A polyvinyl chloride plastic and its preparation method

Abstract

This invention relates to a polyvinyl chloride (PVC) plastic and its preparation method, belonging to the field of PVC plastic technology. The PVC plastic, by weight, comprises 65-75 parts of PVC resin A, 25-35 parts of PVC resin B, 15-20 parts of hyperbranched polyesteramide, 3-5 parts of modified SiO2 aerogel, 2-3 parts of crosslinking agent, 0.5-1 part of rare earth stabilizer, 0.3-0.5 parts of hindered phenolic antioxidant, and 0.8-1.2 parts of calcium stearate. The degree of polymerization (DP) of PVC resin A is 700-900, and the DP of PVC resin B is 2400-2600. The PVC plastic provided by this invention exhibits excellent low-temperature toughness and good weather resistance, effectively avoiding the risk of embrittlement of PVC plastic under harsh low-temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of polyvinyl chloride (PVC) plastics technology, and in particular to a PVC plastic and its preparation method. Background Technology

[0002] Polyvinyl chloride (PVC) is one of the most widely used plastic products in the world today. PVC plastic is widely used in industry, agriculture, construction, electronics, automobiles and other fields. It is a general-purpose plastic that is inexpensive and has excellent flame retardancy, wear resistance, chemical corrosion resistance, mechanical properties, transparency and electrical insulation.

[0003] The processing temperature of PVC is approximately 170-180°C. However, PVC exhibits certain structural defects during synthesis. These defects can lead to degradation of PVC under conditions such as high temperatures, radiation, and shear stress. PVC's melting temperature begins at 80°C, and its degradation temperature typically occurs between 110-120°C. This makes cross-linking difficult before processing, reduces mechanical properties, and causes the product's color to gradually darken, eventually turning brown or even black, affecting its appearance. Therefore, improving the thermal stability of PVC during processing is crucial. This can be achieved in two ways: firstly, through chemical modification to alter the PVC structure and improve its thermal stability; and secondly, by adding various additives or modifiers through blending, filling, and reinforcement to improve its overall performance without altering the PVC molecular structure. Plasticizers are considered important additives in PVC production to enhance its flexibility and processability.

[0004] Chinese invention patent application CN105968647A discloses a method for preparing modified polyvinyl chloride (PVC). The method involves kneading PVC resin, polyurethane, dioctyl phthalate, dibasic lead sulfate, tribasic lead phosphite, calcium stearate, and nano-calcium carbonate at high speed, then extruding and granulating the mixture using a twin-screw extruder, followed by injection molding to obtain modified PVC plastic with good weather resistance, low price, and good stability.

[0005] The modified polyvinyl chloride (PVC) prepared by this invention can effectively improve the thermal stability and low-temperature flexibility of PVC, enhance its toughness, and improve its impact and processing properties. However, dioctyl phthalate (DOP), as a plasticizer, crystallizes and precipitates below -5°C, losing its plasticizing effect and causing localized hardening and embrittlement of PVC. This poses a risk of embrittlement to PVC plastics under harsh low-temperature conditions such as cold chain sealing, extreme cold cables, cold-resistant agricultural films, and automotive parts. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a polyvinyl chloride (PVC) plastic and its preparation method. The PVC plastic provided by this invention exhibits superior low-temperature toughness and good weather resistance, effectively avoiding the risk of embrittlement of PVC plastic under harsh low-temperature conditions.

[0007] In a first aspect, the present invention provides a polyvinyl chloride (PVC) plastic, which, by mass parts, comprises 65-75 parts of PVC resin A, 25-35 parts of PVC resin B, 15-20 parts of hyperbranched polyesteramide, 3-5 parts of modified SiO2 aerogel, 2-3 parts of crosslinking agent, 0.5-1 part of rare earth stabilizer, 0.3-0.5 parts of hindered phenolic antioxidant, and 0.8-1.2 parts of calcium stearate; wherein the degree of polymerization (DP) of PVC resin A is 700-900, and the degree of polymerization (DP) of PVC resin B is 2400-2600.

[0008] In the above technical solution, the short molecular chains of low-polymerization-degree PVC resin result in strong chain segment mobility at low temperatures, thus lowering the glass transition temperature. The long molecular chains of high-polymerization-degree PVC resin intertwine to form a physical cross-linked network, providing rigid support. The blending of the two forms an "island structure," with the low-polymerization-degree phase as the continuous phase, ensuring low-temperature toughness, and the high-polymerization-degree phase as the dispersed phase, resisting external force damage and reducing the embrittlement temperature to -45℃ and below.

[0009] Hyperbranched polyesteramide structures contain 0.5-2 nm cavities, which can release free volume at low temperatures, allowing molecular chain segment movement. The epoxy groups within can react with Cl groups on the PVC resin molecular chains. - A ring-opening reaction occurs, forming covalent bonds to prevent plasticizer migration. Long-chain alkyl groups (C...) 18 It retains its rotational ability at low temperatures, which can improve impact strength.

[0010] The nanopores in the modified SiO2 aerogel collapse under impact, converting mechanical energy into thermal energy, which can improve the impact strength and low-temperature toughness at low temperatures.

[0011] Crosslinking agents can form crosslinked networks at low temperatures to resist brittle fracture.

