Antibacterial and mildew-proof corrugated paper and preparation method thereof

Abstract

The application provides an antibacterial and mildew-proof corrugated paper and a preparation method thereof, and belongs to the technical field of packaging materials.The corrugated paper is prepared by mixing an efficient antibacterial agent into a paper base material and encapsulating the antibacterial agent through a microcapsule technology, so that the uniform distribution and long-acting release of the antibacterial agent in the paper are ensured.The preparation process comprises the following steps: preparation of paper pulp, preparation of the antibacterial agent, preparation of raw paper, coating of an antibacterial protective layer, forming of the corrugated paper and the like.The antibacterial and mildew-proof corrugated paper has excellent antibacterial and mildew-proof effects and good physical properties, is suitable for food, medicine, cosmetics and other products with strict requirements on sanitary conditions, can effectively prevent microbial pollution, and guarantees product quality and safety.

Description

Technical Field

[0001] The invention belongs to the technical field of packaging materials, and particularly relates to antibacterial and mildew-proof corrugated paper and a preparation method thereof. Background Art

[0002] With global economic development and improved living standards, the packaging industry is experiencing growing demand. Corrugated paper, a common packaging material, is widely used for packaging a wide range of goods due to its low cost, light weight, and ease of processing and molding. However, because corrugated paper is primarily composed of plant fibers, it is susceptible to bacterial and mold growth in humid or high-temperature environments. This not only affects the quality and safety of the packaging but can also lead to environmental pollution and resource waste. The antibacterial and anti-fungal properties of corrugated paper are particularly important in applications requiring high hygienic standards, such as food, pharmaceuticals, and cosmetics.

[0003] Although there are some antibacterial and mildew-proof corrugated paper products on the market, they still have some shortcomings in practical applications. For example, the antibacterial and mildew-proof effect is unstable: the antibacterial and mildew-proof effects of existing antibacterial and mildew-proof corrugated paper vary greatly under different environmental conditions (such as humidity and temperature changes). Especially in high-humidity environments, the antibacterial and mildew-proof ingredients may gradually lose their activity, resulting in a weakening of the antibacterial and mildew-proof effect. Poor durability: Some antibacterial and mildew-proof ingredients are easy to fall off or decompose from the corrugated paper after long-term use or multiple treatments (such as washing and friction), thereby affecting its long-term antibacterial and mildew-proof performance. Safety issues: Some antibacterial and mildew-proof ingredients may cause potential harm to the human body and the environment. For example, certain chemicals may cause skin allergies, respiratory irritation and other problems, and even accumulate in the environment, causing long-term effects on the ecosystem.

[0004] To overcome these challenges in existing technologies, researchers and companies are exploring new antibacterial and mildew-proofing technologies and materials, improving corrugated paper production processes to ensure that antibacterial and mildew-proofing ingredients adhere evenly and firmly to the paper surface. For example, methods such as impregnation, spraying, or coating are being used to enhance the binding strength of antibacterial and mildew-proofing ingredients to the paper. Furthermore, existing technologies are developing new materials with more stable antibacterial and mildew-proofing properties by synthesizing or modifying existing materials. These new materials should maintain stable antibacterial and mildew-proofing effects under various environmental conditions and have a longer service life.

[0005] Although the above solutions have improved the performance of existing antibacterial and mildew-proof corrugated paper to a certain extent, there are still some challenges that need to be overcome: such as the long-term stability of the antibacterial and mildew-proof effect, the uniform distribution of antimicrobial agents in the paper, the long-term release of antimicrobial agents, the balance between environmental protection and safety, and the improvement of comprehensive performance.

[0006] Therefore, developing an antibacterial and mildew-proof corrugated paper that is efficient, stable, safe, environmentally friendly, and has excellent comprehensive performance is of great significance for promoting the sustainable development of the packaging industry. Summary of the Invention

[0007] The purpose of the present invention is to provide an antibacterial and mildew-proof corrugated paper and a preparation method thereof. The antibacterial and mildew-proof corrugated paper of the present invention not only has excellent antibacterial and mildew-proof effects, but also can maintain good physical properties. It is suitable for packaging products such as food, medicine, and cosmetics that have strict requirements on sanitary conditions, effectively preventing microbial contamination and ensuring product quality and safety.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] In one aspect, the present invention provides a method for preparing antibacterial and mildew-proof corrugated paper, comprising the following steps:

[0010] (1) Preparation of pulp: Wood pulp and waste paper pulp are mixed as raw materials, and the raw materials are put into a pulper for pulping. After the processing is completed, the pulp is sieved and centrifuged to remove impurities, and the pH value is adjusted to 7-8 to obtain pulp;

