Reversible cross-linked polyethylene, preparation method thereof and application of reversible cross-linked polyethylene in cable material

Abstract

The invention belongs to the technical field of polyolefin cable materials, and particularly relates to a reversible cross-linked polyethylene composition, a reversible cross-linked polyethylene cable material, regenerated reversible cross-linked polyethylene granules, a regenerated reversible cross-linked polyethylene cable material and a preparation method and application thereof. Amino-containing dihydric alcohol is used as a modifying agent and firstly reacts with maleic anhydride grafted polyethylene, PE-g-MAH-OH containing excessive amino-containing dihydric alcohol is obtained through ring opening-ring closing reaction, and PE-g-MAH-OH serving as a key component is matched with polyethylene, fumed silica and an aliphatic amine structure control agent to obtain the reversible crosslinked polyethylene composition. The reversible cross-linked polyolefin cable material prepared by melting, mixing, molding and curing has better mechanical properties, high-pressure oil resistance and reprocessability.

Description

Technical Field

[0001] This application belongs to the field of polyolefin cable material technology, and specifically relates to a reversible cross-linked polyethylene composition, a reversible cross-linked polyethylene cable material, recycled reversible cross-linked polyethylene granules, recycled reversible cross-linked polyethylene cable material, and their preparation methods and applications. Background Technology

[0002] Polyethylene (PE), as the most commonly used material for wires and cables, possesses many excellent properties. However, its poor heat resistance, weather resistance, and relatively low mechanical properties limit its application. A common method to improve the mechanical properties of PE cable materials is to chemically cross-link them, thereby improving the dimensional stability and creep resistance of the cable material. Chemical cross-linking binds PE molecular chains together through irreversible chemical bonds, transforming it from a linear structure into a stable three-dimensional network structure. However, it is currently difficult to specifically disrupt or alter the cross-linked structure formed by irreversible chemical bonds in the polymer. Once a stable three-dimensional network structure is formed through cross-linking, it is difficult to transform it back into a linear structure. Therefore, cross-linked PE cable materials, after molding and curing, lose their recyclability and reprocessability.

[0003] Because waste cross-linked polyethylene (XLPE) cable material is difficult to melt when heated and difficult to recycle, it faces challenges in recycling and has a low reuse rate. Directly landfilling or open-air burning of cable material not only reduces resource utilization but also causes serious environmental pollution, which is inconsistent with the current concept of sustainable development. Therefore, how to scientifically and effectively recycle XLPE cable material is a hot technical issue of concern to both academia and industry.

[0004] Currently, there are two main technical routes for reversibly crosslinked polyethylene cable materials. One is to directly use polar monomers to modify polyethylene and then physically blend it with polyethylene, such as blending ethylene-vinyl acetate copolymer with polyethylene or ethylene-vinyl alcohol copolymer with polyethylene. The second is to first graft 3-amino-1,2,4-triazole and 2-ureido-4[1H]pyrimidinone (Upy) with polar monomer-modified polyethylene, and then blend them with the polyethylene matrix. Both technical routes produce recyclable cable insulation materials, but they both suffer from insufficient performance, particularly uneven distribution of internal hydrogen bonds, which easily leads to insufficient crosslinking, resulting in poor mechanical properties and oil resistance. Among them, the conventional method for introducing 2-ureido-4[1H]pyrimidinone (Upy) into crosslinkable polyethylene compositions is to first synthesize Upy-NCO using 6-methylisocytosine and hexamethylene diisocyanate. However, the thermal stability of its urea bond is poor, and it is easy to deseal at high temperatures during the polyethylene melting and processing to obtain highly active NCO groups, which leads to the reaction of NCO with hydroxyl, amino and other groups to form irreversible crosslinked polyethylene. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application proposes a technical solution that uses an excess of amino-containing diols as modifiers. These diols are first reacted with maleic anhydride-grafted polyethylene, and then combined with ultra-high molecular weight polyethylene, Upy-NCO, and structure control agents to form a reversible cross-linked polyethylene composition. After melt mixing, molding, and curing, a reversible cross-linked polyethylene cable material is obtained. This results in a recyclable, reprocessable, high-mechanical-performance, and high-voltage oil-resistant reversible cross-linked polyethylene cable material.

