Cigarette filter tip capable of effectively intercepting harmful substances in smoke and preparation method of cigarette filter tip

Abstract

The invention provides a cigarette filter tip capable of effectively intercepting harmful substances in smoke and a preparation method thereof, and relates to the technical field of cigarette filter materials, the cigarette filter tip comprises filter tip fibers, the surfaces of the filter tip fibers are modified with reduced curved surface graphene-water-soluble chitosan composite materials, and the reduced curved surface graphene-water-soluble chitosan composite materials are modified with a composite material. The composite material is formed by combining reduced curved graphene and water-soluble chitosan through a covalent bond and / or a non-covalent bond, reduced curved surface graphene and water-soluble chitosan are adopted for composite modification, the reduced curved surface graphene recovers a complete conjugated structure, strong hydrophobic polycyclic aromatic hydrocarbons such as benzopyrene are specifically adsorbed through accumulation action and hydrophobic interaction, and the rejection rate is increased; amino groups and hydroxyl groups in water-soluble chitosan molecules achieve directional chelation adsorption on phenols and other hydrophilic acid harmful substances through hydrogen bonds and electrostatic interaction, the directional chelation adsorption effect is obviously better than that of an existing graphene modified filter tip, and the carcinogenic risk and irritation of smoke are effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of cigarette filter materials technology, and in particular to a cigarette filter tip that can effectively trap harmful substances in cigarette smoke and its preparation method. Background Technology

[0002] With the significant increase in global public health awareness, the harm reduction transformation of the tobacco industry has become an inevitable trend. All 183 parties to the World Health Organization's Framework Convention on Tobacco Control have established strict regulatory systems for cigarette components, and OECD member countries generally implement mandatory standards of tar ≤10mg / cigarette and nicotine ≤1mg / cigarette. Currently, the tobacco industry has achieved an average reduction of 37% in cigarette tar release through multiple patented technologies such as molecular sieve filtration and nanocatalysis, and 84% of newly launched cigarette products globally meet the "low emissions" standard. In the field of filter modification materials, graphene oxide has become a research hotspot due to its unique two-dimensional structure and abundant oxygen-containing functional groups. Graphene-modified filters can achieve a retention rate of 47-82% for 16 preferentially controlled polycyclic aromatic hydrocarbons (PAHs) in cigarette smoke, and its free radical scavenging efficiency is 2.3 times higher than that of activated carbon. Water-soluble polysaccharides (such as chitosan) can adsorb harmful substances such as phenols in cigarette smoke through hydrogen bonding and electrostatic interactions. The combined modification of these two materials has become an important direction for harm reduction technology in cigarette filters. Meanwhile, more than 7,000 chemical substances have been identified in cigarette smoke, of which 93 have been clearly listed as carcinogens. Reducing the content of strong carcinogens such as benzo[a]pyrene and irritants such as phenols in cigarette smoke, while retaining tobacco characteristic aroma substances such as nicotine and solanine alcohol, is the core goal of the current industry's technological research. Existing filter modification technologies still have many shortcomings, making it difficult to achieve the dual goals of "efficiently retaining harmful substances and efficiently retaining beneficial flavor substances": graphene oxide is prone to aggregation when directly dispersed in water, making it difficult to fully utilize its adsorption sites and affecting the retention effect of harmful substances; conventional chitosan has poor water solubility, and existing preparation processes often use acetic acid solution as a solvent, which further aggravates the aggregation of graphene and chitosan and reduces the selective adsorption performance of the material; existing graphene-modified filters generally have a retention rate of less than 88% for strongly hydrophobic carcinogens such as benzo[a]pyrene and a retention rate of less than 85% for phenolic substances, and are prone to excessive loss of characteristic components such as nicotine and solanesol, affecting the smoking experience; some modified materials have poor stability, and their adsorption performance decays significantly after long-term storage, and the preparation process is complex and difficult to meet the needs of industrial production. These shortcomings limit the practical application of existing graphene-chitosan composite modified filters. Therefore, this invention proposes a cigarette filter that can effectively retain harmful substances in cigarette smoke and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0003] To address the aforementioned problems, this invention proposes a cigarette filter tip capable of effectively trapping harmful substances in cigarette smoke and its preparation method. The method employs a composite modification of reduced curved graphene and water-soluble chitosan, restoring the complete shape of the reduced curved graphene. Conjugate structure, through Stacking and hydrophobic interactions enable specific adsorption of strongly hydrophobic polycyclic aromatic hydrocarbons such as benzo[a]pyrene, increasing the rejection rate to [percentage missing]. The amino and hydroxyl groups in water-soluble chitosan molecules achieve targeted chelation and adsorption of hydrophilic acidic harmful substances such as phenols through hydrogen bonding and electrostatic interactions, achieving a retention rate of [missing information]. Both are significantly superior to existing graphene-modified filters, effectively reducing the carcinogenic risk and irritation of flue gas.

