Method and device for removing oiling agent on surface of waste chinlon yarn

Abstract

The invention relates to the technical field of chinlon waste yarn recovery treatment, and provides a chinlon waste yarn surface oiling agent removal method which comprises a first-stage extraction procedure and a second-stage extraction procedure. The primary extraction process comprises the following steps: removing organic silicon and white oil in the waste chinlon yarns by using supercritical CO2; the pressure of the extraction kettle is relieved, and CO2 is gasified and separated from the oil agent; the secondary extraction process comprises the following steps: stirring a mixture of the waste chinlon filaments and the eutectic solvent, and removing fatty acid in the waste chinlon filaments; after extraction, the eutectic solvent is recycled after being filtered; washing the chinlon waste yarns with desalted water to remove the residual eutectic solvent; and drying to obtain the recycled chinlon waste silk. Therefore, different components in the oiling agent are respectively removed through synergistic extraction of the supercritical CO2 and the choline eutectic solvent, and the oiling agent removal efficiency of the waste chinlon yarn is improved. Wastewater containing oil stains is not generated in the extraction process, and an extraction reagent can be recycled. The pollution is small and the recovery cost is low. The invention further provides an oiling agent removing device.

Description

Technical Field

[0001] The present invention belongs to the technical field of nylon waste yarn recycling and processing, and in particular relates to a method and device for removing oil agent from the surface of nylon waste yarn. Background Art

[0002] Nylon uses oil in the spinning process, so a large amount of oil components remain on the surface of nylon waste yarn, including silicone, white oil, fatty acid esters, emulsifiers, antistatic agents, etc.

[0003] The presence of these oils reduces the quality of the recycled waste, making it unsuitable for direct use in melt granulation, chemical depolymerization and other processing steps. Therefore, the effective removal of oils on the surface of waste yarn is a prerequisite for the recycling of nylon waste yarn.

[0004] Oils contain water-insoluble ingredients such as silicone, white oil, and fatty acid esters, making them difficult to remove with water. Using degreasing agents for treatment produces a large amount of wastewater, causing environmental pollution.

[0005] In summary, the existing technology has obvious inconveniences and defects in actual use, so it is necessary to improve it. Summary of the Invention

[0006] In response to the above-mentioned defects, the present invention mainly provides a method for removing oil from the surface of nylon waste yarn, which solves the technical problems of low efficiency in removing oil from nylon waste yarn and high processing cost.

[0007] In order to solve the above problems, the present invention provides a method for removing oil from the surface of nylon waste yarn, which includes a primary extraction process and a secondary extraction process; specifically:

[0008] The primary extraction process comprises the following steps:

[0009] S1, putting nylon waste into a first-stage extraction kettle;

[0010] S2, charging supercritical CO2 into the primary extraction kettle to perform primary extraction treatment on the nylon waste to remove silicone and white oil from the nylon waste;

[0011] The extraction pressure is: 8MPa ~ 20MPa, the extraction time is: 10min ~ 120min; the extraction temperature is: 40℃ ~ 100℃;

[0012] S3, after reaching the predetermined processing time, the first-stage extraction kettle is depressurized to normal pressure, and the extracted oil and supercritical CO2 are discharged from the first-stage extraction kettle 4;

[0013] S4, the pressure of the derived supercritical CO2 decreases, the CO2 gradually gasifies and separates from the oil; the separated gaseous CO2 is filtered and reused;

[0014] The secondary extraction process comprises the following steps:

[0015] Z1, placing the nylon waste after the primary extraction process into the secondary extraction kettle;

[0016] Z2, injecting deep eutectic solvent into the secondary extraction kettle;

[0017] The mass ratio of nylon waste to deep eutectic solvent is 1:2-20;

[0018] Z3, stirring the mixture of the nylon waste and the deep eutectic solvent, and performing a secondary extraction process to remove fatty acids from the nylon waste;

[0019] The extraction time is: 60min~200min; the extraction temperature is: 80℃~200℃;

[0020] Z4, after the secondary extraction process is completed, nitrogen is filled into the secondary extraction kettle to press out the deep eutectic solvent;

[0021] Z5, the extruded deep eutectic solvent is filtered and reused;

[0022] The nylon waste yarns after the secondary extraction process are washed three times with desalted water to remove the low eutectic solvent remaining on the surface; and the nylon waste yarns are recovered after drying.

