Regenerated plastic packaging film material and preparation method thereof

Abstract

The preparation method comprises the following steps: sorting and cleaning waste polyethylene glycol terephthalate bottle chips, and carrying out high-temperature drying treatment, so as to obtain pretreated polyethylene glycol terephthalate; and uniformly mixing the pretreated polyethylene glycol terephthalate, isophorone diisocyanate, the modified polymer and the modified filler, and performing melt extrusion and blow molding to form a film, thereby obtaining the regenerated plastic packaging film material. The modified polymer is formed by copolymerizing hindered phenol compounds, piperidinyl compounds and N-(4-carboxyl phenyl) maleimide free radicals and then grafting poly (ethylene glycol) methacrylate, and the modified filler is formed by coating carbon black with calcium sulfate whiskers to form a core-shell structure and then grafting a silane coupling agent. A molecular chain of the modified polymer contains a hindered phenol structure and a hindered amine structure, so that the ageing resistance of the polymer is improved. The carbon black as a core can induce crazing, and the calcium sulfate whisker as a shell can bridge cracks, so that the mechanical property of the material is improved.

Description

Technical Field

[0001] This invention relates to the field of plastic film materials, and more specifically to a recycled plastic film material and its preparation method. Background Technology

[0002] With the development of the packaging industry, waste polyethylene terephthalate (PET) bottles have become a major component of urban solid waste. Recycling PET bottles has attracted increasing attention due to their high economic, resource, and environmental value. However, the recycling process requires high-temperature melting, which causes some molecular chains to break and oxidize, producing chromophores that absorb visible light. Simultaneously, the decrease in molecular weight and increase in crystallinity lead to increased brittleness and reduced mechanical properties, making it difficult to meet the high mechanical performance requirements of plastics in packaging protection. Therefore, it is necessary to develop a high-mechanical-performance, highly efficient, and anti-yellowing recycled plastic sealing film material to address the issues that need to be addressed in practical applications. Summary of the Invention

[0003] The purpose of this invention is to provide a recycled plastic sealant film and its preparation method, which solves the problems of low mechanical properties and yellowing color of recycled plastic sealant film at present.

[0004] The objective of this invention can be achieved through the following technical solutions: A method for preparing recycled plastic sealant film specifically includes the following steps: Step S1: After sorting and cleaning the recycled polyethylene terephthalate bottle flakes, dry them in a forced-air drying process at 120°C for 12 hours to obtain pretreated polyethylene terephthalate. Step S2: Mix pretreated polyethylene terephthalate, isophorone diisocyanate, modified polymer and modified filler evenly, melt extrude at 250-265℃, blow mold into film, and obtain recycled plastic sealing film material.

[0005] Furthermore, the weight ratio of the pretreated polyethylene terephthalate, isophorone diisocyanate, modified polymer, and modified filler in step S2 is 80-100:40-50:20-30:5-8.

[0006] Furthermore, the modified polymer is prepared by the following steps: Step A1: Mix allyl alcohol and dichloromethane evenly, and under conditions of 60-80 r / min, 0-5℃, and nitrogen gas, stir and add β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and triethylamine, heat to 40-50℃, and react for 20-24 h to obtain the hindered phenolic compound. Mix 1,2,2,6,6-pentamethylpiperidinol, ethyl acrylate, and xylene evenly, and under conditions of 80-100 r / min, 100-110℃, stir and add tetraisopropyl titanate, heat to 130-140℃, and react for 8-10 h to obtain the piperidinyl compound. Step A2: Mix 4-aminobenzoic acid, tetrahydrofuran, and maleic anhydride evenly, and react for 4-6 hours at a speed of 60-80 r / min and a temperature of 20-30℃ to obtain an intermediate. Mix the intermediate, sodium acetate, and toluene evenly, and react for 6-8 hours at a speed of 80-100 r / min and a temperature of 90-100℃ to obtain N-(4-carboxyphenyl)maleimide. Mix the hindered phenolic compound, cyclohexanone, piperidinyl compound, and N-(4-carboxyphenyl)maleimide evenly, and stir and add azobisisobutyronitrile at a speed of 120-150 r / min and a temperature of 80-100℃ under nitrogen gas, and react for 4-6 hours to obtain a carboxyl-containing copolymer. Step A3: Disperse the carboxyl-containing copolymer in tetrahydrofuran. Under conditions of 80-100 r / min and 0-4℃, stir and add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-carboxysuccinimide. Stir for 30-60 min, heat to 20-30℃, add poly(ethylene glycol) methacrylate, and react for 12-24 h to obtain the primary polymer. Mix the primary polymer, 3-mercapto-1-propanol, benzoin dimethyl ether and tetrahydrofuran evenly, and react for 20-30 s under conditions of 110-130 r / min, 20-25℃ and ultraviolet irradiation to obtain the modified polymer.

