WO1996037596A1

WO1996037596A1 - Diswasher detergent with agents providing protection against the corrosion of silver

Info

Publication number: WO1996037596A1
Application number: PCT/EP1996/002045
Authority: WO
Inventors: Jürgen Härer; Helmut Blum; Thomas Holderbaum; Peter Jeschke; Christian Nitsch
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1995-05-22
Filing date: 1996-05-13
Publication date: 1996-11-28
Also published as: DE19518693A1

Abstract

The invention relates to dishwasher detergents containing cystin and isocyanic acid as protective agents against silver corrosion.

Description

"Automatic dishwashing detergent with silver corrosion inhibitor"

The present invention relates to agents for machine cleaning of dishes which contain cystine as a silver corrosion inhibitor. A combination of cystine and isocyanuric acid, which has a synergistic effect with regard to the silver corrosion protection effect, is preferably included.

It is a well known fact that silver "tarnishes" even when it is not in use. It is only a matter of time before it gets dark, brownish, bluish to bluish-black spots or becomes discolored overall and thus "tarnished" in common usage. Problems also frequently arise in the form of tarnishing and discoloration of the silver surfaces when machine cleaning table silver. Silver can react here to sulfur-containing substances that are dissolved or dispersed in the rinsing water, because when cleaning dishes in household dishwashers (HGSM), food residues and thus u. a. mustard, peas, egg and other sulfur-containing compounds such as mercaptoa inoic acid are also added to the washing liquor. The much higher temperatures during machine rinsing and the longer contact times with the sulfur-containing food residues also favor the tarnishing of silver compared to manual rinsing. As a result of the intensive cleaning process in the dishwasher, the silver surface is also completely degreased and therefore more sensitive to chemical influences.

When using active chlorine-containing cleaners, tarnishing can largely be prevented by sulfur-containing compounds, since these compounds are presumably converted into sulfones or sulfates in secondary reactions by oxidation of the sulfidic functions.

However, the problem of tarnishing silver has become an issue again, as an alternative to the active chlorine compounds peroxygen compounds, such as For example, sodium perborate or sodium percarbonate were used, which serve to remove bleachable stains, such as, for example, tea stains / tea deposits, coffee residues, dyes from vegetables, lipstick residues and the like.

The silver surfaces are generally more sensitive to the changed recipe parameters of the new generation of active chlorine-free cleaners with lowered pH values and activated oxygen bleaching. The problem of tarnishing silver surfaces in the field of automatic dishwashing has therefore increased particularly with the introduction of dishwasher detergents containing active oxygen instead of active chlorine.

Avoiding silver corrosion, i.e. The formation of sulfidic, oxidic or chloride deposits on silver is the subject of numerous publications. The corrosion of silver is prevented in these descriptions primarily by so-called silver corrosion protection agents (or simple silver protection agents).

From the British patent specification GB 1 131 738, alkaline dishwashing detergents are known which contain benzotriazoles as a corrosion inhibitor for silver. In US Pat. No. 3,549,539, strongly alkaline, machine-applicable dishwashing detergents are described, which, among other things, are used as oxidizing agents. May contain perborate with an organic bleach activator. As a preventive agent, additives are used also recommended by benzotriazole and iron (III) chloride. European patent specifications EP 135226 and EP 135 227 describe weakly alkaline machine dishwashing detergents containing peroxy compounds and activators, which, among other things, act as silver protection agents. May contain benzotriazoles and fatty acids.

The international applications PCT / EP94 / 01386 and PCT / EP94 / 01387 disclose the use of inorganic or organic redox compounds as silver corrosion inhibitors in machine dishwashing detergents. The international application W094 / 19445 describes the use of certain manganese (III) and manganese (IV) complexes as silver corrosion protection agents in automatic dishwashing detergents.

Patent application EP-A-634478 discloses the use of isocyanuric acid as a silver corrosion inhibitor in machine dishwashing detergents. International application WO94 / 07981 also discloses the use of cysteine and isocyanuric acid as silver protection agents.

