Concentrated grafted PVC efficient flame-retardant master batch material and preparation method thereof

Abstract

The invention relates to a concentrated grafted PVC (polyvinyl chloride) high-efficiency flame-retardant master batch material and a preparation method thereof, and belongs to the technical field of high polymer material modification, the concentrated grafted PVC high-efficiency flame-retardant master batch material comprises the following components by weight: 50-60 parts of end group functionalized PVC; 10 to 15 parts by weight of exfoliated organic montmorillonite; 15 to 20 parts by weight of dopamine coated zinc phosphate; 3-5 parts by weight of a microencapsulated self-healing agent; 0.5 to 1 part by weight of a functionalized carbon nanotube; 5-10 parts by weight of a bio-based plasticizer; 1-3 parts by weight of an antioxidant; 0.25-1 part by weight of a lubricant; the concentrated flame-retardant master batch material with high flame retardance, self-healing property and good mechanical property is prepared by combining a self-healing microcapsule technology, and the compatibility and the stability of the material are remarkably improved through strong interface interaction between modified PVC and a nano material.

Description

Technical Field

[0001] The present invention relates to a concentrated grafted PVC high-efficiency flame retardant masterbatch material and a preparation method thereof, belonging to the technical field of polymer material modification, and specifically relates to a flame retardant masterbatch material with self-healing performance formed by compounding end-functionalized PVC with nanomaterials and a preparation method thereof. Background Art

[0002] Polyvinyl chloride (PVC) is an important general-purpose thermoplastic resin with the molecular formula (C 2 H 3 Cl)n, which has good flame retardancy, corrosion resistance and electrical insulation properties, and is widely used in fields such as construction, wire and cable, packaging, and medical. However, traditional PVC materials will release a large amount of toxic gases and smoke when burning, causing serious harm to the environment and human health.

[0003] At present, the flame retardant modification of PVC mainly adopts physical mixing methods such as adding antimony trioxide, brominated flame retardants, etc. Although this method can improve the flame retardant performance of PVC, there are the following problems: (1) The flame retardant is easy to migrate and precipitate from the matrix, resulting in a reduction in the flame retardant effect; (2) The compatibility between the flame retardant and PVC is poor, affecting the mechanical properties of the material; (3) Toxic smoke is generated during combustion; (4) Some flame retardants are harmful to the environment.

[0004] Wang et al. (Preparation and characterization of flame retardant ABS / montmorillonite nanocomposite. Applied Clay Science, 2004, 251-2: 49-55) studied the synergistic flame retardant effect of montmorillonite and brominated flame retardants in ABS resin, and the results showed that the ABS / organic montmorillonite / brominated flame retardant nanocomposite prepared by the melt blending method has better flame retardant performance. However, this method still uses halogenated flame retardants that are harmful to the environment and does not solve the problem of flame retardant migration.

[0005] Recently, Kianfar et al. (Flame-Retardant Self-Healing Polymers: A Review. Journal of Polymer Science, 2024, 62: 1015-1049) summarized the research progress of polymer materials with synergistic flame retardant and self-healing functions, and pointed out that introducing self-healing characteristics into flame retardant materials can improve the durability and safety of materials, but at the same time, it also faces the possible negative impact of flame retardants on self-healing performance. This research emphasizes the importance of multifunctional flame retardants, but lacks specific research on PVC materials.

[0006] In recent years, nanomaterials such as montmorillonite and carbon nanotubes have shown good application prospects in the field of polymer flame retardancy. Research has shown that montmorillonite can form a barrier layer in polymers, slowing down the transfer of heat and oxygen. At the same time, carbon nanotubes can improve the thermal stability and mechanical properties of materials, forming a network structure to promote carbonization. In addition, by introducing flame retardant groups into the polymer chain through chemical grafting, the compatibility between the flame retardant and the matrix can be significantly improved, reducing the migration of the flame retardant and increasing the flame retardant efficiency.

[0007] However, there is currently little research on multifunctional self-healing grafted PVC flame retardant masterbatches, especially the concentrated masterbatch technology that combines nanomaterials with chemical grafting has not been reported. Therefore, developing a high-efficiency, environmentally friendly, and multifunctional grafted PVC flame retardant masterbatch material has important theoretical and practical significance. Summary of the Invention

[0008] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a concentrated grafted PVC high-efficiency flame retardant masterbatch material and its preparation method. This method combines the end-functionalized PVC with nanomaterials and self-healing microcapsule technology to prepare a concentrated flame retardant masterbatch material with high flame retardancy, self-healing properties, and good mechanical properties.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows: The concentrated grafted PVC high-efficiency flame retardant masterbatch material is composed of the following components by weight: End-functionalized PVC: 50 - 60 parts by weight; Exfoliated organic montmorillonite: 10 - 15 parts by weight; Dopamine-coated zinc phosphate: 15 - 20 parts by weight; Microencapsulated self-healing agent: 3 - 5 parts by weight; Functionalized carbon nanotubes: 0.5 - 1 part by weight; Bio-based plasticizer: 5 - 10 parts by weight; Antioxidant: 1 - 3 parts by weight; Lubricant 0.25 - 1 part by weight; Dispersant 0.25 - 1 part by weight; The end-functionalized PVC is a modified PVC prepared by introducing thiol or amino functional groups into the PVC chain end; the exfoliated organic montmorillonite is a completely exfoliated montmorillonite with an interlayer spacing greater than 3 nm treated with tetraalkylammonium salts; the dopamine-coated zinc phosphate has a core-shell structure formed by in-situ deposition of dopamine on the surface of zinc phosphate; the microencapsulated self-healing agent is a microcapsule containing epoxy monomers and curing agents prepared by interfacial polymerization; the functionalized carbon nanotubes are multi-walled carbon nanotubes treated by oxidation.

