A method for preparing a water-soluble, plastic-free wrapping paper composite film

Abstract

The application relates to the technical field of film materials, and discloses a preparation method of a water-soluble plastic-free packaging paper composite film, which is prepared through cross-linking and flow casting by using genipin as a non-cross-linking agent, glycerol as a plasticizer, gelatin and chitosan as film material substrates and graphene oxide antibacterial modifier as an additive. The antibacterial modifier and fluorine-containing groups are grafted on the surface of the graphene oxide, which can not only improve the mechanical strength of the composite film, but also improve the waterproof performance of the composite film through the physical barrier effect of the graphene oxide and the chemical hydrophobic effect of the fluorine-containing groups. In addition, the natural antibacterial agent, streptococcal lactase, is free of toxicity and can effectively endow the composite film with excellent antibacterial effect.

Description

Technical Field

[0001] This invention relates to the field of membrane materials technology, and specifically to a method for preparing a water-soluble plastic-free packaging paper composite film. Background Technology

[0002] Packaging paper refers to a general term for a class of papers used for packaging purposes. Currently, the main types of packaging paper used in the market include kraft paper, parchment paper, and vellum paper. Depending on the characteristics of different commodities, packaging paper should have corresponding special functions. For example, packaging paper for electronic products and lamps should be waterproof to prevent moisture penetration and damage. Currently, lamination or coating is commonly used to create a hydrophobic surface on the inside of the packaging paper, achieving a waterproof effect. However, conventional petroleum-based film materials such as polyethylene and polypropylene are non-degradable, prone to migration, and pose certain environmental and safety problems. Furthermore, these film materials themselves do not have antibacterial properties; if bacterial erosion occurs during long-term storage, it can easily affect the lifespan of the film material. Moreover, with the promulgation of plastic restriction orders, finding a safe and environmentally friendly alternative material is of great significance.

[0003] Chinese invention patent application number CN201710617390.0 discloses a method for preparing banana cellulose film and its application. This patent uses the ionic liquid 1-allyl-3-methylimidazolium chloride to dissolve and alkalize banana cellulose, and then scrapes the film into a film using a coating device. The prepared film has good mechanical properties and biodegradability. However, the ionic liquid itself has a certain degree of toxicity, and the film prepared by this method has poor waterproof effect and does not have antibacterial effect, which cannot meet the requirements of most packaging papers.

[0004] Based on this, the present invention provides a method for preparing a water-soluble plastic-free packaging paper composite film. By using natural polymer materials as the film material matrix and adding graphene oxide antibacterial modifier, the comprehensive performance of the film material, such as waterproofing and antibacterial properties, is improved, which is conducive to its further application in the field of packaging paper. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a water-soluble plastic-free packaging paper composite film, which solves the problem of environmental pollution caused by conventional plastic base film materials for packaging paper, and also solves the problems of poor waterproof effect and lack of antibacterial properties of packaging paper film materials.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing a water-soluble, plastic-free packaging paper composite film includes the following steps: Step 1: Mix gelatin with pure water and stir at 50-55℃ until completely dissolved to obtain a gelatin solution; Step 2: Add chitosan to glacial acetic acid solution and stir at 45-50℃ until completely dissolved. Add genipin and mix well to obtain chitosan solution. Step 3: Under stirring conditions, mix the gelatin solution and chitosan solution, add glycerin, and stir evenly at a temperature of 50-55℃ to obtain the composite film solution; Step 4: Add graphene oxide antibacterial modifier to the composite film solution, ultrasonically vibrate for 20-30 minutes, spread the obtained composite film dispersion on the surface of a dry and clean plexiglass plate, let it dry naturally to form a film, and then remove the film to obtain a water-soluble plastic-free packaging paper composite film.

[0007] The graphene oxide antibacterial modifier is graphene oxide with fluorine-containing groups and nisin, a natural antibacterial agent, grafted onto its surface.

[0008] Furthermore, in step one, the mass fraction of the gelatin solution is 4-10%.

[0009] Further, in step two, the volume fraction of the glacial acetic acid solution is 1-2%; the mass fraction of the chitosan solution is 2-5%; and the mass ratio of chitosan to genipin is 10:0.05-0.15.

[0010] Furthermore, in step three, the volume ratio of the gelatin solution, chitosan solution, and glycerin is 1.5-2:10:0.5-1.

