Polyolefin composition, polyolefin material and cable

Abstract

The invention provides a polyolefin composition, a polyolefin material and a cable. The polyolefin composition comprises the following raw materials: low-density polyethylene resin; a hindered amine stabilizer accounting for 0.01%-0.05% of the mass of the low-density polyethylene resin; based on the mass of the low-density polyethylene resin, 0.1%-0.45% of an antioxidant; and an organic peroxide accounting for 0.3%-1.0% of the mass of the low-density polyethylene resin. Under the synergistic interaction of the low-density polyethylene resin, the antioxidant and the hindered amine stabilizer, the addition amount of the organic peroxide in the polyolefin composition for cable insulation can be reduced through pre-irradiation modification, and the crosslinking efficiency is improved, so that the adverse effect on a high-voltage cable caused by too high addition amount of the organic peroxide is avoided. In addition, the high-voltage cable processed by the polyolefin material has the characteristics of short degassing time, high production efficiency and short product delivery cycle.

Description

Technical Field

[0001] The invention relates to the field of cable insulation materials, and in particular to a polyolefin composition, a polyolefin material and a cable. Background Art

[0002] With the rapid development of the electric power industry, the demand for high-voltage and ultra-high-voltage power cables is increasing, and the amount of high-voltage cross-linked polyethylene cable insulation materials has also increased accordingly. As the voltage level of cables gradually increases, the requirements for the quality of cable insulation materials have also increased accordingly. There is no significant difference between medium-voltage and high-voltage cable materials in general dielectric and mechanical properties, but there are obvious differences in specific properties, such as impurity size, concentration, volatile substances, extrusion port expansion rate, the effect of processing on melt index, high-temperature aging and extrusion surface quality. The working electric field strength of high-voltage cables is high, and dendrites and electrical aging are the main causes of insulation breakdown. Impurities can cause local electric field multiplication in insulation, forming the initiation point of dendrites, and can also cause local material fatigue to produce micropores. In addition, the rough extrusion surface can easily lead to an uneven surface of the conductor shielding layer, forming a concentrated surface electric field. Furthermore, the high content of volatile substances in the insulation material is the main cause of the formation of micropores. Therefore, it is very important to reduce the amount of crosslinking agent while ensuring the degree of crosslinking.

[0003] Patent application CN201710611220.1 discloses a peroxide crosslinkable composition consisting of polyethylene, 0.005wt% to 0.03wt% of a low molecular weight or low melting point or liquid nitrogen-containing base (such as a hindered amine stabilizer, triallyl cyanurate), one or more antioxidants, and optionally an organic peroxide. Patent application CN02805622.1 discloses a polyethylene composition consisting of (a) polyethylene, (b) [1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione] as a scorch inhibitor; (c) thioester; (d) hindered amine stabilizer; and (e) an organic peroxide, which can minimize the degree of scorch and maximize the crosslink density without the need for excessive peroxide or vulcanization accelerator.

[0004] Patent application No. CN201510286863.4 discloses a cable material comprising polyethylene resin, plasticizer, filler, modifier, polyacrylonitrile, anti-radiation masterbatch, antioxidant, anti-ultraviolet absorber, stabilizer, and lubricant components, wherein each component is blended and granulated by a twin-screw extruder, and then irradiated to obtain a weather-resistant overhead irradiation cross-linked insulated cable material. The stabilizer is a mixture of one or more of benzophenone, hindered phenol, phosphite, and hindered amine stabilizers, and the irradiation dose is 150 kGy.

[0005] In order to improve the cross-linking efficiency, patent application No. CN200410066408.5 uses infrared irradiation special equipment to irradiate and cross-link polyethylene resin compositions added with peroxide cross-linking agents, auxiliary cross-linking agents, antioxidants, and lubricants to form cross-linked polyethylene pipes and wire and cable products. Patent application No. CN201410049215.2 first mixes irradiation cross-linking materials added with multifunctional cross-linking agents such as triallyl cyanurate, triallyl isocyanurate, trimethylol propion trimethacrylate, trimethylol triacrylate, pentaerythritol triacrylate or pentaerythritol tetraacrylate, and 1-5 parts of peroxide masterbatch, and evenly extrude and coat them on the conductive core of wires and cables, and then cross-links them with high-energy electron beams or cobalt sources irradiated with a dose of 60-180 kGy. Patent application No. CN201910517763.6 improves the efficiency of radiation cross-linking manufacturing by adding a peroxide cross-linking agent (more than 1%) and trihydroxypropane triacrylate (more than 2%) to the cable material composition.

[0006] Under normal conditions, radiation can cause polyethylene resin to crosslink and polypropylene resin to degrade. In the prior art, adding hindered amine stabilizers is believed to prevent the adverse effects of radiation on the resin.

[0007] Therefore, when preparing cables by radiation crosslinking in the prior art, it is often necessary to irradiate the wire and cable products, which increases the equipment investment of the cable factory. Although the amount of peroxide used during crosslinking can be reduced or its adverse effects can be reduced by adding low molecular weight or low melting point or liquid nitrogen-containing bases (such as hindered amine stabilizers, triallyl cyanurate), coking inhibitors (such as [1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione]) and hindered amine stabilizers, the effect of this method still needs to be further improved.

[0008] Therefore, compared with the prior art, there is still a need for a polyolefin composition for cable insulation that can be directly processed and formed on existing equipment. As for chemical crosslinking, there is a need to provide a polyolefin composition that is easy to chemically crosslink, thereby reducing the amount of peroxide used during crosslinking, so as to overcome the problem of high volatile matter content of the insulating material in the existing chemical crosslinking method, and the problem that radiation crosslinking requires special equipment. Summary of the invention

[0009] In order to solve the above technical problems, the purpose of the present invention is to provide a polyolefin composition, a polyolefin material and a cable. Through the synergistic interaction of low-density polyethylene resin, antioxidant and hindered amine stabilizer under irradiation conditions, the pre-irradiated insulating material has the characteristic of easy chemical cross-linking. After adding organic peroxide, the polyolefin material is obtained, which can be used to manufacture ultra-high voltage cables after chemical cross-linking.

