Polymer waterproof antibacterial coating packaging box corrugated paper and preparation method thereof

Abstract

The invention discloses packaging box corrugated paper with a high-molecular waterproof antibacterial coating and a preparation method of the packaging box corrugated paper, and belongs to the technical field of packaging material manufacturing. According to the corrugated paper, a cross-linkable compact polymer film-forming layer is formed on the surface of a paper base, nano-silver and organic biguanide antibacterial components are compounded, and migration loss is reduced through multi-site synergistic bacteriostasis and fixation by a coating network, so that water absorption permeation is remarkably reduced and water resistance and antibacterial durability are improved while air permeability and processing adaptability of the paper base are maintained. The method is simple in process, is suitable for continuous coating and large-scale production of the corrugated paper for the packaging box, and can be used for packaging foods, cold chains and humid environments.

Description

Technical Field

[0001] This invention belongs to the field of packaging material manufacturing technology, specifically relating to a polymer waterproof and antibacterial coated corrugated paper for packaging boxes and its preparation method. Background Technology

[0002] Corrugated paper, with its lightweight, low cost, and excellent cushioning properties, is widely used in logistics, food, and precision instrument packaging. However, corrugated paper is mainly composed of plant fibers, has a porous structure, and is highly hydrophilic. In humid environments, it easily absorbs moisture and becomes damp again. This not only leads to a significant decrease in the strength of the cardboard box, causing it to collapse and deform, but also provides a breeding ground for bacteria, mold, and other microorganisms in a damp, cellulose-rich environment. The proliferation of microorganisms can corrode packaging materials, producing odors and stains, and in severe cases, even contaminating the contents of the packaging. This poses a particularly significant hygiene and safety risk, especially in the cold chain transportation of food and medical supplies.

[0003] To overcome the aforementioned shortcomings, existing technologies typically employ modification treatments by coating the surface of corrugated paper with a polymer coating. For example, water-based polyurethane emulsions are used as the base resin, and antibacterial agents are added to impart antibacterial properties to the packaging boxes. Common antibacterial agents include inorganic nano-silver and nano-zinc oxide, or organic quaternary ammonium salts and biguanides. However, existing polymer waterproof and antibacterial coating technologies still have significant limitations.

[0004] First, although inorganic nano-antibacterial agents have good heat resistance, they have high surface energy and are prone to agglomeration in water-based resin matrices. This leads to uneven dispersion in the coating, making it difficult to fully utilize their small size effect, thereby reducing antibacterial efficiency and affecting the density of the coating.

[0005] Secondly, conventional water-soluble organic antibacterial agents (such as common biguanides) are highly hydrophilic and have weak binding force with hydrophobic polymer matrices. In long-term high-humidity environments or when in contact with water, the antibacterial agents easily migrate from the interior of the coating to the surface and dissolve and run off. This precipitation not only causes the antibacterial effect to rapidly decline over time and lacks long-lasting effectiveness, but the microporous channels formed by the lost antibacterial agents can also damage the waterproof integrity of the coating.

[0006] Therefore, developing a polymer-based waterproof and antibacterial coated corrugated paper for packaging boxes that can effectively solve the problems of poor dispersibility, easy aggregation, and loss of antibacterial agents due to insufficient water resistance is a technical challenge that urgently needs to be addressed in this field. Summary of the Invention

[0007] To address the problems of inorganic antibacterial agents easily agglomerating and organic antibacterial agents having poor water resistance and easily leaching away, leading to antibacterial failure and damage to waterproofing in existing antibacterial coatings for corrugated paper packaging boxes, this invention provides a polymeric waterproof and antibacterial coated corrugated paper for packaging boxes and its preparation method. This invention aims to introduce a specific organic-inorganic hybrid composite antibacterial agent and utilize hydrophobic anchoring and carrier dispersion mechanisms to achieve uniform dispersion and stable bonding of antibacterial components in the coating, thereby endowing the corrugated paper with excellent physical waterproofing properties and long-lasting broad-spectrum antibacterial properties.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A type of polymer waterproof and antibacterial coated packaging box corrugated paper, the raw materials of which include corrugated base paper as the substrate and a polymer waterproof and antibacterial coating coated on the surface of the corrugated base paper; The polymer waterproof and antibacterial coating is formed by curing a coating liquid containing the following parts by weight: 60 to 90 parts of waterborne polyurethane emulsion, 5 to 15 parts of waterproof reinforcing agent, 1 to 10 parts of composite antibacterial agent, 1 to 5 parts of crosslinking agent, 0.1 to 1.0 parts of defoamer, 0.1 to 1.0 parts of leveling agent, and 10 to 30 parts of deionized water; Furthermore, the composite antibacterial agent is a complex of adamantyl group-containing biguanide and chitosan-supported silver nanoparticles, wherein the adamantyl group-containing biguanide is 1,1'-nonane-2,8-dimethylbis5-3,5-dimethyladamantane-1-ylbiguanide.

