Preparation method and application of bamboo leaf extract modified plastic composite hard sheet

Abstract

This invention discloses a method for preparing a bamboo leaf extract-modified plastic composite rigid sheet, comprising the following steps: 1) dissolving bamboo leaf extract (BLE) powder in a PVDC emulsion to obtain a BLE@PVDC composite emulsion; 2) adding silver titanium oxide crystals to a water-Tween 80-ethanol mixed solution, ultrasonically dispersing and hydrolyzing, followed by freeze-drying to obtain Ag-TiO2 powder, and adding the Ag-TiO2 powder to an aqueous polyurethane liquid to obtain Ag-TiO2@PU adhesive; 3) subjecting a PVC rigid sheet to surface corona treatment, and sequentially coating the corona-treated PVC rigid sheet with Ag-TiO2@PU adhesive and BLE@PVDC composite emulsion to obtain a bamboo leaf extract-modified composite rigid sheet. This invention, by adding the metal oxide Ag-TiO2 to the PU adhesive layer and loading bamboo leaf extract onto the PVDC layer, results in a product with strong UV resistance and excellent water vapor barrier properties.

Description

Technical Field

[0001] This invention belongs to the field of packaging materials technology, specifically relating to a method for preparing and applying a plastic composite rigid sheet modified with bamboo leaf extract. Background Technology

[0002] Bamboo leaves are a traditional Chinese medicine and an ancient food packaging material. They contain numerous beneficial active substances, including flavonoids, phenolic acids, and bioactive polysaccharides, exhibiting antibacterial, anti-inflammatory, and antioxidant pharmacological activities. Chinese Patent Publication No. CN102246963A discloses a bamboo leaf extract (BLE) and its preparation method. This extract can be used as an additive in the pretreatment of chilled meat, providing antibacterial, bacteriostatic, meat-tenderizing, and color-protecting effects, thus extending the shelf life of chilled meat. Chinese Patent Publication No. CN115581651A discloses a bamboo leaf extract containing flavonoids and its preparation method. This extract can be used as an additive in cosmetics such as shampoos.

[0003] Polyvinylidene chloride (PVDC) is a high-barrier, tough polymer material. It is a thermoplastic polymer with a softening temperature of 160-200℃, possessing a linear polymer chain structure with excellent molecular symmetry. Due to the large number of polar chlorine atoms in the PVDC molecular chain, oxygen and water molecules have difficulty moving within the PVDC molecule, giving it excellent barrier properties against water vapor and oxygen. It also exhibits good heat resistance, transparency, aroma retention, and chemical resistance. Therefore, PVDC is currently recognized as the plastic packaging material with the best overall barrier performance. Coating PVDC emulsion onto materials such as polyvinyl chloride (PVC) to prepare composite rigid sheets can significantly improve the water vapor and oxygen barrier performance of these materials, and it is now widely used in food and pharmaceutical packaging. Figure 1 As shown, commercially available pharmaceutical packaging composite rigid sheets have an additional layer of polyurethane (PU) or other adhesive applied between the PVC layer and the PVDC layer to ensure a tight bond between the PVDC layer and the PVC layer and prevent them from detaching. However, existing PVC / PU / PVDC composite rigid sheets still suffer from poor barrier properties and aging resistance, such as being susceptible to yellowing of the PVDC layer due to heat and ultraviolet radiation.

[0004] The basic framework of metal-oxygen clusters consists of molecular clusters composed of multiple metal atoms interconnected by oxygen bridges. They can be considered a class of small-sized, nano- or sub-nanometer-scale metal oxide materials with organic functional groups on their surface. By removing the organic groups from the surface of metal-oxygen clusters through processes such as hydrolysis and calcination, they can be converted into metal oxides. In 2019, Shuai Chen et al. synthesized silver-titanium oxide clusters.

