Low-loss insulated waterproof cable

Abstract

The invention belongs to the technical field of cable manufacturing improvement, and particularly relates to a low-loss insulating waterproof cable which structurally comprises an inner conductor, an insulating layer and an outer sheath from inside to outside, and the insulating layer comprises, by weight, 100 parts of polyolefin resin, 5-20 parts of polyolefin elastomer, 5-10 parts of chlorinated paraffin, 1-6 parts of foaming agent, 0.2-0.5 part of heat stabilizer and 0.5-1 part of compatilizer. Compared with the prior art, according to the scheme, chlorinated paraffin is migrated and distributed on the surface layer of the extrusion layer in the extrusion process, so that after the viscosity of the area is reduced, the pressure borne by foaming of the area is reduced, foaming is smoother, the number of overall air holes of the insulating layer is increased, and dielectric loss can be further reduced.

Description

Technical Field

[0001] This invention belongs to the field of cable manufacturing improvement technology, and specifically relates to a low-loss insulated waterproof cable. Background Technology

[0002] The basic structure of a cable, from the inside out, mainly includes an inner conductor, an insulation layer, and a sheath layer. Because air bubbles reduce the bulk density of the insulation material, thereby lowering capacitance, and lower capacitance helps reduce energy loss during transmission, foamed insulation layers with a cellular structure distribution often have a lower attenuation constant compared to traditional solid insulation layers, thus reducing the cable's dielectric loss. Furthermore, a uniform cellular structure reduces inhomogeneity in the dielectric, further reducing losses.

[0003] Currently, many methods for preparing foamed insulation layers involve extrusion foaming. The insulating resin and foaming agent are mixed and added to an extruder. As the mixture melts and plasticizes, it reaches the foaming temperature and is then extruded onto the surface of the cable conductor. Within the extruder, the mixture is subjected to strong pressure from the screw back pressure and die head pressure, preventing effective foaming and pore formation. However, once the material is extruded through the die, it immediately loses external pressure and effectively foams internally. Therefore, in this method, molding and foaming occur simultaneously, which helps to streamline the production process.

[0004] However, in this type of process, when the material is pushed out of the extruder die and the pressure disappears and it begins to bubble, the surface temperature of the material will also drop rapidly due to the influence of the external environment. This causes the viscosity of the surface to rise rapidly and solidify. As a result, the foaming agent in the surface area cannot bubble fully and is suppressed. The final product is a foamed insulation layer with a cell distribution in the inner layer, but the surface is still similar to a solid skin. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a low-loss insulated waterproof cable, which, in its layered structure from the inside out, includes an inner conductor, an insulation layer, and an outer sheath.

[0006] When the cable is a single-core cable, the insulation layer is coaxially wrapped around the inner conductor, and the outer sheath is coaxially wrapped around the insulation layer.

[0007] When the cable is a multi-core cable, several inner conductors, each coaxially covered with an insulating layer, are evenly twisted together and then coaxially covered by an outer sheath.

[0008] The insulation layer, by weight, comprises 100 parts polyolefin resin, 5-20 parts polyolefin elastomer, 5-10 parts chlorinated paraffin, 1-6 parts foaming agent, 0.2-0.5 parts heat stabilizer, and 0.5-1 parts compatibilizer.

[0009] As a preferred embodiment, a water-blocking layer is provided between the insulation layer and the outer sheath, and the water-blocking layer is coaxially wrapped around the insulation layer.

[0010] As a preferred embodiment, several inner conductors, each coaxially covered with an insulating layer, are uniformly twisted together as a whole, and a water-blocking layer is provided between the whole and the outer sheath, with the water-blocking layer coaxially covering the whole.

[0011] As a preferred option, chlorinated paraffin is chlorinated paraffin-42.

[0012] Preferably, the foaming agent includes one or a combination of organic foaming agents, inorganic foaming agents, and physical foaming agents.

[0013] Furthermore, the foaming agent is a polymer foaming microsphere among physical foaming agents. This type of foaming filler uses cross-linked polymers as the shell, which is conducive to more uniform dispersion in the resin base. In addition, the structural stability of the shell itself is conducive to the independence of each pore after foaming, and the size of the foam pores is also relatively uniform.

