EP0599888A1

EP0599888A1 - Anti-fouling agent for wet surfaces

Info

Publication number: EP0599888A1
Application number: EP92916595A
Authority: EP
Inventors: Horst Felsch
Original assignee: PREGENZER Bruno
Current assignee: PREGENZER Bruno
Priority date: 1991-08-05
Filing date: 1992-08-03
Publication date: 1994-06-08
Also published as: WO1993002973A1

Abstract

Un agent contre les incrustations, notamment les biofilms, sur des surfaces humides contient un mélange à base d'au moins un acide organique soluble dans l'eau et se dissociant faiblement et d'au moins un peracide organique soluble dans l'eau et se dissociant faiblement.An agent against encrustations, in particular biofilms, on moist surfaces contains a mixture based on at least one water-soluble and weakly dissociating organic acid and at least one water-soluble organic peracid and weakly dissociating.

Description

Agent against deposits on wetted surfaces

The invention relates to an agent against deposits, in particular against biofilms, on wetted surfaces, which contains at least one water-soluble, weakly dissociating, organic acid.

Wet surfaces are primarily understood to mean inner surfaces of pipeline systems or containers in which water or water-containing media are transported and stored. If, for example, hose systems are flowed through by media containing water or water, deposits are formed on the inner surfaces. Since this effect can also be seen in ultrapure water systems, the deposits not only contain deposits of constituents of the flowing medium. Chemical-microbiological analyzes show that this coating is a biofilm which comprises a gel which mainly consists of extracellular, polymeric substances, in particular polysaccharides, and microorganisms which are embedded therein. In technical terms, this biofilm is called "Glycocalyx". The proportion of these extracellular substances ranges between 50% and 90% of the total biofilm. The formation of biofilms is called biofouling in English.

The formation mechanisms of biofilms have already been studied very well: in ultrapure water systems, it is very often microorganisms of the pseudo onas species that use the carbon dioxide dissolved in the water as a carbon source and the oxygen dissolved in the water as a respiratory source and synthesize sugar-like molecules from them to be close to a glycose molecule. Linking such sugar molecules ultimately creates water-insoluble gels, which are usually Adhere very well to the surface of hose systems. Once the gel is glued to the wall of the tube, the microorganisms slip into the protective layer and cannot be rinsed away again by the flow of the liquid carried in the tube. The formation of the biofilms thus serves as protection and therefore with a better multiplication of the microorganisms. Raster electronic investigations have shown that the biofilms are microbiologically densely populated and that very few microorganisms exist outside of this protection in the free-flowing system. The ratio is about 1000 microorganisms in the gel to a microorganism in the free-flowing medium. In the past, this has often led to errors in assessing the degree of contamination of the surfaces. If only the escaping liquid is examined, the degree of contamination is very low. If, on the other hand, the flow is interrupted approximately overnight, then a high level of contamination can be found in the first water emerging. The reason for this is to be seen in the fact that significantly more microorganisms leave the protective biofilm layer with assumed security and pass into the non-flowing medium. It follows from this that the flowing system even promotes the formation of biofilm, since with increasing flow speed the proportion of microorganisms in the protective biofilm increases, in which they can multiply undisturbed. (A standing system would not need the protective biofilm layer physiologically at all.) The biofilms protect the microorganisms so well that it is hardly possible to use disinfectants such as alcohols, aldehydes, chlorine and oxygen releasers, etc. in the usual way Concentrations to a Kei reduced on, because the possibility of the disinfectant to penetrate into the biofilm is extremely poor due to the gel formation. The However, removal of the microorganisms is often particularly important or necessary, for example in the production of ultrapure water, e.g. B. for filling ampoules. The ultrapure water systems themselves supply sterile water, which must also be filled into the ampoules in sterile form. If this does not succeed, long microorganisms get into the ampoules and these then have to be sterilized physically. However, the microorganisms killed in the process are able to form fibrinogens which can cause fever-like diseases in humans. Another example is dental units. For the high-speed turbines, the dentist also needs water to rinse out for the patient, which is then warmed up in the dental unit. The water is withdrawn at intervals as required; there is no withdrawal at all during the night. These are ideal conditions for the formation of bio films and other coverings. Similar conditions exist in the hospital area, especially where many tube systems are used, for example in the dialysis station, but also in the case of artificial ventilation. The humidifiers customary in the home also have an extremely high biofilm formation. In principle, all water supply systems are affected by the formation of such deposits. Biofilms are particularly unfavorable in those which are fed from fixed storage tanks, as is the case above all on ships, larger aircraft and buses.

