Insulating material, preparation method, application and cable

Abstract

The present application provides an insulating material, a preparation method, an application and a cable. The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a crosslinking agent and a co-crosslinking agent; the reactive antioxidant contains a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an acid anhydride group and an acid anhydride derivative group; the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is < 3. The reactive antioxidant can be melt grafted onto the polyethylene molecular chain, and the grafted reactive antioxidant is not easily migrated during use, showing excellent long-term thermal oxidation stability and space charge inhibition ability, thereby improving the electrical properties and heat-oxidative aging resistance of the insulating material.

Description

Technical Field

[0001] The present application relates to the technical field of insulating materials, and particularly to an insulating material, a preparation method, an application and a cable. Background Art

[0002] The huge growth in urban power supply demand poses a major challenge to the long-term stability of the power system, and cable insulating materials play a crucial role in ensuring its safe operation. Cross-linked polyethylene (XLPE) has been widely used as the main material for preparing cable insulating materials due to its excellent electrical, physicochemical and mechanical properties.

[0003] However, the deterioration caused by the long-term aging of cable insulating materials under combined thermal stress and electrical stress is the main cause of power cable failures, and antioxidants often need to be added during the preparation process of cable insulating materials. Although the antioxidants used in related technologies have good anti-aging and anti-scorch characteristics, the dispersion uniformity of the antioxidants in the insulating material is poor, resulting in the deterioration of the local properties of the insulating material. Summary of the Invention

[0004] Based on this, the present application provides an insulating material, a preparation method, an application and a cable with uniform antioxidant dispersion.

[0005] In a first aspect of the present application, an insulating material is provided. The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a cross-linking agent and a co-cross-linking agent; the reactive antioxidant contains a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an acid anhydride group and an acid anhydride derivative group; the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is < 3, and there are no impurity particles with a particle size greater than 70 μm.

[0006] In some embodiments, the reactive antioxidant has at least one of the following characteristics (1)-(3):

[0007] (1) The reactive antioxidant containing an allyl group includes one or more of 2,2'-diallylbisphenol A, 2-allylphenol, 4-allyl-2,6-dimethoxyphenol, 2-allyl-6-methylphenol, 3',5-di-2-propenyl-1,1'-biphenyl-2,4'-diphenol, 4,4'-(1-methylethylidene)bis[5-methyl-2-(2-propenyl)]-phenol and 2-allyl-5-t-butylhydroquinone;

[0008] (2) The reactive antioxidant containing an acrylic group or an acrylate group includes one or more of 2-[1-(2-hydroxy-3,5-di-tert-amylphenyl)ethyl]-4,6-di-tert-amylphenyl acrylate, octadecyl 3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-2-acrylate, 3,5-di-tert-butyl-4-hydroxyphenyl prop-2-enoate, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylic acid, and methyl 3-(3-hydroxy-4-methoxyphenyl)acrylate;

[0009] (3) The reactive antioxidant containing a carboxylic acid group, an acid anhydride group, or an acid anhydride-derived group includes one or more of 4-hydroxyphthalic anhydride, 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionyloxy-2,1-ethanediol ester, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, and 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionic anhydride.

[0010] In some embodiments, the mass ratio of the reactive antioxidant to the initiator is (0.1 - 0.3):(0.1 - 0.2).

[0011] In some embodiments, based on parts by mass, the raw materials for preparing the insulating material include: 100 parts of the polyethylene, 0.1 part - 0.3 part of the reactive antioxidant, 0.1 part - 0.2 part of the initiator, 1.2 parts - 1.6 parts of the crosslinking agent, and 0.1 part - 0.2 part of the co-crosslinking agent.

[0012] In some embodiments, the polyethylene has at least one of the following characteristics (1)-(5):

[0013] (1) The density of the polyethylene is 0.91 g / cm 3 - 0.93 g / cm 3 ;

[0014] (2) The weight-average molecular weight of the polyethylene is 120,000 Da - 180,000 Da;

[0015] (3) The molecular weight distribution index of the polyethylene is 4.5 - 5.5;

[0016] (4) The melt index of the polyethylene at 190 °C and a load of 2.16 kg is 1.9 g / 10 min - 2.1 g / 10 min.

[0017] In some embodiments, the insulating material includes at least one of the following characteristics (1)-(3):

[0018] (1) The crosslinking agent includes one or more of dicumyl peroxide, di-tert-butyl peroxide, bis(tert-butylperoxyisopropyl)benzene, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane;

[0019] (2) The initiator includes one or more of dicumyl peroxide, di-tert-butyl peroxide, bis(tert-butylperoxyisopropyl)benzene, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane;

[0020] (3) The co-crosslinking agent includes one or more of triallyl isocyanurate, triallyl cyanurate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, and 2,4-diphenyl-4-methyl-1-pentene.

[0021] The second aspect of the present application provides a method for preparing an insulating material. The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a crosslinking agent, and a co-crosslinking agent. The reactive antioxidant is a liquid antioxidant. The preparation method includes the following steps:

[0022] Spray the antioxidant onto the shaking polyethylene, then perform rotational mixing and absorption to prepare an intermediate;

[0023] Use a single-screw extruder to melt-extrude the intermediate and the initiator, and pelletize the melt-extruded material to prepare a semi-finished product of antioxidant-grafted modified polyethylene;

[0024] While shaking the semi-finished product, spray a molten liquid containing the crosslinking agent and the co-crosslinking agent into it;

[0025] After finishing spraying, continue to shake for a preset time, then perform heat preservation and absorption to prepare the insulating material;

[0026] Among them, the reactive antioxidant contains a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an acid anhydride group, and an acid anhydride derivative group; the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is < 3, and there are no impurity particles with a particle size greater than 70 μm.

[0027] In some embodiments, the preparation method includes at least one of the following conditions:

[0028] (1) The rotational mixing speed is 30 rpm - 60 rpm, and the time is 50 min - 80 min;

[0029] (2) The absorption temperature is 60°C - 80°C, and the time is 2 h - 4 h;

[0030] (3) The temperature of the melt extrusion is 120°C - 180°C, and the rotation speed is 120 rpm - 180 rpm;

[0031] (4) The rotation speed of the semi-finished product during shaking is 30 rpm - 60 rpm, and the preset time is 50 min - 60 min;

[0032] (5) The temperature for absorption after heat preservation is 70°C - 80°C, and the time is 16 h - 24 h.

[0033] The third aspect of the present application provides a method for preparing an insulating material. The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a crosslinking agent, and a co-crosslinking agent. The reactive antioxidant is a solid antioxidant. The preparation method includes the following steps:

[0034] Mix the reactive antioxidant with a solvent to prepare a premixed solution;

[0035] Perform rotational mixing on the premixed solution and the polyethylene to remove the solvent in the premixed solution and prepare an intermediate;

[0036] Use a single-screw extruder to perform melt extrusion on the intermediate and the initiator, and pelletize the melt-extruded material to prepare a semi-finished product of antioxidant-grafted modified polyethylene;

[0037] While shaking the semi-finished product, spray a molten material solution containing the crosslinking agent and the co-crosslinking agent into it;

[0038] After the spraying is completed, continue to shake for a preset time, and then perform heat preservation and absorption to prepare the insulating material;

[0039] Among them, the reactive antioxidant contains a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an acid anhydride group, and an acid anhydride derivative group; the number of impurity particles with a particle size between 50 μm - 70 μm contained in the polyethylene is < 3, and there are no impurity particles with a particle size greater than 70 μm.

