Antibacterial film material and preparation method thereof

Abstract

The invention discloses an antibacterial film material and a preparation method thereof in the field of film materials. The antibacterial film material comprises the following components in parts by weight: 80-90 parts of a polylactic acid-based polymer, 10-20 parts of poly (butylene adipate-co-terephthalate) (PBAT), 3-5 parts of an antibacterial toughening agent, 0.05-0.1 part of an initiator and 0.2-0.3 part of an antioxidant. Through polymer design and crosslinking, the toughness and tensile resistance of the material are improved, the material is suitable for film application, meanwhile, the flexibility is further enhanced through addition of PBAT, the barrier ability to gas and liquid is improved through structural tightness of the polylactic acid-based polymer, the film has an antibacterial effect through introduction of the antibacterial toughening agent, and the film is suitable for being applied to a thin film. The service life of the material is prolonged; and the material has important value in food hygiene application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of thin film materials, and particularly relates to an antibacterial thin film material and a preparation method thereof. BACKGROUND

[0002] In the field of food packaging, antibacterial thin film materials are gradually becoming an important technology, the purpose of which is not only to extend the shelf life of food, but also to enhance the safety of food. The main 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 are usually only physical barriers. In order to deal with the problem of microbial contamination, antibacterial thin film materials have emerged. These materials usually inhibit the growth of microorganisms by embedding or coating antibacterial agents in the packaging, thereby improving the safety of food.

[0003] Conventional food packaging thin film materials mainly include the following: synthetic polymer thin films: mainly including polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) and the like, these materials are strong, flexible and have good barrier properties. In addition, they are easy to process and form, have good transparency, but have poor degradability, causing environmental burden, and the polymers themselves usually have no antibacterial properties and must be additionally added with antibacterial agents; bio-based polymer thin films: mainly including polylactic acid (PLA), polyhydroxyalkanoate (PHA), starch-based thin films and the like, the materials are biodegradable, reducing the impact on the environment, and materials such as PLA can provide a biologically sourced solution under the condition of meeting food safety, but the mechanical properties (such as toughness and strength) may be inferior to synthetic polymers, and their barrier properties are poor in some cases; composite material thin films: mainly combining synthetic polymers with bio-based polymers or other materials, such as PLA / PBAT composite materials, by combining multiple materials, the advantages can be taken into account, for example, increasing the biodegradability and mechanical strength, the preparation process is complex, and the cost is relatively high; nanocomposite thin films: adding nanoparticles such as silver nanoparticles and zinc oxide nanoparticles in a polymer matrix, the nanoparticles can significantly improve the antibacterial performance, while improving the mechanical properties and thermal stability, further research is still needed on safety and cost, especially the long-term effects of nanomaterials on the human body and the environment. SUMMARY

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present application provides an antibacterial thin film material and a preparation method thereof, by polymer design and crosslinking, the material improves the toughness and tensile strength, making it suitable for thin film applications, while the addition of PBAT further enhances the flexibility, the tightness of the polylactic acid-based polymer increases the barrier ability to gas and liquid, and the introduction of antibacterial toughening agent makes the thin film have antibacterial effect, prolongs the service life of the material and has important value in food hygiene applications.

[0005] To achieve the above object, the technical scheme adopted by the present application is as follows: The present application provides an antibacterial film material and a preparation method thereof, the antibacterial film material comprising 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, antioxidant 0.2-0.3 part;

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

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

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

[0009] A1, dissolve triethylenediamine in anhydrous tetrahydrofuran, slowly add a brominated alcohol compound solution, increase the reaction temperature to carry out substitution reaction, after the reaction is completed, spin evaporation to remove the reaction solvent, add ethyl acetate to redissolve, then add saturated NaCl aqueous solution to wash, collect the organic phase, dry the organic phase with anhydrous magnesium sulfate, spin evaporation to remove the organic solvent, dry to obtain the reactant 1;

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

[0011] Preferably, in step A1, the mass-volume ratio between the triethylenediamine and the brominated alcohol 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 a carboxyl activator and a catalyst, then increase the temperature to carry out prepolymerization, after the reaction is completed, continue to increase the temperature to carry out polymerization, after the reaction is completed, dissolve the reactant in dichloromethane, 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 mass of the carboxyl activator added 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°C, and the reaction time of the prepolymerization reaction is 1.5-2.5h;

