A degradable and recyclable plastic food packaging bag and preparation method thereof

Abstract

The present application relates to the field of packaging bag materials, and more specifically mentions a degradable and recyclable plastic food packaging bag and a preparation method thereof. The degradable and recyclable plastic food packaging bag, in parts by mass, is mainly prepared from the following raw materials: polylactic acid base material, functional resin material, solid particles, plasticizers, antioxidants, light stabilizers and lubricants, etc. The food packaging bag material finally prepared by the present application can effectively deal with the problem of decreased mechanical properties of the packaging bag during long-term use, and can also maintain excellent waterproof, moisture-resistant, heat-resistant and stable properties under high humidity and high ambient temperature conditions. Most importantly, it can cope with the negative impact of the above-mentioned application environment on the mechanical properties and barrier properties of the packaging bag material, and avoid obvious decomposition and breakage, and has very excellent application prospects.

Description

Technical Field

[0001] The present application relates to the field of packaging bag materials, and more specifically to a degradable and recyclable plastic food packaging bag and a preparation method thereof. Background Art

[0002] With growing global awareness of environmental protection, traditional petroleum-based, non-degradable plastic packaging bags are increasingly being restricted due to their resistance to natural degradation and potential environmental pollution. To address environmental concerns and reduce white pollution, the industry is seeking more sustainable alternatives: developing new packaging materials that not only meet food packaging requirements but also exhibit good biodegradability or are easily recyclable. In this context, materials such as polylactic acid (PLA) and polybutylene adipate / terephthalate (PBAT) are being widely researched for their excellent mechanical properties, high transparency, and easy processability.

[0003] However, while these new packaging materials have alleviated the environmental pressures posed by traditional plastics to a certain extent, many practical application issues remain unresolved. For example, existing biodegradable and recyclable packaging bags experience a significant decline in mechanical properties during long-term storage and use, particularly in tensile strength, making it impossible to maintain good packaging performance over long periods of use. Another example is that in humid and hot environments, some biodegradable and recyclable packaging materials experience irreversible decomposition, degradation, and cracking, and their barrier properties also significantly decrease, directly impacting their ability to protect food packaging. Summary of the Invention

[0004] Therefore, to effectively address the above-mentioned existing problems, the present application provides a biodegradable and recyclable plastic food packaging bag and a method for preparing the same. The resulting food packaging bag material can effectively address the problem of decreased mechanical properties of the packaging bag during long-term use, and can also maintain excellent waterproof, moisture-resistant, and heat-resistant properties in high humidity and high temperature environments. Most importantly, it can address the negative impact of the above-mentioned application environments on the mechanical and barrier properties of the packaging bag material, and avoid obvious decomposition and damage, thus having excellent application prospects.

[0005] As a preferred embodiment, the degradable and recyclable plastic food packaging bag is prepared from the following raw materials, in parts by mass: 50-70 parts of polylactic acid base material, 20-30 parts of functional resin material, 2-5 parts of solid particles, 4-10 parts of plasticizer, 0.5-1 part of antioxidant, 0.3-0.5 part of light stabilizer, 0.5-1.5 parts of lubricant, 0.5-1 part of antistatic agent, and 1-3 parts of compatibilizer.

[0006] As a preferred embodiment, the number average molecular weight of the polylactic acid base material is 40,000 to 70,000 Da.

[0007] As a more preferred embodiment, the number average molecular weight of the polylactic acid base material is 50,000 to 55,000 Da.

[0008] As a preferred embodiment, the intrinsic viscosity of the polylactic acid base material is 0.6-0.8 dL / g, condition: 25°C.

[0009] As a more preferred embodiment, the intrinsic viscosity of the polylactic acid base material is 0.64-0.74 dL / g, condition: 25°C.

[0010] As a preferred embodiment, the mass ratio of the polylactic acid base material to the functional resin material is (55~65): (20~27).

[0011] As a preferred embodiment, the functional resin material is a composition of modified PBAT and modified starch-based resin.

