GB2074866A - Bactericidal Compositions - Google Patents

Abstract

The invention relates to a bactericidal composition and to its method of manufacture. A method of producing a bactericidal composition is characterised by the fact that a concentrated solution of a mono- or di-aldehyde and a quaternary ammonium is formed, the components are kept in contact at high concentration for a period of from several hours to several days, and the solution is then corrected to its use concentration. There is also described a bactericidal composition comprising an acid aqueous solution of glutaraldehye and formaldehyde in quantities such that the concentration of the formaldehyde solution is less than a concentration in which formaldehyde has bactericidal properties. The bactericidal compositions are particularly useful for disinfecting production equipment in food industries and in particular in the milk and drinks industries.

Description

SPECIFICATION Bactericidal Compositions The present invention relates to a bactericidal composition as well as to its method of manufacture.

The present invention is applicable to all industries, in particular food industries such as those of milk, meat or beer, where sporicidal and bactericidal cleansing of the production lines or ambient air is necessary.

The Applicant has already disclosed the synergy of formaldehyde and an organic salt whereof the positively charged ion has a high molecular weight, in order to propose a bactericidal composition which is effective at very high dilutions.

The quantity of raw materials used in such a synergistic composition was clearly reduced and replacement of part of the formaldehyde by a quaternary ammonium salt made it possible to reduce considerably the disagreeable secondary effects of formaldehyde, in particular its odour and its corrosive action. The immunity of the microorganisms was also clearly reduced owing to the fact that, with equivalent effectiveness, the concentrations used were greatly reduced. As regards its active components, the composition in aqueous solution comprised essentially formaldehyde and a quaternary ammonium salt.

It became apparent that the composition based on formaldehyde and quaternary ammonium no longer had the drawbacks inherent in each of its components taken separately and that a synergistic effect occurred between the two components when the composition was used under certain conditions.

Research has been carried out both in order to improve the synergy and to reduce the quantities of raw materials used as well as to remove the odour of formaldehyde, since it was necessary to maintain a slight excess of formaldehyde in order to achieve good adsorption on the quaternary ammonium and thus good synergy.

Unfortunately, it was apparent that the quaternary ammonium salts were difficult to remove by rinsing and tended to become concentrated and consequently, for disinfecting production equipment in food industries and in particular in the milk industry, there was a tendency to use Javel water or a composition based on iodine, phosphoric acid and a surface-active agent.

According to the present invention there is provided a method for the preparation of a bactericidal composition in aqueous solution, which comprises mixing in solution at least one mono or dialdehyde with a quaternary ammonium, characterised by the fact that a concentrated solution is formed with these two components, that the components are kept at a high concentration for a period of between several hours and several days, that the solution is then corrected to its use concentration.

It was found that mixing of the components at a high concentration makes it possible to increase the synergy on condition that the dilution to the use concentration is carried out after a sufficiently long period of time. This contact time before dilution depends on the concentration of the products in the mother solution and may be comprised between several hours and several days. The time taken for the mother solution to reach an acid pH makes it possible to follow the synergy and thus, according to the initial concentrations used or the nature of the quaternary ammonium or aldehyde, a man skilled in the art will be able to determine the contact time which will be necessary in order that synergy occurs under optimum conditions.

The method according to the invention is applicable to the preparation of all bactericidal compositions whatever the nature of the components chosen. By way of example, monoaldehydes or dialdehydes which are economically and practically the most advantageous for formaldehyde and glutaraldehyde. Amongst the quaternary ammoniums used, organic salts which have been satisfactory are those in which the positively charged ion has a high molecular weight and has an active aliphatic chain in its molecule. Dimethyl alkyl benzyl chloride or lauryl dimethyl benzyl bromide have proved satisfactory. More generally, one can use a quaternary ammonium salt where of the alkyl grouping is a straight chain of CaH" to C,8H33.

It is possible to manufacture a bactericidal composition according to the invention which comprises a lower concentration of formaldehyde, and dialdehyde, such as glutaraldehyde. Such a composition has little or no odour of formaldehyde.

To this end, the invention also proposes to use glutaraldehyde in an acid aqueous solution which makes it possible to stabilise the glutaraldehyde. This is an abnormal use of glutaraldehyde insofar as it is normally only in alkaline solution that it possesses disinfectant qualities.

However, the associated use of formaldehyde at a concentration such that, under the conditions of use of the composition, the concentration of formaldehyde is less than a concentration at which an aqueous solution of formaldehyde has bactericidal properties, makes it possible to preserve the disinfectant qualities of glutaraldehyde, even though it is then used under abnormal pH conditions.