The metering of conventional disinfectants into flowing media has therefore been unsuccessful in combating biofilm to date, apart from that they are largely non-biodegradable and toxic, which limits their use from the outset. AT-PS 382 310 describes a method for decalcifying, disinfecting and cleaning mouth showers, toothbrushes, cleaning cups, humidifiers and respiratory and inhalation devices. The means for carrying out the method corresponding to the type mentioned at the outset consist of a mixture of 15 to 80% by weight of lactic, glycolic, wine, lemon, formic, acetic and / or propionic acid with the addition of 10 to 60% by weight of ethanol, isopropanol and / or n- Propanol, 5% by weight of water and, if appropriate, traces of essential oils, which should act on the surfaces for about 8 to 12 hours. A sufficient limescale content of the wetting water is a prerequisite for the effectiveness of this anti-coating agent, since limescale is incorporated into the biofilm, which the acids contained in the medium dissolve. It leaves gaps in the biofilm into which the agent with microbicidal properties can penetrate. As this breaks the protection, the acids can act against the microorganisms. The antimicrobial effect of these acids is only mediocre, but they have the decisive advantage that they are completely biodegradable and can be degraded without residue, ie they are decomposed into carbon dioxide and water. Regular use of the agent keeps the formation of biofilms behind. Another advantage is that these acids can also be used in the food sector or are already present. For example, lemonades and other carbonated soft drinks contain lactic or citric acid. Propionic acid is present in sauerkraut and also protects it from icrobial spoilage. About 5% to 7% of acetic acid is contained in the vinegar. The optimum of the antimicrobial activity of the organic acids mentioned is in the acidic pH range between 3 and 5. Their activity against bacteria is usually better than that against fungi. The microorganisms are killed primarily by precipitation of the species' own protein, as a result of which the microorganism is primarily damaged in its external appearance. However, metabolic functions and enzyme systems in the interior of the attacked microorganisms are also inhibited or destroyed. To do this, however, it is necessary that the acid can penetrate through the semipermeable membrane of the microorganisms. Since this is only possible for very small molecules, only the undissociated acid molecule can penetrate, the proportion of which is very high with the specified organic acids. On the one hand, these dissociate so far in water that the at least optimal pH range between 3 and 5 is reached, but on the other hand so little that the required acid molecules are retained. Because no hydration takes place, only these are able to penetrate semipermeable membranes of microorganisms and to get inside microorganisms. Highly hydrated anions, on the other hand, are too large due to the water molecules surrounding them to be able to penetrate the microorganisms. This also explains why, for example, strong inorganic acids, such as, for example, hydrochloric acid, nitric acid or sulfuric acid, in corresponding dilutions are only slightly effective antimicrobially, while the effectiveness of weak, organic acids is considerably higher. However, since the microorganisms cannot be reached by the acids when the surface of the biofilm is closed, the lack of lime deposits considerably reduces the effectiveness of the acids. Mechanical removal of the biofilm is described in US Pat. No. 4,419,248. Accordingly, the biofilm is cooled in such a way that the water contained in the biofilm (up to 95%) is converted into long and sharp ice crystals. The surface of the bio film is broken open, and after thawing, the biofilm can be partially washed away by the flowing medium. However, the method can only be used to a very limited extent, since temperatures between -8 * and -19 * C and a corresponding outlay on equipment are necessary for this.

The invention has now set itself the task of improving the anti-fouling agent mentioned at the outset in such a way that it is also effective against biofilms without lime inclusions and thus eliminates existing ones and prevents their formation.

According to the invention, this is achieved with an agent in which the weakly dissociating organic acid is mixed with at least one water-soluble, weakly dissociating organic peracid.

It is known, see, for example, Römpp, Chemie Lexikon, 9th edition under the corresponding keywords, that the water-soluble peroxycarboxylic acids (organic peracids), in particular peroxyformic acid (peroxymethanoic acid) and peroxyacetic acid

(Peroxyethanoic acid) have antimicrobial effects and can be used as disinfectants. Above all, the antimicrobial effect of peroxyacetic acid is extremely strong even in very low concentrations. Their optimal effect unfolds in the range between pH 2.5 and 4. Thus, at a concentration of 0.2%, influenza, Newcastle and Rotaviruses inactivated. Adenoviruses, vaccine viruses and enteroviruses are inactivated after a few minutes. In addition to viruses, the disinfectant effectiveness of peroxyacetic acid also affects bacteria and fungi. With the bacteria, a concentration of 20 to 50 micrograms per milliliter is sufficient with an exposure time of two minutes. This means that a 0.002 to 0.005% peroxyacetic acid is able to kill practically all germs within two minutes. It is known that the effect of peroxyacetic acid can be further increased by adding about 33% alcohol.

