GB1602251A - Foam-generating aqueous compositions - Google Patents

Description

(54) FOAM-GENERATING AQUEOUS COMPOSITIONS (71) We, RHONE-POULENC INDUSTRIES, a French Body Corporate of 22, Avenue Montaigne, 75 Paris 8eme, France, 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: The present invention relates to foam-generating aqueous compositions which can in particular be used in the prevention of fires, or in fire-fighting.

In the text which follows the compositions according to the invention will be described by the term "concentrated emulsifier". They are compositions which can, after dilution with water, generate a foam on stirring. The composition obtained by diluting the concentrated emulsifier with water will be referred to as "foaming mixture".

It is known that protective foams, whatever their application, such as for dustcombatting, decontamination of confined spaces, protection against fire or fire-fighting, must combine various properties such as a high expansion ratio, a high foam stability over a period of time, a high water retention, and the ability to leave, after settling out, a protective film on the treated medium, or on the treated carrier. Furthermore, the foaming composition from which the foams are produced must exhibit good storage stability under use conditions. for example good resistance to low temperatures.

Though numerous compositions containing a variety of constituents have been proposed, concentrated emulsifiers which generate a foam which possesses, to a high degree, all the above-mentioned properties are not yet available. In general, the compositions of the prior art contain water, a surface-active agent, a foam stabiliser and an additive which acts as an anti-freeze and facilitates dissolving the various constituents of the mixture in the aqueous phase.

There have now been found according to the present invention, concentrated aqueous compositions which generate particularly stable foams having a high water retention capacity and producing a protective film after settling out, which aqueous compositions comprise water, a foaming surface-active agent, a foam stabiliser and an additive acting as an anti-freeze and a co-solvent as well as a hetero-polysaccharide of high molecular weight which results from the fermentation of a carbohydrate under the action of bacteria of the genus Xanthomonas.

The present invention provides an aqueous composition which contains A) from 70% to 30 Sc by weight of water and B) from 30% to 70% by weight of an organic mixture consisting of: A) from 10 to 60air of surface-active agent B) from 1 to 10% and preferably from 2 to 8% of foam stabiliser C) from 20 to 60ass of anti-freeze additive and D) from 1 to 309 of the hetero-polysaccharide.

The hetero-polysaccharides which are employed in the compositions of the invention are those which are obtained by fermentation of a great variety of carbohydrates (sugars and starches) under the action of bacteria of the genus Xanthomonas, for example the following species: Xaiidiornotias cantpestris, Xanthomonas begonia, Xanthomonas phaseoli, Xanthomonas heterae. Xanthomonas incanae, Xanthomonas carotae or Xanthomonas translucens, or of the genus Arthrobacter, or of a yeast of the genus Cryp to coccus, such as Cryptococcus laurentü, variety Flavescens.The processes for obtaining the above-mentioned heteropolysaccharides have formed the subject of numerous publications and patents (see, for example, United States Patents Nos. 3,020,206, 3,000,790 and 3,096,293). Amongst these various hetero-polysaccharides, those resulting from the fermentation of carbohydrates under the action of Xanthomonas campestris are preferably used.

The nature of the surface-active agent a) is not critical provided it is a foaming agent i.e.

one capable of producing a foam, and it is possible to employ ionic (cationic, anionic or amphoteric) or non-ionic compounds. These compounds are known and are widely described in the technical literature. As regards the choice of the surface-active agent, reference may be made, for example, to Kirk-Othmer, Encyclopaedia of Chemical Technology, volume 19, pages 512 to 566.

As examples of anionic surface-active agents which can be used in the composition of the invention there may be mentioned the alkali metal sulphonates, such as the alkylsulphonates, the arylsulphonates or the alkylarylsulphonates, in particular the alkylbenzenesulphonates such as sodium dodecylbenzenesulphonate, sodium tridecylbenzenesulphonate, sodium nonylbenzenesulphonate, sodium hexadecylbenzenesulphonate and sodium decylbenzenesulphonate, the alkali metal salts of dialkyl sulphosuccinates derived from long chain alcohols, such as the sodium salts of di-(2-ethylhexyl) sulphosuccinate, didecyl sulphosuccinate, dilauryl sulphosuccinate, dioctyl sulphosuccinate and ditridecyl sulphosuc ci nate, the dialkyl sulphates or the mixed alkyl/alkanolamine or alkyl/alkali metal sulphates such as sodium lauryl sulphate, ammonium lauryl sulphate, sodium 2-ethylhexyl sulphate and sodium olely sulphate.