[0011] (2) Preparation of microcapsule antibacterial agent: silver nitrate, zinc sulfate, copper sulfate, tea polyphenols, thyme essential oil and citric acid are dissolved in deionized water to prepare an antibacterial agent solution; gelatin, chitosan and polylactic acid are dissolved in deionized water, heated and stirred to prepare a wall material solution; the antibacterial agent solution is added to the wall material solution, stirred to obtain a mixed solution, and the mixed solution is spray-dried to obtain a microcapsule antibacterial agent;

[0012] (3) Preparation of base paper: adding the microcapsule antimicrobial agent to the pulp, using a high-speed stirrer to fully mix, feeding the pulp mixed with the microcapsule antimicrobial agent into a papermaking machine, and then dehydrating, pressing, and drying to obtain base paper;

[0013] (4) Coating of the antibacterial protective layer: mixing a microcapsule antibacterial agent, corn starch, polyvinyl alcohol, a defoaming agent, a wetting agent, a plasticizer, and deionized water to prepare a coating, coating the coating on the surface of the base paper, pressing the coating into the paper fibers through a coating roller, and drying and calendering the coated base paper;

[0014] (5) Forming of corrugated paper: The corrugated paper includes face paper, corrugated core paper and bottom paper. The face paper and bottom paper are the base paper after drying and calendering in step (4). The base paper after drying and calendering in step (4) is fed into a corrugating forming machine, and the base paper is pressed into a wave shape by a corrugating roller to form a corrugated core paper. Corn starch glue is coated on the inner sides of the face paper and bottom paper, and then the corrugated core paper is sandwiched in the middle and hot-pressed and bonded by a hot press. The hot-pressed corrugated paper is cooled and shaped to obtain the antibacterial and mildew-proof corrugated paper.

[0015] Furthermore, the mass ratio of the wood pulp to the waste paper pulp in step (1) is 1:0.1-0.2.

[0016] Furthermore, the mass parts of the components in the antibacterial solution in step (2) are as follows: 2-4 parts of silver nitrate, 1-2 parts of zinc sulfate, 1-2 parts of copper sulfate, 1-2 parts of tea polyphenols, 0.5-0.8 parts of thyme essential oil, and 0.3-0.5 parts of citric acid; the mass concentration of the antibacterial solution is 6-10%.

[0017] Furthermore, the mass parts of each component in the wall material solution in step (2) are as follows: 6-8 parts of gelatin, 3-5 parts of chitosan, and 1-2 parts of polylactic acid; the mass concentration of the wall material solution is 10-15%, and the heating temperature is 60-70°C.

[0018] Furthermore, the mass ratio of the antibacterial agent solution to the wall material solution in step (2) is 1:2-4.

[0019] Furthermore, the parameters of the spray drying in step (2) are set as follows: feed rate: 10-20 mL / min, nozzle pressure: 0.2-0.4 MPa, air inlet temperature: 140-160°C, and air outlet temperature: 80-90°C.

[0020] The present invention selects silver nitrate, zinc sulfate and copper sulfate as main antibacterial agents. When silver nitrate is used in combination with zinc sulfate and copper sulfate, its antibacterial effect can be enhanced. Silver ions can act together with zinc ions and copper ions to form a composite antibacterial system, thereby improving the breadth and depth of the antibacterial spectrum. In addition, tea polyphenols, thyme essential oil and citric acid are added. When tea polyphenols are used in combination with metal ions (such as silver ions, zinc ions and copper ions), the destructive effect on bacterial cell membranes can be enhanced. Thyme essential oil is a natural antibacterial agent with an inhibitory effect on various bacteria and fungi. It can destroy bacterial cell membranes, interfere with their metabolic functions, and thus inhibit their growth. Thyme essential oil is also volatile and permeable and can form a protective film on the surface of paper to prevent bacterial invasion. Citric acid can form a complex with metal ions, improve its stability and solubility, thereby enhancing the antibacterial effect. Citric acid can also enhance the flexibility and tear resistance of paper. When used in combination, multiple antimicrobial ingredients, including silver nitrate, zinc sulfate, copper sulfate, tea polyphenols, thyme essential oil, and citric acid, can act on different targets on bacteria and fungi, forming a multi-target antimicrobial system. For example, silver ions can disrupt bacterial cell membranes, zinc and copper ions can interfere with bacterial protein synthesis and enzyme activity, tea polyphenols can interfere with bacterial DNA replication and protein synthesis, thyme essential oil can disrupt bacterial cell membranes, and citric acid can adjust the pH value of the antimicrobial solution. This multi-target antimicrobial system can enhance the breadth and depth of antimicrobial efficacy, effectively killing and inhibiting the growth of a wide range of bacteria and fungi.

