Antibacterial film material and method for preparing the same

Abstract

The application discloses an antibacterial film material in the field of film materials and a preparation method thereof, and comprises the following components in parts by weight: polylactic acid-based polymer 80-90 parts, polybutylene adipate terephthalate (PBAT) 10-20 parts, antibacterial toughening agent 3-5 parts, initiator 0.05-0.1 part and antioxidant 0.2-0.3 part. Through polymer design and crosslinking, the material improves the toughness and tensile capacity, is suitable for film application, the addition of PBAT further enhances the flexibility, the compactness of the polylactic acid-based polymer increases the barrier capacity to gas and liquid, the introduction of the antibacterial toughening agent enables the film to have antibacterial effect, prolongs the service life of the material and has important value in food hygiene application.

Description

Technical Field

[0001] This invention belongs to the field of thin film materials technology, specifically referring to an antibacterial thin film material and its preparation method. Background Technology

[0002] In the food packaging industry, antimicrobial film materials are gradually becoming an important technology, aiming not only to extend the shelf life of food but also to enhance its safety. The primary function of food packaging is to protect the quality and safety of food and extend its shelf life. Traditional packaging materials such as plastics, paper, and metals typically only provide physical barriers. To address the problem of microbial contamination, antimicrobial film materials have emerged. These materials typically inhibit the growth of microorganisms by embedding or coating antimicrobial agents within the packaging, thereby improving food safety.

[0003] Common food packaging film materials mainly include the following: Synthetic polymer films: mainly including polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), etc. These materials are strong, flexible and have good barrier properties. In addition, they are easy to process and mold, and have good transparency, but their biodegradability is poor, which burdens the environment. The polymers themselves usually do not have antibacterial properties and antibacterial agents must be added. Bio-based polymer films: mainly include polylactic acid (PLA), polyhydroxyalkanoates (PHA), starch-based films, etc. The materials are biodegradable, reducing the impact on the environment. Materials such as PLA can provide biological solutions while meeting food safety requirements, but their mechanical properties (such as toughness and strength) may not be as good as synthetic polymers, and their barrier properties are poor in some cases. Composite material films: mainly combine synthetic polymers with bio-based polymers or other materials, such as PLA / PBAT composites. By combining multiple materials, advantages can be combined, such as increasing biodegradability and mechanical strength. The preparation process is complex and the cost is relatively high. Nanocomposite material films: nanoparticles, such as silver nanoparticles and zinc oxide nanoparticles, are added to the polymer matrix. Nanoparticles can significantly improve antibacterial properties, while also improving mechanical properties and thermal stability. Safety and cost still need in-depth research, especially the long-term effects of nanomaterials on the human body and the environment. Summary of the Invention

[0004] In view of the above situation and to overcome the defects of the prior art, the present invention provides an antibacterial film material and its preparation method. Through polymer design and cross-linking, the material improves its toughness and tensile strength, making it suitable for film applications. At the same time, the addition of PBAT further enhances its flexibility, and the compact structure of polylactic acid-based polymers increases the barrier ability against gases and liquids. The introduction of antibacterial toughening agents gives the film antibacterial effects, extends the service life of the material, and has important value in food hygiene applications.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention proposes an antibacterial film material and its preparation method, wherein the antibacterial film material comprises the following components in parts by weight: 80-90 parts of polylactic acid-based polymer, 10-20 parts of polybutylene adipate / terephthalate (PBAT), 3-5 parts of antibacterial toughening agent, 0.05-0.1 parts of initiator, and 0.2-0.3 parts of antioxidant;

[0006] Preferably, the initiator includes at least one of dicumyl peroxide (DCP), 1,1-di-tert-butylcyclohexane peroxide (DBPC), and di-tert-butyl peroxide (DTBP);

[0007] Preferably, the antioxidant includes at least one of antioxidant 1010, antioxidant 1076, antioxidant 1098, and antioxidant 3114;

[0008] Preferably, the preparation method of the polylactic acid-based polymer specifically includes the following steps:

[0009] A1. Dissolve triethylenediamine in anhydrous tetrahydrofuran, slowly add a bromoalcohol compound solution, raise the reaction temperature to carry out the substitution reaction, after the reaction is completed, remove the reaction solvent by rotary evaporation, add ethyl acetate to redissolve, add saturated NaCl aqueous solution for washing, collect the organic phase, dry the organic phase with anhydrous magnesium sulfate, remove the organic solvent by rotary evaporation, and after drying, obtain reactant 1.

[0010] Preferably, in step A1, the bromoethanol compound includes at least one of 2-bromoethanol, 3-bromopropanol, and 4-bromo-1-butanol;

[0011] Preferably, in step A1, the mass-to-volume ratio of the triethylenediamine to the bromoethanol compound is 0.6-0.75 mg / mL;

[0012] Preferably, in step A1, the stirring speed of the substitution reaction is 300-500 rpm, the reaction temperature of the substitution reaction is 40-50℃, and the reaction time of the substitution reaction is 24-36 h.

