Recyclable modified base membrane and preparation method thereof

Abstract

The invention discloses a recyclable modified base membrane and a preparation method thereof, and relates to the technical field of recycling of base membranes. The method comprises the following steps: drying a recycled base membrane, removing moisture, introducing a reversible covalent bond, introducing a disulfide bond through dithiodiethanol, and breaking and recombining under the action conditions of heat and mechanical force; in addition, amino is introduced through triethylene tetramine, a three-dimensional dynamic network with imine bonds as crosslinking points is formed through a hydrothermal reaction, and remodeling and repairing are achieved; by adding the nanocellulose, the elasticity modulus of the modified base membrane is increased, so that the toughness and tensile strength of the remodeled base membrane are improved; the grafting rate and the uniformity are improved by introducing a functional group on the nano cellulose.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of recycling of base film, and particularly relates to a recyclable modified base film and a preparation method thereof. BACKGROUND

[0002] As a necessary substrate of the composite current collector, the polymer substrate has good flame retardance and insulation, can effectively block the current and prevent the spread of thermal runaway, and avoids the short circuit problem caused by metal burrs of the traditional current collector. With the popularization and use of the composite current collector, the positive and negative materials can be recycled after the battery is scrapped, but the polymer film in the composite current collector can only be separated by chemical method and does not have recyclability. The cost of the polymer substrate is high, and the polymer substrate is a consumable product.

[0003] In the prior art, the cost can be reduced by recycling the scrapped base film, but the mechanical properties of the recycled base film are reduced after being melted for many times, and cracks, pores and cracks are generated in the process of tensile reshaping. Even after the film is formed, the use of the recycled base film to prepare the composite current collector will also cause the decrease of the tensile strength and elongation. The main reasons may be as follows: the molecular weight decreases due to the molecular chain rupture, so that the material strength decreases; the crystal structure and molecular orientation are damaged in the reshaping process, so that stress concentration points are caused and cracks are easily generated, so that the impact strength and toughness decrease; and the additives are damaged, so that the performance is affected. Therefore, the present application provides a recyclable modified base film and a preparation method thereof to solve the above technical problems. SUMMARY

[0004] The present application aims to provide a recyclable modified base film and a preparation method thereof to solve the problems in the prior art.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: A recyclable modified base film comprises the following mass components: 80-100 parts of recycled base film, 20-25 parts of glass fiber, 10-20 parts of polyolefin, 5-10 parts of bromine flame retardant, and 3-20 parts of additive.

[0006] Further, the recycled base film is any one or a mixture of multiple of PET (polyethylene terephthalate), PP (polypropylene) and PEI (polyethylene imine).

[0007] Further, the polyolefin material is any one or a combination of multiple of polyethylene, polypropylene, polystyrene, ethylene-propylene copolymer, ethylene-propylene-butene copolymer and cyclic olefin copolymer.

[0008] Further, the additive is a mixture of any one or multiple of dithiodiethanol, functionalized nanocellulose and triethylenetetramine.

[0009] Furthermore, the functionalized nanocellulose is any one of carboxylated nanocellulose, aminolated nanocellulose, and thiolated nanocellulose.

[0010] A method for preparing a recyclable modified base film includes the following steps: drying the recycled base film, then hot-melting it at high temperature, cooling it down, then adding glass fiber, polyolefin, brominated flame retardant, and additives and stirring for 1-2 hours, then extruding it through a mold, and then performing stretching treatment, heat setting, air cooling, slitting, thickness measurement, corona treatment, and finally winding it up to obtain the modified base film.

[0011] Furthermore, the temperature of the high-temperature hot melt is 270~290℃.

[0012] Furthermore, the process conditions for the stretching treatment are as follows: the longitudinal stretching preheating roller is set at a temperature of 50~70℃, the slow stretching roller at a temperature of 70~90℃, the fast stretching roller at a temperature of 20~40℃, the cooling roller at a temperature of 30℃ or 50℃, the longitudinal stretching ratio is set to 2.5~3.5 times, the transverse stretching preheating roller is set at a temperature of 80~90℃, the slow stretching roller at a temperature of 90~110℃, and the transverse stretching ratio is set to 3~4 times.

