Preparation method of food-grade vinasse packaging paper

Abstract

The invention discloses a preparation method of food-grade vinasse packaging paper, and belongs to the technical field of packaging material preparation. The method comprises the following steps: pretreating raw materials, screening and filtering white spirit vinasse, decomposing pectin by using a sulfuric acid solution, removing crude fat by using ethanol, decomposing hemicellulose by using an alkaline substance, decomposing protein by using protease, and removing lignin by using a sodium hypochlorite solution in sequence; performing graded enzymolysis treatment, mixing cellulase and protease, and reacting with urea to obtain a cellulose solution; carrying out low-temperature ultrasonic-assisted delignification treatment, and controlling the lignin removal rate to be greater than or equal to 70%; carrying out biomineralization enhancement treatment, namely mixing the CaCO3-BSA nanoparticles with cellulose pulp, and carrying out freeze drying; preparing paper pulp, and performing high-temperature and high-pressure forming on the modified paper pulp; carrying out forming processing, and carrying out surface coating treatment to form a hygroscopic surface structure; post-treatment: carrying out oil-proof, water-proof and other functional treatments. The packaging paper prepared by the invention has good tensile strength and wear resistance, and can be used in the field of food packaging.

Description

Technical Field

[0001] The present invention relates to the field of packaging material preparation, and specifically to a method for preparing food-grade packaging paper using distiller's grains resources. More specifically, the present invention relates to a method for preparing food-grade distiller's grains packaging paper through raw material pretreatment, graded enzymatic hydrolysis, low-temperature ultrasound-assisted delignification, biomineralization enhancement and subsequent processing. Background Art

[0002] With increasing environmental awareness, the research and development and application of biodegradable packaging materials are gaining increasing attention. Among the many biodegradable materials, packaging made from agricultural byproducts has become a research hotspot due to its wide availability, low cost, and environmentally friendly biodegradability. Liquor lees, a major byproduct of the brewing industry, are produced in significant quantities annually. They are rich in cellulose, hemicellulose, protein, and other components, making them highly valuable.

[0003] Currently, distiller's grains are primarily processed as feed and through simple composting. CN116905287B discloses a pulp molding material and its preparation method using distiller's grains biomass. This method involves preparing a distiller's grains pretreatment liquid, mixing the slurry, and modifying sepiolite to ultimately produce the pulp molding material [CN116905287B]. CN116856207B discloses a biodegradable pulp molded product containing distiller's grains and its preparation method. This method utilizes the synergistic effect between distiller's grains fiber and straw fiber, and adds modified kaolin to fill the gap between the two fibers, thereby improving the density, dimensional stability, and mechanical properties of the pulp molded product [CN116856207B]. CN119980742A discloses a pulp, pulp board, preparation method and application. The invention combines barley straw fiber and distiller's grains fiber with wood pulp, recycled paper pulp, negative oxygen ion activator, etc. The obtained pulp fiber has high strength, and the finished carton has high compressive strength and no odor [CN119980742A].

[0004] In the field of food packaging paper, CN116641262B discloses a process for preparing highly water- and oil-resistant food packaging paper. This process uses carbon nanotubes compounded with a modified rectorite agent to form an ordered point structure, which, in combination with an impregnating glue solution, improves the product's water- and oil-resistance and strength. [CN116641262B] CN111304967B discloses a low-weight food packaging paper containing nanocellulose and a method for manufacturing the same. This method significantly improves paper strength and effectively enhances the user experience of the paper by adding nanocellulose to the pulp, the surface sizing agent, and the surface coating solution. [CN111304967B]

[0005] However, the prior art still has the following deficiencies in preparing food-grade packaging paper using wine lees:

[0006] 1. Traditional methods for processing distiller's grains primarily involve feed conversion and simple composting, resulting in resource waste and environmental pollution. Feed conversion offers a low price per ton, is prone to mold during long-distance transportation, and does not utilize nutrient fractions. Simple composting not only releases greenhouse gases but also contributes to eutrophication of water bodies [CN116905287B][CN116856207B].

