Paper inflatable packaging film and preparation method thereof

Abstract

The invention relates to the field of packaging materials, and particularly discloses a paper inflatable packaging film and a preparation method thereof. The inflatable paper packaging film comprises a protective layer, an isolating layer, a starch kraft paper layer and an antibacterial layer which are arranged in sequence, the raw materials for preparing the protective layer comprise soybean protein isolate and polyvinyl alcohol; the raw materials for preparing the isolating layer comprise soybean protein isolate, epoxy triglyceride and stearic acid; the antibacterial layer is prepared from the following raw materials: lauryl gallate and chitosan. The paper inflatable packaging film has good gas barrier property, moisture barrier property and antibacterial ability, also has good mechanical stability, almost does not have the problems of gas leakage and water leakage in use, and greatly widens the application of the paper inflatable packaging film in the field of food packaging.

Description

Technical Field

[0001] This application relates to the technical field of packaging materials, and in particular to a paper-based inflatable packaging film and its preparation method. Background Technology

[0002] Inflatable packaging film is a flexible packaging material that forms a cushioning structure through gas filling. Its applications cover industrial manufacturing, commercial logistics, and specialized fields, such as the protection of precision instruments and cold chain food transportation. Previously, commonly used inflatable packaging films were co-extruded from nylon and polyethylene; however, they posed environmental threats at every stage of manufacturing, use, and recycling. In recent years, paper packaging has gained popularity due to its biodegradability, safety, renewability, and recyclability. Kraft paper, made from natural cellulose fibers, has better tear strength, high toughness, and resistance to deformation compared to ordinary paper, making inflatable paper packaging film a popular packaging material.

[0003] Due to the safety characteristics of paper-based inflatable packaging films, they are more commonly used in food packaging, especially for foods with short shelf lives such as bread, pastries, and dried fruits, whose flavor can change significantly depending on storage conditions. However, kraft paper has drawbacks such as poor gas barrier properties and high hydrophilicity, which can lead to air and water leakage during use, thus limiting its application in the food packaging field. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a paper-based inflatable packaging film and its preparation method.

[0005] This application provides a paper-based inflatable packaging film, comprising a protective layer, an isolation layer, a starch kraft paper layer, and an antibacterial layer arranged sequentially. The raw materials used to prepare the protective layer include soy protein isolate and polyvinyl alcohol in a weight ratio of (3-5):(3-5). The raw materials used to prepare the isolation layer include soy protein isolate, glycidyl triglyceride, and stearic acid in a weight ratio of 20:(1-3):(1-3). The raw materials used to prepare the antibacterial layer include lauryl gallate and chitosan in a weight ratio of (0.7-0.8):1.

[0006] By adopting the above technical solution, this application designs the paper inflatable packaging film as a layered structure. The outermost layer exposed during use is a protective layer with high mechanical stability, excellent sealing performance, and superior water and gas barrier capabilities, which significantly improves the stability of the paper inflatable packaging film and ensures food quality. The innermost antibacterial layer is in direct contact with the food and has the ability to capture bacteria and kill bacteria upon contact, providing a longer shelf life for the food in the paper inflatable packaging film. The isolation layer and the starch kraft paper layer both have good water resistance, oil resistance, and gas barrier effects, as well as good mechanical strength. Therefore, the paper inflatable packaging film of this application has good gas barrier properties, moisture barrier properties, and antibacterial capabilities, while also having good mechanical stability. During use, there will be almost no air or water leakage problems, greatly expanding its application in the food packaging field.

[0007] Specifically, this application first utilizes starch to coat both sides of kraft paper to form a starch-coated kraft paper layer, which improves the mechanical strength and waterproof ability of the kraft paper. Then, a blend of epoxy triglyceride, soy protein isolate, and stearic acid is coated on one side of the starch-coated kraft paper layer to form a separating layer. The epoxy triglyceride improves the hydrophobic effect of the soy protein isolate, and the reaction product of the two provides a coating with both waterproof and oil-repellent advantages. Furthermore, this application adds stearic acid. The stearic acid distributed internally further hinders the passage of water molecules within the epoxy triglyceride-modified soy protein isolate system, forming a tortuous path and reducing the water molecule passage rate. The stearic acid distributed on the surface forms a hydrophobic structure. Therefore, this separating layer has excellent hydrophobic and oil-repellent capabilities. The excellent film-forming properties of soy protein isolate enhance the bonding force between kraft paper fibers, giving the paper-based inflatable packaging film greater mechanical strength. Subsequently, this application coats a blend of soy protein isolate and polyvinyl alcohol on the other side of the isolation layer to obtain a protective layer. Soy protein isolate has excellent oxygen barrier properties and mechanical strength, while polyvinyl alcohol can form a film with good waterproof capabilities and tensile strength. The blended and coated protective layer effectively isolates external moisture and air. Finally, this application coats a graft product of gallic acid lauryl ester and chitosan on the other side of the starch kraft paper layer to form an antibacterial layer. This antibacterial layer has electrostatic and hydrophobic interactions, which can capture and fix bacteria, giving the antibacterial layer the ability to capture and kill bacteria through contact, effectively reducing the rate of food spoilage.

