Multi-component compounded stable extrusion insulating material and preparation method thereof

Abstract

The invention belongs to the technical field of materials, and particularly relates to a multi-component compounded stable extrusion insulating material and a preparation method thereof. The invention relates to a multi-component compounded stable extrusion insulating material which is prepared from the following raw materials in percentage by weight: 70-99 parts of low-density polyethylene; 5-20 parts of modified resin; 0.8 to 1.5 parts of a cross-linking agent; 0.2 to 0.6 part of a cross-linking agent auxiliary agent; and 0.5 part of an antioxidant. Through cooperation of binary base material blending, low-crosslinking multi-component additive system optimization and a flexible mixing stable extrusion process, the synergistic effect of the binary base material blending, the low-crosslinking multi-component additive system optimization and the flexible mixing stable extrusion process can be brought into full play, the crystal form of the compound insulation material is improved, the phonon transmission free path is enhanced, the content of a crosslinking agent is reduced, the melt flow stability of the insulation material is enhanced, and low-temperature stable extrusion is achieved; product defects are reduced, and production efficiency and sample quality are improved. Impurities and scorching melting points are effectively filtered, the product quality stability and the production process are greatly improved, the comprehensive electrical mechanical and heat-conducting properties of the cable are systematically improved, and effective preparation of the large-length cable is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials, and particularly relates to a multi-component compounded and stably extruded insulating material and a preparation method thereof. Background Art

[0002] The future new power system faces extreme operating environments such as ultra-large capacity, long distance, and complex terrain. High-voltage cross-linked polyethylene (XLPE) cables, with the cross-linking absorption process, can build a stable three-dimensional molecular structure, thus possessing excellent thermal stability and dielectric strength, and have gradually become the key power transmission and transformation equipment for large city power grids and new power systems.

[0003] Currently, the content of peroxide cross-linking agent in domestic conventional insulating materials is too high (DCP≥1.7%), resulting in too high scorch point and gel content of high-temperature extruded insulating materials, difficult degassing, and the purity and comprehensive performance of the materials are difficult to meet the requirements.

[0004] Currently, various modification methods such as nano-modification, grafting modification, copolymerization modification, and blending modification are being widely used in the research field of high-voltage cable insulating materials. Among them, although nano-modification has unique advantages, it has problems such as complex and cumbersome subsequent processes, high costs, and difficult to precisely control the dispersion of nano-particles. Copolymerization modification faces many challenges in the early synthesis process, such as high technical difficulty, harsh reaction conditions, and high requirements for monomer selection and ratio; grafting modification mainly adds specific graft monomers or initiators to effectively improve the surface properties, compatibility, or functionality of the material, thereby improving the comprehensive performance of the material to a certain extent; blending modification is to select modified resins with similar molecular structures for blending treatment on the premise of not changing the basic properties of the main base material to achieve the goal of optimizing the material properties, and in some cases, it can act as an efficient nucleating agent to promote the crystallization process of the material. However, there are still many limitations and uncertainties in the selection of the blend phase at present, such as difficult to precisely control the interfacial interaction between blend phases, lack of systematic theoretical guidance for optimizing the blend ratio, and the long-term stability of the blend system needs to be further studied and verified.

[0005] By adding a modified resin with similar physicochemical properties to the base material, without changing the overall formulation, on the one hand, it can partially replace peroxide cross-linking, reduce the dosage of cross-linking agent, and effectively reduce the generation of by-products; on the other hand, the introduced modified resin usually has excellent mechanical processing properties, enabling the regulation of the long-term stable extrusion process of the blend system, thereby enhancing the comprehensive electrical and mechanical properties of the compounded insulating material. For example, in patents CN 116041827 B and CN 117720780A, low-density polyethylene and vinyl copolymers with similar structures are blended, but the resulting compounded insulating material only improves the electrical and mechanical properties of the material, and does not mention the effective thermal conductivity of the insulating material, which has a greater impact on the long-term operation of high-voltage cables. In addition, there is a lack of in-depth research on the long-term extrusion process of the compounded insulating material, and the pressure and temperature fluctuations are not monitored in real time, making it difficult to ensure the stable manufacturing of large-length cross-linked polyethylene cables.

