Flame-retardant cable for rail transit

Abstract

The invention discloses a flame-retardant cable for rail transit, and belongs to the technical field of cables. The cable is composed of a conductor, an insulating layer and a protective sleeve which are sequentially arranged from inside to outside. Wherein the material of the protective sleeve takes polypropylene as a matrix, so that the cable is endowed with excellent mechanical property and electrical insulation property; compared with common carbon black, the modified carbon black has better compatibility with a polypropylene matrix, can enhance the flame retardant property of the cable, and has less influence on the mechanical properties of the matrix; the prepared organic modifier molecules and the inorganic carbon black have a synergistic effect, so that the flame retardant property of the cable is greatly enhanced, the heat resistance and the mechanical property of the cable can be enhanced, and the cable is not easy to fall off and has long and stable performance; therefore, the prepared cable is excellent in mechanical property, has stable and efficient flame-retardant and heat-resistant properties, is halogen-free and environment-friendly, and has important application value in the technical field of cables.

Description

Technical Field

[0001] The present invention belongs to the technical field of cables, and in particular, relates to a flame-retardant cable for rail transit. Background Art

[0002] Rail transit refers to a type of transportation tool or transportation system in which operating vehicles need to travel on specific tracks. Common rail transit includes traditional railways (ordinary railways, intercity railways and urban railways), subways, light rails and trams, in addition to new rail transit such as magnetic levitation rail systems and monorail systems. In the transmission of electric energy in rail transit, the use of power cables is indispensable, and the performance of the cables is highly required.

[0003] The composition of the cable can be generally divided into three main structural components: conductor, insulation layer and sheath, as well as filling elements and tensile elements. Since the outermost layer of the cable is protected by the sheath, the performance of the sheath determines whether the performance of the cable is excellent; common cable sheath materials include polypropylene, polyethylene, cross-linked polyethylene, polyvinyl chloride, etc., among which polypropylene is referred to as PP, which is a polymer formed by polyaddition reaction of propylene. It is a thermoplastic synthetic resin with excellent performance, chemical resistance, heat resistance, electrical insulation, high-strength mechanical properties and good high-wear processing performance, and has high volume resistivity and dielectric strength. It can be recycled and reused, and is a very high-quality cable material. However, when using polypropylene as a cable for rail transit, it is inevitable to modify it to flame retardant, because the polypropylene oxygen index is 18 and it is flammable. It will continue to burn after leaving the fire and emit the smell of petroleum. Once it catches fire, it will pose a huge threat to the safety of human life and property. Therefore, it is very necessary to modify polypropylene to flame retardant.

[0004] At present, flame-retardant polypropylene on the market generally uses halogen-containing flame retardants represented by polybrominated diphenyl ethers and polybrominated biphenyls. However, when these halogen flame-retardant materials burn, they release a large amount of smoke and toxic and harmful hydrogen halide gas, which seriously pollutes the environment. Therefore, it is urgent to invent a halogen-free flame-retardant cable for rail transit to meet the higher demands in the field of cable technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a flame retardant cable for rail transit.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A flame-retardant cable for rail transit consists of a conductor, an insulating layer and a protective sheath which are arranged in sequence from the inside to the outside.

[0008] Furthermore, the conductor is a pure copper conductor.

[0009] Furthermore, the insulating layer is cross-linked polyethylene.

[0010] Furthermore, the material of the protective cover includes the following raw materials in parts by weight: 80-100 parts of polypropylene resin, 12-20 parts of modified carbon black, 0.2-0.4 parts of initiator, 5-15 parts of modifier, and 3-5 parts of lubricant.

[0011] Furthermore, the initiator is one of benzoyl peroxide and lauroyl peroxide.

[0012] Furthermore, the lubricant is one of paraffin and stearamide fatty acid.

[0013] The prepared protective cover material takes polypropylene as the matrix, which gives the material excellent mechanical properties and electrical insulation properties.