Amongst the cationic surface-active agents which may be employed, there may be mentioned the quaternary ammonium salts of tertiary amines and especially of amines containing at least one aliphatic radical with a high carbon number, such as trimethylstearylammonium chloride or sulphate. lauryldimethylbenzylammonium chloride or sulphate, and myristyldimethylbenzylammonium chloride or sulphate.

Finally, as non-ionic surface-active agents, it is possible to employ, for example, the condensation products of ethylene oxide with fatty alcohols or with alkylphenols.

Amongst the abovementioned surface-active agents, the mixed sulphates of aliphatic fatty alcohols having at least 8 carbon atoms and of alkali metals, and the quaternary ammonium salts containing at least one aliphatic radical with at least 8 carbon atoms are particularly suitable and are used preferentially in the compositions of the invention.

The foam stabiliser b) is the product which is intended to prevent the foam from settling out; it is possible to employ a great variety of compounds which are well known to those skilled in the art. However, it is preferred to employ aliphatic fatty alcohols containing from 8 to 25 carbon atoms in the aliphatic radical, such as lauryl, myristyl and cetyl alcohol.

The anti-freeze is a glycol or polyol or an ether thereof, i.e. an ether of a glycol or polyol and an alkanol, these compounds containing at least 4 carbon atoms in total, such as diethylene glycol, diglyme and butoxyethanol.

The concentrated emulsifiers according to the invention can be obtained by adding the various ingredients together or separately to water which can, where appropriate, contain the anti-freeze; depending on the circumstances, it is also possible to dissolve or disperse one or two ingredients in the water and the other or others in the anti-freeze and then to mix the solutions and/or dispersions thus obtained.

To obtain foams from the compositions according to the invention, these compositions are first of all diluted by adding from. say, 10 times to 50 times their weight of water. The foaming mixture thus obtained is then stirred by means of a gas such as air, nitrogen or argon by the usual means well known to those skilled in the art, in order to generate the foam. For this purpose. it is possible to employ any type of apparatus which ensures sufficient dispersion of a gas in a liquid and vigorous stirring of the latter. The system may be a system for injecting a gas into a liquid by means of a nozzle and a Venturi tube or, for example, a system of stirring by means of a turbine.

Because of the properties which they exhibit, the compositions according to the invention can be employed for numerous applications. Thus they can be employed for combatting dust in enclosed spaces or in the open air: for example they can be used to free enclosed spaces. which have - accidentally or otherwise - been contaminated by toxic or radioactive dusts, from the contaminant by filling the said spaces completely with foam; they can also be employed to prevent the diffusion of dusts from a great variety of supports or carriers.

Thus. the dusts generated by a mineral conveyor such as a coal conveyor in the bottom of a mine can be suppressed: the foams can also be used to fix dusts which are present on a great variety of lumps of materials. for example charcoal or (hard) coal pitch.

The same process can be used to combat pollution of surfaces by accidental diffusion of particles of toxic or radioactive substances, for example on the ground. In this connection, the foams obtained by the process of the invention can be used to prevent the spreading resulting in greater contamination - of natural ground on which toxic or radioactive dusts have been dumped, prevention being by the formation of a protective film of hetero-polysaccharide on the surface of the ground.

Also, the compositions according to the present invention are particularly suitable for obtaining foams which are valuable for preventing fires or for fire-fighting. In fact, their ease of use, their high expansion ratio, their stability and their film-forming character make them particularly suitable for filling large volumes and for forming barriers which prevent the free circulation of a gas such as air which is necessary for combustion.

In this connection, it is possible to envisage the use of the compositions as a preventive.

