Cold-resistant low-smoke halogen-free polyolefin marine cable for polar region

Abstract

The invention discloses a polar cold-resistant low-smoke halogen-free polyolefin marine cable, which is suitable for-50 DEG C to + 70 DEG C extreme low-temperature marine environments such as polar scientific investigation ships, north ship ships and polar port power supply facilities, and solves the problems of low-temperature embrittlement, insulation failure, substandard safety and environmental protection and the like of the existing cable. The cable sequentially comprises a tinned copper conductor, a semi-conductive EPR conductor shielding layer, an EPR and XLPE composite insulating layer, a semi-conductive EPR insulating shielding layer, a halogen-free polyolefin-magnesium hydroxide lining layer, a tinned copper wire braided armor layer and a thermosetting low-smoke halogen-free polyolefin outer sheath from inside to outside, the sectional area of the conductor is 0.5 mm < 2 >-400 mm < 2 >, and the medium voltage grade is 6 / 10 kV or 8.7 / 15 kV. The medium-voltage cable has excellent cold resistance, high safety, long durability and medium-voltage high-power transmission adaptability, meets the IMO environmental protection standard, fills the technical blank of medium-voltage cables for polar ships, and promotes power transmission upgrading of polar equipment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cable materials, and particularly relates to a polar cold-resistant low-smoke halogen-free polyolefin marine cable. BACKGROUND

[0002] With the continuous growth of the number of global polar ships (such as polar icebreakers, research ships, and Arctic route container ships) and polar port fixed power supply facilities. Such equipment is long-term served in the extremely low temperature marine environment below-50℃, and at the same time faces multiple severe working conditions such as salt spray corrosion, ship vibration, mechanical impact, ice and snow coverage, and so on, which puts forward performance requirements far beyond the conventional marine standards for the core power transmission component, i.e. marine cable.

[0003] As the "blood vessels" of the power system of polar ships, marine cables directly determine the reliability and safety of power transmission, navigation and communication, and research equipment operation of the ships. On the one hand, the polar extreme low temperature will cause the brittleness and mechanical strength reduction of ordinary cable materials, and easily cause problems such as cracking of the insulation layer, peeling of the sheath, and failure of the conductor shielding, thereby causing safety accidents such as short circuit and electric leakage; on the other hand, during the sailing and operation of the ships, the cable needs to withstand frequent bending, impact and salt spray corrosion, and therefore requires excellent flexibility, mechanical damage resistance and corrosion resistance.

[0004] At present, the demand for medium-voltage power cables (6 / 10kV, 8.7 / 15kV) for polar ships is particularly urgent - such cables are mainly used for power transmission of the main power distribution system, propulsion system and high-power research equipment of the ships, and the performance stability thereof directly affects the endurance and safety of the ships. However, the existing conventional marine cables generally have problems such as insufficient cold resistance, serious attenuation of electrical and mechanical properties in extreme environments, and non-compliance with environmental protection indicators, and are difficult to adapt to the severe requirements of polar environments.

[0005] The thickness design of the insulation layer and the metal shielding structure of the existing medium-voltage marine cables are not optimized for polar low-temperature environments: the insulation layer thickness of 6 / 10kV grade cables is generally less than 3.5mm, and the insulation layer thickness of 8.7 / 15kV grade cables is less than 4.5mm, and the insulation breakdown field strength significantly decreases at low temperature; the cross section of the metal shielding layer is less than 4.0mm 2 , the direct current resistance at 20℃ is more than 1.5Ω / km, which cannot effectively realize fault current conduction and electric field shielding, and the resistance fluctuation amplitude at low temperature is more than 8%, which affects the action accuracy of the protection device. At the same time, the insulation layer processing technology is rough, and precise blending dispersion, cross-linking and cooling processes are not used, which results in poor dielectric performance and mechanical property stability at low temperature, and cannot adapt to the severe requirements of polar ship high-power power transmission. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a polar cold-resistant low-smoke halogen-free polyolefin marine cable, which solves the above technical problems existing in the prior art.