[0012] Rare earth ions in rare earth stabilizers can chelate HCl produced by the decomposition of PVC resin, inhibiting autocatalytic degradation. They can also absorb ultraviolet light, inhibiting photoaging and embrittlement at low temperatures.

[0013] Hindered phenolic antioxidants can capture free radicals and block oxidation reactions. At the same time, rare earth ions can regenerate phenolic hydroxyl groups, improving antioxidant efficiency.

[0014] The metal soaps in calcium stearate form a lubricating layer in the PVC resin melt, reducing friction between molecular chains and decreasing extruder torque. At the same time, its weak alkalinity can neutralize trace amounts of HCl, and work synergistically with rare earth stabilizers to inhibit autocatalytic degradation.

[0015] Optionally, the preparation steps of the hyperbranched polyester amide are as follows: diethanolamine, stearic acid, epoxidized soybean oil, and tetrabutyl titanate in a molar ratio of 1:2.5-3.0:05-0.7:0.4-0.6 are stirred and reacted at 175-185℃ for 1-2 hours, then acrylic acid and diisophenylene peroxide are added and stirring is continued to obtain a mixture, wherein the molar ratio of diethanolamine, acrylic acid, and diisophenylene peroxide is 1:0.1-0.3:0.5-0.15. Then the mixture is poured into hot water at 80-90℃, the mass ratio of the mixture to water is 1:4-6, and stirred for 15-25 minutes. The upper melt is then taken, quenched in cold water, and granulated.

[0016] In the above technical solution, diethanolamine, as the hyperbranching core, provides the N-(CH2CH2OH)2 bifunctional group, stearic acid (C 17 H 35 COOH, as a long-chain carboxylic acid, introduces flexible alkyl side chains. Epoxidized soybean oil contains 4-6 epoxy groups, which can provide branching points and reactive sites. Epoxidized soybean oil can further increase branching through free radical grafting. Tetrabutyl titanate can undergo catalytic esterification / amidation reactions. Acrylic acid (CH2=CH-COOH) can provide double bonds for free radical grafting; the introduced acrylate bonds can react with the Cl- of PVC. - An addition reaction occurs. Dicumyl peroxide can initiate a free radical reaction. Unreacted stearic acid and acrylic acid dissolve in hot water, ensuring complete dissolution of impurities. Rapid cooling with cold water causes the molten hyperbranched polyesteramide to solidify quickly, preventing crystallization. Hyperbranched cavities and flexible chains work synergistically to plasticize at low temperatures.

[0017] Optionally, the preparation steps of the modified SiO2 aerogel are as follows: SiO2 aerogel nanopowder is dried at 95-105℃ for 0.5-1.5h; SiO2 aerogel nanopowder, 3-aminopropyltriethoxysilane, and ethanol are mixed in a mass ratio of 1:0.45-0.5:15-20; the mixture is stirred at 75-85℃ for 25-35min; after filtration, it is washed with ethanol 2-3 times to obtain an amino aerogel; the amino aerogel, ε-caprolactone, and stannous octoate are mixed in a mass ratio of 1:2-4:0.01-0.05; the mixture is stirred at 110-130℃ for 1-3h; after cooling, it is ground into powder; after freezing at -40℃ for 10-12h, it is vacuum dried at 0.1kPa and 55-65℃ for 3-5h to obtain the modified SiO2 aerogel.

[0018] In the above technical solution, removing adsorbed water from the surface of the aerogel nanoparticles and exposing the silanol groups (≡Si-OH) can improve the activity of subsequent reactions. The oxygen group in 3-aminopropyltriethoxysilane ethyl hydrolyzes to generate silanol (Si-OH), which condenses with the hydroxyl groups on the aerogel surface. The introduction of the amino group (-NH2) provides an active site for subsequent ring-opening polymerization. Stirring at 75-85℃ can accelerate the condensation reaction while preventing ethanol from boiling. Temperatures >110℃ ensure the melting of ε-caprolactone.

[0019] The molecular weight of polycaprolactone can be controlled within 1-3 hours of reaction. Aerogel nanopores can buffer stress concentration and prevent brittle fracture. Polycaprolactone retains its flexibility even under extremely cold conditions. Through surface amination and melt grafting, a flexible interface layer is constructed while preserving the porous properties of aerogel, achieving toughening of polymer materials in extreme environments.

[0020] Optionally, the preparation steps of the rare earth stabilizer are as follows: dissolve lanthanum chloride and cerium chloride in hot water at 55-65℃, add citric acid, and stir until completely dissolved. The molar ratio of lanthanum chloride, cerium chloride, and citric acid is 1-3:1:3-5. Add ammonia dropwise until the pH is 6-7. When the solution turns transparent blue-green, keep it at 75-85℃ for 25-35 minutes, and spray dry it for 0.5-1 hours at an inlet temperature of 190-210℃, an outlet temperature of 80-100℃, and an atomization pressure of 0.1-0.5MPa to obtain microsphere particles.

