GB1584845A

GB1584845A - Disinfectant concentrates

Info

Publication number: GB1584845A
Application number: GB953578A
Authority: GB
Original assignee: Akzo NV
Current assignee: Akzo NV
Priority date: 1977-03-12
Filing date: 1978-03-10
Publication date: 1981-02-18
Also published as: DE2710929C2; LU79210A1; FR2382898A1; FR2382898B1; ATA166378A; AT356290B; DK103578A; DE2710929A1; BE864742A; CH642822A5; CA1107643A; NL7802174A

Abstract

The invention relates to disinfectant concentrates for the beverages industry which contain a combination of nitric acid, hydrofluoric acid and water. Substances which are employed as disinfectants for destroying germs found in the pipes, tanks and apparatus of the beverages industry due to contaminant residues are chlorine-releasing substances, quaternary ammonium compounds, iodophores and peracetic acid in an equilibrium with hydrogen peroxide. The disadvantages of these compositions are that they are malodorous, bulky, foaming or have a limited spectrum of germicidal action. Nitric acid on its own is unimportant as a disinfectant since it is aggressive in character. Hydrofluoric acid has germicidal properties, but has not been employed due to its toxicity and corrosiveness. In a combination of hydrofluoric acid with nitric acid, lower concentrations suffice to kill the yeasts and bacteria when allowed to act over a short period. Nitric acid on its own only kills bacteria but is ineffective against yeasts. Hydrofluoric acid at low concentrations is ineffective against most bacteria. The combination of nitric acid and hydrofluoric acid is active against all bacteria found in the beverages industry and has a synergistically increased activity against yeasts.

Description

(54) DISINFECTANT CONCENTRATES (71) We, AKZO NV of IJssellaan 82, Arnhem, Netherlands, a body corporate organised under the laws of Holland do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to disinfectant concentrates; more particularly, it relates to disinfectant concentrates for the beverage industry and to the diluted solutions prepared from them.

When processing beverages, such as beer, milk, lemonade or mineral water, it is impossible to prevent residues of impurities forming in the pipes, tanks and apparatus. These residues, as well as the beverages themselves, constitute nutrient media for many micro-organisms. Although the original concentration of bacteria may be reduced by cleaning the soiled surfaces, this is by no means sufficient to prevent re-infection of the beverages which are to be processed. It is therefore necessary, and customary, to kill the remaining bacteria by treatment with disinfectant solutions or disinfectant gases or by heat treatment. Chlorine carriers, such as hypochlorites or chlorocyanuric acid salts, have proved to be suitable disinfectants used as aqueous dilutions, but the unpleasant odour thereof, which is to some extent transmitted to the beverages, is a serious disadvantage.

Quaternary ammonium compounds have also proved to be suitable disinfectants, but they mainly kill gram positive bacteria and, owing to the substantivity thereof, they cannot be completely washed off the surfaces.

Another disadvantage of these quaternary ammonium compounds is the vigorous foaming thereof, which interferes with circulating or spray disinfecting processes. Iodiphores, i.e. non-iogenic wetting agents containing dissolved iodine, also tend to foam and to leave a brown deposit on the treated surface.

Peracetic acid in equilibrium with excess hydrogen peroxide has recently been used for disinfectant purposes, but it tends to decompose rapidly in the presence of organic residues and therefore has only a limited storage life which makes such solutions uneconomical in use. There is the additional disadvantage that, owing to the relatively low electrical conductivity of these solutions, they require the addition of strong acids if they are to be automatically metered through conductivity control systems and recovered for storage.

Since it has recently become more customary to employ the principle of automatic metering of disinfectant solutions, the problem arose of developing a strongly acid disinfectant which would be free from the disadvantages of the disinfectants known in the art, such as substantivity, foam stability and limited bactericidal spectrum.

Nitric acid is of only limited usefulness because of its corrosive nature and consequent practical disadvantages for continuous disinfection and has therefore remained unimportant.

Although hydrofluoric acid was known to have bactericidal properties, it has not been used as a disinfectant because of its toxicity and corrosiveness.

Although nitric acid destroys the gram positive and gram negative bacteria occurring in the beverage industry, such as pseudomonas, proteus, coli and staphylococci, it is completely ineffective with yeasts. Investigations on hydrofluoric acid have shown that, at the low concentrations which must be observed because of its toxicity, it kills yeasts within a relatively short time, but is largely ineffective against bacteria, except pseudomonas.

