High barrier antibacterial flexible packaging material and preparation method thereof

Abstract

The invention discloses a high barrier antibacterial flexible packaging material and a preparation method thereof, belonging to the technical field of flexible packaging composite materials. The flexible packaging material is composed of an outer layer, a barrier antibacterial layer and an inner heat-sealing layer from the outside to the inside; wherein the raw materials of the barrier antibacterial layer include 85 to 95 parts by weight of EVOH resin and 5 to 15 parts of an antibacterial modifier; the antibacterial modifier is an amine organic molecular cage composite nanosilver. The EVOH resin provides good barrier properties for the material, and the nanosilver in the amine organic molecular cage composite nanosilver can slowly release silver ions, giving the flexible packaging material certain antibacterial properties, and the composite of the amine organic molecular cage can improve the dispersibility of the nanosilver in the matrix resin on the one hand, and help improve the water absorption of the material on the other hand, reduce the influence of moisture on the EVOH resin, and effectively solve the problem of decreased barrier properties of the EVOH resin in a humid environment and increased probability of microbial contamination.

Description

Technical Field

[0001] The invention belongs to the technical field of flexible packaging composite materials, and in particular relates to a high-barrier antibacterial flexible packaging material and a preparation method thereof. Background Art

[0002] Flexible packaging materials can meet the packaging requirements of various items in daily life. They are ideal materials for packaging convenient foods, daily necessities, and small-packaged goods in supermarkets that are easy to store and put away. However, as consumers' requirements for food safety and hygiene continue to increase, the performance and functions of packaging materials are increasingly valued. Traditional flexible packaging materials such as polyethylene, polypropylene, and polyethylene terephthalate, although they have good mechanical properties and processing properties, have obvious deficiencies in barrier properties and antibacterial functions. Especially in the field of food and pharmaceutical packaging, high barrier properties can effectively extend the shelf life of products and prevent internal products from being contaminated, thereby ensuring product safety and quality.

[0003] The barrier packaging materials widely used at present mainly include polyvinylidene chloride, ethylene-vinyl alcohol copolymer (EVOH) and nitrile resin. Among them, EVOH resin has good gas barrier and moisture barrier properties. When used for food packaging materials, it can prevent oxygen and other gases from penetrating from the outside to prevent the packaged food, beverages, etc. from being contaminated and deteriorated. It can also fill nitrogen or carbon dioxide inside the packaging bag to extend the storage time of food and improve the aroma retention of food. In addition, the hydrophilic groups contained in EVOH resin make it have strong hygroscopic properties, but after absorbing water, the barrier properties of EVOH resin will decrease, and with the adsorption of water and the decrease in barrier properties, it also provides an environment for the growth of microorganisms, which will affect the quality and service life of the products inside the package. Summary of the invention

[0004] The object of the present invention is to provide a high barrier antibacterial flexible packaging material and a preparation method thereof, so as to solve the problem of poor barrier and antibacterial properties of the flexible packaging material.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] In the first aspect, the present invention provides a high barrier antibacterial flexible packaging material, which is composed of an outer layer, a barrier antibacterial layer and an inner heat-sealing layer from the outside to the inside; the raw materials of the barrier antibacterial layer include 85 to 95 parts by weight of EVOH resin and 5 to 15 parts by weight of an antibacterial modifier; the antibacterial modifier is an amine organic molecular cage composite nanosilver.

[0007] Preferably, the mass ratio of the outer layer, the barrier antibacterial layer and the inner heat-sealing layer is (25-40): (20-30): (30-45).

[0008] Preferably, the raw materials of the inner heat-sealing layer include 70 to 80 parts by weight of linear low-density polyethylene, 10 to 15 parts by weight of polypropylene and 5 to 8 parts by weight of maleic anhydride grafted polyethylene;

[0009] The raw material of the outer layer includes one of PET resin, PA resin and EVA resin.