[0013] A2. Place L-lactic acid in a flask, add carboxyl activator and catalyst, raise the temperature to carry out prepolymerization reaction, after the reaction is completed, continue to raise the temperature to carry out polymerization reaction, after the reaction is completed, add dichloromethane to dissolve the reactants, filter, collect the filtrate, add anhydrous methanol to precipitate, filter, collect the precipitate, grind and dry to obtain oligomeric polylactic acid.

[0014] Preferably, in step A2, the added mass of the carboxyl activator is 0.08-0.1% of the mass of L-lactic acid, and the carboxyl activator includes at least one of methanesulfonic acid, toluenesulfonic acid, sulfosuccinic acid, p-toluenesulfonyl chloride, and p-toluenesulfonic acid;

[0015] Preferably, in step A2, the mass of the catalyst added is 0.1-0.2% of the mass of L-lactic acid, and the catalyst includes at least one of stannous chloride, stannous oxide, and dibutyltin dilaurate;

[0016] Preferably, in step A2, the reaction temperature of the prepolymerization reaction is 130-140℃, and the reaction time of the prepolymerization reaction is 1.5-2.5h;

[0017] Preferably, in step A2, the polymerization reaction temperature is 170-180℃, the polymerization reaction time is 4-6h, and the vacuum degree of the polymerization reaction is maintained at atmospheric pressure of 800-1000Pa.

[0018] A3. Mix fumaric acid with reactant 1 prepared in step A1, add hydroquinone as a polymerization inhibitor, mix evenly, introduce flowing nitrogen gas, raise the reaction temperature to carry out esterification reaction, and after the reaction is completed, cool to obtain reactant 2.

[0019] Preferably, in step A3, the mass ratio of fumaric acid to reactant 1 is 0.45-0.57:1;

[0020] Preferably, in step A3, the mass of the polymerization inhibitor hydroquinone added is 1.36%-1.6% of the mass of fumaric acid;

[0021] Preferably, in step A3, the reaction temperature of the esterification reaction is 140-160℃, and the reaction time of the esterification reaction is 5-6h;

[0022] A4. Take the oligomeric polylactic acid prepared in step A2 and reactant 2 prepared in step A3 and add it to the reaction vessel. Add the catalyst stannous chloride dihydrate and mix evenly. Then add p-toluenesulfonic acid monohydrate and raise the reaction temperature to carry out the first-order polymerization reaction. After the reaction is completed, maintain the reaction temperature to carry out the second-order polymerization reaction. After the reaction is completed, add chloroform to completely dissolve the reaction products in the reaction system. Add anhydrous methanol for precipitation treatment. After filtration, collect the solid and dry it to obtain polylactic acid-based polymer.

[0023] Preferably, in step A4, the added mass of stannous chloride dihydrate is 4.5%-6.8% of the mass of reactant 2;

[0024] Preferably, in step A4, the mass of p-toluenesulfonic acid monohydrate added is 3.9%-5.6% of the mass of reactant 2;

[0025] Preferably, in step A4, the reaction temperature of the first-order polymerization reaction is 180-200℃, and the reaction time of the first-order polymerization reaction is 15-20h;

[0026] Preferably, in step A4, the reaction temperature of the second-order polymerization reaction is 140-160℃, and the reaction time of the second-order polymerization reaction is 24-36h;

[0027] This invention also provides a method for preparing an antibacterial film material, specifically comprising the following steps:

[0028] S1. Dissolve 5,5-dimethylhydantoin in anhydrous ethanol, add sodium hydroxide, mix well, add 3-bromopropene / ethanol solution, raise the reaction temperature to carry out reflux reaction, after the reaction is completed, cool, filter, collect the filtrate, and then rotary evaporate and purify to obtain the antibacterial toughening agent.

[0029] Preferably, in step S1, the mass ratio of 5,5-dimethylhydantoin to sodium hydroxide is 1:0.7-0.9;

[0030] Preferably, in step S1, the mass-to-volume ratio of 5,5-dimethylhydantoin to 3-bromopropene is 0.7-1 g / mL;

[0031] Preferably, in step S1, the reflux reaction temperature is 70-80℃ and the reflux reaction time is 6-8h;

[0032] S2. Polylactic acid polymer and poly(butylene adipate / terephthalate) are placed in a mixer for melt blending. The antibacterial toughening agent, initiator and antioxidant prepared in step S1 are added. After mixing for 4-6 minutes, the mixture is placed on a metal plate for air cooling. After cooling, the antibacterial film material is obtained.

[0033] Preferably, in step S2, the temperature of the melt blending treatment is 180-190℃, the rotation speed of the melt blending treatment is 50-70 rpm, and the melt blending time is 3-5 min.

