Fire-extinguishing flame-retardant temperature-sensitive hydrogel as well as preparation method and application thereof

Abstract

The invention discloses fire-extinguishing flame-retardant temperature-sensitive hydrogel as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. The flame retardant solution and the chitosan solution are mixed and stirred, then a polyethylene glycol solution is added, stirring continues, and chitosan colloid is obtained; adding a heat-sensitive agent, a cross-linking agent and an initiator into water, then adding the obtained mixed solution into the chitosan colloid, carrying out heating reaction, and then filtering to obtain the fire-extinguishing flame-retardant temperature-sensitive hydrogel. The hydrogel prepared by the invention has good thermosensitivity, forms a carbon layer at a high temperature, has dual effects of flame retardance and fire extinguishment, and is suitable for the fields of fire fighting, buildings, textiles, electronics and the like. The materials used for preparing the hydrogel are all biodegradable materials and are environmentally friendly; the preparation method is simple, easy to operate and suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a fire-extinguishing, flame-retardant, temperature-sensitive hydrogel and a preparation method and application thereof. Background Art

[0002] Hydrogel is a polymer material with a three-dimensional network structure that can absorb a large amount of water and maintain high mechanical strength. The excellent properties of hydrogel make it widely used in medicine, agriculture, cosmetics and many other fields. In recent years, with the improvement of fire safety and environmental protection requirements, the development of materials with both flame retardant properties and environmentally friendly properties has received more and more attention.

[0003] Thermosensitive hydrogels are materials that can respond to changes in ambient temperature and undergo physical or chemical changes, and are often used in smart materials and their applications. However, traditional hydrogel materials are difficult to function effectively in high-temperature environments because they do not have good flame retardant properties. Summary of the invention

[0004] In order to solve the above problems in the prior art, the present invention provides a fire-extinguishing, flame-retardant, temperature-sensitive hydrogel and a preparation method and application thereof.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a fire-extinguishing flame-retardant temperature-sensitive hydrogel, comprising the following steps:

[0007] (1) mixing a flame retardant solution and a chitosan solution, stirring until they are completely dissolved to form a transparent and uniform solution, then adding a polyethylene glycol solution, and continuing to stir until the solution is transparent to obtain a chitosan colloid;

[0008] The purpose of this step is to fully dissolve chitosan and form a preliminary gel skeleton. The addition of polyethylene glycol helps to improve the flexibility and water absorption capacity of the gel.

[0009] (2) adding a thermosensitizer, a crosslinking agent and an initiator into water, and then adding the obtained mixed solution into the chitosan colloid obtained in step (1), heating for reaction, and then filtering to obtain the fire-extinguishing flame-retardant thermosensitive hydrogel.

[0010] As a preferred technical solution of the present invention, in step (1), the concentration of the flame retardant solution is 0.2-0.4wt%, the concentration of the chitosan solution is 0.3-0.5wt%, the mass ratio of the flame retardant solution to the chitosan solution is (13-17):16, the concentration of the polyethylene glycol solution is 0.4-0.6wt%, and the mass ratio of the polyethylene glycol solution to the flame retardant solution is (3-5):1.

[0011] As a preferred technical solution of the present invention, in step (1), the molecular weight of the chitosan is 300,000 to 500,000 Da to ensure that it has good solubility and biocompatibility; the molecular weight of the polyethylene glycol is 400 to 600 Da, which can improve the flexibility and moisturizing ability of the hydrogel and has good biocompatibility.

[0012] As a preferred technical solution of the present invention, in step (1), the flame retardant includes one or more of sodium bicarbonate, carbonate compounds, phosphate compounds, N series compounds, P series compounds, borate compounds and metal hydroxides.

[0013] The carbonate compound includes one or more of sodium carbonate, ammonium bicarbonate and magnesium carbonate, the phosphate compound includes one or more of sodium hydrogen phosphate, potassium dihydrogen phosphate, aluminum phosphate and trisodium phosphate, and the metal hydroxide includes aluminum hydroxide.