[0006] In a first aspect, a reversible crosslinked polyethylene composition comprises: a reaction product of an amino-containing diol and maleic anhydride-grafted polyethylene, a polyethylene resin, fumed silica, Upy-NCO, and a structure control agent.

[0007] The general structural formula of amino-containing diols is: or R1 is selected from alkyl groups with 1 to 6 carbon atoms; R2 and R3 may be the same or different and are selected from H or alkyl groups with 1 to 4 carbon atoms.

[0008] Preferably, R1 is selected from alkyl groups having 1 to 4 carbon atoms;

[0009] Preferably, the hydroxyl group of the amino-containing diol is selected from primary or secondary hydroxyl groups;

[0010] Preferably, the amino group of the amino-containing diol is selected from amino-NH2 or imino-NH-;

[0011] The maleic anhydride-grafted polyethylene is selected from maleic anhydride-grafted polyethylene with a maleic anhydride grafting rate ranging from 0.5 to 1 wt%.

[0012] The specific preparation method of the reaction product of amino-containing diol and maleic anhydride grafted polyethylene is as follows: the amino-containing diol is reacted with maleic anhydride grafted polyethylene at a temperature of 130-160℃, and then the temperature is lowered to 40-80℃ and the solvent is removed by vacuum distillation; wherein, the number of molar amino groups in the amino-containing diol is greater than the number of molar anhydride groups in the maleic anhydride grafted polyethylene.

[0013] Preferably, the amino-containing diol is selected from one or more combinations of 2-amino-1,3-propanediol, 3-amino-1,2-propanediol, diethanolamine and diisopropanolamine;

[0014] The polyethylene resin is selected from one or more combinations of ultra-high molecular weight polyethylene, low-density polyethylene, high-density polyethylene and linear low-density polyethylene;

[0015] Preferably, the reversible crosslinked polyethylene composition further includes an antioxidant, said antioxidant being selected from one or a combination of hindered phenolic antioxidants and phosphite antioxidants;

[0016] Preferably, the antioxidant is selected from a combination of hindered phenolic antioxidants and phosphite antioxidants;

[0017] Preferably, the hindered phenolic antioxidant is selected from antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] ester);

[0018] Preferably, the phosphite antioxidant is selected from antioxidant 168 (tris[2,4-di-tert-butylphenyl]phosphite);

[0019] Preferably, the reversible crosslinked polyethylene composition further includes a lubricant selected from polyethylene wax;

[0020] The chemical structural formula of Upy-NCO is:

[0021] The structure control agent is selected from aliphatic amines containing 10 to 20 carbon atoms, wherein the aliphatic chain can be linear, branched, or cyclic. The structure control agent is used to capture isocyanate groups generated during Upy-NCO descaling.

[0022] Preferably, the structure control agent is selected from octadecylamine.

[0023] Further, by weight, the reversible crosslinked polyethylene composition comprises: 90-110 parts by weight of the reaction product of amino-containing diol and maleic anhydride grafted polyethylene, 140-160 parts by weight of polyethylene resin, 10-20 parts by weight of fumed silica, 10-25 parts by weight of Upy-NCO, and 5-20 parts by weight of structure control agent.

[0024] The molar ratio of the hydroxyl group in the product of the reaction between an amino-containing diol and maleic anhydride-grafted polyethylene to the isocyanate group in Upy-NCO is 100:(80-100).

[0025] Preferably, the reversible crosslinked polyethylene composition comprises, by weight, 90-110 parts by weight of the reaction product of amino-containing diol and maleic anhydride grafted polyethylene, 140-160 parts by weight of polyethylene resin, 10-20 parts by weight of fumed silica, 10-25 parts by weight of Upy-NCO, 5-20 parts by weight of structure control agent, 1-5 parts by weight of antioxidant, and 1-5 parts by weight of lubricant.

[0026] Secondly, the application of the above-described reversible cross-linked polyethylene composition in reversible cross-linked polyolefin cable materials.

[0027] Thirdly, a reversible cross-linked polyethylene cable material is obtained by mixing, extruding, molding and curing the reversible cross-linked polyethylene composition described above.

[0028] Fourthly, a method for preparing reversible cross-linked polyethylene cable material specifically includes the following steps:

[0029] S1. Add and mix the reaction product of amino-containing diol and maleic anhydride grafted polyethylene, Upy-NCO, fumed silica, antioxidant and lubricant according to the formula amount, and carry out reactive melt blending.