[0006] Therefore, how to develop a new generation of formulated insulating materials, improve the comprehensive electrical, mechanical and thermal properties of insulating materials, achieve a high degree of cross-linking in a low-crosslinking system of insulating materials, and meet the ultra-purified stable extrusion with low pressure fluctuations over a long time has important technological breakthroughs and potential market value. Summary of the Invention

[0007] Aiming at the deficiencies existing in the above-mentioned prior art, the present invention provides a multi-component compounded stable extrusion insulating material and its preparation method. The purpose is to realize how to select a low-density polyethylene compounded modified resin system and introduce polyethylene-vinyl acetate (PEVA). Its ester functional group can reduce the intermolecular force between molecular chains, thereby reducing the processing temperature of the material, improving fluidity, and making the processing process easier and more stable; PEVA contains polyethylene segments and has high molecular regularity and crystallinity. This regular molecular structure enables PEVA to form a relatively tight molecular arrangement in the blended cable insulating material, improving the density and crystallization stability of the material, thereby enhancing the comprehensive electrical and mechanical properties; in addition, due to the high crystallinity and relatively good thermal stability of the polyethylene segments, the addition of PEVA in the blend usually enhances the specific heat and temperature resistance of the material, which can synergistically increase the phonon transport mean free path of the material, thereby enhancing the effective thermal conductivity and thermal stability of the insulation, reducing material aging and performance degradation caused by high temperature, and improving the reliability and safety of the cable; the blended multi-phase structure can synergistically optimize the additive system to achieve low-temperature and high-crosslinking extrusion of the compounded insulating material, and significantly improve the comprehensive electrical, mechanical and thermal properties of the compounded insulating material.

[0008] The technical solution adopted by the present invention to achieve the above purpose is:

[0009] A multi-component compounded stable extrusion insulating material is composed of the following raw materials in parts by weight:

[0010] 70 - 99 parts of low - density polyethylene;

[0011] 5 - 20 parts of modified resin;

[0012] 0.8 - 1.5 parts of cross - linking agent;

[0013] 0.2 - 0.6 parts of cross - linking agent assistant;

[0014] 0.5 part of antioxidant.

[0015] Furthermore, the modified resin is polyethylene - vinyl acetate (PEVA).

[0016] Furthermore, the cross - linking agent is peroxide DCP.

[0017] Furthermore, the cross - linking agent assistant is any one or several of triallyl cyanurate or triallyl isocyanurate or trimethylolpropane trimethacrylate or polytriallyl isocyanurate.

[0018] Furthermore, the antioxidant is thiodiphenol antioxidant 300: hindered phenol antioxidant 1010: phosphite antioxidant 168 = 3:1:1.

[0019] A preparation method of a multi - component compound stable extrusion insulating material, comprising the following steps:

[0020] Take low - density polyethylene and modified resin according to the weight parts of the multi - component compound stable extrusion insulating material, mix them evenly in a twin - screw extruder and then extrude pellets to obtain compound binary - phase pellets;

[0021] Blend and compound the obtained compound binary - phase pellets with an antioxidant, then conduct multi - stage long - time uniform blending in a flexible mixer, extrude and draw them into long strips, cut them into pellets underwater and dehydrate them, and then absorb them after constant - temperature cross - linking in a storage tank to obtain a multi - component compound high - voltage insulating composition;

[0022] Thermally press and cross - link the multi - component compound high - voltage insulating composition to form a thin - layer structure.

[0023] Furthermore, the twin - screw extruder adopts a multi - stage extrusion method, and the multi - stage extrusion temperatures are: feed inlet: 130 °C, melting section: 150 °C, extrusion section: 175 °C, outlet temperature: 180 °C.

[0024] Furthermore, the weight part ratio of the antioxidant is: thiodiphenol antioxidant 300: hindered phenol antioxidant 1010: phosphite antioxidant 168 = 3:1:1.

[0025] Furthermore, in the flexible mixer, a customized 5-layer filter screen is installed, and the combination is: 40 / 80 / 300-400 / 100 / 40 mesh, and the corresponding filter screen pore sizes are: 450 / 220 / 60-45 / 175 / 450 μm;

[0026] The production capacity is achieved at 50-100 kg / h through underwater pelletizing;

[0027] The rotation speed is 60 rpm / min, and the feeding rate is 18 rpm / min; the stable extrusion fluctuation of the outlet pressure ≤ 0.6 MPa;

[0028] The dehydration and drying is to add a crosslinking agent and a crosslinking agent assistant at 50-75 °C in the mixing system, and the rotation speed of the mixing system is 2-8 rpm;

[0029] The absorption time after constant temperature crosslinking in the storage tank is 6-10 h, and the temperature is 50 °C - 80 °C;

[0030] The flexible mixer is a single-screw reciprocating mixing and extrusion machine, and the heating zone temperatures are: the feeding port is 120 °C or 130 °C or 140 °C, the melting section is 150 °C or 160 °C or 170 °C, and the extrusion section is 170 °C or 180 °C; the rotation speed is 60 rpm / min; the feeding rate is 29 rpm / min; the stable extrusion fluctuation range of the outlet pressure ≤ 0.6 MPa;

[0031] The pressure fluctuation range of the multi-component compounded insulating granule during long-term extrusion for 50 h ≤ 0.6 MPa;

[0032] The rotation speed of the storage tank is 5-7 rpm, the absorption temperature after heat preservation is 60-70 °C, the storage tank is kept at a constant temperature for absorption for 6-10 h, the temperature is 50 °C - 80 °C, and the high-temperature crosslinking degree of the insulating granule is above 88%.