[0010] By adopting the above technical scheme, the high barrier antibacterial flexible packaging material of the present invention is a co-extruded composite film, wherein the middle layer is a barrier antibacterial layer, which is mainly composed of EVOH resin and antibacterial modifier, and the EVOH resin has a unique molecular segment structure, wherein the hydroxyl groups contained therein have a strong bonding effect with the intermolecular hydrogen bonds, the cohesive force is strong, the molecular chains are tightly stacked, and small molecules are difficult to penetrate, thus providing the material with good barrier properties, and the flexible packaging material of the present invention is also composited with an outer layer and an inner heat-sealing layer, wherein the outer layer raw materials include PET resin (polyethylene terephthalate), PA resin (polyamide resin) and EVA resin (ethylene-vinyl acetate copolymer), which can cooperate with the barrier antibacterial layer to a certain extent to improve the barrier properties of the packaging material.

[0011] In addition, the barrier antibacterial layer of the present invention is also added with amine organic molecular cage composite nanosilver, which can slowly release silver ions, penetrate the bacterial cell membrane, increase the permeability of the cell membrane, leak the cell contents, and cause cell death. It can also interfere with the normal metabolic process of bacteria, inhibit the normal replication and growth of bacteria, and thus give the flexible packaging material certain antibacterial properties. The amine organic molecular cage has a large number of cavity structures, and the nanosilver with antibacterial properties can therefore be loaded inside the cavity, which can well avoid the problem that the nanosilver particles are difficult to disperse evenly in the resin due to the small particle size, and also reduce the precipitation phenomenon of the nanosilver particles during use, greatly extending the service life of the material. Further, the active groups contained on the amine organic molecular cage can also react with the active groups in the EVOH resin or connect in the form of hydrogen bonds, thereby improving the interface bonding force between the antibacterial modifier and the matrix resin, and also reducing the intermolecular gap, thereby improving the barrier properties of the packaging material.

[0012] EVOH resin has strong hydrophilicity, and thus the hygroscopicity of flexible packaging materials is strong, which can improve the moisture resistance of packaging materials. However, on the other hand, due to the gradual increase in adsorbed water, the resin structure will change from the original glass state to a highly elastic state, resulting in the formation of small molecule diffusion channels, which will reduce its barrier properties. The amine organic molecular cages in the antibacterial modifier also contain polar groups, which can help absorb and store water, and the amine organic molecular cages can increase the cavity gap after absorbing water, so that the nanosilver loaded inside is gradually released. The more water, the more nanosilver is released, which effectively solves the problem of reduced barrier properties of EVOH resin in humid environments and increased probability of microbial contamination.

[0013] Preferably, the raw materials of the antibacterial modifier include amine organic molecular cage and soluble silver salt in a mass ratio of 1: (0.05-0.1).

[0014] Preferably, the soluble silver salt includes a combination of one or more of silver nitrate, silver acetate, silver citrate and silver oxalate.

[0015] Preferably, the antibacterial modifier is prepared according to the following method:

[0016] Preparation of amine organic molecular cages: under nitrogen atmosphere, tris(2-aminoethyl)amine and pyrrole-2,6-dicarboxaldehyde are dissolved in solvents respectively, the obtained solutions are mixed with each other, the temperature is raised to 50-55°C, and the mixture is stirred for reaction for 24-36 hours, and then filtered, washed, spin-dried and recrystallized to obtain imine organic molecular cages, and then reduced by a reducing agent, extracted and acidified with hydrochloric acid to obtain amine organic molecular cages;

[0017] Composite of nanosilver: add amine organic molecular cage to solvent, add soluble silver salt, stir and mix at room temperature for 2 to 3 hours, add reducing agent at -5 to 0°C, continue stirring for 20 to 30 minutes, and obtain amine organic molecular cage composite nanosilver, i.e. antibacterial modifier, through separation, freeze drying and grinding.

[0018] Preferably, the reducing agent includes one or a combination of sodium borohydride, potassium borohydride and sodium triacetoxyborohydride; the amount of the reducing agent added during the preparation of the amine organic molecular cage is 45-50% of the mass of the imine organic molecular cage; the amount of the reducing agent added during the composite process of nanosilver is 30-35% of the mass of the amine organic molecular cage.

[0019] Preferably, the mass ratio of tris(2-aminoethyl)amine to pyrrole-2,6-dicarbaldehyde is (0.7-0.8):1.

[0020] Preferably, the solvent in the preparation process of the amine organic molecular cage includes one of anhydrous methanol, anhydrous ethanol and N,N-dimethylformamide.

[0021] Preferably, the solvent in the nanosilver compounding process includes one of methanol, ethanol, chloroform and water.