[0007] The purpose of the present application can be achieved by the following technical solutions: A polar cold-resistant low-smoke halogen-free polyolefin marine cable, the cable comprises, from the inside to the outside, a conductor, a conductor shielding layer, an insulation layer, an insulation shielding layer, an inner liner, an armor layer and an outer sheath, and the working environment temperature range is -50℃~+70℃. The conductor is a tinned copper conductor, and the cross-sectional area is 0.5mm 2 ~400mm 2 ; The insulation layer is a composite insulation system of EPR and XLPE, and the dielectric constant fluctuation amplitude is ≤3% and the volume resistivity fluctuation amplitude is ≤8% at -50℃ environment; The conductor shielding layer and the insulation shielding layer are both made of semi-conductive EPR material, and the volume resistivity is ≤100Ω・cm, the volume resistivity fluctuation amplitude is ≤15% at -50℃, and the conductor and the insulation layer are 100% covered; The inner liner is a composite material of halogen-free polymer and magnesium hydroxide, the thickness is 1.2mm~2.2mm, the adhesion to the armor layer is ≥20N / 10mm at -50℃, and the impact strength is ≥5kJ / m 2 ; The armor layer is a tinned copper wire braid layer, the braid coverage density is ≥95%, and the direct current resistance of the armor layer is ≤1.5Ω / km, the resistance fluctuation amplitude is ≤5%, and the resistance fluctuation amplitude is ≤5% at -50℃; The outer sheath is a thermosetting low-smoke halogen-free polyolefin, 0.5%~1.0% hindered phenolic antioxidant and 2%~3% nano carbon black are added, the thickness is 2.0mm~5.2mm, the tensile strength retention rate is ≥85% and the elongation at break retention rate is ≥75% at -50℃; Wherein, the obtained cable has a service life of ≥35 years at -50℃ environment, no crack under 8J impact energy once, no cracking in bending, and the insulation resistance retention rate is ≥70% after 1000 times of temperature cycle of -50℃~+70℃.

[0008] Further, the tinned copper layer on the surface of the tinned copper conductor of the conductor has a thickness of ≥8μm.

[0009] Further, the conductor shielding layer and the insulation shielding layer form 100% coverage, and the armor layer forms a coverage rate of ≥90%.

[0010] Further, the processing technology of the insulation layer comprises the following steps: S1, low temperature blending: The cold-resistant modifier is blended with the EPR, XLPE base material at 80-100 DEG C, the stirring speed is controlled to be 500-800 r / min, 0.3%-0.5% maleic anhydride grafted polyethylene compatibilizer is added, and the uniformity of the cold-resistant modifier is greater than or equal to 90%; S2, silane crosslinking: The two-step silane crosslinking is adopted, i.e., the pre-crosslinking temperature is 110-120 DEG C, the secondary crosslinking temperature is 140-150 DEG C, and the silane crosslinking degree is greater than or equal to 75%; S3, gradient cooling process: After extrusion molding, gradient water temperature cooling of 60 DEG C to 40 DEG C to 20 DEG C is adopted, and the cooling rate is controlled to be 2-5 DEG C / min.

[0011] Further, the inner lining layer is a composite material of halogen-free polyolefin and magnesium hydroxide, the addition amount of the magnesium hydroxide is 15%-20% of the total mass of the inner lining layer base material, and the impact strength of the inner lining layer is greater than or equal to 5 kJ / m 2 at-50 DEG C.

[0012] Further, the wire diameter of the armor layer is 0.15 mm-0.25 mm, and after braiding, heat setting treatment is carried out at 120-130 DEG C for 30-60 min, the braiding pitch of the armor layer is 10-15 mm, and the loose rate of the braided structure is less than or equal to 2% after heat setting.

[0013] Further, the size of the nano carbon black added in the outer sheath is 20-30 nm.

[0014] Further, in S1, 50-100 nm nano-silicon dioxide modifier is added, the agglomerate particle size of the modifier is less than or equal to 200 nm, and the addition amount is 3%-5% of the total mass of the insulation base material.

[0015] Further, the conductor shielding layer / insulation shielding layer has a volume resistivity fluctuation amplitude of less than or equal to 15% at-50 DEG C, an interface peeling strength of greater than or equal to 1.5 N / mm with the insulation layer, and no interface delamination after being frozen at-50 DEG C for 24 h.