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

[0018] A3, mixing fumaric acid with the reactant 1 prepared in step A1, adding the polymerization inhibitor hydroquinone, uniformly mixing, introducing flowing nitrogen, increasing the reaction temperature to perform esterification, after the reaction is completed, cooling, and obtaining the reactant 2;

[0019] Preferably, in step A3, the mass ratio between the fumaric acid and the 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 the fumaric acid;

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

[0022] A4, taking the oligomeric polylactic acid prepared in step A2 and the reactant 2 prepared in step A3 into a reaction kettle, adding the catalyst stannous chloride dihydrate, uniformly mixing, adding p-toluenesulfonic acid monohydrate, increasing the reaction temperature to perform first-order polymerization, maintaining the reaction temperature to perform second-order polymerization after the reaction is completed, adding chloroform to completely dissolve the reaction product in the reaction system, adding anhydrous methanol to perform sedimentation treatment, after suction filtration, collecting the solid, drying, and obtaining a polylactic acid-based polymer;

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

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

[0025] Preferably, in step A4, the reaction temperature of the first-order polymerization reaction is 180-200 DEG C, 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 DEG C, and the reaction time of the second-order polymerization reaction is 24-36h.

[0027] The application further provides a preparation method of the antibacterial film material, and specifically comprises the following steps:

[0028] S1, 5, 5-dimethyl hydantoin is dissolved in anhydrous ethanol, sodium hydroxide is added, mixed uniformly, 3-bromopropylene / ethanol solution is added, the reaction temperature is increased to carry out reflux reaction, after the reaction is completed, cooling, filtration, collection of filtrate, rotary evaporation, purification, to obtain antibacterial toughening agent;

[0029] Preferably, in step S1, the mass ratio between the 5, 5-dimethyl hydantoin and sodium hydroxide is 1:0.7-0.9;

[0030] Preferably, in step S1, the mass-volume ratio between the 5, 5-dimethyl hydantoin and 3-bromopropylene is 0.7-1g / mL;

[0031] Preferably, in step S1, the reaction temperature of the reflux reaction is 70-80 DEG C, and the reaction time of the reflux reaction is 6-8h.

[0032] S2, the polylactic acid-based polymer and the polybutylene adipate terephthalate are placed in a banbury mixer for melt blending treatment, the antibacterial toughening agent prepared in step S1, an initiator and an antioxidant are added, and the mixing is continued for 4-6min, then the wind cooling treatment is carried out on the metal plate, and the antibacterial film material is obtained after cooling.

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

[0034] The application has the following beneficial effects:

[0035] The application provides an antibacterial film material and a preparation method thereof. The application improves the toughness and tensile capacity of the material through polymer design and crosslinking, so that the material is suitable for film application. The addition of PBAT further enhances the flexibility. The structure of the polylactic acid-based polymer increases the barrier capacity to gas and liquid. The introduction of the antibacterial toughening agent makes the film have antibacterial effect, prolongs the service life of the material, and has important value in food hygiene application. In the application, the polylactic acid (PLA) has good mechanical properties but high brittleness and poor toughness. Through chain extension and copolymerization modification of A1-A4, flexible chain segments can be introduced and the molecular weight can be increased, so that the toughness can be improved. The nucleophilic substitution reaction of triethylenediamine (containing active amino groups) and bromoalcohol compound (containing hydroxyl and bromo groups) generates amine derivatives containing hydroxyl (-OH), which can introduce flexible amine chain segments to increase the flexibility of the molecular chain of the polylactic acid-based polymer. After esterification with fumaric acid, flexible chain segments derived from fumaric acid are introduced, and the double bond provides active sites for subsequent crosslinking, increases the connectivity of the molecular chain, and the low molecular weight PLA is the polymer base. The flexible chain segments (amine groups and ester groups) improve the flexibility of the molecular chain, and the mild crosslinking forms a three-dimensional network structure, which can disperse stress and reduce molecular chain sliding, significantly improving the brittleness of PLA and improving the toughness. 5,5-dimethyl hydantoin is a typical antibacterial matrix, and its derivatives can release active substances such as hypochlorous acid through hydrolysis or oxidation, which can effectively kill bacteria (such as gram-positive bacteria and negative bacteria). The introduction of allyl does not destroy the antibacterial structure of hydantoin, which ensures the antibacterial activity. The molecular weight of the polylactic acid-based polymer is increased after chain extension, and the intermolecular force is enhanced. The network structure formed by moderate crosslinking further improves the tensile capacity. The flexible chain segments of polybutylene adipate / terephthalate, the flexible amine / ester chain segments in the polylactic acid-based polymer, and the allyl chain segments of the antibacterial toughening agent synergistically increase the flexibility of the molecular chain. The crosslinking network disperses the impact stress, significantly improves the brittleness of PLA, and improves the elongation at break and impact resistance. The polylactic acid-based polymer itself has a certain crystallinity, and the molecular arrangement is relatively tight. Chain extension and crosslinking reduce the intermolecular gap and reduce the penetration channels of gas (such as O2 and CO2) and water. The 5,5-dimethyl hydantoin derivative can release active antibacterial substances to effectively inhibit the reproduction of bacteria. The antibacterial film material described in the application realizes the comprehensive improvement of mechanical properties, barrier properties and antibacterial properties through molecular design and component synergy, and is suitable for food packaging and other scenes with high requirements for comprehensive performance of the material. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Stress-strain curves of the film materials prepared in examples 1-3 and comparative examples 1-3 of the application;

