A flame-retardant cable sheath material and a method for producing the same

Abstract

The present application relates to the technical field of cable, in particular to a kind of flame-retardant cable sheath material and preparation method thereof.The flame-retardant cable sheath material of the present application is prepared from polyvinyl chloride resin, plasticizer, modified magnesium-aluminum hydrotalcite-based flame retardant, stabilizer and lubricant, which innovatively constructs multiple flame-retardant systems by intercalating modified magnesium-aluminum hydrotalcite with bisquinolinium quaternary ammonium salt and benzoylated melamine.The specific preparation includes: synthesizing bisquinolinium quaternary ammonium salt from 2,6-bis(bromomethyl)naphthalene and quinoline, intercalating modified magnesium-aluminum hydrotalcite with quaternary ammonium salt, modifying melamine with benzoyl chloride, preparing composite flame retardant, and two-step banburying and granulating process.This technology solves the problems of poor dispersibility, weak interfacial bonding and insufficient flame-retardant synergy of traditional flame-retardant material fillers, making the product have high mechanical strength and excellent flame retardancy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cables, in particular to a flame-retardant cable sheath material and a preparation method thereof. BACKGROUND

[0002] With the rapid development of power transmission and communication technology, cable sheath materials, as the key components for protecting internal conductors, have increasingly stringent performance requirements. In particular, in special application scenarios such as rail transit, high-rise buildings, and petrochemical industry, cable sheaths not only need to have good mechanical strength and weather resistance, but also must meet strict flame-retardant standards. However, traditional flame-retardant cable sheath materials still face the contradiction between filler dispersibility and interface combination in technical implementation. For example, the compatibility of inorganic fillers with polymer matrices (such as PVC) is poor, which easily leads to filler agglomeration and interface defects, and the filler-matrix interface combined by van der Waals force only depends on physical mixing, which is prone to phase separation under long-term thermal aging or mechanical stress, thereby causing a balance problem between flame-retardant efficiency and mechanical properties.

[0003] Currently, surface-modified fillers such as silane coupling agents are often used for treatment to improve the compatibility of fillers with polymer matrices. For example, the inorganic filler modified magnesium hydroxide in the patent technical document CN115181377A discloses a low-temperature-resistant and anti-cracking high-flame-retardant sheath material, a preparation method thereof, and a cable. However, this method can only improve the surface wettability and cannot solve the problem of interlayer amplification, which still has a certain impact on the mechanical properties of the sheath material.

[0004] Under this background, it is urgent to develop a new type of flame-retardant cable sheath material through molecular structure design and process innovation. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a flame-retardant cable sheath material and a preparation method thereof to solve the technical problems of poor filler dispersibility, weak interface combination, and insufficient flame-retardant synergistic effect in traditional flame-retardant materials.

[0006] To achieve the above purpose, the present application provides a flame-retardant cable sheath material prepared from the following raw materials in parts by weight: 90-100 parts of polyvinyl chloride resin, 20-30 parts of plasticizer, 50-60 parts of modified magnesium-aluminum hydrotalcite-based flame retardant, 5-10 parts of stabilizer, and 1-3 parts of lubricant.

[0007] The preparation steps of the modified magnesium-aluminum hydrotalcite-based flame retardant are as follows:

[0008] S1: Dissolve quinoline and 2,6-bis(bromomethyl)naphthalene in toluene, and reflux at 105-110℃ for 12-14h. After the reaction is completed, cool and stand, separate and purify the product by recrystallization, and dry it in an oven to obtain a bisquinoline quaternary ammonium salt;

[0009] S2: Dissolve the bisquinolinium quaternary ammonium salt in deionized water, stir and disperse uniformly, then add magnesium-aluminum hydrotalcite powder, stir at a constant temperature of 60-90℃ for 1-2h, after the reaction is completed, centrifugal filtration is performed, the obtained precipitate is washed with ethanol for 3 times, and vacuum drying is performed at 60℃ for 12h to obtain modified magnesium-aluminum hydrotalcite;

[0010] S3: Dissolve melamine in N,N-dimethylformamide, then slowly add benzoyl chloride, then warm to 80-84℃, and react for 5-6h, then purify the product and dry at 60℃ to obtain modified melamine;

