Insulating materials, preparation methods, applications and cables

Abstract

The present application provides an insulating material, a preparation method, an application and a cable, wherein the insulating material comprises a first resin, a second resin, an antioxidant, a crosslinking agent and a crosslinking aid; the first resin comprises a low-density polyethylene, with a weight average molecular weight of 120000Da-180000Da and a molecular weight distribution index of 4.5-5.5; the second resin comprises one or both of a high-molecular-weight high-density polyethylene and an ultra-high-molecular-weight polyethylene, the weight average molecular weight of the high-molecular-weight high-density polyethylene is 250000Da-350000Da, and the molecular weight distribution index is 1.5-5.5; the weight average molecular weight of the ultra-high-molecular-weight polyethylene is 2000000Da-2400000Da, and the molecular weight distribution index is 6.0-8.0. The insulating material has excellent temperature resistance and electrical properties.

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] Low-density polyethylene (LDPE) has good elongation, electrical insulation, easy processing and chemical stability, and has wide application value in the field of wires and cables. However, LDPE has a low melting point (usually Tm≈110℃) and poor mechanical properties, which limits the thermomechanical and electrical properties of LDPE at high temperatures, thereby affecting the temperature resistance and electrical properties of cross-linked polyethylene insulation materials. How to improve the temperature resistance and electrical properties of cross-linked polyethylene insulation materials is one of the key technical problems that need to be solved urgently. Summary of the invention

[0003] Based on this, the present application provides an insulating material, a preparation method, an application and a cable.

[0004] The first aspect of the present application provides an insulating material, comprising a first resin, a second resin, an antioxidant, a crosslinking agent and a crosslinking aid;

[0005] The first resin comprises low-density polyethylene, the weight average molecular weight of the low-density polyethylene is 120000Da-180000Da, and the molecular weight distribution index is 4.5-5.5;

[0006] The second resin includes one or more of high molecular weight high density polyethylene and ultra high molecular weight polyethylene, the weight average molecular weight of the high molecular weight high density polyethylene is 250000Da-350000Da, and the molecular weight distribution index is 1.5-5.5; the weight average molecular weight of the ultra high molecular weight polyethylene is 2000000Da-2400000Da, and the molecular weight distribution index is 6.0-8.0.

[0007] In some embodiments, the mass of the first resin accounts for 90%-99% of the total mass of the first resin and the second resin.

[0008] In some embodiments, based on 100 parts by weight of the first resin and the second resin, the insulating material includes 0.1-0.3 parts of the antioxidant, 0.8-1.2 parts of the crosslinking agent, and 0.2-0.3 parts of the crosslinking aid.

[0009] In some embodiments, the density of the low-density polyethylene is 0.91 g / cm 3 -0.93g / cm 3The melting point is 105℃-115℃, and the melt index at 190℃ and 2.16kg load is 1.9g / 10min-2.1g / 10min.

[0010] In some embodiments, the density of the high molecular weight high density polyethylene is 0.94 g / cm 3 -0.96g / cm 3 The melting point is 125℃-135℃, and the melt index is 3.0g / 10min-10.0g / 10min at 190℃ and 21.6kg load.

[0011] In some embodiments, the density of the ultra-high molecular weight polyethylene is 0.92 g / cm 3 -0.96g / cm 3 The melting point is 130℃-140℃, and the melt index at 190℃ and 21.6kg load is 0.1g / 10min-0.25g / 10min.

[0012] In some embodiments, the antioxidant includes one or more of 4,4'-thiobis(6-tert-butyl-3-methylphenol), 1,3,5-trimethyl-2,4,6-tri(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, pentaerythritol tetra(bis-T-butylhydroxyhydrocinnamate) ester, and β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0013] In some embodiments, the crosslinking agent includes one or more of diisopropylbenzene peroxide, di-tert-butylperoxyisopropylbenzene, benzoyl peroxide, di-tert-butyl peroxide, tert-butylisopropylbenzene peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0014] In some embodiments, the crosslinking aid includes one or more of triallyl isocyanurate, trimethylolpropane trimethacrylate, and 2,4-diphenyl-4-methyl-1-pentene.

[0015] The second aspect of the present application provides a method for preparing an insulating material, comprising the following steps:

[0016] The first resin and the second resin are mixed and then subjected to first extrusion granulation to prepare a composite resin material;

[0017] The composite resin material is mixed with an antioxidant and then subjected to a second extrusion granulation to prepare a semi-finished product material;

[0018] The semi-finished material is mixed with a cross-linking agent and a cross-linking auxiliary agent and then subjected to post-absorption treatment to prepare the insulating material;

[0019] Wherein, the first resin comprises low-density polyethylene, the weight average molecular weight of the low-density polyethylene is 120000Da-180000Da, and the molecular weight distribution index is 4.5-5.5;

[0020] The second resin includes high molecular weight high density polyethylene and ultra high molecular weight polyethylene. The weight average molecular weight of the high molecular weight high density polyethylene is 250000Da-350000Da, and the molecular weight distribution index is 1.5-5.5; the weight average molecular weight of the ultra high molecular weight polyethylene is 2000000Da-2400000Da, and the molecular weight distribution index is 6.0-8.0.

