MXPA00009562A - Method for automatically testing and controlling surface-active contents in aqueous solutions used in a process - Google Patents

Abstract

The invention relates to a method for automatically testing and controlling the surface-active contents in aqueous solutions used in a process. According to said method, the following operations are carried out under control of a program:a) a sample having a predetermined volume is extracted from the aqueous solution;b) solids contained in said sample are optionally removed;c) said sample is optionally diluted in water at a ratio which is predetermined or determined based on the result of a preliminary determination;d) the surface-active contents is determined by selective adsorption, by electrochemical or chromatographic approach, by dissociation into volatile components, by stripping of said volatile components and their detection, or by addition of a reactive agent which modifies the interaction of said sample with an electromagnetic radiation proportionally to the surface-active contents and by measuring the variation of said interaction;e) the result of said determination is stored on a data medium or used as a base for further computation and/or the result of said determination or of further determinations is transmitted to a remote place from where it is possible to take action in the course of the determinations. Measurements for monitoring the bath can be carried out automatically based on predetermined criteria or on demand from a remote place. The inventive method reduces the personnel required for controlling and monitoring the bath and increases process safety.

Description

SUPERVISION AND AUTOMATIC CONTROL OF SURFACTANT CONTENT IN AQUEOUS SOLUTIONS FOR PROCESSES This invention relates to a method for the automatic monitoring and control of aqueous process solutions containing non-ionic ammonium and / or cationic surfactants Examples of these process solutions are bleach for large-scale washing ^ Textile scale cleaning baths for hard surfaces and iron phosphating solutions containing surfactant The method is designed in particular for technical process solutions in the metal working industry such as in automobile manufacturing It makes it possible to automatically monitor the functional capacity 5 as characterized by the parameter "surfactant content" of the process solution and ^ P if it is necessary to supplement the process solution automatically or by external request or introduce other measures of bath maintenance The particular method is designed so that the results of the determinations of The surfactant is transferred to a separate location from the process solution. It is also possible to intervene in the automatic measurement procedure of a location 5 separated from the process solution or start the process. repetition of measurement or other maintenance measures ^ P of bath The "separate location of the process solution" can be left, for example, in a control system of higher level in a control room 5 of the works in which it is located the process solution, or at a point outside the works The cleaning of metal parts before processing them represents a requirement ^ conventional in the metal working industry The 0 metal parts may be contaminated, for example, with pigment earth dust metal abrasion coolant corrosion prevention oils or mold release agents Before processing, such as in particular before the anti-corrosion treatment (v gr, 5 phosphatation anodization chrome, reaction with complex fluorides etc) or before a painting, these ^ fc impurities must be removed by means of an appropriate cleaning solution Spraying, immersion or combined processes are considered for this If you use 0 aqueous process solutions containing surfactant for cleaning, which additionally contain phosphoric acid, a call is made Non-film-forming phosphating simultaneously with cleaning The clean metal parts are coated simultaneously with a phosphate when doing this Amorphous corrosion proof and / or oxide layer The Q processes of this type are widely used in the metal working industry as combined cleaning and corrosion proof processes. When applied to 5 iron-containing material they are called 'phosphatation of iron The industrial non-phosphating cleaners in the metal working industry as a rule are alkaline (pH value of about 7 and above 0 for example 9 to 12) The basic components are alkalis (alkali metal hydroxides, carbonates, silicates, phosphates) borates) as well as for the present purposes non-ionic ammonium and / or cationic surfactants Cleaners frequently contain as additional auxiliary components complex formation agents (gluconates polyphosphates salts of ? k ammocarboxylic acids such as ethylenediamma tetraacetate or nitrotacetate salts of phosphorus acids such as hydroxyethane or diphosphomatic acid salts of phosphono-butane or carboxylic acids or other phosphonic or phosphonocarboxylic acids) anti-corrosion agents such as salts of carboxylic acids having 6 to 12 carbon atoms, alkanolamines and foam inhibitors such as alkoxylates capped from the extreme group of alcohols having 6 to 16 carbon atoms. carbon in the alkyl radical If the cleaner baths do not contain any ammonium surfactants cationic surfactants can be used. The cleaners can also contain both nonionic and ionic surfactants. The cleaners generally contain as nonionic surfactants ethoxylates propoxylates and / or ethoxylates / propoxylates of alcohols or alkylammers having 6 to 16 carbon atoms in the alkyl radical which can also be be capped in end group Alkyl sulfates of fatty alcohol ether and alkylsulfonates are widely used as surfactants to ions Alkylbenzene sulphonates are still encountered but are disadvantageous in terms of environment Cationic surfactants in particular are considered to be cationic alkylammonium compounds having at least one alkyl radical of 8 or more carbon atoms. It is known in the prior art to manually determine the nonionic surfactants in aqueous process solutions such as in cleansing baths by means of a color indicator. The method is conventional. l in this case, a reagent that forms a color complex with non-ionic surfactants is added to a sample taken from the process solution. color complex is preferably extracted towards a ^ P organic solvent not miscible in all proportions with water and light absorption thereof is then determined photometrically at a particular wavelength.

