HU218021B - Silver-corrosion protection agents (ii) and mashine cleaning agents containing thereof - Google Patents

Abstract

The invention concerns the use of organic redox compounds, in particular ascorbic acid, indole, methionine, N-(C1-C4 alkyl) glycines, 2-phenylglycine or coupler and/or development compounds selected from the group comprising diaminopyridines, aminohydroxypyridines, dihydroxypyridines, heterocyclic hydrazones, aminohydroxypyrimidines, dihydroxypyrimidines, tetraaminopyrimidines, triaminohydroxypyrimidines, diaminodihydroxypyrimidines, dihydroxynaphthalines, naphthols, pyrazolones, hydroxyquinolines, aminoquinolines, primary aromatic amines which have, in addition, a free hydroxy or amino group, or a hydroxy or amino group substituted with C1-C4 alkyl or C2-C4 hydroxyalkyl groups, at the ortho, meta or para position, and di- or trihydroxybenzenes as silver-corrosion protection agents in dishwasher washing agents, in particular low-alkali dishwaster washing agents.

Description

FIELD OF THE INVENTION The present invention relates to silver corrosion protection agents and to mechanical cleaning agents containing them.

It is a well-known fact that silver "runs" even when not in use. It is only a matter of time before you get dark, brownish, bluish, bluish-black spots, or completely discolor so that it "runs" according to normal language usage.

In practice, there is also a problem with the "run-in" and discoloration of silver surfaces, even when machine cleaning silverware. The silver can then react with sulfur-containing substances which are soluble or dispersible in the rinse water, since food residues such as mustard, peas, eggs and other sulfur-containing compounds, such as mercapto-amino acids, are incorporated into the dishwasher when cleaning dishes. Higher temperatures during machine washing and longer contact time with sulfur-containing food residues also contribute to the silver "run-in" compared to hand washing. In addition, due to the intensive cleaning process in the dishwasher, the silver surface will be completely greasy and thus more sensitive to chemical influences.

The use of active chlorine-containing cleaners can be largely prevented by "run-in" caused by sulfur-containing compounds, as these compounds are converted to sulfones or sulfates by secondary reactions through oxidation of sulfide functions.

However, the problem of silver penetration has again become topical when active oxygen compounds such as sodium perborate or sodium percarbonate have been used as an alternative to the active chlorine compounds, which are used to remove decolourable impurities such as tea stains / tea extracts, coffee residues and vegetable colorings.

These active oxygen compounds are used primarily in state-of-the-art low-alkali machine rinse aids of the next generation of detergents, together with bleach activators. These modem agents generally contain building blocks with the following functions: builder components (complexing agents / dispersants), alkaline carriers, bleach system (bleach + bleach activator), enzymes and wetting agents (surfactants).

Silver surfaces are significantly more sensitive to the new formulation parameters of the new generation of pH-reduced active chlorine-free detergents and active oxygen bleaches. During machine washing, these agents release the actual bleaching agent, i.e., hydrogen peroxide or active oxygen. The bleaching effect of the active oxygen detergent is enhanced by bleach activators so that good bleaching effect can be achieved at low temperatures. In the presence of these bleach activators, peracetic acid is formed as a reactive intermediate. Under these changed washing conditions, not only sulphide coatings, but also oxidative "coatings" are formed mainly on the silver surface due to the oxidative "attack" of the intermediate peroxides or active oxygen. In case of high salinity, additional chloride coatings may be formed. In addition, the silver hardness is enhanced by the higher hardness of the water during the washing process.

The prevention of silver corrosion, i.e., the formation of sulfide, oxide or chloride coatings on silver, is the subject of numerous publications. In these descriptions, the corrosion of silver is first of all prevented by so-called silver protective agents.

British Patent No. 1,131,738 discloses alkaline dishwashing detergents containing benzotriazoles as silver corrosion inhibitors. U.S. Pat. No. 3,549,539 discloses highly alkaline, machine-usable dishwashing detergents which, among other things, may contain perborate as an oxidizing agent, together with an organic bleach activator. Additives, including benzotriazole and ferric chloride, are also suggested as penetration inhibitors. A preferred pH range is 7 to 11.5. EP 135 226 and EP 135 227 disclose weakly alkaline, machine-usable dishwashing detergents containing peroxy compounds and activators which may contain, among others, benzotriazoles and fatty acids for the protection of silver. Finally, it is known from DE 41 28 672 that peroxy compounds, which are activated by the addition of known organic bleach activators, prevent the penetration of silver moieties in highly alkaline detergents.

