RU2764689C1 - Water solution for extinguishing fires - Google Patents

Abstract

FIELD: fire extinguishing.

SUBSTANCE: invention relates to the field of fire extinguishing, in particular to water-based compositions used to extinguish forest fires and to protect wood, wooden structures and materials from fire. An aqueous solution for extinguishing fires contains water, liquid glass with a modulus of 2.5-3.2 and a surfactant. It additionally contains a thickener - carboxymethyl cellulose and a fire retardant - azofoska. As a surfactant, the solution contains a mixture of an alkyl polyglycoside and sodium alpha-olefin sulfonate, taken in a weight ratio of 1:1, with the following content of components, wt.%:

EFFECT: invention provides a high fire-retardant ability of the solution for extinguishing fires.

1 cl, 2 tbl

Description

The invention relates to the field of fire extinguishing, in particular to water-based compositions used in extinguishing forest fires and for protecting wood, wooden structures and materials from fire.

Known foaming composition for extinguishing fires containing normal secondary or primary sodium alkyl sulfates of the C ₆ -C ₁₆ fraction, urea (urea), polyethylene glycol with a molecular weight of 400-5000, urea chromate and water (patent RU 2110307, IPC A62D 1/02, 10.05 .1998).

The disadvantages of the known composition are the use of urea chromate due to the relatively high toxicity.

A fire extinguishing composition is known (ed. mon. SU 1813464, IPC A62D 1/00, 05/07/1993), including a liquid halohydrocarbon, a solvent, an aqueous dispersion stabilizer and water, characterized in that it contains laprol as a solvent, and as a stabilizer - cationic fluorine-containing surfactant, chemically related to quaternary ammonium salts.

The disadvantage of the extinguishing composition is the use of a fluorine-containing cationic surfactant as a dispersion stabilizer. Despite the fact that the content of the stabilizer is relatively small, the cost of consumption of the extinguishing agent can sometimes be equal to the cost of the burning substrate. In addition, fluorine-containing compounds are toxic.

A composition has been developed (patent RU 2270712, IPC A62D 1/02, 11/16/2004) containing sodium alkyl sulfates of primary higher fatty alcohols of the C ₈ -C ₁₀ fraction, sodium alkyl sulfates of primary higher fatty alcohols of the C ₁₂ -C ₁₄ fraction, sodium sulfoethoxylates of primary higher fatty alcohols of the C ₁₂ -C ₁₄ fraction, primary higher fatty alcohols of the C ₁₂ -C ₁₄ fraction, urea, n-butyl alcohol, butyl cellosolve, neonol, oxanol and water. This composition provides high fire-extinguishing capacity, expansion rate and foam stability for working solutions with a volume fraction of 6%.

However, the disadvantage of the above composition is that it can be used when the concentration of the working solution is not lower than 3% (vol.). An attempt to reduce the working concentration by increasing the concentration of surfactants in the composition leads to an increase in viscosity, loss of fluidity.

A composition is also known (patent RU 2694924, IPC A62D 1/00, 07/18/2019), including sodium liquid glass with a silicate module of 2.3-3.6, sodium hydroxide, urea, water-soluble simple ether with terminal hydroxyl groups or water-soluble polyhydric alcohol , sulfonol, foaming agent, water, acid hardener (phosphoric acid 75-85%). The result is a formulation with low viscosity and high adhesion, low curing time and storage stability.

However, the main disadvantage of this composition is the complexity of preparing the fire extinguishing composition. Caustic soda and phosphoric acid contained in the composition are highly hazardous substances, which makes it difficult to use this invention to extinguish forest fires.

Also known (patent RU 2730074, IPC A62D 1/00, 08/17/2020) is an aqueous solution for extinguishing fires containing water, liquid glass with a modulus of 2.5-3.2 and a high molecular weight surfactant, while additionally containing Preventol D2 , and as a high molecular weight surfactant xanthan gum, in the following ratio of the components of the solution, wt. %:

liquid glass 10-50, xanthan gum 0.05-0.8, Preventol D2 0.1 water rest.

However, the composition has a low foaming capacity and insufficient biological stability and aggregative stability due to the content of a natural biopolymer in its composition, which does not allow achieving high efficiency in fire extinguishing, preventive protection of surfaces from fire, as well as limited storage time. In addition, the composition poorly wets burning and charred surfaces and does not penetrate well into the pores of wood.

