Insulating material, preparation method, application and cable

Abstract

The invention provides an insulating material, a preparation method, application and a cable. The insulating material is prepared from the following raw materials: polyethylene, a reactive antioxidant, an initiator, a cross-linking agent and an assistant cross-linking agent. The reactive antioxidant comprises one or more of a hindered phenol group, 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 the particle size of 50-70 microns contained in the polyethylene is less than 3. The reactive antioxidant can be grafted to a polyethylene molecular chain through melting, and the grafted reactive antioxidant is not easy to migrate in the use process and shows excellent long-term thermal oxidation stability and space charge inhibition capability, so that the electrical performance and thermo-oxidative aging resistance of the insulating material are improved.

Description

Technical Field

[0001] The present application relates to the technical field of insulating materials, and in particular 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 insulation plays a vital role in ensuring its safe operation. Cross-linked polyethylene (XLPE) has been widely used as the main material for preparing cable insulation due to its excellent electrical, physical, chemical and mechanical properties.

[0003] However, the degradation of cable insulation materials caused by long-term aging under comprehensive thermal stress and electrical stress is the main cause of power cable failures, and antioxidants are often added during the preparation of cable insulation materials. Although the antioxidants used in the relevant technology have good anti-aging and anti-scorch properties, the dispersion uniformity of the antioxidants in the insulation materials is poor, resulting in the degradation of local performance of the insulation materials. Summary of the invention

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

[0005] The first aspect of the present application provides an insulating material, wherein 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 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 less than 3, and does not contain 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 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;

[0008] (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;

[0009] (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-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.

[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, the raw materials for preparing the insulating material include, by weight: 100 parts of the polyethylene, 0.1 parts to 0.3 parts of the reactive antioxidant, 0.1 parts to 0.2 parts of the initiator, 1.2 parts to 1.6 parts of the cross-linking agent and 0.1 parts to 0.2 parts of the auxiliary cross-linking agent.

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

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

[0014] (2) The weight average molecular weight of the polyethylene is 120,000 Da to 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 is 1.9 g / 10 min to 2.1 g / 10 min at 190° C. and a load of 2.16 kg.

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

[0018] (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;

[0019] (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;

[0020] (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.

[0021] The second aspect of the present application provides a method for preparing an insulating material, wherein 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, wherein the reactive antioxidant is a liquid antioxidant, and the preparation method comprises the following steps:

[0022] The antioxidant is sprayed into the polyethylene in a shaking state, followed by rotational mixing and absorption to prepare an intermediate;

[0023] 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;

[0024] The semi-finished product is shaken while a molten liquid containing the cross-linking agent and the auxiliary cross-linking agent is sprayed therein,

[0025] 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;

[0026] 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 less than 3, and the polyethylene does not contain 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 is performed at a speed of 30 rpm to 60 rpm and a time of 50 min to 80 min;

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

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

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

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

[0033] The third aspect of the present application provides a method for preparing an insulating material, wherein 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, wherein the reactive antioxidant is a solid antioxidant, and the preparation method comprises the following steps:

[0034] Mixing the reactive antioxidant with a solvent to prepare a premix solution;

[0035] The premixed solution and the polyethylene are rotationally mixed to remove the solvent in the premixed solution to prepare an intermediate;

[0036] 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;

[0037] 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;

[0038] 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;

[0039] 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 less than 3, and the polyethylene does not contain 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 rotational mixing is performed at a speed of 20 rpm to 40 rpm and a time of 30 min to 60 min;

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

[0043] (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;

[0044] (4) The temperature of the absorption after the insulation is 70°C-80°C, and the time is 16h-24h.

[0045] The fourth aspect of the present application provides a method for preparing an insulating material, wherein 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, wherein some of the reactive antioxidants are liquid antioxidants, and the remaining reactive antioxidants are solid antioxidants, and the preparation method comprises the following steps:

[0046] Mixing the solid antioxidant with a solvent to prepare a premix solution;

[0047] After first rotating and mixing the premixed solution containing the solid antioxidant and the polyethylene, the solvent in the premixed solution is removed to prepare a first intermediate;

[0048] 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;

[0049] 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;

[0050] 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;

[0051] 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;

[0052] 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 less than 3, and the polyethylene does not contain impurity particles with a particle size greater than 70 μm.

