Preparation method of anti-knife-hitting polylactic acid fiber filter rod

Abstract

The present invention provides a method for preparing a polylactic acid fiber filter rod that is resistant to being cut, and relates to the technical field of cigarette preparation, and includes the following steps: S1: obtaining a first component raw material polylactic acid with a left-handed isomer content of a first predetermined value, to obtain a core component; S2: obtaining a second component polylactic acid with a left-handed isomer content of a second predetermined value, to obtain a skin component; S3: mixing the core component and the skin component according to a preset ratio to obtain a polylactic acid fiber tow with a skin-core structure, and forming the original polylactic acid filter rod; S4: using an alloy knife for cutting to obtain a polylactic acid fiber filter rod. The present invention is simple and convenient, and by controlling the proportion and preparation of the polylactic acid raw material, the uniformity of the inner layer structure is improved, the generation of nodes is reduced, and damage to the cutter during high-speed cutting is avoided, and the cutter uses an alloy knife to effectively ensure that the polylactic acid fiber filter rod can be stably cut, and the cutting quality of the filter rod is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of cigarette preparation, and in particular to a method for preparing a polylactic acid fiber filter rod that is resistant to being cut. Background Art

[0002] Polylactic acid (PLA) is a polymer material made by fermenting starch from renewable plant resources to produce lactic acid, which is then chemically synthesized. It has good recyclability and biodegradability and has the following characteristics: 1. It uses renewable plant resources (corn, wheat, beets, rice, potatoes, sweet potatoes, etc.) and organic waste (corn cobs or roots, stems, leaves, skins, etc. of other crops) as raw materials, getting rid of the dependence on wood and oil resources and meeting the requirements of sustainable development; 2. It can be completely biodegraded and will naturally decompose into water and carbon dioxide after a certain period of time in the natural environment without causing environmental pollution. The generated carbon dioxide is reused through plant photosynthesis, becoming a permanent, closed carbon cycle system, and is a veritable "green material"; 3. Compared with the three major synthetic fibers of polyester, nylon and acrylic, the energy consumption of producing polylactic acid fiber is lower, and it is a polymer material with relatively low resource and environmental load; 4. It has good processing performance and can be produced by the melt spinning method of general thermoplastic resin.

[0003] At present, polylactic acid fiber has been developed for use in fields such as cigarette tow, but there are great differences in the performance requirements between polylactic acid fiber for cigarette tow and conventional polylactic acid tow for clothing. For example, polylactic acid fiber for clothing must meet the requirements of fiber spinning, weaving, fabric printing and dyeing, washing, and ironing, must have high crystallinity, orientation, and mechanical strength, be able to withstand temperatures of 80 to 100°C, must not dissolve or swell in detergent aqueous solutions and dry cleaning solvents, require a certain degree of hygroscopicity, and at the same time, the less other gaseous substances in the surrounding environment are adsorbed, the better. However, as a tobacco tow, it needs to meet the following requirements: (1) The filter rod made of it is non-toxic, odorless and safe; (2) The tow has good stability and can meet the requirements of filter rod forming equipment and process; (3) It has appropriate rigidity and curling properties, so that it has good elasticity and looseness. With a small amount of tow filling, after adding plasticizers or adhesives, the filter rod can meet certain hardness, suction resistance and appearance quality requirements, and have a high rod output rate; (4) It has sufficient heat resistance, and the filter tip does not collapse or deform during the smoking process of the cigarette; (5) It has a high filtration efficiency for harmful components in the smoke; (6) It does not affect the sensory quality of the cigarette. Therefore, it is necessary to develop special spinning and post-processing process technologies to meet the requirements of tobacco use.