[0021] In the above technical solution, the dissolution of rare earth salts (55-65℃ hot water) can break the LaCl3 / CeCl3 water of crystallization structure and release free La. 3+ Ce 3+ Ions, free La 3+ Ce 3+ The ions undergo a coordination reaction with citric acid, La 3+ It can form a tetradentate chelate with citric acid, Ce 3+ The ions can undergo tripentate chelation and water coordination with citric acid. Adding ammonia to adjust the pH is crucial. If the pH is < 6, the citric acid is not completely deprotonated, meaning the -COOH group is not dissociated, resulting in insufficient complexation. If the pH is > 7, the rare earth hydroxide La(OH)3 precipitate is formed. A transparent blue-green solution indicates the formation of a stable [La(C6H7O7)2] precipitate. - During spray drying, when droplets dry instantaneously, the complex molecules align in a specific direction: the hydrophobic ends (C6H7O7) - Inward, hydrophilic end (La) 3+ / Ce 3+ -OH2) outwards.

[0022] La 3+ It can chelate the HCl produced by the decomposition of PVC resin, thus inhibiting autocatalytic degradation.3+ It can absorb ultraviolet light. Ce in the complex 3+ Ce 4+ Redox reactions can enhance durability. The carboxyl group in citric acid can capture alkyl radicals (R·), and rare earth ions catalyze the decomposition of peroxides.

[0023] Optionally, the crosslinking agent is a dynamic crosslinking agent, and the preparation steps of the dynamic crosslinking agent are as follows: adding tetrahydrofuran methacrylate and bismaleimide to ethanol at a molar ratio of 1-3:1, stirring at 40-50℃ and 100-300rpm for 40-60min, removing the solvent by rotary evaporation, and drying under vacuum at 55-65℃ to obtain the dynamic crosslinking agent.

[0024] In the above technical solution, tetrahydrofuran methacrylate provides a furan ring and an acrylate double bond. The bismaleimide contains two maleimide groups, serving as crosslinking nodes. Ethanol promotes uniform mixing and prevents premature Diels-Alder (DA) reaction at high temperatures. Rotary evaporation removes ethanol, avoiding the influence of residual solvent. Vacuum drying further removes trace amounts of solvent while preventing DA reaction triggering. The furan ring and maleimide groups undergo a Diels-Alder reaction at low temperatures, requiring no catalyst and proceeding spontaneously. The bismaleimide groups connect multiple PVC chains, improving mechanical strength. The acrylate double bond can copolymerize with free radicals on the PVC resin, improving interfacial compatibility.

[0025] Secondly, the present invention provides a method for preparing polyvinyl chloride plastic, the method comprising the following steps:

[0026] Raw material pretreatment: The polyvinyl chloride resin A and polyvinyl chloride resin B are dried by blowing at 75-85℃ for 3-5 hours, and the modified SiO2 aerogel is dried under vacuum at 115-125℃ for 1-3 hours.

[0027] Premixing and dispersion: Add dried polyvinyl chloride resin A, polyvinyl chloride resin B, hyperbranched polyester amide, and calcium stearate, and mix at 55-65℃ for 4-6 min. Add rare earth stabilizer and hindered phenolic antioxidant, cool to 35-45℃, and then add modified SiO2 aerogel. Mix at 700-900 rpm for 8-12 min. Finally, add crosslinking agent and mix at 200-400 rpm for 3-8 min to obtain the mixture.

[0028] Reactive extrusion: The mixture is placed into the hopper of a twin-screw extruder and injected by the rotating screw. At room temperature, it is conveyed through the feeding zone and then sequentially passes through the three sections of the twin-screw extruder: the plasticizing zone, the reaction zone, and the cross-linking zone. The material is shaped and extruded at 135°C to form a complete material.

[0029] Cryogenic stretching orientation: The extruded material is immediately placed in an ethanol bath at -25 to -35°C for cooling and shaping, and then subjected to biaxial stretching in an environmental chamber at -25 to -35°C.

[0030] Heat setting and post-treatment: The stretched material is heat-treated in a hot air circulating oven at 65-75℃ for 8-12 minutes, then cooled and cut to obtain the polyvinyl chloride plastic.

[0031] In the above technical solution, during premixing and dispersion, hyperbranched polyesteramide is first melt-coated to cover PVC particles, forming a flexible pre-coating. Aerogel is added at low temperature to prevent agglomeration and maintain particle rigidity, and finally, a DA crosslinking agent is added to prevent premature reaction.

[0032] Optionally, the temperature of the plasticizing zone is 155-165℃ and the residence time is 40-50s, the temperature of the reaction zone is 175-185℃ and the residence time is 55-65s, and the temperature of the crosslinking zone is 135-145℃ and the residence time is 85-95s.

[0033] In the above technical solution, the long-chain alkyl groups of the hyperbranched polyesteramide interpenetrate the PVC segments in the plasticizing zone, increasing the free volume and lowering the Tg. In the reaction zone, the polycaprolactone graft layer can melt and entangle with the PVC resin molecular chains. The crosslinking zone can promote the Diels-Alder crosslinking reaction, forming a dynamic covalent network.

[0034] Optionally, the longitudinal tensile ratio in the biaxial stretching is 1.3-1.7, the transverse tensile ratio is 0.8-1.2, and the stretching rate is 8-12 mm / min.

[0035] In the above technical solution, the tensile force can cause the molecular chains to align along the direction of the external force, forming oriented microcrystals.

[0036] Thirdly, the polyvinyl chloride (PVC) plastic prepared by the present invention or a method for preparing PVC plastic can be used in cold chain sealing, cold-resistant cables, cold-resistant agricultural films, automotive parts, and harsh low-temperature environments.

