WO2019054861A1

WO2019054861A1 - Fire extinguishing solution

Info

Publication number: WO2019054861A1
Application number: PCT/NL2018/050597
Authority: WO
Inventors: Stephen James Picken; Yuemei LIN; Robbie Wouter Hendrikus KERSTE; Marinus Cornells Maria VAN LOOSDRECHT; Jure ZLOPASA
Original assignee: Technische Universiteit Delft
Priority date: 2017-09-13
Filing date: 2018-09-12
Publication date: 2019-03-21
Also published as: NL2019536B1

Abstract

The present invention is in the field of a bio-degradable fire extinguishing solution, and a method of extinguishing a fire wherein the present solution is provided and a coating formed. The biodegradable components are readily available. The present solution is non-toxic and in addition a biodegradable agent is nowadays required under government regulations.

Description

Fire extinguishing solution

FIELD OF THE INVENTION

The present invention is in the field of a bio-degradable fire extinguishing solution, and a method of extinguishing a fire using said solution. The biodegradable components are readily available. The present solution is non-toxic and in addition a biodegradable agent is nowadays required under government regulations.

BACKGROUND OF THE INVENTION

Fire may be symbolized by a tetrahedron, which symbol char^¬ acterizes itself by four (tetra) elements, namely oxygen, heat, fire source, and an uninhibited chain reaction. An optimized agent should preferably provide a chemical/physical ac^¬ tion in all four of the tetrahedron domains.

A burning process can be chemically symbolized in the following reaction scheme:

CnH_m + 0₂ -_^through ignition → C0₂ +H₂0

wherein CnH_m is a fuel source. Ignition is considered to take place through heat. However in reality the reaction is much more complex and typically comprising various intermediate and often incomplete steps. These steps may form radicals. If these could be captured or immobilized the fire process may be interrupted and the fire may be easily extinguished.

A typical burning process may be divided into three phases, a growth phase, a burning phase, and an extinguishing phase, each with an accompanying temperature profile. In addition there also is a spatial gradient. A heat gradient has a typical temperature profile from a peripheral temperature of about 20°C to a central temperature of some 1200° C or higher.

Traditional firefighting additives or foams are typically attacking only one of the four sides of the Tetrahedron (cooling down, covering a burning source, removing oxygen, and interrupting the chain reaction) and are therefore often not very effective.

Typical standard tests for extinguishing a fire are given in European norm EN 3-7:2004 +A1 : 2007. For extinguishing flammable liquid fires (B Class) with foam products there is a distinction made in the EN standards between miscible (EN

1568-3, March 2008) and immiscible liquids {EN 1568-4, March 2008). The EN 3-7:2004 +A1 : 2007 standard specifies characteristics, performance requirements and test methods for portable fire extinguishers. Reference to the suitability of an extinguisher for use on gaseous fires (class C fires) are at the manufacturer's discretion, but are applied only to powder type extinguishers which have gained a class B or class A and class B rating. Fire extinguishers with a Class A rating are effec^¬ tive against fires involving paper, wood, textiles, and plastics. The primary chemical used to fight these fires is mono- ammonium phosphate, because of its ability to smother fires in these types of materials. Fire extinguishers with a Class B rating are effective against flammable liquid fires. These can be fires where cooking liquids, oil, gasoline, kerosene, or paint have become ignited. Two commonly used chemicals are effective in fighting these types of fires. Mono-ammonium phosphate effectively smothers the fire, while sodium bicarbonate induces a chemical reaction which extinguishes the fire.

Various prior art fire extinguishers are available. Water and foam fire extinguishers extinguish the fire by taking away the heat element of the fire triangle. Foam agents also separate the oxygen element from the other elements. Carbon Dioxide fire extinguishers extinguish fire by taking away the oxygen element of the fire triangle and also by removing the heat with a very cold discharge. Dry Chemical fire extinguishers extinguish the fire primarily by interrupting the chemical reaction of the fire triangle. A widely used type of fire extinguisher is the multipurpose dry chemical that is effective on Class A, B, and C fires. This agent also works by creating a barrier between the oxygen element and the fuel element on Class A fires. Ordinary dry chemical is for Class B & C fires only. It is considered important to use a correct extinguisher for a given purpose. Using an incorrect agent can allow the fire to re-ignite after apparently being extinguished successfully. Carbon dioxide can be used on Class B & C fires. They are usually ineffective on Class A fires. Water extinguishers are for Class A fires only.

