A high-strength BOPA film and its preparation method

Abstract

The present invention relates to the technical field of nylon film preparation, and particularly relates to a high-strength BOPA film and a preparation method thereof. By weight parts, the high-strength BOPA film comprises: 75-92 parts of nylon 6, 5-20 parts of modified cashew phenol, 1-3 parts of slip agent, 0.5-1 part of compatibilizer, 0.5-1.5 parts of dispersant, 1-5 parts of modified Ti 3 C 2 T x nanosheets. The film has excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of nylon film preparation, and particularly relates to a high-strength BOPA film and a preparation method thereof. Background Art

[0002] Biaxially oriented nylon film (BOPA) has excellent heat resistance, chemical solvent resistance, and advantages such as light weight, low cost, and environmental friendliness, and is widely used in packaging fields such as food, medicine, cosmetics, and mechanical electronics. Currently, BOPA film is the third largest biaxially oriented flexible packaging material after biaxially oriented polypropylene film (BOPP) and biaxially oriented polyester film (BOPET). The polymer material used to prepare BOPA film is nylon 6 resin, which is a polymer with repeating amide groups on the main chain formed by ring-opening polymerization of caprolactam.

[0003] With the economic development of our country and the improvement of people's living quality, higher and higher requirements are put forward for the performance of packaging materials. Although biaxially oriented nylon film has good mechanical properties, it still cannot meet the actual application requirements in some application fields, such as pharmaceutical blister packaging and heavy object packaging that need to bear large load intensities. Therefore, the present invention proposes a high-strength BOPA film and a preparation method thereof to solve the above existing problems. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, one of the purposes of the present invention is to provide a high-strength BOPA film, which has excellent mechanical properties.

[0005] Another purpose of the present invention is to provide a preparation method of a high-strength BOPA film, and the preparation process is simple.

[0006] One of the purposes of the present invention is achieved by adopting the following technical solutions:

[0007] A high-strength BOPA film, in parts by weight, the high-strength BOPA film comprises: 75 - 92 parts of nylon 6, 5 - 20 parts of modified cashew phenol, 1 - 3 parts of slip agent, 0.5 - 1 part of compatibilizer, 0.5 - 1.5 parts of dispersant, 15 parts of modified Ti 3 C 2 T x nanosheets.

[0008] Further, the preparation method of the modified Ti 3 C 2 T x nanosheets is as follows:

[0009] (1) Ti 3 C 2 T xThe nanosheets, 4-bromoaniline, and isoamyl nitrite are mixed and stirred for reaction, and bromobenzene-Ti is obtained through purification. 3 C 2 T x Nanosheets;

[0010] (2) The bromobenzene-Ti from step (1) 3 C 2 T x The nanosheets, tetrakis(triphenylphosphine)palladium, and cuprous iodide are added to a mixed solution of toluene and triethylamine. After stirring for 1 - 1.5 h, 1,3,5-triethynylbenzene and 1,4-dibromobenzene are added for reaction, and modified Ti 3 C 2 T x nanosheets are obtained through purification.

[0011] Furthermore, in step (2), the mass ratio of cuprous iodide, tetrakis(triphenylphosphine)palladium, bromobenzene-Ti 3 C 2 T x nanosheets, 1,3,5-triethynylbenzene, and 1,4-dibromobenzene is 1:(5 - 6):(9 - 11):(3 - 5):(12 - 15); the volume ratio of toluene to triethylamine is 1:1; the reaction temperature is 95 - 110 °C, and the reaction time is 68 - 76 h.

[0012] Furthermore, in step (1), the dosage ratio of isoamyl nitrite, Ti 3 C 2 T x nanosheets, and 4-bromoaniline is 1 mL:(25 - 35) mg:(550 - 600) mg; the stirring reaction temperature is 55 - 65 °C, and the stirring reaction time is 8 - 10 h.

[0013] Furthermore, the preparation method of the Ti 3 C 2 T x nanosheets in step (1) is as follows: According to the dosage ratio of LiF, Ti 3 AlC 2 powder, and hydrochloric acid of 1 g:(0.5 - 1) g:(8 - 15) mL; LiF is added to the hydrochloric acid solution, and then Ti 3 AlC 2 powder is added for etching. After centrifugation, a precipitate is obtained, and through ultrasonic stratification and purification, Ti 3 C 2 T x nanosheets are obtained; the concentration of the hydrochloric acid is 5 - 10 mol / L; the etching temperature is 40 - 55 °C, and the etching time is 36 - 48 h.