[0037] In summary, the present invention has at least one of the following beneficial technical effects:

[0038] 1. By adding low-polymerization-degree PVC resin and high-polymerization-degree PVC resin, the two are blended to form an "island structure". The low-polymerization-degree phase is the continuous phase, which ensures low-temperature toughness, while the high-polymerization-degree phase is the dispersed phase, which resists external force damage and reduces the embrittlement temperature to -45℃ and below.

[0039] 2. By adding hyperbranched polyesteramide, a 0.5-2nm cavity exists within the structure, which can release free volume at low temperatures, allowing molecular chain segment movement. The epoxy groups within can react with Cl on the PVC resin molecular chain. - A ring-opening reaction occurs, forming covalent bonds to prevent plasticizer migration; long-chain alkyl groups (C16- ... 18 It retains its rotational ability at low temperatures, which can improve impact strength.

[0040] 3. By adding modified SiO2 aerogel, the nanopores in it collapse under impact, converting mechanical energy into heat energy, which can improve the impact strength and low-temperature toughness at low temperatures.

[0041] 4. By adding a cross-linking agent, a cross-linked network can be formed at low temperatures to resist brittle fracture.

[0042] 5. By adding rare earth stabilizers, rare earth ions can chelate the HCl produced by the decomposition of PVC resin, inhibiting autocatalytic degradation. At the same time, they can absorb ultraviolet light and inhibit photoaging and embrittlement at low temperatures. Adding hindered phenolic antioxidants can capture free radicals and block oxidation reactions. Meanwhile, rare earth ions can regenerate phenolic hydroxyl groups, improving antioxidant efficiency.

[0043] 6. By adding calcium stearate, the metal soaps in it form a lubricating layer in the PVC resin melt, reducing friction between molecular chains and reducing extruder torque. At the same time, its weak alkalinity can neutralize trace amounts of HCl, and work synergistically with rare earth stabilizers to inhibit autocatalytic degradation. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to the embodiments.

[0045] All materials used in the following examples are available for purchase on the market.

[0046] Example 1: This example discloses a polyvinyl chloride plastic #1 and its preparation method.

[0047] By weight, the polyvinyl chloride plastic comprises 65 parts polyvinyl chloride resin A, 35 parts polyvinyl chloride resin B, 15 parts hyperbranched polyesteramide, 5 parts modified SiO2 aerogel, 2 parts crosslinking agent, 0.5 parts rare earth stabilizer, 0.3 parts hindered phenolic antioxidant, and 0.8 parts calcium stearate; the degree of polymerization (DP) of polyvinyl chloride resin A is 700, and the degree of polymerization (DP) of polyvinyl chloride resin B is 2400.

[0048] In this embodiment, dicumyl peroxide is selected as the crosslinking agent. In other embodiments, vinyltrimethoxysilane or trimethylolpropane triacrylate may also be selected as the crosslinking agent. Antioxidant 1010 is selected as the hindered phenolic antioxidant. In other embodiments, hindered phenolic antioxidants such as antioxidant 1076, antioxidant 2246, and antioxidant 3114 may also be selected.

[0049] The preparation method of polyvinyl chloride plastic includes the following steps:

[0050] S1. Raw material pretreatment: The polyvinyl chloride resin A and polyvinyl chloride resin B are dried in a forced-air dryer at 70°C for 4 hours, and the modified SiO2 aerogel is dried in a vacuum at 120°C for 2 hours.

[0051] S2. Preparation of hyperbranched polyester amide: Diethanolamine, stearic acid, epoxidized soybean oil, and tetrabutyl titanate in a molar ratio of 1:2.8:0.6:0.5 were stirred at 180°C for 2 hours. Then, acrylic acid and diisophenylene peroxide were added and stirring was continued to obtain a mixture. The molar ratio of diethanolamine, acrylic acid, and diisophenylene peroxide was 1:0.2:0.1. The mixture was then poured into hot water at 85°C with a mass ratio of 1:5 between the mixture and water. The mixture was stirred for 20 minutes. The upper melt was taken, quenched in cold water, and then pelletized.

[0052] S3. Preparation of modified SiO2 aerogel: SiO2 aerogel nanoparticles were dried at 100℃ for 1 h. SiO2 aerogel nanoparticles, 3-aminopropyltriethoxysilane, and ethanol were mixed in a mass ratio of 1:0.48:18 and stirred at 80℃ for 30 min. After filtration, the mixture was washed three times with ethanol to obtain an amino aerogel. The amino aerogel, ε-caprolactone, and stannous octoate were mixed in a mass ratio of 1:3:0.03 and stirred at 120℃ for 2 h. After cooling, the mixture was ground into powder and frozen at -40℃ for 12 h. Then, it was vacuum dried at 0.1 kPa and 60℃ for 4 h to obtain the modified SiO2 aerogel.

[0053] S4. Preparation of rare earth stabilizer: Lanthanum chloride and cerium chloride were dissolved in hot water at 60°C, citric acid was added, and the mixture was stirred until completely dissolved. The molar ratio of lanthanum chloride, cerium chloride, and citric acid was 2:1:4. Ammonia water was added dropwise until the pH reached 6-7. When the solution turned transparent blue-green, it was kept at 80°C for 30 min and then spray-dried for 0.8 h at an inlet temperature of 200°C, an outlet temperature of 90°C, and an atomization pressure of 0.3 MPa to obtain microsphere particles.