[0021] In some embodiments, the step of mixing the semi-finished product with the cross-linking agent and the cross-linking auxiliary agent and then performing post-absorption treatment comprises:

[0022] Spraying a mixed liquid containing the cross-linking agent and the cross-linking aid into the semi-finished product while shaking the semi-finished product;

[0023] After the spraying is finished, continue shaking for the preset time and then keep warm.

[0024] In some embodiments, the preparation method includes at least one of the following conditions:

[0025] (1) The shaking speed is 30 rpm-60 rpm;

[0026] (2) The shaking temperature is 60°C-70°C;

[0027] (3) The preset time is 50min-60min;

[0028] (4) The temperature of the heat preservation treatment is 70°C-80°C, and the time is 16h-24h.

[0029] In some embodiments, the extrusion temperature of the first extrusion granulation is 150° C.-200° C., and the rotation speed of the twin-screw extruder used is 120 rpm-180 rpm.

[0030] In some embodiments, the extrusion temperature of the second extrusion granulation is 130° C.-180° C., and the rotation speed of the twin-screw extruder used is 150 rpm-200 rpm.

[0031] The third aspect of the present application provides an application of the insulating material of the first aspect of the present application or the insulating material prepared by the preparation method of the second aspect of the present application in preparing a cable.

[0032] The fourth aspect of the present application provides a cable, wherein the raw materials for preparing the cable include the insulating material of the first aspect of the present application or the insulating material prepared by the preparation method of the second aspect of the present application.

[0033] In some embodiments, the cable is a submarine cable.

[0034] The insulating material provided above includes a first resin and a second resin used in a compound, and the weight average molecular weight and molecular weight distribution index of the first resin, as well as the weight average molecular weight and molecular weight distribution index of the second resin are respectively regulated within an appropriate range, and at least has the following beneficial effects: first, the second resin can carry the network at high temperature, prevent the thermal creep of low-density polyethylene under its load, so that the high-temperature thermal creep performance of the insulating material finally obtained is improved; secondly, the amount of cross-linking agent used is effectively reduced under the premise of ensuring the degree of cross-linking, the risk of pre-cross-linking is reduced, the production cycle and efficiency of the insulating material are improved, and the production cost of the insulating material is reduced. Thirdly, by blending the second resin and the first resin, the electrical insulation performance and dielectric strength of the first resin are improved, and the performance of the blended resin is more stable, thereby improving the electrical properties of the insulating material finally obtained. DETAILED DESCRIPTION

[0035] 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.

[0036] 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.

[0037] 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".

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] In the description of the application, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0046] 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.

[0047] If there is no special explanation, all the steps of the present application can be performed sequentially or randomly, preferably sequentially.

[0048] Low-density polyethylene (LDPE) has a low melting point (usually Tm≈110°C) and poor mechanical properties, which limits the thermomechanical and electrical properties of LDPE at high temperatures, thereby affecting the temperature resistance and electrical properties of cross-linked polyethylene insulation materials.

[0049] The most common way to improve the heat resistance and electrical properties of low-density polyethylene is cross-linking. The cross-linking reaction allows long-chain polyethylene molecules to combine in the form of covalent bonds to form a network structure, which significantly improves the mechanical properties, heat resistance and electrical properties of the material, and can increase the heat resistance temperature of LDPE from 70°C to above 100°C.

[0050] Peroxide chemical crosslinking technology is a commonly used crosslinking method in the field of high-voltage cables. Peroxides decompose under heat to form free radicals with high chemical activity. The free radicals capture hydrogen atoms in polyethylene molecules to form macromolecular free radicals. The macromolecular free radicals react with each other to form carbon-carbon crosslinks to obtain crosslinked polyethylene. However, although some performance of low-density polyethylene is improved after peroxide crosslinking, the crosslinking byproducts produced during the crosslinking process and the impurities brought by the degassing treatment will affect the service life of the cable and cause the cable insulation performance to deteriorate; at the same time, in order to ensure the stability of the network structure of the insulation material, that is, the high-temperature creep resistance, a high degree of crosslinking is often required, and a high content of crosslinking agent needs to be added, which increases the risk of pre-crosslinking caused by the decomposition of the crosslinking agent during the cable processing, and locally forms glue points / pores / scorched particles that block the filter, reducing the production cycle and production efficiency of the insulation material, and having an adverse effect on the overall performance of the cable; moreover, if the content of auxiliary agents such as crosslinking agents is too high, the compatibility / dispersion problems between the auxiliary agents will cause an increase in material defects and a decrease in the electrical performance of the insulation material.

[0051] Based on the above problems, the present application adopts a blend of two polyethylene materials to form a blend matrix compound system, and respectively regulates the weight average molecular weight, molecular weight distribution index and melt index of the two polyethylene materials to improve the temperature resistance and electrical properties of the cross-linked polyethylene insulation material while reducing the amount of cross-linking agent.

[0052] One or more embodiments of the present application provide an insulating material, including a first resin, a second resin, an antioxidant, a cross-linking agent and a cross-linking aid; the first resin includes low-density polyethylene (LDPE), the weight average molecular weight of the low-density polyethylene is 120,000Da-180,000Da, and the molecular weight distribution index is 4.5-5.5; the second resin includes one or both of high molecular weight high-density polyethylene (HMWHDPE) and ultra-high molecular weight polyethylene (UHMWPE), the weight average molecular weight of the high molecular weight high-density polyethylene is 250,000Da-350,000Da, and the molecular weight distribution index is 1.5-5.5; the weight average molecular weight of the ultra-high molecular weight polyethylene is 2,000,000Da-2,400,000Da, and the molecular weight distribution index is 6.0-8.0.