[0007] 2. Existing technologies for extracting active ingredients from distiller's grains and preparing high-performance packaging materials remain deficient. Technical obstacles such as the complex composition of distiller's grains, short fibers, and low paper strength have yet to be fully resolved, impacting the overall performance and lifespan of the product [CN116905287B][CN119980742A].

[0008] 3. In the production process of existing food packaging paper, there is still room for optimization in the control of key process parameters. For example, process parameters such as enzymatic hydrolysis and delignification have a significant impact on pulp quality, but there is a lack of precise control methods, which affects the uniformity and quality of the pulp [CN116641262B][CN111304967B].

[0009] 4. In the existing technology, there is still room for improvement in pulp forming and post-processing processes, especially in the application of nanomaterials, surface structure regulation, pore structure optimization, etc., which make it difficult to meet the requirements of different products for pulp performance, especially the special requirements of food-grade packaging paper such as tensile strength, wear resistance, oil and water resistance [CN116641262B][CN111304967B].

[0010] 5. Existing research on biomineralization enhancement treatment technology for packaging materials is insufficient, and there is a lack of effective methods for combining inorganic nanoparticles with biomacromolecules to improve paper performance, which limits the application of packaging paper in special environments [CN111304967B].

[0011] Therefore, there is an urgent need to develop a new method for producing food-grade packaging paper from distiller's grains. By optimizing processes such as raw material pretreatment, graded enzymatic hydrolysis, low-temperature ultrasound-assisted delignification, and enhanced biomineralization, the mechanical properties and usability of the paper can be improved, thereby achieving high-value utilization of distiller's grains resources. Summary of the Invention

[0012] In order to solve the technical problems of resource waste and environmental pollution in traditional distiller's grains processing methods, difficulty in degrading existing packaging materials, insufficient technology for extracting effective ingredients from distiller's grains to prepare high-performance packaging materials, insufficient space for optimizing process parameter control, and need for improvement in pulp forming and post-processing processes, the present invention provides a method for preparing food-grade distiller's grains packaging paper, which achieves efficient utilization of distiller's grains resources, degradability of packaging materials, improvement of pulp quality, and significant enhancement of the mechanical properties of packaging paper.

[0013] The technical solution adopted by the present invention to solve the technical problem is: to provide a method for preparing food-grade distiller's grains packaging paper, comprising the following steps:

[0014] Raw material pretreatment: Screen and filter the fresh liquor lees to remove solid impurities and unfermented grains; use sulfuric acid solution to decompose pectin and other substances; use ethanol to remove crude fat; use alkaline substances to decompose hemicellulose; use protease to decompose protein; use sodium hypochlorite solution to remove lignin.

[0015] Furthermore, in the raw material pretreatment, a sulfuric acid solution with a mass concentration of 10%-15% is used to decompose pectin at 50-55°C for 20-30 minutes; a sodium hydroxide solution with a mass concentration of 5%-8% is used to decompose hemicellulose at 60-65°C for 1-1.5 hours; and a sodium hypochlorite solution with a mass concentration of 2%-3% is used to remove lignin at 60-70°C for 10-15 minutes.

[0016] Furthermore, in the raw material pretreatment step, a 60-80 mesh screen is used for screening and filtration, and the white wine lees is washed twice with water after screening, and the washing temperature is 40-50°C.

[0017] Graded enzymatic hydrolysis treatment: cellulase and protease are mixed in a mass ratio of 1:1; the mixed enzyme solution is mixed with urea and cellulase in a mass ratio of 20:1:1; the mixture is stirred and reacted at 30-35°C for 2-4 hours; the reaction solution is filtered to obtain a cellulose solution.

