Bio-based packaging material with anti-oxidation effect and preparation method of bio-based packaging material

Abstract

The invention relates to the field of biodegradable high polymer materials, and discloses a bio-based packaging material with an anti-oxidation effect and a preparation method of the bio-based packaging material. 40 to 60 parts of polyhydroxyalkanoate; 10-20 parts of a composite antioxidant filler; the composite antioxidant filler is prepared by the following steps: (a) crushing sodium bentonite until the specific surface area is 45-55 m < 2 > / g and the particle size distribution D90 is less than or equal to 10 microns; (b) mixing bentonite powder and water according to the ratio of 1kg: 5L to form dispersion liquid with the solid content of 18%, and adding 0.3% sodium hexametaphosphate dispersing agent; (c) adding cerium nitrate; and (d) heating the product to 1050 DEG C at a speed of 8 DEG C / min, and calcining for 2 hours. Through the intercalation structure of the bentonite-based composite filler, an inorganic antioxidant component is organically combined with a bio-based polymer matrix, so that a breakthrough in long-acting oxidation resistance is realized in a completely biodegradable polylactic acid / polyhydroxyalkanoate system, and the technical bottleneck that traditional bioplastics are easy to oxidize and degrade is solved; and a sustainable solution is provided for green packaging materials.

Description

Technical Field

[0001] The present invention relates to the field of biodegradable polymer materials, in particular to a bio-based packaging material with antioxidant effect and a preparation method thereof. Background Art

[0002] With socioeconomic development and improved living standards, consumers are placing higher demands on the safety and shelf life of products such as food and medicine. The non-degradability of traditional petroleum-based plastic packaging is causing increasingly serious environmental pollution, making the development of biodegradable materials a global priority. Polylactic acid (PLA), a fully biodegradable, green material, demonstrates great potential in the packaging field due to its excellent processing properties and biocompatibility. However, PLA itself lacks antioxidant properties, making it difficult to effectively protect easily oxidized products (such as oily foods and active pharmaceutical ingredients). Functional modification is urgently needed to enhance its overall performance.

[0003] Currently, the mainstream approach to improving the functionality of PLA is to add antioxidant active ingredients to the matrix. However, most antioxidants are severely inactivated during high-temperature melt processing due to thermal decomposition or structural damage, resulting in the final material's actual antioxidant performance far below expectations. Although researchers have attempted to improve the thermal stability of antioxidants through coating and modification, their activity retention still cannot meet the long-term antioxidant protection requirements of high-value-added products.

[0004] During the high-temperature melting process of existing PLA-based antioxidant packaging materials, the antioxidant active ingredients undergo irreversible inactivation due to insufficient thermal stability, resulting in a significant decrease in the antioxidant performance of the material after processing, and the inability to achieve efficient and long-lasting antioxidant protection function. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a bio-based packaging material with antioxidant effect and a preparation method thereof, which solves the problem that the antioxidant active ingredients of existing biodegradable packaging materials are easily inactivated during high-temperature melting processing.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A bio-based packaging material with antioxidant effect, comprising:

[0007] 40-60 parts of polylactic acid;

[0008] 40-60 parts of polyhydroxyalkanoate;

[0009] 10-20 parts of composite antioxidant filler;

[0010] The composite antioxidant filler is prepared by the following steps:

[0011] (a) Grind the sodium bentonite to a specific surface area of 45 to 55 m 2 / g, particle size distribution D90≤10μm;

[0012] (b) Bentonite powder was mixed with water at a ratio of 1 kg:5 L to form a dispersion with a solid content of 18%, and 0.3% sodium hexametaphosphate dispersant was added;

[0013] (c) Add cerium nitrate to Ce 3+ Calculate 1.5% of the weight of bentonite, sodium carbonate, cerium salt molar ratio of 1.2:1, and dioctadecyl dimethyl ammonium chloride, add amount of 5%, react at 70 ° C for 3 hours;

[0014] (d) The product was heated to 1050° C. at a rate of 8° C. / min and calcined for 2 hours to obtain a composite material with an interlayer spacing of 1.5 to 1.8 nm and a CeO 2 loading of 15% to 18 wt %.

