Mixture of non-polymer organic components with fire retardancy, preparation method and use

Abstract

The present invention relates to a pyrophosphate-free mixture with fire retardancy, characterised in that it comprises a mixture of non-polymer organic components, wherein at least a first compound of the mixture acts as a hydrogen-bridge donor and at least a second compound of the mixture acts as a hydrogen-bridge acceptor. The invention also relates to a method for preparing the fire-retardant mixture and to the use thereof as a fire retardant in extinguishing forest fires.

Description

[0001] DESCRIPTION

[0002] MIXTURE OF NON-POLYMERIC ORGANIC COMPONENTS WITH FLAME RETARDANT CAPABILITY, METHOD OF PREPARATION AND USE

[0003] TECHNICAL SECTOR

[0004] The present invention falls within the category of flame retardant compounds and mixtures (or combustion retardants) that can be used in open spaces for the control and extinguishing of large fires, primarily forest fires. The invention also relates to the method of preparation of these compounds and to their use in fire suppression.

[0005] BACKGROUND OF THE INVENTION

[0006] Flame retardants currently used in firefighting are inorganic compounds, primarily phosphorus and nitrogen. In particular, a combustion retardant formulation (FIRE-TROL) is commercially available and is the most widely used for fighting forest fires worldwide. Although this formulation has proven effective, its main component is pyrophosphates, which, due to their non-biodegradable nature, end up accumulating in aquifers and causing eutrophication by promoting the growth of algae and plants, especially at the high concentrations that can be reached in water as a result of firefighting efforts. In contrast to this formulation, the present invention describes mixtures of harmless or very low-toxicity compounds that, while biodegradable, act as flame retardants.

[0007] There are also numerous organic compounds whose flame-retardant or fire-extinguishing properties have been determined. The flame-retardant effect is understood as the ability of some compounds or mixtures to inhibit the combustion of a combustible material by coating its surface, either by extinguishing the flame or by slowing the progression of the fire front compared to its absence.

[0008] Among the non-polymeric organic compounds used in fire suppression, a common type includes those containing halogens. For example, application CA2052887 refers to a fire-retardant composition comprising at least one compound selected from dichloropentafluoropropane isomers.

[0009] Likewise, application WO2015104004 refers to a combustion-extinguishing composition comprising a carboxylic acid derivative and a pyrotechnic agent.

[0010] The vast majority of non-halogenated organic compounds are flammable and have no flame-retardant properties. Some types of organic compounds used in fire suppression are halogenated compounds that can generate highly toxic gases during their transformation, in addition to having very adverse effects on the environment. For example, chlorinated compounds generate phosgene, which is a highly toxic compound in certain percentages.

[0011] In the marketing of flame retardants, the brominated variety is the most widely used. These brominated organic compounds are very effective in plastics, textiles, electronics, clothing, and furniture, but they have the drawback of being highly neurotoxic compounds, which is why they are not used as fire retardants in forest fires.

[0012] The present invention arises from the unexpected and unpredictable flame-retardant properties of mixtures of two or more flammable organic compounds. This unexpected activity results from self-assembly and the formation of sufficiently strong hydrogen bonds between the components of the mixture. This strong interaction renders the combustion process endergonic, allowing the flame to be extinguished, which is the basis of the object of the present invention.

[0013] DESCRIPTION OF THE INVENTION

[0014] A first object of the invention is a pyrophosphate-free mixture or composite with flame-retardant capacity, not based on the use of polymeric materials, and suitable for use in fire extinguishing (preferably forest fires), characterized in that it comprises a mixture of non-polymeric organic components of low toxicity and biodegradability, where: a.at least one of the components of the mixture acts as a hydrogen bond donor, being preferably selected from a group consisting of dicyandiamide, urea, malonic acid, glycerol, guanidine, 1,1-dimethylurea, oxalic acid, ethylene glycol and derivatives, trifluoroacetamide, 1-methylurea, imidazole, 1,3-dimethylurea, lactic acid, resorcinol, 2-imidazoline, arginine, benzoic acid, benzyl alcohol, propyleneurea, thiourea, 4-hydroxybenzoic acid, succinic acid, acetamide, benzamide, levulinic acid, gallic acid, ammonium formate, tartaric acid, malonic acid and derivatives, adipic acid, oleic acid, linoleic acid, stearic acid, trimyristin, citric acid and isocitric acid, as well as any combinations thereof; b.and at least one of the components of the mixture acts as a hydrogen bond acceptor, being preferably selected from a group consisting of lidocaine or an ester-type derivative, proline, histidine, nicotinic acid, (phenylmethyl)triphenylphosphonium chloride, alanine, methyltriphenylphosphonium bromide, glycine, ethanolamine, betaine, ammonium formate, and ammonium oxalate, as well as any combinations thereof.

[0015] Preferably, the molar ratio of the hydrogen bond acceptor and donor compound can vary from 1:5 to 5:1.

[0016] Surprisingly, and not predictably by an expert in the field, it has been found that the mixture of two or more non-polymeric organic compounds that individually may be flammable (such as those described above) results in a mixture with flame-retardant properties due to the formation of strong hydrogen bonds that increase its thermodynamic stability, to the point that its flammability disappears, thus acting as flame retardants.

[0017] This union or self-assembly of the mixture components occurs spontaneously, resulting in a supramolecular aggregate that can be characterized as a distinct entity from its individual components, based on its properties. The origin of self-assembly is the establishment of a strong intermolecular interaction that maintains the bond between the mixture components. In the present invention, the interaction that originates self-assembly and is therefore responsible for the flame-retardant effect is hydrogen bonding. These interactions between hydrogen bond donors and acceptors decrease the entropy difference of the phase transition and increase the stability of the aggregate compared to its individual components. The strength of the hydrogen bonds is related to the phase transition temperature, thermodynamic stability, and other properties of the mixture.The present invention reveals that these forces can become sufficiently intense to negatively affect the enthalpy of combustion of the aggregate compared to that of its individual components.