[0022] By adopting the above technical scheme, after the imine organic molecular cage is formed, it is also reduced and hydrochloric acid treated. Through the action of the reducing agent, the unstable imine bond on the imine organic molecular cage is reduced to an amine group, and the structure of the organic molecular cage becomes more stable, which is beneficial to the subsequent processing of flexible packaging materials. In addition, after hydrochloric acid acidification, the active sites on the surface of the amine organic molecular cage are significantly improved, which can provide more abundant coordination sites for the subsequent growth and loading of nanosilver, and smoothly realize the composite of nanosilver.

[0023] The amine organic molecular cage can not only form a tight connection with the EVOH resin to improve the barrier properties of the material, but also absorb water and swell, helping to improve the hygroscopicity of the material and store moisture. After swelling, it is conducive to the slow release of nanosilver, effectively avoiding the growth of microorganisms in a humid environment and improving the antibacterial properties of the flexible packaging material.

[0024] Preferably, the antimicrobial modifier is also grafted with a polyethyleneimine segment.

[0025] Preferably, the raw materials for the antibacterial modifier grafted polyethyleneimine chain segment include imine organic molecular cage composite nanosilver, polyethyleneimine and maleic anhydride in a mass ratio of 1: (0.6-0.8): (0.3-0.4).

[0026] More preferably, the molecular weight of polyethyleneimine is 2000-2500 g / mol.

[0027] Preferably, the antimicrobial modifier grafted polyethyleneimine chain segment is prepared according to the following method: adding imine organic molecular cage composite nanosilver and maleic anhydride to a solvent, stirring and reacting at room temperature for 12 to 24 hours, and obtaining a pretreated product by filtering and dialysis; adding the pretreated product and polyethyleneimine to a phosphate buffer solution with a pH value of 7 to 8, stirring and reacting at 40 to 50° C. for 12 to 24 hours, and obtaining the antimicrobial modifier grafted polyethyleneimine chain segment by centrifugal filtration and dialysis.

[0028] Preferably, the solvent includes one of N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran and acetone.

[0029] By adopting the above technical scheme, the antibacterial modifier of the present invention is also grafted with a polyethyleneimine segment, which is a polyelectrolyte segment. The large amount of amine groups and ammonium ions contained in the polyethyleneimine segment can make the segment carry a large amount of positive charge, and electrostatic interaction occurs between the negative charge on the surface of bacteria, interfering with the normal physiological function of bacteria, increasing the permeability of cell membranes, and causing cell membrane structure damage. The grafting of polyethyleneimine segments can improve the antibacterial effect of the antibacterial modifier and always provide good antibacterial properties for flexible packaging materials. In addition, the introduction of polyethyleneimine segments gradually forms a three-dimensional network structure between the antibacterial modifier and the EVOH resin molecular chain, which improves the mechanical properties of the material while reducing the generation of molecular diffusion channels, and improves the binding force of the antibacterial modifier to water molecules, thereby reducing the adverse effects of moisture on EVOH resin.

[0030] In addition, the compatibility between EVOH resin and the base material of the inner heat-sealing layer is poor, and the bonding force between the layers is reduced. However, by introducing polyethyleneimine chain segments, a cross-linked network structure is formed between the EVOH resin and the polyethyleneimine chain segments, which can interact with the compatibilizer in the inner heat-sealing layer, thereby improving the mutual bonding force between the barrier antibacterial layer and the inner heat-sealing layer, thereby improving the barrier properties, mechanical properties and service life of the flexible packaging material.

[0031] In a second aspect, the present invention provides a method for preparing a high barrier antibacterial flexible packaging material, comprising the following process steps:

[0032] S1. Weigh the EVOH resin and the antibacterial modifier according to the corresponding mass parts, mix them evenly, and then melt extrude them at 170 to 190 ° C to obtain a barrier antibacterial masterbatch;

[0033] S2. Weigh linear low-density polyethylene, polypropylene and maleic anhydride grafted polyethylene in corresponding parts by mass, mix them evenly and melt extrude them at 150 to 175 ° C to obtain an inner heat-seal masterbatch;

[0034] S3. Melt and plasticize the barrier antibacterial masterbatch, inner heat-sealing masterbatch and outer layer raw material respectively according to the corresponding mass ratio, and then obtain a high barrier antibacterial flexible packaging material by co-extrusion.

