Cigarette filter rod and method of making the same

Abstract

The application discloses a cigarette filter rod and a preparation method thereof. The raw material of the cigarette filter rod comprises the following components in parts by weight: 70-80 parts of polybutylene adipate terephthalate, 20-30 parts of polylactic acid, and 1.5-2 parts of modified basalt fiber. The modified basalt fiber has epoxy groups on the surface. The cigarette filter rod uses polybutylene adipate terephthalate and polylactic acid which is easy to biodegrade as the main resin of the raw material of the cigarette filter rod, and adds the modified basalt fiber with the epoxy groups on the surface, realizes chain extension and crosslinking of the polylactic acid and the polybutylene adipate terephthalate, solves the problem that the activity of the chain extender affects the uniformity of the material, and simultaneously increases the compatibility between the main resins. The cigarette filter rod is easy to degrade, has no pollution to the environment, and has excellent heat insulation and mechanical properties.

Description

Technical Field

[0001] This application relates to the field of cigarette filter technology, and in particular to a cigarette filter and its preparation method. Background Technology

[0002] Currently, the main filter material used in cigarettes is cellulose acetate, which can be biodegraded in the presence of sunlight and water, but the degradation process is slow and time-consuming. Furthermore, the molding process of cigarette filters requires the use of plasticizers for bonding and the wrapping of tipping paper, making the degradation of cellulose acetate in the filter even more difficult. Therefore, researchers are constantly searching for safe and non-toxic filter materials that are environmentally friendly and can replace cellulose acetate. Summary of the Invention

[0003] This invention provides a cigarette filter rod and its preparation method to solve the technical problem that filter rod materials are not easily degraded and pollute the environment in the prior art.

[0004] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0005] In a first aspect, the present invention provides a cigarette filter rod, the raw material of which comprises the following components in parts by weight: 70-80 parts of polybutylene adipate terephthalate, 20-30 parts of polylactic acid, and 1.5-2 parts of modified basalt fiber; wherein the modified basalt fiber has epoxy groups on its surface.

[0006] Furthermore, the modified basalt fiber is obtained by modifying basalt fiber with anhydrides having the following structure.

[0007]

[0008] R1 and R2 are each independently selected from one or more of the following: a monoalkenyl group having 2 to 5 carbon atoms, an alkenyl group substituted with a benzene ring and having 2 to 3 carbon atoms in the main chain, and a phenyl group substituted with an alkenyl group having 2 to 3 carbon atoms.

[0009] Furthermore, the preparation method of the modified basalt fiber includes the following steps:

[0010] S1. The basalt fiber is cut and steam-exploded and then impregnated in a first solvent. The unsaturated acid anhydride and catalyst are added to the solvent, and the reaction is heated.

[0011] S2. The basalt fiber treated in step S1 is immersed in the second solvent and peroxy acid is added dropwise. After the reaction is completed, the modified basalt fiber is obtained by filtration.

[0012] Furthermore, the first solvent is selected from one or more of dimethyl sulfoxide, dimethylformamide, and N-methylpyrrolidone.

[0013] Furthermore, the second solvent is selected from one or more of dichloromethane, chloroform, benzene, diethyl ether, acetone, and dioxane.

[0014] Furthermore, the catalyst is selected from one or more of ferrous chloride, aluminum chloride, ferrous sulfate, and aluminum sulfate.

[0015] Furthermore, the peroxyacid is selected from one or more of persulfate, persulfate, persulfate salts, pernitric acid, perphosphoric acid, perphosphoric acid, performic acid, peracetic acid, perpropionic acid, perbenzoic acid, m-chloroperbenzoic acid, and nitroperbenzoic acid.

[0016] Furthermore, the mass ratio of the unsaturated anhydride added in step S1 to the basalt fiber is 1-2:3-5.

[0017] Furthermore, the reaction temperature in step S1 is 40℃~75℃.

[0018] Furthermore, in step S1, the length of the basalt fiber after cutting is controlled between 1 μm and 5 μm; the steam pressure of the steam explosion is between 0.6 MPa and 0.8 MPa, the explosion time is less than 0.05 s, and the pressure holding time is between 5 s and 10 s.