The above agents/extinguishers are however typically limited in their applicability, do not extinguish a fire sufficiently, may be toxic to humans and the environment, are not degradable, may not be storage stable, etc.

Incidentally some documents recite alginate suspensions and the like. US 2,902,446 Al recites methods of preparing suspensions of (sodium) alginate in concentrated preparations for the production of foams for fire extinguishing, though the document is not directly clear on amounts used.

Some documents recite compositions that slightly resemble those of the present invention, but these typically contain further constituents, are not aimed at fire extinguishing, which is clearly different from preventing a fire from happening (such as a coating or a retardant) , and are different in further details thereof. US 2016/251533 Al recites composition for forming a coating on concrete or the like. The ranges for the constituents of said composition are much broader. In addition most of these compositions can not be used for fire extinguishing. Paramita Das in Nature.COM (5 January 2017, p. 1- 13) relates to a coating which is fire retardant. The composition for forming said coating uses CMC, which is not a biopol- ymer. In addition the CMC is surface modified with tri- chloro (1H, 1H, 2H, 2H,perfluorooctyl) silane in order to obtain the required fire retardant coating. Said coating is considered to be poisonous to organisms in general and not biocompatible. Botao Qin in Environ Sci Pollut Res (2017, Vol. 24, p. 24657-24665) recites preventing spontaneous coal combustion by using a solution comprising high amounts of clay (15-55 wt.%), such as 35 wt . % for the small scale test, 15 wt . % in fig. 3, 35 wt.% in figs. 5 and 6, 15-55 wt.% in fig 7, and 35 wt.% in fig. 9 (the % mentioned relates to an amount of AFG relative to an amount of coal) . As a consequence the viscosities are extremely high (at a shear rate of 1/s in the order of 5 Pa.s) which makes it virtually impossible to spray such compositions. An article by Vilcinskas in Polymer Composites 2018, vol. 39, (October 11 2016), p. E236-E249 does not relate to fire extinguishing and recite primarily composite films formed and characteristics thereof. The percentages mentioned relate to an amount of filler in the films. The only composition mentioned has 1 wt.% sodium alginate but is silent on the amount of GO. US 2002/100897 Al relates to a fire retardant composition comprising further constituents and always uses ammonium polyphosphate (typically well above 90 wt.%), which are diluted 5:1, with small amounts of biopolymer added thereto (about 0.112 wt.%). US 3,976,580 A recites a composition that comprises sulfate as flame retardant for lower burning temperature cellulosic materials, bicarbonate as gassing agent for foam generation, Aerosol 22 as foaming and wetting agent, and polyacrylamide and bentonite for forming a gel.

Hence there still is a need for relative simple and effective method of extinguishing fire and a product therefor, which overcomes one or more of the above mentioned disadvantages without jeopardizing beneficial characteristics.

SUMMARY OF THE INVENTION

The present invention relates in a first aspect to a fire extinguishing solution according to claim 1 which is sprayable .

With respect to the present biopolymers, and in particular bacterial alginate reference is made to the following publications, wherein various details of obtaining said biopolymers are described: PCT/NL2017/050164 (Alginate acetone extraction), PCT/NL2015/050432 (Biopolymer extraction),

PCT/NL2017/050584 (Extraction of biopolymers),

PCT/NL2017/050469 (Urea alginate thermoset resin), and Li et al. in "Characterization of alginate-like exopolysaccharides isolated from aerobic granular sludge in pilot plant", Water Research, Elsevier, Amsterdam, NL, Vol. 44, No. 11 (June 1 2010), pp. 3355-3364); these documents, and their contents, are incorporated by reference.

The present solution comprises a binding agent. The binding agent is non-toxic to humans, biodegradable, water soluble, and biocompatible forming at the most a small harm to plants and animals. The binding agent is selected from biopolymers, oligomers of said biopolymers, copolymers of said biopolymers, and combinations thereof. It further comprises platelet nano- particles. The binding agent and nanoparticles are present in a solvent, typically being water. The present solution may be considered as a free flowing visco-elastic solution. Such a solution, when entered into a container, typically takes the form of the container in a few seconds, whereas very viscous solutions may take up to a minute. It has been found that upon application to a heat source, such as a fire, the present com^¬ position forms a coating, as is detailed below.