[0013] Furthermore, the heat setting process conditions are as follows: heat setting temperature is 180~200℃, time is 4~6s, and air cooling is performed to 40~60℃.

[0014] In the above technical solution, the recovered base membrane is first dried to remove moisture. Then, by introducing reversible covalent bonds, such as disulfide bonds (-SS-), dithiodiethanol is added to the recovered base membrane. Through an alcoholysis reaction, it combines with the C=C bonds in the base membrane, and under the action of heat and mechanical force, it breaks and reassembles. In addition, reversible covalent bonds and amine groups are introduced to form a three-dimensional dynamic network with imine bonds as crosslinking points through a hydrothermal reaction, thereby achieving remodeling and repair. By adding nanocellulose, the elastic modulus of the modified base membrane is increased, thereby improving the toughness and tensile strength of the remodeled base membrane.

[0015] Furthermore, the carboxylated nanocellulose is prepared by the following process: nanocellulose and carboxylating reagent are added to deionized water and mixed, the pH is adjusted to 9.5~10.5, and the mixture is reacted at a temperature of 50~70℃ for 3~5 hours. After filtration and drying, carboxylated nanocellulose is obtained.

[0016] Furthermore, the carboxylating agent is prepared by compounding TEMPO (2,2,6,6-tetramethylpiperidineoxy), NaBr (sodium bromide), and NaClO (sodium hypochlorite), with the mass ratio of TEMPO, NaBr, and NaClO being 1:(0.01~0.05):(0.1~0.5):(1~5).

[0017] Furthermore, the mass ratio of nanocellulose, carboxylating agent, and ethanol solution is 1:(3~8):(20~25).

[0018] Furthermore, the aminated nanocellulose is prepared by the following process: nanocellulose and 3-aminopropyltriethoxysilane are added to an ethanol solution, stirred evenly, the pH is adjusted to 4-5 with acetic acid, and the reaction is carried out at a temperature of 50-70°C for 3-5 hours. After filtration and drying, aminated nanocellulose is obtained.

[0019] Furthermore, the mass ratio of nanocellulose, 3-aminopropyltriethoxysilane, and ethanol solution is 1:(5~10):(20~25).

[0020] Furthermore, the thiolated nanocellulose is prepared by the following process: nanocellulose and (3-mercaptopropyl)trimethoxysilane are added to an ethanol solution, stirred evenly, the pH is adjusted to 4-5 with acetic acid, and the reaction is carried out at a temperature of 70-80°C for 2-3 hours. After filtration and drying, thiolated nanocellulose is obtained.

[0021] Furthermore, the mass ratio of nanocellulose, (3-mercaptopropyl)trimethoxysilane, and ethanol solution is 1:(5~10):(20~25).

[0022] Furthermore, the ethanol solution is prepared from anhydrous ethanol and deionized water, with a volume ratio of anhydrous ethanol to deionized water of 95:5.

[0023] In the above technical solutions, the abundant hydroxyl groups on the surface of nanocellulose are the main reaction sites, but their reactivity is usually lower than that of amine and carboxyl groups. When disulfide bond molecules (such as carboxylic acids and amines containing disulfide bonds) are grafted onto cellulose, the reaction may be incomplete and uneven. Therefore, this invention improves the grafting rate and uniformity of disulfide bonds by introducing functional groups onto nanocellulose.

[0024] In addition, the added active groups will also exist on the surface of the repaired film. When the alumina underlayer is vapor-deposited, it can combine with the active groups to form chemical bonds, thereby improving the adhesion between the underlayer and the base film. Lithium hexafluorophosphate in the electrolyte will form HF with water to corrode the alumina. After forming chemical bonds, it is difficult to corrode, thereby improving the chemical corrosion resistance of the modified base film.

[0025] Furthermore, 3 to 5 parts of modifier are added to the modified base film.

[0026] Furthermore, the modifier is prepared by the following process: S1: Add styrene-maleic anhydride copolymer to tetrahydrofuran, stir, then add 4-aminophenylboronic acid and catalyst, purge with nitrogen, stir and react at 80~90℃ for 4~8h, rotary evaporate, filter, dry to obtain modified intermediate; S2: Add the modified intermediate to tetrahydrofuran, stir, then add 3-mercapto-1,2-propanediol and magnesium sulfate, under nitrogen protection, and stir for 20-24 hours at 70-80°C to obtain the modifier.

