A method for testing the quality of waste solvent recovery liquid from coating waste solvents

Abstract

The present invention provides a method for testing the quality of waste solvent recovery liquid from waste painting solvents, comprising the following steps: Step S1: subjecting the recovered liquid filtered by a membrane filtration treatment device to a solvency test, a shrinkage test, a resistance test, a chromatography test, and a cleanliness test; depositing the recovered waste solvent liquid that passes the solvency test, shrinkage test, resistance test, chromatography test, and cleanliness test into a recovered solvent barrel and storing it in a designated area for use in paint mixing rooms for tank washing, long and short flushing of painting robots, gun washing in spot repair rooms, and tank wiping by cleaning robots / paint mixing rooms; the present invention has the advantage of verifying the chemical properties of the filtered recovered solvent, ensuring that the recovered solvent meets the quality requirements for use in a coating production line. By performing the following tests on the recovered solvent's chemical properties, it is ultimately determined whether the recovered solvent's performance is qualified.

Description

Technical Field

[0001] The present invention relates to the field of coating technology, and in particular to a method for inspecting the quality of waste solvent recovery liquid for recovering and treating coating waste solvent based on an RO membrane filtration method. Background Art

[0002] The coating line generates a large amount of waste solvents during processes such as robot gun washing, paint mixing room tank washing, and spot repair spray gun washing. Waste solvents account for the second largest proportion of all factory waste, and it is expensive to treat them as hazardous waste. At the same time, the effective ingredients contained in the waste solvents are not recycled and reused, which also causes a waste of resources and fails to reduce the procurement cost of cleaning solvents.

[0003] Our company utilizes RO reverse osmosis (RO) membrane filtration to recover waste solvents. The RO membrane filtration process follows: waste solvent collection—waste solvent filtration equipment for recovery—recovery liquid shrinkage and cleanliness testing—recovered solvent application on-site—and waste solvent recollection. However, to ensure the safety of waste solvents during actual use, a standardized test method is urgently needed to verify the chemical properties of recovered solvents after filtration. Summary of the Invention

[0004] In view of the above problems, the purpose of the present invention is to provide a method for testing the quality of waste solvent recovery liquid from coating waste solvents, which is used to ensure that the recovered solvent performance meets the quality requirements of coating production lines. By conducting the following tests to verify the chemical properties of the recovered solvent, the recovered solvent performance is ultimately determined to be qualified, thus overcoming the shortcomings of the above-mentioned prior art.

[0005] The present invention provides a method for testing the quality of waste solvent recovery liquid from waste coating solvents, which specifically includes the following steps:

[0006] Step S1: subjecting the waste solvent clear liquid filtered by the membrane filtration treatment equipment to a solubility test, a shrinkage test, a resistance test, a chromatography test, a cleanliness test, and a density test;

[0007] Step S2: Simulating the long and short flushing and color changing time of the coating production line, setting the paint flow plate to flash dry for 30 seconds and flash dry for 5 minutes to perform solubility tests;

[0008] Step S21: Prepare test materials, cleaning solvent stock solution (Solvent No. 0), first-pass waste solvent recovery solution (Solvent No. 1), second-pass recovery solution (Solvent No. 2), third-pass recovery solution (Solvent No. 3), Hongqi red paint, Arctic white paint, burette, 15CM*15CM glass piece;

[0009] Step S22: Set the solvent titration quantity in the burette to 30 drops, select one each of the Red Flag red paint flow plate and the Arctic white paint flow plate, flash dry for 30 seconds, place them at a 20° angle under their respective burettes, and then use a burette filled with a stock solution of cleaning solvent (Solvent No. 0) to slowly titrate to the middle of the lower paint flow plate, titrating 30 drops. Place them in a safe place after the titration is completed.

[0010] Step S23: Set the solvent titration quantity in the burette to 30 drops, select one Red Flag red paint flow plate and one Arctic white paint, flash dry for 5 minutes, place them at a 20° angle under their respective burettes, and then use a burette filled with a stock solution of cleaning solvent (Solvent No. 0) to slowly titrate to the middle of the lower paint flow plate, titrating 30 drops. Place them in a safe place after the titration is completed.