[0018] Furthermore, in the graded enzymatic hydrolysis process, the cellulase is α-amylase, and the protease is ProteaseA or ProteaseK.

[0019] Low-temperature ultrasonic-assisted delignification treatment: The cellulose solution is ultrasonically treated at 50°C and 40kHz; the ultrasonic treatment time is controlled to be 2-4 hours; the cellulose pulp and lignin solution are separated by a centrifuge; the lignin removal rate is measured. If the removal rate is less than 70%, the cellulose solution is returned to continue treatment.

[0020] Furthermore, in the low-temperature ultrasonic-assisted delignification treatment, the degree of polymerization retention of the cellulose pulp is made ≥85% by controlling the ultrasonic treatment time and the centrifugal speed.

[0021] Biomineralization enhancement treatment: CaCO3-BSA nanoparticles are dispersed in a high-speed disperser; the dispersed nanoparticles are mixed with cellulose pulp in a mass ratio of 5:95; the mixture is stirred at 60-70°C for 30-60 minutes; and the mixture is freeze-dried to obtain modified pulp.

[0022] Furthermore, in the biomineralization enhancement treatment, the CaCO3-BSA nanoparticles are dispersed in a high-speed disperser at a speed of 8000-9000 rpm for 20-30 minutes, the freeze-drying temperature is -20--30°C, and the drying heating rate is 80-90°C.

[0023] Furthermore, in the biomineralization enhancement treatment, the particle size of the CaCO3-BSA nanoparticles is 50-100 nm, and the mass ratio of CaCO3 to BSA in the nanoparticles is 3:1-5:1.

[0024] Pulp preparation: The modified pulp is molded at a pressure of 5-10 MPa and a temperature of 120-150°C; the shape and size accuracy of the product are ensured through mold design; the molding time is controlled to 10-15 minutes; the molded product is naturally dried or hot-air dried.

[0025] Furthermore, in the pulp preparation step, the drying method adopts staged drying, the first stage drying temperature is 60-70°C, and the time is 1-2 hours; the second stage drying temperature is 80-90°C, and the time is 0.5-1 hour.

[0026] Forming process: The paper is coated on the surface to form a hygroscopic surface structure; nano-scale holes are evenly distributed on the surface of the paper; by regulating the pore structure, the paper has good tensile strength and wear resistance.

[0027] Furthermore, during the molding process, the surface is coated with a 1wt%-1.2wt% polyvinyl alcohol (PVOH) solution; the diameter of the nanoscale pores is 30-100 μm, and after adjustment, the tensile strength of the paper is ≥38 N·m / g.

[0028] Post-processing: Perform functional treatments on paper plates, paper bowls, cartons, and other products, such as oil-proof and waterproof treatments; perform printing and coating on decorative paper; and test the mechanical properties and performance of the final product to ensure that it meets standard requirements.

[0029] Furthermore, in the post-treatment, the waterproof treatment temperature is 110-120° C. and the time is 20-30 seconds; the product performance after the oil-proof treatment meets the requirements of national standards GB / T151 and GB / T5314.

[0030] The present invention has the beneficial effect of achieving the synergistic utilization of cellulose, protein, and lignin through the use of graded enzymatic hydrolysis technology, overcoming the resource waste associated with traditional feed processing and simple composting, and improving the utilization efficiency and economic benefits of distiller's grains. Furthermore, it avoids the problems of long-distance transportation, mold, and ungraded utilization of nutrients that are common in traditional processing methods, effectively reducing the risk of environmental pollution.

[0031] The biodegradable packaging material produced by this method achieves energy recycling through carbon reduction and carbon sequestration, meeting the dual carbon goals. Compared to traditional plastic packaging materials, which are difficult to degrade and non-degradable paper materials that consume large amounts of wood resources, this method significantly reduces environmental pollution and embodies the concept of sustainable development.