[0030] S2. Add octadecylamine, a structure control agent, and polyethylene resin to the mixture described in step S1, and obtain reversible cross-linked polyethylene granules through melt mixing, extrusion, cooling, and granulation.

[0031] S3. Add the reversible cross-linked polyethylene granules obtained in step S2 to a cable extruder for extrusion molding, and then cure them to obtain reversible cross-linked polyethylene cable material.

[0032] Preferably, the reactive melt blending conditions in step S1 are a rotation speed of 50-150 rpm and a temperature of 100-140°C.

[0033] Preferably, the melting and mixing conditions in step S2 are a rotation speed of 50-150 rpm and a temperature of 135-160℃;

[0034] Preferably, the extrusion molding temperature in step S3 is 135-160℃;

[0035] Preferably, the curing temperature in step S3 is 150-180℃.

[0036] Fifthly, a recycled reversible cross-linked polyethylene granule is obtained by crushing the above-mentioned reversible cross-linked polyethylene cable material using a crusher, mixing and stirring at a temperature of 135-160℃, and then extruding and granulating it.

[0037] Sixthly, a recycled reversible cross-linked cable material is obtained by extrusion molding and curing steps from the recycled reversible cross-linked polyethylene granules described above;

[0038] The extrusion molding temperature is 135-160℃; the curing temperature is 150-180℃.

[0039] The seventh aspect concerns the application of the above-described reversible cross-linked polyethylene cable material and / or the above-described recycled reversible cross-linked polyethylene cable material as materials in the manufacture of cables.

[0040] The beneficial effects of this invention are as follows: Using an amino-containing diol as a modifier, it first reacts with maleic anhydride-grafted polyethylene, and through a ring-opening-ring-closing reaction, PE-g-MAH-OH containing an excess of amino-containing diol is obtained. This PE-g-MAH-OH is then used as a key component in combination with polyethylene, fumed silica, and a fatty amine structure control agent to obtain a reversible cross-linked polyethylene composition. The reversible cross-linked polyolefin cable material prepared after melt mixing, molding, and curing exhibits better mechanical properties, high-voltage oil resistance, and reprocessability. The addition of fumed silica to the composition allows its surface Si-OH to participate in reversible hydrogen bond cross-linking. The addition of a fatty amine as a structure control agent allows the NCO released from Upy-NCO at high temperatures to preferentially react with the amino groups, preventing irreversible cross-linking and the formation of a three-dimensional network structure that would render the material unprocessable. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 High-temperature 1H NMR spectra of CMG5094 maleic anhydride modified linear low-density polyethylene, the product prepared in Example 1, and the molten mixture obtained in step S1 of Example 4 ( 1 H-NMR, test temperature 120℃, solvent: deuterated tetrachloroethane 1,1,2,2-tetrachloroethane-d2), wherein: (a) CMG5094 maleic anhydride modified linear low-density polyethylene; (b) product prepared in Example 1; (c) molten mixture of product prepared in Example 1 and Upy-NCO; d) hydroxyl marker peak; e) 6-methylisocytosine marker peak; f) methyl marker peak in 6-methylisocytosine; g) marker peak of solvent deuterated tetrachloroethane.

[0043] Figure 2 The ATR-FTIR test results of the reversible cross-linked polyethylene cable materials prepared for Upy-NCO, Example 4 and Example 5, wherein (a) Upy-NCO; (b) the molten mixture obtained by step S1 of Example 4; and (c) the molten mixture obtained by step S1 of Example 5.

[0044] Figure 3Differential scanning calorimetry (DSC) results for CMG5094 maleic anhydride modified linear low-density polyethylene, the product prepared in Example 1, and the molten mixture obtained in step S1 of Example 4, including the peak temperature (°C) of the endothermic peak and the area (J / g) obtained by integrating the endothermic peak, wherein (a) is CMG5094 maleic anhydride modified linear low-density polyethylene; (b) is the product prepared in Example 1; and (c) is the molten mixture of the product prepared in Example 1 and Upy-NCO. Detailed Implementation

[0045] 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.

[0046] 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.

[0047] 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.

[0048] The preparation of Upy-NCO, wherein the structural formula of Upy-NCO is shown below:

[0049] .