[0011] Step S24: repeating steps S22 and S23 to complete the titration of the first recovery liquid of the Hongqi red paint and the Arctic white paint to the third recovery liquid of the flash-drying 30 seconds and the flash-drying 5 minutes;

[0012] Step S25: By comparing the dissolving power of the cleaning solvent stock solution and the recovery solvents with different times on the Red Flag red paint flow plate and the Arctic white paint, if the dissolving power of the solvents with different times is close to that of the cleaning solvent stock solution and no obvious weakening is observed, it is qualified, otherwise it is unqualified;

[0013] Step S3: shrinkage test;

[0014] Step S31: prepare test materials, high temperature resistant film, third pass waste solvent (Solvent No. 3), Red Flag red paint, Arctic white paint, and manual spray gun;

[0015] Step S32: mixing the third-pass waste solvent into the Red Flag red paint and the Arctic white paint at a dilution ratio of 10%, respectively, loading the mixture into a manual spray gun, and spraying the high-temperature resistant film;

[0016] Step S33: The sprayed high-temperature resistant film is placed in a 90° drying room for drying for 30 minutes.

[0017] Step S34: Take out the high temperature resistant film from step S33 from the drying room and observe it under the indoor light source to confirm whether there are shrinkage holes. If there are shrinkage holes, it is unqualified and needs to be scrapped. Otherwise, it is qualified.

[0018] Step S4: Resistance test:

[0019] Step S41: preparing test materials, a resistance meter, a plastic cup, a waste solvent recovery solution, a varnish and paint cleaning solvent, and a primer cleaning solvent;

[0020] Step S42: inserting the resistance meter into the plastic cups containing the waste solvent recovery liquid, the varnish and paint cleaning solvent, and the primer cleaning solvent, respectively, selecting the GΩ gear, and performing resistance testing, where 1 GΩ = 1000 MΩ;

[0021] Step S43: Compare the test results of step S42 to confirm whether the resistance value of the waste solvent recovery liquid is close to the resistance value of the BKNP cleaning solvent stock solution (varnish and color paint DL95) and the BKNP cleaning solvent stock solution (primer DL95-PC);

[0022] Step S44: Detecting whether the resistance of the waste solvent recovery liquid in step S42 meets the requirement of ≥1MΩ, wherein if the resistance is ≥1MΩ, it is qualified; otherwise, it is unqualified and needs to be scrapped;

[0023] Step S5: Chromatographic test:

[0024] Step S51: preparing test materials, waste solvent first-pass recovery solution (Solvent No. 1), second-pass recovery solution (Solvent No. 2), third-pass recovery solution (Solvent No. 3), and BKNP cleaning solvent stock solution (DL95);

[0025] Step S52: The first-pass recovered liquid of the waste solvent (Solvent No. 1), the second-pass recovered liquid (Solvent No. 2), the third-pass recovered liquid (Solvent No. 3), and the BKNP cleaning solvent stock solution (DL95) are respectively placed in a gas chromatograph for chromatographic detection and analysis;

[0026] Step S53: Detecting whether the waste solvent recovered from multiple passes (from the first to the third pass) contains a curing agent component (isocyanate). If it contains a curing agent component, it is unqualified and needs to be scrapped;

[0027] Step S54: comparing the butanol, ethyl acetate, cyclohexanone, butyl acetate, and trimethyl-tetramethyl mixed benzene contents detected in the BKNP cleaning solvent stock solution (DL95) with the multi-pass recovered waste solvent to confirm the solubility change trend of the multi-pass recovered waste solvent;

[0028] Step S55: Detecting whether the silicone component that is likely to cause shrinkage cavities is contained;

[0029] Step S6: Cleanliness test:

[0030] Step S61: Prepare test materials, 200 ml of waste solvent recovery liquid, a 300-mesh filter, a magnifying glass, and scissors;

