Water tree resistant cable and method of making the same

Abstract

The application belongs to the technical field of electricity, and discloses a water treeing-resistant cable and a preparation method thereof. The cable comprises at least one cable core, the cable core comprises a conductor and an electric insulation layer arranged around the conductor, the electric insulation layer is prepared by extrusion coating of a thermoplastic insulation material on the outside of the conductor, and annealing heat treatment is performed after extrusion. The thermoplastic insulation material comprises a propylene polymer grafted with an oxygen-containing polar monomer and an optional second monomer, an optional propylene polymer, an optional elastomer and an auxiliary agent, the auxiliary agent comprises an antioxidant and a water treeing inhibitor. The annealing heat treatment conditions comprise: in an inert gas environment, the heat treatment temperature is 50-120 DEG C, and the heat treatment time is 2-12 h. The cable has long-term stable water treeing resistance.

Description

Technical Field

[0001] This invention belongs to the field of electrical technology, specifically relating to a water-resistant tree cable and a method for preparing the water-resistant tree cable. Background Technology

[0002] Water trees are a significant factor affecting cable lifespan. They primarily form due to long-term erosion from moisture in the air or soil, forming in gaps, defects, or impurities within the material. To reduce water tree formation, water tree inhibitors are commonly added. These inhibitors typically possess highly polar functional groups that absorb moisture penetrating the insulation layer, preventing water molecules from migrating with the electric field. Another approach is to add substances that react with water without affecting electrical performance.

[0003] Patent document US20140363671 discloses a cable with a non-crosslinked polyolefin insulation layer modified with epoxy groups. It mentions that the introduction of epoxy groups can improve the water-tree resistance of the insulation material, but does not describe the specific effects or the corresponding insulation material performance parameters. Furthermore, due to the preparation method and the characteristics of the epoxy groups, the insulation material can gel under the influence of heat and moisture during processing and operation, which adversely affects its electrical properties and recyclability.

[0004] Patent document CN111354507A discloses a water-tree resistant cable whose insulation layer is composed of a thermoplastic polypropylene-based material and at least one oxygen-containing compound with a melting temperature greater than 110°C, effectively preventing the precipitation of traditional liquid-phase or small-molecule water-tree resistant agents during processing. However, due to the polarity difference between the oxygen-containing compound and the polyolefin, dispersion problems caused by the aggregation of polar groups easily occur at the stated addition amount, thereby affecting its water-tree resistant effect. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a water-resistant cable and its preparation method, which exhibits long-term stable water-resistant properties.

[0006] A first aspect of the present invention provides a water-resistant tree cable, the cable comprising at least one cable core, the cable core comprising a conductor and an electrical insulation layer disposed around the conductor, the electrical insulation layer being formed by extruding a thermoplastic insulating material over the outside of the conductor and then subjecting it to annealing heat treatment.

[0007] The thermoplastic insulating material comprises an oxygen-containing polar monomer and an optional second monomer grafted modified propylene polymer, an optional propylene polymer, an optional elastomer, and additives, the additives comprising antioxidants and water tree inhibitors.

[0008] The annealing heat treatment conditions include: in an inert gas environment, a heat treatment temperature of 50-120℃, and a heat treatment time of 2-12h.

[0009] The second aspect of the present invention provides a method for preparing the above-mentioned water-resistant tree cable, the method comprising: preparation of the cable core: mixing an oxygen-containing polar monomer and an optional second monomer-grafted modified propylene polymer, an optional propylene polymer, an optional elastomer and an additive, and melt-extruding and granulating to obtain a thermoplastic insulating material;

[0010] The cable core is obtained by extruding an electrical insulation layer onto the outside of a conductor using thermoplastic insulating material, followed by annealing heat treatment.

[0011] The cable of this invention possesses long-term stable water-tree resistance. By selecting propylene polymers grafted with oxygen-containing polar monomers and optionally a second monomer as raw materials for the electrical insulation layer, this invention effectively improves the electrical performance and water-tree resistance of the cable. Furthermore, heat treatment during the cable core manufacturing process can further enhance the cable's water-tree resistance.

[0012] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0013] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0014] According to a first aspect of the present invention, the present invention provides a water-resistant tree cable, the cable comprising at least one cable core, the cable core comprising a conductor and an electrical insulation layer disposed around the conductor, the electrical insulation layer being formed by extruding a thermoplastic insulating material over the outside of the conductor and then subjecting it to annealing heat treatment after extrusion;

[0015] The thermoplastic insulating material comprises an oxygen-containing polar monomer and an optional second monomer grafted modified propylene polymer, an optional propylene polymer, an optional elastomer, and additives, the additives comprising antioxidants and water tree inhibitors.

[0016] The annealing heat treatment conditions include: in an inert gas environment, a heat treatment temperature of 50-120℃, and a heat treatment time of 2-12h.

[0017] In a preferred embodiment, the annealing heat treatment conditions include: in an inert gas environment, a heat treatment temperature of 60-110°C, more preferably 80-100°C, and a heat treatment time of 2.5-10h, more preferably 3-8h.

[0018] In this invention, the cable can be a DC cable or an AC cable, preferably a medium- or low-voltage DC or AC cable. In this invention, low voltage (LV) represents a voltage below 1 kV, medium voltage (MV) represents a voltage in the range of 1 kV to 40 kV, high voltage (HV) represents a voltage above 40 kV, preferably above 50 kV, and ultra-high voltage (EHV) represents a voltage of at least 230 kV.

