WO2004101866A2

WO2004101866A2 - Method and devices for increasing the service life of a process solution for chemical-reductive metal coating

Info

Publication number: WO2004101866A2
Application number: PCT/DE2004/001043
Authority: WO
Inventors: Reinhard Schwarz; Klaus Fischwasser; Alexander Schiffer
Original assignee: Blasberg Werra Chemie Gmbh
Priority date: 2003-05-12
Filing date: 2004-05-12
Publication date: 2004-11-25
Also published as: EP2039810A8; WO2004101866A3; EP2039810A3; EP2039810A2; DE10322120A1; EP1623058A2

Abstract

The invention relates to a method and devices for increasing the service life of a process solution used for chemical-reductive metal deposition. In said method, the pH-value is adjusted and the ions of the coating metal are replenished without interfering counter-ions by feeding the process solution, optionally after dilution, to at least one weakly acidic cation exchanger that is charged with ions of the coating metal. The reduction medium is replenished either in an auxiliary circuit or in a diluted process solution. Preferably, interfering cations originating in the reduction medium are eliminated with the aid of a strongly acidic, proton-charged cation exchanger and interfering anions with the aid of a weakly alkaline anion exchanger. During the metal deposition process, interfering cations that accumulate in the process solution are preferably eliminated with the aid of a strongly acidic, proton-charged cation exchanger. Said method permits a practically constant composition of the process solution with a negligible impurity content, producing a coating of exceptional quality. The increase in the service life of the process solution improves the cost-effectiveness and environmental compatibility of the chemical-reductive metal coating.

Description

Methods and devices for extending the service life of a process solution for chemical-reductive metal coating

The invention relates to a driving method and to extending the useful life of a process solution used in chemical-reductive metal deposition. Chemical-reductive metal deposition is used to coat workpieces with a metal coating (Cu, Ni, Ag or Au).

For the chemical-reductive metal deposition of non-ferrous metals (non-ferrous metals) on the surface of a base material (e.g. metal or pretreated plastic), the following, greatly simplified reaction equation can be set up for nickel deposition:

3 NaH ₂ PO ₂ + 3 H ₂ O + NiSO ₄ → 3 NaH ₂ PO ₃ + H ₂ SO ₄ + Ni + 2 H ₂ (Equation 1)

In the chemical-reductive metal deposition, reducing agents (here NaH ₂ PO ₂ ) and metal ions of the coating metal (here Ni ²⁺ ) are consumed and at the same time the oxidized reducing agent (here NaH ₂ PO ₃ ) and protons are formed as reaction products, equivalent to the amount of metal deposited. whereby these lower the pH in the process solution.

Due to numerous side reactions, approximately 3.3 mol of the reducing agent are required for the deposition of one mole of nickel. Elemental phosphorus, which is formed from the reducing agent by side reactions, is also alloyed into the resulting metal layer.

According to the prior art, the reducing agent and the metal ions of the coating metal are subsequently metered in by adding the corresponding salts and the pH is adjusted by adding alkalis to the process solution. The process of metal deposition, the pH adjustment, the subsequent dosing of the used components and the removal of base material accumulate foreign substances in the process solution, which disrupt the process of metal deposition and negatively affect the quality of the layers produced. In order to remove the foreign matter, the process solution is usually partially discarded, although its complex treatment makes it difficult to treat it in terms of wastewater. The usual unit of measurement for the service life of the process solution is the metal throughput MTO (= "metal turn-over"). This is referred to as 1 MTO if the metal content of the process solution is converted once and added again. According to the prior art, the compressive stress decreases disadvantageous in the nickel-phosphorus layer after 2 to 4.5 MTO into a tensile stress and therefore the service life of the process solution is usually limited to 5 MTO.

In order to extend the useful life of a process solution for chemical-reductive nickel deposition, it is necessary to separate the foreign substances that have been entered using suitable ner processes. Various ner processes are proposed for this purpose: Regeneration processes were already described in US 2,726,968 and US 2,726,969 in 1953, in which a weakly basic anion exchange material activated with phosphinic acid is used for the regeneration of process solutions for chemical-reductive nickel deposition. This is intended to separate orthophosphite from the process solution and to release hypophosphite into the process solution. The weakly basic anion exchange materials are directly loaded with process solution, which is why the pH value of the process solution must not exceed pH 5, otherwise the weakly basic anion exchange material from the hypophosphite loading is converted back into the form of the free base, which is not capable of ion exchange , This ner driving does not separate disruptive cations. The metal ions are metered in by adding nickel salts, whereby according to US Pat. No. 2,726,969, the use of basic nickel salts such as nickel hydroxide or nickel carbonate should simultaneously achieve a pH adjustment without the use of further alkalis. However, the use of these poorly soluble compounds has the disadvantage that they contaminate the process solution with solids that can be built into the deposited metal layers and thus negatively influence their properties. These ner driving have not prevailed in practice, since in particular the use of phosphinic acid for activating the anion exchanger impairs their economic viability.

DD 36 889 discloses a process for the continuous regeneration of acidic solutions for chemical nickel plating, in which the solution is a combination of a nickel-loaded weakly acidic cation exchanger and a hypo- phosphite-loaded, (weakly to) moderately strong basic anion exchanger. The weakly acidic cation exchanger is to be used to adjust the pH and to replenish nickel ions, while the weak to moderately basic anion exchanger is to be used to replenish hypophosphite and to separate orthophosphite. The weakly acidic cation exchanger and the (weakly to moderately strong) basic anion exchanger with coordinated capacities are connected in series.

The functioning of the cation exchanger is to be monitored in DD 36 889 via the coloring of the weakly acidic cation exchange resin. As soon as this has changed from green (nickel loading) to a yellowish white (unloaded exchanger), the exchangers should be regenerated. This color change of the weakly acidic cation exchange resin is very difficult to use for checking the functionality of the ion exchanger, since a process solution for chemical-reductive nickel deposition itself is colored intensely green.

In the regeneration of the weakly to moderately basic anion exchanger, the transfer to the hypophosphite loading should be carried out in DD 36 889 by applying a hypophosphite solution to the anion exchanger previously loaded with chloride. In the case of a weakly to moderately basic anion exchanger in the chloride loading, however, an exchange of chloride for hypophosphite is not possible since chloride is more firmly bound by the exchanger than hypophosphite and even orthophosphite.

Due to the circuit described in DD 36 889 - weakly acidic cation exchanger in front of weak to moderately basic anion exchanger - the weakly acidic cation exchanger raises the pH to pH values above pH 5. After a weakly to moderately basic anion exchanger only in a pH range lower pH 4 is fully functional, the upstream of a weakly acidic cation exchanger described in DD 36 889 and the resulting shift in the pH value result in an uncontrolled release of anions which were bound to the weakly basic anion exchanger. In the process according to DD 36 889, the use of a strongly acidic cation exchanger is excluded, since this causes the pH of the solution to drop too much and this would not lead to optimal separation conditions. Sulfate or chloride ions present in the solution would interfere with the second part of the regeneration system described in DD 36 889, which regulates the household of the hypophosphite and orthophosplite ions.

Because of the deficits described, the regeneration process described in DD 36 889 could not prevail in operational practice.

The use of regeneration processes, which are based on the principle of action of membrane electrolysis, are proposed in a number of documents, with different cell configurations being used. Patent specification DE 43 10 366 proposes a membrane electrolysis cell with 4 chambers in which the orthophosphite formed in the chemical-reductive nickel deposition is to be reduced in the cathode space of the electrolysis cell. However, from DE 198 49 278 and our own investigations it is known that the cathodic reduction of the orthophosphite to hypophosphite does not take place, so that no regeneration of the process solution can be achieved by means of the method described in DE 43 10 366. US Pat. No. 5,419,821 therefore proposes to add a precipitation step to the membrane electrolysis cell described in DE 43 10 366 in order to remove the orthophosphite by adding magnesium or calcium hydroxide. The input materials consumed by the separation process (nickel ions and reducing agents) should be supplied in the form of nickel sulfate (addition to the process solution) and phosphinic acid (addition to the catholyte). The sulfate should be removed from the catholyte as barium sulfate by adding barium hydroxide. The risk of the membranes of the membrane electrolysis cell becoming blocked is very high in this process, since saturated solutions are present after filtration of the sparingly soluble salts.

The use of a membrane electrolysis cell is also described in the patents DE 198 51 180 (EP 1 006 213) for the regeneration of a process solution for chemical-reductive metal deposition. In this process, the anions of the process solution are electrodialytically converted into an acidic one in the membrane electrolysis cell Auxiliary circuit transferred, which is separated from the process solution by the membranes of the membrane electrolysis cell. In the auxiliary circuit, the anions are separated by a weakly basic anion exchanger, which was previously converted into the hypophosphite loading by using phosphinic acid. The use of phosphinic acid impairs the economics of the process. In a special embodiment of the process according to DE 198 51 180, the use of a weakly acidic cation exchanger in combination with the membrane electrolysis cell and the weakly basic hypophosphite-loaded anion exchanger is also described. This weakly acidic cation exchanger is to be used to replenish nickel ions: For this purpose it is connected with its inlet to the weakly basic anion exchanger and with its outlet to a chamber of the membrane electrolysis cell that contains the process solution. Part of the acidic hypophoshite-containing solution of the auxiliary circuit is led over the weakly acidic cation exchanger, which is loaded with nickel ions. The effluent of the weakly acidic cation exchanger is fed to the process solution via the chamber of the membrane electrolysis cell. In order to avoid the entry of disruptive components, such as Na ions, from the auxiliary circuit into the process solution, this arrangement requires the use of phosphinic acid as a source of hypophosphite, which has a negative impact on the economics of the process. According to DE 198 51 180, the required pH value is adjusted by adding alkalis to the process solution and leads to an increasing salt content, which limits the service life of the process solution, since the process described in DE 198 51 180 does not cause any cationic foreign substances from the process solution can be removed. In addition, the use of phosphinic acid impairs the economics of the process.

The patent specifications DE 198 49 278 (EP 1 123 424) and EP 1 239 057 describe two-stage electrodialysis processes which are intended to handle the separation task required for the regeneration of the process solution. An auxiliary circuit is required to separate the anion mixture, in which the pH is raised to pH> 8. This is necessary so that orthophosphite is present as a divalent anion. By using a selective anion exchange membrane that only allows monovalent anions to pass through, the divalent anions (sulfate, Orthophosphite) and the monovalent anions are returned to the process solution. Practical experience has shown, however, that the selectivity of the available anion exchange membranes is not sufficient to achieve the required separation of orthophosphite and hypophosphite, so that the separated hypophosphite cannot be returned to the process solution. Therefore, the cleaning of the process solution is only possible through high material losses, the material losses being compensated for by adding fresh chemicals to the process solution. The contents of the auxiliary circuit are treated using wastewater technology, whereby compliance with the limit value for the parameter phosphorus requires considerable effort since the auxiliary circuit still contains considerable amounts of hypophosphite.

The object of the invention is to provide methods and devices with which the useful life of a process solution for chemical-reductive metal coating can be extended.

The object is achieved by a method for extending the useful life of a process solution for chemical-reductive metal deposition, in which the reducing agent and metal ions of the coating metal used in the metal deposition are replenished and the pH in the process solution is adjusted. The metal ions are subsequently metered in and the pH is adjusted with the aid of at least one weakly acidic cation exchanger which is loaded with ions of the coating metal. For this purpose, the pH value in the process solution is monitored and, if the pH value of the process solution drops, part of the process solution, if appropriate after dilution, is passed through the weakly acidic cation exchanger 14.

The solution prepared by the weakly acidic cation exchanger 14 is fed directly back into the process solution.

The functionality of the weakly acidic cation exchanger is monitored by checking the pH in the effluent of the weakly acidic cation exchanger 14, with the pH value being approximated in the effluent of the weakly acidic cation exchanger Cation exchanger to the pH of the process solution of the cation exchanger is loaded again with ions of the coating metal for reuse.

It was found that with the aid of the weakly acidic cation exchanger, the pH of an acidic process solution can be adjusted in parallel with the subsequent metering in of the metal ions. This is achieved in that the weakly acidic cation exchanger, when it comes into contact with the process solution, binds the H ⁺ ions formed during the metal deposition. This advantageously eliminates the need to add alkalis and metal salts to the process solution in accordance with the prior art in order to bind the H ions and to replenish the used metal ions.

By metering in the ions of the coating metal without disruptive counterions and adjusting the pH without addition of alkali, the process according to the invention with the weakly acidic cation exchanger considerably reduces the salt input into the process solution. This simple method, in which a conventional system for chemical-reductive metal deposition only has to be supplemented with the weakly acidic cation exchanger according to the invention, can significantly extend the useful life of the process solution.

The solution is enriched with ions of the coating metal by the weakly acidic cation exchanger. The risk of undesired metal deposition from such enriched solutions is high, especially when there is a sufficient amount of reducing agent.

An undesired metal deposition is minimized by the direct introduction, according to the invention, of the solution which is prepared by the weakly acidic cation exchanger (and enriched with ions of the coating metal) into the process solution.

Depending on the desired phosphorus content (2.5% to over 15%) in the deposited metal layer, the pH value of the process solution is adjusted to a SET value from pH 3 to pH 6. The phosphorus content of the deposited metal layer increases with the H + ion concentration in the process solution. As soon as the pH value of the process solution has dropped by 0.1 to a maximum of 1 pH unit below the target value during the metal deposition, the process solution, if necessary after dilution, is applied to the weakly acidic cation exchanger, which is loaded with ions of the coating metal is started.