[0033] Furthermore, it is hot-pressed and crosslinked and formed in a tablet press. Among them, the pressure of the tablet press is 300-500 KN, the hot-pressing melting temperature is 110-130 °C, the crosslinking hot-pressing temperature is 150-220 °C, and the crosslinking time is 5-20 min.

[0034] The present invention has the following beneficial effects and advantages:

[0035] Compared with the prior art, for a multi-component compounded stable extrusion insulating material and its preparation method of the present invention, through the cooperation of binary base material blending, low-crosslinking multi-component additive system optimization and flexible mixing and stable extrusion process, the synergistic effects of the three can be fully exerted. The main differences and advantages compared with the prior art are as follows:

[0036] (1) Adding ethylene-vinyl acetate to the original low-density polyethylene, its molecular structures such as ester group functional groups and common ethylene chain segments can enhance the flexibility of its own molecular chains and also be transmitted to the low-density polyethylene base material, enabling the molecular chains to adjust their conformations during the crystallization process and better adapt to the needs of crystal growth, thereby making the crystallization more perfect; in addition, the steric hindrance of the ester group will hinder the diffusion and stacking of molecular chains during the crystallization process, slow down the crystal growth rate, and make the crystallization process proceed more uniformly, which is conducive to the formation of fine and uniform grain structures and improves the crystal morphology of the compounded insulating material.

[0037] (2) The common polyethylene chain segments of ethylene-vinyl acetate and low-density polyethylene can improve the material compatibility while synergistically optimizing the crystallization behavior of the insulating material, promoting the construction of high-quality crystal structures, thereby strengthening the phonon transport mean free path, reducing the interface scattering, enhancing the thermal diffusion efficiency of the insulating material, and strengthening the thermal conductivity of the material.

[0038] (3) Under the guarantee of the binary multiphase base blend system, it is possible to prepare the insulating material formula of the low-crosslinking long-time stable extrusion system, effectively reduce the content of crosslinking agent, enhance the melt flow stability of the insulating material ≤0.6 MPa, and even achieve low-temperature stable extrusion ≤180 °C, thereby reducing the defects of products, improving production efficiency and sample quality.

[0039] (4) By adopting the reciprocating single-screw extrusion process and the supporting multi-layer dense filter screen combination structure customized for processing, it is possible to effectively filter out impurities and the burning point of scorch, so that there are no defects ≥25 μm in the insulating pellets extruded for a long time, and the product quality stability and production process are greatly improved.

[0040] (5) The present invention establishes a full-process insulation preparation strategy from base material compounding - crosslinking optimization - extrusion process control of cable insulating materials, which can effectively improve the cable insulation extrusion process, greatly reduce the generation of by-products, thereby systematically improving the comprehensive electrical properties of cables and realizing the effective preparation of long-length cables. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein:

[0042] Figure 1 is the graph of the temperature and pressure fluctuations at the extrusion outlet of the insulating material of the present invention;

[0043] Figure 2 is the graph of the comparison of the effective thermal conductivities of the insulating materials of the examples and the control examples of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] To more clearly understand the above objects, features, and advantages of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0045] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0046] The following refers to Figure 1 and Figure 2 to describe the technical solutions of some embodiments of the present invention.

[0047] Embodiment 1

[0048] The present invention provides an embodiment, which is a multi-component compound stable extrusion insulating material, composed of the following raw materials in parts by weight;

[0049] 88.05 parts of low-density polyethylene, 10 parts of modified resin, 1.2 parts of cross-linking agent; 0.25 parts of cross-linking agent assistant, 0.5 parts of antioxidant.

[0050] A preparation method of a multi-component compound stable extrusion insulating material includes the following steps:

[0051] Step 1. According to the above weight ratio of 88.05:10, take low-density polyethylene base material and modified resin polyethylene-vinyl acetate (PEVA), and uniformly blend and extrude pellets in a twin-screw extruder to obtain compound binary-phase pellets;

[0052] The extrusion is carried out after uniform mixing in the twin-screw extruder. Among them, the twin-screw extruder adopts a multi-stage extrusion method, and the multi-stage extrusion temperature in the twin-screw extruder is: feed inlet: 130 °C, melting section: 150 °C, extrusion section: 175 °C, outlet temperature: 180 °C.

