EP0131282B1 - Process for coating cans open at one end - Google Patents
Process for coating cans open at one end Download PDFInfo
- Publication number
- EP0131282B1 EP0131282B1 EP84107925A EP84107925A EP0131282B1 EP 0131282 B1 EP0131282 B1 EP 0131282B1 EP 84107925 A EP84107925 A EP 84107925A EP 84107925 A EP84107925 A EP 84107925A EP 0131282 B1 EP0131282 B1 EP 0131282B1
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- EP
- European Patent Office
- Prior art keywords
- cans
- bath
- coating
- paint
- electrodeposition
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D13/00—Electrophoretic coating characterised by the process
- C25D13/12—Electrophoretic coating characterised by the process characterised by the article coated
- C25D13/14—Tubes; Rings; Hollow bodies
Definitions
- the invention relates to a method for coating one-sided open cans such as metallic cans by means of the immersion lacquer process with lacquer, in which the individual cans are washed, coated on the outside and inside, the cans being coated with an anionic ETL lacquer as the anode and when coating with cationic ETL lacquer can be switched as a cathode, dried and then optionally printed and dried again.
- the cans treated in this way can also be crimped at the open end.
- ETL electro dip painting process
- Cans which are closed on one side cannot simply be coated electrophoretically, because it is necessary for a uniform coating that the air in the can completely escapes. Therefore, the mechanical engineering industry has developed special methods that are carried out step by step, i.e. it is painted in individual successive steps, for example first on the inside.
- the cans for the interior painting are kept on the floor and at the same time the necessary electrical contacts are made.
- a counter electrode is inserted into the can from the open end, which must be at a short distance of 0.25 to 5 mm from the inner wall of the can, so that the shape of the electrode has to be adapted very precisely to that of the can.
- the cans Because of the complicated structure of the corresponding system, the cans have to be coated individually one after the other, so that only very short coating times of 10 to 500 msec are available if one wants to achieve a high can throughput.
- liquid In closed systems, for example in a vertical arrangement (EP-50 045, EP-19 669, GB-PS-1 117 831, US-PS-3 922 213 and DE-OS-2 929 570), liquid must be pumped at high speeds, in order to be able to alternately carry out ETL liquid and water rinsing in short periods of time and to remove the gases (oxygen or hydrogen, depending on the polarity) that arise during the ETL coating.
- the approximately horizontally arranged cans must be rotated in order to achieve an even coating. (DE-OS-2 633 179 and US-PS-4 107 016). When blowing out the cans, there is a great risk of contamination.
- the older EP-A-118 756 (Art 54 (3) and (4)) describes a process in which the cans are immersed at an angle in the electro-immersion bath. In the process described in US-A-2,362,474, the cans can only be coated individually and in succession.
- the object of the invention is to simplify the coating of metal cans which are open on one side in such a way that coating can be carried out on the outside as well as on the inside in one continuous operation.
- the cans are passed through the immersion bath at the same time to a plurality of them, wherein for the coating they are immersed vertically and with the bottom closed in the electrodeposition bath, filled with bath liquid from above by means of a filler neck and for lifting out of the immersion bath be tilted so that their opening is facing downward and that the counter electrode is outside the cans in the electro-immersion bath.
- the invention makes it possible to coat metal cans which are open on one side at the same time on the outside and inside in one work step and to dry immediately thereafter and, if appropriate, to print or label them.
- the mechanical effort and space requirements are relatively low, so that an economical mode of operation is possible. For example, up to 16 cans at the same time, i.e. passed side by side through an electro-dip bath and thereby coated with lacquer.
- the trimmed or untrimmed cans are vertical, i.e. pressed with the bottom down into the ETL basin or - more advantageously, faster - filled with bath liquid through a filler neck.
- the cans When transporting through the ETL basin, the cans are either immersed under the bath surface or, particularly with untrimmed cans, advantageously guided so that the can opening is above the bath liquid surface.
- they To lift the cans out of the immersion bath, they are tilted again so that their opening lies downwards so that the liquid in the cans can drain off completely.
- the transport element can be an endless conveyor belt or an endless chain on which the cans hang practically vertically or stand on it, ie the conveyor belt can run above the surface of the bath or be guided through the ETL immersion bath.
- the cans for coating are passed through an immersion bath and it is also possible to pass several cans next to one another through the immersion bath at the same time, even with mass production with high throughput, sufficiently long coating times can be achieved in order to be able to apply even higher-quality paint coatings properly .
- a coating time of 1 to 120 seconds a pigmented or unpigmented lacquer is applied electrophoretically using direct current, the wet film deposited on the cans having a sheet resistance of at least 0.6 x 108 ohms. cm.
- the cans to be coated are switched via the holding device when using an anionic ETL lacquer as an anode and when using a cationic ETL lacquer as a cathode.
- the counter electrode is located at a distance from the cans in the immersion bath.
- the inner coating is carried out with the aid of a so-called wrap-around, which achieves the coating in the deposited film because of its maximum insulating effect, or with the aid of an inner electrode inserted into the can.
- the electrophoretic coating is such that the wall opposite the counterelectrode, i.e. the outer wall of the can is coated.
- the wet wall that builds up initially isolates the outer wall.
- the electric field lines then migrate into the interior of the can, where the deposition continues.
- the deposition time and the insulating effect of the material, characterized by the sheet resistance must be coordinated in order to achieve a good grip. The longer the coating time, the higher the layer resistance due to the increase in the layer thickness and through electro-osmotic processes which are used to reduce the content of neutralizing agent or for electrochemical dewatering.
- the lower limit of the coating time should therefore be over 3 seconds, in particular over 5 seconds and particularly suitably over 10 seconds.
- the upper limit is determined by the length of the immersion bath, the transport speed and the amount of hollow bodies to be coated to be managed. In order to achieve an economically acceptable level, the upper limit should expediently be less than 60 seconds and preferably less than 30 seconds of coating time.
- the amount of film applied depends on the deposition voltage, which is between 50 and 400 volts. With increasing tension, the wrap is improved. In order to avoid electrical breakdowns, the voltage is either continuously increased or a short bias is used, i.e. Before the actual coating, voltages of less than 100 volts are used for 0.1 to 0.5 seconds.
- the wet film resistance required for good insulation should be as high as possible.
- its lower limit is limited by the desired short coating time.
- the lower limit should be at least 1 x 10 8 ohm-cm, expediently above 1.5 x 10 8 ohm-cm and preferably above 2 x 10 8 ohm-cm.
- the upper limit is therefore below 10 x 10 8 , suitably below 7 x 10 8 and preferably below 4 x 10 8 ohm-cm.
- the bath conductivity which is determined by the degree of neutralization of the binder, is above 800 gScm- 1 , expediently above 1200 and preferably above 1600 gScm- 1 lies.
- Both anionic and cationic resins can be used as binders, the anionic ones being preferred for acidic and the cationic ones for basic fillings.
- the anionic resins such as maleinized or acrylated butadiene oils, maleinized natural oils, epoxy esters and acrylate resins containing carboxyl groups, acrylic epoxy resins, unmodified or modified with fatty acids have an acid number of 30 to 180, in particular between 40 and 80, and are at least partially neutralized with ammonia, amines or amino alcohols . Easily volatile amines are produced so that they can be removed from the film as completely as possible with the desired short burn-in times of 30 seconds to 300 seconds. Ammonia is particularly preferred.
- crosslinking takes place either oxidatively via unsaturated double bonds or by thermal reaction with corresponding crosslinking agents such as phenolic resins or amine-formaldehyde resins.
- corresponding crosslinking agents such as phenolic resins or amine-formaldehyde resins.
- External or self-crosslinking acrylate resins are preferred for the production of white lacquer coatings.
- Acrylated or maleinized epoxy esters or epoxy acrylates are preferred for coating with clear lacquers.
