Preparation method, product and application of polypropylene packaging material

Abstract

The invention provides a preparation method, a product and application of a polypropylene packaging material, and relates to the technical field of food packaging and fresh keeping. The technical scheme of preparing a component A and a component B step by step and then mixing and granulating comprises the following steps: mixing the component A MXD6, polypropylene (PP) and cobalt stearate at a high speed; the component B comprises PP, an antioxidant 1098 (the CAS number is 23128-74-7, the molecular formula is C40H64N2O4), cobalt stearate and a transition metal catalyst, and the PP, the antioxidant 1098, the cobalt stearate and the transition metal catalyst are subjected to twin-screw melt blending, extrusion, granulation, modification and drying; the high-concentration oxygen-absorbing master batch is blended with a main body PP (polypropylene), and the mixture is processed and formed by equipment such as a film blowing machine and the like. The material is good in component compatibility and free of layered precipitation, has the functions of passive barrier and active oxygen uptake, can prolong the shelf life of food sensitive to oxygen, is stable in process parameters and is suitable for large-scale industrial production. The packaging box is suitable for packaging food which is extremely sensitive to oxygen, such as liquid milk, fruit juice and edible oil.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of food packaging and preservation, and particularly relates to a preparation method of a polypropylene (PP) packaging material with active oxygen absorption and passive barrier functions, a product and application thereof. BACKGROUND

[0002] Polypropylene (PP) packaging materials are widely used in the field of food packaging due to their light weight, chemical corrosion resistance, excellent mechanical properties and low cost. The current mainstream PP packaging materials on the market are mainly divided into three categories: 1. Single-layer PP film, which is low in cost but poor in oxygen barrier performance, and is only suitable for short-term storage of food (such as bread and snacks); 2. PP composite film (such as PP / EVOH / PP), which improves the oxygen barrier property through the EVOH layer, but still belongs to "passive barrier" and cannot remove the initial residual oxygen inside the package; 3. PP packaging with added oxygen absorber, which usually uses the method of packaging the oxygen absorber pouch together with the food, which has the risk of oxygen absorber leakage and cannot be effectively integrated with the PP substrate, and is not suitable for liquid food packaging.

[0003] In the prior art, although some studies have attempted to blend MXD6 (m-xylylenediamine adipamide) with PP to impart oxygen absorption function, there are two major problems: first, the compatibility of MXD6 and PP is poor, and direct blending can easily cause delamination and precipitation, resulting in a decrease in the mechanical properties of the material; second, the process parameters are unstable, such as improper control of the mixing order of the components and drying conditions, which can result in low oxygen absorption efficiency and difficulty in meeting the needs of large-scale industrial production. Therefore, it is an urgent problem in the current food packaging field to develop a PP packaging material with good component compatibility, stable process, and both active oxygen absorption and passive barrier properties. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of a polypropylene packaging material, a product and application thereof, which solves the compatibility problem of MXD6 and PP by optimizing the component ratio and step-by-step preparation process, while ensuring process stability, realizing large-scale production, and providing long-term preservation packaging for foods that are extremely sensitive to oxygen.

[0005] In one aspect, the present application provides a preparation method of a polypropylene packaging material, comprising the following steps: S1: preparing component A: uniformly mixing MXD6, PP and a transition metal catalyst; S2: preparing component B: melt blending and modifying extrusion of PP, antioxidant 1098 and a transition metal catalyst, cooling and granulating, and drying for 3.5-4.5 hours; S3: mixing and granulation: melt blending, extruding, cooling, and granulating the A component obtained in step S1 and the dried B component obtained in step S2 to prepare a high-concentration oxygen-absorbing master batch; S4: processing and molding: directly blending the oxygen-absorbing master batch obtained in step S3 and the main packaging material PP, and then processing using a plastic processing device.

[0006] Further, the MXD6 in step S1 is 58-70 parts by mass, the PP is 6-15 parts by mass, and the transition metal catalyst is 2-4 parts by mass.

[0007] Further, the transition metal catalyst is cobalt stearate.

[0008] Further, the purity of the cobalt stearate is 99%.