[0008] Preferably, the raw materials used to prepare the starch kraft paper layer include starch and kraft paper, and the starch includes pea starch and sweet potato starch.

[0009] Preferably, the weight ratio of pea starch to sweet potato starch is 1:(1-2).

[0010] By adopting the above technical solution, this application utilizes a blend of pea starch and sweet potato starch to cover the complex pores on the surface of kraft paper, thereby enhancing the moisture-proof, gas-barrier, and mechanical properties of the kraft paper. Pea starch significantly improves the tensile strength of the kraft paper while exhibiting low moisture absorption and excellent gas-barrier properties. Sweet potato starch significantly enhances the moisture-proof capability of the kraft paper, greatly reducing water vapor permeation from both sides. Therefore, the starch-coated kraft paper layer of this application combines water-barrier and gas-barrier effects, and also possesses high mechanical strength. This application further controls the weight ratio of pea starch to sweet potato starch; when the ratio is (1-2):1, the synergistic effect between the two is optimal.

[0011] Preferably, the raw materials used to prepare the isolation layer include soy protein isolate, epoxy glycerol triester and stearic acid in a weight ratio of 10:1:1.

[0012] By adopting the above technical solution, this application strictly controls the weight ratio of soy protein isolate, epoxy glycerol triester and stearic acid to 10:1:1, which maximizes the water and oil barrier capabilities of the isolation layer. If the amount of epoxy glycerol triester and stearic acid is insufficient, it will not be able to effectively isolate water and oil and improve mechanical strength. However, if the amount of epoxy glycerol triester is too large, it will lead to an excessive proportion of lipophilic substances in the system, reducing the oil barrier effect of the isolation layer.

[0013] Preferably, the raw materials used to prepare the antibacterial layer include gallic acid lauryl ester and chitosan in a weight ratio of 0.75:1.

[0014] By adopting the above technical solution, this application strictly controls the weight ratio of gallic acid lauryl ester and chitosan, and controls the grafting rate of the two products. At this point, the grafting rate is most suitable, so that the product has good antibacterial effect, while ensuring that the rigid structure of the chitosan molecular chain is not excessively damaged. Increasing the grafting amount of gallic acid lauryl ester will lead to a decrease in the tensile strength and elongation at break of the film formed by the product, which will damage the mechanical properties of the antibacterial layer.

[0015] Secondly, this application provides a method for preparing a paper-based inflatable packaging film, comprising the following steps: mixing starch gelatinized liquid at a concentration of 1.5-2 g / m³. 2 The kraft paper is coated on both sides with a certain amount of coating, dried, and a starch kraft paper layer is obtained. Then, on one side of the starch kraft paper layer, a coating is applied at 5-10 g / m². 2 Apply the release coating at a certain amount, dry it, and obtain the release layer. Apply the release coating to the other side of the starch kraft paper layer at a rate of 6-8 g / m. 2 The antibacterial coating is applied at a certain amount, dried for the first time at 40-60℃, washed with alcohol, and dried a second time to obtain the antibacterial layer. The antibacterial layer is then applied to the surface of the isolation layer at a rate of 5-10 g / m². 2The protective layer coating is applied, dried, and rehydrated to obtain the protective layer; after finishing, a paper-based inflatable packaging film is obtained; the preparation method of the isolation layer coating is as follows: soy protein isolate, epoxy glyceryl triester, stearic acid, and silane coupling agent are dispersed in water and stirred to obtain the isolation layer coating; the preparation method of the antibacterial layer coating is as follows: chitosan is dispersed in acetic acid, an initiator is added under acidic environment and inert gas protection, stirring is continued, then lauryl gallate is added, the pH of the system is adjusted to neutral after a period of reaction, the solid precipitates, is filtered, washed, and dried to obtain the product powder, which is then dissolved to obtain the antibacterial layer coating; the preparation method of the protective layer coating is as follows: soy protein isolate is dispersed in water, polyvinyl alcohol and plasticizer are added under alkaline environment and blended to obtain the protective layer coating.

[0016] Preferably, according to 6-7g / m 2 The coating amount of the isolation layer is 8-9 g / m². 2 The coating amount is applied to the protective layer.

[0017] By adopting the above technical solution, this application obtains a starch kraft paper layer, a release layer, a protective layer, and an antibacterial layer by coating, and strictly controls the coating amount during coating, resulting in a paper-based inflatable packaging film that combines good gas barrier properties, moisture barrier properties, and antibacterial ability, while also possessing good mechanical stability. The silane coupling agent used in this application is silane coupling agent KH560, the plasticizer is glycerol, and the initiators are hydrogen peroxide and ascorbic acid. These are merely illustrative examples; those skilled in the art can make adaptive adjustments according to actual needs, and should not be construed as limiting the scope of protection of this application.