[0018] Along with the flame retardant activity of the mixture, other criteria that the components of the mixture meet are:

[0019] • presenting minimal negative effects on vegetation and ecosystems at the concentrations that can be reached if used in the extinction of forest fires;

[0020] • biodegradability, so that they do not persist indefinitely in the environment;

[0021] • Water solubility and / or short persistence in aqueous media. This is a key aspect, as water is a universal solvent in fire extinguishing. Since the self-assembly that generates the flame retardant effect is due to hydrogen bonding, the components of the mixture are soluble in water. Furthermore, self-assembly is not observed in this medium, as the interaction of each component with the water predominates. However, when the water evaporates, due to its low boiling point, the components of the mixture recombine and, at that moment, produce the desired retardant effect. This is why, in aqueous media, the self-assembly mixture cannot be considered present; it forms as the water evaporates.

[0022] Other desirable properties are wide availability and low cost, stability, and easy handling.

[0023] Among the strong interactions capable of altering the enthalpy of combustion, there is a wide variety of possible combinations of starting components. This wide range of options is a significant advantage, as it allows for control over the physical and phase properties of the self-assembling mixtures. Among these properties is the ability to dissolve solutes of very different natures. Thus, in particular embodiments of the invention, the mixture may comprise at least one additional additive, which may preferably be selected from a group consisting of: a. water, preferably in a percentage between 50% and 95%; b. at least one inorganic or organic compound with acidic or basic chemical properties, preferably in a percentage equal to or less than 30% by weight of the total mixture.In preferred embodiments of the invention, the acid additive shall be selected from a group consisting of hydrochloric acid, sulfuric acid, sulfonic acid, carbonic acid, and carboxylic acid, as well as any combination thereof. As a basic additive, a carbonate or bicarbonate of an alkali or alkaline earth metal, preferably selected from a group consisting of sodium, potassium, magnesium, and calcium, as well as ammonium carbonate, shall preferably be used. These additives may be pure or dissolved in an aqueous medium and allow the pH value of the self-assembling mixture and the corresponding aqueous solutions to be regulated to near-neutral values ​​and, preferably, within the range of 5 to 9. The final pH value may also depend on the nature of the soil where the retarder is to be used; c. at least one solid compound onto which the mixture is impregnated.Preferably, the solid compound may be selected from a group consisting of clays (preferably selected from montmorillonite, sepiolite, and kaolin) and agricultural waste (preferably straw from agricultural crops such as rice, wheat, barley, and tiger nuts, among others), as well as any combination thereof (for example, as adobe). In preferred embodiments of the invention, the percentage of the flame retardant mixture impregnating the solid compound may vary between 5% and 40% by weight, and more preferably between 5% and 10% by weight; d. at least one coloring substance or pigment, suitable for visualizing the area where the flame retardant mixture is to be applied. The pigments may be natural, preferably metal oxides and more preferably iron oxides (reds), or biodegradable natural organic colorants such as those obtained from insects, mollusks, plants, and fruits.The percentage of these colorants shall preferably be less than 5% by weight and preferably less than 1%. Thus, as indicated, in particular embodiments of the invention, the mixtures may be used neat. In other embodiments of the invention, the mixtures may be used in aqueous solution of the desired concentration (preferably between 5% and 10% by weight). Finally, the mixtures may also be used supported on flame-retardant or non-flammable solids. The water used to dissolve the flame-retardant mixtures may be fresh or seawater.

[0024] One of the general characteristics of the mixtures described here, due to their flame-retardant effect, is that while the individual compounds may be solid at room temperature, their mixture produces a significant decrease in the melting point, sometimes exceeding 100 °C, and in many cases, the mixture can become liquid at room temperature (approximately 25 °C). This effect is due to the strong interaction established between the components of the mixture, which results in the crystalline lattice of the individual components not being at its most stable when the mixture is formed.

[0025] Additionally, the invention relates to a method for preparing mixtures of hydrogen donor and acceptor compounds. Specifically, this method may comprise preparing the mixture simply by intimately mixing its components, either by grinding the components together (when at least one is a solid) or by evaporating solutions of the compounds. In some cases, a change of physical state is observed, resulting in a viscous liquid mixture. This change of physical state reflects the strong interaction between the two compounds, which spontaneously undergo self-assembly. Any other method of preparing the mixtures, such as melting the components and pouring one component onto the other with stirring, or dissolving the components in aqueous solution, either together or separately, and then mixing them, is also suitable for preparing the self-assembling mixture with flame-retardant properties.

[0026] In embodiments where the mixture is used to impregnate solids that act as a carrier, impregnation can be carried out by dissolving the mixture or its components in an aqueous medium and then adding the desired amount of solid. The suspension is then stirred, and the water is slowly evaporated by heating, forced air circulation, vacuum, or a combination of these methods. Alternatively, the impregnated solid can be recovered by filtration or centrifugation. Other suitable impregnation methods include painting or aerosol spraying, among others.

[0027] When a solid material is impregnated with self-assembling mixtures that have flame-retardant properties, this solid material may offer additional functionalities. For example, when the flame-retardant self-assembling mixture impregnates rice straw, it may contain seeds of shrubs characteristic of the forest area affected by the fire. In this way, in addition to the fire-retardant effect, the mixture can aid in the reforestation of the affected forest area. Other functions of the impregnated material may include preventing the erosion of damaged soil by heavy rains or providing desirable nutrients or phytosanitary compounds.

