CN115710409A - Bio-based antibacterial packaging film and preparation method thereof - Google Patents
Bio-based antibacterial packaging film and preparation method thereof Download PDFInfo
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- CN115710409A CN115710409A CN202210979382.1A CN202210979382A CN115710409A CN 115710409 A CN115710409 A CN 115710409A CN 202210979382 A CN202210979382 A CN 202210979382A CN 115710409 A CN115710409 A CN 115710409A
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
- Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics
Abstract
The invention discloses a bio-based bacteriostatic packaging film and a preparation method thereof. According to the invention, poly adipic acid/butylene terephthalate (PBAT) and PLA are blended, and at least one of chitosan, nano silver and nano zinc oxide is added as a bacteriostatic agent, so that the obtained PLA/PBAT composite film has good mechanical properties and good barrier properties, and the performance defects existing when the PLA material is used as a food packaging film are well improved.
Description
Technical Field
The invention relates to the technical field of food packaging, in particular to a bio-based antibacterial packaging film and a preparation method thereof.
Background
At present, plastic packaging plays a leading role in the field of food packaging, but most plastics such as polyvinyl chloride (PVC), polyethylene (PE) and the like take non-renewable petroleum as a raw material, and because the plastics cannot be naturally degraded and are not renewable, the characteristics of influencing food safety and the like are achieved, white pollution is brought to the environment, and the health of people is also harmed. With the improvement of consciousness, consumers pursue more environment-friendly, safe, green and organic foods, so that the development of biodegradability is more and more emphasized.
The bio-based materials comprise bio-source degradable high polymer materials and artificially synthesized degradable high polymer materials, the most common bio-source degradable high polymer materials at present comprise starch, protein, chitosan, polyhydroxyalkanoate (PHA) and Polyhydroxybutyrate (PHB), and the high polymer materials prepared by using the materials as raw materials have poor mechanical strength and toughness, for example, starch-based degradable plastics have high brittleness and are easy to crack, and can be damaged in the food packaging process. The artificially synthesized degradable high polymer material mainly comprises polylactic acid (PLA), local butanediol succinate (PBS), polyvinyl alcohol (PVA), polypropylene carbonate (PPC) and Polycaprolactone (PCL), wherein the PLA is a completely biodegradable polymer material obtained by polymerizing lactic acid serving as a main raw material, and the polylactic acid (PLA) is sufficient in raw material source, renewable, small in pollution in the production process and an ideal green high polymer material. PLA as a packaging material has good transparency and mechanical properties, no toxicity, no irritation, easy processing and forming, good biocompatibility and the like, and is a most successful bio-based packaging material developed in markets at home and abroad so far. However, PLA has the disadvantage of being very brittle and not bacteriostatic when used as a food packaging film, such as a food preservative film.
Disclosure of Invention
The invention mainly aims to provide a bio-based antibacterial packaging film and a preparation method thereof, and aims to solve the problems of high brittleness and no antibacterial property when PLA is used as a food packaging film.
In order to achieve the purpose, the invention provides a bio-based antibacterial packaging film, and the constituent materials of the bio-based antibacterial packaging film comprise PLA, PBAT and a bacteriostatic agent, wherein the bacteriostatic agent comprises at least one of chitosan, nano silver and nano zinc oxide.
Optionally, the mass of the PLA, PBAT, and the bacteriostatic agent is 70 parts, 500-1000 parts, and 10-50 parts, respectively, in parts by mass.
Optionally, the chitosan is analytically pure, and the degree of deacetylation is 80-95%.
Optionally, the particle size of the nano silver is 10-80 nm, and the purity is more than 99.9%.
Optionally, the particle size of the nano zinc oxide is 10-80 nm, and the purity is more than 90%.
Optionally, the thickness of the bio-based antibacterial packaging film is 0.2-0.8 mm.
In order to achieve the purpose, the invention provides a preparation method of the bio-based antibacterial packaging film, which comprises the following steps:
drying the PLA and the PBAT;
mixing the dried PLA and PBAT with a bacteriostatic agent in a melt blending manner to obtain bacteriostatic master batches;
drying the antibacterial master batch;
and preparing the dried antibacterial master batch into a film by a tape casting method to obtain the bio-based antibacterial packaging film.
Optionally, mixing the dried PLA and PBAT with a bacteriostatic agent in a melt blending manner to obtain a bacteriostatic masterbatch, including:
adding the dried PLA, PBAT and the bacteriostatic agent into a double-screw extruder, and granulating after melt extrusion to obtain bacteriostatic master batches; wherein the temperature of a screw zone of the double-screw extruder is set to be 175-185 ℃, 180-190 ℃, 175-185 ℃, the temperature of a die orifice is set to be 160-170 ℃, and the rotating speed of the screw is set to be 50-100 r/min.
