EP0808894B1 - Method for cleaning cutlery - Google Patents

Abstract

A method for cleaning utensils or dishes involves spray pre-washing, followed by the main wash and final rinsing. the novelty is that the following are separately dosed into the pre-wash solution : (i) an alkali component and (ii) a complex-former. Also claimed is a kit containing (i) and (ii).

Description

a) Vorreinigen durch Besprühen mit einer Vorreinigungslösung;

b) Hauptreinigen;

c) Nachspülen.

The present invention relates to a method for cleaning dishes, comprising the steps:

a) pre-cleaning by spraying with a pre-cleaning solution;

b) main cleaning;

c) rinsing.

The automatic cleaning of dishes is both private and commercial Area widespread. To remove dried, baked and / or food, dye, protein or starch is usually the addition of a or several detergents are required for the wash liquor. These cleaners are also said to arise of coverings (e.g. tannins or lime) due to incomplete cleaning Prevent on the dishes or remove any deposits that have already formed.

From DE-A 37 07 366 a method for machine dishwashing is known in which the dishes are pre-cleaned by spraying on a cleaning solution after a specified exposure time in a main cleaning area by the Wash liquor is washed off again. The pre-cleaner solution is made up of a ready-made Pre-cleaner made by dilution. The pre-cleaner contains an alkali component and a complexing agent for water softening.

DE-A 43 39 503 describes this procedure as disadvantageous because it is a mixture of Alkaline component and complexing agent is difficult to wash off the dishes and because of that Complexing agents as water softeners only become fully effective in the main cleaning area unfold. This prior art therefore teaches that the pre-cleaner solution to be sprayed on should not contain any complexing agents, but only an alkali component. The complexing agent is added separately to the wash liquor and not to the dishes sprayed on.

The present invention has for its object to provide a method for cleaning To create dishes of the type mentioned, which has a good cleaning effect economical use of cleaning agents, especially the expensive complexing agent, having.

• wenigstens eine Alkalikomponente,
• wenigstens ein Komplexbildner.

The invention solves this problem in that the following components are metered into the pre-cleaner solution separately:

• at least one alkali component,
• at least one complexing agent.

Some terms used in the context of the invention are explained below.

The term "pre-cleaner solution" actually means spraying on the dishes brought into contact solution, which by diluting the components or Components of the pre-cleaner is obtained with water. With these components or Components of the pre-cleaner will usually be concentrates.

The term "pre-cleaning" denotes a process preceding the main cleaning, which does not necessarily have to be the first process step. Within the scope of the invention can also further pre-cleaning steps, which are not defined in claim 1, be upstream. For example, a first pre-cleaning step (pre-rinsing) be provided for removing coarse impurities.

The term “spraying” or “spraying” means bringing the pre-cleaning solution into contact with the dishes in such a way that they are at least largely from the pre-cleaner solution is wetted. It is preferably a finely divided spraying.

The term "separate metering into the pre-cleaner solution" means that the pre-cleaner solution from at least the two components alkali component and complexing agent is produced by mixing. It is preferably diluted with water. This Mixing is preferably done immediately before spraying onto the dishes. The separate metering can be done by metered addition of the components into a premix tank happen, the pre-mix tank then feeds the spray nozzle or the spray nozzles. However, the pre-cleaner components can also be used directly with a metering pump dose into the water jet that feeds the spray nozzles. After all, it is still possible that the different components of the pre-cleaner solution can be sprayed from separate spray nozzles and are only immediately in situ combine on the dishes to form the pre-cleaning solution.

The term "main cleaning" refers to one that follows pre-cleaning Process in which the dishes are showered and / or washed around by a washing liquor. Only the sprayed on in the pre-cleaning step can be used as a cleaner in this wash liquor Pre-cleaner solution, which is diluted accordingly by the wash liquor, use Find. However, other detergents can also be added to the wash liquor, the usual ingredients such as surfactants, enzymes, disinfectants, and conventional additives and auxiliaries such as, for example, solubilizers, defoamers, fragrances, Contain dyes, thickeners, preservatives and hardness dispersants. In this context it should be noted that the list of components the precleaner solution in claim 1 is not conclusive, the substances mentioned or Auxiliaries can also be contained in components of the pre-cleaner or Pre-cleaner solution can be added.

The term "rinsing" includes all of the main cleaning according to the invention subsequent cleaning and / or rinsing steps. It is within the scope of the invention conceivable that another main cleaning step with a main cleaning other cleaner connects. As a rule, however, in step 1) main rinsing immediately rinse (usually with a normal Rinse aid) if necessary, follow (further) rinsing with water. All of these variations are included in the term "rinse" used in claim 1.

An alkali component is an alkaline reaction in aqueous solution Material. Preferred alkali components are alkali metal hydroxides, especially sodium and / or potassium hydroxide. Everyone is a complexing agent in the sense of the invention Substance that makes up the hardness of water metal ions (especially alkaline earth metal ions) can keep in solution by complex formation.