[0054] S5. Premixing and Dispersion: Add dried polyvinyl chloride resin A, polyvinyl chloride resin B, hyperbranched polyester amide, and calcium stearate and mix at 60°C for 5 min. Add rare earth stabilizer and hindered phenolic antioxidant. After cooling to 40°C, add modified SiO2 aerogel and mix at 800 rpm for 10 min. Finally, add crosslinking agent and mix at 300 rpm for 5 min to obtain the mixture.

[0055] S6. Reactive Extrusion: The mixture is placed into the hopper of a twin-screw extruder and injected by the rotating screw. At room temperature, it is conveyed through the feeding zone and then sequentially passes through three sections of the twin-screw extruder: the plasticizing zone, the reaction zone, and the crosslinking zone. The temperature of the plasticizing zone is 160°C and the residence time is 45s. The temperature of the reaction zone is 180°C and the residence time is 60s. The temperature of the crosslinking zone is 140°C and the residence time is 90s. The material is shaped and extruded at 135°C to form a complete material.

[0056] S7. Cryogenic stretching orientation: The extruded material is immediately placed in a -30℃ ethanol bath for cooling and shaping, and then subjected to biaxial stretching in a -30℃ environmental chamber. The longitudinal stretching ratio is 1.5, the transverse stretching ratio is 1, and the stretching rate is 10mm / min.

[0057] S8. Heat setting and post-treatment: The stretched material is heat-treated in a 70°C hot air circulating oven for 10 minutes, cooled and cut to obtain the polyvinyl chloride plastic #1.

[0058] Example 2: This example discloses a polyvinyl chloride plastic #2 and its preparation method.

[0059] By weight, the polyvinyl chloride plastic comprises 75 parts polyvinyl chloride resin A, 25 parts polyvinyl chloride resin B, 20 parts hyperbranched polyesteramide, 3 parts modified SiO2 aerogel, 3 parts trimethylolpropane triacrylate, 1 part rare earth stabilizer, 0.5 parts antioxidant 3114, and 1.2 parts calcium stearate; the degree of polymerization (DP) of polyvinyl chloride resin A is 900, and the degree of polymerization (DP) of polyvinyl chloride resin B is 2600.

[0060] The preparation method is the same as in Example 1.

[0061] Example 3: This example discloses a polyvinyl chloride plastic #3 and its preparation method.

[0062] By weight, the polyvinyl chloride plastic comprises 70 parts polyvinyl chloride resin A, 30 parts polyvinyl chloride resin B, 18 parts hyperbranched polyesteramide, 4 parts modified SiO2 aerogel, 2.5 parts vinyltrimethoxysilane, 0.8 parts rare earth stabilizer, 0.4 parts antioxidant 1076, and 1 part calcium stearate; the degree of polymerization (DP) of polyvinyl chloride resin A is 800, and the degree of polymerization (DP) of polyvinyl chloride resin B is 2500.

[0063] The preparation method is the same as in Example 1.

[0064] Example 4: This example discloses a polyvinyl chloride plastic #4 and its preparation method.

[0065] By weight, the polyvinyl chloride plastic comprises 70 parts polyvinyl chloride resin A, 30 parts polyvinyl chloride resin B, 18 parts hyperbranched polyesteramide, 4 parts modified SiO2 aerogel, 2.5 parts dynamic crosslinking agent, 0.8 parts rare earth stabilizer, 0.4 parts antioxidant 1076, and 1 part calcium stearate; the degree of polymerization (DP) of polyvinyl chloride resin A is 800, and the degree of polymerization (DP) of polyvinyl chloride resin B is 2500.

[0066] The preparation method of polyvinyl chloride plastic includes the following steps:

[0067] S1. Raw material pretreatment: The polyvinyl chloride resin A and polyvinyl chloride resin B are dried in a forced-air dryer at 70°C for 4 hours, and the modified SiO2 aerogel is dried in a vacuum at 120°C for 2 hours.

[0068] S2. Preparation of hyperbranched polyester amide: Diethanolamine, stearic acid, epoxidized soybean oil, and tetrabutyl titanate in a molar ratio of 1:2.8:0.6:0.5 were stirred at 180°C for 2 hours. Then, acrylic acid and diisophenylene peroxide were added and stirring was continued to obtain a mixture. The molar ratio of diethanolamine, acrylic acid, and diisophenylene peroxide was 1:0.2:0.1. The mixture was then poured into hot water at 85°C with a mass ratio of 1:5 between the mixture and water. The mixture was stirred for 20 minutes. The upper melt was taken, quenched in cold water, and then pelletized.

[0069] S3. Preparation of modified SiO2 aerogel: SiO2 aerogel nanoparticles were dried at 100℃ for 1 h. SiO2 aerogel nanoparticles, 3-aminopropyltriethoxysilane, and ethanol were mixed in a mass ratio of 1:0.48:18 and stirred at 80℃ for 30 min. After filtration, the mixture was washed three times with ethanol to obtain an amino aerogel. The amino aerogel, ε-caprolactone, and stannous octoate were mixed in a mass ratio of 1:3:0.03 and stirred at 120℃ for 2 h. After cooling, the mixture was ground into powder and frozen at -40℃ for 12 h. Then, it was vacuum dried at 0.1 kPa and 60℃ for 4 h to obtain the modified SiO2 aerogel.