Optionally, the step of preparing the dried antibacterial master batch into a film by a tape casting method to obtain a bio-based antibacterial packaging film includes:
preparing the dried antibacterial master batch into a film through a cast film testing machine to obtain a bio-based antibacterial packaging film; wherein, the temperature of the screw zone of the cast film testing machine is set to 178-182 ℃, 182-188 ℃ and 178-182 ℃, the temperature of the die orifice is set to 160-170 ℃, and the rotating speed of the screw is set to 20-50 r/min.
Optionally, in the step of drying the PLA and PBAT: the drying temperature of the PLA and the PBAT is 35 to 45 ℃, and the drying time is 2 to 4 hours; and/or the presence of a gas in the atmosphere,
the step of drying the antibacterial master batch comprises the following steps: the drying temperature of the antibacterial master batch is 35-45 ℃, and the drying time is 2-4 h.
In the technical scheme provided by the invention, poly (butylene adipate terephthalate) (PBAT) and PLA are blended, and at least one of chitosan, nano silver and nano zinc oxide is added as a bacteriostatic agent, so that the obtained PLA/PBAT composite film has good mechanical property and good barrier property, and the performance defect of the PLA material when used as a food packaging film is well improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of an embodiment of a method for preparing a bio-based bacteriostatic packaging film provided by the invention;
FIG. 2 is an apparent photograph of films obtained in examples of the present invention and comparative examples;
FIG. 3 shows the results of water contact angle tests of films prepared according to examples of the present invention and comparative examples;
FIG. 4 shows the results of mechanical property tests of films obtained in examples of the present invention and comparative examples;
FIG. 5 shows the results of barrier property tests of films obtained in examples of the present invention and comparative examples;
FIG. 6 shows the results of the measurement of the E.coli-inhibiting performance of the films according to the examples and comparative examples;
FIG. 7 shows the results of the bacteriostatic performance test of the films prepared in the examples and comparative examples of the present invention against Staphylococcus aureus.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially. In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, technical solutions between the various embodiments may be combined with each other, but must be based on the realization of the capability of a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
PLA as a packaging material has good transparency and mechanical properties, no toxicity, no irritation, easy processing and forming, good biocompatibility and the like, and is a most successful bio-based packaging material developed in markets at home and abroad so far. However, PLA has the disadvantage of being very brittle and non-bacteriostatic when used as a food packaging film, such as a food preservative film.
In view of this, the present invention provides a bio-based antibacterial packaging film, the constituent materials of which include PLA, PBAT and a bacteriostatic agent, where the bacteriostatic agent includes at least one of chitosan, nano silver and nano zinc oxide.
Polylactic acid (PLA) is a completely biodegradable polymer material obtained by polymerizing lactic acid serving as a main raw material, has sufficient raw material source, is renewable, has little pollution in the production process, and is an ideal green high polymer material. PLA as a packaging material has good transparency and mechanical properties, no toxicity, no irritation, easy processing and forming, good biocompatibility and the like, and is a most successful bio-based packaging material developed in markets at home and abroad so far. The poly (butylene adipate terephthalate) (PBAT) is aliphatic-aromatic copolyester, the PBAT has low elastic modulus, high elongation at break and good ductility, the PBAT has the comprehensive properties of aliphatic polyester and aromatic polyester due to the main chain structure characteristics of the PBAT, and the polyester material has relatively high flexibility because the crystal structure is damaged after copolymerization.
Chitosan (Chitosan, CS) is a derivative of chitin, is composed of randomly distributed β - (1-4) -D glucosamine (deacetylation unit) and N-acetyl-D-glucosamine (acetyl unit) chains, and is one of the most abundant bio-based degradation materials at present. Researches prove that the chitosan has antibacterial, antioxidant and ultraviolet blocking capabilities, and further researches show that the CS and PBAT can not generate chemical interaction through melt blending and can improve the degradation rate of the composite material. Inorganic Nanoparticles (NPs) have many advantages as antimicrobial agents, such as outstanding bacteriostatic properties, good compatibility. The nanometer zinc oxide particles (ZnONPs) show the outstanding characteristics of no toxicity, strong antibacterial activity, excellent mechanical property and the like, so that the nanometer zinc oxide particles become candidate materials of reinforced polymers. Nano silver particles (AgNPs) have been extensively studied in the field of bacteriostasis, agNPs as bacteriostats can inactivate enzymes and weaken bacterial cells, and the three main mechanisms of AgNPs as bacteriostats are: 1. breakdown of lipopolysaccharides and forcing the produced peptides into cells and disrupting the cell membrane; 2. enter bacterial cells, break down DNA and organize their proliferation; 3. AgNPs decompose into silver particles to generate active oxygen free radicals, thereby inactivating bacteria. The research of the invention finds that the higher inhibition effect on staphylococcus aureus and escherichia coli can be achieved when the AgNPs content is lower.
