Low-temperature impact resistant food packaging material and preparation method and application thereof

Abstract

The application provides a low-temperature impact-resistant food packaging material and a preparation method and application thereof. The low-temperature impact-resistant food packaging material comprises the following raw materials in parts by mass: 100 parts by mass of polylactic acid, 1-10 parts by mass of modified layered double hydroxide, and 5-40 parts by mass of hyperbranched polyester. The modified layered double hydroxide is obtained by treating layered double hydroxide with a complex anionic surfactant and then treating the layered double hydroxide with an organic cationic compound with a long alkyl chain. The complex anionic surfactant comprises a first anionic surfactant and a second anionic surfactant. The first anionic surfactant comprises sodium dodecyl sulfonate. The second anionic surfactant comprises a sulfonate anionic surfactant containing an amide bond and a catechol structure. Through the above formula design, the impact toughness of the material at low temperature can be improved while the mechanical properties of polylactic acid are maintained, and the material can be applied to the field of food packaging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food packaging, in particular to a low-temperature impact resistant food packaging material and a preparation method and application thereof. BACKGROUND

[0002] With the promotion of plastic ban and the increasing environmental awareness of people, biodegradable materials are increasingly widely used in the field of food packaging. As a biodegradable and environmentally friendly material, polylactic acid (PLA) has good mechanical strength and transparency, and is one of the solutions to replace traditional petroleum-based plastic packaging materials.

[0003] However, PLA itself is relatively brittle and has weak low-temperature impact resistance, which limits its application in cold storage and frozen food packaging. In a low-temperature environment, PLA resin is prone to cracking and breaking, which affects the integrity of the packaging. The brittleness of polylactic acid material is a technical bottleneck that hinders the large-scale promotion of polylactic acid in frozen packaging.

[0004] In the prior art, researchers mostly improve the toughness of PLA by adding toughening agents or elastomers. For example, patent CN105623218B discloses an inorganic composite nano antibacterial heat-resistant polylactic acid master batch, which mainly relies on a large amount of toughening and plasticizing agents and lubricating and plasticizing agents to improve the toughness of PLA. However, the problem with the above patent is that adding a large amount of toughening and plasticizing agents and lubricating and plasticizing agents improves the toughness at the expense of reducing the rigidity and transparency of PLA. In addition, due to compatibility problems, there may be migration problems during subsequent use, which does not meet the relevant regulatory requirements for food contact materials.

[0005] Therefore, it is necessary to modify PLA to develop a PLA material with excellent comprehensive performance and low-temperature impact resistance to meet the application requirements in the field of food packaging. SUMMARY

[0006] The present application provides a low-temperature impact resistant food packaging material and a preparation method and application thereof. The food packaging material introduces modified layered double hydroxide (LDH) and hyperbranched polyester into the polylactic acid matrix, thereby maintaining the original mechanical properties of PLA while having good low-temperature impact resistance.

[0007] In a first aspect, the application provides a low-temperature impact resistant food packaging material, comprising the following raw materials by mass: 100 parts of polylactic acid, 1-10 parts of modified layered double hydroxide, and 5-40 parts of hyperbranched polyester; wherein the modified layered double hydroxide is obtained by treating layered double hydroxide with a complex anionic surfactant, and then treating the layered double hydroxide with an organic cationic compound having a long alkyl chain; the complex anionic surfactant comprises a first anionic surfactant and a second anionic surfactant; wherein the first anionic surfactant comprises at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium laurate; and the second anionic surfactant comprises a sulfonate anionic surfactant containing an amide bond and a catechol structure.

[0008] According to the application, by introducing modified layered double hydroxide and hyperbranched polyester into polylactic acid, the interface compatibility between the filler and the PLA matrix is good, which can improve the low-temperature toughness of PLA, and at the same time, the original high strength of PLA is not reduced, and the problems of packaging deformation, collapse, rupture, etc. caused by the decrease in strength are reduced.

[0009] Specifically, by introducing modified layered double hydroxide into PLA, the strength and toughness of PLA can be improved. First, the layered double hydroxide is treated with a complex anionic surfactant. The first anionic surfactant can replace the original inorganic anions in the interlayer of LDH through ion exchange, and the long alkyl chain of the first anionic surfactant can expand the interlayer spacing of LDH by hydrophobic effect and steric hindrance, which can reduce the interaction between the interlayers of LDH, so that the material can slide between the interlayers to absorb impact energy when subjected to low-temperature impact. At the same time, it provides a basis for the subsequent intercalation and anchoring of the second anionic surfactant. The second anionic surfactant can partially intercalate in the LDH with expanded interlayer spacing due to its molecular structure, thereby further increasing the interlayer spacing and enhancing the interlayer sliding ability of LDH. The sulfonate anionic surfactant containing an amide bond and a catechol structure can be chelated with metal ions on the LDH layer by the catechol structure, thereby being stably combined with the LDH surface. The amide bond can form hydrogen bonds with the carbonyl group of PLA, and the sulfonate is a strong electron-withdrawing group that can enhance the polarity of the amide group through electron-withdrawing effect, thereby forming more stable hydrogen bonds when the amide group contacts the carbonyl group in PLA, which is conducive to the transmission of stress to the LDH phase, thereby making the material exhibit better low-temperature toughness at low temperatures. This treatment not only increases the interlayer spacing of LDH, but also enhances the interface compatibility between the layered double hydroxide and PLA, providing good surface activity for the subsequent treatment of the organic cationic compound.

[0010] Then, after being treated by the organic cationic compound with long alkyl chain, part of the cations can enter the interlayer of LDH and combine with the anions through electrostatic interaction, further expanding the interlayer spacing, and part of the cations can be adsorbed on the surface of the LDH treated by the complex anion surfactant through hydrophobic interaction or electrostatic interaction. The LDH treated in the above manner can increase the low-temperature toughness of PLA while ensuring the strength, the organic cationic compound with long alkyl chain further improves the interfacial compatibility, the amide group can form hydrogen bonds with PLA, and the catechol group can strongly bind to LDH, thereby enhancing the interfacial bonding force between LDH and the PLA matrix. External stress can be effectively transferred from PLA to LDH, reducing stress concentration and cracking of the PLA body, and at the same time, the modified LDH has an expanded interlayer spacing. When the crack propagates to the LDH, the lamellar structure can slip and consume energy, thereby inhibiting the continuous propagation of the crack. The modified LDH nanoplatelets have good compatibility with the PLA matrix and can be uniformly dispersed in the PLA matrix. The modified LDH nanoplatelets with catechol groups, amide bonds and long alkyl chains can act as heterogeneous nucleation sites and promote the formation of fine crystals on the particle surface, thereby assisting in improving the toughness of the material.

