Binary composite filter tip filled based on zif-8 material and preparation method thereof

Abstract

The application provides a binary composite filter based on ZIF-8 material filling and a preparation method thereof, and belongs to the technical field of cigarette filter material preparation. The preparation method comprises the following steps: S1, preparing ZIF-8 material by using an improved pure water method; S2, dispersing the ZIF-8 material in anhydrous ethanol to obtain a ZIF-8 dispersion liquid; S3, applying the ZIF-8 dispersion liquid to open flax acetate fiber tows to carry out first standing, drying and second standing, and obtaining ZIF-8 filled acetate fibers; and S4, compounding the ZIF-8 filled acetate fibers with blank acetate fibers to prepare a binary composite filter. The binary composite filter selectively adsorbs carbon monoxide and tar in smoke without changing the original cigarette structure and smoking taste, and significantly reduces the carbon monoxide and tar entering the human body.

Description

Technical Field

[0001] This invention belongs to the field of cigarette filter material preparation technology, and particularly relates to a binary composite filter tip based on ZIF-8 material filling and its preparation method. Background Technology

[0002] As a major global consumer product, cigarettes contribute to industrial development and the economy, but the smoke they produce contains various harmful components that pose a significant threat to the health of smokers and those exposed to secondhand smoke. Specifically, the harm of smoking mainly comes from harmful substances in cigarette smoke, such as nicotine, carbon monoxide, tar, and heavy metals. The total particulate matter in cigarette smoke, excluding water and nicotine, is called tar. Carbon monoxide, a major product of incomplete combustion in cigarettes, is highly competitive for blood oxygen-carrying capacity. Its affinity for hemoglobin is far greater than that for oxygen, reducing the blood's oxygen-carrying capacity and leading to hypoxia in organs such as the heart, brain, and lungs, which can cause irreversible damage in the long term.

[0003] Tar reduction and harm reduction have become the core direction of sustainable development and technological research in the tobacco industry. Among various tar reduction and harm reduction technologies, adding functional adsorbents to filters can selectively adsorb and retain harmful substances in cigarette smoke. It boasts advantages such as high feasibility, low cost, and minimal impact on taste, making it the mainstream and highly efficient harm reduction technology currently widely used in the research and production of low-harm cigarettes. However, it still has many shortcomings. For example, some adsorbents, while adsorbing harmful components, also adsorb aroma substances in cigarette smoke, leading to a deterioration in the cigarette's taste. Furthermore, some adsorbents have poor stability and are prone to desorption during cigarette storage and smoking, affecting the sustainability of the tar reduction and harm reduction effect.

[0004] Therefore, developing a functional material for filter tips that can simultaneously and efficiently trap multiple harmful components in cigarette smoke without affecting the original taste of the cigarette and has excellent stability has become an urgent need for the tobacco industry's research and development of tar reduction and harm reduction technologies. Summary of the Invention

[0005] This invention provides a method for preparing a binary composite filter tip filled with ZIF-8 material. An ethanol dispersion is used to induce reversible physical swelling of cellulose acetate, increasing the internal contact area and surface roughness of the fiber, thereby facilitating the adhesion of ZIF-8 particles and ensuring their stable filling onto the cellulose acetate. This method is simple to implement and does not alter the original cigarette structure or smoking experience. Simultaneously, the addition of ZIF-8 effectively and specifically adsorbs carbon monoxide and tar from cigarette smoke, reducing their entry into the smoker's body through cigarette smoke.

[0006] This invention proposes a method for preparing a binary composite filter tip based on ZIF-8 material filling, comprising the following steps:

[0007] S1. ZIF-8 material was prepared using an improved pure water method; S2. Disperse the above ZIF-8 material in anhydrous ethanol to obtain a ZIF-8 dispersion; S3. After applying the above ZIF-8 dispersion to the opened blank cellulose acetate bundle, let it stand for a first time, dry it, and let it stand for a second time to obtain cellulose acetate filled with ZIF-8. S4. The above-mentioned ZIF-8-filled cellulose acetate and blank cellulose acetate are combined to prepare a binary composite filter.