[0050] Referring to the literature DOI:10.14133 / j.cnki.1008-9357.20200608002, Upy-NCO monomer was synthesized using 2-amino-4-hydroxy-6-methylpyrimidine (MIC) and hexamethylene diisocyanate (HDI) as raw materials, where n(HDI):n(MIC) = 6:1, with excess HDI containing isocyanate groups, while retaining the isocyanate group (NCO) at one end to not participate in the reaction, thus obtaining a white solid powder, Upy-NCO.

[0051] The structure of Upy-NCO is characterized as follows: 1H-NMR (CDCl3, 400 MHz): δ1.26-1.66 (6H, 1.35(tt, J = 7.00, 7.00 Hz), 1.41 (tt, J = 7.37, 7.00 Hz), 1.58 (tt, J = 7.23,7.00 Hz)), 1.77 (2H, tt, J = 7.37, 6.93 Hz), 2.46 (3H, s), 3.18 (2H, t, J =7.23 Hz), 4.09 (2H, t, J = 6.93 Hz), 5.84 (1H, s).

[0052] 13 C-NMR (CDCl3, 400 MHz): δ 18.8, 26.8, 27.3, 29.5, 31.4, 40.0, 43.5, 113.2, 122.5, 150.4, 155.7, 157.8, 168.4.

[0053] Therefore, the chemical reaction formula for the synthesis of Upy-NCO is determined as follows:

[0054]

[0055] Example 1

[0056] Modification reaction of PE-g-MAH: 200g of maleic anhydride-modified linear low-density polyethylene (CMG5094, a readily soluble polymer with a maleic anhydride grafting rate of 0.5-1.0 wt%) was dissolved in 100mL of xylene and added to a reaction flask. Then, 5.47g (0.06mol) of 2-amino-1,3-propanediol was added. The mixture was heated to 140℃ for 4 hours under stirring and nitrogen protection to allow the amino group to undergo a ring-opening and ring-closing reaction with the anhydride, thus completing the hydroxyl grafting reaction. After the reaction, the solvent xylene was removed by vacuum distillation at 60℃ and 0.05 bar. The resulting PE-g-MAH-OH and excess 2-amino-1,3-propanediol were then vacuum dried at 40℃ for 24 hours for later use. Based on the molar amount of 2-amino-1,3-propanediol, the hydroxyl content of the product prepared in Example 1 (including PE-g-MAH-OH and excess 2-amino-1,3-propanediol) is 58.40 mmol / 100g.

[0057] Example 2

[0058] For the modification reaction of PE-g-MAH-OH, the 2-amino-1,3-propanediol in Example 1 was replaced with 4.56 g (0.05 mol) of 3-amino-1,2-propanediol, and the remaining steps were the same as in Example 1. Based on the molar amount of 3-amino-1,2-propanediol, the hydroxyl content of the product prepared in Example 2 (including PE-g-MAH-OH and excess 3-amino-1,2-propanediol) was 48.89 mmol / 100g.

[0059] Example 3

[0060] For the modification reaction of PE-g-MAH-OH, the 2-amino-1,3-propanediol in Example 1 was replaced with 10.66 g (0.08 mol) of diisopropanolamine, and the remaining steps were the same as in Example 1. Based on the molar amount of diisopropanolamine added, the hydroxyl content of the product prepared in Example 3 (including PE-g-MAH-OH and excess diisopropanolamine) was 75.95 mmol / 100 g.

[0061] Example 4

[0062] The composition of the product is as follows: 145 parts by weight of ultra-high molecular weight polyethylene YUHWA HIDEN U050-F (Daihan Oil & Chemical Co., Ltd., melt temperature Tm=135℃, average molecular weight 5.5×106 g / mol); 100 parts by weight of the product prepared in Example 1; 14.6 parts by weight of Upy-NCO; 4 parts by weight of antioxidant 1010 pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; 3 parts by weight of antioxidant 168 tris(2,4-di-tert-butyl)phenyl phosphite; 15 parts by weight of fumed silica AEROSIL300 (Evonik Chemicals); 3 parts by weight of lubricant polyethylene wax; and 10 parts by weight of structure control agent octadecylamine. The molar ratio of the hydroxyl groups to the isocyanate groups of the product prepared in Example 1 is 100:85.58.