However, the cited literature reference also shows that the peroxycarboxylic acids dissolved in water very quickly break down into the corresponding carboxylic acid and hydrogen peroxide. Hydrogen peroxide also has a slightly antimicrobial effect, but also has the disadvantage of poor stability because it quickly breaks down in water and oxygen. The oxidizing effect of the nascent oxygen on the gel of the biofilm is therefore much too short to show a lasting effect. The particularly suitable peroxyacetic acid therefore has no long-term effect. This can be proven by iodometric measurements.

If diluted peroxyacetic acid solutions are titrated iodometrically, 90% of the available oxygen is released spontaneously. The last 10% can be detected in the further five minutes, after which the oxygen has been used up and only the acetic acid and water which are practically ineffective against the gel of the biofilm are present. It has now been shown that this disadvantage of the release of all of the oxygen does not occur in the shortest possible time in the mixture of organic peracid with organic acid according to the invention, which are both water-soluble and weakly dissociate. For the preferred use of peroxyacetic acid, iodometric measurements show that long-term release of the oxygen takes place. Only about a third of the oxygen is released spontaneously, while the remaining two thirds split off for a period of up to ten hours. The biofilms are thus exposed to a long-term attack by nascent oxygen Oxygen bubbles act mechanically on the attacked coating, so that it ultimately detaches itself from the inner surface of the hose line or the container. The reasons for the surprising long-term effect have not yet been fully clarified. They should be due to the mixture with the organic weakly dissociating acid and thus ultimately in the pH range of about 3 - 5.

Furthermore, it has been shown that there is also a synergistic increase in the antimicrobial effect, since the mixture with the weakly dissociating organic acids known from AT-PS 382 310, in particular lactic acid, has a more antimicrobial effect than the individual components same concentration and same exposure time. The dissociation of the peroxyacetic acid is further reduced in the mixture with the other organic acids, and thus the proportion of cell-permeable acid molecules is increased. In order to achieve this increase in activity, of course only acids which cannot themselves be oxidized may be used. Phenols, aldehydes, ketones, disulfites, etc. are therefore to exclude. Lactic acid, acetic acid and the other acids mentioned above are essentially stable against oxidation.

Another advantage of the agent according to the invention is that peroxyacetic acid ultimately breaks down into the sub-compounds acetic acid, oxygen and water, that is to say three physiologically completely harmless compounds are formed.

When using highly concentrated lactic acids (between 80 and 90%) it is known that a high percentage (up to 80%) of this acid is in lactone form, ie. H. a ring-shaped compound has formed from two molecules of lactic acid by water escaping. However, this lowers the antimicrobial effectiveness because there are fewer protons for lowering the pH and many larger molecules which can no longer penetrate cells. To split the lactone rings, diluted solutions are usually boiled for several hours. The addition of peroxyacetic acid surprisingly also lowers the lactone content, which should also be responsible for the antimicrobial activity increase of the lactic acid-peroxyacetic acid system.

The dissolution of calcareous deposits mentioned in AT-PS 382 310 naturally also occurs with the agent according to the invention. Acid-soluble fractions incorporated in the biofilm, such as lime or lime-like compounds, are also dissolved out with CO ₂ evolution and thus tear additional holes in the gel.

The agent according to the invention thus acts simultaneously in several ways: 1. The long-term release of nascent oxygen causes substantial damage to a microorganism-protecting gel.

2. The fine oxygen bubbles, which are formed over a long period, act mechanically on already damaged bio films and detach them.

3. The mixture of weakly dissociated organic acids and peracids synergistically increases the antimicrobial activity. 4. acid-resistant coverings and covering parts, such as. B. lime or the like are dissolved.

Another disadvantage of oxygen-releasing per-compounds described in the literature is that they are spontaneously inactivated by blood. Blood contains the ferment catalase, which peroxyacetic acid instantaneously decomposes with the elimination of oxygen in the sense of the reaction equation CH3COOOH + H ₂ 0 - CH ₃ C00H + H ₂ 0 ₂ , the H ₂ 0 _{2 being} H ₂ 0 and Oxygen decays further. This sudden elimination of oxygen would lead to spontaneous foaming in systems in which blood can also occur (e.g. in dental units) and, in connection with this, to possible malfunctions of the subsequent devices (e.g. amalgam separators). The mixture according to the invention, in particular of lactic acid and peroxyacetic acid, also prevents this spontaneous reaction, presumably due to the depot effect described above. Peroxyacetic acid molecules that are still active have a destructive effect on the ferment catalase, so that catalysis-related oxygen elimination no longer takes place. The experiment shows that only a brief foaming of a mixture of lactic acid and peracetic acid can be observed when it comes into contact with blood. Thereafter, the evolution of oxygen is completely eliminated since the catalase is destroyed. While maintaining one It is therefore sometimes not necessary to add additional defoamers to the minimum concentration.

