Method for recovering polyester material
By using microwave drying and dynamic melt filtration technology in the polyester material recycling method, the problems of uneven hot air drying and easy jamming of static filters are solved, and more efficient drying and filtration are achieved, improving recycling quality and processing stability.
Patent Information
- Application Number
- CN202410126528.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-12-21
- Filing Date
- 2024-01-30
- Publication Date
- 2025-06-24
AI Technical Summary
In the existing polyester material recycling methods, hot air drying has limitations, resulting in uneven drying and moisture residue affecting subsequent processability; static filters are prone to pressure rise and filter hole deformation due to impurities stuck, affecting quality and processability.
The microwave drying procedure is used to improve drying uniformity and reduce moisture content; the dynamic melt filtration mechanism is used to make the PET flow direction at a tangent angle to the filter surface, avoiding the problem of impurities stuck due to the vertical flow direction.
It effectively improves the drying uniformity and recycling quality of polyester materials, reduces the decline in inherent viscosity, and improves the stability and process efficiency of subsequent processing.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for recycling a material, and more particularly to a method for recycling a polyester material. Background Art
[0002] In the mechanical recycling method of waste polyester (polyethylene terephthalate, PET for short), the conventional technique is to subdivide waste PET (crush PET bottles and film products into pieces, cut fabrics into shreds), wash, dry, melt and extrude, and then go through procedures such as melt filtration and granulation to obtain recycled PET (r-PET).
[0003] In the mechanical recycling process of PET, the drying and filtration procedures are quite important, which are related to quality, including hue, impurity content, and inherent viscosity (IV), etc., as well as process efficiency (production capacity, pressure loss). Generally, the conventional technique is to use hot air drying and a static filter to filter impurities. However, when using hot air to dry waste PET, due to the easy adhesion and agglomeration of shreds or pieces, the drying has limitations, and some PET retains moisture. The PET with residual moisture entering high-temperature extrusion will cause degradation (decrease in IV) and poor hue. When using a static mechanism for impurity filtration, the flow direction of molten PET is perpendicular to the surface of the filter, and impurities (solids) are easily stuck in the holes of the filter, causing the pressure to rise, and then the filter holes are deformed or disintegrated, and the impurities cannot be filtered out, affecting the quality and thus the subsequent processability. Due to these two disadvantages, it will affect the subsequent processability. Especially when processed into PET bottles, the IV is insufficient, there are residual impurities, and the hue is too yellow. In spinning, due to the residual impurities, the filaments are easily broken, affecting the spinning process.
[0004] Based on the above, a method for recycling a polyester material has been developed to improve the subsequent processability, which is an important topic that needs to be studied currently. Summary of the Invention
[0005] The present invention provides a method for recycling a polyester material, which can improve the subsequent processability and enhance the quality and process efficiency of recycled PET.
[0006] The method for recycling a polyester material of the present invention includes the following steps. First, after the polyester material is subdivided and washed, it is dried using a microwave drying process. Then, after the dried polyester material is melt-extruded, the molten polyester material is melt-filtered at a tangential angle to the surface of the filter. Next, the melt-filtered polyester material is cooled and pelletized.
[0007] In an embodiment of the present invention, after the polyester material is subdivided and washed, it is first dried using a hot air drying process and then dried using a microwave drying process.
[0008] In one embodiment of the present invention, the drying temperature of the hot air drying process is 40°C to 150°C, the drying time is 5 minutes to 80 minutes, and the wind speed is 1 m / s to 50 m / s.
[0009] In one embodiment of the present invention, the size of the subdivided polyester material is less than 5x5 cm 2 。
[0010] In one embodiment of the present invention, the drying temperature of the microwave drying process is 30°C to 125°C, the drying time is 0.1 minute to 5 minutes, and the microwave power is 1 kw to 100 kw.
[0011] In one embodiment of the present invention, the moisture content of the polyester material after drying by the microwave drying process is less than 1,000 ppm (0.1%).
[0012] In one embodiment of the present invention, the temperature for melt extrusion is 220°C to 300°C.
[0013] In one embodiment of the present invention, the temperature for melt filtration is 230°C to 290°C.
[0014] In one embodiment of the present invention, the pore diameter of the filter is 10 μm to 100 μm.
[0015] In one embodiment of the present invention, the tangential velocity of the fluid of the molten polyester material and the pores of the filter is 10 m / min to 200 m / min.
[0016] In one embodiment of the present invention, the pressure for filtration is 10 bar to 100 bar.
[0017] In one embodiment of the present invention, the filtered polyester material is cooled to a temperature of 30°C to 90°C.