However, since the silver protection agents known from the prior art do not always meet the high requirements for good silver protection agents, there is a need for new, improved silver protection agents or synergistic combinations of silver protection agents which are suitable for use in automatic dishwashers.

The present invention relates to an agent for machine cleaning of dishes, containing 15 to 60% by weight, preferably 30 to 50% by weight of a builder component, 5 to 25% by weight, preferably 10 to 15% by weight of one Oxygen-based bleaching agents, in each case based on the total agent, and silver corrosion protection agents, cystine being present as the silver corrosion protection agent.

Cystine is preferably present in an amount of 0.005 to 3% by weight, particularly preferably 0.05 to 1% by weight and in particular 0.1 to 0.5% by weight, based on the total agent. Isocyanuric acid, which is then used in amounts of 0.01 to 5% by weight, preferably 0.1 to 2% by weight and in particular 0.3 to 1% by weight, is suitable as an additional silver protection agent which synergistically reinforces the silver protection effect. %, based on the total automatic dishwashing detergent, is included. The weight ratio of cystine to isocyanuric acid is preferably between 1:10 and 2: 1, particularly preferably between 1:10 and 1: 2, and in particular between 1: 8 and 1: 3.

Cystine and isocyanuric acid interact synergistically with regard to the silver corrosion protection effect.

Corresponding comparative examples are described in the example part. Surprisingly, it has been found that the silver protective action of cystine exceeds that of cysteine. In addition, the silver corrosion protection effect of a combination of cystine and isocyanuric acid is also significantly better than that of a combination of cysteine and isocyanuric acid.

The silver corrosion-preventing effect according to the invention can be observed within a wide range of formulations for automatic dishwashing detergents, e.g. in the presence of builder systems consisting predominantly of citrate, or those based on citrate and polycarboxylate, or also in the presence of phosphate builders. The alkali carrier system can also be varied widely, e.g. Soda / bicarbonate, disilicate or soda / disilicate.

The dishwashing detergents according to the invention are not exclusively, but preferably lower alkali dishwashing detergents of the newer generation. The problem of silver corrosion is particularly evident in these. Low-alkaline agents in the sense of the invention are agents whose 5% by weight aqueous solution has a pH of 8.0 to 11.5, preferably 9.0 to 10.5, at 20 ° C.

In principle, all builders usually used in machine dishwashing detergents are possible as builder components, especially water-soluble builder components, e.g. B. polymeric alkali metal phosphates, which may be in the form of their alkaline neutral or acidic sodium or potassium salts. Examples include: tetrasodium diphosphate, disodium dihydrogen diphosphate, pentasodium triphosphate, so-called sodium hexametaphosphate and the corresponding potassium salts or mixtures of sodium hexametaphosphate and the corresponding potassium salts or mixtures of sodium and potassium salts. The amounts of phosphate are in the range of up to about 60% by weight, based on the total agent; for ecological reasons, however, the agents according to the invention are preferably free of such phosphates. Other possible builder components are e.g. B. organic polymers of native or synthetic origin, especially polycarboxylates, which act in particular in hard water systems as co-builders. For example, polyacrylic acids and copolymers of maleic anhydride and acrylic acid and the sodium salts of these poly- mer acids. Commercial products include Sokal, n ( ^R ) CP 5 and PA 30 from BASF, Alcosperse ( ^R ) 175 or 177 from Alco, LMW ( ^R ) 45 N and SP02 N from Norsohaas. The native polymers include, for example, oxidized starch (e.g. German patent application P 4228786.3) and polyamino acids such as polyglutamic acid or polyaspartic acid, e.g. B. from the companies Cygnus and SRCHEM.

Crystalline layered silicates such as the product sold by Hoechst AG under the trade name Na-SKS-6 are suitable. Other possible builder components are naturally occurring hydroxycarboxylic acids such as. B. mono-, dihydroxysuccinic acid, α-hydroxypropionic acid and gluconic acid.

