Modified polypropylene as well as preparation method and application thereof

Abstract

The invention relates to the field of high polymer materials, in particular to modified polypropylene as well as a preparation method and application thereof. According to the modified polypropylene provided by the invention, polypropylene is modified by adopting the alkenyl-containing aromatic heterocyclic compound with a specific Ra substituent group on the alkenyl, so that the obtained modified polypropylene not only has high mechanical strength, but also can keep high energy storage density and storage efficiency at a high working temperature; therefore, the energy storage dielectric material prepared from the modified polypropylene also has high mechanical strength, can keep high energy storage density and storage efficiency at high working temperature, and is particularly suitable for being used as a capacitor film of a polymer dielectric capacitor working in a high temperature and high field. The modified polypropylene provided by the invention solves the problem of poor energy storage performance of a commercial polypropylene film under high temperature and high field, and meanwhile, the aromatic hybrid modified polypropylene material is simple in preparation process, meets the requirements of large-scale industrial production and has market potential and application value.

Description

Technical Field

[0001] The invention relates to the field of polymer materials, in particular to modified polypropylene and a preparation method and application thereof. Background Art

[0002] Polymer film capacitors have outstanding advantages such as high voltage resistance, high power density and low cost. They have been widely used in hybrid vehicle inverters, power grid frequency modulation, new energy grid connection, advanced electronic equipment, etc. Biaxially oriented polypropylene (BOPP) has been used as the most advanced dielectric film material due to its high charge and discharge efficiency and mature large-scale preparation process. However, due to its low dielectric constant, the capacitor discharge energy density is low, so the capacitor usually occupies more than 30% of the volume and weight of the equipment, and the miniaturization of modern electronic and electrical systems is inevitably restricted. In addition, due to the constraints of its own structural characteristics, BOPP also has a low glass transition temperature. Therefore, the discharge energy density and charge and discharge efficiency drop significantly in harsh high-temperature service environments, and an additional refrigeration system has to be used to maintain its efficient operation, which will not only further increase the cost, but also increase the volume and weight accordingly.

[0003] At present, there are three main strategies to solve the problem of poor energy storage performance of polymer dielectric films under high temperature and high field: 1) Constructing multilayer or heterojunction structures to inhibit carrier injection or inhibit carrier transport has been proven to be an effective method. For example, depositing wide bandgap inorganic layers (such as SiO2 and Al2O3) on the surface of polymer dielectric films can introduce high interface barriers and reduce charge injection; 2) Introducing deep traps in the polymer dielectric matrix to capture carriers is also beneficial to reduce leakage current and improve the energy storage performance of polymer dielectrics at high temperatures. For example, adding wide bandgap inorganic nanofillers such as BN to polymer dielectrics; 3) Synthesizing new polymer materials through structural design can adjust the glass transition temperature and band gap, thereby directly improving its energy storage performance under high temperature and high electric field. However, the above strategies all have problems such as complex preparation process and difficulty in large-scale industrial production. Therefore, it is more market potential and application value to develop a new type of modified polypropylene dielectric energy storage material with simple preparation process and meeting the requirements of large-scale industrial production. Summary of the invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a modified polypropylene and a preparation method and application thereof. The modified polypropylene provided by the present invention can maintain high energy storage density and storage efficiency at high working temperature. The energy storage medium material prepared by the modified polypropylene can maintain excellent dielectric properties and energy storage capacity at higher temperatures, and is suitable for use in operating environments with high temperature and high electric field strength.

[0005] The present invention provides a modified polypropylene, which is obtained from polypropylene and an alkenyl-containing aromatic heterocyclic compound;

[0006] The alkenyl-containing aromatic heterocyclic compound is selected from at least one of the compounds having the structure of Formula 1 or Formula 2;

[0007] Formula I; Formula II;

[0008] Among them, the R a One selected from substituted or unsubstituted C4~C6 epoxy 1~3 alkenyl, substituted or unsubstituted C4~C6 heteroaryl containing only one heteroatom, and substituted or unsubstituted C4~C6 biheteroaryl containing only two heteroatoms, wherein the heteroatom is selected from O, S or Se;

[0009] The R b , R c and R d Independently selected from a hydrogen atom, a substituted or unsubstituted C1~C5 alkyl group.

