Rat-proof and ant-proof cable for rail transit and preparation method thereof

Abstract

The invention discloses a rat-proof and termite-proof cable for rail transit and a preparation method thereof, and belongs to the technical field of rail transit cables. Comprising a conductor, an insulating layer and an anti-rat and anti-termite sheath layer, wherein the rat-and-ant-proof sheath layer is prepared from the following raw materials in parts by weight: 70 to 80 parts of ethylene-vinyl acetate copolymer, 15 to 20 parts of aluminum hydroxide, 3 to 5 parts of compatilizer, 4 to 8 parts of rat-and-ant-proof agent, 1 to 2 parts of processing aid, 0.8 to 1.2 parts of antioxidant and 0.1 to 0.2 part of initiator. Wherein the rat-and-ant-proof agent is obtained by compounding toosendanin and a self-made terpenoid auxiliary agent, the terpenoid auxiliary agent can provide flame retardance and rat-and-ant-proof performance of the cable, and the performance is stable; the prepared cable does not need traditional metal armoring, so that the laying difficulty and cost are reduced; the insulating layer and the sheath layer are molded through extrusion, the process is simple, and the cable is suitable for industrial production. Therefore, the cable has important application value in the technical field of rail transit cables.

Description

Technical Field

[0001] This invention belongs to the field of rail transit cable technology, specifically, it relates to a rodent- and ant-proof rail transit cable and its preparation method. Background Technology

[0002] With the rapid development of rail transit, subways, light rail, and other rail transit systems have become core components of urban public transportation. As key carriers for signal transmission and power supply, the stability and reliability of rail transit cables directly affect the safe operation of the rail transit system. However, in actual rail transit applications, especially in areas such as underground tunnels, viaducts, and ground stations, cables often face the severe challenge of damage from rodents and other organisms. These organisms, driven by gnawing habits, nesting needs, or the search for food and water, actively gnaw on the cable sheath, leading to cable damage, conductor exposure, and even short circuits. This can cause major safety accidents such as power outages, signal failures, and even fires, resulting in significant economic losses and social impact.

[0003] To address the issue of rodent and termite infestation in cables, existing technologies have proposed physical protection solutions. These solutions primarily involve adding a metal armor layer to the outer layer of the cable, such as steel wire armor or steel tape armor, utilizing the hardness of metal to resist rodent and termite attacks. However, this approach has significant drawbacks: the metal armor layer significantly increases the cable's weight and outer diameter, raising production costs and causing considerable inconvenience during transportation, laying, and installation, especially in confined spaces like rail transit tunnels where construction becomes significantly more difficult. Furthermore, the metal armor layer is prone to corrosion under prolonged vibration and humidity, leading to a sharp decline in its protective performance and rendering it ineffective against rodent and termite damage in the long term.

[0004] In summary, current rodent- and termite-proofing technologies for rail transit cables still have many shortcomings and cannot meet the actual needs of safe, stable, and long-term operation of rail transit systems. Therefore, there is an urgent need in the industry to develop a cable that combines rodent- and termite-proofing with flame-retardant properties. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a rodent- and ant-proof cable for rail transit and its preparation method.

[0006] The objective of this invention can be achieved through the following technical solutions: A rodent-proof cable for rail transit includes a conductor, an insulation layer, and a rodent-proof sheath.

[0007] As a further technical solution, the material of the insulating layer includes the following raw materials in parts by weight: 80-90 parts linear low-density polyethylene, 3-5 parts crosslinking sensitizer, 1-2 parts processing aid, and 0.8-1.2 parts antioxidant.

[0008] As a further technical solution, the material of the rodent-proof sheath layer includes the following raw materials in parts by weight: 70-80 parts ethylene-vinyl acetate copolymer, 15-20 parts aluminum hydroxide, 3-5 parts compatibilizer, 4-8 parts rodent-proof agent, 1-2 parts processing aid, 0.8-1.2 parts antioxidant and 0.1-0.2 parts initiator.

[0009] As a further technical solution, the processing aid is one of polypropylene wax, glyceryl monostearate, zinc stearate, calcium stearate, and stearic acid.

[0010] As a further technical solution, the antioxidant is a phenolic antioxidant.

[0011] As a further technical solution, the rodent repellent is a mixture of azadirachtin and terpenoid adjuvants in a weight ratio of 1:1.