Preferred builder components are the salts of citric acid, in particular sodium citrate. Anhydrous trisodium citrate or preferably trisodium citrate dihydrate are suitable as sodium citrate. Trisodium citrate dihydrate can be used as a fine or coarse crystalline powder. Depending on the pH ultimately set in the agents according to the invention, the acids corresponding to citrate can also be present.

Sodium perborate mono- and tetrahydrate or sodium percarbonate are primarily considered as oxygen-based bleaches. The use of sodium percarbonate has advantages because it has a particularly favorable effect on the corrosion behavior on glasses. The oxygen-based bleach is therefore preferably a percarbonate salt, in particular sodium percarbonate. So-called bleach activators are often used in amounts of up to 10% by weight, preferably 1 to 6% by weight, to activate the bleaching agents in the dishwasher. Organic bleach activators are e.g. PAG (pentaacetylglucose), DADHT (1,5-diacetyl-2,4-dioxo-hexahydro-l, 3,5-triazine) and ISA (isatoic anhydride), but preferably N, N, N ', N'-tetraacetylethylenediamine (TAED ). In addition, the addition of small amounts of known bleach stabilizers such as, for example, phosphonates, borates or metaborates and metasilicates as well as magnesium salts such as magnesium sulfate can also be useful.

To better remove protein, fat or starch-containing food residues, the dishwashing detergents according to the invention contain enzymes, Amylases, lipases and cellulases, for example proteases such as BLAP ( ^R ) 140 from Henkel; Optimase ( ^R ) -M-440, Optimase ( ^R ) -M-330, Opticlean ( ^R ) -M-375, Opticlean ( ^R ) -M-250 from Solvay Enzymes; Maxacal ( ^R ) CX 450,000, Maxapem ( ^R ) from Ibis; Savinase ( ^R ) 4.0 T, 6.0 T, 8.0 T from Novo; Esperase () T from Ibis and amylases such as Termamyl ( ^R ) 60 T, 90 T from Novo; Amylase-LT ( ^R ) from Solvay Enzymes or Maxamyl ( ^R ) P 5000, CXT 5000 or CXT 2900 from Ibis; Lipases such as Lipolase ( ^R ) 30 T from Novo; Cellulases such as Celluzym ( ^R ) 0.7 T from Novo Nordisk, or cutinases. The dishwashing agents preferably contain proteases and / or amylases.

The agents according to the invention preferably additionally contain the alkali carriers contained in conventional machine dishwashing agents, such as. B. alkali silicates, alkali carbonates and / or alkali hydrogen carbonates. The alkali carriers commonly used include carbonates, hydrogen carbonates and alkali silicates with a molar ratio SiO 2 / M2O (M = alkali atom) of 1.5: 1 to 2.5: 1. Alkali silicates can be used in amounts of up to 30% by weight. , based on the total agent. The use of the highly alkaline metasilicates as alkali carriers is preferably avoided. The alkali carrier system preferably used in the agents according to the invention is a mixture of essentially carbonate and hydrogen carbonate, preferably sodium carbonate and hydrogen carbonate, in an amount of up to 50% by weight, preferably 10 to 40% by weight, based on the total Means, is included. Depending on which pH value is ultimately desired or set, the ratio of carbonate and bicarbonate used varies; Usually, however, an excess of sodium hydrogen carbonate is used, so that the weight ratio between hydrogen carbonate and carbonate is generally 1: 1 to 15: 1.