[0010] To achieve the above object, the present invention provides a polyolefin composition, wherein the raw material composition of the polyolefin composition comprises:

[0011] (A) low density polyethylene resin;

[0012] (B) 0.01% to 0.05% of a hindered amine stabilizer based on the mass of the low density polyethylene resin;

[0013] (C) 0.1% to 0.45% of an antioxidant based on the mass of the low-density polyethylene resin; and

[0014] (D) 0.3% to 1.0% of an organic peroxide based on the mass of the low-density polyethylene resin.

[0015] According to a specific embodiment of the present invention, preferably, the amount of the hindered amine stabilizer in (B) is 0.03%-0.05%.

[0016] According to a specific embodiment of the present invention, preferably, the amount of the antioxidant in (C) is 0.15%-0.35%.

[0017] According to a specific embodiment of the present invention, preferably, the amount of the organic peroxide in (D) is 0.5%-1.0%.

[0018] According to a specific embodiment of the present invention, preferably, the melt flow rate of the low-density polyethylene resin is 1.8-2.6 g / 10 min.

[0019] According to a specific embodiment of the present invention, preferably, the density of the low-density polyethylene resin is 0.916-0.925 g / cm 3 .

[0020] According to a specific embodiment of the present invention, preferably, the content of impurities with a size of 50-150 μm in the low-density polyethylene resin is ≤20 / 1000 g.

[0021] According to a specific embodiment of the present invention, preferably, the low-density polyethylene resin is prepared by a high-pressure bulk polymerization method, which specifically includes the following steps: high-purity ethylene is subjected to a free radical polymerization reaction under the conditions of 150-300MPa and 150-330°C in an atmosphere of trace oxygen or air and under the initiation of organic peroxides and / or inorganic peroxides to obtain a product.

[0022] According to a specific embodiment of the present invention, preferably, the conditions of the free radical polymerization reaction are a polymerization pressure of 250-280 MPa and a polymerization temperature of 250-320°C.

[0023] According to a specific embodiment of the present invention, preferably, the hindered amine stabilizer includes bis(2,2,6,6,-tetramethyl-4-piperidinyl) sebacate (GW-770, light stabilizer 770), bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate (GW-123, light stabilizer 123), 2,2,6,6-tetramethyl-4-piperidinyl stearate (GW-3853, light stabilizer 3853), poly{(6-morpholinyl-5-triazine-2,4-diyl)(2,2,6,6-tetramethylpiperidinyl)iminohexamethylene[(2,2,6,6-tetramethylpiperidinyl)-imino]} (GW-3346, light stabilizer 3346), poly{[6-[(1,1,3,3-tetramethylbutyl)amino]]-1,3,5-triazine-2 ,4-[(2,2,6,6,-tetramethyl-piperidinyl)imino]-1,6-hexanediamine[(2,2,6,6-tetramethyl-4-piperidinyl)imino]}(GW-944, Light Stabilizer 944), poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol) succinate (GW-622, Light Stabilizer 622), high molecular weight triazine-piperidinyl condensate (GW-119, Light Stabilizer 119), polymer of the reaction product of N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine with 2,4,6-trichloro-1,3,5-triazine and N-butyl-1-butylamine and N-butyl-2,2,6,6-tetramethyl-4-piperidinamine (GW-2020, Light Stabilizer 2020), structural unit containing -(TMPM) m1 -polymeric hindered amine stabilizer, structural unit comprising -(PMPM) m2 - one or a combination of two or more of the polymerizable hindered amine stabilizers, etc.; wherein TMPM is a structural unit obtained by the polymerization reaction of 2,2,6,6-tetramethylpiperidinol-4-methylacrylate, and PMPM is a structural unit obtained by the polymerization reaction of 1,2,2,6,6-pentamethylpiperidinol-4-methylacrylate; m1 and m2 represent the degree of polymerization, and m1 and m2 are 4-100.

[0024] In some specific embodiments, preferably, the structural unit comprises -(TMPM) m1 -The polymeric hindered amine stabilizer is poly-2,2,6,6-tetramethylpiperidinol-4-methylacrylate; the structural unit comprises -(PMPM) m2 -The polymeric hindered amine stabilizer is dodecyl poly 1,2,2,6,6-pentamethylpiperidinol-4-methacrylate.

[0025] In some specific embodiments, the polymerization reaction of TMPM or PMPM monomers can adopt various existing polymerization techniques.

[0026] According to a specific embodiment of the present invention, preferably, the antioxidant includes a phenolic antioxidant, or a composite antioxidant of a phenolic antioxidant and other antioxidants; wherein the phenolic antioxidant may use a single type of phenolic antioxidant, or an antioxidant mixed with two or more phenolic antioxidants, and such a mixed antioxidant is referred to as a mixed phenolic antioxidant in the present invention.

[0027] In some specific embodiments, preferably, the other antioxidants include one or a combination of two or more of phosphite antioxidants, hydrazide antioxidants and thioester antioxidants.

[0028] In some specific embodiments, preferably, in the composite antioxidant, the phenolic antioxidant is the main antioxidant, and the other antioxidants are auxiliary antioxidants.

[0029] In some specific embodiments, preferably, the mass ratio of the primary antioxidant to the secondary antioxidant is 1:1-5:1, more preferably 2:1-4:1.

[0030] In some specific embodiments, preferably, the phenolic antioxidant includes one or a combination of two or more of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol (antioxidant 1010), 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene (antioxidant 330), β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076), 4,4'-thiobis(6-tert-butyl-3-methylphenol) (antioxidant 300), etc.

[0031] In some specific embodiments, preferably, the other antioxidants include one or a combination of two or more of tris(2,4-di-tert-butylphenyl)phosphite (antioxidant 168), N,N'-bis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), thiodipropionate, etc.

[0032] In some specific embodiments, preferably, the composite antioxidant includes a mixture of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol (antioxidant 1010) and tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168), β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (antioxidant 1076) and N,N'-bis[β(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine (antioxidant The invention can be selected from the group consisting of a mixture of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol (antioxidant 1010) and N,N'-bis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (antioxidant 1024), and a mixture of 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene (antioxidant 330) and thiodipropionic acid ester, or a combination of two or more thereof.

[0033] According to a specific embodiment of the present invention, preferably, the organic peroxide in (D) includes one or a combination of two or more of tert-butyl peroxyisopropyl carbonate, tert-butyl peroxylaurate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butyl peroxyacetate, di-tert-butyl diperoxyphthalate, tert-butyl peroxymaleic acid, cyclohexanone peroxide, tert-butyl peroxybenzoate, diisopropyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl peroxide isopropyl benzene, tert-butyl hydroperoxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butyl-peroxy)hexane-3, and α,α'-bis-tert-butylperoxy-1,4-diisopropylbenzene.

