CZ234895A3 - Protecting agent against silver i corrosion - Google Patents

Abstract

The invention concerns the use of inorganic redox compounds, in particular salts and/or complexes of metals selected from the group comprising Mn, Ti, Zr, Hf, V, Co, and Ce, as silver-corrosion protection agents in dishwasher washing-up agents, in particular low-alkali dishwasher washing-up agents.

Description

Silver corrosive preservative I

Field of technology

The invention relates to a corrosion protection agent for silver I for use in dishwashing compositions.

Prior art

It is a well-known fact that silver, if not used, will fail. It is only a matter of time before dark, brownish, bluish to bluish-black spots form or the silver changes color overall and, as usual, is faded.

Even with machine cleaning of table silver in practice, problems arise again and again in the form of faded or discolored silver surfaces. Here, silver can react to sulfur-containing substances which are contained in or dispersed in the rinsing water, since when washing dishes in household automatic dishwashers (HGSM), food residues are introduced into the washing water and thus e.g. also mustard, peas, eggs and other sulfur-containing substances such as mercaptoamino acids. Also, much higher temperatures and longer contact times with sulfur-containing food residues that are present during machine rinsing support the handling of silver compared to manual rinsing. In addition, the intensive cleaning process in the washing machine completely degreases the silver surface and makes it more sensitive to chemical influences.

When using detergents containing active chlorine, the depletion of silver by the action of sulfur-containing compounds can be greatly prevented, since these compounds are converted into a secondary reaction to sulfones or sulfates by the oxidation of sulfide functions.

However, the problem of handling silver became topical again when active oxygen compounds, such as sodium perborate or sodium percarbonate, began to be used alternately with active chlorine compounds to remove bleachable contaminants such as tea stains, tea deposits, coffee grounds, dyes. from vegetables, lipstick residues and the like.

These active oxygen compounds are used mainly in modern weakly alkaline detergents from the new generation of detergents together with bleach activators. These modern compositions consist in total of the following functional components: basic component (complexing agent / dispersant), alkali metal carrier, bleach system (bleach + bleach activator), enzymes and wetting agents (surfactants).

Silver surfaces react fundamentally more sensitively to the changed parameters of the new, active chlorine-free formulation of detergents with reduced pH values and activated oxygen bleaching. During machine washing, these compositions release their own bleaching agent during cleaning, namely hydrogen peroxide or active oxygen. The bleaching action of cleaning agents containing active oxygen is enhanced by bleach activators, so that a good bleaching effect is achieved even 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 sulfide (sulfide) is formed in the presence of silver, but also oxide coatings on the surface of the silver, preferably due to oxidative disruption of the transiently formed peroxides or active oxygen. In addition, chlorine-containing coatings can be formed at high salt loads. In addition, the silver content is enhanced by the higher residual hardness of the water during the cleaning process.

The removal of silver corrosion, ie the formation of sulfide, oxide or chloride coatings on silver, is the subject of numerous publications. In these publications, the corrosion of silver is mainly dealt with by so-called silver protection agents.

British Patent Specification No. GB 1 131 738 discloses alkaline dishwashing detergents which contain benzotriazoles as corrosion inhibitors for silver. U.S. Pat. No. 3,549,539 discloses strongly alkaline dishwasher detergents which may contain, inter alia, e.g. perborate with organic bleach activator. Strongly alkaline, dishwasher safe compositions are described which may contain, inter alia, e.g. perborate with organic bleach activator. As a means of preventing sagging, additives of e.g. also benzotriazole or ferric chloride. In this case, pH values of preferably 7 to 11.5 are given. European Patent Specifications Nos. 135,226 and 135,227 describe weakly alkaline, dishwasher safe compositions containing peroxy compounds and activators, which may contain, inter alia, e.g. benzotriazoles and fatty acids. Finally, it is known from German Patent Specification DE 41 28 672 that peroxy compounds which are activated by the addition of known organic bleach activators prevent the treatment (loss) of silver parts in strongly alkaline detergents.

The essence of the invention

Unexpectedly, it has now been found that inorganic redox-active substances, in particular salts or complex compounds of certain metals, which have not yet been described as silver corrosion protection agents, are effective in preventing silver corrosion in dishwashers.

The subject of the invention is the use of inorganic redox-active substances in dishwashing preparations as corrosion protection agents.

The term corrosion must be interpreted in its broadest sense, used in chemistry, in particular, corrosion is meant to mean any still recognizable change in the surface of metal, here silver, whether it is a point of color change or a large area.

Inorganic redox-active substances are those inorganic substances which are susceptible to easily reversible oxidation and / or reduction. Thus, for example, oxides, hydroxides or halides of ammonium salts or alkali metal or alkaline earth metal salts do not fall within this definition.