In an example the biopolyraer is bacterial aerobic granular sludge or anammox granular sludge, and is selected form ex- opolysaccharide, preferably comprising mannuronic acid and guluronic acid residues, block-copolymers comprising uronic acid residues, alginate, lipids, and combinations thereof, or wherein the biopolymer is an algae biopolymer. In an example, the exopolysaccharides are block-copolymers comprising uronic acid (e.g. mannuronic acid and guluronic acid) residues. Espe^¬ cially bacterial aerobic granular sludge or anammox granular sludge has been found to produce high amounts of biopolymers, in good quality. By nature the biopolymers produced as such vary in their characteristics, e.g. composition, molecular weight, etc.

Aerobic granular sludge and anammox granular sludge, and the processes used for obtaining them are known to a person skilled in the art. For the uninitiated, reference is made to Water Research, 2007, doi : 10.1016/j . watres .2007.03.044 (anammox granular sludge) and Water Science and Technology, 2007, 55(8-9), 75-81 (aerobic granular sludge). This type of sludge is also known as Nereda^® sludge.

The bacterial alginate relate to extracellular polymeric substances that comprise high-molecular weight compounds (typically >5 kDa) secreted by microorganisms into their environment. Extracellular polymeric substances are mostly composed of polysaccharides and proteins, and may include other macro- molecules such as DNA, lipids and humic substances. Extracellular polymeric substances preferably obtainable from granular sludge do not require further purification or treatment to be used for some applications, hence can be applied directly. When the extracellular polymeric substances are obtained from granular sludge the extracellular polymeric substances are preferably isolated from bacteria (cells) and/or other non-extracellular polymeric substances.

The obtained biopolymers resemble those of the prior art, but may be different in certain aspects, such as characterized in the claims; i.e. compared to e.g. algae alginate chemical and physical characteristics are found to be different, such as a lipid content is much higher {2-5 wt.%).

It is noted that the present invention is in principle equally suited for biopolymers in general.

With the term "microbial process" here a microbiological conversion is meant.

The present solution comprises 0.1-5 wt.% binding agent and 0.1-5 wt.% nanoparticles, wherein the nanoparticles are platelet particles. The nanoparticles are selected from clay minerals, and reduced graphene oxide, and hexagonal boron nitride (BN) . It is believed that the combination of binding agent and platelet nanoparticles form a coating on burning substance, during fire extinguishing. It is observed that the coating is formed most likely by a combination of a chemical reaction of the binding agent, re-orientation of the nanoparticles, typically such that they are aligned substantially in a plane parallel to a surface of the solution, interaction of the reacted binding agent and nanoparticles, therewith forming a coating on the burning substance. Said coating is relatively thin and its integrity is found to be maintained over time, at least during a few minutes, being sufficient to unexpectedly extinguish the fire quickly and effectively. In addition much less ash and flying particles are produced. The present solution is typically water-based.

In the present solution a length, and likewise a width, of the nanoparticles is significantly larger than a height thereof, such as at least a factor 5 larger, such as 10-1000 times larger. This factor is also referred to as aspect ratio, the aspect ratio being 10-1000. In the present solution a length, and likewise a width, of the nanoparticles is from 10-2000 nm, preferably 20-1000 nm, more preferably 30-500 nm, even more preferably 50-300 nm, such as 100-200 nm, whereas a height is typically from 1-10 nm, such as 2-5 nm.

The present solution has a dynamic viscosity (@ 20 °C; ASTM D445 typically @ shear rate of 1/sec) of 1-1000 mPa*s, preferably 2-500 mPa*s, more preferably 5-300 mPa*s, such as 10-250 mPa*s, and/or a kinematic viscosity (@ 20 °C; ASTM D445 typically @ shear rate of 1/sec) of 0.7-1000 mm²/s, preferably 0.8-500 mmVs, such as 1-250 mm²/s, and a density of 0.99-1.5 g/cm³, preferably 1.02-1.35 g/cm³, more preferably 1.05-1.30 g/cm³, such as 1.1-1.25 g/cm³. It is relatively surprising that both the present biopolymer and nanoparticles can be dissolved in sufficient amounts, form a sprayable solution, and have the fire extinguishing properties.

