Storage-stable solution comprising hypochlorous acid and / or hypochlorite

Abstract

The present patent application relates to a process for preparing a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, comprising the following steps: a. introducing an aqueous NaCl solution into an electrolysis cell (1) which comprises a cathode space (2) and an anode space (3) separated from one another by a separator (4), with the aqueous NaCl solution being introduced via a first feed line (5) into the cathode space (2) and via a second feed line (6) into the anode space (3), and with the aqueous NaCl solution comprising more than 100 ppm of NaCl, b. applying a direct current to a cathode in the cathode space (2) and to an anode in the anode space (3) to generate a cathode solution in the cathode space (2) and an anode solution in the anode space (3), and c. mixing a portion of the cathode solution with the aqueous NaCl solution before it is introduced into the anode space (3) and / or with the anode solution in the anode space (3) and / or with the anode solution in an offtake line (7) assigned to the anode space (3), or adding an NaOH solution to the anode space (3) and / or to an offtake line (7) assigned to the anode space (3), to prepare a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite that has a pH of 5 to 6 and can be taken off via offtake line (7).

Description

[0001] STORAGE-STABLE SOLUTION COMPRISING HYPOCHLOROUS ACID OR.

[0002] HYPOCHLORITE

[0003] TECHNICAL FIELD

[0004] The present invention relates to processes for the preparation of storage-stable aqueous solutions comprising hypochlorous acid and / or salts thereof.

[0005] BACKGROUND OF THE INVENTION

[0006] Hypochlorous acid and its salts (hypochlorites), also known as active chlorine, can be produced using a variety of processes. One frequently used process involves the electrolysis of a NaCl solution, usually using electrolysis cells. Since the electrolysis of NaCl solutions can produce explosive gas mixtures (oxygen and chlorine gas at the anode and hydrogen at the cathode), the electrolysis cell contains a membrane or diaphragm that separates the cell into an anode and a cathode compartment. Only small ions such as sodium and hydroxide ions can pass through the membranes or diaphragms, so there is no mixing of the solutions produced at the anode or cathode.This separation creates an acidic, oxidizing solution with excellent disinfecting properties in the anode compartment, and a basic, reducing solution in the cathode compartment. The solution created in the anode compartment is called the anolyte, and the solution created in the cathode compartment is called the catholyte. The solutions created by this process are also known as electrochemically activated (EGA) solutions.

[0007] The antimicrobial effectiveness of the anolyte solution is due to the interaction of the oxidative ions (hypochlorous acid), which have a relatively high redox potential, and the low pH value. ECA solutions have been shown to kill 99.99% of germs and are over 100 times more effective than conventional chlorine bleach, for example. Thanks to their non-selective antimicrobial effectiveness, they also do not contribute to the development of resistance. The effectiveness of ECA solutions against bacteria, fungi, viruses, algae and spores has been scientifically proven. For this reason, ECA solutions are used, among other things, in drinking water treatment and for the disinfection of medical equipment in hospitals, for example. ECA solutions are also used in plant breeding and animal husbandry.In certain countries, ECA solutions are also used in food production, where ECA solutions can come into both direct and indirect contact with food.

[0008] In addition to their use as disinfectants, ECA solutions have proven to be very effective in treating wounds and burns, so they have also proven their worth in the medical treatment of humans and animals.

[0009] The diverse use of ECA solutions in a variety of fields demonstrates the usefulness of aqueous solutions containing hypochlorous acid. However, it has been shown that the solutions produced using previous methods have a relatively short storage stability, so that the concentration of hypochlorous acid or hypochlorite in these solutions decreases significantly over time. Due to this decrease in concentration, the solution loses its effectiveness and can no longer be used effectively.

[0010] It is therefore an object of the present invention to provide a process which makes it possible to produce a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite.

[0011] SUMMARY OF THE INVENTION

[0012] Therefore, the present invention relates to a process for producing a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, comprising the steps of: a. introducing an aqueous NaCl solution into an electrolysis cell (1) which comprises a cathode compartment (2) and an anode compartment (3) which are separated by a separator

[0013] (4) are separated from one another, wherein the aqueous NaCl solution is introduced into the cathode compartment (2) via a first feed line (5) and into the anode compartment (3) via a second feed line (6), and wherein the aqueous NaCl solution comprises more than 100 ppm NaCl, b. applying a direct current to a cathode in the cathode compartment (2) and to an anode in the anode compartment (3) to produce a cathode solution in the cathode compartment (2) and an anode solution in the anode compartment (3), and c.Mixing a portion of the cathode solution with the aqueous NaCl solution before introducing it into the anode compartment (3) and / or with the anode solution in the anode compartment (3) and / or with the anode solution in a discharge line (7) associated with the anode compartment (3), or adding a NaOH solution to the anode compartment (3) and / or to a discharge line (7) associated with the anode compartment (3) in order to produce a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite which can be discharged via discharge line (7) and which has a pH value of 5 to 6.

[0014] It has surprisingly been found that the electrolysis of a NaCl solution comprising more than 100 ppm NaCl enables the production of a storage-stable solution comprising hypochlorous acid and / or hypochlorite if the pH of the produced solution is adjusted to 5 to 6.

[0015] A further aspect of the present invention relates to a process for producing a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, comprising the steps of: a. introducing an aqueous NaCl solution into an electrolysis cell which comprises a cathode compartment and an anode compartment which are separated from one another by a separator, the aqueous NaCl solution being introduced into the cathode compartment via a first feed line and into the anode compartment via a second feed line, and the aqueous NaCl solution comprising more than 100 ppm NaCl, b. applying a direct current to a cathode in the cathode compartment and to an anode in the anode compartment to produce a cathode solution in the cathode compartment and an anode solution in the anode compartment, and c.Mixing a portion of the cathode solution with the aqueous NaCl solution before introducing it into the anode compartment and / or with the anode solution in the anode compartment and / or with the anode solution in a drain associated with the anode compartment or adding a NaOH solution to the anode compartment and / or to a drain associated with the anode compartment in order to produce a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite which can be discharged via a drain and has a pH value of 5 to 6, wherein the introduction of the aqueous NaCl solution into the electrolysis cell and the discharge of the storage-stable aqueous solution from the electrolysis cell at a flow rate of 0.1 m / s to 2 m / s.

[0016] It has surprisingly been found that the flow rate selected in the electrolysis process according to the invention can influence the stability of the aqueous solution produced. This means that if a specific flow rate is selected for the electrolysis, this can lead to a stable product with a lower degradation rate of the hypochlorous acid or hypochlorite.

[0017] The object of the invention can also be achieved by a process for producing a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, comprising the steps of: a. introducing an aqueous NaCl solution into an electrolysis cell which comprises a cathode compartment and an anode compartment which are separated from one another by a membrane, wherein the aqueous NaCl solution is introduced via a first feed line into the cathode compartment and via a second feed line into the anode compartment, and wherein the aqueous NaCl solution comprises more than 100 ppm NaCl and has an electrical conductivity of less than 30 mS / cm, preferably less than 5 mS / cm, b. applying a direct current to a cathode in the cathode compartment and to an anode in the anode compartment to produce a cathode solution in the cathode compartment and an anode solution in the anode compartment, and c. mixing a portion of the cathode solution

[0018] ■ with the aqueous NaCl solution before its introduction into the anode compartment and / or

[0019] ■ with the anode solution in the anode compartment and / or

[0020] ■ with the anode solution in a drain associated with the anode compartment, or

[0021] Addition of a NaOH solution

[0022] ■ into the anode compartment and / or

[0023] ■ in a drain associated with the anode compartment in order to produce a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite which can be discharged via the drain and which has a pH value of 5 to 6.

