Hydrogel fire extinguishing agent based on modified lignin and preparation method thereof

Abstract

The invention provides a hydrogel fire extinguishing agent based on modified lignin and a preparation method of the hydrogel fire extinguishing agent. The hydrogel fire extinguishing agent comprises the following raw materials in parts by weight: 15-30 parts of acetylated lignin, 50-100 parts of sodium trimetaphosphate, 50-250 parts of expanded graphite and 2000-2500 parts of water. According to the hydrogel fire extinguishing agent, acetylated lignin is added, a three-dimensional network structure support is provided, expanded graphite is filled, and a three-dimensional network structure is finally formed, so that the adhesive force of the hydrogel fire extinguishing agent is improved, the hydrogel fire extinguishing agent is more firmly attached to the surface of a comburent, a fire source is effectively covered, and the fire extinguishing effect is improved; and meanwhile, the acetylated lignin improves the stability of the hydrogel fire extinguishing agent, so that the mass loss rate of the hydrogel fire extinguishing agent is reduced in a high-temperature environment, a good adhesion state can be kept, and the fire extinguishing effect can be continuously achieved.

Description

Technical Field

[0001] The invention relates to the technical field of fire extinguishing agents, and in particular to a hydrogel fire extinguishing agent based on modified lignin and a preparation method thereof. Background Art

[0002] Hydrogel fire extinguishing agent is a new type of fire extinguishing agent that combines the cooling effect of water and the physical barrier effect of gel. Hydrogel fire extinguishing agent can form a gel-like covering layer on the surface of the burning object, which can effectively isolate oxygen and prevent the combustion reaction from continuing. At the same time, because it contains a large amount of water, it can continuously absorb heat and play a role in cooling down. Compared with traditional fire extinguishing agents, hydrogel fire extinguishing agent has better fire extinguishing performance, especially in suppressing re-ignition.

[0003] In the current firefighting field, the demand for efficient, environmentally friendly and multifunctional fire extinguishing agents is increasing, and hydrogel fire extinguishing agents are developing in the direction of high performance, low cost and environmental friendliness. Although polymer hydrogels based on polyacrylic acid have been widely used in the field of fire extinguishing, there is still the problem of weak adhesion. Currently, researchers are exploring how to optimize the composition and structure of hydrogels to make them have better thermal stability, rheological properties, etc., to meet the fire extinguishing needs of different types of fires.

[0004] The Chinese invention patent document with publication number CN111184975A ​​discloses a lignin-based polymer hydrogel fire extinguishing agent and a preparation method thereof. The hydrogel fire extinguishing agent is prepared by compounding lignin or a lignin derivative with polyacrylic acid. However, the lignin has a strong hydrophilicity and insufficient lipophilicity, and is difficult to play a significant role in oily or non-aqueous combustibles. The used lignin is not modified, and the lignin macromolecular structure is complex, the molecular activity is low, it is not easy to graft, and the compatibility with polyacrylic acid resin is poor, which leads to difficulties in preparing the composite hydrogel fire extinguishing agent, and it is difficult to form a hydrogel fire extinguishing agent with stable performance, which affects the fire extinguishing effect and the stability of product quality. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to improve the stability and adhesion of the hydrogel fire extinguishing agent.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] The first aspect of the present invention provides a hydrogel fire extinguishing agent based on modified lignin, comprising the following raw materials in parts by weight: 15-30 parts of acetylated lignin, 50-100 parts of sodium trimetaphosphate and 50-250 parts of expanded graphite.

[0008] Beneficial effects: The hydrogel fire extinguishing agent of the present invention provides a three-dimensional network structure support by adding acetylated lignin, and finally forms a three-dimensional network structure by filling with expanded graphite, thereby improving the adhesion of the hydrogel fire extinguishing agent, making it more firmly attached to the surface of the burning object, effectively covering the fire source, and improving the fire extinguishing effect; at the same time, the acetylated lignin improves the stability of the hydrogel fire extinguishing agent, so that the mass loss rate of the hydrogel fire extinguishing agent is reduced in a high temperature environment, and it can maintain a good adhesion state and continue to play a fire extinguishing role.