[0005] Ag 10 Ti 28 (μ2-O) 12 (μ3-O) 30 (BC) 38 (HBC)2(CH3CN)6(H2O)2 (HBC is benzoic acid) We found that the Ag-TiO2 material converted from it has good antibacterial properties. Currently, there are no reports on the application of Ag-TiO2 material to composite rigid sheets. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a method for preparing and applying a plastic composite rigid sheet modified with bamboo leaf extract, specifically achieved through the following technical solution:

[0007] A method for preparing a plastic composite rigid sheet modified with bamboo leaf extract includes the following steps:

[0008] 1) Dissolve bamboo leaf extract BLE powder in PVDC emulsion at a mass ratio of 1:10-10000 to obtain BLE@PVDC composite emulsion;

[0009] 2) Mix silver titanium oxide clusters at a mass ratio of 1:50-1000

[0010] Ag 10 Ti 28 (μ2-O) 12 (μ3-O) 30 (BC) 38 (HBC)2(CH3CN)6(H2O)2 crystals were added to a mixed solution of water-Tween 80-ethanol and dispersed and hydrolyzed by ultrasonication to obtain an Ag-TiO2 suspension. The Ag-TiO2 suspension was freeze-dried to obtain Ag-TiO2 powder. The Ag-TiO2 powder was added to an aqueous polyurethane liquid and mixed evenly to obtain Ag-TiO2@PU adhesive.

[0011] 3) The PVC rigid sheet is subjected to surface corona treatment. After corona treatment, a layer of Ag-TiO2@PU adhesive is coated on the PVC rigid sheet. After coating, it is dried by hot air. Then, BLE@PVDC composite emulsion is coated on the Ag-TiO2@PU layer. After coating, hot air drying and curing treatment are carried out in sequence to obtain a composite rigid sheet modified with bamboo leaf extract.

[0012] Further, the bamboo leaf extract BLE powder in step 1) is prepared by the following method: the washed and dried bamboo leaves are placed in a high-speed blender, and water is added to the bamboo leaves at a mass ratio of 1:2-10 for high-speed blending. The blending process is carried out for 10-120 minutes. The mixture after high-speed blending is heated to boiling for 5-10 minutes, cooled to room temperature, and then filtered to obtain a bamboo leaf extract (BLE) aqueous solution. The BLE aqueous solution is then distilled under reduced pressure at 40℃-90℃ to remove water and obtain BLE powder.

[0013] Furthermore, the mass ratio of bamboo leaves to water was 1:6, the cell wall breaking time was 30 minutes, the mixture was heated to boiling time for 6 minutes, and the BLE aqueous solution was distilled under reduced pressure at 60℃.

[0014] Furthermore, the blender uses 8 stainless steel serrated blades, and the speed during blending is 18,000 rpm to 72,000 rpm, with 58,000 rpm being the preferred speed.

[0015] Furthermore, in step 2), the silver titanium oxide cluster

[0016] Ag 10 Ti 28 (μ2-O) 12 (μ3-O) 30 (BC) 38 (HBC)2(CH3CN)6(H2O)2 crystals were prepared by the following method: 16.6 g of silver acetate, 61 g of benzoic acid, 1 mL of glacial acetic acid, and 50 mL of tetraisopropoxide were dissolved in 1 L of acetonitrile. The resulting solution was heated at 80 °C for 24 hours, then cooled to room temperature. After the solvent was slowly evaporated for one week, silver-titanium oxide clusters were obtained.

[0017] Ag 10 Ti 28 (μ2-O) 12 (μ3-O) 30 (BC) 38 (HBC)2(CH3CN)6(H2O)2 crystals.

[0018] Further, in step 2), the mass ratio of water, Tween 80 and ethanol in the water-Tween 80-ethanol mixed solution is 100:0.5-10:10-200, preferably 100:1:80.

[0019] 7 Further, in step 2), the ultrasonic frequency is 10-50 kHz, preferably 28 kHz.

