Composite hollow filter rod and method for manufacturing the same

Abstract

The application provides a composite hollow filter rod and a preparation method thereof, and relates to the technical field of hollow filter rods.The composite hollow filter rod comprises a cellulose acetate part and a polylactic acid part arranged on the inner side of the cellulose acetate part.The cellulose acetate part has a ring structure, and the outer diameter of the polylactic acid part is equal to the inner diameter of the cellulose acetate part.The polylactic acid part is provided with a hollow hole.The cellulose acetate part is formed by curing cellulose acetate filaments under the action of high-temperature steam.The polylactic acid part is formed by curing polylactic acid filaments under the action of heated air.The application has the advantages of simple structure, the combination of the outer cellulose acetate part and the inner polylactic acid part to form the hollow filter rod, the effective use of heated air to effectively form the polylactic acid part, the increase of the decomposition characteristics of polylactic acid in the polylactic acid part, the reduction of pollution, low raw material cost, the easy processing of polylactic acid, and the beauty and practicality of the hollow filter rod.

Description

Technical Field

[0001] This invention relates to the field of hollow filter rod technology, and in particular, to a composite hollow filter rod and its preparation method. Background Technology

[0002] With the continuous development of cigarette production technology, cigarette types and appearances have become more diversified. Cigarettes with unique shapes are more likely to be favored by people, thus giving rise to a new type of filter rod: the hollow filter rod.

[0003] The production of hollow filter rods using cellulose acetate tow is a relatively mature technology. For example, Chinese invention patent CN111436650A discloses a method for preparing a hollow cooling filter rod, composed of tow, cooling material, and curing agent. It is manufactured using a high-temperature steam-accelerated curing process on a hollow filter rod forming machine with appropriate molds. The outer solid part of the filter rod is a smooth cylindrical structure with a certain degree of elasticity and hardness, suitable for cigarette packing. The inner hollow part has a straight-through cavity structure similar to a corrugated pipe, providing good heat transfer and cooling effects when smoke passes through it. Because of the straight-through structure in the middle of the filter rod, it also results in very low draw resistance. When used in new tobacco products, it more than doubles the amount of cigarette atomization while cooling, satisfying the smoker's experience and providing a new solution for improving cigarette quality and developing new tobacco products.

[0004] Polylactic acid (PLA) is a polymer material produced by fermenting starch from renewable plant resources to obtain lactic acid, which is then chemically synthesized. It possesses excellent recyclability and biodegradability, exhibiting the following characteristics: 1. It uses renewable plant resources (corn, wheat, sugar beets, rice, potatoes, sweet potatoes, etc.) and organic waste (corn cobs or roots, stems, leaves, peels, etc. from other crops) as raw materials, eliminating dependence on wood and petroleum resources and meeting the requirements of sustainable development; 2. It is completely biodegradable, naturally decomposing into water and carbon dioxide in the natural environment over time, without causing environmental pollution. The generated carbon dioxide is reused through plant photosynthesis, forming a perpetual, closed carbon cycle system, making it a truly "green material"; 3. Compared to the three major synthetic fibers—polyester, nylon, and acrylic—the production of PLA fiber consumes less energy, making it a polymer material with relatively low resource and environmental impact; 4. It has good processing performance and can be produced as tow using general thermoplastic resin melt spinning methods.

[0005] Because polylactic acid (PLA) has the advantages of being inexpensive, easily degradable, and pollution-free compared to cellulose acetate, research on the preparation of PLA filter rods is very important. However, the current technology for producing hollow tube filter rods using PLA filament bundles is indeed lacking.

[0006] The production of hollow filter rods from cellulose acetate tow is carried out by rapid curing with steam heating. However, hollow filter rods are usually round holes. During the molding process, by selecting mandrels of different shapes, hollow filter rods of various special shapes can be made. If steam heating is used for molding, steam condensation is likely to occur at the bends of special shapes, causing unevenness in the hollow hole walls and making the filter rod shape more irregular.

[0007] Moreover, polylactic acid (PLA) is a thermoplastic aliphatic polyester with a low glass transition temperature. Under high temperature conditions, it will become rigid and thermally collapse. In the early stages of producing hollow filter rods using PLA filaments, steam heating was also used to test the production of filter rods. However, the steam temperature was too high, the effect was not good, the filter rods were irregular in shape, and normal production could not be achieved.