[0011] S4: Disperse the modified magnesium-aluminum hydrotalcite and the modified magnesium-aluminum hydrotalcite in DMF, ultrasonic dispersion is performed until uniform, then continue to stir for 12-24h, then perform suction filtration, washing and drying on the obtained reaction solution to obtain a modified magnesium-aluminum hydrotalcite-based flame retardant;

[0012] The amount ratio of the quinoline, 2,6-bis(bromomethyl)naphthalene and toluene in step S1 is 2.7-3g:3.1-3.5g:120-150ml;

[0013] The amount ratio of the bisquinolinium quaternary ammonium salt, deionized water and magnesium-aluminum hydrotalcite powder in step S2 is 1-2g:50-100ml:2-10g;

[0014] The amount ratio of the melamine, N,N-dimethylformamide and benzoyl chloride in step S3 is 1-1.5g:20-25g:4-5g;

[0015] The amount ratio of the modified magnesium-aluminum hydrotalcite, the modified magnesium-aluminum hydrotalcite and DMF in step S4 is 3-4g:1-1.5g:200ml.

[0016] Preferably, the polyvinyl chloride resin is SG-3 type.

[0017] Preferably, the plasticizer is one of trioctyl trimellitate and dioctyl adipate.

[0018] Preferably, the stabilizer is a calcium-zinc composite stabilizer.

[0019] Preferably, the lubricant is one of zinc stearate and polyethylene wax.

[0020] Preferably, the magnesium-aluminum hydrotalcite powder in step S2 is Jusheng JS1273.

[0021] Further, the present application also provides a preparation method of the flame-retardant cable sheath material, which comprises the following steps:

[0022] (1) Put the polyvinyl chloride resin and stabilizer into a high-speed mixing cylinder and mix by stirring, when the temperature reaches 50-60℃, add half of the plasticizer, when the temperature reaches 90-95℃, add the remaining plasticizer, stir and heat to 140-145℃, to obtain a PVC premix;

[0023] (2) Put the modified magnesium-aluminum hydrotalcite-based flame retardant, lubricant and PVC premix into a banbury mixer and plasticize, when the temperature rises to 150-160℃, process the pot once, when the banbury temperature reaches 170-175℃, transport the blended mixture to a single screw extruder for extrusion and granulation to obtain a primary granulated material, put the primary granulated material into a banbury mixer and re-banbury to heat to 150-160℃, transport the blended mixture to a single screw extruder for extrusion and granulation to obtain a flame-retardant cable sheath material.

[0024] The beneficial effects of the present application are:

[0025] The present application realizes the optimization of the interface bonding between the filler and the polymer matrix through a specific chemical modification process, so that the material can realize more effective stress transfer and energy dissipation when subjected to external force, thereby exhibiting excellent mechanical strength and impact resistance.

[0026] The present application constructs a multi-scale synergistic flame-retardant system through innovative molecular structure design, introduces a specific structure of flame-retardant component, and the material can play a role in both gas phase and condensed phase when decomposed by heat, this double action mechanism significantly improves the flame-retardant efficiency of the material, so that it can meet higher standards of fire protection.

[0027] The present application realizes the comprehensive improvement of the comprehensive performance of the flame-retardant cable sheath material through innovative material design and process optimization. This technical solution not only meets the current demand for high-performance sheath materials in the cable industry, but also provides a new solution for cable safety protection in special application scenarios. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below with specific examples.

[0029] Example 1: A preparation method of a flame-retardant cable sheath material, the specific steps are as follows:

[0030] (1) Dissolve 2.7g quinoline and 3.1g 2,6-bis(bromomethyl)naphthalene in 120ml toluene, reflux at 105℃ for 12h, after the reaction is completed, cool and stand, separate and purify the product by recrystallization, and dry it in an oven to obtain a bisquinoline quaternary ammonium salt;

[0031] (2) 1 g of bisquinolinium quaternary ammonium salt was dissolved in 50 ml of deionized water, stirred and uniformly dispersed, 2 g of magnesium-aluminum hydrotalcite powder was added, stirred at 60°C for 1 h, after the reaction was completed, centrifugal filtration was carried out, the obtained precipitate was washed with ethanol for 3 times, and vacuum dried at 60°C for 12 h to obtain modified magnesium-aluminum hydrotalcite;

[0032] (3) 1 g of melamine was dissolved in 20 g of N,N-dimethylformamide, then 4 g of benzoyl chloride was slowly added, and then the temperature was increased to 80°C, and reacted for 5 h, the product was purified and dried at 60°C to obtain modified melamine;

[0033] (4) 3 g of modified magnesium-aluminum hydrotalcite and 1 g of modified melamine were dispersed in 200 ml of DMF, uniformly dispersed by ultrasonic dispersion, and then stirred for 12 h, the obtained reaction solution was filtered, washed, dried to obtain a modified magnesium-aluminum hydrotalcite-based flame retardant;

[0034] (5) 90 g of polyvinyl chloride resin and 5 g of calcium-zinc composite stabilizer were put into a high-speed mixing cylinder and stirred and mixed at a speed of 200 rpm, when the temperature rose to 50°C, 10 g of trioctyl trimellitate was added, when the temperature rose to 90°C, the remaining trioctyl trimellitate was added, and the stirring was heated to 140°C to obtain a PVC premix;

[0035] (6) 50 g of modified magnesium-aluminum hydrotalcite-based flame retardant, 1 g of polyethylene wax and PVC premix were put into a banbury mixer for plasticizing, after the temperature rose to 150°C, the kettle was processed once; when the mixing temperature reached 170°C, the obtained mixture was transported to a single screw extruder for extrusion and granulation to obtain a primary granulation material; the primary granulation material was put into a banbury mixer and re-mixed and heated to 150°C, and the obtained mixture was transported to a single screw extruder for extrusion and granulation to obtain a flame-retardant cable sheath material.

[0036] Example 2: a preparation method of a flame-retardant cable sheath material, the specific steps are as follows:

[0037] (1) 2.8 g of quinoline and 3.3 g of 2,6-bis(bromomethyl)naphthalene were dissolved in 140 ml of toluene, and refluxed at 108°C for 13 h, after the reaction was completed, the product was separated and purified by recrystallization, and dried in an oven to obtain bisquinolinium quaternary ammonium salt;

[0038] (2) 1.5 g of bisquinolinium quaternary ammonium salt was dissolved in 70 ml of deionized water, stirred and uniformly dispersed, 6 g of magnesium-aluminum hydrotalcite powder was added, stirred at 75°C for 2 h, after the reaction was completed, centrifugal filtration was carried out, the obtained precipitate was washed with ethanol for 3 times, and vacuum dried at 60°C for 12 h to obtain modified magnesium-aluminum hydrotalcite;

[0039] (3) 1.3 g melamine was dissolved in 23 g N,N-dimethylformamide, then 4.5 g benzoyl chloride was slowly added, and then the temperature was raised to 82°C, and the reaction was carried out for 5 h. The product was purified and dried at 60°C to obtain modified melamine;

[0040] (4) 3.5 g modified magnesium-aluminum hydrotalcite and 1.3 g modified melamine were dispersed in 200 ml DMF, and after ultrasonic dispersion, stirring was continued for 18 h. The obtained reaction solution was subjected to suction filtration, washing, drying to obtain a modified magnesium-aluminum hydrotalcite-based flame retardant;

[0041] (5) 95 g polyvinyl chloride resin and 8 g calcium-zinc composite stabilizer were put into a high-speed mixing cylinder, and stirred and mixed at a speed of 250 rpm. When the temperature rose to 55°C, 12.5 g of trioctyl trimellitate was added. When the temperature rose to 93°C, the remaining trioctyl trimellitate was added. The stirring was heated to 143°C to obtain a PVC premix;

[0042] (6) 55 g modified magnesium-aluminum hydrotalcite-based flame retardant, 2 g polyethylene wax, and PVC premix were put into a banbury mixer for plasticizing. After the temperature rose to 155°C, the pot was treated once. When the banbury temperature reached 172°C, the blended mixture was transported to a single screw extruder for extrusion and granulation to obtain a primary granulated material. The primary granulated material was put into a banbury mixer for re-densification and heating to 155°C. The blended mixture was transported to a single screw extruder for extrusion and granulation to obtain a flame-retardant cable sheath material.

[0043] Example 3: A preparation method of a flame-retardant cable sheath material, the specific steps are as follows:

[0044] (1) 3 g quinoline and 3.5 g 2,6-bis(bromomethyl)naphthalene were dissolved in 150 ml toluene, and refluxed at 110°C for 14 h. After the reaction was completed, the product was separated and purified by recrystallization, and then dried in an oven to obtain a bisquinoline quaternary ammonium salt;

[0045] (2) 2 g bisquinoline quaternary ammonium salt was dissolved in 100 ml deionized water, and after stirring and dispersing uniformly, 10 g magnesium-aluminum hydrotalcite powder was added. The mixture was stirred at 90°C for 2 h. After the reaction was completed, centrifugal filtration was carried out. The obtained precipitate was washed with ethanol for 3 times, and then dried at 60°C under vacuum for 12 h to obtain modified magnesium-aluminum hydrotalcite;

[0046] (3) 1.5 g melamine was dissolved in 25 g N,N-dimethylformamide, then 5 g benzoyl chloride was slowly added, and then the temperature was raised to 84°C, and the reaction was carried out for 6 h. The product was purified and dried at 60°C to obtain modified melamine;

[0047] (4) 4 g modified Mg-Al hydrotalcite and 1.5 g modified melamine were dispersed in 200 ml DMF, after ultrasonic dispersion, stirring was continued for 24 h, the obtained reaction solution was filtered, washed, dried, and a modified Mg-Al hydrotalcite-based flame retardant was obtained;

[0048] (5) 100 g PVC resin and 10 g calcium-zinc composite stabilizer were put into a high-speed mixing cylinder, and stirred and mixed at a speed of 300 rpm. When the temperature rose to 60°C, 15 g of trioctyl trimellitate was added. When the temperature rose to 95°C, the remaining trioctyl trimellitate was added. Stirring and heating to 145°C obtained a PVC premix;

[0049] (6) 60 g modified Mg-Al hydrotalcite-based flame retardant, 3 g polyethylene wax, and PVC premix were put into a banbury mixer for plasticizing. After the temperature rose to 160°C, the pot was processed once. When the banbury temperature reached 175°C, the obtained mixture was transported to a single screw extruder for extrusion and granulation to obtain a primary granulated material. The primary granulated material was put into a banbury mixer for re-plasticizing and heating to 160°C. The obtained mixture was transported to a single screw extruder for extrusion and granulation to obtain a flame-retardant cable sheath material.

[0050] Comparative Example 1: The difference from Example 2 is that 2,6-bis(bromomethyl)naphthalene is replaced by 1,4-dibromobutane, and the specific steps are as follows:

[0051] (1) 2.8 g quinoline and 3.3 g 1,4-dibromobutane were dissolved in 140 ml toluene, and refluxed at 108°C for 13 h. After the reaction was completed, the product was separated and purified by recrystallization, and dried in an oven to obtain a bisquinoline quaternary ammonium salt;

[0052] (2) 1.5 g bisquinoline quaternary ammonium salt was dissolved in 70 ml deionized water, and stirred and dispersed uniformly. Then 6 g Mg-Al hydrotalcite powder was added, and stirred at 75°C for 2 h. After the reaction was completed, centrifugal filtration was performed. The obtained precipitate was washed with ethanol for 3 times, and dried at 60°C under vacuum for 12 h to obtain modified Mg-Al hydrotalcite;

[0053] (3) 1.3 g melamine was dissolved in 23 g N,N-dimethylformamide, then 4.5 g benzoyl chloride was slowly added, and then the temperature was raised to 82°C, and reacted for 5 h. The product was purified and dried at 60°C to obtain modified melamine;

[0054] (4) 3.5 g modified Mg-Al hydrotalcite and 1.3 g modified melamine were dispersed in 200 ml DMF, after ultrasonic dispersion, stirring was continued for 18 h, the obtained reaction solution was filtered, washed, dried, and a modified Mg-Al hydrotalcite-based flame retardant was obtained;

[0055] (5) Put 95 g of polyvinyl chloride resin and 8 g of calcium-zinc composite stabilizer into a high-speed mixing cylinder, and stir and mix at a speed of 250 rpm. When the temperature rises to 55°C, add 12.5 g of trioctyl trimellitate. When the temperature rises to 93°C, add the remaining trioctyl trimellitate. Stir and heat to 143°C to obtain a PVC premix;

[0056] (6) Put 55 g of modified magnesium-aluminum hydrotalcite-based flame retardant, 2 g of polyethylene wax, and the PVC premix into an internal mixer for plasticizing. When the temperature rises to 155°C, perform a first pot scanning treatment. When the internal mixing temperature reaches 172°C, transport the blended mixture to a single-screw extruder for granulation to obtain a first granulation compound. Put the first granulation compound into an internal mixer for re-mixing and heating to 155°C. Transport the blended mixture to a single-screw extruder for granulation to obtain a flame-retardant cable sheath material.

[0057] Comparative Example 2: The difference from Example 2 is that bisquinolinium quaternary ammonium salt is replaced by n-octyl trimethyl ammonium bromide. The specific steps are as follows:

[0058] (1) Dissolve 1.5 g of n-octyl trimethyl ammonium bromide in 70 ml of deionized water, stir and disperse uniformly, then add 6 g of magnesium-aluminum hydrotalcite powder. Stir at 75°C for 2 h. After the reaction is completed, centrifugal filtration is performed. The obtained precipitate is washed with ethanol for 3 times and dried at 60°C under vacuum for 12 h to obtain modified magnesium-aluminum hydrotalcite;

[0059] (1) Dissolve 1.3 g of melamine in 23 g of N,N-dimethylformamide, then slowly add 4.5 g of benzoyl chloride, and then heat to 82°C. React for 5 h. Purify the product and dry at 60°C to obtain modified melamine;

[0060] (2) Disperse 3.5 g of modified magnesium-aluminum hydrotalcite and 1.3 g of modified melamine in 200 ml of DMF. After ultrasonic dispersion, continue stirring for 18 h. The obtained reaction liquid is subjected to suction filtration, washing, and drying to obtain a modified magnesium-aluminum hydrotalcite-based flame retardant;

[0061] (3) Put 95 g of polyvinyl chloride resin and 8 g of calcium-zinc composite stabilizer into a high-speed mixing cylinder, and stir and mix at a speed of 250 rpm. When the temperature rises to 55°C, add 12.5 g of trioctyl trimellitate. When the temperature rises to 93°C, add the remaining trioctyl trimellitate. Stir and heat to 143°C to obtain a PVC premix;

[0062] (4) Put 55 g of modified magnesium-aluminum hydrotalcite-based flame retardant, 2 g of polyethylene wax, and PVC premix into the internal mixer for plasticizing, and when the temperature rises to 155°C, perform the first time of pot scanning; when the internal mixing temperature reaches 172°C, the blended mixture is transported to a single screw extruder for extrusion and granulation to obtain the first granulation compound; the first granulation compound is put into the internal mixer for re-mixing and heating to 155°C, and the blended mixture is transported to a single screw extruder for extrusion and granulation to obtain the flame-retardant cable sheath material.

[0063] Comparative Example 3: The difference from Example 2 is that benzoyl chloride is replaced by isobutyryl chloride, and the specific steps are as follows:

[0064] (1) Dissolve 2.8 g of quinoline and 3.3 g of 2,6-bis(bromomethyl)naphthalene in 140 ml of toluene, and reflux at 108°C for 13 h. After the reaction is completed, cool and stand, separate and purify the product by recrystallization, and dry it in an oven to obtain a bisquinoline quaternary ammonium salt;

[0065] (2) Dissolve 1.5 g of bisquinoline quaternary ammonium salt in 70 ml of deionized water, stir and disperse uniformly, then add 6 g of magnesium-aluminum hydrotalcite powder, and stir at 75°C for 2 h. After the reaction is completed, centrifugal filtration is performed, the obtained precipitate is washed with ethanol for 3 times, and vacuum dried at 60°C for 12 h to obtain a modified magnesium-aluminum hydrotalcite;

[0066] (3) Dissolve 1.3 g of melamine in 23 g of N,N-dimethylformamide, then slowly add 4.5 g of isobutyryl chloride, and then heat to 82°C and react for 5 h. The product is purified and dried at 60°C to obtain a modified melamine;

[0067] (4) Disperse 3.5 g of modified magnesium-aluminum hydrotalcite and 1.3 g of modified melamine in 200 ml of DMF, ultrasonically disperse uniformly, and then continue to stir for 18 h. The obtained reaction liquid is filtered, washed, and dried to obtain a modified magnesium-aluminum hydrotalcite-based flame retardant;

[0068] (5) Put 95 g of polyvinyl chloride resin and 8 g of calcium-zinc composite stabilizer into a high-speed mixing cylinder, and stir and mix at a speed of 250 rpm. When the temperature rises to 55°C, add 12.5 g of trioctyl trimellitate, and when the temperature rises to 93°C, add the remaining trioctyl trimellitate. Stir and heat to 143°C to obtain a PVC premix.

[0069] (6) Put 55 g of modified magnesium-aluminum hydrotalcite-based flame retardant, 2 g of polyethylene wax, and PVC premix into the internal mixer for plasticizing, and when the temperature rises to 155°C, perform a pot cleaning once. When the internal mixing temperature reaches 172°C, the blended mixture is transported to a single screw extruder for extrusion and granulation to obtain a primary granulated material. The primary granulated material is put into the internal mixer for re-mixing and heating to 155°C, and the blended mixture is transported to a single screw extruder for extrusion and granulation to obtain a flame-retardant cable sheath material.

[0070] Comparative Example 4: The difference from Example 2 is that magnesium-aluminum hydrotalcite and melamine are directly added, and the specific steps are as follows:

[0071] (1) Put 95 g of polyvinyl chloride resin and 8 g of calcium-zinc composite stabilizer into a high-speed mixing cylinder and stir and mix at a speed of 250 rpm. When the temperature rises to 55°C, add 12.5 g of trioctyl trimellitate, and when the temperature rises to 93°C, add the remaining trioctyl trimellitate. Stir and heat to 143°C to obtain a PVC premix.

[0072] (2) Put 40.1 g of magnesium-aluminum hydrotalcite, 14.9 g of melamine, 2 g of polyethylene wax, and the PVC premix into the internal mixer for plasticizing, and when the temperature rises to 155°C, perform a pot cleaning once. When the internal mixing temperature reaches 172°C, the blended mixture is transported to a single screw extruder for extrusion and granulation to obtain a primary granulated material. The primary granulated material is put into the internal mixer for re-mixing and heating to 155°C, and the blended mixture is transported to a single screw extruder for extrusion and granulation to obtain a flame-retardant cable sheath material.

[0073] Performance Test

[0074] Tensile properties: According to GB / T 1040.2-2022, standard dumbbell-shaped samples (2 mm thick) were tested using a universal testing machine at a tensile speed of 50 mm / min, and the test standards are shown in Table 1.

[0075] Impact strength: According to GB / T 1843-2008, cantilever beam impact tests were performed, with a sample notch depth of 2 mm and a pendulum energy of 5.5 J. The results were averaged from 10 tests, and the test standards are shown in Table 1.

[0076] Limiting oxygen index (LOI) test: According to GB / T 2406.3-2022, the sheath material obtained in the examples and comparative examples was injection molded into standard samples (size 100 mm x 6.5 mm x 3 mm). During testing, the sample was vertically fixed in the combustion cylinder, and oxygen-nitrogen mixed gas was introduced to ignite the top end of the sample. By adjusting the oxygen concentration, the lowest oxygen concentration required for the sample to burn 50 mm within 30 seconds was determined. Each test was repeated 5 times, and the results were averaged to 0.1%, and the test results are shown in Table 1.

[0077] Vertical burning performance test: The sheath material obtained from the examples and comparative examples was injection molded into a sample with a diameter of 20 mm and a length of 1.5 m according to GB / T 18380.12-2022, which was vertically hung in a burning box, and a propane torch was used to apply flame to the lower end of the sample for 40 s. The test results are shown in Table 1.