[0014] Furthermore, the modified carbon black is prepared by the following steps:

[0015] Mix N-(4-sulfonic acid phenyl) maleic acid amide with deionized water, stir until dissolved, add carbon black, remove water under vacuum, put into a muffle furnace and keep warm at 180-200°C for 5-6 hours, take out, wash with water 2-3 times, and dry in a drying oven at 100°C for 8 hours to obtain modified carbon black.

[0016] Furthermore, the usage ratio of the N-(4-sulfonic acid phenyl) maleic acid amide, deionized water and carbon black is 5.5g:100mL:1g.

[0017] Carbon black is modified by using a derivative of maleic anhydride and a solid phase method. This method can enhance the hydrophobicity of the carbon black surface and improve the compatibility of carbon black with polypropylene, so that a small amount of carbon black can greatly enhance the flame retardant properties of the matrix and has little effect on the mechanical properties of the matrix.

[0018] Furthermore, the modifier is prepared by the following steps:

[0019] S1. In a three-necked flask equipped with a stirring device, phenylphosphonyl dichloride, p-hydroxybenzaldehyde, toluene and triethylamine (acid binding agent) were mixed and stirred uniformly, the reaction temperature was controlled to 65° C., and the reaction was kept warm for 5 hours. After the reaction was completed, triethylamine hydrochloride was removed by filtration, and the filtrate was washed three times with saturated brine, concentrated and recrystallized to obtain intermediate 1; the ratio of phenylphosphonyl dichloride, p-hydroxybenzaldehyde, toluene and triethylamine was 19.3 g:24.4 g:150 mL:30 mL;

[0020] Phenylphosphonyl dichloride reacts with p-hydroxybenzaldehyde, and the molar ratio of the two is controlled to be close to 1:2, so that two -Cl groups on the phenylphosphonyl dichloride participate in the reaction, and triethylamine removes the hydrogen chloride generated by the reaction to obtain intermediate 1; the specific reaction process is as follows:

[0021]

[0022] S2. Add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and toluene into a three-necked flask equipped with a stirring device. Stir for 30 minutes under nitrogen protection, then add half of the amount of phosphorus pentasulfide (P2S5), heat to 60°C, react for 3 hours, then continue to add the other half of the amount of phosphorus pentasulfide, react at 50°C for 12 hours. After the reaction is completed, filter, remove the solvent from the filtrate under reduced pressure, dissolve it with chloroform, add saturated sodium bicarbonate solution dropwise under nitrogen protection, continue stirring for 20 minutes, let stand for stratification, take the organic phase and remove the solvent by reduced pressure distillation to obtain intermediate 2; the ratio of DOPO, toluene and phosphorus pentasulfide is 21.6g:100mL:11.1g;

[0023] DOPO reacts with phosphorus pentasulfide to introduce sulfur into the structure of DOPO to obtain intermediate 2. The specific reaction process is as follows:

[0024]

[0025] S3, add intermediate 1, intermediate 2 and toluene to a three-necked flask with a reflux condenser and mechanical stirring, and continue to introduce N2 protection, heat to 90 ° C, stir for 30 min, and after all the solids are dissolved, heat to 140 ° C and react for 6 h. After the reaction is completed, reduce pressure and filter, wash the filter residue with a mixed solvent of ethyl acetate and petroleum ether (the volume ratio of the two is 1:1) 3-4 times, and vacuum dry to obtain intermediate 3; the ratio of intermediate 1, intermediate 2, and toluene is 36.6 g:48.1 g:150 mL;

[0026] The active PH bond in the structure of intermediate 2 can react with the C=O bond of the aldehyde group in the intermediate 1 molecule. By controlling the molar ratio of the two to be close to 2:1, two aldehyde groups on intermediate 1 participate in the reaction to obtain intermediate 3.

