Polyolefin insulating material as well as preparation method and application thereof

Abstract

The invention discloses a polyolefin insulating material as well as a preparation method and application thereof, and belongs to the field of high polymer materials. The polyolefin insulating material is prepared from 25 to 45 parts of high-density polyethylene, 20 to 40 parts of linear low-density polyethylene and 20 to 35 parts of tracking-resistant additive. The polyolefin insulating material has excellent flame retardance, tracking resistance and high-temperature oxidation resistance, is used for preparing a spacer used for a distribution network power transmission line, can improve the problems of high-temperature aging, short circuit and the like of the distribution network power transmission line and reduce fire disasters, and is recyclable and environment-friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of insulating materials, in particular to a polyolefin insulating material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of China's power industry, high-voltage power transmission has become one of the main ways of long-distance power transmission in power systems. When the power transmission network is laid in some old urban areas, due to the narrow streets and dense buildings in the old urban areas, the space for laying the distribution network lines is limited. In order to meet the demand for residential electricity, multiple parallel circuits may occur. In addition, some industrial parks need to lay multiple distribution lines at the same time to meet the demand for electricity, which may also result in multiple parallel circuits. In these scenarios, the distance between the distribution network lines will be reduced, and the air gap between the lines cannot withstand the electric field strength under the high-voltage line, which is prone to short circuit. Moreover, in areas where strong winds often occur, the power transmission lines of the distribution network may also be affected by wind, resulting in swinging, contact, and friction of the power lines, which may cause line short circuit tripping. When the distribution power transmission lines need to cross rivers, lakes, and other water areas, due to the large span, the insulation stability of the conductors also faces challenges.

[0003] In order to stabilize the distance between the conductors in the distribution network lines, avoid the problem of friction short circuit, and improve the stability of the conductors in the distribution network lines, a spacer rod is generally used as an auxiliary structure. However, the existing polymer spacer rod has the problems of poor flame retardance and electrical tracking resistance, and cannot obtain good use stability. In the long-term use process, it may cause short circuit of the distribution network lines and fire.

[0004] Therefore, it is urgent to develop an insulating spacer rod with excellent flame retardance and electrical tracking resistance to improve the short circuit problem of the distribution power transmission lines. SUMMARY

[0005] The present application provides a polyolefin insulating material and a preparation method and application thereof. The polyolefin insulating material has excellent flame retardance and electrical tracking resistance, and can improve the short circuit problem of the distribution power transmission lines when used to prepare a spacer rod.

[0006] In a first aspect, the present application provides a polyolefin insulating material, which comprises the following raw materials in parts by weight: 25-45 parts of high-density polyethylene, 20-40 parts of linear low-density polyethylene, and 20-35 parts of an electrical tracking resistance aid.

[0007] In a possible implementation, the molecular weight of the high-density polyethylene is 40000-300000 g / mol;

[0008] And / or, the density of the high-density polyethylene is 0.946-0.956 g / cm 3 .

[0009] In a possible implementation, the linear low density polyethylene has a density of 0.915-0.935 g / cm 3 ;

[0010] The linear low density polyethylene comprises a metallocene linear low density polyethylene.

[0011] In a possible implementation, the anti-tracking agent comprises at least one of magnesium hydroxide, aluminum hydroxide, nano calcium carbonate.

[0012] In a possible implementation, the raw material of the polyolefin insulation material further comprises at least one of a compatibilizer, a lubricant, a colorant, an antioxidant, a light stabilizer or a hydrophobic agent.

[0013] In a possible implementation, the raw material of the polyolefin insulation material further comprises 2-4 parts of compatibilizer, 0.3-0.6 parts of lubricant, 0.1-2.5 parts of colorant, 0.3-0.6 parts of antioxidant, 0.1-0.6 parts of light stabilizer and 0.1-0.4 parts of hydrophobic agent, according to weight fraction.

[0014] In a possible implementation, the compatibilizer comprises maleic anhydride grafted polyethylene and / or maleic anhydride grafted polyolefin elastomer;

[0015] And / or, the lubricant comprises at least one of silicone oil, polyethylene wax, stearic acid, polyphthalamide fluorine-containing agent;

[0016] And / or, the colorant comprises at least one of color masterbatch and color powder;

[0017] And / or, the antioxidant comprises at least one of antioxidant 1010, antioxidant 168, antioxidant DLTDP;

[0018] And / or, the light stabilizer comprises at least one of UV-944, UV-622, UV-531;

[0019] And / or, the hydrophobic agent comprises at least one of polysiloxane, fluorocarbon surfactant, calcium stearate, zinc stearate, magnesium stearate.

