Food waterproof and oil-proof paper and preparation method thereof

Abstract

The application relates to the papermaking technical field and particularly relates to a food waterproof and oil-proof paper and a preparation method thereof, which is composed of a base paper and a coating layer covering the surface of the base paper; the base paper comprises the following preparation raw materials: sisal fiber, polylactic acid fiber, water glass, nano silicon dioxide, starch and polyacrylamide; the coating layer is prepared by coating a coating liquid on the surface of the base paper and then drying and calendering to obtain the coating layer; the coating liquid comprises the following preparation raw materials: modified fucoidan, polybutylene succinate, modified nano cellulose, sorbitol, polyaluminum silicate sulfate, polyvinyl alcohol, sodium thiosulfate and water. The food waterproof and oil-proof paper has the advantages that the waterproof and oil-proof properties are improved, the food preservation effect is improved, and the food has certain antibacterial property and strength.

Description

Technical Field

[0001] The present application relates to the field of papermaking technology, and in particular to a food waterproof and oil-proof paper and a preparation method thereof. Background Art

[0002] With the improvement of living standards, people have higher and higher demands for environmental protection and safety of food packaging. Traditional plastic food packaging materials are prone to polluting the environment and affecting public health and safety. Therefore, green packaging materials have become an inevitable trend in the development of modern food packaging.

[0003] Paper-based materials, due to their biodegradability, strong renewability, and ease of surface modification, have gained widespread recognition as a versatile substrate and are considered the most promising green and sustainable packaging material. They are widely used in the packaging industry. However, paper-based materials' high porosity, strong hydrophilicity, and lack of oil resistance significantly limit their use in food packaging.

[0004] Therefore, improving paper's oil and water resistance is key to expanding its application in food packaging. Currently, two common methods for treating paper are paper-plastic composites and paper coating. Paper-plastic composites typically offer excellent barrier and heat-sealing properties, but they are not conducive to paper recycling. Paper coating offers simple processing and ease of production. However, the inherent properties of ordinary base paper remain unchanged, and its compatibility with the coating is limited. The choice of coating itself, along with the overall performance of food-grade water and oil-proof paper, can also be affected. Summary of the Invention

[0005] The present application aims to overcome at least one of the defects of the prior art and provide a food waterproof and oil-proof paper and a preparation method thereof. The food waterproof and oil-proof paper improves the waterproof and oil-proof properties through the combination of raw materials while having certain antibacterial properties and strength, thereby improving the food preservation effect.

[0006] In a first aspect, the embodiments of the present application provide a food waterproof and oil-proof paper, which is implemented by the following technical solutions:

[0007] A food waterproof and oil-proof paper, comprising a base paper and a coating layer covering the surface of the base paper;

[0008] The base paper comprises the following raw materials in parts by weight: 10-15 parts of sisal fiber, 3-5 parts of polylactic acid fiber, 2-4 parts of water glass, 1-1.5 parts of nano silicon dioxide, 1-2 parts of starch, and 1-2 parts of polyacrylamide;

[0009] The preparation of the coating layer comprises the following steps: applying the coating liquid to the surface of the base paper, and then drying and calendering to obtain the coating layer;

[0010] The coating liquid comprises the following raw materials by weight: modified fucoidan 15-25 parts, polybutylene succinate 8-15 parts, modified nanocellulose 1-2 parts, sorbitol 1-1.5 parts, polyaluminum silicate sulfate 0.5-1.5 parts, polyvinyl alcohol 0.1-0.5 parts, sodium thiosulfate 0.1-0.3 parts, and water 50-70 parts.

[0011] The food waterproof and oil-proof paper according to the embodiment of the present application has at least the following beneficial effects:

[0012] The food waterproof and oil-proof paper of the present application has certain antibacterial property and strength while improving waterproof and oil-proof property through the selection and collocation of raw materials of the base paper and the coating layer, thereby improving food preservation effect.

[0013] The sisal fiber of the present application has high toughness and tensile strength, and the addition of polylactic acid fiber can improve the uniformity and flexibility of the paper, and the combination of the two can synergistically improve the tensile strength, burst strength and tear strength of the paper; in addition, the sisal fiber naturally contains lignin and pectin, and has certain antibacterial property; the polylactic acid fiber can enhance the barrier property of the paper to oil, and in combination with the pore structure of the sisal fiber, the air permeability of the paper can be better controlled.

[0014] The silica acid colloid generated by the hydrolysis of the water glass of the present application can be adsorbed on the surface of the fiber, promote the combination between the fibers through hydrogen bond and van der Waals force, improve the tensile strength and burst strength of the paper, and the negatively charged silica acid colloid can form a flocculation network with starch and the like, reduce the loss of fine fibers and nanometer silicon dioxide, and improve the utilization rate of raw materials; in the beating or papermaking process, the adsorption of the silica acid colloid can also make the sisal fiber and the polylactic acid fiber disperse uniformly, and improve the paper evenness.

