WO2000009780A1

WO2000009780A1 - Automatic regulation and control of cleansing baths

Info

Publication number: WO2000009780A1
Application number: PCT/EP1999/005637
Authority: WO
Inventors: Ibolya Bartik-Himmler; Wolfgang Krey; Werner Opitz; Lutz Hüsemann; Bernd Schenzle; Peter Kuhm; Detlef Bohnhorst; Arnulf Willers; Herbert Puderbach; Hans-Willi Kling; Reiner Moll
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1998-08-13
Filing date: 1999-08-04
Publication date: 2000-02-24
Also published as: SK2212001A3; CZ2001551A3; HUP0102852A2; BG105244A; CA2369064A1; YU10901A; SI20535A; KR20010072441A; JP2002522647A; AU5419499A; DE19836720A1; TR200100328T2; AR020183A1; EP1109950A1; CN1312866A

Abstract

The invention relates to a method for controlling cleansing baths, characterized in that at least two of i) tenside contents, ii) inorganically and/or organically bound carbon load, iii) alkalinity, are measured in a program-controlled manner and in that a) depending on the result of the measurements additional components are added and/or one or more bath maintenance measures are initiated and/or b) the results of the measurements and/or data derived from the measurement results are transmitted to at least one remote destination which is situated in a room different from the one housing the device for carrying out the above measurements.

Description

"Automatic inspection and control of detergent baths"

The invention relates to a method for automatically checking and controlling detergent baths, in particular detergent baths in the metalworking industry or in vehicle construction. The essence of the invention is that at least 2 selected control parameters are determined automatically and programmatically and the results of the determinations and / or data derived from the results of the determinations are transmitted to a remote destination which is not in the immediate vicinity of the cleaning bath. Depending on the result of the determinations, further determinations and / or bathroom maintenance measures can be triggered programmatically or by requests from the remote destination. Depending on the result of the determinations, control measurements can also be program-controlled or initiated on request. The remote destination can be, for example, in a higher-level process control system, in a control center of the plant in which the detergent bath is located, or at a location outside the plant.

The cleaning of metal parts before further processing is a standard task in the metal processing industry. The metal parts can be contaminated, for example, with pigment dirt, dust, metal abrasion, corrosion protection oils, cooling lubricants or forming aids. Before further processing, such as before corrosion protection treatment (eg phosphating, chromating, anodizing, reaction with complex fluorides, etc.) or before painting, these contaminants must be removed with a suitable cleaning solution. Spraying, dipping or combined processes can be used for this. Industrial cleaners in the metalworking industry are generally alkaline (pH values in the range above 7, for example 9 to 12). Their basic components are alkalis (alkali metal hydroxides, carbonates, silicates, phosphates, borates) as well as non-ionic and / or anionic surfactants. Frequently, the cleaners contain as additional auxiliary components complexing agents (gluconates, polyphosphates, salts of aminocarboxylic acids such as ethylenediamine tetraacetate or nitrilotriacetate, salts of phosphonic acids such as salts of hydroxyethane diphosphonic acid, phosphono butane tricarboxylic acid or other phosphonic or phosphonocarboxylic acids), corrosion protection means such as salts of carboxylic acids with 6 to 12 carbon atoms, alkanolamines and foam inhibitors such as, for example, end-capped alkoxylates of alcohols with 6 to 16 carbon atoms in the alkyl radical. If the cleaning baths do not contain any anionic surfactants, cationic surfactants can also be used.

The cleaners generally contain, as nonionic surfactants, ethoxylates, propoxylates and / or ethoxylates / propoxylates of alcohols or alkylamines having 6 to 16 carbon atoms in the alkyl radical, which can also be end group-capped. Alkyl sulfates and alkyl sulfonates are widely used as anionic surfactants. Alkylbenzenesulfonates can also be found, but they are disadvantageous from an environmental point of view. Cationic alkylammonium compounds with at least one alkyl radical with 8 or more carbon atoms are particularly suitable as cationic surfactants.

The alkalis in the cleaning bath contribute to its cleaning ability. For example, they saponify saponifiable impurities such as fats and thereby make them water-soluble. They also help to remove insoluble dirt from the metal surface by negatively charging the surfaces through the adsorption of OH ions and thereby causing an electrostatic repulsion. Through such reactions, possibly also through Dragging, alkalinity is consumed so that the cleaning effect wears off over time. It is therefore customary to check the alkalinity of the cleaning baths at certain times and, if necessary, to supplement the solution with new active ingredients or to replace it entirely. This check is carried out either manually or locally by an automatic titrator. The alkalinity is usually checked by titration with a strong acid. The operating staff assesses the alkalinity based on the acid consumption and takes the necessary measures such as bathroom additions or bathroom renewal. This currently customary procedure assumes that operating personnel are in the vicinity of the cleaning bath at the required check times. The shorter control intervals are desired, the more the operator is used for the control measurements.

A method is known from EP-A-806 244 for automatically determining the pH of a solution and for metering in acid or alkali in the event of deviations. The task in this document is to keep the pH of a liquid stream at a predetermined value. An acid-base titration is not carried out with this method. It is necessary to check the functionality of this system on site. It is not possible to intervene in the process of pH measurements and dosing measures from a remote location.

It is known in the prior art to manually determine the nonionic surfactants in aqueous process solutions, such as, for example, in detergent baths, using a color indicator. The usual procedure here is to add a reagent to a sample taken from the process solution which forms a color complex with nonionic surfactants. This color complex is preferably extracted into an organic solvent which is not miscible with water in any ratio, and the light absorption at a specific wavelength is then determined photometrically. As a reagent for the formation of the color complex For example, tetrabromophenolphthalein ethyl ester can be used. Before the extraction into an organic solvent, preferably into a chlorinated hydrocarbon, the process solution is mixed with a buffer system for the pH range 7.

It is also known to determine nonionic surfactants in the presence of ionic surfactants. The ionic surfactants are separated from the sample by ion exchangers. The nonionic surfactants not bound in the ion exchanger are determined with the aid of the refractive index of the solution leaving the exchange column. The refractive index is preferably measured as a function of the elution time, the integral is determined for the part of the curve which deviates from the refractive index of the pure eluent, and this integral is compared with the values obtained from calibration measurements.

Alternatively, but less precisely, the extreme value of the refractive index can be measured and the surfactant content can be determined from this by comparison with a calibration curve.

Anionic and cationic surfactants in aqueous solutions can be detected, for example, by titration with Hyamin ^R 1622 (= N-benzyl-N, N-dimethyl-N-4 (1.1.3.3.-tetramethyl-butyl) -phenoxy-ethoxyethylammonium chloride) and potentiometric end point determination . For this purpose, the sample is mixed with a known amount of Na dodecyl sulfate, titrated with hyamine and the end point of the titration is determined with an ion-sensitive electrode.

Alternatively, anionic surfactants can also be determined by titration with 1,3-didecyl-2-methylimidazolium chloride. An electrode with an ion-sensitive membrane is used as the detector. The electrode potential depends on the concentration of the measuring ions in the solution. Depending on the result of this tenside determination, which requires a lot of personnel, the operating personnel of the system supplement the process solution with one or more additional components. The method therefore makes it necessary for operating personnel to be at the location of the system, at least at the time when the surfactant is determined. So it is labor-intensive, especially in multi-shift operation. Documenting the results for quality control and quality assurance requires additional effort.