[0023] According to the method for removing surface oil from nylon waste silk of the present invention, the extraction pressure in step S2 is 10 MPa to 16 MPa; the extraction time is 30 min to 90 min; and the extraction temperature is 60° C. to 80° C.

[0024] According to the method for removing surface oil from nylon waste yarns of the present invention, in the step Z2, the mass ratio of the nylon waste yarns to the deep eutectic solvent is 1:5-10.

[0025] According to the method for removing surface oil from nylon waste silk of the present invention, the extraction time of the Z3 step is: 100 min to 160 min; the extraction temperature is: 120° C. to 160° C.; and the stirring speed is 100 rpm.

[0026] According to the method for removing surface oil from nylon waste yarn of the present invention, the drying process of the nylon waste yarn in the secondary extraction step is: passing hot nitrogen at 80° C. and drying for 2 hours.

[0027] According to the method for removing surface oil from nylon waste silk of the present invention, the low eutectic solvent of the secondary extraction step includes choline chloride and lactic acid, and the molar ratio of the two is 1:2.

[0028] A device for removing oil from the surface of nylon waste yarn, comprising:

[0029] A primary extraction unit, used to perform the primary extraction process of the method for removing the surface oil agent of nylon waste silk;

[0030] A secondary extraction unit, used to perform the secondary extraction process of the method for removing the surface oil agent of nylon waste silk;

[0031] The primary extraction unit comprises:

[0032] A first-stage extraction kettle is used to hold nylon waste and perform a first-stage extraction process; the first-stage extraction kettle is provided with an exhaust valve;

[0033] Gas cylinders for storing CO2;

[0034] A high-pressure pump is connected to the first-stage extraction kettle and the gas storage cylinder, and is used to deliver the CO2 in the gas storage cylinder into the first-stage extraction kettle and enable the CO2 to reach a supercritical CO2 state in the first-stage extraction kettle;

[0035] The separation kettle is used to store the supercritical CO2 extracted from the first-stage extraction kettle and gradually reduce the pressure to gasify the CO2 and separate it from the oil;

[0036] The gas filter tank is connected to the separation kettle and the first-stage extraction kettle, and is also connected to the gas storage cylinder; it is used to filter the gasified CO2 and return it to the gas storage cylinder;

[0037] The secondary extraction unit comprises:

[0038] A secondary extraction kettle is used to hold nylon waste and perform a secondary extraction treatment step; the secondary extraction kettle is provided with a stirrer for performing the stirring extraction step;

[0039] Solvent storage tank, used to store deep eutectic solvent and pump deep eutectic solvent into the secondary extraction kettle;

[0040] Temporary storage tank, used to store the deep eutectic solvent after extraction;

[0041] A primary filter and a secondary filter are sequentially connected between the temporary storage tank and the solvent storage tank.

[0042] According to the device for removing surface oil from nylon waste silk of the present invention, the kettle bodies of the first-level extraction kettle and the second-level extraction kettle both have hollow interlayers; hot water is circulated in the interlayer of the first-level extraction kettle for heating; and heat transfer oil is circulated in the interlayer of the second-level extraction kettle for heating.

[0043] The device for removing surface oil from nylon waste yarn according to the present invention further includes a waste oil storage tank; the waste oil storage tank is connected to the primary filter, the secondary filter and the separation kettle.

[0044] According to the device for removing surface oil from nylon waste yarn of the present invention, the secondary extraction unit further comprises a deep eutectic solvent preparation mechanism;

[0045] The deep eutectic solvent preparation mechanism includes a preparation tank, which is provided with a first storage tank and a second storage tank; the choline chloride and lactic acid are added to the preparation tank through the first storage tank and the second storage tank respectively according to a predetermined ratio;

[0046] The preparation tank is provided with a stirrer, and choline chloride and lactic acid are stirred at 60° C. into a uniform transparent liquid to obtain the deep eutectic solvent.

