JP2014529455A - How to bleach kitchen utensils in a dishwasher - Google Patents

Abstract

The present invention is for bleaching kitchen utensils in a dishwasher comprising the step of in situ activation of a bleach activator with reactive oxygen species generated in situ in the dishwasher by electrolysis of an aqueous solution. Concerning the method. [Selection] Figure 1

Description

  The present invention relates to a method for bleaching kitchen utensils with a dishwasher and to a combination of a dishwasher and an electrolysis cell installed in the inflow line outside the dishwasher or a battery-operated electrolysis cell installed in the washroom.

  For the bleaching of kitchen utensils such as pottery and cutlery, bleach and / or bleach activators (bleaching) are usually used to remove various types of soils, especially tea and coffee stains, from the kitchen utensils to be washed. Cleaning compositions containing the agent precursor) are used. In this context, “actual” bleaching agents, such as singlet oxygen, are only formed in situ from the bleaching agent and / or bleach activator used.

  Examples of bleaching agents are hydrogen peroxide sources such as sodium percarbonate and sodium perborate, which form hydrogen peroxide in the presence of water, which then decomposes at temperatures above 60 ° C. This produces water and singlet oxygen. When using a hydrogen peroxide source, the bleaching action thus only takes place at temperatures above 60 ° C.

  Examples of bleach activators include acyl derivatives such as tetraacetylethylenediamine (TAED) and sodium p-nonanoyloxybenzenesulfonate (NOBS). Acyl derivative bleach activators are used with hydrogen peroxide sources. Following the release of hydrogen peroxide from the hydrogen peroxide source, the acyl derivative bleach activator reacts with hydrogen peroxide with the formation of peroxycarboxylic acid. Peroxycarboxylic acids generally decompose even at room temperature, with the formation of carboxylic acids and singlet oxygen. However, depending on the hydrogen peroxide source used, hydrogen peroxide is released only at relatively high temperatures, for example, sodium percarbonate forms hydrogen peroxide only at temperatures above 50 ° C. in the presence of water. . Therefore, in the case of the acyl derivative bleach activator / hydrogen peroxide source combination, the bleaching effect occurs only at a relatively high temperature depending on the hydrogen peroxide source used.

  Hydrogen peroxide and many peroxycarboxylic acids such as peroxyacetic acid cannot be added directly to dishwashing detergents because they are unstable and consequently non-preservable.

  DE 10104470 and WO2007 / 052064 describe general cleaning compositions for use in dishwashers which can also contain bleaching agents and / or bleach activators.

US 6,387,238 describes a method of producing an antibacterial solution containing peroxyacetic acid. This method involves the formation of peroxyacetic acid as well as the electrolysis of hydrogen peroxide, peroxide ions or peroxide radicals, and the reaction of this species with an acetyl donor. Example 1 describes the production of peroxyacetic acid electrolytically (current intensity: 5 A, current density: 100 mA / cm ² , voltage: 10 V).

WO 2006/117201 describes a method for cleaning, disinfecting and disinfecting dishes and other kitchen utensils using a cleaning liquid, in which diamond and / or lead / tin placed in the cleaning liquid is described. As a result of the direct application of current to the electrode, which is an electrode, OH radicals are generated in the cleaning liquid, and these OH radicals allow for the cleaning, disinfection and disinfection of dishes and other kitchenware. The current density at the electrode is between 5 A / dm ² (= 500 mA / cm ² ) and 300 A / dm ² (= 30 A / cm ² ).

  US 2002/023847 describes a method for producing a cleaning solution by electrolysis of water and an apparatus for cleaning and sterilizing objects such as dishes and clothes. This apparatus comprises, for example, an electrolysis chamber having an ion exchange membrane that separates the anode chamber from the cathode chamber. The cathode chamber contains tap water and the anode chamber contains salt water. During electrolysis, an aqueous sodium hydroxide solution is produced in the cathode chamber and an aqueous HOCl solution is produced in the anode chamber. The aqueous sodium hydroxide solution is pumped from the cathode chamber, and the object to be cleaned is sprayed with the aqueous sodium hydroxide solution.