Surprisingly, it has now been found that organic redox active substances, especially those commonly used as oxidation dyes, as coupling and / or developing compounds not previously described as silver corrosion protection agents, effectively inhibit the corrosion of silver in dishwashing machines.

The present invention relates to the use of organic, redox active substances as silver corrosion inhibitors in dish cleaning compositions.

The word "corrosion" is the broadest meaning of the term used in chemistry, which refers to a change in the surface of a metal, here silver, which is visually recognizable, whether it is a point-like discoloration or a large-area penetration.

"Organic redox active substances" are organic substances that can undergo readily reversible oxidation and / or reduction. For example, typical complexing agents such as EDTA (ethylenediaminetetraacetate) or hydroxyethane disulfonic acids and related compounds are not included in this definition.

Suitable organic redox active substances according to the spirit of the invention include, for example, ascorbic acid (vitamin C), indole, methionine (alpha-aminogammamethylmercaptic acid).

Also suitable are N-mono- (C 1 -C 4) alkylglycines such as Ν, Ν-dimethylglycine and 2-phenylglycine.

Certain coupling and / or developing compounds known from oxidative fabric dyeing are also particularly suitable.

Preferably, the organic materials used to prevent silver corrosion are coupling and / or developing2

HU 218 021 Β compounds; include compounds of the following groups: diaminopyridines, amino-hydroxypyridines, dihydroxypyridines, heterocyclic hydrazones, amino-hydroxypyrimidines, dihydroxypyrimidines, tetraaminopyrimidines, triamino-hydroxypyridines, diaminohydroxypyrimidines, dihydroxynaphthalenes, naphthalenes, pyrazoles, hydroxyquinolines, aminoquinolines; primary aromatic amines having a hydroxy or amino group substituted in the ortho, meth or para position by another free or substituted C 1-4 alkyl group or C 2-4 hydroxyalkyl group; and di- or trihydroxybenzenes.

According to the present invention, the coupling and development compounds used to prevent silver corrosion are materials of the aforementioned groups commonly used for oxidation dyes. Examples of such developmental and linking compounds are found, for example, in Venkantaraman, The Chemistry of Synthetic Dyes, Volume V, Academic Press New York / London, 1971, pages 478-495, and in the literature cited therein. Particularly useful in preventing silver corrosion are p-hydroxyphenylglycine, 2,4-diaminophenol, 5-chloro-2,3-pyridinediol, 1- (p-aminophenyl) morpholine, hydroquinone, pyrocatechin, hydroxyhydroquinone, compounds of gallic acid, phloroglucin and pyrogallol.

Preferably, the organic redox active materials are coated, i.e., are water-resistant but are readily soluble at the purification temperature in order to prevent premature decomposition or oxidation upon storage. Preferred coatings which can be applied by the Sandwik melting coating known in the food industry are paraffins, microwaxes, natural waxes such as kamaubia wax, candelilla wax, beeswax, high melting alcohols such as hexadecanol, soaps and fats. According to the process, a solid coating material at room temperature is applied to the material to be coated in a molten state, for example by continuously spraying a spray mist of the molten coating material into a continuous stream. The melting point should be selected such that the coating material will easily dissolve or melt rapidly in the dishwasher when subsequently used. Therefore, for most applications, the melting point is ideally in the range of 45 ° C to 65 ° C, preferably 50 ° C to 60 ° C.

The organic redox active substances described above are particularly useful for inhibiting silver corrosion when they are contained in low-alkaline detergents for machine cleaning of vessels. This is all the more surprising since the anti-corrosion agents of these silver corrosion agents are not diminished by the oxygen-based bleaching agents normally present in low alkaline cleaning compositions.

Therefore, a further object of the present invention is to provide non-alkaline detergent compositions suitable for machine washing of dishes having a pH of 8 to 11.5, preferably 9 to 10.5, by weight; the solutions comprise from 15 to 60% by weight, preferably from 30 to 50% by weight, of water-soluble builder components, from 5 to 25%, preferably from 10 to 15% by weight of oxygen bleach, from 1 to 10% by weight, preferably from 2 to 6% by weight an organic bleach activator, 0.1 to 5% by weight, preferably 0.5 to 2.5% by weight, of enzyme (all components apply to the total agent) and an anti-corrosion agent, and the anti-silver corrosion agent is an organic redox active material. Particularly suitable are ascorbic acid, indole, methionine, N-mono (C1-C4 alkyl) glycine, N, N'-di- (C1-C4 alkyl) glycine and 2-phenylglycine, but especially and / or development compounds which belong to the following groups: diaminopyridines, amino-hydroxypyridines, dihydroxypyridines, heterocyclic hydrazones, amino-hydroxypyrimidines, dihydroxypyrimidines, tetraaminopyrimidines, triamino-hydroxypyrimidines, diaminimidines, dihydroxynaphthalenes, naphthols, pyrazolones, hydroxyquinolines, aminoquinolines; primary aromatic amines having a hydroxy or amino group substituted in the ortho, meta or para position by another free or C 1-4 alkyl or C 2-4 hydroxyalkyl group; and di- or trihydroxybenzenes.

