High-strength flame-retardant packaging material and method for producing the same

Abstract

The application relates to the technical field of packaging materials, in particular to a high-strength flame-retardant packaging material and a preparation method thereof. According to weight parts, the packaging material comprises the following raw materials: 70-90 parts of polylactic acid, 6-12 parts of polybutylene adipate terephthalate, 4-15 parts of a flame retardant, 3-7 parts of modified montmorillonite, 3-5 parts of maleic anhydride grafted polypropylene, 0.3-0.5 parts of an antioxidant and 0.5-1 part of a lubricant. The packaging material has excellent flame-retardant performance, bacteriostatic performance, barrier performance and mechanical performance.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, and in particular to a high-strength flame-retardant packaging material and its preparation method. Background Technology

[0002] Cigarette packaging films have traditionally used biaxially oriented polypropylene (BOPP) film. While this film offers advantages such as good transparency, excellent dimensional stability, high mechanical strength, and strong water vapor barrier properties, it is non-degradable. Currently, research has explored the use of biodegradable polylactic acid (PLA) in cigarette packaging to replace polypropylene film. For example, patent application CN110774714A discloses a biodegradable biaxially oriented polylactic acid cigarette film, made from polylactic acid through biaxial stretching, overcoming the non-degradability problem of existing polypropylene cigarette films.

[0003] However, traditional polylactic acid (PLA) films lack sufficient strength, making it difficult to meet the requirements of dimensional stability and smooth appearance in cigarette packaging. Furthermore, PLA exhibits significant flammability, failing the UL-94 vertical burning test and possessing a limiting oxygen index of only 20%, severely limiting its applications. Therefore, it is necessary to provide a high-strength, flame-retardant packaging material to address these issues. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, one of the objectives of this invention is to provide a high-strength flame-retardant packaging material with excellent flame-retardant properties, antibacterial properties, barrier properties and mechanical properties.

[0005] The second objective of this invention is to provide a method for preparing a high-strength flame-retardant packaging material that is easy to implement.

[0006] One of the objectives of this invention is achieved through the following technical solution: A high-strength flame-retardant packaging material, by weight, comprises the following raw materials: 70-90 parts polylactic acid, 6-12 parts polybutylene terephthalate-adipate, 4-15 parts flame retardant, 3-7 parts modified montmorillonite, 3-5 parts maleic anhydride-grafted polypropylene, 0.3-0.5 parts antioxidant, and 0.5-1 parts lubricant; The structural formula of the flame retardant is: .

[0007] Preferably, the preparation process of the modified montmorillonite is as follows: (1) Add 3-mercaptopropyltriethoxysilane to an aqueous methanol solution, adjust the pH and stir, then add montmorillonite and reflux reaction, purify, and obtain mercapto-modified montmorillonite; (2) Under the protection of an inert gas, the mercaptomodified montmorillonite was added to tetrahydrofuran, then camphene and a photoinitiator were added, the reaction was carried out by irradiation, and the mixture was purified to obtain the modified montmorillonite.

[0008] This invention first prepares thiolized montmorillonite by coupling 3-mercaptopropyltriethoxysilane with the silane of montmorillonite, and then prepares modified montmorillonite by the thiol group of thiolized montmorillonite reacting with the double bond of camphene to undergo a thiol-ene click reaction.

[0009] Preferably, in step (1), the mass ratio of montmorillonite to 3-mercaptopropyltriethoxysilane is 1:(0.75-1); the pH is adjusted to 4.5-5; the stirring temperature is 50-55℃ and the stirring time is 1-3h; and the reflux reaction time is 12-16h.

[0010] Preferably, in step (2), the mass ratio of mercaptomodified montmorillonite, camphene, and photoinitiator is 1:(0.6-0.9):(0.012-0.024); the photoinitiator is 2,2-dimethoxy-1,2-diphenyl ethyl ketone; and the irradiation reaction time is 4-8 h.

[0011] Preferably, the flame retardant is prepared as follows: (a) Under inert gas protection, diphenylmethylhydrazine hydrochloride was added to methanol, followed by triethylamine for acid-base neutralization, and then a methanol solution of 2,4,6-trichloro-5-pyrimidinecarboxaldehyde and triethylamine were added for cyclization reaction. After purification, intermediate 1 was obtained. The structural formula of intermediate 1 is: (b) The intermediate 1 was added to dimethyl sulfoxide, and then diethyl (2-aminoethyl)phosphonate hydrochloride and N,N-diisopropylethylamine were added. The mixture was heated and purified to obtain the flame retardant.

