Antibacterial mildew-proof corrugated paper and preparation method thereof

Abstract

The invention provides antibacterial and mildew-proof corrugated paper and a preparation method thereof, and belongs to the technical field of packaging materials. According to the corrugated paper, the efficient antibacterial agent is doped into the paper base material, and the paper base material is packaged through a microcapsule technology, so that uniform distribution and long-acting release of the antibacterial agent in the paper are ensured. The preparation process comprises the steps of paper pulp preparation, antibacterial agent preparation, raw paper preparation, antibacterial protection layer coating, corrugated paper forming and the like. The antibacterial and mildewproof corrugated paper has excellent antibacterial and mildewproof effects, can keep good physical properties, is suitable for packaging products such as food, medicines and cosmetics with strict requirements on sanitary conditions, effectively prevents microbial contamination 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 the development of the global economy and the improvement of people's living standards, the demand for the packaging industry is growing. As a common packaging material, corrugated paper is widely used in the packaging of various commodities due to its advantages such as low cost, light weight, and easy processing and molding. However, since the main component of corrugated paper is plant fiber, this characteristic makes it easy to breed bacteria and mold in a humid or high temperature environment, which not only affects the quality and safety of the packaging, but also may cause environmental pollution and waste of resources. Especially in the fields of food, medicine, cosmetics and other fields with high requirements for hygiene conditions, the antibacterial and anti-mildew properties of corrugated paper are particularly important.

[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] In order to overcome these problems in the existing technology, researchers and enterprises are exploring new antibacterial and mildew-proof technologies and materials, improving the production process of corrugated paper, and ensuring that the antibacterial and mildew-proof components can be evenly and firmly attached to the surface of the paper. For example, methods such as impregnation, spraying or coating are used to improve the binding force between the antibacterial and mildew-proof components and the paper. In addition, the existing technology develops new materials with more stable antibacterial and mildew-proof properties by synthesizing or modifying existing materials. These new materials should be able to maintain stable antibacterial and mildew-proof effects under different 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 the antibacterial agent in the paper, the long-term release of the antibacterial agent, 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 of 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] 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 pulping machine for pulping. After the processing is completed, the raw materials are 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: dissolving silver nitrate, zinc sulfate, copper sulfate, tea polyphenols, thyme essential oil and citric acid in deionized water to prepare an antibacterial agent solution; dissolving gelatin, chitosan and polylactic acid in deionized water, heating and stirring to prepare a wall material solution; adding the antibacterial agent solution to the wall material solution, stirring to obtain a mixed solution, and spray drying the mixed solution 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 defoamer, 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 comprises face paper, corrugated core paper and bottom paper, wherein the face paper and bottom paper are the base paper dried and calendered in step (4). The base paper dried and calendered 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 between and heat-pressed and bonded by a heat press. The heat-pressed and bonded corrugated paper is cooled and shaped to obtain the antibacterial and mildew-proof corrugated paper.

[0015] Furthermore, in step (1), the mass ratio of the wood pulp to the waste paper pulp 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 weight proportions 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.

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

[0019] Furthermore, the spray drying parameters 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, 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 that has 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 also has volatility and permeability, and can form a protective film on the surface of paper to prevent bacterial invasion. Citric acid can form a complex with metal ions to improve its stability and solubility, thereby enhancing the antibacterial effect. Citric acid can also enhance the flexibility and tear resistance of paper. When multiple antibacterial ingredients such as silver nitrate, zinc sulfate, copper sulfate, tea polyphenols, thyme essential oil and citric acid are used together, they can act on different targets of bacteria and fungi to form a multi-target antibacterial system. For example, silver ions can destroy bacterial cell membranes, zinc ions 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 destroy bacterial cell membranes, and citric acid can adjust the pH value of the antibacterial solution. The multi-target antibacterial system can improve the breadth and depth of the antibacterial effect and effectively kill and inhibit the growth of a variety of bacteria and fungi.

