Microwave-heatable modified polypropylene composite packaging material and preparation method thereof

Abstract

The invention belongs to the technical field of packaging materials, and discloses a microwave-heatable modified polypropylene composite packaging material and a preparation method thereof, the microwave-heatable modified polypropylene composite packaging material is characterized in that the microwave-heatable modified polypropylene composite packaging material sequentially comprises a modified polypropylene barrier layer, a reinforced connecting layer and a heat-sealing layer from outside to inside, the reinforced connecting layer is a nylon layer and has a thickness of 15-25 [mu] m, the heat-sealing layer is a polypropylene heat-sealing layer, and the thickness of the heat-sealing layer is 10-25 [mu] m. The thickness of the modified polypropylene barrier layer is 40-60 microns, and the modified polypropylene barrier layer is prepared from the following raw materials in parts by weight: 80-90 parts of polypropylene resin, 5-10 parts of modified montmorillonite, 3-5 parts of a toughening agent, 6-8 parts of graphene, 0.3-2 parts of a lubricating agent and 0.5-1.5 parts of an antioxidant; the modified montmorillonite is montmorillonite-loaded tea polyphenol, the antioxidant is prepared by compounding antioxidants 1010 and 168 according to a mass ratio of 1: (2-1), and due to the addition of the modified montmorillonite, the optimization of the composite packaging material in thermal stability, antibacterial property, barrier property and toughness is realized, the strict requirements of microwave heating packaging are met, and the food safety and consumption experience are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of packaging materials, and particularly relates to a modified polypropylene composite packaging material capable of being heated by microwaves and a preparation method thereof. BACKGROUND

[0002] At present, plastic packaging is widely used, and resin material packaging brings great convenience to consumers. With the vigorous development of the take-out industry, the market has higher requirements for the functionality of packaging materials, especially the comprehensive performance in terms of thermal stability, barrier property, toughness and antibacterial property, which has become the core index for measuring the quality of microwave heating packaging.

[0003] Early microwave heating packaging such as traditional three-edge sealed bags and ordinary standing bags cannot meet the actual needs due to the limitations of material performance. On the one hand, insufficient thermal stability leads to deformation, melting and even release of harmful substances when the packaging is heated in a microwave; on the other hand, the lack of barrier property makes oxygen and water vapor easily penetrate, not only shortening the shelf life of food, but also intensifying the increase of internal pressure in the bag due to excessive accumulation of water vapor when heated, which provides a breeding ground for microorganisms; at the same time, materials with insufficient toughness are easily damaged and torn at the edge under the action of internal pressure generated by steam expansion, which leads to spattering of the contents, affecting the use experience, and increasing the risk of microbial contamination due to the exposure of the damaged part, which poses a significant safety hazard.

[0004] The microwaveable food packaging on the market still has obvious performance shortcomings: one type is traditional soft packaging, which has low material consumption, but has poor barrier property, weak thermal stability, and lacks antibacterial design, so it needs to be cut by the consumer and transferred to a container for heating, which is not only cumbersome to operate, but also loses the preservation advantage of sealed packaging, and is easily contaminated by environmental microorganisms during the secondary transfer process; the other type is a hard packaging box, which can be heated directly, but uses thick and heavy materials, which not only have poor toughness adaptability, but also have difficulty in balancing barrier property, thermal stability and antibacterial property.

[0005] Therefore, it is of great significance to develop a new composite packaging material with excellent thermal stability, high barrier property, strong toughness and durable antibacterial property to solve the problems of existing microwave heating packaging, improve food safety, extend the shelf life, reduce the risk of microbial contamination and optimize the consumer experience. SUMMARY

