Polypropylene resin composition, high-temperature-resistant polymer film containing polypropylene resin composition as well as preparation method and application of polypropylene resin composition

Abstract

The invention provides a polypropylene resin composition, a high-temperature-resistant polymer film containing the same as well as a preparation method and application of the high-temperature-resistant polymer film. The polypropylene resin composition is prepared from the following components in percentage by mass: 79.7 to 98.9 percent of polypropylene resin, 1 to 20 percent of cycloolefin copolymer and 0.1 to 0.3 percent of irradiation cross-linking agent, the glass transition temperature of the cycloolefin copolymer is 120 to 160 DEG C; the film containing the polypropylene resin composition has the advantages of high thermal deformation temperature, low thermal shrinkage rate, good high temperature resistance, no influence on the dielectric property of a film capacitor, small dielectric loss, capability of carrying out two-way stretching at a high stretching ratio, and low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of capacitor materials, and in particular relates to a polypropylene resin composition, a high temperature resistant polymer film containing the same, and a preparation method and application thereof. Background Art

[0002] Film capacitors are widely used in wind power converters, photovoltaic inverters, new energy vehicle inverters, high-voltage direct current transmission and other fields due to their non-polarity, high insulation impedance, excellent frequency characteristics and low dielectric loss. Polypropylene film is the main dielectric material of film capacitors due to its high breakdown field strength, low dielectric loss, excellent self-healing, high energy storage density, ultra-thinness and low cost. It is widely used in modern electronic and electrical equipment; among them, biaxially oriented polypropylene film is the first choice as a dielectric material for capacitors. However, biaxially oriented polypropylene film has poor high temperature resistance. The upper temperature limit of existing polypropylene film capacitors is about 110°C. When the operating temperature of the capacitor exceeds 85°C, most of the film performance decreases, such as a sharp drop in breakdown strength and a sharp increase in leakage loss, which can easily cause capacitor operation failures and affect the safe and stable operation of the entire equipment system.

[0003] In the prior art, the heat resistance of polypropylene film is often improved by adding additives, inorganic particles or cycloolefin copolymers to polypropylene. After adding additives and inorganic particles to polypropylene to form a film, the dielectric constant difference between the additives and inorganic particles in the film and the polymer matrix is ​​too large, which will increase the local electric field and reduce the electrical strength of the film, greatly increase the dielectric loss, and seriously affect the dielectric properties of the capacitor film; in addition, in order to effectively improve the relevant properties of polypropylene film, a variety of additives and a large amount of additives are usually added to the formula. However, too many types or contents of additives will cause the additives to have poor dispersibility and uneven distribution in the system, and easily produce impurities, further reducing the dielectric properties of the polypropylene film and affecting the use of the polypropylene film; after adding cycloolefin copolymers to polypropylene resin to form a film, although physical defects will not occur in the polymer capacitor film, the addition of cycloolefin copolymers can only slightly improve the heat resistance of the capacitor film, and the heat resistance of the polypropylene film is limited. This is because cycloolefin copolymers have poor compatibility with polyethylene and polypropylene, and phase separation will gradually occur during long-term use, resulting in reduced heat resistance of the material and affecting product quality.

[0004] Cyclic olefin copolymer is an amorphous transparent polymer material with a cyclic olefin structure. It has the advantages of high transparency, good dimensional stability, low water absorption, excellent air tightness, chemical corrosion resistance, heat resistance, and easy processing and molding. It is widely used in optical resins and films, biomedicine, polyolefin modification and other fields. However, the high brittleness caused by the high glass transition temperature of cyclic olefin copolymer makes it very limited in processing. For example, when using cyclic olefin copolymer as a raw material to make capacitor film, the high brittleness of cyclic olefin copolymer makes it difficult or impossible to perform biaxial stretching of cyclic olefin copolymer capacitor film. Therefore, the capacitor film formed by cyclic olefin copolymer can only be prepared on a special machine and cannot be stretched at a high stretch ratio, which is not conducive to the preparation of capacitor film.