The present solution does not comprise F, or at least not is noteworthy amounts.

In a second aspect the present invention relates to a method of extinguishing a fire, comprising providing the present solution, adding the solution to a fire, optionally increasing the viscosity of the solution, such as to 10-10⁷ Pa*s, e.g. 10³-10⁶ Pa*s, optionally re-orienting nanoparticles, optionally allowing the binder to undergo a Maillard reaction and/or a caramelisation, optionally forming a coating of the binding agent and nanoparticles, and extinguishing the fire.

The present binding agent and nanoparticles may be mixed into the present solution just before extinguishing the fire, or may be present in the solution already. Likewise a foam comprising the present solution may be formed, and said foam may be applied to the fire. Likewise the present solution may be used as a fire retard-ant or used in a product.

Thereby the present invention provides a solution to one or more of the above mentioned problems.

Advantages of the present invention are detailed throughout the description.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to a solution according to claim 1.

In an exemplary embodiment of the present solution the binding agent is selected polysaccharides, polypeptides, such as proteins, natural gums, such as guar gum, xanthan gum, locust bean gum, chicle gum, dammar gum, and polymer precursors, such as oligomers. In principle a wide range of binding agents may be applied, alone or in combination. It is however preferred to use biopolymers, such as alginate.

It is preferred that at least one polypeptide or protein is present, as these contribute significantly to fire extinguishing; solutions comprising said polypeptide or protein perform better than ones comprising only a biopolymer, such as alginate. It is also preferred that no polyphosphate is present, such as ammonium polyphosphate, especially as there is no need for such further compounds in view of fire extinguishing properties .

In an exemplary embodiment of the present solution the binding agent has a molecular weight of > 2 kDa, preferably 10-300 kDa, more preferably 30-150 kDa, such as 50-100 kDa. It has been found that especially these high molecular weight agents form good coatings under elevated temperatures typically being present during fires and the like.

In an exemplary embodiment of the present solution the binding agent is capable of undergoing a Maillard reaction and/or a caramelisation, such as biopolymers and polypeptides. It has been found that these agents form very good strong coatings, which prevent e.g. oxygen from entering a fire.

In an exemplary embodiment of the present solution the binding agent is non-ionic, or ionic, such as cationic and anionic. In view of sufficient water solubility the binding agent is preferably ionic.

In an exemplary embodiment of the present solution the solvent comprises 90-100 wt . % water, preferably 92-99,9 wt . % , such as 99-99,8 wt.%. In other words, the solution is water- based, apart from possibly small or trace amounts of other solvents and/or additives being naturally present in water, such as salts.

In an exemplary embodiment the present solution comprises 0.2-5 wt.% binding agent, preferably 0.5-4 wt.%, more preferably 0.8-3 wt.%, such as 1.0-2 wt.%, e.g. 1.5 wt.%. It has been found that relatively small amounts already provide the desired effects, as detailed through the description. Especially good results have been achieved with biopolymers, such as ALE, extracted with biobased amine material comprising at least two amine groups.

In an exemplary embodiment the present solution comprises 0.2-5 wt.% nanoparticles, preferably 0.5-4 wt.%, more preferably 0.8-3 wt.%, such as 1.0-2 wt.%, e.g. 1.5 wt.%. Also here it has been found that relatively small amounts already provide the desired effects, as detailed through the description .

The content of binding agents may be on the lower end of the claimed range, whereas the amount of nanoparticles is preferably > 2 wt.%.

The content of the binding agent and nanoparticles together is 0.5-7 wt.%, preferably 1-6 wt.%, such as 2-5 wt.%, e.g. 3-4 wt . % .

In an exemplary embodiment of the present solution the biopolymers are ionic biopolymers, such as alginate or bacterial alginate (ALE) , preferably with a monovalent cation, such as Na⁺, H⁺, and NH₄ ⁺.