[0014] Further, the preparation method of the modified cardanol is as follows:

[0015] React the purified cardanol, paraformaldehyde and 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and obtain the modified cardanol through purification.

[0016] Further, the purification process of the purified cardanol is as follows: Mix cashew nut oil and a small amount of zeolite for vacuum distillation, collect the low-boiling substances below 200 °C, and then collect the fraction at 200 - 240 °C under a vacuum of 1000 Pa.

[0017] Further, the molar ratio of the purified cardanol, paraformaldehyde, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane is 1:(0.2 - 0.5):(0.5 - 1); the reaction temperature is 80 - 95 °C, and the reaction time is 1 - 2 h.

[0018] Further, the slip agent is one or more of oleic acid amide, silicone oil, and polyethylene wax; the compatibilizer is one or two of ethylene-acrylic acid copolymer and epoxy resin; the dispersant is silica.

[0019] The second object of the present invention is achieved by the following technical solution:

[0020] The preparation method of the above high-strength BOPA film includes the following steps:

[0021] According to the above weight parts, mix nylon 6, modified cardanol, slip agent, compatibilizer, dispersant, and modified Ti 3 C 2 T x nanosheets evenly to obtain a premix; the premix is melt-extruded, cast, biaxially stretched, and shaped.

[0022] Further, the temperature of the biaxial stretching is 150 - 170 °C; the biaxial stretching ratio is (2.5×2.5)-(3.5×3.5); the shaping temperature is 160 - 180 °C.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The high-strength BOPA film of the present invention adds raw materials such as modified Ti 3 C 2 T x nanosheets and modified cardanol. When used in combination, they can improve the overall mechanical properties of the nylon film. Specifically, the modified Ti 3 C 2 T x nanosheets are prepared using 4-bromoaniline containing an amino group and Ti 3C 2 T x React with the hydroxyl groups on the surface of the nanosheets to obtain bromobenzene-modified Ti 3 C 2 T x Nanosheets, and then use the Sonogashira–Hagihara reaction to graft-polymerize 1,3,5-triethynylbenzene and 1,4-dibromobenzene onto the bromobenzene-modified Ti 3 C 2 T x Nanosheets. The modified Ti 3 C 2 T x Nanosheets can form strong electrostatic interactions or hydrogen bond interactions with the nylon 6 main chain due to the presence of negatively charged hydrophilic functional groups (such as -OH, -O, and -F) on their surface, thereby improving their compatibility and dispersibility, making the modified Ti 3 C 2 T x Nanosheets can effectively transfer stress, thereby enhancing the mechanical properties of the film; on the other hand, the modified Ti 3 C 2 T x The highly rigid backbone of the conjugated polymer grafted on the surface of the nanosheets also endows the nylon film with higher tensile strength. The modified cardanol is prepared by one-step synthesis using Mannich reaction with cardanol, amino-terminated tetramethyldisiloxane, and paraformaldehyde as raw materials. The long-chain carbon structure and tetramethyldisiloxane structure contained in the modified cardanol can endow the nylon film with better flexibility, thereby enhancing the mechanical properties of the nylon film. The experimental results show that the tensile strength of the BOPA film of the present invention reaches above 323 MPa (MD) and 328 MPa (TD); the elongation at break of the BOPA film reaches above 149% (MD) and 151% (TD); the puncture resistance of the BOPA film reaches above 22.8 N. Detailed implementation manners

[0025] The following further describes the present invention in combination with specific implementation manners. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined to form new embodiments. The specific conditions not specified in the embodiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are all conventional products obtained through commercial channels.

[0026] The preparation process of purified cardanol in the embodiment is as follows:

[0027] In a container equipped with N 2In a 500 mL three-necked flask equipped with protection, a condenser, a thermometer and a magnetic rotor, add 250 g of cashew nut oil and a small amount of zeolite. Insert a thermosensitive thermometer into the left mouth of the flask to control the solution temperature. Perform vacuum distillation using a vacuum oil pump. First, collect the low-boiling substances below 200 °C, then replace the condensation receiving device, and collect the fraction at 200 - 240 °C under a vacuum of 1000 Pa to obtain purified cardanol.

[0028] (I) Example

[0029] Example 1

[0030] A high-strength BOPA film, by weight, the film consists of 80 parts of nylon 6, 12 parts of modified cardanol, 2 parts of oleic acid amide, 0.7 part of ethylene-acrylic acid copolymer, 1.1 parts of silica, and 2 parts of modified Ti 3 C 2 T x nanosheets.