[0020] In a possible implementation, the colorant comprises carbon black, and the mass of the carbon black is not more than 2.5% of the total mass of the raw material of the polyolefin insulation material.

[0021] In a second aspect, the application provides a preparation method of the polyolefin insulation material, comprising: sequentially performing a treatment comprising melting and solidification on a raw material mixture comprising high density polyethylene, linear low density polyethylene and anti-tracking agent, to obtain the polyolefin insulation material.

[0022] In a third aspect, the present application provides a spacer rod comprising the polyolefin insulating material or the polyolefin insulating material prepared by the above method.

[0023] The present application provides a polyolefin insulating material, a preparation method and application thereof. The polyolefin insulating material is prepared by using 25-45 parts of high-density polyethylene, 20-40 parts of linear low-density polyethylene and 20-35 parts of an electric tracking resistant additive as raw materials. The polyolefin insulating material has excellent flame retardance and electric tracking resistance. The polyolefin insulating material is used for preparing a spacer rod, which can improve the short circuit problem of a power transmission line. The obtained spacer rod can be recycled and reused. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The spacer rod provided by the present application is shown in the structure diagram.

[0025] Reference signs are explained as follows:

[0026] 100 - spacer rod;

[0027] 110 - locking bolt;

[0028] 120 - rubber clamping block;

[0029] 130 - hinge;

[0030] 140 - chuck. DETAILED DESCRIPTION

[0031] The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, the same numbers are used to indicate the same or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all the implementations consistent with the present application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present application as detailed in the appended claims.

[0032] First, the terms involved in the present application are explained:

[0033] Spacer rod: refers to a key component installed on an overhead line using split conductors in the field of power transmission, which is used to fix the spacing between multiple sub-conductors in the same phase, prevent the sub-conductors from colliding with each other, suppress harmful vibrations and ensure the safe and stable operation of the line.

[0034] Water tree: some micro-channels developed in a polymer insulating material when water, electric stress and certain inducing factors such as impurities, protrusions, space charges or ions exist.

[0035] Electric tree: is from the microscope can be observed in the crosslinked polyethylene cable insulation layer of air gap, impurities or moisture and the surface unevenness between the shielding layer and the insulation layer and other dendritic defects.

[0036] The existing spacer rod has the technical problems of poor flame retardance and poor electric tracking resistance.

[0037] The polyolefin insulation material provided by the embodiment of the present application uses high-density polyethylene and linear low-density polyethylene in combination and adjusts the amount of use, and adds an electric tracking resistance aid, thereby improving the mechanical properties, flame retardance and electric tracking resistance of the insulation material. The spacer rod prepared therefrom solves the technical problems of poor electric tracking resistance and non-flame retardance of the spacer rod, improves the service life thereof, and can be recycled and reused.

[0038] The technical solutions of the present application and how the technical solutions of the present application solve the above technical problems will be described in detail below with specific examples. The following specific examples can be combined with each other, and the same or similar concepts or processes can not be described again in some examples. The embodiments of the present application will be described below with reference to the accompanying drawings.

[0039] Unless otherwise specified, the raw materials used in the present application are commercially available.

[0040] The polyolefin insulation plate material provided by the embodiment of the present application comprises, in terms of weight fraction, high-density polyethylene 25-45 parts, linear low-density polyethylene 20-40 parts and electric tracking resistance aid 20-35 parts.

[0041] High-density polyethylene (HDPE) generally has a high crystallinity of more than 70%, and its molecular chains are closely arranged and regular, which can form larger and more perfect spherulites. These spherulites are rigid by themselves, but the amorphous regions connected by tie molecules between them can absorb energy and prevent crack propagation when impacted, contributing to certain toughness. Linear low-density polyethylene (LLDPE) has a short branch structure and a lower crystallinity, generally 40-60%, and will form smaller and less perfect spherulites or microcrystals. Linear low-density polyethylene has a large number of amorphous regions and molecular chain entanglements caused by short branches, which can effectively dissipate impact energy, so that linear low-density polyethylene has toughness. When high-density polyethylene and linear low-density polyethylene are blended, when the HDPE content is relatively high, it constitutes a continuous phase or a co-continuous phase, and its larger and relatively perfect spherulite structure provides skeletal support. LLDPE acts as a dispersed phase or fills the amorphous regions between / inside the HDPE spherulites. The presence of LLDPE can plasticize the crystal regions of HDPE, hinder the excessive growth of HDPE spherulites, make the spherulite size smaller and less perfect, and provide more entanglement points. This refined morphology is beneficial to improve the toughness of the polyolefin insulation material.