[0016] Further, the cable is a medium-voltage power cable, the voltage grade is 6 / 10 kV or 8.7 / 15 kV, and the reference cross section of the metal shielding per phase is greater than or equal to 5.0 mm 2 ; the metal shielding direct current resistance is less than or equal to 1.2 omega / km at 20 DEG C, and the insulation layer thickness is greater than or equal to 4.0 mm for the 6 / 10 kV grade and greater than or equal to 5.0 mm for the 8.7 / 15 kV grade.

[0017] The beneficial effects of the present application are: 1. The application solves the problem of brittleness and insulation failure of traditional cables in -50℃ polar environment through innovative insulation system design and precise process control. On the one hand, the EPR and XLPE composite insulation system is adopted, combined with cold-resistant modifier (POE elastomer), nano-silicon dioxide modifier and maleic anhydride grafted polyethylene compatibilizer, through 80~100℃ low temperature blending, two-step silane crosslinking (crosslinking degree ≥75%) and 60℃→40℃→20℃ gradient cooling process, the dielectric constant fluctuation amplitude of the insulation layer is ≤3% and the volume resistivity fluctuation amplitude is ≤8% at -50℃, which is much better than the traditional single insulation material (fluctuation amplitude is more than 5% and 10% respectively), ensuring uniform electric field distribution and no insulation breakdown risk at extremely low temperature; on the other hand, the conductor shielding layer and insulation shielding layer are selected from customized semi-conductive EPR material, the volume resistivity fluctuation amplitude is ≤15% at -50℃, and the conductor and insulation layer form 100% full coverage, combined with the -50℃ tensile strength retention rate of the outer sheath (adding 0.5%~1.0% hindered phenol antioxidant and 2%~3% nano carbon black) ≥85%, the breaking elongation retention rate ≥75%, realizing the stability of cable flexibility and mechanical strength in the temperature range of -50℃~+70℃, no crack after 8J impact, no cracking after bending, completely adapting to the harsh working conditions such as polar ship vibration and ice and snow impact.

[0018] 2. The inner liner layer of the application adopts EVA resin and magnesium hydroxide (addition amount 15%~20%) composite material, which balances the flame retardant performance and mechanical performance while ensuring the impact strength ≥5kJ / m 2 at -50℃ and the adhesion to the armor layer ≥20N / 10mm.

[0019] 3. The application greatly improves the anti-aging, anti-damage and long-term service ability of the cable through structural design optimization and process upgrading. The armor layer adopts tinned copper wire braided structure (wire diameter 0.15mm~0.25mm), after 120~130℃ heat setting treatment for 30~60min, the braided coverage density is ≥95%, the loose rate is ≤2% at -50℃, and the direct current resistance is ≤1.5Ω / km, the high and low temperature resistance fluctuation amplitude is ≤5%, which not only effectively resists mechanical wear and salt spray corrosion during ship navigation, but also ensures the stability of fault current conduction; the high adhesion (≥20N / 10mm) design of the inner liner layer and the armor layer can prevent interfacial peeling in low temperature environment and prevent water from entering the cable to cause conductor corrosion and insulation deterioration; combined with the high crosslinking degree of the insulation layer and the antioxidant addition of the outer sheath, the service life of the cable in -50℃ environment is ≥35 years. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description.

[0021] Figure 1 is a schematic diagram of the overall cross-sectional structure of the cable of the embodiment of the present application; Figure 2 is a schematic diagram of the processing flow of the insulating layer of the embodiment of the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0023] As shown in Figure 1 , the present application provides a low-smoke halogen-free polyolefin cable suitable for the polar extreme environment of 50℃ to +70℃ of the application-invention, covering three application scenarios of medium-voltage power transmission, low-voltage power lighting and communication instrument signal transmission, which can meet the power supply, equipment control and data transmission requirements of polar research vessels, icebreakers and other ships, and has excellent low-temperature toughness, electrical stability, weather resistance and long service life characteristics.