[0004] To achieve the purpose of this invention, the invention is achieved through the following technical solution: a cigarette filter tip that can effectively trap harmful substances in cigarette smoke, comprising filter tip fibers, wherein the surface of the filter tip fibers is modified with a reduced curved graphene-water-soluble chitosan composite material, wherein the composite material is formed by the combination of reduced curved graphene and water-soluble chitosan through covalent bonds and / or non-covalent bonds. The filter fiber is processed into a modified fiber segment of a cigarette filter, and the modified fiber segment and the conventional acetate fiber segment together form a cigarette filter.

[0005] A further improvement is that the reduced curved graphene is obtained by reducing curved graphene with a reducing agent, specifically: the curved graphene is ultrasonically dispersed to obtain a curved graphene dispersion, and then reduced by ascorbic acid to obtain reduced curved graphene.

[0006] A further improvement is that the water-soluble chitosan is carboxymethyl chitosan, and the mass ratio of the carboxymethyl chitosan to the reduced curved graphene is 1.5-5:1.

[0007] A further improvement is that the filter tip fiber is cellulose acetate, and the reduced curved graphene-water-soluble chitosan modification layer on the surface of the cellulose acetate is uniform and dense.

[0008] Further improvements are made in that: the main structure of the cigarette filter is a binary or ternary structure; the binary structure consists of a conventional cellulose acetate segment and a modified fiber segment, and the length of the modified fiber segment accounts for 0.3-0.7 times the total length of the cigarette filter; the ternary structure consists of alternating conventional cellulose acetate segments, modified fiber segments, and conventional cellulose acetate segments, with the modified fiber segment located in the middle section and its length accounting for 0.4-0.7 times the total length of the cigarette filter.

[0009] A method for preparing a cigarette filter that can effectively trap harmful substances in cigarette smoke includes the following steps: S1: Preparation of curved graphene; S2: Ultrasonically disperse curved graphene in water to form a curved graphene dispersion; S3: Add water-soluble chitosan to the dispersion and stir until homogeneous to obtain a mixture; S4: Add a reducing agent to the mixture, control the reaction temperature and reaction time, reduce the curved graphene to obtain a reduced curved graphene-water-soluble chitosan dispersion; S5: Immerse the filter tip fiber in the dispersion, and dry it after immersion to obtain the modified filter tip fiber; S6: Modified fiber segments, which are processed into the main structure of cigarette filters, are combined with conventional acetate fiber segments to form cigarette filters.

[0010] Further improvements are made in the following aspects: In S2, the ultrasonic dispersion time is 5-60 minutes, the concentration of the curved graphene dispersion is 0.5-10 mg / ml, the ultrasonic power is 100-300 W, and the water temperature is controlled to not exceed 35℃ during the ultrasonic process.

[0011] A further improvement is made in S3, where the stirring rate is 300-500 rpm, and the water-soluble chitosan is prepared as an aqueous solution and slowly added dropwise to the dispersion at a rate of 0.5-1.5 ml / min. After the addition is completed, stirring is continued for 20-30 minutes.