[0014] As a preferred option, during the cable manufacturing process, polyolefin resin, polyolefin elastomer, chlorinated paraffin, foaming agent, heat stabilizer and compatibilizer are thoroughly mixed and then uniformly extruded onto the surface of the inner conductor to form an insulation layer that is coaxial with the inner conductor.

[0015] As a preferred embodiment, after extruding the insulating layer onto the surface of the inner conductor to form an insulating layer, the resulting insulating layer is subjected to irradiation crosslinking treatment with an irradiation dose of 10–15 Mrad.

[0016] Furthermore, the insulating layer, by weight, also includes 1 to 2 parts of a crosslinking sensitizer, such as trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, etc.

[0017] As a preferred embodiment, the water-blocking tape is evenly wrapped around the surface of the insulation layer to form a water-blocking layer that is coaxial with the insulation layer. After the components of the outer sheath are fully mixed, they are evenly extruded onto the surface of the water-blocking layer to form an outer sheath that is coaxial with the water-blocking layer.

[0018] As a preferred embodiment, the water-blocking tape is evenly wrapped around the surface of a composite material formed by twisting together several inner conductors covered with insulating layers, thereby forming a water-blocking layer coaxially with the composite material. After the components of the outer sheath are fully mixed, they are evenly extruded onto the surface of the water-blocking layer, thereby forming an outer sheath coaxially with the water-blocking layer.

[0019] Furthermore: after the components of the outer sheath are fully mixed at high speed, they are extruded and granulated through an extruder. The resulting granules are then uniformly extruded onto the surface of the water-blocking layer through an extruder, thereby forming an outer sheath that is coaxially arranged with the water-blocking layer.

[0020] Further: After extruding the outer sheath onto the surface of the water-blocking layer to form an outer sheath, the resulting outer sheath is subjected to irradiation crosslinking treatment with an irradiation dose of 10–15 Mrad.

[0021] The beneficial effects of this invention are as follows: the insulation layer of this solution uses polyolefin as the base resin, which is beneficial to ensuring the mechanical properties of the insulation layer; the foaming agent is blended and dispersed in the matrix resin. When the mixture leaves the extruder through the die and is extruded onto the surface of the inner conductor, the foaming agent in the material is freed from the strong pressure restraint inside the extruder and tends to bubble. However, since the solution strength of polyolefin is often high, the surface temperature of the extruded material drops first after leaving the extruder, causing the viscosity of this part of the material to rise rapidly, thereby greatly suppressing the bubbling of the foaming agent in this part of the material.

[0022] Chlorinated paraffin has traditionally been used as an external lubricant in resin extrusion molding. Due to its polar chlorine groups, it has poor compatibility with polyolefins. Therefore, during processing, it tends to migrate outward to the space between the molten material and the inner wall of the extruder barrel to act as a separating film, preventing the material from sticking to the barrel wall. As a result, very little of it is added.

[0023] Based on this, the preferred method is to add chlorinated paraffin-42 to polyolefins for co-extrusion. Compared with some other types of chlorinated paraffins that are more suitable as external lubricants, chlorinated paraffin-42 has a relatively lower chlorine content and lower polarity. In addition, a small amount of compatibilizer is added in this method to intervene, so that when chlorinated paraffin-42 is melt-co-extruded with polyolefins, although there is still a certain tendency to migrate outward, it will not precipitate significantly between the extruded material and the barrel wall. Instead, it will migrate more within the molten material to the outer surface of the extruded material.

[0024] On the other hand, this solution significantly increases the amount of chlorinated paraffin-42, causing more chlorinated paraffin-42 to migrate and disperse in the extrusion layer near the outer surface. Since chlorinated paraffin-42 itself has low viscosity, it also reduces the viscosity of the extrusion layer surface. This allows the extrusion layer to maintain a certain degree of softening even after the surface temperature drops after being extruded from the die, thus ensuring that the foaming agent dispersed in this surface area can still effectively bubble, promoting the degree of foaming in this area.