[0008] Therefore, in order to solve the above problems, it is necessary for us to design a reasonable and efficient composite hollow filter rod. Summary of the Invention

[0009] The purpose of this invention is to provide a composite hollow filter rod with a simple structure. It uses an outer cellulose acetate part and an inner polyfiber part to form a hollow filter rod. It not only effectively uses heated air to form the polyfiber part, but also increases the polylactic acid in the polyfiber part, which is easy to decompose, thus reducing the amount of pollution. It also has low raw material cost. By utilizing the easy processing properties of polylactic acid, the hollow filter rod is more beautiful and practical.

[0010] To achieve the above objectives, the present invention employs the following technical solution:

[0011] A composite hollow filter rod includes an acetate fiber section and a polyfiber section disposed inside the acetate fiber section;

[0012] The cellulose acetate section has a ring structure, the outer diameter of the polyfiber section is equal to the inner diameter of the cellulose acetate section, and the polyfiber section is provided with a hollow hole;

[0013] The acetate fiber section is formed by solidifying acetate fiber bundles under high-temperature steam heating.

[0014] The polyfiber section is formed by curing polylactic acid fiber bundles under the heating of heated air.

[0015] As a preferred embodiment of the present invention, a forming paper is provided on the outer side of the acetate fiber portion.

[0016] As a preferred embodiment of the present invention, the inner wall of the forming paper is coated with an activated carbon layer.

[0017] As a preferred embodiment of the present invention, the hollow hole shape includes heart-shaped, square, circular, and plum blossom-shaped.

[0018] As a preferred embodiment of the present invention, the number of hollow holes is at least one.

[0019] As a preferred embodiment of the present invention, the polylactic acid fiber bundle has a core-sheath type bundle structure.

[0020] As a preferred embodiment of the present invention, the content of L-lactic acid monomer in the raw material for preparing polylactic acid fiber tow is not less than 90%.

[0021] This invention also provides a method for preparing a composite hollow filter rod, comprising the following steps:

[0022] S1: Insert the first inner core into the molding cavity;

[0023] S2: The cellulose acetate bundle is fed into the molding cavity, steam is injected into the molding cavity, and the cellulose acetate bundle is heated and solidified to obtain the cellulose acetate part;

[0024] S3: After the acetate fiber section cools down, the first inner core is pulled out and the second inner core is inserted into the molding cavity;

[0025] S4: The polylactic acid fiber bundle is fed into the inner side of the acetate section in the molding cavity, heated air is introduced into the molding cavity, and the polylactic acid fiber bundle is heated and cured to obtain the polylactic acid fiber section.

[0026] As a preferred embodiment of the present invention, when performing step S2, the temperature range of the introduced steam is 140°C to 170°C;

[0027] When performing step S4, the temperature of the heated air is in the range of 65°C to 85°C.

[0028] As a preferred embodiment of the present invention, when performing step S3, the outer diameter of the second inner core is smaller than the outer diameter of the first inner core.

[0029] The beneficial effects of the composite hollow filter rod and its preparation method of the present invention are as follows: the structure is simple, and the hollow filter rod is formed by combining the outer cellulose acetate part and the inner polyfiber part. It not only effectively uses heated air to form the polyfiber part, but also increases the polylactic acid in the polyfiber part to make it easy to decompose, thereby reducing the amount of pollution. Moreover, the raw material cost is low. The easy processing characteristics of polylactic acid make the hollow filter rod more beautiful and practical. Attached Figure Description

[0030] Figure 1 This is a cross-sectional schematic diagram of an embodiment of a composite hollow filter rod according to the present invention;

[0031] Figure 2 This is a cross-sectional schematic diagram of another embodiment of a composite hollow filter rod according to the present invention;

[0032] Figure 3 This is a schematic flowchart of a method for preparing a composite hollow filter rod according to the present invention.

[0033] In the figure: 1. Acetate fiber section, 11. Forming paper, 12. Activated carbon layer, 2. Polyfiber section, 21. Hollow pore. Detailed Implementation

[0034] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0035] 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 the modules and steps set forth in these embodiments do not limit the scope of the invention.

[0036] At the same time, it should be understood that, for ease of description, the process shown in the attached diagram is not performed in isolation, but rather involves multiple steps that overlap.

[0037] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0038] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0039] Techniques, methods, and systems known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of this specification.

[0040] Example 1: As Figure 1 As shown, a composite hollow filter rod includes an acetate fiber section 1 and a polyfiber section 2 disposed inside the acetate fiber section 1.

[0041] The cellulose acetate section 1 has an annular structure, the outer diameter of the polyfiber section 2 is equal to the inner diameter of the cellulose acetate section 1, and the polyfiber section 2 is provided with a hollow hole 21.

