A biodegradable composite filter rod with high filtration performance and a preparation method thereof

Abstract

The application discloses a biodegradable composite filter rod with high filtration performance and a preparation method thereof. The composite filter rod comprises a filter core and a formed paper wrapped on the filter core. The filter core comprises a longitudinal filter fiber body and at least one transverse filter microporous membrane sheet. The transverse filter microporous membrane sheet is arranged at one end and / or both ends and / or a middle section of the longitudinal filter fiber body and is axially perpendicular to the longitudinal filter fiber body. The longitudinal filter fiber body and the transverse filter microporous membrane sheet are both prepared from two or more than two biodegradable materials and / or modified materials, and the materials of the two are the same or different. The composite filter rod prepared by the application has the advantages of novel structure, obviously improved filtration performance, good shape maintaining capability and shelf life, and good use value and application prospect.

Description

Technical Field

[0001] This invention relates to polymer chemical materials, specifically to a biodegradable composite filter rod with high filtration performance and its preparation method. Background Technology

[0002] Tobacco contains various alkaloids such as nicotine, nornicotine, neonicotinoids, and pseudoestipine. When burned, it produces a complex tar mixture containing carbon monoxide, polycyclic aromatic hydrocarbons, ammonia, hydrogen cyanide, nitric oxide, and other harmful substances. These harmful substances cause tobacco smoke to become thick and emit a pungent odor; they also make the tar viscous, depositing in the respiratory tract and lungs of the smoker, posing a threat to the health of both the smoker and those around them. Therefore, smoking is considered a harmful behavior and has been restricted and controlled globally.

[0003] With the development of the times, smokers have begun to pay attention to the health implications of smoking, making "tar reduction and harm reduction" a key focus of the tobacco industry. From tobacco leaf cultivation to cigarette production, companies have conducted extensive research and development on tar reduction and harm reduction at every stage of cigarette production. Studies have shown that the material and quality of cigarette filters are closely related to the amount of tar inhaled. Filter rods (hereinafter referred to as filter rods) can adsorb and filter harmful substances such as tar in smoke, reducing the amount of tar entering the body, and can also improve the taste of cigarettes to some extent. Therefore, improving the material and quality of filter rods is the most direct means of reducing tar and harm in cigarettes.

[0004] Traditional filter rods are made of polypropylene, but due to its weak adsorption capacity, poor smoke filtration, and strong pungent taste, it has been gradually phased out of the market. Furthermore, its raw material is derived from petroleum, a non-renewable resource that cannot be biodegraded, leading to severe environmental pollution. Currently, cellulose acetate is the commonly used filter rod material. Compared to polypropylene, cellulose acetate has a stronger filtration capacity. Its raw material is selected from high-quality perennial wood and has a degree of recyclability, making it a preferred material for cigarette filters. However, using cellulose acetate to prepare filter rods also has many drawbacks. For example, the preparation of cellulose acetate filters requires wet spinning to produce filter tow suitable for cigarettes, a process often accompanied by a series of highly polluting chemical treatments. Moreover, cellulose acetate degrades slowly, and large-scale use in a short period can also lead to environmental pollution and increase subsequent treatment costs. Additionally, cellulose acetate is expensive, resulting in higher raw material costs and thus higher additional costs for cigarettes. In addition, with the continuous development of environmental protection concepts, more and more attention is being paid to sustainable development and environmental protection. Since logging will affect forest resources and the environment, some manufacturers have begun to look for more environmentally friendly alternative materials.

[0005] In recent years, there have been reports proposing the use of fully biodegradable polymeric materials to prepare filter rods. For example, Chinese patent document CN102763897B discloses a method for preparing polylactic acid (PLA) fiber filter rods, which uses fully biodegradable PLA fibers to prepare cigarette filter rods, offering advantages such as recyclable raw materials and easily degradable waste. However, this patent also points out that the filtration capacity of this filter rod is similar to that of cellulose acetate filter rods, and it has not yet achieved a significant improvement in reducing harmful substances and tar. Through research and analysis, it has been found that the main reasons why the filtration performance of PLA fiber filter rods has not been significantly improved are as follows:

[0006] 1) PLA is a relatively non-polar material, while some harmful components in tar are polar molecules, such as polycyclic aromatic hydrocarbons and hydrocyanic acid. These polar molecules and non-polar PLA materials have mutual repulsion, making it difficult for them to be adsorbed by PLA fibers, thus the performance of reducing harm and tar cannot be improved.

[0007] 2) PLA is composed of a single repeating unit of lactic acid molecules, and its molecular structure is relatively simple. Therefore, when PLA fibers are directly used to make filter rods, there are not enough active sites on their surface, and the adsorption capacity is limited. It is difficult to effectively capture harmful components in cigarette smoke, which is also an important reason why its harm reduction and tar reduction performance cannot be improved.

[0008] 3) Existing cigarette filters (including polylactic acid fiber filters) have fiber bundles that are axially arranged along the direction of smoke inhalation, resulting in a low interception rate of gaseous and particulate matter in the smoke.

[0009] Furthermore, production practice has revealed that filter rods made directly from existing biodegradable materials, including PLA fibers, suffer from low hardness, shrinkage, and poor shape retention during storage. Moreover, the short shelf life of biodegradable materials makes polylactic acid fiber filter rods mismatched with the shelf life of cigarettes, thus limiting their application in the filter rod field.

[0010] Therefore, how to further improve the effect of biodegradable material filter rods on flue gas filtration, while ensuring that their shape retention and shelf life meet the requirements, has become a new and urgent problem to be solved in the research and development of tar reduction and harm reduction. Summary of the Invention

[0011] To address the aforementioned problems, this invention provides a high-performance biodegradable composite filter rod and its preparation method. The method modifies existing polymer materials to improve their adsorption capacity for harmful substances in cigarette smoke, and improves the filter rod structure by using a transverse microporous membrane to increase the smoke interception rate, thereby enhancing the filter rod's filtration performance and improving tar reduction and harm mitigation effects. Furthermore, by employing a composite of multiple biodegradable materials in the filter rod manufacturing process, the hardness and shelf life of the filter rod are improved, meeting the production requirements of cigarettes. The specific technical solution is as follows:

[0012] First, the present invention provides a high-performance biodegradable composite filter rod, comprising a filter element and a shaped roll of paper wrapped around the filter element. The filter element comprises a longitudinal filter fiber body and at least one transverse filter microporous membrane. The transverse filter microporous membrane is disposed at one and / or both and / or the middle section of the longitudinal filter fiber body and is perpendicular to the axial direction of the longitudinal filter fiber body. Both the longitudinal filter fiber body and the transverse filter microporous membrane are made of two or more biodegradable materials and / or modified materials thereof, and the materials of the two are the same or different.

[0013] As a preferred technical solution, the longitudinal filter fiber body is prepared by composite fiber of two or more biodegradable materials selected from polylactic acid, polybutylene terephthalate / adipate, polybutylene succinate, polycaprolactone, polypropylene carbonate, polyglycolic acid and their modified fibers; the microporous filter membrane is prepared by electrospinning of one or more biodegradable materials selected from polylactic acid, polybutylene terephthalate / adipate, polybutylene succinate, polycaprolactone, polypropylene carbonate, polyglycolic acid and their modified materials into a spinning solution.