[0024] In particular, the pH of the solution prepared by the process according to the invention influences the stability of the hypochlorous acid and / or hypochlorite present therein. The greatest stability was observed at a pH of 5 to 6. Therefore, the pH of the aqueous solution according to the invention prepared during electrolysis is adjusted to 5 to 6. The pH can be adjusted in a variety of ways.

[0025] Firstly, the pH value can be adjusted by introducing a portion of the cathode solution (catholyte) into the anode compartment. The catholyte which is formed during electrolysis has a high pH value (more than 10) due to the formation of hydroxide ions. This high pH value makes it possible to increase the pH value of the anolyte in the anode compartment to 5 to 6. Without this addition, the pH value of the anolyte would fall below 4. The catholyte can be introduced into the anolyte in a variety of ways, although it is particularly preferred to create a connection between the cathode and anode compartments and to control the feed of the catholyte into the anode compartment via a valve which is preferably pH-controlled. Corresponding devices are sufficiently described in the prior art (see, for example, EP 1 074 515). Alternatively, the catholyte can be brought into contact with the aqueous NaCl solution before it is introduced into the anode compartment.This is achieved, for example, by mixing a portion of the catholyte with the aqueous NaCl solution before introducing it into the anode compartment, which is then introduced into the anode compartment. Thus, the pH of the anolyte is adjusted via the supply line of the aqueous NaCl solution. The amount of catholyte that is brought into contact with the aqueous NaCl solution is preferably controlled via a valve that is coupled to a sensor that measures the pH of the storage-stable aqueous solution according to the invention derived from the anode compartment.

[0026] It has been shown according to the invention that it is also possible to adjust the pH of the storage-stable aqueous solution according to the invention by mixing the anolyte with a portion of the catholyte. In this case, a certain amount of catholyte is added to the anolyte, which is sufficient to adjust the pH of the derived anolyte, the aqueous solution according to the invention, to 5 to 6. In addition to the catholyte or alternatively thereto, the anolyte can be admixed with an aqueous solution containing NaOH and / or KOH in order to adjust the pH of the final product to 5 to 6.

[0027] Alternatively, the pH can also be adjusted to the desired value by adding a NaOH solution to the anode compartment and / or to a drain associated with the anode compartment. The NaOH solution preferably has a NaOH concentration of 0.5 to 5%, preferably 1 to 5%.

[0028] The anode and cathode preferably comprise or consist of metals such as titanium, wherein the anode additionally comprises an electrocatalytically active layer (for the oxidation of chloride ions) which contains metal oxides such as ruthenium oxide, iridium oxide, titanium oxide or mixtures thereof.

[0029] The anode chamber and the cathode chamber of the electrolysis cell used according to the invention are separated by a separator. The separator separates the solution in one chamber from the solution in the other chamber, allowing the migration of selected ions between the chambers. Examples of separators that can be used are semipermeable diaphragms or ion-selective membranes. The separators used can comprise a ceramic based on metal oxides, such as aluminum oxide, which may optionally contain other oxides such as zirconium oxide and yttrium oxide. Ion-selective membranes can, for example, comprise perfluorinated hydrocarbon, which may optionally contain ionic sulfonate groups. Known membranes include those from DuPont, which are sold under the trade name Nafion®.

[0030] At a pH value above 7, an increased amount of chlorate forms in solutions containing hypochlorous acid or hypochlorite, which impairs the continued stability of such solutions and can have toxic effects at higher concentrations. Below pH 6, however, there is an increased formation of chlorine gas, which can be expelled from the solution, thus also negatively affecting the stability of the solution according to the invention.

[0031] A further aspect of the present invention relates to a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite which can be prepared by a process of the present invention.

[0032] BRIEF DESCRIPTION OF THE CHARACTERS

[0033] Fig. 1 shows the schematic structure of a plant for producing the aqueous solution according to the invention.

[0034] DESCRIPTION OF THE EMBODIMENTS

[0035] Using the process according to the invention, storage-stable aqueous solutions comprising hypochlorous acid and / or hypochlorite can be produced. "Storage-stable" in relation to the aqueous solution according to the invention means that the concentration of the hypochlorous acid or of the hypochlorite after electrolysis in the solution decreases by less than 30% and at most 10 to 30% over a longer period of time, for example 6 to 12 months at room temperature (approx. 20 °C). It has been shown that in solutions produced by conventional processes not according to the invention, the concentration of the hypochlorous acid or of the hypochlorite decreases by at least 50% within days or weeks. Such solutions cannot be described as storage-stable according to the invention. Adequate storage stability of the solution according to the invention can be determined according to the invention in a "rapid process" by determining its content of hypochlorous acid or hypochlorite.Hypochlorite is determined after storage at a temperature of 54 ° C. If the content of hypochlorous acid or hypochlorite after 14 days of storage is more than 50% of the initial value (measured immediately after its preparation), the solution can be described as storage-stable.

[0036] Chlorine can occur in water or in aqueous solutions in several forms. The three different forms OC1~, HOC1 and Cl2 are subsumed under the term "active chlorine". The exact concentration of the individual forms of this freely available chlorine ("free available chlorine"; FAC) depends, among other things, on the pH value of the water or the aqueous solution and can be determined using the method according to DIN EN ISO 7939-1 as a "rapid method" (see e.g.

[0037] 9c93-26a758b6a 058 ). This is a titrimetric method in which the freely available chlorine is brought into contact with N,N-diethyl-1,4-phenylenediamine (DPD), producing a red compound at a pH of 6.2 to 6.5. Titration is carried out with a standard solution of ammonium iron(II) sulfate until the red color disappears.

[0038] During storage, the pH of the solutions prepared according to the invention may fall below 5. This does not affect storage stability per se, since it has been shown that the pH immediately after preparation of the solution according to the invention is crucial. At this point, it should be between 5 and 6. If the pH is higher than 6 or lower than 5, this negatively affects storage stability.

[0039] Storage stability has various advantages. Aqueous solutions comprising hypochlorous acid and / or hypochlorite, which are produced using conventional methods, must be transported from the production site to the site of use in a short time due to their short storage stability. Alternatively, the solutions are produced on site and used immediately afterwards. This means that a production facility is required at each site of use. The process according to the invention produces solutions that are stable for months. This results in enormous logistical advantages and also opens up new areas of application (e.g. medical use for end consumers).

[0040] The electrolysis cell used according to the invention is operated at a voltage of 5 to 40 volts, preferably 10 to 30 volts, and a current of 40 to 1000 amperes, preferably 50 to 600 amperes. It has been shown that the formation of hypochlorous acid or hypochlorite proceeds particularly well in these ranges.

[0041] Fig. 1 shows the schematic structure of a plant suitable for producing the aqueous solution according to the invention. Water is first mixed with a preferably saturated NaCl solution and introduced via lines 5 and 6 into the cathode compartment 2 and anode compartment 3 of the electrolysis cell 1. The anolyte, from which the solution according to the invention is obtained and which comprises hypochlorous acid or hypochlorite, is removed from the anode chamber via outlet line 7. V1 and V2 represent lines by means of which catholyte from the cathode compartment can be fed either into outlet line 7 and / or into feed line 6 in order to adjust the pH of the anolyte.

[0042] According to a particularly preferred embodiment of the present invention, the aqueous NaCl solution has an electrical conductivity of less than 30 mS / cm, preferably from 1 to 30 mS / cm, even more preferably from 5 to 30 mS / cm, even more preferably from 10 to 30 mS / cm.

