High-performance polyvinyl chloride cable material and preparation method thereof

Abstract

This invention relates to the field of cable technology, specifically to a high-performance polyvinyl chloride (PVC) cable material and its preparation method. The cable material is based on PVC resin, combined with plasticizers and multifunctional flame-retardant composite fillers, with the filler content being 85-95 parts by weight per 100 parts by weight of resin. The multifunctional flame-retardant composite filler employs a multi-layered interface design: using magnesium hydroxide / calcium carbonate as the core, it first undergoes silane treatment to introduce epoxy sites, then constructs a phytic acid-tin-calcium-zinc chelate layer, and immobilizes double-grafted modified carboxymethyl-β-cyclodextrin, ultimately forming a tannic acid-metal ion polyphenol network layer. The preparation method includes pre-plasticization, segmented mixing with filler addition, and extrusion granulation. This invention effectively improves the filler-matrix interface compatibility, enhances flame retardancy, mechanical properties, and thermal stability, and solves the problem of insufficient durability in high-filler systems.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and in particular to a high-performance polyvinyl chloride cable material and its preparation method. Background Technology

[0002] Polyvinyl chloride (PVC) cable materials are widely used in the wire and cable industry due to their excellent comprehensive performance. To meet increasingly stringent flame retardant safety standards, high proportions of inorganic flame retardants such as magnesium hydroxide and calcium carbonate have become key methods to improve the flame retardant rating of materials. However, the introduction of high proportions of inorganic fillers often leads to a series of interfacial compatibility problems. The significant polarity difference between inorganic filler particles and the organic PVC matrix results in uneven dispersion of the filler in the matrix, making it prone to agglomeration and thus becoming stress concentration points, severely deteriorating the mechanical properties of the material, especially leading to a decrease in tensile strength and elongation at break. Simultaneously, the weak physical adsorption between the filler and the matrix makes it difficult to effectively transfer stress. During long-term use or thermal aging, microcracks are more likely to develop at interfacial defects, affecting the service life and reliability of cable products.

[0003] On the other hand, to achieve the necessary flexibility and processing fluidity, a large amount of plasticizer needs to be added to the formulation of PVC cable materials. In highly filled systems, these small organic molecule plasticizers not only compete with inorganic fillers for matrix space, but are also prone to uneven distribution at the filler-matrix interface or migration and precipitation to the surface over time. This migration of plasticizers not only leads to gradual hardening and embrittlement of the material, resulting in loss of low-temperature flexibility, but may also cause problems such as sticky surfaces and decreased electrical insulation performance. Furthermore, the migrated plasticizers may become flammable, to some extent offsetting the flame-retardant effect of the inorganic fillers, making it difficult to synergistically optimize flame-retardant efficiency with mechanical properties and durability.

[0004] Traditional interface modification methods, such as treating the filler surface with a single silane coupling agent, can improve dispersibility to some extent, but the resulting interface layer is often relatively simple, with limited anchoring ability for plasticizers, and it is difficult to cope with the erosion of acidic substances such as hydrogen chloride generated during PVC processing and use due to thermal decomposition. Acidic environments disrupt conventional interfacial bonding, accelerate the separation of fillers from the matrix, and may catalyze further degradation of PVC resin. Therefore, developing a multifunctional interface construction strategy that can simultaneously achieve strong interfacial bonding and buffer against acidic degradation products has become a key challenge in overcoming the technical bottlenecks of high-filler, high-performance PVC cable materials. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a high-performance polyvinyl chloride cable material and its preparation method, so as to solve the problems of poor interfacial compatibility between highly filled inorganic flame-retardant fillers and PVC matrix, easy migration of plasticizers leading to insufficient material durability, and difficulty in synergistically improving flame retardant efficiency and mechanical properties.

[0006] To achieve the above objectives, the present invention provides a high-performance polyvinyl chloride cable material, comprising polyvinyl chloride resin, plasticizer, and multifunctional flame-retardant composite filler. The multifunctional flame-retardant composite filler comprises magnesium hydroxide / calcium carbonate inorganic core particles and an interface layer coated on the surface of the inorganic core particles. The interface layer comprises an epoxy-containing site layer formed by hydrolysis and condensation of an epoxy-containing silane coupling agent, a phytic acid-tin-calcium-zinc chelate layer located outside the epoxy-containing site layer, and a tannic acid-metal ion polyphenol network layer located outside the phytic acid-tin-calcium-zinc chelate layer. Furthermore, the interface layer is immobilized with double-grafted modified carboxymethyl-β-cyclodextrin.

[0007] Preferably, the amount of the multifunctional flame-retardant composite filler is 85-95 parts by weight per 100 parts by weight of the polyvinyl chloride resin.

[0008] Preferably, the plasticizer includes diisononyl phthalate and di-n-octyl adipate.

[0009] Preferred options also include epoxidized soybean oil.

[0010] Preferably, it also includes the synergistic flame retardant antimony trioxide.

[0011] Preferably, it also includes a calcium-zinc composite heat stabilizer and an acrylic resin processing aid.

[0012] Preferably, the preparation steps of the multifunctional flame-retardant composite filler are as follows: (1) The magnesium hydroxide and calcium carbonate mixed particles were reacted with the hydrolysate of 3-glycidoxypropyltrimethoxysilane to obtain magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface. (2) The magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface are mixed with phytic acid aqueous solution. Stannous salt is added first, followed by calcium salt and zinc salt to construct phytic acid-tin-calcium-zinc chelate layer. Then, double-grafted modified carboxymethyl-β-cyclodextrin is added and immobilized. Tannic acid is added and zinc salt and calcium salt are introduced to form tannic acid-metal ion polyphenol network layer to obtain multifunctional flame retardant composite filler.

[0013] Preferably, in step (1), the mass ratio of magnesium hydroxide, calcium carbonate and 3-glycidoxypropyltrimethoxysilane is 500:350:8-12.

[0014] Preferably, in step (2), the concentration of the phytic acid aqueous solution is 8wt%-12wt%, and the pH is 6.

[0015] Preferably, in step (2), the stannous salt is stannous chloride dihydrate, the calcium salt is calcium acetate, and the zinc salt is zinc acetate.

[0016] Preferably, in step (2), based on the amount of magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface, the amount of phytic acid aqueous solution used to construct the phytic acid-tin-calcium-zinc chelate layer is 800g, the amount of stannous salt is 6-8g, the amount of calcium salt is 4-6g, and the amount of zinc salt is 2-4g.

[0017] Preferably, in step (2), based on the amount of magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface, the amount of double-grafted modified carboxymethyl-β-cyclodextrin used to construct the metal ion polyphenol network layer is 7-11g, tannic acid is 14-24g, zinc salt is 3-5g, and calcium salt is 1-3g.

[0018] The preferred preparation steps for double-grafted modified carboxymethyl-β-cyclodextrin are as follows: (a) Sodium carboxymethyl-β-cyclodextrin undergoes a long-chain fatty acylation reaction with lauroyl chloride to obtain dodecanoyl-modified carboxymethyl-β-cyclodextrin; (b) Epichlorohydrin was used to epoxidize dodecanoyl-modified carboxymethyl-β-cyclodextrin to obtain dodecanoyl-modified carboxymethyl-β-cyclodextrin with epoxy groups on the surface; (c) React dodecanoyl-modified carboxymethyl-β-cyclodextrin with epoxy groups on its surface with 3-aminopropyltriethoxysilane to obtain double-grafted modified carboxymethyl-β-cyclodextrin.

