Preparation method of weather-resistant flame-retardant chlorinated polyvinyl chloride plastic for charging pile

Abstract

The present invention relates to a method for preparing weather-resistant and flame-retardant chlorinated polyvinyl chloride (PVC) plastic for charging piles, belonging to the field of polymer cable material technology. The method includes: flame retardant synthesis, in which hexachlorocyclotriphosphazene undergoes a three-step substitution reaction with octadecyl alcohol, 4-amino-2,2,6,6-tetramethylpiperidine, and phenol under a temperature gradient, and is purified to obtain a modified flame retardant; mixing, in which 100 parts by weight of CPVC / PVC resin are lightly mixed with 4-6 parts by weight of calcium / zinc stabilizer; 45-55 parts by weight of dioctyl terephthalate and 8-12 parts by weight of flame retardant are added and heavily mixed; then 30-40 parts by weight of calcined kaolin, 1-1.2 parts by weight of pentaerythritol stearate, and polyethylene wax are added, mixed evenly, and cold-mixed; the dry mixture is extruded by a twin-screw extruder and water-cooled into pellets to obtain the final product. This invention improves the compatibility and uniform dispersion of the flame retardant in chlorinated polyvinyl chloride resin or polyvinyl chloride resin matrix, avoiding the problem of easy precipitation of traditional flame retardants.

Description

Technical Field

[0001] This invention relates to the field of polymer cable materials, specifically a method for preparing weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles. Background Technology

[0002] Charging piles are widely used in various fields of supporting facilities for new energy vehicles. Under the premise of ensuring operational safety, existing charging pile equipment is developing towards high flame retardancy, long-term weather resistance and high strength. Among them, the long-term safety of materials in complex outdoor environments is receiving increasing attention, and the requirements for the flame retardancy and anti-aging indicators of charging pile shell and cable materials are high. Chlorinated polyvinyl chloride (CPVC) or polyvinyl chloride (PVC) plastic is the key matrix material of charging piles, and the structure of its flame retardant and the blending process directly affect the various properties and weather resistance and flame retardancy indicators of the material. Currently, most PVC plastics used in charging piles rely on the addition of traditional flame retardants to improve fire resistance. However, due to the limitations of the molecular structure characteristics of traditional flame retardants and the mixing and processing technology, their compatibility and uniform dispersion in the resin matrix are poor, which easily leads to surface precipitation problems. This compatibility defect not only causes the material to easily break the main chain and become brittle during photo-oxidative aging, resulting in a significant decrease in performance and weather resistance over time, but also makes it difficult to achieve both long-term flame retardancy and flexible reinforcement through limited modification methods. The comprehensive performance indicators of existing materials can no longer meet the needs of modern charging piles for long-term development in harsh outdoor environments. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles, so as to solve the problems mentioned in the background art.