- the cationic resins such as butadiene oil aminoalkylimides, Mannich bases of phenolic resins, Michael addition products of primary and / or secondary amines and / or alkanolamines on resins with unsaturated double bonds or amino epoxy resins have an amine number of 30 to 120 mg KOH / g / solid resin, preferably from 50 to 90, and are at least partially neutralized with organic monocarboxylic acids such as carbonic acid, formic acid, acetic acid, lactic acid etc.
- Blocked isocyanates or resins which contain ester groups capable of transesterification are preferably used as crosslinking agents.
- the binders are neutralized with the neutralizing agents and, if appropriate, diluted with deionized or distilled water in the presence of solvents.
- Suitable solvents are primary, secondary and / or tertiary alcohols, ethylene or propylene glycol mono- or diether, diacetone alcohol or even small amounts of non-water-dilutable solvents such as petroleum hydrocarbon.
- the lowest possible solvent content is desirable, advantageously below 15% by weight and preferably less than 5 wt .-%, the worsens with increasing solvent content.
- the bath solid is generally between 5 and 30% by weight, in particular over 10 and under 20% by weight. With increasing solids, the bath conductivity is increased and the deposition equivalent (amperes x sec / g) is reduced, whereby the wrap can be increased. Due to the high concentration of layer-forming ions, the layer resistance goes through a maximum.
- the bath temperature is between 20 and 35 ° C. As the temperature drops, the wrap increases. Temperatures below 20 ° C are uneconomical because the heat generated by the ETL coating has to be dissipated again by plenty of cooling water. Temperatures above 35 ° C make it difficult to run the bath because too much solvent evaporates and hydrolysis on the binder system produces fluctuations in the electrical data.
- the coating agent can additionally contain customary lacquer aids such as catalysts, leveling agents, anti-foaming agents, lubricants, etc.
- additives should be selected that do not interfere with water at the pH of the bath, do not carry in any interfering foreign ions, and do not turn out to be irreversible when standing for a long time.
- the binders can be used pigmented or unpigmented. Such materials can be used as pigments and fillers which, owing to their small particle size below 10 ⁇ m, particularly below 5 ⁇ m, can be stably dispersed into the lacquer and can be stirred up again when standing. They must not contain any interfering foreign ions and must not react chemically with water or the neutralizing agent.
- the pigmentation can be both white and colored; white is preferred. With the additional incorporation of interference pigments, it is possible to apply metal effect coatings such as B. aluminum, gold, etc. to achieve.
- the pigments such as B. Titanium dioxide are ground in a concentrated regrind and then adjusted with a further binder to a pigment-binder ratio of about 0.1: 1 to 0.7: 1.
- the wrap is increased by the incorporation of pigments.
- pigments it is also possible to use finely powdered, insoluble resins, such as powdered polycarbonates, epoxy resins or blocked polyisocyanates, the amounts added being chosen so that they do not exceed the maximum sheet resistance.
- the binder, pigment content, bath solids content, solvent content, choice of neutralizing agent and the degree of neutralization are coordinated with the coating conditions such as bath temperature, deposition voltage and deposition time in such a way that a complete full coating takes place in the electrocoating bath (ETL bath), which after baking inside the can Layer thicknesses of at least 3 microns, preferably at least 4 microns, most preferably at least 5 microns and at most 10 microns, especially at most 7 microns is pore-free.
- the electrodeposition is done in an immersion bath.
- the cans which are closed on one side can be practically vertical, i.e. with the aid of a magnetic, electromagnetic or mechanical holding device, which also means vacuum holding. with the opening facing upwards, under the bath surface of the ETL basin.
- the filling of the can is supported by pumping in additional bath material via a filler neck, which can also be designed as a hollow electrode. Direct current is used as the current source.
- the cans are electrically connected via the holding device as an anode or as a cathode.
- the counter electrode is always outside in the electro-immersion bath.
- the can Due to the encapsulation of the paint and the deposition voltage and coating time required for the respective can shape, the can is completely coated on the inside and outside.
- This process has the advantage that the entire coating is carried out in a single process step and, due to the low mechanical expenditure on the hanger, many cans can be coated side by side at the same time.
- An auxiliary electrode can also be inserted into the box to provide support, especially when high throughput speeds are required.
- the immersion electrode has a shape not determined by the can and is less than half the diameter of the can. It is preferably arranged so that it is inserted into the interior of the cans at the same time as the can holder.
- the auxiliary electrode can be made hollow. Filtered varnish is pumped into the can through this feed line.
- the inner coating is carried out after filling the vertical cans with an inner electrode and the outer coating is carried out in the usual way with a second counter electrode in the ETL bath.
- the untrimmed cans are only so far immersed that they are completely coated after trimming. On the other hand, it must be ensured that the edges of the can do not dip under the surface of the bath. This makes it possible to coat the outside with a different paint first on the inside and then in a further step in a second ETL basin.
- the coating can also be carried out simultaneously on the inside and outside with two different paint qualities,
- the cans are emptied by rotating the cans, with the can bottom being raised.
- the hanger When the hanger is extended, it is rinsed together with the cans first with ultrafiltrate and then with water, to which an emulsifier can optionally be added to avoid wetting problems.
- the paint is baked in at times of 1 to 300 seconds at temperatures of 180 to 250 ° C.
- the conveyor belt with buckets and cans is fed through the furnace.
- the can bottom can be predried and provided with a protective auxiliary layer. Afterwards, the transfer can take place on a conveyor belt leading through the drying oven.
- the opening of the can can be directed downwards or preferably upwards.
- Continuous coating in the ETL tank enriches the amine with an anionic binder and carboxylic acid with a cationic one.
- the refill materials are either neutralized correspondingly lower or the excess neutralizing agents are removed by electrodialysis.
- the rinsing water is enriched by ultrafiltration and returned to the paint basin, which increases the degree of utilization of the paint and removes unwanted foreign ions.
- An anionic, self-crosslinking acrylate resin according to DE-AS-1 669 107 was neutralized with ammonia and diluted to a solids content of 15% by weight with deionized water.
- a flanged can (diameter 56 mm, length 116 mm) was held at the flanged edge with an electrically conductive clamp and carefully immersed completely in a conductive container insulated against earth and filled with diluted lacquer with a diameter of 19 cm.
- the direct current from a voltage source was connected to the socket and the other pole to the outer vessel.
- the coating was carried out with an auxiliary electrode with a diameter of 1 cm, which was immersed in the can 8 cm deep.
- the can was baked for 3 minutes at 215 ° C in a convection oven. The can was completely covered on the inside and outside with a thin and pore-tight clear lacquer. For measured values, see Table 1.
- the binder from Example 1 was pigmented with 0.4 part by weight of titanium dioxide to 1 part by weight of binder and, after neutralization with ammonia, diluted to a solids content of 9% by weight.
- the coating was carried out without an auxiliary electrode.
- the can was completely covered with a white varnish.
- the porosity, measured in an electrolyte solution at 4 volts, is 5 mA after 30 seconds.Measured values see Table 1.
- a cationic amino epoxy resin according to DE-OS-3 122 641 was pigmented with 0.4 part by weight of a mixture of 99 parts by weight of titanium dioxide and 1 part by weight of carbon black and, after neutralization with formic acid, to a solids content of 15 parts by weight. % diluted with deionized water. The coating was carried out without an auxiliary electrode. The can was completely covered with a gray varnish. For measured values, see Table 1.
Abstract
Description
Die Erfindung betrifft ein Verfahren zum Beschichten einseitig offener Dosen wie metallischer Dosen mittels des Eintauchlack-Verfahrens mit Lack, bei dem die einzelnen Dosen gewaschen, außen und innen beschichtet, wobei die Dosen beim Beschichten mit einem anionischen ETL-Lack als Anode und beim Beschichten mit kationischem ETL-Lack als Kathode geschaltet werden, getrocknet und danach gegebenenfalls bedruckt und erneut getrocknet werden. Die so behandelten Dosen können außerdem am offenen Ende gebördelt werden.The invention relates to a method for coating one-sided open cans such as metallic cans by means of the immersion lacquer process with lacquer, in which the individual cans are washed, coated on the outside and inside, the cans being coated with an anionic ETL lacquer as the anode and when coating with cationic ETL lacquer can be switched as a cathode, dried and then optionally printed and dried again. The cans treated in this way can also be crimped at the open end.