[0021] The present invention utilizes microcapsule technology to encapsulate the antimicrobial agent inside the wall material, protecting it from the influence of the external environment and prolonging the active time of the antimicrobial agent. The antimicrobial agent is not easily exposed to oxygen inside the microcapsule, which reduces the possibility of oxidation and degradation and maintains the high efficiency of the antimicrobial agent. Microcapsule technology can achieve the slow release of the antimicrobial agent by controlling the thickness and porosity of the wall material, ensuring the long-lasting antimicrobial effect of the antimicrobial agent in the paper. It can also make the antimicrobial agent evenly distributed in the paper, avoiding the problem of local concentration being too high or too low, and improving the uniformity and stability of the antimicrobial effect. The microcapsule wall material has good water resistance and is not easy to dissolve or lose even during the water washing process, thus maintaining the effective ingredients of the antimicrobial agent and ensuring the durability of the antimicrobial effect. It also has good friction resistance and is not easy to fall off even after multiple frictions, thus maintaining the effective ingredients of the antimicrobial agent and ensuring the durability of the antimicrobial effect. The microcapsule wall material selected by the present invention also has good mechanical properties and can enhance the strength, flexibility and tear resistance of the paper.

[0022] Furthermore, the amount of the microcapsule antibacterial agent added in step (3) is 0.5-1% of the mass of the pulp.

[0023] Furthermore, the mass parts of each component in the coating in step (4) are as follows: 8-15 parts of microcapsule antibacterial agent, 18-25 parts of corn starch, 8-15 parts of polyvinyl alcohol, 0.3-0.6 parts of defoaming agent, 0.3-0.6 parts of wetting agent, 0.5-2 parts of plasticizer, and 50-70 parts of deionized water.

[0024] Furthermore, the defoaming agent is selected from one or more of polydimethylsiloxane, white oil, glyceryl stearate, and tributyl phosphate; the wetting agent is selected from one or more of ethylene glycol butyl ether, sodium lauryl sulfate, isopropyl alcohol, nonylphenol polyoxyethylene ether, and sorbitan monooleate; and the plasticizer is selected from one or more of dioctyl phthalate, epoxy soybean oil, acetyl tributyl citrate, dioctyl sebacate, and polyethylene adipate.

[0025] Furthermore, in step (4), the drying temperature is 80-90° C., the drying time is 30-60 seconds; the calendering pressure is 10-20 MPa, and the calendering speed is 60-90 m / min.

[0026] The microcapsule antimicrobial agent of the present invention is encapsulated by microencapsulation technology to ensure the uniform distribution and long-term release of the antimicrobial agent in the paper. Other ingredients in the coating (such as corn starch and polyvinyl alcohol) can enhance the stability and release effect of the microcapsule antimicrobial agent, ensuring the durability of the antimicrobial effect. Polyvinyl alcohol, as a film-forming agent, can improve the transparency and water resistance of the coating, ensuring the stability and durability of the coating; corn starch, as a binder, can enhance the adhesion of the coating, so that the coating forms a uniform protective layer on the surface of the paper; the defoamer can eliminate bubbles in the coating and prevent the coating from generating bubbles during the coating process; the wetting agent can reduce the surface tension of the coating, improve the wettability of the coating on the paper surface, and ensure the uniformity and integrity of the coating; the plasticizer can increase the flexibility and ductility of the coating and prevent the coating from cracking during the drying process. Polyvinyl alcohol and corn starch can improve the flexibility and breakage resistance of the coating and enhance the physical properties of the paper. The water resistance of polyvinyl alcohol and the film-forming property of corn starch can prevent the coating from falling off during the washing process, ensuring the durability of the antimicrobial effect. Plasticizers can improve the flexibility and tear resistance of the coating, prevent the coating from falling off during friction, and ensure the durability of the antibacterial effect.

[0027] Furthermore, the hot pressing temperature of the hot pressing bonding in step (5) is 110-130°C, the hot pressing pressure is 0.1-0.3MPa, and the hot pressing time is 20-30 seconds; the cooling temperature of the cooling and shaping is 20-30°C, and the cooling time is 30-60 seconds.

[0028] Another aspect of the present invention provides antibacterial and mildew-proof corrugated paper prepared by the method.

[0029] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0030] 1. Excellent antibacterial and anti-mildew effect

[0031] The antimicrobial solution of the present invention contains multiple antimicrobial ingredients that work synergistically and can effectively kill and inhibit the growth of multiple bacteria and molds. The high-efficiency antimicrobial agent is encapsulated through microencapsulation technology to ensure uniform distribution and long-term release of the antimicrobial agent in paper. Microencapsulation technology can protect the antimicrobial agent from the influence of the external environment, prolong its active time, and thus improve the antimicrobial and mildew-proof effect.

