Preparation method of polylactic acid antibacterial film

Abstract

The invention relates to the technical field of films, in particular to a preparation method of a polylactic acid antibacterial film. The polylactic acid antibacterial film is prepared from the following raw materials in parts by weight: 80-95 parts of a polylactic acid base material, 3-10 parts of a first antibacterial material, 2-8 parts of a second antibacterial material, 4-12 parts of a first reinforcing material, 2-5 parts of a second reinforcing material and 1-3 parts of a dispersing aid. According to the preparation method, phenolic acid molecules penetrate through microbial cell membranes through a hydrophobic effect to destroy membrane integrity, flavone components are combined with bacterial DNA topoisomerase to inhibit nucleic acid replication, and the two substances generate a synergistic effect through a pi-pi conjugation effect, so that the antibacterial performance of the polylactic acid film can be remarkably improved; in addition, kudzuvine root polysaccharide and konjac glucomannan form a slow-release layer on the surface of the film, antibacterial components are gradually released through hydrogen bonds, the antibacterial performance of the film can be kept for a long time, and the problem that a traditional antibacterial agent is prone to migration and failure is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of thin films, and specifically to a polylactic acid antibacterial thin film and a preparation method thereof. Background Art

[0002] Polylactic acid (PLA) thin film is a new type of biodegradable material. In recent years, it has been widely used in the fields of packaging, agriculture, biomedicine, and textiles. With its unique biocompatibility and environmental safety, it has become an important force in promoting green development. Major scientific research institutions and companies around the world have increased their investment in the research and production of polylactic acid thin films.

[0003] In the prior art, the antibacterial property of polylactic acid thin films is often imparted by adding antibacterial agents. However, this method of adding antibacterial agents results in poor dispersion of the antibacterial agents in the polylactic acid thin film matrix, and there is a problem that the added antibacterial agents are prone to migration and failure.

[0004] Based on this, the present invention provides a polylactic acid antibacterial thin film and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to provide a polylactic acid antibacterial thin film and a preparation method thereof. The polylactic acid antibacterial thin film prepared by the present invention not only has good and lasting antibacterial properties, but also has a relatively high tensile strength, overcoming the problem that the thin film is easily torn.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A polylactic acid antibacterial thin film, comprising the following raw materials in parts by weight: 80 - 95 parts of a polylactic acid base material, 3 - 10 parts of a first antibacterial material, 2 - 8 parts of a second antibacterial material, 4 - 12 parts of a first reinforcing material, 2 - 5 parts of a second reinforcing material, and 1 - 3 parts of a dispersion aid.

[0007] Preferably, the dispersion aid is prepared by modifying bentonite with cetyltrimethylammonium bromide through an ion exchange method, and the particle size of the dispersant is ≤500 nm.

[0008] Preferably, the preparation method of the polylactic acid base material comprises the following steps: Select corn starch as the raw material, transfer it to a gelatinizer after pulverizing and passing through a 60 - mesh sieve, add deionized water, adjust the pH value to 6.5, start the gelatinizer and set the temperature at 100 - 120°C, gelatinize for 30 min and then cool to 35 - 40°C, inoculate lactic acid bacteria, then place it in a fermentation tank, set the stirring speed at 80 - 100 r / min, the aeration rate at 0.5 vvm, continuously ferment for 36 - 48 h to obtain a fermentation broth. The fermentation broth is filtered through a plate - and - frame filter, decolorized with activated carbon, concentrated under reduced pressure to a solid content of (60 - 70)%, and then through a melt polycondensation reaction to obtain L - type polylactic acid resin, which is the polylactic acid base material for use.

[0009] Preferably, in the preparation process of the polylactic acid base material, the mass ratio of deionized water to corn starch raw material is 3:1, the set temperature of the melt polycondensation reaction is 170-180 °C, and the vacuum degree is -(0.09-0.1) MPa.

[0010] Preferably, the preparation method of the first antibacterial material includes the following steps: Select dry wormwood and honeysuckle, mix them in a mass ratio of 1:1, then add them to a multi-functional extraction tank, add deionized water, set the rotation speed to 50-80 r / min, the temperature to 90-95 °C, decoct for 2-3 h, take the decoction liquid, filter out impurities with a plate and frame filter press to obtain a filtrate, transfer the filtrate to a precipitation tank, add 95% ethanol, let it stand and precipitate for 12-14 h, take the precipitate and place it in a horizontal centrifuge, set the rotation speed to 4000-5000 r / min, the centrifugation time to 15-20 min, take the supernatant and place it in a vacuum drying oven, set the temperature to 50-60 °C, the vacuum degree to -0.08 MPa, concentrate until the water content ≤ 5%, and then pulverize and pass through a 200-mesh sieve to obtain the first antibacterial material.