[0011] The hyperbranched polyester in the PLA system acts as a flexible phase on one hand, and as a stress concentration point to absorb energy when subjected to stress impact, thereby increasing the toughness; on the other hand, when blended with PLA, the hyperbranched polyester can increase the molecular weight spacing between the PLA molecular chains, thereby increasing the free volume of molecular motion of the PLA matrix and the movement ability of the PLA molecular chains. Therefore, at low temperatures, the PLA can still maintain good toughness.

[0012] Through the above-mentioned raw materials, the balance between strength and toughness of PLA can be achieved. The modified LDH improves the interfacial bonding force through its rigid nanosheet structure and the hydrogen bonds and hydrophobic interactions formed with the PLA matrix, can effectively transfer and bear stress, and ensures the strength of the material. At the same time, its expanded interlayer spacing can slip under impact to inhibit crack propagation, and the hyperbranched polyester acts as a dispersed flexible phase to absorb a large amount of impact energy by inducing crazing and shear bands, thereby improving the low-temperature toughness. The two can synergistically increase the low-temperature toughness of the material without sacrificing the strength, thereby obtaining a PLA material resistant to low-temperature impact.

[0013] In some embodiments, the sulfonate anionic surfactant containing amide bonds and catechol structures is obtained by condensation of a benzoic acid compound with a catechol structure with taurine; wherein the benzoic acid compound with a catechol structure is 3,4-dihydroxybenzoic acid.

[0014] In some of the above embodiments, the carboxyl group in the benzoic acid compound with catechol structure can be amidated and condensed with the amino group in the taurine molecule to form a sulfonate anionic surfactant containing an amide bond and a catechol structure. The catechol group can form a strong coordination bond with the metal ions on the LDH layer, thereby enhancing the interfacial bonding between the surfactant and the inorganic filler and the polymer matrix.

[0015] In some embodiments, the sulfonate anionic surfactant containing an amide bond and a catechol structure is prepared by the following method:

[0016] M1: 10 parts by mass of 3,4-dihydroxybenzoic acid, 40-60 parts by mass of acetic anhydride, and 0.5-1 part by mass of anhydrous sodium acetate are mixed and reacted at 80-100°C for 2-4 hours to obtain 3,4-diacetyloxybenzoic acid;

[0017] M2: 10 parts by mass of 3,4-diacetyloxybenzoic acid, 15-25 parts by mass of thionyl chloride, and 0.1-0.5 parts by mass of N,N-dimethylformamide are mixed in 60-100 parts by mass of anhydrous tetrahydrofuran, and reacted at 60-70°C for 4-6 hours to obtain a 3,4-diacetyloxybenzoyl chloride intermediate;

[0018] M3: 8-12 parts by mass of taurine, 2-4 parts by mass of sodium hydroxide are dissolved in 80-200 parts by mass of deionized water, and then mixed with 10 parts by mass of the 3,4-diacetyloxybenzoyl chloride intermediate, 40-80 parts by mass of tetrahydrofuran, and 3-5 parts by mass of triethylamine, and reacted at 20-30°C for 10-14 hours to obtain a solution containing 3,4-diacetyloxy-N-(2-sulfonatoethyl) benzamide sodium salt;

[0019] M4: 20-40 parts by mass of methanol and 4-8 parts by mass of sodium hydroxide are added to the above solution containing 3,4-diacetyloxy-N-(2-sulfonatoethyl) benzamide sodium salt, and reacted at 20-30°C for 2-4 hours. The pH is adjusted to 7-8 using 0.1 mol / L hydrochloric acid, and then the product is obtained by distillation under reduced pressure, washing, and drying to obtain 3,4-dihydroxy-N-(2-sulfonatoethyl) benzamide sodium salt as a sulfonate anionic surfactant containing an amide bond and a catechol structure.

[0020] In some of the above embodiments, the reaction conditions and the amount ratio of each step in the preparation process of the sulfonate anionic surfactant containing an amide bond and a catechol structure are specifically described. Under these conditions, an anionic surfactant containing both an amide bond and a catechol structure can be obtained.

[0021] In some embodiments, the long alkyl chain bearing organic cationic compound comprises a long chain quaternary ammonium cationic compound with a carbon chain length of C14-C18.

[0022] In some of the above embodiments, the inventors found that the long alkyl chain bearing organic cationic compound with a carbon chain length of C14-C18 results in a PLA material with better low temperature toughness. This can be attributed to the fact that the long alkyl chain, when the organic cationic compound is used to treat the LDH, serves as a compatibility agent on one hand, by its hydrophobic segment to bind with PLA molecules, improving the dispersion of LDH in the matrix, and on the other hand, part of the cation binds with the interlayer anions of the LDH through electrostatic interaction, further expanding the interlayer distance. This kind of compound can act as a molecular bridge, one end of which binds with the LDH, and the other end of which physically entangles with the PLA molecules, thereby improving the efficiency of stress transfer from PLA to LDH. As an example, in one embodiment of the present application, the long alkyl chain bearing organic cationic compound used is cetyltrimethylammonium chloride.

[0023] In some embodiments, the method for preparing the modified layered double hydroxide comprises the following steps:

[0024] S1: dispersing the layered double hydroxide in water, adding a complex anion surfactant under an inert atmosphere to replace the inorganic anions between the layers of the layered double hydroxide, to obtain a complex anion surfactant treated layered double hydroxide;

[0025] S2: dispersing the complex anion surfactant treated layered double hydroxide of S1 and the long alkyl chain bearing organic cationic compound in an aqueous ethanol solution, to allow part of the organic cation to enter the interlayer, to obtain the modified layered double hydroxide.

