FIELD OF THE INVENTION

The present invention is in the field of a biodegradable long term fire retardant concentrate, a fire retardant solution comprising said fire retardant concentrate, a method of retarding a fire using said solution, a method of preparing said long term fire retardant concentrate, and a method of preparing said fire retardant solution.

BACKGROUND OF THE INVENTION

The present invention is in the field of a biodegradable long term fire retardant concentrate, a fire retardant solution, and use thereof. Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi, typically into simpler harmless, for the environment non-toxic, products.

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

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

CnHm + O2 through ignition CO2 +H2O

wherein CnHm is a fire 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 bounded 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.

The present invention is focused on the growth phase and intends to limit growth of the fire by providing a fire retardant. Various prior art fire retardants are available. However these retardants are relatively toxic to life in general and to an environment to which the retardant is provided. They typically comprise large amounts of polyphosphates (typically > 93%), and corrosion inhibitors (some 1.5%, such as sodium ferrocyanide) . They are typically effective and storage stable.

Some documents relate to aqueous concentrates for fire extinguishing. For instance US 6,322,726 B1 recites a concentrate comprising a salt(s), which is optimized in terms of rheological and viscosity stability, by addition of a rheological modifier (s) for increasing viscosity and elasticity (polygalactoman- nan gum(s)), and an effective amount of a stabilizing compound selected from the group consisting of aliphatic carboxylic acids aliphatic polycarboxylic acids, aliphatic and alicyclic organic compounds having at least three hydroxyl groups, glycols, mixtures thereof and the like, wherein water is present in an amount at least sufficient to solubilize the stabilizing compound (s) up to an amount at which said thickening compound is activated. The concentrate typically comprises toxic and non-de- gradable substances as tolyltriazole, molybdate, and dimercapto- thiadiazole. CN 109 260 644 A recites a water fire extinguishing agent and a preparation method thereof. The water fire extinguishing agent comprises by weight 1-10% of water-soluble ammonium salt, 3-5% of hydrophilic solid particle, 3-15% of flame retardant, 10-20% of antifreeze agent, typically ethylene glycol or glycerol, 0.3-0.5% of thickener, 0.5-1% of foaming agent and the balance water, no further solvent being present. The flame retardants are one or more of triethyl phosphate, tributyl phosphate, triphenyl phosphate, tricresyl phosphate, and dimethyl methyl phosphate, which are no salts but organic liquid substances. Qin et al. in Environ. Sci. Pollut. Res (2017), 24, p. 24657-24665 (doi 10.1007/sll356-017-9982-5) recites aqueous clay suspensions stabilized by alginate fluid gels for coal spontaneous combustion prevention and control. These suspensions have a very high viscosity (typically 35% clay and 0.3-6% alginate with a viscosity of »10 Pas), are intended for underground coal fires, and have further nothing to do with the present invention. US 2001/035517 Al recites a fugitive color fire retardant composition, the colorant initially colors the composition to a hue which contrasts with the hue of ground vegetation. The examples show relatively low concentrations of salt, typically comprising > 70% water. Hence there still is a need for a relative simple and effective long term fire retardant, which overcomes one or more of the above mentioned disadvantages without jeopardizing benefi ^¬ cial characteristics.

SUMMARY OF THE INVENTION

The present invention relates in a first aspect to a biodegradable long term fire retardant concentrate comprising an aqueous concentrate. It is aimed at long term stability for storage, a high viscosity, and to be applied as a diluted solution with sufficient viscosity and fire retardant properties. Said solution can be applied from air and from the ground. Manufacture of the concentrate is found difficult in view of the large amounts of components (e.g. a high salt level), and to arrive at a composition that is stable over time and stable at elevated temperatures, and hence the present invention also relates to a method of preparing said fire retardant concentrate, and fire retardant solution. The concentrate comprises 0.2-5 wt.% biopolymer comprising polysaccharide, preferably 0.5-3 wt.%, 7-25 wt.% phosphate salt, preferably 7-15 wt.%, such as 8- 12 wt.%, 15-40 wt.% sulfate salt, preferably 15-30 wt.%, such as 18-25 wt.%, 1-10 wt.% solvent, preferably 1-8 wt.%, such as 3-6 wt.%, 0.0-10 wt.% thickener, preferably 0.5-8 wt.%, such as 1-5 wt.%, 0.5-20 wt.% nanoparticles, wherein the nanoparticles are selected from clay minerals, silicate minerals, and combinations thereof, preferably 1-15 wt.%, such as 2-10 wt.%, 0.05-2 wt.% colorant, preferably 0.1-1.5 wt.%, such as 0.2-1 wt.%, and 40-60 wt.% water, such as 45-55 wt.%, with the proviso that at least one of phosphate and sulfate comprises ammonium, and with the proviso that no F is present, wherein all wt.% are relative to a total weight of the composition. All of the components are fully biodegradable, non-toxic to human beings and to the environment. The present solution may be used as a spray, may be nebulized, or as a flow. It is found to be very effective to retard a fire in certain direction and therewith direct the fire in another direction. By doing so fire extinguishing is limited to certain areas and therefore much more effective, as is supported by tests under standard conditions. In addition the present agent fully decomposes into products not being harmful to the environment and human beings within 28 days under typical conditions. and typically within 14 days. The present concentrate is stable for longer periods of time, typically more than 3-6 months and hence can be stored for at least said periods. Test under varying temperatures and conditions indicate a storage stability of at least 5 years. In addition it consumes relatively little space, and can therefore also be stored on location, such as a strategic supply, or moved to said location quickly, without any problem.