[0027] Furthermore, the catalyst is pyridine.

[0028] In the above technical solution, by adding styrene-maleic anhydride copolymer, a benzene ring is introduced to increase the strength and stability of the recycled base membrane. Simultaneously, the anhydride in the styrene-maleic anhydride copolymer can serve as a grafting active site, introducing 4-aminophenylboronic acid to obtain a modified intermediate. The amino group reacts with the anhydride ring to form an imide bond, which is then grafted onto the side chain of the copolymer via a boron-oxygen (BO) bond. The borate group further reacts with the hydroxyl group in 3-mercapto-1,2-propanediol to form a borate ester bond, thus obtaining the final modifier containing mercapto and boron-oxygen side chains. Magnesium sulfate, as a dehydrating agent, introduces boron... Oxide and mercapto groups can improve the remodeling and repair performance of recycled base membranes. The broken boron-oxygen bonds undergo esterification condensation to form new BOC bonds. Mercapto groups and boron oxide groups have a synergistic effect. Utilizing the mutual reaction between mercapto groups, reversible disulfide bonds are generated, achieving performance recovery. While ensuring good mechanical properties of the base membrane, the number of recycling cycles is increased, and costs are reduced. By adding bromine-based flame retardants and functionalized nanocellulose, crosslinking with the active groups of the copolymer side chains occurs during blending, producing a synergistic reinforcing effect with the copolymer and improving the mechanical properties and strength of the recycled base membrane.

[0029] Furthermore, the mass ratio of styrene-maleic anhydride copolymer, tetrahydrofuran, 4-aminophenylboronic acid, and catalyst is 1:(20~25):(0.5~0.8):(0.1~0.5).

[0030] Furthermore, the mass ratio of the modified intermediate, tetrahydrofuran, 3-mercapto-1,2-propanediol, and magnesium sulfate is 1:(20~25):(0.5~0.8):(3~5).

[0031] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention achieves remodeling and repair by introducing reversible covalent bonds into the base film raw material under the action of heat and mechanical force; by adding nanocellulose, the elastic modulus of the modified base film is increased, thereby improving the toughness and tensile strength of the remodeled base film.

[0032] 2. This invention improves the grafting rate and uniformity of reversible covalent bonds by introducing functionalized groups onto nanocellulose. In addition, the added active groups also exist on the surface of the repaired film. When the alumina underlayer is vapor-deposited, these active groups can combine with the active groups to form chemical bonds, thereby improving the adhesion between the underlayer and the base film. Lithium hexafluorophosphate in the electrolyte will form HF with water to corrode the alumina. After forming chemical bonds, it is difficult to corrode, thus improving the chemical corrosion resistance of the modified base film to electrolyte.

[0033] 3. The modifier of this invention improves the remodeling and repair performance of the recycled base membrane by introducing boronoxy groups and thiol groups. The broken boron-oxygen bonds undergo esterification condensation again to form new BOC bonds. The thiol groups and boronoxy groups have a synergistic effect. Utilizing the mutual reaction between thiol groups, reversible disulfide bonds are generated to restore performance. While ensuring good mechanical properties of the base membrane, the number of recycling times is increased and costs are reduced. By adding bromine-based flame retardants and functionalized nanocellulose, crosslinking with the active groups of the copolymer side chains occurs during blending, producing a synergistic reinforcing effect with the copolymer and improving the mechanical properties and strength of the recycled base membrane. Detailed Implementation

[0034] 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.

[0035] In the following specific embodiments, unless otherwise specified, the number of “parts” refers to parts by mass; The recycled base film is a mixture of polyethylene terephthalate, polyimide, and polybutylene terephthalate, with a mass ratio of 1:0.5:1. Brominated flame retardant, Deca-BDE, CAS: 1163-19-5; polyolefin, polypropylene, molecular weight 10000Da; nanocellulose, model PH-102; PET, grade BS-W; glass fiber, average length 100nm, average diameter 10nm. Styrene-maleic anhydride copolymer, model SMA1000P; the ethanol solution is prepared from anhydrous ethanol and deionized water in a volume ratio of 95:5. Example 1:

