A natural polyphenol antioxidant intercalated mica, and a preparation method and application thereof

Abstract

The application discloses natural polyphenol antioxidant intercalation modified mica and a preparation method and application thereof. The preparation method comprises the following steps: (1) placing mica in a reaction container, cooling to room temperature after calcination, and obtaining heat-activated mica; (2) adding the heat-activated mica into a nitric acid solution for reflux stirring, naturally cooling to room temperature, filtering, washing, and drying to obtain acidified mica; (3) adding the acidified mica into saturated brine for reflux stirring, standing, filtering, washing, and drying to obtain sodiumized mica; and (4) adding the sodiumized mica into a natural polyphenol antioxidant solution, adjusting the system to be weakly acidic, ultrasonically treating at 60-65 DEG C for 3-4 h, cooling to room temperature, standing, filtering, and washing to obtain natural polyphenol antioxidant intercalation modified mica. The natural polyphenol antioxidant is bonded to the mica by physical / chemical means through the intercalation modification method, and a multifunctional organic-inorganic material with antioxidant, preservative, fresh-keeping and migration resistance is developed.

Description

Technical Field

[0001] The present invention relates to the technical field of food packaging material antioxidants, and in particular to natural polyphenol antioxidant intercalated modified mica, a preparation method thereof, and applications thereof. Background Art

[0002] Food oxidation and spoilage are the primary cause of food quality degradation. Traditionally, antioxidants or preservatives have been added directly to food to prevent oxidation. However, as public awareness of food safety grows, this approach is increasingly resisted by consumers. However, food antioxidant packaging, which pre-adds antioxidants to packaging materials, removes oxygen, free radicals, or metal ions that may be present between the packaging and the food, thereby protecting food quality and extending its shelf life. This has become an emerging food packaging and preservation method.

[0003] Traditional synthetic phenolic antioxidants offer excellent efficacy, simple production methods, and low cost. However, the migration of their byproducts and impurities poses potential environmental and human health risks. Consequently, a growing number of researchers have begun researching natural antioxidants. For example, a paper (J. Appl. Polym. Sci. 2020, 137, 48: e49599) reports that puerarin can be used as a highly effective natural stabilizer for polyethylene and polypropylene. A paper (J. Therm. Anal. Calorim. 2020, 164: 1657-1665) reports that an antioxidant (AOB) extracted from bamboo leaves improves the thermal, oxidative, and processing stability of polypropylene, achieving efficacy comparable to the commercially available Irganox 1010. However, the limited availability of antioxidants fails to meet the demands of existing technologies. Summary of the Invention

[0004] The present invention provides a natural polyphenol antioxidant intercalated modified mica, as well as its preparation method and application. This natural polyphenol antioxidant intercalated modified mica possesses antioxidant, antiseptic, and fresh-keeping properties. When added as an additive to packaging materials, it not only improves the processing stability, thermal stability, and thermo-oxidative stability of polyolefins, but more importantly, it removes oxygen, free radical oxidants, or metal ions between food and packaging bags, extending the shelf life of food and improving the antioxidant durability of polyolefin packaging materials.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing natural polyphenol antioxidant intercalated modified mica comprises the following steps:

[0007] (1) placing mica in a reaction vessel, calcining it and then naturally cooling it to room temperature to obtain heat-activated mica;

[0008] (2) adding the heat-activated mica to the nitric acid solution, maintaining the solid-liquid ratio of the heat-activated mica to the nitric acid solution at 3%-5%, reflux stirring at 90°C-110°C for 1.5-2.5 hours, naturally cooling to room temperature, filtering, washing to neutrality, and drying to obtain acidified mica;

[0009] (3) Add the acidified mica to saturated salt water, keeping the solid-liquid ratio of the acidified mica to the saturated salt water at 3%-5%, reflux and stir at 90°C-110°C for 2.5-3.5 hours, let it stand overnight, filter, and wash to remove Cl - , dried to obtain sodium mica;

[0010] (4) Adding sodium-modified mica to a natural polyphenol antioxidant solution to adjust the system to weak acidity, wherein the natural polyphenol antioxidant is selected from one or more of phytic acid, curcumin and quercetin, and maintaining the ratio of the amount of sodium-modified mica to the amount of natural polyphenol antioxidant at 1:20-30, ultrasonically treating at 60°C-65°C for 3-4 hours, cooling to room temperature and standing overnight, filtering, and washing with pure water to obtain natural polyphenol antioxidant intercalated modified mica.

