Antibacterial functional food packaging film and preparation method thereof

Abstract

The invention relates to the technical field of packaging materials, and discloses an antibacterial functional food packaging film and a preparation method thereof. The packaging film is formed by blending, extruding, and blowing a film with low-density polyethylene as the main raw material, a compatibilizer, a synergistic antibacterial agent, and a fiber coating material, etc. The synergistic antibacterial component is a nano zinc oxide with a biomass antibacterial agent tannic acid grafted on the surface. After the tannic acid is immobilized on the surface of the nano zinc oxide, it will not be easily volatilized and migrated, and will continue to exert its own broad-spectrum antibacterial properties, and cooperate with the photocatalytic antibacterial effect of the nano zinc oxide, giving the polyethylene film good long-term antibacterial properties. The addition of the fiber coating material can improve the density of the polyethylene film, improve the air tightness and high temperature resistance. In addition, the fiber coating material can exert the effects of stress load transfer and absorption, and can make the prepared polyethylene film have excellent mechanical strength.

Description

Technical Field

[0001] The invention relates to the technical field of packaging materials, and in particular to an antibacterial functional food packaging film and a preparation method thereof. Background Art

[0002] With the rapid development of the modern food industry and the improvement of consumers' health awareness, the safety and functionality of food packaging materials have become the focus of attention. Polyethylene, as a widely used plastic material, has the characteristics of being non-toxic, tasteless, odorless, and chemically stable. It does not react with ingredients in food, thus ensuring the safety and quality of food and meeting the safety standards of food packaging materials. Therefore, it occupies an important position in the field of food packaging. However, traditional polyethylene packaging films have deficiencies in antibacterial properties and poor air tightness, making it difficult to meet the market's higher requirements for food safety and shelf life. In addition, the heat resistance of polyethylene packaging films is poor, which makes it difficult to use them in some prefabricated food packaging fields that require microwave heating. Therefore, it is urgent to modify polyethylene and enhance its comprehensive performance to further expand the application of polyethylene in the field of food packaging films.

[0003] The invention patent with application number CN202211675969.X discloses an antibacterial polyethylene food-grade packaging film and a preparation method thereof. The modified nano zirconium phosphate silver-loaded antibacterial agent and nano zinc oxide antibacterial agent are compounded as antibacterial additives to modify polyethylene, which can enhance the antibacterial properties of polyethylene. Therefore, the addition and modification method can effectively improve the comprehensive performance of polyethylene film. However, there are interface problems between inorganic nanomaterials and polymer materials such as polyethylene. The incompatibility between them will lead to a decrease in the mechanical properties of the material. Based on this, the present invention provides a polyethylene composite film with good antibacterial and other functionalities, which can be directly used as a food packaging film. Summary of the invention

[0004] In order to solve the problems mentioned in the background technology, the object of the present invention is to provide an antibacterial functional food packaging film and a preparation method thereof.

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

[0006] A method for preparing an antibacterial functional food packaging film, wherein the food packaging film is made of the following raw materials in parts by weight:

[0007]

[0008] The preparation method comprises the following steps:

[0009] S1. Weigh each raw material according to its weight and set aside;

[0010] S2, putting all the raw materials into a mixer and mixing them evenly, then feeding them into a screw extruder through a feeding hopper, and melt-extruding and granulating them at 180-220° C. to obtain pellets;

[0011] S3. Place the pellets in a film blowing machine, use a 3-5 stage heating film blowing machine, control the temperature to 150-160°C, 155-165°C, 160-170°C, 165-175°C, 160-170°C, and then perform cast film forming, winding, and cutting processes.

[0012] As a further embodiment of the present invention, the compatibilizer is maleic anhydride grafted polyethylene or maleic anhydride grafted polypropylene.

[0013] As a further embodiment of the present invention, the preparation method of the synergistic antibacterial component comprises the following steps:

[0014] Step A, dispersing nano zinc oxide in N,N-dimethylformamide solvent, then adding diglycidyl ether monomer and stannous chloride to the formed dispersion, stirring after the addition, raising the temperature to 120-140° C. under nitrogen protection, keeping the temperature for 4-6 hours, centrifuging out the solid material, and obtaining epoxidized nano zinc oxide;

[0015] Step B, adding epoxidized nano zinc oxide to ethanol solvent, ultrasonicating for 20-30 minutes, then adding tannic acid and catalyst, after the addition, gradually raising the temperature to 60-70°C, stirring for 3-5 hours, cooling and discharging, centrifuging to obtain synergistic antibacterial components.

