A method for preparing a silk fibroin-based hydrophobic and oleophobic packaging coating

Abstract

The application discloses a preparation method of a silk protein-based hydrophobic and oleophobic packaging coating, comprising the following steps: (1) preparing a silk protein solution; (2) arranging the silk protein solution on paper to form paper with a silk protein layer; (3) converting the silk protein from a random coil structure into a beta-sheet structure with hydrophobic and oleophobic properties through heat treatment or silk protein conformation transition induced solvent treatment; (4) taking the paper in step (3) and pressing the same by using a roller with a micrometer and / or nanometer array pattern to form a concave-convex array structure; and (5) taking the paper in step (4) and irradiating the same under ultraviolet light. Compared with a traditional synthetic polymer coating, the silk protein-based hydrophobic and oleophobic coating has significant environmental protection advantages, including biocompatibility, biodegradability and improved hydrophobic and oleophobic properties. Application of the coating can greatly reduce environmental pollution and meet the current demand for sustainable packaging materials.

Description

Technical Field

[0001] This invention belongs to the field of biomaterials applied to food packaging, specifically relating to a method for preparing a hydrophobic and oleophobic packaging coating based on silk protein, which is used for the inner layer of food packaging boxes, disposable tableware boxes and water cups. Background Technology

[0002] As global plastic pollution worsens, governments, businesses, and consumers are seeking more environmentally friendly packaging solutions. Against this backdrop, the development of new, environmentally friendly packaging materials has become urgent. Particularly in the food packaging sector, demand is growing while concerns about the environmental impact and food safety of packaging materials are becoming increasingly stringent. Therefore, finding new materials to replace traditional plastics is not only an inevitable choice for solving environmental problems but also an important strategy for addressing consumer health concerns.

[0003] Among numerous alternative materials, bio-based materials demonstrate immense potential due to their renewable and biodegradable origins. These materials are typically derived from nature, such as plants and microorganisms, and can be processed into various packaging products through biotechnology or chemical methods. Simultaneously, their biodegradability means they can be effectively absorbed by nature after use, significantly reducing the environmental burden. In particular, using naturally derived silk protein as a coating for paper packaging materials offers multiple benefits, improving packaging performance while responding to calls for environmental protection and sustainable development. As a natural protein, silk protein's biocompatibility and biodegradability ensure its effective decomposition by nature after use, greatly reducing the environmental burden. The hydrophobic and oleophobic properties exhibited by specially treated silk protein coatings are crucial for keeping food dry, extending shelf life, and protecting the integrity of packaging materials. Furthermore, this coating enhances the physical properties of paper packaging, such as increasing strength and durability, thus more effectively protecting food during transportation and storage, reducing damage and waste. The natural properties of silk protein also mean that paper packaging using this coating is safe for human health, reducing the use of chemicals and the potential risk of food contamination. It is worth mentioning that silk protein coatings are flexible in application, easily integrated into existing production lines through spraying, dip coating, and other methods. Their functionality and versatility also bring additional features such as antibacterial and UV resistance to paper packaging. In terms of environmental protection and sustainable development, from raw material acquisition to the production process and final product degradation, silk protein coatings exhibit minimal environmental impact throughout their entire lifecycle, providing the food packaging industry with a forward-looking material option that not only improves packaging performance and safety but also meets contemporary demands for environmental protection and sustainable development.

[0004] However, achieving widespread application of silk protein materials in food packaging faces multiple challenges. First, ensuring uniform application and long-term stability of silk protein coatings on packaging materials is a major hurdle. The key lies in precise control of the processing and curing process, including solvent selection, application temperature, humidity control, and optimization of curing time. These require meticulous process adjustments to ensure the consistency and performance stability of the final coating. Furthermore, the cost-effectiveness of silk protein coatings is a crucial consideration. Its production cost may be high for large-scale applications, encompassing not only raw material procurement costs but also processing and energy consumption. Therefore, there is an urgent need to explore a feasible method for applying silk protein in food packaging. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a hydrophobic and oleophobic packaging coating based on silk fibroin. This coating can replace traditional synthetic polymer materials and be used in the inner layer of food packaging, disposable tableware boxes and water cups, etc., solving the problems of existing polymer materials being difficult to degrade, having poor environmental friendliness, poor biofriendliness and poor biocompatibility.

