CH655011A5 - METHOD FOR CONTROLLING THE ALTERATION OF TECHNICAL LIQUIDS USING NITROIMIDAZOLE DERIVATIVES. - Google Patents

Description

The present invention relates to a method of combating the alteration of technical fluids caused by strict anaerobic bacteria which are sulfatoreductive.

The deterioration of technical liquids (either organic liquids containing water or aqueous liquids containing organic products), caused by the proliferation of microorganisms which meta-

bole organic product with parallel formation of harmful metaioli, is a widespread problem in many branches of industry. This growth of microorganisms requires the presence of free water in the organic liquid (oil for example) since, although microorganisms can often pass into the organic phase, their growth and their activity are mainly confined in the aqueous phase . It is practically impossible to exclude from the organic liquid the small initial quantities of water required for the beginning of the growth of microorganisms and, in fact, water is deliberately incorporated, in greater or lesser quantity, in many organic liquids used in industry.

A wide variety of bacteria, molds and yeasts are responsible for spoiling bodily fluids, and it is virtually impossible to exclude all of these microorganisms from such fluids. As examples of organic liquids and aqueous liquids containing organic products subject to bacterial deterioration, mention may be made of mineral and vegetable oils and industrial liquids which contain them, in particular combustible oils, lubricants, hydraulic fluids based on mineral oil. , oil-in-water emulsions (O / W, for example cutting oils), water-in-oil emulsions (E, H, for example hydraulic fluids based on these emulsions), aqueous solutions and emulsions of glycols used as liquids 'machining.

Other aqueous liquids containing organic products subject to serious bacterial deterioration include water-based paints, residual pulp solutions with sulfite, and even mainly inorganic fluids such as process water, electroplating solutions and injection water for oil wells.

The alteration of organic liquids and aqueous liquids containing organic materials (for example mineral or vegetable oils) due to bacterial proliferation can have the effect of:

- corrosion of metal tanks (for example during fuel storage, extraction and processing of mineral oils) or machine tools (for example in the machining, drilling, grinding and rolling of metals ), the alteration affecting the machining liquids used as lubricants and coolants during metalworking;

- the decomposition of additives in lubricating oils, with the consequence of reducing the lubricating properties of oils;

The reduction of the emulsifiers of the sulfate or sulfonate type, the reduction or the oxidation of the emulsifiers and corrosion inhibitors containing nitrogen, with as a consequence the deterioration or the instability of the O / W and W / O emulsions;

- reduction of the oil / water interfacial tension in the fuel tanks, which leads to poor separation of the water and contamination of the fuel by this water;

- the clogging of pipes, filters and orifices by bacterial bodies.

The oxygen content in organic liquids and aqueous liquids containing organic products used in industry is often low and can be further reduced by the growth of aerobic or optional aerobic microorganisms, which promotes the growth of strict sulfatoreductive anaerobes.

In the present text, strict anaerobic sulfatoréducteur means a strict anaerobic micro-organism capable of metabolically extracting oxygen from a compound which contains sulfur in the oxidized state by bringing it to a reduced state (generally hydrogen sulfide ) or capable of metabolically reducing elemental sulfur to hydrogen sulfide. Examples of strict anaerobic bacteria responsible for industrial alterations include: Desulfovibrio desulfuricans. Desulfovibrio gigas and Desulfotomaculum nigrificcms (Clostridium nigrificans or Desulfovibrio orientisi.

Strict sulphator reducing anaerobes metabolically reduce sulphates and sulphonates such as emulsifiers containing sulphates and sulphonates, for example alkyl sulphate emulsifiers

5

10

15

20

25

30

35

40

45

50

55

60

65

3

655 Oli and alkylarylsulfonates, sulfur oils and greases and sulfate ions present in water, with release of hydrogen sulfide. This results in particularly severe problems of deterioration in organic liquids and in aqueous liquids containing organic products [for example mineral and vegetable oils (combustible or lubricating oils), Hydraulic suides based on mineral oil, O / W emulsions (machining fluids), W / O emulsions (eg hydraulic fluids), aqueous glycol solutions or emulsions used as machining fluid], with the production of foul smells, corrosion due to the release of hydrogen sulfide and destruction of emulsifiers, which leads to deterioration and instability of the emulsions.

Strict sulfatoreductive anaerobic bacteria cause similar problems in sulfite pulp waste water, water-based paints, oil injection water, waste water, electroplating solutions, sealed circuits of cooling (temperature exchangers and heating and water cooling systems), hot water storage and distribution systems, and in the gas joints of gasometers.

This deterioration causes particularly troublesome problems in the water which settles at the bottom of the tanks of heating oils and in the injection water for oil drilling.

