Denture cleansing tablet

The invention relates to a cleaning tablet for automatic cleaning of dentures in aqueous solution according to the preamble of the main claim.

Cleaning tablets for dentures, such as z. B. are described in DE-OS 21 33 710, are used in such a way that they are placed in water with the denture to be cleaned at the same time, whereupon the cleaning tablet then disintegrates with more or less strong gas evolution and releases active ingredients which the attack and remove dirt deposits adhering to the denture.

Such cleaning tablets, as they are also the subject of DE-PSn 23 12 847, 25 48 469, 26 58 450, and 27 41 072, in EP-PSn 0 010 412, 0 028 005 and 0 102 418 and the EP OS 0 133 354, 0 149 308, 0 157 464 and 0 225 658 essentially contain oxygen-releasing substances for oxidizing and disinfecting (such as monopersulfates and / or perborates), inorganic softeners and limescale binders (such as phosphates and / or polyphosphates, chelating agents, like EDTA, gas-generating carriers, such as carbonates and / or bicarbonates, citric acid, tartaric acid, amidosulfonic acid or its salts, disinfectants, such as benzoates and / or alkylbenzoates, as well as lubricants, binders and / or disintegrants, surfactants, coloring additives and finally flavoring agent (s). The pH values ​​when dissolved in water fluctuate, depending on the composition, between acidic, neutral and alkaline. In most cases, these are quick-cleaning tablets, ie those with a cleaning time of 10 to 15 minutes; in some cases, however, they are slow-acting tablets with relatively long application times, in which the full cleaning effect with regard to the denture treated therein is only achieved in about 1 to 2 hours.

All of the tablets described above have a disadvantage with regard to the cleaning of dentures, which is typical for the composition and the practical application: the formation of the perborate oxygen in the desired active form via the ion HOO- takes place satisfactorily only at temperatures above 60 ° C. Usually, dentures are cleaned by the user at about 30 to 40 ° C in 10 to 15 minutes, so that with the known cleaning tablets a large part of the intended oxidizing and disinfecting effect of the oxygen-releasing substances does not come into play.

A cleaning tablet of the generic type is known from EP-OS 0 253 772, in which a phosphate combination is provided as the phosphorus compound, as such it supports the cleaning process or participates in it, while polymeric fluorocarbon is used as a binder. A problem with the use of such a hydrophobic fluorocarbon is that when the cleaning tablet is dissolved, because of its hydrophobic nature, it not only makes it difficult to dissolve as such, but also floats in the dissolved cleaning liquor in a manner that separates the reactants and thus delays cleaning. The use of such a polymeric, hydrophobic binder also makes it understandable why a high activator content of 5 to 15% by weight is used in the cleaning tablet according to EP-OS 0 253 772, this proportion at the expense of the content of substances which are actually effective for cleaning goes. In addition, as already mentioned, inorganic phosphates are used in the known cleaning tablet, which, like the EDTA used, are also effective as metal binders, but are not considered to be harmless because of the possible environmental influences.

EP-A-0 323 049 discloses a denture cleaning tablet which contains sodium hydrogen carbonate, citric acid, perborate and persulfate, perborate / peroxide activator in an amount of 0.5 to 5% by weight and optionally surfactants, lubricants, preservatives, flavorings and complexing agents, wherein the complexing agents can be selected from phosphates, aminopolycarboxylates or 0.1-1% by weight of phosphonic acids or their salts. All denture cleaners described in the examples of the publication contain phosphates and / or aminocarboxylates.

In contrast, the object of the invention is to provide a generic cleaning tablet which, without reducing the stability and effectiveness, contains no environmentally harmful phosphates and / or aminopolycarboxylates.

According to the invention, this object is achieved by the features listed in the characterizing part of the main claim. Particularly preferred embodiments of the invention are the subject of the dependent claims.