[0006] To solve the above technical problems, the following technical solution is adopted:

[0007] A method for preparing a hydrophobic and oleophobic packaging coating based on silk fibroin, characterized by comprising the following steps:

[0008] (1) Preparation of silk protein solution;

[0009] (2) Apply the silk protein solution onto the paper to form a paper with a silk protein layer;

[0010] (3) By heat treatment or solvent treatment induced by conformational change of silk protein, the random coil structure of silk protein is transformed into a β-sheet structure with hydrophobic and oleophobic properties.

[0011] After optimization, in step (1), antibacterial materials are added to the prepared silk protein solution. By adding antibacterial materials, the antibacterial properties of the silk protein layer can be improved, thereby giving the packaging a certain degree of antibacterial properties.

[0012] After optimization, the antibacterial material is one or more of the following: a combination of natural antibacterial peptides, lactic acid and lactate, a combination of pectin and chitosan, or a combination of natural essential oils and honey. The above-mentioned antibacterial material is a water-soluble, edible, natural antibacterial material that is non-toxic and harmless, making the treated silk protein layer harmless to the human body and reducing the use of chemical substances and the potential risk of food contamination.

[0013] After optimization, one of the finishing methods in step (2) is as follows: the silk protein solution is prepared into an adhesive silk protein film, and the silk protein film is applied to paper by pressing to form paper with a silk protein layer. This finishing method can enhance the adhesion of silk protein to paper.

[0014] After optimization, the preparation of the viscous silk fibroin membrane is as follows: the silk fibroin solution is poured into a film-forming tray and then dried under natural conditions to form a film; the film-forming process is carried out under ultraviolet light protection, and edible salt ions are added during the film-forming process. The ultraviolet light protection prevents bacterial contamination during the film-forming and drying process; the addition of edible salt ions increases the viscosity of the silk fibroin membrane.

[0015] After optimization, one of the finishing methods in step (2) is to coat the paper with a silk protein solution to form a paper with a silk protein layer.

[0016] After optimization, step (3) heat treatment: the paper is heat-treated at a temperature of 40-100℃. Through heat treatment, the silk fibroin is transformed from a random coil structure into a β-sheet structure with hydrophobic and oleophobic properties, thereby enhancing the hydrophobic and oleophobic properties of the silk fibroin layer.

[0017] After optimization, step (3) involves solvent treatment to induce conformational change in silk fibroin: The paper with the silk fibroin layer is soaked in a solution of 65%-85% ethanol, 40%-60% methanol, 65%-85% acetone, or 10%-30% chitosan for 0.5-2 hours. This solvent treatment induces conformational change in silk fibroin, transforming it from a random coil structure into a β-sheet structure with hydrophobic and oleophobic properties, thereby enhancing the hydrophobic and oleophobic properties of the silk fibroin layer.

[0018] After optimization, the preparation method further includes pressing a textured array structure: taking a piece of paper with a silk fibroin layer, pressing it with a roller having a micron and / or nanometer array pattern, and after pressing, the silk fibroin layer forms a textured array structure with a scale of 100nm-5μm. This array form can significantly improve the hydrophobic and oleophobic properties of the silk fibroin layer.

[0019] After optimization, the preparation method further includes ultraviolet irradiation treatment: taking paper with a silk fibroin layer and irradiating it under ultraviolet light with a wavelength of 100-400 nm for 10 min to 24 h. Ultraviolet irradiation can further improve the hydrophobic and oleophobic properties of the silk fibroin layer.

[0020] The above technical solution has the following beneficial effects:

[0021] Compared to traditional synthetic polymer coatings, the silk protein-based hydrophobic and oleophobic coating of this invention has significant environmental advantages, including biocompatibility, biodegradability, and improved hydrophobic and oleophobic properties. The application of this coating will greatly reduce environmental pollution and meet the current demand for sustainable packaging materials.