[0031] Step S61: Pour the waste solvent recovery liquid into a 300-mesh filter bag for filtration, use scissors to cut off the folded filter screen after filtration, observe the filter screen with a magnifying glass, and score and evaluate the waste solvent recovery liquid according to the cleanliness evaluation standard;

[0032] Step S62: comparing the score of the waste solvent recovery liquid with the qualified mark of the cleanliness evaluation standard to determine whether the waste solvent recovery liquid is qualified;

[0033] Step S7: Density test:

[0034] Step S71: Prepare test materials, 50 ml of waste solvent recovery solution, BYK density cup, and balance;

[0035] Step S72: First, weigh the density cup. Pour the waste solvent recovery liquid into the BYK density cup until the liquid level is just below the edge. Place the lid with holes on top of the cup and gently rotate it downward to close it tightly. The sample will slightly overflow from the small holes but will not spray out. Wipe off the sample that overflows from the lid and weigh the density cup filled with the sample. Divide the weight displayed on the balance (minus the weight of the density cup) by the volume of the density cup to obtain the density of the recovery liquid.

[0036] Step S73: Repeat the measurement three times to obtain an average value, compare the average value with the density standard range, and confirm whether it is within the qualified range;

[0037] Step S8: The waste solvent clear liquid that has passed the solubility test, shrinkage test, resistance test, chromatography test and cleanliness test is stored in a recovery solvent barrel and stored in a designated area for use in washing tanks in the paint mixing room, long and short flushing of painting robots, washing guns in the spot repair room, and wiping tanks in the cleaning robot / paint mixing room.

[0038] As a preferred embodiment of the present invention, step S5 also includes step S55: detecting whether the recovered liquid contains silicone components that are prone to cause shrinkage cavities. The chromatographic test can be used to test whether the recovered liquid contains components that cause shrinkage cavities (silicones), so that prevention and control measures can be taken in advance.

[0039] The advantages and positive effects of the present invention are:

[0040] 1. The present invention verifies the chemical properties of the recovered solvent after filtration to ensure that the recovered solvent meets the quality requirements of the coating production line. The chemical properties of the recovered solvent are verified by the following tests to determine whether the recovered solvent performance is qualified.

[0041] 2. The present invention uses standardized test verification methods to conduct standardized tests on its chemical properties (solubility, shrinkage, cleanliness, electrical resistance, density, and solvent chromatographic composition), thereby solving the verification of waste solvents on the quality requirements of robot gun head cleaning in the coating line and tank washing in the paint mixing room.

[0042] 3. The present invention adds a solvency test to ensure that the recovery solvent's solvency is sufficient to clean paints with strong tinting strength, primarily colored paints such as red and white. This ensures that no residual colored paint remains after the robot gun head is cleaned, preventing discoloration and quality defects in the sprayed product. If the recovery solvent's solvency is insufficient, it may be necessary to mix some of the original cleaning solvent before use to improve its overall solvency.

[0043] 4. The present invention adds a shrinkage cavity test, the purpose of which is to ensure that the recovery solvent does not contain silicone-like chemical components that are prone to cause shrinkage cavities, and to ensure that the sprayed products do not produce shrinkage cavity defects, otherwise it is easy to cause batch products to be scrapped or returned for repair.

[0044] 5. The present invention adds a resistance test, the purpose of which is to ensure that the resistance of the recovered solvent must meet the requirement of ≥1MΩ, otherwise the painting robot will have a high-voltage alarm, resulting in inability to produce.

[0045] 6. The present invention increases the chromatography test, and its purpose is to recover the solvent as a mixed solution, comprising primer, paint, varnish and corresponding diluent components mixed into the cleaning solvent, and to confirm the solubility change trend by understanding the names and proportions of the chemical components in the recovered solvent. At the same time, through the chromatography test, it can be known whether the recovered solvent after RO membrane filtration contains a curing agent component (isocyanate). The absence of a curing agent component can ensure that the recovered solvent cleans the robot gun head and is not prone to residue. In addition, the chromatography test can also test whether the recovered liquid contains components that cause shrinkage cavities (silicones), and to do a good job of prevention and control in advance.