[0010] Preferably, the tetraalkylammonium salt is dioctadecyldimethylammonium chloride; the epoxy monomer is bisphenol A epoxy resin; and the curing agent is an imidazole series curing agent.

[0011] Preferably, the bio-based plasticizer is epoxidized soybean oil; the antioxidant is pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, the lubricant is calcium stearate, and the dispersant is Disper BYK-190.

[0012] The preparation method of the concentrated grafted PVC highly efficient flame retardant masterbatch material comprises the following steps: (1) Prepare end-functionalized PVC; (2) Prepare exfoliated organomontmorillonite; (3) Prepare dopamine-coated zinc phosphate; (4) Prepare microencapsulated self-healing agent; (5) Prepare functionalized carbon nanotubes; (6) Mix the above components, and prepare the concentrated grafted PVC flame retardant masterbatch material by solution mixing method and extrusion process.

[0013] Preferably, the preparation method of the end-functionalized PVC in the step (1) comprises: (a) Add PVC resin into DMSO solvent, stir at 80 °C for 1 hour to completely dissolve PVC; (b) Add tetrabutylammonium bromide as a phase transfer catalyst, and continue stirring for 30 minutes; (c) Dissolve mercaptoethylamine hydrochloride in DMSO, and slowly add it to the above solution; (d) React at 65 ± 2 °C for 4 hours under nitrogen protection to obtain an end-functionalized PVC solution; (e) Slowly pour the end-functionalized PVC solution into deionized water to precipitate end-functionalized PVC; (f) Filter and collect the precipitate, wash it with deionized water 3 times, and dry it in vacuum at 60 °C for 24 hours to obtain end-functionalized PVC.

[0014] Preferably, the preparation method of the exfoliated organomontmorillonite in the step (2) comprises: (a) Add sodium montmorillonite into deionized water, stir for 24 hours to obtain a uniformly dispersed montmorillonite suspension; (b) Dissolve the tetraalkylammonium salt in hot water, slowly add it to the montmorillonite suspension, and stir at 80 °C for 6 hours; (c) Centrifuge and separate, collect the precipitate, and wash it with deionized water until there is no chloride ion; (d) The obtained precipitate was dried at 80 °C for 24 hours and ground into powder to obtain organic montmorillonite; (e) The organic montmorillonite was added to tetrahydrofuran and ultrasonically treated for 2 hours to form an exfoliated organic montmorillonite dispersion.

[0015] Preferably, the preparation method of dopamine-coated zinc phosphate in step (3) includes: (a) Zinc phosphate was added to deionized water and ultrasonically dispersed for 30 minutes; (b) A pH = 8.5, 0.5 mol / L Tris-HCl buffer solution was prepared; (c) Dopamine hydrochloride was dissolved in the Tris-HCl buffer solution, and then the zinc phosphate suspension was added; (d) Stirred at room temperature for 24 hours, while maintaining the solution pH value at 8.5 ± 0.2; (e) Centrifuged to separate, the precipitate was collected and washed 3 times successively with deionized water and ethanol; (f) Vacuum dried at 60 °C for 24 hours and ground into powder to obtain dopamine-coated zinc phosphate.

[0016] Preferably, the preparation method of the microencapsulated self-healing agent in step (4) includes: (a) The epoxy monomer and the curing agent were mixed and added to epoxy soybean oil, and stirred to form a homogeneous mixture to obtain an oil phase; (b) Gum arabic and gelatin were dissolved in deionized water, and the pH was adjusted to 4.0 to form an aqueous phase; (c) The oil phase was slowly added to the aqueous phase, and stirred at 45 °C at a speed of 800 rpm to form a stable emulsion; (d) Urea-formaldehyde prepolymer solution was added and the pH was adjusted to 8.5; (e) The temperature was lowered to 5 °C and maintained for 1 hour, then raised to 60 °C and reacted for 4 hours; (f) Centrifuged to separate, the microcapsules were collected and washed with ethanol and deionized water; (g) Vacuum dried at 40 °C for 12 hours to obtain the microencapsulated self-healing agent.

[0017] Preferably, the preparation method of the concentrated grafted PVC flame retardant masterbatch in step (6) includes: (a) The end-functionalized PVC was dissolved in THF to form a 10 wt% end-functionalized PVC solution; (b) The exfoliated organic montmorillonite dispersion was mixed with the end-functionalized PVC solution and ultrasonically treated for 1 hour to obtain a first mixture; (c) Add zinc phosphate coated with dopamine to the first mixture and stir for 1 hour to obtain the second mixture; (d) Add the microencapsulated self-healing agent to the second mixture and stir gently for 30 minutes to obtain the third mixture; (e) Disperse the functionalized carbon nanotubes in THF, ultrasonicate for 30 minutes, and then add them to the third mixture to obtain the fourth mixture; (f) Add epoxy soybean oil, antioxidant, lubricant, and dispersant to the fourth mixture and stir evenly to obtain the final mixture; (g) Rotate the final mixture under reduced pressure at 40 °C to evaporate most of the solvent and obtain the concentrated material; (h) Transfer the concentrated material to a twin-screw extruder and extrude it at a temperature of 165 - 175 °C and a screw speed of 150 rpm; (i) Cool the extrudate with water and pelletize it to obtain the concentrated grafted PVC flame retardant masterbatch material.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention prepares a concentrated flame retardant masterbatch material with high flame retardancy, self-healing property, and good mechanical properties by compounding end-functionalized PVC with nanomaterials and combining the self-healing microcapsule technology. Through the strong interfacial interaction between the modified PVC and the nanomaterials, the compatibility and stability of the material are significantly improved.

