Fire extinguishing microcapsule with EVA ultraviolet crosslinking barrier material as wall material and preparation process thereof

Abstract

The invention discloses a fire extinguishing microcapsule with an EVA ultraviolet crosslinking barrier material as a wall material and a preparation process of the fire extinguishing microcapsule. According to the fire extinguishing microcapsule with the EVA ultraviolet crosslinking barrier material as the wall material, the whole fire extinguishing microcapsule is spherical or sphere-like, a composite material of EVA and graphene is used as the wall material, a core material is wrapped in the wall material, the thickness of the wall material is 10-50 microns, and the diameter of the fire extinguishing microcapsule is 300-500 microns. The excellent gas barrier property of the EVA and graphene composite wall material is utilized, volatilization of perfluorohexanone is effectively blocked, the storage stability of the fire extinguishing microcapsule is improved, the service life of the fire extinguishing microcapsule is prolonged, and the effective content of a fire extinguishing agent during fire extinguishing is guaranteed.

Description

Technical fields:

[0001] This invention relates to the field of fire extinguishing materials technology, specifically to a fire extinguishing microcapsule with EVA ultraviolet cross-linked barrier material as the wall material and its preparation process. Background technology:

[0002] Fires pose a serious threat to human life and property, making the development of efficient and environmentally friendly fire extinguishing materials crucial. Perfluorohexanone (PFH), as a novel environmentally friendly fire extinguishing agent, possesses excellent fire extinguishing performance, such as an ozone depletion potential (ODP) of 0 and a global warming potential (GWP) of only 1, a short atmospheric lifetime, and environmental friendliness. Furthermore, it is non-toxic to humans and non-corrosive to electronic equipment, making it suitable for various fire extinguishing scenarios, especially in energized environments. However, PPH has a low boiling point (approximately 49°C) and is highly volatile, posing numerous inconveniences for its storage and use alone, thus limiting its application. To address the storage and use issues of PPH, it is often formulated into microcapsules. Traditional microcapsule wall materials have shortcomings in terms of gas barrier properties, mechanical properties, and thermal stability. For example, some wall materials cannot effectively prevent the volatilization of PPH, leading to a decrease in the extinguishing agent content during microcapsule storage and affecting the fire extinguishing effect; some wall materials are prone to rupture at high temperatures, failing to guarantee accurate release of PPH during a fire. In addition, existing fire extinguishing microcapsules need to be improved in terms of fire extinguishing efficiency and the diversity of applicable scenarios.

[0003] Perfluorohexanone, as a novel environmentally friendly fire extinguishing agent, possesses excellent fire extinguishing performance and environmental characteristics. However, due to its low boiling point and high volatility, special measures must be taken during storage and use; otherwise, its fire extinguishing effect and service life will be affected. Regarding the application of microencapsulation technology for fire extinguishing agent storage, several studies have applied this technology to the encapsulation of various fire extinguishing agents. For example, patent CN108743212A discloses a fire extinguishing microcapsule using melamine-formaldehyde resin as the wall material and heptafluoropropane as the core material. This microcapsule solves the problem of heptafluoropropane leakage to some extent. However, the gas barrier properties and thermal stability of the melamine-formaldehyde resin wall material are limited, making it prone to decomposition in high-temperature fire environments, affecting the release efficiency of the fire extinguishing agent.

[0004] In the selection of microcapsule wall materials, EVA, as a commonly used polymer material, is used in the preparation of microcapsule wall materials due to its good flexibility and processability. As mentioned in "Preparation and Performance Study of EVA Microcapsules" (Polymer Materials Science and Engineering, 2018, 34(8):112-116), EVA microcapsules have certain gas barrier properties, but when used alone, their barrier effect on low-boiling-point substances is not good, making it difficult to meet the requirements for long-term storage of perfluorohexanone. Existing fire extinguishing microcapsules have shortcomings in terms of gas barrier properties, mechanical properties, thermal stability, and compatibility with perfluorohexanone, and cannot meet the requirements for efficient, stable, and environmentally friendly fire extinguishing. Summary of the Invention:

[0005] To address the problems existing in the prior art, this invention proposes a fire extinguishing microcapsule with EVA ultraviolet cross-linked barrier material as the wall material and its preparation process. The fire extinguishing microcapsule proposed in this invention utilizes the excellent gas barrier properties of the EVA and graphene composite wall material to effectively block the volatilization of perfluorohexanone, improve the storage stability of the fire extinguishing capsule, extend its service life, and ensure the effective content of the fire extinguishing agent during fire extinguishing.

[0006] The purpose of this invention is to provide a fire extinguishing microcapsule with EVA ultraviolet cross-linking barrier material as the wall material. The fire extinguishing microcapsule is spherical or quasi-spherical in shape. The composite material of EVA and graphene is used as the wall material, and the core material is wrapped inside the wall material. The wall material thickness is 10-50 μm, and the diameter of the fire extinguishing microcapsule is 300-500 μm.

[0007] The structural design of the fire extinguishing microcapsule proposed in this invention ensures that it can effectively prevent the volatilization of perfluorohexanone during storage, and can rapidly rupture and release the core material in the event of a fire.

