Environment-friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable and preparation method thereof

Abstract

The present application relates to the technical field of cable, in particular to an environment-friendly flame-retardant oxidation-resistant chlorinated polyvinyl chloride cable and a preparation method thereof, which comprises the following raw materials: chlorinated polyvinyl chloride, dioctyl terephthalate, nano aluminum hydroxide, composite flame retardant, calcium-zinc stabilizer, epoxy soybean oil and nano clay. In the present application, the composite flame retardant forms an organic-inorganic synergistic core-shell structure in micro-nano scale, hexaphenoxycyclophosphazene provides phosphorus source flame-retardant function, and polyborosilazane forms a borosilicon nitride ceramic network after heat treatment, effectively improving the carbon layer stability and thermal oxidation resistance of the material. Meanwhile, modified silicon dioxide serves as an inorganic skeleton reinforcing phase, improving the dispersibility and interfacial adhesion of the flame retardant in the CPVC matrix. Through the synergistic effect, the flame-retardant efficiency, thermal stability and mechanical strength of the cable material are significantly improved, and the smoke release and toxicity are reduced.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and more specifically, to an environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable and its preparation method. Background Technology

[0002] Chlorinated polyvinyl chloride (CPVC) cables are widely used in high-temperature, flame-retardant power, communication, and construction fields due to their higher chlorine content, excellent heat resistance, flame retardancy, and mechanical strength. However, traditional CPVC cables may still release toxic gases and fumes under high temperature or open flame conditions, and their flame-retardant system and thermal stability still need to be improved. To improve their flame-retardant performance, flame retardants (such as chlorinated paraffins and brominated aromatic hydrocarbons) are often used, but such flame-retardant systems are prone to producing corrosive gases (such as HCl) and carcinogens during combustion, which can cause serious harm to equipment and human health.

[0003] Currently, although flame retardants can improve the flame retardant performance of CPVC to a certain extent, their poor thermal stability leads to a decrease in flame retardant efficiency during processing and use, and also affects the mechanical and insulation properties of the cable. In view of this, we propose an environmentally friendly flame-retardant and antioxidant chlorinated polyvinyl chloride cable and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide an environmentally friendly flame-retardant and antioxidant chlorinated polyvinyl chloride (CPVC) cable and its preparation method, in order to solve the problem mentioned in the background art that although flame retardants can improve the flame retardant performance of CPVC to a certain extent, their poor thermal stability leads to a decrease in flame retardant efficiency during processing and use, and also affects the mechanical and insulation properties of the cable.

[0005] To achieve the above objectives, the present invention provides an environmentally friendly, flame-retardant, and antioxidant chlorinated polyvinyl chloride cable, comprising the following raw materials: chlorinated polyvinyl chloride, dioctyl terephthalate, nano aluminum hydroxide, composite flame retardant, calcium-zinc stabilizer, epoxidized soybean oil, and nano clay. The composite flame retardant is prepared by co-dissolving hexaphenoxycyclotriphosphazene with polyborosilicate and then hybridizing it in situ with modified silica.

[0006] Preferably, the composition includes 70-85 parts by weight of chlorinated polyvinyl chloride, 15-25 parts by weight of dioctyl terephthalate, 20-30 parts by weight of nano aluminum hydroxide, 10-18 parts by weight of composite flame retardant, 3-5 parts by weight of calcium-zinc stabilizer, 4-8 parts by weight of epoxidized soybean oil, and 5-10 parts by weight of nano clay.

[0007] Preferably, the preparation method of the composite flame retardant is as follows: S1.1 Add silica to 95% ethanol at a mass ratio of 1:10; add γ-aminopropyltriethoxysilane and stir at 60℃ and 300-400 rpm for 2-3 hours; filter and dry at 80℃ for 8 hours to obtain modified silica. S1.2 Add hexaphenoxycyclotriphosphazene and polyborosilicate to N,N-dimethylformamide, heat to 110-120℃, stir at 200-300 rpm for 1.5-2 hours, and then sonicate in a sealed container at 200W power for 30 minutes to obtain a 10-20wt% mixed solution. S1.3. Add the mixed solution dropwise to the modified silica emulsion at a rate of 1 mL / min, and stir at a speed of 6000-8000 rpm for 30-60 min. Let it stand to remove bubbles to obtain the hybrid solution. S1.4. The hybrid liquid is pre-crosslinked by heat treatment at 150-170℃ for 2-4 hours under nitrogen atmosphere, and then heat-treated at 300-350℃ for 1-2 hours; cooled to room temperature and vacuum dried at 80℃ for 6-8 hours; and then sieved through a 100-mesh sieve to obtain the composite flame retardant.