[0053] When the proportion of the modified resin PEVA is 10%, which is lower than the range value of 7-10%, the comprehensive performance improvement of the compounded insulating granule is not obvious; when the content of the modified resin is higher than the range value of 7-10%, too many two-phase interfaces of low-density polyethylene and polyethylene-vinyl acetate are introduced, and the overall dispersibility and interfacial compatibility of the material are affected, the extrusion pressure fluctuates significantly, and the extrusion stability decreases. Different from traditional modified resins such as low-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer EVA, etc., polyethylene-vinyl acetate contains ester-based functional groups and common polyethylene chain segments, which can synergistically build a uniform and dense crystal structure and improve the interfacial compatibility of the two phases, thereby enhancing the comprehensive electrical, mechanical, and thermal properties, endowing the insulating material with excellent thermal stability and long-term extrusion stability, etc., reducing material aging and performance degradation caused by high temperature, and improving the reliability and safety of the cable.

[0054] Step 2. Blend and compound the compounded base material obtained in the previous step with 0.5 parts of antioxidant. The antioxidant is taken in the following three kinds according to the weight ratio: thiodiphenol antioxidant 300: hindered phenol antioxidant 1010: phosphite antioxidant 168 = 3:1:1; then carry out multi-stage long-term (≥48h) uniform blending in a flexible mixer. The multi-stages include: the feed inlet, the melting section, and the extrusion section. After that, the extrusion pressure fluctuation range within 50h is ≤0.6MPa, and it is pulled into a long strip after being extruded at the outlet of the customized filter screen. The rotation speed during the extrusion process is 60rpm / min, and the feeding rate is 18rpm / min. Then, it is dehydrated and dried at 50°C for 24h after underwater pelletizing, and then cross-linked and absorbed in a storage tank. Specifically, it means spraying and adding cross-linking agents, cross-linking agent assistants, etc. in a constant temperature environment of 60°C, and the rotation speed of the mixing system is 6rpm; the particles are mixed and dried with the composite cross-linking agent and then heat-preserved and absorbed to obtain the multi-component compounded high-voltage insulating composition; in this embodiment, it is preferred to use a "BUSS" flexible mixer for better results.

[0055] In Step 2, during the BUSS flexible mixing and extrusion process: the heating temperatures of each heating zone are respectively set as: feed inlet: 120°C, 130°C, 140°C, melting section: 150°C, 160°C, 170°C, extrusion section: 170°C and 180°C;

[0056] In Step 2, during the BUSS flexible mixing and extrusion process: install a customized 5-layer filter screen, and the combination is: 40 / 80 / 300-400 / 100 / 40 mesh, and the corresponding filter screen pore diameters are: 450 / 220 / 60-45 / 175 / 450μm, and the production capacity is 50-100kg / h through underwater pelletizing;

[0057] In Step 2, during the BUSS flexible mixing and extrusion process: the rotation speed is 60rpm / min, and the feeding rate is 18rpm / min; the stable extrusion fluctuation of the outlet pressure is ≤0.6MPa;

[0058] In Step 2, after crosslinking at a constant temperature in the storage tank for 8 hours, the temperature is 60°C, and the rotation speed of the storage tank is 6 rpm. Under this process, the high-temperature crosslinking degree of the insulating pellets can be ensured to be above 88%.

[0059] Finally, 1.3 parts of crosslinking agent peroxide DCP and 0.25 parts of crosslinking agent assistant are added, and after heat preservation and absorption treatment, a multi-component compound high-voltage insulating composition, namely multi-component compound high-voltage insulating pellets, is finally obtained.

[0060] Step 3. The multi-component compound insulating pellets obtained in Step 2 are hot-pressed and crosslinked into shape in a tablet press. The pressure is 350 KN, the initial hot-pressing melting temperature is 120°C, the crosslinking hot-pressing temperature is 180°C, and the crosslinking time is 15 minutes. The crosslinking process of the insulating pellets is the best, and a thin-layer sample is obtained after water cooling.

[0061] For the multi-component compound cable insulating material prepared in this example, 10 parts of modified resin polyethylene-vinyl acetate, 1.2 parts of crosslinking agent, 0.25 parts of crosslinking agent assistant, and the long-term extrusion pressure fluctuation of the compound insulating material ≤ 0.6 MPa.