[0024] The following will describe the technical solutions in detail through three groups of typical embodiments of medium-voltage power cables, low-voltage power lighting cables and communication instrument cables, and all parameters are verified by laboratory small-scale tests and pilot tests.

[0025] Preparation of conductor 101: Oxygen-free copper wire (purity ≥ 99.97%) is selected as the conductor base material, and a tin-plated copper conductor is prepared by bundle twisting process: 19 single copper wires with a diameter of 0.1 mm are twisted into a strand, and the twisting pitch is controlled to be 12 times the outer diameter of the conductor 101 to ensure the tightness of the twisting. Acidic electroplating process is used for tin plating treatment, and the electroplating solution is selected to be stannous sulfate-sulfuric acid system, the current density is controlled to be 1.5 A / dm 2 , the electroplating temperature is 25℃, and the electroplating time is 12s, so as to ensure that the thickness of the tin plating layer on the surface of the conductor 101 is ≥8μm (determined by eddy current thickness gauge, and the average thickness of 10 randomly selected test points is 8.5μm). The cross-sectional area of the finished conductor is accurately controlled to be 0.5mm 2 , and the direct current resistance (20℃) is 36Ω / km, which meets the requirement of electrical conductivity.

[0026] Preparation of conductor shielding layer 102: The semi-conductive EPR material is used as the base material of the conductor shielding layer 102, and the formula composition is: EPR resin 80 parts, conductive carbon black 25 parts, cold-resistant plasticizer 5 parts, and antioxidant 0.5 part. The above raw materials are added to a high-speed mixer and mixed at 80°C for 15 min at a stirring rate of 600 r / min to ensure uniform mixing. Then, the shielding layer is extruded on the surface of the conductor 101 through a single-screw extruder (screw diameter 30 mm, length-diameter ratio 25:1), the extrusion temperature is controlled at 120°C-140°C, the extrusion speed is 5 m / min, and the shielding layer thickness is accurately controlled at 0.8 mm through a mold to ensure 100% full wrapping of the conductor 101 (no exposed copper and local thin spot defects are detected by visual inspection and ultrasonic thickness gauge).

[0027] The finished conductor shielding layer 102 is tested: the volume resistivity is 80Ω·cm (≤100Ω·cm) at 25°C, and the volume resistivity is 88Ω·cm at -50°C with a fluctuation range of 10% (≤15%); the interfacial peeling strength with the subsequent insulation layer 103 is 1.8 N / mm (≥1.5 N / mm), and after being frozen at -50°C for 24 h, no interface delamination is observed by slicing.

[0028] As shown in Figure 2 , the insulation layer 103 is prepared (EPR and XLPE composite insulation system, thickness 4.0 mm), which specifically includes the following steps: S1: Low-temperature blending selects EPR resin 70 parts and XLPE resin 30 parts as base material, adds cold-resistant modifier (POE elastomer) 15 parts, maleic anhydride grafted polyethylene compatibilizer 0.4 parts (0.4% of the total mass of the base material), and nano-silicon dioxide modifier (particle size 50-100 nm) 4 parts (4% of the total mass of the base material).

[0029] The above raw materials are added to the feeding section of a twin-screw extruder (screw diameter 45 mm, length-diameter ratio 30:1) and blended at 90°C, with a screw speed of 700 r / min. The dispersion uniformity is tested (SEM observation of cross section, and the proportion of modifier agglomerates is counted) to ensure that the dispersion uniformity is ≥95% (agglomerate particle size ≤180 nm).

[0030] S2: Silane crosslinking uses a two-step silane crosslinking process: the blended material is extruded on the surface of the conductor shielding layer 102 through an extruder (extrusion temperature 130°C-150°C), and then enters a pre-crosslinking box for 4 h of heat preservation at 115°C to complete the pre-crosslinking; then it is transferred to a secondary crosslinking tank for 8 h of heat preservation at 145°C to complete the secondary crosslinking. The crosslinking degree is tested by Soxhlet extraction method, and the result is 78% (≥75%).