[0009] Preferably, the raw materials include the following parts by weight: 20-30 parts of acetylated lignin, 65-100 parts of sodium trimetaphosphate, 150-250 parts of expanded graphite and 2500 parts of water.

[0010] The second aspect of the present invention provides a method for preparing the above-mentioned hydrogel fire extinguishing agent based on modified lignin, comprising the following steps: adding a strong base to water, adding sodium trimetaphosphate thereto, leaving it for a period of time, and then adding expanded graphite and acetylated lignin thereto to react, and finally obtaining a hydrogel fire extinguishing agent.

[0011] Preferably, the strong base is sodium hydroxide or potassium hydroxide.

[0012] Preferably, the reaction temperature is 45-65° C., and the reaction time is 1-4 h.

[0013] Preferably, the reaction is carried out at a constant temperature in a water bath.

[0014] Preferably, the preparation method of the acetylated lignin is as follows: lignin is dissolved in pyridine, and acetic anhydride is added thereto for reaction to obtain the acetylated lignin.

[0015] Preferably, the lignin is first dried and then ground into powder, which is dissolved in pyridine.

[0016] Preferably, the reaction temperature is 20-120° C., and the reaction time is 12-60 h.

[0017] Preferably, the weight ratio of lignin to acetic anhydride is 1:3-10.

[0018] The advantages of the present invention are:

[0019] The present invention utilizes acetylated lignin to replace the silane coupling agent, and after cost accounting, the production cost of the fire extinguishing agent is reduced by 25%. In addition, lignin is widely available and inexpensive, and the cost can be effectively controlled during large-scale production, which is beneficial to the market promotion of the hydrogel fire extinguishing agent.

[0020] The present invention uses renewable lignin as raw material, reduces dependence on petroleum-based chemicals, and significantly reduces the amount of organic solvents used in the preparation process, conforms to the concept of green environmental protection, and reduces negative impacts on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a three-dimensional mesh diagram of the modified lignin-based hydrogel fire extinguishing agent in this embodiment;

[0022] Figure 2 The figures are fire extinguishing effect diagrams of the hydrogel fire extinguishing agents prepared in Example 1 and Comparative Example 1; Figure a is a fire extinguishing effect diagram of the hydrogel fire extinguishing agent prepared in Comparative Example 1; and Figure b is a fire extinguishing effect diagram of the hydrogel fire extinguishing agent prepared in Example 1. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0025] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0026] Example 1

[0027] This embodiment provides a hydrogel fire extinguishing agent based on modified lignin and a preparation method thereof, which specifically comprises the following steps:

[0028] (1) Preparation of acetylated lignin:

[0029] Place 1 part of lignin in an oven at 80°C for 24 hours to fully remove the moisture contained in the lignin, grind the dried lignin into powder, stir and dissolve it with 10 parts of pyridine, then add 3 parts of acetic anhydride, react at 20°C for 48 hours, precipitate the reaction product, wash and dry it, and it is acetylated lignin. The reaction equation is as follows:

[0030]

[0031] (2) Preparation of hydrogel fire extinguishing agent:

[0032] Dissolve 1 part of sodium hydroxide in 2500 parts of deionized water, add 66 parts of sodium trimetaphosphate to dissolve, and leave at room temperature for 0.5 hours, then add 150 parts of expanded graphite and stir thoroughly, then add 20 parts of acetylated lignin and continue stirring, then keep the temperature at 45°C in a water bath for 1 hour to allow the acetylated lignin to fully swell, and obtain a hydrogel fire extinguishing agent.

[0033] Example 2

[0034] This embodiment provides a hydrogel fire extinguishing agent based on modified lignin and a preparation method thereof, which specifically comprises the following steps:

[0035] (1) Preparation of acetylated lignin:

[0036] Place 1 part of lignin in an oven at 80°C for 24 hours to fully remove the moisture contained in the lignin, grind the dried lignin into powder, stir and dissolve it with 10 parts of pyridine, then add 5 parts of acetic anhydride, react at 40°C for 36 hours, precipitate the reaction product, wash and dry it to obtain acetylated lignin.

