Method for recycling cellulose acetate

Abstract

A method for recycling cellulose acetate, which comprises the following steps: dissolving the waste tow, waste filter rod or waste mouth rod generated in the process of producing filter rod for cigarettes after removing impurities in acetic acid aqueous solution, filtering, water solution precipitation, solid-liquid separation, washing to remove the forming paper, water pine paper and TiO2, and obtaining diacetate cellulose with quality meeting the use requirements of downstream products. The present application can completely remove the residual forming paper and water pine paper and TiO2 in the prior art. The quality of cellulose acetate before and after regeneration is compared, and it is found that AV and IV fluctuate slightly, which does not affect the use, but the PV value of regenerated cellulose acetate increases greatly, which shows that filtering and washing can significantly remove residual impurities, the quality of regenerated cellulose acetate is significantly improved, and the commercial use requirements are met; the present application has a very positive effect on reducing production cost and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of cigarettes and relates to a method for recycling and reusing cellulose acetate, especially a method for recycling and reusing waste filaments, waste filter rods and waste filter tips generated during the production of cigarette filter rods. Background Technology

[0002] The tobacco industry commonly uses cellulose acetate tow (cellulose acetate tow) to make cigarette filter rods, which plays a crucial role in reducing tar and harmful substances, enhancing aroma, and preserving moisture in Chinese-style cigarettes. However, the production process of cellulose acetate tow, the processing of the tow into filter rods, and the winding of the filter rods generate a certain proportion of waste tow, waste filter rods, and waste filter tips. Statistics show that the tobacco industry generates approximately 6,000-9,000 tons of waste tow, waste filter rods, and waste filter tips annually, resulting in economic losses of approximately 250-350 million yuan.

[0003] Currently, the methods for handling these waste cellulose acetate bundles, filter rods, and filter tips include: 1. Paying for processing themselves, with most of the waste being transported to waste treatment plants for incineration, resulting in economic losses; 2. Discarding or landfilling most of the cellulose acetate bundles as waste, causing environmental pollution; 3. Selling them to waste collectors, allowing them to flow into society.

[0004] To solve this technical challenge in the industry, it is necessary to scientifically and rationally recycle and reuse waste materials such as waste tows, waste filter rods, and waste filter tips. This has positive implications for the tobacco industry, national interests, public health, social resources, and the environment.

[0005] CN1063725A reports a method for obtaining recycled filaments from waste filaments through dissolution, pressure filtration, degassing, spinning, oiling, crimping, and drying, effectively reducing waste and lowering costs. CN101864608B reports a method for obtaining recycled filaments through washing, drying, dissolution, filtration, degassing, spinning, crimping, and drying, resulting in qualified filament quality and good economic benefits. CN102704324B reports a method for peeling and separating waste filaments, then mixing them with papermaking raw materials in a specific ratio to produce recycled filter paper, which, when made into filter rods, exhibits good tar filtration effects. CN109778588A reports a method for preparing filter materials from waste filaments through degreasing, washing, drying, and then wet-laid web forming, achieving good filtration effects. CN112871970A reports a method for obtaining recycled filaments from waste filter rods through peeling, washing, acetone dissolution, pulverization, solid-liquid separation, filtration, centrifugation, and spinning, effectively removing residual paper. The inventions described above all involve reprocessing waste filaments and filter rods into filaments through dissolution and filtration to achieve recycling. These processes require the removal of the filter tip forming paper. In practice, the removal of the forming paper is not very effective. Moreover, after dissolution, the cellulose in the forming paper becomes fluffy and easily entangles with the cellulose acetate filaments. Furthermore, TiO2 in the filaments cannot be effectively removed by washing, resulting in a lot of broken ends and fly waste during the regeneration process, leading to an unsatisfactory actual recycling effect. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of this invention is to provide a new method for recycling and reusing cellulose acetate.

[0007] The technical solution of the present invention to solve the aforementioned technical problem is: a method for recycling and reusing cellulose acetate, wherein waste filaments, waste filter rods or waste nozzle rods generated during the production of cigarette filter rods are dissolved in an aqueous acetic acid solution, and after filtration, aqueous solution precipitation, solid-liquid separation and washing to remove forming paper, tipping paper and TiO2, cellulose diacetate with quality meeting the requirements of downstream products is obtained.