[0062] As Figure 1 shown, Figure 1 is the diagram of the extrusion outlet temperature and pressure fluctuation of the insulating material of the present invention. The diagram shows the schematic diagram of the long-term extrusion pressure and temperature fluctuation of the compound stable extrusion insulating material for two days.

[0063] Example 2

[0064] The present invention further provides an example, which is a multi-component compound stable extrusion insulating material, composed of the following raw materials in parts by weight:

[0065] 93.05 parts of low-density polyethylene, 5 parts of modified resin, 1.2 parts of crosslinking agent; 0.25 parts of crosslinking agent assistant, 0.5 parts of antioxidant.

[0066] A preparation method of a multi-component compound stable extrusion insulating material includes the following steps:

[0067] Step 1. According to the above weight ratio of 93.05:5, take low-density polyethylene base material and modified resin polyethylene-vinyl acetate PEVA, and carry out screw extrusion and uniform blending to obtain binary-phase pellets for standby;

[0068] Step 2. The same as in Example 1;

[0069] Step 3. The same as in Example 1.

[0070] For the multi-component compounded cable insulating material prepared in this embodiment, the number of parts of the modified resin polyethylene-vinyl acetate (PEVA) is 5 parts, the cross-linking agent is 1.2 parts, the cross-linking agent assistant is 0.25 parts, and the long-term extrusion pressure fluctuation is ≤0.8 MPa.

[0071] Example 3

[0072] The present invention further provides an embodiment, which is a multi-component compounded and stably extruded insulating material, composed of the following raw materials in parts by weight:

[0073] 83.05 parts of low-density polyethylene, 15 parts of modified resin, 1.2 parts of cross-linking agent; 0.25 parts of cross-linking agent assistant, 0.5 parts of antioxidant.

[0074] A preparation method of a multi-component compounded and stably extruded insulating material includes the following steps:

[0075] Step 1. Take the low-density polyethylene base material and the modified resin polyethylene-vinyl acetate (PEVA) according to the above weight ratio of 83.05:15, and carry out screw extrusion and uniform blending to obtain a binary-phase pellet for standby;

[0076] Step 2. The same as in Example 1;

[0077] Step 3. The same as in Example 1.

[0078] For the multi-component compounded cable insulating material prepared in this embodiment, the number of parts of the modified resin polyethylene-vinyl acetate is 15 parts, the cross-linking agent is 1.2 parts, the cross-linking agent assistant is 0.25 parts, and the long-term extrusion pressure fluctuation is ≤1.0 MPa.

[0079] Example 4

[0080] The present invention further provides an embodiment, which is a multi-component compounded and stably extruded insulating material, composed of the following raw materials in parts by weight:

[0081] 78.05 parts of low-density polyethylene, 20 parts of modified resin, 1.2 parts of cross-linking agent; 0.25 parts of cross-linking agent assistant, 0.5 parts of antioxidant.

[0082] A preparation method of a multi-component compounded and stably extruded insulating material includes the following steps:

[0083] Step 1. Take the low-density polyethylene base material and the modified resin polyethylene-vinyl acetate (PEVA) according to the above weight ratio of 78.05:20, and carry out screw extrusion and uniform blending to obtain a binary-phase pellet for standby;

[0084] Step 2. The same as in Example 1;

[0085] Step 3. The same as in Example 1.

[0086] For the multi-component compounded cable insulating material prepared in this example, the number of parts of the modified resin polyethylene-vinyl acetate is 20 parts, the crosslinking agent is 1.2 parts, the crosslinking agent assistant is 0.25 parts, and the long-term extrusion pressure fluctuation is ≤1.4 MPa.

[0087] Example 5

[0088] The present invention further provides an example, which is a multi-component compounded and stably extruded insulating material, composed of the following raw materials in parts by weight:

[0089] 88.25 parts of low-density polyethylene, 10 parts of modified resin, 1.0 part of crosslinking agent; 0.25 part of crosslinking agent assistant, 0.5 part of antioxidant.

[0090] A preparation method of a multi-component compounded and stably extruded insulating material includes the following steps:

[0091] Step 1. The same as in Example 1;

[0092] Step 2. Finally, add 1.0 part of crosslinking agent peroxide DCP and 0.25 part of crosslinking agent assistant, and carry out heat preservation and absorption treatment to finally obtain a multi-component compounded insulating material;

[0093] Step 3. The same as in Example 1.

[0094] For the multi-component compounded cable insulating material prepared in this example, the number of parts of the modified resin polyethylene-vinyl acetate is 10 parts, the crosslinking agent is 1.0 part, the crosslinking agent assistant is 0.25 part, and the long-term extrusion pressure fluctuation is ≤0.6 MPa.