[0007] Further, in step A1, the ratio of allyl alcohol, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, and triethylamine is 1 mmol:1.3 mmol:25 mL, the molar ratio of 1,2,2,6,6-pentamethylpiperidinol and ethyl acrylate is 1.8:1, and the amount of tetraisopropyl titanate is 0.3-0.4% of the mass of 1,2,2,6,6-pentamethylpiperidinol.

[0008] Further, in step A2, the molar ratio of 4-aminobenzoic acid and maleic anhydride is 1:1.1, the ratio of intermediate, sodium acetate and toluene is 23.5g:0.5g:120mL, the molar ratio of hindered phenolic compound, piperidinyl compound and N-(4-carboxyphenyl)maleimide is 1:1:1, and the amount of azobisisobutyronitrile is 3-7% of the mass of hindered phenolic compound.

[0009] Further, in step A3, the ratio of the carboxyl-containing copolymer, tetrahydrofuran, poly(ethylene glycol) methacrylate, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and N-carboxysuccinimide is 1.2 g: 50 mL: 2.3 mmol: 2.3 mmol: 3.5 g, the average molecular weight of poly(ethylene glycol) methacrylate is 1500 g / mol, the molar ratio of carbon-carbon double bonds on the primary polymer to mercapto groups on 3-mercapto-1-propanol is 1.2:0.2, and the amount of benzoin dimethyl ether is 2-5% of the mass of the primary polymer.

[0010] Furthermore, the modified filler is prepared by the following steps: Step B1: Disperse trisodium phosphate in deionized water, add calcium sulfate whiskers at a temperature of 20-25℃ and a frequency of 30-40kHz, and sonicate for 2-5 minutes to obtain pretreated calcium sulfate whiskers. Step B2: Mix carbon black and nitric acid evenly, and react for 2-4 hours at a speed of 150-200 r / min and a temperature of 60-70℃. Cool to room temperature, filter to remove the filtrate, and obtain carboxylated carbon black. Disperse the carboxylated carbon black in deionized water, and stir and add pretreated calcium sulfate whiskers at a speed of 100-120 r / min, a temperature of 60-80℃, and a pH of 9-10. React for 5-8 hours to obtain pretreated filler. Step B3: The pretreated filler is dispersed in tetrahydrofuran and stirred at a speed of 200-300 r / min, a temperature of 60-80℃, and a pH of 4-5. 3-Aminopropyltrimethoxysilane is added and the reaction is carried out for 8-10 h to obtain the modified filler.

[0011] Furthermore, the ratio of trisodium phosphate, deionized water, and calcium sulfate whiskers used in step B1 is 0.2 mmol: 10 mL: 0.3 g.

[0012] Furthermore, in step B2, the ratio of carbon black to nitric acid is 1g:100mL, the mass fraction of nitric acid is 65%, and the ratio of carboxylated carbon black to pretreated calcium sulfate whiskers is 1g:5g.

[0013] Furthermore, the amount of 3-aminopropyltrimethoxysilane used in step B3 is 3-5% of the mass of the pretreatment filler.

[0014] The beneficial effects of the present invention: The recycled plastic sealing film material prepared by the present invention uses isophorone diisocyanate as a coupling agent. The isocyanate group of the coupling agent undergoes an acyluration reaction with the hydroxyl groups of pretreated polyethylene terephthalate and modified polymer, and at the same time undergoes a nucleophilic addition reaction with the amino group of the modified filler. The film is then obtained by melt extrusion and blow molding.