[0012] Further improvements are made in the following aspects: In S4, the reducing agent is ascorbic acid, and the mass ratio of ascorbic acid to curved graphene is 0.5-2:1; the reaction temperature is 70-90℃, the reaction time is 2-6 hours, and the reaction is stirred intermittently to ensure uniform reduction.

[0013] Further improvements are made in the following aspects: In step S5, the impregnation time is 0.5-2 hours, and the impregnation process is assisted by ultrasound; the drying temperature is 60℃, the drying time is 2-6 hours, and the drying process adopts a gradual heating method; the dried modified filter fiber is rinsed with deionized water before subsequent processing.

[0014] The beneficial effects of this invention are as follows: 1. This invention employs a composite modification of reduced curved graphene and water-soluble chitosan, which restores the complete surface of the graphene. Conjugate structure, through Stacking and hydrophobic interactions enable specific adsorption of strongly hydrophobic polycyclic aromatic hydrocarbons such as benzo[a]pyrene, increasing the rejection rate to [percentage missing]. The amino and hydroxyl groups in water-soluble chitosan molecules achieve targeted chelation and adsorption of hydrophilic acidic harmful substances such as phenols through hydrogen bonding and electrostatic interactions, achieving a retention rate of [missing information]. Both are significantly superior to existing graphene-modified filters, effectively reducing the carcinogenic risk and irritation of flue gas.

[0015] 2. This invention, through the construction of surface polarity gradients and the regulation of interlayer steric hindrance, effectively prevents the excessive adsorption and loss of characteristic components such as nicotine and solanesol while efficiently retaining harmful substances. The nicotine retention rate reaches [percentage missing]. The retention rate of solanesol reached It preserves the original flavor of tobacco to the greatest extent and solves the technical problem of poor taste in existing modified filters.

[0016] 3. This invention uses curved graphene as the substrate, whose three-dimensional wrinkled structure can effectively avoid agglomeration. Combined with the coating modification of water-soluble chitosan, the dispersion performance of the material is further improved. Ascorbic acid is used as a reducing agent, and the reduction conditions are mild, allowing for precise control of the reduction degree and avoiding the problems of decreased water solubility and agglomeration caused by excessive reduction. The preparation process does not require the use of harmful solvents, the process steps are simple, the reaction conditions are easy to control, and the adsorption performance of the product decreases only slightly after long-term storage. Its stability is far superior to existing products, making it suitable for large-scale industrial production. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the cigarette filter structure in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the cigarette filter structure in Embodiment 2 of the present invention; Figure 3 This is a SEM image of the graphene from the present invention; Figure 4 This is a SEM image of the curved graphene of the present invention; Figure 5 This is a SEM image of the reduced graphene oxide of the present invention; Figure 6 The images show the FTIR images of the curved graphene and the modified reduced curved graphene-water-soluble chitosan of the present invention. The upper red curve is the FTIR image of the modified reduced curved graphene-water-soluble chitosan, and the bottom black curve is the FTIR image of the curved graphene. Detailed Implementation

[0018] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0019] Example 1 according to Figure 1 , 2 As shown in Figures 3, 4, 5, and 6, this embodiment proposes a cigarette filter that can effectively trap harmful substances in smoke and its preparation method. The prepared reduced-surface graphene-water-soluble chitosan modified cigarette filter that effectively traps harmful substances in smoke is achieved through the following methods and steps, wherein each reagent is calculated according to parts by weight.

