Method for modifying high-barrier PVA (Polyvinyl Alcohol) composite film by utilizing bamboo shoot shells

Abstract

The invention discloses a method for modifying a high-barrier PVA (Polyvinyl Alcohol) composite membrane by utilizing bamboo shoot shells, which comprises the following steps: uniformly mixing 1-5 parts by mass of quaternized bamboo shoot shell cellulose, 1-5 parts by mass of polylactic acid-polylysine copolymer, 30-50 parts by mass of polyvinyl alcohol, 5-15 parts by mass of ethylene-methyl acrylate copolymer, 10-30 parts by mass of ethylene-vinyl alcohol copolymer and 0.1-1 part by mass of antioxidant; then putting the premix into a double-screw extruder, and carrying out melt blending extrusion, granulation and compression molding, so as to obtain the PVA composite film. Compared with the prior art, the preparation method has the beneficial effects that quaternized bamboo shoot shell cellulose is firstly prepared from bamboo shoot shells, then the quaternized bamboo shoot shell cellulose, the polylactic acid-polylysine copolymer, the polyvinyl alcohol, the ethylene-methyl acrylate copolymer and the ethylene-vinyl alcohol copolymer are subjected to blending modification, and the obtained PVA composite film has excellent barrier performance and antibacterial performance.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, and in particular to a method for modifying a high-barrier PVA composite film by utilizing bamboo shoot shells. Background Art

[0002] Polyvinyl alcohol (PVA) is the hydrolysis product of polyvinyl acetate. It has a relatively regular molecular structure and is a semi-crystalline polymer. Due to the differences in the structure, degree of alcoholysis and degree of polymerization of PVA, it has diverse properties, such as barrier properties, biodegradability, solubility, etc., and is widely used in food packaging.

[0003] Bamboo shoots are an important green food and economic crop. my country is rich in bamboo shoot resources. The southern mountainous area of ​​Anhui Province is one of the main production areas of bamboo shoots. During the bamboo shoot processing season every year, a large amount of processing by-products pile up and are not effectively utilized, resulting in a waste of resources. Bamboo shoot shells, as a by-product of bamboo shoot processing, account for 30%-40% of the whole bamboo shoots. They are mainly composed of cellulose, hemicellulose and lignin. Using them as raw materials for extracting nanocellulose is a utilization of agricultural waste, which has a positive role in promoting green environmental protection.

[0004] However, there are few reports on how to use bamboo shoots to further improve the barrier and antibacterial properties of PVA. Summary of the invention

[0005] In order to solve the problems mentioned in the above background technology, the present invention provides a method for modifying a high-barrier PVA composite film using bamboo shoot shells.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A method for modifying a high-barrier PVA composite film using bamboo shoot shells comprises the following steps: 1-5 parts of quaternized bamboo shoot cellulose, 1-5 parts of polylactic acid-polylysine copolymer, 30-50 parts of polyvinyl alcohol, 5-15 parts of ethylene-methyl acrylate copolymer, 10-30 parts of ethylene-vinyl alcohol copolymer and 0.1-1 part of antioxidant are mixed uniformly by weight to prepare a premix, and then the premix is ​​put into a twin-screw extruder for melt blending and extrusion, granulation and compression molding to obtain a PVA composite film.

[0007] Preferably, the preparation method of the quaternized bamboo shoot shell cellulose is as follows: Mix choline chloride and lactic acid, heat until the solution is transparent and uniform, add bamboo shoot shells and acetic anhydride, stir to react, filter, wash with water until neutral, and dry to obtain intermediate A; The intermediate A and hydrochloric acid solution were mixed evenly, ultrasonically treated, FeCl3 was added, and the reaction was stirred. After the reaction was completed, the product was ultrasonically treated, cooled, dialyzed to neutrality with a dialysis bag, and dried to obtain the intermediate B; The intermediate B is dispersed in DMSO, heated and stirred, 2-bromoethylsulfonyl chloride is added dropwise for reaction, filtered, washed with ethanol, and dried to obtain brominated bamboo shoot cellulose; The brominated bamboo shoot cellulose is dispersed in DMF, heated and stirred, dodecyl dimethyl tertiary amine is added, stirred and reacted, cooled, dialyzed in ethanol, and dialyzed in deionized water to obtain quaternized bamboo shoot cellulose.