[0019] Furthermore, in step S2, the peroxyacid is added under water bath conditions, with the water bath temperature being 0℃~30℃.

[0020] Furthermore, the raw materials of the cigarette filter rod also include the following components by weight: 5 to 10 parts filler and 0.3 to 0.6 parts lubricant.

[0021] Furthermore, the filler is selected from one or more of nano-calcium carbonate, talc, and hollow glass microspheres.

[0022] Furthermore, the lubricant is selected from one or more of white oil, amide wax, polyethylene wax, and polypropylene wax.

[0023] In a second aspect, the present invention provides a method for preparing the above-mentioned cigarette filter rod, comprising the following steps: mixing the polybutylene adipate terephthalate, the polylactic acid, and the modified basalt fiber in a specified ratio, and sequentially spinning them into bundles, opening them with low-pressure air, applying adhesive, and then extruding them to obtain the cigarette filter rod.

[0024] Furthermore, the extrusion molding temperature is 100℃~170℃.

[0025] The cigarette filter rod provided by this invention uses polybutylene adipate terephthalate (PBT) and readily biodegradable polylactic acid (PLA) as the main resins for the filter rod, and adds modified basalt fibers with epoxy groups on their surface. This achieves chain extension and crosslinking of PLA and PBT, solving the problem of the chain extender's activity affecting material uniformity, and simultaneously increasing the compatibility between the main resins. The resulting cigarette filter rod is easily degradable, environmentally friendly, and possesses excellent thermal insulation and mechanical properties. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] In a first aspect of this application, a cigarette filter rod is provided, the raw material of which includes the following components in parts by weight: 70-80 parts of polybutylene adipate terephthalate, 20-30 parts of polylactic acid, and 1.5-2 parts of modified basalt fiber; the modified basalt fiber has epoxy groups on its surface.

[0028] Polylactic acid (PLA), a biodegradable polymer, is a renewable raw material. It is polymerized from lactic acid obtained through fermentation of starch in plants, with lactic acid as the main raw material. It possesses good mechanical strength and biocompatibility, is non-irritating and non-toxic to humans, and its final degradation products are carbon dioxide and water, which can be absorbed and utilized by plants, aligning with the green concept of sustainable development in today's society. However, PLA exhibits a slow crystallization rate and low crystallinity during processing, resulting in insufficient mechanical stability of the final product.

[0029] In order to toughen polylactic acid, this application uses a biodegradable thermoplastic elastomer to modify it by blending. The biodegradable thermoplastic elastomer is polybutylene adipate terephthalate (PBAT). As an aromatic polyester, PBAT can provide good performance and processing properties.

[0030] To achieve crosslinking and copolymerization of PLA and PBAT in a system, chain extenders are typically added. However, the resulting blend still exhibits several drawbacks. Firstly, it suffers from low melt strength in the molten state, making product molding difficult and resulting in uneven wall thickness. Secondly, its glass transition temperature is low, causing the molded product to remain amorphous for extended periods, making it highly susceptible to deformation. The crystalline material is hard and brittle, with poor impact resistance and significantly lower temperature resistance than general-purpose plastics like polyethylene and polypropylene. Furthermore, some chain extenders are highly reactive, leading to excessive local crosslinking of the resin and a "sharkskin" effect on the product surface. These shortcomings severely limit the application of biodegradable materials in cigarette filter manufacturing.

[0031] In this embodiment, surface-modified basalt fibers are added to the raw materials of the cigarette filter rod. These fibers contain epoxy groups on their surface, enabling chain extension and crosslinking of PLA and PBAT without affecting product uniformity due to the activity of the chain extender. This also increases the compatibility between the main resins. The resulting cigarette filter rod is easily degradable, environmentally friendly, and possesses excellent thermal insulation and mechanical properties.

[0032] In some embodiments, the modified basalt fibers are obtained by modifying basalt fibers with unsaturated acid anhydrides having the following structure.