[0008] The composite flame retardant is a core-shell hybrid particle, with modified silica as the core and a cross-linked blend of hexaphenoxycyclotriphosphazene and polyborosilicate as the shell; its apparent molecular weight is 2-5 × 10⁻⁵. 4 Da, the average particle size is 0.5-2μm.

[0009] Preferably, in S1.1, the amount of γ-aminopropyltriethoxysilane added accounts for 5-10 wt% of the silicon dioxide.

[0010] Preferably, in S1.2, the mass ratio of hexaphenoxycyclotriphosphazene to polyborosilicate is 1.0-2.0:1.

[0011] Preferably, in step S1.3, the mass ratio of modified silica to the mixed solution is 1:2.0-3.0.

[0012] Preferably, in step S1.3, the modified silica emulsion is prepared by dispersing modified silica in a mixture of N,N-dimethylformamide and ethanol, and sonicating for 30 minutes to obtain a modified silica emulsion with a concentration of 5 wt%; the volume ratio of N,N-dimethylformamide to ethanol is 7:3.

[0013] On the other hand, the present invention provides a method for preparing an environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable, which is used to produce the above-mentioned environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable, comprising the following steps: S2.1 Weigh the following raw materials in parts by weight: 70-85 parts by weight of chlorinated polyvinyl chloride, 15-25 parts by weight of dioctyl terephthalate, 20-30 parts by weight of nano aluminum hydroxide, 10-18 parts by weight of composite flame retardant, 3-5 parts by weight of calcium-zinc stabilizer, 4-8 parts by weight of epoxidized soybean oil and 5-10 parts by weight of nano clay. S2.2 Add chlorinated polyvinyl chloride and calcium-zinc stabilizer to a high-speed mixer and mix at 300-400 rpm for 3-5 minutes at 60°C to obtain a dry mixture; Dioctyl terephthalate and epoxidized soybean oil are heated to 50°C, and a composite flame retardant is added and stirred at 500-600 rpm until a paste is formed, thus obtaining a plasticizer paste. Add the plasticizer paste to the dry mix, heat to 90°C and mix at 1200 rpm for 8-12 minutes. Add activated nano aluminum hydroxide and nano clay, and continue mixing until the material temperature reaches 110°C to obtain the mixture. S2.3. The mixture is extruded through a twin-screw extruder to obtain a melt; the melt is then water-cooled after being extruded through a coat hanger-type die, with a cooling water temperature of 18-22℃ and a vacuum sizing pressure of 0.08-0.12MPa, to obtain an environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable.

[0014] Preferably, in step S2.2, the activated nano-aluminum hydroxide is obtained by adding nano-aluminum hydroxide and 3-(2,3-epoxypropoxy)propyltrimethoxysilane to anhydrous ethanol at a mass ratio of 1:0.02, ultrasonically dispersing for 30 min, and drying at 80°C; the solid-liquid ratio of nano-aluminum hydroxide to anhydrous ethanol is 1:5.

[0015] Preferably, in S2.3, the twin-screw extrusion temperature parameters are: zone 1 160-165℃, zone 2 170-175℃, zone 3 175-180℃, zone 4 175-180℃, and die head 175-180℃; the screw speed is 200-250 rpm.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride (CPVC) cable and its preparation method are described. The composite flame retardant forms an organic-inorganic synergistic core-shell structure at the micro-nano scale. Hexaphenoxycyclotriphosphazene provides the phosphorus source for flame retardancy. Polyboronsilazane forms a borosilicate-nitrogen ceramic network after heat treatment, effectively improving the carbon layer stability and thermal oxidation resistance of the material. Simultaneously, modified silica serves as an inorganic skeleton reinforcing phase, improving the dispersion and interfacial adhesion of the flame retardant in the CPVC matrix. Through this synergistic effect, the flame retardant efficiency, thermal stability, and mechanical strength of the cable material are significantly improved, while reducing smoke release and toxicity. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention provides an environmentally friendly, flame-retardant, and antioxidant chlorinated polyvinyl chloride cable, comprising the following raw materials: chlorinated polyvinyl chloride, dioctyl terephthalate, nano aluminum hydroxide, composite flame retardant, calcium-zinc stabilizer, epoxidized soybean oil, and nano clay. The composite flame retardant is prepared by co-dissolving hexaphenoxycyclotriphosphazene with polyborosilicate and then hybridizing it in situ with modified silica.

