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

Abstract

The invention relates to the technical field of cables, in particular to an environment-friendly flame-retardant antioxidant chlorinated polyvinyl chloride cable and a preparation method thereof, and the environment-friendly flame-retardant antioxidant chlorinated polyvinyl chloride cable comprises the following raw materials: chlorinated polyvinyl chloride, dioctyl terephthalate, nano aluminum hydroxide, a composite flame retardant, a calcium-zinc stabilizer, epoxidized soybean oil and nano clay. The composite flame retardant forms an organic-inorganic synergistic core-shell structure on a micro-nano scale, hexaphenoxy cyclotriphosphazene provides a phosphorus source flame-retardant function, and polyborosilazane forms a boron-silicon-nitrogen ceramic network after heat treatment, so that the carbon layer stability and thermal oxidation resistance of the material are effectively improved; meanwhile, the modified silicon dioxide is used as an inorganic skeleton reinforcing phase, so that the dispersity and the interface bonding performance of the flame retardant in a CPVC matrix are improved; through the synergistic effect, the flame retardant efficiency, thermal stability and mechanical strength of the cable material are remarkably improved, and smoke release and toxicity are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cable, in particular to an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable and a preparation method thereof. BACKGROUND

[0002] Chlorinated polyvinyl chloride (CPVC) cable is widely used in high-temperature, high-flame-retardant power, communication, building and other fields due to its higher chlorine content, excellent heat resistance, flame retardance and mechanical strength. However, the traditional CPVC cable may still release toxic gas and smoke under high temperature or open flame conditions, and its flame-retardant system and thermal stability still need to be improved. In order to improve its flame-retardant performance, flame retardants such as chlorinated paraffin and brominated aromatic hydrocarbon are often used, but such flame-retardant systems are prone to produce corrosive gases (such as HCl) and carcinogens during combustion, causing serious harm to equipment and human health.

[0003] At present, although the flame retardant can improve the flame retardant performance of CPVC to a certain extent, its thermal stability is poor, which leads to the decrease of flame retardant efficiency of the material during processing and use, and affects the mechanical properties and insulation properties of the cable. In view of this, an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable and a preparation method thereof are proposed. SUMMARY

[0004] The present application aims to provide an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable and a preparation method thereof, to solve the problem that the flame retardant can improve the flame retardant performance of CPVC to a certain extent, but its thermal stability is poor, which leads to the decrease of flame retardant efficiency of the material during processing and use, and affects the mechanical properties and insulation properties of the cable.

[0005] To achieve the above-mentioned purpose, the present application provides an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable, 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. The composite flame retardant is prepared by in-situ hybridization of hexaphenoxyl cyclotriphosphazene and polysilazane co-dissolved with modified silicon dioxide.

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

[0007] Preferably, the preparation method of the composite flame retardant is as follows: S1.1, adding silica into 95% mass concentration ethanol with mass ratio of 1:10; adding γ-aminopropyl triethoxysilane, stirring at 60℃ with speed of 300-400rpm for 2-3h; drying at 80℃ for 8h after filtration, to obtain modified silica; S1.2, adding hexaphenoxycyclotriphosphazene and polyborosilazane into N,N-dimethylformamide, heating to 110-120℃, stirring at speed of 200-300rpm for 1.5-2h, then ultrasonicating in a closed container for 30min with power of 200W, to obtain a mixed solution with concentration of 10-20wt%; S1.3, dropping the mixed solution into the modified silica emulsion at a rate of 1mL / min, keeping stirring at speed of 6000-8000rpm for 30-60min, standing to remove bubbles to obtain a hybrid liquid; S1.4, pre-crosslinking the hybrid liquid at 150-170℃ for 2-4h under nitrogen atmosphere, then heat treating at 300-350℃ for 1-2h; cooling to room temperature, drying at 80℃ under vacuum for 6-8h; sieving through a 100 mesh sieve to obtain a composite flame retardant.