JP2003 / 211104A describes a cleaning device having a cleaning water generating unit including at least one of a cathode and an anode containing conductive diamond on the surface of the electrode. An example of the cleaning device is a dishwasher (tableware scrubber). In all cases, “functional” water has bactericidal properties. Example 3 describes the production of an aqueous solution of persulfate by electrolysis (5A, 120 cm ² , 15 minutes, 14V) of a 0.6% strength aqueous sodium sulfate solution using a boron-doped diamond electrode.

  In WO2009 / 067838, washings, textiles, dishes, floors and cars are cleaned, sanitized, disinfected and odor neutralized with electrolytic or hot water using oxidized radicals generated by boron-doped diamond electrodes. A method for is described. With oxidizing radicals, the cleaning strength required for this purpose can only be achieved with a diamond electrode having an overvoltage of 4 volts.

  EP 1944403 describes a post-treatment of a washing device, for example washing water from a washing machine, and a method of reusing it in the washing device for post-treated washing water, which method is in particular post-treated. A process is provided in which the wash water is treated electrochemically. In this step, the organic components of the wash water to be post-treated, such as surfactants or soil components, are decomposed by ozone, hypochlorous acid (HOCl) or other reactive oxygen species. During electrolysis, for example, a diamond electrode can be used, and a high voltage is applied so that high-concentration ozone is formed.

  US 2003/0414202 describes the production of electrolyzed water by electrolysis of an alkaline electrolyte, which can be taken for cleaning and disinfection. The alkaline electrolyte is selected from the group consisting of at least one electrolyte selected from the group consisting of sodium carbonate, potassium carbonate, sodium phosphate and sodium hypochlorite, and the group consisting of sodium chloride, potassium chloride, sodium bromide and potassium bromide A mixture with further electrolytes. Nickel ferrite can be used as the anode. The invention can be used in many applications, for example for cleaning and disinfecting hot water in public baths.

  DE 10336588 A1 describes a method for removing / decolorizing colored substances / residues in liquids and from surfaces, especially in dishwashers and washing machines. In this method, the liquid circulates continuously through the channel between the electrodes. By doing so, the colored molecules are directly anodized at the electrode surface. Also, “active” oxygen and “active” chlorine are produced at the electrode surface, and their accumulation likewise results in the removal / decolorization of colored substances / residues in and from the liquid. A titanium anode having a titanium oxide layer can be used as an anode, for example.

  DE102006037905 describes a dishwasher with an electrolysis cell for producing bleach from the recycled salt of a water softener. During electrolysis, depending on the type of regenerated salt, the salt solution produces an oxidatively active substance (bleach), specifically a chlorine and sodium chlorite solution or a potassium hypochlorite solution. Hydrogen gas and oxygen gas are produced as by-products. The electrode is preferably made of a corrosion-resistant material that is also coated with a catalyst, for example an electrode made of a titanium substrate with an oxide coating of noble metal oxide and noble metal doping. However, it is also possible to use other electrode materials such as conductive diamond, platinum, tin oxide and stainless steel.

DE10104470 WO2007 / 052064 US 6,387,238 WO2006 / 117201 US2002 / 023847 JP2003 / 211104A WO2009 / 067838 EP 1944403 US2003 / 0414202 DE103336588A1 DE102006037905

  The object of the present invention was to provide a method for bleaching kitchenware in a dishwasher which achieves excellent bleaching results even at temperatures below 45 ° C.

  Furthermore, the process according to the invention is technically feasible (no accumulation of unstable bleaching agents such as hydrogen peroxide or peroxycarboxylic acid), economical (low power consumption) and gentle on the dishwasher (corrosion) None), it is also desirable to be gentle on kitchenware (no unwanted discoloration).

  This object is achieved by the method of claim 1 and by the combination in claims 21 and 22.

  The method for bleaching kitchen utensils with the dishwasher of the present invention comprises the step of activating the bleach activator in situ by reactive oxygen species generated in situ in the dishwasher by electrolysis of an aqueous solution. Including.

FIG. 1 is a schematic diagram of an experimental apparatus used in the examples.

  Dishwashers include all kinds of dishwashers, ie household dishwashers for home use (household dishwashers) and dishwashers that can be used commercially (industrial and commercial dishwashers) Machine).

  Kitchen utensils include all types of kitchen utensils such as pottery, cutlery, pots and glassware.