The invention is based on the surprising finding that the individual needs Dosing of alkali component on the one hand and complexing agent on the other hand in the to be sprayed on a pre-cleaning solution compared to the process of DE-A 43 39 503 improved cleaning effect with economical consumption of Cleaner (especially complexing agent) enables. The invention has recognized that in In contrast to the technical teaching of the font mentioned, the complexing agents do their full Efficacy does not only develop in the wash cycle, but surprisingly as a component the sprayed pre-cleaner solution significantly improve the cleaning effect. The reason for this cleaning-supporting effect of the complexing agent is not conclusive clarified, however, the inventors suspect that the complexing agent has the network effect the pre-cleaner solution improved, so that the penetration of the alkali component in the dirt and thus the swelling and the subsequent Removing the contaminants is improved. This applies in particular to nitrogen-containing complexing agents.

It has been shown that the difficult rinsability complained of in DE-A 43 39 503 is disadvantageous the pre-cleaner solution while spraying on the alkali component and Complexing agent does not occur when both components according to the invention the actual If necessary, be dosed separately. As a rule, you will be the metered Amount of alkali component depends on the degree of soiling of the dishes make, while the complexing agent is usually dependent on the hardness of the used Water is metered.

The alkali component preferably contains 5-50%, more preferably 10-40% total alkalinity calculated as NaOH. Unless otherwise, all percentages are indicated, percentages by weight. The total alkalinity is calculated in each case as NaOH. For example, if the alkalinity is added as potassium hydroxide, it must Weight fraction based on the molecular weight ratios of NaOH and KOH in weight fraction NaOH can be converted. Potassium hydroxide is preferred as the alkali component, since it has been shown that potassium salt cleaners compared to sodium salt cleaners Cleaners have an improved cleaning effect and are easier to rinse out are. There is no plausible explanation for this empirical finding. So far the rest The use of potassium salts is added to detergent ingredients as alkali metal salts preferred for the same reason. However, it should be noted that in the context of the Invention the use of, for example, sodium salts is readily possible.

The alkali component is particularly preferably a relatively high-dose aqueous Solution with a total alkalinity in the range 30-50%. With heavily soiled dishes can be a pre-cleaner solution with a relatively high proportion of alkali spray on the dishes.

Chelating agents are preferably used as complexing agents. For the purposes of the invention, all substances which can form chelate coordination compounds with metals (in particular alkaline earth metals such as calcium and magnesium) are. The use of at least four-toothed ligants is preferred, further preferred are six-toothed ligands as chelating agents. Well-suited chelating agents are:
NTA; EDTA; Gluconic acid; Phosphonic acids; N- (2-hydroxyethyl) iminodiacetic acid; 1,2,3,4-cyclopentanetetracarboxylic acid; Citric acid; Malic acid; Tartaric acid, lactic acid; O-carboxymethyl tartronic acid; O-carboxymethyloxy succinic acid; Salts of the aforesaid substances.

As already mentioned, the list of components made in claim 1 is the final cleaning solution. In the context of the invention can in the pre-cleaner solution furthermore, for example, a surfactant component and / or an oxidation component be dosed. The term "surfactant component" means any substances containing surfactants. Surfactants in the sense of the invention are all substances that affect the interfacial tension can lower an aqueous solution. They are anionic, cationic, non-ionic and amphoteric surfactants can be used. Suitable surfactants are in Römpps Chemielexikon, 9th edition, vol. 6, pp. 4495 ff, under the keyword "Tenside" and in Ullmanns Encyclopedia of Industrial Chemistry, 5th ed., Vol. 8, p.315 ff, under the keyword "Detergents" listed. Nonionic or amphoteric surfactants can preferably be used, for example surfactants from the class of fatty alkoxylates and N-alkylaminocarboxylates. In this context, the disodium salt or is an example Dipotassium salt of capryliminodipropionic acid called. The surfactant additive sets the surface tension of the pre-cleaner solution and improves and speeds up cleaning through faster infiltration and removal of dirt deposits as well by emulsification in the wash liquor during subsequent main cleaning. The surfactant additive can, in particular, clean rough surfaces (e.g. used Plastic dishes) improve the penetrability of the pre-cleaner solution is improved in the roughened plastic surface.

An oxidation component in the sense of the invention is any component that at least has an oxidizing effect on parts of the dirty dishes. Be exemplary in this connection active chlorine-containing compounds such as Chlorite, hypochlorite and compounds containing active oxygen, such as hydrogen peroxide solutions, Peracids or their salts called.

If necessary, the alkali component and / or the complexing agent can also be others Components included. Examples include phosphonic acids or their salts, which can be part of the alkali component, for example, and accordingly the preparation of the pre-cleaner solution can be metered in together with this. Usable Examples of phosphonic acids are phosphonobutane tricarboxylic acid; Aminotrismethylenephosphonic acid, their homologues based on ethylenediamine, diethylenetriamine or hexamethylenediamine; Hydroxyethane diphosphonic acid. The is preferred Use of phosphonobutane tricarboxylic acid or its potassium salt.

The total alkalinity of the sprayed pre-cleaner solution is 0.5-3%. The share of Complexing agent in the sprayed-on pre-cleaner solution is preferably 0.05-5%, more preferably 0.05-3%, more preferably 0.1-2%.