[0018] In one embodiment of the present invention, the inherent viscosity (IV) of the recycled polyester material is 0.45 dl / g to 1.30 dl / g, and the decrease in the inherent viscosity (IV) is less than 0.06 dl / g.
[0019] In one embodiment of the present invention, the filter is made of mesh weaving or laser drilling.
[0020] In one embodiment of the present invention, the fluid direction of the polyester material is at a tangential angle to the filter surface. The filter is fixed, and the fluid of the polyester material flows through the side, and the fluid of the polyester material is in tangential contact with the filter.
[0021] In one embodiment of the present invention, the fluid direction of the polyester material is at a tangential angle to the filter surface. The filter rotates, and the fluid of the polyester material is in tangential contact with the filter.
[0022] In an embodiment of the present invention, the speed at which the fluid of the polyester material flows through the filter holes of the filter is from 0.1 m / min to 10 m / min.
[0023] Based on the above, the present invention provides a method for recycling polyester materials. By using a penetrating and targeted microwave drying process, the drying uniformity can be improved, enabling the moisture to be evenly reduced to the specified requirements without local under-drying. In addition, the method for recycling polyester materials of the present invention also uses a dynamic melting filtration mechanism, causing the flow direction of the PET to contact the surface of the filter at a tangential angle, avoiding the flow direction of the molten PET being perpendicular to the surface of the filter. The clean PET melt flows through the filter holes due to pressure, and solid impurities are discharged outside without directly clogging the filter holes. In this way, the quality and process efficiency of the recycled PET can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] None DETAILED DESCRIPTION OF THE EMBODIMENTS
[0025] Hereinafter, embodiments of the present invention will be described in detail. However, these embodiments are illustrative, and the disclosure of the present invention is not limited thereto.
[0026] In this document, a range represented by "one numerical value to another numerical value" is a summary representation method to avoid listing all the numerical values in the range in the specification one by one. Therefore, the description of a specific numerical range covers any numerical value within that numerical range and the smaller numerical ranges defined by any numerical value within that numerical range, as if the arbitrary numerical value and the smaller numerical range were written out in the specification.
[0027] The present invention provides a method for recycling polyester materials, including the following steps. First, after the polyester materials are subdivided and cleaned, they are dried using a microwave drying process. Then, after the dried polyester materials are melt-extruded, the fluid of the molten polyester material is melt-filtered at a tangential angle with the surface of the filter. Next, the filtered polyester materials are cooled and pelletized.
[0028] In this embodiment, the polyester materials are, for example, waste polyester materials, which may include but are not limited to waste plastic bottles, waste film products, or waste textiles, with an impurity content of 3 wt% or less. The impurities may include sand, iron, PE, PP, PVC, or nylon, etc. During the process of subdividing the polyester materials, for example, plastic bottles and film products are broken into pieces, and fabrics are cut into shreds. The size of the subdivided polyester materials is, for example, less than 5x5 cm 2 , preferably less than 3x3 cm 2 .
[0029] In this embodiment, drying is performed using a microwave drying process. The drying temperature of the microwave drying process is, for example, 30°C to 125°C, preferably, for example, 40°C to 105°C. The drying time is, for example, 0.1 minute to 5 minutes, preferably, for example, 0.5 minute to 3 minutes. The microwave power is, for example, 1 kW to 100 kW, preferably, for example, 2 kW to 50 kW. In addition, after the polyester material is subdivided and cleaned, it can also be dried first using a hot air drying process in the front-end treatment and then using a microwave drying process in the back-end treatment. The drying temperature of the hot air drying process is, for example, 40°C to 150°C, preferably, for example, 50°C to 125°C. The drying time is, for example, 5 minutes to 80 minutes, preferably, for example, 10 minutes to 60 minutes. The air velocity is, for example, 1 m / s to 50 m / s, preferably, for example, 2 m / s to 30 m / s. Using the microwave drying process can effectively control the moisture content. The moisture content of the polyester material after being dried by the microwave drying process is, for example, less than 1,000 ppm (0.1%), preferably, for example, less than 500 ppm (0.05%).
[0030] In this embodiment, the dried polyester material is melt-extruded. The temperature for melt-extrusion is, for example, 220°C to 300°C, preferably, for example, 210°C to 290°C.