[0034] The beneficial effects achieved by this invention are as follows:

[0035] This invention provides an antibacterial film material and its preparation method. Through polymer design and crosslinking, the material's toughness and tensile strength are improved, making it suitable for film applications. At the same time, the addition of PBAT further enhances its flexibility. The compact structure of the polylactic acid-based polymer increases its barrier properties against gases and liquids. The introduction of antibacterial toughening agents gives the film antibacterial effects, extends the material's service life, and has important value in food hygiene applications. In this invention, polylactic acid (PLA) has good mechanical properties but is brittle and has poor toughness. Through chain extension and copolymerization modification with A1-A4, flexible segments can be introduced and the molecular weight can be increased, thus improving its toughness. Triethylenediamine (containing active amino groups) undergoes a nucleophilic substitution reaction with bromoalcohol compounds (containing hydroxyl and brominated groups) to generate amine derivatives containing hydroxyl (-OH), which can introduce flexible amine segments and increase the molecular chain flexibility of the PLA polymer. After esterification with fumaric acid, fumaric acid-derived flexible segments are introduced, and the double bonds provide active sites for subsequent crosslinking, increasing the connectivity of the molecular chain. Oligomeric PLA is the polymer base, and the flexible segments (amine and ester groups) enhance the molecular chain flexibility. Light crosslinking forms a three-dimensional network structure, which can disperse stress, reduce molecular chain slippage, significantly improve the brittleness of PLA, and enhance its toughness. 5,5-Dimethylhydantoin is a typical antibacterial precursor. Its derivatives can release active substances such as hypochlorous acid through hydrolysis or oxidation, effectively killing bacteria (such as Gram-positive and Gram-negative bacteria). The introduction of allyl groups does not destroy the antibacterial structure of hydantoin, ensuring its antibacterial activity. After chain extension, the molecular weight of polylactic acid (PLA) polymers increases, enhancing intermolecular forces. Moderate cross-linking forms a network structure, further improving tensile strength. The flexible segments of poly(butylene adipate / terephthalate), the flexible amine / ester segments in PLA polymers, and the allyl segments of the antibacterial toughening agent synergistically increase molecular chain flexibility. The cross-linked network disperses impact stress, significantly improving the brittleness of PLA and increasing elongation at break and impact resistance. PLA polymers themselves have a certain degree of crystallinity and a relatively compact molecular arrangement; chain extension and cross-linking reduce intermolecular gaps, decreasing the penetration channels for gases (such as O2 and CO2) and moisture. 5,5-Dimethylhydantoin derivatives can release active antibacterial substances, effectively inhibiting bacterial growth. The antibacterial film material of this invention achieves a comprehensive improvement in mechanical properties, barrier properties, and antibacterial properties through molecular design and component synergy, making it suitable for scenarios such as food packaging where the comprehensive performance of materials is required. Attached Figure Description

[0036] Figure 1 The stress-strain curves are those of the thin film materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0037] Figure 2 The graph shows the antibacterial efficiency results of the thin film materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention;

[0038] Figure 3 The graphs show the CO2 / O2 transmittance results of the thin film materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0039] Figure 4 The graph shows the H2O transmittance results of the thin film materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0040] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0043] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the experimental materials and test strains used in the following examples were purchased from commercial channels.

[0044] The materials used in this invention were purchased from the following sources:

[0045] PBAT, polybutylene adipate / terephthalate, CasNo: 55231-08-8, purchased from Shanghai Yuanye Biotechnology Co., Ltd., item number: V12362.

[0046] Example 1

[0047] This embodiment provides an antibacterial film material, which comprises the following components in parts by weight: 80 parts of polylactic acid-based polymer, 20 parts of polybutylene adipate / terephthalate, 3 parts of antibacterial toughening agent, 0.1 parts of dicumyl peroxide, and 0.2 parts of antioxidant 1010;

[0048] The preparation method of polylactic acid-based polymers specifically includes the following steps:

[0049] A1. Accurately weigh 1.5 g of triethylenediamine and dissolve it in 50 mL of tetrahydrofuran. Dissolve 2 mL of 2-bromoethanol in 10 mL of tetrahydrofuran to obtain a 2-bromoethanol solution. Add the 2-bromoethanol solution dropwise to the reaction system at a rate of 0.1 mL / min and stir at 400 rpm. After the addition is complete, raise the reaction temperature to 40 °C and react for 24 h. After the reaction is complete, remove excess tetrahydrofuran by rotary evaporation. Add ethyl acetate to fully dissolve the reaction product, then add saturated NaCl aqueous solution for washing. After washing, collect the organic phase and dry it with anhydrous magnesium sulfate. Remove the organic solvent by rotary evaporation and dry to obtain reactant 1.

