A group-processed polylactic acid fiber filter rod and preparation method thereof

Abstract

The present invention provides a group-processed polylactic acid fiber filter rod and a preparation method thereof, which relates to the technical field of cigarette preparation, and comprises an inner core and an outer skin, wherein the inner core and the outer skin are both composited by a plurality of polylactic acid fiber bundles, the polylactic acid fiber bundles of the inner core are prepared by a first component raw material, and the polylactic acid fiber bundles in the outer skin are prepared by a second component raw material, the content of the left-lactic acid monomer of the first component raw material is higher than the content of the left-lactic acid monomer of the second component raw material, and a dispersant is added to the first component raw material, and triacetin is added to the second component raw material. The present invention is simple in configuration, and the properties of the polylactic acid raw material are strictly controlled, so that all outer skins have a uniform crystallinity, all inner cores also have a uniform crystallinity, and the nodes are evenly distributed when the bundles are crystallized, and the obtained polylactic acid fiber filter rod has a gradual crystallinity inside and outside, the processing process is more stable, and the adsorption performance of the filter rod is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of cigarette preparation, and in particular to a group-processed polylactic acid fiber filter rod and a preparation method thereof. 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 CN103074716A relates to a skin-core type polylactic acid cigarette tow and filter rod and its preparation method. The single fiber in the tow is a skin-core structure composed of an inner core and an outer skin. The main resins of the skin layer and the core layer are both polylactic acid. The weight ratio of the skin layer resin to the core layer resin is 20:80~40:60. The crystallinity of the tow skin layer and the core layer is 3-25% and 25-60% respectively. The melting points of the skin layer and the core layer are 120-150oC and 150-175oC respectively. The above invention combines the advantages of both the core layer and the skin layer. The core layer provides higher physical and mechanical properties and heat resistance, and the skin layer provides good adhesion. Common plasticizers (such as triacetin) can be conveniently used for filter rod molding. In addition, the skin-core type polylactic acid tow provided by the above invention has good biodegradability in its core layer and skin layer, and is an environmentally friendly cigarette tow.

[0005] However, the filter rod preparation structure still has the following problems: the skin layer resin and the core layer resin are both made of composite spinning of multiple raw materials, the properties of the polylactic acid raw materials are not controlled, the differences in the degree of crystallization of the various raw materials, the positions and numbers of the fiber bundle nodes are quite different, making the processing process of the above-mentioned skin-core type polylactic acid fiber bundle unstable.

[0006] Therefore, in order to solve the above problems, it is necessary for us to design a reasonable and efficient group-processed polylactic acid fiber filter rod. Summary of the invention

[0007] The object of the present invention is to provide a group-processed polylactic acid fiber filter rod, which has a simple configuration and strictly controls the properties of the polylactic acid raw material, so that all outer skins have a uniform crystallinity, all inner cores also have a uniform crystallinity, and the nodes are evenly distributed when the filament bundle is crystallized. The inner and outer sides of the polylactic acid fiber filter rod obtained have a gradual crystallinity, and the processing process is more stable.

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

[0009] A group-processed polylactic acid fiber filter rod comprises an inner core and an outer skin arranged on the outside of the inner core, wherein the inner core and the outer skin are both composited from a plurality of polylactic acid fiber bundles, the polylactic acid fiber bundles in the inner core are prepared from a first component raw material, and the polylactic acid fiber bundles in the outer skin are prepared from a second component raw material, the content of L-lactic acid monomers in the first component raw material is higher than that in the second component raw material, and a dispersant is added to the first component raw material, and triacetin is added to the second component raw material; the polylactic acid fiber bundles in the inner core are made by drawing stress-induced crystallization to improve the crystallinity of the polylactic acid fiber bundles in the inner core.

[0010] As a preferred embodiment of the present invention, the ratio of the number of polylactic acid fiber bundles in the inner core layer and the outer skin layer is between 30:70 and 35:65.

[0011] As a preferred embodiment of the present invention, nucleating agents are added to both the first component raw material and the second component raw material, and the content of the nucleating agent in the first component raw material is not less than the content of the nucleating agent in the second component raw material.

[0012] As a preferred embodiment of the present invention, a transition layer is arranged between the inner core and the outer skin, and the transition layer is composited by a plurality of polylactic acid fiber bundles, and the content of L-lactic acid monomer in the component raw materials used in the polylactic acid fiber bundles in the transition layer is not higher than the content of L-lactic acid monomer in the first component raw material and is not lower than the content of L-lactic acid monomer in the second component raw material.