[0018] Preferably, the initial drying is a gradient temperature increase, specifically: First, raise the temperature to 40℃ and dry for 1-2 hours. Then raise the temperature to 50℃ and dry for 1-2 hours. Finally, raise the temperature to 60℃ and dry for 1-2 hours, and then perform alcohol washing.

[0019] By adopting the above technical solution, this application uses a gradient heating method in the first drying process when preparing the antibacterial layer. The first heating stage can avoid the problem of film cracking caused by rapid solvent evaporation as much as possible. The second heating stage can promote the orderly arrangement of molecular weight and achieve higher crystallinity. The third heating stage can further reduce the residual solvent content after the antibacterial layer is basically formed and improve its structural stability. Compared with direct heating, gradient heating can make the antibacterial layer more dense and firm, which further improves its waterproof, bacterial capture and contact sterilization capabilities.

[0020] Preferably, during the gradient heating process, the heating rate is controlled to be 2-3℃ / min.

[0021] By adopting the above technical solution, this application further controls the heating rate during gradient heating, thereby further improving its antibacterial and water-blocking capabilities. If the heating rate is too fast, the crystallinity inside the antibacterial layer will be greatly reduced, which will have a negative impact on its mechanical strength, water-blocking capability, gas-blocking capability, and bactericidal capability to varying degrees. If the heating rate is too low, the solvent will not evaporate completely, the surface roughness of the antibacterial layer will increase, the water contact angle will decrease, and water molecules will be more likely to escape, thus reducing its water-blocking effect.

[0022] In summary, this application has the following beneficial technical effects: 1. This application designs the paper inflatable packaging film as a layered structure. The outermost layer exposed during use is a protective layer with high mechanical stability, good sealing performance, and excellent water and gas barrier capabilities, which greatly improves the stability of the paper inflatable packaging film and provides a guarantee for food quality. The innermost antibacterial layer is in direct contact with the food and has the ability to capture bacteria and kill bacteria upon contact, which can provide a longer shelf life for the food in the paper inflatable packaging film. The isolation layer and the starch kraft paper layer both have good water resistance, oil resistance, and gas barrier effects, and also have good mechanical strength. 2. In the preparation method of this application, a starch kraft paper layer, a separating layer, a protective layer and an antibacterial layer are prepared sequentially by coating, and the coating amount is strictly controlled during coating, resulting in a paper-based inflatable packaging film that has good gas barrier properties, moisture barrier properties and antibacterial ability, as well as good mechanical stability. Detailed Implementation

[0023] Material source Unless otherwise specified, all raw materials used in this application are commercially available products, specifically: Kraft paper, food grade, 80g / m² 2 ; Potato starch, sweet potato starch, and pea starch are all food-grade. Polyvinyl alcohol, with an enzymatic hydrolysis degree of 85-90%; Chitosan, 100 kDa; Lauryl gallate, 98% purity.

[0024] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0025] Example 1.1 A method for preparing a paper-based inflatable packaging film includes the following steps: S1. Disperse 50g of potato starch in distilled water to obtain a 5wt% potato starch gelatinization solution. Stir at 95℃ to gelatinize. After complete gelatinization, stir and cool at room temperature. Then add 1.5wt% glycerol and stir until homogeneous. Subsequently, add 2g / m 2 The coating amount was adjusted to coat both sides of the kraft paper, and then dried at 50°C for 24 hours to obtain a starch kraft paper layer. S2. Disperse 200g of soy protein isolate in water to obtain an 8wt% soy protein isolate solution. Stir at 50℃ until completely dissolved, and add sodium hydroxide to adjust the pH to 9. Then disperse 10g of epoxy glyceryl triester, 30g of stearic acid, and 2g of silane coupling agent KH560 in water and stir at 60℃ for 1 hour to obtain the isolation layer coating. Then apply the coating at a ratio of 10g / m 2 The coating amount was adjusted to coat one side of the starch kraft paper layer, and dried at 50°C for 5 minutes to obtain the isolation layer. S3. Disperse 240g of soy protein isolate in water to obtain an 8wt% soy protein isolate solution. Stir at 50℃ until completely dissolved. Add sodium hydroxide to adjust the pH to 10. Add 400g of polyvinyl alcohol and stir for 1 hour. Then add 48g of glycerin and continue stirring for 20 minutes to obtain a protective coating. Apply the coating at a concentration of 5g / m 2 The isolation layer was coated on one side and dried at 50°C for 24 hours, followed by rehumidification at 40% humidity and 20°C for 24 hours to obtain the protective layer; S4, 200g of chitosan was dispersed in 8L of acetic acid aqueous solution (2%, v / v), and 1.3g of hydrogen peroxide and 0.7g of ascorbic acid were added under the conditions of pH=4 and nitrogen protection, and stirring was continued. Then 160g of gallic acid lauryl ester was added, and the reaction was carried out at room temperature for 24 hours. The pH of the system was adjusted to neutral, and the solid precipitated. The solid was collected by suction filtration, washed with 85wt% ethanol, and freeze-dried for 24 hours to obtain the product powder. The powder was dispersed in 8L of acetic acid aqueous solution (2%, v / v) to obtain the antibacterial coating layer, according to 8g / m 2 The coating amount was adjusted to coat the other side of the starch kraft paper layer. The coating was first dried at 60°C for 5 hours, washed with 85wt% ethanol, and then dried again at 40°C overnight to obtain the antibacterial layer. S5. After sorting, a paper-based inflatable packaging film is obtained.

