Recycling method of polyester material

Abstract

PURPOSE: To provide a recycling method of a polyester material.SOLUTION: A recycling method of a polyester material includes steps of: fragmentation and cleaning a polyester material, followed by drying by using a microwave drying processing, melting and extruding the dried polyester material, and conducting melting filtration in a manner that a flow direction of the melting polyester material becomes a tangent angle to a surface of a filter, cooling the filtered polyester material, and pelletizing.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for recycling materials, and particularly to a method for recycling polyester materials.

Background Art

[0002] In the mechanical recycling method of waste polyester (polyethylene terephthalate (PET)), the conventional technology performs subdivision (crushing of PET bottles and film products, shredding of fabrics, etc.), washing, drying, melting, and extrusion, and then obtains recycled PET (r-PET) through processes such as melt filtration and granulation.

[0003] In the mechanical recycling process of PET, the drying and filtration steps are very important and are related to qualities such as color tone, impurity content, and intrinsic viscosity (IV), as well as process efficiency (capacity, pressure loss). In the conventional technology, hot air drying and static filters are used to filter impurities. However, when using warm air to dry waste PET, fragments and pieces are likely to adhere and aggregate, so drying is limited. Some PET has residual moisture, and when this PET containing residual moisture is extruded at high temperature, it causes deterioration (decrease in IV) and poor color tone. When filtering impurities by a static mechanism, the flow direction of the molten PET is perpendicular to the surface of the filter, so impurities (solids) are likely to clog the filter holes, and as the pressure increases, deformation and damage occur in the filter holes. If impurities cannot be filtered, it will affect the quality, and thereby affect the subsequent processability. Based on the above two drawbacks, it will affect the subsequent processability. In particular, when processing into PET bottles, the IV is insufficient, impurities remain, and the color tone becomes too yellow. Spinning is likely to cause yarn breakage due to residual impurities, which also affects the spinning process.

[0004] Based on the above, developing a recycling method for polyester materials to improve subsequent processability has currently become an important issue to be studied.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention provides a recycling method for polyester materials that can improve subsequent processability and enhance the quality and process efficiency of recycled PET.

Means for Solving the Problems

[0006] The recycling method of the polyester material of the present invention includes the following steps. First, the polyester material is subdivided and washed, and then dried using a microwave drying process. Then, the dried polyester material is melted and extruded, and melt filtration is performed so that the flow direction of the molten polyester material forms a tangential angle with respect to the surface of the filter. Next, the melted and filtered polyester material is cooled and pelletized.

[0007] In one embodiment of the present invention, after being subdivided and washed, first, the polyester material is 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 polyester material after being subdivided is less than 5×5 cm 2 and less.

[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 output of the microwave is 1 kw to 100 kw.

[0011] In one embodiment of the present invention, the water content of the polyester material after drying in 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 holes of the filter is 10 μm to 100 μm.

[0015] In one embodiment of the present invention, the tangential velocity of the flow of the molten polyester material and the filter holes 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 intrinsic viscosity (IV) of the recycled polyester material is 0.45 dl / g to 1.30 dl / g, and the decrease in the intrinsic viscosity (IV) is less than 0.06 dl / g.

[0019] In one embodiment of the present invention, the filter is mesh woven or laser drilled.

[0020] In one embodiment of the present invention, the flow direction of the polyester material forms a tangential angle with respect to the surface of the filter. The filter is fixed such that the flow of the polyester material flows along the side surface, and the flow of the polyester material is in tangential contact with the filter.

[0021] In one embodiment of the present invention, the flow direction of the polyester material forms a tangential angle with respect to the surface of the filter, and the filter adopts a rotating method to bring the flow of the polyester material into tangential contact with the filter.

[0022] In one embodiment of the present invention, the flow rate of the polyester material flowing through the filter holes of the filter is 0.1 m / min to 10 m / min.