[0019] Hexaphenoxycyclotriphosphazene CAS: 1184-10-7, purchased from Hubei Zhenbo Chemical Co., Ltd.

[0020] Polyborosilazane CAS: 475645-84-2, purchased from Zhengzhou Huiju Chemical Co., Ltd.

[0021] γ-aminopropyltriethoxysilane, CAS: 919-30-2, purchased from Hubei Xinkang Pharmaceutical Chemical Co., Ltd.

[0022] Silica CAS: 14808-60-7, purchased from Anhui Kerun Nanotechnology Co., Ltd.

[0023] 3-(2,3-epoxypropoxy)propyltrimethoxysilane (CAS: 2530-83-8), dioctyl terephthalate (CAS: 6422-86-2), and epoxidized soybean oil (CAS: 8013-07-8) were all purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0024] Chlorinated polyvinyl chloride (PVC) CAS: 68648-82-8, purchased from Wuhan Jiyesheng Chemical Co., Ltd.

[0025] Nano aluminum hydroxide (CAS: 21645-51-2, purity ≥99.8%, particle size 50-80nm) was purchased from Shanghai Yubo Biotechnology Co., Ltd.

[0026] The nano-clay is natural montmorillonite, purchased from Zhejiang Fenghong Clay Chemical Co., Ltd.

[0027] The calcium-zinc stabilizer is a calcium-zinc composite stabilizer, model 619WII, purchased from Jiangxi Hongyuan Chemical Co., Ltd.

[0028] The activated nano-aluminum hydroxide was obtained by adding nano-aluminum hydroxide and 3-(2,3-epoxypropoxy)propyltrimethoxysilane to anhydrous ethanol at a mass ratio of 1:0.02, ultrasonically dispersing for 30 min, and drying at 80°C; the solid-liquid ratio of nano-aluminum hydroxide to anhydrous ethanol was 1:5.

[0029] The modified silica emulsion is obtained by dispersing modified silica in a mixture of N,N-dimethylformamide and ethanol, and sonicating for 30 minutes to obtain a modified silica emulsion with a concentration of 5 wt%; the volume ratio of N,N-dimethylformamide to ethanol is 7:3.

[0030] Example 1: A method for preparing an environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable, comprising the following steps: S2.1 Weigh the following raw materials by weight: 70 parts chlorinated polyvinyl chloride, 15 parts dioctyl terephthalate, 20 parts nano aluminum hydroxide, 10 parts composite flame retardant, 3 parts calcium zinc stabilizer, 4 parts epoxidized soybean oil and 5 parts nano clay. S2.2 Add chlorinated polyvinyl chloride and calcium-zinc stabilizer to a high-speed mixer and mix at 400 rpm for 5 minutes at 60°C to obtain a dry mixture; Dioctyl terephthalate and epoxidized soybean oil were heated to 50°C, and a composite flame retardant was added and stirred at 600 rpm until a paste was formed, thus obtaining a plasticizer paste. Add the plasticizer paste to the dry mix, heat to 90°C and mix at 1200 rpm for 12 minutes. Add activated nano aluminum hydroxide and nano clay, and continue mixing until the material temperature reaches 110°C to obtain the mixture. S2.3. The mixture is extruded through a twin-screw extruder with the following temperature parameters: Zone 1 160℃, Zone 2 170℃, Zone 3 175℃, Zone 4 175℃, Die 175℃, and screw speed 250 rpm to obtain a melt. The melt is then water-cooled after being extruded through a coat hanger-type die with a cooling water temperature of 20℃ and a vacuum sizing pressure of 0.1 MPa to obtain an environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable.

[0031] The preparation method of the composite flame retardant is as follows: S1.1 Add silica to 95% ethanol at a mass ratio of 1:10; add γ-aminopropyltriethoxysilane at 5 wt% of silica, stir at 60°C and 400 rpm for 3 h; filter and dry at 80°C for 8 h to obtain modified silica. S1.2 Add hexaphenoxycyclotriphosphazene and polyborosilicate (mass ratio 1.0:1) to N,N-dimethylformamide, heat to 120°C, stir at 300 rpm for 2 h, and then sonicate in a sealed container at 200 W for 30 min to obtain a 10 wt% mixed solution. S1.3. The mixed solution is added dropwise to the modified silica emulsion (mass ratio 2.0:1) at a rate of 1 mL / min, and stirred at 6000 rpm for 60 min. After standing to remove bubbles, the hybrid solution is obtained. S1.4. The hybrid liquid is pre-crosslinked by heat treatment at 170°C for 4 hours under nitrogen atmosphere, and then heat-treated at 350°C for 2 hours; cooled to room temperature and vacuum dried at 80°C for 8 hours; and then sieved through a 100-mesh sieve to obtain the composite flame retardant.