[0015] Modified polymers: The hydroxyl groups on allyl alcohol react with the acyl chloride groups on β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride to generate ester groups, yielding hindered phenolic compounds. 1,2,2,6,6-pentamethylpiperidinol undergoes transesterification with ethyl acrylate under the catalysis of tetraisopropyl titanate to yield piperidinyl compounds. The amino group on 4-aminobenzoic acid attacks the five-membered ring of maleic anhydride, causing ring-opening, yielding an intermediate containing carboxyl and amide structures. This intermediate is then subjected to intramolecular dehydration and ring-closure under heating to yield N-(4-carboxyphenyl)maleimide. The carbon-carbon double bonds on the hindered phenolic compounds, piperidinyl compounds, and N-(4-carboxyphenyl)maleimide undergo free radical polymerization under the action of an initiator to generate carboxyl-containing polymers. After the carboxyl groups on the carboxyl-containing polymer are reactivated, they undergo an esterification reaction with the hydroxyl groups at the ends of the poly(ethylene glycol) methacrylate chain to obtain a primary polymer. Under the action of photoinitiation, the carbon-carbon double bonds on the primary polymer and the mercapto groups on 3-mercapto-1-propanol react to introduce hydroxyl groups into the molecular chain, thus obtaining a modified polymer.

[0016] Modified filler: Trisodium phosphate decomposes into sodium hydrogen phosphate and sodium hydroxide in aqueous solution. At 20-25℃, the solubility product of calcium sulfate is greater than that of calcium hydrogen phosphate. Therefore, after adding calcium sulfate whiskers, the sulfate ions on their surface will be replaced by hydrogen phosphate ions, forming a calcium hydrogen phosphate film on the surface. At the same time, hydroxyl groups combine with calcium ions on the surface to form calcium hydroxide. Carbon black is oxidized by concentrated nitric acid, introducing a large number of carboxyl functional groups to obtain carboxylated carbon black. Carboxylated carbon black bonds with hydroxyl groups in calcium hydroxide to form a calcium acetate structure, thus obtaining a pretreated filler. The Ca-OH on the hydrated layer and fracture surface of the pretreated filler can bond with the Si-OH on γ-aminopropyltriethoxysilane to form a modified filler.

[0017] The modified polymer molecular chain contains hindered phenolic structures. Due to steric hindrance, hydrogen atoms are released, forming stable phenoxy radicals. These released hydrogen atoms can capture free radicals generated under thermo-oxidative conditions, blocking free radical chain reactions and thus improving the polymer's resistance to thermo-oxidative aging. Bridging the rigid structure containing benzene rings enhances the steric hindrance effect, imparting a rigid structure to the material and improving the thermal stability of the matrix material. The molecular chain contains hindered amine structures, which can capture free radicals, destroy hydrogen peroxides, and quench high-energy excited molecules within the polymer, preventing photo-aging. Grafting poly(ethylene glycol) methacrylate segments onto the modified polymer molecular chain forms an elastomer. Its flexible long-chain structure can undergo significant deformation upon impact, absorbing and dissipating a large amount of energy. Through mechanisms such as inducing crazes and terminating crack propagation, it significantly improves the material's fracture toughness and impact strength. Calcium sulfate whiskers coat carbon black, forming a core-shell structure that works synergistically. Carbon black, as the core, can induce crazes and plastic deformation, absorbing energy, while calcium sulfate whiskers, as the shell, can bridge cracks, bear loads, and further dissipate energy through pull-out and deflection mechanisms, thereby improving the mechanical properties of the material. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: A method for preparing a recycled plastic sealant film, specifically including the following steps: Step S1: After sorting and cleaning the recycled polyethylene terephthalate bottle flakes, dry them in a forced-air drying process at 120°C for 12 hours to obtain pretreated polyethylene terephthalate. Step S2: Mix pretreated polyethylene terephthalate, isophorone diisocyanate, modified polymer and modified filler evenly, melt extrude at 250°C, blow mold into film, and obtain recycled plastic sealing film material.

[0020] The weight ratio of the pretreated polyethylene terephthalate, isophorone diisocyanate, modified polymer and modified filler in step S2 is 80:40:20:5.

