Flame-retardant cable for railway

Abstract

The invention discloses a flame-retardant cable for a railway, and belongs to the technical field of railway cables. The cable is composed of a conductor, an insulating layer, a metal shielding layer and a sheath layer which are sequentially arranged from inside to outside. According to the prepared cable, the insulating layer adopts the mica tape, so that the flame retardant property of the cable can be enhanced to a certain extent; the sheath material takes polypropylene as a matrix, so that the cable is endowed with excellent mechanical property and electrical insulation property; the self-made flame retardant is added into the sheath material, and the flame retardant molecules contain various functional groups, so that the flame retardance and the heat resistance of the cable can be greatly enhanced to a certain extent, the performance is long-term and stable, and the cable is not easy to fall off; therefore, the prepared cable is excellent in mechanical property, stable and efficient in flame retardance and heat resistance to a certain degree, free of halogen and phosphorus and environmentally friendly, and has important application value in the technical field of railway cables.

Description

Technical Field

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

[0002] In recent years, with the rapid development of railway transportation, the control of railway systems has become more and more complex, and the number of electrical control devices has increased. The use of railway cables is indispensable in the transmission of railway power. Therefore, the performance requirements for cables are also getting higher and higher.

[0003] The composition of cables can be generally divided into three main structural components: conductors, insulation layers and sheaths, as well as filling components and tensile components. The outermost layer of the cable is protected by the sheath and is in direct contact with the external environment, so the sheath determines whether the performance of the cable is excellent; the current sheath materials mainly include PVC (polyvinyl chloride), PE (polyethylene), PP (polypropylene), rubber, mica tape, etc. Among them, polypropylene has excellent mechanical strength, the highest softening temperature among thermoplastic resins, good low temperature resistance, aging resistance, and wear resistance, and has a high volume resistivity and dielectric strength. It can be recycled and reused, and is a very high-quality cable material.

[0004] In recent years, electrical fire accidents in railway locomotives and vehicles have occurred frequently, and the flame retardant problem of wires and cables has gradually attracted the attention of countries around the world. Ordinary polypropylene materials do not have flame retardancy, so flame retardants are often added to achieve flame retardant effects. However, the commonly used flame retardants on the market are halogen flame retardants. These flame retardants release a large amount of smoke and toxic and corrosive gases when burned, which seriously hinders people's safe evacuation and fire fighting, causing serious losses of life and property. Therefore, it is urgent to invent a halogen-free flame retardant cable for railways to meet the higher demands in the field of railway 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 railways.

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

[0007] A flame-retardant cable for railways is composed of a conductor, an insulating layer, a metal shielding layer and a sheath layer which are arranged in sequence from the inside to the outside.

[0008] Furthermore, the conductor is made of copper wire.

[0009] Furthermore, the material of the insulating layer is mica tape.

[0010] Furthermore, the material of the metal shielding layer is a copper wire braided mesh.

[0011] Furthermore, the material of the sheath layer includes the following raw materials in parts by weight: 80-90 parts of polypropylene resin, 12-18 parts of high-density polyethylene, 0.1-0.3 parts of initiator, 4-6 parts of antioxidant, 5-15 parts of flame retardant, and 3-5 parts of lubricant.

[0012] The prepared sheath material takes polypropylene as a matrix, which gives the sheath material excellent mechanical properties and electrical insulation properties.

[0013] Furthermore, the initiator is one of benzoyl peroxide and lauroyl peroxide.

[0014] Furthermore, the antioxidant is a phosphite antioxidant.

[0015] Furthermore, the processing aid is one of paraffin and zinc stearate.