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

[0054] (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;

[0055] (2) The second rotational mixing is performed at a speed of 30 rpm to 60 rpm for 50 min to 80 min;

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

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

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

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

[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 the preparation method of the second aspect of the present application, the insulating material prepared by the preparation method of the third aspect of the present application, or the insulating material prepared by 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, the raw materials for preparing the cable include the insulating material of the first aspect of the present application, the insulating material prepared by the preparation method of the second aspect of the present application, the insulating material prepared by the preparation method of the third aspect of the present application, or the insulating material prepared by the preparation method of the fourth aspect of the present application.

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

[0063] The above-mentioned insulating material, the raw materials for its preparation include polyethylene, reactive antioxidant, initiator, cross-linking agent and auxiliary cross-linking agent, the number of impurity particles with a particle size between 50μm-70μm contained in the polyethylene is less than 3, and there is no impurity particle with a particle size greater than 70μm, the reactive antioxidant can be grafted onto the polyethylene molecular chain by melting, and the grafted reactive antioxidant is more evenly distributed on the polyethylene molecular chain, which can better fill the weak points that may appear between the molecular chains at the microscopic level, disperse the electric field stress, thereby improving the DC breakdown strength, and then 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, the antioxidant molecules are not easy to migrate and precipitate, and can form an anti-oxidation "protective area" locally for a long time, preventing direct contact between oxygen and polyethylene molecular chains, and reducing the probability of oxidation reaction, thereby improving the thermal oxygen aging resistance of the insulating material. In addition, by melt grafting, reactive antioxidants are added to the polymer main chain, which overcomes the deficiency of low molecular weight additive antioxidants that are easy to migrate and lose, while avoiding the disadvantages of high molecular weight antioxidants that have poor compatibility with polyethylene resins and low effective concentrations, thereby improving the dispersibility and stability of antioxidants in polyolefins. DETAILED DESCRIPTION

[0064] For ease of understanding of the present invention, the application will be described more fully below with reference to relevant embodiments. The following provides preferred embodiments of the application. However, the 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 disclosure of the application more thorough and comprehensive.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein 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 terms "and / or", "or / and", and "and / or" used herein include any one of two or more related listed items, and also include any and all combinations of the related listed items, wherein the any and all combinations include any combination of two related listed items, any more related listed items, or all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in the present application, the technical solution undoubtedly includes technical solutions connected by "logical and", and also undoubtedly includes technical solutions connected by "logical or".

[0067] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0068] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0069] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0070] The temperature parameters in this application, unless otherwise specified, allow 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 the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0071] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc., shall be based on the ability 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 the present application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0073] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

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

[0075] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0076] If there is no special explanation, all the steps of the present application can be performed sequentially or randomly, preferably sequentially.

[0077] The degradation of cable insulation materials caused by long-term aging under comprehensive thermal stress and electrical stress is the main cause of power cable failures. It is often necessary to add antioxidants during the preparation of cable insulation materials. Common antioxidants in the cross-linked polyethylene insulation industry include antioxidant 300, antioxidant 1010, antioxidant 330, antioxidant 1035, etc. Although they have good anti-aging and anti-scorch properties, they have poor compatibility with the matrix resin and are easy to migrate, resulting in irregular dispersion of antioxidants in the matrix resin, causing local degradation of insulation performance.

[0078] Based on the above problems, the present application adopts a reactive antioxidant and adds the reactive antioxidant to the polymer main chain by melt grafting, thereby overcoming the deficiency of low molecular weight additive antioxidants that are easy to migrate and lose, while avoiding the disadvantages of high molecular weight antioxidants that have poor compatibility with polyethylene resins and low effective concentrations.

[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 cross-linking agent, and a cross-linking aid; the reactive antioxidant contains one or more of a hindered phenol group and 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 less than 3, and there are no impurity particles with a particle size greater than 70 μm. It can be understood that the raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a cross-linking agent, and a cross-linking aid, and the number of impurity particles with a particle size between 50 μm and 70 μm contained in the polyethylene is less than 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 weak points that may appear between the molecular chains at the microscopic level, disperse the electric field stress, thereby improving the DC breakdown strength, and then 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 chemical bonds. 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 easy to migrate and precipitate. It can form an anti-oxidation "protective area" locally for a long time, preventing direct contact between oxygen and polyethylene molecular chains, reducing the probability of oxidation reactions, and thus improving the thermal oxygen aging resistance of the insulation material. At the same time, the reactive antioxidant is added to the polymer main chain through melt grafting, which overcomes the disadvantage of easy migration loss of low molecular weight additive antioxidants, and avoids the disadvantages of poor compatibility and low effective concentration of high molecular weight antioxidants with polyethylene resins, thereby improving the dispersibility and stability of antioxidants in polyolefins.

