DE1621915A1 - Process for the electrical deposition of paints and suitable device for this - Google Patents

Description

DR. A. KÖHLER. M, 8CHROS) EA

PATENT ANWAtTB I MÜNCHW 13 FRAia.JOMIH. *! *. 4 »

PK - 1948

Ford - Werke, Aktiengesellschaft, Cologne-Deute

Process for the electrical separation of .

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Paint and suitable device /

The invention relates to an improved method for electrically induced deposition of paints or coatings from aqueous dispersions. In particular, the invention is concerned with one embodiment in which a conventional coating bath contained within two or more coating units is and between these two or more unity ten is circulated. The invention also relates to a device particularly suitable for this purpose.

The electrically induced deposition of a paint or a coating on electrically conductive objects is described, for example, in American Patent 3,230,162, to which reference is made here in particular. This process consists of an anodic deposition using an aqueous dispersion of a water-soluble amino compound, including ammonia, and the paint or coating material ₉ which contains a film-forming paint or coating binder, the predominant proportion of which is a synthetic polycarboxylic acid resin, and which is used for over - ·

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The object to be coated is immersed in the dispersion and used as the anode of the electrodeposition cell, while a cathode in contact with this dispersion is spaced from the object to be coated and an electrical potential difference is set between these electrodes, whereby a water-resistant film of the resin is formed the anode, d _o h. the object to be coated. The; Film deposition is practically uniform by itself and is terminated by itself due to the nature of the resin used, since this resin is a material which is deposited in practically direct proportion to the current flow between anode and cathode and builds up a film, its electrical resistance increases sharply with depth "

The anodic deposition is used in the present description to explain the present process, since it has a greater industrial application and is better clarified, as cathodic deposition, the for cathodic Deposable paints or coatings suitable resins contain in their molecular structure functional groups that result in ionic sites of positive charge during ionization, and to the negative electrode of the electro-separation cell are attracted »are examples of such groups Amine ~ and substituted amine groups, for example quaternary Ammonia groups. The diapereion of such resins is through

in
Addition of water-soluble acidic dispersing aids

BATH ORIGINAL

caused, for example, by water-soluble * compounds containing carboxyl acid groups and suitably buffered inorganic acids, for which buffered phosphoric acid; an example is. For those skilled in the art, it goes without saying that the present process can be used for both anodic and cathodic deposition is applicable.

Furthermore, it is known that two or more to be covered Objects can be present at the same time in an Obereugsbad. It is also known that two workpieces can work at the same time, coated in the bath at different coating voltages can be «d, h · the potential difference between the work · * · piece A) and the cathode or cathodes of primary effectiveness in »coating of the workpiece A) can be compared to the between the workpiece B) and the cathode ode? the cathodes of primary effectiveness when coating the workpiece B) be different. .

In practice, there have been many over-plating of workpieces different size and shape within a single tlbersugsbehältere often problems with the arrangement of the lines both inside and outside the coating tank and these problems continue to be complicated if so one wishes to coat such different workpieces with different tensions «

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According to the present method, a common coating bath is circulated between two or more coating containers. The transfer containers are connected by fluid connection lines "which are preferably arranged in a practically parallel arrangement and equipped with independent electrical devices for inducing the electrodeposition" Common or separate power supply lines and common or separate supplementary supply lines and painting or coating equipment can be used. A common heat exchange unit can be used for use with the common bath material. A uniform coating can be obtained and pumping means can be applied to Badübertragungen _E to cause a movement of the bath _T can be reduced or avoided whereby the previously used separate movement devices on two coating lines due to the common BadflUssigkeit. To this extent, the system has considerable advantages over the operation of two completely separate units and considerable advantages over the operation of two coating lines in a single unit or the coating within a single unit with different coating conditions applied at different locations within the bath will.,

According to the invention, there is an improvement in a method for coating a first electrode in an electrical Circuit containing the first electrode, a second electrode

109848/0269 bathroom original.