The functionality of the weakly acidic cation exchanger is monitored by checking the pH in the inlet (or in the solution to be added) and in the outlet of the weakly acidic cation exchanger. The capacity of the weakly acidic cation exchanger is exhausted as soon as the pH in the outlet of the exchanger has almost matched that of the feed (difference <0.2 pH units).

At the end of the usage period, i.e. H. when the capacity of the ion exchange column is exhausted, the ion exchange material can be exchanged or the flow of the process solution can be redirected to another cation exchanger.

By comparing the pH value in the course of the weakly acidic cation exchanger with the pH value of the process solution, the end of the period of use of the weakly acidic cation exchanger can be determined according to the invention before the pH value and the ion content of the coating metal in the process solution reach the tolerance range of the process leaves. The method according to the invention therefore makes it possible to keep the ion content of the coating metal and the pH of the process solution almost constant.

Due to the almost constant process conditions in the chemical-reductive metal coating, a particularly uniform deposition of the metal on the workpiece to be coated is achieved according to the invention.

The term ion exchanger is understood in the sense of the present invention in each case a device which, for. B. in the form of a column, column or filter chamber is either partially or completely filled with an ion exchange material. Organic or inorganic ion exchange materials are used, these having functional groups which are capable of ion exchange. The ion exchange materials can be solid or liquid. According to the structure The functional groups of the ion exchange material used can be characterized in more detail, for example as a strongly acidic or weakly acidic cation exchanger or as a weakly basic or strongly basic anion exchanger. The substances bound by the ion exchanger can be removed again from the functional groups by regeneration, regeneration being possible in cocurrent or countercurrent.

In the text below, a diluted process solution is understood to mean a process solution which is diluted (for example by mixing with the rinsing solution) to a content of 5% to 90% of the concentration of the process solution, preferably 10 to 50%. By rinsing the coated workpiece after the metal coating, ingredients of the process solution are dragged into the rinsing solution. As a result, foreign substances such as the oxidized reducing agent, the counterions of the reducing agent, as a rule Na ⁺ , and other disruptive ions also get into the rinsing solution. The rinsing solution thus also represents a diluted process solution from which the foreign substances can be removed. In the further text, the term diluted process solution therefore includes the rinsing solution.

The metering of the metal ions of the coating metal consumed in the metal deposition is carried out by feeding the process solution or a dilute process solution onto a weakly acidic cation exchanger which is loaded with the cations of the coating metal. This releases metal ions into the process solution. As a result, no interfering counterions are advantageously introduced into the process solution.

Surprisingly, the process solution can be brought into direct contact with ion exchange materials without this leading to any significant metal deposition on the materials. This can be achieved by cooling the process solution to temperatures <60 ° C before feeding it to the ion exchanger. Alternatively, metal deposition on the ion exchange materials can be avoided by applying a dilute process solution to the ion exchange materials. The process solution is preferred (if necessary after dilution) with a Flow rate below 20 m / h, particularly preferably below 10 m / h, given to the ion exchanger (s).

Another component of the invention is a method for extending the useful life of a process solution for chemical-reductive metal deposition, in which the reducing agent used in the metal deposition, as well as the metal ions of the coating metal, is metered in and the pH in the process solution is adjusted, with an anion exchange for the removal of interfering anions in a membrane electrolysis cell with an additional auxiliary circuit between the process solution and the auxiliary circuit via anion exchange membranes.

In this process, the reducing agent in the form of a salt, preferably NaH ₂ PO ₂ , or a salt solution is replenished into the auxiliary circuit, which contains a regeneration solution. The contact and exchange of anions between the regeneration solution and the process solution or a dilute process solution takes place via anion exchange membranes in the membrane electrolysis cell. In the auxiliary circuit, the interfering cations originating from the reducing agent are separated off via a strongly acidic cation exchanger loaded with protons, while interfering anions are removed from the regeneration solution using a weakly basic anion exchanger which is present in its starting form as a free base.

The anion exchange membranes of the membrane electrolysis cell retain cations with the exception of protons and allow anions to pass between the process solution and the regeneration solution. Therefore, the anions acting as reductants, preferably H ₂ P0 ₂ ^~ , can pass through this membrane and migrate from the regeneration solution into the process solution. On the other hand, the counterions of the reducing agent (nations) are retained by the membranes and therefore cannot migrate from the regeneration solution into the process solution. A cation-free subsequent metering of the reducing agent, preferably H ₂ P0 ₂ ^" , into the process solution is thus achieved. The used and oxidized reductant, preferably orthophosphite (H ₂ P0 ₃ ^" ), and the counterions of the salt used for the subsequent metering can be obtained from the process solution of the coating metal migrate through the anion exchange membrane into the regeneration solution. Process- and a regeneration solution in a membrane electrolysis cell are brought into contact in separate chambers, the electrodialytic transport of the ions being brought about by an electric field induced by applying a voltage to the electrodes of the membrane electrolysis cell. The number of chambers in between determines the level of tension. A voltage drop of approx. 2 volts is to be expected per base unit of three cells, whereby the conductance of the solution in the chamber also influences the level of the voltage to be applied.

The special arrangement of the membranes ensures that the anions of the reducing agent and the foreign substances (oxidized reducing agent and possibly the counterions of the added salt of the coating metal) migrate through the membranes from the process solution into the regeneration solution, as a result of which the regeneration solution is enriched with foreign substances.

In order to avoid salt formation in the regeneration solution, disruptive anions are separated by passing the regeneration solution over a weakly basic anion exchanger. After the redosing of the reducing agent in the form of a commercially available salt into the regeneration solution, the counterions of the reducing agent, such as, for. B. Na ⁺ , are separated. For this purpose, the control solution is additionally passed through a strongly acidic cation exchanger which is loaded with H ⁺ ions. The strongly acidic cation exchanger removes sodium ions and replaces them with H ⁺ ions, so that an accumulation of sodium ions in the regeneration solution is prevented. The H ⁺ ions, on the other hand, are consumed by the cathodic electrode process or when the weakly basic anion exchanger is activated, and are thus removed from the regeneration solution.

As soon as the capacity of the ion exchanger is exhausted, the ion exchanger is regenerated. In the case of the weakly basic anion exchanger, this is carried out using sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution or ammonia; in the case of the strongly acidic cation exchanger, regeneration is carried out using hydrochloric or sulfuric acid. The resulting eluates are treated using wastewater technology. By using the strongly acidic cation exchanger according to the invention, surprisingly, separate activation of the weakly basic anion exchanger after its regeneration can even be dispensed with in the auxiliary circuit, since the salts contained in the auxiliary circuit are partially converted into the corresponding acids and added to the active groups of the anion exchanger.

The volume flow of process solution Vp, which is passed over the membrane electrolysis cell to set the desired concentration C _F , _g , can be calculated according to equation 2, which is valid for the steady state.

'F, e.g.

VP = '™ -V _EA (l ~ γ _R )' (Equation 2)

^C F, z ^C F, R 'Fg

Its value is determined by the foreign matter input into the process solution (IDF), the foreign matter concentrations in the inlet (C _F , _Z ) and in the outlet (C _F , _R ) of the cleaning device and by the degree of recirculation of the towed components (Y _R ). The mass flow of the foreign substance input can be determined from the deposited amount of nickel via the stoichiometry. The degree of recirculation depends on the proportion of the rinsing solution that is transferred to the coating container to compensate for evaporation losses, and can be between 0 and 1.

The use of the combination of strongly acidic cation exchanger and weakly basic anion exchanger according to the invention in the auxiliary circuit of a membrane electrolysis cell with the arrangement of the chambers described below has the advantage that the reducing agent can be replenished into the process solution without disruptive cations and disruptive anions can be separated from the process solution, and none in the auxiliary circuit Interfering cations are accumulated.

In a preferred embodiment of the invention, the above-described redosing of the reducing agent and the removal of disruptive anions in the auxiliary circuit are combined with the previously described pH adjustment and redosing of the ions of the coating metal with the aid of the weakly acidic cation exchanger loaded with ions of the coating metal. In this embodiment, the ions of the coating metal are replenished according to the invention a smaller amount of foreign matter is introduced into the process solution without interfering anions. As a result, only a small amount of foreign matter has to be separated by the membrane electrolysis cell.

In a further embodiment of the invention, the above-described redosing of the reducing agent and the removal of disruptive anions in the auxiliary circuit are combined with a method in which disruptive cations, which accumulate in the process solution during metal deposition, are separated off with the aid of at least one strongly acidic cation exchanger. that was previously loaded with protons.

This separation of the interfering cations is preferably carried out temporarily as required in a special cleaning process. This essentially serves to remove cations which are introduced into the process solution during the metal deposition from the base material. For this purpose, the process solution is brought into contact with a strongly acidic cation exchanger that was previously loaded with protons.

In this cleaning process, however, the ions of the metal to be deposited contained in the process solution are also removed and protons are introduced into the process solution. The cations of the coating metal then have to be replenished and the protons introduced when cleaning the process solution have to be removed again. In order to be able to use the cations of the coating metal again, the eluate, which is obtained when the strongly acidic cation exchanger is regenerated, is used after loading the pH of the weakly acidic cation exchanger with the cations of the coating metal.

The ions of the coating metal are preferably replenished through a weakly acidic cation exchanger which is loaded with the corresponding cations of the coating metal. At the same time, this binds the protons that were introduced into the process solution by the cleaning process.

With low metal throughputs, however, the use of a membrane electrolysis cell with an auxiliary circuit is associated with relatively high costs.

Another component of the invention is therefore a method for extending the useful life of a process solution for chemical-reductive metal deposition to which the reducing agent consumed in the metal deposition and the metal ions of the metal to be replenished are added and the pH in the process solution is adjusted, disruptive cations and anions which accumulate in the process solution during metal deposition using ion exchange processes from the process solution or a diluted one Process solution to be removed. For the removal of interfering cations, at least one strongly acidic cation exchanger is used for this purpose, which was previously loaded with protons, while the weakly basic anion exchanger for the removal of the interfering anions is converted into the protonated form by protons. The protons which the strongly acidic cation exchanger releases as described above when it binds interfering cations are preferably used for this purpose. In this process, the reducing agent is preferably added in the form of a water-soluble salt, preferably sodium hypophosphite (NaH ₂ P0 ₂ ), or a corresponding solution directly into the process solution or into a dilute process solution.

The interfering anions are separated off using the weakly basic anion exchanger and the interfering cations using the strongly acidic cation exchanger, preferably from a dilute process solution. The interfering cations are preferably separated from the rinsing system by the strongly acidic cation exchanger and the interfering anions are separated by the weakly basic anion exchanger. After the strongly acidic cation exchanger not only separates the cationic impurities from the base material but also the cations of the coating metal that are carried into the rinsing solution, the strongly acidic cation exchanger has to be regenerated more frequently than if it is part of a separate auxiliary circuit of the membrane electrolysis cell. The rinsing solution cleaned in this way is returned to the process solution to compensate for the evaporation losses that occur during metal deposition.

In a preferred embodiment of the invention, the above-described method for separating interfering anions or interfering cations from a dilute process solution (or rinsing solution) with the pH value adjustment described above and subsequent metering of the metal ions using the metal ion-laden weak acid Cation exchanger combined. The metal ions of the coating metal are preferably fed into the previously cleaned solution with the aid of a weakly acidic cation exchanger which has previously been loaded with the metal ions of the coating metal. As a result, the pH in the returned solution is raised and the metal ions of the coating metal separated off by the strongly acidic cation exchanger are returned to the process solution. The eluate of the strongly acidic cation exchanger can be used after loading the pH of the weakly acidic cation exchanger with the metal ions of the coating metal.

This simplified process and plant technology also leads to a significant reduction in the foreign substance content in the process solution, but does not enable the good use of materials that can be achieved with the membrane electrolysis cell with auxiliary circuit described above.

Furthermore, the invention relates to a device for extending the useful life of a process solution for the chemical-reductive metal deposition, consisting of at least one weakly acidic cation exchanger for use for pH adjustment and the subsequent metering of ions of the coating metal in a system for the chemical-reductive metal deposition. The device has elements which serve to connect the inlet and outlet of the weakly acidic cation exchanger 14 to at least one container which contains process solution, diluted process solution, cooled process solution or pretreated process solution. Furthermore, the device contains associated peripherals, such as. B. pumps, valves, measuring devices for pH, conductivity, temperatures.

The weakly acidic cation exchanger 14 is connected with its inlet to at least one container which contains process solution, diluted process solution or cooled process solution or pretreated process solution. The drain of the weakly acidic cation exchanger 14 is connected directly to at least one container that contains process solution. In addition, the device contains measuring devices for monitoring the pH of the process solution and the pH in the outlet of the weakly acidic cation exchanger 14. The solution is enriched with ions of the coating metal by the weakly acidic cation exchanger. The risk of undesired metal deposition from such enriched solutions is high, especially when there is a sufficient amount of reducing agent. The inventive direct introduction of the process of the weakly acidic cation exchanger into the process solution minimizes undesired metal separation between the cation exchanger and the process bath.

The measuring device for monitoring the pH value in the outlet of the weakly acidic cation exchanger 14 makes it possible to continuously monitor the functionality of the weakly acidic cation exchanger, since the weakly acidic cation exchanger, as long as it is loaded with ions of the coating metal, increases the pH value of the ( acidic) solution. As soon as the ion exchanger is discharged, the pH of the drain corresponds to that of the solution added.