[0035] Preferably, the melting and plasticizing temperature of the barrier antibacterial masterbatch is 180-190°C, the melting and plasticizing temperature of the inner heat-sealing masterbatch is 160-180°C, and the melting and plasticizing temperature of the outer layer raw material is 250-270°C.

[0036] Beneficial effects of the present invention:

[0037] 1. The soft packaging material in the present invention is composed of an outer layer, a barrier antibacterial layer and an inner heat-sealing layer, wherein the raw materials of the barrier antibacterial layer include EVOH resin and an antibacterial modifier, the unique molecular segment structure of EVOH gives the material good barrier properties, and the antibacterial modifier is an amine organic molecular cage composite nanosilver, which gives the material good antibacterial properties. The amine organic molecular cage composite nanosilver can form a tight connection with the EVOH resin, improve the barrier properties of the material, and can also absorb water and swell, helping to improve the hygroscopicity of the material and store water, and after swelling, it is conducive to the slow release of nanosilver, effectively avoiding the breeding of microorganisms in a humid environment, and improving the antibacterial properties of the soft packaging material.

[0038] 2. The antibacterial modifier of the present invention is also grafted with polyethyleneimine chain segments. In addition to improving the antibacterial properties of the material, the introduction of polyethyleneimine chain segments can form a three-dimensional network structure between the antibacterial modifier and the EVOH resin, reducing the generation of molecular diffusion channels. It can also interact with the compatibilizer in the inner heat-sealing layer to improve the mutual bonding force between the barrier antibacterial layer and the inner heat-sealing layer, thereby improving the barrier properties, mechanical properties and service life of the flexible packaging material. DETAILED DESCRIPTION

[0039] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Preparation Example

[0041] Preparation Example 1, an antibacterial modifier, is prepared according to the following method:

[0042] Preparation of amine organic molecular cages: Under a nitrogen atmosphere, 38 g of tris(2-aminoethyl)amine and 50 g of pyrrole-2,6-dicarboxaldehyde are respectively dissolved in 100 mL of anhydrous methanol, the obtained solutions are mixed, the temperature is raised to 50°C, and the mixture is stirred for reaction for 30 hours, and then filtered, washed, spin-dried and recrystallized to obtain an imine organic molecular cage; the imine organic molecular cage is added to anhydrous methanol, sodium borohydride of 45% of the mass of the imine organic molecular cage is added, heated to 45°C and refluxed for 12 hours, the imine organic molecular cage is reduced, and then extracted with dichloromethane, added to 150 mL of a 1 mol / L hydrochloric acid aqueous solution for acidification for 30 minutes, and finally washed and freeze-dried to obtain the amine organic molecular cage;

[0043] Composite of nanosilver: Take 20g of the above-obtained amine organic molecular cage and add it to 100mL of chloroform, add 0.8g of silver nitrate, stir and mix at room temperature for 3h, then add 7g of sodium borohydride at 0°C, continue stirring for 30min, and obtain amine organic molecular cage composite nanosilver, i.e., antibacterial modifier, by separation, freeze drying and grinding.

[0044] Preparation Example 2, an antibacterial modifier, is different from Preparation Example 1 only in that, during the preparation of the amine organic molecular cage, the amount of sodium borohydride added is 50% of the mass of the imine organic molecular cage; and the amount of silver nitrate added is 0.5 g.

[0045] Preparation Example 3, an antibacterial modifier, is different from Preparation Example 1 only in that, during the composite process of nanosilver, the amount of silver nitrate added is 1 g, and the amount of sodium borohydride added is 6 g.

[0046] Preparation Example 4, an antibacterial modifier, is different from Preparation Example 1 only in that the amount of silver nitrate added is 0.2 g.

[0047] Preparation Example 5, an antibacterial modifier, is different from Preparation Example 1 only in that the amount of silver nitrate added is 1.5 g.