Examples of inorganic redox-active substances are those based on different degrees of sulfur oxidation, such as NagS2Og (sodium sulphate, sodium thiosulphate), Na ₂ S ₂ O ₄ (sodium dithionite) or Na ₂ S ₂ O ₅ (sodium metabisulphite). ).

However, salts or complex compounds of certain metals are particularly preferred. It is preferred to use a metal and / or metal complexes selected from the group of salts or complexes of manganese, titanium, zirconium, hafnium, vanadium, cobalt and cerium to prevent corrosion of silver, the metals being found in one of the oxidation stages II, III, IV, V or VI.

The definition for the oxidation state is given, for example, in Rompp Chemie Lexikon, Georg Thieme Verlag Stuttgart / New York, 9th ed., 1991, p. 3168.

The metal salts or complexes used should be at least partially soluble in water. Opposite ions suitable for salt formation include all customary, once, twice or threefoldly negatively charged inorganic anions, for example oxide, sulfate, nitrate, fluoride residues or also organic anions, such as stearate.

Metal complexes within the meaning of the invention are compounds which consist of a central atom and of one or more ligands. The central atom is one of the above metals in one of the above oxidation states. Ligands are nautical molecules or anions which are polyvalent or monovalent, the term ligand within the meaning of the invention is explained in more detail, for example, in Rompp Chemie Lexikon, Georg Thieme Verlag Stuttgart / New York, 9th ed., 1990, p. 2507. metal does not balance the charge of the central atom and the charge of the ligand or ligands to zero, then depending on whether there is an excess of cationic or anionic charge, either one or more of the above anions or one or more of the above cations, e.g. sodium, potassium or ammonium, the charge equalizes. Suitable complexing agents are, for example, citrate, acetylacetonate or 1-hydroxyethane-1,1-diphosphonate.

Particularly preferred metal salts and / or metal complexes can be selected from the group consisting of MnSO 4, manganese citrate, manganese stearate, manganese acetylacetonate, 1-hydroxyethane-1,1-diphosphonate, manganese, V ₂ O _5> V 2, VO _2> TiSO ₄ , KgTiFg, K ₂ ZrF ₆ , Co (NO ₃ ) ₃ , as well as mixtures thereof. MnSO ₄ is particularly preferred

These metal salts or metal complexes are in general commercially available substances which can be used according to the invention without prior purification in order to protect silver against corrosion.

Thus, for example, a mixture of pentavalent and tetravalent vanadium ( ^ν 2θ5 'V0 ₂ »^ ₂ 0 ₄ ), known from the production of SO ₃ (contact method), as well as titanyl sulfate, TiOSO 2, formed by diluting a solution of Ti (So ₄ ) ₂ , is suitable.

Inorganic redox-active substances, in particular metal salts or complexes, are preferably coated, i.e. completely coated with a waterproof but easily soluble material at purification temperatures, in order to prevent their premature decomposition or oxidation during storage. Preferred coating materials which are applied according to known processes, for example by the Sandwik hot-melt coating process from the food industry, are paraffins, microwaxes, waxes of natural origin, such as carnauba wax, cannulated wax, beeswax, high-melting alcohols, for example hexadecanol, soaps. or fatty acids. In this case, a coating material which is solid at room temperature is applied in the molten state to the coated material, for example by passing the fine-grained coated material in a continuous stream through a misty, also continuously formed, zone of molten coating material. The melting point must be chosen so that the coating material can be easily dissolved or melted in the dishwasher the next time the silver corrosion inhibitors are used. The melting point should therefore ideally be between 45 ° C and 65 ° C and preferably between 50 ° C and 60 ° C for most applications.

However, the inorganic redox-active substances described above are particularly suitable for preventing the corrosion of silver when contained in weakly alkaline dishwasher detergents. This is all the more surprising given that these silver corrosion inhibitors are not damaged by the presence of oxygen-based bleaching agents, which are usually present in weakly alkaline cleaning agents.

Another object of the invention is therefore to provide weakly alkaline dishwasher detergents whose one percent solutions (% by weight) have a pH of 8 to 11.5, preferably 9 to 10.5 and contain 15 to 60% by weight, preferably 30 to 50%. % by weight of water-soluble base component, 5 to 25% by weight, preferably 10 to 15% by weight of bleach and oxygen base, 1 to 10% by weight, preferably 2 to 6% by weight of organic bleach activator containing O- or N-acyl groups containing 1 to 12 carbon atoms,

0.1 to 5% by weight, preferably 0.5 to 2.5% by weight, of enzyme, in each case based on the weight of the whole composition and the silver corrosion protection agent, the inorganic redox active substance being present as the silver corrosion agent. Particularly suitable are metal salts and / or metal complexes selected from the group of salts and / or complexes of manganese, titanium, zirconium, hafnium, vanadium, cobalt and cerium, the metals being in one of the oxidation states II, III, IV, V or VI .