The invention is based on the surprising finding that it is possible to overcome the problems of the known cleaning tablets described at the outset by using an organic phosphonic acid as metal binder and for stabilizing the peroxide - and without a hydrophobic polymeric binder. This also provides a hydrolysis-stable complexing agent z. B. for alkali metals and heavy metals and also replaces the phosphates / polyphosphates and EDTA, which are problematic from an environmental point of view, and which represent the inorganic complexing agents in the previously known cleaning agents for dentures. When the cleaning tablet is dissolved, the peroxide is not hindered by an inert polymer, but is stabilized in the cleaning tablet by a substance which, in the cleaning process after dissolving, has the effect of keeping the activator effect, inherent in the water, free of negative influences inherent in the system . According to the invention, an activator content of only 0.5 to 3.0% by weight is therefore sufficient, as a result of which the proportion of actually active substances in the cleaning tablet can be increased further. This is also achieved in that in the cleaning tablet according to the invention, because of the high effectiveness of the activator, five to ten parts of polyphosphates, as are common in the cleaning tablets according to the prior art, can be replaced by only one part of phosphonates.

The full effectiveness of the peroxide and activator in the cleaning liquor, without floating "foreign material" in the form of z. B. hydrophobic polymer ensures that over the entire cleaning period of z. B. 15 minutes despite the slowly falling temperature of the cleaning liquor in a water glass or the like. the full effectiveness of the peroxides is obtained, as is the subject of a preferred embodiment of the invention, used as (an) activator tetraacetylethylenediamine (TAED), so the release of active oxygen in the form desired for the cleaning and antimicrobial effect can be achieved via the formation the highly effective peracetic acid significantly strengthen and stabilize.

The hydrolysis-stable organic phosphonic acids or their salts used according to the invention have an increased lime, metal and in particular iron-binding effect and at the same time have a dispersing / deflocculating effect. The provision of the cleaning tablet, preferably provided according to the invention, with a dye system of the type claimed gives the possibility of optically following the cleaning process until the end of the main cleaning and also of the entire cleaning. In the course of the cleaning process in this embodiment there follows a quantitative weakening of the color intensity, followed by a qualitative color change before decolourization occurs.

It is characteristic of the cleaning tablet according to the invention that it contains no environmentally harmful inorganic phosphates, polyphosphates and organic complexing agents based on aminocarboxylic acids (eg EDTA). The cleaning and antimicrobial effect is insensitive to temperature in the field of practical use, ie the tablet can be used with an optimal cleaning effect in the range from approx. 25 ° C to approx. 45 ° C.

The perborate activator used in the cleaning tablet according to the invention initiates a reaction mechanism in aqueous solution which can be simplified as follows:<chemistry id="chem0001" num="0001"><img file="EP0334060B1_D0001.tif" /></chemistry><chemistry id="chem0002" num="0002"><img file="EP0334060B1_D0002.tif" /></chemistry>

It is important that peracetic acid is formed as an intermediate, which then breaks down into acetic acid and oxygen. The activated oxygen release of the perborate leads to a significantly improved cleaning effect.

The antimicrobial effect of the cleaning tablet according to the invention achieved via the perborate / peroxide activator, with peracetic acid as an intermediate, also exceeds expectations. It has been shown that even at high dilutions and within short exposure times, sterility is achieved, the specific composition of the cleaning tablet being variable in a manner familiar to the person skilled in the art in accordance with the purposes achieved in each case. In order to obtain bacteria-free cultures after 48 hours of incubation, with a peracetic acid concentration of 0.002 to 0.005% by weight, an exposure time of 2 to 10 minutes to the usual test bacteria (Escherichia coli, Staphylococcus aureus, Streptococcus mutans, Pseudomonas aeruginosa, Proteus vulgaris) Bacillus mesenterieus) to kill them. The same applies to filamentous and shoot fungi (Trichophyton rubrum, Candida albicans). Even with the enteroviruses known to be resistant, the cleaning tablet according to the invention requires a concentration which is several times lower, due to the peracetic acid present, than in the H₂O₂ used to date.

While the formulations of most known denture cleaners contain inorganic phosphates and polyphosphates for lime formation and dispersion and organic complexing agents based on aminocarboxylic acids, such as EDTA and NTA, the cleaning tablet according to the invention does not require such additives. This is advantageous because the polyphosphates are sensitive to hydrolysis, i.e. that is, they hydrolyze in aqueous solution to form orthophosphates and thereby lose their dispersing action, whereas EDTA has no dispersing method in the first place. Furthermore, it should be noted that inorganic phosphates and z. B. EDTA are not harmless from an environmental point of view, since some cause problems due to the enrichment of the receiving water with oxygen-consuming plants, the others due to the difficult degradability.

