A method for recovering cellulose diacetate from waste filter rods for cigarettes

Abstract

The application discloses a method for recycling cellulose diacetate in waste filter rods for cigarettes, and sequentially comprises the following steps: A, surface humidification; B, sectioning; C, low-shear paper stripping; D, separation of forming paper; E, microwave heating-high-speed airflow blowing to remove glycerol triacetate; F, preparation of a high liquid-solid ratio solution; G, standing and discharge of precipitate; H, secondary dissolution and concentration; I, fractional filtration; and J, spinning. The method reduces impurities in the spinning slurry during the recycling process, simplifies the subsequent filtration link, and can efficiently and conveniently implement the waste filter rod recycling of the filament bundle.

Description

Technical Field

[0001] This invention belongs to the field of cellulose acetate recycling, processing and testing technology, and specifically relates to a method for recycling cellulose diacetate from waste tobacco filter rods. Background Technology

[0002] my country's tobacco industry requires a large quantity of cellulose diacetate tow for making cigarette filter rods. The production of these filter rods generates a significant amount of waste filter rods, which were previously disposed of through incineration and landfill, resulting in energy waste and environmental pollution. Therefore, recycling and reusing waste cellulose diacetate has significant social and economic value in terms of resource conservation, emission reduction, circular economy, environmental improvement, and turning waste into treasure. At the same time, waste filter rod recycling is a recognized technical challenge in the industry, presenting significant difficulties and challenges.

[0003] Currently, the conventional process for recycling cellulose diacetate from waste cigarette filter rods involves soaking, paper stripping, washing, and drying. However, the water washing method for removing triacetin from the filter rods is energy-intensive and generates a significant amount of wastewater. Furthermore, the excessive shearing and water dispersion during the recycling process results in a large number of micron-sized fragments of formed paper in the resulting filter rod cellulose sheets. These impurities make it difficult to filter the spinning slurry during subsequent use. In conventional filtration processes, all formed paper impurities in the filter rod cellulose sheets need to be retained through a high-precision filtration stage, leading to high filter material consumption and filtration costs. Therefore, waste filter rod recycling technology faces numerous bottlenecks in terms of economy, environmental protection, and safety. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recovering cellulose diacetate from waste filter rods used in tobacco processing. This method reduces impurities in the spinning slurry during the recovery process, thereby simplifying the subsequent filtration process. It is efficient, convenient to implement, and easy to operate for recovering filaments from waste filter rods.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for recovering cellulose diacetate from waste tobacco filter rods includes the following steps: A. Surface humidification; B. Cut into segments; C. Low-shear paper stripping; D. Separate the forming paper; E. Microwave heating-high-speed airflow purging to remove triacetin; F. Prepare solutions with high liquid-to-solid ratios; G. Let stand and drain the sediment; H. Secondary dissolution and concentration; I. Hierarchical filtration; J. Spinning.

[0006] Optionally, in step A: the waste filter rods are surface-humidified, and the moisture content of the humidified waste filter rods is controlled within the range of 40%-80%, so as to reduce the strength of the surface forming paper of the waste filter rods while maintaining a tensile strength of more than 30%.

[0007] Optionally, in step B: the waste filter rod after surface humidification is cut into segments, and the segment length is controlled within the range of 1-2 cm.

[0008] Optionally, in step C: the humidified waste filter rod is subjected to low-shear paper stripping, with the shearing rate controlled within the range of 100-2000 s. -1 To maintain the integrity of the formed paper after peeling.

[0009] Optionally, in step D: the formed paper is separated from the material flow, and the separation method can be one or a combination of the following: centrifugal separation, pneumatic separation, and negative pressure adsorption.

[0010] Optionally, in step E: microwave heating-high-speed airflow purging to remove triacetin.

[0011] Optionally, in step F: using acetone as a solvent, the waste filter rod vinegar sheet is added to a dissolving vessel for dissolution, with a solution concentration range of 3%-10%.

[0012] Optionally, in step G: after standing, a portion of the formed paper in the high liquid-to-solid ratio solution settles to the bottom of the container by gravity; high paper content waste liquid is discharged from the bottom of the container; the waste liquid is evaporated in an evaporator to recover acetone from the solution.

[0013] Optionally, in step H: the high liquid-to-solid ratio solution after the precipitate is discharged is used as a solvent and mixed with acetate flakes or waste filaments to form a slurry with a concentration range of 26.5%-28.5%.

[0014] Optionally, in step I: the slurry is subjected to staged filtration, with the final stage filtration having an accuracy of 1-10 micrometers.

[0015] Optionally, in step J: a dry spinning process is used, in which the slurry is extruded through the fiber holes and the solvent evaporates in the spinning channel to form cellulose diacetate fibers.