[0019] According to the present invention, the cable core comprises, from the inside out: a conductor, an optional conductor shielding layer, an electrical insulation layer, an optional electrical insulation shielding layer, and an optional metal shielding layer. The electrical insulation shielding layer is subjected to annealing heat treatment after extrusion. The conductor shielding layer, the electrical insulation shielding layer, and the metal shielding layer can be provided as needed, and are generally used in cables of 6kV and above.

[0020] In this invention, the cable further includes a sheath layer and optional armor. The sheath layer is disposed on the outside of the cable core and includes an outer sheath layer and an optional inner sheath layer. The armor is disposed between the inner sheath layer and the outer sheath layer.

[0021] According to the present invention, the cable may include one or more cable cores. When the cable includes two or more cable cores, the cable includes a filler layer and a wrapping layer. The filler layer is formed by filler material filled between each cable core. The wrapping layer covers the outside of all cable cores to ensure that the cable cores and the filler layer are circular, to prevent the cable cores from being scratched by the armor, and to play a flame-retardant role.

[0022] In this invention, the conductor, conductor shielding layer, electrical insulation shielding layer, metal shielding layer, armor, sheathing layer, filling layer, and wrapping tape layer that make up the cable can all be made using conventional materials and conventional methods in the field.

[0023] Specifically, the conductor is typically a conductive element made of metallic materials, preferably aluminum, copper, or other alloys, including one or more metallic wires. The DC resistance and the number of individual wires of the conductor must comply with the requirements of GB / T3956. Preferably, the conductor has a tightly stranded circular structure with a nominal cross-sectional area of ​​800 mm² or less. 2 Alternatively, a split conductor structure may be used, with a nominal cross-sectional area greater than or equal to 1000 mm². 2 The number of conductors shall not be less than 170.

[0024] The thermoplastic insulating material of this invention can also be used as the base material for shielding materials. The thermoplastic insulating material used in the electrical insulation shielding layer of the cable and the thermoplastic insulating material used in the shielding material can be the same or different. The materials of the conductor shielding layer and the electrical insulation shielding layer contain thermoplastic insulating material, carbon black, and elastomer. The ratio of thermoplastic insulating material, carbon black, and elastomer is adjusted according to mechanical properties. Preferably, based on the total amount of thermoplastic insulating material, carbon black, and elastomer, the content of thermoplastic insulating material is 40-65 wt%, the content of carbon black is 20-40 wt%, and the content of elastomer is 15-25 wt%. Antioxidants, copper inhibitors, processing aids, etc., may also be added to the shielding material, using conventional dosages.

[0025] The shielding material has a volume resistivity of <1.0 Ω·m at 23℃ and <3.5 Ω·m at 90℃. At 230℃ and under a 2.16 kg load, the melt flow rate is typically 0.01-30 g / 10 min, preferably 0.05-20 g / 10 min, more preferably 0.1-10 g / 10 min, and even more preferably 0.2-8 g / 10 min; tensile strength ≥12.5 MPa; and elongation at break ≥150%. The thinnest point of the conductor shielding layer has a thickness of not less than 0.5 mm, and the average thickness is not less than 1.0 mm.

[0026] The metal shielding layer can be a copper strip shielding layer or a copper wire shielding layer.

[0027] The filler layer can be a polymer material, such as PE, PP, PVC, or recycled rubber material.

[0028] The armor layer is usually made of galvanized steel / stainless steel / aluminum alloy wire or strip armor, which is formed by wrapping a single layer of armor to the left or a double layer of armor with the inner layer to the right and the outer layer to the left. The wire or strip armor should be tight to minimize the gap between adjacent wires / strips.

[0029] The sheath layer can be made of any one of polyvinyl chloride, polyethylene, and low-smoke halogen-free materials. The sheath layer may include an outer sheath layer or an inner sheath layer.

[0030] All of the above-mentioned layers can be fabricated using conventional methods in the art. For example, the conductor shielding layer, electrical insulation layer, electrical insulation shielding layer, and sheathing layer can be formed by extrusion coating using an extruder, while the metal shielding layer and armor can be formed by wrapping.

[0031] According to the present invention, in the thermoplastic insulating material, the content of the grafted oxygen-containing polar monomer and optional second monomer structural unit is 0.1-6 wt%, preferably 0.5-5 wt%, more preferably 1-4 wt%, and the xylene-soluble content is 0-70 wt%, preferably 0.5-65 wt%. The melt flow rate of the thermoplastic insulating material at 230°C and 2.16 kg load is 0.2-7 g / 10 min, preferably 0.5-5 g / 10 min, more preferably 1-3.5 g / 10 min. The flexural modulus of the electrical insulating layer is 200-800 MPa, preferably 300-600 MPa, more preferably 350-550 MPa.

[0032] In this invention, the propylene polymer can be a homogeneous or heterogeneous propylene homopolymer or propylene copolymer, and the content of the copolymer monomer in the propylene polymer is 0-25 wt%, preferably 0-20 wt%. The melt flow rate of the propylene polymer at 230°C and 2.16 kg load is 0.5-10 g / 10 min, preferably 1-7 g / 10 min, and the melting temperature Tm is 110-180°C, preferably 120-170°C.