[0009] Furthermore, the structure of the 1,1'-nonane-2,8-diylbis5-3,5-dimethyladamantane-1-ylbiguanide is as follows: .

[0010] Furthermore, the solid content of the aqueous polyurethane emulsion is 30% to 50%, and the aqueous polyurethane emulsion is selected from cationic aqueous polyurethane emulsion or nonionic aqueous polyurethane emulsion.

[0011] Furthermore, the waterproofing enhancer is selected from one or more of paraffin emulsions, methyltrimethoxysilane, and perfluoroalkyl acrylate copolymer emulsions.

[0012] Furthermore, the crosslinking agent is selected from one or more of trimethylolpropane-tris(3-aziridinylpropionate), pentaerythritol-tris(3-aziridinylpropionate), 3-glycidyl etheroxypropyltrimethoxysilane, and 3-glycidyl etheroxypropylmethyldiethoxysilane.

[0013] Furthermore, the defoamer is selected from one or more of BYK-024 and Wacker SD-860.

[0014] Furthermore, the leveling agent is selected from one or more of BYK-333 and EFKA-3580.

[0015] Furthermore, the chitosan in the composite antibacterial agent has a molecular weight of 50,000 to 200,000 Daltons, a degree of deacetylation of chitosan of ≥85%, and a particle size of nano-silver of 10 to 50 nanometers.

[0016] A method for preparing a polymer-modified waterproof and antibacterial coated corrugated paper for packaging boxes includes the following steps: The first step is to prepare a chitosan-supported silver nanocomposite. Chitosan is dissolved in an aqueous acetic acid solution, and an aqueous silver nitrate solution is added. After the addition is complete, a reducing agent is added to carry out the reaction. After the reaction is completed, the product is centrifuged, washed, and freeze-dried. The second step is to prepare an organic antibacterial agent solution by dissolving 1,1'-nonane-2,8-diylbis5-3,5-dimethyladamantane-1-ylbiguanide in an organic solvent; The third step is to prepare a composite antibacterial agent. The chitosan-supported silver nanocomposite obtained in the first step is dispersed in deionized water, and the organic antibacterial agent solution prepared in the second step is added while stirring. After the reaction, the composite antibacterial agent is dried. The fourth step is to prepare the coating solution. Weigh out the water-based polyurethane emulsion and deionized water by weight and mix them. Add the composite antibacterial agent prepared in the third step and disperse it. Then add the waterproofing enhancer, crosslinking agent, defoamer and leveling agent in sequence and mix evenly. The fifth step is coating and curing. The coating liquid prepared in the fourth step is applied to the surface of the corrugated base paper and then sent into the drying tunnel for drying and curing.

[0017] Furthermore, in the first step, the volume concentration of the acetic acid aqueous solution is 1% to 2%, the mass fraction of the chitosan solution is 2% to 5%, the concentration of the silver nitrate aqueous solution is 0.01 mol / L to 0.05 mol / L, the mass ratio of chitosan to silver nitrate is 5:1 to 10:1, the reducing agent is sodium borohydride or sodium citrate, the reaction temperature is 40°C to 60°C, and the reaction time is 1 hour to 3 hours. In the second step, the organic antibacterial agent solution has a mass fraction of 5% to 15%, and the organic solvent is selected from ethanol, isopropanol, N,N-dimethylformamide, or mixtures thereof.