If appropriate, surfactants, in particular weakly foaming nonionic surfactants, can also be added to the agents according to the invention, which improve the detachment of fatty food residues, as wetting agents to improve the rinse aid effect, as granulating aids or as dispersing aids for better, homogeneous distribution of the aforementioned silver corrosion inhibitors in the washing liquor and on the silver top serve areas. Their amount is then preferably up to 15% by weight, in particular 1 to 8% by weight, particularly preferably 2 to 8% by weight. Extremely low-foam connections are usually used. These preferably include Ci2-Ci8-alkylpolyethylene glycol polypropylene glycol ethers, each with up to 8 moles of ethylene oxide and propylene oxide units in the molecule. But you can also use other, known as low-foam nonionic surfactants, such as. B. Ci2-Ci8-alkylpolyethylene glycol-polybutylene glycol ether, each with up to 8 moles of ethylene oxide and butylene oxide units in the molecule, end-capped alkylpolyalkylene glycol mixed ethers and the foaming but ecologically attractive C8-Ci4-alkylpolyglucosides with a degree of polymerization of about 1 - 4 (e.g. APG ( ^R ) 225 and APG ( ^R ) 600 from Henkel) and / or Ci2-Ci4-alkyl polyethylene glycols with 3 - 8 ethylene oxide units in the molecule. A bleached quality should be used, since otherwise brown granules are formed. Also suitable are surfactants from the family of glucamides, such as, for example, alkyl-N-methyl-glucamides (alkyl = fatty alcohol with the C chain length C6-C14). It is partially advantageous if the surfactants described are used as mixtures, for. B. the combination of alkyl polyglycoside with fatty alcohol ethoxylates or glucamides with alkyl polyglycosides etc.

If the cleaning agents foam too much during use, they can still contain up to 6% by weight, preferably about 0.5 to 4% by weight, of a foam-suppressing compound, preferably from the group of silicone oils, mixtures of silicone oil and hydrophobized silica, Paraffin oil / Guerbet alcohols, paraffins, hydrophobized silica, the bisstearic acid amides and other other known commercially available defoamers can be added. Other optional additives are e.g. B. Perfume oils.

Of course, the cleaning agents according to the invention can optionally contain, in addition to cystine or in addition to cystine and isocyanuric acid, further silver corrosion protection agents of the prior art described above.

The dishwashing detergents according to the invention are preferably in the form of powder, granular or tablet-like preparations which are in themselves can be produced in a customary manner, for example by mixing, granulating, roller compacting and / or by spray drying.

To produce cleaning agents according to the invention in tablet form, the procedure is preferably such that all constituents are mixed with one another in a mixer and the mixture is used by means of conventional tablet presses, for example eccentric presses or rotary presses, with pressures in the range from 200 ^• 10-5 Pa to 1 500 • 10 * 5 Pa pressed. In this way, unbreakable tablets are obtained which, under application conditions, dissolve sufficiently quickly and have a flexural strength of normally more than 150 N. A tablet produced in this way preferably has a weight of 15 g to 40 g, in particular 20 g to 30 g, with a diameter from 35 m to 40 mm.

The manufacture of machine dishwashing detergents in the form of non-dusting, storage-stable, free-flowing powders and / or granules with high bulk densities in the range from 750 to 1000 g / l is characterized in that in a first process stage, the builder components are at least partially liquid Mixing components are mixed while increasing the bulk density of this premix and subsequently - if desired after an intermediate drying - the further components of the dishwasher detergent, including the silver protection agents, are combined with the premix obtained in this way.

The agents to be used can be used both in household dishwashers and in commercial dishwashers. They are added by hand or using suitable dosing devices. The application concentrations in the cleaning liquor are about 2 to 8 g / 1, preferably 2 to 5 g / 1.

The rinse program is generally supplemented and ended with a few intermediate rinse cycles with clear water and a rinse cycle with a common rinse aid following the cleaning cycle. After drying, not only are completely clean dishes which are impeccable from a hygienic point of view, but above all also bright silver silver cutlery. Examples

Silver spoons (type WMF, hotel cutlery, form Berlin) were cleaned with a silver cleaner, degreased with petrol and dried. A dishwashing detergent solution was then prepared from 500 g of water at 35 ° C. with a hardness of 16 ° d and 2.5 g of a cleaner (for the respective composition, see the tables below). Silver corrosion inhibitors were then added (compositions 5-8: cystine; compositions 9-12: isocyanuric acid; compositions 13-25: cystine + isocyanuric acid. Compositions 1-4 contain no silver corrosion inhibitor). Then the silver spoons were immersed and the solution heated to 65 ° C. The final temperature of 65 ° C was reached after about 20 minutes; the silver spoons were then left in the solution for a further 10 minutes, then removed, rinsed with water and assessed visually. The tarnishing colors in the range 0 to 5 were evaluated:

(0 = no change, 1 = completely matted (hardly discolored) surface, 2 = partially (stain-like) (black) staining, 3 = moderate full-coverage discoloration, 4 = all-over dark / violet staining, 5 ^{** • *} black staining (even to striped) The results are shown in the tables.