[0014] As a further preferred technical solution, the longitudinal filter fiber body is prepared by composite of polylactic acid fiber and modified polybutylene terephthalate / adipate fiber and / or modified polybutylene succinate fiber; wherein, the amount of modified polybutylene terephthalate / adipate fiber is 1 / 20 to 1 / 5 of the mass of polylactic acid fiber, and the amount of modified polybutylene succinate fiber is 1 / 6 to 1 / 3 of the mass of polylactic acid fiber;

[0015] As a further preferred technical solution, the microporous filter membrane is prepared by electrospinning of a spinning solution made of polylactic acid and modified polybutylene terephthalate / adipate and / or modified polybutylene succinate; wherein the amount of modified polybutylene terephthalate / adipate is 2 to 3 times the mass of polylactic acid, and the amount of modified polybutylene succinate is 3 to 5 times the mass of polylactic acid.

[0016] As a preferred technical solution, the modified polybutylene terephthalate / adipate and the modified polybutylene succinate are modified polymer products with terephthalate / adipate and polybutylene succinate as the main components, glycerol as the grafting agent, and maleic anhydride-grafted polyvinyl alcohol as the grafting monomer, respectively; wherein, the amount of glycerol is 0.1% to 1% of the weight of the terephthalate / adipate or polybutylene succinate raw material; and the maleic anhydride-grafted polyvinyl alcohol is 0.1% to 1% of the weight of the polybutylene succinate or polyterephthalate / adipate.

[0017] The aforementioned high-filtration-performance biodegradable composite filter rod, wherein the modified poly(butylene terephthalate) / poly(dibutyl adipate) is prepared by the following steps:

[0018] S1-1) Esterification and branching: PTA and AA, the raw materials used to prepare poly(butylene terephthalate) adipate, are mixed with BDO in the required molar ratio for primary esterification reaction; when the esterification rate reaches more than 90%, the products of the two primary esterification reactions are combined for die esterification; and glycerol is added during the esterification reaction to obtain poly(butylene terephthalate) adipate branched oligomers; the esterification reaction parameters are: temperature 230-240℃, pressure 70-80kPa, reaction time 80-100min, followed by reaction under high vacuum 30-50kPa for 3-4h;

[0019] S1-2) Prepolymerization: When the esterification rate of diesterification reaches more than 95%, the obtained poly(terephthalic acid / butyl adipate) branched oligomer is injected into the prepolymerization reactor. The temperature of the prepolymerization reactor is controlled at 235-240℃ and the pressure is 1-3kPa. The prepolymerization reaction is carried out for 1-2 hours to obtain the poly(terephthalic acid / butyl adipate) branched prepolymer.

[0020] S1-3) Final Polymerization Grafting: Maleic anhydride-grafted polyvinyl alcohol is added to the obtained branched prepolymer of poly(terephthalic acid) / butyl adipate. The temperature of the prepolymerization reactor is controlled at 235-240℃ and the pressure at 95-110Pa. The final polymerization reaction is carried out for 5-30 minutes to obtain the modified poly(terephthalic acid) / butyl adipate polymer.

[0021] S1-4) Pelletizing and Drying: After the degree of polymerization of the modified poly(terephthalic acid / butyl adipate) polymer reaches the predetermined viscosity, it is fed into a pelletizing device for pelletizing and drying to obtain modified poly(terephthalic acid / butyl adipate) particles, which are then prepared into spinning solution and fibers for later use.

[0022] As a preferred technical solution, in step S1-1), the amount of glycerol added during esterification and branching is 0.1% to 1% of the weight of the oligomer; in step S1-3), the amount of maleic anhydride-grafted polyvinyl alcohol added during final polymerization is 0.1% to 1% of the weight of the poly(butylene terephthalate) / poly(diethyl terephthalate) branched prepolymer; in step S1-4), the melt index of the modified poly(butylene terephthalate) / poly(diethyl terephthalate) polymer fed into the cooling pelletizing equipment is 3 to 5 g / 10 min (190°C, 2.16 kg).

[0023] The aforementioned high-filtration-performance biodegradable composite filter rod, wherein the modified polybutylene succinate is prepared by the following steps:

[0024] S2-1) Esterification and branching: Succinic acid and butanediol, the raw materials used to prepare polybutylene succinate, are esterified in the required molar ratio; at the same time, 0.1% to 1% of glycerol by weight of the total polymer material is added, and the esterification reaction temperature is controlled at 230 to 240°C, the pressure at 30 to 50 kPa, and the reaction is carried out for 2 hours to obtain branched oligomers of polybutylene succinate.

[0025] S2-2) Prepolymerization: The temperature of the reactor is controlled at 235-240℃ and the pressure is controlled at 1-3kPa. The reaction is carried out for 3-4 hours to obtain the branched prepolymer of polybutylene succinate.

[0026] S2-3) Final Polycondensation Grafting: Add 0.1% to 1% of maleic anhydride grafted polyvinyl alcohol to the obtained branched polybutylene succinate prepolymer, and continue to control the reaction temperature at 235 to 240°C and the pressure at 100 to 110 Pa to carry out the final polycondensation reaction for 5 to 30 minutes to obtain the modified polybutylene succinate polymer.

[0027] S2-4) Pelletizing and Drying: The modified polybutylene succinate polymer is fed into a pelletizing device, pelletized, and then dried to obtain modified polybutylene succinate particles, which are then used to prepare spinning solution and fibers for later use.

[0028] Secondly, the present invention provides a method for preparing the aforementioned high-filtration-performance biodegradable composite filter rod, comprising the following steps:

[0029] 1) Preparation of transverse filtration microporous membrane: Biodegradable material particles for preparing transverse filtration microporous membrane are added to a solvent, and a certain amount of inorganic salt is added. The mixture is stirred under heating conditions to prepare a spinning solution. Electrospinning is then performed to obtain a biodegradable fiber membrane. The biodegradable fiber membrane is then cut into circular pieces of the corresponding diameter according to the actual cigarette size to obtain a biodegradable transverse filtration microporous membrane.

[0030] 2) Preparation of longitudinal filter fiber body: The biodegradable material fibers used to prepare the longitudinal filter fiber body are opened and mixed in proportion. Then, the biodegradable adhesive is evenly sprayed on the opened fiber bundles. The fiber bundles are then bonded together to form a fiber bundle. Finally, the fiber bundles are cut into the specified lengths according to the filter rod design requirements to obtain the longitudinal filter fiber body.

[0031] 3) Preparation of composite filter rod: The biodegradable adhesive is then evenly sprayed onto the end face of the longitudinal filter fiber body that needs to be bonded and the bonding surface of the transverse filter microporous membrane. The transverse filter microporous membrane is assembled into the predetermined position of the longitudinal filter fiber body according to the design requirements, and then wrapped with shaped roll paper to form a complete composite filter rod.