[0005] Patent publication CN116368175A discloses a capacitor comprising a biaxially stretched film as a dielectric, wherein the biaxially stretched film comprises a mixture of polypropylene and cycloolefin polymer, wherein the proportion of cycloolefin polymer in the mixture is 3-18% by weight. The film produced by the patent has high temperature resistance and high dielectric strength at room temperature, but polypropylene and cycloolefin polymer have poor compatibility, and the film produced by blending the two will gradually phase separate during subsequent use, affecting the operational stability of the film, easily causing capacitor failure, and threatening the safe operation of power electronic equipment.

[0006] Patent CN103448254A discloses a method for preparing polypropylene capacitor film, comprising the following steps: stretching and filming the following polypropylene raw material composition in the following weight proportions: 100 parts of polypropylene resin, 0.05-0.15 parts of photoinitiator, 3-5 parts of cross-linking agent, and 0.25-0.35 parts of hindered phenol antioxidant, and then irradiating with ultraviolet (UV). The film that has been treated by irradiation and cross-linking is sent to a winder for winding to obtain a finished film. Although the heat resistance and breakdown strength of the polypropylene film obtained by this process are improved, the types and amounts of additives in the patented film-making process are too many, which easily produces impurities and uneven distribution problems, thereby reducing the dielectric properties of the polypropylene film and affecting the use of the polypropylene film.

[0007] Therefore, it is an urgent problem to be solved in the art to develop a resin composition of polypropylene-cycloolefin copolymer that maintains unchanged dielectric properties, has good high temperature resistance, low heat shrinkage, and can be biaxially stretched, and to use it to prepare biaxially stretched film capacitors. Summary of the invention

[0008] In view of the shortcomings of the prior art, the object of the present invention is to provide a polypropylene resin composition, a high temperature resistant polymer film containing the same, and a preparation method and application thereof. The film containing the polypropylene resin composition has the characteristics of high hot forming temperature and low heat shrinkage, good high temperature resistance and stable dielectric properties, small dielectric loss, and can be biaxially stretched at a high stretch ratio, and low cost.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a polypropylene resin composition, which comprises, by weight percentage, 79.7-98.9% of a polypropylene resin, 1-20% of a cycloolefin copolymer and 0.1-0.3% of a radiation crosslinking agent; the glass transition temperature of the cycloolefin copolymer is 120-160°C.

[0011] In the present invention, 79.7-98.9% of the polypropylene resin may be, for example, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, etc.

[0012] In the present invention, 1-20% of the cycloolefin copolymer can be, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0013] In the present invention, 0.1-0.3% of the radiation crosslinking agent can be, for example, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, etc.

[0014] In the present invention, the glass transition temperature of the cycloolefin copolymer is 120-160°C, for example, it can be 120°C, 122°C, 125°C, 128°C, 130°C, 132°C, 135°C, 138°C, 140°C, 142°C, 145°C, 148°C, 150°C, 152°C, 155°C, 158°C, 160°C, etc.; preferably, it is 150-160°C.

[0015] In the present invention, the glass transition temperature of the cycloolefin copolymer is within the above-defined range, which can improve the high temperature resistance of the film. After the cycloolefin copolymer is mixed into the polypropylene resin, the polymer film processing conditions will not be changed. At the same time, the obtained film can be biaxially stretched, which is beneficial to the preparation of biaxially stretched film capacitors.

[0016] In the present invention, the cycloolefin copolymer comprises a repeating unit A and a repeating unit B; the repeating unit A comprises a repeating unit having a structure shown in general formula I; the repeating unit B comprises at least one repeating unit having a structure shown in general formula II and / or at least one repeating unit having a structure shown in general formula III; the molar ratio of the repeating unit A to the repeating unit B is 1:(0.77~1.33).

[0017] General formula I.

[0018] General formula II.

[0019] General formula III.

[0020] The dotted lines in Formula I, Formula II and Formula III independently represent the connection sites of the repeating units.