[0080] In addition, the reactive antioxidant 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 derivative group, taking into account the functions of both an antioxidant and an anti-scorch agent, effectively reducing the cost of cable production, improving the scorch resistance of insulating material products, and reducing the risk of impurity particles that may appear during the cable production and processing.

[0081] Furthermore, the number of impurity particles with a particle size between 50μm and 70μm in the polyethylene is less than 3, and there are no impurity particles with a particle size greater than 70μm. Therefore, on the one hand, it helps to evenly disperse the antioxidant in the polyethylene, so as to give 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 voltage, the insulation resistance is significantly improved, and the dielectric loss is significantly reduced. In terms of processing performance, the pure polyethylene melt has better fluidity, higher melt uniformity, and lower risk of scorching during the production of insulating materials, so as to ensure the high quality and efficient production of products.

[0082] In some exemplary embodiments, the allyl group-containing reactive antioxidant 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 optional 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-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.

[0084] In some optional embodiments, 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-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 the polyethylene, and ensure that the grafting reaction proceeds at an appropriate reaction rate without inducing excessive side reactions (such as excessive cross-linking or degradation of polyethylene molecular chains), thereby affecting the quality and performance of the product.

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

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

[0088] The mass fraction of the initiator contained in the raw material 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 a range between any two of the above mass fractions.

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

[0090] The weight fraction of the auxiliary cross-linking agent contained in the raw material 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 a range between any two of the above weight fractions.

[0091] When the mass fractions of reactive antioxidant, initiator, cross-linking agent and auxiliary cross-linking agent contained in the raw materials for preparing the insulating material are respectively within the above ranges, the synergistic effect can be exerted to the greatest extent; wherein, the initiator can initiate the grafting reaction between the reactive antioxidant and the insulating material at an appropriate reaction rate, thereby giving full play to the antioxidant effect of the antioxidant and preventing the oxidative degradation of the polymer molecular chains; the cross-linking agent and the auxiliary cross-linking agent cooperate to form a three-dimensional network structure between the molecular chains of the insulating material, making the cross-linking structure more uniform.

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

[0093] In some optional embodiments, the weight average molecular weight of polyethylene is 120000Da-180000Da; it can be but not limited to 120000Da, 125000Da, 130000Da, 135000Da, 140000Da, 145000Da, 150000Da, 155000Da, 160000Da, 165000Da, 170000Da, 175000Da, 180000Da or the range between any two of the above weight average molecular weights. When the weight average molecular weight of polyethylene is within the above range, the degree of entanglement between polyethylene molecular chains is moderate, and the diffusion path of antioxidant molecules in polyethylene is smoother, which is more conducive to improving its uniform dispersion. At the same time, regulating the weight average molecular weight of polyethylene helps to improve its compatibility with antioxidants and reduce phase separation. On the other hand, controlling the weight-average molecular weight of polyethylene within the above-mentioned range can make the active sites on the molecular chain more easily accessible to the antioxidant molecules, so that the antioxidant can be more evenly distributed around the active sites of the polyethylene molecular chain during the grafting or physical mixing process, which is beneficial to the uniform dispersion of the antioxidant in the polyethylene, thereby improving the modification effect of the antioxidant.

[0094] As a possible embodiment, the molecular weight distribution index of polyethylene is 4.5-5.5; for example, it can be but 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 indexes. When the molecular weight distribution index of polyethylene is within the above range, the molecular chain length of polyethylene is relatively more uniform, which reduces the diffusion difference and 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 dispersed in a stable synergistic environment.

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

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

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

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

[0099] In some embodiments, 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.

[0100] 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 cross-linking agent, and a cross-linking aid, wherein the reactive antioxidant is a liquid antioxidant, and the preparation method includes the following steps:

[0101] The antioxidant is sprayed into polyethylene in a shaking state, followed by rotational mixing and absorption to prepare an intermediate; the intermediate and the initiator are melt-extruded by a single-screw extruder, and the melt-extruded material is granulated to prepare a semi-finished product of antioxidant-grafted modified polyethylene; a molten liquid containing a cross-linking agent and an auxiliary cross-linking agent is sprayed into the semi-finished product while shaking the semi-finished product, and after the spraying is completed, the semi-finished product is continuously shaken for a preset time, and then the product is heat-insulated and absorbed to prepare an insulating material; wherein 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 less than 3, and no impurity particles with a particle size greater than 70 μm are contained.