It was surprisingly found that, when using a combination of hydrofluoric acid and nitric acid, much smaller concentrations are sufficient to destroy yeast within a short time without the bactericidal action being thereby reduced. Some bacteria, for example staphylococci, were even found to be killed within a shorter time.

To obviate the problem, it was therefore proposed to use disinfectant concentrates containing a combination of nitric acid and hydrofluoric acid for the beverage industry.

The pronounced synergistic effect of the combination according to the present invention on yeasts is particularly surprising in view of the fact that hydrofluoric acid alone destroys yeasts only after 5 minutes while nitric acid has no effect on yeasts even when used at high concentrations for long periods. The combination according to the present invention, on the other hand, is completely effective on all organisms occurring in the beverage industry within only 2.5 minutes, for example at a concentration of 200 ppm of hydrofluoric acid and 4750 ppm of nitric acid.

The disinfectant solution according to the present invention is non-foaming and non-substantive and its conductivity may be controlled so that it may suitably be employed in the beverage industry by the method of continuous circulating disinfection.

The concentrate for preparing the disinfectant solution used according to the present invention is composed of a mixture of from 1 to 3% hydrofluoric acid and from 20 to 50% nitric acid, based on anhydrous substance and water. It has also been found advisable to reduce the proportion of nitric acid which is essential for the synergistic effect and to replace it by sulphuric acid, thereby preventing the formation of nitrous vapours.

For this variation, it has been found suitable to use a mixture of 2% hydrofluoric acid, 10% nitric acid, 19% sulphuric acid and water. The solution prepared for use may contain sulphuric acid at a concentration of from 1500 to 3000 ppm.

The concentrate may also contain small quantities of urea to prevent the formation of nitrous vitriol and inhibitors to prevent aluminium corrosion. The proportion of urea may be up to 1%.

When the disinfectant solutions are trickled over the walls of the containers, certain zones may fail to be wetted so that the disinfectant solution fails to kill the organisms in these zones. Surface active substances are therefore added to the concentrate to prevent these difficulties. Fluorinated wetting agents are found to be particularly suitable for this purpose because of the high concentration of oxidizing nitric acid. Anionic fluorinated wetting agents which are saturated and therefore resistant to oxidation, such as fluoroalkyl carboxylates and/or perfluoroalkyl sulphonates, are suitable for this purpose. It has been found suitable to reduce the proportion of nitric acid and replace it by from 0.1 to 0.5% of wetting agent, based on the quantity of anhydrous substance and water.

In one preferred embodiment of the present invention the disinfectant solution contains from 150 to 200 ppm of hydrofluoric acid and from 3000 to 5000 ppm of nitric acid. It is generally preferred that, in addition to from 750 to 1000 ppm of nitric acid, from 1500 to 3000 ppm, particularly from 1500 to 2000 ppm, of sulphuric acid be present. Urea may desirably be present at a concentration of up to 100 ppm. Also, a fluorinated, anionic saturated wetting agent may desirably be present at a concentration of from 10 to 50 ppm.

Preparations containing the combination of active ingredients according to the present invention have excellent bactericidal properties. They effectively kill gram negative and gram positive bacteria, such as pseudomonas aeruginosa, staphylococcus aureus, escherichia coli and proteus vulgaris, as well as yeasts, and are therefore suitable for use in breweries and dairies, as well as in the nonalcoholic beverage industry.

The present invention will now be described and specifically with the aid of Examples.

In these Examples, hydrofluoric acid, nitric acid, the disinfectants known in the art and the disinfectant concentrate according to the present invention are each tested separately for bactericidal action.

The bactericidal properties are investigated along the lines laid down by the Deutschen Gesellschaft fir Hygiene und Mikrobiologie (third supplementary edition, publishers Gustaw Fischer, Stuttgart).