[0004] For example, Chinese patent invention patent CN111789285A provides a method for preparing a polylactic acid cooling modified tow filter rod, which comprises the following steps: polylactic acid masterbatch, SEBS and PP are uniformly mixed, and then melt-polymerized online at a temperature of 140°C to 200°C, extruded by a screw, and then cooled and melt-spun, and then the polylactic acid tow is obtained through drawing, curling, drying and shaping, and then the filter rod is formed and prepared on a conventional filter rod machine. The polylactic acid cooling modified tow filter rod prepared by the above invention has a higher melting point than the traditional polylactic acid tow filter rod, and has greatly improved heat resistance. It avoids the phenomenon of head shrinkage in heat-not-burn tobacco products, and at the same time has a significant effect on reducing the smoke temperature, solving the problem of high smoke temperature, strong heat tingling and poor smoking comfort of heat-not-burn tobacco products, and is suitable for industrial production.

[0005] However, the above filter rod preparation method still has the following problems: the melting point and crystallinity of PLA are related to the molecular weight of the polymer and the content of L-lactic acid monomer; when the crystallinity of polylactic acid is high, the temperature resistance is good, but when the crystallinity is high, nodes are easily formed. When the filament bundle is formed into a filter rod, the nodes are randomly distributed at different positions of the filament bundle. When the filter rod is rolled and cut, due to the high-speed movement of the filter rod and the difference in the force of the node and the filament bundle when the cutter is applied, it is easy to cause the blade to notch or even break, resulting in frequent shutdown of the roll-joining machine, uneven cross-section of the filter rod, deformation of the filter rod, and inconsistent roundness index; on the other hand, due to the large number of crystallization points of the filament bundle, the specific surface area of ​​the filter rod filament bundle is also affected, which has a greater impact on the filtration efficiency and aroma substances of the filter rod, thereby causing a greater impact on the sensory quality of the cigarette.

[0006] Therefore, in order to solve the above problems, it is very necessary for us to design a reasonable method for preparing a polylactic acid fiber filter rod that is anti-knife. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing a polylactic acid fiber filter rod that is resistant to knife cutting. The method is simple and convenient. By controlling the proportion and preparation of the polylactic acid raw materials, a sheath-core type polylactic acid fiber with a multi-layer structure is obtained, and the uniformity of its inner layer structure is improved, that is, the crystal distribution in the polylactic acid fiber is more uniform, the generation of nodes is reduced, and damage to the cutter during high-speed cutting is avoided. The cutter adopts an alloy knife to effectively ensure that the polylactic acid fiber filter rod can be stably cut, thereby effectively improving the cutting quality of the filter rod.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for preparing a polylactic acid fiber filter rod that is resistant to knife-beating comprises the following steps:

[0010] S1: obtaining polylactic acid having a left-handed isomer content of a first predetermined value to obtain a first component raw material, and inducing crystallization by drawing stress during spinning of the first component raw material to obtain a core wire component;

[0011] S2: obtaining polylactic acid having a levorotatory isomer content of a second predetermined value to obtain a second component raw material, and adding triacetin to the second component raw material to obtain a cortex component;

[0012] S3: mixing the core component and the skin component according to a preset ratio to obtain a polylactic acid fiber tow with a skin-core structure, and molding a plurality of clusters of the polylactic acid fiber tows to obtain an original polylactic acid filter rod;

[0013] S4: using an alloy knife to cut the original polylactic acid filter rod to obtain a polylactic acid fiber filter rod.

[0014] As a preferred embodiment of the present invention, after executing step S4, the method further includes:

[0015] S5: Compounding the cut portion of the polylactic acid fiber filter rod.

[0016] As a preferred embodiment of the present invention, when performing step S3, in all the polylactic acid fiber tows of the skin-core structure of the same batch of original polylactic acid filter rods, the origin, batch and purification steps of all the first component raw materials are the same;

[0017] In all the sheath-core structured polylactic acid fiber bundles of the same batch of original polylactic acid filter rods, the origin, batch and purification steps of all the second component raw materials are the same.

[0018] As a preferred embodiment of the present invention, when executing step S2, the second predetermined value is not higher than the first predetermined value.

[0019] As a preferred embodiment of the present invention, when performing steps S1 and S2, a nucleating agent and a dispersing agent are added to the first component raw material and the second component raw material respectively.