Die zunehmend verschärften Anforderungen des Umweltschutzes führen zu Überlegungen, wie das Elektrotauchlackier-Verfahren (ETL) für die Dosenhersteller-Industrie als vollautomatisches Lackierverfahren eingeführt werden kann. Es ist bekannt, beidseitig offene Dosenrümpfe für dreiteilige Dosen oder auch eine zu beschichtende Schweißnaht durch Eintauchen in ein Elektrotauchbad elektrophoretisch zu lackieren (US-PS-3 694 336, DE-OS-2 116 715). Die Dosenkörper sind hierbei einfach zu handhaben, weil sie noch keinen Boden haben und die Badflüssigkeit zum Beschichten problemlos eintreten und nach dem Beschichten ebenso problemlos wieder auslaufen kann.The increasingly stringent requirements of environmental protection lead to considerations as to how the electro dip painting process (ETL) can be introduced as a fully automatic painting process for the can manufacturing industry. It is known to paint can bodies open on both sides for three-part cans or a weld seam to be coated electrophoretically by immersing them in an electrodeposition bath (US Pat. No. 3,694,336, DE-OS-2 116 715). The can bodies are easy to handle because they do not yet have a bottom and the bath liquid for coating can enter easily and can also run out again after coating.
Einseitig geschlossene Dosen lassen sich nicht einfach elektrophoretisch beschichten, weil es für eine gleichförmige Beschichtung notwendig ist, daß die in der Dose befindliche Luft vollständig entweicht. Daher wurden von der Maschinenbauindustrie spezielle Methoden entwickelt, bei denen schrittweise vorgegangen wird, d.h. es wird in einzelnen aufeinanderfolgenden Schritten lackiert, beispielsweise zunächst innen.Cans which are closed on one side cannot simply be coated electrophoretically, because it is necessary for a uniform coating that the air in the can completely escapes. Therefore, the mechanical engineering industry has developed special methods that are carried out step by step, i.e. it is painted in individual successive steps, for example first on the inside.
Die hierfür bekannten Konstruktionen haben einige Gemeinsamkeiten. So werden die Dosen für die Innenlackierung am Boden gehalten und dabei zugleich die notwendigen elektrischen Kontakte hergestellt. Eine Gegenelektrode wird in die Dose vom offenen Ende eingefahren, die mit geringem Abstand von 0,25 bis 5 mm zur Innenwand der Dose liegen muß, so daß die Form der Elektrode sehr genau an die der Dose anzupassen ist. Wegen des komplizierten Aufbaues der entsprechenden Anlage müssen die Dosen einzeln nacheinander beschichtet werden, so daß nur sehr kurze Beschichtungszeiten von 10 bis 500 msec zur Verfügung stehen, wenn man einen hohen Dosendurchsatz erreichen will. Bei geschlossenen Systemen in beispielsweise senkrechter Anordnung (EP-50 045, EP-19 669, GB-PS-1 117 831, US-PS-3 922 213 und DE-OS-2 929 570) muß Flüssigkeit mit hohen Geschwindigkeiten gepumpt werden, um abwechselnd ETL-Flüssigkeit und eine Wasserspülung in kurzen Zeitspannen durchführen zu können und die bei der ETL-Beschichtung entstehenden Gase (Sauerstoff oder Wasserstoff, je nach Polung) abzuführen. Bei offenen Systemen müssen die etwa waagerecht angeordneten Dosen gedreht werden, um eine gleichmäßige Beschichtung zu erzielen. (DE-OS-2 633 179 und US-PS-4 107 016). Beim Ausblasen der Dosen ergibt sich eine große Verschmutzungsgefahr.The constructions known for this have some things in common. In this way, the cans for the interior painting are kept on the floor and at the same time the necessary electrical contacts are made. A counter electrode is inserted into the can from the open end, which must be at a short distance of 0.25 to 5 mm from the inner wall of the can, so that the shape of the electrode has to be adapted very precisely to that of the can. Because of the complicated structure of the corresponding system, the cans have to be coated individually one after the other, so that only very short coating times of 10 to 500 msec are available if one wants to achieve a high can throughput. In closed systems, for example in a vertical arrangement (EP-50 045, EP-19 669, GB-PS-1 117 831, US-PS-3 922 213 and DE-OS-2 929 570), liquid must be pumped at high speeds, in order to be able to alternately carry out ETL liquid and water rinsing in short periods of time and to remove the gases (oxygen or hydrogen, depending on the polarity) that arise during the ETL coating. In the case of open systems, the approximately horizontally arranged cans must be rotated in order to achieve an even coating. (DE-OS-2 633 179 and US-PS-4 107 016). When blowing out the cans, there is a great risk of contamination.
Der Nachteil dieser bekannten Konstruktionen besteht darin, daß die Dosen mit hohem mechanischen Aufwand einzeln nacheinander beschichtet werden müssen. Der große Platzbedarf der Anlage macht eine wirtschaftliche Massenproduktion fast unmöglich. Innenelektroden können nur in Dosen mit geraden glatten Wänden paßgenau eingefahren werden, d.h. von der Zylinderform abweichende Dosenformen führen zu großen Schwierigkeiten. Wegen des geringen Abstandes der Innenelektrode zur Dosenwand besteht die Gefahr von Kurzschlüssen sowie von elektrischen Durchschlägen in Zonen sehr hoher Stromdichte. Dementsprechend müssen Lacke mit niedrigem Schichtwiderstand eingesetzt werden, um mit niedrigen elektrischen Spannungen störungsfrei in den zur Verfügung stehenden kurzen Zeiten die Beschichtung anbringen zu können.The disadvantage of these known constructions is that the cans have to be coated individually one after the other with a high mechanical outlay. The large space requirement of the system makes economical mass production almost impossible. Inner electrodes can only be inserted with a precise fit in cans with straight, smooth walls, i.e. Can shapes deviating from the cylindrical shape lead to great difficulties. Because of the small distance between the inner electrode and the can wall, there is a risk of short circuits and electrical breakdowns in very high current density zones. Accordingly, lacquers with a low sheet resistance have to be used in order to be able to apply the coating without problems in the short times available with low electrical voltages.
Die ältere EP-A-118 756 (Art 54 (3) und (4)) beschreibt ein Verfahren, in dem die Dosen schräg in das Elektrotauchbad eingetaucht werden. In dem in der US-A-2 362 474 beschriebenen Verfahren können die Dosen nur einzeln und nacheinander beschichtet werden.The older EP-A-118 756 (Art 54 (3) and (4)) describes a process in which the cans are immersed at an angle in the electro-immersion bath. In the process described in US-A-2,362,474, the cans can only be coated individually and in succession.
Der Erfindung liegt die Aufgabe zugrunde, das Beschichten von einseitig offenen metallischen Dosen derart zu vereinfachen, daß in einem kontinuierlichen Arbeitsgang sowohl außen als auch innen beschichtet werden kann.The object of the invention is to simplify the coating of metal cans which are open on one side in such a way that coating can be carried out on the outside as well as on the inside in one continuous operation.