[0047] In summary, the method for removing surface oil from nylon waste yarns disclosed herein utilizes synergistic extraction using supercritical CO2 and a choline-based deep eutectic solvent to remove different components of the oil, thereby improving the efficiency of removing the oil from nylon waste yarns. The surface oil content of the treated nylon waste yarns is reduced to approximately 0.3%. The extraction process does not produce oily wastewater, and the extraction reagents can be reused. This method minimizes pollution and reduces recycling costs. The present invention also provides a device for removing surface oil from nylon waste yarns. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the structure of the primary extraction unit of the present invention;

[0049] Figure 2 It is a schematic structural diagram of the secondary extraction unit of the present invention;

[0050] In the figure: 1-gas cylinder, 11-flow meter, 12-gas filter tank; 2-valve, 21-exhaust valve, 22-drain valve; 3-high-pressure pump, 31-centrifugal pump; 4-first-stage extraction kettle, 41-second-stage extraction kettle; 5-separation kettle, 51-temporary storage tank; 6-waste oil storage tank, 61-first-stage filter, 62-second-stage filter; 7-preparation tank, 71-first storage tank, 72-second storage tank; 8-solvent storage tank. DETAILED DESCRIPTION

[0051] See also Figure 1 and Figure 2 The present invention provides a method for removing surface oil from nylon waste yarn, comprising a primary extraction process and a secondary extraction process; specifically:

[0052] The primary extraction process comprises the following steps:

[0053] S1, putting nylon waste into the first-stage extraction kettle 4;

[0054] S2, charging supercritical CO2 into the primary extraction kettle 4, performing a primary extraction treatment on the nylon waste to remove silicone and white oil from the nylon waste;

[0055] The extraction pressure is: 8MPa ~ 20MPa, the extraction time is: 10min ~ 120min; the extraction temperature is: 40℃ ~ 100℃;

[0056] Preferably, the extraction pressure in step S2 of the present invention is 10 MPa to 16 MPa; the extraction time is 30 min to 90 min; and the extraction temperature is 60° C. to 80° C.

[0057] Under high pressure, supercritical CO2 can fully penetrate into the fiber gaps of nylon waste yarn, weakening the van der Waals force between the fiber and the oil agent, thereby effectively dissolving components such as silicone and white oil on the surface of the waste yarn, and separating such oil agents from the surface of the waste yarn.

[0058] As an embodiment, the first-stage extraction kettle 4 has a hollow interlayer on its body, and hot water is circulated in the interlayer for heating, so that the temperature in the kettle is constant and controllable.

[0059] S3, after reaching the predetermined processing time, the primary extraction kettle 4 is depressurized to normal pressure, and the extracted oil and supercritical CO2 are discharged from the primary extraction kettle 4;

[0060] As the pressure in the first-stage extraction vessel 4 drops sharply, the CO2 changes from a supercritical state to a gaseous state. During this phase transition, the volume of the CO2 expands by more than 300 times, releasing a large amount of Gibbs free energy (approximately 10-15 kJ / mol). This converts the CO2 gas into high-speed fluid microjets, which in turn generate high instantaneous shear stress (up to 5-7 GPa) on the surface of the nylon waste fibers.

[0061] This transient shear stress exceeds the binding force of the fiber's internal fibrils and even exceeds the yield strength of the nylon's amorphous regions. Under this high transient shear stress, the fiber fibrils are broken up and the amorphous regions are destroyed, resulting in a low molecular chain packing density. This allows the deep eutectic solvent in the secondary extraction process to enter the fibrils and amorphous regions, extracting the residual oil.

