Method for catalytic degradation of polyimide by ionic liquid

Abstract

The application provides a method for degrading polyimide by using ionic liquid as a catalyst, and belongs to the technical field of waste plastic recycling and resource utilization. The method comprises the following steps: uniformly mixing an ionic liquid catalyst, polyimide, water and an organic solvent, and then performing a hydrolysis reaction; the ionic liquid catalyst is a compound with a structure shown in formula I or formula II: in formula I and formula II, R is an alkyl group, a nitrile alkyl group, a hydroxyalkyl group, an ester group or an ether group; R2 is a nitrile alkyl group, a hydroxyalkyl group, an ester group, an ether group or an alkyl group, and R3 is a C1-C3 alkyl group; Y is Cl, Br, OAc, CH3CH2COO, CF3COO or (CF3SO2)2N. 1 – – – – – – – The application has the advantages of mild reaction conditions (such as 100 DEG C), simple separation and the like, can efficiently catalyze the hydrolysis reaction of waste polyimide, and has a wide industrial application prospect.​​​​​​​

Description

Technical Field

[0001] This invention relates to the field of waste plastic recycling and resource utilization technology, and in particular to a method for the catalytic degradation of polyimide using ionic liquids. Background Technology

[0002] Polyimide is a polymer whose main chain contains imide groups (─CO─N─CO─). It possesses excellent temperature resistance, chemical corrosion resistance, good mechanical properties, and outstanding thermal stability, and is widely used in photoresists, separation membranes, aerospace, and microelectronics industries. The demand for polyimide is increasing daily with the development of related industries. However, the production and use of polyimide generate a significant amount of waste. Traditional incineration or landfill methods result in resource waste and environmental pollution. Therefore, from the perspective of environmental protection and sustainable development, the recycling of polyimide deserves attention.

[0003]

[0004] Given the high bond energy of amide bonds in polyimides, effective cleavage of the amide carbon-nitrogen bonds typically requires an alkaline environment, i.e., treating polyimides with strong alkalis to achieve the hydrolytic cleavage of the five-membered rings. However, this process using strong alkalis corrodes equipment and has low degradation efficiency. Therefore, to meet the demands of contemporary green and sustainable development, the development of simple, efficient, and multifunctional catalysts for the efficient degradation of polyimides is urgently needed. Summary of the Invention

[0005] Based on the above, the purpose of this invention is to provide a method for the catalytic degradation of polyimide using ionic liquids. This invention uses ionic liquids as catalysts, which offers advantages such as mild reaction conditions, simple separation, high degradation efficiency, and recyclable catalysts.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for catalytic degradation of polyimide using ionic liquid involves mixing an ionic liquid catalyst, polyimide, water, and an organic solvent evenly before carrying out a hydrolysis reaction.

[0008] The ionic liquid catalyst is a compound with the structure shown in Formula I or Formula II:

[0009]

[0010] In Equations I and II, R 1 R1 is alkyl, cyanoalkyl, hydroxyalkyl, ester, or ether; R2 is cyanoalkyl, hydroxyalkyl, ester, ether, or alkyl; R3 is C 1- C3 alkyl; Y – For Cl – ,Br– OAc – CH3CH2COO – CF3COO – Or (CF3SO2)2N – .

[0011] In some embodiments of the present invention, the ionic liquid catalyst is aminoethyltriethylammonium bromide, hydroxyethyltriethylammonium acetate, ethoxyoxytriethyltrifluoroacetate, methoxytriethylpropionate, 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-cyanomethyl-3-methylimidazolium trifluoroacetate, 1-aminoethyl-3-methylimidazolium bromide, or 1-hydroxyethyl-3-imidazolium acetate. The structural formulas are shown in formulas IL-1 to IL-8.

[0012]

[0013] Different ionic liquids have different effects on the reaction yield. When the cation is an ether-substituted ammonium cation and the anion is a trifluoroacetate ion (IL-3), the ionic liquid has the best degradation effect on polyimide.

[0014] In some embodiments of the present invention, the molar ratio of the ionic liquid catalyst to the polyimide unit is (0.05-5):1.

