Polypropylene composite material as well as preparation method and application thereof

Abstract

The invention discloses a polypropylene composite material and a preparation method and application thereof, the polypropylene composite material comprises a polymer component accounting for 95-100% by weight of the composite material, and the polymer component comprises a) polypropylene and b) a cycloolefin polymer component; wherein the weight percentage of the polypropylene accounts for 70%-95% of the weight percentage of the polymer component; the cycloolefin polymer component at least contains one CBC (cycloolefin block copolymer) or COP (cycloolefin polymer) and at most contains one COC (cycloolefin copolymer); the mechanical loss factor tan delta of an unstretched film formed by the polypropylene composite material at 125 DEG C is less than or equal to 0.12, wherein the mechanical loss factor tan delta is measured under the conditions that the thickness is 0.5 mm, the stretching mode is adopted, the vibration frequency is 1Hz and the temperature rising speed is 5 DEG C / min. According to the invention, a specific type of cycloolefin polymer component is added into polypropylene, and the range of a mechanical loss factor tan delta of an unstretched film formed by the composite material at 125 DEG C is controlled, so that the film-forming property of the composite material and the high-temperature dielectric strength of a capacitor film formed by the composite material can be remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of polypropylene composite material technology, and particularly relates to a polypropylene composite material, its preparation method and application. Background Technology

[0002] Polypropylene composites, especially biaxially oriented polypropylene (BOPP) films, have become key dielectric materials for metallized film capacitors in power electronics and new energy vehicles due to their low dielectric loss factor and high dielectric strength. With industrial upgrading, particularly the development of electric vehicle drive systems, photovoltaic inverters, and pulse power equipment towards higher power density and miniaturization, more stringent requirements are being placed on the upper limit of capacitor operating temperature, long-term operational reliability, and lifespan. The long-term operating temperature of conventional BOPP capacitor films typically does not exceed 105℃. The problems of electrical performance degradation, accelerated thermal aging, and shortened lifespan under sustained high temperatures (such as 125℃ and above) or high-temperature, high-field-strength coupling stress are becoming increasingly prominent, becoming a key technical bottleneck restricting the performance and reliability of high-end power electronic equipment.

[0003] Currently, the industry has made numerous attempts to improve the high-temperature electrical properties of BOPP films, such as adding various antioxidants and stabilizers to inhibit thermo-oxidative aging, blending with high-melting-point polymers, or using multilayer co-extrusion structures. However, inorganic additives may introduce defects, affecting the uniformity and dielectric strength of the film, while organic additives are prone to migration or volatilization at high temperatures, leading to unstable performance. Therefore, while maintaining the excellent basic electrical properties and good processability of BOPP films, substantially improving their electrical performance and service life under long-term high-temperature (125°C) conditions through material formulation or process innovation is a pressing technical problem to be solved in the field of capacitor films. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a polypropylene composite material. By adding a specific type of cyclic olefin polymer component to polypropylene and controlling the range of the mechanical loss factor tanδ of the unstretched film formed by the composite material at 125°C, the film-forming properties of the composite material and the high-temperature dielectric strength of the capacitor film formed by the composite material can be significantly improved.

[0005] The aforementioned polypropylene composite material comprises a polymer component accounting for 95% to 100% by weight of the composite material, wherein the polymer component comprises:

[0006] a) Polypropylene, and

[0007] b) Cycloolefin polymer components;

[0008] The polypropylene comprises 70% to 95% by weight of the polymer component.

[0009] The cyclic olefin polymer component contains at least one CBC or COP and at most one COC;

[0010] The mechanical loss factor tanδ of the unstretched film formed by the polypropylene composite material at 125°C, measured under the conditions of 0.5 mm thickness, stretching mode, vibration frequency 1 Hz, and heating rate 5 °C / min, is ≤0.12.