[0031] Among them, the preparation process of the modified Ti 3 C 2 T x nanosheets is as follows:

[0032] (1) According to the dosage ratio of LiF, Ti 3 AlC 2 powder, and hydrochloric acid of 1 g: 0.7 g: 12 mL, add LiF to an 8 mol / L hydrochloric acid solution, then add Ti 3 AlC 2 powder, etch at 50 °C for 40 h, centrifuge to obtain a precipitate, wash the precipitate until the pH is neutral, and filter to obtain multi-layer Ti 3 C 2 T x nanosheets. Add the multi-layer Ti 3 C 2 T x nanosheets to deionized water, ultrasonically delaminate at 450 W for 0.5 h, then centrifuge at a speed of 3500 rpm for 8 min, and then freeze-dry at -50 °C for 36 h to obtain Ti 3 C 2 T x nanosheets; according to the dosage ratio of amyl nitrite, Ti 3 C 2 T x nanosheets, and 4-bromoaniline of 1 mL: 30 mg: 580 mg, add Ti 3 C 2 T xMix the nanosheets with 4-bromoaniline, and then slowly add isoamyl nitrite. Stir and react at 60 °C for 9 h. After the reaction is completed, add DMF to the reaction solution, filter to collect the solid precipitate, wash it with DMF until the filtrate becomes colorless, and then wash it with methanol to remove DMF. Dry it under vacuum to obtain bromobenzene-Ti 3 C 2 T x nanosheets

[0033] (2) According to the mass ratio of cuprous iodide, tetrakis(triphenylphosphine)palladium, and bromobenzene-Ti 3 C 2 T x nanosheets, 1,3,5-triethynylbenzene, and 1,4-dibromobenzene being 1:5.6:10:4:13, add the bromobenzene-Ti from step (1) 3 C 2 T x nanosheets, tetrakis(triphenylphosphine)palladium, and cuprous iodide to a mixed solution of toluene and triethylamine (1:1, v / v), stir for 1.2 h, then add 1,3,5-triethynylbenzene and 1,4-dibromobenzene, react at 100 °C for 70 h, filter to collect the product, wash the product successively with acetone, methanol, dichloromethane, and ether, and dry it under vacuum to obtain modified Ti 3 C 2 T x nanosheets

[0034] The preparation process of modified cardanol is as follows:

[0035] According to the mass ratio of purified cardanol, paraformaldehyde, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane being 1:0.4:0.8, add purified cardanol, paraformaldehyde, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane to a four-necked flask equipped with a stirrer, a thermometer, and a condenser reflux tube. After stirring evenly at a speed of 60 rpm, react at 90 °C for 1.5 h, separate out the water by vacuum distillation, and then cool to room temperature to obtain it

[0036] The preparation method of the above high-strength BOPA film is as follows:

[0037] According to the stated parts by weight, mix nylon 6, modified cardanol, oleic acid amide, ethylene-acrylic acid copolymer, silica, and modified Ti 3 C 2 T x nanosheets evenly to prepare a premix; add the premix to a twin-screw extruder, set the processing temperature of each zone of the twin-screw extruder to 240 °C, melt and extrude to granulate to obtain masterbatch; add the masterbatch to a casting machine for extrusion casting, and then perform biaxial stretching on the cast film at 160 °C and a magnification of 3×3, and then carry out shaping at 170 °C

[0038] Example 2

[0039] A high-strength BOPA film, by weight, the film consists of 75 parts of nylon 6, 5 parts of modified cashew phenol, 1 part of oleamide and silicone oil mixture (the ratio of the two is 1:1), 0.5 part of epoxy resin, 0.5 part of silicon dioxide, and 1 part of modified Ti 3 C 2 T x nanosheets.

[0040] Among them, the preparation process of the modified Ti 3 C 2 T x nanosheets is as follows:

[0041] (1) According to the dosage ratio of LiF, Ti 3 AlC 2 powder, hydrochloric acid of 1 g: 0.5 g: 8 mL, add LiF to 5 mol / L hydrochloric acid solution, and then add Ti 3 AlC 2 powder, etch at 40 °C for 48 h, centrifuge to obtain a precipitate, wash the precipitate until the pH is neutral, filter to obtain multi-layer Ti 3 C 2 T x nanosheets, add the multi-layer Ti 3 C 2 T x nanosheets to deionized water, ultrasonically layer at 450 W for 0.5 h, then centrifuge at 3500 rpm for 8 min, and then freeze-dry at -50 °C for 36 h to obtain Ti 3 C 2 T x nanosheets; according to the dosage ratio of amyl nitrite, Ti 3 C 2 T x nanosheets, 4-bromoaniline of 1 mL: 25 mg: 550 mg, mix Ti 3 C 2 T x nanosheets and 4-bromoaniline, and then slowly add amyl nitrite, stir and react at 55 °C for 10 h. After the reaction is completed, add DMF to the reaction solution, filter to collect the solid precipitate, wash with DMF until the filtrate becomes colorless, and then wash with methanol to remove DMF, and dry in vacuum to obtain bromobenzene-Ti 3 C 2 T x nanosheets.