[0019] 2. The exfoliated organic montmorillonite in the present invention is completely exfoliated to form a nano-sheet structure, which forms a dense maze structure during combustion, effectively blocking the transfer of oxygen and heat and improving the flame retardant performance of the material. Compared with traditional layered silicates, the exfoliated organic montmorillonite has a larger specific surface area and better dispersibility, and can form a more uniform composite structure with the PVC matrix.

[0020] 3. Zinc phosphate coated with dopamine not only acts as a compatibilizer but also releases phosphoric acid during combustion to promote the carbonization of the matrix and form a dense carbon layer. The dopamine coating layer forms a network structure with the functionalized carbon nanotubes and end-functionalized PVC through π-π interactions and hydrogen bonds, enhancing the thermal stability and mechanical properties of the material.

[0021] 4. The functionalized carbon nanotubes form a three-dimensional heat conduction network, improving the thermal conductivity of the material, enhancing the mechanical properties of the material, and forming a stable network carbon layer during combustion. The interaction between the carbon nanotubes and dopamine can form a synergistic flame retardant effect, promoting heat dispersion, preventing local heat accumulation, and significantly reducing the heat release rate and smoke release amount of the material.

[0022] 5. Microencapsulated self-healing agents can repair the microcracks generated during the use of materials, extend the service life of materials, and also participate in the flame retardant process, releasing non-combustible gases to dilute combustible gases. The curing network formed by epoxy-based epoxy monomers and imidazole curing agents can effectively repair the microcracks of materials and maintain the integrity and performance of materials.

[0023] 6. The concentrated grafted PVC flame retardant masterbatch material of the present invention can achieve excellent flame retardant effects by adding 5% - 10% to ordinary PVC, and has a very high cost performance. When this material burns, the smoke density generated is reduced by more than 40%, and the release of toxic gases is reduced by more than 50%, greatly improving the safety of the material.

[0024] 7. In terms of chemical mechanism, the present invention forms a dual flame retardant mechanism in the gas phase and the condensed phase through the synergistic effect of multiple components: in the gas phase, the phosphorus-oxygen free radicals released by the decomposition of zinc phosphate can capture the active free radicals in the combustion chain reaction; in the condensed phase, dopamine and exfoliated organic montmorillonite promote the formation of a carbon layer, and at the same time, carbon nanotubes form a heat conduction network to block the transfer of heat and oxygen, greatly improving the flame retardant performance and thermal stability of the material. Detailed implementation methods

[0025] The present invention will be further described in detail below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto.

[0026] The raw materials and reagents are as follows: 1. Polyvinyl chloride (PVC): Suspension polymerization PVC resin, K value is 70, and the average molecular weight is about 100,000; 2. Montmorillonite: Sodium-based montmorillonite, cation exchange capacity: 145 meq / 100g, specific surface area: 750 - 800 m² / g; 3. Tetraalkylammonium salt: Dioctadecyl dimethyl ammonium chloride, purity ≥ 98%; 4. Dopamine hydrochloride: Purity ≥ 98%, Aladdin Reagent Co., Ltd.; 5. Zinc phosphate: Purity ≥ 99%, Sinopharm Chemical Reagent Co., Ltd.; 6. Epoxidized soybean oil: Epoxy value ≥ 6.5%; 7. Multi-walled carbon nanotubes (MWCNTs): Purity ≥ 95%, diameter: 20 - 30nm, length: 10 - 30μm; 8. Mercaptoethylamine hydrochloride: CAS No.: 156 - 57 - 0, purity ≥ 98%, Shanghai Macklin Biochemical Co., Ltd.; 9. Epoxy monomer: Bisphenol A epoxy resin, epoxy equivalent is 184 - 190g / eq; 10. Curing agent: 2-methylimidazole, CAS No.: 693-98-1, purity ≥ 99%, model EMI-24, product of Bayer AG, Germany, commonly used in low-temperature curing systems of epoxy resins, with high curing activity, fast curing speed and low dosage; 11. Antioxidant: Antioxidant 1010, pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, CAS No.: 6683-19-8, purity ≥ 98%, BASF (China) Co., Ltd.; 12. Phase transfer catalyst: Tetrabutylammonium bromide, CAS No.: 1643-19-2, purity ≥ 99%, Shanghai Aladdin Biochemical Technology Co., Ltd.; 13. Dimethyl sulfoxide (DMSO): Analytical pure, Sinopharm Chemical Reagent Co., Ltd.; 14. Tetrahydrofuran (THF): Analytical pure, Sinopharm Chemical Reagent Co., Ltd.; 15. Gum arabic: Food grade; 16. Gelatin: Food grade; 17. Urea-formaldehyde prepolymer: Solids content 50%, Beijing Orient Chemical Plant.

[0027] The preparation method of the concentrated grafted PVC high-efficiency flame retardant masterbatch material of the present invention includes the following steps.

[0028] Example 1

[0029] 1. Preparation method of end-functionalized PVC: (1) Add 10 g of PVC resin to 100 mL of DMSO solvent, stir at 80 °C for 1 hour to completely dissolve the PVC; (2) Add 0.5 g of tetrabutylammonium bromide as a phase transfer catalyst and continue stirring for 30 minutes; (3) Dissolve 1 g of mercaptoethylamine hydrochloride in 20 mL of DMSO and slowly add it dropwise to the above solution; (4) React at 65 ± 2 °C for 4 hours under nitrogen protection to obtain an end-functionalized PVC solution; (5) Slowly pour the end-functionalized PVC solution into 500 mL of deionized water to precipitate the end-functionalized PVC; (6) Filter and collect the precipitate, wash it 3 times with deionized water, and dry it in vacuum at 60 °C for 24 hours to obtain end-functionalized PVC.