[0020] As a preferred embodiment of the present invention, the percentage of the nucleating agent added to the first component raw material in the entire first component raw material is not lower than the percentage of the nucleating agent added to the second component raw material in the entire second component raw material;

[0021] And the difference between the percentage of the nucleating agent added in the first component raw material to the entire first component raw material and the percentage of the nucleating agent added in the second component raw material to the entire second component raw material does not exceed 5%.

[0022] As a preferred embodiment of the present invention, when executing step S1, before the first component raw material is crystallized to obtain the core wire component, it is ensured that the first component raw material is evenly dispersed;

[0023] When performing step S2, before adding triacetin to the second component raw material to obtain the cortex component, ensure that the second component raw material is evenly dispersed.

[0024] As a preferred embodiment of the present invention, when executing step S3: the core wire component and the skin layer component are mixed according to a preset ratio, and the composition ratio of the core wire component ranges from 30% to 35%.

[0025] As a preferred embodiment of the present invention, before executing step S4, steel knives are respectively installed on both sides of the alloy knife to prevent triacetin from adhering to the side of the alloy knife when the alloy knife cuts the polylactic acid fiber filter rod.

[0026] As a preferred embodiment of the present invention, the steel knife is provided with a sharpening structure for grinding off the triacetin adhering to the side of the steel knife online and a stretching structure for keeping the steel knife shielding the alloy knife when the sharpening structure sharpens the steel knife.

[0027] The beneficial effects of the preparation method of the polylactic acid fiber filter rod that is resistant to knife-cutting of the present invention are: simple and convenient, through the control of the proportion and preparation of the polylactic acid raw materials, a sheath-core type polylactic acid fiber with a multi-layer structure is obtained, and the uniformity of its inner layer structure is improved, that is, the crystal distribution in the polylactic acid fiber is more uniform, the generation of nodes is reduced, and damage to the cutter during high-speed cutting is avoided. The cutter adopts an alloy knife to effectively ensure that the polylactic acid fiber filter rod can be stably cut, thereby effectively improving the cutting quality of the filter rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic flow chart of a method for preparing a polylactic acid fiber filter rod that is resistant to knife punching according to the present invention;

[0029] Figure 2 It is a schematic diagram of a cutter structure in a method for preparing a polylactic acid fiber filter rod that is resistant to knife hitting according to the present invention;

[0030] Figure 3 It is a side structural schematic diagram of a cutter structure in a method for preparing a polylactic acid fiber filter rod that is resistant to knife hitting according to the present invention;

[0031] Figure 4 The present invention is a schematic diagram of the side structure of a steel knife of a cutting knife structure in a method for preparing a polylactic acid fiber filter rod that is resistant to knife hitting. DETAILED DESCRIPTION

[0032] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0033] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangements of modules and structures set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

[0034] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0035] Technologies, methods, and systems known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and systems should be considered part of the authorization specification.

[0036] Embodiment 1: Figure 1 As shown, a method for preparing a polylactic acid fiber filter rod that is resistant to knife punching comprises the following steps:

[0037] S1: obtaining polylactic acid having a left-handed isomer content of a first predetermined value to obtain a first component raw material, and inducing crystallization by drawing stress during spinning of the first component raw material to obtain a core wire component;

[0038] Generally speaking, the first predetermined value ranges from 95% to 98%, that is, the first component raw material contains 95% to 98% of the left-handed isomer (that is, L-lactic acid monomer). With such a high content of the left-handed isomer, the melting point of the first component raw material will also be higher. During the spinning and post-processing process, the low-temperature crystallization is induced by the drawing stress. The crystallinity of the filament bundle after drawing is improved, and the thermal stability of the filament bundle size is improved, which can be better curled and shaped, ensuring that the filament bundle has suitable rigidity and curling properties, and has good elasticity and looseness, and lower thermal shrinkage performance.