[0037] (2) Preparation of hydrogel fire extinguishing agent:

[0038] Dissolve 1 part of sodium hydroxide in 2500 parts of deionized water, add 83 parts of sodium trimetaphosphate to dissolve, and leave at room temperature for 0.5 hours, then add 200 parts of expanded graphite and stir thoroughly, then add 25 parts of acetylated lignin and continue stirring, and then keep the temperature at 50°C in a water bath for 2 hours to allow the acetylated lignin to fully swell, to obtain a hydrogel fire extinguishing agent.

[0039] Example 3

[0040] This embodiment provides a hydrogel fire extinguishing agent based on modified lignin and a preparation method thereof, which specifically comprises the following steps:

[0041] (1) Preparation of acetylated lignin:

[0042] Place 1 part of lignin in an oven at 80°C for 24 hours to fully remove the moisture contained in the lignin, grind the dried lignin into powder, stir and dissolve it with 10 parts of pyridine, then add 10 parts of acetic anhydride, react at 100°C for 12 hours, precipitate the reaction product, wash and dry it to obtain acetylated lignin.

[0043] (2) Preparation of hydrogel fire extinguishing agent:

[0044] Dissolve 1 part of sodium hydroxide in 2500 parts of deionized water, add 100 parts of sodium trimetaphosphate to dissolve, and leave at room temperature for 0.5 hours, then add 250 parts of expanded graphite and stir thoroughly, then add 30 parts of acetylated lignin and continue stirring, and then keep the temperature at 65°C in a water bath for 3 hours to allow the acetylated lignin to fully swell, to obtain a hydrogel fire extinguishing agent.

[0045] Example 4

[0046] This embodiment provides a hydrogel fire extinguishing agent based on modified lignin and a preparation method thereof, which specifically comprises the following steps:

[0047] (1) Preparation of acetylated lignin:

[0048] Place 1 part of lignin in an oven at 80°C for 24 hours to fully remove the moisture contained in the lignin, grind the dried lignin into powder, stir and dissolve it with 10 parts of pyridine, then add 8 parts of acetic anhydride, react at 120°C for 12 hours, precipitate the reaction product, wash and dry it, which is acetylated lignin.

[0049] (2) Preparation of hydrogel fire extinguishing agent:

[0050] Dissolve 1 part of sodium hydroxide in 2500 parts of deionized water, add 100 parts of sodium trimetaphosphate to dissolve, and leave at room temperature for 0.5 hours, then add 250 parts of expanded graphite and stir thoroughly, then add 30 parts of acetylated lignin and continue stirring, and then keep the temperature at 45°C in a water bath for 2 hours to allow the acetylated lignin to fully swell, to obtain a hydrogel fire extinguishing agent.

[0051] Comparative Example 1

[0052] This comparative example provides a polyacrylic acid super absorbent resin hydrogel fire extinguishing agent and a preparation method thereof, which are as follows:

[0053] Formosa Plastics 0.3wt% of a polyacrylic acid type super absorbent resin, 0.033wt% of diatomaceous earth, 0.033wt% of kaolin, 0.033wt% of bentonite and the remainder of water are mixed for 0.5min to obtain a polyacrylic acid type super absorbent resin hydrogel fire extinguishing agent.

[0054] Comparative Example 2

[0055] This comparative example provides a polyacrylic acid hydrogel fire extinguishing agent based on modified lignin and a preparation method thereof, as follows:

[0056] (1) Preparation of acetylated lignin: The preparation method of acetylated lignin in this comparative example is the same as that in Example 4.

[0057] (2) Preparation of polyacrylic acid hydrogel fire extinguishing agent: 0.3 wt% of polyacrylic acid super absorbent resin -Pac·SAP1, 0.15wt% of acetylated lignin and the balance of water were mixed for 2 minutes to obtain a polyacrylic acid hydrogel fire extinguishing agent.