[0006] To solve the problems mentioned in the background art, the purpose of the present application is to disclose a microwave-heatable modified polypropylene composite packaging material and a preparation method thereof. The comprehensive performance of the material is optimized by introducing modified montmorillonite, which can be directly used for microwave heating. The modified montmorillonite is prepared by pretreating γ-aminopropyl triethoxysilane and then reacting with tea polyphenol, which gives the compatibility of montmorillonite and organic matrix, and the tea polyphenol introduces antibacterial activity, so that the montmorillonite improves the barrier property, thermal stability and toughness of the material while giving persistent antibacterial function.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] A microwave-heatable modified polypropylene composite packaging material, characterized by comprising, from outside to inside, a modified polypropylene barrier layer, a reinforcing connecting layer and a heat-sealing layer. The reinforcing connecting layer is a nylon layer with a thickness of 15-25 μm. The heat-sealing layer is a polypropylene heat-sealing layer with a thickness of 40-60 μm. The modified polypropylene barrier layer comprises the following raw materials by weight: polypropylene resin 80-90 parts, modified montmorillonite 5-10 parts, toughening agent 3-5 parts, graphene 6-8 parts, lubricant 0.3-2 parts, and antioxidant 0.5-1.5 parts. The modified montmorillonite is montmorillonite loaded with tea polyphenol. The antioxidant is a compound of antioxidant 1010 and 168 in a mass ratio of 1:2-1.

[0009] Further preferably, the toughening agent is one or more of ternary ethylene-propylene rubber, binary ethylene-propylene rubber and cis-butadiene rubber.

[0010] Further preferably, the lubricant is one or more of zinc stearate, paraffin and polyethylene wax.

[0011] Further preferably, the antioxidant is a compound of antioxidant 1010 and 168 in a mass ratio of 1:2-1.

[0012] Further preferably, the preparation method of the modified montmorillonite comprises the following steps:

[0013] A1. γ-aminopropyl triethoxysilane and montmorillonite are added to a mixed solution of deionized water and anhydrous ethanol, and reacted at 70-80℃ for 2-4h to obtain a turbid solution;

[0014] A2. Tea polyphenol is added to the solution, stirred for 10-15min, and reacted at 70-80℃ for 12-16h.

[0015] A3. The reacted solution is cooled to room temperature, centrifuged and washed until the pH is neutral, dried, and the modified montmorillonite is obtained.

[0016] Further preferably, the mass ratio of γ-aminopropyl triethoxysilane, montmorillonite and tea polyphenol is 1:5:2-1.

[0017] Further preferably, the preparation method of the microwave-heatable modified polypropylene composite packaging material comprises the following steps:

[0018] S1, polypropylene resin, modified montmorillonite, toughening agent, graphene, lubricant, antioxidant are added into a high-speed mixer and mixed at a rotation speed of 800-1000 r / min for 10-15 min to obtain a mixture;

[0019] S2, the mixture is added into a twin-screw extruder, melt blended, and then water-cooled and pelletized to obtain modified polypropylene granules, and the modified polypropylene granules are added into a single-screw extrusion casting machine and extruded and cast into a film at 190-210℃ to obtain a modified polypropylene barrier layer;

[0020] S3, the modified polypropylene barrier layer, the nylon reinforced connecting layer, and the heat-sealing layer are sequentially compounded by a dry compounding process, using polyurethane adhesive, at a coating speed of 150-200 m / min, a pressure of 0.3-0.5 MPa, and a drying temperature of 60-70℃, and then aged at 40-50℃ for 24-48 h to obtain a multi-layer composite substrate;

[0021] S4, the composite substrate is processed into a packaging product of a preset shape by a bag making machine, and an exhaust microchannel is designed at the heat-sealed edge of the bag body to obtain a microwave-heatable modified polypropylene composite packaging material.

[0022] Further preferably, the exhaust microchannel in S4 is composed of intermittent heat-sealing lines with a width of 1-2 mm.

[0023] The beneficial effects of the present application are as follows:

[0024] In the present application, the modified montmorillonite is treated with γ-aminopropyl triethoxysilane, and the hydrolysis product reacts with the hydroxyl groups on the surface of the montmorillonite to form covalent bonds, so that the surface of the montmorillonite is grafted with organic groups, and the compatibility of the montmorillonite with the polypropylene resin is significantly improved. The tea polyphenol increases the antibacterial rate of the composite film against Escherichia coli and Staphylococcus aureus, and the antibacterial effect is durable, significantly reducing the risk of deterioration of food caused by packaging pollution. At the same time, the oxygen transmission rate and the water vapor transmission rate of the composite film are reduced, which can effectively block oxygen and water vapor and prolong the shelf life of food. The tensile strength and impact strength of the composite film are improved, which can resist the impact of internal pressure when the microwave heating bag expands, avoid bag damage or edge tearing, and solve the problem of insufficient toughness of traditional materials.