[0016] Furthermore, the flame retardant is prepared by the following steps:

[0017] A1. Add thionyl chloride to a 150 ml round-bottom flask equipped with a thermometer and a stirring device, place the device at -5 ° C, and add 3-butene-1-ol dropwise. After the addition is completed, stir for 15 min. After the stirring is completed, add L-cystine. Stir the reaction at room temperature for 12 h. After the reaction is completed, concentrate with a rotary evaporator, and then wash with ether 4-5 times to obtain an intermediate;

[0018] Under the catalysis of thionyl chloride, 3-butene-1-ol and L-cystine react to obtain an intermediate; the specific reaction process is as follows:

[0019]

[0020] A2. Add sodium hydroxide to a three-necked round-bottom flask filled with methanol solution, stir and heat to 50°C, stir continuously to dissolve the sodium hydroxide, then add the intermediate, continue stirring to completely dissolve the intermediate, then add glyoxal dropwise until the addition of glyoxal is complete, continue stirring, and heat the device to 70°C, reflux for 6h, and after the reaction is complete, filter, wash the filter residue with anhydrous ethanol, then wash with anhydrous ether, and vacuum dry to obtain a flame retardant;

[0021] Sodium hydroxide is used as a condensation agent, and the amino group in the intermediate molecule condenses with the aldehyde group in the glyoxal molecule to form an imine group (C=N Schiff base structure) to obtain a flame retardant; the specific reaction process is as follows:

[0022]

[0023] Furthermore, in step A1, the ratio of thionyl chloride, 3-butene-1-ol and L-cystine is 7.7 mL:50 mL:24 g.

[0024] Furthermore, in step A2, the ratio of the amount of methanol solution, sodium hydroxide, intermediate, and glyoxal is 100 mL: 4 g: 34.8 g: 5.8 g.

[0025] The flame retardant prepared is a Schiff base macrocyclic compound. Schiff base mainly refers to a compound containing imine or azomethine characteristic groups. Due to its special structure, it can be used as a self-crosslinking unit to form a relatively stable crosslinking network in a lower temperature range. It is considered to be an effective carbonizing agent. The -C=N- double bond of the Schiff base can generate a nitrogen-containing six-atom ring at a higher temperature. These six-atom ring structures enable the polymer to form a stable crosslinking network and give them higher flame retardant properties. At the same time, when the matrix burns, NH 3 Nitrogen-containing non-flammable gases such as sulphuric acid can dilute flammable gases and reduce the oxygen concentration around the material, thereby producing a flame retardant effect on the gas phase. Moreover, since the flame retardant is a macrocyclic compound, it has better heat resistance and stability than ordinary Schiff bases. In addition, the flame retardant molecules also contain sulfur elements and carbon-carbon double bond structures. The introduced sulfur elements 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 synergize with the Schiff base to greatly enhance the flame retardancy of the polypropylene matrix. Finally, the introduction of carbon-carbon double bonds in the flame retardant molecules can produce cross-linking with the matrix under the action of the initiator, which not only further enhances the stability of the flame retardant, but also reduces the influence of the flame retardant on the mechanical properties of the matrix.

[0026] Beneficial effects of the present invention:

[0027] 1. The cable prepared by the present invention uses mica tape as the insulation layer, which can enhance the flame retardant performance of the cable to a certain extent;

[0028] 2. The sheath material is based on polypropylene, which gives the cable excellent mechanical properties and electrical insulation properties;

[0029] 3. Self-made flame retardant is added to the sheath material. The flame retardant molecules contain various functional groups, which can greatly enhance the flame retardancy and heat resistance of the cable to a certain extent. The performance is long-lasting and stable and not easy to fall off;

[0030] Therefore, the cable prepared by the present invention has excellent mechanical properties, stable and efficient flame retardancy and a certain degree of heat resistance, is halogen-free and phosphorus-free, is environmentally friendly, and has important application value in the field of railway cable technology. DETAILED DESCRIPTION

[0031] 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.