[0032] Example 2: A method for preparing an environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable, comprising the following steps: S2.1 Weigh the following raw materials by weight: 85 parts chlorinated polyvinyl chloride, 25 parts dioctyl terephthalate, 30 parts nano aluminum hydroxide, 18 parts composite flame retardant, 5 parts calcium zinc stabilizer, 8 parts epoxidized soybean oil and 10 parts nano clay. S2.2 Add chlorinated polyvinyl chloride and calcium-zinc stabilizer to a high-speed mixer and mix at 400 rpm for 5 minutes at 60°C to obtain a dry mixture; Dioctyl terephthalate and epoxidized soybean oil were heated to 50°C, and a composite flame retardant was added and stirred at 600 rpm until a paste was formed, thus obtaining a plasticizer paste. Add the plasticizer paste to the dry mix, heat to 90°C and mix at 1200 rpm for 12 minutes. Add activated nano aluminum hydroxide and nano clay, and continue mixing until the material temperature reaches 110°C to obtain the mixture. S2.3. The mixture is extruded through a twin-screw extruder with the following temperature parameters: Zone 1 160℃, Zone 2 170℃, Zone 3 175℃, Zone 4 175℃, Die 175℃, and screw speed 250 rpm to obtain a melt. The melt is then water-cooled after being extruded through a coat hanger-type die with a cooling water temperature of 20℃ and a vacuum sizing pressure of 0.1 MPa to obtain an environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable.

[0033] The preparation method of the composite flame retardant is as follows: S1.1 Add silica to 95% ethanol at a mass ratio of 1:10; add γ-aminopropyltriethoxysilane at 10wt% of silica, and stir at 60℃ and 400rpm for 3h; filter and dry at 80℃ for 8h to obtain modified silica. S1.2 Add hexaphenoxycyclotriphosphazene and polyborosilicate (mass ratio 2.0:1) to N,N-dimethylformamide, heat to 120°C, stir at 300 rpm for 2 h, and then sonicate in a sealed container at 200 W for 30 min to obtain a 20 wt% mixed solution. S1.3. The mixed solution is added dropwise to the modified silica emulsion (mass ratio 3.0:1) at a rate of 1 mL / min, and stirred at 6000 rpm for 60 min. After standing to remove bubbles, the hybrid solution is obtained. S1.4. The hybrid liquid is pre-crosslinked by heat treatment at 170°C for 4 hours under nitrogen atmosphere, and then heat-treated at 350°C for 2 hours; cooled to room temperature and vacuum dried at 80°C for 8 hours; and then sieved through a 100-mesh sieve to obtain the composite flame retardant.

[0034] Example 3: A method for preparing an environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable, comprising the following steps: S2.1 Weigh the following raw materials by weight: 78 parts chlorinated polyvinyl chloride, 20 parts dioctyl terephthalate, 25 parts nano aluminum hydroxide, 14 parts composite flame retardant, 4 parts calcium zinc stabilizer, 6 parts epoxidized soybean oil and 7 parts nano clay. S2.2 Add chlorinated polyvinyl chloride and calcium-zinc stabilizer to a high-speed mixer and mix at 400 rpm for 5 minutes at 60°C to obtain a dry mixture; Dioctyl terephthalate and epoxidized soybean oil were heated to 50°C, and a composite flame retardant was added and stirred at 600 rpm until a paste was formed, thus obtaining a plasticizer paste. Add the plasticizer paste to the dry mix, heat to 90°C and mix at 1200 rpm for 12 minutes. Add activated nano aluminum hydroxide and nano clay, and continue mixing until the material temperature reaches 110°C to obtain the mixture. S2.3. The mixture is extruded through a twin-screw extruder with the following temperature parameters: Zone 1 160℃, Zone 2 170℃, Zone 3 175℃, Zone 4 175℃, Die 175℃, and screw speed 250 rpm to obtain a melt. The melt is then water-cooled after being extruded through a coat hanger-type die with a cooling water temperature of 20℃ and a vacuum sizing pressure of 0.1 MPa to obtain an environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable.