[0015] The starch of the present application can improve the bonding strength between the fibers through charge effect. The nanometer silicon dioxide can fill the pores between the fibers of the paper, reduce water permeability, and at the same time improve the mechanical strength of the paper.

[0016] The fucoidan of the present application has good film-forming property, good water resistance and air permeability, and can protect food from easy spoilage and deterioration; the acetylsalicylic acid modified fucoidan has a hydrophilic group introduced, and the solubility in water is improved, which can enhance the flexibility of the film, and at the same time increase the interaction points between the fucoidan and the fibers, thereby improving the bonding strength between the coating layer and the base paper.

[0017] The polybutylene succinate of the present application can form a chemical bond with the fibers of the base paper, thereby improving the dry strength and wet strength of the paper; the flexible molecular chain can reduce the brittleness of the paper, so that the paper can maintain strength while improving folding resistance and toughness; the hydrophobic property can effectively reduce the water absorption rate of the paper, and at the same time reduce the water vapor and oxygen transmission rates, reduce the moisture absorption and oxidation of food, and prolong the food preservation period.

[0018] The modified nanocellulose of the present application has a large specific surface area and abundant hydroxyl groups, and can be tightly combined with fibers, thereby improving the inter-fiber bonding force and the strength of paper, and improving the reliability of food packaging paper.

[0019] According to some embodiments of the present application, the weight ratio of the base paper to the coating liquid on each surface is 1:0.08-0.15.

[0020] According to some embodiments of the present application, the drying temperature is 70°C.

[0021] According to some embodiments of the present application, the drying time is 30 minutes.

[0022] According to some embodiments of the present application, after drying, the step of placing the dried sample in a constant temperature and humidity environment for equilibrium is also included.

[0023] Furthermore, the balancing time is 24 hours.

[0024] Furthermore, the temperature of the constant temperature and humidity environment is 22-24° C., and the relative humidity of the constant temperature and humidity environment is 48%-52%.

[0025] According to some embodiments of the present application, the method for preparing the modified fucoidan comprises the following steps:

[0026] Add fucoidan to acetylsalicylic acid solution, add 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stir, react at a temperature of 70-90°C for 2h-4h, then cool the solution, adjust the pH to 6.5-7.5, dialyze with tap water for 40h-50h, dialyze with distilled water for 20h-30h, and then freeze-dry to obtain modified fucoidan.

[0027] Furthermore, the usage ratio of the fucoidan, the acetylsalicylic acid and the 1-ethyl-(3-dimethylaminopropyl)carbodiimide is (5-10) mg:(0.04-0.06) mmol:(0.05-0.1) mmol.

[0028] According to some embodiments of the present application, the preparation method of the modified nanocellulose includes the following steps: taking 40.0g of nanocellulose and adding 60mL of water, and obtaining a nanocellulose suspension through high-speed shearing; taking 1.0g of stearic acid and adding it to 20mL of ethanol solution, heating and stirring at a temperature of 85°C to dissolve, heating the nanocellulose suspension to 85°C and then adding and blending, stirring at 85°C for 2h to obtain modified nanocellulose.

[0029] According to some embodiments of the present application, the preparation of the base paper comprises the following steps:

[0030] S1. The sisal fibers, polylactic acid fibers and 80-100 parts of water were mixed and continuously beaten to a beating degree of 50-55 ° SR to obtain a fiber slurry;

[0031] S2. Add water glass and nano-silica to the fiber slurry, stir for 30-60min, and mix again and continuously beat to a beating degree of 30-40° SR to obtain a mixed slurry;

[0032] S3. Add starch and polyacrylamide, mix evenly with the mixed slurry, dilute to a concentration of 0.1-0.6% for online printing, and use a Fourdrinier papermaking machine to make wet paper sheets. After pressing, preliminary drying is performed to obtain base paper.

[0033] According to some embodiments of the present application, the preparation of the coating solution comprises the following steps:

[0034] A1. Add modified fucoidan, polyvinyl alcohol, and aluminum polysilicate sulfate to water according to parts by weight and stir at 50-60°C and 5000-10000 rpm for 30-45 minutes. Then adjust the speed to 100-300 rpm, add sorbitol and sodium thiosulfate, and continue stirring at 60-70°C and 150-300 rpm for 45-60 minutes to obtain a premix.

[0035] A2. The modified nanocellulose is prepared into a suspension having a concentration of 2-6%;

[0036] A3. Add polybutylene succinate and modified nanocellulose suspension to the premix and stir at room temperature at a speed of 1000-3000 r / min for 30-45 min to obtain a coating solution.