[0037] Figure 2 Antibacterial efficiency results of the film materials prepared in examples 1-3 and comparative examples 1-3 of the application;

[0038] Figure 3 CO2 / O2 permeation ratio results of the thin film material prepared for the present application examples 1-3 and comparative examples 1-3;

[0039] Figure 4 H2O permeation rate results of the thin film material prepared for the present application examples 1-3 and comparative examples 1-3.

[0040] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated in and constitute a part of the specification, illustrate embodiments of the present application and, together with the description, serve to explain the present application, and do not limit the present application. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of the present application.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art. In addition, any method and material similar or equivalent to those described herein can be used in the present application. The preferred methods and materials described herein are only for demonstration, but cannot limit the content of the present application.

[0043] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials and strains used in the following examples are all purchased from commercial channels unless otherwise specified.

[0044] The sources of the materials used in the present application are as follows:

[0045] PBAT, polybutylene adipate terephthalate, CasNo: 55231-08-8, purchased from Shanghai Yuan Ye Biotechnology Co., Ltd., product code: V12362.

[0046] Example 1

[0047] The present embodiment provides an antibacterial thin film material, which comprises the following components by weight: polylactic acid-based polymer 80 parts, polybutylene adipate terephthalate 20 parts, antibacterial toughening agent 3 parts, dicumyl peroxide 0.1 part, antioxidant 1010 0.2 part.

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

[0049] A1, accurately take triethylene diamine 1.5g dissolved in 50mL tetrahydrofuran, 2mL 2-bromoethanol is dissolved in 10mL tetrahydrofuran to obtain 2-bromoethanol solution, according to 0.1mL / min 2-bromoethanol solution is added dropwise into the reaction system, stirring at 400rpm, after the dropwise addition is completed, the reaction temperature is increased to 40℃, after 24h, the reaction is completed, after the reaction, the excess tetrahydrofuran is removed by rotary evaporation, ethyl acetate is added to dissolve the reaction product, then saturated NaCl aqueous solution is added for washing, after washing, the organic phase is collected and dried with anhydrous magnesium sulfate, after removing the organic solvent by rotary evaporation, drying, the reaction product 1 is obtained;

[0050] A2, accurately take L-lactic acid 10g into a flask, add 0.1g p-toluenesulfonic acid and 0.1g stannous chloride, stir at 200rpm, increase the temperature to 140℃, react for 2h, then adjust the pressure value of the reaction system to 800Pa, continue to increase the temperature to 180℃, continue to react for 6h, after the reaction system is cooled to room temperature, dissolve the reaction product with dichloromethane, filter, collect the filtrate, add anhydrous methanol for precipitation, filter, collect the precipitate, grind, and then place in a vacuum drying oven at 60℃ for 24h to obtain oligomeric polylactic acid;

[0051] A3, accurately take fumaric acid 1.5g into a reaction kettle, add 2.6g of reaction product 1 prepared in step A1, mix, then add 20.5mg of hydroquinone as a polymerization inhibitor, introduce flowing nitrogen into the reaction system, after 30min, increase the reaction temperature to 150℃ for esterification, react for 2h, then maintain the reaction temperature and reduce the vacuum degree of the reaction system to 100Pa, continue to react for 4h, the reaction is completed, cool to obtain reaction product 2;