[0032] 4) Drying and balancing: Dry the complete composite filter rod and then put it into the balancing chamber for a certain period of time to obtain a high-performance biodegradable composite filter rod.

[0033] As a preferred technical solution, in step 1), the preparation of the transverse filtration microporous membrane is as follows:

[0034] The solvent used is one or a mixture of ethyl acetate, N,N-dimethylformamide, and chloroform;

[0035] The heating temperature is 30–75℃, the stirring speed is 50–80 rpm, and the stirring time is 0.1–4 hours.

[0036] The mass fraction concentration of the prepared spinning solution is 5%–20%;

[0037] The parameters for electrospinning are as follows: the translation speed of the injection system is 100-500 mm / min, the rotation speed of the receiving roller is 10-100 rpm / min, the spinning speed is 1-10 mL / h, the receiving distance is 10-30 cm, the applied voltage is 10-50 kV, and the spinning time is 10-120 min.

[0038] The obtained transverse filtration microporous membrane has a fiber size of approximately 80–120 nm and a pore size of approximately 0.5–1.5 μm.

[0039] As a preferred technical solution, in step 2), the preparation of the longitudinal filter fiber body is as follows:

[0040] The biodegradable material used to prepare the longitudinal filter fiber body has a fiber bundle density of 3-5 ktex and a single filament linear density of 1.5-2.5 dtex.

[0041] The unfolded width is 15-25cm;

[0042] After opening, the fiber bundles are mixed by layering or by combing and hybridization.

[0043] When mixing by layering, the modified poly(butylene terephthalate) / butylene adipate fiber or the modified polybutylene succinate fiber is divided into at least 3 parts and uniformly sandwiched in the polylactic acid fiber layer.

[0044] The beneficial effects of this invention are:

[0045] 1) This invention improves the existing cigarette filter structure by adding a transverse filter membrane to the traditional single longitudinal filter fiber bundle as the filter element. This increases the smoke interception surface and the interception rate of harmful components in the smoke. Simultaneously, this invention modifies the biodegradable material used to prepare the filter element, increasing the polar groups on it to improve the adsorption effect and capacity for relevant harmful substances in the smoke, thereby improving the filter element's filtration performance and enhancing its tar reduction and harm reduction effects. Furthermore, this invention uses two or more biodegradable materials in combination to prepare the filter element, improving the filter element's hardness and shelf life, meeting the usage requirements of cigarettes, and making biodegradable materials suitable for use in cigarette filters.

[0046] 2) The present invention preferably uses polylactic acid (PLA) and modified polybutylene terephthalate (PET) / adipate fiber and / or modified polybutylene succinate (PBS) to prepare the filter element, and limits the amount of modified PET / PET fiber to 1 / 10 to 1 / 5 of the mass of PLA fiber, the amount of modified PBS fiber to 1 / 6 to 1 / 3 of the mass of PLA fiber, the amount of modified PET / PET fiber to 2 to 3 times the mass of PLA fiber, and the amount of modified PBS fiber to 3 to 5 times the mass of PLA fiber, so as to fully ensure the filtration performance of the filter rod for harmful components in flue gas, while ensuring the hardness and shelf life of the filter rod.

[0047] 3) This invention is the first to use glycerol as a grafting agent and maleic anhydride-grafted polyvinyl alcohol as a grafting monomer. The ratio of glycerol to maleic anhydride-grafted polyvinyl alcohol is controlled so that the grafted groups on the molecular chains of the modified phthalic acid / butyl adipate fiber and polybutylene succinate adapt to the capture of polar components in flue gas, thereby improving the adsorption and containment capacity of the filter rod for harmful components.

[0048] 4) The transverse filter microporous membrane prepared by the present invention controls the fiber size to about 100 nm and the pore size to about 1 μm, so that the size of the filter pores is suitable for filtration, thereby intercepting harmful components while maintaining the good taste of cigarettes.

[0049] 5) The composite filter rod prepared by this invention has a novel structure, significantly improved filtration performance, and good shape retention and shelf life, thus having good use value and application prospects. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the high-filtration-performance biodegradable composite filter rod of the present invention.

[0051] Figure 2 This is an electron microscope image showing the microstructure of the transverse filtration microporous membrane in the high-composite filter rod of the present invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments.

[0053] Example 1

[0054] This embodiment describes a high-performance biodegradable composite filter rod and its preparation method. The composite filter rod includes a filter element and a shaped roll of paper wrapped around the filter element; as shown below. Figure 1 As shown, the filter element includes a longitudinal filter fiber body and at least one transverse filter microporous membrane. The transverse filter microporous membrane is disposed at one and / or both and / or the middle section of the longitudinal filter fiber body and is perpendicular to the axial direction of the longitudinal filter fiber body. Both the longitudinal filter fiber body and the transverse filter microporous membrane are made of two or more biodegradable materials and / or modified materials thereof, and their materials may be the same or different. That is, this embodiment improves the existing cigarette filter rod structure by adding a transverse filter membrane to the traditional simple longitudinal filter fiber bundle as the filter element, thereby increasing the smoke interception surface and the interception rate of harmful components in the smoke. At the same time, the biodegradable material used to prepare the filter element is modified to improve the adsorption effect and adsorption capacity of related harmful substances in the smoke, thereby improving the filter rod's filtration performance and tar reduction effect. In addition, the filter rod is made of two or more biodegradable materials, which improves its hardness and shelf life, meets the needs of cigarette use, and makes biodegradable materials more suitable for application in cigarette filter rods.

[0055] The composite filter rod described in this embodiment is made of two or more biodegradable materials selected from polylactic acid (PLA), polybutylene terephthalate (PBAT), polybutylene succinate (PBS), polycaprolactone (PCL), polypropylene carbonate (PPC), polyglycolic acid (PGA), and their modified fibers. Preferably, it is a composite of polylactic acid fibers and modified polybutylene terephthalate / polybutylene adipate fibers and / or modified polybutylene succinate fibers. The microporous filter membrane is prepared by electrospinning of a spinning solution made from one or more biodegradable materials selected from polylactic acid, polybutylene terephthalate / polybutylene adipate, polybutylene succinate, polycaprolactone, polypropylene carbonate, polyglycolic acid, and their modified materials. Preferably, it is prepared by electrospinning of polylactic acid and modified polybutylene terephthalate / polybutylene adipate and / or modified polybutylene succinate. When the longitudinal filter fiber body is composed of polylactic acid fiber and modified poly(butylene terephthalate) / (butylene adipate) fiber and / or modified poly(butylene succinate) fiber, the amount of modified poly(butylene terephthalate) / (butylene adipate) fiber is 1 / 20 to 1 / 5 of the mass of polylactic acid fiber, and the amount of modified poly(butylene succinate) fiber is 1 / 6 to 1 / 3 of the mass of polylactic acid fiber; when the transverse filter microporous membrane is prepared by combining polylactic acid with modified poly(butylene terephthalate) / (butylene adipate) and / or modified poly(butylene succinate), the amount of modified poly(butylene terephthalate) / (butylene adipate) is 2 to 3 times the mass of polylactic acid, and the amount of modified poly(butylene succinate) is 3 to 5 times the mass of polylactic acid.