Die Aufgabe wird dadurch gelöst, daß die Dosen zu mehreren nebeneinander gleichzeitig durch das Tauchbad geführt werden, wobei sie zum Beschichten senkrecht und mit geschlossenem Boden nach unten weisend in das Elektrotauchbad eingetaucht, von oben mittels eines Füllstutzens mit Badflüssigkeit gefüllt und zum Ausheben aus dem Tauchbad so gekippt werden, daß ihre Öffnung nach unten gerichtet ist, und daß sich die Gegenelektrode außerhalb der Dosen im Elektrotauchbad befindet.The object is achieved in that the cans are passed through the immersion bath at the same time to a plurality of them, wherein for the coating they are immersed vertically and with the bottom closed in the electrodeposition bath, filled with bath liquid from above by means of a filler neck and for lifting out of the immersion bath be tilted so that their opening is facing downward and that the counter electrode is outside the cans in the electro-immersion bath.
Durch die Erfindung ist es möglich einseitig offene metallische Dosen in einem Arbeitsgang gleichzeitig außen und innen zu beschichten und unmittelbar anschließend zu trocknen und gegebenenfalls zu bedrucken oder zu etikettieren. Der mechanische Aufwand und der Platzbedarf sind verhältnismäßig gering, so daß eine wirtschaftliche Betriebsweise möglich ist. Beispielsweise können bis zu 16 Dosen gleichzeitig, d.h. nebeneinander durch ein Elektrotauch-Bad hindurchgeführt und dabei mit Lack beschichtet werden.The invention makes it possible to coat metal cans which are open on one side at the same time on the outside and inside in one work step and to dry immediately thereafter and, if appropriate, to print or label them. The mechanical effort and space requirements are relatively low, so that an economical mode of operation is possible. For example, up to 16 cans at the same time, i.e. passed side by side through an electro-dip bath and thereby coated with lacquer.
Die beschnittenen oder unbeschnittenen Dosen werden erfindungsgemäß senkrecht, d.h. mit dem Boden nach unten in das ETL-Becken gedrückt oder -vorteilhafter, schneller- innen durch einen Füllstutzen mit Badflüssigkeit gefüllt. Beim Transport durch das ETL-Becken werden die Dosen entweder unter die Badoberfläche getaucht oder besonders bei unbeschnittenen Dosen vorteilhaft so geführt, daß die Dosenöffnung oberhalb der Badflüssigkeitsoberfläche liegt. Zum Ausheben der Dosen aus dem Tauchbad werden diese wieder so gekippt, daß ihre Öffnung nach unten liegt, damit die in den Dosen befindliche Flüssigkeit vollständig ablaufen kann.The trimmed or untrimmed cans are vertical, i.e. pressed with the bottom down into the ETL basin or - more advantageously, faster - filled with bath liquid through a filler neck. When transporting through the ETL basin, the cans are either immersed under the bath surface or, particularly with untrimmed cans, advantageously guided so that the can opening is above the bath liquid surface. To lift the cans out of the immersion bath, they are tilted again so that their opening lies downwards so that the liquid in the cans can drain off completely.
Das Transportelement kann ein endloses Förderband oder auch eine endlose Kette sein, an der die Dosen praktisch senkrecht hängen oder auf ihr stehen, d.h. das Transportband kann oberhalb der Badoberfläche verlaufen oder auch durch das ETL-Tauchbad geführt werden.The transport element can be an endless conveyor belt or an endless chain on which the cans hang practically vertically or stand on it, ie the conveyor belt can run above the surface of the bath or be guided through the ETL immersion bath.
Da die Dosen zum Beschichten durch ein Tauchbad geführt werden und es dabei auch möglich ist, nebeneinander mehrere Dosen gleichzeitig durch das Tauchbad zu führen, können selbst bei Massenproduktion mit hohem Durchsatz ausreichend lange Beschichtungszeiten erreicht werden, um auch höher-wertige Lackbeschichtungen einwandfrei aufbringen zu können. So wird beispielsweise bei einer Beschichtungszeit von 1 bis 120 Sekunden ein pigmentierter oder nichtpigmentierter Lack mittels Gleichstrom elektrophoretisch aufgetragen, wobei der auf den Dosen abgeschiedene Naßfilm einen Schichtwiderstand von mindestens 0,6x 108 Ohm . cm hat.Since the cans for coating are passed through an immersion bath and it is also possible to pass several cans next to one another through the immersion bath at the same time, even with mass production with high throughput, sufficiently long coating times can be achieved in order to be able to apply even higher-quality paint coatings properly . For example, with a coating time of 1 to 120 seconds, a pigmented or unpigmented lacquer is applied electrophoretically using direct current, the wet film deposited on the cans having a sheet resistance of at least 0.6 x 108 ohms. cm.
Die zu beschichtenden Dosen werden über die Haltevorrichtung bei Verwendung eines anionischen ETL-Lackes als Anode und bei Verwendung eines kationischen ETL-Lackes als Kathode geschaltet. Die Gegenelektrode befindet sich jeweils im Abstand von den Dosen im Tauchbad. Die Innenbeschichtung erfolgt je nach Ausführungsform mit Hilfe eines sogenannten Umgriffs, der die Lackierung wegen seiner möglichst hohen isolierenden Wirkung im abgeschiedenen Film erzielt, oder mit Hilfe einer in die Dose eingeführten Innenelektrode.The cans to be coated are switched via the holding device when using an anionic ETL lacquer as an anode and when using a cationic ETL lacquer as a cathode. The counter electrode is located at a distance from the cans in the immersion bath. Depending on the embodiment, the inner coating is carried out with the aid of a so-called wrap-around, which achieves the coating in the deposited film because of its maximum insulating effect, or with the aid of an inner electrode inserted into the can.
Um einen möglichst hohem Umgriff zu erzielen, müssen eine Reihe von Faktoren bei der Entwicklung des Lackes beachtet werden. Die elektrophoretische Beschichtung verläuft so, daß zuerst die der Gegenelektrode gegenüberliegende Wand, d.h. die Außenwand der Dose beschichtet wird. Durch den sich aufbauenden Naßfilm wird zunächst die äußere Wand isoliert. Die elektrischen Feldlinien wandern dann in das Innere der Dose, wo sich die Abscheidung fortsetzt. Die Abscheidezeit und die Isolierwirkung des Materials, charakterisiert durch den Schichtwiderstand, müssen aufeinander abgestimmt sein, um einen gutem Umgriff zu erzielen. Je länger die Beschichtungszeit, desto höher wird der Schichtwiderstand durch die Steigerung der Schichtdicke und durch elektroosmotische Vorgänge, die zur Verringerung des Gehaltes an Neutralisationsmittel oder zur elektrochemischen Entwässerung gebraucht werden. Die untere Grenze der Beschichtungszeit sollte deshalb über 3 Sekunden, insbesondere über 5 Sekunden und besonders zweckmäßig über 10 Sekunden liegen. Die obere Grenze wird bestimmt durch die Länge des Tauchbades, die Transportgeschwindigkeit und die zu bewältigende Menge der zu beschichtenden Hohlkörper. Um auf ein wirtschaftlich vertretbares Maß zu kommen, sollte die obere Grenze zweckmäßig unter 60 Sekunden und vorzugsweise unter 30 Sekunden Beschichtungsdauer liegen. Die aufgebrachte Menge Film ist von der Abscheidespannung abhängig, die zwischen 50 und 400 Volt liegt. Mit steigender Spannung wird eine Verbesserung des Umgriffes erzielt. Um elektrische Durchbrüche zu vermeiden, wird entweder die Spannung kontinuierlich hochgeregelt oder mit kurzer Vorspannung gearbeitet, d.h. vor der eigentlichen Beschichtung wird 0,1 bis 0,5 sec mit Spannungen von unter 100 Volt gearbeitet.In order to achieve the highest possible wrap, a number of factors must be taken into account when developing the coating. The electrophoretic coating is such that the wall opposite the counterelectrode, i.e. the outer wall of the can is coated. The wet wall that builds up initially isolates the outer wall. The electric field lines then migrate into the interior of the can, where the deposition continues. The deposition time and the insulating effect of the material, characterized by the sheet resistance, must be coordinated in order to achieve a good grip. The longer the coating time, the higher the layer resistance due to the increase in the layer thickness and through electro-osmotic processes which are used to reduce the content of neutralizing agent or for electrochemical dewatering. The lower limit of the coating time should therefore be over 3 seconds, in particular over 5 seconds and particularly suitably over 10 seconds. The upper limit is determined by the length of the immersion bath, the transport speed and the amount of hollow bodies to be coated to be managed. In order to achieve an economically acceptable level, the upper limit should expediently be less than 60 seconds and preferably less than 30 seconds of coating time. The amount of film applied depends on the deposition voltage, which is between 50 and 400 volts. With increasing tension, the wrap is improved. In order to avoid electrical breakdowns, the voltage is either continuously increased or a short bias is used, i.e. Before the actual coating, voltages of less than 100 volts are used for 0.1 to 0.5 seconds.