Preferred dishwashing compositions contain metal salts or metal complexes selected from the group: MnSO, manganese citrate, manganese stearate, manganese acetylacetonate, 1-dihydroxyethane-1,1-diphosphonate manganese, V ₂ 0 _5> ^ν 2θ4 ' ^v0 2' ^K 2 ^TiF 6 'K ₂ ZrFg, CoSO 2, CoNO 3), Ce (NO ₂ ) ₃ , as well as mixtures thereof. MnSO 4 is particularly preferred.

Inorganic redox-active substances, in particular metal salts and / or metal complexes, are preferably present in the compositions according to the invention in a total amount of 0.05 to 6% by weight, preferably 0.2 to 2.5% by weight, based on the total amount. means.

Inorganic bleach activators containing O- or N-acyl groups having 1 to 12 carbon atoms are substances in which at least one acyl group having 1 to 12 carbon atoms, preferably an acetyl group, is attached to an oxygen atom or an atom nitrogen, contained in the substance, and the perhydrolysis of which gives alkanoic acids having 1 to 12 carbon atoms, preferably peracetic acid.

Suitable building blocks which are water-soluble are, in principle, all the components customarily used in dishwasher compositions, for example polymeric alkaline phosphates, which may be present in the form of their alkaline neutral or acidic sodium or potassium salts. Examples are tetrasodium diphosphate, disodium dihydrogen diphosphate, pentasodium triphosphate, so-called sodium hexametaphosphate, as well as the corresponding potassium salts or mixtures of sodium hexametaphosphate, as well as the corresponding potassium salts or mixtures of sodium and potassium salts. The amount of phosphate is in the range of up to about 30% by weight, based on the total composition, but preferably the compositions according to the invention are free of such phosphates. Other possible water-soluble components are, for example, organic polymers of natural or synthetic origin, in particular polycarboxylates, which act as auxiliary components, in particular in hard water. Examples are polyacrylic acids and copolymers of maleic anhydrides and acrylic acid, as well as sodium salts of these polymeric acids. Commonly available products are, for example, Sokalan ^R CP 5 and PA 30, by BASF, Alcosperse ^R 175 or 177 fy. Alco, LMW ^R 45 N and SP02 N fy. Norsohaas. Natural polymers include, for example, oxidized starch (for example German Patent Specification No. P 42 28 786.3) and polyamino acids, such as polyglutamic acid or polyaspartic acid, for example from Cygnus or SRCHEM.

Other possible building blocks are naturally occurring hydroxycarboxylic acids, such as mono- or dihydroxysuccinic acid, alpha-hydroxypropionic acid and gluconic acid. Preferred building blocks are citric acid salts, especially sodium citrate. Suitable sodium citrates are anhydrous sodium citrate or, preferably, sodium citrate dihydrate. Sodium citrate dihydrate can be used as a fine or coarse crystalline powder.

Depending on the pH occurring in the compositions according to the invention, acids corresponding to citrate may also occur.

Suitable oxygen-based bleaching agents are, in particular, sodium perborate mono- and tetrahydrate or sodium percarbonate. The use of sodium percarbonate has its advantages, as it has a particularly favorable effect on the corrosion behavior of glass articles. The oxygen-based bleaching agent is therefore preferably a salt of percarbonate, in particular sodium percarbonate. Since active oxygen develops its full effect on its own only at higher temperatures, so-called bleach activators are used for its activation in dishwashers. Bleach activators are organic activators containing O- or N-acyl groups having 1 to 12 carbon atoms, for example PAG (pentaacetylglucose), DADHT (1,5-diacetyl-2,4-dioxo-hexahydro-1,3,5- triazine) and ISA (isationic anhydride), but preferably N, N, N, N-tetraacetylethylene diamine (TAED). In addition, it may also be expedient to add small amounts of known bleach stabilizers, for example phosphonates, borates or metaborates and metasilicates, as well as magnesium salts, such as magnesium sulfate.

To better separate food residues containing protein, fat or starch, the dishwashing compositions according to the invention contain enzymes, such as proteases, amylases, lipases and cellulases, for example proteases, such as BLAP ^R 140 from Henkel.