Peroxycarboxylic acids as high-energy compounds disintegrate very quickly, especially in highly dilute aqueous solution. The reaction equation given above also shows that water is particularly favorable for the cleavage. The agent used according to the invention contains hardly any water, since all acids are highly concentrated, as mentioned 80-90% high-viscosity lactic acid is preferably used. The stabilization can be increased further if the organic peracid is contained in a mixture which contains a second water-soluble organic acid and hydrogen peroxide. The second organic acid is preferably the carboxylic acid corresponding to the peroxycarboxylic acid.

Peroxyacetic acid is preferably mixed with almost 100% acetic acid (glacial acetic acid) and hydrogen peroxide. Thus the molecule water is hardly available for the decomposition reaction. Peroxyacetic acid-acetic acid-hydrogen peroxide-lactic acid mixtures are therefore considerably more stable than peroxyacetic acid-water mixtures. For additional stabilization of the above all diluted agent, it is preferably further provided that the mixture contains peroxyacetic acid, acetic acid and hydrogen peroxide in the weight ratio of the equilibrium reaction.

It is known to stabilize aqueous peroxyacetic acid solutions by adding acetic acid and H ₂ 0 ₂ in equilibrium. It is not known that this system also works in concentrated or dilute lactic acid or the other acids mentioned. This results in a further preferred embodiment, according to which the agent consists of two components which are miscible before use, of which the first component comprises the first organic acid and any additives which may be present, and the second component comprises the organic peracid , the second organic acid, the hydrogen peroxide and optionally the ethylenediaminetetraacetic acid. The user receives a concentrate in which the peroxyacetic acid in

10 tamed and largely undecomposed form is included. For the preparation of the working solution, this concentrate can be greatly diluted, depending on the purpose Verwendungs¬ tens or hundreds of times, überraschender¬ example has been found here that in this comparison ^5, the peracetic acid dilution delayed responding and their oxygen over a longer tet abspal¬ period, that is, the advantages that apply to the concentrate, are sung still present, also in an application-oriented diluted Lö¬ but characterized pH has the optimum ²⁰ 3 to 5 Once the peroxyacetic acid has done its oxidizing and disinfecting work, a well-tolerated, physiological product remains, namely dilute acetic acid mixed with the carrier acid (lactic acid, acetic acid, ^25th citric acid, etc.). The agent can therefore also

Disinfection of water treatment systems can be used because such a physiological mixture can remain in the water. It can also get into the mouth of a dental patient. The water glass contained in the rinsing ³⁰ but not tastes slightly sour, unpleasant. In terms of taste, this is in any case better than with the usual addition of hydrogen peroxide solutions. For fresh water treatment equation also has an effect that a dilution of 1: 100 also has a lime-removing effect.

Example 1:

To prepare 1 kg of an agent according to the invention, the following are used (standard preparation): 980.6 g 80% lactic acid 10 g 40% peroxyacetic acid 3.2 g glacial acetic acid 6 g 30% hydrogen peroxide 0.2 g ethylenediaminetetraacetic acid

Example 2:

980.6 g 90% lactic acid 10 * g 40% peroxyacetic acid 3.2 g glacial acetic acid 6 g 30% hydrogen peroxide 0.2 g ethylenediaminetetraacetic acid

Dilution for use 1: 2 to 1: 300

Example 3:

To remove stubborn microbial deposits in plastic pipes and tubes, 1 kg contains: 942 g 90% lactic acid 30 g 40% peroxyacetic acid

9.6 g glacial acetic acid 18 g 30% hydrogen peroxide 0.4 g ethylenediaminetetraacetic acid

The concentrate can either be used undiluted or diluted up to 1:20.

Example 4:

For the disinfection and descaling of fresh water, e.g. B. in dental systems, contains 1 kg: 978.6 g 80% lactic acid 10 g 40% peroxyacetic acid 3.2 g glacial acetic acid

6 g 30% hydrogen peroxide 0.2 g ethylenediaminetetraacetic acid 2 g essential peppermint oil

In a dilution of 1: 500 to 1: 800, the agent may also get into the patient's mouth. It neither tastes unpleasant nor is it toxicologically harmful.