[0032] Embodiment 1

[0033] Preparation of flame retardant:

[0034] A1. Add 7.7 mL of thionyl chloride to a 150 mL round-bottom flask equipped with a thermometer and a stirring device, place the device at -5 ° C, and add 50 mL of 3-butene-1-ol dropwise. After the addition is completed, stir for 15 min. After stirring, add 24 g of L-cystine. Stir the reaction at room temperature for 12 h. After the reaction is completed, concentrate with a rotary evaporator, and wash with ether 4-5 times to obtain an intermediate;

[0035] A2. Add 4 g of sodium hydroxide to a three-necked round-bottom flask containing 100 mL of methanol solution, stir and heat to 50 ° C, stir continuously to dissolve the sodium hydroxide, then add 34.8 g of the intermediate, continue stirring to completely dissolve the intermediate, and then add 5.8 g of glyoxal dropwise until the addition of glyoxal is complete, continue stirring, and heat the device to 70 ° C, reflux for 6 hours, and after the reaction is complete, filter, wash the filter residue with anhydrous ethanol, then wash with anhydrous ether, and vacuum dry to obtain a flame retardant.

[0036] Embodiment 2

[0037] Preparation of flame retardant:

[0038] A1. Add 15.4 mL of thionyl chloride to a round-bottom flask equipped with a thermometer and a stirring device, place the device at -5 ° C, and add 100 mL of 3-butene-1-ol dropwise. After the addition is completed, stir for 15 min. After the stirring is completed, add 48 g of L-cystine. Stir the reaction at room temperature for 12 h. After the reaction is completed, concentrate with a rotary evaporator, and wash with ether 4 times to obtain an intermediate;

[0039] A2. Add 8 g of sodium hydroxide to a three-necked round-bottom flask containing 200 mL of methanol solution, stir and heat to 50 ° C, stir continuously to dissolve the sodium hydroxide, then add 69.6 g of the intermediate, continue stirring to completely dissolve the intermediate, and then add 11.6 g of glyoxal dropwise until the addition of glyoxal is complete, continue stirring, and heat the device to 70 ° C, reflux for 6 hours, and after the reaction is complete, filter, wash the filter residue with anhydrous ethanol, then wash with anhydrous ether, and vacuum dry to obtain a flame retardant.

[0040] Embodiment 3

[0041] Preparation of sheath layer materials:

[0042] 80g of polypropylene resin and 12g of high-density polyethylene were placed in a vacuum oven and dried at 100°C for 12h. The dried raw materials, 0.1g of benzoyl peroxide, 4g of antioxidant 168, 5g of the flame retardant 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 a sheath layer material.

[0043] Embodiment 4

[0044] Preparation of sheath layer materials:

[0045] 85g of polypropylene resin and 15g of high-density polyethylene were placed in a vacuum oven and dried at 100°C for 12h. The dried raw materials, 0.2g of lauroyl peroxide, 5g of antioxidant 168, 10g of the flame retardant prepared in Example 1 and 4g of zinc stearate were first added to a mixer and stirred for 30min, and then added to a twin-screw extruder, melt-blended and extruded to obtain a sheath layer material.

[0046] Embodiment 5

[0047] Preparation of sheath layer materials:

[0048] 90 g of polypropylene resin and 18 g of high-density polyethylene were placed in a vacuum oven and dried at 100° C. for 12 h. The dried raw materials, 0.3 g of lauroyl peroxide, 6 g of antioxidant 168, 15 g of the flame retardant prepared in Example 1 and 5 g of zinc stearate 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 a sheath layer material.

[0049] Embodiment 6

[0050] Copper wire is used as a conductor, and mica tape is coated on the conductor to form an insulating layer, and then a copper wire mesh is wrapped around the surface of the insulating layer to form a metal shielding layer; then 90g of polypropylene resin and 18g of high-density polyethylene are placed in a vacuum oven and dried at 100°C for 12h, and the dried raw materials, 0.3g of initiator, 6g of antioxidant 168, 15g of the flame retardant prepared in Example 1 and 5g of lubricant are first added to a mixer and stirred for 30min, and then added to a twin-screw extruder, melt-blended, extruded and coated on the surface of the metal shielding layer to obtain a flame-retardant cable for railways.