[0043] According to a further preferred embodiment of the present invention, the aqueous NaCl solution has an electrical conductivity of 1 to 5 mS / cm, preferably 1.5 to 4.5 mS / cm, more preferably 2 to 4 mS / cm, even more preferably 2.5 to 4 mS / cm.

[0044] The stability of hypochlorous acid or hypochlorite in an aqueous solution depends on the electrical conductivity. The higher this conductivity, the more unstable the solution becomes with respect to hypochlorous acid or hypochlorite. The lowest range of electrical conductivity is defined by the minimum concentration of 100 ppm NaCl in the solution to be electrolyzed. It has surprisingly been found that the process according to the invention is suitable both for the electrolysis of NaCl solutions with a high salt concentration (at an electrical conductivity of up to 30 mS / cm) and for the electrolysis of NaCl solutions with a low salt concentration (at an electrical conductivity of up to 5 mS / cm) in order to produce a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite.

[0045] The electrical conductivity is measured using known methods (such as those according to ISO 7888) at a temperature of approximately 22 °C.

[0046] Depending on the electrical conductivity of the NaCl solution used, this includes different NaCl concentrations and evaporation residues.

[0047] According to a preferred embodiment of the present invention, the aqueous NaCl solution comprises 2000 to 15000 ppm, preferably 3000 to 15000 ppm, more preferably from 4000 to 12000 ppm, even more preferably from 5000 to 10000 ppm, NaCl.

[0048] According to a particularly preferred embodiment of the present invention, the aqueous NaCl solution has an evaporation residue of 2 to 15 g / l, preferably of 3 to 15 g / l, even more preferably of 5 to 15 g / l, even more preferably of 5 to 10 g / l.

[0049] According to a further preferred embodiment of the present invention, the aqueous NaCl solution comprises 200 to 2000 ppm, preferably 300 to 1500 ppm, even more preferably from 300 to 1000 ppm, even more preferably from 300 to 700 ppm, NaCl.

[0050] The NaCl solution which is used for electrolysis and introduced into the anode and cathode chambers preferably comprises 200 to 2000 ppm NaCl. The relatively small amount of NaCl in the electrolysis solution has the advantage that the solution according to the invention which is produced therewith and which comprises hypochlorite or hypochlorous acid is also low in NaCl. This is particularly advantageous with regard to the corrosiveness of the solution towards, for example, iron or iron-containing objects. It has been shown that the solution produced according to the invention has a significantly lower corrosiveness than comparable solutions from the prior art which were produced using other processes.

[0051] According to a preferred embodiment of the present invention, the aqueous NaCl solution has an evaporation residue of 1200 to 2000 mg / l, preferably of 1300 to 1900 mg / l, even more preferably of 1400 to 1800 mg / l.

[0052] The evaporation residue, which can be determined by evaporating (i.e., removing volatile compounds such as water) one liter of the aqueous NaCl solution, indicates the amount of non-volatile compounds, such as salts, in the solution. Since the stability of the aqueous solution according to the invention can be influenced by the amount of ions present, the evaporation residue in the aqueous NaCl solution should ideally not exceed a certain concentration.

[0053] According to a particularly preferred embodiment of the present invention, the aqueous NaCl solution is prepared by mixing a saturated aqueous NaCl solution and water, wherein the water has a conductivity of less than 2 mS / cm, preferably less than 1.5 mS / cm, even more preferably less than 1 mS / cm.

[0054] The NaCl solution introduced into the electrolysis cell is preferably prepared by mixing a saturated aqueous NaCl solution and water. The water used should also have a low electrical conductivity to prevent the total conductivity from exceeding 5 mS / cm. In a particularly preferred embodiment, the water used can be deionized or distilled.

[0055] According to a preferred embodiment of the present invention, the water used to prepare the aqueous NaCl solution from a saturated NaCl solution has an electrical conductivity between 0.1 and 2 mS / cm, preferably between 0.2 and 1.5 mS / cm, even more preferably between 0.4 and 1 mS / cm.

[0056] According to a further preferred embodiment of the present invention, the water has an evaporation residue of 5 to 500 mg / l, preferably of 5 to 300 mg / l, even more preferably of 10 to 250 mg / l.

[0057] According to a preferred embodiment of the present invention, the aqueous NaCl solution and / or the water has a pH of 6.8 to 9.5, preferably of 7 to 9.2.

[0058] According to a particularly preferred embodiment of the present invention, the aqueous NaCl solution and / or the water has a carbonate concentration, ie concentration of HCOsA, of 10 to 500 ppm, preferably of 20 to 400 ppm, even more preferably of 30 to 300 ppm, even more preferably of 40 to 250 ppm.

[0059] It has surprisingly been shown that the carbonate hardness (expressed as the concentration of HCO3-) of the aqueous NaCl solution introduced into the anode or cathode compartment, or of the water used to prepare the aqueous NaCl solution, can influence the stability of the aqueous solution according to the invention. Carbonate hardness (KH) is the proportion of alkaline earth ions that bind to carbonates (CO3 2 -) and hydrogen carbonates (HCO 3 ~) are bound and dissolved in water.

[0060] According to a preferred embodiment of the present invention, the aqueous NaCl solution comprises less than 0.3 ppm, preferably less than 0.3 ppm, even more preferably less than 0.2 ppm, of copper ions, nickel ions and / or iron ions.

[0061] The stability of hypochlorous acid or hypochlorite in aqueous solutions is also influenced by the content of metal ions, particularly copper, nickel, and iron ions. If their concentration is below certain limits, the storage stability of the aqueous solutions prepared according to the invention is further increased.

[0062] According to a preferred embodiment of the present invention, the aqueous NaCl solution comprises less than 0.02 ppm, preferably less than 0.01 ppm, of nitrate ions and / or nitrite ions. It is advantageous if the aqueous NaCl solution has a low proportion of nitrate ions and / or nitrite ions in order to obtain a stable electrolysis product.

[0063] According to a further preferred embodiment of the present invention, the aqueous NaCl solution comprises less than 500 ppm, preferably less than 400 ppm, even more preferably less than 300 ppm, of sulfate ions, phosphate ions and / or orthosilicate ions.

[0064] The stability of the aqueous solution according to the invention can be further increased if the aqueous NaCl solution comprises less than 500 ppm of sulfate ions, phosphate ions and / or orthosilicate ions.

[0065] According to yet another preferred embodiment of the present invention, the aqueous NaCl solution comprises less than 50 ppm, preferably less than 40 ppm, even more preferably less than 30 ppm, even more preferably less than 20 ppm, calcium ions and / or magnesium ions.

[0066] It has been shown that too high a concentration of calcium or magnesium ions in the aqueous NaCl solution can lead to a product that has a lower stability.

[0067] According to a particularly preferred embodiment of the present invention, the aqueous NaCl solution comprises 20 to 200 ppm, preferably 50 to 100 ppm, of an inorganic buffer.

[0068] Surprisingly, it has been found that the addition of an inorganic buffer substance to the NaCl solution used has a positive effect on the storage stability of the solution according to the invention and increases it even further.

[0069] According to a further preferred embodiment of the present invention, the inorganic buffer comprises bicarbonate. Preferably, the electrolysis solution is admixed with 10 to 500 ppm, preferably 20 to 400 ppm, more preferably 30 to 300 ppm, even more preferably 40 to 250 ppm, of carbonate ions in the form of, for example, sodium bicarbonate.

[0070] In particular, the use of carbonates, such as bicarbonates, has shown positive effects on storage stability, with sodium bicarbonate being used preferably. According to a particularly preferred embodiment of the present invention, the aqueous NaCl solution is introduced into the electrolysis cell and the storage-stable aqueous solution is discharged from the electrolysis cell at a flow rate of 0.2 m / s to 1.8 m / s, preferably from 0.2 m / s to 1.5, even more preferably from 0.2 m / s to 1.2, even more preferably from 0.2 m / s to 1 m / s.