[0028] Finally, the invention also relates to the use of the claimed self-assembling mixtures as flame retardants in fighting forest fires, particularly those mixtures that also meet the criteria of being benign to the environment, vegetation, and natural ecosystems. Furthermore, combinations of widely available and low-cost compounds are preferred.

[0029] DETAILED DESCRIPTION OF THE INVENTION

[0030] Among the combinations of organic molecules that donate and accept hydrogen bonds, those with the most effective fire retardant activity are those exhibiting the highest endothermic peak in thermogravimetric profiles. The value of this endothermic peak indicates greater stability in self-assembly and greater resistance to combustion. In this regard, among the most commonly used components for generating these mixtures of organic molecules that undergo self-assembly and are free of pyrophosphates are certain aminoamides and, most preferably, lidocaine (melting point 69°C), which is an affordable, biodegradable, and non-toxic compound.In combination with a hydrogen donor (DH) species, which must meet the same biorenewability and non-toxicity characteristics, such as urea (melting point 133°C), dicyandiamide (melting point 209°C), preferably renewable carboxylic acids (oxalic, succinic, citric, and lactic, among others), amino acids, natural polyols such as glycerol, and carbohydrates. With all these compounds, lidocaine is able to form biorenewable and non-toxic self-assembling mixtures, with low melting points (between 0°C and 50°C) in some cases, making it possible to handle them as liquid mixtures at room temperature (between 10°C and 35°C).

[0031] In principle, organic compounds undergo endothermic combustion. Lidocaine and urea are two examples of this general rule. Thus, during the thermogravimetric analysis of lidocaine, two endothermic signals are observed, the first centered at 75°C and the second centered at 250°C, which could be due, respectively, to moisture loss and oxidative degradation.

[0032] Furthermore, thermogravimetric analysis of urea exhibits a two-step decomposition resulting from the sequential decomposition of the reactions NH2CONH2(NH2CONH2NH3+ HNCO and HNCO + H2O NH3+ CO2) occurring, respectively, in the temperature range between 150°C and 270°C. In addition, five endothermic signals are observed centered at 140°C, 220°C, 240°C, 386°C, and 407°C, respectively.

[0033] In one particular embodiment of the invention, the mixture may be a combination of solid lidocaine and solid urea in a 1:1 weight ratio, in the presence of one equivalent of hydrochloric acid (37% aqueous solution). This mixture is liquid at room temperature (25°C) and has a pH value between 7 and 9. Impregnation of a combustible object such as wood or paper with this mixture produces an unexpected flame-retardant effect.

[0034] It has therefore been demonstrated that the combination of lidocaine and urea in the indicated proportion does not exhibit the calorimetric behavior of the individual components, but rather releases less heat of combustion. These differences in the thermodynamics of the combustion reaction are due to donor-acceptor self-assembly, which establishes a strong interaction between the two components.

[0035] Thus, in a preferred embodiment of the invention, the hydrogen bond acceptor compound is lidocaine or an ester derivative, and the donor compound is dicyanamide or urea. Even more preferably, the molar ratio between them can vary between 1:1 and 1:2.

[0036] In another preferred embodiment of the invention, the hydrogen bond donor compound is glycine and the acceptor compound is urea or dicyandiamide, preferably in a molar ratio that can vary between 1:1 and 1:2.

[0037] In another preferred embodiment of the invention, the hydrogen-bonding compound is ammonium formate and the hydrogen-bonding acceptor is selected from glycine, urea, and dicyandiamide. More preferably, the molar ratio of these components can vary between 1:1 and 1:2.

[0038] BRIEF DESCRIPTION OF THE FIGURES

[0039] Figures 1 and 2 show examples of composite structures that give rise to self-assembling mixtures with a flame-retardant effect that are representative, but not limiting, of the present invention.

[0040] Figure 1 shows a group of hydrogen-accepting organic molecules that can be used in the preparation of self-assembling mixtures with flame-retardant properties that are the subject of the present invention.

[0041] Figure 2 shows a group of hydrogen-donating organic molecules that can be used in the preparation of self-assembling mixtures with flame-retardant properties that are the subject of the present invention.

[0042] EXAMPLES

[0043] The following are non-limiting examples of the present invention.

[0044] Example 1

[0045] Formation of self-assembling mixtures of lidocaine (LIC) and urea. In a 100 ml flask at room temperature, 30 mmol (7.02 g) of lidocaine (LIC), 30 mmol (1.80 g) of urea, and 30 mmol (1.09 g) of hydrochloric acid are introduced. The resulting mixture is heated to 80°C for 12 h. After this time, a liquid mixture of 1 LIC / 1 Urea / 1 HCl is obtained, with an approximate pH value between 8 and 9. This fire-retardant mixture can be used directly, diluted in fresh or seawater to a concentration of approximately 10% or less, or used to impregnate solid substrates.

[0046] This mixture, when applied to a strip of cardboard two centimeters wide by ten centimeters long and left to dry, prevents the cardboard from burning, even when subjected to prolonged exposure to a blowtorch flame. In contrast, the same piece of cardboard burns completely when a flame is brought near it, igniting the cardboard, and then left to burn completely in the absence of the flame that started the fire.

[0047] Example 2

[0048] Formation of self-assembling mixtures between lidocaine and dicyandiamide (DCD). Proceed as in Example 1, replacing the mass of urea with 30 mmol (2.52 g) of dicyandiamide (DCD), using the same quantities of lidocaine and hydrochloric acid. Heat the resulting mixture to 80°C for 10 hours. After this time, the liquid mixture 1L / 1DCD / 1HCl is obtained, with a pH value between 7 and 8. This fire-retardant mixture can be used directly, diluted, or used to impregnate solid substrates.