[0012] As a preferred embodiment, the mass ratio of the modified PBAT to the modified starch-based resin is (1.5~3): (0.5~1.5).

[0013] As a more preferred embodiment, the mass ratio of the modified PBAT to the modified starch-based resin is (2-2.5): (1-1.2).

[0014] As a preferred embodiment, the preparation method of the modified PBAT specifically includes the following steps: S1: mixing PBAT with maleic anhydride, adding dicumyl peroxide and reactively extruding in a twin-screw extruder at a temperature of 160-180°C and a residence time of 20-25 minutes to obtain functionalized PBAT; S2: mixing functionalized PBAT, terephthalic acid, itaconic acid and 1,4-butanediol and adding them to a reactor, heating to 150-160°C under nitrogen protection, stirring and reacting for 2-3 hours to generate a pretreated product; S3: continuing to gradually heat to 180-190°C and continue the reaction for 1-2 hours until the acid value of the reaction system drops to 10 mg KOH / g or less, then cool the pretreated material to 120-130°C, add epoxy soybean oil, glycidyl methacrylate and trimethylolpropane triacrylate, and react at a speed of 100-120 rpm for 2-3 hours; S4: finally add dicumyl peroxide, stir evenly, then heat to 160-170°C, react for 1-1.5 hours, and after the reaction is completed, quickly cool to room temperature to obtain the product.

[0015] As a preferred embodiment, the mass ratio of PBAT to maleic anhydride is (8-10): (0.6-1).

[0016] As a preferred embodiment, the mass ratio of the functionalized PBAT, terephthalic acid, itaconic acid and 1,4-butanediol is (8.5~9.5): (1~1.5): (0.6~0.8): (0.3~0.6).

[0017] As a preferred embodiment, the mass ratio of the pretreated material, epoxy soybean oil, glycidyl methacrylate and trimethylolpropane triacrylate is (12-13): (0.2-0.4): (2-2.2): (1.1-1.4).

[0018] By adding modified PBAT, in addition to further effectively improving the mechanical properties of the packaging bag material, it can effectively ensure the aging resistance, thermal stability, and waterproof and moisture resistance of the packaging bag under high temperature, high humidity and long-term storage environments, thereby greatly reducing the negative impact of the above-mentioned usage on the mechanical properties of the packaging bag material.

[0019] The modified PBAT added in this application can form a microscopic phase separation structure through the multi-flexible segments formed by it and the rigid segments of the polylactic acid base material, thereby effectively absorbing impact energy and improving mechanical toughness. On the other hand, the hydrophobic segments of the modified PBAT can be more easily embedded in the surface structure of the material, thereby greatly reducing the surface hydrophilic groups by using the hydrophobic segments and cross-linked structures, and reducing the pore size of the micropores in the surface film layer, thereby providing greater surface resistance for the penetration of water and active molecules, and through the introduction of functional monomers, its denser internal cross-linked structure network and heat-resistant groups greatly increase the glass transition temperature of the material system, thereby obtaining excellent comprehensive properties such as waterproof, moisture-resistant, heat-resistant and aging-resistant in a high humidity environment.

[0020] Finally, the added modified PBAT can interact with the polylactic acid base material through the added active reaction structure and the added modified starch-based resin, improve the interfacial bonding effect, form a co-continuous structure, and form a uniform and dense dispersed phase in the polylactic acid continuous phase. While effectively transmitting stress and absorbing energy, it can better cope with the relative slip phenomenon through the cross-linking of molecular chains, thereby obtaining excellent mechanical stability and thermal stability in long-term use or complex use environments; and the construction of a more complex internal three-dimensional network structure can improve the mutual adhesion between molecular chains, improve the mechanical effect, and hinder the further penetration of water molecules.