[0018] Furthermore, in the third step, the mass fraction of the chitosan-supported silver nanocomposite dispersion is 0.5% to 2%, the mass ratio of the organic antibacterial agent to the chitosan-supported silver nanocomposite is 1:5 to 5:1, and the drying method is spray drying or vacuum drying.

[0019] Furthermore, in the fourth step, after adding the composite antibacterial agent, high-shear grinding and dispersion are carried out until the particle size of the powder in the system is less than 50 micrometers. The coating liquid after uniform mixing needs to be filtered through a 200-mesh filter. In the fifth step, the coating method is roller coating, spray coating or curtain coating, and the drying and curing temperature is 80 degrees Celsius to 120 degrees Celsius.

[0020] The synergistic mechanism of this invention lies in constructing an organic-inorganic hybrid antibacterial network that resists migration. First, the abundant amino and hydroxyl groups on the chitosan molecular chain serve as stabilizers and dispersants for silver nanoparticles. Through in-situ reduction technology, silver nanoparticles are anchored onto chitosan segments, effectively inhibiting the aggregation of inorganic silver nanoparticles in the polymer matrix. The nano-size effect enhances the release efficiency and contact bactericidal ability of silver ions. Simultaneously, the excellent film-forming properties of chitosan promote the uniform dispersion of the antibacterial agent in the aqueous polyurethane matrix. Secondly, the introduced 1,1'-nonane-2,8-diylbis(5-3,5-dimethyladamantane-1-ylbiguanide) possesses a unique amphiphilic structural design. The biguanide group, with its strong positive charge, adsorbs and disrupts bacterial cell membranes, while the hydrophobic adamantyl group plays a crucial hydrophobic anchoring role. Utilizing its significant steric hindrance and lipophilic properties, it firmly locks the organic antibacterial molecules within the hydrophobic resin matrix network formed by the waterborne polyurethane and waterproofing reinforcing agent, significantly reducing the risk of water migration and loss of traditional small-molecule biguanide antibacterial agents in humid environments. Finally, the ion interference and metabolic blocking mechanisms of chitosan-loaded silver nanoparticles, combined with the physical membrane disruption mechanism of the adamantyl biguanide derivative, work synergistically on the coating surface and within the coating, achieving a balance between rapid sterilization and long-lasting antibacterial action. Simultaneously, the dense cross-linked network constructed with the cross-linking agent ensures that the corrugated paper maintains both excellent waterproof performance and long-lasting, broad-spectrum antibacterial activity, fundamentally solving the technical problem of antibacterial agents easily precipitating out and causing failure and damage to the waterproof integrity of the coating in existing technologies.

[0021] Compared with the prior art, the beneficial effects of the present invention are: 1. By utilizing chitosan as a biomacromolecule carrier, the active groups on its molecular chain complex with silver ions and reduce them in situ, uniformly anchoring the silver nanoparticles and preventing secondary aggregation between particles. This structural design allows the antibacterial components to be dispersed in a microscopically uniform state within the waterborne polyurethane matrix. While ensuring the density and uniformity of the coating, it fully leverages the small size effect of nanomaterials and avoids surface defects caused by aggregation.

[0022] 2. By combining chitosan-loaded silver nanoparticles with a specific adamantyl group-containing biguanide derivative, a multi-layered bactericidal mechanism was constructed, utilizing the ion release of silver nanoparticles, the electrostatic adsorption of chitosan, and the physical disruption of bacterial cell membranes by the biguanide derivative. Compared with single antibacterial agents, this compound system has a broader antibacterial spectrum and higher bactericidal efficiency, effectively addressing the complex microbial environment during logistics and transportation, and is less likely to induce bacterial resistance.

[0023] 3. The introduced 1,1'-nonane-2,8-diylbis(5-3,5-dimethyladamantane-1-ylbiguanidine) contains an adamantyl group with significant steric hindrance and high hydrophobicity. This group acts as a hydrophobic anchor during coating curing, firmly locking the antibacterial molecules within the hydrophobic resin matrix. This significantly reduces the migration and solubility of the antibacterial agent in humid environments, preventing loss of the antibacterial agent due to moisture erosion. This ensures that the corrugated cardboard packaging maintains stable antibacterial protective properties and waterproof integrity even under long-term use or high humidity conditions. Attached Figure Description