[0040] In some embodiments, the preparation method includes at least one of the following conditions:

[0041] (1) The rotation speed of the rotational mixing is 20 rpm - 40 rpm, and the time is 30 min - 60 min;

[0042] (2) The temperature of the melt extrusion is 120°C - 200°C, and the rotation speed is 120 rpm - 180 rpm;

[0043] (3) The rotation speed of the semi-finished product during shaking is 30 rpm - 60 rpm, and the preset time is 50 min - 60 min;

[0044] (4) The temperature absorbed after heat preservation is 70°C - 80°C, and the time is 16h - 24h.

[0045] The fourth aspect of the present application provides a preparation method of an insulating material. The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a crosslinking agent, and a co-crosslinking agent. Some of the reactive antioxidants are liquid antioxidants, and the remaining reactive antioxidants are solid antioxidants. The preparation method includes the following steps:

[0046] Mix the solid antioxidant with a solvent to prepare a premixed solution;

[0047] After the premixed solution containing the solid antioxidant is subjected to the first rotational mixing with the polyethylene, remove the solvent in the premixed solution to prepare a first intermediate;

[0048] Spray the liquid antioxidant into the shaking first intermediate, and then perform the second rotational mixing and absorption to prepare a second intermediate;

[0049] Use a single-screw extruder to melt-extrude the second intermediate and the initiator, and granulate the melt-extruded material to prepare a semi-finished product of antioxidant-grafted modified polyethylene;

[0050] While shaking the semi-finished product, spray a molten liquid containing the crosslinking agent and the co-crosslinking agent into it;

[0051] After the spraying is completed, continue to shake for a preset time, and then perform heat preservation and absorption to prepare the insulating material;

[0052] Among them, the reactive antioxidant contains a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an acid anhydride group, and an acid anhydride derivative group; the number of impurity particles with a particle size between 50μm - 70μm contained in the polyethylene is < 3, and there are no impurity particles with a particle size greater than 70μm.

[0053] In some embodiments, the preparation method includes at least one of the following conditions:

[0054] (1) The rotation speed of the first rotational mixing is 20rpm - 40rpm, and the time is 30min - 60min;

[0055] (2) The rotation speed of the second rotational mixing is 30rpm - 60rpm, and the time is 50min - 80min;

[0056] (3) The temperature of the absorption is 60°C - 80°C, and the time is 2h - 4h;

[0057] (4) The temperature of the melt extrusion is 120°C - 200°C, and the rotation speed is 120 rpm - 180 rpm;

[0058] (5) The rotation speed of the semi-finished product during shaking is 30 rpm - 60 rpm, and the preset time is 50 min - 60 min;

[0059] (6) The temperature for absorption after heat preservation is 70°C - 80°C, and the time is 16 h - 24 h.

[0060] The fifth aspect of the present application provides an application of the insulating material of the first aspect of the present application, the insulating material prepared by using the preparation method of the second aspect of the present application, the insulating material prepared by using the preparation method of the third aspect of the present application, or the insulating material prepared by using the preparation method of the fourth aspect of the present application in the preparation of cables.

[0061] The sixth aspect of the present application provides a cable, and the raw materials for preparing the cable include the insulating material of the first aspect of the present application, the insulating material prepared by using the preparation method of the second aspect of the present application, the insulating material prepared by using the preparation method of the third aspect of the present application, or the insulating material prepared by using the preparation method of the fourth aspect of the present application.

[0062] In some embodiments, the cable is a submarine cable.

[0063] For the above-provided insulating material, its raw materials for preparation include polyethylene, a reactive antioxidant, an initiator, a crosslinking agent, and a co-crosslinking agent. The number of impurity particles with a particle size between 50 μm - 70 μm in the polyethylene is < 3, and there are no impurity particles with a particle size greater than 70 μm. The reactive antioxidant can be melt-grafted onto the polyethylene molecular chain, and the grafted reactive antioxidant is more evenly distributed on the polyethylene molecular chain, which can better fill the possible weak points between molecular chains at the microscopic level, disperse the electric field stress, thereby improving the DC breakdown strength and further enhancing the electrical properties of the insulating material. At the same time, the grafted reactive antioxidant is connected to the polyethylene molecular chain in the form of a chemical bond. On the one hand, it can play an antioxidant role, stabilize the molecular structure, terminate the free radical chain reaction, and prevent the breakage and rearrangement of molecular chains; on the other hand, the grafted reactive antioxidant has a high compatibility with polyethylene, and the antioxidant molecules are not easily migrated and precipitated, and can form an antioxidant "protection area" locally for a long time, preventing the direct contact between oxygen and the polyethylene molecular chain, and reducing the probability of oxidation reaction, thereby improving the heat-resistant oxygen aging performance of the insulating material. In addition, by melt-grafting the reactive antioxidant onto the polymer main chain, the deficiencies of low-molecular-weight additive antioxidants being easily migrated and lost are overcome, and at the same time, the disadvantages of poor compatibility between high-molecular-weight antioxidants and polyethylene resin and low effective concentration are avoided, improving the dispersibility and stability of the antioxidant in polyolefins. Detailed Embodiments

[0064] To facilitate the understanding of the present invention, the present application will be described more comprehensively below with reference to relevant embodiments. The following gives the preferred embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosed content of the present application more thorough and comprehensive.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0066] The term "and / or", "or / and", "and / or" as used herein includes any one of two or more related listed items, as well as any and all combinations of the related listed items. The said any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items. It should be noted that when at least two conjunctions selected from "and / or", "or / and", "and / or" are used to connect at least three items, it should be understood that in this application, this technical solution undoubtedly includes the technical solution connected by "logical AND", and also undoubtedly includes the technical solution connected by "logical OR".

[0067] In this application, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, and also includes an open technical solution containing the listed features.

[0068] In this application, regarding the numerical range, unless otherwise specified, the above numerical range is considered continuous and includes the minimum value and the maximum value of this range, as well as each value between such minimum value and maximum value. Further, when the range refers to an integer, it includes each integer between the minimum value and the maximum value of this range. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0069] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recorded; and any lower limit can be combined with other lower limits to form a range not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or an upper limit to be combined with any other point or single numerical value or with other lower limits or upper limits to form a range not explicitly recorded.

[0070] The temperature parameters in this application, unless otherwise specifically defined, allow for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0071] In this text, the "suitable" in expressions such as "suitable combination method", "suitable method", "any suitable method", etc. is subject to being able to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0072] In this application, terms such as "further", "even further", "especially", etc. are used for descriptive purposes, indicating differences in content, but should not be construed as limiting the scope of protection of this application.

[0073] In this application, "optionally", "optional", "option" mean optional, that is, either selected from one of the two alternative options of "yes" or "no". If "optional" appears multiple times in a technical solution, unless otherwise specifically stated and there are no contradictions or mutual restrictions, each "optional" is independent.