[0037] In a second aspect, the present invention provides a method for preparing the aforementioned waterproof and oil-proof food paper, which is achieved through the following technical solutions:

[0038] A method for preparing food waterproof and oil-proof paper comprises the following steps:

[0039] The coating liquid is coated on both sides of the surface of the base paper, and then dried and calendered to obtain the food waterproof and oil-proof paper.

[0040] The method for preparing food waterproof and oil-proof paper according to the embodiment of the present application has at least the following beneficial effects:

[0041] The preparation method of the present application has simple steps, does not require the use of complex production equipment, has low cost, is pollution-free during the manufacturing process, does not emit toxic substances, does not harm the health of operators, and is suitable for industrial production. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present application more clear, further detailed description will be made in combination with specific embodiments. The embodiments described herein are only part of the embodiments of the present application, and cannot be understood as a limitation on the protection scope of the present application. Embodiment 1

[0043] Preparation of food waterproof and oil-proof paper:

[0044] (1) Preparation of base paper: 13 parts of sisal fiber, 4 parts of polylactic acid fiber and 90 parts of water were mixed and continuously beaten according to weight parts, and the beating degree was 53°SR to obtain a fiber slurry; 3 parts of water glass and 1.3 parts of nano-silicon dioxide were added to the fiber slurry, stirred for 45 min, and continuously beaten again, and the beating degree was 35°SR to obtain a mixed slurry; 1.5 parts of starch and 1.5 parts of polyacrylamide were added and uniformly mixed with the mixed slurry, and were diluted to a wire concentration of 0.1-0.6%, and a wet paper sheet was prepared by a long net paper machine, and after pressing, preliminary drying was performed to obtain a base paper;

[0045] (2) Preparation of modified fucoidan: fucoidan was added to an acetylsalicylic acid solution, 1-ethyl-(3-dimethylaminopropyl) carbonyldiimide was added, stirred, reacted at a temperature of 80℃ for 3h, then the solution was cooled and the pH was adjusted to 7, and the solution was dialyzed with tap water for 45h and distilled water for 25h, and then freeze-dried to obtain modified fucoidan, wherein the amount ratio of fucoidan, acetylsalicylic acid and 1-ethyl-(3-dimethylaminopropyl) carbonyldiimide is 8mg:0.05mmol:0.07mmol;

[0046] (3) Preparation of modified nano-cellulose: 40.0g of nano-cellulose was added to 60mL of water, and a nano-cellulose suspension was prepared by high-speed shearing; 1.0g of stearic acid was added to 20mL of ethanol solution and dissolved by heating and stirring at a temperature of 85℃, and the nano-cellulose suspension was heated to 85℃ and then added to the mixture, and stirred at 85℃ for 2h to prepare modified nano-cellulose;

[0047] (4) Preparation of coating liquid: 20 parts of modified fucoidan, 0.3 parts of polyvinyl alcohol and 1 part of polyaluminum silicate sulfate were added to 60 parts of water according to weight parts, and stirred at a temperature of 55°C and a rotation speed of 7500 r / min for 38 minutes, then the rotation speed was adjusted to 200 r / min, and 1.2 parts of sorbitol and 0.2 parts of sodium thiosulfate were added, and the mixture was stirred at a temperature of 65°C and a rotation speed of 220 r / min for 52 minutes to obtain a premix; 1.5 parts of modified nanocellulose were prepared into a suspension with a concentration of 2-6%; 12 parts of polybutylene succinate and the modified nanocellulose suspension were added to the premix, and stirred at room temperature and a rotation speed of 2000 r / min for 38 minutes to obtain a coating liquid;

[0048] (5) After the coating liquid is applied to both sides of the base paper surface, it is dried at a temperature of 70°C for 30 minutes, and then placed in a constant temperature and humidity environment at a temperature of 23°C and a relative humidity of 50% for 24 hours for equilibrium. After calendering, food waterproof and oil-proof paper is obtained, wherein the weight ratio of the base paper to the coating liquid on each surface is 1:0.11. Example 2

[0049] Preparation of food waterproof and greaseproof paper:

[0050] (1) Preparation of base paper: 15 parts of sisal fiber, 3 parts of polylactic acid fiber and 100 parts of water were mixed and continuously beaten to a beating degree of 50°SR to obtain a fiber slurry; 4 parts of water glass and 1 part of nano-silicon dioxide were added to the fiber slurry, stirred for 60 minutes, and mixed again and continuously beaten to a beating degree of 30°SR to obtain a mixed slurry; 2 parts of starch and 1 part of polyacrylamide were added, mixed evenly with the mixed slurry, diluted to a web concentration of 0.1-0.6%, and wet paper sheets were made using a Fourdrinier papermaking machine. After pressing, preliminary drying was performed to obtain base paper;

[0051] (2) Preparation of modified fucoidan: fucoidan was added to acetylsalicylic acid solution, 1-ethyl-(3-dimethylaminopropyl)carbodiimide was added, stirred, and reacted at 90°C for 2 h. The solution was then cooled and the pH was adjusted to 7.5. The solution was dialyzed with tap water for 40 h and distilled water for 30 h, and then freeze-dried to obtain modified fucoidan. The ratio of fucoidan, acetylsalicylic acid, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide was 5 mg:0.06 mmol:0.05 mmol.