[0042] (2) According to copper(I) iodide, tetrakis(triphenylphosphine)palladium, bromobenzene-Ti 3 C2 T x The mass ratio of nanosheets, 1,3,5-triethynylbenzene, and 1,4-dibromobenzene is 1:5:9:5:12. Add the bromobenzene-Ti from step (1) 3 C 2 T x Nanosheets, tetrakis(triphenylphosphine)palladium, cuprous iodide were added to a mixed solution of toluene and triethylamine (1:1, v / v) and stirred for 1 h. Then 1,3,5-triethynylbenzene and 1,4-dibromobenzene were added, and the reaction was carried out at 95 °C for 76 h. The product was collected by filtration, and the product was washed successively with acetone, methanol, dichloromethane, and ether, and dried in vacuo to obtain modified Ti 3 C 2 T x Nanosheets.

[0043] The preparation process of the modified cardanol is as follows:

[0044] According to the mass ratio of purified cardanol, paraformaldehyde, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane of 1:0.5:1, purified cardanol, paraformaldehyde, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane were added to a four-necked flask equipped with a stirrer, a thermometer, and a condenser reflux tube. After stirring evenly at a speed of 60 rpm, the reaction was carried out at 80 °C for 2 h. The water was separated by vacuum distillation, and then cooled to room temperature to obtain it.

[0045] The preparation method of the above high-strength BOPA film is as follows:

[0046] According to the stated parts by weight, nylon 6, modified cardanol, a mixture of oleic acid amide and silicone oil, epoxy resin, silica, and modified Ti 3 C 2 T x Nanosheets were mixed evenly to obtain a premix; the premix was added to a twin-screw extruder, and the processing temperature of each zone of the twin-screw extruder was set at 240 °C. After melt extrusion and granulation, masterbatch was obtained; the masterbatch was added to a casting machine for extrusion casting, and then the cast film was biaxially stretched at 150 °C with a magnification of 3.5×3.5, and then shaped at 160 °C to obtain the product.

[0047] Example 3

[0048] A high-strength BOPA film, in parts by weight, the film is composed of 92 parts of nylon 6, 5-20 parts of modified cardanol, 3 parts of oleic acid amide, a mixture of silicone oil and polyethylene wax (mixed in a ratio of 1:1:1), 1 part of an ethylene-acrylic acid copolymer, a mixture of epoxy resin (mixed in a ratio of 1:1), 1.5 parts of silica, and 5 parts of modified Ti 3 C 2 T x Nanosheets.

[0049] Among them, the modified Ti 3 C 2 T x The preparation process of the nanosheets is as follows:

[0050] (1) According to the dosage ratio of LiF, Ti 3 AlC 2 powder, and hydrochloric acid of 1 g: 1 g: 15 mL, add LiF to 10 mol / L hydrochloric acid solution, and then add Ti 3 AlC 2 powder. Etch at 55 °C for 36 h, centrifuge to obtain a precipitate, wash the precipitate until the pH is neutral, and filter to obtain multilayer Ti 3 C 2 T x nanosheets. Add the multilayer Ti 3 C 2 T x nanosheets to deionized water, ultrasonically delaminate at 450 W for 0.5 h, then centrifuge at a speed of 3500 rpm for 8 min, and then freeze-dry at -50 °C for 36 h to obtain Ti3C2Tx nanosheets; according to the dosage ratio of isoamyl nitrite, Ti 3 C 2 T x nanosheets, and 4-bromoaniline of 1 mL: 35 mg: 600 mg, mix the Ti 3 C 2 T x nanosheets and 4-bromoaniline, and then slowly add isoamyl nitrite. Stir and react at 65 °C for 8 h. After the reaction is completed, add DMF to the reaction solution, collect the solid precipitate by filtration, wash with DMF until the filtrate becomes colorless, and then wash with methanol to remove DMF. Dry under vacuum to obtain bromobenzene-Ti 3 C 2 T x nanosheets.