[0019] Preferably, in step (a), the mass ratio of sodium carboxymethyl-β-cyclodextrin salt to lauroyl chloride is 100:45-55.

[0020] Preferably, in step (b), the mass ratio of epichlorohydrin to dodecanoyl-modified carboxymethyl-β-cyclodextrin is 54-66:80.

[0021] Preferably, in step (c), the mass ratio of dodecanoyl-modified carboxymethyl-β-cyclodextrin with epoxy groups on its surface to 3-aminopropyltriethoxysilane is 60:27-33.

[0022] Furthermore, the present invention also provides a method for preparing high-performance polyvinyl chloride cable material, comprising the following steps: S1: Polyvinyl chloride resin is pre-plasticized and mixed with processing aids, heat stabilizers, lubricants, antioxidants and at least a portion of plasticizers to obtain pre-plasticized polyvinyl chloride dry mix; S2: The preplasticized PVC dry mix is ​​subjected to intensive mixing. During the intensive mixing process, multifunctional flame-retardant composite filler is added in stages, and the remaining plasticizer and / or epoxidized soybean oil and synergistic flame retardant are added to obtain high-performance PVC cable material blank. S3: Extrude and granulate the high-performance polyvinyl chloride cable material blank to obtain high-performance polyvinyl chloride cable material.

[0023] Preferably, in step S1, the pre-plasticization is carried out at 110°C and maintained for 2 minutes.

[0024] Preferably, in step S2, the rotor speed of the internal mixer is 60 rpm and the jacket temperature is 150°C. When the torque reaches its peak and then drops slightly and the material temperature reaches 155°C, the multifunctional flame-retardant composite filler is added twice within 2 minutes. After all the filler is added, the internal mixer continues to mix for 3 minutes. Then, diisononyl phthalate plasticizer, di-n-octyl adipate plasticizer, epoxidized soybean oil and antimony trioxide are added and the internal mixer continues to mix for 2 minutes.

[0025] Preferably, in step S3, the extrusion granulation uses a co-rotating parallel twin-screw extruder, with the barrel temperatures in each zone being 150℃, 160℃, 165℃, and 170℃ respectively, the screw speed being 190-210 rpm, and the vacuum degree being -0.09MPa to -0.07MPa.

[0026] The beneficial effects of this invention are: This invention significantly improves the overall performance of PVC cable materials by constructing a multi-layered, multifunctional organic-inorganic hybrid interface structure on the surface of multi-component inorganic fillers. The innermost layer of this interface structure is firmly bonded to the filler surface through the hydrolytic condensation of silanes containing epoxy groups, forming a stable reaction site platform. This platform provides a solid chemical anchoring point for the step-by-step assembly of subsequent functional layers, ensuring the stability of the entire interface structure under high-shear processing and long-term use environments, effectively preventing filler agglomeration and performance degradation caused by interface layer detachment.

[0027] Based on the aforementioned epoxy site layer, a chelate network layer is further introduced, formed by phytic acid and various metal ions (such as tin, calcium, and zinc ions). In this network layer, the polyphosphate groups of phytic acid form a stable coordination structure with the metal ions, which not only enhances the mechanical strength of the interface layer itself, but more importantly, in the early stage of thermal decomposition of polyvinyl chloride, this structure can effectively capture and neutralize the released acidic small molecules such as hydrogen chloride, slowing down their catalytic degradation of the polyvinyl chloride molecular chain, thereby significantly extending the thermal stability time of the material and broadening the processing window.

[0028] Beyond the phytic acid-metal chelate layer, a specially designed double-grafted modified cyclodextrin derivative is introduced. This derivative molecule possesses both hydrophobic long-chain alkyl groups and silane groups capable of participating in interfacial reactions. The long-chain alkyl groups are compatible with the plasticizer molecules through hydrophobic interactions, while the cavity structure of the cyclodextrin can encapsulate the plasticizer, together constraining it. The silane groups then react with the active sites in the interfacial layer, immobilizing the cyclodextrin derivative on the filler surface. This design achieves immobilized and slow-release of the plasticizer in the interfacial region, greatly suppressing the macroscopic migration of the plasticizer in the matrix and its precipitation to the surface, thus ensuring that the material maintains excellent flexibility and mechanical property retention even after thermal aging.

[0029] The outermost layer of tannic acid cross-links with metal ions to form a polyphenol-metal network, further enhancing the density and thermal stability of the interfacial layer. This network promotes the formation of a continuous and robust carbon layer at high temperatures, creating a synergistic effect with the carbonization of the inner phytic acid-metal system. Together, they cover the filler and matrix surfaces, providing excellent thermal and oxygen barrier properties. Simultaneously, this network also possesses a certain dynamic complexing ability towards acidic substances, providing additional protection for the material.

[0030] Ultimately, by optimizing the processing technology and adopting a segmented feeding method, the multifunctional filler with complex interface structures was introduced at the appropriate time during the plasticization process of polyvinyl chloride (PVC), ensuring the uniform dispersion of filler particles and the integrity of the interface structure. The synergistic effect between each interface functional layer, the PVC, and the additive system resulted in a balanced and significant improvement in the final cable material's flame retardancy, mechanical strength, heat aging resistance, and processing stability. 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. Detailed Implementation