[0042] The inventors found that too high HDPE content increases the rigidity of the polyolefin insulation material, i.e. weakens its toughness, due to the presence of rigid spherulites in the HDPE, which cannot be dispersed by the relatively small amount of linear low density polyethylene.

[0043] When the amount of HDPE is relatively reduced, while the amount of LLDPE is relatively increased, the supporting effect of HDPE is weakened, and no longer forms an effective continuous skeleton or large spherulite network. At this time, the LLDPE becomes the main continuous phase, and in the LLDPE-dominated polyolefin material system, the crystal regions are smaller, more and more imperfect, and a large number of small crystal region interfaces become potential stress concentration points. Moreover, the number and strength of the tie molecules connecting the crystal regions may not be as effective as the tie molecule network connecting the large spherulites in the HDPE-dominated system, and the branched structure of the LLDPE will also limit the stretching and entanglement density of the molecular chains, thereby weakening the toughness of the polyolefin insulation material.

[0044] In order to obtain a polyolefin insulation material with excellent mechanical properties and being beneficial to practical application, the polyolefin insulation material provided in the present application contains high density polyethylene in an amount of 25-45 parts by weight, and contains linear low density polyethylene in an amount of 20-40 parts by weight.

[0045] At the same time, by adding an electrical tracking resistance aid, the polyolefin insulation material prepared has excellent electrical tracking resistance and flame retardancy.

[0046] In order to obtain higher electrical tracking resistance, the amount of the electrical tracking resistance aid is increased, which will cause excessive rigid particles to induce stress concentration in the material, resulting in poor mechanical properties of the polyolefin insulation material, and further affecting its aging resistance and use stability.

[0047] The high density polyethylene has a molecular weight of 40,000-300,000 g / mol and a density of 0.945-0.956 g / cm3.

[0048] In order to enable the polyolefin insulation material to have more excellent insulation, specifically, the high density polyethylene can include Borstar® 3364 of Borealis, 7000F of Borealis, UNIGARD™ 6098 of Dow, 5000S of Shanghai Petrochemical, LE0592 of Exxon Mobil, etc. These high density polyethylenes have ultra-high electrical insulation performance and long-term stability, and very low dielectric loss factor, so that less heat is generated at high voltage, and overheating aging of the insulation layer can be avoided.

[0049] The linear low density polyethylene has a density of 0.915-0.935 g / cm3 and includes a metallocene-catalyzed linear low density polyethylene.

[0050] In order to make the polyolefin insulation material of the present application have better long-term anti-aging and low-temperature toughness, and be able to be applied in harsh environments, specifically, the linear low-density polyethylene can include Exxon 218W, Dow 3518, Sinopec 7042, Borealis FB2230, etc. The metallocene catalyst can precisely control the molecular structure of the linear low-density polyethylene, so that the molecular chain of the obtained metallocene-catalyzed linear low-density polyethylene is more entangled, the ability to resist external damage is improved, and the toughness can still be maintained in a low-temperature environment. The above-mentioned linear low-density polyethylenes are all prepared by metallocene catalysis, have more long-chain branches, and can better combine with high-density polyethylene at the molecular level to achieve the improvement of mechanical properties such as crack resistance.

[0051] The tracking resistance aid includes at least one of magnesium hydroxide, aluminum hydroxide, and nano calcium carbonate.

[0052] After the magnesium hydroxide and the aluminum hydroxide are decomposed by heat, water vapor can be released to dilute oxygen, and a ceramic barrier can be formed to further block combustion and isolate heat. Moreover, as alkaline compounds, the magnesium hydroxide and the aluminum hydroxide can neutralize acidic substances to prevent acid-catalyzed carbonization reactions and reduce the degree of carbonization of the polyolefin insulation material. The nano calcium carbonate can fill the micro gaps of the polyolefin insulation material, block the expansion of the carbonization channel, and also improve the hardness and wear resistance of the material to resist the ablation of the electric arc. The present application preferably uses at least one of the above-mentioned three compounds as a tracking resistance aid to obtain a polyolefin insulation material with excellent tracking resistance performance and good flame retardance.

[0053] In order to obtain better processing performance and use effect, the polyolefin insulation material of the present application further includes at least one of a compatibilizer, a lubricating aid, a color aid, an antioxidant, a light stabilizer, or a hydrophobic aid.

