A purification method for polyimide resin

Abstract

The present invention provides a method for purifying polyimide resin, which relates to the field of polyimide resin. By using ultrasonic-composite solvent cleaning method for polyimide and ultrasonic semi-permeable membrane filtration method, impurities such as unreacted monomers, oligomers, catalysts, etc. in the polyimide can be effectively removed, so as to obtain a pure polyimide resin with a relatively narrow molecular weight distribution. The present invention innovatively uses the technology of ultrasonic cleaning with composite solvent and ultrasonic combined with polytetrafluoroethylene semi-permeable membrane, which greatly improves the purity of polyimide.

Description

Technical Field

[0001] The present invention relates to the field of polyimide resins, and more particularly to a novel purification method for polyimide resins. Background Art

[0002] Polyimide resins belong to polymer materials, and their molecular weights are usually distributed within a certain range, and they are themselves a "mixture". During the preparation process of polyimide resins, it is often necessary to add auxiliaries such as catalysts, and these substances usually remain in the finally obtained polyimide resins. In addition, unreacted monomers or oligomers often remain in the polyimide resins. The presence of these residual impurities will greatly reduce the performance of the polyimide resins. Therefore, it is necessary to purify the polyimide resins to improve their performance.

[0003] Since there are many reasons for the generation of impurities in polymer materials, it is necessary to select a suitable and effective purification method according to the specific situation. There are various purification methods reported for polymer materials before. For example, for the metal catalyst residues in polymer products, in the prior art, the properties of the metal catalyst residues are utilized to form chelates with other substances, and then the obtained chelates are dissolved with an appropriate solvent, while the polymer is precipitated and filtered, so as to achieve the purpose of purifying the polymer products.

[0004] For another example, in order to more thoroughly remove the mechanical impurities remaining in the polymer products and the low-molecular-weight molecular chains in the resin, a purification method for polyimide resins by filtering the raw material solution and using a purification solvent can be adopted (Patent CN113817167A). This method mainly uses filtration and a purification agent to dissolve and remove impurities such as residual solvents and catalysts.

[0005] However, the above methods have poor effects and efficiencies in removing residual solvents, volatile small molecule compounds, catalyst residues, and low-molecular-weight molecular chains. Summary of the Invention

[0006] In view of this, the present invention provides a novel purification method for polyimide resins. By the ultrasonic-composite solvent cleaning method for polyimide and the ultrasonic semi-permeable membrane filtration method, impurities such as unreacted monomers, oligomers, and catalysts in the polyimide can be removed, so as to obtain high-purity polyimide resins. The present invention innovatively uses the technologies of ultrasonic cleaning with a composite solvent and ultrasonic waves combined with a polytetrafluoroethylene semi-permeable membrane, which greatly improves the purity of the polyimide.

[0007] A purification method for a polyimide (PI) resin provided by the present invention is carried out according to the following steps:

[0008] S1. Crush the PI resin with a 200-mesh sieve of a crusher;

[0009] S2. Add it to the PI powder in a container with a composite solvent to obtain a PI mixture;

[0010] S3. Place the mixture container in an ultrasonic cleaner set at a certain temperature, perform ultrasonic cleaning for a certain period of time, and then filter and dry to obtain crude PI powder;

[0011] S4. Add the crude PI powder obtained in S3 to an electronic-grade good solvent to make a solution with a certain concentration;

[0012] S5. Push the solution prepared in S4 into an ultrasonic semi-permeable membrane filter through a plunger pump for filtration to obtain a purified PI solution.

[0013] According to a purification method of a polyimide resin provided by the present invention, the purpose of crushing in step S1 is to increase the specific surface area of the PI resin, which is convenient for improving the purification efficiency.