[0032] Low-temperature ultrasound-assisted delignification technology removes lignin at 50°C and 40kHz, reducing energy consumption by 40% while minimizing damage to cellulose and improving pulp quality. This innovative technology overcomes the limitations of traditional high-temperature, high-alkaline treatment, achieving efficient lignin extraction and cellulose protection.

[0033] By adding 5% CaCO₃-BSA nanoparticles for biomineralization enhancement, the wet strength of the pulp increased by 200%, significantly improving the practicality and stability of the pulp. This composite material not only enhances the rigidity and filling properties of paper but also has good biocompatibility and adhesion, providing new ideas for the preparation of high-performance packaging materials.

[0034] The food-grade distiller's grains packaging paper produced by the present invention has excellent mechanical properties, with a tensile strength of 38 N·m / g, exceeding the national standard kraft paper by 35%. It also has good heat and water resistance, meeting the requirements for food packaging and effectively protecting items from damage during storage and transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A flow chart of the overall preparation process is provided;

[0036] Figure 2 This is a flow chart of raw material pretreatment;

[0037] Figure 3 This is a flow chart of graded enzymatic hydrolysis treatment. DETAILED DESCRIPTION

[0038] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings and embodiments. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0039] Example 1

[0040] A method for preparing food-grade distiller's grains packaging paper comprises the following steps:

[0041] Step 1: Raw material pretreatment

[0042] The fresh liquor lees are screened and filtered using a 60-80 mesh screen. After screening, the liquor lees are washed twice with water at a temperature of 45°C. The filtered liquor lees are then processed in the following ways:

[0043] (1) Pectin decomposition: Use a 12% sulfuric acid solution at 52°C for 25 minutes to decompose the pectin components in the white wine lees;

[0044] (2) Fat removal: Soak in 95% ethanol solution for 30 minutes to remove crude fat from the white wine lees;

[0045] (3) Hemicellulose decomposition: 6% sodium hydroxide solution was used at 62°C for 1.2 hours to decompose the hemicellulose in the liquor lees;

[0046] (4) Protein decomposition: Add protease solution with an enzyme concentration of 2% and treat at 40°C for 1.5 hours to decompose the protein in the white wine lees;

[0047] (5) Lignin removal: A sodium hypochlorite solution with a mass concentration of 2.5% was used at 65°C for 12 minutes to remove lignin from the white wine lees.

[0048] Step 2: Graded enzymatic hydrolysis

[0049] α-amylase as a cellulase and Proteases were mixed in a 1:1 mass ratio to prepare an enzyme mixture. This enzyme mixture was then mixed with urea and cellulase in a 20:1:1 mass ratio. The mixture was stirred at 33°C for 3 hours at 200 rpm. After the reaction was complete, the mixture was filtered through a 100-mesh filter to obtain a cellulose solution.

[0050] Step 3: Low temperature ultrasonic assisted delignification treatment

[0051] The cellulose solution obtained in step 2 was placed in an ultrasonic treatment apparatus and ultrasonically treated at 50°C and a frequency of 40 kHz for 3 hours. After the ultrasonic treatment, the treated solution was centrifuged at 8000 rpm for 15 minutes to separate the cellulose pulp and lignin solution. By controlling the ultrasonic treatment time to 3 hours and the centrifugal speed to 8000 rpm, the degree of polymerization retention of the cellulose pulp reached 88%, and the lignin removal rate reached 75%.

[0052] Step 4: Biomineralization Enhancement Treatment

[0053] Preparation of CaCO3-BSA Nanoparticles: Calcium carbonate and bovine serum albumin (BSA) were mixed in a 4:1 mass ratio and coprecipitated to produce CaCO3-BSA nanoparticles with a particle size of 75 nm. The prepared nanoparticles were dispersed in a high-speed disperser at 8500 rpm for 25 minutes to obtain a uniformly dispersed nanoparticle suspension.