[0004] The technical solution of the present invention includes: preparing a multifunctional modified flame retardant, mixing, and extruding granulation; The preparation of the multifunctional modified flame retardant includes: a first-step substitution reaction, a second-step substitution reaction, a third-step substitution reaction, and purification; The first step of the substitution reaction involves mixing hexachlorocyclotriphosphazene, anhydrous tetrahydrofuran, and triethylamine, then adding a tetrahydrofuran solution of octadecyl alcohol dropwise at 0-5°C and maintaining the temperature to obtain intermediate solution A. The second step of the substitution reaction involves heating the intermediate A solution to 45-50°C, adding a tetrahydrofuran solution of 4-amino-2,2,6,6-tetramethylpiperidine, and reacting at a constant temperature to obtain the intermediate B solution. The third step of the substitution reaction involves adding phenol and anhydrous potassium carbonate to the intermediate B solution, heating to 65-70°C, and refluxing to obtain a reaction mixture. The purification process involves cooling the reaction mixture to room temperature, filtering it, collecting the filtrate, concentrating the filtrate, adding the concentrated filtrate dropwise to ice water to precipitate a precipitate, collecting the precipitate and washing it, and then vacuum drying it to obtain a multifunctional modified flame retardant. The mixing process involves adding chlorinated polyvinyl chloride resin or polyvinyl chloride resin and calcium / zinc composite heat stabilizer to a high-speed mixer and mixing at low speed to 55-65°C to obtain a first mixture; adding dioctyl terephthalate, dioctyl phthalate, and the aforementioned multifunctional modified flame retardant to the first mixture and mixing at high speed to 100-110°C to obtain a second mixture; adding calcined kaolin, pentaerythritol stearate, and polyethylene wax to the second mixture, mixing, and then discharging the mixture into a cold mixer for cooling to obtain a dry mixture; The extrusion granulation process involves adding the dry mixture to a twin-screw extruder, melting and blending it, extruding it into strands, cooling it with water, and then pelletizing it to obtain weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles. In the mixture, by weight, 100 parts of chlorinated polyvinyl chloride resin or polyvinyl chloride resin, 45-55 parts of dioctyl terephthalate and dioctyl phthalate, 8-12 parts of multifunctional modified flame retardant, 30-40 parts of calcined kaolin, 4-6 parts of calcium / zinc composite heat stabilizer, and 1-1.2 parts of pentaerythritol stearate and polyethylene wax.

[0005] Preferably, in the first step of the substitution reaction, the molar ratio of hexachlorocyclotriphosphazene to octadecyl alcohol is 1:2 to 1:2.1; In the second substitution reaction, the molar ratio of hexachlorocyclotriphosphazene to 4-amino-2,2,6,6-tetramethylpiperidine is 1:2 to 1:2.1. In the third substitution reaction, the molar ratio of hexachlorocyclotriphosphazene to phenol is 1:2.1 to 1:2.3.

[0006] Preferably, in the first step of the substitution reaction, the heat preservation reaction time is 3.5-4.5 hours. In the second substitution reaction, the isothermal reaction time is 5.5-6.5 h; In the third substitution reaction, the reflux reaction time is 11-13 hours.

[0007] Preferably, in the purification process, the filtrate is concentrated to 1 / 4 to 1 / 3 of its original volume; The washing process involves alternating between deionized water and ethanol. The vacuum drying temperature is 55-65℃, and the time is 22-26h.

[0008] Preferably, in the mixture, chlorinated polyvinyl chloride resin or polyvinyl chloride resin and calcium / zinc composite heat stabilizer are added to a high-speed mixer and mixed at low speed to 55-65°C to obtain a first mixture; Dioctyl terephthalate, dioctyl phthalate, and the multifunctional modified flame retardant were added to the first mixture, and the mixture was mixed at high speed to 100-110°C to obtain the second mixture. Add calcined kaolin, pentaerythritol stearate, and polyethylene wax to the second mixture, and continue mixing to 110-120°C; The material is discharged into a cold mixer and cooled to 35-40℃ to obtain a dry mixture.

[0009] Preferably, in the extrusion granulation, the temperature of the twin-screw extruder is 140-150℃ in zone one, 150-160℃ in zone two, 155-165℃ in zone three, 160-170℃ in zone four, and 160-170℃ at the die head.

[0010] Preferably, in the mixture, the weight ratio of dioctyl terephthalate to dioctyl phthalate is 7:3 to 8:2. The weight ratio of pentaerythritol stearate to polyethylene wax is 2.5:1 to 3:1; The polyvinyl chloride resin is a suspension polyvinyl chloride resin with a degree of polymerization of 1000; The particle size of the calcined kaolin is 1200-1300 mesh.