[0033] Example 1: Step 1: Long-chain fatty acid acylation of carboxymethyl-β-cyclodextrin Weigh 100g of sodium carboxymethyl-β-cyclodextrin (Shanghai Aladdin Biochemical Technology Co., Ltd., item number C303636) and add it to a three-necked flask equipped with a mechanical stirrer and reflux condenser. Then add 300mL of anhydrous N,N-dimethylformamide and stir at 40℃ for 30min. Then add 27g of triethylamine and add 45g of lauroyl chloride dropwise over 1h with a dropping funnel while stirring. After the addition is complete, continue stirring at 40℃ for 2.5h. After the reaction is complete, add 200mL of deionized water and 50mL of glacial acetic acid to the system to quench the remaining acyl chloride. After stirring for 30min, pour the reaction solution into cold water to precipitate the solid. After filtration, wash with water and anhydrous ethanol three times each, and dry under vacuum at 50℃ for 12h to obtain dodecanoyl-modified carboxymethyl-β-cyclodextrin for later use. Step 2: Epoxidation of carboxymethyl-β-cyclodextrin with dodecanoyl groups introduced onto the surface Weigh 80g of dodecanoyl-modified carboxymethyl-β-cyclodextrin and add it to a three-necked flask equipped with a mechanical stirrer. Then add 200mL of deionized water and 200mL of anhydrous isopropanol mixed solvent. Stir and disperse at 40℃ for 30min to form a uniform suspension. Then add 14g of sodium hydroxide. After that, add 54g of epichlorohydrin dropwise over 1h at 40℃. After the addition is complete, continue stirring at 40℃ for 3.5h. After the reaction is complete, distill under reduced pressure and pour the concentrated liquid into cold water. Let it stand to precipitate solid. After filtration, wash with water and anhydrous ethanol three times each. Dry under vacuum at 50℃ for 12h to obtain dodecanoyl-modified carboxymethyl-β-cyclodextrin solid with epoxy groups on the surface. Step 3: Preparation of double-grafted modified carboxymethyl-β-cyclodextrin Weigh 60g of epoxy-containing dodecanoyl-modified carboxymethyl-β-cyclodextrin and add it to a three-necked flask equipped with a mechanical stirrer and reflux device. Then add 300mL of anhydrous ethanol to form a suspension. Stir at 50℃ for 10min and add 27g of 3-aminopropyltriethoxysilane. Continue stirring at 50℃ for 3.5h. After the reaction is completed, cool to room temperature and pour the reaction solution into anhydrous diethyl ether to precipitate the solid. After filtration, wash with ethanol and diethyl ether three times in sequence and dry under vacuum at 50℃ for 12h to obtain double-grafted modified carboxymethyl-β-cyclodextrin. Step 4: Preparation of epoxy site inorganic core particles Weigh 500g of magnesium hydroxide flame retardant filler (KISUMA5-C produced by KISUMA (Dandong) High-Tech Materials Technology Co., Ltd., with a particle size D50 of 0.9μm), and weigh 350g of light calcium carbonate (average particle size 1μm). Mix the two thoroughly and add them to a stainless steel stirred tank equipped with a heating and stirring device. Then add 900mL of anhydrous ethanol and 100mL of deionized water to the tank and stir to form a magnesium hydroxide / calcium carbonate slurry. Separately, weigh 8g of... 3-Glycidyl etheroxypropyltrimethoxysilane was added to 100 mL of ethanol and 20 mL of deionized water and stirred. 2 g of glacial acetic acid was added dropwise. After hydrolysis at room temperature for 15 min, the hydrolysate was added to the aforementioned magnesium hydroxide / calcium carbonate slurry within 30 min. The reaction was continued to be stirred at 50 °C for 1.5 h. After the reaction was completed, stirring was stopped, the mother liquor was removed by filtration, and the filter cake was washed three times each with ethanol and deionized water. The cake was then vacuum dried at 110 °C for 6 h to obtain magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface. Step 5: Preparation of Multifunctional Flame-Retardant Composite Filler Weigh 800g of magnesium hydroxide / calcium carbonate composite particles with epoxy sites on their surface and add them to a stirred tank equipped with a heating and stirring device. Separately, prepare 800g of an 8wt% phytic acid aqueous solution in a beaker, adjust the pH to 6 with sodium hydroxide solution, and then add this phytic acid solution to the stirred tank all at once at 60℃. Stir for 25 min. Next, weigh 6g of stannous chloride dihydrate, dissolve it in 100mL of deionized water, and add it to the stirred tank. Continue stirring at 60℃ for 35 min. Then, weigh 4g of calcium acetate and 2g of zinc acetate, dissolve them in 100mL of water, and add them to the stirred tank. Stir at 60℃ for 15 min to obtain an inorganic particle suspension system with a phytic acid-tin-calcium-zinc chelate layer on the surface. Then, weigh 7g of double-grafted modified carboxymethyl-β-cyclodextrin and add it to a beaker, followed by 1... A mixture of 60 mL ethanol and 40 mL deionized water was stirred at room temperature to form a uniform dispersion. This dispersion was then added to an inorganic particle suspension system with a phytic acid-tin-calcium-zinc chelate layer on the surface within 5 min. The mixture was stirred at 60 °C for 25 min. 16 g of tannic acid was weighed and dissolved in 400 mL of deionized water to form a tannic acid solution. This solution was then added to the system at 60 °C and stirred for 15 min. 3 g of zinc acetate and 1 g of calcium acetate were weighed and dissolved in 100 mL of water and added to the system. The mixture was stirred at 60 °C for 35 min. After the reaction was complete, stirring was stopped, and the suspension was filtered. The filter cake was washed with deionized water until the filtrate was nearly neutral, then washed three times with ethanol. Finally, the wet filter cake was dried in a vacuum drying oven at 110 °C for 6 h to obtain a multifunctional flame-retardant composite filler. Step Six: Preparation of Preplasticized Polyvinyl Chloride Dry Mix Weigh 1000g of polyvinyl chloride resin powder (SG5 grade polyvinyl chloride resin produced by Xinjiang Tianye Co., Ltd., with a K value of approximately 65-68 and an average degree of polymerization of approximately 950-1100), add it to a high-speed mixer equipped with heating and speed control, and then add 15g of acrylic resin processing aid (transparent polyvinyl chloride processing aid ACR produced by Zibo Huaxing Additives Co., Ltd.). Add 25g of calcium-zinc composite heat stabilizer for cables (NV-7611232 calcium-zinc stabilizer for cables manufactured by Novista), then add 5g of PVC heat stabilizer β-diketone, 3g of paraffin wax, 2g of stearic acid, 6g of calcium stearate, and 2g of antioxidant 1010. Start the high-speed mixer and stir at room temperature for 2 minutes. Then turn on the heating function and heat the material to 80°C. Add 235g of diisononyl phthalate plasticizer and 95g of di-n-octyl adipate plasticizer. Continue heating and high-speed stirring to raise the material temperature to 110°C and maintain it for 2 minutes. Then discharge the material and let it cool naturally to 50°C to obtain pre-plasticized PVC dry mix. Step 7: Intensive mixing, adding multifunctional flame-retardant composite filler and plasticizer in stages. Set the rotor speed of a mixer to 60 rpm and the jacket temperature to 150℃. After the temperature of the mixing chamber stabilizes, add 1400g of pre-plasticized PVC dry mix to the mixer, close the mixing chamber and start mixing. When the torque reaches its peak and then drops slightly and the material temperature reaches 155℃, add a total of 850g of multi-functional flame-retardant composite filler in two batches within 2 minutes. After each addition, ensure thorough mixing. After all the filler has been added, continue mixing for 3 minutes. Then add 95g of diisononyl phthalate plasticizer, 40g of di-n-octyl adipate plasticizer, 45g of epoxidized soybean oil (D-39 epoxidized soybean oil from Galata Chemicals), and 18g of antimony trioxide fine powder. Continue mixing for 2 minutes. Then discharge and cool the material to obtain a high-performance PVC cable preform for extrusion. Step 8: Extrusion Granulation The cable material blank obtained in step seven is cooled and crushed, and then fed into a co-rotating parallel twin-screw extruder with a vacuum exhaust device. The temperature of each zone of the barrel is set to 150℃, 160℃, 165℃ and 170℃ respectively, the screw speed is about 190 rpm, and the vacuum degree is controlled at -0.07MPa. After extrusion into strips, the material is water-cooled and then pelletized to obtain high-performance polyvinyl chloride cable material.

