Heteroaromatic ring-containing modified polypropylene composite material, preparation method thereof and capacitor film

Abstract

The invention provides a heteroaromatic ring-containing modified polypropylene composite material and a preparation method thereof, and a capacitor film, the heteroaromatic ring-containing modified polypropylene composite material comprises the following raw materials by mass: 70-98.89% of polypropylene, 1-22.5% of a cycloolefin copolymer, 0.1-5% of a heteroaromatic ring-containing modified polypropylene compound, 0-2% of a nucleating agent, and 0-0.5% of an antioxidant; the preparation raw materials of the heteroaromatic ring-containing modified polypropylene compound comprise polypropylene and an alkenyl-containing heteroaromatic ring-containing compound. The alkenyl-containing heteroaromatic compound has a compound as shown in a formula I or a formula II. The heteroaromatic ring-containing modified polypropylene composite material is particularly suitable for a high-temperature thin-film capacitor film, has excellent high-temperature working performance, and can keep high energy storage efficiency and energy storage density at a relatively high temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of polypropylene materials, and particularly relates to an aromatic heterocyclic modified polypropylene composite material, a preparation method thereof, and a capacitor film. Background Art

[0002] Polymer film capacitors have been widely used in many key fields due to their outstanding advantages such as high voltage resistance, high power density, and low cost. They play an important role especially in hybrid vehicle inverters, power grid frequency modulation, new energy grid connection, and advanced electronic devices. Among them, biaxially oriented polypropylene (BOPP) has become one of the most advanced dielectric film materials at present due to its excellent charge-discharge efficiency and mature large-scale preparation process. The BOPP film has high insulation strength, low dielectric loss, and good mechanical properties, making it perform excellently in high-voltage and high-frequency application scenarios. However, although the BOPP material performs excellently in many aspects, its relatively low dielectric constant (usually about 2.2) results in a low discharge energy density of the capacitor, which makes the capacitor usually occupy more than 30% of the volume and weight in the device, seriously restricting the development trend of modern electronic and electrical systems towards miniaturization and lightweight. In addition, another significant disadvantage of the BOPP material is its poor heat resistance, which makes its performance under high-temperature environments unsatisfactory. In a harsh high-temperature service environment, the molecular chain movement of the BOPP film intensifies, resulting in a significant decrease in its dielectric properties and mechanical strength, and further causing a substantial reduction in the discharge energy density and charge-discharge efficiency of the capacitor. To maintain the efficient operation of the capacitor in a high-temperature environment, it is usually necessary to introduce an additional refrigeration system to lower the working temperature. However, this solution not only increases the complexity and manufacturing cost of the system but also further increases the volume and weight of the device, which runs counter to the design concept of modern electronic and electrical devices pursuing high efficiency and compactness.

[0003] Although BOPP film capacitors play an important role in the existing technology, their limitations in low dielectric constant and low glass transition temperature restrict their performance in high-temperature and high electric field strength application scenarios. To address these issues, researchers are actively exploring various solutions. One solution is to synthesize new polymer materials through molecular structure design, which can directly regulate the glass transition temperature and bandgap of the materials, thereby significantly enhancing their energy storage performance at high temperatures and high electric fields. For example, by introducing rigid chain segments or polar groups, the thermal stability and dielectric constant of the polymer can be improved. However, the synthesis of new polymer materials usually involves complex chemical reactions and strict process conditions, resulting in high preparation costs and difficulty in meeting the requirements of large-scale industrial production. Another solution is to introduce deep traps into the polymer dielectric matrix to capture carriers. Deep traps can bind free carriers and reduce their migration under the action of an electric field, thereby significantly reducing the leakage current. For example, adding inorganic nano-fillers with wide bandgaps (such as boron nitride, etc.) to the polymer dielectric can form deep trap energy levels in the matrix while improving the thermal stability and mechanical strength of the material. However, issues such as the dispersion uniformity of nano-fillers, interfacial compatibility, and the interaction between fillers and the matrix still remain key challenges restricting their industrial applications. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an aromatic heterocyclic modified polypropylene composite material, its preparation method, and a capacitor film. This composite material is particularly suitable for the manufacture of high-temperature film capacitors and maintains excellent dielectric properties and energy storage capabilities at high temperatures and high electric field strengths.

[0005] The present invention provides an aromatic heterocyclic modified polypropylene composite material, which includes the following raw materials by mass fraction:

[0006] 70 - 98.89% of polypropylene, 1 - 22.5% of cycloolefin copolymer, 0.1 - 5% of aromatic heterocyclic modified polypropylene compound, 0 - 2% of nucleating agent, and 0 - 0.5% of antioxidant;

[0007] The preparation raw materials of the aromatic heterocyclic modified polypropylene compound include polypropylene and an alkenyl aromatic heterocyclic compound;

[0008] The alkenyl aromatic heterocyclic compound has a compound of formula I or formula II;

[0009]

[0010] R a is selected from one of 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, and the heteroatom is selected from O, S, or Se;

[0011] R b 、R c and R d are each independently selected from hydrogen and a substituted or unsubstituted C1-C5 alkyl group.

[0012] Preferably, the R a are each independently selected from one of the groups represented by Formula III to Formula IX;

[0013]

[0014]

[0015] wherein, the X1-X4 and the X 1 -X 4 are each independently selected from O, S or Se;

[0016] the R1-R 21 and the R 1 -R 10 are each independently selected from halogen, hydroxyl, amino, aldehyde, carboxyl, isocyanate, acyl chloride, cyano, hydrogen atom, sulfonic acid group, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C3-C8 cycloalkyl group, a substituted or unsubstituted C1-C8 alkoxy group, a substituted or unsubstituted C1-C8 ester group, and a substituted or unsubstituted C1-C8 amino group.

[0017] Preferably, the substituted group is selected from halogen, hydroxyl, amino, aldehyde, carboxyl, isocyanate, acyl chloride, cyano, hydrogen atom, sulfonic acid group, a C1-C5 alkyl group, a C3-C8 cycloalkyl group, a C1-C8 alkoxy group, a C1-C8 ester group or a C1-C8 amino group.