In fact, the role of formaldehyde in the solution appears to be multiple, since the formaldehyde simultaneously: maintains the pH of the acid solution, participates in the blocking of the aldehyde functions of glutaraldehyde, i.e. blocking the functions which polymerise when the pH is alkaline, and gives rise, with glutaraldehyde, to the appearance of a synergistic effect which, for the same disinfectant effectiveness, makes it possible to reduce by half the quantity of glutaraldehyde in the solution.

This is particularly advantageous if one takes into account the fact that glutaraldehyde is an expensive product.

However, the concentration of formaldehyde in the solution remains sufficiently low in order that the solution does not have the drawbacks of odours and corrosive action inherent in formaldehyde in the concentrations in which it is normally used as a disinfectant, which are approximately one hundred times greater.

Consequently, a bactericidal composition constituting a further aspect of the invention and intended in particular for disinfecting production equipment in feed industries, is characterised in that it comprises an acid aqueous solution of glutaraldehyde and formaldehyde in quantities such that the concentration of formaldehyde in the solution is less than a concentration in which formaldehyde has bactericidai properties.

An advantage of the method according to the invention is that it is applicable to all mono- and dialdehydes whilst improving the synergy of the compositions obtained and making it possible to prepare a range of very diversified products for solving special bactericidal problems. It is thus possible to improve the sporicidal action or due to the existance of a volatile fraction of the composition, to apply the latter to certain food manufacturing processes.

The compositions prepared in this way have excellent stability since they can be stored for an unlimited time without special precautions. They retain their bactericidal property after prolonged heating up to 1 200C for 30 minutes. They retain their effectiveness in the case of treatments with an acid or alkaline pH. They suffer little from the action of organic materials and retain good effectiveness in their presence.

In order to reveal the effectiveness of the antiseptics used, the reality of the synergy and the improvements provided by the method consisting of giving the components a high concentration before correcting them to the use concentration, the test known by the name Trois 5 has been used.

This test defines the effectiveness of an antiseptic as being the optimum concentration at which this antiseptic is capable of reducing by 1 05 times the number of five strains of micro-organisms after 5 minutes of contact. The reference strains are as follows: Pseudomonas fluorescens, Kebsiella Pneumaniac, Staphylococcus Aureus, Saccharomyces Cerevisiae, Stretococcus Fecalis. The optimum concentration at which the antiseptic is active under these conditions is expressed as "per thousand of pure active material" (O/ooPAM) in the solution.

The effectiveness of the following pure products was measured, the results of which are given hereafter: Dimethyl alkyl benzyl chloride 0.1 6 /ooPAM Formaldehyde 0.100/ooPAM Glutaraldehyde 0.1 70/ooPAM From this test, we can conclude that glutaraldehyde is more effective than formaldehyde as regards the strains considered.

In order to demonstrate the synergy of formaldehyde and dimethyl alkyl benzyl chloride, one measure the effectiveness of an aqueous solution of 12% by weight dimethyl alkyl benzyl chloride and 10.8% by weight formaldehyde. The effectiveness of this solution relative to quaternary ammonium is 0.060/oo where as it is 0.05zoo relative to formaldehyde. Under these conditions, this bactericidal composition I prepared in this way makes it possible to same on the two components: if one refers to the effectivness of the components used alone, one will see that composition I makes it possible to use 2.66 times less quaternary ammonium and 98 times less formaldehyde, whilst remaining effective. An advantageous synergy is thus produced between the two components.

A composition II was prepared as an aqueous solution and contained 10.4% dimethyl alkyl benzyl chloride and 5.4% glutaraldehyde. The effectiveness relative to quaternary ammonium was measured at 0.05 /ooPAM whereas that relative to glutaraldehyde is 0.027 O/ooPAM. If these results are compared with the effectiveness of pure products, it will be found that dimethyl alkyl benzyl chloride is 3.2 times more active in composition II but glutaraldehyde is 6.48 times more active.

By comparing the results obtained with the two compositions, it will be found that one uses less quaternary ammonium with glutaraldehyde than with formaldehyde.

The synergy has also been demonstrated with other quaternary ammoniums and in particular lauryl dimethyl benzyl bromide.

Tests have also been carried out in order to establish the optimum ratio of quaternary ammonium and aldehyde used. In the case of a mono-aldehyde, i.e. for example for composition I, the ratio in solution is close to 1. It has been found that when a dialdehyde is used, the quantity of aldehyde divided by 2 and the ratio of quaternary ammonium/aldehyde is close to 1/0.5.

The discovery of better synergy from the method according to the invention was made on compositions I and II at different concentrations. In the first case, the dilution of the composition to the percentage of active materials indicated was carried out at t=0, i.e. immediately after the mixing of the concentrated components. In the second case, this dilution was carried out after 24 hours contact between quaternary ammonium and the mono or dialdehyde at high concentration.

