Polypropylene-based composite material and preparation method thereof, cable insulation material and high-voltage cable

Abstract

The invention discloses a polypropylene-based composite material and a preparation method thereof, a cable insulation material and a high-voltage cable. The polypropylene-based composite material is prepared from the following raw materials in parts by weight: 80 to 120 parts of polypropylene resin and 0.25 to 0.5 part of antioxidant; the antioxidant comprises a first natural phenol antioxidant or an antioxidant composition containing a second natural phenol antioxidant and a phosphite ester antioxidant. According to the antioxidant composition of the natural phenol antioxidant or the natural phenol antioxidant and the phosphite antioxidant in a specific proportion, the activity of hydrogen atoms in phenolic hydroxyl groups of the natural phenol antioxidant is relatively high, and the natural phenol antioxidant is easily combined with free radicals and the like to generate a stable complex with relatively large steric hindrance, so that the oxygen aging reaction is reduced. The phosphite ester antioxidant captures and neutralizes peroxide to generate stable alcohol or ether so as to reduce the aging rate. Degradation caused by chain scission and oxidation in the processing and using processes of polypropylene can be effectively inhibited, and the electrical performance of the composite material is improved.

Description

Technical Field

[0001] The invention relates to the field of organic polymer materials, and in particular to a polypropylene-based composite material and a preparation method thereof, a cable insulating material and a high-voltage cable. Background Art

[0002] Cross-linked polyethylene insulated high-voltage cables are widely used in long-distance and long-span transmission lines due to their large capacity, high reliability and maintenance-free. However, cross-linked polyethylene cables have the problems of limited cable transmission capacity, increased production costs and cycles due to cross-linked byproducts, reduced electrical insulation performance, and difficulty in recycling. Polypropylene is a typical non-polar polymer material with the characteristics of thermoplasticity and recyclability. It has the advantages of excellent insulation performance, high heat resistance, simple processing technology and low production cost. Thermoplastic polypropylene high-voltage cables have become a new generation of environmentally friendly cables that can replace cross-linked polyethylene and meet the development requirements of future power grids.

[0003] However, traditional polypropylene composite materials will break their molecular chains and suffer from thermal oxidation aging under heat and oxygen conditions. The changes in appearance are mainly manifested as discoloration, powdering, and brittle cracking. The changes in macroscopic performance are mainly manifested as a sharp drop in breaking strength and elongation at break, and a rapid decline in electrical performance. The service life of the product is greatly shortened, resulting in a huge waste of materials. The discarded products are difficult to degrade under natural conditions and return to nature, which in turn pollutes the environment. Summary of the invention

[0004] Based on this, it is necessary to provide a polypropylene composite material with good oxidation resistance and electrical properties and a preparation method thereof, a cable insulation material and a high-voltage cable.

[0005] The present application provides a polypropylene-based composite material, wherein the raw materials thereof include, by weight: 80 to 120 parts of polypropylene resin and 0.25 to 0.5 parts of antioxidant;

[0006] The antioxidant comprises a first natural phenolic antioxidant or an antioxidant composition comprising a second natural phenolic antioxidant and a phosphite antioxidant, wherein the mass of the second natural phenolic antioxidant in the antioxidant composition is greater than or equal to the mass of the phosphite antioxidant.

[0007] In one embodiment, the antioxidant includes the first natural phenolic antioxidant or an antioxidant composition of the second natural phenolic antioxidant and the phosphite antioxidant in a mass ratio of (1-5):1.

[0008] In one embodiment, the antioxidant satisfies one or both of the following conditions:

[0009] (1) The first natural phenolic antioxidant and the second natural phenolic antioxidant each independently include one or more of resveratrol, α-tocopherol and quercetin;

[0010] (2) The phosphite antioxidant includes one or more of antioxidant 168, tridecyl phosphite, antioxidant 508T and antioxidant 619.

[0011] In one embodiment, the melt index of the polypropylene resin at 230° C.×2.16 kg load is 2 g / 10 min to 3 g / 10 min.

[0012] The present application also provides a method for preparing a polypropylene-based composite material, comprising the following steps:

[0013] Prepare raw materials according to the above-mentioned polypropylene-based composite material;

[0014] The polypropylene-based composite material is prepared by melt-blending the raw materials.