[0042] The acetate fiber section 1 is formed by solidifying acetate fiber bundles under high-temperature steam heating;

[0043] The polylactic acid fiber section 2 is formed by curing polylactic acid fiber bundles under the heating of heated air.

[0044] In this invention, a hollow filter rod can be prepared by adopting a structure in which the outer side is a cellulose acetate section 1 and the inner side is a polyfiber section 2. In this way, the cellulose acetate section 1 on the outer side has a mature process, and the polyfiber section 2 on the inner side can effectively reduce pollution, use inexpensive raw materials, and improve the smoking experience.

[0045] The thermoforming process for cellulose acetate section 1 is relatively well-established, involving the curing and molding of cellulose acetate filament bundles under high-temperature steam heating. However, the thermoforming process for polylactic acid is severely lacking. Since most cellulose acetate hollow filter rods are heated by steam, with steam temperatures reaching over 170°C, and polylactic acid is a thermoplastic aliphatic polyester with a low glass transition temperature, it will stiffen and thermally collapse under high-temperature conditions. Therefore, the molding effect of polylactic acid hollow filter rods using high-temperature steam heating is extremely poor.

[0046] After numerous experiments and summaries, it was found that the heating temperature required for the preparation of polylactic acid hollow filter rods is less than 100℃, as steam will condense into water, making steam heating unsuitable. Therefore, heating air was used to heat the polylactic acid fiber bundles, which were then solidified and formed.

[0047] Pure air is heated to a predetermined temperature and then brought into contact with polylactic acid fiber bundles that have been opened and fed into the molding unit. The polylactic acid fiber bundles are heated and cured to produce polylactic acid filter rods.

[0048] In this way, the outer cellulose acetate section 1 is formed by high-temperature steam heating, and the inner polyfiber section 2 is formed by hot air heating, thus obtaining a composite hollow filter rod.

[0049] It is best to use a molding preparation device to mold the above-mentioned composite hollow filter rod. The molding preparation device mainly includes a molding cavity, and an inner core is provided in the molding cavity. When the first inner core is inserted into the molding cavity, the opened cellulose acetate bundle is fed into the molding cavity, steam is filled into the molding cavity, and the cellulose acetate bundle is heated and cured to obtain the cellulose acetate part; then the first inner core is pulled out, a thinner second inner core is inserted, the opened polylactic acid fiber bundle is sent into the inner side of the cellulose acetate part in the molding cavity, heated air is filled into the molding cavity, and the polylactic acid fiber bundle is heated and cured to obtain the polylactic acid fiber part;

[0050] After the entire polyfiber section has cooled down, the second inner core is extracted, and the composite hollow filter rod is taken out.

[0051] The parameters for opening and forming during the preparation of acetate fiber section 1 are as follows:

[0052] Table 1.1 Main process parameters for the production of cellulose acetate filter rods

[0053]

[0054] The preparation process of the above cellulose acetate filter rods is already very mature.

[0055] Furthermore, when preparing the polyfiber part 2, the air arriving at the molding cavity needs to be pure and at a predetermined temperature. Therefore, the air needs to be filtered first to ensure that it meets the pure air standard. Then, the pure air is heated and input into the molding cavity.

[0056] The aforementioned predetermined temperature, which is the heating temperature of polylactic acid, and also the temperature range of the air reaching the molding cavity after heating, is 65°C to 85°C.

[0057] The experiment investigated the effects of different hot air temperatures on filter rod molding production, as well as the physical properties and appearance of the filter rods. The results are as follows:

[0058] Table 2.1 Effect of different hot air temperatures on polylactic acid molding (24.0 mm × 120 mm)

[0059]

[0060] In other words, when using polylactic acid (PLA) filaments to produce hollow filter rods, production is poor when the hot air temperature is below 60°C because the filter rods cannot solidify quickly during the molding process. This results in deformed filter rods with poor roundness and low hardness. Production is normal when the hot air temperature is between 65°C and 85°C, and the filter rod specifications and appearance meet the requirements. However, when the hot air temperature exceeds 90°C, production deteriorates, and the roundness and concentricity of the filter rods worsen. Therefore, a hot air temperature of 65°C to 85°C is suitable for producing hollow filter rods, as this temperature is significantly lower than the high-temperature steam temperature used in the preparation of cellulose acetate filter rods.

[0061] It should be noted that the polylactic acid fiber tow feed specification at the molding cavity is preferably 30000d×2~33000d×2 (equivalent to 60000~66000d).