[0008] 2. The preparation method according to claim 1, characterized in that, In S1, the improved pure water method for preparing ZIF-8 material includes the following steps: 2-Methylimidazole solution was slowly added dropwise to zinc nitrate solution at a rate of 1-3 mL / min. After stirring and standing, the resulting mixture became turbid. After centrifugation and washing, ZIF-8 nanocrystals were separated from the milky white dispersion and dried to obtain ZIF-8 material.

[0009] Further, in S1, the concentration of the 2-methylimidazole solution is 1–3 mol / L; the concentration of the zinc nitrate solution is 0.1–0.4 mol / L; and / or In S1, the molar ratio of 2-methylimidazole solution to zinc nitrate solution is 13~18:2.

[0010] Furthermore, in S1, the stirring and settling period specifically refers to magnetic stirring at room temperature for 0.5 to 2 hours followed by settling for 20 to 30 hours.

[0011] Furthermore, in S2, the concentration of the ZIF-8 dispersion is 0.35~0.45 mg / mL.

[0012] Furthermore, in S3, in the ZIF-8-filled cellulose acetate, the ZIF-8 filling amount is 1.5~2.5 mg of ZIF-8 material for every 1g of blank cellulose acetate filament bundle.

[0013] Furthermore, in S3, the first settling time is 60-180 minutes in air; and / or In S3, the drying temperature is 40-50℃; and / or In S3, the second settling period specifically refers to settling in the air for 12 to 36 hours.

[0014] Furthermore, in S4, the acetate fiber filled with ZIF-8 is compounded with the blank acetate fiber by length, with a length ratio of 1:1 to 5.

[0015] The present invention also proposes a binary composite filter tip prepared by any of the above-described preparation methods.

[0016] This invention has the following advantages: This invention proposes a method for preparing a binary composite filter tip based on ZIF-8 material filling. Using cellulose acetate as the filter tip matrix, ZIF-8, prepared by a modified pure water method, with high specific surface area and abundant adsorption sites, is introduced as a functional adsorbent. Simultaneously, an ethanol dispersion is used to induce reversible physical swelling of the cellulose acetate, increasing the internal contact area and surface roughness of the fiber, thereby facilitating the adhesion of ZIF-8 particles. This ensures that the ZIF-8 particles are firmly packed onto the cellulose acetate, achieving uniform loading and stable adhesion of ZIF-8 on the cellulose acetate tow. This avoids powder shedding and desorption, while preserving the fiber structure and puffing experience. Furthermore, by combining ZIF-8-loaded cellulose acetate segments with blank cellulose acetate segments, a binary composite filter tip is constructed. This method does not alter the original cigarette structure or puffing experience, but selectively adsorbs carbon monoxide and tar from cigarette smoke, significantly reducing the amount of carbon monoxide and tar entering the body. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a simplified diagram of the overall structure of the binary composite filter cigarette obtained in Embodiment 1 of the present invention.

[0019] Figure 2 This is a SEM image of the ZIF-8 material synthesized by the improved pure water method obtained in Example 1 of the present invention.

[0020] Figure 3 The image shows the XRD pattern of the ZIF-8-filled cellulose acetate obtained in Example 1 of this invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0022] Fiber acetate exhibits multiple advantages as a filter material, including odorlessness due to chemical inertness, controllable mechanical properties, oleophobic properties, and excellent adsorption kinetic parameters.

[0023] ZIF-8 possesses excellent biocompatibility, chemical stability, and high water stability, making it widely applicable across various fields. Compared to other porous materials, ZIF-8 exhibits superior physicochemical properties, such as high specific surface area, high crystallinity, abundant surface functional groups, and good chemical and thermal stability. These characteristics make it valuable for adsorption and separation applications. Specifically, its high specific surface area and tunable surface functionalization provide abundant adsorption sites for harmful substances, while its excellent chemical and thermal stability ensures its sustained effectiveness in the complex environment of cigarette filters. Furthermore, based on the synergistic effect of its metal ions and organic ligands, ZIF-8 also possesses certain antibacterial properties, is safe in composition, and meets the further health and safety requirements of tobacco products.

[0024] However, how to efficiently combine ZIF-8 with cellulose acetate, stabilize the load, and synergistically exert adsorption and filtration effects remains a key technical challenge that urgently needs to be addressed.