[0048] Preparation Example 6, an antibacterial modifier, prepared according to the following method:

[0049] Preparation of imine organic molecular cage: Under nitrogen atmosphere, 38 g of tris(2-aminoethyl)amine and 50 g of pyrrole-2,6-dicarboxaldehyde were dissolved in 100 mL of anhydrous methanol, the obtained solutions were mixed, the temperature was raised to 50°C, stirred for 30 hours, and then filtered, washed, dried and recrystallized to obtain the imine organic molecular cage;

[0050] Composite of nanosilver: Take 20g of the above-obtained imine organic molecular cage and add it to 100mL of chloroform, add 0.8g of silver nitrate, stir and mix at room temperature for 3h, then add 7g of sodium borohydride at 0°C, continue stirring for 30min, and obtain imine organic molecular cage composite nanosilver, i.e., antibacterial modifier, by separation, freeze drying and grinding.

[0051] Preparation Example 7, an antibacterial modifier, prepared according to the following method:

[0052] Under a nitrogen atmosphere, 38 g of tris(2-aminoethyl)amine and 50 g of pyrrole-2,6-dicarbaldehyde were dissolved in 100 mL of anhydrous methanol respectively, the obtained solutions were mixed with each other, the temperature was raised to 50°C, the reaction was stirred for 30 hours, and then the imine organic molecular cage was obtained through suction filtration, washing, spin drying and recrystallization; the imine organic molecular cage was added to anhydrous methanol, 45% of the mass of the imine organic molecular cage was added with sodium borohydride, heated to 45°C and refluxed for 12 hours, the imine organic molecular cage was reduced, and then after extraction with dichloromethane, it was added to 150 mL of 1 mol / L hydrochloric acid aqueous solution for acidification for 30 minutes, and finally washed and freeze-dried to obtain the amine organic molecular cage, i.e., the antibacterial modifier.

[0053] Preparation Example 8, an antibacterial modifier, is different from Preparation Example 1 only in that the obtained amine organic molecular cage composite nanosilver is also subjected to polyethyleneimine grafting treatment, and specifically comprises the following steps:

[0054] 10 g of the amine organic molecular cage composite nanosilver obtained in Preparation Example 1 and 4 g of maleic anhydride were added to 100 mL of N,N-dimethylformamide, stirred and reacted at room temperature for 15 h, and a pretreated product was obtained by filtration and dialysis; the pretreated product and 7 g of polyethyleneimine (average molecular weight of 2100 g / mol) were added to a phosphate buffer solution with a pH value of 7.5, stirred and reacted at 45°C for 20 h, and then centrifuged and dialyzed to obtain an antibacterial modifier, on which a polyethyleneimine segment was grafted.

[0055] Preparation Example 9, an antibacterial modifier, is different from Preparation Example 8 only in that the amount of polyethyleneimine added is 8 g.

[0056] Preparation Example 10, an antibacterial modifier, is different from Preparation Example 8 only in that the amount of polyethyleneimine added is 6 g and the amount of maleic anhydride added is 3 g.

[0057] Preparation Example 11, an antibacterial modifier, is different from Preparation Example 8 only in that the amount of polyethyleneimine added is 4 g.

[0058] Preparation Example 12, an antibacterial modifier, is different from Preparation Example 8 only in that the amount of polyethyleneimine added is 10 g.

[0059] Example

[0060] Example 1, a high barrier antibacterial flexible packaging material, is prepared according to the following process steps:

[0061] Weigh 90 parts of EVOH resin (polyethylene content 32%) and 10 parts of the antibacterial modifier prepared in Preparation Example 1, mix them evenly, and then melt-extrude at 170-190° C. to obtain a barrier antibacterial masterbatch;

[0062] Weigh 75 parts of linear low-density polyethylene (melt flow rate of 2 g / 10 min), 12 parts of polypropylene (average molecular weight of 15000 g / mol) and 6 parts of maleic anhydride grafted polyethylene, mix them evenly and melt extrude them at 150-175°C to obtain an internal heat-sealing masterbatch;

[0063] The barrier antibacterial masterbatch, inner heat-sealing masterbatch and PET resin (average molecular weight of 20,000 g / mol) in a mass ratio of 25:40:35 were melt-plasticized respectively, and then a high barrier antibacterial flexible packaging material was obtained by co-extrusion.

[0064] Example 2, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the mass fraction of EVOH resin is 85 parts, and the mass fraction of the antibacterial modifier prepared in Preparation Example 1 is 15 parts.

[0065] Example 3, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the mass fraction of EVOH resin is 85 parts, and the mass fraction of the antibacterial modifier prepared in Preparation Example 1 is 5 parts.