[0046] 7. The present invention adds a cleanliness test, the purpose of which is to ensure that the recovered solvent does not contain particles, fibers and other substances, otherwise it will affect the first-time pass rate of the next product and increase the cost of grinding and polishing.

[0047] 8. The present invention adds a density test, the purpose of which is to test whether the physical properties of the recovered solvent after filtration have changed, thereby ensuring basic physical properties.

[0048] 9 By examining the dissolving power and chemical composition ratio of the recovered solvent over multiple passes, the present application can confirm whether the dissolving power and effective chemical composition of the recovered solvent are attenuated due to multiple filtration passes, thereby failing to guarantee the effective use of the recovered solvent. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 2 is a comparison diagram of the dissolving power test results of the present invention.

[0050] Figure 2 It is a comparison diagram of the shrinkage test of the present invention. DETAILED DESCRIPTION

[0051] In the following description, for illustrative purposes, numerous specific details are set forth to provide a comprehensive understanding of one or more embodiments. However, it will be apparent that the embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form to facilitate description of one or more embodiments.

[0052] The method for testing the quality of the waste solvent recovery liquid of the coating waste solvent provided in this embodiment specifically includes the following steps:

[0053] Step S1: subjecting the waste solvent recovery liquid filtered by the membrane filtration treatment equipment to a solubility test, a shrinkage test, a resistance test, a chromatography test, a cleanliness test, and a density test.

[0054] See Figure 1 , the solubility test in this embodiment includes:

[0055] Step S2: Simulating the long and short flushing and color changing time of the coating production line, setting the paint flow plate to flash dry for 30 seconds and flash dry for 5 minutes to perform solubility tests;

[0056] Step S21: Prepare test materials, cleaning solvent stock solution (Solvent No. 0), first-pass waste solvent recovery solution (Solvent No. 1), second-pass recovery solution (Solvent No. 2), third-pass recovery solution (Solvent No. 3), Hongqi red paint, Arctic white paint, burette, 15CM*15CM glass piece;

[0057] Step S22: Set the solvent titration quantity in the burette to 30 drops, select one each of the Red Flag red paint flow plate and the Arctic white paint flow plate, flash dry for 30 seconds, place them at a 20° angle under their respective burettes, and then use a burette filled with a stock solution of cleaning solvent (Solvent No. 0) to slowly titrate to the middle of the lower paint flow plate, titrating 30 drops. Place them in a safe place after the titration is completed.

[0058] Step S23: Set the solvent titration quantity in the burette to 30 drops, select one Red Flag red paint flow plate and one Arctic white paint flow plate, flash dry for 5 minutes, place them at a 20° angle under their respective burettes, and then use a burette filled with a stock solution of cleaning solvent (Solvent No. 0) to slowly titrate to the middle of the lower paint flow plate, titrating 30 drops. Place them in a safe place after the titration is completed.

[0059] Step S24: repeating steps S22 and S23 to complete the titration of the first recovery liquid of the Hongqi red paint and the Arctic white paint to the third recovery liquid of the flash-drying 30 seconds and the flash-drying 5 minutes;

[0060] Step S25: By comparing the dissolving power of the cleaning solvent stock solution and the recovery solvent with different times on the Hongqi red paint flow plate and the Arctic white paint flow plate, the dissolving power of the solvent with different recovery times and the cleaning solvent stock solution is close, and no obvious weakening is observed, which means it is qualified.

[0061] See Figure 2 , the shrinkage test step S2 in this embodiment:

[0062] Step S31: prepare test materials, high temperature resistant film, third pass waste solvent (Solvent No. 3), Red Flag red paint, Arctic white paint, and manual spray gun;

[0063] Step S32: mixing the third-pass waste solvent into the Red Flag red paint and the Arctic white paint at a dilution ratio of 10%, respectively, loading the mixture into a manual spray gun, and spraying the high-temperature resistant film;

[0064] Step S33: The sprayed high-temperature resistant film is placed in a 90° drying room for drying for 30 minutes.