[0102] In the preparation method, the antioxidant, crosslinking agent and auxiliary crosslinking agent are added by spraying, that is, the polyethylene is allowed to absorb the antioxidant, crosslinking agent and auxiliary crosslinking agent under more uniform temperature conditions by liquid immersion absorption, thereby further improving the uniform dispersion of the antioxidant from the process aspect.

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

[0104] As a possible implementation manner, the antioxidant and polyethylene are tumble mixed for 50-80 minutes; for example, it may be but is not limited to 50 minutes, 60 minutes, 70 minutes, 80 minutes or a range between any two of the above times.

[0105] It should be noted that the rotation speed and time for rotating and mixing the antioxidant and polyethylene can be combined in any suitable manner, and both can be selected from any rotation speed and time for rotating and mixing the antioxidant and polyethylene described in this article.

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

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

[0108] It should be noted that the absorption temperature and time can be combined in any appropriate manner, and both can be selected from any absorption temperature and time described in this article.

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

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

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

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

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

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

[0115] It should be noted that the temperature and time of absorption after insulation can be combined in any appropriate manner, and both can be selected from any temperature and time of absorption after insulation described in this article.

[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 cross-linking agent and an auxiliary cross-linking agent, wherein 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; rotating and mixing the premix solution with polyethylene, removing the solvent in the premix solution, and preparing an intermediate; melt-extrude the intermediate and the initiator using a single-screw extruder, granulating the melt-extruded material, and preparing a semi-finished product of antioxidant-grafted modified polyethylene; shaking the semi-finished product while spraying a molten liquid containing a cross-linking agent and an auxiliary cross-linking agent therein; continuing to shake for a preset time after spraying, 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 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 less than 3, and no impurity particles with a particle size greater than 70 μm are contained.

[0117] In the preparation method, the solid antioxidant is prepared into a premixed solution and then mixed with polyethylene, and the cross-linking agent and the auxiliary cross-linking agent are added by spraying, which is conducive to the polyethylene absorbing the antioxidant, the cross-linking agent and the auxiliary cross-linking agent under more uniform temperature conditions, and further improves the uniform dispersion of the antioxidant from the process aspect.

[0118] In some embodiments, the solvent used in preparing the premix solution includes xylene.

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

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

[0121] It should be noted that the rotation speed and time for rotating and mixing the premixed solution containing an antioxidant and polyethylene can be combined in any suitable manner, and both can be selected from any rotation speed and time for rotating and mixing the premixed solution containing an antioxidant and polyethylene described in this article.

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

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

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

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

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

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

[0128] It should be noted that the temperature and time of absorption after insulation can be combined in any appropriate manner, and both can be selected from any temperature and time of absorption after insulation described in this article.

[0129] 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 cross-linking agent, and a cross-linking aid, 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:

[0130] A solid antioxidant is mixed with a solvent to prepare a premix solution; the premix solution and polyethylene are subjected to a first rotational mixing, and the solvent in the premix solution is removed to prepare a first intermediate; a liquid antioxidant is sprayed into the first intermediate in a shaking state, and then a second rotational mixing and absorption is performed to prepare a second intermediate; the second intermediate and an initiator are melt-extruded by a single-screw extruder, and the melt-extruded material is granulated to prepare a semi-finished product of antioxidant-grafted modified polyethylene; while shaking the semi-finished product, a molten liquid containing a cross-linking agent and a co-cross-linking agent is sprayed into the semi-finished product; after the spraying is completed, the product is continuously shaken for a preset time, and then the product is heat-insulated and then absorbed 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 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 less than 3, and no impurity particles with a particle size greater than 70 μm are contained.

[0131] It should be noted that the "first intermediate", "second intermediate", "first rotational mixing", "second rotational mixing" and the like mentioned in the context are only used 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, "first", "second" and the like only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0132] In the preparation method, the solid antioxidant is prepared into a premixed solution and then mixed with polyethylene, and the liquid antioxidant, cross-linking agent and auxiliary cross-linking agent are added by spraying, which is conducive to the polyethylene absorbing the antioxidant, cross-linking agent and auxiliary cross-linking agent under more uniform temperature conditions, and further improves the uniform dispersion of the antioxidant from the process aspect.

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

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

[0135] It should be noted that the rotation speed and time for the first rotational mixing of the premixed solution containing solid antioxidants and polyethylene can be combined in any appropriate manner, and both can be selected from any rotation speed and time for the first rotational mixing of the premixed solution containing solid antioxidants and polyethylene described in this article.