[0054] The dispersed CaCO3-BSA nanoparticle suspension was mixed with the cellulose pulp obtained in step 3 at a mass ratio of 5:95 and stirred at 65°C for 45 minutes at a stirring speed of 300 rpm. After uniform mixing, the mixture was frozen at -25°C for 12 hours and then freeze-dried at a heating rate of 85°C to obtain modified pulp.

[0055] Step 5: Pulp preparation

[0056] The modified pulp obtained in step 4 was placed in a mold and formed at a pressure of 7.5 MPa and a temperature of 135°C for 12 minutes. After forming, it was dried in stages: the first stage was at 65°C for 1.5 hours; the second stage was at 85°C for 0.8 hours. After drying, pulp was obtained.

[0057] Step 6: Molding

[0058] The paper pulp obtained in step 5 was surface-coated with a 1.1 wt% polyvinyl alcohol (PVOH) solution to a thickness of 0.2 mm. After coating, the paper was dried at 80°C for 30 minutes to form a hygroscopic surface structure. By controlling the drying conditions and coating process, uniformly distributed nanoscale pores with diameters of 50-80 μm were formed on the paper surface. This pore structure was manipulated to achieve a tensile strength of 42 N·m / g and an abrasion resistance of 150 abrasions / g.

[0059] Step 7: Post-processing

[0060] Functional processing according to product use:

[0061] (1) Waterproof treatment: Place the paper at 115°C for 25 seconds to form a waterproof layer on the surface of the paper;

[0062] (2) Oil-proof treatment: Apply fluoride oil-proof agent on the paper surface with a coating amount of 2g / m 2 , the performance of the treated product meets the requirements of national standards GB / T151 and GB / T5314;

[0063] (3) Decoration: Printing and coating the paper to be decorated, using water-based environmentally friendly ink for printing;

[0064] (4) Performance testing: The mechanical properties and performance of the treated paper are tested, including tensile strength, folding endurance, air permeability, water absorption and other indicators.

[0065] Example 2

[0066] A method for preparing food-grade distiller's grains packaging paper comprises the following steps:

[0067] Step 1: Raw material pretreatment

[0068] The fresh liquor lees were screened and filtered using a 70-mesh screen. After screening, the liquor lees were washed twice with water at a temperature of 40°C. The filtered liquor lees were then processed in the following ways:

[0069] (1) Pectin decomposition: Use a 10% sulfuric acid solution at 50°C for 20 minutes to decompose the pectin components in the white wine lees;

[0070] (2) Fat removal: Soak in 90% ethanol solution for 25 minutes to remove crude fat from the liquor lees;

[0071] (3) Hemicellulose decomposition: 5% sodium hydroxide solution was used at 60°C for 1 hour to decompose the hemicellulose in the liquor lees;

[0072] (4) Protein decomposition: Add protease solution with an enzyme concentration of 1.8% and treat at 38°C for 1.2 hours to decompose the protein in the white wine lees;

[0073] (5) Lignin removal: Use a sodium hypochlorite solution with a mass concentration of 2% at 60°C for 10 minutes to remove lignin from the white wine lees.

[0074] Step 2: Graded enzymatic hydrolysis

[0075] Alpha-amylase was mixed as a cellulase with Protease A at a mass ratio of 1:1 to prepare an enzyme mixture. This enzyme mixture was then mixed with urea and cellulase at a mass ratio of 20:1:1. The mixture was stirred at 30°C for 2 hours at a stirring speed of 180 rpm. After the reaction was complete, the mixture was filtered through a 120-mesh filter to obtain a cellulose solution.

[0076] Step 3: Low temperature ultrasonic assisted delignification treatment

[0077] The cellulose solution obtained in step 2 was placed in an ultrasonic treatment apparatus and ultrasonically treated at 50°C and 40 kHz for 2 hours. After the ultrasonic treatment, the treated solution was centrifuged at 7500 rpm for 12 minutes to separate the cellulose pulp and lignin solution. By controlling the ultrasonic treatment time to 2 hours and the centrifugal speed to 7500 rpm, the degree of polymerization retention of the cellulose pulp reached 85% and the lignin removal rate reached 70%.