[0016] Compared with the prior art, the beneficial effects of this invention are: 1. This invention involves spraying and humidifying the surface of waste filter rods before peeling them off, and then cutting them into 1-2cm segments. This reduces the strength and grit of the formed paper on the surface of the waste filter rods, thereby reducing the shearing force required for subsequent peeling and preventing the formation of a large number of micron-sized formed paper fragments due to excessive shearing during the peeling process. The sequence of humidification followed by cutting helps reduce the strength of the waste filter rods, minimizes airborne debris during the cutting process, and improves the working environment. By controlling the amount of humidification applied to the formed paper on the surface of the waste filter rods, the density difference between the formed paper and cellulose diacetate increases after humidification, which is beneficial for material separation in the subsequent separation process.

[0017] 2. This invention uses a dual-action approach of microwave heating and high-speed airflow purging to treat waste filter rods after paper removal, thereby removing triacetin from the waste filter rods and avoiding the formation of large amounts of wastewater caused by conventional hot water washing processes. It also avoids the problem of the high temperature required to reach the high boiling point of triacetin when using heating and volatilization alone, or the safety risks caused by high temperatures in the equipment during implementation. The combined use of microwave heating and high-speed airflow purging reduces the heating temperature and energy consumption compared to simple heating and volatilization processes.

[0018] 3. This invention provides a two-step method for preparing waste filter rod cellulose acetate flakes-acetone slurry. First, a high liquid-to-solid ratio solution (3%-10% by mass) of waste filter rod cellulose acetate flakes-acetone is prepared to obtain a low-viscosity, high-flow-rate solution. By allowing the high liquid-to-solid ratio solution to stand, some of the formed paper impurities in the solution settle to the bottom of the container under gravity; another portion of the formed paper impurities are separated by their own gravity, reducing the amount of impurities that need to be retained in the subsequent high-precision filtration stage. The solution with high impurity content is discharged at the bottom of the equipment, and the solution is evaporated to dryness in an evaporator. Acetone is recovered from the solution, and the residue is disposed of as solid waste. Then, the solution is mixed and dissolved with conventional waste filaments / cellulose diacetate flakes to prepare a high-concentration slurry (26.5%-28.5% by mass). After conventional filtration, the slurry can be used for spinning. Compared with the conventional one-step slurry preparation and filtration process, this two-step slurry preparation and sedimentation method separates some impurities, saving filter material costs; at the same time, the reduced amount of impurities in the slurry during the filtration stage increases the filtration throughput. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method steps of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments. Example 1

[0021] The specific steps for recycling cellulose diacetate from waste cigarette filter rods are as follows: A. Surface humidification: The waste filter rods are humidified by quantitative spraying of deionized water, and the moisture content of the waste filter rods after treatment is 80%. B. Cutting: Use a waste filter rod cutting machine to cut the waste filter rods of different lengths after surface humidification into 2cm segments. C. Low-shear paper stripping: A squeeze-type paper stripper is used to strip the paper from the humidified waste filter rods at a shear rate of 100s. -1 ; D. Separate the forming paper by using centrifugal separation equipment to separate the forming paper from the material flow; E. Microwave heating-high-speed airflow purging to remove triacetin: A dryer with a newly added microwave heating module and high-speed airflow module is used to remove triacetin from the waste filter rod fragments after humidification and paper stripping. The drying temperature is 110℃ and the fan frequency is 50Hz. F. High liquid-to-solid ratio dissolution: Dissolve the waste filter rod vinegar sheet in acetone to prepare a 3% concentration solution; G. Settling and discharging sediment: After the waste filter rod recovery tow / acetone solution has been settling for 4 hours, a portion of the formed paper settles to the bottom of the container. The bottom liquid is drained and the waste liquid is evaporated to dryness. The high paper content solution is discharged from the bottom and the solution is evaporated to dryness in an evaporator. H. Secondary dissolution and concentration: With a target concentration of 26.5%, the solution after the precipitate is discharged is mixed with waste fibers from cellulose diacetate production and stirred thoroughly to form cellulose diacetate acetone slurry. I. Staged filtration: The slurry is filtered through a filter basket and a filter press with a filtration accuracy of 1-10 μm to obtain the slurry for spinning. J. Spinning: The filtered slurry is pumped to the spinning machine to spin cellulose diacetate fibers. Example 2

[0022] The specific steps for recycling cellulose diacetate from waste cigarette filter rods are as follows: A. Surface humidification: The waste filter rods are humidified by quantitative spraying of deionized water, and the moisture content of the waste filter rods after treatment is 40%. B. Cutting: Use a waste filter rod cutting machine to cut the waste filter rods of different lengths into 1cm segments after surface humidification. C. Low-shear paper stripping: A squeeze-type paper stripper is used to strip the humidified waste filter rods, with a shear rate of 2000s. -1 ; D. Separate the forming paper by using a negative pressure adsorption separation device to separate the forming paper from the material flow; E. Microwave heating-high-speed airflow purging to remove triacetin: A dryer with a newly added microwave heating module and high-speed airflow module is used to remove triacetin from the waste filter rod fragments after humidification and paper stripping. The drying temperature is 110℃ and the fan frequency is 50Hz. F. Prepare a high liquid-to-solid ratio solution by dissolving the waste filter rod vinegar sheet in acetone to prepare a 10% concentration solution. G. Settling and discharging sediment: After the waste filter rod recovery tow / acetone solution has been settling for 12 hours, a portion of the formed paper settles to the bottom of the container. The bottom liquid is drained and the waste liquid is evaporated to dryness. The high paper content solution is discharged from the bottom and the solution is evaporated to dryness in an evaporator. H. Secondary dissolution and concentration: With a target concentration of 28.5%, the solution after removing the precipitate is mixed with conventional acetic acid tablets and stirred thoroughly to form a cellulose diacetate acetone slurry. I. Staged filtration: The slurry is filtered through a filter basket and a filter press with a filtration accuracy of 1-10 μm to obtain the slurry for spinning. J. Spinning: The filtered slurry is pumped to the spinning machine by a slurry pump to spin cellulose diacetate fibers.