[0020] S1: Prepare curved graphene according to the applicant's patent "Curved Graphene and Preparation Method Thereof"; S2: The curved graphene is further ultrasonically dispersed for 10 minutes and dispersed in water to form a curved graphene dispersion with a concentration of 4 mg / ml; S3: Further, carboxymethyl chitosan is gradually added to the aqueous solution of S2 while stirring at 300 rpm. The mass of carboxymethyl chitosan added is twice that of the curved graphene. S4: Add ascorbic acid of 1 times the mass of the curved graphene to reduce the curved graphene, control the solution temperature to 80 degrees, and react for 4 hours; S5: Cellulose acetate impregnated in reduced curved graphene-water-soluble chitosan dispersion for 1 hour; S6: Take out and dry at 60 degrees for 3 hours to obtain filter fiber modified with reduced curved graphene-water soluble chitosan.

[0021] The filter fibers prepared in the above steps are processed into a binary structure cigarette filter, such as... Figure 1 One part of the binary structure is a conventional cellulose acetate segment, while the other part is cellulose acetate modified with reduced-surface graphene-water-soluble chitosan, which is the modified fiber segment. The length of the cellulose acetate modified with reduced-surface graphene-water-soluble chitosan accounts for 0.5 times the total length.

[0022] The prepared cigarette holders were tested, and the benzo[a]pyrene retention rate was 92%; the phenolic substance retention rate was 84%; the nicotine retention rate was 88%; and the solanesol retention rate was 90%. Products prepared using the same structure and the method described in patent CN104389234A were tested, and the benzo[a]pyrene retention rate was 85%, the phenolic substance retention rate was 81%, the nicotine retention rate was 80%, and the solanesol retention rate was 81%.

[0023] To determine the long-term stability of the product's performance, it was sealed in a cigarette box at room temperature for 90 days before testing. The results showed a benzo[a]pyrene retention rate of 92%, a phenolic substance retention rate of 83%, a nicotine retention rate of 87%, and a solanesol retention rate of 88%. In contrast, the product prepared using the method described in patent CN104389234A showed a benzo[a]pyrene retention rate of 81%, a phenolic substance retention rate of 76%, a nicotine retention rate of 78%, and a solanesol retention rate of 75%.

[0024] According to GB / T 22838.5-2024 "Determination of physical properties of cigarettes and filter rods - Part 5: Cigarette draw resistance and filter rod pressure drop", the pressure drop was 510 Pa, which meets the national standard requirements.

[0025] Based on ISO 10993-5 (GB / T 16886.5) Medical Devices Biological Evaluation—In Vitro Cytotoxicity Test, the cell viability rate was 89% as determined by the MTT assay, which was 11% higher than that of the blank sample (untreated cellulose acetate filter).

[0026] Example 2 according to Figure 1 , 2 As shown in Figures 3, 4, 5, and 6, this embodiment proposes a cigarette filter that can effectively trap harmful substances in smoke and its preparation method. The preparation of the cigarette filter that can effectively trap harmful substances in smoke is achieved through the following methods and steps, wherein each reagent is calculated according to parts by weight.

[0027] S1: Prepare curved graphene according to the applicant's patent "Curved Graphene and Preparation Method Thereof"; S2: The curved graphene is further ultrasonically dispersed for 20 minutes and dispersed in water to form a curved graphene dispersion with a concentration of 2 mg / ml; S3: Further, carboxymethyl chitosan is gradually added to the aqueous solution of S2 while stirring at 400 rpm. The mass of carboxymethyl chitosan added is 3 times that of the curved graphene. S4: Add 1.5 times the mass of the curved graphene with ascorbic acid to reduce the curved graphene, control the solution temperature to 75 degrees, and react for 6 hours; S5: Cellulose acetate impregnated in reduced curved graphene-water-soluble chitosan dispersion for 2 hours; S6: Take out and dry at 60 degrees for 4 hours to obtain filter fiber modified with reduced curved graphene-water soluble chitosan.

[0028] The filter fibers prepared in the above steps are processed into ternary structure cigarette filters, such as... Figure 2 One part of the ternary structure is the conventional cellulose acetate segment located on both sides, while the middle part is the cellulose acetate modified by reduced curved graphene-water-soluble chitosan, which is the modified fiber segment. The length of the cellulose acetate modified by reduced curved graphene-water-soluble chitosan accounts for 0.6 times the total length.

