Composite cable insulating material doped with modified silica and preparation method thereof

Abstract

The present application belongs to the field of wire and cable insulation materials. The epoxy poly-alpha olefin oligomer, two components containing epoxy groups, epoxy modified silica and acrylic acid grafting material are introduced into the curable cable material composite system, thereby improving the flexibility, low temperature brittleness and aging resistance of the cable material. Finally, in addition to using carboxyl-epoxy crosslinking, the cable material cured product also introduces a blocked isocyanate as a crosslinking agent, which is unblocked to form a highly reactive isocyanate at high temperatures, which is crosslinked with the hydroxyl group formed after the ring opening of the carboxyl-epoxy group, thereby reducing the dielectric loss of the cable material and improving its breakdown strength.

Description

Technical Field

[0001] This invention belongs to the field of wire and cable insulation materials, and specifically relates to a composite cable insulation material, a method for curing the composite cable insulation material, and the resulting cured product. Background Technology

[0002] Polyethylene is widely used in cable insulation materials due to its excellent electrical properties, good processability, and low cost. However, it is prone to accumulating space charge. The accumulation of a large amount of charge can cause electric field distortion and insulation aging, reduce the dielectric stability of polyethylene insulation materials, and even lead to breakdown at low voltages.

[0003] Based on the above problems, a new design concept for insulation materials has been proposed. This involves embedding electrically stable polyethylene molecules within a cross-linked polymer framework structure, constructing a network structure through a high-temperature cross-linking reaction, thereby obtaining a high-performance insulation material. However, cross-linked polymers are thermosetting, and excessively high cross-linking network density leads to poor material flexibility. Under excessive bending or low-temperature conditions, the insulation layer is prone to damage, resulting in cable failure. This performance disadvantage is particularly pronounced in data cables with smaller outer diameters. Therefore, it is necessary to improve the flexibility of composite cable insulation materials while simultaneously considering both insulation performance and aging resistance. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to develop a highly flexible cable insulation material to improve its low-temperature performance, while also improving the dielectric properties of the cable insulation material, which has positive significance for its processing performance and expansion of application fields.

[0005] Firstly, a composite cable insulation material includes:

[0006] Linear low-density polyethylene, acrylic grafted material, epoxidized hydrocarbons, epoxy-modified silica, blocked isocyanate and antioxidants;

[0007] The melt index of linear low-density polyethylene ranges from 1.0 to 3.0 g / 10 min.

[0008] The acrylic grafting material is selected from one or more combinations of ethylene-acrylic acid copolymer, propylene-acrylic acid copolymer and ethylene-octene-acrylic acid copolymer; preferably, the acrylic grafting material is selected from ethylene-acrylic acid copolymer; the melt index of the acrylic grafting material is in the range of 1-50 g / 10 min.

[0009] The acrylic acid content in the acrylic grafting material is 5-20%;

[0010] The general structural formula of epoxide hydrocarbons is:

[0011] R1 and R2 are selected from straight-chain aliphatic hydrocarbons, branched non-cyclic aliphatic hydrocarbons, or cyclic aliphatic hydrocarbons with 4-50 carbon atoms.

[0012] Preferably, R1 and R2 are selected from straight-chain aliphatic hydrocarbons with 4-50 carbon atoms or branched non-cyclic aliphatic hydrocarbons;

[0013] Preferably, the epoxidized hydrocarbons are selected from epoxidized polyalphaolefin oligomers.

[0014] Epoxy-modified silica is prepared by the sol-gel method, and its raw materials include: organic esters of orthosilicate and silane coupling agents containing epoxy groups;

[0015] Preferably, the organic ester of orthosilicate is selected from any one or a combination of orthosilicate, ethyl orthosilicate and propyl orthosilicate;

[0016] Preferably, the epoxy-containing silane coupling agent is selected from any one or a combination of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and γ-(2,3-epoxypropoxy)propyltriethoxysilane;

[0017] Furthermore, the steps for preparing epoxy-modified silica by the sol-gel method specifically include: dissolving an organic ester of orthosilicate and a silane coupling agent containing an epoxy group in an alcohol solvent, adjusting the pH of the system to 3.5-4.5, reacting at a reaction temperature of 40-80℃ for 10-40 hours, evaporating the alcohol solvent to obtain a gel, drying the gel, crushing it, and sieving it to obtain epoxy-modified silica;

[0018] Preferably, the alcohol solvent is selected from methanol, ethanol, n-propanol, or a mixture of isopropanol and water;

[0019] Preferably, the gel is dried at 70-100°C.