[0036] A recyclable modified base membrane comprises the following components by weight: 100 parts recycled base membrane, 20 parts glass fiber, 10 parts polyolefin, 5 parts brominated flame retardant, and 3 parts dithiodiethanol. A method for preparing a recyclable modified base film includes the following steps: drying the recycled base film, then hot-melting it at 280°C, cooling it to 150°C, then adding glass fiber, polyolefin, brominated flame retardant, and dithiodiethanol and stirring for 1 hour, extruding it through a die, and then stretching it. The longitudinal stretching preheating roller is set to a temperature of 60°C, the slow stretching roller to a temperature of 80°C, the fast stretching roller to a temperature of 30°C, and the cooling roller to a temperature of 30°C, with a longitudinal stretching ratio of 3 times. The transverse stretching preheating roller is set to a temperature of 85°C, the slow stretching roller to a temperature of 100°C, and the transverse stretching ratio is set to 3.5 times. The heat setting temperature is 190°C for 5 seconds, and after setting, it is air-cooled to 50°C. After slitting, thickness measurement, corona treatment, and winding, the modified base film is obtained. Example 2:

[0037] This embodiment provides a method for preparing a recyclable modified base membrane, wherein the amount of dithiodiethanol added is 5% of the mass of the recycled base membrane; the remaining component ratios and preparation process are the same as in Example 1. Example 3:

[0038] This embodiment provides a method for preparing a recyclable modified base membrane, wherein the amount of dithiodiethanol added is 7% of the mass of the recycled base membrane; the remaining component ratios and preparation process are the same as in Example 1. Example 4:

[0039] This embodiment provides a method for preparing a recyclable modified base membrane, in which dithiodiethanol is replaced with triethylenetetramine, and the amount of triethylenetetramine added is 3% of the mass of the recycled base membrane; the remaining component ratios and preparation process are the same as in Example 1. Example 5:

[0040] This embodiment provides a method for preparing a recyclable modified base membrane, in which dithiodiethanol is replaced with triethylenetetramine, and the amount of triethylenetetramine added is 5% of the mass of the recycled base membrane; the remaining component ratios and preparation process are the same as in Example 1. Example 6:

[0041] This embodiment provides a method for preparing a recyclable modified base membrane, in which dithiodiethanol is replaced with triethylenetetramine, and the amount of triethylenetetramine added is 7% of the mass of the recycled base membrane; the remaining component ratios and preparation process are the same as in Example 1. Example 7:

[0042] A recyclable modified base membrane comprises the following components by weight: 100 parts recycled base membrane, 20 parts glass fiber, 10 parts polyolefin, 5 parts brominated flame retardant, 5 parts dithiodiethanol, and 9 parts aminated nanocellulose. A method for preparing a recyclable modified base film includes the following steps: drying the recycled base film, then hot-melting it at 280°C, cooling it to 150°C, then adding glass fiber, polyolefin, brominated flame retardant, dithiodiethanol and aminated nanocellulose and stirring for 1 hour, extruding it through a die, and then stretching it. The longitudinal stretching preheating roller is set to 60°C, the slow stretching roller to 80°C, the fast stretching roller to 30°C, and the cooling roller to 30°C, with a longitudinal stretching ratio of 3 times. The transverse stretching preheating roller is set to 85°C, the slow stretching roller to 100°C, and the transverse stretching ratio to 3.5 times. The heat setting temperature is 190°C for 5 seconds, and after setting, it is air-cooled to 50°C. After slitting, thickness measurement, corona treatment, and winding, the modified base film is obtained. Aminated nanocellulose was prepared by the following process: nanocellulose and 3-aminopropyltriethoxysilane were added to an ethanol solution, stirred evenly, the pH was adjusted to 4 with acetic acid, and the reaction was carried out at 60°C for 4 hours. After filtration and drying, aminated nanocellulose was obtained. The mass ratio of nanocellulose, 3-aminopropyltriethoxysilane and ethanol solution was 1:5:20. Example 8:

[0043] A recyclable modified base membrane comprises the following components by weight: 100 parts recycled base membrane, 20 parts glass fiber, 10 parts polyolefin, 5 parts brominated flame retardant, 5 parts dithiodiethanol, and 11 parts carboxylated nanocellulose. A method for preparing a recyclable modified base film includes the following steps: drying the recycled base film, then hot-melting it at 280°C, cooling it to 150°C, then adding glass fiber, polyolefin, brominated flame retardant, dithiodiethanol, and carboxylated nanocellulose and stirring for 1 hour, extruding it through a die, and then stretching it. The longitudinal stretching preheating roller is set to 60°C, the slow stretching roller to 80°C, the fast stretching roller to 30°C, and the cooling roller to 30°C, with a longitudinal stretching ratio of 3 times. The transverse stretching preheating roller is set to 85°C, the slow stretching roller to 100°C, and the transverse stretching ratio to 3.5 times. The heat setting temperature is 190°C for 5 seconds, and after heat setting, it is air-cooled to 50°C. After slitting, thickness measurement, corona treatment, and winding, the modified base film is obtained. Carboxylated nanocellulose was prepared by the following process: nanocellulose and carboxylating reagent were added to deionized water and mixed, the pH was adjusted to 9.5, and the mixture was reacted at 60°C for 4 hours. After filtration and drying, carboxylated nanocellulose was obtained. The carboxylating reagent was prepared by compounding TEMPO, NaBr, and NaClO, with a mass ratio of TEMPO, NaBr, and NaClO of 1:0.04:0.3:3. The mass ratio of nanocellulose, carboxylating reagent, and ethanol solution was 1:5:20. Example 9:

[0044] A recyclable modified base membrane comprises the following components by weight: 100 parts recycled base membrane, 20 parts glass fiber, 10 parts polyolefin, 5 parts brominated flame retardant, 5 parts dithiodiethanol, and 13 parts mercapto-modified nanocellulose. A method for preparing a recyclable modified base film includes the following steps: drying the recycled base film, then hot-melting it at 280°C, cooling it to 150°C, then adding glass fiber, polyolefin, brominated flame retardant, dithiodiethanol and mercapto-modified nanocellulose and stirring for 1 hour, extruding it through a die, and then stretching it. The longitudinal stretching preheating roller is set to 60°C, the slow stretching roller to 80°C, the fast stretching roller to 30°C, and the cooling roller to 30°C, with a longitudinal stretching ratio of 3 times. The transverse stretching preheating roller is set to 85°C, the slow stretching roller to 100°C, and the transverse stretching ratio to 3.5 times. The heat setting temperature is 190°C for 5 seconds, and after setting, it is air-cooled to 50°C. After slitting, thickness measurement, corona treatment, and winding, the modified base film is obtained. Thiol-modified nanocellulose was prepared by the following process: nanocellulose and (3-mercaptopropyl)trimethoxysilane were added to an ethanol solution, stirred evenly, the pH was adjusted to 4 with acetic acid, and the reaction was carried out at 75°C for 2.5 h. After filtration and drying, thiol-modified nanocellulose was obtained. The mass ratio of nanocellulose, (3-mercaptopropyl)trimethoxysilane and ethanol solution was 1:5:20.

[0045] Example 10: A recyclable modified base membrane comprises the following components by weight: 100 parts recycled base membrane, 20 parts glass fiber, 10 parts polyolefin, 5 parts brominated flame retardant, 5 parts triethylenetetramine, and 11 parts mercapto-modified nanocellulose. A method for preparing a recyclable modified base film includes the following steps: drying the recycled base film, then hot-melting it at 280°C, cooling it to 150°C, then adding glass fiber, polyolefin, brominated flame retardant, triethylenetetramine, and thiolated nanocellulose, and stirring at 60°C for 1 hour, extruding it through a die, and then stretching it. The longitudinal stretching preheating roller is set to 60°C, the slow stretching roller to 80°C, the fast stretching roller to 30°C, and the cooling roller to 30°C, with a longitudinal stretching ratio of 3 times. The transverse stretching preheating roller is set to 85°C, the slow stretching roller to 100°C, and the transverse stretching ratio to 3.5 times. The heat setting temperature is 190°C for 5 seconds, and after heat setting, it is air-cooled to 50°C. After slitting, thickness measurement, corona treatment, and winding, the modified base film is obtained. Thiol-modified nanocellulose was prepared by the following process: nanocellulose and (3-mercaptopropyl)trimethoxysilane were added to an ethanol solution, stirred evenly, the pH was adjusted to 4 with acetic acid, and the reaction was carried out at 75°C for 2.5 h. After filtration and drying, thiol-modified nanocellulose was obtained. The mass ratio of nanocellulose, (3-mercaptopropyl)trimethoxysilane and ethanol solution was 1:5:20.