[0063] Example 5

[0064] The composition includes 155 parts by weight of ultra-high molecular weight polyethylene YUHWA HIDEN U050-F, 100 parts by weight of the product prepared in Example 1, 17.1 parts by weight of Upy-NCO, 4 parts by weight of antioxidant 1010 pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3 parts by weight of antioxidant 168 tris(2,4-di-tert-butyl)phenyl phosphite, 15 parts by weight of fumed silica AEROSIL 300 (Evonik Chemicals), 3 parts by weight of lubricant polyethylene wax, and 10 parts by weight of structure control agent octadecylamine. The molar ratio of the hydroxyl groups to the isocyanate groups of the product prepared in Example 1 is 100:99.82.

[0065] Example 6

[0066] The composition includes 145 parts by weight of ultra-high molecular weight polyethylene YUHWA HIDEN U050-F, 100 parts by weight of the product prepared in Example 2, 13 parts by weight of Upy-NCO, 4 parts by weight of antioxidant 1010 pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3 parts by weight of antioxidant 168 tris(2,4-di-tert-butyl)phenyl phosphite, 15 parts by weight of fumed silica AEROSIL 300 (Evonik Chemicals), 3 parts by weight of lubricant polyethylene wax, and 10 parts by weight of structure control agent octadecylamine. The molar ratio of the hydroxyl groups to the isocyanate groups of the product prepared in Example 2 is 100:90.63.

[0067] Example 7

[0068] The composition includes 155 parts by weight of ultra-high molecular weight polyethylene YUHWA HIDEN U050-F, 100 parts by weight of the product prepared in Example 2, 14.3 parts by weight of Upy-NCO, 4 parts by weight of antioxidant 1010 pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3 parts by weight of antioxidant 168 tris(2,4-di-tert-butyl)phenyl phosphite, 15 parts by weight of fumed silica AEROSIL 300 (Evonik Chemicals), 3 parts by weight of lubricant polyethylene wax, and 10 parts by weight of structure control agent octadecylamine. The molar ratio of the hydroxyl groups to the isocyanate groups of the product prepared in Example 2 is 100:99.71.

[0069] Example 8

[0070] The composition includes 145 parts by weight of ultra-high molecular weight polyethylene YUHWA HIDEN U050-F, 100 parts by weight of the product prepared in Example 3, 20 parts by weight of Upy-NCO, 4 parts by weight of antioxidant 1010 pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3 parts by weight of antioxidant 168 tris(2,4-di-tert-butyl)phenyl phosphite, 15 parts by weight of fumed silica AEROSIL 300 (Evonik Chemicals), 3 parts by weight of lubricant polyethylene wax, and 12 parts by weight of structure control agent octadecylamine. The molar ratio of the hydroxyl groups to the isocyanate groups of the product prepared in Example 3 is 100:89.77.

[0071] Example 9

[0072] The composition includes 155 parts by weight of ultra-high molecular weight polyethylene YUHWA HIDEN U050-F, 100 parts by weight of the product prepared in Example 3, 22.2 parts by weight of Upy-NCO, 4 parts by weight of antioxidant 1010 pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3 parts by weight of antioxidant 168 tris(2,4-di-tert-butyl)phenyl phosphite, 15 parts by weight of fumed silica AEROSIL 300 (Evonik Chemicals), 3 parts by weight of lubricant polyethylene wax, and 14 parts by weight of structure control agent octadecylamine. The molar ratio of the hydroxyl groups to the isocyanate groups of the product prepared in Example 3 is 100:99.65.

[0073] Comparative Example 1

[0074] The modification reaction of PE-g-MAH-OH was carried out in the same manner as in Example 1, except that after the reaction was completed, the solvent xylene was removed by vacuum distillation at 60°C and 0.05 bar. The remaining mixture was then washed with acetone, filtered, and the filter residue was vacuum dried at 40°C for 24 hours for later use.

[0075] Comparative Example 2

[0076] The composition includes 155 parts by weight of ultra-high molecular weight polyethylene YUHWA HIDEN U050-F, 100 parts by weight of PE-g-MAH-OH prepared in Comparative Example 1, 14.6 parts by weight of Upy-NCO, 4 parts by weight of antioxidant 1010 pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3 parts by weight of antioxidant 168 tris(2,4-di-tert-butyl)phosphite, 15 parts by weight of fumed silica AEROSIL300 (Evonik Chemicals), 3 parts by weight of lubricant polyethylene wax, and 10 parts by weight of structure control agent octadecylamine.