[0024] Figure 1 Fourier transform infrared (FTIR) characterization images of the composite antibacterial agent obtained in Example 1 of this invention and the control sample without the introduction of 1,1'-nonane-2,8-dimethylbis5-3,5-dimethyladamantane-1-ylbiguanide. Detailed Implementation

[0025] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Preparation Example 1: Preparation of the adamantyl group-containing biguanide 1,1'-nonane-2,8-diylbis5-3,5-dimethyladamantane-1-ylbiguanide: ; A1: CAS: 19982-08-2; A2: CAS: 504-66-5; A3: {nitrogen subunit [(3,5-dimethyltricyclo[3.3.1.1]} 3,7 [dec-1-yl)amino]methyl}azine carbide nitrile; A4: CAS: 66929-06-4.

[0027] Under a continuous nitrogen atmosphere, 5.00 g of A1 and 40 mL of 1-butanol were added to a reaction flask and stirred until evenly dispersed. 2.44 mL of concentrated hydrochloric acid was slowly added dropwise, and after the addition was complete, the mixture was stirred for 10 minutes. Then, 3.00 g of solid A2 and 10 mL of 1-butanol were added. The reaction mixture was placed in a preheated oil bath and heated to 125 °C, and stirred for 16 hours. After the reaction was complete, the mixture was cooled to room temperature. The reaction solution was transferred to a round-bottom flask, and most of the n-butanol solvent was removed by rotary evaporation under reduced pressure, yielding a viscous, pale yellow, oily residue. The residue was dissolved in 100 mL of dichloromethane and transferred to a separatory funnel. The organic phase was washed twice with 30 mL of deionized water and once with 30 mL of saturated brine to remove inorganic salts and residual water-soluble impurities. The organic layer was dried over anhydrous sodium sulfate for 30 minutes. The desiccant was removed by filtration, and the filtrate was concentrated under reduced pressure to obtain a grayish-white crude product solid. The crude product was purified by recrystallization. The crude product was dissolved in a hot ethyl acetate / n-hexane (1:2, v / v) mixture, slowly cooled to room temperature, and then placed in a 4°C refrigerator overnight to crystallize. The crystals were collected by filtration, washed with cold n-hexane, and dried under vacuum to constant weight to give 5.87 g of A3.

[0028] 1 HNMR (CDCl3): 6.35(m,1H),5.42(m,2H),2.18-2.12(m,1H),1.85(d,2H),1.70-1.58(m,4H),1.45-1.28(m,4H),1.20-1.12(m,2H),0.86(s,6H).

[0029] Under a continuous nitrogen atmosphere, 1.69 g of A4 and 30 ml of 2-ethoxyethanol were added to a reaction flask and stirred until evenly dispersed. Then, 1.05 ml of concentrated hydrochloric acid was slowly added dropwise, followed by stirring for 10 minutes. Subsequently, 5.87 g of A3 and 15 ml of 2-ethoxyethanol were added. The reaction mixture was placed in a preheated oil bath and heated to 140 °C, and stirred for 18 hours. After the reaction was complete, the mixture was cooled to room temperature. The mixture was then transferred to a single-necked flask, and most of the 2-ethoxyethanol was removed using a rotary evaporator under reduced pressure, yielding a viscous, yellow, oily residue. 50 ml of 2M NaOH aqueous solution was added to the residue, and the mixture was stirred for 30 minutes. The aqueous phase was extracted three times with 60 ml of dichloromethane, and the organic phases were combined. The organic phase was washed successively with 50 ml of deionized water and 50 ml of saturated brine, then dried over anhydrous sodium sulfate, and the desiccant was removed by filtration. The filtrate was concentrated under reduced pressure to obtain a crude product solid. Purification was performed by rapid column chromatography with basic alumina as the stationary phase and a gradient elution of DCM:MeOH:NH3·H2O = 95:4:0.5 to 90:9:1. The fraction containing the target product was collected, concentrated, and dried to obtain 4.24 g of 1,1'-nonane-2,8-diylbis5-3,5-dimethyladamantane-1-ylbiguanidine.

[0030] 1 HNMR (CDCl3): 7.50(s,4H),3.12(m,2H),2.50(d,2H),2.00(s,4H),1.85(m,2H),1.70-1.47(m,12H),1.44-1.13(m,26H),0.82(s,12H).