[0050] A2. Accurately weigh 10g of L-lactic acid and place it in a flask. Add 0.1g of p-toluenesulfonic acid and 0.1g of stannous chloride. Stir the mixture at 200rpm and raise the temperature to 140℃. After reacting for 2 hours, adjust the pressure in the reaction system to 800Pa. Continue to raise the temperature to 180℃ and continue to react for 6 hours. After the reaction system cools to room temperature, add dichloromethane to dissolve the reaction product, filter, collect the filtrate, add anhydrous methanol to precipitate, filter, collect the precipitate, grind it, and place it in a vacuum drying oven at 60℃ for 24 hours to obtain oligomeric polylactic acid.

[0051] A3. Accurately weigh 1.5g of fumaric acid and place it in a reaction vessel. Add 2.6g of reactant 1 prepared in step A1. After mixing, add 20.5mg of hydroquinone as a polymerization inhibitor. Pour flowing nitrogen gas into the reaction system. After 30min, raise the reaction temperature to 150℃ to carry out the esterification reaction. After reacting for 2h, maintain the reaction temperature and lower the vacuum of the reaction system to 100Pa. Continue the reaction for 4h. After the reaction is completed, cool to obtain reactant 2.

[0052] A4. Accurately weigh 10.0 g of the oligomeric polylactic acid prepared in step A2 and place it in a reaction vessel. Add 1.2 g of reactant 2 prepared in step A3, 56 mg of stannous chloride dihydrate, and 47 mg of p-toluenesulfonic acid monohydrate in sequence. Raise the reaction temperature to 180°C to carry out the first-order polymerization reaction and reduce the vacuum degree in the reaction environment to 20 Pa. React for 20 h. After the reaction is completed, lower the reaction temperature to 150°C to carry out the second-order polymerization reaction. Keep the pressure in the reaction environment constant and continue to react for 36 h. After the reaction is completed, wait for the reaction system to cool to room temperature, add chloroform to completely dissolve the reactants, and continue to add anhydrous ethanol until no more precipitate appears. Filter, collect the solid, and vacuum dry to obtain polylactic acid-based polymer.

[0053] This embodiment also provides a method for preparing an antibacterial film material, which specifically includes the following steps:

[0054] S1. Accurately weigh 5.0 g of 5,5-dimethylhydantoin and dissolve it in 50 mL of anhydrous ethanol. Add 4.0 g of sodium hydroxide and mix well. Then, dissolve 7.0 mL of 3-bromopropene in 30 mL of anhydrous ethanol to obtain a 3-bromopropene / ethanol solution. Add the solution dropwise to the reaction system at a rate of 1 mL / min. Stir the reaction system at a rate of 180 rpm. After the addition is complete, raise the reaction temperature to 75 °C and react for 7 h. After the reaction is complete, cool, filter to remove impurities, collect the filtrate, remove excess solvent by rotary evaporation, and purify to obtain the antibacterial toughening agent.

[0055] S2. Place polylactic acid-based polymer and poly(butylene adipate / terephthalate) in a mixer, adjust the temperature to 180°C and the rotation speed to 50 rpm, and perform melt blending. After 3 minutes, add the antibacterial toughening agent, dicumyl peroxide and antioxidant 1010 prepared in step S1, continue mixing for 6 minutes, and then place it on a metal plate for air cooling. After cooling, the antibacterial film material is obtained.

[0056] Example 2

[0057] This embodiment provides an antibacterial film material, which comprises the following components in parts by weight: 85 parts of polylactic acid polymer, 15 parts of polybutylene adipate / terephthalate, 4 parts of antibacterial toughening agent, 0.05 parts of 1,1-di-tert-butylcyclohexane peroxide, and 0.25 parts of antioxidant 1076;

[0058] The preparation method of polylactic acid-based polymers specifically includes the following steps:

[0059] A1. Accurately weigh 1.5 g of triethylenediamine and dissolve it in 50 mL of tetrahydrofuran. Dissolve 2.5 mL of 3-bromopropanol in 10 mL of tetrahydrofuran to obtain a 3-bromopropanol solution. Add the 3-bromopropanol solution dropwise to the reaction system at a rate of 0.1 mL / min and stir at 500 rpm. After the addition is complete, raise the reaction temperature to 50 °C and react for 30 h. After the reaction is complete, remove excess tetrahydrofuran by rotary evaporation. Add ethyl acetate to fully dissolve the reaction product, then add saturated NaCl aqueous solution for washing. After washing, collect the organic phase and dry it with anhydrous magnesium sulfate. Remove the organic solvent by rotary evaporation and dry to obtain reactant 1.

[0060] A2. Accurately weigh 10g of L-lactic acid and place it in a flask. Add 0.08g of p-toluenesulfonic acid and 0.2g of stannous chloride. Stir the mixture at 200rpm and raise the temperature to 130℃. After reacting for 2.5h, adjust the pressure in the reaction system to 1000Pa. Continue to raise the temperature to 170℃ and continue to react for 4h. After the reaction system cools to room temperature, add dichloromethane to dissolve the reaction product, filter, collect the filtrate, add anhydrous methanol to precipitate, filter, collect the precipitate, grind it, and place it in a vacuum drying oven at 60℃ for 24h to obtain oligomeric polylactic acid.

