Water-blocking fireproof cable and preparation method thereof

Abstract

The invention discloses a water-blocking fireproof cable and a preparation method thereof, and relates to the technical field of cables. The cable sequentially comprises a conductor, a nano-montmorillonite modified polyethylene waterproof layer, a magnesium hydroxide modified epoxy resin insulating layer and a basalt fiber modified ceramic silicone rubber fireproof sheath from inside to outside, wherein the nano-montmorillonite modified polyethylene, the magnesium hydroxide modified epoxy resin and the basalt fiber modified ceramic silicone rubber are all prepared by a specific process, so that the water blocking performance, the fireproof performance and the mechanical strength of the cable are remarkably improved. Through targeted modification design of the three materials, the problems that an existing cable is difficult to consider both water resistance and fire resistance and poor in mechanical stability at high temperature are solved, the preparation process is simple and controllable, and the cable is suitable for large-scale production and has good application prospects.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to a water-blocking fireproof cable and its preparation method. Background Technology

[0002] Cables are widely used in power transmission, communications, and other fields. In special environments such as underground tunnels, high-rise buildings, and ships, extremely high requirements are placed on the water-blocking and fire-resistant performance of cables. Existing water-blocking cables mostly use wrapping water-blocking tape or extrusion of ordinary polyethylene water-blocking layers, which have limited water-blocking effect and are prone to moisture penetration after long-term use. Fire-resistant cables often use fire-resistant materials such as ceramicized silicone rubber and mica tape, but these materials experience a significant decrease in mechanical strength when burning at high temperatures, are prone to breakage, and have poor compatibility with water-blocking layers, making it difficult to simultaneously meet the high-performance requirements of water blocking and fire resistance.

[0003] To address the aforementioned issues, this invention specifically modifies three core materials—polyethylene, epoxy resin, and ceramicized silicone rubber—to improve the performance of the water-blocking layer, insulation layer, and fire-resistant sheath, while simultaneously optimizing the structural compatibility of each layer, thus producing a cable with excellent water-blocking, fire-resistant properties, and good mechanical stability. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a water-blocking fireproof cable and its preparation method, which is particularly outstanding in terms of water blocking, fire resistance and high-temperature mechanical stability. The preparation process is simple and controllable, suitable for large-scale production, and can be widely used in scenarios with stringent requirements for cable performance, such as underground tunnels, high-rise buildings, and ships. It has important practical value and market prospects.

[0005] Technical solution: A water-blocking fireproof cable, comprising, from the inside out, a conductor, a water-blocking layer, an insulation layer, and a fireproof sheath, with the following thickness percentages: conductor 30%-35%, water-blocking layer 10%-15%, insulation layer 20%-25%, and fireproof sheath 25%-30%;

[0006] Preferably, the conductor is a copper conductor with a single wire diameter of 0.4 mm and a total cross-sectional area of ​​10 mm² (the actual total cross-sectional area after twisting 79 single wires is approximately 9.92 mm²), and is composed of 79 copper wires twisted together with a twisting pitch of 35 mm.

[0007] Preferably, the water-blocking layer is nano-montmorillonite modified polyethylene, and its raw materials include, by weight: 100 parts polyethylene, 5 parts nano-montmorillonite, 2 parts silane coupling agent KH550, and 10101 parts antioxidant.

[0008] Preferably, the insulating layer is a magnesium hydroxide-modified epoxy resin, the raw materials for which, by weight, include: 100 parts of epoxy resin E-51, 30 parts of modified magnesium hydroxide, 8 parts of curing agent diethylenetriamine, and 1 part of accelerator 2-methylimidazole.

[0009] Preferably, the fireproof sheath is made of basalt fiber modified ceramicized silicone rubber, and its raw materials include, by weight: 100 parts ceramicized silicone rubber, 8 parts chopped basalt fiber, 2 parts vulcanizing agent dicumyl peroxide, and 1 part co-vulcanizing agent triallyl isocyanurate.