[0054] Since the above-mentioned tracking resistance aid is an inorganic particle, its surface is hydrophilic, while the high-density polyethylene and the linear low-density polyethylene are organic substances, their surfaces are hydrophobic, and the interface bonding between them is poor. They are easy to agglomerate during mixing and processing, which leads to the deterioration of processing fluidity. Therefore, when preparing the polyolefin insulation material, a compatibilizer can be added to improve the mixing compatibility and processability between the raw materials. Based on the polyolefin insulation material prepared by taking polyethylene as the main component in the present application, specifically, the compatibilizer includes maleic anhydride grafted polyethylene and / or maleic anhydride grafted polyolefin elastomer, and the compatibilizer has good compatibility with the high-density polyethylene and the linear low-density polyethylene. It should be noted that the compatibilizer used in the present application is not limited to the above-mentioned types, and other compatibilizers that can achieve similar effects are also applicable.

[0055] Since low molecular weight lubricant additives can migrate out with the increase of use time, not only the surface resistance of the material will be affected, but also the insulation aging will be accelerated. Therefore, in the present application, according to the characteristics of the high density polyethylene and linear low density polyethylene used, the variety of lubricant additives with high compatibility is selected. Specifically, the lubricant additives can include silicone oil, polyethylene wax, stearic acid, polyphthalamide fluorine-containing additives, etc.

[0056] By adding internal lubricant additives such as stearic acid and polyphthalamide fluorine-containing additives, the interchain force can be weakened, and when the polyolefin insulation material is prepared, the melt has better flowability during extrusion or injection molding, thereby reducing the processing energy consumption. By adding external lubricant additives such as silicone oil and polyethylene wax, the adhesion of the melt to the equipment during processing can be reduced, the demolding property of the material is improved, and the surface finish of the polyolefin insulation material is improved.

[0057] Based on the fact that the polyolefin insulation material in the present application can be used as a spacer, color aids can also be added during preparation to provide color identification and distinguish the phase line, ground wire, etc. Specifically, the color aid can include at least one of color masterbatch and color powder. The color masterbatch can include PE color masterbatch, PP color masterbatch, ABS color masterbatch, PVC color masterbatch, EVA color masterbatch, etc., and the pigments contained therein can include phthalocyanine red, phthalocyanine blue, phthalocyanine green, sun-resistant big red, macromolecular red, macromolecular yellow, permanent yellow, permanent purple, azo red, etc. The color powder can include carbon black, titanium white powder, iron oxide pigment, cobalt blue, bismuth yellow, titanium nickel yellow, cerium red, etc. It should be noted that the color aid used in the present application is not limited to the above-mentioned types, and other color aids that can achieve similar effects are also applicable.

[0058] When the color aid includes carbon black, the mass of the carbon black is not more than 2.5% of the total mass of the raw materials.

[0059] Since carbon black has a certain conductivity, when the addition amount exceeds 2.5%, the carbon black particles will form a continuous conductive network in the polyolefin insulation material, making the insulation material become a semiconductor or even a conductor. Moreover, a high content of carbon black will destroy the crystallinity of the polyolefin, increase the crystallinity of the material, and water molecules will penetrate along the carbon black-polyolefin interface, accelerating the aging of the material.

[0060] The present application can also add antioxidants to cut off the thermal oxidative degradation chain in the material, improve the antioxidant property of the polyolefin insulation material, and prevent the material surface from being brittle and cracking. In order to obtain better antioxidant property, specifically, the antioxidant in the present application can include antioxidant 1010, antioxidant 168, antioxidant DLTDP, etc. It should be noted that the antioxidant used in the present application is not limited to the above-mentioned types, and other antioxidants that can achieve similar effects are also applicable.

[0061] In order to obtain better anti-photoaging property, a light stabilizer can also be added in the present application. Specifically, the light stabilizer can include UV-944, UV-622, UV-531, etc. It should be noted that, in order to avoid acid-base conflict, when the light stabilizer includes hindered amine light stabilizer, the light stabilizer needs to be used in cooperation with the antioxidant. It should be noted that the light stabilizer used in the present application is not limited to the above-mentioned types, and other light stabilizers capable of achieving similar effects are also applicable.