[0011] During the ultrasonic heating and mixing process of the natural polyphenol antioxidant and the sodium-treated mica, the natural polyphenol antioxidant is adsorbed and bonded in the mica layer through physical or chemical action under the physical action of ultrasound, thereby realizing intercalation and exfoliation modification of the mica.

[0012] The mica is white sericite with monoclinic crystals and a flaky structure. The average particle size of the mica powder is about 10 microns.

[0013] Phytic acid (Formula 1), a natural compound derived from seeds and fruits, has antioxidant activity and the ability to inhibit reactive hydrogen peroxide. Adding phytic acid to either PE or PP improves the polyolefin's UV stability and reduces degradation.

[0014]

[0015] Formula 1

[0016] Curcumin (as shown in Formula 2), a polyphenol compound derived from the rhizome of turmeric, has good antioxidant activity and can scavenge free radicals and hydrogen peroxide. It also has metal chelating activity. When added to PE, it can improve the thermal and oxidative stability and processing stability of polyethylene.

[0017]

[0018] Formula 2

[0019] Quercetin (shown in Formula 3), a flavonoid compound, is widely found in fruits, leaves, vegetables, and fruits. It has antioxidant, antibacterial, and anti-inflammatory properties. When added to PE, quercetin exhibits an antioxidant effect greater than 1010 at the same dosage.

[0020]

[0021] Formula 3

[0022] Preferably, the calcination conditions in step (1) are calcination at 650°C-750°C and keeping the temperature for 1.5-2.5 h.

[0023] Preferably, step (2) specifically comprises the following steps: adding the heat-activated mica to a 5 mol / L HNO3 solution, maintaining the solid-liquid ratio of the heat-activated mica to the nitric acid solution at 4%, reflux stirring at 100°C for 2 h, naturally cooling to room temperature, filtering, washing with pure water until neutral, and drying in a forced air drying oven at 100°C to obtain the acidified mica.

[0024] Preferably, step (3) comprises the following steps: adding the acidified mica to saturated saline solution, maintaining the solid-liquid ratio of the acidified mica to the saturated saline solution at 4%, stirring under reflux at 100°C for 3 h, standing overnight, filtering, and washing with pure water to remove Cl - , and dried to obtain sodium mica. Use 0.1 mol / L AgNO3 solution to check whether there is Cl in the filtrate. - exist.

[0025] Preferably, the solvent used in the preparation of the natural polyphenol antioxidant solution in step (4) is one of water, ethanol or sodium hydroxide aqueous solution, and the weakly acidic pH of the system is adjusted to 5.

[0026] Preferably, the natural polyphenol antioxidant is a mixture of phytic acid and quercetin or curcumin and quercetin. The molar ratio of phytic acid to quercetin in the mixture of phytic acid and quercetin is 1:1, and the molar ratio of curcumin to quercetin in the mixture of curcumin and quercetin is 1:1.

[0027] The present invention also protects the natural polyphenol antioxidant intercalation modified mica obtained by the preparation method.

[0028] Another object of the present invention is to protect the natural polyphenol antioxidant intercalated modified mica and use it as an inorganic additive in food packaging materials for antioxidant preservation.