In the technical scheme provided by the invention, poly (butylene adipate terephthalate) (PBAT) and PLA are blended, and at least one of chitosan, nano silver and nano zinc oxide is added as a bacteriostatic agent, so that the obtained PLA/PBAT composite film has good mechanical property and good barrier property, and the performance defect of the PLA material when used as a food packaging film is well improved.
Further, in a specific embodiment of the present invention, the addition ratio of each component material of the bio-based antibacterial packaging film is as follows: the mass portions of the PLA, the PBAT and the bacteriostatic agent are respectively 70 portions, 500-1000 portions and 10-50 portions.
The bacteriostatic agent comprises at least one of chitosan, nano silver and nano zinc oxide, and the bacteriostatic agent can only comprise chitosan, nano silver or nano zinc oxide, and can also be a combination of any two or three of chitosan, nano silver and nano zinc oxide. In a first embodiment of the present invention, the bacteriostatic agent is chitosan, specifically, the chitosan is analytically pure, and the deacetylation degree is 80-95%. Furthermore, the addition amount of the chitosan is 10-50 parts by mass.
In a second embodiment of the present invention, the bacteriostatic agent is nano silver, specifically, the nano silver has a particle size of 10 to 80nm and a purity of more than 99.9%. Furthermore, the addition amount of the nano silver is 10-20 parts by mass.
In a third embodiment of the present invention, the bacteriostatic agent is nano zinc oxide, specifically, the nano zinc oxide has a particle size of 10 to 80nm and a purity of more than 90%. Furthermore, the addition amount of the nano zinc oxide is 10-20 parts by mass.
In addition, in the embodiment provided by the invention, the thickness of the bio-based antibacterial packaging film is 0.2-0.8 mm. Therefore, the bio-based antibacterial packaging film is easy to process and has good mechanical property, antibacterial property and usability.
Based on the bio-based antibacterial packaging film provided by the invention, the invention further provides a preparation method of the bio-based antibacterial packaging film, the PLA, the PBAT and the bacteriostatic agent are fully mixed by adopting a melt blending mode, and then the film is prepared by a tape casting method, and fig. 1 shows an embodiment of the preparation method of the bio-based antibacterial packaging film provided by the invention. Referring to fig. 1, in this embodiment, the preparation method of the bio-based bacteriostatic packaging film includes the following steps:
step S10, drying the PLA and the PBAT;
s20, mixing the dried PLA and PBAT with a bacteriostatic agent in a melt blending mode to obtain bacteriostatic master batches;
s30, drying the antibacterial master batch;
and S40, preparing the dried antibacterial master batch into a film by a tape casting method to obtain the bio-based antibacterial packaging film.
First, the PLA and PBAT raw materials, preferably pellets, which may be dried, for example, in an air-blast drying oven or a vacuum drying oven, are dried to remove moisture therefrom and avoid degradation thereof during subsequent high-temperature processing. And then, sufficiently and uniformly mixing the dried PLA, PBAT and the bacteriostatic agent in a melt blending mode, and preparing granules to obtain bacteriostatic master batches, wherein the melt blending can be performed in an open mill or internal mixing mode and the like. And then, drying the prepared antibacterial master batch to remove moisture in the antibacterial master batch, wherein the drying mode can be drying in an air-blast drying oven or a vacuum drying oven, for example. And finally, preparing the dried antibacterial master batch into a required film by adopting a tape casting method, thus obtaining the bio-based antibacterial packaging film.
According to the preparation method of the bio-based antibacterial packaging film, poly adipic acid/butylene terephthalate (PBAT) and PLA are blended, and at least one of chitosan, nano-silver and nano-zinc oxide is added as a bacteriostatic agent, so that the obtained PLA/PBAT composite film has good mechanical property and good barrier property, and the performance defect of a PLA material when used as a food packaging film is well improved; meanwhile, the process is simple, and the prepared product has stable performance and is easy to realize large-scale industrial production.
In some embodiments of the invention, said melt blending is achieved by a twin-screw extruder, in particular, step S20 comprises: adding the dried PLA, PBAT and the bacteriostatic agent into a double-screw extruder, and granulating after melt extrusion to obtain bacteriostatic master batches; wherein the temperature of a screw zone of the double-screw extruder (along the material conveying direction) is set to 175-185 ℃, 180-190 ℃ and 175-185 ℃, the temperature of a die orifice is set to 160-170 ℃, the rotating speed of the screw is set to 50-100 r/min, preferably: the temperature of the screw zone is set to 180 ℃, 185 ℃ and 180 ℃ in sequence, the temperature of the die orifice is 165 ℃, and the rotating speed of the screw is 70r/min. In addition, in the embodiment of the invention, in order to uniformly disperse the bacteriostatic agent in the base material, the prepared bacteriostatic master batch is put into a double-screw extruder, and the step of melt blending is repeated for 2 to 3 times, so as to obtain the bacteriostatic master batch with uniformly distributed bacteriostatic agent.