[0039] S2: obtaining polylactic acid having a levorotatory isomer content of a second predetermined value to obtain a second component raw material, and adding triacetin to the second component raw material to obtain a cortex component;

[0040] The second predetermined value is not higher than the first predetermined value; generally speaking, the second predetermined value ranges from 92% to 95%, and the second component raw material contains 92% to 95% of the left-handed isomer, and triacetin needs to be added to the second component raw material. Under the action of triacetin, the filament bundle swells and bonds, and can finally be combined with the core wire component obtained from the first component raw material to obtain a well-bonded skin-core structure polylactic acid filament bundle.

[0041] S3: mixing the core component and the skin component according to a preset ratio to obtain a polylactic acid fiber tow with a skin-core structure, and molding a plurality of clusters of the polylactic acid fiber tows to obtain an original polylactic acid filter rod;

[0042] The fibers are melt-extruded through a screw extruder and passed through a filter to remove impurities. The fibers are then spun through a three-leaf spinneret at a certain spinning temperature. The newly spun fibers are cooled by a process air-conditioning device. Oil is applied to the surface of the fibers to improve the post-processing performance. The fibers are wound at an appropriate winding rate and temporarily stored in a fiber barrel. In the post-spinning process, the spun fibers are bundled, stretched in a water bath at a certain temperature, and then crimped in a crimping machine to achieve the required linear density, number of crimps and other indicators.

[0043] It should be noted that each polylactic acid fiber tow is a tow with a sheath-core structure.

[0044] S4: using an alloy knife to cut the original polylactic acid filter rod to obtain a polylactic acid fiber filter rod.

[0045] The original polylactic acid filter rod obtained in step S3 is relatively long and needs to be cut into multiple sections to obtain a polylactic acid fiber filter rod of a predetermined length.

[0046] It should be noted that: when executing step S3, in all the sheath-core structured polylactic acid fiber tows of the same batch of original polylactic acid filter rods, the origin, batch and purification steps of all the first component raw materials are the same;

[0047] In all the sheath-core structured polylactic acid fiber bundles of the same batch of original polylactic acid filter rods, the origin, batch and purification steps of all the second component raw materials are the same.

[0048] It can also be understood that: in an original polylactic acid filter rod, or in a batch of original polylactic acid filter rods cut at the same time, the first component raw materials in all the polylactic acid fiber bundles are all the same; the second component raw materials in all the polylactic acid fiber bundles are also all the same.

[0049] In this way, the crystallinity of the core wire components in all the produced polylactic acid fiber tows is evenly distributed, it is not easy to produce large agglomerates, and it is not easy to cause impact damage to the alloy knife during slitting.

[0050] And use alloy knives for slitting. Alloy knives have greater hardness and better cutting effect on crystal points. They are not prone to damage or breakage, which may cause the slitting machine to stop. The machine has high operating stability and improves the cutting quality of the filter rods.

[0051] The invention discloses a method for preparing a polylactic acid fiber filter rod which is resistant to knife cutting. The method is simple and convenient. By controlling the proportion and preparation of polylactic acid raw materials, a sheath-core type polylactic acid fiber with a multi-layer structure is obtained, and the uniformity of the inner layer structure is improved, that is, the crystal distribution in the polylactic acid fiber is more uniform, the generation of nodes is reduced, and damage to the cutter during high-speed cutting is avoided. The cutter adopts an alloy knife to effectively ensure that the polylactic acid fiber filter rod can be stably cut, thereby effectively improving the cutting quality of the filter rod.

[0052] Embodiment 2: Still as Figure 1 The figure is only one of the embodiments of the present invention. Based on the first embodiment, the method for preparing a polylactic acid fiber filter rod that is resistant to knife punching of the present invention further includes, after executing step S4:

[0053] S5: Compounding the cut portion of the polylactic acid fiber filter rod.

[0054] In fact, the filter rod at the cutting part is composed of polylactic acid tow with less crystallization, or the cutting part is composited with other types of tows such as acetate filter rod and polypropylene filter rod.