[0015] In one embodiment, the melt blending method includes one or both of internal mixing and extrusion.

[0016] In one embodiment, the melt blending temperature is 180°C to 200°C.

[0017] In one embodiment, the melt blending time is 5 min to 10 min.

[0018] Furthermore, the present application provides a cable insulation material, comprising the above-mentioned polypropylene-based composite material.

[0019] Furthermore, the present application provides a high-voltage cable, comprising the polypropylene-based composite material as described above and the cable insulation material as described above.

[0020] The polypropylene-based composite material provided by the present application uses a specific proportion of natural phenolic antioxidants or an antioxidant composition of natural phenolic antioxidants and phosphite antioxidants as an antioxidant. Since the hydrogen atom activity in the phenolic hydroxyl group of the natural phenolic antioxidant is high, it is easy to combine with peroxy radicals, alkyl radicals and hydroxyl radicals to generate a more stable complex with greater steric hindrance, thereby eliminating free radicals, inhibiting free radical generation, reducing oxygen aging reactions, and improving the antioxidant and electrical properties of the polypropylene-based composite material. Antioxidants can also use a specific proportion of natural phenolic antioxidants and phosphite antioxidants as antioxidants. Phosphite antioxidants reduce the aging rate by capturing and neutralizing peroxides (such as ROOH / ROOR) to generate stable alcohols or ethers (such as ROH / ROOR). The composition of the antioxidant defined above can effectively inhibit the degradation caused by chain breaking and oxidation of polypropylene during processing and use, and can further improve the electrical properties of the polypropylene composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a bar chart of the oxidation induction time of the polypropylene-based insulating material prepared in Examples 1 to 6 and Comparative Examples 1 to 5 of the present application.

[0023] Figure 2 This is an AC breakdown field strength diagram of the polypropylene-based insulating material prepared in Examples 1 to 6 and Comparative Examples 1 to 5 of the present application.

[0024] Figure 3 The spatial charge distribution diagrams during the polarization process of the polypropylene-based insulating materials prepared in Examples 2 to 4 and Comparative Examples 2 to 4 of the present application, wherein (a) is Example 4, (b) is Comparative Example 2, (c) is Example 3, (d) is Comparative Example 4, (e) is Example 2, and (f) is Comparative Example 3. DETAILED DESCRIPTION

[0025] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0027] The term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items, wherein the any and all combinations include any combination of two related listed items, any more related listed items, or all related listed items. For example, "A and / or B" includes three parallel solutions: A, B, and "a combination of A and B".

[0028] In this article, unless otherwise specified, "one or more" means any one of the listed items or any combination of the listed items. Similarly, "one or more" and other expressions that mean "one or more" are also understood in the same way unless otherwise specified.

[0029] In this document, "further", "further", "particularly", "for example", "such as", "example", "for example", etc. are used for descriptive purposes, indicating that the previous and subsequent technical solutions are related in terms of the content covered, but should not be understood as limiting the previous technical solution, nor can they be understood as limiting the scope of protection of this document. In this document, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0030] Herein, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If multiple "optional" items appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" item is independent of each other. In this application, descriptions such as "optionally contain", "optionally include", etc. mean "contain or not contain". "Optional component X" means that component X exists or does not exist, or means that component X is contained or not contained.

[0031] In this document, the terms "first", "second", "third", "fourth", etc. in "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0032] In this article, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0033] Herein, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is considered to be continuous and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval only refers to integers within the numerical interval, including the two endpoint integers of the numerical range, and each integer between the two endpoints, is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0034] Herein, the term "room temperature" or "normal temperature" generally refers to 4°C~35°C, for example, 20°C±5°C. In some embodiments herein, "room temperature" or "normal temperature" refers to 10°C~30°C. In some embodiments herein, "room temperature" or "normal temperature" refers to 20°C~30°C.

[0035] In this article, if there are multiple steps involved in the method flow, unless there is a clear different description in this article, there is no strict order restriction for the execution of these steps, and they can be executed in other orders than described. Moreover, any step can include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn, alternating or simultaneously with other steps or parts of sub-steps or stages of other steps.