[0021] The present invention uses microcapsule technology to wrap the antibacterial agent inside the wall material, protect it from the influence of the external environment, and prolong the active time of the antibacterial agent. The antibacterial agent is not easy to contact with oxygen inside the microcapsule, which reduces the possibility of oxidation and degradation and maintains the high efficiency of the antibacterial agent. Microcapsule technology can achieve the slow release of the antibacterial agent by controlling the thickness and porosity of the wall material, ensure the long-term antibacterial effect of the antibacterial agent in the paper, and can also make the antibacterial agent evenly distributed in the paper, avoid the problem of excessive or low local concentration, and improve the uniformity and stability of the antibacterial effect. The microcapsule wall material has good water resistance, is not easy to dissolve or lose even in the water washing process, maintains the effective ingredients of the antibacterial agent, and ensures the durability of the antibacterial effect; at the same time, it has good friction resistance, is not easy to fall off even after multiple frictions, maintains the effective ingredients of the antibacterial agent, and ensures the durability of the antibacterial effect. The microcapsule wall material selected by the present invention also has good mechanical properties, which 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 weight parts of the components 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; the plasticizer is selected from one or more of dioctyl phthalate, epoxy soybean oil, acetylcitrate tributyl ester, dioctyl sebacate, and polyethylene adipate.

[0025] Furthermore, in step (4), the drying temperature 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.

[0026] The microcapsule antibacterial agent of the present invention is encapsulated by microcapsule technology to ensure the uniform distribution and long-term release of the antibacterial agent in paper. Other components in the coating (such as corn starch and polyvinyl alcohol) can enhance the stability and release effect of the microcapsule antibacterial agent and ensure the durability of the antibacterial effect. Polyvinyl alcohol, as a film-forming agent, can improve the transparency and water resistance of the coating and ensure the stability and durability of the coating; corn starch, as an adhesive, can enhance the adhesion of the coating and form 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 surface of the paper, 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 tear 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 and ensure the durability of the antibacterial 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, in step (5), the hot pressing temperature of the hot pressing bonding 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 antibacterial agent solution of the present invention contains a variety of antibacterial ingredients, which have a synergistic effect and can effectively kill and inhibit the growth of a variety of bacteria and molds; the high-efficiency antibacterial agent is encapsulated by microencapsulation technology to ensure the uniform distribution and long-term release of the antibacterial agent in the paper. The microencapsulation technology can protect the antibacterial agent from the influence of the external environment and prolong its active time, thereby improving the antibacterial and antifungal 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 effect on the mechanical properties of the paper and improves the edge crush strength and bursting strength of the paper.

[0034] 3. Excellent durability

[0035] Microcapsule antibacterial agents have good water resistance and friction resistance. Even during washing and after multiple frictions, they can remain stable and will not easily flow away, ensuring the durability of the antibacterial and anti-mildew effects.

[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 meets the concept of sustainable development. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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, and the following is an exemplary description:

[0040] Coniferous wood 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., No.: ZKCC 153474.

[0046] Escherichia coli was purchased from China Industrial Microbiology Culture Collection Center, No.: CICC 10899.

[0047] Aspergillus niger was purchased from Beijing Zhongke Quality Inspection Biotechnology Co., Ltd., 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 at a mass ratio of 1:0.15, and the raw materials were put into a pulping machine for pulping. 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, centrifuged to remove impurities, and 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, inlet air temperature: 150°C, outlet air temperature: 85°C;

[0052] (3) Preparation of base paper: adding microcapsule antimicrobial agent to pulp, the amount of microcapsule antimicrobial agent added is 0.8% of the mass of pulp, using a high-speed stirrer to fully mix, the stirring speed is 1500rpm, the stirring time is 30 minutes, the pulp mixed with microcapsule antimicrobial agent is sent to the wire part of the papermaking machine, the pulp is evenly spread and preliminarily dehydrated by the vibration and vacuum effect of the wire part, and then enters the pressing part, the excess water is squeezed out by the pressing roller, and a wet paper web with a certain dryness is formed, and finally enters the drying part, and the wet paper web 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 weight to prepare a coating, and the coating was coated on the surface of the base paper, and the coating was pressed into the paper fiber by a coating roller, and the coated base paper was dried and calendered, the drying temperature was 90° C., the drying time was 40 seconds, the calendering pressure was 15 MPa, and the calendering speed was 70 m / min;

[0054] (5) Forming of corrugated paper: The corrugated paper comprises face paper, corrugated core paper and backing paper, wherein the face paper and the backing paper are the base paper dried and calendered in step (4). The base paper dried and calendered 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 (corn starch and water are mixed in a ratio of 1:10, heated to 80°C, and stirred for 30 minutes until they are completely dissolved to obtain corn starch glue) is coated on the inner sides of the face paper and the backing 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 0.2 MPa, and the hot-pressing time is 30 seconds. The hot-pressed corrugated paper is cooled and shaped at a cooling temperature of 25°C and a cooling time of 40 seconds to obtain 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 at a mass ratio of 1:0.15, and the raw materials were put into a pulping machine for pulping. 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, centrifuged to remove impurities, and the pH value was adjusted to 7 to obtain pulp.