0ptimase ^R -M-440, Optimase ^ -M-330, Opticlean ^R -M-375,

R R

Opticlean -M-250 from Solvay Enzymes, Maxacal CX 450,000,

R R

Maxapem from Ibis, Savinase 4.0 T, 6.0 T, 8.0 T from

R R

Novo, Esperase T from Ibis and amylases such as Termamyl 60 T, p

T, Novo, Amylase-LT, Solvay Enzymes or

Maxamy ^R P 5000, CXT 5000 or CXT 2900, by Ibis, lipases,

R R as Lipolase 30 T, from Novo, cellulases, such as Celluzym 0.7 T, from Novo Nordisk. Preferably, the dishwashing compositions contain proteases and / or amylases.

Preferably, the compositions according to the invention further comprise alkali carriers contained in customary, weakly alkaline dishwasher detergents, such as alkali metal silicates, carbonates and / or bicarbonates. Alkali carriers commonly used include alkali metal carbonates, bicarbonates and silicates with a molar ratio of S1O2 / M2O (M = alkali metal atom)

1.5: 1 to 2.5: 1. Alkali metal silicates can be present in amounts of up to 30% by weight, based on the total composition. The use of strongly alkaline metasilicates as alkali carriers is preferably dispensed with. The alkali carrier system preferably used in the compositions of the invention is a mixture of substantially carbonate and bicarbonate, preferably sodium carbonate and bicarbonate, which is present in an amount of up to 60% by weight, preferably 10 to 40% by weight, based on the total composition. Depending on which pH is ultimately desired or adjusted, the ratio of carbonate used to bicarbonate used varies, but usually an excess of sodium bicarbonate is used, so that the weight ratio between bicarbonate to carbonate is usually 1: 1 to 15: 1.

Wetting agents may also be optionally added to the compositions according to the invention, in particular low-foaming nonionic wetting agents, which serve to better release greasy food residues and serve as wetting agents, granulating agents or dispersing agents for better, homogeneous distribution of said silver corrosion protection agents in mice. bath and silver surface. Their amount is then up to 5% by weight, preferably up to 2% by weight. Extremely few foaming compounds are usually used. These preferably include an alkyl polyethylene glycol-polypropylene glycol ether having 12 to 18 carbon atoms, in each case up to 8 moles of ethylene oxide and propylene oxide units per molecule. However, it is also possible to use other nonionic surfactants known as non-foaming agents, such as alkylpolyethylene glycol-polybutylene glycol ether having 12 to 18 carbon atoms, in each case up to 8 moles of ethylene oxide and butylene oxide units per molecule. foaming but environmentally attractive alkyl polyglucosides with 8 to 14 carbon atoms and a degree of polymerization of about 1 to 4 (for example APG ^R 225 and APG ^ 600, from Henkel) and / or alkyl polyethylene glycols having 12 to 14 carbon atoms and with 3 to 8 ethylene oxide units in the molecule. Bleached grades should be used, otherwise a brown granulate will form. Also suitable are wetting agents from the group of glucamides, such as alkyl-N-methylglucamides (alkyl = fatty alcohol with a carbon chain length of 6 to 14 carbon atoms). It is in part advantageous to use the described wetting agents as mixtures, for example combinations of alkyl polyglucosides with fatty alcohol ethoxylates or glucamides with alkyl polyglycosides, etc.

If the cleaning agents foam too strongly in use, up to 6% by weight, preferably about 0.5 to 4% by weight, of a suds suppressing compound can be added, preferably from the group of silicone oils, a mixture of silicone oil and hydrophobic silicic acid, paraffinic oils / beta-alcohols and paraffins, hydrophobic silicic acids, bistearic acid amides and other known known defoaming agents can also be used. Other possible additives are, for example, perfume oils.

The dishwashing compositions according to the invention are preferably in the form of powder, granular or tablet formulations, which can be prepared in a customary manner, for example by mixing, granulating, compressing, rolling and / or spray-drying.

For the production of the cleaning compositions according to the invention in the form of tablets, the process is preferably carried out by mixing all the components in a mixing device and compressing the mixture with compression pressures in the range of 200 using tablet presses, for example eccentric presses or circumferential rotor presses 11. $ 10 Pa to 1500. 10 ^ Pa. Thus, solid and yet sufficiently rapidly soluble tablets with a flexural strength of usually over 150 N are obtained without difficulty.

Preferably, the tablet thus produced weighs from 15 g to 40 g, in particular 20 g to 30 g with a diameter of 35 mm to 40 mm.

The production of dishwashing compositions in dishwashers in the form of non-dusting powders and / or granules with high bulk densities in the range from 750 to 1000 g / l during storage is characterized in that in the first partial process step the basic components are mixed with at least part liquid of the components of the mixture, increasing the bulk density of this premix and then, optionally after an intermediate drying step, combining the other components of the dishwasher detergent composition, including inorganic, redox-active substances, with the premix thus obtained.