[0056] In this embodiment, the modified polybutylene terephthalate / adipate and the modified polybutylene succinate are modified polymer products based on terephthalate / adipate and polybutylene succinate, respectively, with glycerol as a grafting agent and maleic anhydride-grafted polyvinyl alcohol as a grafting monomer; wherein, the amount of glycerol is 0.1% to 1% of the weight of the terephthalate / adipate or polybutylene succinate raw material; and the maleic anhydride-grafted polyvinyl alcohol is 0.1% to 1% of the weight of the polybutylene succinate or polyterephthalate / adipate.

[0057] Specifically, the preparation method of the modified polybutylene terephthalate (PBAT) includes the following steps:

[0058] S1-1) Esterification and branching: PTA and AA, the raw materials used to prepare poly(butylene terephthalate) adipate, are mixed with BDO at the required molar ratio for primary esterification reaction; when the esterification rate reaches more than 90%, the products of the two primary esterification reactions are combined for die esterification; glycerol is added during the esterification reaction to obtain branched oligomers of poly(butylene terephthalate) adipate; the amount of glycerol added during the esterification and branching reaction is 0.1% to 1% of the weight of the oligomer; the primary esterification reaction parameters are: temperature 230 to 240°C, pressure 70 to 80 kPa, reaction time 80 to 100 min; the die esterification reaction parameters are: temperature 235 to 240°C, high vacuum 30 to 50 kPa, reaction time 3 to 4 h.

[0059] S1-2) Prepolymerization: When the esterification rate of diesterification reaches more than 95%, the obtained poly(terephthalic acid / butyl adipate) branched oligomer is injected into the prepolymerization reactor. The temperature of the prepolymerization reactor is controlled at 235-240℃ and the pressure is 1-3kPa. The prepolymerization reaction is carried out for 1-2 hours to obtain the poly(terephthalic acid / butyl adipate) branched prepolymer.

[0060] S1-3) Final Polymerization Grafting: Maleic anhydride-grafted polyvinyl alcohol is added to the obtained poly(butylene adipate) branched prepolymer, and the temperature of the prepolymerization reactor is controlled at 235-240℃ and the pressure at 95-110 Pa for a final polycondensation reaction of 5-30 min to obtain the modified poly(butylene adipate) polymer; the amount of maleic anhydride-grafted polyvinyl alcohol added in the final polymerization grafting is 0.1%-1% of the weight of the poly(butylene adipate) branched prepolymer.

[0061] S1-4) Pelletizing and Drying: After the degree of polymerization of the modified poly(terephthalic acid) / butyl adipate polymer reaches the predetermined viscosity (melt mass flow rate, i.e. melt index of 3-5 g / 10 min), it is fed into a pelletizing device for pelletizing and drying to obtain modified poly(terephthalic acid) / butyl adipate particles, which are then prepared into spinning solution and fibers for later use.

[0062] The method for preparing the modified polybutylene succinate (PBS) includes the following steps:

[0063] S2-1) Esterification and branching: Succinic acid and butanediol, the raw materials used to prepare polybutylene succinate, are esterified in the required molar ratio; at the same time, 3% of the total weight of the polymer material is added as glycerol, and the esterification reaction temperature is controlled at 230-240℃, the pressure at 30-50kPa, and the reaction is carried out for 2 hours to obtain polybutylene succinate branched oligomer.

[0064] S2-2) Prepolymerization: The temperature of the reactor is controlled at 235-240℃ and the pressure is controlled at 1-3kPa. The reaction is carried out for 3-4 hours to obtain the branched prepolymer of polybutylene succinate.

[0065] S2-3) Final Polycondensation Grafting: Add 0.1% to 1% of maleic anhydride grafted polyvinyl alcohol to the obtained branched polybutylene succinate prepolymer, and continue to control the reaction temperature at 235 to 240°C and the pressure at 100 to 110 Pa to carry out the final polycondensation reaction for 5 to 30 minutes to obtain the modified polybutylene succinate polymer.

[0066] S2-4) Pelletizing and Drying: The modified polybutylene succinate polymer is fed into a pelletizing device, pelletized, and then dried to obtain modified polybutylene succinate particles, which are then used to prepare spinning solution and fibers for later use.

[0067] The method for preparing the high-performance biodegradable composite filter rod described in this embodiment includes the following steps:

[0068] 1) Preparation of transverse filtration microporous membrane: Biodegradable material particles for preparing transverse filtration microporous membranes are added to a solvent, and a certain amount of inorganic salt is added. The mixture is stirred under heating conditions to prepare a spinning solution, which is then electrospun to obtain a biodegradable fiber membrane. The biodegradable fiber membrane is then cut into circular pieces of the corresponding diameter according to the actual cigarette size, thus obtaining the biodegradable transverse filtration microporous membrane. The solvent is one or a mixture of ethyl acetate, N,N-dimethylformamide, and chloroform. The heating temperature is 30–75℃, and the stirring speed is 50–6000 rpm. The stirring time was 0.1–4 h at 80 rpm; the mass fraction concentration of the prepared spinning solution was 5%–20%; the electrospinning parameters were: the translation speed of the injection system was 100–500 mm / min, the rotation speed of the receiving roller was 10–100 rpm / min, the spinning speed was 1–10 mL / h, the receiving distance was 10–30 cm, the applied voltage was 10–50 kV, and the spinning time was 10–120 min; the obtained transverse filtration microporous membrane had a fiber size of approximately 80–120 nm and a pore size of approximately 0.5–1.5 μm.

[0069] 2) Preparation of longitudinal filter fiber body: The biodegradable material fibers used to prepare the longitudinal filter fiber body are opened and mixed in proportion. Then, the biodegradable adhesive is evenly sprayed on the opened fiber bundles. The fiber bundles are then bonded together to form a fiber bundle. Finally, the fiber bundles are cut into the specified lengths according to the filter rod design requirements to obtain the longitudinal filter fiber body.

[0070] 3) Preparation of composite filter rod: The biodegradable adhesive is then evenly sprayed onto the end face of the longitudinal filter fiber body that needs to be bonded and the bonding surface of the transverse filter microporous membrane. The transverse filter microporous membrane is assembled into the predetermined position of the longitudinal filter fiber body according to the design requirements, and then wrapped into a roll of paper to form a complete composite filter rod. The biodegradable material fiber bundle density used to prepare the longitudinal filter fiber body is 3-5 ktex, and the single filament linear density is 1.5-4 dtex. The unfolded width is 15-25 cm. The unfolded fiber bundles can be mixed by layer-by-layer stacking or by combing and hybridization. When mixing by layer-by-layer stacking, the modified poly(butylene terephthalate) / butylene adipate fiber or the modified poly(butylene succinate) fiber is divided into at least 3 parts and evenly stacked in the polylactic acid fiber layer.

[0071] 4) Drying and balancing: Dry the complete composite filter rod and then place it in a balancing chamber for more than 6 hours to obtain a high-performance biodegradable composite filter rod.