[0033] According to the present invention, the comonomer of the propylene copolymer may be selected from at least one of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene, preferably ethylene and / or 1-butene.

[0034] In this invention, the oxygen-containing polar monomer is at least one of the following: siloxane monomers, acrylate monomers, acid anhydride monomers, and acrylic monomers containing unsaturated double bonds; preferably, acrylate monomers and / or acid anhydride monomers; more preferably, methyl methacrylate monomers, hydroxypropyl methacrylate monomers, or maleic anhydride.

[0035] In this invention, the second monomer is an aromatic olefin monomer, preferably styrene.

[0036] According to the present invention, the thermoplastic insulating material contains at least one oxygen-containing polar monomer and optionally a second monomer grafted onto a propylene polymer. That is, the oxygen-containing polar monomer and optionally a second monomer grafted onto the propylene polymer in the material of the electrical insulating layer can be a single oxygen-containing polar monomer and optionally a second monomer grafted onto the propylene polymer, or it can be a propylene polymer grafted onto two or more oxygen-containing polar monomers and optionally a second monomer.

[0037] The propylene polymer grafted with the oxygen-containing polar monomer and optionally the second monomer of the present invention can be prepared using conventional methods in the prior art, as long as the application requirements are met. Preferably, the propylene polymer grafted with the oxygen-containing polar monomer and optionally the second monomer is prepared by the following method:

[0038] a. Place the propylene polymer in a closed reactor and replace it with an inert gas;

[0039] b. Add the free radical initiator, oxygen-containing polar monomer, and optional second monomer to a closed reactor and stir to mix;

[0040] c. Optionally add a swelling aid and optionally cause the reaction system to swell;

[0041] d. Optionally add a dispersant to raise the temperature of the reaction system to the grafting reaction temperature and carry out the grafting reaction;

[0042] e. Optionally, the reaction product is filtered and dried to obtain an oxygen-containing polar monomer and, optionally, a second monomer-grafted modified propylene polymer.

[0043] According to the present invention, the inert gas can be any of the inert gases commonly used in the art, including but not limited to nitrogen and argon.

[0044] In this invention, the free radical initiator is selected from peroxide-based free radical initiators; the peroxide-based free radical initiator is preferably selected from at least one of benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, lauroyl peroxide, dodecyl peroxide, tert-butyl peroxide, diisopropyl peroxide, tert-butyl peroxide (2-ethylhexanoate), and dicyclohexyl peroxide.

[0045] According to the present invention, based on the mass of the propylene polymer, the amount of the oxygen-containing polar monomer and the optional second monomer can be 1-12%, preferably 1.5-9%, and more preferably 1.7-7%. When the second monomer is included, the amount of the second monomer can be determined as needed. Preferably, the amount of the oxygen-containing polar monomer accounts for more than 20 wt% of the total amount of the oxygen-containing polar monomer and the second monomer.

[0046] The mass ratio of the free radical initiator to the oxygen-containing polar monomer and the optional second monomer is 0.1-6:100, preferably 0.5-5:100.

[0047] According to the present invention, the swelling agent is an organic solvent that has a swelling effect on olefin polymers, and may be an ether solvent, ketone solvent, aromatic solvent, or alkane solvent. The swelling agent is preferably at least one of the following organic solvents: chlorobenzene, polychlorinated benzene, alkanes or cycloalkanes with more than 6 carbon atoms, benzene, C1-C4 alkyl-substituted benzene, C2-C6 aliphatic ether, C3-C6 aliphatic ketone, and decahydronaphthalene; more preferably, it is selected from at least one of benzene, toluene, xylene, chlorobenzene, tetrahydrofuran, diethyl ether, acetone, hexane, cyclohexane, decahydronaphthalene, and heptane. Based on the mass of the propylene polymer, the amount of the swelling agent is 1-30%, preferably 10-25%.

[0048] In this invention, the swelling conditions include: the swelling temperature can be 30-60℃, and the time can be 1-5 hours.

[0049] The dispersant is water or an aqueous solution of sodium chloride. The water is deionized water, and the aqueous solution of sodium chloride can be of any conventionally used concentration. Based on the mass of the propylene polymer, the amount of the dispersant is 50-300%.

[0050] In this invention, the temperature of the grafting reaction is 80-130℃, preferably 85-120℃; the time is 0.5-10 hours, preferably 1-6 hours.

[0051] According to the present invention, all materials in the grafting reaction system can be added at once or at different stages of the reaction.

[0052] In this invention, the antioxidant is selected from at least one of hindered phenolic antioxidants, hindered amine antioxidants, phosphite antioxidants, and thiolated antioxidants. The antioxidant is preferably pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2′-methylenebis(4-methyl-6-tert-butylphenol), 2,4,6-tris(3′,5′-di-tert-butyl-4′-hydroxybenzyl)trimethylbenzene, N,N′-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, 2,2′-thiobis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2 At least one of the following: ′,2-oxamido-bis-[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4′-thiobis(6-tert-butyl-3-methylphenol), triphenyl phosphite, tris[2,4-di-tert-butylphenyl]phosphite, and dilauryl thiodipropionate.

[0053] According to the present invention, the water tree inhibitor is selected from polyols and their polymers, polyol esters and their polymers, ethoxylated fatty acids and their amide derivatives, preferably polyethylene glycol and polyethylene glycol stearate.