[0011] Preferably, in the preparation process of the first antibacterial material, the mass ratio of wormwood, honeysuckle and deionized water is 1:1:10, and the mass ratio of the filtrate to 95% ethanol is 1:1.6.

[0012] Preferably, the preparation method of the second antibacterial material includes the following steps: Select bamboo leaves and dandelion in a mass ratio of 3:1, mix them and pulverize them to a particle size ≤ 2 mm, transfer them to an ultrasonic extraction tank, set the frequency to 40 kHz, the power to 500 w, the temperature to 50 °C, add 75% ethanol solution, and continuously extract for 40-50 min to obtain an extract. The mass ratio of bamboo leaves, dandelion and 75% ethanol solution is 3:1:60. Transfer the extract to a rotary evaporator and concentrate it to one-fifth of the original volume, then transfer it to a freeze dryer, set the cold trap temperature to -50 °C, the vacuum degree to 10 Pa, and dry for 20-24 h to obtain the second antibacterial material.

[0013] Preferably, the preparation method of the first reinforcing material includes the following steps: Select konjac and kudzu root in a mass ratio of 2:1, slice them and mix them. The slice thickness is 2-3 mm, then transfer them to an alkali-resistant reaction kettle, add a 5% sodium hydroxide solution with a material-liquid ratio of 1:8, set the temperature to 23-25 °C, the rotation speed to 100-120 r / min, soak for 20-24 h to obtain a soaking solution, then place it in a plate and frame filter press, adjust the pH value of the soaking solution to 4.5 with 10% hydrochloric acid filtrate, precipitate flocculates, then wash the flocculates with deionized water until neutral, transfer them to a spray drying tower, set the inlet air temperature to 180 °C, the outlet air temperature to 85 °C, and continuously dry for 1-2 h to obtain the first reinforcing material.

[0014] Preferably, the preparation method of the second reinforcing material comprises the following steps: Select seaweed and aloe vera gel in a mass ratio of 1:1, put them into a high-speed homogenizer, set the rotation speed at 20000 - 22000 r / min, continuously process for 5 - 7 min to obtain a homogenized slurry, inject it into a freeze-drying chamber, set the pre-freezing temperature at -40 °C, the sublimation stage temperature at -20 °C, the vacuum degree at 20 Pa, dry for 45 - 48 h, and then crush it with an air-flow pulverizer to a particle size less than or equal to 50 μm to obtain the second reinforcing material.

[0015] Preferably, the preparation method of the polylactic acid antibacterial film comprises the following steps: S1: Weigh the polylactic acid base material, the first antibacterial material, the second antibacterial material, the first reinforcing material, the second reinforcing material and the dispersion aid as required, put them into a mixer, set the temperature less than or equal to 55 °C, the rotation speed at 700 - 800 r / min, and premix for 20 - 30 min to obtain a mixed material; S2: Put the mixed material into a twin-screw extruder for melt blending, extrude the melt to a cooling roll for winding and then slit and package to obtain the polylactic acid antibacterial film; S3: In S2, the aspect ratio of the twin-screw extruder is 40:1, the temperature of the screw partition in the first zone is 160 °C, the second zone is 170 °C, the third zone is 175 °C, the die head is 170 °C, the screw rotation speed is 50 - 60 r / min, the surface of the cooling roll is chrome-plated, the temperature is set at 15 - 20 °C, and the linear speed of the cooling roll is (2 - 3) m / min.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. In this preparation method, chlorogenic acid contained in Artemisia argyi, phenolic acid substances contained in luteoloside in Lonicera japonica, flavonoid components contained in rutin in bamboo leaves and chicoric acid in Taraxacum officinale form a composite antibacterial system. Phenolic acid molecules penetrate the microbial cell membrane through hydrophobic interaction, destroy the membrane integrity, and flavonoid components bind to bacterial DNA topoisomerase to inhibit nucleic acid replication. The two substances produce a synergistic effect through π-π conjugation effect, which can significantly improve the antibacterial performance of the polylactic acid film. In addition, puerarin polysaccharide and konjac glucomannan form a slow-release layer on the film surface, and gradually release antibacterial components through hydrogen bonds, which can maintain the antibacterial performance of the film for a long time and solve the problem that traditional antibacterial agents are prone to migration and failure.

[0017] 2. In this preparation method, the linear molecules in puerarin starch and the branched-chain structure of konjac glucomannan crosslink during the alkali treatment to form a three-dimensional network skeleton. Sodium alginate and aloe polysaccharide further strengthen the network nodes through calcium ion chelation, thus acting as physical crosslinking points in the polylactic acid matrix, increasing the resistance to molecular chain slippage, and further greatly improving the tensile strength of the pure polylactic acid film, overcoming the defect that degradable films are prone to tearing.