[0030] 2. Preparation method of exfoliated organophilic montmorillonite: (1) Take 5 g of sodium montmorillonite, add it to 500 mL of deionized water, and stir for 24 hours to obtain a uniformly dispersed montmorillonite suspension; (2) Dissolve 1.5 g of dimethyldioctadecylammonium chloride in 100 mL of hot water, slowly add it to the montmorillonite suspension, and stir at 80 °C for 6 hours; (3) Centrifuge (5000 rpm, 20 minutes), collect the precipitate, and wash it with deionized water until there is no chloride ion (detected with AgNO3 solution); (4) Dry the obtained precipitate at 80 °C for 24 hours, grind it into powder to obtain organic montmorillonite; (5) Add the organic montmorillonite to THF (concentration 10 mg / mL), ultrasonically treat for 2 hours to form a exfoliated organic montmorillonite dispersion for standby.

[0031] 3. Preparation method of dopamine-coated zinc phosphate: (1) Take 5 g of zinc phosphate, add it to 200 mL of deionized water, and ultrasonically disperse for 30 minutes; (2) Prepare 200 mL of 0.5 mol / L Tris-HCl buffer solution (pH = 8.5); (3) Dissolve 2 g of dopamine hydrochloride in the buffer solution, and then add the zinc phosphate suspension; (4) Stir at room temperature for 24 hours, and maintain the solution pH value at 8.5 ± 0.2 during this period (adjusted with NaOH solution); (5) Centrifuge (8000 rpm, 30 minutes), collect the precipitate, and wash it 3 times with deionized water and ethanol in sequence; (6) Vacuum dry at 60 °C for 24 hours, grind it into powder to obtain dopamine-coated zinc phosphate.

[0032] 4. Preparation method of microencapsulated self-healing agent: (1) Mix 1.5 g of bisphenol A epoxy resin with 0.5 g of imidazole curing agent, add it to 20 mL of epoxy soybean oil, and stir to form a homogeneous mixture to obtain the oil phase; (2) Prepare the aqueous phase: Dissolve 1 g of arabic gum and 1 g of gelatin in 100 mL of deionized water, and adjust the pH to 4.0 (adjusted with dilute HCl); (3) Slowly add the oil phase to the aqueous phase, stir at 45 °C at a speed of 800 rpm for 30 minutes to form a stable emulsion; (4) Add 10 mL of urea-formaldehyde prepolymer solution (40 wt%), and adjust the pH to 8.5 (adjusted with NaOH solution); (5) Lower the temperature to 5 °C, keep it for 1 hour, then raise the temperature to 60 °C and react for 4 hours; (6) Centrifuge (3000 rpm, 10 minutes), collect the microcapsules, and wash them 2 times with ethanol and deionized water; (7) It was dried in vacuum at 40 °C for 12 hours to obtain the microencapsulated self-healing agent.

[0033] 5. Preparation method of functionalized carbon nanotubes: (1) Take 1 g of multi-walled carbon nanotubes and add them to 100 mL of a mixed acid solution (H2SO4:HNO3 = 3:1, volume ratio); (2) Ultrasonically treat for 2 hours at 70 °C, and then stir for 12 hours; (3) Dilute the mixture with a large amount of deionized water and collect the solid product by suction filtration; (4) Wash with deionized water until neutral, and then wash with ethanol twice; (5) Dry in vacuum at 80 °C for 24 hours to obtain functionalized carbon nanotubes.

[0034] 6. Preparation method of urea-formaldehyde prepolymer: (a) Add 100 g of deionized water to a three-necked flask and dissolve 30 g of urea; (b) Slowly add 50 g of formaldehyde solution (37 wt% aqueous solution) under stirring conditions; (c) Add a small amount of NaOH solution to adjust the pH to 8.0 - 8.5; (d) Stir and react at 70 - 75 °C for 90 minutes; (e) After cooling to room temperature, adjust the pH to 6.8 - 7.2 with glacial acetic acid; (f) Obtain a urea-formaldehyde prepolymer solution with a solids content of about 50 wt%, store it in a refrigerator at 4 °C, and the service life does not exceed 7 days.

[0035] 7. The preparation method of the concentrated grafted PVC flame retardant masterbatch is as follows: (1) Dissolve 50 g of end-functionalized PVC in 500 mL of THF to form a 10 wt% end-functionalized PVC solution; (2) Mix 250 mL of exfoliated organic montmorillonite dispersion (containing 10 g of organic montmorillonite) with the end-functionalized PVC solution, and ultrasonically treat for 1 hour to obtain a first mixture; (3) Add 15 g of dopamine-coated zinc phosphate to the first mixture and stir for 1 hour to obtain a second mixture; (4) Add 3 g of the microencapsulated self-healing agent to the second mixture and stir gently for 30 minutes (to avoid damaging the microcapsules) to obtain a third mixture; (5) Disperse 0.5 g of functionalized carbon nanotubes in 100 mL of THF, ultrasonically treat for 30 minutes, and then add it to the third mixture to obtain a fourth mixture; (6) Add 5 g of epoxidized soybean oil, 1 g of antioxidant, 0.25 g of lubricant and 0.25 g of dispersant to the fourth mixture, and stir evenly to obtain the final mixture; (7) Rotate and evaporate the final mixture under reduced pressure at 40 °C to remove most of the solvent and obtain the concentrated material; (8) Transfer the concentrated material to a twin-screw extruder and extrude it at a temperature of 170 °C and a screw speed of 150 rpm; (9) Cool the extrudate with water and pelletize it to obtain the concentrated grafted PVC flame retardant masterbatch material.