[0021] The modified polymer is prepared by the following steps: Step A1: Allyl alcohol and dichloromethane were mixed evenly, and under nitrogen gas conditions at 60 r / min, 0 °C, and with stirring, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and triethylamine were added. The mixture was heated to 40 °C and reacted for 20 h to obtain the hindered phenolic compound. 1,2,2,6,6-pentamethylpiperidinol, ethyl acrylate and xylene were mixed evenly, and under 80 r / min, 100 °C, and with stirring, tetraisopropyl titanate was added. The mixture was heated to 130 °C and reacted for 8 h to obtain the piperidinyl compound. Step A2: 4-Aminobenzoic acid, tetrahydrofuran, and maleic anhydride are mixed evenly and reacted at 60 r / min and 20 °C for 4 h to obtain an intermediate. The intermediate, sodium acetate, and toluene are mixed evenly and reacted at 80 r / min and 90 °C for 6 h to obtain N-(4-carboxyphenyl)maleimide. The hindered phenolic compound, cyclohexanone, piperidinyl compound, and N-(4-carboxyphenyl)maleimide are mixed evenly and stirred at 120 r / min and 80 °C with nitrogen gas introduced, and azobisisobutyronitrile is added and reacted for 4 h to obtain a carboxyl-containing copolymer. Step A3: Disperse the carboxyl-containing copolymer in tetrahydrofuran. Stir and add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-carboxysuccinimide at 80 r / min and 0°C. Stir for 30 min, heat to 20°C, add poly(ethylene glycol) methacrylate, and react for 12 h to obtain the primary polymer. Mix the primary polymer, 3-mercapto-1-propanol, benzoin dimethyl ether and tetrahydrofuran evenly, and react for 20 s at 110 r / min, 20°C and ultraviolet irradiation to obtain the modified polymer.

[0022] In step A1, the ratio of allyl alcohol, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, and triethylamine is 1 mmol:1.3 mmol:25 mL, the molar ratio of 1,2,2,6,6-pentamethylpiperidinol and ethyl acrylate is 1.8:1, and the amount of tetraisopropyl titanate is 0.3% of the mass of 1,2,2,6,6-pentamethylpiperidinol.

[0023] In step A2, the molar ratio of 4-aminobenzoic acid to maleic anhydride is 1:1.1, the ratio of intermediate, sodium acetate, and toluene is 23.5 g:0.5 g:120 mL, the molar ratio of hindered phenolic compound, piperidinyl compound, and N-(4-carboxyphenyl)maleimide is 1:1:1, the amount of hindered phenolic compound is 1 mmol, and the amount of azobisisobutyronitrile is 3% of the mass of hindered phenolic compound.

[0024] The ratio of carboxyl-containing copolymer, tetrahydrofuran, poly(ethylene glycol) methacrylate, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and N-carboxysuccinimide in step A3 is 1.2 g: 50 mL: 2.3 mmol: 2.3 mmol: 3.5 g. The average molecular weight of poly(ethylene glycol) methacrylate is 1500 g / mol. The molar ratio of carbon-carbon double bonds on the primary polymer to mercapto groups on 3-mercapto-1-propanol is 1.2:0.2. The amount of benzoin dimethyl ether is 2% of the mass of the primary polymer.

[0025] The modified filler is prepared by the following steps: Step B1: Disperse trisodium phosphate in deionized water, add calcium sulfate whiskers at a temperature of 20℃ and a frequency of 30kHz, and sonicate for 2 minutes to obtain pretreated calcium sulfate whiskers. Step B2: Mix carbon black and nitric acid evenly, and react for 2 hours at a speed of 150 r / min and a temperature of 60℃. After cooling to room temperature, filter to remove the filtrate to obtain carboxylated carbon black. Disperse the carboxylated carbon black in deionized water, and stir and add pretreated calcium sulfate whiskers at a speed of 100 r / min, a temperature of 60℃ and a pH of 9. React for 5 hours to obtain pretreated filler. Step B3: The pretreated filler was dispersed in tetrahydrofuran, stirred and 3-aminopropyltrimethoxysilane was added under the conditions of 200 r / min, 60℃, and pH 4-5, and the reaction was carried out for 8 h to obtain the modified filler.

[0026] The ratio of trisodium phosphate, deionized water, and calcium sulfate whiskers used in step B1 is 0.2 mmol: 10 mL: 0.3 g.

[0027] In step B2, the ratio of carbon black to nitric acid is 1g:100mL, the mass fraction of nitric acid is 65%, and the ratio of carboxylated carbon black to pretreated calcium sulfate whiskers is 1g:5g.

[0028] The amount of 3-aminopropyltrimethoxysilane used in step B3 is 3% of the mass of the pretreated filler.