[0034] The present invention also provides a polyolefin material, which is prepared from the above polyolefin composition, wherein the preparation method of the polyolefin material comprises the following steps:

[0035] (1) mixing a low-density polyethylene resin, a hindered amine stabilizer, and an antioxidant and then melt-plasticizing;

[0036] (2) filtering the melted and plasticized composition, and then cooling it to form composition particles;

[0037] (3) irradiating the composite particles to obtain a pre-irradiated insulating material;

[0038] (4) Adding organic peroxide to the pre-irradiated insulating material to obtain a polyolefin material.

[0039] According to a specific embodiment of the present invention, preferably, the reaction temperature of the melt plasticization is 130-250°C, more preferably 160-210°C.

[0040] According to a specific embodiment of the present invention, preferably, the mesh size of the filter is less than 150 microns, more preferably less than 100 microns.

[0041] According to a specific embodiment of the present invention, preferably, the irradiation comprises a high-energy electron beam or a cobalt source; the irradiation dose is 15-50 kGy, more preferably 20-40 kGy.

[0042] According to a specific embodiment of the present invention, preferably, the branching degree of the pre-irradiated insulating material is 1.5-1.9%.

[0043] According to a specific embodiment of the present invention, preferably, the long chain branch content index of the pre-irradiated insulating material is 0.95-1.13.

[0044] According to a specific embodiment of the present invention, preferably, the pre-irradiated insulating material has an internal double bond content of 0.20-0.40%, and an end double bond content of 0.15-0.35%.

[0045] According to a specific embodiment of the present invention, the organic peroxide is usually added to the pre-irradiated insulation material in a liquid state to obtain the polyolefin material.

[0046] In the above preparation method, the organic peroxide is usually sprayed onto the granular pre-irradiated insulating material, and the organic peroxide can also be added by dipping, spraying, etc.

[0047] According to a specific embodiment of the present invention, preferably, the method for preparing the above-mentioned polyolefin material specifically comprises the following steps:

[0048] (1) mixing a low-density polyethylene resin, a hindered amine stabilizer, and an antioxidant and then melt-plasticizing;

[0049] (2) filtering the melted and plasticized composition through a filter with a mesh size of less than 150 μm, and then cooling the composition to form composition particles;

[0050] (3) The composite particles are irradiated with a high-energy electron beam or a cobalt source at a dose of 15-50 kGy to obtain a pre-irradiated insulating material;

[0051] (4) Adding organic peroxide to the pre-irradiated insulating material to obtain a polyolefin material for cable insulation.

[0052] The present invention also provides a cable, which is prepared from the above polyolefin composition or the above polyolefin material, wherein the cable can be used for high-voltage cables of 35 kV and above.

[0053] According to a specific embodiment of the present invention, preferably, the thickness of the insulation layer coated on the conductor in the cable is 8-30 mm, more preferably 12-26 mm.

[0054] According to a specific embodiment of the present invention, preferably, the preparation process of the cable is to extrude and coat the polyolefin material onto a conductor at 80-130° C. to obtain a high-voltage cable.

[0055] According to a specific embodiment of the present invention, preferably, the high-voltage cables of 35 kV and above need to undergo a degassing process before use.

[0056] In some specific embodiments, preferably, the degassing conditions of the degassing process are: degassing temperature 60-75° C., and degassing time 5-10 days.

[0057] Cross-linked polyethylene is widely used as the main insulating material for power cables due to its superior thermal, electrical, mechanical and processing properties. In the production process of cross-linked polyethylene cables, peroxide cross-linking agents such as diisopropylbenzene peroxide (DCP) will generate cross-linking by-products such as acetophenone, cumyl alcohol, alpha methylstyrene, methane, etc. during the cross-linking process. The DCP by-products retained inside the cross-linked polyethylene cable will reduce the mechanical and insulating properties of the cross-linked polyethylene cable and cause local discharge, thereby endangering the long-term operation reliability of the cable. Therefore, the production process of cross-linked polyethylene cables must have sufficient degassing time to discharge the cross-linking by-products and ensure the main insulation performance of the cross-linked polyethylene cable.

[0058] However, too long degassing time will lead to reduced production efficiency and longer delivery cycle of cross-linked polyethylene cables. Too high degassing temperature will cause the insulation of cross-linked polyethylene cables to soften and deform due to heat. Short degassing time or too low degassing temperature will lead to poor degassing effect and unqualified insulation performance of cross-linked polyethylene cables. Therefore, a degassing process is required when producing high-voltage and ultra-high-voltage cables. The degassing time varies greatly depending on the product. In principle, the thicker the insulation, the longer the time. High-voltage cables range from 5 days to 15 days (or even longer), while medium-voltage cables are mostly 5 days or less.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) Under the synergistic interaction of low-density polyethylene resin, antioxidant and hindered amine stabilizer, the pre-irradiated insulation material can be directly obtained by irradiating plastic particles, and the process is simple to operate. At the same time, the amount of organic peroxide added in the polyolefin composition for cable insulation can be reduced through pre-irradiation modification, and the chemical cross-linking efficiency can be improved, thereby avoiding the adverse effects of excessive addition of organic peroxide on high-voltage cables.

[0061] (2) Polyolefin materials used for cable insulation can be directly processed into high-voltage cables on existing cable production equipment without increasing the equipment investment of the cable factory.

[0062] (3) Polyolefin materials for cable insulation are used to process high-voltage cables of 35KV and above, and have the characteristics of short degassing time, high production efficiency and short product delivery cycle. DETAILED DESCRIPTION

[0063] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0064] The sources of raw materials and testing methods used in the embodiments of the present invention are as follows:

[0065] Common low-density polyethylene resin LDPE production processes mainly include tubular process and kettle process. Both production processes can adjust the molecular weight distribution, structure, long-chain branching degree and long-chain branching distribution of the product by changing the process parameters. Among them, the present invention adopts the tubular process to prepare low-density polyethylene, and the polyethylene raw material that meets the requirements of the present invention can be obtained by adjusting the process parameters under the existing technology.