[0010] Preferably, the preparation method of the nano-montmorillonite modified polyethylene is as follows: nano-montmorillonite is added to deionized water at 80°C, stirred and dispersed for 30 minutes to obtain a nano-montmorillonite suspension with a mass concentration of 5%, silane coupling agent KH550 is added, and the mixture is stirred and reacted at a constant temperature for 2 hours. After filtration, the filter cake is dried in an oven at 110°C for 4 hours to obtain modified nano-montmorillonite; polyethylene, modified nano-montmorillonite and antioxidant 1010 are mixed and fed into a twin-screw extruder, and melt-blended and extruded at 160°C and a screw speed of 300 r / min. After cooling, nano-montmorillonite modified polyethylene is obtained.

[0011] Preferably, the preparation method of the magnesium hydroxide modified epoxy resin is as follows: magnesium hydroxide is placed in a plasma treatment instrument and surface treated under the conditions of discharge power of 300W and treatment time of 15 minutes to obtain modified magnesium hydroxide; epoxy resin E-51 is heated to 60°C, modified magnesium hydroxide is added, and the mixture is stirred and dispersed for 40 minutes; then, curing agent diethylenetriamine and accelerator 2-methylimidazole are added in sequence, and the mixture is stirred for another 20 minutes to obtain magnesium hydroxide modified epoxy resin.

[0012] Preferably, the preparation method of the basalt fiber modified ceramicized silicone rubber is as follows: short chopped basalt fibers are placed in a 10% hydrochloric acid solution and soaked at 80°C for 2 hours. After filtration, they are washed with deionized water until neutral and dried in an oven at 120°C for 3 hours to obtain modified basalt fibers. The ceramicized silicone rubber, modified basalt fibers, vulcanizing agent dicumyl peroxide, and co-vulcanizing agent triallyl isocyanurate are mixed and kneaded in a two-roll mill at 120°C and a roll gap of 1.5 mm for 20 minutes to obtain basalt fiber modified ceramicized silicone rubber.

[0013] A method for preparing a water-blocking fire-resistant cable includes the following steps:

[0014] S1. Preparation of nano-montmorillonite modified polyethylene water-blocking layer material, magnesium hydroxide modified epoxy resin insulating layer material and basalt fiber modified ceramicized silicone rubber fireproof sheath material, the specific preparation method is as described in claims 1-4;

[0015] S2. Copper wires are stranded to prepare a conductor. Nano-montmorillonite modified polyethylene is extruded onto the outer surface of the conductor at 160°C and 15MPa extrusion pressure using an extruder to form a water-blocking layer with a thickness of 1.2mm.

[0016] S3. Apply magnesium hydroxide-modified epoxy resin to the outer surface of the water-blocking layer using a casting process, and cure it at 80°C for 3 hours to form an insulating layer with a thickness of 2.0 mm.

[0017] S4. Basalt fiber modified ceramicized silicone rubber is extruded onto the outer surface of the insulation layer at 150°C and 12MPa using an extruder. Then, it is vulcanized at 170°C for 40 minutes to form a 5.0mm thick fireproof sheath, resulting in a water-blocking fireproof cable.

[0018] In step S2, the screw length-to-diameter ratio of the extruder is 25:1, and the die head temperature is 165℃; in step 4, the screw length-to-diameter ratio of the extruder is 20:1, and the die head temperature is 155℃.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The nano-montmorillonite-modified polyethylene of the water-blocking layer forms a dense barrier structure, which not only blocks external water penetration but also reduces the erosion of the insulation layer by water (water will reduce the insulation performance of epoxy resin); at the same time, the magnesium hydroxide-modified epoxy resin of the insulation layer forms a dense cross-linked structure after curing, which further blocks the diffusion of a small amount of water that has penetrated to the conductor, forming a "double water-blocking barrier".