O / W emulsions and aqueous glycol solutions or emulsions used as machining liquids, for example as coolants for rolling mills or machine tools, which contain mineral or vegetable oils or glycols, emulsifiers, inhibitors of corrosion and water with, if desired, greases, soaps and small amounts of special additives serving as plasticizers, defoamers and high pressure additives, are widely used in metalworking. These liquids perform a number of functions, in particular lubrication and reduction of the temperature at the workpiece-tool interface, prolonging the life of the tool, elimination of chips and filings, and cooling of the metal sheet during operations. rolling or stamping. For reasons of economy it is essential that the machining liquid can be recycled. Such a liquid normally contains 1 to 15% by volume of oil and / or glycols and is used at temperatures ranging from ambient temperature to 40-60 ° C. Thus the coolants of machine tools operate at temperatures just above the ambient. Their oil and / or glycol content varies from 1% in grinding coolers (where the elimination of heat, to maintain dimensional accuracy, is of primary importance) to 15% in severe machining operations where lubrication is an essential necessity. Coolants for rolling mills generally have an oil and / or glycol content of 2 to 5% and work at a higher temperature, often from 40 to 60 ° C.

These machining liquids are quite sensitive to bacterial contamination and their oxygen content often becomes very low, especially when the liquid is not in use. This fact promotes the growth of strict sulfator-reducing bacteria, which leads to the problems mentioned above.

The fight against this bacterial alteration is therefore of major importance for the recycling of various machining fluids.

Attempts have already been made to prevent this alteration by incorporating various biocides, but the properties required of a satisfactory product are extremely severe and relatively few of them have had commercial success. Thus such a product, apart from its effectiveness in destroying or inhibiting the growth of microorganisms, must preferably be non-toxic and non-irritant, have satisfactory stability over a suitable duration in the appropriate temperature and pH ranges, have a preferential solubility in water to be there at an adequate concentration, non-preferential solubility in the organic phase, and to be compatible with the system to be protected (for example not to affect the characteristics and the stability of the emulsions, not to cause do not modify the system pH and, in the case of heating oil

20

or in machining, do not produce unwanted ash during combustion).

Various phenols (e.g. p-chloro m-cresol and phenol), heavy metal compounds, formaldehyde-generating products and other biocidal products have already been used, with varying degrees of success, but the safety of many of them has been questioned. There is therefore a permanent need for a new method of combating alterations due to the growth of strict anaerobic bacteria which are sulfatoreductive.

10 It is known that (2-hydroxyethyl) -1 2-methyl-5-nitroimidazole (hereinafter referred to as metronidazole), 1,2-dimethyl-5-nitroimidazole (hereinafter dimetridazole), (2-hydroxypropyl) -1 methyl-5-nitro-imidazole (hereinafter secnidazole) and 2-methyl-isopropyl-5-nitro-imidazole (hereinafter ipronidazole) are active against pro-15 tozoans, amoebas and certain anaerobic bacteria that can infect humans and animals.

Strict sulfa-reducing anaerobic bacteria are not a recognized cause of infections in humans and animals, and to date it has not been suggested that these products are effective against strict sulfating-reducing anaerobic bacteria in human or veterinary medicine. nor that they are effective in combating the deterioration of technical fluids caused by the aforementioned bacteria.

Metronidazole, dimetridazole, secnidazole and ipronidazole therefore did not present themselves to specialists in search of new ways to combat the deterioration of industrial liquids due to these microorganisms, and it did not appear that these products have the combination of other properties necessary for them to be used successfully.

3 °

It has now been unexpectedly found that the nitroimidazole derivatives of dimetridazole, metronidazole, secnidazole and ipronidazole can be used in this fight. It is understood that the term "nitro-imidazole derivatives" used below means dimetridazole, metronidazole, secnidazole and ipronidazole.

The present invention therefore relates to a process for combating industrial contamination caused by strict anaerobic bacteria which are sulfatoreductive in organic industrial liquids containing water or in aqueous industrial liquids containing organic products, this process comprising incorporating into the aqueous phase of a sufficient amount of at least one ni-tro-imidazole derivative as defined to prevent the growth of said bacteria.

The concentration of nitro-imidazole derivatives (which, according to the invention, can be used separately or simultaneously) is generally between 100 and 500 ppm (more especially 100 ppm) relative to the total volume of the liquid to be protected. However, lower or higher concentrations can be used, depending on the particular problem to be solved, the suitable concentration being easily determined by appropriate tests.

Nitro-imidazole derivatives do not have preferential solubility in the organic phase of organic liquids containing water or aqueous liquids containing organic products, they are sufficiently soluble in the aqueous phase to give effective concentrations prohibiting the proliferation of said bacteria, they are neither toxic nor irritating, unlike most agents previously used for the same purpose, they have satisfactory stability for a sufficient time in the appropriate temperature and pH ranges, they do not harm the characteristics 60 ques neither to the stability of the O / W or W / O emulsions, cause neither foam nor foam, do not affect the pH and are not a source of undesirable ash.

The nitro-imidazole derivatives used in the process according to the invention can be added as such to industrial liquids to be treated, but they are preferably added in the form of solutions, suspensions or emulsions in suitable solvents such as water, glycols (e.g. ethylene glycol), dimethylformamide, dimethylacetamide, liquid hydrocarbons (e.g. kero-

655 Oli

4

sene) and their mixtures which may, if necessary, contain one or more surfactants.