[0074] In the description of the application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0075] If there is no special instruction, all implementation manners and optional implementation manners of this application can be combined with each other to form a new technical solution. If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0076] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, and preferably sequentially.

[0077] The deterioration caused by the long-term aging of cable insulating materials under combined thermal stress and electrical stress is the main cause of power cable failures, and antioxidants often need to be added during the preparation process of cable insulating materials. Commonly used antioxidants in the cross-linked polyethylene insulating material industry include antioxidant 300, antioxidant 1010, antioxidant 330, antioxidant 1035, etc. Although they have good anti-aging and anti-scorch characteristics, they have poor compatibility with the matrix resin and are prone to migration, resulting in irregular dispersion of the antioxidant in the matrix resin and causing deterioration of the local insulation performance.

[0078] Based on the above problems, this application uses reactive antioxidants, and the reactive antioxidants are added to the polymer main chain through melt grafting, overcoming the deficiency of easy migration and loss of low molecular weight additive antioxidants, and at the same time avoiding the disadvantages of poor compatibility between high molecular weight antioxidants and polyethylene resin and low effective concentration.

[0079] One or more embodiments of the present application provide an insulating material. The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a crosslinking agent, and a co-crosslinking agent; the reactive antioxidant contains a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an anhydride group, and an anhydride-derived group; the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is < 3, and there are no impurity particles with a particle size greater than 70 μm. Understandably, the raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a crosslinking agent, and a co-crosslinking agent, and the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is < 3, and there are no impurity particles with a particle size greater than 70 μm. The reactive antioxidant can be melt-grafted onto the polyethylene molecular chain, and the grafted reactive antioxidant is more evenly distributed on the polyethylene molecular chain, which can better fill the possible weak points between the molecular chains at the microscopic level, disperse the electric field stress, thereby improving the DC breakdown strength and further improving the electrical properties of the insulating material. At the same time, the grafted reactive antioxidant is connected to the polyethylene molecular chain in the form of a chemical bond. On the one hand, it can play an antioxidant role, stabilize the molecular structure, terminate the free radical chain reaction, and prevent the breakage and rearrangement of the molecular chain; on the other hand, the grafted reactive antioxidant has a high compatibility with polyethylene, and the antioxidant molecules are not easily migrated and precipitated, and can form an antioxidant "protection area" locally for a long time, preventing the direct contact between oxygen and the polyethylene molecular chain, and reducing the probability of the occurrence of the oxidation reaction, thereby improving the heat-resistant oxygen aging performance of the insulating material. At the same time, by melt-grafting, the reactive antioxidant is added to the polymer main chain, overcoming the deficiency of the easy migration and loss of the low-molecular-weight additive antioxidant, and at the same time avoiding the disadvantages of the poor compatibility between the high-molecular-weight antioxidant and the polyethylene resin and the low effective concentration, and improving the dispersibility and stability of the antioxidant in the polyolefin.

[0080] In addition, the reactive antioxidant simultaneously has a hindered phenol group and at least one of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an anhydride group, and an anhydride-derived group, taking into account the functions of the antioxidant and the scorch retarder, effectively reducing the production cost of the cable, improving the scorch resistance characteristics of the insulating material product, and reducing the risk of possible impurity particles during the cable production and processing process.

[0081] Furthermore, the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is < 3, and there are no impurity particles with a particle size greater than 70 μm. Thus, on the one hand, it helps the antioxidant to be uniformly dispersed in the polyethylene, thereby giving full play to its antioxidant effect; on the other hand, the degree of electric field distortion caused by impurities will be greatly reduced, the polyethylene material can better withstand high voltages, the insulation resistance is significantly increased, and the dielectric loss is significantly reduced. In terms of processing performance, the pure polyethylene has better melt fluidity, higher melt uniformity, and lower scorching risk during the production of insulating materials, ensuring the high-quality and efficient production of products.

[0082] In some exemplary embodiments, the reactive antioxidant containing an allyl group includes one or more of 2,2'-diallylbisphenol A, 2-allylphenol, 4-allyl-2,6-dimethoxyphenol, 2-allyl-6-methylphenol, 3',5-di-2-propenyl-1,1'-biphenyl-2,4'-diphenol, 4,4'-(1-methylethylidene)bis[5-methyl-2-(2-propenyl)]-phenol, and 2-allyl-5-t-butylhydroquinone.

[0083] In some alternative embodiments, the reactive antioxidant containing an acrylic acid group or an acrylate group includes one or more of 2-[1-(2-hydroxy-3,5-di-tert-amylphenyl)ethyl]-4,6-di-tert-amylphenyl acrylate, octadecyl 3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-2-acrylate, 3,5-di-tert-butyl-4-hydroxyphenyl prop-2-enoate, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylic acid, and methyl 3-(3-hydroxy-4-methoxyphenyl)acrylate.

[0084] In some alternative embodiments, the reactive antioxidant containing a carboxylic acid group, an acid anhydride group, or an acid anhydride-derived group includes one or more of 4-hydroxyphthalic anhydride, 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionyloxy-2,1-ethylene glycol ester, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, and 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionic anhydride.

[0085] In some embodiments, the mass ratio of the reactive antioxidant to the initiator is (0.1 - 0.3):(0.1 - 0.2); for example, it can be, but is not limited to, (0.1 - 0.3):(0.1 - 0.2), (0.12 - 0.3):(0.11 - 0.2), (0.14 - 0.3):(0.12 - 0.2), (0.16 - 0.3):(0.13 - 0.2), (0.18 - 0.3):(0.14 - 0.2), (0.2 - 0.3):(0.15 - 0.2), (0.1 - 0.28):(0.1 - 0.19), (0.1 - 0.26):(0.1 - 0.18), (0.1 - 0.24):(0.1 - 0.17), (0.1 - 0.22):(0.1 - 0.16), or (0.1 - 0.2):(0.1 - 0.15), etc. When the mass ratio of the reactive antioxidant to the initiator is within the above range, sufficient active sites can be provided during the preparation of the insulating material to initiate the grafting reaction between the antioxidant and polyethylene, and ensure that the grafting reaction proceeds at a suitable reaction rate without triggering excessive side reactions (such as excessive cross-linking or degradation of the polyethylene molecular chain), thereby affecting the quality and performance of the product.

[0086] In some embodiments, by mass, the raw materials for preparing the insulating material include: 100 parts of polyethylene, 0.1 part - 0.3 part of a reactive antioxidant, 0.1 part - 0.2 part of an initiator, 1.2 parts - 1.6 parts of a cross-linking agent, and 0.1 part - 0.2 part of a co-cross-linking agent.

[0087] As a non-limiting example, the mass fraction of the reactive antioxidant contained in the raw materials can be, but is not limited to, 0.1 part, 0.15 part, 0.2 part, 0.25 part, 0.3 part, or the range between any two of the above mass fractions, etc.

[0088] The mass fraction of the initiator contained in the raw materials can be, but is not limited to, 0.1 part, 0.12 part, 0.14 part, 0.16 part, 0.18 part, 0.2 part, or the range between any two of the above mass fractions, etc.

[0089] The mass fraction of the cross-linking agent contained in the raw materials can be, but is not limited to, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, or the range between any two of the above mass fractions, etc.