[0018] 3. In this preparation method, while the first antibacterial agent, the second antibacterial agent, the first reinforcing agent, and the second reinforcing agent cooperate synergistically to improve the film properties, their raw material characteristics do not interfere with the material degradation process. At the same time, alginate and aloe polysaccharide form a hydrophilic channel, accelerating the penetration of environmental moisture and coupling with the microbial enzymatic hydrolysis, promoting the uniform disintegration of the material in compost or soil. The amino acids and polysaccharide components in aloe vera gel further soften the material surface, and at the same time, cooperate with plant fibers to form a microscopic pore structure, achieving a balance between air permeability and barrier performance. Each component achieves stable compounding through intermolecular hydrogen bonds and ionic interactions, and releases active ingredients in stages during the degradation period, not only ensuring the degradation rate, but also supplementing organic matter to the soil after degradation, forming an ecological virtuous cycle. Detailed implementation mode

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Example 1

[0020] A polylactic acid antibacterial film comprises the following raw materials in parts by weight: 80 parts of polylactic acid base material, 3 parts of the first antibacterial agent, 2 parts of the second antibacterial agent, 4 parts of the first reinforcing agent, 2 parts of the second reinforcing agent, and 1 part of a dispersion aid.

[0021] In some embodiments, the dispersion aid is prepared by modifying bentonite with cetyltrimethylammonium bromide by an ion exchange method, and the particle size of the dispersant is ≤500 nm.

[0022] In some embodiments, the preparation method of the polylactic acid base material comprises the following steps: Select corn starch as the raw material, transfer it to a gelatinizer after pulverizing and passing through a 60-mesh sieve, add deionized water, adjust the pH value to 6.5, start the gelatinizer at a set temperature of 100 °C, cool it to 35 °C after gelatinizing for 30 min, inoculate lactic acid bacteria, then place it in a fermentation tank, set the stirring speed at 80 r / min, the ventilation volume at 0.5 vvm, and continue to ferment for 36 h to obtain a fermentation broth. The fermentation broth is filtered through a plate and frame, decolorized with activated carbon, concentrated under reduced pressure to a solid content of 60%, and then through a melt polycondensation reaction to obtain an L-type polylactic acid resin, which is the polylactic acid base material for use.

[0023] In some embodiments, during the preparation of the polylactic acid base material, the mass ratio of deionized water to corn starch raw material is 3:1, and the set temperature of the melt polycondensation reaction is 170 °C, and the vacuum degree is -0.09 MPa.

[0024] In some embodiments, the preparation method of the first antibacterial material comprises the following steps: Select dry wormwood and honeysuckle, mix them in a mass ratio of 1:1, then add them to a multi-functional extraction tank, add deionized water, set the rotation speed at 50 r / min, the temperature at 90 °C, decoct for 2 h, take the decoction liquid, filter out impurities with a plate-and-frame filter press to obtain a filtrate, transfer the filtrate to a precipitation tank, add 95% ethanol, let it stand and precipitate for 12 h, take the precipitate and place it in a horizontal centrifuge, set the rotation speed at 4000 r / min, the centrifugation time at 15 min, take the supernatant and place it in a vacuum drying oven, set the temperature at 50 °C, the vacuum degree at -0.08 MPa, concentrate until the water content ≤ 5%, then crush it through a 200-mesh sieve to obtain the first antibacterial material.

[0025] In some embodiments, during the preparation of the first antibacterial material, the mass ratio of wormwood, honeysuckle and deionized water is 1:1:10, and the mass ratio of the filtrate and 95% ethanol is 1:1.6.

[0026] In some embodiments, the preparation method of the second antibacterial material comprises the following steps: Select bamboo leaves and dandelion in a mass ratio of 3:1, mix them and crush them to a particle size ≤ 2 mm, transfer them to an ultrasonic extraction tank, set the frequency at 40 kHz, the power at 500 w, the temperature at 50 °C, add a 75% ethanol solution, continuously extract for 40 min to obtain an extract. The mass ratio of bamboo leaves, dandelion and 75% ethanol solution is 3:1:60. Transfer the extract to a rotary evaporator to concentrate it to one-fifth of the original volume, then transfer it to a freeze dryer, set the cold trap temperature at -50 °C, the vacuum degree at 10 Pa, and dry for 20 h to obtain the second antibacterial material.