[0061] A3. Accurately weigh 1.5g of fumaric acid and place it in a reaction vessel. Add 3.0g of reactant 1 prepared in step A1. After mixing, add 22.5mg of hydroquinone as a polymerization inhibitor. Pour flowing nitrogen gas into the reaction system. After 30min, raise the reaction temperature to 140℃ to carry out the esterification reaction. After reacting for 2h, maintain the reaction temperature and lower the vacuum of the reaction system to 100Pa. Continue the reaction for 4h. After the reaction is completed, cool to obtain reactant 2.

[0062] A4. Accurately weigh 15.0 g of the oligomeric polylactic acid prepared in step A2 and place it in a reaction vessel. Add 1.2 g of reactant 2 prepared in step A3, 81 mg of stannous chloride dihydrate, and 68 mg of p-toluenesulfonic acid monohydrate in sequence. Raise the reaction temperature to 190℃ to carry out the first-order polymerization reaction and reduce the vacuum degree in the reaction environment to 20 Pa. React for 18 h. After the reaction is completed, lower the reaction temperature to 140℃ to carry out the second-order polymerization reaction. Keep the pressure in the reaction environment constant and continue to react for 30 h. After the reaction is completed, wait for the reaction system to cool to room temperature, add chloroform to completely dissolve the reactants, and continue to add anhydrous ethanol until no more precipitate appears. Filter, collect the solid, and vacuum dry to obtain polylactic acid-based polymer.

[0063] This embodiment also provides a method for preparing an antibacterial film material, which specifically includes the following steps:

[0064] S1. Accurately weigh 5.0 g of 5,5-dimethylhydantoin and dissolve it in 50 mL of anhydrous ethanol. Add 4.5 g of sodium hydroxide and mix well. Then, dissolve 5.0 mL of 3-bromopropene in 30 mL of anhydrous ethanol to obtain a 3-bromopropene / ethanol solution. Add the solution dropwise to the reaction system at a rate of 1 mL / min. Stir the reaction system at a rate of 180 rpm. After the addition is complete, raise the reaction temperature to 80 °C and react for 6 h. After the reaction is complete, cool, filter to remove impurities, collect the filtrate, and remove excess solvent by rotary evaporation. After purification, the antibacterial toughening agent is obtained.

[0065] S2. Place polylactic acid-based polymer and poly(butylene adipate / terephthalate) in a mixer, adjust the temperature to 180°C and the rotation speed to 70 rpm, and perform melt blending. After 4 minutes, add the antibacterial toughening agent, 1,1-di-tert-butylcyclohexane peroxide and antioxidant 1076 prepared in step S1, continue mixing for 5 minutes, and then place it on a metal plate for air cooling. After cooling, the antibacterial film material is obtained.

[0066] Example 3

[0067] This embodiment provides an antibacterial film material, which comprises the following components in parts by weight: 90 parts of polylactic acid polymer, 10 parts of poly(butylene adipate / terephthalate), 5 parts of antibacterial toughening agent, 0.075 parts of di-tert-butyl peroxide, and 0.3 parts of antioxidant 1098;

[0068] The preparation method of polylactic acid-based polymers specifically includes the following steps:

[0069] A1. Accurately weigh 1.5 g of triethylenediamine and dissolve it in 50 mL of tetrahydrofuran. Dissolve 2 mL of 4-bromo-1-butanol in 10 mL of tetrahydrofuran to obtain a 4-bromo-1-butanol solution. Add the 4-bromo-1-butanol solution dropwise to the reaction system at a rate of 0.1 mL / min and stir at 300 rpm. After the addition is complete, raise the reaction temperature to 45 °C and react for 36 h. After the reaction is complete, remove excess tetrahydrofuran by rotary evaporation. Add ethyl acetate to fully dissolve the reaction product, then add saturated NaCl aqueous solution for washing. After washing, collect the organic phase and dry it with anhydrous magnesium sulfate. Remove the organic solvent by rotary evaporation and dry to obtain reactant 1.

[0070] A2. Accurately weigh 10g of L-lactic acid and place it in a flask. Add 0.1g of p-toluenesulfonic acid and 0.15g of stannous chloride. Stir the mixture at 200rpm and raise the temperature to 135℃. After reacting for 1.5h, adjust the pressure in the reaction system to 900Pa. Continue to raise the temperature to 175℃ and continue to react for 5h. After the reaction system cools to room temperature, add dichloromethane to dissolve the reaction product, filter, collect the filtrate, add anhydrous methanol to precipitate, filter, collect the precipitate, grind it, and place it in a vacuum drying oven at 60℃ for 24h to obtain oligomeric polylactic acid.