[0029] The prepared cigarette holder was tested and found to have a benzo[a]pyrene retention rate of 90%, a phenolic substance retention rate of 86%, a nicotine retention rate of 90%, and a solanesol retention rate of 91%. A product prepared using the same structure and the method described in patent CN104389234A was tested and found to have a benzo[a]pyrene retention rate of 87%, a phenolic substance retention rate of 80%, a nicotine retention rate of 78%, and a solanesol retention rate of 83%.

[0030] To determine the long-term stability of the product's performance, it was placed in a sealed cigarette box at room temperature for 90 days before testing. The results showed a benzo[a]pyrene retention rate of 89%, a phenolic substance retention rate of 84%, a nicotine retention rate of 87%, and a solanesol retention rate of 90%. In contrast, the product prepared using the method described in patent CN104389234A showed a benzo[a]pyrene retention rate of 80%, a phenolic substance retention rate of 75%, a nicotine retention rate of 76%, and a solanesol retention rate of 72%.

[0031] According to GB / T 22838.5-2024 "Determination of physical properties of cigarettes and filter rods - Part 5: Cigarette draw resistance and filter rod pressure drop", the pressure drop was 670 Pa, which meets the national standard requirements.

[0032] Using ISO 10993-5 (GB / T 16886.5) Medical Devices Biological Evaluation—In Vitro Cytotoxicity Test as the standard, the cell viability rate was 87% as determined by the MTT assay, which was 8.75% higher than that of the blank sample (untreated cellulose acetate filter).

[0033] Example 3 according to Figure 1 , 2 As shown in Figures 3, 4, 5, and 6, this embodiment proposes a cigarette filter tip that can effectively trap harmful substances in cigarette smoke and its preparation method. The prepared cigarette filter tip can be used for conventional cigarette paper-wrapped filter fibers or for disposable plastic-wrapped filter fibers.

[0034] The cigarette filter prepared according to this method is compared with cigarette filter paper modified with graphene oxide and other derivatives in terms of benzo[a]pyrene retention rate, phenolic substance retention rate, nicotine retention rate, and solanesol retention rate in Table 1 below.

[0035]

[0036] The product of this invention outperforms other graphene modification methods in terms of benzo[a]pyrene retention rate, phenolic substance retention rate, nicotine retention rate, and solanesol retention rate, because: Benzo[a]pyrene is a strongly hydrophobic condensed-ring aromatic hydrocarbon with a large π-conjugated system and is a key carcinogen controlled by tobacco smoke. Commercially available graphene oxide and its modified materials... The conjugated structure is destroyed by oxidation. The interaction is extremely weak, and adsorption relies solely on weak hydrophobic interactions, resulting in a low retention rate.

[0037] Phenolic compounds are hydrophilic, acidic, small molecules found in flue gas; they are irritating and harmful components, and their adsorption depends on hydrogen bonding and electrostatic interactions between acids and bases. While graphene oxide contains numerous polar oxygen-containing groups on its surface that can adsorb phenols via hydrogen bonding, exhibiting a moderate retention rate, it lacks directional selectivity. This invention achieves directional retention through acid-base complexation, increasing the retention rate to [a higher level]. However, hydrophobic modification and excessive reduction weaken hydrogen bonding, thus reducing the retention rate.

[0038] Nicotine is the core characteristic component of tobacco. It is of medium polarity and directly affects the smoking experience. Its application requires high retention.

[0039] The polar groups of graphene oxide form strong hydrogen bonds / electrostatic adsorption with nicotine, resulting in excessive nicotine loss and low retention rate. However, all directional modification routes of modified graphene oxide can reduce surface polarity and weaken non-specific adsorption, generally improving the retention rate. The present invention has the best retention performance, achieving "retaining harmful substances while minimizing nicotine loss".