[0095] Example 6

[0096] The present invention further provides an example, which is a multi-component compounded and stably extruded insulating material, composed of the following raw materials in parts by weight:

[0097] 87.75 parts of low-density polyethylene, 10 parts of modified resin, 1.5 parts of crosslinking agent; 0.25 part of crosslinking agent assistant, 0.5 part of antioxidant.

[0098] A preparation method of a multi-component compounded and stably extruded insulating material includes the following steps:

[0099] Step 1. The same as in Example 1;

[0100] Step 2. Finally, add 1.5 crosslinking agent peroxide DCP and 0.25 part of crosslinking agent assistant, and carry out heat preservation and absorption treatment to finally obtain a multi-component compounded insulating material;

[0101] Step 3. The same as in Example 1.

[0102] For the multi-component compound cable insulating material prepared in this embodiment, the number of parts of the modified resin polyethylene-vinyl acetate is 10 parts, the crosslinking agent is 1.5 parts, the crosslinking agent assistant is 0.25 part, and the long-term extrusion pressure fluctuation ≤ 0.6 MPa.

[0103] Example 7

[0104] The present invention also provides an embodiment, which is a multi-component compound stable extrusion insulating material, composed of the following raw materials by weight:

[0105] 87.55 parts of low-density polyethylene, 10 parts of modified resin, 1.7 parts of crosslinking agent; 0.25 part of crosslinking agent assistant, 0.5 part of antioxidant.

[0106] A preparation method of a multi-component compound stable extrusion insulating material includes the following steps:

[0107] Step 1. The same as in Example 1;

[0108] Step 2. Finally, add 1.7 parts of crosslinking agent peroxide DCP and 0.25 part of crosslinking agent assistant, carry out heat preservation and absorption treatment, and finally obtain a multi-component compound insulating material;

[0109] Step 3. The same as in Example 1.

[0110] For the multi-component compound cable insulating material prepared in this embodiment, the number of parts of the modified resin polyethylene-vinyl acetate is 10 parts, the crosslinking agent is 1.7 parts, the crosslinking agent assistant is 0.25 part, and the long-term extrusion pressure fluctuation ≤ 0.6 MPa.

[0111] Example 8

[0112] The present invention also provides an embodiment, which is a multi-component compound stable extrusion insulating material, composed of the following raw materials by weight:

[0113] 88.05 parts of low-density polyethylene, 1 ten parts of modified resin, 1.2 parts of crosslinking agent; 0.25 part of crosslinking agent assistant, 0.5 part of antioxidant.

[0114] A preparation method of a multi-component compound stable extrusion insulating material includes the following steps:

[0115] Step 1. The same as in Example 1;

[0116] Step 2. The same as in Example 1;

[0117] Step 3. Hot press and crosslink the multi-component compound insulating pellets obtained in Step 2 in a tablet press, the pressure is \alpha KN, the initial hot press melting temperature is 120 °C, the crosslinking hot press temperature is 160 °C, the crosslinking time is 15 min, the crosslinking process of the insulating pellets is the best, and a thin layer sample is obtained through water cooling. It should be noted that there is an unclear value "\alpha" in the original text for the pressure value in Step 3 of Example 8. It is recommended to check and correct the original text for accurate translation. Here, it is temporarily translated according to the format requirements.

[0118] For the multi-component compounded cable insulating material prepared in this example, the number of parts of the modified resin polyethylene-vinyl acetate is 10 parts, the cross-linking agent is 1.2 parts, the cross-linking agent assistant is 0.25 parts, the cross-linking hot pressing temperature is 160 °C, and the long-term extrusion pressure fluctuation is ≤0.6 MPa.

[0119] Example 9

[0120] The present invention also provides an example, which is a multi-component compounded and stably extruded insulating material, composed of the following raw materials by weight parts:

[0121] 88.05 parts of low-density polyethylene, 10 parts of modified resin, 1.2 parts of cross-linking agent; 0.25 parts of cross-linking agent assistant, 0.5 parts of antioxidant.

[0122] A preparation method of a multi-component compounded and stably extruded insulating material includes the following steps:

[0123] Step 1. The same as in Example 1;

[0124] Step 2. The same as in Example 1;

[0125] Step 3. Hot press and cross-link the multi-component compounded insulating pellets obtained in Step 2 in a tablet press, with a pressure of 350 KN, an initial hot press melting temperature of 120 °C, a cross-linking hot press temperature of 200 °C, a cross-linking time of 15 min. The cross-linking process of the insulating pellets is the best, and a thin-layer sample is obtained through water cooling.