A suitable formulation consists, for example, of a suspension prepared by mixing the following ingredients (weight / volume):

dimetridazole microfin 25%

Texofor M6 4%

Arylan CA 6%

Attagel 50 1%

Kerosene (deodorized) qs 100% by volume

Texofor M6 is an ethoxylated oleic acid containing 6 mol of ethylene oxide per mole of oleic acid;

Aryan CA is calcium dodecylbenzenesulfonate;

Attagel 50 is a swelling clay of the attapulgite type.

Concentrates can also be prepared which, after dilution with the appropriate amount of water, can prepare machining liquids which contain the oils and / or glycols, emulsifiers and corrosion inhibitors usual in these concentrates and a proportion of derivatives of nitro-imidazole sufficient to give, after dilution, the desired concentration in the machining liquid obtained. The concentrate generally contains 0.05 to 5% W / V of the nitroimidazole derivative.

If desired, the aforementioned nitro-imidazole derivatives can be used in combination with known agents as mentioned above, for example phenols, heavy metals or formaldehyde generating products.

Said nitro-imidazole derivatives also make it possible to combat the alteration caused by nitratoreductive and nitri-toreductive bacteria in industrial liquids (organic and containing water, or aqueous and containing organic materials).

Trial I

a) Metronidazole

The advantageous properties of the abovementioned nitro-imidazole derivatives are demonstrated in tests 1 to 4 below.

Tests I to 4:

5 A ctiritê against strict anaerobic bacteria sulfatoréductrices Method I

The test products are incorporated (by adding the appropriate quantity of their aqueous solution at 5000 ppm) at concentrations of 50, 100, 250 and 500 ppm in an HE emulsion highly contaminated by sulfatoreductive bacteria (previously, took samples contaminated emulsion, free from the tested products, which will serve as controls). Samples of the contaminated oil are taken immediately after the addition of the test product, and after 3. 5 and 24 h.

Iron sulfite agar (Oxoid Ltd.) is prepared and distributed into tubes (10 cm3 per tube). It is sterilized in an autoclave at 1 bar (102 kPa) for 15 min and the tubes are capped with Astell caps which ensure a hermetic closure and thus allow anaerobic growth.

20

The tubes are placed in a water bath at 50 ° C to maintain the agar in the liquid state, seed with a loop (1.50 cm3) of the contaminated H'E emulsion and incubate at 37 ° C for 5 d.

The tubes are then rated according to the scale below:

25 + + + + + completely black - no inhibition

+ + + + good growth, but not completely black

+++ gray-black inhibition spots and grows

++ gray with black spots

+ clear except for a few black spots

30 0 clear - complete inhibition

The following results are obtained:

Metronidazole concentration (ppm)

Contact time with metronidazole

At once

3 hrs

5 a.m.

24h

0 (witness)

+ + + + +

. +++++

4-4-4-4-4-

-1 — i- 4 -! - b

50

+ + + + +

4-4-4-4-4-

4-4- +

+ +

100

+ 4 — h + +

4-4-4-4-4-

+ +

+

250

+ + + +

4-4-4-

+

0

500

+ + +

4-4-

+

0

b) Dimetridazole

Dimetridazole concentration (ppm)

Contact time with dimetridazole

At once

3 hrs

5 a.m.

24h

0 (witness) 50 100 250 500

+ + + + + + + + + + + + + + + + + + + + +

+ + + + +

4 — f- 4 — î- + + +

+ +

+

+ + + + + + + + + + + +

+

0

+ 4 — h + + + + +

+

0 0

Trial 2

a) Metronidazole

Metronidazole concentration (ppm)

Contact time with metronidazole

At once

3 hrs

5 a.m.

24h

0 (witness) 100 200 500

4—1- + + + + + + +

+ + + + + + +

+ 4 — h + + + +

+ +

+

+ + + + +

+

+

+ + + + +

+

0

655 Oli b) Dimetridazole

Dimetridazole concentration (ppm)

Contact time with dimetridazole

At once

3 hrs

5 a.m.

24h

0 (witness)

+ + + +

+ + + +

+ + + +

+ + + +

100

4- + 4- +

+ + +

+

0

200

+ + +

+

0

0

500

+ * + *

0

0

0

Trial 3

a) Metronidazole

Metronidazole concentration (ppm)

Contact time with metronidazole

At once

3 hrs

5 a.m.

24h

25

-1—1 -! - H

+ + +

+ + +

+ + +

50

+ + + +

+ + +

+ + +

+ + +

100

+ + + +

+ + +

+

+

b) Dimetridazole

Dimetridazole concentration (ppm)

Contact time with dimetridazole

At once

3 hrs

5 a.m.

24h

15

+ + + +

+ + +

+ +

+ +

50

+ + + +

+ + +

+ +

+ +

100

+ + + +

+ + +

+

+

Test 4:

Method II

In flasks containing 100 cm3 of aqueous solution at 50, 100, 250 or 500 ppm of the product to be tested, 0.1 cm3 of an O / W emulsion highly contaminated with strict anaerobic sulfatoreductive bacteria is added. A control flask is also prepared without the product to be tested. We take samples:

- from the control flask, immediately after adding the oil, 40

- of all vials, after 3, 5, 24 and 48 h.