By comparing the pH value in the course of the weakly acidic cation exchanger with the pH value of the process solution, the exhaustion of the weakly acidic cation exchanger can be determined according to the invention before the pH value and the content of the process solution in ions of the coating metal leaves the tolerance range of the process. The device therefore makes it possible to keep the content of ions in the coating metal and the pH of the process solution almost constant.

The measuring device for monitoring the pH value is also suitable for connection to a computer and thus enables an automatic change to a second cation exchanger and the automatic control of the regeneration process. For its use according to the invention, the weakly acidic cation exchanger is loaded with the cations of the coating metal. This is preferably done in two steps: First, the weakly acidic cation exchanger is converted into the salt form with a lye, preferably with sodium hydroxide, for conditioning. For loading, it is then brought into contact with a water-soluble salt of the coating metal in dissolved form. In the case of chemical-reductive nickel deposition, for example an aqueous solution of nickel sulfate or nickel chloride is chosen for loading with metal ions.

The loading with metal ions is preferably carried out in two stages with differently concentrated metal salt solutions, with the second stage - preferably by means of a circulation - being completely loaded with metal ions of the coating metal. This step-by-step procedure ensures a complete transfer of the weakly acidic resin into the charge with ions of the coating metal and, at the same time, good use of the ions of the coating metal used.

After the loading process, the ion exchanger is washed with deionized water in order to remove the corresponding sodium salts from the ion exchanger so that they are not introduced into the process solution as foreign substances. When used according to the invention, the weakly acidic cation exchanger is charged with process solution and releases metal ions into it. At the same time, it binds protons. The maximum proton absorption capacity of the weakly acidic cation exchanger is achieved when it is completely converted into the salt form. The capacity is controlled via the pH value in its process. The pH value in the outlet of the weakly acidic cation exchanger drops when the metal ions have completely discharged and approaches the pH value of the inlet of the weakly acidic cation exchanger.

When fully discharged, the weakly acidic cation exchanger is in the H form. For the new use according to the invention, the weakly acidic cation exchanger must be converted back into the salt form with an alkali and then loaded with ions of the coating metal. The weakly acidic cation exchanger regenerated in this way can be used again for pH adjustment and for the replenishment of metal ions. The weakly acidic cation exchanger has a high selectivity for protons, so that the protons formed in the chemical-reductive metal deposition are bound by this cation exchanger. In return, the metal ions previously bound to the cation exchanger are released into the process solution.

The divalent cations used for metal deposition are more strongly bound by the weakly acidic cation exchanger than monovalent cations. The exchanger can therefore advantageously be converted into the salt form in a simple manner with sodium hydroxide solution and then loaded with the divalent cations of the coating metal. The column capacity of the weakly acidic cation exchanger is chosen according to the desired service life and the amount of metal to be deposited.

The cation exchanger preferably contains a weakly acidic cation exchanger material with carboxylic acid groups as functional groups.

It was found that the weakly acidic cation exchanger was brought into direct contact with the process solution and not only did the ions of the coating metal be replenished, but the pH of the process solution could also be adjusted. This is achieved in that the weakly acidic cation exchanger, when it comes into contact with the process solution, binds the H ⁺ ions formed during the metal deposition. By using the weakly acidic cation exchanger loaded with the cations of the coating metal, the addition of lye and metal salts to the process solution, which is necessary according to the prior art, is advantageously unnecessary in order to bind the H ⁺ ions and to replenish the used metal ions.

Since the pH value in the process solution can surprisingly also be set with the aid of the weakly acidic cation exchanger which is brought into contact with process solution, the addition of alkalis to the process solution, which is necessary according to the prior art, is also unnecessary.

By metering in the ions of the coating metal without interfering counterions and adjusting the pH without addition of alkali, the weakly acidic cation exchanger according to the invention compared to the prior art Technology, the necessary salt input into the process solution is considerably reduced. If a conventional system for chemical-reductive metal deposition is supplemented solely with the weakly acidic cation exchanger according to the invention, the service life of the process solution can be significantly extended.

Another object of the invention is a device for extending the useful life of a process solution for chemical-reductive metal deposition, consisting of at least one strongly acidic cation exchanger loaded with H + ions for use in the removal of disruptive cations in a system for chemical-reductive metal deposition. The device has elements for circulating the process solution or cooled or pretreated process solution via the strongly acidic cation exchanger 15. The strongly acidic cation exchanger 15 is connected with its inlet and outlet directly to at least one container which contains process solution, diluted process solution or cooled process solution or pretreated process solution. Furthermore, the device contains associated peripherals, such as. B. pumps, valves, measuring devices for pH, conductivity, temperatures.

The strongly acidic H + ion-loaded cation exchanger binds polyvalent ions and only releases equivalent amounts of H + ions until its capacity is exhausted. The cations bound to the exchanger are only removed when a sufficiently concentrated regeneration acid (e.g. hydrochloric acid, approx. 80 to 100 g / 1) is applied to the exchanger. This allows the removal of unwanted cations from the process solution.

Compounds which contain sulfonic acid groups as functional groups and are capable of ion exchange are used as the strongly acidic cation exchange materials. Depending on the concentration ratios, these bind all cationic metal ions and ammonium ions more strongly than protons. As a result, these cations from the feed solution are bound by the ion exchanger, while at the same time an equivalent amount of protons are released to the solution. According to the invention, the strongly acidic cation exchanger is used to remove cations from the process solution, the diluted process solution, the rinsing solution or the Regeneration solution used, for which the strongly acidic cation exchange material is converted into the H ⁺ form. This is done by applying an acid in the required concentration to the cation exchanger, with hydrochloric or sulfuric acid normally being used in practice.

The exhaustion of the column capacity of the exchanger is determined by measuring the conductivity in the inlet and outlet of the cation exchanger, a decrease in the difference in the inlet and outlet indicating the exhaustion of the column capacity of the strongly acidic cation exchanger.

To regenerate the loaded strongly acidic cation exchange material, it is converted back into its H ⁺ form by adding an excess of acid. The protons displace the bound cations from the functional groups of the exchanger. A larger excess of acid and possibly a higher acid concentration is required to remove polyvalent cations than to remove monovalent cations.

This device advantageously removes cationic foreign substances originating from the base material, such as Al ³⁺ , Sn ²⁺ , Zn ^2+, etc., as well as the disruptive cations of the replenished reducing agent, which can accumulate in the process solution.

The invention also relates to the combination of the weakly acidic cation exchanger described above with the strongly acidic cation exchanger described above in a device for use in a plant for chemical-reductive metal deposition in order to extend the useful life of a process solution for chemical-reductive metal deposition. The device contains at least one strongly acidic cation exchanger for the removal of interfering cations, which is connected in series or in parallel with at least one weakly acidic cation exchanger for use in adjusting the pH and replenishing ions of the coating metal. The device also has elements which serve to connect the weakly acidic cation exchanger and the strongly acidic cation exchanger to at least one container which contains process solution, dilute process solution, cooled process solution or pretreated process solution. Furthermore, the device contains associated peripherals, such as. B. pumps, valves, measuring devices for pH, conductivity, temperatures. The invention further relates to the combination of the strongly acidic cation exchanger described above with a weakly basic anion exchanger in a device for extending the service life of a process solution for chemical-reductive metal deposition. This device for use in a plant for chemical-reductive metal deposition consists of at least one strongly acidic cation exchanger for the removal of interfering cations with at least one weakly basic anion exchanger connected in series or in parallel with it for the removal of interfering anions. The device also has elements which serve to connect the strongly acidic cation exchanger and the weakly basic anion exchanger to at least one container which contains process solution, dilute process solution, cooled process solution or pretreated process solution. Furthermore, the device contains associated peripherals, such as. B. pumps, valves, measuring devices for pH, conductivity, temperatures.

Inorganic or organic materials with weakly basic functional groups, preferably with tertiary amines, are preferably used as weakly basic anion exchange materials. The weakly basic anion exchange material has specific selectivities and therefore binds sulfate, chloride and orthophosphite more strongly than hypophosphite. To use the weakly basic anion exchanger according to the invention, the functional groups of the weakly basic anion exchanger material have to be converted from the form of the free base into a protonated cationic form which is capable of ion exchange. This is done by taking up protons, for example by releasing acid. Due to the selectivity of the ion exchange material, certain anions, such as sulfate or orthophosphite, are preferably bound. These can also displace anions that are less firmly bound by the anion exchanger, such as hypophosphite, from the functional groups capable of ion exchange. This results in the separation of a given anion mixture. So that the exchanger is not converted from the cationic form into the free base form, which as an uncharged group is not capable of ion exchange, an acidic solution must always be applied to the weakly basic anion exchanger. The strongly acidic cation exchanger and the weakly basic anion exchanger are preferably connected in series, so that the outflow of the strongly acidic cation exchanger is connected to the feed of the weakly basic anion exchanger. When used according to the invention, the strongly acidic cation exchanger releases protons (H + ions) which are used for converting the functional groups of the weakly basic anion exchanger from the form of the free base to the protonated form which is capable of ion exchange. The strongly acidic cation exchanger thus adjusts the pH of the solution to an acidic value which is required for the use of the weakly basic anion exchanger. The weakly basic anion exchanger is regenerated by feeding in sodium hydroxide solution, as a result of which the weakly basic anion exchanger is converted from the protonated form into the form of the free base. In this form, the functional group no longer carries a charge and is therefore not capable of ion exchange. This allows all previously bound anions to be removed quantitatively from anion exchange material. After a rinsing process with demineralized water, the weakly basic anion exchanger can be used again for the removal of disruptive anions according to the invention.

The weakly basic anion exchanger separates the oxidized reducing agent and possibly the counterions of the replenished coating metal, and the disruptive counterions of the replenishing reducing agent are separated by the strongly acidic cation exchanger. Subsequent metering of the reducing agent in the form of a salt or as a corresponding salt solution therefore advantageously does not lead to a salting-up of the process solution when the combination of strongly acidic cation exchanger and weakly basic anion exchanger is used. Through the use of the strongly acidic cation exchanger according to the invention, activation of the weakly basic anion exchanger by phosphinic acid is not necessary.

In one embodiment of the invention, the device in which the strongly acidic cation exchanger is combined with the weakly basic anion exchanger as described above additionally contains at least one as described above Weakly acidic cation exchanger described for the pH adjustment and replenishment of ions of the coating metal.

Accordingly, this device additionally has elements which serve to connect the weakly acidic cation exchanger to at least one container, the process solution, dilute process solution, cooled process solution or pretreated process solution.

Furthermore, the invention relates to the combination of the strongly acidic H + ions-loaded strongly acidic cation exchanger 15 described above with the weakly acidic cation exchanger 14 loaded with ions of the coating metal.

In this combination, the strongly acidic cation exchanger is preceded by the weakly acidic cation exchanger.

Due to the strongly acidic cation exchanger loaded with H + ions, disruptive cations are removed from the process solution. B. come from the material to be coated. At the same time, however, ions of the coating metal are also bound by the strongly acidic cation exchanger and the pH in the applied solution is lowered. By giving up the strongly acidic cation exchanger on the weakly acidic cation exchanger, the pH of the solution is raised again and enriched with ions of the coating metal.

The combination of the strongly acidic H + ions-loaded strongly acidic cation exchanger 15 with the weakly acidic cation exchanger 14 loaded with ions of the coating metal thus advantageously makes it possible to remove disturbing cations from the process solution, to adjust the pH and to enrich the process solution with ions of the coating metal.

Another object of the invention is a device for extending the useful life of a process solution for chemical-reductive metal deposition for use in a system for chemical-reductive metal deposition, consisting of a membrane electrolysis cell with an auxiliary circuit. This device contains in the auxiliary circuit at least one weakly basic anion exchanger and at least one strongly acidic cation exchanger connected in series or in parallel with this.

When this device is used, the reducing agent consumed by the metal deposition is metered into the auxiliary circuit in the form of a salt or a salt solution.

The anion exchange membranes have on their surface functional groups with positively charged portions, which cause anions to pass through this membrane, while cations, with the exception of protons, cannot cross this barrier.

The membrane electrolysis cell consists of an anode (+) and a cathode (-) and at least four chambers arranged between the electrodes, which are separated from one another by ion-selective membranes.

The first chamber, the anode chamber 6, contains the anode and a dilute acid. This chamber is separated by a cation exchange membrane from a second chamber, the enrichment chamber 7, which contains regeneration solution. In the direction of the cathode, this chamber is separated from the third chamber 8 by an anion exchange membrane, which contains the process solution. The fourth chamber, the replenishment chamber 12, contains the cathode and is filled with regeneration solution. It is separated from the third chamber 8, which contains the process solution, by an anion exchange membrane.

The second, third and fourth chambers 7, 8 and 12 form a base unit which can be repeated several times to increase the membrane area used within the membrane electrolysis cell in order to be able to cope with a higher material throughput. However, when the total membrane area is increased by multiple arrangement of the chambers 7, 8 and 12, only one anode chamber 6 and one cathode are required, the replenishment chamber 12 of the base unit, which is furthest from the anode, contains a cathode.

Furthermore, the device contains elements which connect the third chamber 8 of the membrane electrolysis cell with at least one container, the cooled process solution, diluted cooled process solution, or pretreated cooled Process solution contains, serve, and preferably associated peripherals, such as. B. pumps, valves, measuring devices for pH, conductivity, temperatures.

The anion exchange membrane carries on its surface functional groups with positively charged groups which cause anions to pass through this membrane, while cations with the exception of protons cannot cross this barrier.

By feeding the process solution into a chamber of the membrane electrolysis plant, which is delimited by two anion exchange membranes and which is in contact with regeneration solution via the anion exchange membranes, anions migrate between the process solution and regeneration solution through the electric field applied between the electrodes.

