CN116731363A - Preparation method of long-acting antibacterial degradable polylactic acid food packaging film - Google Patents

Preparation method of long-acting antibacterial degradable polylactic acid food packaging film Download PDF

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CN116731363A
CN116731363A CN202310873654.4A CN202310873654A CN116731363A CN 116731363 A CN116731363 A CN 116731363A CN 202310873654 A CN202310873654 A CN 202310873654A CN 116731363 A CN116731363 A CN 116731363A
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polylactic acid
antibacterial
triazole
soybean oil
food packaging
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张建纲
曹文
刘雄
包建娜
陈文兴
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Yangzhou Huitong Biological New Material Co ltd
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Yangzhou Huitong Biological New Material Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2491/00—Characterised by the use of oils, fats or waxes; Derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/0091—Complexes with metal-heteroatom-bonds
    • 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

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  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
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Abstract

The invention relates to a preparation method of a long-acting antibacterial degradable polylactic acid food packaging film in the field of packaging materials, which utilizes the amino reaction of epoxy groups and amino-modified triazole to introduce triazole ligands into epoxidized soybean oil, and then the ligands coordinate and fix antibacterial metal ions to obtain triazole functionalized epoxidized soybean oil-M with antibacterial compound + The method comprises the steps of carrying out a first treatment on the surface of the And then the polylactic acid and the polylactic acid are fused and blended to prepare a film, so that the long-acting antibacterial degradable polylactic acid food packaging film is obtained. The antibacterial compound has better stability and longer antibacterial effect, and can effectively avoid the migration of the antibacterial compound from the film to food. And, the triazole functionalized epoxidized soybean oil-M of the present invention + After the polylactic acid is added, the epoxy group of the polylactic acid can react with the terminal hydroxyl of the polylactic acid to form a graft copolymer, so that the polylactic acid film has excellent flexibility, and meanwhile, the binding fastness of the antibacterial metal ions and the polylactic acid can be further improved. The product of the invention can be used as food packaging material.

Description

Preparation method of long-acting antibacterial degradable polylactic acid food packaging film
Technical Field
The invention relates to the field of packaging materials, in particular to a preparation method of a long-acting antibacterial degradable polylactic acid food packaging film.
Background
Polylactic acid is a bio-based polymer obtained by polymerizing lactic acid obtained by fermenting starch extracted from plants such as corn and lactide. The modified polypropylene has excellent mechanical performance, physical performance, biocompatibility and biodegradability, and has wide application prospects in food packaging, textile manufacturing and the like. However, polylactic acid itself has disadvantages of large brittleness, poor antibacterial performance, etc., and cannot be directly used as a film packaging material.
In the prior art, patent CN113185825a discloses a preparation method of a tear-resistant and degradable polylactic acid food packaging film, which uses nano silicon dioxide particles as a core layer and uniformly distributed chitin nano whisker-based polymetanol lactone elastomer as a shell layer, wherein the tear-resistant performance is improved to a certain extent, but the preparation process is complex, and the packaging film is not suitable for industrial production and does not have antibacterial performance. Patent CN113861642a discloses a PLA/PBF/POE-g-GMA/ZnO composite material for antibacterial food packaging, which is obtained by modifying nano zinc oxide with a silane coupling agent and mixing with polylactic acid; the PLA/PBF/POE-g-GMA/ZnO composite material is prepared by uniformly mixing PLA, PBF, POE-g-GMA and master batch by a melt blending method, but the introduced PBF and POE are still petroleum-based materials. Patent CN113583411a discloses that polylactic acid, polycaprolactone and starch are used as raw materials to prepare the composite antibacterial agent containing titanium dioxide, but in the mode, the composite antibacterial agent is compounded with a polymer through physical blending, the dispersibility is poor, dispersing agents are needed to be added to solve the problem of uneven dispersion of nano materials, and even so, the composite antibacterial agent is extremely easy to separate out in the later period due to poor compatibility of the composite antibacterial agent and the polymer, and long-acting antibacterial cannot be achieved.
Therefore, the development of the degradable polylactic acid packaging film with long-acting antibacterial property and good toughness has important significance.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method of a long-acting antibacterial degradable polylactic acid food packaging film, and the prepared polylactic acid food packaging film has better stability and longer antibacterial effect, and can effectively avoid migration of antibacterial compounds from the film to food; and the antibacterial metal ion-polylactic acid composite material has a toughening effect, and can further improve the compatibility and the binding fastness of the antibacterial metal ion and the polylactic acid.