[0071] The flow rate selected in the electrolysis process according to the invention also influences the stability of the produced aqueous solution. This means that if a specific flow rate is selected for the electrolysis, this can lead to an even more stable product with a lower degradation rate of the hypochlorous acid or hypochlorite.

[0072] During the process according to the invention, the electrolysis cell is preferably brought to a temperature of 2°C to 20°C, more preferably 3°C to 15°C, even more preferably 5°C to 10°C.

[0073] Cooling the electrolysis cell and thus the anolyte or catholyte contained therein also leads to a more stable end product and a lower chlorate concentration in the manufactured product. Alternatively or additionally, the salt solution supplied to the cathode and anode compartments can be brought to a temperature of 2°C to 20°C, more preferably 3°C to 15°C, and even more preferably 5°C to 10°C, before introduction. By continuously supplying cooled salt solution, the temperature in the electrolysis cell can be reduced accordingly. This would also make it possible to forgo cooling the electrolysis cell.

[0074] According to a preferred embodiment of the present invention, the molar ratio between chlorate ions and hypochlorous acid and / or hypochlorite in the storage-stable solution immediately after its preparation and / or discharge from the electrolysis cell is less than 1:50, preferably less than 1:60, even more preferably less than 1:80. A further aspect of the present invention relates to a storage-stable aqueous solution producible by a process according to the invention.

[0075] According to a preferred embodiment of the present invention, the storage-stable solution has an electrical conductivity of less than 4 mS / cm, preferably less than 3 mS / cm, even more preferably less than 2.5 mS / cm.

[0076] According to a further preferred embodiment of the present invention, the storage-stable solution has an electrical conductivity of 0.5 to 4 mS / cm, preferably of 1 to 3 mS / cm, even more preferably of 1.2 to 3 mS / cm, even more preferably of 1.4 to 2.5 mS / cm.

[0077] The conductivity of the storage-stable solution is typically lower than that of the aqueous NaCl solution introduced into the anode or cathode chamber. Electrolysis produces chloride ions in the anode chamber, including chlorine, which is expelled from the anolyte during electrolysis. This removes ions from the system.

[0078] According to yet another preferred embodiment of the present invention, the storage-stable solution comprises between 50 and 1500 ppm, preferably between 100 and 1000, more preferably between 150 and 800, even more preferably between 200 and 600 ppm, of hypochlorous acid and / or hypochlorite.

[0079] With the process according to the invention it is possible to produce a stable aqueous solution which comprises between 50 and 1500 ppm of hypochlorous acid and / or hypochlorite.

[0080] According to a further preferred embodiment of the present invention, the ratio between hypochlorous acid and / or hypochlorite and chloride ions in the storage-stable solution is 1:1.2 to 1:2.8, preferably 1:1 to 1:1.5 to 1:2.5, even more preferably 1:1.7 to 1:2.1.

[0081] The process according to the invention produces a storage-stable solution that preferably has these ratios between hypochlorous acid and / or hypochlorite and chloride ions. During storage of the solution, this ratio may change over time due to degradation of the hypochlorous acid or hypochlorite; however, it is crucial that this ratio prevails immediately after electrolysis. This ratio also has a positive effect on storage stability.

[0082] According to a preferred embodiment of the present invention, the molar ratio between chlorate ions and hypochlorous acid and / or hypochlorite in the storage-stable solution is less than 1:10, preferably less than 1:20, even more preferably less than 3:100.

[0083] According to a further preferred embodiment of the present invention, the molar ratio between chlorate ions and hypochlorous acid and / or hypochlorite in the storage-stable solution increases from less than 1:60 to a maximum of 1:10 after 18 months of storage at 22 °C.

[0084] It has surprisingly been found that the solution according to the invention or the solution that can be produced using the process according to the invention has a relatively low chlorate content immediately after its production. Using processes known from the prior art, solutions are produced which already have a relatively high chlorate content at the beginning of storage, i.e. immediately after their production. Furthermore, it has been found that the solution according to the invention or the solution that can be produced using the process according to the invention surprisingly still has a comparatively low chlorate content even after 18 months of storage.

[0085] According to a particularly preferred embodiment of the present invention, the storage-stable aqueous solution comprises chlorate in a concentration of less than 50 ppm, preferably less than 40 ppm, even more preferably less than 30 ppm, even more preferably less than 25 ppm, even more preferably less than 20 ppm.

[0086] In solution, hypochlorous acid or hypochlorite disproportionates over time to chlorate and chloride. Due to the measures taken in the preparation of the aqueous solution according to the invention, the concentration of chlorate is relatively low compared to solutions prepared by conventional processes, in which the hypochlorous acid or hypochlorite degrades quickly. Chlorate has toxic effects in high concentrations, which would limit its therapeutic use, for example. The solution according to the invention always has a chlorate content of less than 50 ppm after production and also during storage.

[0087] For the durability of the solution according to the invention, it has been shown that a ratio of chlorate to FAC of less than 3.5 during production or immediately thereafter is particularly advantageous, since at this ratio hypochlorous acid or hypochlorite is degraded to the least extent.

[0088] According to a preferred embodiment of the present invention, the storage-stable aqueous solution has a pH of 4 to 6.

[0089] Immediately after preparation of the solution according to the invention, the pH of the solution may drop. Surprisingly, it has been shown that the initial pH immediately after preparation is important for storage stability.

[0090] According to a particularly preferred embodiment of the present invention, the storage-stable aqueous solution comprises less than 0.3 ppm, preferably less than 0.2 ppm, of copper ions, nickel ions and / or iron ions.

[0091] According to a preferred embodiment of the present invention, the storage-stable aqueous solution comprises less than 0.1 ppm, preferably less than 0.05 ppm, even more preferably less than 0.01 ppm, of nitrate ions and / or nitrite ions.

[0092] According to a further preferred embodiment of the present invention, the storage-stable aqueous solution comprises less than 500 ppm, preferably less than 400 ppm, even more preferably less than 300 ppm, of sulfate ions, phosphate ions and / or orthosilicate ions.

[0093] According to a particularly preferred embodiment of the present invention, the storage-stable aqueous solution comprises less than 50 ppm, preferably less than 40 ppm, even more preferably less than 30 ppm, even more preferably less than 20 ppm, calcium ions and / or magnesium ions.

[0094] According to a preferred embodiment of the present invention, the storage-stable aqueous solution has a redox potential of 1,000 to 1,500 mV, preferably of 1,100 to 1,400 mV, even more preferably of 1,150 to 1,300 mV.

[0095] According to a particularly preferred embodiment of the present invention, the storage-stable aqueous solution has an evaporation residue of 200 to 1500 mg / l, preferably of 500 to 1250 mg / l, even more preferably of 600 to 1200 mg / l.

[0096] The stable solution according to the invention can be used for all purposes such as known solutions comprising hypochlorous acid and hypochlorite, in particular as a disinfectant, for water disinfection, surface disinfection, wound disinfection, wound healing, plant cultivation, and the like.