[0033]

[0034] R1 and R2 are each independently selected from one or more of the following: a monoalkenyl group having 2 to 5 carbon atoms, an alkenyl group substituted with a benzene ring and having 2 to 3 carbon atoms in the main chain, and a phenyl group substituted with an alkenyl group having 2 to 3 carbon atoms.

[0035] In this embodiment, the modification principle of basalt fiber is as follows: an anhydride reacts with the hydroxyl and amino groups present on the fiber surface through esterification, forming carbon-carbon double bonds on the fiber surface via ester groups. Then, peroxy acid is used to oxidize the carbon-carbon double bonds to epoxy groups. These epoxy groups can undergo ring-opening addition reactions with the hydroxyl and carboxyl groups of PLA and PBAT molecular chains, thereby achieving cross-linking between PLA and PBAT molecules and increasing system compatibility.

[0036] The results of numerous experiments show that not all unsaturated acid anhydrides can achieve ideal product performance. When the carbon chains of the groups in the unsaturated acid anhydrides with the above-mentioned structure are too long, although this structure reduces the aggregation of basalt fibers in the system, it increases the interfacial energy between the modified basalt fibers and polyester molecules, making it difficult for PLA / PBAT to arrange itself regularly on the surface of the layered basalt fibers. Furthermore, the benzene ring, as a rigid structure, can increase the hardness of polyester materials when introduced into polyester molecules; therefore, the groups in the unsaturated acid anhydrides can also be selected from monoalkenyl groups containing 2 to 3 carbon atoms of a benzene ring.

[0037] In some embodiments, the preparation method of modified basalt fiber includes the following steps:

[0038] S1. Basalt fibers are cut and steam-exploded and then impregnated in the first solvent. Unsaturated acid anhydride and catalyst are added to the solvent, and the mixture is heated. After the reaction is completed, the product is obtained.

[0039] S2. The product obtained in step S1 is immersed in the second solvent and peroxy acid is added dropwise. After the reaction is completed, the product is filtered to obtain modified basalt fiber.

[0040] In this embodiment, before modifying the surface of the basalt fiber, a steam explosion treatment is performed. The purpose is to make the basalt fiber contain more porous structures, which facilitates subsequent modification and bonding with the polyester system. Specifically, in step S1, the length of the basalt fiber after cutting is controlled between 1 μm and 5 μm; the steam pressure for steam explosion is 0.6 MPa to 0.8 MPa, the explosion time is less than 0.05 s, and the pressure holding time is 5 s to 10 s.

[0041] The first solvent is selected from one or more of dimethyl sulfoxide, dimethylformamide, and N-methylpyrrolidone. The second solvent is selected from one or more of dichloromethane, chloroform, benzene, diethyl ether, acetone, and dioxane. The catalyst is selected from one or more of ferrous chloride, aluminum chloride, ferrous sulfate, and aluminum sulfate. In the embodiments of this application, the reaction between the acid anhydride and the hydroxyl group requires an acidic catalyst to promote the reaction, but commonly used concentrated sulfuric acid is not suitable in this system because sulfuric acid will undergo an addition reaction with the double bond. In order to facilitate the separation of the product and improve its purity, easily removable iron and aluminum salts are selected as catalysts.

[0042] In some embodiments, the mass ratio of unsaturated anhydride to basalt fiber added in step S1 is 1–2:3–5. When modifying the surface of basalt fiber, the amount of unsaturated anhydride used needs to be controlled to maintain an appropriate system viscosity; otherwise, the reduction of hydroxyl and amino groups on the surface of the modified basalt fiber will decrease the hydrogen bond content in the system, correspondingly weakening the system viscosity, which is detrimental to the stable molding of the obtained cigarette filter rod.