[0008] Preferably, the mass ratio of choline chloride, lactic acid, bamboo shoot shells and acetic anhydride is (50-150):(400-600):(20-40):(20-40).

[0009] Preferably, the mass ratio of the intermediate A, 10wt% hydrochloric acid solution, and FeCl3 is (5-15): (300-500): (1-3g).

[0010] Preferably, the mass ratio of the intermediate B and 2-bromoethylsulfonyl chloride is (1-3): (1-3).

[0011] Preferably, the mass ratio of brominated bamboo shoot cellulose to dodecyldimethyl tertiary amine is (1-3): (1-3).

[0012] Preferably, the parameters of the twin-screw extruder are: temperature setting: 90±10℃ in zone 1, 130±10℃ in zone 2, 150±10℃ in zone 3, 180±10℃ in zone 4, 200±10℃ in zone 5, 210±10℃ in zone 6, 215±10℃ in zone 7, and 220±10℃ in zone 8.

[0013] Preferably, the compression molding conditions are: compression molding at 220-230° C. for 1-3 min.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention first prepares quaternized bamboo shoot husk cellulose from bamboo shoot husks, and then blends and modifies it with polylactic acid-polylysine copolymer, polyvinyl alcohol, ethylene-methyl acrylate copolymer, and ethylene-vinyl alcohol copolymer. The obtained PVA composite film has excellent barrier properties and antibacterial properties.

[0015] 2. Compared with the single use of quaternized bamboo shoot cellulose and polylactic acid-polylysine copolymer, the inventors found that the simultaneous use of the two can greatly improve the barrier properties of the composite film and has an obvious synergistic enhancement effect. DETAILED DESCRIPTION

[0016] Unless otherwise specified, the raw materials and reagents used in the present invention are commercially available or can be prepared by known methods.

[0017] Some of the raw materials come from the following sources: Ethylene-vinyl alcohol copolymer: Kurary Co., Ltd., Japan, F104B; Polyvinyl alcohol (PVA): Sinopec, type 1788; Ethylene-methyl acrylate copolymer: Dow Chemical Company, AC1125; Polylactic acid-polylysine copolymer: Xi'an Qiyue Biological, Q-0343352 Bamboo shoots: Origin: Taihu Lake, Anhui.

[0018] Preparation Example 1 Mix 100g of choline chloride and 500g of lactic acid, heat until the solution is transparent and uniform, add 30g of bamboo shoot shells and 30g of acetic anhydride, stir and react at 100°C for 5h, filter, wash with water until neutral, and dry to obtain intermediate A; 10g of intermediate A and 400g of 10wt% hydrochloric acid solution were mixed evenly, ultrasonically treated for 2h, 2g of FeCl3 was added, and the mixture was stirred at 95℃ for 3h. After the reaction, the product was ultrasonically treated for 0.5h, cooled to room temperature, dialyzed to neutrality with a dialysis bag, and dried to obtain intermediate B; Disperse 5 g of intermediate B in DMSO (dimethyl sulfoxide), heat to 90°C, add 5 g of 2-bromoethylsulfonyl chloride dropwise and react for 2 h, filter, wash with ethanol, and dry to obtain brominated bamboo shoot cellulose; Disperse 5 g of brominated bamboo shoot cellulose in DMF (N, N-dimethylformamide), heat to 80°C, add 10 g of dodecyl dimethyl tertiary amine, stir at 80°C for 5 h, cool to room temperature, dialyze in ethanol for 24 h, and dialyze in deionized water for 24 h to obtain quaternized bamboo shoot cellulose.

[0019] Preparation Example 2 The difference between this preparation example and preparation example 1 is that 20 g of bamboo shoot shells are added, and the rest is exactly the same as in preparation example 1.