The ethyl ester of tetrabromophenolphthalemate for example can be used as the reagent to form the color complex before extraction to an organic solvent, preferably to a hydrocarbon The process solution in this case is mixed with a buffer system having a pH of 7. It is also known how to determine the nonionic surfactants in the presence of ionic surfactants. The ionic surfactants here are separated from the sample by ion exchangers. 5 non-ionic surfactants not bound in the ion exchanger are determined from the refractive index of The process solution leaving the interchanger column The ammonium and cationic surfactants in aqueous process solutions can be detected, for example, by titration with Hyamyl "" 1622 (= N-benzyl-N-dimethyl-N-4-chloride. 1 1 3 3 -tetramethylbutyl) phenoxyethoxyethylamine) and potentiometric endpoint determination For this the sample is shown with a known amount of Na-dodecyl. the titration with Hyamm is carried out and the end point of the titration is determined using an ion-sensitive electrode Alternatively the ammonium surfactaptes can also be determined by titration with 1 3-d? dec? -2-met chloride ? l? m? dazol? An electrode that has an ion-sensitive membrane is used for detector The electrode potential depends on the concentration of the test ions in the process solution Depending on the result of this determination of surfactant that involves the deployment of personnel, the operating personnel of the plant supplements the process solution with one or more supplementary components. The procedure in this way makes it necessary for the operating personnel to be on standby at the plant site at least during the periods of the Surfactant termination The procedure is intense staff therefore, particularly in multi-shift operation The documentation of the results for quality control and quality safety purposes involves additional expense. Conversely, an object of the present invention is to automate and document the process solution monitoring by surfactant determination in such a way that at least the results of the surfactant determination are stored in a data carrier and / or output. Preferably the measuring equipment used itself must be checked and calibrated and an alarm message transmitted to a remote point in In case of malfunctioning Additionally, it should preferably be possible to check the ing capacity of the measuring equipment and the results of the • Measurement from a remote point It should also be possible to 0 intervene in the measurement procedure and in the maintenance measures for the process solutions from a remote point The number of personnel deployed in the supervision and control of the process solutions should be reduced by the desired remote control 5 This problem is solved by a method for the automatic monitoring and control of the surfactant content of an aqueous process solution where according to the control program (a) a sample having a predetermined volume 0 it is taken from the aqueous solution of process (b) if the sample is required, it is released from solids, (c) if the sample is required it is diluted with water in a previously established relation or a determined one as the result of a previous determination P (d) the content of surfactants is determined by selective adsorption, electrochemically chromatographically dividing into volatile compounds depending on said volatile compounds and detection thereof or by addition of a reagent that varies the interaction of the sample with W electromagnetic radiation in proportion to the content of surfactants and measurement of the variation of said interactionR.

, Y (e) the result of the determination is stored in a data carrier and / or used as a basis for additional calculations and / or the result of the determination or additional calculations is transmitted to a remote location For those present For purposes, an aqueous solution of particular processes is a cleaning solution for hard surfaces in particular for metal surfaces or an iron phosphating solution. Process solutions of this type are known variously in the prior art and are widely used in the industry. metal work The sample volume taken in (a) can ^ P permanently programmed into the control section of the measuring equipment to be used for the method Preferably the sample volume size can be varied from a remote point The control program can be further created in such a way as to cause the sample volume to be used depending on the result of a previous measurement. For example a ^ correspondingly larger sample volume can be selected from the lower the surfactant content of the process solution The accuracy of the surfactant determination can be optimized in this way When reference is made to a 'remote location' in the context of the method of according to the present invention is meant a location that is not directly placed or at least in visual contact with the process solution. The remote location for example may be a central process control system 0 as part of a total process for the surface treatment of metallic parts, supervises and controls a cleaning bath as a subsidiary function. The "remote location" can also be a central control room from which the total process 5 is monitored and controlled and which for example is located in a room other than the process solution can also be considered as a "remote location" however a point outside the works in which the process solution is located. It is possible in this way that the process solution is monitored and control by specialists who are outside the works in which the latter is located This way it is necessary much less frequently than specialized personnel are at 0 the location of the process solution The appropriate data lines with which the results of Surfactant determinations, as well as control commands can be transmitted are known 5 Between the sample taking and the actual measurement, it may be desirable to release the sample of solids in the ^ fc optional step (b) This is not necessary in the case of a process solution loaded only lightly with solids If the solids content is too high, however, Measuring equipment valves can be blocked and the sensors dirty. Therefore, it is recommended that the solids be removed from the sample. This can occur automatically by filtration or alternatively 5 by using a cyclone or a centrifuge.