The anions are transported from the process solution through the anion exchange membrane into the second chamber 7, which acts as an enrichment chamber and is connected to the fourth chamber 12 via a weakly basic anion exchanger. The reductant is metered into the fourth chamber 12 directly, or indirectly into a buffer tank for the auxiliary circuit 10 that acts as a metering container and is connected to this chamber. The fourth chamber 12 is therefore to be regarded as a metering chamber.

This combination according to the invention of the strongly acidic cation exchanger with the weakly basic anion exchanger can surprisingly even dispense with separate activation of the weakly basic anion exchanger after its regeneration in the auxiliary circuit since the salts contained in the auxiliary circuit are partially converted into the corresponding acids and added to the active groups of the anion exchanger ,

The membrane electrolysis cell described above is preferably combined with an auxiliary circuit with the weakly acidic and strongly acidic cation exchangers described above. The device for extending the useful life of a process solution for chemical-reductive metal deposition contains, in addition to the membrane electrolysis cell with an auxiliary circuit with an integrated strongly acidic cation exchanger and weakly basic anion exchanger, at least one weakly acidic cation exchanger and / or at least one further strongly acidic cation exchanger. The device also has elements with which the membrane electrolysis system with auxiliary circuit, the weakly acidic cation exchanger or the strongly acidic cation exchanger when used in a system for chemical-reductive metal deposition with a container, the process solution, diluted process solution, cooled process solution and / or pretreated Process solution contains to be connected.

The additional strongly acidic cation exchanger separates disruptive cations from the process solution. For this purpose, the process solution, diluted process solution, cooled process solution or pretreated process solution is preferably applied to it. The strongly acidic cation exchanger in the auxiliary circuit is not able to do this, because - due to the cell configuration in the membrane electrolysis plant - no cationic foreign substances with the exception of Ff ^{1 "} can get into the auxiliary circuit from the process solution.

By combining the membrane electrolysis cell with the weakly acidic cation exchanger according to the invention, a smaller amount of foreign matter is introduced into the process solution by replenishing the ions of the coating metal without disruptive anions. As a result, only a small amount of foreign matter has to be separated by the membrane electrolysis cell.

In a preferred embodiment of the invention, the above-mentioned ion exchangers are column exchangers which are filled with a solid, water-insoluble, ion exchange material. The organic or inorganic ion exchange material contains functional groups that are capable of ion exchange. These column exchangers can be regenerated in the same or opposite form.

In an alternative embodiment of the invention, the above-mentioned ion exchange materials are each part of a filter or membrane apparatus. This contains a regenerable, organic or inorganic ion exchange material, which is preferably introduced into the filter or membrane apparatus in a form capable of ion exchange. In a further embodiment of the invention, liquid ion exchange materials are used in at least one of the ion exchange materials used. In this embodiment, the ion exchanger (s) each consist of a container which contains a liquid which is immiscible with the process solution and in which an ion exchange material is distributed or dissolved. In this embodiment, the ion exchange material preferably consists of a reagent which contains the functional groups required for the ion exchange effect, such as are used, for example, in reactive extraction.

Another object of the invention is a plant for chemical-reductive metal deposition consisting of:

At least one coating container,

• a flushing system,

• and at least one of the devices described above for extending the service life of a process solution for chemical-reductive metal deposition.

Furthermore, the system contains connecting lines between the individual components and the associated peripherals, such as pumps, valves, measuring devices for pH value, conductivity, temperatures etc. The coating container contains the process solution in which the workpiece to be coated is immersed.

In its simplest form of filling, the system according to the invention consists of a coating container, a rinsing system and a device as described above with a weakly acidic cation exchanger for pH adjustment and subsequent metering of the metal to be separated, which is connected to the coating container with inlet and outlet.

In a second embodiment, the system additionally contains a weakly basic anion exchanger for the removal of interfering anions. In this combination, the introduction of the metal ions without disruptive anions enables the weakly basic anion exchanger to be used particularly efficiently, since it therefore essentially only the anions of the oxidized reducing agent, as a rule Orthophosphite, from which the reducing agent, usually hypophosphite, has to be separated.

In a further embodiment, the system additionally contains a strongly acidic cation exchanger for the separation of interfering cations.

In one embodiment of the system, the inlet and outlet of the weakly acidic or strongly acidic cation exchanger are directly connected to the coating container.

The process solution is preferably cooled before it is brought into contact with the sensitive components of the devices, in particular the ion exchange materials and the membranes. As a result of the cooling, the

The risk of undesired metal deposition on these components is reduced.

The process solution prepared by the device must be in the

Coating container is returned, raised to the process temperature again.

In a preferred embodiment of the system described above, the

Inlet and outlet of the weakly acidic or strongly acidic cation exchanger are therefore connected to the coating container via a heat exchanger. By the

The heat exchanger uses the energy of the cooling process to warm up the cleaned process solution.

In a preferred embodiment, the system contains a device as described above with a weakly acidic cation exchanger, a strongly acidic cation exchanger and a weakly basic anion exchanger.

The rinsing solution is a diluted process solution and can be added to the process solution to compensate for evaporation losses.

In an advantageous embodiment, the strongly acidic cation exchanger and the weakly basic anion exchanger are connected in series or in parallel with the rinsing system. The inlet of the weakly acidic cation exchanger is connected to the rinsing system or the regeneration tank and the outlet of the weakly acidic cation exchanger to the coating tank. In this embodiment, disruptive cations and anions are separated by the combination of strongly acidic cation exchanger and weakly basic anion exchanger described in the rinsing system. To compensate for evaporation losses, part of the rinsing solution is preferably fed into the process solution via the weakly acidic cation exchanger described, which is loaded with ions of the evacuation metal. As a result, both interfering cations and anions can advantageously be burned off in this system, metal ions can be replenished and the pH can be adjusted. The function of this system depends on the amount of process solution being carried into the rinsing solution and the evaporation losses.

In a particular embodiment of the system, the strongly acidic cation exchanger and the weakly basic anion exchanger are connected in series or in parallel with an additional regeneration tank 16 which is connected to the flushing system and is filled with a mixture of flushing solution and process solution.

In this system, disturbing cations and anions are separated and the cleaned solution is returned from a mixture of rinsing solution and process solution. In this system, the removal of foreign substances and the replenishment of ions of the coating metal advantageously take place largely independently of the amount of process solution being carried into the rinsing solution. In addition, the pH value in the regeneration tank can be set to a value that is most suitable for the cleaning process.

In a further preferred embodiment, the plant according to the invention contains, as the core, a membrane electrolysis cell with an auxiliary circuit, as described above, in which the process solution and auxiliary circuit are separated from one another by anion exchange membranes. The auxiliary circuit contains at least one weakly basic anion exchanger and one strongly acidic cation exchanger as further components.

The membrane electrolysis cell is preferably charged with process solution which has been cooled by the heat exchanger. For this purpose, the third chamber 8 is the Membrane electrolysis cell with its inlet and outlet connected to the coating container via a heat exchanger. In a preferred embodiment, a storage container for process solution 5 to be cleaned and a stacking container for cleaned process solution 13 are additionally connected between the heat exchanger and the membrane electrolysis cell.

In the membrane electrolysis cell, anions from the process solution are transported electrodialytically into the auxiliary circuit. The anion mixture is separated by the weakly basic anion exchanger. This removes the oxidized reducing agent and other disruptive anions (e.g. sulfate, chloride, orthophosphite). In a preferred embodiment, several weakly basic anion exchangers are connected in series in order to improve the separation performance and to increase the capacity in the auxiliary circuit.

The reducing agent is subsequently metered into the auxiliary circuit, the counterions of the reducing agent, preferably Na ⁺ ions, being prevented from being transported into the process solution through the anion exchange membranes. The setting of the acidic process conditions in the auxiliary circuit and the removal of the counterions of the reducing agent, preferably Na ⁺ ions, is carried out by means of a strongly acidic cation exchanger in the H ⁺ form. By contacting the process solution with the auxiliary circuit in the membrane electrolysis cell, the reducing agent is introduced into the process solution in a cation-free manner.

The process parameters required for the separation of the anions can advantageously be set by separating the process solution and auxiliary circuit in the auxiliary circuit without the composition of the process solution having to be changed at the same time.

The system with membrane electrolysis cell and auxiliary circuit preferably contains at least one weakly acidic cation exchanger as described above for adjusting the pH and for replenishing ions of the coating metal. In one embodiment, the weakly acidic cation exchanger is connected to the coating container and process solution is applied directly to it. To separate disruptive cations from the process solution, the system with a membrane electrolysis cell with auxiliary circuit preferably contains, in addition to the strongly acidic cation exchanger in the auxiliary circuit, at least one strongly acidic cation exchanger as described above, to which process solution or a dilute process solution is applied.

In one embodiment of the system with an auxiliary circuit, the strongly acidic cation exchanger is connected to the coating container. In this embodiment, the process solution is applied directly to it.

In a further embodiment of the system with membrane electrolysis cell and auxiliary circuit, the strongly acidic cation exchanger is connected with its inlet to the rinsing system and with its outlet to a storage container for process solution 5 to be cleaned. This storage container is connected between the coating container and the third chamber 8 of the membrane electrolysis cell. In this embodiment, a part of the rinsing solution is freed from interfering cations by the strongly acidic cation exchanger, an equivalent amount of protons being released. This pretreated and diluted process solution is preferably processed in a membrane electrolysis cell with an auxiliary circuit.

In a further embodiment of the system with a membrane electrolysis cell with an auxiliary circuit, the weakly acidic cation exchanger is connected in a regeneration circuit with inlet and outlet to the additional stacking container which contains the process solution prepared by the membrane electrolysis cell.

In a plant with a membrane electrolysis cell with an auxiliary circuit, the weakly acidic cation exchanger is connected in another preferred embodiment with its inlet to the third chamber of the membrane electrolysis cell and with its outlet via the heat exchanger to the coating container. A stack container for cleaned process solution (13) is preferably connected between the inlet of the weakly acidic cation exchanger and the third chamber of the membrane electrolysis cell. The invention also relates to the use of H + ions loaded strongly acidic cation exchange material or H + ions loaded strongly acidic cation exchangers for the removal of interfering cations to extend the useful life of a process solution for chemical-reductive metal deposition.

Another object of the invention is the use of a combination of a.) Weakly basic anion exchange material or weakly basic anion exchangers 9 for the removal of interfering anions and b.) H + ions loaded strongly acidic cation exchange material or H + ions loaded strongly acidic cation exchangers 11, 15 for the removal disruptive cations to extend the useful life of a process solution for chemical-redulctive metal deposition.

Another object of the invention is the use of a combination of a.) Weakly acidic cation exchange material or weakly acidic cation exchangers for pH adjustment and replenishment of ions of the coating metal and b.) Ions-loaded strongly acidic cation exchange material or H + ions-loaded strongly acidic cation exchangers 11, 15 for the removal of interfering cations to extend the useful life of a process solution for chemical-redulctive metal deposition.

Furthermore, the invention relates to the use of a combination of a.) Weakly basic anion exchange material or weakly basic anion exchangers 9 for the removal of interfering anions and b.) Weakly acidic cation exchange material or weakly acidic cation exchangers 14 for the pH adjustment and replenishment of ions of the coating metal and c .) strongly acidic cation exchange material or strongly acidic cation exchangers 11, 15 for the removal of interfering cations to extend the useful life of a process solution for the chemical-redulctive metal deposition. The weakly acidic cation exchanger loaded with ions of the metal used is preferably used as the last step in the workup. Its process is initiated directly in the process solution.

Compared to the prior art, the useful life of a process solution for the chemical-redulctive metal coating can be considerably extended by the invention. This advantageously results in a considerable saving in starting materials. At the same time, disposal costs are reduced, which are not insignificant according to the state of the art.

Furthermore, the invention advantageously achieves almost constant process conditions in the chemical-reductive metal coating and thus a particularly uniform deposition of the metal on the workpiece to be coated. Due to the low foreign matter content of the process solution, which is achieved in the system according to the invention, nickel-phosphorus layers can be deposited which are in the compressive stress range, which in particular brings about the quality of the coating of the deposition.

Exemplary embodiments of the invention are shown and described schematically with the aid of the following drawings. Show:

Fig. 1 plant with weakly acidic cation exchanger for pH adjustment and replenishment of ions of the coating metal

Fig. 2: System with heat exchanger and weakly acidic cation exchanger for pH adjustment and replenishment of ions of the coating metal

Fig. 3: System with weakly acidic cation exchanger for pH adjustment and replenishment of ions of the coating metal as well as weakly basic anion exchanger and strongly acidic cation exchanger for the separation of interfering ions from the rinsing solution Fig. 4: Plant for adjusting the pH value and replenishing ions of the coating metal and separating interfering ions from a dilute process solution

5: Device for replenishing the reducing agent and for separating disruptive anions in a membrane electrolytic cell with an auxiliary circuit

Fig. 6: Extended device for replenishing the reducing agent and for separating disruptive anions in a membrane electrolysis cell with auxiliary circuit

Fig. 7: System with membrane electrolytic cell with auxiliary circuit

Fig. 8: System with membrane electrolysis cell with auxiliary circuit and weakly acidic cation exchanger for pH adjustment and replenishment of ions of the coating metal

Fig. 9: System with membrane electrolysis cell with auxiliary circuit, weakly acidic cation exchanger for pH adjustment and replenishment of ions of the coating metal and strongly acidic cation exchanger for regeneration of the process solution

Fig. 10: System with membrane electrolytic cell with auxiliary circuit, a weakly acidic cation exchanger connected to the stacking container for pH adjustment and replenishment of ions of the coating metal and strongly acidic cation exchanger for regeneration of the process solution

Fig. 11: System with membrane electrolytic cell with auxiliary circuit and indirect regeneration of the process solution via the rinsing system, as well as pH adjustment and replenishment of ions of the coating metal by a between the stacking container and. Coating tank switched weakly acidic cation exchanger 1 shows a diagram of a plant for chemical-reductive metal coating, in which the required ions of the coating metal are replenished without disturbing anions by means of a weakly acidic cation exchanger 14 loaded with ions of the coating metal, and at the same time the pH of the process solution is adjusted and thus the useful life the process solution can be extended.