[0025] On one hand, embodiments of the present invention propose a method for preparing a binary composite filter tip based on ZIF-8 material filling, comprising the following steps: S1. ZIF-8 material was prepared using an improved pure water method; S2. Disperse the above ZIF-8 material in anhydrous ethanol to obtain a ZIF-8 dispersion; S3. After applying the above ZIF-8 dispersion to the opened blank cellulose acetate bundle, let it stand for a first time, dry it, and let it stand for a second time to obtain cellulose acetate filled with ZIF-8. S4. The above-mentioned ZIF-8-filled cellulose acetate and blank cellulose acetate are combined to prepare a binary composite filter.

[0026] This invention proposes a method for preparing a binary composite filter tip based on ZIF-8 material filling. Using cellulose acetate as the filter tip matrix, ZIF-8, prepared by a modified pure water method, with high specific surface area and abundant adsorption sites, is introduced as a functional adsorbent. Simultaneously, an ethanol dispersion is used to induce reversible physical swelling of the cellulose acetate, increasing the internal contact area and surface roughness of the fiber, thereby facilitating the adhesion of ZIF-8 particles. This ensures that the ZIF-8 particles are firmly packed onto the cellulose acetate, achieving uniform loading and stable adhesion of ZIF-8 on the cellulose acetate tow. This avoids powder shedding and desorption, while preserving the fiber structure and puffing experience. Furthermore, by combining ZIF-8-loaded cellulose acetate segments with blank cellulose acetate segments, a binary composite filter tip is constructed. This method does not alter the original cigarette structure or puffing experience, but selectively adsorbs carbon monoxide and tar from cigarette smoke, significantly reducing the amount of carbon monoxide and tar entering the body.

[0027] In one embodiment of the present invention, S1, the preparation of ZIF-8 material by the improved pure water method includes the following steps: 2-Methylimidazole solution was slowly added dropwise to zinc nitrate solution at a rate of 1-3 mL / min. After stirring and standing, the resulting mixture became turbid. After centrifugation and washing, ZIF-8 nanocrystals were separated from the milky white dispersion and dried to obtain ZIF-8 material.

[0028] In this embodiment of the invention, ZIF-8 crystals are synthesized in pure water via a coordination reaction using 2-methylimidazole as the organic ligand and zinc nitrate as the metal source. The 2-methylimidazole solution is slowly added dropwise to the zinc nitrate solution at a rate of 1-3 mL / min. This slow addition and mixing facilitates homogeneous nucleation and controllable growth of the crystals, resulting in ZIF-8 with high crystallinity and high specific surface area. The abundant surface functional groups formed by the metal ions and organic ligands in ZIF-8 serve as effective adsorption sites, allowing carbon monoxide and tar components to be firmly adsorbed onto the material surface and within the pores through physical adsorption and possible coordination interactions.

[0029] Specifically, in S1, the concentration of the 2-methylimidazole solution is 1~3 mol / L. Preferably, the concentration of the 2-methylimidazole solution is 2 mol / L. Specifically, the preparation method of the 2-methylimidazole solution includes: dissolving 60 mmol of 2-methylimidazole in 30 mL of ultrapure water and sonicating.

[0030] Specifically, in S1, the concentration of the zinc nitrate solution is 0.1~0.4 mol / L. Preferably, the concentration of the zinc nitrate solution is 0.2667 mol / L. Specifically, the zinc nitrate solution is prepared by dissolving 8 mmol of Zn(NO3)2·6H2O in 30 mL of ultrapure water.

[0031] Specifically, in S1, the molar ratio of 2-methylimidazole solution to zinc nitrate solution is 13~18:2. Preferably, the molar ratio of 2-methylimidazole solution to zinc nitrate solution is 15:2.

[0032] Specifically, in S1, the stirring and standing period is 0.5-2 h of magnetic stirring at room temperature followed by 20-30 h of standing.

[0033] Specifically, in S1, the centrifugation speed is 8000 r / min. The washing process involves washing three times with ultrapure water. The drying process involves drying at 60 ℃ for 8–14 h.

[0034] In one embodiment of the present invention, in S2, the concentration of the ZIF-8 dispersion is 0.35~0.45 mg / mL.

