Solution separation method of polyetherimide / polysulfone compound

Abstract

The invention discloses a solution separation method of a polyetherimide / polysulfone compound. The method comprises the following steps: dissolving the polyetherimide / polysulfone compound in a first solvent to obtain a mixture solution; a solution dissolving and separating method is adopted, tetrahydrofuran is taken as a main component in a second solvent, and polar solvents such as ethanol and water are used cooperatively, so that polyetherimide is separated out quickly and efficiently, effective separation of polyetherimide and polysulfone is realized, the obtained recycled polymer is good in purity, high in yield and good in mechanical property, the additional value of the recycled product can be effectively improved, and the method is suitable for industrial production. The cyclic utilization value of the compound is improved.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material recovery, and in particular to a method for separating a polyetherimide / polysulfone complex solution. Background Art

[0002] Polyetherimide (PEI) has good heat resistance and mechanical properties, and can be widely used in high temperature resistant terminals, IC bases, lighting equipment, liquid delivery equipment, aircraft internal parts, medical equipment and household appliances. Polysulfone (PSF or PSU) is a thermoplastic resin containing sulfone groups (-SO2-) and arylene groups in the main chain of the molecule, and also has good heat resistance and mechanical properties. It is very suitable for making heat-resistant parts, insulating parts, wear-resistant parts, instrument parts and medical equipment parts. Modified products of polysulfone made of polysulfone, polyimide, polyetheretherketone and fluoroplastics can further improve its impact strength, elongation, solvent resistance, environmental resistance, processing performance, etc.

[0003] In medical or food applications, products need to meet the requirements of retaining properties after repeated exposure to high-temperature sterilization (sterilization at 130-138°C for up to 100, 500, or even 1000 cycles). General plastic materials such as PP melt and deform at higher autoclave temperatures and are difficult to continue using. Therefore, plastic resins that can withstand high-temperature sterilization and high-pressure sterilization are needed. Since both polyetherimide and polysulfone have good heat resistance and mechanical properties, they are often used in the medical and food fields to prepare parts that require repeated high-temperature boiling and sterilization. However, pure polyetherimide has poor hydrolysis stability and polysulfone has poor heat resistance. Both of them are difficult to meet demanding use requirements when used alone. Blending and modifying polyetherimide and polysulfone can improve the hydrolysis resistance and solvent resistance of the product.

[0004] CN101802099A discloses a polyetherimide / polyphenylene ether sulfone blend, the blend comprising 25-90 wt% polyetherimide and 10-75 wt% polyphenylene ether sulfone (PSU), the composition maintaining good hydrolytic stability and being able to withstand steam autoclave at 130-138° C. The multi-axial impact energy after exposure to steam autoclave at 130-138° C. for 300 hours is greater than or equal to 20 ft-lbs (27 J).

[0005] CN103732688A discloses a sterilized polyetherimide / polyphenylene ether sulfone article, the polymer composition contains 20 to 80 wt% of polyphenylene ether sulfone; and 20 to 80 wt% of polyetherimide. When sterilized with hydrogen peroxide plasma or hydrogen peroxide vapor, the article has unexpected resistance to color change and transparency, as well as resistance to loss of mechanical properties.

[0006] For medical devices or food devices made of polyetherimide / polysulfone, it is difficult to separate polyetherimide from polysulfone when recycling by physical process, and only polyetherimide / polysulfone blends can be obtained. In most cases, downstream recycling hopes to obtain as pure polyetherimide polymers and polysulfone polymers as possible to improve the recycling value of the products. Summary of the invention

[0007] Aiming at the problem that polyetherimide and polysulfone in polyetherimide / polysulfone blend recycled materials are difficult to separate, the invention provides a solution separation method for polyetherimide and polysulfone. The invention adopts a double solution configuration to effectively and quickly separate polysulfone and polyetherimide, and recovers polyetherimide polymer and polysulfone polymer with high purity, and the recovered material has good mechanical properties.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for separating polyetherimide / polysulfone complexes by solution, comprising the steps of:

[0010] Step 1, dissolving a polyetherimide / polysulfone complex in a first solvent to obtain a mixture solution;

[0011] Step 2, adding the mixture solution dropwise into the second solvent, stirring continuously during the dropping process to obtain a precipitated polymer, filtering to obtain a polyetherimide filter cake and a filtrate containing polysulfone, washing the filter cake with the second solvent, and drying to obtain primary recovered polyetherimide;