[0008] Furthermore, the method includes the following steps:

[0009] S1: Cut the waste filaments, waste filter rods, and nozzle rods into small pieces, and then put them into the paper stripper to remove the formed paper;

[0010] S2: Loosen the filter rod or disperse the airflow to obtain fluffy fibers;

[0011] S3: Wash the filter rod thoroughly to remove triacetin and TiO2;

[0012] S4: Dehydrate and dry the washed fibers;

[0013] S5: Use airflow to loosen the dehydrated and dried fibers a second time, and then use cyclone removal and gravity principle to further remove residual forming paper and tipping paper;

[0014] S6: Dissolve the fibers obtained after step S5 in an aqueous acetic acid solution and stir to dissolve;

[0015] S7: The acetic acid slurry obtained in step S6 is filtered to further remove residual forming paper, cork paper and TiO2. Then, precipitation, solid-liquid separation, washing and drying are performed to obtain the finished product cellulose diacetate.

[0016] Optionally, in step S1, the length of the small segments obtained by cutting the waste filaments, waste filter rods, and nozzle rods is 3-5 cm.

[0017] Optionally, in step S1, after the removal of the forming paper, the residual quality of the forming paper is controlled at 1-5%.

[0018] Optionally, in step S3, the filter rod is washed with deionized hot water through a two-stage countercurrent spiral drum washing process.

[0019] Optionally, in step S3, the temperature of the deionized water is 30-90 degrees Celsius, preferably 40-50 degrees Celsius.

[0020] Optionally, in step S3, the total washing time is approximately 30-60 minutes, preferably 40-50 minutes.

[0021] Optionally, in step S3, the mass ratio of the filter rod to deionized water, hereinafter referred to as the first solid-liquid ratio, is 1:6-1:10, preferably 1:6-1:8.

[0022] After washing in step S3, the triacetin content is less than 0.5%, the TiO2 content is preferably less than 0.5%, and the content of the forming paper and the tipping paper is less than 1%.

[0023] Optionally, in step S4, the drying temperature is 100-170 degrees Celsius, preferably 110-120 degrees Celsius.

[0024] Optionally, in step S4, the drying time is 20-60 min, preferably 30-40 min.

[0025] Optionally, in step S4, the content of triacetin after drying is less than 0.5%, preferably less than 0.1%; the content of TiO2 after drying is preferably less than 0.1%, and the content of the forming paper and the cork paper is preferably less than 0.5%.

[0026] Optionally, in step S4, the moisture content of the dried fiber is less than 5%, preferably less than 3%.

[0027] Optionally, after step S5, the residual amount of the formed paper and the tipping paper is less than 0.4%, preferably less than 0.2%.

[0028] Optionally, in step S6, the concentration of the acetic acid aqueous solution is 40-80%, preferably 55-60%.

[0029] Optionally, in step S6, the temperature of the acetic acid aqueous solution is 30-70 degrees Celsius, preferably 45-55 degrees Celsius.

[0030] Optionally, in step S6, the stirring time is 0.5-1h, preferably 0.5h.

[0031] Optionally, in step S6, the mass ratio of cellulose acetate to aqueous acetic acid solution, hereinafter referred to as the second solid-liquid ratio, is 1:2-1:10, preferably 1:4-1:6.

[0032] Optionally, in step S7, the pore size of the acetic acid slurry filtered is preferably less than 5 μm; preferably, after washing in step S7, the triacetin content is preferably less than 0.03%, the TiO2 content is preferably less than 0.04%, and the content of forming paper and tipping paper is preferably less than 0.05%; preferably, after precipitation in step S7, the triacetin content is preferably less than 0.002%, the TiO2 content is preferably less than 0.003%, and the content of forming paper and tipping paper is preferably less than 0.007%.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] 1. This invention involves second-stage opening of the dried filament bundles through airflow, followed by further removal of residual forming paper and tipping paper using cyclone removal and gravity principles, achieving deep impurity removal;

[0035] 2. In this invention, the purified fiber bundles are dissolved in an aqueous acetic acid solution. After filtration, aqueous solution precipitation, solid-liquid separation, and washing, the residual forming paper, cork paper, and TiO2 in the prior art can be completely removed. The cellulose acetate obtained after drying is of excellent quality and meets the requirements for commercial use.