[0021] As a preferred embodiment, the preparation method of the modified starch-based resin specifically includes the following steps: S1: mixing natural corn starch with deionized water, stirring evenly to form a starch suspension, and then adding sodium hydroxide to the starch suspension to adjust the pH to 8~10; S2: under stirring conditions, slowly adding maleic anhydride, stirring for 10~15 minutes to ensure uniform dispersion, continuing to add octenylsuccinic anhydride and epichlorohydrin and ensure uniform mixing, heating to 55~60℃ and continuously stirring the reaction for 3~5 hours to ensure that the reaction is fully completed; S3: after the reaction is completed, neutralizing the reaction system with acetic acid to a pH of 6~7, stopping the reaction, and obtaining the product by repeatedly washing with deionized water to remove unreacted substances.

[0022] As a preferred embodiment, the mass ratio of the native corn starch to maleic anhydride is (6-8): (1.2-1.4).

[0023] As a preferred embodiment, the mass ratio of the native corn starch, octenylsuccinic anhydride and epichlorohydrin is (6-8): (1.5-1.8): (0.3-0.5).

[0024] As a preferred embodiment, the solid particles are at least one of silicon dioxide, carbon nanotubes, calcium carbonate, talc and glass fibers.

[0025] As a more preferred embodiment, the solid particles are silicon dioxide or calcium carbonate.

[0026] As a more preferred embodiment, the solid particles are silicon dioxide.

[0027] As a preferred embodiment, the average particle size of the silicon dioxide is 15-30 nm.

[0028] As a more preferred embodiment, the plasticizer is a composition of acetyl tributyl citrate and polypropylene adipate.

[0029] As a preferred embodiment, the mass ratio of acetyl tributyl citrate to polypropylene adipate is (5-6): (1.2-2).

[0030] As a preferred embodiment, the antioxidant is Irganox 1010 or Irganox 1076.

[0031] As a more preferred embodiment, the antioxidant is Irganox 1076.

[0032] As a preferred embodiment, the light stabilizer is Tinuvin 622 or Chimassorb 944.

[0033] As a more preferred embodiment, the light stabilizer is Tinuvin 622.

[0034] As a preferred embodiment, the lubricant is at least one of calcium stearate, zinc stearate, ethylene bisstearamide and polyethylene wax.

[0035] As a more preferred embodiment, the lubricant is calcium stearate.

[0036] As a preferred embodiment, the antistatic agent is glycerol monostearate or ethoxylated fatty amine.

[0037] As a more preferred embodiment, the antistatic agent is ethoxylated fatty amine.

[0038] As a preferred embodiment, the compatibilizer is a composition of maleic anhydride grafted polypropylene and ethylene-methyl acrylate copolymer.

[0039] As a preferred embodiment, the mass ratio of the maleic anhydride grafted polypropylene to the ethylene-methyl acrylate copolymer is (3-5): (1.2-2.4).

[0040] As a more preferred embodiment, the mass ratio of the maleic anhydride grafted polypropylene to the ethylene-methyl acrylate copolymer is (3.5-4.2): (1.6-1.8).

[0041] As a preferred embodiment, the preparation method of the degradable and recyclable plastic food packaging bag specifically includes the following steps: S1: adding a polylactic acid base material and a functional resin material into a high-speed mixer, mixing them evenly at a temperature of 100-120°C, and fully dispersing them to form a homogeneous mixture; S2: first adding solid particles, plasticizers and antioxidants to the mixture, and continuing to stir at the same temperature for 10-15 minutes until completely fused, and finally adding the remaining raw materials, raising the temperature to 130-140°C and stirring for 10-15 minutes to obtain a final mixture; S3: sending the final mixture into a twin-screw extruder, melt-blending in the temperature range of 180-200°C, and then extruding it into a film or bag-shaped product through a mold, cooling and forming it, and cutting and trimming it to obtain the final mixture.

[0042] This application has the following beneficial effects:

[0043] 1. The biodegradable and recyclable plastic food packaging bag provided in this application can effectively deal with the problem of decreased mechanical properties of the packaging bag during long-term use, and can maintain excellent waterproof, moisture-resistant, heat-resistant and other properties even in high humidity and high ambient temperature conditions. Most importantly, it can cope with the negative impact of the above-mentioned application environment on the mechanical and barrier properties of the packaging bag material, and avoid obvious decomposition and breakage, and has very excellent application prospects.