[0011] This invention provides a method for preparing weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles, which has the following improvements and advantages compared with the prior art: 1. This invention synthesizes a multifunctional modified flame retardant by sequentially reacting hexachlorocyclotriphosphazene with octadecyl alcohol, 4-amino-2,2,6,6-tetramethylpiperidine, and phenol in a three-step substitution reaction. This design combines a phosphazene flame-retardant skeleton with a piperidine structure with excellent weather resistance and anti-aging properties within the same molecule, synergistically meeting the stringent requirements of charging piles for high flame retardancy and long-term weather resistance in complex outdoor environments. At the same time, the long carbon chain structure introduced by octadecyl alcohol significantly improves the compatibility and uniform dispersion of this flame retardant in chlorinated polyvinyl chloride resin or polyvinyl chloride resin matrix, avoiding the problem of easy precipitation of traditional flame retardants. 2. This invention scientifically combines the matrix resin and multi-dimensional additives, using chlorinated polyvinyl chloride or polyvinyl chloride resin with a polymerization degree of 1000 as the matrix, and strictly controlling the ratio of dioctyl terephthalate to dioctyl phthalate to give the material excellent flexibility. At the same time, ultrafine calcined kaolin with a particle size of 1200-1300 mesh and a calcium / zinc composite heat stabilizer are added. The high-mesh kaolin plays a significant reinforcing role in the matrix, significantly improving the mechanical strength of the material. Combined with the environmentally friendly calcium / zinc composite heat stabilizer, the heat resistance and stability of the material are greatly enhanced, ensuring the long-term safety of the charging pile shell or cable. 3. The preparation method of this invention is designed with a scientific step-by-step temperature-controlled mixing process and precise extrusion granulation parameters. During the mixing process, by controlling the specific feeding sequence and temperature range from low speed to high speed, and by compounding pentaerythritol stearate and polyethylene wax in a specific weight ratio as an internal and external lubrication system, not only is the efficient and uniform dispersion of the multifunctional modified flame retardant and various inorganic powders ensured, but also the melting, plasticizing and processing fluidity of the material in the twin-screw extruder are improved, making the extrusion strands smoother and effectively improving the density and quality stability of the final plastic granules. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. Example 1