[0036] According to the above preparation method, a concentrated grafted PVC high-efficiency flame retardant masterbatch material with the following weight composition is obtained: End-functionalized PVC: 50 parts by weight; Exfoliated organic montmorillonite: 10 parts by weight; Dopamine-coated zinc phosphate: 15 parts by weight; Microencapsulated self-healing agent: 3 parts by weight; Functionalized carbon nanotubes: 0.5 parts by weight; Bio-based plasticizer: 5 parts by weight; Antioxidant: 1 part by weight; Lubricant 0.25 parts by weight, dispersant 0.25 parts by weight, the lubricant is calcium stearate, and the dispersant is modified polyacrylate, trade name Disper BYK-190, BYK Chemie GmbH, Germany, which is a high-efficiency dispersant for polymer systems.

[0037] Example 2

[0038] The preparation method is the same as that of Example 1, but the amounts of each component are adjusted to obtain a concentrated grafted PVC high-efficiency flame retardant masterbatch material with the following weight composition: End-functionalized PVC: 55 parts by weight; Exfoliated organic montmorillonite: 12 parts by weight; Dopamine-coated zinc phosphate: 18 parts by weight; Microencapsulated self-healing agent: 4 parts by weight; Functionalized carbon nanotubes: 0.8 parts by weight; Bio-based plasticizer: 8 parts by weight; Antioxidant: 2 parts by weight; Lubricant 0.5 parts by weight, dispersant 0.5 parts by weight, the lubricant is calcium stearate, and the dispersant is modified polyacrylate, trade name Disper BYK-190, BYK Chemie GmbH, Germany, which is a high-efficiency dispersant for polymer systems.

[0039] The preparation process is the same as that of Example 1, with slight adjustments to the specific parameters: 1. Preparation of end - group functionalized PVC: Use 1.2 g of mercaptoethylamine hydrochloride and react for 5 hours; 2. Preparation of exfoliated organic montmorillonite: Use 6 g of sodium - based montmorillonite and stir for 8 hours; 3. Preparation of dopamine - coated zinc phosphate: Use 6 g of zinc phosphate and 2.5 g of dopamine hydrochloride and stir for 30 hours; 4. Preparation of micro - encapsulated self - healing agent: Use 2 g of bisphenol A epoxy resin and 0.7 g of imidazole curing agent and stir for 45 minutes; 5. Preparation of functionalized carbon nanotubes: Use 1.5 g of multi - walled carbon nanotubes, ultrasonically treat for 2.5 hours and stir for 15 hours.

[0040] Example 3

[0041] The preparation method is the same as that of Example 1, but the amounts of each component are adjusted to obtain a concentrated grafted PVC high - efficiency flame - retardant masterbatch material with the following composition by weight: End - group functionalized PVC: 60 parts by weight; Exfoliated organic montmorillonite: 15 parts by weight; Dopamine - coated zinc phosphate: 20 parts by weight; Micro - encapsulated self - healing agent: 5 parts by weight; Functionalized carbon nanotubes: 1 part by weight; Bio - based plasticizer: 10 parts by weight; Antioxidant: 3 parts by weight; Lubricant 1 part by weight, dispersant 1 part by weight. The lubricant is calcium stearate, and the dispersant is modified polyacrylate, trade name Disper BYK - 190, BYK Chemie GmbH, Germany, which is a highly efficient dispersant for polymer systems.

[0042] The preparation process is the same as that of Example 1, with slight adjustments to the specific parameters: 1. Preparation of end - group functionalized PVC: Use 1.5 g of mercaptoethylamine hydrochloride and react for 6 hours; 2. Preparation of exfoliated organic montmorillonite: Use 7.5 g of sodium - based montmorillonite and stir for 36 hours; 3. Preparation of dopamine - coated zinc phosphate: Use 10 g of zinc phosphate and 3 g of dopamine hydrochloride and stir for 36 hours; 4. Preparation of micro - encapsulated self - healing agent: Use 2.5 g of bisphenol A epoxy resin and 0.8 g of imidazole curing agent and stir for 55 minutes; 5. Preparation of functionalized carbon nanotubes: Use 2 g of multi - walled carbon nanotubes, ultrasonically treat for 3 hours and stir for 18 hours.

[0043] Comparative Example 1 The preparation method is the same as that of Example 1, but without using end-functionalized PVC, and directly using ordinary PVC resin. The composition is as follows: Ordinary PVC resin: 50 parts by weight; Exfoliated organic montmorillonite: 10 parts by weight; Dopamine-coated zinc phosphate: 15 parts by weight; Microencapsulated self-healing agent: 3 parts by weight; Functionalized carbon nanotubes: 0.5 part by weight; Bio-based plasticizer: 5 parts by weight; Antioxidant: 1 part by weight; Lubricant 0.25 part by weight, dispersant 0.25 part by weight.

[0044] Comparative Example 2 The preparation method is the same as that of Example 1, but without using dopamine-coated zinc phosphate, and directly using pure zinc phosphate. The composition is as follows: End-functionalized PVC: 50 parts by weight; Exfoliated organic montmorillonite: 10 parts by weight; Zinc phosphate: 15 parts by weight; Microencapsulated self-healing agent: 3 parts by weight; Functionalized carbon nanotubes: 0.5 part by weight; Bio-based plasticizer: 5 parts by weight; Antioxidant: 1 part by weight; Lubricant 0.25 part by weight, dispersant 0.25 part by weight.

[0045] Comparative Example 3 The preparation method is the same as that of Example 1, but without using the microencapsulated self-healing agent. The composition is as follows: End-functionalized PVC: 53 parts by weight; Exfoliated organic montmorillonite: 10 parts by weight; Dopamine-coated zinc phosphate: 15 parts by weight; Functionalized carbon nanotubes: 0.5 part by weight; Bio-based plasticizer: 5 parts by weight; Antioxidant: 1 part by weight; Lubricant 0.25 part by weight, dispersant 0.25 part by weight.