[0027] In some embodiments, the preparation method of the first reinforcing material comprises the following steps: Select konjac and kudzu root in a mass ratio of 2:1, slice them and mix them. The slice thickness is 2 mm, then transfer them to an alkali-resistant reaction kettle, add a 5% sodium hydroxide solution with a material-liquid ratio of 1:8, set the temperature at 23 °C, the rotation speed at 100 r / min, soak for 20 h to obtain a soaking solution, then place it in a plate-and-frame filter press, adjust the pH value of the soaking solution to 4.5 with 10% hydrochloric acid filtrate to precipitate flocculates, then wash the flocculates with deionized water until neutral, transfer them to a spray drying tower, set the inlet air temperature at 180 °C, the outlet air temperature at 85 °C, and continuously dry for 1 h to obtain the first reinforcing material.

[0028] In some embodiments, the preparation method of the second reinforcing material comprises the following steps: Select seaweed and aloe vera gel in a mass ratio of 1:1, put them into a high-speed homogenizer, set the rotation speed at 20000 r / min, continuously process for 5 min to obtain a homogenate, inject it into a freeze-drying chamber, set the pre-freezing temperature at -40 °C, the sublimation stage temperature at -20 °C, the vacuum degree at 20 Pa, dry for 45 h, and then crush it with a jet mill to a particle size less than or equal to 50 μm to obtain the second reinforcing material.

[0029] In some embodiments, a method for preparing a polylactic acid antibacterial film includes the following steps: S1: Weigh the polylactic acid base material, the first antibacterial material, the second antibacterial material, the first reinforcing material, the second reinforcing material, and the dispersion aid as required and put them into a mixer. Set the temperature to be less than or equal to 55 °C, the rotation speed to 700 r / min, and premix for 20 min to obtain a mixed material. S2: Put the mixed material into a twin-screw extruder for melt blending. After the melt is extruded and wound on a cooling roll, it is slit and packaged to obtain a polylactic acid antibacterial film. S3: In S2, the aspect ratio of the twin-screw extruder is 40:1. The temperature of the screw partition in the first zone is 160 °C, the second zone is 170 °C, the third zone is 175 °C, the die head is 170 °C, the screw rotation speed is 50 r / min, the surface of the cooling roll is chrome-plated, the temperature is set to 15 °C, and the linear speed of the cooling roll is 2 m / min. Example 2

[0030] A polylactic acid antibacterial film includes the following raw materials in parts by weight: 95 parts of polylactic acid base material, 10 parts of the first antibacterial material, 8 parts of the second antibacterial material, 12 parts of the first reinforcing material, 5 parts of the second reinforcing material, and 3 parts of dispersion aid.

[0031] In some embodiments, the dispersion aid is prepared by modifying bentonite with cetyltrimethylammonium bromide by an ion exchange method, and the particle size of the dispersant is ≤500 nm.

[0032] In some embodiments, the method for preparing the polylactic acid base material includes the following steps: Select corn starch as the raw material, crush it through a 60-mesh sieve and transfer it to a gelatinizer. Add deionized water, adjust the pH value to 6.5, start the gelatinizer and set the temperature to 120 °C. After gelatinization for 30 min, cool it to 40 °C, inoculate lactic acid bacteria, and then put it into a fermentation tank. Set the stirring rotation speed to 100 r / min, the ventilation volume to 0.5 vvm, and continuously ferment for 48 h to obtain a fermentation broth. The fermentation broth is filtered by a plate and frame, decolorized with activated carbon, concentrated under reduced pressure to a solid content of 70%, and then through a melt polycondensation reaction to obtain an L-type polylactic acid resin, which is the polylactic acid base material for use.

[0033] In some embodiments, during the preparation of the polylactic acid base material, the mass ratio of deionized water to corn starch raw material is 3:1, and the set temperature of the melt polycondensation reaction is 180 °C, and the vacuum degree is -0.1 MPa.

[0034] In some embodiments, the preparation method of the first antibacterial material comprises the following steps: Select dry wormwood and honeysuckle, mix them in a mass ratio of 1:1, then add them to a multi-functional extraction tank, add deionized water, set the rotation speed at 80 r / min, the temperature at 95 °C, decoct for 3 h, take the cooking liquid, add it to a plate and frame filter to remove impurities to obtain a filtrate, transfer the filtrate to a precipitation tank, add 95% ethanol, let it stand and precipitate for 14 h, take the precipitate and place it in a horizontal centrifuge, set the rotation speed at 5000 r / min, the centrifugation time at 20 min, take the supernatant and place it in a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, concentrate it until the water content ≤ 5%, then pulverize it and pass it through a 200-mesh sieve to obtain the first antibacterial material.