[0025] In summary, this solution controls the migration of chlorinated paraffin to the surface of the extruded material by selecting the type and polarity of the chlorinated paraffin and by intervening with a compatibilizer, ensuring that it is mainly dispersed in the surface layer of the extruded material. Furthermore, significantly increasing the amount of chlorinated paraffin significantly reduces the overall viscosity of the extruded layer surface, thereby reducing the pressure on foaming in this area and facilitating foaming. The inner layer of the extruded material itself cools relatively slowly, maintaining a softened state for a certain period to accommodate the foaming and pore formation of the foaming agent. Therefore, the improvements in this solution increase the overall degree of foaming and the number of pores in the extruded insulation layer, further reducing cable loss.

[0026] In addition, chlorinated paraffin itself has lubricating and antioxidant properties; and in order to inhibit the degradation of chlorinated paraffin-42 due to high temperature during extrusion, a heat stabilizer is specifically added to this solution. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the low-loss insulated waterproof cable of this application, in which several inner conductors covered with insulation layers are twisted together. In this diagram, 1 is the inner conductor, 2 is the insulation layer, 3 is the water-blocking layer, 4 is the outer sheath, and 5 is the filler. Detailed Implementation

[0028] Example 1

[0029] 100 parts by weight of polyethylene (Yanshan Petrochemical YJ35), 12 parts by weight of thermoplastic polyolefin elastomer (DuPont EVA 750), 8 parts by weight of chlorinated paraffin-42, and 5 parts by weight of expandable microspheres (StarMicrocel) were added. 100 parts by weight of heat stabilizer F-20, 0.6 parts by weight of compatibilizer PE-g-MAH (CMG5904), and 1 part by weight of trimethylolpropane triacrylate were thoroughly mixed in a high-speed mixer and then added to a twin-screw extruder at 90℃~120℃ (zone 1: 90℃, zone 2: 100℃, zone 3: 110℃, zone 4: 115℃, zone 5: 120℃, die 110℃, screw length-to-diameter ratio 30:1, screw speed 30 rpm) to melt and coaxially and uniformly extruded onto the surface of a copper inner conductor. Within 10 minutes, the resulting extruded layer was subjected to irradiation crosslinking treatment with an irradiation dose of 10Mrad. The thickness of the insulation layer obtained after irradiation was approximately 2.2mm. The mechanical properties of the obtained insulation layer were tested according to GB / T 2951 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers". The dielectric constant and dielectric loss tangent of the obtained insulation layer were tested using a KST-221 fully automatic anti-interference dielectric loss tester. (Since the KST-221 fully automatic anti-interference dielectric loss tester is more suitable for testing planar samples, after extruding the planar insulation board through a flat die with a width of 1.2 mm (which is consistent with the discharge width of the annular die used for extruding the insulation layer in this embodiment) according to the composition and process parameters of this embodiment, the board was subjected to 10Mrad irradiation crosslinking treatment within 10 minutes, and then the required samples were cut from the insulation board and tested in the KST-221 fully automatic anti-interference dielectric loss tester. The same applies below.) Three samples were taken for testing and the average value was calculated. The results are shown in Table 1.

[0030] The water-blocking tape is uniformly wrapped around the surface of the insulating layer obtained in this embodiment to form a water-blocking layer that is coaxial with the insulating layer.

[0031] 100 parts by weight of polypropylene (Yanshan Petrochemical 1396D), 15 parts by weight of thermoplastic polyolefin elastomer (POE8150), 2 parts by weight of zinc stearate, 0.5 parts by weight of antioxidant 736, and 1 part by weight of trimethylolpropane triacrylate were thoroughly mixed in a high-speed mixer and then added to a twin-screw extruder at 160°C–200°C (zone 1: 160°C, zone 2: 175°C, zone 3: 185°C, zone 4: 195°C, zone 5: 200°C, die 190°C, screw length-to-diameter ratio 25:1, screw speed 90 rpm) to melt and coaxially and uniformly extrude onto the surface of the water-blocking layer obtained in this embodiment. Within 10 minutes, the resulting extruded layer was subjected to irradiation crosslinking treatment with an irradiation dose of 10 Mrad to obtain the outer sheath.