[0049] When a strip of cardboard is impregnated with this mixture and allowed to dry, the cardboard becomes resistant to combustion even when exposed to a blowtorch flame. In comparison, a strip of the same cardboard burns completely when a flame is lit on it.

[0050] Example 3

[0051] Formation of aqueous mixtures of lidocaine, urea, and sodium bicarbonate. Proceed according to the procedure and quantities indicated in Example 1, heating the mixture to 80°C for 10 h. After this time, gradually add a solution of 2.52 g of sodium bicarbonate (30 mmol) in 50 ml of water with a pH of 10 to this LIC and urea mixture and stir for another 2 h at 80°C. The final aqueous solution (1 part LIC / 1 part urea / 1 part HCl / 1 part NaHCO3) with fire-retardant properties can be used directly, diluted in fresh or salt water to an approximate concentration of 10%, or used to impregnate solid substrates.

[0052] When a strip of cardboard is impregnated with this mixture and allowed to dry completely, the cardboard becomes fire-resistant, preventing a blowtorch flame from igniting it. In contrast, the same strip of cardboard burns completely when a blowtorch flame is applied.

[0053] Example 4: Preparation of aqueous solutions of lidocaine, dicyandiamide, and sodium bicarbonate. Proceed as in Example 2, placing 30 mmol (7.02 g) of lidocaine (LIC), 30 mmol (2.52 g) of dicyandiamide (DCD), and 30 mmol (1.09 g) of hydrochloric acid in a 100 mL volumetric flask at room temperature. Heat the resulting mixture to 80°C for 10 hours. After this time, gradually add a solution of 2.52 g of sodium bicarbonate (30 mmol) in 50 mL of water to the self-assembling mixture and stir the solution for 2 hours at 80°C. Other bases that can also be used are potassium bicarbonate, magnesium bicarbonate, and calcium bicarbonate, in the corresponding weights to maintain the molar ratio. The final aqueous mixture 1LIC / 1DCD / 1HCI / 1NaHCO3 obtained with a fire retardant effect has an approximate pH value of 7. This mixture can be used directly, can be diluted, or can be used to impregnate solid supports.

[0054] As in the previous examples, a combustion test of cardboard strips or wood chips comparing a sample impregnated with the 1LIC / 1DCD / 1HCI / 1NaHCO3 mixture after being allowed to dry demonstrates its flame retardant effect.

[0055] Example 5

[0056] Impregnation of aqueous suspensions of lidocaine and dicyandiamide onto clays. In a 100 ml flask, 30 mmol (7.02 g) of lidocaine (LIC), 30 mmol (2.52 g) of dicyandiamide (DCD), and 30 mmol (1.09 g) of hydrochloric acid are introduced at room temperature. The resulting solution is heated to 80°C for 10 h. After this time, a solution of 2.52 g of sodium bicarbonate (30 mmol) in 50 ml of water is added to this solution gradually with constant stirring. After the addition is complete, stirring is continued for 2 hours at 80°C. Two g of montmorillonite are added to the aqueous solution consisting of 1 LIC / 1 DCD / 1 HCl / 1 NaHCO3, and the mixture is stirred for 2 h at 80°C. After this time, the water is completely evaporated by heating to 80°C. This solid can be used directly or it can be pressed and ground to obtain particles of suitable dimensions, preferably between 100 and 500 µm, for use.

[0057] Unexpectedly, a synergistic effect was observed from the combination of the soluble compound mixture 1LIC / 1DCD / 1HCl / 1NaHCO3 and montmorillonite. This synergistic effect of the adsorption of the mixture onto montmorillonite on the flame retardant effect can be demonstrated by comparing the flame retardant effect on cardboard strips or wood chips when thoroughly impregnated with: i) a solution of 1LIC / 1DCD / 1HCl / 1NaHCO3 at a 1:2 dilution with respect to Example 4, or with ii) a suspension of 1 g of montmorillonite after being heated to 80 °C, or with iii) a suspension of Example 5 herein at a 1:2 dilution, and noting that only the specimens prepared according to Ni exhibit the desired flame retardant effect. This greater synergistic efficiency observed for the combination of 1LIC / 1DCD / 1HCI / 1NaHCO3 with montmorillonite could be due to the self-assembly of the mixture components, resulting in novel properties not found in the independent components.

[0058] Example 6

[0059] Impregnation of lidocaine and dicyandiamide mixtures on straw. In a 100 ml flask, 30 mmol (7.02 g) of lidocaine (LIC), 30 mmol (2.52 g) of dicyandiamide (DCD), and 30 mmol (1.09 g) of hydrochloric acid are introduced at room temperature. The resulting mixture is heated to 80°C for 10 hours. After this time, a solution of 2.52 g of sodium bicarbonate (30 mmol), or the appropriate amount of a bicarbonate of another metal, in 50 ml of water is gradually added to the previous solution, and the mixture is stirred for 2 hours at 80°C. One g of rice straw is then added to the final aqueous mixture consisting of 1 LIC / 1 DCD / 1 HCl / 1 NaHCO3, and the mixture is stirred for 2 hours at 80°C. The rice straw must be ground beforehand until particles smaller than 1 mm are obtained. After this time, the water is completely evaporated by heating to 80°C.The resulting solid can be used directly or can be appropriately modified, by pressing, grinding and sieving, for use.