[0020] Furthermore, in step 2), the waterborne polyurethane liquid has a solid content of 35%, a viscosity of 100 mPa·s, and a density of 1.02 g / cm³. 3The mass ratio of Ag-TiO2 powder to aqueous polyurethane liquid is 1:20-10000, preferably 1:1000.

[0021] Furthermore, in step 3), the density of the PVC rigid sheet is 1.35-1.45 g / cm³. 3 Preferred concentration: 1.40 g / cm³ 3 The thickness is 200μm-400μm, preferably 250μm; the coating amount of Ag-TiO2@PU adhesive is 1.5g / m². 2 The hot air drying temperature is 60-90℃, preferably 80℃; the drying time of Ag-TiO2@PU adhesive is 10-30s, preferably 20s; the coating amount of BLE@PVDC composite emulsion is 20-60g / m². 2 40g / m 2 The drying time of the BLE@PVDC composite emulsion is 20-80s, preferably 30s, the curing temperature is 30℃, and the curing time is 48 hours.

[0022] The application of the bamboo leaf extract-modified plastic composite rigid sheet prepared by any one of the preparation methods described in claims 1-9 in high-barrier food packaging materials or high-barrier pharmaceutical packaging materials.

[0023] This invention improves the existing preparation method of PVC / PU / PVDC composite rigid sheets by adding Ag-TiO2 metal oxide to the PU adhesive layer and loading bamboo leaf extract onto the PVDC layer. This improves the product obtained by this application, which has strong resistance to ultraviolet radiation and excellent water vapor barrier properties, and can be better applied to food or pharmaceutical packaging. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the cross-sectional structure of a PVC / PU / PVDC composite rigid sheet in the prior art;

[0025] Figure 2 A schematic cross-sectional view of the plastic composite rigid sheet modified with bamboo leaf extract prepared in Example 1;

[0026] Figure 3 A comparison of the UV-Vis transmission spectra of the plastic composite rigid sheet modified with bamboo leaf extract prepared in Example 1 and the PVC / PU / PVDC composite rigid sheet.

[0027] Figure 4 This is a comparison chart of the water vapor transmission rate test results of the plastic composite rigid sheet modified with bamboo leaf extract prepared in Example 1 and the PVC / PU / PVDC composite rigid sheet. Detailed Implementation

[0028] The present application will be further described in detail below with reference to specific embodiments and accompanying drawings, so as to better understand the present technical solution.

[0029] Example 1

[0030] Preparation of BLE@PVDC composite emulsion:

[0031] 50g of washed and dried bamboo leaves were placed in a high-speed blender with 300g of water and blended at 58,000 rpm for 30 minutes to obtain a mixture. The mixture was then boiled for 6 minutes, cooled to room temperature, and filtered to obtain an aqueous solution of bamboo leaf extract. The aqueous solution of bamboo leaf extract was then distilled under reduced pressure at 60°C to remove water, yielding bamboo leaf extract (BLE) powder.

[0032] The PVDC emulsion prepared according to the method of Example 1 in Chinese Patent Publication No. CN104114585A;

[0033] 2g of bamboo leaf extract (BLE) powder was dissolved in 4000g of PVDC emulsion and mixed evenly to obtain BLE@PVDC composite emulsion.

[0034] Preparation of Ag-TiO2@PU adhesive:

[0035] 16.6 g of silver acetate, 61 g of benzoic acid, 1 mL of glacial acetic acid, and 50 mL of tetraisopropoxide were dissolved in 1 L of acetonitrile. The resulting solution was heated at 80 °C for 24 hours, then cooled to room temperature. After the solvent was slowly evaporated over one week, the silver titanium oxide cluster Ag was obtained. 10 Ti 28 (μ2-O) 12 (μ3-O) 30 (BC) 38 (HBC)2(CH3CN)6(H2O)2 crystals. 1g of silver titanium oxide cluster Ag... 10 Ti 28 (μ2-O) 12 (μ3-O) 30 (BC) 38 (HBC)2(CH3CN)6(H2O)2 crystals were added to 200g of a water-Tween 80-ethanol mixed solution (where the mass ratio of water, Tween 80, and ethanol was 100:1:80), and dispersed and hydrolyzed using ultrasound at 28kHz to obtain an Ag-TiO2 suspension. The Ag-TiO2 suspension was further freeze-dried to obtain Ag-TiO2 powder. 0.5g of Ag-TiO2 powder was added to 500g of aqueous polyurethane (PU) liquid with a solid content of 35% to obtain Ag-TiO2@PU adhesive.