In (c), the sample, if required, is diluted (^) with water in a previously established relation or one established as a result of a predetermination In (d) the surfactant content is determined by various methods that will be explained in detail below The result of the determination can be stored in a data carrier in step (e) ^ P Additionally or alternatively thereto can be used as the basis for additional calculations In addition, the result of the termination or the result of the additional calculations can be transmitted to a remote location and stored again in a data carrier and / or be output from there. By "outputting 5 the result of the termination" it is implied that the last one is sent to a process control system ^ ft upper level or is displayed on a screen so that it is discernible to a human or print. The location of the display or the output of the result may be the 0"remote location" indicated above. It is preferable that the results of the individual determinations they are stored in a data carrier at least during a pre-established time interval so that they can then be evaluated, for example for quality assurance purposes.

Surfactant determinations, however, do not That they exit directly as such or stored in data carriers. Instead, they can also be used directly as a basis for calculations.

Additional 5, where the results of these additional calculations are displayed or stored. For example, instead of the current surfactant content, the trend in the concentration of surfactant and / or the ^ P relative change of the same can be displayed Or the Current surfactant contents are converted to "% of the target content". In the simplest case, the method according to the present invention operates in such a way that from (a) to (e) are repeated in accordance with a I5 previously established time interval The previously established time interval is determined ^ by the requirements of the operator of the process solution and can include any time interval from a few minutes to several days. For quality control, it is preferable that the previously established time intervals remain, for example between 5 minutes and 2 hours. For example, a measurement can be carried out every 15 minutes. The method according to the present invention, however, can also be carried out in accordance with the present invention. such that from (a) to (e) are repeated after ^ P time intervals that become progressively shorter the longer the results of two successive determinations differ from one another. control for the method according to the present invention can therefore itself decide whether the time intervals between the individual determinations should be shortened or lengthened Naturally ^ P it is necessary to previously establish in the control system the instruction as to what time intervals should be selected for which differences between the results of successive determinations In addition the method according to the present invention can be carried out in such a way that (a) to (e) are made at any time on the basis of an external request In this way For example, immediate supervision of the surfactant content of the process solution can be assumed if quality problems are detected in successive steps. The measurement of the surfactant content can therefore be controlled in time (in accordance with fixed time intervals). or even controlled by event (in the case of detected changes or by external request) 5 Preferably the method of compliance with the present invention is carried out in such a way that the measuring equipment used is itself supervised and if recalibration is necessary. It can be provided in this connection that, after a previously established time interval or after a previously established number of determinations or on the basis of an external request the functional capacity of the measurement equipment used is checked by control measurements of one or more conventional solutions A conventional process solution having known surfactant content is measured for this check This check is closer to reality if it is used as the conventional solution of a conventional process solution whose composition approximates as closely as possible to the process solution to be tested. In the method according to the present invention it can also be provided that the functional capacity of the measuring equipment was bought Check by measuring one or more conventional solutions if the results of two successive measurements differ by a previously established amount. In this way it can be distinguished if the differences discovered in the surfactant content of the process solution are real and require measurements. d? bath maintenance or if they are caused by a failure in the measurement system Depending on the result of the test of the measuring equipment used, the surfactant content determinations that have been conducted between the current and previous control measurements can be provided with a status code that indicates the reliability of said determinations If for example the successive control measurements for the verification of the measuring equipment used have shown that the latter is operating correctly the surfactant content determinations can be provided with a status code 'in order' If the results of the control measurements differ in a previously established minimum quantity the surfactant content determinations that have been conducted in the meantime for example can be provided with the 'doubtful' status code Furthermore they can be provided depending on the result of the equipment check measurement used the automatic determination of the surfactant content is continued and / or one or more of the following steps is carried out analysis of discovered differences correction of the measurement equipment completion of the determination of the content of surfactant sending a status message or an alarm signal to a higher level process control system or monitoring unit ie at a remote location The measuring equipment can therefore decide for itself accordingly with previously established criteria if it has sufficient functional capacity that the determinations of the surfactant content can be continued or if the • Differences are detected that have required intervention or manual The method can be further designed in such a way that the surfactants whose content in the process solution will be determined are non-ionic surfactants The procedure should be adopted for the determination of the same can be such that a reagent is added in (d) that varies in proportion to the content of surfactants not The interaction of the sample with electromagnetic radiation and measures the variation of said interaction. For example, the reagent can be a complex of two substances A and B in which nonionic surfactants displace substance B of the complex with substance A and doing so changes the color or fluorescence properties of the substance B For example 5 the substance B can be a fluorescent substance or a dye that is capable of complexing with, for example, dextran or starch as an example of a substance A As a component of the complex substance B has particular color or fluorescence properties If displaced from the complex, these properties change by measuring the absorption of light or fluorescent radiation it can be detected which portion of substance B is not in complex with substance A Substance A is selected here in such a way that during the addition of nonionic surfactants, substance B is displaced from the complex and formed in place a complex with non-ionic surfactants The amount of substance B displaced from the complex with A is then proportional to the amount of added non-ionic surfactants The amount of added non-ionic