[0032] 2. Good physical properties

[0033] The coating components of the antimicrobial protective layer have been carefully selected and proportioned to ensure that the coating has a positive impact on the mechanical properties of the paper, improving the edge crush strength and bursting strength of the paper.

[0034] 3. Excellent durability

[0035] The microcapsule antibacterial agent has good water resistance and friction resistance. It can remain stable even during washing and after multiple frictions and will not be easily lost, ensuring the durability of the antibacterial and anti-mildew effect.

[0036] 4. Safety and environmental protection

[0037] The antibacterial components selected in the present invention are friendly to the human body and the environment, will not cause skin allergies, respiratory tract irritation and other problems, and meet environmental protection and safety requirements; the wall material components are all degradable materials, which reduces pollution to the environment and is in line with the concept of sustainable development. DETAILED DESCRIPTION

[0038] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0039] Unless otherwise specified, the raw materials used in the present invention are all commercially available products. The following is an exemplary description:

[0040] Softwood pulp was purchased from Shandong Sun Paper Co., Ltd.

[0041] Waste paper pulp was purchased from Nine Dragons Paper (Holdings) Limited.

[0042] Polylactic acid was purchased from Kingfa Science & Technology Co., Ltd., product brand: K2003D.

[0043] Corn starch was purchased from Jilin Songyuan Grain Group Co., Ltd.

[0044] Polyvinyl alcohol was purchased from Anhui Wanwei High-tech Materials Co., Ltd., product brand: Wanwei PVA.

[0045] Staphylococcus aureus was purchased from Beijing Zhongke Zhijian Biotechnology Co., Ltd., number: ZKCC 153474.

[0046] Escherichia coli was purchased from China Industrial Culture Collection Center, number: CICC 10899.

[0047] Aspergillus niger was purchased from Beijing Zhongke Quality Inspection Biotechnology Co., Ltd., with the license number: ZKCC 153712.

[0048] Example 1

[0049] This embodiment provides a method for preparing antibacterial and mildew-proof corrugated paper, comprising the following steps:

[0050] (1) Preparation of pulp: softwood pulp and waste paper pulp were mixed as raw materials in a mass ratio of 1:0.15, and the raw materials were placed in a pulper for beating. The beating degree was adjusted to 25°SR to ensure the fiber separation and suspension of the pulp. The beating time was 30 minutes, and the beating concentration was 4%. After the treatment, the pulp was passed through a 200-mesh sieve and centrifuged to remove impurities. The pH value was adjusted to 7 to obtain pulp.

[0051] (2) Preparation of microcapsule antibacterial agent: 4 parts of silver nitrate, 1.5 parts of zinc sulfate, 1 part of copper sulfate, 2 parts of tea polyphenols, 0.6 parts of thyme essential oil and 0.4 parts of citric acid were dissolved in deionized water to prepare an antibacterial agent solution with a total mass concentration of 8%; 7 parts of gelatin, 4 parts of chitosan and 1.5 parts of polylactic acid were dissolved in deionized water and stirred at 70°C to prepare a wall material solution with a total mass concentration of 12%; the antibacterial agent solution was added to the wall material solution at a mass ratio of 1:3, stirred evenly to obtain a mixed solution, and the mixed solution was spray-dried to obtain a microcapsule antibacterial agent. The spray drying parameters were set as follows: feed rate: 15 mL / min, nozzle pressure: 0.3 MPa, air inlet temperature: 150°C, air outlet temperature: 85°C;

[0052] (3) Preparation of base paper: Add microcapsule antimicrobial agent to paper pulp at an amount of 0.8% of the mass of the pulp. Use a high-speed stirrer to fully mix the pulp at a stirring speed of 1500 rpm for 30 minutes. Feed the pulp mixed with microcapsule antimicrobial agent into the wire section of the papermaking machine. Vibration and vacuum action of the wire section spread the pulp uniformly and preliminarily dehydrate it. Then, the pulp enters the pressing section, where excess water is squeezed out by the pressing roller to form a wet paper web with a certain dryness. Finally, the pulp enters the drying section and is dried by a multi-stage drying cylinder to obtain base paper.

[0053] (4) Coating of antibacterial protective layer: 12 parts of microcapsule antibacterial agent, 20 parts of corn starch, 11 parts of polyvinyl alcohol, 0.5 parts of defoaming agent (glyceryl stearate), 0.4 parts of wetting agent (sodium lauryl sulfate), 1 part of plasticizer (dioctyl phthalate) and 60 parts of deionized water were mixed by mass to prepare a coating, which was applied to the surface of the base paper and pressed into the paper fibers by a coating roller. The coated base paper was dried and calendered at a drying temperature of 90°C, a drying time of 40 seconds, a calendering pressure of 15 MPa, and a calendering speed of 70 m / min.