[0018] Preferably, the alkenyl-containing aromatic heterocyclic compound is at least one selected from methyl benzothiophene-2-yl methacrylate, methyl oxolene-2-yl methacrylate, methyl 2,2'-bithiophen]-5-yl methacrylate, methyl furfuryl methacrylate and methyl thiophene-2-yl methacrylate.

[0019] Preferably, the polypropylene is a copolymerized polypropylene or a homopolymerized polypropylene with a melt flow rate of 1-10 g / 10 min;

[0020] the isotacticity of the homopolymerized polypropylene is between 95-99%, the ash content is less than 40 ppm, the molecular weight distribution is between 3-7, and the melting temperature is between 110-160 °C;

[0021] The comonomer of the copolymerized polypropylene is at least one selected from C2-C8 α-olefins other than propylene.

[0022] Preferably, the nucleating agent is selected from one or more of dibenzylidene sorbitol, bis(p-methyl dibenzylidene) sorbitol, bis(3,4-dimethyl dibenzylidene) sorbitol, bis(4-methyl dibenzylidene) sorbitol, bis(p-ethyl benzylidene) sorbitol, bis(p-methyl benzylidene) sorbic acid, bis-(p-ethyl dibenzylidene isopropyl) sorbitol, bis(p-chloro substituted benzylidene) sorbitol, bis(p-chloromethyl dibenzylidene) sorbitol, 4,4'-(dimethylthio dibenzylidene) sorbitol, 1-propyl-1,3,2,4,-bis(p-n-propyl dibenzylidene) sorbitol, dehydroabietic acid, dehydroabietate, disproportionated rosin acid, disproportionated rosin salt, sodium salt of 2,2'-methylene-bis-(4,6-di-tert-butylphenyl) phosphate;

[0023] The antioxidant is selected from one or more of hindered phenol antioxidants, phosphite antioxidants and thioester antioxidants.

[0024] Preferably, the glass transition temperature of the cycloolefin copolymer is 120 to 150 °C.

[0025] Preferably, the content of the structural unit derived from the alkenyl aromatic heterocyclic compound in the aromatic heterocyclic modified polypropylene compound is 0.1 wt% to 40 wt%.

[0026] The present invention provides a method for preparing the aromatic heterocyclic modified polypropylene composite material described in the above technical solution, comprising the following steps:

[0027] Mix polypropylene, cycloolefin copolymer, aromatic heterocyclic modified polypropylene compound, nucleating agent and antioxidant, and pelletize to obtain the aromatic heterocyclic modified polypropylene composite material.

[0028] The present invention provides a high-temperature capacitor film made of the aromatic heterocyclic modified polypropylene composite material described in the above technical solution.

[0029] The present invention provides an aromatic heterocyclic modified polypropylene composite material, which includes the following raw materials by mass fraction: 70 to 98.89% of polypropylene, 1 to 22.5% of cycloolefin copolymer, 0.1 to 5% of aromatic heterocyclic modified polypropylene compound, 0 to 2% of nucleating agent and 0 to 0.5% of antioxidant; the preparation raw materials of the aromatic heterocyclic modified polypropylene compound include polypropylene and alkenyl aromatic heterocyclic compound; the alkenyl aromatic heterocyclic compound has a compound of formula I or formula II. The aromatic heterocyclic modified polypropylene composite material is particularly suitable for high-temperature thin-film capacitor films, which have excellent high-temperature working performance and can maintain high energy storage efficiency and energy storage density at higher temperatures. Description of the Drawings

[0030] Figure 11H NMR spectrum of methyl thiophene-2-methylacrylate in Example 1;

[0031] Figure 2 1H NMR spectrum of methyl benzo[b]thiophene-2-methylacrylate in Example 2;

[0032] Figure 3 1H NMR spectrum of methyl oxolene-2-ylmethylacrylate in Example 3;

[0033] Figure 4 1H NMR spectrum of methyl 2,2'-bithiophen]-5-ylmethylacrylate in Example 4;

[0034] Figure 5 1H NMR spectrum of methyl 2-pyridylmethylacrylate in Comparative Example 4;

[0035] Figure 6 Schematic diagram of the appearance of the aromatic heterocyclic modified polypropylene composite material B1 obtained in Example 5;

[0036] Figure 7 Schematic diagram of the appearance of the film obtained by biaxially stretching the aromatic heterocyclic modified polypropylene composite material B1 obtained in Example 5;

[0037] Figure 8 Graph showing the comparison data of discharge energy density and charge-discharge efficiency in Examples and Comparative Examples. Detailed implementation mode

[0038] The present invention provides an aromatic heterocyclic modified polypropylene composite material, which includes the following raw materials by mass fraction:

[0039] 70-98.89% of polypropylene, 1-22.5% of cycloolefin copolymer, 0.1-5% of aromatic heterocyclic modified polypropylene compound, 0-2% of nucleating agent, and 0-0.5% of antioxidant;

[0040] The preparation raw materials of the aromatic heterocyclic modified polypropylene compound include polypropylene and an alkenyl aromatic heterocyclic compound;

[0041] The alkenyl aromatic heterocyclic compound has a compound of Formula I or Formula II;

[0042]

[0043] R a is selected from one of a substituted or unsubstituted C4-C6 epoxy 1-3 alkenyl, a substituted or unsubstituted C4-C6 heteroaryl containing only one heteroatom, and a substituted or unsubstituted C4-C6 biheteroaryl containing only two heteroatoms, and the heteroatom is selected from O, S or Se;

[0044] R b 、 R c and R d are independently selected from one of hydrogen and substituted or unsubstituted C1-C5 alkyl groups.

[0045] As a dielectric energy storage material, this composite material has excellent high-temperature working performance and can maintain high energy storage density and energy storage efficiency at relatively high temperatures.

[0046] The raw materials for preparing the aromatic heterocyclic modified polypropylene composite material provided by the present invention include 70-98.89% of polypropylene, specifically, it can be 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%.

