Crosslinkable polyethylene cable material and preparation method therefor

Abstract

The present invention relates to the field of insulation materials for high-voltage cables, and specifically relates to a crosslinkable polyethylene cable material and a preparation method therefor. The preparation method comprises: (1) mixing low-density polyethylene, an antioxidant and titanate-modified zinc oxide, and subjecting the resulting mixture to first mixing, so as to obtain a first mixed material, wherein the antioxidant is a phenolic acrylate antioxidant; (2) bringing the first mixed material into contact with an initiator, and performing second mixing, so as to obtain a second mixed material; and (3) filtering the second mixed material, and then subjecting same to extrusion granulation, so as to obtain a crosslinkable polyethylene cable material. The preparation method provided in the present invention can significantly improve the aging performance, especially the photoaging resistance, of the crosslinkable polyethylene cable material, and significantly prolong the service life of the crosslinkable polyethylene cable material.

Description

Cross-linkable polyethylene cable material and method for preparing the same

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Chinese Patent Application No. 202411118774.4, filed on August 15, 2024, the contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of high-voltage cable insulation materials, in particular to a cross-linkable polyethylene cable material and a method for preparing the same. BACKGROUND

[0004] The working environment of high-voltage cables is generally complex, and is easily affected by light and heat, which leads to a decrease in the insulation performance of the cable and a shorter operating life. In order to prolong the service life of the cable, it is necessary to prepare an insulation cable with excellent light aging resistance and heat resistance.

[0005] Among them, light aging refers to the aging change of insulation materials due to the irradiation of ultraviolet light, visible light and infrared light and other light under sunlight irradiation. The influence of light aging on electric wires and cables mainly manifests in two aspects. First, light aging can cause changes in the physical properties of insulation materials. The surface of insulation materials subjected to light irradiation for a long time will show cracking, cracking, peeling and other phenomena, thereby reducing the tensile strength and elongation at break of the insulation materials. Second, light aging can affect the electrical properties of insulation materials. Light irradiation can change the dielectric constant of insulation materials, increase dielectric loss, and cause a decrease in the withstand electric field strength.

[0006] Heat resistance includes heat aging resistance and heat deformation resistance. Among them, heat aging resistance refers to the increase in the temperature of the insulation of the high-voltage cable due to the high ambient temperature or the heat generated by the power equipment itself during operation. Under the action of high temperature, the mechanical strength of the high-voltage cable decreases, the structure deforms, the material loses elasticity due to oxidation and polymerization, or the insulation is broken down due to material cracking, resulting in a decrease in voltage. Heat deformation resistance refers to the good dimensional stability and rigidity of the high-voltage cable under heat, and the high-voltage cable basically does not deform under heat.

[0007] At present, the most common raw material for preparing high-voltage cables is cross-linkable polyethylene cable material. However, the light aging resistance and heat aging resistance of cross-linkable polyethylene cable material are poor. In order to inhibit or delay the aging process of cross-linked polyethylene and prolong the operating life of high-voltage cables, the traditional method is to add an antioxidant to the raw material.

[0008] A polyethylene grafted hindered phenolic antioxidant, its preparation method and use are disclosed in CN112048030A. The introduction of long-chain alkyl groups into the structure of the polyethylene grafted hindered phenolic antioxidant can greatly increase the molecular weight of the antioxidant, effectively reduce the physical loss of the antioxidant during the processing and use process, and enhance the long-term antioxidant capacity and migration resistance. However, this method has two main shortcomings: ① The reaction raw material is polyethylene-vinyl acetate copolymer, and the polyethylene insulation obtained by two-step method for grafting antioxidant has poor processing performance because it is difficult to ensure that all raw materials are fully reacted during the reaction process and it is difficult to precipitate the unreacted products; ② A large amount of organic solvents such as xylene and ethanol are required during the test process, which causes environmental pollution, and is only suitable for small-batch preparation and cannot be used for large-batch preparation of high-voltage insulated cables.

[0009] A recyclable antioxidant grafted polyolefin high-voltage direct current cable insulation material and its preparation method are disclosed in CN111393572A. In this method, a reactive antioxidant containing a polar group is added to a thermoplastic polyolefin, and an initiator is used to initiate a melt grafting reaction to bond the small molecule antioxidant to the polyolefin molecular chain, thereby reducing the space charge caused by the addition of the antioxidant and adjusting the trap energy level and distribution characteristics inside the material to inhibit the accumulation of space charge inside the material. However, the oxidation induction period of the grafted polyolefin insulation material prepared by this method is short, and its heat aging resistance has not been significantly improved.

