High-stability anti-reburning foam extinguishing agent and preparation method thereof

Abstract

This invention discloses a highly stable anti-reignition foam fire extinguishing agent and its preparation method, which is formulated from C8-10 alkyl glycosides, C12-14 alkyl glycosides, low-substituted hydroxypropyl starch, sorbitol, and citrate buffer. The long and short chain alkyl glycosides optimize the oil-water interface film, while the starch and sorbitol form a hydration system to slow down foam drainage and improve storage stability. In the fire, sorbitol undergoes dehydration and absorbs heat, and co-carbonizes with starch at low temperatures to generate a dense, barrier carbon layer, effectively inhibiting fuel volatilization and extending the anti-reignition time. This formulation avoids the problem of alcohol vaporization and foam breakage, exhibits significant synergistic effects among its components, is easy to prepare, and the apparent viscosity of the finished product at 25°C is suitable for conventional fire-fighting equipment, making it suitable for flammable liquid oil pool fires. This fire extinguishing agent is a water-based foam concentrate that can be directly sprayed without dilution, and possesses excellent physicochemical and fire-extinguishing properties.

Description

Technical Field

[0001] This invention belongs to the field of fire-fighting foam extinguishing agent technology, specifically relating to a highly stable anti-reignition foam extinguishing agent and its preparation method. Background Technology

[0002] Fires involving flammable liquid storage tanks and chemical oil leaks are often extinguished by covering and smothering the fire with water-based foam extinguishing agents. However, most commercially available foam extinguishing agents are compounded with single carbon chain alkyl glycosides, resulting in weak foam film strength, rapid liquid release, and short half-life at room temperature. After being applied to the oil surface, they are easily damaged by rapid drainage, making it difficult to form a long-lasting, airtight barrier layer, thus posing a high risk of fire reignition.

[0003] To improve foam stability, existing solutions often add large amounts of high-viscosity polyols such as glycerol or high-molecular-weight thickeners. Although this can slow down drainage, it significantly increases the viscosity of the original liquid, exceeding the adaptability range of fire spraying equipment, and the foaming ratio drops sharply. When some solutions are combined with starch-based char-forming aids, they simply mix sugar alcohols and starch without any synergistic regulatory effect. Starch has a high activation energy for char formation, and a continuous char layer cannot be formed in time in the low-temperature range of the fire. After the liquid film ruptures due to temperature rise, insulation gaps are likely to appear.

[0004] Meanwhile, traditional formulations have a single buffer system, are prone to acidification during storage, and are susceptible to stratification and solid precipitation during high and low temperature cyclic storage, exhibiting poor resistance to hard water. Most preparation processes require high-temperature pregelatinization of starch, resulting in high energy consumption and complex production processes. Currently, there is a lack of environmentally friendly anti-reignition foam extinguishing agents that combine low viscosity for easy spraying, long-lasting foam stability, low-temperature in-situ continuous charring, and excellent storage stability. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a highly stable anti-reignition foam extinguishing agent and its preparation method. This extinguishing agent exhibits excellent foam stability, can continuously form char in situ to prevent reignition, has a viscosity suitable for fire spraying, good storage performance, and is environmentally friendly. It can meet the application requirements for extinguishing flammable liquid fires and providing long-term anti-reignition effects.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A highly stable, reignition-resistant foam fire extinguishing agent, wherein the fire extinguishing agent is prepared from the following raw materials in parts by weight: 3.0-5.0 parts of C8-10 alkyl glycoside, 1.5-2.5 parts of C12-14 alkyl glycoside, 0.2-0.6 parts of low-substituted hydroxypropyl starch, 4.0-7.0 parts of sorbitol, 0.3-0.6 parts of citrate, and deionized water to make up to 100 parts.

[0007] Preferably, the molar degree of substitution of the low-substituted hydroxypropyl starch is 0.08-0.18.

[0008] Preferably, the citrate is selected from one or more of trisodium citrate and disodium citrate, and the addition of citrate can adjust the pH of the fire extinguishing agent system to 7.0-8.5.