[0062] In the atmospheric environment, moisture inevitably invades the material. The invasion of moisture is the main factor of water treeing of insulating materials. In order to make the polyolefin insulating material have higher hydrophobicity and reduce the risk of tracking, a hydrophobicity aid can also be added in the present application to inhibit the wetting of the surface of the polyolefin insulating material. Specifically, the hydrophobicity aid can include polysiloxane, fluorocarbon surfactant, stearate, etc.

[0063] Since ammonium perfluorooctanoate and perfluorosulfonic acid have persistent pollution to the environment, therefore, when the fluorocarbon surfactant is selected as the hydrophobicity aid, the fluorocarbon surfactant is preferably at least one of perfluoroalkyl quaternary ammonium salt, perfluorocarboxybetaine, and perfluoropolyether alcohol.

[0064] Considering that some stearates have problems of heavy metal pollution and ionic conduction, in the present application, the stearate is preferably at least one of calcium stearate, zinc stearate, and magnesium stearate.

[0065] It should be noted that the hydrophobicity aid used in the present application is not limited to the above-mentioned types, and other hydrophobicity aids capable of achieving similar effects are also applicable.

[0066] It can be understood that, in order to use polyolefin insulating materials with more excellent performance, the present application adjusts the addition amount of each aid.

[0067] Further, the polyolefin insulating material also includes 2-4 parts of a compatibilizer, 0.3-0.6 parts of a lubricant aid, 0.1-2.5 parts of a color aid, 0.3-0.6 parts of an antioxidant, 0.1-0.6 parts of a light stabilizer, and 0.1-0.4 parts of a hydrophobicity aid, in terms of weight fraction.

[0068] In the present application, when the addition amount of the compatibilizer is too small, the interface compatibility between the inorganic components and other organic components in the raw material is poor, and the inorganic components are not uniformly dispersed in the material, which can cause the mechanical properties of the obtained polyolefin insulating material to be poor, and the high-temperature oxidation resistance and tracking resistance to be reduced.

[0069] Excessive lubricant aid can block the interchain force, causing the tensile strength and elongation at break of the polyolefin insulating material to decrease. Moreover, too much lubricant aid can also precipitate and migrate to the surface of the insulating layer, forming a weak interface and reducing the impact toughness and environmental stress cracking resistance of the material.

[0070] Excessive antioxidants will decompose to produce small polar molecules during high-temperature processing, migrate to the surface of the material to form a heat conduction channel, resulting in a decrease in the volume resistivity of the material and weakening of the insulation performance. At the same time, the antioxidant molecules will also occupy the gap between the polymer molecular chains, destroying the integrity of the crystal, and further affecting the mechanical properties of the polyolefin insulation material.

[0071] Excessive light stabilizers will also migrate to the surface of the material, reducing the volume resistivity of the material. Moreover, ultraviolet absorber type light stabilizers will photolyze to generate colored quinone structures under ultraviolet light, resulting in an increase in the yellowing rate of the polyolefin insulation material and a shortening of the service life of the material.

[0072] When the total amount of antioxidants and light stabilizers is excessive, the obtained polyolefin insulation material is prone to polarization under an electric field, the local field strength is distorted, and the probability of the occurrence of electrical treeing is increased.

[0073] The preparation method of the polyolefin insulation material provided in the embodiments of the present application comprises the following steps:

[0074] Specifically, the preparation method of the polyolefin insulation material comprises the following steps:

[0075] Step one, after weighing the raw materials including high-density polyethylene, linear low-density polyethylene and electrical tracking resistance aid, the raw materials are placed in a high-speed mixer, stirred at room temperature for 1-3 min at a speed of 200-500 rpm, and preliminarily mixed to obtain a mixture;

[0076] Step two, the mixture is placed into the hopper of a double-screw extruder, and then enters the double-screw extruder to perform the processes of melting, mixing, extrusion, cooling and granulation, and the heating temperature of each process is controlled at 180-260℃. Then, drying is performed to obtain the polyolefin insulation material.

[0077] Due to the differences in the melting temperatures or pyrolysis temperatures of the components in the raw materials, in order to achieve better mixing effect of the components during processing, in the present application, the temperature of the mixture during melting in the double-screw extruder is 180-260℃.

[0078] In the embodiments of the present application, a spacer rod is also provided, which comprises the above-mentioned polyolefin insulation material. The spacer rod is used for network transmission lines, has a long application period, can effectively improve the short circuit problem of the line, reduce the incidence of fire, and the material can also be recycled and reused.