[0020] Preparation Example 3 The difference between this preparation example and preparation example 1 is that 40 g of bamboo shoot shells are added, and the rest is exactly the same as in preparation example 1. Example 1

[0021] A method for modifying a high-barrier PVA composite film using bamboo shoot shells comprises the following steps: In parts by mass, 3 parts of quaternized bamboo shoot cellulose (obtained in Preparation Example 1), 3 parts of polylactic acid-polylysine copolymer, 30 parts of polyvinyl alcohol, 10 parts of ethylene-methyl acrylate copolymer, 20 parts of ethylene-vinyl alcohol copolymer, and 0.5 parts of antioxidant are mixed uniformly to prepare a premix, and then the premix is ​​put into a twin-screw extruder for melt blending and extrusion, granulation, and compression molding to obtain a PVA composite film with a thickness of 100 μm.

[0022] The parameters of the twin-screw extruder are as follows: temperature settings: 90°C in zone 1, 130°C in zone 2, 150°C in zone 3, 180°C in zone 4, 200°C in zone 5, 210°C in zone 6, 215°C in zone 7, and 220°C in zone 8.

[0023] The compression molding conditions are: compression molding at 225° C. for 2 min. Example 2

[0024] The difference between this embodiment and embodiment 1 is that: 1 part of quaternized bamboo shoot shell cellulose is used, and the rest is exactly the same as in embodiment 1. Example 3

[0025] The difference between this embodiment and embodiment 1 is that 5 parts of quaternized bamboo shoot shell cellulose are used, and the rest is exactly the same as in embodiment 1. Example 4

[0026] The difference between this embodiment and embodiment 1 is that: 1 part of polylactic acid-polylysine copolymer is used, and the rest of the components are exactly the same as those in embodiment 1. Example 5

[0027] The difference between this embodiment and embodiment 1 is that: 5 parts of polylactic acid-polylysine copolymer are used, and the rest of the parts are exactly the same as those in embodiment 1. Example 6

[0028] The difference between this embodiment and embodiment 1 is that: 3 parts of quaternized bamboo shoot shell cellulose (obtained in Preparation Example 2) are used, and the rest is exactly the same as in embodiment 1. Example 7

[0029] The difference between this embodiment and embodiment 1 is that: 3 parts of quaternized bamboo shoot shell cellulose (obtained in Preparation Example 3) are used, and the rest is exactly the same as in embodiment 1.

[0030] Comparative Example 1 The difference between this comparative example and Example 1 is that: 0 parts of quaternized bamboo shoot shell cellulose are used, and the rest are exactly the same as in Example 1.

[0031] Comparative Example 2 The difference between this comparative example and Example 1 is that: 0 part of polylactic acid-polylysine copolymer is used, and the rest is exactly the same as Example 1.

[0032] Comparative Example 3 The difference between this comparative example and Example 1 is that: 0 parts of quaternized bamboo shoot cellulose and 0 parts of polylactic acid-polylysine copolymer are used, and the rest is exactly the same as in Example 1.

[0033] Tests and Results Oxygen permeability test: using ASTM D-1434 standard differential pressure gas permeameter, test conditions, 25 ° C, 50% RH.

[0034] Antibacterial test: First, the PVA composite films obtained in Examples 1-7 and Comparative Examples 1-3 were cut into samples with a length of 3 mm, and then 1 mL of the samples with a bacterial content of 10 7 The suspension of Escherichia coli with 100 CFU / mL was added to 49 mL of phosphate buffer solution, and 1 g of the sample was added as the experimental group, and the group without the sample was used as the blank group. The suspension was shaken at room temperature for 10 h, and 1 ml was inoculated into beef extract peptone basal medium respectively, and cultured at 37°C for 24 h. The experiment was repeated 5 times, and the viable bacteria were counted and the average value was taken to calculate the inhibition rate. The inhibition rate = (the number of colonies in the blank group - the number of colonies in the experimental group) / the number of colonies in the blank group × 100%. The results are shown in Table 1.

[0035] Table 1

[0036] As can be seen from Table 1, the composite films prepared in Examples 1-5 of the present application all have excellent barrier properties and antibacterial properties.