[0026] In some of the above embodiments, the modification of the layered double hydroxide by the above steps of pre-anion intercalation and post-cation adsorption enables the LDH to interact with the PLA matrix. In the above modification process, the first step is to treat the LDH with a composite anionic surfactant. The catechol group in the composite anionic surfactant can form a stable bond with the metal ions in the LDH layer, and then the amide bond is formed. Subsequently, the long alkyl chain organic cation is adsorbed by hydrophobic interaction and electrostatic adsorption. The modified LDH has good interfacial compatibility with the PLA matrix. The long alkyl chain can be entangled with the PLA molecular chain by hydrophobic interaction, thereby improving the dispersibility of the LDH in the PLA matrix. The expanded interlayer spacing can enable the LDH to absorb and dissipate energy by lamellar slip when subjected to external force impact. At low temperatures, the stress will preferentially break the hydrogen bond between the amide bond and the carbonyl group of PLA due to the strong bonding of the catechol group, thereby reducing the possibility of irreversible destruction of the weak ionic bond between the anionic surfactant and the LDH, which causes the anionic surfactant to desorb from the LDH. The broken hydrogen bond can absorb impact energy and reconfigure, thereby enabling the stress to be effectively transferred from the PLA to the LDH at low temperatures. The physical entanglement of the alkyl chain with the PLA matrix can also improve the interfacial bonding and the efficiency of stress transfer from the PLA to the LDH filler, thereby improving the low-temperature toughness of the system.

[0027] In some embodiments, step S1 comprises: S1 comprises dispersing 100 parts of the layered double hydroxide in 300-500 parts of water, adding 100-200 parts of the first anionic surfactant and 20-60 parts of the sulfonate anionic surfactant containing an amide bond and a catechol structure under nitrogen protection, and reacting at 60-80°C for 18-24 hours to obtain the layered double hydroxide treated with the composite anionic surfactant.

[0028] In some of the above embodiments, based on 100 parts of the layered double hydroxide, 100-200 parts of the first anionic surfactant and 20-60 parts of the sulfonate anionic surfactant containing an amide bond and a catechol structure are used. The first anionic surfactant can displace the original inorganic anion due to its molecular structure, thereby expanding the interlayer spacing. The sulfonate anionic surfactant containing an amide bond and a catechol structure has low interlayer exchange efficiency due to the large steric hindrance and layer interaction, and preferentially adheres to the surface of the LDH particles. This layer of coating not only provides certain hydrophobicity, but also provides a good reaction platform for the electrostatic adsorption of cations in step S2, thereby facilitating the improvement of the low-temperature resistance of the material.

[0029] In some embodiments, step S2 comprises: dispersing 100 parts of the layered double hydroxide treated by the composite anionic surfactant and 50-100 parts of the organic cationic compound with long alkyl chain in 400-600 parts of the aqueous ethanol solution, and reacting at 40-60℃ for 6-12h to obtain the modified layered double hydroxide.

[0030] In some embodiments described above, based on 100 parts of the layered double hydroxide treated by the composite anionic surfactant, 50-100 parts of the organic cationic compound with long alkyl chain is used, and the reaction is carried out in 400-600 parts of the aqueous ethanol solution at 40-60℃ for 6-12h, which can realize sufficient action between the cation and the LDH, change the surface of the LDH from hydrophilic to partially hydrophobic, further enhance the interfacial compatibility of the LDH and the PLA matrix, and provide favorable conditions for stress transfer, thereby helping to improve the toughness of the material under low-temperature impact conditions.

[0031] In some embodiments, the LDH has a flake diameter of 0.5-2μm. The LDH with the flake diameter in the above range is beneficial to form a continuous layered structure in the PLA matrix, which can provide effective stress transfer, thereby improving the low-temperature toughness of the material while ensuring the strength. As an example, in an embodiment of the present application, the LDH with a flake diameter of 0.7μm is used.

[0032] In some embodiments, the polylactic acid comprises poly-L-lactic acid with a weight average molecular weight of 100000Da-200000Da. The poly-L-lactic acid with the weight average molecular weight in the above range has good strength and can meet the performance requirements of low-temperature resistant food packaging materials. As an example, in an embodiment of the present application, the poly-L-lactic acid with a weight average molecular weight of 140000Da is used.

[0033] In some embodiments, the hyperbranched polyester comprises one of G2-G4 generation hyperbranched polyester, and the hyperbranched polyester molecule has an aliphatic skeleton and a carboxyl or hydroxyl end group.

[0034] In some of the above embodiments, the hyperbranched polyester with G2-G4 aliphatic skeleton and terminal functional groups of hydroxyl or carboxyl groups can result in the best low-temperature toughness of the PLA material. The hyperbranched polyester with aliphatic skeleton itself has good low-temperature toughness. Compared with hyperbranched polyesters of higher generations, the G2-G4 hyperbranched polyesters can have more suitable molecular size and branching structure, which can be uniformly dispersed in the PLA matrix as nanoparticles, effectively initiate crazing and dissipate energy when impacted, and improve the low-temperature toughness. At the same time, the G2-G4 hyperbranched polyesters have more terminal hydroxyl or carboxyl functional groups than the hyperbranched polyesters of lower generations. These functional groups can form a hydrogen bond network with the PLA molecular chain on the one hand, significantly improve the compatibility and prevent phase separation, and on the other hand, act as a potential nucleating agent to induce the PLA to form fine and regular crystal structure, reducing the brittleness caused by large spherocrystals. More importantly, these functional groups can produce electrostatic interaction with the layered double hydroxide modified by long alkyl chain cations, like a "molecular bridge" to firmly combine the inorganic nano-filler with the organic polymer matrix, enhance the interfacial strength, further improve the stress transfer between the matrix and the LDH, improve the mechanical enhancement effect of the LDH on the PLA material, thereby weakening the possible decrease in mechanical properties after adding the flexible component, thereby improving the impact resistance of the material at low temperature while maintaining the strength of the material.

[0035] In some embodiments, the weight average molecular weight of the hyperbranched polyester is 2000-12000 Da. As an example, in an embodiment of the present application, a G3 generation carboxyl-terminated hyperbranched polyester with a weight average molecular weight of 6400 Da is used.