[0032] Example 2

[0033] 100 parts by weight of polyethylene (Yanshan Petrochemical YJ35), 10 parts by weight of POE 8150, 10 parts by weight of chlorinated paraffin-42, and 6 parts by weight of expandable microspheres (StarMicrocel) were mixed. 100 parts by weight of heat stabilizer F-20, 1 part by weight of compatibilizer PE-g-MAH (CMG5904), and 1.3 parts by weight of trimethylolpropane triacrylate were thoroughly mixed in a high-speed mixer and then added to a twin-screw extruder at 90℃~120℃ (zone 1: 90℃, zone 2: 100℃, zone 3: 110℃, zone 4: 115℃, zone 5: 120℃, die 110℃, screw length-to-diameter ratio 30:1, screw speed 30 rpm). The mixture was melted and coaxially and uniformly extruded onto the surface of a copper inner conductor. Within 10 minutes, the resulting extruded layer was subjected to irradiation crosslinking treatment with an irradiation dose of 10 Mrad. The thickness of the resulting insulation layer after irradiation was approximately 2.4 mm (according to GB / T). The mechanical properties of the obtained insulation layer were tested according to 2951 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers"; the dielectric constant and dielectric loss tangent of the obtained insulation layer were tested using a KST-221 fully automatic anti-interference dielectric loss tester. Three samples were taken for each test, and the average value was calculated. The results are shown in Table 1.

[0034] The water-blocking tape is uniformly wrapped around the surface of the insulating layer obtained in this embodiment to form a water-blocking layer that is coaxial with the insulating layer.

[0035] 100 parts by weight of polypropylene (Yanshan Petrochemical 1396D), 15 parts by weight of thermoplastic polyolefin elastomer (POE8150), 2 parts by weight of zinc stearate, 0.5 parts by weight of antioxidant 736, and 1 part by weight of trimethylolpropane triacrylate were thoroughly mixed in a high-speed mixer and then added to a twin-screw extruder at 160°C–200°C (zone 1: 160°C, zone 2: 175°C, zone 3: 185°C, zone 4: 195°C, zone 5: 200°C, die 190°C, screw length-to-diameter ratio 25:1, screw speed 90 rpm) to melt and coaxially and uniformly extrude onto the surface of the water-blocking layer obtained in this embodiment. Within 10 minutes, the resulting extruded layer was subjected to irradiation crosslinking treatment with an irradiation dose of 10 Mrad to obtain the outer sheath.

[0036] Example 3

[0037] 100 parts by weight of polyethylene (Yanshan Petrochemical YJ35), 6 parts by weight of POE 8480, 6 parts by weight of chlorinated paraffin-42, and 3 parts by weight of expandable microspheres (StarMicrocel) were mixed. 100 parts by weight of heat stabilizer F-20, 0.5 parts by weight of compatibilizer PE-g-MAH (CMG5904), and 1 part by weight of trimethylolpropane triacrylate are thoroughly mixed in a high-speed mixer. This mixture is then added to a twin-screw extruder and melted at 90℃~120℃ (zone 1: 90℃, zone 2: 100℃, zone 3: 110℃, zone 4: 115℃, zone 5: 120℃, die temperature 110℃, screw length-to-diameter ratio 30:1, screw speed 30 rpm). The melted mixture is then coaxially and uniformly extruded onto the surface of a copper inner conductor. Within 10 minutes, the resulting extruded layer is subjected to irradiation crosslinking treatment with an irradiation dose of 10 Mrad. The resulting insulation layer thickness after irradiation is approximately 1.9 mm (according to GB / T). The mechanical properties of the obtained insulation layer were tested according to 2951 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers"; the dielectric constant and dielectric loss tangent of the obtained insulation layer were tested using a KST-221 fully automatic anti-interference dielectric loss tester. Three samples were taken for each test, and the average value was calculated. The results are shown in Table 1.

[0038] The inner conductors covered with insulating layers obtained in the above-described seven basic embodiments are uniformly twisted together to form a whole, and then the water-blocking tape is uniformly wrapped around the surface of the whole to form a water-blocking layer that is coaxial with the whole.