[0054] (5) Forming of corrugated paper: corrugated paper includes face paper, corrugated core paper and bottom paper, wherein the face paper and bottom paper are the base paper after drying and calendering in step (4), the base paper after drying and calendering in step (4) is fed into a corrugating forming machine, and the base paper is pressed into a wave shape by a corrugating roller to form corrugated core paper, corn starch glue (corn starch and water are mixed in a ratio of 1:10, heated to 80°C, stirred for 30 minutes, until completely dissolved, to prepare corn starch glue) is coated on the inner side of the face paper and bottom paper, and then the corrugated core paper is sandwiched in the middle and hot-pressed by a hot press, the hot-pressing temperature of the hot-pressing bonding is 120°C, the hot-pressing pressure is 0.2MPa, and the hot-pressing time is 30 seconds, the hot-pressed corrugated paper is cooled and shaped, the cooling temperature is 25°C, and the cooling time is 40 seconds, thus obtaining the antibacterial and mildew-proof corrugated paper.

[0055] Example 2

[0056] This embodiment provides a method for preparing antibacterial and mildew-proof corrugated paper, comprising the following steps:

[0057] (1) Preparation of pulp: softwood pulp and waste paper pulp were mixed as raw materials in a mass ratio of 1:0.15, and the raw materials were placed in a pulper for beating. The beating degree was adjusted to 25°SR to ensure the fiber separation and suspension of the pulp. The beating time was 30 minutes, and the beating concentration was 4%. After the treatment, the pulp was passed through a 200-mesh sieve and centrifuged to remove impurities. The pH value was adjusted to 7 to obtain pulp.

[0058] (2) Preparation of microcapsule antibacterial agent: 2 parts of silver nitrate, 2 parts of zinc sulfate, 2 parts of copper sulfate, 2 parts of tea polyphenols, 0.5 parts of thyme essential oil and 0.3 parts of citric acid were dissolved in deionized water by mass to prepare an antibacterial agent solution with a mass concentration of 8%; 7 parts of gelatin, 3 parts of chitosan and 2 parts of polylactic acid were dissolved in deionized water and stirred at 70°C to prepare a wall material solution with a mass concentration of 15%; the antibacterial agent solution was added to the wall material solution at a mass ratio of 1:3, stirred evenly to obtain a mixed solution, and the mixed solution was spray-dried to obtain a microcapsule antibacterial agent. The spray drying parameters were set as follows: feed rate: 15 mL / min, nozzle pressure: 0.3 MPa, air inlet temperature: 150°C, air outlet temperature: 85°C;

[0059] (3) Preparation of base paper: Add microcapsule antimicrobial agent to paper pulp at an amount of 1% of the mass of the pulp, and use a high-speed stirrer to fully mix the pulp at a stirring speed of 1500 rpm for 30 minutes. The pulp mixed with microcapsule antimicrobial agent is fed into the wire section of the papermaking machine. The vibration and vacuum effect of the wire section make the pulp evenly spread and preliminarily dehydrated. Then, the pulp enters the pressing section, where excess water is squeezed out by the pressing roller to form a wet paper web with a certain dryness. Finally, the pulp enters the drying section and is dried by a multi-stage drying cylinder to produce base paper.

[0060] (4) Coating of antibacterial protective layer: 10 parts of microcapsule antibacterial agent, 22 parts of corn starch, 15 parts of polyvinyl alcohol, 0.5 parts of defoaming agent (tributyl phosphate), 0.4 parts of wetting agent (ethylene glycol butyl ether), 1 part of plasticizer (epoxidized soybean oil) and 60 parts of deionized water were mixed by mass to prepare a coating, which was applied to the surface of the base paper and pressed into the paper fibers by a coating roller. The coated base paper was dried and calendered at a drying temperature of 90°C, a drying time of 40 seconds, a calendering pressure of 15 MPa, and a calendering speed of 70 m / min.

[0061] (5) Forming of corrugated paper: corrugated paper includes face paper, corrugated core paper and bottom paper, wherein the face paper and bottom paper are the base paper after drying and calendering in step (4), the base paper after drying and calendering in step (4) is fed into a corrugating forming machine, and the base paper is pressed into a wave shape by a corrugating roller to form corrugated core paper, corn starch glue (corn starch and water are mixed in a ratio of 1:10, heated to 80°C, stirred for 30 minutes, until completely dissolved, to prepare corn starch glue) is coated on the inner side of the face paper and bottom paper, and then the corrugated core paper is sandwiched in the middle and hot-pressed by a hot press, the hot-pressing temperature of the hot-pressing bonding is 120°C, the hot-pressing pressure is 0.2MPa, and the hot-pressing time is 30 seconds, the hot-pressed corrugated paper is cooled and shaped, the cooling temperature is 25°C, and the cooling time is 40 seconds, thus obtaining the antibacterial and mildew-proof corrugated paper.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing antibacterial and mildew-proof corrugated paper, which differs from Example 1 in that the mass parts of the components in the antibacterial agent solution in step (2) are as follows: 5 parts of silver nitrate, 2 parts of zinc sulfate, 1 part of copper sulfate, 0.5 parts of tea polyphenols, 0.1 parts of thyme essential oil, and 0.9 parts of citric acid.