[0031] In this embodiment, the fluid direction of the molten polyester material is at a tangential angle to the filter surface for melt filtration, and filtration is performed using a dynamic filtration mechanism. For example, the filter moves or rotates, and the molten polyester material directly enters the filter; or the filter is fixed, and the molten polyester material enters at a side angle. Both of these methods can maintain the fluid direction of the molten polyester material at a tangential angle to the filter surface and avoid a perpendicular angle. In this way, the clean molten polyester material flows through the filter holes, and solid impurities do not directly block the filter holes and can be discharged to the outside. The temperature for filtration is, for example, 230°C to 290°C, preferably, for example, 210°C to 290°C. The tangential velocity of the fluid of the molten polyester material and the filter holes of the filter is, for example, 10 m / min to 200 m / min, preferably, for example, 15 m / min to 150 m / min. The velocity of the fluid of the polyester material flowing through the filter holes is 0.1 to 10 m / min, preferably, for example, 0.2 m / min to 10 m / min. The pressure for filtration is, for example, 10 bar to 100 bar, preferably, for example, 20 bar to 80 bar. The aperture diameter of the filter holes of the filter is, for example, 10 μm to 100 μm, preferably, for example, 20 μm to 80 μm. For example, mesh weaving or laser drilling is used to meet this aperture specification requirement. The fluid direction of the molten polyester material is at a tangential angle to the filter surface. The filter is fixed and the fluid of the polyester material flows through the side, with the fluid in tangential contact with the filter; or the filter rotates, with the fluid in tangential contact with the filter, to improve the melt filtration efficiency and quality.
[0032] In this embodiment, the filtered polyester material is cooled to a temperature of, for example, 30°C to 90°C, preferably, for example, 40°C to 80°C. The inherent viscosity (IV) of the recycled polyester material is higher than, for example, 0.45 dl / g to 1.30 dl / g, and the decrease in the inherent viscosity (IV) is lower than, for example, 0.06 dl / g.
[0033] Hereinafter, the method for recycling the polyester material proposed by the present invention will be described in detail by way of experimental examples. However, the following experimental examples are not intended to limit the present invention.
[0034] Experimental Examples
[0035] Example 1.
[0036] The recycled PET bottles were crushed (<3x3 cm 2 ) and washed. Then, 100.3 kg of bottle chips were taken, with IV = 0.81 dl / g, moisture content of 4,800 ppm, and impurities such as sand and PP of 0.2%. They were dried with hot air at 105°C and a wind speed of 10 m / s for 15 minutes, and then dried with a 36 kw microwave dryer for 10 minutes. The moisture content of the randomly sampled bottle chips was 210 ± 40 ppm, with an average of 198 ppm. Then, they were extruded at 250°C in an extruder and melt-filtered with a rotary filter. The filter holes of the filter were 50 um, the tangential velocity of the fluid on the filter was 20 m / s, the velocity of the fluid flowing through the filter holes was 0.8 m / s, and the pressure was increased from 50 to 51 bar (50↗51 bar). The filtered PET resin was cooled to 60°C with 25°C cooling water and pelletized with a pelletizer. 99.5 kg of r-PET resin pellets were obtained (yield 99.5%), IV = 0.79, and the decrease in IV (ΔIV) was only 0.02.
[0037] Examples 2 to 6
[0038] The feeding specifications, drying conditions, and filter conditions were changed respectively, and the rest were the same as in Example 1. The test data are shown in Table 1.
[0039] As can be seen from Table 1, drying with microwave can effectively reduce the moisture content and improve the drying uniformity. The moisture content can be effectively controlled to effectively improve the PET feeding specifications; the PET resin fluid flows through the surface of the filter in a tangential manner, the process pressure is stable, the filtration system can improve the efficiency and avoid blockage, and it can be stably operated. The yield is maintained above 99.0%, thereby achieving the stability of quality.
[0040] Table 1
[0041]
[0042]
[0043] Comparative Example 1
[0044] After the recycled PET bottles were crushed (<3x3 cm 2 ), and washed, 100.3 kg of bottle chips were taken, with IV = 0.81 dl / g, moisture 0.1% (1000 ppm), and impurities such as sand and PP 0.2%. They were dried with hot air at 105°C and a wind speed of 10 m / s for 30 minutes. The moisture content of the randomly sampled bottle chips was 8,500 ± 4,300 ppm, with an average of 8,310 ppm. Then, they were extruded in an extruder at 250°C and filtered through a fixed filter. The filter pores were 50 µm, the fluid was perpendicular to the filter contact surface, the flow rate of the fluid through the pores was 0.8 m / s, the pressure was 50 - 67 bar, and the filtered PET resin was cooled to 60°C with 25°C cooling water and pelletized with a pelletizer. 93.7 kg of r-PET resin pellets were obtained (yield 93.7%), IV = 0.72, and the IV decrease (ΔIV) was as high as 0.09.