[0008] The composite flame retardant is a core-shell hybrid particle, wherein the modified silica is the core and the blend crosslinking product of hexaphenoxycyclotriphosphazene and polyborosilazane is the shell; the apparent molecular weight thereof is 2-5×10 4 Da, and the average particle size of the particle is 0.5-2μm.

[0009] Preferably, in S1.1, the amount of γ-aminopropyl triethoxysilane added accounts for 5-10wt% of the silica.

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

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

[0012] Preferably, in S1.3, the modified silica emulsion is obtained by dispersing the modified silica in a mixed solution of N,N-dimethylformamide / ethanol, ultrasonicating for 30min to obtain a modified silica emulsion with concentration of 5wt%; the volume ratio of N,N-dimethylformamide to ethanol is 7:3.

[0013] In another aspect, the present application provides a preparation method of an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable, for making the environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable described above, comprising the following steps: S2.1, respectively, take the following weight parts of raw materials: chlorinated polyvinyl chloride 70-85 parts by weight, dioctyl terephthalate 15-25 parts by weight, nano-aluminum hydroxide 20-30 parts by weight, composite flame retardant 10-18 parts by weight, calcium-zinc stabilizer 3-5 parts by weight, epoxy soybean oil 4-8 parts by weight and nano-clay 5-10 parts by weight; S2.2, the chlorinated polyvinyl chloride and calcium-zinc stabilizer are added to a high-speed mixer, mixed at 60℃ for 3-5min at a speed of 300-400rpm to obtain dry mixture; The dioctyl terephthalate and epoxy soybean oil are heated to 50℃, the composite flame retardant is added and stirred at a speed of 500-600rpm until it becomes paste to obtain a plasticizer paste; The plasticizer paste is added to the dry mixture, heated to 90℃ and mixed at a speed of 1200rpm for 8-12min, the activated nano-aluminum hydroxide and nano-clay are added and continue to mix until the material temperature is 110℃ to obtain a mixture; S2.3, the mixture is extruded by a double screw extruder to obtain a melt; the melt is extruded through a clothes hanger type die and formed by water cooling, the cooling water temperature is 18-22℃, the vacuum sizing pressure is 0.08-0.12MPa to obtain an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable.

[0014] Preferably, in S2.2, the activated nano-aluminum hydroxide is obtained by adding nano-aluminum hydroxide and 3-(2,3-epoxypropoxy) propyl trimethoxysilane in a mass ratio of 1:0.02 into anhydrous ethanol, ultrasonic dispersion for 30min and drying at 80℃; the solid-liquid ratio of nano-aluminum hydroxide to anhydrous ethanol is 1:5.

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

[0016] Compared with the prior art, the present application has the following advantages: In the environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable and the preparation method thereof, the composite flame retardant forms an organic-inorganic synergistic core-shell structure in micro-nano scale, hexaphenoxycyclotriphosphazene provides phosphorus source flame-retardant function, polyborosilazane forms a borosilicon nitrogen ceramic network after heat treatment, effectively improves the carbon layer stability and heat oxidation resistance of the material, and the modified silicon dioxide as an inorganic skeleton reinforcing phase improves the dispersibility and interfacial adhesion performance 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, and the smoke release and toxicity are reduced. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0018] The present application provides an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable, comprising the following raw materials: chlorinated polyvinyl chloride, dioctyl terephthalate, nano aluminum hydroxide, composite flame retardant, calcium-zinc stabilizer, epoxy soybean oil and nano clay. The composite flame retardant is prepared by in-situ hybridization of hexaphenoxy cyclotriphosphazene and polysilazane, and modified silicon dioxide.

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

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

[0021] Gamma-aminopropyl triethoxysilane CAS: 919-30-2, purchased from Hubei Xinkang Pharmaceutical Chemical Co., Ltd.

[0022] Silicon dioxide CAS: 14808-60-7, purchased from Anhui Kunrun Nanotechnology Co., Ltd.