[0010] The modified polypropylene provided by the present invention is obtained from polypropylene and an alkenyl-containing aromatic heterocyclic compound, and its structure includes a structural unit derived from the polypropylene and a structural unit derived from the alkenyl-containing aromatic heterocyclic compound. In the modified polypropylene provided by the present invention, the content of the structural unit derived from the alkenyl-containing aromatic heterocyclic compound is 0.1 wt% to 40 wt%, preferably 0.1 wt% to 30 wt%.

[0011] In the present invention, the "structural unit" means that it is a part of the modified polypropylene, and its form is not limited. The "structural unit" can be a repeating unit or a non-repeating independent unit. Specifically, the "structural unit derived from the polypropylene monomer" refers to a structural unit formed by the polypropylene. The "structural unit derived from the alkenyl-containing aromatic heterocyclic compound" refers to a structural unit formed by the alkenyl-containing aromatic heterocyclic compound.

[0012] The modified polypropylene provided by the present invention is specifically obtained by grafting polypropylene and alkenyl-containing aromatic heterocyclic compounds, wherein the structural units derived from the alkenyl-containing aromatic heterocyclic compounds are in a grafted state. The grafting reaction described in the present invention is a free radical polymerization reaction. Therefore, the "in a grafted state" refers to the state in which the reactant forms a connection with another reactant after free radical polymerization, and the connection includes both direct connection and indirect connection. In the present invention, "the structural unit derived from the alkenyl-containing aromatic heterocyclic compound is in a grafted state" means that the structural unit derived from the alkenyl-containing aromatic heterocyclic compound forms a covalent connection (grafting) with the structural unit derived from the polypropylene.

[0013] In the grafting reaction process of the present invention, the heterocyclic vinyl monomers can be polymerized to form a certain amount of ungrafted polymers. The term "modified polypropylene" of the present invention includes both the product (crude product) directly obtained by grafting polypropylene and alkenyl-containing aromatic heterocyclic compounds, and the modified polypropylene pure product obtained by further purifying the product.

[0014] The alkenyl aromatic heterocyclic compound of the present invention is selected from at least one of the compounds having the structure shown in Formula 1 or Formula 2; wherein the R b , R c and R d is independently selected from a hydrogen atom, a substituted or unsubstituted C1~C5 alkyl group; a It is selected from a substituted or unsubstituted C4~C6 epoxy 1~3 alkenyl group, a substituted or unsubstituted C4~C6 heteroaryl group containing only one heteroatom, and a substituted or unsubstituted C4~C6 heteroaryl group containing only two heteroatoms, wherein the heteroatom is selected from O, S or Se.

[0015] Preferably, the R a Independently selected from a substituted or unsubstituted C6 epoxy3 alkenyl group, a substituted or unsubstituted single heteroatom C4 heteroaryl group, and a substituted or unsubstituted bi-single heteroatom C4 heteroaryl group.

[0016] More preferably, the R a Independently selected from one of the groups represented by formula III to formula X;

[0017] Formula III; Formula IV; Formula V; Formula VI;

[0018] Formula VII; Formula VIII;

[0019] Formula IX;

[0020] Among them, the X1~X4 and the X 1~ X 4 are independently selected from O, S or Se; said R1~R 21 and the R 1 ~R 10is independently selected from halogen, hydroxyl, amino, aldehyde, carboxyl, isocyanate, acyl chloride, cyano, hydrogen atom, sulfonic acid, substituted or unsubstituted C1~C5 alkyl, substituted or unsubstituted C3~C8 cycloalkyl, substituted or unsubstituted C1~C8 alkoxy, substituted or unsubstituted C1~C8 ester, substituted or unsubstituted C1~C8 amine; the substituted group is selected from halogen, hydroxyl, amino, aldehyde, carboxyl, isocyanate, acyl chloride, cyano, hydrogen atom, sulfonic acid, C1~C5 alkyl, C3~C8 cycloalkyl, C1~C8 alkoxy, C1~C8 ester or C1~C8 amine. Preferably, X1~X4 and X 1~ X 4 are independently selected from O or S; said R1~R 21 and the R 1 ~R 10 Independently selected from substituted or unsubstituted C1~C5 alkyl, substituted or unsubstituted C3~C8 cycloalkyl, the substituted group is selected from one or more of halogen, hydroxyl or amino.