[0040] Solanesol is a long-chain hydrophobic terpene alcohol and a beneficial active ingredient in tobacco. Its relatively large molecular size means its retention rate is primarily determined by pore size and hydrophobicity matching. Graphene oxide itself is highly hydrophilic and exhibits weak adsorption of hydrophobic solanesol, resulting in a low basic retention rate. However, the stacking of layers can easily cause localized retention, resulting in poor stability. Modified graphene, especially the product of this invention, can avoid the blockage of pores by large-molecule solanesol, increasing the retention rate to [percentage missing]. And it has the best stability.

[0041] Figure 3 , 4 Figures 5 and 6 show SEM images of graphene, curved graphene, and reduced curved graphene, respectively. Graphene, with its planar structure and lack of polar functional groups, exhibits extremely weak electrostatic / chelate adsorption of nicotine, heavy metals, and polar aldehydes and ketones, and is prone to aggregation, limiting the available adsorption sites. Curved graphene, on the other hand, has a more complex surface with a three-dimensional structure, rich in oxygen-containing groups such as hydroxyl, carboxyl, carbonyl, and epoxy groups. The electrostatic interactions, hydrogen bonds, and coordination chelation of these groups synergistically enhance its adsorption capacity for polar / ionic pollutants such as heavy metal ions, nicotine, and formaldehyde, with carboxyl and hydroxyl groups providing ample chemical binding sites. However, due to its strong hydrophilicity and damaged conjugated structure, it has weak affinity for hydrophobic tar and polycyclic aromatic hydrocarbons. To address this, curved graphene was further partially reduced and modified with water-soluble chitosan, retaining the advantages of curved graphene. Chitosan, through covalent bonding (amidation reaction: -COOH and...),... Non-covalent bonds (hydrogen bonds, electrostatic attraction) grafted onto the curved graphene surface provide the richest chemisorption sites. The addition of amino and hydroxyl groups significantly expands the hydrogen bond and electrostatic sites, further enhancing the adsorption of polar harmful substances such as nicotine and aldehydes and ketones.

[0042] Figure 6The table shows a comparison of FTIR spectra of curved graphene and reduced curved graphene modified with water-soluble chitosan. The spectra confirm that curved graphene is rich in hydroxyl, carbonyl, carboxyl, and epoxy groups. In contrast, the FTIR spectra of the reduced curved graphene-water-soluble chitosan modified material show a large number of nitrogen-containing groups, indicating successful modification. The XPS data in Table 2 show that the nitrogen content increased from 0.94% in curved graphene to 7.26% in the reduced curved graphene-water-soluble chitosan modified material. Simultaneously, under the action of the reducing agent ascorbic acid, the oxygen content decreased from 29.63% in curved graphene to 20.64% in the reduced curved graphene-water-soluble chitosan modified material.

[0043]

[0044] The restored surface of graphene The hybrid carbon conjugated structure is a "molecular recognition center" for the specific adsorption of benzo[a]pyrene, through... Stacking interactions enable structure matching and recognition, while hydrophobic interactions facilitate selective enrichment of the environment. The synergistic effect of these two processes makes reduced-surface graphene a highly efficient material for treating polycyclic aromatic hydrocarbon pollutants such as benzo[a]pyrene. This material is based on... The specific adsorption of the structure provides an important technical approach for the precise removal of hydrophobic aromatic pollutants.

[0045] Further, water-soluble chitosan selectively adsorbs hydrophilic phenolic substances, with the amino group at the C2 position of its molecular chain (…). The C3 / C6 hydroxyl groups (-OH) form specific multi-point hydrogen bonds with the phenolic hydroxyl groups (Ph-OH) of phenols, precisely binding through electrostatic interactions of amino protonation. Because both are hydrophilic polar structures, this results in directional, selective, and high-affinity adsorption. This adsorption is similar to the adsorption of hydrophobic benzo[a]pyrene by reduced graphene oxide. The hydrophobic mechanisms are completely complementary.