[0009] Further, the mixing in step S1 refers to mixing for 4-6 min at a rotation speed of 450-550 r / min by a high-speed mixer.

[0010] Further, the mixing in step S1 refers to mixing for 5 min at a rotation speed of 500 r / min by a high-speed mixer.

[0011] Further, the relative molecular mass of the MXD6 in step S1 is 33,000, and the melting point is 240°C.

[0012] The above step S1 ensures the preliminary dispersion of MXD6 and PP by a specific rotation speed and time, and the cobalt stearate is premixed in advance to reduce the subsequent catalytic dead angle.

[0013] Further, the PP in step S2 is 58-70 parts by mass, the antioxidant is 1098 10-24 parts by mass, and the transition metal catalyst is 4-6 parts by mass.

[0014] Further, the transition metal catalyst is cobalt stearate.

[0015] Further, the purity of the cobalt stearate is 99%.

[0016] Further, the CAS number of the antioxidant 1098 in step S2 is 23128-74-7, and the molecular formula is C 40 H 64 N2O4.

[0017] Further, the melt blending and modified extrusion in step S2 refer to blending using a double screw extruder, setting the screw rotation speed at 550-570 r / min and the extrusion temperature at 190-210 DEG C; the cooling temperature is 60-65 DEG C; the drying time is 3.5-4 hours and the temperature is 55-65 DEG C.

[0018] Further, the melt blending and modified extrusion in step S2 refer to blending using a double screw extruder, setting the screw rotation speed at 560 r / min and the extrusion temperature at 200 DEG C; the cooling temperature is 60 DEG C; the drying time is 4 hours and the temperature is 60 DEG C.

[0019] Further, in step S3, the melt blending refers to blending by a double screw extruder at a screw rotation speed of 550-570 r / min, and the extrusion temperature is 195-205 DEG C; the cooling refers to cooling to a temperature of 55-65 DEG C.

[0020] Further, in step S3, the screw rotation speed of the double screw extruder is 560 r / min, and the extrusion temperature is 200 DEG C; the cooling is cooling to a temperature of 60 DEG C.

[0021] Further, in step S4, the plastic processing equipment includes a film blowing machine, a casting machine and an injection molding machine.

[0022] In another aspect, the application provides a polypropylene packaging material prepared according to the above method.

[0023] In still another aspect, the application provides a use of the polypropylene packaging material, which is used for packaging of oxygen extremely sensitive food. The oxygen extremely sensitive food refers to food whose shelf life is shortened by more than 50% when the oxygen concentration in the package exceeds 0.1 vol% at 25 DEG C. The food includes but is not limited to liquid food such as liquid milk, fruit juice and plant protein beverage; oil and fat food such as edible oil, nuts and high-fat snacks; and easily oxidized food such as cooked meat products and baked food.

[0024] Compared with the prior art, the application has the following technical effects: By selecting specific proportions of MXD6, PP, antioxidant 1098 and cobalt stearate and using a specific process of preparing two components A and B in steps and then melt blending, the dispersion state of each functional component is precisely controlled to make each component stable and compatible. The prepared polypropylene packaging material has high oxygen absorption rate, stable mechanical properties, no delamination or precipitation, and can significantly prolong the shelf life of food; and the process parameter range is wide and suitable for industrial production. DETAILED DESCRIPTION

[0025] The following examples are used to explain the present application and do not limit the scope of protection of the present application. Any equivalent embodiments or changes made by those skilled in the art without departing from the technical spirit of the present application shall fall within the scope of protection of the present application.

[0026] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with examples.

[0027] Example 1 1, Preparation of A component: take MXD6 70 parts, PP 15 parts, cobalt stearate 4 parts by weight, put into a high-speed mixer, mix at 500 r / min for 5 min; 2, Preparation of B component: take PP 70 parts, antioxidant 1098 24 parts, cobalt stearate 6 parts by weight, put into a twin-screw extruder (560 r / min, 200°C) for melt extrusion; cool to 60°C and cut into particles, dry at 60°C for 4 hours; 3, Mixing and granulation: physically mix A component and B component at a ratio of 1:1, put into a twin-screw extruder (560 r / min, 200°C) for extrusion, cooling and granulation, to obtain oxygen-absorbing masterbatch; 4, Molding: blend the oxygen-absorbing masterbatch with the main body PP at a ratio of 1:8, and blow into a film with a thickness of 50 μm using a film blowing machine.