[0010] Therefore, there is an urgent need to provide a cross-linkable polyethylene cable material with excellent light aging resistance and heat resistance and a preparation method thereof. SUMMARY

[0011] The purpose of the present application is to solve the problem of poor light aging resistance and heat resistance of the cross-linkable polyethylene cable material in the prior art, and to provide a cross-linkable polyethylene cable material and a preparation method thereof.

[0012] To achieve the above-mentioned purpose, the first aspect of the present application provides a preparation method of a cross-linkable polyethylene cable material, wherein the method comprises the following steps:

[0013] (1) mixing low-density polyethylene, antioxidant and titanate modified zinc oxide to perform first mixing to obtain a first mixed material; wherein the antioxidant is a phenolic acrylate antioxidant;

[0014] (2) contacting the first mixed material with an initiator to perform second mixing to obtain a second mixed material;

[0015] (3) filtering the second mixed material and then performing extrusion granulation to obtain a cross-linkable polyethylene cable material.

[0016] Preferably, the low-density polyethylene has a molecular weight of 5x10 4 -7x10 4 g / mol, a molecular weight distribution of 4.5-6.5, and a branching degree of ≥14.5 ‰.

[0017] Preferably, the phenolic acrylate antioxidant is selected from one or more of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate, 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenol acrylate, and 3,5-di-tert-butyl-4-hydroxybenzyl acrylate.

[0018] Preferably, the preparation method of the titanate-modified zinc oxide comprises: mixing a titanate coupling agent and nano-zinc oxide and then performing a modification reaction to obtain the titanate-modified zinc oxide.

[0019] Preferably, the titanate coupling agent is a titanate coupling agent containing a dioctyl phosphoric acyloxy group.

[0020] Preferably, the titanate coupling agent is selected from one or more of isopropyl tris(dioctyl phosphoric acyloxy) titanate, isopropyl dioctyl phosphoric acyloxy (dioctyl phosphoric acyloxy) titanate, and neoalkoxy tris(dioctyl phosphoric acyloxy) titanate.

[0021] Preferably, the mass ratio of the titanate coupling agent to the nano-zinc oxide is 0.5-6.5:100.

[0022] Preferably, the operation conditions of the modification reaction include: a stirring speed of 1000-3000 rpm, a modification reaction temperature of 70-120℃, and a modification reaction time of 20-50 min.

[0023] Preferably, the mass ratio of the low-density polyethylene, the antioxidant, and the titanate-modified zinc oxide is 100:0.1-0.3:0.5-1.5.

[0024] Preferably, the first mixing speed of the first mixing is 100-400 rpm, and the first mixing temperature is 100-180℃.

[0025] Preferably, the half-life of the initiator is 0.5-1.5 h, and the half-life temperature is ≥130℃.

[0026] Preferably, the initiator is at least one selected from dicumyl peroxide, di-tert-butyl peroxide, diisopropylbenzene hydroperoxide, cumyl hydroperoxide, and tert-butyl hydroperoxide.

[0027] Preferably, the mass ratio of the low-density polyethylene to the initiator is 100:0.5-3.

[0028] Preferably, the second mixing speed of the second mixing is 100-400 rpm, and the second mixing temperature is 100-160 DEG C.

[0029] Preferably, the filtering is performed in a screen changer provided with at least four layers of filter screens; wherein the mesh number of the filter screens is ≤600 mesh.

[0030] The second aspect of the present application provides a cross-linkable polyethylene cable material prepared by the method of the first aspect of the present application.

[0031] Through the above technical solutions, the present application has the following beneficial technical effects:

[0032] 1) The preparation method of the cross-linkable polyethylene cable material provided in the present application can significantly improve the aging performance, especially the light aging resistance, of the cross-linkable polyethylene cable material, and significantly prolong the service life of the cross-linkable polyethylene cable material, by selecting a specific antioxidant, adding titanium ester modified zinc oxide, and adjusting the addition sequence of raw materials.

[0033] 2) The preparation method of the cross-linkable polyethylene cable material provided in the present application has a simple process flow and low production cost, and can produce super-clean chemical cross-linking polyethylene cable material on a large scale. DETAILED DESCRIPTION

[0034] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The endpoints of the ranges and any values should be considered to be open-ended ranges, unless the context clearly indicates the closed-ended nature of the range. Thus, the endpoints of the ranges are not limited to the precise values stated.

[0035] The first aspect of the present application provides a preparation method of a cross-linkable polyethylene cable material, wherein the method comprises the following steps:

[0036] (1) mixing low-density polyethylene, an antioxidant and titanium ester modified zinc oxide, and then performing first mixing to obtain a first mixed material; wherein the antioxidant is a phenolic acrylate antioxidant;

[0037] (2) contacting the first mixed material with an initiator to perform second mixing to obtain a second mixed material;

[0038] (3) filtering the second mixed material, and then performing extrusion granulation to obtain a cross-linkable polyethylene cable material.

