Polynorbornene imide for winding insulation as well as preparation method and application of polynorbornene imide

Abstract

The invention discloses polynorbornene imide for winding insulation as well as a preparation method and application of the polynorbornene imide, and belongs to the technical field of electrical insulation materials and preparation of the electrical insulation materials. The invention solves the problem of low polymerization degree of the existing polynorbornene imide. Compared with a traditional DCM solvent, the binary solvent system composed of DMF and ethyl acetate is used for preparing polynorbornene imide, the polymerization effect is obviously improved, and the polymer yield is as high as 17.3%. Compared with the polynorbornene, the polynorbornene imide film prepared by the preparation method has the advantages that an imide group is introduced, and the imide group has a relatively strong electron attraction effect, so that the electrophilic property of the polynorbornene is enhanced, and the breakdown field strength of the polynorbornene imide can reach 500MV / m. The preparation process provided by the invention is simple, feasible, pollution-free, low in required equipment cost and suitable for large-scale production, has important scientific research value, and also has huge application potential and market prospect.

Description

Technical Field

[0001] The invention relates to polynorbornene imide for winding insulation and a preparation method and application thereof, belonging to the technical field of electrical insulating materials and preparation thereof. Background Art

[0002] As people's demand for electricity continues to increase, the operating load and voltage of electrical equipment are also gradually increasing, and the performance requirements for winding insulation materials are becoming higher and higher. Although existing winding insulation materials can meet basic needs to a certain extent, with the continuous improvement of electrical equipment's requirements for long-term stability, mechanical properties, and chemical corrosion resistance, the performance of existing materials has gradually become difficult to meet these higher standards. In addition, most traditional winding insulation materials also have toxic problems in the preparation process, which not only causes environmental pollution, but also makes the process more complicated. Therefore, the development of new winding insulation materials to improve their performance under complex working conditions has become an important research direction in the field of electrical engineering.

[0003] As a winding insulation material, poly (norbornene imide) has significant advantages and functions. First, it exhibits excellent electrical insulation under high electric fields, and its electrical conductivity is two orders of magnitude lower than that of the common material polyetherimide (PEI), which makes it have significant advantages among dielectric polymers. In addition, poly (norbornene imide) has the characteristics of wide band gap and short charge jumping distance, which help to improve the electrical insulation performance of the material. However, the preparation effect of existing poly (norbornene imide) is not ideal. The degree of polymerization is not high when using traditional dichloromethane for preparation, and although polymerization can be successfully achieved by using other single solvents (such as DMF or ethyl acetate), the yield is low. These methods have failed to obtain poly (norbornene dianhydride) with a higher yield, and the yield is less than 10%. Therefore, it is very necessary to provide an efficient preparation method for poly (norbornene imide). Summary of the invention

[0004] Aiming at the problem of low polymerization degree of existing polynorbornene imide, the present invention provides a polynorbornene imide for winding insulation and a preparation method and application thereof.

[0005] The technical solution of the present invention:

[0006] One of the objects of the present invention is to provide a method for preparing polynorbornene imide for winding insulation, the method comprising the following steps:

[0007] (1) dissolving 5-norbornene-2,3-dicarboximide in a binary solvent in a nitrogen environment without water or oxygen to form a solution A;

[0008] (2) dissolving the Grubbs II catalyst in a binary solvent in an anhydrous and oxygen-free nitrogen environment to form solution B;

[0009] (3) In an anhydrous and oxygen-free nitrogen environment, solution A and solution B are mixed and stirred to obtain a mixed solution, the mixed solution is reacted at 50° C. for 6-8 hours, and then a stop agent is added and stirred for 30 minutes to stop the reaction;

[0010] (4) Under light-proof conditions, the reaction solution obtained in (3) is added dropwise to a cold methanol solution to obtain a solid product, and the solid product is subjected to Soxhlet extraction using methanol as a solvent for 45-50 hours, and finally vacuum dried at 60° C. to obtain polynorbornene imide.

[0011] It is further defined that the binary solvent consists of N,N-dimethylformamide and ethyl acetate.

[0012] It is further defined that the volume ratio of N,N-dimethylformamide to ethyl acetate in the binary solvent is 4:1.