[0052] (3) Preparation of modified nanocellulose: 40.0 g of nanocellulose was added to 60 mL of water and subjected to high-speed shearing to obtain a nanocellulose suspension; 1.0 g of stearic acid was added to 20 mL of ethanol solution and heated and stirred at 85 °C to dissolve; the nanocellulose suspension was heated to 85 °C and then added to the blending mixture, and stirred at 85 °C for 2 h to obtain modified nanocellulose;

[0053] (4) Preparation of coating liquid: 25 parts of modified fucoidan, 0.1 parts of polyvinyl alcohol and 1.5 parts of polyaluminum silicate sulfate were added to 50 parts of water according to weight parts, and stirred at a temperature of 60°C and a speed of 5000 r / min for 45 minutes, then the speed was adjusted to 100 r / min, and 1.5 parts of sorbitol and 0.1 parts of sodium thiosulfate were added, and the mixture was stirred at a temperature of 70°C and a speed of 150 r / min for 60 minutes to obtain a premix; 1 part of modified nanocellulose was prepared into a suspension with a concentration of 2-6%; 15 parts of polybutylene succinate and the modified nanocellulose suspension were added to the premix, and stirred at room temperature and a speed of 1000 r / min for 45 minutes to obtain a coating liquid;

[0054] (5) After the coating liquid is applied to both sides of the base paper surface, it is dried at a temperature of 70°C for 30 minutes, and then placed in a constant temperature and humidity environment at a temperature of 22°C and a relative humidity of 52% for 24 hours. After calendering, food waterproof and oil-proof paper is obtained, wherein the weight ratio of the base paper to the coating liquid on each surface is 1:0.08. Example 3

[0055] Preparation of food waterproof and greaseproof paper:

[0056] (1) Preparation of base paper: 10 parts of sisal fiber, 5 parts of polylactic acid fiber and 80 parts of water were mixed and continuously beaten to a beating degree of 55°SR to obtain a fiber slurry; 2 parts of water glass and 1.5 parts of nano-silicon dioxide were added to the fiber slurry, stirred for 30 minutes, and mixed again and continuously beaten to a beating degree of 40°SR to obtain a mixed slurry; 1 part of starch and 2 parts of polyacrylamide were added, mixed evenly with the mixed slurry, diluted to a web concentration of 0.1-0.6%, and wet paper sheets were made using a Fourdrinier papermaking machine. After pressing, preliminary drying was performed to obtain base paper;

[0057] (2) Preparation of modified fucoidan: fucoidan was added to acetylsalicylic acid solution, 1-ethyl-(3-dimethylaminopropyl)carbodiimide was added, stirred, and reacted at 70°C for 4 h. The solution was then cooled and the pH was adjusted to 6.5. The solution was dialyzed with tap water for 50 h and distilled water for 20 h, and then freeze-dried to obtain modified fucoidan. The ratio of fucoidan, acetylsalicylic acid, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide was 10 mg:0.04 mmol:0.1 mmol.

[0058] (3) Preparation of modified nanocellulose: 40.0 g of nanocellulose was added to 60 mL of water and subjected to high-speed shearing to obtain a nanocellulose suspension; 1.0 g of stearic acid was added to 20 mL of ethanol solution and heated and stirred at 85 °C to dissolve; the nanocellulose suspension was heated to 85 °C and then added to the blending mixture, and stirred at 85 °C for 2 h to obtain modified nanocellulose;

[0059] (4) Preparation of coating liquid: 15 parts of modified fucoidan, 0.5 parts of polyvinyl alcohol and 0.5 parts of polyaluminum silicate sulfate were added to 70 parts of water according to weight parts, and stirred at a temperature of 50°C and a rotation speed of 10,000 r / min for 30 minutes, and then the rotation speed was adjusted to 300 r / min, and 1 part of sorbitol and 0.3 parts of sodium thiosulfate were added, and the mixture was stirred at a temperature of 60°C and a rotation speed of 300 r / min for 45 minutes to obtain a premix; 2 parts of modified nanocellulose were prepared into a suspension with a concentration of 2-6%; 8 parts of polybutylene succinate and the modified nanocellulose suspension were added to the premix, and stirred at room temperature and a rotation speed of 3,000 r / min for 30 minutes to obtain a coating liquid;

[0060] (5) After the coating liquid is applied to both sides of the base paper surface, it is dried at a temperature of 70°C for 30 minutes, and then placed in a constant temperature and humidity environment at a temperature of 24°C and a relative humidity of 48% for 24 hours. After calendering, food waterproof and oil-proof paper is obtained, wherein the weight ratio of the base paper to the coating liquid on each surface is 1:0.15. Example 4