[0014] Sodium bicarbonate, as an important component of thermosensitive hydrogel, plays a key role. Sodium bicarbonate can decompose rapidly under high temperature conditions, releasing carbon dioxide and water vapor. These inert gases can not only dilute the oxygen content in the air, but also absorb a large amount of heat, thereby effectively inhibiting the spread of flames. Therefore, sodium bicarbonate has good flame retardant and fire extinguishing effects. In order to further improve the flame retardant properties and versatility of hydrogels, other similar inorganic salts or organic flame retardant additives can be selected to achieve similar or even better flame retardant effects. For example, according to the type of fire, the additive salt can be replaced with one or a combination of carbonate compounds, phosphate compounds, N series compounds, P series compounds, borate compounds, metal hydroxides, etc., to achieve a better fire extinguishing effect.

[0015] As a preferred technical solution of the present invention, in step (2), the thermosensitive agent includes N-isopropylacrylamide, the cross-linking agent includes N,N-methylenebisacrylamide, and the initiator includes one or more of potassium persulfate, azobisisobutyronitrile, benzoyl peroxide, tert-butyl peroxide and ammonium persulfate; in the mixed solution, the concentration of the thermosensitive agent is 0.8-1.2wt%, the concentration of the cross-linking agent is 0.08-0.12wt%, the concentration of the initiator is 0.08-0.12wt%, and the mass ratio of the mixed solution to the chitosan colloid is (1.5-2.5):1.

[0016] As a preferred technical solution of the present invention, in step (2), the reaction is carried out under an inert atmosphere at a temperature of 50 to 60° C. for 1 to 2 hours.

[0017] As a preferred technical solution of the present invention, it also includes the step of drying the fire-extinguishing flame-retardant temperature-sensitive hydrogel until the water is completely evaporated; the drying temperature is 25-60°C.

[0018] The present invention also provides a fire extinguishing, flame retardant, and temperature-sensitive hydrogel prepared according to the method for preparing the fire extinguishing, flame retardant, and temperature-sensitive hydrogel described above.

[0019] The present invention also provides an application of the fire-extinguishing, flame-retardant, temperature-sensitive hydrogel described above in fire-extinguishing and flame-retardant materials.

[0020] As a preferred technical solution of the present invention, the fire extinguishing and flame retardant materials include fire retardant coatings for building materials, fire retardant textile fabrics, electronic equipment and fire fighting equipment.

[0021] The gel can be stored and shipped dry and rehydrated by adding water when needed.

[0022] The fire extinguishing and flame retardant mechanism of the fire extinguishing and flame retardant hydrogel of the present invention: When the hydrogel encounters high temperature, the following reactions will occur: first, the flame retardant decomposes under heating conditions and releases inert gases, which can inhibit the burning of flames; second, the hydrogel adheres to the surface of the combustible to form an isolation layer, which further shrinks at high temperatures and forms a dense carbon layer, thereby isolating oxygen from the combustible and achieving a flame retardant effect. In addition, since the hydrogel has good water absorption capacity, when the temperature rises, the evaporation of water can absorb part of the heat, further reducing the flame temperature.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The hydrogel prepared by the present invention has good temperature sensitivity and is sensitive to temperature changes. It can react quickly when encountering fire and release flame-retardant gas. Its unique cross-linked network structure and the addition of flame retardants enable the hydrogel to form a carbon layer at high temperature, which can effectively inhibit the spread of flames when encountering fire, playing a dual role of flame retardancy and fire extinguishing. It exhibits excellent flame retardancy and fire extinguishing properties under high temperature conditions and is suitable for fire protection, construction, textiles, electronics and other fields. Building materials: As part of building fire retardant coatings, the hydrogel can effectively inhibit the spread of fire. Textiles: Can be used in the manufacture of fire-retardant fabrics to provide flame retardant protection. Electronic equipment: Can be used as a fireproof material for batteries and circuit boards to prevent overheating and fire. Firefighting equipment: This material can be used as one of the main components in a fire extinguisher as a fire extinguishing agent.