[0011] Furthermore, in step four, the liquid-to-solid ratio of the composite membrane liquid and the graphene oxide antibacterial modifier is 200-300:0.05-0.1.

[0012] Furthermore, in step four, the preparation method of the graphene oxide antibacterial modifier includes the following steps: Step 1: Graphene oxide is dispersed in toluene, 4,4'-(hexafluoroisopropene) phthalic anhydride and catalyst are added, stirred well, protected with nitrogen, stirred at room temperature for 4-8 hours, the solid material is separated by centrifugation, washed, and vacuum dried to obtain graphene oxide intermediate. Step 2: Place the graphene oxide intermediate in tetrahydrofuran, sonicate for 20-40 minutes, add nisin and stir well, stir at room temperature for 12-18 hours, discharge, wash, and vacuum dry to obtain the graphene oxide antibacterial modifier.

[0013] Furthermore, in the first step, the catalyst is p-toluenesulfonic acid.

[0014] Furthermore, in the second step, the mass ratio of the graphene oxide to nisin is 1:2-5.5.

[0015] Through the above technical solution, the hydroxyl groups in the graphene oxide structure can undergo esterification condensation with the maleic anhydride group at one end of the 4,4'-(hexafluoroisopropene)phthalic anhydride structure under the action of p-toluenesulfonic acid, to obtain a graphene oxide intermediate modified with fluorinated segments and maleic anhydride groups. The maleic anhydride groups modified on its surface can undergo condensation reaction with the amino groups in the nisin structure at room temperature, thereby grafting the natural antibacterial agent nisin onto the surface of graphene oxide, to obtain an antibacterial modifier of graphene oxide containing fluorinated segments and the natural antibacterial agent nisin on its surface.

[0016] The beneficial effects of this invention are: This invention relates to an antibacterial modifier of graphene oxide during the crosslinking process of gelatin and chitosan. After surface modification, graphene oxide can overcome the van der Waals forces between the sheets, achieving a uniform dispersion effect. This improves its dispersibility in the composite membrane liquid, allowing it to be uniformly dispersed in the composite membrane and avoiding the problem of negative effects on the composite membrane caused by graphene oxide agglomeration.

[0017] The graphene oxide antibacterial modifier prepared in this invention contains fluorinated segments and nisin, a natural antibacterial agent. Due to the unique layered structure and ultra-high strength of graphene oxide, it can improve the mechanical strength of the composite membrane and enhance its waterproof performance through physical barrier properties. Furthermore, the fluorinated segments in the graphene oxide antibacterial modifier have low surface energy, resulting in a chemical hydrophobic effect. Therefore, a synergistic effect of physical barrier and chemical hydrophobicity can be achieved, further improving the waterproof performance of the composite membrane. In addition, nisin, as a natural antibacterial agent, is non-toxic and effectively imparts excellent antibacterial properties to the composite membrane.

[0018] The gelatin and chitosan used in this invention are both natural polymer materials. Therefore, the composite membrane does not contain any plastic components and has good biodegradability, thus avoiding environmental pollution. Furthermore, gelatin is a protein macromolecule with numerous hydrophilic groups on its molecular chain, which gives the composite membrane good water solubility.

[0019] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0021] A method for preparing a water-soluble, plastic-free packaging paper composite film includes the following steps: Step 1: Mix 10g of gelatin with pure water and stir at 50℃ until completely dissolved to prepare a gelatin solution with a mass fraction of 4%. Step 2: Add 10g of chitosan to a 1% (v / v) glacial acetic acid solution and stir at 45°C until completely dissolved. Add 0.05g of genipin and mix well to prepare a 2% (w / v) chitosan solution. Step 3: Under stirring conditions, mix 15 mL of gelatin solution with 100 mL of chitosan solution, add 5 mL of glycerol, and stir evenly at 50°C to obtain composite membrane solution; Step 4: Add 0.05g of graphene oxide antibacterial modifier to 200mL of composite membrane solution, ultrasonically vibrate for 20min, spread the obtained composite membrane dispersion on the surface of a dry and clean plexiglass plate, let it dry naturally to form a film, and then remove the film to obtain a water-soluble plastic-free packaging paper composite film.