surfactants can be inferred from the change in light absorption or fluorescence, said change being caused by the amount of B released For example a reagent can be used as a A salt of a cationic dye with tetraphenyl borate amions. Nonionic surfactants can displace the salt dye after they have been converted to a barium complex by the addition of barium ions. This method of converting non-complex surfactants into complex cationically charged and this way to make them accessible to reactions that respond to cations is also described in the literature as the "activation" of non-ionic surfactants. The method is described, for example, in Vytras K, Kvora ova V and Zeeman I (1989) Analyst 114, page 1435 ff The amount of cationic dye released from the reagent is proportional to the amount of the non-ionic surfactants present. If the absorption spectrum of the dye changes during release the amount of dye released can be 0 determined by the photometric measurement of a band of dye. Suitable absorption This method of determination can be simplified if a salt of a cationic dye which is soluble only in an organic solvent immiscible with water is used as the reactant, while the released dye itself is soluble in water and leads to a dye-like coloration. the aqueous phase The reverse procedure is also naturally possible a water soluble salt of an organic dye is used, where the dye The release method is soluble only in an organic phase. By releasing the dye in exchange for the non-ionic surfactants and extracting the released dye into the other respective phase, it can be determined photometrically in the latter in a simple manner. suitable for the determination of surfactants ^ P cationic Since the latter are already positively charged, the "activation" with barium cations described above is superfluous. In addition, the reagent can be a substance that forms a complex with the ammonium surfactants themselves, which has different color or fluorescence to the free reagent For example the ^ P reagent may be colorless in the visible region, 0 while the complex thereof with non-ionic surfactants absorbs electromagnetic radiation in the visible region, ie has a color OR the maximum of light absorption ie the color of the reagent not combined differs from that of the complex with the 5 non-ionic surfactants The reagent however, may also show fluorescence properties ^ P particular that vary during the complex formation of non-ionic surfactants For example the free reagent can fluoresce while the formation of 0 complex with non-ionic surfactants rapidly quenches the fluorescence In all cases it is possible, measuring the absorption of light for that is previously established or fluorescent radiation to determine the concentration of the reagent complex and 5 non-ionic surfactants and therefore the concentration of the non-ionic surfactants themselves ^ H A reagent that forms a complex with the non-ionic surfactants that can be extracted into a non-miscible organic solvent is preferably added in (d) in all proportions with water Next, an extraction of the complex consisting of non-ionic surfactants and the reagent added to the organic solvent not miscible in all proportions with water is carried This can occur by intense mixing of the two phases, for example by stirring or preferably by movement. The mixing of the two phases is completed after extraction, so that a phase separation towards an aqueous phase and a If the phase separation is required to be completed, it can be checked by appropriate methods, such as electrical conductivity determination or the measurement of light absorption or light scattering nebulosity. This is followed by the actual measurement of the content of non-ionic surfactants For this, the organic phase, which contains the complex consisting of non-ionic surfactants and added reagent, is exposed to electromagnetic radiation that can interact with the complex dissolved in the organic phase. For example, it can be used as radiation visible electromagnetic or ultraviolet radiation whose absorption by the complex ^ P consisting of non-ionic surfactants and added reagent is determined It is also possible however that a reagent be used whose complex with the non-ionic surfactants produce a characteristic signal during nuclear resonance or electron spin resonance measurements The signal resistance expressed as the weakening of a vibration ^ P electromagnetic in the corresponding frequency band (absorption) 0 can be correlated with the concentration of the complex Instead of the absorption effects the emission effects can also be used to determine the concentration For example a reagent can be selected whose complex with 5 surfactant Non-ionic in the organic solvent absorbs electromagnetic radiation of a particular jp wavelength and in turn emits electromagnetic radiation of a longer wavelength whose intensity is measured. An example of this is the measurement of the fluorescent radiation 0 during irradiation of the sample with visible or ultraviolet light The interaction of the organic phase with electromagnetic radiation can, in principle, occur directly after the termination of the phase separation in the same vessel in which it is carried out phase separation Depending on the measurement method used to determine the interaction of the organic phase with electromagnetic radiation however it is preferable to extract the organic phase or a part of it and feed it to the actual measurement equipment along a line It is in particularly possible in this way to provide appropriate cells for measurement Consequently a preferred embodiment of the present invention involves, after (f), separating the organic phase from the aqueous phase and feeding it to the measuring equipment Said separation of the organic phase is particularly recommended if the organic solvent not miscible in all proportions with water is a halogen-containing solvent with a density greater than water After carrying out the phase separation the organic phase is then placed in the lower part of the container and can be withdrawn in a descending manner. Examples of halogen-containing solvent are dichloromethane or higher boiling halogenated hydrocarbons, particular chlorinated or fluorinated hydrocarbons such as trichlorotpf luoretane These solvents should be discarded after use in accordance with the provisions of local statutes Since this can be expensive there is the possibility of preparing the solvent used again, for example by treatment with activated carbon and / or ^ P by distillation and re-use for the measurement process In a preferred embodiment of the present In the invention, an agent that is subjected to a color reaction with the nonionic surfactant in the organic phase is added as the reactant. The interaction of the organic phase with electromagnetic radiation can be measured ^ P as the absorption of light at a previously established wavelength 0 A conventional photometer is appropriate for this purpose For example, tetrabromophenolphthalein ethyl ester can be used as the color reagent In this case, the sample from the aqueous process solution it must be mixed with a buffer system having a pH of about 7 said buffer system. for example it can be a solution of ^ Aqueous process of dihydrogen phosphates and hydrogen phosphates ST adopts a procedure here so that the amount of the buffer solution is substantially greater than the amount of sample of the process solution containing surfactant If ethyl ester of tetrabromophenolphthalein is used as the color reagent, the measurement of the Light absorption in (g) is preferably carried out at a wavelength of 610 nm In the preferred embodiment, the use of 3,3,5-tetrabromophenolphthalein ethyl ester as