[0012] This invention uses 2,4,6-trichloro-5-pyrimidinecarboxaldehyde and diphenylmethylhydrazine hydrochloride as raw materials to construct a pyrazolopyrimidine skeleton through a cyclization reaction to obtain intermediate 1; then, through a substitution reaction between intermediate 1 and (2-aminoethyl)phosphonate diethyl ester hydrochloride, a phosphonate structure is introduced to obtain a flame retardant.

[0013] Preferably, in step (a), the molar ratio of 2,4,6-trichloro-5-pyrimidinecarboxaldehyde to diphenylmethylhydrazine hydrochloride is 1:(1-1.2); in the acid-base neutralization reaction, the molar ratio of diphenylmethylhydrazine hydrochloride to triethylamine is 1:(2-2.5), the temperature is 0-5℃, and the time is 0.5-1h; in the cyclization reaction, the molar ratio of diphenylmethylhydrazine hydrochloride to triethylamine is 1:(1-1.1), the temperature is -10~0℃, and the time is 3-5h; and the concentration of the methanol solution of 2,4,6-trichloro-5-pyrimidinecarboxaldehyde is 0.4-0.5mol / L.

[0014] Preferably, in step (b), the molar ratio of intermediate 1, (2-aminoethyl)phosphonate diethyl ester hydrochloride, and N,N-diisopropylethylamine is 1:(2.4-3.2):(3.2-4); the heating reaction is carried out at a temperature of 100-120°C for 18-24 hours.

[0015] Preferably, the polylactic acid has a weight-average molecular weight of 100,000-120,000; the antioxidant is antioxidant 1010 or antioxidant 1076; and the lubricant is polyethylene wax.

[0016] The second objective of this invention is achieved by the following technical solution: The preparation method of the above-mentioned high-strength flame-retardant packaging material includes the following steps: The raw materials are mixed according to the stated weight proportions, and then extruded, cast, biaxially stretched, and shaped.

[0017] Preferably, the extrusion temperature is 160-190℃; the longitudinal and transverse stretching ratios in the biaxial stretching are both 2-4 times, and the temperature is 75-110℃.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a high-strength flame-retardant packaging material comprising polylactic acid, polybutylene terephthalate-adipate, flame retardant, modified montmorillonite, maleic anhydride-grafted polypropylene, antioxidant, and lubricant. This packaging material possesses excellent flame-retardant, antibacterial, barrier, and mechanical properties.

[0019] 2. This invention enhances the flame retardant and antibacterial properties of packaging materials by adding flame retardants. These flame retardants achieve high-efficiency flame retardancy based on the synergistic effect of a phosphorus-nitrogen-aromatic ring ternary structure: on the one hand, the phosphonates and nitrogen-containing heterocycles they contain synergistically catalyze char formation and gas release during combustion, rapidly constructing a thick, dense, expanded char layer on the material surface, effectively isolating heat and oxygen; on the other hand, the phosphorus-containing free radicals (such as PO·, HPO·) generated by the pyrolysis of phosphonates can capture highly reactive free radicals that maintain the combustion chain reaction, while the non-combustible gases such as NH3 and N2 released by the decomposition of nitrogen-containing heterocycles can dilute the concentration of oxygen and combustible gases in the flame zone, thereby effectively inhibiting flame spread; furthermore, the diphenylmethyl groups in the flame retardant molecule, as a highly efficient char source and thermally stable framework, can effectively increase the char yield, optimize the density and high-temperature resistance of the char layer, forming a complementary and synergistic flame retardant system with phosphonates and nitrogen-containing heterocycles, significantly improving the flame retardant performance of the material. In addition, the pyrazolopyrimidine skeleton in the flame retardant molecule has certain antibacterial activity, giving the material excellent antibacterial properties; while the phosphonate structure and nitrogen-containing heterocycles effectively improve the dispersibility and interfacial bonding of the flame retardant in the polylactic acid matrix by forming hydrogen bonds with the polylactic acid molecular chain, thereby improving the compatibility between the two.