[0047] In the present invention, the polypropylene is copolymerized polypropylene or homopolymerized polypropylene, preferably homopolymerized polypropylene; the melt flow rate of the polypropylene is 1-10 g / 10 min, specifically, it can be 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 9 g / 10 min or 10 g / 10 min, preferably 2-8 g / 10 min.

[0048] The isotacticity of the homopolymerized polypropylene is 95-99%, preferably 96-98%;

[0049] The ash content of the homopolymerized polypropylene is less than 40 ppm, preferably less than 35 ppm; the molecular weight distribution is between 3 and 7, preferably between 4 and 6; the melting temperature is between 110 and 160 °C, preferably between 120 and 150 °C.

[0050] The comonomer of the copolymerized polypropylene is preferably at least one of C2-C8 α-olefins other than propylene.

[0051] In a specific embodiment, the polypropylene is Borealis, with the grade of HC300BF.

[0052] The raw materials for preparing the aromatic heterocyclic modified polypropylene composite material provided by the present invention include 1-22.5% of cycloolefin copolymer, specifically, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22% or 22.5%. The glass transition temperature of the cycloolefin copolymer in the present invention is 120-150 °C. The cycloolefin copolymer in the present invention is preferably selected from one or more of Topas 6013, Topas 6015, Topas 5013 and APEL series.

[0053] The raw materials for preparing the aromatic heterocyclic modified polypropylene composite provided by the present invention include 0.1-5% of aromatic heterocyclic modified polypropylene, specifically, it can be 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5% or 5.0%.

[0054] In the present invention, the raw materials for preparing the aromatic heterocyclic modified polypropylene include polypropylene and an alkenyl aromatic heterocyclic compound;

[0055] The alkenyl aromatic heterocyclic compound has a compound of formula I or formula II;

[0056]

[0057] R a is selected from one of a substituted or unsubstituted C4-C6 epoxy 1-3 alkenyl, a substituted or unsubstituted C4-C6 heteroaryl containing only one heteroatom, and a substituted or unsubstituted C4-C6 biheteroaryl containing only two heteroatoms, and the heteroatom is selected from O, S or Se; preferably, R a is selected from one of a substituted or unsubstituted C6 epoxy 3 alkenyl, a substituted or unsubstituted single heteroatom C4 heteroaryl, and a substituted or unsubstituted bi single heteroatom C4 heteroaryl.

[0058] More preferably, the R a is independently selected from one of the groups shown in formula III to formula IX;

[0059]

[0060] k]] wherein, the X1-X4 and the X 1 -X 4 are independently selected from O, S or Se;

[0061] The R1-R 21 and the R 1 -R 10 are independently selected from one of a halogen, a hydroxyl group, an amino group, an aldehyde group, a carboxyl group, an isocyanate group, an acyl chloride group, a cyano group, a hydrogen atom, a sulfonic acid group, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C3-C8 cycloalkyl group, a substituted or unsubstituted C1-C8 alkoxy group, a substituted or unsubstituted C1-C8 ester group, and a substituted or unsubstituted C1-C8 amino group.

[0062] In the present invention, the R1-R 21 and the R 1 -R 10When selected from at least one of substituted C1-C5 alkyl, substituted C3-C8 cycloalkyl, substituted C1-C8 alkoxy, substituted C1-C8 ester group, and substituted C1-C8 amino group, the substituted group is selected from halogen, hydroxyl, amino, aldehyde group, carboxyl group, isocyanate group, acyl chloride group, cyano group, hydrogen atom, sulfonic acid group, C1-C5 alkyl, C3-C8 cycloalkyl, C1-C8 alkoxy, C1-C8 ester group or C1-C8 amino group, preferably from halogen, hydroxyl or amino group.

[0063] In Formula I and Formula II, R b , R c and R d are independently selected from one of hydrogen, substituted or unsubstituted C1-C5 alkyl.

[0064] The alkenyl aromatic heterocyclic compound described in the present invention is selected from at least one of methyl benzothiophene-2-methyl acrylate, methyl oxolene-2-yl acrylate, methyl 2,2'-bithiophene]-5-yl acrylate, methyl furfuryl acrylate and methyl thiophene-2-methyl acrylate.

[0065] In the present invention, when preparing the aromatic heterocyclic modified polypropylene, the polypropylene and the alkenyl aromatic heterocyclic compound are preferably reacted in the presence of an initiator. The initiator is benzoyl peroxide.

[0066] Specifically, the aromatic heterocyclic modified polypropylene described in the present invention is preferably prepared by the following method:

[0067] Mix polypropylene, alkenyl aromatic heterocyclic compound and initiator in a protective gas atmosphere, swell it in water, and then react to obtain an aromatic heterocyclic modified polypropylene compound.

[0068] In the present invention, polypropylene, alkenyl aromatic heterocyclic compound and initiator are mixed in a protective gas atmosphere for 20 min to 40 min; then deoxygenated water is added and swollen 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 an aromatic heterocyclic modified polypropylene compound.

[0069] The above-mentioned aromatic heterocyclic modified polypropylene compound is obtained by reacting polypropylene and alkenyl aromatic heterocyclic compound, and its structure includes a structural unit derived from the polypropylene and a structural unit derived from the alkenyl aromatic heterocyclic compound. In the present invention, the content of the structural unit derived from the alkenyl aromatic heterocyclic compound in the aromatic heterocyclic modified polypropylene is 0.1 wt% to 40 wt%, preferably 0.1 to 30 wt%.