[0046] The reduced-surface graphene-water-soluble chitosan composite material achieves selective adsorption of target pollutants by constructing a surface polarity gradient and regulating interlayer steric hindrance, while reducing unnecessary adsorption. For moderately polar nicotine, the strong hydrophilic polarity of the outer layer of water-soluble chitosan forms a polar barrier and electrostatic repulsion between like charges, and nicotine has no phenolic hydroxyl groups. The conjugated structure of reduced-curved graphene prevents it from forming specific interactions with chitosan or reduced-curved graphene, thus leading to its repulsion. For the hydrophobic macromolecule solanesol, chitosan chain intercalation allows the reduced-curved graphene to form a fixed narrow interlayer spacing of 0.8–1.2 nm and a surface polymeric network barrier, creating strong steric hindrance that prevents the macromolecule from entering the adsorption domain. Simultaneously, the strong hydrophilic surface and the strong hydrophobicity of solanesol create a polarity conflict, further inhibiting non-specific adsorption. The reduced-curved graphene-water-soluble chitosan composite system uses polarity differences to screen for moderately polar small molecules and steric hindrance to screen for hydrophobic macromolecules, while retaining the ability of reduced-curved graphene to interact with hydrophobic aromatic compounds. While adsorbing and chitosan hydrogen-bonded / electrostatically adsorbing hydrophilic phenols, it achieves low adsorption and high repulsion of nicotine and solanesol.

[0047] During the modification of curved graphene, it was found that when the amount of carboxymethyl chitosan added was less than 1.5 times, the performance improvement was limited due to incomplete coating. However, when the amount was greater than 5 times, the adsorption sites of graphene were blocked due to steric hindrance. When ascorbic acid was added for reduction, amounts below 0.5 times could not effectively remove oxygen-containing groups, while amounts above 2 times would lead to excessive removal of oxygen-containing groups, i.e., over-reduction, resulting in a significant decrease in water solubility and excessive aggregation.

[0048] This invention employs a composite modification of reduced curved graphene and water-soluble chitosan, which restores the complete surface of the graphene. Conjugate structure, through Stacking and hydrophobic interactions enable specific adsorption of strongly hydrophobic polycyclic aromatic hydrocarbons such as benzo[a]pyrene, increasing the rejection rate to [percentage missing]. The amino and hydroxyl groups in water-soluble chitosan molecules achieve targeted chelation and adsorption of hydrophilic acidic harmful substances such as phenols through hydrogen bonding and electrostatic interactions, achieving a retention rate of [missing information]. Both are significantly superior to existing graphene-modified filters, effectively reducing the carcinogenic risk and irritation of cigarette smoke. This invention, through the construction of surface polarity gradients and the control of interlayer steric hindrance, effectively avoids excessive adsorption and loss of characteristic components such as nicotine and solanine alcohol while efficiently retaining harmful substances, with a nicotine retention rate reaching [percentage missing]. The retention rate of solanesol reached This invention preserves the original flavor of tobacco to the maximum extent and solves the technical problem of poor taste in existing modified filters. Using curved graphene as the substrate, its three-dimensional wrinkled structure effectively prevents agglomeration. Combined with the coating modification of water-soluble chitosan, the dispersion performance of the material is further improved. Ascorbic acid is used as a reducing agent, resulting in mild reduction conditions and precise control of the reduction degree, avoiding excessive reduction that leads to decreased water solubility and agglomeration. The preparation process does not require harmful solvents, the process steps are simple, the reaction conditions are easy to control, and the adsorption performance of the product shows only slight decay after long-term storage, with stability far superior to existing products, making it suitable for large-scale industrial production.

[0049] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cigarette filter tip capable of effectively trapping harmful substances in cigarette smoke, comprising filter fibers, characterized in that: The filter tip fiber surface is modified with a reduced curved graphene-water-soluble chitosan composite material, which is formed by the combination of reduced curved graphene and water-soluble chitosan through covalent and / or non-covalent bonds. The filter fiber is processed into a modified fiber segment of a cigarette filter, and the modified fiber segment and the conventional acetate fiber segment together form a cigarette filter.