[0054] In this invention, the elastomer may be selected from at least one of POE, PBE, EPR, EPDM, SEBS and SBS.

[0055] According to a second aspect of the present invention, the present invention provides a method for preparing the above-mentioned water-resistant tree cable, the method comprising: mixing an oxygen-containing polar monomer and an optional second monomer grafted and modified propylene polymer, an optional propylene polymer, an optional elastomer and an additive, and melt-extruding and granulating to obtain a thermoplastic insulating material;

[0056] The cable core is obtained by extruding an electrical insulation layer onto the outside of a conductor using thermoplastic insulating material, followed by annealing heat treatment.

[0057] Based on the total mass of the propylene polymer, the propylene polymer, and the elastomer grafted with the oxygen-containing polar monomer and the optional second monomer, the amount of the propylene polymer grafted with the oxygen-containing polar monomer and the optional second monomer is 50% or more, preferably greater than 55%, more preferably greater than 60%, the amount of the antioxidant is greater than 2000 ppm, preferably 3000-5000 ppm, and the amount of the water tree inhibitor is 3000-15000 ppm, preferably 5000-10000 ppm.

[0058] In addition, depending on the product requirements, other additives may be added to this invention, such as processing aids, UV stabilizers, voltage stabilizers, antioxidants, and stabilizers. The types and amounts of other additives are conventional and known to those skilled in the art.

[0059] The processing aid may be selected from at least one of fluorinated compounds, polypropylene wax, polyethylene wax, fatty acid esters, and mineral oil, preferably at least one of polypropylene wax, fatty acid esters, and mineral oil. The amount of the processing aid is 0.2-4 wt%, preferably 0.5-2 wt%.

[0060] In this invention, melt extrusion granulation can be carried out using conventional equipment in the prior art, preferably a twin-screw extruder. The temperature of the melt extrusion granulation can be 180-250℃, preferably 185-230℃, and more preferably 190-220℃.

[0061] According to the present invention, the preparation method further includes: covering the outside of the conductor with a conductor shielding layer, an optional electrical insulation shielding layer, and an optional metal shielding layer; the conductor shielding layer is obtained by extruding a shielding material and covering the outside of the conductor, the electrical insulation layer is covered on the outside of the conductor shielding layer, the electrical insulation shielding layer is obtained by extruding a shielding material and covering the outside of the electrical insulation layer, and after annealing heat treatment, a metal shielding layer is formed by wrapping with metal strip / or metal wire to obtain the cable core.

[0062] The cable core is covered with a sheath layer and optional armor, the sheath layer including an outer sheath layer and an optional inner sheath layer; the outer sheath layer is formed by extruding sheath layer material on the outside of the cable core; or, the inner sheath layer is formed by extruding sheath layer material on the outside of the cable core, and armor made of galvanized steel / stainless steel / aluminum alloy wire or metal strip is wrapped around the outside of the inner sheath layer to form armor, and then the outer sheath layer is formed by extruding sheath layer material on the outside of the armor.

[0063] According to a specific embodiment of the present invention, the cable is prepared as follows:

[0064] Cable core preparation: Multiple monofilament conductors (such as copper) are bundled together, and then the bundled monofilament conductors are twisted together to obtain the conductor (conductor core). Conductor shielding material and electrical insulation material particles are co-extruded onto the conductor core using an extruder to form a conductor shielding layer + electrical insulation layer, or a conductor shielding layer + electrical insulation layer + electrical insulation shielding layer (outer shielding layer). This is followed by annealing heat treatment under the same conditions as described above. Copper strip or copper wire is then wrapped around the outside of the electrical insulation layer / electrical insulation shielding layer to form a metallic shielding layer.

[0065] Preparation of the inner sheath layer: The sheath layer granules are extruded outside the metal shielding layer through an extruder to form the inner sheath layer.

[0066] Armor preparation: Use galvanized steel / stainless steel / aluminum alloy to make metal wire or metal strip armor. The single layer of armor is wrapped around the inner sheath layer from left to right, or the inner layer of double armor is wrapped around the outer layer from left to right. The metal wire or metal strip armor should be tight to minimize the gap between adjacent metal wires / metal strips.

[0067] Preparation of the outer sheath layer: The sheath layer granules are extruded outside the armor through an extruder to form the outer sheath layer, thus producing the cable.

[0068] The substances and parameters not limited in this invention can be selected according to existing technology, which is a conventional technical means in this field.

[0069] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0070] In the following preparation examples, embodiments, and comparative examples, the data were obtained using the following test methods:

[0071] 1. Determination of comonomer content in propylene polymers:

[0072] The content of comonomers was determined by quantitative Fourier transform infrared (FTIR) spectroscopy. The correlation of the determined comonomer content was calibrated by quantitative nuclear magnetic resonance (NMR) spectroscopy. Based on quantitative... 13 The calibration method for the C-NMR spectrometer results was performed according to conventional methods in the art.

[0073] 2. Determination of xylene-soluble content (XS):

[0074] The test shall be conducted according to the method specified in GB / T 24282-2009.