In an exemplary embodiment of the present solution the biopolymers are extracellular polymeric substances obtainable from granular sludge. Especially good results are obtained with biopolymers that have been extracted with a biobased amine material comprising at least two amine groups. These biopolymers can be used as directly obtained from the extraction. Apparently the amounts (0.2-10 wt.%, such as 1-5 wt.%) of biobased amine material per se, being present in the extracted biopolymers, contribute to the present advantageous effects. The biobased material comprising at least two amine groups is preferably selected from one or more of primary and secondary amines, such as alkyl diamine, dialkyl diamine, al- kanol diamine, alkyl alkanol diamine, aldehyde diamine, dial- dehyde diamine, imine diamine, di-imine diamine, aldehyde imine diamine, urea, Ν,Ν' -dialkylurea, N-monoalkylurea, wherein each alkyl/alkanol/aldehyde is independently selected from C1-C12 alkyls/alkanol/aldehyde, preferably Ci-Ce alkyls/al- kanol/aldehyde, such as methyl, ethyl, propyl, iso-propyl, butyl, pentyl, and hexyl, with the proviso that the at least two amine groups are preferably not attached to a same carbon of the alkyl/alkanol. Preferably at least one of the amine groups is attached to the same carbon as the aldehyde or imine, preferably two or more amine groups are attached to the same carbon as the aldehyde or imine. A most preferred example is urea. Also urea-alginate can be used, optionally having small amounts (1-2 wt.%) of urea being present from the extraction.

In an exemplary embodiment of the present solution the granular sludge is one or more of aerobic granular sludge and anammox granular sludge.

In an example the granular sludge has been substantially produced by bacteria belonging to the order Pseudomonadaceae, such as pseudomonas and/or Acetobacter bacteria (aerobic granular sludge) ; or, by bacteria belonging to the order Plancto- mycetales (anammox granular sludge) , such as Brocadia anammox- idans, Kuenenia stuttgartiensis or Brocadia fulgida; or, combinations thereof.

In an example the extracellular polymeric substances are in aqueous solution at a concentration in the range of 0.1-30 % w/w, preferably 1-10 % w/w, most preferably 4-10 % w/w, such as 5-8 % w/w.

In an example the extracellular polymeric substances comprise a major portion consisting exopolysaccharides , and a minor portion, such as less than 30 % w/w, typically less than 10 %w/w, consisting of lipids and/or other components more hydrophobic than the exopolysaccharides. Extracellular polymeric substances obtained from granular sludge having a major portion of exopolysaccharides and a minor portion of lipids have been found to provide very effective water resistance.

In an example the extracellular polymeric substances comprise at least 50 % w/w exopolysaccharides, preferably at least 60 % w/w exopolysaccharides, most preferably at least 75 % w/w exopolysaccharides, such as at least 90 % w/w exopolysaccharides, more preferably wherein an exopolysaccharide content is less than 100 % and the isolated extracellular polymeric substances further may comprise 0.1-10 w/w% lipids, such as 0.2-5 w/w%. The exopolysaccharide content is preferably not 100 %, as a remainder has been found to contribute to the present advantageous effects.

The present biopolymers may be characterized by various (further) parameters. They may be different in various aspects from e.g. known comparable chemically or otherwise obtainable polymers, such as in viscosity behaviour, molecular weight, hydrophobicity, lipid content, microstructure (as can be observed under an electron microscope), etc. For instance, the lipid content of the present biopolymers is much higher than those of prior art comparable biopolymers, namely 2-5 wt.%, such as 3-4 wt . %. Analysis of an exemplary biopolymer using a PerkinElmer 983 double beam dispersive IR spectrometer shows approximately 3.2 wt.% peaks that are attributed to lipids. Typically the present biopolymers, as well other molecular substances obtained from biological source in general, are also less pure, i.e. a mixture of polymers is obtained.

The present biopolymer may relate to an alginate, such as ALE. This is different from the alginates e.g. obtainable by the above pilot plant alginates in various aspects. For in^¬ stance it may have a decreasing dynamic viscosity with increasing shear rate (@ 25 °C) , wherein a relative decrease is from 5-50% reduction in dynamic viscosity per 10-fold increase in shear rate. It may have a dynamic viscosity of > 1-1000 mPa*s (@ 25 °C, ASTM D445 @ shear rate of 1/sec) . It may have a number averaged weight of > 10,000 Dalton, preferably > 50,000 Da, such as > 100,000 Da. It may have a hydrophilic part and hydrophobic part. It may have a tensile strength (according to ISO 37; DIN 53504) of 1-150 MPa . It may have a flexural strength (according to ISO 178) of 5-250 MPa. And it may relate to combinations of the above.