1 consists of a coating container 1, a multi-stage rinsing system 3 in cascade connection and a weakly acidic cation exchanger 14, as well as connecting lines and associated peripherals, such as pumps, valves, measuring devices for pH, conductivity, temperatures, etc. The latter were for reasons the clarity is not shown in Fig. 1. The coating container 1 contains process solution in which a workpiece 2 to be coated is immersed. The workpiece 2 to be coated has a surface made of steel.

The multi-stage rinsing system 3 consists of three cascade-connected containers which contain an aqueous rinsing solution. Between the left and right washing containers 3, as indicated by the broken line in FIG. 1 but not shown, a further washing container is arranged. The left rinse tank 3 contains an inlet for fresh water. The right washing container 3 is connected to the coating container 1.

The weakly acidic cation exchanger 14 is connected with its inlet and outlet to the coating container 1, so that a certain volume flow of the process solution can be passed through it.

The weakly acidic cation exchanger consists of an ion exchange column 14 which is filled with the weakly acidic cation exchanger polymer Lewatit CNP 80 from Bayer AG, Leverkusen, Germany. However, comparable weakly acidic cation exchange polymers from other manufacturers, such as C 104 from Purolite, Ratingen, Germany.

This weakly acidic cation exchange polymer is loaded with ions of the coating metal before use. For this purpose, the ion exchanger is first converted into the salt form with sodium hydroxide solution and then loaded with ions of the coating metal by applying a metal salt solution. In the case of chemical Reductive nickel plating is used to load the weakly acidic cation exchange polymer with nickel ions, for which purpose a NiSO ₄ solution is passed over the ion exchange column. This loading takes place in two steps with nickel salt solutions of different concentrations, with a deficit of nickel ions being applied to the ion exchanger in the first loading step. Due to the selectivity of the cation exchanger, an almost complete removal of the nickel ions from the feed solution is achieved, which is discarded after loading and treated with waste water. In the second loading step, by using an excess of nickel ions when loading the ion exchanger and circulating the feed solution, the weakly acidic cation exchanger is fully loaded with nickel.

After the nickel loading process, the weakly acidic cation exchanger is washed with deionized water in order to remove interfering ions from the polymer bulk layer. This rinsing process removes the excess nickel ions from the polymer bulk layer. The sequence of the second fraction of the loading process is stacked together with the first fraction of the rinsing water and used as the first loading fraction in the subsequent loading of the weakly acidic cation exchanger.

The process solution is composed in a known manner. When newly prepared, the ions of the coating metal in the form of nickel sulfate (6.0 g Ni ²⁺ / 1) are added to it. The reducing agent is added in the form of sodium hypophosphite (17.0 g H ₂ PO ₂ 71). The solution is buffered in the pH 4 to pH 5 range by the organic acids contained in the process solution.

To deposit nickel-phosphorus alloys on the steel surface of a workpiece 2 to be coated, the system shown in FIG. 1 is used as follows:

The temperature of the process solution, which surrounds the workpiece 2 to be coated, is adjusted to 85 ° C. Metal ions deposit on the steel surface of the workpiece 2 to be coated. During the deposition, elemental phosphorus, which is formed from the reductant by secondary reactions, is also alloyed into the resulting metal layer, which results in a nickel-phosphorus alloy. The redox process of chemical-reductive metal deposition oxidizes the reducing agent sodium hypophosphite to sodium orthophosphite. This consumption of reducing agent is compensated for by adding sodium hypophosphite to the process solution.

Due to the metal deposition, the pH value and the nickel content in the process solution also decrease. The pH value in the process solution is therefore monitored. If the pH of the process solution drops below a specified value, e.g. from pH 4.5 to pH 4.2, then a partial stream of the process solution is passed through the weakly acidic cation exchanger 14 in a circuit at a flow rate of <5 m / h. This results in an increase in the nickel content from 5 g / 1 to 8 g / 1 and an increase in the pH from 4.2 to pH> 5 in the course of the weakly acidic cation exchanger 14.

The functionality of the weakly acidic cation exchanger is monitored by checking the pH in the outlet of the weakly acidic cation exchanger 14. With increasing metal release, the weakly acidic cation exchanger is converted into the H ⁺ form, which is why the pH value in the outlet of the cation exchanger drops. If the pH value in the outlet of the weakly acidic cation exchanger approaches the pH value of the process solution (in this case pH 4.5), the cation exchanger is transferred back to the nickel loading for reuse, as described at the beginning.

In the case of metal coating, the high treatment temperatures result in evaporation losses in the process solution. These evaporation losses are compensated for in the rinsing solution from the rinsing system 3, through the line shown by an arrow in FIG. 1, from the right rinsing bath into the process solution, since the concentration of the rinse water constituents is highest in this container. listed, which were obtained in the comparative test described.

In the comparative test (see right column of the table), the salt content in the process solution rises to high values after a metal throughput of 5.5 MTO due to the foreign substances introduced or formed (in particular Na ⁺ , SO ^{2 "} , H ₂ PO ₃ ^" ) , so that at this point the deposition rate drops to <5 μm / h at 90 ° C and the properties of the deposited layers no longer meet the requirements.

When the weakly acidic cation exchanger 14 is used according to the invention (see the two middle columns of the table), however, the SO ₄ ^" content of the process solution does not increase with increasing metal throughput, since the nickel ions are introduced into the process solution without disturbing SO ₄ ^2" . In contrast to the comparative experiment, the Na ⁺ content rises considerably more slowly here, since the pH is adjusted without adding NaOH to the process solution. By using the weakly acidic cation exchanger 14, the process solution can increase by up to the slower increase in the foreign substance content can be used for a metal throughput of approx. 8 MTO. The service life of the process solution is thus almost doubled through the use of the weakly acidic cation exchanger 14 according to the invention.

FIG. 2 shows a diagram of a plant for chemical-reductive metal coating with a weakly acidic cation exchanger 14, which also has a heat exchanger 4 the coating container 1 is connected. With regard to the coating container 1 and the rinsing system 3, this system is constructed in accordance with the system from FIG. 1. As further components, this system contains a storage container 5 and a stacking container 13, which are each connected to the coating container 1 via the heat exchanger 4.

The structure of the weakly acidic cation exchanger 14 corresponds to that of FIG. 1. In contrast to FIG. 1, however, in this system it is not directly connected to the coating container 1, but with its inlet to the storage container 5 and with its outlet to the stacking container 13 ,

In principle, the metal coating in this installation is as described for FIG. 1. However, the weakly acidic cation exchanger 14 is loaded with cooled process solution. For this purpose, a volume flow of the process solution is passed over the heat exchanger 4 and cooled in it from the treatment temperature of 85 ° C to temperatures <50 ° C. This cooled solution is collected in the storage container 5 and passed out of it via the weakly acidic cation exchanger 14. By means of the weakly acidic cation exchanger 14, in an analogy to FIG. 1, the treated solution is enriched with nickel ions and the pH is raised. The treated solution is collected in the stacking container 13 and fed back to the coating container 1 via the heat exchanger 4.

By using the heat exchanger 4, the weakly acidic cation exchanger 14 is charged with a cooled process solution, which increases the risk of chemical-reductive metal deposition on the

Cation exchange polymer significantly reduced.

3 shows a diagram of a plant for chemical-reductive metal coating, in which the service life of the process solution can be extended, with a weakly acidic cation exchanger 14 for replenishing the metal ions and adjusting the pH, as well as a strongly acidic cation exchanger 15 and a weakly basic anion exchanger 9 for the removal of interfering ions from the rinsing solution. With regard to the coating container 1 and the rinsing system 3, the structure of the system corresponds to the system shown in FIG. 1.

The structure of the weakly acidic cation exchanger 14 corresponds to that of the cation exchanger described for FIG. 1. In contrast to FIG. 1, however, rinsing solution is applied to the weakly acidic cation exchanger 14. Therefore, in contrast to FIG. 1, the weakly acidic cation exchanger 14 is connected with its inlet to the right-hand container of the rinsing system 3, in which the rinsing solution with the highest concentration of carried-out components of the process solution is located. The drain of the weakly acidic cation exchanger 14 is connected to the coating container 1.

As further components, this system contains a strongly acidic cation exchanger 15 and a weakly basic anion exchanger 9, which are connected to the right-hand container of the rinsing system 3 in a regeneration circuit. The inlet of the strongly acidic cation exchanger 15 is connected to the right rinse tank 3 and its outlet is connected to the inlet of the weakly basic anion exchanger 9. The drain of the weakly basic anion exchanger 9 is in turn connected to the right rinse tank 3.

The strongly acidic cation exchanger 15 consists of an ion exchange column which is filled with the strongly acidic, macroporous cation exchange polymer, Lewatit SP 112 from Bayer AG, Leverkusen, Germany, in the H ⁺ loading. Comparable strongly acidic polymers from other manufacturers, such as the strongly acidic cation exchange polymer C 150 from Purolite, Ratingen, Germany, can also be used. Before use, the strongly acidic cation exchanger 15 is charged with hydrochloric acid and thereby loaded with protons.

The weakly basic anion exchanger 9 consists of a column filled with the weakly basic, macroporous anion exchanger polymer, Lewatit MP 62 from Bayer AG, Leverkusen, Germany. Comparable weakly basic anion exchange polymers from other manufacturers, such as the weakly basic anion exchange polymer A 100 from Purolite, Ratingen, Germany, can also be used. Before use, the weakly basic Anion exchanger 9 is charged with sodium hydroxide solution, thereby converting the anion exchanger polymer into the form of the free base.

The column capacity of the ion exchange column 15 filled with cation exchange material in the IT form is higher than the column capacity of the ion exchange column 9 filled with weakly basic anion exchange material.

The metal coating in this system is carried out analogously to the procedure described for FIG. 1, but the rinsing solution which is fed to the coating container 1 to compensate for evaporation losses is processed with the ion exchangers 9, 14, 15. For the chemical-reductive deposition of nickel on steel surfaces, the workpiece 2 is treated in the coating container 1 at a temperature of the process solution of approximately 85 ° C. The process solution has a pH of 4.5 and a nickel content of 6.0 g / 1 at the beginning of the process. The metal deposition reduces the pH value and the nickel content in the process solution.

After coating, the coated workpiece 2 is immersed in the rinsing container of the rinsing system 3. With the workpiece, part of the process solution is dragged into the rinsing solution of the rinsing system. A certain mass flow of components, including the foreign substances produced, is transferred from the process solution to the rinsing solution by means of the electrolyte extraction, whereby a cleaning effect is achieved in the process solution. This means that some of the protons and other ions that are formed by the chemical-reductive nickel deposition get from the process solution into the rinsing solution. The rinsing solution is therefore a diluted process solution.

To compensate for evaporation losses in the process solution, the rinsing solution is passed over the weakly acidic nickel-loaded cation exchanger 14, which is constructed and loaded as described in relation to FIG. 1. This releases nickel ions into the solution and binds protons. Thus, the process solution with the supplied rinsing solution is simultaneously supplied with ions of the coating metal, and the consumption caused by the metal deposition is compensated. At the same time, protons are withdrawn from the supplied solution by the weakly acidic cation exchanger 14: the pH of the process solution is also reduced with the supplied rinsing solution set. The capacity of the weakly acidic cation exchanger 14 is checked, as described in relation to FIG. 1, by measuring the pH value in its flow.

The used reducing agent is then metered in by adding sodium lyophosphite to the process solution.

To prepare the rinsing solution, a volume flow is passed over the strongly acidic cation exchanger 15 in the IT loading. The strongly acidic cation exchanger 15 binds interfering cations, which come primarily from the reducing agent and the base material of the workpiece to be coated, and releases protons into the solution. However, nickel ions are also removed from the rinsing solution.

According to its selectivity, the strongly acidic cation exchanger 15 binds cations in the solution until its capacity limit is reached and releases an equivalent amount of protons into the solution. In addition to the cations of the reducing agent and the alkali used to adjust the pH, the cations of the coating metal and the cations originating from the base material are also removed, polyvalent cations preferably being bound.

The exhaustion of the capacity of the cation exchanger 15 is controlled, as is customary in the prior art, by measuring the conductivity in the inlet and outlet of the cation exchanger 15. As soon as the difference in the conductivity values in the inlet and outlet of the cation exchanger 15 has dropped below a defined value, the strongly acidic cation exchanger 15 is regenerated.

For regeneration, it is again loaded with protons in a known manner by adding hydrochloric acid at a concentration of 70 g / 1 to 100 g / 1 and can be used again after a rinsing process with fully demineralized water to extend the useful life of the process solution.