[0021] Wherein, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 , R 28 , R 29 , R 30 , R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 , R 38 Each independently represents a hydrogen atom, a halogen, an alkyl group, a cycloalkyl group or an aryl group.

[0022] In the present invention, the alkyl group includes an alkyl group having a carbon number greater than or equal to 1, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, etc.; the cycloalkyl group includes a cycloalkyl group having a carbon number greater than or equal to 3, for example, 3, 4, 5, 6, 7, 8, 9, 10, etc.; the aryl group includes an aryl group having a carbon number greater than or equal to 6, for example, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, etc.

[0023] In the formula, m1, m2, n1, and n2 are each independently selected from an integer greater than or equal to 0, for example, 0, 1, 2, 3, 4, 5, 6, etc.; preferably, m1, m2, n1, and n2 are each independently selected from 0 or 1.

[0024] In the present invention, a cyclic olefin copolymer with a specific structure is used, that is, the cyclic olefin copolymer includes a repeating unit A derived from an olefin (general formula I), and a repeating unit derived from a cyclic non-conjugated diene as shown in general formula II, and / or a repeating unit derived from a cyclic olefin as shown in general formula III. It has a rigid ring structure, can improve the temperature resistance of the capacitor film, and controls the content of the cyclic olefin copolymer within a specific range, which is not only beneficial to improving the high temperature resistance of the capacitor, but also has good dielectric properties and low cost, and can prepare a biaxially stretched film capacitor.

[0025] In the present invention, the molar ratio of the repeating unit A to the repeating unit B is 1:(0.77-1.33), wherein the specific value in (0.77-1.33) can be, for example, 0.77, 0.78, 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, 0.98, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.33, etc.

[0026] In the present invention, the repeating unit B comprises any one of a combination of at least one repeating unit of the structure shown in the general formula II and at least one repeating unit of the structure shown in the general formula III, at least one repeating unit of the structure shown in the general formula II, or at least one repeating unit of the structure shown in the general formula III. When the repeating unit B comprises a combination of at least one repeating unit of the structure shown in the general formula II and at least one repeating unit of the structure shown in the general formula III, the molar ratio of the repeating unit of the structure shown in the general formula II to the repeating unit of the structure shown in the general formula III is (10-55):1, wherein the specific value in (10-55) can be, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, etc.

[0027] In the present invention, the radiation crosslinking agent includes triallyl isocyanurate and / or trimethylolpropane trimethacrylate.

[0028] In the present invention, the polypropylene resin includes capacitor-grade polypropylene resin, and the melting point of the polypropylene resin is 155-175°C, for example, 155°C, 160°C, 165°C, 170°C, 175°C, etc.

[0029] In a second aspect, the present invention provides a high temperature resistant polymer film, wherein the material of the high temperature resistant polymer film comprises the polypropylene resin composition according to the first aspect.

[0030] In the present invention, the heat deformation temperature of the high temperature resistant polymer film is 145~160°C, for example, it can be 145°C, 146°C, 147°C, 148°C, 149°C, 150°C, 151°C, 152°C, 153°C, 154°C, 155°C, 156°C, 157°C, 158°C, 159°C, 160°C, etc.

[0031] In a third aspect, the present invention provides a method for preparing the high temperature resistant polymer film according to the second aspect, the preparation method comprising the following steps:

[0032] (1) melting the polypropylene resin composition, extruding and casting, and obtaining a blended polypropylene film;

[0033] (2) biaxially stretching and heat-setting the blended polypropylene film obtained in step (1) to obtain a biaxially stretched polypropylene film;

[0034] (3) The biaxially oriented polypropylene film obtained in step (2) is subjected to radiation cross-linking to obtain the high temperature resistant polymer film.

[0035] In the present invention, the preparation method achieves cross-linking enhancement by melting the polypropylene resin composition, extruding and casting, biaxially stretching, and then irradiating and cross-linking. The addition of a radiation cross-linking agent can increase the cross-linking degree of the film prepared by the present invention, improve the compatibility stability of the cycloolefin copolymer and polypropylene, and further improve the high temperature resistance of the material.