[0012] As a further technical solution, the terpene adjuvant is prepared through the following steps: A1. In a dry round-bottom flask, add citral, 4-aminostyrene and anhydrous ethanol in sequence. Add a magnetic stir bar and start stirring. Add 2-3 drops of acetic acid to the flask. After the addition is complete, install a reflux apparatus, heat to 78-80℃, and reflux for 3-4 hours. After the reaction is complete, after post-treatment, the intermediate product of terpene auxiliaries is obtained. A2. In a dry round-bottom flask, add the terpene auxiliary intermediate, diethyl phosphite, and anhydrous toluene in sequence. Add a magnetic stir bar and start stirring. Then add triethylamine (alkaline catalyst) dropwise, controlling the system temperature to not exceed 35°C during the dropwise addition. After the dropwise addition is complete, stir for 10-20 minutes, install a reflux device, and then heat to 110-115°C. Reflux the reaction for 5-6 hours. After the reaction is complete, the terpene auxiliary is obtained after post-processing.

[0013] As a further technical solution, the ratio of citral to 4-aminostyrene in step A1 is 15.2g:13.3-14.7g.

[0014] As a further technical solution, in step A2, the ratio of the amount of terpene adjuvant intermediate, diethyl phosphite and triethylamine is 25.3g:15.5-17.3g:1.1g.

[0015] The reaction formula for preparing terpene adjuvants in this invention is as follows: In the preparation of terpenoid adjuvants, the present invention uses an excess of 4-aminostyrene in step A1 to ensure complete reaction of neraldehyde and avoid unreacted aldehyde residue affecting product performance; glacial acetic acid, as a protic acid catalyst, can promote the reaction; in step A2, an excess of diethyl phosphite ensures complete addition reaction of C=N bonds and avoids substrate residue; triethylamine, as a basic catalyst, can promote the reaction.

[0016] The terpenoid additive prepared in this invention belongs to monoterpenes and can repel rodents and ants through its odor. The azadirachtin in the raw material is a tetracyclic triterpenoid with a strong bitter taste. It can activate sensitive bitter taste receptors in the oral cavity of mammals, producing a strong aversion and repelling rodents. Furthermore, it can physiologically inhibit the development and feeding of termites. Combining azadirachtin with the terpenoid additive produces a synergistic enhancement effect, improving the rodent and ant repellency of the matrix. In addition, this invention introduces phosphate esters as flame-retardant groups into the terpenoid additive, which can synergistically work with the inorganic flame retardant aluminum hydroxide, significantly improving the flame retardancy of the cable. Finally, this invention introduces unsaturated double bonds at one end of the additive, which can cross-link with the matrix under the action of an initiator, improving the additive's migration resistance and making its rodent and ant repellency more durable.

[0017] As a further technical solution, the material of the rodent-proof sheath layer is prepared through the following steps: Ethylene-vinyl acetate copolymer, aluminum hydroxide, compatibilizer, rodent repellent, processing aid, antioxidant and initiator are added to a high-speed mixer and stirred at 1000-1200 rpm for 10-20 minutes to obtain a mixture. The mixture is then fed into a twin-screw extruder, melt-blended, extruded, cooled and granulated to obtain the rodent repellent sheath material.

[0018] This invention also provides a method for preparing rodent- and ant-proof rail transit cables, comprising the following steps: Step 1: Place the copper wire into a stranding machine for stranding to obtain a stranded conductor; Step 2: Put the insulating material into a high-speed mixer and mix for 15-20 minutes. Then add it into a twin-screw extruder. The material melts in the extruder. The stranded conductor is passed through the die of the extruder head at a uniform speed to achieve the extrusion coating of the insulating layer. Then it is put into a crosslinking box for irradiation crosslinking treatment to form an insulating layer. Step 3: Put the material of the rodent-proof sheath layer into a high-speed mixer and mix for 15-20 minutes. Then add it into a twin-screw extruder. The material melts in the extruder and is extruded to cover the surface of the insulation layer to form a rodent-proof sheath layer. After cooling, the rodent-proof rail transit cable is obtained.

[0019] As a further technical solution, the stranding speed is 800-1000 r / min, and the stranding pitch is 12-16 times the conductor diameter.

[0020] As a further technical solution, the high-speed mixer has a rotation speed of 1500-2000 rpm.