[0012] Step 3, pouring the filtrate containing polysulfone in step 2 into the precipitate to precipitate polysulfone, washing the filter cake with ethanol after filtering, and drying to obtain primary recovered polysulfone;

[0013] Step 4, adding the polysulfone filter cake obtained in step 3 to a tetrahydrofuran solvent for dissolution, filtering to obtain a filter cake containing polyetherimide and a tetrahydrofuran solution containing polysulfone; washing and drying the filter cake containing polyetherimide with ethanol to obtain secondary recovered polyetherimide; pouring the tetrahydrofuran solution containing polysulfone into ethanol for precipitation, filtering, washing and drying the filter cake with ethanol to obtain recovered polysulfone;

[0014] The first solvent comprises 100 parts of a polyimide good solvent and 10-90 parts of a polysulfone good solvent in parts by mass; the second solvent comprises 100 parts of tetrahydrofuran, 50-90 parts of ethanol, 10-30 parts of water, and 0.01-2 parts of a surfactant in parts by mass.

[0015] Both polyetherimide and polysulfone have good solubility in polar aprotic solvents, such as N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, cyclopentane sulfone, etc. It is difficult to separate polyetherimide from polysulfone. However, polyetherimide cannot be dissolved in tetrahydrofuran, while polysulfone has good solubility in tetrahydrofuran solvent. If the polyetherimide / polysulfone blend is directly placed in tetrahydrofuran and heated to dissolve, when the polysulfone content in the blend is greater than 50%, polyetherimide and polysulfone can be separated. However, when the polysulfone content is below 50%, polysulfone appears as a dispersed phase in the blend, and it is difficult to separate the polysulfone by dissolving it in tetrahydrofuran.

[0016] Based on this, the present invention dissolves the polyetherimide / polysulfone blend in a first solvent, and then, utilizing the solubility difference between the two in tetrahydrofuran, drops the solution into a second solvent mainly composed of tetrahydrofuran to rapidly precipitate the polyetherimide, thereby separating the polyetherimide from the polysulfone.

[0017] However, in actual operation, the polyetherimide / polysulfone solution is directly added dropwise into the pure tetrahydrofuran solvent, and it is difficult for the polyetherimide to precipitate quickly. Moreover, with the addition of the polyetherimide / polysulfone solution, the content of the first solvent in the second solvent also increases, and a large amount of polyetherimide will remain in the mixed solvent and cannot be precipitated. The present invention unexpectedly found that adding solvents such as ethanol and water to tetrahydrofuran and supplemented with a small amount of surfactant can accelerate the precipitation of polyetherimide from the mixed solvent, improve the precipitation effect of polyetherimide, and effectively and quickly separate the two.

[0018] Preferably, the polyimide good solvent is selected from at least one of N,N-dimethylacetamide, N-methylpyrrolidone, cyclopentane, dimethyl sulfoxide, hexamethylphosphoric triamide, N-cyclohexylpyrrolidone, N,N-dimethylacetamide, N-methylcaprolactam, chloroform and m-cresol;

[0019] Preferably, the polysulfone good solvent is selected from at least one of N-methylpyrrolidone, sulfolane, dimethyl sulfoxide, N-cyclohexylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and tetrahydrofuran.

[0020] Further preferably, the polyimide good solvent is selected from at least one of chloroform, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide, and may be further preferably chloroform or N,N-dimethylacetamide;

[0021] More preferably, the polysulfone good solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylacetamide and sulfolane, and more preferably dimethyl sulfoxide, sulfolane or tetrahydrofuran.

[0022] Preferably, the first solvent comprises 100 parts of a polyimide good solvent and 10-50 parts of a polysulfone good solvent in parts by mass.

[0023] In the polyetherimide / polysulfone composite, the weight proportion of polyetherimide is 50-99%, and the weight proportion of polysulfone is 1-50%.

[0024] The precipitating liquid is selected from ethanol and / or water.

[0025] The surfactant includes at least one of sodium oleate, stearylamine, sodium laurate, coconut amine, sodium stearate, AES, sodium lauryl sulfate, dodecylamine, sodium dodecylbenzene sulfonate, and polyvinyl alcohol, and polyvinyl alcohol may be further preferred.

[0026] Preferably, in step 1, the dissolution temperature is 40-90° C. and the dissolution time is 1-10 hours.

[0027] Further preferably, the dissolution temperature in step 1 is 50-80° C. and the dissolution time is 1-3 hours, so that all the raw materials are basically dissolved. During the dissolution process, a reflux condenser is used to cool and reflux the low boiling point solvent to avoid volatilization loss of the low boiling point solvent.