[0021] (2) The magnesium hydroxide in the insulation layer decomposes endothermally at high temperatures, and the released moisture can reduce the temperature of the combustion zone. At the same time, the resulting magnesium oxide inorganic layer forms the first heat insulation barrier. The basalt fiber reinforced ceramicized silicone rubber of the fireproof sheath forms the second ceramicized heat insulation layer at high temperatures. The two barriers work together to block heat transfer and slow down the temperature rise of the conductor. In addition, the epoxy resin cross-linking structure of the insulation layer can inhibit the spread of flames, forming a dual synergy of "flame retardant + heat insulation" with the ceramicized fireproof function of the sheath.

[0022] (3) The basalt fiber reinforced structure of the fireproof sheath enhances the overall mechanical strength of the cable, providing mechanical protection for the internal water-blocking layer and insulation layer, and preventing interlayer cracking caused by stretching and bending during laying; the flexible polyethylene matrix of the water-blocking layer can buffer external stress and reduce the impact on the rigid insulation layer; the epoxy resin of the insulation layer forms a tight bond with the water-blocking layer and sheath through the casting process, improving the interlayer peel strength. The three work together to form a "rigid-flexible-reinforced" structural system, taking into account both mechanical performance and structural stability.

[0023] (4) The antioxidant 1010 in the water-blocking layer works synergistically with nano-montmorillonite to delay the oxidative aging of polyethylene and extend its water-blocking life; the accelerator 2-methylimidazole in the insulation layer optimizes the curing degree of epoxy resin, reduces internal defects, and improves the long-term stability of insulation performance; the vulcanizing agent triallyl isocyanurate in the fireproof sheath enhances the vulcanization crosslinking density of silicone rubber and works synergistically with basalt fiber to resist high-temperature aging. The anti-aging components and modified materials in each layer work synergistically to ensure that the water-blocking, fireproofing, and insulation performance of the cable does not degrade during long-term use (design life of 20 years). Attached Figure Description

[0024] Figure 1 This is a graph showing the performance test results of the embodiment and the comparative example. Detailed Implementation

[0026] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Example 1

[0028] The preparation method is as follows:

[0029] Preparation of water-blocking layer material: 50nm nano-montmorillonite particles were added to deionized water at 80℃ and stirred for 30 minutes to prepare a 5% mass concentration suspension. 2 parts of silane coupling agent KH550 were added, and the mixture was stirred at 80℃ for 2 hours. After filtration, the filter cake was dried in an oven at 110℃ for 4 hours to obtain modified nano-montmorillonite. 100 parts of polyethylene, 5 parts of modified nano-montmorillonite and 1 part of antioxidant 1010 were mixed and fed into a twin-screw extruder. The mixture was melt-blended and extruded at 160℃ and 300r / min. After cooling, nano-montmorillonite modified polyethylene was obtained.

[0030] Preparation of insulating layer material: Magnesium hydroxide with a particle size of 1 μm was placed in a plasma treatment instrument and treated at 300W power for 15 minutes to obtain modified magnesium hydroxide; 100 parts of epoxy resin E-51 were heated to 60℃, 30 parts of modified magnesium hydroxide were added, and the mixture was stirred and dispersed for 40 minutes. Then, 8 parts of diethylenetriamine and 1 part of 2-methylimidazole were added in sequence, and the mixture was stirred for another 20 minutes to obtain magnesium hydroxide modified epoxy resin.

[0031] Preparation of fireproof sheath material: Short basalt fibers with a length of 3 mm and a diameter of 13 μm were immersed in a 10% hydrochloric acid solution and soaked at 80°C for 2 hours. After filtration, they were washed with deionized water until neutral and dried in an oven at 120°C for 3 hours to obtain modified basalt fibers. 100 parts of ceramicized silicone rubber, 8 parts of modified basalt fibers, 2 parts of dicumyl peroxide and 1 part of triallyl isocyanurate were mixed and kneaded in a two-roll mill at 120°C and a roll gap of 1.5 mm for 20 minutes to obtain basalt fiber modified ceramicized silicone rubber.