[0022] Silk fibroin, with its renewable and biodegradable origin, presents enormous potential. Derived from silkworms, silk fibroin can be processed into various packaging products through biotechnology or chemical methods. Simultaneously, its biodegradability means it can be effectively absorbed by nature after use, significantly reducing the environmental burden. Therefore, silk fibroin can both improve packaging performance and respond to the calls for environmental protection and sustainable development. As a natural protein, silk fibroin's biocompatibility and biodegradability ensure its effective decomposition by nature after use, greatly reducing the environmental burden. The silk fibroin coating treated in this invention exhibits hydrophobic and oleophobic properties, crucial for maintaining food dryness, extending shelf life, and protecting the integrity of packaging materials. Furthermore, the silk fibroin coating of this invention can enhance the physical properties of paper packaging, such as improving packaging strength and durability, thereby more effectively protecting food during transportation and storage, reducing damage and waste. The natural properties of silk fibroin also mean that paper packaging using this coating is safe for human health, reducing the use of chemicals and the potential risk of food contamination. It's worth noting that silk protein coatings offer flexible application methods, easily integrating into existing production lines through spraying, dip coating, and other techniques. Furthermore, functional finishing adds additional properties to paper packaging, such as antibacterial and UV resistance. In terms of environmental protection and sustainable development, silk protein coatings exhibit minimal environmental impact throughout their entire lifecycle, from raw material acquisition to production and final product degradation. This provides the food packaging industry with a forward-looking material option, enhancing packaging performance and safety while meeting contemporary demands for environmental protection and sustainable development. Detailed Implementation

[0023] This invention aims to provide a method for preparing a hydrophobic and oleophobic packaging coating based on silk fibroin. This coating can replace traditional synthetic polymer materials and be used in the inner layer of food packaging, disposable tableware boxes and water cups, etc., solving the problems of existing polymer materials such as difficulty in degradation, poor environmental friendliness, poor biofriendliness and poor biocompatibility.

[0024] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0025] Example 1

[0026] (1) The commonly used preparation techniques for silk protein aqueous solution are adopted, namely, silk protein aqueous solution is prepared by degumming, salt dissolution and dialysis.

[0027] (2) The silk protein solution is poured into a film-forming tray and then dried under natural conditions to form a viscous silk protein film. The film-forming process is carried out under ultraviolet light protection, and edible salt ions are added during the film-forming process. The silk protein film is then pressed onto paper to form a paper with a silk protein layer, the film layer being 3 micrometers thick.

[0028] Example 2

[0029] (1) The commonly used preparation techniques for silk protein aqueous solution are adopted, namely, silk protein aqueous solution is prepared by degumming, salt dissolution and dialysis.

[0030] (2) The silk protein solution is poured into a film-forming tray and then dried under natural conditions to form a viscous silk protein film. The film-forming process is carried out under ultraviolet light protection, and edible salt ions are added during the film-forming process. The silk protein film is then pressed onto paper to form a paper with a silk protein layer, the film layer being 3 micrometers thick.

[0031] (3) Heat-treat the paper at 60°C for 30 minutes to transform the silk protein from a random coil structure to a β-sheet structure with hydrophobic and oleophobic properties.

[0032] Example 3

[0033] (1) The commonly used preparation techniques for silk protein aqueous solution are adopted, namely, silk protein aqueous solution is prepared by degumming, salt dissolution and dialysis.

[0034] (2) The silk protein solution is poured into a film-forming tray and then dried under natural conditions to form a viscous silk protein film. The film-forming process is carried out under ultraviolet light protection, and edible salt ions are added during the film-forming process. The silk protein film is then pressed onto paper to form a paper with a silk protein layer, the film layer being 3 micrometers thick.

[0035] (3) Heat-treat the paper at 60°C for 30 minutes to transform the silk protein from a random coil structure to a β-sheet structure with hydrophobic and oleophobic properties.

[0036] (4) Take the paper processed in step (3) and press it with a roller with micron and / or nano array pattern. After pressing, the silk protein layer forms a concave-convex array structure with a scale of 500nm.

[0037] Example 4

[0038] (1) The commonly used preparation techniques for silk protein aqueous solution are adopted, namely, silk protein aqueous solution is prepared by degumming, salt dissolution and dialysis.