The specific technical scheme of the invention is as follows: a preparation method of a long-acting antibacterial degradable polylactic acid food packaging film comprises the following steps:
(1) Mixing the epoxidized soybean oil with amino-modified triazole, adding a free radical accelerator, and carrying out heating and melting reaction to obtain triazole functionalized epoxidized soybean oil; the epoxy group of the epoxidized soybean oil is in excess compared with the amino group of the amino-modified triazole;
(2) Dissolving triazole functionalized epoxidized soybean oil in an organic solvent, adding a solution containing antibacterial metal ions, stirring for reaction, so that a ligand in the triazole functionalized epoxidized soybean oil is coordinated with the antibacterial metal ions, self-assembling and polymerizing to obtain a solution containing an antibacterial metal coordination polymer, and drying to obtain triazole functionalized epoxidized soybean oil-M; m is an antibacterial metal ion, and the chemical structure is as follows:
wherein M is an antibacterial metal ion;
(3) Slicing polylactic acid and functionalizing triazole epoxidized soybean oil-M + After being uniformly mixed, the mixture is added into a double-screw extruder for melt blending, so as to obtain the antibacterial polylactic acid composite master batch;
(4) And (3) adopting single-screw hot melt extrusion blow molding to form a film on the antibacterial polylactic acid composite master batch to obtain the long-acting antibacterial degradable polylactic acid food packaging film.
The invention introduces triazole ligand into the epoxidized soybean oil by utilizing the reaction of epoxy groups on the epoxidized soybean oil molecules and amino groups on amino-modified triazole, and then the ligand coordinates and fixes antibacterial metal ions to obtain the triazole functionalized epoxy with antibacterial compoundSoybean oil-M + The method comprises the steps of carrying out a first treatment on the surface of the And then the film is prepared by melt blending the polylactic acid and polylactic acid, so as to obtain the long-acting antibacterial degradable polylactic acid food packaging film. Because the antibacterial metal ions and the epoxidized soybean oil can form stronger metal coordination interaction, when the antibacterial composite is added to the polylactic acid, compared with a conventional physical blending mode, the antibacterial composite has better antibacterial stability and longer antibacterial effect, and can effectively avoid migration of the antibacterial composite from the film to food. Meanwhile, the triazole functionalized epoxidized soybean oil-M of the invention + The epoxy soybean oil is an epoxidized vegetable oil, and the number of epoxy groups of the epoxidized vegetable oil depends on the degree and the condition of the epoxidation reaction. In general, epoxidized soybean oil has 3 to 5 epoxy groups per oil molecule, which can be ring-opened in chemical reactions, reacted with other compounds, and triazole functionalized epoxidized soybean oil-M during blending with polylactic acid chips + The residual epoxy groups can react with the hydroxyl groups at the tail ends of the polylactic acid to further form a graft copolymer, so that the problem of high brittleness of the polylactic acid material can be solved, the transparent long-acting antibacterial polylactic acid film material can be obtained, the compatibility of antibacterial metal ions and the polylactic acid can be further improved, and the binding fastness of the antibacterial ions can be further improved. It is therefore noted that the epoxy group in the epoxidized soybean oil needs to be in excess with respect to the amino group of the amino-modified triazole, and that too small an amount of the amino-modified triazole may result in poor antimicrobial durability of the final film or in more complex antimicrobial agents required to achieve desired antimicrobial durability. If the amount of the amino-modified triazole added is too large, no residual epoxy group reacts with the polylactic acid, and the bonding property between the composite antibacterial agent and the polylactic acid system cannot be further improved.
Preferably, in the step (1), the molar ratio of the epoxidized soybean oil to the amino-modified triazole is 1 (1-4).
Preferably, in the step (1), the free radical accelerator is N, N dimethyl-1-octadecyl amine accounting for 0.1 to 0.5 percent of the weight of the epoxidized soybean oil.
Preferably, in the step (1), the heating and melting temperature is 90-110 ℃, and the heating and melting reaction time is 5-10h.
Preferably, in the step (1), the amino-modified triazole is 4-amino-4H-1, 2, 4-triazole or 3-amino-4H-1, 2, 4-triazole.
Preferably, in the step (2), the antibacterial metal ion is Cu 2+ 、Ag + 、Zn 2+ One or more of the following.