[0090] The mass fraction of the co-cross-linking agent contained in the raw materials can be, but is not limited to, 0.1 part, 0.12 part, 0.14 part, 0.16 part, 0.18 part, 0.2 part, or the range between any two of the above mass fractions, etc.

[0091] When the mass fractions of the reactive antioxidant, initiator, crosslinking agent, and co-crosslinking agent contained in the raw materials for preparing the insulating material are within the above ranges respectively, the synergistic effect can be maximally exerted; among them, the initiator can initiate the graft reaction between the reactive antioxidant and the insulating material at an appropriate reaction rate, thereby fully exerting the antioxidant effect of the antioxidant and preventing the oxidative degradation of the polymer molecular chain; the crosslinking agent and the co-crosslinking agent cooperate to form a three-dimensional network structure between the molecular chains of the insulating material, making the crosslinked structure more uniform.

[0092] In some embodiments, the density of the polyethylene is 0.91 g / cm 3 -0.93 g / cm 3 ; for example, it can be but is not limited to 0.91 g / cm 3 、0.915 g / cm 3 、0.92 g / cm 3 、0.925 g / cm 3 、0.93 g / cm 3 or the range between any two of the above densities, etc.

[0093] In some alternative embodiments, the weight-average molecular weight of the polyethylene is 120,000 Da - 180,000 Da; it can be but is not limited to 120,000 Da, 125,000 Da, 130,000 Da, 135,000 Da, 140,000 Da, 145,000 Da, 150,000 Da, 155,000 Da, 160,000 Da, 165,000 Da, 170,000 Da, 175,000 Da, 180,000 Da or the range between any two of the above weight-average molecular weights, etc. When the weight-average molecular weight of the polyethylene is within the above range, the entanglement degree between the polyethylene molecular chains is moderate, and the diffusion path of the antioxidant molecules in the polyethylene is smoother, which is more conducive to improving its uniform dispersion. At the same time, regulating the weight-average molecular weight of the polyethylene helps to improve its compatibility with the antioxidant and reduce the phase separation phenomenon. On the other hand, controlling the weight-average molecular weight of the polyethylene within the above range can make the active sites on the molecular chain more easily accessible to the antioxidant molecules, so that during the grafting or physical mixing process, the antioxidant can be more evenly distributed around the active sites of the polyethylene molecular chain, which is beneficial to the uniform dispersion of the antioxidant in the polyethylene and thus improves the modification effect of the antioxidant.

[0094] As a possible implementation, the molecular weight distribution index of polyethylene is 4.5 - 5.5; for example, it can be, but is not limited to, 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, or the range between any two of the above molecular weight distribution indices, etc. When the molecular weight distribution index of polyethylene is within the above range, the length of the polyethylene molecular chain is relatively more uniform, reducing the diffusion difference, which is beneficial to the uniformity of the antioxidant grafting reaction. At the same time, the synergistic effect between different molecular weight parts of polyethylene can be enhanced, so that the antioxidant can be better uniformly dispersed in a stable synergistic environment.

[0095] In some alternative implementation manners, the melt index of polyethylene at 190 °C and a load of 2.16 kg is 1.9 g / 10 min - 2.1 g / 10 min; for example, it can be, but is not limited to, 1.9 g / 10 min, 1.92 g / 10 min, 1.94 g / 10 min, 1.96 g / 10 min, 1.98 g / 10 min, 2.0 g / 10 min, 2.02 g / 10 min, 2.04 g / 10 min, 2.06 g / 10 min, 2.08 g / 10 min, 2.1 g / 10 min, or the range between any two of the above melt indices, etc.

[0096] It should be noted that the test conditions for the "melt index of low-density polyethylene" mentioned in the context are: at a temperature of 190 °C and a load of 2.16 kg, the test is carried out in accordance with ASTM D1238 standard.

[0097] In some implementation manners, the crosslinking agent includes one or more of dicumyl peroxide, di-tert-butyl peroxide, bis(tert-butylperoxyisopropyl)benzene, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0098] As a possible implementation, the initiator includes one or more of dicumyl peroxide, di-tert-butyl peroxide, bis(tert-butylperoxyisopropyl)benzene, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0099] In some embodiments, the co-crosslinking agent includes one or more of triallyl isocyanurate, triallyl cyanurate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, and 2,4-diphenyl-4-methyl-1-pentene.

[0100] One or more embodiments of the present application provide a method for preparing an insulating material, and this preparation method can be used to prepare the above-mentioned insulating material. The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a crosslinking agent, and a co-crosslinking agent. The reactive antioxidant is a liquid antioxidant. The preparation method includes the following steps:

[0101] The antioxidant is sprayed onto polyethylene in a shaking state, followed by rotational mixing and absorption to prepare an intermediate; a single-screw extruder is used to melt-extrude the intermediate and an initiator, and the melt-extruded material is pelletized to prepare a semi-finished product of antioxidant-grafted modified polyethylene; while shaking the semi-finished product, a molten liquid containing a crosslinking agent and a co-crosslinking agent is sprayed into it, and after the spraying is completed, shaking continues for a preset time, and then heat preservation and absorption are carried out to prepare an insulating material; wherein, the reactive antioxidant contains a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an acid anhydride group, and an acid anhydride-derived group; the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is < 3, and there are no impurity particles with a particle size greater than 70 μm.

[0102] In this preparation method, the antioxidant, crosslinking agent, and co-crosslinking agent are added by spraying, that is, the polyethylene absorbs the antioxidant, crosslinking agent, and co-crosslinking agent under more uniform temperature conditions by means of liquid impregnation absorption, further improving the uniform dispersion of the antioxidant from the process aspect.

[0103] In some embodiments, the rotation speed during the rotational mixing of the antioxidant and polyethylene is 30 rpm - 60 rpm; for example, it can be but is not limited to 30 rpm, 35 rpm, 40 rpm, 45 rpm, 50 rpm, 55 rpm, 60 rpm, or the range between any two of the above rotation speeds, etc.

[0104] As a possible embodiment, the rotational mixing time of the antioxidant and polyethylene is 50 min - 80 min; for example, it can be but is not limited to 50 min, 60 min, 70 min, 80 min, or the range between any two of the above times, etc.

[0105] It should be noted that the rotation speed and time during the rotational mixing of the antioxidant and polyethylene can be combined in any suitable manner, and both can be selected from any of the rotation speeds and times during the rotational mixing of the antioxidant and polyethylene described herein.

[0106] In some embodiments, the absorption temperature is 60°C - 80°C; for example, it can be but is not limited to 60°C, 65°C, 70°C, 75°C, 80°C, or the range between any two of the above temperatures, etc.

[0107] As a possible embodiment, the absorption time is 2 h - 4 h; for example, it can be but is not limited to 2 h, 3 h, 4 h, or the range between any two of the above times, etc.

[0108] It should be noted that the absorption temperature and time can be combined in any suitable manner, and the two can be selected respectively from any absorption temperature and time described herein.

[0109] In some alternative embodiments, the temperature of the melt extrusion is 120°C - 180°C; for example, it can be, but is not limited to, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, or the range between any two of the above temperatures, etc.