[0008] Preferably, the core material is perfluorohexanone, and the amount of graphene added in the EVA and graphene composite material is 1-5 wt%. The perfluorohexanone core material achieves efficient fire extinguishing through multiple mechanisms during the fire extinguishing process, including physical heat absorption and cooling, chemical inhibition of chain reactions, and isolation of oxygen.

[0009] In EVA-graphene composites, EVA has good flexibility, processability, and certain gas barrier properties, while graphene has excellent mechanical properties, high specific surface area, and outstanding gas barrier properties. The wall material formed by the composite of the two combines the advantages of both.

[0010] Further preferred, the amount of graphene added in the EVA-graphene composite material is 1-3 wt%.

[0011] The VA content (mass fraction) in the EVA proposed in this invention is 50%-80%. On the one hand, increasing the VA content can increase its solubility in solvents at room temperature and make it easier to undergo emulsification reactions. On the other hand, increasing the VA content can enhance its dispersibility with graphene.

[0012] Preferably, the composite material of EVA and graphene further includes an ultraviolet crosslinking agent, and the mass ratio of EVA, graphene and ultraviolet crosslinking agent is (93.0-98.5):(1-5):(0.5-2.0).

[0013] To enhance the mechanical properties of EVA, this invention introduces a UV crosslinking system into the EVA-graphene composite material. Through UV crosslinking, the mechanical properties of the capsule wall material are further improved. The graphene selected in this invention is a single-layer or few-layer (≤5 layers) graphene powder with a sheet diameter of 1-10 μm. Single-layer or few-layer graphene possesses superior mechanical and gas barrier properties, enabling it to more effectively form a dense layered network structure within the EVA matrix, thus extending the diffusion path of gas molecules. Graphene with a sheet diameter in the 1-10 μm range ensures both its dispersibility within the EVA matrix and the formation of an effective "maze effect." If the graphene sheet diameter is too small (e.g., less than 1 μm), the overlap between the graphene sheets is poor, making it difficult to form a complete barrier network. If the sheet diameter is too large (e.g., greater than 10 μm), the graphene is prone to agglomeration during dispersion, failing to disperse uniformly in the EVA matrix and instead forming defects in the wall material, affecting gas barrier performance and mechanical properties. Furthermore, the selected graphene has a purity ≥95%, and the low impurity content avoids the influence of impurities on the interfacial bonding force between EVA and graphene, ensuring the overall performance of the composite wall material. Simultaneously, the graphene undergoes surface hydroxylation modification, resulting in a certain amount of hydroxyl groups on the modified graphene surface, which enhances its compatibility and interfacial interaction with the EVA matrix, further improving the mechanical and gas barrier properties of the composite wall material.

[0014] Further preferably, the ultraviolet crosslinking aid includes an ultraviolet crosslinking agent and a photoinitiator. The ultraviolet crosslinking agent is selected from one or more of triallyl triisocyanate, tert-butylperoxycarbonate-2-ethylhexyl ester and trimethylolpropane triacrylate. The photoinitiator is benzophenone. The mass ratio of the ultraviolet crosslinking agent to the photoinitiator is 2:1.

[0015] Further optimization yields a mass ratio of EVA, graphene, and UV crosslinking agent of (95.5-97.5):(1-3):1.5.

[0016] Preferably, the graphene is hydroxylated modified graphene.

[0017] This invention also protects the preparation process of the fire extinguishing microcapsules using EVA ultraviolet cross-linked barrier material as the wall material, comprising the following steps:

[0018] (1) Preparation of graphene dispersion: Graphene is added to N-methylpyrrolidone, and sodium dodecylbenzenesulfonate is added. The mixture is mixed evenly to disperse the graphene evenly in N-methylpyrrolidone to obtain graphene dispersion.

[0019] (2) Mixing EVA and graphene: Add EVA and UV crosslinking agent to the graphene dispersion obtained in step (1), heat to 70℃-90℃ in a water bath or oil bath, and stir for 4-6 hours to fully dissolve EVA and mix it evenly with graphene to obtain EVA-graphene-crosslinking agent mixed solution.

[0020] (3) Perfluorohexanone emulsification: Add emulsifier to deionized water, with the emulsifier concentration controlled at 2-3 wt%, and then slowly add perfluorohexanone. The mass ratio of perfluorohexanone to deionized water is 1:(5-10). Stir for 30-40 minutes to form a stable perfluorohexanone emulsion.

[0021] (4) Microcapsule preparation: The EVA-graphene-crosslinking agent mixed solution obtained in step (2) is slowly added dropwise to the perfluorohexanone emulsion obtained in step (3) while stirring. After the addition is complete, stirring is continued for 1.5-2.5 hours to allow EVA-graphene to form a wall material on the surface of the perfluorohexanone droplets through phase separation. The formed microcapsules are then cured, washed, and dried to obtain the fire extinguishing microcapsules with EVA ultraviolet crosslinking barrier material as the wall material.