[0036] In some embodiments, the first anionic surfactant includes sodium dodecyl sulfonate. In some of the above embodiments, the inventors found that when sodium dodecyl sulfonate is used to treat the LDH, the low-temperature toughness of the PLA material is better, which can be due to the fact that the sulfonate group has strong ionicity, can be more effectively replaced into the interlayer of the LDH by ion exchange, expand the interlayer spacing, and make the lamellar structure have greater slip to consume more energy, thereby enhancing the low-temperature toughness of the PLA material.

[0037] In some embodiments, the raw material further includes 0.1-0.5 parts by mass of an antioxidant, and the antioxidant includes at least one of antioxidant 1010 and antioxidant 168. By introducing the antioxidant into the system, the oxidation of polylactic acid and pyrocatechol groups during the processing and use can be effectively reduced, and the mechanical property decline caused by oxidation can be reduced, thereby further ensuring the stability of the material performance during long-term use.

[0038] In a second aspect, the present application provides a method for preparing a low-temperature impact-resistant food packaging material, comprising:

[0039] The raw material contained in the food packaging material according to any one of the embodiments of the first aspect is provided;

[0040] The raw material is mixed and melt-extruded to obtain the food packaging material.

[0041] According to the present application, in the food packaging material prepared by the above method, the modified layered double hydroxide and the polylactic acid matrix form a good interfacial bond, which can improve the low-temperature impact toughness while maintaining the original high strength of the polylactic acid; at the same time, the introduction of hyperbranched polyester further provides a flexible phase and intermolecular free volume for the system, thereby increasing the energy absorption and stress dispersion capacity of the PLA material, so that the obtained food packaging material can maintain good mechanical properties and stability in a low-temperature environment, reducing the problems of deformation, collapse or damage caused by brittle fracture during the packaging process and use.

[0042] In a third aspect, the present application provides a food packaging bag comprising the low-temperature impact-resistant food packaging material according to any one of the embodiments of the first aspect or the food packaging material prepared by the method according to any one of the embodiments of the second aspect.

[0043] According to the present application, the food packaging bag made of the above food packaging material can maintain high strength and high toughness in a low-temperature environment, reducing the problems of rupture and leakage caused by brittle fracture, thereby improving the safety and integrity of food during storage and transportation, and meeting the requirements of cold chain packaging for low-temperature impact resistance.

[0044] Compared with the prior art, the present application has at least the following beneficial effects:

[0045] By synergistically introducing modified layered double hydroxide and hyperbranched polyester into the polylactic acid system, the catechol groups and amide bonds synergistically improve the interfacial bonding between LDH-PLA, reduce the interfacial debonding between LDH and PLA under low-temperature stress impact conditions, utilize strong coordination groups to achieve interfacial anchoring, and optimize stress transmission and dissipation through various interactions, thereby simultaneously improving the rigidity and toughness in the matrix and improving the balance between low-temperature impact resistance and mechanical strength of the material. Thus, the prepared food packaging material not only has normal-temperature mechanical properties, but also has certain low-temperature impact toughness, which can meet the use requirements in cold chain transportation, frozen storage and other environments, reducing the deformation, collapse and rupture of the packaging. DETAILED DESCRIPTION

[0046] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments.

[0047] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" and the like means that the specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. The exemplary expressions of the above terms in the present specification do not necessarily refer to the same embodiment or example. Also, the specific feature, structure, material or characteristic described can be combined in any one or more embodiments or examples in a suitable manner.

[0048] Further, the terms "first", "second", and the like are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Thus, the features defined with "first", "second" can include at least one of the features, explicitly or implicitly. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, and the like, unless otherwise specifically limited.

[0049] In the description of the present specification, "parts" means "mass parts" unless otherwise specifically described.

[0050] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are for the purpose of explanation of the present application only, and cannot be understood as a limitation on the present application. In the embodiments, the specific techniques or conditions not described are performed according to the techniques or conditions described in the literature in the art or according to the product manual. The reagents or instruments not described by the manufacturer are all conventional products that can be obtained by purchase on the market.

[0051] LDH, model FM-300, magnesium-aluminum ratio 4.3, average particle size 0.7 μm;

[0052] Aliphatic hyperbranched polyester: G3 generation carboxyl-terminated hyperbranched polyester HyperC103, weight average molecular weight 6400; G1 generation carboxyl-terminated hyperbranched polyester HyperC101, weight average molecular weight 1000;

[0053] Aromatic hyperbranched polyester: G3 generation carboxyl-terminated hyperbranched polyester HyperC203, weight average molecular weight 5200;

[0054] Cetyltrimethylammonium chloride, CAS No. 112-02-7;

[0055] Antioxidant 1010, CAS No. 6683-19-8;

[0056] Polylactic acid, poly-L-lactic acid RE110 for extrusion, weight average molecular weight 140000 Da;

[0057] Sodium methylolaur-oyl taurate, CAS No. 137-20-2;

[0058] Octyltrimethylammonium chloride, CAS No.: 10108-86-8;

[0059] Sodium dodecylsulfonate, CAS No.: 2386-53-0;

[0060] 3,4-Dihydroxybenzoic acid, CAS No.: 99-50-3;

[0061] Taurine, CAS No.: 107-35-7;

[0062] Sodium laurate, CAS No.: 629-25-4.