[0034] Example 2: Step 1: Long-chain fatty acid acylation of carboxymethyl-β-cyclodextrin Weigh 100g of sodium carboxymethyl-β-cyclodextrin (Shanghai Aladdin Biochemical Technology Co., Ltd., item number C303636) and add it to a three-necked flask equipped with a mechanical stirrer and reflux condenser. Then add 300mL of anhydrous N,N-dimethylformamide and stir at 40℃ for 30min. Then add 30g of triethylamine and add 50g of lauroyl chloride dropwise over 1h with a dropping funnel while stirring. After the addition is complete, continue stirring at 40℃ for 3h. After the reaction is complete, add 200mL of deionized water and 50mL of glacial acetic acid to the system to quench the remaining acyl chloride. After stirring for 30min, pour the reaction solution into cold water to precipitate the solid. After filtration, wash with water and anhydrous ethanol three times each, and dry under vacuum at 50℃ for 12h to obtain dodecanoyl-modified carboxymethyl-β-cyclodextrin for later use. Step 2: Epoxidation of carboxymethyl-β-cyclodextrin with dodecanoyl groups introduced onto the surface Weigh 80g of dodecanoyl-modified carboxymethyl-β-cyclodextrin and add it to a three-necked flask equipped with a mechanical stirrer. Then add 200mL of deionized water and 200mL of anhydrous isopropanol mixed solvent. Stir and disperse at 40℃ for 30min to form a uniform suspension. Then add 16g of sodium hydroxide. After that, add 60g of epichlorohydrin dropwise over 1h at 40℃. After the dropwise addition is complete, continue stirring at 40℃ for 4h. After the reaction is completed, distill under reduced pressure and pour the concentrated liquid into cold water. Let it stand to precipitate solid. After filtration, wash with water and anhydrous ethanol 3 times each. Dry under vacuum at 50℃ for 12h to obtain dodecanoyl-modified carboxymethyl-β-cyclodextrin solid with epoxy groups on the surface. Step 3: Preparation of double-grafted modified carboxymethyl-β-cyclodextrin Weigh 60g of epoxy-containing dodecanoyl-modified carboxymethyl-β-cyclodextrin and add it to a three-necked flask equipped with a mechanical stirrer and reflux device. Then add 300mL of anhydrous ethanol to form a suspension. After stirring at 50℃ for 10min, add 30g of 3-aminopropyltriethoxysilane and continue stirring at 50℃ for 4h. After the reaction is completed, cool to room temperature and pour the reaction solution into anhydrous diethyl ether to precipitate the solid. After filtration, wash with ethanol and diethyl ether three times in sequence, and dry under vacuum at 50℃ for 12h to obtain double-grafted modified carboxymethyl-β-cyclodextrin. Step 4: Preparation of epoxy site inorganic core particles Weigh 500g of magnesium hydroxide flame retardant filler (KISUMA5-C produced by KISUMA (Dandong) High-Tech Materials Technology Co., Ltd., with a particle size D50 of 0.9μm), and weigh 350g of light calcium carbonate (average particle size 1μm). Mix the two thoroughly and add them to a stainless steel stirred tank equipped with a heating and stirring device. Then add 900mL of anhydrous ethanol and 100mL of deionized water to the tank and stir to form a magnesium hydroxide / calcium carbonate slurry. Separately, weigh 10g of... 3-Glycidyl etheroxypropyltrimethoxysilane was added to 100 mL of ethanol and 20 mL of deionized water and stirred. 2 g of glacial acetic acid was added dropwise. After hydrolysis at room temperature for 20 min, the hydrolysate was added to the aforementioned magnesium hydroxide / calcium carbonate slurry within 30 min. The reaction was continued at 50 °C for 2 h. After the reaction was completed, stirring was stopped, the mother liquor was removed by filtration, and the filter cake was washed three times each with ethanol and deionized water. The cake was then vacuum dried at 110 °C for 6 h to obtain magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface. Step 5: Preparation of Multifunctional Flame-Retardant Composite Filler Weigh 800g of magnesium hydroxide / calcium carbonate composite particles with epoxy sites on their surface and add them to a stirred tank equipped with a heating and stirring device. Separately, prepare 800g of a 10wt% phytic acid aqueous solution in a beaker, adjust the pH to 6 with sodium hydroxide solution, and then add this phytic acid solution to the stirred tank all at once at 60℃. Stir for 30 min. Next, weigh 7g of stannous chloride dihydrate, dissolve it in 100mL of deionized water, and add it to the stirred tank. Continue stirring at 60℃ for 40 min. Then, weigh 5g of calcium acetate and 3g of zinc acetate, dissolve them in 100mL of water, and add them to the stirred tank. Stir at 60℃ for 20 min to obtain an inorganic particle suspension system with a phytic acid-tin-calcium-zinc chelate layer on the surface. Then, weigh 9g of double-grafted modified carboxymethyl-β-cyclodextrin and add it to a beaker, followed by 1... A uniform dispersion was formed by mixing 60 mL of ethanol and 40 mL of deionized water at room temperature. This dispersion was then added to an inorganic particle suspension system with a phytic acid-tin-calcium-zinc chelate layer on the surface within 5 min. The mixture was stirred at 60 °C for 30 min. 20 g of tannic acid was weighed and dissolved in 400 mL of deionized water to form a tannic acid solution. This solution was then added to the system at 60 °C and stirred for 20 min. 4 g of zinc acetate and 2 g of calcium acetate were weighed and dissolved in 100 mL of water and added to the system. The mixture was stirred at 60 °C for 40 min. After the reaction was complete, stirring was stopped, and the suspension was filtered. The filter cake was washed with deionized water until the filtrate was nearly neutral, then washed three times with ethanol. Finally, the wet filter cake was dried in a vacuum drying oven at 110 °C for 6 h to obtain a multifunctional flame-retardant composite filler. Step Six: Preparation of Preplasticized Polyvinyl Chloride Dry Mix Weigh 1000g of polyvinyl chloride resin powder (SG5 grade polyvinyl chloride resin produced by Xinjiang Tianye Co., Ltd., with a K value of approximately 65-68 and an average degree of polymerization of approximately 950-1100), add it to a high-speed mixer equipped with heating and speed control, and then add 15g of acrylic resin processing aid (transparent polyvinyl chloride processing aid ACR produced by Zibo Huaxing Additives Co., Ltd.). Add 25g of calcium-zinc composite heat stabilizer for cables (NV-7611232 calcium-zinc stabilizer for cables produced by Novista), then add 5g of PVC heat stabilizer β-diketone, 3g of paraffin wax, 2g of stearic acid, 6g of calcium stearate, and 2g of antioxidant 1010. Start the high-speed mixer and stir it at room temperature for 2 minutes. Then turn on the heating function and heat the material to 80°C. Add 245g of diisononyl phthalate plasticizer and 105g of di-n-octyl adipate plasticizer. Continue heating and high-speed stirring to raise the material temperature to 110°C and hold for 2 minutes. Then discharge the material and let it cool naturally to 50°C to obtain pre-plasticized PVC dry mix. Step 7: Intensive mixing, adding multifunctional flame-retardant composite filler and plasticizer in stages. Set the rotor speed of a mixer to 60 rpm and the jacket temperature to 150℃. After the temperature of the mixing chamber stabilizes, add 1400g of pre-plasticized PVC dry mix to the mixer, close the mixing chamber and start mixing. When the torque reaches its peak and then drops slightly and the material temperature reaches 155℃, add a total of 900g of multifunctional flame-retardant composite filler in two batches within 2 minutes. After each addition, ensure thorough mixing. After all the filler has been added, continue mixing for 3 minutes. Then add 105g of diisononyl phthalate plasticizer, 45g of di-n-octyl adipate plasticizer, 50g of epoxidized soybean oil (D-39 epoxidized soybean oil from Galata Chemicals), and 20g of antimony trioxide fine powder. Continue mixing for 2 minutes. Then discharge and cool the material to obtain a high-performance PVC cable preform for extrusion. Step 8: Extrusion Granulation The cable material blank obtained in step seven is cooled and crushed, and then fed into a co-rotating parallel twin-screw extruder with a vacuum exhaust device. The temperature of each zone of the barrel is set to 150℃, 160℃, 165℃ and 170℃ respectively, the screw speed is about 200 rpm, and the vacuum degree is controlled at -0.08MPa. The extruded material is formed into strips, which are then water-cooled and pelletized to obtain high-performance polyvinyl chloride cable material.