[0032] Cable forming: Copper wires are stranded to form a conductor. Nano-montmorillonite modified polyethylene is extruded onto the conductor at 160℃ and 15MPa using an extruder (screw length-to-diameter ratio 25:1, die head temperature 165℃) to form a water-blocking layer. Magnesium hydroxide modified epoxy resin is poured onto the water-blocking layer and cured at 80℃ for 3 hours to form an insulation layer. Basalt fiber modified ceramicized silicone rubber is extruded onto the insulation layer at 150℃ and 12MPa using an extruder (screw length-to-diameter ratio 20:1, die head temperature 155℃) to form a fireproof sheath at 170℃ for 40 minutes, resulting in the finished cable.

[0033] Example 2

[0034] A water-blocking fireproof cable has the same structure as Example 1, except that: the amount of modified nano-montmorillonite added to the water-blocking layer is 6 parts, the amount of modified magnesium hydroxide added to the insulation layer is 35 parts, and the amount of modified basalt fiber added to the fireproof sheath is 10 parts; the preparation process parameters remain unchanged.

[0035] Example 3

[0036] A water-blocking fireproof cable has the same structure as Example 1, except that: the amount of modified nano-montmorillonite added to the water-blocking layer is 4 parts, the amount of modified magnesium hydroxide added to the insulation layer is 25 parts, and the amount of modified basalt fiber added to the fireproof sheath is 6 parts; the preparation process parameters remain unchanged.

[0037] Comparative Example 1

[0038] A cable with the same structure as in Example 1, except that: the water-blocking layer is made of unmodified polyethylene, the insulation layer is made of unmodified epoxy resin E-51, and the fireproof sheath is made of unmodified ceramicized silicone rubber; no material modification step is performed in the preparation process, and the remaining parameters are the same as in Example 1.

[0039] Comparative Example 2

[0040] A cable with the same structure as Example 1, except that: only the water-blocking layer is made of nano-montmorillonite modified polyethylene, the insulation layer is made of unmodified epoxy resin E-51, and the fireproof sheath is made of unmodified ceramicized silicone rubber; the manufacturing process only modifies the water-blocking layer material, and the remaining steps are the same as in Example 1.

[0041] Comparative Example 3

[0042] A cable with the same structure as in Example 1, except that: the water-blocking layer is unmodified polyethylene, the insulation layer is magnesium hydroxide-modified epoxy resin, and the fireproof sheath is unmodified ceramicized silicone rubber; the preparation process only modifies the insulation material, and the remaining steps are the same as in Example 1.

[0043] Comparative Example 4

[0044] A cable with the same structure as in Example 1, except that: the water-blocking layer is unmodified polyethylene, the insulation layer is unmodified epoxy resin E-51, and the fireproof sheath is basalt fiber modified ceramicized silicone rubber; the preparation process only modifies the fireproof sheath material, and the remaining steps are the same as in Example 1.

[0045] Test methods

[0046] Water resistance performance: The water penetration was measured by immersion test at 1.0 MPa water pressure for 24 hours in accordance with GB / T18424-2019.

[0047] Fire resistance performance: Conduct a fire resistance test at 950℃ for 180 minutes according to GB / T19216.21-2003 and observe whether it can continue or break.

[0048] Mechanical properties: The tensile strength and elongation at break of the cable sheath at room temperature were tested according to GB / T1040.1-2018; the residual tensile strength of the sheath after burning at 950℃ for 1 hour was tested according to GB / T1040.1-2018.

[0049] Insulation performance: The breakdown field strength of the insulation layer is tested according to GB / T1408.1-2016.

[0050] The test data shows that the cables of Examples 1-3 are significantly better than those of Comparative Examples 1-4 in all aspects of performance:

[0051] In terms of water-blocking performance, the water permeation of Examples 1-3 was only 4-6 mg, which is much lower than 45 mg in Comparative Example 1 and 22-42 mg in the single-modified comparative example. This indicates that the nano-montmorillonite modified polyethylene water-blocking layer can effectively block water permeation, and its synergistic effect with other modified layers further enhances the water-blocking effect.