In an exemplary embodiment of the present solution the nanoparticles are selected from montmorillonite (MMT) . It is preferred to use 0.1-10 wt . % clay mineral. It has been found that fires are extinguished more efficiently, using less water, and the alginate and clay are considered to form a coating, which coating does not set fire. It is preferred to use 0.2-5 wt.% alginate, such as 1-2.5 wt.%. It is preferred to use 0.2-5 wt.% clay mineral, such as 1-2.5 wt.%. In an example the present clay minerals are one or more of a natural or artificial clay, the clay preferably being a monovalent cation clay. The clay preferably has a cationic exchange capacity of 2-200 meq/100 grams clay at a pH of 7, more preferably 5-150 meq/100 grams, even more preferably 10-120 meq/100 grams. It has been found that clays having a relatively higher CEC perform better in terms of relevant characteristics for the present invention. The clay may comprise one or more of H+, Na+, K+, Lit. The clay may be a tetrahedral-octahedral-tetrahedral (TOT) -clay (or 2:1 clay), such as a kaolin clay, such as kao- linite, dickite, halloysite and nacrite, a smectite clay, such as bentonite, montmorillonite, nontronite and saponite, an il- lite clay, a chlorite clay. Also a silicate mineral, such as mica, such as biotite, lepidolite, muscovite, phlogopite, zinnwaldite, clintonite, and allophane, are applicable as well as platelet like particles.

In an exemplary embodiment the present solution comprises 10^"5-10^"2 M buffer, such as H⁺, phosphate, borate, carbonate, bicarbonate, or comprises 10^~5-10^~2 M OH^", or HC1, such as 10^"5-10-² M, and/or 0.1-3 wt.% biocide. The buffer as well as the biocide improve storage stability.

In an exemplary embodiment the present solution consists of 0.1-5 wt.% binding agent, 0.1-5 wt.% nanoparticles , 0-10^-2 buffer, 0-3 wt.% biocide, and water, apart from trace or small amounts naturally being present in the water used.

In a second aspect the present invention relates to a method of extinguishing a fire.

The invention is further detailed by the accompanying figures and. examples, which are exemplary and explanatory of nature and are not limiting the scope of the invention. To the person skilled in the art it may be clear that many variants, being obvious or not, may be conceivable falling within the scope of protection, defined by the present claims .

FIGURES

Figures 1-4 show experiments.

DETAILED DESCRIPTION OF THE FIGURES

Fig.l: dipped in water (1} and in fire extinguishing (r) agent, the left sample burns readily on exposure to the gas burner .

Fig.2: as fig.l with a different angle of view.

Fig. 3 and 4: after the gas burner test, the left hand block of wood is substantially oxidized, whereas the right hand one is only partially damaged due to the applied fire extinguishing agent. The block of wood in figure 4 was impregnated for a longer time compared to the block of figure 3 and ignition of the fire did not occur in the right hand block (the one impregnated with the fire extinguishing solution) . The non-impregnated block was basically just ash and fell apart upon contact.

EXAMPLES/EXPERIMENTS

The invention although described in detailed explanatory con- text may be best understood in conjunction with the accompa^¬ nying examples and figures.

Preparation of the Na-Alg/ M suspension:

Commercially available MMT (Cloisite Na+ (MMT), Southern Clay Products Inc., Rockwood) was dispersed in deionized water under vigorous stirring for 24 h to achieve a 3 wt . % exfoliated dispersion, without any remaining visible agglomerates. Na-Alginate (M/G = 1.56, Mw = 150 kg/mol) purchased from

Sigma-Aldrich was used as received. Na-Alg was dissolved using deionized water to form a 3 wt.% solution. The MMT suspension was subsequently mixed with Na-Alg solution and was further mixed for 24 h. The total solid content was kept at 3 wt.% with MMT concentrations of 50 wt.% with respect to the mass of Na-Alg.