Iron sulfite agar (Oxoid Ltd.) is prepared and distributed into tubes (10 cm3 per tube). We sterilize in the autoclave under

1 bar (102 kPa) for 15 min and the tubes are capped with Astell caps which ensure a hermetic closure and thus allow anaerobic growth.

The tubes are placed in a water bath at 50 ° C. to maintain the agar in the liquid state, the seeds are inoculated with a loop (1.50 cm 3) of the contaminated O / W emulsion and incubated at 37 ° C. for 7 d. Note the action of the products tested on the strict anaerobic sulfatoreductive bacteria present in the contaminated emulsion, as described above. The following results are obtained:

a) Metronidazole

Metronidazole concentration (ppm)

Contact time with metronidazole

At once

3 hrs

5 a.m.

24h

48 h

0 (witness) 50 100 250 500

+ + + + +

+ + + + + + + + + + + + + + + +

-1—1 — i — h + + +

+ + + + + + + + + + + +

H — h +

-i — h + ^ —h

-1 — i — h +

0 0

+ + + + + + +

0 0 0

b) Dimetridazole

Dimetridazole concentration (ppm)

Contact time with dimetridazole

At once

3 hrs

5 a.m.

24h

48 h

0 (witness) 50 100 250 500

H — i — 1—1— | -

+ + + + +

H — H H -! - h + • + +

+ +

+

+ + + + +

H — 1—1 — f- + +

+

0

+ + + + + + + +

+

0 0

- \ - h H — 1 — l- + +

0 0 0

655 Oli 6

c) Ipronidazole

Ipronidazole concentration (ppm)

Contact time with ipronidazole

At once

3 hrs

5 a.m.

24h

48 h

0 (witness)

4-4-4-4-4-

4-4-4-4-4-

4 — i — h 4 — b

H — i — b 4 — b

"1 — b 4- ~ i — b

50

-

4-4-4-4-4-

4-4-4-4-

+ + +

+ +

100

-

4 — h H — h

4-4-4-

4-4-

+

250

-

4-4 — b

H — h

+

0

500

-

+ + +

+

0

0

d) Secnidazole

Secnidazole concentration (ppm)

Contact time with secnidazole

At once

3 hrs

5 a.m.

24h

48 h

0 (witness) 50 100 250 500

4-4-4-4-4-

4-4-4-4-4-4-4-4-4-4--1—1 — b H — b 4-4-4-4-4-4-4-

4 — b H — 1 — b

H — i — b H — b + + + +

+ +

+

4-4-4-4-4-

H — i — 1 — b + + +

0 0

-i — i — 1 -! - b

-î — i — b +

0 0

e) Kathon MW 886

Kathon MW 886 concentration (ppm)

Contact time with the Kathon MW 886

At once

3 hrs

5 a.m.

24h

48 h

0 (witness) 50 100 250 500

4-4-4-4-4-

4- -b "b -b -b + + + + +

+ + + + + + + + +

-b "b 4-

-b -b + + -b + + + +

+ + + +

-b "b -b + +

4-4-4-4-4-

-b H — b + + +

+ +

+

4-4-4-4-4- + +

4-0 0

f) Grotan TK2

Grotan TK2 concentration (ppm)

Contact time with Grotan TK2

At once

3 hrs

5 a.m.

24h

48 h

0 (witness) 250 500 750 1000

4 "-b ~ b" b "b

+ + + + + + + + + +

-b -b -b -b

4 "H — b +++

4-4-4-4-4-4-4-4-4-4-4-4-4-

4-4- +

4-4-4-4-4-4-4-4-

4-4-4- +

0

H — b H — 1 — b + +

4 — b 0 0

g) Bodoxin

Bodoxin concentration (ppm)

Contact time with Bodoxin

At once

3 hrs

5 a.m.

24h

48 h

0 (witness) 250 500 750 1000

4-4-4-4-4-

4-4-4-4-4-4-4-4-4-4-4-4-4-4-4-4-4-4-4- +

4-4-4-4-4-4- 4—1 — b 4-4-4-4- 4-4-

4-4-4-4-4 * 4-4-4-4-4-4-0

4-4-4-4-4-4-4-4-0 0

Kathon MW 886, Grotan TK2 and Bodoxin are commercial industrial biocides used to combat strict anaerobic sulfatoreductive bacteria.

The results obtained in trials 1, 2, 3 and 4 confirm that metronidazole, dimetridazole, ipronidazole and secnidazole inhibit the production of sulfide by strict anaerobic sulfatoreductive bacteria, the effective concentration in these trials 1 to 4 being close 100 ppm. The effective concentration for Kathon MW 886, which can cause severe skin and skin irritation

6 ”eyes, is also close to 100 ppm. For Grotan TK2 and Bodoxin, the effective concentration is higher, around 500 ppm.

The compatibility of the nitro-imidazoles according to the invention with machining fluids of the H E emulsion type, prepared from commercial con-65 centers, is demonstrated by tests 5 to 8 below, in which the concentrates are:

Concentrate A: emulsion for ordinary cutting oil - used at a dose of 2 to 3% V V (by volume).

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Concentrate B: ordinary cutting oil - used at a dose of 1 to 4% V / V.