[0052] A4, accurately take 10.0g of oligomeric polylactic acid prepared in step A2 into a reaction kettle, add 1.2g of reaction product 2 prepared in step A3, 56mg of stannous chloride dihydrate, and 47mg of p-toluenesulfonic acid monohydrate in sequence, increase the reaction temperature to 180℃ for first-order polymerization, and reduce the vacuum degree of the reaction environment to 20Pa, react for 20h, after the reaction is completed, reduce the reaction temperature to 150℃ for second-order polymerization, maintain the pressure in the reaction environment, and continue to react for 36h, after the reaction is completed, cool the reaction system to room temperature, dissolve the reaction product in chloroform, and continue to add anhydrous ethanol until no precipitate appears, filter, collect the solid, and vacuum dry to obtain a polylactic acid-based polymer;

[0053] The embodiment also provides a preparation method of an antibacterial film material, which specifically comprises the following steps:

[0054] S1, accurately take 5, 5-dimethyl hydantoin 5.0 g dissolved in 50 mL of anhydrous ethanol, add sodium hydroxide 4.0 g, mix uniformly, take 3-bromo propylene 7.0 mL dissolved in 30 mL of anhydrous ethanol to obtain 3-bromo propylene / ethanol solution, then add to the reaction system at a speed of 1 mL / min, the reaction system is stirred at a speed of 180 rpm, after the addition is completed, the reaction temperature is increased to 75℃, and the reaction is carried out for 7h, the reaction is completed, cooled, filtered to remove impurities, the filtrate is collected, the excess solvent is removed by rotary evaporation, and the antibacterial toughening agent is obtained after purification;

[0055] S2, the polylactic acid-based polymer and polybutylene adipate terephthalate are placed in an internal mixer, the temperature is adjusted to 180℃, and the rotating speed is adjusted to 50rpm, and the melt blending treatment is carried out, 3min later, the antibacterial toughening agent prepared in step S1, dicumyl peroxide and antioxidant 1010 are added, and the mixing is continued for 6min, then placed on a metal plate for air cooling treatment, and the antibacterial film material is obtained after cooling.

[0056] Example 2

[0057] The antibacterial film material provided by the embodiment includes the following components by weight: polylactic acid-based polymer 85 parts, polybutylene adipate terephthalate 15 parts, antibacterial toughening agent 4 parts, 1,1-di-tert-butyl peroxide cyclohexane 0.05 parts, antioxidant 1076 0.25 parts;

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

[0059] A1, accurately take triethylene diamine 1.5 g dissolved in 50 mL of tetrahydrofuran, dissolve 2.5 mL of 3-bromo propyl alcohol in 10 mL of tetrahydrofuran to obtain a 3-bromo propyl alcohol solution, add the 3-bromo propyl alcohol solution to the reaction system dropwise at a speed of 0.1 mL / min, stir at a speed of 500 rpm, after the addition is completed, increase the reaction temperature to 50℃, and react for 30h, after the reaction is completed, remove the excess tetrahydrofuran by rotary evaporation, add ethyl acetate to dissolve the reaction product, wash with saturated NaCl aqueous solution, collect the organic phase after washing, dry with anhydrous magnesium sulfate, remove the organic solvent by rotary evaporation, and dry to obtain the reaction product 1;

[0060] A2, accurately take L-lactic acid 10 g in a flask, add 0.08 g of p-toluene sulfonic acid and 0.2 g of stannous chloride, stir the reaction at a speed of 200 rpm, raise the temperature to 130℃, after 2.5 h of reaction, adjust the pressure value of the reaction system to 1000 Pa, continue to raise the temperature to 170℃, continue to react for 4 h, after the reaction system is cooled to room temperature, add dichloromethane to dissolve the reaction product, filter, collect the filtrate, add anhydrous methanol for precipitation, filter, collect the precipitate, grind, and then place in a vacuum drying oven at 60℃ for 24 h to obtain oligomeric polylactic acid;