[0072] Example 2

[0073] This embodiment describes the preparation of a high-performance biodegradable composite filter rod. The filter element of this composite filter rod includes a longitudinal filter fiber body and three transverse microporous membrane sheets. The transverse microporous membrane sheets are respectively axially and vertically arranged at both ends and the middle of the longitudinal filter fiber body. Both the longitudinal filter fiber body and the transverse microporous membrane sheets are prepared by combining polylactic acid (PLA) with modified poly(butylene terephthalate) / adipate. In the longitudinal filter fiber body, the amount of modified PLA / adipate fiber is 1 / 5 of the mass of PLA fiber; in the transverse microporous membrane sheets, the amount of modified PLA / adipate is 3 times the mass of PLA. The preparation method of this composite filter rod is as follows:

[0074] First, the synthesis of modified polybutylene terephthalate (PET) includes the following steps:

[0075] S1-1) Esterification and Branching: The raw materials used to prepare poly(butylene terephthalate) / poly(diethyl terephthalate) were mixed with PTA and BDO in a molar ratio of 1:2 and AA and BDO in a molar ratio of 1:1.6. These were injected into separate esterification reactors for initial esterification. The initial esterification temperature was controlled at 235℃, the pressure at 75kPa, and the reaction time at 90min. Subsequently, the reaction was carried out at 40kPa for 3.5h. When the esterification rate reached over 90%, the initial esterification products of both were simultaneously injected into another esterification reactor in a mass ratio of 48:52. Glycerol was added simultaneously for diesterification. The amount of glycerol added was 0.2% of the total mass of the two initial esterification products. The diesterification temperature was controlled at 235℃, the pressure at 75kPa, and the reaction time at 90min. Subsequently, the reaction was carried out at 40kPa for 3.5h, yielding branched oligomers of poly(butylene terephthalate) / poly(diethyl terephthalate).

[0076] S1-2) Prepolymerization: When the esterification rate of diesterification reaches more than 95%, the obtained poly(terephthalic acid / butyl adipate) branched oligomer is injected into the prepolymerization reactor. The temperature of the prepolymerization reactor is controlled at 235℃ and the pressure is 2kPa. The prepolymerization reaction is carried out for 1.5h to obtain the poly(terephthalic acid / butyl adipate) branched prepolymer.

[0077] S1-3) Final Polycondensation Grafting: Add 0.5% by weight of maleic anhydride-grafted polyvinyl alcohol to the obtained poly(butylene adipate) branched prepolymer, and continue to control the temperature of the prepolymerization reactor at 235℃ and the pressure at 105Pa for 15 minutes to carry out the final polycondensation reaction to obtain the modified poly(butylene adipate) polymer.

[0078] S1-4) Pelletizing and Drying: After the degree of polymerization of the modified poly(terephthalic acid) / butyl adipate polymer reaches the predetermined viscosity (melt index of 3-5 g / 10 min), it is fed into a pelletizing device for pelletizing and drying to obtain modified poly(terephthalic acid) / butyl adipate particles for later use.

[0079] Then, the composite filter rod is prepared, specifically including the following steps:

[0080] 1) Preparation of transverse filtration microporous membrane: 1.5g of the prepared modified poly(butylene terephthalate) / poly(diethyl terephthalate) particles and 0.5g of polylactic acid particles were taken at a mass ratio of 3:1 and dissolved in 20mL of ethyl acetate (EA) / N,N-dimethylformamide (DMF) mixed solvent (volume ratio of 6:4). Then, 20mg of LiCl was added and stirred for 3h under heating conditions (45℃) at a stirring speed of 60rpm to prepare a spinning solution with a mass fraction of 10%. Electrospinning was carried out, specifically: the electrospinning machine was used, the translation speed of the push system was 300mm / min, the rotation speed of the receiving roller was set to 30rpm / min, the spinning speed was 2mL / h, the receiving distance was 20cm, and the spinning was carried out for 40min under an applied voltage of 35kV to obtain a biodegradable fiber membrane. Then, the obtained biodegradable fiber membrane was dried in a vacuum drying oven at 40°C for 5 hours to allow the solvent to evaporate completely, thus obtaining a biodegradable fiber membrane with the following microstructure: Figure 2 As shown, its fiber size is approximately 100 nm, pore size is approximately 1 μm, and thickness is approximately 100 μm. Finally, the biodegradable fiber membrane is cut into circular pieces of the corresponding diameter (8 mm) according to the actual cigarette size, thus obtaining a biodegradable transverse filtration microporous membrane.

[0081] 2) Preparation of longitudinal filter fiber body: The prepared modified poly(butylene terephthalate) / poly(diethyl terephthalate) particles are extruded through a melt extruder to prepare modified poly(butylene terephthalate) / poly(diethyl terephthalate) fibers with a tow linear density of 3.5 ktex and a single filament linear density of 2.0 dtex. The prepared modified poly(butylene terephthalate) / poly(diethyl terephthalate) fibers and polylactic acid fibers of the same specifications are taken at a mass ratio of 1:5 and opened separately using a filter rod forming unit. The opening width is 18-23 cm. After combing and mixing, 5% of the weight of triacetin binder (purchased from Shandong Chenyu Chemical Co., Ltd., food grade, purity 99%) is sprayed to bond and aggregate the fiber tow into a fiber bundle. Then, according to the filter rod design requirements, the longitudinal filter fiber body is cut into 24 mm long sections.

[0082] 3) Preparation of composite filter rods: The longitudinal filter fiber body is cut in the middle, and the adhesive is evenly sprayed on the end face of the longitudinal filter fiber body that needs to be bonded and the bonding surface of the transverse filter microporous membrane. The three transverse filter microporous membranes are combined at both ends and the middle of the longitudinal filter fiber body, using a 40g / m² adhesive. 3 Ordinary forming paper with a width of 26.5mm is rolled into composite filter rods with a specification of 24mm×ф8mm.

[0083] 4) Drying and balancing: Dry the prepared composite filter rod and place it in a balancing chamber for 10 hours to obtain a high-performance biodegradable composite filter rod (filter rod 1).

[0084] Example 3

[0085] This embodiment also describes the preparation of a high-performance biodegradable composite filter rod. The composite filter rod contains two transverse microporous membrane sheets, which are axially and vertically disposed at both ends of a longitudinal filter fiber body. Both the longitudinal filter fiber body and the transverse microporous membrane sheets are prepared from a composite of polylactic acid and modified polybutylene succinate. In the longitudinal filter fiber body, the amount of modified polybutylene succinate fiber is 1 / 3 of the mass of polylactic acid fiber; in the transverse microporous membrane sheets, the amount of modified polybutylene succinate is 5 times the mass of polylactic acid. The preparation method of this composite filter rod is as follows:

[0086] First, modified polybutylene succinate is prepared, and the specific method includes the following steps:

[0087] S2-1) Esterification and branching: Succinic acid and butanediol, the raw materials used to prepare polybutylene succinate, are esterified in the required molar ratio; at the same time, 3% of the total weight of the esterification reaction polymer is added as glycerol, the esterification reaction temperature is controlled at 235℃, the pressure is 50kPa, and the reaction is carried out for 2h to obtain polybutylene succinate branched oligomer.