[0009] Preferably, the apparent viscosity of the finished fire extinguishing agent concentrate at 25°C is 80-200 mPa·s.

[0010] Preferably, the extinguishing agent has a foam separation half-life of not less than 25 minutes at room temperature.

[0011] Preferably, the preparation method of the highly stable anti-reignition foam fire extinguishing agent includes the following steps: S1. Add deionized water to a stirred tank, add citrate, stir at 200-300 r / min, and continue stirring for 8-12 min until the citrate is completely dissolved to obtain a uniform buffer base solution; S2. Under the condition of stirring speed of 200-300r / min, slowly add C8-10 alkyl glycoside and C12-14 alkyl glycoside to the buffer base solution in sequence. After the addition is completed, stir at a constant speed for 15-25min to fully mix the two alkyl glycosides. S3. Continue stirring at a speed of 200-300 r / min. First, add sorbitol and stir for 5-10 minutes until completely dissolved. Then, slowly and evenly sprinkle in low-substituted hydroxypropyl starch. After the addition is complete, continue stirring for 30-40 minutes until the starch is completely dispersed and there are no white agglomerated particles in the system. Filter to remove trace impurities to obtain the finished high-stability anti-reignition foam fire extinguishing agent.

[0012] Preferably, the operating temperature during the entire process of S1-S3 is stably controlled between 20-35℃. The beneficial effects of this invention are as follows: This invention combines long- and short-chain alkyl glycosides, low-substituted hydroxypropyl starch, sorbitol, and citrate to prepare a direct-spray foam concentrate. The synergistic effects of the formulation are significant: the apparent viscosity of the concentrate is 92-191 mPa·s, with balanced transport and film-forming properties; the system pH is stable at 7.2-8.3, eliminating the risk of pipeline corrosion; it exhibits excellent foaming and long-lasting foam retention; the system remains homogeneous after high and low temperature cycling and low-temperature cold resistance tests, demonstrating strong stability over a wide temperature range; it can quickly form a film to isolate oxygen in fire situations; the dual carbon sources co-carbonize at low temperatures to form a dense heat-insulating layer, resulting in rapid fire extinguishing and significantly better resistance to reignition than various control samples; the raw materials are readily available, preparation is simple, and it can be used directly without dilution. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0014] Example 1: This Example 1 describes a highly stable, reignition-resistant foam fire extinguishing agent, prepared from the following raw materials in parts by weight: 4.0 parts of C8-10 alkyl glycoside, 2.0 parts of C12-14 alkyl glycoside, 0.4 parts of low-substituted hydroxypropyl starch (molar substitution degree 0.12), 5.5 parts of sorbitol, 0.45 parts of citrate (trisodium citrate), and deionized water to make up to 100 parts; This embodiment describes a method for preparing a highly stable, reignition-resistant foam fire extinguishing agent. The specific preparation steps are as follows: S1. Add deionized water to a stirred tank, add trisodium citrate, and stir at 28℃ and 250r / min for 10min to completely dissolve the trisodium citrate and obtain a uniform buffer base solution. S2. Maintain a temperature of 28°C and a stirring speed of 250 r / min. Slowly add C8-10 alkyl glycosides and C12-14 alkyl glycosides in sequence. After the addition is complete, continue stirring for 20 min to ensure that the two alkyl glycosides are fully mixed. S3. Maintain a temperature of 28℃ and a rotation speed of 250r / min. First, add sorbitol and stir for 8 minutes until completely dissolved. Then, slowly and evenly sprinkle in low-substituted hydroxypropyl starch. After the feeding is completed, stir continuously for 35 minutes until the starch is completely dispersed without any white agglomerated particles. Filter to remove trace impurities and obtain the finished product, a high-stability anti-reignition foam fire extinguishing agent.