[0110] In some exemplary embodiments, the rotational speed of the melt extrusion is 120 rpm - 180 rpm; for example, it can be, but is not limited to, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, or the range between any two of the above rotational speeds, etc.

[0111] In some embodiments, the rotational speed of the semi-finished product shaking is 30 rpm - 60 rpm; for example, it can be, but is not limited to, 30 rpm, 35 rpm, 40 rpm, 45 rpm, 50 rpm, 55 rpm, 60 rpm, or the range between any two of the above rotational speeds, etc.

[0112] As a possible embodiment, the preset time is 50 min - 60 min; for example, it can be, but is not limited to, 50 min, 52 min, 54 min, 56 min, 58 min, 60 min, or the range between any two of the above preset times, etc.

[0113] In some embodiments, the absorption temperature after heat preservation is 70°C - 80°C; for example, it can be, but is not limited to, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, or the range between any two of the above temperatures, etc.

[0114] As a possible embodiment, the absorption time after heat preservation is 16 h - 24 h; for example, it can be, but is not limited to, 16 h, 18 h, 20 h, 22 h, 24 h, or the range between any two of the above temperatures, etc.

[0115] It should be noted that the absorption temperature and time after heat preservation can be combined in any suitable manner, and the two can be selected respectively from any absorption temperature and time after heat preservation described herein.

[0116] One or more embodiments of the present application provide a method for preparing an insulating material, which can be used to prepare the above-mentioned insulating material. The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a crosslinking agent, and a co-crosslinking agent. The reactive antioxidant is a solid antioxidant. The preparation method includes the following steps: mixing the reactive antioxidant with a solvent to prepare a premixed solution; rotating and mixing the premixed solution with polyethylene to remove the solvent in the premixed solution and prepare an intermediate; using a single-screw extruder to melt-extrude the intermediate and the initiator, and granulating the melt-extruded material to prepare a semi-finished product of antioxidant-grafted modified polyethylene; spraying a molten material solution containing a crosslinking agent and a co-crosslinking agent while shaking the semi-finished product; continuing to shake for a preset time after the spraying ends, and then performing heat preservation and absorption to prepare the insulating material; wherein the reactive antioxidant contains a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an acid anhydride group, and an acid anhydride derivative group; the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is < 3, and there are no impurity particles with a particle size greater than 70 μm.

[0117] In this preparation method, the solid antioxidant is prepared into a premixed solution and then mixed with polyethylene, and the crosslinking agent and the co-crosslinking agent are added by spraying, which is beneficial to enabling polyethylene to absorb the antioxidant, the crosslinking agent, and the co-crosslinking agent under more uniform temperature conditions, and further improving the uniform dispersion of the antioxidant from the process aspect.

[0118] In some embodiments, the solvent used for preparing the premixed solution includes xylene.

[0119] In some embodiments, the rotation speed when rotating and mixing the premixed solution containing the antioxidant and polyethylene is 20 rpm - 40 rpm; for example, it can be, but is not limited to, 20 rpm, 25 rpm, 30 rpm, 35 rpm, 40 rpm, or the range between any two of the above rotation speeds, etc.

[0120] As a possible embodiment, the rotation time when rotating and mixing the premixed solution containing the antioxidant and polyethylene is 30 min - 60 min; for example, it can be, but is not limited to, 30 min, 40 min, 50 min, 60 min, or the range between any two of the above times, etc.

[0121] It should be noted that the rotation speed and time when rotating and mixing the premixed solution containing the antioxidant and polyethylene can be combined in any suitable manner, and both can be selected from any of the rotation speeds and times when rotating and mixing the premixed solution containing the antioxidant and polyethylene described herein.

[0122] In some embodiments, the temperature of melt extrusion is 120°C - 200°C; for example, it can be, but is not limited to, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, or the range between any two of the above temperatures, etc.

[0123] In some exemplary embodiments, the rotation speed of melt extrusion is 120 rpm - 180 rpm; for example, it can be, but is not limited to, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, or the range between any two of the above rotation speeds, etc.

[0124] In some embodiments, the rotation speed of the semi-finished product shaking is 30 rpm - 60 rpm; for example, it can be, but is not limited to, 30 rpm, 35 rpm, 40 rpm, 45 rpm, 50 rpm, 55 rpm, 60 rpm, or the range between any two of the above rotation speeds, etc.

[0125] As a possible embodiment, the preset time is 50 min - 60 min; for example, it can be, but is not limited to, 50 min, 52 min, 54 min, 56 min, 58 min, 60 min, or the range between any two of the above preset times, etc.

[0126] In some embodiments, the temperature after heat preservation and absorption is 70°C - 80°C; for example, it can be, but is not limited to, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, or the range between any two of the above temperatures, etc.

[0127] As a possible embodiment, the time after heat preservation and absorption is 16 h - 24 h; for example, it can be, but is not limited to, 16 h, 18 h, 20 h, 22 h, 24 h, or the range between any two of the above temperatures, etc.

[0128] It should be noted that the temperature and time after heat preservation and absorption can be combined in any suitable manner, and both can be selected from any of the temperatures and times after heat preservation and absorption described herein respectively.

[0129] One or more embodiments of the present application provide a method for preparing an insulating material, and this preparation method can be used to prepare the above-mentioned insulating material. The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a cross-linking agent, and a co-cross-linking agent. Some of the reactive antioxidants are liquid antioxidants, and the remaining reactive antioxidants are solid antioxidants. The preparation method includes the following steps:

[0130] Mix a solid antioxidant with a solvent to prepare a premixed solution; after the first rotational mixing of the premixed solution and polyethylene, remove the solvent in the premixed solution to prepare a first intermediate; spray a liquid antioxidant into the shaking first intermediate and then perform a second rotational mixing and absorption to prepare a second intermediate; use a single-screw extruder to melt-extrude the second intermediate and an initiator, and pelletize the melt-extruded material to prepare a semi-finished product of antioxidant-grafted modified polyethylene; while shaking the semi-finished product, spray a molten feed liquid containing a crosslinking agent and a co-crosslinking agent into it; continue shaking for a preset time after the spraying is completed, and then perform heat preservation and absorption to prepare an insulating material; wherein, the reactive antioxidant contains a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an acid anhydride group, and an acid anhydride derivative group; the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is < 3, and there are no impurity particles with a particle size greater than 70 μm.

[0131] It should be noted that the "first intermediate", "second intermediate", "first rotational mixing", "second rotational mixing", etc. mentioned in the context are only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, the "first", "second", etc. only serve the purpose of non-exhaustive enumeration and description, and should be understood not to constitute a closed limitation on the quantity.

[0132] In this preparation method, preparing the solid antioxidant into a premixed solution and then mixing it with polyethylene, and using the spraying method to add the liquid antioxidant, crosslinking agent, and co-crosslinking agent are beneficial to enabling polyethylene to absorb the antioxidant, crosslinking agent, and co-crosslinking agent under more uniform temperature conditions, and further improving the uniform dispersion of the antioxidant from the process aspect.

[0133] In some embodiments, the rotation speed during the first rotational mixing of the premixed solution containing the solid antioxidant and polyethylene is 20 rpm - 40 rpm; for example, it can be but not limited to 20 rpm, 25 rpm, 30 rpm, 35 rpm, 40 rpm, or the range between any two of the above rotation speeds, etc.