A) Test Method: Suspension test according to DGHM Test Bacteria: Pseudomonas aeruginosa Staphylococcus aureus Escherichia coli Proteus vulgaris Sacharomyces diastaticus 1. Bacteriological activity of a preparation consisting of hydrofluoric acid and water +=bacterial growth - =no bacterial growth Concentration 100 ppm Time of action in minutes 0.5 1 2.5 5 10 Pseudomonasaerug. +++ +++ +++ Staphylococcus aureus +++ Escherichia coli +++ +++ +++ +++ +++ Proteus vulgaris +++ +++ +++ Saccharomyces diast. +++ +++ +++ +± Concentration 150 ppm Time of action in minutes 0.5 1 2.5 5 10 Pseudomonas aerug. - +++ +++ - Staphylococcus aureus +++ +++ +++ +++ Escherichia coli +++ +++ +++ +++ +++ +++ Proteus vulgaris +++ +++ +++ +++ Saccharomyces diast. +++ +++ ±- --- Concentratio.n 200 pm - Time of action in minutes - 0.5 1 2.5-- - 5 10 Pseudomonas aerug. +++ +++ Staphylococcus aureus +++ +++ +++ +++ Escherichia coli +++ +++ +++ +*+ +++ Proteus vulgaris +++ +++ +++ +++ ++i +++ Saccharomyces diast. +++ +++ +++ It is found that hydrofluoric acid destroys pseudomonas and yeast only~when used at a concentration of 200 ppm and for 5 minutes. It is ineffective against all other bacteria.

2. Bactericidal activity of nitric acid at various concentrations: Concentration 2000 ppm Time of action in minutes 0.5 1 2.5 5 10 Pseudomonas aerug. --- -- --- Staphylococcus aureus +++ +++ +++ Escherichia coli +++ +++ +++ -- Proteus vulgaris --- --- --- -- - Saccharomyces diast. ~ +++ +++ +++ +++ +++ Concentration 3000 ppm Time of action in minutes 0.5 1 2.5 5 10 Pseudomonas aerug. --- - -- Staphylococcus aureus +++ +++ ±- -- Escherichia coli +++ -- --- -- Proteus vulgaris --- --- --- - Saccharomyces diast. +++ +++ +++ +++ +++ Concentration 4000 ppm Time ofaction in minutes 0.5 - 1 2.5 5 10 S Pseudomonas aerug. --- -- --- ~~~~ Staphylococcus aureus +++ +++ -- Escherichia coli +++ --- ---- --- -- Proteus vulgaris --- --- --- -- Saccharomyces diast. +++ +++ ++f +++ +++ These results demonstrate that at the high concentration of 4000 ppm, nitric acid destroys bacteria after only 2.5 minutes. The following Table, however, shows that it does not destroy yeasts after 10 minutes or even after 20 minutes.

Concentration 5000 ppm Time of action in minutes 5 10 15 20 Pseudomonas aerug.

Staphyloccus aureus --- --- --- --- Escherichia coli --- -- Proteus vulgaris - --- --- -- Saccharomyces diast. +++ +++ +++ Concentration 10,000 ppm Time of action in minutes 5 10 15 20 Pseudomonas aerug. -- -- -- - Staphylococcus aureus Escherichia coli -- Proteus vulgaris --- --- --- -- Saccharomyces diast. +++ +++ +++ +++ (The above is for comparison purposes only).

3. Bactericidal action of the combination of hydrofluoric acid and nitric acid according to the present invention at test concentrations of the solution of 0.750/, and 1%.

Concentration Time of action in minutes HNO3=3560 ppm HF = 150 ppm 0.5 - 1 2.5 5 10 Pseudomonas aerug. - --- -- ---- Staphylococcus aureus +++ +++ -- -- Escherichia coli +++ - -- ~~~~ -- Proteus vulgaris -- -- -- -- Saccharomyces diast. +++ +++ +++ - - Concentration Time of action in minutes HNO3=4750 ppm HF = 200 ppm 0.5 1 2.5 5 10 Pseudomonas aerug. -- --- -- Staphylococcus aureus +++ -- --- -- Escherichia coli +± -- --- -- Proteus vulgaris -- --- -- Saccharomyces diast. +++ +++ --- --- -- The results of this experiment clearly demonstrate the synergistic increase in the action on yeasts obtained by the combination according to the present invention. At a concentration of hydrofluoric acid of 200 ppm and of nitric acid at 4750 ppm, both the yeasts and all bacteria are destroyed after 2.5 minutes.

WHAT WE CLAIM IS: 1. A disinfectant concentrate for the beverage industry, which contains a combination of (a) hydrofluoric acid, (b) nitric acid and (c) water.

2. A concentrate as claimed in claim 1 which contains sulphuric acid, urea, a fluorinated anionic saturated wetting agent and/or corrosion inhibitor.