[0021] In certain embodiments of the present invention, the alkenyl-containing aromatic heterocyclic compound is selected from at least one of benzo[b]thiophene-2-methyl methacrylate, oxol-2-yl methyl methacrylate, 5-(2,2'-bithienyl)methyl methacrylate, furfuryl methyl methacrylate or thiophene-2-methyl methacrylate.

[0022] The polypropylene described in the present invention is homopolypropylene or copolymer polypropylene, preferably homopolypropylene; the particle size of the polypropylene is 20 mesh to 60 mesh, preferably 30 mesh to 55 mesh; the ash content of the polypropylene is less than 40 ppm, preferably 20 ppm to 35 ppm; the flexural modulus of the polypropylene is 1550 MPa to 1750 MPa, preferably 1600 MPa to 1700 MPa.

[0023] The polypropylene of the present invention has at least one of characteristics 1 to 3:

[0024] Feature 1: The melt flow rate at 230°C and 2.16 kg load is 0.8 g / 10min~10 g / 10min, preferably 1 g / 10min~9 g / 10min;

[0025] Feature 2: The melting temperature Tm is above 120°C, preferably 120°C to 150°C;

[0026] Feature 3: The isotacticity is greater than 95%, preferably 96%~98%.

[0027] The polypropylene of the present invention is obtained from a polypropylene comonomer, and the polypropylene comonomer is selected from at least one of C2 to C8 α-olefins other than propylene, preferably selected from at least one of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene. More preferably, the polypropylene comonomer is at least one of ethylene and 1-butene. More preferably, the polypropylene is obtained by combining propylene and ethylene.

[0028] The present invention also provides a method for preparing the modified polypropylene described in any of the above technical solutions, comprising the following steps: reacting polypropylene and an alkenyl-containing aromatic heterocyclic compound in the presence of an initiator to obtain the modified polypropylene.

[0029] Specifically, polypropylene, an alkenyl aromatic heterocyclic compound and an initiator are mixed under a protective gas atmosphere, swelled in water, and then reacted to obtain modified polypropylene. In certain embodiments of the present invention, polypropylene, an alkenyl aromatic heterocyclic compound and an initiator are mixed under a protective gas atmosphere for 20 min to 40 min, deoxygenated water is added thereto and swelled at 40° C. to 60° C. for 1.5 h to 2.5 h, and the temperature is raised to 90° C. to 120° C. for reaction for 3 h to 5 h to obtain modified polypropylene.

[0030] The polypropylene and the alkenyl aromatic heterocyclic compound of the present invention are the same as those described above and will not be described in detail; the initiator is a free radical initiator, which is selected from at least one of dibenzoyl peroxide, azobisisobutyronitrile, azobisisoheptylnitrile, diisopropyl peroxide, ditert-butyl peroxide, ditert-butyl peroxide, lauroyl peroxide, dodecyl peroxide, tert-butyl perbenzoate, and diisopropyl peroxydicarbonate. The mass ratio of the polypropylene and the alkenyl aromatic heterocyclic compound of the present invention is (100: (0.2-30)); the mass ratio of the initiator to the alkenyl aromatic heterocyclic compound can be (0.1-20):100.