In fact, these very stable aqueous foams can be used as protection in a place which is exposed to fire and is not accessible, for example a rear stall of a mine, especially of a coal mine. If this foam is directed into the rear stall, it acts as an air-tight barrier and prevents contact between the mineral and the air. The fines are stuck together, which results in a very great reduction in oxidation, and hence in the temperature rise of the mineral.

On the other hand, a foam which has a very low settling-out index can at one and the same time serve as a protective barrier against oxygen and as a cooling agent. In fact, the possibility, offered by an aqueous foam, of uniformly spreading (substantial) amounts of water in a heterogeneous solid, without a downwards migration of this water, allows one to consider this solid as being uniformly impregnated with water. If a rise in temperature takes place, the heat liberated is absorbed by the vaporisation of the water. This phenomenon can suffice to reduce or even stop an "in situ" oxidation reaction.

Furthermore, these foams also exhibit good stability to heat, so that they can be used advantageously for fighting fires, such as, for example, fires in hydrocarbon tanks. These foams also constitute an advantageous means of extinguishing a fire in a rear stall of a mine, in view of the fact that the aqueous foam is the only vehicle for water which can easily be introduced into a rear stall of a mine without damaging the equipment of the stall.

The Examples which follow further illustrate the invention.

Example 1 A foam having a swelling ratio of 10 is prepared by adding, to 95 parts by weight of water, 5 parts by weight of a concentrated foaming solution having the following composition by weight: A) 44.32C/c of an organic part containing: a) 32.5% by weight of sodium dodecyl sulphate b) 4.33cm by weight of lauryl alcohol c) 54.15CTF by weight of (3-butoxyethanol d) 9.02% by weight of a hetero-polysaccharide obtained by fermentation of a carbohydrate under the action of Xanthomonas campestris.

B) 55.68% of water.

The term swelling ratio (or degree of expansion) is applied to the ratio of the volume of foam to the volume of liquid from which it has been generated.

The foam thus obtained has a 50% settling out index of 100 hours (the term settling out index is applied to the time required by the foam to lose 50% of its weight).

By way of comparison, a foam with a swelling ratio of 10 was prepared in the same manner from an aqueous composition obtained by adding, to 95 parts by weight of water, 5 parts by weight of a foaming solution having the following composition by weight: A) 429 of an organic part containing: a) 35.71% of sodium dodecyl sulphate b) 4.76% by weight of lauryl alcohol c) 59.5% by weight of ss-butoxyethanol B) 58% of water.

The 50% settling out index was 20 minutes.

Example 2 Following the procedure in Example 1, 95 parts by weight of water are mixed with 5 parts by weight of a foaming mixture having the following composition by weight (relative to the sum of the water in the organic part taken as 100): water 52.2% sodium dodecyl sulphate 13.5% lauryl alcohol 1.8% ss-butoxyethanol 22.5% hetero-polysaccharide of Example 1 10% 5 Parts by weight of Raney nickel are then added to 95 parts by weight of the diluted foaming composition.

Using nitrogen as the carrier gas, a foam with a swelling ratio of 10 is prepared in an open 1 litre vessel. This foam is left for 48 hours exposed to the air, without observing the slightest incident, in spite of the pyrophoric character of the Raney nickel. After 48 hours the foam is destroyed by sprinkling with acetone. The acetone solution containing suspended nickel is centrifuged for 3 minutes at 3,000 g (acceleration due to gravity). The residue is taken up in 20 times its volume of water and the aqueous suspension is then stirred for 1 hour. Thereafter the Raney nickel is filtered under an inert atmosphere. After drying, it is found to ignite spontaneously in air.

Example 3 A foam having a swelling ratio of 75, obtained from a diluted foaming composition prepared by adding, to 95 parts by weight of water, 5 parts by weight of a concentrated foaming mixture having the following composition by weight: water 56.84% sodium dodecyl sulphate 14.7% lauryl alcohol 1.96% P-butoxyethanol 24.5% hetero-polysaccharide of Example 1 2 % is introduced into a 10 litre vessel filled with alumina spheres.

The foam fills all the voids between the spheres and covers the surface of the vessel. After 36 hours' storage, the foam still covers the alumina.