Der für eine gute Isolation notwendige Naßfilmwiderstand sollte im Prinzip so hoch wie möglich sein. Seine untere Grenze wird jedoch durch die gewünschte kurze Beschichtungszeit begrenzt. So sollte die untere Grenze mindestens bei 1 x 108 Ohm - cm, zweckmäßig über 1,5 x 108 Ohm - cm und vorzugsweise über 2 x 108 Ohm - cm liegen. Je höher der Schichtwiderstand, dest dünner ist die erreichbare Schicht auf der Dosenwand. Die obere Grenze liegt daher unter 10 x 108, zweckmäßig unter 7 x 108 und vorzugsweise unter 4 x 108 Ohm - cm. Um für die elektrophoretische Abscheidung analog den Faradayschen Gesetzen die notwendige elektrische Strommenge zur Verfügung zu stellen, ist es notwendig, daß die Badleitfähigkeit, die durch den Neutralisationsgrad des Bindemittels bestimmt wird, über 800 gScm-1, zweckmäßig über 1200 und vorzugsweise über 1600 gScm-1 liegt.In principle, the wet film resistance required for good insulation should be as high as possible. However, its lower limit is limited by the desired short coating time. The lower limit should be at least 1 x 10 8 ohm-cm, expediently above 1.5 x 10 8 ohm-cm and preferably above 2 x 10 8 ohm-cm. The higher the layer resistance, the thinner the achievable layer on the can wall. The upper limit is therefore below 10 x 10 8 , suitably below 7 x 10 8 and preferably below 4 x 10 8 ohm-cm. In order to provide the necessary amount of electrical current for electrophoretic deposition analogous to Faraday's laws, it is necessary that the bath conductivity, which is determined by the degree of neutralization of the binder, is above 800 gScm- 1 , expediently above 1200 and preferably above 1600 gScm- 1 lies.
Als Bindemittel können sowohl anionische als auch kationische Harze verwendet werden, wobei die anionischen für saure, die kationischen für basische Füllungen bevorzugt werden. Die anionischen Harze wie maleinisierte oder acrylierte Butadienöle, maleinisierte natürlich Öle, carboxylgruppenhaltige Epikoteester und Acrylatharze, Acrylepoxidharze, unmodifizierte oder mit Fettsäuren modifizierte Polyeter haben eine Säurezahl von 30 bis 180, insbesondere zwischen 40 und 80 und werden mit Ammoniak, Aminen oder Aminoalkoholen mindestens anteilweise neutralisiert. Bevorzeugt werden leicht flüchtige Amine, damit sie bei den gewünschten kurzen Einbrennzeiten von 30 Sek. bis 300 Sek. möglichst vollständig aus dem Film entfernt werden. Besonders bevorzugt ist Ammoniak.Both anionic and cationic resins can be used as binders, the anionic ones being preferred for acidic and the cationic ones for basic fillings. The anionic resins such as maleinized or acrylated butadiene oils, maleinized natural oils, epoxy esters and acrylate resins containing carboxyl groups, acrylic epoxy resins, unmodified or modified with fatty acids have an acid number of 30 to 180, in particular between 40 and 80, and are at least partially neutralized with ammonia, amines or amino alcohols . Easily volatile amines are produced so that they can be removed from the film as completely as possible with the desired short burn-in times of 30 seconds to 300 seconds. Ammonia is particularly preferred.
Die Vernetzung erfolgt entweder oxidativ über ungesättigte Doppelbindungen oder durch thermische Reaktion mit entsprechenden Vernetzungsmitteln wie Phenolharze oder Amin-Formaldehydharze. Zur Herstellung von Weißlackbeschichtungen werden fremd- oder selbstvernetzende Acrylatharze bevorzugt. Zur Beschichtung mit Klarlacken werden acrylierte oder maleinisierte Epoxidester oder Epoxyacrylate bevorzugt.The crosslinking takes place either oxidatively via unsaturated double bonds or by thermal reaction with corresponding crosslinking agents such as phenolic resins or amine-formaldehyde resins. External or self-crosslinking acrylate resins are preferred for the production of white lacquer coatings. Acrylated or maleinized epoxy esters or epoxy acrylates are preferred for coating with clear lacquers.
Die kationischen Harze wie Butadienöl-Aminoalkylimide, Mannichbasen von Phenolharzen, Michael-Additionsprodukte von primären und/oder sekundären Aminen und/oder Alkanolaminen an Harze mit ungesättigten Doppelbindungen oder Amino-Epoxidharze haben eine Aminzahl von 30 bis 120 mg KOH/g/Festharz, vorzugsweise von 50 bis 90, und werden mit organischen Monocarbonsäuren wie Kohlensäure, Ameisensäure, Essigsäure, Milchsäure usw. mindestens anteilweise neutralisiert. Als Vernetzungsmittel dienen vorzugsweise blockierte Isocyanate oder Harze, die umesterungsfähige Estergruppen enthalten.The cationic resins such as butadiene oil aminoalkylimides, Mannich bases of phenolic resins, Michael addition products of primary and / or secondary amines and / or alkanolamines on resins with unsaturated double bonds or amino epoxy resins have an amine number of 30 to 120 mg KOH / g / solid resin, preferably from 50 to 90, and are at least partially neutralized with organic monocarboxylic acids such as carbonic acid, formic acid, acetic acid, lactic acid etc. Blocked isocyanates or resins which contain ester groups capable of transesterification are preferably used as crosslinking agents.
Die Bindemittel werden mit den Neutralisationsmitteln anneutralisiert und gegebenenfalls in Gegenwart von Lösemitteln mit entionisiertem oder destilliertem Wasser verdünnt. Als Lösemittel sind geeignet primäre, sekundäre und/oder tertiäre Alkohole, Äthylen- oder Propylenglykol-mono- oder -diether, Diacetonalkohol oder auch geringe Anteile von nicht wasserverdünnbaren Lösemitteln wie Benzinkohlenwasserstoff.The binders are neutralized with the neutralizing agents and, if appropriate, diluted with deionized or distilled water in the presence of solvents. Suitable solvents are primary, secondary and / or tertiary alcohols, ethylene or propylene glycol mono- or diether, diacetone alcohol or even small amounts of non-water-dilutable solvents such as petroleum hydrocarbon.
Es wird ein möglichst niedriger Gehalt an Lösemitteln angestrebt, zweckmäßig unter 15 Gew.-% und vorzugsweise unter 5 Gew.-%, dem mit steigendem Lösemittelgehalt verschlechtert sich der Umgriff.The lowest possible solvent content is desirable, advantageously below 15% by weight and preferably less than 5 wt .-%, the worsens with increasing solvent content.
Der Badfestkörper liegt im allgemeinen zwischen 5 und 30 Gew.-%, insbesondere über 10 und unter 20 Gew- %. Mit steigendem Festkörper wird die Badleitfähigkeit erhöht und das Abscheideäquivalent (Ampere x sec/g) herabgesetzt, wodurch der Umgriff gesteigert werden kann. Durch die hohe Konzentration an schichtbildenden Ionen geht dabei der Schichtwiderstand durch ein Maximum.The bath solid is generally between 5 and 30% by weight, in particular over 10 and under 20% by weight. With increasing solids, the bath conductivity is increased and the deposition equivalent (amperes x sec / g) is reduced, whereby the wrap can be increased. Due to the high concentration of layer-forming ions, the layer resistance goes through a maximum.