[0036] 3. The present invention compares the quality of cellulose acetate before and after regeneration and finds that: before regeneration, the key indicators of cellulose acetate are AV 55.5%, IV 1.64, PV 45, 5080 5µm particles, and 10010 2µm particles; after regeneration, the key indicators of cellulose acetate are AV 55%, IV 1.62, PV 70, 280 5µm particles, and 1750 2µm particles. AV and IV fluctuate slightly and do not affect use, but the PV value increases significantly and the particle count decreases significantly. This indicates that filtration and washing can significantly remove residual impurities, and the quality of regenerated cellulose acetate is significantly improved, which is of great significance for the later use of regenerated cellulose acetate. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments.

[0038] By passing unused waste filament bundles, waste filter rods, or nozzle rods through the following key processes, the forming paper and tipping paper can be effectively removed, and the resulting cellulose diacetate meets the quality requirements of downstream spinning, plastics, and other applications.

[0039] The filter clogging value (PV) test method involves dissolving vinegar tablets in acetone to prepare a 9.5% concentration solution, then filtering the slurry with filter paper at 1.5 atmospheres, and obtaining the value based on the filtration volume.

[0040] The acetylation value (AV)% = 6000 * degree of substitution / (162 + 42 * degree of substitution), where the degree of substitution is obtained by acid-base titration.

[0041] Intrinsic viscosity (IV): The intrinsic viscosity was obtained by dissolving the acetic acid tablets in acetone to prepare a 0.25% concentration solution and measuring it using an Ubbelohde viscometer.

[0042] Particle count: Dissolve the vinegar tablets in acetone to prepare a 3.0% concentration solution, and detect the particle count using a particle counter.

[0043] Example 1

[0044] 1. Cut waste filaments, waste filter rods, and nozzle rods into 3cm lengths, then put them into a paper peeler to remove the formed paper and tipping paper, leaving 1% paper residue;

[0045] 2. Loosen the filter rod or disperse the airflow;

[0046] 3. Wash the filter rod countercurrently with 50-degree deionized hot water for a total washing time of about 40 minutes to remove triacetin, TiO2, etc. The first solid-liquid ratio is 1:8.

[0047] 4. Centrifuge the filter rod to remove water, and dry it at 120 degrees Celsius for 30 minutes; after drying, the triacetin content is 0.5%, the TiO2 content is 0.4%, and the moisture content is 3%.

[0048] 5. Use airflow to open the paper a second time, and then use gravity difference and cyclone to remove the remaining forming paper and tipping paper. At this time, the paper residue is 0.24%.

[0049] 6. Dissolve the separated fiber bundles in a 60% acetic acid aqueous solution and stir at 50 degrees Celsius for 1 hour. The second solid-liquid ratio is 1:5.

[0050] 7. Filter the cellulose acetate slurry to remove residual forming paper, cork paper, and TiO2, then precipitate, separate the solid and liquid, wash, and dry to obtain the finished cellulose diacetate. Control the time from when the cellulose tow dissolves in the acetic acid aqueous solution to when the cellulose acetate flakes precipitate to within 3 hours to avoid a decrease in the viscosity and acetic acid flakes due to excessive time.

[0051] 8. Tested relevant indicators: AV54.5%, PV51, IV1.58, 5um particle count 2811, 2um particle count 4479, triacetin content 0.024%, TiO2 content 0.025%, paper content 0.018%.

[0052] Example 2

[0053] 1. Cut waste filaments, waste filter rods, and nozzle rods into 5cm lengths, then put them into a paper peeler to remove the formed paper and tipping paper, leaving 5% paper residue;

[0054] 2. Loosen the filter rod or disperse the airflow;

[0055] 3. Wash the filter rod countercurrently with 50-degree deionized hot water for a total washing time of about 40 minutes to remove triacetin, TiO2, etc. The first solid-liquid ratio is 1:8.

[0056] 4. Centrifuge the filter rod to remove water, and dry it at 120 degrees Celsius for 30 minutes; after drying, the triacetin content is 0.5%, the TiO2 content is 0.4%, and the moisture content is 3%.

[0057] 5. Use airflow to open the paper a second time, and then use gravity difference and cyclone to remove the remaining forming paper and tipping paper. At this time, the paper residue is 0.9%.

[0058] 6. Dissolve the separated fiber bundles in a 60% acetic acid aqueous solution and stir at 50 degrees Celsius for 1 hour. The second solid-liquid ratio is 1:5.