[0058] Comparative Example 3

[0059] This comparative example provides a lignin-based polyacrylic acid hydrogel fire extinguishing agent and a preparation method thereof, which is as follows: 0.3 wt% of a polyacrylic acid super absorbent resin -Pac·SAP1, 0.05wt% alkali lignin, 0.1wt% corn straw enzymatic lignin and the rest of water were mixed for 2 minutes to obtain a polyacrylic acid hydrogel fire extinguishing agent.

[0060] Comparative Example 4

[0061] This comparative example provides a hydrogel fire extinguishing agent and a preparation method thereof. Compared with Example 4, this comparative example is different in that: no expanded graphite is added.

[0062] Comparative Example 5

[0063] This comparative example provides a hydrogel fire extinguishing agent and a preparation method thereof. Compared with Example 4, this comparative example is different in that acetylated lignin is replaced with lignin.

[0064] Comparative Example 6

[0065] This comparative example provides a hydrogel fire extinguishing agent and a preparation method thereof. Compared with Example 4, this comparative example is different in that: no acetylated lignin is added.

[0066] Experimental example

[0067] The fire extinguishing agents prepared in the embodiments and comparative examples were subjected to performance tests, and the test items were as follows:

[0068] 1. Pull-off performance test: The hydrogel fire extinguishing agent prepared in the embodiment and the comparative example was evenly coated on the stainless steel surface, and the coating area was 10 cm 2 , forming a hydrogel layer, and then bonding another piece of stainless steel to the surface of the hydrogel layer with an adhesive to form a "sandwich" structure, and using a universal material testing machine to test and record relevant parameters. The specific data are shown in Table 1.

[0069] 2. Shear performance test: The hydrogel fire extinguishing agent prepared in the embodiment and the comparative example was evenly coated on the stainless steel surface, with a coating area of ​​10 cm 2, forming a hydrogel layer, and then covering another piece of stainless steel to form a double-layer structure, using a fixture to fix the double-layer structure, ensuring that the shear direction is parallel to the interface, and using a universal material testing machine to test and record relevant parameters. The specific data are shown in Table 1.

[0070] 3. Contact angle test: The hydrogel fire extinguishing agent prepared in the embodiment and the comparative example was evenly coated on the stainless steel surface to ensure uniform thickness, and then distilled water was dripped on the surface of the hydrogel fire extinguishing agent using a micro syringe, with a droplet volume of 5 microliters, and the contact angle was analyzed using the instrument's own software to record the static contact angle. The specific data are shown in Table 1.

[0071] 4. Adhesion time test: The hydrogel fire extinguishing agent prepared in the embodiment and the comparative example was uniformly coated on the stainless steel surface to ensure uniform thickness, and then placed in a constant temperature and humidity chamber at 60°C and 80% humidity to observe the total time from the start of coating to the complete fall-off or loss of adhesion of the hydrogel fire extinguishing agent. The specific data are shown in Table 1.

[0072] 5. Fire extinguishing test: simulate wood fire scene indoors, the fire source is dry wood, the volume is 0.2m 3 The fire was extinguished under the conditions of an ambient temperature of 25°C and a relative humidity of 50%, and the complete fire extinguishing time was recorded. Three groups of experiments were carried out for each hydrogel fire extinguishing agent to obtain the average fire extinguishing time. At the same time, a temperature sensor was used to measure the temperature change at the center of the flame. The specific data are shown in Table 1; the temperature from the beginning of the fire extinguishing and the temperature at 1 minute after the fire extinguishing were recorded, and the cooling rate was calculated. The specific data are shown in Table 1.

[0073] 6. 1A fire extinguishing test: refer to the standard GB17835-2008 "Water-based fire extinguishing agent" for fire extinguishing test. The fuel is wood pile. The time to completely extinguish 1A is recorded. The specific data is shown in Table 1.