[0070] The raw materials for preparing the aromatic heterocyclic modified polypropylene composite provided by the present invention include 0-2% of a nucleating agent, specifically 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%. In the present invention, the nucleating agent is selected from one or more of dibenzylidene sorbitol, bis(p-methyl dibenzylidene) sorbitol, bis(3,4-dimethyl dibenzylidene) sorbitol, bis(4-methyl dibenzylidene) sorbitol, bis(p-ethyl benzylidene) sorbitol, bis(p-methyl benzylidene) sorbic acid, bis-(p-ethyl dibenzylidene isopropyl) sorbitol, bis(p-chloro substituted benzylidene) sorbitol, bis(p-chloromethyl dibenzylidene) sorbitol, 4,4'-(dimethylthio dibenzylidene) sorbitol, 1-propyl-1,3,2,4,-bis(p-n-propyl dibenzylidene) sorbitol, dehydroabietic acid, dehydroabietate, disproportionated rosin acid, disproportionated rosin salt, and sodium salt of 2,2'-methylene-bis-(4,6-di-tert-butylphenyl) phosphate; preferably one or more of dibenzylidene sorbitol, bis(p-methyl dibenzylidene) sorbitol, bis(3,4-dimethyl dibenzylidene) sorbitol, dehydroabietic acid, disproportionated rosin salt, and sodium salt of 2,2'-methylene-bis-(4,6-di-tert-butylphenyl) phosphate.

[0071] The raw materials for preparing the aromatic heterocyclic modified polypropylene composite provided by the present invention include 0-0.5% of an antioxidant, specifically 0%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. In the present invention, the antioxidant is selected from one or more of hindered phenol antioxidants, phosphite antioxidants, and thioester antioxidants, preferably one or more of hindered phenol antioxidants and / or phosphite antioxidants.

[0072] In a specific embodiment, the aromatic heterocyclic modified polypropylene composite, by mass fraction, includes the following raw materials:

[0073] 90% of polypropylene, 8% of cycloolefin copolymer, 1% of aromatic heterocyclic modified polypropylene compound, 0.8% of nucleating agent, and 0.1% of antioxidant.

[0074] The present invention provides a method for preparing the aromatic heterocyclic modified polypropylene composite according to the above technical solution, including the following steps:

[0075] Mix polypropylene, cycloolefin copolymer, aromatic heterocyclic modified polypropylene compound, nucleating agent, and antioxidant, and pelletize to obtain the aromatic heterocyclic modified polypropylene composite.

[0076] The above materials are fully and evenly mixed in a high-speed mixer, and then the above mixture is continuously added into a twin-screw extruder at the preheating temperature. The backmixing ratio of the screw combination is adjusted, and water is used for pelletizing to obtain an aromatic heterocyclic modified polypropylene composite material.

[0077] In the present invention, the preheating temperature is 100 - 300 °C, preferably 120 - 280 °C, more preferably 150 - 250 °C; specifically, it can be 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C or 250 °C. The mixing time in the twin-screw extruder is 0.5 - 20 min, preferably 1 - 15 min, more preferably 2 - 10 min.

[0078] The above aromatic heterocyclic modified polypropylene composite material prepared by the present invention is an aromatic heterocyclic polypropylene dielectric energy storage composite material, which can be applied in high-temperature energy storage dielectric materials, and is particularly suitable for high-temperature thin-film capacitor films.

[0079] The present invention provides a high-temperature capacitor film made from the aromatic heterocyclic modified polypropylene composite material described in the above technical solution.

[0080] This high-temperature capacitor film aims to meet the requirements of electronic devices under harsh environmental conditions.

[0081] The present invention conducts performance tests on the above high-temperature capacitor film:

[0082] Determination of flexural modulus: It is determined according to the method specified in GB / T 9341--2008.

[0083] Determination of ash content of the aromatic heterocyclic modified polypropylene compound material: It is determined according to the method specified in GB / T 9345.1--2008.

[0084] Determination of melt flow rate MFR: According to the method specified in GB / T 3682-2018, using a CEAST company 7026 type melt indexer, it is determined at 230 °C under a load of 2.16 kg.

[0085] Determination of melting temperature Tm: A differential scanning calorimeter is used to analyze the melting process and crystallization process of the material. The specific operation is as follows: Under nitrogen protection, 5 - 10 mg of the sample is measured from 20 °C to 200 °C using a three-stage heating and cooling measurement method, and the melting and crystallization processes of the material are reflected by the change in heat flow, so as to calculate the melting temperature Tm.

[0086] Determination of grafting efficiency η and parameter M: Put 10 g of the grafted product into a Soxhlet extractor, extract with acetone for 24 hours to remove unreacted monomers and their homopolymers, obtain the pure grafted product, dry and weigh it, and calculate parameter M and grafting efficiency η. Parameter M represents the content of structural units derived from aromatic heterocyclic vinyl monomers in the aromatic heterocyclic olefin-grafted modified polypropylene material. In the present invention, the calculation formulas for M and η are as follows:

[0087]

[0088] In the above formulas, W0 is the mass of the polypropylene matrix; W1 is the mass of the grafted product before extraction; W_{2} is the mass of the grafted product after extraction; W_{3} is the mass of the aromatic heterocyclic vinyl monomer added.

[0089] Thickness of the capacitor film: It is measured according to the method specified in GB / T 13542.3-2006, and the measuring method is the micrometer method.

[0090] Determination of dielectric constant and dielectric loss factor: It is measured according to the method specified in GB / T 1409-2006.

[0091] Determination of energy storage density and energy storage efficiency: It is measured with reference to the methods specified in the following literature.

[0092] Bo, S.; Jiawei, Z.; et al. Chemical Transformation of Polyurethane into Valuable Polymers. National Science Review, 2025, 12, nwae393.