The closest in composition and achievement of the technical result to the proposed invention is an aqueous solution for extinguishing fires (patent RU 2275951, IPC A62D 1/00, 10.05.2006) containing water in an amount of 50-95 wt. %, liquid glass with a module of 2.5-3.2 in the amount of 5-50 wt. %, additionally containing a high molecular weight surfactant based on polyvinyl alcohol, toluene and water in the amount of 0.001-0.1 kg per cubic meter of water in solution. Known composition provides a decrease in temperature in the combustion zone, is heat-resistant and has an insulating ability due to the evaporation of free water. The presence of a surfactant in a given composition of the solution improves its dispersion during spraying and fixing on the combustion surface and increases the wettability of the combustion surface with the solution.

The main disadvantage of this composition is that its use requires a large amount of water (from 50 to 95 wt.%) to effectively extinguish fires.

The objective of the present invention is to provide an effective flame retardant composition that is easy to prepare, the availability of the substances used and is environmentally friendly.

The technical result of the invention is the high fire-retardant ability of the solution for extinguishing fires.

The set technical result is achieved by the fact that an aqueous solution for extinguishing fires, including water, liquid glass with a modulus of 2.5-3.2 and a surfactant, while additionally contains a thickener - carboxymethyl cellulose and a flame retardant - azophoska, and as a surface-active agent the active substance solution contains a mixture of alkylpolyglycoside and sodium alpha-olefinsulfonate, taken in a mass ratio of 1:1, with the following content, wt. %:

liquid glass with module 2.5-3.2 10-40 carboxymethylcellulose 1.25-1.5 mixture of alkyl polyglycoside and sodium alpha-olefinsulfonate, taken in a mass ratio of 1:1 0.75-1 Azofoska 15-20 water up to 100.

Carboxymethylcellulose (CMC) (TU 2231-034-07507908-2001) is a thickener.

Liquid glass has a silicate module value of 2.5 to 3.2 (GOST 13078-81) acts as a film insulating coating.

Azofoska (TU 2186-039-00203789-2003) plays the role of a flame retardant due to the content of phosphorus in its composition, which is a fire retardant. In addition, the nitrogen-phosphorus-potassium additive acts as a mineral fertilizer, which, when dissolved, quickly penetrates to the roots of damaged plants and contributes to the rapid restoration of landscape biocenosis after a fire.

Surfactant (surfactant) in the form of a mixture of alkyl polyglycoside (APG) and sodium alpha-olefinsulfonate (AOS), taken in a mass ratio of 1: 1, is used to improve surface wettability and better impregnation by reducing the surface tension of solutions, as well as for foaming composition during quenching.

Water has a cooling effect because it absorbs a lot of heat when it evaporates.

The addition of CMC increases the viscosity of the fire extinguishing aqueous solution, reduces the spreading rate due to the formation of "viscous water". Such water forms a film that sticks to the burning material and lasts longer than ordinary water.

During thermal degradation, the used phosphorus-containing flame retardants are converted into polyphosphoric acid, which in the condensed phase catalyzes the processes of dehydration of the pyrolyzable polymer substrate and leads to its carbonization.

When extinguishing fires, first the water evaporates, which was diluted with liquid glass, then the water evaporates from the liquid glass itself. Liquid glass turns into a solid state, the so-called xerogel. But it also contains molecular, chemically bound water. On further heating, a film is formed. At high temperatures, a layer of inorganic non-combustible foam of great thickness is formed. This foam has a very low thermal conductivity and isolates the access of oxygen to the combustible surface. The object stops further burning and smoldering.

Reducing the concentration of liquid glass below 10 wt. % leads to a deterioration in the fire retardant ability, the difference in extinguishing effect from water becomes insignificant.

With a decrease in azofoska ˂15 wt %, its properties as a flame retardant decrease.

With a simultaneous increase in liquid glass ˃40 wt. %. and azofoski ˃20 wt. %. the solubility of the composition deteriorates and a stone-like product with a strong smell of ammonia is formed.

With an increase in carboxymethylcellulose ˃1.5 wt. %. the viscosity of the composition increases significantly (which interferes with the effective use of the solution), and the use of this component ˂ 1.25 wt. %. not efficient enough.

The combination of surfactants in the range of 0.75-1 wt% is characterized by a critical concentration of micellization, therefore, has the best values of foaming and foam stability. Going beyond this interval leads to a deterioration in the surface properties of the compositions.

Composition preparation example

For the flame retardant solution was weighed 1.5 g of carboxymethylcellulose were placed in a flask with 47.5 g of pre-heated to 40 ... 50 ^{° C} water, stirred until complete dissolution. After cooling the CMC solution with constant stirring, the following components are added: liquid glass - 30 g, azophoska - 20 g and a mixture of surfactants - 1 g (0.5 g of alkyl polyglycoside and 0.5 g of sodium alpha-olefinsulfonate).