[0031] The present invention also provides an energy storage dielectric material obtained from the modified polypropylene described in any of the above technical solutions or the modified polypropylene obtained by the preparation method described in any of the above technical solutions. Specifically, the energy storage dielectric material is obtained by processing the modified polypropylene; the energy storage dielectric material is a capacitor film, a supercapacitor film, an electrostatic film or a battery separator, preferably an electrostatic film or a capacitor film. The weight content of the modified polypropylene in the energy storage dielectric material of the present invention is 20 wt%~100 wt%, preferably 40 wt%~100 wt%, more preferably 60 wt%~100 wt%, more preferably 80 wt%~100 wt%, and even more preferably 90 wt%~100 wt%.

[0032] The present invention also provides a capacitor film obtained by the modified polypropylene described in any of the above technical solutions or the modified polypropylene obtained by the preparation method described in any of the above technical solutions. The capacitor film described in the present invention is one layer or multiple layers, preferably one layer; the thickness of the capacitor film is less than 15 microns, preferably less than 10 microns. At least one layer of the capacitor film described in the present invention is obtained by biaxially stretching the modified polypropylene described in the present invention. The capacitor film obtained by the modified polypropylene described in the present invention can be used as an energy storage dielectric material in polymer dielectric capacitors working under high temperature and high field.

[0033] The capacitive film of the present invention has at least one of the following characteristics a to f:

[0034] Feature a: The operating temperature of the capacitive film is ≥100°C, preferably 110°C~150°C;

[0035] Feature b: The breakdown field strength of the capacitive film at 125° C. is ≥500 MV / m, preferably 500 MV / m~750 MV / m;

[0036] Feature c: The dielectric constant of the capacitive film at 125°C and 100 Hz is greater than 2.2, preferably 2.3-2.5;

[0037] Feature d: The dielectric loss of the capacitor film at 125°C and 100 Hz is less than 1.0E-3, preferably 1.0E-6 to 2E-5;

[0038] Feature e: The energy storage density of the capacitor film at 125°C and 300 MV / m is greater than 0.8 J / cm 3 , preferably 0.9 J / cm 3 ~1.5 J / cm 3 ;

[0039] Feature f: The energy storage efficiency of the capacitor film at 125° C. and 300 MV / m is greater than 90.0%, preferably 93.0% to 99.0%.

[0040] The present invention provides a modified polypropylene and a preparation method and application thereof. The modified polypropylene provided by the present invention adopts a polypropylene having a specific R aThe polypropylene is modified by the aromatic heterocyclic compound containing alkenyl groups of the substituted groups, and the obtained modified polypropylene not only has high mechanical strength, but also can maintain high energy storage density and storage efficiency at high working temperature. Therefore, the energy storage medium material obtained from the modified polypropylene of the present invention also has high mechanical strength, and can also maintain high energy storage density and storage efficiency at high working temperature, and is particularly suitable as a capacitor film of a polymer dielectric capacitor working under high temperature and high field. The modified polypropylene provided by the present invention solves the problem of poor energy storage performance of commercial polypropylene films under high temperature and high field. At the same time, the preparation process of the aromatic hybrid modified polypropylene material is simple, meets the requirements of large-scale industrial production, and has market potential and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is the monomer NMR spectrum used in Example 1;

[0042] Figure 2 is the monomer NMR spectrum used in Example 2;

[0043] Figure 3 is the monomer NMR spectrum used in Example 3;

[0044] Figure 4 This is the monomer NMR spectrum used in Comparative Example 3;

[0045] Figure 5 This is the monomer NMR spectrum used in Comparative Example 5;

[0046] Figure 6 It is a data chart comparing the energy storage density and efficiency in the embodiment and the comparative example. DETAILED DESCRIPTION

[0047] The present invention discloses a modified polypropylene and a preparation method and application thereof. A person skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the same. It should be particularly noted that all similar substitutions and modifications are obvious to a person skilled in the art and are considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method and application of this article without departing from the content, spirit and scope of the present invention to realize and apply the technology of the present invention.

[0048] Determination of ash content of polypropylene / polypropylene dielectric energy storage materials: Determine according to the method specified in GB / T 9345.1-2008.

[0049] Isotacticity of polypropylene: Determine according to the method specified in GB / T 2412-2008.