Die Badtemperatur liegt zwischen 20 und 35°C. Mit fallender Temperatur erhöht sich der Umgriff. Temperaturen unter 20°C sind unwirtschaftlich, weil die bei der ETL-Beschichtung entstehende Wärme durch viel Kühlwasser wieder abgeführt werden muß. Temperaturen über 35°C erschweren die Badführung, weil zu viel Lösungsmittel verdunstet und Hydrolyseerscheinungen am Bindemittelsystem Schwankungen in den elektrischen Daten erzeugen.The bath temperature is between 20 and 35 ° C. As the temperature drops, the wrap increases. Temperatures below 20 ° C are uneconomical because the heat generated by the ETL coating has to be dissipated again by plenty of cooling water. Temperatures above 35 ° C make it difficult to run the bath because too much solvent evaporates and hydrolysis on the binder system produces fluctuations in the electrical data.
Das Überzugsmittel kann zusätzlich übliche lacktechnische Hilfsmittel wie Katalysatoren, Verlaufmittel, Antischaummittel, Gleitmittel usw. enthalten. Naturgemäß sind solch Zusatzstoffe auszuwählen, die mit Wasser bei dem pH-Wert des Bades keine störenden Reaktionen eingehen, keine störenden Fremdionen einschleppen und beim längeren Stehen nicht in nicht aufrührbarer form ausfallen.The coating agent can additionally contain customary lacquer aids such as catalysts, leveling agents, anti-foaming agents, lubricants, etc. Naturally, additives should be selected that do not interfere with water at the pH of the bath, do not carry in any interfering foreign ions, and do not turn out to be irreversible when standing for a long time.
Die Bindemittel können pigmentiert oder unpigmentiert eingesetzt werden. Als Pigmente und Füllstoffe können solche Materialien eingesetzt werden, die aufgrund ihrer geringen Teilchengröße unter 10 um, besonders unter 5 µm, in den Lack stabil eindispergiert werden können und sich beim Stehen wieder aufrühren lassen. Sie dürfen keine störenden Fremdionen enthalten und dürfen mit Wasser oder dem Neutralisationsmittel nicht chemisch reagieren.The binders can be used pigmented or unpigmented. Such materials can be used as pigments and fillers which, owing to their small particle size below 10 μm, particularly below 5 μm, can be stably dispersed into the lacquer and can be stirred up again when standing. They must not contain any interfering foreign ions and must not react chemically with water or the neutralizing agent.
Die Pigmentierung kann sowohl weiß als auch farbig sein; weiß wird bevorzugt. Bei zusätzlichem Einbau von Interferenzpigmenten ist es möglich, Metall-Effekt-Lackierungen wie z. B. Aluminium, Gold usw. zu erzielen.The pigmentation can be both white and colored; white is preferred. With the additional incorporation of interference pigments, it is possible to apply metal effect coatings such as B. aluminum, gold, etc. to achieve.
Die Pigmente wie z. B. Titandioxid werden in einem konzentrierten Mahlgut angerieben und danach mit weiterem Bindemittel auf ein Pigment-Bindemittel-Verhältnis von etwa 0.1 : 1 bis 0.7 : 1 eingestellt. Durch den Einbau von Pigmenten wird der Umgriff gesteigert. Anstelle von Pigmenten können auch fein pulverisierte nicht lösliche Harze wie pulverisierte Polykohlenwasserstoffharze, Epoxidharze oder blockierte Polyisocyanate eingesetzt werden, wobei die Zusatzmengen so ausgewählt werden, daß sie das Maximum des Schichtwiderstandes nicht überschreiten. Bindemittel, Pigmentgehalt, Badfestkörper, Lösemittelgehalt, Auswahl des Neutralisationsmittels und der Neutralisationsgrad werden so mit den Beschichtingsbedingungen wie Badtemperatur, Abscheidespannung und Abscheidezeit abgestimmt, daß in dem Elektrotauchlackbad (ETL-Bad) eine vollständige Ganzbeschichtung erfolgt, die nach dem Einbrennen im Inneren der Dose bei Schichtdicken von mindestens 3 µm, bevorzugt mindestens 4 µm, ganz bevorzugt mindestens 5 µm und höchstens 10 um, besonders höchstens 7 um porenfrei ist.The pigments such as B. Titanium dioxide are ground in a concentrated regrind and then adjusted with a further binder to a pigment-binder ratio of about 0.1: 1 to 0.7: 1. The wrap is increased by the incorporation of pigments. Instead of pigments, it is also possible to use finely powdered, insoluble resins, such as powdered polycarbonates, epoxy resins or blocked polyisocyanates, the amounts added being chosen so that they do not exceed the maximum sheet resistance. The binder, pigment content, bath solids content, solvent content, choice of neutralizing agent and the degree of neutralization are coordinated with the coating conditions such as bath temperature, deposition voltage and deposition time in such a way that a complete full coating takes place in the electrocoating bath (ETL bath), which after baking inside the can Layer thicknesses of at least 3 microns, preferably at least 4 microns, most preferably at least 5 microns and at most 10 microns, especially at most 7 microns is pore-free.
Die Elektrotauchlackierung (ETL) erfolgt in einem Tauchbad. Die einseitig geschlossenen Dosen können mit Hilfe einer magnetischen, elektromagnetischen oder mechanischen Halteeinrichtung, worunter auch die Haltung mit Vakuum verstanden wird, praktisch senkrecht, d.h. mit der Öffnung nach oben, unter die Badoberfläche des ETL-Beckens gedrückt werden. Die Befüllung der Dose wird dabei durch Einpumpen von zusätzlichem Badmaterial über einen Füllstutzen, der gleichzeitig als Hohlelektrode ausgebildet sein kann, unterstützt. Als Stromquelle dient Gleichstrom. Die Dosen wird über die Haltevorrichtung je nach Bindemittelart als Anode oder als Kathode elektrisch angeschlossen. Die Gegenelektrode befindet sich grundsätzlich außerhalb im Elektrotauchbad. Aufgrund des Umgriffs des Lackes und der für die jeweilige Dosenform notwendigen Abscheidespannung und Beschichtungszeit wird die Dose vollständig innen und außen beschichtet. Dieses Verfahren hat den Vorteil, daß die Ganzbeschichtung in einem einzigen Verfahrensschritt erfolgt und durch den geringen mechanischen Aufwand am Gehänge viele Dosen gleichzeitig nebeneinander beschichtet werden können.The electrodeposition (ETL) is done in an immersion bath. The cans which are closed on one side can be practically vertical, i.e. with the aid of a magnetic, electromagnetic or mechanical holding device, which also means vacuum holding. with the opening facing upwards, under the bath surface of the ETL basin. The filling of the can is supported by pumping in additional bath material via a filler neck, which can also be designed as a hollow electrode. Direct current is used as the current source. Depending on the type of binder, the cans are electrically connected via the holding device as an anode or as a cathode. The counter electrode is always outside in the electro-immersion bath. Due to the encapsulation of the paint and the deposition voltage and coating time required for the respective can shape, the can is completely coated on the inside and outside. This process has the advantage that the entire coating is carried out in a single process step and, due to the low mechanical expenditure on the hanger, many cans can be coated side by side at the same time.