In the cleaning tablet according to the invention, both of the aforementioned product groups, which are not unproblematic from an environmental point of view, are kept away from the overall composition. The highly effective lime and metal binders used for the first time in cleaning tablets for dentures in the form of organic complexing agents based on phosphonic acid or The salts are resistant to hydrolysis, have a corrosion-preventing effect and additionally improve the cleaning process in that, in synergistic interaction with the perborate activator, they stabilize the oxygen donor or the oxygen release and at the same time have good dispersing and deflocculating properties.

Practically all known or commercially available cleaning tablets for dentures prescribe warm water, some up to 50 ° C, for the cleaning liquor. With most conventional formulations, this is also absolutely necessary in order to bring the active oxygen of the peroxide into solution in good time. However, other disadvantages have to be accepted, e.g. B. faster hydrolysis, weaker dispersion / deflocculation, limited corrosion prevention. As a result of the effect according to the invention of the peroxide activator / stabilizer and the hydrolysis-stable organic complexing agents based on phosphonic acid and by eliminating the hydrolysis-sensitive inorganic polyphosphates, the cleaning tablet according to the invention does not have the disadvantages described above. In addition, it is also fully effective from room temperature and not only at the hot water temperatures previously required in practice. For the user, there is no longer any justified concern about the cleaning and disinfection effect if the temperature of the warm cleaning liquor recommended by the manufacturer is not tracked properly.

With the known cleaning tablets, a perfect sensory / visual tracking of the course and the end of the cleaning process has so far not been possible. Even with the known two-layer tablets, only a pre-cleaning intermediate stage can be seen, while the completion of the main and final cleaning remains hidden from the user. The previously used colors of the tablets (e.g. blue, pink) can still be seen long after the washing process is finished, even if a different effect is aimed at.

If, on the other hand, the dye system proposed according to the invention is used, the problems which previously existed with regard to the optical tracking of the cleaning process can be eliminated. This involves the use of a redox-sensitive dye with a relatively weak oxidation potential in combination with a dye of a different color that is independent of the redox potential. The protons released by the oxidation of the pollutants and a certain proton release from the other tablet substances cause a quantitative reduction in the dye intensity, followed by a qualitative change in color before decolourization occurs. The time course depends on the degree of contamination of the denture and partly also on the temperature and pH of the water. For practically all applications, however, the end of the main cleaning phase can be made optically traceable by the color change and the end of the cleaning process optimized for the intended exposure time by complete decolorization. According to the invention, this can be achieved by means of various relevant color systems, a green-turquoise color being produced when the combination provided here with indigo-disulfonic acid, disodium salt and quinophthalone-disulfonic acid, disodium salt. The color intensity decreases in the course of the cleaning process and then changes to green-yellow (end of main cleaning) before decolorization takes place (end of cleaning).

The cleaning tablet according to the invention can be constructed in the following composition ranges:<tables id="tabl0001" num="0001"><img file="EP0334060B1_D0003.tif" /></tables><tables id="tabl0002" num="0002"><img file="EP0334060B1_D0004.tif" /></tables>

A cleaning tablet according to the invention is described below on the basis of a specific exemplary embodiment: 30% by weight sodium perborate monohydrate 20% by weight potassium monopersulfate 20% by weight sodium hydrogen carbonate 5% by weight sodium carbonate 4% by weight sodium sulfate 7% by weight citric acid, sodium salt 1.5% by weight of tetraacethylene diamine 1.5% by weight of organic phosphonic acids or their salts 4% by weight of polyethylene glycol 20,000 1.5% by weight polyvinylpyrrolidone 1.5% by weight Aerosil 200/300 0.75% by weight sodium dodecylbenzenesulfonate 0.5% by weight hardened triglycerides 1% by weight of fatty alcohol polyglycol ether 1% by weight preservative 0.5% by weight of peppermint powder, and 0.25% by weight indigotine L-Blue 2 and quinoline yellow L-yellow 3, were compressed as powder or in granular form in equal proportions to form a cleaning tablet using known techniques. The resulting cleaning tablet after dissolving had a pH in the cleaning liquor of 9.0, at a temperature of the cleaning liquor of 30 ° C., the cleaning process, the course of which was fully visually traceable by means of a corresponding color change, being completed after about 10 minutes was.