[0070] S4. Preparation of rare earth stabilizer: Lanthanum chloride and cerium chloride were dissolved in hot water at 60°C, citric acid was added, and the mixture was stirred until completely dissolved. The molar ratio of lanthanum chloride, cerium chloride, and citric acid was 2:1:4. Ammonia water was added dropwise until the pH reached 6-7. When the solution turned transparent blue-green, it was kept at 80°C for 30 min and then spray-dried for 0.8 h at an inlet temperature of 200°C, an outlet temperature of 90°C, and an atomization pressure of 0.3 MPa to obtain microsphere particles.

[0071] S5. Preparation of dynamic crosslinking agent: Tetrahydrofuran methacrylate and bismaleimide were added to ethanol at a molar ratio of 2:1 and stirred at 45°C and 200 rpm for 50 min. The solvent was removed by rotary evaporation and dried under vacuum at 60°C to obtain the dynamic crosslinking agent.

[0072] S6. Premixing and Dispersion: Add dried polyvinyl chloride resin A, polyvinyl chloride resin B, hyperbranched polyester amide, and calcium stearate to the mixture and mix at 60°C for 5 min. Add rare earth stabilizer and hindered phenolic antioxidant. After cooling to 40°C, add modified SiO2 aerogel and mix at 800 rpm for 10 min. Finally, add crosslinking agent and mix at 300 rpm for 5 min to obtain the mixture.

[0073] S7. Reactive Extrusion: The mixture is placed into the hopper of a twin-screw extruder and injected by the rotating screw. At room temperature, it is conveyed through the feeding zone and then sequentially passes through three sections of the twin-screw extruder: the plasticizing zone, the reaction zone, and the crosslinking zone. The temperature of the plasticizing zone is 160°C and the residence time is 45s. The temperature of the reaction zone is 180°C and the residence time is 60s. The temperature of the crosslinking zone is 140°C and the residence time is 90s. The material is shaped and extruded at 135°C to form a complete material.

[0074] S8. Cryogenic stretching orientation: The extruded material is immediately placed in a -30℃ ethanol bath for cooling and shaping, and then subjected to biaxial stretching in a -30℃ environmental chamber. The longitudinal stretching ratio is 1.5, the transverse stretching ratio is 1, and the stretching rate is 10mm / min.

[0075] S9. Heat setting and post-treatment: The stretched material is heat-treated in a 70°C hot air circulating oven for 10 minutes, cooled and cut to obtain the polyvinyl chloride plastic #4.

[0076] Comparative Example 1: This comparative example provides a comparative polyvinyl chloride plastic D1 that is the same as in Example 4, except that a polyvinyl chloride resin with a degree of polymerization (DP) of 1600 is used instead of polyvinyl chloride resin A with a degree of polymerization (DP) of 800 and polyvinyl chloride resin B with a degree of polymerization (DP) of 2500.

[0077] Comparative Example 2: This comparative example provides a comparative polyvinyl chloride plastic D2 that is the same as that in Example 4, except that: polyesteramide is used instead of hyperbranched polyesteramide.

[0078] Comparative Example 3: This comparative example provides a comparative polyvinyl chloride plastic D3 that is the same as that in Example 4, except that SiO2 aerogel nanoparticles are used instead of modified SiO2 aerogel.

[0079] Comparative Example 4: This comparative example provides a comparative polyvinyl chloride plastic D4, which is the same as Example 4, except that: lanthanum chloride and cerium chloride are dissolved in hot water at 55-65℃ and stirred until completely dissolved. The molar ratio of lanthanum chloride to cerium chloride is 2:1. The mixture is spray-dried for 0.5-1h at an inlet temperature of 190-210℃, an outlet temperature of 80-100℃, and an atomization pressure of 0.1-0.5MPa to obtain microsphere particles.

[0080] The polyvinyl chloride (PVC) plastics #1-#4 obtained in Examples 1-4 and the comparative PVC plastics D1-D4 obtained in Comparative Examples 1-4 were subjected to embrittlement temperature testing (GB / T5470-2008), -60℃ impact strength testing (ISO179-1), tensile strength testing (GB / T1040.2-2006), fracture toughness testing (ISO13586-2018), low-temperature flexural modulus at -50℃ (ASTMD790), and 1000h UV aging color difference ΔE testing (ISO4892-3). The test results are shown in Table 1.

[0081] Example performance Embrittlement temperature (°C) Impact strength at -60℃ (kJ / m²) Tensile strength (MPa) <![CDATA[Fracture toughness (MN / m 3 / 2 ).]]> Low-temperature flexural modulus (MPa) UV aging color difference ΔE Example 1 -60 25.1 34.8 19.1 1495 2 Example 2 -61 25.4 35.1 19.2 1483 1.8 Example 3 -63 26.2 35.8 19.6 1470 1.5 Example 4 -65 26.8 36.4 20.1 1427 1.4 Comparative Example 1 -29 20.1 29.5 16.2 1584 2.5 Comparative Example 2 -45 18.2 30.7 18.2 1503 2.3 Comparative Example 3 -35 21.7 30.9 15.5 1494 2.3 Comparative Example 4 -56 22.9 31.8 18.8 1487 2.9

[0082] The data from Examples 1-3, especially Example 3, show that by using a reasonable ratio of polyvinyl chloride (PVC) plastic components in this application, the obtained PVC plastic exhibits superior performance in terms of embrittlement temperature, impact strength at -60°C, tensile strength, fracture toughness, low-temperature flexural modulus, and UV aging color difference ΔE.