[0020] 3. This invention improves the mechanical and barrier properties of packaging materials by adding modified montmorillonite. The modified montmorillonite has a rigid camphor-based framework grafted onto its surface, which, in synergy with the nano-reinforcing effect of montmorillonite itself, enhances the tensile strength and elastic modulus of the material. Simultaneously, the hydrophobicity of the camphor-based framework and the lamellar barrier effect of montmorillonite work together to effectively reduce the permeability of water vapor and oxygen, thereby improving the material's barrier properties. Attached Figure Description

[0021] Figure 1 The image shows a SEM image of the modified montmorillonite obtained in Example 1 of this invention. Detailed Implementation

[0022] The present invention will now be further described with reference to the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0023] In the examples, the grafting rate of maleic anhydride-grafted polypropylene was 1.2-1.5%, and the melt index was 300-350 g / 10 min; Preparation Example 1 This preparation example provides a modified montmorillonite, and the preparation process is as follows: (1) With the ratio of montmorillonite, 3-mercaptopropyltriethoxysilane and methanol aqueous solution being 1g:0.9g:70mL, 3-mercaptopropyltriethoxysilane was added to 90% (v / v) methanol aqueous solution, the pH was adjusted to 4.7 with 0.2mol / L acetic acid solution, and after stirring at 52℃ for 2h, montmorillonite was added, the temperature was raised, and the reaction was refluxed for 4h. After filtration, the mixture was washed with methanol and dried under vacuum to obtain mercapto-modified montmorillonite. (2) Under nitrogen protection, the mercaptomodified montmorillonite, camphene, 2,2-dimethoxy-1,2-diphenyl ethyl ketone, and tetrahydrofuran were ultrasonically dispersed in tetrahydrofuran at a ratio of 1 g: 0.8 g: 0.02 g: 70 mL. Then, camphene and 2,2-dimethoxy-1,2-diphenyl ethyl ketone (CAS: 24650-42-8) were added. The mixture was reacted under UV light (60 W, 214 nm) for 6 h, filtered, washed successively with tetrahydrofuran and ethanol, and vacuum dried to obtain modified montmorillonite. The SEM image of the modified montmorillonite is shown in [reference needed]. Figure 1 .

[0024] Preparation Example 2 This preparation example provides a modified montmorillonite, and the preparation process is as follows: (1) With the ratio of montmorillonite, 3-mercaptopropyltriethoxysilane and methanol aqueous solution being 1g:0.75g:60mL, 3-mercaptopropyltriethoxysilane was added to 90% (v / v) methanol aqueous solution, the pH was adjusted to 4.5 with 0.2mol / L acetic acid solution, and stirred at 50℃ for 3h. Montmorillonite was then added, the temperature was raised, and the reaction was refluxed for 5h. After filtration, the mixture was washed with methanol and dried under vacuum to obtain mercapto-modified montmorillonite. (2) Under nitrogen protection, the mercaptomodified montmorillonite, camphene, 2,2-dimethoxy-1,2-diphenyl ethyl ketone and tetrahydrofuran were ultrasonically dispersed in tetrahydrofuran at a ratio of 1 g: 0.6 g: 0.012 g: 60 mL. Then camphene and 2,2-dimethoxy-1,2-diphenyl ethyl ketone were added. The mixture was reacted for 4 h under ultraviolet light (60 W, 214 nm), filtered, washed with tetrahydrofuran and ethanol in sequence, and dried under vacuum to obtain modified montmorillonite.

[0025] Preparation Example 3 This preparation example provides a modified montmorillonite, and the preparation process is as follows: (1) With the ratio of montmorillonite, 3-mercaptopropyltriethoxysilane and methanol aqueous solution as 1g:1g:80mL, 3-mercaptopropyltriethoxysilane was added to 90% (v / v) methanol aqueous solution, the pH was adjusted to 5 with 0.2mol / L acetic acid solution, stirred at 55℃ for 1h, montmorillonite was added, the temperature was raised, the reaction was refluxed for 3h, filtered, washed with methanol, and dried under vacuum to obtain mercapto-modified montmorillonite; (2) Under nitrogen protection, the mercaptomodified montmorillonite, camphene, 2,2-dimethoxy-1,2-diphenyl ethyl ketone and tetrahydrofuran were ultrasonically dispersed in tetrahydrofuran at a ratio of 1 g: 0.9 g: 0.024 g: 80 mL. Then camphene and 2,2-dimethoxy-1,2-diphenyl ethyl ketone were added. The mixture was reacted under ultraviolet light (60 W, 214 nm) for 8 h. After filtration, the mixture was washed with tetrahydrofuran and ethanol in sequence and dried under vacuum to obtain modified montmorillonite.