[0035] In some embodiments, during the preparation of the first antibacterial material, the mass ratio of wormwood, honeysuckle and deionized water is 1:1:10, and the mass ratio of the filtrate to 95% ethanol is 1:1.6.

[0036] In some embodiments, the preparation method of the second antibacterial material comprises the following steps: Select bamboo leaves and dandelion in a mass ratio of 3:1, mix them and pulverize them to a particle size ≤ 2 mm, transfer them to an ultrasonic extraction tank, set the frequency at 40 kHz, the power at 500 w, the temperature at 50 °C, add a 75% ethanol solution, continuously extract for 50 min to obtain an extract, the mass ratio of bamboo leaves, dandelion and 75% ethanol solution is 3:1:60, transfer the extract to a rotary evaporator to concentrate it to one-fifth of the original volume, transfer it to a freeze dryer, set the cold trap temperature at -50 °C, the vacuum degree at 10 Pa, and dry for 24 h to obtain the second antibacterial material.

[0037] In some embodiments, the preparation method of the first reinforcing material comprises the following steps: Select konjac and kudzu root in a mass ratio of 2:1, slice them and mix them, the slice thickness is 3 mm, then transfer them to an alkali-resistant reaction kettle, add a 5% sodium hydroxide solution with a material-liquid ratio of 1:8, set the temperature at 25 °C, the rotation speed at 120 r / min, soak for 24 h to obtain a soaking solution, then place it in a plate and frame filter press, adjust the pH value of the soaking solution to 4.5 with 10% hydrochloric acid filtrate, precipitate flocculates, then wash the flocculates with deionized water until neutral, transfer them to a spray drying tower, set the inlet air temperature at 180 °C, the outlet air temperature at 85 °C, and continuously dry for 2 h to obtain the first reinforcing material.

[0038] In some embodiments, the preparation method of the second reinforcing material comprises the following steps: Select seaweed and aloe vera gel in a mass ratio of 1:1, put them into a high-speed homogenizer, set the rotation speed at 22000 r / min, continuously process for 7 min to obtain a homogenate, inject it into a freeze-drying chamber, set the pre-freezing temperature at -40 °C, the sublimation stage temperature at -20 °C, the vacuum degree at 20 Pa, dry for 48 h, and then pulverize it with an air flow pulverizer to a particle size less than or equal to 50 μm to obtain the second reinforcing material.

[0039] In some embodiments, a method for preparing a polylactic acid antibacterial film includes the following steps: S1: Weigh the polylactic acid base material, the first antibacterial agent, the second antibacterial agent, the first reinforcing agent, the second reinforcing agent, and the dispersion aid as required, and put them into a mixer. Set the temperature to be less than or equal to 55 °C, the rotation speed to 800 r / min, and premix for 30 min to obtain a mixed material. S2: Put the mixed material into a twin-screw extruder for melt blending. After the melt is extruded and wound on a cooling roll, it is slit and packaged to obtain a polylactic acid antibacterial film. S3: In S2, the aspect ratio of the twin-screw extruder is 40:1. The temperature of the first zone of the screw is 160 °C, the second zone is 170 °C, the third zone is 175 °C, the die head is 170 °C, the screw rotation speed is 60 r / min, the surface of the cooling roll is chrome-plated, the temperature is set to 20 °C, and the linear speed of the cooling roll is 3 m / min. Example 3

[0040] A polylactic acid antibacterial film includes the following raw materials in parts by weight: 85 parts of polylactic acid base material, 7 parts of the first antibacterial agent, 6 parts of the second antibacterial agent, 9 parts of the first reinforcing agent, 3 parts of the second reinforcing agent, and 2 parts of dispersion aid.

[0041] In some embodiments, the dispersion aid is prepared by modifying bentonite with cetyltrimethylammonium bromide by an ion exchange method, and the particle size of the dispersant is ≤500 nm.

[0042] In some embodiments, the method for preparing the polylactic acid base material includes the following steps: Select corn starch as the raw material, transfer it to a gelatinizer after pulverizing and passing through a 60-mesh sieve, add deionized water, adjust the pH value to 6.5, start the gelatinizer and set the temperature to 110 °C. After gelatinization for 30 min, cool it to 38 °C, inoculate lactic acid bacteria, then put it into a fermentation tank, set the stirring rotation speed to 90 r / min, the aeration rate to 0.5 vvm, and continue fermentation for 42 h to obtain a fermentation broth. The fermentation broth is filtered by a plate and frame, decolorized with activated carbon, concentrated under reduced pressure to a solid content of 65%, and then through a melt polycondensation reaction to obtain an L-type polylactic acid resin, which is the polylactic acid base material for use.