Example 5: For applications in which the coagulation of the blood is important, 1 kg contains: 930.6 g 80% lactic acid 50 g solid citric acid 10 g 40% peroxyacetic acid 3.2 g glacial acetic acid

6 g 30% hydrogen peroxide 0.2 g ethylenediaminetetraacetic acid

Blood clotting is prevented by the formation of calcium salts.

Other possible compositions are:

Example 6:

930.6 g 80% lactic acid 50 g tartaric acid 10 g 40% peroxyacetic acid 3.2 g glacial acetic acid

6 g 30% hydrogen peroxide 0.2 g ethylenediaminetetraacetic acid

Example 7:

920.6 g 90% lactic acid 60 g 25% formic acid

10 g of 0% peroxy formic acid 3, 2 g of glacial acetic acid

6 g of 30% hydrogen peroxide

0.2 g of ethylenediaminetetraacetic acid

Example 8:

880.6 g 80% lactic acid 100 g glycolic acid 10 g 40% peroxyacetic acid 3.2 g glacial acetic acid

6 g 30% hydrogen peroxide 0.2 g ethylenediaminetetraacetic acid

Example 9:

If the agent according to the invention is to be used where strong foaming is to be expected, an anti-foaming agent can also be incorporated. 1 kg then contain:

930.6 g 80% lactic acid 50 g defoamer, e.g. B. Antispumin ^R BT 10 g 40% peroxyacetic acid 3.2 g glacial acetic acid 6 g 30% hydrogen peroxide

0.2 g ethylenediaminetetraacetic acid

Example 10:

Mixtures of essential oils can also be incorporated to improve the flavor, especially when used in fresh water systems. In order to achieve good emulsifiability, the addition of an emulsifier is necessary. In this case 1 kg contain:

978.59 g 80% _. Lactic acid 0.01 g emulsifier, e.g. B. Intrasol ^R WL, 10 g 40% peroxyacetic acid 3, 2 g of glacial acetic acid

6 g 30% hydrogen peroxide 0.2 g ethylenediaminetetraacetic acid 1 g peppermint oil l g essential eucalyptus oil

In all examples, the ethylenediaminetetraacetic acid is used to bind complex metal traces of black metal, which would otherwise catalyze the decay of the acetic acid.

In summary, the agent according to the invention provides for the first time a highly effective anti-coating agent, the components of which on the one hand are biodegradable and residue-free, and on the other hand are completely physiological or disintegrate into physiological substances without toxicologically harmful decomposition products after they have taken effect. The synergistic antibacterial effect, the long-lasting release of the oxygen which is split off and the destruction of the catalase permit a very varied use of the agent in which the different acids mixed together form a buffer system which, even at a dilution of 1: 500, always still contains pH values around 3.5. The area of use itself can be determined by producing a concentrate and choosing the dilution option. Higher concentrations serve to remove existing deposits, and lower concentrations are sufficient as a deposit-inhibiting additive to water treatment systems.

The percentages given each represent percentages by weight, and the names given in Examples 9 and 10 for the defoamer and the emulsifier are registered trademarks of Chemische -Fabrik Stockhausen, D-4150 Krefeld, Germany.

Claims

Patent claims:

1. Agents against coverings, in particular against biofilms, on wetted surfaces which contain at least one water-soluble, weakly dissociating, organic acid, characterized in that the weakly dissociating organic acid with at least one water-soluble, weakly dissociating, organic Peracid is mixed.

2. Composition according to claim l, characterized in that the organic acid is mixed with peroxyacetic acid.

3. Composition according to claim 1 or 2, characterized gekenn¬ characterized in that the organic peracid is contained in a mixture which contains a second water-soluble organic acid and hydrogen peroxide.

4. Composition according to claim 3, characterized in that the mixture contains peroxyacetic acid, acetic acid and hydrogen peroxide in the weight ratio of the equilibrium reaction.

5. Agent according to one of claims 1 to 4, characterized in that it additionally contains ethylenediamine traamic acid.

6. Agent according to one of claims 1 to 5, in which the at least one organic acid is lactic acid, which is mixed with additives and optionally with at least one further water-soluble, weakly dissociating organic acid, characterized in that the additives Antifoam and / or an emulsifier.

7. Composition according to one of claims 3 to 6, characterized in that it consists of two components which are miscible before use, of which the first component comprises the first organic acid and any additives present, and the second component comprises the organic peracid , contains the second organic acid, the hydrogen peroxide, and optionally the ethylenediaminetetraacetic acid.