Preferably, in step (2), the organic solvent is dichloromethane; the solution containing the antibacterial metal ions is a methanol solution containing the antibacterial metal ions.
Preferably, in step (3), the triazole functionalized epoxidized soybean oil-M + The addition amount of the poly (lactic acid) is 3-35% of the weight of the poly (lactic acid) slice.
Preferably, in the step (3), the extrusion temperature of the twin-screw extruder is 120-150 ℃ and the screw rotating speed is 40-80rpm.
Preferably, in the step (4), the extrusion temperature of the single screw hot melt extrusion blow molding film forming process is 120-160 ℃, the screw rotating speed is 30-60rpm, and the film thickness is 60-100 mu m.
Compared with the prior art, the invention has the following technical effects:
(1) The invention introduces triazole ligand into the epoxidized soybean oil by utilizing the reaction of epoxy group on the epoxidized soybean oil and amino group on amino-modified triazole, and then the ligand coordinates and fixes antibacterial metal ions to obtain triazole functionalized epoxidized soybean oil-M with antibacterial compound + The method comprises the steps of carrying out a first treatment on the surface of the And then the film is prepared by melt blending the polylactic acid and polylactic acid, so as to obtain the long-acting antibacterial degradable polylactic acid food packaging film. Compared with the conventional physical blending mode, the antibacterial compound has better stability and longer antibacterial effect, and can effectively avoid migration of the antibacterial compound from the film to food.
(2) Triazole functionalized epoxidized soybean oil-M of the present invention + After the polymer is added into polylactic acid, epoxy groups of the polymer can react with terminal hydroxyl groups of the polylactic acid to form a graft copolymer, so that the polymer has a toughening effect, and meanwhile, the compatibility and the binding fastness of antibacterial metal ions and the polylactic acid can be further improved.
(3) The polylactic acid food packaging film provided by the invention has the advantages that the antibacterial rate of the polylactic acid food packaging film to various bacteria can reach more than 99%, the stability is good, and the antibacterial time is long.
(4) The invention has the advantages of easily obtained raw materials, simple preparation process, no byproducts in the preparation process, realization of industrial production and expansion of the application of the polylactic acid in the field of food packaging.
Detailed Description
The invention is further described below with reference to examples. Description of some raw materials in the examples: polylactic acid 2003D was purchased from nature works, usa, epoxidized Soybean Oil (ESO) was purchased from Macklin, shanghai, and amino-modified triazole was purchased from beloward reagent.
Example 1
Preparation of composite antibacterial agent 1
The amount of ESO used in the epoxidized soybean oil is 50g (mole number: 0.05 mole), the amount of 4-amino-4H-1, 2, 4-triazole is 3.5g (mole number: 0.05 mole) and the amount of N, N-dimethyl-1-octadecylamine is 0.15g (the amount is 0.3% of the weight of the epoxidized soybean oil), wherein the epoxy group of the soybean oil is excessive compared with the amino group of the amino-modified triazole; mixing, adding into a flask, reacting at 100deg.C for 6 hr to obtain product, dissolving the obtained product in dichloromethane, adding 10ml of cupric chloride methanol solution (0.5 g/ml), stirring under magnetic stirrer to coordinate with metal ion, self-assembling to obtain metal coordination solution containing antibacterial ion, evaporating solvent, vacuum drying at 80deg.C for 24 hr to obtain composite antibacterial agent ESO-Cu 2+ 。
Example 2:
preparation of composite antibacterial agent 2
Epoxidized soybean oil ESO (50 g), 4-amino-4H-1, 2, 4-triazole (3.5 g) and N, N dimethyl-1-octadecylamine (0.25 g) were mixed, wherein the epoxy group of the soybean oil was in excess of the amino group of the amino-modified triazole; mixing, adding into a flask, reacting at 100deg.C for 6 hr to obtain product, dissolving the obtained product in dichloromethane, adding 6ml of silver nitrate methanol solution (0.5 g/ml), stirring under magnetic stirrer to coordinate with metal ion, self-assembling to obtain metal coordination solution containing antibacterial ion, evaporating solvent, and adding 8Vacuum drying at 0deg.C for 24 hr to obtain composite antibacterial agent ESO-Ag + 。
Example 3:
preparation of composite antibacterial agent 3
Epoxidized soybean oil ESO (50 g), 4-amino-4H-1, 2, 4-triazole (3.5 g) and N, N dimethyl-1-octadecylamine (0.05 g) were mixed, wherein the epoxy group of the soybean oil was in excess of the amino group of the amino-modified triazole; mixing, adding into a flask, reacting at 100deg.C for 6 hr to obtain product, dissolving the obtained product in dichloromethane, adding 10ml zinc chloride methanol solution (0.5 g/ml), stirring under magnetic stirrer to coordinate with metal ion, self-assembling to obtain metal coordination solution containing antibacterial ion, evaporating solvent, vacuum drying at 80deg.C for 24 hr to obtain composite antibacterial agent ESO-Zn 2+ 。
The metal ions in examples 1-3 may be single or complex, that is, ag in any proportion + 、Cu 2+ 、Zn 2+ Has good antibacterial effect.