[0015] Preferably, the pulverization in step (a) is carried out using a jet mill with a pressure of 1.0 MPa and a cycle number of 3 times.

[0016] Preferably, in step (b), the dispersion is subjected to ultrasonic treatment at a power of 300-450 W, a frequency of 30-35 kHz, and a time of 20-30 minutes.

[0017] Preferably, the composite material obtained in step (d) has a specific surface area of 40m 2 / g, and the mesopore volume accounts for ≥80%.

[0018] Preferably, after melt processing at 180° C., the antioxidant activity retention rate is ≥92%, and the tensile strength is ≥25 MPa.

[0019] A method for preparing a bio-based packaging material with antioxidant effect comprises the following steps:

[0020] (S1) The composite antioxidant filler and the silane coupling agent KH-550 were mixed in a weight ratio of 1:0.07 and treated at 100°C under nitrogen for 45 minutes; (S2) PLA, PHA and the treated filler were added to a twin-screw extruder with an aspect ratio of 48:1, a rotation speed of 300 rpm, zone temperature control: zone 1 170°C, zone 2 190°C, zone 3 205°C, and a screw shear rate of 600s. -1 ;

[0021] (S3) After the melt is extruded through the die, it is cooled by liquid nitrogen spray at 80℃ / s to obtain a film with a thickness of 0.1mm

[0022] Preferably, in step (S1), the coupling agent is sprayed twice, with an interval of 15-20 minutes between each spraying.

[0023] Preferably, in step (S2), the melt pressure is ≤6 MPa, and the die temperature is 195-205°C.

[0024] Preferably, in step (S3), after cooling, the film is subjected to biaxial stretching treatment, with a longitudinal stretching ratio of 3:1, a transverse stretching ratio of 4:1, and a stretching temperature of 75-85°C.

[0025] The present invention provides a bio-based packaging material with antioxidant properties and a preparation method thereof. It has the following beneficial effects:

[0026] 1. The present invention organically combines inorganic antioxidant components with a bio-based polymer matrix through the intercalation structure of bentonite-based composite fillers, achieving a breakthrough in long-term antioxidant performance in a fully biodegradable polylactic acid / polyhydroxyalkanoate system, solving the technical bottleneck of easy oxidative degradation of traditional bioplastics and providing a sustainable solution for green packaging materials.

[0027] 2. The present invention introduces a dioctadecyl quaternary ammonium salt with a specific molecular structure as an intercalation modifier to construct a nanoscale active site distribution network between bentonite layers, thereby increasing the dispersion efficiency of antioxidant components and the exposure rate of active centers by orders of magnitude, forming an organic-inorganic synergistic antioxidant system and achieving a multiplier effect of antioxidant performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Flowchart of the present invention. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. 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 making creative efforts are within the scope of protection of the present invention.

[0030] The polylactic acid described in the following examples is the polylactic acid 4044D produced by NatureWorks, USA; the polyhydroxyalkanoate is the polyhydroxyalkanoate produced by Mirel, USA.

[0031] The remaining raw materials are all common raw materials that can be purchased by those skilled in the art.

[0032] Example 1:

[0033] Please see the attached Figure 1 The present invention provides a bio-based packaging material with antioxidant effect and a preparation method thereof, comprising:

[0034] Raw material composition by weight: 50 parts of polylactic acid; 50 parts of polyhydroxyalkanoate; 15 parts of antioxidant filler;

[0035] The antioxidant filler is prepared by the following method:

[0036] S1. Take bentonite and crush it to 300 mesh to obtain bentonite powder;

[0037] S2. The bentonite powder was added to water and stirred to obtain a bentonite powder dispersion; wherein the amount of bentonite powder and water ratio is 1kg: 5L;

[0038] S3 was added to the bentonite dispersion cerium sulfate and sodium carbonate, the reaction was stirred for 3h, and the solid product was separated by filtration; the amount of bentonite dispersion and cerium sulfate and sodium carbonate ratio of 1L: 22g: 6g;

[0039] S4. calcining the solid product at 1100° C. for 2 h to obtain a calcined product; taking the calcined product to obtain the antioxidant filler.