[0026] Preparation Example 4 This preparation example provides a flame retardant, and the preparation process is as follows: (a) Under nitrogen protection, diphenylmethylhydrazine hydrochloride was added to methanol to prepare a 0.46 mol / L methanol solution of diphenylmethylhydrazine hydrochloride; triethylamine was added dropwise to the above solution at 4 °C with a molar ratio of diphenylmethylhydrazine hydrochloride to triethylamine of 1:2.2, and the mixture was stirred for 0.6 h to obtain an acid-base neutralized system; a 0.44 mol / L methanol solution of 2,4,6-trichloro-5-pyrimidinecarboxaldehyde and triethylamine were added dropwise to the above system with a molar ratio of 1:1.1:1.155, and the mixture was subjected to a cyclization reaction at -5 °C for 4 h; after the reaction was completed, the solvent was removed by rotary evaporation, and the residue was purified by column chromatography (V 石油醚 V 乙酸乙酯 =95:5), yielding intermediate 1 (yield 79.7%); the NMR and mass spectrometry results for intermediate 1 are as follows: 1 HNMR: (C 18 H 12 N4Cl2, 400MHz, DMSO- d6 ) δ: 6.26 (s, 1H), 7.16-7.31 (m, 10H), 7.96 (s, 1H). MS (ESI) m / z=354.04 [M].

[0027] (b) Intermediate 1, (2-aminoethyl)phosphonate diethyl hydrochloride, N,N-diisopropylethylamine, and DMSO were dissolved in dimethyl sulfoxide (DMSO) at a ratio of 0.25 mmol:0.7 mmol:0.9 mmol:4 mL. Then, (2-aminoethyl)phosphonate diethyl hydrochloride (CAS: 1089328-92-6) and N,N-diisopropylethylamine were added, and the mixture was stirred for 40 min and heated to 110 °C for 20 h. After the reaction was completed, the reaction solution was cooled to room temperature, diluted with ethyl acetate, washed successively with deionized water and saturated brine, dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by column chromatography (V). 石油醚 V乙酸乙酯 =2:1→1:2), yielding a flame retardant (yield 76.3%); the NMR and mass spectrometry results of the flame retardant are as follows: 1 HNMR: (C 30 H 42 N6O6P2, 400MHz, DMSO- d6 ) δ: 1.34-1.38 (t, 12H), 1.98-2.02 (m, 4H), 3.28-3.32 (t, 4H), 4.17-4.21 (m, 8H), 6.05 (s, 1H), 6.26 (s, 1H), 7.01 (s, 1H), 7.16-7.31 (m, 10H), 7.96 (s, 1H). MS (ESI) m / z=644.26 [M].

[0028] Preparation Example 5 This preparation example provides a flame retardant, and the preparation process is as follows: (a) Under nitrogen protection, diphenylmethylhydrazine hydrochloride was added to methanol to prepare a 0.44 mol / L methanol solution of diphenylmethylhydrazine hydrochloride; triethylamine was added dropwise to the above solution at 0 °C with a molar ratio of diphenylmethylhydrazine hydrochloride to triethylamine of 1:2, and the mixture was stirred for 1 h to obtain an acid-base neutralization system; a 0.4 mol / L methanol solution of 2,4,6-trichloro-5-pyrimidinecarboxaldehyde and triethylamine were added dropwise to the above system with a molar ratio of 1:1:1, and the mixture was subjected to a cyclization reaction at -10 °C for 5 h; after the reaction was completed, the solvent was removed by rotary evaporation, and the residue was purified by column chromatography (V 石油醚 V 乙酸乙酯 =95:5), to obtain intermediate 1 (yield 76.1%); the NMR and mass spectrometry results of intermediate 1 were consistent with those of preparation example 4.

[0029] (b) Intermediate 1, (2-aminoethyl)phosphonate diethyl hydrochloride, N,N-diisopropylethylamine, and DMSO were dissolved in DMSO at a ratio of 0.25 mmol:0.6 mmol:0.8 mmol:3 mL. Then, (2-aminoethyl)phosphonate diethyl hydrochloride and N,N-diisopropylethylamine were added, and the mixture was stirred for 30 min and heated to 100 °C for 24 h. After the reaction was complete, the reaction solution was cooled to room temperature, diluted with ethyl acetate, washed successively with deionized water and saturated brine, dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by column chromatography (V... 石油醚 V 乙酸乙酯 =2:1→1:2), yielding a flame retardant (yield 73.5%); the NMR and mass spectrometry results of the flame retardant were consistent with those of Preparation Example 4.