  The active oxygen species is usually an active oxygen species having at least one oxygen atom having an oxidation number of -1. Examples of reactive oxygen species having at least one oxygen atom with an oxidation number of -1 are hydrogen peroxide, hydrogen peroxide anion, perhydroxyl radical, hydroxyl radical, superoxide anion and ozone.

  Preferably, the reactive oxygen species is selected from the group consisting of hydrogen peroxide, hydrogen peroxide anion, perhydroxyl radical and hydroxyl radical. Particularly preferably, the reactive oxygen species is selected from the group consisting of hydrogen peroxide, hydrogen peroxide anions and perhydroxyl radicals.

  Reactive oxygen species are preferably generated by electrolyzing water present in an aqueous solution.

  Electrolysis can be performed in an electrolysis cell comprising at least one anode / cathode pair. The electrolysis cell can comprise one anode / cathode pair or a plurality of anode / cathode pairs connected in series. Preferably, the electrolysis cell comprises a plurality of anode / cathode pairs connected in series. The anode / cathode pair connection can be monopolar or bipolar. Bipolar connection is preferred.

  The anode is made of the following materials: carbon such as graphite, glass carbon and conductive diamond; noble metals such as platinum and gold; metal oxides such as iridium oxide, chromium oxide, lead oxide, palladium oxide and ruthenium oxide; or mixed metal oxidation Things can be included.

  Preferably, the anode comprises graphite, conductive diamond or platinum.

  Particularly preferably, the anode comprises a material capable of achieving a high oxygen overvoltage, for example conductive diamond or platinum.

  The anode very particularly preferably comprises conductive diamond.

  Conductive diamond is diamond that is doped with different atoms, so that the diamond doped with different atoms conducts current. Suitable heteroatoms are, for example, boron or nitrogen.

  Preferably, the anode is an anode comprising conductive diamond, which is boron doped diamond.

  An anode containing conductive diamond usually includes a carrier material and conductive diamond.

  Suitable support materials are niobium, silicon, tungsten, titanium, silicon carbide, tantalum and graphite, and ceramic support materials such as titanium suboxide. Preferred support materials are niobium, titanium and silicon. A particularly preferred carrier material is niobium.

  The cathode can include the following materials: carbon, such as graphite, glass carbon and conductive diamond; metals such as iron and nickel; steels such as stainless steel; or noble metals such as platinum.

  The cathode very particularly preferably comprises conductive diamond or steel.

  Preferably, the cathode is a cathode comprising conductive diamond, which is boron doped diamond.

  Cathodes containing conductive diamond usually contain a carrier material and conductive diamond.

  Suitable support materials are niobium, silicon, tungsten, titanium, silicon carbide, tantalum and graphite, and ceramic support materials such as titanium suboxide. Preferred support materials are niobium, titanium and silicon. A particularly preferred carrier material is niobium.

  An anode or cathode containing conductive diamond can be prepared by a CVD (“chemical vapor deposition”) method. Such diamond electrodes are commercially available from, for example, Condias GmbH or Adamant-Technologies.

  The anode or cathode containing conductive diamond can be prepared by the HTHP (“high temperature and high pressure”) method. In this method, industrial diamond powder is mechanically incorporated on the surface of the metal sheet of the carrier. Such diamond electrodes are also commercially available from, for example, pro aqua Diamondeletrodren Production GmbH.

  In one embodiment according to the present invention, the anode comprises boron doped diamond and the dishwasher housing is constructed of steel, preferably stainless steel, and functions as the cathode. Thus, in this embodiment, the dishwasher is part of the electrolysis cell.

  The housing of the dishwasher is preferably not part of the electrolysis cell.

  In a further preferred embodiment according to the invention, both the anode and the cathode comprise boron doped diamond. This embodiment has the advantage that the polarity of the electrode can be switched, and can remove deposits that may occur on the electrode. The polarity of the electrodes can be switched, for example, every 5 seconds to every 200 minutes, or between individual cleaning cycles.

The electrolysis cell preferably has an effective electrode surface (electrode size) of 0.5 to 1000 cm ² , preferably 1 to 500 cm ² , particularly preferably 2 to 100 cm ² . In this context, the effective electrode surface refers to the electrode surface of one or more anodes that are in contact with the aqueous solution and face one or more cathodes during electrolysis. When the anode is placed between two cathodes (when multiple anode / cathode pairs are connected in series), the effective electrode surface of the one or more anodes is the electrode surface facing the cathode Based on the sum of

  In a preferred embodiment according to the present invention, both the anode and the cathode contain boron-doped diamond, and the electrodes are preferably the same size, so the effective electrode surface remains the same when the polarity of the electrodes is switched.