[0077] Comparative Example 3

[0078] The composition comprises: 145 parts by weight of ultra-high molecular weight polyethylene YUHWA HIDEN U050-F, 100 parts by weight of the product prepared in Example 1, 14.6 parts by weight of Upy-NCO, 4 parts by weight of antioxidant 1010 pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3 parts by weight of antioxidant 168 tris(2,4-di-tert-butyl)phenyl phosphite, 3 parts by weight of lubricant polyethylene wax, and 10 parts by weight of structure control agent octadecylamine. The molar ratio of the hydroxyl groups to the isocyanate groups of the product prepared in Example 1 is 100:85.58.

[0079] Comparative Example 4

[0080] The composition includes 145 parts by weight of ultra-high molecular weight polyethylene YUHWA HIDEN U050-F, 100 parts by weight of the product prepared in Example 1, 14.6 parts by weight of Upy-NCO, 4 parts by weight of antioxidant 1010 pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3 parts by weight of antioxidant 168 tris(2,4-di-tert-butyl)phenyl phosphite, 15 parts by weight of fumed silica AEROSIL300 (Evonik Chemicals), and 3 parts by weight of lubricant polyethylene wax. The molar ratio of the hydroxyl groups to the isocyanate groups of the product prepared in Example 1 is 100:85.58.

[0081] Based on the reversible cross-linked polyethylene compositions of Examples 4-9 and Comparative Examples 2-4, the corresponding reversible cross-linked cable materials were prepared by the following steps.

[0082] S1. Under the conditions of 120 r / min and 120 °C, the products prepared in Examples 1-3, Upy-NCO, fumed silica, antioxidant 1010, antioxidant 168 and lubricant polyethylene wax are added and mixed according to the formula amount, and the mixture is stirred in a reactive melt blending for 30 minutes to obtain a mixture.

[0083] S2. Add the structure control agent octadecylamine and ultra-high molecular weight polyethylene YUHWAHIDEN U050-F to the mixture described in step S1. Mix and stir for 10 minutes at a speed of 120 r / min and a temperature of 150°C. After melt mixing, extrusion, cooling and granulation, reversible cross-linked polyethylene granules are obtained.

[0084] S3. Add the reversible cross-linked polyethylene granules obtained in step S2 to a cable extruder for extrusion molding. The extrusion molding temperature is 150℃. The extruded cable is then cured at a temperature of 150-160℃ to obtain reversible cross-linked polyethylene cable material.

[0085] Comparative Example 2 used the modified PE-g-MAH-OH prepared in Comparative Example 1, and the reactive monomers in PE-g-MAH-OH were dissolved and separated with acetone. Comparative Example 3 did not add fumed silica, and Comparative Example 4 did not add the structure control agent octadecylamine.

[0086] The performance tests of the reversible cross-linked polyethylene cable materials prepared in Examples 4-9 and Comparative Examples 2-4 are as follows.

[0087] Mechanical properties: The tensile strength and elongation at break of the reversible cross-linked polyethylene cable material samples were tested, as well as the retention rate of tensile strength and elongation at break after oil immersion, acid immersion, and alkali immersion. Tensile strength and elongation at break were tested according to the test methods in JB / T 10437 using a WDW-10C universal testing machine. The tensile speed during the test was 50 mm / min and remained constant.

[0088] Mechanical property testing after crushing and reshaping: The processed reversible cross-linked polyethylene cable material was crushed into smaller blocks in a crusher. These blocks were collected and mixed and stirred at 140°C for 10 minutes. The reversible cross-linked polyethylene granules were obtained by extrusion and granulation according to the above steps. Among them, the reversible cross-linked polyethylene cable materials of Examples 4-9 and Comparative Example 3 can be remelted and molded after recycling and crushing to obtain regenerated reversible cross-linked polyethylene granules. The reversible cross-linked polyethylene cable material of Comparative Example 2 cannot be remelted and molded after recycling and crushing.