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

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

[0138] It should be noted that the rotation speed and time of the second rotational mixing can be combined in any appropriate manner, and both can be selected from any second rotational mixing rotation speed and time described in this document.

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

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

[0141] It should be noted that the absorption temperature and time can be combined in any appropriate manner, and both can be selected from any absorption temperature and time described in this article.

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

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

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

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

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

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

[0148] It should be noted that the temperature and time of absorption after insulation can be combined in any appropriate manner, and both can be selected from any temperature and time of absorption after insulation described in this article.

[0149] In some embodiments, the solvent used in preparing the premix solution includes xylene.

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

[0151] One or more embodiments of the present application provide a cable, the raw material of which includes 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 cable has a carrying voltage of 500 kV and below.

[0154] It should be noted that the “carrying voltage” mentioned in this context refers to the voltage at which the cable can operate safely and stably.

[0155] The technical scheme of the present invention is 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 are not intended to limit the scope of the present invention. The experimental methods for which specific conditions are not specified in the following embodiments are preferably referred to the guidance given in the present invention, and can also be carried out according to the experimental manual or conventional conditions in the art, or according to the conditions recommended by the manufacturer, or with reference to experimental methods known in the art.

[0156] In the following specific embodiments, the measured parameters of raw material components may have slight deviations within the range of weighing accuracy unless otherwise specified. For temperature and time parameters, acceptable deviations caused by instrument test accuracy or operation accuracy are allowed.

[0157] 1. Preparation of insulating materials

[0158] 1. Formula 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] In Table 1-1 and Table 1-2, "TMPTMA" means trimethylolpropane trimethacrylate; "BIPB" means 1,4-di-tert-butylperoxyisopropylbenzene; each "part" means 100 g. Molecular weight means weight average molecular weight.

[0165] 2. Preparation process

[0166] In the above-mentioned embodiments and comparative examples, the reactive antioxidant used in Embodiment 1, Embodiment 2 and Embodiments 12-15 is a liquid antioxidant, and the preparation method comprises the following steps:

[0167] Step S1, firstly, introduce low-density polyethylene particles into a shaking tank at a shaking tank temperature of 75°C; secondly, spray the antioxidant into the shaking tank for rotational mixing for 60 minutes at a speed of 35rpm; then, shake dry and let stand for absorption at a temperature of 75°C and a standing time of 3h to obtain a uniformly dispersed intermediate.

[0168] Step S2, directly adding the intermediate prepared in step S1 into a single-screw extruder, adding an initiator in proportion, filtering the material through a high-mesh filter after melt extrusion, and then water-cooling and granulating to obtain 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, and 180°C, and the extruder speed is 150rpm.

[0169] Step S3, firstly, fully melt the cross-linking agent and the auxiliary cross-linking agent in an insulation tank and filter out impurities through a filter screen, and the temperature of the insulation tank is 75°C; secondly, introduce them into a mixing tank in proportion and mechanically stir for 5 minutes, the temperature of the mixing tank is 75°C, and the stirring speed is 15rpm; then, spray and inject them into a shaking tank containing semi-finished products, the temperature of the shaking tank is 70°C, and the shaking time after spraying is continued for 60 minutes at a speed of 35rpm; finally, introduce the materials in the shaking tank into an insulation tank for sufficient insulation and absorption, the insulation temperature is 75°C, the insulation time is 18h, and the polyethylene cable insulation material is obtained after cooling.

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

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

[0172] Step S2, directly adding the intermediate prepared in step S1 into a single screw extruder, adding an initiator in proportion, filtering the material through a high-mesh filter after melt extrusion, and then water-cooling and granulating to obtain a semi-finished product of antioxidant grafted modified polyethylene; wherein the temperature of each zone of the extruder in Examples 3-4, 6-7 and 9 is 120°C, 130°C, 140°C, 150°C, 155°C, 160°C, 165°C, 170°C, 180°C, and the extruder speed is 150rpm; the temperature of each zone of the extruder in Examples 5, 8 and 10-11 is 125°C, 135°C, 145°C, 150°C, 160°C, 170°C, 180°C, 185°C, 195°C, and the extruder speed is 150rpm.

[0173] Step S3, firstly, fully melt the cross-linking agent and the auxiliary cross-linking agent in an insulation tank and filter out impurities through a filter screen, and the temperature of the insulation tank is 75°C; secondly, introduce them into a mixing tank in proportion and mechanically stir for 5 minutes, the temperature of the mixing tank is 75°C, and the stirring speed is 15rpm; then, spray and inject them into a shaking tank containing semi-finished products, the temperature of the shaking tank is 70°C, and the shaking time after spraying is continued for 60 minutes at a speed of 35rpm; finally, introduce the materials in the shaking tank into an insulation tank for sufficient insulation and absorption, the insulation temperature is 75°C, the insulation time is 18h, and the polyethylene cable insulation material is obtained after cooling.