Example 4 A foam identical to that of Example 3 is introduced into a heap of coal which has been strongly aerated and which has an internal temperature of 40"C. After introducing the foam, it is found tha the temperature of the coal falls gradually to the ambient value. The foam, which constitutes a barrier providing insulation from the oxygen of the air, interrupts the oxidation processes of the coal.

Example 5 A foam produced from the same mixture as that of Example 2 is used to cover a quantity of finely divided coal placed in the bottom of a vessel 40 cm in diameter. After the foam has completely settled out (after several days), a tight mesh covers and agglomerates the surface of the finely divided coal: the latter no longer emits dust when agitated.

Example 6 A foam obtained from the same mixture as that of Example 2 is poured onto a heap of ungraded gravel. The foam is generated by means of a fire-fighting nozzle equipped, at its end, with a strainer covered with a fabric having a mesh size of 8011. The foam thus obtained consists of very fine bubbles. It is very stable. After 4 days, the heap is still covered with a protective mat of foam.

After 7 days, a protective film has formed on the surface of the heap.

Example 7 A foam (I) produced from the same mixture as that of Example 3 is used for extinguishing a tank containing 13 litres of burning petrol F. The dimensions of the tank are in accordance with Standard Specification AFNOR NFS 61, 902.

After combustion has taken place for one minute, the foam is poured onto the burning tank; the extinction time, and the amount of foam required to produce extinction, are noted.

An identical test was carried out with an emulsifier (II) not containing a heteropolysaccharide.

The emulsifier (II) has the following composition by weight: triethanolamine dodecyl sulphate 20% Clo to C20 fatty alcohol 5% ss-butoxyethanol 20% sodium dodecanoate 1% water 39% urea 9% This emulsifier has a composition similar to certain commercially available emulsifiers.

The extinguishing foams are prepared from diluting aqueous mixtures obtained by adding 5 parts by weight of each of the two emulsifiers to 95 parts by weight of water.

The results entered in the Table below were obtained: Foams Period of injection Weight of Extinction time of the foam foam used (II) 45 seconds 4.200 kg 4 minutes 47 seconds (I) 20 seconds 1,880 kg 32 seconds Example 8 A 4 litre cylindrical vessel is provided at its bottom with a constriction, a settling-out attachment and a tube for admitting foam into the bottom of the vessel; this vessel is filled with small lumps of petroleum pitch (1 to 2 centimetres), placed on metal gauze resting on the constriction of the vessel: these small lumps are covered with a fine black dust which flies when the lumps are handled and which leaves black marks on the fingers.

A foam with a swelling ratio of 6, produced from the same mixture as that of Example 1, is used to fill this vessel through the abovementioned inlet tube.

When the foam is poured off and the pitch dried in air at ambient temperature, it is found that on the one hand dust has been carried into the decanter liquid and that on the other hand the small lumps are at least partially covered with a fine film. It is found furthermore that these small lumps no longer suffer from the disadvantage of causing dust to fly when they are handled or of leaving black marks on the hands, as this dust has partly been removed and partly been fixed by the film of residual polymer. An identical test carried out with reference emulsifier of Example 1, that is to say the emulsifier which does not contain polysaccharide. showed that the small lumps still allowed dust to escape during handling and left black marks on the hands.

WHAT WE CLAIM IS: 1. An aqueous composition comprising water, a foaming surface-active agent, a foam

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

Claims (15)

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

   end, with a strainer covered with a fabric having a mesh size of 8011. The foam thus obtained consists of very fine bubbles. It is very stable. After 4 days, the heap is still covered with a protective mat of foam.

   After 7 days, a protective film has formed on the surface of the heap.

   Example 7 A foam (I) produced from the same mixture as that of Example 3 is used for extinguishing a tank containing 13 litres of burning petrol F. The dimensions of the tank are in accordance with Standard Specification AFNOR NFS 61, 902.

   After combustion has taken place for one minute, the foam is poured onto the burning tank; the extinction time, and the amount of foam required to produce extinction, are noted.

   An identical test was carried out with an emulsifier (II) not containing a heteropolysaccharide.