[0036] The present application provides a polypropylene-based composite material, wherein the raw materials thereof include, by weight: 80 to 120 parts of polypropylene resin and 0.25 to 0.5 parts of antioxidant;

[0037] The antioxidant comprises a first natural phenolic antioxidant or an antioxidant composition comprising a second natural phenolic antioxidant and a phosphite antioxidant, and the mass of the second natural phenolic antioxidant in the antioxidant composition is greater than or equal to the mass of the phosphite antioxidant.

[0038] Further, the above-mentioned natural phenolic antioxidant is a natural antioxidant derived from biomass raw materials, which reduces environmental pollution and energy loss and has no toxic side effects. The polypropylene-based composite material provided by the present application uses a specific proportion of natural phenolic antioxidants or an antioxidant composition comprising natural phenolic antioxidants and phosphite antioxidants as an antioxidant. Since the hydrogen atom activity in the phenolic hydroxyl group of the natural phenolic antioxidant is high, it is easy to combine with peroxy radicals, alkyl radicals and hydroxyl radicals to generate a more stable complex with greater steric hindrance, thereby eliminating free radicals, inhibiting free radical generation, reducing oxygen aging reactions, and improving the antioxidant and electrical properties of polypropylene-based composite materials. Antioxidants can also use a specific proportion of natural phenolic antioxidants and phosphite antioxidants as an antioxidant. The phosphite antioxidants reduce the aging rate by capturing and neutralizing peroxides (such as ROOH / ROOR) to generate stable alcohols or ethers (such as ROH / ROOR). The antioxidant composition defined above can effectively inhibit the degradation of polypropylene caused by chain scission and oxidation during processing and use, and can further improve the electrical properties of the polypropylene composite material.

[0039] In a specific example, the antioxidant includes a first natural phenolic antioxidant or an antioxidant composition comprising a second natural phenolic antioxidant and a phosphite antioxidant in a mass ratio of (1-5):1.

[0040] It can be understood that the antioxidant includes an antioxidant composition of a natural phenolic antioxidant and a phosphite antioxidant in a mass ratio of but not limited to 1:1, 2:1, 3:1, 4:1 or 5:1.

[0041] In a specific example, the first natural phenolic antioxidant and the second natural phenolic antioxidant each independently include one or more of resveratrol, α-tocopherol and quercetin.

[0042] In a specific example, the phosphite antioxidant includes one or more of antioxidant 168 , tridecyl phosphite, antioxidant 508T, and antioxidant 619 .

[0043] The above-mentioned natural phenol antioxidants and phosphite antioxidants work together to reduce the oxidation products produced by polypropylene during the thermal oxidative aging process, significantly improving the thermal oxidative aging resistance of polypropylene. The design of the antioxidant system can effectively capture space charges and improve the electrical insulation performance of the system.

[0044] In a specific example, the melt index of the polypropylene resin at 230°C×2.16kg load is 2g / 10min~3g / 10min. Specifically, the melt index of the polypropylene resin at 230°C×2.16kg load may be, but is not limited to, 2g / 10min, 2.1g / 10min, 2.2g / 10min, 2.3g / 10min, 2.4g / 10min, 2.5g / 10min, 2.6g / 10min, 2.7g / 10min, 2.8g / 10min, 2.9g / 10min or 3g / 10min.

[0045] Furthermore, the density of the polypropylene resin is 0.5 g / cm 3 ~1.5g / cm 3 Specifically, the density of the polypropylene resin may be, but is not limited to, 0.5 g / cm 3 , 0.7 g / cm 3 , 0.8 g / cm 3 , 0.9 g / cm 3 , 1 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 , 1.3 g / cm 3 , 1.4 g / cm 3 or 1.5 g / cm 3 .

[0046] The present application also provides a method for preparing a polypropylene-based composite material, comprising the following steps:

[0047] Prepare raw materials according to the above-mentioned polypropylene-based composite material;

[0048] The raw materials are melt-blended to prepare a polypropylene-based composite material.

[0049] In a specific example, the melt blending method includes one or both of internal mixing and extrusion.

[0050] In a specific example, the temperature of melt blending is 180° C. to 200° C. Specifically, the temperature of melt blending may be, but is not limited to, 180° C., 185° C., 190° C., 195° C. or 200° C.