[0031] Example 1: Preparation of a polymer-coated waterproof and antibacterial corrugated paper for packaging boxes: A type of polymer waterproof and antibacterial coated packaging box corrugated paper, the raw materials of which include corrugated base paper as the substrate and a polymer waterproof and antibacterial coating coated on the surface of the corrugated base paper.

[0032] The polymer waterproof and antibacterial coating is formed by curing a coating liquid containing the following parts by weight: The mixture contains 75 parts waterborne polyurethane emulsion, 10 parts waterproofing enhancer, 5 parts composite antibacterial agent, 3 parts crosslinking agent, 0.5 parts defoamer, 0.5 parts leveling agent, and 20 parts deionized water.

[0033] The aqueous polyurethane emulsion is selected from cationic aqueous polyurethane emulsions with a solid content of 40%. The waterproofing enhancer is selected from methyltrimethoxysilane; The crosslinking agent is selected from trimethylolpropane-tris(3-aziridinylpropionate); The defoamer is selected from BYK-024; The leveling agent is selected from BYK-333.

[0034] The composite antibacterial agent is a complex of adamantyl group biguanide and chitosan-supported silver nanoparticles, wherein the adamantyl group biguanide is the product prepared using Preparation Example 1; The chitosan has a molecular weight of 100,000 Daltons and a degree of deacetylation of 90%. The particle size of nano-silver is 20 to 30 nanometers.

[0035] Its preparation method includes the following steps: The first step was to prepare a chitosan-loaded silver nanocomposite: Chitosan was dissolved in a 1.5% (v / v) aqueous acetic acid solution to prepare a 3% (w / w) chitosan solution. Under continuous stirring, a 0.02 mol / L aqueous silver nitrate solution was added dropwise at a rate of 50 mL per liter of chitosan solution, controlling the mass ratio of chitosan to silver nitrate to be 8:1. After the addition was complete, the temperature was raised to 50°C, and sodium citrate, in an equal molar amount to silver nitrate, was added as a reducing agent. The mixture was stirred at a constant temperature for 2 hours. After the reaction was completed, the product was centrifuged at 8000 rpm for 15 minutes. The precipitate was washed three times with deionized water and then freeze-dried to obtain the chitosan-loaded silver nanocomposite. The second step is to prepare an organic antibacterial agent solution: dissolve the 1,1'-nonane-2,8-diylbis5-3,5-dimethyladamantane-1-ylbiguanide obtained in Preparation Example 1 in anhydrous ethanol to prepare an organic antibacterial agent solution with a mass fraction of 10%. The third step is to prepare a composite antibacterial agent: The chitosan-loaded silver nanocomposite obtained in the first step is dispersed in deionized water to prepare a dispersion with a mass fraction of 1%. Under stirring at 800 rpm, the organic antibacterial agent solution prepared in the second step is slowly added, and the mass ratio of the organic antibacterial agent to the chitosan-loaded silver nanocomposite is controlled at 2:1. After stirring and reacting for 1 hour, the mixture is dried by spray drying. The inlet air temperature of the spray dryer is 180℃ and the outlet air temperature is 80℃ to obtain the composite antibacterial agent. Step 4, preparation of coating solution: First, add the specified weight of deionized water and cationic waterborne polyurethane emulsion to a stirred tank, and stir at 500 rpm for 10 minutes to mix evenly. Then, add the composite antibacterial agent prepared in step 3, and grind and disperse it using a high shear disperser at 3000 rpm for 30 minutes until the particle size of the powder in the system is less than 50 micrometers. Then, add methyltrimethoxysilane, trimethylolpropane-tris(3-aziridinylpropionate), BYK-024 and BYK-333 in sequence. Stir for 5 minutes after each additive is added. After all additives are added, stir continuously at 800 rpm for 20 minutes until uniform. Finally, filter the uniformly mixed coating solution through a 200-mesh filter to obtain the coating solution. Step 5, Coating and Curing: The coating liquid prepared in Step 4 is uniformly coated onto the surface of the corrugated base paper with a basis weight of 120 grams per square meter using a roller coating method. The coating amount is 15 to 20 grams of wet film per square meter. Then, the coated corrugated base paper is sent into the drying tunnel and dried and cured at 100 degrees Celsius for 3 minutes. After cooling to room temperature, the high polymer waterproof and antibacterial coated packaging box corrugated paper is obtained.