[0061] Preparation of food waterproof and greaseproof paper:

[0062] (1) Preparation of base paper: 12 parts of sisal fiber, 4 parts of polylactic acid fiber and 85 parts of water were mixed and continuously beaten to a beating degree of 52°SR to obtain a fiber slurry; 3 parts of water glass and 1.2 parts of nano-silicon dioxide were added to the fiber slurry, stirred for 40 minutes, and mixed again and continuously beaten to a beating degree of 35°SR to obtain a mixed slurry; 1.5 parts of starch and 1.8 parts of polyacrylamide were added, mixed evenly with the mixed slurry, diluted to a web concentration of 0.1-0.6%, and wet paper sheets were made using a Fourdrinier papermaking machine. After pressing, preliminary drying was performed to obtain base paper;

[0063] (2) Preparation of modified fucoidan: fucoidan was added to acetylsalicylic acid solution, 1-ethyl-(3-dimethylaminopropyl)carbodiimide was added, stirred, and reacted at 80°C for 3 h. The solution was then cooled and the pH was adjusted to 6. The solution was dialyzed with tap water for 45 h and distilled water for 25 h, and then freeze-dried to obtain modified fucoidan. The ratio of fucoidan, acetylsalicylic acid, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide was 6 mg:0.05 mmol:0.08 mmol.

[0064] (3) Preparation of modified nanocellulose: 40.0 g of nanocellulose was added to 60 mL of water and subjected to high-speed shearing to obtain a nanocellulose suspension; 1.0 g of stearic acid was added to 20 mL of ethanol solution and heated and stirred at 85 °C to dissolve; the nanocellulose suspension was heated to 85 °C and then added to the blending mixture, and stirred at 85 °C for 2 h to obtain modified nanocellulose;

[0065] (4) Preparation of coating liquid: 20 parts of modified fucoidan, 0.3 parts of polyvinyl alcohol and 1 part of polyaluminum silicate sulfate were added to 60 parts of water according to weight parts, and stirred at a temperature of 55°C and a speed of 7000 r / min for 40 minutes, then the speed was adjusted to 200 r / min, and 1.4 parts of sorbitol and 0.2 parts of sodium thiosulfate were added, and the mixture was stirred at a temperature of 68°C and a speed of 200 r / min for 50 minutes to obtain a premix; 1.5 parts of modified nanocellulose were prepared into a suspension with a concentration of 2-6%; 10 parts of polybutylene succinate and the modified nanocellulose suspension were added to the premix, and stirred at room temperature and a speed of 2000 r / min for 35 minutes to obtain a coating liquid;

[0066] (5) After the coating liquid is applied to both sides of the base paper surface, it is dried at a temperature of 70°C for 30 minutes, and then placed in a constant temperature and humidity environment at a temperature of 23°C and a relative humidity of 51% for 24 hours for equilibrium. After calendering, food waterproof and oil-proof paper is obtained, wherein the weight ratio of the base paper to the coating liquid on each surface is 1:0.1.

[0067] Comparative Example 1

[0068] Preparation of food waterproof and greaseproof paper:

[0069] (1) Preparation of base paper: 13 parts of sisal fiber, 4 parts of polylactic acid fiber and 90 parts of water were mixed and continuously beaten to a beating degree of 53°SR to obtain a fiber slurry; 3 parts of water glass and 1.3 parts of nano-silicon dioxide were added to the fiber slurry, stirred for 45 minutes, and mixed again and continuously beaten to a beating degree of 35°SR to obtain a mixed slurry; 1.5 parts of starch and 1.5 parts of polyacrylamide were added, mixed evenly with the mixed slurry, diluted to a web concentration of 0.1-0.6%, and wet paper sheets were made using a Fourdrinier papermaking machine. After pressing, preliminary drying was performed to obtain base paper;

[0070] (2) Preparation of modified nanocellulose: 40.0 g of nanocellulose was added to 60 mL of water and subjected to high-speed shearing to obtain a nanocellulose suspension; 1.0 g of stearic acid was added to 20 mL of ethanol solution and heated and stirred at 85 °C to dissolve; the nanocellulose suspension was heated to 85 °C and then added to the blending mixture, and stirred at 85 °C for 2 h to obtain modified nanocellulose;