[0053] It should be noted that the "first resin", "second resin" 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 should be understood not to constitute a closed limitation on quantity.

[0054] As a non-limiting example, the weight average molecular weight of the low density polyethylene 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 a range between any two of the above weight average molecular weights, etc.

[0055] The molecular weight distribution index of the low density polyethylene may 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 a range between any two of the above molecular weight distribution indices.

[0056] The weight average molecular weight of the high molecular weight high density polyethylene can be, but is not limited to, 250,000 Da, 255,000 Da, 260,000 Da, 265,000 Da, 270,000 Da, 275,000 Da, 280,000 Da, 285,000 Da, 290,000 Da, 295,000 Da, 300,000 Da, 305,000 Da, 310,000 Da, 315,000 Da, 320,000 Da, 325,000 Da, 330,000 Da, 335,000 Da, 340,000 Da, 345,000 Da, 350,000 Da or a range between any two of the above weight average molecular weights, etc.

[0057] The molecular weight distribution index of the high molecular weight high density polyethylene can be but is not limited to 1.5, 1.7, 2, 2.3, 2.5, 2.8, 3, 3.3, 3.5, 3.8, 4, 4.3, 4.5, 4.8, 5, 5.3, 5.5 or a range between any two of the above values.

[0058] The weight average molecular weight of the ultra-high molecular weight polyethylene may be, but is not limited to, 2,000,000 Da, 2,050,000 Da, 2,100,000 Da, 2,150,000 Da, 2,200,000 Da, 2,250,000 Da, 2,300,000 Da, 2,350,000 Da, 2,400,000 Da or a range between any two of the above weight average molecular weights.

[0059] The molecular weight distribution index of the ultra-high molecular weight polyethylene can be, but is not limited to, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0 or a range between any two of the above values.

[0060] When the weight average molecular weight, molecular weight distribution index and melt index of the first resin and the weight average molecular weight and molecular weight distribution index of the second resin are respectively regulated within the above ranges, at least the following interactions may occur between the two resins: (1) The second resin has a high molecular weight and a relatively rigid molecular chain, which makes the second resin have a higher melting point; when the two are blended, the rigid molecular chain of the second resin can hinder the movement of the LDPE molecular chain to a certain extent, and at a temperature higher than the melting point of low-density polyethylene, the high-melting-point microcrystals in the second resin can be relied on to resist the deformation of the insulating material, thereby improving the heat resistance of the insulating material; (2) The blending of the first resin and the second resin can form more crystal nuclei, promote the crystallization process, and the co-crystallization effect effectively improves the crystallinity of the first resin. The crystalline region can more effectively resist the transfer of heat and restrict the movement of the molecular chain, thereby increasing the melting point of the blended resin and effectively improving the high-temperature creep resistance of the insulating material; (3) When a composite polyethylene resin is used, the two polyethylene resins can be connected through the chaining and captured entanglement between the chain segments, providing additional network stability for the insulating material; (4) The weight average molecular weight of the second resin can effectively resist the transfer of heat and restrict the movement of the molecular chain, thereby improving the high-temperature creep resistance of the insulating material; (5) The weight average molecular weight of the second resin can effectively resist the transfer of heat and restrict the movement of the molecular chain, thereby improving the high-temperature creep resistance of the insulating material; (6) The weight average molecular weight of the second resin can effectively resist the transfer of heat and restrict the movement of the molecular chain, thereby improving the high-temperature creep resistance of the insulating material; (7) The weight average molecular weight of the second resin can effectively resist the transfer of heat and restrict the movement of the molecular chain, thereby improving the high-temperature creep resistance of the insulating material; (8) The weight average molecular weight of the second resin can effectively resist the transfer of heat and restrict the movement of the molecular chain, thereby improving the high-temperature creep The weight-average molecular weight of the first resin is much greater than the weight-average molecular weight of the first resin, and the molecular weight distribution of the first resin is narrow, so that there are fewer small molecular and supramolecular impurities in the blended resin, and the electrical properties of the insulating material are effectively improved. Under the combined action of the electric field and the thermal field, the breakdown field strength is relatively high; (5) After the two resins are blended, the molecular chains are entangled and intertwined with each other, the internal structure of the blend is more uniform, and the amount of cross-linking agent used can be effectively reduced. Under the condition of ensuring a certain degree of cross-linking, the impurity content in the insulating material is effectively reduced, so that the dielectric strength of the final insulating material is higher and the performance is more stable; (6) The co-crystallization of the first resin and the second resin makes the crystalline structure of the insulating material more regular. Under the action of the electric field, it is more difficult for electrons to pass through the tightly arranged molecular chain structure, which effectively reduces the conductivity of the material and improves the electrical properties of the insulating material; (7) Low-density polyethylene, high-molecular-weight high-density polyethylene, and ultra-high molecular weight polyethylene are all polyethylene materials. The blending compatibility of the same materials is relatively good. The spatial charge accumulation caused by the microscopic interface of the two different materials and the electric field distortion caused by the local structural differences can be ignored, so that the material maintains good electrical breakdown characteristics.