[0062] The experiment investigated the effects of different hot air temperatures on filter rod molding production, as well as the physical properties and appearance of the filter rods. The results are as follows:

[0063] Table 1.2 Forming of polylactic acid (PLA) tows with different total deniers (24.0 mm × 120 mm)

[0064] In other words, when using polylactic acid (PLA) tow to produce conventional hollow filter rods, production is poor when the total denier of the tow is below 26,000 d × 2 (i.e., 52,000 denier), resulting in poor roundness and low hardness of the filter rods. Production is normal when the total denier is between 30,000 d × 2 and 33,000 d × 2 (equivalent to 60,000 to 66,000 d), and the filter rod specifications and appearance meet requirements. When the total denier exceeds 35,000 d × 2 (i.e., 70,000 d), production deteriorates, and the filter rod specifications fluctuate more significantly. Therefore, for producing conventional hollow filter rods, a PLA tow specification of 30,000 d × 2 to 33,000 d × 2 (equivalent to 60,000 to 66,000 d) is suitable.

[0065] Furthermore, in the process of preparing polylactic acid hollow filter rods, an application port for applying triacetin is set at the molding cavity, and triacetin needs to be applied to the polylactic acid fiber bundles to improve the molding effect.

[0066] The experiment investigated the effects of different amounts of triacetylglycerol applied on the production of filter rods, as well as the physical properties and appearance of the filter rods. The results are as follows:

[0067] Table 1.3 Effect of different triacetylglycerol application amounts on molding (24.0 mm × 120 mm)

[0068]

[0069]

[0070] In other words, when using polylactic acid (PLA) tow to produce hollow filter rods, production is acceptable when the triacetin content is below 10%, but the filter rods are not well-formed and have low hardness. When the triacetin content is between 12% and 16%, production is normal, and the filter rod specifications and appearance meet the requirements. When the triacetin content exceeds 18%, production deteriorates, and the filter rod specifications fluctuate more significantly. Therefore, a triacetin content of 12% to 16% is suitable for producing PLA hollow filter rods.

[0071] The present invention discloses a composite hollow filter rod and its preparation method. The structure is simple, using an outer cellulose acetate part and an inner polyfiber part to form a hollow filter rod. It not only effectively uses heated air to shape the polyfiber part, but also increases the polylactic acid in the polyfiber part to make it easily decomposed, thus reducing the amount of pollution. Moreover, the raw material cost is low. The easy processing characteristics of polylactic acid make the hollow filter rod more beautiful and practical.

[0072] Example 2, as Figure 1 , 2As shown, this is only one embodiment of the present invention. Based on the first embodiment, in a composite hollow filter rod of the present invention, a forming paper 11 is provided on the outside of the cellulose acetate part 1 for further covering and shielding after the cellulose acetate part 1 is formed.

[0073] Furthermore, the inner wall of the forming paper 11 is coated with an activated carbon layer 12, which can effectively filter a certain amount of flue gas in the smoke generation section and prevent impurities in the air outside the filter rod from entering the filter rod.

[0074] Furthermore, the hollow hole 21 can be heart-shaped, square, round, or plum blossom-shaped; more precisely, the cross-sectional shape of the second inner core can be heart-shaped, five-pointed star-shaped, round, or plum blossom-shaped, or even other irregular structures, so that the polylactic acid fiber filter rod has hollow holes 21 of the corresponding shape.

[0075] Obviously, the number of hollow holes 21 is at least one, that is, the hollow holes in the fiber section 2 can be provided in multiple ways.

[0076] Finally, the polylactic acid fiber bundle has a core-sheath type structure. The content of L-lactic acid monomer in the raw material for preparing the polylactic acid fiber bundle is not less than 90%, which ensures the crystallinity of the polylactic acid fiber and the high thermal stability of the bundle size. Triacetin can also be added to the polylactic acid raw material. Under the action of triacetin, the bundle swells and bonds, resulting in a well-bonded core-sheath type polylactic acid fiber bundle.

[0077] It should be noted that the first inner core is first inserted into the molding cavity for heating and molding of the acetate fiber portion. After the temperature drops, the second inner core is then inserted into the molding cavity for heating and molding of the polylactic acid fiber portion.

[0078] Here, the second inner core is a hollow cavity, and a first through hole is provided on the outer wall of the second inner core. The second inner core is a channel for heating air to enter, and then passes through the first through hole to reach the molding cavity to heat the polyfiber part 2.

[0079] Of course, the first inner core is a cylindrical part with a dense structure.