[0025] (2) The materials used to prepare the hydrogel in the present invention are all biodegradable materials and are environmentally friendly; the preparation method is simple and easy to operate, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 Flow chart of preparing fire extinguishing flame retardant hydrogel in Example 1;

[0028] Figure 2 This is a scanning electron microscope image of the fire extinguishing and flame retardant hydrogel prepared in Example 1;

[0029] Figure 3 The appearance of the fire-extinguishing flame-retardant hydrogel prepared in Example 1 at different temperatures, wherein (a) is the appearance at room temperature, (b) is the appearance at 70°C, and (c) is the appearance at 120°C;

[0030] Figure 4 This is a graph showing the water loss rate test results of the fire-extinguishing and flame-retardant hydrogel prepared in Example 1 at different temperatures. DETAILED DESCRIPTION

[0031] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0032] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0033] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0034] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] In the following examples, room temperature refers to 25 to 35° C., which will not be described again.

[0037] Example 1

[0038] The preparation steps of the fire-retardant temperature-sensitive hydrogel are as follows:

[0039] (1) Preparation of chitosan colloid: 0.3 wt% sodium bicarbonate solution and 0.4 wt% chitosan (molecular weight 400000Da) solution were mixed in a mass ratio of 15:16 and stirred until completely dissolved to form a transparent and uniform solution. Then 0.5 wt% polyethylene glycol (molecular weight 500Da) solution was added in a mass ratio of 4:1 to the sodium bicarbonate solution, and stirring was continued until the solution was transparent to obtain chitosan colloid.

[0040] (2) Preparation of thermosensitive hydrogel: Thermosensitive agent N-isopropylacrylamide, crosslinking agent N,N-methylenebisacrylamide and initiator potassium persulfate were dissolved in deionized water, and the concentrations of N-isopropylacrylamide, N,N-methylenebisacrylamide and potassium persulfate in the mixed solution were 1wt%, 0.1wt% and 0.1wt%, respectively. The mixed solution was added to the chitosan colloid obtained in step (1), and the mass ratio of the mixed solution to the chitosan colloid was 2:1. Nitrogen was introduced to exhaust the air, and the mixture was heated to 55°C under a nitrogen atmosphere for reaction for 1.5h. After the reaction was completed, the obtained mixture was filtered to remove impurities to obtain a preliminary gel material (wet gel containing water).

[0041] (3) Filtration and drying of the hydrogel: The preliminary gel material obtained in step (2) is dried at room temperature until the water is completely evaporated to obtain a solid fire-extinguishing, flame-retardant, temperature-sensitive hydrogel.

[0042] The flow chart of preparing fire-extinguishing flame-retardant temperature-sensitive hydrogel in this embodiment is as follows Figure 1 The scanning electron microscope image of the fire-extinguishing, flame-retardant, temperature-sensitive hydrogel obtained in step (3) is shown in FIG. Figure 2 As shown by Figure 2 It can be seen that the hydrogel surface is smooth and contains flame retardant particles, which can achieve better coating effect on the surface of objects and play a better role in thermal conductivity when used.

[0043] The stability of the fire-extinguishing flame-retardant temperature-sensitive hydrogel obtained in step (3) of this embodiment was tested by placing it at room temperature, 70°C and 120°C for 10 minutes, respectively. Figure 3 As shown in (a), (b) and (c), Figure 3 It can be seen that the hydrogel can flow freely like water at room temperature and solidify after reaching the response temperature, which allows the hydrogel to adhere to the surface of the object after being sprayed out and continue to maintain its physical properties as the temperature continues to rise.

[0044] The water loss rate of the wet gel containing water obtained in step (2) of this embodiment at different temperatures (100°C, 200°C, 300°C) was tested. It was placed in a constant temperature box and heated to the specified temperature. The test duration was 20 minutes. The results are as follows: Figure 4 As shown by Figure 4 It can be seen that the final water loss rate is 47% at 100°C, and as the test temperature increases, it completely loses water at 300°C, at which time the water loss rate is 96%. This shows that the hydrogel can absorb a large amount of heat during high-temperature fires, and can reduce the temperature of the surface of objects to achieve a continuous flame retardant effect.