[0044] 2. The modified PBAT added to the degradable and recyclable plastic food packaging bag provided in this application can comprehensively enhance the various properties of the food packaging bag, especially effectively ensure the aging resistance, thermal stability, and waterproof and moisture resistance of the packaging bag under high temperature, high humidity and long-term storage environments, thereby greatly reducing the negative impact of the above-mentioned usage on the mechanical properties of the packaging bag material.

[0045] 3. A degradable and recyclable plastic food packaging bag provided in the present application, by further adding a modified starch-based resin to the packaging bag material, not only continues the excellent degradable and recyclable performance of the packaging bag system, but also can absorb and disperse the external force through the molecular chain network structure of the modified starch-based resin, thereby effectively preventing the formed cracks from further expanding. On the other hand, it is easier to form a membrane hydrophobic barrier, reduce the overall water absorption, form a more stable covalent bond network structure, inhibit the thermal motion of the molecular chains of starch and polylactic acid materials, and prevent excessive agglomeration of internal particles during use or preparation through lubrication, thereby ensuring the stability of the overall performance. DETAILED DESCRIPTION

[0046] The following embodiments are merely practical examples used to illustrate and explain the technical solutions in the specification and should not limit the scope of the claims to be protected by this application.

[0047] Example 1

[0048] The raw materials of the degradable and recyclable plastic food packaging bag, calculated by mass, are: 61.5 parts of polylactic acid base material, 24.2 parts of functional resin material, 3.2 parts of solid particles, 5.8 parts of plasticizer, 0.6 part of antioxidant, 0.3 part of light stabilizer, 0.8 part of lubricant, 0.6 part of antistatic agent, and 2.2 parts of compatibilizer.

[0049] The polylactic acid base material has a number average molecular weight of 52,000 Da and an intrinsic viscosity of 0.68 dL / g at 25° C., and is purchased from NatureWorks LLC, USA, as a 3052D product.

[0050] The functional resin material is a composition of modified PBAT and modified starch-based resin, with a mass ratio of 2.3:1.2.

[0051] The preparation method of modified PBAT specifically includes the following steps, calculated by mass: S1: 9.5 parts of PBAT and 0.8 parts of maleic anhydride are mixed, 0.08 parts of diisopropylbenzene peroxide are added and reactively extruded in a twin-screw extruder at a temperature of 170°C and a residence time of 22 minutes to obtain functionalized PBAT; S2: 8.8 parts of functionalized PBAT, 1.3 parts of terephthalic acid, 0.75 parts of itaconic acid and 0.4 parts of 1,4-butanediol are mixed and added to a reactor, the temperature is raised to 155°C under nitrogen protection, and the reaction is stirred for 2.5 hours to generate a pretreated product; S3: the temperature is gradually raised to 182°C and the reaction is continued for 1.5 hours until the acid value of the reaction system drops to 10 mgKOH / g or less, then cool 12.5 parts of the pretreated material to 120°C, add 0.3 parts of epoxy soybean oil, 2.1 parts of glycidyl methacrylate and 1.2 parts of trimethylolpropane triacrylate, and react at 120 rpm for 3 hours; S4: finally add 0.11 parts of diisopropylbenzene peroxide, stir evenly, raise the temperature to 165°C, react for 1.5 hours, and after the reaction is completed, quickly cool to room temperature to obtain the product.

[0052] PBAT was purchased from BASF of Germany as Ecoflex® F Blend C1200.

[0053] Epoxidized soybean oil was purchased as an industrial plasticizing grade product from Hubei Xingyan New Material Technology Co., Ltd., China.