[0088] S2-2) Prepolymerization: The temperature of the reactor is controlled at 240℃ and the pressure is controlled at 3kPa. The reaction is carried out for 3.5h to obtain the branched prepolymer of polybutylene succinate.

[0089] S2-3) Final Polycondensation Grafting: Add 1% by weight of maleic anhydride-grafted polyvinyl alcohol to the obtained branched polybutylene succinate prepolymer, continue to control the reaction temperature at 240℃ and the pressure at 105Pa, and carry out the final polycondensation reaction for 20min to obtain the modified polybutylene succinate polymer.

[0090] S2-4) Pelletizing and Drying: The modified polybutylene succinate polymer is fed into a pelletizing device, pelletized, and then dried to obtain modified polybutylene succinate particles for later use.

[0091] Then, the composite filter rod is prepared, specifically including the following steps:

[0092] 1) Preparation of transverse filtration microporous membrane: 2.5g of modified polybutylene succinate particles and 0.5g of polylactic acid particles were prepared at a mass ratio of 5:1 and dissolved in 20mL of ethyl acetate (EA). Then, 20mg of LiCl was added and the mixture was stirred for 3 hours at 55rpm under heating conditions (50℃) to prepare a 15% (w / w) spinning solution. Electrospinning was then performed using an electrospinning machine. The translational speed of the feeding system was 250mm / min, the rotational speed of the receiving roller was set to 40rpm / min, the spinning speed was 3mL / h, and the receiving distance was 25cm. Spinning was carried out for 50 minutes under an applied voltage of 40kV to obtain a biodegradable fiber membrane. The obtained biodegradable fiber membrane was then dried in a vacuum drying oven at 45℃ for 6 hours to allow the solvent to fully evaporate, resulting in a biodegradable fiber membrane with a fiber size of approximately 200nm, a pore size of approximately 2μm, and a thickness of 150μm. Finally, the biodegradable fiber membrane is cut into circular pieces of the corresponding diameter (8mm) according to the actual cigarette size, thus obtaining a biodegradable transverse filter microporous membrane.

[0093] 2) Preparation of longitudinal filter fiber body: The prepared modified polybutylene succinate particles are extruded through a melt extruder to prepare modified polybutylene succinate fibers with a tow linear density of 4 ktex and a single filament linear density of 2.0 dtex; the prepared modified polybutylene succinate fibers and polylactic acid fibers of the same specification are taken at a mass ratio of 1:3 and opened separately using a filter rod forming unit. The opening width is 18-23 cm. They are mixed by layering. The modified polybutylene succinate fibers are divided into 3 equal parts and evenly sandwiched in the polylactic acid fiber layer. Then, 5% of the weight of the tow binder (same as in Example 2) is sprayed to bond the fiber tow into a bundle. Then, according to the filter rod design requirements, the longitudinal filter fiber body is cut into 24 mm long sections.

[0094] 3) Preparation of composite filter rods: The adhesive is then evenly sprayed onto the bonding surfaces of the longitudinal filter fiber body and the transverse filter microporous membrane. The two transverse filter microporous membranes are then combined at both ends of the longitudinal filter fiber body, using a 40g / m² adhesive. 3 Ordinary forming paper with a width of 26.5mm is rolled into composite filter rods with a specification of 24mm×ф8mm.

[0095] 4) Drying and balancing: Dry the prepared composite filter rod and place it in a balancing chamber for 10 hours to obtain a high-performance biodegradable composite filter rod (filter rod 2).

[0096] Example 4

[0097] This embodiment also prepares a high-performance biodegradable composite filter rod. This composite filter rod contains a transverse microporous membrane, which is axially and vertically positioned in the middle of the longitudinal filter fiber body. Both the longitudinal filter fiber body and the transverse microporous membrane are prepared from polylactic acid (PLA) combined with modified poly(butylene terephthalate) / poly(butylene adipate) and modified poly(butylene succinate). In the longitudinal filter fiber body, the amount of modified PLA / butylene adipate is 1 / 10 of the mass of PLA fiber, and the amount of modified poly(butylene succinate) fiber is 1 / 5 of the mass of PLA fiber. In the transverse microporous membrane, the amount of modified PLA / butylene adipate is twice the mass of PLA fiber, and the amount of modified poly(butylene succinate) is three times the mass of PLA. The preparation methods of the modified PLA / butylene adipate and modified poly(butylene succinate) are the same as in Examples 2 and 3. The preparation method of this composite filter rod is as follows:

[0098] 1) Preparation of transverse filtration microporous membrane: Take 3g of modified polybutylene succinate particles, 2g of modified polybutylene terephthalate / butylene adipate particles, and 1g of polylactic acid particles in a mass ratio of 3:2:1, dissolve them in 30mL of ethyl acetate (EA) / N,N-dimethylformamide (DMF) mixed solvent (volume ratio 6:4), then add 30mg of LiCl and stir for 4h at 60℃ under heating conditions. The stirring speed is 70rpm to prepare a spinning solution with a mass fraction of 20%. Electrospinning is carried out, specifically: using an electrospinning machine, the translation speed of the push system is 400mm / min, the rotation speed of the receiving roller is set to 80rpm / min, the spinning speed is 5mL / h, the receiving distance is 30cm, and spinning is carried out for 80min under an applied voltage of 45kV to obtain a biodegradable fiber membrane. Then, the obtained biodegradable fiber membrane was dried in a vacuum drying oven at 45°C for 10 hours to allow the solvent to fully evaporate, resulting in a biodegradable fiber membrane with a fiber size of approximately 100 nm, a pore size of approximately 1.5 μm, and a thickness of 100 μm. Finally, the biodegradable fiber membrane was cut into circular pieces of the corresponding diameter (8 mm) according to the actual cigarette size, thus obtaining a biodegradable transverse filtration microporous membrane.

[0099] 2) Preparation of longitudinal filter fiber body: Take 1 part of modified poly(butylene terephthalate) / poly(butylene adipate) fiber, 3 parts of modified poly(butylene succinate) fiber, and 10 parts of polylactic acid fiber with the same specifications as the modified poly(butylene terephthalate) / poly(butylene adipate) fiber by mass. Open them with a filter rod forming machine, with an opening width of 18-23 cm. Comb and mix them evenly. Then spray 5% of the weight of the fiber bundle with an adhesive (same as in Example 2) to bond the fiber bundle into a bundle. Then cut the longitudinal filter fiber body with a length of 24 mm according to the filter rod design requirements.

[0100] 3) Preparation of composite filter rods: The longitudinal filter fiber body is cut in the middle, and then the adhesive is evenly sprayed on the cross-section of the cut longitudinal filter fiber body and both sides of the transverse filter microporous membrane. The transverse filter microporous membrane is then assembled in the middle of the longitudinal filter fiber body, using a 40g / m² adhesive. 3 Ordinary forming paper with a width of 26.5mm is rolled into composite filter rods with a specification of 24mm×ф8mm.