[0014] According to a purification method of a polyimide resin provided by the present invention, the composite solvent in step S2 is a nitrogen-containing polar solvent such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylformamide, N,N-diethylformamide, N-methylcaprolactam, N,N,N',N'-tetramethylurea; a lactone-based polar solvent such as β-propiolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone; dimethyl sulfoxide; acetonitrile; fatty acid esters such as ethyl lactate and butyl lactate; ethers such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dioxane, tetrahydrofuran, methyl cellosolve acetate, and ethyl cellosolve acetate; a phenolic solvent such as cresols, etc., which is a mixture of two or more substances in a certain ratio.

[0015] According to a purification method of a polyimide resin provided by the present invention, the ratio of the composite solvent is one of 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1. If more than two solvents are selected, it is preferred to select two main solvents for mixing.

[0016] According to a purification method of a polyimide resin provided by the present invention, the composite solvent in step S2 mainly dissolves and removes impurities such as unreacted monomers, organic catalysts, and oligomers.

[0017] According to a purification method of a polyimide resin provided by the present invention, the temperature of the ultrasonic cleaner in step S3 is set between 40°C and 60°C.

[0018] According to a purification method of a polyimide resin provided by the present invention, the cleaning time of the ultrasonic cleaner in step S3 is 0.5 - 2 h.

[0019] A purification method of polyimide resin provided by the present invention, wherein the mass fraction of the solution in step S4 is between 8% and 15%.

[0020] A purification method of polyimide resin provided by the present invention, wherein the semi-permeable membrane material used in step S5 is polytetrafluoroethylene, and preferably a polytetrafluoroethylene semi-permeable membrane with a pore size that can pass substances with a molecular weight below 2000 is selected.

[0021] A purification method of polyimide resin provided by the present invention, wherein the flow rate of the PI resin solution in step S5 is 1 mL / min to 10 mL / min.

[0022] A purification method of polyimide resin provided by the present invention, wherein the purified PI solution obtained in step S5 has a very narrow molecular weight distribution.

[0023] A purification method of polyimide resin provided by the present invention, wherein the residual monomer rate of the purified PI solution obtained in step S5 is less than 0.3%.

[0024] A purification method of polyimide resin provided by the present invention, wherein the catalyst residue rate of the purified PI solution obtained in step S5 is less than 0.1%.

[0025] The present invention also provides a high-purity polyimide resin prepared by the above purification method.

[0026] Beneficial effects

[0027] The present invention provides a purification method of polyimide resin. By using the ultrasonic-composite solvent cleaning method for polyimide and the ultrasonic semi-permeable membrane filtration method, impurities such as unreacted monomers, oligomers, and catalysts in the polyimide can be removed, thereby obtaining a pure polyimide resin with a very narrow molecular weight distribution. The present invention innovatively uses the technologies of ultrasonic cleaning with a composite solvent and ultrasonic waves combined with a polytetrafluoroethylene semi-permeable membrane, which greatly improves the purity of the polyimide. Description of the drawings

[0028] Figure 1 It is a schematic diagram of the novel purification method of polyimide resin in the embodiment of the present invention, wherein 1: crusher; 2: crude polyimide resin + composite solvent tank; 3: ultrasonic machine; 4: polyimide resin solution tank; 5: plunger pump; 6: electronic grade good solvent tank; 7: ultrasonic-semi-permeable membrane filtration device; 8: purified polyimide resin recovery tank; 9: filtered waste liquid tank; 10, 11, 12, 13 are valves; 14: polytetrafluoroethylene semi-permeable membrane. Detailed implementation manners

[0029] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0030] Unless the context clearly requires otherwise, the words such as "comprising", "including" and the like in the whole specification and claims should be interpreted as the meaning of including rather than exclusive or exhaustive; that is, the meaning of "including but not limited to".