[0063] Preparation of sulfonate anionic surfactant containing amide bond and catechol structure:

[0064] M1: 10 parts by mass of 3,4-dihydroxybenzoic acid, 50 parts by mass of acetic anhydride, and 0.75 parts by mass of anhydrous sodium acetate were mixed and reacted at 85°C for 3 hours. After the reaction, the product was washed with deionized water and dried at 50°C to obtain 3,4-diacetyloxybenzoic acid;

[0065] M2: 10 parts by mass of 3,4-diacetyloxybenzoic acid was dissolved in 80 parts by mass of anhydrous tetrahydrofuran, and 20 parts by mass of thionyl chloride was added dropwise under stirring in an ice water bath at 0°C. After the dropwise addition was completed, 0.3 parts by mass of N,N-dimethylformamide was added, and the mixture was reacted at 65°C for 5 hours. After the reaction, the thionyl chloride and the solvent were removed by distillation under reduced pressure at 45°C to obtain a 3,4-diacetyloxybenzoyl chloride intermediate;

[0066] M3: 10 parts by mass of taurine was dissolved in 100 parts by mass of deionized water, and 3 parts by mass of sodium hydroxide was added under stirring in an ice water bath at 0°C to obtain a taurine sodium aqueous solution. Then, 10 parts by mass of 3,4-diacetyloxybenzoyl chloride intermediate and 4 parts by mass of triethylamine were dissolved in 60 parts by mass of tetrahydrofuran at 0°C to obtain a mixed solution of the 3,4-diacetyloxybenzoyl chloride intermediate. The mixed solution of the 3,4-diacetyloxybenzoyl chloride intermediate was added to the taurine sodium aqueous solution, and the mixture was reacted at 25°C for 12 hours to obtain a solution containing 3,4-diacetyloxy-N-(2-sulfonatoethyl) benzamide sodium salt;

[0067] M4: To the above solution containing 3,4-diacetyloxy-N-(2-sulfonatoethyl) benzamide sodium salt, 30 parts by mass of methanol and 6 parts by mass of sodium hydroxide were added, and the mixture was reacted at 25°C for 3 hours. The pH was adjusted to 7.5 using 0.1 mol / L hydrochloric acid, and after removing water and organic solvents by distillation under reduced pressure, the mixture was washed three times with anhydrous ethanol and dried at 60°C to obtain 3,4-dihydroxy-N-(2-sulfonatoethyl) benzamide sodium salt as a sulfonate anionic surfactant containing an amide bond and catechol structure.

[0068] Preparation of carboxylate anionic surfactant containing an amide bond and catechol structure:

[0069] N1: 10 parts by mass of 3,4-dihydroxybenzoic acid, 50 parts by mass of acetic anhydride, and 0.75 parts by mass of anhydrous sodium acetate were mixed and reacted at 85°C for 3 hours. After the reaction, the mixture was washed with deionized water and dried at 50°C to obtain 3,4-diacetyloxybenzoic acid.

[0070] N2: 10 parts by mass of 3,4-diacetyloxybenzoic acid was dissolved in 80 parts by mass of anhydrous tetrahydrofuran, and 20 parts by mass of thionyl chloride was added dropwise under stirring in an ice water bath at 0°C. After the dropwise addition was completed, 0.3 parts by mass of N,N-dimethylformamide was added, and the mixture was reacted at 65°C for 5 hours. After the reaction, thionyl chloride and the solvent were removed by distillation under reduced pressure at 45°C to obtain 3,4-diacetyloxybenzoyl chloride intermediate.

[0071] N3: 10 parts by mass of glycine was dissolved in 100 parts by mass of deionized water, and 3 parts by mass of sodium hydroxide was added under stirring in an ice water bath at 0°C to obtain a glycine sodium aqueous solution. Then, 10 parts by mass of 3,4-diacetyloxybenzoyl chloride intermediate and 4 parts by mass of triethylamine were dissolved in 60 parts by mass of tetrahydrofuran to obtain a mixed solution of 3,4-diacetyloxybenzoyl chloride intermediate. The mixed solution of 3,4-diacetyloxybenzoyl chloride intermediate was added to the glycine sodium aqueous solution, and the mixture was reacted at 25°C for 12 hours to obtain a solution containing 3,4-diacetyloxy-N-(carboxymethyl) benzamide sodium salt.

[0072] N4: To the above solution containing 3,4-diacetyloxy-N-(carboxymethyl) benzamide sodium salt, 30 parts by mass of methanol and 6 parts by mass of sodium hydroxide were added, and the mixture was reacted at 25°C for 3 hours. The pH was adjusted to 7.5 using 0.1 mol / L hydrochloric acid, and after removing water and organic solvents by distillation under reduced pressure, the mixture was washed three times with anhydrous ethanol and dried at 60°C to obtain 3,4-dihydroxy-N-(carboxymethyl) benzamide sodium salt as a carboxylate anionic surfactant containing an amide bond and catechol structure.

[0073] Preparation Example 1

[0074] Preparation of modified layered double hydroxide:

[0075] S1 : 100 parts of layered double hydroxide was dispersed in 400 parts of CO2-removed deionized water, 150 parts of sodium dodecyl sulfonate and 40 parts of sulfonate anionic surfactant containing amide bond and catechol structure were added under nitrogen protection, and the mixture was reacted at 70°C for 20 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain anionic surfactant-treated layered double hydroxide.

[0076] S2: 100 parts of the above-mentioned anionic surfactant-treated layered double hydroxide and 70 parts of cetyltrimethylammonium chloride were dispersed in 500 parts of 60% volume concentration ethanol aqueous solution, and the mixture was reacted at 50°C for 8 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain the modified layered double hydroxide.

[0077] Preparation Example 2

[0078] Preparation of modified layered double hydroxide:

[0079] S1 : 100 parts of layered double hydroxide was dispersed in 400 parts of CO2-removed deionized water, 150 parts of sodium dodecyl sulfonate and 40 parts of sulfonate anionic surfactant containing amide bond and catechol structure were added under nitrogen protection, and the mixture was reacted at 70°C for 20 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain anionic surfactant-treated layered double hydroxide.

[0080] S2: 100 parts of the above-mentioned anionic surfactant-treated layered double hydroxide and 70 parts of cetyltrimethylammonium chloride were dispersed in 500 parts of 60% volume concentration ethanol aqueous solution, and the mixture was reacted at 50°C for 8 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain the modified layered double hydroxide.

[0081] Preparation Example 3

[0082] Preparation of modified layered double hydroxide:

[0083] S1 : 100 parts of layered double hydroxide was dispersed in 400 parts of CO2-removed deionized water, 150 parts of sodium dodecyl sulfonate and 40 parts of sulfonate anionic surfactant containing amide bond and catechol structure were added under nitrogen protection, and the mixture was reacted at 70°C for 20 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain anionic surfactant-treated layered double hydroxide.

[0084] S2: 100 parts of the above anionic surfactant-treated layered double hydroxide and 70 parts of cetyltrimethylammonium chloride were dispersed in 500 parts of an ethanol aqueous solution having a volume concentration of 60%, and reacted at 50°C for 8 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain the modified layered double hydroxide.