  The distance between the anode and the cathode is preferably from 0.1 to 20 mm, preferably from 0.5 to 10 mm, particularly preferably from 1 to 5 mm.

  The anode and cathode are preferably not spatially separated from one another, for example by a membrane.

  The electrolysis cells that can be used are the types of electrolysis cells known to those skilled in the art, for example split or non-split flow cells, capillary gap cells or plate stack cells. A particularly preferred electrolysis cell is an undivided flow cell.

  The electrolysis cell can be either a built-in part of the dishwasher or a separate component.

  If the electrolysis cell is a built-in part of the dishwasher, the electrolysis cell can be incorporated, for example, in the submersion area of the washing tub, preferably outside the washing room, or the electrolysis cell is attached to the inflow line in the dishwasher Or the electrolysis cell can be incorporated into additional water circulation in the dishwasher.

  A dishwasher that includes an electrolysis cell that is incorporated into an additional water circulation within the dishwasher also forms part of the present invention.

  If the electrolysis cell is a separate component, the electrolysis cell is attached to, for example, an inflow line outside the dishwasher, for example a fresh water supply device between a water tap and the dishwasher, or battery operated in the washroom It can be used as an electrolytic cell.

  Commercially available dishwashers generally do not include an electrolytic cell as a built-in component. Thus, the electrolysis cell is preferably used as a separate component. The electrolysis cell is particularly preferably a battery-operated electrolysis cell used in the washing room of a dishwasher.

  The combination of a dishwasher and an electrolytic cell installed in the inflow line outside the dishwasher also forms part of the present invention.

  The combination of a dishwasher and a battery-operated electrolysis cell installed in the washing room also forms part of the present invention.

The electrolysis is preferably in the range from 0.5 to 1000 mA / cm ² , particularly preferably in the range from 1 to 500 mA / cm ² , very particularly preferably in the range from 10 to 200 mA / cm ² , based on the effective electrode surface. Most preferably, it is carried out at a current density in the range of 50 to 100 mA / cm ² .

  The electrolysis is preferably performed at a current strength of 0.02 to 30A. A current strength in the range of 0.1 to 16 A is particularly preferred, and a current strength in the range of 0.1 to 10 A is very particularly preferred.

  A dishwasher wash program typically includes a wash cycle and a rinse cycle. The dishes are washed in the wash cycle, and the rinse cycle serves to remove the rinse water and dry the dishes. The cleaning cycle can include two or more sub-cleaning cycles, such as one or more pre-cleaning cycles and one or more main cleaning cycles.

  The electrolysis can be performed over the entire time of the dishwasher program, but is preferably performed only at one or more time intervals during the dishwashing program. Preferably, the electrolysis is performed here or at a plurality of time intervals before or during the wash cycle. The time interval during which the electrolysis takes place can be between 5 seconds and 120 minutes, preferably between 5 seconds and 60 minutes, particularly preferably between 1 minute and 30 minutes, in particular between 5 minutes and 15 minutes. The electrolysis is carried out before or during the washing cycle, particularly preferably at a plurality of intervals between 1 and 30 minutes, preferably between 5 and 15 minutes.

  The process according to the invention is carried out at a temperature in the range from 10 to 95 ° C., preferably in the range from 15 to 90 ° C., particularly preferably in the range from 20 to 65 ° C., very particularly preferably in the range from 20 to 40 ° C., for example 30 ° C. It can be carried out.

  This process is preferably carried out at temperatures up to 60 ° C., preferably up to 40 ° C., particularly preferably up to 30 ° C.

  An aqueous solution is an aqueous solution that contains an electrolyte and thereby conducts current. An example of an aqueous solution that contains an electrolyte and thereby conducts current is an aqueous solution based on tap water.

  In the case of performing electrolysis, the aqueous solution may contain an additive. However, the additive can also only be added to the aqueous solution during or after electrolysis.

  Examples of additives include bleach activators, dishwashing detergents, rinse aids and regenerated salts.

  A preferred additive is a bleach activator.