[0061] In summary, the insulating material provided by the present application includes a first resin and a second resin used in a compound, and the weight average molecular weight, molecular weight distribution index and melt index of the first resin are respectively regulated, and the weight average molecular weight and molecular weight distribution index of the second resin are within an appropriate range, which has at least the following beneficial effects: First, the second resin can carry the network at high temperature to prevent the thermal creep of low-density polyethylene under its load, so that the high-temperature thermal creep performance of the insulating material finally obtained is improved; secondly, the amount of cross-linking agent used is effectively reduced under the premise of ensuring the degree of cross-linking, the risk of pre-cross-linking is reduced, the production cycle and efficiency of the insulating material are improved, and the production cost of the insulating material is reduced. Thirdly, by blending the second resin and the first resin, the electrical insulation performance and dielectric strength of the first resin are improved, and the performance of the blended resin is more stable, thereby improving the electrical properties of the insulating material finally obtained.

[0062] In some embodiments, the mass of the first resin accounts for 90%-99% of the total mass of the first resin and the second resin; for example, it may be but not limited to 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or the range between any two of the above values. Correspondingly, the mass of the second resin accounts for 1%-10% of the total mass of the first resin and the second resin; for example, it may be but not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the range between any two of the above values. When the amount of the first resin and the second resin is controlled in the above range, the co-crystallization of the two resins is promoted, the crystallinity of the matrix resin is effectively improved, and the high temperature creep resistance and electrical properties of the insulating material are improved. When the amount of the second resin is too high, the toughness of the insulating material may decrease. In addition, too much resin blending may introduce impurities or make the microstructure inside the material loose, so that the volume resistivity decreases, thereby affecting the electrical insulation performance of the insulating material. When the amount of the second resin is too low, the mechanical strength of the material may be insufficient and the high temperature creep resistance is limited.

[0063] In some embodiments, based on 100 parts by weight of the total weight of the first resin and the second resin, the insulating material includes 0.1 to 0.3 parts of an antioxidant, 0.8 to 1.2 parts of a crosslinking agent, and 0.2 to 0.3 parts of a crosslinking aid.

[0064] As a non-limiting example, based on 100 parts by weight of the total weight of the first resin and the second resin, the weight of the antioxidant may be, but is not limited to, 0.1 parts, 0.2 parts, 0.3 parts, or a range between any two of the above weights.

[0065] Based on 100 parts by weight of the total weight of the first resin and the second resin, the weight of the crosslinking agent may be, but is not limited to, 0.8 parts, 0.9 parts, 1 parts, 1.1 parts, 1.2 parts or a range between any two of the above weights.

[0066] Based on 100 parts by weight of the total weight of the first resin and the second resin, the weight of the crosslinking aid may be, but is not limited to, 0.2 parts, 0.25 parts, 0.3 parts, or a range between any two of the above weights.

[0067] The content of cross-linking agent affects the electrical properties and temperature stability of the insulating material, the content of antioxidant affects the aging resistance of the insulating material, and the cross-linking auxiliary agent affects the processing characteristics of the insulating material. There is a complex mutual inhibition between the various auxiliary agents. When the amount of antioxidant, cross-linking agent and cross-linking auxiliary agent in the insulating material is within the above range, the scorch resistance, electrical properties and thermomechanical properties of the insulating material reach a comprehensive and optimal state.

[0068] As a possible embodiment, the density of low-density polyethylene is 0.91 g / cm 3 -0.93g / cm 3 , for example, but not limited to 0.91 g / 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.

[0069] In some exemplary embodiments, the melting point of low-density polyethylene is 105°C-115°C; for example, it can be but not limited to 105°C, 106°C, 107°C, 108°C, 109°C, 110°C, 111°C, 112°C, 113°C, 114°C, 115°C or the range between any two of the above temperatures. When the melting point of low-density polyethylene is regulated within the above range, the LDPE crystallinity is relatively high, and the crystalline region can act as a physical cross-linking point, enhancing the overall mechanical properties of the material, making the insulating material less likely to break when subjected to external force. At the same time, the volume resistivity is relatively high, which can effectively prevent the conduction of current and has better insulation performance.

[0070] In some embodiments, at 190°C and 2.16 kg load, the melt index of the low density polyethylene is 1.9 g / 10min-2.1 g / 10min; 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.

[0071] 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.

[0072] In some embodiments, the density of the high molecular weight high density polyethylene is 0.94 g / cm 3 -0.96g / cm 3 ; For example, it can be but not limited to 0.94g / cm 3 , 0.942g / cm 3 , 0.944g / cm 3 , 0.946g / cm 3 , 0.948g / cm 3 , 0.95g / cm 3 , 0.952g / cm 3 , 0.954g / cm 3 、0.956g / cm 3 , 0.958g / cm 3 , 0.96g / cm 3 Or the range between any two of the above densities, etc.