[0036] In the present invention, the method for preparing the polypropylene resin composition in step (1) comprises: mixing a polypropylene resin with a cycloolefin copolymer to obtain the polypropylene resin composition.

[0037] In the present invention, the radiation cross-linking method in step (3) comprises using gamma rays for radiation cross-linking.

[0038] In the present invention, the dose of the radiation cross-linking is 15 to 45 kGy, for example, it can be 15 kGy, 16 kGy, 17 kGy, 18 kGy, 19 kGy, 20 kGy, 21 kGy, 22 kGy, 23 kGy, 24 kGy, 25 kGy, 26 kGy, 27 kGy, 28 kGy, 29 kGy, 30 kGy, 31 kGy, 32 kGy, 33 kGy, 34 kGy, 35 kGy, 36 kGy, 37 kGy, 38 kGy, 39kGy, 40 kGy, 41 kGy, 42 kGy, 43 kGy, 44 kGy, 45 kGy, etc.

[0039] In the present invention, when the irradiation dose is within a specific range, the obtained film has a higher thermal deformation temperature, a lower thermal shrinkage rate, and better high temperature resistance; and it can be ensured that the dielectric properties of the film are not affected.

[0040] In a fourth aspect, the present invention provides a film capacitor, wherein a base film of the film capacitor is made of the polypropylene resin composition described in the first aspect or the high temperature resistant polymer film described in the second aspect.

[0041] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The polypropylene resin composition provided by the present invention adopts a cycloolefin copolymer with a specific glass transition temperature and a radiation crosslinking agent to compound with a polypropylene resin, thereby improving the compatibility stability of the cycloolefin copolymer and the polypropylene, being beneficial to increasing the thermal deformation temperature of the film capacitor, reducing the thermal shrinkage rate of the film capacitor, and improving its high temperature resistance, without affecting the dielectric properties of the film capacitor, and having low dielectric loss; the biaxially stretched film capacitor can be prepared, and the material cost is low. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0045] The materials used in the present invention are as follows:

[0046] Polypropylene resin (PP)

[0047] Capacitor grade polypropylene resin: Borclean™ HC318BF, melting point 165°C, melt flow index 3.2 g / 10min (230°C, 2.16 kg).

[0048] Cyclic Olefin Copolymer (COC)

[0049] In the present invention, the raw materials for synthesizing COC include the structural compound represented by the general formula II and / or the structural compound represented by the general formula III, as shown below, and specifically may include compound IIa, compound IIIb, compound IIIa, etc.; the compound IIa, compound IIIb, and compound IIIa can all be prepared by existing compounds in the prior art, such as dicyclopentadiene (A), ethylidene norbornene (B), norbornene (C), etc. as raw materials.

[0050] In the present invention, the reaction routes for preparing the compound IIa and compound IIIa are as follows.

[0051]

[0052]

[0053] The specific steps include: in the presence of a solvent (toluene, the amount used is sufficient to dissolve the compounds), reacting compound A and compound B, or compound A and compound C, respectively, at 240° C. for 60 minutes, and obtaining compound IIa or compound IIIa with a purity greater than 99% by reduced pressure distillation.

[0054] In the present invention, the reaction route for preparing the compound IIIb is as follows.

[0055]

[0056]

[0057] The specific steps include: mixing compound A with a Ru catalyst, introducing hydrogen into the mixture, wherein the molar ratio of hydrogen to compound A is 1:1, and performing selective hydrogenation to obtain compound D. Then, in the presence of a solvent (hexane, in an amount sufficient to dissolve the compounds), compound A and compound D are reacted at 230° C. for 60 minutes, and compound IIIb with a purity greater than 99% is obtained by reduced pressure distillation.

[0058] COC-1: The structural formula is ; The molecular structure comprises repeating unit A (ethylene repeating unit) and repeating unit B (IIa repeating unit and ethylidene norbornene repeating unit); the molar ratio of the repeating unit A to the repeating unit B is 1:1.27; in the repeating unit B, the molar ratio of the IIa repeating unit to the ethylidene norbornene repeating unit is 13:1, and the glass transition temperature (Tg) is 150°C.