[0126] For the multi-component compounded cable insulating material prepared in this example, the number of parts of the modified resin polyethylene-vinyl acetate is 10 parts, the cross-linking agent is 1.2 parts, the cross-linking agent assistant is 0.25 parts, the cross-linking hot pressing temperature is 200 °C, and the long-term extrusion pressure fluctuation is ≤0.6 MPa.

[0127] Example 10

[0128] The present invention also provides an example, which is a multi-component compounded and stably extruded insulating material, composed of the following raw materials by weight parts:

[0129] 98.05 parts of low-density polyethylene, 0 part of modified resin, 1.2 parts of cross-linking agent; 0.25 parts of cross-linking agent assistant, 0.5 parts of antioxidant.

[0130] A preparation method of a multi-component compounded and stably extruded insulating material includes the following steps:

[0131] Step 1. Only take low-density polyethylene as the blending matrix according to the above weight ratio of 98.5:0;

[0132] Step 2. The same as in Example 1;

[0133] Step 3. The same as in Example 1.

[0134] For the multi-component compounded cable insulating material prepared in this embodiment, the number of parts of the modified resin polyethylene-vinyl acetate is 0 part, the crosslinking agent is 1.2 parts, the crosslinking agent assistant is 0.25 part, the crosslinking hot pressing temperature is 180 °C, and the long-term extrusion pressure fluctuation ≤ 1.0 MPa.

[0135] As Figure 2 shown, Figure 2 This is a comparison of the thermal conductivity test results of the multi-component compounded stable extrusion insulating materials of the embodiments and comparative examples of the present invention.

[0136] The breakdown field strength of the sample was tested using a spherical electrode breakdown system in a room temperature insulating oil environment, the tensile properties of the insulating materials corresponding to different preparation conditions were tested using an electronic universal testing machine, and the effective thermal conductivity of the materials was tested using a laser thermal conductivity meter. The test results of the multi-component compounded stable extrusion insulating material prepared by the present invention are shown in Table 1.

[0137] Table 1 Test results of multi-component compounded stable extrusion insulating materials

[0138]

[0139] Comparing Examples 1-4 with Example 10, it is found that as the mass fraction of the modified resin increases from 0 wt% to 20 wt%, the comprehensive electrical, tensile mechanical and thermal properties of the multi-component compounded insulating material first increase and then decrease, and there is an optimal content of 10 wt%. At this time, the breakdown field strength of the material reaches the maximum value of 398 kV / mm, the tensile strength is 17.4 MPa, the elongation at break is 675%, the effective thermal conductivity is 0.385 W / (m·K), and the extremely low pressure fluctuation ≤ 0.6 MPa. The main reason is that at the optimal content of the modified resin, the compounded insulating material has both a certain tensile strength and can ensure sufficient flexibility. The vinyl acetate groups on the molecular chain of the modified resin have a certain polarity. During the mixing process, van der Waals forces and dipole-induced dipole interactions will occur between the carbon atoms on the molecular chain of low-density polyethylene, thereby improving the compatibility and bonding force between the two polymers and ensuring excellent electrical and mechanical properties of the material. At the same time, the polyethylene chain segments of the modified resin with this content can promote the uniform compatibility of the two phases and act as a sufficient amount of heterogeneous nucleation, enabling low-density polyethylene to form more crystal nuclei, thereby achieving grain refinement, increasing crystallinity, strengthening the phonon transport mean free path, improving the effective thermal conductivity and thermal stability of the material, and finally realizing the long-term stable extrusion of the compounded insulating material with low pressure and temperature fluctuations.

[0140] It is found by comparing Example 1 with Examples 5-7 that for a binary-phase multicomponent base material, the compounding of a low crosslinking agent and a crosslinking agent assistant can maximize the crosslinking degree of the compounded insulating material, thereby ensuring the comprehensive electrical, mechanical and thermal properties of the insulating material. When the content of the crosslinking agent is too low, the insulating material is insufficiently crosslinked, and the performance of the insulating material drops significantly; when the content of the crosslinking agent is too high, excessive crosslinking bonds restrict the free movement of molecular chains, making it difficult to slide and extend freely. Therefore, the mechanical tensile properties of the material drop significantly.

[0141] It is found by comparing Example 1 with Examples 8-9 that a relatively low crosslinking temperature may make the crystallization process dominant. Since the crosslinking reaction is inhibited and crystallization is easier to occur, resulting in an increase in crystallinity and no obvious improvement in the amorphous region, the meaning of crosslinking is lost; at a relatively high crosslinking temperature, over-crosslinking easily occurs, forming too many crosslinking bonds between molecular chains, and the toughness of the material drops significantly, becoming more brittle, resulting in a significant drop in the tensile strength and elongation at break of the material.