[0134] As a possible embodiment, the time for the first rotational mixing of the premixed solution containing the solid antioxidant and polyethylene is 30 min - 60 min; for example, it can be but not limited to 30 min, 40 min, 50 min, 60 min, or the range between any two of the above times, etc.

[0135] It should be noted that the rotation speed and time for the first rotational mixing of the premixed solution containing the solid antioxidant and polyethylene can be combined in any suitable manner, and both can be selected respectively from any of the rotation speeds and times for the rotational mixing of the premixed solution containing the solid antioxidant and polyethylene described herein.

[0136] In some embodiments, the rotation speed for the second rotational mixing is 30 rpm - 60 rpm; for example, it can be, but is not limited to, 30 rpm, 35 rpm, 40 rpm, 45 rpm, 50 rpm, 55 rpm, 60 rpm, or the range between any two of the above rotation speeds, etc.

[0137] As a possible embodiment, the time for the second rotational mixing is 50 min - 80 min; for example, it can be, but is not limited to, 50 min, 60 min, 70 min, 80 min, or the range between any two of the above times, etc.

[0138] It should be noted that the rotation speed and time for the second rotational mixing can be combined in any suitable manner, and both can be selected respectively from any of the rotation speeds and times for the second rotational mixing described herein.

[0139] In some embodiments, the absorption temperature is 60°C - 80°C; for example, it can be, but is not limited to, 60°C, 65°C, 70°C, 75°C, 80°C, or the range between any two of the above temperatures, etc.

[0140] As a possible embodiment, the absorption time is 2 h - 4 h; for example, it can be, but is not limited to, 2 h, 3 h, 4 h, or the range between any two of the above times, etc.

[0141] It should be noted that the absorption temperature and time can be combined in any suitable manner, and both can be selected respectively from any of the absorption temperatures and times described herein.

[0142] In some embodiments, the melt extrusion temperature is 120°C - 200°C; for example, it can be, but is not limited to, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180, 190, 200, or the range between any two of the above temperatures, etc.

[0143] In some exemplary embodiments, the rotation speed for melt extrusion is 120 rpm - 180 rpm; for example, it can be, but is not limited to, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, or the range between any two of the above rotation speeds, etc.

[0144] In some embodiments, the rotation speed of the semi-finished product shaking is 30 rpm - 60 rpm; for example, it can be, but is not limited to, 30 rpm, 35 rpm, 40 rpm, 45 rpm, 50 rpm, 55 rpm, 60 rpm, or the range between any two of the above rotation speeds, etc.

[0145] As a possible embodiment, the preset time is 50 min - 60 min; for example, it can be, but is not limited to, 50 min, 52 min, 54 min, 56 min, 58 min, 60 min, or the range between any two of the above preset times, etc.

[0146] In some embodiments, the temperature absorbed after heat preservation is 70°C - 80°C; for example, it can be, but is not limited to, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, or the range between any two of the above temperatures, etc.

[0147] As a possible embodiment, the time absorbed after heat preservation is 16 h - 24 h; for example, it can be, but is not limited to, 16 h, 18 h, 20 h, 22 h, 24 h, or the range between any two of the above temperatures, etc.

[0148] It should be noted that the temperature and time absorbed after heat preservation can be combined in any suitable manner, and both can be selected from any of the temperatures and times absorbed after heat preservation described herein respectively.

[0149] In some embodiments, the solvent used when preparing the premixed solution includes xylene.

[0150] One or more embodiments of the present application provide an application of the above-mentioned insulating material or the insulating material prepared by the above-mentioned preparation method in the preparation of cables.

[0151] One or more embodiments of the present application provide a cable, and the raw materials of the cable include the above-mentioned insulating material or the insulating material prepared by the above-mentioned preparation method.

[0152] In some of these embodiments, the cable is a submarine cable.

[0153] As a non-limiting example, the load-bearing voltage of the cable is 500 kV and below.

[0154] It should be noted that the "load-bearing voltage" described in the context refers to the voltage at which the cable can operate safely and stably.

[0155] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. For the experimental methods without specific conditions noted in the following embodiments, the guidelines given in the present invention are preferentially referred to, and it is also possible to follow the experimental manuals or conventional conditions in the art, or the conditions recommended by the manufacturer, or refer to the experimental methods known in the art.

[0156] In the following specific embodiments, regarding the measurement parameters of the raw material components, if there is no special explanation, there may be slight deviations within the weighing accuracy range. Regarding the temperature and time parameters, acceptable deviations caused by instrument test accuracy or operation accuracy are allowed.

[0157] I. Preparation of Insulating Material

[0158] 1. Formulation Composition

[0159] The formulation compositions of Examples 1-11 are shown in Table 1-1, and the formulation compositions of Examples 12-23 and Comparative Examples 1-4 are shown in Table 1-2.

[0160] Table 1-1

[0161]

[0162] Table 1-2

[0163]

[0164] Among them, in Table 1-1 and Table 1-2, "TMPTMA" represents trimethylolpropane trimethacrylate; "BIPB" represents 1,4-bis(tert-butylperoxy) isopropylbenzene; each "part" represents 100 g. The molecular weight represents the weight-average molecular weight.

[0165] 2. Preparation Process

[0166] In the above-mentioned examples and comparative examples, the reactive antioxidants used in Examples 1, 2 and Examples 12-15 are liquid antioxidants, and the preparation method includes the following steps:

[0167] Step S1: First, import low-density polyethylene particles into a shaking tank, and the temperature of the shaking tank is 75°C; secondly, spray the antioxidant into the shaking tank and rotate and mix for 60 minutes at a rotation speed of 35 rpm; then, after shaking dry, let it stand for absorption, and let it stand at 75°C for 3 hours to obtain a uniformly dispersed intermediate.

[0168] Step S2: Directly add the intermediate prepared in Step S1 into a single-screw extruder, add an initiator in proportion, after melt extrusion, filter the material through a high-mesh filter and then cool it by water to granulate, obtaining a semi-finished product of antioxidant-grafted modified polyethylene; wherein, the temperatures of each zone of the extruder are 120°C, 130°C, 140°C, 150°C, 155°C, 160°C, 165°C, 170°C, 180°C, and the rotation speed of the extruder is 150 rpm.

[0169] Step S3: First, fully melt the crosslinking agent and the co-crosslinking agent respectively in an insulation tank and filter out impurities through a filter screen, the temperature of the insulation tank is 75°C; secondly, introduce them into a mixing tank in proportion and mechanically stir for 5 min, the temperature of the mixing tank is 75°C, and the stirring speed is 15 rpm; then, spray and inject them into a rocking tank filled with the semi-finished product, the temperature of the rocking tank is 70°C, and the time for continuous rocking after spraying is 60 min, and the rotation speed is 35 rpm; finally, introduce the material in the rocking tank into the insulation tank for sufficient heat preservation and absorption, the heat preservation temperature is 75°C, and the heat preservation time is 18 h, and after cooling, a polyethylene cable insulating material is obtained.