[0025] In summary, the modified montmorillonite is modified by structure and chemically modified to optimize the thermal stability, antibacterial property, barrier property, and toughness of the composite packaging material, meet the harsh requirements of microwave heating packaging, and significantly improve the food safety and consumer experience. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0027] Embodiment 1: a preparation method of modified montmorillonite, comprising the following steps:

[0028] A1, 10 g of γ-aminopropyl triethoxysilane and 50 g of montmorillonite are added into a mixed solution of 700 mL of deionized water and anhydrous ethanol, and a turbid solution is obtained by reacting at 75 DEG C for 3 h;

[0029] A2, 10 g of tea polyphenol is added into the solution, stirred for 10 min, and reacted at 75 DEG C for 15 h;

[0030] A3, the reacted solution is cooled to room temperature, washed to neutral pH after centrifugation, and dried to obtain modified montmorillonite.

[0031] Embodiment 2: a microwave-heatable modified polypropylene composite packaging material, comprising the following weight parts of raw materials:

[0032] from outside to inside, a modified polypropylene barrier layer, a reinforcing connecting layer and a heat sealing layer, the reinforcing connecting layer is a nylon layer with a thickness of 25 μm, the heat sealing layer is a polypropylene heat sealing layer with a thickness of 40 μm, the modified polypropylene barrier layer comprises the following weight parts of raw materials: 90 parts of polypropylene resin, 5 parts of modified montmorillonite, 5 parts of ethylene-propylene-diene rubber, 6 parts of graphene, 2 parts of zinc stearate and 0.5 parts of antioxidant; the modified montmorillonite is tea polyphenol loaded montmorillonite prepared in embodiment 1, and the antioxidant is a compound of antioxidant 1010 and 168 with a mass ratio of 1:2.

[0033] The above preparation method comprises the following steps:

[0034] S1, polypropylene resin, modified montmorillonite, toughening agent, graphene, lubricant and antioxidant are added into a high-speed mixer and mixed at a speed of 1000 r / min for 10 min to obtain a mixture;

[0035] S2, the mixture is added into a double-screw extruder, melt blended, water-cooled and pelletized to obtain modified polypropylene pellets, and the modified polypropylene pellets are added into a single-screw extrusion casting machine and extruded and cast into a film at 210 DEG C to obtain a modified polypropylene barrier layer;

[0036] S3, the modified polypropylene barrier layer, the nylon reinforced connecting layer and the heat sealing layer are sequentially compounded by dry compounding process, polyurethane adhesive is used, the coating speed is 150 m / min, the pressure is 0.5 MPa, the drying temperature is 60 DEG C, and after compounding, the multilayer composite base material is obtained by curing at 50 DEG C for 24 h;

[0037] S4, the composite base material is processed into a packaging product with a preset shape by a bag making machine, and exhaust microchannels are designed at the heat sealing edges of the bag body, to obtain a microwave-heatable modified polypropylene composite packaging material.

[0038] Example 3: A microwave-heatable modified polypropylene composite packaging material, comprising the following weight parts of raw materials:

[0039] from outside to inside, a modified polypropylene barrier layer, a reinforced connecting layer and a heat sealing layer, the reinforced connecting layer is a nylon layer with a thickness of 20 microns, the heat sealing layer is a polypropylene heat sealing layer with a thickness of 50 microns, the modified polypropylene barrier layer comprises the following weight parts of raw materials: polypropylene resin 85 parts, modified montmorillonite 6 parts, ethylene-propylene rubber 4 parts, graphene 7 parts, paraffin 1 part, antioxidant 1 part; the modified montmorillonite is montmorillonite loaded with tea polyphenol prepared in Example 1, and the antioxidant is a compound of antioxidant 1010 and 168 with a mass ratio of 1:1.