[0031] S3: After cross-linking, the insulation layer 103 immediately enters the three-section cooling water tank, sequentially passing through the first section with water temperature of 60°C, the second section with water temperature of 40°C, and the third section with water temperature of 20°C. The water temperature of each section is precisely controlled by a constant temperature control system, and the cooling rate is maintained at 3°C / min (the surface temperature change of the insulation layer 103 is monitored in real time by a temperature sensor), so as to avoid internal stress residues caused by rapid cooling.

[0032] The finished insulation layer 103 is tested: the dielectric constant is 2.3 (-50°C) (2.25 at 25°C), with a fluctuation amplitude of 2.2% (≤3%); the volume resistivity is 1.2 x 10 14 Ω·m (1.1 x 10 14 Ω·m at 25°C), with a fluctuation amplitude of ≤8%. By adjusting the process parameters and optimizing the addition amount of nano-silicon dioxide to 4.5 parts, the volume resistivity at -50°C is retested to be 1.18 x 10 14 Ω·m, with a fluctuation amplitude of 7.3%.

[0033] Preparation of the insulation shielding layer 104: The same semi-conductive EPR material formula and extrusion process as the conductor shielding layer 102 are used to extrude and cover the surface of the insulation layer 103, with a thickness of 0.8 mm, so as to ensure 100% full wrapping of the insulation layer 103 (no shielding layer missing area is detected by ultrasonic scanning). The finished product has the same performance as the conductor shielding layer 102: the volume resistivity at 25°C is 75 Ω·cm, the fluctuation amplitude at -50°C is 12%, the interfacial peeling strength with the insulation layer 103 is 1.7 N / mm, and there is no delamination after freezing at -50°C.

[0034] Preparation of the inner lining layer 105 (thickness 1.2 mm): Halogen-free polyolefin (EVA resin, VA content 18%) is selected as the base material, 18 parts (18% of the total mass of the base material) of magnesium hydroxide (particle size 2 μm, flame retardant grade), 0.3 parts (0.3% of the total mass of the EVA base material) of antioxidant, and 0.5 parts of zinc stearate lubricant are added. The raw materials are added to a high-speed mixer (100°C, rotation speed 800 r / min, mixing time 10 min), and then extruded and covered on the surface of the insulation shielding layer 104 by a single screw extruder (extrusion temperature 120°C-140°C), with a thickness of 1.2 mm (detected by a laser thickness gauge, deviation ±0.05 mm).

[0035] The finished inner lining layer 105 is tested: the adhesion with the subsequent armored layer 106 at -50°C is 22 N / 10 mm (≥20 N / 10 mm); the impact strength is 5.5 kJ / m 2 (≥5 kJ / m 2 ) by a simply supported beam impact testing machine (pre-treated at -50°C for 2 h, impact energy 2.75 J).

[0036] The preparation of the armor layer 106 (tinned copper wire braided layer): Select tinned copper wire (wire diameter 0.15 mm, tinned copper layer thickness ≥5 μm) as the braiding raw material, and use a high-speed braiding machine (braiding head number 16 spindles) for braiding. The braiding pitch is controlled to be 10 mm. The actual coverage density is 96% (≥95%) calculated by the braiding coverage density calculation formula (coverage density = (total number of braided wires × wire diameter) / braiding pitch × 100%). After braiding, the cable is placed in a hot air oven for heat setting treatment, the temperature is 120°C, and the heat preservation time is 60 min to eliminate the braiding stress.

[0037] The finished armor layer 106 is tested: the direct current resistance at 25°C is 1.3 Ω / km (≤1.5 Ω / km), and the resistance fluctuation amplitude is 3% (≤5%); the direct current resistance at -50°C is 1.36 Ω / km, and the fluctuation amplitude is 4.6% (≤5%); after being frozen at -50°C for 24 h, the braiding pitch change is measured, and the looseness rate is 1.2% (≤2%).