The present products have been tested by CEREN in France, and the results on performance was better than the existing products which have an dilution in water of 20 to 25% to reach the wind tunnel test. This product already reach the same performance level by 13,5%. The results on toxicity and biodegradability are as follows : 1- Toxicity on Bacteria: EC 50 (30 Min) >1% ISO 11348-3; 2- Ecotoxicity Fish: EC 50 (96h) >100 mg/L OECD 203; 3- Ecotoxicity daphanids EC 50 (48h) >100 mg/L OECD 202; and 4- Ecotoxicity algae EC 50 (72h) >100 mg/L OECD 201. Biodegradability 100 % in 17 days according to OECD 301B. The products have a density of about 1.24 g/cm ³ (EN ISO 12185) , a pH of about 7.7, a freezing point of about -10°C, a viscosity of about 2000 mPas, and being not corrosive (ASTM D 665 and ASTM D130) These are considered very satisfying results, also in view of future government regulations .

In a second aspect the present invention relates to a fire retardant solution comprising 10-15 wt.% of the present concentrate and 85-90 wt.% water.

In a third aspect the present invention relates to a method of preparing a fire retardant concentrate according to the invention, comprising mixing all polysaccharide and 20-30% of the solvent thereby obtaining a first mixture, dispersing said first mixture in all the water at 500-700 rpm until a smooth gel is formed, adding all sulfate and all phosphate at 600-800 rpm until a thinner gel is formed, adding all thickener, the remainder of the solvent, until the thickener is fully dispersed, adding all the nanoparticles until a homogeneous mixture is obtained, and adding all colorant.

In a fourth aspect the present invention relates to a method of preparing a fire retardant solution comprising providing 10- 15 wt.% of the concentrate, and mixing the concentrate with 85- 90 wt.% water.

In a fifth aspect the present invention relates to retarding a fire comprising providing an fire retardant solution according to the invention, limiting propagation of the fire in at least one direction by providing the fire retardant solution at a side of the fire in the at least one direction, and further, in a sixth aspect, to extinguishing a fire, by retarding the, and extinguishing the fire in another direction.

In summary the present solution is 100% biodegradable, nontoxic for nature of all kinds, no residues are left behind, liquid starts after the fire acting as a fertilizer, it prevents pollution of unburned particles on big scale, it provides very fast retardation of fires, typically six times faster than water, no re-ignition occurs, once the fire is extinguished it will not reignite, it is 100% biodegradable, it is nontoxic to lower forms of organisms such as bacteria, fish, daphanids and algae, and it is not harmful for people, other animals and nature in general.

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

Advantages of the present description are detailed throughout the description.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to a biodegradable long term fire retardant concentrate according to claim

1.

In an exemplary embodiment the present long term fire retardant concentrate may comprise 1-7 wt.% ammonium, preferably 2-5 wt.%, such as 3.5-4.5 wt.%.

In an exemplary embodiment of the present long term fire retardant concentrate no polyphosphate is present, such as ammonium polyphosphate.

In an exemplary embodiment of the present long term fire retardant concentrate a weight ratio sulfate:phosphate is from 1:1 to 5:1, preferably from 1.5:1 to 3:1, 1.5:1 to 2.5:1, e.g.

2.2: 1-1.8:1. The sulfate may be in the form of diammonium sulfate, and/or the phosphate in the form of diammonium hydrogen phosphate. It is found that such a concentrate, or the diluted solution thereof provide even better fire extinguishing properties, as both the fire is limited, such as limited from spreading and/or extending, and a layer of fire extinguisher is formed over objects on fire, therewith contributing to smothering or extinguishing the fire. For instance about 53 gr/1 (NH4)2HPO4 and 100 gr/1 (NH4)2SO4 may be used.