[0055] You can also add fragrance to the composite parts. The filtration efficiency of aldehydes and ketones in the fragrance components is lower than that of acetate filter rods. The increase of cyclopentanones will lead to sensory irritation and increased woody smell, and the increase of phenolic substances will also lead to an increase in woody smell.

[0056] In this way, the aroma transparency, fineness and sweetness of the composite filter stick tobacco are improved.

[0057] Furthermore, when performing steps S1 and S2, a nucleating agent and a dispersing agent are added to the first component raw material and the second component raw material, respectively.

[0058] The nucleating agent can increase the crystallinity of the entire tow, while the dispersing agent can effectively reduce the probability of crystallization into agglomerates, further making the crystallinity of the polylactic acid fiber tow high and uniform, so as to facilitate slitting.

[0059] Here, the percentage value of the nucleating agent added to the first component raw material in the entire first component raw material is not lower than the percentage value of the nucleating agent added to the second component raw material in the entire second component raw material;

[0060] And the difference between the percentage of the nucleating agent added in the first component raw material to the entire first component raw material and the percentage of the nucleating agent added in the second component raw material to the entire second component raw material does not exceed 5%.

[0061] In addition, when executing step S1, before the first component raw material is crystallized to obtain the core wire component, ensure that the first component raw material is evenly dispersed;

[0062] When performing step S2, before adding triacetin to the second component raw material to obtain the cortex component, ensure that the second component raw material is evenly dispersed.

[0063] Furthermore, when executing step S3: the core wire component and the skin layer component are mixed according to a preset ratio, and the composition ratio of the core wire component ranges from 30% to 35%.

[0064] Embodiment 3: Still as Figures 1 to 4The figure shown is only one of the embodiments of the present invention. On the basis of any of the above embodiments, in a method for preparing a polylactic acid fiber filter rod that is resistant to knife hitting, before executing step S4, steel knives 2 are respectively installed on both sides of the alloy knife 1 to prevent triacetin from adhering to the side of the alloy knife 1 when the alloy knife 1 cuts the polylactic acid fiber filter rod 00.

[0065] In addition, the steel knife 2 is provided with a sharpening structure 4 for grinding off the triacetin adhering to the side of the steel knife 2 online and a stretching structure 5 for keeping the steel knife 2 shielding the alloy knife 1 when the sharpening structure 4 sharpens the steel knife.

[0066] The two cutters are arranged on the same cutter shaft 3. When the cutter shaft 3 rotates, the two cutters are driven to cut the polylactic acid fiber filter rod at the same time. The alloy knife 1 is circular, and it is the main body of cutting the polylactic acid fiber filter rod. Therefore, the outer edge of the alloy knife 1 cuts the polylactic acid fiber filter rod 00; in addition, the steel knife 2 is arranged on the outside of the alloy knife 1, so that the blade 2 of the steel knife 2 is flush with the edge of the alloy knife 1, and the polylactic acid fiber filter rod can be cut synchronously.

[0067] Here, the hardness of the alloy knife 1 is higher than that of the steel knife 2, so that the wire bundle alloy knife 1 is convenient for cutting the crystallized wire bundle in the polylactic acid fiber filter rod. As the main body for cutting the polylactic acid fiber filter rod, the alloy knife 1 has high hardness and the blade is not easily damaged when colliding with the crystallization point.

[0068] In addition, the steel knife 2 is detachably arranged on the side of the alloy knife 1 to prevent triacetin from adhering to the side of the alloy knife 1 when cutting the polylactic acid fiber filter rod. The steel knife 2 blocks the outside of the cutting part of the alloy knife 1, so that triacetin will only adhere to the side of the steel knife 2 away from the alloy knife 1, and will not adhere to the side of the alloy knife 1.

[0069] Here, the blade 2 of the steel knife 2 is flush with the edge of the alloy knife 1, mainly because the steel knife 2 completely blocks the part of the side of the alloy knife 1 that contacts the polylactic acid fiber filter rod to prevent triacetin from adhering to the side of the alloy knife 1.