  Bleach activators are usually compounds that react with reactive oxygen species, specifically hydrogen peroxide, hydrogen peroxide anions or perhydroxyl radicals to give peroxycarboxylic acids or peroxyimino acids. Both peroxycarboxylic acids and peroxyimino acids can decompose with the formation of singlet oxygen.

  The bleach activator that reacts with hydrogen peroxide to obtain a peroxycarboxylic acid can preferably be an acyl derivative.

  The acyl radical of the acyl derivative can have the following formula:

Wherein R ¹ is C _1-20 -alkyl or C _6-10 -aryl,
Or

In the formula, L ¹ is C _1-20 -alkylene or C _{6-10 -arylene} .

Preferably R ¹ is C _1-10 -alkyl or phenyl, particularly preferably R ¹ is C _1-3 -alkyl. Very particularly preferably R ¹ is methyl.

Preferably L ¹ is phenylene or naphthylene, particularly preferably L ¹ is phenylene. Preferably, formula (2) has the following formula:

  An acyl derivative in which the acyl radical has formula (1) is preferred over an acyl derivative in which the acyl radical has formula (2).

Examples of C _1-3 -alkyl are methyl, ethyl, n-propyl and isopropyl. C _1-10 -alkyl may be unbranched or branched. Examples of C _1-10 -alkyl are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl. N-nonyl and n-decyl, n-undecyl, n-dodecyl. C _1-20 -alkyl may be unbranched or branched. Examples of C _1-20 -alkyl are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl. N-nonyl, n-decyl, n-undecyl, n-dodecyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n - there is a nonadecyl and n- eicosyl _{(C 20).}

C _6-10 -aryl may be phenyl or naphthyl.

C _1-20 -alkylene may be unbranched or branched. Examples of C _1-20 -alkylene include methylene, ethylene, propylene, isopropylene, butylene, sec-butylene, isobutylene, tert-butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, undecylene, dodecylene, tridecylene, tetradecylene, 2-decyl-butylene, there pentadecylene, hexadecylene, heptadecylene, octadecylene and nonadecylene and Eikoshiren _{(C 20).}

Examples of C _6-10 -arylene include phenylene and naphthalene.

  Examples of acyl derivative bleach activators include poly-O-acylated polyols, O-acylated phenol derivatives, carboxylic anhydrides, O-acylated hydroxylamines, O-acylated cyanuric acid derivatives, poly -N-acylated polyamines, N-acylated aniline derivatives, poly-N-acylated heterocycles containing at least one nitrogen, N-acylated urea derivatives, N-acylated amides, N-acylated imides And N-acylated sulfonamides.

  Examples of poly-O-acylated polyols include diacetyl glycol and triacetin, and poly-O-acetylated sugar alcohols and sugars such as hexaacetyl sorbitol, hexaacetyl mannitol, pentaacetyl glucose, tetraacetyl xylose and octaacetyl lactose As well as tetraacetylgluconolactone.

  Examples of O-acylated phenol derivatives include sodium p-nonanoyloxybenzenesulfonate (NOBS), sodium p-isononanoyloxybenzenesulfonate, sodium p-benzoyloxybenzenesulfonate, sodium p-nonanoyloxybenzoate. And sodium p-decanoyloxybenzoate.

  Examples of carboxylic acid anhydrides are phthalic anhydride and benzoic anhydride.

  Examples of O-acylated hydroxylamines include O-benzoyl-N, N-succinylhydroxylamine, O-acetyl-N, N-succinylhydroxylamine and O, N, N-triacetylhydroxylamine.

  Examples of O-acylated cyanuric acid derivatives include triacetyl cyanuric acid and tribenzoyl cyanuric acid.

  Examples of poly-N-acylated polyamines include tetraacetylmethylenediamine, tetraacetylethylenediamine (TAED), and tetraacetylhexylenediamine.

  An example of an N-acylated aniline derivative is N, N-diacetylaniline.

  Examples of poly-N-acylated heterocycles containing at least one nitrogen include 1,3-diacetyl-5,5-dimethylhydantoin, tetraacetylglycoluril, 1,5-diacetyl-2,2-dioxo-hexahydro. -1,3,5-triazine, 1,5-diacetyl-2,4-dioxohexahydro-1,3,5-triazine, 1,5-diacetyl-2,4-dioxohexahydro-1,3 , 5-triazine, 1,4-diacetyl-2,5-diketopiperazine, 1,3-diacetyl-4,5-diacetoxyimidazoline and monoacetylmaleic hydrazide.