[0023] 3-(2,3-epoxypropoxy) propyl trimethoxysilane CAS: 2530-83-8, dioctyl terephthalate CAS: 6422-86-2, and epoxy soybean oil CAS: 8013-07-8, all purchased from Shanghai Yuan Ye Biological Technology Co., Ltd.

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

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

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

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

[0028] The activated nano-aluminum hydroxide is obtained by adding nano-aluminum hydroxide and 3-(2,3-epoxypropoxy) propyl trimethoxysilane with a mass ratio of 1:0.02 into anhydrous ethanol, ultrasonic dispersion for 30 min, and drying at 80℃; the solid-liquid ratio of nano-aluminum hydroxide and anhydrous ethanol is 1:5.

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

[0030] Example 1: A preparation method of an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable, comprising the following steps: S2.1, respectively, the following weight parts of raw materials are weighed: chlorinated polyvinyl chloride 70 parts by weight, dioctyl terephthalate 15 parts by weight, nano-aluminum hydroxide 20 parts by weight, composite flame retardant 10 parts by weight, calcium-zinc stabilizer 3 parts by weight, epoxy soybean oil 4 parts by weight and nano-clay 5 parts by weight; S2.2, chlorinated polyvinyl chloride and calcium-zinc stabilizer are added to a high-speed mixer, mixed at 60℃ and 400rpm for 5min to obtain dry mixture; Dioctyl terephthalate and epoxy soybean oil are heated to 50℃, and the composite flame retardant is added and stirred at 600rpm until it becomes a paste to obtain a plasticizer paste; The plasticizer paste is added to the dry mixture, heated to 90℃ and mixed at 1200rpm for 12min, then the activated nano-aluminum hydroxide and nano-clay are added and continue to mix until the material temperature reaches 110℃ to obtain a mixture; S2.3, the mixture is extruded by a double-screw extruder with temperature parameters of: zone 1 160℃, zone 2 170℃, zone 3 175℃, zone 4 175℃, die 175℃, and screw speed 250rpm to obtain a melt; the melt is extruded through a clothes hanger die and then water-cooled to form, with cooling water temperature 20℃ and vacuum sizing pressure 0.1MPa, 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, silica is added to 95% mass concentration ethanol with a mass ratio of 1:10; 5wt% of γ-aminopropyl triethoxysilane is added, stirred at 60℃ and 400rpm for 3h; after filtration, dried at 80℃ for 8h to obtain modified silica; S1.2, add hexaphenoxycyclotriphosphazene and polysilazane (mass ratio 1.0:1) into N,N-dimethylformamide, heat to 120℃, stir at 300 rpm for 2 h, then ultrasonic in a closed container at 200 W for 30 min to obtain a 10 wt% mixed solution; S1.3, add the mixed solution to the modified silica emulsion (mass ratio 2.0:1) at a rate of 1 mL / min, keep stirring at 6000 rpm for 60 min, and stand to degas to obtain a hybrid liquid; S1.4, heat the hybrid liquid at 170℃ for 4 h for pre-crosslinking, then heat at 350℃ for 2 h; cool to room temperature, vacuum dry at 80℃ for 8 h; screen through a 100 mesh sieve to obtain a composite flame retardant.