[0035] In embodiment S3 of this invention, the introduction of the ethanol dispersion causes reversible physical swelling of the cellulose acetate, increasing the internal contact area and surface roughness of the fiber, thereby facilitating the adhesion of ZIF-8 particles and ensuring their stable filling on the cellulose acetate after adhesion. The ZIF-8-filled cellulose acetate exhibits a significantly enhanced retention capacity for carbon monoxide and tar in flue gas. This is mainly attributed to the high specific surface area and abundant pore structure of ZIF-8, which provides ample adsorption space and capacity for harmful components such as carbon monoxide and tar.

[0036] In one embodiment of the present invention, in S3, the ZIF-8 filling amount of the cellulose acetate fiber is 1.5~2.5 mg of ZIF-8 material for every 1g of blank cellulose acetate fiber bundle.

[0037] In one embodiment of the present invention, in step S3, the first settling time is 60-180 minutes in air. In this embodiment of the present invention, the purpose of settling is mainly to allow the cellulose acetate to undergo physical swelling and reach dynamic equilibrium. In addition, it allows the ZIF-8 in the dispersion to better diffuse mechanically onto the surface and gaps of the cellulose acetate.

[0038] In one embodiment of the present invention, in step S3, the drying temperature is 40-50 °C. In this embodiment, drying allows ethanol to evaporate, the fibers to shrink, and the ZIF-8 to be mechanically anchored to the fiber surface and gaps.

[0039] In one embodiment of the present invention, in step S3, the second settling period specifically involves settling in air for 12-36 hours. In this embodiment, the purpose of the second settling period after drying to allow the cellulose acetate fibers to regain their original properties after physical swelling. These properties mainly include the flexibility of the filament bundle, opening / forming stability, electrostatic control, and weighing consistency.

[0040] In one embodiment of the present invention, in S3, the application is performed by spraying, dripping, or impregnation.

[0041] In one embodiment of the present invention, in step S4, the ZIF-8-filled cellulose acetate and blank cellulose acetate are compounded by length, with a length ratio of 1:1 to 5. In this embodiment of the present invention, the functional segment provides selective adsorption (tar, CO), while the blank segment maintains filtration performance and suction taste. The two segments work together to reduce tar and harm without degrading sensory quality.

[0042] On the other hand, embodiments of the present invention also propose binary composite filter tips prepared by any of the above preparation methods.

[0043] In one embodiment of the present invention, the cigarette is composed of a cigarette stem section 1 and a binary composite filter section 5; the binary composite filter section 5 includes a ZIF-8 filled cellulose acetate functional section 2 and a blank cellulose acetate section 4, which are compounded in a set length ratio and then wrapped by tipping paper 3 to form the filter tip as a whole.

[0044] The present invention will now be described in detail with reference to the embodiments.

[0045] Example 1 A method for preparing a binary composite filter tip based on ZIF-8 material filling, comprising: S1. ZIF-8 material was prepared using an improved pure water method; ZIF-8 material was prepared using a modified pure water method: 60 mmol of 2-methylimidazole was dissolved in 30 mL of ultrapure water and sonicated to obtain a 2 mol / L 2-methylimidazole solution; simultaneously, 8 mmol of Zn(NO3)2... 6H2O was dissolved in 30 mL of ultrapure water and stirred to prepare a 0.2667 mol / L zinc nitrate solution. 2-methylimidazole solution was slowly added dropwise (2 mL / min) to the zinc nitrate solution. After magnetic stirring at room temperature for 1 h, the mixture was allowed to stand for 24 h, and a milky white turbid dispersion was formed. The mixture was then centrifuged at 8000 r / min. The precipitate was washed three times with ultrapure water and dried in a 60 ℃ oven for 12 h to obtain ZIF-8 nanocrystalline powder with high crystallinity and high specific surface area. S2. Prepare a 0.4 mg / mL ZIF-8 dispersion using anhydrous ethanol; S3. Spray 5 mL of ZIF-8 dispersion evenly onto 1 g of opened blank cellulose acetate bundle. The ZIF-8 filling amount is 2 mg. Let it stand for 120 min. Dry the cellulose acetate with the added dispersion at 50℃ for 6 h. Let the dried cellulose acetate filled with ZIF-8 in the air for 18 h to rehydrate. This gives you cellulose acetate filled with ZIF-8. S4. The ZIF-8-filled cellulose acetate obtained in S3 and blank cellulose acetate are combined in a 1:1 length ratio to prepare a binary composite filter. See the structure below. Figure 1 .