[0066] Example 4, a high barrier antibacterial flexible packaging material, differs from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of the antibacterial modifier prepared in Preparation Example 2; the raw materials of the inner heat-sealing masterbatch are 70 parts of linear low-density polyethylene, 15 parts of polypropylene and 8 parts of maleic anhydride grafted polyethylene.

[0067] Example 5, a high barrier antibacterial flexible packaging material, differs from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of the antibacterial modifier prepared in Preparation Example 3; the raw materials of the inner heat-sealing masterbatch are 80 parts of linear low-density polyethylene, 10 parts of polypropylene and 5 parts of maleic anhydride grafted polyethylene.

[0068] Example 6, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the mass ratio of the barrier antibacterial masterbatch, the inner heat-sealing masterbatch and the PET resin is 20:45:35.

[0069] Example 7, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the mass ratio of the barrier antibacterial masterbatch, the inner heat-sealing masterbatch and the PET resin is 30:30:40.

[0070] Example 8, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of the antibacterial modifier prepared in Preparation Example 4.

[0071] Example 9, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of the antibacterial modifier prepared in Preparation Example 5.

[0072] Example 10, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of the antibacterial modifier prepared in Preparation Example 8.

[0073] Example 11, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of the antibacterial modifier prepared in Preparation Example 9.

[0074] Example 12, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of the antibacterial modifier prepared in Preparation Example 10.

[0075] Example 13, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of the antibacterial modifier prepared in Preparation Example 11.

[0076] Example 14, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of the antibacterial modifier prepared in Preparation Example 12.

[0077] Comparative Example

[0078] Comparative Example 1 is a high barrier antibacterial flexible packaging material, which is different from Example 1 only in that the mass fraction of the antibacterial modifier prepared in Preparation Example 1 is 2 parts.

[0079] Comparative Example 2 is a high barrier antibacterial flexible packaging material, which is different from Example 1 only in that the mass fraction of the antibacterial modifier prepared in Preparation Example 1 is 20 parts.

[0080] Comparative Example 3, a high barrier antibacterial flexible packaging material, is different from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of the antibacterial modifier prepared in Preparation Example 6.

[0081] Comparative Example 4 is a high barrier antibacterial flexible packaging material, which is different from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of the antibacterial modifier prepared in Preparation Example 7.

[0082] Comparative Example 5 is a high barrier antibacterial flexible packaging material, which is different from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is replaced by an equal amount of nanosilver (average particle size of 10-15 nm).

[0083] Comparative Example 6 is a high barrier antibacterial flexible packaging material, which is different from Example 1 only in that the antibacterial modifier prepared in Preparation Example 1 is not added to the barrier antibacterial masterbatch.

[0084] Performance testing

[0085] 1. Barrier performance test:

[0086] (1) Water vapor permeability: The water vapor permeability (g / m2) of the flexible packaging materials obtained in the examples and comparative examples was measured according to the relevant records in GB / T 1037-2021 “Determination of water vapor permeability of plastic films and sheets - Cup weight gain and weight loss method”. 2 *24h) for testing;

[0087] (2) Oxygen permeability: The oxygen permeability (mL / m2) of the flexible packaging materials obtained in the examples and comparative examples was measured according to the relevant records in GB / T 1038.1-2022 "Test method for gas permeability of plastic films and sheets - Part 1: Differential pressure method". 2 *24h) for testing;

[0088] The test results are shown in Table 1.

[0089] 2. Antibacterial performance test: According to the relevant records in GB / T 31402-2023 "Determination of antibacterial activity on the surface of plastics and other non-porous materials", the antibacterial properties of the flexible packaging materials obtained in the embodiments and comparative examples were tested. The detected bacteria were Escherichia coli and Staphylococcus aureus. The test results are shown in Table 2.

[0090] 3. Peel strength performance test: According to the relevant records in GB / T 10004-2008 "Plastic composite films for packaging, dry composite bags, extrusion composite", the peel strength (N / 15mm) of the flexible packaging materials obtained in the examples and comparative examples was tested. The test results are shown in Table 3.