[0021] The beneficial effects of this invention are: Advantage 1: This invention uses azadirachtin and self-made terpenoid adjuvants in combination, which has a compound rodent and termite repellent mechanism that combines bitter taste to repel rodents, odor to repel insects, and inhibition of termite development. Advantage 2: The introduction of phosphate ester flame-retardant groups into terpene auxiliaries synergistically enhances flame-retardant properties with aluminum hydroxide in the sheath; Advantage 3: Terpenoid adjuvants contain unsaturated double bonds at the end, which can cross-link with the sheath matrix under the action of initiators, preventing adjuvant migration and extending the lifespan of rodent and ant protection; Advantage 4: The resulting cable does not require traditional metal armor, reducing cable weight and volume, and lowering installation difficulty and cost; Advantage 5: The insulation layer and sheath layer are formed by twin-screw melt blending and extrusion molding, which is a simple process and suitable for industrial production; In summary, this invention achieves a balance between lightweight, durable, and process-feasible cables while ensuring high efficiency in rodent and ant prevention and flame retardancy, making it applicable to the field of rail transit cable technology. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1 Preparation of terpenoid adjuvants: A1. In a dry round-bottom flask, add 15.2g citral, 13.3g 4-aminostyrene and 100mL anhydrous ethanol in sequence. Add a magnetic stir bar and start stirring. Add 2 drops of acetic acid dropwise to the flask. After the addition is complete, install a reflux apparatus, heat to 78℃, and reflux for 3 hours. After the reaction is complete, cool the reaction solution to room temperature, remove anhydrous ethanol by vacuum distillation, add petroleum ether, stir well, and refrigerate in a 0-5℃ refrigerator for 1 hour. The solid precipitates, is filtered, and the filter cake is washed twice with cold petroleum ether and dried under vacuum to obtain the intermediate product of terpene adjuvant. A2. In a dry round-bottom flask, add 25.3g of terpene auxiliary intermediate, 15.5g of diethyl phosphite and 100mL of anhydrous toluene in sequence. Add a magnetic stir bar and start stirring. Then add 1.1g of triethylamine dropwise, controlling the system temperature to not exceed 35℃ during the dropwise addition. After the dropwise addition is complete, stir for 10min, install a reflux device, and then heat to 110℃ and reflux for 5h. After the reaction is complete, cool the reaction solution to room temperature, distill under reduced pressure, add a petroleum ether / ethyl acetate mixed solvent (volume ratio 4:1) to the residue, stir evenly, and refrigerate in a 0-5℃ refrigerator for 2h to precipitate solid. Filter, wash the filter cake twice with a cold mixed solvent (below 5℃), collect the filter cake, and dry under vacuum to obtain the terpene auxiliary. Materials for preparing the rodent- and ant-proof sheath layer: 70 parts of ethylene-vinyl acetate copolymer, 15 parts of aluminum hydroxide, 3 parts of maleic anhydride-grafted polyethylene, 4 parts of rodent repellent (a mixture of azadirachtin and terpene auxiliaries in a 1:1 weight ratio), 1-2 parts of calcium stearate, 0.8 parts of antioxidant 264 and 0.1 parts of dicumyl peroxide were added to a high-speed mixer and stirred at 1000 rpm for 10 minutes to obtain a mixture. The mixture was then fed into a twin-screw extruder, melt-blended, extruded, cooled, and granulated to obtain the rodent repellent sheath material. A method for preparing a rodent- and ant-proof cable for rail transit includes the following steps: Step 1: Place the copper wire (0.2mm in diameter) into a stranding machine for stranding to obtain a stranded conductor; Step 2: Mix 80 parts of linear low-density polyethylene, 3 parts of triallyl isocyanurate, 1 part of calcium stearate and 0.8 parts of antioxidant 264 in a high-speed mixer for 15 minutes, then add the mixture to a twin-screw extruder. The material melts in the extruder, and the stranded conductor is passed through the die of the extruder head at a uniform speed to achieve the extrusion coating of the insulation layer. Then, it is placed in a crosslinking box for irradiation crosslinking treatment (irradiation dose of 70 kGy) to form an insulation layer. Step 3: Put the material of the rodent-proof sheath layer into a high-speed mixer and mix for 15 minutes. Then add it into a twin-screw extruder. The material melts in the extruder and is extruded to cover the surface of the insulation layer to form a rodent-proof sheath layer. After cooling, the rodent-proof rail transit cable is obtained.