[0059] The method for preparing COC-1 used in the present invention comprises the following steps:

[0060] 500 mL of toluene solvent was added to a reactor fully replaced with nitrogen, and compound IIa and ethylidene norbornene were added according to the formula amount. Ethylene gas was introduced at a rate of 60 L per hour. After maintaining at 20° C. for 10 minutes, 5 mg of methylaluminoxane and 0.005 mg of dichloroethylene bis(indenyl)zirconium toluene solution (mass concentration of 50%) were added to the reactor. After polymerization at 20° C. and normal pressure for 1 hour, isopropanol was added to stop the polymerization. Subsequently, a large amount of methanol / acetone mixed solvent (volume ratio of 1:1) was added to the polymer solution to precipitate the polymer. The precipitated polymer was dried in a vacuum oven at 120° C. for 24 hours to obtain the cycloolefin copolymer COC-1.

[0061] COC-2: The structural formula is The molecular structure includes repeating units A (ethylene repeating units) and repeating units B (IIa repeating units and norbornene repeating units); the molar ratio of the repeating units A to B is 1:1.13; in the repeating unit B, the molar ratio of the IIa repeating units to the norbornene repeating units is 16.7:1; Tg is 140°C. The preparation method of COC-2 is the same as that of COC-1, except for the different types and proportions of raw materials.

[0062] COC-3: The structural formula is ; The molecular structure contains repeating unit A (ethylene repeating unit) and repeating unit B (IIIa repeating unit and ethylidene norbornene repeating unit); the molar ratio of the repeating unit A to the repeating unit B is 1:1.17; in the repeating unit B, the molar ratio of the ethylidene norbornene repeating unit to the IIIa repeating unit is 53:1; Tg is 147°C; the preparation method of COC-3 is the same as that of COC-1, the only difference being the type and ratio of raw materials.

[0063] COC-4: The structural formula is ; The molecular structure contains repeating unit A (ethylene repeating unit) and repeating unit B (IIa repeating unit); the molar ratio of the repeating unit A to the repeating unit B is 1:1.33; Tg is 160°C; the preparation method of COC-4 is the same as that of COC-1, the only difference being the type and ratio of raw materials.

[0064] COC-5: The structural formula is ; The molecular structure contains repeating unit A (ethylene repeating unit) and repeating unit B (IIIb repeating unit and ethylidene norbornene repeating unit); the molar ratio of the repeating unit A to the repeating unit B is 1:0.96; in the repeating unit B, the molar ratio of the ethylidene norbornene repeating unit to the IIIb repeating unit is 11.25:1; Tg is 142°C; the preparation method of COC-5 is the same as that of COC-1, the only difference being the type and ratio of raw materials.

[0065] COC-6: The structural formula is consistent with that of COC-4, except that the molar ratio of the repeating unit A to the repeating unit B is 1:0.77; Tg is 120°C; the preparation method of COC-6 is the same as that of COC-1, except that the types and proportions of raw materials are different.

[0066] COC-7: The structural formula is consistent with that of COC-3, except that the molar ratio of the repeating unit A to the repeating unit B is 1:0.12; in the repeating unit B, the molar ratio of the ethylidene norbornene repeating unit to the IIIa repeating unit is 5:1; Tg is 58°C. The preparation method of COC-7 is the same as that of COC-1, except that the types and proportions of raw materials are different.

[0067] COC-8: The structural formula is consistent with that of COC-3, except that the molar ratio of the repeating unit A to the repeating unit B is 1:0.375; Tg is 40° C. The preparation method of COC-8 is the same as that of COC-1, except that the types and proportions of raw materials are different.

[0068] COC-9: The structural formula is consistent with that of COC-5, except that the molar ratio of the repeating unit A to the repeating unit B is 1:0.12; Tg is 80°C; the preparation method of COC-9 is the same as that of COC-1, except that the types and proportions of raw materials are different.