[0046] Example 11: A recyclable modified base membrane comprises the following components by weight: 100 parts recycled base membrane, 20 parts glass fiber, 10 parts polyolefin, 5 parts brominated flame retardant, 3 parts dithiodiethanol, 3 parts triethylenetetramine, and 11 parts mercapto-modified nanocellulose. A method for preparing a recyclable modified base film includes the following steps: drying the recycled base film, then hot-melting it at 280°C, cooling it to 150°C, then adding glass fiber, polyolefin, brominated flame retardant, dithiodiethanol, triethylenetetramine, and thiolated nanocellulose, and stirring at 60°C for 1 hour, extruding it through a die, and then stretching it. The longitudinal stretching preheating roller is set to 60°C, the slow stretching roller to 80°C, the fast stretching roller to 30°C, and the cooling roller to 30°C, with a longitudinal stretching ratio of 3 times. The transverse stretching preheating roller is set to 85°C, the slow stretching roller to 100°C, and the transverse stretching ratio to 3.5 times. The heat setting temperature is 190°C for 5 seconds, and after setting, it is air-cooled to 50°C. After slitting, thickness measurement, corona treatment, and winding, the modified base film is obtained. Thiol-modified nanocellulose was prepared by the following process: nanocellulose and (3-mercaptopropyl)trimethoxysilane were added to an ethanol solution, stirred evenly, the pH was adjusted to 4 with acetic acid, and the reaction was carried out at 75°C for 2.5 h. After filtration and drying, thiol-modified nanocellulose was obtained. The mass ratio of nanocellulose, (3-mercaptopropyl)trimethoxysilane and ethanol solution was 1:5:20.

[0047] Example 12: A recyclable modified base membrane comprises the following components by weight: 100 parts recycled base membrane, 20 parts glass fiber, 10 parts polyolefin, 5 parts brominated flame retardant, 11 parts aminated nanocellulose, and 3 parts modifier. The modifier is prepared by the following process: S1: Add styrene-maleic anhydride copolymer to tetrahydrofuran, stir, then add 4-aminophenylboronic acid and catalyst, purge with nitrogen, stir and react at 8°C for 4 hours, rotary evaporate, filter, dry to obtain modified intermediate; S2: Add the modified intermediate to tetrahydrofuran, stir, then add 3-mercapto-1,2-propanediol and magnesium sulfate, under nitrogen protection, and stir for 20 h at 70°C to obtain the modifier; the remaining component ratios and preparation process are the same as in Example 7.

[0048] Example 13: A recyclable modified base membrane comprises the following components by weight: 100 parts recycled base membrane, 25 parts glass fiber, 15 parts polyolefin, 5 parts brominated flame retardant, 11 parts aminated nanocellulose, and 3 parts modifier. The modifier is prepared by the following process: S1: Add styrene-maleic anhydride copolymer to tetrahydrofuran, stir, then add 4-aminophenylboronic acid and catalyst, purge with nitrogen, stir and react at 80°C for 4 hours, rotary evaporate, filter, and dry to obtain the modified intermediate; S2: Add the modified intermediate to tetrahydrofuran, stir, then add 3-mercapto-1,2-propanediol and magnesium sulfate, under nitrogen protection, and stir for 20 h at 70°C to obtain the modifier; the remaining component ratios and preparation process are the same as in Example 7.

[0049] Example 14: A recyclable modified base membrane comprises the following components by weight: 100 parts recycled base membrane, 25 parts glass fiber, 20 parts polyolefin, 10 parts brominated flame retardant, 11 parts aminated nanocellulose, and 5 parts modifier. The modifier is prepared by the following process: S1: Add styrene-maleic anhydride copolymer to tetrahydrofuran, stir, then add 4-aminophenylboronic acid and catalyst, purge with nitrogen, stir and react at 90°C for 8 hours, rotary evaporate, filter, dry to obtain modified intermediate; S2: Add the modified intermediate to tetrahydrofuran, stir, then add 3-mercapto-1,2-propanediol and magnesium sulfate, under nitrogen protection, and stir for 24 hours at 80°C to obtain the modifier; the remaining component ratios and preparation process are the same as in Example 7.