[0024] Example 2 Preparation of terpenoid adjuvants: A1. In a dry round-bottom flask, add 15.2g citral, 14.7g 4-aminostyrene and 100mL anhydrous ethanol in sequence. Add a magnetic stir bar and start stirring. Add 3 drops of acetic acid dropwise to the flask. After the addition is complete, install a reflux apparatus, heat to 80℃, and reflux for 4 hours. After the reaction is complete, cool the reaction solution to room temperature, remove anhydrous ethanol by vacuum distillation, add petroleum ether, stir well, and refrigerate in a 0-5℃ refrigerator for 1 hour. The solid precipitates, is filtered, and the filter cake is washed twice with cold petroleum ether and dried under vacuum to obtain the terpene adjuvant intermediate product. A2. In a dry round-bottom flask, add 25.3g of terpene auxiliary intermediate, 17.3g of diethyl phosphite, and 100mL of anhydrous toluene in sequence. Add a magnetic stir bar and start stirring. Then add 1.1g of triethylamine dropwise, controlling the system temperature to not exceed 35℃ during the dropwise addition. After the dropwise addition is complete, stir for 20min, install a reflux device, and then heat to 115℃ and reflux for 6h. After the reaction is complete, cool the reaction solution to room temperature, distill under reduced pressure, add a petroleum ether / ethyl acetate mixed solvent (volume ratio 4:1) to the residue, stir evenly, and refrigerate in a 0-5℃ refrigerator for 2h to precipitate solid. Filter, wash the filter cake twice with a cold mixed solvent (below 5℃), collect the filter cake, and dry under vacuum to obtain the terpene auxiliary. Materials for preparing the rodent- and ant-proof sheath layer: 75 parts of ethylene-vinyl acetate copolymer, 17.5 parts of aluminum hydroxide, 4 parts of maleic anhydride-grafted polyethylene, 6 parts of rodent repellent (a mixture of azadirachtin and terpene auxiliaries in a 1:1 weight ratio), 1.5 parts of glyceryl monostearate, 1.0 part of antioxidant 264 and 0.15 parts of dicumyl peroxide were added to a high-speed mixer and stirred at 1200 rpm for 20 minutes to obtain a mixture. The mixture was then fed into a twin-screw extruder, melt-blended, extruded, cooled, and granulated to obtain the rodent repellent sheath material. A method for preparing a rodent- and ant-proof cable for rail transit includes the following steps: Step 1: Place the copper wire (0.2mm in diameter) into a stranding machine for stranding to obtain a stranded conductor; Step 2: Mix 85 parts of linear low-density polyethylene, 4 parts of triallyl isocyanurate, 1.5 parts of glyceryl monostearate and 1.0 part of antioxidant 264 in a high-speed mixer for 20 minutes, then add the mixture to a twin-screw extruder. The material melts in the extruder, and the stranded conductor is passed through the die of the extruder head at a uniform speed to achieve the extrusion coating of the insulation layer. Then, it is placed in a crosslinking box for irradiation crosslinking treatment (irradiation dose of 70 kGy) to form an insulation layer. Step 3: Put the material of the rodent-proof sheath layer into a high-speed mixer and mix for 20 minutes. Then add it into a twin-screw extruder. The material melts in the extruder and is extruded to cover the surface of the insulation layer to form a rodent-proof sheath layer. After cooling, the rodent-proof rail transit cable is obtained.

[0025] Example 3 The only difference between this embodiment and Embodiment 2 is that, in this embodiment, the material for preparing the rodent-proof sheath layer includes the following steps: 80 parts of ethylene-vinyl acetate copolymer, 20 parts of aluminum hydroxide, 5 parts of maleic anhydride-grafted polyethylene, 8 parts of rodent repellent (a mixture of azadirachtin and terpene auxiliaries in a 1:1 weight ratio), 2 parts of polypropylene wax, 1.2 parts of antioxidant 264 and 0.2 parts of dicumyl peroxide were added to a high-speed mixer and stirred at 1200 rpm for 20 minutes to obtain a mixture. The mixture was then fed into a twin-screw extruder, melt-blended, extruded, cooled, and granulated to obtain the rodent repellent sheath material. A method for preparing a rodent- and ant-proof cable for rail transit includes the following steps: Step 1: Place the copper wire (0.2mm in diameter) into a stranding machine for stranding to obtain a stranded conductor; Step 2: Mix 90 parts of linear low-density polyethylene, 5 parts of triallyl isocyanurate, 2 parts of polypropylene wax and 1.2 parts of antioxidant 264 in a high-speed mixer for 20 minutes, then add the mixture to a twin-screw extruder. The material melts in the extruder, and the stranded conductor is passed through the die of the extruder head at a uniform speed to achieve the extrusion coating of the insulation layer. Then, it is placed in a crosslinking box for irradiation crosslinking treatment (irradiation dose of 70 kGy) to form an insulation layer. Step 3: Put the material of the rodent-proof sheath layer into a high-speed mixer and mix for 20 minutes. Then add it into a twin-screw extruder. The material melts in the extruder and is extruded to cover the surface of the insulation layer to form a rodent-proof sheath layer. After cooling, the rodent-proof rail transit cable is obtained.