[0015] Example 2: This Example 2 describes a highly stable, reignition-resistant foam fire extinguishing agent, prepared from the following raw materials in parts by weight: 3.0 parts of C8-10 alkyl glycoside, 1.5 parts of C12-14 alkyl glycoside, 0.2 parts of low-substituted hydroxypropyl starch (molar substitution degree 0.12), 4.0 parts of sorbitol, 0.3 parts of citrate (trisodium citrate), and deionized water to bring the total to 100 parts; The preparation method of the highly stable anti-reignition foam fire extinguishing agent in Example 2 is the same as that in Example 1.

[0016] Example 3: This Example 3 describes a highly stable, reignition-resistant foam fire extinguishing agent, prepared from the following raw materials in parts by weight: 5.0 parts of C8-10 alkyl glycoside, 2.5 parts of C12-14 alkyl glycoside, 0.6 parts of low-substituted hydroxypropyl starch (molar substitution degree 0.12), 7.0 parts of sorbitol, 0.6 parts of citrate (trisodium citrate), and deionized water to make up to 100 parts; The preparation method of the highly stable anti-reignition foam fire extinguishing agent in Example 3 is the same as that in Example 1.

[0017] Comparative Example 1: The extinguishing agent of Comparative Example 1 was prepared from the following raw materials in parts by weight: 4.0 parts of C8-10 alkyl glycoside, 2.0 parts of C12-14 alkyl glycoside, 0.4 parts of low-substituted hydroxypropyl starch (molar substitution degree 0.12), 0.45 parts of citrate (trisodium citrate), and deionized water to make up to 100 parts; The preparation method of the fire extinguishing agent in Comparative Example 1 is the same as that in Example 1, except that sorbitol is not added.

[0018] Comparative Example 2: The extinguishing agent of Comparative Example 2 was prepared from the following raw materials in parts by weight: 6.0 parts of C12-14 alkyl glycoside, 0.4 parts of low-substituted hydroxypropyl starch (molar substitution degree 0.12), 5.5 parts of sorbitol, 0.45 parts of citrate (trisodium citrate), and deionized water to make up to 100 parts; The fire extinguishing agent in Comparative Example 2 was prepared in the same way as in Example 1, except that C8-10 alkyl glycosides were not added, and the amount of C12-14 alkyl glycosides was increased to 6.0 parts.

[0019] Comparative Example 3: The extinguishing agent of Comparative Example 3 was prepared from the following raw materials in parts by weight: 4.0 parts of C8-10 alkyl glycoside, 2.0 parts of C12-14 alkyl glycoside, 5.5 parts of sorbitol, 0.45 parts of citrate (trisodium citrate), and deionized water to bring the total to 100 parts; The preparation method of the fire extinguishing agent in Comparative Example 3 is the same as that in Example 1, except that low-substituted hydroxypropyl starch is not added.

[0020] Comparative Example 4: The extinguishing agent of Comparative Example 4 was prepared from the following raw materials in parts by weight: 4.0 parts of C8-10 alkyl glycoside, 2.0 parts of C12-14 alkyl glycoside, 0.4 parts of ordinary corn starch, 5.5 parts of sorbitol, 0.45 parts of citrate (trisodium citrate), and deionized water to bring the total to 100 parts; The preparation method of the fire extinguishing agent in Comparative Example 4 is the same as that in Example 1, except that the low-substituted hydroxypropyl starch is replaced with an equal weight of ordinary corn starch.

[0021] Comparative Example 5: The extinguishing agent of Comparative Example 5 was prepared from the following parts by weight of raw materials: 6.0 parts of C8-10 alkyl glycoside, 0.4 parts of low-substituted hydroxypropyl starch (molar substitution degree 0.12), 5.5 parts of sorbitol, 0.45 parts of citrate (trisodium citrate), and deionized water to make up to 100 parts; The preparation method of the fire extinguishing agent in Comparative Example 5 is the same as that in Example 1, except that C12-14 alkyl glycosides are not added, and the amount of C8-10 alkyl glycosides is increased to 6.0 parts.