[0069] In the present invention, the cyclic olefin copolymer used contains a cross-linkable group, has good formability and solubility, and can improve the product yield. In addition, the cyclic olefin copolymer also has good heat resistance, mechanical properties, and dielectric properties.

[0070] Examples 1 to 6 and Comparative Examples 1 to 5 respectively provide a polypropylene resin composition, and the formula thereof is shown in Table 1 in terms of mass percentage. The preparation method of the polypropylene resin composition comprises: mixing a polypropylene resin, a cycloolefin copolymer and a radiation crosslinking agent.

[0071] Table 1

[0072]

[0073] In the application examples of the present invention, the polypropylene resin compositions provided in Examples 1 to 6 and Comparative Examples 1 to 5 are used to manufacture biaxially stretched high temperature resistant polymer films with a thickness of 6 μm.

[0074] Application Example 1

[0075] This application example provides a high temperature resistant polymer film, and the preparation method of the high temperature resistant polymer film comprises the following steps:

[0076] (1) The polypropylene resin composition (Example 1) was heated and melted at 250°C, filtered and extruded onto a casting roll at a temperature of 120°C, and blown onto a vertical bonding roll with an air knife to obtain a blended polypropylene film;

[0077] (2) biaxially stretching the blended polypropylene film obtained in step (1), wherein the stretching temperature for longitudinal stretching is 155° C. and the stretching ratio is 5; the stretching temperature for transverse stretching is 165° C. and the stretching ratio is 7, and the biaxially stretched film is heat-set at 165° C. to obtain a biaxially stretched polymer film;

[0078] (3) The biaxially oriented polymer film obtained in step (2) is irradiated and cross-linked using gamma rays with a radiation dose of 45 kGy to obtain the high temperature resistant polymer film.

[0079] Application Example 2

[0080] This application example provides a high temperature resistant polymer film, which differs from application example 1 only in that the polypropylene composition is the composition shown in example 2, the irradiation dose in step (3) is adjusted to 18 kGy, and the other preparation methods are the same as those in example 1.

[0081] Application Example 3

[0082] This application example provides a high temperature resistant polymer film, which differs from application example 1 only in that the polypropylene composition is the composition shown in example 3, the irradiation dose in step (3) is adjusted to 15 kGy, and the other preparation methods are the same as those in example 1.

[0083] Application Example 4

[0084] This application example provides a high temperature resistant polymer film, which differs from application example 1 only in that the polypropylene composition is the composition shown in example 4, the irradiation dose in step (3) is adjusted to 40 kGy, and the other preparation methods are the same as those in example 1.

[0085] Application Example 5

[0086] This application example provides a high temperature resistant polymer film, which differs from application example 1 only in that the polypropylene composition is the composition shown in example 5, the irradiation dose in step (3) is adjusted to 25 kGy, and the other preparation methods are the same as those in example 1.

[0087] Application Example 6

[0088] This application example provides a high temperature resistant polymer film, which differs from application example 1 only in that the polypropylene composition is the composition shown in example 6, the irradiation dose in step (3) is adjusted to 25 kGy, and the other preparation methods are the same as those in example 1.

[0089] Application Example 7

[0090] This application example provides a high temperature resistant polymer film, which differs from application example 3 only in that, in the preparation method, the irradiation dose in step (3) is adjusted to 10 kGy, and other materials and step parameters are the same as those in application example 3.

[0091] Comparative Application Examples 1~3

[0092] Comparative Application Examples 1 to 3 respectively provide a high temperature resistant polymer film, which differs from Application Example 3 only in that the polypropylene resin compositions are the polypropylene resin compositions provided in Comparative Examples 1 to 3, and the other steps, parameters, and preparation methods are the same as those in Application Example 3.

[0093] Comparative Application Example 4

[0094] This comparative application example provides a high temperature resistant polymer film, which differs from application example 1 only in that, in the preparation method, step (3) is not performed, and other materials and step parameters are the same as those in application example 1.