[0029] The present invention selects non-toxic, harmless natural polyphenol antioxidants, bonds them to mica with antiseptic and fresh-keeping functions through physical / chemical reactions, and adds the resulting product as a food packaging material additive to polyolefin resin. This not only improves the processing and molding stability, thermal stability, and thermo-oxidative stability of the packaging material, but more importantly, provides a long shelf life for food, improves the durability of the polyolefin packaging material's antioxidant properties, and is harmless to human health.

[0030] Preferably, the natural polyphenol antioxidant intercalated modified mica is added to a polyolefin matrix resin to prepare a food packaging material. The polyolefin matrix resin includes polyethylene and polypropylene.

[0031] More preferably, the amount of the natural polyphenol antioxidant intercalated modified mica added is 0.4 wt % to 0.6 wt % of the polyolefin matrix resin.

[0032] Compared with existing technologies, the present invention offers the following advantages: the natural polyphenol antioxidant intercalated modified mica possesses both antioxidant, antiseptic, and fresh-keeping properties. When added as an additive to food packaging materials, it not only improves the processing stability, thermal stability, and thermo-oxidative stability of polyolefins, but more importantly, it removes oxygen, free radical oxidants, and metal ions between the food and the packaging bag, extending the shelf life of the food and improving the antioxidant durability of the polyolefin packaging material. Traditional organic compound antioxidants, on the other hand, can leach and migrate from food during use, potentially posing a health hazard to humans. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 These are the XRD spectra of unmodified pure mica and mica modified by heat activation, acidification, sodiumization, and phytic acid intercalation. DETAILED DESCRIPTION

[0034] The present invention will be described in further detail below with reference to the examples. These examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. Experimental methods in the following examples, where specific conditions are not specified, generally follow conventional conditions in the art or conditions recommended by the manufacturer; raw materials and reagents used, unless otherwise specified, are considered to be commercially available through conventional markets.

[0035] Example 1

[0036] A method for preparing natural polyphenol antioxidant intercalated modified mica comprises the following steps:

[0037] (1) Thermal activation of mica: 20 g of sericite raw material was placed in an alumina crucible, heated to 700°C in a resistance furnace, and calcined for 2 h. The heating rate was set as follows: 5°C / min at 200°C; 10°C / min from 200°C to 700°C; and then held at 700°C for 2 h. The product was then naturally cooled to room temperature to obtain thermally activated sericite M1.

[0038] (2) Acidification of mica: Prepare 5 mol / L nitric acid solution, the solid-liquid ratio of thermally activated sericite M1 to HNO3 solution is 4%, add M1 into a round-bottom flask containing 5 mol / L HNO3 solution, reflux at 100°C for 2 h, cool naturally to room temperature, filter, wash with pure water until neutral, and dry the sample at 100°C to obtain acidified sericite M2.

[0039] (3) Sodiumization of mica: Prepare saturated NaCl solution with a solid-liquid ratio of 4% for sericite and saturated NaCl solution. Add M2 into a round-bottom flask containing saturated NaCl solution, reflux and stir at 100 °C for 3 h, let it stand overnight, filter, and wash with pure water to remove Cl. - (Use 0.1 mol / L AgNO3 solution to check the filtrate until there is no Cl - The sodium mica was obtained by drying at 100 °C.

[0040] (4) Natural antioxidant intercalation modified mica: Sodium mica was added to a phytic acid aqueous solution, the system was adjusted to a weakly acidic pH of 5, the ratio of sodium mica to phytic acid was maintained at 1:25, ultrasonicated at 62 °C for 4 h, cooled to room temperature and allowed to stand overnight, filtered, and washed with pure water to obtain phytic acid intercalation modified mica S-1. Figure 1 The figure shows that new diffraction peaks appear near 3.6nm and 1.5nm on the mica {002} crystal plane, indicating that the spacing between mica sheets is increased and phytic acid is effectively intercalated into the mica sheets.

[0041] Example 2

[0042] Example 2 provides a natural polyphenol antioxidant intercalated modified mica, which differs from Example 1 in that the natural antioxidant is an ethanol solution of curcumin, and curcumin intercalated modified mica S-2 is obtained.