reagent d? color the determination of the content of nonionic surfactants can occur as follows an indicator solution containing 100 mg of 3,3,5,5-tetrabromophenolphthalein ethyl ester in 100 ml of ethanol is prepared In addition, a buffer solution is prepared by mixing 200 ml of a commercial buffer solution having a pH of 7 (potassium dihydrogen phosphate / disodium hydrogen phosphate) and 500 ml of a 3 0 M potassium chloride solution with 1,000 ml of water To carry out the determination they are placed 18 ml of the buffer solution in a suitable vessel 50 ul of the sample solution are then added The combined solutions are stirred for about 3 minutes and then 20 ml of di chloromethane are added The contents of the vessel are then mixed vigorously for about 1 minute The phase separation is then expected, which may require for example 20 minutes. Next, the organic phase is separated and measured in a photometer at a wavelength of 610 nm. A 10 nm cell, for example, is appropriate. as the analysis cell The surfactant content of the sample solution is determined by means of a calibration curve. ^ P If the surfactant content is to such a degree that the determination is not reliable, the volume of the sample used for the measurement may be increased. If the surfactant content is elevated to a degree If a light absorption of more than 0 9 occurs, it is recommended that the sample be diluted before the measurement. P Regardless of the selected method, 0 a correlation between the resistance of the test signal and the concentration of the surfactants must be obtained by means of a calibration. previous with surfactant solutions of known concentration and stored If the absorption of light is measured the calibration can also occur by means of appropriate color glasses As an alternative to a previous calibration the ^ P conclusions can be drawn on the surfactant content of the sample by the addition of surfactant / reagent complex at known 0 concentration or multiple superimposed and renewed measurement of the interaction with electromagnetic radiation As an alternative to a determination of the interaction with electromagnetic radiation of a reagent combined with the non-ionic surfactant or displaced from a complex by the last surfactant content no lómeos can be determined chromatographically for Accordingly, any oils and fats present are preferably removed from the sample at the beginning. This can be carried out for example using a Absorbent Next, the sample optionally containing ionic surfactants is passed to an anion and / or cation exchange column, which preferably looks in its disposition to a column ^ P for high-pressure liquid chromatography The concentration of non-ionic surfactants in the solution released from ionic surfactants whose solution leaves the exchange column is preferably determined by means of the refractive index. The quantitative evaluation is preferably conducted here 5 by the external standard method The measurement occurs by a comparison with pure solvent of the ^ P comparison cell and solvent-containing material for analysis of the detector test cell Water or a mixture of water and methanol are considered 0 solvents Before the beginning of a measurement series an HPLC type ion exchange system should calibrate and the comparison cell of the detector rinsed with the solvent for 20 minutes. The 5 solutions that have variable concentrations of the non-ionic surfactants that are to be determined ^ P used for calibration Calibration and sample solutions should be degassed in an ultrasonic bath, for example, for 5 minutes before the injection into the HPLC type system This degassing is important in consideration of the sensitivity of refractive index detection of different qualities of the solvent ^ P If the sample solution is mixed with methanol or before application to the exchange column of HPLC-type ions may precipitate more soluble salts The latter must be filtered through a microfilter before feeding the sample to the HPLC-type system. This method is known for the off-line determination of non-sulphonated portions in sulphates. organic or sulfonates (DIN EN 8799) In addition the following procedure is suitable for the determination of nonionic surfactants or nonionic surfactants ST lixivian using hydrogen halide, preferably using hydrogen iodide, with the formation of volatile alkyl halides of Preference for alkyl iodides Volatile alkyl halides are released from the before the injection of a gas stream into the sample and Detect in an appropriate detector For example, an "Electron Capture Detector" is appropriate for this purpose This method is known as a laboratory method to characterize ethoxylated fatty alcohol (DGF Einh? itsmethode H-III 17 (1994) Surfactants can also be ammonium surfactants The content of these in the sample solution is preferably determined electrochemically in (d) For this, the ammonium surfactants are titrated with appropriate reagents, the titration being monitored by the variation of the electric potential of an appropriate test electrode For example, a method may be adopted here so that the pH of the sample is established between 3 and 4, preferably about 3 5, the sample is titrated with a titration reagent in the presence of an ion-sensitive membrane electrode and the variation in electrode potential is measured The sensitivity of this method can be increased by the sample or mixed with an alcohol having 1 to 3 carbon atoms, preferably with methanol. As the titrating agent, 1,3-d? dec? -l-2-methylimdazolium chloride is preferred An ion-sensitive membrane electrode which preferably has a PVC membrane serves as the test electrode said electrode is known as a "high-sense electrode" An electrode Q plate is preferably used as the reference electrode. Potential formation occurs through a specific interaction as possible between the carrier of ions contained in the PVC membrane and the ions to be determined in the test solution This interaction leads to an equilibrium reaction to a transfer of the test ions from the solution of ^ P test towards the membrane and therefore to the formation 0 of an electrical potential difference in the phase limit of test solution / membrane This potential difference can be measured potentiomotrically (without current) against a reference electrode degree of ion transfer outside the solution of 5 test towards the membrane depends on the concentration The ratio between the concentration of test ions and the ^ electrical potential can be described theoretically by the Nernst equation Due to possible perturbation, it is preferable however to establish the relationship between the electrode potential and the concentration of test ions by calibration using comparison solutions In addition to the ammonium surfactants the surfactants cation can also be determined in the process solution that is to be monitored. use a method for this that is also appropriate •? to determine ammonium surfactants In this? method also the determination occurs electrochemically a predetermined amount of Na-dodecyl sulfate is added to the sample the sample is titrated with Hyamin (ammonium chloride of N-benzyl-N Nd? ptet? lN-4- (l 1 3 3- tetramethylbutyl) phenoxyethoxyethyl) and the final titration product is determined using an electrode sensitive to the ionic surfactants. In addition to the methods mentioned above, the methods are suitable for determining surfactants in which the surfactants are absorbed on appropriate surfaces. and effects that are atpubic to the covering 5 of the surfaces with the surfactants are measured Since the coating of the surfaces with the ^ P surfactants can be assumed to be proportional to the surfactant content below the saturation limit it is