[0029] Example 2, a method for preparing a recycled plastic sealant film, specifically includes the following steps: Step S1: After sorting and cleaning the recycled polyethylene terephthalate bottle flakes, dry them in a forced-air drying process at 120°C for 12 hours to obtain pretreated polyethylene terephthalate. Step S2: Mix pretreated polyethylene terephthalate, isophorone diisocyanate, modified polymer and modified filler evenly, melt extrude at 260°C, blow mold into film, and obtain recycled plastic sealing film material.

[0030] The weight ratio of the pretreated polyethylene terephthalate, isophorone diisocyanate, modified polymer and modified filler in step S2 is 90:45:25:6.

[0031] The modified polymer is prepared by the following steps: Step A1: Allyl alcohol and dichloromethane were mixed evenly, and under nitrogen gas conditions at 70 r / min, 2 °C, and stirring, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and triethylamine were added. The mixture was heated to 45 °C and reacted for 22 h to obtain the hindered phenol compound. 1,2,2,6,6-pentamethylpiperidinol, ethyl acrylate and xylene were mixed evenly, and under 90 r / min, 100 °C, tetraisopropyl titanate was added. The mixture was heated to 135 °C and reacted for 9 h to obtain the piperidinyl compound. Step A2: 4-Aminobenzoic acid, tetrahydrofuran, and maleic anhydride are mixed evenly and reacted at 70 r / min and 25°C for 5 h to obtain an intermediate. The intermediate, sodium acetate, and toluene are mixed evenly and reacted at 90 r / min and 95°C for 7 h to obtain N-(4-carboxyphenyl)maleimide. The hindered phenolic compound, cyclohexanone, piperidinyl compound, and N-(4-carboxyphenyl)maleimide are mixed evenly and stirred at 130 r / min and 90°C with nitrogen gas introduced, and azobisisobutyronitrile is added and reacted for 5 h to obtain a carboxyl-containing copolymer. Step A3: Disperse the carboxyl-containing copolymer in tetrahydrofuran. Stir and add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-carboxysuccinimide at 90 r / min and 2°C. Stir for 40 min, heat to 25°C, add poly(ethylene glycol) methacrylate, and react for 16 h to obtain the primary polymer. Mix the primary polymer, 3-mercapto-1-propanol, benzoin dimethyl ether and tetrahydrofuran evenly, and react for 25 s at 120 r / min, 22°C, and under ultraviolet irradiation to obtain the modified polymer.

[0032] In step A1, the ratio of allyl alcohol, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, and triethylamine is 1 mmol:1.3 mmol:25 mL; the molar ratio of 1,2,2,6,6-pentamethylpiperidinol and ethyl acrylate is 1.8:1; and the amount of tetraisopropyl titanate is 0.3% of the mass of 1,2,2,6,6-pentamethylpiperidinol.

[0033] In step A2, the molar ratio of 4-aminobenzoic acid to maleic anhydride is 1:1.1, the ratio of intermediate, sodium acetate, and toluene is 23.5 g:0.5 g:120 mL, the molar ratio of hindered phenolic compound, piperidinyl compound, and N-(4-carboxyphenyl)maleimide is 1:1:1, the amount of hindered phenolic compound is 2 mmol, and the amount of azobisisobutyronitrile is 4% of the mass of hindered phenolic compound.

[0034] The ratio of carboxyl-containing copolymer, tetrahydrofuran, poly(ethylene glycol) methacrylate, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and N-carboxysuccinimide in step A3 is 1.2 g: 50 mL: 2.3 mmol: 2.3 mmol: 3.5 g. The average molecular weight of poly(ethylene glycol) methacrylate is 1500 g / mol. The molar ratio of carbon-carbon double bonds on the primary polymer to mercapto groups on 3-mercapto-1-propanol is 1.2:0.2. The amount of benzoin dimethyl ether is 3% of the mass of the primary polymer.

[0035] The modified filler is prepared by the following steps: Step B1: Disperse trisodium phosphate in deionized water, add calcium sulfate whiskers at a temperature of 22℃ and a frequency of 35kHz, and sonicate for 3 minutes to obtain pretreated calcium sulfate whiskers. Step B2: Mix carbon black and nitric acid evenly, and react for 3 hours at a speed of 170 r / min and a temperature of 65℃. After cooling to room temperature, filter to remove the filtrate to obtain carboxylated carbon black. Disperse the carboxylated carbon black in deionized water, and stir and add pretreated calcium sulfate whiskers at a speed of 110 r / min, a temperature of 70℃ and a pH of 9. React for 6 hours to obtain pretreated filler. Step B3: The pretreated filler was dispersed in tetrahydrofuran, stirred and 3-aminopropyltrimethoxysilane was added under the conditions of 200 r / min, 70℃ and pH 4, and the reaction was carried out for 9 h to obtain the modified filler.