[0091]

[0092]

[0093]

[0094] According to Table 1, Table 2 and Table 3, combined with Example 1, Example 2 to Example 7, it can be seen that there is no significant difference in water vapor and oxygen permeability, antibacterial property and peel strength between Example 2 to Example 7 and Example 1, indicating that the barrier property and antibacterial property of the flexible packaging materials obtained in Example 2 to Example 7 are not significantly different from those in Example 1. The reason is that the difference between Example 2 to Example 7 and Example 1 is only that the raw materials and their proportions are adjusted within the required range, which has little effect on the performance of the final material.

[0095] Combining Example 1, Example 8, Example 9 and Comparative Example 4, it can be seen that the antibacterial properties of Example 8, Example 9 and Comparative Example 4 are reduced compared with Example 1. The reason is that in Example 8, the amount of silver nitrate added during the preparation of the antibacterial modifier is reduced, resulting in a decrease in the content of nanosilver in the final antibacterial modifier, and the corresponding antibacterial property is reduced. In Comparative Example 4, no silver nitrate is added, so the antibacterial performance is significantly reduced. In Example 9, the amount of nanosilver added is increased. At this time, the amount of nanosilver has reached saturation, and there is no obvious effect on the improvement of antibacterial property, but it has decreased.

[0096] In combination with Example 1, Example 10, and Example 11 to Example 14, it can be seen that compared with Example 1, the water vapor and oxygen permeability of Example 10 are reduced, the antibacterial property is increased, and the peel strength is increased. The reason is that the surface of the antibacterial modifier used in Example 10 is grafted with polyethyleneimine segments. On the one hand, the positive charge carried by the polyethyleneimine segment can generate electrostatic effects with the negative charges on the surface of the bacterial cell membrane, thereby affecting the normal physiological activities of the bacteria and increasing the antibacterial property of the material. On the other hand, the introduction of the polyethyleneimine segment can form a cross-linked network structure with the EVOH resin, which can reduce the diffusion channels of small molecules while enhancing the bonding force with the inner heat sealing layer, thereby improving the peel strength of the material. The only difference between Example 11 and Example 12 compared with Example 10 is that the ratio of raw materials is changed within the required range, which has little effect on the final performance. In Example 13, the grafting amount of polyethyleneimine segments is reduced, and the transmittance, antibacterial property and peel strength are reduced compared with Example 10. The reason is that the reduction of polyethyleneimine segments reduces the mutual binding force with EVOH, reduces the structural density, reduces the barrier property, and the reduction of segments can directly affect the antibacterial property of the material. In Example 14, the amount of polyethyleneimine added during the grafting of polyethyleneimine segments is increased. The increase in grafting rate will cause self-agglomeration, and the binding force with the compatibilizer of the inner heat sealing layer is reduced, thereby reducing the peel strength.

[0097] In combination with Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 6, it can be seen that the antibacterial properties of Comparative Example 1, Comparative Example 2 and Comparative Example 6 are reduced compared with Example 1. The reason is that the amount of antibacterial modifier added is reduced in Comparative Example 1, and accordingly, the antibacterial performance is reduced, especially the peel strength of Comparative Example 1 is reduced compared with Example 1. Due to the lack of added amine organic molecular cages, the bonding strength between the EVOH resin and the inner heat sealing layer is reduced, which leads to a decrease in the peel strength of the material. No antibacterial modifier is added in Comparative Example 6, and the performance decline is very obvious.

[0098] Combining Example 1, Comparative Example 3 and Comparative Example 5, it can be seen that the water vapor and oxygen permeability of Comparative Example 3 are increased compared with Example 1, the antibacterial property is decreased, and the peel strength is decreased. The reason is that the amine organic molecular cage in Comparative Example 3 has not been reduced and acidified, the structure is unstable, the number of active groups is reduced, the binding force is decreased, and the number of nanosilver binding sites is decreased, resulting in a decrease in the content of nanosilver loaded in the material and a decrease in antibacterial performance; the antibacterial property of Comparative Example 5 is significantly decreased compared with Example 1, and the reason is that the antibacterial modifier in Comparative Example 5 does not load nanosilver, and the antibacterial property decreases accordingly. However, due to the presence of the amine organic molecular cage, the adsorption of water by the material can be reduced, affecting the favorable environment for bacterial growth, resulting in the antibacterial property not significantly decreased compared with the material without the addition of the antibacterial modifier.