[0039] In the present application, the inventors have found that by selecting specific antioxidants, adding titanate modified zinc oxide, and adjusting the addition sequence of raw materials, the zero shear viscosity of the cross-linkable cable material can be reduced, the processing performance can be improved, the insulation performance, light aging resistance, heat aging resistance, and heat deformation resistance of the cross-linkable polyethylene cable material can be significantly improved, and the insulation performance and service life of the cross-linkable polyethylene cable material can be significantly prolonged.

[0040] In step (1):

[0041] In a preferred embodiment of the present application, the low-density polyethylene has a molecular weight of 5 x 10 4 -7 x 10 4 g / mol, a molecular weight distribution of 4.5-6.5, and a branching degree of ≥14.5 ‰, preferably 14.5-15.5 ‰.

[0042] In the present application, the molecular weight (i.e., weight average molecular weight) and the molecular weight distribution are tested according to GB / T 36214.1-2018 using a high-temperature gel chromatograph. The branching degree of the low-density polyethylene is represented by the number of methyl groups contained in 1000 carbon atoms and is tested using a Fourier infrared spectrometer according to SH / T1816-2017. The measurement spectrum range is 4000-400 cm -1 , and the resolution is 4 cm -1 .

[0043] In the present application, the phenolic acrylate antioxidant refers to an antioxidant containing a phenolic structure and an acrylate group. When the molecular weight, molecular weight distribution, and branching degree of the low-density polyethylene are within the above-mentioned ranges, the comprehensive performance of the prepared cross-linkable polyethylene cable material is better.

[0044] In a preferred embodiment of the present application, the phenolic acrylate antioxidant is selected from one or more of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate, 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-tolylmethyl)-4-methylphenol acrylate, and 3,5-di-tert-butyl-4-hydroxybenzyl acrylate, preferably two.

[0045] In the present application, the inventors have found that, compared with a single antioxidant, when two antioxidants are added simultaneously, the prepared cross-linkable polyethylene cable material has a longer oxidation induction period and better anti-aging ability. For example, the antioxidants can be 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate and 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenol acrylate at a mass ratio of 1-3:1, or 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenol acrylate and 3,5-di-tert-butyl-4-hydroxybenzyl acrylate at a mass ratio of 1-3:1; or 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate and 3,5-di-tert-butyl-4-hydroxybenzyl acrylate at a mass ratio of 1-3:1.

[0046] In a preferred embodiment of the present application, the preparation method of the titanate modified zinc oxide comprises: mixing a titanate coupling agent and nano zinc oxide and then performing a modification reaction to obtain the titanate modified zinc oxide.

[0047] In the present application, the inventors have found that, when nano zinc oxide is added alone, the cross-linkable polyethylene cable material has poor insulation performance. After the modification of the zinc oxide by the titanate coupling agent, the titanate modified zinc oxide not only improves the mechanical properties of the cross-linkable polyethylene cable material, but also significantly improves the light aging resistance and heat aging resistance of the cross-linkable polyethylene cable material.

[0048] In a preferred embodiment of the present application, the titanate coupling agent is a titanate coupling agent containing a dioctyl phosphoric acyloxy group.

[0049] In a preferred embodiment of the present application, the titanate coupling agent is selected from one or more of isopropyl tris(dioctyl phosphoric acyloxy) titanate (i.e., titanate coupling agent 201), isopropyl dioleic acyloxy(dioctyl phosphoric acyloxy) titanate (i.e., titanate coupling agent 101), and neoalkoxy tris(dioctyl phosphoric acyloxy) titanate (i.e., titanate coupling agent TCA-L38).

[0050] In the present application, the inventors have found that the titanate coupling agent containing a dioctyl phosphoric acyloxy group is more conducive to improving the light aging resistance and heat aging resistance of the cross-linkable polyethylene cable material.

[0051] In a preferred embodiment of the present application, the mass ratio of the titanate coupling agent to the nano zinc oxide is 0.5-6.5:100, preferably 2-5:100.

[0052] In a preferred embodiment of the present application, the operating conditions of the modification reaction include: a stirring speed of 1000-3000 rpm, preferably 1500-2500 rpm; a modification reaction temperature of 70-120°C, preferably 80-100°C; and a modification reaction time of 20-50 min, preferably 30-40 min.

[0053] In the present application, compared with separately adding a titanate coupling agent and nano zinc oxide, the titanate coupling agent and nano zinc oxide are first reacted, so that the titanate coupling agent and nano zinc oxide are compounded together, thereby being able to improve the insulation performance of the cross-linkable polyethylene cable material, and especially significantly improve the light aging resistance of the cross-linkable polyethylene cable material.