Preferred dishwashing detergents contain coupling agents that include phydroxyphenylglycine, 2,4-diaminophenol, 5-chloro-2,3-pyridine, 1- (p-aminophenyl) morpholine, hydroquinone, pyrocatechin. , hydroxyhydroquinone, gallic acid, phloroglucin, pyrogallol and mixtures thereof.

The total amount of organic redox active substances in the agents according to the invention is preferably 0.05 to 6% by weight, preferably 0.2 to 2.5% by weight, based on the total composition.

As a water-soluble component ("builder") that enhances the cleaning effect, in principle, all "builder" formulas commonly used in dish cleaners are contemplated, such as polymeric alkaline phosphates, which may be in the form of their alkaline, neutral or acidic sodium or potassium salts. Exemplary of these compounds are tetrasodium diphosphate, disodium dihydrogen diphosphate, pentanedium triphosphate, so-called sodium hexametaphosphate, and the corresponding potassium salts, or sodium hexametaphosphate and the corresponding potassium and sodium salts. The amount of phosphate is about 30% by weight based on the total mixture; however, the agents of the invention are preferably free of such phosphates. Other possible water-soluble "builder" components are, for example, organic polymers of native or synthetic origin, in particular polycarboxylates, which act as "co-builders", particularly in hard water systems. For example, polyacrylic acids and copolymers of maleic anhydride and acrylic acid as well as sodium salts of these polymeric acids are contemplated. Common commercial products include Sokolan ^R CP 5 and PA 30 (BASF), Alcosperese ^R 175 or 177 (Alco), LMW ^R

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N and SPO2N (Norsohaas). Native polymers include, for example, oxidized starches (e.g., patent application P 42 28 786.3) and polyamino acids, such as polyglutamic acid or polyaspartic acid (e.g., Cygnus or SRCHEM).

Other possible "builder" components are naturally occurring hydroxycarboxylic acids such as mono-, dihydroxybutyric acid, alpha-hydroxypropionic acid and gluconic acid. Preferred "builder" components are salts of citric acid, especially sodium citrate. Anhydrous trisodium citrate, and preferably trisodium citrate dihydrate is preferred as sodium citrate. Trisodium citrate dihydrate may be used as a fine or coarse crystalline powder. Depending on the adjusted pH of the agents of the present invention, citric acids may also be present.

Oxygen-based bleaching agents are primarily sodium perborate mono- and tetrahydrate or sodium percarbonate. The use of sodium percarbonate has the advantage of having a particularly favorable effect on the corrosion behavior of glass. Therefore, the oxygen-based bleaching agent is preferably a percarbonate salt, especially sodium percarbonate. Since the active oxygen does not produce its full effect at elevated temperatures, so-called bleach activators are added to the dishwasher to activate it. Organic bleach activators include, for example, PAG (pentaacetylglucose), DADHT (1,5-diacetyl-2,4-dioxohexahydro-1,3,4-triazine) and ISA (isatoic anhydride), but preferably Ν, Ν, ?,? - tetraacetyl ethylenediamine (TAED). In addition, it may be desirable to use small amounts of known bleach stabilizers, such as phosphonates, borates or metaborates and metasilicates, and magnesium salts such as magnesium sulfate.

To better dissolve protein, fat or starchy food residues, the dishwashing agent of the invention also contains enzymes such as proteases, amylases, lipases and cellulases; as proteases, for example: BLAP ^R 140 (Henkel); Optimase ^R -M440, Optimase ^R -M-330, Opticlean ^R -M-375, Opticlean ^R- M-250 (Solvay Enzymes); Maxacal ^R CX 450,000, Maxapem ^R (Ibis Company); Savinase ^R 4.0 T, 6.0 T, 8.0 T (Novo); Esperase ^R T (Ibis Company); and amylases such as Termamyl ^R 60 T, 90 T (Novo); Amylase-CT ^R (Solvay Enzymes) or Maxamyl ^R P 5000, CXT 5000 or CXT 2900 (Ibis); lipases such as Lipolase ^R 30 T (Novo); cellulases such as Celluzym ^R 0.7T (Novo Nordisk). The dish cleaners preferably contain proteases and / or amylases.