[0080] In this way, when the first inner core is inserted into the molding cavity for heating and molding of the cellulose acetate portion, the cellulose acetate portion can be understood as a concentric ring structure, and steam will not accumulate water droplets at the bends, affecting the molding effect; conversely, when the second inner core is inserted into the molding cavity for heating and molding of the polylactic acid fiber portion, since pure air is introduced, there is no concern about any air accumulation at the irregularly shaped second inner core, and the molding effect can still be guaranteed.

[0081] Example 3, as Figure 3As shown, the present invention also provides a method for preparing a composite hollow filter rod in all the above embodiments, comprising the following steps:

[0082] S1: Insert the first inner core into the molding cavity;

[0083] S2: The opened cellulose acetate bundle is fed into the molding cavity, steam is injected into the molding cavity, and the cellulose acetate bundle is heated and solidified to obtain the cellulose acetate part.

[0084] S3: After the acetate fiber section cools down, the first inner core is pulled out and the second inner core is inserted into the molding cavity;

[0085] S4: The opened polylactic acid fiber bundle is fed into the inner side of the acetate fiber section in the molding cavity, heated air is injected into the molding cavity, and the polylactic acid fiber bundle is heated and cured to obtain the polylactic acid fiber section.

[0086] S5: After the polyfiber section cools down, pull out the second inner core and remove the composite hollow filter rod.

[0087] Here, when performing step S2, the temperature range of the introduced steam is 140°C to 170°C;

[0088] Correspondingly, the temperature range of the heated air is 65°C to 85°C.

[0089] Furthermore, during step S3, the outer diameter of the second inner core is smaller than the outer diameter of the first inner core.

[0090] The present invention discloses a composite hollow filter rod and its preparation method. The structure is simple, using an outer cellulose acetate part and an inner polyfiber part to form a hollow filter rod. It not only effectively uses heated air to shape the polyfiber part, but also increases the polylactic acid in the polyfiber part to make it easily decomposed, thus reducing the amount of pollution. Moreover, the raw material cost is low. The easy processing characteristics of polylactic acid make the hollow filter rod more beautiful and practical.

[0091] This invention is not limited to the specific embodiments described above, and various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made to the above embodiments based on the technical essence of this invention should be included within the scope of protection of this invention.

Claims

1. A composite hollow filter rod, characterized by: It includes an acetate fiber portion (1) and a polyfiber portion (2) disposed inside the acetate fiber portion (1). The cellulose acetate section (1) has an annular structure, the outer diameter of the polyfiber section (2) is equal to the inner diameter of the cellulose acetate section (1), and the polyfiber section (2) is provided with a hollow hole (21). The cellulose acetate section (1) is formed by solidifying cellulose acetate bundles under high-temperature steam heating; The polyfiber section (2) is formed by curing polylactic acid fiber bundles under the heating of heated air; The preparation method of the composite hollow filter rod includes the following steps: S1: Insert the first inner core into the molding cavity; S2: The cellulose acetate bundle is fed into the molding cavity, steam is injected into the molding cavity, and the cellulose acetate bundle is heated and solidified to obtain the cellulose acetate part; S3: After the acetate fiber section cools down, the first inner core is pulled out and the second inner core is inserted into the molding cavity; S4: The polylactic acid fiber bundle is fed into the inner side of the acetate section in the molding cavity, heated air is introduced into the molding cavity, and the polylactic acid fiber bundle is heated and cured to obtain the polylactic acid fiber section.

2. A composite hollow filter rod according to claim 1, characterised in that: A forming paper (11) is provided on the outside of the acetate fiber part (1).

3. A composite hollow filter rod according to claim 2, characterised in that: The inner wall of the forming paper (11) is coated with an activated carbon layer (12).

4. A composite hollow filter rod as defined in claim 1, characterized by: The hollow hole (21) has shapes including heart-shaped, square, round and plum blossom-shaped.

5. A composite hollow filter rod as defined in claim 1, characterized by: The number of hollow holes (21) is at least one.

6. A composite hollow filter rod as defined in claim 1, characterized by: The polylactic acid fiber bundle has a core-sheath type structure.

7. A composite hollow filter rod as defined in claim 1, characterized by: The content of L-lactic acid monomer in the raw materials for preparing polylactic acid fiber tow is not less than 90%.

8. A composite hollow filter rod as defined in claim 1, wherein In the preparation method of the composite hollow filter rod, When performing step S2, the temperature range of the introduced steam is 140°C to 170°C; When performing step S4, the temperature of the heated air is in the range of 65°C to 85°C.

9. A composite hollow filter rod as defined in claim 1, wherein In the preparation method of the composite hollow filter rod, When performing step S3, the outer diameter of the second inner core is smaller than the outer diameter of the first inner core.

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