[0089] The oil immersion resistance test conditions are as follows: The reversible cross-linked polyethylene cable material sample to be tested is placed in a high-temperature, high-pressure autoclave. Kerosene is added and the autoclave is sealed. High-purity nitrogen is then introduced to remove oxygen for 2 hours, and the temperature is raised to 80°C. CO2 and nitrogen gases are then introduced, and the total pressure inside the autoclave is set to 4 MPa, with a CO2 partial pressure of 2.5 MPa. The experiment is conducted for 240 hours under these temperature and pressure conditions. After the experiment, the elongation at break and the retention rate of tensile strength of the cable material sample are determined according to the above method.

[0090] Abrasion resistance: Mass wear test was conducted according to the method of GB / T 3960-2016, and the friction loss mass of the corresponding cable material sample was calculated.

[0091] The test results are listed in Table 1.

[0092] Table 1

[0093]

[0094] Analyzing the data in Table 1, in Comparative Example 1, during the preparation of PE-g-MAH-OH, acetone was used to dissolve and wash the unreacted 2-amino-1,3-propanediol, which was not added to the reversible cross-linked polyethylene composition. This unreacted small molecule can react with Upy-NCO in subsequent mixing steps to form a multi-branched Upy-NCO structure, thereby increasing the hydrogen bonding sites in the reversible cross-linked polyethylene. Therefore, the PE-g-MAH-OH used in Comparative Example 2 lacks unreacted 2-amino-1,3-propanediol, resulting in generally lower tensile strength, retention rate of mechanical properties after remolding, and retention rate of mechanical properties after pressure immersion in oil.

[0095] Comparative Example 3 did not use fumed silica, and the retention rates of tensile strength, tensile strength after pressure immersion in oil, and elongation at break of the corresponding cable material were relatively low. Fumed silica has Si-OH on its surface, which can form hydrogen bonds with Upy grafted to the molecular chain segment. The lack of fumed silica reduces the hydrogen bond density inside the reversible cross-linked polyethylene cable material, thereby leading to a decrease in mechanical strength and pressure resistance to oil.

[0096] Comparative Example 4 did not use aliphatic amines as structure control agents. At high temperatures, the -NH-(C=O)-NH in Upy-NCO was easily deblocked to form -NH2 and -NCO. The -NCO then crosslinked with PE-g-MAH-OH, resulting in an irreversible curing reaction. Although this improved the tensile strength of the cable material and the retention rate of mechanical properties after pressure impregnation, it led to a significant decrease in the elongation at break. Moreover, the cable material could not be crushed and reshaped after curing.

[0097] The reversible cross-linked polyethylene cable materials in Examples 4-9 have a tensile strength of not less than 22 MPa, an elongation at break of not less than 660%, a mechanical property retention rate of not less than 65% after crushing and remolding, and a mechanical property retention rate of not less than 89% after pressure impregnation. They can balance strength and flexibility, as well as the mechanical property retention rate after recycling, crushing and remolding, and pressure impregnation. They achieve dynamic transformation between the three-dimensional network structure and linear structure of polymer molecular chains. The prepared polyethylene cable materials have both excellent mechanical properties and excellent high-pressure impregnation effect, as well as ideal thermoplastic processability. It is expected that they can fundamentally solve the recycling problem of polyethylene products.

[0098] pass Figure 1 High-temperature 1H NMR spectroscopy analysis revealed that the product prepared in Example 1 contained hydroxyl groups. The molten mixture of the product prepared in Example 1 and Upy-NCO showed a decrease in the hydroxyl peak, indicating that the hydroxyl group reacted with the isocyanate group. Simultaneously, a marker peak from the methylisouracil ring appeared, confirming that Upy-NCO can react with the product prepared in Example 1. Figure 2 The infrared spectroscopy results also yielded similar conclusions; the molten mixtures obtained in Examples 4 and 5 after step S1 showed a wavelength of 2200-2300 cm⁻¹. -1 The disappearance of the absorption peak (the marker peak of the -NCO group) indicates that the isocyanate group of Upy-NCO has completely reacted with the hydroxyl group of the product prepared in Example 1.