[0065] Step S34: Take out the high temperature resistant film in step S33 from the drying room, put it under the indoor light source for observation, and confirm that there are no shrinkage holes, that is, it is qualified.

[0066] Resistance test step S4 in this embodiment:

[0067] Step S41: preparing test materials, a resistance meter, a plastic cup, a waste solvent recovery solution, a varnish and paint cleaning solvent, and a primer cleaning solvent;

[0068] Step S42: inserting the resistance meter into the plastic cups containing the waste solvent recovery liquid, the varnish and paint cleaning solvent, and the primer cleaning solvent, respectively, selecting the GΩ gear, and performing resistance testing, where 1 GΩ = 1000 MΩ;

[0069] Step S43: Compare the test results of step S42 (as shown in Table 1) to confirm that the resistance value of the waste solvent recovery liquid is lower than the resistance value of the BKNP cleaning solvent stock solution (varnish and color paint DL95) and the BKNP cleaning solvent stock solution (primer DL95-PC). However, the resistance of the waste solvent recovery liquid meets the requirement of ≥1MΩ, that is, the resistance of the recovery liquid meets the requirements of the painting robot for the cleaning solvent resistance.

[0070]

[0071] Table 1

[0072] Refer to Table 1 for the conclusion: the resistance of the waste solvent recovery liquid is lower than the original wave resistance of the cleaning solvent, and the resistance of the recovery liquid meets the requirements of the coating robot for the cleaning solvent resistance.

[0073] Chromatographic test step S5 in this embodiment:

[0074] Step S51: preparing test materials, waste solvent first-pass recovery solution (Solvent No. 1), second-pass recovery solution (Solvent No. 2), third-pass recovery solution (Solvent No. 3), and BKNP cleaning solvent stock solution (DL95);

[0075] Step S52: The first-pass recovered liquid of the waste solvent (Solvent No. 1), the second-pass recovered liquid (Solvent No. 2), the third-pass recovered liquid (Solvent No. 3), and the BKNP cleaning solvent stock solution (DL95) are placed in a gas chromatograph for chromatographic detection and analysis as shown in the following table;

[0076]

[0077] Table 2

[0078] Step S53: Detecting that the waste solvent recovered multiple times does not contain curing agent components (isocyanate), which means it is qualified;

[0079] Step S54: Compare the butanol, ethyl acetate, cyclohexanone, butyl acetate, and trimethyl-tetramethyl benzene contents of the BKNP cleaning solvent stock solution (DL95) with those of the multi-pass recycled waste solvent to confirm the dissolving power trend of the recycled waste solvent. The comparison shows a decrease in the butanol, ethyl acetate, and cyclohexanone contents, while little change in the butyl acetate and trimethyl-tetramethyl benzene contents. The recovered liquid contains methyl isobutyl ketone, toluene, and xylene, derived from paint, varnish, and the corresponding diluents. Testing indicates that silicone, a component that can cause craters, is not present.

[0080] Cleanliness test step S6 in this embodiment:

[0081] Step S61: Prepare test materials, 200 ml of waste solvent recovery liquid, a 300-mesh filter, a magnifying glass, and scissors;

[0082] Step S61: Pour the waste solvent recovery liquid into a 300-mesh filter bag for filtration, use scissors to cut off the folded filter screen after filtration, observe the filter screen with a magnifying glass, and score and evaluate the waste solvent recovery liquid with reference to the cleanliness evaluation standard (Table 3);

[0083] Step S62: The waste solvent recovery liquid score is compared with the passing mark of the cleanliness evaluation standard. The test indicates that the waste solvent recovery liquid contains one particle with a diameter greater than 100 μm. A 20-point deduction is made compared to the test standard, indicating that the cleanliness level is acceptable. Conclusion: The cleanliness level of the waste solvent recovery liquid meets the requirements for production line use.