  An example of an N-acylated urea derivative is tetraacetylpropylene diurea.

  An example of an N-acylated amide is benzoylcaprolactam.

  An example of an N-acylated imide is N-nonanoyl succinimide.

  Examples of N-acylated sulfonamides include N-methyl-N-mesylacetamide, N-methyl-N-mesylbenzamide, N, N'-dimethyl-N, N'-diacetylsulfuramide and N, N ' -Diethyl-N, N'-dipropanoylsulfurylamide.

  The bleach activator that reacts with hydrogen peroxide to obtain peroxyimino acid may be an ammonium nitrile, such as N-methylmorpholinium acetonitrile hydrogen sulfate, trimethyl ammonium acetonitrile hydrogen sulfate.

  Bleach activators that react with hydrogen peroxide to give peroxycarboxylic acids are preferred. Particularly preferred bleach activators are acyl derivative bleach activators. Very particularly preferred bleach activators are poly-N-acylated polyamines. A particularly preferred bleach activator is tetraacetylethylenediamine (TAED).

  The concentration of the bleach activator in the aqueous solution should be 0.001 to 10% by weight, preferably 0.01 to 5% by weight, particularly preferably 0.02 to 1% by weight, based on the weight of the aqueous solution. Can do.

  The bleach activator can be part of a dish detergent.

  The dishwashing detergent can include customary ingredients for dishwashing detergents, such as hard water softeners, bleaches, bleach activators, bleach catalysts, bleach stabilizers, surfactants and enzymes. In addition, the dish detergent may also include antifoaming agents, corrosion inhibitors and fillers.

  Examples of water softeners are pentasodium triphosphate, sodium carbonate, sodium bicarbonate, soap, zeolites and complexing agents such as ethylenediaminetetraacetic acid (EDTA). Trisodium pentaphosphate or zeolite is the preferred water softener.

  Examples of bleaches are “oxygen” bleaches and “chlorine” bleaches.

  A typical “oxygen” bleach is a source of hydrogen peroxide. Examples of hydrogen peroxide sources include alkali metal perborates such as sodium perborate, alkali metal percarbonates such as sodium percarbonate, alkali metal persulfates such as potassium monopersulfate, alkali metal persilicates. There are salts and alkali metal superphosphates.

  An example of a “chlorine” bleach is sodium hypochlorite.

  “Oxygen-based” bleaching agents, particularly sodium perborate and sodium percarbonate are preferred. The most preferred bleaching agent is sodium percarbonate.

  An example of a bleach stabilizer is phosphonate.

  Examples of surfactants include anionic surfactants such as linear alkyl benzene sulfonates, secondary alkane sulfonates, aliphatic alcohol sulfates and methyl ester sulfates, and nonionic surfactants such as aliphatic alcohol polyglycol ethers. And sugar surfactants.

  Examples of enzymes are amylases, lipases and proteases.

  Examples of antifoaming agents include silicone oil and paraffin oil.

  An example of a corrosion inhibitor is sodium metasilicate.

  An example of a filler is sodium sulfate.

  The regenerated salt is sodium chloride.

  Particularly preferred additives are water softeners, bleach activators, surfactants and enzymes.

  The pH of the aqueous solution is preferably in the range from 2 to 13, particularly preferably in the range from 3 to 12, very particularly preferably in the range from 6 to 11.

  Preferably, for the process according to the invention, the degree of soil removal for bleachable soils such as black tea is achieved at least 20%, preferably at least 50%.

  The degree of dirt removal is determined as follows.

  The determination was made by first smearing the white melamine resin reference substrate under standard conditions (using the following: DM11 Tea Series 096, 2.4 cm × 3.9 cm) and measuring it at 460 nm before and after treatment with the aqueous solution. It is performed by using. The dirt removal is calculated in% from the reflectance value R before and after the method and the reflectance value of the white melamine resin reference substrate according to the following formula.

  All measurements here are made 5 times to obtain an average. The following values were measured for the white melamine resin reference substrate and the standardized melamine substrate DM11.