[0083] Compared to Example 3, Example 4 uses a dynamic crosslinking agent, resulting in PVC plastic #4 with superior properties compared to PVC plastic #3. This is because the furan ring and maleimide groups in the dynamic crosslinking agent of this application undergo a Diels-Alder reaction at low temperatures, which can proceed spontaneously without a catalyst. The bismaleimide groups connect multiple PVC chains, enhancing mechanical strength. The acrylate double bonds can copolymerize with free radicals on the PVC resin, improving interfacial compatibility.

[0084] Compared to Example 4, Comparative Example 1 used PVC resin with a degree of polymerization (DP) of 1600 instead of PVC resin A with a DP of 800 and PVC resin B with a DP of 2500. The resulting comparative PVC plastic D1 exhibited inferior properties compared to PVC plastic #4. This is because the shorter molecular chains of the low-polymerization-degree PVC resin result in stronger chain segment mobility at low temperatures, thus lowering the glass transition temperature. The long molecular chains of the high-polymerization-degree PVC resin intertwine to form a physical cross-linked network, providing rigid support. The blending of these two materials forms an "island structure," with the low-polymerization-degree phase as the continuous phase, ensuring low-temperature toughness, and the high-polymerization-degree phase as the dispersed phase, resisting external force damage and reducing the embrittlement temperature to -45°C and below.

[0085] Compared to Example 4, Comparative Example 2 used polyesteramide instead of hyperbranched polyesteramide. The resulting comparative PVC plastic D2 exhibited inferior properties compared to PVC plastic #4. This is because the hyperbranched polyesteramide structure contains 0.5-2 nm cavities, which can release free volume at low temperatures, allowing molecular chain segment movement. The epoxy groups can undergo ring-opening reactions with Cl⁻ on the PVC resin molecular chain to form covalent bonds, preventing plasticizer migration. Long-chain alkyl groups (C⁻) 18 It retains its rotational ability at low temperatures, which can improve impact strength.

[0086] Compared with Example 4, Comparative Example 3 uses SiO2 aerogel nanopowder instead of modified SiO2 aerogel. The properties of the resulting comparative PVC plastic D3 are not as good as those of PVC plastic #4. This is because the nanopores in the modified SiO2 aerogel collapse under impact, converting mechanical energy into heat energy, which can improve the impact strength and low-temperature toughness at low temperatures.

[0087] Compared to Example 4, Comparative Example 4 did not include the addition of citric acid and ammonia in its rare earth stabilizer preparation method. The resulting comparative PVC plastic D4 exhibited inferior properties compared to PVC plastic #4. This is because the dissolution of rare earth salts (in hot water at 55-65°C) can break the LaCl3 / CeCl3 crystal water structure, releasing free La... 3+ Ce 3+ Ions, free La 3+ Ce 3+ The ions undergo a coordination reaction with citric acid, La 3+ It can form a tetradentate chelate with citric acid, Ce 3+ The ions can undergo tripentate chelation and water coordination with citric acid. Adding ammonia to adjust the pH is crucial. If the pH is < 6, the citric acid is not completely deprotonated, meaning the -COOH group is not dissociated, resulting in insufficient complexation. If the pH is > 7, the rare earth hydroxide La(OH)3 precipitate is formed. A transparent blue-green solution indicates the formation of a stable [La(C6H7O7)2] precipitate. - La 3+It can chelate the HCl produced by the decomposition of PVC resin, thus inhibiting autocatalytic degradation. 3+ It can absorb ultraviolet light. Ce in the complex 3+ Ce 4+ Redox reactions can enhance durability. The carboxyl group in citric acid can capture alkyl radicals (R·), and rare earth ions catalyze the decomposition of peroxides.