Advantages of the Invention

[0023] As described above, the present invention provides a method for recycling polyester materials. By using a permeable and directional microwave drying process, the drying uniformity can be improved, and the moisture can be evenly reduced to meet the standard requirements, so there is no undried part. Furthermore, the method for recycling polyester materials of the present invention also uses a dynamic melt filtration mechanism, and by bringing the flow direction of PET into tangential contact with the surface of the filter at an angle, it prevents the flow direction of the molten PET from being perpendicular to the surface of the filter. Since the clean PET melt flows through the filter holes under pressure, solid impurities can be discharged to the outside without directly clogging the filter holes.

Modes for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described in detail. However, these embodiments are exemplary and do not limit the present invention.

[0025] In this specification, a range indicated by "one numerical value to another numerical value" is a general expression for avoiding listing all numerical values within the range. Therefore, the description of a specific numerical range covers any numerical value within that range and any relatively small numerical range defined by any numerical value within that range, which is the same as if any numerical value and relatively small numerical range described above in this specification were clearly stated.

[0026] The present invention provides a method for recycling a polyester material including the following steps. First, the polyester material is subdivided and washed, and then dried using a microwave drying process. Then, the dried polyester material is melted and extruded, and filtration is performed such that the flow direction of the molten polyester material is at a tangential angle to the surface of the filter. Next, the filtered polyester material is cooled and pelletized.

[0027] In this embodiment, the polyester material can be, for example, a discarded polyester material, including discarded PET bottles, discarded film products, or discarded textiles, but the present invention is not limited thereto. The impurity content is less than 3 wt%, and the impurities can include sand, iron, PE, PP, PVC, or nylon, etc. In the process of subdividing the polyester material, for example, PET bottles and film products are crushed, and textiles are shredded. The size of the polyester material after subdivision is, for example, less than 5×5 cm 2 and preferably less than 3×3 cm 2 and less than.

[0028] In this embodiment, a microwave drying process is used for drying. The drying temperature of the microwave drying process may be, for example, 30°C to 125°C, preferably 40°C to 105°C. The drying time may be, for example, 0.1 minute to 5 minutes, preferably 0.5 minute to 3 minutes. The output of the microwave may be, for example, 1 kW to 100 kW, preferably 2 kW to 50 kW. Also, after the polyester material is subdivided and washed, drying can be performed using a hot air drying process in the pretreatment, and then drying can be performed using a microwave drying process in the post-treatment. The drying temperature of the hot air drying process may be, for example, 40°C to 150°C, preferably 50°C to 125°C. The drying time may be, for example, 5 minutes to 80 minutes, preferably 10 minutes to 60 minutes. The wind speed may be, for example, 1 m / s to 50 m / s, preferably 2 m / s to 30 m / s. The microwave drying process can effectively control the water content. The water content of the polyester material after drying by the microwave drying process may be, for example, less than 1000 ppm (0.1%), preferably less than 500 ppm (0.05%).

[0029] In this embodiment, the dried polyester material is melted and extruded, and the temperature of the melt extrusion may be, for example, 220°C to 300°C, preferably 210°C to 290°C.

[0030] In this embodiment, melt filtration is performed such that the flow direction of the molten polyester material forms a tangential angle with respect to the surface of the filter, and the filtration is performed using a dynamic filtration mechanism. For example, when the filter moves or rotates, the molten polyester material directly enters the filter, and when the filter is fixed, the molten polyester material enters at a side angle. All of these methods can maintain the flow direction of the molten polyester material at a tangential angle with respect to the surface of the filter and prevent it from becoming a perpendicular angle. In this way, the clean molten polyester material can flow through the filter pores and the solid impurities can be discharged to the outside without directly clogging the filter pores. The temperature at which filtration is performed may be, for example, 230°C to 290°C, preferably 210°C to 290°C. The tangential velocity of the flow of the molten polyester material and the filter pores of the filter may be, for example, 10 m / min to 200 m / min, preferably 15 m / min to 150 m / min. The flow rate of the polyester material flowing through the filter pores is 0.1 m / min to 10 m / min, preferably 0.2 m / min to 10 m / min. The pressure at which filtration is performed may be, for example, 10 bar to 100 bar, preferably 20 bar to 80 bar. The pore diameter of the filter pores of the filter may be, for example, 10 μm to 100 μm, preferably 20 μm to 80 μm. For example, mesh weaving or laser drilling is used to achieve such pore diameter specification requirements. The flow direction of the molten polyester material forms a tangential angle with respect to the surface of the filter. By fixing the filter so that the flow of the polyester material flows from the side and bringing the flow into tangential contact with the filter, or by adopting a method in which the filter rotates and bringing the flow into tangential contact with the filter, the efficiency and quality of melt filtration can be improved.