[0037] Comparing Example 1 and Comparative Example 1, it can be seen that the oxygen permeability decreased from 0.69 (Comparative Example 1) to 0.12 (Example 1), a decrease of 0.57; Comparing Example 1 and Comparative Example 2, it can be seen that the oxygen permeability decreased from 0.76 (Comparative Example 2) to 0.12 (Example 1), a decrease of 0.64; Comparing Example 1 and Comparative Example 3, it can be seen that the oxygen permeability decreased from 1.53 (Comparative Example 3) to 0.12 (Example 1), a decrease of 1.41; In other words, the addition of quaternized bamboo shoot shell cellulose and polylactic acid-polylysine copolymer can improve the barrier properties of the composite film. When the two are used at the same time, the barrier properties are optimal and have a synergistic enhancement effect.

[0038] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for modifying a high-barrier PVA composite film using bamboo shoot shells, characterized in that: The steps include: 1-5 parts of quaternized bamboo shoot cellulose, 1-5 parts of polylactic acid-polylysine copolymer, 30-50 parts of polyvinyl alcohol, 5-15 parts of ethylene-methyl acrylate copolymer, 10-30 parts of ethylene-vinyl alcohol copolymer and 0.1-1 part of antioxidant are mixed uniformly by weight to prepare a premix, and then the premix is ​​put into a twin-screw extruder for melt blending and extrusion, granulation and compression molding to obtain a PVA composite film.

2. The method for modifying a high-barrier PVA composite film using bamboo shoot shells according to claim 1, characterized in that: The preparation method of the quaternized bamboo shoot shell cellulose is as follows: Mix choline chloride and lactic acid, heat until the solution is transparent and uniform, add bamboo shoot shells and acetic anhydride, stir to react, filter, wash with water until neutral, and dry to obtain intermediate A; The intermediate A and hydrochloric acid solution were mixed evenly, ultrasonically treated, FeCl3 was added, and the reaction was stirred. After the reaction was completed, the product was ultrasonically treated, cooled, dialyzed to neutrality with a dialysis bag, and dried to obtain the intermediate B; The intermediate B is dispersed in DMSO, heated and stirred, 2-bromoethylsulfonyl chloride is added dropwise for reaction, filtered, washed with ethanol, and dried to obtain brominated bamboo shoot cellulose; The brominated bamboo shoot cellulose is dispersed in DMF, heated and stirred, dodecyl dimethyl tertiary amine is added, stirred and reacted, cooled, dialyzed in ethanol, and dialyzed in deionized water to obtain quaternized bamboo shoot cellulose.

3. The method for modifying a high-barrier PVA composite film using bamboo shoot shells according to claim 1, characterized in that: The mass ratio of choline chloride, lactic acid, bamboo shoot shells and acetic anhydride is (50-150): (400-600): (20-40): (20-40).

4. The method for modifying a high-barrier PVA composite film using bamboo shoot shells according to claim 1, characterized in that: The mass ratio of the intermediate A, 10wt% hydrochloric acid solution and FeCl3 is (5-15): (300-500): (1-3g).

5. The method for modifying a high-barrier PVA composite film using bamboo shoot shells according to claim 1, characterized in that: The mass ratio of the intermediate B and 2-bromoethylsulfonyl chloride is (1-3): (1-3).

6. The method for modifying a high-barrier PVA composite film using bamboo shoot shells according to claim 1, characterized in that: The mass ratio of the brominated bamboo shoot cellulose and dodecyl dimethyl tertiary amine is (1-3): (1-3).

7. The method for modifying a high-barrier PVA composite film using bamboo shoot shells according to claim 1, characterized in that: The parameters of the twin-screw extruder are as follows: temperature setting: zone 1 90±10℃, zone 2 130±10℃, zone 3 150±10℃, zone 4 180±10℃, zone 5 200±10℃, zone 6 210±10℃, zone 7 215±10℃, zone 8 220±10℃.

8. The method for modifying a high-barrier PVA composite film using bamboo shoot shells according to claim 1, characterized in that: The compression molding conditions are: compression molding at 220-230° C. for 1-3 min.

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