[0013] It is further defined that the mass volume ratio of 5-norbornene-2,3-dicarboximide to the binary solvent in (1) is 2 g:25 ml.

[0014] It is further defined that the mass volume ratio of the Grubbs II catalyst to the binary solvent in (1) is 25 mg:5 ml.

[0015] It is further defined that the mass ratio of 5-norbornene-2,3-dicarboximide to Grubbs II catalyst in the mixed solution of (3) is 2 g:25 mg.

[0016] It is further defined that the stopper in (3) is vinyl ethyl ether.

[0017] It is further defined that the temperature of the methanol during cooling in (4) is 0 to 5°C.

[0018] The second object of the present invention is to provide a polynorbornene imide prepared by the above method for winding insulation.

[0019] The third object of the present invention is to provide a method for preparing a polymer film for winding insulation, which specifically comprises: dissolving the above-mentioned polynorbornene imide for winding insulation in N,N-dimethylformamide, and then forming a film on a glass plate by a solution casting method to obtain a wet film, drying the obtained dry film, and vacuum drying the dry film to obtain a polymer film for winding insulation.

[0020] It is further defined that the temperature of the glass sheet is 60°C.

[0021] It is further defined that the drying treatment temperature is 55-65°C and the time is 2 hours.

[0022] It is further defined that the vacuum drying treatment temperature is 55-65°C and the time is 24 hours.

[0023] It is further defined that the thickness of the obtained polymer film for winding insulation is 5-10 μm.

[0024] A fourth object of the present invention is to provide a polymer film for winding insulation prepared by the above method, specifically used as a winding insulation material for the preparation of electrical insulation devices.

[0025] It is further defined that electrical insulation devices include smart grids, new energy vehicles and AC and DC transmission networks.

[0026] Beneficial effects:

[0027] The present invention uses a binary solvent system prepared by N, N-dimethylformamide (DMF) and ethyl acetate in a volume ratio of 4:1 to prepare polynorbornene imide. Compared with the traditional dichloromethane (DCM) solvent, the polymerization effect is significantly improved, and the polymer yield is as high as 17.3%. In addition, the polynorbornene imide film prepared by the present invention introduces an imide group compared with polynorbornene, and the imide group has a strong electron attraction effect, which enhances the electrophilic properties of polynorbornene, so that the polynorbornene imide breakdown field strength can reach 500MV / m. In addition, the preparation process of the polynorbornene imide film provided by the present invention is simple and easy, environmentally friendly, pollution-free, and the required equipment cost is low, which is very suitable for large-scale production, not only has important scientific research value, but also has huge application potential and market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 X-ray diffraction comparison diagram of polynorbornene imide and polynorbornene film prepared in Example 1 and Comparative Example 3;

[0029] Figure 2 It is a comparison diagram of Fourier transform infrared spectra of polynorbornene imide and polynorbornene film prepared in Example 1 and Comparative Example 3;

[0030] Figure 3 Weibull distribution diagram of the breakdown field strength of the polynorbornene imide and polynorbornene films prepared in Example 1 and Comparative Example 3;

[0031] Figure 4 The dielectric constant and dielectric loss spectrum of the polynorbornene imide prepared in Example 1;

[0032] Figure 5 This is the real conductivity spectrum of the polynorbornene imide prepared in Example 1. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0036] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art, and the purity of the solid and liquid reagents used is analytically pure.

[0037] Example 1

[0038] Step 1: dissolving 2 g of 5-norbornene-2,3-dicarboximide monomer in 25 ml of a binary solvent under anaerobic conditions, and stirring evenly at 50° C. to form a solution A;

[0039] The binary solvent is prepared by mixing N,N-dimethylformamide and ethyl acetate in a volume ratio of 4:1.

[0040] Step 2: Place solution A in an oil bath and set the temperature to 50°C;

[0041] Step 3: In a glove box, weigh 25 mg of Grubbs II catalyst and dissolve it in 25 ml of binary solvent to form solution B;

[0042] Step 4: Inject solution B into solution A and stir at 50°C for 6 hours to complete the polymerization reaction.