As the possible alkali metal carbonate content strongly affects the alkalinity of the product, the drying intermediate stage must be carried out in such a way that the decomposition of sodium bicarbonate to sodium carbonate is as small as possible (or at least as constant as possible). This is because the proportion of sodium carbonate formed in addition by drying would have to be taken into account when formulating the granulate formulation. Low drying temperatures not only counteract the decomposition of sodium bicarbonate, but also increase the solubility of the granular detergent in use. Therefore, the temperature of the supply air during drying is advantageous, which on the one hand should be as low as possible in order to prevent the disintegration of the sodium bicarbonate and which on the other hand must be so high as to obtain a product with good storage properties. For drying, the most preferred supply air temperature is about 80 ° C. The granulate itself should not be heated to temperatures above about 60 ° C. In the first partial stage of the mixing process, the liquid component is generally applied to the base component in a mixture with at least one further component of the dishwashing composition. For example, a preliminary stage is possible here, in which the basic component in a mixture with perborate is sprayed with nonionic wetting agents and / or a solution of fragrances and is thoroughly mixed with them. The remaining ingredients are then added and the whole mixture is worked up and homogenized in a mixer. The use of additional amounts of liquid, in particular the supply of additional water, is generally not necessary. The resulting mixture of substances is then in the form of a non-dusting, free-flowing powder with the desired high bulk density in the range of 750 to 1000 g / l.

The pre-granules are then mixed into the finished product with the still missing dishwashing detergent components, including inorganic redox actives. The mixing time in all the cases mentioned here, both in the pre-compaction stage under the influence of the liquid components and in the subsequent final mixing with the other components, is in the range of a few minutes, for example in the range of 1 to 5 minutes.

According to a particular embodiment of the invention, in the production of fine granulate grains, it can be expedient to achieve penetrating stabilization and equalization by applying fine particles to the surface of the formed granulate grains. Particularly suitable for this are small proportions of alkali metal carbonate powder water glass powder.

These products can be used both in household dishwashers and in operating dishwashers. The addition is carried out manually or with suitable dosing devices. The concentration used in the washing bath is approximately 2 to 8 g / l, preferably 2 to 5 g / l.

The dishwashing program is usually completed and terminated by several rinses, followed by a clean water rinsing process, and finally by rinsing in a conventional rinsing agent. After drying, not only are completely clean and hygienically perfect dishes obtained, but above all, brightly shiny silver cutlery components are also obtained.

Examples of embodiments of the invention

Silver spoons (type WMF, hotel cutlery, Form Berlin) were cleaned with a silver cleaner, degreased with petrol and dried. In each case, three spoons were placed in the sideboard basket of the Bosch S712 household dishwasher (HGSM). The cleaning program (65 ° C, 16 ° dH) was now started, 50 g of impurity (1) as well as 30 g of detergent were added directly to the dishwasher during the cleaning program. After rinsing and drying, the dishwashers (HGSM) were opened for 10 minutes, then closed again and the same procedure was followed. After the 10th washing procedure, the spoons were removed and evaluated. For this purpose, the colors of the fading were evaluated in the range from 0 to 4:

(0 = no fading, 1 = completely weak yellow color, = stronger yellow color, 3 = full-area gold to brown color, 4 = purple to black spoon color, values are given in the upper left part of table 1.)

1) Impurity composition: Ketchup 25 G mustard (especially sharp) 25 G roast juice 25 G potato starch 5 G benzoic acid 1 G egg yolk 3 to milk 1/2 1 margarine 92 G tap water 608 ml

At the same time, the removal of tea contamination on porcelain dishes was assessed. Here, the designation was between 0 and 10, where 0 = no tea removal and 10 = complete tea removal, the values in the lower right of Table 1.

Dirt with tea

In the water treatment boiler, 16 liters of cold tap water (16 ° d) were heated briefly to boiling. 96 g of dark tea in a nylon sieve are left to stand for 5 minutes with the lid closed and the tea is transferred to an immersion apparatus with a heating element and a stirrer.

cups of tea are immersed 25 times in one minute at 70 ° C in tea broth. Then the cups are removed and placed with the hole down on the baking sheet to dry.

Detergent composition

First, a basic product with a low alkali metal content was produced, whose 1% solution (by weight) had a pH value of 9.5 in distilled water:

56.0% sodium citrate dihydrate

36.1% sodium bicarbonate

6.1% sodium carbonate, anhydrous

1.8% mixture of nonionic surfactants APG 225 (C 1 -C 10 alkyl oligoglucoside) and Dehydrol® LS 2 (C 2 -C 14 fatty alcohol ethoxylate) in a 1: 1 ratio.

Various tests have been performed with this basic product, the variations of the composition being prescribed by the following recipe. The results are shown in Table 1.