As a result of the cleaning process, the dirt components detached from the surfaces accumulate in the cleaning solution. Pigment dirt can lead to exposure to inorganic carbon. Corrosion protection oils, cooling lubricants or forming aids such as drawing greases and / or detached or leached organic coatings or joining materials result in the cleaning solution being contaminated with organically bound carbon. Since this organically bound carbon is mostly in the form of mineral oils, mineral fats, or oils and fats of animal or vegetable origin, the cleaning solution is often referred to as "fat" for short. Such oils and fats are largely present in the cleaning solution in emulsified form and fats of animal or vegetable origin can, however, be at least partially hydrolyzed by an alkaline cleaning solution. The hydrolysis products can then also be present in dissolved form in the cleaning solution. If the cleaning solution is too high in TOC, it can no longer be guaranteed that it contains the parts to be cleaned freed from oils and greases to the extent necessary, or there is a risk of oils and greases reappearing on the cleaned parts when they are removed from the cleaning solution, so it is necessary to keep the grease load of the cleaning solution below a critical level n to maintain the maximum value that may depend on the reuse of the cleaned parts and the composition of the cleaning solution. With high fat loads, either the surfactant content of the cleaning solution can be increased to increase the fat-dissolving power of the Increase cleaning solution. Or you take bathroom care measures with the aim of reducing the fat content of the cleaning solution. At a given

The maximum limit of fat exposure is definitely necessary. In the simplest

If you trap the cleaning solution in whole or in part, prepare it again or supplement it with fresh cleaning solution. Because of the accruing

Wastewater and because of the need for fresh water, however, efforts are made to separate fats and oils from the cleaning solution and to continue using the cleaning solution, if necessary after adding active ingredients. Suitable devices for this, such as separators or membrane filtration systems are in the

Technology known.

So far, it has been customary to visually assess the cleaning performance of a cleaning solution based on the cleaning result. The operators of the system assess the cleaning performance and take the necessary measures such as bathroom additions or bathroom renovations. This currently customary procedure assumes that operating personnel are in the vicinity of the cleaning bath at the required check times. The shorter inspection intervals are desired, the greater the strain on the operating personnel for the visual assessment.

It has already been proposed in the prior art to determine individual control parameters of detergent baths in a program-controlled manner, to transfer the results of the determinations to a distant destination and, depending on the result of the determinations, to initiate control measurements and / or bathroom maintenance measures automatically or programmatically from there. A method for the automatic control and control of the surfactant content in aqueous process solutions is described in H 3267, the automatic determination of the loading of aqueous cleaning solutions with carbon-containing compounds in H 3268 and the automatic control and control of detergent baths by determining the alkalinity in the German patent application DE 198 02 725.7. The present invention builds on these methods by linking them together. How to proceed with the individual provisions is described in detail in the 3 documents mentioned. The content of these 3 documents is therefore expressly made the subject of this disclosure.

The object of the invention is to enable control and preferably also control of cleaning baths without operating personnel having to be at the location of the cleaning bath for this purpose.

The measuring device used should preferably check and calibrate itself and transmit an alarm message to a remote location in the event of a malfunction. Furthermore, it should preferably be possible to check the functionality of the measuring device and the measurement results from a remote location. Furthermore, it should be possible to intervene in the measurement process and in the bathroom maintenance measures from a remote location. The aim of remote control is to reduce the personnel expenditure for bathroom control and bathroom control of the detergent baths. Provision should be made to determine at least 2 parameters from which the functionality and / or the contamination of the cleaner baths can be recognized. By taking several measured variables into account, more targeted bathroom care measures can be initiated than is possible if only a single measured variable is known.

This object is achieved by a method for checking detergent baths, characterized in that at least two of the following determinations are carried out under program control: i) determination of the content of surfactants, ii) determination of the contamination with inorganic and / or organically bound carbon, iii) determination the alkalinity and that a) depending on the result of the determinations, the dosing of supplementary components and / or one or more bathroom care measures is initiated and / or b) the results of the determinations and / or data derived from the results of the determinations are transmitted to at least one distant destination, which is in a room other than the facility for implementing the provisions.

For example, both the content of surfactants and the exposure to organic and / or inorganic carbon can be determined. Or you determine the content of surfactants and the alkalinity. Or you determine the contamination with organic and / or inorganic carbon and the alkalinity. However, all three parameters are preferably determined in order to obtain a complete picture of the state of the cleaning bath.

How these determinations can be carried out programmatically is described in detail in the documents mentioned above. They can be carried out essentially simultaneously or in succession.

The result of the determination can be stored on a data carrier. Additionally or alternatively, it can be used as the basis for further calculations. The result of the determination or the result of the further calculations is transmitted to a remote destination (= to a “remote location”) and there again stored and / or output on a data carrier. If, in the sense of the method according to the invention, a remote destination or a “ distant place "is meant a place that is not in direct or at least in optical contact with the process solution. The remote location can represent, for example, a central process control system that is part of an overall process Surface treatment of the metal parts as a subtask controls and controls a cleaning bath. The "remote location" can also represent a central control room from which the entire process is controlled and controlled and which is, for example, in a different room than the process solution

However, a "remote location" can also be a place outside the plant in which the cleaning bath is located. This makes it possible for specialists to check and control the process solution that is outside the plant in which it is located it is much less necessary for special staff to be at the location of the cleaning bath.

Suitable data lines with which the results of the determinations and control commands can be transmitted are available in the prior art. “Output of the result of the determination or the further calculation” is understood to mean that this is either passed on to a higher-level process control system or is displayed or printed out on a screen in such a way that it is recognizable to a person defined "distant place". It is preferable that the results of the individual determinations are stored on a data carrier at least for a predetermined time interval, so that they can subsequently be evaluated, for example in the sense of quality assurance. However, the results of the determinations do not have to be output as such or saved on a data carrier. Rather, they can also be used directly as the basis for further calculations, the results of these further calculations being displayed or saved. For example, the trend of the concentration and / or its relative change can be displayed instead of the current content. Or the current salaries are converted into "% of the target salary" or "% of the maximum salary". The said distant destination can be located at least 500 m from the device for carrying out the determinations. In particular, it can also be located outside the plant in which the cleaning bath to be checked is operated. Remote control is therefore provided without the need for operating personnel to be in the immediate vicinity of the cleaning bath.

It can be provided that the results of the determinations and / or the data derived from the results of the determinations are transferred to the remote destination automatically whenever new results of the determinations and / or data derived from the results of the determinations are determined. Alternatively, provision can be made for the results of the determinations and / or the data derived from the results of the determinations to be transmitted to the remote destination upon request from the remote destination.

On the one hand, the individual determinations can be repeated after predetermined time intervals. Alternatively, it can be provided in the program control that the individual determinations are repeated after the shorter time intervals, the more the results of two successive determinations differ. It can also be provided that the determination of a second measurement variable is initiated if the determination of a first measurement variable has resulted in a predetermined critical value or a predetermined change in the value between 2 determinations of this measurement variable. The start of the determination of a measured variable can therefore be made dependent on the result of the determination of another measured variable.

In other words, the method according to the invention can be carried out in such a way that a second determination selected from the determinations i), ii) and iii) is carried out programmatically when a first determination selected from the determinations i), ii) and iii) gives a result that exceeds a predetermined maximum value or falls below a predetermined minimum value or deviates from the previous result of this first determination by a predetermined minimum value.

Of course, it can also be provided that the determinations are made on request from the remote destination.