[0060] The unexpected synergistic effect of combining the 1LIC / 1DCD / 1HCI / 1NaHCO3 mixture with straw becomes apparent when comparing the flame retardant activity of cardboard strips or wood chips impregnated with: i) a solution of 1LIC / 1DCD / 1HCI / 1NaHCO3 at a 1:2 dilution with respect to Example 4, or with ii) a suspension of 0.5 g of ground straw after being heated to 80°C, or with iii) a suspension of Example 6 herein at a 1:2 dilution, and noting that only the specimens prepared according to ii exhibit the desired retardant effect. This greater synergistic efficiency observed for the combination of 1LIC / 1DCD / 1HCI / 1NaHCO3 with straw could be due, as proposed in example 5, to the self-assembly of the water-soluble components of the mixture onto the straw particles, resulting in new properties not found in the independent components.

[0061] Example 7

[0062] Impregnation of mixtures with flame-retardant properties onto clay and straw. In a 100 ml flask at room temperature, 30 mmol (7.02 g) of lidocaine (LIC), 30 mmol (2.52 g) of dicyandiamide (DCD), and 30 mmol (1.09 g) of hydrochloric acid are introduced. The resulting mixture is heated to 80°C for 10 hours. After this time, a solution of 2.52 g of sodium bicarbonate (30 mmol) in 50 ml of water is gradually added to the mixture, which is then stirred for 2 hours at 80°C.

[0063] To the final aqueous mixture of 1LIC / 1DCD / 1HCI / 1NaHCO3 obtained, 2 g of montmorillonite and 1 g of rice straw are added and stirred for 2 hours at 80°C. The mixture of montmorillonite and straw may have been previously modified, forming a mud brick that is ground into particles of millimeter dimensions.

[0064] Example 8

[0065] Formation of self-assembling mixtures of lidocaine and urea supported on montmorillonite. The procedure is the same as in Example 5, replacing the amount of dicyandiamide with 30 mmol (1.80 g) of urea. Alternatively, any of the other compounds shown in Figure 2 that act as hydrogen donors can be used in an amount equivalent to 30 mmol. The resulting solid can be used directly or modified as needed.

[0066] Example 9

[0067] Impregnation of self-assembling mixtures of lidocaine and urea onto straw. The procedure is the same as in Example 6, replacing the amount of dicyandiamide with 30 mmol (1.80 g) of urea. Alternatively, any of the other compounds listed in Figure 2 that act as hydrogen donors can be used in an amount equivalent to 30 mmol. The resulting solid can be used directly or modified as needed. Similar to Example 6, a synergistic effect is observed from the combination of the soluble organic compounds on the ground straw particles when comparing the lack of retarding effect of 1:2 dilute solutions of the soluble compounds or the straw suspension without lidocaine and urea (0.5 g) with the effect observed from the mixture of both.

[0068] Example 10

[0069] Impregnation of adobe bricks with mixtures of lidocaine and urea or another hydrogen donor. Proceed as described in Example 8, replacing the amount of dicyandiamide with 30 mmol (1.80 g) of urea. Alternatively, any of the other compounds listed in Figure 2 that act as hydrogen donors can be used in an amount equivalent to 30 mmol. It is advisable to prepare the adobe bricks by mixing clay and straw, and then grind them into particles of suitable size before impregnating them with the lidocaine and urea mixture. The resulting solid can be used directly or modified as needed.

[0070] Example 11

[0071] Formation of self-assembling mixtures of betaine and urea with subsequent impregnation on montmorillonite. In a 100 ml flask, 15 mmol (2.30 g) of betaine hydrochloride (BETCI) and 30 mmol (1.80 g) of urea are introduced at room temperature. The resulting mixture is heated to 80°C for 5 hours. After this time, a solution of 2.52 g (30 mmol) of sodium bicarbonate in 40 ml of water is slowly added to the flask containing the self-assembling mixture, and the mixture is stirred for 1 hour at 80°C. This aqueous solution can be used as a flame retardant, and the water can be evaporated to obtain the pure mixture.The combination of betaine and urea impregnated on montmorillonite exhibits the synergistic effect previously observed in Example 5, as can be deduced from the lack of retarding effect of the water-soluble organic compounds at a 1:2 dilution, of the 1 g montmorillonite suspension, which is observed for the combination of the soluble compounds with the montmorillonite.

[0072] Alternatively, 2 g of montmorillonite is added to this aqueous solution containing 1BETCI / 2Urea / 2NaHCO3 and stirred for 1 hour at 80°C. The montmorillonite may be ground and sieved prior to impregnation, or the particle size of the material may be modified after impregnation.

[0073] Example 12

[0074] Impregnation of self-assembling mixtures based on betaine and urea onto straw. Proceed as in example 11 to obtain the flame retardant mixture in the indicated quantities. To the final aqueous mixture 1BETCI / 2Urea / 2NaHCO3, add 1 g of rice straw, previously ground to a particle size of approximately 1 millimeter. To this straw impregnated with the flame retardant, shrub seeds can be added at a percentage of 20% by weight to promote the recovery of flora in the fire-damaged area.

[0075] Example 13

[0076] Impregnation of montmorillonite and rice straw adobe nanoparticles with a self-assembling mixture of betaine and urea neutralized with sodium bicarbonate. The procedure outlined in Example 11 is used to prepare a self-assembling mixture of betaine chloride and urea in a 1:2 molar ratio, along with sodium bicarbonate as a pH buffer. Three grams of adobe, previously ground and sieved to 100-200 mesh, are added to this solution, and the mixture is stirred for 2 hours at 80°C. After this time, the water is evaporated. The adobe is obtained by mixing 2 g of montmorillonite with 1 g of ground rice straw in 50 ml of water, stirring for 2 hours at 80°C, and then evaporating the water. The resulting adobe is ground and sieved to the desired particle size.