[0035] Example 3: Step 1: Long-chain fatty acid acylation of carboxymethyl-β-cyclodextrin Weigh 100g of sodium carboxymethyl-β-cyclodextrin (Shanghai Aladdin Biochemical Technology Co., Ltd., item number C303636) and add it to a three-necked flask equipped with a mechanical stirrer and reflux condenser. Then add 300mL of anhydrous N,N-dimethylformamide and stir at 40℃ for 30min. Then add 33g of triethylamine and add 55g of lauroyl chloride dropwise over 1h with a dropping funnel while stirring. After the addition is complete, continue stirring at 40℃ for 3.5h. After the reaction is complete, add 200mL of deionized water and 50mL of glacial acetic acid to the system to quench the remaining acyl chloride. After stirring for 30min, pour the reaction solution into cold water to precipitate the solid. After filtration, wash with water and anhydrous ethanol three times each, and dry under vacuum at 50℃ for 12h to obtain dodecanoyl-modified carboxymethyl-β-cyclodextrin for later use. Step 2: Epoxidation of carboxymethyl-β-cyclodextrin with dodecanoyl groups introduced onto the surface Weigh 80g of dodecanoyl-modified carboxymethyl-β-cyclodextrin and add it to a three-necked flask equipped with a mechanical stirrer. Then add 200mL of deionized water and 200mL of anhydrous isopropanol mixed solvent. Stir and disperse at 40℃ for 30min to form a uniform suspension. Then add 18g of sodium hydroxide. After that, add 66g of epichlorohydrin dropwise over 1h at 40℃. After the addition is complete, continue stirring at 40℃ for 4.5h. After the reaction is complete, distill under reduced pressure and pour the concentrated liquid into cold water. Let it stand to precipitate solid. After filtration, wash with water and anhydrous ethanol three times each. Dry under vacuum at 50℃ for 12h to obtain dodecanoyl-modified carboxymethyl-β-cyclodextrin solid with epoxy groups on the surface. Step 3: Preparation of double-grafted modified carboxymethyl-β-cyclodextrin Weigh 60g of epoxy-containing dodecanoyl-modified carboxymethyl-β-cyclodextrin and add it to a three-necked flask equipped with a mechanical stirrer and reflux device. Then add 300mL of anhydrous ethanol to form a suspension. Stir at 50℃ for 10min and add 33g of 3-aminopropyltriethoxysilane. Continue stirring at 50℃ for 4.5h. After the reaction is completed, cool to room temperature and pour the reaction solution into anhydrous diethyl ether to precipitate the solid. After filtration, wash with ethanol and diethyl ether three times in sequence and dry under vacuum at 50℃ for 12h to obtain double-grafted modified carboxymethyl-β-cyclodextrin. Step 4: Preparation of epoxy site inorganic core particles Weigh 500g of magnesium hydroxide flame retardant filler (KISUMA5-C, produced by KISUMA (Dandong) High-Tech Materials Technology Co., Ltd., with a particle size D50 of 0.9μm), and weigh 350g of light calcium carbonate (average particle size 1μm). Mix the two thoroughly and add them to a stainless steel stirred tank equipped with a heating and stirring device. Then add 900mL of anhydrous ethanol and 100mL of deionized water to the tank and stir to form a magnesium hydroxide / calcium carbonate slurry. Separately, weigh 12g of... 3-Glycidyl etheroxypropyltrimethoxysilane was added to 100 mL of ethanol and 20 mL of deionized water and stirred. 2 g of glacial acetic acid was added dropwise. After hydrolysis at room temperature for 25 min, the hydrolysate was added to the aforementioned magnesium hydroxide / calcium carbonate slurry within 30 min. The reaction was continued to be stirred at 50 °C for 2.5 h. After the reaction was completed, stirring was stopped, the mother liquor was removed by filtration, and the filter cake was washed three times each with ethanol and deionized water. The cake was then vacuum dried at 110 °C for 6 h to obtain magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface. Step 5: Preparation of Multifunctional Flame-Retardant Composite Filler Weigh 800g of magnesium hydroxide / calcium carbonate composite particles with epoxy sites on their surface and add them to a stirred tank equipped with a heating and stirring device. Separately, prepare 800g of a 12wt% phytic acid aqueous solution in a beaker, adjust the pH to 6 with sodium hydroxide solution, and then add this phytic acid solution to the stirred tank all at once at 60℃. Stir for 35 min. Next, weigh 8g of stannous chloride dihydrate, dissolve it in 100mL of deionized water, and add it to the stirred tank. Continue stirring at 60℃ for 45 min. Then, weigh 6g of calcium acetate and 4g of zinc acetate, dissolve them in 100mL of water, and add them to the stirred tank. Stir at 60℃ for 25 min to obtain an inorganic particle suspension system with a phytic acid-tin-calcium-zinc chelate layer on the surface. Finally, weigh 11g of double-grafted modified carboxymethyl-β-cyclodextrin and add it to a beaker, then add... A uniform dispersion was formed by mixing 160 mL of ethanol and 40 mL of deionized water at room temperature. This dispersion was then added to an inorganic particle suspension system with a phytic acid-tin-calcium-zinc chelate layer on the surface within 5 min. The mixture was stirred at 60 °C for 35 min. 24 g of tannic acid was weighed and dissolved in 400 mL of deionized water to form a tannic acid solution. This solution was then added to the system at 60 °C and stirred for 25 min. 5 g of zinc acetate and 3 g of calcium acetate were weighed and dissolved in 100 mL of water and added to the system. The mixture was stirred at 60 °C for 45 min. After the reaction was complete, stirring was stopped, and the suspension was filtered. The filter cake was washed with deionized water until the filtrate was nearly neutral, then washed three times with ethanol. Finally, the wet filter cake was dried in a vacuum drying oven at 110 °C for 6 h to obtain a multifunctional flame-retardant composite filler. Step Six: Preparation of Preplasticized Polyvinyl Chloride Dry Mix Weigh 1000g of polyvinyl chloride resin powder (SG5 grade polyvinyl chloride resin produced by Xinjiang Tianye Co., Ltd., with a K value of approximately 65-68 and an average degree of polymerization of approximately 950-1100), add it to a high-speed mixer equipped with heating and speed control, and then add 15g of acrylic resin processing aid (transparent polyvinyl chloride processing aid ACR produced by Zibo Huaxing Additives Co., Ltd.). Add 25g of calcium-zinc composite heat stabilizer for cables (NV-7611232 calcium-zinc stabilizer for cables manufactured by Novista), then add 5g of PVC heat stabilizer β-diketone, 3g of paraffin wax, 2g of stearic acid, 6g of calcium stearate, and 2g of antioxidant 1010. Start the high-speed mixer and stir at room temperature for 2 minutes. Then turn on the heating function and heat the material to 80°C. Add 255g of diisononyl phthalate plasticizer and 115g of di-n-octyl adipate plasticizer. Continue heating and high-speed stirring to raise the material temperature to 110°C and maintain it for 2 minutes. Then discharge the material and let it cool naturally to 50°C to obtain pre-plasticized PVC dry mix. Step 7: Intensive mixing, adding multifunctional flame-retardant composite filler and plasticizer in stages. Set the rotor speed of a mixer to 60 rpm and the jacket temperature to 150℃. After the temperature of the mixing chamber stabilizes, add 1400g of pre-plasticized PVC dry mix to the mixer, close the mixing chamber and start mixing. When the torque reaches its peak and then drops slightly and the material temperature reaches 155℃, add a total of 950g of multi-functional flame-retardant composite filler in two batches within 2 minutes. After each addition, ensure thorough mixing. After all the filler has been added, continue mixing for 3 minutes. Then add 115g of diisononyl phthalate plasticizer, 50g of di-n-octyl adipate plasticizer, 55g of epoxidized soybean oil (D-39 epoxidized soybean oil from Galata Chemicals), and 22g of antimony trioxide fine powder. Continue mixing for 2 minutes. Then discharge and cool the material to obtain a high-performance PVC cable preform for extrusion. Step 8: Extrusion Granulation The cable material blank obtained in step seven is cooled and crushed, and then fed into a co-rotating parallel twin-screw extruder with a vacuum exhaust device. The temperature of each zone of the barrel is set to 150℃, 160℃, 165℃ and 170℃ respectively, the screw speed is about 210 rpm, and the vacuum degree is controlled at -0.09MPa. The extruded material is formed into strips, which are then water-cooled and pelletized to obtain high-performance polyvinyl chloride cable material.