As a rule, the addition of a separate main cleaner is not used for main cleaning may be necessary because the pre-cleaner components rinsed off the dishes during the main cleaning dissolve in the wash liquor and have a sufficient cleaning effect unfold. The complexing agent separately metered in according to the invention provides during of main cleaning to ensure that any remaining hardness in the wash liquor is complexed and does not form unwanted deposits or deposits. Within the scope of the invention however, alternatively, the addition of a separate main cleaner during the main cleaner step possible.

The invention is explained below using an exemplary embodiment.

The components alkali component and complexing agent for dosing into the pre-cleaner solution were produced according to the following recipe:
40 parts by weight of NaOH and 1.5 parts by weight of phosphonobutane tricarboxylic acid sodium salt were dissolved in 58.5 parts by weight of water.

40 parts by weight of nitrilotriacetic acid sodium salt are used to produce the complexing agent component dissolved in 60 parts by weight of water.

To carry out the cleaning process, a conveyor belt dishwasher with three Stierlen-BTM type 5000 tanks were used. The machine was softened Hamburg city water (residual hardness <1 ° dH) fed. The amount of water in the machine was 300 l, the amount of rinse water was 600 l / h. Before the first cleaning tank was out installed a spray system for spraying the pre-cleaner solution with a throughput 20 l / h was operated.

The dwell times of the dishes in the pre-wash or in front of the spray system The pre-clearing area was 10 s, in the spray area 5 s, in the subsequent main cleaning area 1 - 1.5 min. The temperatures in the pre-clearing area were 45 up to 50 ° C, in the two main cleaning tanks 50 to 55 (first tank) or 55 to 60 ° C (second tank), the temperature in the rinse tank was 75 - 85 ° C.

The fill water quantity of 300 I filled in before starting up the machine was included 96 g of complexing agent component (0.23 g / l) and 450 g of alkali component (1.5 g / l) were added.

In order to maintain this alkali and complexing agent concentration during the operation of the dishwasher in the fill water at a rinse water volume of 600 l / h, had to use the spray system 192 g of complexing agent component per hour and 900 g Alkali components are metered in per hour. The corresponding amounts of alkali and Complexing components were added separately to the pre-spray water, the concentrations in the pre-spray solution (with a pre-spray water volume of 20 l / h) accordingly 9.6 g of complexing agent component and 45 g of alkali component per liter Pre-spray solution.

A test soil from tea tannins on coffee or tea dishes could be used with the specified parameters are completely removed.

Comparative example

Under otherwise the same conditions as in the example according to the invention, the Complexing component dosed directly into the first main cleaning tank and not, as provided according to the invention, in the pre-cleaner solution. This procedure corresponds the technical teaching of the prior art according to DE-A-43 39 503. To achieve the same cleaning effect (complete removal of the test stain from tea tannins) was an increase in the supply of alkali component via the pre-spray solution to a total of 1,080 g / h required. The consumption of alkali components was thus 20% higher, the concentration of the alkali component in the wash liquor had to be increased from 1.5 g / l to 1.8 g / l.

Claims (10)

1. A method of cleaning dishes with the steps of:

   a) precleaning by spraying with a precleaner solution,

   b) main cleaning,

   c) rinsing,

   characterised in that the following components are metered separately into the precleaner solution:

   at least one alkali component,

   at least one complexing agent.
2. A method according to Claim 1, characterised in that the alkali component contains 5 - 50 % by weight, preferably 10 - 40 % by weight, of total alkalinity calculated as NaOH.
3. A method according to Claim 1 or 2, characterised in that the complexing agent is metered in a quantity dependent upon the hardness of the water used.
4. A method according to any one of Claims 1 to 3, characterised in that a chelating agent is used as complexing agent.
5. A method according to Claim 4, characterised in that the chelating agent is chosen from the group comprising:
   NTA; EDTA; gluconic acid; phosphonic acids; N-(2-hydroxyethyl)imino diacetic acid; 1,2,3,4-cyclopentane tetracarboxylic acid; citric acid; malic acid; tartaric acid; lactic acid; O-carboxymethyl tartronic acid; O-carboxymethyloxy succinic acid; salts of aforementioned substances.
6. A method according to any one of Claims 1 to 5, characterised in that additionally at least one of the following components is metered into the precleaner solution:

   a surfactant component,

   an oxidation component.
7. A method according to Claim 6, characterised in that the oxidation component contains at least one compound containing active chlorine.
8. A method according to Claim 6, characterised in that the oxidation component contains at least one compound containing active oxygen.
9. A method according to any one of Claims 1 to 8, characterised in that the total alkalinity of the sprayed on precleaner solution amounts to 0.1 - 5 % by weight, preferably 0.2 - 4 % by weight, more preferably 0.5 - 3 % by weight.
10. A method according to any one of Claims 1 to 9, characterised in that the proportion of the complexing agent or agents in the sprayed-on precleaner solution amounts to 0.05 - 5 % by weight, preferably 0.05 - 3 % by weight, more preferably 0.1 - 2 % by weight.