[0040] The above preparation method comprises the following steps:

[0041] S1, polypropylene resin, modified montmorillonite, toughening agent, graphene, lubricant and antioxidant are added to a high-speed mixer and mixed at a speed of 900 r / min for 10 min to obtain a mixture;

[0042] S2, the mixture is added to a double-screw extruder, melt blended and then water-cooled and pelletized to obtain modified polypropylene pellets, and the modified polypropylene pellets are added to a single-screw extrusion casting machine and extruded and cast into a film at 200 DEG C to obtain a modified polypropylene barrier layer;

[0043] S3, the modified polypropylene barrier layer, the nylon reinforced connecting layer and the heat sealing layer are sequentially compounded by dry compounding process, polyurethane adhesive is used, the coating speed is 160 m / min, the pressure is 0.4 MPa, the drying temperature is 65 DEG C, and after compounding, the multilayer composite base material is obtained by curing at 45 DEG C for 30 h;

[0044] S4, the composite base material is processed into a packaging product with a preset shape by a bag making machine, and exhaust microchannels are designed at the heat sealing edges of the bag body, to obtain a microwave-heatable modified polypropylene composite packaging material.

[0045] Example 4: A microwave-heatable modified polypropylene composite packaging material, comprising the following weight parts of raw materials:

[0046] From outside to inside, it includes a modified polypropylene barrier layer, a reinforced connecting layer and a heat sealing layer, the reinforced connecting layer is a nylon layer with a thickness of 15 μm, the heat sealing layer is a polypropylene heat sealing layer with a thickness of 60 μm, the modified polypropylene barrier layer comprises the following raw materials in parts by weight: polypropylene resin 80 parts, modified montmorillonite 10 parts, butadiene rubber 3 parts, graphene 8 parts, polyethylene wax 0.3 parts, antioxidant 1.5 parts; the modified montmorillonite is montmorillonite loaded with tea polyphenol prepared in Example 1, and the antioxidant is a compound of antioxidants 1010 and 168 with a mass ratio of 1:2.

[0047] The preparation method described above comprises the following steps:

[0048] S1, polypropylene resin, modified montmorillonite, toughening agent, graphene, lubricant and antioxidant are added into a high-speed mixer and mixed at a speed of 800 r / min for 15 min to obtain a mixture;

[0049] S2, the mixture is added into a twin-screw extruder, melt blended, water-cooled and pelletized to obtain modified polypropylene pellets, and the modified polypropylene pellets are added into a single-screw extrusion casting machine and extruded and cast into a film at 190℃ to obtain a modified polypropylene barrier layer;

[0050] S3, the modified polypropylene barrier layer, the nylon reinforced connecting layer and the heat sealing layer are sequentially compounded by dry compounding process, polyurethane adhesive is used, the coating speed is 200 m / min, the pressure is 0.3 MPa, the drying temperature is 70℃, and after compounding, the compound is aged at 40℃ for 48 h to obtain a multi-layer composite substrate;

[0051] S4, the composite substrate is processed into a packaging product with a preset shape by a bag making machine, and an exhaust microchannel is designed at the heat sealing edge of the bag body to obtain a microwave-heatable modified polypropylene composite packaging material.

[0052] Comparative Example 1: A microwave-heatable modified polypropylene composite packaging material, the components and preparation are the same as those of Example 4, except that no modified montmorillonite is added.

[0053] Performance detection

[0054] The microwave-heatable modified polypropylene composite packaging materials prepared in Examples 2-4 and Comparative Example 1 are tested under different conditions, the tensile strength is tested according to GB / T528-2009, the dumbbell-shaped tensile sample is cut into 25mm×4mm, the antibacterial property is tested according to GB / T31402-2015, the square sample is cut from the composite packaging material, the water vapor transmission rate is tested according to GB / T1037-2001, and the square sample with a size of 108mm×108mm is selected for testing, and the data are shown in Table 1.

[0055] Table 1 Microwave-heatable modified polypropylene composite packaging material

[0056]

[0057] As can be seen from the data in Table 1, the microwave-heatable modified polypropylene composite packaging materials prepared in Examples 2-4 have excellent toughness, antibacterial property, barrier property and thermal stability. The tensile strength and antibacterial property of Comparative Example 1, which does not contain modified montmorillonite, are significantly lower than those of Examples 2-4, indicating that the montmorillonite modified by γ-aminopropyl triethoxysilane and tea polyphenol can disperse stress through nanosheet layers and inhibit molecular chain movement, thereby imparting excellent mechanical properties and thermal stability to the material. The antibacterial rate of Comparative Example 1 is much lower than that of Examples 2-4, and the water vapor transmission rate is high, indicating that the tea polyphenol loaded in the modified montmorillonite synergizes with the layered structure, and the effect of Example 3 is the best, which further indicates that the modified montmorillonite can enhance the antibacterial effect and improve the barrier property, thereby solving the problems of insufficient antibacterial property and poor barrier property of traditional materials.