[0061] A3, accurately take fumaric acid 1.5 g in a reaction kettle, add the reaction product 1 prepared in step A1 3.0 g, mix, add hydroquinone 22.5 mg as a polymerization inhibitor, introduce flowing nitrogen into the reaction system, after 30 min, raise the reaction temperature to 140℃ for esterification, after 2 h of reaction, maintain the reaction temperature and reduce the vacuum degree of the reaction system to 100 Pa, continue to react for 4 h, the reaction is completed, cool to obtain reaction product 2;

[0062] A4, accurately take oligomeric polylactic acid 15.0 g prepared in step A2 in a reaction kettle, sequentially add reaction product 2 1.2 g prepared in step A3, stannous chloride dihydrate 81 mg, p-toluenesulfonic acid monohydrate 68 mg, raise the reaction temperature to 190℃ for first-order polymerization, and reduce the vacuum degree of the reaction environment to 20 Pa, react for 18 h, after the reaction is completed, reduce the reaction temperature to 140℃ for second-order polymerization, maintain the pressure in the reaction environment, continue to react for 30 h, after the reaction is completed, cool the reaction system to room temperature, add chloroform to completely dissolve the reaction product, continue to add anhydrous ethanol until no precipitate appears, filter, collect the solid, vacuum dry to obtain polylactic acid-based polymer;

[0063] The embodiment also provides a preparation method of the antibacterial film material, specifically including the following steps:

[0064] S1, accurately take 5,5-dimethyl hydantoin 5.0 g and dissolve in 50 mL of anhydrous ethanol, add sodium hydroxide 4.5 g, mix uniformly, take 3-bromo propylene 5.0 mL and dissolve in 30 mL of anhydrous ethanol to obtain a 3-bromo propylene / ethanol solution, add the solution to the reaction system at a speed of 1 mL / min, stir the reaction system at a speed of 180 rpm, after the addition is completed, raise the reaction temperature to 80℃, react for 6 h, cool, filter to remove impurities, collect the filtrate, rotary evaporate to remove excess solvent, purify to obtain an antibacterial toughening agent;

[0065] S2, the polylactic acid-based polymer, poly(butylene adipate terephthalate) is placed in an internal mixer, the temperature is adjusted to 180℃, the rotating speed is adjusted to 70rpm, and melt blending treatment is carried out, 4min later, the antibacterial toughening agent prepared in step S1, 1,1-di-tert-butyl peroxide cyclohexane and antioxidant 1076 are added, and mixing is continued for 5min, then it is placed on a metal plate for air cooling treatment, and after cooling, an antibacterial film material is obtained.

[0066] Example 3

[0067] The antibacterial film material provided in this embodiment comprises the following components by weight: polylactic acid-based polymer 90 parts, poly(butylene adipate terephthalate) 10 parts, antibacterial toughening agent 5 parts, di-tert-butyl peroxide 0.075 parts, antioxidant 1098 0.3 parts.

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

[0069] A1, accurately weigh 1.5g of triethylene diamine dissolved in 50mL of tetrahydrofuran, dissolve 2mL of 4-bromo-1-butanol in 10mL of tetrahydrofuran to obtain a 4-bromo-1-butanol solution, add the 4-bromo-1-butanol solution dropwise at a rate of 0.1mL / min, stir at a speed of 300rpm, after the dropwise addition is completed, increase the reaction temperature to 45℃, and react for 36h, after the reaction is completed, remove the excess tetrahydrofuran by rotary evaporation, add ethyl acetate to dissolve the reaction product, wash with saturated NaCl aqueous solution, collect the organic phase after washing, and dry with anhydrous magnesium sulfate, remove the organic solvent by rotary evaporation, and dry to obtain the reactant 1;

[0070] A2, accurately weigh 10g of L-lactic acid into a flask, add 0.1g of p-toluenesulfonic acid and 0.15g of stannous chloride, stir at a speed of 200rpm, increase the temperature to 135℃, react for 1.5h, adjust the pressure of the reaction system to 900Pa, continue to increase the temperature to 175℃, continue to react for 5h, cool the reaction system to room temperature, dissolve the reaction product with dichloromethane, filter, collect the filtrate, precipitate with anhydrous methanol, filter, collect the precipitate, grind, and place in a vacuum drying oven at 60℃ for 24h to obtain oligomeric polylactic acid.