[0013] This embodiment provides a weather-resistant and flame-retardant polyvinyl chloride cable material for charging piles, which specifically includes the following steps; S1. Preparation of multifunctional modified flame retardants: The first step of the substitution reaction: 17.38 g of hexachlorocyclotriphosphazene and 150 mL of anhydrous tetrahydrofuran were added to a 500 mL three-necked flask equipped with a mechanical stirrer, a condenser, and a constant-pressure dropping funnel, and stirred until completely dissolved; 12.12 g of triethylamine was added to the system; the reaction system was cooled to 2 °C, and 50 mL of tetrahydrofuran solution containing 27.05 g of octadecyl alcohol was added dropwise over 1 h. After the addition was completed, the reaction was kept at 2 °C for 4 h to obtain intermediate solution A. The role of intermediate solution A is to utilize the long-chain structure of octadecyl alcohol to occupy some of the active sites on the phosphazene ring, providing a long carbon chain basis for subsequent improvement of compatibility with the matrix resin; The second step is the substitution reaction: The intermediate A solution is heated to 47°C, and 40 mL of a tetrahydrofuran solution containing 15.63 g of 4-amino-2,2,6,6-tetramethylpiperidine is added dropwise. After the addition is completed, the mixture is kept at 47°C for 6 h to obtain intermediate B solution. The role of intermediate B solution is to introduce a hindered amine structure into the molecule, giving the final flame retardant the function of resisting ultraviolet rays and thermo-oxidative aging. The third step is the substitution reaction: 10.35g of phenol and 15.20g of anhydrous potassium carbonate are added to the intermediate B solution, and the mixture is heated to 68℃ and refluxed for 12h to obtain a reaction mixture. The role of adding phenol is to block the remaining P-Cl bonds, improve the thermal stability and char-forming ability of the flame retardant, and prevent the release of acidic substances during subsequent processing. Purification: After cooling the reaction mixture to room temperature, filter it under vacuum, collect the filtrate, concentrate the filtrate to 1 / 3 of its original volume, and then slowly add it dropwise to ice water to precipitate the precipitate. After collecting the precipitate, wash it three times alternately with deionized water and ethanol, and dry it under vacuum at 60°C for 24 hours to obtain the multifunctional modified flame retardant. The yield of the multifunctional modified flame retardant prepared in this example was 86.5%, and the purity was 98.2%. The structural characterization data are as follows: (-CH2- stretching vibration), 1595, 1490 (benzene ring skeletal vibration), 1250 (P=N stretching vibration), 1160 (POC stretching vibration), 960 (PNC stretching vibration); 1H-NMR (400MHz, CDCl3, ppm): 7.15-7.35 (m, Ar-H, benzene ring proton), 4.05 (t, -CH2-OP), 1.05-1.65 (m, aliphatic chain and piperidine ring proton), 0.88 (t, -CH3, aliphatic chain terminal methyl); The above characterization data confirm the successful synthesis of the target multifunctional modified flame retardant. S2. Mixing: Weigh out 100 parts by weight of suspension polyvinyl chloride resin with a degree of polymerization of 1000, 35 parts by weight of dioctyl terephthalate, 15 parts by weight of dioctyl phthalate, 10 parts by weight of multifunctional modified flame retardant, 35 parts by weight of calcined kaolin, 5 parts by weight of calcium-zinc composite heat stabilizer, 0.8 parts by weight of pentaerythritol stearate, and 0.3 parts by weight of polyethylene wax. Polyvinyl chloride resin and calcium-zinc composite heat stabilizer are added to a high-speed mixer and mixed at low speed to 60°C to obtain a first mixture. Dioctyl terephthalate, dioctyl phthalate and a multifunctional modified flame retardant are added to the first mixture and mixed at high speed to 105°C to obtain a second mixture. Calcined kaolin, pentaerythritol stearate and polyethylene wax are added to the second mixture and mixed further to 115°C. The mixture is then discharged into a cold mixer and cooled to 38°C to obtain a dry mixture. S3. Extrusion granulation: The above dry mixture is added to a co-rotating twin-screw extruder for melt blending and granulation; the temperature of each zone of the extruder is set as follows: Zone 1 145℃, Zone 2 155℃, Zone 3 160℃, Zone 4 165℃, and the die head 165℃; the material is extruded into strips, cooled by water, and then granulated to obtain cable material granules. Example 2

[0014] The process steps in this embodiment are the same as those in Embodiment 1, the only difference being the parameter adjustments as follows; In the preparation of the multifunctional modified flame retardant, the first substitution reaction used a molar ratio of hexachlorocyclotriphosphazene to octadecyl alcohol of 1:2 and a holding time of 3.5 h; the second substitution reaction used a molar ratio of hexachlorocyclotriphosphazene to 4-amino-2,2,6,6-tetramethylpiperidine of 1:2 and a holding time of 5.5 h; the third substitution reaction used a molar ratio of hexachlorocyclotriphosphazene to phenol of 1:2.1 and a reflux time of 11 h; during purification, the filtrate was concentrated to 1 / 4 of its original volume and dried under vacuum at 55 °C for 22 h. The formula, by weight, is as follows: 100 parts polyvinyl chloride resin, 32 parts dioctyl terephthalate, 13 parts dioctyl phthalate, 8 parts multifunctional modified flame retardant, 30 parts calcined kaolin, 4 parts calcium-zinc composite heat stabilizer, 0.72 parts pentaerythritol stearate, and 0.28 parts polyethylene wax. During mixing, mix at low speed to 55°C, then mix at high speed a second time to 100°C. After adding kaolin and lubricant, mix to 110°C, and then cool to 35°C before discharging. The extrusion granulation temperature is set as follows: Zone 1 140℃, Zone 2 150℃, Zone 3 155℃, Zone 4 160℃, and die head 160℃. Example 3