R (white reference): 0.81
R (DM11 Tea Series 096): 0.47
The reflectance measurement is performed using a spectrophotometer (model Spectrolino manufactured by Gretag Macbeth) under the following conditions: observation angle 10 °, light type D65, and UV filter.

  The process according to the invention is characterized in that it has a very good bleaching effect even at temperatures below 45 ° C. and is particularly suitable for bleaching kitchenware in a dishwasher.

  The method according to the invention is also technically feasible (no accumulation of labile bleach, eg hydrogen peroxide or peroxycarboxylic acid), economical (low power consumption) and gentle on dishwashers (no corrosion) ), Gentle on kitchenware (no unwanted discoloration).

  In addition, the method can show incidental positive effects such as decolorization of aqueous solutions and disinfection, cleaning and odor neutralization of bleached kitchenware.

  FIG. 1 is a schematic diagram of an experimental apparatus used in the examples.

Experimental setup The experiment consisted of a glass 1000 ml jacketed vessel with a mechanical stirrer (IKA stirrer motor with glass stirrer and movable PTFE stirrer) and liquid circulation (Iwaki magnetic pump MD6-230GS01, 80-90 l / h) In particular, an electrolytic cell equipped with a boron-doped diamond electrode (Adamant miniDiaCell, diamond on silicon, 12.5 cm ² electrode area) is used. FIG. 1 shows a schematic diagram of an experimental apparatus.

  The test substrate is made of melamine resin (DM11 Tea Series 096, 2.4 cm × 3.9 cm).

  The following aqueous solution is used.

Aqueous solution A: 700 g of pure water, 10 g of NaHCO ₃
Aqueous solution B: 700 g of pure water, 10 g of NaHCO ₃ , 0.18 g of TAED
Aqueous solution C: 700 g pure water, 10 g NaHCO ₃ , 0.18 g TAED, 0.32 g H ₂ O ₂ solution (30% H ₂ O _{2 in} water)

  TAED is an abbreviation for tetraacetylethylenediamine. Pure water means water that has been demineralized and completely deionized.

The selected TAED concentrations in aqueous solutions B and C correspond to those of standard commercial dishwashing detergents. In aqueous solution C, the molar ratio of H ₂ O ₂ / TAED is 4: 1.

Comparative Examples C1-C3
Aqueous solutions A (C1), B (C2) and C (C3) are supplied to the experimental apparatus. The test substrates are introduced into a jacketed container so that they are completely immersed in the aqueous solution and thereby become wetted. The aqueous solution is circulated by pumping at 40 ° C. for 30 minutes without electrolysis. The test substrate is removed from the experimental apparatus, rinsed thoroughly with pure water, dried by eliminating light.

Example 1
Aqueous solution B is supplied to the experimental apparatus. The test substrate is introduced into a jacketed container so that it is completely immersed in the aqueous solution so that it is wetted. Aqueous solution B is circulated in the experimental apparatus by electrolysis (1.2A) by pumping at 40 ° C. for 30 minutes. The test substrate is removed from the experimental apparatus, rinsed thoroughly with pure water, dried by eliminating light.

Example 2
Aqueous solution B is supplied to the experimental apparatus. The test substrate is introduced into a jacketed container so that it is completely immersed in the aqueous solution so that it is wetted. Aqueous solution B is circulated in the experimental apparatus by electrolysis (1.2A) by pumping at 60 ° C. for 30 minutes. The test substrate is removed from the experimental apparatus, rinsed thoroughly with pure water, dried by eliminating light.

Example 3
The aqueous solution A is circulated in the laboratory apparatus by pumping at 40 ° C. for 10 minutes using electrolysis (1.2 A) without a test substrate. Switch off the current source. 0.18 g TAED and test substrate are added and the resulting aqueous solution is circulated by pumping at 40 ° C. for an additional 30 minutes without applying current. The test substrate is removed from the experimental apparatus, rinsed thoroughly with pure water, dried by eliminating light.

Example 4
Aqueous solution A is circulated in the laboratory apparatus by pumping at 60 ° C. for 10 minutes using electrolysis (1.2 A) without a test substrate. Switch off the current source. 0.18 g TAED and test substrate are added and the resulting aqueous solution is circulated by pumping at 60 ° C. for an additional 30 minutes without applying current. The test substrate is removed from the experimental apparatus, rinsed thoroughly with pure water, dried by eliminating light.