Further, in some embodiments of the present invention, the casting method film making is realized by a casting film tester, specifically, the step S30 includes: preparing the dried antibacterial master batch into a film through a cast film testing machine to obtain a bio-based antibacterial packaging film; wherein, the temperature of a screw region of the casting film testing machine (along the conveying direction of the materials) is sequentially set to 178-182 ℃, 182-188 ℃ and 178-182 ℃, the temperature of a die orifice is set to 160-170 ℃, and the rotating speed of the screw is set to 20-50 r/min, preferably: the temperature of the screw zone was set to 180 ℃, 185 ℃ and 180 ℃ in this order, the die temperature was 165 ℃ and the screw rotation rate was 30r/min.
In addition, in some embodiments of the present invention, the drying treatment of the PLA and PBAT is performed in a forced air drying oven, specifically, the drying temperature of the PLA and PBAT is 35 to 45 ℃, the drying time is 2 to 4 hours, and preferably 3 hours at 40 ℃.
Likewise, in some embodiments of the present invention, the drying of the bacteriostatic mother particles is also performed in a blast drying oven, specifically, the bacteriostatic mother particles are dried at 35-45 ℃ for 2-4 h, preferably at 40 ℃ for 3h.
The technical solutions of the present invention are further described in detail below with reference to specific examples and drawings, it should be understood that the following examples are merely illustrative of the present invention and are not intended to limit the present invention.
The PLA adopted in the following examples is purchased from Shandong grass plastic raw material Ming-Hu, dongguan, PBAT is purchased from Chengyi plastic Co., ltd, dongguan, and chitosan is purchased from chemical reagents Co., ltd, a national medicine group.
Example 1
The bio-based antibacterial packaging film comprises the following components, by mass, 70 parts of PLA, 900 parts of PBAT and 10 parts of chitosan; wherein, the chitosan is analytically pure, and the degree of deacetylation is 80-95%; the thickness of the bio-based antibacterial packaging film is 0.3mm.
Example 2
The bio-based antibacterial packaging film comprises the following components, by mass, 70 parts of PLA, 900 parts of PBAT and 30 parts of chitosan; wherein, the chitosan is analytically pure, and the degree of deacetylation is 80-95%; the thickness of the bio-based antibacterial packaging film is 0.2mm.
Example 3
The bio-based antibacterial packaging film comprises the following components, by mass, 70 parts of PLA, 900 parts of PBAT and 50 parts of chitosan; wherein, the chitosan is analytically pure, and the deacetylation degree is 80-95%; the thickness of the bio-based antibacterial packaging film is 0.4mm.
Example 4
The bio-based antibacterial packaging film comprises the following components, by mass, 70 parts of PLA, 800 parts of PBAT and 10 parts of nano zinc oxide; wherein, the particle size of the nano zinc oxide particles is 20nm, and the purity is more than 90 percent; the thickness of the bio-based antibacterial packaging film is 0.3mm.
Example 5
The bio-based antibacterial packaging film comprises the following components, by mass, 70 parts of PLA, 500 parts of PBAT and 20 parts of nano zinc oxide; wherein, the particle size of the nano zinc oxide particles is 10nm, and the purity is more than 90 percent; the thickness of the bio-based antibacterial packaging film is 0.3mm.
Example 6
The bio-based antibacterial packaging film comprises the following components, by mass, 70 parts of PLA, 600 parts of PBAT and 10 parts of nano silver; wherein, the grain diameter of the nano silver particles is 20nm, and the purity is more than 99.9 percent; the thickness of the bio-based antibacterial packaging film is 0.6mm.
Example 7
The bio-based antibacterial packaging film comprises the following components, by mass, 70 parts of PLA, 1000 parts of PBAT and 20 parts of nano-silver; wherein, the grain diameter of the nano silver particles is 30nm, and the purity is more than 99.9 percent; the thickness of the bio-based antibacterial packaging film is 0.8mm.
Example 8
(1) Weighing the raw materials according to the formula of the embodiment 1, placing PLA and PBAT in a forced air drying oven, and drying for 3h at the temperature of 40 ℃;
(2) Putting the dried PLA, PBAT and the bacteriostatic agent into a double-screw extruder for melt extrusion and granulation, and then putting the obtained granules into the double-screw extruder again for repeating the steps of melt extrusion and granulation for 3 times to obtain bacteriostatic master batches; wherein the temperature of a screw zone of the double-screw extruder is sequentially set to be 180 ℃, 185 ℃ and 180 ℃ along the material conveying direction, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of the screw is set to be 70r/min;
(3) Placing the prepared antibacterial master batch in a forced air drying oven, and drying at 40 deg.C for 3h;
(4) Putting the dried antibacterial master batch into a casting film testing machine to prepare a film with the thickness of 0.3mm, namely preparing the bio-based antibacterial packaging film; wherein the temperature of a screw region of the cast film testing machine is sequentially set to be 180 ℃, 185 ℃ and 180 ℃ along the conveying direction of the material, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of the screw is set to be 30r/min.