[0036] The ratio of trisodium phosphate, deionized water, and calcium sulfate whiskers used in step B1 is 0.2 mmol: 10 mL: 0.3 g.

[0037] In step B2, the ratio of carbon black to nitric acid is 1g:100mL, the mass fraction of nitric acid is 65%, and the ratio of carboxylated carbon black to pretreated calcium sulfate whiskers is 1g:5g.

[0038] The amount of 3-aminopropyltrimethoxysilane used in step B3 is 4% of the mass of the pretreated filler.

[0039] Example 3, a method for preparing a recycled plastic sealant film, specifically includes the following steps: Step S1: After sorting and cleaning the recycled polyethylene terephthalate bottle flakes, dry them in a forced-air drying process at 120°C for 12 hours to obtain pretreated polyethylene terephthalate. Step S2: Mix pretreated polyethylene terephthalate, isophorone diisocyanate, modified polymer and modified filler evenly, melt extrude at 265°C, blow mold into film, and obtain recycled plastic sealing film material.

[0040] The weight ratio of the pretreated polyethylene terephthalate, isophorone diisocyanate, modified polymer and modified filler in step S2 is 100:50:30:8.

[0041] The modified polymer is prepared by the following steps: Step A1: Allyl alcohol and dichloromethane were mixed evenly, and under nitrogen gas conditions at 80 r / min, 5°C, and with stirring, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and triethylamine were added. The mixture was heated to 50°C and reacted for 24 h to obtain the hindered phenolic compound. 1,2,2,6,6-pentamethylpiperidinol, ethyl acrylate and xylene were mixed evenly, and under nitrogen gas conditions at 100 r / min, 110°C, and with stirring, tetraisopropyl titanate was added. The mixture was heated to 140°C and reacted for 10 h to obtain the piperidinyl compound. Step A2: 4-Aminobenzoic acid, tetrahydrofuran, and maleic anhydride are mixed evenly and reacted at 80 r / min and 30°C for 6 h to obtain an intermediate. The intermediate, sodium acetate, and toluene are mixed evenly and reacted at 100 r / min and 100°C for 8 h to obtain N-(4-carboxyphenyl)maleimide. The hindered phenolic compound, cyclohexanone, piperidinyl compound, and N-(4-carboxyphenyl)maleimide are mixed evenly and stirred at 150 r / min and 100°C with nitrogen gas introduced, and azobisisobutyronitrile is added and reacted for 6 h to obtain a carboxyl-containing copolymer. Step A3: Disperse the carboxyl-containing copolymer in tetrahydrofuran. Stir and add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-carboxysuccinimide at 100 r / min and 4 °C. Stir for 60 min, heat to 30 °C, add poly(ethylene glycol) methacrylate, and react for 24 h to obtain the primary polymer. Mix the primary polymer, 3-mercapto-1-propanol, benzoin dimethyl ether and tetrahydrofuran evenly, and react for 30 s at 130 r / min, 25 °C, and under ultraviolet irradiation to obtain the modified polymer.

[0042] In step A1, the ratio of allyl alcohol, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, and triethylamine is 1 mmol:1.3 mmol:25 mL, the molar ratio of 1,2,2,6,6-pentamethylpiperidinol and ethyl acrylate is 1.8:1, and the amount of tetraisopropyl titanate is 0.4% of the mass of 1,2,2,6,6-pentamethylpiperidinol.

[0043] In step A2, the molar ratio of 4-aminobenzoic acid to maleic anhydride is 1:1.1, the ratio of intermediate, sodium acetate, and toluene is 23.5 g:0.5 g:120 mL, the molar ratio of hindered phenolic compound, piperidinyl compound, and N-(4-carboxyphenyl)maleimide is 1:1:1, the amount of hindered phenolic compound is 3 mmol, and the amount of azobisisobutyronitrile is 7% of the mass of hindered phenolic compound.