[0062] S4, the pressure of the discharged supercritical CO2 decreases, CO2 gradually vaporizes and separates from the oil;

[0063] The gaseous CO2 is filtered and then reused; the separated oil is collected and processed;

[0064] The secondary extraction process comprises the following steps:

[0065] Z1, placing the nylon waste after the primary extraction process into the secondary extraction kettle 41;

[0066] Z2, injecting a deep eutectic solvent into the secondary extraction kettle 41;

[0067] The mass ratio of nylon waste to deep eutectic solvent is 1:2-20;

[0068] Preferably, in the step Z2, the mass ratio of nylon waste to deep eutectic solvent is 1:5-10;

[0069] Z3, stirring the mixture of the nylon waste and the deep eutectic solvent, and performing a secondary extraction process to remove fatty acids from the nylon waste;

[0070] The extraction time is: 60min~200min; the extraction temperature is: 80℃~200℃;

[0071] Preferably, the extraction time of step Z3 of the present invention is 100 min to 160 min; the extraction temperature is 120° C. to 160° C.

[0072] More preferably, the stirring speed in step Z3 is 100 rpm.

[0073] As an embodiment, the secondary extraction kettle 41 has a hollow interlayer on its body, and heat transfer oil is circulated in the interlayer for heating, so that the kettle can quickly reach a predetermined extraction temperature.

[0074] Z4, after the secondary extraction process is completed, nitrogen is filled into the secondary extraction kettle 41 to press out the deep eutectic solvent;

[0075] Z5, the pressed deep eutectic solvent is filtered and reused; the separated oil is collected and processed;

[0076] The nylon waste yarns after the secondary extraction process are washed three times with desalted water to remove the low eutectic solvent remaining on the surface; and the nylon waste yarns are recovered after drying.

[0077] Furthermore, the drying process of the nylon waste yarn after the secondary extraction process is as follows: passing hot nitrogen at 80°C for 2 hours;

[0078] As an embodiment, the deep eutectic solvent of the secondary extraction step includes choline chloride and lactic acid, and the molar ratio of the two is 1:2;

[0079] The present invention comprises a choline deep eutectic solvent (DES) composed of choline chloride and lactic acid. The lactic acid has a certain catalytic effect on fatty acid ester oils, decomposing them into alcohols and acids that are more soluble in water, and are easier to remove in subsequent desalted water washing.

[0080] At the same time, the hydrophilic groups (-COOH / -OH) of lactic acid can reconstruct the emulsification system in the oil (the oil contains ionic or non-ionic emulsifiers), encapsulating the fatty acid ester in the reverse micelle core formed by DES, thereby improving the removal efficiency;

[0081] The quaternary ammonium cation of choline chloride in DES can also neutralize the charge with the sulfonate group of the anionic emulsifier in the oil agent, thereby destroying the original oil agent emulsification membrane structure and improving the removal efficiency.

[0082] The inventors used multiple nylon waste yarn samples, adopted the removal method of the present invention, set multiple groups of process parameters, and conducted experiments in multiple embodiments.

[0083] In order to verify the effectiveness of the removal method of the present invention, the inventors also used nylon waste yarn samples and set up two comparative experiments. Specifically:

[0084] Comparative Example 1 (Desalted Water Extraction Treatment)

[0085] Place nylon waste samples and desalted water in an extraction kettle at a mass ratio of 1:10. Stir and extract for 130 minutes at a stirring speed of 100 rpm and an extraction temperature of 80°C.

[0086] Then take out the nylon waste silk sample, pass it into 80℃ hot nitrogen, and dry it for 2 hours to check the oil content of the sample.

[0087] Comparative Example 2 (only two-stage extraction process)

[0088] The aforementioned secondary extraction steps were performed, and the process parameters are shown in Table 1.

[0089] In order to make the experimental results comparable, the inventors pretreated the waste silk samples so that their initial oil content was 1.5%.

[0090] The specific experimental parameters and test results of each embodiment and comparative example are shown in Table 1. (Note: Table 1 only lists the parameters that have changed. The same components and steps can be found in the previous text and will not be repeated here.)

[0091] From the test results, compared with comparative example 1, the oil content of each embodiment treated by the method of the present invention is greatly reduced, and the oil removal effect is good.