In low-alkaline dishwashing detergents, the agents of the present invention preferably contain conventional alkaline carriers such as alkali-silicates, alkali-carbonates and / or alkaline-bicarbonates. Commonly used alkali carriers include carbonates, bicarbonates, and alkali silicates in which SiO ₂ / M ₂ O (M = alkali atom) is 1.5: 1-2.5: 1. The amount of alkali silicates may not exceed 30% by weight of the total agent. As an alkali carrier, it is preferable to avoid strongly alkaline metasilicates. The alkali carrier system preferably used in the compositions of the present invention is a mixture of carbonate and bicarbonate, preferably sodium carbonate and bicarbonate, in an amount up to 60% by weight, preferably 10-40% by weight, based on the total carbon. Depending on the pH desired and the pH finally adjusted, the ratio of added carbonate to bicarbonate will vary; however, an excess of sodium bicarbonate is usually used, so that the weight ratio of bicarbonate to carbonate is generally 1: 1 to 15: 1.

Optionally, surfactants, in particular low-foaming nonionic surfactants, may be added to the agents of the present invention to improve the dissolution of fat-containing food residues and, as wetting agents, granulating aids or dispersants, lead to a better homogeneous distribution of said . The amount of surfactants is then up to 5% by weight, preferably up to 2% by weight. Usually, highly foamed compounds are used. Preferably, these include (C12-C18) alkyl-polyethylene glycol-polypropylene glycol ethers having up to 8 moles of ethylene oxide and propylene oxide units. However, other nonionic surfactants known as foam-free, such as (C12-C18) alkyl-polyethylene glycol-polybutylene glycol ethers containing up to 8 moles of ethylene oxide and butylene oxide moieties and alkylene-terminated "end-capped" alkyl polyols, may also be used. ethers and foaming but ecologically attractive (C 8 -C 14 alkyl) polyglucosides having a degree of polymerization of about 1 to 4 (e.g., APG ^R 225 and APG ^R 600 (Henkel)) and / or (C 12 -C 14 alkyl). polyethylene glycols having 3-8 ethylene oxide units in their molecule are preferably yellowish, otherwise brown granules are formed, and also surfactants of the glucamide family, such as alkyl-N-methylglucamide (alkyl = 6-14 carbon atoms) are suitable. Partially, it is preferred that the surfactants described are used as a mixture, for example, alkyl polyglycoside and fatty acid. alcohol alcohol ethoxylates, or a combination of glucamides and alkyl polyglycosides.

If the cleaning agents are excessively frothy in use, up to 6% by weight, preferably about 0.5-4% by weight of antifoam compound, preferably silicone oils, silicone oils and hydrophobic silicas, paraffin oil / guerbetalalal alcohol blends, paraffins, hydrophobic acid, and other known, commercially available antifoams. Other additives, such as perfume oils, may optionally be used.

The dishwashing detergents of the present invention are preferably powder, granular or tablet formulations which can be prepared in a manner known per se, for example by mixing, granulating, cylindrical compacting and / or spray drying.

Preferably, the tablet detergent of the present invention is prepared by:

GB 218,021 is mixed with all components with each other and the mixture Β tablettapréseléssel conventional, for example by an eccentric or rotary press 200 · 10 ⁵ Pa 150 010 ⁵ Pa pressure press to form tablets. In this way, tablets with a high breaking strength but dissolving at a satisfactory rate under the conditions used, generally having a flexural strength greater than 150 N, are obtained. The tablet thus prepared weighs 15-40 g, in particular 20-30 g, and has a diameter of 35-40 mm.

Typically, a non-dusting, storage-stable, sprayable powder and / or granulate high-density dishwasher detergent in the range of 750-1000 g / l is typically prepared by blending the builder components in a first step of the process. while at least a portion of the components of the liquid mixture are increased the filling density of this premix and then, if desired after intermediate drying, the additional ingredients of the dishwashing detergent, including inorganic redox active agents, are combined with the resulting premix.