[0046] Comparative Example 4 The preparation method is the same as that of Example 1, but using ordinary organic montmorillonite (without exfoliation treatment) instead of exfoliated organic montmorillonite. The composition is as follows: End-functionalized PVC: 50 parts by weight; Ordinary organic montmorillonite: 10 parts by weight; Zinc phosphate coated with dopamine: 15 parts by weight; Microencapsulated self-healing agent: 3 parts by weight; Functionalized carbon nanotubes: 0.5 parts by weight; Bio-based plasticizer: 5 parts by weight; Antioxidant: 1 part by weight; Lubricant 0.25 parts by weight, dispersant 0.25 parts by weight.

[0047] Comparative Example 5 The preparation method is the same as that of Example 1, but ordinary carbon nanotubes (not functionalized) are used instead of functionalized carbon nanotubes, and the composition is as follows: End-functionalized PVC: 50 parts by weight; Exfoliated organic montmorillonite: 10 parts by weight; Zinc phosphate coated with dopamine: 15 parts by weight; Microencapsulated self-healing agent: 3 parts by weight; Ordinary carbon nanotubes: 0.5 parts by weight; Bio-based plasticizer: 5 parts by weight; Antioxidant: 1 part by weight; Lubricant 0.25 parts by weight, dispersant 0.25 parts by weight.

[0048] Comparative Example 6 (blank control group) The preparation method is similar to that of Example 1, but all unmodified raw materials are used, and the composition is as follows: Ordinary PVC resin: 50 parts by weight; Ordinary organic montmorillonite: 10 parts by weight; Zinc phosphate: 15 parts by weight; Ordinary self-healing agent (not microencapsulated): 3 parts by weight; Ordinary carbon nanotubes: 0.5 parts by weight; Bio-based plasticizer: 5 parts by weight; Antioxidant: 1 part by weight; Lubricant 0.25 parts by weight, dispersant 0.25 parts by weight.

[0049] The performance tests are as follows: 1. Flame retardancy test The flame retardancy is tested by the following three standard methods: Limiting oxygen index (LOI) test: According to the standard of GB / T 2406-2009; UL-94 vertical burning test: According to the standard of GB / T 2408-2008; Cone calorimeter test: According to the standard of ISO 5660-1, the heat irradiation intensity is 50 kW / m² The test results are shown in Table 1:

[0050] As can be seen from Table 1, the flame retardancy of Examples 1-3 is significantly better than that of all comparative examples. The oxygen index values of Examples 1-3 are between 32.5% and 35.2%, all higher than those of Comparative Examples 1-6, which are between 28.5% and 31.2%. In the cone calorimeter test, the peak heat release rate and total heat release of the example group are reduced by about 13%-35% and 11%-29% respectively compared with the comparative example group, and the peak smoke release rate is reduced by about 15%-50%.

[0051] It should be noted that the flame retardancy of Comparative Example 4 (using ordinary organic montmorillonite) and Comparative Example 5 (using ordinary carbon nanotubes) has decreased significantly compared with Example 1, indicating that exfoliated organic montmorillonite and functionalized carbon nanotubes play an important role in improving flame retardancy. And the flame retardancy indexes of Comparative Example 6 (blank control group) are the worst, proving that the synergistic effect after modification of all components has significantly improved the flame retardancy of the material.

[0052] Analysis of the flame retardancy mechanism shows that dopamine-coated zinc phosphate releases phosphoric acid during combustion, promotes the carbonization of the PVC matrix, and forms a dense carbon layer; at the same time, exfoliated organic montmorillonite forms a nano-sheet structure, which forms a maze barrier layer during combustion to block the transfer of oxygen and heat; functionalized carbon nanotubes form a heat conduction network to accelerate heat dispersion, avoid local heat accumulation, and form a stable network carbon layer during combustion. This multiple flame retardancy mechanism enables the material to have excellent flame retardancy.

[0053] 2. Self-healing performance test The self-healing performance was tested by the following method: The sample was made into a test strip with dimensions of 50mm×10mm×2mm, a scratch with a length of 20mm, a width of 0.1mm, and a depth of 0.05mm was made on the surface, and the scratched sample was placed at 25°C for 24 hours, and then the healing situation of the scratch was observed. A microscope was used to measure the width of the scratch before and after healing, and the self-healing rate was calculated.

[0054] Self-healing rate (%) = (1 - width of the scratch after healing / initial width of the scratch) × 100%, and the test results are shown in Table 2:

[0055] As can be seen from Table 2, Examples 1-3 have remarkable self-healing performance, with the self-healing rate reaching 72%-81%. The self-healing rates of Comparative Examples 1, 2, 4, and 5 are 61%-70%, while those of Comparative Example 3 (without microencapsulated self-healing agent) and Comparative Example 6 (using ordinary self-healing agent) are only 10% and 7% respectively. This indicates that the microencapsulated self-healing agent plays a key role in the self-healing performance of the material, and end-functionalized PVC can further enhance the self-healing effect.

[0056] Analysis of the self-healing mechanism shows that when microcracks occur on the material surface, the microcapsules rupture, releasing epoxy monomers and curing agents. They react at the crack site to form a crosslinked network, connecting both sides of the crack and achieving self-healing. This repair mechanism can not only restore the surface integrity of the material but also, to a certain extent, restore the mechanical properties of the material and extend its service life.

[0057] 3. Mechanical Property Tests Tensile property tests were carried out according to the standard of GB / T 1040.2-2006, using dumbbell-shaped specimens with a tensile speed of 50 mm / min. The test results are shown in Table 3:

[0058] As can be seen from Table 3, the mechanical properties of Examples 1-3 are superior to all comparative examples. The tensile strength of Examples 1-3 is increased by about 13%-38% compared with Comparative Examples 1-6, the elongation at break is increased by about 13%-79%, and the elastic modulus is increased by about 6%-14%.