[0044] The ratio of carboxyl-containing copolymer, tetrahydrofuran, poly(ethylene glycol) methacrylate, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and N-carboxysuccinimide in step A3 is 1.2 g: 50 mL: 2.3 mmol: 2.3 mmol: 3.5 g. The average molecular weight of poly(ethylene glycol) methacrylate is 1500 g / mol. The molar ratio of carbon-carbon double bonds on the primary polymer to mercapto groups on 3-mercapto-1-propanol is 1.2:0.2. The amount of benzoin dimethyl ether used is 5% of the mass of the primary polymer.

[0045] The modified filler is prepared by the following steps: Step B1: Disperse trisodium phosphate in deionized water, add calcium sulfate whiskers at a temperature of 25℃ and a frequency of 40kHz, and sonicate for 5 minutes to obtain pretreated calcium sulfate whiskers. Step B2: Mix carbon black and nitric acid evenly, and react for 4 hours at a speed of 200 r / min and a temperature of 70℃. After cooling to room temperature, filter to remove the filtrate to obtain carboxylated carbon black. Disperse the carboxylated carbon black in deionized water, and stir and add pretreated calcium sulfate whiskers at a speed of 120 r / min, a temperature of 80℃ and a pH of 10. React for 8 hours to obtain pretreated filler. Step B3: The pretreated filler was dispersed in tetrahydrofuran, stirred and 3-aminopropyltrimethoxysilane was added under the conditions of 300 r / min, 80℃ and pH 5, and the reaction was carried out for 10 h to obtain the modified filler.

[0046] The ratio of trisodium phosphate, deionized water, and calcium sulfate whiskers used in step B1 is 0.2 mmol: 10 mL: 0.3 g.

[0047] In step B2, the ratio of carbon black to nitric acid is 1g:100mL, the mass fraction of nitric acid is 65%, and the ratio of carboxylated carbon black to pretreated calcium sulfate whiskers is 1g:5g.

[0048] The amount of 3-aminopropyltrimethoxysilane used in step B3 is 5% of the mass of the pretreatment filler.

[0049] Comparative Example 1: This comparative example uses carboxylated carbon black instead of pretreatment filler, while the other steps are the same as in Example 1.

[0050] Comparative Example 2: Compared with Example 1, no hindered phenolic compound was added in step A2 of this comparative example, but the remaining steps were the same.

[0051] Comparative Example 3: This comparative example is identical to Example 1 except that no piperidinyl compound was added in step A2.

[0052] The recycled plastic sealant materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested for aging effects under sunlight according to GB / T 16422.2-2014 standard. The test results are shown in Table 1. The sample exposure conditions were cycle 1, the spray cycle was method A, and the test duration was 500 hours. During the test, an opaque covering was used to cover part of the sample to compare the exposed and unexposed surfaces. The surface morphology of the samples before and after aging was observed using a 5x magnifying glass.

[0053] The recycled plastic sealant materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested for tensile modulus according to GB / T1040.2-2022. The test results are shown in Table 1. The dumbbell-shaped specimens were cut with a cutter size of IA, and the standard thickness of the narrow part of the specimen was 4 mm.

[0054] The recycled plastic sealant materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested for cantilever beam impact strength according to the standard GB / T1843-2008. The test results are shown in Table 1. The samples must be unnotch-free and have dimensions of 80 mm in length, 10 mm in width, and 4 mm in thickness.

[0055] Table 1 As shown in Table 1, after 500 hours of xenon arc lamp aging test, the recycled plastic sealant films prepared in Examples 1-3 showed no powdering, cracking, or blistering on their surface morphology. The tensile modulus was in the range of 1344-1403 MPa, and the cantilever beam impact strength was in the range of 35.3-36.1 KJ / m2. This indicates that the present invention has excellent high mechanical properties and anti-aging properties.

[0056] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a recycled plastic sealant film, characterized in that: Specifically, the steps include the following: Step S1: After sorting and cleaning the recycled polyethylene terephthalate bottle flakes, dry them with a forced air to obtain pretreated polyethylene terephthalate. Step S2: Mix pretreated polyethylene terephthalate, isophorone diisocyanate, modified polymer and modified filler evenly, melt extrude, blow mold into film, and obtain recycled plastic sealing film material; The weight ratio of the pretreated polyethylene terephthalate, isophorone diisocyanate, modified polymer and modified filler in step S2 is 80-100:40-50:20-30:5-8.