[0011] This invention utilizes a cyclic olefin polymer component containing at least one CBC or COP and at most one COC in a polypropylene composite material. By adjusting the amount of the component, the mechanical loss factor tanδ at 125°C of the unstretched film formed by the composite material is less than or equal to 0.12. This improves the film-forming properties of the composite material when stretched to form a capacitor film. Furthermore, the resulting capacitor film exhibits low shrinkage and high dielectric strength at high temperatures.

[0012] In some embodiments of the present invention, the elongation at break of the polypropylene composite material, as measured by the type 1B specimen of GB / T 1040.3-2006, is greater than 300%, preferably greater than 450%, and more preferably 450%~800%.

[0013] In some embodiments of the present invention, the crystallinity of the polypropylene composite material is greater than 30%, preferably greater than 40%, more preferably greater than 45%, and most preferably 45%~55%.

[0014] In some embodiments of the present invention, the polypropylene is partially crystalline polypropylene, preferably, the crystallinity of the polypropylene is 30-80%, more preferably 50-80%.

[0015] In some embodiments of the present invention, the melt index of the polypropylene at 230°C / 2.16kg is 1~5 g / 10min, preferably 2~4 g / 10min.

[0016] In some embodiments of the present invention, the polypropylene accounts for 80% to 95% of the polymer component by weight.

[0017] In some embodiments of the present invention, the ash content of the polypropylene is less than 25 ppm, preferably less than or equal to 20 ppm.

[0018] In some embodiments of the present invention, the melting temperature of the polypropylene is greater than 130°C, preferably greater than 150°C, and more preferably 150~180°C.

[0019] In some embodiments of the present invention, the melt index of the cyclic olefin polymer component at 230°C / 2.16 kg is 0.1~5 g / 10 min.

[0020] In some embodiments of the present invention, the glass transition temperature of the cyclic olefin polymer component is greater than 130°C, preferably greater than 140°C, and more preferably 140~180°C.

[0021] In some embodiments of the present invention, the cyclic olefin polymer component accounts for 5% to 30% of the weight percentage of the polymer component.

[0022] In some embodiments of the present invention, the cyclic olefin polymer component contains one COC and at least one CBC.

[0023] In some embodiments of the present invention, the weight percentage of CBC in the cyclic olefin polymer component is 40% to 100%, preferably 40% to 60%.

[0024] In some embodiments of the present invention, the polymer component is also conjugated with an organic semiconductor polymer.

[0025] In some embodiments of the present invention, the conjugated organic semiconductor polymer accounts for 0.01% to 1% of the polymer component by weight.

[0026] In some embodiments of the present invention, the polypropylene composite material also contains other additives.

[0027] In some embodiments of the present invention, the other additives are selected from at least one of plasticizers, light stabilizers, colorants, preservatives, antioxidants, antistatic agents, flame retardants, and reinforcing agents.

[0028] In some embodiments of the present invention, the other additives account for 0 to 5% of the weight percentage of the composite material.

[0029] Another object of the present invention is to provide a method for preparing the above-mentioned polypropylene composite material, which includes the following steps: blending a cyclic olefin polymer component with polypropylene, melt extruding, and obtaining a polypropylene composite material.

[0030] Another object of the present invention is to provide the application of the above-mentioned polypropylene composite material in the preparation of BOPP capacitor film.

[0031] Another object of the present invention is to provide the application of the polypropylene composite material prepared by the above preparation method in the preparation of BOPP capacitor film.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention improves the film-forming properties of the composite material by adding a cyclic olefin polymer component containing at least one CBC or COP and at most one COC to a polypropylene composite material, and by adjusting the amount of the component so that the mechanical loss factor tanδ at 125°C of the unstretched film formed by the composite material is less than or equal to 0.12. Furthermore, the resulting capacitor film has a low shrinkage rate and high dielectric strength at high temperatures. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0035] The raw materials used in the specific embodiments of this invention are all commercially available. The specific models of the polypropylene and cyclic olefin polymer components used are as follows:

[0036] PP: PPH-FC03;

[0037] CBC: CBC1325;

[0038] COP-1: K26R;

[0039] COP-2: K22R;

[0040] COC-1: topas 6013;

[0041] COC-2: TAMT 1520.