[0027]

[0028] S4. In a three-necked flask equipped with a stirring device, the intermediate 3, allyl acetic acid and toluene were stirred and mixed uniformly, dibutyltin oxide (catalyst) and dicyclohexylcarbodiimide (DCC, dehydrating agent) were added, the reaction temperature was controlled to 80°C, and the reaction was kept warm for 8 hours. Stirring was continued during the reaction. After the reaction was completed, the reaction was filtered, and most of the solvent was first removed by rotary evaporation, and then purified by column chromatography (the eluent was a mixed solvent of ethyl acetate / benzene, and the volume ratio of the two was 2:5), and the eluent was removed by rotary evaporation to obtain a modifier; the ratio of the amount of intermediate 3, allyl acetic acid, toluene, dibutyltin oxide and DCC was 83.9g:21.4g:300mL:0.4g:41.2g;

[0029] Under the catalysis of dibutyltin oxide and DCC, the carboxyl group on allyl acetic acid and the hydroxyl group on intermediate 3 undergo esterification reaction. By controlling the molar ratio of the two to be close to 2:1 and a slight excess of allyl acetic acid, the two hydroxyl groups on intermediate 3 participate in the reaction to obtain a modifier; the structure of the modifier is shown below:

[0030]

[0031] The prepared modifier molecule contains a large number of benzene rings and has a rigid structure, which can enhance the mechanical properties and heat resistance of the polypropylene matrix to a certain extent; in addition, the modifier molecule also contains DOPO structure, sulfur element and carbon-carbon double bond, among which DOPO is an environmentally friendly flame retardant with the advantages of high efficiency and low toxicity, good thermal stability, strong flame retardant durability, and can enhance the flame retardant properties of the matrix; the introduced sulfur element can release strong acids such as sulfuric acid under high temperature conditions, promote the dehydration of the substrate into carbon, and can also exert excellent flame retardant properties in the condensed phase, which can play a synergistic role with DOPO and greatly enhance the flame retardant properties of the matrix; finally, the carbon-carbon double bond at one end of the modifier molecule can cross-link with the matrix, enhance the interaction force with the matrix, make the modifier and the matrix more closely connected, and improve the long-term stability of the modifier molecule.

[0032] Beneficial effects of the present invention:

[0033] 1. The cable protective sheath material prepared by the present invention uses polypropylene as a matrix, which gives the cable excellent mechanical properties and electrical insulation properties;

[0034] 2. By modifying carbon black, it has better compatibility with the polypropylene matrix than ordinary carbon black, can enhance the flame retardant properties of the cable, and has little effect on the mechanical properties of the matrix;

[0035] 3. The prepared organic modifier molecules can play a synergistic role with inorganic carbon black, greatly enhancing the flame retardant properties of the cable, and can also enhance the heat resistance and mechanical properties of the cable, and are not easy to fall off, and the performance is long-term and stable;

[0036] Therefore, the cable prepared by the present invention has excellent mechanical properties, stable and efficient flame retardant and heat resistant properties, is halogen-free and environmentally friendly, and has important application value in the field of cable technology. DETAILED DESCRIPTION

[0037] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Embodiment 1

[0039] Preparation of modifier:

[0040] S1. In a three-necked flask equipped with a stirring device, 19.3 g of phenylphosphonic acid dichloride, 24.4 g of p-hydroxybenzaldehyde, 150 mL of toluene and 30 mL of triethylamine were mixed and stirred evenly, the reaction temperature was controlled to 65° C., and the reaction was kept warm for 5 hours. After the reaction was completed, triethylamine hydrochloride was removed by filtration, and the filtrate was washed three times with saturated brine, concentrated and recrystallized to obtain intermediate 1;

[0041] S2, 21.6g DOPO and 100mL toluene were added to a three-necked flask equipped with a stirring device, and stirred for 30min under nitrogen protection, then 5.55g phosphorus pentasulfide was added, and the mixture was heated to 60°C. After reacting for 3h, 5.55g phosphorus pentasulfide was added, and the mixture was reacted at 50°C for 12h. After the reaction was completed, the mixture was filtered, and the solvent was removed from the filtrate under reduced pressure, and the mixture was dissolved in chloroform. 50mL saturated sodium bicarbonate solution was added dropwise under nitrogen protection, and after the addition was completed, the mixture was stirred for 20min, and then the mixture was allowed to stand for stratification. The organic phase was taken and the solvent was removed by distillation under reduced pressure to obtain intermediate 2;