[0097] The present invention is further described by the following embodiments and examples:

[0098] 1. A process for producing a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, comprising the steps of: a. introducing an aqueous NaCl solution into an electrolysis cell (1) which comprises a cathode compartment (2) and an anode compartment (3) which are separated from one another by a separator (4), the aqueous NaCl solution being introduced into the cathode compartment (2) via a first feed line (5) and into the anode compartment (3) via a second feed line (6), the aqueous NaCl solution comprising more than 100 ppm NaCl and having an electrical conductivity of less than 5 mS / cm, b. applying a direct current to a cathode in the cathode compartment (2) and to an anode in the anode compartment (3) to produce a cathode solution in the cathode compartment (2) and an anode solution in the anode compartment (3), and c. Mixing a portion of the cathode solution with the aqueous NaCl solution before introducing it into the anode compartment (3) and / or with the anode solution in the anode compartment

[0099] (3) and / or with the anode solution in a discharge line (7) associated with the anode chamber (3) in order to produce a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite which can be discharged via discharge line (7) and which has a pH value of 5 to 6.

[0100] 2. The method according to embodiment 1, characterized in that the aqueous NaCl solution has an electrical conductivity of 1 to 5 mS / cm, preferably of 1.5 to 4.5 mS / cm, even more preferably of 2 to 4 mS / cm, even more preferably of 2.5 to 4 mS / cm.

[0101] 3. Process according to embodiment 1 or 2, characterized in that the aqueous NaCl solution comprises 200 to 2000 ppm, preferably 300 to 1500 ppm, even more preferably from 300 to 1000 ppm, even more preferably from 300 to 700 ppm, of NaCl.

[0102] 4. Process according to one of embodiments 1 to 3, characterized in that the aqueous NaCl solution has an evaporation residue of 1200 to 2000 mg / l, preferably of 1300 to 1900 mg / l, even more preferably of 1400 to 1800 mg / l.

[0103] 5. The method according to any one of embodiments 1 to 4, characterized in that the aqueous NaCl solution is prepared by mixing a saturated aqueous NaCl solution and water, the water having a conductivity of less than 2 mS / cm, preferably less than 1.5 mS / cm, even more preferably less than 1 mS / cm.

[0104] 6. Method according to embodiment 5, characterized in that the water has an electrical conductivity between 0.1 and 2 mS / cm, preferably between 0.2 and 1.5 mS / cm, even more preferably between 0.4 and 1 mS / cm.

[0105] 7. Process according to embodiment 5 or 6, characterized in that the water has an evaporation residue of 5 to 500 mg / l, preferably of 5 to 300 mg / l, even more preferably of 10 to 250 mg / l.

[0106] 8. Process according to one of embodiments 1 to 7, characterized in that the aqueous NaCl solution and / or the water has a pH of 6.8 to 9.5, preferably of 7 to 9.2.

[0107] 9. Process according to one of embodiments 1 to 8, characterized in that the aqueous NaCl solution and / or the water contains 10 to 500 ppm, preferably 20 to 400 ppm, even more preferably 30 to 300 ppm, even more preferably 40 to 250 ppm, of carbonate ions.

[0108] 10. The method according to any one of embodiments 1 to 9, characterized in that the aqueous NaCl solution comprises less than 0.3 ppm, preferably less than 0.25 ppm, even more preferably less than 0.2 ppm, of copper ions, nickel ions and / or iron ions, and / or less than 0.02 ppm, preferably less than 0.01 ppm, of nitrate ions and / or nitrite ions, and / or less than 500 ppm, preferably less than 400 ppm, even more preferably less than 300 ppm, of sulfate ions, phosphate ions and / or orthosilicate ions, and / or less than 50 ppm, preferably less than 40 ppm, even more preferably less than 30 ppm, even more preferably less than 20 ppm, of calcium ions and / or magnesium ions.

[0109] 11. Process according to one of embodiments 1 to 10, characterized in that the aqueous NaCl solution comprises 20 to 200 ppm, preferably 50 to 100 ppm, of an inorganic buffer.

[0110] 12. The method according to embodiment 11, characterized in that the inorganic buffer comprises bicarbonate.

[0111] 13. Method according to one of the embodiments 1 to 12, characterized in that the introduction of the aqueous NaCl solution into the electrolysis cell (1) and the discharge of the storage-stable aqueous solution from the electrolysis cell (1) takes place at a flow rate of 0.1 m / s to 1 m / s, preferably of 0.2 m / s to 1.0 m / s.

[0112] 14. Process according to one of embodiments 1 to 13, characterized in that the electrolysis cell (1) is brought to a temperature of 2°C to 20°C, preferably of 3°C to 15°C, even more preferably of 5°C to 10°C, during the process.

[0113] 15. A storage-stable aqueous solution producible by a process according to any one of embodiments 1 to 14.

[0114] 16. Storage-stable aqueous solution according to embodiment 15, characterized in that the storage-stable solution has an electrical conductivity of less than 4 mS / cm, preferably less than 3 mS / cm, even more preferably less than 2.5 mS / cm.

[0115] 17. Storage-stable aqueous solution according to embodiment 15 or 16, characterized in that the storage-stable solution has an electrical conductivity of 0.5 to 4 mS / cm, preferably of 1 to 3 mS / cm, even more preferably of 1.2 to 3 mS / cm, even more preferably of 1.4 to 2.5 mS / cm.

[0116] 18. Storage-stable aqueous solution according to any one of embodiments 15 to 17, characterized in that the storage-stable solution comprises between 50 and 1500 ppm, preferably between 100 and 1000, even more preferably between 150 and 800, even more preferably between 200 and 600 ppm, of hypochlorous acid and / or hypochlorite.

[0117] 19. Storage-stable aqueous solution according to any one of embodiments 15 to 18, characterized in that the molar ratio between hypochlorous acid and / or hypochlorite and chloride ions in the storage-stable solution is 1:1.2 to 1:2.8, preferably 1:1 to 1:1.5 to 1:2.5, even more preferably 1:1.7 to 1:2.1.

[0118] 20. Storage-stable aqueous solution according to any one of embodiments 15 to 19, characterized in that the storage-stable aqueous solution comprises chlorate in a concentration of less than 50 ppm, preferably less than 40 ppm, even more preferably less than 30 ppm, even more preferably less than 25 ppm, even more preferably less than 20 ppm.

[0119] 21. A process for producing a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, comprising the steps of: a. introducing an aqueous NaCl solution into an electrolysis cell (1) which comprises a cathode compartment (2) and an anode compartment (3) which are separated from one another by a separator (4), the aqueous NaCl solution being introduced into the cathode compartment (2) via a first feed line (5) and into the anode compartment (3) via a second feed line (6), the aqueous NaCl solution comprising more than 100 ppm NaCl, b. applying a direct current to a cathode in the cathode compartment (2) and to an anode in the anode compartment (3) to produce a cathode solution in the cathode compartment (2) and an anode solution in the anode compartment (3), and c.Mixing a portion of the cathode solution with the aqueous NaCl solution before introducing it into the anode compartment (3) and / or with the anode solution in the anode compartment (3) and / or with the anode solution in a drain line (7) assigned to the anode compartment (3) or adding a NaOH solution to the anode compartment (3) and / or to a drain line (7) assigned to the anode compartment (3) in order to produce a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite which can be discharged via drain line (7) and which has a pH value of 5 to 6, wherein the introduction of the aqueous NaCl solution into the electrolysis cell (1) and the discharge of the storage-stable aqueous solution from the electrolysis cell (1) at a flow rate of 0.1 m / s to 2 m / s.

[0120] 22. The method according to embodiment 21, characterized in that the aqueous NaCl solution has an electrical conductivity of less than 30 mS / cm, preferably from 1 to 30 mS / cm, even more preferably from 5 to 30 mS / cm, even more preferably from 10 to 30 mS / cm.

[0121] 23. The method according to embodiment 21 or 22, characterized in that the aqueous NaCl solution comprises 200 to 2000 ppm, preferably 300 to 1500 ppm, even more preferably from 300 to 1000 ppm, even more preferably from 300 to 700 ppm, of NaCl.