[0074] Table 1

[0075]

[0076] According to the data in Table 1, by comparing Examples 1-4 with Comparative Examples 1-3, Comparative Examples 1-3 belong to polyacrylic acid-based super absorbent resin hydrogel fire extinguishing agents, which are coated on the surface of stainless steel. In a high temperature and high humidity environment, water is easily vaporized, resulting in the super absorbent resin being difficult to adhere to the stainless steel surface. Therefore, the adhesion time of Comparative Examples 1-3 is relatively low, which in turn affects the time of covering the flame, resulting in a long fire extinguishing time and a slow cooling rate, and therefore a poor fire extinguishing effect.

[0077] At the same time, modified lignin or lignin itself is a macromolecular structure. Due to its complex structure, low molecular activity and difficulty in grafting, it has poor compatibility with super absorbent resin, which makes it difficult to prepare hydrogel fire extinguishing agents and it is difficult to form a polyacrylic acid super absorbent resin hydrogel fire extinguishing agent with stable performance, which will affect the fire extinguishing effect and the stability of the fire extinguishing agent quality.

[0078] By comparing Examples 1-4 with Comparative Examples 4 and 6, Comparative Example 4 does not add expanded graphite, and Comparative Example 6 does not add acetylated lignin, so Comparative Examples 4 and 6 cannot form a three-dimensional network structure. This embodiment utilizes the strongly polar hydroxyl, ester, and acetyl groups in the modified lignin structure through physical adsorption, chemical adsorption, and electrostatic action of expanded graphite to form a three-dimensional network structure, which can maintain a good adhesion state in a high temperature and high humidity environment, thereby increasing the coverage area of ​​the flame and significantly improving the fire extinguishing effect.

[0079] By comparing Examples 1-4 with Comparative Example 5, although the lignin and expanded graphite in Comparative Example 5 can form a three-dimensional network structure, since the lignin is not modified, the hydroxyl groups in the lignin increase, making the compatibility with the expanded graphite worse, so the attachment time is low and the fire extinguishing effect is poor.

[0080] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hydrogel fire extinguishing agent based on modified lignin, characterized in that: It includes the following raw materials in parts by weight: 15-30 parts of acetylated lignin, 50-100 parts of sodium trimetaphosphate, 50-250 parts of expanded graphite and 2000-2500 parts of water.

2. The hydrogel fire extinguishing agent based on modified lignin according to claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: 20-30 parts of acetylated lignin, 65-100 parts of sodium trimetaphosphate, 150-250 parts of expanded graphite and 2500 parts of water.

3. The method for preparing a hydrogel fire extinguishing agent based on modified lignin according to claim 1 or 2, characterized in that: The following steps are involved: A strong base is added to water, and sodium trimetaphosphate is added thereto, which is left for a period of time. Expanded graphite and acetylated lignin are then added thereto for reaction, and finally a hydrogel fire extinguishing agent is obtained.

4. The method for preparing a hydrogel fire extinguishing agent based on modified lignin according to claim 3, characterized in that: The strong base is sodium hydroxide or potassium hydroxide.

5. The method for preparing a hydrogel fire extinguishing agent based on modified lignin according to claim 3, characterized in that: The reaction temperature is 45-65° C., and the reaction time is 1-4 h.

6. The method for preparing a hydrogel fire extinguishing agent based on modified lignin according to claim 5, characterized in that: The reaction is carried out at a constant temperature in a water bath.

7. The method for preparing a hydrogel fire extinguishing agent based on modified lignin according to claim 3, characterized in that: The preparation method of the acetylated lignin is as follows: lignin is dissolved in pyridine, and acetic anhydride is added thereto for reaction to obtain the acetylated lignin.

8. The method for preparing a hydrogel fire extinguishing agent based on modified lignin according to claim 7, characterized in that: The lignin is first dried and then ground into powder, which is dissolved in pyridine.

9. The method for preparing a hydrogel fire extinguishing agent based on modified lignin according to claim 7, characterized in that: The reaction temperature is 20-120° C., and the reaction time is 12-60 hours.

10. The method for preparing a hydrogel fire extinguishing agent based on modified lignin according to claim 7, characterized in that: The weight ratio of lignin to acetic anhydride is 1:3-10.

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