[0028] Preferably, the mixed solution is continuously stirred during the dropwise addition in step 2, and the stirring speed is 10-300 rpm.

[0029] In step 1, the mass concentration of the complex in the first solvent is in the range of 1 to 30%.

[0030] In step 2, the volume ratio of the mixture solution to the second solvent is 1:1-100, and can be further preferably 1:5-10.

[0031] In step 3, the volume ratio of the filtrate containing polysulfone to the precipitate is 1:1-10, and can be further preferably 1:5-10.

[0032] In step 3, the filtrate containing polysulfone is cooled to near room temperature and then carried out to the next step.

[0033] In step 4, the dissolution of the polysulfone filter cake is carried out at room temperature.

[0034] Preferably, in step 2 and step 3, the complex solution is added dropwise to the second solvent and the filtrate is poured into the ethanol solution slowly with continuous stirring to allow the polyetherimide or polysulfone to precipitate quickly.

[0035] Preferably, the filter cake in step 2 is washed with the second solvent and then with ethanol;

[0036] Preferably, washing in step 2 or step 3 is generally performed 2-5 times, preferably 3 times.

[0037] The total weight of the recovered polyetherimide obtained by the solution separation method of the present invention is the sum of the weights of the primary recovered polyetherimide obtained in step 2 and the secondary recovered polyetherimide obtained in step 4;

[0038] The recovered polyetherimide and polysulfone obtained by the separation method of the present invention have good mechanical properties, which can effectively improve the added value of the recovered products. For example, the tensile strength of the recovered polyetherimide film after film casting can reach more than 100Mpa;

[0039] The recovery yield of the polyetherimide is above 90%, and the tensile strength is above 100MPa; the recovery yield of the polysulfone is above 90%, and the tensile strength is above 60MPa.

[0040] The recovery yield of the present invention refers to the ratio of the mass of the recovered polyetherimide or polysulfone to the theoretical mass of each in the blend.

[0041] The polyetherimide and polysulfone obtained by the separation method of the present invention not only have high purity, but also have high actual recovery yield, which is closer to the theoretical content of each substance in the composite raw material, and fully realizes the high-value recovery of waste composites. Preferably, all solvents used in the present invention are recycled, which saves costs and is more environmentally friendly.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention adopts a solution dissolution and precipitation method, wherein tetrahydrofuran is mainly used as the second solvent, and polar solvents such as ethanol and water are used in combination, so that polyetherimide is precipitated quickly and efficiently, and effective separation of polyetherimide and polysulfone is achieved. The obtained recycled polymer has good purity, high yield and good mechanical properties, and can effectively improve the added value of the recycled product and the recycling value of the composite. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art can make modifications or equivalent substitutions based on the understanding of the technical scheme of the present invention without departing from the spirit and scope of the technical scheme of the present invention, and all should be included in the protection scope of the present invention.

[0045] The raw materials used in the following specific embodiments are all purchased from the market, and the polyetherimide / polysulfone composite is derived from a homemade polyetherimide / polyphenylsulfone blend, in which the average mass content of polyetherimide is 80%. The polyetherimide and polysulfone recovered in the examples and comparative examples are subjected to FTIR detection to evaluate the recovery purity of the polyetherimide and polysulfone.

[0046] Example 1

[0047] Step 1, prepare a first solvent according to 100 parts by weight of chloroform and 10 parts by weight of dimethyl sulfoxide; prepare a second solvent according to 100 parts by weight of tetrahydrofuran, 50 parts by weight of ethanol, 30 parts by weight of water, and 0.05 parts by weight of polyvinyl alcohol. Put 20g of polyetherimide / polysulfone blend into 180g of the first solvent, heat to 90°C, stir and dissolve for 2 hours to obtain a polyetherimide / polysulfone blend solution, wherein the mass content of the blend in the first solvent is 10%.

[0048] Step 2, slowly drop the polyetherimide / polysulfone blend solution into the second solvent, the volume ratio of the two is 1:5, and the temperature of the second solvent is 50°C. During the dropwise addition, the second solvent is continuously stirred at a stirring speed of 200rpm. After the dropwise addition, polymers are continuously precipitated. After the dropwise addition is completed, stirring is continued for 0.5h, and the second solvent is filtered to obtain a polyetherimide polymer filter cake and a filtrate containing polysulfone. The filter cake is cyclically cleaned 3 times with the prepared second solvent, rinsed 3 times with ethanol, and dried to obtain the recovered polyetherimide polymer.