[0071] A3. Accurately weigh 1.5g of fumaric acid and place it in a reaction vessel. Add 3.3g of reactant 1 prepared in step A1. After mixing, add 24mg of hydroquinone as a polymerization inhibitor. Pour flowing nitrogen gas into the reaction system. After 30min, raise the reaction temperature to 160℃ to carry out the esterification reaction. After reacting for 2h, maintain the reaction temperature and lower the vacuum of the reaction system to 100Pa. Continue the reaction for 3h. After the reaction is completed, cool to obtain reactant 2.

[0072] A4. Accurately weigh 12.0 g of the oligomeric polylactic acid prepared in step A2 and place it in a reaction vessel. Add 1.2 g of reactant 2 prepared in step A3, 66 mg of stannous chloride dihydrate, and 56 mg of p-toluenesulfonic acid monohydrate in sequence. Raise the reaction temperature to 200℃ to carry out the first-order polymerization reaction and reduce the vacuum degree in the reaction environment to 20 Pa. React for 15 h. After the reaction is completed, lower the reaction temperature to 160℃ to carry out the second-order polymerization reaction. Keep the pressure in the reaction environment constant and continue to react for 24 h. After the reaction is completed, wait for the reaction system to cool to room temperature, add chloroform to completely dissolve the reactants, and continue to add anhydrous ethanol until no more precipitate appears. Filter, collect the solid, and vacuum dry to obtain polylactic acid-based polymer.

[0073] This embodiment also provides a method for preparing an antibacterial film material, which specifically includes the following steps:

[0074] S1. Accurately weigh 5.0 g of 5,5-dimethylhydantoin and dissolve it in 50 mL of anhydrous ethanol. Add 3.5 g of sodium hydroxide and mix well. Then, dissolve 6.0 mL of 3-bromopropene in 30 mL of anhydrous ethanol to obtain a 3-bromopropene / ethanol solution. Add the solution dropwise to the reaction system at a rate of 1 mL / min. Stir the reaction system at a rate of 180 rpm. After the addition is complete, raise the reaction temperature to 70 °C and react for 8 h. After the reaction is complete, cool, filter to remove impurities, collect the filtrate, and remove excess solvent by rotary evaporation. After purification, the antibacterial toughening agent is obtained.

[0075] S2. Place polylactic acid-based polymer and poly(butylene adipate / terephthalate) in a mixer, adjust the temperature to 180°C and the rotation speed to 60 rpm, and perform melt blending. After 5 minutes, add the antibacterial toughening agent, di-tert-butyl peroxide and antioxidant 1098 prepared in step S1, continue mixing for 4 minutes, and then place it on a metal plate for air cooling. After cooling, the antibacterial film material is obtained.

[0076] Comparative Example 1

[0077] This comparative example provides a thin film material and its preparation method, which differs from Example 1 only in that: in the composition of the antibacterial thin film material, the same weight parts of commercially available polylactic acid (Yuan Ye, S25341) are used to replace the polylactic acid-based polymer, and the remaining components and component ratios are the same as in Example 1.

[0078] Comparative Example 2

[0079] This comparative example provides a thin film material and its preparation method, which differs from Example 1 only in that: the preparation method of the polylactic acid-based polymer does not include step A1, and in step A4, 1,4-butanediol is used to replace reactant 1 in the same weight proportions, while the remaining components and component ratios are the same as in Example 1.

[0080] Comparative Example 3

[0081] This comparative example provides a thin film material and its preparation method. The only difference between this material and Example 1 is that the antibacterial thin film material does not include an antibacterial toughening agent, while the remaining components and their proportions are the same as in Example 1.

[0082] Experimental Example 1

[0083] This experiment tests the mechanical properties of the antibacterial film materials prepared in Examples 1-3 and Comparative Examples 1-3. The film materials prepared in Examples 1-3 and Comparative Examples 1-3 are made into standard dumbbell-shaped strips and placed on a universal testing machine at a tensile rate of 10 mm / min to test their mechanical properties.

[0084] Figure 1 The stress-strain curves of the film materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention are shown in the figure. Pure polylactic acid exhibits poor toughness. In the stress-strain curves of Examples 1-3 of this invention, the tensile strength is 31.26 MPa, 32.16 MPa, and 30.90 MPa, while the elongation at break reaches 210.52%, 203.31%, and 208.01%, respectively. The tensile strength and elongation at break of Comparative Examples 1-3 are lower than those of this application. The performance of the film material described in Comparative Example 2 is similar to that of Example 3, but the elongation at break is 195.56%. The above data demonstrate that the cross-linking of the fumaric acid segments and the double bond structure in the antibacterial toughening agent has a significant toughening effect on the film material.