Comparative example 1:
preparation of composite antibacterial agent 4
Mixing epoxy soybean oil ESO (50 g), 4-amino-4H-1, 2, 4-triazole (22 g) and N, N dimethyl-1-octadecylamine (0.15 g), adding into a flask, reacting at 100deg.C for 6H to obtain a product, dissolving the obtained product in dichloromethane, adding 10ml zinc chloride methanol solution (0.5 g/ml), stirring under a magnetic stirrer to coordinate with metal ion, self-assembling and polymerizing to obtain metal coordination solution containing antibacterial ion, evaporating solvent, vacuum drying at 80deg.C for 24H to obtain composite antibacterial agent ESO-1-Zn 2+ 。
Comparative example 2:
preparation of composite antibacterial agent 5
Epoxidized soybean oil ESO (50 g), 4-amino-4H-1, 2, 4-triazole (0.85 g) and N, N dimethyl-1-octadecylamine (0.15 g) were mixed, added to a flask, reacted at 100℃for 6 hours to obtain a product, the obtained product was dissolved in methylene chloride, 10ml of zinc chloride methanol solution (0.5 g/ml) was added, and stirred under a magnetic stirrer to further react withMetal ions are coordinated, self-assembled and polymerized to obtain metal coordination solution containing antibacterial ions, solvent is evaporated, and vacuum drying is carried out at 80 ℃ for 24 hours to obtain the composite antibacterial agent ESO-2-Zn 2+ 。
Example 4:
preparation of antibacterial polylactic acid film 1
Slicing the dried polylactic acid and preparing the composite antibacterial agent ESO-Cu in example 1 2+ Adding the components (95/5, 90/10, 80/20 and 70/30) into a double-screw extruder according to the parts by weight, melting and blending, extruding and granulating to obtain the polylactic acid antibacterial composite master batch, wherein the temperatures of all the areas of the double-screw extruder are as follows: 105 ℃, 120 ℃, 130 ℃,140 ℃, 135 ℃, the temperature of the machine head is 125 ℃, and the rotating speed of the screw is controlled to be 50rpm, thus obtaining the polylactic acid antibacterial material 4- (1-4) for standby.
The obtained material was blown into a film by a single screw extrusion film blowing machine, the temperature of each zone of the film blowing machine was 110 ℃,125 ℃,140 ℃,150 ℃,140 ℃, the temperature of the machine head was 130 ℃, the screw rotation speed was 40rpm, and the film thickness was 70 μm.
Example 5:
preparation of antibacterial polylactic acid film 2
95 parts (mass parts) of dried polylactic acid slices and the composite antibacterial agent ESO-Ag prepared in the example 2 + 5 parts (mass parts) of the polylactic acid antibacterial composite master batch are added into a double-screw extruder for melt blending, extrusion granulation is carried out, and the temperature of each region of the double-screw extruder is as follows: 105 ℃, 120 ℃, 130 ℃,140 ℃, 135 ℃, the temperature of the machine head is 125 ℃, and the rotating speed of the screw is controlled to be 50rpm, thus obtaining the polylactic acid antibacterial material for standby.
The obtained material was blown into a film by a single screw extrusion film blowing machine, the temperature of each zone of the film blowing machine was 110 ℃,125 ℃,140 ℃,150 ℃,140 ℃, the temperature of the machine head was 130 ℃, the screw rotation speed was 40rpm, and the film thickness was 70 μm.