[0049] Step 3, slowly add the filtrate containing polysulfone into the continuously stirred ethanol to precipitate, the volume ratio of the filtrate to the ethanol is 1:5, and the temperature of the ethanol is room temperature. Filter to obtain a filter cake, rinse the filter cake with ethanol three times, and dry it to obtain the primary recovered polysulfone.

[0050] Step 4, adding the primary recovered polysulfone obtained in step 3 to tetrahydrofuran solvent again to dissolve, filter, and obtain an insoluble polyetherimide filter cake and a tetrahydrofuran solution containing polysulfone. The polyetherimide filter cake is washed with ethanol three times, and dried to obtain secondary recovered polyetherimide; the polysulfone solution is slowly poured into ethanol for precipitation, and the filter cake is washed with ethanol three times after filtering, and dried to obtain recovered polysulfone.

[0051] In this embodiment, the primary recovery of polyetherimide and the secondary recovery of polyetherimide totaled 15.21g, with a recovery rate of 95.06%, and the recovery of polysulfone was 3.73g, with a recovery rate of 93.25%. No obvious impurities were found in the FTIR spectra of the two polymers. PEI and PSU were cast into films by solution casting and the mechanical properties were tested.

[0052] Example 2

[0053] Step 1, prepare the first solvent according to 100 parts by weight of chloroform and 50 parts by weight of dimethyl sulfoxide; prepare the second solvent according to 100 parts by weight of tetrahydrofuran, 75 parts by weight of ethanol, 25 parts by weight of water, and 0.2 parts by weight of polyvinyl alcohol. Put 20g of polyetherimide / polysulfone blend into 80g of the first solvent, heat to 90°C, and stir and dissolve for 2 hours to obtain a polyetherimide / polysulfone blend solution. The mass content of the blend in the first solvent is 20%.

[0054] Step 2, slowly drop the polyetherimide / polysulfone blend solution into the second solvent, the volume ratio of the two is 1:10, and the temperature of the second solvent is 50°C. During the dropwise addition, the second solvent is continuously stirred at a stirring speed of 200rpm. During the dropwise addition, polymers are continuously precipitated. After the dropwise addition is completed, stirring is continued for 0.5h, and the second solvent is filtered to obtain a polyetherimide polymer filter cake and a filtrate containing polysulfone. The filter cake is cyclically cleaned 3 times with the prepared second solvent, rinsed 3 times with ethanol, and dried to obtain the recovered polyetherimide polymer.

[0055] Step 3, slowly add the filtrate containing polysulfone into the continuously stirred ethanol to precipitate, the volume ratio of the filtrate to the ethanol is 1:5, and the temperature of the ethanol is room temperature. Filter to obtain a filter cake, rinse the filter cake with ethanol three times, and dry it to obtain the primary recovered polysulfone.

[0056] Step 4, adding the primary recovered polysulfone obtained in step 3 to tetrahydrofuran solvent again to dissolve, filter, and obtain an insoluble polyetherimide filter cake and a tetrahydrofuran solution containing polysulfone. The polyetherimide filter cake is washed with ethanol three times, and dried to obtain secondary recovered polyetherimide; the polysulfone solution is slowly poured into ethanol for precipitation, and the filter cake is washed with ethanol three times after filtering, and dried to obtain recovered polysulfone.

[0057] In this embodiment, the primary recovery of polyetherimide and the secondary recovery of polyetherimide totaled 15.63g, with a recovery rate of 97.69%, and the recovery of polysulfone was 3.87g, with a recovery rate of 96.75%. No obvious impurities were found in the FTIR spectra of the two polymers. PEI and PSU were cast into films by solution casting, and the mechanical properties were tested.

[0058] Example 3

[0059] Step 1, prepare the first solvent according to 100 parts by weight of chloroform and 90 parts by weight of dimethyl sulfoxide; prepare the second solvent according to 100 parts by weight of tetrahydrofuran, 90 parts by weight of ethanol, 10 parts by weight of water, and 2 parts by weight of sodium dodecylbenzene sulfonate. Put 20g of polyetherimide / polysulfone complex into 80g of the first solvent, heat to 90°C, stir and dissolve for 2 hours to obtain a polyetherimide / polysulfone complex solution. The mass content of the complex in the first solvent is 20%.