[0013] As a preferred embodiment of the present invention, the number of transition layers is at least two, and the content of L-lactic acid monomer in the component raw material of the polylactic acid fiber bundle adopted in the transition layer close to the inner core is not lower than the content of L-lactic acid monomer in the component raw material of the polylactic acid fiber bundle adopted in the transition layer close to the outer skin.

[0014] As a preferred embodiment of the present invention, the component raw material used for the polylactic acid fiber bundle of the transition layer also has a nucleating agent added thereto, and the nucleating agent content in the component raw material is not higher than the nucleating agent content in the first component raw material and not lower than the nucleating agent content in the second component raw material.

[0015] As a preferred embodiment of the present invention, an acetate fiber bundle layer is arranged on the outer side of the outer skin.

[0016] The present invention also provides a method for preparing a group-processed polylactic acid fiber filter rod, comprising the following steps:

[0017] S1: obtaining polylactic acid having a left-handed isomer content of a first predetermined value, adding a dispersant to obtain a first component raw material, and inducing crystallization by drawing stress during spinning of the first component raw material to obtain a first polylactic acid fiber tow;

[0018] S2: obtaining polylactic acid with a left-handed isomer content of a second predetermined value, adding triacetin to obtain a second component raw material, and spinning the second component raw material into a second polylactic acid fiber tow; the second predetermined value is lower than the first predetermined value;

[0019] S3: Compounding a plurality of first polylactic acid fiber bundles to form an inner core, compounding a plurality of second polylactic acid fiber bundles to form an outer skin, and covering the outer skin on the outer side of the inner core to form a skin-core type polylactic acid fiber filter rod.

[0020] As a preferred embodiment of the present invention, before executing step S3, polylactic acid having a left-handed isomer content of a third predetermined value is obtained to obtain a third polylactic acid fiber tow, and a plurality of the third polylactic acid fiber tows are compounded to form a transition layer;

[0021] When executing step S3, the transition layer is coated on the outer side of the inner core layer, and then the outer skin layer is coated on the outer side of the transition layer.

[0022] As a preferred embodiment of the present invention, after executing step S3, an acetate fiber bundle layer is coated on the outside of the outer skin.

[0023] The beneficial effects of the group-processed polylactic acid fiber filter rod and the preparation method thereof of the present invention are: simple setting, strict control of the properties of the polylactic acid raw material, so that all outer skins have a uniform crystallinity, all inner cores also have a uniform crystallinity, and the nodes are evenly distributed when the filament bundle is crystallized, and the inner and outer sides of the prepared polylactic acid fiber filter rod have a gradual crystallinity, and the processing process is more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a cross-sectional schematic diagram of an embodiment of a group-processed polylactic acid fiber filter rod of the present invention;

[0025] Figure 2 It is a schematic flow chart of a method for preparing a polylactic acid fiber filter rod by group processing according to the present invention;

[0026] In the figure: 1. Inner core, 2. Outer skin, 3. Transition layer, 4. Acetate bundle layer. DETAILED DESCRIPTION

[0027] 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.

[0028] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement and steps of modules and steps set forth in these embodiments do not limit the scope of the present invention.

[0029] At the same time, it should be understood that for the convenience of description, the processes in the drawings are not just performed separately, but multiple steps are performed in an interlaced manner.

[0030] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the present invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0031] 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.

[0032] 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 this specification.

[0033] Embodiment 1: Figure 1 As shown, a group-processed polylactic acid fiber filter rod comprises an inner core 1 and an outer skin 2 arranged on the outside of the inner core 1, wherein the inner core 1 and the outer skin 2 are both composited from a plurality of polylactic acid fiber bundles, the polylactic acid fiber bundles in the inner core 1 are prepared from a first component raw material, and the polylactic acid fiber bundles in the outer skin 2 are prepared from a second component raw material, the content of L-lactic acid monomers in the first component raw material is higher than that in the second component raw material, and a dispersant is added to the first component raw material, and triacetin is added to the second component raw material; the polylactic acid fiber bundles in the inner core 1 are made by drawing stress-induced crystallization to improve the crystallinity of the polylactic acid fiber bundles in the inner core 1.