In one embodiment, the method according to the invention is characterized in that program-controlled i) the determination of the surfactant content is carried out by a) taking a sample with a predetermined volume from the aqueous process solution, b) if desired, the sample is freed from solids, c) if desired, the sample is diluted with water in a predetermined ratio or determined as a result of a predetermination, d) the content of surfactants by selective adsorption, electrochemical, chromatographic, by cleavage into volatile compounds, stripping of these volatile compounds and their detection, or by adding a reagent which changes the interaction of the sample with electromagnetic radiation proportional to the content of surfactants, and determines the change in this interaction.

Furthermore, an embodiment of the method according to the invention is characterized in that ii) the load on inorganic and / or organically bound carbon is determined by program-controlled a) taking a sample with a predetermined volume from the aqueous cleaning solution, b) if desired, the sample freed of solids and / or homogenized, c) if desired, the sample in a predetermined or as a result of a Predetermined ratio diluted with water, d) the content of the sample of inorganic and / or organically bound

Carbon determined using methods known per se.

Depending on the embodiment of sub-step d), the content of the cleaning solution in inorganic carbon ("inorganic carbon", IC), in organic carbon ("total organic carbon", TOC) or the sum of both ("total carbon", TC) The proportion of lipophilic substances in the detergent bath can be determined in particular if an extraction method is used as part of the determination, in which only lipophilic substances are extracted from the cleaning solution and determined in a subsequent step.

A further embodiment of the invention is characterized in that iii) the alkalinity of the detergent bath is determined by acid-base reaction with an acid, program-controlled a) taking a sample with a predetermined volume from a cleaning bath, b) if desired the sample of Solids freed c) selects whether free alkalinity and / or total alkalinity should be determined, and d) titrating the sample by adding an acid or presenting an acid and titrating it with the sample.

The sample volume drawn in the respective sub-step a) can be permanently programmed into the control part of the measuring device to be used for the method. The size of the sample volume can preferably be changed from a remote location. Furthermore, the control program can be designed such that it makes the sample volume to be used dependent on the result of a previous measurement. For example, the sample volume can be selected to be larger the lower the content of the substance to be determined in the detergent bath. This can optimize the accuracy of the determination. Between taking the sample and the actual measurement, it may be desirable to free the sample from solids in the respective optional sub-step b). This is not necessary if the cleaning solution contains only a small amount of solids. If the solids content is too high, however, valves of the measuring device can become blocked and sensors can become dirty. It is therefore recommended to remove solids from the sample. This can be done automatically by filtration or by using a cyclone or a centrifuge.

Before the selected parameter is determined, the sample is diluted with water, if desired, in a predetermined ratio or as a result of a predetermined determination. In sub-step d), the actual determination is carried out using different methods, which are explained in more detail below.

In the simplest case, the method according to the invention works in such a way that the respective determinations are repeated after a predetermined time interval. The predetermined time interval depends on the requirements of the operator of the process solution and can comprise any time interval in the range from a few minutes to several days. For quality assurance, it is preferable that the predetermined time intervals are, for example, between 5 minutes and 2 hours. For example, you can take a measurement every 15 minutes.

However, the method according to the invention can also be carried out in such a way that the respective determinations are repeated after the shorter time intervals, the more the results of two successive determinations differ. The control system for the method according to the invention can therefore decide itself whether the time intervals between the individual determinations should be shortened or extended. Of course, the tax system the instructions are given for which differences between the results of successive determinations which time intervals should be selected.

The 2 or 3 different determinations i), ii) and iii) need not always be carried out in this order in succession. Rather, it is possible to carry out one determination more often than another. This will be done when practice shows that one parameter changes faster than another. For example, the surfactant content can be determined more often than the alkalinity. Or you can program the system so that it depends on the result of one determination whether another determination should be started. For example, provision can be made to determine the alkalinity only when the carbon content of the detergent bath exceeds a predetermined limit. Or it is possible to determine the alkalinity only when the surfactant content of the cleaning bath falls below a specified lower limit. This makes it possible, for example, to select whether only the surfactant component or also the builder component needs to be added to the cleaning bath.

Furthermore, the method according to the invention can be carried out in such a way that the respective determinations are carried out at any time due to an external requirement. In this way, for example, the surfactant content, the alkalinity and / or the fat content of the detergent solution can be checked immediately if quality problems are identified in subsequent process steps. The measurement of the selected determinant can thus be time-controlled (according to fixed time intervals) or event-controlled (if changes are found or due to external requirements). i) Determination of the surfactant content

The process can be designed so that the surfactants whose content is to be determined in the process solution are nonionic surfactants. To determine them, one can proceed by adding a reagent in sub-step d) which changes the interaction of the sample with electromagnetic radiation in proportion to the content of nonionic surfactants, and measures the change in this interaction.

For example, the reagent can be a complex of two substances A and B, the nonionic surfactants displacing substance B from the complex with substance A and the color or fluorescence properties of substance B thereby changing. For example, substance B can be a fluorescent substance or a dye that can form a complex with, for example, dextrans or starch as an example of substance A. As a component of the complex, substance B has certain coloring or fluorescent properties. If it is pushed out of the complex, these properties change. By measuring the light absorption or the fluorescent radiation, it can then be detected which portion of substance B is not in the form of a complex with A. Substance A is selected in such a way that when nonionic surfactants are added, substance B is displaced from the complex and instead a complex is formed with the nonionic surfactants. Then the amount of substance B displaced from the complex with A is proportional to the amount of nonionic surfactants added. The amount of nonionic surfactants added can be inferred from the change in light absorption or fluorescence caused by the amount B released.

For example, a salt of a cationic dye with tetraphenylborate anions can be used as the reagent. Nonionic surfactants can displace the dye from this salt after adding it by adding Has converted barium ions into a cationic complex with barium. This method of converting nonionic surfactants into cationically charged complexes and thereby making accessible reactions which respond to cations is also referred to in the literature as “activation” of the nonionic surfactants. The method is described, for example, in Vytras K. Dvorakova V and Zeeman I (1989) Analyst 1 14, page 1435 ff. The amount of cationic dye released from the reagent is proportional to the amount of nonionic surfactants present. If the absorption spectrum of the dye changes with this release, the amount of dye released can be determined by photometric measurement of a suitable absorption band become.

This method of determination can be simplified if a salt of a cationic dye is used as a reagent which is only soluble in a water-immiscible organic solvent, while the dye released is itself water-soluble and leads to a coloration of the water phase. The reverse procedure is, of course, also suitable: a water-soluble salt of an organic dye is used, the dye released being soluble only in an organic phase. By releasing the dye in exchange for the nonionic surfactants and extracting the released dye in the other phase, it can be determined photometrically in a simple manner.

This method of determination is also suitable for the determination of cationic surfactants. Since these are already positively charged by themselves, the “activation” described above with barium cations is unnecessary.

Furthermore, the reagent can be a substance which itself forms a complex with the anionic surfactants and which has different coloring or fluorescent properties than the free reagent. For example, the reagent in the optical field can be colorless while its complex is with non-ionic surfactants absorb electromagnetic vibrations in the optical range, i.e. have a color. Or the maximum of the light absorption, ie the color, of the unbound reagent differs from that of the complex with the nonionic surfactants. However, the reagent can also show certain fluorescence properties that change when complexing with the nonionic surfactants. For example, the free reagent can fluoresce, while the complex formation with the nonionic surfactants quenches the fluorescence. In all cases, the concentration of the complex of reagent and nonionic surfactants and thus the concentration of the nonionic surfactants themselves can be determined by measuring the light absorption at a predetermined wavelength or the fluorescent radiation.