[0030] Preparation Example 6 This preparation example provides a flame retardant, and the preparation process is as follows: (a) Under nitrogen protection, diphenylmethylhydrazine hydrochloride was added to methanol to prepare a 0.48 mol / L methanol solution of diphenylmethylhydrazine hydrochloride; triethylamine was added dropwise to the above solution at 5 °C with a molar ratio of diphenylmethylhydrazine hydrochloride to triethylamine of 1:2.5, and the mixture was stirred for 0.5 h to obtain an acid-base neutralized system; a 0.5 mol / L methanol solution of 2,4,6-trichloro-5-pyrimidinecarboxaldehyde and triethylamine were added dropwise to the above system with a molar ratio of 1:1.2:1.32, and the mixture was subjected to a cyclization reaction at 0 °C for 3 h; after the reaction was completed, the solvent was removed by rotary evaporation, and the residue was purified by column chromatography (V 石油醚 V 乙酸乙酯 =95:5), to obtain intermediate 1 (yield 77.4%); the NMR and mass spectrometry results of intermediate 1 were consistent with those of preparation example 4.

[0031] (b) Intermediate 1, (2-aminoethyl)phosphonate diethyl hydrochloride, N,N-diisopropylethylamine, and DMSO were dissolved in DMSO at a ratio of 0.25 mmol:0.8 mmol:1 mmol:5 mL. Then, (2-aminoethyl)phosphonate diethyl hydrochloride and N,N-diisopropylethylamine were added, and the mixture was stirred for 45 min and heated to 120 °C for 18 h. After the reaction was complete, the reaction solution was cooled to room temperature, diluted with ethyl acetate, washed successively with deionized water and saturated brine, dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by column chromatography (V... 石油醚 V 乙酸乙酯 =2:1→1:2), yielding a flame retardant (yield 74.8%); the NMR and mass spectrometry results of the flame retardant were consistent with those of Preparation Example 4.

[0032] Example 1 This embodiment provides a high-strength flame-retardant packaging material, which, by weight, includes the following raw materials: 85 parts of polylactic acid (Mw=110,000), 8 parts of poly(butylene terephthalate-adipate-butylene glycol), 10 parts of the flame retardant of Preparation Example 4, 5 parts of the modified montmorillonite of Preparation Example 1, 4 parts of maleic anhydride-grafted polypropylene, 0.4 parts of antioxidant 1010, and 0.6 parts of polyethylene wax.

[0033] This embodiment also provides a method for preparing the above-mentioned high-strength flame-retardant packaging material, including the following steps: According to the above-mentioned weight proportions, the raw materials are added to a twin-screw extruder and extruded at 160-190°C. The extruded materials are then cooled on cooling rollers to obtain cast sheets. The cast sheets are preheated to 95°C and then subjected to biaxial stretching with a longitudinal and transverse stretching ratio of 3 times. After cooling and shaping, the high-strength flame-retardant packaging material is obtained.

[0034] Example 2 This embodiment provides a high-strength flame-retardant packaging material, which, by weight, comprises the following raw materials: 70 parts of polylactic acid (Mw=100,000), 6 parts of poly(butylene terephthalate-adipate-butylene glycol), 4 parts of the flame retardant of Preparation Example 5, 3 parts of the modified montmorillonite of Preparation Example 2, 3 parts of maleic anhydride-grafted polypropylene, 0.3 parts of antioxidant 1010, and 0.5 parts of polyethylene wax.

[0035] This embodiment also provides a method for preparing the above-mentioned high-strength flame-retardant packaging material, including the following steps: According to the above-mentioned weight proportions, the raw materials are added to a twin-screw extruder and extruded at 160-190°C. The extruded materials are then cooled on cooling rollers to obtain cast sheets. The cast sheets are preheated to 75°C and then subjected to biaxial stretching with a longitudinal and transverse stretching ratio of 2 times. After cooling and shaping, the high-strength flame-retardant packaging material is obtained.