[0070] Moreover, there are two steel knives 2, and the two steel knives are closely attached to the two sides of the alloy knife 1. The alloy knife has high hardness and is not easily damaged. The two steel knives are closely attached to the outer sides of the alloy knife respectively, so that triacetin will only adhere to the side of the steel knife away from the alloy knife.

[0071] It should be noted that the sharpening structure 4 will cause the outer edge of the steel knife to be worn away, making the blade of the steel knife shorter. Therefore, in order to facilitate the sharpening of the steel knife, the steel knife 2 is preferably a long blade structure that can extend outward.

[0072] That is, the steel knife 2 includes a plurality of blade units 20, and each of the blade units 20 extends from the cutter shaft 3 to the edge of the alloy knife 1. Each blade unit 20 is generally in the shape of an elongated strip, but is not a strictly rectangular structure. The farther away from the cutter shaft 3, the wider the blade unit 20, and even the two sides of the blade unit 20 can be appropriately bent.

[0073] Here, the cutter shaft 3 is provided with an extension structure 5 for connecting to one end of the blade unit 20 close to the cutter shaft 3, and the extension structure 5 includes a motor arranged on the outside of the cutter shaft 3, a screw rod coaxially connected to the rotating shaft of the motor, and a blade clamp arranged on the screw rod for connecting to one end of the blade unit 20 close to the cutter shaft 3.

[0074] Of course, the blade clamp is provided with a screw hole for facilitating the screw to pass through, the outer side of the screw is provided with an external thread, and the inner side of the screw hole is provided with an internal thread for matching with the external thread.

[0075] That is, the inner end of the blade unit 20 is clamped by the blade clamp, and when the motor drives the screw to rotate, under the principle of screw transmission, the blade clamp and the blade unit extend away from the cutter shaft 3, that is, the blade unit 20 extends outward.

[0076] Here, the motor is a stepper motor, and the steel knife can set the step value of the stepper motor according to its wear condition, that is, according to the sharpening coefficient between the blade unit 20 and the sharpening structure 4, to ensure that the extension amount of the blade unit 20 and the wear amount between the blade unit 20 and the sharpening structure 4 are balanced.

[0077] Of course, a limit block is provided on the screw rod. Once the blade clamp contacts the limit block, it indicates that the blade unit 20 has extended outward to the maximum. At this time, a new blade unit 20 should be replaced. Of course, the motor needs to rotate in the opposite direction at this time so that the blade clamp reaches the position closest to the cutter shaft 3.

[0078] In addition, a limit rod is provided between the motor and the blade clamp and is arranged parallel to the screw rod. The limit rod is arranged smoothly, and a limit rod hole is provided on the blade clamp for facilitating the limit rod to pass through, so that under the restriction of the limit rod, even if the screw rod rotates, the blade unit 20 will not rotate; in this way, not only the structure of the blade unit 20 is stable, but also the blade unit 20 can be effectively prevented from squeezing the side of the alloy knife 1.

[0079] Moreover, the limiting rod and the screw rod are respectively located on both sides of the blade unit 20 .

[0080] The invention discloses a method for preparing a polylactic acid fiber filter rod which is resistant to knife cutting. The method is simple and convenient. By controlling the proportion and preparation of polylactic acid raw materials, a sheath-core type polylactic acid fiber with a multi-layer structure is obtained, and the uniformity of the inner layer structure is improved, that is, the crystal distribution in the polylactic acid fiber is more uniform, the generation of nodes is reduced, and damage to the cutter during high-speed cutting is avoided. The cutter adopts an alloy knife to effectively ensure that the polylactic acid fiber filter rod can be stably cut, thereby effectively improving the cutting quality of the filter rod.