[0058] (2) Preparation of microcapsule antibacterial agent: Dissolve 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 in deionized water to prepare an antibacterial agent solution with a mass concentration of 8%; dissolve 7 parts of gelatin, 3 parts of chitosan and 2 parts of polylactic acid in deionized water, stir at 70°C to prepare a wall material solution with a mass concentration of 15%; add the antibacterial agent solution to the wall material solution at a mass ratio of 1:3, stir evenly to obtain a mixed solution, spray dry the mixed solution to obtain a microcapsule antibacterial agent, and the spray drying parameters are set as follows: feed rate: 15 mL / min, nozzle pressure: 0.3 MPa, inlet air temperature: 150°C, outlet air temperature: 85°C;

[0059] (3) Preparation of base paper: adding microcapsule antimicrobial agent to pulp, the amount of microcapsule antimicrobial agent added is 1% of the mass of pulp, using a high-speed stirrer to fully mix, the stirring speed is 1500rpm, the stirring time is 30 minutes, the pulp mixed with microcapsule antimicrobial agent is sent to the wire section of the papermaking machine, the pulp is evenly spread and preliminarily dehydrated by the vibration and vacuum of the wire section, and then enters the pressing section, the excess water is squeezed out by the pressing roller, and a wet paper web with a certain dryness is formed, and finally enters the drying section, and the wet paper web is dried by a multi-stage drying cylinder to obtain 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 weight to prepare a coating, and the coating was coated on the surface of the base paper, and the coating was pressed into the paper fiber by a coating roller. The coated base paper was dried and calendered at a drying temperature of 90° C. and a drying time of 40 seconds. The calendering pressure was 15 MPa and the calendering speed was 70 m / min.

[0061] (5) Forming of corrugated paper: The corrugated paper comprises face paper, corrugated core paper and backing paper, wherein the face paper and the backing paper are the base paper dried and calendered in step (4). The base paper dried and calendered 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 (corn starch and water are mixed in a ratio of 1:10, heated to 80°C, and stirred for 30 minutes until they are completely dissolved to obtain corn starch glue) is coated on the inner sides of the face paper and the backing 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 0.2 MPa, and the hot-pressing time is 30 seconds. The hot-pressed corrugated paper is cooled and shaped at a cooling temperature of 25°C and a cooling time of 40 seconds to obtain 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 is different 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 encapsulated in microcapsules, 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 is different 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 anti-mildew performance test

[0075] (I) 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 square samples of 5 cm×5 cm respectively 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 square samples of 5 cm × 5 cm, soak the samples in deionized water for 30 minutes, and dry the samples until they are completely dry. Repeat the above steps 3 times, and soak them in deionized water 3 times in total. 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 square samples of 5 cm×5 cm, respectively, and the samples were rubbed using a friction machine for 100 times to obtain friction samples.

[0079] (II) 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 the nutrient broth, cultured at 37°C for 24 hours, and the cultured bacterial solution was diluted to 10^6CFU / mL with sterile saline to obtain a bacterial suspension; on a sterile operating table, each sample was placed in a sterile container, 10mL of the prepared bacterial suspension was added to each container, the container was placed in an oscillator, and oscillated at 150rpm for 15 minutes. After the oscillation, the sample was taken out and rinsed three times with sterile saline, 10mL each time, and the liquid after each rinse was collected and merged into a sterile container, and the collected rinse liquid was diluted 10 times with sterile saline, and an appropriate amount of the diluted bacterial solution was evenly spread on the nutrient agar plate, and the plate was placed in a 37°C constant temperature incubator 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] (III) The fungus species used for the anti-mildew performance test is Aspergillus niger.

[0082] The test steps of anti-mildew performance are as follows: take a loop from the frozen strain and inoculate it on the PDA plate, culture it at 28℃ for 7 days, wash the mold spores on the plate with sterile saline, and prepare a 10^6CFU / mL mold spore suspension; on the sterile operating table, put each sample into a sterile container, add 10mL of the prepared mold spore suspension to each container, let the container stand for 24 hours to allow the spores to adhere to the sample surface, take out the treated sample, place it in a constant temperature and humidity chamber at 28℃ and 90% relative humidity, culture it for 7 days, and observe and record the mold growth on the sample surface every day.