[0066] In a tubular reactor, the temperature is not a constant value but gradually increases from the beginning area to the end area of ​​the reaction tube. The molecules first initiated at low temperature have low conversion rates and lower long chain branching content than the overall long chain branching content of the polymer. The molecules entering the higher temperature and higher conversion reaction area have higher molecular weight and more long chain branches than the initial molecules due to chain transfer reactions. In contrast, in a stirred kettle, the temperature, pressure, and conversion rate of the reaction are constant, so the long chain branching points are basically randomly distributed on the main chain, regardless of molecular weight. The resin obtained from the tubular reactor has the characteristics of comb-type branching, while the resin produced by the kettle reactor has long chain branches distributed in a tree-like manner, showing a nearly spherical morphology in solution.

[0067] Increasing the reaction temperature during the polymerization process increases the melt flow rate of the product and decreases the density. When the reaction temperature increases, both the chain growth rate and the chain transfer rate increase, and the activation energy of the two reactions is 4 and 15 kcal / (g·mol), respectively. Therefore, increasing the temperature is conducive to the chain transfer reaction, so the average relative molecular weight of the low-density polyethylene resin product decreases and the melt flow rate increases. At the same time, when the temperature is increased, the chain transfer rate is accelerated, resulting in macromolecules with more short and long branches, so the branching degree increases, the corresponding crystallinity decreases, and the density of the low-density polyethylene resin product decreases.

[0068] Increasing the polymerization pressure during the polymerization process increases the average relative molecular mass of the low-density polyethylene resin product, reduces the melt flow rate, and increases the density. Under ultra-high pressure conditions, the distance between ethylene molecules is shortened. Increasing the pressure increases the ethylene concentration accordingly, increases the collision opportunities between free radicals and ethylene molecules or between active growth chains and ethylene molecules, promotes the chain growth reaction, and the chain termination reaction is not affected, so the average relative molecular mass increases and the melt flow rate decreases. At the same time, increasing the pressure reduces the branching degree of long and short chains, and fewer long branches can be obtained. The branching degree decreases and the crystallinity increases, so the density increases.

[0069] The molecular structure characteristics of low-density polyethylene resin have a great influence on the quality of polyolefin compositions for cable insulation. The branch content and double bond content of polyolefin materials for cable insulation affect their cross-linking ability, and the long branch content affects the processing stability of the base material. In the production of high-pressure low-density polyethylene products by free radical polymerization, intramolecular chain transfer is prone to produce intramolecular double bond structures (R1R=C=CH2); propylene provides hydrogen atoms in the methyl group to the growing chain, and can form a terminal double bond structure (RCH=CH2) by itself. The double bond content is determined by infrared spectroscopy with reference to the method in the literature "Research on the structural properties of base resins for cross-linked LDPE insulation materials" (Modern Plastic Processing Applications, Issue 4, 2015).

[0070] The branching degree is determined by infrared spectroscopy. Test method: The sample is pressed into a 0.3 mm thick film, and the peak of -CH3 in the resin is tested by infrared spectrometer. The peak of 1378 cm -1 (main chain methylene) and 1368cm -1 The methyl content in polyethylene was calculated by the absorbance at the (methyl end group), and the number of methyl groups per 1000 carbon atoms was used to characterize the relative branching degree of polyethylene.

[0071] Whether the molecular chain structure of polymer materials is linear or branched has a great influence on its fluidity, which comes from both the shape and number of branches and the length of the branches. Generally speaking, short branches have little effect on the viscosity of the material. The shape and length of long branches have a great influence on the viscosity of polymer materials. Regarding the characterization of long branches, NMR or GPC combined with multi-angle laser light scattering (MALLS) is usually used, and the use of dynamic rheology to characterize the degree of long chain branching is a more convenient and quick method developed in recent years.

[0072] Garcia-Franco CA proposed that the dependence of the loss angle δ on the square root of the sum of the squares of the storage modulus and the loss modulus |G*| is affected by the molecular structure of the polymer, especially the long chain branching. Therefore, the loss angle δ corresponding to a certain |G*| value (|G*| = 10 kPa) is calculated according to the formula LCB = 2.5085-2.8178×10 -2δ is used to quantitatively calculate the long chain branch content as a measure of long chain branching (European Polymer Journal, 2008, 44(2):376-391). This value was chosen because it is readily available for a wide range of commercial resins. This method is attractive because it is simple to perform, as only a simple isothermal small angle dynamic shear measurement test is required.

[0073] The volume resistivity test method is carried out in accordance with the standard GB / T 1410-2006, the dielectric constant and dielectric loss tangent are measured in accordance with the standard GB / T 1409-2006, and the thermal extension test [(200±3)℃, 0.20MPa, 15min] is carried out in accordance with the standard GB / T2951.21-2008 to obtain the elongation under load and permanent deformation rate of the cross-linked sample. The anti-puncture field strength is tested in accordance with the standard GB / T1408.1-2006.

[0074] Gel content determination conditions: Cut a stainless steel wire mesh with a hole width of 0.12mm to make a square bag of about 40mm×40mm, and weigh it (W1). Place about 0.3g of the sample in the weighed stainless steel wire mesh bag, seal it and weigh it (W2). Then put the stainless steel wire mesh bag containing the sample into the round-bottom flask. Tie a thin metal wire to the mesh bag. And extend it through the reflux condenser. This can be used to hang the mesh bag so that the bottom edge of the mesh bag almost touches the bottom of the flask. Pour enough xylene into the round-bottom flask to completely immerse the stainless steel wire mesh bag containing the sample. Boil xylene vigorously to ensure that the solution vibrates well. Extract in xylene for 7 hours. After extraction, place the mesh bag containing the sample in a vacuum oven, dry the sample to constant weight, cool and weigh it (W3). Calculate the gel content according to the following calculation formula:

[0075] (W3-W1) / (W2-W1)×100%

[0076] Preparation Example 1

[0077] The preparation method of poly 2,2,6,6-tetramethylpiperidinol-4-methylacrylate in the present invention is as follows:

[0078] 0.1 g of azobisisobutyronitrile, 17 g of 2,2,6,6-tetramethylpiperidinol-4-methylacrylate, and 25 ml of acetone were added to the polymerization tube in sequence, and after uniform mixing, liquid nitrogen cooling, vacuuming, nitrogen flow, and thawing were repeated three times, and the tube was sealed under vacuum and stirred at 70°C for 5 h. The obtained crude product was precipitated in n-hexane and dried to obtain poly-2,2,6,6-tetramethylpiperidinol-4-methylacrylate, and the polymerization degree of the monomer 2,2,6,6-tetramethylpiperidinol-4-methylacrylate was 60.