Results

The results from the experiments indicate that the application of the fire extinguishing solution substantially prevents the oxidation of the wood in the heat of the flame. This is presumably due to the formation of a protective clay containing char layer that seals the surface of the wood/carbonised wood thereby hindering the ingress of oxygen and the escape of volatile combustible components.

In addition, the application of the fire extinguishing solution on burning blocks of wood prevented flying ash and embers. This may be due to a sticky caramelised alginate clay crust holding the burning material in place. The burning material seems to be stuck rather well to the surface.

A further advantage of the present system compared to prior art fire extinguishing agents is the absence of halogenated or organic phosphorous chemicals, and indeed no noxious compounds are expected to result from the carbonisation of the fire extinguishing solution, other than standard caramelisation products .

Indeed, many fire extinguishing agents currently in use are considered to be potentially harmful for the health of the firefighting personnel and the environment by either direct (skin) contact, or as run-off water. For instance the commonly used AFFF (aqueous film forming foam) contains fluorine.

Further experiments The above experiments are repeated with similar compositions and similar results. Tests with 1 wt . % pyrosilicate

(Si20_? ^6_) (not part of the invention), 1.5 wt - % egg protein, 1 wt.% starch, 1.7 wt.% urea-alginate as binding agent, and 2 wt.% graphene and 1 wt.% BN, and combinations thereof, also give satisfactory results.

In comparative tests it has been found that solutions with bacterial alginate (ALE) and clay performs much better than comparable solution with alginate and clay in terms of fire extinguishing. The fire extinguishes quicker and better. Such is considered to relate to aillard reactions, whereas cara- melisation is observed for all biopolymers investigated.

Inventors tested the present solution for extinguishing an A-type class fire and as a fire retardant. When extinguishing the solution was either applied as a solution or as a foam. It was observed that solution with clay perform better than without clay, whereas foams with clay perform worse. Egg protein by itself gave moderate results.

A-type fire Aqueous Solution Foam

Result result

Water 0 0

ALE ++ ++(+)

ALE + T ++(+) +

alginate + +

alginate+MMT + (+) 0

egg protein 0 0

The fire was started e.g. using a piece of wood or a basin filled with gasoline and igniting using a Bunsen-burner . After about 30 seconds, when the fire was burning heavily, fire was extinguished. The present solution comprises 5.0 wt.% of solids in total. When two components were present, such as ALE and MMT, the wt.% was equally divided over the two components, i.e. 2.5 wt.% each.

All solutions performed to some extent. A "+" was given if the fire extinguished fully and no re-ignition occurred. A "++" was given if the fire extinguished fully, a lot of material was left, and no re-ignition occurred. A ^x+4-+" was given if the fire extinguished fully almost immediately and no re- ignition occurred. In all cases the piece of wood could be touched after extinguishing, indicating the surface temperature had dropped to temperatures below 50 °C.

For gasoline fires lighting took place in 1 s, a burn time before start was 30 s, a weight approx. 100 g, a size of basin: 18 x 28 x 4.8 cm and as application device a bucket and small shovel. For a fire basket wood (different sorts) was used, a burn time before start was 15 min, a weight approx. 4- 5 kg, and as application device a domestic plant sprayer was used. Similar tests have been performed on straw, and cotton wool. In addition fire retardation test were performed. The above materials, and further chipboard, and polystyrene, were impregnated with minimal amounts of solution {4-20 gr) . Burning was limited or absent, a burn through time increased significantly compared to wetting with similar amounts, and solutions comprising both clay and biopolymer performed better.

Claims

1. Sprayable solution for fire extinguishing, comprising 0.1-5 wt . % binding agent, wherein the binding agent is selected from biopolymers, oligomers of said biopolymers, copol^¬ ymers of said biopolymers, and combinations thereof,

0.2-5 wt . % nanoparticles , wherein the nanoparticles are platelet particles, wherein the nanoparticles are selected from clay minerals, graphene oxide, reduced graphene oxide, and hexagonal BN, wherein a length, and likewise a width, of the nanoparticles is at least a factor 5 larger than a height thereof, wherein a length, and likewise a width, of the nano^¬ particles is from 10-2000 nm,

comprising 0.3-10 wt . % binding agent and nanoparticles together ,

and

the remainder being solvent, wherein all percentages are based on a total weight of the solution,

wherein the solution has a dynamic viscosity (@ 20 °C; ASTM D445) of 1-1000 mPa*s, and/or a kinematic viscosity (@ 20 °C; AST D445) of 0.7-1000 mm²/s, and a density of 0.99-1.5 g/cm³, with the proviso that no F is present.