[0035] The preparation method of the composite flame retardant is as follows: S1.1 Add silica to 95% ethanol at a mass ratio of 1:10; add γ-aminopropyltriethoxysilane at 8 wt% of silica, and stir at 60°C and 400 rpm for 3 h; filter and dry at 80°C for 8 h to obtain modified silica. S1.2 Add hexaphenoxycyclotriphosphazene and polyborosilicate (mass ratio 1.5:1) to N,N-dimethylformamide, heat to 120°C, stir at 300 rpm for 2 h, and then sonicate in a sealed container at 200 W for 30 min to obtain a 15 wt% mixed solution. S1.3. The mixed solution is added dropwise to the modified silica emulsion (mass ratio of 2.5:1) at a rate of 1 mL / min, and stirred at 6000 rpm for 60 min. After standing to remove bubbles, the hybrid solution is obtained. S1.4. The hybrid liquid is pre-crosslinked by heat treatment at 170°C for 4 hours under nitrogen atmosphere, and then heat-treated at 350°C for 2 hours; cooled to room temperature and vacuum dried at 80°C for 8 hours; and then sieved through a 100-mesh sieve to obtain the composite flame retardant.

[0036] Mechanical property testing: A dumbbell-shaped specimen (1-2 mm thick, 25 mm gauge length) is cut from the cable. The clamping distance of the testing machine is 50 mm, and the tensile rate is 250 mm / min. The initial thickness and width of the specimen are measured, and the cross-sectional area is calculated. The specimen is clamped in the testing machine fixture, and the testing machine is started until the specimen breaks. The maximum force (F) and the gauge length at break (L1) are recorded. The tensile strength (MPa) is calculated according to the formula: F / cross-sectional area, and the elongation at break (%) is calculated as: [(L1-initial gauge length) / initial gauge length]×100%. A higher tensile strength indicates that the cable material has strong resistance to tensile fracture and is suitable for scenarios that require mechanical stress.

[0037] Oxygen Index (LOI) determination: A 100mm×10mm×3mm sample is vertically fixed in the center of the combustion chamber. The oxygen / nitrogen gas mixing ratio is adjusted, and the sample is ignited from the top. If the sample burns for more than 3 minutes or the burning length exceeds 50mm, it is considered to be able to maintain combustion. By adjusting the gas ratio, the minimum oxygen concentration required to maintain combustion is measured, which is the oxygen index (LOI). The calculation formula is LOI = oxygen flow rate / (nitrogen flow rate + oxygen flow rate) × 100%.

[0038] UL-94 flame retardancy rating determination: Hold the 125mm×13mm×3mm sample vertically, ignite the bottom of the sample for 10 seconds, and then remove the flame source; record the first flame extinguishing time (t1); ignite again for 10 seconds and record the second extinguishing time (t2); at the same time, observe whether molten droplets ignite the cotton and whether it continues to burn; repeat the test on 5 samples and rate them.

[0039] Determination of carbon residue: Place 5-10 mg of sample in nitrogen gas and heat from room temperature to 700℃, with a heating rate of 10℃ / min. Record the mass change of the sample during the heating process. When the temperature reaches 700℃ and is kept constant, record the remaining mass. The percentage of the remaining mass relative to the initial mass is the carbon residue.

[0040] The environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cables prepared in Examples 1-3 above were tested, and the performance data of the environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cables are shown in Table 1: Table 1 Performance data of environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cables in Examples 1-3 Example 1 33.9 V-0 23.1 422 45.7 Example 2 34.2 V-0 23.5 428 46.0 Example 3 34.7 V-0 23.7 437 46.3 Based on the above test experiments, Example 3 is considered the optimal example. Example 4: The difference between this example and Example 3 is that the mass ratio of the mixed solution to the modified silica emulsion is 3.0:1.

[0041] Example 5: The difference between this example and Example 3 is that the mass ratio of the mixed solution to the modified silica emulsion is 3.5:1.

[0042] Example 6: The difference between this example and Example 3 is that the amount of γ-aminopropyltriethoxysilane added is 10 wt%.

[0043] Example 7: The difference between this example and Example 3 is that the amount of γ-aminopropyltriethoxysilane added is 12wt%.

[0044] Example 8: The difference between this example and Example 3 is that the mass ratio of hexaphenoxycyclotriphosphazene and polyborosilicate is 2.0:1.

[0045] Example 9: The difference between this example and Example 3 is that the mass ratio of hexaphenoxycyclotriphosphazene and polyborosilicate is 2.5:1.

[0046] Comparative Example 1: The difference between this example and Example 3 is that no composite flame retardant was added.