The amounts in the tables are% by weight.

Raw materials used:

Plurafac LF 403: fatty alcohol alkoxylate from BASF Sokalan CP 5: polycarboxylate from BASF

I. Non-inventive dishwasher detergent

I.l. Without silver corrosion inhibitor

Table 1

Raw materials 1 2 3 4

Trisodium citrate di 45.0 45.0 45.0 45.0 hydrate

Na bicarbonate 33.0 31.0 33.0 29.0

Soda 5.0 5.0 5.0 5.0

Plurafac LF 403 3.0 3.0 5.0 5.0

A ylase 1.0 1.0 1.0 1.0

Protease 1.0 1.0 1.0 1.0

Na percarbonate 12.0 12.0 - -

Na Perborate - - 10.0 10.0

TAED - 2.0 - 4.0

pH 5% solution 9.4 9.4 9.4 9.3

Protection effect: 3.0 4.0 3.0 4.0 Note II. Machine dishwashing detergents according to the invention

II.1. Cystine as a silver anti-corrosion agent

Table 2

Raw materials 5 6 7 8

Trisodium citrate- 45.0 45.0 45.0 45.0 dihydrate

Na hydrogen carbonate 30.9 30.5 30.0 29.0

Soda 5.0 5.0 5.0 5.0

Plurafac LF 403 3.0 3.0 3.0 3.0

Am lase 1.0 1.0 1.0 1.0

Protease 1.0 1.0 1.0 1.0

Na percarbonate 10.0 10.0 10.0 10.0

TAED 4.0 4.0 4.0 4.0

Cystine 0.1 0.5 1.0 2.0

pH 5% solution 9.5 9.5 9.3 9.3

Protection effect 3.0 3.0 1.0 0 Note: II. 2. Cystine + isocyanuric acid as silver corrosion inhibitor

Table 3

Continuation of table 3

Claims

Patent claims

1. Agent for machine cleaning of dishes, containing 15 to 60 wt .-%, preferably 30 to 50 wt .-% of a builder component, 5 to 25 wt .-%, preferably 10 to 15 wt .-% of a bleaching agent on Sau¬ Erstoff basis, each based on the total agent, and Silberkor¬ corrosion protection agent, characterized in that cystine is contained as Silberkorrosi¬ onsschutzmittel.

2. Composition according to claim 1, characterized in that cystine in an amount of 0.005 to 3 wt .-%, preferably 0.05 to 1 wt .-%, and in particular 0.1 to 0.5 wt .-%, based on the total composition.

3. Composition according to claim 1 and 2, characterized in that isocyanuric acid in an amount of 0.01 to 5% by weight, preferably 0.1 to 2% by weight and in particular 0.3 to 1, as additional silver protective agent % By weight, based on the total agent, is contained.

4. Composition according to claim 3, characterized in that the ratio by weight of cystine to isocyanuric acid is between 1:10 and 2: 1, preferably between 1:10 and 1: 2, and in particular between 1: 8 and 1: 3 lies.

5. Composition according to claim 1 to 4, characterized in that its 5 wt .-% aqueous solution at 20 ° C has a pH of 8.0 to 11.5, preferably 9.0 to 10.5.

6. Composition according to claim 1 to 5, characterized in that the builder component is a salt of citric acid, preferably sodium citrate. Agent according to Claims 1 to 6, characterized in that the bleaching agent based on oxygen is a percarbonate salt, preferably sodium percarbonate.