[0071] A3, accurately weigh fumaric acid 1.5 g into a reaction kettle, add the reactant 1 prepared in step A1 3.3 g, after mixing, add hydroquinone 24 mg as a polymerization inhibitor, introduce flowing nitrogen into the reaction system, after 30 min, increase the reaction temperature to 160℃ to carry out esterification reaction, after reaction for 2 h, keep the reaction temperature and reduce the vacuum degree of the reaction system to 100 Pa, continue to react for 3 h, the reaction is completed, and cooling is carried out to obtain the reactant 2;

[0072] A4, accurately weigh the oligomeric polylactic acid 12.0 g prepared in step A2 into a reaction kettle, sequentially add the reactant 2 prepared in step A3 1.2 g, stannous chloride dihydrate 66 mg, and p-toluenesulfonic acid monohydrate 56 mg, increase the reaction temperature to 200℃ to carry out 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, reduce the reaction temperature to 160℃ to carry out second-order polymerization reaction, keep the pressure in the reaction environment unchanged, and continue to react for 24 h, after the reaction is completed, the reaction system is cooled to room temperature, chloroform is added to completely dissolve the reactant, anhydrous ethanol is continuously added until no precipitate appears, filtration is carried out, the solid is collected, and vacuum drying is carried out to obtain a polylactic acid-based polymer;

[0073] The embodiment also provides a preparation method of the antibacterial film material, and specifically comprises the following steps:

[0074] S1, accurately weigh 5,5-dimethyl hydantoin 5.0 g and dissolve it in 50 mL of anhydrous ethanol, add sodium hydroxide 3.5 g, uniformly mix, dissolve 3-bromopropene 6.0 mL in 30 mL of anhydrous ethanol to obtain a 3-bromopropene / ethanol solution, and then add the solution to the reaction system at a speed of 1 mL / min, the reaction system is stirred at a speed of 180 rpm, after the addition is completed, the reaction temperature is increased to 70℃, reaction is carried out for 8 h, the reaction is completed, cooling is carried out, impurities are removed by filtration, the filtrate is collected, excess solvent is removed by rotary evaporation, and purification is carried out to obtain an antibacterial toughening agent;

[0075] S2, the polylactic acid-based polymer and the polybutylene adipate / terephthalate are placed in a banbury mixer, the temperature is adjusted to 180℃, the rotating speed is adjusted to 60 rpm, and melt blending treatment is carried out, 5 min later, the antibacterial toughening agent prepared in step S1, di-tert-butyl peroxide and antioxidant 1098 are added, and mixing is continued for 4 min, then the mixture is placed on a metal plate for air cooling treatment, and after cooling, an antibacterial film material is obtained.

[0076] Comparative Example 1

[0077] The comparative example 1 provides a film material and a preparation method thereof, which is only different from the example 1 in that a commercially available polylactic acid (source leaf, S25341) is used to replace the polylactic acid-based polymer in the same weight part in the components of the antibacterial film material, and the rest of the components and the component ratio are the same as those in the example 1.

[0078] Comparative example 2

[0079] The comparative example 1 provides a film material and a preparation method thereof, which is only different from the example 1 in that a commercially available polylactic acid (source leaf, S25341) is used to replace the polylactic acid-based polymer in the same weight part in the components of the antibacterial film material, and the rest of the components and the component ratio are the same as those in the example 1.

[0080] Comparative example 3

[0081] The comparative example 1 provides a film material and a preparation method thereof, which is only different from the example 1 in that a commercially available polylactic acid (source leaf, S25341) is used to replace the polylactic acid-based polymer in the same weight part in the components of the antibacterial film material, and the rest of the components and the component ratio are the same as those in the example 1.

[0082] Experimental example 1

[0083] The experimental example tests the mechanical properties of the antibacterial film materials prepared in the examples 1-3 and the comparative examples 1-3. The film materials prepared in the examples 1-3 and the comparative examples 1-3 are made into standard dumbbell-shaped samples, and the mechanical properties are tested on a universal testing machine at a tensile rate of 10 mm / min.

[0084] Figure 1 The stress-strain curves of the film materials prepared in the examples 1-3 and the comparative examples 1-3 are shown in the figure. The pure polylactic acid has poor toughness. In the stress-strain curves of the examples 1-3, the tensile strength is 31.26 MPa, 32.16 MPa and 30.90 MPa, and the elongation at break is 210.52%, 203.31% and 208.01%, respectively. The tensile strength and the elongation at break of the comparative examples 1-3 are lower than those of the examples. The performance of the film material in the comparative example 2 is close to that in the example 3, but the elongation at break is 195.56%. The above data show that the crosslinking of the fumaric acid segment and the double bond structure in the antibacterial toughening agent has a significant toughening effect on the film material.