[0045] Example 2

[0046] The preparation steps of the fire-retardant temperature-sensitive hydrogel are as follows:

[0047] (1) Preparation of chitosan colloid: 0.2wt% urea solution and 0.5wt% chitosan (molecular weight 300000Da) solution were mixed in a mass ratio of 13:16 and stirred until completely dissolved to form a transparent and uniform solution. Then 0.4wt% polyethylene glycol (molecular weight 600Da) solution was added, and the mass ratio of polyethylene glycol solution to urea solution was 5:1. The solution was stirred until transparent to obtain chitosan colloid.

[0048] (2) Preparation of thermosensitive hydrogel: Thermosensitive agent N-isopropylacrylamide, crosslinking agent N,N-methylenebisacrylamide and initiator azobisisobutyronitrile were dissolved in deionized water, and the concentrations of N-isopropylacrylamide, N,N-methylenebisacrylamide and potassium persulfate in the mixed solution were 0.8wt%, 0.12wt% and 0.08wt%, respectively. The mixed solution was added to the chitosan colloid obtained in step (1), and the mass ratio of the mixed solution to the chitosan colloid was 1.5:1. Nitrogen was introduced to exhaust the air, and the mixture was heated to 50°C under a nitrogen atmosphere for reaction for 2h. After the reaction was completed, the obtained mixture was filtered to remove impurities to obtain a preliminary gel material (wet gel containing water).

[0049] (3) Filtration and drying of the hydrogel: The preliminary gel material obtained in step (2) is dried at 50° C. until the water is completely evaporated to obtain a solid fire-extinguishing, flame-retardant, temperature-sensitive hydrogel.

[0050] Example 3

[0051] The preparation steps of the fire-retardant temperature-sensitive hydrogel are as follows:

[0052] (1) Preparation of chitosan colloid: 0.4wt% sodium dihydrogen phosphate solution and 0.3wt% chitosan (molecular weight 500000Da) solution were mixed in a mass ratio of 17:16 and stirred until completely dissolved to form a transparent and uniform solution. Then 0.6wt% polyethylene glycol (molecular weight 400Da) solution was added, the mass ratio of polyethylene glycol solution to sodium dihydrogen phosphate solution was 3:1, and stirring was continued until the solution was transparent to obtain chitosan colloid.

[0053] (2) Preparation of thermosensitive hydrogel: Thermosensitive agent N-isopropylacrylamide, crosslinking agent N,N-methylenebisacrylamide and initiator benzoyl peroxide were dissolved in deionized water, and the concentrations of N-isopropylacrylamide, N,N-methylenebisacrylamide and potassium persulfate in the mixed solution were 1.2wt%, 0.08wt% and 0.12wt%, respectively. The mixed solution was added to the chitosan colloid obtained in step (1), and the mass ratio of the mixed solution to the chitosan colloid was 2.5:1. Nitrogen was introduced to exhaust the air, and the mixture was heated to 60°C under a nitrogen atmosphere for reaction for 1h. After the reaction was completed, the mixture was filtered to remove impurities to obtain a preliminary gel material (wet gel containing water).

[0054] (3) Filtration and drying of the hydrogel: The preliminary gel material obtained in step (2) is dried at 60° C. until the water is completely evaporated to obtain a solid fire-extinguishing, flame-retardant, temperature-sensitive hydrogel.

[0055] The gels prepared in steps (2) and (3) of Examples 2 and 3 were tested for water loss and stability according to the method in Example 1. The results obtained were comparable to those in Example 1.

[0056] Comparative Example 1

[0057] Same as Example 1, except that the molecular weight of the chitosan used is 250000Da.

[0058] Comparative Example 2

[0059] Same as Example 1, except that the molecular weight of the polyethylene glycol used is 300 Da.

[0060] Comparative Example 3

[0061] Same as Example 1, except that the reaction in step (2) is carried out under air atmosphere.

[0062] Comparative Example 4

[0063] Same as Example 1, except that the reaction in step (2) is carried out at 40°C.