[0043] Step 5: After the reaction is completed, 5 ml of vinyl ethyl ether is used to terminate the reaction and stirring is continued for 30 min.

[0044] Step 6: Drop the reaction solution into 0-5°C methanol to precipitate a solid product, perform Soxhlet extraction on the solid product for 50 hours, and finally dry it at 60°C for 24 hours to obtain dry polynorbornene imide with a yield of 17.3%.

[0045] Step 7: Dissolve the dried poly(norbornene imide) in a binary solvent to prepare a 5 wt % precursor solution, and stir for 2 h.

[0046] Step 8: The precursor solution is evenly coated on a 60°C glass plate by a solution casting method to obtain a wet film, which is then dried at 60°C for 2 hours to obtain a dry film, and the dry film is then vacuum dried at 60°C for 24 hours to obtain a polyborneol anhydride film with a thickness of 8 μm.

[0047] Comparative Example 1

[0048] The difference between this comparative example and Example 1 is that anhydrous dichloromethane is used as a solvent to replace the binary solvent in step 1 and step 3. The experimental results show that after stirring for 10 hours, the polymerization of 5-norbornene-2,3-dicarboximide cannot be achieved, and polynorbornene imide is not obtained.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Example 1 is that DMF is used as a solvent to replace the binary solvent in step 1 and step 3. The experimental results show that after 8 hours of stirring, although the polymerization of 5-norbornene-2,3-dicarboximide can be achieved, its yield is low, which is 5.3%.

[0051] Comparative Example 3

[0052] Step 1: Under the protection of inert gas, accurately weigh 2 g of norbornene monomer and dissolve it in 20 ml of anhydrous dichloromethane to form a uniform solution A.

[0053] Step 2: In an inert atmosphere glove box, accurately weigh 25 mg of Grubbs II catalyst and dissolve it in 5 ml of anhydrous dichloromethane to form solution B.

[0054] Step 3: Slowly inject solution B into solution A and carry out polymerization reaction at room temperature for 6 hours.

[0055] Step 4: After the polymerization is completed, 5 ml of vinyl ethyl ether is immediately added to terminate the reaction, and stirring is continued at room temperature for 30 min to ensure complete reaction.

[0056] Step 5: Slowly pour the reaction mixture into a large amount of pre-cooled methanol at 0-5°C to precipitate the polymer, then wash it with methanol several times at room temperature to remove unreacted monomers and catalyst residues, and finally vacuum dry it at 60°C for 24 hours to obtain a dry polybornene polymer.

[0057] Step 6: Dissolve the dried polymer in toluene at 110° C. to form a 5 wt % precursor solution, and continue stirring at the temperature for 12 h.

[0058] Step 7: The filtered precursor solution is evenly coated on a glass plate preheated to 60°C to form a wet film, and then dried at the same temperature for 4 hours to form a dry film. Finally, the dry film is further dried in a vacuum environment at 60°C for 24 hours to obtain a polynorbornene film with a thickness uniformly controlled within the range of 8μm.

[0059] Effect Example 1

[0060] (1) Figure 1 The X-ray diffraction comparison diagram of polynorbornene imide and polynorbornene film prepared in Example 1 and Comparative Example 3 shows that the diffraction peak of polynorbornene is very sharp in the low-angle region, indicating that polynorbornene has a good crystal structure. The diffraction peak of polynorbornene imide is relatively wide and has a low intensity, indicating that the order of its crystal structure is not as good as that of polynorbornene after the introduction of the imide group. By observing the width of the diffraction peak, it can be found that the diffraction peak of polynorbornene imide is wider than that of polynorbornene, indicating that the grain size of the imide is small or there is no crystal structure.

[0061] (2) Figure 2 The Fourier transform infrared spectra of the polynorbornene imide and polynorbornene films prepared in Example 1 and Comparative Example 3 are compared. It can be seen from the figure that the wavelength is between 1300 and 1500 cm -1 The stretching vibration absorption peak of the CN bond appears between the two molecules, which is a unique feature of the imide molecule. -1 In the region above 3000cm, an obvious absorption peak can usually be observed, which is mainly caused by the stretching vibration of the C=O bond in the imide molecule, and the intensity of this peak often exceeds the vibration peak of the C=C bond. -1 In the wavelength range, the absorption peak corresponding to the stretching vibration of the CH bond may be weakened because the addition of imide changes the vibration characteristics of the CH bond, indicating that the imide group has been successfully introduced.