[0032] Example 2: A preparation method of an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable, comprising the following steps: S2.1, respectively weigh the following raw materials: chlorinated polyvinyl chloride 85 parts by weight, dioctyl terephthalate 25 parts by weight, nano aluminum hydroxide 30 parts by weight, composite flame retardant 18 parts by weight, calcium-zinc stabilizer 5 parts by weight, epoxy soybean oil 8 parts by weight and nano clay 10 parts by weight; S2.2, add chlorinated polyvinyl chloride and calcium-zinc stabilizer into a high-speed mixer, mix at 400 rpm at 60℃ for 5 min to obtain dry mixture; Heat the dioctyl terephthalate and epoxy soybean oil to 50℃, add the composite flame retardant and stir at 600 rpm until it becomes a paste to obtain a plasticizer paste; Add the plasticizer paste to the dry mixture, heat to 90℃ and mix at 1200 rpm for 12 min, add activated nano aluminum hydroxide and nano clay, continue to mix until the material temperature reaches 110℃ to obtain a mixture; S2.3, extrude the mixture through a twin-screw extruder with 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 extruded through a clothes hanger die and then water-cooled to form, with cooling water temperature 20℃, vacuum sizing pressure 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 into 95% mass concentration ethanol at a mass ratio of 1:10; add 10 wt% of γ-aminopropyl triethoxysilane based on the silica, stir at 60℃ and 400 rpm for 3 h; filter and dry at 80℃ for 8 h to obtain modified silica; S1.2, add hexaphenoxycyclotriphosphazene and polysilazane (mass ratio 2.0:1) into N,N-dimethylformamide, heat to 120℃, stir at 300 rpm for 2h, then ultrasonic in a closed container at 200W for 30min, to obtain a 20wt% mixed solution; S1.3, add the mixed solution to the modified silica emulsion (mass ratio 3.0:1) at a rate of 1mL / min, keep stirring at 6000rpm for 60min, and stand to remove bubbles to obtain a hybrid liquid; S1.4, heat the hybrid liquid at 170℃ for 4h for pre-crosslinking, then heat at 350℃ for 2h, cool to room temperature, vacuum dry at 80℃ for 8h, and sieve through a 100 mesh sieve to obtain a composite flame retardant.

[0034] Example 3: A preparation method of an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable, comprising the following steps: S2.1, respectively weigh the following raw materials: chlorinated polyvinyl chloride 78 parts by weight, dioctyl terephthalate 20 parts by weight, nano aluminum hydroxide 25 parts by weight, composite flame retardant 14 parts by weight, calcium-zinc stabilizer 4 parts by weight, epoxy soybean oil 6 parts by weight, and nano clay 7 parts by weight; S2.2, add chlorinated polyvinyl chloride and calcium-zinc stabilizer to a high-speed mixer, mix at 400rpm at 60℃ for 5min to obtain dry mixture; Heat the dioctyl terephthalate and epoxy soybean oil to 50℃, add the composite flame retardant and stir at 600rpm until it becomes a paste to obtain a plasticizer paste; Add the plasticizer paste to the dry mixture, heat to 90℃ and mix at 1200rpm for 12min, then add activated nano aluminum hydroxide and nano clay, continue to mix until the material temperature reaches 110℃ to obtain a mixture; S2.3, extrude the mixture through a double-screw extruder with temperature parameters as follows: zone 1 160℃, zone 2 170℃, zone 3 175℃, zone 4 175℃, and die 175℃, and screw speed 250rpm to obtain a melt; the melt is extruded through a clothes hanger type die and then water-cooled to form, with cooling water temperature 20℃ and vacuum sizing pressure 0.1MPa, 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 into 95% mass concentration ethanol at a mass ratio of 1:10; add γ-aminopropyl triethoxysilane accounting for 8wt% of the silica, stir at 60℃ and 400rpm for 3h; filter and dry at 80℃ for 8h to obtain modified silica; S1.2, add hexaphenoxycyclotriphosphazene and polysilazane (mass ratio 1.5:1) into N,N-dimethylformamide, heat to 120°C, stir at 300 rpm for 2 h, then ultrasonic in a closed container at 200 W for 30 min to obtain a 15 wt% mixed solution; S1.3, add the mixed solution to the modified silica emulsion (mass ratio 2.5:1) at a rate of 1 mL / min, keep stirring at 6000 rpm for 60 min, and stand to degas to obtain a hybrid liquid; S1.4, heat the hybrid liquid at 170°C for 4 h for pre-crosslinking, then heat at 350°C for 2 h; cool to room temperature, vacuum dry at 80°C for 8 h; sieve through a 100 mesh sieve to obtain a composite flame retardant.