In step d), a reagent is preferably added which forms a complex with the nonionic surfactants and which can be extracted into an organic solvent which is not miscible with water in any ratio. The complex of nonionic surfactants and added reagent is then extracted into the organic solvent, which is not miscible with water in all proportions. This can be done by intensive mixing of the two phases, for example by shaking or preferably by stirring. After this extraction step, the mixing of the two phases is ended, so that phase separation occurs in an aqueous and an organic phase. If desired, the completeness of the phase separation can be checked by suitable methods such as, for example, determining the electrical conductivity or measuring the turbidity by means of light absorption or scattering.

This is followed by the actual measurement of the content of nonionic surfactants. For this purpose, the organic phase, which contains the complex of nonionic surfactants and added reagent, is exposed to electromagnetic radiation, which interacts with the complex dissolved in the organic phase can kick. For example, visible or ultraviolet radiation can be used as electromagnetic radiation, the absorption of which is determined by the complex of nonionic surfactants and added reagent. However, it is also conceivable, for example, that a reagent is used whose complex with the nonionic surfactants delivers a characteristic signal in nuclear magnetic resonance or electron spin resonance measurements. The signal strength, expressed as the attenuation of an electromagnetic vibration in the corresponding frequency band (absorption), can be correlated with the concentration of the complex. Instead of absorption effects, emission effects can also be used to determine the concentration. For example, a reagent can be selected whose complex with nonionic surfactants in the organic solvent absorbs electromagnetic radiation of a certain wavelength and instead emits electromagnetic radiation of a longer wavelength, the intensity of which is measured. An example of this is the measurement of the fluorescence radiation when the sample is irradiated with visible or ultraviolet light.

In principle, the interaction of the interaction of the organic phase with electromagnetic radiation can take place immediately after completion of the phase separation in the same vessel in which the phase separation is carried out. Depending on the measuring method used to determine the interaction of the organic phase with electromagnetic radiation, however, it is preferable to subtract the organic phase or a part thereof and to supply it to the actual measuring device via a line. This makes it possible in particular to provide suitable cuvettes for the measurement. Accordingly, a preferred embodiment of the invention consists in separating the organic phase from the aqueous phase after the sub-step f) and feeding it to the measuring device. For this separation of the organic phase, it is particularly advisable if the organic solvent, which is not miscible with water in all proportions, is a halogen-containing solvent with a density higher than water. To When the phases are separated, the organic phase is then in the lower part of the vessel and can be pulled off downwards.

Examples of suitable halogen-containing solvents are dichloromethane or higher-boiling halogenated hydrocarbons, in particular chlorofluorocarbons such as, for example, trifluorotrichloroethane. These solvents must be disposed of after use in accordance with local legal requirements. Since this can be costly, it makes sense to reprocess the used solvent, for example by treating it with activated carbon and / or by distillation, and to use it again for the measuring method.

In a preferred embodiment of the invention, an agent is added as a reagent which undergoes a color reaction in the organic phase with the nonionic surfactant. As an interaction of the organic phase with electromagnetic radiation, the light absorption at a predetermined wavelength can then be measured. A conventional photometer is suitable for this. For example, tetrabromophenolphthalein ethyl ester can be used as the color reagent. In this case, a buffer system for a pH in the range of 7 must be added to the sample of the aqueous process solution. Such a buffer system can represent, for example, an aqueous solution of dihydrogen phosphates and hydrogen phosphates. The procedure is preferably such that the amount of the buffer solution is substantially larger than the sample amount of the surfactant-containing process solution.

When using tetrabromophenolphthalein ethyl ester as a color reagent, the measurement of the light absorption in sub-step g) is preferably carried out at a wavelength of 610 nm. In the preferred embodiment using 3.3.5.5-

Tetrabromophenolphthaleinethylester as color reagent can determine the

The content of nonionic surfactants is as follows:

An indicator solution is prepared which contains 100 mg of 3,3,5,5-tetrabromophenolphthalein ethyl ester in 100 ml of ethanol. A buffer solution is also prepared by adding 200 ml of a commercially available buffer solution for pH 7

(Potassium dihydrogen phosphate / disodium hydrogen phosphate) and 500 ml of a three molar potassium chloride solution mixed with 1,000 ml of water.

To carry out the determination, 18 ml of the buffer solution are placed in a suitable vessel. 2 ml of indicator solution are added. To do this, add 50 μl of the sample solution. The combined solutions are stirred for about 3 minutes and then 20 ml of dichloromethane are added. Then the vessel is mixed vigorously for about 1 minute. Then wait for the phase separation, which may take 20 minutes, for example. The organic phase is then removed and measured in a photometer at a wavelength of 610 nm. For example, a 10 mm cell is suitable as the analysis cell. The surfactant content of the sample solution is determined using a calibration curve.

If the surfactant content is so low that the determination becomes uncertain, the volume of the sample used for the measurement can be increased. If the surfactant content is so high that light absorption above 0.9 occurs, it is advisable to dilute the sample before the measurement.

Irrespective of the method chosen, a correlation between the strength of the measurement signal and the concentration of the nonionic surfactants must be established and saved by a previous calibration with surfactant solutions of known concentration. When measuring light absorption, calibration can also be carried out using suitable colored glasses. As an alternative to a previous calibration, the addition of surfactant / reagent complex in known concentration or by multiplying and measuring the interaction with electromagnetic radiation again on the surfactant content of the sample.

As an alternative to determining the interaction of a reagent which binds to the nonionic surfactant or is displaced from it by a complex with electromagnetic radiation, the content of nonionic surfactants can be determined chromatographically. For this purpose, any oils and fats that may be present are preferably first removed from the sample. This can be done, for example, with an absorbent. The sample, which may contain ionic surfactants, is then placed on an anion and / or cation exchange column, which is preferably designed in the manner of a column for high-pressure liquid chromatography. The concentration of the nonionic surfactants in the solution freed from the ionic surfactants, which leaves the exchange column, is preferably determined via the refractive index. The quantitative evaluation is preferably carried out using the external standard method. The measurement is carried out by comparison with pure solvent from the comparison cell and solvent with the substance to be analyzed from the measuring cell of the detector. Water or a water-methanol mixture are suitable as solvents.

Before starting a series of measurements, the HPLC-like ion exchange system must be calibrated and the reference cell of the detector rinsed with the solvent for 20 minutes. Different concentrations of solutions of the non-ionic surfactants to be determined are used for calibration. Calibration and sample solutions must be degassed in an ultrasonic bath for 5 minutes, for example, before they are injected into the HPLC-like system. The defined degassing is important because of the sensitivity of the refractive index detection to different solvent qualities. If methanol is added to the sample solution before it is applied to the HPLC-like ion exchange column, insoluble salts can precipitate out. These have to be filtered off by a microfilter before the sample is placed in the HPLC-like system.

This method is known for the off-line determination of unsulfated components in organic sulfates or sulfonates (DIN EN 8799).

The following method is also suitable for determining the nonionic surfactants: the nonionic surfactants are cleaved with hydrogen halide, preferably with hydrogen iodide, to form volatile alkyl halides, preferably alkyl iodides. The volatile alkyl halides are stripped off by blowing a gas stream into the sample and detected in a suitable detector. For example, an "electron capture detector" is suitable for this. This method is known as a laboratory method for characterizing fatty alcohol ethoxylates (DGF standard method H-III 17 (1994)).