[0093] To further illustrate the present invention, the following is a detailed description of an aromatic heterocyclic modified polypropylene composite material, its preparation method and capacitor film provided by the present invention in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0094] Example 1

[0095] Synthesis process of methyl 2-(thiophen-2-yl)acrylate:

[0096] Dissolve 2-thiophene methanol (10 mmol) and the catalyst triethylamine (12 mmol) in dichloromethane and place them in a 500 mL single-necked flask. Under an atmosphere of 0 °C, slowly add methacryloyl chloride (12 mmol) dissolved in dichloromethane dropwise to the above mixed solution. After the addition is complete, react for 10 hours. After the reaction is completed, quench the reaction with saturated sodium bicarbonate solution, then extract it 3 times with dichloromethane, collect the organic phase, dry it with anhydrous magnesium sulfate, concentrate it under reduced pressure, and finally dry it under vacuum for 5 hours to obtain methyl thiophene-2-methylacrylate; Figure 1 It is the NMR spectrum of methyl thiophene-2-methylacrylate;

[0097] Add 5.0 kg of pure polypropylene powder (Borealis, grade HC300BF) to a 50 L reaction kettle equipped with a double-layer four-blade stirring paddle and baffle. Seal the reaction system and displace oxygen with nitrogen. After preparing a homogeneous solution of 7.2 g of benzoyl peroxide (as an initiator) and 500 g of methyl thiophene-2-methylacrylate, add it to the reaction kettle and stir it with the powder for 30 minutes. Then add 17.8 kg of deionized water that has been deoxygenated and raise the temperature to 50 °C to swell for 2 hours. Raise the temperature of the swollen powder to 95 °C and react for 4 hours. After the reaction is completed, cool down, filter out the liquid components, and vacuum dry the product at 70 °C for 10 hours to obtain aromatic heterocyclic modified polypropylene powder A1.

[0098] Example 2

[0099] Synthesis process of methyl benzo[b]thiophene-2-methylacrylate:

[0100] Dissolve benzo[b]thiophene-2-methanol (10 mmol) and the catalyst triethylamine (12 mmol) in dichloromethane and place them in a 500 mL single-necked flask. Under an atmosphere of 0 °C, slowly add methacryloyl chloride (12 mmol) dissolved in dichloromethane dropwise to the above mixed solution. After the addition is complete, react for 10 hours. After the reaction is completed, quench the reaction with saturated sodium bicarbonate solution, then extract it 3 times with dichloromethane, collect the organic phase, dry it with anhydrous magnesium sulfate, concentrate it under reduced pressure, and finally dry it under vacuum for 5 hours to obtain methyl benzo[b]thiophene-2-methylacrylate; Figure 2 It is the NMR spectrum of methyl benzo[b]thiophene-2-methylacrylate;

[0101] 5.0 kg of pure polypropylene powder (Borealis, grade HC300BF) was added to a 50 L reactor equipped with a double-layer four-blade agitator and baffles. The reaction system was sealed, and oxygen was removed by nitrogen replacement. After dissolving 7.2 g of benzoyl peroxide (as an initiator) and 500 g of methyl 2-(benzo[b]thiophen-2-yl)acrylate into a homogeneous solution, it was added to the reactor and stirred with the powder for 30 minutes. Then, 17.8 kg of deoxygenated deionized water was added and the temperature was raised to 50 °C for swelling for 2 hours. The swollen powder was heated to 95 °C and reacted for 4 hours. After the reaction, the temperature was cooled down, the liquid components were filtered off, and the product was vacuum dried at 70 °C for 10 hours to obtain aromatic heterocyclic modified polypropylene powder A2.

[0102] Example 3

[0103] Synthesis process of methyl 2-(oxolan-2-yl)acrylate:

[0104] 2-(Oxolan-2-yl)methanol (10 mmol) and the catalyst triethylamine (12 mmol) were dissolved in dichloromethane and placed in a 500 mL single-necked flask. Methacryloyl chloride (12 mmol) dissolved in dichloromethane was added dropwise to the above mixed solution under an atmosphere of 0 °C. After the addition was completed, the reaction was carried out for 10 hours. After the reaction, the reaction was quenched with saturated sodium bicarbonate solution, and then it was extracted 3 times with dichloromethane. The organic phase was collected, dried over anhydrous magnesium sulfate, concentrated under reduced pressure, and finally vacuum dried for 5 hours to obtain methyl 2-(oxolan-2-yl)acrylate; Figure 3 is the NMR spectrum of methyl 2-(oxolan-2-yl)acrylate;

[0105] 5.0 kg of pure polypropylene powder (Borealis, grade HC300BF) was added to a 50 L reactor equipped with a double-layer four-blade agitator and baffles. The reaction system was sealed, and oxygen was removed by nitrogen replacement. After dissolving 7.2 g of benzoyl peroxide (as an initiator) and 500 g of methyl 2-(oxolan-2-yl)acrylate into a homogeneous solution, it was added to the reactor and stirred with the powder for 30 minutes. Then, 17.8 kg of deoxygenated deionized water was added and the temperature was raised to 50 °C for swelling for 2 hours. The swollen powder was heated to 95 °C and reacted for 4 hours. After the reaction, the temperature was cooled down, the liquid components were filtered off, and the product was vacuum dried at 70 °C for 10 hours to obtain aromatic heterocyclic modified polypropylene powder A3.

[0106] Example 4

[0107] Synthesis process of methyl 2,2'-bithiophen-5-yl methacrylate:

[0108] Dissolve 2,2'-bithiophen]-5-ylmethanol (10 mmol) and the catalyst triethylamine (12 mmol) in dichloromethane and place them in a 500 mL single-necked flask. Under an atmosphere of 0 °C, slowly add methacryloyl chloride (12 mmol) dissolved in dichloromethane dropwise to the above mixed solution. After the addition is complete, react for 10 hours. After the reaction is completed, quench the reaction with saturated sodium bicarbonate solution, then extract it with dichloromethane 3 times, collect the organic phase, dry it with anhydrous magnesium sulfate, concentrate it under reduced pressure, and finally dry it in vacuo for 5 hours to obtain 2,2'-bithiophen]-5-ylmethyl methacrylate; Figure 4 1H NMR spectrum of 2,2'-bithiophen]-5-ylmethyl methacrylate;

[0109] Add 5.0 kg of pure polypropylene powder (Borealis - grade HC300BF) to a 50 L reaction kettle equipped with a double-layer four-blade stirring paddle and baffles. Seal the reaction system and displace oxygen with nitrogen. After preparing a homogeneous solution of 7.2 g of benzoyl peroxide (as an initiator) and 500 g of 2,2'-bithiophen]-5-ylmethyl methacrylate, add it to the reaction kettle and stir and mix it with the powder for 30 minutes. Then add 17.8 kg of deionized water that has been deoxygenated and heat it to 50 °C for swelling for 2 hours. Heat the swollen powder to 95 °C and react for 4 hours. After the reaction is completed, cool it down, filter out the liquid components, and vacuum dry the product at 70 °C for 10 hours to obtain aromatic heterocyclic modified polypropylene powder A4.