[0043] In some embodiments, the raw material of the cigarette filter rod further includes the following components by weight: 5-10 parts filler, 0.3-0.6 parts lubricant. Preferably, the filler is selected from one or more of nano-calcium carbonate, talc, and hollow glass microspheres. The lubricant is selected from one or more of white oil, amide wax, polyethylene wax, and polypropylene wax. The amide wax can be selected from Clariant Licowax C, Ceridust 3910, etc., the polyethylene wax can be selected from Clariant Ceridust 3615, 3620, 3715, 3719, 3731, 3831, etc., and the polypropylene wax can be selected from Clariant PP6252, PP2502, PP2602, VP220, Hubei Xinyu PPW-0960, Dongguan Fengtai Titanium S203, etc.

[0044] The modified basalt fiber added in this embodiment has a layered structure, which enables polylactic acid molecules to form a regular arrangement on its surface, improving the crystallinity of polylactic acid; the carbon chains or benzene rings on the surface of the modified basalt fiber can reduce the interaction force between fiber particles, avoid agglomeration, and improve the dimensional stability of the product.

[0045] In addition, the modified basalt fiber has a chain-like skeleton structure formed by silicon-oxygen bonds, which can form hydrogen bonds with ester bonds, increasing the viscosity of the system and reducing the precipitation of components during the extrusion molding and pelletizing process.

[0046] A second aspect of this application provides a method for preparing the above-mentioned cigarette filter rod, comprising the following steps: mixing polybutylene adipate terephthalate, polylactic acid, and modified basalt fiber in a specified ratio, and sequentially spinning them into bundles, opening them with low-pressure air, applying adhesive, and then extruding them to obtain the cigarette filter rod.

[0047] All reagents used in the following examples were commercially available. The polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) mentioned in the examples and comparative examples were all commercially available. Different manufacturers and different product numbers of PBAT and PLA had no significant impact on the performance of cigarette filter rod materials. In the following examples and comparative examples, the PBAT used was purchased from Hubei Shiteng Chemical Co., Ltd., product number 56892, and the PLA used was purchased from NatureWorks, USA, product number 3052D.

[0048] Example 1

[0049] A cigarette filter rod, the raw materials of which include: 70 parts polybutylene adipate terephthalate, 30 parts polylactic acid, 1.5 parts modified basalt fiber-1, 5 parts nano calcium carbonate, 0.6 parts amide wax Ceridust3910 and 0.2 parts white oil.

[0050] The preparation method of the above-mentioned cigarette filter rod includes: mixing the above-mentioned raw materials evenly in a stirrer, extruding and molding at 100°C and drying to obtain the cigarette filter rod.

[0051] The preparation method of modified basalt fiber-1 includes the following steps:

[0052] S1. 500g of basalt fiber is crushed and cut to a length of 1-2μm. It is then steam-exploded at a steam pressure of 0.8MPa for 0.05s. After holding the pressure for 5s, it is impregnated in N-methylpyrrolidone and 100g of unsaturated acid anhydride with the structure of formula I-1 is added. Ferrous chloride catalyst is added and the mixture is heated to 40℃. After the reaction is completed, the reaction solution is filtered, washed with ethanol and deionized water, and dried.

[0053] S2. The basalt fibers treated in S1 are immersed in diethyl ether, and peroxybenzoic acid is slowly added dropwise in a 0°C water bath. When the carbon-carbon double bond conversion in the reaction system is completed, the reaction is stopped, and the product is filtered, washed and dried to obtain modified basalt fiber-1.

[0054]

[0055] Example 2

[0056] A cigarette filter rod, the raw materials of which include: 80 parts polybutylene adipate terephthalate, 20 parts polylactic acid, 2 parts modified basalt fiber-2, 5 parts hollow glass microspheres, 0.4 parts amide wax Ceridust3910 and 0.2 parts white oil.

[0057] The preparation method of the above-mentioned cigarette filter rod includes: mixing the above-mentioned raw materials evenly in a stirrer, extruding and molding at 120°C and drying to obtain the cigarette filter rod.

[0058] The preparation method of modified basalt fiber-2 includes the following steps:

[0059] S1. 400g of basalt fiber is crushed and cut to a length of 1-2μm. It is then steam-exploded at a steam pressure of 0.7MPa for 0.03s. After holding the pressure for 8s, it is immersed in N-methylpyrrolidone and 200g of unsaturated acid anhydride with the structure of formula I-2 is added. Ferrous chloride catalyst is added and the mixture is heated to 50℃. After the reaction is completed, the reaction solution is filtered, washed with ethanol and deionized water, and dried.