[0036] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that: in step four, no hydrolysate was prepared, and the hydrolysate was not added to the magnesium hydroxide / calcium carbonate slurry within 30 minutes and stirred at 50°C for 2 hours. Instead, 500g of magnesium hydroxide flame retardant filler was mixed with 350g of light calcium carbonate and then directly filtered, washed with ethanol and deionized water in sequence, and vacuum dried at 110°C for 6 hours as in step four of Example 2 to obtain magnesium hydroxide / calcium carbonate composite particles without epoxy sites. Steps five to eight were then performed using these composite particles; the remaining conditions were the same as in Example 2. Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that, instead of preparing an aqueous phytic acid solution in step five, 800g of deionized water was used instead. The pH was adjusted to 6 with sodium hydroxide solution. The suspension containing 800g of magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface was added at 60°C and stirred for 30 minutes. Then, strictly following step five of Example 2, stannous chloride dihydrate, calcium acetate, zinc acetate, double-grafted modified carboxymethyl-β-cyclodextrin dispersion, tannic acid solution, and zinc acetate and calcium acetate were added for final sealing. The mixture was then filtered, washed, and vacuum dried at 110°C for 6 hours. The remaining conditions were the same as in Example 2. Comparative Example 3 The difference between Comparative Example 3 and Example 2 is as follows: In step five, after adding 800g of 10% phytic acid aqueous solution (pH adjusted to 6 with sodium hydroxide solution) at 60°C and stirring for 30 minutes, instead of adding 7g of stannous chloride dihydrate, an equal volume of 100mL of deionized water was added and stirred at 60°C for 40 minutes. Then, following step five of Example 2, 5g of calcium acetate and 3g of zinc acetate (dissolved in 100mL of water) were added, followed by 9g of double-grafted modified carboxymethyl-β-cyclodextrin dispersion, 20g of tannic acid solution, and 4g of zinc acetate and 2g of calcium acetate were added for final sealing and post-treatment. The remaining conditions were the same as in Example 2. Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that in step five, 5g of calcium acetate and 3g of zinc acetate are dissolved in 100mL of water and added to the metal salt in the reactor. In this step, 3g of zinc acetate is replaced by 3g of calcium acetate by the same mass. That is, the 100mL aqueous solution is prepared as 8g of calcium acetate (without zinc acetate) dissolved in 100mL of water and stirred at 60°C for 20min to form a phytic acid-tin-calcium chelate layer system without zinc ions. The other conditions are the same as in Example 2. Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that, in step five, instead of adding 9g of double-grafted modified carboxymethyl-β-cyclodextrin, 9g of sodium carboxymethyl-β-cyclodextrin was stirred at room temperature with the same ethanol / deionized water ratio (160mL ethanol and 40mL deionized water) to form a dispersion. This dispersion was then added to the inorganic particle suspension system with a phytic acid-tin-calcium-zinc chelate layer on the surface within 5 minutes and stirred at 60°C for 30 minutes. Subsequently, tannic acid solution was added as in step five of Example 2, and zinc acetate and calcium acetate were added for final sealing and post-treatment. The remaining conditions were the same as in Example 2. Comparative Example 6: The difference between Comparative Example 6 and Example 2 is that, in step five, instead of adding 9g of double-grafted modified carboxymethyl-β-cyclodextrin, 9g of dodecanoyl-modified carboxymethyl-β-cyclodextrin was stirred at room temperature with the same ethanol / deionized water ratio (160mL ethanol and 40mL deionized water) to form a dispersion. This dispersion was then added to the inorganic particle suspension system with a phytic acid-tin-calcium-zinc chelate layer on the surface within 5 minutes and stirred at 60°C for 30 minutes. Subsequently, tannic acid solution was added as in step five of Example 2, and zinc acetate and calcium acetate were added for final sealing and post-treatment. All other conditions were the same as in Example 2. Comparative Example 7: The difference between Comparative Example 7 and Example 2 is that, in step five, 20g of tannic acid is not added. Instead, an equal volume of 400mL of deionized water is used instead of tannic acid solution and the mixture is stirred at 60°C for 20min. Then, following the steps in Example 2, 4g of zinc acetate and 2g of calcium acetate (dissolved in 100mL of water) are added and stirred at 60°C for 40min. Finally, the mixture is filtered, washed until the filtrate is nearly neutral, washed three times with ethanol, and vacuum dried at 110°C for 6h. The remaining conditions are the same as in Example 2. Performance testing: The molded specimens used for performance testing were uniformly made by pressing each sample particle on a flat vulcanizing machine: the pressing temperature was 170℃, the preheating was 5 min, the pressure was 10 MPa and held for 8 min, and then the specimens were water-cooled to below 40℃ under 10 MPa pressure to demold, resulting in two types of sheets with thicknesses of 1.0 mm and 3.0 mm; all specimens were tested after being conditioned for 24 h at (23±2)℃ and (50±5)% relative humidity.

[0038] Thermogravimetric analysis: Thermogravimetric analysis was performed on the polyvinyl chloride cable sheet (1.0 mm sheet shredded) of the examples and comparative examples. The sample weight was (10.0±0.5) mg, placed in an alumina crucible, and heated from 30 °C to 800 °C at a rate of 10 °C / min under a high-purity nitrogen atmosphere (flow rate 50 mL / min). The 5% weight loss temperature, the maximum weight loss rate temperature, and the residual mass fraction at 600 °C were recorded. The results are shown in Table 1.

[0039] Thermal stability time: Static thermal stability was tested according to GB / T 2917.1-2002 "Determination of hydrogen chloride and any other acidic products at high temperature in blends and products mainly composed of vinyl chloride homopolymers and copolymers - Congo red method". 1.0 mm tablets of each sample were crushed, ground, and then ground until the particle size was less than 1 mm. (2.00 ± 0.01) g of each tablet was weighed and placed at the bottom of a dry test tube. Congo red test paper was inserted so that the lower end of the test paper was 10 mm from the sample surface. The test tube was placed in a 180℃ constant temperature oil bath and the timing was started. The time it took for the lower end of the test paper to change from red to blue was recorded in minutes. Each sample was tested in parallel three times, and the arithmetic mean was taken. The results are shown in Table 1.

[0040] Tensile properties: Tensile tests were conducted according to GB / T 2951.11-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Cables - Part 11: General Test Methods for Thickness and Dimensional Measurement and Mechanical Properties" and in conjunction with GB / T 1040.2-2022 "Determination of Tensile Properties of Plastics - Part 2: Test Conditions for Molded and Extruded Plastics". 5A dumbbell-shaped specimens with a gauge length of 25 mm were punched from 1.0 mm sheet of each sample. The tests were conducted at (23±2)℃ with a tensile speed of 200 mm / min. Tensile strength and elongation at break were recorded. Five specimens were tested for each sample, and the arithmetic mean was taken. The results are shown in Table 1.