[0075] 3. Grafting rate (GD) (n) / GD determination:

[0076] Place 2-4g of the grafted product into a Soxhlet extractor and extract with an organic solvent (ethyl acetate for aromatic olefin monomers, acrylate monomers, and acid anhydrides; acetone for silane monomers) for 24 hours to remove unreacted monomers and their homopolymers, obtaining a pure grafted product. Dry the product, weigh it, and calculate the grafting rate. GD (n) GD represents the grafting rate of the propylene polymer grafted with the oxygen-containing polar monomer and optionally the second monomer in the material. GD represents the content of structural units in the thermoplastic insulating material that are in a grafted state and contain the oxygen-containing polar monomer and optionally the second monomer. In this invention, GD is calculated using the following formula:

[0077]

[0078]

[0079] In the above formulas, w0 is the mass of the propylene polymer; w1 is the mass of the grafted product before extraction; and w2 is the mass of the grafted product after extraction. When the thermoplastic insulating material contains more than one graft, m... n1 It is the mass of the propylene polymer modified by the first oxygen-containing polar monomer and the optional second monomer in the material, m n2 It is the mass of the propylene polymer modified by the second oxygen-containing polar monomer and optionally the second monomer, and so on; m 产品 It refers to the quality of thermoplastic insulating materials.

[0080] 4. Determination of melt flow rate (melt index) MFR:

[0081] The test was performed using a CEAST 7026 melt flow indexer at 230°C and a load of 2.16 kg, according to the method specified in GB / T 3682-2018.

[0082] 5. Determination of melting temperature (melting point) Tm:

[0083] Differential scanning calorimetry (DSC) was used to analyze the melting and crystallization processes of the material. Specifically, under nitrogen protection, 5-10 mg of sample was heated from 20°C to 200°C using a three-stage temperature rise and fall measurement method. The change in heat flow reflected the melting and crystallization processes, and the melting temperature Tm was calculated.

[0084] 6. Determination of flexural modulus:

[0085] The determination shall be carried out in accordance with the method specified in GB / T 9341-2008.

[0086] 7. Measurement of the growth rate of water tree branches:

[0087] The water tree growth characteristics of the cable were prepared and tested according to the method described in "Water Tree Growth Characteristics in Cross-linked Polyethylene Cable Insulation" (Zhou Kai, Huang Kerong et al. High Voltage Engineering, 2019, 45(10): 3207-3213). The water tree growth of the samples was observed at 15, 30 and 60 days.

[0088] The reagents used in the preparation examples, embodiments, and comparative examples are as follows:

[0089] Benzoyl peroxide (BPO), Bailingwei Technology Co., Ltd.;

[0090] Lauroyl peroxide (LPO), Bailingwei Technology Co., Ltd.;

[0091] tert-butyl peroxide (2-ethylhexanoate), Adamas Reagents Ltd.

[0092] Styrene (St), Bailingwei Technology Co., Ltd.;

[0093] Methyl methacrylate (MMA), Bailingwei Technology Co., Ltd.

[0094] Hydroxypropyl methacrylate (HPMA), Bailingwei Technology Co., Ltd.

[0095] Maleic anhydride (MAH), Bailingwei Technology Co., Ltd.;

[0096] Xylene, Bailingwei Technology Co., Ltd.;

[0097] Butyl acrylate (BA), Bailingwei Technology Co., Ltd.;

[0098] Antioxidants: Antioxidant 1035, Antioxidant 1010, Antioxidant 168, Antioxidant 697, Shanghai Kaiyin Chemical Co., Ltd.

[0099] Processing aids (lubricants): PP wax 2602 (Clariant), PPA 5920A (3M, USA);

[0100] Water tree inhibitors: polyethylene glycol, polyethylene glycol stearate, Bailingwei Reagent Co., Ltd.

[0101] Elastomers: Vistamaxx 6102, Vistamaxx 6202, ExxonMobil;

[0102] Propylene polymers are shown in Table 1:

[0103] Table 1

[0104]

[0105] Preparation Examples 1-5

[0106] Weigh out the propylene polymer powder and add it to a reactor equipped with a mechanical stirrer. Seal the reaction system and remove oxygen by nitrogen purging. Add the initiator and a mixture of oxygen-containing polar monomer and optional second monomer, and stir and mix with the powder for 15-20 minutes. Optionally, add a dispersant or swelling aid, in parts by mass. Then heat to the reaction temperature and react for 1-6 hours. After the reaction is complete, cool down and optionally filter to remove the dispersant water. Dry at 70°C for 4 hours to obtain the propylene polymer (modified polypropylene powder) grafted with oxygen-containing polar monomer and optional second monomer. Specific reaction conditions and product properties are shown in Table 2.

[0107] Table 2

[0108]

[0109]

[0110] Examples 1-4

[0111] Preparation of thermoplastic insulating material: Weigh modified polypropylene powder, antioxidant, water tree inhibitor, processing aid, optional propylene polymer, and optional elastomer. The amount of each material is expressed as parts by mass, percentage by mass, or ppm by mass. After thorough mixing with a high-speed mixer, the mixture is added to a twin-screw extruder for granulation to obtain thermoplastic insulating material. The specific preparation conditions and material properties of each embodiment are shown in Tables 3 and 4.

[0112] Preparation of shielding materials for all embodiments: The thermoplastic insulating material, Vistamaxx 6102 and Cabot carbon black VXC 68 of Example 3 were weighed in a mass ratio of 53:20:27. Based on the mass of the thermoplastic insulating material, 5000ppm of antioxidant, 3000ppm of copper inhibitor MD-1024 and 3wt% of white oil were added. After being thoroughly mixed with a high-speed mixer, the mixture was added to a kneader and mixed at 200-220°C to obtain the corresponding inner and outer shielding layer materials.