[0036] like Figure 1 As shown, the composite antibacterial agent obtained in Example 1 and the control sample without the introduction of 1,1'-nonane-2,8-diylbis5-3,5-dimethyladamantane-1-ylbiguanide were characterized by Fourier transform infrared spectroscopy. Both spectra were in the range of approximately 3200-3500 cm⁻¹. -1 A broad peak is observed at approximately 2920 cm⁻¹ (-OH / -NH stretching vibration). -1 With 2850cm -1 An aliphatic CH stretching vibration peak appears at approximately 1650 cm⁻¹, and continues at approximately 1650 cm⁻¹. -1 1580cm -1 and 1150-1020cm -1 The intervals correspond to the chitosan amide / amino-related vibrations and the glycosidic bond COC / CO vibrations, respectively, indicating that the matrix is ​​a chitosan system. Compared with the control, the sample in Example 1 showed better vibrations in the 1600-1550 cm⁻¹ range. -1 Near the biguanide structure (C=N / CN and NH bending-related vibrations), the peak intensity is significantly enhanced and accompanied by a change in peak shape, while the 2920 / 2850 cm⁻¹ peak intensity is significantly enhanced. -1 The increased intensity of the CH peak indicates that the biguanide derivative was successfully introduced and interacted with the chitosan matrix to form a composite antibacterial agent.

[0037] Example 2: The preparation of a polymer waterproof and antibacterial coated packaging box corrugated paper is carried out by referring to the steps of Example 1, except that the cationic waterborne polyurethane emulsion with a solid content of 40% is replaced with a nonionic waterborne polyurethane emulsion with a solid content of 40%, and the rest is the same as in Example 1.

[0038] Example 3: The preparation of a polymer waterproof and antibacterial coated packaging box corrugated paper is carried out by referring to the steps of Example 1, except that trimethylolpropane-tris(3-aziridinylpropionate) is replaced with pentaerythritol-tris(3-aziridinylpropionate), and the rest is the same as in Example 1.

[0039] Example 4: The preparation of a polymer waterproof and antibacterial coated packaging box corrugated paper is carried out by referring to the steps of Example 1, except that trimethylolpropane-tris(3-aziridinylpropionate) is replaced with 3-glycidyl etheroxypropyltrimethoxysilane, and the rest is the same as in Example 1.

[0040] Comparative Example 1: The preparation of a polymer waterproof and antibacterial coated packaging box corrugated paper is carried out by referring to the steps of Example 1, except that the composite antibacterial agent (containing adamantyl group biguanide and chitosan-loaded silver nanoparticles) is replaced with a single chitosan-loaded silver nanoparticle composite, and the rest is the same as in Example 1.

[0041] Comparative Example 2: The preparation of a polymer waterproof and antibacterial coated packaging box corrugated paper is carried out according to the steps of Example 1, except that the composite antibacterial agent (containing a complex of adamantyl group biguanide and chitosan-supported silver nanoparticles) is replaced with a single 1,1'-nonane-2,8-dimethylbis5-3,5-dimethyladamantane-1-ylbiguanide, and the rest is the same as in Example 1.

[0042] Comparative Example 3: The preparation of a polymer waterproof and antibacterial coated packaging box corrugated paper is carried out according to the steps of Example 1, except that the adamantyl group-containing biguanide (1,1'-nonane-2,8-dimethylbis5-3,5-dimethyladamantane-1-ylbiguanide) is replaced with ordinary polyhexamethylene biguanide hydrochloride, and the rest is the same as in Example 1.

[0043] Comparative Example 4: The preparation of a polymer waterproof and antibacterial coated packaging box corrugated paper is carried out by referring to the steps of Example 1, except that 5 parts of the composite antibacterial agent are replaced with 0 parts of the composite antibacterial agent (no composite antibacterial agent is added), and the rest is the same as in Example 1.