[0034] In the present invention, polylactic acid having a left-handed isomer content of a first predetermined value is obtained, a dispersant is added to obtain a first component raw material, and when the first component raw material is spun, crystallization is induced by drawing stress to obtain a first polylactic acid fiber bundle, so that the first polylactic acid fiber bundle has a higher degree of crystallinity and provides higher physical and mechanical properties and heat resistance. The addition of the dispersant can prevent large nodes from forming in the first polylactic acid fiber bundle with high crystallinity, thereby facilitating slitting.

[0035] 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 (i.e., L-lactic acid monomer). With such a high content of the left-handed isomer, the melting point of the first polylactic acid fiber bundle 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 bundle after drawing is improved, and the thermal stability of the bundle size is improved, which can be better curled and shaped, ensuring that the bundle has suitable rigidity and curling properties, and has good elasticity and looseness, and lower thermal shrinkage performance.

[0036] Similarly, polylactic acid having a left-handed isomer content at a second predetermined value is obtained, triacetin is added to obtain a second component raw material, and the second component raw material is spun into a second polylactic acid fiber bundle; the second predetermined value is lower than the first predetermined value; the second polylactic acid fiber bundle has a lower degree of crystallinity than the first polylactic acid fiber bundle, but provides more swelling properties and bonding properties with the addition of triacetin.

[0037] The second predetermined value is not higher than the first predetermined value; generally speaking, the second predetermined value ranges from 92% to 95%, 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 second polylactic acid fiber bundle swells and bonds, and can eventually be combined with the first polylactic acid fiber bundle obtained from the first component raw material to obtain a well-bonded skin-core structure polylactic acid bundle.

[0038] Finally, multiple first polylactic acid fiber bundles are compounded to form an inner core, multiple second polylactic acid fiber bundles are compounded to form an outer skin, and the outer skin is coated on the outer side of the inner core to form a skin-core type polylactic acid fiber filter rod.

[0039] Here, the ratio of the number of polylactic acid fiber bundles in the inner core 1 and the outer skin 2 is between 30:70 and 35:65, that is, the mass ratio of the core and the skin is within this range.

[0040] It should be noted that: in the same batch of polylactic acid fiber filter rods, the origin, batch and purification steps of all the first component raw materials are the same;

[0041] In the same batch of produced polylactic acid fiber filter rods, the origin, batch and purification steps of all second component raw materials are the same.

[0042] It can also be understood that: in a polylactic acid filter rod, or in a batch of polylactic acid filter rods produced at the same time, all the first polylactic acid fiber bundles have the same properties, the crystallinity of all the first polylactic acid fiber bundles produced 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 cutting; the properties of all the second polylactic acid fiber bundles are also the same.

[0043] In this way, the properties of the polylactic acid raw materials are strictly controlled so that all outer skins have a uniform degree of crystallinity, all inner cores also have a uniform degree of crystallinity, and the nodes are evenly distributed when the filaments crystallize, making the processing more stable.

[0044] Moreover, the crystallinity of the first polylactic acid fiber bundle is higher than that of the second polylactic acid fiber bundle, the prepared polylactic acid fiber filter rod has a gradual crystallinity inside and outside, and the multilayer structure is processed in groups.

[0045] This extends the meaning. Since the raw materials of the PLA fiber bundles in the inner core and the outer skin need to ensure the same origin, batch and purification steps, that is, uniqueness, the cigarette factory cannot mix the two types of raw materials for processing under the premise of purchasing the two types of raw materials at the same time. In this case, the two types of raw materials are directly prepared on two different production lines to obtain two different PLA fiber bundles. The L-lactic acid monomer content of the two types of raw materials is compared. The raw materials with high L-lactic acid monomer content are prepared according to the preparation method of the inner core, and the raw materials with low L-lactic acid monomer content are prepared according to the preparation method of the outer skin. Finally, the two PLA fiber bundles distributed inside and outside are combined together, which not only achieves the uniqueness of the single-layer raw material, but also satisfies the gradual change of crystallinity on the inside and outside.

[0046] The invention discloses a group-processed polylactic acid fiber filter rod, which has a simple configuration and strictly controls the properties of the polylactic acid raw material, so that all outer skins have a uniform crystallinity, all inner cores also have a uniform crystallinity, and the nodes are evenly distributed when the filament bundle is crystallized. The inner and outer sides of the obtained polylactic acid fiber filter rod have a gradual crystallinity, and the processing process is more stable.