- 86% by weight of the basic product% by weight of sodium percarbonate

- 10% by weight of TAED

- 2% by weight of paraffin-coated manganese sulphate monohydrate ____________ 1.% by weight of protease% by weight of amylase

Table 1

Tea cleaning / silver corrosion protection

redox-active substance means: depletion of silver / tea > 4nSO4 2.0% ° 7 ^ / 3.9 ⁰ 7 / 3.2 ⁰ / ° / 7 ^ 3 ° τ ' ⁰ τ Τζ, ζ 1.0% ° / 7 5.0 ⁰ // to ⁰ 7 7i, 6 ⁰ 7 /, 8 ⁰ 7 ^θ τ '7 *, ι 0.5% ° 7 / ^{7.3 0} / ⁰ / 73.0 ⁰ / 7ι $ ⁰ τ ' ⁰ / τ *, * 0.4% ⁰ 7 7w ⁰ / Z ⁰ 7 Λ, * ^θ τ '7 *. * ⁰ τ '/ 3.3 0.3% ⁰ / / 5.1 1 7 7 ^1.7 'k cn o \ ⁰ 7 7 ⁰ τ '/ ι, ο ΐ 7 / 3.7 0.2% // 1 7 7 * fi 1 7 7 ^3.1 1 / 78.5 ΐ 7 73.8 2/7 * 3 0.0% ⁰ / / 1.2 2 7 /, 2 ³ 7 7ί $ 3 / / 1.1 ⁴ 7 ', 2 ^{4 of} '7', 6 0.0% 1.0% 1.5% 2.0% 2.5% 3.0%

TAED

- 17 Machine: Bosch S712 dose: 30 g program: 65 ° C water hardness: 16 ° dH tea: 1 = no cleaning = optimal cleaned silver: 0 = no wilting = heavy wilting.

In addition, dishwasher detergents having the compositions listed in Table 2 were prepared. Compounds A-E were used as silver corrosion protection agents:

^{A: V} 2 ° 4 ^{/ V} 2 ° 5

B: Ti0S0 ₄

C: CoS0 ₄

D: CE (N0 ₃ ) ₃

E: Na ₂ S ₂ O ₃ x 5H ₂ 0

X Ό ω ie £ P> z- * Pl CD 14 3 Ό z-x and X X X WHAT 0 b < 3 b X X O N <X > 0 CD cn o x < << 0 X P ' «<O x? r CD X w 3 b 0 X X 0 X X 3 Ό I- * ¢ + X X 0 O 0 C X “< “< Cu. b pl 0 b Pl 'a> X << KX X X pl X X X ⁴ 0 X P> N pl ' C O x * < << X X JD b b < he Z-X 9) < p) N X About pl X X X rn b p) ' 0 0 C CD P> z-x p. X X pl ' b O < 5 x X 3 3 X * 0 x · > « 0 X P) ' X 0 X C X X b) o X 3 X X or X O o < X X Ό 003 cn o> 3 with n3 << P · p. X o < X b X rv o p> X) 3 and x X X X X * 0 Γ0 C X 01 CD P) ' b 93 O < X X w? r H) X b WHAT H> X Pi ' 5 X 93 < X Ul 0 • CCS X 0 'C X X 3 O 01 • X O ' 0 X '· 3 what 93 X H> P- X X X b 3 ω 0 3 what 3 0 «<Q, CD H '0 X ► WHAT X 0 O' b • 3 X- X cn 0 3 what X X 0 0 ÍÍC P> £ * 1 X 0 3 0 N X Θ X 3 3 X << $ ' X About 00 X X * C CD' 3 . 3 • - · po o X * <! ' O Cfl ? r pí W X WHAT 0 N X CD N < O 0 O X b < X · - · H and O H ' > _Z χ C 3 x · p O CD' C b 0 X P> Pi 0 X X ¹

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Μ CD

10.5 > 1.5 1.5 Class— > * ' ro xj 1 10 40 35 1 1 w ro ro ro W »CO 1— * ►- * O O ω 1 O O (HER O 1 XJ ns « JB ** 4 (Jl (Jl (HER > * •and. bO vO * «* O »- * to·* TO·* ro 1 O 1 Ok 1 03 bO • Cn > - · > - * Ok CJ O > - * σ ί · » to* ro XJ 1 O O (Jl 1 1 js. «· * cn cn cn ► * · H- ro ro ro > - * re m o. O OJ 1 O O (HER O 1 cn (HER * w 'xj • XJ (Jl (Jl (Jl Ok bJ vO ro> > - · TO· ro 1 O 1 Ok AND O 03 s «· tn H * M bJ AT) O ro co 1— * > - * > - · ro XJ O VO (Jl and AND • M * « «· cn tn (Jl -with h- · H- » ro ro ro ro o O O ω O O (Jl O 1 he 03 • * * ** 4 (HER (HER cn X » with bJ O H · » ro O and with O 03 VO * cn H- * (Jj WHAT * · * O bO XI > - * r- · ►- * ro • M 1 O vo Ok 1 1 O • cn cn cn