The surfactants can also be anionic surfactants. Their content in the sample solution is preferably determined electrochemically in sub-step d). For this purpose, the anionic surfactants are titrated with suitable reagents, the titration being followed by changing the electrical potential of a suitable measuring electrode.

For example, one can proceed in this way by adjusting the pH of the sample to a range between 3 and 4, preferably to about 3.5, titrating the sample with a titration reagent in the presence of an ion-sensitive membrane electrode and measuring the change in the electrode potential. The sensitivity of this method can be increased by adding an alcohol with 1 to 3 carbon atoms, preferably methanol, to the sample. 1,3-Didecyl-2-methylimidazolium chloride is preferably suitable as the titration reagent. As Measuring electrode is an ion sensitive membrane electrode, preferably with a PVC membrane. Such an electrode is known as a "high sense electrode". A silver electrode is preferably used as the reference electrode. The potential is formed by the most specific possible interaction between the ion carrier contained in the PVC membrane and the ions to be determined in the measurement solution. This interaction leads in an equilibrium reaction to a transition of the measuring ions from the measuring solution into the membrane and thus to the formation of an electrical potential difference at the phase boundary of the measuring solution / membrane.This potential difference can be measured potentiometrically (without current) against a reference electrode The relationship between the measurement ion concentration and the electrical potential can theoretically be described by the Nernst equation, but because of possible interference, it is preferable to use the relationship between the electrode potential Determine ntial and measurement ion concentration by calibration with comparison solutions.

In addition to anionic surfactants, cationic surfactants can also be determined in the process solution to be checked. A method can be used for this, which is also suitable for the determination of anionic surfactants. In this method, too, the determination is carried out electrochemically: a predetermined amount of Na dodecyl sulfate is added to the sample, and the sample is titrated with hyamine (N-benzyl-N, N-dimethyl-N-4 (1.1.3.3.-tetramethyl-buty l) -phenoxy-ethoxyethylammonium chloride) and determines the titration end point with an electrode sensitive to ionic surfactants.

In addition to the above-mentioned methods, processes are suitable for determining the surfactants, in which the surfactants are absorbed on suitable surfaces and effects are measured which are attributable to the fact that the surfaces are coated with the surfactants. Since the surface coverage with the surfactants below the Saturation limit can be set as proportional to the surfactant content, can be inferred from the changes in properties of the surfactant-coated surfaces to the surfactant content of the sample solution after suitable calibration.

For example, one can absorb the surfactants on the surface of a quartz crystal and measure the change in the oscillation frequency of the quartz crystal. Another method is to absorb the surfactants on the surface of a light guide, which may be suitably pretreated. This leads to a change in the refractive index when light passes from the light guide into the surrounding medium, which is reflected in the conductivity of the light guide for light. Depending on the refractive index, the light in the light guide is weakened to different extents or, if the total reflection is lost, no longer arrives at the end of the light guide. By comparing the light intensity emerging at the end of the light guide with that fed in at the beginning, the degree of coverage of the light guide surface with surfactants and thus the surfactant content in the surrounding medium can be determined. The breakdown of total reflection occurs at a certain threshold value of the surfactant content, which can also be used to characterize the surfactant content of the process solution.

ii) Determination of carbon pollution

The determination of the exposure to inorganic and / or organically bound carbon can be carried out as described in more detail in German patent application H 3268. Before determining this parameter, it is advisable to homogenize the sample, for example by vigorous stirring. This ensures an even and fine distribution of the organic impurities present as coarse oil or fat droplets.

If necessary, in step c) the sample is diluted with water in a certain ratio. This ratio can be fixed, but can be changed from a remote location. However, the dilution ratio can also be made dependent on the result of a previous determination of the inorganic and / or organically bound carbon content. This ensures that the carbon content of the sample solution is in a range that allows an optimal determination with the chosen method.

In sub-step d) the inorganically and / or organically bound carbon can be determined, for example, by converting it to CO ₂ and quantitatively determining the CO ₂ formed.

The carbon can be converted to C0 ₂ by oxidation, for example by combustion at elevated temperature in the gas phase. The increased temperature during the combustion is preferably above approximately 600 ° C., for example approximately 680 ° C. The combustion is preferably carried out with air or with oxygen gas in a reaction tube with the aid of a catalyst. Examples of suitable catalysts are noble metal oxides or other metal oxides such as vanadates, vanadium oxides, chromium, manganese or iron oxides. Platinum or palladium deposited on aluminum oxide can also be used as a catalyst. According to this method is obtained directly C0 ₂ -containing combustion gas, the C0 ₂ content can be determined as described below.

As an alternative to combustion in the gas phase, the carbon can also be converted into C0 ₂ using wet chemistry. Here, the carbon of the sample is oxidized with a strong chemical oxidizing agent such as for example with hydrogen peroxide or with peroxodisulfate. If desired, this wet chemical oxidation reaction can be accelerated with the aid of a catalyst of the type mentioned above and / or with UV radiation. In this case, it is preferable to drive off the resulting CO ₂ with a gas stream from the - if necessary acidified - sample in order to determine it quantitatively. It can also be detected in the form of carbonates or carbon bound by C0 ₂ .

Regardless of the method with which gaseous C0 _{2 was} generated, this can be determined quantitatively using one of the following methods. If the amount of sample is known, the inorganic and / or organically bound carbon content of the cleaning solution can be calculated from this. Alternatively, the result of the determination as fat load per 1 detergent bath is specified by a predetermined conversion factor if inorganically bound carbon is not present or has been removed beforehand.

Different methods known in the prior art can be used to determine the CO ₂ content of the gas stream obtained. For example, one can pass the gases through an absorber solution and, for example, measure the weight gain of the absorber solution. Suitable for this is, for example, an aqueous solution of potassium hydroxide, which takes up CO ₂ with the formation of potassium carbonate. As an alternative to determining the weight gain, the change in the electrical conductivity of the absorption solution or its residual alkalinity can be determined after absorption of the C0 ₂ .

The C0 _{2 formed} can also be absorbed on a suitable solid, the weight gain of which is measured. Sodium asbestos, for example, is suitable for this. Of course, both an absorber solution and a Solid absorbers can be replaced when they are exhausted and can no longer bind C0 ₂ .

For an automatically working process, however, it is easier to determine the CO ₂ content of the gas quantitatively by measuring the infrared absorption. The infrared absorption can be determined, for example, at a wavelength of 4.26 μm corresponding to a wave number of 2349 cm ^"1. Devices which can carry out the combustion of the sample and the measurement of the infrared absorption are known in the prior art the TOC system from Shimadzu.

Not only dispersive infrared spectrometers, but also non-dispersive photometers come into consideration for the photometric determination of the C0 content of the combustion gas or the gas expelled from the sample. These are also known as "NDIR devices". Such a device is described for example in DE-A-44 05 881.

With this method of determination, the proportion of carbon that is caused by consciously added active substances in the cleaning solution is also recorded. Examples include surfactants, organic corrosion inhibitors and organic complexing agents. However, their content in the cleaning solution is known within certain fluctuation limits or can be determined separately. The proportion of organically bound carbon due to these active substances can therefore be subtracted from the result of the determination. You then get the portion that is due to the impurities entered. In practice, it is not absolutely necessary to take the carbon content present in the form of active ingredients into account when determining carbon. Rather, it is often sufficient to set an upper limit for the carbon content of the cleaning solution, which already has the active ingredient content considered. The carbon determination then determines whether the carbon load is below or above this maximum limit.