[0040] Preparation method: polylactic acid, polyhydroxyalkanoate and antioxidant filler are mixed evenly and then melt-extruded through a twin-screw machine to obtain the bio-based packaging material with antioxidant effect.

[0041] Example 2:

[0042] Raw material composition by weight: 60 parts of polylactic acid; 40 parts of polyhydroxyalkanoate; 20 parts of antioxidant filler;

[0043] The antioxidant filler is prepared by the following method:

[0044] S1. Take bentonite and crush it to 200 mesh to obtain bentonite powder;

[0045] S2. The bentonite powder was added to water and stirred to obtain a bentonite powder dispersion; wherein the amount of bentonite powder and water ratio is 1kg: 6L;

[0046] S3 was added to the bentonite dispersion cerium sulfate and sodium carbonate, the reaction was stirred for 2h, and the solid product was separated by filtration; the amount of bentonite dispersion and cerium sulfate and sodium carbonate ratio of 1L: 20g: 5g;

[0047] S4. calcining the solid product at 1100° C. for 1 hour to obtain a calcined product; taking the calcined product to obtain the antioxidant filler.

[0048] Preparation method: polylactic acid, polyhydroxyalkanoate and antioxidant filler are mixed evenly and then melt-extruded through a twin-screw machine to obtain the bio-based packaging material with antioxidant effect.

[0049] Example 3:

[0050] Raw material composition by weight: 40 parts of polylactic acid; 60 parts of polyhydroxyalkanoate; 10 parts of antioxidant filler;

[0051] The antioxidant filler is prepared by the following method:

[0052] S1. Take bentonite and crush it to 400 mesh to obtain bentonite powder;

[0053] S2. The bentonite powder was added to water and stirred to obtain a bentonite powder dispersion; wherein the amount of bentonite powder and water ratio is 1kg: 4L;

[0054] S3 was added to the bentonite dispersion cerium sulfate and sodium carbonate, the reaction was stirred for 4h, and the solid product was separated by filtration; the amount of bentonite dispersion and cerium sulfate and sodium carbonate ratio of 1L: 25g: 8g;

[0055] S4. calcining the solid product at 1100° C. for 3 h to obtain a calcined product; taking the calcined product to obtain the antioxidant filler.

[0056] Preparation method: polylactic acid, polyhydroxyalkanoate and antioxidant filler are mixed evenly and then melt-extruded through a twin-screw machine to obtain the bio-based packaging material with antioxidant effect.

[0057] Raw material composition by weight: 50 parts of polylactic acid; 50 parts of polyhydroxyalkanoate; 15 parts of antioxidant filler;

[0058] The antioxidant filler is prepared by the following method:

[0059] S1. Take bentonite and crush it to 300 mesh to obtain bentonite powder;

[0060] S2. The bentonite powder was added to water and stirred to obtain a bentonite powder dispersion; the amount of bentonite powder and water ratio of 1kg: 5L;

[0061] S3 was added to the bentonite dispersion cerium sulfate and sodium carbonate, followed by the addition of dioctadecyl dimethyl ammonium chloride, the reaction was stirred for 3h, and the solid product was separated by filtration; wherein the amount of bentonite dispersion and cerium sulfate, sodium carbonate and dioctadecyl dimethyl ammonium chloride ratio of 1L: 22g: 6g: 30g;

[0062] S4. calcining the solid product at 1100° C. for 2 h to obtain a calcined product; taking the calcined product to obtain the antioxidant filler.

[0063] Preparation method: polylactic acid, polyhydroxyalkanoate and antioxidant filler are mixed evenly and then melt-extruded through a twin-screw machine to obtain the bio-based packaging material with antioxidant effect.

[0064] Experimental Example 1: Comparative Analysis of Antioxidant Performance

[0065] Purpose of the test:

[0066] The scavenging ability of the materials in different examples on DPPH free radicals was verified, and the synergistic effect of quaternary ammonium salt modification was clarified.

[0067] Test method:

[0068] Sample preparation: 20 mg of each example material was taken, crushed, added into 100 mL of methanol, and ultrasonically extracted at 60° C. for 6 h (ultrasonic cleaner: Kunshan KQ-500DE, power 300 W, frequency 40 kHz).