[0016] As a further embodiment of the present invention, in step A, the bisglycidyl ether monomer is at least one of ethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether or 1,4-butanediol diglycidyl ether.

[0017] As a further embodiment of the present invention, in step B, the catalyst is triphenylphosphine.

[0018] As a further embodiment of the present invention, the method for preparing the fiber coating material comprises the following steps:

[0019] Step ①, dispersing wollastonite fiber in toluene to form a uniform dispersion, then adding halogenated acyl halide and triethylamine, stirring at room temperature for 6-9 hours, and centrifuging to obtain modified fiber;

[0020] Step ②, add polybenzimidazole to dimethyl sulfoxide, mix well, add sodium hydride, stir at room temperature for 6-12 hours, then add modified fiber, ultrasonicate for 20-30 minutes, then increase the temperature to 50-60°C, keep warm and stir for 4-8 hours, centrifuge and separate the product to obtain a fiber coating material.

[0021] As a further embodiment of the present invention, in step ①, the halogenated acyl halide substance is any one of chloroacetyl chloride, bromoacetyl chloride or 4-bromobutyryl chloride.

[0022] As a further solution of the present invention, in step ②, the mass ratio of the polybenzimidazole to the modified fiber is 3-4:1.

[0023] As a further embodiment of the present invention, the antioxidant is a mixture of antioxidant 168 and antioxidant 1010, with a mass ratio of 1:1; and the lubricant is any one of calcium stearate, zinc stearate or polyethylene wax.

[0024] An antibacterial functional food packaging film is prepared by adopting the preparation method.

[0025] Beneficial effects of the present invention:

[0026] (1) The synergistic antibacterial component prepared by the present invention is a nano zinc oxide with a biomass antibacterial agent tannic acid grafted on the surface. On the one hand, after being modified by organic matter, an organic transition layer will be formed on the surface of the nano zinc oxide, so that good interfacial compatibility can be generated between the nano zinc oxide and the polyethylene matrix, avoiding the negative effects caused by agglomeration. On the other hand, after being immobilized on the surface of the nano zinc oxide, the tannic acid will not be easily volatilized and migrated, so it can exist in the polyethylene matrix for a long time, continue to exert its own broad-spectrum antibacterial properties, and cooperate with the photocatalytic antibacterial effect of the nano zinc oxide, giving the polyethylene film good long-term antibacterial properties.

[0027] (2) The fiber coating material prepared by the present invention is wollastonite fiber grafted with macromolecular polybenzimidazole. Since the polybenzimidazole structure contains a large number of secondary amine groups, it can interact with the compatibilizer during the high-temperature melting process, thereby causing the polybenzimidazole molecular chain and the polyethylene molecular chain to produce a cross-linking effect of mutual entanglement, thereby forming a micro-cross-linked network structure at the interface between the wollastonite fiber and the polyethylene matrix. This cross-linked network can not only increase the cross-linking density of the polyethylene molecular chain, improve the density of the polyethylene film, reduce the porosity, and improve the air tightness, but also effectively limit the thermal movement of the polyethylene molecular chain, thereby enhancing the high temperature resistance of the polyethylene film. In addition, the wollastonite fiber in the form of a chemically cross-linked core in the polyethylene matrix can effectively exert the effect of stress load transfer and absorption, and can make the prepared polyethylene film have excellent mechanical strength.

[0028] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. DETAILED DESCRIPTION

[0029] The technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than 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.

[0030] Example 1

[0031] An antibacterial functional food packaging film is made of the following raw materials in parts by weight:

[0032]

[0033]

[0034] The preparation method of the food packaging film comprises the following steps:

[0035] S1. Weigh each raw material according to its weight and set aside;

[0036] S2, putting all the raw materials into a mixer and mixing them evenly, then feeding them into a screw extruder through a feeding hopper, and melt-extruding and granulating them at 180° C. to obtain pellets;

[0037] S3. Place the pellets in a film blowing machine, use a 5-stage heating film blowing machine, control the temperature at 155°C, 160°C, 165°C, 170°C, and 165°C in sequence, and then perform cast molding, winding, and cutting processes.

[0038] The antioxidant is a mixture of antioxidant 168 and antioxidant 1010 in a mass ratio of 1:1, and the same applies to the following.