The proportion of organically bound carbon present in the form of lipophilic substances can alternatively be determined by extracting the lipophilic substances into an organic solvent which is not miscible with water in all proportions. After evaporation of the solvent, the lipophilic substances remain and can be determined gravimetrically. However, the procedure is preferably such that the infrared absorption of the lipophilic substances in the extract is determined photometrically. In this context, halogenated hydrocarbons are particularly suitable as water-immiscible organic solvents. A preferred example of this is 1,1,2-trichlorotrifluoroethane. This determination method is based on DIN 38409, part 17. In contrast to this method, the proportion of lipophilic substances in the sample is not determined gravimetrically after the organic solvent has evaporated, but rather photometrically in the organic solvent. The quantitative determination is preferably carried out as in DIN 38409, part 18 by measuring the infrared absorption of the lipophilic substances in the extract at a characteristic oscillation frequency of the CH ₂ group. It is recommended to use such an organic solvent for extraction that does not contain any CH ₂ groups. For example, the infrared absorption band at 3.42 μm (2924 cm ^"1 ) can be used for this photometric determination. This includes all organic substances which have CH ₂ groups and which can be extracted into the organic solvent. Some of these are If the proportion of the surfactants in the cleaning solution is not to be included, it must be determined separately using an alternative method and deducted from the overall result. If necessary, the partition coefficient of the surfactants between the cleaning solution and the organic solvent, which is not miscible with water, must be determined beforehand In practice, however, it may be sufficient to set a maximum of the allowable Determine the load of the cleaning solution with lipophilic substances, which also takes into account the surfactant content. If this maximum value is exceeded, bathroom care measures must be initiated.

In the context of this method, it is recommended that the infrared spectrometer be calibrated with a known amount of a lipophilic substance. For example, a solution of 400 to 500 mg methyl palmitate in 100 ml 1,1,2-trichlorotrifluoroethane is suitable as a calibration solution. This calibration solution is also used to check the function of the IR photometer.

The preferred procedure is to first add a phosphoric acid magnesium sulfate solution to the sample of the cleaning solution. This solution is prepared by dissolving 220 g of crystalline magnesium sulfate and 125 ml of 85% by weight phosphoric acid in deionized water and making up to 1000 g with deionized water. About 20 ml of the phosphoric acid magnesium sulfate solution is added to the sample solution. Then 50 ml of the water-immiscible organic solvent, preferably 1,1,2-trichlorotrifluoroethane, are added. The aqueous and organic phases are mixed, phase separation is effected and the organic phase is isolated. This organic phase is preferably washed again with the phosphoric acid magnesium sulfate solution, the phase separation is brought about again and the organic phase is stripped off. This is transferred to a measuring cuvette and the infrared absorption is measured at an oscillation band of the CH ₂ group. A quartz glass cuvette with a layer thickness of 1 mm, for example, is suitable as the measuring cuvette. From the comparison with the calibration curve, which also contains the blank value of the photometer, the content of lipophilic substances in the sample can be determined using the infrared absorption.

When carrying out the process according to the invention, it may be desirable to use both inorganic carbon and organic carbon Capture carbon (TOC). This is the case, for example, if the sample is burned to determine the carbon content. In this case, dissolved CO ₂ or carbon present in the form of carbonates is also detected if the carbonates split off CO ₂ at the selected combustion temperature. If in this case the inorganic carbon is not to be included, it can be removed by acidifying the sample and blowing out the CO _{2 formed} with a gas such as air or nitrogen. This can be desirable if you only want to determine the "fat load" of the detergent bath. When determining the carbon content in the form of lipophilic substances using the extraction method described above, inorganic carbon is not automatically included.

It is also possible to remove volatile organic compounds from the sample by blowing with a gas such as air or nitrogen before carrying out step d). For example, volatile solvents can be removed before the carbon determination.

iii) Determination of alkalinity

To determine the alkalinity, one can proceed as in the German

Patent application DE 198 02 725.7 described.

In step c), which is special for this method, it is selected whether the free alkalinity and / or the total alkalinity should be determined. This can be entered into the program sequence. For example, both the free alkalinity and the total alkalinity can be determined in one determination cycle. However, the program can also decide to determine one of these two values more frequently than the other. This can be the case, for example, if previous determinations have shown that one of the two values changes faster than the other. Of course, the Choosing whether free alkalinity or total alkalinity should be determined can also be made by an external request. “External requirement” is understood to mean that the automated determination process can be intervened either by a higher-level process control system or manually via a data line.

The terms "free alkalinity" and "total alkalinity" are not clearly defined and are handled differently by different users. For example, certain pH values can be defined up to which titration is required in order to determine either free alkalinity or total alkalinity, for example pH = 8 for free alkalinity, pH = 4.5 for total alkalinity. These preselected pH values must be entered into the control system for the automatic determination procedure. As an alternative to certain pH values, the transition points of certain indicators can also be selected to determine the free alkalinity and the total alkalinity. Alternatively, one can select turning points in the pH value curve and define them as equivalence points for the free alkalinity or the total alkalinity.

The acid-base reaction with an acid is used to actually determine the alkalinity in sub-step d). A strong acid is preferably chosen for this. You can either titrate the sample by adding an acid to the specified criteria for free alkalinity or total alkalinity. Alternatively, you can add the acid and titrate it with the sample.

Various sensors are suitable for tracking the acid-base reaction of the cleaning solution with the acid used for the titration. According to the current state of the art, a pH-sensitive electrode such as a glass electrode will preferably be used. This provides a pH-dependent voltage signal that can be evaluated further. The use of such an electrode is particularly simple in terms of apparatus and is therefore preferred. However, an indicator can also be used to track the acid-base reaction of substep d), the pH-dependent interaction of which is measured with electromagnetic radiation. For example, this indicator can be a classic color indicator, the color change of which is measured photometrically. Alternatively, an optical sensor can be used. This is, for example, a layer of an inorganic or organic polymer with a fixed dye that changes color at a certain pH. As with a classic color indicator, the color change is based on the fact that hydrogen ions or hydroxide ions, which can diffuse into the layer, react with the dye molecules. The change in the optical properties of the layer can be determined photometrically. Alternatively, films such as organic polymers can be used, the refractive index of which changes as a function of the pH. If, for example, a light guide is coated with such a polymer, it can be achieved that total reflection occurs on one side of a threshold value for the refractive index in the light guide, so that a light beam is passed on. On the other side of the threshold value of the refractive index, however, total reflection no longer occurs, so that the light beam leaves the light guide. At the end of the light guide, it can then be detected whether the light is propagated through the light guide or not. Such a device is known as an "Optrode".

Furthermore, inorganic or organic solid bodies can be used as sensors, the electrical properties of which change with the pH of the surrounding solution. For example, an ion conductor can be used, the conductivity of which depends on the concentration of the H ⁺ or OH ^' ions. The pH of the surrounding medium can then be determined by measuring the direct or alternating current conductivity of the sensor. Calibration / control measurements

The method according to the invention is preferably carried out in such a way that the measuring device used for the individual determinations checks itself and, if necessary, recalibrates. For this purpose, it can be provided that the functionality of the measuring device used is checked after a predetermined time interval or after a predetermined number of determinations or on the basis of an external requirement by means of control measurements of one or more standard solutions. A standard solution with known values of the parameter to be determined is measured for testing. This testing is most realistic if a standard cleaning solution is used as the standard solution, the composition of which is as close as possible to the cleaning solution to be tested.