[0062] (3) Figure 3 The Weibull distribution diagram of the breakdown field strength of the polynorbornene imide and polynorbornene films prepared in Example 1 and Comparative Example 3 shows that the introduction of the imide group increases the molecular rigidity, which can improve the interaction between polymer chains, thereby increasing the mechanical strength and stability of the material. In terms of breakdown performance, this means that the material can withstand higher electric field strengths without being damaged, and the breakdown of polynorbornene is increased to 500 MV / m.

[0063] (4) Figure 4The dielectric constant and dielectric loss spectrum of the polynorbornene imide prepared in Example 1 shows that the dielectric constant shows a downward trend in the low frequency band (about 100 Hz to 103 Hz), from about 4.5 to close to 1, and in the high frequency band (about 103 Hz to 105 Hz), the dielectric constant gradually increases to about 4.5. The dielectric loss is very low in the low frequency band, close to 0. As the frequency increases, the dielectric loss gradually increases, reaching about 0.02 in the high frequency band.

[0064] (5) Figure 5 This is the real conductivity spectrum of the polynorbornene imide prepared in Example 1. It can be seen from the figure that the real conductivity of the material increases significantly with the increase of frequency, indicating that its conductivity is very sensitive to frequency. In the high frequency band, the conductivity is high, which may have a certain impact on the insulation performance of the material.

[0065] Although the present invention has been disclosed as above in the preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing polynorbornene imide for winding insulation, characterized in that: include: (1) dissolving 5-norbornene-2,3-dicarboximide in a binary solvent in a nitrogen environment without water or oxygen to form a solution A; (2) dissolving the Grubbs II catalyst in a binary solvent in an anhydrous and oxygen-free nitrogen environment to form solution B; (3) In an anhydrous and oxygen-free nitrogen environment, solution A and solution B are mixed and stirred to obtain a mixed solution, the mixed solution is reacted at 50° C. for 6-8 hours, and then a stop agent is added and stirred for 30 minutes to stop the reaction; (4) under light-proof conditions, the reaction solution obtained in (3) was added dropwise to a cold methanol solution to obtain a solid product, and the solid product was subjected to Soxhlet extraction with methanol as a solution for 45-50 hours, and finally vacuum dried at 60° C. to obtain polynorbornene imide; The binary solvent consists of N,N-dimethylformamide and ethyl acetate.

2. The preparation method according to claim 1, characterized in that: The volume ratio of N,N-dimethylformamide to ethyl acetate in the binary solvent is 4:

1.

3. The preparation method according to claim 1, characterized in that: The mass volume ratio of 5-norbornene-2,3-dicarboximide and the binary solvent in (1) is 2 g:25 ml.

4. The preparation method according to claim 1, characterized in that: (1) The mass volume ratio of Grubbs II catalyst and binary solvent is 25 mg:5 ml.

5. The preparation method according to claim 1, characterized in that: The mass ratio of 5-norbornene-2,3-dicarboximide to Grubbs II catalyst in the mixed solution (3) is 2 g:25 mg.

6. The preparation method according to claim 1, characterized in that: (3) The stopper is vinyl ethyl ether.

7. The preparation method according to claim 1, characterized in that: (4) The temperature of the intermediate cooled methanol is 0-5°C.

8. A polynorbornene imide for winding insulation prepared by the method according to any one of claims 1 to 7.

9. A method for preparing a polymer film for winding insulation, characterized in that: The polynorbornene imide for winding insulation as claimed in claim 8 is dissolved in N,N-dimethylformamide, and then formed into a film on a glass plate by a solution casting method to obtain a wet film, which is dried to obtain a dry film, and the dry film is vacuum dried to obtain a polymer film for winding insulation.

10. A polymer film for winding insulation prepared by the method according to claim 9, characterized in that: Used as winding insulation material in the preparation of electrical insulation devices.

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