[0051] (2) According to the mass ratio of cuprous iodide, tetrakis(triphenylphosphine)palladium, bromobenzene-Ti 3 C 2 T x nanosheets, 1,3,5-triethynylbenzene, and 1,4-dibromobenzene of 1: 6: 11: 7: 15, add the bromobenzene-Ti 3 C 2 T xThe nanosheets, tetrakis(triphenylphosphine)palladium, copper(I) iodide were added to a mixed solution of toluene and triethylamine (1:1, v / v), and stirred for 1.5 h. Then 1,3,5-triethynylbenzene and 1,4-dibromobenzene were added, and the reaction was carried out at 110 °C for 68 h. The product was collected by filtration, and the product was washed successively with acetone, methanol, dichloromethane and ether, and dried under vacuum to obtain modified Ti 3 C 2 T x nanosheets.

[0052] The preparation process of the modified cardanol is as follows:

[0053] According to the mass ratio of purified cardanol, paraformaldehyde and 1,3-bis(3-aminopropyl)tetramethyldisiloxane of 1:0.2:0.5, the purified cardanol, paraformaldehyde and 1,3-bis(3-aminopropyl)tetramethyldisiloxane were added to a four-necked flask equipped with a stirrer, a thermometer and a condenser reflux tube. After stirring evenly at a speed of 60 rpm, the reaction was carried out at 95 °C for 1 h. The water was separated by vacuum distillation, and then cooled to room temperature to obtain the product.

[0054] The preparation method of the above high-strength BOPA film is as follows:

[0055] According to the stated parts by weight, a mixture of nylon 6, modified cardanol, oleic acid amide, silicone oil, polyethylene wax, ethylene-acrylic acid copolymer, epoxy resin, silica and modified Ti 3 C 2 T x nanosheets were mixed evenly to obtain a premix; the premix was added to a twin-screw extruder, and the processing temperature of each zone of the twin-screw extruder was set at 240 °C. After melt extrusion and pelletization, masterbatch was obtained; then the masterbatch was added to a casting machine for extrusion casting, and the cast film was biaxially stretched at 170 °C with a magnification of 2.5×2.5, and then shaped at 180 °C.

[0056] (II) Comparative examples

[0057] Comparative example 1

[0058] The difference between Comparative example 1 and Example 1 is that: Ti 3 C 2 T x nanosheets were used to replace modified Ti 3 C 2 T x nanosheets, and the rest was the same as Example 1.

[0059] Comparative example 2

[0060] The difference between Comparative example 2 and Example 1 is that: the modified cardanol was omitted, and the rest was the same as Example 1.

[0061] Comparative Example 3

[0062] The difference between Comparative Example 3 and Example 1 is that purified cardanol and 1,3-bis(3-aminopropyl)tetramethyldisiloxane are used instead of modified cardanol, and the molar ratio of purified cardanol to 1,3-bis(3-aminopropyl)tetramethyldisiloxane is 1:0.9, and the rest is the same as in Example 1.

[0063] (III) Experimental Examples

[0064] The properties of the films prepared in Examples 1-3 and Comparative Examples 1-3 were tested, and the specific test methods are as follows:

[0065] Tensile strength and elongation at break: Tested according to the experimental conditions of Part 3 of thin films and sheets in GB / T 1040.3-2006, and each sample was repeated 5 times. The experimental results are the average values of 5 repeated experiments. The experimental results are shown in Table 1;

[0066] Puncture resistance: The puncture resistance of the test samples was tested according to GB / T 20218-2021 "Biaxially oriented polyamide (nylon) films", and each sample was repeated 5 times. The experimental results are the average values of 5 repeated experiments. The experimental results are shown in Table 1.

[0067] Table 1

[0068]

[0069] As can be seen from Table 1, the films prepared in Examples 1-3 have excellent mechanical properties. Compared with Examples 1-3, Comparative Example 1 uses Ti 3 C 2 T x nanosheets instead of modified Ti 3 C 2 T x nanosheets, Comparative Example 2 omits modified cardanol, and Comparative Example 3 uses purified cardanol and 1,3-bis(3-aminopropyl)tetramethyldisiloxane instead of modified cardanol, all of which result in a decrease in the mechanical properties of the prepared films. Analysis shows that the modified Ti 3 C 2 T x nanosheets can form strong electrostatic interactions or hydrogen bond interactions with the nylon 6 main chain due to the presence of negatively charged hydrophilic functional groups (such as -OH, -O, and -F) on the surface, thereby improving its compatibility and dispersibility; on the other hand, the high-rigidity backbone structure of the conjugated microporous polymer grafted on its surface endows the nylon film with higher tensile strength and puncture resistance. The combined action of the long-chain carbon structure and the tetramethyldisiloxane structure contained in modified cardanol endows the nylon film with better flexibility, thereby improving the mechanical properties of the nylon film. In summary, the modified Ti 3 C 2 Tx The combined use of nanosheets and modified cardanol can improve the overall mechanical properties of the nylon film.