[0069] Reaction system: 1 mL of the extract was mixed with 4 mL of DPPH methanol solution (100 μmol / L, Sigma-Aldrich D9132) and allowed to stand in the dark for 30 min.

[0070] Absorbance measurement: The absorbance at 517 nm was measured using a UV-Vis spectrophotometer (Shimadzu UV-2600) with pure methanol as the reference cell.

[0071] Clearance calculation:

[0072] (Each experiment was repeated 5 times, and the results are expressed as mean ± standard deviation). control is the absorbance of methanol solution; A sample is the absorbance value of methanol and membrane sample solution; the results are shown in Table 1;

[0073] Table 1. Antioxidant results of bio-based packaging materials

[0074]

[0075] As can be seen from the experimental results in Table 1, the free radical scavenging rate of the bio-based packaging material with antioxidant effect prepared in Example 1 reached 80.6%. This shows that adding the antioxidant filler prepared by the above-mentioned new method to the bio-based packaging material can make the bio-based packaging material have a good antioxidant effect.

[0076] The experimental results in Table 1 show that the antioxidant bio-based packaging material prepared in Example 2 achieved a free radical scavenging rate of 97.1%, demonstrating excellent antioxidant activity. Compared to the antioxidant bio-based packaging material prepared in Example 1, its antioxidant activity was significantly improved. This demonstrates that the antioxidant filler prepared by adding dioctadecyldimethylammonium chloride to a bentonite dispersion, cerium sulfate, and sodium carbonate significantly enhances the antioxidant activity of bio-based packaging materials compared to the antioxidant filler prepared without dioctadecyldimethylammonium chloride.

[0077] Comparative Example 1: PLA / PHA matrix material without antioxidant filler

[0078] Raw material composition (parts by weight):

[0079] 50 parts of polylactic acid (PLA)

[0080] 50 parts of polyhydroxyalkanoate (PHA)

[0081] No added antioxidant fillers

[0082] Preparation method:

[0083] PLA and PHA pellets were dried at 60 °C for 12 h;

[0084] The mixture was melt-blended at 180 °C using a twin-screw extruder (length-to-diameter ratio 40:1, screw speed 200 rpm);

[0085] The melt is hot pressed into a 0.10±0.02mm film at 180℃ and 10MPa pressure in a flat vulcanizer.

[0086] Experimental Example 2:

[0087] 1. Sample Preparation

[0088] The pellets of Examples 1, 2, 3, 4 and the comparative example (without antioxidant filler) were hot pressed into uniform films with a thickness of 0.10±0.02 mm at 180° C. and a pressure of 10 MPa using a flat-plate vulcanizer.

[0089] Use a circular cutter to cut test pieces with a diameter of 10 cm, and prepare 3 parallel samples for each group.

[0090] 2. Test equipment and conditions

[0091] Equipment: Labthink TOY-C1 oxygen permeability meter (valid calibration certificate number: 2023-OD-025)

[0092] Test standard: GB / T 1038-2000 (pressure difference method)

[0093] Environmental conditions: 23±0.5℃, RH50±5%

[0094] Carrier gas: high-purity nitrogen (purity ≥ 99.999%)

[0095] Test pressure gradient: 1atm (high-purity oxygen side) vs. normal pressure (nitrogen side)

[0096] 3. Operation process

[0097] ① Clamp the sample between the test chambers and apply vacuum silicone grease to the sealing ring to prevent air leakage;

[0098] ②Turn on nitrogen purge for 30 minutes to ensure that there is no residual oxygen in the test chamber;

[0099] ③ Start the test program and record the oxygen permeation rate within 24 hours;

[0100] ④ Each group of samples was tested 3 times and the arithmetic mean was taken.

[0101] 4. Data calculation

[0102] Oxygen Transmission Rate (OTR) calculation formula:

[0103]

[0104] in:

[0105] Q: Oxygen permeability (cm 3 )

[0106] d: film thickness (mm)

[0107] A: Test area (0.7854m 2 )

[0108] t: test time (24h)

[0109] Δp: oxygen partial pressure difference (1atm)

[0110] Table 2. Oxygen permeability test results of packaging materials in different examples

[0111]

[0112]

[0113] Data fluctuations in Example 1: The oxygen permeability is between 1.08 and 1.21, which is mainly caused by slight variations in film thickness (0.098 to 0.103 mm) and fluctuations in ambient humidity (49% to 52% RH), and is within the normal performance deviation range of the material.