[0026] Example 1.2 A method for preparing a paper-based inflatable packaging film includes the following steps: S1. Disperse 50g of potato starch in distilled water to obtain a 5wt% potato starch gelatinization solution. Stir at 95℃ to gelatinize. After complete gelatinization, stir and cool at room temperature. Then add 1.5wt% glycerol and stir until homogeneous. Subsequently, add 1.5g / m 2 The coating amount was adjusted to coat both sides of the kraft paper, and then dried at 50°C for 24 hours to obtain a starch kraft paper layer. S2. Disperse 200g of soy protein isolate in water to obtain an 8wt% soy protein isolate solution. Stir at 50℃ until completely dissolved, and add sodium hydroxide to adjust the pH to 9. Then disperse 30g of epoxy glyceryl triester, 10g of stearic acid, and 2g of silane coupling agent KH560 in water and stir at 60℃ for 1 hour to obtain the isolation layer coating. Then apply the coating at a ratio of 5g / m 2 The coating amount was adjusted to coat one side of the starch kraft paper layer, and dried at 50°C for 5 minutes to obtain the isolation layer. S3. Disperse 400g of soy protein isolate in water to obtain an 8wt% soy protein isolate solution. Stir at 50℃ until completely dissolved. Add sodium hydroxide to adjust the pH to 10. Add 240g of polyvinyl alcohol and stir for 1 hour. Then add 80g of glycerin and continue stirring for 20 minutes to obtain the protective coating. Apply at 10g / m 2 The isolation layer was coated on one side and dried at 50°C for 24 hours, followed by rehumidification at 40% humidity and 20°C for 24 hours to obtain the protective layer; S4, 200g of chitosan was dispersed in 8L of acetic acid aqueous solution (2%, v / v), and 1.3g of hydrogen peroxide and 0.7g of ascorbic acid were added under the protection of nitrogen at pH=4. The mixture was stirred continuously, and then 140g of gallic acid lauryl ester was added. After reacting at room temperature for 24 hours, the pH of the system was adjusted to neutral, and a solid precipitated. The solid was collected by filtration, washed with 85wt% ethanol, and freeze-dried for 24 hours to obtain the product powder. This powder was dispersed in 8L of acetic acid aqueous solution (2%, v / v) to obtain the antibacterial coating layer, which was then applied at 6g / m 2 The coating amount was adjusted to coat the other side of the starch kraft paper layer. The coating was first dried at 40°C for 5 hours, washed with 85wt% ethanol, and then dried again at 40°C overnight to obtain the antibacterial layer. S5. After sorting, a paper-based inflatable packaging film is obtained.

[0027] Example 2.1 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that: all potato starch in step S1 is replaced with pea starch, while the rest is the same as in Example 1.1.

[0028] Example 2.2 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that: all potato starch in step S1 is replaced with sweet potato starch, while the rest is the same as in Example 1.1.

[0029] Example 2.3 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that: all potato starch in step S1 is replaced with pea starch and potato starch in a weight ratio of 1:1, while the rest is the same as in Example 1.1.

[0030] Example 2.4 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that: all potato starch in step S1 is replaced with sweet potato starch and potato starch in a weight ratio of 1:1, while the rest is the same as in Example 1.1.

[0031] Example 2.5 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that: all potato starch in step S1 is replaced with pea starch and sweet potato starch in a weight ratio of 1:1, while the rest is the same as in Example 1.1.

[0032] Example 3.1 A method for preparing a paper-based inflatable packaging film differs from Example 2.5 in that the weight ratio of pea starch to sweet potato starch in step S1 is 1:2, while the rest is the same as in Example 2.5.

[0033] Example 3.2 A method for preparing a paper-based inflatable packaging film differs from Example 2.5 in that the weight ratio of pea starch to sweet potato starch in step S1 is 1:0.5, while the rest is the same as in Example 2.5.

[0034] Example 3.3 A method for preparing a paper-based inflatable packaging film differs from Example 2.5 in that the weight ratio of pea starch to sweet potato starch in step S1 is 1:3, while the rest is the same as in Example 2.5.

[0035] Example 4.1 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that: in step S2, the amount of epoxy glycerol triester is 35g and the amount of stearic acid is 5g, while the rest are the same as in Example 1.1.

[0036] Example 4.2 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that: in step S2, the amount of epoxy glycerol triester is 5g, the amount of stearic acid is 5g, and the rest are the same as in Example 1.1.