[0170] In the above-mentioned examples and comparative examples, when the reactive antioxidant used in Examples 3-11 is a solid antioxidant, the preparation method includes the following steps:

[0171] Step S1: First, dissolve the antioxidant in xylene solution until saturated, mix evenly to obtain a premixed solution, and the temperature is 120°C; secondly, add the premixed solution to low-density polyethylene particles, rotate and mix for 60 min, and the rotation speed is 20 rpm; then, fish out the mixed material and dry it under vacuum conditions to remove the residual xylene, obtaining a uniformly dispersed intermediate.

[0172] Step S2: Directly add the intermediate prepared in Step S1 into a single-screw extruder, add an initiator in proportion, after melt extrusion, filter the material through a high-mesh filter and then cool it by water to granulate, obtaining a semi-finished product of antioxidant-grafted modified polyethylene; wherein, in Examples 3-4, 6-7 and 9, the temperatures of each zone of the extruder are 120°C, 130°C, 140°C, 150°C, 155°C, 160°C, 165°C, 170°C, 180°C, and the rotation speed of the extruder is 150 rpm; in Examples 5, 8 and 10-11, the temperatures of each zone of the extruder are 125°C, 135°C, 145°C, 150°C, 160°C, 170°C, 180°C, 185°C, 195°C, and the rotation speed of the extruder is 150 rpm.

[0173] Step S3: First, the crosslinking agent and the co-crosslinking agent are fully melted in the heat preservation tank and the impurities are filtered out through the filter screen. The temperature of the heat preservation tank is 75 °C. Secondly, they are introduced into the mixing tank in proportion and mechanically stirred for 5 min. The temperature of the mixing tank is 75 °C and the stirring speed is 15 rpm. Subsequently, they are sprayed and injected into the shaking tank filled with semi-finished products. The temperature of the shaking tank is 70 °C. After spraying, the shaking continues for 60 min at a speed of 35 rpm. Finally, the materials in the shaking tank are introduced into the heat preservation tank for full heat preservation and absorption. The heat preservation temperature is 75 °C and the heat preservation time is 18 h. After cooling, polyethylene cable insulation materials are obtained.

[0174] II. Performance Test

[0175] The insulation materials prepared in the above-mentioned examples and comparative examples are subjected to DC breakdown strength test and oxidation induction test. The test methods are as follows:

[0176] DC breakdown strength test: It is carried out with reference to the provisions of GB / T 1408.2. The electrodes are column-plate electrodes with a diameter of 25 mm and the arc radius at the edge of the electrodes is 2.5 mm. The test temperature is (70 ± 2) °C and the thickness of the test piece is (0.2 ± 0.02) mm.

[0177] Oxidation induction period (OIT) test: It is carried out with reference to the provisions of GB / T 19466.6. A differential scanning calorimeter is used. It is heated to 200 °C at a rate of 20 °C / min in a nitrogen atmosphere (50 mL / min), and after holding for 5 min, it is switched to an oxygen atmosphere (50 mL / min). Under the condition of holding at 200 °C, the thermal effect is observed and the oxidation induction period time of the specimen is calculated.

[0178] The test results of the above-mentioned examples and comparative examples are shown in Table 2 respectively.

[0179] Table 2

[0180]

[0181] Among them, "OIT" in Table 2 represents the oxidation induction time.

[0182] It can be seen from the result comparison of Examples 1-23 and Comparative Examples 1-4 in Table 2 that the reactive antioxidant graft-modified crosslinked polyethylene insulation material provided by this application has excellent electrical properties and heat-resistant oxygen aging properties.

[0183] It can be seen from the result comparison of Example 1 and Examples 12-15 that by controlling the mass ratio of the reactive antioxidant and the initiator within an appropriate range, the antioxidant molecules can be more effectively grafted onto the polyethylene molecular chain, and side reactions such as crosslinking and degradation do not occur, which is beneficial to further improving the electrical properties and heat-resistant oxygen aging properties of the crosslinked polyethylene insulation material.

[0184] From the comparison of the results of Example 1 and Comparative Examples 3-4, it can be seen that by further regulating the number of impurity particles in polyethylene, it is beneficial to further improve the distribution uniformity of the antioxidant, thereby being beneficial to further enhancing the electrical properties and heat-oxidative aging properties of the crosslinked polyethylene insulating material.

[0185] From the comparison of the results of Example 1 and Examples 16-23, it can be seen that by regulating parameters such as the weight-average molecular weight and molecular weight distribution index of polyethylene within an appropriate range, it is beneficial to further improve the distribution uniformity of the antioxidant, thereby being beneficial to further enhancing the electrical properties and heat-oxidative aging properties of the crosslinked polyethylene insulating material.

[0186] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0187] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. An insulating material, characterized in that: The raw materials for preparing the insulating material include, by weight, 100 parts of polyethylene, 0.1-0.3 parts of a reactive antioxidant, 0.1-0.2 parts of an initiator, 1.2-1.6 parts of a cross-linking agent, and 0.1-0.2 parts of an auxiliary cross-linking agent; the reactive antioxidant contains a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an anhydride group, and an anhydride derivative group; the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is 0, and the polyethylene does not contain impurity particles with a particle size greater than 70 μm; The mass ratio of the reactive antioxidant to the initiator is (0.1-0.3):(0.1-0.2); the weight average molecular weight of the polyethylene is 120000Da-180000Da; and the molecular weight distribution index of the polyethylene is 4.5-5.

5.

2. The insulating material according to claim 1, characterized in that: The reactive antioxidant has at least one of the following characteristics (1)-(3): (1) The reactive antioxidant containing allyl groups includes one or more of 2,2'-diallylbisphenol A, 2-allylphenol, 4-allyl-2,6-dimethoxyphenol, 2-allyl-6-methylphenol, 3',5-di-2-propenyl-1,1'-biphenyl-2,4'-diphenol, 4,4'-(1-methylethylidene)bis[5-methyl-2-(2-propenyl)]-phenol and 2-allyl-5-t-butylhydroquinone; (2) The reactive antioxidant containing an acrylic acid group or an acrylic acid ester group includes one or more of 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, 3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-2-octadecyl acrylate, 3,5-di-tert-butyl-4-hydroxyphenylprop-2-enoate, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)acrylic acid and 3-(3-hydroxy-4-methoxyphenyl)methyl acrylate; (3) The reactive antioxidant containing a carboxylic acid group, an anhydride group or an anhydride derivative group includes one or more of 4-hydroxyphthalic anhydride, 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropanoyloxy-2,1-ethylene glycol ester, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionic anhydride.

3. The insulating material according to claim 1, characterized in that: The polyethylene has at least one of the following characteristics (1)-(2): (1) The density of the polyethylene is 0.91 g / cm 3 -0.93g / cm 3 ; (2) The melt index of the polyethylene is 1.9 g / 10 min to 2.1 g / 10 min at 190° C. and a load of 2.16 kg.

4. The insulating material according to any one of claims 1 to 3, characterized in that: The insulating material includes at least one of the following features (1)-(3): (1) The crosslinking agent includes one or more of dicumyl peroxide, di-tert-butyl peroxide, di-tert-butyl peroxyisopropylbenzene and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; (2) The initiator includes one or more of dicumyl peroxide, di-tert-butyl peroxide, di-tert-butyl peroxycumene and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; (3) The auxiliary cross-linking agent includes one or more of triallyl isocyanurate, triallyl cyanurate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate and 2,4-diphenyl-4-methyl-1-pentene.