If the measuring device determines a value during a control measurement of a standard solution that deviates from the target content by a predetermined minimum amount, the measuring device issues an alarm message locally or preferably at a remote location. The alarm message can contain a suggestion for intervention selected by the control program of the measuring device or the higher-level process control system.

A key point in checking the functionality of the measuring device for alkalinity is the control of the sensor used. For example, this can be a pH-sensitive electrode, in particular a glass electrode. With the help of a buffer solution as a standard solution, it can be checked whether the electrode delivers the expected voltage, whether it responds in the expected time and whether its slope (= voltage change as a function of the pH change) is in the target range. If this is not the case, the measuring device issues an alarm message locally or preferably at a remote location. The alarm message can be triggered by one of the control program of the measuring device or the parent Process control system contain selected proposal for intervention. For example, it can be suggested that the electrode should be cleaned or replaced.

In the method according to the invention it can also be provided that the functionality of the measuring device used is checked by measuring one or more standard solutions if the results of two successive measurements differ by a predetermined amount. This makes it possible to differentiate whether ascertained deviations from the ingredients in the cleaning bath are real and require bathroom care measures or whether they are simulated by an error in the measuring system.

Depending on the result of the verification of the measuring device used, the determinations made between the current and the previous control measurement can be provided with a status indicator which indicates the reliability of these determinations. If, for example, successive control measurements for checking the measuring device used have shown that it is working correctly, the determinations can be provided with a status indicator "OK". If the results of the control measurements differ by a predetermined minimum amount, for example, the determinations made in the meantime can be carried out with the status indicator " doubtful ".

It can also be provided that, depending on the result of the checking of the measuring device used, one continues with the automatic determination of the measured variables and / or carries out one or more of the following actions: analysis of detected deviations, correction of the measuring device, ending the determination of the relevant measured variable, sending one Status message or an alarm signal to a higher-level process control system or a monitoring device, that is to a remote location. If desired, the measuring device can therefore decide, based on predetermined criteria, whether it is so far is functional that all provisions can be continued or whether deviations are found that require manual intervention.

The measuring system used in the method according to the invention is preferably designed in such a way that it automatically monitors the fill levels and / or the consumption of the reagents and solvents used and of rinsing solutions and issues a warning message when the specified minimum fill level is not reached. This can prevent the measuring device from becoming inoperable because it lacks the required chemicals. The fill levels can be monitored using known methods. For example, the containers with the chemicals can stand on a scale that registers the respective weight of the chemicals. Or you can use a swimmer. Alternatively, a minimum level can be checked by a conductivity electrode that is immersed in the chemical container. The warning message to be output by the measuring device is preferably transmitted to the remote location, so that the appropriate measures can be initiated from there. In general, the method according to the invention preferably provides for the results of the determinations and / or the control measurements and / or the calibrations and / or the status signals to be transmitted continuously or at predetermined time intervals and / or on request to a remote location. As a result, control personnel who do not have to be at the location of the detergent bath are continuously informed about its current alkalinity. Depending on the result of the determinations and the control measurements, necessary corrective measures can be taken either automatically via a process control system or by manual intervention.

Within the scope of the method according to the invention it can be provided that for each of the determinations selected from determinations i), ii) and iii) a predetermined time interval or after a predetermined number of determinations or based on a request from the remote destination by checking measurement of one or more standard solutions to check the functionality of the measuring device used and to transmit the result of the inspection to the remote destination. Furthermore, a corresponding check of the functionality of the measuring device used can be initiated if the results of two successive determinations differ by a predetermined amount. The result of this check is also preferably transmitted to the remote destination. Depending on the result of the test of the measuring device used, the determinations of the respective measured variable made between the current and the previous control measurement can be provided with a status indicator which indicates the reliability of these determinations.

In the method according to the invention, it can further be provided that, depending on the result of one or more of the provisions or provisions selected from provisions i), ii) and iii), the subsequent dosing of supplementary components and / or one or more bathroom care measures is initiated from the remote destination. As an alternative or in addition to this, it can be provided that, depending on the result of one or more of the determinations or determinations selected from determinations i), ii) and iii), the subsequent dosing of supplementary components and / or one or more bath care measures is initiated in a program-controlled manner.

Furthermore, it can be provided in the method according to the invention that the subsequent dosing of supplementary components and / or one or more bathroom care measures is initiated in a program-controlled manner if predetermined relationships between the results of at least two of the determinations selected from determinations i), ii) and iii) are determined . The control program for the method is therefore given certain relations between the Results of the individual provisions i), ii). and iii) before, when they occur, additional components are added and / or bathroom care measures are initiated. The decision about this is therefore not dependent on a single measured value, but on at least two measured values of different bath parameters. The relationships at which measures are taken can be changed from the remote location, for example to take account of operational experience. For example, provision can be made for a measure to reduce the grease load in the cleaning bath (full or partial replacement of the bath, removal of grease and / or oil from the bath using separators and / or membrane filtration processes) if, on the one hand, the content of organically bound carbon exceeds a specified maximum content and on the other hand the surfactant content falls below a specified minimum content. Or you can specify a certain maximum value for the sum of surfactant content and fat load, above which a bath care measure is automatically initiated.

Depending on the measured value obtained or the determined change in the measured values, one or more of the following corrective measures can be initiated:

Correction and bathroom care measures

The simplest corrective measure consists in activating a device that doses one or more supplementary components (solution or powder) into the cleaning bath when a predetermined maximum value of inorganic and / or organically bound carbon is exceeded or upon external request. This can, for example, be automated so that, depending on the carbon content determined, a certain amount of supplemental solution or supplementary powder is added to the cleaning bath. The size of the addition portion itself or the time intervals between the individual additions can be varied in the case of predetermined addition portions. This can for example via dosing pumps or weight-controlled. In the method according to the invention it is therefore provided on the one hand that a certain amount of supplementary component is replenished into the cleaning bath in the event of certain deviations from the target value (in particular if the functionality of the measuring device is established by the control measurements). In addition, it can be provided that these measures to supplement the bath are carried out when a predetermined minimum change in the carbon content has been determined. However, this additional metering can also be carried out on the basis of an external requirement, for example from a remote location, regardless of the current carbon content. Replenishing tensides, for example, increases the carbon content of the cleaning solution. The next time the carbon content is determined, this must be taken into account accordingly, which can be done automatically. Adding surfactants increases the oil and fat-carrying capacity of the detergent bath. Accordingly, the tolerable maximum value of the carbon load must be increased, if exceeded, the next bath care measure is initiated. This can be automatically provided in the control program.

Instead of replenishing bath components such as surfactants or if a predetermined maximum level of inorganic and / or organically bound carbon is exceeded, bath maintenance measures can be initiated which reduce the level of inorganic and / or organic bound carbon in the cleaning solution. Such bath care measures have the particular aim of reducing the fat and oil content of the cleaning solution. In the simplest case, this can be done by draining all or part of the cleaning solution and replacing it with fresh cleaning solution. However, it is more economical to add oils and fats from the cleaning solution by measures known in the art such as separation by a separator or separation by membrane filtration remove. Since surfactants are also at least partially discharged in these processes, the cleaning solution must be supplemented accordingly. That too

Initiation of these measures can not only depend on the absolute carbon content

Detergent solution are made dependent, but on a predetermined

Change in carbon content.