[0101] 4) Drying and balancing: Dry the prepared composite filter rod and place it in a balancing chamber for 8 hours to obtain a high-performance biodegradable composite filter rod (filter rod 3).

[0102] Example 5

[0103] This embodiment examines the flue gas filtration effect and taste of the composite filter rods prepared in Examples 2-4, and also examines the shape retention and shelf life of the filter rods.

[0104] The following filter rod was used as a comparative experiment in this embodiment.

[0105] Comparative filter rod 1: Only the longitudinal filter fiber body prepared in Example 2 is used as the filter element, without adding a transverse filter microporous membrane; the specifications and processing method of the filter rod are the same as in Example 2.

[0106] Comparative filter rod 2: Only the longitudinal filter fiber body prepared in Example 3 is used as the filter element, without adding a transverse filter microporous membrane; the specifications and processing method of the filter rod are the same as in Example 3.

[0107] Comparative filter rod 3: Only the longitudinal filter fiber body prepared in Example 4 is used as the filter element, without adding a transverse filter microporous membrane; the specifications and processing method of the filter rod are the same as in Example 4.

[0108] Comparison Filter Rod 4: This filter rod uses only polylactic acid (PLA) fibers to prepare the filter element, without adding modified polybutylene terephthalate (PET) / polybutylene adipate (PBA) fibers or modified polybutylene succinate (PBS) fibers, and without adding transverse microporous membranes. The manufacturing process of this PLA filter rod is as follows: PLA fiber tobacco tow with a tow linear density of 3.5 ktex and a single filament linear density of 2.0 dtex is selected. On a filter rod forming unit, the tow is opened, with an unfolded width of 18–23 cm. A modified binder (same as in Example 2) of 5% by weight of the tow is sprayed on, using a 40 g / m² binder. 3 Ordinary forming paper with a width of 26.5mm is rolled into filter rods with a specification of 24mm×ф8mm.

[0109] The filtration effect was tested by measuring the removal rates of nicotine, tar, and particulate matter on each filter rod (the nicotine removal rate was tested according to standard YC / T185-2004, and the tar and particulate matter removal rate was tested according to standard GB / T 19609-2004).

[0110] Taste evaluation: The cigarette samples to be evaluated were placed in a constant temperature and humidity chamber (22 ℃ RH 60%) for 48 h to equilibrate before evaluation. The evaluation team consisted of professional tasters and conducted the evaluation in a blind manner.

[0111] Shelf life: The shelf life of a product is reflected by its degradation time. The experimental method is as follows: Experiments are conducted according to GB / T 19277.1-2011 "Determination of the final aerobic biodegradability of materials under controlled composting conditions—Method for determining the release of carbon dioxide—Part 1: General Method". The shelf life of the product mentioned in this invention refers to the product's degradation cycle, specifically calculated in days, and does not represent the storage period of the filter rod sample.

[0112] Shape retention: All prepared filter rods were stored in a warehouse at a temperature of 18-25℃ and a humidity of 50%. Each product was stored in standard cigarette packaging. After 6 months, random samples were taken to test the roundness and collapse of the filter rods. Five samples were taken from each product for testing. The roundness test method followed standard GB / T 22838.13-2009, and the average value was taken. Collapse phenomenon: No collapse phenomenon was considered to occur when there was no collapse greater than 0.5mm in the filter rod cut, measured using vernier calipers. Collapse was visually assessed by observing whether the filter rod surface was full and smooth.

[0113] The test results are shown in Table 1.

[0114] Table 1. Test results of nicotine, tar and particulate matter removal rates for each filter rod

[0115]

[0116] As can be seen from the test results in Table 1, compared with the single polylactic acid fiber filter (comparison filter rod 4), the removal rates of tar and particulate matter in cigarette smoke decreased to some extent or remained basically the same after using composite filter rods (comparison filter rod 1, comparison filter rod 2, and comparison filter rod 3). At the same time, the amount of nicotine per cigarette remained basically unchanged, indicating that the addition of modified fiber can improve the filtration of smoke to a certain extent. However, since it only has the longitudinal filter fiber body, the improvement in filtration effect is not significant. After adding filter membranes (filter rod 1, filter rod 2, and filter rod 3) to the filter rods, the removal rates of tar and particulate matter in cigarette smoke decreased significantly, and the more membranes added, the better the filtration effect.

[0117] Taste evaluation results showed that there was little difference in taste among the various filter rods used. However, the product with the addition of a transverse filter microporous membrane had a further reduction in the amount of impurities in the taste. This further demonstrates that the use of the transverse filter microporous membrane further reduces the harmfulness index of cigarettes and improves the filtration performance of the filter rod, providing better protection for smokers.

[0118] The shape retention test results showed that the shelf life (degradation cycle) of both composite filter rods (comparison filter rod 1, comparison filter rod 2, and comparison filter rod 3) and composite filter rods with added transverse filter membranes (filter rod 1, filter rod 2, and filter rod 3) was longer than that of single polylactic acid filter rods (comparison filter rod 4). This indicates that, under the same biodegradability conditions, the shelf life of composite filter rods is superior to that of single polylactic acid filter rods. Furthermore, compared to the comparison filter rods, the invented filter rod products showed no shrinkage or collapse, and their roundness was better than that of the filter rods, meeting the requirements for filter rod use (GB / T 5605-2011).

[0119] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and not restrictive in all respects. Furthermore, it should be understood that although this specification describes embodiments, it does not encompass only one technical solution. This descriptive method is merely for clarity, and those skilled in the art should consider the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-performance biodegradable composite filter rod, comprising a filter element and a shaped roll of paper wrapped around the filter element, characterized in that: The filter element includes a longitudinal filter fiber body and at least one transverse filter microporous membrane. The transverse filter microporous membrane is disposed at one and / or both and / or the middle section of the longitudinal filter fiber body, and is perpendicular to the axial direction of the longitudinal filter fiber body. The longitudinal filter fiber body is prepared by combining polylactic acid fiber with modified poly(butylene terephthalate) / poly(butylene adipate) fiber and / or modified poly(butylene succinate) fiber; the amount of modified poly(butylene terephthalate) / poly(butylene adipate) fiber is 1 / 20 to 1 / 5 of the mass of polylactic acid fiber, and the amount of modified poly(butylene succinate) fiber is 1 / 6 to 1 / 3 of the mass of polylactic acid fiber; The transverse filtration microporous membrane is prepared by electrospinning of a spinning solution made of polylactic acid and modified polybutylene terephthalate / adipate and / or modified polybutylene succinate; the amount of modified polybutylene terephthalate / adipate is 2 to 3 times the mass of polylactic acid, and the amount of modified polybutylene succinate is 3 to 5 times the mass of polylactic acid. The modified polybutylene terephthalate / adipate and the modified polybutylene succinate are modified polymer products based on terephthalate / adipate and polybutylene succinate, respectively, with glycerol as a grafting agent and maleic anhydride-grafted polyvinyl alcohol as a grafting monomer; the amount of glycerol used is 1% to 3% of the weight of the terephthalate / adipate or polybutylene succinate raw material; the amount of maleic anhydride-grafted polyvinyl alcohol is 1% to 1.5% of the weight of the polybutylene succinate or polyterephthalate / adipate.