[0064] Comparative Example 2

[0065] This comparative example provides a method for preparing antibacterial and mildew-proof corrugated paper, which differs from Example 1 in that the thyme essential oil in the antibacterial agent solution in step (2) is replaced by rosemary essential oil.

[0066] Comparative Example 3

[0067] This comparative example provides a method for preparing antibacterial and mildew-proof corrugated paper, which differs from Example 1 in that the gelatin, chitosan and polylactic acid in the wall material solution in step (2) are replaced by gum arabic, sodium alginate and polyvinyl alcohol, respectively.

[0068] Comparative Example 4

[0069] This comparative example provides a method for preparing antibacterial and mildew-proof corrugated paper, which differs from Example 1 in that the antibacterial agent is not microencapsulated, that is, step (2) is replaced by: Preparation of antibacterial agent solution: 4 parts of silver nitrate, 1.5 parts of zinc sulfate, 1 part of copper sulfate, 2 parts of tea polyphenols, 0.6 parts of thyme essential oil and 0.4 parts of citric acid are dissolved in deionized water to prepare an antibacterial agent solution with a mass concentration of 8%.

[0070] Comparative Example 5

[0071] This comparative example provides a method for preparing antibacterial and mildew-proof corrugated paper, which differs from Example 1 in that the coating in step (4) is composed of: 12 parts of microcapsule antibacterial agent, 20 parts of corn starch, 5 parts of polyvinyl alcohol, 0.5 parts of defoaming agent (glyceryl stearate), 1 part of wetting agent (sodium lauryl sulfate), 4 parts of plasticizer (dioctyl phthalate) and 80 parts of deionized water.

[0072] Comparative Example 6

[0073] This comparative example provides a method for preparing antibacterial and mildew-proof corrugated paper, which differs from Example 1 in that the coating in step (4) is composed of: 12 parts of microcapsule antibacterial agent, 20 parts of hydroxypropyl methylcellulose, 11 parts of polyvinyl pyrrolidone, 0.5 parts of defoaming agent (glyceryl stearate), 0.4 parts of wetting agent (sodium lauryl sulfate), 1 part of plasticizer (dioctyl phthalate) and 60 parts of deionized water.

[0074] Performance test 1 Antibacterial and mildew resistance test

[0075] (1) Test sample preparation:

[0076] Initial samples: The antibacterial and mildew-proof corrugated paper prepared in Examples 1-2 and Comparative Examples 1-6 were cut into 5 cm × 5 cm square samples as initial samples;

[0077] Washed samples: Cut the antibacterial and mildew-proof corrugated paper prepared in Examples 1-2 and Comparative Examples 1-6 into 5 cm × 5 cm square samples, soak the samples in deionized water for 30 minutes, and air-dry the samples until completely dry. Repeat the above steps three times, for a total of three deionized water soakings. After drying, use them as washed samples;

[0078] Friction samples: The antibacterial and mildew-proof corrugated papers prepared in Examples 1-2 and Comparative Examples 1-6 were cut into 5 cm×5 cm square samples respectively, and the samples were rubbed using a friction machine for 100 times to prepare friction samples.

[0079] (2) The antibacterial properties were tested on Staphylococcus aureus and Escherichia coli.

[0080] Antibacterial performance test steps: In addition to the above three groups of samples, corrugated paper without antibacterial treatment was prepared as a control sample; a loop of the frozen strain was inoculated into nutrient broth and cultured at 37°C for 24 hours, and the cultured bacterial solution was diluted with sterile saline to 10^6 CFU / mL to obtain a bacterial suspension; on a sterile operating table, each sample was placed in a sterile container, 10 mL of the prepared bacterial suspension was added to each container, the container was placed in an oscillator, and oscillated at 150 rpm for 15 minutes. After the oscillation, the sample was taken out and rinsed three times with sterile saline, 10 mL each time, and the liquid after each rinse was collected and merged into a sterile container. The collected rinse liquid was diluted 10 times with sterile saline, and an appropriate amount of the diluted bacterial solution was evenly spread on a nutrient agar plate. The plate was placed in a 37°C constant temperature incubator and cultured for 24 hours. After the incubation, the number of colonies on the plate was counted and the antibacterial rate was calculated: Antibacterial rate (%) = (1-N t / N c )×100%, where N t is the number of colonies on the test sample, N c is the number of colonies on the control sample.