[0022] The microcapsules proposed in this invention contain graphene with a two-dimensional sheet structure, which, when uniformly dispersed in an EVA matrix, forms a dense and uniform sheet network structure. This structure significantly extends the diffusion path of perfluorohexanone (PFH) gas molecules (i.e., the "maze effect"), thereby effectively reducing the volatilization rate of PPH. Compared to EVA wall materials alone, the composite wall material can significantly improve the barrier effect against PPH, solving the problem of PPH's easy volatilization. Simultaneously, graphene possesses extremely high strength and modulus, and there is a strong interfacial interaction between it and the EVA matrix. When graphene is added to EVA, it can effectively transfer stress and suppress the deformation of the EVA matrix, thereby enhancing the mechanical properties of the composite wall material. This makes the fire extinguishing capsule more resistant to impact and wear during storage and transportation, ensuring the integrity of the core material. Furthermore, EVA itself has a certain degree of thermal stability, while graphene has good thermal conductivity and high-temperature resistance. When combined, graphene rapidly disperses heat, preventing localized overheating that could lead to wall material decomposition and ensuring structural stability of the composite wall material even at high temperatures. This guarantees that the fire extinguishing capsule will not rupture prematurely under high-temperature fire conditions, but will accurately release perfluorohexanone at the appropriate time, ensuring fire extinguishing efficiency. This invention specifically addresses the problems existing in the prior art, achieving a comprehensive improvement in the fire extinguishing capsule's gas barrier properties, mechanical properties, and thermal stability.

[0023] Preferably, the mass ratio of graphene, N-methylpyrrolidone, and sodium dodecylbenzenesulfonate in step (1) is 1:(200-400):(0.2-0.6). The specific method for uniformly mixing the above mixture in step (1) is as follows: the mixture is placed in an ultrasonic cleaner and ultrasonically treated for 2-5 hours to uniformly disperse the graphene in the N-methylpyrrolidone, resulting in a graphene dispersion. Ultrasonic treatment utilizes high-frequency vibration to initially break up the agglomeration between graphene sheets, while the surfactant further improves the stability of graphene in the dispersion.

[0024] Preferably, the mass ratio of EVA, graphene and UV crosslinking agent in step (2) is (93.0-98.5):(1-5):(0.5-2.0).

[0025] Further preferred, the mass ratio of EVA, graphene and UV crosslinking agent in step (2) is (95.5-97.5):(1-3):1.5.

[0026] Preferably, in step (2), the oil bath is heated to 80°C, and the mixture is stirred at a speed of 1000-1500 r / min for 4-6 hours. During this process, the temperature and stirring speed are precisely controlled to ensure that the graphene can be further uniformly dispersed in the EVA solution to form a stable composite system. After it becomes uniform, the temperature is lowered to below 40°C before use.

[0027] Preferably, in step (2), the mass ratio of graphene to perfluorohexanone is 1-3:100, and the mass fraction of graphene in the wall material is 1%-5%.

[0028] Further preferred, the mass fraction of graphene in the wall material is 2%-3%.

[0029] Preferably, the emulsifier in step (3) is Tween-80.

[0030] Step (3) involves adding an emulsifier to deionized water at a concentration of 2-3 wt%, then slowly adding perfluorohexanone at a mass ratio of 1:(5-10) to deionized water. The mixture is then stirred at 4000-5000 r / min for 30-40 min to form a stable perfluorohexanone emulsion. By optimizing the emulsifier concentration, stirring speed, and time, the perfluorohexanone droplet size in the emulsion is mostly distributed between 1-5 μm, providing an ideal foundation for the subsequent preparation of microcapsules.

[0031] Step (4) involves the following steps: The EVA-graphene mixed solution is slowly added dropwise to the perfluorohexanone emulsion through a dropping funnel at a rate of 1-2 drops / second, while stirring at a speed of 300-400 r / min. After the addition is complete, stirring continues for 2 hours, allowing EVA-graphene to form a wall material on the surface of the perfluorohexanone droplets through a phase separation method. This phase separation method utilizes the difference in compatibility between the EVA-graphene mixed solution and the perfluorohexanone emulsion, promoting the aggregation of EVA-graphene on the droplet surface to form the wall material. Curing treatment: The formed microcapsules are placed in a room-temperature ultraviolet lamp box (irradiation power of 300-500 mW / cm²). 2 While stirring, the microcapsules are cured by irradiation for 30-50 seconds to enhance the strength of the wall material. Washing and drying: The cured microcapsules are transferred to centrifuge tubes and centrifuged at 5000 rpm for 10 minutes. The supernatant is discarded, and the precipitate is washed three times with deionized water to remove residual emulsifier and unreacted substances. The precipitate is then placed in a vacuum drying oven and dried at room temperature for 12-24 hours to obtain the final fire extinguishing capsule product. The drying process effectively removes residual moisture from the inside of the microcapsules, avoiding any impact on the performance of perfluorohexanone, and further improving the storage stability of the microcapsules.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] 1. This invention utilizes the excellent gas barrier properties of EVA and graphene composite wall materials to effectively block the volatilization of perfluorohexanone, improve the storage stability of fire extinguishing capsules, extend their service life, and ensure the effective content of fire extinguishing agent during fire extinguishing.

[0034] 2. This invention utilizes graphene to enhance the mechanical properties of EVA wall materials, making the fire extinguishing capsule less prone to breakage during storage and transportation, thus ensuring the integrity of the core material; at the same time, it utilizes the good thermal stability of the composite wall material to ensure accurate and timely release of perfluorohexanone under high-temperature fire conditions, thereby improving fire extinguishing efficiency.