[0043] In some embodiments, during the preparation of the polylactic acid base material, the mass ratio of deionized water to corn starch raw material is 3:1, and the temperature of the melt polycondensation reaction is set to 175 °C, and the vacuum degree is -0.095 MPa.

[0044] In some embodiments, the preparation method of the first antibacterial material comprises the following steps: Select dry wormwood and honeysuckle, mix them in a mass ratio of 1:1, then add them to a multi-functional extraction tank, add deionized water, set the rotation speed at 65 r / min and the temperature at 93 °C, decoct for 2.5 h, take the decoction liquid, add it to a plate and frame filter to remove impurities to obtain a filtrate, transfer the filtrate to a precipitation tank, add 95% ethanol, let it stand and precipitate for 13 h, take the precipitate and place it in a horizontal centrifuge, set the rotation speed at 4500 r / min and the centrifugation time at 18 min, take the supernatant and place it in a vacuum drying oven, set the temperature at 55 °C and the vacuum degree at -0.08 MPa, concentrate until the water content ≤ 5%, then crush and pass through a 200-mesh sieve to obtain the first antibacterial material.

[0045] In some embodiments, during the preparation of the first antibacterial material, the mass ratio of wormwood, honeysuckle and deionized water is 1:1:10, and the mass ratio of the filtrate to 95% ethanol is 1:1.6.

[0046] In some embodiments, the preparation method of the second antibacterial material comprises the following steps: Select bamboo leaves and dandelion in a mass ratio of 3:1, mix them and crush them to a particle size ≤ 2 mm, transfer them to an ultrasonic extraction tank, set the frequency at 40 kHz, the power at 500 w and the temperature at 50 °C, add a 75% ethanol solution, continuously extract for 45 min to obtain an extract, the mass ratio of bamboo leaves, dandelion and 75% ethanol solution is 3:1:60, transfer the extract to a rotary evaporator to concentrate it to one-fifth of the original volume, transfer it to a freeze dryer, set the cold trap temperature at -50 °C and the vacuum degree at 10 Pa, dry for 22 h to obtain the second antibacterial material.

[0047] In some embodiments, the preparation method of the first reinforcing material comprises the following steps: Select konjac and kudzu root in a mass ratio of 2:1, slice them and mix them, the slice thickness is 2.5 mm, then transfer them to an alkali-resistant reaction kettle, add a 5% sodium hydroxide solution with a material-liquid ratio of 1:8, set the temperature at 24 °C and the rotation speed at 110 r / min, soak for 22 h to obtain a soaking solution, then place it in a plate and frame filter press, adjust the pH value of the soaking solution to 4.5 with 10% hydrochloric acid filtrate to precipitate flocculates, then wash the flocculates with deionized water until neutral, transfer them to a spray drying tower, set the inlet air temperature at 180 °C and the outlet air temperature at 85 °C, continuously dry for 1.5 h to obtain the first reinforcing material.

[0048] In some embodiments, the preparation method of the second reinforcing material comprises the following steps: Select seaweed and aloe vera gel in a mass ratio of 1:1, put them into a high-speed homogenizer, set the rotation speed at 21000 r / min, continuously process for 6 min to obtain a homogenate, inject it into a freeze-drying chamber, set the pre-freezing temperature at -40 °C, the sublimation stage temperature at -20 °C and the vacuum degree at 20 Pa, dry for 46 h, and then crush it with a jet mill to a particle size less than or equal to 50 μm to obtain the second reinforcing material.

[0049] In some embodiments, a method for preparing a polylactic acid antibacterial film includes the following steps: S1: Weigh the polylactic acid base material, the first antibacterial agent, the second antibacterial agent, the first reinforcing agent, the second reinforcing agent, and the dispersion aid as required and put them into a mixer. Set the temperature to be less than or equal to 55 °C, the rotation speed to 750 r / min, and premix for 25 min to obtain a mixed material. S2: Put the mixed material into a twin-screw extruder for melt blending. Extrude the melt to a cooling roll for winding, and then slit and package it to obtain the polylactic acid antibacterial film. S3: In S2, the aspect ratio of the twin-screw extruder is 40:1. The temperature of the screw partition is 160 °C in zone 1, 170 °C in zone 2, 175 °C in zone 3, and 170 °C for the die head. The screw rotation speed is 55 r / min. The surface of the cooling roll is chrome-plated, the temperature is set to 18 °C, and the linear speed of the cooling roll is 2.5 m / min.

[0050] Comparative Example 1: "Polylactic Acid PLA" of Anhui Fengyuan Group. Refer to the film performance data in its implementation standard Q / ABFPLA 004-2021.