[0042] S3, in a three-necked flask with a reflux condenser and mechanical stirring, add 36.6g of intermediate 1, 48.1g of intermediate 2 and 150mL of toluene, and continue to introduce N2 protection, heat to 90°C, stir for 30min, and after all the solids are dissolved, heat to 140°C and react for 6h. After the reaction is complete, filter under reduced pressure, wash the residue three times with a mixed solvent of ethyl acetate and petroleum ether (the volume ratio of the two is 1:1), and vacuum dry to obtain intermediate 3;

[0043] S4. In a three-necked flask equipped with a stirring device, 83.9 g of intermediate 3, 21.4 g of allyl acetic acid and 300 mL of toluene were stirred and mixed evenly, 0.4 g of dibutyltin oxide and 41.2 g of dicyclohexylcarbodiimide were added, the reaction temperature was controlled to 80°C, and the reaction was kept warm for 8 hours. Stirring was continued during the reaction. After the reaction was completed, the reaction was filtered, most of the solvent was first removed by rotary evaporation, and then purified by column chromatography (the eluent was a mixed solvent of ethyl acetate / benzene, and the volume ratio of the two was 2:5), and the eluent was removed by rotary evaporation to obtain a modifier.

[0044] Embodiment 2

[0045] Preparation of modifier:

[0046] S1. In a three-necked flask equipped with a stirring device, 38.6 g of phenylphosphonyl dichloride, 48.8 g of p-hydroxybenzaldehyde, 300 mL of toluene and 60 mL of triethylamine were mixed and stirred evenly, the reaction temperature was controlled to 65° C., and the reaction was kept warm for 5 hours. After the reaction was completed, triethylamine hydrochloride was removed by filtration, and the filtrate was washed three times with saturated brine, concentrated and recrystallized to obtain intermediate 1;

[0047] S2, 43.2g DOPO and 200mL toluene were added to a three-necked flask equipped with a stirring device, and stirred for 30min under nitrogen protection, and then 11.1g phosphorus pentasulfide was added, and the mixture was heated to 60°C. After reacting for 3h, 11.1g phosphorus pentasulfide was added, and the mixture was reacted at 50°C for 12h. After the reaction was completed, the mixture was filtered, and the solvent was removed from the filtrate under reduced pressure, and the mixture was dissolved in chloroform. 100mL saturated sodium bicarbonate solution was added dropwise under nitrogen protection, and after the addition was completed, the mixture was stirred for 20min, and then the mixture was allowed to stand for stratification. The organic phase was taken and the solvent was removed by distillation under reduced pressure to obtain intermediate 2;

[0048] S3, in a three-necked flask with a reflux condenser and mechanical stirring, add 73.2g of intermediate 1, 96.2g of intermediate 2 and 300mL of toluene, and continue to introduce N2 protection, heat to 90°C, stir for 30min, and after all the solids are dissolved, heat to 140°C and react for 6h. After the reaction is complete, filter under reduced pressure, wash the filter residue three times with a mixed solvent of ethyl acetate and petroleum ether (the volume ratio of the two is 1:1), and vacuum dry to obtain intermediate 3;

[0049] S4. In a three-necked flask equipped with a stirring device, 167.8 g of intermediate 3, 41.8 g of allyl acetic acid and 600 mL of toluene were stirred and mixed evenly, 0.8 g of dibutyltin oxide and 82.4 g of dicyclohexylcarbodiimide were added, the reaction temperature was controlled to 80°C, and the reaction was kept warm for 8 hours. Stirring was continued during the reaction. After the reaction was completed, the reaction was filtered, most of the solvent was first removed by rotary evaporation, and then purified by column chromatography (the eluent was a mixed solvent of ethyl acetate / benzene, and the volume ratio of the two was 2:5), and the eluent was removed by rotary evaporation to obtain a modifier.