[0037] Example 4.3 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that: in step S2, the amount of epoxy glycerol triester is 20g and the amount of stearic acid is 20g, while the rest are the same as in Example 1.1.

[0038] Example 5.1 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that: in step S4, the amount of lauryl gallate used is 145g, while the rest are the same as in Example 1.1.

[0039] Example 5.2 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that: in step S4, the amount of lauryl gallate used is 150g, while the rest is the same as in Example 1.1.

[0040] Example 5.3 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that: in step S4, the amount of lauryl gallate used is 155g, while the rest is the same as in Example 1.1.

[0041] Example 6.1 A method for preparing a paper-based inflatable packaging film, differing from Example 1.1 in that: in step S2, the release layer coating is applied at a ratio of 7 g / m³. 2 The coating amount is applied to the starch kraft paper layer on one side. In step S3, the protective coating is applied at a rate of 8 g / m². 2 The coating amount was applied to one side of the isolation layer, and the rest were the same as in Example 1.1.

[0042] Example 6.2 A method for preparing a paper-based inflatable packaging film, differing from Example 1.1 in that: in step S2, the release layer coating is applied at a ratio of 6 g / m³. 2 The coating amount is applied to the starch kraft paper layer on one side. In step S3, the protective coating is applied at a rate of 9 g / m². 2 The coating amount was applied to one side of the isolation layer, and the rest were the same as in Example 1.1.

[0043] Example 7.1 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that the initial drying in step S4 is a gradient temperature increase. Specifically, after coating one side of the starch kraft paper layer, the temperature is first raised to 40°C and dried for 2 hours, then raised to 50°C and dried for 1 hour, and finally raised to 60°C and dried for 2 hours, followed by alcohol washing. During the gradient temperature increase, the heating rate is controlled at 1°C / min, and the rest is the same as in Example 1.1.

[0044] Example 7.2 A method for preparing a paper-based inflatable packaging film differs from Example 1.1 in that the initial drying in step S4 is a gradient temperature increase. Specifically, after coating one side of the starch kraft paper layer, the temperature is first raised to 40°C and dried for 2 hours, then raised to 50°C and dried for 2 hours, and finally raised to 60°C and dried for 1 hour, followed by alcohol washing. During the gradient temperature increase, the heating rate is controlled at 1°C / min, and the rest is the same as in Example 1.1.

[0045] Example 8.1 A method for preparing a paper-based inflatable packaging film differs from Example 7.1 in that: during the gradient heating process in step S4, the heating rate is controlled at 2℃ / min, while the rest is the same as in Example 7.1.

[0046] Example 8.2 A method for preparing a paper-based inflatable packaging film differs from Example 7.1 in that: during the gradient heating process in step S4, the heating rate is controlled at 3℃ / min, while the rest is the same as in Example 7.1.

[0047] Example 8.3 A method for preparing a paper-based inflatable packaging film differs from Example 7.1 in that: during the gradient heating process in step S4, the heating rate is controlled at 4℃ / min, while the rest is the same as in Example 7.1.

[0048] Example 9 A method for preparing a paper-based inflatable packaging film includes the following steps: S1. Disperse 20g of pea starch and 30g of sweet potato starch in distilled water to obtain a 5wt% pea starch-sweet potato starch gelatinization solution. Stir at 95℃ to gelatinize. After complete gelatinization, stir and cool at room temperature. Then add 1.5wt% glycerol and stir until homogeneous. Subsequently, add 2g / m 2 The coating amount was adjusted to coat both sides of the kraft paper, and then dried at 50°C for 24 hours to obtain a starch kraft paper layer. S2. Disperse 200g of soy protein isolate in water to obtain an 8wt% soy protein isolate solution. Stir at 50℃ until completely dissolved, and add sodium hydroxide to adjust the pH to 9. Then disperse 20g of epoxy glyceryl triester, 20g of stearic acid, and 2g of silane coupling agent KH560 in water and stir at 60℃ for 1 hour to obtain the isolation layer coating. Then apply the coating at a concentration of 6.5g / m 2 The coating amount was adjusted to coat one side of the starch kraft paper layer, and dried at 50°C for 5 minutes to obtain the isolation layer. S3. Disperse 240g of soy protein isolate in water to obtain an 8wt% soy protein isolate solution. Stir at 50℃ until completely dissolved. Add sodium hydroxide to adjust the pH to 10. Add 400g of polyvinyl alcohol and stir for 1 hour. Then add 48g of glycerin and continue stirring for 20 minutes to obtain the protective coating. (Note: The last sentence appears to be incomplete and possibly refers to a specific coating formula. It doesn't translate directly but can be left as is.) 2 The isolation layer was coated on one side and dried at 50°C for 24 hours, followed by rehumidification at 40% humidity and 20°C for 24 hours to obtain the protective layer; S4, 200g of chitosan was dispersed in 8L of acetic acid aqueous solution (2%, v / v), and 1.3g of hydrogen peroxide and 0.7g of ascorbic acid were added under nitrogen protection at pH=4. The mixture was stirred continuously, and then 150g of gallic acid lauryl ester was added. After reacting at room temperature for 24 hours, the pH of the system was adjusted to neutral, and a solid precipitated. The solid was collected by filtration, washed with 85wt% ethanol, and freeze-dried for 24 hours to obtain the product powder. This powder was dispersed in 8L of acetic acid aqueous solution (2%, v / v) to obtain the antibacterial coating layer. 2 The coating amount was adjusted to coat the other side of the starch kraft paper layer. First, the temperature was raised to 40℃ and dried for 2 hours. Then, the temperature was raised to 50℃ and dried for 1 hour. Finally, the temperature was raised to 60℃ and dried for 2 hours. Then, the paper was washed with alcohol and dried overnight at 40℃ to obtain the antibacterial layer. During the gradient temperature increase, the temperature increase rate was controlled at 2.5℃ / min. S5. After sorting, a paper-based inflatable packaging film is obtained.