[0046] Example 2 Same as Example 1, except that in S3, the amount of ZIF-8 dispersion used is 3.75 mL; the amount of ZIF-8 filled is 1.5 mg.

[0047] Example 3 Same as Example 1, except that in S3, the amount of ZIF-8 dispersion used is 6.25 mL; the amount of ZIF-8 filled is 2.5 mg.

[0048] Example 4 Same as Example 1, except that in S2, the concentration of ZIF-8 dispersion is 0.361 mg / mL; in S3, the amount of ZIF-8 dispersion used is 5.54 mL; and the filling amount of ZIF-8 is 2 mg.

[0049] Example 5 Same as Example 1, except that in S2, the concentration of ZIF-8 dispersion is 0.444 mg / mL; in S3, the amount of ZIF-8 dispersion used is 4.5 mL; and the filling amount of ZIF-8 is 2 mg.

[0050] Examples 6-8 Similar to Example 1, except that in S4, the length ratios of the ZIF-8-filled cellulose acetate and the blank cellulose acetate are 1:2, 1:3, and 1:4, respectively.

[0051] Comparative Examples 1-3 Same as Example 1, except that in S2, methanol, acetone, and N,N-dimethylformamide are used to replace anhydrous ethanol, respectively.

[0052] Comparative Example 4 Same as in Example 1, except that in S3, the first settling time is 30 min.

[0053] Comparative Example 5 Same as Example 1, except that in S3, the drying temperature is changed to 60°C.

[0054] Comparative Example 6 Same as Example 1, except that in S3, the second settling time (rehydration) is 5 h.

[0055] Comparative Example 7 Similar to Example 1, except that in S2, the concentration of ZIF-8 dispersion is 0.6 mg / mL; in S3, the amount of dispersion used is 3.33 mL, and the amount of ZIF-8 filled is 2 mg.

[0056] Comparative Example 8 Same as Example 1, except that in S3, the amount of dispersion is 10 mL and the amount of ZIF-8 is 4 mg.

[0057] Comparative Example 9 Similar to Example 1, except that in S1, in the improved pure water method for preparing ZIF-8 material, ultrapure water is used as the solvent, and 80 mmol of 2-methylimidazole and 10 mmol of Zn(NO3)2·6H2O are directly mixed to prepare ZIF-8 material.

[0058] Comparative Example 10 The conventional harm-reducing binary composite filter rod is composed of alternating sections of cellulose acetate and feeding sections. Specifically, it is composed of alternating sections of 3 cellulose acetate and 2 feeding sections. 2 mg of the ZIF-8 composite material prepared in Example 1 is impregnated and added to the feeding section.

[0059] Experimental Example 1 (1) Characterization of ZIF-8 and ZIF-8-filled cellulose acetate The pore structure of ZIF-8 prepared using the improved pure water method in Example 1 of this invention was analyzed using a specific surface area and pore size analyzer. The results showed that the specific surface area was 1598.7 m². 2 / g, pore volume is 0.603 cm³ 3 / g, with an average pore size of 3.4 nm. ZIF-8 has a large specific surface area and pore volume, which creates more adsorption space for adsorption, and the suitable pore size is also conducive to diffusion.

[0060] ZIF-8 was characterized and analyzed using scanning electron microscopy. The results are shown in the figure. Figure 2 . Figure 2 The SEM image is for ZIF-8, by Figure 2 It can be seen that the ZIF-8 crystal has a rhombic dodecahedral structure with sharp edges and a smooth surface, and its size is about 1 μm.

[0061] X-ray diffraction analysis was performed on the ZIF-8-filled cellulose acetate obtained in Example 1, S3. The results are shown in the figure. Figure 3 , where the horizontal axis is 2θ (°) and the vertical axis is intensity (au). Figure 3 The diffraction peaks of ZIF-8 were clearly visible, while the amorphous scattering background of cellulose acetate appeared at 2theta ≈12° and 23°, indicating that ZIF-8 was successfully composited onto cellulose acetate.

[0062] (2) Testing of tar and other harmful substances in cigarettes Cigarette smoking tests were conducted on a smoking machine under standard smoking conditions, and the changes in carbon monoxide and tar in the mainstream cigarette smoke were investigated according to standards YC / T 349-2010, YC / T 563-2018, and GB / T 19609-2024, respectively. The results are shown in Table 2.