[0095] Comparative Application Example 5

[0096] This comparative application example provides a high temperature resistant polymer film, which differs from Application Example 3 only in that the polypropylene resin composition is the polypropylene resin composition provided in Comparative Example 4, and other materials and step parameters are the same as those in Application Example 3.

[0097] Comparative Application Example 6

[0098] This comparative application example provides a high temperature resistant polymer film, which differs from Application Example 5 only in that the polypropylene resin composition is the polypropylene resin composition provided in Comparative Example 5, and other materials and step parameters are the same as those in Application Example 5.

[0099] Comparative Application Example 7

[0100] This comparative application example provides a high temperature resistant polymer film, which differs from Application Example 5 only in that the polypropylene resin composition is the polypropylene resin composition provided in Comparative Example 5; in the preparation method, the irradiation dose in step (3) is adjusted to 50 kGy, and other materials and step parameters are the same as those in Application Example 5.

[0101] Performance Testing

[0102] The following performance tests were conducted on the films obtained from Examples 1 to 7 and Comparative Application Examples 1 to 7:

[0103] (1) Heat deformation temperature: Tested in accordance with GB / T 1634.2-2019;

[0104] (2) Heat shrinkage rate: Measure the transverse and longitudinal dimensions of the film before and after heating at 120°C for 10 minutes, and calculate the heat shrinkage rate; transverse or longitudinal heat shrinkage rate = (dimension before heating - dimension after heating) / dimension before heating × 100%;

[0105] (3) Dielectric constant: Tested according to GB / T31838.6-2021 method;

[0106] (4) Dielectric loss factor: Tested in accordance with GB / T1409-2006, test conditions are 23°C, 50Hz.

[0107] The specific test results are shown in Table 2, where “ / ” indicates that no radiation cross-linking was performed.

[0108] Table 2

[0109]

[0110] As can be seen from Table 2, the polypropylene resin composition provided by the present invention adopts a specific raw material composition and a film-making process, and the obtained polymer film has a high heat deformation temperature and a low heat shrinkage rate; the heat deformation temperature reaches 135~160°C, and can even reach 145~160°C; the transverse heat shrinkage rate is ≤0.3%, and the longitudinal heat shrinkage rate is ≤1.3%; and the dielectric properties of the film are not affected.

[0111] By comparing Application Example 3 with Comparative Application Examples 1 to 3 and Comparative Application Example 5, it can be seen that the repeating unit ratio and Tg of the cycloolefin copolymer are not within the specific range, and the temperature resistance of the blended film is only slightly higher than that of the film made of a single capacitor-grade polypropylene, but it is much lower than the blended film made by blending the specific cycloolefin copolymer of the present invention with capacitor-grade polypropylene.

[0112] It can be seen from the comparison between Application Example 1 and Comparative Application Example 4 that the temperature resistance of the film is poor due to the special film-making process of the present invention.

[0113] From the comparison between Application Example 3 and Comparative Application Example 5, it can be seen that the temperature resistance of the film made of capacitor-grade polypropylene alone is much lower than that of the blended film made of polypropylene and cycloolefin copolymer.

[0114] By comparing Application Example 5 with Comparative Application Example 6, it can be seen that the crosslinking density of the polypropylene composition film without adding an irradiation crosslinking agent is low. Compared with Comparative Application Example 5, the temperature resistance of the film can only be slightly improved, and the temperature resistance of the blended film cannot be further improved. The film provided by Application Example 5 has a high crosslinking density, thereby significantly improving the temperature resistance of the film.

[0115] By comparing Application Example 7 with Application Example 3, it can be seen that when the polypropylene-cycloolefin copolymer blend film is irradiated with a radiation dose lower than the specified dose of the present invention, the cross-linking degree of the blend film will be lower, resulting in a higher thermal shrinkage rate of the film and lower temperature resistance than the high-temperature resistant film made with the specific radiation dose of the present invention.

[0116] From the comparison of Application Example 5 and Comparative Application Example 7, it can be seen that after the polypropylene-cycloolefin copolymer blend film is irradiated with a high radiation dose without adding an irradiation crosslinking agent, the blend film degrades, resulting in a high thermal shrinkage rate of the blend film and a significant reduction in temperature resistance.