[0073] In some optional embodiments, the melting point of the high molecular weight high density polyethylene is 125°C-135°C; for example, it can be but not limited to 125°C, 126°C, 127°C, 128°C, 129°C, 130°C, 131°C, 132°C, 133°C, 134°C, 135°C or the range between any two of the above melting points. When the melting point of the high molecular weight high density polyethylene is controlled within the above range, on the one hand, the HMWHDPE can have good fluidity during the processing, and when it is blended with other resins, it can be well filled into the gaps of other resins, and the blending system is uniform, which does not affect the electrical properties of the insulating material; on the other hand, a higher temperature is required to melt the HMWHDPE during the processing, so the insulating material obtained by blending it with the first resin has better high temperature creep resistance.

[0074] As a possible embodiment, at 190°C and 21.6kg load, the melt index of the high molecular weight high density polyethylene is 3.0g / 10min-10.0g / 10min; for example, it can be but not limited to 3.0g / 10min, 3.5g / 10min, 4.0g / 10min, 4.5g / 10min, 5.0g / 10min, 5.5g / 10min, 6.0g / 10min, 6.5g / 10min, 7.0g / 10min, 7.5g / 10min, 8.0g / 10min, 8.5g / 10min, 9.0g / 10min, 9.5g / 10min, 10.0g / 10min or the range between any two of the above melt indices, etc. When the melt index of high molecular weight high density polyethylene is within the above range, it has excellent fluidity at a certain temperature and pressure. During the blending process, it helps to mix the resins, enables the two resins to be more evenly dispersed in each other, and improves the electrical insulation performance of the material to a certain extent.

[0075] It should be noted that the test conditions of the "melt index of high molecular weight high density polyethylene" mentioned above and below are: testing at a temperature of 190° C. and a load of 21.6 kg in accordance with ASTM D1238 standard.

[0076] In some optional embodiments, the density of the ultra-high molecular weight polyethylene is 0.92 g / cm 3 -0.96g / cm 3 ; For example, it can be but not limited to 0.92g / cm 3 、0.925g / cm 3 、0.93g / cm 3 , 0.935g / cm 3 、0.94g / cm 3 , 0.945g / cm 3 , 0.95g / cm 3 、0.955g / cm 3 , 0.96g / cm 3 Or the range between any two of the above densities, etc.

[0077] In some embodiments, the melting point of the ultra-high molecular weight polyethylene is 130°C-140°C; for example, it can be but not limited to 130°C, 131°C, 132°C, 133°C, 134°C, 135°C, 136°C, 137°C, 138°C, 139°C, 140°C or a range between any two of the above melting points.

[0078] In some exemplary embodiments, at 190°C and 21.6 kg load, the melt index of the ultra high molecular weight polyethylene is 0.1 g / 10min-0.25 g / 10min; for example, it can be but not limited to 0.1 g / 10min, 0.11 g / 10min, 0.12 g / 10min, 0.13 g / 10min, 0.14 g / 10min, 0.15 g / 10min, 0.16 g / 10min, 0.17 g / 10min, 0.18 g / 10min, 0.19 g / 10min, 0.2 g / 10min, 0.21 g / 10min, 0.22 g / 10min, 0.23 g / 10min, 0.24 g / 10min, 0.25 g / 10min or a range between any two of the above melt indices, etc.

[0079] It should be noted that the test conditions of the "melt index of ultra-high molecular weight polyethylene" mentioned above and below are: testing at a temperature of 190° C. and a load of 21.6 kg in accordance with ASTM D1238 standard.

[0080] In some embodiments, the antioxidant includes one or more of 4,4'-thiobis(6-tert-butyl-3-methylphenol), 1,3,5-trimethyl-2,4,6-tri(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, pentaerythritol tetra(bis-T-butylhydroxyhydrocinnamate) ester, and β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0081] As a possible implementation, the crosslinking agent includes one or more of diisopropylbenzene peroxide, di-tert-butylperoxyisopropylbenzene, benzoyl peroxide, di-tert-butyl peroxide, tert-butylisopropylbenzene peroxide and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0082] In some embodiments, the crosslinking aid includes one or more of triallyl isocyanurate, trimethylolpropane trimethacrylate, and 2,4-diphenyl-4-methyl-1-pentene.

[0083] 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 preparation method comprises the following steps:

[0084] The first resin and the second resin are mixed and then subjected to a first extrusion granulation to prepare a composite resin material; the composite resin material is mixed with an antioxidant and then subjected to a second extrusion granulation to prepare a semi-finished product material; the semi-finished product material is mixed with a cross-linking agent and a cross-linking auxiliary agent and then subjected to a post-absorption treatment to prepare an insulating material;

[0085] Among them, the first resin includes low-density polyethylene, the weight average molecular weight of the low-density polyethylene is 120,000Da-180,000Da, and the molecular weight distribution index is 4.5-5.5; the second resin includes high-molecular-weight high-density polyethylene and ultra-high molecular weight polyethylene, the weight average molecular weight of the high-molecular-weight high-density polyethylene is 250,000Da-350,000Da, and the molecular weight distribution index is 1.5-5.5; the weight average molecular weight of the ultra-high molecular weight polyethylene is 2,000,000Da-2,400,000Da, and the molecular weight distribution index is 6.0-8.0.

[0086] It should be noted that the "first extrusion granulation", "second extrusion granulation" and the like 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, "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.