[0044] Performance testing: 1. Surface water absorption test: The test is conducted according to GB / T1540-2002. A 100mm × 100mm sample is taken, and its absorbency value within 60 minutes is measured. The unit is g / m³. 2 The lower the water absorption value, the better the waterproof performance of the sample surface. The data are shown in Table 1.

[0045] 2. Bacterial inhibition rate and bactericidal rate test: The test was conducted according to GB / T21866-2008, using Escherichia coli (ATCC25922) and Staphylococcus aureus (ATCC6538), common pathogens in the packaging industry, as test strains, with a concentration of 1.0 × 10⁻⁶. 5 -1.0×10 6 The bacterial suspension at CFU / mL was thoroughly contacted with the sample and incubated in a constant temperature incubator at 37±1℃ for 24 hours. The viable count was then determined, and the inhibition rate and bactericidal rate were calculated using the following formulas: The inhibition rate (%) = [(number of viable bacteria in the blank control group - number of viable bacteria in the sample group) / number of viable bacteria in the blank control group] × 100%, and the data are shown in Table 1.

[0046] 3. Antibacterial Long-Lasting Effect Test: To simulate the anti-leaking performance of antibacterial agents under actual humid conditions, samples were cut into 50mm×50mm specimens and placed in deionized water at 25±2℃. The samples were then shaken and soaked at 100r / min for 168 hours. After soaking, the samples were removed and air-dried in a sterile operating table. The inhibition rate against Escherichia coli was then tested according to the above steps, and the antibacterial retention rate was calculated. A higher antibacterial retention rate indicates better antibacterial long-lasting effect. Antibacterial retention rate (%) = (antibacterial inhibition rate of the soaked sample / antibacterial inhibition rate of the unsoaked sample) × 100%, and the data are shown in Table 1.

[0047] Table 1 The composite antibacterial system used in the examples achieves a synergistic effect in the coating through multi-site bactericidal action (broad-spectrum destruction by silver ions / nano silver + strong adsorption and inactivation of cell membranes by biguanides), resulting in stable and sufficient initial antibacterial performance. Simultaneously, the cross-linkable polymer waterproof film-forming method locks the antibacterial components within a dense and continuous coating network, reducing the coating's hydrophilic channels and water absorption. This leads to better water resistance / low water absorption and maintains high antibacterial activity (high antibacterial retention rate) even after immersion. In contrast, in the comparative examples, when the antibacterial component is singular, or when biguanides exist in a more easily migrating and leaching form, or when effective film formation and fixation are lacking, the initial antibacterial trend is either slightly weaker or, although strong, more easily washed away after water immersion, leading to a decrease in retention rate. Without antibacterial agents, only the natural level of the substrate remains, with both initial antibacterial activity and post-immersion retention showing a low trend.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A type of high-polymer waterproof and antibacterial coated corrugated cardboard for packaging boxes, characterized in that, Its raw materials include corrugated base paper as the substrate and a polymer waterproof and antibacterial coating applied to the surface of the corrugated base paper; The polymer waterproof and antibacterial coating is formed by curing a coating liquid containing the following parts by weight: 60 to 90 parts of waterborne polyurethane emulsion, 5 to 15 parts of waterproof reinforcing agent, 1 to 10 parts of composite antibacterial agent, 1 to 5 parts of crosslinking agent, 0.1 to 1.0 parts of defoamer, 0.1 to 1.0 parts of leveling agent, and 10 to 30 parts of deionized water; The composite antibacterial agent is a complex of adamantyl group-containing biguanide and chitosan-supported silver nanoparticles, wherein the adamantyl group-containing biguanide is 1,1'-nonane-2,8-dimethylbis5-3,5-dimethyladamantane-1-ylbiguanide; The structure of the 1,1'-nonane-2,8-diylbis5-3,5-dimethyladamantane-1-ylbiguanide is as follows: 。 2. The high-polymer waterproof and antibacterial coated corrugated cardboard for packaging boxes according to claim 1, characterized in that, The solid content of the aqueous polyurethane emulsion is 30% to 50%, and the aqueous polyurethane emulsion is selected from cationic aqueous polyurethane emulsion or nonionic aqueous polyurethane emulsion.