[0049] Comparative Example 1.1 The difference from Example 1.1 is that the coating order of the isolation layer and the protective layer is reversed, while the rest is the same as in Example 1.1.

[0050] Comparative Example 1.2 The difference from Example 1.1 is that the position of the isolation layer is adjusted to be between the starch kraft paper layer and the antibacterial layer, while the rest is the same as in Example 1.1.

[0051] Comparative Example 2.1 The difference from Example 1.1 is that in step S2, the epoxy glycerol triester and silane coupling agent KH560 are removed, the amount of stearic acid is 40g, and the rest are the same as in Example 1.1.

[0052] Comparative Example 2.2 The difference from Example 1.1 is that in step S2, stearic acid is removed, the amount of epoxy glycerol triester is 40g, and the rest is the same as in Example 1.1.

[0053] Performance testing 1. Water resistance performance: The water vapor permeability (WVP) of the paper-insulated packaging film was tested according to GB / T 1037-2021 "Test Method for Water Vapor Permeability of Plastic Films and Sheets - Cup Method". 2 • 24h), temperature 23℃, relative humidity 90%, the results are recorded in Table 1; 2. Gas barrier properties: The oxygen permeability of the paper-filled packaging film was tested according to GB / T 19789-2021 "Test Method for Oxygen Permeability of Plastic Films and Sheets in Packaging Materials - Coulometric Test" [cm]. 3 / (m 2 Record the results in Table 1. 3. Oil resistance performance: The oil resistance of the paper inflatable packaging film was tested according to GB / T 22805.2-2008 "Determination of oil resistance of paper and paperboard" at a temperature of 23℃ and a relative humidity of 50%. The oil resistance value was recorded in Table 1 (the oil resistance value is divided into 12 grades from 1 to 12, with grade 12 representing the best oil resistance and grade 1 representing the worst oil resistance). 4. Mechanical Properties: The tensile strength TS (MPa) was measured using an HD-B609B-S tensile testing machine. The initial tensile distance was 30 mm, the tensile rate was 50 mm / min, and each sample was measured 5 times, with the average value taken. TS = F max / S,F max S is the maximum load (N), and S is the initial cross-sectional area (mm). 2 Record the results in Table 1; 5. Antibacterial properties: Select fresh yellow apricots with similar color, size, and no mechanical damage or pests. First, clean the surface of the yellow apricots with sterile water, and after drying, set up 29 groups of 50 apricots each (including one blank control group, i.e., no packaging of yellow apricots). Seal the apricots with the paper inflatable packaging film of this application and store them at room temperature. After 10 days, calculate the decay rate. The decay standard is that the skin of the yellow apricots changes color and becomes damaged. These are recorded as decayed individuals. The decay rate % = number of decayed individuals / 50. Record the results in Table 1.

[0054] Table 1 Performance Test Table Data Analysis: As shown in Table 1, the WVP of the paper-based inflatable packaging film in Examples 1.1-1.2 is 243.9 g / m³. 2 ·24h-245.6g / m 2 • Oxygen permeability over 24 hours was 7.6 cm. 3 / (m 2 ·d)-7.8cm 3 / (m 2 ·d), with a grease resistance rating of 8, a TS of 9.45MPa-10.12MPa, and a yellow apricot rot rate of 20%-30%, it can be seen that the paper-based inflatable packaging film of this application does indeed have good gas barrier properties, moisture barrier properties, and antibacterial capabilities, while also having good mechanical stability. Therefore, it will hardly have any problems with air or water leakage during use, which greatly expands its application in the food packaging field.

[0055] In Examples 2.1-2.5, this application changed the type of starch in the starch kraft paper layer. The results showed that the WVP and oxygen permeability of Example 2.5 were significantly reduced, while the TS value increased. It can be seen that this application uses a compound of pea starch and sweet potato starch to coat kraft paper, which can cover the complex pores on the surface of the kraft paper, thereby enhancing the moisture resistance, gas barrier, and mechanical properties of the kraft paper. Among them, pea starch can significantly improve the tensile strength of kraft paper, while having a low moisture absorption rate and excellent gas barrier properties. Sweet potato starch can greatly improve the moisture resistance of kraft paper and greatly reduce the water vapor permeation on both sides of the kraft paper. Therefore, the starch kraft paper layer of this application has both water barrier and gas barrier effects, and also has high mechanical strength.