[0113] Preparation of the cable core in all embodiments: 74 2.5mm copper monofilament conductors are bundled together. Then, the bundled monofilament conductors are twisted together to obtain a copper conductor core. Shielding material and thermoplastic insulating material granules are co-extruded over the conductor core using an extruder to form a conductor shielding layer + an electrical insulation layer + an electrical insulation shielding layer (outer shielding layer). The extrusion temperature is 160-180℃. After coiling, annealing is required. T1 copper is then wrapped around the electrical insulation shielding layer to form a metallic shielding layer.

[0114] Preparation of the inner sheath layer in all embodiments: St-2 grade PVC granules (Dongguan Haichuang Electronics Co., Ltd.) are extruded outside the metal shielding layer to form the inner sheath layer.

[0115] Preparation of armor in all embodiments: Steel wire armor with a nominal diameter of 1.25 mm is made of 304 stainless steel. The single layer of armor is wrapped around the inner sheath layer from left to right. The armor is tight to minimize the gap between adjacent steel wires.

[0116] Preparation of the outer sheath layer in all embodiments: St-2 grade PVC granules (Dongguan Haichuang Electronics Co., Ltd.) are extruded over the armor to form the outer sheath layer.

[0117] The final embodiment yields a 10kV cable. The cable conductor cross-sectional area is 400mm². 2 The average thickness of the conductor shielding layer is 1.1-1.2 mm, the average thickness of the electrical insulation layer is 2.9-3.0 mm, the average thickness of the electrical insulation shielding layer is 1.0-1.1 mm, the average thickness of the metallic shielding layer is 0.9-1.0 mm, the cable insulation eccentricity is 3.5-5%, the average thickness of the armor is 5.8-6.0 mm, the average thickness of the inner sheath is 2.0-2.1 mm, and the average thickness of the outer sheath is 2.5-2.6 mm.

[0118] Comparative Examples 1-4

[0119] The difference between Comparative Example 1 and Example 1 is that no heat treatment was performed during the preparation of the cable core; otherwise, they were the same. The difference between Comparative Example 2 and Example 2 is that an unmodified propylene polymer was used instead of the modified propylene polymer in Example 2 during the preparation of the thermoplastic insulation material; otherwise, they were the same. The difference between Comparative Example 3 and Example 1 is that the annealing heat treatment time during the preparation of the cable core was shorter; otherwise, they were the same. The difference between Comparative Example 4 and Example 1 is that the annealing heat treatment temperature during the preparation of the cable core was higher; otherwise, they were the same. The specific preparation conditions and material properties of each comparative example are shown in Tables 3 and 4, respectively.

[0120] Table 3

[0121]

[0122]

[0123] Table 4

[0124]

[0125] The cables prepared in each embodiment and comparative example were tested for water tree resistance, and the results are shown in Table 5.

[0126] Table 5

[0127]

[0128] By comparing the examples and comparative examples, it can be seen that the water tree growth of the samples obtained by the present invention is effectively suppressed. Comparing the data from Example 1 and Comparative Example 1, it can be seen that the water tree resistance of the unannealed cable is significantly lower than that of the annealed cable. Comparing the data from Example 2 and Comparative Example 2, it can be seen that the long-term water tree resistance of the cable using ungrafted modified polypropylene is lower than that of the cable using grafted modified polypropylene. Comparing the data from Example 1 and Comparative Example 3, it can be seen that a short annealing time does not improve the water tree resistance of the cable. Comparing the data from Example 1 and Comparative Example 4, it can be seen that a high annealing temperature does not improve the water tree resistance of the cable.

[0129] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A water-resistant tree-resistant cable, characterized in that, The cable includes at least one cable core, the cable core including a conductor and an electrical insulation layer disposed around the conductor, the electrical insulation layer being made by extruding a thermoplastic insulating material over the outside of the conductor and then subjecting it to annealing heat treatment; The thermoplastic insulating material comprises an oxygen-containing polar monomer and an optional second monomer grafted modified propylene polymer, an optional propylene polymer, an optional elastomer, and additives, the additives comprising antioxidants and water tree inhibitors. The annealing heat treatment conditions include: in an inert gas environment, a heat treatment temperature of 50-120℃, and a heat treatment time of 2-12h.

2. The water-resistant tree-resistant cable according to claim 1, wherein, The cable core comprises, from the inside out: a conductor, an optional conductor shielding layer, an electrical insulation layer, an optional electrical insulation shielding layer, and an optional metal shielding layer. The materials of the conductor shielding layer and the electrical insulation shielding layer contain thermoplastic insulating material, carbon black and elastomer. Based on the total amount of thermoplastic insulating material, carbon black and elastomer, the content of thermoplastic insulating material is 40-65 wt%, the content of carbon black is 20-40 wt%, and the content of elastomer is 15-25 wt%. The electrically insulating shielding layer is subjected to annealing heat treatment after extrusion. The annealing heat treatment conditions include: in an inert gas environment, the heat treatment temperature is 60-110℃, and the heat treatment time is 2.5-10h.

3. The water-resistant tree-resistant cable according to claim 2, wherein, The electrically insulating shielding layer is subjected to annealing heat treatment after extrusion. The annealing heat treatment conditions include: in an inert gas environment, the heat treatment temperature is 80-100℃, and the heat treatment time is 3-8h.