[0085] Experiment Example 2

[0086] This experiment tested the antibacterial properties of the film materials prepared in Examples 1-3 and Comparative Examples 1-3. For each treatment group, 10 mg of the film material was placed in 4.5 mL of LB agar medium, and 0.5 mL of bacterial suspension was added. The number of viable bacteria in the bacterial suspension was 10. -7CFU / mL (live bacteria including lactic acid bacteria FTQC-35-01 and Escherichia coli Escherichiacoli) were incubated at 37°C and 100 rpm for 24 h. 100 μL of the dilution was then inoculated onto LB agar plates using the spread plate method and incubated at 37°C for 12 h. The number of viable colonies was counted, and the antibacterial efficiency was calculated using the following formula:

[0087] ;

[0088] Where N0 is the colony count in the control group, N i This represents the number of bacterial colonies in the sample group.

[0089] Figure 2 The figures show the antibacterial efficiency results of the film materials prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention. As shown in the figures, the antibacterial efficiency of Examples 1-3 against Escherichia coli remained above 80%, and the antibacterial efficiency against lactic acid bacteria remained above 75%. However, the antibacterial efficiency of Comparative Examples 1-3 against both bacteria was significantly lower than that of the Examples, with an antibacterial efficiency of 57.3%-59.1% against lactic acid bacteria and 62.5%-64.6% against Escherichia coli.

[0090] Experimental Example 3

[0091] This experiment tested the barrier properties of the thin film materials prepared in Examples 1-3 and Comparative Examples 1-3. The thin film materials were tested according to GB / T 1038-2000. The thin film materials prepared in Examples 1-3 and Comparative Examples 1-3 were dissolved in chloroform, poured into a glass plate, allowed to stand to remove bubbles, and vacuum dried at 30°C for 15 days to obtain a film with a thickness of 20 μm. The O2 and CO2 transmittance of the film was measured using a VAC-V2 differential pressure gas permeameter, and the CO2 / O2 transmittance ratio (A) was calculated according to the following formula:

[0092] A = CO2 transmission rate (%) / O2 transmission rate (%);

[0093] Figure 3The figures show the CO2 / O2 permeability results of the thin film materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. As shown in the figures, the selectivity mechanism of the thin film is a solution-diffusion model, which essentially depends on the differences in dissolution and diffusion of the permeating molecules. CO2 is a linear molecule. Although it is nonpolar overall, the two oxygen atoms are highly electronegative, which will form a local charge shift. The quadrupole moment is higher than that of O2, making it easier for CO2 to interact with the polar groups in the polymer, and thus easier to be adsorbed into the polymer. Therefore, Examples 1-3 contain a large number of -COOR groups (ester groups). -COOR is a typical polar group. The polarity of -COOR can generate a directional attraction with the local polarity of CO2, thus exhibiting a high CO2 / O2 permeability. A high CO2 / O2 permeability is beneficial to the preservation of food.

[0094] According to GB / T 26253-2010, the H2O transmittance (WVTR, g·m³) was determined using a Permatran-W3 / 61 water vapor permeameter at a temperature of 25℃ and a humidity of 85%. -2 ·d -1 ); Figure 4 The graphs show the H2O permeability results of the film materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. Suitable H2O permeability can effectively prevent condensation inside the packaging, inhibit microbial growth, and slow down the spoilage rate of fresh food. As shown in the graphs, the WVTR of the film materials prepared in Examples 1-3 is maintained at 500-515 g·m⁻¹. -2 ·d -1 Between the two, the water vapor permeability is higher than that of the control group.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

[0096] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. An antibacterial film material, characterized in that: The antibacterial film material comprises the following components in parts by weight: 80-90 parts of polylactic acid-based polymer, 10-20 parts of polybutylene adipate / terephthalate, 3-5 parts of antibacterial toughening agent, 0.05-0.1 parts of initiator, and 0.2-0.3 parts of antioxidant; wherein the initiator comprises at least one of dicumyl peroxide, 1,1-di-tert-butylcyclohexane peroxide, and di-tert-butyl peroxide; and wherein the antioxidant comprises at least one of antioxidant 1010, antioxidant 1076, antioxidant 1098, and antioxidant 3114. The preparation method of the polylactic acid-based polymer specifically includes the following steps: A1. Dissolve triethylenediamine in anhydrous tetrahydrofuran, slowly add a solution of a bromoalcohol compound, raise the reaction temperature to carry out a substitution reaction, after the reaction is complete, remove the reaction solvent by rotary evaporation, redissolve with ethyl acetate, wash with saturated NaCl aqueous solution, collect the organic phase, dry the organic phase with anhydrous magnesium sulfate, remove the organic solvent by rotary evaporation, and after drying, obtain reactant 1; the bromoalcohol compound includes at least one of 2-bromoethanol, 3-bromopropanol, and 4-bromo-1-butanol; the mass-to-volume ratio of the triethylenediamine to the bromoalcohol compound is 0.6-0.75 g / mL; A2. Place L-lactic acid in a flask, add carboxyl activator and catalyst, raise the temperature to carry out prepolymerization reaction, after the reaction is completed, continue to raise the temperature to carry out polymerization reaction, after the reaction is completed, add dichloromethane to dissolve the reactants, filter, collect the filtrate, add anhydrous methanol to precipitate, filter, collect the precipitate, grind and dry to obtain oligomeric polylactic acid. A3. Mix fumaric acid with reactant 1 prepared in step A1, add hydroquinone as a polymerization inhibitor, mix thoroughly, then purge with flowing nitrogen gas to raise the reaction temperature for esterification. After the reaction is complete, cool to obtain reactant 2. The mass ratio of fumaric acid to reactant 1 is 0.45-0.57:1; the mass of hydroquinone as a polymerization inhibitor is 1.36%-1.6% of the mass of fumaric acid. A4. Take the oligomeric polylactic acid prepared in step A2 and reactant 2 prepared in step A3 and add it to the reaction vessel. Add the catalyst stannous chloride dihydrate and mix evenly. Then add p-toluenesulfonic acid monohydrate and raise the reaction temperature to carry out the first-order polymerization reaction. After the reaction is completed, maintain the reaction temperature to carry out the second-order polymerization reaction. After the reaction is completed, add chloroform to completely dissolve the reaction products in the reaction system. Add anhydrous methanol for precipitation treatment. After filtration, collect the solid and dry it to obtain polylactic acid-based polymer. The method for preparing the antibacterial toughening agent is as follows: 5,5-dimethylhydantoin is dissolved in anhydrous ethanol, sodium hydroxide is added, the mixture is stirred evenly, 3-bromopropene / ethanol solution is added, the reaction temperature is raised to carry out reflux reaction, after the reaction is completed, the mixture is cooled, filtered, the filtrate is collected, and then rotary evaporated and purified to obtain the antibacterial toughening agent.