[0054] In a preferred embodiment of the present application, the mass ratio of the low-density polyethylene, the antioxidant, and the titanate modified zinc oxide is 100:0.1-0.3:0.5-1.5, preferably 100:0.15-0.25:0.8-1.2.

[0055] In the present application, the inventors have found through research that when the mass ratio of the low-density polyethylene, the antioxidant, and the titanate modified zinc oxide is within the above range, the cross-linkable polyethylene cable material prepared in the present application has better comprehensive performance.

[0056] In a preferred embodiment of the present application, the first mixing speed is 100-400 rpm, preferably 200-300 rpm, and the first mixing temperature is 100-180°C, preferably 130-150°C.

[0057] In the present application, the first mixing is performed in a screw extruder, preferably a reciprocating screw extruder. The first mixing speed in the present application refers to the rotation speed of the screw, and the first mixing temperature refers to the set temperature of the screw.

[0058] In step (2), the low-density polyethylene, the antioxidant, and the titanate modified zinc oxide are mixed to obtain a mixture.

[0059] In a preferred embodiment of the present application, the initiator has a half-life temperature ≥ 130°C, preferably 130-200°C, and a purity ≥ 98%, preferably ≥ 99%.

[0060] In the present application, when the half-life temperature of the initiator is within the above range, the cross-linkable polyethylene cable material prepared has better insulation performance, light aging resistance, heat aging resistance, heat deformation resistance, and processing performance.

[0061] In a preferred embodiment of the present application, the initiator is an initiator containing a peroxide bond, further preferably selected from one or more of dicumyl peroxide (half-life of 1 h, half-life temperature of 132℃), di-tert-butyl peroxide (half-life of 1 h, half-life temperature of 141℃), dicumyl hydroperoxide (half-life of 1 h, half-life temperature of 154℃), cumyl hydroperoxide (half-life of 1 h, half-life temperature of 166℃), tert-butyl hydroperoxide (half-life of 1 h, half-life temperature of 185℃).

[0062] In a preferred embodiment of the present application, the initiator is selected from two of dicumyl peroxide, di-tert-butyl peroxide, dicumyl hydroperoxide, cumyl hydroperoxide, tert-butyl hydroperoxide, preferably dicumyl peroxide and tert-butyl hydroperoxide; further preferably dicumyl peroxide and tert-butyl hydroperoxide in a mass ratio of 1-3:1.

[0063] In a preferred embodiment of the present application, the mass ratio of the low-density polyethylene and the initiator is 100:0.5-3, preferably 100:1-2.5.

[0064] In a preferred embodiment of the present application, the second mixing speed is 100-400 rpm, preferably 200-300 rpm; and the second mixing temperature is 100-180℃, preferably 120-140℃.

[0065] In the present application, the second mixing is performed in a screw extruder, preferably a reciprocating screw extruder. The second mixing speed in the present application refers to the rotation speed of the screw, and the second mixing temperature refers to the set temperature of the screw.

[0066] In a preferred embodiment of the present application, the first mixing and the second mixing can be performed in the same screw extruder, or separately in two screw extruders.

[0067] In the present application, when the first mixing and the second mixing are performed in the same screw extruder, the screw extruder comprises a first mixing section and a second mixing section, one feeding port is arranged on each of the first mixing section and the second mixing section, and the feeding port of the second mixing section is arranged at the connection between the first mixing section and the second mixing section. The mixed material from the first mixing section enters the second mixing section together with the initiator from the feeding port of the second mixing section to continue mixing.

[0068] In step (3):

[0069] In a preferred embodiment of the present application, the filtering temperature is 110-180°C, preferably 130-140°C. The filtering speed is controlled by the melt pump speed, preferably 20-80 rpm, preferably 40-60 rpm. The temperature of the melt pump is preferably the same as the filtering temperature.

[0070] In a preferred embodiment of the present application, the filtering is performed in a screen changer equipped with at least four layers of filter screens; wherein the mesh number of the filter screens is ≤600 mesh.

[0071] In a preferred embodiment of the present application, along the flow direction of the second mixed material, the filter screens are arranged in the manner that the mesh number of the two sides is small and the mesh number of the middle is large.

[0072] In the present application, the inventors have found that arranging the filter screens in the manner that the mesh number of the two sides is small and the mesh number of the middle is large can significantly improve the filtering effect, which is helpful to further improve the insulation performance of the cross-linked polyethylene cable.

[0073] In a preferred embodiment of the present application, the filtering is performed in a screen changer equipped with four layers of filter screens; wherein along the flow direction of the second mixed material, the mesh number of the filter screens is 200-400 mesh / 300-500 mesh / 500-600 mesh / 200-300 mesh in turn.

[0074] In a preferred embodiment of the present application, the extrusion granulation is performed in a cutting granulator. The present application does not make special limitations on the cutting granulator.