[0022] The preparation method of the graphene oxide antibacterial modifier includes the following steps: Step 1: Disperse 2g of graphene oxide in toluene, add 3.5g of 4,4'-(hexafluoroisopropene) phthalic anhydride and 0.1g of p-toluenesulfonic acid, stir well, purge with nitrogen, stir at room temperature for 6 hours, centrifuge to separate the solid material, wash, vacuum dry to obtain graphene oxide intermediate. Step 2: Place 1g of graphene oxide intermediate in tetrahydrofuran, sonicate for 30min, add 3g of nisin and stir well, stir at room temperature for 16h, discharge, wash, and vacuum dry to obtain graphene oxide antibacterial modifier. Example 2

[0023] A method for preparing a water-soluble, plastic-free packaging paper composite film includes the following steps: Step 1: Mix 10g of gelatin with pure water and stir at 55℃ until completely dissolved to prepare a gelatin solution with a mass fraction of 8%. Step 2: Add 10g of chitosan to a 2% (v / v) glacial acetic acid solution and stir at 50°C until completely dissolved. Add 0.1g of genipin and mix well to prepare a 4% (w / w) chitosan solution. Step 3: Under stirring conditions, mix 18 mL of gelatin solution with 100 mL of chitosan solution, add 6 mL of glycerol, and stir evenly at 55°C to obtain composite membrane solution; Step 4: Add 0.08g of graphene oxide antibacterial modifier to 260mL of composite membrane solution, ultrasonically vibrate for 25min, spread the obtained composite membrane dispersion on the surface of a dry and clean plexiglass plate, let it dry naturally to form a film, and then remove the film to obtain a water-soluble plastic-free packaging paper composite film.

[0024] The preparation method of the graphene oxide antibacterial modifier is the same as that in Example 1. Example 3

[0025] A method for preparing a water-soluble, plastic-free packaging paper composite film includes the following steps: Step 1: Mix 10g of gelatin with pure water and stir at 55℃ until completely dissolved to prepare a 10% gelatin solution. Step 2: Add 10g of chitosan to a 2% (v / v) glacial acetic acid solution and stir at 50°C until completely dissolved. Add 0.15g of genipin and mix well to prepare a 5% (w / w) chitosan solution. Step 3: Under stirring conditions, mix 20 mL of gelatin solution with 100 mL of chitosan solution, add 10 mL of glycerol, and stir evenly at 55 °C to obtain composite membrane solution; Step 4: Add 0.1g of graphene oxide antibacterial modifier to 300mL of composite membrane solution, ultrasonically vibrate for 30min, spread the obtained composite membrane dispersion on the surface of a dry and clean plexiglass plate, let it dry naturally to form a film, and then remove the film to obtain a water-soluble plastic-free packaging paper composite film.

[0026] The preparation method of the graphene oxide antibacterial modifier is the same as that in Example 1.

[0027] Comparative Example 1 A method for preparing a water-soluble, plastic-free packaging paper composite film includes the following steps: Step 1: Mix 10g of gelatin with pure water and stir at 55℃ until completely dissolved to prepare a gelatin solution with a mass fraction of 8%. Step 2: Add 10g of chitosan to a 2% (v / v) glacial acetic acid solution and stir at 50°C until completely dissolved. Add 0.1g of genipin and mix well to prepare a 4% (w / w) chitosan solution. Step 3: Under stirring conditions, mix 18 mL of gelatin solution with 100 mL of chitosan solution, add 6 mL of glycerol, and stir evenly at 55°C to obtain composite membrane solution; Step 4: After ultrasonically vibrating the composite membrane solution for 25 minutes, spread the obtained composite membrane dispersion on the surface of a dry and clean plexiglass plate. After naturally drying to form a film, remove the film to obtain a water-soluble plastic-free packaging paper composite film.

[0028] Performance testing a. The composite films from Examples 1-3 and Comparative Example 1 (paper cup) of this invention were cut into samples that met the specifications. The tensile properties of the samples were tested according to national standard GB / T 1040.3-2006. The test results are shown in the table below:

[0029] As shown in the table above, the composite films prepared in Examples 1-3 of this invention have high tensile strength and exhibit good mechanical strength. The composite film prepared in Comparative Example 1 has relatively poor tensile strength because it does not contain graphene oxide antibacterial modifier, and therefore cannot utilize the ultra-high strength of graphene oxide to enhance the mechanical properties of the composite film.