[0020] The blocked isocyanate is an isocyanate in which the isocyanate group (-NCO) is blocked using a blocking agent. The blocked isocyanate is selected from aliphatic isocyanate biuret or trimer; preferably, the blocked isocyanate is selected from hexamethylene diisocyanate (HDI) biuret or trimer.

[0021] The blocking agent is selected from one or more of phenols, pyrazoles, oximes and alcohols, and has a dissociation temperature ≥120℃. Preferably, the blocking agent is selected from one or more of phenol, acetylacetone, acetone oxime, cyclohexanone oxime, pyrazole, dimethylpyrazole, ethylene glycol monomethyl ether and diethylene glycol monomethyl ether.

[0022] The antioxidant is selected from hindered phenolic antioxidants; preferably, the hindered phenolic antioxidants include 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-bis(2,6-di-tert-butylphenol), 4,4'-bis(2-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl- Any one or more combinations of 6-tert-butylphenol, 4,4'-butylidene bis(3-methyl-6-tert-butylphenol), 4,4'-isopropylidene bis(2,6-di-tert-butylphenol), 2,2'-methylene bis(4-methyl-6-cyclohexylphenol), 2,2'-methylene bis(4-methyl-6-nonylphenol), 2,2'-isobutylidene bis(4,6-dimethylphenol), 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine and 2,6-bis(2'-hydroxy-3'-tert-butyl-5'-methylbenzyl)-4-methylphenol;

[0023] Further preferred, the antioxidant is selected from 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine.

[0024] Furthermore, the composite cable insulation material also includes inert fillers, which are selected from one or more of magnesium hydroxide, aluminum hydroxide, wollastonite, mica powder, talc powder, kaolin, calcium carbonate, carbon black and silicon dioxide. The inert fillers are sand-milled to an average particle size of no more than 10 μm before being added to the composite cable insulation material.

[0025] Furthermore, the composite cable insulation material also includes an ultraviolet absorber, which is selected from benzophenone compounds; preferably, the ultraviolet absorber is selected from 2-hydroxy-4-n-octyloxybenzophenone (UV531).

[0026] Furthermore, to accelerate the reaction rate between isocyanate groups and hydroxyl groups, the composite cable insulation material also includes a catalyst, which is selected from any one of organotin compounds, organobismuth compounds, or organozinc compounds.

[0027] Preferably, the catalyst is selected from organotin compounds, wherein the organotin compound is selected from any one of dibutyltin dilaurate, stannous octoate, dimethyltin dioctanoate, or dibutyltin thiolate.

[0028] Furthermore, the composite cable insulation material is prepared from the following raw materials in parts by weight: 90-110 parts by weight of linear low-density polyethylene, 50-70 parts by weight of acrylic grafting material, 5-25 parts by weight of epoxidized hydrocarbons, 1-10 parts by weight of epoxy-modified silica, 0.5-3 parts by weight of blocked isocyanate, and 0.5-3 parts by weight of antioxidant.

[0029] Preferably, the composite cable insulation material is prepared from the following raw materials in parts by weight: 90-110 parts by weight of linear low-density polyethylene, 50-70 parts by weight of acrylic grafting material, 5-25 parts by weight of epoxidized hydrocarbons, 1-10 parts by weight of epoxy-modified silica, 0.5-3 parts by weight of blocked isocyanate, 0.5-3 parts by weight of antioxidant, 1-20 parts by weight of inert filler, 0.5-3 parts by weight of ultraviolet absorber, and 0.1-1 parts by weight of catalyst.

[0030] Secondly, the method for molding and curing the composite cable insulation material described above includes: first mixing the cable insulation material, hot pressing it into shape, and then hot curing it to obtain a cured composite cable insulation material.

[0031] Further, the specific steps include: S1, mixing the components of the cable insulation material formula described above at 90-120℃ and 10-100 rpm;

[0032] S2. After mixing, hot press molding is performed at 90-120℃ and 1-20MPa pressure.