[0079] Figure 1 The spacer rod provided in the present application is shown in the structure diagram as Figure 1 The spacer rod 100 provided in the present embodiment comprises:

[0080] Locking bolt 110, used to firmly press the rubber clamp block 120 on the conductor, by applying and maintaining sufficient bolt pre-tightening force, to ensure that the clamp block generates sufficient friction on the conductor, preventing the conductor from sliding or rotating in the clamp head 140; when connecting the arm, hinge 130, clamp head 140 and other components are required, it can also provide mechanical connection. The locking bolt 110 is usually designed with a lock nut, a split pin, a locking washer, etc. to prevent the bolt from loosening and failing under long-term vibration;

[0081] Rubber clamp block 120, used to protect the conductor and provide friction damping. It is usually made of high-elasticity, wear-resistant and aging-resistant rubber (such as silicone rubber, EPDM), wrapped around the conductor surface to avoid direct contact and damage to the conductor (such as flattening and scratching the aluminum strands). In addition, the elastic properties of the rubber can absorb and dissipate the energy of the conductor vibration (micro-wind vibration, sub-span oscillation), reducing the fatigue damage of the vibration to the conductor, the clamp head 140 itself and the spacer rod 100 connection structure;

[0082] Hinge 130, used to provide flexibility for the installation of the spacer rod 100, allowing each "arm" of the spacer rod to bend with the natural curvature of the conductor, avoiding excessive bending stress on the spacer rod itself or the conductor at the conductor low point or corner (rigid connection can cause stress concentration);

[0083] Clamp head 140, used to directly grip and fix the conductor, which can transfer the force (wind load, ice load, dynamic load generated by vibration) received by the conductor and the friction generated by the clamp block to the connecting arm and frame structure of the spacer rod.

[0084] The application also provides a preparation method of the spacer rod, comprising the following steps:

[0085] Step one, put the above-mentioned polyolefin insulating material into a plastic drying machine and dry it at 80℃ for 2 hours;

[0086] Step two, introduce the dried material into the hopper of a prepared injection molding machine, inject it into a mold through the injection molding machine, and obtain the spacer rod after cooling and demolding; wherein the heating temperature of each section of the injection molding machine is controlled at 180~260℃.

[0087] In order to improve the product qualification rate, the application also uses X-ray detection equipment to detect the pores of the produced spacer rod, ensuring that there are no pores inside each product.

[0088] The application will be described in more detail through specific examples.

[0089] Example 1

[0090] Step one, 40 parts of high density polyethylene Dow HDPE 3364, 25 parts of linear low density polyethylene Wanhua Chemical DFDA 7042, 25 parts of electric tracking resistant aid aluminum hydroxide, 2 parts of compatibilizer maleic anhydride grafted polyethylene, 0.4 parts of lubricating aid polyethylene wax, 0.8 parts of color aid PE color masterbatch, 0.6 parts of antioxidant 1010, 0.1 parts of light stabilizer 944 and 0.4 parts of hydrophobic aid silane coupling agent A-172 are weighed according to the weight fraction, then placed in a high-speed mixer, stirred at room temperature for 3 min, the rotation speed is 350 rpm, and preliminary mixing is carried out to obtain a mixture;

[0091] Step two, the mixture is put into the hopper of the double screw extruder, and then melted, mixed, extruded, cooled and granulated in the double screw extruder; wherein the heating temperature during melting is 210 DEG C, and the temperature during mixing and extruding is 180 DEG C. Then dry to obtain a polyolefin insulation material.

[0092] Example 2

[0093] Similar to example 1, except that the mass fractions of the raw materials used are respectively: 45 parts of high density polyethylene Dow HDPE 3364, 20 parts of linear low density polyethylene Wanhua Chemical DFDA 7042, 25 parts of electric tracking resistant aid aluminum hydroxide, 2 parts of compatibilizer maleic anhydride grafted polyethylene, 0.5 parts of lubricating aid polyethylene wax, 2 parts of color aid PE color masterbatch, 0.45 parts of antioxidant 1010, 0.3 parts of light stabilizer 944 and 0.3 parts of hydrophobic aid silane coupling agent A-172.

[0094] Example 3

[0095] Similar to example 2, except that the mass fraction of the compatibilizer used is 1.5 parts.

[0096] Example 4

[0097] Similar to example 1, except that the mass fractions of the raw materials used are respectively: 35 parts of high density polyethylene Dow HDPE 3364, 33 parts of linear low density polyethylene Wanhua Chemical DFDA 7042, 35 parts of electric tracking resistant aid aluminum hydroxide, 4 parts of compatibilizer maleic anhydride grafted polyethylene, 0.6 parts of lubricating aid polyethylene wax, 2.5 parts of color aid PE color masterbatch, 0.3 parts of antioxidant 1010, 0.6 parts of light stabilizer 944 and 0.2 parts of hydrophobic aid silane coupling agent A-172.