[0085] Experimental example 2

[0086] The experimental example tests the antibacterial properties of the film materials prepared in the examples 1-3 and the comparative examples 1-3. 10 mg of the film material in each treatment group is placed in 4.5 mL of LB agar culture solution, and 0.5 mL of bacterial suspension is added. The number of viable bacteria in the bacterial suspension is 10 -7CFU / mL (live bacteria including lactic acid bacteria FTQC-35-01 and Escherichia coli) 37℃, 100 rpm culture for 24h, 100 μL of diluent is inoculated on LB agar plate by coating plate method, 37℃ incubation for 12h, counting the number of live bacteria, and calculating the antibacterial efficiency according to the following formula:

[0087] ;

[0088] Wherein, N0 is the number of colonies of the control group, N i is the number of colonies of the sample group.

[0089] Figure 2 The antibacterial efficiency results of the film materials prepared in Examples 1-3 and Comparative Examples 1-3 of the present application are shown in the figure, the antibacterial efficiency of Examples 1-3 of the present application against Escherichia coli is maintained at more than 80%, and the antibacterial efficiency against lactic acid bacteria is maintained at more than 75%, while the antibacterial efficiency of Comparative Examples 1-3 against the two bacteria is significantly lower than that of the examples, the antibacterial efficiency against lactic acid bacteria is 57.3%-59.1%, and the antibacterial efficiency against Escherichia coli is 62.5%-64.6%.

[0090] Experimental Example 3

[0091] The barrier properties of the film materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested, and the film materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested according to GB / T 1038-2000, the film materials prepared in Examples 1-3 and Comparative Examples 1-3 were dissolved in chloroform, poured into a glass plate and left to deaerate, vacuum dried at 30℃ for 15d, and a film with a thickness of 20 μm was obtained, the O2 and CO2 transmission rates of the film were measured by VAC-V2 type differential pressure gas permeameter, and the CO2 / O2 transmission ratio (A) was calculated according to the following formula:

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

[0093] Figure 3The CO2 / O2 permeation ratio results of the film materials prepared in Examples 1-3 and Comparative Examples 1-3 of the present application are shown in the figure, and the selectivity mechanism of the film is a solution-diffusion model, the essence of which is indeed dependent on the solution and diffusion differences of the permeation molecules, CO2 is a linear molecule, although the whole is non-polar, but the two oxygen atoms have strong electronegativity, which can form local charge shift, and the quadrupole moment is higher than that of O2, so CO2 is more likely to interact with the polar groups in the polymer and thus more easily adsorbed into the polymer, so in Examples 1-3, a large amount of-COOR groups (ester groups) are contained, -COOR is a typical polar group, and the polarity of-COOR can generate directional attraction with the local polarity of CO2, so a higher CO2 / O2 permeation ratio is exhibited, and a higher CO2 / O2 permeation ratio is beneficial to the preservation of food.

[0094] According to GB / T 26253-2010, the H2O permeation rate (WVTR, g·m-2·d-1) was determined at a temperature of 25℃ and a humidity of 85% using a Permatran-W3 / 61 water vapor permeation instrument. -2 ·d -1 ); Figure 4 The H2O permeation rate results of the film materials prepared in Examples 1-3 and Comparative Examples 1-3 of the present application are shown in the figure, and suitable H2O permeability can effectively prevent condensation inside the package, inhibit microbial growth, and slow down the rate of decay of fresh food, as shown in the figure, the WVTR of the film materials prepared in Examples 1-3 is maintained between 500-515 g·m-2·d-1, and the water vapor permeability is higher than that of the comparative examples. -2 ·d -1 );

[0095] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application.

[0096] The above describes the present application and its embodiments, which are not limiting, and the embodiments shown in the drawings are only one of the embodiments of the present application, and the actual application is not limited thereto. In summary, if those skilled in the art are inspired by it, without departing from the purpose of the present application, without creative design, similar ways and embodiments of the technical solution should belong to the protection scope of the present application.