Concentrate C: rolling oil for aluminum which decomposes on pinching the cylinders and then regenerates - used at a dose of 5% V / V.

Concentrate D: semi-synthetic formulation for cutting oil - used as cutting oil at a dose of 1 to 2% V / V.

Concentrate E: ordinary cutting oil - used at a dose of 3 to 5% V / V.

Concentrate F: cutting oil for high-grade finisher - used at a dose of 3% V / V.

Concentrate G: aqueous, oil-free sharpening fluid - used at a dose of 2% V / V.

Test 5:

Emulsion stability

Cutting and rolling oils used in the form of O / W emulsions must maintain their emulsion stability during use. This test checks the stability of these emulsions by noting the tendency of the oil droplets to come together, which is an indication of instability.

O / W emulsions containing commercial concentrates are prepared according to the following technique [standardized test (IP) 263/70 of the British Petroleum Institute]:

The concentrate and distilled water are brought separately to 20 + 4: C. The appropriate volume of water is stirred in a 500 cm 3 conical flask, with a magnetic stirrer, at a speed sufficient to form a vortex just deep enough to reach the bottom of the flask. Using a hypodermic syringe without needle, quickly add the appropriate volume of concentrate, then the appropriate volumes of aqueous solution at 5000 ppm of dimetridazole, metronidazole or ipronidazole to obtain contents of 50, 100, 250 and 500 ppm in the emulsion (total volume 200 cm3), and the mixture is further stirred for 2 min. Control emulsions without dimetridazole, metronidazole or ipronidazole are prepared in the same way. The emulsions are then left to stand at room temperature for 24 h.

A sample of the emulsion is then diluted to 1/2000 with Steriflex No. 1 Saline solution (Allen and Hanbury Ltd.) and the dimensional distribution of the “large” oil droplets is determined in a sample of 0.5 cm3 of this dilution using a Coulter counter (Coulter Electronics Ltd.) with an orifice of 100 (im connected to a P 64 recording analyzer. The emulsions are still left for 7 d and the dimensional distribution of the oil droplets is again determined using the same Coulter counter setup to allow direct comparisons.

As is normal with O / W emulsions which have remained at rest for several days, a separation between oil, coagulate and cream is observed between the two determinations. Before taking the sample for the second determination, the flasks are shaken for 30 s, rotating alternately to the right and to the left.

The following results are obtained:

a) H! E emulsion at 2% Vf V of concentrate A

Metronidazole: an increase in droplets of 2-5 jim3 per 100 ppm of metronidazole at 7 d indicates a very slight instability.

Dimetridazole: stability at 7 d increased slightly, particularly at 50 ppm dimetridazole

Ipronidazole: no significant decrease in stability at 7 d.

b) HjE emulsion at 1% Vi V of concentrate B:

Metronidazole: stability at 7 d slightly improved.

Dimetridazole: slight instability at 7 d for 250 ppm.

Ipronidazole: no significant change in stability at 7 d.

c) O / W emulsion at 3% V / V of concentrate F:

Metronidazole: unchanged at 7 d.

Dimetridazole: unchanged at 7 d.

5 d) H emulsion! E at 3% V / V of concentrate E:

Metronidazole: slight improvement in stability at 7 d.

Dimetridazole: the stability at 7 d is within satisfactory limits.

Ipronidazole: very slight drop in stability to 7 d.

io e) O / W emulsion at 1% VjV of concentrate D:

Metronidazole: unchanged at 7 d.

Dimetridazole: slight improvement in stability at 7 d.

Ipronidazole: very slight decrease in stability to 7 d in the O / W emulsion containing 250 ppm of ipronidazole.

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f) Emulsion H) E at 2% V / V of concentrate G:

Ipronidazole: no significant change at 7 d.

g) O / W emulsion at 2% VI V of concentrate C:

Metronidazole: unchanged.

Dimetridazole: unchanged.

Ipronidazole: very slight drop in stability to 7 d.

These results show that the incorporation of dimetridazole, metronidazole or ipronidazole at concentrations of 50, 100, 250 and 500 ppm in the O / W emulsions has no significant negative action on the emulsion stability.

Test 6:

30 Corrosion

This test checks the ability of O / W emulsions to prevent rusting of machines and products during machining operations, using the following technique (IP 287/74):

The iron shavings are washed with pure acetone without touching them by hand, and they are dried in an oven at 48 ° C. Once dry, the shavings are passed through a 25 mesh English sieve (opening of 0.67 mm , substantially equivalent to the AFNOR module 29 sieve) by rejecting fines.