[0023] In the above embodiments, humidification before cutting reduces the amount of airborne debris during the cutting process, improving the working environment. Compared with the conventional cutting-high-shear paper stripping process, the amount of micron-sized formed paper debris is reduced by 10%. The combined use of microwave heating and high-speed airflow purging reduces energy consumption by 10% compared with the conventional heating and volatilization process. The two-step pulp preparation and sedimentation method separates some impurities, saving 10% of filter material costs and increasing filtration throughput by 10% compared with the conventional one-step pulp preparation and filtration process.

[0024] The foregoing descriptions and embodiments are provided to enable those skilled in the art to understand and apply this invention. Those skilled in the art will readily make various modifications to these contents and apply the general principles described herein to other embodiments without inventive effort. This invention is not limited to the foregoing descriptions and embodiments. Any improvements and modifications made by those skilled in the art based on the disclosure of this invention, without departing from the scope of this invention, should be within the protection scope of this invention.

Claims

1. A method for recovering cellulose diacetate from waste tobacco filter rods, characterized in that, The steps are as follows: A. Surface humidification; B. Cut into segments; C. Low-shear paper stripping; D. Separate the forming paper; E. Microwave heating-high-speed airflow purging to remove triacetin; F. Prepare solutions with high liquid-to-solid ratios; G. Let stand and drain the sediment; H. Secondary dissolution and concentration; I. Hierarchical filtration; J. Spinning.

2. The method for recovering cellulose diacetate from waste tobacco filter rods according to claim 1, characterized in that, In step A: the waste filter rods are surface-humidified, and the moisture content of the waste filter rods after humidification is controlled within the range of 40%-80%. While reducing the strength of the formed paper on the surface of the waste filter rods, the tensile strength is maintained at more than 30%.

3. The method for recovering cellulose diacetate from waste tobacco filter rods according to claim 1, characterized in that, In step B: the waste filter rod after surface humidification is cut into segments, and the segment length is controlled within the range of 1-2cm.

4. The method for recovering cellulose diacetate from waste tobacco filter rods according to claim 1, characterized in that, In step C: the humidified waste filter rods are subjected to low-shear paper stripping, with the shearing rate controlled within the range of 100-2000 s. -1 To maintain the integrity of the formed paper after peeling.

5. The method for recovering cellulose diacetate from waste tobacco filter rods according to claim 1, characterized in that, In step D: the formed paper is separated from the material flow. The separation method can be one of the following or a combination thereof: centrifugal separation, pneumatic separation, negative pressure adsorption.

6. The method for recovering cellulose diacetate from waste tobacco filter rods according to claim 1, characterized in that, In step E: microwave heating followed by high-speed airflow purging removes triacetin.

7. The method for recovering cellulose diacetate from waste tobacco filter rods according to claim 1, characterized in that, In step F: using acetone as a solvent, the waste filter rod vinegar sheet is added to the dissolving vessel for dissolution, with a solution concentration range of 3%-10%.

8. The method for recovering cellulose diacetate from waste tobacco filter rods according to claim 1, characterized in that, In step G: After standing, a portion of the formed paper in the high liquid-to-solid ratio solution settles to the bottom of the container under gravity; high paper content waste liquid is discharged from the bottom of the container; the waste liquid is evaporated in an evaporator to recover acetone from the solution.

9. The method for recovering cellulose diacetate from waste tobacco filter rods according to claim 1, characterized in that, In step H: the high liquid-to-solid ratio solution after the precipitate is discharged is used as a solvent and mixed with acetate flakes or waste filaments to form a slurry with a concentration range of 26.5%-28.5%.

10. The method for recovering cellulose diacetate from waste tobacco filter rods according to claim 1, characterized in that, In step I: the slurry is subjected to staged filtration, with the final stage having a filtration precision of 1-10 micrometers.

11. The method for recovering cellulose diacetate from waste tobacco filter rods according to claim 1, characterized in that, In step J: a dry spinning process is used, the slurry is extruded through the fiber holes, the solvent evaporates in the spinning tunnel, and cellulose diacetate fibers are formed.

Images