[0092] In Comparative Example 2, due to the lack of a supercritical CO₂ extraction step, the nylon waste did not undergo the rapid volume expansion process associated with supercritical CO₂ pressure release phase transition. This resulted in weak fibril separation and amorphous region destruction in the waste fibers. Consequently, the oil that had seeped between the fiber fibrils and into the amorphous regions was not effectively extracted by the deep eutectic solvent.

[0093] Therefore, compared with Comparative Example 2, the synergistic extraction of supercritical CO2 and choline-based low eutectic solvents in the present invention removes oil agents of different components respectively; at the same time, the waste silk undergoes a phase change process of supercritical CO2 in the primary extraction process, so that its fiber fibrils are broken up and the amorphous region is destroyed, resulting in a low packing density of the molecular chains, thereby allowing the low eutectic solvent in the secondary extraction process to enter between the fibrils and the amorphous region, and extract the residual oil agent that has penetrated into the waste silk.

[0094] Table 1: Parameters and test results of each embodiment and comparative example

[0095]

[0096] The present method for removing surface oil from nylon waste yarn utilizes synergistic extraction using supercritical CO2 and a choline-based deep eutectic solvent to remove different components of the oil, improving the efficiency of oil removal from nylon waste yarn. The surface oil content of the treated nylon waste yarn is reduced to approximately 0.3%. The extraction process does not produce oily wastewater, and the extraction reagents can be reused. This minimizes pollution and reduces recycling costs.

[0097] See also Figure 1 and Figure 2 The present invention also provides a device for performing the method for removing the surface oil agent of nylon waste yarn, comprising:

[0098] A primary extraction unit is used to perform the primary extraction process of the method for removing the surface oil agent of nylon waste silk; it includes

[0099] The first-stage extraction kettle 4 is used to contain nylon waste and perform a first-stage extraction process; the first-stage extraction kettle 4 is provided with an exhaust valve 21;

[0100] Gas cylinder 1, used to store CO2;

[0101] The high-pressure pump 3 is connected to the primary extraction kettle 4 and the gas cylinder 1, and is used to send the CO2 in the gas cylinder 1 into the primary extraction kettle 4 and make the CO2 reach a supercritical CO2 state in the primary extraction kettle 4;

[0102] Optionally, the gas cylinder 1 is connected to a flow meter 11;

[0103] Furthermore, a valve 2 is connected between the gas cylinder 1 and the high-pressure pump 3;

[0104] The separation kettle 5 is used to store the oil and supercritical CO2 discharged from the first-stage extraction kettle 4, and gradually reduce the pressure to gasify the CO2 and separate it from the oil;

[0105] Preferably, the oil and supercritical CO2 are discharged from the bottom of the primary extraction kettle 4 into the separation kettle 5. When discharging, the valve 2 between the primary extraction kettle 4 and the separation kettle 5 is first opened. Under the action of a large pressure difference, the oil and supercritical CO2 quickly enter the separation kettle 5 from the primary extraction kettle 4.

[0106] Then, the exhaust valve 21 of the first-stage extraction kettle 4 is opened, and the pressure in the kettle drops rapidly, causing the volume to expand rapidly and CO2 to be quickly gasified and discharged.

[0107] The gas filter tank 12 is connected to the separation kettle 5 and the primary extraction kettle 4, and is also connected to the gas storage cylinder 1; it is used to filter the gasified CO2 and return it to the gas storage cylinder 1;

[0108] Optionally, the gas filter tank 12 is filled with activated carbon, which can effectively remove impurities in the CO2 gas.

[0109] As an embodiment, the separation kettle 5 is connected to the waste oil storage tank 6, and the oil separated from the CO2 enters the waste oil storage tank 6 for centralized collection and post-processing.

[0110] As an embodiment, the separation kettle 5 is provided with an exhaust valve 21 to control the rate at which the pressure in the separation kettle 5 decreases.