[0099] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Furthermore, it should be understood that after reading the above teachings of this application, those skilled in the art can make various alterations or modifications to this application, and the equivalent forms obtained also fall within the scope of protection of this application. It should also be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A reversibly crosslinked polyethylene composition, characterized in that, The composition comprises: a reaction product of an amino-containing diol and a maleic anhydride grafted polyethylene, a polyethylene resin, fumed silica, Upy-NCO and a structure control agent; wherein the amino group-containing diol has the general structure: or ; R1is selected from an alkyl group of 1 to 6 carbon atoms, R2, R3are the same or different and are selected from H or an alkyl group of 1 to 4 carbon atoms; The maleic anhydride grafted polyethylene is selected from maleic anhydride grafted polyethylene with a grafting rate of maleic anhydride ranging from 0.5 to 1 wt%; The specific preparation method of the reaction product of the amino-containing diol and the maleic anhydride grafted polyethylene is: reacting the amino-containing diol with the maleic anhydride grafted polyethylene at a temperature of 130-160℃, and then distilling off the solvent under reduced pressure to cool to 40-80℃; wherein the number of moles of amino in the amino-containing diol is greater than the number of moles of anhydride groups in the maleic anhydride grafted polyethylene; The polyethylene resin is selected from one or a combination of ultra-high molecular weight polyethylene, low-density polyethylene, high-density polyethylene and linear low-density polyethylene; The chemical structural formula of the Upy-NCO is: The structure control agent is selected from aliphatic amines containing 10 to 20 carbon atoms, wherein the aliphatic chain can be linear, branched or cyclic.

2. The reversibly crosslinked polyethylene composition according to claim 1, characterized in that, The reversible crosslinking polyethylene composition further comprises an antioxidant selected from one or a combination of hindered phenolic antioxidants and phosphite antioxidants; And / or, the reversible crosslinking polyethylene composition further comprises a lubricant selected from polyethylene wax.

3. The reversibly crosslinked polyethylene composition of claim 1, wherein The reversible crosslinking polyethylene composition comprises: the reaction product of the amino-containing diol and the maleic anhydride grafted polyethylene 90-110 parts by weight, the polyethylene resin 140-160 parts by weight, the fumed silica 10-20 parts by weight, the Upy-NCO 10-25 parts by weight, and the structure control agent 5-20 parts by weight; Wherein, the molar ratio of hydroxyl groups in the reaction product of the amino-containing diol and the maleic anhydride grafted polyethylene to isocyanate groups in the Upy-NCO is 100:(80-100).

4. Use of the reversible crosslinking polyethylene composition according to any one of claims 1-3 in reversible crosslinking polyolefin cable material.

5. A reversibly crosslinked polyethylene cable compound, characterized in that, The reversible crosslinking polyethylene composition according to any one of claims 1-3 is obtained by mixing, extruding, molding and curing.

6. The process for the preparation of a reversibly crosslinkable polyethylene cable compound according to claim 5, characterized in that The preparation method specifically comprises the following steps: S1, adding, mixing the reaction product of the amino-containing diol and the maleic anhydride grafted polyethylene, the Upy-NCO, the fumed silica, the antioxidant and the lubricant according to the formula amount, and performing reactive melt blending; S2, adding the structure control agent octadecylamine and the polyethylene resin to the mixture of step S1, and obtaining reversible crosslinking polyethylene granules by melt mixing, extruding, cooling and granulating; S3, adding the reversible crosslinking polyethylene granules obtained in step S2 into a cable extruder for extrusion coating molding, and then curing to obtain reversible crosslinking polyethylene cable material.

7. The process for the preparation of a reversibly crosslinkable polyethylene cable compound according to claim 6, characterized in that The reactive melt blending conditions of step S1 are a rotation speed of 50-150 rpm and a temperature of 100-140℃; And / or, the melt mixing conditions of step S2 are a rotation speed of 50-150 rpm and a temperature of 135-160℃; And / or, the extrusion coating molding temperature of step S3 is 135-160℃; And / or, the curing temperature of step S3 is 150-180℃.

8. Recycled reversibly crosslinked polyethylene pellets, characterized in that, The reversible cross-linked polyethylene cable material of claim 5 is broken by a pulverizer, mixed and stirred at a temperature of 135-160 ℃, and then extruded and granulated to obtain regenerated reversible cross-linked polyethylene granules.

9. A recycled, reversibly crosslinked cable material, characterized in that, The regenerated reversible cross-linked polyethylene granules of claim 8 are subjected to an extrusion coating molding and curing step to obtain; The extrusion coating molding temperature is 135-160 ℃, and the curing temperature is 150-180 ℃.

10. Use of the reversible cross-linked polyethylene cable material of claim 5 and / or the regenerated reversible cross-linked polyethylene cable material of claim 9 as a material in manufacturing cables.

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