[0050] Determination of flexural modulus: Determined according to the method specified in GB / T 9341-2008.

[0051] Determination of melt flow rate (MFR): According to the method specified in GB / T 3682-2018, the melt flow rate (MFR) was measured at 230°C and a load of 2.16 kg using a CEAST 7026 melt indexer.

[0052] Determination of melting temperature Tm: Differential scanning calorimeter is used to analyze the melting process and crystallization process of the material. The specific operation is: under nitrogen protection, 5~10 mg of sample is measured from 20℃ to 200℃ using a three-stage temperature rise and fall measurement method, and the change in heat flow reflects the melting and crystallization process of the material, so as to calculate the melting temperature Tm.

[0053] Determination of grafting efficiency η and parameter M: 10 g of the grafted product was placed in a Soxhlet extractor and extracted with acetone for 24 hours to remove unreacted monomers and homopolymers thereof to obtain a pure grafted product, which was dried and weighed to calculate the parameter M and grafting efficiency η. The parameter M represents the content of the structural unit derived from the aromatic heterocyclic vinyl monomer in the aromatic heterocyclic olefin grafted modified polypropylene material. In the present invention, the calculation formulas for M and η are as follows:

[0054]

[0055]

[0056] In the above formula, W0 is the mass of the polypropylene matrix; W1 is the mass of the grafted product before extraction; W2 is the mass of the grafted product after extraction; and W3 is the mass of the added aromatic heterocyclic vinyl monomer.

[0057] Thickness of capacitor film: measured in accordance with the method specified in GB / T 13542.3-2006, using the micrometer method.

[0058] Determination of dielectric constant and dielectric loss factor: Determine according to the method specified in GB / T 1409-2006.

[0059] Energy storage density and energy storage efficiency determination: Determine according to the method specified in the following literature.

[0060] Bo, S.; Jiawei, Z.; et al. Chemical Transformation of Polyurethaneinto Valuable Polymers. National Science Review, 2025, 12, nwae393.

[0061] The polypropylene powders used in all the examples and comparative examples were sieved using a vibrating screen equipped with 16-mesh and 48-mesh screens before the grafting reaction.

[0062] The present invention will be further described below in conjunction with embodiments:

[0063] Example 1

[0064] 5.0 kg of pure polypropylene powder (Borealis-brand HC300BF) screened out from the middle layer of the sieving machine was added to a 50 L reactor equipped with a double-layer four-blade stirring paddle and a baffle. The reaction system was sealed and deoxygenated by nitrogen replacement. 7.2 g of dibenzoyl peroxide and 250 g of benzo[b]thiophene-2-methyl methacrylate were prepared into a uniform solution, added to the reactor and stirred for 30 minutes, and then 17.8 kg of deionized water with deoxygenation was added and heated to 50°C for swelling for 2 hours. The swollen powder was heated to 95°C and reacted for 4 hours. After the reaction was completed, the temperature was cooled, the liquid component was filtered out, and the product was vacuum dried at 70°C for 10 hours to obtain polypropylene grafted modified powder A1.

[0065] Example 2

[0066] 5.0 kg of pure polypropylene powder (Borealis-brand HC300BF) screened out from the middle layer of the sieving machine was added to a 50 L reactor equipped with a double-layer four-blade stirring paddle and a baffle. The reaction system was sealed and deoxygenated by nitrogen replacement. 7.2 g of dibenzoyl peroxide and 500 g of oxacyclopent-2-yl methyl methacrylate were prepared into a uniform solution, added to the reactor and stirred with the powder for 30 minutes, and then 17.8 kg of deoxygenated deionized water was added and heated to 50°C for swelling for 2 hours. The swollen powder was heated to 95°C and reacted for 4 hours. After the reaction was completed, the temperature was cooled, the liquid component was filtered out, and the product was vacuum dried at 70°C for 10 hours to obtain polypropylene grafted modified powder A2.