[0036] Preparation of PVC / Ag-TiO2@PU / BLE@PVDC composite rigid sheet:

[0037] With a density of 1.40 g / cm³ 3 A 250μm thick PVC rigid sheet undergoes surface corona treatment, followed by a 1.5g / m² electrochemical treatment. 2 The coating amount is as follows: a layer of Ag-TiO2@PU adhesive is coated on the corona-treated PVC rigid sheet. After coating, it is dried with hot air at 80℃ for 20 seconds. Then, a layer of Ag-TiO2@PU adhesive is applied on top of the Ag-TiO2@PU layer at a coating density of 40 g / m². 2 The coating amount was further coated with BLE@PVDC composite emulsion. After coating, it was dried with hot air at 80℃ for 30 seconds. Finally, the product was placed at 30℃ for 48 hours to obtain a plastic composite rigid sheet modified with bamboo leaf extract. Its cross-sectional structure diagram is shown below. Figure 2 As shown.

[0038] Comparative Example

[0039] A PVDC emulsion was prepared according to the method in Example 1 of Chinese Patent Publication No. CN104114585A. The emulsion had a density of 1.40 g / cm³. 3 A 250μm thick PVC rigid sheet undergoes surface corona treatment, followed by a 1.5g / m² electrochemical treatment. 2 A layer of PU adhesive is applied to the corona-treated PVC rigid sheet. After coating, it is dried with hot air at 80℃ for 20 seconds. Then, a layer of PU adhesive is applied on top of the PU layer at a rate of 40g / m². 2 The coating amount was further coated with PVDC composite emulsion. After coating, it was dried with hot air at 80℃ for 30 seconds, and finally the product was placed at 30℃ for 48 hours to complete the production of the PVC / PU / PVDC composite rigid sheet as a comparative example. Its ultraviolet-visible transmission spectrum was then measured. Figure 3 ) and water vapor transmission rate ( Figure 4 ).

[0040] Depend on Figure 3 It is evident that the plastic composite rigid sheet modified with bamboo leaf extract, namely the PVC / Ag-TiO2@PU / BLE@PVDC composite rigid sheet, can block a wider range of ultraviolet light compared to the PVC / PU / PVDC composite rigid sheet. Figure 4 It is evident that the PVC / Ag-TiO2@PU / BLE@PVDC composite rigid sheet has a better ability to block water vapor compared to the PVC / PU / PVDC composite rigid sheet.

Claims

1. A method for preparing a plastic composite rigid sheet modified with bamboo leaf extract, characterized in that... Includes the following steps: 1) Dissolve bamboo leaf extract (BLE) powder in PVDC emulsion at a mass ratio of 1:10-10000 to obtain BLE@PVDC composite emulsion; Bamboo leaf extract (BLE) powder is prepared by the following method: put washed and dried bamboo leaves into a high-speed blender, add water to the bamboo leaves at a mass ratio of bamboo leaves to water of 1:2-10 for high-speed blending treatment, blend for 10-120 minutes, heat the blended mixture to boiling for 5-10 minutes, cool to room temperature and filter to obtain bamboo leaf extract (BLE) aqueous solution, and distill the BLE aqueous solution under reduced pressure at 40℃-90℃ to remove water and obtain BLE powder; 2) Mix silver titanium oxide clusters (Ag) at a mass ratio of 1:50-1000. 10 Ti 28 (μ2-O) 12 (μ3-O) 30 (BC) 38 (HBC)2(CH3CN)6(H2O)2 crystals were added to a mixed solution of water-Tween 80-ethanol and dispersed and hydrolyzed by ultrasonication to obtain an Ag-TiO2 suspension. The Ag-TiO2 suspension was freeze-dried to obtain Ag-TiO2 powder. The Ag-TiO2 powder was added to an aqueous polyurethane liquid and mixed evenly to obtain Ag-TiO2@PU adhesive. 3) The PVC rigid sheet is subjected to surface corona treatment. After corona treatment, a layer of Ag-TiO2@PU adhesive is coated on the PVC rigid sheet. After coating, it is dried by hot air. Then, BLE@PVDC composite emulsion is coated on the Ag-TiO2@PU layer. After coating, hot air drying and curing treatment are carried out in sequence to obtain a composite rigid sheet modified with bamboo leaf extract.