[0015] The process steps in this embodiment are the same as those in Embodiment 1, the only difference being the parameter adjustments as follows; In the preparation of the multifunctional modified flame retardant, the first substitution reaction used a molar ratio of hexachlorocyclotriphosphazene to octadecyl alcohol of 1:2.05 and was kept at the temperature for 4 hours; the second substitution reaction used a molar ratio of hexachlorocyclotriphosphazene to 4-amino-2,2,6,6-tetramethylpiperidine of 1:2.05 and was kept at the temperature for 6 hours; the third substitution reaction used a molar ratio of hexachlorocyclotriphosphazene to phenol of 1:2.2 and was refluxed for 12 hours; during purification, the filtrate was concentrated to 0.30 times its original volume and dried under vacuum at 60°C for 24 hours. The formula, by weight, is as follows: 100 parts polyvinyl chloride resin, 37.5 parts dioctyl terephthalate, 12.5 parts dioctyl phthalate, 10 parts multifunctional modified flame retardant, 35 parts calcined kaolin, 5 parts calcium-zinc composite heat stabilizer, 0.79 parts pentaerythritol stearate, and 0.31 parts polyethylene wax. During mixing, mix at low speed to 60°C, then mix at high speed a second time to 106°C. After adding kaolin and lubricant, mix to 114°C, and then cool to 38°C before discharging. The extrusion granulation temperature is set as follows: Zone 1 145℃, Zone 2 155℃, Zone 3 160℃, Zone 4 165℃, and die head 165℃. Example 4

[0016] The process steps in this embodiment are the same as those in Embodiment 1, the only difference being the parameter adjustment and the different matrix resin, as follows; In the preparation of the multifunctional modified flame retardant, the first substitution reaction used a molar ratio of hexachlorocyclotriphosphazene to octadecyl alcohol of 1:2.1 and was kept at a temperature for 4.5 h; the second substitution reaction used a molar ratio of hexachlorocyclotriphosphazene to 4-amino-2,2,6,6-tetramethylpiperidine of 1:2.1 and was kept at a temperature for 6.5 h; the third substitution reaction used a molar ratio of hexachlorocyclotriphosphazene to phenol of 1:2.3 and was refluxed for 13 h; during purification, the filtrate was concentrated to 1 / 3 of its original volume and dried under vacuum at 65 °C for 26 h. The formula, by weight, is as follows: 100 parts chlorinated polyvinyl chloride resin, 44 parts dioctyl terephthalate, 11 parts dioctyl phthalate, 12 parts multifunctional modified flame retardant, 40 parts calcined kaolin, 6 parts calcium-zinc composite heat stabilizer, 0.86 parts pentaerythritol stearate, and 0.34 parts polyethylene wax. During mixing, mix at low speed to 65°C, then mix at high speed a second time to 110°C. After adding kaolin and lubricant, mix to 120°C, and then cool to 40°C before discharging. The extrusion granulation temperature is set as follows: Zone 1 150℃, Zone 2 160℃, Zone 3 165℃, Zone 4 170℃, and die head 170℃.

[0017] Comparative Example 1: The difference between this comparative example and Example 1 is that the first step of the substitution reaction is omitted in the preparation of the multifunctional modified flame retardant. Octadecyl alcohol is not added. Instead, hexachlorocyclotriphosphazene is directly subjected to the second step of substitution reaction with 4-amino-2,2,6,6-tetramethylpiperidine, followed by a phenol blocking reaction. Other operating steps and process parameters are exactly the same as in Example 1.

[0018] Comparative Example 2: The difference between this comparative example and Example 1 is that the second substitution reaction is omitted in the preparation of the multifunctional modified flame retardant, and 4-amino-2,2,6,6-tetramethylpiperidine is not added; only octadecyl alcohol substitution and phenol blocking are carried out. Other operating steps and process parameters are exactly the same as in Example 1.

[0019] Comparative Example 3: The difference between this comparative example and Example 1 is that the reflux temperature of the third substitution reaction is changed to 58°C; the other operating steps and process parameters are exactly the same as those in Example 1.