[0050] Comparative Example 1: This comparative example provides a method for preparing a modified base film, which comprises the following components by mass: 100 parts recycled base film, 20 parts glass fiber, 10 parts polyolefin, and 5 parts brominated flame retardant. The proportions and preparation process of the remaining components are the same as in Example 1.

[0051] Comparative Example 2: This comparative example provides a method for preparing a modified base film, which comprises the following components by mass: 100 parts polyethylene terephthalate, 20 parts glass fiber, 10 parts polyolefin, and 5 parts brominated flame retardant. The proportions and preparation process of the remaining components are the same as in Example 1.

[0052] Comparative Example 3: This comparative example provides a method for preparing a modified base film. The modifier is prepared by the following process: adding styrene-maleic anhydride copolymer to tetrahydrofuran, stirring, then adding 4-aminophenylboronic acid and a catalyst, purging with nitrogen, stirring and reacting at 80°C for 4 hours, rotary evaporation, filtration, and drying to obtain the modifier. The remaining component ratios and preparation process are the same as in Example 12.

[0053] Comparative Example 4: This comparative example provides a method for preparing a modified base film, in which the modifier is replaced with a styrene-maleic anhydride copolymer, and the remaining component ratios and preparation processes are the same as in Example 12.

[0054] The modified base films obtained in Examples 1-14 and Comparative Examples 1-4 were used to prepare samples, and their properties were tested and the test results were recorded.

[0055] Tensile strength test: ASTM D882 was used as the reference standard. An electronic universal testing machine was used. The test conditions were: gauge length 10 mm, tensile speed 50 mm / min, width 15 mm. The tensile strength in the transverse (TD) and longitudinal (MD) directions was measured. Heat shrinkage test: Using ASTM D1204 as the reference standard, the sample was baked at 150°C for 30 minutes. The length changes in the TD and MD directions of the sample before and after heating were measured, and the heat shrinkage rate was calculated.

[0056] Performance Comparison Table

[0057] Based on the data in the table above, the following conclusions can be clearly drawn: The modified base films obtained in Examples 1-14 were compared with those obtained in Comparative Examples 1-4. The test results show that: A comparison of Examples 1-14 with the comparative examples shows that the modified base film of the present invention has excellent mechanical properties and thermal stability.

[0058] Comparing Example 1 with Comparative Example 1, the modified base film obtained in Comparative Example 1, without the addition of additives containing reversible covalent bonds, showed a decrease in tensile strength and an increase in thermal shrinkage rate. This indicates that the addition of dithiodiethanol can improve the remodeling performance of the base film, demonstrating the technical advantage of this invention in adding compounds containing reversible covalent bonds of disulfide and imine bonds to increase the remodeling performance of the recycled base film.

[0059] Comparing Example 1 with Comparative Example 2, which uses an unused base film, the tensile strength and thermal shrinkage rate are comparable to those of the reshaped base film of the present invention. This indicates that the preparation method of the modified base film of the present invention can significantly improve the mechanical properties and thermal stability of the recycled base film. As can be seen from Example 9, it can even be higher than the performance of the unused base film, demonstrating the technical advantages of the modification process of the present invention.

[0060] Comparing Example 12 with Comparative Example 3, the modified base film obtained in Comparative Example 3 does not introduce thiol groups in the modifier. The tensile strength of the recycled base film is improved compared with Comparative Example 1, and the thermal shrinkage rate is reduced. However, the effect is not as good as that of the present invention. This reflects the technical advantage of the modifier in synergistically using borooxy and thiol groups as reversible covalent bonds to enhance the remodeling and repair performance.

[0061] Comparing Example 12 with Comparative Example 4, the modified base film obtained in Comparative Example 3 does not introduce thiol groups in the modifier. The tensile strength of the recycled base film is relatively improved compared with Comparative Example 1, and the thermal shrinkage rate is relatively reduced. However, the effect is not as good as that of the present invention. This reflects the technical advantage of the modifier in synergistically using borooxy and thiol groups as reversible covalent bonds to enhance the remodeling and repair performance.