[0033] S3. After hot pressing, it is thermocured at 160-200℃ and 1-20MPa pressure.

[0034] Thirdly, a cured composite cable insulation material is prepared from the composite cable insulation material described above through the molding and curing method described above.

[0035] Fourthly, the application of the above-mentioned composite cable insulation cured material as a material in cable manufacturing.

[0036] The beneficial effects of this invention are as follows: Introducing epoxidized polyalphaolefin oligomers into the curable cable material composite system allows the epoxidized polyalphaolefin oligomers to act as a lubricant during the material mixing stage. During the thermosetting stage, its terminal epoxy groups undergo a ring-opening reaction with the acrylic graft material, resulting in large-volume side chains that reduce the crystallinity of polyethylene and the crosslinking density of the cured system, while simultaneously improving the low-temperature brittleness of the cable material. Furthermore, the introduction of epoxy-modified silica not only fills and reinforces the cable material but also allows it to undergo a ring-opening reaction with the acrylic graft material through chemical bonding, thus connecting inorganic materials with organic polymers and enhancing the aging resistance of the cable material. Finally, in addition to using carboxyl-epoxy crosslinking, the curable cable material also incorporates blocked isocyanate as a crosslinking agent. At high temperatures, this isocyanate is unblocked to form highly reactive isocyanate, which crosslinks with the hydroxyl groups formed after the carboxyl-epoxy ring-opening process, thereby reducing the dielectric loss and increasing the breakdown strength of the cable material. Detailed Implementation

[0037] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0039] Unless otherwise specified, the experimental conditions used in the examples are generally in accordance with conventional conditions in the art or the conditions recommended by the reagent company. Unless otherwise specified, the materials and reagents used in the examples can be purchased commercially.

[0040] Example 1

[0041] Preparation of epoxy-modified silica: 2.25 mol (531.8 g) of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) was uniformly mixed with 0.75 mol (156.2 g) of tetraethyl orthosilicate and 400 mL of anhydrous ethanol / water mixed solvent (volume ratio 9:1). The pH of the system was adjusted to 3.5-4 with an appropriate amount of formic acid. The reaction system was kept at a constant temperature of 55-60℃ for 12 hours to obtain a uniform and transparent sol. Then, the solvent was evaporated by heating to obtain a gel. The gel was dried at 80℃ to obtain a white powder. The powder was crushed, sieved, and passed through a 400-mesh sieve to prepare epoxy-modified silica for later use.

[0042] Example 2

[0043] Preparation of epoxidized polyalphaolefin oligomers: Polyalphaolefin oligomers (Accenture Technology), 88 wt% formic acid aqueous solution, 30 wt% hydrogen peroxide aqueous solution, 70 wt% sulfuric acid aqueous solution, and ethyl n-propyl ether solvent were added at a mass ratio of 1:0.15:0.75:0.05:0.75. The mixture was stirred and reacted at 75°C for 12 hours. After the reaction was completed, the liquid in the reaction flask was rotary evaporated to remove the azeotrope of water and ethyl n-propyl ether. Then, the mixture was purified by column chromatography. The eluent used in the chromatography column was a mixed solvent of petroleum ether / ethyl acetate with a volume ratio of 10:1. Finally, purified epoxidized polyalphaolefins were obtained. The epoxidized polyalphaolefins specifically included: epoxidized C8 trimer, epoxidized C8 tetramer, epoxidized C10 trimer, and epoxidized C12 dimer.

[0044] The structure of the above-mentioned epoxidized polyalphaolefin was confirmed as follows:

[0045] Epoxidized C8 trimer 13 C-NMR (CDCl3, 100MHz): δ14.06 (3C, s), 22.66 (3C, s), 26.47 (2C, s), 27.75 (1C, s), 29.42 (5C, s), 29.81 (1C, s), 3 0.68(2C,s),31.80(1C,s),31.82(1C,s),31.91(1C,s),36.44(1C,s),39.43(1C,s),50.90(1C,s),59.72(1C,s);

[0046] Epoxidized C8 tetramer 13C-NMR (CDCl3, 100MHz): δ14.05(4C,s),22.64(4C,s),26.46(3C,s),27.77(1C,s),29.40(5C,s),29.82(2C,s),30.66(3 C,s),31.78(2C,s),31.82(1C,s),31.90(1C,s),35.94(1C,s),36.39(1C,s),39.43(2C,s),50.90(1C,s),59.73(1C,s);