[0067] Example 3

[0068] 5.0 kg of pure polypropylene powder (Borealis-brand HC300BF) screened out from the middle layer of the sieving machine was added to a 50 L reactor equipped with a double-layer four-blade stirring paddle and a baffle. The reaction system was sealed and deoxygenated by nitrogen replacement. 7.2 g of dibenzoyl peroxide and 500 g of thiophene-2-methyl methacrylate were prepared into a uniform solution, added to the reactor and stirred with the powder for 30 minutes, and then 17.8 kg of deoxygenated deionized water was added and heated to 50°C for swelling for 2 hours. The swollen powder was heated to 95°C and reacted for 4 hours. After the reaction was completed, the temperature was cooled, the liquid component was filtered out, and the product was vacuum dried at 70°C for 10 hours to obtain polypropylene grafted modified powder A3.

[0069] Example 4

[0070] 5.0 kg of pure polypropylene powder (Borealis-brand HC300BF) screened out from the middle layer of the sieving machine was added to a 50 L reactor equipped with a double-layer four-blade stirring paddle and a baffle. The reaction system was sealed and deoxygenated by nitrogen replacement. 7.2 g of dibenzoyl peroxide and 500 g of 2-vinylthiophene were prepared into a uniform solution, added to the reactor and stirred with the powder for 30 minutes, and then 17.8 kg of deoxygenated deionized water was added and heated to 50°C for swelling for 2 hours. The swollen powder was heated to 95°C and reacted for 4 hours. After the reaction was completed, the temperature was cooled, the liquid component was filtered out, and the product was vacuum dried at 70°C for 10 hours to obtain polypropylene grafted modified powder A4.

[0071] Comparative Example 1

[0072] Pure polypropylene powder was used as comparative example B1.

[0073] Comparative Example 2

[0074] 5.0 kg of pure polypropylene powder (Borealis-brand HC300BF) screened out from the middle layer of the sieving machine was added to a 50 L reactor equipped with a double-layer four-blade stirring paddle and a baffle. The reaction system was sealed and deoxygenated by nitrogen replacement. 7.2 g of dibenzoyl peroxide and 500 g of methyl methacrylate were prepared into a uniform solution, added to the reactor and stirred with the powder for 30 minutes, and then 17.8 kg of deoxygenated deionized water was added and heated to 50°C for swelling for 2 hours. The swollen powder was heated to 95°C and reacted for 4 hours. After the reaction was completed, the temperature was cooled, the liquid component was filtered out, and the product was vacuum dried at 70°C for 10 hours to obtain polypropylene grafted modified powder B2.

[0075] Comparative Example 3

[0076] 5.0 kg of pure polypropylene powder (Borealis-brand HC300BF) screened out from the middle layer of the sieving machine was added to a 50 L reactor equipped with a double-layer four-blade stirring paddle and a baffle. The reaction system was sealed and deoxygenated by nitrogen replacement. 7.2 g of dibenzoyl peroxide and 500 g of benzyl methacrylate were prepared into a uniform solution, added to the reactor and stirred with the powder for 30 minutes, and then 17.8 kg of deoxygenated deionized water was added and heated to 50°C for swelling for 2 hours. The swollen powder was heated to 95°C and reacted for 4 hours. After the reaction was completed, the temperature was cooled, the liquid component was filtered out, and the product was vacuum dried at 70°C for 10 hours to obtain polypropylene grafted modified powder B3.

[0077] Comparative Example 4

[0078] 5.0 kg of pure polypropylene powder (Borealis-brand HC300BF) screened out from the middle layer of the sieving machine was added to a 50 L reactor equipped with a double-layer four-blade stirring paddle and a baffle. The reaction system was sealed and deoxygenated by nitrogen replacement. 7.2 g of dibenzoyl peroxide and 500 g of 2-morpholinoethyl methyl methacrylate were prepared into a uniform solution, added to the reactor and stirred with the powder for 30 minutes, and then 17.8 kg of deoxygenated deionized water was added and heated to 50°C for swelling for 2 hours. The swollen powder was heated to 95°C and reacted for 4 hours. After the reaction was completed, the temperature was cooled, the liquid component was filtered out, and the product was vacuum dried at 70°C for 10 hours to obtain polypropylene grafted modified powder B4.