[0035] 3. This invention provides a fire extinguishing capsule adapted to the properties of perfluorohexanone, comprehensively improving the various performance characteristics of the fire extinguishing capsule and expanding its application in various scenarios such as electronic equipment rooms, large warehouses, and new energy vehicle battery compartments, thereby meeting the needs for efficient, stable, and environmentally friendly fire extinguishing.

[0036] 4. The microcapsules proposed in this invention exhibit significantly improved gas barrier performance. Compared with existing technologies, this invention uses a composite wall material of EVA and graphene, which provides a significantly better barrier effect against perfluorohexanone than traditional wall materials. Experimental data shows that under the same storage conditions (temperature 40℃, relative humidity 70%), the perfluorohexanone volatilization loss rate of the fire extinguishing microcapsules of this invention is only 2-5% after 3 months of storage; while the perfluorohexanone volatilization loss rate of fire extinguishing capsules using pure EVA wall material is as high as 20-30%. This indicates that this invention can effectively solve the problem of perfluorohexanone volatility and significantly improve the storage stability of fire extinguishing microcapsules.

[0037] 5. The composite wall material proposed in this invention exhibits significantly enhanced mechanical properties due to the addition of graphene. Testing with a universal testing machine shows that the compressive strength of the fire extinguishing microcapsules of this invention reaches 30-46 MPa, and the impact strength is 21-25 kJ / m². 2 The compressive strength of a pure EVA wall material fire extinguishing capsule is only 12 MPa, and its impact strength is 6 kJ / m. 2 Although the compressive strength of melamine-formaldehyde resin wall extinguishing capsules can reach 35-45 MPa, their impact strength is relatively low, only 5-8 kJ / m. 2 Furthermore, these materials are brittle and prone to breakage. The fire extinguishing microcapsules of this invention are better able to withstand external impacts and compression during storage and transportation, exhibit superior mechanical properties, and ensure the integrity of the core material.

[0038] 6. The composite wall material proposed in this invention maintains structural stability at 100℃-120℃, and only cracks and releases perfluorohexanone when the temperature reaches 122℃-135℃; while pure EVA wall material begins to soften and deform at 80℃-85℃ and cracks at 90℃. This indicates that the fire extinguishing microcapsules proposed in this invention have good thermal stability and timely response. Attached image description:

[0039] Figure 1 The image shows the SEM microstructure of the fire extinguishing microcapsules obtained in Example 2.

[0040] Figure 2 The image shows the infrared spectrum of the wall material obtained in Example 2. Detailed implementation method:

[0041] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments and implementation schemes of the present invention will be further described in detail below with reference to the accompanying drawings. It is obvious that the described embodiments are only a part of the embodiments of the present invention, not all of them. The following description of at least one example is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0043] The raw materials used in the following examples are as follows: Graphene: 96% purity, hydroxylated; N-methylpyrrolidone: analytical grade; Sodium dodecylbenzenesulfonate: analytical grade; Tween-80: analytical grade. The hydroxylated modified graphene was purchased from Suzhou Carbon-Feng Graphene Technology Co., Ltd., grade: TF-12141; the unmodified graphene was purchased from Suzhou Carbon-Feng Graphene Technology Co., Ltd., grade: GE03.

[0044] Example 1:

[0045] A process for preparing fire extinguishing microcapsules using EVA ultraviolet cross-linked barrier material as the wall material includes the following steps:

[0046] (1) Preparation of graphene dispersion: Weigh 1g of hydroxylated modified graphene and add it to 300g of N-methylpyrrolidone, then add 0.4g of sodium dodecylbenzenesulfonate. Place the above mixture in an ultrasonic cleaner with a power of 300W and ultrasonically treat for 3h (water temperature controlled at 35℃-40℃) to obtain graphene dispersion.

[0047] (2) Mixing EVA and graphene: Weigh 97.5g of EVA resin (VA content 50wt%), add 1g of triallyl triisocyanate and 0.5g of benzophenone, stir evenly and then add to the graphene dispersion, transfer to a three-necked flask, and stir at 1200r / min for 5h in a 42℃ water bath to obtain a mixed solution of EVA-graphene-crosslinking agent.

[0048] (3) Perfluorohexanone emulsification: Measure 500g of deionized water, add 12g of Tween-80 (emulsifier concentration 2.4wt%), stir to dissolve (water temperature 20℃-25℃), slowly add 100g of perfluorohexanone (perfluorohexanone to deionized water mass ratio 1:5), stir with a high-speed stirrer at 4500r / min speed for 35min (ice water bath temperature control ≤38℃) to form an emulsion.

[0049] (4) Microcapsule preparation: The EVA-graphene-crosslinking agent mixed solution was added dropwise to the perfluorohexanone emulsion (dropping rate controlled at 1-2 drops / second), while stirring at 350 r / min (ice-water bath temperature control ≤45℃); after the addition was complete, stirring was continued for 2 h (temperature maintained ≤45℃), and ultraviolet irradiation was performed simultaneously with stirring (irradiation power 400 mW / cm²). 2 The capsules were irradiated and cured for 40 seconds. The resulting capsules were centrifuged (5000 r / min, 10 min), washed three times with deionized water (≤35℃), and dried in a freeze dryer for 24 h to obtain the fire extinguishing microcapsule product.