[0059] 7. Filter the cellulose acetate slurry to remove residual forming paper, cork paper and TiO2, and then perform precipitation, solid-liquid separation, washing and drying to obtain the finished cellulose diacetate.

[0060] 8. Tested relevant indicators: AV55.1%, PV8, IV1.61, 5um particle number 6645, 2um particle number 18722, triacetin content 0.021%, TiO2 content 0.029%, paper content 0.34%.

[0061] Example 3

[0062] 1. Cut waste filaments, waste filter rods, and nozzle rods into 5cm lengths, then put them into a paper peeler to remove the formed paper and tipping paper, leaving 1.2% paper residue;

[0063] 2. Loosen the filter rod or disperse the airflow;

[0064] 3. Wash the filter rod countercurrently with 50-degree deionized hot water for a total washing time of about 40 minutes to remove triacetin, TiO2, etc. The first solid-liquid ratio is 1:8.

[0065] 4. Centrifuge the filter rod to remove water, and dry it at 120 degrees Celsius for 30 minutes. After drying, the triacetin content is 0.5%, the TiO2 content is 0.4%, and the moisture content is 2.5%.

[0066] 5. Use airflow to open the paper a second time, and then use gravity difference and cyclone to remove the remaining forming paper and tipping paper. At this time, the paper residue is 0.05%.

[0067] 6. Dissolve the separated fiber bundles in a 60% acetic acid aqueous solution and stir at 50 degrees Celsius for 1 hour. The second solid-liquid ratio is 1:5.

[0068] 7. Filter the cellulose acetate slurry to remove residual forming paper, cork paper and TiO2, and then perform precipitation, solid-liquid separation, washing and drying to obtain the finished cellulose diacetate.

[0069] 8. Tested relevant indicators: AV55.0%, PV61, IV1.62, 5µm particle count 289, 2µm particle count 1850, triacetin content 0.018%, TiO2 content 0.022%, paper content 0.011%.

[0070] Example 4

[0071] 1. Cut waste filaments, waste filter rods, and nozzle rods into 5cm lengths, then put them into a paper peeler to remove the formed paper and tipping paper, leaving 0.3% paper residue;

[0072] 2. Loosen the filter rod or disperse the airflow;

[0073] 3. Wash the filter rod countercurrently with 50-degree deionized hot water for a total washing time of about 40 minutes to remove triacetin, TiO2, etc. The first solid-liquid ratio is 1:8.

[0074] 4. Centrifuge the filter rod to remove water, and dry it at 120 degrees Celsius for 30 minutes; after drying, the triacetin content is 0.47%, the TiO2 content is 0.37%, and the moisture content is 2.8%.

[0075] 5. Use airflow to open the paper a second time, and then use gravity difference and cyclone to remove the remaining forming paper and tipping paper. At this time, the paper residue is 0.1%.

[0076] 6. Dissolve the separated fiber bundles in a 60% acetic acid aqueous solution and stir at 50 degrees Celsius for 1 hour. The second solid-liquid ratio is 1:5.

[0077] 7. Filter the cellulose acetate slurry to remove residual forming paper, cork paper and TiO2, and then perform precipitation, solid-liquid separation, washing and drying to obtain the finished cellulose diacetate.

[0078] 8. Test relevant indicators: AV55.1%, PV70, IV1.62, 5um particle number 280, 2um particle number 1750, triacetin content 0.01%, TiO2 content 0.019%, paper content 0.009%.

[0079] As can be seen from the above embodiments, when comparing the quality of cellulose acetate before and after regeneration using the method of cellulose acetate recycling of the present invention, on the one hand, AV and IV fluctuate slightly, which does not affect the use; on the other hand, PV value increases significantly, indicating that filtration and washing can significantly remove residual impurities, thus significantly improving the quality of regenerated cellulose acetate.

[0080] The foregoing descriptions and embodiments are provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be easily made to these contents, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the foregoing descriptions and embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from its scope should be within the protection scope of the present invention.