[0020] Comparative Example 4: The difference between this comparative example and Example 1 is that the amount of multifunctional modified flame retardant in the mixture formulation is changed to 5 parts; the amount of other raw materials and the operation steps are exactly the same as in Example 1.

[0021] Comparative Example 5: The difference between this comparative example and Example 1 is that the plasticizer in the mixture formula is changed to only 50 parts of dioctyl phthalate, and dioctyl terephthalate is not added; the amount of other raw materials and the operation steps are exactly the same as in Example 1.

[0022] Performance testing and data sheets: Flame retardancy was determined according to GB / T2406.2, with the limiting oxygen index and flame retardancy rating tested according to the UL94 vertical burning method. Mechanical properties were tested according to GB / T1040.2, including tensile strength and elongation at break. Weather resistance was determined according to GB / T16422.2, involving 720 hours of xenon lamp aging followed by determination of tensile strength retention and elongation at break retention, and observation of surface precipitation. Kaolin particle size was tested using a laser particle size analyzer. The standard is used for measurement; Table 1. Performance test results of each embodiment and comparative example:

[0023] As can be seen from the comparison of the test results of Example 1 and Comparative Example 1 in the table, after omitting the octadecyl alcohol long chain introduced by the first step substitution reaction, the elongation at break, tensile strength retention rate and elongation at break retention rate of the material all decreased significantly, and slight precipitation occurred. Long aliphatic carbon chains can improve the compatibility of flame retardants with polyvinyl chloride matrix and enter the PVC molecular chains to form physical entanglement during melt blending, weakening the inter-molecular forces and reducing local stress concentration caused by inorganic fillers. Without this structure, the dispersion of flame retardants in the matrix becomes poor, the interfacial bonding weakens, and the material is more prone to forming microcracks during stretching and aging, thus reducing mechanical properties and aging retention. At the same time, the small molecule characteristics are enhanced, and the tendency to migrate and precipitate increases. Comparing the test results of Example 1 and Comparative Example 2 in the table, it can be seen that after omitting the 4-amino-2,2,6,6-tetramethylpiperidine introduced by the second substitution reaction, the flame retardant rating did not change significantly, but the retention rates of tensile strength and elongation at break after aging decreased significantly. The underlying mechanism is that the hindered amine structure can be converted into stable nitroxide free radicals in the presence of light and oxygen, which can capture alkyl free radicals and peroxy free radicals generated during the photo-oxidative degradation of polyvinyl chloride, and inhibit dehydrochlorination and main chain breakage. Without this structure, the material is more prone to chain segment breakage and surface embrittlement during xenon lamp aging, thus the weather resistance retention rate decreases significantly. Comparing the test results of Example 1 and Comparative Example 3 in the table, it can be seen that after the temperature of the third substitution reaction was reduced to 58℃, the LOI decreased from 31.8% to 28.6%, the UL94 rating decreased from V-0 to V-1, and the mechanical properties and weather resistance also decreased simultaneously. The underlying mechanism is that the substitution of the remaining P-Cl bonds by phenol requires a sufficient reaction temperature to ensure the degree of substitution. When the temperature is too low, the outer aryl groups are not fully closed, and more active P-Cl bonds remain in the molecule, resulting in a decrease in the structural stability of the product. During processing and aging, it is easier to release acidic substances and induce the degradation of polyvinyl chloride. At the same time, the insufficient number of aryl groups will weaken the char formation of the condensed phase, reduce the continuity of the char layer, and consequently worsen the flame retardant performance. As can be seen from the comparison of the test results of Example 1 and Comparative Example 4 in the table, when the amount of multifunctional modified flame retardant was reduced from 10 parts to 5 parts, the LOI and UL94 ratings decreased significantly, and the aging retention rate also decreased accordingly. The underlying mechanism is that the flame retardant provides a phosphazene skeleton, an aryloxy char structure and a hindered amine anti-aging structure at the same time. When the amount added is insufficient, the effective components that can participate in char formation and gas phase flame suppression during combustion are reduced, resulting in a thinner char layer with poor continuity. During aging, the number of hindered amine groups decreases, reducing the ability to scavenge free radicals. Therefore, both flame retardant and weather resistance are adversely affected. The elongation at break in this comparative example is slightly higher, mainly due to the reduction in rigid components of the system after the reduction of flame retardant. However, this change does not compensate for the decrease in flame retardant and weather resistance. As can be seen from the comparison of the test results of Example 1 and Comparative Example 5 in the table, after the plasticizer was changed to only dioctyl phthalate, the LOI, UL94 rating, tensile strength and aging retention rate all decreased, and the surface precipitation phenomenon was obvious. Dioctyl terephthalate (DTP) has a relatively regular molecular structure and low volatility and migration tendency. When compounded with dioctyl phthalate (DTP), it can achieve a better balance between flexibility and migration resistance. When DTP is used alone, the mobility of small molecule plasticizers in the system is enhanced, making it easier for them to migrate to the material surface and having a stronger dilutive effect on the intrinsic flame retardancy of polyvinyl chloride (PVC). During aging, plasticizer loss can also exacerbate material hardening and embrittlement, thus leading to a simultaneous decline in flame retardancy, mechanical properties, and weather resistance. As can be seen from the data of Examples 1 to 4, by adjusting the ratio of each reactant, the mixing temperature and the extrusion temperature within a limited range, the resulting materials can all achieve V-0 flame retardancy and maintain high tensile strength, elongation at break and aging retention rate, indicating that the method has good process adaptability. Example 4 uses chlorinated polyvinyl chloride resin as the matrix. Although its processing temperature and intrinsic properties are different from those of ordinary polyvinyl chloride, the multifunctional modified flame retardant prepared by this invention and the corresponding process parameters can still achieve excellent flame retardant effect and good weather resistance and mechanical properties. This indicates that the process of the present invention also has good applicability to chlorinated polyvinyl chloride resin; the reaction ratio and formulation used in Example 1 balance the degree of flame retardant grafting, matrix compatibility, filler dosage and plasticizing system, thus the overall performance is relatively balanced; In addition, the specific weight parts of auxiliary raw materials such as calcium-zinc composite heat stabilizer, pentaerythritol stearate and polyethylene wax in Examples 1-4 were adjusted within a range. The range of these auxiliary raw materials is mainly to match different amounts of matrix resin, multifunctional modified flame retardant and plasticizer system, so as to maintain the thermal stability and internal and external lubrication balance of the system at different processing temperatures. Within the aforementioned defined range, adjustments to these auxiliary raw materials can ensure a smooth extrusion granulation process, preventing material degradation or roller sticking. Examples 1-4 all achieved excellent mechanical properties and surface quality without precipitation, confirming the rationality of the formulation range design.