[0062] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A recyclable modified base membrane, characterized in that: It comprises the following components by weight: 80-100 parts recycled base film, 20-25 parts glass fiber, 10-20 parts polyolefin, 5-10 parts brominated flame retardant, and 3-20 parts additives; wherein the additives are any one or a mixture of dithiodiethanol, functionalized nanocellulose, and triethylenetetramine; and the functionalized nanocellulose is any one of carboxylated nanocellulose, aminated nanocellulose, and thiolated nanocellulose.

2. The recyclable modified base membrane according to claim 1, characterized in that: The carboxylated nanocellulose is prepared by the following process: nanocellulose and carboxylating reagent are added to deionized water and mixed, the pH is adjusted to 9.5~10.5, and the mixture is reacted at 50~70℃ for 3~5 hours. After filtration and drying, carboxylated nanocellulose is obtained.

3. The recyclable modified base membrane according to claim 1, characterized in that: The aminated nanocellulose is prepared by the following process: nanocellulose and 3-aminopropyltriethoxysilane are added to an ethanol solution, stirred evenly, the pH is adjusted to 4-5 with acetic acid, and the reaction is carried out at a temperature of 50-70°C for 3-5 hours. After filtration and drying, aminated nanocellulose is obtained.

4. The recyclable modified base membrane according to claim 1, characterized in that: The thiolized nanocellulose is prepared by the following process: nanocellulose and (3-mercaptopropyl)trimethoxysilane are added to an ethanol solution, stirred evenly, the pH is adjusted to 4-5 with acetic acid, and the reaction is carried out at 70-80℃ for 2-3 hours. After filtration and drying, thiolized nanocellulose is obtained.

5. The recyclable modified base membrane according to claim 2, characterized in that: The carboxylating agent is prepared by compounding TEMPO, NaBr, and NaClO, with the mass ratio of TEMPO, NaBr, and NaClO being 1:(0.01~0.05):(0.1~0.5):(1~5).

6. A method for preparing a recyclable modified base film, characterized in that: Includes the following steps: The recycled base film is dried, then subjected to high-temperature hot melting, cooled, and then glass fiber, polyolefin, brominated flame retardant, and additives are added and stirred for 1-2 hours. It is then extruded through a mold, and then subjected to stretching, heat setting, air cooling, slitting, thickness measurement, corona treatment, and finally wound up to obtain the modified base film.

7. The method for preparing a recyclable modified base film according to claim 6, characterized in that: The stretching process conditions are as follows: the longitudinal stretching preheating roller temperature is set at 50~70℃, the slow stretching roller temperature is set at 70~90℃, the fast stretching roller temperature is set at 20~40℃, the cooling roller temperature is set at 30℃ or 50℃, the longitudinal stretching ratio is set at 2.5~3.5 times, the transverse stretching preheating roller temperature is set at 80~90℃, the slow stretching roller temperature is set at 90~110℃, and the transverse stretching ratio is set at 3~4 times; the heat setting process conditions are as follows: the heat setting temperature is 180~200℃, the time is 4~6s, and the temperature is cooled to 40~60℃ by air.

8. The method for preparing a recyclable modified base film according to claim 6, characterized in that: The modified base film also contains 3 to 5 parts of modifier.

9. The method for preparing a recyclable modified base film according to claim 8, characterized in that: The modifier is prepared by the following process: S1: Add styrene-maleic anhydride copolymer to tetrahydrofuran, stir, then add 4-aminophenylboronic acid and catalyst, purge with nitrogen, stir and react at 80~90℃ for 4~8h, rotary evaporate, filter, dry to obtain modified intermediate; S2: Add the modified intermediate to tetrahydrofuran, stir, then add 3-mercapto-1,2-propanediol and magnesium sulfate, under nitrogen protection, and stir for 20-24 hours at 70-80°C to obtain the modifier.

10. The method for preparing a recyclable modified base film according to claim 9, characterized in that: The mass ratio of styrene-maleic anhydride copolymer, tetrahydrofuran, 4-aminophenylboronic acid, and catalyst is 1:(20~25):(0.5~0.8):(0.1~0.5); the mass ratio of modified intermediate, tetrahydrofuran, 3-mercapto-1,2-propanediol, and magnesium sulfate is 1:(20~25):(0.5~0.8):(3~5).

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