[0039] 100 parts by weight of polypropylene (Yanshan Petrochemical 1396D), 15 parts by weight of thermoplastic polyolefin elastomer (POE8150), 2 parts by weight of zinc stearate, 0.5 parts by weight of antioxidant 736, and 1 part by weight of trimethylolpropane triacrylate were thoroughly mixed in a high-speed mixer and then added to a twin-screw extruder at 160°C–200°C (zone 1: 160°C, zone 2: 175°C, zone 3: 185°C, zone 4: 195°C, zone 5: 200°C, die 190°C, screw length-to-diameter ratio 25:1, screw speed 90 rpm) to melt and coaxially and uniformly extrude onto the surface of the water-blocking layer obtained in this embodiment. Within 10 minutes, the resulting extruded layer was subjected to irradiation crosslinking treatment with an irradiation dose of 10 Mrad to obtain the outer sheath.

[0040] Comparative Example 1

[0041] Chlorinated paraffin-42 was not added to the insulating material; all other components and operations were the same as in Example 1.

[0042] 100 parts by weight of polyethylene (Yanshan Petrochemical YJ35), 12 parts by weight of thermoplastic polyolefin elastomer (DuPont EVA 750), and 5 parts by weight of expandable microspheres (StarMicrocel) were mixed. 100 parts by weight of heat stabilizer F-20, 0.6 parts by weight of compatibilizer PE-g-MAH (CMG5904), and 1 part by weight of trimethylolpropane triacrylate are thoroughly mixed in a high-speed mixer and then added to a twin-screw extruder at 90℃~120℃ (zone 1: 90℃, zone 2: 100℃, zone 3: 110℃, zone 4: 115℃, zone 5: 120℃, die temperature 110℃, screw length-to-diameter ratio 30:1, screw speed 30 rpm). The mixture is then melted and coaxially and uniformly extruded onto the surface of a copper inner conductor. Within 10 minutes, the resulting extruded layer is subjected to irradiation crosslinking treatment with an irradiation dose of 10 Mrad. The resulting insulation layer thickness after irradiation is approximately 1.7 mm (according to GB / T). The mechanical properties of the obtained insulation layer were tested according to 2951 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers"; the dielectric constant and dielectric loss tangent of the obtained insulation layer were tested using a KST-221 fully automatic anti-interference dielectric loss tester. Three samples were taken for each test and the average value was calculated. The results are shown in Table 1.

[0043] Comparative Example 2

[0044] Replace the "chlorinated paraffin-42" in the insulating layer material with an equal amount of ordinary "paraffin," while keeping all other components and operations the same as in Example 1:

[0045] 100 parts by weight of polyethylene (Yanshan Petrochemical YJ35), 12 parts by weight of thermoplastic polyolefin elastomer (DuPont EVA 750), 8 parts by weight of paraffin (average molecular weight of about 600 g / mol, similar to "chlorinated paraffin-42" in Example 1), and 5 parts by weight of expandable microspheres (StarMicrocel) were mixed. 100 parts by weight of heat stabilizer F-20, 0.6 parts by weight of compatibilizer PE-g-MAH (CMG5904), and 1 part by weight of trimethylolpropane triacrylate are thoroughly mixed in a high-speed mixer and then added to a twin-screw extruder at 90℃~120℃ (zone 1: 90℃, zone 2: 100℃, zone 3: 110℃, zone 4: 115℃, zone 5: 120℃, die temperature 110℃, screw length-to-diameter ratio 30:1, screw speed 30 rpm). The mixture is then melted and coaxially and uniformly extruded onto the surface of a copper inner conductor. Within 10 minutes, the resulting extruded layer is subjected to irradiation crosslinking treatment with an irradiation dose of 10 Mrad. The thickness of the resulting insulation layer after irradiation is approximately 2.0 mm (according to GB / T). The mechanical properties of the obtained insulation layer were tested according to 2951 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers"; the dielectric constant and dielectric loss tangent of the obtained insulation layer were tested using a KST-221 fully automatic anti-interference dielectric loss tester. Three samples were taken for each test and the average value was calculated. The results are shown in Table 1.