[0022] Performance testing 1. Apparent viscosity of the stock solution at 25℃ The foam extinguishing agent sample was allowed to stand until the temperature stabilized at 25℃. A rotational viscometer with an appropriate range was selected. After cleaning and drying the rotor, it was installed in the viscometer. The rotor was completely immersed in the sample liquid surface. The instrument test temperature was set to a constant 25℃. After the reading stabilized, it was read. The test was performed in parallel for 3 times, and the average value was taken as the final viscosity value to obtain the apparent viscosity of the sample at 25℃.

[0023] Table 1. Apparent viscosity test data of different samples at 25℃.

[0024] The viscosity of the three sets of sample samples at room temperature ranged from 92 to 191 mPa·s, with moderate overall fluidity. Although the viscosity of the five comparative samples was within the sprayable range, the overall viscosity range was narrower than that of the examples. This invention uses a combination of long and short-chain alkyl glycosides, low-substituted hydroxypropyl starch, and sorbitol to synergistically regulate the viscosity of the system. The viscosity of the stock solution is suitable for conventional fire-fighting spraying devices, preventing nozzle clogging due to excessive viscosity and ensuring the formation of a continuous and complete foam film due to insufficient viscosity. Removing or replacing key components alone alters the colloidal network structure of the system, making it impossible to precisely control the viscosity to the optimal range for spraying and film formation. Consequently, the overall performance of on-site delivery and spreading is weaker than that of the examples.

[0025] 2. Half-life of foam separation at room temperature At a normal temperature of 25℃, measure an equal amount of the foam extinguishing agent to be tested, prepare sufficient uniform foam according to a unified foaming standard, and quickly fill it into a standard liquid separation graduated cylinder. Record the moment when the liquid first separates from the bottom of the graduated cylinder and start timing. Continuously observe and record the volume of the liquid separated from the bottom of the graduated cylinder. When the volume of the separated liquid reaches half of the total liquid phase volume of the foam, stop timing. The recorded time is the foam liquid separation half-life of the extinguishing agent.

[0026] Table 2. Half-life test data of foam exudation at room temperature for different samples.

[0027] The foam separation half-life of all three examples exceeded 25 minutes, demonstrating excellent foam liquid retention capacity. Comparative Examples 1, 2, 3, and 5, lacking sorbitol, containing only long-chain glycosides, without modified starch, and containing only short-chain glycosides, all had separation half-lives below 20 minutes, exhibiting rapid foam drainage and short coverage time. Comparative Example 4, using ordinary corn starch instead of modified starch, showed a slight improvement in performance, but was still significantly lower than all other examples. This demonstrates that the combination of long- and short-chain alkyl glycosides with sorbitol and low-substituted hydroxypropyl starch can form a synergistic foam-stabilizing colloidal network, effectively delaying water separation from the foam and significantly extending the duration of the foam's sealed coverage on the oil surface. The absence or substitution of any key component will disrupt the foam-stabilizing system.

[0028] 3. pH value of the system The foam extinguishing agent stock solution to be tested was allowed to stand at a constant temperature of 25°C. After calibrating the benchtop pH meter, the pH electrode was completely immersed in the extinguishing agent stock solution. The sample was gently shaken to ensure that the electrode was in full contact with the liquid. After the instrument reading stabilized, the value was recorded. Each group of samples was tested in parallel three times, and the average value was taken as the pH value of the sample system.

[0029] Table 3 pH data for different sample systems

[0030] The pH values ​​of the examples and all comparative samples remained stable within the slightly neutral range of 7.2-8.3, posing no risk of corrosion from strong acids or bases. The citrate buffer component in the formulation can independently stabilize the pH of the system. The removal or replacement of functional components will not significantly affect the pH of the system. Long-term storage will not result in significant pH shifts. During use, it will not corrode fire tanks or pipelines, nor will it damage the foam molding structure, making it suitable for diesel fire fighting conditions.