with opposite polarity with respect to the first electrode and an aqueous β coating bath between the first and of the second electrode and in contact therewith, wherein an electrical potential difference between the first electrode and the second electrode while setting one DC current is applied through this circuit. While inside the bath in ionized form an organic film-forming Resin is dispersed, which turns out to be a film of practical uniform depth on the "wide electrode practically" deposited in direct proportion to the current, the film deposition obtained causing an increase in the electrical resistance It stands in direct proportion to the current in direct proportion to the strength of the pilm deposition "in that a first coating container charged with a part of the coating bath, a second coating container with a second part of this bath charged and the coating bath between the first container and cycling the second container on a time and speed basis such that the formation any significant chemical or physical change between the portion of the bath in the first container and the portion of the bath in the second container is avoided from having a first electrode and a second electrode spaced apart and placed in contact with the bath in the first container are, and a first electrical potential difference between the first electrode and the second electrode for Electrodeposition of a film of the resin is set on the second electrode, and a third electrode and one

109848/0269 BATH ORIGINAL

fourth electrode in the distance and in contact bit the bath placed in the second container, and a second Potential difference between the third electrode and the fourth electrode for electrodeposition of a film of the Resin is set on the fourth electrode, the Polarity of the third electrode to the fourth electrode is the same; like the polarity of the first electrode to the second electrode

trode is.

In a preferred embodiment for a method for Coating an anode in an electrical circuit which consists of this ilnode, a cathode and an aqueous coating bath between anode and cathode and in contact therewith, with an electrical potential difference between the Anode and cathode below :? Formation of a direct current; applied by the circuit and inside the bath a water-soluble amine and an organ in anionic form! - * see before β film-forming resin, which turns out to be a film of practical uniform depth on the anode practically directly proportio- '

t nal to the stream is deposited, applied and where the he «j

• t

sustained filsa separation an increase in the electrical resistance: Stand against the current in direct proportion to the strength of the Film deposition shows «so that there is a corresponding drop of the current in practically direct proportion to the increase in the thickness of the film deposition at the potential difference er » there, the improvement is that a first coating tank is charged with part of the coating bath, «in

10884-8 / 0289 ' ^{BAD 0RlQmi}

ewelter coating tank with a «large part of the bath. sends and the Uberzuebad between the first tank and the second tank in such a dependence τοη time and speed that the setting of any essential ■ * .. ·; is circulated to chemical or physical changes swiechen the! part of the bath in the first tank and the part of the bath avoided in the second tank, wherein ■ the anode and the cathode at a distance from each other and in loading i stirring with the bath are mounted inside the first tank, and a first electrical potential difference is set between the anode and the cathode for the deposition of a film of the resin on the anode *, and a second anode and a second cathode spaced apart and in contact with the bath within the second tank attached

.and become / a second electrical potential difference between the second anode and the wide cathode are applied to the electrodeposition of a film of Hareoss on the second anode

will. ; ;; ; - ■■■■■ ;: - ■ ■■■ ',' *

according to the invention, together with the device _t suitable for this purpose, is explained below with reference to a preferred embodiment of the invention in connection with the accompanying schematic drawing. '

According to the drawing, there is a first electrical transfer container 10 in Plüssigkelts connection with a second sheet metal addition container 110 through the following described.

109848/0269 bathroom original

1β2-315

directions. The container 10 is electrically grounded and is connected via conductor 11 to a negative terminal point of a DC power source 13. The container 10 contains the electrocoating bath 15 »for example a pigmented polycarboxylic acid resin and diisopropanolamine in aqueous dispersion, such baths usually containing about 5 to about 12% by weight of non-volatile substances conductive object 17, which is carried by a hanger 19, which in turn is carried by a carrier 21 mounted above it. The object 17 is electrically insulated from the conveyor carrier 21 by insulation 23. The object 17 is in electrical connection with a positive terminal point of the power source 13 via the hanging device 19 * line brush 25, busbar 27 and conductor 29. Another workpiece, generally designated by the reference numeral 31, approaches the container 10 according to the drawing

In this embodiment, the electroplating bath 15 flows from container 10 into. container 110 via line 33, valve 35, line 37, heat condensing unit 39t in which the bath in heat exchange relationship with suitable heat exchange media is led, and line 4L becomes part of Badea continuously or 'intermittently withdrawn from the container 110 via the line 43 and in the paint or ÜberaügsdiBpergieinheit 45 out, in which a supplementary

1098Ä870269 bad original

g -

loading is fed into the system · You supplementary loading is transferred to the container 110 outside the unit 45 the line 47 returned

The bath 15 is from the container 110 Su the container 10 over Line 49, pump 51 and line 55 returned. It is also within the scope of the invention to provide a heat exchange unit in Heat exchange relationship with that flowing through the line 53 * to apply the bath material. The bath coating is advantageous between the tanks depending on Time and speed led to the formation of some substantial chemical or physical change or a waste of this kind "wiped out the side of the Bath in container 10 and the portion of the bath in container 110 is avoided, so that the bath composition and the associated operating conditions are the same in each container, what an identical coating in each guide of the workpieces allowed «The container 110 is in electrical connection ( with a negative terminal of a power source 1> via line 55.