[0054] The preparation method of the modified starch-based resin specifically includes the following steps, calculated in parts by mass: S1: mixing 7.5 parts of natural corn starch with 120 parts of deionized water, stirring evenly to form a starch suspension, and then adding sodium hydroxide to the starch suspension to adjust the pH to 9; S2: under stirring conditions, slowly adding 1.3 parts of maleic anhydride, stirring for 12 minutes to ensure uniform dispersion, and then continuing to add 1.6 parts of octenylsuccinic anhydride and 0.4 parts of epichlorohydrin and ensure uniform mixing, heating to 60°C and continuously stirring the reaction for 4.5 hours to ensure that the reaction is fully completed; S3: after the reaction is completed, neutralizing the reaction system with acetic acid to a pH of 6.5 to stop the reaction, and after obtaining the product, repeatedly washing with deionized water to remove unreacted substances is obtained.

[0055] The solid particles are silicon dioxide with an average particle size of 20 nm.

[0056] The plasticizer is a composition of acetyl tributyl citrate and polypropylene adipate, with a mass ratio of 5.6:1.4.

[0057] The antioxidant is Irganox 1076; the light stabilizer is Tinuvin 622; the lubricant is calcium stearate; and the antistatic agent is ethoxylated fatty amine.

[0058] The compatibilizer is a composition of maleic anhydride grafted polypropylene and ethylene-methyl acrylate copolymer, and the mass ratio of the two is 3.8:1.8.

[0059] The preparation method of degradable and recyclable plastic food packaging bags specifically includes the following steps: S1: adding a polylactic acid base material and a functional resin material into a high-speed mixer, mixing them evenly at a temperature of 110°C, and fully dispersing them to form a homogeneous mixture; S2: first adding solid particles, a plasticizer and an antioxidant into the mixture, continuing to stir at the same temperature for 15 minutes until completely fused, and finally adding the remaining raw materials, raising the temperature to 130°C and stirring for 15 minutes to obtain a final mixture; S3: sending the final mixture into a twin-screw extruder, melt-blending within a temperature range of 190°C, and then extruding it into a film or bag-shaped product through a mold, cooling and forming it, and then cutting and trimming it to obtain the final product.

[0060] Example 2

[0061] The only difference between this embodiment and Example 1 is that the raw materials of the degradable and recyclable plastic food packaging bag are, in parts by mass, 55.8 parts of polylactic acid base material, 20.6 parts of functional resin material, 3.4 parts of solid particles, 5.2 parts of plasticizer, 0.5 part of antioxidant, 0.3 part of light stabilizer, 0.6 part of lubricant, 0.5 part of antistatic agent, and 1.5 parts of compatibilizer.

[0062] The functional resin material is a composition of modified PBAT and modified starch-based resin, with a mass ratio of 2.5:1.

[0063] The plasticizer is a composition of acetyl tributyl citrate and polypropylene adipate, with a mass ratio of 5:2.

[0064] The compatibilizer is a composition of maleic anhydride grafted polypropylene and ethylene-methyl acrylate copolymer, and the mass ratio of the two is 4.2:1.6.

[0065] Example 3

[0066] The only difference between this embodiment and Example 1 is that the raw materials of the degradable and recyclable plastic food packaging bag are, in parts by mass, 64.5 parts of polylactic acid base material, 26.8 parts of functional resin material, 4.1 parts of solid particles, 6.4 parts of plasticizer, 0.8 part of antioxidant, 0.4 part of light stabilizer, 1.1 parts of lubricant, 0.6 part of antistatic agent, and 1.9 parts of compatibilizer.

[0067] The functional resin material is a composition of modified PBAT and modified starch-based resin, with the mass ratio of the two being 2:1.2.

[0068] The plasticizer is a composition of acetyl tributyl citrate and polypropylene adipate, with a mass ratio of 6:1.3.

[0069] The compatibilizer is a composition of maleic anhydride grafted polypropylene and ethylene-methyl acrylate copolymer, and the mass ratio of the two is 3.5:1.7.