Since any alkali carbonate content strongly affects the alkalinity of the product, intermediate drying should be carried out in such a way that the decomposition of sodium bicarbonate to sodium carbonate is minimized (or at least possibly constant). The proportion of sodium carbonate that is formed by drying is to be taken into account when formulating the granular formulation. The low drying temperatures not only suppress the decomposition of sodium bicarbonate but also increase the solubility of the granular detergent when used. Therefore, it is preferable to use air which, when drying, has a temperature which is as low as possible to avoid decomposition of the bicarbonate and high enough to obtain a product having good storage properties. Preferably, the inlet air temperature during drying is about 80 ° C. The granulate itself should not be heated above about 60 ° C. In the first step of the mixing process, the "builder" component is usually "blended" with the liquid components by mixing with at least one other component of the detergent. An example of this is a preliminary step in which the "builder" components mixed with the perborate are "whipped" and / or thoroughly mixed with the liquid nonionic surfactants and / or the perfume solution. The remaining components are then added and the whole mixture is carefully blended and homogenized in the mixer. Simultaneous application of additional volumes of liquid, especially the addition of additional water, is generally not required. The resulting material mixture is then generally present as a flowable, non-dusting powder having a fill density of 750-1000 g / l.

The pre-granulate is then mixed with the remaining components of the detergent, including the redox active ingredients, to form the final product. In each of the cases described above, as well as the subsequent compression mixing and the final mixing influenced by the liquid components, the mixing time is a few minutes, for example 1 to 5 minutes.

In a particular embodiment, when preparing fine grain cores, it may be desirable to provide further stabilization and equilibration by dusting the surface of the resulting grain core. Small amounts of water glass powder or powdered alkali carbonates are particularly suitable for this purpose.

The detergents to be used can be used in household and industrial dishwashers. The addition is done manually or with a suitable dispenser. The concentration used in the rinse bath is about 2-8 g / l, preferably 2-5 g / l.

The washing program is usually completed and completed by a rinse after the cleaning process and a final rinse with standard rinse aid. After drying, we obtain not only utensils that are perfectly clean and hygienically sound, but above all, bright sparkling cutlery.

Examples

Silver spoons (WMF type, hotel cutlery, Berlin form) are cleaned with silver cleaner, degreased with gasoline and dried. They are then placed in the cutlery basket of a Bosch S 712 household dishwasher. The cleaning program (65 ° C, 16 ° German hardness [dH]) is started and 50 g of dirt (1) and 30 g of cleaning agent are added directly to the machine. After the rinsing and drying process is completed, the dishwasher is opened for 10 minutes, then closed again and rinsed again in the same way. After rinsing run 10, the spoons are removed and evaluated. To do this, the coloration of the penetration is evaluated on a 0-4 point scale: 0 = no penetration, 1 = full / slight yellow discoloration, 2 = more intense yellow discoloration, 3 = whole surface golden-brown discoloration, 4 = violet-black discoloration; values are shown in Figures 1-3. are shown at the top left of tables. I Contaminant composition:

Ketchup 25g Mustard (extra strong) 25g roast sauce 25g potato starch 5g benzoic acid I g yolk 3 pieces Milk 0.5 liters Margarine 92 g City water 608 ml Simultaneously evaluated the pollution of porcelain tea

removal. Here the grading is on a scale from 0 to 10, where 0 = no removal and 1 O = total removal of tea; values are shown in Figures 1-3. are shown at the bottom right of the table.

Creating tea pollution

In a kettle, 16 liters of cold city water (16 ° dH) is rapidly heated to boiling. The 96 g of black tea in a nylon bag is left to stand in the cauldron and the tea is transferred to a dipping apparatus with heating and stirring.

tea cup was immersed in brewed tea 25 times at 70 ° C for 1 minute. The cups are then hung and placed with their opening down on a tin plate for drying.

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Detergent composition:

First, the following, slightly alkaline basic product is prepared with a 1% w / w solution of distilled water to a pH of 9.5:

56.0% by weight trisodium citrate dihydrate

36.1% by weight of sodium bicarbonate

6.1% by weight of sodium carbonate, anhydrous

1.8% by weight of a nonionic surfactant mixture which is APG

It consists of a mixture of 225 (C8-C10 alkyl oligoglycoside) and Dehydol ^R LS 2 (C12-C14 fatty alcohol2EO-ethoxylate) (1: 1).

With this masterbatch, the variants to be tested according to the following formula were executed. The results are shown in Table 1.