[0047] Epoxidized C10 trimer 13 C-NMR (CDCl3, 100MHz): δ14.04(3C,s),22.65(3C,s),26.42(s),26.54(s),27.77(1C,s),29.36(4C,s),29.40(4C,s),29.43(1C,s),29.60(1C,s) ),29.64(1C,s),29.66(1C,s),30.68(2C,s),31.86(1C,s),31.91(1C,s) ,31.94(1C,s),36.42(1C,s),39.45(1C,s),50.92(1C,s),59.70(1C,s);

[0048] Epoxidized C12 dimer 13 C-NMR (CDCl3, 100MHz): δ14.05(2C,s),22.62(1C,s),22.73(1C,s),29.41(6C,s),29.55(1C,s),29.61(1C,s),29.64(2 C,s),29.66(2C,s),29.68(1C,s),29.71(1C,s),31.91(2C,s),36.35(1C,s),36.45(1C,s),50.92(1C,s),59.70(1C,s).

[0049] Example 3

[0050] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR TM55 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 15 parts by weight of epoxidized C8 trimer prepared in Example 2, 4 parts by weight of epoxy-modified silica prepared in Example 1, 5 parts by weight of calcined kaolin, 1.5 parts by weight of HDI trimer capped with Baxenden BI7992 crosslinking agent, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0051] Mixing and molding of cable insulation material: Mix the components of the above cable insulation material formula in a torque rheometer at 110°C and 90 rpm for 15 min, and then place it in a flat vulcanizing machine for hot pressing at 120°C and 15 MPa for 15 min.

[0052] Thermocuring of cable insulation material: After hot pressing, it is then thermocured at 180℃ and 15MPa for 30 minutes to obtain the corresponding composite cable insulation material.

[0053] Example 4

[0054] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR TM 60 parts by weight of EAA5200 (ExxonMobil, 15wt% acrylic acid, melt index 38g / 10min), 15 parts by weight of epoxidized C8 trimer prepared in Example 2, 6 parts by weight of epoxy-modified silica prepared in Example 1, 6 parts by weight of mica powder, 2 parts by weight of HDI trimer capped with Baxenden BI7992 crosslinking agent, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0055] Mixing, molding and thermosetting of cable insulation material: the steps are the same as in Example 3.

[0056] Example 5

[0057] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR TM55 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 20 parts by weight of epoxidized C8 tetramer prepared in Example 2, 4 parts by weight of epoxy-modified silica prepared in Example 1, 5 parts by weight of calcined kaolin, 1.5 parts by weight of HDI trimer capped with Baxenden BI7992 crosslinking agent, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0058] Mixing, molding and thermosetting of cable insulation material: the steps are the same as in Example 3.

[0059] Example 6

[0060] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR TM 60 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 20 parts by weight of the epoxy C8 tetramer prepared in Example 2, 6 parts by weight of epoxy-modified silica prepared in Example 1, 6 parts by weight of mica powder, 2 parts by weight of HDI trimer capped with Baxenden BI7992 crosslinking agent, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0061] Mixing, molding and thermosetting of cable insulation material: the steps are the same as in Example 3.

[0062] Example 7

[0063] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR TM 55 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 18 parts by weight of epoxidized C8 tetramer prepared in Example 2, 4 parts by weight of epoxy-modified silica prepared in Example 1, 5 parts by weight of calcined kaolin, 1.5 parts by weight of HDI trimer capped with Baxenden BI7992 crosslinking agent, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0064] Mixing, molding and thermosetting of cable insulation material: the steps are the same as in Example 3.

[0065] Example 8

[0066] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR tM 60 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 18 parts by weight of epoxidized C8 tetramer prepared in Example 2, 6 parts by weight of epoxy-modified silica prepared in Example 1, 6 parts by weight of mica powder, 2 parts by weight of HDI trimer capped with Baxenden BI7992 crosslinking agent, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0067] Mixing, molding and thermosetting of cable insulation material: the steps are the same as in Example 3.