[0046] Table 1

[0047]

[0048] Comparative Example 1 corresponds to a conventional extrusion foaming scheme. Compared to Comparative Example 1, Example 1, representing this scheme, incorporates chlorinated paraffin. Through the migration and distribution of chlorinated paraffin during the extrusion process, the overall viscosity of the extruded layer surface decreases. This reduces the pressure on this area during foaming, making foaming smoother and increasing the overall foaming degree of the insulation layer. Therefore, the insulation layer density obtained in Example 1 is significantly lower than that of Comparative Example 1, where foaming the extruded layer surface is more difficult, and it also exhibits lower dielectric loss compared to Comparative Example 1.

[0049] In Comparative Example 2, ordinary paraffin wax was added, which does not migrate and concentrate to the surface of the extruded layer during processing like chlorinated paraffin wax. Therefore, compared to Example 1, the amount of paraffin wax ultimately dispersed on the surface of the extruded layer is significantly insufficient, and the foaming difficulty of the surface layer after extrusion is not effectively reduced. Although the density of the extruded insulating layer is lower than that of Example 1 after the introduction of ordinary paraffin wax in Comparative Example 2, the measured dielectric loss is still higher than that of Example 1. This is likely due to the significant uneven foaming between the inner and outer layers; this is also illustrated by the comparison of mechanical strength between Comparative Example 2 and Example 1.

Claims

1. A low-loss insulated waterproof cable, characterized in that: The cable, in terms of its layer structure, includes an inner conductor, an insulation layer, and an outer sheath from the inside out. The insulation layer, by weight, comprises 100 parts of polyolefin resin, 5 to 20 parts of polyolefin elastomer, 5 to 10 parts of chlorinated paraffin, 1 to 6 parts of foaming agent, 0.2 to 0.5 parts of heat stabilizer, and 0.5 to 1 part of compatibilizer.

2. The low-loss insulated waterproof cable as described in claim 1, characterized in that: The chlorinated paraffin is chlorinated paraffin-42.

3. The low-loss insulated waterproof cable as described in claim 1, characterized in that: The foaming agent includes one or a combination of several of the following: organic foaming agents, inorganic foaming agents, and physical foaming agents.

4. The low-loss insulated waterproof cable as described in claim 3, characterized in that: The foaming agent is a polymer foamed microsphere.

5. The low-loss insulated waterproof cable as described in claim 1, characterized in that: During the manufacturing process of the cable, the polyolefin resin, the polyolefin elastomer, the chlorinated paraffin, the foaming agent, the heat stabilizer, and the compatibilizer are thoroughly mixed and then uniformly extruded onto the surface of the inner conductor to form the insulation layer that is coaxially arranged with the inner conductor.

6. The low-loss insulated waterproof cable as described in claim 5, characterized in that: After the insulating layer is formed by extruding it onto the surface of the inner conductor, the insulating layer is subjected to irradiation crosslinking treatment.

7. The low-loss insulated waterproof cable as described in claim 6, characterized in that: The insulating layer, by weight, also includes 1 to 2 parts of a crosslinking sensitizer, wherein the crosslinking sensitizer is one or a combination of several of the following: trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, and 1,6-hexanediol diacrylate.

8. The low-loss insulated waterproof cable as described in claim 1, characterized in that: A water-blocking layer is provided between the insulation layer and the outer sheath.

9. The low-loss insulated waterproof cable as described in claim 8, characterized in that: During the manufacturing process of the cable, a water-blocking tape is evenly wrapped around the surface of the insulation layer to form a water-blocking layer coaxially with the insulation layer. After the components of the outer sheath are fully mixed, they are evenly extruded onto the surface of the water-blocking layer to form an outer sheath coaxially with the water-blocking layer.

10. The low-loss insulated waterproof cable as described in claim 9, characterized in that: After the outer sheath is formed by extruding it onto the surface of the water-blocking layer, the outer sheath is subjected to irradiation crosslinking treatment.

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