Example 6:
preparation of antibacterial polylactic acid film 3
95 parts (mass parts) of dried polylactic acid slices and the composite antibacterial agent prepared in the example 3ESO-Zn 2+ 5 parts (mass parts) of the polylactic acid antibacterial composite master batch are added into a double-screw extruder for melt blending, extrusion granulation is carried out, and the temperature of each region of the double-screw extruder is as follows: 105 ℃, 120 ℃, 130 ℃,140 ℃, 135 ℃, the temperature of the machine head is 125 ℃, and the rotating speed of the screw is controlled to be 50rpm, thus obtaining the polylactic acid antibacterial material for standby.
The obtained material was blown into a film by a single screw extrusion film blowing machine, the temperature of each zone of the film blowing machine was 110 ℃,125 ℃,140 ℃,150 ℃,140 ℃, the temperature of the machine head was 130 ℃, the screw rotation speed was 40rpm, and the film thickness was 70 μm.
Comparative example 3:
preparation of control polylactic acid film 1
Adding 95 parts by weight of dried polylactic acid slices and 5 parts by weight of epoxidized soybean oil ESO into a double-screw extruder for melt blending, and extruding and granulating to obtain the polylactic acid antibacterial composite master batch, wherein the temperatures of all the areas of the double-screw extruder are as follows: 105 ℃, 120 ℃, 130 ℃,140 ℃, 135 ℃, the temperature of the machine head is 125 ℃, and the rotating speed of the screw is controlled to be 50rpm, thus obtaining the polylactic acid antibacterial material for standby.
The obtained material was blown into a film by a single screw extrusion film blowing machine, the temperature of each zone of the film blowing machine was 110 ℃,125 ℃,140 ℃,150 ℃,140 ℃, the temperature of the machine head was 130 ℃, the screw rotation speed was 40rpm, and the film thickness was 70 μm.
Comparative example 4:
preparation of control polylactic acid film 2
Adding 99 parts by mass of dried polylactic acid slices and 1 part by mass of dried copper chloride into a double-screw extruder for melt blending, and extruding and granulating to obtain the polylactic acid antibacterial composite master batch, wherein the temperatures of all the areas of the double-screw extruder are as follows: 105 ℃, 120 ℃, 130 ℃,140 ℃, 135 ℃, the temperature of the machine head is 125 ℃, and the rotating speed of the screw is controlled to be 50rpm, thus obtaining the polylactic acid antibacterial material for standby.
The obtained material was blown into a film by a single screw extrusion film blowing machine, the temperature of each zone of the film blowing machine was 110 ℃,125 ℃,140 ℃,150 ℃,140 ℃, the temperature of the machine head was 130 ℃, the screw rotation speed was 40rpm, and the film thickness was 70 μm.
Comparative example 5:
preparation of control polylactic acid film 3
95 parts (mass parts) of dried polylactic acid slices and the composite antibacterial agent 4ESO-1-Zn prepared in comparative example 1 2+ 5 parts (mass parts) of the polylactic acid antibacterial composite master batch are added into a double-screw extruder for melt blending, extrusion granulation is carried out, and the temperature of each region of the double-screw extruder is as follows: 105 ℃, 120 ℃, 130 ℃,140 ℃, 135 ℃, the temperature of the machine head is 125 ℃, and the rotating speed of the screw is controlled to be 50rpm, thus obtaining the polylactic acid antibacterial material for standby.
The obtained material was blown into a film by a single screw extrusion film blowing machine, the temperature of each zone of the film blowing machine was 110 ℃,125 ℃,140 ℃,150 ℃,140 ℃, the temperature of the machine head was 130 ℃, the screw rotation speed was 40rpm, and the film thickness was 70 μm.
Comparative example 6:
preparation of control polylactic acid film 4
95 parts (mass parts) of dried polylactic acid slices and the 5ESO-2-Zn composite antibacterial agent prepared in comparative example 2 2+ 5 parts (mass parts) of the polylactic acid antibacterial composite master batch are added into a double-screw extruder for melt blending, extrusion granulation is carried out, and the temperature of each region of the double-screw extruder is as follows: 105 ℃, 120 ℃, 130 ℃,140 ℃, 135 ℃, the temperature of the machine head is 125 ℃, and the rotating speed of the screw is controlled to be 50rpm, thus obtaining the polylactic acid antibacterial material for standby.
The obtained material was blown into a film by a single screw extrusion film blowing machine, the temperature of each zone of the film blowing machine was 110 ℃,125 ℃,140 ℃,150 ℃,140 ℃, the temperature of the machine head was 130 ℃, the screw rotation speed was 40rpm, and the film thickness was 70 μm.