[0047] Embodiment 2, still as Figure 1 The figure shown is only one of the embodiments of the present invention. On the basis of the first embodiment, in a group-processed polylactic acid fiber filter rod of the present invention, nucleating agents are added to both the first component raw material and the second component raw material, and the nucleating agent content in the first component raw material is not lower than the nucleating agent content in the second component raw material, thereby further increasing the crystallinity gradient between the inner and outer sides of the polylactic acid fiber filter rod.

[0048] In addition, a transition layer 3 is arranged between the inner core 1 and the outer skin 2, and the transition layer is composited by a plurality of polylactic acid fiber bundles, and the content of L-lactic acid monomer in the component raw materials used by the polylactic acid fiber bundles in the transition layer 3 is not higher than the content of L-lactic acid monomer in the first component raw material and is not lower than the content of L-lactic acid monomer in the second component raw material.

[0049] In fact, the number of transition layers 3 is at least two, and the content of L-lactic acid monomer in the component raw materials of the polylactic acid fiber bundle used in the transition layer 3 close to the inner core 1 is not lower than the content of L-lactic acid monomer in the component raw materials of the polylactic acid fiber bundle used in the transition layer 3 close to the outer skin 2.

[0050] The multiple transition layers 3 are also processed in groups, and multiple production lines can be used to process multiple raw materials to form polylactic acid fiber bundles, and finally they are coated layer by layer according to the content of left-lactic acid monomer.

[0051] In addition, a nucleating agent is also added to the component raw materials used in the polylactic acid fiber bundle of the transition layer 3, and the nucleating agent content in the component raw materials is not higher than the nucleating agent content in the first component raw materials and is not lower than the nucleating agent content in the second component raw materials. In the case of multiple transition layers, the more nucleating agent is added to the component raw materials used in the polylactic acid fiber bundle of the transition layer 3 closer to the inner side.

[0052] Finally, a acetate fiber bundle layer is arranged on the outside of the outer skin 2, that is, a layer of acetate fiber bundle outer layer is covered on the outside of the polylactic acid fiber bundle filter rod, and the bonding effect and adsorption performance of the acetate fiber bundle layer are utilized to make the filter rod structure more stable and the adsorption performance of the filter rod is guaranteed.

[0053] Embodiment three, as Figure 2 As shown, the present invention also provides a method for preparing a group-processed polylactic acid fiber filter rod in all the above embodiments, comprising the following steps:

[0054] S1: obtaining polylactic acid having a left-handed isomer content of a first predetermined value, adding a dispersant to obtain a first component raw material, and inducing crystallization by drawing stress during spinning of the first component raw material to obtain a first polylactic acid fiber tow;

[0055] S2: obtaining polylactic acid with a left-handed isomer content of a second predetermined value, adding triacetin to obtain a second component raw material, and spinning the second component raw material into a second polylactic acid fiber tow; the second predetermined value is lower than the first predetermined value;

[0056] S3: Compounding a plurality of first polylactic acid fiber bundles to form an inner core, compounding a plurality of second polylactic acid fiber bundles to form an outer skin, and covering the outer skin on the outer side of the inner core to form a skin-core type polylactic acid fiber filter rod.

[0057] Before executing step S3, polylactic acid having a left-handed isomer content of a third predetermined value is obtained to obtain a third polylactic acid fiber tow, and a plurality of the third polylactic acid fiber tows are compounded to form a transition layer;

[0058] When executing step S3, the transition layer is coated on the outer side of the inner core layer, and then the outer skin layer is coated on the outer side of the transition layer.

[0059] After executing step S3, the outer side of the outer skin is covered with an acetate fiber bundle layer.

[0060] The invention discloses a group-processed polylactic acid fiber filter rod and a preparation method thereof. The arrangement is simple and the properties of the polylactic acid raw material are strictly controlled so that all outer skins have a uniform crystallinity, all inner cores also have a uniform crystallinity, and the nodes are evenly distributed when the filament bundle is crystallized. The inner and outer sides of the prepared polylactic acid fiber filter rod have a gradual crystallinity, the processing process is more stable, and the adsorption performance of the filter rod is guaranteed.