[0174] 2. Performance Test

[0175] The insulating materials prepared in the above embodiments and comparative examples were subjected to a DC breakdown strength test and an oxidation induction test, and the test methods were as follows:

[0176] DC breakdown strength test: refer to GB / T 1408.2, the electrode is a column-plate electrode with a diameter of 25 mm, the arc radius of the electrode edge is 2.5 mm, the test temperature is (70±2)℃, and the test piece thickness is (0.2±0.02) mm.

[0177] Oxidation induction period (OIT) test: refer to GB / T 19466.6, use differential scanning calorimeter, raise the temperature to 200℃ at a rate of 20℃ / min in a nitrogen atmosphere (50mL / min), keep the temperature constant for 5min, then switch to oxygen atmosphere (50mL / min), observe the thermal effect and calculate the oxidation induction period of the sample at a constant temperature of 200℃.

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

[0179] Table 2

[0180]

[0181] In Table 2, "OIT" stands for oxidation induction time.

[0182] From the comparison of the results of Examples 1-23 and Comparative Examples 1-4 in Table 2, it can be seen that the reactive antioxidant grafted modified cross-linked polyethylene insulation material provided in the present application has excellent electrical properties and heat-oxidative aging resistance.

[0183] By comparing the results of Example 1 and Examples 12-15, it can be seen that by regulating 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 without producing side reactions such as cross-linking and degradation, which is beneficial to further improve the electrical properties and heat-oxidative aging resistance of the cross-linked 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 helping to further improve the electrical properties and heat-oxidation aging resistance of the cross-linked polyethylene insulation material.

[0185] By comparing 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 helping to further improve the electrical properties and heat-oxidation aging resistance of the cross-linked polyethylene insulation material.

[0186] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0187] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An insulating material, characterized in that: The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a cross-linking agent and a cross-linking aid; 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 less than 3, and the polyethylene does not contain impurity particles with a particle size greater than 70 μm.

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 mass ratio of the reactive antioxidant to the initiator is (0.1-0.3):(0.1-0.2).

4. The insulating material according to claim 1, characterized in that: The raw materials for preparing the insulating material include, by weight: 100 parts of the polyethylene, 0.1 to 0.3 parts of the reactive antioxidant, 0.1 to 0.2 parts of the initiator, 1.2 to 1.6 parts of the cross-linking agent and 0.1 to 0.2 parts of the auxiliary cross-linking agent.

5. The insulating material according to claim 1, characterized in that: The polyethylene has at least one of the following characteristics (1)-(5): (1) The density of the polyethylene is 0.91 g / cm 3 -0.93g / cm 3 ; (2) The weight average molecular weight of the polyethylene is 120,000 Da to 180,000 Da; (3) The molecular weight distribution index of the polyethylene is 4.5-5.5; (4) 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.

6. The insulating material according to any one of claims 1 to 5, 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 peroxyisopropylbenzene 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.

7. A method for preparing an insulating material, characterized in that: 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 is a liquid antioxidant, and 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 less than 3, and the polyethylene does not contain impurity particles with a particle size greater than 70 μm.

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 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.

9. A method for preparing an insulating material, characterized in that: The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a cross-linking agent and a cross-linking aid, the reactive antioxidant is a solid antioxidant, and 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 less than 3, and the polyethylene does not contain impurity particles with a particle size greater than 70 μm.

10. The preparation method according to claim 9, 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.

11. A method for preparing an insulating material, characterized in that: The raw materials for preparing the insulating material include polyethylene, a reactive antioxidant, an initiator, a cross-linking agent and a cross-linking aid, some of the reactive antioxidants are liquid antioxidants, and the remaining reactive antioxidants are solid antioxidants. 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 less than 3, and the polyethylene does not contain impurity particles with a particle size greater than 70 μm.

12. The preparation method according to claim 11, 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 for 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.

13. Use of the insulating material according to any one of claims 1 to 6 or the insulating material prepared by the preparation method according to any one of claims 7 to 12 in preparing a cable.

14. 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 6 or the insulating material prepared by the preparation method as described in any one of claims 7 to 12.

15. The cable according to claim 14, characterized in that The cable is a submarine cable.

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