[0056] In Examples 3.1-3.3, the weight ratio of pea starch and sweet potato starch was changed. The results showed that the paper-based inflatable packaging films of Examples 2.5 and 3.1 had good comprehensive performance, and all indicators were at a high level. However, the WVP of Example 3.2 was much higher than that of Examples 2.5 and 3.1, the oxygen permeability of Example 3.3 was increased, and the TS was lower than that of Examples 2.5 and 3.1. It can be seen that the present application further controlled the weight ratio of pea starch and sweet potato starch to (1-2):1, so that the synergistic effect between the two reached the optimal level.

[0057] In Examples 4.1-4.3, this application changed the amount of epoxy triglyceride and stearic acid added. The grease resistance value of Example 4.1 decreased significantly, and the grease resistance value and TS of Example 4.2 both decreased, while WVP and oxygen permeability also increased to some extent. The paper-based inflatable packaging film of Example 4.3 has good comprehensive performance, and all indicators are at a high level. It can be seen that this application controls the weight ratio of soy protein isolate, epoxy triglyceride and stearic acid to 10:1:1, which maximizes the water and oil barrier capabilities of the isolation layer. If the amount of epoxy triglyceride and stearic acid is insufficient, it will not be able to effectively isolate water and oil and improve mechanical strength. However, if the amount of epoxy triglyceride is too large, it will lead to an excessive proportion of lipophilic substances in the system, reducing the oil barrier effect of the isolation layer.

[0058] In Examples 5.1-5.3, the amount of lauryl gallate was adjusted. The results showed that the paper-based inflatable packaging film of Example 5.2 had good comprehensive performance, with all indicators at a high level. The WVP of Example 5.1 was too high, and the rotting rate of Example 5.3 was too high. It can be seen that by strictly controlling the weight ratio of lauryl gallate and chitosan, the product has good antibacterial effect while ensuring that the rigid structure of the chitosan molecular chain is not excessively damaged. Increasing the grafting amount of lauryl gallate will lead to a decrease in the tensile strength and elongation at break of the film formed by the product, which will damage the mechanical properties of the antibacterial layer.

[0059] In Examples 6.1-6.2, this application changed the coating amount of the isolation layer and the protective layer. The results showed that the paper inflatable packaging film had good comprehensive performance, and all indicators were at a high level. It can be seen that this application adjusted the layer thickness by strictly controlling the coating amount between each layer, so that the layer structure distribution was more reasonable, and a paper inflatable packaging film with good gas barrier, moisture barrier and antibacterial ability, as well as good mechanical stability was obtained.

[0060] In Examples 7.1-7.2, this application changed the operation in the preparation of the antibacterial layer. The initial drying method was changed to gradient heating. The results showed that the paper inflatable packaging film had good comprehensive performance, and all indicators were at a high level. It can be seen that gradient heating, compared with direct heating, can make the antibacterial layer more dense and firm, which further improves its waterproof, bacterial capture and contact sterilization capabilities.

[0061] In Examples 8.1-8.3, the heating rate during gradient heating was changed. The results showed that the paper inflatable packaging film of Examples 8.1-8.2 had better data, especially WVP and oxygen permeability, which were significantly lower than those of Examples 7.1 and 8.3, and TS was much higher than that of Example 8.3. It can be seen that by further controlling the heating rate during gradient heating, the antibacterial ability and water-blocking ability of the present application have been further improved.

[0062] In Example 9, this application strictly controlled the types of starch in the starch kraft paper layer and the ratio between different starches, the amount of epoxy triglyceride and stearic acid added in the release layer, and the amount of gallic acid lauryl ester in the antibacterial layer. Furthermore, it optimized the coating amount of the release layer and protective layer, as well as several parameters during the drying process of the antibacterial layer. The results showed that the WVP of the paper-based inflatable packaging film was 168.4 g / m³. 2 • Oxygen permeability over 24 hours was 5.8 cm. 3 / (m 2 ·d), with a grease resistance rating of 9, a TS of 11.13 MPa, and a yellow apricot rot rate as low as 14%, it can be seen that this application integrates the optimal factors between different layers and can indeed achieve a significant optimization effect on the comprehensive performance of paper inflatable packaging film.

[0063] In Comparative Examples 1.1-1.2, this application changed the arrangement order and composition of the layer structure. The results showed that the overall performance of the paper inflatable packaging film decreased significantly. It can be seen that this application designs the paper inflatable packaging film as a layer structure. The outer layer exposed during use is a protective layer with high mechanical stability, good sealing performance and excellent water and gas barrier capabilities, which greatly improves the stability of the paper inflatable packaging film and provides a guarantee for food quality. The innermost antibacterial layer is in direct contact with the food and has the ability to capture bacteria and kill bacteria through contact, which can provide a longer shelf life for the food in the paper inflatable packaging film. The isolation layer and the starch kraft paper layer both have good water resistance, oil resistance and gas barrier effects, and also have good mechanical strength.