[0031] 4. Storage stability test Take equal amounts of each test foam extinguishing agent stock solution and seal them in a standard transparent storage bottle. First, place them in a 50℃ constant temperature oven for 24 hours, then transfer them to a -5℃ low temperature environment for 24 hours to complete one high and low temperature cycle. Repeat the cycle 5 times. After all cycles are completed, restore the sample to 25℃ room temperature and let it stand for 2 hours. Visually observe whether there are any abnormal phenomena such as layering, turbidity, precipitation, or solid precipitation in the liquid in the bottle, so as to determine the storage stability of the sample.

[0032] Table 4. Data on storage stability tests of different samples

[0033] After five cycles of accelerated storage at alternating high and low temperatures, the liquids in the three sets of examples remained transparent and homogeneous, without any deterioration phenomena such as stratification, turbidity, or solid precipitation; while the five comparative sets all exhibited varying degrees of turbidity, stratification, flocculent or particulate precipitation defects. This demonstrates that the combination of long and short chain alkyl glycosides, sorbitol, and low-substituted hydroxypropyl starch synergistically enhances the miscibility and compatibility of the components within the system, making phase separation less likely to occur under fluctuating temperature conditions; removing or replacing any key component alone would disrupt the colloidal stability of the system, making it prone to deterioration and stratification during long-term high and low temperature storage, and significantly reducing shelf stability.

[0034] 5. Oil pool fire extinguishing and reignition resistance test A standard steel oil tank was selected under normal temperature and pressure at 25℃. An equal amount of No. 0 diesel oil was added as the combustion medium. After the diesel oil was ignited and pre-burned for 60 seconds, an equal amount of the foam extinguishing agent to be tested was sprayed evenly at the same injection pressure and distance. The extinguishing time from the start of the spray to the complete extinguishing of the open flame in the oil tank was recorded. After the fire was extinguished, diesel oil was continuously and uniformly added to the bottom of the oil tank to keep the fuel supply to the oil surface uninterrupted. Timing was started until the open flame reappeared in the oil tank. This time was the anti-reignition time. Each group of samples was tested in parallel for 3 times. The average extinguishing time and the average anti-reignition time were taken as the final test results.

[0035] Table 5. Data on fire extinguishing and reignition resistance tests of different oil pool samples.

[0036] The three sets of examples extinguished open flames in the oil pool in only 26-32 seconds, significantly faster than all control samples. The examples showed a reignition resistance time of 42-55 minutes, while the five comparative examples had a maximum of only 23 minutes, and the rest were all less than 20 minutes, indicating that reignition occurred within a short time. The combination of long and short chain alkyl glycosides can quickly spread on the fuel surface to form a dense barrier film to isolate oxygen. Sorbitol and low-substituted hydroxypropyl starch synergistically generate a continuous heat-insulating char layer upon high-temperature dehydration, with a dual effect to inhibit fuel volatilization. Without a carbon source, with a single glycoside system, or with ordinary starch replacing modified starch, it is impossible to form a complete and long-lasting barrier char layer and a dense liquid film, resulting in a significant decrease in fire extinguishing efficiency, anti-burning, and anti-reignition performance.

[0037] 6. Foaming ratio and 25% separation time test At room temperature of 25℃, a certain amount of the original solution to be tested was taken and foamed at a constant air flow rate using a standardized foaming device to ensure that the foaming conditions were completely consistent. The total volume of the foam after expansion was recorded, and the foaming ratio was calculated. The foam was allowed to stand continuously, and the time it took for the precipitated liquid to reach 25% of the total liquid phase mass of the initial foam was recorded. Each group of samples was tested in parallel for 3 times and the average value was taken.

[0038] Table 6. Test data on foaming ratio and 25% separation time for different samples.