4. The water-resistant tree-resistant cable according to claim 1, wherein, The cable includes a sheath and optional armor, the sheath being disposed outside the cable core, the sheath including an outer sheath and optional inner sheath, and the armor being disposed between the inner sheath and the outer sheath. When a cable comprises two or more cores, the cable includes a filler layer and a wrapping layer, wherein the filler layer is formed by filler material filling between the cores and the wrapping layer covers the outside of all cores.

5. The water-resistant tree-resistant cable according to claim 1, wherein, In the thermoplastic insulating material, the content of grafted oxygen-containing polar monomers and optional second monomer structural units is 0.1-6 wt%, and the content of xylene-soluble substances is 0-70 wt%; the melt flow rate of the thermoplastic insulating material at 230℃ and 2.16 kg load is 0.2-7 g / 10 min; and the flexural modulus of the electrical insulating layer material is 200-800 MPa.

6. The water-resistant tree-resistant cable according to claim 5, wherein, In the thermoplastic insulating material, the content of the grafted oxygen-containing polar monomer and the optional second monomer structural unit is 0.5-5 wt%.

7. The water-resistant tree-resistant cable according to claim 6, wherein, In the thermoplastic insulating material, the content of the grafted oxygen-containing polar monomer and the optional second monomer structural unit is 1-4 wt%.

8. The water-resistant tree-resistant cable according to claim 5, wherein, The xylene-soluble content in the thermoplastic insulating material is 0.5-65 wt%.

9. The water-resistant tree-resistant cable according to claim 5, wherein, The melt flow rate of thermoplastic insulating materials at 230℃ and 2.16 kg load is 0.5-5 g / 10 min.

10. The water-resistant tree-resistant cable according to claim 9, wherein, The melt flow rate of thermoplastic insulating materials at 230℃ and 2.16 kg load is 1-3.5 g / 10 min.

11. The water-resistant tree-resistant cable according to claim 5, wherein, The flexural modulus of the electrical insulation layer material is 300-600 MPa.

12. The water-resistant tree-resistant cable according to claim 11, wherein, The flexural modulus of the electrical insulation layer material is 350-550 MPa.

13. The water-resistant tree-resistant cable according to claim 1, wherein, The propylene polymer is a propylene homopolymer or a propylene copolymer, and the content of the copolymer monomer in the propylene polymer is 0-25 wt%; the melt flow rate of the propylene polymer at 230℃ and 2.16 kg load is 0.5-10 g / 10 min, and the melting temperature Tm is 110-180℃. The oxygen-containing polar monomer is at least one of the following: siloxane monomers containing unsaturated double bonds, acrylate monomers, acid anhydride monomers, and acrylic monomers; The second monomer is an aromatic olefin monomer.

14. The water-resistant tree-resistant cable according to claim 13, wherein, The content of comonomers in propylene polymers is 0-20 wt%.

15. The water-resistant tree-resistant cable according to claim 13, wherein, The propylene polymer has a melt flow rate of 1-7 g / 10 min at 230°C and 2.16 kg load, and a melt temperature Tm of 120-170°C.

16. The water-resistant tree-resistant cable according to claim 13, wherein, The comonomer of the propylene copolymer is selected from at least one of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene.

17. The water-resistant tree-resistant cable according to claim 16, wherein, The comonomers of the propylene copolymer are ethylene and / or 1-butene.

18. The water-resistant tree-resistant cable according to claim 13, wherein, The oxygen-containing polar monomer is an acrylate monomer and / or an anhydride monomer.

19. The water-resistant tree-resistant cable according to claim 18, wherein, The oxygen-containing polar monomer is methyl methacrylate monomer, hydroxypropyl methacrylate monomer, or maleic anhydride.

20. The water-resistant tree-resistant cable according to claim 13, wherein, The second monomer is styrene.

21. The water-resistant tree-resistant cable according to any one of claims 1-20, wherein, The thermoplastic insulating material contains at least one oxygen-containing polar monomer and optionally a second monomer grafted modified propylene polymer.

22. The water-resistant tree-resistant cable according to claim 21, wherein, The propylene polymer grafted with the oxygen-containing polar monomer and optionally a second monomer was prepared by the following method: a. Place the propylene polymer in a closed reactor and replace it with an inert gas; b. Add the free radical initiator, oxygen-containing polar monomer, and optional second monomer to a closed reactor and stir to mix; c. Optionally add a swelling aid and optionally cause the reaction system to swell; d. Optionally add a dispersant to raise the temperature of the reaction system to the grafting reaction temperature and carry out the grafting reaction; e. Optionally, the reaction product is filtered and dried to obtain an oxygen-containing polar monomer and, optionally, a second monomer-grafted modified propylene polymer.

23. The water-resistant tree-resistant cable according to claim 22, wherein, The free radical initiator is selected from peroxide-based free radical initiators; Based on the mass of the propylene polymer, the amount of the oxygen-containing polar monomer and the optional second monomer is 1-12%; The mass ratio of the amount of the free radical initiator to the amount of the oxygen-containing polar monomer and the optional second monomer is 0.1-6:

100. The swelling agent is selected from at least one of benzene, toluene, xylene, chlorobenzene, tetrahydrofuran, diethyl ether, acetone, hexane, cyclohexane, decahydronaphthalene, and heptane; the amount of the swelling agent is 1-30% based on the mass of the propylene polymer; The dispersant is an aqueous solution of water or sodium chloride; the amount of the dispersant used is 50-300% based on the mass of the propylene polymer. The grafting reaction is carried out at a temperature of 80-130℃ for 0.5-10 hours.