In the bath 15 in the vessel 110 is an electrically conductive object 127 is immersed "is supported by a hanger _t which is in turn held by an over-mounted conveyor 121st The object 117 is insulated from the conveying device 121 by insulation 125. The object 1j7 is in electrical connection

109848/0269

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with a positive terminal of a power source 113 via the Hanging device 119, wire brush 124, supply line rail 127 and ladder 129.

An electrical potential difference between about 50 and about 500 volts is applied between the object 17 and the container 10 and maintained between article 117 and container 110. The upper range of the voltage is determined by the ability of the deposited resin, an electrically induced one Resist cracking, for sure. Usually this potential difference is between about 100 and about 250 volts in in any case · Of course, the electrical potential » different; between the object 17 and the tank IG practical be the same as the electrical potential difference between the object 117 and the container T10. In a further preferred embodiment, the potential difference is between the electrons in contact with the bath in the one container is greater than the potential difference between the electrodes in contact with the bath in the second container, for example at least about 25 volts larger «This can be in the Case be favorable «where the objects to be covered in a tank relatively more difficult due to indented and / or shielded surfaces are to be coated. In certain cases it may prove beneficial to use a coating tension maintain in a tank that is about 50 to 150 volts higher solder than those in the other container.

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^N The applied herein, the term "amino compounds include both amines and ammonia. Preferred are waseerlös-Hehe amines beiapielßweiee Äthanolarain, Diisopropanolaein, morpholine, and other similar compounds used" ammonia, if used, preferably used in conjunction with an amine, the latter the greater proportion of the Löslichmachungaeigenschaften is because ammonia is more volatile, and may cause the bath greater and more rapid changes in the _t pH. Although the optimal temperature of the bath may vary somewhat with the composition of the coating applied, such baths are gewähnlich at temperatures in Range from about 18 to about 30 ¹ S operated "

The term "coating" or "paint ¹¹ by electrochemical deposition used here includes both the deposition of finely ground figment and / or filler in the ionizable resin referred to as a binder, as well as the deposition of the binder without pigment and / or filler, or only with a very low content of it, which, however, may be colored if desired, such as the deposition of other surface coatings which can be reducible in water and which contain the binder, and which can generally be described as roughly analogous to enamel, lacquers or other lacquer bases coating material is designated for this deposition * as ⁿ painting "or" coating ". Thus, the binder through the Elektroabscheidung.zu a water»

permanent film is converted, and is finally converted into a permanent "film resistant to normal operating conditions by the final curing" consist practically of the total amount or practically the total amount of the mass that has been deposited to form the film, or it can consist of a carrier for pigmentary and / or mineral filler material or other resins on which it exerts the desired effect for the deposition of the film are present. Suitable resins include those described in US Pat. No. 3,230,162, but are not specifically limited to these. The preferred resins for anodic deposition have an acid number between about 30 and about 300 and an electrical equivalent weight between about 1000 and about 20,000 Separates energy · The conditions, procedures and calculations that can be used to determine the electrical equivalent weight are described in detail in the American patent J 230 162 listed above.