[0036] Example 3 This embodiment provides a high-strength flame-retardant packaging material, which, by weight, comprises the following raw materials: 90 parts of polylactic acid (Mw=120,000), 12 parts of poly(butylene terephthalate-adipate-butylene glycol), 15 parts of the flame retardant of Preparation Example 6, 7 parts of modified montmorillonite of Preparation Example 3, 5 parts of maleic anhydride-grafted polypropylene, 0.5 parts of antioxidant 1076, and 1 part of polyethylene wax.

[0037] This embodiment also provides a method for preparing the above-mentioned high-strength flame-retardant packaging material, including the following steps: According to the above-mentioned weight proportions, the raw materials are added to a twin-screw extruder and extruded at 160-190°C. The extruded materials are then cooled on cooling rollers to obtain cast sheets. The cast sheets are preheated to 110°C and then subjected to biaxial stretching with a longitudinal and transverse stretching ratio of 4 times. After cooling and shaping, the high-strength flame-retardant packaging material is obtained.

[0038] Comparative Example 1 The difference between this comparative example and Example 1 is that the flame retardant used in Example 4 is omitted.

[0039] Comparative Example 2 The difference between this comparative example and Example 1 is that the modified montmorillonite in Preparation Example 1 is replaced with montmorillonite.

[0040] Experimental Example 1 The water vapor barrier properties of the packaging materials prepared in the examples or comparative examples were tested according to standard GB / T 1037-2021, and the results are shown in Table 1. The oxygen barrier properties of the packaging materials prepared in the examples or comparative examples were tested according to standard GB / T 1038.1-2022, and the results are shown in Table 1.

[0041] Table 1 The results in Table 1 show that the high-strength flame-retardant packaging material of the present invention exhibits extremely low water vapor and oxygen permeability, demonstrating excellent barrier properties. Comparative Example 2, lacking modified montmorillonite, showed a significant decrease in barrier performance, proving that modified montmorillonite is a key component for improving the barrier properties of the packaging material. In summary, the present invention effectively extends the diffusion path of gas molecules through the layered barrier effect of modified montmorillonite, giving the packaging material excellent barrier capabilities.

[0042] Experimental Example 2 Antibacterial properties: The antibacterial properties of the packaging materials prepared in the examples or comparative examples were tested according to standard QB / T 31402-2015. The test strains were Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 25922. The test results are shown in Table 2.

[0043] Table 2 The results in Table 2 show that the high-strength flame-retardant packaging material provided by this invention exhibits excellent inhibitory effects against both Staphylococcus aureus and Escherichia coli. Comparative Example 1, lacking the addition of a flame retardant, showed a significantly reduced antibacterial rate, indicating that the flame retardant is a key component contributing to the material's high antibacterial properties. Comparative Example 2, without the addition of modified montmorillonite, showed an antibacterial rate essentially the same as the examples, demonstrating that modified montmorillonite has no significant impact on the material's antibacterial properties. In summary, this invention, by introducing a flame retardant containing a pyrazolopyrimidine skeleton, enables the packaging material to possess excellent antibacterial properties.

[0044] Experimental Example 3 Mechanical properties: The tensile strength and elastic modulus of the packaging materials prepared in the examples or comparative examples were tested using a universal electronic testing machine in accordance with the standard GB / T 1040.3-2006. The tensile rate was 50 mm / min. The results are shown in Table 3.

[0045] Flame retardant properties: The limiting oxygen index (LOI) of the packaging materials prepared in the examples or comparative examples was tested according to GB / T 2406.2-2009 "Determination of flammability of plastics by oxygen index method - Part 2: Room temperature test". The results are shown in Table 3.

[0046] Table 3 The results in Table 3 show that the packaging material of the present invention possesses both excellent mechanical and flame-retardant properties. The LOI of Comparative Example 1 is significantly lower, but its tensile strength and elastic modulus are essentially the same as those of Example 1, demonstrating that the flame retardant is the key component for improving flame-retardant performance while having little impact on mechanical properties. The tensile strength and elastic modulus of Comparative Example 2 are much lower than those of the examples, while its LOI is comparable to that of Example 1, indicating that the modified montmorillonite mainly contributes to mechanical reinforcement and has little impact on flame-retardant performance. In summary, the present invention, through the rational compounding of flame retardant and modified montmorillonite, enables the packaging material to simultaneously achieve high tensile strength, high elastic modulus, and excellent flame-retardant properties.