possible after appropriate calibration to draw conclusions regarding the surfactant content of the sample solution from the changes in properties of surfactant-coated surfaces. , the surfactants can be absorbed on the surface of an oscillator crystal and the variation in the oscillation frequency of the crystal of oscillate measurement An additional method involves absorbing the surfactants in the, optionally of previously treated appropriately, surface d? a light guide This leads to a variation in the index of refraction in the passage of light outside the light guide to the surrounding medium whose variation becomes noticeable in the conductivity of the light guide for light Depending on the refractive index, the light in the guide ^ P light is attenuated to varying degrees or, in the case of I Q total reflection loss at the light guide end no longer appears at all The degree of coverage of the light guide surface with surfactants and therefore the surfactant content in the surrounding medium, can be determined by comparing the intensity light that comes out at the end of the light guide with that fed at the beginning The shock of the ^ P total reflection occurs at a particular threshold value of the surfactant content that can also be used to characterize the surfactant content of the process solution The method according to the present invention is applicable to any process solutions. It is particularly designed for process solutions in the metal working industry by example in the manufacture of automobiles For example the aqueous process solution can be a cleaning solution These cleaning solutions are used, for example for the cleaning of automobile bodies before phosphating For monitoring and control of said cleaning solution, it can be provided that by falling short of a minimum value previously established for the surfactant content or in response to an external request, a # device that measures one or more supplementary components towards the cleaning solution A supplementary component is considered, for example that is a supplementary solution containing all the active substances of the cleaning solution in the correct quantitative ratio The supplementary solution so Therefore, it may contain, in addition to the surfactants tested, additional active substances of the ^ P cleaning solution, such as additional surfactants d substances? Alkalis formation complexing agents and corrosion inhibitors Alternately 0 to this the supplemental solution may contain only the surfactants, while the other active agents of the cleaning solution are measured repeatedly at a clock pulse or under complete control if necessary. According to separate specifications In this respect, the size of the own portion x? added or in the case of added portions exactly established in advance the time intervals between the individual additions can be varied can occur for example by means of metering pumps or controlled by weight In the method according to the present invention, therefore, it is provided, on the one hand, that in case of deviations * & particular values of the target value (in particular if the functional capacity of the measuring equipment has been determined by the test measurements), a particular amount of supplementary component is measured repeatedly towards the process solution. On the other hand, this subsequent measurement can also be 5, however, in response to an external request, for example from a remote location independently of the ^ P Current content of surfactants In a further embodiment of the present invention, the process solution is supplemented as a production function with a pre-established amount of supplementary component per unit introduced For example, it can be determined for a cleaning bath for car bodies what amount of supplementary component is added per 5 body cleaned The compliance monitoring the present invention of the surfactant content or of the P value the interruption of the basic measurement then serves to monitor and document the success of said previously established addition and also to achieve by a further measurement dependent of additional result a more constant mode of operation of the bath In this way, the quality fluctuations are reduced. Preferably, the measurement system ^ P used in the method according to the present invention is designed to automatically check the filling levels and / or the consumption of the reagents used. (color or fluorescence reagent standard titration solution and solvent test solutions buffer solution or 5 auxiliary solutions) and issues a warning message if a previously established minimum fill level is not filled ^ Measuring equipment in this way can be prevented from being able to function because it lacks the required chemicals. Checking filling levels 0 can occur by known methods. For example, containers containing chemicals can be on a scale. which registers the respective weight of the chemical products Or else a float is inserted Alternatively a minimum filling level can be checked by a conductivity electrode that is immersed in the container containing the chemical The warning message to be issued by the measuring equipment is preferably transmitted to the remote location, so that relevant measures can be initiated from there In general, it is preferably provided in the method according to the present invention that the results of the determination and / or • the verification measurements and / or the 0 calibrations and / or the status signals are transmitted continuously or at pre-established time intervals and / or at the request of a remote location. In this way, the verification personnel do not have to be present at the location of the process solution are regularly informed of its current surfactant content. Depending on the result of the ^ fc determinations and verification measurements, the required corrective measures can be assumed either automatically by a process control system or by manual intervention The method according to the present invention naturally presupposes that the corresponding equipment is available. The latter comprises a controller, preferably a computer-controlled controller. which controls the measurement sequence on a basis dependent on time or event You must also ^ P understand the required reagent vessels, tubes, valves, measuring and measuring devices etc. to control and measure sample flows. of the equipment must be suitable for the intended use, for example be made of stainless steel and / or of plastic material. The control electronics of the measuring equipment should comprise an interface of ^ corresponding input-output, in order to be able to 0 communicate with a remote location The method according to the present invention makes it possible on the one hand, to check the surfactant content of on-site process solutions and initiate corrective measures beforehand established without manual intervention The process safety is improved in this way and a result is achieved ? k of constantly reliable process The outputs of the target values can be detected quickly and corrected automatically or manually before they are affects the result of the process On the other hand, the preference test data is transmitted to a remote location, so that the operating or supervising personnel also ST report regularly the status of the process solution if they are not in the immediate proximity of it Personnel costs for the monitoring and control of the process solution can be considerably reduced in this way. The requirements of a modern quality security system are filled by documenting the data received in the method according to the present invention. The consumption of chemical product can be documented and optimized.