[0051] In a specific example, the time of melt blending is 5 min to 10 min. Specifically, the time of melt blending can be, but is not limited to, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min.

[0052] In a specific example, the rotation speed of melt blending is 80 r / min to 120 r / min. Specifically, the rotation speed of melt blending can be, but is not limited to, 80 r / min, 85 r / min, 90 r / min, 95 r / min, 100 r / min, 105 r / min, 110 r / min, 115 r / min or 120 r / min.

[0053] Furthermore, the present application provides a cable insulation material, comprising the above-mentioned polypropylene-based composite material.

[0054] Furthermore, the present application provides a high-voltage cable, comprising the polypropylene-based composite material as described above and the cable insulation material as described above.

[0055] The present application is further described in detail below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are preferably referred to the guidance given in the present application, and can also be based on the experimental manuals or conventional conditions in the art, can also be based on the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0056] In the following specific embodiments, the measured parameters of raw material components may have slight deviations within the range of weighing accuracy unless otherwise specified. For temperature and time parameters, acceptable deviations caused by instrument test accuracy or operation accuracy are allowed. "Normal temperature" refers to 25°C; "normal pressure" refers to 100KPa or 101KPa.

[0057] The polypropylene resin in the following examples and comparative examples was purchased from Yanshan Petrochemical Co., Ltd. with a brand name of K8003, resveratrol was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. with a molecular weight of 228.24, quercetin was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a molecular weight of 302.24, and antioxidant 168 was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a molecular weight of 646.94.

[0058] Example 1

[0059] This embodiment provides a polypropylene-based composite material, wherein the raw materials include 100 parts of polypropylene resin, 0.2 parts of resveratrol and 0.1 parts of antioxidant 168 in parts by mass.

[0060] The preparation method of the polypropylene-based composite material comprises the following steps:

[0061] 100 parts of polypropylene resin, 0.2 parts of resveratrol, and 0.1 parts of antioxidant 168 were weighed as raw materials. The above raw materials were placed in an internal mixer for melt blending to obtain a polypropylene-based insulating material. The melt blending process was: temperature 180° C., time 5 minutes, and rotation speed 80 r / min.

[0062] Example 2

[0063] This embodiment provides a polypropylene-based composite material, wherein the raw materials include 100 parts of polypropylene resin, 0.24 parts of resveratrol and 0.06 parts of antioxidant 168 in parts by mass.

[0064] The preparation method of the polypropylene-based composite material comprises the following steps:

[0065] 100 parts of polypropylene resin, 0.24 parts of resveratrol, and 0.06 parts of antioxidant 168 were weighed as raw materials. The above raw materials were placed in an internal mixer for melt blending to obtain a polypropylene-based insulating material. The melt blending process was: temperature 180° C., time 5 minutes, and rotation speed 80 r / min.

[0066] Example 3

[0067] This embodiment provides a polypropylene-based composite material, wherein the raw materials include 100 parts of polypropylene resin, 0.15 parts of resveratrol and 0.15 parts of antioxidant 168 in parts by mass.

[0068] The preparation method of the polypropylene-based composite material comprises the following steps:

[0069] 100 parts of polypropylene resin, 0.15 parts of resveratrol, and 0.15 parts of antioxidant 168 were weighed as raw materials. The above raw materials were placed in an internal mixer for melt blending to obtain a polypropylene-based insulating material. The melt blending process was: temperature 180° C., time 5 minutes, and rotation speed 80 r / min.

[0070] Example 4

[0071] This embodiment provides a polypropylene-based composite material, wherein the raw materials include 100 parts of polypropylene resin and 0.3 parts of resveratrol by weight.

[0072] The preparation method of the polypropylene-based composite material comprises the following steps:

[0073] 100 parts of polypropylene resin and 0.3 parts of resveratrol were weighed as raw materials. The raw materials were placed in an internal mixer for melt blending to obtain a polypropylene-based insulating material. The melt blending process was: temperature 180° C., time 5 minutes, and rotation speed 80 r / min.

[0074] Example 5

[0075] This embodiment provides a polypropylene-based composite material, wherein the raw materials include 100 parts of polypropylene resin, 0.2 parts of quercetin and 0.1 parts of antioxidant 168 in parts by mass.