[0087] The preparation method of the insulating material provided in the present application is to mix the first resin and the second resin and then perform extrusion processing and granulation processing to prepare a composite resin material, which can effectively combine the advantages of each and make up for the performance defects of a single resin. During the extrusion process, the first resin and the second resin can be fully mixed under the action of high temperature and high shear force, so that the two resins are evenly distributed in the composite resin material, thereby improving the quality stability of the product; the granular composite resin material is easier to feed and melt in the subsequent insulating material processing process, and can better adapt to different molding process requirements, thereby improving production efficiency and product quality. In addition, both the extrusion process and the granulation process are process processes that can be carried out continuously, which can achieve large-scale and efficient production.

[0088] In some embodiments, the step of mixing the semi-finished product with the cross-linking agent and the cross-linking auxiliary agent and then performing post-absorption treatment comprises:

[0089] The semi-finished product is shaken while a mixed liquid containing a cross-linking agent and a cross-linking aid is sprayed therein; after the spraying is completed, the semi-finished product is shaken for a preset time, and then a post-absorption treatment is performed.

[0090] It can be understood that applying the mixed liquid containing the cross-linking agent and the cross-linking aid by shaking and spraying is conducive to the uniform application of the cross-linking agent and the cross-linking aid on the surface of the semi-finished material; the subsequent heat preservation treatment is conducive to the penetration of the cross-linking agent and the cross-linking aid into the interior of the semi-finished material, so that the cross-linking agent and the cross-linking aid can be evenly distributed in the insulating material, thereby improving the quality of the insulating material.

[0091] In some embodiments, the shaking speed 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 speeds.

[0092] As a possible implementation manner, the temperature of the shaking pot used for shaking is 60°C-70°C; for example, it can be but not limited to 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C or a range between any two of the above temperatures.

[0093] In some embodiments, the preset shaking time is 50 min-60 min; for example, it can be but not limited to 50 min, 52 min, 54 min, 56 min, 58 min, 60 min or a range between any two of the above times.

[0094] As a possible implementation manner, the temperature of the post-absorption treatment 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.

[0095] In some optional embodiments, the insulation treatment time is 16 hours to 24 hours; for example, it can be but not limited to 16 hours, 18 hours, 20 hours, 22 hours, 24 hours or a range between any two of the above times.

[0096] It should be noted that the temperature and time of the post-absorption treatment can be combined in any appropriate manner, and both can be selected from any temperature and time of the post-absorption treatment described in this article.

[0097] As a non-limiting example, the extrusion temperature of the first extrusion granulation is 150°C-200°C; for example, it can be but not limited to 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C or a range between any two of the above temperatures.

[0098] In some optional embodiments, the speed of the twin-screw extruder used in the first extrusion granulation is 120rpm-180rpm; for example, it can be but not limited to 120rpm, 130rpm, 140rpm, 150rpm, 160rpm, 170rpm, 180rpm or a range between any two of the above speeds.

[0099] It should be noted that the extrusion temperature of the first extrusion granulation and the speed of the twin-screw extruder can be combined in any appropriate manner, and both can be selected from any extrusion temperature of the first extrusion granulation and the speed of the twin-screw extruder described in this article.

[0100] As a non-limiting example, the extrusion temperature of the second extrusion granulation is 130°C-180°C; for example, it can be but not limited to 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C or a range between any two of the above temperatures.

[0101] In some optional embodiments, the speed of the twin-screw extruder used in the second extrusion granulation is 150rpm-200rpm; for example, it can be but not limited to 150rpm, 160rpm, 170rpm, 180rpm, 190rpm, 200rpm or a range between any two of the above speeds.

[0102] It should be noted that the extrusion temperature and the twin-screw extruder speed of the second extrusion granulation can be combined in any appropriate manner, and both can be selected from any extrusion temperature and twin-screw extruder speed of the second extrusion granulation described in this article.

[0103] 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.

[0104] One or more embodiments of the present application provide a cable, the raw material of the cable including an insulating material or an insulating material prepared by the above-mentioned preparation method.

[0105] In some of these embodiments, the cable is a submarine cable.

[0106] As a non-limiting example, the cable has a carrying voltage of 500 kV and below.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 1. Preparation of insulating materials

[0111] 1. Formula composition

[0112] The formulations of the embodiments and comparative examples are shown in Table 1.

[0113] Table 1

[0114]

[0115] Table 2

[0116]

[0117] In the above table, Mw represents the weight average molecular weight of low-density polyethylene, in Da; D represents the molecular weight distribution index; MFR represents the melt index, in g / 10min; ρ represents the density, in g / cm 3 ; mp represents melting point, in °C. Antioxidant 300 represents 4,4'-thiobis(6-tert-butyl-3-methylphenol); DCP represents diisopropylbenzene peroxide; TMPTMA represents trimethylolpropane trimethacrylate.

[0118] 2. Preparation process

[0119] The preparation processes of Examples 1-17 and Comparative Examples 1-12 are as follows:

[0120] Step S1, after uniformly mixing the first resin and the second resin, feeding them into a twin-screw extruder and subjecting them to two first extrusion granulation processes, to obtain a composite resin material; wherein the temperature distribution of each zone of the twin-screw extruder is 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 190°C, 200°C, and the screw speed is 150rpm.

[0121] Step S2, stirring and mixing the composite resin material and the antioxidant evenly, and then feeding them into a twin-screw extruder for two second extrusion granulation to obtain a semi-finished product; wherein the temperature distribution of each zone of the twin-screw extruder is 130°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, and 180°C, and the screw speed is 180rpm.