[0028] Example 2 1, Preparation of A component: take MXD6 58 parts, PP 6 parts, cobalt stearate 2 parts by weight, put into a high-speed mixer, mix at 500 r / min for 5 min; 2, Preparation of B component: take PP 58 parts, antioxidant 1098 10 parts, cobalt stearate 4 parts by weight, put into a twin-screw extruder (560 r / min, 200°C) for melt extrusion; cool to 60°C and cut into particles, dry at 60°C for 4 hours; 3, Mixing and granulation: physically mix A component and B component at a ratio of 1:1, put into a twin-screw extruder (560 r / min, 200°C) for extrusion, cooling and granulation, to obtain oxygen-absorbing masterbatch; 4, Molding: blend the oxygen-absorbing masterbatch with the main body PP at a ratio of 1:8, and blow into a film with a thickness of 50 μm using a film blowing machine.

[0029] Comparative Example 1 1, Direct mixing: take MXD6 70 parts, PP 85 parts, cobalt stearate 10 parts, antioxidant 1098 24 parts by weight, put into a high-speed mixer and mix for 5 min; 2. Extrusion granulation: the mixture was put into a twin-screw extruder (560 r / min, 200°C) for extrusion, cooling and granulation to obtain an oxygen-absorbing master batch; 3. Molding: same as Example 1, to prepare a 50 μm film.

[0030] Comparative Example 2: 1. Preparation of Component A: same as Example 1; 2. Preparation of Component B: same as Example 1, but no drying after granulation; 3. Mixing, granulation and molding: same as Example 1, to prepare a 50 μm film.

[0031] Determination of oxygen absorption rate: 1. Sample preparation: the polypropylene films prepared in Example 1, Comparative Examples 1 and 2 and a commercially available ordinary blister packaging (Oxynex®, Japan Daisel) were cut into rectangular samples of 20 cm x 15 cm, and 3 samples were prepared in parallel in each group to ensure no damage or creases. The films were heat-sealed on three sides using a heat sealer (temperature 180°C, pressure 0.3 MPa, time 2 s) to form an open bag (volume about 300 mL); 200 mL of oxygen-nitrogen gas mixture with an initial oxygen content of 9.50 ppm was injected into the bag, and the open end was immediately heat-sealed and immersed in water to vacuum to -0.05 MPa, and no bubbles for 30 s were considered as a qualified seal.

[0032] 2. Instruments and reagents 2.1 Detection instrument: headspace gas chromatograph with thermal conductivity detector (TCD) (with 5Å molecular sieve column), 1 mL headspace sampling needle with sealing gasket, heat sealer, constant temperature and humidity chamber.

[0033] 2.2 Standard gas: oxygen-nitrogen mixed standard gas with oxygen concentration of 1 ppm, 5 ppm, 10 ppm and 20 ppm (purity ≥ 99.999%).

[0034] 3. Test conditions 3.1 Sample storage: the sealed bags were stored in a constant temperature and humidity chamber at a temperature of 25±1°C and a relative humidity of 50±2%, avoiding light.

[0035] 3.2 Chromatographic parameters: high-purity nitrogen gas as carrier gas (flow rate 30 mL / min), column temperature 40°C, injection port 150°C (injection volume 0.5 mL, split ratio 10:1), detector 200°C.

[0036] 4. Test procedure 4.1 Calibration curve drawing: 4 kinds of standard gas were injected for detection, and the oxygen peak area was recorded; the oxygen concentration (ppm) was taken as the abscissa, and the peak area was taken as the ordinate, and the calibration curve was fitted.

[0037] 4.2 Sample detection: 0.5 mL was sampled from the sealed bag by penetrating it with a sample needle at the 1st, 2nd, 3rd, 5th, 7th, 8th, 10th day of storage (the penetration site was sealed with silicone rubber), and the sample was detected by injection; the oxygen concentration (ppm) was calculated according to the calibration curve.