[0076] The preparation method of the polypropylene-based composite material comprises the following steps:

[0077] 100 parts of polypropylene resin, 0.2 parts of quercetin, and 0.1 parts of antioxidant 168 were weighed as raw materials. The above raw materials were placed in an internal mixer for melt blending to obtain a polypropylene-based insulating material. The melt blending process was: temperature 180°C, time 5 minutes, and rotation speed 80r / min.

[0078] Example 6

[0079] This embodiment provides a polypropylene-based composite material, wherein the raw materials include 100 parts of polypropylene resin and 0.3 parts of quercetin by weight.

[0080] The preparation method of the polypropylene-based composite material comprises the following steps:

[0081] 100 parts of polypropylene resin and 0.3 parts of quercetin were weighed as raw materials. The raw materials were placed in an internal mixer for melt blending to obtain a polypropylene-based insulating material. The melt blending process was: temperature 180°C, time 5 minutes, and rotation speed 80r / min.

[0082] Comparative Example 1

[0083] This comparative example provides a polypropylene-based composite material, wherein the raw materials include 100 parts of polypropylene resin by weight.

[0084] The preparation method of the polypropylene-based composite material comprises the following steps:

[0085] 100 parts of polypropylene resin were weighed without adding antioxidant. The above raw materials were placed in an internal mixer for melt blending to obtain polypropylene-based insulation material. The melt blending process was: temperature 180°C, time 5 minutes, speed 80r / min.

[0086] Comparative Example 2

[0087] This comparative example provides a polypropylene-based composite material, wherein the raw materials include 100 parts of polypropylene resin and 0.3 parts of antioxidant 168 by weight.

[0088] The preparation method of the polypropylene-based composite material comprises the following steps:

[0089] 100 parts of polypropylene resin and 0.3 parts of antioxidant 168 were weighed as raw materials. The above raw materials were placed in an internal mixer for melt blending to obtain a polypropylene-based insulating material. The melt blending process was: temperature 180°C, time 5 minutes, and rotation speed 80r / min.

[0090] Comparative Example 3

[0091] This comparative example provides a polypropylene-based composite material, wherein the raw materials include 100 parts of polypropylene resin and 0.2 parts of resveratrol in parts by mass.

[0092] The preparation method of the polypropylene-based composite material comprises the following steps:

[0093] 100 parts of polypropylene resin and 0.2 parts of resveratrol were weighed as raw materials. The raw materials were placed in an internal mixer for melt blending to obtain a polypropylene-based insulating material. The melt blending process was: temperature 180° C., time 5 minutes, and rotation speed 80 r / min.

[0094] Comparative Example 4

[0095] This comparative example provides a polypropylene-based composite material, wherein the raw materials include 100 parts of polypropylene resin, 0.1 parts of resveratrol and 0.2 parts of antioxidant 168 in parts by mass.

[0096] The preparation method of the polypropylene-based composite material comprises the following steps:

[0097] 100 parts of polypropylene resin, 0.1 parts of resveratrol, and 0.2 parts of antioxidant 168 were weighed as raw materials. The above raw materials were placed in an internal mixer for melt blending to obtain a polypropylene-based insulating material. The melt blending process was: temperature 180° C., time 5 minutes, and rotation speed 80 r / min.

[0098] Comparative Example 5

[0099] The comparative example provides a polypropylene-based composite material, wherein the raw materials include 100 parts of polypropylene resin and 0.3 parts of antioxidant 1010 in parts by mass.

[0100] The preparation method of the polypropylene-based composite material comprises the following steps:

[0101] 100 parts of polypropylene resin and 0.3 parts of antioxidant 1010 were weighed as raw materials. The above raw materials were placed in an internal mixer for melt blending to obtain a polypropylene-based insulating material. The melt blending process was: temperature 180°C, time 5 minutes, and rotation speed 80r / min.

[0102] Detection method and result analysis

[0103] Based on GB / T 19466.6-2009 and GB / T 1408.1-2016 as standard requirements, oxidation induction time test and AC breakdown strength test were performed on Examples 1-6 and Comparative Examples 1-5.

[0104] Based on GB / T 19466.6-2009, the results of the oxidation induction time (OIT) test are as follows: Figure 1 As shown and Table 1.