[0098] Example 5

[0099] Similar to Example 1, except that the mass fractions of the raw materials used were as follows: 25 parts of high-density polyethylene Dow HDPE 3364, 40 parts of linear low-density polyethylene Wanhua Chemical DFDA 7042, 30 parts of tracking resistance aid aluminum hydroxide, 3 parts of compatibilizer maleic anhydride grafted polyethylene, 0.3 parts of lubrication aid polyethylene wax, 0.1 parts of color aid PE color masterbatch, 0.4 parts of antioxidant 1010, 0.5 parts of light stabilizer 944, and 0.1 parts of hydrophobic aid silane coupling agent A-172.

[0100] Example 6

[0101] Similar to Example 1, except that no hydrophobic aid was added.

[0102] Comparative Example 1

[0103] Similar to Example 1, except that the mass fraction of the tracking resistance aid used was 15 parts.

[0104] Comparative Example 2

[0105] Similar to Example 1, except that the mass fraction of the tracking resistance aid used was 40 parts.

[0106] Comparative Example 3

[0107] Similar to Example 2, except that the mass fraction of the high-density polyethylene Dow HDPE 3364 used was 50 parts.

[0108] Comparative Example 4

[0109] Similar to Example 2, except that the mass fraction of the linear low-density polyethylene Wanhua Chemical DFDA 7042 used was 15 parts.

[0110] Comparative Example 5

[0111] Similar to Example 5, except that the mass fraction of the linear low-density polyethylene Wanhua Chemical DFDA 7042 used was 50 parts.

[0112] Test Examples The polyolefin insulation materials obtained in Examples 1-6 and Comparative Examples 1-5 above were tested for the following properties:

[0113] Tensile strength: tested in accordance with GB / T 2951.11-2008;

[0114] Nominal strain at break: tested in accordance with GB / T 2951.11-2008;

[0115] Environmental stress cracking resistance: tested in accordance with GB / T 2951.41-2008 at F0, 500 h;

[0116] 200℃ oxidation induction time: tested by differential scanning calorimetry according to ASTM-D3895-07;

[0117] tracking and erosion resistance: tested according to GB / T 6553-2024;

[0118] hydrophobicity grade: tested according to GB / T 24622-2022;

[0119] flame retardancy: tested according to UL-94 plastic materials flammability test standard;

[0120] The test results are shown in Table 1:

[0121] Table 1

[0122]

[0123] As can be seen from the data in Table 1, the polyolefin insulation material provided by the application has excellent mechanical properties, aging resistance and tracking resistance.

[0124] Compared with Example 3, the polyolefin insulation material obtained in Example 2 has a longer 200℃ oxidation induction time, which shows that the use of the compatibilizer helps to improve the compatibility between the raw materials, thereby helping to improve the oxidation resistance of the polyolefin insulation material.

[0125] Compared with Example 6, the polyolefin insulation material obtained in Example 5 has a longer 200℃ oxidation induction time and better hydrophobicity, which shows that the presence of the hydrophobicity aid not only enables the polyolefin insulation material to have good hydrophobicity, but more importantly, can improve the high-temperature oxidation resistance of the polyolefin insulation material.

[0126] Compared with Comparative Example 1, the polyolefin insulation material obtained in Example 1 has better toughness, high-temperature oxidation resistance, tracking resistance and flame retardancy, which shows that the use of the tracking resistance aid helps to improve the toughness, high-temperature oxidation resistance and tracking resistance of the polyolefin insulation material. However, too low a dosage of the tracking resistance aid will deteriorate the toughness, high-temperature oxidation resistance, tracking resistance and flame retardancy of the polyolefin insulation material.

[0127] Compared with Comparative Example 2, the polyolefin insulation material obtained in Example 1 has better toughness, high-temperature oxidation resistance and hydrophobicity, which shows that the use of the tracking resistance aid helps to improve the toughness, high-temperature oxidation resistance and hydrophobicity of the polyolefin insulation material. However, too high a dosage of the tracking resistance aid will also deteriorate the toughness, high-temperature oxidation resistance and hydrophobicity of the polyolefin insulation material.