Example 9
(1) Weighing the raw materials according to the formula of the embodiment 2, placing PLA and PBAT in a forced air drying oven, and drying for 4h at the temperature of 35 ℃;
(2) Putting the dried PLA, PBAT and the bacteriostatic agent into a double-screw extruder for melt extrusion and granulation, and then putting the obtained granules into the double-screw extruder again for repeating the steps of melt extrusion and granulation for 3 times to obtain bacteriostatic master batches; wherein the temperature of a screw zone of the double-screw extruder is sequentially set to be 180 ℃, 185 ℃ and 180 ℃ along the material conveying direction, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of the screw is set to be 70r/min;
(3) Placing the prepared antibacterial master batch in a forced air drying oven, and drying at 35 deg.C for 4h;
(4) Putting the dried antibacterial master batch into a casting film testing machine to prepare a film with the thickness of 0.3mm, namely preparing the bio-based antibacterial packaging film; wherein the temperature of a screw region of the cast film testing machine is sequentially set to be 180 ℃, 185 ℃ and 180 ℃ along the conveying direction of the material, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of the screw is set to be 30r/min.
Example 10
(1) Weighing the raw materials according to the formula of the embodiment 3, placing PLA and PBAT in a forced air drying oven, and drying for 2h at the temperature of 45 ℃;
(2) Putting the dried PLA, PBAT and the bacteriostatic agent into a double-screw extruder for melt extrusion and granulation, and putting the obtained granules into the double-screw extruder again for repeating the steps of melt extrusion and granulation for 3 times to obtain bacteriostatic master batches; wherein the temperature of a screw zone of the double-screw extruder is sequentially set to be 180 ℃, 185 ℃ and 180 ℃ along the material conveying direction, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of the screw is set to be 70r/min;
(3) Placing the prepared antibacterial master batch in a forced air drying oven, and drying at 45 deg.C for 2h;
(4) Putting the dried antibacterial master batch into a casting film testing machine to prepare a film with the thickness of 0.3mm, namely preparing the bio-based antibacterial packaging film; wherein, the temperature of a screw region of the cast film testing machine (along the conveying direction of the material) is sequentially set to be 180 ℃, 185 ℃ and 180 ℃, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of the screw is set to be 30r/min.
Example 11
(1) Weighing the raw materials according to the formula of the embodiment 4, placing PLA and PBAT in a forced air drying oven, and drying for 3h at the temperature of 40 ℃;
(2) Putting the dried PLA, PBAT and the bacteriostatic agent into a double-screw extruder for melt extrusion and granulation, and then putting the obtained granules into the double-screw extruder again for repeating the steps of melt extrusion and granulation for 3 times to obtain bacteriostatic master batches; wherein the temperature of a screw zone of the double-screw extruder is sequentially set to be 175 ℃, 180 ℃ and 175 ℃ along the material conveying direction, the temperature of a die orifice is set to be 160 ℃, and the rotating speed of a screw is set to be 100r/min;
(3) Placing the prepared antibacterial master batch in a forced air drying oven, and drying at 40 ℃ for 3h;
(4) Putting the dried antibacterial master batch into a casting film testing machine to prepare a film with the thickness of 0.3mm, namely preparing the bio-based antibacterial packaging film; wherein, the temperature of a screw region of the cast film testing machine is set to 178 ℃, 182 ℃ and 178 ℃ along the conveying direction of the material in sequence, the temperature of a die orifice is set to 160 ℃, and the rotating speed of the screw is set to 50r/min.
Example 12
(1) Weighing the raw materials according to the formula of the embodiment 5, placing PLA and PBAT in a forced air drying oven, and drying for 3h at the temperature of 40 ℃;
(2) Putting the dried PLA, PBAT and the bacteriostatic agent into a double-screw extruder for melt extrusion and granulation, and putting the obtained granules into the double-screw extruder again for repeating the steps of melt extrusion and granulation for 3 times to obtain bacteriostatic master batches; wherein the temperature of a screw zone of the double-screw extruder is sequentially set to 185 ℃, 190 ℃ and 185 ℃ along the material conveying direction, the temperature of a die orifice is set to 170 ℃, and the rotating speed of the screw is set to 50r/min;
(3) Placing the prepared antibacterial master batch in a forced air drying oven, and drying at 40 deg.C for 3h;
(4) Putting the dried antibacterial master batch into a casting film testing machine to prepare a film with the thickness of 0.3mm, namely preparing the bio-based antibacterial packaging film; wherein, the temperature of a screw region of the cast film testing machine is set to 182 ℃, 188 ℃ and 182 ℃ along the conveying direction of the material in sequence, the temperature of a die orifice is set to 170 ℃, and the rotating speed of the screw is set to 20r/min.