[0084]

[0085] Table 3

[0086] Density test step S7 in this embodiment:

[0087] Step S71: Prepare test materials, 50 ml of waste solvent recovery solution, BYK density cup, and balance;

[0088] Step S72: First, weigh the density cup. Pour the waste solvent recovery liquid into the BYK density cup until the liquid level is just below the edge. Place the lid with holes on the top of the density cup and gently rotate it downward to close it tightly. The sample will slightly overflow from the small holes but will not spray out. Wipe off the sample that overflows from the lid and weigh the density cup filled with the sample. Divide the weight displayed on the balance (minus the weight of the density cup) by the volume of the density cup to obtain the density of the recovery liquid.

[0089] Step S73: Repeat the measurement three times to obtain an average value, compare the average value with the density standard range (Table 4), and confirm that it is within the qualified range;

[0090] name Density standard range First measurement Second measurement The third measurement average value Solvent recovery 0.86-0.94g / ml 0.874 0.873 0.873 0.873

[0091] Table 4

[0092] Step S8: The waste solvent recovery liquid that has passed the solubility test, shrinkage test, resistance test, chromatography test, cleanliness test and density test is stored in a recovery solvent barrel and stored in a designated area for use in washing tanks in the paint mixing room, long and short flushing of painting robots, washing guns in the spot repair room, and wiping tanks in the cleaning robot / paint mixing room.