[0059] The mechanical properties of Comparative Example 4 and Comparative Example 5 are slightly lower than those of Example 1 but higher than those of Comparative Example 6, indicating that exfoliated organic montmorillonite and functionalized carbon nanotubes have obvious effects on improving the mechanical properties of the material. The mechanical property indexes of Comparative Example 6 are the worst, reflecting the important influence of the synergistic effect of all modified components on the mechanical properties of the material.

[0060] The mechanism of mechanical property improvement can be attributed to the following aspects: 1. A strong interfacial interaction is formed between end-functionalized PVC and nano-fillers, improving the compatibility and mechanical properties of the material; 2. The nano-sheet structure of exfoliated organic montmorillonite can effectively hinder crack propagation and enhance the mechanical properties of the material; 3. Functionalized carbon nanotubes form a three-dimensional heat conduction network, enhancing the material; 4. The dopamine coating layer forms a network structure with functionalized carbon nanotubes and end-functionalized PVC through π-π interaction and hydrogen bonding, further enhancing the mechanical properties of the material.

[0061] 4. Thermal Stability Tests The thermal stability of the materials was tested using a thermogravimetric analyzer (TGA) with a heating rate of 10 °C / min, a temperature range from room temperature to 800 °C, and a nitrogen atmosphere. The test results are shown in Table 4: Table 4 Thermal stability test results

[0062] As can be seen from Table 4, the thermal stability of Examples 1-3 is better than that of all comparative examples. The initial decomposition temperature of Examples 1-3 is about 7-23 °C higher than that of Comparative Examples 1-6, the maximum decomposition temperature is about 13-35 °C higher, and the char residue rate at 600 °C is about 4.7-10.3 percentage points higher.

[0063] The thermal stability of Comparative Examples 4 and 5 is slightly lower than that of Example 1, indicating that exfoliated organic montmorillonite and functionalized carbon nanotubes have a positive effect on improving the thermal stability of the materials. The thermal stability of Comparative Example 6 is the worst, indicating that the combined action of all modified components has a significant effect on improving the thermal stability.

[0064] The mechanism of the improved thermal stability can be attributed to the following aspects: 1. Strong interfacial interactions are formed between the end-functionalized PVC and the nano-fillers, restricting the movement of molecular chains and improving the thermal stability; 2. Dopamine-coated zinc phosphate releases phosphoric acid at high temperatures, promoting the carbonization of the materials and improving the thermal stability; 3. The nano-sheet structure of exfoliated organic montmorillonite forms a maze barrier, hindering the thermal-oxidative degradation and improving the thermal stability; 4. Functionalized carbon nanotubes form a thermal conduction network, accelerating the heat dispersion, avoiding local heat accumulation, and improving the thermal stability.

[0065] 5. Test on the effect of masterbatch addition To evaluate the actual application effect of the concentrated grafted PVC highly efficient flame retardant masterbatch materials, the masterbatches of Examples 1-3 and Comparative Examples 1-6 were added to ordinary PVC at ratios of 5% and 10% respectively to prepare PVC composites, and their flame retardant properties were tested. The test results are shown in Table 5:

[0066] As can be seen from Table 5, adding the concentrated grafted PVC highly efficient flame retardant masterbatch materials of the present invention to ordinary PVC can significantly improve the flame retardant properties of the materials. When 5% of Examples 1-3 is added, the oxygen index value can be increased to 29.5-30.8%, and the UL-94 rating reaches V-0 level; when 10% is added, the oxygen index value can be increased to 31.2-32.5%. In contrast, when 5% of Comparative Examples 1-5 is added, only the V-1 level can be achieved, and only when 10% is added can the V-0 level be achieved; while when 10% of Comparative Example 6 is added, only the V-1 level can be achieved.

[0067] Regarding the peak heat release rate, when 5% was added in Examples 1 - 3, it was 210 - 230 kW / m², and when 10% was added, it decreased to 175 - 195 kW / m², both lower than the values with the same addition ratios in the comparative examples, indicating that the flame retardant masterbatch of the present invention can more effectively inhibit the heat release during material combustion.

[0068] These results show that the concentrated grafted PVC high - efficiency flame retardant masterbatch material of the present invention has excellent flame retardant effects. In practical applications, adding only 5% can significantly improve the flame retardant performance of ordinary PVC, with high cost - effectiveness and broad application prospects.

[0069] In summary, the concentrated grafted PVC high - efficiency flame retardant masterbatch material of the present invention performs excellently in terms of flame retardant performance, self - healing performance, mechanical properties, and thermal stability. Especially through the modification treatment and synergistic effect of each component, the material properties are comprehensively improved. Compared with each comparative example, the present invention has obvious advantages in various performance indicators, proving the innovation and practical value of the invention.

Claims

1. Concentrated grafted PVC high-efficiency flame retardant masterbatch material, characterized by: By weight, it is composed of the following components: End-group functionalized PVC: 50-60 parts by weight; Exfoliated organic montmorillonite: 10-15 parts by weight; Dopamine coated zinc phosphate: 15-20 parts by weight; Microencapsulated self-healing agent: 3-5 parts by weight; Functionalized carbon nanotubes: 0.5-1 parts by weight; Bio-based plasticizer: 5-10 parts by weight; Antioxidant: 1-3 parts by weight; Lubricant 0.25-1 parts by weight; Dispersant 0.25-1 parts by weight; The end-functionalized PVC is a modified PVC prepared by introducing a thiol or amino functional group into the end of the PVC chain; the exfoliated organic montmorillonite is a completely exfoliated montmorillonite with an interlayer spacing greater than 3 nm treated with a tetraalkylammonium salt; the dopamine-coated zinc phosphate has a core-shell structure, which is formed on the surface of the zinc phosphate by an in-situ deposition method of dopamine; the microencapsulated self-healing agent is a microcapsule containing an epoxy monomer and a curing agent prepared by an interfacial polymerization method; and the functionalized carbon nanotube is an oxidized multi-walled carbon nanotube.