[0047] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A high-strength flame-retardant packaging material, characterized in that, By weight, it includes the following raw materials: 70-90 parts polylactic acid, 6-12 parts polybutylene terephthalate-adipate, 4-15 parts flame retardant, 3-7 parts modified montmorillonite, 3-5 parts maleic anhydride-grafted polypropylene, 0.3-0.5 parts antioxidant, and 0.5-1 parts lubricant. The structural formula of the flame retardant is: 。 2. The high-strength flame-retardant packaging material according to claim 1, characterized in that, The preparation process of the modified montmorillonite is as follows: (1) Add 3-mercaptopropyltriethoxysilane to an aqueous methanol solution, adjust the pH and stir, then add montmorillonite and reflux reaction, purify, and obtain mercapto-modified montmorillonite; (2) Under the protection of an inert gas, the mercaptomodified montmorillonite was added to tetrahydrofuran, then camphene and a photoinitiator were added, the reaction was carried out by irradiation, and the mixture was purified to obtain the modified montmorillonite.

3. The high-strength flame-retardant packaging material according to claim 2, characterized in that, In step (1), the mass ratio of montmorillonite to 3-mercaptopropyltriethoxysilane is 1:(0.75-1); the pH is adjusted to 4.5-5; the stirring temperature is 50-55℃ and the stirring time is 1-3h; the reflux reaction time is 3-5h.

4. The high-strength flame-retardant packaging material according to claim 2, characterized in that, In step (2), the mass ratio of mercaptomodified montmorillonite, camphene, and photoinitiator is 1:(0.6-0.9):(0.012-0.024); the photoinitiator is 2,2-dimethoxy-1,2-diphenyl ethyl ketone; and the irradiation reaction time is 4-8 h.

5. The high-strength flame-retardant packaging material according to claim 1, characterized in that, The preparation process of the flame retardant is as follows: (a) Under inert gas protection, diphenylmethylhydrazine hydrochloride was added to methanol, followed by triethylamine for acid-base neutralization, and then a methanol solution of 2,4,6-trichloro-5-pyrimidinecarboxaldehyde and triethylamine were added for cyclization reaction. After purification, intermediate 1 was obtained. The structural formula of intermediate 1 is: (b) The intermediate 1 was added to dimethyl sulfoxide, and then diethyl (2-aminoethyl)phosphonate hydrochloride and N,N-diisopropylethylamine were added. The mixture was heated and purified to obtain the flame retardant.

6. The high-strength flame-retardant packaging material according to claim 5, characterized in that, In step (a), the molar ratio of 2,4,6-trichloro-5-pyrimidinecarboxaldehyde to diphenylmethylhydrazine hydrochloride is 1:(1-1.2); in the acid-base neutralization reaction, the molar ratio of diphenylmethylhydrazine hydrochloride to triethylamine is 1:(2-2.5), the temperature is 0-5℃, and the time is 0.5-1h; in the cyclization reaction, the molar ratio of diphenylmethylhydrazine hydrochloride to triethylamine is 1:(1-1.1), the temperature is -10~0℃, and the time is 3-5h; the concentration of the methanol solution of 2,4,6-trichloro-5-pyrimidinecarboxaldehyde is 0.4-0.5mol / L.

7. The high-strength flame-retardant packaging material according to claim 5, characterized in that, In step (b), the molar ratio of intermediate 1, (2-aminoethyl)phosphonate diethyl ester hydrochloride, and N,N-diisopropylethylamine is 1:(2.4-3.2):(3.2-4); the heating reaction is carried out at a temperature of 100-120°C for 18-24 hours.

8. The high-strength flame-retardant packaging material according to claim 1, characterized in that, The polylactic acid has a weight-average molecular weight of 100,000-120,000; the antioxidant is antioxidant 1010 or antioxidant 1076; and the lubricant is polyethylene wax.

9. A method for preparing a high-strength flame-retardant packaging material according to any one of claims 1-8, characterized in that, Includes the following steps: The raw materials are mixed according to the stated weight proportions, and then extruded, cast, biaxially stretched, and shaped.

10. The method for preparing the high-strength flame-retardant packaging material according to claim 9, characterized in that, The extrusion temperature is 160-190℃; the longitudinal and transverse stretching ratios in the biaxial stretching are both 2-4 times, and the temperature is 75-110℃.

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