[0085] Comparative Preparation Example 1

[0086] Preparation of modified layered double hydroxide:

[0087] S1: 100 parts of layered double hydroxide were dispersed in 400 parts of CO2-removed deionized water, and 190 parts of sodium dodecyl sulfonate was added under nitrogen protection, and reacted at 70°C for 20 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain an anionic surfactant-treated layered double hydroxide.

[0088] S2: 100 parts of the above anionic surfactant-treated layered double hydroxide and 70 parts of cetyltrimethylammonium chloride were dispersed in 500 parts of an ethanol aqueous solution having a volume concentration of 60%, and reacted at 50°C for 8 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain the modified layered double hydroxide.

[0089] Comparative Preparation Example 2

[0090] Preparation of modified layered double hydroxide:

[0091] S1: 100 parts of layered double hydroxide were dispersed in 400 parts of CO2-removed deionized water, and 190 parts of a sulfonate anionic surfactant containing an amide bond and a catechol structure was added under nitrogen protection, and reacted at 70°C for 20 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain an anionic surfactant-treated layered double hydroxide.

[0092] S2: 100 parts of the above anionic surfactant-treated layered double hydroxide and 70 parts of cetyltrimethylammonium chloride were dispersed in 500 parts of an ethanol aqueous solution having a volume concentration of 60%, and reacted at 50°C for 8 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain the modified layered double hydroxide.

[0093] Comparative Preparation Example 3

[0094] Preparation of modified layered double hydroxide:

[0095] S1: 100 parts of the layered double hydroxide was dispersed in 400 parts of CO2-removed deionized water, 150 parts of sodium dodecyl sulfonate and 40 parts of sodium methyl oleyl taurate were added under nitrogen protection, and the mixture was reacted at 70°C for 20 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain an anionic surfactant-treated layered double hydroxide.

[0096] S2: 100 parts of the anionic surfactant-treated layered double hydroxide and 70 parts of cetyltrimethylammonium chloride were dispersed in 500 parts of an ethanol aqueous solution with a volume concentration of 60%, and the mixture was reacted at 50°C for 8 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain the modified layered double hydroxide.

[0097] Comparative Preparation Example 4

[0098] Preparation of the modified layered double hydroxide:

[0099] S1: 100 parts of the layered double hydroxide was dispersed in 400 parts of CO2-removed deionized water, 150 parts of sodium dodecyl sulfonate and 40 parts of sodium methyl oleyl taurate were added under nitrogen protection, and the mixture was reacted at 70°C for 20 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain an anionic surfactant-treated layered double hydroxide.

[0100] S2: 100 parts of the anionic surfactant-treated layered double hydroxide and 70 parts of cetyltrimethylammonium chloride were dispersed in 500 parts of an ethanol aqueous solution with a volume concentration of 60%, and the mixture was reacted at 50°C for 8 h. After the reaction was completed, it was cooled to 20°C, filtered, washed, and dried to obtain the modified layered double hydroxide.

[0101] Example 1

[0102] Preparation of the low-temperature impact-resistant food packaging material:

[0103] 100 parts of poly-L-lactic acid, 5 parts of the modified layered double hydroxide obtained in Preparation Example 1, 20 parts of G3 generation carboxyl-terminated hyperbranched polyester HyperC103, and 0.3 parts of antioxidant 1010 were uniformly mixed, and then fed into a twin-screw extruder for melt extrusion and granulation at 180°C to obtain low-temperature impact-resistant food packaging material granules. The granules were fed into a film blowing machine for film blowing at 180°C to obtain the low-temperature impact-resistant food packaging material.

[0104] Example 2

[0105] Preparation of the low-temperature impact-resistant food packaging material:

[0106] The preparation was substantially the same as in Example 1, except that the modified layered double hydroxide obtained in Preparation Example 2 was used.

[0107] Example 3

[0108] Preparation of food packaging material resistant to low-temperature impact:

[0109] The same as Example 1, except that the modified layered double hydroxide obtained in Preparation Example 3 was used.

[0110] Example 4

[0111] Preparation of food packaging material resistant to low-temperature impact:

[0112] 100 parts of poly-L-lactic acid, 5 parts of the modified layered double hydroxide obtained in Preparation Example 1, 20 parts of G3 generation carboxyl-terminated hyperbranched polyester HyperC203, and 0.3 parts of antioxidant 1010 were uniformly mixed, added to a twin-screw extruder, and melt-extruded and granulated at 180°C to obtain food packaging material resistant to low-temperature impact. The granules were added to a film blowing machine and blown into a film at 180°C to obtain food packaging material resistant to low-temperature impact.

[0113] Example 5

[0114] Preparation of food packaging material resistant to low-temperature impact:

[0115] 100 parts of poly-L-lactic acid, 5 parts of the modified layered double hydroxide obtained in Preparation Example 1, 20 parts of G3 generation carboxyl-terminated hyperbranched polyester HyperC203, and 0.3 parts of antioxidant 1010 were uniformly mixed, added to a twin-screw extruder, and melt-extruded and granulated at 180°C to obtain food packaging material resistant to low-temperature impact. The granules were added to a film blowing machine and blown into a film at 180°C to obtain food packaging material resistant to low-temperature impact.

[0116] Comparative Example 1

[0117] Preparation of food packaging material resistant to low-temperature impact:

[0118] 100 parts of poly-L-lactic acid, 5 parts of the modified layered double hydroxide obtained in Preparation Example 1, 20 parts of G3 generation carboxyl-terminated hyperbranched polyester HyperC203, and 0.3 parts of antioxidant 1010 were uniformly mixed, added to a twin-screw extruder, and melt-extruded and granulated at 180°C to obtain food packaging material resistant to low-temperature impact. The granules were added to a film blowing machine and blown into a film at 180°C to obtain food packaging material resistant to low-temperature impact.