[0068] Example 9

[0069] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR TM 55 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 15 parts by weight of epoxidized C12 dimer prepared in Example 2, 4 parts by weight of epoxy-modified silica prepared in Example 1, 5 parts by weight of calcined kaolin, 1.5 parts by weight of HDI trimer capped with Baxenden BI7992 crosslinking agent, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0070] Mixing, molding and thermosetting of cable insulation material: the steps are the same as in Example 3.

[0071] Example 10

[0072] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR TM60 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 15 parts by weight of epoxidized C12 dimer prepared in Example 2, 6 parts by weight of epoxy-modified silica prepared in Example 1, 6 parts by weight of mica powder, 2 parts by weight of HDI trimer capped with Baxenden BI7992 crosslinking agent, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0073] Mixing, molding and thermosetting of cable insulation material: the steps are the same as in Example 3.

[0074] Comparative Example 1

[0075] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR TM 55 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 9 parts by weight of epoxy-modified silica prepared in Example 1, 5 parts by weight of calcined kaolin, 1.5 parts by weight of crosslinking agent Baxenden BI7992-terminated HDI trimer, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0076] Mixing, molding and thermosetting of cable insulation material: the steps are the same as in Example 3.

[0077] Comparative Example 2

[0078] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR TM 55 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 20 parts by weight of the epoxidized C8 trimer prepared in Example 2, 5 parts by weight of calcined kaolin, 2 parts by weight of HDI trimer capped with Baxenden BI7992 crosslinking agent, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0079] Mixing, molding and thermosetting of cable insulation material: the steps are the same as in Example 3.

[0080] Comparative Example 3

[0081] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR TM 55 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 15 parts by weight of the epoxidized C8 trimer prepared in Example 2, 4 parts by weight of the epoxy-modified silica prepared in Example 1, 5 parts by weight of calcined kaolin, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0082] Mixing, molding and thermosetting of cable insulation material: the steps are the same as in Example 3.

[0083] Comparative Example 4

[0084] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR tM 55 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 10 parts by weight of epoxidized soybean oil (Jiangsu Pulesi), 4 parts by weight of epoxy-modified silica prepared in Example 1, 5 parts by weight of calcined kaolin, 1.5 parts by weight of crosslinking agent Baxenden BI7992-terminated HDI trimer, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0085] Mixing, molding and thermosetting of cable insulation material: the steps are the same as in Example 3.

[0086] Comparative Example 5

[0087] Cable insulation material formulation: 100 parts by weight of linear low-density polyethylene (LLDPE) (Yanshan Petrochemical LD100BW, melt index 2.0 g / 10 min), ESCOR TM55 parts by weight of EAA5200 (ExxonMobil, 15 wt% acrylic acid), 15 parts by weight of epoxidized C8 trimer prepared in Example 2, 4 parts by weight of epoxy-modified silica prepared in Example 1, 5 parts by weight of calcined kaolin, 1.5 parts by weight of TDI prepolymer capped with Baxenden BI7641 crosslinking agent, 1.5 parts by weight of 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), 1 part by weight of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), and 0.2 parts by weight of stannous octoate.

[0088] Mechanical properties were tested in the performance testing section. Tensile strength and elongation at break were measured for cable insulation samples from Examples 3-10 and Comparative Examples 1-5. Tensile strength and elongation at break were also measured after heat aging, as well as the impact embrittlement temperature. Tensile strength and elongation at break were tested according to the method in JB / T 10437. The heat aging test involved aging at 150℃ for 240 hours before testing tensile strength and elongation at break. Tensile strength and elongation at break were measured using a WDW-10C universal testing machine at a constant tensile speed of 250 mm / min. The impact embrittlement temperature test was conducted according to the method in GB / T 5740, with the temperature at which the sample breakage rate reached 50% defined as the embrittlement temperature T. 50 And record it.

[0089] Insulation performance: The breakdown field strength of different samples at 80℃ was tested using the Weibull breakdown field strength test. The specific test method was to turn on the DC power supply and increase the voltage at a rate of 0.5kV / mm until the cable insulation sample broke down, and record the breakdown voltage value displayed on the oscilloscope.

[0090] Because the test results of breakdown field strength are highly random, the breakdown voltage of each sample was tested 15 times and the breakdown field strength data was analyzed using the Weibull probability distribution. The cumulative distribution function expression of the breakdown field strength is shown in the following equation (1).