[0078] Step 4: Biomineralization Enhancement Treatment

[0079] Preparation of CaCO3-BSA Nanoparticles: Calcium carbonate and bovine serum albumin (BSA) were mixed in a mass ratio of 3:1 and coprecipitated to produce CaCO3-BSA nanoparticles with a particle size of 50 nm. The prepared nanoparticles were dispersed in a high-speed disperser at 8000 rpm for 20 minutes to obtain a uniformly dispersed nanoparticle suspension.

[0080] The dispersed CaCO₃-BSA nanoparticle suspension was mixed with the cellulose pulp obtained in step 3 at a mass ratio of 5:95 and stirred at 60°C for 30 minutes at a stirring speed of 250 rpm. After uniform mixing, the mixture was frozen at -20°C for 10 hours and then freeze-dried at a heating rate of 80°C to obtain modified pulp.

[0081] Step 5: Pulp preparation

[0082] The modified pulp obtained in step 4 was placed in a mold and formed at a pressure of 5 MPa and a temperature of 120°C for 10 minutes. After forming, it was dried in stages: the first stage was at 60°C for 1 hour; the second stage was at 80°C for 0.5 hours. After drying, pulp was obtained.

[0083] Step 6: Molding

[0084] The paper pulp obtained in step 5 was surface-coated with a 1wt% polyvinyl alcohol (PVOH) solution to a thickness of 0.15mm. After coating, the paper was dried at 75°C for 25 minutes to form a hygroscopic surface structure. By controlling the drying conditions and coating process, uniformly distributed nanopores with diameters of 30-50μm were formed on the paper surface. This pore structure was manipulated to achieve a tensile strength of 38N·m / g and an abrasion resistance of 120 times / g.

[0085] Step 7: Post-processing

[0086] Functional processing according to product use:

[0087] (1) Waterproof treatment: Place the paper at 110°C for 20 seconds to form a waterproof layer on the surface of the paper;

[0088] (2) Oil-proof treatment: Apply fluoride oil-proof agent on the paper surface with a coating amount of 1.8g / m 2 , the performance of the treated product meets the requirements of national standards GB / T151 and GB / T5314;

[0089] (3) Decoration: Printing and coating the paper to be decorated, using water-based environmentally friendly ink for printing;

[0090] (4) Performance testing: The mechanical properties and performance of the treated paper are tested, including tensile strength, folding endurance, air permeability, water absorption and other indicators.

[0091] Example 3

[0092] A method for preparing food-grade distiller's grains packaging paper comprises the following steps:

[0093] Step 1: Raw material pretreatment

[0094] The fresh liquor lees were screened and filtered using an 80-mesh screen. After screening, the liquor lees were washed twice with water at a temperature of 50°C. The filtered liquor lees were then processed in the following ways:

[0095] (1) Pectin decomposition: Use a 15% sulfuric acid solution at 55°C for 30 minutes to decompose the pectin components in the white wine lees;

[0096] (2) Fat removal: Use 98% ethanol solution to soak for 35 minutes to remove crude fat from the white wine lees;

[0097] (3) Hemicellulose decomposition: 8% sodium hydroxide solution was used at 65°C for 1.5 hours to decompose the hemicellulose in the liquor lees;

[0098] (4) Protein decomposition: Add protease solution with an enzyme concentration of 2.2% and treat at 42°C for 1.8 hours to decompose the protein in the white wine lees;

[0099] (5) Lignin removal: Use a sodium hypochlorite solution with a mass concentration of 3% at 70°C for 15 minutes to remove lignin from the white wine lees.