[0077] Example 14

[0078] Formation of self-assembling mixtures of betaine and dicyandiamide neutralized with sodium bicarbonate and their subsequent use for impregnating montmorillonite. In a 100 mL flask, 20 mmol (3.07 g) of betaine hydrochloride (BETCI) and 20 mmol (1.68 g) of dicyandiamide (DCD) are introduced at room temperature. The resulting mixture is heated to 80°C for 5 hours to allow spontaneous self-assembly of both molecules. After this time, a solution of 1.68 g of sodium bicarbonate (20 mmol) in 40 mL of water is slowly added, and the solution is stirred for 1 hour at 80°C. Two g of montmorillonite are then added to the final aqueous mixture 1BETCI / 1DCD / 1NaHCO3, and the mixture is stirred for 1 hour at 80°C. Water is evaporated at 80°C to obtain impregnated montmorillonite. This material can be pressed, ground, and sieved for proper handling.

[0079] Example 15

[0080] Impregnation of a self-assembling mixture of betaine and dicyandiamide on rice straw. The self-assembling mixture of betaine hydrochloride and dicyandiamide is prepared and neutralized with sodium bicarbonate as indicated in Example 14. The impregnation is then carried out following the procedure indicated in Example 14, replacing the clay with 1 g of rice straw in the form of flakes.

[0081] Example 16

[0082] Impregnation of the self-assembling mixture of betaine hydrochloride and dicyandiamide in adobe. The procedure is as indicated in example 14, replacing the 2 g of montmorillonite with 3 g of ground and sieved adobe, with a particle size of 100 to 200 mesh. Subsequently, this sticky material can be pressed and ground for proper handling.

[0083] Example 17

[0084] Formation of self-assembling mixtures between betaine hydrochloride and dicyandiamide neutralized by ammonium bicarbonate. In a 100 ml flask, 20 mmol (3.07 g) of betaine hydrochloride (BETCI) and 20 mmol (1.68 g) of dicyandiamide (DCD) are introduced at room temperature. The resulting mixture is heated to 80 °C for 3 hours. After this time, a solution of 1.58 g (20 mmol) of ammonium bicarbonate in 30 ml of water is gradually added to the self-assembling mixture, and the solution is stirred for 1 hour at 80 °C. The resulting aqueous mixture, 1BETCI / 1DCD / 1(NH4)HCO3, with a fire-retardant effect, can be used directly or diluted in fresh or seawater to a concentration of 10% or less. Alternatively, this self-assembly mixture can be used to impregnate solid supports such as those mentioned in previous examples.

[0085] Example 18

[0086] Impregnation of the self-assembling mixture of betaine hydrochloride and dicyandiamide neutralized with ammonium bicarbonate in clays. The procedure is the same as in Example 17, and the aqueous solution of betaine hydrochloride and dicyandiamide neutralized with ammonium bicarbonate is used to impregnate 2 g of montmorillonite. The process is carried out by mechanical stirring for 1 hour and slow evaporation of the water at 80°C. A similar procedure can be used to impregnate other types of natural clays, such as sepiolite, kaolin, halloysite, and vermiculite, among others.

[0087] Example 19

[0088] Impregnation of the self-assembling mixture of betaine hydrochloride and dicyandiamide neutralized with ammonium bicarbonate in rice straw. Proceed as in Example 18, replacing the montmorillonite with 1 g of rice straw. Alternatively, straw from other crops, such as tiger nut straw or other types of agricultural waste suitably treated as shavings, sawdust, or other particles, can be used as a carrier for the retarder.

[0089] Example 20

[0090] Impregnation of the self-assembling mixture of betaine hydrochloride and dicyandiamide neutralized with ammonium bicarbonate in adobe. The procedure is the same as in Example 18, replacing the montmorillonite with 3 g of adobe in particulate form. The adobe is prepared by any method such as that indicated in Example 7, mixing 2 g of montmorillonite or other micronized clay with 1 g of rice straw or straw from another crop, and proceeding to mix it in aqueous suspension, drying it by evaporation of the water, grinding it into particles, and sieving the particles.

[0091] Example 21

[0092] Formation of self-assembling mixtures of glycine hydrochloride and dicyandiamide, neutralized by potassium bicarbonate. In a 100 mL flask at room temperature, 20 mmol (2.23 g) of glycine hydrochloride (GLI) and 20 mmol (1.68 g) of dicyandiamide (DCD) are introduced. The resulting mixture is heated to 80 °C for 3 hours. After this time, another solution of 2 g (20 mmol) of potassium bicarbonate in 30 mL of water is slowly added to the solution, and the mixture is stirred for 1 hour at 80 °C. The final aqueous solution formed by 1GLI / 1DCD / 1HCl / 1KHCO3 can be concentrated by evaporating the water at 80 °C or can be used diluted to a concentration between 5 and 20% by weight in water.

[0093] Example 22

[0094] Impregnation of the self-assembling mixture of glycine hydrochloride and dicyandiamide onto montmorillonite or silicates. Proceed as in Example 21, adding 2 g of montmorillonite or another natural or synthetic clay or silicate to the self-assembling mixture of glycine hydrochloride and dicyanamide. Stir the suspension for 1 hour at 80°C. After this time, the water evaporates at 80°C while maintaining mechanical stirring of the suspension, resulting in a sticky residue of clay coated with the self-assembling mixture. Example 23

[0095] Impregnation of the self-assembling mixture of glycine hydrochloride and dicyandiamide in agricultural straw. The procedure is the same as in example 22, replacing the montmorillonite with 1 g of rice straw or straw from another agricultural crop, or with wood chips or sawdust from biomass waste.

[0096] Example 24

[0097] Impregnation of the self-assembling mixture of glycine hydrochloride and dicyandiamide in adobe. Proceed as in example 22, replacing the montmorillonite with 3 g of adobe prepared as indicated in example 7.