[0047] Comparative Example 2: The difference between this example and Example 3 is that no composite flame retardant was added, and hexaphenoxycyclotriphosphazene was added directly.

[0048] Comparative Example 3: The difference between this example and Example 3 is that the silica in the composite flame retardant was not modified.

[0049] Comparative Example 4: The difference between this example and Example 3 is that no composite flame retardant was added, and polyborosilicate was added directly.

[0050] Table 2 Performance data of cables in Examples 3-9 and Comparative Examples 1-4 Example 3 34.7 V-0 23.7 437 46.3 Example 4 34.2 V-0 23.4 426 46.1 Example 5 33.6 V-0 22.4 408 45.1 Example 6 34.0 V-0 22.9 421 45.6 Example 7 33.1 V-0 22.2 392 44.8 Example 8 34.1 V-0 23.0 423 45.4 Example 9 33.3 V-0 22.5 394 44.2 Comparative Example 1 25.3 V-2 13.9 293 21.2 Comparative Example 2 28.1 V-1 17.2 325 24.9 Comparative Example 3 26.4 V-2 15.4 309 23.6 Comparative Example 4 27.6 V-1 16.1 328 24.8 Comparing Examples 3, 4, and 5, it can be seen that as the mass ratio of the mixed solution to the modified silica emulsion increases, the oxygen index of the cable decreases from 34.7% to 33.6%, the carbon residue decreases from 23.7% to 22.4%, the tensile strength decreases from 46.3 MPa to 45.1 MPa, and the elongation at break also decreases from 437% to 408%. This is because an increased mass ratio means a relative increase in the organic phase (i.e., the co-solution system of hexaphenoxycyclotriphosphazene and polyborosilicate), while the inorganic phase (i.e., modified SiO2) decreases. 2) The relative reduction leads to a poorer coating effect of inorganic components in the composite flame retardant, resulting in an incomplete core-shell structure and a reduced degree of hybridization, thereby weakening the shielding and char-forming effects of the flame retardant. At the same time, as a rigid inorganic particle, SiO2 has a certain reinforcing effect in the composite material, and a decrease in its content will also lead to a decrease in mechanical properties. When the mass ratio exceeds 3.0 (Example 5), excess hexaphenoxycyclotriphosphazene is coated on the surface of SiO2, hindering the interfacial reaction between PBSZ and SiO2, resulting in a discontinuous ceramic network and a decrease in flame retardant efficiency.

[0051] In Examples 3, 6, and 7, as the amount of γ-aminopropyltriethoxysilane (KH-550) added increased, the cable performance gradually decreased. The oxygen index decreased from 34.7% to 33.1%, the char residue decreased from 23.7% to 22.2%, the tensile strength decreased from 46.3 MPa to 44.8 MPa, and the elongation at break decreased from 437% to 392%. The main reason is that KH-550, as a silane coupling agent, can effectively improve the interfacial compatibility between silica and organic flame retardant components when added in appropriate amounts, promote the formation of core-shell structures, enhance its dispersibility and interfacial bonding strength in the CPVC matrix, and thus improve flame retardancy and mechanical properties. However, when the amount added is excessive (Example 7), the excess KH-550 will form a hydrophobic organic layer on the surface, hindering subsequent hybridization reactions and leading to a decrease in emulsion stability. In addition, the amine and ethoxy groups in KH-550 undergo side reactions at high temperatures, producing unstable small molecules that affect the thermal stability and flame retardant properties of the material.

[0052] The comparison between Examples 3, 8, and 9 shows that as the relative proportion of hexaphenoxycyclotriphosphazene increases, the oxygen index gradually decreases from 34.7% to 33.3%, the char residue decreases from 23.7% to 22.5%, and the tensile strength also decreases from 46.3 MPa to 44.2 MPa. This is because hexaphenoxycyclotriphosphazene, as a phosphorus-containing gas-phase flame retardant, mainly releases P / O free radicals for gas-phase flame retardancy during high-temperature decomposition. However, excessive hexaphenoxycyclotriphosphazene can lead to an overabundance of gas-phase flame-retardant components in the system. In addition, the high proportion of polyborosilazane (PBSZ) sacrifices its role in condensed phase char formation and heat insulation. Furthermore, hexaphenoxycyclotriphosphazene is prone to migration and precipitation at processing temperatures, resulting in uneven distribution in the matrix, which affects flame retardant efficiency and long-term processing stability. PBSZ, on the other hand, is a condensed phase flame retardant rich in borosilicate nitrogen structure, which can form a dense char layer and improve char residue during combustion. When its proportion is insufficient, its synergistic contribution to flame retardancy and heat resistance is weakened, making it difficult to fully realize the performance advantages of composite flame retardants in CPVC.