2. The method for preparing a plastic composite rigid sheet modified with bamboo leaf extract as described in claim 1, characterized in that... The mass ratio of bamboo leaves to water was 1:6, the cell wall breaking time was 30 minutes, the mixture was heated to boiling time for 6 minutes, and the BLE aqueous solution was distilled under reduced pressure at 60℃.

3. The method for preparing a plastic composite rigid sheet modified with bamboo leaf extract as described in claim 1, characterized in that... The blender uses 8 stainless steel serrated blades and operates at a speed of 18,000-72,000 rpm during blending.

4. The method for preparing a plastic composite rigid sheet modified with bamboo leaf extract as described in claim 1, characterized in that... Step 2) Silver Titanium Oxide Cluster Ag 10 Ti 28 (μ2-O) 12 (μ3-O) 30 (BC) 38 (HBC)2(CH3CN)6(H2O)2 crystals were prepared by the following method: 16.6 g of silver acetate, 61 g of benzoic acid, 1 mL of glacial acetic acid, and 50 mL of tetraisopropoxide were dissolved in 1 L of acetonitrile. The resulting solution was heated at 80 °C for 24 hours, then cooled to room temperature. After slowly evaporating the solvent for one week, the silver titanium oxide cluster Ag was obtained. 10 Ti 28 (μ2-O) 12 (μ3-O) 30 (BC) 38 (HBC)2(CH3CN)6(H2O)2 crystals.

5. The method for preparing a plastic composite rigid sheet modified with bamboo leaf extract as described in claim 1, characterized in that... In step 2), the mass ratio of water, Tween 80, and ethanol in the water-Tween 80-ethanol mixed solution is 100:0.5-10:10-200.

6. The method for preparing a plastic composite rigid sheet modified with bamboo leaf extract as described in claim 1, characterized in that... In step 2), the ultrasonic frequency is 10-50 kHz.

7. The method for preparing a plastic composite rigid sheet modified with bamboo leaf extract as described in claim 1, characterized in that... In step 2), the waterborne polyurethane liquid has a solid content of 35%, a viscosity of 100 mPa·s, and a density of 1.02 g / cm³. 3 The mass ratio of Ag-TiO2 powder to aqueous polyurethane liquid is 1:20-10000.

8. The method for preparing a plastic composite rigid sheet modified with bamboo leaf extract as described in claim 1, characterized in that... In step 3), the density of the PVC rigid sheet is 1.35-1.45 g / cm³. 3 The thickness is 200μm-400μm; the coating weight of Ag-TiO2@PU adhesive is 1.5g / m². 2 The hot air drying temperature is 60-90℃, and the drying time for Ag-TiO2@PU adhesive is 10-30 seconds; the coating amount of BLE@PVDC composite emulsion is 20-60 g / m². 2 The drying time of the BLE@PVDC composite emulsion is 20-80 seconds, the curing temperature is 30℃, and the curing time is 48 hours.

9. The application of the bamboo leaf extract-modified plastic composite rigid sheet prepared by any one of claims 1-8 in high-barrier food packaging materials or high-barrier pharmaceutical packaging materials.

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