[0039] The foaming ratios of the three sets of examples remained stable at 6.9-7.8, with fluffy and uniform foam exhibiting good formability. The 25% separation time was no less than 16.5 minutes, demonstrating excellent water retention and foam stability. All comparative examples, lacking sorbitol, low-substituted hydroxypropyl starch, or long- and short-chain alkyl glycoside complexes, exhibited problems such as decreased foaming ratio, accelerated foam drainage, and easy collapse of the foam skeleton. Comparative example 4, where ordinary starch replaced modified starch, showed a slight improvement in performance, but was still significantly inferior to the examples of this invention.

[0040] 7. Low-temperature cold resistance stability test Seal an equal amount of the test foam extinguishing agent concentrate in a standard transparent sample bottle and place it in a -10℃ low temperature environment for 72 hours. After the test, take out the sample and let it stand at 25℃ for 2 hours to recover. Visually observe whether each sample shows any abnormalities such as freezing, turbidity, layering, gelation, or precipitation to evaluate the product's low temperature storage stability.

[0041] Table 7. Low-temperature cold resistance stability test data of different samples

[0042] After undergoing a prolonged, rigorous low-temperature test at -10°C, the three sets of examples maintained a consistently transparent and homogeneous system without freezing, stratification, turbidity, or precipitation, demonstrating excellent low-temperature storage stability. The comparative examples, lacking key synergistic components, exhibited significantly reduced system compatibility at low temperatures, resulting in varying degrees of turbidity, stratification, and flocculent precipitation. This indicates that sorbitol effectively improves the system's low-temperature antifreeze performance, and the combination of low-substituted hydroxypropyl starch with long and short-chain alkyl glycosides maintains system homogeneity at low temperatures, giving the fire extinguishing agent of this invention excellent wide-temperature storage compatibility.

Claims

1. A highly stable anti-reignition foam fire extinguishing agent, characterized in that, The extinguishing agent is prepared from the following raw materials in parts by weight: 3.0-5.0 parts of C8-10 alkyl glycoside, 1.5-2.5 parts of C12-14 alkyl glycoside, 0.2-0.6 parts of low-substituted hydroxypropyl starch, 4.0-7.0 parts of sorbitol, 0.3-0.6 parts of citrate, and deionized water to make up to 100 parts.

2. The highly stable anti-reignition foam extinguishing agent according to claim 1, characterized in that, The molar degree of substitution of the low-substituted hydroxypropyl starch is 0.08-0.

18.

3. The highly stable anti-reignition foam extinguishing agent according to claim 1, characterized in that, The citrate is selected from one or more of trisodium citrate and disodium citrate. Adding citrate can adjust the pH of the fire extinguishing agent system to 7.0-8.

5.

4. The highly stable anti-reignition foam extinguishing agent according to claim 1, characterized in that, The apparent viscosity of the finished fire extinguishing agent at 25°C is 80-200 mPa·s.

5. The highly stable anti-reignition foam extinguishing agent according to claim 1, characterized in that, The extinguishing agent has a foam separation half-life of not less than 25 minutes at room temperature.

6. A method for preparing a highly stable, reignition-resistant foam fire extinguishing agent according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Add deionized water to a stirred tank, add citrate, stir at 200-300 r / min, and continue stirring for 8-12 min until the citrate is completely dissolved to obtain a uniform buffer base solution; S2. Under the condition of stirring speed of 200-300r / min, slowly add C8-10 alkyl glycoside and C12-14 alkyl glycoside to the buffer base solution in sequence. After the addition is completed, stir at a constant speed for 15-25min to fully mix the two alkyl glycosides. S3. Continue stirring at a speed of 200-300 r / min. First, add sorbitol and stir for 5-10 minutes until completely dissolved. Then, slowly and evenly sprinkle in low-substituted hydroxypropyl starch. After the addition is complete, continue stirring for 30-40 minutes until the starch is completely dispersed and there are no white agglomerated particles in the system. Filter to remove trace impurities to obtain the finished high-stability anti-reignition foam fire extinguishing agent.

7. The method for preparing a highly stable anti-reignition foam fire extinguishing agent according to claim 6, characterized in that, The operating temperature of S1-S3 is stably controlled between 20-35℃ throughout the entire process.

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