[0031] In this embodiment, the filtered polyester material is cooled to a temperature of 30°C to 90°C, preferably 40°C to 80°C. The inherent viscosity (IV) of the recycled polyester material is, for example, greater than 0.45 dl / g to 1.30 dl / g, and the decrease in the inherent viscosity (IV) is, for example, less than 0.06 dl / g.

[0032] Hereinafter, the above-mentioned recycling method of the polyester material of the present invention will be described in detail with reference to experimental examples. However, the following experimental examples do not limit the present invention. Experimental Example Example 1

[0033] The recycled PET bottle was crushed (3×3 cm 2 ) and washed, and then 100.3 kg of PET bottle pieces were obtained. Here, IV = 0.81 dl / g, the water content was 4,800 ppm, and impurities such as sand and PP were 0.2%. Drying was performed for 15 minutes at a wind speed of 10 m / s using hot air at 105°C, and then drying was performed for 10 minutes using a 36 kw microwave dryer. The water content of the randomly sampled PET bottle pieces was 210 ± 40 ppm, and the average was 198 ppm. Next, extrusion was performed at 250°C using an extruder, and melt filtration was performed using a rotary filter. The filter holes of the filter were 50 um. The tangential velocity of the flow in the filter was 20 m / s. The flow velocity through the filter holes was 0.8 m / s. The pressure 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. The obtained r-PET resin pellets were 99.5 kg (yield 99.5%), IV = 0.79, and the decrease in IV (ΔIV) decreased by only 0.02. Examples 2 to 6

[0034] The specifications of the feed materials, drying conditions, and filter conditions were changed respectively, but the rest was the same as in Example 1. The test data is as shown in Table 1.

[0035] As can be seen from Table 1, by microwave-drying the bottle pieces, moisture can be effectively reduced and drying uniformity can be improved. Moisture can be effectively controlled, and the specifications of the PET feedstock can be effectively improved. The flow of the PET resin tangentially flows over the surface of the filter, and the process pressure is stable. The filtration system can improve efficiency and prevent clogging. Since stable operation can be carried out and a yield of 99.0% or more can be maintained, quality stability can be achieved.

[0036]

Table 1

[0037] The recycled PET bottles were crushed (3×3 cm 2 ) and washed, and then 100.3 kg of PET bottle pieces were obtained. Here, IV = 0.81 dl / g, the water content was 0.1% (1000 ppm), and impurities such as sand and PP were 0.2%. Drying was carried out for 30 minutes at a wind speed of 10 m / s using hot air at 105°C. The water content of randomly sampled PET bottle pieces was 8,500 ± 4,300 ppm, and the average was 8,310 ppm. Next, extrusion was carried out at 250°C using an extruder, and filtration was carried out using a fixed filter. The filter holes of the filter were 50 μm. The flow was perpendicular to the contact surface of the filter. The flow rate through the filter holes was 0.8 m / s. The pressure was 50 - 67 bar. The filtered PET resin was cooled to 60°C with cooling water at 25°C and pelletized with a pelletizer. The obtained r-PET resin pellets were 93.7 kg (yield 93.7%), IV = 0.72, and the decrease in IV (ΔIV) was as high as 0.09. Comparative Examples 2 - 6

[0038] The specifications of the feedstock, drying conditions, and filter conditions were each changed, while the rest remained the same as in Comparative Example 1. The test data are as shown in Table 2. As can be seen from Table 2, the bottle pieces are dried with hot air only. There are limitations in that it affects the uniformity and moisture cannot be effectively controlled, resulting in a decrease in the specifications of the PET feedstock. The flow of the PET resin flows perpendicular to the surface of the filter, and the process pressure continues to increase. The filtration system is prone to clogging and cannot perform stable operations. The yield is less than 97.0%, and the decrease in IV (ΔIV) is 0.06 or more, so the quality stability and process smoothness are reduced.