[0122] 24. Process according to one of embodiments 21 to 23, characterized in that the aqueous NaCl solution has an evaporation residue of 1200 to 2000 mg / l, preferably of 1300 to 1900 mg / l, even more preferably of 1400 to 1800 mg / l.

[0123] 25. The process according to embodiment 21 or 22, characterized in that the aqueous NaCl solution comprises 2000 to 15000 ppm, preferably 3000 to 15000 ppm, even more preferably 4000 to 12000 ppm, even more preferably 5000 to 10000 ppm, of NaCl. 26. The process according to any one of embodiments 21, 22, or 25, characterized in that the aqueous NaCl solution has an evaporation residue of 2 to 15 g / l, preferably 3 to 15 g / l, even more preferably 5 to 15 g / l, even more preferably 5 to 10 g / l.

[0124] 27. The method according to any one of embodiments 21 to 26, characterized in that the aqueous NaCl solution is prepared by mixing a saturated aqueous NaCl solution and water, the water having a conductivity of less than 2 mS / cm, preferably less than 1.5 mS / cm, even more preferably less than 1 mS / cm.

[0125] 28. Method according to embodiment 27, characterized in that the water has an electrical conductivity between 0.1 and 2 mS / cm, preferably between 0.2 and 1.5 mS / cm, even more preferably between 0.4 and 1 mS / cm.

[0126] 29. Process according to embodiment 27 or 28, characterized in that the water has an evaporation residue of 5 to 500 mg / l, preferably of 5 to 300 mg / l, even more preferably of 10 to 250 mg / l.

[0127] 30. Process according to one of embodiments 21 to 29, characterized in that the aqueous NaCl solution and / or the water has a pH of 6.8 to 9.5, preferably of 7 to 9.2.

[0128] 31. Process according to one of embodiments 21 to 30, characterized in that the aqueous NaCl solution and / or the water contains 10 to 500 ppm, preferably 20 to 400 ppm, even more preferably 30 to 300 ppm, even more preferably 40 to 250 ppm, of carbonate ions.

[0129] 32. Process according to one of embodiments 21 to 31, characterized in that the aqueous NaCl solution comprises less than 0.3 ppm, preferably less than 0.25 ppm, even more preferably less than 0.2 ppm, of copper ions, nickel ions and / or iron ions, and / or less than 0.02 ppm, preferably less than 0.01 ppm, of nitrate ions and / or nitrite ions, and / or less than 500 ppm, preferably less than 400 ppm, even more preferably less than 300 ppm, of sulfate ions, phosphate ions and / or orthosilicate ions, and / or less than 50 ppm, preferably less than 40 ppm, even more preferably less than 30 ppm, even more preferably less than 20 ppm, of calcium ions and / or magnesium ions.

[0130] 33. Process according to one of embodiments 21 to 32, characterized in that the aqueous NaCl solution comprises 20 to 200 ppm, preferably 50 to 100 ppm, of an inorganic buffer.

[0131] 34. The method according to embodiment 33, characterized in that the inorganic buffer comprises bicarbonate.

[0132] 35. Method according to one of embodiments 21 to 34, characterized in that the introduction of the aqueous NaCl solution into the electrolysis cell (1) and the discharge of the storage-stable aqueous solution from the electrolysis cell (1) takes place at a flow velocity of 0.2 m / s to 1.8 m / s, preferably from 0.2 m / s to 1.5, even more preferably from 0.2 m / s to 1.2, even more preferably from 0.2 m / s to 1 m / s.

[0133] 36. Process according to one of embodiments 21 to 35, characterized in that the electrolysis cell (1) is brought to a temperature of 2°C to 20°C, preferably of 3°C to 15°C, even more preferably of 5°C to 10°C, during the process.

[0134] 37. Process according to one of embodiments 21 to 36, characterized in that the molar ratio between chlorate ions and hypochlorous acid and / or hypochlorite in the storage-stable solution immediately after its preparation and / or discharge from the electrolysis cell (1) is less than 1:50, preferably less than 1:60, even more preferably less than 1:80.

[0135] 38. A storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, preferably producible by a process according to any one of embodiments 21 to 37.

[0136] 39. Storage-stable aqueous solution according to embodiment 38, characterized in that the storage-stable solution has an electrical conductivity of less than 4 mS / cm, preferably less than 3 mS / cm, even more preferably less than 2.5 mS / cm.

[0137] 40. Storage-stable aqueous solution according to embodiment 38 or 39, characterized in that the storage-stable solution has an electrical conductivity of 0.5 to 4 mS / cm, preferably of 1 to 3 mS / cm, even more preferably of 1.2 to 3 mS / cm, even more preferably of 1.4 to 2.5 mS / cm.

[0138] 41. Storage-stable aqueous solution according to any one of embodiments 38 to 40, characterized in that the storage-stable solution comprises between 50 and 1500 ppm, preferably between 100 and 1000, even more preferably between 150 and 800, even more preferably between 200 and 600 ppm, of hypochlorous acid and / or hypochlorite.

[0139] 42. Storage-stable aqueous solution according to any one of embodiments 38 to 41, characterized in that the molar ratio between hypochlorous acid and / or hypochlorite and chloride ions in the storage-stable solution is 1:1.2 to 1:2.8, preferably 1:1 to 1:1.5 to 1:2.5, even more preferably 1:1.7 to 1:2.1.

[0140] 43. Storage-stable aqueous solution according to any one of embodiments 37 to 41, characterized in that the molar ratio between chlorate ions and hypochlorous acid and / or hypochlorite in the storage-stable solution is less than 1:10, preferably less than 1:20, even more preferably less than 3:100.

[0141] 44. Storage-stable aqueous solution according to any one of embodiments 37 to 41, characterized in that the molar ratio between chlorate ions and hypochlorous acid and / or hypochlorite in the storage-stable solution increases from less than 1:60 to a maximum of 1:10 after 18 months of storage at 22°C.

[0142] 45. A storage-stable aqueous solution according to any one of embodiments 37 to 44, characterized in that the storage-stable aqueous solution comprises chlorate in a concentration of less than 50 ppm, preferably less than 40 ppm, even more preferably less than 30 ppm, even more preferably less than 25 ppm, even more preferably less than 20 ppm. EXAMPLES

[0143] Materials & Methods Determination of Storage Stability To test the long-term stability or storage stability of a product using an accelerated method, normal long-term aging is simulated by heating the product over a specific period of time. This test provides reliable data regarding the storage stability of a product. To conduct the test, a product sample is placed in a glass bottle, then sealed, and heated at a constant temperature for a defined period in an oven. In these examples, the determination of storage stability was carried out according to the CIPAC MT46.3 method (CIPAC; Collaborative International Pesticides Analytical Council).

[0144] In the following examples, in which the influence of various parameters on the stability of hypochlorous acid and hypochlorite was investigated, approximately 500 ml of each sample was placed in a glass bottle, which was then sealed with a lid containing a polyethylene insert. The sealed glass bottles were placed in an oven at a temperature of 54 °C (+ / - 2 °C) for a maximum of 14 days. At the beginning, i.e. before filling the samples into the bottles, after 2 days, after 7 days, and after 14 days, the glass bottles were removed from the oven and allowed to cool to room temperature. The aged solutions from the glass bottles were then investigated.