The rinsing solution acidified by the strongly acidic cation exchanger 15 is now passed over the weakly basic anion exchanger 9, which is in the form of the free base. This binds disruptive anions, such as. B. the anions of the oxidized reducing agent orthosphoshite, in which the acids formed by the strongly acidic cation exchanger 15 are first attached to the functional groups. By the acid the tertiary amines, the functional groups of the ion-exchange are protonated and thereby converted into the Ammom ^'to form. Only the ammonium form is capable of anion exchange. Due to the selectivity of the ion exchange polymer, certain anions, such as, for example, sulfate or orthophosphite, are preferably bound and can also displace anions which are less firmly bound by the anion exchanger, such as, for example, hypophosphite, from the functional groups capable of ion exchange. This separates the anion mixture. So that the anion exchange polymer is not converted from the ammonium form into the form of the free base, which as an uncharged group is not capable of ion exchange, an acidic solution is always added to the weakly basic anion exchanger 9.

The weakly basic anion exchanger 9 is regenerated by feeding in sodium hydroxide solution, as a result of which the weakly basic anion exchanger 9 is converted from the ammonium form into the form of the free base. In this form, the functional group has no charge and is therefore not capable of ion exchange. This allows all of the previously bound anions to be removed quantitatively from the anion exchange polymer. After a rinsing process with deionized water, the weakly basic anion exchanger 9 can be used again for the removal of interfering anions.

The rinsing solution further cleaned by the weakly basic anion exchanger 9 is returned to the rinsing system, where, as described above, it is fed to the coating container 1 via the weakly acidic cation exchanger 14 to compensate for evaporation losses in the process solution. This preparation of the rinsing solution by the strongly acidic cation exchanger 15 and the weakly basic anion exchanger 9 takes place in batch operation. The strongly acidic cation exchanger 15 in this system also removes ions of the coating metal that have entered the rinsing solution from the process solution. However, these are replenished by the weakly acidic cation exchanger 14.

The eluate resulting from the regeneration of the strongly acidic cation exchanger 15 is used again after loading the pH value with sodium hydroxide solution to pH> 4.5 for loading the weakly acidic cation exchanger 14, whereby the separated metal ions of the coating metal are not lost. However, the eluate is only used as long as it is not contaminated with the metal ions of the base material from the workpieces 2 to be coated, which are foreign substances

The indirect cleaning of the process solution via the rinsing system 3 has the advantage that the concentration of the reducing agent and the metal ions of the coating metal in the rinsing solution are lower than in the process solution. This reduces the risk that sensitive components of the cleaning device, such as e.g. Ion exchange materials that are inadvertently chemically reductively metallized.

Due to the removal of disruptive anions from the rinsing solution described in this embodiment and the replenishment of nickel ions via a weakly acidic cation exchanger 14 loaded with nickel ions, an extension of the service life of the process solution can be achieved with sufficiently high drag-out and evaporation losses. The amount of drag required to clean the process solution is determined using equation 2. In the present example, the following parameters were determined in the process solution with a specific drag-out of 300 ml / m ² after 6 MTO and 12 MTO throughput.

When this system is used according to the invention, the SO ₄ ^{2 "} content of the process solution does not increase with the metal throughput, since the nickel ions are acidic cation exchanger 14 without an interfering anion (SO ₄ ^" ) are introduced into the process solution. In comparison to the prior art, the concentration of sodium ions increases considerably more slowly, since the pH is adjusted by the weakly acidic cation exchanger 14 and not, as is the case after the state of the art, by adding sodium hydroxide solution to the process solution. Compared to the system from FIG. 1, there is an additional reduction in the concentration of sodium ions and oxidized reducing agent (H ₂ PO ₃ ^" ), since with the aid of the strongly acidic cation exchanger 15 Sodium ions and with the aid of the weakly basic anion exchanger 9 H ₂ PO ₃ ^' ions are removed. As a result, the service life of the process solution can be extended from approx. 5.5 MTO to approx. 12 MTO.

In order to be able to stabilize the orthophosphite content at a value <120 g / 1 via the electrolyte extraction into the rinsing solution, an electrolyte extraction> 4 1 / m ² would be required if 10 μm nickel was deposited.

4 shows a diagram of a plant for chemical-reductive metal coating, in which the service life of the process solution can be extended, with a weakly acidic cation exchanger 14 for replenishing the metal ions and adjusting the pH, as well as a strongly acidic cation exchanger 15 and a weakly basic one Anion exchanger 9 for the separation of interfering ions from a dilute process solution.

With regard to the coating container 1 and the rinsing system 3, the structure of the system corresponds to the system shown in FIG. 1. The right rinse tank 3 is not connected directly to the coating tank 1 in this system, but to an additional regeneration tank 16. This connection enables the regeneration tank 16 to be supplied with rinsing solution. There is also a connection from the coating container 1 to the regeneration container 16, through which this process solution can be supplied. Through this connection, the required amount of process solution can be removed from the coating container 1, which is required for the complete transfer of the foreign substances formed during the chemical-reductive metal deposition into the regeneration container 16. The regeneration tank 16 is connected to a strongly acidic cation exchanger 15 and a weakly basic anion exchanger 9, which are connected in series. The inlet of the strongly acidic cation exchanger 15 is connected to the regeneration tank 16 and its outlet is connected to the inlet of the weakly basic anion exchanger 9. The outflow of the weakly basic anion exchanger 9 is in turn connected to the regeneration container 16. In addition, the feed of the weakly basic anion exchanger 9 is connected directly to the regeneration tank 16 via an additional line. Through this connection, the weakly basic anion exchanger 9 will be charged directly with the diluted process solution if necessary. These two ion exchangers 9, 15 correspond in their respective structure and in their mode of operation to those from FIG. 3.

The inlet of the weakly acidic cation exchanger 14 is connected to the regeneration tank 16 and the outlet of the weakly acidic cation exchanger 14 is connected to the coating tank 1. The weakly acidic cation exchanger 14 corresponds to the cation exchanger described in FIG. 1 in terms of its structure and mode of operation. The metal coating in this system is carried out analogously to the procedure described for FIG 9, 14 and 15 mixed with process solution in a regeneration tank 16. As a result, the required amount of process solution which is required for the complete transfer of the foreign substances formed in the chemical-reductive metal deposition into the regeneration tank 16 can be removed from the coating tank 1. In contrast to FIG. 3, the reducing agent is replenished in the regeneration tank 16 in this system.

For the chemical-reductive deposition of nickel on steel surfaces, the workpiece 2 is treated in the coating container 1 at a temperature of approximately 85 ° C. The process solution has a pH of 4.5 and a nickel content of 6.0 g / 1 at the beginning of the process. The metal deposition reduces the pH value and the nickel content in the process solution. The reducing agent NaH ₂ PO ₂ is subsequently metered into the regeneration tank 16 in aqueous solution. To prepare the process solution, a certain volume of the process solution is fed from the coating container 1 to the regeneration container 16 and is diluted there with rinsing solution. This diluted process solution is passed from the regeneration tank 16 in a partial flow over the strongly acidic cation exchanger 15 in the H ⁺ loading. This binds disruptive cations, which come primarily from the reducing agent and the base material of the workpiece to be coated, and releases protons into the solution. However, nickel ions are also removed from the solution. The acidified solution is placed on a weakly basic anion exchanger 9, which is in the form of the free base. By giving up the acidified solution, it is converted into the protonated form capable of anion exchange. Due to the selectivity of the anion exchange polymer, anions such as sulfate or orthophosphite are more strongly bound and anions which are less firmly bound by the exchange polymer can be displaced again by the exchanger 9. This achieves the preferred binding of sulfate and orthophosphite, which removes these anions from the diluted process solution. The outflow of the weakly basic anion exchanger 9 is returned to the regeneration container 16, so that an efficient removal of the interfering ions is possible via the circuit.

The cleaned solution is fed from the regeneration tank 16 via the weakly acidic cation exchanger 14 into the coating tank 1 in order to compensate for the evaporation losses. This ensures that the protons introduced during the cleaning process are removed again and that the ions of the coating metal are simultaneously introduced into the process solution without a disruptive anion.

Due to the direct connection of the coating container 1 and the regeneration container 16, the required volume of process solution is transferred into the regeneration container 16 and passed out of it via the ion exchanger. In the plant from FIG. 4, the volume of process solution passed through the ion exchanger can advantageously be set in the rinsing water, in contrast to the plant from FIG. 3, regardless of the value of the electrolyte drag-out. The desired concentration of foreign substances in the process solution can be set by setting the volume flow of process solution. Its value is calculated using equation 2. By avoiding the accumulation of foreign substances, the useful life of the process solution in the system described here from FIG. 4 can be extended significantly above 20 MTO.

5 shows a diagram of a device for extending the useful life of the process solution, in which the redosing agent is replenished and disruptive anions are separated off in an auxiliary circuit.

The core of this device is a membrane electrolysis cell. This consists of a cathode (-) and an anode (+) and each of the chambers 6, 7, 8, 12, which are arranged between the electrodes, these chambers forming a basic unit. To increase the capacity, the membrane electrolytic cell can be expanded by further chambers 7, 8 and 12, these being arranged between the chambers 6 and 7.

The chambers 6 and 7 and the chambers 12 and 7 are each separated from one another by a cation exchange membrane K1. The chambers 7 and 8 are each separated by an anion exchange membrane AI, and the chambers 8 and 12 are separated by an anion exchange membrane A2. Membranes of the Neosepta CMX type, from Tokuyama Soda, Tokuyama City, Japan, are used as the cation exchange membrane K1 and AI and A2 membranes of the Neosepta AMX type, Tokuyama Soda, Tokuyama City, Japan, are used as anion exchange membranes.

In addition to the membrane electrolysis cell, the device contains a weakly basic anion exchanger 9 for separating the anion mixture and a strongly acidic cation exchanger 11 for removing interfering cations. These are part of the auxiliary circuit of the membrane electrolysis cell. The structure and loading of the strongly acidic cation exchanger 11 of the auxiliary circuit corresponds to that of the strongly acidic cation exchanger 15 from FIG. 3. The weakly basic anion exchanger 9 also corresponds to that from FIG. 3 in construction and loading. Furthermore, the device contains a buffer container 10, in which the reducing agent to be added is added. The inlet of the weakly basic anion exchanger 9 is connected to chamber 7 and the outlet to the buffer container 10. An auxiliary circuit is set up by connecting the buffer container 10 to the chamber 12. The buffer container 10 is connected in a further small circuit to the inlet and outlet of the strongly acidic cation exchanger 11. The two ion exchange columns 9, 11 are acted on in a known manner with the aid of pumps, in a DC mode. Alternatively, a countercurrent mode of operation is also possible.

Furthermore, the device contains a storage container 5 for the process solution to be processed and a stacking container 13 for the processed process solution. The storage container 5 is connected to the inlet and the stacking container 13 to the outlet of the chamber 8 of the membrane electrolysis system.

The chambers 8 of the membrane electrolysis system or the storage container 5 and stacking container 13, which are filled with process solution, are shown hatched. The chambers without hatching contain regeneration solution 7, 12 or a dilute acid (chamber 6). The regeneration solution consists of an aqueous sodium hypophosphite solution (approx. 50 g / 1) and is partially converted into phosphinic acid by the action on the strongly acidic cation exchanger 15. Due to the electro-dialytic transport of the anions from the process solution, the regeneration solution also contains certain amounts of these anions, these amounts being dependent on the state of charge of the anion exchanger 9.

To extend their useful life, the anions in this device are removed cation-free from a process solution that was used in the chemical-reductive metal deposition, and at the same time the reductant is added. For this purpose, as explained by way of example for the chemically reductive nickel coating, the procedure is as follows:

The reservoir 5 is filled with cooled, process solution to be prepared. The process solution is passed from the reservoir 5 into the chambers 8 of the membrane electrolysis cell delimited by anion exchange membranes AI and A2. The anions contained in the process solution (sulfate, chloride, hypophosphite, orthophosphite and in some cases also the anions of the organic acids contained in the process solution) migrate through the anion exchange membrane AI by electro-dialysis and get into the chamber 7, which is delimited by the cation exchange membrane K 1 to the anode (+) or to the chamber 12 and in which there is a dilute acid. Protons, which are formed by water decomposition at the anode (+), enter the chamber 7 from the anode chamber 6 and, together with the electrodialytically transported anions, form the corresponding free acids. The anions are prevented from passing into the anode chamber 6 or into the chamber 12 by the cation exchange membrane K1.

The acid mixture in chamber 7 is passed over the weakly basic anion exchanger 9 in the form of the free base. The weakly basic anion exchanger 9 binds the acids formed in chamber 7 until its capacity is fully utilized. At the same time, it is converted from the form of the free base to the protonated form. He then preferentially binds sulfate, chloride and orthophosphite ions and releases an equivalent amount of previously bound hypophosphite ions.

The flow of the anion exchanger 9 is transferred to the buffer tank 10 of the auxiliary circuit. There the reducing agent is added in the form of sodium lyophosphite. The regeneration solution is passed from this buffer container in a small circuit over a strongly acidic cation exchanger 11 which is loaded with protons. This cation exchanger 11 removes the sodium ions which have entered the regeneration solution as sodium hypophosphite as a result of the subsequent addition of the reducing agent.

The regeneration solution is passed from the buffer container 10 into the chamber 12 of the membrane electrolysis cell, the terminal chamber 12 of the membrane electrolysis cell containing the cathode (-). The hypophosphite ions migrate electrodialytically from the chamber 12 through the anion exchange membrane A2 into the process solution located in the chamber 8.

Since no cations are removed from the process solution by the regeneration process in the membrane electrolysis cell, the salt content in the prepared process solution does not change by the regeneration process. Only sulfate, chloride and orthophosphite ions are removed from the solution and replaced by an equivalent amount of hypophosphite ions. This enriches the process solution with reducing agents. The process solution prepared in this way is created from the Katmner 8 passed into the stacking container 13 and can be used again for the chemical-reductive metal coating.