[0036] Mechanical property determination: cut dumbbell-shaped samples (thickness 1-2 mm, gauge length 25 mm) from the cable, the distance between the test machine clamps is 50 mm, and the tensile rate is 250 mm / min; measure the initial thickness and width of the sample, calculate the cross-sectional area; clamp the sample in the test machine clamps, start the test machine until the sample breaks, record the maximum force (F) and the gauge length at break (L1); calculate the tensile strength (MPa) = F / cross-sectional area, and the elongation at break (%) = [(L1-initial gauge length) / initial gauge length] x 100%; higher tensile strength indicates that the cable material has strong tensile fracture resistance, and is suitable for scenarios that require mechanical stress.

[0037] Determination of oxygen index: vertically fix a sample with a size of 100 mm x 10 mm x 3 mm in the center of the combustion cylinder, adjust the oxygen / nitrogen gas mixture ratio, and ignite the sample from the upper end; if the sample burns for more than 3 minutes or the burning length exceeds 50 mm, it is considered to be able to sustain combustion; by adjusting the gas ratio, the lowest oxygen concentration that can sustain combustion is measured, which is the oxygen index (LOI); the calculation formula is LOI = oxygen flow rate / (nitrogen flow rate + oxygen flow rate) x 100%.

[0038] Determination of UL-94 flame retardant grade: vertically clamp a 125 mm x 13 mm x 3 mm sample, ignite the bottom end of the sample for 10 seconds, then remove the flame; record the first flame extinguishing time (t1); ignite again for 10 seconds, record the second extinguishing time (t2); at the same time, observe whether there are molten droplets that can ignite cotton and whether the burning continues; repeat the test on 5 samples to grade.

[0039] Determination of carbon residue: 5-10 mg of sample was placed in nitrogen, from room temperature to 700℃, the heating rate was generally 10℃ / min; record the mass change of the sample during the heating process, when the temperature reached 700℃ and 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 cable prepared in the above examples 1-3 was determined, and the performance data of the environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable are shown in Table 1: Table 1 Performance data of environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable of examples 1-3 Example / Comparative Example Oxygen Index UL-94 Flame Retardant Rating Char Yield Elongation at Break Tensile Strength Mpa 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 According to the above test experiment, example 3 is the optimal example; Example 4: Compared with example 3, the difference is that the mass ratio of the mixed solution to the modified silica emulsion is 3.0:1.

[0041] Example 5: Compared with example 3, the difference is that the mass ratio of the mixed solution to the modified silica emulsion is 3.5:1.

[0042] Example 6: Compared with example 3, the difference is that the addition amount of γ-aminopropyl triethoxysilane is 10wt%.

[0043] Example 7: Compared with example 3, the difference is that the addition amount of γ-aminopropyl triethoxysilane is 12wt%.

[0044] Example 8: Compared with example 3, the difference is that the mass ratio of hexaphenoxy cyclotriphosphazene and polyborosilazane is 2.0:1.

[0045] Example 9: Compared with example 3, the difference is that the mass ratio of hexaphenoxy cyclotriphosphazene and polyborosilazane is 2.5:1.

[0046] Comparative example 1: Compared with example 3, the difference is that no composite flame retardant is added.

[0047] Comparative example 2: Compared with example 3, the difference is that no composite flame retardant is added, and hexaphenoxy cyclotriphosphazene is directly added.

[0048] Comparative example 3: Compared with example 3, the difference is that the silica in the composite flame retardant is not modified.

[0049] Comparative example 4: Compared with example 3, the difference is that no composite flame retardant is added, and polyborosilazane is directly added.