Comparative example 7:
preparation of control polylactic acid film 5
And drying the polylactic acid slices for later use.
The obtained material was blown into a film by a single screw extrusion film blowing machine, the temperature of each zone of the film blowing machine was 110 ℃,125 ℃,140 ℃,150 ℃,140 ℃, the temperature of the machine head was 130 ℃, the screw rotation speed was 40rpm, and the film thickness was 70 μm.
Performance testing
And (3) testing the mechanical properties of polylactic acid:
the antibacterial PLA materials prepared in examples 4 to 6 and comparative examples 3 to 7 were used as test samples, tensile strength test was referred to GB/T1040.2-2006 "determination of tensile properties of plastics", the test instrument was an INSTRON-34TM-30 universal material tester, dumbbell-shaped bars with a specification of 50mm x 5mm x 2mm were used, 5 samples were tested per group, and the results were averaged. The tensile strength test results are shown in Table 1.
Antibacterial performance test:
the antibacterial property test was conducted with reference to GB/T31402-2015 test method for antibacterial property of Plastic surface by taking the antibacterial PLA films prepared in examples 4-6 and comparative examples 3-7 as test samples. The experimental strains are staphylococcus aureus and escherichia coli. The antibacterial property test results are shown in Table 1.
Antimicrobial performance durability test:
the polylactic acid films prepared in the examples and comparative examples were immersed in a solution (water, 10% (V/V) ethanol, 3% (V/V) acetic acid) of a simulated food medium, and taken out after standing for 30 days, and subjected to antibacterial performance test.
TABLE 1 mechanical Properties and antibacterial Property test results of antibacterial polylactic acid films of examples 4 to 6 and comparative examples 3 to 7
As can be seen from a comparison of the data of examples 4-6 in Table 1, epoxidized soybean oil ESO-M modified with antibacterial metal ions and aminotriazole + The antibacterial agent can effectively improve the antibacterial performance of the polylactic acid film, and the antibacterial effect of silver ions is optimal. The antibacterial rate can still reach 99.9% under the lowest load. Because the excessive epoxy groups on the epoxidized soybean oil can react with the hydroxyl groups at the end of the polylactic acid, the antibacterial metal ions can be effectively fixed in the PLA matrix, are not easy to separate out, and improve the antibacterial durability of the polylactic acidEnsuring food safety. The addition of ESO can improve the toughness of polylactic acid, and 20wt% of ESO-Cu is added 2+ The breaking elongation of the polylactic acid is improved from 5.6% to 403%.
In comparative example 3, the toughness of polylactic acid was improved but the antibacterial performance was not improved by simply adding epoxidized soybean oil. The antibacterial rate in comparative example 4 is obviously reduced after soaking in the solution for 30 days, which shows that the antibacterial ion content of the soaked film is low, and the antibacterial ion is separated out after long-time soaking, so that the antibacterial ion in the polylactic acid film is not firmly combined with the polylactic acid. In comparative example 5, the antibacterial agent of comparative example 1 having no residual epoxy group was used, and it was found that the epoxy group of epoxidized soybean oil was completely consumed by an excessive amount of triazole, and a good toughening effect could not be obtained. While comparative example 6 uses the antibacterial agent of a small amount of the triazole ligand of comparative example 2, it is known that a small amount of the triazole ligand may cause the antibacterial ion to be incompletely coordinated and free, resulting in deterioration of the antibacterial durability of the polylactic acid film.
In conclusion, the composite antibacterial agent disclosed by the invention can be added into polylactic acid to realize long-acting antibacterial effect, and meanwhile, the toughness of the polylactic acid can be improved, and the safety and the storage period of food can be effectively improved when the composite antibacterial agent is used as a food packaging material.
And (3) screening the dosage of the epoxidized soybean oil and the amino-modified triazole:
based on example 1, the amount of ESO in the epoxidized soybean oil was fixed by 50g, and the amount of 4-amino-4H-1, 2, 4-triazole was changed so that the molar ratio of the two was as shown in the following table, while ensuring that the epoxy group of soybean oil was in excess compared with the amino group of amino-modified triazole. The obtained composite antibacterial agent was prepared according to the polylactic acid chips and the composite antibacterial agent ESO-Cu in example 4 2+ The antibacterial polylactic acid film is prepared according to the mass fraction of 80/20, and then tested to obtain the data listed in the following table 2:
table 2: dosage screening table of epoxidized soybean oil and amino-modified triazole
As can be seen from Table 2, the molar amount of epoxidized soybean oil to amino-modified triazole is 1: (1-4) the effect is most excellent.