[0038] The preparation of the outer sheath 107 (thickness 2.0 mm): Select a thermosetting low-smoke halogen-free polyolefin base material (ethylene-vinyl acetate copolymer and aluminum hydroxide, magnesium hydroxide composite base material, oxygen index ≥32%), add hindered phenolic antioxidant 0.8 parts (0.8% of the total mass of the base material), and nano carbon black (particle size 25 nm) 2.5 parts (2.5% of the total mass of the base material). After the raw materials are uniformly mixed in a double screw extruder (screw temperature 130°C-160°C), they are extruded on the surface of the armor layer 106, and the thickness is controlled to be 2.0 mm (laser thickness gauge detection, deviation ±0.1 mm).

[0039] The finished outer sheath 107 is tested: the tensile strength at -50°C is 12.5 MPa (14.5 MPa at 25°C), and the retention rate is 86.2% (≥85%); the elongation at break is 225% (300% at 25°C), and the retention rate is 75% (≥75%), which meets the requirements.

[0040] Special indicators of medium voltage cable This embodiment is a 6 / 10 kV medium voltage power cable. A metal shielding layer (wrapped with copper tape, reference section 5.0 mm 2 ) is arranged outside the insulation and shielding layer 104. The direct current resistance of the metal shielding layer at 20°C is 1.1 Ω / km (≤1.2 Ω / km). The thickness of the insulation layer 103 is strictly controlled to be 4.0 mm (meeting the requirement of ≥4.0 mm for 6 / 10 kV grade).

[0041] Example 2: Medium section medium voltage cable (8.7 / 15 kV, conductor 101 section area 200 mm 2 ) Conductor 101 preparation: The oxygen-free copper wire (single wire diameter 2.0 mm) is selected, and the regular twisting process (twisting layer number 5 layers, opposite twisting direction between layers) is adopted to prepare the tinned copper conductor 101, and the cross-sectional area is 200 mm 2 The tinning process adopts hot melting tinning, and the tinning layer thickness is 10 μm (average thickness 10.5 μm ≥ 8 μm). The finished conductor 20 ℃ direct current resistance is 0.09 Ω / km.

[0042] Conductor shielding layer 102 and insulation shielding layer 104: The same semi-conductive EPR material and process as in Example 1 are adopted, and the shielding layer thickness is 1.0 mm, which ensures 100% coverage. Test results: 25 ℃ volume resistivity 90 Ω·cm, -50 ℃ fluctuation amplitude 13%, interface peeling strength 1.6 N / mm, no delamination.

[0043] Insulation layer 103 preparation (thickness 5.0 mm): S1: low temperature blending EPR (EP35) 65 parts, XLPE (FB2310) 35 parts, cold resistance modifier (POE8780) 20 parts, maleic anhydride grafted polyethylene compatibilizer 0.5 parts (0.5%), nano-silicon dioxide 5 parts (5%), blending at 85 ℃, stirring rate 800 r / min, dispersion uniformity 96%, agglomerate particle size 190 nm.

[0044] S2: silane crosslinking pre-crosslinking temperature 120 ℃ (3 h), secondary crosslinking temperature 150 ℃ (6 h), crosslinking degree 80%.

[0045] S3: gradient cooling 60 ℃→40 ℃→20 ℃, cooling rate 4 ℃ / min.

[0046] Test results: -50 ℃ dielectric constant fluctuation amplitude 2.8%, volume resistivity fluctuation amplitude 7.8%, which meets the requirements.

[0047] Inner liner layer 105 (thickness 1.8 mm): Halogen-free polyolefin base material, magnesium hydroxide addition amount 20%, extrusion thickness 1.8 mm. Test: -50 ℃ adhesion 25 N / 10 mm, impact strength 6.0 kJ / m 2 .

[0048] Armoring layer 106: Tinned copper wire diameter 0.20 mm, braiding pitch 12 mm, coverage density 97%, heat setting temperature 125 ℃, holding time 45 min. Test: 25 ℃ direct current resistance 1.2 Ω / km, -50 ℃ fluctuation amplitude 4%, loose rate 1.5%.

[0049] Outer sheath 107 (thickness 4.0 mm): Thermoset low smoke halogen-free polyolefin, hindered phenolic antioxidant 1.0%, nano carbon black 3.0% (20 nm length dimension); test: -50 °C tensile strength retention rate 88%, elongation at break retention rate 78%.