[0081] (3) The fungus used in the anti-mildew performance test is Aspergillus niger.

[0082] The following steps were used to test the anti-mold performance: a loopful of the frozen strain was inoculated onto a PDA plate and cultured at 28°C for 7 days. The mold spores on the plate were washed off with sterile saline to prepare a 106 CFU / mL mold spore suspension. On a sterile operating table, each sample was placed in a sterile container and 10 mL of the prepared mold spore suspension was added to each container. The container was allowed to stand for 24 hours to allow the spores to adhere to the sample surface. The treated sample was removed and placed in a constant temperature and humidity chamber at 28°C and 90% relative humidity for 7 days. The mold growth on the sample surface was observed and recorded daily.

[0083] Samples were scored for mold growth according to the following criteria:

[0084] Level 0: no mold growth;

[0085] Level 1: A small amount of mold growth, accounting for less than 10% of the total area;

[0086] Level 2: Mold growth is significant, covering 10%-30% of the total area;

[0087] Level 3: Mold growth is very high, covering 30%-60% of the total area;

[0088] Level 4: Mold growth is very severe, covering more than 60% of the total area.

[0089] The antibacterial and mildew-proof performance test results are shown in Tables 1-3.

[0090] Table 1 Test results of antibacterial and antifungal properties of initial samples

[0091]

[0092]

[0093] Table 2 Test results of antibacterial and antifungal properties of washed samples

[0094]

[0095] Table 3 Test results of antibacterial and antifungal properties of friction samples

[0096]

[0097] The above test results show that the corrugated paper prepared by the present invention has excellent antibacterial and mildew-proof properties, and even after washing and rubbing, the sample still has strong antibacterial and mildew-proof properties. The mass parts of each component in the antibacterial agent solution are different in comparative example 1, and particularly the content of silver nitrate is higher, which may cause the synergistic effect between the antibacterial agent to weaken, and even high-content silver nitrate may produce an inhibitory effect on other antibacterial components (such as tea polyphenols and thyme essential oil), reducing overall antibacterial activity; Metal ions such as silver nitrate are easily dissolved or lost during washing, and are more likely to fall off during friction, causing the effective ingredient of the antibacterial agent to reduce, and antibacterial effect declines. Thyme essential oil is replaced with rosemary essential oil in comparative example 2, although rosemary essential oil also has certain antibacterial effect, but its antibacterial spectrum and antibacterial activity are not as good as thyme essential oil, causing overall antibacterial effect to decline; In addition, according to washing and rubbing results, it can be seen that rosemary essential oil is more likely to fall off during washing or rubbing, causing antibacterial effect to decline. In Comparative Example 3, the gelatin, chitosan, and polylactic acid in the wall material solution were replaced with gum arabic, sodium alginate, and polyvinyl alcohol, respectively. These replacement ingredients may not offer the same encapsulation efficiency and stability as the original ingredients, resulting in poor antimicrobial release. In Comparative Example 4, the antimicrobial agent was not microencapsulated, resulting in uneven distribution within the paper and unstable antimicrobial efficacy. Unencapsulated antimicrobial agent easily dissolves or falls off during washing and friction, significantly reducing antimicrobial efficacy. The choice of coating components in Comparative Examples 5 and 6 may result in poor coating stability, impacting antimicrobial release.

[0098] Performance test 2 strength test

[0099] The antibacterial and mildew-proof corrugated papers prepared in Examples 1-2 and Comparative Examples 1-6 were cut into 5 cm×5 cm square samples as test samples.

[0100] The edge crush strength is tested according to the requirements of GB / T 6546-1998 "Corrugated board - Determination of edge crush strength", and the bursting strength is tested according to the requirements of GB / T 1539-2007 "Corrugated board - Determination of bursting strength".

[0101] The test results are shown in Table 4:

[0102] Table 4 Strength test results

[0103]

[0104]

[0105] The above results show that the corrugated paper prepared by the present invention has excellent edge crush strength and bursting strength, indicating that the microcapsule antimicrobial agent used in the present invention has little effect on the mechanical properties of the paper and may even enhance the strength of the paper. The edge crush strength and bursting strength of Comparative Examples 3 and 4 decreased slightly, possibly because the packaging wall material was changed, resulting in poor packaging effect. Even when the antimicrobial agent was not encapsulated, the antimicrobial agent had a negative impact on the mechanical properties of the paper. The edge crush strength and bursting strength of Comparative Examples 5 and 6 decreased significantly, possibly because the replacement of the coating component resulted in insufficient support for the coating on the paper, causing the paper to become loose and affecting its strength.