81-86% by weight of basic product 5-12% by weight of sodium percarbonate

0-10% by weight of TAED

0-2% by weight paraffin-coated manganese sulfate monohydrate% by protease 10 1% by weight amylase

Table 1

Tea Removal / Protection against Silver Corrosion

Machine: Bosch S 712

Dosage: 30 g

Program: 65 ° C Universal

Water hardness: 16 ° dH

Tea: 1 = no cleaning

10 = optimal cleaning

Silver: 0 = no run

4 = strong penetration

Rcdoxaktív substance: pyrocatchin Numbers: Bubbling silver / tea 3.0% 2.0% ^{0 2 0 3 0 8} 1.5% ^{0 3} 3 5 2 10 1.0% 1 ³ 2 ⁶ 0.5% 0.2% 0.0% 5 ¹⁰ 0.0% 1.0% 2.0% 3.0% 4.0% 10.0%

TAED

Table 2

Tea Removal / Protection against Silver Corrosion

Machine: Bosch S 712

Dosage: 30 g

Program: 65 ° C Universal

Water hardness: 16 ° dH

Tea: 1 = no cleaning

10 = optimal cleaning

Silver: 0 = no entry

4 = strong penetration

Rcdoxactive substance: Gallic acid Numbers: custard run / tca 3.0% ^{3 8}

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Table 2 (continued)

Rcdoxactive substance: Gallic acid Numbers: cyst penetration / tea 2.0% 4 ³ 4 ³ 4 1.5% 1.0% 0.5% ³ 0.2% 0.0% ² 0.0% 1.0% 2.0% 3.0% 4.0% 10.0%

TAED

Table 3

Tea Removal / Protection against Silver Corrosion

Machine: Bosch S 712 Dosage: 30 g Program: 65 ° C Universal Water Hardness: 16 ° dH Tea: 1 = No Cleaning 10 = Optimal Cleaning Silver: 0 = No Penetration 4 = Heavy Penetration

Further, dishwashing detergents were prepared with the following composition (see Table 4). The following compounds A-M were used as silver corrosion protection agents:

A: p-hydroxyphenylglycine

B: 2,4-diaminophenol

D: 1- (p-aminophenyl) morpholine

E: Ascorbic acid 60

F: N-monomethylglycine G: N, N-dimethylglycine H: 2-hydroxy-4-aminopyrimidine 1: 2,4-dihydroxy-5-methylpyrimidine K: indole

L: methionine

M: 2-Phenylglycine

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Table 4 (data by weight)

1 2 3 4 5 6 7 8 9 10 Soda - 27 8 - 26 8 - 26 8 - Nα-bicarbonate - - 31 - - 30 - - 30 - Na-disilicate 35 20 - 35 20 - 35 20 - 34 Trisodium citrate dihydrate 40 25.5 44 40 25.5 44 39 25.5 43 39 Polycarboxylate (Sokolan CP5, BASF) 10 10 - 10 10 - 10 10 - 10 Na Percarbonate - 10 10 - 10 10 - 10 10 - N? -Perborate monohydrate 7 - - 7 - - 7 - - 7 TAED 2 3 2 2 3 2 2 3 2 2 C | -Zsíralkoholetoxilát ₂ -C _l4-22EO (Dehydol LS2, Henkel) 1 0.75 1 1 0.75 1 1 0.75 1 1 C ₈ -C ₁₀ alkyl oligoglucoside (APG 225, Henkel) 1 0.75 1 1 0.75 1 1 0.75 1 1 protease 1.5 1 1 1.5 1 1 1.5 1 1 1.5 amylase 1.5 1 1 1.5 1 1 1.5 1 1 1.5 Protects against silver corrosion (THE) (B) (C) (D) (E) (F) (G) (H) (I) (R) times, A-M 1 1 1 1 2 2 2 2 3 3 PH of a 1% aqueous solution 10.5 11 9.5 10.5 11 9.5 10.5 11 9.5 10.5

Continuation of Table 4 (data by weight)