A 35 mm square is drawn in pencil in the center of a filter paper (Whatman No. 5, qualitative, 90 mm) which is placed at the bottom of a Petri dish. Using a spatula and a template, the square is covered with a single layer of chips. We remove the template and pipette on the shavings doses of 2 cm3 of emulsions (prepared as in test 5) containing a range of concent-45 tr levels, so that the entire surface of the box is covered and that the shavings are well wetted. The lid is then placed on the box. After 2 h, the filter paper is removed, washed with tap water and allowed to dry. We place a transparent grid on the square, we appreciate the stained surface and we express it in percent. To make the estimation easier, the rusty surface must occupy 10 to 60% of the square. This determines the critical dilution at which a significant increase in the stained area appears. For each concentrate, a series of O / W emulsions at critical dilution containing 50,100, 250 or 500 ppm of metronidazole, dimetridazole or 55 ipronidazole are prepared and these emulsions are subjected to the same test. The results are as follows:

a) O / W emulsion at 2.5% concentrate A

Nitro-imidazole concentration (ppm)

Stained area (%)

Metronidazole

Dimetridazole

0 (witness)

8

2

50

10

4

100

10

6

250

1

8

500

0

10

20

25

655 Oli

8

A slight decrease in the stained area is observed for 250 and 500 ppm of metronidazole. Repeated tests confirm this observation. Slight increase in the area stained with dimetridazole.

b) H! E emulsion at 4% V / V of concentrate B

f) H E emulsion at 5 "» V V of concentrate E

Nitro-imidazole concentration (ppm)

Stained area (%)

Metronidazole

Dimetridazole

Ipronidazole

0 (witness)

15

15

65

50

20

18

60

100

30

25

60

250

35

30

40

500

40

40

50

Nitro-imidazole concentration (ppm)

Stained area (%)

Metronidazole

Dimetridazole

0 (witness)

50

20

50

60

20

100

50

20

250

70

40

500

70

50

Nitro-imidazole concentration (ppm)

Stained area (%)

Metronidazole

Dimetridazole

0 (witness)

25

20

50

30

25

100

25

30

250

20

35

500

20

45

These results show that, at the concentrations tested, neither metronidazole nor dimetridazole significantly interfere with the anticorrosive properties of the emulsions.

There is a slight increase in the stained area with both metronidazole and dimetridazole, a slight decrease with ipronidazole. 20

c) O / W emulsion at 5% VI V of concentrate C

g) O / W emulsion at 2 "o V V of concentrate G

Nitro-imidazole concentration (ppm)

Stained area (%)

Ipronidazole

0 (witness)

15

50

3

100

3

250

3

500

3

30

There is a slight decrease in the stained area.

There is a slight increase in the stained area for both metronidazole and dimetridazole.

d) Ht E emulsion at 2% V "V of concentrate D

Nitro-imidazole concentration (ppm)

Stained area (%)

Metronidazole

Dimetridazole

Ipronidazole

0 (witness)

40

35

30

50

40

40

25

100

40

50

55

250

40

50

30

500

40

40

15

There is no change with metronidazole, but a slight increase in rust with dimetridazole; with ipronidazole, there is a slight increase at 100 ppm and a slight decrease at 50, 250 and 500 ppm.

Test 7:

3J Action on pH

H E emulsions are prepared as indicated in test 5 and the pH is measured on days 1 and 7 after the preparation, using a pH meter equipped with an Ingold electrode. The following results are obtained;

40

a) 2.5% V V emulsion of concentrate A

Nitro-imidazole concentration (ppm)

pH

Metronidazole

Dimetridazole

Ipronidazole day 1

day 7

day 1

day 7

day 1

day 7

0 (witness)

8.8

8.6

8.9

8.8

9.76

9.21

50

8.8

8.7

8.9

8.8

9.97

9.93

100

9.0

8.6

8.9

8.8

9.76

9.30

250

8.9

8.6

8.8

8.8

9.88

9.50

500

8.8

8.6

8.8

8.8

9.95

9.81

e) O / W emulsion at 3% V / V of concentrate F

Nitro-imidazole concentration (ppm)

Stained area (%)

Metronidazole

Dimetridazole

0 (witness)

40

45

50

60

20

100

30

45

250

30

30

500

30

25

There is a slight variation with metronidazole and dimetridazole.

b) Emulsion at 4lo V ', V of concentrate B

Nitro-imidazole concentration (ppm)

pH

Metronidazole

Dimetridazole

Ipronidazole day 1

day 7

day 1

day 7

day 1

day 7

0 (witness)

9.4

9.0

9.2

9.0

9.78

8.89

50

9.2

9.0

9.2

9.0

9.81

9.17

100

9.2

8.9

9.2

9.0

9.89

9.20

250

9.2

9.0

9.2

9.0

10.10

9.35

500

9.2

9.0

9.2

9.0

9.94

9.26

9

655 Oli c) 5% VjV emulsion of concentrate C

Nitro-imidazole concentration (ppm)

PH

Metronidazole

Dimetridazole

Ipronidazole day 1

day 7

day 1

day 7

day 1

day 7

0 (witness)

8.2

8.0

8.2

8.0

8.40

8.46

50

8.2

8.0

8.2

8.1

8.43

8.53

100

8.1

8.0

8.2

8.0

8.41

8.50

250

8.2

8.1

8.2

8.0

8.43

8.50

500

8.2

8.0

8.2

8.0

8.68

8.81

d) 2% VjV emulsion of concentrate D

Nitro-imidazole concentration (ppm)

pH

Metronidazole

Dimetridazole

Ipronidazole day 1

day 7

day 1

day 7

day 1

day 7

0 (witness)