[0031] A purification method of polyimide resin comprises the following steps:

[0032] Crush the PI resin with a 200-mesh sieve of a pulverizer, add the PI powder into a container of a composite solvent in a certain ratio to obtain a PI mixture, put the mixture container into an ultrasonic cleaner with a set temperature for ultrasonic cleaning for a certain time, then filter and dry to obtain coarse PI powder, add the obtained coarse PI powder into an electronic-grade good solvent to make a solution with a certain concentration, and push the solution into an ultrasonic semi-permeable membrane filter through a plunger pump for filtration to obtain a purified PI solution, which specifically includes the following steps (see the flow Figure 1 ):

[0033] a. Open valves 10 and 12, close other valves, and pump the coarse PI resin solution into the ultrasonic semi-permeable membrane filter through a plunger pump.

[0034] b. After all the PI resin solution is fed, close valve 10, open valve 11, introduce an electronic-grade good solvent, and push the resin solution for further filtration.

[0035] c. After a period of time, close valve 12, open valve 13, collect the purified PI resin, and then close valve 11.

[0036] The present invention will be further described below with reference to embodiments:

[0037] Embodiment 1

[0038] Crush 1 kg of PI resin with a 200-mesh sieve of a crusher, add it to the ultrasonic machine container, and add 1 kg of a composite solvent with a mass ratio of NNMP:DMF = 1:3 to the PI powder to obtain a PI resin suspension. Set the ultrasonic machine to 50 °C for ultrasonic cleaning for 2 h, filter and dry to obtain coarse PI powder. Add the obtained coarse PI powder to 9 kg of electronic-grade m-cresol to prepare a PI resin solution with a mass fraction of 10%. Push this solution into a ultrasonic - semipermeable membrane filter through a plunger pump at a rate of 3 mL / min for filtration to obtain a further purified PI solution. The specific steps are as follows:

[0039] a. Open valves 10 and 12, close other valves, and pump the coarse PI resin solution into the ultrasonic - semipermeable membrane filter through a plunger pump.

[0040] b. After all the PI resin solution has been fed, close valve 10, open valve 11, introduce electronic-grade m-cresol, and push the resin solution for further filtration. At this time, the solution flow rate is 8 mL / min.

[0041] c. After 2 h, close valve 12, open valve 13, collect the purified PI resin, and then close valve 11.

[0042] Example 2

[0043] Crush 1 kg of PI resin with a 200-mesh sieve of a crusher, add it to the ultrasonic machine container, and add it to a composite solvent container with a ratio of NMP:DMF = 1:4 to the PI powder to obtain a PI suspension. Set the ultrasonic machine temperature to 50 °C for ultrasonic cleaning for 2 h, filter and dry to obtain coarse PI powder. Add the obtained coarse PI powder to 9 kg of electronic-grade m-cresol to prepare a solution with a mass fraction of 10%. Push this solution into a ultrasonic - semipermeable membrane filter through a plunger pump at a rate of 3 mL / min for filtration to obtain a further purified PI solution. The specific steps are as follows:

[0044] a. Open valves 10 and 12, close other valves, and pump the coarse PI resin solution into the ultrasonic - semipermeable membrane filter through a plunger pump.

[0045] b. After all the PI resin solution has been fed, close valve 10, open valve 11, introduce electronic-grade good solvent, and push the resin solution for further filtration. At this time, the solution flow rate is 8 mL / min.

[0046] c. After 2 h, close valve 12, open valve 13, collect the purified PI resin, and then close valve 11.

[0047] Comparative Example 1

[0048] Crush 1 kg of PI resin with a 200-mesh sieve of a crusher, add it to an ultrasonic machine, add a composite solvent with a mass ratio of NNMP:DMF = 1:11 to the PI powder to obtain a PI suspension, set the ultrasonic machine to 50 °C for ultrasonic cleaning for 2 h, filter and dry to obtain coarse PI powder, add the obtained coarse PI powder to 9 kg of electronic-grade m-cresol to prepare a PI resin solution with a mass fraction of 10%, and push the solution into an ultrasonic semi-permeable membrane filter through a plunger pump for filtration to obtain a further purified PI solution, which specifically includes the following steps:

[0049] a. Open valves 10 and 12, close other valves, and pump the coarse PI resin solution into the ultrasonic semi-permeable membrane filter through a plunger pump.