[0051] Comparative Example 1

[0052] The flame retardant in Example 5 is replaced by a commercially available halogen-containing flame retardant of equal quality, and the remaining steps are the same as those in Example 5 to obtain a sheath layer material.

[0053] Comparative Example 2

[0054] Commercially available polypropylene cable material was used.

[0055] Embodiments 3, 4, 5, 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:

[0056] The tensile properties are determined using the national standard GB / T 1040.2 "Determination of tensile properties of plastics Part 2: Test conditions for molded and extruded plastics";

[0057] The sample was placed in an environment of 150°C and oxidized with hot air for 48 hours, and then the tensile strength was measured (test standard GB / T1040.2), and the retention rate of tensile strength was calculated; the retention rate of tensile strength = tensile strength after test / tensile strength before test × 100%;

[0058] The smoke density is measured using the national standard GB / T 8323.2 "Plastic smoke generation Part 2: Single chamber method for determination of smoke density test method";

[0059] The limiting oxygen index was determined by using the national standard GB / T 2406 "Test method for combustion performance of plastics"; then Examples 3, 4, 5 and Comparative Example 1 were placed at room temperature for 200 days, and the limiting oxygen index was determined again;

[0060] The measured results are shown in the following table:

[0061]

[0062] It can be seen from the above table that the flame retardancy and heat resistance of the sheath material prepared in the embodiments of the present invention are higher than those of the control example; in addition, in embodiments three to five, as the amount of flame retardant used continues to increase, the flame retardancy and heat resistance of the embodiments are continuously enhanced, and the influence on the mechanical properties is small. Moreover, after standing at room temperature for 200 days, the embodiments can still maintain excellent flame retardancy and stable performance. The use of the sheath material for cables can greatly enhance the performance of the cables. Therefore, the present invention has important application value in the field of railway cable technology.

[0063] 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.

[0064] 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 railway use, which is composed of a conductor, an insulating layer, a metal shielding layer and a sheath layer arranged in sequence from the inside to the outside, characterized in that: The material of the sheath layer includes the following raw materials in parts by weight: 80-90 parts of polypropylene resin, 12-18 parts of high-density polyethylene, 0.1-0.3 parts of initiator, 4-6 parts of antioxidant, 5-15 parts of flame retardant, and 3-5 parts of lubricant.

2. A flame-retardant railway cable according to claim 1, characterized in that: The flame retardant is prepared by the following steps: A1. Add thionyl chloride to a flask, place at -5°C, and add 3-butene-1-ol dropwise. After the addition is complete, stir. After the stirring is complete, add L-cystine. Stir the reaction at room temperature for 12 hours. After the reaction is complete, concentrate and wash to obtain an intermediate. A2. Add sodium hydroxide to a flask containing methanol solution, stir and heat to 50°C, stir continuously to dissolve the sodium hydroxide, then add the intermediate, continue stirring to completely dissolve the intermediate, then add glyoxal dropwise until the addition of glyoxal is complete, continue stirring, reflux at 70°C for 6h, and after the reaction is complete, filter, wash and dry to obtain a flame retardant.

3. A flame-retardant railway cable according to claim 2, characterized in that: In step A1, the ratio of thionyl chloride, 3-butene-1-ol and L-cystine is 7.7 mL:50 mL:24 g.

4. A flame-retardant railway cable according to claim 2, characterized in that: The ratio of the amount of methanol solution, sodium hydroxide, intermediate and glyoxal used in step A2 is 100 mL: 4 g: 34.8 g: 5.8 g.

5. A flame-retardant cable for railway use according to claim 1, characterized in that: The initiator is one of benzoyl peroxide and lauroyl peroxide.

6. A flame-retardant cable for railway use according to claim 1, characterized in that: The antioxidant is a phosphite antioxidant.

7. A flame-retardant cable for railway use according to claim 1, characterized in that: The processing aid is one of paraffin and zinc stearate.

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