[0070] Comparative Example 1

[0071] The only difference between this comparative example and Example 1 is that the raw materials of the degradable and recyclable plastic food packaging bag are, in parts by mass, 70 parts of polylactic acid base material, 10.5 parts of functional resin material, 4.1 parts of solid particles, 4.2 parts of plasticizer, 0.6 part of antioxidant, 0.3 part of light stabilizer, 0.5 part of lubricant, 0.5 part of antistatic agent, and 1.2 parts of compatibilizer.

[0072] Comparative Example 2

[0073] The only difference between this comparative example and Example 1 is that the raw materials of the degradable and recyclable plastic food packaging bag are, in parts by mass, 52.2 parts of polylactic acid base material, 36.8 parts of functional resin material, 2.2 parts of solid particles, 5.8 parts of plasticizer, 1 part of antioxidant, 0.3 part of light stabilizer, 0.8 part of lubricant, 0.6 part of antistatic agent, and 2.8 parts of compatibilizer.

[0074] Comparative Example 3

[0075] The only difference between this comparative example and Example 1 is that the functional resin material is a composition of modified PBAT and modified starch-based resin, and the mass ratio of the two is 5:0.6.

[0076] Comparative Example 4

[0077] The only difference between this comparative example and Example 1 is that the functional resin material is a composition of modified PBAT and modified starch-based resin, and the mass ratio of the two is 1:2.5.

[0078] Comparative Example 5

[0079] The only difference between this comparative example and Example 1 is as follows: the preparation method of the modified PBAT specifically includes the following steps, calculated in parts by mass: S1: 15.5 parts of PBAT and 0.2 parts of maleic anhydride are mixed, 0.08 parts of dicumyl peroxide are added, and reactive extrusion is carried out in a twin-screw extruder at a temperature of 170° C. and a residence time of 22 minutes to obtain functionalized PBAT; S2: 8.8 parts of functionalized PBAT, 1.5 parts of terephthalic acid, 0.9 parts of itaconic acid and 0.8 parts of 1,4-butanediol are mixed and added to a reactor, and the temperature is raised to 155° C. under nitrogen protection, and the reaction is stirred for 2.5 hours to generate a pretreated product; S3: The temperature is gradually raised to 182° C. and the reaction is continued for 1.5 hours until the acid value of the reaction system drops to 10 mg KOH / g or less, then cool 12.5 parts of the pretreated material to 120°C, add 0.3 parts of epoxy soybean oil, 2.1 parts of glycidyl methacrylate and 1.2 parts of trimethylolpropane triacrylate, and react at 120 rpm for 3 hours; S4: finally add 0.11 parts of diisopropylbenzene peroxide, stir evenly, raise the temperature to 165°C, react for 1.5 hours, and after the reaction is completed, quickly cool to room temperature to obtain the product.

[0080] Comparative Example 6

[0081] The only difference between this comparative example and Example 1 is as follows: the preparation method of the modified PBAT specifically includes the following steps, calculated in parts by mass: S1: 9.5 parts of PBAT and 0.8 parts of maleic anhydride are mixed, 0.08 parts of diisopropylbenzene peroxide are added, and reactive extrusion is carried out in a twin-screw extruder at a temperature of 170° C. and a residence time of 22 minutes to obtain functionalized PBAT; S2: 12 parts of functionalized PBAT, 0.6 parts of terephthalic acid, 0.15 parts of itaconic acid and 0.2 parts of 1,4-butanediol are mixed and added to a reactor, and the temperature is raised to 155° C. under nitrogen protection, and the reaction is stirred for 2.5 hours to generate a pretreated product; S3: The temperature is gradually raised to 182° C. and the reaction is continued for 1.5 hours until the acid value of the reaction system drops to 10 mg KOH / g or less, then cool 12.5 parts of the pretreated material to 120°C, add 0.1 parts of epoxy soybean oil, 0.8 parts of glycidyl methacrylate and 0.3 parts of trimethylolpropane triacrylate, and react at 120 rpm for 3 hours; S4: finally add 0.11 parts of diisopropylbenzene peroxide, stir evenly, raise the temperature to 165°C, react for 1.5 hours, and after the reaction is completed, quickly cool to room temperature to obtain the product.