The viscosity of the compositions was measured using a capillary glass viscometer of the VPZh-4 brand with a capillary diameter of d = 3.55 cm according to the time of liquid outflow from the capillary, which was determined using an electronic stopwatch with an accuracy of ±0.01 s at a temperature of fire extinguishing compositions of 20°C (GOST 10028-81).

Tests for flame retardant properties were carried out: 1 - under radiation exposure (using an installation consisting of 4 lamps with halogen tubes with a power of 500 W and a reflector); 2 - when exposed to a gas flow (using a building hair dryer, the air temperature of which is 600 ⁰ С).

Preparation for testing and testing methodology comply with regulatory documents (GOST 16363-98, GOST R 53292-2009).

Pre-dried in a heating cabinet at a temperature of 103 ⁰ C to a constant weight, wooden bars were smeared on all sides with the studied compositions in 2 layers, 20 minutes after that, a building hair dryer and an installation with halogen lamps were directed at the samples at a distance of 1.5 cm. The temperature was measured at three points: 1 - darkening, 2 - the appearance of a spark, 3 - after 2 and 5 minutes, respectively, then the depth of burnout was measured to analyze visual damage.

The group of fire-retardant efficiency was evaluated according to GOST 16363-98 according to the weight loss of the tested sample:

,

,

where m _1i is the mass of the sample before testing, g; m _2i is the mass of the sample after testing, g; i is the sample number.

With a weight loss of not more than 9% for the fire retardant composition, 1 group of fire retardant efficiency is established, with a weight loss of the sample from 9% to 25% - 2 group of fire retardant efficiency, with a weight loss of more than 25% it is considered that this composition does not provide fire protection of wood and is not fire retardant.

The formulation of an aqueous solution for extinguishing fires and the test result are presented in table 1.

Table 1

Table 1 shows that with an increase in the content of liquid glass in solutions, the viscosity decreases. This is due to the fact that water glass is part of the liquid glass, therefore, solutions with the addition of liquid glass are more dilute.

A more viscous solution is less crushed into small drops, which, on the one hand, reduces their loss, and on the other hand, reduces runoff (adhesion forces between wood and liquid increase), due to which penetration into the pores of wood slows down. However, highly viscous solutions are undesirable when extinguishing fires, since the method of their application in practice becomes more complicated.

To achieve the technical result, the compositions No. 2, No. 3 and No. 4, belonging to the 1st group of fire retardant efficiency, are the best.

The results of additional tests are shown in table 2.

table 2

From the experience with radiation exposure in table 2 it can be seen that the time of appearance of smoke and darkening is longer in compositions No. 2, No. 3 and No. 4 and the temperature in the fire seat is lower compared to the prototype, which determines the effectiveness of these compositions for improving the fire retardant properties of wood. Compositions under No. 2, No. 3 and No. 4 belong to group 1 of fire retardant efficiency, since P < 9 (Table 1), which is also confirmed by the time of the beginning of the darkening of a wooden bar, which is more than 50 s. The rest of the compositions (according to the prototype and No. 1) belong to the 2nd group of fire retardant efficiency, since 9 < P < 25.

When using a building hair dryer, compositions No. 2, No. 3, No. 4, as well as the composition according to the prototype, stood out, since the bars did not catch fire after 2 minutes. Composition No. 1 does not have sufficient flame retardant efficiency due to low concentrations of added components. According to the calculated efficiency, compositions No. 2 - No. 4 and the prototype composition belong to group 1 of fire retardant efficiency, since P < 9. Only composition No. 2 belongs to group 2 of fire retardant efficiency, since 9 < P < 25.

The recommended compositions are No. 2, No. 3 and No. 4, as they have better performance compared to the prototype and have the best fire efficiency.

The proposed optimal ratio of components according to the invention provides high fire retardant performance. A decrease in the declared composition of the main components leads to a deterioration in performance. The main advantage of the invention is the ease of preparation of the composition, the availability of the substances used and the gentle effect of the invention on the environment.

Thus, an aqueous solution for extinguishing fires, including water, liquid glass with a modulus of 2.5-3.2, a thickener - carboxymethyl cellulose, a fire retardant - azophoska and a surfactant in the form of a mixture of alkyl polyglycoside and sodium alpha-olefin sulfonate, taken in a mass ratio 1:1, with the declared content of components, has a high fire retardant ability.

Claims (2)

An aqueous solution for extinguishing fires, including water, liquid glass with a modulus of 2.5-3.2 and a surfactant, characterized in that the solution additionally contains a thickener - carboxymethyl cellulose and a fire retardant - azophoska, and as a surfactant the solution contains a mixture of alkylpolyglycoside and sodium alpha-olefinsulfonate, taken in a mass ratio of 1:1, with the following content of components, wt.%: