PVC flame-retardant cable and preparation method thereof

Abstract

This invention discloses a PVC flame-retardant cable and its preparation method, belonging to the field of polymer composite material technology. The preparation method involves mixing a zinc molybdate-zirconia composite flame retardant with polyvinyl chloride, chlorinated polyvinyl chloride, plasticizer, stabilizer, lubricant, and antioxidant in a specific ratio, followed by melt blending and extrusion granulation to obtain the PVC flame-retardant cable. This invention significantly improves the flame-retardant performance, smoke suppression performance, and heat resistance of the cable through the synergistic flame-retardant effect of zinc molybdate and zirconium oxide, as well as a unique core-shell morphology design, making it suitable for high-rise buildings, subways, nuclear power plants, and other locations with high fire safety requirements.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, specifically relating to a PVC flame-retardant cable and its preparation method. Background Technology

[0002] Cables, as a key carrier for electrical energy transmission, are widely used in many fields such as construction, transportation, and energy. With the ever-increasing demands for power supply in modern society, cables not only need to have excellent conductivity but also superior flame-retardant properties to prevent fires.

[0003] Polyvinyl chloride (PVC) is widely used as insulation and sheathing material for wires and cables due to its excellent electrical insulation, corrosion resistance, and cost advantages. However, ordinary PVC cable materials have problems such as rapid flame spread, large smoke release, and release of toxic gases when burned, which seriously threaten personnel safety and equipment operation. To address this technical problem, existing technologies incorporate flame-retardant materials into cable materials to improve their flame-retardant properties. For example, CN121895670A adds ammonium polyphosphate modified with 5-hydroxymethylfurfural and phenylguanidine carbonate as a flame retardant to power cables, improving the flame retardancy of the sheath layer. The modification of ammonium polyphosphate with 5-hydroxymethylfurfural and phenylguanidine carbonate involves the surface hydroxyl and amino groups of the reactants acting on the polyphosphate, improving its dispersibility. Simultaneously, the polyphosphate generated at high temperatures promotes the dehydration and carbonization of the reaction products, fostering char layer formation and releasing ammonia and nitrogen, thus diluting the concentration of oxygen and combustible gases and acting as an oxygen barrier, thereby enhancing the flame retardancy of the sheath layer. However, these organic flame retardants are prone to decomposition or migration at high temperatures, reducing the cable's heat distortion temperature and long-term service temperature. CN103965540B discloses adding aluminum hydroxide and magnesium hydroxide to cable sheaths to improve their flame-retardant properties. However, this method requires a large amount of flame retardant; otherwise, the flame-retardant performance will be insufficient. Furthermore, high-filler content of flame-retardant fillers often severely damages the material's toughness, leading to a significant decrease in its impact resistance and potentially affecting melt flowability, thus increasing processing difficulty. Therefore, developing a PVC-based cable material that combines high flame retardancy with easy processing is of significant practical importance. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art and provide a high flame retardant and low smoke cable material and its preparation method.

[0005] The technical solution is as follows: A method for preparing a flame-retardant PVC cable material is as follows: (1) Dissolve zinc source, molybdenum source, urea and EDTA in ethylene glycol at a molar ratio of 1:1:(2-4):(0.1-0.5), stir evenly and transfer to a microwave reactor for reaction under microwave conditions; after the reaction is completed, cool, centrifuge, wash and dry to obtain zinc molybdate; Specifically, the zinc source is selected from at least one of zinc nitrate, zinc chloride, and zinc acetate; Specifically, the molybdenum source is selected from at least one of sodium molybdate, potassium molybdate, and ammonium molybdate; Specifically, the molar ratio of zinc source to molybdenum source is 1:0.8~1.2, preferably 1:1.

[0006] Specifically, the temperature of the microwave hydrothermal reaction is 140~200℃, and the time is 10~60 minutes.

[0007] (2) Disperse the zinc molybdate obtained in step (1) in a mixed solvent of deionized water and ethylene glycol and ultrasonically disperse it evenly; then add zirconium source and stir evenly; adjust the pH of the system to 8~11 with alkaline solution; transfer the mixture to a hydrothermal reactor and react at 120~200℃ for 6~24 hours; after the reaction is completed, cool, centrifuge, wash, dry, and calcine at 300-500℃ for 1-2 hours.

[0008] Specifically, the zirconium source is selected from at least one of zirconium oxychloride, zirconium nitrate, and zirconium n-propoxide.

[0009] Specifically, the volume ratio of deionized water to ethylene glycol is (8-9):1.

[0010] Specifically, the alkaline solution used to adjust the pH is ammonia.

[0011] The composite flame retardant prepared by the above method has zinc molybdate exhibiting a rod-like structure with a high aspect ratio, and zirconium oxide particles growing on the surface of the rod.

[0012] (3) Weigh the cable material according to the following mass: 50-80 parts of polyvinyl chloride, 10-20 parts of chlorinated polyvinyl chloride, 5-15 parts of zinc molybdate-zirconia composite flame retardant, 10-20 parts of plasticizer, 3-10 parts of stabilizer, 1-5 parts of lubricant, and 1-2 parts of antioxidant; premix the PVC, CPVC and composite flame retardant in a high-speed mixer for 3-5 minutes; add the plasticizer, stabilizer, lubricant and antioxidant, and continue mixing for 5-10 minutes to make the material fully and evenly mixed. The mixing temperature is 80-110℃; add it to a twin-screw extruder for melt blending and extrusion to obtain the cable material.

[0013] Specifically, the plasticizer is at least one of trioctyl trimellitate, dioctyl phthalate, and dioctyl terephthalate.

[0014] Specifically, the stabilizer is an organotin stabilizer or a calcium-zinc composite stabilizer.

[0015] Specifically, the lubricant is at least one of polyethylene wax and oxidized polyethylene wax.

[0016] Specifically, the antioxidant is bisphenol A or a phosphite antioxidant.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention combines high aspect ratio rod-shaped zinc molybdate with nano-zirconia nanoparticles. The rod-shaped zinc molybdate, with its large aspect ratio, readily forms an overlapping network within the polymer matrix, facilitating the construction of a continuous barrier layer. The nano-zirconia particles grow on the rod-shaped surface. In the early stages of combustion, zinc molybdate catalyzes the removal of HCl from polyvinyl chloride (PVC) and chlorinated PVC, promoting cross-linking and char formation, thus reducing aromatic compounds that contribute to black smoke at the source. Zirconia, at high temperatures, promotes the graphitization and ceramization of the char layer, forming a dense and hard protective layer that effectively isolates heat and oxygen transport. The synergistic effect of both significantly reduces the heat release rate and smoke release rate during combustion. Attached Figure Description

[0018] Appendix Figure 1 This is a scanning electron microscope image of the zinc molybdate-zirconia composite material of this application. Detailed Implementation

[0019] The present invention will be further illustrated below through specific embodiments and comparative examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example 1

[0020] Weigh and Dissolved in 50 mL ethylene glycol, 30 mmol urea and 2 mmol EDTA were added and stirred until dissolved. The mixture was transferred to a 100 mL microwave-safe reactor and reacted at 160 °C for 20 minutes. After cooling, it was centrifuged, washed three times each with deionized water and ethanol, and dried under vacuum at 80 °C for 12 hours to obtain rod-shaped zinc molybdate. TEM observation showed that the obtained zinc molybdate was rod-shaped, with a diameter of approximately 30-80 nm and a length of approximately 1.5-3 μm.

[0021] Take the above zinc molybdate and disperse it in a mixed solvent of 80 mL deionized water and 10 mL ethylene glycol, and sonicate for 30 minutes. Add 3 mmol of [unclear - possibly a specific ingredient or solution]. The mixture was stirred and dissolved, and the pH was adjusted to 10 with ammonia. It was then transferred to a 100 mL hydrothermal reactor and reacted at 160°C for 12 hours. After cooling, it was centrifuged, washed with deionized water and ethanol, and dried at 80°C to obtain the zinc molybdate-zirconia composite flame retardant.

[0022] Weigh the following components by weight: 70 parts polyvinyl chloride (PVC), 20 parts chlorinated PVC, 10 parts zinc molybdate-zirconia composite flame retardant, 10 parts dioctyl phthalate (DOP), 5 parts calcium-zinc composite stabilizer, 3 parts polyethylene wax, and 2 parts bisphenol A. Premix the PVC, CPVC, and composite flame retardant in a high-speed mixer for 3 minutes. Add the other components and continue mixing at 100°C for 8 minutes. Add the mixture to a twin-screw extruder for granulation. Extrude the granules to prepare samples for performance testing. Example 2

[0023] The difference from Example 1 is that 8 parts of zinc molybdate-zirconia composite flame retardant were used, while the rest were the same as in Example 1.

[0024] Comparative Example 1 The difference from Example 1 is that the zinc molybdate prepared in Example 1 is used directly to replace the composite flame retardant, while the rest is the same as in Example 1.

[0025] Comparative Example 2 The difference from Example 1 is that the flame retardant is zirconium oxide prepared by the method of Example 1, without the need to introduce zinc molybdate.

[0026] Comparative Example 3 The difference from Example 1 is that urea is not added in step one; instead, KOH is used to adjust the pH to obtain zinc molybdate, and then zirconia is grown according to the method in Example 1. The rest is the same as in Example 1.

[0027] Comparative Example 4 The difference from Example 1 is that EDTA is not added in step one to obtain zinc molybdate, and then zirconia is grown according to the method of Example 1. The rest is the same as in Example 1.

[0028] Comparative Example 5 The difference from Example 1 is that the conventional hydrothermal method is used instead of the microwave reaction method in Example 1, and the hydrothermal temperature is controlled at 160°C and the reaction time is 10 hours. The rest is the same as in Example 1.

[0029] Flame retardant performance test: The limiting oxygen index of the above examples and comparative examples was tested according to GB / T 2406-2009; The smoke density levels of the above examples and comparative examples were tested according to GB / T 8627; The heat distortion temperatures of the above embodiments and comparative examples were tested according to GB / T 1634.2. The performance results are shown in Table 1:

[0030] As shown in Table 1 above, the zinc molybdate-zirconia composite flame retardant prepared by this invention exhibits significant synergistic flame retardant and smoke suppression effects. Example 1 achieved an LOI of 36.2%, a smoke density rating of 44, and a heat distortion temperature as high as 117℃, demonstrating significantly superior overall performance compared to the comparative examples. The structure of the composite flame retardant is crucial for achieving its excellent performance. In Comparative Examples 3-4, the zinc molybdate was granular, while in Comparative Example 5, it was short rod-shaped. Therefore, the addition of urea and EDTA, as well as the microwave-assisted hydrothermal method, are necessary conditions for obtaining the target morphology.

[0031] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the scope of specific implementation methods based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A PVC flame-retardant cable, comprising the following components: 50-80 parts of polyvinyl chloride, 10-20 parts of chlorinated polyvinyl chloride, 5-15 parts of zinc molybdate-zirconia composite flame retardant, 10-20 parts of plasticizer, 3-10 parts of stabilizer, 1-5 parts of lubricant, and 1-2 parts of antioxidant.

2. A process for the preparation of a PVC flame-retardant cable as claimed in claim 1, characterized in that Includes the following steps: Step 1: Dissolve zinc source, molybdenum source, urea and EDTA in ethylene glycol at a molar ratio of 1:1:(2-4):(0.1-0.5), stir well and transfer to a microwave reactor for reaction under microwave conditions; after the reaction is completed, cool, centrifuge, wash and dry to obtain zinc molybdate; Step 2: Disperse the zinc molybdate obtained in Step 1 in a mixed solvent of deionized water and ethylene glycol, and ultrasonically disperse until uniform; add zirconium source and stir until uniform; adjust the pH of the system to 8-11 with alkaline solution; transfer the mixture to a hydrothermal reactor and react at 120-200℃ for 6-24 hours; after the reaction, cool, centrifuge, wash, dry, and calcine at 300-500℃ for 1-2 hours to obtain zinc molybdate-zirconia composite flame retardant; Step 3: Weigh out 50-80 parts of polyvinyl chloride, 10-20 parts of chlorinated polyvinyl chloride, 5-15 parts of zinc molybdate-zirconia composite flame retardant, 10-20 parts of plasticizer, 3-10 parts of stabilizer, 1-5 parts of lubricant, and 1-2 parts of antioxidant by weight. Premix polyvinyl chloride, chlorinated polyvinyl chloride and zinc molybdate-zirconia composite flame retardant in a high-speed mixer for 3-5 minutes; Add plasticizer, stabilizer, lubricant and antioxidant, and continue mixing for 5 to 10 minutes to ensure the material is fully and evenly mixed. The mixing temperature is 80 to 110°C. Add the mixture to a twin-screw extruder for melt blending and extrusion to obtain cable material.

3. The method for preparing PVC flame-retardant cable according to claim 2, characterized in that, In step one, the zinc source is selected from at least one of zinc nitrate, zinc chloride, and zinc acetate; the molybdenum source is selected from at least one of sodium molybdate, potassium molybdate, and ammonium molybdate; the temperature of the microwave hydrothermal reaction is 140~200℃, and the time is 10~60 minutes.

4. The process for the preparation of PVC flame retardant cable as claimed in claim 2, wherein, In step two, the zirconium source is selected from at least one of zirconium oxychloride, zirconium nitrate, and zirconium n-propoxide; the volume ratio of deionized water to ethylene glycol is (8-9):1; and the alkaline solution used to adjust the pH is ammonia.

5. The method for preparing PVC flame-retardant cable according to claim 2, wherein the plasticizer is at least one of trioctyl trimellitate, dioctyl phthalate, and dioctyl terephthalate; the stabilizer is an organotin stabilizer or a calcium-zinc composite stabilizer; the lubricant is at least one of polyethylene wax and oxidized polyethylene wax; and the antioxidant is bisphenol A or a phosphite antioxidant.

6. A cable jacket characterized by, The cable material prepared by any one of claims 2-5 is extruded.

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