[0098] Example 25

[0099] Formation of self-assembling mixtures of lidocaine and glycerol. In a 100 mL flask at room temperature, 20 mmol (4.69 g) of lidocaine (LIC), 20 mmol (1.46 mL) of glycerol (GLC, average molecular weight 10,000), and 30 mmol (0.73 g) of hydrochloric acid are introduced. The resulting mixture is heated to 80°C for 6 hours. After this time, the solution is neutralized by the slow addition of 2 g of potassium bicarbonate (20 mmol) in 40 mL of water. The solution is stirred for 2 hours at 80°C. The final aqueous mixture 1LIC / 1GLC / 1HCl / 1KHCO3 can be used directly, diluted to a concentration between 5 and 20% by weight, or concentrated by evaporating the water at 80°C under mechanical stirring.

[0100] Example 26

[0101] Impregnation of the self-assembling mixture of lidocaine and glycerol in montmorillonite or silicates. The procedure is as indicated in example 25. Once the neutralized aqueous solution of ILIC / IGLC / IHCI / IKHCO3 has been obtained, 2 g of montmorillonite or another natural clay or natural or synthetic silicate are added to this solution, and the suspension is mechanically stirred for 2 hours at 80°C. The water is then completely evaporated by heating to 80°C under constant mechanical stirring.

[0102] Example 27

[0103] Impregnation of the self-assembling mixture of lidocaine and glycerol in rice straw. The procedure is as in example 26, replacing the montmorillonite with 1 g of rice straw or straw from another crop, or sawdust or shavings from biomass, and the suspension is stirred at 80°C under constant mechanical agitation until complete evaporation of the water.

[0104] Example 28

[0105] Impregnation of the self-assembling mixture of lidocaine and glycerol in adobe. Proceed as in example 26, replacing the montmorillonite with 3 g of adobe. The adobe can be prepared as indicated in example 7.

[0106] Example 29

[0107] Obtaining colored solids with fire-retardant properties by impregnating adobe with a self-assembling mixture of lycodaine and glycerol. The procedure is the same as in example 28, but 0.016 g of PureMarin® commercial dye is added to the 1LIC / 1GLC / 1HCI / 1KHCO3 self-assembling solution, and the solution is homogenized for 3 hours at 80°C before adding the 3 g of adobe.

[0108] Example 30

[0109] Colored sample with fire-retardant effect obtained by impregnating adobe with the self-assembling mixture of (phenylmethyl)triphenylphosphonium chloride and glycerol. In a 100 ml flask, 20 mmol (7.77 g) of (phenylmethyl)triphenylphosphonium chloride (BfCl) and 20 mmol (1.46 ml) of glycerol (GLC) are introduced at room temperature. The resulting mixture is heated to 80°C for 5 hours. After this time, a solution of 2 g (20 mmol) of potassium bicarbonate in 60 ml of water is slowly added, and the solution is stirred for 1 hour at 80°C. To the final aqueous solution 1BfCI / 1GLC / 1KHC03, add 3 g of adobe prepared as indicated in example 7 and 0.016 g of PureMarin® commercial dye and the suspension is mechanically stirred at 80°C for a sufficient time to achieve complete evaporation of the water.

[0110] Example 31

[0111] Colored sample with fire-retardant effect obtained by impregnating adobe with the self-assembling mixture of glycine and glycerol. In a 100 ml flask, 20 mmol (1.5 g) of glycine (Gli) and 20 mmol (1.46 ml) of glycerol (GLC, average molecular weight 10,000) are introduced at room temperature. The resulting mixture is heated to 80°C for 5 hours. After this time, a solution of 2 g of potassium bicarbonate (20 mmol) in 60 ml of water is slowly added, and the solution is stirred for 1 hour at 80°C. To the aqueous mixture consisting of IGN / IGLC / IKHCO3, 3 g of adobe prepared as indicated in Example 7 and 0.016 g of PureMarin® commercial dye are added. The suspension is mechanically stirred at 80°C until complete evaporation of the water is achieved, obtaining a sticky residue with flame retardant properties.

[0112] Example 32

[0113] Formation of self-assembling mixtures of ammonium formate and urea. In a 50 ml flask, 60 mmol (3.78 g) of ammonium formate (AFM) and 60 mmol (3.60 g) of urea are introduced at room temperature. The resulting mixture is heated to 80 °C for 12 h. After this time, a viscous 1AFM / 1Urea mixture is obtained, which solidifies upon cooling at room temperature. This fire-retardant mixture can be diluted in water at concentrations between 5 and 50% by weight or used to impregnate solid substrates such as clays, natural or synthetic silicates, biomass waste, and others. A dye can also be added to allow for the geographical identification of the mixture's location.

[0114] Example 33

[0115] Formation of self-assembling mixtures between ammonium formate and dicyandiamide. In a 50 ml flask, 60 mmol (3.78 g) of ammonium formate (FDA) and 60 mmol (5.04 g) of dicyandiamide (DCD) are introduced at room temperature. The resulting mixture is heated to 80°C for 12 h. After this time, upon cooling to room temperature, the solid mixture 1FDA / 1DCD is obtained. This fire-retardant mixture can be diluted for use in water at concentrations between 5 and 50% by weight or can be used to impregnate solid substrates such as those indicated in Example 32.

[0116] Example 34

[0117] Formation of self-assembling mixtures of ammonium formate and glycine. In a 50 ml flask, 60 mmol (3.78 g) of ammonium formate (FDA) and 60 mmol (4.50 g) of glycine (GLI) are introduced at room temperature. The resulting mixture is heated to 80°C for 12 h. After this time, a viscous 1FDA / 1GLI mixture is obtained, which solidifies upon cooling at room temperature. This fire-retardant mixture can be diluted in water at concentrations between 5 and 50% by weight or can be used to impregnate solid substrates, as shown in Example 32.