2. A cigarette filter tip according to claim 1, characterized in that: The reduced curved graphene is prepared by reducing curved graphene with a reducing agent. Specifically, the curved graphene is ultrasonically dispersed to obtain a curved graphene dispersion, and then reduced by ascorbic acid to obtain reduced curved graphene.

3. A cigarette filter tip according to claim 1, characterized in that: The water-soluble chitosan is carboxymethyl chitosan, and the mass ratio of carboxymethyl chitosan to reduced curved graphene is 1.5-5:

1.

4. A cigarette filter tip according to claim 1, characterized in that: The filter tip fiber is cellulose acetate, and the reduced curved graphene-water-soluble chitosan modification layer on the surface of the cellulose acetate is uniform and dense.

5. A cigarette filter tip according to claim 1, characterized in that: The main structure of a cigarette filter is a binary or ternary structure; the binary structure consists of a conventional cellulose acetate segment and a modified fiber segment, and the length of the modified fiber segment accounts for 0.3-0.7 times the total length of the cigarette filter; the ternary structure consists of alternating conventional cellulose acetate segments, modified fiber segments, and conventional cellulose acetate segments, with the modified fiber segment located in the middle section and its length accounting for 0.4-0.7 times the total length of the cigarette filter.

6. A method for preparing a cigarette filter capable of effectively trapping harmful substances in cigarette smoke, applied to the cigarette filter capable of effectively trapping harmful substances in cigarette smoke as described in any one of claims 1-5, characterized in that, Includes the following steps: S1: Preparation of curved graphene; S2: Ultrasonically disperse curved graphene in water to form a curved graphene dispersion; S3: Add water-soluble chitosan to the dispersion and stir until homogeneous to obtain a mixture; S4: Add a reducing agent to the mixture, control the reaction temperature and reaction time, reduce the curved graphene to obtain a reduced curved graphene-water-soluble chitosan dispersion; S5: Immerse the filter tip fiber in the dispersion solution, and dry it after immersion to obtain the modified filter tip fiber; S6: Modified fiber segments, which are processed into the main structure of cigarette filters, are combined with conventional acetate fiber segments to form cigarette filters.

7. The method for preparing a cigarette filter tip capable of effectively trapping harmful substances in smoke according to claim 6, characterized in that: In step S2, the ultrasonic dispersion time is 5-60 minutes, the concentration of the curved graphene dispersion is 0.5-10 mg / ml, the ultrasonic power is 100-300 W, and the water temperature is controlled to not exceed 35℃ during the ultrasonic process.

8. The method for preparing a cigarette filter tip capable of effectively trapping harmful substances in smoke according to claim 6, characterized in that: In step S3, the stirring rate is 300-500 rpm, and the water-soluble chitosan is prepared as an aqueous solution and slowly added dropwise to the dispersion at a rate of 0.5-1.5 ml / min. After the addition is completed, stirring is continued for 20-30 minutes.

9. A method for preparing a cigarette filter tip capable of effectively trapping harmful substances in smoke according to claim 6, characterized in that: In step S4, the reducing agent is ascorbic acid, and the mass ratio of ascorbic acid to curved graphene is 0.5-2:1; the reaction temperature is 70-90℃, the reaction time is 2-6 hours, and the reaction is stirred intermittently to ensure uniform reduction.

10. A method for preparing a cigarette filter tip capable of effectively trapping harmful substances in smoke according to claim 6, characterized in that: In step S5, the impregnation time is 0.5-2 hours, and the impregnation process is assisted by ultrasound; the drying temperature is 60℃, the drying time is 2-6 hours, and the drying process adopts a gradual heating method; the dried modified filter fiber is rinsed with deionized water before subsequent processing.

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