[0060] Step 2, slowly drop the polyetherimide / polysulfone complex solution into the second solvent, the volume ratio of the two is 1:10, and the temperature of the second solvent is 50°C. During the dropwise addition, the second solvent is continuously stirred at a stirring speed of 200rpm. After the dropwise addition is completed, the solution is heated to 60°C for atmospheric distillation to volatilize and remove the chloroform in the solution. During the distillation process, as the chloroform content gradually decreases, polymers are continuously precipitated, and the second solvent is filtered to obtain a polyetherimide polymer filter cake and a filtrate containing polysulfone. The filter cake is circulated and cleaned 3 times with the prepared second solvent, rinsed 3 times with ethanol, and dried to obtain the recovered polyetherimide polymer.

[0061] Step 3, slowly add the filtrate containing polysulfone into the continuously stirred ethanol to precipitate, the volume ratio of the filtrate to the ethanol is 1:5, and the temperature of the ethanol is room temperature. Filter to obtain a filter cake, rinse the filter cake with ethanol three times, and dry to obtain the recovered polysulfone polymer.

[0062] Step 4, adding the primary recovered polysulfone obtained in step 3 to tetrahydrofuran solvent again to dissolve, filter, and obtain an insoluble polyetherimide filter cake and a tetrahydrofuran solution containing polysulfone. The polyetherimide filter cake is washed with ethanol three times, and dried to obtain secondary recovered polyetherimide; the polysulfone solution is slowly poured into ethanol for precipitation, and the filter cake is washed with ethanol three times after filtering, and dried to obtain recovered polysulfone.

[0063] In this embodiment, the primary recovery of polyetherimide and the secondary recovery of polyetherimide totaled 15.39g, with a recovery rate of 96.19%, and the recovery of polysulfone was 3.82g, with a recovery rate of 95.5%. No obvious impurities were found in the FTIR spectra of the two polymers. PEI and PSU were cast into films by solution casting, and the mechanical properties were tested.

[0064] Comparative Example 1

[0065] The composite was recovered according to the process of Example 1, except that the ratio of the second solvent was different from that of Example 1. The second solvent was 100 parts of tetrahydrofuran, 10 parts of ethanol, 1 part of water, and 0.1 part of polyvinyl alcohol.

[0066] In step 3, the complex solution was added dropwise to the second solvent and stirred at 50° C. It was found that the polymer precipitated slowly and in a very small amount, so the next separation operation could not be performed.

[0067] Comparative Example 2

[0068] The composite was recovered according to the process of Example 2, except that the second solvent was used in a different ratio. The second solvent was 100 parts of tetrahydrofuran, 90 parts of ethanol, and 30 parts of water. During the precipitation process, the polymer gradually condensed together to form a large mass of colloid, which was difficult to enter the next separation operation.

[0069] Comparative Example 3

[0070] The composite was recovered according to the process of Example 2, except that the ratio of the second solvent was different from that of Example 2. The second solvent was 100 parts of tetrahydrofuran, 90 parts of ethanol, 100 parts of water, and 0.2 parts of polyvinyl alcohol. During the precipitation process, the polymer would adhere to form large flocs, affecting the separation efficiency of PEI and PSU.

[0071] Table 1 Yield and mechanical properties of PEI and PSU recovered in Examples and Comparative Examples

[0072] Serial number Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 PEI recovery mass / g 15.21 15.63 15.39 / / 14.93 PEI recovery yield / % 95.06 97.69 96.19 93.31 PEI tensile strength / MPa 109.7 113.2 111.8 / / 98.9 PEI elongation at break / % 13.6 21.7 18.7 / / 16.2 PSU recovery mass / g 3.73 3.87 3.82 / / 3.17 PSU recovery yield / % 93.25 96.75 95.5 / / 79.25 PSU tensile strength / MPa 67.7 68.4 67.9 / / 65.9 PSU breaking elongation / % 37.3 51.6 43.2 / / 31.3

[0073] As shown in Table 1, Examples 1 to 3 and Comparative Examples 1 to 2 show that in the polyetherimide / polysulfone solution separation process, the solvent formulation design affects the degree of separation of polyetherimide and polysulfone. Adding an appropriate amount of ethanol, water and surfactant to the second solvent is conducive to the precipitation of polyetherimide from the solution, improving the separation efficiency of polyetherimide and polysulfone, thereby obtaining a higher yield.