[0119] Comparative Example 2

[0120] Preparation of food packaging material resistant to low-temperature impact:

[0121] The 100 parts of poly-L-lactic acid, 5 parts of modified layered double hydroxide obtained in Comparative Preparation Example 2, G3 generation carboxyl-terminated hyperbranched polyester HyperC103, and 0.3 parts of antioxidant 1010 were uniformly mixed, and then added into a twin-screw extruder for melt extrusion and granulation at 180°C to obtain granules of the low-temperature impact-resistant food packaging material. The granules were added into a film blowing machine for film blowing at 180°C to obtain the low-temperature impact-resistant food packaging material.

[0122] Comparative Example 3

[0123] Preparation of the low-temperature impact-resistant food packaging material:

[0124] The 100 parts of poly-L-lactic acid, 5 parts of modified layered double hydroxide obtained in Comparative Preparation Example 3, 20 parts of G3 generation carboxyl-terminated hyperbranched polyester HyperC103, and 0.3 parts of antioxidant 1010 were uniformly mixed, and then added into a twin-screw extruder for melt extrusion and granulation at 180°C to obtain granules of the low-temperature impact-resistant food packaging material. The granules were added into a film blowing machine for film blowing at 180°C to obtain the low-temperature impact-resistant food packaging material.

[0125] Comparative Example 4

[0126] Preparation of the low-temperature impact-resistant food packaging material:

[0127] The 100 parts of poly-L-lactic acid, 5 parts of modified layered double hydroxide obtained in Comparative Preparation Example 4, 20 parts of G3 generation carboxyl-terminated hyperbranched polyester HyperC103, and 0.3 parts of antioxidant 1010 were uniformly mixed, and then added into a twin-screw extruder for melt extrusion and granulation at 180°C to obtain granules of the low-temperature impact-resistant food packaging material. The granules were added into a film blowing machine for film blowing at 180°C to obtain the low-temperature impact-resistant food packaging material.

[0128] Comparative Example 5

[0129] Preparation of the low-temperature impact-resistant food packaging material:

[0130] The 100 parts of poly-L-lactic acid, 5 parts of modified layered double hydroxide obtained in Comparative Preparation Example 4, 20 parts of G3 generation carboxyl-terminated hyperbranched polyester HyperC103, and 0.3 parts of antioxidant 1010 were uniformly mixed, and then added into a twin-screw extruder for melt extrusion and granulation at 180°C to obtain granules of the low-temperature impact-resistant food packaging material. The granules were added into a film blowing machine for film blowing at 180°C to obtain the low-temperature impact-resistant food packaging material.

[0131] Comparative Example 6

[0132] Preparation of the low-temperature impact-resistant food packaging material:

[0133] 100 parts of poly-L-lactic acid and 0.3 parts of antioxidant 1010 were uniformly mixed, and then were fed into a twin-screw extruder for melt extrusion and granulation at 180°C to obtain the food packaging material with low-temperature impact resistance. The granules were fed into a film blowing machine for film blowing at 180°C to obtain the food packaging material with low-temperature impact resistance.

[0134] Test section

[0135] The granules obtained by granulation in each of the above examples were respectively made into dumbbell-shaped standard samples and notched impact 1A standard samples by an injection molding machine. Tensile tests were performed using a universal testing machine. The standard for the tensile test was ASTM D638-2022 "Standard Test Methods for Tensile Properties of Plastics". The test was repeated three times, and the average value was taken.

[0136] A notched impact test was performed using a simply supported beam impact testing machine. The standard for the 0°C notched impact test was GB / T1043.1-2018 "Determination of the Izod Impact Properties of Plastics - Part 2: Non-Instrumented Impact Test". The notched sample was adjusted in an ice-water mixture at 0°C for half an hour. The notched impact test was performed within 10 seconds after the adjustment was completed. The test was repeated 10 times, and the average value was taken.

[0137] Universal testing machine, model CMT6104;

[0138] Simply supported beam impact testing machine, model BLD-CJ20.

[0139] Table 1

[0140]

[0141] According to Table 1, each embodiment shows higher 0℃ notched impact strength compared with Comparative Examples 1-6, indicating that the technical solution provided by the present application can significantly improve the low-temperature toughness of the food packaging material. The reason may be that in Comparative Example 1, the LDH is only treated with sulfonate anionic surfactant, lacking the hydrogen bonding of amide bond and PLA carbonyl and the strong combination of catechol and LDH, the interfacial bonding capacity decreases, the stress transfer efficiency decreases, and thus the low-temperature impact strength decreases; in Comparative Example 2, only the sulfonate anionic surfactant containing amide bond and catechol structure is used, indicating that when the anionic surfactant with this structure is used alone, the anion intercalation efficiency is low, and the energy absorption capacity of LDH interlayer slip is weakened, thereby leading to the decrease of low-temperature impact resistance; in Comparative Example 3, the sulfonate anionic surfactant containing amide bond is used instead of the sulfonate anionic surfactant containing amide bond and catechol structure, since the LDH and the anionic surfactant only rely on ionic bond, when the low-temperature stress is transferred from the PLA matrix to the LDH, the ionic bond may be irreversibly broken under the action of stress, leading to the desorption of the anionic surfactant from the surface of the LDH, resulting in the failure of interfacial bonding and stress transfer, and thus the impact resistance decreases; in Comparative Example 4, the carboxylate anionic surfactant containing amide bond and catechol structure is used instead of the sulfonate anionic surfactant containing amide bond and catechol structure, the hydrogen bond of amide bond and PLA molecular chain is weak, and the interfacial bonding is weakened, so when the LDH is treated with the sulfonate anionic surfactant containing amide bond, the material shows the best toughness under low-temperature impact; in Comparative Example 5, no hyperbranched polyester is added, and the system relies on the modified LDH for toughening, lacking the flexible phase to absorb and dissipate impact energy, leading to the decrease of impact resistance; Comparative Example 6 is a pure PLA system, and the strength and toughness are the lowest.

[0142] According to Examples 1 and 2, using different carbon chain length organic cationic compounds has certain influence on the strength and toughness of the food packaging material. The physical entanglement of shorter alkyl chain with PLA molecule is weaker than that of long alkyl chain, leading to the decrease of interfacial bonding force of the system, and the reinforcing and toughening effect of the modified LDH is weaker than that of the organic cationic compound with long alkyl chain.