[0045] Comparative Examples 2 to 6
[0046] The feed specifications, drying conditions, and filter conditions were changed respectively, and the rest was the same as in Comparative Example 1. The test data are shown in Table 2. It can be seen from Table 2 that when the bottle chips were only dried with hot air, the drying had limitations and affected the uniformity, the moisture could not be effectively controlled, and the PET feed specification was reduced; when the PET resin fluid flowed through the filter surface vertically, the process pressure continued to rise, the filtration system was prone to blockage, and it could not be stably operated. The yield was less than 97.0%, and the IV decrease (ΔIV) was higher than 0.06, thereby reducing the quality stability and the process smoothness.
[0047] Table 2
[0048]
[0049] In summary, the present invention provides a method for recycling polyester materials. By using a penetrating and targeted microwave drying process, the drying uniformity can be improved, enabling the moisture to be evenly reduced to the specified requirements without local undried phenomena. In addition, the recycling method of polyester materials of the present invention also uses a dynamic melt filtration mechanism, making the flow direction of PET contact the filter surface at a tangential angle, avoiding the flow direction of molten PET being perpendicular to the filter surface. The clean PET melt flows through the filter holes due to pressure, and solid impurities are discharged to the outside without directly blocking the filter holes. The present invention mainly aims to effectively control the moisture of the raw materials (feedstock), effectively improve the PET feedstock specifications, maintain the stability of the filtration system during the process, enhance the efficiency of the filtration system to avoid blockage, thereby achieving the stability of quality, significantly improving the smooth operation of the production line, and effectively reducing energy consumption.
Claims
1. A method for recycling polyester materials, characterized in that: include: After the polyester material is subdivided and washed, it is dried using a microwave drying process; After the dried polyester material is melted and extruded, the melted polyester material is filtered at a tangent angle to the filter surface; and The filtered polyester material was cooled and pelletized.
2. The method for recycling polyester materials according to claim 1, characterized in that: After the polyester material is subdivided and cleaned, it is first dried using a hot air drying process and then dried using the microwave drying process.
3. The method for recycling polyester materials according to claim 2, characterized in that: The hot air drying process has a drying temperature of 40° C. to 150° C., a drying time of 5 minutes to 80 minutes, and a wind speed of 1 m / s to 50 m / s.
4. The method for recycling polyester materials according to claim 1, characterized in that: The polyester material is subdivided into smaller sizes than 5x5 cm 2 .
5. The method for recycling polyester materials according to claim 1, characterized in that: The drying temperature of the microwave drying process is 30° C. to 125° C., the drying time is 0.1 minute to 5 minutes, and the microwave power is 1 kW to 100 kW.
6. The method for recycling polyester materials according to claim 1, characterized in that: The moisture content of the polyester material after being dried by the microwave drying process is less than 1,000 ppm.
7. The method for recycling polyester materials according to claim 1, characterized in that: The temperature for melt extrusion is 220°C to 300°C.
8. The method for recycling polyester materials according to claim 1, characterized in that: The temperature at which the filtration is carried out is 230°C to 290°C.
9. The method for recycling polyester materials according to claim 1, characterized in that: The filter has a pore size of 10 μm to 100 μm.
10. The method for recycling polyester materials according to claim 1, characterized in that: The tangential velocity of the molten polyester material fluid and the filter holes of the filter is 10 m / min to 200 m / min.
11. The method for recycling polyester materials according to claim 1, characterized in that: The filtration is carried out at a pressure of 10 bar to 100 bar.
12. The method for recycling polyester materials according to claim 1, characterized in that: The filtered polyester material is cooled to a temperature of 30°C to 90°C.
13. The method for recycling polyester materials according to claim 1, characterized in that: The inherent viscosity of the recycled polyester material is 0.45 dl / g to 1.30 dl / g, and the decrease in the inherent viscosity is less than 0.06 dl / g.
14. The method for recycling polyester materials according to claim 1, characterized in that: The filter is mesh-woven or laser-drilled.
15. The method for recycling polyester materials according to claim 1, characterized in that: The direction of the fluid of the polyester material is at a tangent angle to the surface of the filter. The filter is fixed so that the fluid of the polyester material flows through the side and the fluid of the polyester material is in tangential contact with the filter.
16. The method for recycling polyester materials according to claim 1, characterized in that: The direction of the polyester material fluid is at a tangent angle to the filter surface, and the filter is rotated to bring the polyester material fluid into tangential contact with the filter.
17. The method for recycling polyester materials according to claim 1, characterized in that: The speed at which the polyester material fluid flows through the filter pores of the filter is 0.1 m / min to 10 m / min.