[0099] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0100] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. High barrier antibacterial flexible packaging material, characterized in that: The flexible packaging material is composed of an outer layer, a barrier antibacterial layer and an inner heat-sealing layer from the outside to the inside; the raw materials of the barrier antibacterial layer include 85-95 parts by weight of EVOH resin and 5-15 parts by weight of an antibacterial modifier; the antibacterial modifier is an amine organic molecular cage composite nanosilver; The antibacterial modifier is prepared according to the following method: Preparation of amine organic molecular cage: under nitrogen atmosphere, tris(2-aminoethyl)amine and pyrrole-2,6-dicarboxaldehyde are dissolved in solvents respectively, the obtained solutions are mixed, the temperature is raised to 50-55°C, stirred for reaction for 24-36h, and then filtered, washed, spin-dried and recrystallized to obtain imine organic molecular cage, and then reduced by a reducing agent, extracted and acidified with hydrochloric acid to obtain amine organic molecular cage, the reducing agent includes one or a combination of sodium borohydride, potassium borohydride and sodium triacetoxyborohydride, and the amount of reducing agent added is 45-50% of the mass of the imine organic molecular cage; Composite of nanosilver: add amine organic molecular cage to solvent, add soluble silver salt, stir and mix at room temperature for 2 to 3 hours, add reducing agent at -5 to 0°C, continue stirring for 20 to 30 minutes, and obtain amine organic molecular cage composite nanosilver, i.e. antibacterial modifier, through separation, freeze drying and grinding.

2. The high barrier antibacterial flexible packaging material according to claim 1, characterized in that: The mass ratio of the outer layer, the barrier antibacterial layer and the inner heat-sealing layer is (25-40): (20-30): (30-45).

3. The high barrier antibacterial flexible packaging material according to claim 1, characterized in that: The raw materials of the inner heat-sealing layer include 70 to 80 parts by weight of linear low-density polyethylene, 10 to 15 parts by weight of polypropylene and 5 to 8 parts by weight of maleic anhydride grafted polyethylene; The raw material of the outer layer includes one of PET resin, PA resin and EVA resin.

4. The high barrier antibacterial flexible packaging material according to claim 1, characterized in that: The raw materials of the antibacterial modifier include an amine organic molecular cage and a soluble silver salt in a mass ratio of 1: (0.05-0.1).

5. The high barrier antibacterial flexible packaging material according to claim 1, characterized in that: The amount of reducing agent added during the nano-silver compounding process is 30-35% of the mass of the amine organic molecular cage.

6. The high barrier antibacterial flexible packaging material according to claim 1, characterized in that: The antibacterial modifier is also grafted with a polyethyleneimine segment.

7. The high barrier antibacterial flexible packaging material according to claim 6, characterized in that: The raw materials of the antibacterial modifier grafted with polyethyleneimine chain segment include amine organic molecular cage composite nano silver, polyethyleneimine and maleic anhydride in a mass ratio of 1: (0.6-0.8): (0.3-0.4).

8. The high barrier antibacterial flexible packaging material according to claim 6, characterized in that: The antibacterial modifier grafted polyethyleneimine chain segment is prepared according to the following method: adding amine organic molecular cage composite nanosilver and maleic anhydride into a solvent, stirring and reacting at room temperature for 12 to 24 hours, and obtaining a pretreated product by filtering and dialysis; adding the pretreated product and polyethyleneimine into a phosphate buffer solution with a pH value of 7 to 8, stirring and reacting at 40 to 50° C. for 12 to 24 hours, and obtaining the antibacterial modifier grafted polyethyleneimine chain segment by centrifugal filtration and dialysis.

9. A method for preparing a high barrier antibacterial flexible packaging material according to any one of claims 1 to 8, characterized in that: The process steps include: S1. Weigh the EVOH resin and the antibacterial modifier according to the corresponding mass parts, mix them evenly, and then melt extrude them at 170 to 190 ° C to obtain a barrier antibacterial masterbatch; S2. Weigh linear low-density polyethylene, polypropylene and maleic anhydride grafted polyethylene in corresponding parts by mass, mix them evenly and melt extrude them at 150 to 175 ° C to obtain an internal heat-sealing masterbatch; S3. Melt and plasticize the barrier antibacterial masterbatch, inner heat-sealing masterbatch and outer layer raw material respectively according to the corresponding mass ratio, and then obtain a high barrier antibacterial flexible packaging material by co-extrusion casting.

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