6 shows a diagram of a device for extending the service life of the process solution, in which the reducing agent is replenished and interfering anions are removed in an auxiliary circuit of a membrane electrolysis cell. In order to increase the throughput, the membrane electrolytic cell is expanded by additional chambers compared to FIG. 5. This membrane electrolysis system contains 40 units of the chambers 7, 8, 12. However, for the sake of simplicity, only three units of the chambers 7, 8, 12 are shown in FIG. 6.

The additional chambers increase the membrane area required for ion transport, via which the process and regeneration solutions are in contact with each other. This means that the transport performance required to burn off a given load of foreign substances can be achieved in the preparation process.

In order to extend the useful life of a process solution that was used in the chemical-reductive metal deposition, the process solution used in this device is enriched with reducing agent and, at the same time, disruptive anions are separated from it. The procedure for this is analogous to the description of FIG. A voltage of 90 V is applied to the expanded membrane electrolysis cell with 40 units.

FIG. 7 shows a schematic of a plant for chemical-reductive metal coating, in which the useful life of the process solution is extended by the removal of interfering anions and the metering of the reducing agent in a membrane electrolytic cell with an auxiliary circuit. With regard to the coating container 1, the rinsing system 3 and the heat exchanger 4, this system is constructed in accordance with the system from FIG. 2. As an additional component, the system contains a device for the removal of interfering anions and for the subsequent addition of the reductant, in which the anion mixture is separated in an auxiliary circuit. The structure of the device corresponds to that of FIG. 6 and contains 40 units of the chambers 7, 8, 12. In FIG. 7, however, only two units of the chambers 7, 8, 12 are shown in the simpler illustration. The storage container 5 and the stacking container 13 of the Devices are connected to the coating container 1 via the heat exchanger 4, as in FIG. 2.

For the chemical-reductive deposition of nickel on steel surfaces, the procedure in this system is as follows: The workpiece 2 is treated in the coating container 1 at a temperature of approximately 85 ° C. in analogy to the description of FIG. 1. The process solution has a pH of 4.5 and a nickel content of 6.0 g / 1 at the beginning of the process. The metal deposition reduces the pH value and the nickel content in the process solution. The used ions of the coating metal are subsequently metered in by adding nickel sulfate to the process solution. The pH is adjusted by adding sodium hydroxide solution to the process solution.

The metering of the reducing agent and the removal of interfering anions are carried out in this system in an auxiliary circuit as described for FIG. 5. For this purpose, a certain volume of the process solution is removed from the coating container 1 and, according to the description of FIG. 2, cooled to temperatures <50 ° C. via the heat exchanger 4 and collected in the storage container 5. The required volume volume is calculated using equation (2). For cooling in the heat exchanger 4, processed process solution is used, which is removed from the stacking container 13 for this purpose and is passed into the process solution.

The process solution, as described for FIG. 5, is brought into contact with the auxiliary circuit in the membrane electrolysis cell from the storage container 5. A voltage of 90 V is applied to the membrane electrolytic cell with 40 units. In the membrane electrolytic cell, disruptive anions are separated from the process solution by contact with the auxiliary circuit and the applied voltage, and at the same time reducing agent is metered into the process solution without cations. The processed process solution is fed to the stacking container 13 and brought back to the process temperature via the heat exchanger 4 analogously to the description of FIG. 2 and returned to the coating container 1.

When using the system according to the invention, the following parameters for the process solution result depending on the metal throughput:

The removal of disruptive anions and the cation-free subsequent dosing of the reducing agent in the auxiliary circuit significantly reduce the increase in foreign matter. With the plant shown in FIG. 7, however, no cations can be removed from the process solution. The pH is adjusted by adding sodium hydroxide solution to the process solution, which means that cations have entered the process solution. Due to the resulting salting, this limits the service life of the process solution, which increases the hypophosphite concentration in the process solution.

By separating interfering anions in the auxiliary circuit and replenishing the reductant without interfering cations, the service life of the process solution can be extended to at least 12 MTO, the orthophosphite concentration in the process solution being increased by the volume of process solution that is passed through the membrane electrolytic cell adjusted and a sharp increase in the hypophosphite concentration in the process solution is avoided. The volume flows are calculated according to equation 2.

Fig. 8 shows a diagram of a plant for chemical-reductive metal coating, in which the service life of the process solution by a weakly acidic cation exchanger 14 for replenishing the ions of the coating metal and adjusting the pH and the removal of disruptive anions and the replenishment of Reducing agent is extended in an auxiliary circuit. The system according to FIG. 8 is constructed analogously to that from FIG. 7 and additionally contains a weakly acidic cation exchanger 14, as described for FIG. 1, and which is connected to the coating container 1 as in FIG. 1. The devices described in exemplary embodiments 1 and 5 are thus used in combination.

The procedure for the chemical-reductive deposition of nickel on steel surfaces in this system is as follows: the workpiece 2 is treated in the coating container 1 at a temperature of approximately 85 ° C. analogously to the description of FIG. 1. The process solution has a pH of 4.5 and a nickel content of 6.0 g / 1 at the beginning of the process. The metal deposition reduces the pH value and the nickel content in the process solution. The metering of the used metal ions and the adjustment of the pH in the process solution is carried out, as described for FIG. 1, with the aid of the weakly acidic cation exchanger 14. The metering in of the reductant and the removal of disruptive anions are carried out in this system via an auxiliary circuit, such as to Fig. 5 described.

Since the use of the weakly acidic cation exchanger 14 according to the invention does not introduce any interfering anions into the process solution when the metal ions are replenished, considerably smaller amounts of foreign matter have to be separated from the process solution. Salting of the process solution is also avoided, since no sodium hydroxide solution and therefore no additional cations are introduced into the process solution to adjust the pH. This enables the extensive removal of orthophosphite without simultaneously increasing the hypophosphite content above the target value in the process solution.

By replenishing the ions of the coating metal and the reducing agent without interfering ions, the removal of interfering anions from the process solution and the avoidance of adding sodium hydroxide solution to the process solution to adjust the pH, the composition of the process solution is stabilized over a longer period of time and almost steady state with regard to the pH value, the concentrations of sulfate, Na, hypophosphite and orthophosphite reached. The composition of the process solution in the steady state is as follows Parameters shown in tabular form characterize and correspond to a bath age of approx. 1 MTO.

This steady state advantageously corresponds to a fresh process solution in the important parameters such as pH value, nickel content and deposition rate. Since the ions of the coating metal and reducing agent are replenished without disturbing counterions in this system, and thus the positive effects of the devices from FIGS. 1 and 5 complement one another, the useful life of the process solution is further extended. The service life of the process solution in the system from Fig. 8 is, however, due to the entry of other foreign substances, e.g. of cations from the base material of the workpiece to be coated.

FIG. 9 shows a diagram of a system with an auxiliary circuit and weakly acidic cation exchanger 14, which contains a strongly acidic cation exchanger 15 for the removal of disruptive cations from the process solution. The system according to FIG. 9 is constructed analogously to FIG. 8 and additionally contains a strongly acidic cation exchanger 15. This strongly acidic cation exchanger 15 is connected with the inlet and outlet with the coating container 1. The structure of the strongly acidic cation exchanger 15 corresponds to that from FIG. 3. This system, like the system from FIG. 8, contains a strongly acidic cation exchanger 11 in the auxiliary circuit of the membrane electrolysis cell, the task of which is to separate disruptive cations from the auxiliary circuit which are added of Reducing agent are entered as sodium hypophosphite in the regeneration solution. Since the auxiliary circuit and the process solution are separated from one another by the anion exchange membranes AI and A2, cations are not transported from the process solution into the auxiliary circuit. With the aid of the strongly acidic cation exchanger 11, no disruptive cations can be separated from the process solution.

The procedure for the chemical-reductive deposition of nickel on steel surfaces in the plant from FIG. 9 corresponds to that which was described for the plant from FIG. 8.

During the chemical-reductive coating process, secondary processes such as Pickling processes that lead to the entry of foreign matter from the base material into the process solution, the foreign matter in the process solution usually being in a cationic form. These foreign substances limit the service life of the process solution in particular if the service life of the process solution is prolonged by the described devices by removing other interfering substances or the reduced introduction of interfering substances, such as sulfate and sodium ions in particular.

By using the additional strongly acidic cation exchanger 15, an accumulation of disruptive cationic foreign substances in the process solution is eliminated in a cleaning process. For this purpose, a volume of process solution is passed over the cation exchanger 15 loaded with protons, as described for FIG. 3. According to its selectivity, the strongly acidic cation exchanger 15 binds cations in the solution until its capacity limit is reached, polyvalent cations preferably being bound, and releases an equivalent amount of protons into the solution. In particular, it binds cations that come from the base material and interfere with the process of chemical-reductive metal deposition, but also the cations of the coating metal.

The protons released during the cleaning are removed and the ions of the coating metal removed during cleaning with the ions are supplied in that the process solution, as described for FIG. 1, is passed over the weakly acidic cation exchanger 14. The regeneration of the strongly acidic cation exchanger 15 takes place, as described for FIG. 3, by rinsing the cation exchanger with

Hydrochloric acid. By separating the cationic foreign substances with the aid of the strongly acidic cation exchanger 15, a further extension of the service life of the process solution can be achieved.

10 shows a schematic of a membrane electrolytic cell with auxiliary circuit and weakly acidic cation exchanger 14, which is connected to the stacking container 13 and which contains a strongly acidic cation exchanger 15 for the separation of interfering cations from the process solution. The system according to FIG. 10 contains the same system components as FIG. 9, however the inflow and outflow of the weakly acidic cation exchanger 14 are not connected to the coating container 1 but to the stacking container 13.

The chemical-reductive deposition of nickel on steel surfaces in this system takes place in analogy to the description of FIG. 8. Thereby, the reducing agent is replenished and disruptive anions are removed analogously to the description of FIG. 5 in a membrane electrolysis cell with an auxiliary circuit.

A certain volume of process solution is removed from the coating container 1 and cooled to temperatures <50 ° C. via the heat exchanger 4 and collected in the storage container 5. Prepared process solution is used for cooling, which for this purpose is removed from the stacking container 13 and passed into the coating container 1. The cooling of the cooled solution by the removal of interfering anions and the subsequent addition of reducing agent takes place by contact with the auxiliary circuit in the membrane electrolysis cell, as was described for FIG. 5.

The difference to the system from FIG. 8 is that in the system described here, cooled and prepared process solution is passed from the stacking container 13 for further metering of the used ions of the coating metal and for adjusting the pH value over the weakly acidic cation exchanger 14 loaded with nickel ions , Since in this embodiment of the plant cooled process solution is added to the weakly acidic cation exchanger 14, the risk of undesired nickel deposition on the ion exchange polymer is reduced. This procedure according to the invention is particularly useful if a fairly high concentration of hypophosphite in the cleaned process solution has been achieved by the removal of interfering anions with simultaneous replenishment of hypophosphite, since the risk of undesired redulctive metal deposition increases with the concentration of the reducing agent.

For the cleaning process for the removal of interfering cations, the strongly acidic cation exchanger 15 is used as described for FIG. 9.

11 shows a schematic of a membrane electrolysis cell with an auxiliary circuit, in which the inlet of the strongly acidic cation exchanger 15 is connected to the rinsing system 3 for the purpose of indirect cleaning of the process solution. The system according to FIG. 11 contains the same components as that according to FIG. 9. In contrast to the system according to FIG. 9, the inlet of the weakly acidic cation exchanger 14 is not with the coating container 1 but with the stacking container 13 and its outlet via the Heat exchanger 4 connected to the coating container 1. In a further difference to the system according to FIG. 9, the strongly acidic cation exchanger 15 is connected to the rinsing system 3 with its inlet and with the outlet container 5 with its outlet. The heat exchanger 4 uses the required cooling process when transferring process solution from the coating container 1 to the storage container 5 for heating the prepared solution. A heat exchanger can be dispensed with, provided that only small volumes of process solution for cleaning the process solution have to be transferred from the coating container 1 into the storage container 5.

The procedure for the chemical-reductive deposition of nickel on steel surfaces in this system is as follows: the workpiece 2 is treated in the coating container 1 at a temperature of approximately 85 ° C. analogously to the description of FIG. 1. The process solution has a pH of 4.5 and a nickel content of 6.0 g / 1 at the beginning of the process. The metal deposition reduces the pH value and the nickel content in the process solution. After coating, the coated workpiece 2 is immersed in the rinsing container of the rinsing system 3. With the workpiece, part of the process solution is dragged into the rinsing solution of the rinsing system 3. Interfering cations and anions from the process solution also get into the rinsing system 3. The pH value and the replenishment of ions of the coating metal are carried out by the weakly acidic cation exchanger 14, which is connected between the stacking container 13 and coating container 1.

The metering of the reducing agent and the removal of interfering anions is carried out in this system in a membrane electrolysis cell with an auxiliary circuit, as described in FIG. 5, the diluted process solution being applied to the membrane electrolysis cell. For this purpose, rinsing solution from the rinsing system 3 is passed over the strongly acidic cation exchanger 15, as a result of which disruptive cations are removed from the rinsing solution. So that adequate cleaning of the process solution can be achieved even without high specific electrolyte carry-out, a certain volume of the process solution is fed from the coating container 1 via the heat exchanger 4 (optional) to the storage container 5. The volume required depends on the amount of metal deposited and is calculated using equation (2).