5. A method for preparing an insulating material, characterized in that: The raw materials for preparing the insulating material include, by weight, 100 parts of polyethylene, 0.1 to 0.3 parts of a reactive antioxidant, 0.1 to 0.2 parts of an initiator, 1.2 to 1.6 parts of a cross-linking agent, and 0.1 to 0.2 parts of an auxiliary cross-linking agent. The reactive antioxidant is a liquid antioxidant. The preparation method includes the following steps: The antioxidant is sprayed into the polyethylene in a shaking state, followed by rotational mixing and absorption to prepare an intermediate; Using a single-screw extruder to melt-extrude the intermediate and the initiator, and granulating the melt-extruded material to prepare a semi-finished product of antioxidant-grafted modified polyethylene; Spraying a molten liquid containing the cross-linking agent and the auxiliary cross-linking agent into the semi-finished product while shaking the semi-finished product; After the spraying is finished, the shaking is continued for a preset time, and then the insulation is carried out and then absorbed to prepare the insulating material; The reactive antioxidant comprises a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an anhydride group and an anhydride derivative group; the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is 0, and the polyethylene does not contain impurity particles with a particle size greater than 70 μm; The mass ratio of the reactive antioxidant to the initiator is (0.1-0.3):(0.1-0.2); the weight average molecular weight of the polyethylene is 120000Da-180000Da; and the molecular weight distribution index of the polyethylene is 4.5-5.

5.

6. The preparation method according to claim 5, characterized in that: The preparation method comprises at least one of the following conditions: (1) The rotational mixing is performed at a speed of 30 rpm to 60 rpm and a time of 50 min to 80 min; (2) The absorption temperature is 60°C-80°C and the absorption time is 2h-4h; (3) The temperature of the melt extrusion is 120°C-180°C, and the rotation speed is 120rpm-180rpm; (4) The speed of shaking the semi-finished product is 30 rpm-60 rpm, and the preset time is 50 min-60 min; (5) The temperature of the absorption after the insulation is 70°C-80°C, and the time is 16h-24h.

7. A method for preparing an insulating material, characterized in that: The raw materials for preparing the insulating material include, by weight, 100 parts of polyethylene, 0.1 to 0.3 parts of a reactive antioxidant, 0.1 to 0.2 parts of an initiator, 1.2 to 1.6 parts of a cross-linking agent, and 0.1 to 0.2 parts of an auxiliary cross-linking agent. The reactive antioxidant is a solid antioxidant. The preparation method includes the following steps: Mixing the reactive antioxidant with a solvent to prepare a premix solution; The premixed solution and the polyethylene are rotationally mixed to remove the solvent in the premixed solution to prepare an intermediate; Using a single-screw extruder to melt-extrude the intermediate and the initiator, and granulating the melt-extruded material to prepare a semi-finished product of antioxidant-grafted modified polyethylene; Spraying a molten liquid containing the cross-linking agent and the auxiliary cross-linking agent into the semi-finished product while shaking the semi-finished product; After the spraying is finished, the shaking is continued for a preset time, and then the insulation is carried out and then absorbed to prepare the insulating material; The reactive antioxidant comprises a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an anhydride group and an anhydride derivative group; the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is 0, and the polyethylene does not contain impurity particles with a particle size greater than 70 μm; The mass ratio of the reactive antioxidant to the initiator is (0.1-0.3):(0.1-0.2); the weight average molecular weight of the polyethylene is 120000Da-180000Da; and the molecular weight distribution index of the polyethylene is 4.5-5.

5.

8. The preparation method according to claim 7, characterized in that: The preparation method comprises at least one of the following conditions: (1) The rotational mixing is performed at a speed of 20 rpm to 40 rpm and a time of 30 min to 60 min; (2) The temperature of the melt extrusion is 120°C-200°C, and the rotation speed is 120rpm-180rpm; (3) The semi-finished product is shaken at a speed of 30 rpm to 60 rpm, and the preset time is 50 min to 60 min; (4) The temperature of the absorption after the insulation is 70°C-80°C, and the time is 16h-24h.

9. A method for preparing an insulating material, characterized in that: The raw materials for preparing the insulating material include, by weight, 100 parts of polyethylene, 0.1 to 0.3 parts of a reactive antioxidant, 0.1 to 0.2 parts of an initiator, 1.2 to 1.6 parts of a cross-linking agent, and 0.1 to 0.2 parts of an auxiliary cross-linking agent, part of the reactive antioxidant is a liquid antioxidant, and the remaining reactive antioxidant is a solid antioxidant. The preparation method includes the following steps: Mixing the solid antioxidant with a solvent to prepare a premix solution; After first rotating and mixing the premix solution and the polyethylene, the solvent in the premix solution is removed to prepare a first intermediate; Spraying the liquid antioxidant into the first intermediate in a shaking state and then performing a second rotation mixing and absorption to prepare a second intermediate; Using a single-screw extruder to melt-extrude the second intermediate and the initiator, and granulating the melt-extruded material to prepare a semi-finished product of antioxidant-grafted modified polyethylene; Spraying a molten liquid containing the cross-linking agent and the auxiliary cross-linking agent into the semi-finished product while shaking the semi-finished product; After the spraying is finished, the shaking is continued for a preset time, and then the insulation is carried out and then absorbed to prepare the insulating material; The reactive antioxidant comprises a hindered phenol group and one or more of an allyl group, an acrylic acid group, an acrylate group, a carboxylic acid group, an anhydride group and an anhydride derivative group; the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is 0, and the polyethylene does not contain impurity particles with a particle size greater than 70 μm; The mass ratio of the reactive antioxidant to the initiator is (0.1-0.3):(0.1-0.2); the weight average molecular weight of the polyethylene is 120000Da-180000Da; and the molecular weight distribution index of the polyethylene is 4.5-5.

5.

10. The preparation method according to claim 9, characterized in that: The preparation method comprises at least one of the following conditions: (1) The first rotational mixing is performed at a speed of 20 rpm to 40 rpm and a time of 30 min to 60 min; (2) The second rotational mixing is performed at a speed of 30 rpm to 60 rpm for 50 min to 80 min; (3) The absorption temperature is 60°C-80°C and the absorption time is 2h-4h; (4) The temperature of the melt extrusion is 120°C-200°C, and the rotation speed is 120rpm-180rpm; (5) The speed of shaking the semi-finished product is 30 rpm-60 rpm, and the preset time is 50 min-60 min; (6) The temperature of the absorption after the insulation is 70°C-80°C, and the time is 16h-24h.

11. Use of the insulating material according to any one of claims 1 to 4 or the insulating material prepared by the preparation method according to any one of claims 5 to 10 in preparing a cable.

12. A cable, characterized in that: The raw material for preparing the cable includes the insulating material as described in any one of claims 1 to 4 or the insulating material prepared by the preparation method as described in any one of claims 5 to 10.

13. The cable according to claim 12, characterized in that The cable is a submarine cable.

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