[0079] Preparation Example 2

[0080] The preparation method of dodecyl poly-1,2,2,6,6-pentamethylpiperidinol-4-methylacrylate in the present invention is as follows:

[0081] 0.15g 2-cyano-2-propyl dodecyl trithiocarbonate, 0.1g dibenzoyl peroxide, 11g 1,2,2,6,6-pentamethylpiperidinol-4-methylacrylate, and 20ml acetone were added to the polymerization tube in sequence, and after uniform mixing, liquid nitrogen cooling-vacuuming-nitrogen-thawing were repeated 3 times, and the tube was sealed under vacuum and stirred at 85°C for 8h. The obtained crude product was precipitated in methanol / water (v / v, 1 / 1), and after drying, dodecyl poly 1,2,2,6,6-pentamethylpiperidinol-4-methylacrylate was obtained, and the polymerization degree of the monomer 1,2,2,6,6-pentamethylpiperidinol-4-methylacrylate was 80.

[0082] Example 1

[0083] This embodiment provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0084] The low-density polyethylene resin (melt flow rate 2.0 g / 10 min, density 0.918 g / cm 3 , impurity content 15 / 1000g), 0.03% of poly 2,2,6,6-tetramethylpiperidinol-4-methylacrylate based on the mass of polyethylene, and 0.11% of antioxidant 1010 based on the mass of polyethylene are melt-plasticized at 170-200°C. The melt-plasticized composition is filtered through a filter with a mesh of 150 microns, and then cooled to form composition particles. The composition particles are irradiated with a dose of 16kGy of a cobalt source to obtain a pre-irradiated insulating material. 0.32% of an organic peroxide (di-tert-butyl peroxide) based on the mass of polyethylene is added to the pre-irradiated insulating material by spraying to obtain a polyolefin material for cable insulation.

[0085] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 80-120° C. to obtain a 35 kV high voltage cable with an insulation layer thickness of 12 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 60° C. and a degassing time of 5 days.

[0086] Example 2

[0087] This embodiment provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0088] The low-density polyethylene resin (melt flow rate 1.8 g / 10 min, density 0.920 g / cm 3, impurity content 10 / 1000g), 0.02% of dodecyl poly 1,2,2,6,6-pentamethylpiperidinol-4-methylacrylate based on the mass of polyethylene, and 0.42% of antioxidant 1076 based on the mass of polyethylene are melt-plasticized at 180-210°C. The melt-plasticized composition is filtered through a filter with a mesh of 150 microns, and then cooled to form composition particles. The composition particles are irradiated with a high-energy electron beam dose of 20kGy to obtain a pre-irradiated insulating material. 0.40% of organic peroxide (tert-butyl peroxide isopropylbenzene) based on the mass of polyethylene is added to the pre-irradiated insulating material in an impregnated manner to obtain a polyolefin material for cable insulation.

[0089] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 85-125° C. to obtain a 110 kV high voltage cable with an insulation layer thickness of 17 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 70° C. and a degassing time of 7 days.

[0090] Example 3

[0091] This embodiment provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0092] The low-density polyethylene resin (melt flow rate 2.2 g / 10 min, density 0.920 g / cm 3 , impurity content 8 / 1000g), 0.04% GW-770 based on the mass of polyethylene, 0.20% antioxidant 300 based on the mass of polyethylene are melt-plasticized at 160-200°C. The melt-plasticized composition is filtered through a filter with a mesh of 100 microns, and then cooled to form composition particles. The composition particles are irradiated with a high-energy electron beam dose of 48kGy to obtain a pre-irradiated insulating material. 0.51% organic peroxide (tert-butyl peroxylaurate) based on the mass of polyethylene is added to the pre-irradiated insulating material in a splashing manner to obtain a polyolefin material for cable insulation.

[0093] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 90-118° C. to obtain a 220 kV high voltage cable with an insulation layer thickness of 26 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 75° C. and a degassing time of 6 days.

[0094] Example 4

[0095] This embodiment provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0096] The low-density polyethylene resin (melt flow rate 2.4 g / 10 min, density 0.917 g / cm 3, impurity content 13 / 1000g), 0.03% GW-123 based on the mass of polyethylene, 0.33% composite antioxidant (antioxidant 1010: antioxidant 168 = 2:1) based on the mass of polyethylene are melt-plasticized at 160-190°C. The melt-plasticized composition is filtered through a filter with a mesh of 120 microns, and then cooled to form composition particles. The composition particles are irradiated with a dose of 23kGy of a cobalt source to obtain a pre-irradiated insulating material. 0.95% of an organic peroxide (α,α'-di-tert-butylperoxy-1,4-diisopropylbenzene) based on the mass of polyethylene is added to the pre-irradiated insulating material by spraying to obtain a polyolefin material for cable insulation.

[0097] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 90-130° C. to obtain a 110 kV high voltage cable with an insulation layer thickness of 17 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 62° C. and a degassing time of 8 days.

[0098] Example 5

[0099] This embodiment provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0100] The low-density polyethylene resin (melt flow rate 2.3g / 10min, density 0.919g / cm 3 , impurity content 18 / 1000g), 0.05% GW-3853 based on the mass of polyethylene, 0.15% composite antioxidant (antioxidant 1076: antioxidant 1024 = 4:1) based on the mass of polyethylene are melt-plasticized at 160-200°C. The melt-plasticized composition is filtered through a filter with a mesh of 100 microns, and then cooled to form composition particles. The composition particles are irradiated with a dose of 27kGy of a cobalt source to obtain a pre-irradiated insulating material. 0.75% of an organic peroxide (di-tert-butyl diperoxyphthalate) based on the mass of polyethylene is added to the pre-irradiated insulating material in an impregnated manner to obtain a polyolefin material for cable insulation.

[0101] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 90-125° C. to obtain a 35 kV high voltage cable with an insulation layer thickness of 12 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 71° C. and a degassing time of 6 days.