2. The high-filtration-performance biodegradable composite filter rod according to claim 1, characterized in that: The preparation method of the modified polybutylene terephthalate / adipate includes the following steps: S1-1) Esterification and Branching: Terephthalic acid and adipic acid, the raw materials used to prepare poly(butylene terephthalate) adipate, are separately mixed with 1,4-butanediol at the required molar ratio for primary esterification. When the esterification rate reaches more than 90%, the products of the two primary esterification reactions are combined for die esterification. Glycerol is added during the die esterification reaction to obtain branched oligomers of poly(butylene terephthalate) adipate. The primary esterification reaction parameters are: temperature 230-235℃, pressure 70-80kPa, and reaction time 80-100min. The die esterification reaction parameters are: temperature 235-240℃, pressure 30-50kPa, and reaction time 3-4h. S1-2) Prepolymerization: When the esterification rate of diesterification reaches more than 95%, the obtained poly(terephthalic acid / butyl adipate) branched oligomer is injected into the prepolymerization reactor. The temperature of the prepolymerization reactor is controlled at 235-240℃ and the pressure is 1-3 kPa. The prepolymerization reaction is carried out for 1-2 hours to obtain the poly(terephthalic acid / butyl adipate) branched prepolymer. S1-3) Final Polymerization Grafting: Maleic anhydride-grafted polyvinyl alcohol is added to the obtained branched prepolymer of poly(terephthalic acid) / butyl adipate. The temperature of the prepolymerization reactor is controlled at 235-240℃ and the pressure at 95-110Pa. The final polymerization reaction is carried out for 5-30 minutes to obtain the modified poly(terephthalic acid) / butyl adipate polymer. S1-4) Pelletizing and Drying: After the degree of polymerization of the modified poly(terephthalic acid / butyl adipate) polymer reaches the predetermined viscosity, it is fed into a pelletizing device for pelletizing and drying to obtain modified poly(terephthalic acid / butyl adipate) particles, which are then prepared into spinning solution and fibers for later use.

3. The high-filtration-performance biodegradable composite filter rod according to claim 2, characterized in that: In step S1-1), the amount of glycerol added during the esterification branching is 0.1% to 1% of the oligomer weight; In steps S1-3), the amount of maleic anhydride-grafted polyvinyl alcohol added in the final polymerization graft is 0.1% to 1% of the weight of the poly(butylene terephthalate) / poly(dibutyl adipate) branched prepolymer; In steps S1-4), the melt mass flow rate of the modified poly(butylene terephthalate) polymer fed into the cooling pelletizing equipment is 3-5 g / 10 min.

4. The high-filtration-performance biodegradable composite filter rod according to claim 3, characterized in that: The preparation method of the modified polybutylene succinate includes the following steps: S2-1) Esterification and branching: Succinic acid and butanediol, the raw materials used to prepare polybutylene succinate, are esterified in the required molar ratio; at the same time, 0.1% to 1% of glycerol by weight of the total polymer material is added, and the esterification reaction temperature is controlled at 230 to 235°C, the pressure at 30 to 50 kPa, and the reaction is carried out for 2 hours to obtain branched oligomers of polybutylene succinate. S2-2) Prepolymerization: The temperature of the reactor is raised to 235-240℃, the pressure is controlled at 1-3kPa, and the reaction is carried out for 3-4 hours to obtain the branched prepolymer of polybutylene succinate. S2-3) Final Polycondensation Grafting: Add 0.1% to 1% of maleic anhydride grafted polyvinyl alcohol to the obtained branched polybutylene succinate prepolymer, and continue to control the reaction temperature at 235 to 240°C and the pressure at 100 to 110 Pa to carry out the final polycondensation reaction for 5 to 30 minutes to obtain the modified polybutylene succinate polymer. S2-4) Pelletizing and Drying: The modified polybutylene succinate polymer is fed into a pelletizing device, pelletized, and then dried to obtain modified polybutylene succinate particles, which are then used to prepare spinning solution and fibers for later use.

5. A method for preparing a high-filtration-performance biodegradable composite filter rod according to any one of claims 1-4, characterized in that: Includes the following steps: 1) Preparation of transverse filtration microporous membrane: Biodegradable material particles for preparing transverse filtration microporous membrane are added to a solvent, and a certain amount of inorganic salt is added. The mixture is stirred under heating conditions to prepare a spinning solution. Electrospinning is then performed to obtain a biodegradable fiber membrane. The biodegradable fiber membrane is then cut into circular pieces of the corresponding diameter according to the actual cigarette size to obtain a biodegradable transverse filtration microporous membrane. 2) Preparation of longitudinal filter fiber body: The biodegradable material fibers used to prepare the longitudinal filter fiber body are opened and mixed in proportion. Then, the biodegradable adhesive is evenly sprayed on the opened fiber bundles. The fiber bundles are then bonded together to form a fiber bundle. Finally, the fiber bundles are cut into the specified lengths according to the filter rod design requirements to obtain the longitudinal filter fiber body. 3) Preparation of composite filter rod: The biodegradable adhesive is then evenly sprayed onto the end face of the longitudinal filter fiber body that needs to be bonded and the bonding surface of the transverse filter microporous membrane. The transverse filter microporous membrane is assembled into the predetermined position of the longitudinal filter fiber body according to the design requirements, and then wrapped with shaped roll paper to form a complete composite filter rod. 4) Drying and balancing: Dry the complete composite filter rod and then put it into the balancing chamber for a certain period of time to obtain a high-performance biodegradable composite filter rod.

6. The method for preparing the high-filtration-performance biodegradable composite filter rod according to claim 5, characterized in that: In step 1), the preparation of the transverse filtration microporous membrane is as follows: The solvent used is one or a mixture of ethyl acetate, N,N-dimethylformamide, and chloroform; The heating temperature is 30–75℃, the stirring speed is 50–80 rpm, and the stirring time is 0.1–4 hours. The mass fraction concentration of the prepared spinning solution is 5%–20%; The parameters for electrospinning are as follows: the translation speed of the injection system is 100-500 mm / min, the rotation speed of the receiving roller is 10-100 rpm / min, the spinning speed is 1-10 mL / h, the receiving distance is 10-30 cm, the applied voltage is 10-50 kV, and the spinning time is 10-120 min. The obtained transverse filtration microporous membrane has a fiber size of 80–120 nm and a pore size of 0.5–1.5 μm.

7. The method for preparing the high-filtration-performance biodegradable composite filter rod according to claim 5, characterized in that: In step 2), the preparation of the longitudinal filter fiber body is as follows: The biodegradable material used to prepare the longitudinal filter fiber body has a fiber bundle density of 3-5 ktex and a single filament linear density of 1.5-4 dtex. The unfolded width is 15-25cm; After opening, the fiber bundles are mixed by layering or by combing and hybridization. When mixing by layering, the modified poly(butylene terephthalate) / butylene adipate fiber or the modified polybutylene succinate fiber is divided into at least 3 parts and uniformly sandwiched in the polylactic acid fiber layer.

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