2. Solution according to claim 1, wherein the binding agent is selected from polysaccharides ,—natural gums, such as guar gum, xanthan gum, locust bean gum, chicle gum, dammar gum, and polypeptides, such as—proteins, preferably with the proviso that at least one polypeptide or protein is present, and pref^¬ erably with the proviso that no polyphosphate is present, such as ammonium polyphosphate.

3. Solution according to any of the preceding claims, wherein the binding agent has a molecular weight of > 2 kDa, preferably 10-300 kDa, more preferably 30-150 kDa, such as 50- 100 kDa.

4. Solution according to any of the preceding claims, wherein the binding agent is capable of undergoing a Maillard reaction and/or a caramelisation .

5. Solution according to any of the preceding claims, wherein the binding agent is non-ionic, or ionic, such as cat- ionic and anionic.

6. Solution according to any of the preceding claims, wherein the solvent comprises 90-100 wt.% water, preferably 92-99.9 wt.%, wherein percentages are based on a total weight of the solvent.

7. Solution according to any of the preceding claims, comprising 0.2-5 wt.% binding agent, preferably 0.5-5 wt.%, more preferably 1-3 wt.%.

8. Solution according to any of the preceding claims, comprising 0.2-4 wt.% nanoparticles, preferably 0.5-3 wt.%, more preferably 1-3 wt.%.

9. Solution according to any of the preceding claims, comprising 0.5-7 wt.% binding agent and nanoparticles together, preferably 1-6 wt.%, such as 2-5 wt.%, e.g. 3-4 wt.%.

10. Solution according to any of the preceding claims, wherein the binding agent are biopolymers that are ionic biopolymers, such as alginate or bacterial alginate (ALE) , preferably a biopolymer with a monovalent cation.

11. Solution according to any of the preceding claims, wherein the binding agent are biopolymers that are extracellular polymeric substances obtainable from granular sludge, preferably extracted with a biobased amine material comprising at least two amine groups.

12. Solution according to claim 11, wherein the granular sludge is one or more of aerobic granular sludge and anammox granular sludge.

13. Solution according to any of the preceding claims, wherein the nanoparticles are selected from MMT .

14. Solution according to any of the preceding claims, wherein a length, and likewise a width, of the nanoparticles is 10-1000 times larger than a height thereof.

15. Solution according to any of the preceding claims, wherein a length, and likewise a width, of the nanoparticles is from 20-1000 ran, preferably 30-500 nm, more preferably 50- 300 nm, such as 100-200 nm.

16. Solution according to any of the preceding claims, with a dynamic viscosity (@ 20 °C; ASTM D445) of 2-500 mPa*s, preferably 5-300 mPa*s, such as 10-250 mPa*s, and/or a kinematic viscosity (@ 20 °C; ASTM D445) of 0.8-500 , such as 1-250 iM²/s, and a density of 1.02-1.35 g/cm³, preferably 1.05-1.30 g/cm³, such as 1.1-1.25 g/cm³.

17. Solution according to any of the preceding claims, com^¬ prising 10^"5-10^-2 M buffer, such as NH₄ ⁺, phosphate, borate, carbonate, bicarbonate, or comprises 10^"5-10^-2 M OH^", and HC1, and/or 0.1-3 wt.% biocide.

18. Solution according to any of the preceding claims, con sisting of 0.1-5 wt.% binding agent, 0.1-5 wt.% nanoparticles , 0-10"² M buffer, 0-3 wt.% biocide, and water.

19. Method of extinguishing a fire, comprising

providing a solution according to any of the preceding claims,

adding the solution to a fire, and

extinguishing the fire.

20. Method according to claim 19, further comprising increasing the viscosity of the solution, such as to 10-10

Pa*s,

re-orienting nanoparticles,

allowing the binder to undergo a Maillard reaction and/or caramelisation, and

forming a coating of the binding agent and nanoparticles.