[0039]

Table 2

[0040] As described above, the present invention provides a method for recycling polyester materials. By using a microwave drying process with permeability and directivity, the drying uniformity can be improved and moisture can be evenly reduced to the specification requirements, so there are no undried parts. Furthermore, the method for recycling polyester materials of the present invention also uses a dynamic melt filtration mechanism, and by making the flow direction of PET contact the surface of the filter at a tangential angle, it prevents the flow direction of the molten PET from becoming perpendicular to the surface of the filter. Due to the clean PET melt flowing through the filter pores under pressure, solid impurities can be discharged to the outside without directly clogging the filter pores. The present invention mainly aims to effectively control the moisture of the raw material (feedstock), effectively improve the specifications of the PET feedstock, and maintain the stability of the filtration system in the process. The filtration system can improve efficiency and avoid clogging, thereby achieving quality stability, greatly improving the smoothness of the production line operation, and effectively reducing energy consumption.

Industrial Applicability

[0041] The recycling method of the polyester material of the present invention can be applied to the field of waste PET recycling.

Claims

1. After subdividing and washing the polyester material, drying the polyester material using a microwave drying process, after melting and extruding the dried polyester material, performing filtration such that the flow direction of the melted polyester material forms a tangential angle with respect to the surface of the filter, cooling and pelletizing the filtered polyester material, A method for recycling a polyester material comprising the above steps.

2. The method for recycling a polyester material according to claim 1, wherein after subdividing and washing the polyester material, first, drying the polyester material using a hot air drying process, and then drying using the microwave drying process.

3. The method for recycling a polyester material according to claim 2, wherein 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.

4. The size of the polyester material after subdivision is 5×5 cm ２ The method for recycling a polyester material according to claim 1, wherein the size is less than 5×5 cm

5. The method for recycling a polyester material according to claim 1, wherein 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 power of the microwave is 1 kw to 100 kw.

6. The method for recycling a polyester material according to claim 1, wherein the water content of the polyester material after drying by the microwave drying process is less than 1,000 ppm.

7. The method for recycling a polyester material according to claim 1, wherein the temperature for melt extrusion is 220°C to 300°C.

8. The method for recycling a polyester material according to claim 1, wherein the temperature for filtration is 230°C to 290°C.

9. The method for recycling a polyester material according to claim 1, wherein the pore diameter of the filter holes of the filter is 10 μm to 100 μm.

10. The method for recycling a polyester material according to claim 1, wherein the tangential speed of the flow of the molten polyester material and the filter holes of the filter is 10 m / min to 200 m / min.

11. The method for recycling a polyester material according to claim 1, wherein the pressure for filtration is 10 bar to 100 bar.

12. The method for recycling a polyester material according to claim 1, wherein the filtered polyester material is cooled to a temperature of 30°C to 90°C.

13. The intrinsic viscosity (IV) of the recycled polyester material is 0.45 dl / g to 1.30 dl / g, and the decrease amount of the intrinsic viscosity (IV) is less than 0.06 dl / g. The method for recycling a polyester material according to claim 1.

14. The method for recycling a polyester material according to claim 1, wherein the filter uses mesh weaving or laser perforation.

15. The flow direction of the polyester material forms a tangential angle with the surface of the filter, the filter is fixed so that the flow of the polyester material flows from the side, and the flow of the polyester material is in tangential contact with the filter. The method for recycling a polyester material according to claim 1.

16. The flow direction of the polyester material forms a tangential angle with the surface of the filter, the filter adopts a rotating method, and the flow of the polyester material is brought into tangential contact with the filter. The method for recycling a polyester material according to claim 1.

17. The flow rate of the polyester material flowing through the filter holes of the filter is 0.1 m / min to 10 m / min. The method for recycling a polyester material according to claim 1.

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