[0110] Example 5

[0111] Fully mix 9.00 kg of pure polypropylene powder (Borealis - grade HC300BF), 0.80 kg of high-temperature resistant cycloolefin copolymer (Topas 6013), 0.10 kg of aromatic heterocyclic modified polypropylene powder A1, 0.08 kg of dehydroabietic acid (nucleating agent), and 0.01 kg of hindered phenol antioxidant in a 30 L high-speed mixer. Then continuously add the above mixture to a twin-screw extruder with a preheating temperature of 200 °C (length-to-diameter ratio 52:1) through a feeder. Adjust the backmixing ratio of the screw combination and control the mixing time to be 2.5 min. Cut the strands through water to obtain aromatic heterocyclic modified polypropylene composite material B1.

[0112] Example 6

[0113] 9.00 kg of pure polypropylene powder (Borealis - grade HC300BF), 0.80 kg of high - temperature resistant cycloolefin copolymer (Topas 6013), 0.10 kg of aromatic heterocyclic modified polypropylene powder A2, 0.08 kg of dehydroabietic acid (nucleating agent), and 0.01 kg of hindered phenolic antioxidant were thoroughly mixed in a 30 - L high - speed mixer. Then, the above mixture was continuously added into a twin - screw extruder preheated to 200 °C (length - to - diameter ratio 52:1) through a feeder. The back - mixing ratio of the screw combination was adjusted, and the mixing time was controlled at 2.5 min. After water - granulation, a composite material B2 containing aromatic heterocyclic modified polypropylene was obtained.

[0114] Example 7

[0115] 9.00 kg of pure polypropylene powder (Borealis - grade HC300BF), 0.80 kg of high - temperature resistant cycloolefin copolymer (Topas 6013), 0.10 kg of aromatic heterocyclic modified polypropylene powder A3, 0.08 kg of dehydroabietic acid (nucleating agent), and 0.01 kg of hindered phenolic antioxidant were thoroughly mixed in a 30 - L high - speed mixer. Then, the above mixture was continuously added into a twin - screw extruder preheated to 200 °C (length - to - diameter ratio 52:1) through a feeder. The back - mixing ratio of the screw combination was adjusted, and the mixing time was controlled at 2.5 min. After water - granulation, a composite material B3 containing aromatic heterocyclic modified polypropylene was obtained.

[0116] Example 8

[0117] 9.00 kg of pure polypropylene powder (Borealis - grade HC300BF), 0.80 kg of high - temperature resistant cycloolefin copolymer (Topas 6013), 0.10 kg of aromatic heterocyclic modified polypropylene powder A4, 0.08 kg of dehydroabietic acid (nucleating agent), and 0.01 kg of hindered phenolic antioxidant were thoroughly mixed in a 30 - L high - speed mixer. Then, the above mixture was continuously added into a twin - screw extruder preheated to 200 °C (length - to - diameter ratio 52:1) through a feeder. The back - mixing ratio of the screw combination was adjusted, and the mixing time was controlled at 2.5 min. After water - granulation, a composite material B4 containing aromatic heterocyclic modified polypropylene was obtained.

[0118] Comparative Example 1

[0119] Pure polypropylene powder (Borealis - grade HC300BF) was used as Comparative Example C1.

[0120] Comparative Example 2

[0121] 5.0 kg of pure polypropylene powder (Borealis - grade HC300BF) was added to a 50 L reactor equipped with a double - layer four - blade agitator and baffles. The reaction system was sealed, and oxygen was removed by nitrogen replacement. After preparing a homogeneous solution of 7.2 g of benzoyl peroxide (as an initiator) and 500 g of methyl methacrylate (purchased from Anychem Co., Ltd.), the solution was added to the reactor and stirred with the powder for 30 minutes. Then, 17.8 kg of deoxygenated deionized water was added and the temperature was raised to 50 °C for swelling for 2 hours. The swollen powder was heated to 95 °C and reacted for 4 hours. After the reaction, the temperature was cooled, the liquid components were filtered off, and the product was vacuum - dried at 70 °C for 10 hours to obtain non - aromatic heterocyclic - modified polypropylene powder A5.

[0122] 9.00 kg of pure polypropylene powder (Borealis - grade HC300BF), 0.80 kg of high - temperature resistant cycloolefin copolymer (Topas 6013), 0.10 kg of non - aromatic heterocyclic - modified polypropylene powder A5, 0.08 kg of dehydroabietic acid (nucleating agent), and 0.01 kg of hindered phenolic antioxidant were thoroughly mixed uniformly in a 30 L high - speed mixer. Then, the above - mentioned mixture was continuously added to a twin - screw extruder with a pre - heating temperature of 200 °C (length - to - diameter ratio 52:1) through a feeder. The back - mixing ratio of the screw combination was adjusted, and the mixing time was controlled at 2.5 min. After passing through a water - ring pelletizer, non - aromatic heterocyclic - modified polypropylene composite material C2 was obtained.

[0123] Comparative Example 3

[0124] 5.0 kg of pure polypropylene powder (Borealis - grade HC300BF) was added to a 50 L reactor equipped with a double - layer four - blade agitator and baffles. The reaction system was sealed, and oxygen was removed by nitrogen replacement. After preparing a homogeneous solution of 7.2 g of benzoyl peroxide (as an initiator) and 500 g of 2 - morpholinoethyl methacrylate (purchased from Anychem Co., Ltd.), the solution was added to the reactor and stirred with the powder for 30 minutes. Then, 17.8 kg of deoxygenated deionized water was added and the temperature was raised to 50 °C for swelling for 2 hours. The swollen powder was heated to 95 °C and reacted for 4 hours. After the reaction, the temperature was cooled, the liquid components were filtered off, and the product was vacuum - dried at 70 °C for 10 hours to obtain non - aromatic heterocyclic - modified polypropylene powder A6.