[0042] Example 1

[0043] This embodiment provides a polypropylene composite material, which, by weight, comprises 70 parts PP and 30 parts CBC;

[0044] The specific preparation steps are as follows: Polypropylene and cyclic olefin polymer components are mixed and added to the extrusion equipment according to the weight parts. The temperature of the feeding section of the extrusion equipment is controlled at 235~245℃, the temperature of the melting section is 250~265℃, and the temperature of the homogenization section is 250~260℃. Polypropylene composite material PC1 is obtained by extrusion.

[0045] Examples 2-11 and Comparative Examples 1-2

[0046] The above embodiments and comparative examples provide a polypropylene composite material, which differs from Example 1 only in the type / amount of raw materials, as shown in Table 1. Polypropylene composite materials PC2~PC13 were obtained respectively, wherein PC2~PC11 correspond to Examples 2~11 in sequence, and PC12~PC13 correspond to Examples 1~2 in sequence, and the rest are consistent with Example 1.

[0047] The following properties of the above polypropylene composites PC1~PC13 were characterized, and the results are shown in Table 1:

[0048] A. Mechanical loss factor

[0049] Polypropylene composite materials PC1~PC13 were extruded into unstretched films with a thickness of 0.5 mm by melt extrusion. Using a dynamic thermomechanical analyzer (DMA), the unstretched film was heated from -100℃ to 180℃ at a heating rate of 5℃ / min under stretching mode, vibration frequency of 1Hz and air conditions to obtain viscoelastic-temperature curves. The mechanical loss factor tanδ at 125℃ was calculated based on the storage modulus at 125℃ / loss modulus at 125℃.

[0050] B. Elongation at break

[0051] According to the method of GB / T 1040.3-2006, polypropylene composite materials PC1~PC13 were respectively made into type 1B specimens, and their stress-strain curves were determined by a universal tensile testing machine at a tensile speed of 300 mm / min to obtain the elongation at break.

[0052] C. Crystallinity

[0053] The crystallinity of polypropylene composites PC1 to PC13 was determined by differential scanning calorimetry (DSC). The method involved first heating the material from room temperature to 200°C, holding it at that temperature for 5 minutes, then cooling it back to room temperature, and finally heating it back to 200°C at a rate of 5°C / min. The DSC curves were obtained, and the crystallinity was calculated based on the enthalpy change.

[0054] Table 1: Composition and properties of composite materials PC1~PC13

[0055]

[0056] Application Examples 1-11 and Comparative Application Examples 1-2

[0057] This application example and the comparative application example provide a capacitor film, and the specific preparation steps are as follows:

[0058] S1. The polypropylene composite materials PC1 to PC13 obtained in Examples 1 to 11 and Comparative Examples 1 to 2 were extruded to obtain unstretched films with a thickness of 0.15 mm. The films were cut into 100 mm × 100 mm pieces and subjected to biaxial stretching using a stretching device. The stretching method was either simultaneous biaxial stretching or sequential stretching, with the stretching occurring first longitudinally and then laterally. The temperature was within the biaxial film-forming temperature range in Table 2, the speed was 10% per second, and the stretching ratio was 6 times in the longitudinal direction (machine direction, MD) and 8 times in the transverse direction (TD). Capacitor films CF1 to CF13 were obtained according to the order of the composite materials. CF1 to CF11 corresponded to Application Examples 1 to 11 in sequence, and CF12 to CF13 were compared with Application Examples 1 to 2 in sequence.

[0059] The film-forming properties of the above polypropylene composites PC1~PC13 under biaxial stretching are expressed as follows, and the results are shown in Table 2:

[0060] ●: Good film formation was achieved in all 10 tensile tests;

[0061] ○: Good film formation can be achieved in 8-9 out of 10 tensile tests;

[0062] △: Good film formation can be achieved in 3 to 7 out of 10 tensile tests;

[0063] X: In 10 tensile tests, good film formation can be achieved in 0-2 tests.