24. The water-resistant tree-resistant cable according to claim 23, wherein, The peroxide radical initiator is selected from at least one of benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, lauroyl peroxide, dodecyl peroxide, tert-butyl peroxide, diisopropyl peroxide, tert-butyl peroxide, and dicyclohexyl peroxide.

25. The water-resistant tree-resistant cable according to claim 23, wherein, Based on the mass of the propylene polymer, the amount of the oxygen-containing polar monomer and the optional second monomer is 1.5-9%.

26. The water-resistant tree-resistant cable according to claim 25, wherein, Based on the mass of the propylene polymer, the amount of the oxygen-containing polar monomer and the optional second monomer is 1.7-7%.

27. The water-resistant tree-resistant cable according to claim 23, wherein, The mass ratio of the free radical initiator to the oxygen-containing polar monomer and the optional second monomer is 0.5-5:

100.

28. The water-resistant tree-resistant cable according to claim 23, wherein, Based on the mass of the propylene polymer, the amount of the swelling agent is 10-25%.

29. The water-resistant tree-resistant cable according to claim 23, wherein, The grafting reaction is carried out at a temperature of 85-120℃ for 1-6 hours.

30. The water-resistant tree-resistant cable according to claim 1, wherein, The antioxidant is selected from at least one of hindered phenolic antioxidants, hindered amine antioxidants, phosphite antioxidants, and thiolated antioxidants; The water tree inhibitor is selected from polyols and their polymers, polyol esters and their polymers, ethoxylated fatty acids and their amide derivatives.

31. The water-resistant tree-resistant cable according to claim 30, wherein, The antioxidants are pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)trimethylbenzene, N,N'-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, 2,2'-thiobis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2' At least one of the following: 2-oxamido-bis-[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4'-thiobis(6-tert-butyl-3-methylphenol), triphenyl phosphite, tris[2,4-di-tert-butylphenyl]phosphite, and dilauryl thiodipropionate.

32. The water-resistant tree-resistant cable according to claim 30, wherein, The water tree inhibitor is polyethylene glycol or polyethylene glycol stearate.

33. The water-resistant tree-resistant cable according to claim 30, wherein, The elastomer is selected from at least one of POE, PBE, EPR, EPDM, SEBS and SBS.

34. The method for preparing the water-resistant resin-resistant cable according to any one of claims 1-33, characterized in that, The preparation method includes: mixing an oxygen-containing polar monomer and an optional second monomer-grafted modified propylene polymer, an optional propylene polymer, an optional elastomer and additives, and then melt-extruding and granulating the mixture to obtain a thermoplastic insulating material. The cable core is obtained by extruding an electrical insulation layer onto the outside of the conductor using thermoplastic insulating material, followed by annealing heat treatment. Based on the total mass of the propylene polymer, propylene polymer and elastomer grafted with oxygen-containing polar monomer and optional second monomer, the amount of antioxidant is greater than 2000 ppm and the amount of water tree inhibitor is 3000-15000 ppm. The temperature for melt extrusion granulation is 180-250℃.

35. The method for preparing the water-resistant resin-resistant cable according to claim 34, wherein, The antioxidant is used in an amount of 3000-5000 ppm, based on the total mass of the propylene polymer, propylene polymer and elastomer grafted with oxygen-containing polar monomer and optional second monomer.

36. The method for preparing the water-resistant resin-resistant cable according to claim 34, wherein, The amount of the water tree inhibitor is 5000-10000 ppm, based on the total mass of the propylene polymer, propylene polymer and elastomer grafted with oxygen-containing polar monomer and optional second monomer.

37. The method for preparing the water-resistant resin-resistant cable according to claim 34, wherein, The temperature for melt extrusion granulation is 185-230℃.

38. The method for preparing the water-resistant resin-resistant cable according to claim 37, wherein, The temperature for melt extrusion granulation is 190-220℃.

39. The method for preparing the water-resistant resin-resistant cable according to claim 34, wherein, The preparation method further includes: covering the outside of the conductor with a conductor shielding layer, an optional electrical insulation shielding layer, and an optional metal shielding layer; the conductor shielding layer is obtained by extruding shielding material and covering the outside of the conductor, the electrical insulation layer is covered on the outside of the conductor shielding layer, the electrical insulation shielding layer is obtained by extruding shielding material and covering the outside of the electrical insulation layer, after annealing heat treatment, the metal shielding layer is formed by wrapping with metal strip / or metal wire to obtain the cable core; The cable core is covered with a sheath layer and optional armor, the sheath layer including an outer sheath layer and an optional inner sheath layer; the outer sheath layer is formed by extruding sheath layer material on the outside of the cable core; or, the inner sheath layer is formed by extruding sheath layer material on the outside of the cable core, and armor made of galvanized steel / stainless steel / aluminum alloy wire or metal strip is wrapped around the outside of the inner sheath layer to form armor, and then the outer sheath layer is formed by extruding sheath layer material on the outside of the armor.

Images