[0128] Compared with Comparative Example 3, the tensile strength of the polyolefin insulation material obtained in Example 1 is slightly lower, but the toughness and environmental stress cracking resistance are better, which shows that the increase of the mass fraction of the high-density polyethylene used helps to improve the tensile strength of the polyolefin insulation material, but deteriorates the nominal strain at break performance and environmental stress cracking resistance of the polyolefin insulation material.

[0129] Compared with Comparative Example 4 and Comparative Example 5, the polyolefin insulation material obtained in Example 1 has better tensile strength and high-temperature oxidation resistance, which shows that controlling the addition mass fraction of the linear low-density polyethylene in 20-40 parts helps to simultaneously improve the mechanical properties and high-temperature oxidation resistance of the polyolefin insulation material. When the amount of the linear low-density polyethylene is too much, the mechanical properties and high-temperature oxidation resistance of the polyolefin insulation material will be deteriorated.

[0130] In summary, the polyolefin insulation material provided in the present application has excellent high-temperature oxidation resistance, tracking resistance and flame retardancy, and is used for preparing spacer rods, which can improve the problems of line high-temperature aging, short circuit and the like, reduce the incidence of fire, and the material can be recycled and reused.

[0131] Finally, it should be noted that: other embodiments of the application will be readily apparent to those skilled in the art upon considering the specification and practicing the application disclosed herein. The present application is intended to cover any variations, uses or adaptive changes to the present application that follow the general principles of the present application and include common knowledge or conventional technical means in the art that are not disclosed by the present application, and are not limited to the precise structures described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present application is only limited by the appended claims.

Claims

1. A polyolefin insulation material, characterized in that: The invention comprises the following raw materials in parts by weight: 25-45 parts of high-density polyethylene, 20-40 parts of linear low-density polyethylene and 20-35 parts of an anti-tracking agent.

2. The polyolefin insulation material according to claim 1, characterized in that: The molecular weight of the high-density polyethylene is 40,000-300,000 g / mol; And / or, the density of the high-density polyethylene is 0.946-0.956 g / cm³.

3. The polyolefin insulation material according to claim 1 or 2, characterized in that: The density of the linear low-density polyethylene is 0.915-0.935 g / cm³; The linear low density polyethylene includes metallocene-catalyzed linear low density polyethylene.

4. The polyolefin insulation material according to claim 1, characterized in that: The anti-tracking agent includes at least one of magnesium hydroxide, aluminum hydroxide, and nano-calcium carbonate.

5. The polyolefin insulation material according to claim 1, characterized in that: The raw materials of the polyolefin insulation material further include at least one of a compatibilizer, a lubricating agent, a coloring agent, an antioxidant, a light stabilizer or a hydrophobic agent.

6. The polyolefin insulation material according to claim 5, characterized in that: In parts by weight, the raw materials of the polyolefin insulation material further include 2-4 parts of a compatibilizer, 0.3-0.6 parts of a lubricating agent, 0.1-2.5 parts of a coloring agent, 0.3-0.6 parts of an antioxidant, 0.1-0.6 parts of a light stabilizer and 0.1-0.4 parts of a hydrophobic agent.

7. The polyolefin insulation material according to claim 6, characterized in that: The compatibilizer includes maleic anhydride grafted polyethylene and / or maleic anhydride grafted polyolefin elastomer; And / or, the lubricating agent includes at least one of silicone oil, polyethylene wax, stearic acid, and polyphthalamide fluorine-containing additives; And / or, the color auxiliary agent includes at least one of a masterbatch and a color powder; And / or, the antioxidant includes at least one of antioxidant 1010, antioxidant 168, and antioxidant DLTDP; And / or, the light stabilizer includes at least one of UV-944, UV-622, and UV-531; And / or, the hydrophobic additive includes at least one of polysiloxane, fluorocarbon surfactant, and stearate.

8. The polyolefin insulation material according to claim 5, characterized in that: The color additive includes carbon black, and the mass of the carbon black does not exceed 2.5% of the total mass of the raw materials of the polyolefin insulation material.

9. A method for preparing the polyolefin insulation material according to any one of claims 1 to 8, characterized in that: The following steps are involved: The raw material mixture including high-density polyethylene, linear low-density polyethylene and anti-tracking auxiliary agent is sequentially subjected to treatments including melting and solidification to obtain the polyolefin insulation material.

10. A spacer bar, characterized in that: The invention comprises the polyolefin insulating material according to any one of claims 1 to 8 or the polyolefin insulating material prepared by the preparation method according to claim 9.

Images