[0064] In Comparative Examples 2.1-2.2, this application changed the internal composition of the isolation layer. The results showed that the overall performance of the paper inflatable packaging film decreased significantly. It can be seen that epoxy triglyceride can improve the hydrophobic effect of soy protein isolate. The reaction product of the two can form a coating that has the dual advantages of being waterproof and oil-proof. Stearic acid can further hinder the passage of water molecules in the epoxy triglyceride-modified soy protein isolate system, which is not water-absorbing, forming a tortuous path and reducing the passage rate of water molecules. The stearic acid distributed on the surface can form a hydrophobic structure. Therefore, the isolation layer has good hydrophobic and oil-proof capabilities. The excellent film-forming properties of soy protein isolate can enhance the bonding force between kraft paper fibers, giving the paper inflatable packaging film greater mechanical strength.

[0065] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A paper-based inflatable packaging film, characterized in that, It includes a protective layer, an isolation layer, a starch kraft paper layer, and an antibacterial layer arranged in sequence; The raw materials used to prepare the protective layer include soy protein isolate and polyvinyl alcohol in a weight ratio of (3-5):(3-5); The raw materials used to prepare the isolation layer include soy protein isolate, epoxy glycerol triester and stearic acid in a weight ratio of 20:(1-3):(1-3); The raw materials used to prepare the antibacterial layer include gallic acid lauryl ester and chitosan in a weight ratio of (0.7-0.8):

1.

2. The paper-based inflatable packaging film according to claim 1, characterized in that, The raw materials used to prepare the starch kraft paper layer include starch and kraft paper, and the starch includes pea starch and sweet potato starch.

3. The paper-based inflatable packaging film according to claim 2, characterized in that, The weight ratio of pea starch to sweet potato starch is 1:(1-2).

4. The paper-based inflatable packaging film according to claim 1, characterized in that, The raw materials used to prepare the isolation layer include soy protein isolate, epoxy glycerol triester and stearic acid in a weight ratio of 10:1:

1.

5. The paper-based inflatable packaging film according to claim 1, characterized in that, The raw materials used to prepare the antibacterial layer include gallic acid lauryl ester and chitosan in a weight ratio of 0.75:

1.

6. A method for preparing a paper-based inflatable packaging film according to any one of claims 1-5, characterized in that, Includes the following steps: The starch gelatinization solution was prepared at a concentration of 1.5-2 g / m³. 2 The kraft paper is coated on both sides with a certain amount of coating, dried, and a starch kraft paper layer is obtained. Then, on one side of the starch kraft paper layer, a coating is applied at 5-10 g / m². 2 Apply the release coating at a certain amount, dry it, and obtain the release layer. Apply the release coating to the other side of the starch kraft paper layer at a rate of 6-8 g / m. 2 The antibacterial coating is applied at a certain amount, dried for the first time at 40-60℃, washed with alcohol, and dried a second time to obtain the antibacterial layer. The antibacterial layer is then applied to the surface of the isolation layer at a rate of 5-10 g / m². 2 The protective coating is applied, dried, and rehumidified to obtain the protective layer; after finishing, a paper-based inflatable packaging film is obtained. The method for preparing the isolation layer coating is as follows: dispersing soy protein isolate, epoxy glyceryl triester, stearic acid and silane coupling agent in water, stirring, to obtain the isolation layer coating; The preparation method of the antibacterial coating is as follows: Chitosan is dispersed in acetic acid, an initiator is added under acidic environment and inert gas protection, stirring is continued, then lauryl gallate is added, the pH of the system is adjusted to neutral after a period of reaction, solid precipitates, is filtered, washed, dried, and the product powder is obtained. After dissolving it, the antibacterial coating is obtained. The protective coating is prepared by dispersing soy protein isolate in water, adding polyvinyl alcohol and plasticizer under alkaline conditions, and continuing to blend to obtain the protective coating.

7. The method for preparing a paper-based inflatable packaging film according to claim 6, characterized in that, According to 6-7g / m 2 The coating amount of the isolation layer is 8-9 g / m². 2 The coating amount is applied to the protective layer.

8. The method for preparing a paper-based inflatable packaging film according to claim 6, characterized in that, The initial drying process involves a gradient temperature increase, specifically: First, raise the temperature to 40℃ and dry for 1-2 hours. Then raise the temperature to 50℃ and dry for 1-2 hours. Finally, raise the temperature to 60℃ and dry for 1-2 hours, and then perform alcohol washing.

9. The method for preparing a paper-based inflatable packaging film according to claim 8, characterized in that, During the gradient heating process, the heating rate is controlled to be 2-3℃ / min.

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