[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 more, accounting for 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 test results of antibacterial and anti-mildew properties 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 in Comparative Example 1 are different, especially the content of silver nitrate is high, which may cause the synergistic effect between the antibacterial agents to weaken, and even high content of silver nitrate may inhibit other antibacterial components (such as tea polyphenols and thyme essential oil), reducing the 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, resulting in a reduction in the effective ingredients of the antibacterial agent, and a decrease in antibacterial effect. In Comparative Example 2, thyme essential oil is replaced with rosemary essential oil. Although rosemary essential oil also has a certain antibacterial effect, its antibacterial spectrum and antibacterial activity are not as good as thyme essential oil, resulting in a decrease in the overall antibacterial effect; in addition, according to the results of washing and rubbing, it can be seen that rosemary essential oil is more likely to fall off during washing or rubbing, resulting in a decrease in antibacterial effect. In Comparative Example 3, gelatin, chitosan and polylactic acid in the wall material solution are replaced with gum arabic, sodium alginate and polyvinyl alcohol, respectively. The encapsulation efficiency and stability of these alternative components may not be as good as the original components, resulting in poor release of the antibacterial agent. In Comparative Example 4, the antibacterial agent is not encapsulated in microcapsules, resulting in uneven distribution of the antibacterial agent in the paper, unstable antibacterial effect, and unencapsulated antibacterial agent is easy to dissolve or fall off during washing and friction, and the antibacterial effect is significantly reduced. The selection of coating components in Comparative Examples 5 and 6 may result in poor stability of the coating, affecting the release effect of the antibacterial agent.

[0098] Performance Test 2 Strength Test

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

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

[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 compression strength and bursting strength, indicating that the microcapsule antibacterial agent used in the present invention has little effect on the mechanical properties of paper and may even enhance the strength of paper. The edge compression strength and bursting strength of Comparative Examples 3 and 4 decreased slightly, which may be due to the change of the packaging wall material, resulting in poor packaging effect, or even when the antibacterial agent is not packaged, the antibacterial agent has a negative impact on the mechanical properties of paper. The edge compression strength and bursting strength of Comparative Examples 5 and 6 decreased significantly, which may be due to the replacement of the coating components, resulting in insufficient support for the coating on the paper, so the paper becomes loose and affects the 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 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: wood pulp and waste paper pulp are mixed as raw materials, and the raw materials are put into a pulping machine for pulping. After the processing is completed, the raw materials are sieved and centrifuged to remove impurities, and the pH value is adjusted to 7-8 to obtain pulp; (2) Preparation of microcapsule antibacterial agent: dissolving silver nitrate, zinc sulfate, copper sulfate, tea polyphenols, thyme essential oil and citric acid in deionized water to prepare an antibacterial agent solution; dissolving gelatin, chitosan and polylactic acid in deionized water, heating and stirring to prepare a wall material solution; adding the antibacterial agent solution to the wall material solution, stirring to obtain a mixed solution, and spray drying the mixed solution to obtain a microcapsule antibacterial agent; (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; (4) coating of the antibacterial protective layer: mixing a microcapsule antibacterial agent, corn starch, polyvinyl alcohol, a defoamer, 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; (5) Forming of corrugated paper: The corrugated paper comprises face paper, corrugated core paper and bottom paper, wherein the face paper and bottom paper are the base paper dried and calendered in step (4). The base paper dried and calendered 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 between and heat-pressed and bonded by a heat press. The heat-pressed and bonded corrugated paper is cooled and shaped to obtain the antibacterial and mildew-proof corrugated paper.

2. The preparation method according to claim 1, characterized in that: The mass ratio of wood pulp to waste paper pulp in step (1) is 1:0.1-0.

2.

3. The preparation method according to claim 1, characterized in that: 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%.

4. The preparation method according to claim 1, characterized in that: The weight proportions 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.

5. The preparation method according to claim 1, characterized in that: The mass ratio of the antibacterial agent solution to the wall material solution in step (2) is 1:2-4.

6. The preparation method according to claim 1, characterized in that: The spray drying parameters 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, air outlet temperature: 80-90°C.

7. The preparation method according to claim 1, characterized in that: The amount of the microcapsule antibacterial agent added in step (3) is 0.5-1% of the mass of the pulp.

8. The preparation method according to claim 1, characterized in that: The weight parts of the components 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; The defoamer 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; the plasticizer is selected from one or more of dioctyl phthalate, epoxy soybean oil, acetylcitrate tributyl ester, dioctyl sebacate, and polyethylene adipate; In step (4), the drying temperature 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.

9. 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 0.1-0.3MPa, 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.

10. An antibacterial and mildew-proof corrugated paper prepared by the method according to any one of claims 1 to 9.

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