[0051] Comparative Example 2: The difference between this comparative example and Experiment 1 is that in the process of preparing the polylactic acid antibacterial film in this comparative example, the first antibacterial agent and the second antibacterial agent are not added.

[0052] Comparative Example 3: The difference between this comparative example and Experiment 1 is that in the process of preparing the polylactic acid antibacterial film in this comparative example, the first reinforcing agent and the second reinforcing agent are not added.

[0053] Perform performance tests on the polylactic acid antibacterial films prepared in Examples 1-3 and Comparative Examples 1-3. The test items and test methods are as follows: Antibacterial rate test: Detect according to the standard of GB / T 31402-2015 and record the data in Table 1. Tensile properties: Detect according to the standard of GB / T 1040.3-2006 and record the data in Table 1. Degradation performance: Detect according to the standard of ISO 14855-1 and record the data in Table 1.

[0054] Table 1:

[0055] It can be seen from the comparison and analysis of the data in Table 1 that the polylactic acid antibacterial film prepared by the preparation methods of Examples 1-3 has significantly improved antibacterial performance, tensile strength, and degradation rate compared with the films prepared by the preparation methods of Comparative Examples 1-3.

[0056] It can be seen from the comparison and analysis of the data in Table 1 that the antibacterial rate and degradation rate of the polylactic acid antibacterial film prepared by the preparation methods of Examples 1-3 are significantly improved compared with those of Comparative Example 1, while the tensile strength is close to that of the commercially available polylactic acid film in Comparative Example 1, indicating that adding the first antibacterial agent, the second antibacterial agent, the first reinforcing agent and the second reinforcing agent in the preparation process of the polylactic acid antibacterial film can significantly improve the antibacterial performance and degradation rate of the film.

[0057] It can be seen from the comparison and analysis of the data in Table 1 that the antibacterial rate of the polylactic acid antibacterial film prepared by the preparation methods of Examples 1-3 is significantly improved compared with those of Comparative Example 1 and Comparative Example 3, indicating that adding the first antibacterial agent and the second antibacterial agent in the preparation process of the polylactic acid antibacterial film can significantly improve the antibacterial performance of the film.

[0058] It can be seen from the comparison and analysis of the data in Table 1 that the tensile strength of the polylactic acid antibacterial film prepared by the preparation methods of Examples 1-3 is significantly improved compared with those of Comparative Example 2 and Comparative Example 3, indicating that adding the first reinforcing agent and the second reinforcing agent in the preparation process of the polylactic acid antibacterial film can significantly improve the tensile performance of the film.

[0059] It can be seen from the comparison and analysis of the data in Table 1 that the 180-day degradation rate of the polylactic acid antibacterial film prepared by the preparation methods of Examples 1-3 and Comparative Example 2 is significantly improved compared with those of Comparative Example 1 and Comparative Example 3, indicating that adding the first antibacterial agent, the second antibacterial agent, the first reinforcing agent and the second reinforcing agent in the preparation process of the polylactic acid antibacterial film can significantly improve the 180-day degradation rate of the film.

[0060] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0061] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art in the relevant technical field can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A polylactic acid antibacterial film, characterized in that: The invention comprises the following raw materials in parts by weight: 80-95 parts of a polylactic acid base material, 3-10 parts of a first antibacterial material, 2-8 parts of a second antibacterial material, 4-12 parts of a first reinforcing material, 2-5 parts of a second reinforcing material and 1-3 parts of a dispersing aid.

2. The polylactic acid antibacterial film according to claim 1, characterized in that: The dispersing aid is prepared by modifying bentonite with hexadecyltrimethylammonium bromide through an ion exchange method, and the particle size of the dispersant is ≤500nm.

3. The polylactic acid antibacterial film according to claim 1, characterized in that: The preparation method of the polylactic acid base material comprises the following steps: selecting corn starch as a raw material, crushing it through a 60-mesh sieve and then transferring it to a gelatinizer, adding deionized water, adjusting the pH value to 6.5, starting the gelatinizer and setting the temperature to 100-120° C., cooling to 35-40° C. after gelatinization for 30 minutes, inoculating lactic acid bacteria, and then placing it in a fermentation tank, setting the stirring speed to 80-100 r / min and the ventilation volume to 0.5 vvm, and continuing fermentation for 36-48 hours to obtain a fermentation liquid, filtering the fermentation liquid through a plate and frame filter, decolorizing it with activated carbon, and concentrating it under reduced pressure to a solid content of (60-70)%, and then performing a melt polycondensation reaction to obtain an L-type polylactic acid resin, i.e., the polylactic acid base material, for standby use.