[0082] Comparative Example 7

[0083] The only difference between this comparative example and Example 1 is that the preparation method of the modified starch-based resin specifically includes the following steps, calculated in parts by mass: S1: 7.5 parts of natural corn starch are mixed with 120 parts of deionized water, and stirred evenly to form a starch suspension, and then sodium hydroxide is added to the starch suspension to adjust the pH to 9; S2: Under stirring conditions, 0.8 parts of maleic anhydride are slowly added, and stirred for 12 minutes to ensure uniform dispersion, and then 0.2 parts of octenylsuccinic anhydride and 0.2 parts of epichlorohydrin are added to ensure uniform mixing, and the temperature is raised to 60°C and the stirring reaction is continued for 4.5 hours to ensure that the reaction is fully completed; S3: After the reaction is completed, acetic acid is used to neutralize the reaction system to pH 6.5 to stop the reaction. After obtaining the product, it is repeatedly washed with deionized water to remove unreacted matter.

[0084] Performance Testing

[0085] 1. The food packaging bags prepared in the examples and comparative examples were tested for biodegradability in accordance with the standard GB / T 20197-2006. The average values ​​of 10 groups of tests were recorded in Table 1.

[0086] 2. The tensile strength and elongation at break of the food packaging bags prepared in the Examples and Comparative Examples were tested with reference to ASTM D638. The results were averaged over 10 groups of tests and are reported in Table 1.

[0087] 3. The food packaging bags prepared in the Examples and Comparative Examples were subjected to heat and aging resistance tests at 55°C ± 2°C and 75% relative humidity for 400 hours. After the tests, the bags were taken out and their tensile strength was tested according to the method in Performance Test 2. The tensile strength retention rate after the heat and aging resistance tests was calculated based on the tensile strength values ​​before and after the tests. Tensile strength retention rate (%) = tensile strength after the test / tensile strength before the test. The results were averaged over 10 tests and reported in Table 1.

[0088] 4. The food packaging bags prepared in the examples and comparative examples were tested for water resistance and moisture permeability in accordance with ASTM E96. The results were averaged from 10 groups of tests and are reported in Table 1.

[0089]

[0090] Judging from the final performance test results of the embodiments and comparative examples, comparative examples 1 to 7 achieved worse performance results than the embodiments. However, the embodiments, due to the use of a modified resin composition, significantly improved the molecular segment adhesion and three-dimensional network construction within the packaging material system, thereby enhancing the material system's absorption and dissipation of external stress, and enhancing its resistance to inter-molecular chain slippage. In addition, the density of surface hydrophobic groups was significantly increased, surface micropores were reduced, and moisture penetration resistance was enhanced. Thus, excellent moisture and active molecule resistance was maintained even in high humidity and high temperature environments, thereby achieving excellent mechanical property retention and waterproof and moisture permeability resistance.