Example 13
(1) Weighing the raw materials according to the formula of the embodiment 6, placing PLA and PBAT in a forced air drying oven, and drying for 3h at the temperature of 40 ℃;
(2) Putting the dried PLA, PBAT and the bacteriostatic agent into a double-screw extruder for melt extrusion and granulation, and then putting the obtained granules into the double-screw extruder again for repeating the steps of melt extrusion and granulation for 3 times to obtain bacteriostatic master batches; wherein the temperature of a screw zone of the double-screw extruder is sequentially set to be 180 ℃, 185 ℃ and 180 ℃ along the material conveying direction, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of the screw is set to be 60r/min;
(3) Placing the prepared antibacterial master batch in a forced air drying oven, and drying at 40 deg.C for 3h;
(4) Putting the dried antibacterial master batch into a casting film testing machine to prepare a film with the thickness of 0.3mm, namely preparing the bio-based antibacterial packaging film; wherein the temperature of a screw region of the cast film testing machine is sequentially set to be 180 ℃, 185 ℃ and 180 ℃ along the conveying direction of the material, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of the screw is set to be 40r/min.
Example 14
(1) Weighing the raw materials according to the formula of the embodiment 7, placing PLA and PBAT in a forced air drying oven, and drying for 3h at the temperature of 40 ℃;
(2) Putting the dried PLA, PBAT and the bacteriostatic agent into a double-screw extruder for melt extrusion and granulation, and putting the obtained granules into the double-screw extruder again for repeating the steps of melt extrusion and granulation for 3 times to obtain bacteriostatic master batches; wherein the temperature of a screw zone of the double-screw extruder is sequentially set to be 180 ℃, 185 ℃ and 180 ℃ along the material conveying reverse direction, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of a screw is set to be 80r/min;
(3) Placing the prepared antibacterial master batch in a forced air drying oven, and drying at 40 ℃ for 3h;
(4) Putting the dried antibacterial master batch into a casting film testing machine to prepare a film with the thickness of 0.3mm, namely preparing the bio-based antibacterial packaging film; wherein the temperature of a screw region of the cast film testing machine is sequentially set to be 180 ℃, 185 ℃ and 180 ℃ along the conveying direction of the material, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of the screw is set to be 30r/min.
Comparative example 1
(1) Weighing 70 parts by mass of PLA and 900 parts by mass of PBAT, placing the PLA and the PBAT in a blast drying oven, and drying for 3 hours at the temperature of 40 ℃;
(2) Putting the dried PLA and PBAT into a double-screw extruder for melt extrusion and granulation to obtain mixed master batches; wherein the temperature of a screw zone of the double-screw extruder is sequentially set to be 180 ℃, 185 ℃ and 180 ℃ along the material conveying reverse direction, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of a screw is set to be 70r/min;
(3) Placing the prepared mixed master batch in a forced air drying oven, and drying at 40 ℃ for 3h;
(4) Putting the dried mixed master batch into a casting film testing machine to prepare a film with the thickness of 0.3mm, namely preparing the bio-based antibacterial packaging film; wherein, the temperature of a screw region of the cast film testing machine is sequentially set to be 180 ℃, 185 ℃ and 180 ℃ along the conveying direction of the material, the temperature of a die orifice is set to be 165 ℃, and the rotating speed of the screw is set to be 30r/min.
The films prepared in the above examples 8 to 14 and comparative example 1 were subjected to performance tests, including an apparent performance test, a melt index test (using master batch as a test sample), a surface contact angle test, a mechanical performance test, an oxygen barrier performance test, and a bacteriostatic performance test, and the specific test methods may refer to related test standards, wherein the bacteriostatic performance test is performed using escherichia coli and staphylococcus aureus, and absorbance at a wavelength of 600nm is measured.
For convenience of description, the films prepared in examples 8 to 14 are hereinafter referred to as PLA/PBAT/C1, PLA/PBAT/C3, PLA/PBAT/C5, PLA/PBAT/Z1, PLA/PBAT/Z2, PLA/PBAT/A1, and PLA/PBAT/A2 in this order, and the film prepared in comparative example 1 is referred to as PLA/PBAT.
Test results and analysis:
(1) Apparent Properties
FIG. 2 is a photograph showing samples of films obtained in examples 8 to 14 of the present invention and comparative example 1. From FIG. 2, it can be seen that the obtained films have a gray tone and show a grayish yellow or grayish red color depending on the formulation.
(2) Melt index test
TABLE 1 melt index test results
| Sample (I) | MFR(g/min) |
| PLA/PBAT | 4.9±0.7 |
| PLA/PBAT/C1 | 5.0±0.8 |
| PLA/PBAT/C3 | 5.2±0.6 |
| PLA/PBAT/C5 | 4.9±1.2 |
| PLA/PBAT/Z1 | 4.2±0.6 |
| PLA/PBAT/Z2 | 3.3±0.4 |
| PLA/PBAT/A1 | 4.1±0.7 |
| PLA/PBAT/A | 3.6±0.7 |
Table 1 shows Melt Flow Rate (MFR) of master batches prepared by melt extrusion in examples 8 to 14 and comparative example 1 at 190 ℃ under a load of 2.16kg, wherein the MFR test results of the examples are between 3.6 and 5.2, which indicates that the samples have small fluctuation and stable performance after the bacteriostatic agent is added. Specifically, the MFR is increased after the chitosan is added, which shows that the viscosity of a material system is reduced, the fluidity of the blended master batch is reduced, and the MFR shows a low value after the nano particles are added, which shows that the nano particles can improve the flow property of the material, so that the blended material is more stable to form.