[0064] Table 2: Film-forming properties of composite materials PC1~PC13

[0065]

[0066] The following properties of the well-formed capacitor films CF1~CF13 obtained by the above-mentioned simultaneous biaxial stretching method are characterized, and the results are shown in Table 3:

[0067] A. Shrinkage rate: Using the longitudinal and transverse sides of capacitor films CF1~CF13 as the long sides, cut out samples with a length of 150mm and a width of 10mm; place the above samples in an oven at 125℃ for 10min and then take them out and let them cool naturally at room temperature, and measure their longitudinal shrinkage rate at 125℃ and transverse shrinkage rate at 125℃ respectively.

[0068] B. Ratio of transverse elongation at break to longitudinal elongation at break: Using the longitudinal and transverse sides of capacitor films CF1~CF13 as the long sides, cut out specimens with a length of 150mm and a width of 10mm; measure the stress-strain curves of the specimens using a universal tensile testing machine, and obtain the transverse elongation at break and the longitudinal elongation at break, and then calculate the ratio between the two.

[0069] C. Breakdown strength: Refer to GB / T 13542.2-2021 "Films for Electrical Insulation - Part 2: Test Methods" to test the breakdown strength of capacitor films CF1~CF13 at different temperatures. Fifty points on the capacitor film were selected as test points, and the result was the average value calculated after discarding the 5 highest and 5 lowest values, expressed as V / μm.

[0070] Table 3: Characteristics of capacitor films CF1~CF13

[0071]

[0072] As shown in Table 3, the capacitor films CF1-CF11 prepared from the polypropylene composite materials PC1-PC11 obtained in Examples 1-11 of the present invention have excellent high-temperature dielectric strength.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading this application specification, they can still modify or make equivalent substitutions to the specific implementation of the present invention, but these modifications or changes do not depart from the protection scope of the pending claims of the present invention.

Claims

1. A polypropylene composite material, characterized in that, The composite material comprises a polymer component comprising 95% to 100% by weight, wherein the polymer component comprises: a) Polypropylene, and b) Cycloolefin polymer components; The polypropylene comprises 70% to 95% by weight of the polymer component. The cyclic olefin polymer component contains at least one CBC or COP and at most one COC; The mechanical loss factor tanδ of the unstretched film formed by the polypropylene composite material at 125°C, measured under the conditions of 0.5 mm thickness, stretching mode, vibration frequency 1 Hz, and heating rate 5 °C / min, is ≤0.

12.

2. The composite material according to claim 1, characterized in that, The composite material has an elongation at break greater than 300% as determined by the type 1B specimen of GB / T 1040.3-2006.

3. The composite material according to claim 1, characterized in that, The crystallinity of the composite material is greater than 30%.

4. The composite material according to claim 1, characterized in that, The polypropylene accounts for 80% to 95% of the weight percentage of the polymer component.

5. The composite material according to claim 1, characterized in that, The cyclic olefin polymer component contains one COC and at least one CBC.

6. The composite material according to claim 1, characterized in that, In the cyclic olefin polymer component, the weight percentage of CBC accounts for 40% to 100% of the cyclic olefin polymer component.

7. The composite material according to claim 1, characterized in that, The glass transition temperature of the cyclic olefin polymer component is greater than 130°C.

8. The method for preparing the polypropylene composite material according to any one of claims 1 to 7, characterized in that, The process includes the following steps: blending a cyclic olefin polymer component with polypropylene, followed by melt extrusion to obtain a polypropylene composite material.

9. The use of the polypropylene composite material according to any one of claims 1 to 7 in the preparation of BOPP capacitor film.

10. The application of the polypropylene composite material prepared by the preparation method according to claim 8 in the preparation of BOPP capacitor film.

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