[0088] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A polyvinyl chloride plastic, characterized by, The polyvinyl chloride plastic comprises 65-75 parts of polyvinyl chloride resin A, 25-35 parts of polyvinyl chloride resin B, 15-20 parts of hyperbranched polyester amide, 3-5 parts of modified SiO2 aerogel, 2-3 parts of crosslinking agent, 0.5-1 part of rare earth stabilizer, 0.3-0.5 part of hindered phenolic antioxidant, and 0.8-1.2 parts of calcium stearate; the polyvinyl chloride resin A has a polymerization degree DP of 700-900, and the polyvinyl chloride resin B has a polymerization degree DP of 2400-2600; The preparation steps of the hyperbranched polyester amide are as follows: diethanolamine, stearic acid, epoxy soybean oil and tetrabutyl titanate with a molar ratio of 1:2.5-3.0:0.5-0.7:0.4-0.6 are stirred and reacted at 175-185℃ for 1-2h, then acrylic acid and dicumyl peroxide are added for continuous stirring to obtain a mixture, the molar ratio of diethanolamine, acrylic acid and dicumyl peroxide is 1:0.1-0.3:0.05-0.15, then the mixture is poured into hot water at 80-90℃, the mass ratio of the mixture to water is 1:4-6, stirring is carried out for 15-25min, the upper layer of the melt is taken out, quenched in cold water and then cut into particles; The preparation steps of the modified SiO2 aerogel are as follows: SiO2 aerogel nano powder is dried at 95-105℃ for 0.5-1.5h, then the SiO2 aerogel nano powder, 3-aminopropyl triethoxysilane and ethanol are mixed at a mass ratio of 1:0.45-0.5:15-20, stirring is carried out at 75-85℃ for 25-35min, then the mixture is filtered and washed with ethanol for 2-3 times to obtain amino aerogel, then the amino aerogel, ε-caprolactone and stannous octoate are mixed at a mass ratio of 1:2-4:0.01-0.05, stirring is carried out at 110-130℃ for 1-3h, then the mixture is ground into powder after cooling, the powder is frozen at -40℃ for 10-12h, then vacuum drying is carried out at 0.1kPa and 55-65℃ for 3-5h to obtain the modified SiO2 aerogel; The preparation steps of the rare earth stabilizer are as follows: lanthanum chloride and cerium chloride are dissolved in hot water at 55-65℃, citric acid is added and stirred until completely dissolved, the molar ratio of lanthanum chloride, cerium chloride and citric acid is 1-3:1:3-5, ammonia water is added dropwise until the pH is 6-7, the solution becomes transparent blue-green, the solution is kept at 75-85℃ for 25-35min, then spray drying is carried out at an inlet temperature of 190-210℃, an outlet temperature of 80-100℃ and a atomization pressure of 0.1-0.5MPa for 0.5-1h to obtain microspherical particles.

2. A polyvinyl chloride plastic as claimed in claim 1, wherein, The crosslinking agent is a dynamic crosslinking agent, and the preparation steps of the dynamic crosslinking agent are as follows: tetrahydrofurfuryl methacrylate and bismaleimide are added into ethanol at a molar ratio of 1-3:1, stirring is carried out at 40-50℃ and 100-300rpm for 40-60min, then the solvent is removed by rotary evaporation, and vacuum drying is carried out at 55-65℃ to obtain the dynamic crosslinking agent.

3. A method for producing the polyvinyl chloride plastic according to claim 1 or 2, characterized by, The preparation method comprises the following steps: Raw material pretreatment: the polyvinyl chloride resin A and polyvinyl chloride resin B are blown dry at 75-85℃ for 3-5h, and the modified SiO2 aerogel is vacuum dried at 115-125℃ for 1-3h; Premix dispersion: the dried polyvinyl chloride resin A, polyvinyl chloride resin B, hyperbranched polyester amide, calcium stearate are mixed at 55-65℃ for 4-6min, the rare earth stabilizer and hindered phenolic antioxidant are added, and the temperature is lowered to 35-45℃, then the modified SiO2 aerogel is added, and mixed at 700-900rpm for 8-12min; finally, the crosslinking agent is added, and mixed at 200-400rpm for 3-8min to obtain a mixture; Reaction extrusion: the mixture is placed in the hopper of a double screw extruder, injected by screw rotation, transported through the feeding zone at room temperature, and then sequentially passes through three sections of the double screw extruder: plasticizing zone, reaction zone, and crosslinking zone, and the complete material is shaped extruded at 135℃; Deep cooling stretching orientation: the extruded material is immediately placed in an ethanol bath cooled at -25--35℃ for shaping, and then bidirectional stretching is carried out in an environmental box at -25--35℃; Heat setting and post-processing: the stretched material is heat treated in a hot air circulating oven at 65-75℃ for 8-12min, cooled and cut into a shape to obtain the polyvinyl chloride plastic.

4. The method of claim 3, wherein the polyvinyl chloride plastic is prepared by adding the polyvinyl chloride resin, the plasticizer, the stabilizer, and the filler to a mixer and mixing them at a temperature of 150 to 200°C for 1 to 3 hours. The temperature of the plasticizing zone is 155-165℃, and the residence time is 40-50s, the temperature of the reaction zone is 175-185℃, and the residence time is 55-65s, and the temperature of the crosslinking zone is 135-145℃, and the residence time is 85-95s.

5. The method of claim 3, wherein the polyvinyl chloride plastic is prepared by adding the polyvinyl chloride resin, the plasticizer, the stabilizer, and the filler to a mixer and mixing them at 80°C to 100°C for 1 to 3 hours. In the bidirectional stretching, the longitudinal stretching ratio is 1.3-1.7, the transverse stretching ratio is 0.8-1.2, and the stretching rate is 8-12mm / min.

6. Use of polyvinyl chloride plastic in cold chain sealing, cold resistant cable, cold resistant agricultural film, automobile parts and harsh low temperature condition environment, characterized in that, The polyvinyl chloride plastic as claimed in claim 1 or 2, or the polyvinyl chloride plastic prepared by the preparation method as claimed in any one of claims 3-5. The polyvinyl chloride plastic as claimed in claim 1 or 2, or the polyvinyl chloride plastic prepared by the preparation method as claimed in any one of claims 3-5.