[0058] In the description of the present specification, the description referring to the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0059] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only illustrative of the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A microwaveable modified polypropylene composite packaging material and a method for preparing the same, characterized in that, From outside to inside, the modified polypropylene barrier layer, the reinforced connecting layer and the heat sealing layer are sequentially included, the reinforced connecting layer is a nylon layer with a thickness of 15-25 μm, the heat sealing layer is a polypropylene heat sealing layer with a thickness of 40-60 μm, and the modified polypropylene barrier layer includes the following raw materials in parts by weight: polypropylene resin 80-90 parts, modified montmorillonite 5-10 parts, toughening agent 3-5 parts, graphene 6-8 parts, lubricant 0.3-2 parts, and antioxidant 0.5-1.5 parts. The modified montmorillonite is montmorillonite loaded with tea polyphenol.

2. The microwaveable modified polypropylene composite packaging material according to claim 1, characterized in that, The toughening agent is one or more of ternary ethylene-propylene rubber, binary ethylene-propylene rubber and cis-butadiene rubber.

3. The microwaveable modified polypropylene composite packaging material according to claim 1, characterized in that, The lubricant is one or more of zinc stearate, paraffin and polyethylene wax.

4. The microwaveable modified polypropylene composite packaging material according to claim 1, characterized in that, The antioxidant is a compound of antioxidant 1010 and 168 with a mass ratio of 1:2-1.

5. The microwaveable modified polypropylene composite packaging material according to claim 1, characterized in that, The preparation method of the modified montmorillonite includes the following steps: A1, γ-aminopropyl triethoxysilane and montmorillonite are added to a mixed solution of deionized water and anhydrous ethanol, and a turbid solution is obtained by reacting at 70-80 ℃ for 2-4 h; A2, tea polyphenol is added to the solution, stirred for 10-15 min, and reacted at 70-80 ℃ for 12-16 h; A3, the reacted solution is cooled to room temperature, washed to neutral pH after centrifugation, and dried to obtain the modified montmorillonite.

6. The microwaveable modified polypropylene composite packaging material according to claim 5, characterized in that, The mass ratio of γ-aminopropyl triethoxysilane, montmorillonite and tea polyphenol is 1:5:2-1.

7. A process for the preparation of a microwaveable modified polypropylene composite packaging material according to any one of claims 1 to 5, characterized in that, The following steps are included: S1, polypropylene resin, modified montmorillonite, toughening agent, graphene, lubricant and antioxidant are added to a high-speed mixer and mixed at a speed of 800-1000 r / min for 10-15 min to obtain a mixture; S2, the mixture is added to a twin-screw extruder, melt blended, water-cooled and pelletized to obtain modified polypropylene pellets, and the modified polypropylene pellets are added to a single-screw extrusion casting machine and extruded and cast into a film at 190-210 ℃ to obtain a modified polypropylene barrier layer; S3, the modified polypropylene barrier layer, the nylon reinforced connecting layer and the heat sealing layer are sequentially compounded by dry compounding process, polyurethane adhesive is used, the coating speed is 150-200 m / min, the pressure is 0.3-0.5 MPa, the drying temperature is 60-70 ℃, and the compounded material is aged at 40-50 ℃ for 24-48 h to obtain a multi-layer composite substrate; S4, the composite substrate is processed into a packaging product with a preset shape by a bag making machine, and an exhaust microchannel is designed at the heat sealing edge of the bag body to obtain a modified polypropylene composite packaging material that can be heated by microwave.

8. The microwaveable modified polypropylene composite packaging material according to claim 7, characterized in that, The exhaust microchannel in S4 is composed of intermittent heat sealing lines with a width of 1-2 mm.

Images