[0070] The above embodiments are only the preferred embodiments of the present invention, and the scope of protection of the present invention cannot be limited thereby. Any non-substantive changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. A high-strength BOPA film, characterized in that: In parts by weight, the high-strength BOPA film comprises: 75-92 parts of nylon 6, 5-20 parts of modified cardanol, 1-3 parts of lubricant, 0.5-1 parts of compatibilizer, 0.5-1.5 parts of dispersant, 1-5 parts of modified Ti3C2T x Nanosheets; The modified Ti3C2T x The preparation method of the nanosheets is as follows: (1) Ti3C2T x Nanosheets, 4-bromoaniline, and isoamyl nitrite were mixed and stirred to react, and bromobenzene-Ti3C2T was obtained after purification. x Nanosheets; (2) Replacing the bromobenzene-Ti3C2T x Nanosheets, tetrakis(triphenylphosphine)palladium, and cuprous iodide were added to a mixed solution of toluene and triethylamine, stirred for 1-1.5 h, and then 1,3,5-triethynylbenzene and 1,4-dibromobenzene were added to react. The modified Ti3C2T x Nanosheets; The preparation method of the modified cardanol is as follows: The purified cardanol, polyformaldehyde and 1,3-bis(3-aminopropyl)tetramethyldisiloxane are reacted to obtain modified cardanol after purification.

2. The high-strength BOPA film according to claim 1, characterized in that: The cuprous iodide, tetrakis(triphenylphosphine)palladium, bromobenzene-Ti3C2T3 x The mass ratio of nanosheets, 1,3,5-triethynylbenzene and 1,4-dibromobenzene is 1:(5-6):(9-11):(3-5):(12-15); the volume ratio of toluene and triethylamine is 1:1; the reaction temperature is 95-110°C and the reaction time is 68-76h.

3. The high-strength BOPA film according to claim 1, characterized in that: The isopentyl nitrite, Ti3C2T x The dosage ratio of the nanosheets and 4-bromoaniline is 1 mL: (25-35) mg: (550-600) mg; the stirring reaction temperature is 55-65° C., and the stirring reaction time is 8-10 hours.

4. The high-strength BOPA film according to claim 1, characterized in that: Ti3C2T in step (1) x The preparation method of the nanosheets is as follows: according to the dosage ratio of LiF, Ti3AlC2 powder and hydrochloric acid being 1g: (0.5-1)g: (8-15)mL; LiF is added to the hydrochloric acid solution, and then Ti3AlC2 powder is added for etching, and a precipitate is obtained after centrifugation, and Ti3C2T is obtained by ultrasonic stratification and purification. x Nanosheets; the concentration of the hydrochloric acid is 5-10 mol / L; the etching temperature is 40-55° C., and the etching time is 36-48 h.

5. The high-strength BOPA film according to claim 1, characterized in that: In the preparation method of modified cardanol, the mass ratio of the purified cardanol, polyformaldehyde, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane is 1:(0.2-0.5):(0.5-1); the reaction temperature is 80-95° C., and the reaction time is 1-2 h.

6. The high-strength BOPA film according to claim 1, characterized in that: The lubricant is one or more of oleic acid amide, silicone oil and polyethylene wax; the compatibilizer is one or two of ethylene-acrylic acid copolymer and epoxy resin; and the dispersant is silicon dioxide.

7. The method for preparing the high-strength BOPA film according to claim 1, characterized in that: The following steps are involved: According to the weight proportions, nylon 6, modified cardanol, lubricant, compatibilizer, dispersant and modified Ti3C2T x The nanosheets are mixed uniformly to obtain a premix; the premix is ​​melt-extruded, cast, biaxially stretched, and shaped.

8. The method for preparing the high-strength BOPA film according to claim 7, characterized in that: The temperature of the biaxial stretching is 150-170°C; the ratio of the biaxial stretching is (2.5×2.5)-(3.5×3.5); and the temperature of the shaping is 160-180°C.

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