[0071] (3) Preparation of coating liquid: 20 parts of fucoidan, 0.3 parts of polyvinyl alcohol and 1 part of polyaluminum silicate sulfate were added to 60 parts of water according to weight parts, and stirred at a temperature of 55°C and a rotation speed of 7500 r / min for 38 minutes, then the rotation speed was adjusted to 200 r / min, and 1.2 parts of sorbitol and 0.2 parts of sodium thiosulfate were added, and the mixture was stirred at a temperature of 65°C and a rotation speed of 220 r / min for 52 minutes to obtain a premix; 1.5 parts of modified nanocellulose were prepared into a suspension with a concentration of 2-6%; 12 parts of polybutylene succinate and the modified nanocellulose suspension were added to the premix, and stirred at room temperature and a rotation speed of 2000 r / min for 38 minutes to obtain a coating liquid;

[0072] (4) After the coating liquid is applied to both sides of the base paper surface, it is dried at a temperature of 70°C for 30 minutes, and then placed in a constant temperature and humidity environment at a temperature of 23°C and a relative humidity of 50% for 24 hours for equilibrium. After calendering, food waterproof and oil-proof paper is obtained, wherein the weight ratio of the base paper to the coating liquid on each surface is 1:0.11.

[0073] Comparative Example 2

[0074] Preparation of food waterproof and greaseproof paper:

[0075] (1) Preparation of base paper: 13 parts of sisal fiber, 4 parts of polylactic acid fiber and 90 parts of water were mixed and continuously beaten to a beating degree of 53°SR to obtain a fiber slurry; 1.3 parts of nano-silica was added to the fiber slurry, stirred for 45 minutes, and mixed and continuously beaten to a beating degree of 35°SR to obtain a mixed slurry; 1.5 parts of starch and 1.5 parts of polyacrylamide were added, mixed evenly with the mixed slurry, diluted to a web concentration of 0.1-0.6%, and wet paper sheets were made using a Fourdrinier papermaking machine. After pressing, preliminary drying was performed to obtain base paper;

[0076] (2) Preparation of modified fucoidan: fucoidan was added to acetylsalicylic acid solution, 1-ethyl-(3-dimethylaminopropyl)carbodiimide was added, stirred, and reacted at 80°C for 3 h. The solution was then cooled and the pH was adjusted to 7. The solution was dialyzed with tap water for 45 h and distilled water for 25 h, and then freeze-dried to obtain modified fucoidan. The ratio of fucoidan, acetylsalicylic acid, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide was 8 mg:0.05 mmol:0.07 mmol.

[0077] (3) Preparation of modified nanocellulose: 40.0 g of nanocellulose was added to 60 mL of water and subjected to high-speed shearing to obtain a nanocellulose suspension; 1.0 g of stearic acid was added to 20 mL of ethanol solution and heated and stirred at 85 °C to dissolve; the nanocellulose suspension was heated to 85 °C and then added to the blending mixture, and stirred at 85 °C for 2 h to obtain modified nanocellulose;

[0078] (4) Preparation of coating liquid: 20 parts of modified fucoidan, 0.3 parts of polyvinyl alcohol and 1 part of polyaluminum silicate sulfate were added to 60 parts of water according to weight parts, and stirred at a temperature of 55°C and a rotation speed of 7500 r / min for 38 minutes, then the rotation speed was adjusted to 200 r / min, and 1.2 parts of sorbitol and 0.2 parts of sodium thiosulfate were added, and the mixture was stirred at a temperature of 65°C and a rotation speed of 220 r / min for 52 minutes to obtain a premix; 1.5 parts of modified nanocellulose were prepared into a suspension with a concentration of 2-6%; 12 parts of polybutylene succinate and the modified nanocellulose suspension were added to the premix, and stirred at room temperature and a rotation speed of 2000 r / min for 38 minutes to obtain a coating liquid;

[0079] (5) After the coating liquid is applied to both sides of the base paper surface, it is dried at a temperature of 70°C for 30 minutes, and then placed in a constant temperature and humidity environment at a temperature of 23°C and a relative humidity of 50% for 24 hours for equilibrium. After calendering, food waterproof and oil-proof paper is obtained, wherein the weight ratio of the base paper to the coating liquid on each surface is 1:0.11.

[0080] Comparative Example 3

[0081] Preparation of food waterproof and greaseproof paper:

[0082] (1) Preparation of base paper: 13 parts of sisal fiber, 4 parts of polylactic acid fiber and 90 parts of water were mixed and continuously beaten to a beating degree of 53°SR to obtain a fiber slurry; 3 parts of water glass and 1.3 parts of nano-silicon dioxide were added to the fiber slurry, stirred for 45 minutes, and mixed again and continuously beaten to a beating degree of 35°SR to obtain a mixed slurry; 1.5 parts of starch and 1.5 parts of polyacrylamide were added, mixed evenly with the mixed slurry, diluted to a web concentration of 0.1-0.6%, and wet paper sheets were made using a Fourdrinier papermaking machine. After pressing, preliminary drying was performed to obtain base paper;

[0083] (2) Preparation of modified fucoidan: fucoidan was added to acetylsalicylic acid solution, 1-ethyl-(3-dimethylaminopropyl)carbodiimide was added, stirred, and reacted at 80°C for 3 h. The solution was then cooled and the pH was adjusted to 7. The solution was dialyzed with tap water for 45 h and distilled water for 25 h, and then freeze-dried to obtain modified fucoidan. The ratio of fucoidan, acetylsalicylic acid, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide was 8 mg:0.05 mmol:0.07 mmol.