[0039] Example 2

[0040] An antibacterial functional food packaging film is made of the following raw materials in parts by weight:

[0041]

[0042] The preparation method of the food packaging film comprises the following steps:

[0043] S1. Weigh each raw material according to its weight and set aside;

[0044] S2, putting all the raw materials into a mixer and mixing them evenly, then feeding them into a screw extruder through a feeding hopper, and melt-extruding and granulating them at 200° C. to obtain pellets;

[0045] S3. Place the pellets in a film blowing machine, use a 5-stage heating film blowing machine, control the temperature at 155°C, 160°C, 165°C, 170°C, and 165°C in sequence, and then perform cast molding, winding, and cutting processes.

[0046] Example 3

[0047] An antibacterial functional food packaging film is made of the following raw materials in parts by weight:

[0048]

[0049] The preparation method of the food packaging film comprises the following steps:

[0050] S1. Weigh each raw material according to its weight and set aside;

[0051] S2, putting all the raw materials into a mixer and mixing them evenly, then feeding them into a screw extruder through a feeding hopper, and melt-extruding and granulating them at 220° C. to obtain pellets;

[0052] S3. Place the pellets in a film blowing machine, use a 5-stage heating film blowing machine, control the temperature at 155°C, 160°C, 165°C, 170°C, and 165°C in sequence, and then perform cast molding, winding, and cutting processes.

[0053] Comparative Example 1

[0054] An antibacterial functional food packaging film is made of the following raw materials in parts by weight:

[0055]

[0056] The preparation method of the food packaging film comprises the following steps:

[0057] S1. Weigh each raw material according to its weight and set aside;

[0058] S2, putting all the raw materials into a mixer and mixing them evenly, then feeding them into a screw extruder through a feeding hopper, and melt-extruding and granulating them at 200° C. to obtain pellets;

[0059] S3. Place the pellets in a film blowing machine, use a 5-stage heating film blowing machine, control the temperature at 155°C, 160°C, 165°C, 170°C, and 165°C in sequence, and then perform cast molding, winding, and cutting processes.

[0060] Comparative Example 2

[0061] An antibacterial functional food packaging film is made of the following raw materials in parts by weight:

[0062]

[0063]

[0064] The preparation method of the food packaging film comprises the following steps:

[0065] S1. Weigh each raw material according to its weight and set aside;

[0066] S2, putting all the raw materials into a mixer and mixing them evenly, then feeding them into a screw extruder through a feeding hopper, and melt-extruding and granulating them at 200° C. to obtain pellets;

[0067] S3. Place the pellets in a film blowing machine, use a 5-stage heating film blowing machine, control the temperature at 155°C, 160°C, 165°C, 170°C, and 165°C in sequence, and then perform cast molding, winding, and cutting processes.

[0068] Comparative Example 3

[0069] An antibacterial functional food packaging film is made of the following raw materials in parts by weight:

[0070]

[0071] The preparation method of the food packaging film comprises the following steps:

[0072] S1. Weigh each raw material according to its weight and set aside;

[0073] S2, putting all the raw materials into a mixer and mixing them evenly, then feeding them into a screw extruder through a feeding hopper, and melt-extruding and granulating them at 200° C. to obtain pellets;

[0074] S3. Place the pellets in a film blowing machine, use a 5-stage heating film blowing machine, control the temperature at 155°C, 160°C, 165°C, 170°C, and 165°C in sequence, and then perform cast molding, winding, and cutting processes.

[0075] Comparative Example 4

[0076] An antibacterial functional food packaging film is made of the following raw materials in parts by weight:

[0077]

[0078] The preparation method of the food packaging film comprises the following steps:

[0079] S1. Weigh each raw material according to its weight and set aside;

[0080] S2, putting all the raw materials into a mixer and mixing them evenly, then feeding them into a screw extruder through a feeding hopper, and melt-extruding and granulating them at 200° C. to obtain pellets;

[0081] S3. Place the pellets in a film blowing machine, use a 5-stage heating film blowing machine, control the temperature at 155°C, 160°C, 165°C, 170°C, and 165°C in sequence, and then perform cast molding, winding, and cutting processes.

[0082] The synergistic antibacterial components in the above examples and comparative examples were prepared by the following method:

[0083] Step A, dispersing 3.5 g of nano zinc oxide in N,N-dimethylformamide solvent, then adding 2.8 g of ethylene glycol diglycidyl ether and 0.01 g of stannous chloride to the formed dispersion, stirring after the addition, raising the temperature to 140° C. under nitrogen protection, keeping the temperature for 5 hours, and centrifuging the solid material to obtain epoxidized nano zinc oxide;

[0084] The epoxide value of epoxidized nano zinc oxide was tested by hydrochloric acid-acetone titration test method. 0.2 g of epoxidized nano zinc oxide was weighed as a sample for titration test. The result showed that the epoxide value was 2.418 mmol / g.