[0078] Table 1 Performance test results

[0079]

[0080] Data analysis: The flame-retardant cable sheath material prepared by the present application exhibits excellent comprehensive performance. First, the tensile strength is maintained at a high level of 17.8-18.5 MPa, indicating that the modified magnesium-aluminum hydrotalcite forms a stable interfacial bond with the PVC matrix. Second, the impact resistance is relatively excellent, suggesting that the material can effectively dissipate energy through the slip of nanoscale hydrotalcite layers and the plastic deformation of polymer chains when subjected to dynamic load. Finally, the LOI value is as high as 34.0-35.5% and all pass the V-0 level vertical burning test, reflecting the unique flame-retardant synergistic effect of the naphthalene ring structure of the brominated quaternary ammonium salt and the benzoyl-modified melamine.

[0081] From the performance comparison of Example 2 and Comparative Example 1 in Table 1, it can be seen that the use of 2,6-bis(bromomethyl)naphthalene instead of 1,4-dibromobutane as a raw material results in a significant improvement in both mechanical properties and flame-retardant properties. This significant improvement may be due to the special advantages of the naphthalene ring structure: First, the rigid planar structure and larger molecular size of the naphthalene ring help to form a more stable quaternary ammonium salt intermediate, which has more complete intercalation with magnesium-aluminum hydrotalcite, thereby improving the dispersion and interfacial bonding strength of the filler in the polymer matrix. Second, the conjugated system of the naphthalene ring may enhance the thermal stability of the bromine-based flame retardant. Third, the naphthalene ring structure may produce a synergistic effect with benzoylated melamine through π-π stacking, promoting the formation of a more dense carbon layer. This difference in molecular structure leads to changes in the flame-retardant mechanism, allowing the material to establish a more perfect synergistic barrier system during combustion. At the same time, the steric hindrance effect of the naphthalene ring structure may affect the arrangement and movement of the polymer molecular chain, thereby optimizing the mechanical performance of the material.

[0082] From the performance comparison of Example 2 and Comparative Example 2 in Table 1, it can be seen that the use of bisquinolinium quaternary ammonium salt instead of n-octyl trimethyl ammonium bromide as a modifier makes the material exhibit a certain degree of improvement in mechanical properties, flame retardant properties and the like. This is mainly because, on the one hand, the rigid aromatic ring structure in the bisquinoline molecule can produce stronger binding force with benzoylated melamine through π-π interaction, thereby improving the dispersion state and interfacial bonding strength of the filler in the polymer matrix; at the same time, the larger steric hindrance of the bisquinoline molecule can more effectively expand the interlayer spacing of the hydrotalcite, providing more sufficient space for the insertion of polymer segments, which helps to improve the mechanical properties of the material; on the other hand, the nitrogen atoms in the bisquinoline structure can participate in the free radical capture reaction in the flame retardant process, thereby enhancing the gas phase flame retardant effect and optimizing the carbonization process and thermal stability performance of the material at high temperature.

[0083] From the performance comparison of Example 2 and Comparative Example 3 in Table 1, it can be seen that the use of benzoyl chloride instead of isobutyryl chloride to modify melamine makes the material produce beneficial effects in flame retardant properties and mechanical properties. This may be because the aromatic ring structure of benzoyl group has planar conjugation characteristics, which can produce stronger interaction with benzoylated melamine through π-π stacking, thereby optimizing the dispersion state of the flame retardant in the polymer matrix; at the same time, the conjugated system of benzoyl group can promote the formation of more stable carbon layer during the thermal decomposition of melamine, and this carbon layer structure can more effectively block heat transfer and oxygen diffusion; in addition, the larger steric hindrance of benzoyl group can affect the arrangement of melamine molecules in the polymer network, thereby improving the mechanical property performance of the material.

[0084] From the performance comparison of Example 2 and Comparative Example 4 in Table 1, it can be seen that the functionalization treatment of magnesium-aluminum hydrotalcite and melamine by chemical modification process makes the material produce significant improvement in mechanical properties and flame retardant properties compared to directly physically mixing the two components. This performance difference may be due to the multiple advantages brought by chemical modification: first, the intercalation treatment of bisquinolinium quaternary ammonium salt can effectively expand the interlayer spacing of hydrotalcite, and the benzoylation reaction can introduce active groups on the surface of melamine molecules, and these two modification processes together promote the formation of stronger interfacial interaction between the flame retardant and the polymer matrix; second, chemical modification can change the surface properties of the filler, making its dispersion in the polymer melt optimized, thereby constructing a more uniform three-dimensional network structure; third, the modified components can produce a synergistic effect through chemical bonding or intermolecular forces, promoting the formation of a more dense carbon layer during the thermal decomposition of the material, and through molecular-level structural design, not only the compatibility of the filler and the matrix is improved, but also the thermal decomposition path and carbon layer quality of the flame retardant are optimized, thereby realizing the synergistic improvement of the comprehensive performance of the material.