[0043] Example 3

[0044] Example 3 provides a natural polyphenol antioxidant intercalated modified mica, which differs from Example 1 in that the natural antioxidant is a sodium hydroxide alkaline aqueous solution of quercetin, to obtain quercetin intercalated modified mica S-3.

[0045] Example 4

[0046] Example 4 provides preparation of a multifunctional antioxidant PE film, which differs from Example 1 in that the natural antioxidant is selected as a sodium hydroxide alkaline aqueous solution of a curcumin and quercetin blend, wherein the molar ratio of curcumin to quercetin is 1:1, to obtain curcumin / quercetin complex intercalation modified mica S-4.

[0047] Example 5

[0048] Example 5 provides preparation of a multifunctional antioxidant PE film, which differs from Example 1 in that the natural antioxidant is selected as a sodium hydroxide alkaline aqueous solution of a curcumin and quercetin blend, wherein the molar ratio of curcumin to quercetin is 1:1, to obtain curcumin / quercetin complex intercalation modified mica S-4.

[0049] Example 5 provides preparation of a multifunctional antioxidant PE film, which differs from Example 1 in that the natural antioxidant is selected as a sodium hydroxide alkaline aqueous solution of a curcumin and quercetin blend, wherein the molar ratio of curcumin to quercetin is 1:1, to obtain curcumin / quercetin complex intercalation modified mica S-4.

[0050] Example 6

[0051] Example 5 provides preparation of a multifunctional antioxidant PE film, which differs from Example 1 in that the natural antioxidant is selected as a sodium hydroxide alkaline aqueous solution of a curcumin and quercetin blend, wherein the molar ratio of curcumin to quercetin is 1:1, to obtain curcumin / quercetin complex intercalation modified mica S-4.

[0052] Example 7

[0053] Example 5 provides preparation of a multifunctional antioxidant PE film, which differs from Example 1 in that the natural antioxidant is selected as a sodium hydroxide alkaline aqueous solution of a curcumin and quercetin blend, wherein the molar ratio of curcumin to quercetin is 1:1, to obtain curcumin / quercetin complex intercalation modified mica S-4.

[0054] Example 8

[0055] Example 5 provides preparation of a multifunctional antioxidant PE film, which differs from Example 1 in that the natural antioxidant is selected as a sodium hydroxide alkaline aqueous solution of a curcumin and quercetin blend, wherein the molar ratio of curcumin to quercetin is 1:1, to obtain curcumin / quercetin complex intercalation modified mica S-4.

[0056] Example 9

[0057] Example 5 provides preparation of a multifunctional antioxidant PE film, which differs from Example 1 in that the natural antioxidant is selected as a sodium hydroxide alkaline aqueous solution of a curcumin and quercetin blend, wherein the molar ratio of curcumin to quercetin is 1:1, to obtain curcumin / quercetin complex intercalation modified mica S-4.

[0058] Example 10

[0059] Example 5 provides preparation of a multifunctional antioxidant PE film, which differs from Example 1 in that the natural antioxidant is selected as a sodium hydroxide alkaline aqueous solution of a curcumin and quercetin blend, wherein the molar ratio of curcumin to quercetin is 1:1, to obtain curcumin / quercetin complex intercalation modified mica S-4.

[0060] Example 11

[0061] Example 5 provides preparation of a multifunctional antioxidant PE film, which differs from Example 1 in that the natural antioxidant is selected as a sodium hydroxide alkaline aqueous solution of a curcumin and quercetin blend, wherein the molar ratio of curcumin to quercetin is 1:1, to obtain curcumin / quercetin complex intercalation modified mica S-4.

[0062] Comparative Example 1

[0063] 0.5% hindered phenol antioxidant 1076 was added in PE, cast film was made and tested.