[0050] Product Features: These fire extinguishing microcapsules are spherical with a particle size of 300-500 μm. Tests show that after 3 months of storage at 40℃ and 70% relative humidity, the perfluorohexanone volatilization loss rate is 3.0%. After UV cross-linking, the compressive strength reaches 38 MPa, and the impact strength is 20 kJ / m². 2 The combination of 50% VA and 1% graphene results in a wall material with moderate flexibility and good barrier properties. Thermal stability tests show that the microcapsules remain stable at 115℃ and rupture at 132℃, releasing the extinguishing agent.

[0051] Example 2:

[0052] A process for preparing fire extinguishing microcapsules using EVA ultraviolet cross-linked barrier material as the wall material includes the following steps:

[0053] (1) Preparation of graphene dispersion: Weigh 3g of hydroxylated modified graphene and add it to 350g of N-methylpyrrolidone, then add 0.6g of sodium dodecylbenzenesulfonate. Place the above mixture in an ultrasonic cleaner with a power of 300W and ultrasonically treat for 4h (water temperature controlled at 35℃-40℃) to obtain graphene dispersion.

[0054] (2) Mixing EVA and graphene: Weigh 95.5g of EVA resin (VA content 50wt%), add 1g of triallyl triisocyanate and 0.5g of benzophenone, stir evenly and then add to the graphene dispersion. Transfer to a three-necked flask, place in a 42℃ water bath, and stir at 1300r / min for 6h to obtain an EVA-graphene-crosslinking aid mixed solution.

[0055] (3) Perfluorohexanone emulsification: Measure 600g of deionized water, add 15g of Tween-80 (emulsifier concentration 2.5wt%), stir to dissolve (water temperature 20℃-25℃), slowly add 100g of perfluorohexanone (perfluorohexanone to deionized water mass ratio 1:5), stir with a high-speed stirrer at 4500r / min speed for 35min (ice water bath temperature control ≤38℃) to form an emulsion.

[0056] (4) Microcapsule preparation: The EVA-graphene-crosslinking agent mixed solution was added dropwise to the perfluorohexanone emulsion (dropping rate controlled at 1-2 drops / second), while stirring at 350 r / min (ice-water bath temperature control ≤45℃); after the addition was complete, stirring was continued for 2 h (temperature maintained ≤45℃), and ultraviolet irradiation was performed simultaneously with stirring (irradiation power 400 mW / cm²). 2 The capsules were irradiated and cured for 40 seconds. The resulting capsules were centrifuged (5000 r / min, 10 min), washed three times with deionized water (≤35℃), and dried in a freeze dryer for 24 h to obtain the fire extinguishing microcapsule product.

[0057] Product Features: These fire extinguishing microcapsules are spherical in shape, with a particle size of 300-500 μm (see product details). Figure 1 The infrared spectrum of its wall material is shown below. Figure 2 After storage at 40℃ and 70% relative humidity for 3 months, the volatilization loss rate of perfluorohexanone was 2.4%; after UV crosslinking, the compressive strength reached 46 MPa, and the impact strength was 24 kJ / m. 2 In this embodiment, the addition of 3% graphene improved the mechanical and barrier properties of the wall material compared to that of Example 1 with 1% graphene. Thermal stability experiments showed that the microcapsules remained stable at 120°C and ruptured at 135°C, releasing the fire extinguishing agent.

[0058] Example 3:

[0059] A process for preparing fire extinguishing microcapsules using EVA ultraviolet cross-linked barrier material as the wall material includes the following steps:

[0060] (1) Preparation of graphene dispersion: Weigh 1g of hydroxylated modified graphene and add it to 300g of N-methylpyrrolidone, then add 0.4g of sodium dodecylbenzenesulfonate. Place the above mixture in an ultrasonic cleaner with a power of 300W and ultrasonically treat for 3h (water temperature controlled at 35℃-40℃) to obtain graphene dispersion.

[0061] (2) Mixing EVA and graphene: Weigh 97.5g of EVA resin (VA content 80wt%), add 1g of triallyl triisocyanate and 0.5g of benzophenone, stir evenly and then add to the graphene dispersion. Transfer to a three-necked flask, place in a 42℃ water bath, and stir at 1200r / min for 5h to obtain an EVA-graphene-crosslinking aid mixed solution.

[0062] (3) Perfluorohexanone emulsification: Measure 500g of deionized water, add 12g of Tween-80 (emulsifier concentration 2.4wt%), stir to dissolve (water temperature 20℃-25℃), slowly add 100g of perfluorohexanone (perfluorohexanone to deionized water mass ratio 1:5), stir with a high-speed stirrer at 4500r / min speed for 35min (ice water bath temperature control ≤38℃) to form an emulsion.

[0063] (4) Microcapsule preparation: The EVA-graphene-crosslinking agent mixed solution was added dropwise to the perfluorohexanone emulsion (dropping rate controlled at 1-2 drops / second), while stirring at 350 r / min (ice-water bath temperature control ≤45℃); after the addition was complete, stirring was continued for 2 h (temperature maintained ≤45℃), and ultraviolet irradiation was performed simultaneously with stirring (irradiation power 400 mW / cm²). 2 The capsules were irradiated and cured for 40 seconds. The resulting capsules were centrifuged (5000 r / min, 10 min), washed three times with deionized water (≤35℃), and dried in a freeze dryer for 24 h to obtain the fire extinguishing microcapsule product.