[0079] Comparative Example 5

[0080] 5.0 kg of pure polypropylene powder (Borealis-brand HC300BF) screened out from the middle layer of the sieving machine was added to a 50 L reactor equipped with a double-layer four-blade stirring paddle and a baffle. The reaction system was sealed and deoxygenated by nitrogen replacement. 7.2 g of dibenzoyl peroxide and 500 g of 2-pyridyl methyl methacrylate were prepared into a uniform solution, added to the reactor and stirred with the powder for 30 minutes, and then 17.8 kg of deoxygenated deionized water was added and heated to 50°C for swelling for 2 hours. The swollen powder was heated to 95°C and reacted for 4 hours. After the reaction was completed, the temperature was cooled, the liquid component was filtered out, and the product was vacuum dried at 70°C for 10 hours to obtain polypropylene grafted modified powder B5.

[0081] The monomers used in the above-mentioned Examples 1 to 3 and Comparative Examples 3 and 5 were subjected to nuclear magnetic resonance detection. Figure 1~Figure 5 As shown, Figure 1 is the monomer NMR spectrum used in Example 1, Figure 2 is the monomer NMR spectrum used in Example 2, Figure 3 is the monomer NMR spectrum used in Example 3, Figure 4 is the monomer NMR spectrum used in Comparative Example 3, Figure 5 This is the monomer NMR spectrum used in Comparative Example 5.

[0082] All the powders obtained above were subjected to a biaxial stretching method to prepare film products, and various performance parameters of all the obtained film products were tested. The results are shown in Tables 1 and 2, where Table 1 is a summary of the basic characterization test results of the materials described in the examples and comparative examples, and Table 2 is a summary of the dielectric and energy storage performance test results of the films of the materials described in the examples and comparative examples.

[0083] Table 1

[0084]

[0085] From the test results in Table 1 above, it can be seen that compared with Comparative Example 1, the ash content, melt mass, melting temperature and bending modulus of Examples 1 to 3 are not much different, indicating that there is not much difference in the basic performance test after the aromatic heterocyclic groups are grafted on the pure polypropylene powder; further, compared with Comparative Examples 2 to 5, the grafting rate and film thickness of Examples 1 to 3 are not much different, indicating that the grafting of aromatic heterocyclic groups on the polypropylene material is successful.

[0086] Table 2

[0087]

[0088] From the test results in Table 2 above, it can be seen that compared with Comparative Example 1, the breakdown field strength, energy storage density, and energy storage efficiency of Examples 1 to 3 are greatly improved, indicating that the film material of aromatic heterocyclic grafted modified polypropylene not only has a higher breakdown field strength and a low dielectric loss value, but also can maintain a high energy storage density and energy storage efficiency at a higher operating temperature; and, compared with Comparative Examples 2 and 3, under the condition of similar grafting rates, the breakdown field strength, energy storage density, and energy storage efficiency of Examples 1 to 3 are also more excellent, while maintaining a lower dielectric loss value; In addition, compared with Examples 1 to 3, Comparative Example 4 containing non-aromatic oxygen-containing heterocyclic groups has lower breakdown field strength, energy storage density, energy storage efficiency and higher dielectric loss, proving that aromatic heterocyclic grafting modification is beneficial to improving dielectric properties and energy storage performance; further, compared with Examples 1 to 3, Comparative Example 5 containing other types of aromatic heterocyclic modified with ester groups has poor effects in improving breakdown field strength, energy storage density, energy storage efficiency, etc., which indicates that the synergistic effect of ester groups and aromatic heterocyclic grafting modification improves the problem of poor energy storage performance of polypropylene at high temperatures. Figure 6 As shown, Figure 6 It is a data chart comparing the energy storage density and efficiency in the embodiment and the comparative example.