[0145] Determination of freely available chlorine

[0146] The concentration of freely available chlorine in the samples was determined using the method according to DIN EN ISO 7939-1. The pH of the sample solutions was adjusted to approximately 6.2 to 6.5, and N,N-diethyl-1,4-phenylenediamine (DPD) was added. The addition of DPD caused the sample solution to turn red. The content of freely available chlorine was determined by subsequent titration with a standard solution of ammonium iron(II) sulfate until the red color disappeared.

[0147] The content of freely available chlorine was determined by multiplying it by a factor of 0.74 into the content of hypochlorous acid or hypochlorite.

[0148] Example 1: Influence of pH on the storage stability of the aqueous solution according to the invention

[0149] To investigate the influence of pH on the storage stability of the aqueous solution containing hypochlorous acid or hypochlorite, solutions were prepared using the method according to the invention. The pH of the solutions was adjusted to 4, 5, 6, 7, and 7.4 by adding the cathode solution to the anode solution. These solutions were subjected to the aging process described above. The temperature of the solutions in the gas cylinders was kept constant at 54 °C, and the concentrations of freely available chlorine, and thus of the hypochlorous acid or hypochlorite, were determined before the aging process and after 2, 7, and 14 days. Distilled water was used in each process step to prepare the solutions containing hypochlorous acid or hypochlorite. The electrolysis was carried out at 20 volts and 60 amperes direct current. The flow rate was 0.8 m / s. The measured values ​​are listed in the following table:

[0150] Table A:

[0151] Table A clearly shows that adjusting the pH to between 5 and 6 can result in significantly increased storage stability with regard to the degradation of hypochlorous acid or hypochlorite. Adjusting the pH is essential to enable the production of a storage-stable aqueous solution.

[0152] In addition to the free available chloride (FAC) content, the chlorate content was measured according to ISO 10304-4. Surprisingly, it was found that this was below 50 ppm for all samples with pH 5 and 6. Up to day 7, the chlorate content at pH 5 and 6 was even less than 20 ppm. In contrast, in the samples with pH 7 and 7.4, a chlorate content of at least 50 ppm was determined by ion chromatography as early as day 0 and 2.

[0153] Example 2 : Influence of carbonate hardness on the storage stability of the aqueous solution

[0154] The carbonate hardness, expressed in the concentration of HCO3A present in the water or NaCl solution used in the process, can also influence the storage stability of the solution produced by the process according to the invention with regard to the degradation of the hypochlorous acid or hypochlorite. Therefore, distilled water containing different concentrations of HCO3 (added in the form of sodium bicarbonate) was used to produce the NaCl-containing electrolysis solution. The pH of the aqueous solution produced was adjusted to approximately 6.5, as described in Example 1. The solution produced by electrolysis was subjected to an accelerated aging process, as described in Example 1. The temperature was kept constant at 54°C during the stability test. The FAC measurements were carried out after 0 and 14 days.

[0155] Table B :

[0156] Table B shows the change in FAC expressed in % after 2 weeks of storage at 54 °C as described above. The results show that the amount of HCO3 present can influence the storage stability of the solutions prepared according to the invention, which may further increase stability. Example 3: Influence of various anions and cations on the storage stability of the aqueous solution

[0157] To investigate the influence of various anions and cations on the storage stability of an aqueous solution produced according to the invention by electrolysis, electrolysis solutions with different concentrations of copper, nickel, iron, calcium, magnesium, nitrate, nitrite, sulfate, phosphate and orthosilicate ions were prepared. For this purpose, distilled water was mixed with NaCl and with different concentrations of the ions mentioned here in the form of chloride or sodium salts and then introduced into the anode and cathode compartment of an electrolysis cell and subjected to electrolysis as described in Example 1. The aqueous solutions produced in this way, which had a pH of approx. 6, were subjected to an accelerated aging process as described in Example 1.The temperature was kept constant at 54 ° C and after 14 days the change in FAC present was compared with a product according to Example 1 with pH 6 ( "Reference").

[0158] Table C : n no or + / - 10% FAC change compared to reference j FAC decrease >10% compared to reference

[0159] Example 4 : Influence of flow rate on storage stability of the aqueous solution

[0160] During electrolysis to produce the solutions according to the invention, the salt solution is introduced into the anode and cathode chambers at a specific flow rate. The aqueous solution according to the invention comprising hypochlorous acid or hypochlorite is obtained from the anode compartment at the same flow rate. To investigate the influence of the flow rate during electrolysis on the storage stability of the electrolysis product, the electrolysis was carried out at different flow rates, as described in Example 1. The electrolysis products were subjected to an accelerated aging process as described in Example 1. The flow rates for introducing and discharging the storage-stable aqueous solution into and from the electrolysis cell varied between 0.61 m / s and 0.88 m / s.The temperature during the stability test was kept constant at 54 ° C, and the FAC and chlorate content was determined after 0 and 14 days. Distilled water was used to prepare the electrolysis solutions.

[0161] Table D :

[0162] Table D shows that the flow rate has an additional influence on the storage stability of the electrolysis product and can lead to an even more stable product. It was found that increasing the flow rate leads to a more stable product with a lower chlorate concentration.

Claims

REQUIREMENTS:

1. Method for producing a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, comprising the steps of: a. Introducing an aqueous NaCl solution into an electrolysis cell (1) comprising a cathode compartment (2) and an anode compartment (3) separated by a separator (4) are separated from each other, wherein the aqueous NaCl solution is introduced into the cathode compartment (2) via a first supply line (5) and into the anode compartment (3) via a second supply line (6), and wherein the aqueous NaCl solution comprises more than 100 ppm NaCl, b. applying a direct current to a cathode in the cathode compartment (2) and to an anode in the anode compartment (3) to generate a cathode solution in the cathode compartment (2) and an anode solution in the anode compartment (3), and c.Mixing a portion of the cathode solution with the aqueous NaCl solution before introducing it into the anode compartment (3) and / or with the anode solution in the anode compartment (3) and / or with the anode solution in a drain (7) associated with the anode compartment (3), or adding an NaOH solution to the anode compartment (3) and / or to a drain (7) associated with the anode compartment (3) in order to produce a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, which can be drained via drain (7) and has a pH of 5 to 6.

2. A process for producing a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, comprising the steps of: a. Introducing an aqueous NaCl solution into an electrolysis cell (1) comprising a cathode compartment (2) and an anode compartment (3) separated from each other by a separator (4), wherein the aqueous NaCl solution is introduced into the cathode compartment (2) via a first inlet (5) and into the anode compartment (3) via a second inlet (6), and wherein a. the aqueous NaCl solution contains more than 100 ppm NaCl, b. applying a direct current to a cathode in the cathode compartment (2) and to an anode in the anode compartment (3) to generate a cathode solution in the cathode compartment (2) and an anode solution in the anode compartment (3), and c.Mixing a portion of the cathode solution with the aqueous NaCl solution before its introduction into the anode compartment (3) and / or with the anode solution in the anode compartment (3) and / or with the anode solution in a drain (7) associated with the anode compartment (3) or adding a NaOH solution to the anode compartment (3) and / or to a drain (7) associated with the anode compartment (3) in order to produce a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, which has a pH of 5 to 6 and can be drained via drain (7), wherein the aqueous NaCl solution is introduced into the electrolysis cell (1) and the storage-stable aqueous solution is drained from the electrolysis cell (1) at a flow rate of 0.1 m / s to 2 m / s.

3. Method according to claim 1 or 2, characterized in that the aqueous NaCl solution has an electrical conductivity of less than 30 mS / cm, preferably less than 5 mS / cm.

4. Method according to one of claims 1 to 3, characterized in that the aqueous NaCl solution has an electrical conductivity of 1 to 30 mS / cm, preferably of 5 to 30 mS / cm, more preferably of 10 to 30 mS / cm.