[0125] 9.00 kg of pure polypropylene powder (Borealis - grade HC300BF), 0.80 kg of high - temperature resistant cycloolefin copolymer (Topas 6013), 0.10 kg of non - aromatic heterocyclic modified polypropylene powder A6, 0.08 kg of dehydroabietic acid (nucleating agent) and 0.01 kg of hindered phenolic antioxidant were thoroughly mixed in a 30 L high - speed mixer. Then the above mixture was continuously added into a twin - screw extruder with a pre - heating temperature of 200 °C (length - to - diameter ratio 52:1) through a feeder. The back - mixing ratio of the screw combination was adjusted, and the mixing time was controlled at 2.5 min. After passing through water - ring pelletization, a non - aromatic heterocyclic modified polypropylene composite material C3 was obtained.

[0126] Comparative Example 4

[0127] Synthesis process of methyl 2 - pyridylmethacrylate:

[0128] 2 - Pyridinemethanol (10 mmol) and catalyst triethylamine (12 mmol) were dissolved in dichloromethane and placed in a 500 mL single - neck flask. Methacryloyl chloride (12 mmol) dissolved in dichloromethane was added dropwise to the above - mentioned mixed solution under an atmosphere of 0 °C. After the drop - wise addition, the reaction was carried out for 10 hours. After the reaction, the reaction was quenched with saturated sodium bicarbonate solution, and then it was extracted 3 times with dichloromethane. The organic phase was collected, dried over anhydrous magnesium sulfate, concentrated under reduced pressure and finally vacuum - dried for 5 hours to obtain the compound methyl 2 - pyridylmethacrylate; Figure 5 is the NMR spectrum of methyl 2 - pyridylmethacrylate;

[0129] 5.0 kg of pure polypropylene powder (Borealis - grade HC300BF) was added to a 50 L reaction kettle equipped with a double - layer four - blade stirring paddle and baffles. The reaction system was sealed, and oxygen was removed by nitrogen replacement. After 7.2 g of benzoyl peroxide (as an initiator) and 500 g of methyl 2 - pyridylmethacrylate were formulated into a homogeneous solution, they were added to the reaction kettle and stirred with the powder for 30 minutes. Then 17.8 kg of deoxygenated deionized water was added and the temperature was raised to 50 °C for swelling for 2 hours. The swollen powder was heated to 95 °C and reacted for 4 hours. After the reaction, the temperature was cooled down, the liquid components were filtered off, and the product was vacuum - dried at 70 °C for 10 hours to obtain pyridine - ring modified polypropylene powder A7.

[0130] 9.00 kg of pure polypropylene powder (Borealis - grade HC300BF), 0.80 kg of high - temperature resistant cycloolefin copolymer (Topas 6013), 0.10 kg of pyridine - ring modified polypropylene powder A7, 0.08 kg of dehydroabietic acid (nucleating agent), and 0.01 kg of hindered phenol antioxidant were thoroughly mixed in a 30 - L high - speed mixer. Then, the above mixture was continuously added into a twin - screw extruder with a pre - heating temperature of 200 °C (length - to - diameter ratio 52:1). The back - mixing ratio of the screw combination was adjusted, and the mixing time was controlled at 2.5 min. After passing through a water - ring pelletizer, a composite material C4 containing aromatic heterocyclic - modified polypropylene was obtained.

[0131] All the modified polypropylene powders A1 - A7 obtained above were subjected to basic characterization tests, and the results are summarized in Table 1:

[0132] Table 1 Basic characterization test results of all modified polypropylene powders A1 - A7

[0133] Grafting rate η(%) Ash content (ppm) Melt mass (g / 10min) Melting temperature (°C) A1 9.1 23 3.4 162.9 A2 9.0 24 3.3 163.0 A3 9.2 22 3.2 163.2 A4 9.1 23 3.2 163.3 A5 9.2 22 3.2 163.1 A6 9.1 23 3.3 163.2 A7 9.1 23 3.2 163.3

[0134] From the test results in Table 1 above, it can be seen that the grafting rate, ash content, melt index, and melting temperature of the modified polypropylene in Examples 1 - 4 and Comparative Examples 2 - 4 are not very different, indicating that the monomers grafted onto the pure polypropylene powder are successful, and further indicating that there are no significant differences in the basic performance tests of these polypropylene modified materials.

[0135] The materials B1 - B4 in Examples 5 - 8 and the materials C1 - C4 in Comparative Examples 1 - 4 were respectively prepared into film products by the biaxial stretching method, and various performance parameters of all the obtained film products were tested. The results are shown in Table 2:

[0136] Table 2 Dielectric and energy storage performance test results of the films made from the materials in Examples and Comparative Examples

[0137]

[0138] As can be seen from the test results in Table 3, on the basis that the film thickness and flexural modulus are not much different, compared with C1 in Comparative Example 1, the breakdown field strength, discharge energy density, and charge-discharge efficiency of B1-B4 in Examples 5-8 have all increased significantly, indicating that the aromatic heterocyclic graft-modified polypropylene composite film not only has a high breakdown field strength and a low dielectric loss value, but can also maintain a high discharge energy density and charge-discharge efficiency at a working temperature of 130°C; compared with the polypropylene composite materials C2 and C3 without aromatic heterocyclic modification in Comparative Example 2 and Comparative Example 3, the breakdown field strength, discharge energy density, and charge-discharge efficiency of B1-B4 in Examples 5-8 are all better, and at the same time the loss value is lower, indicating that the polypropylene composite material containing aromatic heterocyclic modification has a more obvious effect in improving various properties; in addition, compared with the polypropylene composite material C4 containing other types of heterocycles (such as pyridine ring) in Comparative Example 4, the breakdown field strength, discharge energy density, and charge-discharge efficiency of B1-B4 in Examples 5-8 are also more excellent, and at the same time can maintain a lower dielectric loss value, further proving that the aromatic heterocyclic modification technology is more unique in improving dielectric properties and enhancing energy storage performance. All the above test results consistently show that the aromatic heterocyclic graft-modification technology has improved the problem of poor energy storage performance of polypropylene at high temperatures.