Table 2: (all data in% by weight)

AND

I— ¹

AND

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O

Table 2 - continued

- r · > - * ~ 6- » NJ N3 ₁ lu i » O O LU 1 O O CT «Ο 1 O* « « w • XJ * 4 CT CT CT w Λ LO lu S3 M * AND·* > - * NJ 1 O 1 LU LU H- * * O 09 NJ CT and X »O TO* ** LU LU w * * - * NJ * 4 1 O 03 X » 1 1 LU ui CT CT _ _u »* M · -and. O ►- * O O LU t O O NJ ** N3 > - * * CT it 1 CT X » • M * 4 CT CT CT it x * rn · H · * to* b-A nj 1 »- * Λ N3 1— · • and 1 LU it 09 CTI CT ►- * __ O Xb 3 » W * LU LU ►— w * * N3 > 4 1 O 03 1 1 o> CT CT CT > - W CT 03 > * O O AT) O O NJ to-* AND N3 •and • Xk 03 CT * 4 * 4 * CT CT CT -_ _u <o CT O ►- · * Mb Xk N3 * CT NJ 1 O ¹ LU 1 it 4 03 . O ct a w ca • • • ř \ a VO 03 4 * 1 AND it CT U7 _t . what » ►- · NJ M NJ NJ ct m > ** ► — ► O O Hive 1 O O AND 03 1 CT O « « *> 4 CT CT CT

Η (O i

Silver spoons were always rated 0 to 1, ie no or very weak fading. In addition, sets 1 to 20 have shown an excellent cleaning effect against bleachable soils such as tea.

Identical compositions, but without silver-corrosion agents A-D, also worked very well against bleachable soils, but produced yellow to purple discolorations on silver spoons (ratings 2 to 4).

Electronic measurements

Sample preparation:

For the examination, silver wire (d = 2 mm, 99.99%) was used as test material instead of silver cutlery.

Sections of approximately 10 cm in length were cut from this silver wire, and a portion of the sample immersed in the measuring solution was abraded with SiC sandpaper (600 grit). The samples were then rinsed well with double distilled water and, if appropriate. adhering residues after grinding are wiped off with a cloth, not forming castings. This procedure was optionally repeated several times, until an optically perfect impression. After grinding, the samples were used immediately for measurement to prevent the reaction of metallic silver with laboratory air. The effective surface of the sample 2 immersed in the solution was 0.70 cm.

Electrolytes and electrodes:

The experiments were performed in a Durav glass flask. The said silver wires (A = 0.70 cm) served as measuring electrodes. The counter electrode consisted of a gold plate (99.99%) with an area of 1 cm. As reference electrode was based on the alkaline electrolytic solution is selected from NaOH electrode of Hg / Hg0 / 0 microns which was connected with the electrolyte via the Haber-Luggin capillary _of _ vu. Measurements were performed with 5 g / l of detergent in 16 ° tap tap water with a salt load of approximately 600 mg (dry matter).

To prepare detergent solutions, the weakly alkaline base product (see above) was first dissolved and the solution heated to 65 ° C. Just before the measurement, a bleaching agent and a bleach activator and / or a silver corrosion protection agent were added. An electrochemical measurement was then performed. In electrochemical experiments, the electrolyte solutions were heated to 65 ° C and purged with air.

Apparatus and sensing of measured curves:

To read the current-voltage curves, the potential of the electrodes was increased from -0.62 V, relative to a standard hydrogen electrode (SHE), at a constant rate. After increasing by a total of 1.1 V, the potential was then reduced at the same rate. A standard potentiostat was used for this, consisting of a coupling amplifier, a radical amplifier, an adder and an impedance converter, as well as a function generator (Prodis 16, by Intelligent Control CLZ GmbH).

Results:

The characterization of the corrosion behavior was performed on the basis of the current-voltage curves. Substantial information comes from the passage of the current-voltage curve to zero (quiescent potential, which sets itself even without external influence of the potential) and from the slope of the zero-pass curve (reciprocal polarization resistance) E. Heitz, R. Henkhaus, A. Rahmel, Corrosion Studies in the Experiment Verlag Chemie (1983), p. 31, H. Kaesche, The Corrosion of Metal. 2nd ed., Springer Verlag (1979), pp. 117 ff. At the same time, the potential for the zero crossing is shifted to lower values by the addition of a silver corrosion protection agent and the slope is reduced. The corrosion of silver is thus considerably reduced by the addition of a silver corrosion protection agent, so that it is also electrochemically measurable.

composition position of pitch pass in detergent zero E (mV) (SHE) zero pass di / dE (mA / V) basic product (87%) 435 + 12% percarbonate + 1% TAED basic product (87%) 360 + 12% of percarbonate + 1% anti-corrosion agent for silver * basic product (86.5%) 405 + 12% percarbonate + 1% TAED + 0.5% anti-corrosion agent for silver * basic product (86%) 375 + 12% percarbonate + 1% TAED + 1% anti-corrosion agent for silver *

0.3

0.6

Anti-corrosion agent for silver: manganese sulphate monohydrate.