[0122] Step S3, first, fully melt the cross-linking agent and the cross-linking auxiliary agent 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 and mechanically stir for 5 minutes, the temperature of the mixing tank is 70°C, and the stirring speed is 15rpm; then, spray and inject them into the post-absorption shake tank filled with semi-finished materials, the shake tank temperature is 70°C, and after the spraying is completed, continue to shake for 60 minutes, and the shake tank speed is 35rpm; finally, introduce the material in the shake tank into an insulation tank for post-absorption insulation treatment, the temperature is 75°C, the time is 18h, and the finished insulating material is obtained after cooling.

[0123] 2. Performance Test

[0124] The insulating materials prepared in the above embodiments and comparative examples were subjected to AC breakdown strength test, volume resistivity test, crystallinity and melting temperature test and thermal elongation test, and the test methods were as follows:

[0125] The AC breakdown strength test is carried out in accordance with GB / T 1408.1. The test temperature is (90±2)℃ and the test piece thickness is (0.20±0.02)mm.

[0126] The volume resistivity test is carried out in accordance with GB / T 31838.2. The test temperature is (70±2)℃, the test field strength is 20kV / mm, and the test piece thickness is (0.20±0.02)mm.

[0127] The crystallinity and melting temperature were tested by differential scanning calorimetry. The DSC test was carried out under the protection of high-purity nitrogen. The nitrogen flow rate was controlled at 50 mL / min. Aluminum pans were selected as sample pans and reference pans. The sample weight was about 6 mg. The melting-crystallization test process was adopted.

[0128] The thermal elongation test was carried out in accordance with the provisions of GB / T 2951.21. The specimen was the 5A specimen in GB / T 1040.2. The test temperature was (200±3)℃, the specimen thickness was (1.0±0.1)mm, a load of 0.2MPa was applied under the specimen, and the heat treatment was performed for 15min.

[0129] The test results of the above embodiments and comparative examples are shown in Table 3.

[0130] Table 3

[0131]

[0132] From the comparison of the results of Examples 1-17 and Comparative Examples 1-14, it can be seen that the insulating material of the present application can effectively improve the volume resistivity, AC breakdown voltage and crystallinity of the insulating material, reduce the thermal creep elongation of the insulating material, and increase the melting temperature of the blended resins, thereby achieving a synergistic improvement in the heat resistance and electrical properties of the insulating material by compounding the first resin and the second resin, and respectively regulating the weight average molecular weight and molecular weight distribution index of the first resin, and the weight average molecular weight and molecular weight distribution index of the second resin within an appropriate range.

[0133] It can be seen from Comparative Example 1 that, when the amount of cross-linking agent, antioxidant and cross-linking aid is the same, the insulating material prepared only with low-density polyethylene creeps rapidly after being heated at high temperature, and fails and breaks rapidly after 15 minutes. It can be seen from Comparative Example 3 that the insulating material with 2wt% low molecular weight second resin added can only slightly improve the creep resistance, reaching a thermal creep elongation of 150% after being heated at high temperature for 15 minutes. On the contrary, it can be seen from Examples 1-2 and Comparative Example 4 that for the insulating material containing high molecular weight high density polyethylene or ultra-high molecular weight polyethylene blend, the creep strain reaches 50%-75% after 15 minutes, which is comparable to the thermal creep performance of pure low density polyethylene insulating material of high cross-linking system (Comparative Example 2).

[0134] It can be seen from the results of Examples 2 and 7-10 that when ultra-high molecular weight polyethylene and low-density polyethylene are blended to prepare insulating materials, the load-bearing network can be further improved by generating more connecting chains between the remaining grains, thereby further improving the heat resistance and electrical properties of the insulating materials.

[0135] From the comparison of the results of Example 1, Examples 3-4 and Comparative Examples 3-4, it can be seen that when high molecular weight high density polyethylene and low density polyethylene are used to prepare the insulating material, regulating the weight average molecular weight of the high molecular weight high density polyethylene within a certain range is conducive to improving the heat resistance and electrical properties of the insulating material. When the weight average molecular weight of the high molecular weight high density polyethylene exceeds this range, the improvement of the heat resistance and electrical properties of the insulating material is limited as the weight average molecular weight increases, and there is even the possibility of deterioration.

[0136] Similarly, from the comparison of the results of Example 1, Examples 5-6 and Comparative Examples 5-6, the comparison of the results of Example 2, Examples 7-8 and Comparative Examples 7-8, the comparison of the results of Example 2, Examples 9-10 and Comparative Examples 9-10, the comparison of the results of Example 1, Example 11 and Comparative Examples 11-12, and the comparison of the results of Example 1, Examples 12-13 and Comparative Examples 13-14, it can be learned that the weight average molecular weight of the first resin, the molecular weight distribution index of the first resin, the weight average molecular weight of the second resin and the molecular weight distribution index of the second resin need to be respectively regulated within an appropriate range, which is beneficial to improving the temperature resistance and electrical properties of the insulating material.

[0137] From the comparison of the results of Example 1 and Examples 14-17, it can be seen that by adjusting the amount of the first resin and the second resin, the electrical properties and temperature resistance of the insulating material can be further improved.

[0138] 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.