[0064] Comparative Example 2

[0065] 0.5% unmodified mica powder was added in PE, cast film was made and tested.

[0066] Example 12

[0067] 0.5% phytic acid intercalated modified mica S-1 was added in PE, melt co-extruded 5 times by twin screw extruder and mechanical property test was conducted.

[0068] Example 13

[0069] 0.5% curcumin intercalated modified mica S-2 was added in PE, melt co-extruded 5 times by twin screw extruder and mechanical property test was conducted.

[0070] Example 14

[0071] 0.5% quercetin intercalated modified mica S-3 was added in PE, melt co-extruded 5 times by twin screw extruder and mechanical property test was conducted.

[0072] Example 15

[0073] 0.5% curcumin / quercetin complex intercalated modified mica S-4 was added in PE, melt co-extruded 5 times by twin screw extruder and mechanical property test was conducted.

[0074] Example 16

[0075] 0.5% phytic acid / quercetin complex intercalated modified mica S-5 was added in PE, melt co-extruded 5 times by twin screw extruder and mechanical property test was conducted.

[0076] Comparative Example 3

[0077] 0.5% hindered phenol antioxidant 1076 was added in PE, melt co-extruded 5 times by twin screw extruder and mechanical property test was conducted.

[0078] Comparative Example 4

[0079] 0.5% unmodified mica powder was added in PE, melt co-extruded 5 times by twin screw extruder and mechanical property test was conducted.

[0080] Oxidation induction time determination

[0081] The test was conducted on a DSC thermal analysis instrument. O2 and N2 were connected, and the gas switching device was turned on to adjust the flow rates of both gases to (50±5) ml / min. The gas flow rate was then switched to N2. A disc with a diameter slightly smaller than the inner diameter of an aluminum crucible was cut from the modified polyethylene film sample using a hole punch and placed flat inside the crucible. The empty crucible and the sample crucible were then placed in the reference and sample furnaces of the sample cell, respectively. N2 was passed through the sample chamber for 25 minutes before heating. The polyethylene sample was heated to 200°C at a rate of 20°C / min and held at that temperature for 5 minutes. After the hold time expired, the flow rate was immediately switched to O2 at a rate of (50±5) ml / min, with the switching point designated as the test zero. The test was terminated when the oxidation exotherm reached its maximum value as recorded on the thermal curve.

[0082] Mechanical properties testing

[0083] The mechanical properties of the samples were characterized by tensile testing. The tensile tests were performed on a 20 kN sensor at a speed of 50 mm / min.

[0084] Test results:

[0085] Table 1 Test results of oxidation induction time of PE samples with different additives

[0086] sample Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Comparative Example 1 Comparative Example 2 Oxidation induction period (min) 30 30 28 36 37 32 13.35 10

[0087] Table 2 Mechanical properties test results of PE samples with different additives

[0088] sample Example 12 Example 13 Example 14 Example 15 Example 16 Comparative Example 3 Comparative Example 4 Retention rate of elongation at break after 5 extrusions (%) 92% 93% 91% 95% 96% 78% 64%

[0089] The test results in Tables 1 and 2 show that, in Examples 6-8, the addition of the prepared natural polyphenol antioxidant intercalated modified mica to PE resulted in significantly longer oxidative induction times than those obtained with the commercially available antioxidant 1076 and mica powder. In Examples 9-10, the addition of a multifunctional natural polyphenol antioxidant intercalated modified mica to PE resulted in an approximately 20% increase in oxidative induction time compared to that of Examples 6-8, and a 12% increase compared to the simple physical blending of curcumin-intercalated modified mica S-2 and quercetin-intercalated modified mica S-3 in PE resin in Example 11. This demonstrates that the intermolecular synergy between the two natural antioxidants produces an antioxidant effect greater than 1+1. In Examples 12-16, the elongation at break of the modified PE remained essentially unchanged after five melt coextrusion cycles, while the elongation at break of the PE with the addition of 1076 and mica powder decreased significantly.