For the control and the control of the surfactant content and / or the alkalinity it can be provided that, if the content falls below a predetermined minimum value or upon an external request, a device is activated which doses one or more supplementary components into the cleaning solution. As a supplementary component, for example, a supplementary solution can be considered which contains all the active ingredients of the cleaning solution in the correct proportions. In addition to the controlled ingredients, the supplementary solution can therefore contain other active ingredients in the cleaning solution, such as, for example, surfactants, builder substances, alkalis, complexing agents and corrosion inhibitors. As an alternative to this, the supplementary solution can contain only surfactants or only alkalis, while the other active ingredients in the detergent solution are added, if necessary due to separate determinations, timed or throughput-controlled.

The size of the addition portion itself or the time intervals between the individual additions can be varied in the case of predetermined addition portions. This can be done, for example, via dosing pumps or weight-controlled. In the method according to the invention it is therefore provided, on the one hand, that in the event of certain deviations from the target value (in particular if the functionality of the measuring device is established through the control measurements), a certain amount of supplementary component is replenished into the process solution. On the other hand, this additional dosing can also be carried out on the basis of an external requirement, for example from a remote location, regardless of the current content of surfactants and / or alkalis. In a further embodiment of the invention, the process solution is supplemented, depending on the throughput, with a predetermined amount of supplementary component per unit implemented. For example, in the case of a cleaning bath for automobile bodies, it is possible to determine the amount of supplementary component to be added per cleaned body. The control of the surfactant content or the alkalinity according to the invention then serves to control and document the success of this predetermined addition and to achieve a more constant operating mode of the cleaning bath by additional result-dependent fine metering, possibly also by suspending the basic metering. This reduces quality fluctuations.

Of course, the method according to the invention presupposes that the corresponding device is made available. This contains a controller, preferably a computer controller, which controls the measurement process as a function of time and / or events. It must also contain the necessary reagent vessels, pipes, valves, dosing and measuring devices etc. for controlling and measuring the sample streams. The materials should be adapted to the intended use, for example made of stainless steel and / or plastic. The control electronics of the measuring device should have a corresponding input-output interface in order to be able to communicate with a remote location.

The method according to the invention makes it possible, on the one hand, to check the contents of cleaning baths on site and to initiate predetermined corrective measures without manual intervention. This increases process reliability and achieves a consistently reliable cleaning result. Deviations from the target values can be recognized early and corrected automatically or manually before the cleaning result deteriorates. On the other hand, the measurement data are preferably transmitted to a remote location, so that operating or supervisory staff also continuously monitor the state of the cleaning bath is informed if it is not in its immediate vicinity. The personnel expenditure for checking and controlling the cleaning bath can hereby be reduced considerably. By documenting the data collected in the method according to the invention, the requirements of modern quality assurance are taken into account. Chemical consumption can be documented and optimized.

Claims

claims

1. A method for checking detergent baths, characterized in that at least two of the following determinations are carried out under program control:

i) determination of the content of surfactants, ii) determination of the contamination with inorganic and / or organically bound

Carbon, iii) determination of alkalinity

and that a) depending on the result of the determinations, the dosing of supplementary components and / or one or more bathroom care measures is initiated and / or b) the results of the determinations and / or data derived from the results of the determinations are transmitted to at least one distant destination, which is in a room other than the facility for implementing the provisions.

2. The method according to claim 1, characterized in that the distant destination is at least 500 m away from the device for carrying out the determinations.

3. The method according to one or both of claims 1 and 2, characterized in that the transmission of the results of the determinations and / or of the data derived from the results of the determinations to the remote destination takes place automatically whenever new results of the determinations and / or derived from the results of the determinations Data are determined.

4. The method according to one or both of claims 1 and 2, characterized in that the transmission of the results of the determinations and / or of the data derived from the results of the determinations to the remote destination takes place on request from the remote destination.

5. The method according to one or more of claims 1 to 4, characterized in that the individual determinations are repeated after predetermined time intervals.

6. The method according to one or more of claims 1 to 4, characterized in that the individual determinations are repeated after the shorter time intervals, the more the results of two successive determinations differ.

7. The method according to one or more of claims 1 to 4, characterized in that the determinations are made on request from the remote destination.

8. The method according to one or more of claims 1 to 4, characterized in that a second determination selected from the provisions i), ii) and iii) is carried out under program control when a first determination from the provisions i), ii) and iii ) selected determination delivers a result which exceeds a predetermined maximum value or falls below a predetermined minimum value or deviates from the previous result of this first determination by a predetermined minimum value.

. Method according to one or more of claims 1 to 8, characterized in that program-controlled i) the determination of the content of surfactants is carried out by a) taking a sample with a predetermined volume from the aqueous process solution, b) if desired the sample of solids freed, c) if desired, the sample is diluted with water in a predetermined ratio or determined as a result of a predetermination, d) the content of surfactants by selective adsorption, electrochemically, chromatographically, by cleavage into volatile compounds, stripping of these volatile compounds and their detection, or by adding a reagent which changes the interaction of the sample with electromagnetic radiation in proportion to the content of surfactants, and measuring the change in this interaction,

10. The method according to one or more of claims 1 to 8, characterized in that ii) the determination of the load with inorganic and / or organically bound carbon is carried out by program-controlled a) taking a sample with a predetermined volume from the aqueous cleaning solution , b) if desired, the sample is freed from solids and / or homogenized, c) if desired, the sample is diluted with water in a predetermined ratio or determined as a result of a predetermination, d) the content of the sample of inorganic and / or organically bound carbon with itself known methods determined.

11. The method according to one or more of claims 1 to 8, characterized in that iii) the alkalinity of the cleaner bath by acid-base reaction with an acid determined, program-controlled a) taking a sample with a predetermined volume from a cleaning bath, b) if desired, the sample freed from solids c) selects whether free alkalinity and / or total alkalinity should be determined, and d) the sample by adding titrates an acid or presents an acid and titrates it with the sample.

12. The method according to one or more of claims 1 to 11, characterized in that for each of the determinations selected from the determinations i), ii) and iii) after a predetermined time interval or after a predetermined number of determinations or on the basis of a request from by checking the measurement of one or more standard solutions, the remote destination checks the functionality of the measuring device used and transmits the result of the check to the remote destination.

13. The method according to one or more of claims 1 to 11, characterized in that for each of the determinations selected from the determinations i), ii) and iii) by control measurement of one or more standard solutions, the functionality of the measuring device used is checked if the results two successive determinations differ by a predetermined amount, and the result of the verification is transmitted to the remote destination.

14. The method according to claim 12 or 13, characterized in that, depending on the result of the test of the measuring device used, the determinations made between the current and the previous control measurement are provided with a status indicator which indicates the reliability of the latter Indicates determinations.

15. The method according to one or more of claims 1 to 14, characterized in that, depending on the result of one or more of the determination or determinations selected from the determinations i), ii) and iii) from the remote destination, the subsequent dosing of supplementary components and / or initiates one or more bathroom care measures.

16. The method according to one or more of claims 1 to 14, characterized in that, depending on the result of one or more of the determinations or determinations selected from the determinations i), ii) and iii), the replenishment of supplementary components and / or one or initiates several bathroom care measures.

17. The method according to one or more of claims 1 to 14, characterized in that program-controlled introduction of supplementary components and / or one or more bathroom care measures is initiated if predetermined relationships between the results of at least two of the provisions of i), ii) and iii) selected provisions are identified.