[0030] b. Pour the well-melted beef and chicken extract peptone medium into a petri dish, cool until solidified, add 0.1 mL of Escherichia coli suspension with a concentration of 10⁻⁵ CFU / mL, spread evenly, and prepare a plate. Cut the composite membranes prepared in Examples 1-3 and Comparative Example 1 of this invention into circular samples with a diameter of 0.8 cm, and place them tightly against the center of the plate. Invert the plate and incubate in an incubator at 37°C for 24 h. Record the diameter of the inhibition zone using calipers to evaluate the antibacterial effect of the composite membrane. Generally, the larger the diameter of the inhibition zone, the better the antibacterial effect, and vice versa. Use an SDC-100S contact angle meter to test the water contact angle of the composite membranes prepared in Examples 1-3 and Comparative Example 1 of this invention. The test results are shown in the table below:

[0031] As shown in the table above, the composite membranes prepared in Examples 1-3 of this invention exhibit good antibacterial properties and a large water contact angle, thus demonstrating good hydrophobicity. The composite membrane prepared in Comparative Example 1, without the addition of graphene oxide antibacterial modifier, relies solely on the antibacterial and hydrophobic properties of chitosan itself; therefore, its antibacterial and waterproof performance is only average.

[0032] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a water-soluble, plastic-free packaging paper composite film, characterized in that, Includes the following steps: Step 1: Mix gelatin with pure water and stir at 50-55℃ until completely dissolved to obtain a gelatin solution; Step 2: Add chitosan to glacial acetic acid solution and stir at 45-50℃ until completely dissolved. Add genipin and mix well to obtain chitosan solution. Step 3: Under stirring conditions, mix the gelatin solution and chitosan solution, add glycerin, and stir evenly at a temperature of 50-55℃ to obtain the composite film solution; Step 4: Add graphene oxide antibacterial modifier to the composite film solution, ultrasonically vibrate for 20-30 minutes, spread the obtained composite film dispersion on the surface of a dry and clean plexiglass plate, let it dry naturally to form a film, and then remove the film to obtain a water-soluble plastic-free packaging paper composite film. The graphene oxide antibacterial modifier is graphene oxide with fluorine-containing groups and nisin, a natural antibacterial agent, grafted onto its surface.

2. The method for preparing a water-soluble plastic-free packaging paper composite film according to claim 1, characterized in that, In step one, the mass fraction of the gelatin solution is 4-10%.

3. The method for preparing a water-soluble plastic-free packaging paper composite film according to claim 1, characterized in that, In step two, the volume fraction of the glacial acetic acid solution is 1-2%; the mass fraction of the chitosan solution is 2-5%; and the mass ratio of chitosan to genipin is 10:0.05-0.

15.

4. The method for preparing a water-soluble plastic-free packaging paper composite film according to claim 1, characterized in that, In step three, the volume ratio of the gelatin solution, chitosan solution, and glycerin is 1.5-2:10:0.5-1.

5. The method for preparing a water-soluble plastic-free packaging paper composite film according to claim 1, characterized in that, In step four, the liquid-to-solid ratio of the composite membrane liquid and the graphene oxide antibacterial modifier is 200-300:0.05-0.

1.

6. The method for preparing a water-soluble plastic-free packaging paper composite film according to claim 1, characterized in that, In step four, the preparation method of the graphene oxide antibacterial modifier includes the following steps: Step 1: Graphene oxide is dispersed in toluene, 4,4'-(hexafluoroisopropene) phthalic anhydride and catalyst are added, stirred well, protected with nitrogen, stirred at room temperature for 4-8 hours, the solid material is separated by centrifugation, washed, and vacuum dried to obtain graphene oxide intermediate. Step 2: Place the graphene oxide intermediate in tetrahydrofuran, sonicate for 20-40 minutes, add nisin and stir well, stir at room temperature for 12-18 hours, discharge, wash, and vacuum dry to obtain the graphene oxide antibacterial modifier.

7. The method for preparing a water-soluble plastic-free packaging paper composite film according to claim 6, characterized in that, In the first step, the catalyst is p-toluenesulfonic acid.

8. The method for preparing a water-soluble plastic-free packaging paper composite film according to claim 6, characterized in that, In the second step, the mass ratio of graphene oxide to nisin is 1:2-5.5.

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