Determination of the degree of dirt removal The dirt removal is determined by subjecting the test substrate made of melamine resin to a reflection measurement at 460 nm before and after treatment with an aqueous solution. Dirt removal was calculated in% from the reflectance value R before and after treatment and the reflectance value of the white reference substrate made of melamine resin according to the following formula.

  The reflectance measurement is performed using a spectrophotometer (model Spectrolino manufactured by Gretag Macbeth) under the following conditions: observation angle 10 °, light type D65, and UV filter.

  The degree of stain removal after processing of the test substrates of Comparative Examples C1 to C3 and Examples 1 to 4 is as follows.

Table 1
The pure cleaning effect of aqueous solution A results in 21% soil removal (C1). As expected, the addition of TAED (C2) only leads to a slight improvement in soil removal to 25%. Also as expected, as a result of the addition of H ₂ O ₂ (C3), the bleach precursor (TAED) is activated and achieves 48% soil removal.

  Example 1 shows that using the method according to the present invention, using the same amount of TAED at 40 ° C., higher soil removal (60%) can be achieved than Comparative Method C3 (48%). Example 2 shows that soil removal increases to 67% as a result of increasing the temperature to 60 ° C.

  Examples 3 and 4 show that it is also possible to first activate the aqueous solution by electrolysis for 10 minutes and then add TAED. It is therefore possible to achieve very good soil removal with a low current supply.

Claims (22)

  A method for bleaching kitchenware in a dishwasher comprising the step of in situ activating a bleach activator with reactive oxygen species generated in situ in the dishwasher by electrolysis of an aqueous solution.   The method of claim 1, wherein the reactive oxygen species is an active oxygen species having at least one oxygen atom having an oxidation number of −1.   The method of claim 2, wherein the reactive oxygen species is selected from the group consisting of hydrogen peroxide, hydrogen peroxide anion, perhydroxyl radical, and hydroxyl radical.   The method according to claim 1, wherein the electrolysis is performed in an electrolysis cell comprising at least one anode / cathode pair.   The method of claim 4, wherein the anode comprises conductive diamond.   The method of claim 5, wherein the anode comprises boron doped diamond.   7. A method according to any one of claims 4 to 6, wherein the cathode comprises diamond doped with boron.   The method according to any one of claims 4 to 7, wherein the electrolytic cell is a built-in part of the dishwasher.   The method according to any one of claims 4 to 7, wherein the electrolysis cell is a separate component from the dishwasher.   The method according to claim 9, wherein the electrolysis cell is attached to an inflow line outside the dishwasher or used as a battery-powered electrolysis cell in a washroom. The electrolysis is in the range of 10 to 200 mA / cm ^2, preferably in a current density in the range of 50~100mA / cm ^2, The method according to any one of claims 1 to 10.   12. A method according to any one of the preceding claims, wherein the electrolysis is performed at a current density in the range of 0.1 to 16A, preferably in the range of 0.1 to 10A.   13. A method according to any one of the preceding claims, wherein the electrolysis is performed at one or more time intervals before or during a wash cycle, from 1 minute to 30 minutes, preferably from 5 minutes to 15 minutes. .   14. Process according to any one of claims 1 to 13, which is carried out at a temperature in the range of 20 to 65 ° C, preferably in the range of 20 to 40 ° C.   15. The aqueous solution contains an additive during the electrolysis, or an additive is added to the aqueous solution after the electrolysis. Method.   The method of claim 15, wherein the bleach activator is one of the additives. The bleach activator is an acyl derivative, and the acyl radical of the acyl derivative has the following formula:

Wherein R ¹ is C _1-20 -alkyl or C _6-10 -aryl,
Or

_Wherein L ¹ is C _1-20 -alkylene or C _{6-10 -arylene} .
The method according to claim 1, comprising:   18. A method according to any one of claims 1 to 17, wherein the bleach activator is a poly-N-acylated polyamine.   The method according to any one of claims 1 to 18, wherein the bleach activator is tetraacetylethylenediamine (TAED).   20. A method according to any one of claims 1 to 19, wherein the pH of the aqueous solution is in the range of 3 to 12, preferably in the range of 6 to 11.   A combination of a dishwasher and an electrolysis cell installed in the inflow line outside the dishwasher.   A combination of a dishwasher and a battery-operated electrolysis cell installed in the washing room.

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