[0111] A secondary extraction unit is used to perform the secondary extraction process of the method for removing the surface oil agent of nylon waste silk;

[0112] The secondary extraction kettle 41 is used to contain nylon waste and perform secondary extraction treatment;

[0113] Optionally, a stirrer is provided in the secondary extraction kettle 41 for performing the stirring extraction step;

[0114] The solvent storage tank 8 is used to store the deep eutectic solvent and pump the deep eutectic solvent into the secondary extraction kettle 41;

[0115] Optionally, a centrifugal pump 31 is connected between the secondary extraction kettle 41 and the solvent storage tank 8 to pump the deep eutectic solvent into the secondary extraction kettle 41 .

[0116] Furthermore, a drain valve 22 is provided at the bottom of the secondary extraction kettle 41 to discharge the oil accumulated in the kettle at regular intervals.

[0117] Temporary storage tank 51, used to store the deep eutectic solvent after extraction;

[0118] The temporary storage tank 51 and the solvent storage tank 8 are connected in sequence to a primary filter 61 and a secondary filter 62;

[0119] Optionally, both the primary filter 61 and the secondary filter 62 are connected to the waste oil storage tank 6;

[0120] After the deep eutectic solvent is processed by the primary filter 61 and the secondary filter 62 to remove polar oils such as antistatic agents and emulsifiers, it enters the solvent storage tank 8 for reuse. The filtered oil enters the waste oil storage tank 6 for centralized collection and subsequent treatment.

[0121] Optionally, a centrifugal pump 31 is connected between the temporary storage tank 51 and the primary filter 61 to pump the deep eutectic solvent into the primary filter 61 and the secondary filter 62 for processing.

[0122] As an embodiment, the secondary extraction unit further includes a deep eutectic solvent preparation mechanism, including a preparation tank 7, wherein the preparation tank 7 is provided with a first storage tank 71 and a second storage tank 72; choline chloride and lactic acid are added to the preparation tank 7 through the first storage tank 71 and the second storage tank 72 in a predetermined ratio, respectively;

[0123] The preparation tank 7 is provided with a stirrer, and choline chloride and lactic acid are stirred at 60° C. into a uniform transparent liquid to obtain the deep eutectic solvent.

[0124] Optionally, the preparation tank 7 is connected to the solvent storage tank 8 via a centrifugal pump 31 ; the prepared deep eutectic solvent can be directly pumped into the solvent storage tank 8 for standby use.

[0125] In summary, the present invention provides a method for removing surface oil from nylon waste yarn. Through synergistic extraction using supercritical CO2 and a choline-based deep eutectic solvent, different components of the oil are removed separately, improving the efficiency of oil removal from nylon waste yarn. The surface oil content of the treated nylon waste yarn is reduced to approximately 0.3%. The extraction process does not produce oily wastewater, and the extraction reagents can be reused. This method minimizes pollution and reduces recycling costs. The present invention also provides a device for removing surface oil from nylon waste yarn.

[0126] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for removing surface oil from nylon waste yarn, characterized in that: It includes primary extraction process and secondary extraction process; specifically: The primary extraction process comprises the following steps: S1, putting nylon waste into a first-stage extraction kettle; S2, charging supercritical CO2 into the primary extraction kettle to perform primary extraction treatment on the nylon waste to remove silicone and white oil from the nylon waste; The extraction pressure is: 8MPa ~ 20MPa, the extraction time is: 10min ~ 120min; the extraction temperature is: 40℃ ~ 100℃; S3, after the predetermined processing time is reached, the first-stage extraction kettle is depressurized to normal pressure; the extracted oil and supercritical CO2 are discharged from the first-stage extraction kettle; S4, the pressure of the discharged supercritical CO2 decreases, the CO2 gradually gasifies and separates from the oil; the separated gaseous CO2 is filtered and reused; The secondary extraction process comprises the following steps: Z1, placing the nylon waste after the primary extraction process into the secondary extraction kettle; Z2, injecting deep eutectic solvent into the secondary extraction kettle; The mass ratio of nylon waste to deep eutectic solvent is 1:2-20; Z3, stirring the mixture of the nylon waste and the deep eutectic solvent, and performing a secondary extraction process to remove fatty acids from the nylon waste; The extraction time is: 60min~200min; the extraction temperature is: 80℃~200℃; Z4, after the secondary extraction process is completed, nitrogen is filled into the secondary extraction kettle to press out the deep eutectic solvent; Z5, the extruded deep eutectic solvent is filtered and reused; The nylon waste yarns after the secondary extraction process are washed three times with desalted water to remove the low eutectic solvent remaining on the surface; and the nylon waste yarns are recovered after drying.