[0041] Mechanical retention rate after thermal aging: Thermal aging test was carried out according to GB / T 2951.12-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Cables - Part 12: General Test Methods - Thermal Aging Test Method". 1.0 mm dumbbell samples were placed in a forced-air drying oven and aged at 100℃ for 168 h. After being removed, they were restored for 16 h at (23±2)℃ and (50±5)% relative humidity. Then, the tensile strength and elongation at break were measured according to the tensile performance conditions, and the retention rate of tensile strength and elongation at break (%) were calculated. The results are shown in Table 1.

[0042] Oxygen Index: The limiting oxygen index was tested according to GB / T 2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test". 3.0 mm sheets of each sample were cut into test strips of (80±2) mm × (10±0.5) mm × (3.0±0.1) mm and tested at (23±2) ℃. An oxygen / nitrogen mixed gas was used, and the critical oxygen volume fraction was determined according to the concentration increment / decrement procedure specified in the standard and expressed as a percentage. Each sample was tested in parallel for 5 times and the average was taken. The results are shown in Table 1.

[0043] Vertical combustion performance The combustion behavior was tested according to GB / T 2408-2021 "Determination of Burning Performance of Plastics - Horizontal and Vertical Methods". Each sample was cut into 125mm×13mm×3.0mm test strips from 3.0mm sheet material. The vertical method was applied under a 50W flame for 10s and then removed. The flaming time and the flameless time were recorded and the total afterflame time was calculated. The results are shown in Table 1.

[0044]

[0045] Data Analysis: As can be seen from the data in Examples 1-3 of Table 1, the high-performance polyvinyl chloride cable material prepared by this invention exhibits a high initial thermal decomposition temperature and a high temperature corresponding to the maximum weight loss rate in thermogravimetric analysis, and maintains a high residual mass fraction at high temperatures. This indicates that the organic-inorganic interface layer constructed on the filler surface can rapidly generate a relatively dense carbon layer and form a heat-insulating and oxygen-barrier shielding structure when heated. Simultaneously, its long Congo red thermal stability time indicates that the interface layer has a continuous absorption and complexation capacity for released hydrogen chloride, which can weaken the autocatalytic dechlorination process. Mechanical testing shows that the material possesses both high tensile strength and high elongation at break, and the retention rate remains at a high level after thermal aging. This indicates that the interfacial bonding introduced by 3-glycidyl etheroxypropyltrimethoxysilane and the interaction between the double-grafted modified carboxymethyl-β-cyclodextrin and the plasticizer jointly inhibit plasticizer migration and microcrack initiation. The oxygen index and vertical combustion afterflame performance further demonstrate that the endothermic water-releasing dilution effect of magnesium hydroxide, combined with the catalytic char formation promoted by phytic acid-metal salt and tannic acid-metal salt, allows flame retardancy and durability to be balanced within the same system.

[0046] As can be seen from the data in Example 2 and Comparative Example 1 in Table 1, when the magnesium hydroxide / calcium carbonate filler was not treated with 3-glycidoxypropyltrimethoxysilane, the overall thermal stability and flame retardancy indicators declined, while the mechanical properties and aging retention rate decreased even more significantly. The main reason is that the lack of a silane layer results in insufficient bonding points between the filler and the polyvinyl chloride matrix, making the filler more prone to agglomeration and stress concentration during stretching, leading to earlier microcrack propagation. Simultaneously, the pores and defects at the interface provide channels for hydrogen chloride diffusion, allowing acidic products from the Congo red method to reach the test paper more quickly, thus shortening the thermal stability time. Because the interfacial shielding structure is difficult to form continuously, the endothermic water release of magnesium hydroxide and the charring effects of phytic acid-metal salt and tannic acid-metal salt are difficult to effectively superimpose at the same interface, making it difficult to simultaneously improve flame retardancy and durability.

[0047] As can be seen from the data in Table 1 for Example 2 and Comparative Example 2, under the conditions of retaining the 3-glycidyl etheroxypropyltrimethoxysilane surface layer and tannic acid treatment, the lack of phytic acid leads to a deterioration in high-temperature residue, oxygen index, and vertical combustion performance, while some mechanical properties can still be maintained at a high level. This is because phytic acid contains polyphosphate groups, which can form a multi-point complex network structure with stannous chloride dihydrate, calcium acetate, and zinc acetate. This network structure is more easily dehydrated upon heating to form a phosphorus-rich char layer, and it also has the ability to absorb and slowly release hydrogen chloride. When phytic acid is absent, metal ions struggle to form a stable phytate structure, resulting in a decrease in the continuity of the char layer. This makes it difficult for the endothermic water release effect of magnesium hydroxide to be fixed by the char layer and transformed into a durable shielding effect. Therefore, the multi-coordinated framework provided by phytic acid and the synergistic char formation by metal ions cannot be replaced by a single component.

[0048] As can be seen from the data in Example 2 and Comparative Example 3 in Table 1, when phytic acid is present but stannous chloride dihydrate is not added, the thermal stability time, oxygen index, and vertical combustion afterflame performance all decrease, and the retention rate after aging also tends to decrease. The main reason may be that stannous phytate salt formed by stannous chloride dihydrate and phytic acid is more likely to promote the further cross-linking of the conjugated structure generated after dehydrochlorination of PVC segments into char during the heating stage, and to form a denser composite char layer together with tannate salts involving zinc acetate; when the stannous component is missing, phytic acid exists more in the form of calcium salt or zinc salt, the catalytic char formation efficiency decreases, resulting in insufficient high-temperature structural stability. In addition, the complexation effect of stannous salt on acidic products is weakened, causing the color change to occur earlier in the thermal stability test, thereby weakening the synergistic improvement of flame retardancy and durability.

[0049] As can be seen from the data in Table 1 for Example 2 and Comparative Example 4, when zinc acetate was not used, some thermal decomposition initiation-related indicators and the Congo red method thermal stability time may not have decreased synchronously, and may even have increased slightly. However, the oxygen index and vertical combustion afterflame still showed unfavorable changes. This abnormal trend can be explained as follows: In the PVC system, zinc ions can both form zinc tannates with tannic acid to promote char formation and may also locally generate more reactive zinc chloride to promote the initial dehydrochlorination reaction. When zinc ions are missing, the chain reaction of the initial acidic products is partially inhibited, resulting in a slight improvement in the initiation decomposition and thermal stability time. However, due to the absence of zinc tannates, a key char-forming component, the densification degree of the char layer decreases, and the dilution effect of magnesium hydroxide and the shielding effect of phytic acid-metal salt are difficult to maintain for a long time, ultimately leading to an overall flame retardant index that is not as good as that of Example 2.