The process solution, as described for FIG. 5, is brought into contact with the auxiliary circuit in the membrane electrolysis cell from the storage container 5. The voltage that is applied to the membrane electrolysis system is 90 V in the case of 40 units. In the membrane electrolysis cell, disruptive anions are removed from the process solution by contact with the auxiliary circuit, and reducing agents are replenished cation-free into the process solution. The process solution prepared in this way is removed from the stacking container 13 and passed over the weakly acidic cation exchanger 14 loaded with nickel ions in order to replenish the used metal ions and to adjust the pH. The drain of the weakly acidic cation exchanger 14 is fed to the coating container 1 and used to compensate for the evaporation losses.

It is advantageous with this configuration of the process technology that a diluted process solution is applied to the regeneration system. The lower concentration of ingredients (ions of the coating metal, reducing agent) reduces the risk of undesired metal deposition on sensitive components of the cleaning device, such as membranes and ion exchange polymers. The treatment of the process solution according to the invention achieves a steady state at a concentration level which corresponds to a bath age of approximately 1 MTO and is characterized by the following parameters of the process solution shown in table form:

This steady state advantageously corresponds to a fresh process solution in the important parameters such as pH value, nickel content and deposition rate. By varying the volume flows of process solution that are brought into contact with the auxiliary circuit, compositions of the process solution can be set that correspond to a bath age of 1 to 4 MTO.

List of the reference symbols used:

1 coating container

2 workpiece to be coated

3 (multi-stage) rinsing system

4 heat exchangers

5 storage containers for process solution to be cleaned

6 anode chamber of the membrane electrolytic cell

7 Enrichment chamber of the auxiliary circuit of the membrane electrolysis cell

8 chamber of the membrane electrolysis cell with process solution to be cleaned

9 weakly basic anion exchanger for the separation of the anion mixture

10 buffer tanks for the auxiliary circuit

11 strongly acidic cation exchangers in the auxiliary circuit

12 Regeneration chamber of the auxiliary circuit of the membrane electrolysis cell

13 stacking containers for cleaned process solution

14 weakly acidic cation exchangers for replenishing the coating metal

15 strongly acidic cation exchangers for cleaning the process solution

16 regeneration tanks + anode

- cathode

A1, A2 anion exchange membranes

Kl cation exchange membrane

H O fresh water

NaH ₂ PO ₂ reductant

Claims

claims

1. A method for extending the useful life of a process solution for chemical-reductive metal deposition, in which the reducing agent used in the metal deposition and ions of the coating metal are replenished and the pH of the process solution is adjusted, the replenishment of the ions of the coating metal and the pH The value is set with the aid of at least one weakly acidic cation exchanger (14) loaded with ions of the coating metal, characterized in that the pH of the process solution is monitored, that when the pH of the process solution drops, part of the process solution, if necessary after dilution, is passed through the weakly acidic cation exchanger (14) and the solution prepared by the weakly acidic cation exchanger (14) is fed directly back into the process solution that, via the control of the pH value in the outlet of the weakly acidic cation exchanger (14), the functionality d it is monitored weakly acidic cation exchanger that when the pH value in the outlet of the weakly acidic cation exchanger approaches the pH value of the process solution, the cation exchanger is again loaded with ions of the coating metal for use again.

2.Procedure to extend the service life of a process solution for chemical-reductive metal deposition, in which the reducing agent used in the metal deposition and ions of the coating metal are replenished and the pH in the process solution is adjusted, with anions in a membrane electrolytic cell with an additional auxiliary circuit between the Process solution and the auxiliary circuit can be exchanged via the anion exchange membranes (AI, A2), characterized in that the reducing agent is metered into the auxiliary circuit in the form of a salt or a salt solution, with disruptive cations originating from the reductant using a strongly acidic H + ion loaded cation exchanger (11) and interfering anions can be removed from the auxiliary circuit with the aid of a weakly basic anion exchanger (9).

3. The method according to claim 2, characterized in that the pH value adjustment and the metering of the ions of the coating metal is carried out with the aid of at least one weakly acidic cation exchanger (14) loaded with ions of the coating metal.

4. The method according to claim 2 or 3, characterized in that during the metal deposition in the process solution accumulating interfering cations are separated with the aid of at least one strongly acidic H + ion-loaded cation exchanger (15).

5. A method for extending the useful life of a process solution for chemical-reductive metal deposition, in which the reducing agent used in the metal deposition and ions of the coating metal are replenished, and the pH of the process solution is adjusted, using a cation exchanger to remove cations from the Process solution is used, characterized in that, in the metal deposition, interfering cations accumulating in the process solution with the aid of at least one strongly acidic H + ion-loaded cation exchanger (15) and in the metal deposition, interfering anions accumulating in the process solution with the aid of at least one weakly basic anion exchanger (9) be burned off from the process solution or a diluted process solution.

6. The method according to claim 5, characterized in that the pH adjustment and the subsequent metering of the ions of the coating metal is carried out with the aid of at least one weakly acidic cation exchanger (14) loaded with ions of the coating metal.

7. Device for extending the useful life of a process solution for chemical-reductive metal deposition, consisting of at least one

, weakly acidic cation exchanger (14) for use in adjusting the pH and replenishing ions of the coating metal in a system for chemical-redulctive metal deposition, characterized in that the device has elements for recycling the process solution or cooled or pretreated process solution by the weakly acidic cation exchanger (14) has that the weakly acidic cation exchanger (14) is connected with its inlet to at least one container containing process solution, diluted process solution or cooled process solution or pretreated process solution, that the weakly acidic cation exchanger (14) with its outlet is directly connected to at least one Container containing the process solution is connected that the device has measuring devices for monitoring the pH of the process solution (p. 33) and the pH in the outlet of the weakly acidic cation exchanger (14).

8. Device for extending the useful life of a process solution for chemical-reductive metal deposition in a system for chemical-reductive metal deposition, the device containing at least one cation exchanger for use in the removal of cations, characterized in that the cation exchanger is a strongly acidic with H + -Ions loaded cation exchanger (15) is that the device has elements for recycling the process solution or cooled or pretreated process solution through the strongly acidic cation exchanger (15), that the strongly acidic cation exchanger (15) with its inlet and outlet directly with at least one container, containing process solution, diluted process solution or cooled process solution or pretreated process solution.

9. Device for extending the useful life of a process solution for chemical-reductive metal deposition in a system for chemical-redulctive metal deposition, the device containing at least one cation exchanger for use in the removal of cations, characterized in that the cation exchanger is a strongly acidic one with H + -Ions loaded cation exchanger (15) is that the Norrichtung at least one weakly acidic cation exchanger (14) connected in series or parallel to the strongly acidic cation exchanger (15) for use for pH adjustment and Νachdosing of ions of the coating metal in a plant for the chemical-reductive metal deposition contains the elements for connecting the strongly acidic cation exchanger (15) and the weakly acidic cation exchanger (14) with at least one container, the process solution, diluted process solution, cooled process solution and / or pretreatment contains the last process solution.

10. The device for extending the useful life of a process solution for chemical-reductive metal deposition, the device containing at least one cation exchanger for use in the removal of cations, and at least one weakly basic anion exchanger (9), characterized in that the cation exchanger is a strongly acidic with H + -Ions loaded cation exchanger (15) is that the strongly acidic cation exchanger (15) with its inlet is connected directly to at least one container which contains process solution, diluted process solution or cooled process solution or pretreated process solution, that the strongly acidic cation exchanger (15) is connected to its Process with a weakly basic anion exchanger (9) for the removal of interfering anions is connected to the weakly basic anion exchanger (9) with a container containing the process solution, diluted process solution or cooled process solution or pretreated process oil solution contains, is connected.

11. The device for extending the useful life of a process solution for the chemical-redulctive metal deposition according to claim 10, characterized in that it additionally has at least one weakly acidic cation exchanger (14) for adjusting the pH and replenishing ions of the coating metal and elements for connecting the weakly acidic cation exchanger (14) with at least one container containing process solution, diluted process solution, cooled process solution and / or pretreated process solution.

12. Device for extending the useful life of a process solution for chemical-reductive metal deposition for use in a system for chemical-reductive metal deposition. Consisting of a membrane electrolysis cell with an auxiliary circuit, which contains at least one weakly basic anion exchanger (9) and at least one strongly acidic cation exchanger (11) connected in series or parallel to it, the membrane electrolysis cell consisting of at least one anode +, one cathode -, and at least four in between there are chambers arranged in series, the anode being contained in the first chamber, the anode chamber (6), the anode chamber (6) being in contact with the second, the enrichment chamber (7) via a cation exchange membrane (Kl), the third chamber (8) via anion exchange membranes (AI, A2) with the second, the enrichment chamber (7) and the fourth, the redosing chamber (12), in contact, the enrichment chamber (7) and redosing chamber (12) being part of the auxiliary circuit and with the weakly basic anion exchanger (9) and the strongly acidic cation exchanger (11) are connected, the contact between n Process solution and auxiliary circuit via the anion exchange membranes (AI, A2) in the third chamber (8), the chambers (7), (8) and (12) together form a base unit that can be repeated several times within the membrane electrolysis cell and the device elements for connecting the third chamber (8) of the membrane electrolytic cell with at least one container which contains cooled process solution, diluted cooled process solution, and / or pretreated cooled process solution.

13. Device for extending the useful life of a process solution for chemical-reductive metal deposition according to claim 12, characterized in that it additionally has at least one weakly acidic cation exchanger (14) for adjusting the pH and replenishing ions of the coating metal and / or strongly acidic cation exchanger (15) for the removal of interfering cations and elements for connecting the weakly acidic cation exchanger (14) and / or strongly acidic cation exchanger (15) with at least one container which contains process solution, diluted process solution, cooled process solution and / or pretreated process solution.

14. Device according to one of claims 7 to 13, characterized in that the ion exchanger (s) (9, 11, 14, 15) are column exchangers which contain at least one solid, water-insoluble, organic or inorganic ion exchange material and regenerate in cocurrent or countercurrent can be.

15. Device according to one of claims 7 to 13, characterized in that the ion exchanger (s) (9, 11, 14, 15) are each part of a filter or membrane apparatus which contains at least one regenerable, organic or inorganic ion exchange material.

16. Device according to one of claims 7 to 13, characterized in that the ion exchanger (s) (9, 11, 14, 15) each consists of a container which is a liquid which is immiscible with the process solution and in which an ion exchange material is distributed, contains.

17. Plant for the chemical-redulctive metal deposition, consisting of at least one coating container (1), a rinsing system (3) and associated peripherals, such as. B. pumps, valves, measuring devices for pH, conductivity, temperatures, characterized in that it contains at least one device for extending the useful life of a process solution for the chemical-redulctive metal deposition according to one of claims 7 to 16.

18. Plant according to claim 17 with at least one device according to claim 11, characterized in that the strongly acidic cation exchanger (15) and the weakly basic anion exchanger (9) in series or parallel connection with the flushing system (3) or an additional, with the flushing system ( 3) connected regeneration tank (16) and the inlet of the weakly acidic cation exchanger (14) with the rinsing system (3) or the regeneration tank (16) and the outlet of the weakly acidic cation exchanger (14) with the coating tank (1).

19. Plant according to claim 17, with at least one device according to claim 7 and / or 8, characterized in that the inlet and outlet of the weakly acidic cation exchanger (14) and / or the strongly acidic cation exchanger (15) directly or via a heat exchanger (4th ) are connected to the coating container (1).

20. Plant according to claim 17 with at least one device according to claim 12, characterized in that the third chamber (8) of the membrane electrolysis cell is connected to the coating container (1) via a heat exchanger (4).

21. Plant according to claim 20 with at least one device according to claim 8, characterized in that the strongly acidic cation exchanger (15) with its inlet with the rinsing system (3) and with its outlet via an additional storage container (5) which is between the coating container (1 ) and the third chamber (8) of the membrane electrolysis cell is connected.

22. Plant according to claim 20 or 21 with at least one device according to claim 7, characterized in that the weakly acidic cation exchanger (14) with its inlet connected to the third chamber (8) of the membrane electrolytic cell and with its outlet via the heat exchanger (4) the coating container (1) is connected.

23. Use of star acidic H + ion-loaded cation exchange material or H + ion loaded strongly acidic cation exchangers (11, 15) for the removal of interfering cations to extend the useful life of a process solution for chemically reductive metal deposition.

24. Use of a combination of a.) Weakly basic anion exchange material or weakly basic anion exchangers (9) for the removal of interfering anions and b.) H + ion-loaded cation exchange material or H + ion-loaded strongly acidic cation exchangers (11, 15) for the removal of interfering cations to extend the service life of a process solution for chemically reductive metal deposition.

25. Use of a combination of a.) Weakly acidic cation exchange material or weakly acidic cation exchangers (14) for adjusting the pH and replenishing ions of the coating metal and b.) H + ion-loaded cation exchange material or H + ion-loaded strongly acidic cation exchangers (11 , 15) for the removal of interfering cations to extend the useful life of a process solution for chemically reductive metal deposition

26. Use of a combination of a.) Weakly basic anion exchange material or weakly basic

Anion exchangers (9) for the removal of disruptive anions and b.) H + ions loaded with strongly acidic cation exchange material or H + ions loaded with strongly acidic cation exchangers (11, 15) for the removal of disruptive

Cations and c.) Weakly acidic cation exchange material or weakly acidic

Cation exchangers (14) for pH adjustment and replenishment of

Ions of the coating metal to extend the service life of a process solution for chemical reductive metal deposition.