[0090] This invention utilizes an intercalation modification method to physically and chemically bond one or more natural polyphenol antioxidants to mica, creating a multifunctional organic-inorganic material with antioxidant, anti-corrosion, freshness-preserving, and migration-resistant properties. When added as an additive to polyolefin packaging materials, this material not only improves the processing stability, thermal stability, and thermo-oxidative stability of the polyolefin, but more importantly, it removes oxygen, free radical oxidants, and metal ions between the food and the packaging bag, extending the shelf life of the food and significantly extending the antioxidant durability of the polyolefin packaging material. It also ensures food safety and avoids the potential health hazards posed by the precipitation and migration of traditional organic small molecule antioxidants.

[0091] The description of the above embodiments is only used to help understand the technical solution and core ideas of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention. These improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing natural polyphenol antioxidant intercalated modified mica, characterized in that: The steps include: (1) placing mica in a reaction vessel, calcining it and then naturally cooling it to room temperature to obtain heat-activated mica; (2) adding the heat-activated mica to the nitric acid solution, maintaining the solid-liquid ratio of the heat-activated mica to the nitric acid solution at 3%-5%, reflux stirring at 90°C-110°C for 1.5-2.5 hours, naturally cooling to room temperature, filtering, washing to neutrality, and drying to obtain acidified mica; (3) Add the acidified mica to saturated salt water, keeping the solid-liquid ratio of the acidified mica to the saturated salt water at 3%-5%, reflux and stir at 90°C-110°C for 2.5-3.5 hours, let it stand overnight, filter, and wash to remove Cl - , dried to obtain sodium mica; (4) Sodium-modified mica is added to a natural polyphenol antioxidant solution to adjust the system to weak acidity. The natural polyphenol antioxidant is a mixture of phytic acid and quercetin or curcumin and quercetin. The ratio of the amount of sodium-modified mica to the natural polyphenol antioxidant is maintained at 1:20-30. The solution is ultrasonicated at 60°C-65°C for 3-4 hours, cooled to room temperature and allowed to stand overnight, filtered, and washed with pure water to obtain natural polyphenol antioxidant intercalated modified mica.

2. The preparation method according to claim 1, characterized in that The calcination conditions in step (1) are 650°C-750°C and kept warm for 1.5-2.5 h.

3. The preparation method according to claim 1, characterized in that The specific steps of step (2) are as follows: adding the heat-activated mica to a 5 mol / L HNO3 solution, maintaining the solid-liquid ratio of the heat-activated mica to the nitric acid solution at 4%, reflux stirring at 100°C for 2 h, naturally cooling to room temperature, filtering, washing with pure water until neutral, and drying in a forced air drying oven at 100°C to obtain the acidified mica.

4. The preparation method according to claim 1, characterized in that The specific steps of step (3) are as follows: add the acidified mica to saturated salt water, keep the solid-liquid ratio of the acidified mica to the saturated salt water at 4%, reflux and stir at 100°C for 3h, let it stand overnight, filter, wash and remove Cl - , dried to obtain sodium mica.

5. The preparation method according to claim 1 or 4, characterized in that The solvent used in the preparation of the natural polyphenol antioxidant solution in step (4) is one of water, ethanol or sodium hydroxide aqueous solution.

6. The natural polyphenol antioxidant intercalated modified mica obtained by the preparation method according to any one of claims 1 to 5.

7. Use of the natural polyphenol antioxidant intercalated modified mica according to claim 6 as an inorganic additive in the antioxidant and fresh-keeping of food packaging materials.

8. The use according to claim 7, characterized in that The natural polyphenol antioxidant intercalation-modified mica is added into a polyolefin matrix resin to prepare food packaging materials.

9. The use according to claim 8, characterized in that The addition amount of natural polyphenol antioxidant intercalated modified mica is 0.4 wt%~0.6 wt% of the polyolefin matrix resin.

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