2. The method for removing surface oil from nylon waste according to claim 1, wherein: The extraction pressure of step S2 is 10 MPa to 16 MPa; the extraction time is 30 min to 90 min; and the extraction temperature is 60° C. to 80° C.

3. The method for removing surface oil from nylon waste according to claim 1, wherein: In the Z2 step, the mass ratio of the nylon waste yarn to the deep eutectic solvent is 1:5-10.

4. The method for removing surface oil from nylon waste according to claim 1, wherein: The extraction time of the Z3 step is 100 min to 160 min; the extraction temperature is 120° C. to 160° C.; and the stirring speed is 100 rpm.

5. The method for removing surface oil from nylon waste according to claim 1, wherein: The drying process of the nylon waste in the secondary extraction step is: passing hot nitrogen at 80° C. and drying for 2 hours.

6. The method for removing surface oil from nylon waste according to any one of claims 1 to 5, characterized in that: The deep eutectic solvent of the secondary extraction step includes choline chloride and lactic acid, and the molar ratio of the two is 1:

2.

7. A device for removing oil from the surface of nylon waste yarn, characterized in that: include: A primary extraction unit, configured to perform the primary extraction step of the method for removing surface oil from nylon waste silk according to claim 6; A secondary extraction unit, used to perform the secondary extraction process of the method for removing surface oil from nylon waste silk as claimed in claim 6; The primary extraction unit comprises: A first-stage extraction kettle is used to hold nylon waste and perform a first-stage extraction process; the first-stage extraction kettle is provided with an exhaust valve; Gas cylinders for storing CO2; A high-pressure pump is connected to the first-stage extraction kettle and the gas storage cylinder, and is used to deliver the CO2 in the gas storage cylinder into the first-stage extraction kettle and enable the CO2 to reach a supercritical CO2 state in the first-stage extraction kettle; The separation kettle is used to store the supercritical CO2 extracted from the first-stage extraction kettle and gradually reduce the pressure to gasify the CO2 and separate it from the oil; The gas filter tank is connected to the separation kettle and the first-stage extraction kettle, and is also connected to the gas storage cylinder; it is used to filter the gasified CO2 and return it to the gas storage cylinder; The secondary extraction unit comprises: A secondary extraction kettle is used to hold nylon waste and perform a secondary extraction treatment step; the secondary extraction kettle is provided with a stirrer for performing the stirring extraction step; Solvent storage tank, used to store deep eutectic solvent and pump deep eutectic solvent into the secondary extraction kettle; Temporary storage tank, used to store the deep eutectic solvent after extraction; A primary filter and a secondary filter are sequentially connected between the temporary storage tank and the solvent storage tank.

8. The device for removing surface oil from nylon waste yarn according to claim 7, characterized in that: The kettle bodies of the primary extraction kettle and the secondary extraction kettle both have hollow interlayers; hot water is circulated into the interlayer of the primary extraction kettle for heating; and heat transfer oil is circulated into the interlayer of the secondary extraction kettle for heating.

9. The device for removing surface oil from nylon waste yarn according to claim 7, wherein: It also includes a waste oil storage tank; the waste oil storage tank is connected to the primary filter, the secondary filter and the separation kettle.

10. The device for removing surface oil from nylon waste yarn according to any one of claims 7 to 9, characterized in that: The secondary extraction unit further includes a deep eutectic solvent preparation mechanism; The deep eutectic solvent preparation mechanism includes a preparation tank, which is provided with a first storage tank and a second storage tank; the choline chloride and lactic acid are added to the preparation tank through the first storage tank and the second storage tank respectively according to a predetermined ratio; The preparation tank is provided with a stirrer, and choline chloride and lactic acid are stirred at 60° C. into a uniform transparent liquid to obtain the deep eutectic solvent.

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