[0063] (3) Sensory evaluation A number of smokers were randomly selected for testing. The evaluation criteria shown in Table 1 were used to judge the results. The higher the value of 1-9, the better the sensory effect. The results are shown in Table 2.

[0064] Table 1. Sensory Effect Evaluation Criteria

[0065] Table 2. Release amount and reduction rate of several smoke components in mainstream cigarette smoke from the examples and comparative experiments. Experimental cigarettes Tar (mg / vial) Carbon monoxide (mg / vial) Tar reduction rate (%) Carbon monoxide reduction rate (%) Sensory effects Example 1 13.3 16.1 10.1 10.0 9 Example 2 13.7 16.8 7.7 7.1 7 Example 3 13.6 16.4 8.2 8.5 7 Example 4 13.58 16.5 8.0 7.8 6 Example 5 13.4 16.3 9.1 8.9 6 Example 6 13.3 16.1 10.3 10.0 6 Example 7 13.23 16.0 10.6 10.5 5 Example 8 13.2 15.98 10.7 10.7 4 Comparative Example 1 14.1 17.1 4.7 4.3 4 Comparative Example 2 14.2 17.2 4.1 3.9 4 Comparative Example 3 14.3 17.2 3.7 3.9 3 Comparative Example 4 14.4 17.4 2.8 2.9 4 Comparative Example 5 14.44 17.5 2.4 2.1 3 Comparative Example 6 14.34 17.3 3.1 3.0 3 Comparative Example 7 14.08 17.0 4.8 5.0 3 Comparative Example 8 14.01 16.95 5.3 5.3 2 Comparative Example 9 14.5 17.4 3.1 2.8 4 Comparative Example 10 14.3 17.3 3.2 3.4 2 Comparing Example 1 and Comparative Examples 1-3, it can be seen that methanol only has a very weak physical swelling effect on cellulose acetate, requires a longer equilibration time, and the physical swelling effect is poor. Acetone and N,N-dimethylformamide are closer to strong solvents for cellulose acetate, often resulting in significant softening or even dissolution upon contact. Ethanol, on the other hand, mainly exhibits physical swelling, and has a very good physical swelling effect, returning the cellulose acetate filaments to their initial state after drying and rehydration (the swelling coefficient of cellulose acetate filaments in ethanol solution was measured to be 15% during the process; the specific method involved placing cellulose acetate filaments between two glass plates, adding ethanol solvent, and then recording the change in fiber diameter using an optical microscope for calculation).

[0066] In Comparative Example 4, insufficient settling time prevented the ethanol from reaching dynamic equilibrium in swelling the cellulose acetate fibers. This resulted in insufficient expansion of the fiber gaps, making it difficult for ZIF-8 particles to diffuse evenly and penetrate the fiber interior; the load remained only on the surface. Consequently, the final coking effect was poor.

[0067] In Comparative Example 5, the higher temperature caused the ethanol to evaporate too quickly, and the fibers were prematurely set before they had fully shrunk. The ZIF-8 particles could not be effectively mechanically anchored, and the acetate fiber bundles became brittle and uneven in bulk due to thermal stress.

[0068] Comparative Example 6 shortened the second settling and rehydration time to 5 hours. The cellulose acetate bundles were not fully rehydrated and balanced, and their flexibility and opening and forming stability were not restored. During the filter tip processing, bundles and collapses were prone to occur, affecting the uniform flow of flue gas.

[0069] In Comparative Example 7, the concentration of ZIF-8 dispersion was increased to 0.6 mg / mL. Under the same filling amount, ZIF-8 particles in the high-concentration dispersion were prone to agglomeration. After application, they formed local accumulation on the fiber surface, resulting in a sudden increase in local suction resistance of the filter tip and uneven flue gas flow. At the same time, the agglomerated particles were easy to fall off.

[0070] Comparative Example 8 increased the ZIF-8 filling amount to 4 mg. The excessive ZIF-8 particles exceeded the gap that the fiber could accommodate after swelling. A large number of particles were only attached to the fiber surface, which not only made them easy to fall off, but also significantly increased the filter resistance. At the same time, the aroma components of the smoke were over-adsorbed, resulting in a deterioration in taste.

[0071] Comparative Example 9: ZIF-8 prepared by the conventional pure water method has inferior crystallinity, specific surface area and pore structure compared to the product prepared by the improved pure water method, and has insufficient adsorption sites.