[0114] Example 4 has an abnormally low value: After adding dioctadecyldimethylammonium chloride, the oxygen permeability is significantly reduced (0.89 to 1.02), but this component may lead to a decrease in mechanical properties (cross-validation is required in combination with the data of Experimental Example 3). Although the oxygen permeability is lower, its tensile strength drops to 18 MPa (see Experimental Example 3), and the overall performance is inferior to that of Example 1.

[0115] Comparative Example High oxygen permeability: The oxygen permeability of the base material without antioxidant filler is greater than 3.0, proving that the composite filler plays a decisive role in improving the barrier performance.

[0116] While 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 these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A bio-based packaging material with antioxidant effect, characterized in that: include: 40-60 parts of polylactic acid; 40-60 parts of polyhydroxyalkanoate; 10-20 parts of composite antioxidant filler; The composite antioxidant filler is prepared by the following steps: (a) Grind the sodium bentonite to a specific surface area of 45 to 55 m 2 / g, particle size distribution D90≤10μm; (b) Bentonite powder was mixed with water at a ratio of 1 kg:5 L to form a dispersion with a solid content of 18%, and 0.3% sodium hexametaphosphate dispersant was added; (c) Add cerium nitrate to Ce 3+ Calculate 1.5% of the weight of bentonite, sodium carbonate, 1.2:1 molar ratio of cerium salt, and dioctadecyldimethylammonium chloride, 5% addition amount, react at 70℃ for 3 hours; (d) The product was heated to 1050° C. at a rate of 8° C. / min and calcined for 2 hours to obtain a composite material with an interlayer spacing of 1.5 to 1.8 nm and a CeO 2 loading of 15% to 18 wt %.

2. The bio-based packaging material with antioxidant effect according to claim 1, characterized in that: The pulverization in step (a) is carried out using a jet mill with a pressure of 1.0 MPa and a cycle number of 3 times.

3. The bio-based packaging material with antioxidant effect according to claim 1, characterized in that: In step (b), the dispersion is subjected to ultrasonic treatment at a power of 300-450 W, a frequency of 30-35 kHz, and a time of 20-30 minutes.

4. The bio-based packaging material with antioxidant effect according to claim 1, characterized in that: The composite material obtained in step (d) has a specific surface area of 40m 2 / g, and the mesopore volume accounts for ≥80%.

5. The bio-based packaging material with antioxidant effect according to claim 1, characterized in that: After melt processing at 180℃, the antioxidant activity retention rate is ≥92% and the tensile strength is ≥25MPa.

6. A method for preparing a bio-based packaging material with antioxidant effect, according to the bio-based packaging material with antioxidant effect according to any one of claims 1 to 5, characterized in that: The following steps are involved: (S1) mixing the composite antioxidant filler and the silane coupling agent KH-550 in a weight ratio of 1:0.07, and treating at 100° C. under nitrogen protection for 45 minutes; (S2) PLA, PHA, and treated fillers were added to a twin-screw extruder with an aspect ratio of 48:1, a rotation speed of 300 rpm, zone temperature control: zone 1 170 °C, zone 2 190 °C, zone 3 205 °C, and a screw shear rate of 600 s -1 ; (S3) After the melt is extruded through the die, it is cooled by liquid nitrogen spray at 80°C / s to produce a film with a thickness of 0.1 mm.

7. The method for preparing a bio-based packaging material with antioxidant effect according to claim 6, characterized in that: In step (S1), the coupling agent is sprayed twice, with an interval of 15-20 minutes between each spraying.

8. The method for preparing a bio-based packaging material with antioxidant effect according to claim 6, characterized in that: In step (S2), the melt pressure is ≤6 MPa and the die temperature is 195-205°C.

9. The method for preparing a bio-based packaging material with antioxidant effect according to claim 6, characterized in that: After cooling in step (S3), the film is subjected to biaxial stretching treatment, with a longitudinal stretching ratio of 3:1, a transverse stretching ratio of 4:1, and a stretching temperature of 75-85°C.

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