11 12 13 14 15 16 17 18 19 20 Soda 26 8 - 25.5 8 - 26 7 - 26 Nα-bicarbonate - 30 - - 29 - - 29 - - Na-disilicate 19.5 - 34 19 - 34 18.5 - 34 18.5 Trisodium citrate dihydrate 25 43 38 25 43 38 24 43 38 24 Polycarboxylate (Sokolan CP5, BASF) 10 - 10 10 - 10 10 - 9 10 Na Percarbonate 10 10 - 10 10 - 10 10 - 10 N? -Perborate monohydrate - - 7 - - 7 - - 7 - TAED 3 2 2 3 2 2 3 2 2 3 Fatty alcohol ethoxylate (Dehydol LS2, Henkel company) 0.75 1 1 0.75 1 1 0.75 1 1 0.75 Alkyl Oligoglucoside (APG 225 from Henkel) 0.75 1 1 0.75 1 1 0.75 1 1 0.75 protease 1 1 1.5 1 1 1 1.5 1 1.5 1 amylase 1 1 1.5 1 1 1.5 1 1 1.5 1 Silver corrosion protection agent, M (L) 3 (M) 3 (THE) 4 (B) 4 (C) 4 (D) 4 (E) 5 (F) 5 (G) 5 (H) 5 PH of a 1% aqueous solution 11 9.5 10.5 11 9.5 10.5 11 9.5 10.5 11

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All the silver channels were rated 0-1 ("no or very poor run").

Identical formulations, however, which did not contain A-M silver corrosion inhibitors, caused yellow-violet discoloration on silver spoons (rating 2-4).

Electrochemical measurements

Preparation of trial

Silver wire (diameter: 2 mm, 99%) was used as the test material instead of silver cutlery. Pieces of this silver were always cut off about 10 cm long and the portion of the probe immersed in the standard solution was polished with silica carbide abrasive paper (grain 600). The samples were then rinsed thoroughly with double-distilled water and any adhering abrasive residue was wiped off with a non-fibrous cloth. This procedure was repeated several times, as appropriate, until the test produced an optically perfect impression. After grinding, probes were immediately measured to prevent the metallic silver from reacting with laboratory air. The probe immersed in the solution had an effective surface area of 0.70 cm ² .

Electrolytes and Electrodes

The experiments were performed in a rough glass cuvette. The silver electrodes (A = 0.70 cm ² ) were used as measuring electrodes. The counter electrode consisted of 1 cm ² gold plate (99.99%). As reference electrode, with respect to the alkaline electrolyte solution, a Hg / HgO / 0.1M NaOH electrode was contacted with the electrolyte solution through a Haber-Luggin capillary. Measurements were made with tap water (16 ° dH), 5 g / l of detergent solution, containing about 600 mg of salt (dry matter).

When using the detergent solution, the low alkaline stock (see above) was first dissolved and heated to 65 ° C. Immediately prior to measurement, bleach and bleach activator and / or silver corrosion protection agent were added. This was followed by electrochemical measurement. During the electrochemical experiments, the electrolyte solutions were kept at 65 ° C and rinsed with air.

Instrument and measurement curve

To record current-voltage curves, the electrode potential (relative to the standard hydrogen electrode) was increased at a constant rate starting from -0.62 V. After a total increase of 1.1 V, the potential was reduced at the same rate. His function was a standard potentiostat consisting of a feedback amplifier, a differential amplifier, an addition and an impedance converter, and a function generator (Prodis 16, from Intelligent Controls CLZ GmbH). Results

Corrosion was characterized using current-voltage curves. Relevant information was provided by the zero transition of the current curves (the resting potential, which self-adjusts without any change in external potential) and the slope of the curve at the neutral transition (reciprocal polarization resistance) (Heitz E., Henkhaus R., Rahmel A., Korrosionskunde im Experiment). Verlag Chenie (1983), p. 31; Kaesche H., Die Corrosion Dér Metalle, 2nd edition, Springer Verlag (1979), p. Meanwhile, when the silver corrosion protection agent is added, the zero-transfer potential shifts to lower values and the slope of the curve decreases. Thus, the corrosion of silver is significantly reduced electrochemically by the addition of a corrosion inhibitor.

Detergent composition Location of zero transfer E (mV) (standard hydrogen electrode) Zero transition slope di / dE (mA / V) Basic products (86%) + 12% percarbonate + 2% hydroquinone 319 0.5

Claims (19)