[0081] The present invention is not limited to the above specific implementations, and the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made to the above implementations based on the technical essence of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a polylactic acid fiber filter rod that is resistant to knife-beating, characterized in that: The following steps are involved: S1: obtaining polylactic acid having a left-handed isomer content of a first predetermined value to obtain a first component raw material, and inducing crystallization by drawing stress during spinning of the first component raw material to obtain a core wire component; S2: obtaining polylactic acid having a levorotatory isomer content of a second predetermined value to obtain a second component raw material, and adding triacetin to the second component raw material to obtain a cortex component; the second predetermined value is not higher than the first predetermined value; S3: mixing the core component and the skin component according to a preset ratio to obtain a polylactic acid fiber tow with a skin-core structure, and molding a plurality of clusters of the polylactic acid fiber tows to obtain an original polylactic acid filter rod; When executing step S3, in all the polylactic acid fiber tows of the sheath-core structure of the same batch of original polylactic acid filter rods, the origin, batch and purification steps of all the first component raw materials are the same; In all the PLA fiber tows of the skin-core structure of the same batch of original PLA filter rods, the origin, batch and purification steps of all the second component raw materials are the same; The crystallinity in the core component of all the produced polylactic acid fiber tows is evenly distributed, and the crystallinity in the skin component is evenly distributed; S4: using an alloy knife to cut the original polylactic acid filter rod to obtain a polylactic acid fiber filter rod; Before executing step S4, steel knives are respectively installed on both sides of the alloy knife to prevent triacetin from adhering to the side of the alloy knife when the alloy knife cuts the polylactic acid fiber filter rod; The steel knife is provided with a sharpening structure for grinding off the triacetin adhering to the side of the steel knife online and a stretching structure for keeping the steel knife shielding the alloy knife when the sharpening structure is sharpening the steel knife; The alloy knife and the steel knife are arranged on the same cutter shaft. When the cutter shaft rotates, the two cutters are driven to cut the polylactic acid fiber filter rod at the same time. The alloy knife is round, and the edge of the alloy knife cuts the polylactic acid fiber filter rod; the steel knife is arranged on the outside of the alloy knife so that the blade of the steel knife is flush with the edge of the alloy knife; The steel knife includes a plurality of blade units, and each of the blade units is extended from the cutter axis to the edge of the alloy knife. Each blade unit is generally in the shape of a long strip, and the farther away from the cutter axis, the wider the blade unit is. The extension structure includes a motor arranged on the outside of the cutter shaft, a screw rod coaxially connected to the rotating shaft of the motor, and a blade clamp arranged on the screw rod for connecting to one end of the blade unit close to the cutter shaft; the inner end of the blade unit is clamped by the blade clamp, and when the motor drives the screw rod to rotate, under the principle of screw rod transmission, the blade clamp and the blade unit are extended in a direction away from the cutter shaft, that is, the blade unit is extended outward.

2. The method for preparing a knife-proof polylactic acid fiber filter rod according to claim 1, characterized in that: After executing step S4, the method further includes: S5: Compounding the cut portion of the polylactic acid fiber filter rod.

3. The method for preparing a knife-proof polylactic acid fiber filter rod according to claim 1, characterized in that: When performing steps S1 and S2, a nucleating agent and a dispersing agent are added to the first component raw material and the second component raw material respectively.

4. The method for preparing a knife-proof polylactic acid fiber filter rod according to claim 3, characterized in that: The percentage of the nucleating agent added to the first component raw material in the entire first component raw material is not lower than the percentage of the nucleating agent added to the second component raw material in the entire second component raw material; And the difference between the percentage of the nucleating agent added in the first component raw material to the entire first component raw material and the percentage of the nucleating agent added in the second component raw material to the entire second component raw material does not exceed 5%.

5. The method for preparing a knife-proof polylactic acid fiber filter rod according to claim 1, characterized in that: When executing step S1, before the first component raw material is crystallized to obtain the core wire component, ensuring that the first component raw material is evenly dispersed; When performing step S2, before adding triacetin to the second component raw material to obtain the cortex component, ensure that the second component raw material is evenly dispersed.

6. The method for preparing a knife-proof polylactic acid fiber filter rod according to claim 1, characterized in that: When executing step S3: the core wire component and the skin layer component are mixed according to a preset ratio, and the composition ratio of the core wire component ranges from 30% to 35%.

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