The inventive device for electroplating electrically conductive objects with organic film-forming Haraen ionizable in water consists of two or more separate coating baths connected as first electrodes, all second electrodes of opposite polarity

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162191 $

switched! objects to be coated within the respective Containers, direct current supply and discharge devices for the electrodes and liquid lines for circulating the Bath liquid between the respective coating containers nit associated pumping and valve devices "

In preferred embodiments, the device has a or several heat exchange units in the circuit lines on. A coating material dispersing and coating material is also preferred Supplementary unit with corresponding inlets and outlets to one of the coating bath tanks available «

The invention has been described in detail above on the basis of preferred embodiments without implying any thereon is limited, as numerous changes and for those skilled in the art Modifications are given «,

109848/0269

Claims (1)

PATEH! CLAIM 1. A process for coating electrically conductive objects ixt an electrical circuit _t the ATE of a first electrode, "the electrically conductive object second electrode of opposite polarity to the first electrode and an aqueous plating bath between the st counter" and and the first electrode and in contact therewith exists, whereby an electrical potential difference is applied between the first electrode and the object with the formation of a direct current within the circuit and in the bath in ionized form an organic film-forming resin, which aich al β film of practically the same strength essentially directly to the current deposited proportionally on the object and as a deposited film , shows an increase in electrical resistance for the current directly proportional to the bead of the film deposition, is dispersed, characterized in , that a first coating container is charged with a portion of the aqueous coating _{bath and} a second coating container is charged with a second portion of the bath and the coating bath between the first container and the second container at such a rate that the formation of any substantial chemical or physical changes between the part of the bath in the first 101848/0269 bathroom original '■;. ■ · t621915 container and the part of the bath in the second container is prevented, is circulated, with one at the same time a first electrode and a first counterpart to the second Electrode at a distance from each other in contact with the bath inside the first container and a first electrical Applying phototential differentials between the first electrode and the object for electrodeposition of a resin film on the object and a third electrode and a second electrically conductive object as a fourth electrode spaced apart from one another brings in contact with the bath in the second container and a second electrical potential difference «between the third Electrode and the object for electrodeposition of a resin film on the object and the polarity of the third electrode to the second object is equal to the polarity of the first electrode to the first item is 2. .Verfahren according to claim -1y characterized in that the first potential lfferenfe in the same size as the second Potential difference is applied, 109848/0269 / 4 5- Process according to claim t, characterized _v Dess a first electrical potential difference of greater height than the second el & ktriöche potential difference applied is ο 4. The method according to claim 3 » characterized in that a first electrical potential difference _fi which is at least 25 volts greater than the zv / eite electrical potential difference is applied *, 5. The method according to claim 1 bio 4 _V by geke nnzeiohne1 ₁ that ala filmbildcmdes resin a synthetic poly carbonic acid resin which is dispersed in the bath by means of a water-soluble amino compound, and optionally pigmented * is used ₀ Method according to claim 5 * characterized in this way. the second electrode and the fourth electrode in contact with the bath are positively charged with respect to the first electrode and the third electrode. 7. The method according to claim 1 big 6, characterized in that a flow of the bath from the first container is continuously fed into the second container and a flow of the coating bath from the second container is continuously fed into the first coating container » BATH ORIGINAL 109848/0269 Method according to Claims 1 to 6, characterized in that »a flow of the bath from the first container is intermittently fed into the second container, and a flow of the bath from the second container is fed intermittently into the first container. 9 »Method according to claims 1 to 8, characterized in that the objects to be coated are connected as anode and a water-soluble amine and an organic film-forming resin are dispersed in the bath. 10. The method according to claim 9 "characterized" in that both the first and the second electrical potential difference are in the range of about 50 to about 500 volts. 11. The method according to claim 9 * characterized in that " the electrical PotentiaXdifferenzert are in the * range from about 100 to about 250 volts * 12. The method according to claim 9 bie 11, characterized ^ that the first electrical potential difference is at least 50 volts greater than the second electrical potential difference « 13 «Method according to claim t to 12», characterized in that the bath is in the heat exchanger during circulation 105040/0269 exchange with a heat exchange chinedium when passing between the first container and the second container " Device "for electrocoating electrically conductive objects with organic film-forming ionizing resins, characterized by two or more coating _{bath containers (IQ 11} 110) connected as first electrodes, objects to be coated as second electrodes of opposite polarity I17" 1t7), DC supply and discharge devices «To the electrodes (15» 29 * 19, 1.1 * 129, 119, 55) and lines (59, 53, 33 * 37, 41) for circulating the bath liquid (15) between the coating containers (10, 110) with associated pump and valve devices _o. ο Device according to claim 14 * characterized by a heat exchange unit (39) in the circuit lines » 16 · Device according to opposition 14 or 15 _# · characterized by a coating material diapering and supplementing unit (45) with inlets and outlets (43 ₉ 47) to one of the coating bath tanks. 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