[0024] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles, characterized in that, include: Preparation of multifunctional modified flame retardants: mixing, extrusion granulation; The preparation of the multifunctional modified flame retardant includes: a first-step substitution reaction, a second-step substitution reaction, a third-step substitution reaction, and purification; The first step of the substitution reaction involves mixing hexachlorocyclotriphosphazene, anhydrous tetrahydrofuran, and triethylamine, then adding a tetrahydrofuran solution of octadecyl alcohol dropwise at 0-5°C and maintaining the temperature to obtain intermediate solution A. The second step of the substitution reaction involves heating the intermediate A solution to 45-50°C, adding a tetrahydrofuran solution of 4-amino-2,2,6,6-tetramethylpiperidine, and reacting at a constant temperature to obtain the intermediate B solution. The third step of the substitution reaction involves adding phenol and anhydrous potassium carbonate to the intermediate B solution, heating to 65-70°C, and refluxing to obtain a reaction mixture. The purification process involves cooling the reaction mixture to room temperature, filtering it, collecting the filtrate, concentrating the filtrate, adding the concentrated filtrate dropwise to ice water to precipitate a precipitate, collecting the precipitate and washing it, and then vacuum drying it to obtain a multifunctional modified flame retardant. The mixing process involves adding chlorinated polyvinyl chloride resin or polyvinyl chloride resin and calcium / zinc composite heat stabilizer to a high-speed mixer and mixing at low speed to 55-65°C to obtain a first mixture; adding dioctyl terephthalate, dioctyl phthalate, and the aforementioned multifunctional modified flame retardant to the first mixture and mixing at high speed to 100-110°C to obtain a second mixture; adding calcined kaolin, pentaerythritol stearate, and polyethylene wax to the second mixture, mixing, and then discharging the mixture into a cold mixer for cooling to obtain a dry mixture; The extrusion granulation process involves adding the dry mixture to a twin-screw extruder, melting and blending it, extruding it into strands, cooling it with water, and then pelletizing it to obtain weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles. In the mixture, by weight, 100 parts of chlorinated polyvinyl chloride resin or polyvinyl chloride resin, 45-55 parts of dioctyl terephthalate and dioctyl phthalate, 8-12 parts of multifunctional modified flame retardant, 30-40 parts of calcined kaolin, 4-6 parts of calcium / zinc composite heat stabilizer, and 1-1.2 parts of pentaerythritol stearate and polyethylene wax.