[0039] (2) The silk protein solution is poured into a film-forming tray and then dried under natural conditions to form a viscous silk protein film. The film-forming process is carried out under ultraviolet light protection, and edible salt ions are added during the film-forming process. The silk protein film is then pressed onto paper to form a paper with a silk protein layer, the film layer being 3 micrometers thick.

[0040] (3) Heat-treat the paper at 60°C for 30 minutes to transform the silk protein from a random coil structure to a β-sheet structure with hydrophobic and oleophobic properties.

[0041] (4) Take the paper processed in step (3) and press it with a roller with micron and / or nano array pattern. After pressing, the silk protein layer forms a concave-convex array structure with a scale of 500nm.

[0042] (5) Take the paper processed in step (4) and irradiate it under ultraviolet light with a wavelength of 290nm for 60 minutes.

[0043] Example 5

[0044] (1) The commonly used preparation technology of silk protein aqueous solution is adopted, namely, the silk protein aqueous solution is prepared by degumming, salt dissolution and dialysis, and lactic acid and lactate are added to the silk protein solution.

[0045] (2) The silk protein solution is coated onto the paper using a brush coating process to form a paper with a silk protein layer, the film thickness being 500 nanometers.

[0046] (3) Heat-treat the paper at 60°C for 30 minutes to transform the silk protein from a random coil structure to a β-sheet structure with hydrophobic and oleophobic properties.

[0047] Example 6

[0048] (1) The commonly used preparation technology of silk protein aqueous solution is adopted, namely, the silk protein aqueous solution is prepared by degumming, salt dissolution and dialysis, and lactic acid and lactate are added to the silk protein solution.

[0049] (2) The silk protein solution is coated onto the paper using a brush coating process to form a paper with a silk protein layer, the film thickness being 500 nanometers.

[0050] (3) Heat-treat the paper at 60°C for 30 minutes to transform the silk protein from a random coil structure to a β-sheet structure with hydrophobic and oleophobic properties.

[0051] (4) Take the paper processed in step (3) and press it with a roller with micron and / or nano array pattern. After pressing, the silk protein layer forms a concave-convex array structure with a scale of 500nm.

[0052] Example 7

[0053] (1) The commonly used preparation technology of silk protein aqueous solution is adopted, namely, the silk protein aqueous solution is prepared by degumming, salt dissolution and dialysis, and lactic acid and lactate are added to the silk protein solution.

[0054] (2) The silk protein solution is coated onto the paper using a brush coating process to form a paper with a silk protein layer, the film thickness being 500 nanometers.

[0055] (3) Heat-treat the paper at 60°C for 30 minutes to transform the silk protein from a random coil structure to a β-sheet structure with hydrophobic and oleophobic properties.

[0056] (4) Take the paper processed in step (3) and press it with a roller with micron and / or nano array pattern. After pressing, the silk protein layer forms a concave-convex array structure with a scale of 500nm.

[0057] (5) Take the paper processed in step (4) and irradiate it under ultraviolet light with a wavelength of 290nm for 60 minutes.

[0058] Example 8

[0059] (1) The commonly used preparation technology of silk protein aqueous solution is adopted, namely, the silk protein aqueous solution is prepared by degumming, salt dissolution and dialysis, and lactic acid and lactate are added to the silk protein solution.

[0060] (2) A silk protein solution is coated onto paper using a spraying process to form a paper with a silk protein layer, the film thickness being 50 nanometers.

[0061] (3) Heat-treat the paper at 60°C for 30 minutes to transform the silk protein from a random coil structure to a β-sheet structure with hydrophobic and oleophobic properties.

[0062] Example 9

[0063] (1) The commonly used preparation technology of silk protein aqueous solution is adopted, namely, the silk protein aqueous solution is prepared by degumming, salt dissolution and dialysis, and lactic acid and lactate are added to the silk protein solution.

[0064] (2) A silk protein solution is coated onto paper using a spraying process to form a paper with a silk protein layer, the film thickness being 50 nanometers.

[0065] (3) Heat-treat the paper at 60°C for 30 minutes to transform the silk protein from a random coil structure to a β-sheet structure with hydrophobic and oleophobic properties.

[0066] (4) Take the paper processed in step (3) and press it with a roller with micron and / or nano array pattern. After pressing, the silk protein layer forms a concave-convex array structure with a scale of 500nm.