Zur Unterstützung, insbesondere wenn große Durchlaufgeschwindigkeiten gewünscht werden, kann zusätzlich eine Hilfselektrode in die Dose eingeführt werden. Die Tauchelektrode hat eine nicht von der Dose bestimmte Form und liegt im Durchmesser unter dem halben Durchmesser der Dose. Sie wird vorzugsweise so angeordnet, daß sie gleichzeitig mit der Dosenhalterung in das Innere der Dosen eingeführt wird. Um in der Dose eine Strömung zu erzielen, welche die Lackqualität verbessert, kann die Hilfselektrode hohl ausgeführt werden. Durch diese Zuleitung wird filtrierter Lack in die Dose gepumpt. Durch Einbau von Düsen in das Elektrophoresebecken, die auf den gewölbten Dosenboden gerichtet sind, können zusätzlich durch gerichtete Lackströme Gasblasen von der Bodenwand entfernt werden.An auxiliary electrode can also be inserted into the box to provide support, especially when high throughput speeds are required. The immersion electrode has a shape not determined by the can and is less than half the diameter of the can. It is preferably arranged so that it is inserted into the interior of the cans at the same time as the can holder. In order to achieve a flow in the can which improves the paint quality, the auxiliary electrode can be made hollow. Filtered varnish is pumped into the can through this feed line. By installing nozzles in the electrophoresis basin, which are directed onto the arched can base, gas bubbles can also be removed from the base wall by directed paint streams.
In einer anderen Ausführungsform des Verfahrens wird die Innenbeschichtung nach Befüllen der senkrecht stehenden Dosen mit einer Innenelektrode und die Außenbeschichtung in üblicher Weise mit einer zweiten Gegenelektrode im, ETL-Bad durchgeführt. Die unbeschnittenen Dosen werden dabei nur so weit eingetaucht, daß sie nach dem Beschneiden vollständig beschichtet sind. Andererseits ist darauf zu achten, daß die Dosenkanten nicht unter die Badoberfläche tauchen. Hierdurch ergibt sich die Möglichkeit, erst innen und dann in einem weiteren Arbeitsgang in einem zweiten ETL-Becken außen mit einem anderen Lack zu beschichten. Die Beschichtung kann auch gleichzeitig innen und außen mit zwei unterschiedlichen Lackqualitäten erfolgen,In another embodiment of the method, the inner coating is carried out after filling the vertical cans with an inner electrode and the outer coating is carried out in the usual way with a second counter electrode in the ETL bath. The untrimmed cans are only so far immersed that they are completely coated after trimming. On the other hand, it must be ensured that the edges of the can do not dip under the surface of the bath. This makes it possible to coat the outside with a different paint first on the inside and then in a further step in a second ETL basin. The coating can also be carried out simultaneously on the inside and outside with two different paint qualities,
Das Entleeren der Dosen erfolgt durch Drehen der Dosen, wobei der Dosenboden nach oben geführt wird. Beim Ausfahren des Gehänges wird es zusammen mit den Dosen zuerst mit Ultrafiltrat und dann mit Wasser, dem gegebenenfalls zum Vermeiden von Benetzungsstörungen ein Emulgator zugesetzt werden kann, abgespült. Danach erfolgt das Einbrennen des Lackes bei Zeiten von 1 bis 300 Sekunden bei Temperaturen von 180 bis 250°C. Dabei wird das Transportband mit Gehänge und Dosen geschlossen durch den Ofen geführt. In einer bevorzugten Ausführungsform kann der Dosenboden vorgetrocknet und mit einer schützenden Hilfsschicht versehen werden. Danach kann die Übergabe auf ein durch den Trockenofen führendes Förderband erfolgen. Die Öffnung der Dose kann nach unten oder bevorzugt nach oben gerichtet sein.The cans are emptied by rotating the cans, with the can bottom being raised. When the hanger is extended, it is rinsed together with the cans first with ultrafiltrate and then with water, to which an emulsifier can optionally be added to avoid wetting problems. Then the paint is baked in at times of 1 to 300 seconds at temperatures of 180 to 250 ° C. The conveyor belt with buckets and cans is fed through the furnace. In In a preferred embodiment, the can bottom can be predried and provided with a protective auxiliary layer. Afterwards, the transfer can take place on a conveyor belt leading through the drying oven. The opening of the can can be directed downwards or preferably upwards.
Beim kontinuierlichen Beschichten im ETL-Becken reichert sich bei einem anionischen Bindemittel das Amin, bei einem kationischen die Carbonsäure an. Zum Ausgleichen dieses Effektes werden die Nachfüllmaterialien entweder entsprechend niedriger anneutralisiert oder die überschüssigen Neutralisationsmittel durch Elektrodialyse entfernt. Das Spülwasser wird durch Ultrafiltration angereichert und wieder in das Lackbecken zurückgegeben, wodurch der Ausnutzungsgrad des Lackes steigt und störende Fremdionen entfernt werden.Continuous coating in the ETL tank enriches the amine with an anionic binder and carboxylic acid with a cationic one. To compensate for this effect, the refill materials are either neutralized correspondingly lower or the excess neutralizing agents are removed by electrodialysis. The rinsing water is enriched by ultrafiltration and returned to the paint basin, which increases the degree of utilization of the paint and removes unwanted foreign ions.
Ein anionisches, selbstvernetzendes Acrylatharz nach DE-AS-1 669 107 wurde mit Ammoniak anneutralisiert und auf einen Festkörper von 15 Gew.-% mit entionisiertem Wasser verdünnt. Eine gebördelte Dose (Durchmesser 56 mm, Länge 116 mm) wurde am Bördelrand mit einer elektrisch leitenden Klammer gehalten und vorsichtig in ein gegen Erde isoliertes leitendes, mit verdünntem Lack gefülltes Gefäß mit einem Durchmesser von 19 cm vollständig eingetaucht. Der Gleichstrom einer Spannungsquelle wurde an die Dose und mit dem anderen Pol an das Außengefäß angeschlossen. Die Beschichtung erfolgte mit einer Hilfselektrode mit einem Durchmesser von 1 cm, die in die Dose 8 cm tief eintauchte. Nach Abspülen mit Wasser wurde die Dose 3Minuten bei 215°C im Umluftofen eingebrannt. Die Dose war innen und außen vollständig mit einem dünnen und porendichten Klarlack überzogen. Meßwerte vergleiche Tabelle 1.An anionic, self-crosslinking acrylate resin according to DE-AS-1 669 107 was neutralized with ammonia and diluted to a solids content of 15% by weight with deionized water. A flanged can (diameter 56 mm, length 116 mm) was held at the flanged edge with an electrically conductive clamp and carefully immersed completely in a conductive container insulated against earth and filled with diluted lacquer with a diameter of 19 cm. The direct current from a voltage source was connected to the socket and the other pole to the outer vessel. The coating was carried out with an auxiliary electrode with a diameter of 1 cm, which was immersed in the can 8 cm deep. After rinsing with water, the can was baked for 3 minutes at 215 ° C in a convection oven. The can was completely covered on the inside and outside with a thin and pore-tight clear lacquer. For measured values, see Table 1.
Das Bindemittel aus Beispiel 1 wurde mit 0.4 Gew.-Teilen Titandioxid auf 1 Gew.-Teil Bindemittel pigmentiert und nach Neutralisation mit Ammoniak auf einen Festkörper von 9 Gew.-% verdünnt. Die Beschichtung erfolgte ohne Hilfselektrode. Die Dose war vollständig mit einem weißen Lack überzogen. Die Porigkeit, gemessen in einer Elektrolytlösung bei 4 Volt Spannung, beträgt nach 30 Sekunden 5 mA.Meßwerte vergleiche Tabelle 1.The binder from Example 1 was pigmented with 0.4 part by weight of titanium dioxide to 1 part by weight of binder and, after neutralization with ammonia, diluted to a solids content of 9% by weight. The coating was carried out without an auxiliary electrode. The can was completely covered with a white varnish. The porosity, measured in an electrolyte solution at 4 volts, is 5 mA after 30 seconds.Measured values see Table 1.