Use of organic redox active substances in dishwashing detergents as silver corrosion protection agents. Use according to claim 1, characterized in that the organic redox active substance is ascorbic acid, indole or methionine. Use according to claim 1, characterized in that the organic redox active substance is an N-mono (C 1 -C 4 alkyl) glycine, N, N-di (C 1 -C 4 alkyl) glycine or 2-phenyl glycine. Use according to claim 1, characterized in that the organic redox active substance is a diaminopyridines, amino-hydroxypyridines, dihydroxypyridines, heterocyclic hydrazones, amino-hydroxypyrimidines, dihydroxypyrimidines, tetraaminopyrimidines , triaminohydroxypyrimidines, diaminohydroxypyrimidines, dihydroxynaphthalenes, naphthols, pyrazolones, hydroxyquinolines, aminoquinolines; primary aromatic amines having a hydroxy or amino group substituted at the ortho, meta or para position with another free or substituted C 1-4 alkyl group or C 2-4 hydroxyalkyl group; and a coupling and / or developing compound belonging to the group of di- or trihydroxybenzenes. Use according to claim 4, characterized in that the coupling or developmental compound is p-hydroxyphenylglycine, 2,4-diaminophenol, 5-chloro-2,3-pyridinediol, 1- (p- member of the group consisting of aminophenyl) morpholine, hydroquinone, pyrocatechin, hydroxyhydroquinone, gallic acid, phloroglucin and pyrogallol. Low-alkali agent for cleaning utensils having a pH of 8 to 11.5, preferably 9 to 10.5, and preferably 15 to 60%, preferably 30 to 50% by weight of a water-soluble builder component of a 1% w / w solution of the agent. 5 to 25% by weight, preferably 10 to 15% by weight of oxygen-based bleach, 1-10% by weight, preferably 2-6% by weight of organic bleach activator, 0.1 to 5% by weight, preferably 0.5 to 2.5% by weight of enzyme, It contains an anti-corrosion agent, characterized in that the anti-silver corrosion agent is an organic redox active substance. 7. A low alkaline cleaning agent for containers according to claim 6, characterized in that the silver corrosion protection agent contains ascorbic acid, indole. Low alkaline agent according to claim 6, characterized in that N-mono- (C 1-4 alkyl) glycine, N, Ndi (C 1-4 alkyl) glycine or 2-phenyl is used as a silver corrosion protection agent. contains glycine. Low alkaline cleaning agent for machine cleaning according to claim 6, characterized in that the silver corrosion protection agent comprises a coupling and / or development reagent which is diaminopyridines, aminohydroxypyridines, dihydroxypyridines, heterocyclic hydrazones. , amino-hydroxypyrimidines, dihydroxypyrimidines, tetraaminopyrimidines, triamino-hydroxypyrimidines, diamino-dihydroxypyrimidines, dihydroxynaphthalenes, naphthols, pyrazolones, hydroquinolines, aminoquinolines; primary aromatic amines having a hydroxy or amino group substituted at the ortho, meta or para position with another free or C 1-4 alkyl group or C 2-4 hydroxyalkyl group; and belongs to the group of di- or trihydroxybenzenes. 10. An agent according to claim 9, wherein the coupling or developing compound is p-hydroxyphenylglycine, 2,4-diaminophenol, 5-chloro-2,3-pyridinediol, 1- (p) -aminophenyl) -morpholine, hydroquinone, pyrocatechin, hydroxyhydroquinone, gallic acid, phloroglucin and pyrogallol. 11. An agent according to any one of claims 1 to 3, characterized in that the organic redox active is present in an amount of 0.05 to 6% by weight, preferably 0.2 to 2.5% by weight, based on the total agent. 12. A 6-11. An agent according to any one of claims 1 to 5, characterized in that the water-soluble builder component is a salt of citric acid, preferably sodium citrate. 13. A 6-12. An agent according to any one of claims 1 to 4, characterized in that the bleaching agent is an oxygen-based percarbonate salt, preferably sodium percarbonate. 14. Figures 6-13. An agent according to any one of claims 1 to 3, characterized in that the organic bleach activator is N, Ν, Ν ', N'-tetraacetyl ethylenediamine (TAED). 15. A 6-14. An agent according to any one of claims 1 to 3, characterized in that the enzyme is an amylase and / or protease. 16. An agent according to any one of claims 1 to 4, further comprising up to 60% by weight, preferably 10-40% by weight of the total agent, of an alkaline carrier system consisting essentially of carbonate and bicarbonate, preferably sodium carbonate and sodium bicarbonate. 17. An agent according to any one of claims 1 to 4, further comprising up to 5% by weight, preferably up to 2% by weight of the total agent, of a surfactant, preferably a low foaming nonionic surfactant. 18. An agent according to any preceding claim, characterized in that it is present as a tablet obtainable by pressing 2 to 10 ⁷ Pa to 1.5 · 10 ⁸ Pa pressing pressure mixing of all the ingredients in blender and blend tablet press machine. 19. An agent according to any one of claims 1 to 3, characterized in that it is in the form of a powder or granules and has a filling density of 750 to 1000 g / l. Published by the Hungarian Patent Office, Budapest Responsible: Zsuzsanna Törőcsik Head of Unit