[0102] Example 6

[0103] This embodiment provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0104] The low-density polyethylene resin (melt flow rate 1.9 g / 10 min, density 0.921 g / cm3 , impurity content 16 / 1000g), 0.01% GW-944 based on the mass of polyethylene, 0.26% composite antioxidant (antioxidant 330: thiodipropionate = 3:1) based on the mass of polyethylene are melt-plasticized at 180-200°C. The melt-plasticized composition is filtered through a filter with a mesh of 150 microns, and then cooled to form composition particles. The composition particles are irradiated with a dose of 30 kGy of a cobalt source to obtain a pre-irradiated insulating material. 0.52% of an organic peroxide (diisopropylbenzene peroxide) based on the mass of polyethylene is added to the pre-irradiated insulating material in a splashing manner to obtain a polyolefin material for cable insulation.

[0105] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 80-128° C. to obtain a 220 kV high voltage cable with an insulation layer thickness of 26 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 68° C. and a degassing time of 10 days.

[0106] Example 7

[0107] This embodiment provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0108] The low-density polyethylene resin (melt flow rate 2.5g / 10min, density 0.922g / cm 3 , impurity content 14 / 1000g), 0.03% GW-622 based on the mass of polyethylene, 0.35% mixed phenolic antioxidant (antioxidant 1010: antioxidant 1076 = 1:1) based on the mass of polyethylene are melt-plasticized at 160-190°C. The melt-plasticized composition is filtered through a filter with a mesh of 120 microns, and then cooled to form composition particles. The composition particles are irradiated with a dose of 35kGy of a cobalt source to obtain a pre-irradiated insulating material. 0.61% organic peroxide (tert-butyl peroxy isopropyl carbonate) based on the mass of polyethylene is added to the pre-irradiated insulating material in an impregnated manner to obtain a polyolefin material for cable insulation.

[0109] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 80-122° C. to obtain a 110 kV high voltage cable with an insulation layer thickness of 17 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 70° C. and a degassing time of 9 days.

[0110] Example 8

[0111] This embodiment provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0112] The low-density polyethylene resin (melt flow rate 2.1 g / 10 min, density 0.923 g / cm3 , impurity content 12 / 1000g), 0.04% GW-3346 based on the mass of polyethylene, 0.22% mixed phenolic antioxidant (antioxidant 1076: antioxidant 330 = 1:2) based on the mass of polyethylene are melt-plasticized at 160-200°C. The melt-plasticized composition is filtered through a filter with a mesh of 150 microns, and then cooled to form composition particles. The composition particles are irradiated with a high-energy electron beam dose of 42kGy to obtain a pre-irradiated insulating material. 0.72% of organic peroxide (diisopropyl peroxide: tert-butyl peroxyisopropyl carbonate = 1:1) based on the mass of polyethylene is added to the pre-irradiated insulating material in a spraying manner to obtain a polyolefin material for cable insulation.

[0113] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 85-120° C. to obtain a 220 kV high voltage cable with an insulation layer thickness of 26 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 65° C. and a degassing time of 8 days.

[0114] Comparative Example 1

[0115] This comparative example provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0116] The low-density polyethylene resin (melt flow rate 2.0 g / 10 min, density 0.918 g / cm 3 , impurity content 15 / 1000g), 0.03% of poly 2,2,6,6-tetramethylpiperidinol-4-methylacrylate based on the mass of polyethylene, and 0.11% of antioxidant 1010 based on the mass of polyethylene are melt-plasticized at 170-200°C. The melt-plasticized composition is filtered through a filter with a mesh of 150 microns, and then cooled to form composition particles. 0.32% of organic peroxide (di-tert-butyl peroxide) based on the mass of polyethylene is added to the composition particles by spraying to obtain a polyolefin material for cable insulation.

[0117] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 80-120° C. to obtain a 35 kV high voltage cable with an insulation layer thickness of 12 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 60° C. and a degassing time of 5 days.

[0118] Comparative Example 2

[0119] This comparative example provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0120] The low-density polyethylene resin (melt flow rate 1.8 g / 10 min, density 0.920 g / cm 3, impurity content 10 / 1000g), 0.02% of dodecyl poly 1,2,2,6,6-pentamethylpiperidinol-4-methylacrylate based on the mass of polyethylene, and 0.42% of antioxidant 1076 based on the mass of polyethylene are melt-plasticized at 180-210°C. The melt-plasticized composition is filtered through a filter with a mesh of 150 microns, and then cooled to form composition particles. The composition particles are irradiated with a high-energy electron beam dose of 10kGy to obtain a pre-irradiated insulating material. 0.40% of organic peroxide (tert-butyl peroxide isopropylbenzene) based on the mass of polyethylene is added to the pre-irradiated insulating material in an impregnated manner to obtain a polyolefin material for cable insulation.

[0121] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 85-125° C. to obtain a 110 kV high voltage cable with an insulation layer thickness of 17 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 70° C. and a degassing time of 7 days.

[0122] Comparative Example 3

[0123] This comparative example provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0124] A low-density polyethylene resin (melt flow rate 2.2g / 10min, density 0.920g / cm3, impurity content 8 / 1000g), 0.04% GW-770 based on the mass of polyethylene, and 0.20% antioxidant 300 based on the mass of polyethylene are melt-plasticized at 160-200°C. The melt-plasticized composition is filtered through a filter with a mesh of 100 microns, and then cooled to form composition particles. The composition particles are irradiated with a high-energy electron beam dose of 60kGy to obtain a pre-irradiated insulating material. 0.51% of an organic peroxide (tert-butyl peroxylaurate) based on the mass of polyethylene is added to the pre-irradiated insulating material in a splashing manner to obtain a polyolefin material for cable insulation.

[0125] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 90-118° C. to obtain a 220 kV high voltage cable with an insulation layer thickness of 26 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 75° C. and a degassing time of 6 days.

[0126] Comparative Example 4

[0127] This comparative example provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0128] The low-density polyethylene resin (melt flow rate 2.4 g / 10 min, density 0.917 g / cm 3, impurity content 13 / 1000g), 0.33% of the composite antioxidant (antioxidant 1010: antioxidant 168 = 2:1) based on the mass of polyethylene is melt-plasticized at 160-190°C. The melt-plasticized composition is filtered through a filter with a mesh of 120 microns, and then cooled to form composite particles. The composite particles are irradiated with a dose of 23kGy of a cobalt source to obtain a pre-irradiated insulating material. 0.95% of an organic peroxide (α,α'-di-tert-butylperoxy-1,4-diisopropylbenzene) based on the mass of polyethylene is added to the pre-irradiated insulating material by spraying to obtain a polyolefin material for cable insulation.