Claims (33)

1 - . 1 - A method for the automatic monitoring and control of the surfactant content of an aqueous process solution in which under the control of program (a) a sample having a predetermined volume of the aqueous process solution is taken, ^ P ( b) if required, the sample is freed from 0 solids, (c) if required the sample is diluted with water in a previously established ratio or determined as the result of a previous determination, 5 (d) the surfactant content The ST is determined by chromatographically-selective electrophoretic adsorption by dividing into volatile compounds, purifying said volatile compounds and detecting them, or by adding a reagent that varies the interaction of the sample with electromagnetic radiation in proportion to the surfactant content and measurement of the variation 25 of said interaction and QP (e) the result of the determination is stored in a data carrier and / or used as a basis for further calculations and / or the result of the determination or additional calculations is transmitted to a remote location

2 - A method in accordance with W claim 1, wherein the aqueous process solution 10 is a cleaning solution or iron phosphating solution

3 - A method according to either or both of claims 1 and 2, wherein from (a) to (e) are repeated after a pre-set time interval 15 set forth

4 - A method of conformance with one or both of the claims 1 and 2 wherein from (a) to 8e) are repeated after time intervals that become progressively shorter the more the 20 results of two differ successive determinations among themselves

5 - A method according to one or both of claims 1 and 2 wherein from (a) to (e) are executed on the basis of an external request

6 - A method of compliance with one or more of 25 claims 1 to 5, wherein, after a After a pre-established number of determinations or on the basis of an external request, the functional capacity of the measuring equipment used is checked by means of control measurement of one or more conventional solutions. A method according to one or more of claims 1 to 5, wherein the capacity The functional P of the measuring equipment used is checked by means of control measurement of one or more conventional solutions if the results of two successive determinations differ by a previously established amount. A method of conformity with either or both of the claims 6 and 7 wherein depending on the result of the measurement equipment check P used the surfactant content determinations that have occurred between the current measurement and the previous control are provided with a state code which characterizes the reliability of said determinations of the surfactant content 9 - A method according to one or both of claims 6 and 7 wherein depending on the result of the verification of the measuring equipment 5 used, the automatic determination of the content of the Surfactants are continued and / or one or more of the following ^ P steps is carried out analysis of discovered differences, correction of the measuring equipment termination of the surfactant content determinations, sending a status message or an elongation signal to a higher level process control system or a monitoring unit 10 - A method of conformance with one or more of claims 1 to 9, wherein the surfactants are 10 non-ionic surfactants 11 - A method according to claim 10, wherein in (d) a reagent is added which varies, in proportion to the content of nonionic surfactants, the interaction of the sample with radiation 15 electromagnetic, and measures the variation of said interaction QP 12 - A method according to claim 11, wherein the reagent is a complex of two substances A and B, the non-ionic surfactants that displace the substance B complex d? with the substance A and in doing so change the color or fluorescence properties of substance B 13 - A method according to claim 11, wherein the reagent is a substance 5 which forms a complex with ammonium surfactants, which has different color or fluorescence properties to a • free reagent 14 - A method according to claim 13, wherein a reagent is added in (d) 5 which forms a complex with non-ionic surfactants, which can be extracted into an organic solvent not iscible in all proportions with water, after the addition of the reagent, the sample being extracted with the organic solvent a phase separation towards an aqueous phase and 10 an organic being carried out and the interaction of the organic phase with electromagnetic radiation being measured 15 - A method according to claim 14, wherein, after the separation of In this step, the organic phase is separated from the aqueous phase 16 - A method according to one or both of the claims 14 and 15, wherein the solvent which is not miscible in all proportions with water is used as the solvent contains halogen 20 < 3 has a higher density than water 1