[0061] 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 group-processed polylactic acid fiber filter rod, characterized in that: The invention comprises an inner core (1) and an outer skin (2) arranged outside the inner core (1), wherein the inner core (1) and the outer skin (2) are both composited from a plurality of polylactic acid fiber bundles, the polylactic acid fiber bundles in the inner core (1) are prepared from a first component raw material, and the polylactic acid fiber bundles in the outer skin (2) are prepared from a second component raw material, the content of L-lactic acid monomers in the first component raw material is higher than the content of L-lactic acid monomers in the second component raw material, and a dispersant is added to the first component raw material, and triacetin is added to the second component raw material; the polylactic acid fiber bundles in the inner core (1) are prepared by drawing stress-induced crystallization, so as to improve the crystallinity of the polylactic acid fiber bundles in the inner core (1); Obtaining polylactic acid having a left-handed isomer content of a first predetermined value, adding a dispersant to obtain a first component raw material, inducing crystallization through drawing stress during spinning of the first component raw material, and obtaining a first polylactic acid fiber tow, wherein the first polylactic acid fiber tow has a higher degree of crystallinity and is not prone to forming large nodes, and is convenient for slitting; Obtaining polylactic acid having a left-handed isomer content of a second predetermined value, adding triacetin to obtain a second component raw material, spinning the second component raw material to obtain a second polylactic acid fiber tow having more swelling performance and bonding performance; The second predetermined value is not higher than the first predetermined value; A plurality of first polylactic acid fiber bundles are compounded to form an inner core, a plurality of second polylactic acid fiber bundles are compounded to form an outer skin, and the outer skin is coated on the outer side of the inner core to form a skin-core type polylactic acid fiber filter rod.

2. The group-processed polylactic acid fiber filter rod according to claim 1, characterized in that: The ratio of the number of polylactic acid fiber bundles in the inner core (1) and the outer skin (2) is in the range of 30:70 to 35:

65.

3. The group-processed polylactic acid fiber filter rod according to claim 1, characterized in that: Nucleating agents are added to both the first component raw material and the second component raw material, and the content of the nucleating agent in the first component raw material is not less than the content of the nucleating agent in the second component raw material.

4. The polylactic acid fiber filter rod processed in groups according to claim 1, characterized in that: A transition layer (3) is provided between the inner core (1) and the outer skin (2), the transition layer being composited from a plurality of polylactic acid fiber bundles, and the content of L-lactic acid monomers in the component raw materials used in the polylactic acid fiber bundles in the transition layer (3) is not higher than the content of L-lactic acid monomers in the first component raw material and is not lower than the content of L-lactic acid monomers in the second component raw material.

5. The group-processed polylactic acid fiber filter rod according to claim 4, characterized in that: The number of the transition layers (3) is at least two, and the content of L-lactic acid monomer in the component raw material used for the polylactic acid fiber bundles of the transition layer (3) close to the inner core (1) is not lower than the content of L-lactic acid monomer in the component raw material used for the polylactic acid fiber bundles of the transition layer (3) close to the outer skin (2).

6. The group-processed polylactic acid fiber filter rod according to claim 4, characterized in that: The component raw material used for the polylactic acid fiber bundle of the transition layer (3) also has a nucleating agent added thereto, and the content of the nucleating agent in the component raw material is not higher than the content of the nucleating agent in the first component raw material and not lower than the content of the nucleating agent in the second component raw material.

7. The group-processed polylactic acid fiber filter rod according to claim 1, characterized in that: A acetate fiber bundle layer (4) is arranged on the outside of the outer skin (2).

8. The method for preparing a group-processed polylactic acid fiber filter rod according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: obtaining polylactic acid having a left-handed isomer content of a first predetermined value, adding a dispersant to obtain a first component raw material, and inducing crystallization by drawing stress during spinning of the first component raw material to obtain a first polylactic acid fiber tow; S2: obtaining polylactic acid with a left-handed isomer content of a second predetermined value, adding triacetin to obtain a second component raw material, and spinning the second component raw material into a second polylactic acid fiber tow; the second predetermined value is lower than the first predetermined value; S3: Compounding a plurality of first polylactic acid fiber bundles to form an inner core, compounding a plurality of second polylactic acid fiber bundles to form an outer skin, and covering the outer skin on the outer side of the inner core to form a skin-core type polylactic acid fiber filter rod.

9. The method for preparing a group-processed polylactic acid fiber filter rod according to claim 8, characterized in that: Before executing step S3, polylactic acid having a left-handed isomer content of a third predetermined value is obtained to obtain a third polylactic acid fiber tow, and a plurality of the third polylactic acid fiber tows are compounded to form a transition layer; When executing step S3, the transition layer is coated on the outer side of the inner core layer, and then the outer skin layer is coated on the outer side of the transition layer.

10. The method for preparing a group-processed polylactic acid fiber filter rod according to claim 8, characterized in that: After executing step S3, the outer side of the outer skin is covered with an acetate fiber bundle layer.

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