[0075] In a preferred embodiment of the present application, the extrusion granulation is preferably followed by drying treatment to obtain the cross-linkable polyethylene cable material.

[0076] The second aspect of the present application provides a cross-linkable polyethylene cable material prepared by the method of the first aspect of the present application.

[0077] In a preferred embodiment of the present application, the cross-linkable polyethylene cable material has a dielectric strength of 38-43 kV / mm, an oxidation induction period of 83-97 min, a retention rate of elongation at break after xenon lamp aging of 56-66%, and a Vicat softening temperature of 88-93°C.

[0078] In the present application, the cross-linkable polyethylene cable material has a high dielectric strength, a long oxidation induction period, a high retention rate of elongation at break after xenon lamp aging, and a high Vicat softening temperature, and has excellent insulation performance, light aging resistance, heat aging resistance, and heat deformation resistance.

[0079] In a preferred embodiment of the present application, the cross-linkable polyethylene cable material has a zero shear viscosity of 15000-15500 Pa.s at 130℃.

[0080] In the present application, the cross-linkable polyethylene cable material has a relatively small zero shear viscosity at 130℃, indicating that the product has good flow properties and low processing difficulty.

[0081] The present application will be described in detail below through examples.

[0082] The initiator is a commercially available product with a purity of ≥99%.

[0083] The reciprocating screw extruder comprises a first mixing section and a second mixing section, and two feeding ports, one of which is arranged at the first mixing section and the other is arranged at the connection between the first mixing section and the second mixing section.

[0084] The preparation method of the titanate coupling agent modified zinc oxide A is as follows: 2 g of isopropyl tris(dioctyl pyrophosphato) titanate (titanate coupling agent 201) and 100 g of nano zinc oxide are placed in a reactor, mixed, and then modified at 80℃ and 2000 rpm for 40 min to obtain the titanate modified zinc oxide A.

[0085] The preparation method of the titanate coupling agent modified zinc oxide B is as follows: 5 g of isopropyl dioleic acid ester (dioctyl phosphoric acid ester) titanate (titanate coupling agent 101) and 100 g of nano zinc oxide are placed in a reactor, mixed, and then modified at 100℃ and 2000 rpm for 30 min to obtain the titanate modified zinc oxide B.

[0086] The preparation method of the titanate modified zinc oxide C is as follows: 1 g of neoalkoxy tris(dioctyl phosphoric acid ester) titanate (titanate coupling agent TCA-L38) and 100 g of nano zinc oxide are placed in a reactor, mixed, and then modified at 120℃ and 1000 rpm for 20 min to obtain the titanate modified zinc oxide C.

[0087] Example 1

[0088] (1) 100 parts by weight of low-density polyethylene CL2120P (molecular weight 5.0 x 10 4g / mol, a molecular weight distribution of 6.5, and a branching degree of 14.5 ‰), 0.2 parts by weight of an antioxidant (a mixture of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monopropenoate and 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenol propenoate at a mass ratio of 1:1), and 1.0 parts by weight of a titanate modified zinc oxide A were added into a reciprocating single screw extruder by means of a loss-in-weight electronic scale, first mixing was performed in a first mixing section, and a first mixed material was obtained; wherein the rotating speed of the screw in the first mixing section was 200 rpm, and the screw temperature was set to 130-150°C.

[0089] (2) 2.0 parts by weight of dicumyl peroxide was added into the second mixing section, and after contacting with the above first mixed material, second mixing was performed, and a second mixed material was obtained; wherein the rotating speed of the screw in the second mixing section was 200 rpm, and the screw temperature was set to 120-130°C.

[0090] (3) The above second mixed material was pumped into a continuous mesh-type melt filter through a melt pump, impurities were filtered out, and then extrusion granulation and dehydration were performed, a small amount of extrusion granules were taken out and sent to an impurity detector, and the remaining material was sent into a dryer for drying, and a cross-linkable polyethylene cable material was obtained.

[0091] Wherein the rotating speed of the melt pump was 40 rpm, and the temperature of the melt pump was 130°C; four layers of stainless steel filter screens were installed in the continuous mesh-type melt filter, and the specifications of the stainless steel filter screens were 200 mesh / 300 mesh / 500 mesh / 300 mesh in sequence along the flow direction, and the temperature of the screen changer was 130°C.