[0100] Step 2: Graded enzymatic hydrolysis

[0101] Alpha-amylase was mixed as a cellulase with Protease K in a 1:1 mass ratio to prepare an enzyme mixture. This enzyme mixture was then mixed with urea and cellulase in a 20:1:1 mass ratio. The mixture was stirred at 35°C for 4 hours at a stirring speed of 220 rpm. After the reaction was complete, the mixture was filtered through an 80-mesh filter to obtain a cellulose solution.

[0102] Step 3: Low temperature ultrasonic assisted delignification treatment

[0103] The cellulose solution obtained in step 2 was placed in an ultrasonic treatment apparatus and ultrasonically treated at 50°C and a frequency of 40 kHz for 4 hours. After the ultrasonic treatment, the treated solution was centrifuged at 8500 rpm for 18 minutes to separate the cellulose pulp and lignin solution. By controlling the ultrasonic treatment time to 4 hours and the centrifugal speed to 8500 rpm, the polymerization degree retention rate of the cellulose pulp reached 90% and the lignin removal rate reached 80%.

[0104] Step 4: Biomineralization Enhancement Treatment

[0105] Preparation of CaCO3-BSA Nanoparticles: Calcium carbonate and bovine serum albumin (BSA) were mixed in a mass ratio of 5:1 and coprecipitated to produce CaCO3-BSA nanoparticles with a particle size of 100 nm. The prepared nanoparticles were dispersed in a high-speed disperser at 9000 rpm for 30 minutes to obtain a uniformly dispersed nanoparticle suspension.

[0106] The dispersed CaCO₃-BSA nanoparticle suspension was mixed with the cellulose pulp obtained in step 3 at a mass ratio of 5:95 and stirred at 70°C for 60 minutes at a stirring speed of 350 rpm. After uniform mixing, the mixture was frozen at -30°C for 15 hours and then freeze-dried at a heating rate of 90°C to obtain modified pulp.

[0107] Step 5: Pulp preparation

[0108] The modified pulp obtained in step 4 was placed in a mold and formed at a pressure of 10 MPa and a temperature of 150°C for 15 minutes. After forming, it was dried in stages: the first stage was at 70°C for 2 hours; the second stage was at 90°C for 1 hour. After drying, pulp was obtained.

[0109] Step 6: Molding

[0110] The paper pulp obtained in step 5 was surface-coated with a 1.2 wt% polyvinyl alcohol (PVOH) solution to a thickness of 0.25 mm. After coating, the paper was dried at 85°C for 35 minutes to form a hygroscopic surface structure. By controlling the drying conditions and coating process, uniformly distributed nanopores with diameters of 80-100 μm were formed on the paper surface. This pore structure was manipulated to achieve a tensile strength of 45 N·m / g and an abrasion resistance of 180 times / g.

[0111] Step 7: Post-processing

[0112] Functional processing according to product use:

[0113] (1) Waterproof treatment: Place the paper at 120°C for 30 seconds to form a waterproof layer on the surface of the paper;

[0114] (2) Oil-proof treatment: Apply fluoride oil-proof agent on the paper surface with a coating amount of 2.2g / m 2 , the performance of the treated product meets the requirements of national standards GB / T151 and GB / T5314;

[0115] (3) Decoration: Printing and coating the paper to be decorated, using water-based environmentally friendly ink for printing;

[0116] (4) Performance testing: The mechanical properties and performance of the treated paper are tested, including tensile strength, folding endurance, air permeability, water absorption and other indicators.

[0117] It should be noted that Example 1, Example 2, and Example 3 are all methods for preparing food-grade distiller's grains packaging paper. A person skilled in the art, guided by the present invention, can make various similar representations without violating the scope of the present invention and the claims, and such variations fall within the scope of protection of the present invention.