2. The method for preparing weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles according to claim 1, characterized in that, In the first step of the substitution reaction, the molar ratio of hexachlorocyclotriphosphazene to octadecyl alcohol is 1:2 to 1:2.

1. In the second substitution reaction, the molar ratio of hexachlorocyclotriphosphazene to 4-amino-2,2,6,6-tetramethylpiperidine is 1:2 to 1:2.

1. In the third substitution reaction, the molar ratio of hexachlorocyclotriphosphazene to phenol is 1:2.1 to 1:2.

3.

3. The method for preparing weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles according to claim 1, characterized in that, In the first step of the substitution reaction, the heat preservation reaction time is 3.5-4.5 hours. In the second substitution reaction, the isothermal reaction time is 5.5-6.5 h; In the third substitution reaction, the reflux reaction time is 11-13 hours.

4. The method for preparing weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles according to claim 1, characterized in that, In the purification process, the filtrate is concentrated to 1 / 4 to 1 / 3 of its original volume; The washing process involves alternating between deionized water and ethanol. The vacuum drying temperature is 55-65℃, and the time is 22-26h.

5. The method for preparing weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles according to claim 1, characterized in that, In the mixing process, chlorinated polyvinyl chloride resin or polyvinyl chloride resin and calcium / zinc composite heat stabilizer are added to a high-speed mixer and mixed at low speed to 55-65°C to obtain a first mixture. Dioctyl terephthalate, dioctyl phthalate, and the multifunctional modified flame retardant were added to the first mixture, and the mixture was mixed at high speed to 100-110°C to obtain the second mixture. Add calcined kaolin, pentaerythritol stearate, and polyethylene wax to the second mixture, and continue mixing to 110-120°C; The material is discharged into a cold mixer and cooled to 35-40℃ to obtain a dry mixture.

6. The method for preparing weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles according to claim 1, characterized in that, In the extrusion granulation process, the temperature of the twin-screw extruder is 140-150℃ in zone one, 150-160℃ in zone two, 155-165℃ in zone three, 160-170℃ in zone four, and 160-170℃ at the die head.

7. The method for preparing weather-resistant and flame-retardant chlorinated polyvinyl chloride plastic for charging piles according to claim 1, characterized in that, In the mixture, the weight ratio of dioctyl terephthalate to dioctyl phthalate is 7:3 to 8:

2. The weight ratio of pentaerythritol stearate to polyethylene wax is 2.5:1 to 3:1; The polyvinyl chloride resin is a suspension polyvinyl chloride resin with a degree of polymerization of 1000; The particle size of the calcined kaolin is 1200-1300 mesh.

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