[0092] Example 2

[0093] (1) 100 parts by weight of low-density polyethylene pellets CL2120P (a molecular weight of 5.0 x 10 4 g / mol, a molecular weight distribution of 6.5, and a branching degree of 14.5 ‰), 0.15 parts by weight of an antioxidant (2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenol propenoate and 3,5-di-tert-butyl-4-hydroxybenzyl propenoate at a mass ratio of 2:1), and 0.8 parts by weight of a titanate modified zinc oxide B were added into a reciprocating single screw extruder by means of a loss-in-weight electronic scale, first mixing was performed in a first mixing section, and a first mixed material was obtained; wherein the rotating speed of the screw in the first mixing section was 300 rpm, and the screw temperature was set to 140-150°C.

[0094] (2) 2.5 parts by weight of an initiator (2 ：1,1,1,3,3-pentaphenyl-2-propyl peroxide and tert-butyl hydroperoxide) is added into the second mixing section to contact with the first mixing material, and then the second mixing is carried out to obtain the second mixing material; wherein the rotation speed of the screw of the second mixing section is 300 rpm, and the screw temperature is set to be 125-135°C;

[0095] (3) The second mixing material is pumped into the continuous mesh type melt filter through the melt pump, and after the impurities are filtered out, the extrusion granulation and dehydration are carried out, a small amount of extrusion particles is branched to the impurity detector, and the remaining material is sent into the dryer to be dried to obtain the cross-linkable polyethylene cable material;

[0096] The rotation speed of the melt pump is 60 rpm, and the temperature of the melt pump is 140°C; four layers of stainless steel filter screens are installed in the continuous mesh type melt filter, and the specifications of the stainless steel filter screens are 200 mesh / 400 mesh / 600 mesh / 200 mesh in turn along the flow direction, and the filtering temperature is 140°C.

[0097] Example 3

[0098] (1) 100 parts by weight of low-density polyethylene pellets CL2120P (molecular weight is 5.0 x 10 4 g / mol, molecular weight distribution is 6.5, and branching degree is 14.5‰) and 0.25 parts by weight of an antioxidant (mass ratio of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate and 3,5-di-tert-butyl-4-hydroxybenzyl acrylate is 2.5:1) and 1.2 parts by weight of a titanate modified zinc oxide A are added into the reciprocating single screw extruder through the loss-in-weight electronic scale, the first mixing is carried out in the first mixing section to obtain the first mixing material; wherein the rotation speed of the screw of the first mixing section is 250 rpm, and the screw temperature is set to be 135-145°C;

[0099] (2) 1.0 parts by weight of di-tert-butyl peroxide is added into the second mixing section to contact with the first mixing material, and then the second mixing is carried out to obtain the second mixing material; wherein the rotation speed of the screw of the second mixing section is 250 rpm, and the screw temperature is set to be 130-140°C;

[0100] (3) The second mixing material is pumped into the continuous mesh type melt filter through the melt pump, and after the impurities are filtered out, the extrusion granulation and dehydration are carried out, a small amount of extrusion particles is branched to the impurity detector, and the remaining material is sent into the dryer to be dried to obtain the cross-linkable polyethylene cable material;

[0101] The rotation speed of the melt pump is 50 rpm, and the temperature of the melt pump is 140°C; four layers of stainless steel filter screens are installed in the continuous mesh type melt filter, and the specifications of the stainless steel filter screens are 400 mesh / 500 mesh / 600 mesh / 300 mesh in turn along the flow direction, and the filtering temperature is 140°C.

[0102] Example 4

[0103] (1) 100 parts by weight of low-density polyethylene pellets 2240H (molecular weight 7.0 x 10 4 g / mol, molecular weight distribution 4.5, branching degree 15.5 ‰), 0.12 parts by weight of antioxidant 3,5-di-tert-butyl-4-hydroxybenzyl acrylate, and 1.5 parts by weight of titanate-modified zinc oxide C were added to a reciprocating single-screw extruder by means of a loss-in-weight electronic scale, first kneading was performed in a first kneading section, and a first-kneaded material was obtained; wherein the rotation speed of the screw of the first kneading section was 400 rpm, and the screw setting temperature was 110-125°C.

[0104] (2) 0.5 parts by weight of cumene hydroperoxide was added to the second kneading section, and after contacting with the above first-kneaded material, second kneading was performed, and a second-kneaded material was obtained; wherein the rotation speed of the screw of the second kneading section was 400 rpm, and the screw setting temperature was 100-115°C.

[0105] (3) The above second-kneaded material was pumped to a continuous mesh-type melt filter through a melt pump, after filtering out impurities, extrusion granulation and dehydration were performed, a small amount of extruded particles was diverted to an impurity detector, and the remaining material was sent to a dryer for drying, and a cross-linkable polyethylene cable material was obtained.

[0106] Wherein the rotation speed of the melt pump was 20 rpm, and the temperature of the melt pump was 140°C; four layers of stainless steel filter screens were installed in the continuous mesh-type melt filter, and along the flow direction, the specifications of the stainless steel filter screens were 300 mesh / 400 mesh / 600 mesh / 300 mesh in turn, and the filtering temperature was 140°C.