2. The concentrated grafted PVC high-efficiency flame-retardant masterbatch material according to claim 1, characterized in that: The tetraalkylammonium salt is dioctadecyldimethylammonium chloride; the epoxy monomer is bisphenol A type epoxy resin; and the curing agent is an imidazole series curing agent.

3. The concentrated grafted PVC high-efficiency flame-retardant masterbatch material according to claim 1, characterized in that: The bio-based plasticizer is epoxidized soybean oil; the antioxidant is pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxy)phenylpropionate; the lubricant is calcium stearate; and the dispersant is Disper BYK-190.

4. The method for preparing the concentrated grafted PVC high-efficiency flame-retardant masterbatch material according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Preparation of end-group functionalized PVC; (2) Preparation of exfoliated organic montmorillonite; (3) Preparation of dopamine-coated zinc phosphate; (4) preparing microencapsulated self-healing agents; (5) Preparation of functionalized carbon nanotubes; (6) The above components are mixed to prepare a concentrated grafted PVC flame retardant masterbatch material through a solution mixing method and an extrusion process.

5. The preparation method according to claim 4, characterized in that: The method for preparing the terminal functionalized PVC in step (1) comprises: (a) Add PVC resin into DMSO solvent and stir at 80°C for 1 hour to completely dissolve the PVC; (b) adding tetrabutylammonium bromide as a phase transfer catalyst and continuing stirring for 30 minutes; (c) dissolving mercaptoethylamine hydrochloride in DMSO and slowly adding dropwise to the above solution; (d) reacting at 65±2°C for 4 hours under nitrogen protection to obtain a terminal functionalized PVC solution; (e) slowly pouring the end-group functionalized PVC solution into deionized water to precipitate the end-group functionalized PVC; (f) The precipitate was collected by filtration, washed three times with deionized water, and dried in a vacuum oven at 60 °C for 24 h to obtain end-group functionalized PVC.

6. The preparation method according to claim 4, characterized in that: The method for preparing the exfoliated organic montmorillonite in step (2) comprises: (a) adding sodium montmorillonite into deionized water and stirring for 24 hours to obtain a uniformly dispersed montmorillonite suspension; (b) dissolving a tetraalkylammonium salt in hot water, slowly adding the solution to the montmorillonite suspension, and stirring at 80°C for 6 hours; (c) centrifugation, collecting the precipitate, and washing with deionized water until there is no chloride ion; (d) drying the obtained precipitate at 80° C. for 24 hours, grinding it into powder, and obtaining organic montmorillonite; (e) The organic montmorillonite is added to tetrahydrofuran and subjected to ultrasonic treatment for 2 h to form an exfoliated organic montmorillonite dispersion.

7. The preparation method according to claim 4, characterized in that: The method for preparing dopamine-coated zinc phosphate in step (3) comprises: (a) Zinc phosphate was added to deionized water and ultrasonically dispersed for 30 min; (b) preparing pH = 8.5, 0.5 mol / L Tris-HCl buffer; (c) dissolving dopamine hydrochloride in Tris-HCl buffer and then adding zinc phosphate suspension; (d) stirring at room temperature for 24 hours, during which the pH value of the solution was maintained at 8.5 ± 0.2; (e) centrifugation, collecting the precipitate, and washing it three times with deionized water and ethanol; (f) Drying under vacuum at 60 °C for 24 h and grinding into powder to obtain dopamine-coated zinc phosphate.

8. The preparation method according to claim 4, characterized in that: The method for preparing the microencapsulated self-healing agent in step (4) comprises: (a) mixing an epoxy monomer and a curing agent, adding the mixture to epoxy soybean oil, and stirring the mixture to form a uniform mixture to obtain an oil phase; (b) dissolving gum arabic and gelatin in deionized water and adjusting the pH to 4.0 to form an aqueous phase; (c) slowly adding the oil phase into the water phase and stirring at 800 rpm at 45°C to form a stable emulsion; (d) adding urea-formaldehyde prepolymer solution and adjusting the pH to 8.5; (e) lowering the temperature to 5°C, maintaining for 1 hour, and then raising the temperature to 60°C and reacting for 4 hours; (f) collecting the microcapsules by centrifugation and washing them with ethanol and deionized water; (g) The microencapsulated self-healing agent was obtained by vacuum drying at 40 °C for 12 h.

9. The preparation method according to claim 6, characterized in that: The method for preparing concentrated grafted PVC flame retardant masterbatch in step (6) comprises: (a) dissolving the end-functionalized PVC in THF to form a 10 wt % end-functionalized PVC solution; (b) mixing the exfoliated organic montmorillonite dispersion with the end-group functionalized PVC solution, and subjecting the mixture to ultrasonic treatment for 1 hour to obtain a first mixed solution; (c) adding dopamine-coated zinc phosphate to the first mixed solution and stirring for 1 hour to obtain a second mixed solution; (d) adding the microencapsulated self-healing agent to the second mixed solution and gently stirring for 30 minutes to obtain a third mixed solution; (e) dispersing the functionalized carbon nanotubes in THF, adding the mixture to the third mixed solution after ultrasonication for 30 minutes to obtain a fourth mixed solution; (f) adding epoxidized soybean oil, antioxidant, lubricant and dispersant to the fourth mixed solution, stirring evenly to obtain a final mixture; (g) the final mixture was subjected to rotary evaporation under reduced pressure at 40° C. to remove most of the solvent to obtain a concentrated material; (h) transferring the concentrated material to a twin-screw extruder and extruding the material at a temperature of 165-175° C. and a screw speed of 150 rpm; (i) Cooling the extrudate with water and pelletizing it to obtain a concentrated grafted PVC flame retardant masterbatch material.

Images