[0085] Step B: add 2.4 g of epoxidized nano zinc oxide to ethanol solvent, ultrasonicate for 25 min, then add 6 g of tannic acid and 0.05 g of triphenylphosphine. After the addition, gradually increase the temperature to 65°C, stir for 4 h, cool and discharge, centrifuge to obtain a synergistic antibacterial component.

[0086] Similarly, the epoxy value of 0.2g of the synergistic antibacterial component was tested again using the hydrochloric acid-acetone method, and the result showed that it was 0.551mmol / g. It is speculated that in step A, through the catalytic action of stannous chloride, the hydroxyl group on the surface of the nano zinc oxide undergoes a ring-opening addition with the epoxy group at one end of the ethylene glycol diglycidyl ether structure, thereby introducing an epoxy substituent group on the surface of the nano zinc oxide. In step B, the phenolic hydroxyl group in the tannic acid structure can undergo a further ring-opening reaction with the epoxy group of the epoxidized nano zinc oxide under the action of triphenylphosphine, thereby modifying the tannic acid on the surface of the nano zinc oxide to obtain a synergistic antibacterial component.

[0087] The fiber coating materials in the above examples and comparative examples were prepared by the following method:

[0088] Step ①, dispersing 1.5 g of wollastonite fiber in toluene to form a uniform dispersion, then adding 3.4 g of bromoacetyl chloride and 0.5 g of triethylamine, stirring at room temperature for 8 h after addition, and centrifuging to obtain modified fiber;

[0089] Step ②, add 4.5g polybenzimidazole to dimethyl sulfoxide, mix well, add 0.2g sodium hydride, stir at room temperature for 9h, then add 1.2g modified fiber, ultrasonicate for 30min, then raise the temperature to 60°C, keep stirring for 9h, centrifuge and separate the product to obtain a fiber coating material.

[0090] The fiber coating material was analyzed for organic elements using a TQ-3 organic element analyzer, and the test results showed that the percentage of carbon element was 19.74% and the percentage of nitrogen element was 6.61%. Therefore, the principle of the above technical solution is: first, triethylamine is used as an acidifying agent to promote the esterification condensation between the silanol groups on the surface of the wollastonite fiber and the acyl chloride groups in the bromoacetyl chloride structure to form a wollastonite fiber modified with a halogen substituent, i.e., a modified fiber, and then sodium hydride is used as a catalyst to catalyze the substitution of the secondary amine groups in the polybenzimidazole structure with the halogen substituents of the modified fiber, thereby grafting the polybenzimidazole macromolecules on the surface of the wollastonite fiber to obtain a fiber coating material.

[0091] Test Case

[0092] According to the standard GB / T 1040.3-2006, the tensile properties were tested. After the samples of the same batch were heated at 150°C for 12 hours, the tensile properties were tested again, and the high temperature resistance was evaluated.

[0093] According to the standard GB / T 1038.1-20222, the air permeability test is carried out;

[0094] According to the standard QB / T 2591-2003, the packaging films in Examples 1 to 3 and Comparative Examples 1 to 4 were cut into test samples of composite specifications, and placed in an environment of 25°C and 50% relative humidity for 3 months, and then the antibacterial performance test was performed, and the bacterial species selected was Escherichia coli;

[0095] The results are shown in Table 1:

[0096] Table 1 - Performance test results

[0097]

[0098] The analysis and test results show that the packaging film made by adding synergistic antibacterial components and fiber coating materials has excellent mechanical properties, and the tensile strength does not decrease significantly after heat treatment. It has excellent high temperature resistance. In addition, the air permeability and antibacterial properties are also excellent. After the synergistic antibacterial component is replaced with tannic acid, the antibacterial performance is weakened due to the possible precipitation during storage. After the synergistic antibacterial component is removed, the antibacterial performance is significantly reduced.

[0099] In addition, after replacing the fiber coating with wollastonite fiber without surface treatment, there is not only the problem of incompatibility, but also the inability to increase the density of polyethylene molecular chains because the micro-cross-linked network structure cannot be formed between the interfaces. Therefore, the mechanical properties, high temperature resistance and air permeability are significantly reduced. After directly removing the fiber coating, the advantages of wollastonite fiber cannot be utilized, so the mechanical properties, high temperature resistance and air permeability are further reduced.