[0038] 4.3 Data recording: the average value of 3 parallel samples in each group was taken, and the results are shown in Table 1.

[0039] Table 1: Comparison of oxygen content of polypropylene packaging Unit: ppm

[0040] As can be seen from Table 1, the oxygen content of the ordinary blister packaging in the market slightly increases instead, indicating that the ordinary packaging in the market does not have the function of actively absorbing oxygen. In Example 1 of the present application, the oxygen content continuously and stably decreases from 9.50 ppm at the 1st day to 9.02 ppm at the 10th day. This shows that the oxygen-absorbing component in the material prepared in Example 1 of the present application is successfully activated and continuously functions, which can effectively remove the oxygen in the packaging and realize the active preservation function of food. The smooth decrease in data also proves the stability of the process and the good compatibility of the components. In Comparative Example 1, the oxygen content of the packaging material prepared by directly mixing all the raw materials hardly changes at all, and remains at a high level of 9.45-9.50 ppm throughout. This proves that the step-by-step preparation process is crucial. Direct mixing may cause problems such as poor compatibility of MXD6 with PP and uneven dispersion of the oxygen-absorbing catalyst, so that the oxygen-absorbing reaction cannot effectively proceed, and the material has almost no active oxygen-absorbing function. In Comparative Example 2, the oxygen content of the packaging material prepared without drying the B component slightly decreases (from 9.50 ppm to 9.39 ppm), but the oxygen-absorbing speed and efficiency are much lower than those of Example 1. This highlights the key role of the drying step of the B component. Moisture may poison the activity of the transition metal catalyst (cobalt stearate) or interfere with the oxygen-absorbing chemical reaction. The lack of a drying step will seriously reduce the oxygen-absorbing performance of the material.

Claims

1. A process for the production of a polypropylene packaging material, characterized in that, The method comprises the following steps: S1: preparing component A: uniformly mixing MXD6, PP and transition metal catalyst; S2: preparing component B: melt blending and modifying extrusion of PP, antioxidant 1098 and transition metal catalyst, cooling and granulating, and drying for 3.5-4.5 hours; S3: mixing and granulating: melt blending, extruding, cooling and granulating the component A obtained in step S1 and the dried component B obtained in step S2 to prepare high-concentration oxygen-absorbing masterbatch; S4: processing and molding: directly blending the oxygen-absorbing masterbatch obtained in step S3 with the main packaging material PP, and then processing by using a plastic processing equipment.

2. The method of claim 1, wherein, In step S1, the MXD6 is 58-70 parts by mass, the PP is 6-15 parts by mass, and the transition metal catalyst is 2-4 parts by mass.

3. The method of claim 2, wherein, The transition metal catalyst is cobalt stearate.

4. The method of claim 1, wherein, In step S1, the mixing is performed by a high-speed mixer at a rotation speed of 450-550 r / min for 4-6 min.

5. The method of claim 1, wherein, In step S2, the PP is 58-70 parts by mass, the antioxidant 1098 is 10-24 parts by mass, and the transition metal catalyst is 4-6 parts by mass; the transition metal catalyst is cobalt stearate.

6. The method of claim 1, wherein, The CAS number of the antioxidant 1098 in step S2 is 23128-74-7, and the molecular formula is C 40 H 64 N2O4; the melt blending and modification extrusion refers to using a double screw extruder, setting the screw rotation speed to 550~570r / min, the extrusion temperature to 190~210℃ for blending; the cooling temperature is 60~65℃; the drying temperature is 55~65℃.

7. The method of any one of claims 1, wherein, In step S3, the melt blending is performed by a double-screw extruder at a screw rotation speed of 550-570 r / min, and the extruding temperature is 195-205℃; the cooling is performed by reducing the temperature to 55-65℃.

8. The method of claim 1, wherein, In step S4, the plastic processing equipment includes a film blowing machine, a casting machine and an injection molding machine.

9. A polypropylene packaging material, characterized in that The method is prepared according to any one of claims 1-8.

10. Use of a polypropylene packaging material, characterized in that The packaging material of claim 9 is used for packaging oxygen-sensitive food.

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