[0053] Comparative Example 1, without the addition of composite flame retardant, had an oxygen index of only 25.3%, a char residue of only 13.9%, an elongation at break of 293%, and a tensile strength of 21.2 MPa, far lower than the performance indicators of other examples. This indicates that CPVC, without the addition of flame retardant additives, has very limited flame retardancy and thermal stability, and is a typical combustible polymer. When it burns, it produces a large number of molten droplets and toxic gases, which can easily cause a fire. The low char residue indicates that its pyrolysis process cannot form a stable char layer, lacking thermal shielding and oxygen barrier effects. The main reason for the decline in mechanical properties is that no functional inorganic filler (such as SiO2) or reinforcing structure was added. The intermolecular forces of the system itself are weak, making it susceptible to thermal degradation during processing and causing severe chain breakage. In addition, the lack of a network structure due to the absence of flame retardant also leads to a loose molecular arrangement, which in turn affects the tensile strength and ductility of the material.

[0054] Comparative Example 2 introduced hexaphenoxycyclotriphosphazene as a flame retardant into the CPVC matrix, which increased its oxygen index to 28.1%, char residue to 17.2%, elongation at break to 325%, and tensile strength to 24.9 MPa. Hexaphenoxycyclotriphosphazene is a typical phosphorus-containing organic gas-phase flame retardant, which mainly relies on thermal decomposition to release PO· free radicals, inhibiting chain reactions in the early stages of combustion. In addition, without the dispersion and synergistic effect of inorganic particles such as SiO2, hexaphenoxycyclotriphosphazene is prone to agglomeration or precipitation in the CPVC matrix, failing to fully exert its effect and instead causing a decrease in the thermal stability of the system. In terms of mechanical properties, hexaphenoxycyclotriphosphazene itself is a small molecule, and excessive addition can easily have a plasticizing effect, leading to a decrease in intermolecular bonding forces, thereby reducing the tensile strength and elongation of the material.

[0055] In Comparative Example 3, the SiO2 was not modified with KH-550, resulting in an oxygen index of 26.4%, a char residue of 15.4%, an elongation at break of 309%, and a tensile strength of 23.6 MPa. The core reason for its performance degradation is that unmodified silica is a hydrophilic particle with poor surface activity, exhibiting extremely poor dispersibility in organic systems and readily agglomerating. Agglomerated SiO2 particles not only fail to uniformly coat the organic flame retardant but also form microscopic defects, affecting the interfacial bonding force of the composite material and ultimately leading to a significant decrease in mechanical properties. Simultaneously, a stable core-shell structure cannot be formed, and there is a lack of interfacial bonding between hexaphenoxycyclotriphosphazene and polyborosilazane and SiO2, resulting in an incomplete composite flame retardant structure and consequently reduced flame retardant performance.

[0056] Comparative Example 4 only added PBSZ (polyborosilicate), with an oxygen index of 27.6%, char residue of 16.1%, elongation at break of 328%, and tensile strength of 24.8 MPa. PBSZ is a typical condensed-phase flame retardant, which can generate a porous char layer during pyrolysis, helping to isolate oxygen and heat and improve char residue. However, due to the lack of gas-phase flame retardant synergy with hexaphenoxycyclotriphosphazene, it cannot effectively inhibit free radical diffusion in the early stage of combustion. At the same time, PBSZ undergoes a thermal cross-linking process at high temperatures. If it is added directly to CPVC without sufficient dispersion and coating, it will lead to discontinuous char formation due to poor dispersibility, affecting the thermal insulation effect. In terms of mechanical properties, the macromolecular structure of PBSZ has limited effect on enhancing the rigidity of the system, and it is prone to interfacial discontinuity when a core-shell structure is not formed, which reduces mechanical performance.