[0050] Table 2 Performance data of cables of Examples 3-9 and Comparative Examples 1-4 Example / Comparative Example Oxygen Index UL-94 Flame Retardant Rating Char Yield Elongation at Break Tensile Strength Mpa 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 As can be seen from Comparative Example 3, Example 4 and Example 5, as the mass ratio of the mixed solution to the modified silica emulsion continuously 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 decreases from 437% to 408%; this is because the increase in the mass ratio means that the organic phase (i.e. the hexaphenoxy cyclotriphosphazene and polyborosilazane co-solvent system) increases relatively, while the inorganic phase (i.e. modified SiO2) decreases relatively, resulting in a poor coating effect of the inorganic component in the composite flame retardant, incomplete core-shell structure, and reduced hybridization degree, thereby weakening the shielding and carbonization of the flame retardant; at the same time, SiO2 as a rigid inorganic particle has a certain reinforcing effect in the composite material, and the decrease in the content also causes the mechanical properties to decrease; when the mass ratio exceeds 3.0 (Example 5), excess hexaphenoxy cyclotriphosphazene is wrapped on the surface of SiO2, hindering the interface reaction between PBSZ and SiO2, resulting in a discontinuous ceramic network and a decrease in flame retardant efficiency.

[0051] In Example 3, Example 6 and Example 7, as the amount of γ-aminopropyl triethoxysilane (KH-550) continuously increases, the cable performance gradually decreases, the oxygen index decreases from 34.7% to 33.1%, the carbon residue decreases from 23.7% to 22.2%, the tensile strength decreases from 46.3 MPa to 44.8 MPa, and the elongation at break decreases 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, promote the formation of core-shell structure, enhance its dispersibility and interfacial bonding strength in the CPVC matrix, and thus improve the flame retardance and mechanical properties; however, when the amount of KH-550 is excessive (Example 7), the excess KH-550 will form a hydrophobic organic layer on the surface, hindering the subsequent hybridization reaction and causing the emulsion stability to decrease; in addition, the amine group and ethoxyl group in KH-550 undergo side reactions at high temperatures, producing unstable small molecules, affecting the thermal stability and flame retardance of the material.

[0052] From the comparison of Example 3, Example 8 and Example 9, it can be seen that as the relative proportion of hexaphenoxycyclotriphosphazene increases, the oxygen index gradually decreases from 34.7% to 33.3%, the carbon 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 retardation during high-temperature decomposition, but excessive hexaphenoxycyclotriphosphazene can cause too much gas-phase flame retardant in the system, sacrificing the role of polyboron silazane (PBSZ) in the condensed phase in terms of carbon formation and heat insulation; in addition, hexaphenoxycyclotriphosphazene is prone to migration and precipitation at processing temperature, resulting in uneven distribution in the matrix and affecting the flame retardant efficiency and long-term processing stability; PBSZ, as a condensed-phase flame retardant rich in boron-silicon-nitrogen structure, can form a dense carbon layer during combustion and increase the carbon residue; when its proportion is insufficient, its synergistic flame retardation and heat resistance contribution is weakened, making it difficult for the composite flame retardant to fully exert its performance advantages in CPVC.

[0053] Comparative Example 1 does not add a composite flame retardant, and its oxygen index is only 25.3%, the carbon residue is only 13.9%, the elongation at break is 293%, and the tensile strength is 21.2 MPa, which is much lower than the performance indicators of other examples; this shows that the CPVC body has very limited flame retardancy and thermal stability without the addition of flame retardant additives, and is a typical flammable polymer; it produces a large amount of molten droplets and toxic gases during combustion, which can easily cause fires; the low carbon residue indicates that it cannot form a stable carbon layer during pyrolysis, lacking heat shielding and oxygen isolation; the main reason for the decline in mechanical properties is that no functional inorganic fillers (such as SiO2) or reinforcing structures are added, the intermolecular forces of the system itself are weak, and the molecular chains are easily degraded by heat during processing, resulting in severe chain scission; in addition, the lack of network structure brought by the flame retardant also leads to loose molecular arrangement, which further affects the tensile strength and ductility of the material.