Composition / O.050/ooA.M. O.50IooA.M. 1.00/ooA.M.

Dilution at t=0 No action No action Effective Dilution at t=24 hrs No action Effective Effective Composition II 0.08 /ooA.M. 0.16 0IooA.M. 0.24 0/ooA.M.

Dilution at t=O No action Effective Effective Dilution at t=24 hrs Effective Effective Effective It will be noted that the compositions, whether based on mono-aldehyde or dialdehyde have increased effectiveness when the dilution time is 24 hours.

During the period of contact of the components having a high concentration, the pH of the mixture develops towards a more acid pH in order to become stabilised after approximately 10 days.

The pH for composition I passes from 6 to 4 over a period of 10 days, that of composition II from 5.5 to 3.75.

It should be ncted that in the case of immediate dilution to the dose at which the components are used, not facilitating contact at high concentrations, the pH of the dilute solution does not develop over a period of time. This contact which allows better synergy may thus be controlled by development to a more acid pH. If the components are very concentrated initially, the contact time necessary to obtain better synergy will be only a few hours whereas it could be from 4 to 5 days if the products are very dilute.

The compositions such as I and II already described and obtained from quaternary ammonium and a concentrated mono or dialdehyde may be diluted to the composition indicated after 24 hours. If this dilution occurs later, one will note a drop in the pH of the mother solution, but it has been shown that this development no longer favours the synergy beyond a certain duration. Therefore it is no longer useful to wait for stabilisation of the pH of the mother solution which occurs substantially at the end of 1 0 days, in order to proceed with dilution. Whatever the concentration of the components of the mother solution, it has been found heating to a temperature of 600 during the contact time made it possible to reduce this period of time.

In order to obtain the compositions I and II at the dilutions indicated, concentrated components for example of pure quaternary ammoniums with a 30% mono or dialdehyde in water were used for the mother solution.

The method according to the invention makes it possible to prepare bactericidal compositions of which the applications will be diverse and this is at extremely low concentrations, owing to the synergy, in order to eliminate secondary consequences in particular as regards corrosion, toxicity and the odour of the antiseptics used. By way of example, the compositions I and II described at their use concentration could be diluted again to one thousandth when they are intended to be used in the industries indicated.

As a non-limiting example, good results were obtained by preparing a bactericidal composition based on glutaraldehyde and formaldehyde in the following proportions: -formic aldehyde, 30%:36% solution, -glutaric aldehyde, 50%:1 1% solution, -pH of the solution, of the order of 3 to 4.

This solution was used diluted to a value of the order of 5/1000 to 19/0; its pH was thus of the order of 6.

Claims (11)

Claims

1. Method for the preparation of a bactericidal composition in aqueous solution, which comprises mixing in solution at least one mono or dialdehyde with a quaternary ammonium, characterised by the fact that a concentrated solution is formed with these two components, that the components are kept at a high concentration for a period of between several hours and several days, that the solution is then corrected to its use concentration.

2. Method according to Claim 1, characterised in that the contact time of the components is of the order of several hours when they are very concentrated and of several days when they are already diluted.

3. Method for the preparation ofua bactericidal composition in aqueous solution according to Claim 1 or 2, characterised by the fact that the contact time of the components is sufficient when the pH of the mother solution has developed to an acid pH.

4. Method for the preparation of a bactericidal composition in aqueous solution according to one of the preceding claims, characterised by the fact that the mother solution is heated during the contact time of the components at high concentration.

5. Bactericidal composition characterised in that it comprises an acid aqueous solution of glutaraldehyde and formaldehyde in quantities such that the concentration of the formaldehyde solution is less than a concentration in which the formaldehyde has bactericidal properties.

6. Composition according to Claim 5, characterised in that the pH of the solution is of the order of 6.

7. Composition according to Claim 5, characterised in that it is obtained by dilution to a value of the order of 5/1000 to 1% of a solution comprising 36% of a 30% solution of formaldehyde and 11% of a 50% solution of glutaraldehyde and having a pH of the order of 3 to 4.

8. Bactericidal composition in aqueous solution, characterised by the fact that one of the components is a monoaldehyde and the ratio of quaternary ammonium/monoaldehyde is substantially equal to 1.

9. Bactericidal composition in aqueous solution, characterised by the fact that a dialdehyde is used and that the ratio of quaternary ammonium/aldehyde is substantially equal to 2.

10. A method of producing a bactericidal composition substantially as hereinbefore described.

11. A bactericidal composition substantially as hereinbefore described.