[0106] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing antibacterial and mildew-proof corrugated paper, comprising the following steps: (1) Preparation of pulp: Mix wood pulp and waste paper pulp as raw materials, put the raw materials into a pulper for pulping, sieve and centrifuge to remove impurities, adjust the pH value to 7-8, and obtain pulp; (2) Preparation of microcapsule antibacterial agent: silver nitrate, zinc sulfate, copper sulfate, tea polyphenols, thyme essential oil and citric acid are dissolved in deionized water to prepare an antibacterial agent solution; gelatin, chitosan and polylactic acid are dissolved in deionized water, heated and stirred to prepare a wall material solution; the antibacterial agent solution is added to the wall material solution, stirred to obtain a mixed solution, and the mixed solution is spray-dried to obtain a microcapsule antibacterial agent; (3) Preparation of base paper: Add the microcapsule antimicrobial agent to the pulp, use a high-speed stirrer to fully mix it, send the pulp mixed with the microcapsule antimicrobial agent into the papermaking machine, and produce the base paper after dehydration, pressing and drying; (4) Coating of the antibacterial protective layer: Mix the microcapsule antibacterial agent, corn starch, polyvinyl alcohol, defoamer, wetting agent, plasticizer and deionized water to prepare a coating, apply the coating to the surface of the base paper, press the coating into the paper fibers through a coating roller, and dry and calender the coated base paper; (5) Forming of corrugated paper: The corrugated paper includes face paper, corrugated core paper and bottom paper. The face paper and bottom paper are the base paper after drying and calendering in step (4). The base paper after drying and calendering in step (4) is fed into a corrugating forming machine, and the base paper is pressed into a wave shape by a corrugating roller to form a corrugated core paper. Corn starch glue is coated on the inner sides of the face paper and bottom paper, and then the corrugated core paper is sandwiched in the middle, and hot pressing and bonding are performed by a hot press. The hot pressed corrugated paper is cooled and shaped to obtain the antibacterial and mildew-proof corrugated paper. The mass ratio of the wood pulp to the waste paper pulp in step (1) is 1:0.1-0.2; The mass parts of the components in the antibacterial solution in step (2) are as follows: 2-4 parts of silver nitrate, 1-2 parts of zinc sulfate, 1-2 parts of copper sulfate, 1-2 parts of tea polyphenols, 0.5-0.8 parts of thyme essential oil, and 0.3-0.5 parts of citric acid; the mass concentration of the antibacterial solution is 6-10%; The weight parts of the components in the wall material solution in step (2) are as follows: 6-8 parts of gelatin, 3-5 parts of chitosan, and 1-2 parts of polylactic acid; the weight concentration of the wall material solution is 10-15%, and the heating temperature is 60-70°C; The mass ratio of the antibacterial agent solution to the wall material solution in step (2) is 1:2-4; The amount of the microcapsule antibacterial agent added in step (3) is 0.5-1% of the pulp mass; The weight parts of the components in the coating in step (4) are as follows: 10-12 parts of microcapsule antibacterial agent, 20-22 parts of corn starch, 11-15 parts of polyvinyl alcohol, 0.3-0.6 parts of defoaming agent, 0.3-0.6 parts of wetting agent, 0.5-2 parts of plasticizer, and 50-70 parts of deionized water; The defoaming agent is selected from one or more of polydimethylsiloxane, white oil, glyceryl stearate, and tributyl phosphate; the wetting agent is selected from one or more of ethylene glycol butyl ether, sodium lauryl sulfate, isopropyl alcohol, nonylphenol polyoxyethylene ether, and sorbitan monooleate; and the plasticizer is selected from one or more of dioctyl phthalate, epoxy soybean oil, acetyl tributyl citrate, dioctyl sebacate, and polyethylene adipate.

2. The preparation method according to claim 1, characterized in that The parameters of the spray drying in step (2) are set as follows: feed rate: 10-20 mL / min, nozzle pressure: 0.2-0.4 MPa, air inlet temperature: 140-160°C, and air outlet temperature: 80-90°C.

3. The preparation method according to claim 1, characterized in that The drying temperature in step (4) is 80-90° C., and the drying time is 30-60 seconds; the calendering pressure is 10-20 MPa, and the calendering speed is 60-90 m / min.

4. The preparation method according to claim 1, characterized in that The hot pressing temperature of the hot pressing bonding in step (5) is 110-130°C, the hot pressing pressure is 0.1-0.3 MPa, and the hot pressing time is 20-30 seconds; the cooling temperature of the cooling and setting is 20-30°C, and the cooling time is 30-60 seconds.

5. An antibacterial and mildew-proof corrugated paper prepared by the method according to any one of claims 1 to 4.

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