9.4

9.2

9.4

9.2

9.63

9.00

50

9.4

9.2

9.3

9.2

9.72

9.10

100

9.4

9.0

9.4

9.2

9.69

9.18

250

9.4

9.2

9.4

9.2

9.85

9.26

500

9.4

9.2

9.4

9.2

9.81

9.14

e) 5% V / V emulsion of concentrate E

Nitro-imidazole concentration (ppm)

pH

Metronidazole

Dimetridazole

Ipronidazole day 1

day 7

day 1

day 7

day 1

day 7

0 (witness)

9.5

9.2

9.4

9.2

9.94

9.53

50

9.4

9.2

9.4

9.3

10.01

9.60

100

9.4

9.2

'9.4

9.2

9.98

9.60

250

9.4

9.2

9.5

9.3

9.98

9.54

500

9.5

9.3

9.5

9.3

10.02

9.60

0 3.5% V / V emulsion of F concentrate

Nitro-imidazole concentration (ppm)

pH

Metronidazole

Dimetridazole day 1

day 7

day 1

day 7

0 (witness)

9.1

9.0

9.0

8.9

50

9.0

8.9

9.1

8.9

100

9.1

8.9

9.1

9.0

250

9.1

9.0

9.0

8.9

500

9.1

9.0

9.0

9.0

g) 2% V / V emulsion of concentrate G

Nitro-imidazole concentration (ppm)

PH

Ipronidazole day 1

day 7

0 (witness)

10.01

9.06

50

10.18

9.54

100

10.12

9.48

250

10.12

9.56

500

10.16

9.56

These results show that at the concentrations tested, neither metronidazole nor dimetridazole nor ipronidazole affect the pH of the emulsions in significant proportions.

Test 8:

Foaming characteristics

This test (IP 312/74) makes it possible to determine the foaming characteristics of the emulsions, according to the following technique:

O / W emulsions are prepared according to the method of test 5, but by replacing the distilled water with synthetic hard water [calcium sulphate solution of total hardness equivalent to 200 + 10 ppm of calcium carbonate, prepared by dissolving 0.344 g S04Ca, 2H20 in 1 l of distilled water].

100 cm3 of emulsion are poured into a 250 cm3 graduated cylinder, it is capped and stirred vigorously for 15 s. Then place the test piece vertically and note the total volume (foam and liquid) immediately and after 1, 5, 10 and 15 min. Foam can also form on top of the foam, but this foam tends to burst leaving pockets of air and it is difficult to assess the height of the foam. The foam, being denser, is seen better and, for convenience, it is the level of foam which is noted.

With concentrate C, dilution with synthetic hard water produced a precipitate, which was not altered by the addition of metroni-dazole, dimetridazole or ipronidazole. The test was repeated by diluting the concentrate C with distilled water, and it is the results concerning this dilution which are reported below.

The results are as follows:

a) Emulsion at 1% V / V of concentrate B

Metronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

120

100

100

100

100

50

120

101

100

100

100

100

120

100

100

100

100

250

120

100

100

100

100

500

125

101

100

100

100

Dimetridazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

130

100

100

100

100

50

120

100

100

100

100

100

120

100

100

100

100

250

130

100

100

100

100

500

130

100

100

100

100

Ipronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

202

174

152

142

131

50

182

176

164

132

130

100

194

182

154

138

134

250

198

188

158

134

132

500

198

184

154

141

131

b) 1% VjV emulsion of concentrate D

Metronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

> 250

> 250

250

150

140

50

> 250

> 250

250

140

125

100

> 250

> 250

235

150

135

250

> 250

> 250

250

140

130

500

> 250

> 250

250

145

130

> 250 = level of foam above the line 250 cm3.

655011

10

Dimetridazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

> 250

> 250

250

140

125

50

> 250

> 250

250

150

130

100

> 250

> 250

240

135

120

250

> 250

> 250

250

150

135

500

> 250

> 250

250

145

125

> 250 - level of foam above the line 250 cm3.

Ipronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

190

190

188

146

132

50

193

188

146

138

130

100

206

204

126

124

122

250

192

176

162

140

130

500

212

190

140

128

120

c) 3% Vf V emulsion of concentrate F

Metronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

150

108

105

104

104

50

145

110

108

106

106

100

130

112

108

106

104

250

140

108

106

104

104

500

160

108

104

104

102

Dimetridazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

145

106

104

104

102

50

140

108

106

104

104

100

150

108

108

106

104

250

145

110

106

104

104

500

160

108

104

104

102

d) Emulsion at 3% VjV of concentrate E

Metronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

> 250

> 250

220

170

150

50

> 250

> 250

230

170

150

100

> 250

> 250

230

150

140

250

> 250

> 250

> 250

160

140

500

> 250

> 250

240

180

140

> 250 = level of foam above the line 250 cm3.

Dimetridazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

> 250

> 250

210

140

140

50

> 250

> 250

220

170

150

100

> 250

> 250

210

180

160

250

> 250

> 250

240

180

160

500

> 250

> 250

220

170

150

> 250 = level of foam above the line 250 cm3.

Ipronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

168

108

102

102

100

50

172

1 ~ i ~ i

110

104

102

100

168

118

108

104

102

250

166

120

108

106

102

500

192

114

106

104

102

e) Emulsion at 2 ".o Y V of concentrate A

Metronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

140

103

101

100

100

50

130

106

104

101

100

100

140

104

102

100

100

250

135

106

104

101

100

500

140

106

105

104

102

Dimetridazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

135

103

101

101

101

50

150

110

101

101

100

100

155

112

102

100

100

250

130

101

101

100

100

500

140

104

101

100

100

Ipronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

246

122

114

110

106

50

230

116

114

110

102

100

212

140

128

118

114

250

202

128

112

110

106

500

> 250

116

108

104

100

> 250 = level of foam above the line 250 cm3.

0 3% VjV emulsion of concentrate C

Metronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

101

100

100

100

100

50

100

100

100

100

100

100

100

100

100

100

100

250

100

100

100

100

100

500

100

100

100

100

î 00

Dimetridazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

102

100

100

100

100

50

100

100

100

100

100

100

100

100

100

100

100

250

100

100

100

i 00

100

500

100

100

100

100

100

5

10

15

20

25

30

35

40

45

50

55

60

65

11

655 Oli

Ipronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

152

132

116

110

108

50

142

112

108

106

104

100

136

110

106

104

102

250

142

112

108

104

102

500

152

114

110

108

104

g) 2% VjV emulsion of concentrate G

Ipronidazole concentration (ppm)

Total volume after rest (min)

0

1

5

10

15

0 (witness)

100

100

100

100

100

50

100

100

100

100

100

100

100

100

100

100

100

250

100

100

100

100

100

500

100

100

100

100

100

These results show that the addition of metronidazole, dimetridazole or ipronidazole at the indicated concentrations does not cause significant differences in the foaming of the emulsions studied.

The following example illustrates a concentrate which makes it possible, after suitable dilution with water, to obtain a machining liquid according to the invention.

Example:

A suspension is prepared by mixing: Dimetridazole microfin Texofor M6 Arylan CA Attagel 50

Deodorized kerosene q.s.p.

25% weight / volume 4% weight / volume 6% weight / volume 1% weight / volume 100% by volume

11 of this concentrate is mixed with 99 l of ordinary cutting oil concentrate and 1001 of concentrate containing 2500 ppm of dimetridazole is obtained. By diluting these 100 liters of concentrate in 24001 20 of water, 2500 liters of machining liquid containing 100 ppm of dimetridazole are obtained.

R

Claims (13)

655 Oli 1. A method of combating the deterioration of technical liquids, either organic and containing water, or aqueous and containing organic matter, by strict anaerobic bacteria, which is characterized in that the aqueous phase is incorporated into the at least one nitro-imidazole derivative chosen from dimetridazole, metronid-azole, secnidazole and ipronidazole in an amount sufficient to prevent the growth of said bacteria. 2. Method according to claim 1, characterized in that the technical liquid is a petroleum or vegetable oil containing water, or an aqueous liquid containing a petroleum or vegetable oil. 2 3. Method according to one of claims 1 or 2, characterized in that the technical liquid is a combustible or lubricating oil, a hydraulic fluid based on mineral oil, an O / W or W / O emulsion, a solution or aqueous emulsion of glycols for machining liquid, waste water from sulfite paper pulp, water-based paint, injection water for oil drilling, waste water, electroplating solution, sealed circuit cooling system, a hot water storage and distribution system or a gasometer water seal. 4. Method according to claim 3, characterized in that the O / W emul-sion is a machining liquid. 5. Method according to claim 3, characterized in that the W / O emul-sion is a hydraulic fluid. 6. Method according to one of claims 1 to 5, characterized in that, in an organic liquid containing water or in an aqueous liquid containing organic material, a solution, suspension or emulsion comprising at least one is added. nitro-imidazole chosen from dimetridazole, metronidazole, secnidazole and ipronidazole and water, glycols, ethyl oxalate, dimethylformamide, dimethylacetamide, liquid hydrocarbons or their mixtures and, if necessary, at least a surfactant. 7. Method according to one of claims 1 to 6, characterized in that 100 to 500 ppm of nitro-imidazole derivatives are incorporated, relative to the total volume of the technical liquid, in the aqueous phase of said liquid. 8. Method according to one of claims 1 to 6, characterized in that incorporates into the aqueous phase of the technical liquid 100 ppm, relative to the total volume of the technical liquid, nitro-imidazole derivatives. 9. Method according to one of claims 1 to 8, characterized in that the nitro-imidazole derivatives are used in combination with one or more agents for combating the alteration of said technical liquids. 10. Method according to claim 9, characterized in that the known agents are chosen from p-chloro m-cresol, phenol, compounds of heavy metals and formaldehyde generators. 11. Method according to one of claims 1 to 10, characterized in that the strict anaerobic bacteria which are sulfatoreductive are Desid-fovibrio desulfuricans, Desulfovibrio gigas and / or Desulfotomaculum ni-grificans. 12. Method according to one of claims 1 to 11, characterized in that the nitro-imidazole used is dimetridazole. 13. Method according to one of claims 1 to 11, characterized in that the nitro-imidazole used is metronidazole.