2. The antibacterial film material according to claim 1, characterized in that: In step A1, the stirring speed of the substitution reaction is 300-500 rpm, the reaction temperature is 40-50℃, and the reaction time is 24-36 h.

3. The antibacterial film material according to claim 2, characterized in that: In step A2, the added mass of the carboxyl activator is 0.08%-0.1% of the mass of L-lactic acid, and the carboxyl activator includes at least one of methanesulfonic acid, toluenesulfonic acid, sulfosuccinic acid, p-toluenesulfonyl chloride, and p-toluenesulfonic acid; the added mass of the catalyst is 0.1-0.2% of the mass of L-lactic acid, and the catalyst includes at least one of stannous chloride, stannous oxide, and dibutyltin dilaurate.

4. The antibacterial film material according to claim 3, characterized in that: In step A2, the reaction temperature of the prepolymerization reaction is 130-140℃, and the reaction time of the prepolymerization reaction is 1.5-2.5h; the reaction temperature of the polymerization reaction is 170-180℃, the reaction time of the polymerization reaction is 4-6h, and the vacuum degree of the polymerization reaction is maintained at atmospheric pressure of 800-1000Pa.

5. The antibacterial film material according to claim 4, characterized in that: In step A3, the esterification reaction temperature is 140-160℃, and the esterification reaction time is 5-6h.

6. The antibacterial film material according to claim 5, characterized in that: In step A4, the added mass of stannous chloride dihydrate is 4.5%-6.8% of the mass of reactant 2; the added mass of p-toluenesulfonic acid monohydrate is 3.9%-5.6% of the mass of reactant 2; the reaction temperature of the first-stage polymerization reaction is 180-200℃, and the reaction time of the first-stage polymerization reaction is 15-20h; the reaction temperature of the second-stage polymerization reaction is 140-160℃, and the reaction time of the second-stage polymerization reaction is 24-36h.

7. A method for preparing an antibacterial film material according to any one of claims 1-6, characterized in that: Specifically, the steps include the following: S1. Dissolve 5,5-dimethylhydantoin in anhydrous ethanol, add sodium hydroxide, mix well, add 3-bromopropene / ethanol solution, raise the reaction temperature to carry out reflux reaction, after the reaction is completed, cool, filter, collect the filtrate, and then rotary evaporate and purify to obtain the antibacterial toughening agent. S2. Place polylactic acid-based polymer and poly(butylene adipate / terephthalate) in a mixer for melt blending. Add the antibacterial toughening agent, initiator and antioxidant prepared in step S1. Continue mixing for 4-6 minutes, then place on a metal plate for air cooling. After cooling, obtain the antibacterial film material.

8. The method for preparing an antibacterial film material according to claim 7, characterized in that: In step S1, the mass ratio of 5,5-dimethylhydantoin to sodium hydroxide is 1:0.7-0.9; the mass-to-volume ratio of 5,5-dimethylhydantoin to 3-bromopropene is 0.7-1 g / mL; the reflux reaction temperature is 70-80℃, and the reflux reaction time is 6-8 h.

9. The method for preparing an antibacterial film material according to claim 8, characterized in that: In step S2, the temperature of the melt blending treatment is 180-190℃, the rotation speed of the melt blending treatment is 50-70 rpm, and the melt blending time is 3-5 min.

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