[0117] In summary, in the present invention, the polypropylene resin composition is compounded with polypropylene in a specific ratio by adding a cycloolefin copolymer with a specific Tg and an irradiation crosslinking agent, so that the film including the polypropylene resin composition has good high temperature resistance and basically does not affect the dielectric properties of the film; further, by blending the polypropylene resin composition and matching the gamma-ray irradiation process, it is helpful to further improve the temperature resistance of the film. The high-temperature resistant polymer capacitor film obtained by controlling the raw material ratio, irradiation dose and irradiation crosslinking agent content of the present invention has a high thermal deformation temperature and a low thermal shrinkage rate, which can not only ensure that the dielectric constant of the film remains unchanged, but also enhance the high temperature resistance of the film.

[0118] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A polypropylene resin composition, characterized in that The polypropylene resin composition comprises, by weight percentage, 79.7-98.9% polypropylene resin, 1-20% cycloolefin copolymer and 0.1-0.3% radiation crosslinking agent; The glass transition temperature of the cycloolefin copolymer is 120-160°C.

2. The polypropylene resin composition according to claim 1, characterized in that The cycloolefin copolymer comprises repeating units A and repeating units B; The repeating unit A comprises a repeating unit having a structure shown in general formula I; The repeating unit B comprises at least one repeating unit having a structure shown in the general formula II and / or at least one repeating unit having a structure shown in the general formula III; Formula I; Formula II; Formula III; Wherein, the dotted lines in Formula I, Formula II, and Formula III each independently represent the connection site of the repeating unit; R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 , R 28 , R 29 , R 30 , R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 , R 38 Each independently represents any one of a hydrogen atom, a halogen, an alkyl group, a cycloalkyl group or an aryl group; m1, m2, n1, n2 are each independently selected from an integer greater than or equal to 0; The molar ratio of the repeating unit A to the repeating unit B is 1:(0.77-1.33).

3. The polypropylene resin composition according to claim 2, characterized in that The repeating unit B includes at least one repeating unit of the structure shown in general formula II and at least one repeating unit of the structure shown in general formula III, and the molar ratio of the repeating unit of the structure shown in general formula II to the repeating unit of the structure shown in general formula III is (10~55):

1.

4. The polypropylene resin composition according to claim 1, characterized in that The radiation crosslinking agent includes triallyl isocyanurate and / or trimethylolpropane trimethacrylate; The polypropylene resin includes capacitor-grade polypropylene resin, and the melting point of the polypropylene resin is 155-175°C.

5. A high temperature resistant polymer film, characterized in that: The material of the high temperature resistant polymer film comprises the polypropylene resin composition according to any one of claims 1 to 4.

6. The high temperature resistant polymer film according to claim 5, characterized in that: The heat deformation temperature of the high temperature resistant polymer film is 145-160°C.

7. A method for preparing a high temperature resistant polymer film according to claim 5 or 6, characterized in that: The preparation method comprises the following steps: (1) melting the polypropylene resin composition, extruding and casting, and obtaining a blended polypropylene film; (2) biaxially stretching and heat-setting the blended polypropylene film obtained in step (1) to obtain a biaxially stretched polypropylene film; (3) The biaxially oriented polypropylene film obtained in step (2) is subjected to radiation cross-linking to obtain the high temperature resistant polymer film.

8. The preparation method according to claim 7, characterized in that: The preparation method of the polypropylene resin composition in step (1) comprises: mixing a polypropylene resin with a cycloolefin copolymer and a radiation crosslinking agent to obtain the polypropylene resin composition.

9. The preparation method according to claim 7, characterized in that: The radiation cross-linking method in step (3) includes using gamma rays for radiation cross-linking; The radiation cross-linking dose is 15-45 kGy.

10. A film capacitor, characterized in that: The base film of the film capacitor is made of the polypropylene resin composition according to any one of claims 1 to 4 or the high temperature resistant polymer film according to claim 5 or 6.

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