[0105] Based on GB / T 1408.1-2016, the AC breakdown strength test results are as follows: Figure 2 As shown and Table 1.

[0106] The space charge test of Examples 2-4 and Comparative Examples 2-4 was carried out by the electroacoustic pulse method. The samples were polarized at an electric field strength of 60 kV / mm, a polarization time of 3600 s, and an experimental temperature of 25°C. The results are as follows: Figure 3 shown.

[0107] Table 1

[0108]

[0109] It can be seen from the above comparison that 0.3 parts of resveratrol was added in Example 4, and the oxidation induction time of the polypropylene formula material reached 30.4min. Compared with the comparative example 1 in which no antioxidant was added, the antioxidant effect was greatly improved, and it was better than the comparative example 5 in which 0.3 parts of antioxidant 1010 were added. As the main antioxidant, the phenolic antioxidant has active hydrogen atoms in the molecular structure, which are easy to detach and combine with the macromolecular chain free radicals R· or ROO· to ​​generate hydrogen peroxide and stable phenoloxy free radicals (ArO·). Due to the increase in the number of ortho-substituents of the phenoloxy free radical, its spatial hindrance effect is increased, so that it is protected by the adjacent larger volume groups, and the stability of the phenoloxy free radical is improved. In addition, since the phenoloxy free radical is in the same large conjugated system as the benzene ring, it is relatively stable and has low activity. It cannot trigger a chain reaction and can only combine with another active free radical to terminate a free radical again to generate a relatively stable compound, thereby terminating the chain reaction. The stability of phenol oxygen free radicals can prevent the antioxidant from being consumed too quickly due to direct oxidation, and can also reduce chain transfer reactions, thereby improving its antioxidant performance. Secondary antioxidants can decompose macromolecular hydrogen peroxide ROOH to generate stable compounds to prevent the development of chain reactions. The two can significantly reduce the occurrence of chain reactions in synergy. This shows that natural antioxidants can eliminate free radicals and prevent chain reactions in polypropylene. This method can be used as an environmentally friendly alternative to commercial antioxidants.

[0110] In Example 1, Example 2 and Example 3, the natural antioxidant resveratrol is compounded with antioxidant 168. The reduction of resveratrol content should theoretically reduce its oxidation induction time. In Comparative Example 3, when 0.2 parts of resveratrol is added alone, the oxidation induction time is 15.3min. In Comparative Example 2, when antioxidant 168 is added alone, the oxidation induction time is only 1.8min, and the effect is very poor when used alone. However, when resveratrol is compounded with antioxidant 168 (Examples 1-3), the oxidation induction time is still maintained at more than 30min, which is much higher than the effect when the two components are used alone. It shows that the phenolic structure of resveratrol and the phosphite structure of antioxidant 168 can play a good synergistic role after mixing, and can remove free radicals and hydroperoxides generated when the molecular chain breaks, thereby preventing subsequent chain reactions.

[0111] For another natural antioxidant, quercetin, in Example 6, when 0.3 parts of quercetin was used alone, the oxidation induction time was 24.6 minutes; in Example 5, after 0.2 parts of quercetin was mixed with 0.1 parts of antioxidant 168, the two antioxidants also exerted a synergistic effect, and the oxidation induction time reached 25.7 minutes. This also proves the feasibility of compounding natural antioxidants with commercial antioxidants.

[0112] In terms of AC breakdown strength, Figure 2 As shown, all the test results after adding 0.3 parts of antioxidant / compound antioxidant are basically consistent with the pure sample (Comparative Example 1), which proves that the addition of a small amount of antioxidant has almost no effect on the excellent electrical breakdown performance of polypropylene, but greatly increases the oxidation resistance.

[0113] Figure 3 The spatial charge distribution test was conducted for Examples 2-4 and Comparative Examples 2-4. The results showed that in Example 3, when the compounding ratio of antioxidant 168 to resveratrol was 1, the effect was the best, the charge injection amount brought by the internal electric field over time was the lowest, and there was no obvious electric field distortion. As the pressurization time increased, the sample showed a phenomenon of increased injected charge over time. Among them, Comparative Example 2 ( Figure 3 b), when 0.3 parts of antioxidant 168 are added, the maximum electric field distortion rate reaches 8.50%, while in Example 4, when 0.3 parts of resveratrol are added ( Figure 3 a), the maximum electric field distortion is only 3.82%, and the electric field distortion rate decreases by 55%. Figure 3 The df of the comparative example 4, the embodiment 2, and the comparative example 3 are different in that the compounding ratio of resveratrol and the antioxidant 168 is adjusted. Compared with the comparative example 2, after compounding with resveratrol, the electric field distortion rate is significantly reduced, and the internal charge density is also reduced. This shows that after compounding with resveratrol, the electric field distortion rate can be effectively reduced, traps are introduced, and the mobility of carriers is reduced.