In an exemplary embodiment the present long term fire retardant concentrate the phosphate and/or sulfate may comprise a cation selected from H ⁺ , Na ⁺ , K ⁺ , NHί ⁺ , and Ca ²⁺ , and combinations thereof, preferably NHV.

In the present long term fire retardant concentrate the solvent is selected from aliphatic, branched, and partly saturated C ₁ -C ₆ alcohols, aliphatic, branched, and partly saturated C ₁ -C ₆ diols, aliphatic, branched, and partly saturated C ₁ -C ₁₀ mono-, di- , tri-, and oligo ethers (CnH2 _n +2O _m ; nÎ[l-10], m³l, e.g. me [1-5]), and combinations thereof, preferably isopropyl alcohol (CAS 67- 63-0), propylene glycol (CAS 57-55-6), 2, 5, 7, 10-tetraoxaundecane (CAS 4431-83-8), and propanol.

In an exemplary embodiment of the present long term fire retardant concentrate the biopolymer is selected from biopolymers, oligomers of said biopolymers, copolymers of said biopolymers, and combinations thereof.

In an exemplary embodiment of the present long term fire retardant concentrate the biopolymer has a molecular weight of > 2 kDa, preferably 10-300 kDa, more preferably 30-150 kDa, such as 50-100 kDa.

In an exemplary embodiment of the present long term fire retardant concentrate the biopolymer is selected from alginate or bacterial alginate (KYMERA) , preferably extracellular polymeric substances obtainable from granular sludge, wherein the granular sludge preferably is one or more of aerobic granular sludge and anammox granular sludge.

In the present long term fire retardant concentrate the thickener is selected from natural gums, such as guar gum, xan- than gum, locust bean gum, chicle gum, dammar gum, and polypeptides, such as proteins.

In an exemplary embodiment of the present long term fire retardant concentrate the thickener has a molecular weight of > 50 kDa, preferably 100-1500 kDa, more preferably 200-1000 kDa, such as 300-800 kDa.

In the present long term fire retardant concentrate the con ^¬ centrate has a dynamic viscosity (@ 20 ºC; ASTM D445) of 1500- 2500 mPa*s, preferably 1800-2200 mPa*s, such as 1900-2100 mPa*s, and/or may have a kinematic viscosity (@ 20 °C; ASTM D445) of 1070-1925 mm ² /s, and/or a density of 1.25-1.5 g/cm ³ , such as 1.3- 1.4 g/cm ³ , such as 1.33-1.38 g/cm ³ , and/or wherein the pH is from 6.5-7.5.

In an exemplary embodiment of the present concentrate 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 pre-sent 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+, Li+. The clay may be a tetrahedral-octahedral-tetrahedral (TOT) -clay (or 2:1 clay) , such as a kaolin clay, such as kaolinite, dickite, hal- loysite and nacrite, a smectite clay, such as bentonite, montmorillonite, nontronite and saponite, an illite 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 the present concentrate the colorant is selected from natural pigments, such as vegetable pigments, and metal oxides, such as iron oxide, preferably natural pigments.

The one or more of the above examples and embodiments may be combined, falling within the scope of the invention.

EXAMPLES The invention is further detailed by the accompanying example, which is 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.

Example

Preparation of fire retardant concentrate. 20 gr IPA and 18 gr alginate (Satialgine SHOO of Algaia) were thoroughly mixed and dispersed in 1000 gr of water under mixing with a rotary mixer at 500-700 rpm. When a homogeneous gel is formed, without clods, 400 gr of NH ₄ SO ₄ and 212 gr H(NH4) ₂ PO ₄ are added. The speed of the rotary mixer is increase with 100 rpm, and the gel becomes somewhat thinner. Thereafter 60 gr guar gum and 60 gr IPA are mixed, and then dispersed in the gel under thorough mixing. In an alternative to IPA 2,5,7, 10-tetraoxaundecane (TOU) is used, providing similar results. Then 140 gr kaolin clay is slowly added under constant mixing until a homogenous mixture is formed. Finally 12 gr red vegetable pigment is added. The formed concentrate has a pH of about 7, and a viscosity of 2000 mPa*s (±10%) . The concentrate may then be mixed with water in a ratio of 13.5% concentrate and 86.5% water, therewith forming a solution. The viscosity of the solution is from 50-500 mPa*s, and typically 320 mPa*s (±10%). It has a density of 1.05-1.15 gr/cm ³ , typically about 1.08 gr/cm ³ .