[0064] The hydrogel prepared in Comparative Example 1 has poor fluidity and cannot be sprayed together with water. In addition, due to the poor fluidity of the hydrogel, it begins to solidify before responding to the temperature and loses its function of covering objects.

[0065] The hydrogels prepared in Comparative Examples 2 to 4 cannot form a three-dimensional cross-linked network structure and cannot play a good coating role on the surface of objects. In Comparative Examples 3 and 4, due to incomplete cross-linking reaction, the hydrogel layer coated on the surface of the object is relatively thin, which greatly reduces the flame retardant effect.

[0066] It can be seen from this that the preparation method according to the present invention can achieve flame retardancy while ensuring the fluidity of the hydrogel.

[0067] The above description is only a preferred specific implementation manner of the present invention, and the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a fire-extinguishing flame-retardant temperature-sensitive hydrogel, characterized in that: The following steps are involved: (1) mixing a flame retardant solution and a chitosan solution, stirring, then adding a polyethylene glycol solution, and continuing to stir to obtain a chitosan colloid; (2) adding a thermosensitizer, a crosslinking agent and an initiator into water, and then adding the obtained mixed solution into the chitosan colloid obtained in step (1), heating for reaction, and then filtering to obtain the fire-extinguishing flame-retardant thermosensitive hydrogel.

2. The method for preparing the fire-extinguishing flame-retardant temperature-sensitive hydrogel according to claim 1, characterized in that: In step (1), the concentration of the flame retardant solution is 0.2-0.4wt%, the concentration of the chitosan solution is 0.3-0.5wt%, the mass ratio of the flame retardant solution to the chitosan solution is (13-17):16, the concentration of the polyethylene glycol solution is 0.4-0.6wt%, and the mass ratio of the polyethylene glycol solution to the flame retardant solution is (3-5):

1.

3. The method for preparing the fire-extinguishing flame-retardant temperature-sensitive hydrogel according to claim 1, characterized in that: In step (1), the molecular weight of the chitosan is 300,000 to 500,000 Da, and the molecular weight of the polyethylene glycol is 400 to 600 Da.

4. The method for preparing the fire-extinguishing flame-retardant temperature-sensitive hydrogel according to claim 1, characterized in that: In step (1), the flame retardant includes one or more of sodium bicarbonate, carbonate compounds, phosphate compounds, N series compounds, P series compounds, borate compounds and metal hydroxides.

5. The method for preparing the fire-extinguishing flame-retardant temperature-sensitive hydrogel according to claim 1, characterized in that: In step (2), the thermosensitive agent includes N-isopropyl acrylamide, the cross-linking agent includes N,N-methylenebisacrylamide, and the initiator includes one or more of potassium persulfate, azobisisobutyronitrile, benzoyl peroxide, tert-butyl peroxide and ammonium persulfate; in the mixed solution, the concentration of the thermosensitive agent is 0.8-1.2wt%, the concentration of the cross-linking agent is 0.08-0.12wt%, the concentration of the initiator is 0.08-0.12wt%, and the mass ratio of the mixed solution to the chitosan colloid is (1.5-2.5):

1.

6. The method for preparing the fire-extinguishing flame-retardant temperature-sensitive hydrogel according to claim 1, characterized in that: In step (2), the reaction is carried out under an inert atmosphere at a temperature of 50 to 60° C. for 1 to 2 h.

7. The method for preparing the fire-extinguishing flame-retardant temperature-sensitive hydrogel according to claim 1, characterized in that: The method also includes a step of drying the fire-extinguishing, flame-retardant, temperature-sensitive hydrogel.

8. A fire extinguishing, flame retardant, temperature-sensitive hydrogel prepared according to the method for preparing a fire extinguishing, flame retardant, temperature-sensitive hydrogel according to any one of claims 1 to 7.

9. Use of the fire-extinguishing, flame-retardant, temperature-sensitive hydrogel according to claim 8 in fire-extinguishing and flame-retardant materials.

10. The use according to claim 9, characterized in that: The fire extinguishing and flame retardant materials include fire retardant coatings for building materials, fire retardant textile fabrics, electronic equipment and fire fighting equipment.

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