[0064] Product Features: This fire extinguishing capsule is spherical with a particle size of 300-500μm. Tests show that after 3 months of storage at 40℃ and 70% relative humidity, the perfluorohexanone volatilization loss rate is 2.7%. After UV cross-linking, its compressive strength reaches 30MPa, and its impact strength is 25kJ / m². 2 The EVA resin, with a VA content of 80% and graphene of 1%, softens the wall material but improves impact resistance and provides good barrier properties. Thermal stability tests show that the capsule remains stable at 100°C and ruptures at 122°C, releasing the extinguishing agent.

[0065] Example 4:

[0066] A process for preparing fire extinguishing microcapsules using EVA ultraviolet cross-linked barrier material as the wall material includes the following steps:

[0067] (1) Preparation of graphene dispersion: Weigh 3g of hydroxylated modified graphene and add it to 350g of N-methylpyrrolidone, then add 0.6g of sodium dodecylbenzenesulfonate. Place the above mixture in an ultrasonic cleaner with a power of 300W and ultrasonically treat for 4h (water temperature controlled at 35-40℃) to obtain graphene dispersion.

[0068] (2) Mixing EVA and graphene: Weigh 95.5g of EVA resin (VA content 80%), add 1g of triallyl isocyanate and 0.5g of benzophenone, stir evenly and then add to the graphene dispersion. Transfer to a three-necked flask, place in a 42℃ water bath, and stir at 1300r / min for 6h to obtain an EVA-graphene-crosslinking aid mixed solution.

[0069] (3) Perfluorohexanone emulsification: Measure 600g of deionized water, add 15g of Tween-80 (emulsifier concentration 2.5wt%), stir to dissolve (water temperature 20℃-25℃), slowly add 100g of perfluorohexanone (perfluorohexanone to deionized water mass ratio 1:5), stir with a high-speed stirrer at 4500r / min speed for 35min (ice water bath temperature control ≤38℃) to form an emulsion.

[0070] (4) Microcapsule preparation: The EVA-graphene-crosslinking agent mixed solution was added dropwise to the perfluorohexanone emulsion (dropping rate controlled at 1-2 drops / second), while stirring at 350 r / min (ice-water bath temperature control ≤45℃); after the addition was complete, stirring was continued for 2 h (temperature maintained ≤45℃), and ultraviolet irradiation was performed simultaneously with stirring (irradiation power 400 mW / cm²). 2 The capsules were irradiated and cured for 40 seconds. The resulting capsules were centrifuged (5000 r / min, 10 min), washed three times with deionized water (≤35℃), and dried in a freeze dryer for 24 h to obtain the fire extinguishing microcapsule product.

[0071] Product Features: These fire extinguishing microcapsules are spherical with a particle size of 300-500 μm. Tests show that after 3 months of storage at 40℃ and 70% relative humidity, the perfluorohexanone volatilization loss rate is only 2.4%. After UV cross-linking, the compressive strength reaches 33 MPa, and the impact strength is 23 kJ / m². 2 The EVA resin with 80% VA content, combined with 3% graphene, softens the wall material. However, the addition of graphene improves its compressive strength compared to 1% VA, resulting in good barrier properties. Thermal stability tests show that the capsule remains stable at 104℃ and ruptures at 125℃, releasing the extinguishing agent.

[0072] Example 5

[0073] Similar to Example 2, except that: in step (1), the mass ratio of graphene to perfluorohexanone is 2:100, and the mass ratio of graphene, N-methylpyrrolidone, and sodium dodecylbenzenesulfonate is 1:200:0.2; in step (2), the mass ratio of EVA (VA content 50%), graphene, and UV crosslinking agent is 97:2:1, the oil bath is heated to 70°C, and stirred for 6 hours to fully dissolve the EVA and mix it evenly with the graphene; in step (3), the emulsifier concentration is 2wt%, the mass ratio of perfluorohexanone to deionized water is 1:10, and then the mixture is stirred at 4000 r / min for 40 min using a high-speed stirrer; in step (4), the irradiation power is 300 mW / cm. 2 Irradiation curing for 50 seconds.

[0074] Product Features: These fire extinguishing microcapsules are spherical with a particle size of 300-500 μm. Tests show that after 3 months of storage at 40℃ and 70% relative humidity, the perfluorohexanone volatilization loss rate is only 2.8%. After UV cross-linking, the compressive strength reaches 34 MPa, and the impact strength is 21 kJ / m². 2 Thermal stability tests showed that the capsule remained stable at 116°C, but ruptured at 133°C, releasing the fire extinguishing agent.