[0084] (3) Preparation of modified nanocellulose: 40.0 g of nanocellulose was added to 60 mL of water and subjected to high-speed shearing to obtain a nanocellulose suspension; 1.0 g of stearic acid was added to 20 mL of ethanol solution and heated and stirred at 85 °C to dissolve; the nanocellulose suspension was heated to 85 °C and then added to the blending mixture, and stirred at 85 °C for 2 h to obtain modified nanocellulose;

[0085] (4) Preparation of coating liquid: 20 parts of modified fucoidan, 0.3 parts of polyvinyl alcohol and 1 part of polyaluminum silicate sulfate were added to 60 parts of water according to weight parts, and stirred at a temperature of 55°C and a rotation speed of 7500 r / min for 38 minutes, then the rotation speed was adjusted to 200 r / min, and 1.2 parts of sorbitol and 0.2 parts of sodium thiosulfate were added, and the mixture was stirred at a temperature of 65°C and a rotation speed of 220 r / min for 52 minutes to obtain a premix; 1.5 parts of modified nanocellulose were prepared into a suspension with a concentration of 2-6%; 12 parts of acrylic resin and the modified nanocellulose suspension were added to the premix, and stirred at room temperature and a rotation speed of 2000 r / min for 38 minutes to obtain a coating liquid;

[0086] (5) After the coating liquid is applied to both sides of the base paper surface, it is dried at a temperature of 70°C for 30 minutes, and then placed in a constant temperature and humidity environment at a temperature of 23°C and a relative humidity of 50% for 24 hours for equilibrium. After calendering, food waterproof and oil-proof paper is obtained, wherein the weight ratio of the base paper to the coating liquid on each surface is 1:0.11.

[0087] Experimental Example 1

[0088] The food waterproof and oil-proof papers prepared in Examples 1-4 and Comparative Examples 1-3 were tested respectively. The test items included: KIT oil-proof grade, water absorption, tear strength, and oxygen permeability. The test methods were as follows:

[0089] Water absorption is tested according to GB / T1540-2002;

[0090] Tear strength is tested according to GB / T 455-2002;

[0091] The oxygen permeability is tested in accordance with the standard GB / T19789-2021.

[0092] Performance test data is shown in Table 1 below:

[0093]

[0094] As can be seen from Table 1, the comprehensive performance of the food waterproof and oil-proof paper of Examples 1-4 of the present application is good. With the mutual combination of specific raw material ratios, the oil resistance grade, water resistance, strength, and gas barrier properties can all reach a high level.

[0095] The fucoidan in the raw materials of the coating liquid of Comparative Example 1 has not been modified with acetylsalicylic acid, and the rest are the same as in Example 1. The tear strength of the food waterproof and oil-proof paper prepared in Comparative Example 1 is significantly reduced, indicating that the present application uses acetylsalicylic acid-modified fucoidan. The fucoidan modified with acetylsalicylic acid introduces hydrophilic groups, which improves its solubility in water, enhances the flexibility of the film, and increases the interaction points between fucoidan and fibers, thereby improving the bonding strength between the coating layer and the base paper.

[0096] No water glass was added to the raw materials of the base paper of Comparative Example 2, and the rest were the same as in Example 1. The tear strength of the food waterproof and oil-proof paper prepared in Comparative Example 2 was significantly reduced, and the oil resistance grade, water resistance, and gas barrier properties all deteriorated. This shows that the silicate colloid generated by the hydrolysis of the water glass of the present application can be adsorbed on the fiber surface, promoting the bonding between fibers through hydrogen bonds and van der Waals forces, thereby improving the tensile strength and burst resistance of the paper. At the same time, the negatively charged silicate colloid can form a flocculation network with starch, etc., reducing the loss of fine fibers and nano-silica, and improving the utilization rate of raw materials; during the pulping or papermaking process, the adsorption of silicate colloid can also make the sisal fibers and polylactic acid fibers evenly dispersed, thereby improving the uniformity of the paper.

[0097] In the raw materials of the coating liquid of Comparative Example 3, the polybutylene succinate was replaced with an equal amount of acrylic resin, and the rest were the same as in Example 1. The tear strength of the food waterproof and oil-proof paper prepared in Comparative Example 3 was reduced, and the oil resistance grade, water resistance, and gas barrier properties were all deteriorated, indicating that the polybutylene succinate of the present application can improve the dry strength and wet strength of the paper by forming chemical bonds with the base paper fibers; its flexible molecular chain can reduce the brittleness of the paper, thereby improving its folding resistance and toughness while maintaining its strength; its hydrophobic properties can effectively reduce the water absorption rate of the paper, while reducing the water vapor and oxygen permeability, reducing the moisture absorption and oxidation of food, and extending the shelf life of food.