[0074] Comparative Example 2 shows that if no surfactant is added in the second solvent, the polymer precipitated will be bonded. It is unfavorable for the later separation operation. Comparative Example 3 shows that if the content of ethanol and water in the second solvent is too much, the precipitation of the polymer will be accelerated, and a small amount of polysulfone will be brought out and precipitated during the precipitation of PEI, which will not only affect the overall recovery efficiency, but also affect the tensile strength of PEI. The residual of a small amount of polysulfone will cause the tensile strength of PEI to be low, but because PSU and PEI have certain compatibility, the elongation at break is not significantly affected.

Claims

1. A method for separating a polyetherimide / polysulfone complex solution, characterized in that: Includes steps: Step 1, dissolving a polyetherimide / polysulfone complex in a first solvent to obtain a mixture solution; Step 2, adding the mixture solution dropwise into the second solvent, stirring continuously during the dropping process to obtain a precipitated polymer, filtering to obtain a polyetherimide filter cake and a filtrate containing polysulfone, washing the filter cake with the second solvent, and drying to obtain primary recovered polyetherimide; Step 3, pouring the filtrate containing polysulfone in step 2 into the precipitate to precipitate polysulfone, washing the filter cake with ethanol after filtering, and drying to obtain primary recovered polysulfone; Step 4, adding the polysulfone filter cake obtained in step 3 to a tetrahydrofuran solvent for dissolution, filtering to obtain a filter cake containing polyetherimide and a tetrahydrofuran solution containing polysulfone; washing and drying the filter cake containing polyetherimide with ethanol to obtain secondary recovered polyetherimide; pouring the tetrahydrofuran solution containing polysulfone into ethanol for precipitation, filtering, washing and drying the filter cake with ethanol to obtain recovered polysulfone; The first solvent comprises 100 parts of a polyimide good solvent and 10-90 parts of a polysulfone good solvent in parts by mass; the second solvent comprises 100 parts of tetrahydrofuran, 50-90 parts of ethanol, 10-30 parts of water, and 0.01-2 parts of a surfactant in parts by mass.

2. The method for separating the polyetherimide / polysulfone complex solution according to claim 1, characterized in that: The polyimide good solvent is selected from at least one of N,N-dimethylacetamide, N-methylpyrrolidone, cyclopentane, dimethyl sulfoxide, hexamethylphosphoric triamide, N-cyclohexylpyrrolidone, N,N-dimethylacetamide, N-methylcaprolactam, chloroform and m-cresol; The polysulfone good solvent is selected from at least one of N-methylpyrrolidone, sulfolane, dimethyl sulfoxide, N-cyclohexylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and tetrahydrofuran.

3. The method for separating the polyetherimide / polysulfone complex solution according to claim 1, characterized in that: The polyimide good solvent is selected from at least one of chloroform, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide; The polysulfone good solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylacetamide and sulfolane; The precipitating liquid is selected from ethanol and / or water.

4. The method for separating the polyetherimide / polysulfone complex solution according to claim 1, characterized in that: The first solvent includes 100 parts of a polyimide good solvent and 10-50 parts of a polysulfone good solvent in parts by mass.

5. The method for separating the polyetherimide / polysulfone complex solution according to claim 1, characterized in that: The surfactant includes at least one of sodium oleate, stearylamine, sodium laurate, coconut amine, sodium stearate, AES, sodium lauryl sulfate, dodecylamine, sodium dodecylbenzene sulfonate, and polyvinyl alcohol.

6. The method for separating the polyetherimide / polysulfone complex solution according to claim 1, characterized in that: In step 1, the dissolution temperature is 40-90° C. and the dissolution time is 1-10 hours.

7. The method for separating the polyetherimide / polysulfone complex solution according to claim 1, characterized in that: In step 2, the mixed solution is continuously stirred during the dropwise addition process, and the stirring speed is 10-300 rpm.

8. The method for separating the polyetherimide / polysulfone complex solution according to claim 1, characterized in that: In step 1, the mass concentration of the complex in the first solvent is in the range of 1 to 30%; In step 2, the volume ratio of the mixture solution to the second solvent is 1:5-10; In step 3, the volume ratio of the filtrate containing polysulfone to the precipitate is 1:1-10.

9. The method for separating the polyetherimide / polysulfone complex solution according to claim 1, characterized in that: The tensile strength of the recovered polyetherimide is above 100 MPa; the tensile strength of the recovered polysulfone is above 60 MPa.

10. The method for separating a polyetherimide / polysulfone complex solution according to claim 1, characterized in that: The recovery yield of the polyetherimide is above 90%; the recovery yield of the polysulfone is above 90%.