(3) Surface contact Angle test
FIG. 3 shows the results of the water contact angle test of the films obtained in examples 8 to 14 and comparative example 1.
As can be seen from fig. 3, the hydrophobic PLA and the hydrophobic PBAT still exhibit hydrophobic characteristics after blending, and the water contact angle of the blended film decreases after adding different amounts of chitosan, which is due to the presence of amino groups, so that the chitosan has certain hydrophilicity (actually, the chitosan contains hydrophilic parts (D-glucosamine, D-glucosamine) and hydrophobic parts (N-acetylated residues), and the amino groups are considered to play a dominant role according to the test results). In addition, the blended membrane is found to exhibit various degrees of hydrophilicity after the addition of inorganic nanoparticles, and generally the value of the water contact angle of the nanocomposite membrane depends on the type of the nanofiller, such as shape, size, concentration, hydrophilicity and hydrophobicity, and compatibility with the polymer matrix and dispersibility in the polymer. For nano zinc oxide (ZnONPs), the action mechanism may be that ZnONPs can modify the free volume of the interface between the nanoparticle and the polymer matrix, thereby increasing the permeability of polar water molecules. In addition, znONPs are disclosed as having a hydrophilic effect which alters the hydrophilic effect of the membrane.
(4) Mechanical Property test
FIG. 4 shows the results of mechanical property tests of the films obtained in examples 8 to 14 and comparative example 1.
It can be clearly observed from fig. 4 that there is no obvious change rule in the tensile strength of the PLA/PBAT-based blended film after adding chitosan, and a small amount of chitosan can achieve a good filling effect, resulting in an increase in the tensile strength, which may be due to the fact that the chitosan can be filled in the gaps of the polymer base material, resulting in better mechanical properties, but results in a decrease in the tensile strength as the content of chitosan increases. The efficiency of inorganic nano filler reinforcement and the dispersion degree of the inorganic nano filler in a matrix polymer are main control parameters for effectively transferring stress on the interface of a PLA/PBAT matrix and the inorganic nano filler, so that the tensile strength of the matrix is influenced, and as can be seen from figure 4, the tensile strength of a blending film is suddenly changed after ZnONPs is added, so that the content of ZnONPs is large during melt blending, aggregation is prone to be caused, and the blending film is easy to break; and after nano silver (AgNPs) is added, a small increase in tensile strength of the blended film can be seen, which is probably caused by an increase in the interactions between PLA/PBAT molecules and in molecular chains. It can be considered that the nanoparticles act as a filling enhancement effect. After chitosan with different contents is added, the elongation at break of the PLA/PBAT-based blended film is improved to different degrees, which means that crack propagation of the blended film can be effectively hindered after the chitosan is filled in the substrate. The elongation at break of the inorganic nano particles is reduced, and the elongation at break is reduced because the movement of PLA/PBAT matrix chain segments is limited and interaction force is generated after the nano filler is doped. In addition, agNPs are dispersed as a discontinuous phase in the PLA/PBAT matrix to prevent the movement of matrix molecular chains.
(5) Test for Barrier Properties
FIG. 5 shows the results of barrier property tests of films obtained in examples 8 to 14 and comparative example 1.
As can be seen from FIG. 5, compared with the pure PLA/PBAT composite film, the oxygen permeability coefficient of the blend film is reduced after the bacteriostatic agent is added, which indicates that the oxygen barrier property of the blend film is improved to different degrees. The oxygen barrier effect is achieved after the chitosan and the metal nano material are added, probably because the chitosan and the inorganic metal nano particles play a filling role, and the gas transmission path is prolonged. It can be observed that the oxygen barrier capability of the blended film increases with the chitosan content, which means that the chitosan is dispersed relatively uniformly in the PLA/PBAT matrix. Although the content of nano zinc oxide particles and nano silver particles was increased, the oxygen barrier property did not seem to be significantly changed. It is believed that the small-sized inorganic metal nanoparticles at higher concentrations may more easily aggregate in the PLA/PBAT to cause agglomeration.
(6) Test of bacteriostatic Property
FIGS. 6 and 7 show the results of the bacteriostatic properties of the films prepared in examples 8 to 14 and comparative example 1 against E.coli and Staphylococcus aureus, respectively.