[0114] It can be seen that the polypropylene-based composite material provided in the present application, by limiting the composition of the antioxidant in its raw materials, is combined with natural phenolic antioxidants and phosphite antioxidants to reduce the oxidation products produced by polypropylene during the thermal oxidative aging process, thereby significantly improving the thermal oxidative aging resistance of polypropylene, and the design of the antioxidant system can effectively capture space charges and improve the electrical insulation performance of the system.

[0115] As a natural phenolic antioxidant, resveratrol shows unique advantages in polypropylene cable insulation materials. Its most prominent highlight is its natural origin and environmental protection characteristics. As a natural compound extracted from plants, it not only provides antioxidant performance that is superior to traditional synthetic antioxidants 1010, but also has stronger environmental friendliness and sustainability. Against the background of the growing demand for green materials in modern industry, resveratrol and natural polyphenol antioxidants can be used in combination with traditional antioxidants or alone to reduce the potential harmful residues and environmental pollution problems of synthetic antioxidants. In addition, it shows good material compatibility during the processing process, without significantly reducing the material performance. It ensures the feasibility of industrial application and becomes an ideal choice for realizing the green upgrade of polypropylene cable insulation materials.

[0116] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0117] The above-described embodiments only express several implementation methods of the present invention, which are convenient for understanding the technical solutions of the present invention in detail, but they cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided by the present invention are all within the protection scope of the claims attached to the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the contents of the attached claims, and the description and drawings can be used to explain the contents of the claims.

Claims

1. A polypropylene-based composite material, characterized in that: The raw materials include, by weight: 80 to 120 parts of polypropylene resin and 0.25 to 0.5 parts of antioxidant; The antioxidant comprises a first natural phenolic antioxidant or an antioxidant composition comprising a second natural phenolic antioxidant and a phosphite antioxidant, wherein the mass of the second natural phenolic antioxidant in the antioxidant composition is greater than or equal to the mass of the phosphite antioxidant.

2. The polypropylene-based composite material according to claim 1, characterized in that: The antioxidant includes the first natural phenolic antioxidant or an antioxidant composition of the second natural phenolic antioxidant and the phosphite antioxidant in a mass ratio of (1-5):

1.

3. The polypropylene-based composite material according to claim 1 or 2, characterized in that: The antioxidant meets one or both of the following conditions: (1) The first natural phenolic antioxidant and the second natural phenolic antioxidant each independently include one or more of resveratrol, α-tocopherol and quercetin; (2) The phosphite antioxidant includes one or more of antioxidant 168, tridecyl phosphite, antioxidant 508T and antioxidant 619.

4. The polypropylene-based composite material according to claim 1 or 2, characterized in that: The melt index of the polypropylene resin at 230° C.×2.16 kg load is 2 g / 10 min to 3 g / 10 min.

5. A method for preparing a polypropylene-based composite material, characterized in that: The following steps are involved: A raw material prepared according to the polypropylene-based composite material according to any one of claims 1 to 4; The polypropylene-based composite material is prepared by melt-blending the raw materials.

6. The preparation method according to claim 5, characterized in that: The melt blending method includes one or both of internal mixing and extrusion.

7. The preparation method according to claim 5 or 6, characterized in that: The temperature of the melt blending is 180°C to 200°C.

8. The preparation method according to claim 5 or 6, characterized in that: The melt blending time is 5 min to 10 min.

9. A cable insulation material, characterized in that: The invention comprises the polypropylene-based composite material according to any one of claims 1 to 4.

10. A high voltage cable, characterized in that: It comprises the polypropylene-based composite material as described in any one of claims 1 to 4 and the cable insulation material as described in claim 9.

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