[0139] 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: It includes a first resin, a second resin, an antioxidant, a cross-linking agent and a cross-linking auxiliary agent; The first resin comprises low-density polyethylene, the weight average molecular weight of the low-density polyethylene is 120000Da-180000Da, and the molecular weight distribution index is 4.5-5.5; The second resin includes one or both of high molecular weight high density polyethylene and ultra high molecular weight polyethylene, wherein the weight average molecular weight of the high molecular weight high density polyethylene is 250000Da-350000Da, and the molecular weight distribution index is 1.5-5.5; the weight average molecular weight of the ultra high molecular weight polyethylene is 2000000Da-2400000Da, and the molecular weight distribution index is 6.0-8.0; The mass of the first resin accounts for 90%-99% of the total mass of the first resin and the second resin.

2. The insulating material according to claim 1, characterized in that: Based on 100 parts by weight of the total weight of the first resin and the second resin, the insulating material includes 0.1 to 0.3 parts of the antioxidant, 0.8 to 1.2 parts of the crosslinking agent, and 0.2 to 0.3 parts of the crosslinking aid.

3. The insulating material according to claim 1, characterized in that: The density of the low-density polyethylene is 0.91 g / cm 3 -0.93g / cm 3 The melting point is 105℃-115℃, and the melt index at 190℃ and 2.16kg load is 1.9g / 10min-2.1g / 10min.

4. The insulating material according to claim 1, characterized in that: The density of the high molecular weight high density polyethylene is 0.94 g / cm 3 -0.96g / cm 3 The melting point is 125℃-135℃, and the melt index is 3.0g / 10min-10.0g / 10min at 190℃ and 21.6kg load.

5. The insulating material according to claim 1, characterized in that: The density of the ultra-high molecular weight polyethylene is 0.92 g / cm 3 -0.96g / cm 3 The melting point is 130℃-140℃, and the melt index at 190℃ and 21.6kg load is 0.1g / 10min-0.25g / 10min.

6. The insulating material according to any one of claims 1 to 5, characterized in that: The antioxidant includes one or more of 4,4'-thiobis(6-tert-butyl-3-methylphenol), 1,3,5-trimethyl-2,4,6-tri(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, pentaerythritol tetra(bis-T-butylhydroxyhydrocinnamate) ester and b-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

7. The insulating material according to any one of claims 1 to 5, characterized in that: The crosslinking agent includes one or more of diisopropylbenzene peroxide, di-tert-butylperoxyisopropylbenzene, benzoyl peroxide, di-tert-butyl peroxide, tert-butylisopropylbenzene peroxide and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

8. The insulating material according to any one of claims 1 to 5, characterized in that: The crosslinking auxiliary agent includes one or more of triallyl isocyanurate, trimethylolpropane trimethacrylate and 2,4-diphenyl-4-methyl-1-pentene.

9. A method for preparing an insulating material, characterized in that: The steps include: The first resin and the second resin are mixed and then subjected to first extrusion granulation to prepare a composite resin material; The composite resin material is mixed with an antioxidant and then subjected to a second extrusion granulation to prepare a semi-finished product material; The semi-finished material is mixed with a cross-linking agent and a cross-linking auxiliary agent and then subjected to post-absorption treatment to prepare the insulating material; Wherein, the first resin comprises low-density polyethylene, the weight average molecular weight of the low-density polyethylene is 120000Da-180000Da, and the molecular weight distribution index is 4.5-5.5; The second resin includes high molecular weight high density polyethylene and ultra high molecular weight polyethylene, the weight average molecular weight of the high molecular weight high density polyethylene is 250000Da-350000Da, and the molecular weight distribution index is 1.5-5.5; the weight average molecular weight of the ultra high molecular weight polyethylene is 2000000Da-2400000Da, and the molecular weight distribution index is 6.0-8.0; The mass of the first resin accounts for 90%-99% of the total mass of the first resin and the second resin.

10. The preparation method according to claim 9, characterized in that: The step of mixing the semi-finished product with the cross-linking agent and the cross-linking auxiliary agent and then performing post-absorption treatment comprises: Spraying a mixed liquid containing the cross-linking agent and the cross-linking aid into the semi-finished product while shaking the semi-finished product; After the spraying is finished, continue shaking for the preset time and then keep warm.

11. The preparation method according to claim 10, characterized in that: The preparation method comprises at least one of the following conditions: (1) The shaking speed is 30 rpm-60 rpm; (2) The shaking temperature is 60°C-70°C; (3) The preset time is 50min-60min; (4) The temperature of the heat preservation treatment is 70°C-80°C, and the time is 16h-24h.

12. The preparation method according to any one of claims 9 to 11, characterized in that: The extrusion temperature of the first extrusion granulation is 150° C.-200° C., and the rotation speed of the twin-screw extruder is 120 rpm-180 rpm.

13. The preparation method according to any one of claims 9 to 11, characterized in that: The extrusion temperature of the second extrusion granulation is 130° C.-180° C., and the rotation speed of the twin-screw extruder is 150 rpm-200 rpm.

14. Use of the insulating material according to any one of claims 1 to 8 or the insulating material prepared by the preparation method according to any one of claims 9 to 13 in preparing a cable.

15. 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 8 or the insulating material prepared by the preparation method as described in any one of claims 9 to 13.

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

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