[0015] In some embodiments of the present invention, the molar ratio of the ionic liquid catalyst to the polyimide unit is (0.1 to 0.5):1.

[0016] In some embodiments of the present invention, the molar ratio of the ionic liquid catalyst to the polyimide unit is 0.2:1.

[0017] In some embodiments of the present invention, the organic solvent is N,N-dimethylformamide; the molar ratio of the ionic liquid catalyst to the N,N-dimethylformamide is 1:(5.0 to 15.0).

[0018] In some embodiments of the present invention, the molar ratio of the ionic liquid catalyst to the N,N-dimethylformamide is 1:(5.0 to 10.0).

[0019] In some embodiments of the present invention, the molar ratio of the ionic liquid catalyst to the N,N-dimethylformamide is 1:(8.0 to 10.0).

[0020] In some embodiments of the present invention, the molar ratio of the ionic liquid catalyst to the N,N-dimethylformamide is 1:8.

[0021] In some embodiments of the present invention, the molar ratio of the ionic liquid catalyst to water is 1:(5 to 50.0).

[0022] In some embodiments of the present invention, the molar ratio of the ionic liquid catalyst to water is 1:(10.0 to 20.0).

[0023] In some embodiments of the present invention, the molar ratio of the ionic liquid catalyst to water is 1:(10.0 to 16.0).

[0024] In some embodiments of the present invention, the molar ratio of the ionic liquid catalyst to water is 1:10.

[0025] In some embodiments of the present invention, the hydrolysis reaction is carried out at a temperature of 60–140°C for a duration of 8–18 hours.

[0026] In some embodiments of the present invention, the hydrolysis reaction is carried out at a temperature of 80–130°C for a time of 12–18 hours.

[0027] In some embodiments of the present invention, the hydrolysis reaction is carried out at a temperature of 100–120°C for a time of 12–16 hours.

[0028] In some embodiments of the present invention, the hydrolysis reaction is carried out at a temperature of 100°C for 12 hours.

[0029] In some embodiments of the present invention, after the hydrolysis reaction is completed, the reaction solution is further cooled to room temperature, and then an extractant is added to the reaction solution for extraction. After extraction, the upper organic phase is collected, and then concentrated and purified to obtain diamine and dianhydride monomers; the lower aqueous phase is collected, and then evaporated to dryness to obtain an ionic liquid, which can be recycled.

[0030] In some embodiments of the present invention, the extractant is n-hexane, diethyl ether, butyl ether, methyl acetate, or ethyl acetate.

[0031] The present invention discloses the following technical effects:

[0032] This invention uses ionic liquid as a catalyst, which has the advantages of mild reaction conditions (such as 100°C) and simple separation. It can efficiently catalyze the hydrolysis reaction of waste polyimide and has broad industrial application prospects. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the process for the ionic liquid-catalyzed degradation of polyimide according to the present invention. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] according to Figure 1 The flowchart shown illustrates the hydrolysis reaction of polyimide, with the specific steps as follows:

[0041] Before the reaction, polyimide powder, N,N-dimethylformamide, water, and ionic liquid catalyst were sequentially added to the reactor. Under stirring and heating conditions, the reaction solution became homogeneous. After the reaction was completed, the mixture was allowed to cool to room temperature. An extractant was then added to the reaction solution, and the product and catalyst were observed to separate into layers: the upper layer consisted of dianhydride and diamine monomers, while the lower layer was the ionic liquid. Subsequently, the upper liquid was poured into a round-bottom flask for concentration, and column chromatography yielded the target product. After simple heating and drying, the lower layer could be recycled back into the reaction.

[0042] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0043] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0044] Examples 1-8

[0045] Polyimide (PI, 2.5 mmol monomer), water (5.0 mmol), N,N-dimethylformamide (6.0 mmol), and different ionic liquids (0.5 mmol) were added to a 25 mL reaction vessel and transferred to an oil bath set at 100 °C. The mixture was stirred and heated for 12 hours. After the reaction was terminated, the mixture was cooled to room temperature. Then, 5 mL of ethyl acetate was added to the reaction solution, and the mixture was extracted three times. The upper organic phase was collected, concentrated, and column chromatography was performed to obtain p-phenylenediamine and bisphenol A type diether tetracarboxylic acid. The lower ionic liquid was dried in a vacuum drying oven at 80 °C for 12 hours and could be directly used for the next reaction.