[0050] Medium voltage special indicators 8.7 / 15 kV grade, metal shielding reference section 6.0 mm 2 , 20 °C DC resistance 1.0 Ω / km; insulation layer 103 thickness 5.0 mm (comply with ≥5.0 mm requirement).

[0051] Example 3: Large section medium voltage cable (8.7 / 15 kV, conductor 101 cross-sectional area 400 mm 2 ) Conductor 101 preparation: Oxygen-free copper wire monofilament diameter 2.5 mm, regular stranding (6 layers), cross-sectional area 400 mm 2 , hot melt tin plating layer thickness 12 μm, 20 °C DC resistance 0.045 Ω / km.

[0052] Shielding layer: Thickness 1.2 mm, semi-conductive EPR material, same performance as the previous two examples, meet 100% coverage and resistivity requirements.

[0053] Insulation layer 103 (thickness 5.2 mm): Blending temperature 100 °C, stirring rate 500 r / min, compatibilizer 0.3%, nano silica 3%, crosslinking degree 76%, cooling rate 2 °C / min. Test: -50 °C dielectric constant fluctuation 2.5%, volume resistivity fluctuation 7.0%.

[0054] Inner liner layer 105 (thickness 2.2 mm): Magnesium hydroxide addition amount 15%, test: -50 °C adhesion 23 N / 10 mm, impact strength 5.8 kJ / m 2 .

[0055] Armoring layer 106: Tinned copper wire diameter 0.25 mm, braiding pitch 15 mm, coverage density 98%, heat setting temperature 130 °C, holding time 30 min. Test: 25 °C DC resistance 1.1 Ω / km, -50 °C fluctuation amplitude 3.8%, bulkiness 1.0%.

[0056] Outer sheath 107 (thickness 5.2 mm): Hindered phenolic antioxidant 0.5%, nano carbon black 2.0% (30 nm). Test: -50 °C tensile strength retention rate 87%, elongation at break retention rate 76%.

[0057] Medium voltage special indicators Metal shield reference section 8.0 mm 2 , 20℃ DC resistance 0.9 Ω / km; insulation layer 103 thickness 5.2 mm ≥ 5.0 mm.

[0058] The finished cables of the above three embodiments were subjected to comprehensive performance tests, and the test items and results are shown in Table 1 below: Table 1

[0059] The life test used an accelerated aging test: aging at 120℃ for 1000h, and extrapolating the service life at -50℃; the temperature cycle test conditions were: -50℃ for 4h→ warming to +70℃ (1h)→ +70℃ for 4h→ cooling to -50℃ (1h), completing 1 cycle, a total of 1000 times.

[0060] The specific embodiment ensures that the finished cable completely meets all the technical limitations of the claims by precisely controlling the material formula, processing technology and performance parameters of each component, can serve stably for a long time in the polar extreme low temperature environment, and is suitable for various high requirement ship power transmission scenes.

[0061] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A polar hard-weather low smoke, halogen-free polyolefin marine cable characterized in that, The cable comprises, from inside to outside, a conductor (101), a conductor shielding layer (102), an insulation layer (103), an insulation shielding layer (104), an inner liner layer (105), an armor layer (106) and an outer sheath (107), and the working environment temperature range is -50℃~+70℃; The conductor (101) is a tinned copper conductor with a cross-sectional area of 0.5 mm 2 400 mm 2 ; The insulation layer (103) is a composite insulation system of EPR and XLPE, and the dielectric constant fluctuation amplitude is ≤3% and the volume resistivity fluctuation amplitude is ≤8% at -50℃ environment; The conductor shielding layer (102) and the insulation shielding layer (104) are both made of semi-conductive EPR material, and the volume resistivity is ≤100Ω·cm, and the volume resistivity fluctuation amplitude is ≤15% at -50℃, forming 100% coverage to the conductor (101) and the insulation layer (103); The inner lining layer (105) is a composite material of halogen-free polymer and magnesium hydroxide, with a thickness of 1.2mm-2.2mm, an adhesion to the armor layer at -50℃ of ≥20N / 10mm, and an impact strength of ≥5kJ / m 2 ; The armor layer (106) is a tinned copper wire braided layer, and the braided coverage density is ≥95%, and the direct current resistance of the armor layer (106) is ≤1.5Ω / km, and the resistance fluctuation amplitude is ≤5%, and the resistance fluctuation amplitude is ≤5% at -50℃; The outer sheath (107) is a thermosetting low-smoke halogen-free polyolefin, and 0.5%~1.0% hindered phenolic antioxidant and 2%~3% nano carbon black are added, and the thickness is 2.0mm~5.2mm, and the tensile strength retention rate is ≥85% and the elongation at break retention rate is ≥75% at -50℃; The obtained cable has a service life of ≥35 years at -50℃ environment, no crack after 8J impact energy once, no cracking after bending, and the insulation resistance retention rate is ≥70% after 1000 times of temperature cycle of -50℃~+70℃.