[0060] S2. The basalt fibers treated in S1 are immersed in diethyl ether, and peroxybenzoic acid is slowly added dropwise in a 10°C water bath. When the carbon-carbon double bond conversion in the reaction system is completed, the reaction is stopped, and the product is filtered, washed and dried to obtain modified basalt fiber-2.

[0061]

[0062] Example 3

[0063] A cigarette filter rod, the raw materials of which include: 80 parts polybutylene adipate terephthalate, 20 parts polylactic acid, 2 parts modified basalt fiber-3, 2 parts nano calcium carbonate, 3 parts hollow glass microspheres, 0.3 parts amide wax Ceridust3910 and 0.2 parts white oil.

[0064] The preparation method of the above-mentioned cigarette filter rod includes: mixing the above-mentioned raw materials evenly in a stirrer, extruding and molding at 170°C and drying to obtain the cigarette filter rod.

[0065] The preparation method of modified basalt fiber-3 includes the following steps:

[0066] S1. 300g of basalt fiber is crushed and cut to a length of 1-2μm. It is then steam-exploded at a steam pressure of 0.8MPa for 0.02s. After holding the pressure for 5s, it is impregnated in N-methylpyrrolidone and 200g of unsaturated acid anhydride with the structure of formula I-3 is added. Ferrous chloride catalyst is added and the mixture is heated to 60℃. After the reaction is completed, the reaction solution is filtered, washed with ethanol and deionized water, and dried.

[0067] S2. The basalt fibers treated in S1 are immersed in diethyl ether, and peroxybenzoic acid is slowly added dropwise in a 20°C water bath. When the carbon-carbon double bond conversion in the reaction system is completed, the reaction is stopped, and the product is filtered, washed and dried to obtain modified basalt fiber-3.

[0068]

[0069] Example 4

[0070] A cigarette filter rod, the raw materials of which include: 80 parts polybutylene adipate terephthalate, 20 parts polylactic acid, 2 parts modified basalt fiber-4, 5 parts nano calcium carbonate, 5 parts hollow glass microspheres, 0.3 parts amide wax Ceridust3910 and 0.2 parts white oil.

[0071] The preparation method of the above-mentioned cigarette filter rod includes: mixing the above-mentioned raw materials evenly in a stirrer, extruding and molding at 150°C and drying to obtain the cigarette filter rod.

[0072] The preparation method of modified basalt fiber-4 includes the following steps:

[0073] S1. 300g of basalt fiber is crushed and cut to a length of 1-2μm. It is then steam-exploded at a steam pressure of 0.8MPa for 0.02s. After holding the pressure for 5s, it is immersed in N-methylpyrrolidone and 200g of unsaturated acid anhydride with the structure of formula I-4 is added. Ferrous chloride catalyst is added and the mixture is heated to 75℃. After the reaction is completed, the reaction solution is filtered, washed with ethanol and deionized water, and dried.

[0074] S2. The basalt fibers treated in S1 are immersed in diethyl ether, and peroxybenzoic acid is slowly added dropwise in a 30°C water bath. When the carbon-carbon double bond conversion in the reaction system is completed, the reaction is stopped, and the product is filtered, washed and dried to obtain modified basalt fiber-4.

[0075]

[0076] Example 5

[0077] This embodiment is basically the same as embodiment 4, except that modified basalt fiber-5 is used in the raw materials.

[0078] The preparation method of modified basalt fiber-5 includes the following steps:

[0079] S1. 300g of basalt fiber is crushed and cut to a length of 1-2μm. It is then steam-exploded under a steam pressure of 0.8MPa for 0.02s. After holding the pressure for 5s, it is immersed in N-methylpyrrolidone and 200g of unsaturated acid anhydride with the structure of formula I-5 is added. Ferrous chloride catalyst is added and the mixture is heated to 75℃. After the reaction is completed, the reaction solution is filtered, washed with ethanol and deionized water, and dried.