[0075] Example 6

[0076] Similar to Example 2, except that: in step (1), the mass ratio of graphene, N-methylpyrrolidone, and sodium dodecylbenzenesulfonate is 1:400:0.6; in step (2), the mass ratio of EVA, graphene, and UV crosslinking agent is 96:2:2, and the mixture is heated in an oil bath to 90°C and stirred for 4 hours to fully dissolve the EVA and mix it evenly with the graphene; in step (3), the emulsifier concentration is 3wt%, the mass ratio of perfluorohexanone to deionized water is 1:5, and then the mixture is stirred at 5000 r / min for 30 minutes using a high-speed stirrer; in step (4), the irradiation power is 500 mW / cm². 2 Irradiation curing for 30 seconds.

[0077] Product Features: These fire extinguishing microcapsules are spherical with a particle size of 300-500 μm. Tests show that after 3 months of storage at 40℃ and 70% relative humidity, the perfluorohexanone volatilization loss rate is only 2.7%. After UV cross-linking, the compressive strength reaches 36 MPa, and the impact strength is 22 kJ / m². 2 Thermal stability tests showed that the capsule remained stable at 118°C, but ruptured at 134°C, releasing the fire extinguishing agent.

[0078] Comparative Example 1: Pure EVA wall material (no graphene, no UV crosslinking)

[0079] A process for preparing fire extinguishing microcapsules includes the following steps:

[0080] (1) Weigh 100g of EVA resin (VA content 50wt%) and dissolve it in 350g of N-methylpyrrolidone (stirred in an oil bath at 80℃ for 4h) to obtain an EVA solution.

[0081] (2) Perfluorohexanone emulsification: Measure 600g of deionized water, add 15g of Tween-80 (emulsifier concentration 2.5wt%), stir to dissolve (water temperature 20℃-25℃), slowly add 100g of perfluorohexanone (perfluorohexanone to deionized water mass ratio 1:5), stir with a high-speed stirrer at 4500r / min speed for 35min (ice water bath temperature control ≤38℃) to form an emulsion.

[0082] (3) Microcapsule preparation: EVA solution was added dropwise to perfluorohexanone emulsion (dropping rate controlled at 1-2 drops / second) while stirring at 350 r / min (ice-water bath temperature controlled ≤45℃); after the addition was complete, stirring was continued for 2 h (temperature maintained ≤45℃). The obtained capsules were centrifuged (5000 r / min, 10 min), washed 3 times with deionized water (≤35℃), and dried in a freeze dryer for 24 h to obtain the fire extinguishing microcapsule product.

[0083] Product Features: This fire extinguishing capsule is spherical with a particle size of 300-500μm. Tests show that after 3 months of storage at 40℃ and 70% relative humidity, the perfluorohexanone volatilization loss rate is 32%. Its compressive strength reaches 12MPa, and its impact strength is 6kJ / m². 2 Thermal stability tests showed that the capsule remained stable at 80°C, but ruptured at 90°C, releasing the fire extinguishing agent.

[0084] Comparative Example 2: EVA + Graphene (without UV crosslinking)

[0085] A process for preparing fire extinguishing microcapsules includes the following steps:

[0086] (1) Preparation of graphene dispersion: Weigh 3g of hydroxylated modified graphene and add it to 350g of N-methylpyrrolidone, then add 0.6g of sodium dodecylbenzenesulfonate. Place the above mixture in an ultrasonic cleaner with a power of 300W and ultrasonically treat for 4h (water temperature controlled at 35℃-40℃) to obtain graphene dispersion.

[0087] (2) Mixing EVA and graphene: Weigh 97g of EVA resin (VA content 50wt%) and add it to the graphene dispersion. Transfer to a three-necked flask, place in a 42℃ water bath, and stir at 1300r / min for 6h to obtain an EVA-graphene mixed solution.

[0088] (3) Perfluorohexanone emulsification: Measure 600g of deionized water, add 15g of Tween-80 (emulsifier concentration 2.5wt%), stir to dissolve (water temperature 20℃-25℃), slowly add 100g of perfluorohexanone (perfluorohexanone to deionized water mass ratio 1:5), stir with a high-speed stirrer at 4500r / min speed for 35min (ice water bath temperature control ≤38℃) to form an emulsion.

[0089] (4) Microcapsule preparation: The EVA-graphene mixed solution was added dropwise to the perfluorohexanone emulsion (the dropping rate was controlled at 1-2 drops / second), while stirring at 350 r / min (ice-water bath temperature control ≤45℃); after the addition was completed, stirring was continued for 2 h (temperature maintained ≤45℃). The obtained capsules were centrifuged (5000 r / min, 10 min), washed 3 times with deionized water (≤35℃), and dried in a freeze dryer for 24 h to obtain the fire extinguishing microcapsule product.

[0090] Product Features: This fire extinguishing capsule is spherical with a particle size of 300-500μm. Tests show that after 3 months of storage at 40℃ and 70% relative humidity, the perfluorohexanone volatilization loss rate is 2.6%. Its compressive strength reaches 25MPa, and its impact strength is 10kJ / m². 2 Thermal stability tests showed that the capsule remained stable at 90°C, but ruptured at 100°C, releasing the fire extinguishing agent.

[0091] Comparative Example 3: Low VA content EVA (VA = 28 wt%) + hydroxylated modified graphene

[0092] Same as Example 2, except that the VA content of the EVA resin is 28 wt%.