2. The polar hardy low smoke, halogen free polyolefin marine cable of claim 1, wherein, The tinned copper layer on the surface of the tinned copper conductor of the conductor (101) has a thickness of ≥8μm.

3. The polar hardy low smoke, halogen free polyolefin marine cable of claim 1, wherein, The conductor shielding layer (102) and the insulation shielding layer (104) form 100% coverage, and the armor layer (106) forms coverage of ≥90%.

4. The polar hardy low smoke, halogen free polyolefin marine cable of claim 1, wherein, The processing technology of the insulation layer (103) comprises the following steps: S1, low temperature blending: Blend the cold-resistant modifier with EPR and XLPE base material at 80~100℃, control the stirring speed at 500~800r / min, add 0.3%~0.5% maleic anhydride grafted polyethylene compatibilizer, and make the cold-resistant modifier dispersion uniformity ≥90%; S2, silane crosslinking: Use two-step silane crosslinking, i.e. pre-crosslinking temperature 110~120℃ and secondary crosslinking temperature 140~150℃, so that the silane crosslinking degree is ≥75%; S3, gradient cooling process: After extrusion molding, use 60℃→40℃→20℃ gradient water temperature cooling, and control the cooling rate at 2~5℃ / min.

5. The polar low temperature low smoke, halogen free, polyolefin marine cable of claim 1, wherein, The inner lining layer (105) is a composite material of halogen-free polyolefin and magnesium hydroxide, the amount of magnesium hydroxide added is 15% to 20% of the total mass of the inner lining layer base material, and the impact strength of the inner lining layer at -50℃ is ≥5kJ / m 2 .

6. The polar hardy low smoke, halogen free polyolefin marine cable of claim 1, wherein, The wire diameter of the armor layer (106) is 0.15mm~0.25mm, and after braiding, it is heat set at 120~130℃ for 30~60min, and the braiding pitch of the armor layer (106) is 10~15mm, and the loose rate of the braided structure is ≤2% at -50℃ after heat setting.

7. The polar low temperature low smoke, halogen free, polyolefin marine cable of claim 1, wherein, The nano carbon black added in the outer sheath (107) has a size of 20~30nm.

8. The polar low temperature low smoke, halogen free, polyolefin marine cable of claim 4, wherein, In S1, 50~100nm nano silica modifier is added, the modifier agglomerate particle size is ≤200nm, and the addition amount is 3%~5% of the total mass of the insulation base material.

9. The polar low temperature low smoke, halogen free, polyolefin marine cable of claim 1, wherein, The conductor shielding layer (102) / insulation shielding layer (104) has a volume resistivity fluctuation amplitude of ≤15% at -50 DEG C, an interface peeling strength of ≥1.5 N / mm with the insulation layer (103), and no interface delamination after being frozen at -50 DEG C for 24 h.

10. The polar low temperature low smoke, halogen free, polyolefin marine cable of claim 1, wherein, The cable is a medium voltage power cable, voltage class 6 / 10 kV or 8.7 / 15 kV, with a metallic shield reference section ≥ 5.0 mm per phase 2 ; a metallic shield DC resistance at 20°C ≤ 1.2 Ω / km, and an insulation layer thickness ≥ 4.0 mm for the 6 / 10 kV class and ≥ 5.0 mm for the 8.7 / 15 kV class.

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