[0091] P(E b )=1-exp[(E b / E0) β (1)

[0092] In the formula, P(E) b The electric field strength is E. b The probability of breakdown at time E b E0 is the electric field strength at the point of breakdown, E0 is the scale parameter used to characterize the electric field strength corresponding to a breakdown probability of 63.2%, and β is the shape parameter used to characterize the dispersion of the breakdown field strength.

[0093] The electric field strength of the cable insulation samples of Examples 3-10 and Comparative Examples 1-5 was tested respectively when the breakdown probability was 63.2% at 80°C.

[0094] The test results are listed in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] The data analysis in Table 1 shows that the cable insulation samples of Examples 3-10 can maintain a more balanced mechanical strength, toughness and aging resistance, with tensile strength not less than 18MPa, elongation at break greater than 300%, embrittlement temperature less than -35℃, and breakdown field strength greater than 300kV / mm.

[0099] Epoxidized polyalphaolefin oligomers react with carboxyl groups in ethylene-acrylic acid copolymers via epoxy groups. The large, long side chains in these oligomers toughen the material and reduce the crosslinking density of the cured system. In Comparative Example 1, without the addition of epoxidized polyalphaolefin oligomers, the elongation at break of the corresponding cable insulation sample significantly decreased, while the low-temperature embrittlement temperature increased to -10℃. In Comparative Example 4, epoxidized soybean oil was used instead of epoxidized polyalphaolefin oligomers. Each molecular chain contained multiple epoxy groups, leading to excessive crosslinking in the cured system, which was detrimental to improving elongation at break and low-temperature toughness. Epoxy-modified silica introduces carbon chains and epoxy groups onto the surface of silica particles, improving compatibility with LLDPE and ethylene-acrylic acid copolymers. The epoxy groups can also react with carboxyl groups in the ethylene-acrylic acid copolymer, thus acting as crosslinking sites in the crosslinking reaction of the cured system, thereby improving the mechanical strength and aging resistance of the cable insulation material. In Comparative Example 2, without the addition of epoxy-modified silica, the tensile strength and mechanical properties after thermal aging of the corresponding cable insulation sample significantly decreased.

[0100] The HDI trimer used as a capping agent is 3,5-dimethylpyrazole and diethylene glycol monomethyl ether. The unsealing temperature is 120-150℃. The preceding epoxidized polyalphaolefin oligomer and epoxy-modified silica undergo a ring-opening reaction between the epoxy groups and the carboxyl groups in the ethylene-acrylic acid copolymer to form ester and hydroxyl groups. The unsealed isocyanate then reacts with the newly formed hydroxyl groups. Because hydroxyl groups, like carboxyl groups, are strongly polar groups containing active hydrogen, if only epoxy groups react with carboxyl groups, a high content of hydroxyl groups is generated simultaneously with the formation of ester groups. This hydroxyl content leads to increased dielectric loss and is detrimental to the breakdown strength of the insulation material. Therefore, this application adds a capping HDI trimer as a crosslinking agent to react with the hydroxyl groups, thereby reducing the hydroxyl content of the cable insulation material and improving insulation performance. In Comparative Example 3, without the addition of the capping HDI trimer, the tensile strength and breakdown field strength of the corresponding cable insulation sample decreased. Comparative Example 5 used a 3,5-dimethylpyrazole-terminated TDI prepolymer as a crosslinking agent. The final cable insulation curing system had higher tensile strength, but significantly lower elongation at break and a certain degree of decrease in low-temperature toughness. This is because the aliphatic isocyanate curing agent does not contain rigid benzene rings, and the cured cable insulation has better flexibility and low-temperature impact resistance.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite cable insulation material, characterized in that, Composite cable insulation materials include: Linear low-density polyethylene, acrylic grafted material, epoxidized hydrocarbons, epoxy-modified silica, blocked isocyanate and antioxidants; The melt index of linear low-density polyethylene ranges from 1.0 to 3.0 g / 10 min. The acrylic grafting material is selected from one or more combinations of ethylene-acrylic acid copolymer, propylene-acrylic acid copolymer and ethylene-octene-acrylic acid copolymer; The melt flow index of the acrylic grafted material ranges from 1 to 50 g / 10 min. The acrylic acid content in the acrylic grafting material is 5-20%; The general structural formula of epoxide hydrocarbons is: Among them, R1 and R2 of the general formula of epoxide hydrocarbons are selected from straight-chain aliphatic hydrocarbons, branched non-cyclic aliphatic hydrocarbons or cyclic aliphatic hydrocarbons with 4-50 carbon atoms. Epoxy-modified silica is prepared by the sol-gel method, and its raw materials include: organic esters of orthosilicate and silane coupling agents containing epoxy groups; Blocked isocyanates are isocyanates in which the isocyanate group (-NCO) is blocked using a blocking agent. Blocked isocyanates are selected from aliphatic isocyanate biuret or trimers. The blocking agent is selected from one or more of phenols, pyrazoles, oximes and alcohols, and its dissociation temperature is ≥120℃; The antioxidant is selected from hindered phenolic antioxidants; The composite cable insulation material is prepared from the following raw materials in parts by weight: 90-110 parts by weight of linear low-density polyethylene, 50-70 parts by weight of acrylic grafting material, 5-25 parts by weight of epoxidized hydrocarbons, 1-10 parts by weight of epoxy-modified silica, 0.5-3 parts by weight of blocked isocyanate, and 0.5-3 parts by weight of antioxidant.