   The emulsifier (II) has the following composition by weight: triethanolamine dodecyl sulphate 20% Clo to C20 fatty alcohol 5% ss-butoxyethanol 20% sodium dodecanoate 1% water 39% urea 9% This emulsifier has a composition similar to certain commercially available emulsifiers.

   The extinguishing foams are prepared from diluting aqueous mixtures obtained by adding 5 parts by weight of each of the two emulsifiers to 95 parts by weight of water.

   The results entered in the Table below were obtained: Foams Period of injection Weight of Extinction time of the foam foam used (II) 45 seconds 4.200 kg 4 minutes

   47 seconds (I) 20 seconds 1,880 kg 32 seconds Example 8 A 4 litre cylindrical vessel is provided at its bottom with a constriction, a settling-out attachment and a tube for admitting foam into the bottom of the vessel; this vessel is filled with small lumps of petroleum pitch (1 to 2 centimetres), placed on metal gauze resting on the constriction of the vessel: these small lumps are covered with a fine black dust which flies when the lumps are handled and which leaves black marks on the fingers.

   A foam with a swelling ratio of 6, produced from the same mixture as that of Example 1, is used to fill this vessel through the abovementioned inlet tube.

   When the foam is poured off and the pitch dried in air at ambient temperature, it is found that on the one hand dust has been carried into the decanter liquid and that on the other hand the small lumps are at least partially covered with a fine film. It is found furthermore that these small lumps no longer suffer from the disadvantage of causing dust to fly when they are handled or of leaving black marks on the hands, as this dust has partly been removed and partly been fixed by the film of residual polymer. An identical test carried out with reference emulsifier of Example 1, that is to say the emulsifier which does not contain polysaccharide. showed that the small lumps still allowed dust to escape during handling and left black marks on the hands.

   WHAT WE CLAIM IS: 1. An aqueous composition comprising water, a foaming surface-active agent, a foam

   stabiliser, an additive, A) from 30% to 70% by weight of water B) from 70% o 30% by weight of an organic mixture having the following composition by weight: a) from 10 to 60% of surface-active agent b) from 1 to 10% of foam stabiliser c) from 20 to 60% of anti-freeze additive which is a glycol, a polyol, an ether of a glycol and an alkanol, or an ether of a polyol and an alkanol, these compounds having a total of at least 4 carbon atoms, and d) from 1 to 30% of hetero-polysaccharide resulting from the fermentation of a carbohydrate under the action of bacteria of the genus Xanthomonas.
2. 2. A composition according to claim 1, in which the hetero-polysaccharide is one obtained by the fermentation of carbohydrates under the action of Xanthomonas campestris.
3. 3. A composition according to claim 1 or 2 in which the surface-active agent is a mixed sulphate of an alkali metal and an aliphatic fatty alcohol having at least 8 carbon atoms or a quaternary ammonium salt containing at least one aliphatic radical having at least 8 carbon atoms.
4. 4. A composition according to claim 3, in which the surface-active agent is sodium dodecyl sulphate.
5. 5. A composition according to any one of claims 1 to 4 in which the foam stabiliser is a fatty alcohol containing from 8 to 25 carbon atoms.
6. 6. A composition according to claim 5, in which the foam stabiliser is lauryl alcohol.
7. 7. A composition according to any one of claims 1 to 6 in which the anti-freeze additive is ss-butoxyethanol.
8. 8. A composition according to claim 1 substantially as hereinbefore described.
9. 9. Process for obtaining a stable foam which comprises introducing gas into a solution obtained by adding to a composition as claimed in any one of the preceding claims from 10 times to 50 times its weight of water.
10. 10. A stable foam whenever obtained by a process as claimed in claim 9.
11. 11. A method of providing a protective coating on a surface which comprises applying thereto a foam as claimed in claim 10.
12. 12. A method of combatting dust which comprises applying thereto a foam as claimed in claim 10.
13. 13. A method of extinguishing or preventing a fire at a locus which comprises applying to the locus a foam as claimed in claim 10.
14. 14. A method according to claim 13 in which the locus is a rear stall of a coal mine gallery.
15. 15. A method according to claim 13 in which the fire is a hydrocarbon fire.