[0050] As can be seen from the data in Example 2 and Comparative Examples 5 and 6 in Table 1, when the double-grafted modified carboxymethyl-β-cyclodextrin was replaced with sodium carboxymethyl-β-cyclodextrin or carboxymethyl-β-cyclodextrin modified only with lauroyl chloride, the elongation at break retention and vertical burning performance of the materials after aging showed more significant fluctuations, and the mechanical properties exhibited a non-monotonic change of increasing and decreasing. The reason is that the hydrophilic ionic properties of sodium carboxymethyl-β-cyclodextrin make it easier to introduce hygroscopic microdomains, resulting in poor compatibility with plasticizers. After thermal aging, it is more likely to form micropores and interface delamination, leading to a decrease in retention. While modification with only lauroyl chloride improves compatibility with plasticizers and makes the initial flexibility higher, it lacks the interface anchoring points brought by 3-aminopropyltriethoxysilane grafting, making the cyclodextrin segments more prone to migration or rearrangement, and difficult to stabilize the filler-matrix interface in the long term. Therefore, it is evident that only through the dual-functional coupling of lauroyl group improving compatibility and silane grafting providing anchoring can plasticizer regulation and interface strengthening be achieved simultaneously.

[0051] As can be seen from the data in Table 1 for Example 2 and Comparative Example 7, while maintaining the phytic acid-stannous chloride dihydrate-calcium acetate / zinc acetate layer structure, the lack of tannic acid leads to a decrease in the oxygen index, an increase in the vertical combustion afterflame time, and a reduction in the high-temperature residual mass fraction. The main reason is that tannic acid contains polyphenolic hydroxyl groups, which can form zinc tannates with zinc ions and rapidly dehydrate and condense upon heating, generating a carbon layer framework rich in aromatic structures. This carbon layer, superimposed on the phytate system, can form a continuous shielding layer on the filler surface, reducing the exchange of heat and combustible decomposition products. When tannic acid is absent, the system mainly relies on the endothermic water release of magnesium hydroxide and the charring effect of phytate, resulting in insufficient carbon layer strength and continuity. Therefore, the combination of phytate and tannate in Example 2 exhibits an unexpected synergistic effect.

[0052] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A high-performance polyvinyl chloride cable material, characterized in that, It is prepared by including polyvinyl chloride resin, plasticizer and multifunctional flame retardant composite filler, and the amount of multifunctional flame retardant composite filler is 85-95 parts by weight per 100 parts by weight of polyvinyl chloride resin. The preparation steps of the multifunctional flame-retardant composite filler are as follows: (1) The magnesium hydroxide and calcium carbonate mixed particles were reacted with the hydrolysate of 3-glycidoxypropyltrimethoxysilane to obtain magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface. (2) The magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface are mixed with phytic acid aqueous solution. Stannous salt is added first, followed by calcium salt and zinc salt to construct phytic acid-tin-calcium-zinc chelate layer. Then, double-grafted modified carboxymethyl-β-cyclodextrin is added and immobilized. Tannic acid is added and zinc salt and calcium salt are introduced to form tannic acid-metal ion polyphenol network layer to obtain multifunctional flame retardant composite filler. In step (1), the mass ratio of magnesium hydroxide, calcium carbonate, and 3-glycidoxypropyltrimethoxysilane is 500:350:8-12; in step (2), based on the amount of 800g of magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface, the amount of phytic acid aqueous solution used to construct the phytic acid-tin-calcium-zinc chelate layer is 800g, the amount of stannous salt is 6-8g, the amount of calcium salt is 4-6g, and the amount of zinc salt is 2-4g; in step (2), based on the amount of 800g of magnesium hydroxide / calcium carbonate composite particles with epoxy sites on the surface, the amount of double-grafted modified carboxymethyl-β-cyclodextrin used to construct the metal ion polyphenol network layer is 7-11g, the amount of tannic acid is 14-24g, the amount of zinc salt is 3-5g, and the amount of calcium salt is 1-3g; The preparation steps of double-grafted modified carboxymethyl-β-cyclodextrin are as follows: (a) Sodium carboxymethyl-β-cyclodextrin undergoes a long-chain fatty acylation reaction with lauroyl chloride to obtain dodecanoyl-modified carboxymethyl-β-cyclodextrin; (b) Epichlorohydrin was used to epoxidize dodecanoyl-modified carboxymethyl-β-cyclodextrin to obtain dodecanoyl-modified carboxymethyl-β-cyclodextrin with epoxy groups on the surface; (c) React dodecanoyl-modified carboxymethyl-β-cyclodextrin with epoxy groups on its surface with 3-aminopropyltriethoxysilane to obtain double-grafted modified carboxymethyl-β-cyclodextrin.

2. The high-performance polyvinyl chloride cable material according to claim 1, characterized in that, The plasticizers include diisononyl phthalate and di-n-octyl adipate.

3. The high-performance polyvinyl chloride cable material according to claim 1, characterized in that, The raw materials for preparing the high-performance polyvinyl chloride cable material also include epoxidized soybean oil, antimony trioxide as a synergistic flame retardant, calcium-zinc composite heat stabilizer, and acrylic resin processing aids.

4. The high-performance polyvinyl chloride cable material according to claim 1, characterized in that, In step (2), the concentration of the phytic acid aqueous solution is 8wt%-12wt%, and the pH is 6.

5. The high-performance polyvinyl chloride cable material according to claim 1, characterized in that, In step (2), the stannous salt is stannous chloride dihydrate, the calcium salt is calcium acetate, and the zinc salt is zinc acetate.

6. The high-performance polyvinyl chloride cable material according to claim 1, characterized in that, In step (a), the mass ratio of sodium carboxymethyl-β-cyclodextrin salt to lauroyl chloride is 100:45-55; in step (b), the mass ratio of epichlorohydrin to dodecanoyl-modified carboxymethyl-β-cyclodextrin is 54-66:80; in step (c), the mass ratio of dodecanoyl-modified carboxymethyl-β-cyclodextrin with epoxy groups on its surface to 3-aminopropyltriethoxysilane is 60:27-33.

7. A method for preparing high-performance polyvinyl chloride cable material according to any one of claims 1-6, characterized in that, Includes the following steps: S1: Polyvinyl chloride resin is pre-plasticized and mixed with processing aids, heat stabilizers, lubricants, antioxidants and at least a portion of plasticizers to obtain pre-plasticized polyvinyl chloride dry mix; S2: The preplasticized PVC dry mix is ​​subjected to intensive mixing. During the intensive mixing process, multifunctional flame-retardant composite filler is added in stages, and the remaining plasticizer and / or epoxidized soybean oil and synergistic flame retardant are added to obtain high-performance PVC cable material blank. S3: Extrude and granulate the high-performance polyvinyl chloride cable material blank to obtain high-performance polyvinyl chloride cable material.

8. The method for preparing high-performance polyvinyl chloride cable material according to claim 7, characterized in that, In step S1, the pre-plasticization temperature is 110°C and maintained for 2 minutes.

9. The method for preparing high-performance polyvinyl chloride cable material according to claim 7, characterized in that, In step S2, the internal mixer rotor speed is 60 rpm and the jacket temperature is 150°C. When the torque reaches its peak and then drops slightly and the material temperature reaches 155°C, the multifunctional flame-retardant composite filler is added twice within 2 minutes. After all the filler is added, the internal mixer continues to mix for 3 minutes. Then, diisononyl phthalate plasticizer, di-n-octyl adipate plasticizer, epoxidized soybean oil and antimony trioxide are added and the internal mixer continues to mix for 2 minutes.

10. The method for preparing high-performance polyvinyl chloride cable material according to claim 7, characterized in that, In step S3, the extrusion granulation uses a co-rotating parallel twin-screw extruder, with the barrel temperatures in each zone being 150℃, 160℃, 165℃, and 170℃ respectively, the screw speed being 190-210 rpm, and the vacuum degree being -0.09MPa to -0.07MPa.

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