Escherichia coli (e.coli), a representative of gram-negative bacteria, whose cell membrane comprises a peptidoglycan layer and an outer membrane composed of lipopolysaccharides and phospholipids, is difficult to destroy and is a highly resistant microorganism; staphylococcus aureus (s. Aureus), a representative of gram-positive bacteria, a food-borne pathogenic microorganism, is also one of the most common causes of infection.
As can be seen from fig. 6 and 7, the blended film containing the nano-silver particles has the best antibacterial effect, which accords with the efficient antibacterial mechanism of the metal nanoparticles, while the blended film containing chitosan has a relatively weak antibacterial effect, which is considered to be related to the content of chitosan, and although the antibacterial mechanism of chitosan is not completely elucidated, the proposed antibacterial mechanism of chitosan mainly includes: 1. the interaction of the positive charge of the chitosan amino group with the negative charge of the microbial cell membrane results in leakage of proteins and other intracellular components; 2. the adsorption of chitosan to DNA molecules prevents transcription of DNA to RNA; 3. the chitosan can be used as chelating agent of nutrient substance, and can inhibit toxin generation and microorganism growth. According to the three bacteriostasis mechanisms, ideal inhibition effect on microorganisms is hardly caused when the concentration of chitosan is small. The 72h test result shows that the three bacteriostatic agents have certain bacteriostatic durability, and the remarkable good durable bacteriostatic effect is shown even if the content of the nano zinc oxide particles and the nano silver particles is low, which is related to the bacteriostatic principle of the nano zinc oxide particles.
The above is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.
Claims (10)
1. The utility model provides a bio-based antibacterial packaging film which characterized in that, bio-based antibacterial packaging film's component material includes PLA, PBAT and bacteriostatic agent, bacteriostatic agent includes at least one in chitosan, nanometer silver and the nanometer zinc oxide.
2. The bio-based bacteriostatic packaging film according to claim 1, wherein the mass parts of the PLA, the PBAT and the bacteriostatic agent are 70 parts, 500-1000 parts and 10-50 parts respectively.
3. The bio-based bacteriostatic packaging film according to claim 1, wherein the chitosan is analytically pure and has a deacetylation degree of 80-95%.
4. The bio-based antibacterial packaging film according to claim 1, wherein the nano silver has a particle size of 10-80 nm and a purity of more than 99.9%.
5. The bio-based antibacterial packaging film according to claim 1, wherein the nano zinc oxide has a particle size of 10-80 nm and a purity of more than 90%.
6. The bio-based bacteriostatic packaging film according to claim 1, wherein the thickness of the bio-based bacteriostatic packaging film is 0.2-0.8 mm.
7. A method for preparing a bio-based bacteriostatic packaging film according to any one of claims 1 to 6, characterized by comprising the following steps:
drying the PLA and the PBAT;
mixing the dried PLA and PBAT with a bacteriostatic agent in a melt blending manner to obtain bacteriostatic master batches;
drying the antibacterial master batch;
and preparing the dried antibacterial master batch into a film by a tape casting method to obtain the bio-based antibacterial packaging film.
8. The preparation method of the bio-based antibacterial packaging film according to claim 7, wherein the step of mixing the dried PLA and PBAT with the antibacterial agent by melt blending to obtain the antibacterial masterbatch comprises:
adding the dried PLA, PBAT and the bacteriostatic agent into a double-screw extruder, and granulating after melt extrusion to obtain bacteriostatic master batches; wherein the temperature of a screw zone of the double-screw extruder is set to be 175-185 ℃, 180-190 ℃, 175-185 ℃, the temperature of a die orifice is set to be 160-170 ℃, and the rotating speed of the screw is set to be 50-100 r/min.
9. The method for preparing the bio-based antibacterial packaging film according to claim 7, wherein the step of preparing the dried antibacterial master batch into a film by a tape casting method to obtain the bio-based antibacterial packaging film comprises the following steps:
preparing the dried antibacterial master batch into a film through a casting film testing machine to obtain a bio-based antibacterial packaging film; wherein, the temperature of a screw region of the casting film testing machine is set to 178-182 ℃, 182-188 ℃ and 178-182 ℃, the temperature of a die orifice is set to 160-170 ℃, and the rotating speed of the screw is set to 20-50 r/min.
10. The method for preparing a bio-based bacteriostatic packaging film according to claim 7, wherein the step of drying the PLA and PBAT comprises: the drying temperature of the PLA and the PBAT is 35 to 45 ℃, and the drying time is 2 to 4 hours; and/or the presence of a gas in the gas,
the step of drying the antibacterial master batch comprises the following steps: the drying temperature of the antibacterial master batch is 35-45 ℃, and the drying time is 2-4 h.
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| CN112662145A (en) * | 2020-12-21 | 2021-04-16 | 内蒙古农业大学 | Bacteriostatic degradable respiratory membrane with self-contraction performance, preparation method and application |
| CN114015211A (en) * | 2021-12-01 | 2022-02-08 | 山东农业大学 | Full-degradable antibacterial food packaging film and preparation method thereof |
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