[0118] Example 35 Formation of self-assembling mixtures between glycine and urea. In a 50 ml flask, 30 mmol (2.25 g) of glycine (GLI), 60 mmol (3.60 g) of urea, and 30 mmol (1.09 g) of hydrochloric acid (37%) are introduced at room temperature. The resulting mixture is heated to 80°C for 6 h. After this time, the viscous mixture 1LCI / 2urea / 1HCl is obtained, which, upon removal of water under reduced pressure of 40 mm Hg, solidifies again at room temperature (25°C). This fire-retardant mixture can be diluted in water at a concentration between 5 and 50% by weight or can be used to impregnate solid substrates such as any of those indicated in previous examples.

[0119] Example 36

[0120] Formation of self-assembling mixtures between glycine and dicyandiamide. In a 50 ml flask at room temperature, 30 mmol (2.25 g) of glycine (GLI), 30 mmol (2.52 g) of dicyandiamide (DCD), and 60 mmol (2.18 g) of hydrochloric acid are introduced. The resulting mixture is heated to 80°C for 7 hours. After this time, a viscous mixture of 1LCI / 1DCD / 2HCL with a pH between 1 and 3 is obtained. This fire-retardant mixture can be diluted in water for use at concentrations between 5 and 50% by weight or can be used to impregnate solid supports such as those indicated in Example 32.

Claims

CLAIMS 1. A flame-retardant mixture, free of pyrophosphates, characterized in that it comprises a mixture of non-polymeric organic components: a. at least one first compound of the mixture acts as a hydrogen bond donor; and b. at least one second compound of the mixture acts as a hydrogen bond acceptor.

2. Mixture according to claim 1, wherein the molar ratio of the hydrogen bond donor compound and the hydrogen bond acceptor compound ranges from 1:5 to 5:

1.

3. Mixture according to claim 1 or 2, wherein the hydrogen bond donor compound is selected from a group consisting of dicyandiamide, urea, malonic acid, glycerol, guanidine, 1,1-dimethylurea, oxalic acid, ethylene glycol and derivatives, trifluoroacetamide, 1-methylurea, imidazole, 1,3-dimethylurea, lactic acid, resorcinol, 2-imidazoline, arginine, benzoic acid, benzyl alcohol, propyleneurea, thiourea, 4-hydroxybenzoic acid, succinic acid, acetamide, benzamide, levulinic acid, gallic acid, ammonium formate, tartaric acid, malonic acid and derivatives, adipic acid, oleic acid, linoleic acid, stearic acid, trimyristin, citric acid and isocitric acid, as well as any combinations thereof.

4. Mixture according to claim 3, wherein the hydrogen bond donor compound is selected from a group consisting of dicyandiamide, urea, glycerol, guanidine, 1,1-dimethylurea, ethylene glycol and derivatives, trifluoroacetamide, 1-methylurea, imidazole, 1,3-dimethylurea, resorcinol, arginine, benzyl alcohol, propyleneurea, thiourea, acetamide, benzamide, ammonium formate and trimyristin, as well as any combinations thereof.

5. A mixture according to any one of the preceding claims, wherein the hydrogen bond acceptor compound is selected from a group consisting of lidocaine or an ester-type derivative, proline, histidine, nicotinic acid, (phenylmethyl)triphenylphosphonium chloride, alanine, methyltriphenylphosphonium bromide, glycine, ethanolamine, betaine, ammonium formate, and ammonium oxalate, as well as any combinations thereof.

6. Mixture according to claim 5, wherein the hydrogen bond acceptor compound is selected from a group consisting of lidocaine or an ester-type derivative, proline, histidine, nicotinic acid, (phenylmethyl)triphenylphosphonium chloride, alanine, methyltriphenylphosphonium bromide, glycine, ethanolamine, ammonium formate, and ammonium oxalate, as well as any combinations thereof.

7. Mixture according to any one of the preceding claims, wherein said mixture further comprises water, in a percentage between 50% and 95% of the total weight of the mixture.

8. Mixture according to any one of the preceding claims, wherein said mixture further comprises at least one inorganic or organic compound with acid or base chemical properties, in a percentage equal to or less than 30% by weight of the total weight of the mixture.

9. Mixture according to claim 8, wherein the compound with acidic chemical properties is selected from a group consisting of hydrochloric acid, sulfuric acid, sulfonic acid, carbonic acid and carboxylic acid, as well as any combinations thereof.

10. Mixture according to claim 8, wherein the compound with basic chemical properties is selected from a group consisting of an alkali metal carbonate or bicarbonate, ammonia, amine, or metal hydroxides.

11. Mixture according to any one of the preceding claims, wherein said mixture further comprises at least one solid compound onto which the mixture is impregnated.

12. Mixture according to claim 11, wherein said solid compound is selected from a group consisting of clays and at least one agricultural waste, as well as any combinations thereof.

13. Mixture according to claim 11 or 12, wherein the mixture is impregnating the solid compound in a percentage between 5 and 40% by weight.

14. Mixture according to any one of the preceding claims, wherein said mixture further comprises at least one coloring substance or pigment.

15. Method of preparing a mixture according to any one of claims 1 to 14, characterized in that it comprises intimately mixing at least a first compound of the mixture that acts as a hydrogen bond donor and at least a second compound of the mixture that acts as a hydrogen bond acceptor.

16. A method according to claim 15, further comprising impregnation with at least one solid.

17. Use of a mixture according to any one of claims 1 to 14 as a flame retardant in fighting forest fires.

18. Use according to claim 17, wherein the mixture is used in aqueous solution or supported on at least one fire-retardant or flammable solid.