7 - A method according to claim 1 or 14, wherein an agent that is subjected to a color reaction with the nonionic surfactant in the organic phase is added as reagent. , the 25 interaction of the organic phase with radiation electromagnetic being measured as the absorption of light at ^ P a previously established wavelength 1

8 - A method according to claim 17 wherein ethyl ester of 5 tetrabromophenolphthalein as a color reagent and the aqueous process solution is mixed with a buffer system having a pH of 7 - A method of compliance with the P ^ claim 18 wherein the absorption measurement 10 light in (g) is carried out at a wavelength of 610 nm 20 - A method according to claim 10 wherein the content of nonionic surfactants is determined chromatographically. Claim 20 wherein if the oils are required and ^ P greases are removed from the sample by means of an absorbent any ionic surfactants present are separated using an ammonium exchange column. 20 and / or cation and the variation in the refractive index of the solution released from the ionic surfactants and leaving the exchange column is measured 22 - A method according to claim 10 wherein the nonionic surfactants are leached using hydrogen halide with the formation of volatile alkali halides and the volatile alkali halides P are separated and detected. A method according to one or more of claims 1 to 9 wherein the surfactants are 5 ammonium surfactants, the content of which is determined electrochemically in (d) 24 - A method according to claim 23 wherein the pH of the sample is ^ P establishes between 3 and 4 the sample titrated with a 10 titration reagent in preeencia d? an ion-sensitive membrane electrode and the variation in electrode potential is measured. A method according to claim 24, wherein the sample is mixed with a 15 alcohol having 1 to 3 carbon atoms 26 - A method according to one or both of the AA of claims 24 and 25, wherein 1 3-d? Dec? L-2-met? L? M is used ? dazole? or as titration reagent 20 27 - A method according to any of claims 1 to 9 wherein surfactants are cationic surfactants the content of which is determined electrochemically in (d) 28 - A method of compliance with claim 25 or claim 27. wherein a pre-determined amount of Na-dodecyl sulfate is added ^ P to the sample the sample is titrated with Hyamin (ammonium chloride of N-benzyl-N Nd? met? lN-4- (1 1 3 3 -tetra-methylbutyl) phenoxyethoxyethyl) ) and the final titration product is determined by means of an ion-sensitive electrode 2

9 - A method according to one or more of claims 1 to 9 wherein the surfactants are ^ P absorb on the surface of an oscillator crystal and the variation in the oscillation frequency of the oscillator crystal is measured 30 - A method according to one or more of claims 1 to 9 wherein the surfactants are selectively adsorbed on the surface of a fiber of Glass and the variation in refraction of light from the glass fiber surface is detected ^ P 31 - A method according to one or more of claims 1 to 30 wherein a cleaning solution is used as an aqueous solution of process and 20 by falling short of a previously established minimum value for the content of non-ionic ammonium or cationic surfactants or upon request a device is activated that measures one or more supplementary components towards the cleaning solution 5 32 - A method of conformance with one or more of lae claims 1 to 31 where loe nivelee d? (F filling and / or consumption of the reagents used is automatically monitored and when falling short of a previously set minimum filling level a warning message is issued 33 - A method of conformance with one or more of claims 1 to 32 in where the results of the determination and / or of the verification measurements • Wt and / or of the calibration and / or the status signals are transmitted continuously or at pre-established time intervals and / or upon request at a location different from the location of the determination SUMMARY OF THE INVENTION A method for the automatic monitoring and control of the surfactant content in an aqueous solution for process, where, according to the control of the program: a) ST takes a sample having a predetermined volume of the aqueous solution for process b) if required, the sample is released from solids c) if required, the sample is diluted with water at a pre-established or determined rate as a result of a previous determination 5 d) the content of the surfactants is determined by selective adsorption, by methods: p electrochemical, chromatographic, by dissociation in volatile compounds, by drag d? such volatile compounds and the detection of these, or by the addition of a reagent that modifies the interaction of the sample with electromagnetic radiation in proportion to the content of the surfactants, and the extent of the variation of this interaction. e) the result of the determination is stored in ^ P a data carrier and / or is used as a basis for other calculations and / or the result of the determination or of the other calculations is transmitted to a remote location. It is also possible to intervene from there in the realization of the determinations. The measures of the maintenance of a bath can be initiated automatically ^ P or by request from a remote place according to predetermined criteria The method reduces the number of people to supervise and maintain the bath and increases the safety of the process,