[0139] The present invention provides an aromatic heterocyclic-containing modified polypropylene composite material, which comprises the following raw materials in terms of mass fraction: 70-98.89% of polypropylene, 1-22.5% of cycloolefin copolymer, 0.1-5% of aromatic heterocyclic-containing modified polypropylene compound, 0-2% of nucleating agent, and 0-0.5% of antioxidant; the preparation raw materials of the aromatic heterocyclic-containing modified polypropylene compound include polypropylene and an alkenyl aromatic heterocyclic compound; the alkenyl aromatic heterocyclic compound has a compound of formula I or formula II. The aromatic heterocyclic-containing modified polypropylene composite material is particularly suitable for high-temperature thin-film capacitor films, which has excellent high-temperature working performance and can maintain high energy storage efficiency and energy storage density at a relatively high temperature. It also solves the problem of insufficient energy storage performance of commercial polypropylene films under high-temperature and high-field conditions. In addition, the preparation process of the aromatic heterocyclic-modified polypropylene material is simple, suitable for large-scale industrial production, and has broad market prospects and application value.

[0140] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A kind of aromatic heterocyclic modified polypropylene composite material, by mass fraction, comprises the following raw materials: 70 - 98.89% of polypropylene, 1 - 22.5% of cycloolefin copolymer, 0.1 - 5% of aromatic heterocyclic modified polypropylene compound, 0 - 2% of nucleating agent and 0 - 0.5% of antioxidant; The preparation raw materials of the aromatic heterocyclic modified polypropylene compound include polypropylene and alkenyl aromatic heterocyclic compound; The alkenyl aromatic heterocyclic compound has a compound of formula Ⅰ or formula Ⅱ; R a selected from one of 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; R b 、R c and R d are each independently selected from the group consisting of hydrogen, substituted or unsubstituted C1-C5 alkyl.

2. The aromatic heterocyclic modified polypropylene composite material according to claim 1, wherein Said R a is independently selected from one of the groups represented by Formula III to Formula IX; wherein, the X1 to X4 and the X 1 ~X 4 are independently selected from O, S or Se; The R1 to R 21 and the R 1 to R 10 are independently selected from the group consisting of halogen, hydroxyl, amino, aldehyde, carboxyl, isocyanate, acyl chloride, cyano, hydrogen atom, sulfonic acid group, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C3-C8 cycloalkyl, substituted or unsubstituted C1-C8 alkoxy, substituted or unsubstituted C1-C8 ester group, and substituted or unsubstituted C1-C8 amino group.

3. The aromatic heterocyclic modified polypropylene composite material according to claim 1, wherein The substituted groups are selected from halogen, hydroxyl, amino, aldehyde group, carboxyl group, isocyanate group, acyl chloride group, cyano group, hydrogen atom, sulfonic acid group, C1 - C5 alkyl, C3 - C8 cycloalkyl, C1 - C8 alkoxy, C1 - C8 ester group or C1 - C8 amino group.

4. The aromatic heterocyclic modified polypropylene composite material according to claim 1, characterized in that The alkenyl aromatic heterocyclic compound is selected from at least one of methyl benzo[b]thiophene - 2 - methylacrylate, oxolane - 2 - yl methylacrylate, methyl 2,2'-bithiophen]-5-yl methacrylate, methyl furfuryl methacrylate and thiophene - 2 - methylacrylate.

5. The aromatic heterocyclic modified polypropylene composite material according to claim 1, characterized in that, The polypropylene is a copolymerized polypropylene or a homopolypropylene with a melt flow rate of 1 - 10 g / 10min; The isotacticity of the homopolypropylene is between 95 - 99%, the ash content is lower than 40 ppm, the molecular weight distribution is between 3 - 7, and the melting temperature is between 110 - 160 °C; The comonomer of the copolymerized polypropylene is selected from at least one of C2 - C8 α - olefins except propylene.

6. The aromatic heterocyclic modified polypropylene composite material according to claim 1, characterized in that, The nucleating agent is selected from one or more of dibenzylidene sorbitol, bis(4 - methyl dibenzylidene) sorbitol, bis(3,4 - dimethyl dibenzylidene) sorbitol, bis(4 - methyl dibenzylidene) sorbitol, bis(4 - ethyl dibenzylidene) sorbitol, bis(4 - methyl dibenzylidene) sorbic acid, bis-(4 - ethyl dibenzylidene isopropyl) sorbitol, bis(4 - chloro substituted dibenzylidene) sorbitol, bis(4 - chloromethyl dibenzylidene) sorbitol, 4,4’-(dimethylthio dibenzylidene) sorbitol, 1 - propyl - 1,3,2,4,-bis(4 - n - propyl dibenzylidene) sorbitol, dehydroabietic acid, dehydroabietate, disproportionated rosin acid, disproportionated rosin salt, sodium salt of 2,2’-methylene - bis-(4,6 - di - tert - butylphenyl) phosphate; The antioxidant is selected from one or more of hindered phenol antioxidants, phosphite antioxidants and thioester antioxidants.

7. The aromatic heterocyclic modified polypropylene composite material according to claim 1, characterized in that, The glass transition temperature of the cycloolefin copolymer is 120 - 150 °C.

8. The aromatic heterocyclic modified polypropylene composite material according to claim 1, wherein The content of the structural unit derived from the alkenyl aromatic heterocyclic compound in the aromatic heterocyclic modified polypropylene compound is 0.1 wt% - 40 wt%.

9. A preparation method of the aromatic heterocyclic modified polypropylene composite material according to any one of claims 1 - 8, comprising the following steps: Mix polypropylene, cycloolefin copolymer, aromatic heterocyclic modified polypropylene compound, nucleating agent and antioxidant, and pelletize to obtain the aromatic heterocyclic modified polypropylene composite material.

10. A high-temperature capacitive film, characterized in that, Prepared from the aromatic heterocyclic modified polypropylene composite material according to any one of claims 1 - 8.

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