[0080] S2. The basalt fibers treated in S1 are immersed in diethyl ether, and peroxybenzoic acid is slowly added dropwise in a 30°C water bath. When the carbon-carbon double bond conversion in the reaction system is completed, the reaction is stopped, and the product is filtered, washed and dried to obtain modified basalt fiber-5.

[0081]

[0082] Example 6

[0083] This embodiment is basically the same as embodiment 4, except that modified basalt fiber-6 is used in the raw materials.

[0084] The preparation method of modified basalt fiber-6 is the same as that of modified basalt fiber-4, except that the mass of the unsaturated acid anhydride with the structure of formula I-4 is 300g.

[0085] Example 7

[0086] This embodiment is basically the same as embodiment 4, except that modified basalt fiber-7 is used in the raw materials.

[0087] The preparation method of modified basalt fiber-7 is the same as that of modified basalt fiber-4, except that the length of the basalt fiber used is controlled at 3 to 4 μm.

[0088] Example 8

[0089] This embodiment is basically the same as embodiment 4, except that modified basalt fiber-8 is used in the raw materials.

[0090] The preparation method of modified basalt fiber-8 is the same as that of modified basalt fiber-4, except that the length of the basalt fiber used is controlled at 4 to 5 μm.

[0091] Comparative Example 1

[0092] This comparative example is basically the same as Example 4, except that modified basalt fiber-9 is used in the raw materials.

[0093] The preparation method of modified basalt fiber-9 is the same as that of modified basalt fiber-4, except that only the basalt fiber is subjected to steam explosion.

[0094] Comparative Example 2

[0095] This comparative example is basically the same as Example 4, except that modified basalt fiber-4 is not used in the raw materials.

[0096] Comparative Example 3

[0097] A cigarette filter rod, the raw materials of which include: 80 parts polybutylene adipate terephthalate, 20 parts polylactic acid, 2 parts Jia Yi Rong SG20, 5 parts nano calcium carbonate, 5 parts hollow glass microspheres, 0.3 parts amide wax and 0.2 parts white oil.

[0098] The preparation method of the above-mentioned cigarette filter rod includes: mixing the above-mentioned raw materials evenly in a stirrer, extruding and molding at 150°C and drying to obtain the cigarette filter rod.

[0099] The cigarette filter rods obtained in Examples 1 to 8 and Comparative Examples 1 to 3 were subjected to the following performance tests, and the test results are shown in Table 1:

[0100] Hardness: The hardness was determined in accordance with GB / T22838.6-2009 Determination of physical properties of cigarettes and filter rods - Part 6: Hardness.

[0101] Tensile strength: Tested in accordance with GB / T14337-2008 Test method for tensile properties of chemical fiber short fiber;

[0102] Elongation at break: Tested in accordance with GB / T14337-2008 Test method for tensile properties of chemical fiber short fiber;

[0103] Thermal insulation: The obtained material is made into the shape of a cigarette holder, and then the inhalation action of a smoker is simulated. The temperature on the outside of the cigarette holder is measured. When the temperature is below 30℃, it is considered qualified.

[0104] Processability: Observe the extrusion molding rate of the material and whether there is any glue trapping or chipping at the rear end of the filter rod during the slitting stage. If there is no such phenomenon, it is qualified.

[0105] Table 1. Performance test results of cigarette filter rods from Examples 1 to 8 and Comparative Examples 1 to 3.

[0106]

[0107] As shown in Table 1, the cigarette filter rod material provided in this application possesses hardness and mechanical properties suitable for processing and use environments: hardness reaches 85% or higher, tensile strength is not less than 27.5 MPa, and elongation at break reaches 68.1% or higher. The use of modified basalt fiber improves the hardness and mechanical properties of the PLA / PBAT resin system, and also enhances the compatibility between the two resins. The cross-linked network formed by the reaction between functional groups and the presence of intermolecular forces give the filter rod material good processability and dimensional stability. The steam explosion of the basalt fiber before modification increases its porosity, thus improving the thermal insulation performance of the filter rod material to a certain extent. Compared to filter rod materials prepared using chain extenders in existing technologies, the filter rod material with modified basalt fiber provided in this application has greater application advantages, and the resulting cigarette filter material has a promising market prospect in the cigarette material field.