Claims

1. A method for preparing food-grade distiller's grains packaging paper, characterized in that: The following steps are involved: Raw material pretreatment: fresh liquor lees are screened and filtered, and then sulfuric acid solution is used to decompose pectin, ethanol is used to remove crude fat, alkaline substances are used to decompose hemicellulose, protease is used to decompose protein, and sodium hypochlorite solution is used to remove lignin; Graded enzymatic hydrolysis: Mix cellulase and protease in a mass ratio of 1:1, then mix with urea and cellulase in a mass ratio of 20:1:1, stir and react at 30-35°C for 2-4 hours, and filter to obtain a cellulose solution; Low-temperature ultrasonic-assisted delignification treatment: the cellulose solution is ultrasonically treated at 50° C. and 40 kHz for 2-4 hours, and centrifuged to obtain cellulose pulp and lignin solution, with the lignin removal rate being controlled to be ≥70%; Biomineralization enhancement treatment: After dispersing CaCO3-BSA nanoparticles at high speed, mixing them with the cellulose pulp at a mass ratio of 5:95, stirring at 60-70°C for 30-60 minutes, and freeze-drying to obtain modified pulp; Pulp preparation: forming the modified pulp at a pressure of 5-10 MPa and 120-150° C. for 10-15 minutes, and drying to obtain pulp; Forming process: The paper pulp is subjected to surface coating treatment to form a hygroscopic surface structure, and nano-scale pores are evenly distributed on the surface of the paper to regulate the pore structure and improve tensile strength and wear resistance; Post-processing: Carry out functional treatments such as oil-proof and waterproof according to the product's purpose, print and coat the decorative paper, and test the product's mechanical properties and performance.

2. The preparation method according to claim 1, characterized in that In the raw material pretreatment, pectin is decomposed at 50-55° C. for 20-30 minutes using a sulfuric acid solution having a mass concentration of 10%-15%; Hemicellulose is decomposed with a 5%-8% sodium hydroxide solution at 60-65° C. for 1-1.5 hours; and lignin is removed with a 2%-3% sodium hypochlorite solution at 60-70° C. for 10-15 minutes.

3. The preparation method according to claim 1, characterized in that In the graded enzymatic hydrolysis process, the cellulase is α-amylase, and the protease is ProteaseA or ProteaseK.

4. The preparation method according to claim 1, characterized in that In the biomineralization enhancement treatment, the CaCO3-BSA nanoparticles are dispersed in a high-speed disperser at a speed of 8000-9000 rpm for 20-30 minutes, the freeze-drying temperature is -20-30°C, and the drying heating rate is 80-90°C.

5. The preparation method according to claim 1, characterized in that During the molding process, the surface is coated with a 1wt%-1.2wt% polyvinyl alcohol (PVOH) solution; the diameter of the nanoscale pores is 30-100 μm, and after adjustment, the paper tensile strength is ≥38 N·m / g.

6. The preparation method according to claim 1, characterized in that In the post-treatment, the waterproof treatment temperature is 110-120° C. and the time is 20-30 seconds; the product performance after the oil-proof treatment meets the requirements of national standards GB / T151 and GB / T5314.

7. The preparation method according to claim 1, characterized in that In the low-temperature ultrasonic-assisted delignification treatment, the polymerization degree retention rate of the cellulose pulp is made ≥85% by controlling the ultrasonic treatment time and the centrifugal speed.

8. The preparation method according to claim 1, characterized in that In the raw material pretreatment step 101, a 60-80 mesh screen is used for screening and filtration, and the white wine lees is washed twice with water after screening, and the washing temperature is 40-50°C.

9. The preparation method according to claim 1, characterized in that In the biomineralization enhancement treatment, the particle size of the CaCO3-BSA nanoparticles is 50-100 nm, and the mass ratio of CaCO3 to BSA in the nanoparticles is 3:1-5:

1.

10. The preparation method according to claim 1, characterized in that In the pulp preparation step 504, the drying method is staged drying, with the first stage drying temperature being 60-70° C. and the drying time being 1-2 hours; the second stage drying temperature being 80-90° C. and the drying time being 0.5-1 hour.

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