[0100] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for preparing an antibacterial functional food packaging film, characterized in that: The food packaging film is made of the following raw materials in parts by weight: The preparation method comprises the following steps: S1. Weigh each raw material according to its weight and set aside; S2, putting all the raw materials into a mixer and mixing them evenly, then feeding them into a screw extruder through a feeding hopper, and melt-extruding and granulating them at 180-220° C. to obtain pellets; S3, placing the pellets in a film blowing machine, using a 3-5 stage heating film blowing machine, controlling the temperature to 150-160°C, 155-165°C, 160-170°C, 165-175°C, 160-170°C, and then performing cast molding, winding, and cutting processes; The synergistic antibacterial component is prepared by the following method: Step A, dispersing 3.5 g of nano zinc oxide in N,N-dimethylformamide solvent, then adding 2.8 g of ethylene glycol diglycidyl ether and 0.01 g of stannous chloride to the formed dispersion, stirring after the addition, raising the temperature to 140° C. under nitrogen protection, keeping the temperature for 5 hours, and centrifuging the solid material to obtain epoxidized nano zinc oxide; Step B, adding 2.4 g of epoxidized nano zinc oxide to an ethanol solvent, ultrasonicating for 25 min, then adding 6 g of tannic acid and 0.05 g of triphenylphosphine, after the addition, gradually raising the temperature to 65° C., stirring for 4 h, cooling and discharging, centrifuging to obtain a synergistic antibacterial component; The fiber coating material is prepared by the following method: Step ①, dispersing 1.5 g of wollastonite fiber in toluene to form a uniform dispersion, then adding 3.4 g of bromoacetyl chloride and 0.5 g of triethylamine, stirring at room temperature for 8 h after addition, and centrifuging to obtain modified fiber; Step ②, add 4.5g polybenzimidazole to dimethyl sulfoxide, mix well, add 0.2g sodium hydride, stir at room temperature for 9h, then add 1.2g modified fiber, ultrasonicate for 30min, then raise the temperature to 60°C, keep stirring for 9h, centrifuge and separate the product to obtain a fiber coating material.

2. The method for preparing an antibacterial functional food packaging film according to claim 1, characterized in that: The compatibilizer is maleic anhydride grafted polyethylene or maleic anhydride grafted polypropylene.

3. The method for preparing an antibacterial functional food packaging film according to claim 1, characterized in that: The preparation method of the synergistic antibacterial component comprises the following steps: Step A, using stannous chloride as a catalyst and using a bisglycidyl ether monomer to modify nano zinc oxide to obtain epoxidized nano zinc oxide; Step B: In an ethanol solvent, tannic acid is used in combination with a catalyst to graft-modify epoxidized nano zinc oxide to obtain a synergistic antibacterial component.

4. The method for preparing an antibacterial functional food packaging film according to claim 3, characterized in that: In step A, the bisglycidyl ether monomer is at least one of ethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether or 1,4-butanediol diglycidyl ether.

5. The method for preparing an antibacterial functional food packaging film according to claim 3, characterized in that: In step B, the catalyst is triphenylphosphine.

6. The method for preparing an antibacterial functional food packaging film according to claim 1, characterized in that: The preparation method of the fiber coating material comprises the following steps: Step ①, in a toluene medium, using a halogenated acyl halide substance to modify wollastonite fiber to obtain modified fiber; Step ②, using sodium hydride as a catalyst, using polybenzimidazole as a coating modification material in N,N-dimethylformamide, and graft coating the modified fiber to obtain a fiber coating material.

7. The method for preparing an antibacterial functional food packaging film according to claim 6, characterized in that: In step ①, the halogenated acyl halide substance is any one of chloroacetyl chloride, bromoacetyl chloride or 4-bromobutyryl chloride.

8. The method for preparing an antibacterial functional food packaging film according to claim 6, characterized in that: In step ②, the mass ratio of the polybenzimidazole to the modified fiber is 3-4:

1.

9. The method for preparing an antibacterial functional food packaging film according to claim 1, characterized in that: The antioxidant is a mixture of antioxidant 168 and antioxidant 1010, with a mass ratio of 1:1; the lubricant is any one of calcium stearate, zinc stearate or polyethylene wax.

10. An antibacterial functional food packaging film, characterized in that: The method is prepared according to any one of claims 1 to 9.

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