2. The method for preparing a recycled plastic sealant film according to claim 1, characterized in that: The modified polymer is prepared by the following steps: Step A1: Allyl alcohol and dichloromethane were mixed and stirred, and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and triethylamine were added. The mixture was heated and reacted to obtain a hindered phenolic compound. 1,2,2,6,6-pentamethylpiperidinol, ethyl acrylate and xylene were mixed and stirred, and tetraisopropyl titanate was added. The mixture was heated and reacted to obtain a piperidinyl compound. Step A2: Mix 4-aminobenzoic acid, tetrahydrofuran and maleic anhydride evenly and react to obtain an intermediate. Mix the intermediate, sodium acetate and toluene evenly and react to obtain N-(4-carboxyphenyl)maleimide. Mix the hindered phenolic compound, cyclohexanone, piperidinyl compound and N-(4-carboxyphenyl)maleimide evenly, stir and add azobisisobutyronitrile, and react to obtain a carboxyl-containing copolymer. Step A3: Disperse the carboxyl-containing copolymer in tetrahydrofuran, stir and add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-carboxysuccinimide, stir, heat, add poly(ethylene glycol) methacrylate, and react to obtain the primary polymer. Mix the primary polymer, 3-mercapto-1-propanol, benzoin dimethyl ether and tetrahydrofuran evenly and react to obtain the modified polymer.

3. The method for preparing a recycled plastic sealant film according to claim 2, characterized in that: In step A1, the ratio of allyl alcohol, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, and triethylamine is 1 mmol:1.3 mmol:25 mL; the molar ratio of 1,2,2,6,6-pentamethylpiperidinol and ethyl acrylate is 1.8:1; and the amount of tetraisopropyl titanate is 0.3%-0.4% of the mass of 1,2,2,6,6-pentamethylpiperidinol.

4. The method for preparing a recycled plastic sealant film according to claim 2, characterized in that: In step A2, the molar ratio of 4-aminobenzoic acid to maleic anhydride is 1:1.1, the ratio of intermediate, sodium acetate, and toluene is 23.5g:0.5g:120mL, the molar ratio of hindered phenolic compound, piperidinyl compound, and N-(4-carboxyphenyl)maleimide is 1:1:1, and the amount of azobisisobutyronitrile is 3-7% of the mass of the hindered phenolic compound.

5. The method for preparing a recycled plastic sealant film according to claim 2, characterized in that: In step A3, the ratio of the carboxyl-containing copolymer, tetrahydrofuran, poly(ethylene glycol) methacrylate, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and N-carboxysuccinimide is 1.2 g: 50 mL: 2.3 mmol: 2.3 mmol: 3.5 g. The molar ratio of the carbon-carbon double bond on the primary polymer to the mercapto group on 3-mercapto-1-propanol is 1.2: 0.

2. The amount of benzoin dimethyl ether used is 2-5% of the mass of the primary polymer.

6. The method for preparing a recycled plastic sealant film according to claim 1, characterized in that: The modified filler is prepared by the following steps: Step B1: Disperse trisodium phosphate in deionized water, add calcium sulfate whiskers, and sonicate to obtain pretreated calcium sulfate whiskers; Step B2: Mix carbon black and nitric acid evenly, react, cool to room temperature, filter to remove filtrate, and obtain carboxylated carbon black. Disperse carboxylated carbon black in deionized water, stir and add pretreated calcium sulfate whiskers, react to obtain pretreated filler. Step B3: The pretreated filler is dispersed in tetrahydrofuran, stirred and 3-aminopropyltrimethoxysilane is added to carry out the reaction to obtain the modified filler.

7. The method for preparing a recycled plastic sealant film according to claim 6, characterized in that: The ratio of trisodium phosphate, deionized water, and calcium sulfate whiskers used in step B1 is 0.2 mmol: 10 mL: 0.3 g.

8. The method for preparing a recycled plastic sealant film according to claim 6, characterized in that: In step B2, the ratio of carbon black to nitric acid is 1g:100mL, the mass fraction of nitric acid is 65%, and the ratio of carboxylated carbon black to pretreated calcium sulfate whiskers is 1g:5g.

9. The method for preparing a recycled plastic sealant film according to claim 6, characterized in that: The amount of 3-aminopropyltrimethoxysilane used in step B3 is 3-5% of the mass of the pretreatment filler.

10. A recycled plastic sealant film, characterized in that: Prepared according to any one of the preparation methods described in claims 1-9.

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