5. Method according to any one of claims 1 to 4, characterized in that the aqueous NaCl solution comprises 2000 to 15000 ppm, preferably 3000 to 15000 ppm, more preferably 4000 to 12000 ppm, more preferably 5000 to 10000 ppm, NaCl.

6. Method according to any one of claims 1 to 5, characterized in that the aqueous NaCl solution has an evaporation residue of 2 to 15 g / l, preferably of 3 to 15 g / l, more preferably of 5 to 15 g / l, and more preferably of 5 to 10 g / l.

7. A process for producing a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, comprising the steps of: a. introducing an aqueous NaCl solution into an electrolysis cell (1) comprising a cathode compartment (2) and an anode compartment (3) separated from each other by a separator (4), wherein the aqueous NaCl solution is introduced into the cathode compartment (2) via a first supply line (5) and into the anode compartment (3) via a second supply line (6), and wherein the aqueous NaCl solution comprises more than 100 ppm NaCl and has an electrical conductivity of less than 5 mS / cm, b. applying a direct current to a cathode in the cathode compartment (2) and to an anode in the anode compartment (3) to generate a cathode solution in the cathode compartment (2) and an anode solution in the anode compartment (3), and c.Mixing a portion of the cathode solution with the aqueous NaCl solution before its introduction into the anode compartment (3) and / or with the anode solution in the anode compartment (3) and / or with the anode solution in a drain (7) associated with the anode compartment (3) in order to produce a storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, which can be drained via drain (7) and has a pH of 5 to 6.

8. Method according to one of claims 1 to 3 or 7, characterized in that the aqueous NaCl solution has an electrical conductivity of 1 to 5 mS / cm, more preferably of 1.5 to 4.5 mS / cm, more preferably of 2 to 4 mS / cm, more preferably of 2.5 to 4 mS / cm.

9. Method according to one of claims 1 to 3, 7 or 8, characterized in that the aqueous NaCl solution comprises 200 to 2000 ppm, preferably 300 to 1500 ppm, more preferably 300 to 1000 ppm, more preferably 300 to 700 ppm, NaCl.

10. Method according to any one of claims 1 to 3, 7 to 9, characterized in that the aqueous NaCl solution has an evaporation residue of 1200 to 2000 mg / l, preferably of 1300 to 1900 mg / l, more preferably of 1400 to 1800 mg / l.

11. Method according to any one of claims 1 to 10, characterized in that the introduction of the aqueous NaCl solution into the electrolysis cell (1) and the discharge of the storage-stable aqueous solution from the electrolysis cell (1) are carried out with a flow rate of 0.1 m / s to 2 m / s, preferably from 0.12 m / s to 1.8 m / s, more preferably from 0.1 m / s to 1 m / s, more preferably from 0.2 m / s to 1.5 m / s, more preferably from 0.2 m / s to 1.2 m / s, more preferably from 0.2 m / s to 1.0 m / s.

12. Method according to any one of claims 1 to 11, characterized in that the aqueous NaCl solution is produced by mixing a saturated aqueous NaCl solution and water, wherein the water has a conductivity of less than 2 mS / cm, preferably less than 1.5 mS / cm, more preferably less than 1 mS / cm.

13. Method according to claim 12, characterized in that the water has an electrical conductivity between 0.1 and 2 mS / cm, preferably between 0.2 and 1.5 mS / cm, more preferably between 0.4 and 1 mS / cm.

14. Method according to any one of claims 1 to 13, characterized in that the water has an evaporation residue of 5 to 500 mg / l, preferably of 5 to 300 mg / l, more preferably of 10 to 250 mg / l.

15. Method according to any one of claims 1 to 14, characterized in that the aqueous NaCl solution and / or the water has a pH value of 6.8 to 9.5, preferably of 7 to 9.

2.

16. Method according to any one of claims 1 to 15, characterized in that the aqueous NaCl solution and / or the water has a carbonate ion concentration of 10 to 500 ppm, preferably 20 to 400 ppm, more preferably 30 to 300 ppm, more preferably 40 to 250 ppm.

17. A method according to any one of claims 1 to 16, characterized in that the aqueous NaCl solution comprises less than 0.3 ppm, preferably less than 0.25 ppm, even more preferably less than 0.2 ppm, copper ions, nickel ions and / or iron ions, and / or less than 0.02 ppm, preferably less than 0.01 ppm, nitrate ions and / or nitrite ions, and / or less than 500 ppm, preferably less than 400 ppm, even more preferably less than 300 ppm, sulfate ions, phosphate ions and / or orthosilicate ions, and / or less than 50 ppm, preferably less than 40 ppm, even more preferably less than 30 ppm, even more preferably less than 20 ppm, calcium ions and / or magnesium ions.

18. Method according to any one of claims 1 to 17, characterized in that the aqueous NaCl solution comprises 20 to 200 ppm, preferably 50 to 100 ppm, of an inorganic buffer.

19. Method according to claim 18, characterized in that the inorganic buffer comprises hydrogen carbonate.

20. Method according to one of claims 1 to 19, characterized in that the electrolysis cell (1) is brought to a temperature of 2°C to 20°C, preferably 3°C to 15°C, more preferably 5°C to 10°C during the method.

21. Method according to any one of claims 1 to 20, characterized in that the molar ratio between chlorination ions and hypochlorous acid and / or hypochlorite in the storage-stable solution immediately after its preparation and / or derivation from the electrolysis cell (1) is less than 1:50, preferably less than 1:60, more preferably less than 1:

80.

22. A storage-stable aqueous solution comprising hypochlorous acid and / or hypochlorite, obtainable by a method according to any one of claims 1 to 21.

23. Storage-stable aqueous solution according to claim 22, characterized in that the storage-stable solution has an electrical conductivity of less than 4 mS / cm, preferably less than 3 mS / cm, more preferably less than 2.5 mS / cm.

24. Storage-stable aqueous solution according to claim 22 or 23, characterized in that the storage-stable solution has an electrical conductivity of 0.5 to 4 mS / cm, preferably of 1 to 3 mS / cm, more preferably of 1.2 to 3 mS / cm, and more preferably of 1.4 to 2.5 mS / cm.

25. Storage-stable aqueous solution according to one of claims 22 to 24, characterized in that the storage-stable solution comprises hypochlorous acid and / or hypochlorite at a concentration between 50 and 1500 ppm, preferably between 100 and 1000 ppm, more preferably between 150 and 800 ppm, and more preferably between 200 and 600 ppm.

26. Storage-stable aqueous solution according to one of claims 22 to 25, characterized in that the molar ratio between hypochlorous acid and / or hypochlorite and chloride ions in the storage-stable solution is 1:1.2 to 1:2.8, preferably 1:1 to 1:1.5 to 1:2.5, more preferably 1:1.7 to 1:2.

1.

2. A storage-stable aqueous solution according to one of claims 22 to 26, characterized in that the molar ratio between chlorination ions and hypochlorous acid and / or hypochlorite in the storage-stable solution is less than 1:10, preferably less than 1:20, more preferably less than 3:

100.

28. Storage-stable aqueous solution according to one of claims 22 to 27, characterized in that the molar ratio between chlorination ions and hypochlorous acid and / or hypochlorite in the storage-stable solution increases from less than 1:60 to a maximum of 1:10 after 18 months of storage at 22°C.

29. A storage-stable aqueous solution according to one of claims 22 to 28, characterized in that the storage-stable aqueous solution comprises chlorate in a concentration of less than 50 ppm, preferably less than 40 ppm, more preferably less than 30 ppm, more preferably less than 25 ppm, more preferably less than 20 ppm.

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