[0129] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 90-130° C. to obtain a 110 kV high voltage cable with an insulation layer thickness of 17 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 62° C. and a degassing time of 8 days.

[0130] Comparative Example 5

[0131] This comparative example provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0132] The low-density polyethylene resin (melt flow rate 2.3g / 10min, density 0.919g / cm 3 , impurity content 18 / 1000g), 0.05% GW-3853 based on the mass of polyethylene is melt-plasticized at 160-200°C. The melt-plasticized composition is filtered through a filter with a mesh of 100 microns, and then cooled to form composition particles. The composition particles are irradiated with a dose of 27kGy of a cobalt source to obtain a pre-irradiated insulating material. 0.75% of an organic peroxide (di-tert-butyl diperoxyphthalate) based on the mass of polyethylene is added to the pre-irradiated insulating material in an impregnated manner to obtain a polyolefin material for cable insulation.

[0133] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 90-125° C. to obtain a 35 kV high voltage cable with an insulation layer thickness of 12 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 71° C. and a degassing time of 6 days.

[0134] Comparative Example 6

[0135] This comparative example provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0136] The low-density polyethylene resin (melt flow rate 1.0 g / 10 min, density 0.918 g / cm 3, impurity content 30 / 1000g), 0.01% GW-944 based on the mass of polyethylene, 0.26% composite antioxidant (antioxidant 330: thiodipropionate = 3:1) based on the mass of polyethylene are melt-plasticized at 180-200°C. The melt-plasticized composition is filtered through a filter with a mesh of 150 microns, and then cooled to form composition particles. The composition particles are irradiated with a dose of 30 kGy of a cobalt source to obtain a pre-irradiated insulating material. 0.52% of an organic peroxide (diisopropylbenzene peroxide) based on the mass of polyethylene is added to the pre-irradiated insulating material in a splashing manner to obtain a polyolefin material for cable insulation.

[0137] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 80-128° C. to obtain a 220 kV high voltage cable with an insulation layer thickness of 26 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 68° C. and a degassing time of 10 days.

[0138] Comparative Example 7

[0139] This comparative example provides a method for preparing a polyolefin material for cable insulation and a high-voltage cable, which comprises the following steps:

[0140] The low-density polyethylene resin (melt flow rate 3.0 g / 10 min, density 0.925 g / cm 3 , impurity content 10 / 1000g), 0.03% GW-622 based on the mass of polyethylene, 0.35% composite antioxidant (antioxidant 1010: antioxidant 1076 = 1:1) based on the mass of polyethylene are melt-plasticized at 160-190°C. The melt-plasticized composition is filtered through a filter with a mesh of 120 microns, and then cooled to form composition particles. The composition particles are irradiated with a dose of 35kGy of a cobalt source to obtain a pre-irradiated insulating material. 0.61% of an organic peroxide (tert-butyl peroxy isopropyl carbonate) based on the mass of polyethylene is added to the pre-irradiated insulating material in an impregnated manner to obtain a polyolefin material for cable insulation.

[0141] The prepared polyolefin material for cable insulation is extruded and coated onto a conductor at 80-122° C. to obtain a 110 kV high voltage cable with an insulation layer thickness of 17 mm. The degassing process conditions of the high voltage cable are a degassing temperature of 70° C. and a degassing time of 9 days.

[0142] The following will analyze and compare the specific experimental data for the performance of pre-irradiated insulation materials and high-voltage cables. The experimental results are shown in Table 1 and Table 2:

[0143] Table 1. Comparison of pre-irradiated insulating material properties of the embodiments and comparative examples

[0144]

[0145]

[0146] Table 2. Comparison of high voltage cable performance between the embodiment and the comparative example

[0147]

[0148]

[0149] By comparing the data of the examples and comparative examples in Table 1 and Table 2, it can be seen that the pre-irradiated insulating material obtained according to the technical solution of the present invention has a high double bond content, and can achieve a high crosslinking efficiency (high gel content) at a low amount of organic peroxide added to obtain a high-voltage cable. At the same time, the melt flow rate (MFR) of Examples 1-8 after irradiation is the same as the MFR value of the base resin used, indicating that no crosslinking occurs after pre-irradiation, but only the structure of the low-density polyethylene resin is changed, making it easy to chemically crosslink. The MFR values ​​of Comparative Examples 3-5 are all reduced compared to the MFR values ​​of the base resin used, indicating that a certain amount of crosslinking occurs after irradiation.

[0150] In addition, the polyolefin material can be processed into high-voltage cables by using existing cable production equipment, and has the characteristics of smooth surface, low impurity content, less volatiles and excellent performance. The insulating material of the present invention can discharge volatiles within a short degassing time (no more than 10 days) after cross-linking, and has lower elongation under load, permanent deformation rate, and higher gel content, puncture resistance and volume resistivity.

[0151] If no irradiation is performed (Comparative Example 1) or the irradiation dose is not within the scope of the present invention (Comparative Example 2, Comparative Example 3), or the composition lacks necessary components (Comparative Example 4, Comparative Example 5), and the obtained composition is cross-linked under the condition of low peroxide addition, the cross-linked insulating material has a higher elongation under load, permanent deformation rate, and lower gel content and puncture resistance, and the purpose of the present invention cannot be achieved.

[0152] The inventors of the present invention have found that by selecting appropriate polyethylene resins, under appropriate irradiation doses, low-density polyethylene resins, antioxidants, and hindered amine stabilizers can jointly produce unexpected changes: the low-density polyethylene resins are not cross-linked, but the structure undergoes certain changes. This change can produce good results, so that the obtained pre-irradiated insulating material has the characteristics of being easy to chemically cross-link, thereby having a high cross-linking efficiency (high gel content) at a relatively low amount of organic peroxide added. The technical solution of the present invention can be used to process high-voltage cables by utilizing existing cable production equipment, and obtain cables with smooth surfaces, few impurities and volatiles, and excellent performance.

Claims

1. A polyolefin composition, wherein The raw material composition of the polyolefin composition comprises: (A) low-density polyethylene resin; (B) 0.01% to 0.05% of a hindered amine stabilizer, based on the mass of the low-density polyethylene resin; (C) 0.1% to 0.45% of an antioxidant based on the mass of the low-density polyethylene resin; and (D) 0.3% to 1.0% of an organic peroxide based on the mass of the low-density polyethylene resin.