[0050] b. After all the PI resin solution has been fed, close valve 10, open valve 11, introduce an electronic-grade good solvent, and push the resin solution for further filtration. At this time, the solution flow rate is 8 mL / min.

[0051] c. After 2 h, close valve 12, open valve 13, collect the purified PI resin, and then close valve 11.

[0052] Comparative Example 2

[0053] Crush 1 kg of PI resin with a 200-mesh sieve of a crusher, add it to an ultrasonic machine, add the PI powder to a composite solvent container with a mass ratio of NNMP:DMF = 1:13 to obtain a PI resin suspension, set the ultrasonic machine temperature to 50 °C for ultrasonic cleaning for 2 h, filter and dry to obtain coarse PI powder, add the obtained coarse PI powder to 9 kg of electronic-grade m-cresol to prepare a PI resin solution with a mass fraction of 10%, and push the solution into an ultrasonic semi-permeable membrane filter through a plunger pump for filtration to obtain a further purified PI solution, which specifically includes the following steps:

[0054] a. Open valves 10 and 12, close other valves, and pump the coarse PI resin solution into the ultrasonic semi-permeable membrane filter through a plunger pump.

[0055] b. After all the PI resin solution has been fed, close valve 10, open valve 11, introduce a good solvent, and push the resin solution for further filtration. At this time, the solution flow rate is 8 mL / min.

[0056] c. After 2 h, close valve 12, open valve 13, collect the purified PI resin, and then close valve 11.

[0057] Test the residual monomer rate and catalyst residue rate of the PI resins obtained in Examples 1-2 and Comparative Examples 1-2.

[0058] The test results are shown in the following table:

[0059]

[0060] It can be seen from the above results that when the compound solvent ratio is 1:3 or 1:4, high-purity PI resin can be obtained.

[0061] It is easy for those skilled in the art to understand that on the premise of no conflict, the above preferred solutions can be freely combined and superimposed.

Claims

1. A purification method of polyimide PI resin, characterized in that Proceed as follows: S1. Crush the PI resin with a 200-mesh sieve of a pulverizer; S2. Add it to a container with a composite solvent to obtain a PI mixture; S3. Place the mixture container in an ultrasonic cleaner with a set temperature, perform ultrasonic cleaning for a certain time, and then filter and dry to obtain coarse PI powder; S4. Add the coarse PI powder obtained in S3 to an electronic-grade good solvent to make a solution with a certain concentration; S5. Push the solution prepared in S4 into an ultrasonic semi-permeable membrane filter through a plunger pump for filtration to obtain a purified PI solution; The composite solvent in step S2 is a mixture prepared from N-methyl-2-pyrrolidone and N,N-dimethylformamide in a ratio of 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, or 1:

1.

2. The purification method of a polyimide PI resin according to claim 1, wherein The temperature of the ultrasonic cleaner in step S3 is set between 40°C and 60°C.

3. A purification method of a polyimide PI resin according to claim 1, characterized in that The cleaning time of the ultrasonic cleaner in step S3 is 0.5 - 2 h.

4. The purification method of a polyimide PI resin according to claim 1, characterized in that The mass fraction of the solution in step S4 is between 8% and 15%.

5. A purification method of a polyimide PI resin according to claim 1, characterized in that The semi-permeable membrane material used in step S5 is polytetrafluoroethylene; The flow rate of the PI resin solution in step S5 is 1 mL / min - 10 mL / min; The residual monomer rate of the purified PI solution obtained in step S5 is less than 0.3%; The catalyst residue rate of the purified PI solution obtained in step S5 is less than 0.1%.

6. A purification method of a polyimide PI resin according to claim 1, characterized in that The semi-permeable membrane used in step S5 is a polytetrafluoroethylene semi-permeable membrane with a molecular weight of less than 2000.

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