3. The high-polymer waterproof and antibacterial coated corrugated cardboard for packaging boxes according to claim 1, characterized in that, The waterproofing enhancer is selected from one or more of paraffin emulsion, methyltrimethoxysilane, and perfluoroalkyl acrylate copolymer emulsion.

4. The high-polymer waterproof and antibacterial coated corrugated cardboard for packaging boxes according to claim 1, characterized in that, The crosslinking agent is selected from one or more of the following: trimethylolpropane-tris(3-aziridinylpropionate), pentaerythritol-tris(3-aziridinylpropionate), 3-glycidyl etheroxypropyltrimethoxysilane, and 3-glycidyl etheroxypropylmethyldiethoxysilane.

5. The high-polymer waterproof and antibacterial coated corrugated cardboard for packaging boxes according to claim 1, characterized in that, The defoamer is selected from one or more of BYK-024 and Wacker SD-860; The leveling agent is selected from one or more of BYK-333 and EFKA-3580.

6. The high-polymer waterproof and antibacterial coated corrugated cardboard for packaging boxes according to claim 1, characterized in that, The chitosan in the composite antibacterial agent has a molecular weight of 50,000 to 200,000 Daltons, a degree of deacetylation of chitosan greater than or equal to 85%, and a particle size of nano-silver of 10 to 50 nanometers.

7. A method for preparing a polymer waterproof and antibacterial coated corrugated cardboard packaging box according to any one of claims 1 to 6, characterized in that, Includes the following steps: The first step is to prepare the chitosan-supported silver nanocomposite by dissolving chitosan in an aqueous acetic acid solution, adding an aqueous silver nitrate solution, adding a reducing agent after the addition is complete, and centrifuging, washing and freeze-drying the product after the reaction is complete. The second step is to prepare an organic antibacterial agent solution by dissolving 1,1'-nonane-2,8-diylbis5-3,5-dimethyladamantane-1-ylbiguanide in an organic solvent; The third step is to prepare a composite antibacterial agent. The chitosan-supported silver nanocomposite obtained in the first step is dispersed in deionized water, and the organic antibacterial agent solution prepared in the second step is added under stirring. After the reaction, the composite antibacterial agent is dried. The fourth step is to prepare the coating solution. Weigh out the water-based polyurethane emulsion and deionized water by weight and mix them. Add the composite antibacterial agent prepared in the third step and disperse it. Then add the waterproofing enhancer, crosslinking agent, defoamer and leveling agent in sequence and mix them evenly. The fifth step is coating and curing. The coating liquid prepared in the fourth step is applied to the surface of the corrugated base paper and then sent into the drying tunnel for drying and curing.

8. The method for preparing the polymer waterproof and antibacterial coated corrugated paper for packaging boxes according to claim 7, characterized in that, In the first step, the volume concentration of the acetic acid aqueous solution is 1% to 2%, the mass fraction of the chitosan solution is 2% to 5%, the concentration of the silver nitrate aqueous solution is 0.01 mol / L to 0.05 mol / L, the mass ratio of chitosan to silver nitrate is 5:1 to 10:1, the reducing agent is sodium borohydride or sodium citrate, the reaction temperature is 40°C to 60°C, and the reaction time is 1 hour to 3 hours. In the second step, the organic antibacterial agent solution has a mass fraction of 5% to 15%, and the organic solvent is selected from ethanol, isopropanol, N,N-dimethylformamide, or mixtures thereof.

9. The method for preparing the polymer waterproof and antibacterial coated corrugated paper for packaging boxes according to claim 7, characterized in that, In the third step, the mass fraction of the chitosan-supported silver nanocomposite dispersion is 0.5% to 2%, the mass ratio of the organic antibacterial agent to the chitosan-supported silver nanocomposite is 1:5 to 5:1, and the drying method is spray drying or vacuum drying.

10. The method for preparing the polymer waterproof and antibacterial coated corrugated paper for packaging boxes according to claim 7, characterized in that, In the fourth step, after adding the composite antibacterial agent, high-shear grinding and dispersion are carried out until the particle size of the powder in the system is less than 50 micrometers. The coating liquid after uniform mixing needs to be filtered through a 200-mesh filter. In the fifth step, the coating method is roller coating, spray coating or curtain coating, and the drying and curing temperature is 80 degrees Celsius to 120 degrees Celsius.

Images