[0054] Comparative Example 2 only introduces hexaphenoxycyclotriphosphazene as a flame retardant in the CPVC matrix, and its oxygen index increases to 28.1%, the carbon residue is 17.2%, the elongation at break is 325%, and the tensile strength is 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 to inhibit chain reactions in the early stage of combustion; in addition, in the absence of the dispersion and synergistic effect of SiO2 and other inorganic particles, hexaphenoxycyclotriphosphazene is prone to agglomeration or precipitation in the CPVC matrix, which cannot fully play its role, but on the contrary, it can cause the thermal stability of the system to decrease; in terms of mechanical properties, hexaphenoxycyclotriphosphazene itself is a small molecule, and excessive addition can easily cause plasticization, leading to a decrease in intermolecular bonding force and thus a decrease in tensile strength and elongation of the material.

[0055] The SiO2 in Comparative Example 3 is not modified by KH-550, the oxygen index is 26.4%, the carbon residue is 15.4%, the elongation at break is 309%, and the tensile strength is 23.6 MPa; the core reason for the performance decline is that the unmodified SiO2 is a hydrophilic particle with poor surface activity and poor dispersibility in the organic system, and it is easy to agglomerate; the agglomerated SiO2 particles are not only difficult to uniformly coat with organic flame retardants, but also form micro defects, affecting the interfacial bonding force of the composite material, and ultimately leading to a significant decrease in mechanical properties; at the same time, a stable core-shell structure cannot be formed, and there is a lack of interfacial bonding between hexaphenoxy cyclotriphosphazene and polysilazane and SiO2, the composite flame retardant structure is incomplete, and the flame retardant performance is also reduced.

[0056] Comparative Example 4 only adds PBSZ (polysilazane), the oxygen index is 27.6%, the carbon residue is 16.1%, the elongation at break is 328%, and the tensile strength is 24.8 MPa; PBSZ is a typical condensed phase flame retardant, which can generate a porous carbon layer during pyrolysis, helping to isolate oxygen and heat and improve carbon residue; but due to the lack of gas phase flame retardant synergy of hexaphenoxy cyclotriphosphazene, it cannot effectively inhibit the diffusion of free radicals in the initial stage of combustion; at the same time, PBSZ has a thermal crosslinking process at high temperature, and when it is directly added to CPVC without being fully dispersed and coated, it will cause discontinuous carbonization due to poor dispersibility, affecting the heat insulation effect; in terms of mechanical properties, the rigid reinforcing effect of the PBSZ macromolecular structure on the system is limited, and the interface is discontinuous when the core-shell structure is not formed, which reduces the mechanical performance.

[0057] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly flame-retardant antioxidant chlorinated polyvinyl chloride cable, characterized in that, The raw materials include chlorinated polyvinyl chloride, dioctyl terephthalate, nano aluminum hydroxide, composite flame retardant, calcium-zinc stabilizer, epoxy soybean oil and nano clay. The composite flame retardant is prepared by in-situ hybridization of hexaphenoxy cyclotriphosphazene and polysilazane co-dissolved with modified silica.

2. The environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable according to claim 1, characterized in that, The chlorinated polyvinyl chloride is 70-85 parts by weight, the dioctyl terephthalate is 15-25 parts by weight, the nano aluminum hydroxide is 20-30 parts by weight, the composite flame retardant is 10-18 parts by weight, the calcium-zinc stabilizer is 3-5 parts by weight, the epoxy soybean oil is 4-8 parts by weight, and the nano clay is 5-10 parts by weight.

3. The environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable of claim 2, wherein the antioxidant is at least one selected from the group consisting of a hindered phenol antioxidant, a phosphorus antioxidant, and a sulfur antioxidant. The preparation method of the composite flame retardant is as follows: S1.1, the silica is added into 95% ethanol with a mass ratio of 1:10; γ-aminopropyl triethoxysilane is added, stirred at 60°C and a speed of 300-400 rpm for 2-3 hours; after filtration, it is dried at 80°C for 8 hours to obtain modified silica; S1.2, hexaphenoxy cyclotriphosphazene and polysilazane are added into N,N-dimethylformamide, heated to 110-120°C, stirred at a speed of 200-300 rpm for 1.5-2 hours, and then ultrasonic treated in a closed container at a power of 200W for 30 minutes to obtain a mixed solution with a concentration of 10-20wt%; S1.3, the mixed solution is added dropwise into the modified silica emulsion at a rate of 1mL / min, stirred at a speed of 6000-8000 rpm for 30-60 minutes, and then left to deaerate to obtain a hybrid liquid; S1.4, the hybrid liquid is first pre-crosslinked at 150-170°C for 2-4 hours and then heat treated at 300-350°C for 1-2 hours under nitrogen atmosphere; cooled to room temperature, vacuum dried at 80°C for 6-8 hours; sieved through a 100 mesh sieve to obtain the composite flame retardant.