Claims

1. A degradable and recyclable plastic food packaging bag, characterized by: The raw materials for the preparation are as follows, by mass: 50-70 parts of polylactic acid base material, 20-30 parts of functional resin material, 2-5 parts of solid particles, 4-10 parts of plasticizer, 0.5-1 part of antioxidant, 0.3-0.5 part of light stabilizer, 0.5-1.5 parts of lubricant, 0.5-1 part of antistatic agent, and 1-3 parts of compatibilizer; The number average molecular weight of the polylactic acid base material is 40,000~70,000 Da, and the intrinsic viscosity is 0.6~0.8 dL / g, at 25°C; The functional resin material is a composition of modified PBAT and modified starch-based resin, with a mass ratio of (1.5~3): (0.5~1.5); The solid particles are at least one of silicon dioxide, carbon nanotubes, calcium carbonate, talc and glass fiber; The plasticizer is a composition of acetyl tributyl citrate and polypropylene adipate in a mass ratio of (5-6): (1.2-2); The compatibilizer is a composition of maleic anhydride grafted polypropylene and ethylene-methyl acrylate copolymer; The preparation method of modified PBAT includes: S1: mixing PBAT with maleic anhydride, adding diisopropylbenzene peroxide and reactively extruding in a twin-screw extruder at a temperature of 160-180°C and a residence time of 20-25 minutes to obtain functionalized PBAT; S2: mixing functionalized PBAT, terephthalic acid, itaconic acid and 1,4-butanediol and adding them to a reactor, heating to 150-160°C under nitrogen protection, stirring and reacting for 2-3 hours to generate a pretreated product; S3: continuing to gradually increase the temperature to 150-160°C and stirring for 2-3 hours to generate a pretreated product. The temperature is raised to 180-190°C and the reaction is continued for 1-2 hours until the acid value of the reaction system drops below 10 mgKOH / g. The pretreated product is then cooled to 120-130°C and epoxy soybean oil, glycidyl methacrylate and trimethylolpropane triacrylate are added. The reaction is continued at a speed of 100-120 rpm for 2-3 hours. S4: Finally, dicumyl peroxide is added, the mixture is stirred evenly, and the temperature is raised to 160-170°C and the reaction is continued for 1-1.5 hours. After the reaction is completed, the mixture is quickly cooled to room temperature to obtain the product. The mass ratio of PBAT and maleic anhydride is (8-10): (0.6-1); the mass ratio of functionalized PBAT, terephthalic acid, itaconic acid and 1,4-butanediol is (8.5-9.5): (1-1.5): (0.6-0.8): (0.3-0.6); The mass ratio of pretreatment material, epoxy soybean oil, glycidyl methacrylate and trimethylolpropane triacrylate is (12~13): (0.2~0.4): (2~2.2): (1.1~1.4); The preparation method of the modified starch-based resin includes the following steps: S1: mixing natural corn starch with deionized water, stirring uniformly to form a starch suspension, and then adding sodium hydroxide to the starch suspension to adjust the pH to 8-10; S2: slowly adding maleic anhydride under stirring conditions, stirring for 10-15 minutes to ensure uniform dispersion, then adding octenylsuccinic anhydride and epichlorohydrin to ensure uniform mixing, heating to 55-60° C., stirring continuously for 3-5 hours to ensure the reaction is fully completed; S3: after the reaction is completed, neutralizing the reaction system with acetic acid to a pH of 6-7 to stop the reaction, and repeatedly washing the obtained product with deionized water to remove unreacted matter to obtain the product; The mass ratio of natural corn starch and maleic anhydride is (6~8):(1.2~1.4); the mass ratio of natural corn starch, octenylsuccinic anhydride and epichlorohydrin is (6~8):(1.5~1.8):(0.3~0.5).

2. The degradable and recyclable plastic food packaging bag according to claim 1, characterized in that: The antioxidant is Irganox 1010 or Irganox 1076; the light stabilizer is Tinuvin 622 or Chimassorb 944.

3. The degradable and recyclable plastic food packaging bag according to claim 2, characterized in that: The antistatic agent is glycerol monostearate or ethoxylated fatty amine.

4. The degradable and recyclable plastic food packaging bag according to claim 3, characterized in that: The mass ratio of the maleic anhydride grafted polypropylene to the ethylene-methyl acrylate copolymer is (3-5): (1.2-2.4).

5. A method for preparing the degradable and recyclable plastic food packaging bag according to any one of claims 1 to 4, characterized in that: The specific steps include: S1: Add the polylactic acid base material and the functional resin material into a high-speed mixer, mix them evenly at a temperature of 100-120°C, and fully disperse them to form a homogeneous mixture; S2: First add solid particles, plasticizers and antioxidants into the mixture, continue stirring at the same temperature for 10-15 minutes until they are completely fused, and finally add the remaining raw materials, heat to 130-140°C and stir for 10-15 minutes to obtain the final mixture; S3: Send the final mixture into a twin-screw extruder, melt blend in the temperature range of 180-200°C, and then extrude it into a film or bag-shaped product through a mold, cool and form it, and then cut and trim it to obtain the final product.

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