)

Claims 1.) Process for the continuous pretreatment of a particular for the production of lithographic planographic printing plates serving metal foil tape, which is preferably made of aluminum or an aluminum alloy, by mechanical, chemical or electrochemical roughening and / or anodic oxidation, which is used to avoid or remove · sludge-like deposits on the Lets ultrasound act on metal surfaces during and / or after the pretreatment stages, characterized in that during the action of ultrasound the metal foil belt and the treatment liquid in contact therewith at one speed moved from 0.5 - 50 m / sec relative to each other. 2. The method according to claim 1, characterized characterized in that the metal foil tape and this contacting treatment liquid with a Speed of 5 - 15 m / sec can be moved relative to each other. 209830/0130 3. The method according to claim 1 or 2, characterized in that the treatment liquid through a narrow gap at the uniform moving metal foil tape along. 4. The method according to any one of the preceding claims, characterized in that ultrasound can act at a frequency of 10 - 40 kHz. 5. The method according to any one of the preceding claims, characterized in that the metal foil strip several times in succession during the electrochemical roughening and / or anodic oxidation treated electrolytically and with ultrasound. 6. The method according to any one of the claims 1 to 4, characterized in that the metal foil strip during the electrochemical roughening and / or anodic oxidation treated simultaneously electrolytically and with ultrasound. 7. The method according to claim 5 or 6, characterized in that the metal foil strip is treated electrolytically and with ultrasound on the same surface . 209830/0130 8. The method according to claim 5 or 6, characterized in that the metal foil strip on different surfaces are treated electrolytically and with ultrasound. 9. Device for performing the method according to one or more of the preceding Claims, consisting essentially of one or more guide rollers for the metal foil strip of at least one of which is connected to a drive element, means for conveying treatment liquid from a storage container into the Free space surrounding metal foil strip as well as electrodes and ultrasonic oscillators, characterized in that the electrodes (9) and ultrasonic transducers (10) facing the metal foil strip (1) over a surface area surrounding free space with the formation of a gap-shaped Limit the treatment channel (8). 10. The device according to claim 9 »characterized in that the electrodes (9) simultaneously are designed as an ultrasonic oscillator (10). 209830/0130 11. The device according to claim 9 » characterized in that the electrodes (9) and ultrasonic transducer (10) face the same metal foil surface in multiple alternating rows. 12. The device according to claim 9, characterized in that the electrodes (9) and Ultrasonic transducer (IQ) different metal foil surfaces face. 13. Device according to one of claims 9 to 12, characterized in that the Electrodes (9) and / or ultrasonic oscillators (10) can be at least partially dimmed by means of screens (19) are. Ik. Device according to one of the claims 9 to 13, characterized in that the electrodes (9) only on the side facing the metal foil strip (1) are electrically conductive. 209830/0130