[0067] Example 10

[0068] (1) The commonly used preparation technology of silk protein aqueous solution is adopted, namely, the silk protein aqueous solution is prepared by degumming, salt dissolution and dialysis, and lactic acid and lactate are added to the silk protein solution.

[0069] (2) A silk protein solution is coated onto paper using a spraying process to form a paper with a silk protein layer, the film thickness being 50 nanometers.

[0070] (3) Heat-treat the paper at 60°C for 30 minutes to transform the silk protein from a random coil structure to a β-sheet structure with hydrophobic and oleophobic properties.

[0071] (4) Take the paper processed in step (3) and press it with a roller with micron and / or nano array pattern. After pressing, the silk protein layer forms a concave-convex array structure with a scale of 500nm.

[0072] (5) Take the paper processed in step (4) and irradiate it under ultraviolet light with a wavelength of 290nm for 60 minutes.

[0073] The contact angle of the samples prepared in Examples 1-10 was tested using a Dataphysics OCA 40 instrument at an operating temperature of 25°C. Water and edible oil were used as the detection liquids. The results are shown in Table 1.

[0074] Table 1

[0075]

[0076]

[0077] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A method for the preparation of a hydrophobic and oleophobic packaging coating based on silk fibroin, characterized by The method comprises the following steps: (1) preparation of a silk fibroin solution; (2) pouring the silk fibroin solution into a film forming tray and drying the silk fibroin solution into a film in a natural state to obtain a sticky silk fibroin film; The film forming process is carried out under the protection of an ultraviolet lamp, and edible salt ions are added during the film forming process; The silk fibroin film is arranged on paper by pressing to form paper with a silk fibroin layer; (3) transforming the silk fibroin from a random coil structure into a β-sheet structure with hydrophobic and oleophobic properties by heat treatment or silk fibroin conformation transition induced solvent treatment; the heat treatment comprises heat treating the paper at a temperature of 40-100°C for 1 min to 5 h; the silk fibroin conformation transition induced solvent treatment comprises immersing the paper with the silk fibroin layer in 65%-85% acetone or 10%-30% chitosan aqueous solution for 0.5-2 h; (4) taking the paper treated in step (3), and pressing the paper with a roller with a micrometer and / or nanometer array pattern, so that the silk fibroin layer forms a concave-convex array structure with a size of 100 nm-5 μm; (5) taking the paper treated in step (4), and irradiating the paper under ultraviolet light with a wavelength of 100-400 nm for 10 min to 24 h.

2. A method for the preparation of a hydrophobic and oleophobic packaging coating based on silk fibroin, characterized by The method comprises the following steps: (1) preparation of a silk fibroin solution; (2) coating the silk fibroin solution on paper by a brush coating process or a spray coating process to form paper with a silk fibroin layer; (3) transforming the silk fibroin from a random coil structure into a β-sheet structure with hydrophobic and oleophobic properties by heat treatment or silk fibroin conformation transition induced solvent treatment; the heat treatment comprises heat treating the paper at a temperature of 40-100°C for 1 min to 5 h; the silk fibroin conformation transition induced solvent treatment comprises immersing the paper with the silk fibroin layer in 65%-85% acetone or 10%-30% chitosan aqueous solution for 0.5-2 h; (4) taking the paper treated in step (3), and pressing the paper with a roller with a micrometer and / or nanometer array pattern, so that the silk fibroin layer forms a concave-convex array structure with a size of 100 nm-5 μm; (5) taking the paper treated in step (4), and irradiating the paper under ultraviolet light with a wavelength of 100-400 nm for 10 min to 24 h.

3. A method of making a hydrophobic and oleophobic packaging coating based on silk fibroin according to claim 1 or 2, characterized in that: In step (1), an antibacterial material is added to the prepared silk fibroin solution.

4. A method of making a hydrophobic and oleophobic packaging coating based on silk fibroin according to claim 3, characterized in that: The antibacterial material is one or more of a natural antibacterial peptide, a combination of lactic acid and lactic acid salt, a combination of pectin and chitosan, or a combination of natural essential oil and honey.

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