2. The polyolefin composition according to claim 1, wherein The amount of the hindered amine stabilizer is 0.03%-0.05%; Preferably, the amount of the antioxidant is 0.15%-0.35%; Preferably, the amount of the organic peroxide is 0.5%-1.0%.

3. The polyolefin composition according to claim 1, wherein The melt flow rate of the low-density polyethylene resin is 1.8-2.6 g / 10 min; Preferably, the density of the low-density polyethylene resin is 0.916-0.925 g / cm 3 ; Preferably, the content of impurities with a size of 50-150 μm in the low-density polyethylene resin is ≤20 pieces / 1000 g; Preferably, the low-density polyethylene resin is prepared by a high-pressure bulk polymerization method, which specifically includes the following steps: high-purity ethylene is subjected to a free radical polymerization reaction under the conditions of 150-300 MPa and 150-330° C. in an atmosphere of trace oxygen or air, under the initiation of organic peroxides and / or inorganic peroxides to obtain a product.

4. The polyolefin composition according to claim 1 or 2, wherein The hindered amine stabilizers include bis(2,2,6,6,-tetramethyl-4-piperidinyl) sebacate, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2,2,6,6-tetramethyl-4-piperidinyl stearate, poly{(6-morpholinyl-5-triazine-2,4-diyl)(2,2,6,6-tetramethylpiperidinyl)iminohexamethylene[(2,2,6,6-tetramethylpiperidinyl)-imino]}, poly{[6-[(1,1,3,3-tetramethylbutyl)amino]]-1,3,5-triazine-2,4-[(2,2, [(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexanediylene]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]}, poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol) succinate, high molecular weight triazine-piperidine condensate, polymers of the reaction products of N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine with 2,4,6-trichloro-1,3,5-triazine and N-butyl-1-butylamine and N-butyl-2,2,6,6-tetramethyl-4-piperidinamine, structural units containing -(TMPM)] m1 -polymeric hindered amine stabilizer, structural unit containing -(PMPM) m2 -One or a combination of two or more polymeric hindered amine stabilizers; Wherein, TMPM is a structural unit obtained by polymerization of 2,2,6,6-tetramethylpiperidinol-4-methylacrylate, and PMPM is a structural unit obtained by polymerization of 1,2,2,6,6-pentamethylpiperidinol-4-methylacrylate; m1 and m2 represent the degree of polymerization, and m1 and m2 are 4-100; Preferably, the structural unit comprises -(TMPM) m1 -The polymeric hindered amine stabilizer is poly-2,2,6,6-tetramethylpiperidinol-4-methylacrylate; the structural unit comprises -(PMPM) m2 -The polymeric hindered amine stabilizer is dodecyl poly 1,2,2,6,6-pentamethylpiperidinol-4-methylacrylate.

5. The polyolefin composition according to claim 1 or 2, wherein The antioxidant includes a phenolic antioxidant, or a composite antioxidant of a phenolic antioxidant and other antioxidants; Preferably, the other antioxidants include one or a combination of two or more of phosphite antioxidants, hydrazide antioxidants and thioester antioxidants.

6. The polyolefin composition according to claim 5, wherein In the composite antioxidant, the phenolic antioxidant is the main antioxidant, and the other antioxidants are auxiliary antioxidants; Preferably, the mass ratio of the primary antioxidant to the secondary antioxidant is 1:1-5:1, more preferably 2:1-4:

1.

7. The polyolefin composition according to claim 5 or 6, wherein The phenolic antioxidant includes one or a combination of two or more of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol, 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 4,4'-thiobis(6-tert-butyl-3-methylphenol).

8. The polyolefin composition according to any one of claims 5 to 7, wherein The other antioxidants include one or a combination of two or more of tris(2,4-di-tert-butylphenyl)phosphite, N,N'-bis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, and thiodipropionate; Preferably, the composite antioxidant includes one or a combination of two or more of a mixture of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol and tris(2,4-di-tert-butylphenyl)phosphite, a mixture of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and N,N'-bis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, a mixture of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol and N,N'-bis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, and a mixture of 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene and thiodipropionate.

9. The polyolefin composition according to claim 1 or 2, wherein The organic peroxide in (D) includes one or a combination of two or more of tert-butyl peroxyisopropyl carbonate, tert-butyl peroxylaurate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butyl peroxyacetate, di-tert-butyl diperoxyphthalate, tert-butyl peroxymaleic acid, cyclohexanone peroxide, tert-butyl peroxybenzoate, diisopropyl benzene peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl peroxyisopropyl benzene, tert-butyl hydroperoxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butyl-peroxy)hexane-3, and α,α'-bis-tert-butylperoxy-1,4-diisopropyl benzene.

10. A polyolefin material, which is prepared from the polyolefin composition according to any one of claims 1 to 9, wherein The preparation method of the polyolefin material comprises the following steps: (1) mixing low-density polyethylene resin, hindered amine stabilizer, and antioxidant and then melt-plasticizing; (2) filtering the melted and plasticized composition and then cooling it to form composition particles; (3) irradiating the composite particles to obtain a pre-irradiated insulating material; (4) Adding organic peroxide to the pre-irradiated insulating material to obtain a polyolefin material.

11. The polyolefin material according to claim 10, wherein The reaction temperature of the melt plasticization is 130-250°C, preferably 160-210°C.

12. The polyolefin material according to claim 10, wherein The irradiation includes high-energy electron beam or cobalt source; the irradiation dose is 15-50 kGy, preferably 20-40 kGy.

13. The polyolefin material according to claim 10, wherein The branching degree of the pre-irradiated insulating material is 1.5-1.9%; Preferably, the long chain branch content index of the pre-irradiated insulating material is 0.95-1.13; Preferably, the content of internal double bonds in the pre-irradiated insulating material is 0.20-0.40%, and the content of terminal double bonds is 0.15-0.35%.

14. A cable, which is prepared from the polyolefin composition according to any one of claims 1 to 9 or the polyolefin material according to any one of claims 10 to 13, wherein: This cable is a high voltage cable that can be used for 35kV and above.

15. The cable according to claim 14, wherein The thickness of the insulation layer coated on the conductor in the cable is 8-30 mm, more preferably 12-26 mm; Preferably, the cable is prepared by extruding and coating the polyolefin material onto a conductor at 80-130° C. to obtain a high-voltage cable.

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