[0108] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A cigarette filter rod, characterized by, The raw material comprises the following components in parts by weight: 70-80 parts of polybutylene adipate terephthalate, 20-30 parts of polylactic acid, 1.5-2 parts of modified basalt fiber; the modified basalt fiber has an epoxy group on the surface; The modified basalt fiber is modified by unsaturated acid anhydride on basalt fiber and has the following structure, wherein R1 and R2 are each independently selected from one or more of a mono-alkenyl group with 2-5 carbon atoms, an alkenyl group with 2-3 carbon atoms substituted with a benzene ring, and a benzene group substituted with an alkenyl group with 2-3 carbon atoms.

2. A cigarette filter according to claim 1, characterised in that, The preparation method of the modified basalt fiber comprises the following steps: S1, cutting the basalt fiber, steam explosion, and then soaking in a first solvent, adding unsaturated acid anhydride and a catalyst, and heating to react; S2, soaking the basalt fiber treated in step S1 in a second solvent, and dropping in a peroxy acid, and filtering to obtain the modified basalt fiber after the reaction is completed.

3. A cigarette filter according to claim 2, characterised in that, The first solvent is selected from one or more of dimethyl sulfoxide, dimethyl formamide, and N-methyl pyrrolidone; and / or The second solvent is selected from one or more of dichloromethane, trichloromethane, benzene, diethyl ether, acetone, and dioxane.

4. A cigarette filter according to claim 2, characterised in that, The catalyst is selected from one or more of ferrous chloride, aluminum chloride, ferrous sulfate, and aluminum sulfate.

5. A cigarette filter according to claim 2, characterised in that, The peroxy acid is selected from one or more of peroxymonosulfuric acid, peroxodisulfuric acid, peroxodisulfate, peroxynitric acid, peroxymonophosphoric acid, peroxodiphosphoric acid, peroxyformic acid, peroxyacetic acid, peroxypropionic acid, peroxybenzoic acid, m-chloroperbenzoic acid, and nitroperoxybenzoic acid.

6. A cigarette filter according to claim 2, characterised in that, The mass ratio of the unsaturated acid anhydride to the basalt fiber added in step S1 is 1-2:3-5; and / or The reaction temperature in step S1 is 40-75°C.

7. A cigarette filter according to claim 2, characterised in that, The length of the basalt fiber after cutting in step S1 is controlled to be 1-5 μm; the steam pressure of the steam explosion is 0.6-0.8 MPa, the explosion time is less than 0.05 s, and the pressure maintaining time is 5-10 s.

8. A cigarette filter according to claim 2, characterised in that, The peroxy acid is added under water bath conditions in step S2, and the water bath temperature is 0-30°C.

9. A cigarette filter rod according to any one of claims 1 to 8, characterised in that, The raw material of the cigarette filter stick further comprises the following components in parts by weight: 5-10 parts of a filler, and 0.3-0.6 parts of a lubricant.

10. A cigarette filter according to claim 9, characterised in that, The filler is selected from one or more of nano calcium carbonate, talcum powder, and hollow glass microspheres; and / or The lubricant is selected from one or more of white oil, amide wax, polyethylene wax, and polypropylene wax.

11. A process for the production of a cigarette filter rod according to any one of claims 1 to 10, characterized in that, The method comprises the following steps: The polybutylene adipate terephthalate, the polylactic acid, and the modified basalt fiber are mixed according to the ratio, and then are sequentially subjected to spinning into a bundle, low-pressure air opening, and glueing, and then are extruded to obtain the cigarette filter stick.

12. A process for producing a cigarette filter rod according to claim 11, characterised in that, The temperature of the extrusion molding is 100-170°C.

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