[0052] Regarding fire resistance, Examples 1-3 maintained conductivity during a 180-minute fire resistance test at 950℃, while all comparative examples failed. This indicates that the high-temperature fire resistance stability of the cable was significantly improved after synergistic modification of the three materials, enabling it to maintain circuit conductivity under prolonged high-temperature conditions. Comparative Example 3 (insulation layer modification only) had a fire resistance time of only 80 minutes, and Comparative Example 4 (sheath modification only) had a fire resistance time of 120 minutes, while Examples 1-3 all achieved a fire resistance time of 180 minutes. This demonstrates that the synergistic flame-retardant effect of the insulation layer and sheath significantly extended the fire resistance time.

[0053] In terms of mechanical properties, the room temperature tensile strength of Examples 1-3 reached 17.8-19.2 MPa, the elongation at break reached 310-330%, and the residual tensile strength after combustion reached 7.9-8.5 MPa, significantly higher than the comparative examples. This indicates that the modified material and the matching of each layer structure are improved, enabling the cable to maintain good mechanical stability after combustion at both room temperature and high temperature. Furthermore, the interlayer peel strength of Example 1 reached 1.8 N / mm, an increase of 125% compared to Comparative Example 1 (0.8 N / mm). After repeated bending tests (bending radius 10 times the cable diameter, bending 100 times), the cables of Examples 1-3 showed no interlayer delamination or water leakage, while Comparative Examples 1-4 all showed varying degrees of interlayer cracking, indicating that the overall structure synergistically ensured the cable's laying adaptability and long-term reliability.

[0054] Regarding insulation performance, the breakdown field strength of Examples 1-3 reached 27-29 kV / mm, higher than the 18-22 kV / mm of the comparative examples, indicating that the magnesium hydroxide-modified epoxy resin insulation layer can effectively improve the insulation withstand voltage performance of the cable. Furthermore, in Comparative Example 2 (water-blocking layer modified only), after 24 hours under 1.0 MPa water pressure, the insulation layer breakdown field strength dropped to 16 kV / mm; while in Example 1, under the same conditions, the breakdown field strength remained at 26 kV / mm, demonstrating that the synergistic effect of the water-blocking layer and the insulation layer effectively protected the stability of the insulation performance.

[0055] In Example 2, due to the slightly higher amount of modified filler added, the various properties were slightly better than those in Examples 1 and 3. This indicates that increasing the amount of modified filler within a reasonable range can further improve the cable performance. However, excessive addition may lead to a decrease in the material's processing performance, and it needs to be controlled within an appropriate range.

[0056] After 1000 hours of thermal aging test (120℃), the moisture permeation of Example 1 was still ≤8mg, the breakdown field strength was ≥25kV / mm, the fire resistance time was ≥150 minutes, and the degradation rate of each performance was ≤10%; while the moisture permeation of Comparative Example 1 increased to 60mg, the breakdown field strength decreased to 12kV / mm, the fire resistance time was only 40 minutes, and the degradation rate exceeded 50%, which fully demonstrates the role of component synergy in ensuring long-term performance.

[0057] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A water-blocking fireproof cable, characterized in that, From the inside out, it consists of a conductor, a water-blocking layer, an insulation layer, and a fireproof sheath, with the following thickness percentages: conductor 30%-35%, water-blocking layer 10%-15%, insulation layer 20%-25%, and fireproof sheath 25%-30%. The conductor is a copper conductor with a single wire diameter of 0.4 mm and a total cross-sectional area of ​​10 mm². It is made of 79 copper wires twisted together with a twist pitch of 35 mm. The water-blocking layer is made of nano-montmorillonite modified polyethylene, and its raw materials include, by weight: 100 parts polyethylene, 5 parts nano-montmorillonite, 2 parts silane coupling agent KH550, and 10101 parts antioxidant. The insulating layer is a magnesium hydroxide-modified epoxy resin, and its raw materials, by weight, include: 100 parts of epoxy resin E-51, 30 parts of modified magnesium hydroxide, 8 parts of curing agent diethylenetriamine, and 1 part of accelerator 2-methylimidazole. The fireproof sheath is made of basalt fiber modified ceramicized silicone rubber, and its raw materials, by weight, include: 100 parts ceramicized silicone rubber, 8 parts chopped basalt fiber, 2 parts vulcanizing agent dicumyl peroxide, and 1 part co-vulcanizing agent triallyl isocyanurate.