[0098] Although the embodiments of the present application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions or variations may be made to these embodiments without departing from the principles and purpose of the present application, and that the technical solutions after these changes, modifications, substitutions or variations will fall within the scope of protection of the present application.

Claims

1. A food waterproof and oil-proof paper, characterized in that: It consists of a base paper and a coating layer covering the surface of the base paper; The base paper comprises the following raw materials in parts by weight: 10-15 parts of sisal fiber, 3-5 parts of polylactic acid fiber, 2-4 parts of water glass, 1-1.5 parts of nano silicon dioxide, 1-2 parts of starch, and 1-2 parts of polyacrylamide; The preparation of the coating layer comprises the following steps: applying the coating liquid to the surface of the base paper, and then drying and calendering to obtain the coating layer; The coating solution comprises the following raw materials in parts by weight: 15-25 parts of modified fucoidan, 8-15 parts of polybutylene succinate, 1-2 parts of modified nanocellulose, 1-1.5 parts of sorbitol, 0.5-1.5 parts of polyaluminum silicate sulfate, 0.1-0.5 parts of polyvinyl alcohol, 0.1-0.3 parts of sodium thiosulfate, and 50-70 parts of water; The preparation method of the modified fucoidan comprises the following steps: Add fucoidan to an acetylsalicylic acid solution, add 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stir, and react at a temperature of 70-90°C for 2-4 hours, then cool the solution and adjust the pH to 6.5-7.5, dialyze with tap water for 40-50 hours, dialyze with distilled water for 20-30 hours, and then freeze-dry to obtain modified fucoidan; The preparation method of the modified nanocellulose comprises the following steps: adding 40.0 g of nanocellulose to 60 mL of water, and obtaining a nanocellulose suspension through high-speed shearing; adding 1.0 g of stearic acid to 20 mL of ethanol solution, heating and stirring at 85° C. to dissolve the solution; heating the nanocellulose suspension to 85° C., adding the mixture, and stirring at 85° C. for 2 hours to obtain the modified nanocellulose.

2. The food waterproof and oil-proof paper according to claim 1, characterized in that: The usage ratio of the fucoidan, the acetylsalicylic acid and the 1-ethyl-(3-dimethylaminopropyl)carbodiimide is (5-10) mg:(0.04-0.06) mmol:(0.05-0.1) mmol.

3. The food waterproof and oil-proof paper according to claim 1, characterized in that: The preparation of the base paper comprises the following steps: S1. The sisal fiber, polylactic acid fiber and 80-100 parts of water were mixed and continuously beaten to a beating degree of 50-55 ° SR to obtain a fiber slurry; S2. Add water glass and nano-silica to the fiber slurry, stir for 30-60min, and mix again and continuously beat to a beating degree of 30-40° SR to obtain a mixed slurry; S3. Add starch and polyacrylamide, mix evenly with the mixed slurry, dilute to a concentration of 0.1-0.6% for online printing, and use a Fourdrinier papermaking machine to make wet paper sheets. After pressing, preliminary drying is performed to obtain base paper.

4. The food waterproof and oil-proof paper according to claim 1, characterized in that: The preparation of the coating solution comprises the following steps: A1. Add modified fucoidan, polyvinyl alcohol, and aluminum polysilicate sulfate to water according to parts by weight and stir at 50-60°C and 5000-10000 rpm for 30-45 minutes. Then adjust the speed to 100-300 rpm, add sorbitol and sodium thiosulfate, and continue stirring at 60-70°C and 150-300 rpm for 45-60 minutes to obtain a premix. A2. The modified nanocellulose is prepared into a suspension having a concentration of 2-6%; A3. Add polybutylene succinate and modified nanocellulose suspension to the premix and stir at room temperature at a speed of 1000-3000 r / min for 30-45 min to obtain a coating solution.

5. The food waterproof and oil-proof paper according to claim 1, characterized in that: The weight ratio of the base paper to the coating liquid on each surface is 1:0.08-0.

15.

6. The food waterproof and oil-proof paper according to claim 1, characterized in that: The drying temperature is 70° C., and / or the drying time is 30 minutes.

7. The food waterproof and oil-proof paper according to claim 1, characterized in that: After the drying, the method further includes placing the dried sample in a constant temperature and humidity environment for equilibrium.

8. A method for preparing the food waterproof and oil-proof paper according to any one of claims 1 to 7, characterized in that: The following steps are involved: The coating liquid is coated on both sides of the surface of the base paper, and then dried and calendered to obtain the food waterproof and oil-proof paper.

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