[0107] Example 5

[0108] (1) 100 parts by weight of low-density polyethylene pellets 2220H (molecular weight 6.0 x 10 4 g / mol, molecular weight distribution 5.5, branching degree 15.2 ‰), 0.28 parts by weight of antioxidant 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate, and 0.6 parts by weight of titanate-modified zinc oxide C were added to a reciprocating single-screw extruder by means of a loss-in-weight electronic scale, first kneading was performed in a first kneading section, and a first-kneaded material was obtained; wherein the rotation speed of the screw of the first kneading section was 100 rpm, and the screw setting temperature was 160-175°C.

[0109] (2) 3.0 parts by weight of tert-butyl hydroperoxide was added to the second kneading section, and after contacting with the above first-kneaded material, second kneading was performed, and a second-kneaded material was obtained; wherein the rotation speed of the screw of the second kneading section was 100 rpm, and the screw setting temperature was 160-175°C.

[0110] (3) the second mixed material is pumped into a continuous mesh type melt filter through a melt pump, impurities are filtered out, and then the material is extruded, granulated, and dehydrated, a small amount of the extruded particles is branched to an impurity detector, and the remaining material is sent into a dryer to be dried, thereby obtaining the cross-linkable polyethylene cable material;

[0111] The melt pump has a rotation speed of 80 rpm and a temperature of 170°C. The continuous mesh type melt filter is provided with four layers of stainless steel filter screens, and the specifications of the stainless steel filter screens are 200 mesh / 500 mesh / 600 mesh / 300 mesh in sequence along the flow direction. The filter temperature is 170°C.

[0112] Example 6

[0113] The same as example 1, except that the antioxidant is 0.2 parts by weight of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate.

[0114] Comparative Example 1

[0115] The same as example 5, except that the antioxidant 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate is replaced by antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol)) in equal quality.

[0116] Comparative Example 2

[0117] The same as example 5, except that the order of adding the initiator and the antioxidant is changed.

[0118] Comparative Example 3

[0119] The same as example 5, except that step (2) is omitted.

[0120] The low-density polyethylene, the antioxidant, the titanate modified zinc oxide, and the initiator are mixed to perform first mixing, thereby obtaining a first mixed material. The first mixed material is pumped into a continuous mesh type melt filter through a melt pump, impurities are filtered out, and then the material is extruded, granulated, and dehydrated, a small amount of the extruded particles is branched to an impurity detector, and the remaining material is sent into a dryer to be dried, thereby obtaining the cross-linkable polyethylene cable material.

[0121] Comparative Example 4

[0122] The same as example 5, except that the titanate modified zinc oxide C is replaced by a mixture of nano zinc oxide and neoalkoxy tris(dioctylphosphato) titanate in a mass ratio of 100:1 in equal quality.

[0123] Test Example 1

[0124] The insulation performance, light aging resistance, heat aging resistance, heat deformation resistance and processing performance of the cross-linkable polyethylene cable material prepared in Examples 1-6 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1.

[0125] The performance test methods of the cross-linkable polyethylene cable material are as follows:

[0126] The cross-linkable polyethylene cable material prepared in Examples 1-6 and Comparative Examples 1-4 was respectively placed in a mold with a thickness of 1 mm, the mold was heated to 180℃, and was pressed at 15 MPa for 900 s, then demolded, and dried in a vacuum drying oven at 70℃ for 24 h to obtain a test sample.

[0127] The dielectric strength of the test sample was tested according to GB / T1408.1-2006; the oxidation induction period (200℃) of the cross-linkable polyethylene cable material granules was tested by DSC according to GB / T19466.1-2004; and the Vicat softening temperature of the cross-linkable polyethylene cable material injection molded sample was tested by a Vicat softening temperature tester according to GB / T 1633-2000.

[0128] The light aging resistance test method is as follows: xenon lamp aging test was carried out according to GB / T16422.2, the irradiance was 0.51 W / (m 2 ·nm) (narrow band 340 nm), the black mark temperature was 65℃, the test box temperature was 38℃, the humidity was 50% RH, the 102 min drying and 18 min spraying cycle alternated, and the aging time was 800 hours. After the aging test was completed, the elongation retention rate of the sample was tested.

[0129] The zero shear viscosity test method is as follows: the cross-linkable polyethylene cable material was placed in a mold with a thickness of 2 mm, the mold was heated to 130℃, and was pressed at 15 MPa for 300 s, then demolded to obtain an uncross-linked test sample, and the zero shear viscosity of the test sample was tested at 130℃.