4. The polylactic acid antibacterial film according to claim 1, characterized in that: During the preparation of the polylactic acid base material, the mass ratio of the deionized water to the corn starch raw material is 3:1, the melt polycondensation reaction is set at a temperature of 170-180° C., and the vacuum degree is - (0.09-0.1) MPa.

5. The polylactic acid antibacterial film according to claim 1, characterized in that: The preparation method of the first antibacterial material comprises the following steps: selecting dry wormwood and honeysuckle in a mass ratio of 1:1, then adding them into a multifunctional extraction tank, adding deionized water, setting the speed to 50-80r / min, the temperature to 90-95°C, decocting for 2-3h, taking the cooking liquid and adding it into a plate and frame filter press to filter out impurities to obtain a filtrate, transferring the filtrate into a precipitation tank, adding 95% ethanol, standing and settling for 12-14h, taking the precipitate and placing it into a horizontal centrifuge, setting the speed to 4000-5000r / min, the centrifugation time to 15-20min, taking the supernatant and placing it into a vacuum drying oven, setting the temperature to 50-60°C, the vacuum degree to -0.08MPa, concentrating to a water content of ≤5%, and then crushing it through a 200-mesh sieve to obtain the first antibacterial material.

6. The polylactic acid antibacterial film according to claim 5, characterized in that: During the preparation of the first antibacterial material, the mass ratio of the wormwood, honeysuckle and deionized water is 1:1:10, and the mass ratio of the filtrate to 95% ethanol is 1:1.

6.

7. The polylactic acid antibacterial film according to claim 5, characterized in that: The preparation method of the second antibacterial material comprises the following steps: selecting bamboo leaves and dandelions in a mass ratio of 3:1, mixing them and crushing them to a particle size of ≤2mm, transferring them to an ultrasonic extraction tank, setting the frequency to 40kHz, the power to 500w, and the temperature to 50°C, adding 75% ethanol solution, and continuously extracting for 40-50min to obtain an extract, wherein the mass ratio of the bamboo leaves, dandelions and 75% ethanol solution is 3:1:60, transferring the extract to a rotary evaporator and concentrating it to one-fifth of the original volume, transferring it to a freeze dryer, setting the cold trap temperature to -50°C, the vacuum degree to 10Pa, and drying it for 20-24h to obtain a second antibacterial material.

8. The polylactic acid antibacterial film according to claim 7, characterized in that: The preparation method of the first reinforcing material comprises the following steps: selecting konjac and kudzu root slices in a mass ratio of 2:1 and mixing them, the slice thickness is 2-3 mm, and then transferring them to an alkali-resistant reactor, adding 5% sodium hydroxide solution with a solid-liquid ratio of 1:8, setting the temperature to 23-25°C, the speed to 100-120r / min, soaking for 20-24h to obtain a soaking liquid, and then placing it in a plate and frame filter press, adjusting the pH value of the soaking liquid to 4.5 by 10% hydrochloric acid filtrate, precipitating flocs, and then washing the flocs to neutrality with deionized water, transferring them to a spray drying tower, setting the inlet temperature to 180°C and the outlet temperature to 85°C, and continuously drying for 1-2h to obtain the first reinforcing material.

9. The method for preparing the polylactic acid antibacterial film according to claim 7, characterized in that: The preparation method of the second reinforcing material comprises the following steps: selecting seaweed and aloe vera gel in a mass ratio of 1:1, putting them into a high-speed homogenizer, setting the speed to 20000-22000r / min, continuously treating for 5-7min to obtain a homogenate, injecting it into a freeze drying chamber, setting the pre-freezing temperature to -40°C, the sublimation stage temperature to -20°C, the vacuum degree to 20Pa, drying for 45-48h, and then crushing them with a jet mill to a particle size of less than or equal to 50μm to obtain a second reinforcing material.

10. The method for preparing the polylactic acid antibacterial film according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: Weigh the polylactic acid base material, the first antibacterial material, the second antibacterial material, the first reinforcing material, the second reinforcing material and the dispersing aid as needed and put them into a mixer, set the temperature to be less than or equal to 55°C, the speed to 700-800r / min, premix for 20-30min to obtain a mixture; S2: putting the mixed material into a twin-screw extruder for melt blending, extruding the melt onto a cooling roller for winding, and then slitting and packaging to obtain a polylactic acid antibacterial film; S3: The aspect ratio of the twin-screw extruder in S2 is 40:1, the screw zone temperature is 160°C in zone 1, 170°C in zone 2, 175°C in zone 3, the die head is 170°C, the screw speed is 50-60r / min, the cooling roller surface is chrome-plated, the temperature is set at 15-20°C, and the cooling roller linear speed is (2-3) m / min.

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