Claims (15)

PATENT CLAIMS Use of inorganic redox-active substances in dishwashing compositions as an anticorrosive agent for silver, characterized in that the inorganic redox-active substances are at least partially metal salts and / or metal acids selected from the group of salts and / or complexes of manganese, titanium, zirconium, hafnium, vanadium, barium and cerium and the metals are in one of the oxidation stages II, III, IV, V or VI. 2. The method according to claim 1, characterized in that the metal salt and / or metal complexes are selected from the group MnS0 _4, citrate, manganese stearate, manganese acetylacetonate, manganese, 1-hydroxyethane-l, 1-diphosphonate, manganese ⁱⁿ 2 ° 5> ⁱⁿ 2 ° 4 ' ^Ti0S0 4> K ₂ TiF ₆ , KgZrFg, CoSC> ₄ , Co (NO ₃ ) _2> Ce (NO ₃ ) ₃ · Use according to claim 2, characterized in that the metal salt is MnSO ₄ . 4. A low-alkaline dishwashing detergent composition whose 1% by weight solutions have a pH of 8 to 11.5, preferably 9 to 10.5, containing 15 to 60% by weight, preferably 30 to 50% by weight of the base. water-soluble components, 5 to 25% by weight, preferably 10 to 15% by weight, of an oxygen-based bleaching agent, 1 to 10% by weight, preferably 2 to 6% by weight of an organic bleach activator containing 0- or N- % of an acyl group having 1 to 12 carbon atoms, 0.1 to 5% by weight, preferably 0.5 to 10% by weight 2.5% by weight of the enzyme, based on all agents, and an anticorrosive agent, characterized in that the anticorrosive agent contains salts and / or metal complexes which are at least partially soluble in water. and selected from the group of salts and / or complexes of manganese, titanium, zirconium, hafnium, vanadium, cobalt and cerium, and these metals are in one of the oxidation stages II, III, IV, V or VI. Composition according to claim 4, characterized in that the metal salts and / or metal complexes are selected from the group consisting of MnSO 4, manganese citrate, manganese stearate, manganese acetylacetonate, manganese 1-hydroxyethane-1,1-diphosphonate , VgOg, V ₂ 0 _4, V0 _{2-thiosulfonic,} KgTiFg, K ₂ ZrF _g, CoS0 _4> Co (N0 _{3) 2,} Ce (N0 _{3) third} 6. A composition according to claim 4 wherein the metal salt is MnSO4. Composition according to claims 4 to 6, characterized in that it contains inorganic, redox-active substances in an amount of 0.05 to 6% by weight, preferably 0.2 to 2.5% by weight of the total composition. Composition according to claims 4 to 7, characterized in that the basic water-soluble component is a salt of citric acid, preferably sodium citrate. Composition according to claims 4 to 8, characterized in that the oxygen-based bleaching agent is a percarbonate salt, preferably sodium percarbonate. Composition according to claims 4 to 9, characterized in that the organic bleach activator containing O- or N-acyl groups of 1 to 12 carbon atoms is Ν, Ν, Ν, N--tetraacetylethylenediamine (TAED). Composition according to claims 4 to 10, characterized in that the enzyme is an amylase and / or a protease. Composition according to Claims 4 to 11, characterized in that it further contains up to 60% by weight, preferably 10 to 40% by weight, based on the total composition, of an alkali metal support system consisting essentially of a carbonate or bicarbonate, preferably a carbonate sodium and sodium bicarbonate. Composition according to claims 4 to 12, characterized in that it contains up to 5% by weight, preferably up to 2% by weight, based on the entire composition, of wetting agents, preferably low foaming nonionic surfactants. Composition according to claims 4 to 13, characterized in that it is in the form of tablets and is obtainable by mixing all of its constituents in a mixing device and compressing the mixture by means of a tablet press at compression pressures of 2.10 ⁷ Pa up to 1.5.10 ⁸ Pa. Composition according to claims 4 to 14, characterized in that it is in the form of a powder or granulate and has a bulk density of 750 g / l to 1000 g / l.