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 a polylactic acid-based polymer, 10-20 parts of polybutylene adipate / terephthalate, 3-5 parts of an antibacterial toughening agent, 0.05-0.1 parts of an initiator, and 0.2-0.3 parts of an antioxidant; the initiator comprises at least one of dicumyl peroxide, 1,1-di-tert-butyl peroxide cyclohexane, and di-tert-butyl peroxide; 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 comprises the following steps: A1, take triethylenediamine and dissolve it in anhydrous tetrahydrofuran, slowly add bromohydrin compound solution, raise reaction temperature to carry out substitution reaction, after reaction finishes, rotary evaporation removes reaction solvent, adds ethyl acetate to redissolve, adds saturated NaCl aqueous solution to wash, after collecting organic phase, uses anhydrous magnesium sulfate to dry organic phase, rotary evaporation removes organic solvent, after drying, obtains reactant 1; A2, L-lactic acid is placed in a flask, after adding a carboxyl activator and a catalyst, the temperature is raised to carry out prepolymerization, after the reaction is completed, the temperature is continued to be raised to carry out polymerization, after the reaction is completed, methylene chloride is added to dissolve the reactants, filtered, after collecting the filtrate, anhydrous methanol is added to precipitate, filtered, after collecting the precipitate, ground, dried, and obtained oligomeric polylactic acid; A3, taking fumaric acid and reactant 1 prepared in step A1, mixing, adding polymerization inhibitor hydroquinone, mixing evenly, passing flowing nitrogen, raising the reaction temperature to carry out esterification reaction, and cooling after the reaction is completed to obtain reactant 2; A4. Take the oligomeric polylactic acid prepared in step A2 and the reactant 2 prepared in step A3, add them into a reactor, add stannous chloride dihydrate as a catalyst, mix well, add p-toluenesulfonic acid monohydrate, increase the reaction temperature to carry out a first-order polymerization reaction, maintain the reaction temperature to carry out a second-order polymerization reaction, and after the reaction is completed, add chloroform to completely dissolve the reaction product in the reaction system, add anhydrous methanol for sedimentation treatment, collect the solid after suction filtration, and dry to obtain a polylactic acid-based polymer.

2. The antibacterial film material according to claim 1, characterized in that: In step A1, the bromohydrin compound includes at least one of 2-bromoethanol, 3-bromopropanol, and 4-bromo-1-butanol; the mass volume ratio of triethylenediamine to the bromohydrin compound is 0.6-0.75 mg / mL; the stirring speed of the substitution reaction is 300-500 rpm, the reaction temperature of the substitution reaction is 40-50° C., and the reaction time of the substitution reaction 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 the 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 the 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° C., and the reaction time of the prepolymerization reaction is 1.5-2.5 hours; the reaction temperature of the polymerization reaction is 170-180° C., and the reaction time of the polymerization reaction is 4-6 hours. The vacuum degree of the polymerization reaction is maintained at 800-1000 Pa at atmospheric pressure.

5. The antibacterial film material according to claim 4, characterized in that: In step A3, the mass ratio of fumaric acid to reactant 1 is 0.45-0.57:1; the added mass of the polymerization inhibitor hydroquinone is 1.36%-1.6% of the mass of the fumaric acid; the reaction temperature of the esterification reaction is 140-160° C., and the reaction time of the esterification reaction is 5-6 hours.

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

7. A method for preparing the antibacterial film material according to any one of claims 1 to 6, characterized in that: The specific steps include: S1. Dissolve 5,5-dimethylhydantoin in anhydrous ethanol, add sodium hydroxide, mix well, add 3-bromopropylene / ethanol solution, increase the reaction temperature to perform reflux reaction, cool after the reaction is completed, filter, collect the filtrate, rotary evaporate, and purify to obtain an antibacterial toughening agent; S2. Place the polylactic acid-based polymer and polybutylene adipate / terephthalate in an internal mixer for melt blending, add the antibacterial toughening agent, initiator and antioxidant prepared in step S1, continue mixing for 4-6 minutes, place on a metal plate for air cooling, and after cooling, obtain an 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 volume ratio of 5,5-dimethylhydantoin to 3-bromopropylene is 0.7-1 g / mL; the reaction temperature of the reflux reaction is 70-80° C., and the reaction time of the reflux reaction 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 process is 180-190°C, the rotation speed of the melt blending process is 50-70 rpm, and the melt blending time is 3-5 minutes.

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