[0026] Comparative Example 1 The difference between this comparative example and Example 3 is that in this comparative example, the rodent repellent does not contain terpenoid additives and is entirely composed of azadirachtin, which is used to prepare the cable.

[0027] Comparative Example 2 The difference between this comparative example and Example 3 is that in this comparative example, the rodent repellent does not contain terpene auxiliaries, but is replaced with an equal amount of triethyl phosphate to obtain the cable.

[0028] Performance tests were conducted on the materials of the sheath layers prepared in Examples 1, 2, and 3, and Comparative Examples 1 and 2: The oxygen index was determined according to GB / T 2406.2 standard; the oxygen index of the samples other than Comparative Example 1 was determined after standing at room temperature for 200 days. The performance test results are shown in Table 1: Table 1 Examples 1, 2, and 3, along with Comparative Example 1, were tested according to JB / T 10696.9-2011 standard to determine the termite infestation level and the protection level against rats. The samples were left to stand at room temperature for 200 days. The results are shown in Table 2. Table 2 As can be seen from the table above, the material of the sheath layer obtained by the embodiment of the present invention has both rodent and insect repellency and flame retardancy properties compared with the comparative example, and its performance is stable. Therefore, the present invention has important application value in the field of rail transit cable technology.

[0029] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A rodent- and termite-proof cable for rail transit, comprising a conductor, an insulation layer, and a rodent- and termite-proof sheath layer, characterized in that, The material of the rodent-proof sheath layer includes the following raw materials in parts by weight: 70-80 parts ethylene-vinyl acetate copolymer, 15-20 parts aluminum hydroxide, 3-5 parts compatibilizer, 4-8 parts rodent-proof agent, 1-2 parts processing aid, 0.8-1.2 parts antioxidant and 0.1-0.2 parts initiator.

2. The rodent- and ant-proof cable for rail transit according to claim 1, characterized in that, The rodent repellent is a mixture of azadirachtin and terpenoid adjuvants in a weight ratio of 1:

1.

3. The rodent- and ant-proof cable for rail transit according to claim 2, characterized in that, The terpene adjuvant is prepared by the following steps: A1. In a flask, add citral, 4-aminostyrene and anhydrous ethanol in sequence, start stirring, add 2-3 drops of acetic acid dropwise to the flask, after the addition is complete, reflux at 78-80℃ for 3-4 hours, the reaction is complete, and the intermediate product of terpene auxiliaries is obtained. A2. In a flask, add the intermediate product of terpenoid adjuvant, diethyl phosphite and anhydrous toluene in sequence, start stirring, then add triethylamine dropwise. After the addition is complete, stir for 10-20 minutes, then reflux at 110-115℃ for 5-6 hours. When the reaction is complete, the terpenoid adjuvant is obtained.

4. The rodent- and ant-proof cable for rail transit according to claim 3, characterized in that, In step A1, the ratio of citral to 4-aminostyrene is 15.2g:13.3-14.7g.

5. The rodent- and ant-proof cable for rail transit according to claim 3, characterized in that, In step A2, the ratio of the amount of terpene adjuvant intermediate, diethyl phosphite, and triethylamine is 25.3g:15.5-17.3g:1.1g.

6. The rodent- and ant-proof cable for rail transit according to claim 1, characterized in that, The insulating layer is made of the following raw materials in parts by weight: 80-90 parts linear low-density polyethylene, 3-5 parts crosslinking sensitizer, 1-2 parts processing aid, and 0.8-1.2 parts antioxidant.

7. The rodent- and ant-proof cable for rail transit according to claim 1, characterized in that, The processing aid is one of polypropylene wax, glyceryl monostearate, zinc stearate, calcium stearate, and stearic acid.

8. The rodent- and ant-proof cable for rail transit according to claim 1, characterized in that, The antioxidant is a phenolic antioxidant.

9. A method for preparing a rodent- and ant-proof cable for rail transit, used to prepare the rodent- and ant-proof cable for rail transit as described in any one of claims 1-8, characterized in that, Includes the following steps: Copper wires are stranded in a stranding machine to obtain a stranded conductor. The insulation material is mixed in a high-speed mixer and then added to a twin-screw extruder to be extruded and coated onto the surface of the stranded conductor. Then, it is irradiated and cross-linked to form an insulation layer. The rodent-proof sheath material is mixed in a high-speed mixer and then added to a twin-screw extruder to be extruded and coated onto the surface of the insulation layer to form a rodent-proof sheath. After cooling, a rodent-proof rail transit cable is obtained.

Images