[0093] Product Features: This fire extinguishing capsule is spherical with a particle size of 300-500μm. However, due to its low VA content, uneven wall material formation, and perfluorohexanone volatilization loss rate exceeding 30%, the yield is low. Testing showed that after 3 months of storage at 40℃ and 70% relative humidity, the perfluorohexanone volatilization loss rate was 22%. Its compressive strength reaches 28MPa, and its impact strength is 12kJ / m². 2 Thermal stability tests showed that the capsule remained stable at 86°C, but ruptured at 104°C, releasing the fire extinguishing agent.

[0094] Comparative Example 4:

[0095] Same as Example 2, except that the graphene was not hydroxylated and unmodified graphene was used.

[0096] Product Features: This fire extinguishing capsule is spherical with a particle size of 300-500 μm; however, due to the unmodified graphene, its dispersibility is poor. Testing showed that after 3 months of storage at 40℃ and 70% relative humidity, the perfluorohexanone volatilization loss rate was 12%; its compressive strength reaches 18 MPa, and its impact strength is 8 kJ / m². 2 Thermal stability tests showed that the capsule remained stable at 98°C, but ruptured at 105°C, releasing the fire extinguishing agent.

[0097] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A fire extinguishing microcapsule with EVA ultraviolet crosslinking barrier material as wall material, characterized in that, The fire extinguishing microcapsule is in a spherical or spherical-like shape as a whole, the composite material of EVA and graphene is a wall material, the core material is wrapped inside the wall material, the thickness of the wall material is 10-50μm, and the diameter of the fire extinguishing microcapsule is 300-500μm.

2. The fire extinguishing microcapsule with EVA ultraviolet crosslinking barrier material as wall material according to claim 1, characterized in that, The core material is perfluorohexanone, and the adding amount of graphene in the composite material of EVA and graphene is 1-5wt%.

3. The fire extinguishing microcapsule with EVA ultraviolet crosslinking barrier material as wall material according to claim 1 or 2, characterized in that, The composite material of EVA and graphene further comprises an ultraviolet crosslinking aid, and the mass ratio of EVA, graphene and the ultraviolet crosslinking aid is (93.0-98.5):(1-5):(0.5-2.0).

4. The fire extinguishing microcapsule with EVA ultraviolet crosslinking barrier material as wall material according to claim 3, characterized in that, The ultraviolet crosslinking aid comprises an ultraviolet crosslinking agent and a photoinitiator, the ultraviolet crosslinking agent is selected from one or more of triallyl isocyanurate, tert-butyl peroxy-2-ethylhexyl carbonate and trimethylolpropane triacrylate, the photoinitiator is benzophenone, and the mass ratio of the ultraviolet crosslinking agent to the photoinitiator is 2:

1.

5. The fire extinguishing microcapsule with EVA ultraviolet crosslinking barrier material as wall material according to claim 1, characterized in that, The graphene is hydroxyl-modified graphene.

6. The process for the preparation of fire extinguishing microcapsules with EVA ultraviolet cross-linked barrier material as wall material according to claim 1, characterized in that, The method comprises the following steps: (1) Preparation of graphene dispersion liquid: graphene is added into N-methyl pyrrolidone, then sodium dodecyl benzene sulfonate is added, the mixture is uniformly mixed to uniformly disperse the graphene in the N-methyl pyrrolidone, and the graphene dispersion liquid is obtained; (2) Mixing of EVA and graphene: EVA and an ultraviolet crosslinking aid are added into the graphene dispersion liquid obtained in step (1), heated to 70-90℃ in a water bath or oil bath, and stirred for 4-6h to fully dissolve the EVA and uniformly mix the EVA with the graphene, so as to obtain an EVA-graphene-crosslinking aid mixed solution; (3) Emulsification of perfluorohexanone: an emulsifying agent is added into deionized water, the concentration of the emulsifying agent is controlled to be 2-3wt%, then perfluorohexanone is slowly added, the mass ratio of the perfluorohexanone to the deionized water is 1:(5-10), and stirred for 30-40min to form a stable perfluorohexanone emulsion; (4) Preparation of microcapsule: the EVA-graphene-crosslinking aid mixed solution obtained in step (2) is slowly added into the perfluorohexanone emulsion obtained in step (3) while stirring, after the addition is completed, the stirring is continued for 1.5-2.5h, the EVA-graphene forms a wall material on the surface of the perfluorohexanone droplets through phase separation, the formed microcapsule is subjected to curing treatment, and after washing and drying, the fire extinguishing microcapsule with the EVA ultraviolet crosslinking barrier material as the wall material is obtained.

7. The manufacturing process of claim 6, wherein, In step (1), the mass ratio of the graphene, N-methyl pyrrolidone and sodium dodecyl benzene sulfonate is 1:(200-400):(0.2-0.6).

8. The manufacturing process of claim 6, wherein, In step (2), the mass ratio of the EVA, graphene and ultraviolet crosslinking aid is (93.0-98.5):(1-5):(0.5-2.0).

9. The production process according to claim 6 or 8, characterized in that, In step (2), the oil bath is heated to 80℃, and the stirring is performed at a stirring speed of 1000-1500r / min for 4-6h.

10. The manufacturing process of claim 6, wherein, In step (2), the mass ratio of the graphene and perfluorohexanone is 1-3:100, and the mass fraction of the graphene in the wall material is 1%-5%.

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