[0046]

[0047] Table 1. Reaction conditions and results of Examples 1-8

[0048]

[0049]

[0050] Examples 9-13

[0051] Using the ionic liquid IL-3 from Example 3, which showed the best performance, as the catalyst, and with the same reaction conditions as in Example 2, the catalyst performance was studied at different temperatures. The results are listed in Table 2.

[0052] Table 2 shows the reaction conditions and results of Examples 9-13.

[0053] 9 60 22 10 80 40 11 100 89 12 110 91 13 120 92

[0054] Examples 14-16

[0055] Using the ionic liquid IL-3 from Example 3 as a catalyst, the reaction was carried out at 100°C, with other reaction conditions being the same as in Example 3. The effect of different ionic liquid / water molar ratios on the product yield was investigated, and the results are listed in Table 3.

[0056] Table 3 Reaction conditions and results of Examples 14-16

[0057] 14 1 / 5 68 15 1 / 10 89 16 1 / 15 91

[0058] Examples 17-19

[0059] Using the ionic liquid IL-3 from Example 3 as a catalyst, the reaction was carried out at 100°C and with an ionic liquid / water molar ratio of 1 / 10. Other reaction conditions were the same as those in Example 3. The effect of different reaction times on the product yield was investigated, and the results are listed in Table 4.

[0060] Table 4. Reaction conditions and results of Examples 17-19

[0061] 17 8 65 18 12 89 19 16 90

[0062] Examples 20-25

[0063] Catalyst recycling: Using the dried ionic liquid recovered in Example 3 as the catalyst, the catalyst recycling performance was studied at 100°C for 12 hours and at an ionic liquid / water molar ratio of 1 / 10. The results are listed in Table 6.

[0064] Table 6. Reaction conditions and results of Examples 20-25

[0065] 20 0 89 21 1 92 22 2 90 23 3 91 24 4 88 25 5 86

[0066] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for catalytic degradation of polyimide using ionic liquids, characterized in that, The ionic liquid catalyst, polyimide, water, and organic solvent are mixed evenly and then subjected to a hydrolysis reaction. The ionic liquid catalyst is aminoethyltriethylammonium bromide, hydroxyethyltriethylammonium acetate, ethoxyoxytriethyltrifluoroacetate, methoxytriethylpropionate, 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-nitrilemethyl-3-methylimidazolium trifluoroacetate, 1-aminoethyl-3-methylimidazolium bromide, or 1-hydroxyethyl-3-imidazolium acetate.

2. The method for catalytic degradation of polyimide using ionic liquids according to claim 1, characterized in that, The molar ratio of the ionic liquid catalyst to the polyimide unit is (0.05~5):

1.

3. The method for ionic liquid-catalyzed degradation of polyimide according to claim 1, characterized in that, The organic solvent is N,N-dimethylformamide; the molar ratio of the ionic liquid catalyst to the N,N-dimethylformamide is 1:(5.0~15.0).

4. The method for ionic liquid-catalyzed degradation of polyimide according to claim 1, characterized in that, The molar ratio of the ionic liquid catalyst to water is 1:(5~50.0).

5. The method for catalytic degradation of polyimide using ionic liquids according to claim 1, characterized in that, The hydrolysis reaction is carried out at a temperature of 60~140 ℃ for a time of 8~18 h.

6. The method for catalytic degradation of polyimide using ionic liquids according to claim 1, characterized in that, After the hydrolysis reaction is completed, the process further includes cooling the reaction solution to room temperature and then adding an extractant to the reaction solution for extraction.

7. The method for catalytic degradation of polyimide using ionic liquids according to claim 6, characterized in that, The extractant is n-hexane, diethyl ether, butyl ether, methyl acetate, or ethyl acetate.

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