Ein kationisches Amino-Epoxidharz nach DE-OS-3 122 641 wurde mit 0.4 Gew.-Teilen eines Gemisches aus 99 Gew.-Teilen Titandioxid und 1 Gew.-Teil Ruß pigmentiert und nach Neutralisation mit Ameisensäure auf einen Festkörper von 15 Gew.-% mit entionisiertem Wasser verdünnt. Die Beschichtung erfolgte ohne Hilfselektrode. Die Dose war vollständig mit einem grauen Lack überzogen. Meßwerte vergleiche Tabelle 1.
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT84107925T ATE46370T1 (en) | 1983-07-12 | 1984-07-06 | PROCESS FOR COATING CANS OPEN ON ONE SIDE. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19833325068 DE3325068A1 (en) | 1983-07-12 | 1983-07-12 | METHOD FOR COATING SINGLE-SIDED OPEN HOLLOW BODIES |
| DE3325068 | 1983-07-12 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0131282A2 EP0131282A2 (en) | 1985-01-16 |
| EP0131282A3 EP0131282A3 (en) | 1985-09-11 |
| EP0131282B1 true EP0131282B1 (en) | 1989-09-13 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP84107925A Expired EP0131282B1 (en) | 1983-07-12 | 1984-07-06 | Process for coating cans open at one end |
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| Country | Link |
|---|---|
| US (1) | US4529492A (en) |
| EP (1) | EP0131282B1 (en) |
| JP (1) | JPS6039199A (en) |
| AT (1) | ATE46370T1 (en) |
| CA (1) | CA1227161A (en) |
| DE (2) | DE3325068A1 (en) |
| ES (1) | ES8504275A1 (en) |
| ZA (1) | ZA845310B (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3425435A1 (en) * | 1984-07-11 | 1986-01-23 | Schmalbach-Lubeca AG, 3300 Braunschweig | METHOD FOR DECORATING AND CORROSION-PREVENTING LACQUERING OF METALLIC CAN HULLS |
| GB2192407B (en) * | 1986-07-07 | 1990-12-19 | Metal Box Plc | Electro-coating apparatus and method |
| DE3728762A1 (en) * | 1987-08-28 | 1989-03-09 | Basf Lacke & Farben | BINDING AGENT FOR CATHODIC ELECTRIC DIP PAINTING |
| CA2030033C (en) * | 1989-11-16 | 1997-06-24 | Karsten Loeck | Process and a device for anodic or cathodic electro-coating of hollow bodies, particularly cans |
| US7767070B2 (en) * | 2004-08-13 | 2010-08-03 | Ppg Industries Ohio, Inc. | Processes for coating of objects |
| US7947160B2 (en) * | 2004-08-13 | 2011-05-24 | Ppg Industries Ohio, Inc. | System for coating objects |
| US7943028B2 (en) * | 2004-08-13 | 2011-05-17 | Ppg Industries Ohio, Inc. | Method for coating objects |
| US20060032730A1 (en) * | 2004-08-13 | 2006-02-16 | Kaufman Paul J | Belt conveyor apparatus |
| WO2014146117A2 (en) | 2013-03-15 | 2014-09-18 | Modumetal, Inc. | A method and apparatus for continuously applying nanolaminate metal coatings |
| CA2961507C (en) | 2014-09-18 | 2024-04-09 | Modumetal, Inc. | Methods of preparing articles by electrodeposition and additive manufacturing processes |
| CA2961508C (en) | 2014-09-18 | 2024-04-09 | Modumetal, Inc. | A method and apparatus for continuously applying nanolaminate metal coatings |
| DE102015122467A1 (en) * | 2015-12-21 | 2017-06-22 | Dürr Systems Ag | Plant and method for treating workpieces |
| US11286575B2 (en) * | 2017-04-21 | 2022-03-29 | Modumetal, Inc. | Tubular articles with electrodeposited coatings, and systems and methods for producing the same |
| US11519093B2 (en) | 2018-04-27 | 2022-12-06 | Modumetal, Inc. | Apparatuses, systems, and methods for producing a plurality of articles with nanolaminated coatings using rotation |
Family Cites Families (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2215166A (en) * | 1937-02-15 | 1940-09-17 | Crosse & Blackwell Ltd | Method of coating metal for foodstuff containers |
| US2362474A (en) * | 1941-07-25 | 1944-11-14 | Manning Bowman & Co | Electroplating apparatus |
| US3253943A (en) * | 1963-03-04 | 1966-05-31 | Union Carbide Corp | Bottle coating machine |
| AT294278B (en) * | 1967-09-08 | 1971-11-10 | Stolllack Ag | Process for the electrocoating of hollow bodies |
| US3483907A (en) * | 1967-10-02 | 1969-12-16 | Juliana M Corridon | Tote bag |
| US3660266A (en) * | 1968-02-12 | 1972-05-02 | Ashdee Corp | Electrocoating equipment accessory |
| US3694336A (en) * | 1969-06-02 | 1972-09-26 | Continental Can Co | Method for can electrodeposition |
| US3620952A (en) * | 1969-06-02 | 1971-11-16 | Continental Can Co | Mechanical apparatus for electrodeposition of cans |
| US3801485A (en) * | 1972-09-01 | 1974-04-02 | American Can Co | Apparatus and method for electrodepositing a coating on interior surfaces of container bodies |
| US3849284A (en) * | 1972-09-01 | 1974-11-19 | American Can Co | Apparatus method and valve for electrodepositing a coating on interior surfaces of container bodies |
| US3922213A (en) * | 1974-10-23 | 1975-11-25 | Aluminum Co Of America | Method and apparatus for uniformly electrocoating the interior of a shaped metal container |
| BR7608760A (en) * | 1976-06-07 | 1978-07-25 | Standard Chem Co Inc | PROCESS AND APPLIANCE FOR ELECTRICALLY COVERING A PIECE SURFACE |
| US4094760A (en) * | 1977-07-25 | 1978-06-13 | Aluminum Company Of America | Method and apparatus for differentially and simultaneously electrocoating the interior and exterior of a metal container |
| US4210507A (en) * | 1978-09-18 | 1980-07-01 | Aluminum Company Of America | Electrocoating flow control electrode and method |
| US4400251A (en) * | 1981-06-05 | 1983-08-23 | Aluminum Company Of America | Method and apparatus for simultaneously electrocoating the interior and exterior of a metal container |
| DE3304940A1 (en) * | 1983-02-12 | 1984-08-16 | Herberts Gmbh, 5600 Wuppertal | METHOD FOR COATING SINGLE-SIDED OPEN HOLLOW BODIES |
-
1983
- 1983-07-12 DE DE19833325068 patent/DE3325068A1/en not_active Withdrawn
-
1984
- 1984-07-06 AT AT84107925T patent/ATE46370T1/en not_active IP Right Cessation
- 1984-07-06 DE DE8484107925T patent/DE3479747D1/en not_active Expired
- 1984-07-06 EP EP84107925A patent/EP0131282B1/en not_active Expired
- 1984-07-10 CA CA000458519A patent/CA1227161A/en not_active Expired
- 1984-07-10 ES ES534164A patent/ES8504275A1/en not_active Expired
- 1984-07-10 US US06/629,566 patent/US4529492A/en not_active Expired - Fee Related
- 1984-07-10 ZA ZA845310A patent/ZA845310B/en unknown
- 1984-07-11 JP JP59142470A patent/JPS6039199A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0440440B2 (en) | 1992-07-02 |
| DE3325068A1 (en) | 1985-01-24 |
| ZA845310B (en) | 1985-03-27 |
| ATE46370T1 (en) | 1989-09-15 |
| ES534164A0 (en) | 1985-04-01 |
| ES8504275A1 (en) | 1985-04-01 |
| US4529492A (en) | 1985-07-16 |
| CA1227161A (en) | 1987-09-22 |
| EP0131282A2 (en) | 1985-01-16 |
| JPS6039199A (en) | 1985-02-28 |
| EP0131282A3 (en) | 1985-09-11 |
| DE3479747D1 (en) | 1989-10-19 |
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