[0093] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for testing the quality of waste solvent recovery liquid from coating waste solvent, characterized in that: The following steps are involved: Step S1: subjecting the waste solvent recovery liquid filtered by the membrane filtration treatment equipment to a solubility test, a shrinkage test, a resistance test, a chromatography test, a cleanliness test, and a density test; Step S2: Simulating the long and short flushing and color changing time of the coating production line, setting the paint flow plate to flash dry for 30 seconds and flash dry for 5 minutes to perform solubility tests; Step S21: prepare test materials, cleaning solvent stock solution, first-pass waste solvent recovery solution, second-pass waste solvent recovery solution, third-pass waste solvent recovery solution, Hongqi red paint, Arctic white paint, burette, 15cm*15cm glass piece; Step S22: Set the solvent titration quantity in the burette to 30 drops, select one each of the Red Flag red paint flow plate and the Arctic white paint flow plate, flash dry for 30 seconds, place them at a 20° angle under their respective burettes, and then use a burette filled with a stock solution of cleaning solvent (Solvent No. 0) to slowly titrate to the middle of the lower paint flow plate, titrating 30 drops. Place them in a safe place after the titration is completed. Step S23: Set the solvent titration quantity in the burette to 30 drops, select one Red Flag red paint flow plate and one Arctic white paint flow plate, flash dry for 5 minutes, place them at a 20° angle under their respective burettes, and then use a burette filled with a stock solution of cleaning solvent (Solvent No. 0) to slowly titrate to the middle of the lower paint flow plate, titrating 30 drops. Place them in a safe place after the titration is completed. Step S24: repeating steps S22 and S23 to complete the titration of the first recovery liquid of the Hongqi red paint and the Arctic white paint to the third recovery liquid of the flash-drying 30 seconds and the flash-drying 5 minutes; Step S25: By comparing the dissolving power of the cleaning solvent stock solution and the recovery solvents with different times on the Hongqi red paint flow plate and the Arctic white paint flow plate, if the dissolving power of the solvents with different times is close to that of the cleaning solvent stock solution and no obvious weakening is observed, it is qualified, otherwise it is unqualified; Step S3: shrinkage test; Step S31: prepare test materials, high temperature resistant film, third coat of waste solvent, Red Flag red paint, Arctic white paint, and manual spray gun; Step S32: mixing the third-pass waste solvent into the Red Flag red paint and the Arctic white paint at a dilution ratio of 10%, respectively, loading the mixture into a manual spray gun, and spraying the high-temperature resistant film; Step S33: The sprayed high temperature resistant film is placed in a 90 ° drying room for drying, the drying time is 30 minutes; Step S34: Take out the high temperature resistant film obtained in step S33 from the drying room and place it under an indoor light source for observation to confirm whether there are shrinkage holes. If shrinkage holes are found, the film is unqualified and needs to be scrapped. Otherwise, the film is qualified. Step S4: Resistance test: Step S41: preparing test materials, a resistance meter, a plastic cup, a waste solvent recovery solution, a varnish and paint cleaning solvent, and a primer cleaning solvent; Step S42: inserting the resistance meter into the plastic cups containing the waste solvent recovery liquid, the varnish and paint cleaning solvent, and the primer cleaning solvent, respectively, selecting the GΩ gear, and performing resistance testing, where 1 GΩ = 1000 MΩ; Step S43: comparing the detection result of step S42 to confirm whether the resistance value of the waste solvent recovery liquid is close to the resistance values ​​of the varnish and paint cleaning solvent and the primer cleaning solvent; Step S44: Detecting whether the resistance of the waste solvent recovery liquid in step S42 meets the requirement of ≥1MΩ, wherein if the resistance is ≥1MΩ, it is qualified; otherwise, it is unqualified and needs to be scrapped; Step S5: Chromatographic test: Step S51: preparing test materials, first-pass recovery liquid of waste solvent, second-pass recovery liquid, third-pass recovery liquid, and cleaning solvent stock solution; Step S52: putting the first-pass recovered liquid of the waste solvent, the second-pass recovered liquid, the third-pass recovered liquid, and the original cleaning solvent solution into a gas chromatograph for chromatographic detection and analysis; Step S53: Detecting whether the waste solvent recovered multiple times in step S52 contains a curing agent component. If it contains a curing agent component, it is unqualified and needs to be scrapped; Step S54: comparing the butanol, ethyl acetate, cyclohexanone, butyl acetate, and trimethyl-tetramethyl mixed benzene contents detected in the cleaning solvent stock solution with those of the multi-pass recovered waste solvent to confirm the solubility change trend of the multi-pass recovered waste solvent; Step S6: Cleanliness test: Step S61: Prepare test materials, 200 ml of waste solvent recovery liquid, a 300-mesh filter, a magnifying glass, and scissors; Step S61: Pour the waste solvent recovery liquid into a 300-mesh filter bag for filtration, use scissors to cut off the folded filter screen after filtration, observe the filter screen with a magnifying glass, and score and evaluate the waste solvent recovery liquid according to the cleanliness evaluation standard; Step S62: comparing the score of the waste solvent recovery liquid with the qualified mark of the cleanliness evaluation standard to determine whether the waste solvent recovery liquid is qualified; Step S7: Density test: Step S71: Prepare test materials, 50 ml of waste solvent recovery solution, a density cup, and a balance; Step S72: First, weigh the density cup. Pour the waste solvent recovery liquid into the density cup until the liquid level is just below the edge. Place the lid with holes on the top of the density cup and gently rotate it downward to close it tightly. The sample will slightly overflow from the small holes but will not spray out. Wipe off the sample overflowing from the lid and weigh the density cup filled with the sample. Divide the weight displayed on the balance by the volume of the density cup to obtain the density of the recovery liquid. Step S73: Repeat the measurement three times to obtain an average value, compare the average value with the density standard range, and confirm whether it is within the qualified range; Step S8: The waste solvent recovery liquid that has passed the solubility test, shrinkage test, resistance test, chromatography test, cleanliness test, and density test is stored in a recovery solvent barrel and stored in a designated area for use in washing tanks in the paint mixing room, long and short flushing of painting robots, washing guns in the spot repair room, and wiping tanks in the cleaning robot / paint mixing room.

2. The method for inspecting the quality of waste solvent recovery liquid of a coating waste solvent according to claim 1, characterized in that: Step S5 also includes step S55: detecting whether the silicone component that is likely to cause shrinkage cavities is contained.

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