[0142] In the description of this specification, the descriptions of terms such as "one embodiment", "some embodiments", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or instance. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0143] 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 them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific implementation manners of the present invention, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A multi-component compounded and stably extruded insulating material, characterized in that: It consists of the following raw materials by weight parts: 70 - 99 parts of low - density polyethylene; 5 - 20 parts of modified resin; 0.8 - 1.5 parts of cross - linker; 0.2 - 0.6 parts of cross - linker assistant; 0.5 part of antioxidant.

2. The multicomponent compound stable extrusion insulating material according to claim 1, wherein: The modified resin is polyethylene - vinyl acetate (PEVA).

3. A multi-component compound stable extrusion insulating material according to claim 1, characterized in that: The cross - linker is peroxide DCP.

4. A multi-component compound stable extrusion insulating material according to claim 1, characterized in that: The cross - linker assistant is any one or several of triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate, or poly(triallyl isocyanurate).

5. A multi-component compound stable extrusion insulating material according to claim 1, characterized in that: The antioxidant is thiodiphenol antioxidant 300: hindered phenol antioxidant 1010: phosphite antioxidant 168 = 3:1:

1.

6. A preparation method of a multi-component compound stable extrusion insulating material, characterized in that: It includes the following steps: Take low - density polyethylene and modified resin according to the weight parts of a multi - component compounded and stably extruded insulating material described in claim 1, mix them evenly in a twin - screw extruder and then extrude pellets to obtain compounded binary - phase pellets; Blend and compound the obtained compounded binary - phase pellets with the antioxidant, then conduct multi - stage and long - time uniform blending in a flexible mixer, extrude and draw them into long strips, cut the pellets underwater and dehydrate them, and then absorb them after constant - temperature cross - linking in a storage tank to obtain a multi - component compounded high - voltage insulating composition; Thermally press and cross - link the multi - component compounded high - voltage insulating composition to form a thin - layer structure.

7. The preparation method of a multi-component compounded and stably extruded insulating material according to claim 6, characterized in that: The twin - screw extruder adopts a multi - stage extrusion method, and the multi - stage extrusion temperatures are: feed inlet: 130°C, melting section: 150°C, extrusion section: 175°C, outlet temperature: 180°C.

8. The preparation method of a multi-component compounded and stably extruded insulating material according to claim 6, characterized in that: The weight - part ratio of the antioxidant is: thiodiphenol antioxidant 300: hindered phenol antioxidant 1010: phosphite antioxidant 168 = 3:1:

1.

9. The preparation method of a multi-component compound stable extrusion insulating material according to claim 6, characterized in that: at In the flexible mixer, a customized 5 - layer filter screen is installed, and the combination is: 40 / 80 / 300 - 400 / 100 / 40 mesh, and the corresponding filter - screen pore diameters are: 450 / 220 / 60 - 45 / 175 / 450μm; The production capacity is achieved at 50 - 100 kg / h through underwater pelletizing; The rotation speed is 60 rpm / min, the feeding rate is 18 rpm / min; the stable extrusion fluctuation of the outlet pressure ≤0.6 MPa; The dehydration and drying is to add the cross - linker and cross - linker assistant at 50 - 75°C in the mixing system, and the rotation speed of the mixing system is 2 - 8 rpm; The absorption time after constant - temperature cross - linking in the storage tank is 6 - 10 h, and the temperature is 50°C - 80°C; The flexible mixer is a single - screw reciprocating mixing and extruding machine, and the heating - zone temperatures are: feed inlet is 120°C or 130°C or 140°C, melting section is 150°C or 160°C or 170°C, extrusion section is 170°C or 180°C; the rotation speed is 60 rpm / min; the feeding rate is 29 rpm / min; the stable extrusion fluctuation range of the outlet pressure ≤0.6 MPa; The pressure fluctuation range during the long - time extrusion of the multi - component compounded insulating pellets for 50 h ≤0.6 MPa; The rotation speed of the storage tank is 5 - 7 rpm, the absorption temperature after heat preservation is 60 - 70°C, the storage tank is kept at a constant temperature for absorption for 6 - 10 h, the temperature is 50°C - 80°C, and the high - temperature cross - linking degree of the insulating pellets is above 88%.

10. The preparation method of a multi-component compounded and stably extruded insulating material according to claim 6, characterized in that: Hot pressing and crosslinking molding in a tablet press, wherein the pressure of the tablet press is 300 - 500 KN, the hot pressing melting temperature is 110 - 130 °C, the crosslinking hot pressing temperature is 150 - 220 °C, and the crosslinking time is 5 - 20 min.

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