[0089] In summary, the present invention provides a high-operating-temperature aromatic heterocyclic modified polypropylene dielectric energy storage material and its application as a capacitor film in the preparation of high-temperature energy storage dielectric materials. The polypropylene dielectric energy storage material has a high operating temperature and can maintain high energy storage efficiency and energy storage density at a relatively high operating temperature. Furthermore, the problem of poor energy storage performance of commercial polypropylene films under high temperature and high field is solved. At the same time, the preparation process of the aromatic heterocyclic modified polypropylene material is simple, meets the requirements of large-scale industrial production, and has market potential and application value.

[0090] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A modified polypropylene, characterized in that: It is obtained from polypropylene and an alkenyl-containing aromatic heterocyclic compound; The alkenyl-containing aromatic heterocyclic compound is selected from at least one of the compounds having the structure of Formula 1 or Formula 2; Formula I; Formula II; Among them, the R a One selected from substituted or unsubstituted C4~C6 epoxy 1~3 alkenyl, substituted or unsubstituted C4~C6 heteroaryl containing only one heteroatom, and substituted or unsubstituted C4~C6 biheteroaryl containing only two heteroatoms, wherein the heteroatom is selected from O, S or Se; The R b , R c and R d Independently selected from a hydrogen atom, a substituted or unsubstituted C1~C5 alkyl group.

2. The modified polypropylene according to claim 1, characterized in that The R a Independently selected from a substituted or unsubstituted C6 epoxy3 alkenyl group, a substituted or unsubstituted C4 heteroaryl group containing only one heteroatom, and a substituted or unsubstituted C4 biheteroaryl group containing only two heteroatoms.

3. The modified polypropylene according to claim 1, characterized in that The R a Independently selected from one of the groups represented by formula III to formula X; Formula III; Formula IV; Formula V; Formula VI; Formula VII; Formula VIII; Formula IX; Among them, the X1~X4 and the X 1~ X 4 Independently selected from O, S or Se; R1~R 21 and the R 1 ~R 10 Independently selected from halogen, hydroxyl, amino, aldehyde, carboxyl, isocyanate, acyl chloride, cyano, hydrogen, sulfonic acid, substituted or unsubstituted C1~C5 alkyl, substituted or unsubstituted C3~C8 cycloalkyl, substituted or unsubstituted C1~C8 alkoxy, substituted or unsubstituted C1~C8 ester, substituted or unsubstituted C1~C8 amine.

4. The modified polypropylene according to claim 3, characterized in that The substituted group is selected from halogen, hydroxyl, amino, aldehyde, carboxyl, isocyanate, acyl chloride, cyano, hydrogen atom, sulfonic acid, C1~C5 alkyl, C3~C8 cycloalkyl, C1~C8 alkoxy, C1~C8 ester or C1~C8 amine.

5. The modified polypropylene according to claim 1, characterized in that The alkenyl-containing aromatic heterocyclic compound is selected from at least one of benzo[b]thiophene-2-methyl methacrylate, oxol-2-yl methyl methacrylate, 5-(2,2'-bithienyl)methyl methacrylate, furfuryl methyl methacrylate and thiophene-2-methyl methacrylate.

6. The modified polypropylene according to any one of claims 1 to 4, characterized in that: In the modified polypropylene, the content of the structural unit derived from the alkenyl-containing aromatic heterocyclic compound is 0.1 wt% to 40 wt%.

7. The modified polypropylene according to any one of claims 1 to 4, characterized in that: The polypropylene is obtained from polypropylene monomers, and the polypropylene monomers are selected from at least one of C2-C8 α-olefins except propylene.

8. The method for preparing the modified polypropylene according to any one of claims 1 to 7, characterized in that: The following steps are involved: In the presence of an initiator, polypropylene and an alkenyl-containing aromatic heterocyclic compound are reacted to obtain modified polypropylene.

9. An energy storage medium material obtained from the modified polypropylene according to any one of claims 1 to 7 or the modified polypropylene obtained by the preparation method according to claim 8.

10. The energy storage medium material according to claim 9, characterized in that: The energy storage dielectric material is a capacitor film.

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