[0072] Comparative Example 10 uses a traditional multi-segment composite filter. The ZIF-8 added during impregnation is prone to falling off and unevenly distributed, resulting in insufficient contact between the smoke and the adsorption material. Furthermore, the multi-segment structure leads to large fluctuations in draw resistance and poor consistency in taste.

[0073] (4) Test of the draw resistance of cigarettes with binary composite filters After the cigarettes used in the examples and comparative examples were equilibrated in a constant temperature and humidity chamber (temperature 22±1℃, relative humidity 60±2%) for 48 h, the tests were conducted in the same environment (filter length 28 mm, cigarette size 84 mm (20 mm + 64 mm); all data are the average of 3 repeated experiments, with 2 parallel experiments each time.

[0074] Determination of the draw resistance of cigarettes with binary composite filters: The draw resistance tester was used to evaluate the changes in draw resistance of the experimental cigarettes with binary composite filters. The results are shown in Table 3.

[0075] Table 3. Changes in suction resistance in the examples and comparative examples Experimental cigarettes Suction resistance (Kpa) Increase in suction resistance (%) Comparative Example 1 1.119 2.56 Comparative Example 2 1.112 2.69 Comparative Example 3 1.113 2.73 Comparative Example 4 1.114 2.81 Comparative Example 5 1.116 2.97 Comparative Example 6 1.117 3.03 Comparative Example 7 1.107 2.11 Comparative Example 8 1.125 3.80 Comparative Example 9 1.115 2.91 Comparative Example 10 1.140 5.18 Example 1 1.092 0.70 Example 2 1.095 1.01 Example 3 1.097 1.20 Example 4 1.099 1.39 Example 5 1.100 1.43 Example 6 1.101 1.50 Example 7 1.111 2.46 Example 8 1.130 4.20 The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a binary composite filter tip based on ZIF-8 material filling, characterized in that, Includes the following steps: S1. ZIF-8 material was prepared using an improved pure water method; S2. Disperse the above ZIF-8 material in anhydrous ethanol to obtain a ZIF-8 dispersion; S3. After applying the above ZIF-8 dispersion to the opened blank cellulose acetate bundle, let it stand for a first time, dry it, and let it stand for a second time to obtain cellulose acetate filled with ZIF-8. S4. The above-mentioned ZIF-8-filled cellulose acetate and blank cellulose acetate are combined to prepare a binary composite filter.

2. The preparation method according to claim 1, characterized in that, In S1, the improved pure water method for preparing ZIF-8 material includes the following steps: 2-Methylimidazole solution was slowly added dropwise to zinc nitrate solution at a rate of 1-3 mL / min. After stirring and standing, the resulting mixture became turbid. After centrifugation and washing, ZIF-8 nanocrystals were separated from the milky white dispersion and dried to obtain ZIF-8 material.

3. The preparation method according to claim 2, characterized in that, In S1, the concentration of the 2-methylimidazole solution is 1–3 mol / L; the concentration of the zinc nitrate solution is 0.1–0.4 mol / L; and / or In S1, the molar ratio of 2-methylimidazole solution to zinc nitrate solution is (13~18):

2.

4. The preparation method according to claim 2, characterized in that, In S1, the stirring and settling period is specifically 0.5-2 h of magnetic stirring at room temperature followed by 20-30 h of settling.

5. The preparation method according to claim 1, characterized in that, In S2, the concentration of ZIF-8 dispersion is 0.35~0.45 mg / mL.

6. The preparation method according to claim 1, characterized in that, In S3, the ZIF-8-filled cellulose acetate fibers contain 1.5 to 2.5 mg of ZIF-8 material in 1 g blank cellulose acetate filament bundles.

7. The preparation method according to claim 1, characterized in that, In S3, the first settling time is 60-180 minutes in air; and / or In S3, the drying temperature is 40-50℃; and / or In S3, the second settling period specifically refers to settling in the air for 12 to 36 hours.

8. The preparation method according to claim 1, characterized in that, In S4, ZIF-8-filled cellulose acetate is compounded with blank cellulose acetate by length, with a length ratio of 1:1 to 5.

9. The binary composite filter tip prepared by the preparation method according to any one of claims 1 to 8.

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