Claims

1. A method for recycling and reusing cellulose acetate, characterized in that: The waste fiber bundles, waste filter rods, or waste nozzle rods generated during the production of cigarette filter rods are dissolved in an acetic acid aqueous solution. After filtration, aqueous solution precipitation, solid-liquid separation, and washing to remove forming paper, tipping paper, and TiO2, cellulose diacetate is obtained that meets the quality requirements of downstream products. Before dissolving the impurity-removed fiber bundles in the acetic acid aqueous solution, they are thoroughly washed, and then the dehydrated and dried fibers are loosened a second time using airflow. Residual forming paper and tipping paper are further removed using cyclone removal and gravity principles. This process includes the following steps: S1: Cut the waste filaments, waste filter rods, and nozzle rods into small pieces, and then put them into the paper stripper to remove the formed paper; S2: Loosen the filter rod or disperse the airflow to obtain fluffy fibers; S3: Wash the filter rod thoroughly to remove triacetin and TiO2; S4: Dehydrate and dry the washed fibers; S5: Use airflow to loosen the dehydrated and dried fibers a second time, and then use cyclone removal and gravity principle to further remove residual forming paper and tipping paper; S6: Dissolve the fibers obtained after step S5 in an aqueous acetic acid solution and stir to dissolve; S7: The acetic acid slurry obtained in step S6 is filtered to further remove residual forming paper, cork paper and TiO2. Then, precipitation, solid-liquid separation, washing and drying are performed to obtain the finished cellulose diacetate. In step S6, the concentration of the acetic acid aqueous solution is 40-80%; the temperature of the acetic acid aqueous solution is 30-70 degrees Celsius; the stirring time is 0.5-1 hour; and the mass ratio of cellulose acetate to acetic acid aqueous solution is 1:2-1:

10. After washing in step S7, the triacetin content is less than 0.03%, the TiO2 content is less than 0.04%, and the content of forming paper and tipping paper is less than 0.05%.

2. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S1, the waste filaments, waste filter rods, and nozzle rods are cut into segments with a length of 3-5 cm.

3. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S1, after the removal of the forming paper, the residual quality of the forming paper is controlled at 1-5%.

4. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S3, the filter rod is washed with deionized hot water through a first-stage countercurrent spiral drum washing process.

5. The method for recycling and reusing cellulose acetate according to claim 4, characterized in that: The temperature of the deionized hot water is 30-90 degrees Celsius.

6. The method for recycling and reusing cellulose acetate according to claim 4, characterized in that: The temperature of the deionized hot water is 40-50 degrees Celsius.

7. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: After washing in step S3, the triacetin content is less than 0.5%, the TiO2 content is less than 0.5%, and the content of forming paper and tipping paper is less than 1%.

8. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S3, the total washing time is 30-60 minutes.

9. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S3, the total washing time is 40-50 minutes.

10. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S3, the mass ratio of the filter rod to deionized water is 1:6 to 1:

10.

11. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S3, the mass ratio of the filter rod to deionized water is 1:6 to 1:

8.

12. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S4, the drying temperature is 100-170 degrees Celsius.

13. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S4, the drying temperature is 110-120 degrees Celsius.

14. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S4, the drying time is 20-60 minutes.

15. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S4, the drying time is 30-40 minutes.

16. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S4, the content of triacetin after drying is less than 0.5%.

17. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S4, the content of triacetin after drying is less than 0.1%.

18. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S4, the TiO2 content after drying is less than 0.1%, and the content of the formed paper and the cork paper is less than 0.5%.

19. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S4, the moisture content of the dried fiber is less than 5%.

20. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S4, the moisture content of the dried fiber is less than 3%.

21. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: After step S5, the residual amount of the formed paper and tipping paper is less than 0.4%.

22. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: After step S5, the residual amount of the formed paper and tipping paper is less than 0.2%.

23. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S6, the concentration of the acetic acid aqueous solution is 55-60%.

24. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S6, the temperature of the acetic acid aqueous solution is 45-55 degrees Celsius.

25. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S6, the stirring time is 0.5 hours.

26. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S6, the mass ratio of cellulose acetate to aqueous acetic acid solution is 1:4 to 1:

6.

27. The method for recycling and reusing cellulose acetate according to claim 1, characterized in that: In step S7, the pore size of the acetic acid slurry is less than 5 μm.

28. The method for recycling and reusing cellulose acetate according to claim 2, characterized in that: After precipitation in step S7, the triacetin content is less than 0.002%.

29. The method for recycling and reusing cellulose acetate according to claim 2, characterized in that: After precipitation in step S7, the TiO2 content is less than 0.003%.

30. The method for recycling and reusing cellulose acetate according to claim 2, characterized in that: After precipitation in step S7, the content of the formed paper and tipping paper is less than 0.007%.