[0143] According to Examples 1 and 3, using different types of anionic surfactants has certain influence on the toughness of the food packaging material. When the LDH is treated with sulfonate anionic surfactant, the material shows the best toughness at low temperature.

[0144] According to the embodiments 1, 4-5, it is found that the different kinds of hyperbranched polyesters have certain influence on the strength and toughness of the food packaging material. When the hyperbranched polyester used has too low a number of substituents, the number of terminal functional groups is low, which leads to a decrease in the effect of the hyperbranched polyester on the PLA and the modified LDH, and a decrease in the interface strengthening effect. Meanwhile, the molecular size and branched structure of the hyperbranched polyester may not be able to fully induce crazing and increase the free volume, and the energy absorption of external impact is limited, which leads to a limited toughening effect. When the aromatic skeleton hyperbranched polyester is used, the molecular skeleton itself is rigid and flexible, and it is difficult for the hyperbranched polyester to absorb impact energy at low temperatures and to act as a flexible phase, which leads to a limited toughening effect on the material.

[0145] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A food packaging material resistant to low-temperature impact, characterized in that, The raw materials include the following parts by weight: 100 parts by weight of polylactic acid, 1-10 parts by weight of modified layered double hydroxide, and 5-40 parts by weight of hyperbranched polyester; The modified layered double hydroxide is obtained by treating the layered double hydroxide with a composite anionic surfactant and then with an organic cationic compound with a long alkyl chain. The composite anionic surfactant includes a first anionic surfactant and a second anionic surfactant; The first anionic surfactant includes at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium laurate; the second anionic surfactant includes a sulfonate anionic surfactant containing an amide bond and a catechol structure. The sulfonate anionic surfactant containing amide bonds and catechol structures was prepared by the following method: M1: Mix 10 parts by mass of 3,4-dihydroxybenzoic acid, 40-60 parts by mass of acetic anhydride, and 0.5-1 parts by mass of anhydrous sodium acetate, and react at 80-100℃ for 2-4 hours to obtain 3,4-diacetoxybenzoic acid; M2: Mix 10 parts by weight of 3,4-diacetoxybenzoic acid, 15-25 parts by weight of thionyl chloride, and 0.1-0.5 parts by weight of N,N-dimethylformamide in 60-100 parts by weight of anhydrous tetrahydrofuran, and react at 60-70°C for 4-6 hours to obtain 3,4-diacetoxybenzoyl chloride intermediate; M3: Dissolve 8-12 parts by weight of taurine and 2-4 parts by weight of sodium hydroxide in 80-200 parts by weight of deionized water, then mix with 10 parts by weight of 3,4-diacetoxybenzoyl chloride intermediate, 40-80 parts by weight of tetrahydrofuran, and 3-5 parts by weight of triethylamine, and react at 20-30°C for 10-14 hours to obtain a solution containing sodium salt of 3,4-diacetoxy-N-(2-sulfonylethyl)benzamide; M4: Add 20-40 parts by mass of methanol and 4-8 parts by mass of sodium hydroxide to the above solution containing sodium 3,4-diacetoxy-N-(2-sulfonylethyl)benzamide. React at 20-30°C for 2-4 hours. Adjust the pH to 7-8 with 0.1 mol / L hydrochloric acid. After vacuum distillation, washing and drying, 3,4-dihydroxy-N-(2-sulfonylethyl)benzamide sodium salt is obtained as a sulfonate anionic surfactant containing amide bonds and catechol structures.

2. The food packaging material according to claim 1, characterized in that, The organic cationic compounds with long alkyl chains include long-chain quaternary ammonium cationic compounds with carbon chain lengths of C14 to C18.

3. The food packaging material according to claim 1, characterized in that, The method for preparing the modified layered double hydroxide includes the following steps: S1: Disperse the layered double hydroxide in water, add a composite anionic surfactant under an inert atmosphere to replace the inorganic anions between the layers of the layered double hydroxide, and obtain the layered double hydroxide treated with the composite anionic surfactant. S2: The layered double hydroxide treated with the composite anionic surfactant described in step S1 and the organic cationic compound with a long alkyl chain are dispersed in an aqueous ethanol solution, so that some organic cations enter the interlayer to obtain the modified layered double hydroxide.

4. The food packaging material according to claim 3, characterized in that, Step S1 includes: dispersing 100 parts of layered double hydroxide in 300-500 parts of water, adding 100-200 parts of a first anionic surfactant and 20-60 parts of a sulfonate anionic surfactant containing amide bonds and catechol structure under nitrogen protection, and reacting at 60-80°C for 18-24 hours to obtain a layered double hydroxide treated with a composite anionic surfactant.

5. The food packaging material according to claim 3, characterized in that, Step S2 includes: dispersing 100 parts of a layered double hydroxide treated with a composite anionic surfactant and 50-100 parts of an organic cationic compound with a long alkyl chain in 400-600 parts of an aqueous ethanol solution, and reacting at 40-60°C for 6-12 hours to obtain the modified layered double hydroxide.

6. The food packaging material according to any one of claims 1 to 5, characterized in that, The raw materials meet at least one of the following conditions: 1) The polylactic acid includes poly-L-lactic acid, wherein the weight-average molecular weight of the poly-L-lactic acid is 100,000 Da to 200,000 Da; 2) The hyperbranched polyester includes G2~G4 generation hyperbranched polyester, wherein the hyperbranched polyester molecule has an aliphatic skeleton and the end groups are carboxyl or hydroxyl groups; 3) The weight-average molecular weight of the hyperbranched polyester is 2000~7000 Da; 4) The first anionic surfactant includes sodium dodecyl sulfonate; 5) The raw materials also include: 0.1 to 0.5 parts by weight of antioxidant, wherein the antioxidant includes at least one of antioxidant 1010 and antioxidant 168.

7. A method for preparing food packaging materials resistant to low-temperature impact, characterized in that, include: Provide the raw materials contained in the food packaging material according to any one of claims 1 to 6; The raw materials are mixed, melted, and extruded to obtain food packaging materials.

8. A food packaging bag, characterized in that, This includes the low-temperature impact resistant food packaging material as described in any one of claims 1 to 6, or the food packaging material prepared by the method described in claim 7.

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