4. The environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable of claim 3, wherein the antioxidant is at least one selected from the group consisting of a hindered phenol antioxidant, a phosphorus antioxidant, and a sulfur antioxidant. In S1.1, the addition amount of γ-aminopropyl triethoxysilane accounts for 5-10wt% of the silica.

5. The environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable of claim 3, wherein the antioxidant is at least one selected from the group consisting of a hindered phenol antioxidant, a phosphorus antioxidant, and a sulfur antioxidant. In S1.2, the mass ratio of hexaphenoxy cyclotriphosphazene to polysilazane is 1.0-2.0:

1.

6. The environmentally friendly flame retardant and oxidation resistant chlorinated polyvinyl chloride cable of claim 3, wherein, In S1.3, the mass ratio of modified silica to mixed solution is 1:2.0-3.

0.

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

3.

8. A process for the preparation of an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable for the production of an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable according to any one of claims 1 to 7, characterized in that The preparation method of the environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable is as follows: S2.1, the following raw materials are weighed respectively: chlorinated polyvinyl chloride 70-85 parts by weight, dioctyl terephthalate 15-25 parts by weight, nano aluminum hydroxide 20-30 parts by weight, composite flame retardant 10-18 parts by weight, calcium-zinc stabilizer 3-5 parts by weight, epoxy soybean oil 4-8 parts by weight, and nano clay 5-10 parts by weight; S2.2, the chlorinated polyvinyl chloride and the calcium-zinc stabilizer are added into a high-speed mixer, mixed at a speed of 300-400 rpm at 60°C for 3-5 minutes to obtain dry mixture; The dioctyl terephthalate and the epoxy soybean oil are heated to 50℃, the composite flame retardant is added to be stirred to paste at a speed of 500-600 rpm, to obtain a plasticizer paste; The plasticizer paste is added to the dry mixture, the temperature is raised to 90℃, and the mixture is stirred at a speed of 1200 rpm for 8-12 min, the activated nano-aluminum hydroxide and the nano-clay are added, and the mixing is continued until the material temperature is 110℃, to obtain a mixture; S2.3, the mixture is extruded by a double screw extruder to obtain a melt; the melt is extruded through a hanger die and then formed by water cooling, the cooling water temperature is 18-22℃, the vacuum sizing pressure is 0.08-0.12 MPa, to obtain an environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable.

9. The method for preparing the environmentally friendly flame-retardant and oxidation-resistant chlorinated polyvinyl chloride cable according to claim 8, characterized in that, In the S2.2, the activated nano-aluminum hydroxide is prepared by adding nano-aluminum hydroxide and 3-(2,3-epoxypropoxy) propyl trimethoxysilane at a mass ratio of 1:0.02 into anhydrous ethanol, ultrasonic dispersion for 30 min, and drying at 80℃ to obtain; the solid-liquid ratio of the nano-aluminum hydroxide and the anhydrous ethanol is 1:

5.

10. A process for the preparation of environment friendly flame retardant and oxidation resistant chlorinated polyvinyl chloride cable as claimed in claim 8, wherein the said process is characterized by, In the S2.3, the temperature parameters of the double screw extrusion are as follows: zone 1, 160-165℃; zone 2, 170-175℃; zone 3, 175-180℃; zone 4, 175-180℃; die, 175-180℃; the screw rotation speed is 200-250 rpm.