The above example is only one of the specific embodiments selected by the present invention, and the application of the present invention is not limited to the above examples, and it should be understood that the ordinary changes and substitutions made by those skilled in the art within the scope of the present invention should fall within the scope of the appended claims.

Claims (10)

1. A preparation method of a long-acting antibacterial degradable polylactic acid food packaging film is characterized by comprising the following steps of: the method comprises the following steps:
(1) Mixing the epoxidized soybean oil with amino-modified triazole, adding a free radical accelerator, and carrying out heating and melting reaction to obtain triazole functionalized epoxidized soybean oil; the epoxy group of the epoxidized soybean oil is in excess compared with the amino group of the amino-modified triazole;
(2) Dissolving triazole functionalized epoxidized soybean oil in an organic solvent, adding a solution containing antibacterial metal ions, stirring for reaction to coordinate ligands in the triazole functionalized epoxidized soybean oil with the antibacterial metal ions, self-assembling and polymerizing to obtain a solution containing antibacterial metal coordination polymer, and drying to obtain the triazole functionalized epoxidized soybean oil-M + The method comprises the steps of carrying out a first treatment on the surface of the M is an antibacterial metal ion;
(3) Slicing polylactic acid and functionalizing triazole epoxidized soybean oil-M + After being uniformly mixed, the mixture is added into a double-screw extruder for melt blending, so as to obtain the antibacterial polylactic acid composite master batch;
(4) And (3) adopting single-screw hot melt extrusion blow molding to form a film on the antibacterial polylactic acid composite master batch to obtain the long-acting antibacterial degradable polylactic acid food packaging film.
2. The method for preparing the long-acting antibacterial degradable polylactic acid food packaging film according to claim 1, which is characterized in that: in the step (1), the molar ratio of the epoxidized soybean oil to the amino-modified triazole is 1 (1-4).
3. The method for preparing the long-acting antibacterial degradable polylactic acid food packaging film according to claim 1 or 2, which is characterized in that: in the step (1), the free radical accelerator is N, N dimethyl-1-octadecylamine, and the dosage is 0.1-0.5% of the weight of the epoxidized soybean oil.
4. The method for preparing the long-acting antibacterial degradable polylactic acid food packaging film according to claim 1 or 2, which is characterized in that: in the step (1), the heating and melting temperature is 90-110 ℃ and the reaction time is 5-10h.
5. The method for preparing the long-acting antibacterial degradable polylactic acid food packaging film according to claim 1 or 2, which is characterized in that: in the step (1), the amino-modified triazole is 4-amino-4H-1, 2, 4-triazole or 3-amino-4H-1, 2, 4-triazole.
6. The method for preparing the long-acting antibacterial degradable polylactic acid food packaging film according to claim 1, which is characterized in that: in the step (2), the antibacterial metal ion is Cu 2+ 、Ag + 、Zn 2+ One or more of the following.
7. The method for preparing the long-acting antibacterial degradable polylactic acid food packaging film according to claim 1, which is characterized in that: in the step (2), the organic solvent is dichloromethane; the solution containing the antibacterial metal ions is a methanol solution containing the antibacterial metal ions.
8. The method for preparing the long-acting antibacterial degradable polylactic acid food packaging film according to claim 1, which is characterized in that: in step (3), the triazole functionalized epoxidized soybean oil-M + The addition amount of the poly (lactic acid) is 3-35% of the weight of the poly (lactic acid) slice.
9. The method for preparing the long-acting antibacterial degradable polylactic acid food packaging film according to claim 1 or 8, which is characterized in that: in the step (3), the extrusion temperature of the double-screw extruder is 120-150 ℃, and the screw rotating speed is 40-80rpm.
10. The method for preparing the long-acting antibacterial degradable polylactic acid food packaging film according to claim 1, which is characterized in that: in the step (4), a single screw extrusion film blowing machine is adopted for blowing into films, the extrusion temperature in the film blowing process is 120-160 ℃, the screw rotating speed is 30-60rpm, and the film thickness is 60-100 mu m.
CN202310873654.4A 2023-07-17 2023-07-17 Preparation method of long-acting antibacterial degradable polylactic acid food packaging film Pending CN116731363A (en)

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