[0057] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable, characterized in that, The ingredients include: chlorinated polyvinyl chloride, dioctyl terephthalate, nano aluminum hydroxide, composite flame retardant, calcium-zinc stabilizer, epoxidized soybean oil, and nano clay. The composite flame retardant is prepared by co-dissolving hexaphenoxycyclotriphosphazene with polyborosilicate and then hybridizing it in situ with modified silica. The composition includes 70-85 parts by weight of chlorinated polyvinyl chloride, 15-25 parts by weight of dioctyl terephthalate, 20-30 parts by weight of nano aluminum hydroxide, 10-18 parts by weight of composite flame retardant, 3-5 parts by weight of calcium zinc stabilizer, 4-8 parts by weight of epoxidized soybean oil, and 5-10 parts by weight of nano clay. The preparation method of the composite flame retardant is as follows: S1.1 Add silica to 95% ethanol at a mass ratio of 1:10; add γ-aminopropyltriethoxysilane and stir at 60℃ and 300-400 rpm for 2-3 hours; filter and dry at 80℃ for 8 hours to obtain modified silica. S1.2 Add hexaphenoxycyclotriphosphazene and polyborosilicate to N,N-dimethylformamide, heat to 110-120℃, stir at 200-300 rpm for 1.5-2 hours, and then sonicate in a sealed container at 200W power for 30 minutes to obtain a 10-20wt% mixed solution. S1.

3. Add the mixed solution dropwise to the modified silica emulsion at a rate of 1 mL / min, and stir at a speed of 6000-8000 rpm for 30-60 min. Let it stand to remove bubbles to obtain the hybrid solution. S1.

4. The hybrid liquid is pre-crosslinked by heat treatment at 150-170℃ for 2-4 hours under nitrogen atmosphere, and then heat-treated at 300-350℃ for 1-2 hours; cooled to room temperature and vacuum dried at 80℃ for 6-8 hours; and then sieved through a 100-mesh sieve to obtain the composite flame retardant. In step S1.2, the mass ratio of hexaphenoxycyclotriphosphazene to polyborosilicate is 1.0-2.0:1; in step S1.3, the mass ratio of modified silica to the mixed solution is 1:2.0-3.

0.

2. The environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable according to claim 1, characterized in that, In S1.1, the amount of γ-aminopropyltriethoxysilane added accounts for 5-10 wt% of the silicon dioxide.

3. The environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable according to claim 1, characterized in that, In step S1.3, the modified silica emulsion is prepared by dispersing modified silica in a mixture of N,N-dimethylformamide and ethanol, and sonicating for 30 minutes to obtain a modified silica emulsion with a concentration of 5 wt%; the volume ratio of N,N-dimethylformamide to ethanol is 7:

3.

4. A method for preparing an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable, used to manufacture the environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable as described in any one of claims 1-3, characterized in that, The preparation method of the environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable is as follows: S2.1 Weigh the following raw materials in parts by weight: 70-85 parts by weight of chlorinated polyvinyl chloride, 15-25 parts by weight of dioctyl terephthalate, 20-30 parts by weight of nano aluminum hydroxide, 10-18 parts by weight of composite flame retardant, 3-5 parts by weight of calcium-zinc stabilizer, 4-8 parts by weight of epoxidized soybean oil and 5-10 parts by weight of nano clay. S2.2 Add chlorinated polyvinyl chloride and calcium-zinc stabilizer to a high-speed mixer and mix at 300-400 rpm for 3-5 minutes at 60°C to obtain a dry mixture; Dioctyl terephthalate and epoxidized soybean oil are heated to 50°C, and a composite flame retardant is added and stirred at 500-600 rpm until a paste is formed, thus obtaining a plasticizer paste. Add the plasticizer paste to the dry mix, heat to 90°C and mix at 1200 rpm for 8-12 minutes. Add activated nano aluminum hydroxide and nano clay, and continue mixing until the material temperature reaches 110°C to obtain the mixture. In S2.2, activated nano-aluminum hydroxide is obtained by adding nano-aluminum hydroxide and 3-(2,3-epoxypropoxy)propyltrimethoxysilane to anhydrous ethanol at a mass ratio of 1:0.02, ultrasonically dispersing for 30 min, and drying at 80°C; the solid-liquid ratio of nano-aluminum hydroxide to anhydrous ethanol is 1:

5. S2.

3. The mixture is extruded through a twin-screw extruder to obtain a melt; the melt is then water-cooled after being extruded through a coat hanger-type die, with a cooling water temperature of 18-22℃ and a vacuum sizing pressure of 0.08-0.12MPa, to obtain an environmentally friendly, flame-retardant, and oxidation-resistant chlorinated polyvinyl chloride cable.

5. The preparation method of the environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable according to claim 4, characterized in that, In S2.3, the twin-screw extrusion temperature parameters are: Zone 1 160-165℃, Zone 2 170-175℃, Zone 3 175-180℃, Zone 4 175-180℃, and Die head 175-180℃; the screw speed is 200-250 rpm.