2. The composite cable insulation material according to claim 1, characterized in that, The specific steps for preparing epoxy-modified silica by the sol-gel method include: dissolving an organic ester of orthosilicate and a silane coupling agent containing an epoxy group in an alcohol solvent, adjusting the pH of the system to 3.5-4.5, reacting at a reaction temperature of 40-80℃ for 10-40 hours, evaporating the alcohol solvent to obtain a gel, drying the gel, crushing it, and sieving it to obtain epoxy-modified silica.

3. The composite cable insulation material according to claim 2, characterized in that, The alcohol solvent is selected from methanol, ethanol, n-propanol, or a mixture of isopropanol and water; And / or, the gel is dried at 70-100°C.

4. The composite cable insulation material according to claim 1, characterized in that, The composite cable insulation material includes an inert filler, which is selected from one or more of the following: magnesium hydroxide, aluminum hydroxide, wollastonite, mica powder, talc powder, kaolin, calcium carbonate, carbon black and silicon dioxide. The inert filler is milled to an average particle size of no more than 10 μm before being added to the composite cable insulation material.

5. The composite cable insulation material according to claim 1, characterized in that, The composite cable insulation material includes ultraviolet absorbers, which are selected from benzophenone compounds.

6. The composite cable insulation material according to claim 1, characterized in that, The composite cable insulation material includes a catalyst, which is selected from any one of organotin compounds, organobismuth compounds, or organozinc compounds.

7. The composite cable insulation material according to claim 1, characterized in that, The composite cable insulation material is prepared from the following raw materials in parts by weight: 90-110 parts by weight of linear low-density polyethylene, 50-70 parts by weight of acrylic grafting material, 5-25 parts by weight of epoxidized hydrocarbons, 1-10 parts by weight of epoxy-modified silica, 0.5-3 parts by weight of blocked isocyanate, 0.5-3 parts by weight of antioxidant, 1-20 parts by weight of inert filler, 0.5-3 parts by weight of ultraviolet absorber, and 0.1-1 parts by weight of catalyst.

8. A method for molding and curing the composite cable insulation material as described in any one of claims 1-7, characterized in that, First, the cable insulation material is mixed, hot-pressed and molded, and then thermo-cured to obtain a cured composite cable insulation material.

9. The molding and curing method according to claim 8, characterized in that, The specific steps for molding and curing include: S1. Mix the components of the cable insulation material formula described above at 90-120℃ and 10-100 rpm. S2. After mixing, hot press the mixture at 90-120℃ and 1-20MPa. S3. After hot pressing, it is thermocured at 160-200℃ and 1-20MPa pressure.

10. A cured composite cable insulation material, characterized in that, The composite cable insulation material according to any one of claims 1-7 is prepared by the molding and curing method according to any one of claims 8-9.

11. An application characterized in that, The use of the composite cable insulation cured material as described in any one of claims 1-7 as a material in the manufacture of cables.

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