[0130] Table 1

[0131] Wherein, the greater the dielectric strength, the better the insulation performance of the material; the higher the elongation retention rate, the better the light aging resistance of the material; the longer the oxidation induction period, the better the heat aging resistance of the material; the higher the Vicat softening temperature, the better the heat deformation resistance of the material; and the smaller the zero shear viscosity, the better the processing performance of the material. As can be seen from Table 1, the cross-linkable polyethylene cable material prepared in the present application has excellent insulation performance, light aging resistance, heat aging resistance, heat deformation resistance and processing performance.

[0132] It can be seen from the comparison between the comparative example 1 and the example 6 that, compared with a single antioxidant, when two antioxidants are added simultaneously, the heat aging resistance and light aging resistance of the cross-linkable polyethylene cable material prepared are better.

[0133] It can be seen from the comparison between the comparative example 5 and the comparative example 1 that, by using the specific antioxidant in the application, the oxidation induction period of the cross-linkable polyethylene cable material prepared is longer, and the heat aging resistance is better.

[0134] It can be seen from the comparison between the comparative example 5 and the comparative examples 2 and 3 that, the addition sequence of the raw materials has a significant influence on the insulation performance, light aging resistance and heat aging resistance of the cross-linkable polyethylene cable material.

[0135] It can be seen from the comparison between the comparative example 5 and the comparative example 4 that, the modification of zinc oxide has a significant influence on the insulation performance, light aging resistance and heat aging resistance of the cross-linkable polyethylene cable material.

[0136] The preferred embodiments of the application are described in detail above, but the application is not limited thereto. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as the disclosed content of the application, and all belong to the protection scope of the application. The endpoints and any values disclosed in the text are not limited to the exact range or value, and these ranges or values should be understood as including values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in the text.

Claims

1. A process for the preparation of a cross-linkable polyethylene cable compound, characterized in that, The method comprises the following steps: (1) mixing low-density polyethylene, antioxidant and titanate modified zinc oxide, and then performing first mixing to obtain first mixed material; wherein the antioxidant is phenolic acrylate antioxidant; (2) contacting the first mixed material with initiator and performing second mixing to obtain second mixed material; (3) filtering the second mixed material and then performing extrusion granulation to obtain cross-linkable polyethylene cable material.

2. The method of claim 1, wherein, The low-density polyethylene has a molecular weight of 5 x 10 4 -7 x 10 4 g / mol, a molecular weight distribution of 4.5-6.5, and a degree of branching of > 14.5 ‰.

3. The method of claim 1 or 2, wherein, The phenolic acrylate antioxidant is selected from one or more of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate, 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenol acrylate and 3,5-di-tert-butyl-4-hydroxybenzyl acrylate.

4. The method of claim 1, wherein, The preparation method of the titanate modified zinc oxide comprises: mixing titanate coupling agent and nano zinc oxide, and then performing modification reaction to obtain titanate modified zinc oxide.

5. The method of claim 4, wherein, The titanate coupling agent is a titanate coupling agent containing dioctyl phosphoric acyloxy group.

6. The method of claim 5, wherein, The titanate coupling agent is selected from one or more of isopropyl tris(dioctyl phosphoric acyloxy) titanate, isopropyl dioctanoate acyloxy(dioctyl phosphoric acyloxy) titanate and neoalkoxy tris(dioctyl phosphoric acyloxy) titanate.

7. The method of claim 4, wherein, The mass ratio of the titanate coupling agent to nano zinc oxide is 0.5-6.5:

100.

8. The method of claim 4, wherein, The operation conditions of the modification reaction comprise: stirring speed of 1000-3000 rpm, modification reaction temperature of 70-120℃ and modification reaction time of 20-50 min.

9. The method of claim 1, wherein, The mass ratio of the low-density polyethylene, antioxidant and titanate modified zinc oxide is 100:0.1-0.3:0.5-1.

5.

10. The method of claim 1, wherein, The first mixing speed is 100-400 rpm, and the first mixing temperature is 100-180℃.

11. The method of claim 1, wherein, The half-life of the initiator is 0.5-1.5 h, and the half-life temperature is ≥130℃.

12. The method of claim 1, wherein, The initiator is selected from one or more of dicumyl peroxide, di-tert-butyl peroxide, diisopropylbenzene peroxide, isopropylbenzene peroxide and tert-butyl hydroperoxide.

13. The method of claim 1, wherein, The mass ratio of the low-density polyethylene to initiator is 100:0.5-3.

14. The method of claim 1, wherein, The second mixing speed is 100-400 rpm, and the second mixing temperature is 100-160℃.

15. The method of claim 1, wherein, The filtering is performed in a screen changer provided with at least four layers of filter screens; wherein the mesh number of the filter screens is ≤600 mesh.

16. Cross-linkable polyethylene cable material prepared by the method according to any one of claims 1-15.

Images