2. The water-blocking fireproof cable according to claim 1, characterized in that, The preparation method of the nano-montmorillonite modified polyethylene is as follows: nano-montmorillonite is added to deionized water at 80°C and stirred and dispersed for 30 minutes to obtain a nano-montmorillonite suspension with a mass concentration of 5%. Silane coupling agent KH550 is added, and the mixture is stirred and reacted at a constant temperature for 2 hours. After filtration, the filter cake is dried in an oven at 110°C for 4 hours to obtain modified nano-montmorillonite. Polyethylene, modified nano-montmorillonite, and antioxidant 1010 are mixed and fed into a twin-screw extruder. The mixture is melt-blended and extruded at 160°C and a screw speed of 300 r / min. After cooling, nano-montmorillonite modified polyethylene is obtained.

3. The water-blocking fireproof cable according to claim 1, characterized in that, The preparation method of the magnesium hydroxide modified epoxy resin is as follows: magnesium hydroxide is placed in a plasma treatment instrument and surface treated under the conditions of discharge power of 300W and treatment time of 15 minutes to obtain modified magnesium hydroxide; epoxy resin E-51 is heated to 60°C, modified magnesium hydroxide is added, and the mixture is stirred and dispersed for 40 minutes; then, curing agent diethylenetriamine and accelerator 2-methylimidazole are added in sequence, and the mixture is stirred for another 20 minutes to obtain magnesium hydroxide modified epoxy resin.

4. The water-blocking fireproof cable according to claim 1, characterized in that, The preparation method of the basalt fiber modified ceramicized silicone rubber is as follows: short basalt fibers are placed in a 10% hydrochloric acid solution and soaked at 80°C for 2 hours. After filtration, they are washed with deionized water until neutral and dried in an oven at 120°C for 3 hours to obtain modified basalt fibers. The ceramicized silicone rubber, modified basalt fibers, vulcanizing agent dicumyl peroxide and co-vulcanizing agent triallyl isocyanurate are mixed and kneaded in a two-roll mill at 120°C and a roll gap of 1.5 mm for 20 minutes to obtain basalt fiber modified ceramicized silicone rubber.

5. A method for preparing a water-blocking fire-resistant cable as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of nano-montmorillonite modified polyethylene water-blocking layer material, magnesium hydroxide modified epoxy resin insulating layer material and basalt fiber modified ceramicized silicone rubber fireproof sheath material, the specific preparation method is as described in claims 1-4; S2. Copper wires are stranded to prepare a conductor. Nano-montmorillonite modified polyethylene is extruded onto the outer surface of the conductor at 160°C and 15MPa extrusion pressure using an extruder to form a water-blocking layer with a thickness of 1.2mm. S3. Apply magnesium hydroxide-modified epoxy resin to the outer surface of the water-blocking layer using a casting process, and cure it at 80°C for 3 hours to form an insulating layer with a thickness of 2.0 mm. S4. Basalt fiber modified ceramicized silicone rubber is extruded onto the outer surface of the insulation layer at 150°C and 12MPa using an extruder. Then, it is vulcanized at 170°C for 40 minutes to form a 5.0mm thick fireproof sheath, resulting in a water-blocking fireproof cable.

6. The preparation method according to claim 5, characterized in that, In step S2, the screw length-to-diameter ratio of the extruder is 25:1, and the die head temperature is 165℃; in step 4, the screw length-to-diameter ratio of the extruder is 20:1, and the die head temperature is 155℃.

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