[0085] Those skilled in the art should understand that the above discussion of any embodiment is only intended to be exemplary in nature and is not intended to suggest that the present application is limited to these examples; under the concept of the present application, the above embodiments or technical features among different embodiments can be combined, steps can be implemented in any order, and there are many other variations of different aspects of the present application as described above, which are not provided in details for the sake of brevity.

Claims

1. A flame-retardant cable jacketing compound characterized by, The modified magnesium-aluminum hydrotalcite-based flame retardant is prepared by the following steps: S1: dissolving quinoline and 2,6-bis(bromomethyl)naphthalene in toluene and reacting at 105-110℃ for 12-14h, separating and purifying the product, and drying to obtain bisquinoline quaternary ammonium salt; S2: dissolving the bisquinoline quaternary ammonium salt in deionized water, adding magnesium-aluminum hydrotalcite powder, and stirring at constant temperature at 60-90℃ for 1-2h, after the reaction is completed, purifying and drying to obtain modified magnesium-aluminum hydrotalcite; S3: mixing melamine, N,N-dimethylformamide and benzoyl chloride, stirring uniformly, then heating to 80-84℃, reacting for 5-6h, purifying and drying the product to obtain modified melamine; S4: dispersing the modified magnesium-aluminum hydrotalcite and the modified melamine in DMF, uniformly ultrasonic dispersing, then continuously stirring for 12-24h, and purifying the product to obtain the modified magnesium-aluminum hydrotalcite-based flame retardant; The amount ratio of the quinoline, 2,6-bis(bromomethyl)naphthalene and toluene in step S1 is 2.7-3g:3.1-3.5g:120-150ml; The amount ratio of the bisquinoline quaternary ammonium salt, deionized water and magnesium-aluminum hydrotalcite powder in step S2 is 1-2g:50-100ml:2-10g; The amount ratio of the melamine, N,N-dimethylformamide and benzoyl chloride in step S3 is 1-1.5g:20-25g:4-5g; The amount ratio of the modified magnesium-aluminum hydrotalcite, modified melamine and DMF in step S4 is 3-4g:1-1.5g:200ml. The PVC resin is SG-3 type.

2. The flame-retardant cable jacket material of claim 1, wherein, The plasticizer is one of trioctyl trimellitate and dioctyl adipate.

3. The flame-retardant cable jacket material of claim 1, wherein The stabilizer is calcium-zinc composite stabilizer.

4. The flame-retardant cable jacket material of claim 1, wherein, The lubricant is one of zinc stearate and polyethylene wax.

5. The flame-retardant cable jacket material of claim 1, wherein, The magnesium-aluminum hydrotalcite powder in step S2 is Jusheng JS1273.

6. The flame-retardant cable jacket material of claim 1, wherein, The method comprises the following steps:

7. A process for the preparation of a flame-retardant cable sheath compound according to any one of claims 1 to 6, characterized in that (1) putting the PVC resin and the stabilizer into a high-speed mixing cylinder, mixing and stirring, when the temperature reaches 50-60℃, adding half of the plasticizer, when the temperature reaches 90-95℃, adding the remaining plasticizer, stirring and heating to 140-145℃ to obtain PVC premix; (2) putting the modified magnesium-aluminum hydrotalcite-based flame retardant, the lubricant and the PVC premix into a banbury mixer to plasticize, when the temperature rises to 150-160℃, processing the pot once, when the banbury temperature reaches 170-175℃, conveying the obtained mixture to a single screw extruder to pelletize to obtain primary pelletized material, putting the primary pelletized material into the banbury mixer to re-mix and heat to 150-160℃, conveying the obtained mixture to a single screw extruder to pelletize to obtain flame-retardant cable sheath material. ​

Images