3. A disinfectant solution comprising water and a concentrate as claimed in claim 1 or claim 2 which contains hydrofluoric acid at a concentration of from 100 to 300 ppm, and nitric acid at a concentration of from 2,000 to 5,000 ppm.

4. A solution as claimed in claim 3 which contains from 150 to 200 ppm of hydrofluoric acid and from 3000 to 5000 ppm of nitric acid.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

These results demonstrate that at the high concentration of 4000 ppm, nitric acid destroys bacteria after only 2.5 minutes. The following Table, however, shows that it does not destroy yeasts after 10 minutes or even after 20 minutes.

Concentration 5000 ppm Time of action in minutes

5 10 15 20 Pseudomonas aerug.

Staphyloccus aureus --- --- --- --- Escherichia coli --- -- Proteus vulgaris - --- --- -- Saccharomyces diast. +++ +++ +++ Concentration 10,000 ppm Time of action in minutes

5 10 15 20 Pseudomonas aerug. -- -- -- - Staphylococcus aureus Escherichia coli -- Proteus vulgaris --- --- --- -- Saccharomyces diast. +++ +++ +++ +++ (The above is for comparison purposes only).

3. Bactericidal action of the combination of hydrofluoric acid and nitric acid according to the present invention at test concentrations of the solution of 0.750/, and 1%.

Concentration Time of action in minutes HNO3=3560 ppm HF = 150 ppm 0.5 - 1 2.5 5 10 Pseudomonas aerug. - --- -- ---- Staphylococcus aureus +++ +++ -- -- Escherichia coli +++ - -- ~~~~ -- Proteus vulgaris -- -- -- -- Saccharomyces diast. +++ +++ +++ - - Concentration Time of action in minutes HNO3=4750 ppm HF = 200 ppm 0.5 1 2.5 5 10 Pseudomonas aerug. -- --- -- Staphylococcus aureus +++ -- --- -- Escherichia coli +± -- --- -- Proteus vulgaris -- --- -- Saccharomyces diast. +++ +++ --- --- -- The results of this experiment clearly demonstrate the synergistic increase in the action on yeasts obtained by the combination according to the present invention. At a concentration of hydrofluoric acid of 200 ppm and of nitric acid at

4750 ppm, both the yeasts and all bacteria are destroyed after 2.5 minutes.

WHAT WE CLAIM IS: 1. A disinfectant concentrate for the beverage industry, which contains a combination of (a) hydrofluoric acid, (b) nitric acid and (c) water.
2. A concentrate as claimed in claim 1 which contains sulphuric acid, urea, a fluorinated anionic saturated wetting agent and/or corrosion inhibitor.
3. A disinfectant solution comprising water and a concentrate as claimed in claim 1 or claim 2 which contains hydrofluoric acid at a concentration of from 100 to 300 ppm, and nitric acid at a concentration of from 2,000 to 5,000 ppm.
4. A solution as claimed in claim 3 which contains from 150 to 200 ppm of hydrofluoric acid and from 3000 to 5000 ppm of nitric acid.
5. A disinfectant concentrate as claimed in claim 1, in which part of the nitric

acid is replaced by sulphuric acid.
6. A disinfectant solution as claimed in claim 5 which, in addition to from 750 to 1,000 ppm of nitric acid, contains sulphuric acid at a concentration of from 1,500 to 3,000 ppm.
7. A disinfectant solution as claimed in claim 6, which contains sulphuric acid at a concentration of from 1500 to 2000 ppm.
8. A disinfectant solution as claimed in claim 4, which contains urea at a concentration of up to 100 ppm.
9. A disinfectant concentrate as claimed in claim 1, in which the proportion of nitric acid is reduced and is replaced by from 0.1 to 0.5% of a fluorinated anionic, saturated wetting agent, based on the quantity of anhydrous substance and water.
10. A disinfectant concentrate as claimed in claim 9, in which the wetting agent is a fluoroalkyl carboxylate and/or perfluoroalkyl sulphonate.
11. A disinfectant solution as claimed in claim 2, which contains the fluorinated, anionic saturated wetting agent at a concentration of from 10 to 50 ppm.
12. A disinfectant concentrate or solution as claimed in any of claims 1 to 11 substantially as herein described with reference to any of the Examples.