[0050] Embodiment 3

[0051] Preparation of modified carbon black:

[0052] Mix 5.5 g of N-(4-sulfonic acid phenyl) maleic acid amide with 100 mL of deionized water and stir until dissolved, then add 1 g of carbon black, remove the water under vacuum, put it into a muffle furnace and keep it at 180°C for 5 hours, take it out, wash it with water twice, and dry it in a drying oven at 100°C for 8 hours to obtain modified carbon black.

[0053] Embodiment 4

[0054] Materials for making protective cover:

[0055] 80g of polypropylene resin was placed in a vacuum oven and dried at 100°C for 24h. The dried polypropylene resin, 12g of the modified carbon black prepared in Example 3, 0.2g of benzoyl peroxide, 5g of the modifier prepared in Example 1 and 3g of paraffin were first added to a mixer and stirred for 30min, and then added to a twin-screw extruder, melt-blended and extruded to obtain the material of the protective cover.

[0056] Embodiment 5

[0057] Materials for making protective cover:

[0058] 90 g of polypropylene resin was placed in a vacuum oven and dried at 100° C. for 24 h. The dried polypropylene resin, 16 g of the modified carbon black prepared in Example 3, 0.3 g of lauroyl peroxide, 10 g of the modifier prepared in Example 2 and 4 g of stearamide fatty acid were first added to a mixer and stirred for 30 min. The mixture was then added to a twin-screw extruder, melt-blended and extruded to obtain the material for the protective cover.

[0059] Embodiment 6

[0060] Materials for making protective cover:

[0061] 100 g of polypropylene resin was placed in a vacuum oven and dried at 100° C. for 24 h. The dried polypropylene resin, 20 g of the modified carbon black prepared in Example 3, 0.4 g of lauroyl peroxide, 15 g of the modifier prepared in Example 2 and 5 g of stearamide fatty acid were first added to a mixer and stirred for 30 min. The mixture was then added to a twin-screw extruder for melt blending and extrusion to obtain the material for the protective sleeve.

[0062] Embodiment 7

[0063] Cross-linked polyethylene is extruded on a pure copper conductor to form an insulating layer; 100 g of polypropylene resin is placed in a vacuum oven and dried at 100° C. for 24 h; the dried polypropylene resin and 20 g of the modified carbon black prepared in Example 3, 0.4 g of lauroyl peroxide, 15 g of the modifier prepared in Example 2 and 5 g of stearamide fatty acid are first added to a mixer and stirred for 30 min, and then added to a twin-screw extruder for melt blending, and extruded and coated on the surface of the insulating layer through an extruder to obtain a flame-retardant cable for rail transit.

[0064] Comparative Example 1

[0065] The modifying agent in Example 6 is replaced by a commercially available halogen-containing flame retardant of equal quality, and the remaining steps are the same as those in Example 6 to obtain the material of the protective cover.

[0066] Comparative Example 2

[0067] Commercially available polypropylene cable material was used.

[0068] Embodiments 4, 5, 6, and comparative examples 1 and 2 were made into corresponding shapes to be tested according to different test standards, and the following performance tests were performed:

[0069] The tensile properties are determined using the national standard GB / T 1040.2-2006 "Determination of tensile properties of plastics Part 2: Test conditions for molded and extruded plastics";

[0070] The sample was placed in an environment of 180°C and oxidized with hot air for 72 hours, and then the tensile strength was measured (test standard GB / T1040.2-2006), and the retention rate of tensile strength was calculated; the retention rate of tensile strength = tensile strength after test / tensile strength before test × 100%;

[0071] The national standard GB / T2406-2008 "Test method for combustion performance of plastics" is used to measure the limiting oxygen index of the sample before and after being placed at room temperature for 180 days;

[0072] The smoke density is measured using the national standard GB / T8323.2-2008 "Plastic smoke generation Part 2: Single chamber method for determining smoke density test method";

[0073] The measured results are shown in the following table:

[0074]

[0075] It can be seen from the above table that the polypropylene protective sheath material prepared in the embodiment of the present invention has higher mechanical properties, flame retardancy and heat resistance than the control example, is halogen-free, emits little smoke, and has long-term stable performance. Using it for cables can enhance the corresponding performance of the cables. Therefore, the present invention has important application value in the field of cable technology.

[0076] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0077] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A flame-retardant cable for rail transit, consisting of a conductor, an insulating layer and a protective sheath arranged in sequence from the inside to the outside, characterized in that: The material of the protective cover comprises the following raw materials in parts by weight: 80-100 parts of polypropylene resin, 12-20 parts of modified carbon black, 0.2-0.4 parts of initiator, 5-15 parts of modifier, and 3-5 parts of lubricant.

2. A flame-retardant cable for rail transit according to claim 1, characterized in that: The modifying agent is prepared by the following steps: S1, mixing phenylphosphonyl dichloride, p-hydroxybenzaldehyde, toluene and triethylamine, controlling the reaction temperature to 65°C, keeping the temperature for 5 hours, filtering after the reaction is completed, washing the filtrate with saturated brine, concentrating and recrystallizing to obtain intermediate 1; S2. Add DOPO and toluene into a three-necked flask, stir for 30 minutes under nitrogen protection, then add half of the amount of phosphorus pentasulfide, heat to 60°C, react for 3 hours, then continue to add the other half of the amount of phosphorus pentasulfide, react at 50°C for 12 hours, and after the reaction is completed, filter, remove the solvent from the filtrate under reduced pressure, dissolve it with chloroform, add saturated sodium bicarbonate solution dropwise under nitrogen protection, continue stirring for 20 minutes, let stand for stratification, take the organic phase and distill under reduced pressure to obtain intermediate 2; S3, add intermediate 1, intermediate 2 and toluene into a three-necked flask, and continue to introduce N2 protection, heat to 90°C, stir for 30 minutes, and after all the solids are dissolved, heat to 140°C and react for 6 hours. After the reaction is complete, filter under reduced pressure, wash the filter residue, and vacuum dry to obtain intermediate 3; S4. Stir and mix the intermediate 3, allyl acetic acid and toluene evenly, add dibutyltin oxide and dicyclohexylcarbodiimide, and react at 80°C for 8 hours with continuous stirring during the reaction. After the reaction is completed, filter, first rotary evaporate, purify by column chromatography, and rotary evaporate to obtain a modifier.

3. A flame-retardant cable for rail transit according to claim 2, characterized in that: In step S1, the ratio of phenylphosphonic acid dichloride, p-hydroxybenzaldehyde, toluene and triethylamine is 19.3 g:24.4 g:150 mL:30 mL.

4. A flame-retardant cable for rail transit according to claim 2, characterized in that: In step S2, the ratio of DOPO, toluene and phosphorus pentasulfide is 21.6 g:100 mL:11.1 g.

5. A flame-retardant cable for rail transit according to claim 2, characterized in that: In step S3, the ratio of the amount of intermediate 1, intermediate 2, and toluene is 36.6 g:48.1 g:150 mL.

6. A flame-retardant cable for rail transit according to claim 2, characterized in that: In step S4, the ratio of the amount of intermediate 3, allyl acetic acid, toluene, dibutyltin oxide, and DCC is 83.9 g: 21.4 g: 300 mL: 0.4 g: 41.2 g.

7. The flame-retardant cable for rail transit according to claim 1, characterized in that: The modified carbon black is prepared by the following steps: N-(4-sulfonic acid phenyl) maleic acid amide is mixed with deionized water, stirred until dissolved, and then carbon black is added. After the water is removed under vacuum, the mixture is placed in a muffle furnace and kept at 180-200° C. for 5-6 hours, taken out, washed, and dried in a drying oven to obtain modified carbon black.

8. A flame-retardant cable for rail transit according to claim 7, characterized in that: The usage ratio of the N-(4-sulfonic acid phenyl) maleic acid amide, deionized water and carbon black is 5.5 g:100 mL:1 g.

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