Antibacterial and fresh-keeping packaging box material and preparation method thereof

Abstract

The present application relates to the technical field of biomass conversion materials, and discloses an antibacterial and fresh-keeping packaging box material and a preparation method thereof. The present application uses waste paper pulp and bamboo pulp as biomass fiber raw materials, and forms a paper-based base layer through beating modification and papermaking; cinnamyl aldehyde is embedded with β-cyclodextrin and then dispersed and compounded with zeolite powder to prepare slow-release fresh-keeping particles; the slow-release fresh-keeping particles are added into a film-forming system composed of oxidized starch, chitosan, polyvinyl alcohol, tea polyphenol and citric acid to obtain an antibacterial and fresh-keeping coating liquid, which is applied to the surface of the inner side of the packaging box to form a paper-based base layer, and then dried, polished and humidified to obtain the antibacterial and fresh-keeping packaging box material. The present application can improve the retention capacity of volatile fresh-keeping active components, and make the packaging box material have the strength of the paper-based base layer, antibacterial and mildew-inhibiting properties and sustained fresh-keeping effect.

Description

Technical Field

[0001] This invention relates to the field of biomass conversion materials technology, and in particular to an antibacterial and preservative packaging box material and its preparation method. Background Technology

[0002] With the increasing demand for the distribution of fruits, vegetables, fresh food, and baked goods, packaging materials are increasingly required to possess antibacterial, antifungal, and preservation functions in addition to their supporting, cushioning, and transport protection roles. Current packaging materials are typically based on plant fiber pulps such as waste paper pulp, wood pulp, and bamboo pulp. These are processed through pulping, mixing, papermaking, drying, and calendering to create a paper base material, which is then die-cut, creasing, folding, and gluing to form the packaging box. To improve the antibacterial and preservation properties of paper-based packaging materials, existing technologies also incorporate chitosan, tea polyphenols, plant essential oils, or other natural antibacterial and preservation components into the pulp system or coat them onto the surface of the cardboard, forming a functional layer with antibacterial, antifungal, or preservation properties on the inside of the packaging box.

[0003] However, volatile preservative active ingredients such as cinnamaldehyde, if directly added to the coating solution or directly coated onto the paperboard surface, are prone to volatilization and migration during coating drying and storage, resulting in rapid initial release and significant decline in preservation effect later. Simply increasing the amount of preservative active ingredients to extend the effect time can easily increase the cost of packaging materials and may affect the ring crush strength, burst strength, moisture resistance, and box-making performance of the paper base material. Therefore, how to stably fix volatile preservative active ingredients on the surface of paper base packaging materials and within the surface fiber pores, while maintaining controllable costs, and achieving a sustained antibacterial and preservation effect, remains a problem that needs improvement in existing paper base antibacterial and preservation packaging materials. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that when volatile preservative active components are directly added to the coating liquid of paper-based packaging materials or directly coated on the surface of cardboard in the prior art, they are prone to volatilization and migration during coating, drying and storage, resulting in low retention rate of preservative active components and decay of antibacterial and preservative effects in the later stage. To this end, we propose an antibacterial and preservative packaging box material and its preparation method.

[0005] To achieve the above objectives, this application adopts the following technical solution: a method for preparing an antibacterial and preservative packaging box material, comprising the following steps:

[0006] S1. Based on the oven-dry weight, take 60-85 parts of waste paper pulp and 15-40 parts of bamboo pulp, mix them, and then perform pulping treatment. Add cationic starch, microfibrillated cellulose, wet strength agent and retention aid to the pulped mixture to obtain modified pulp.

[0007] S2. Cinnamaldehyde was added to the β-cyclodextrin aqueous dispersion for encapsulation treatment to obtain cinnamaldehyde-β-cyclodextrin inclusion complex. Then, the cinnamaldehyde-β-cyclodextrin inclusion complex was dispersed and compounded with zeolite powder to obtain slow-release preservation granules.

[0008] S3. Disperse or dissolve oxidized starch, chitosan and polyvinyl alcohol in water to obtain a film-forming solution. Add tea polyphenols, citric acid and the slow-release preservative granules obtained in step S2 to the film-forming solution to obtain an antibacterial preservative coating solution.

[0009] S4. The modified pulp obtained in step S1 is made into a paper base layer;

[0010] S5. Apply the antibacterial and fresh-keeping coating liquid obtained in step S3 to the surface of the paper base layer to form the inner side of the packaging box, so that the antibacterial and fresh-keeping coating liquid forms an antibacterial and fresh-keeping functional layer on the surface of the paper base layer and partially penetrates into the surface fiber pores of the paper base layer.

[0011] S6. The paper base layer after step S5 is dried, calendered and conditioned to obtain antibacterial and fresh-keeping packaging box material.

[0012] Preferably, in step S1, the beating degree of the mixed slurry is 32°SR-40°SR.

[0013] Preferably, in step S1, based on 100 parts of the total oven-dry mass of waste paper pulp and bamboo pulp, the amount of cationic starch added is 1.8-3.2 parts, the amount of microfibrillated cellulose added is 0.2-0.6 parts, the amount of wet strength agent added is 0.4-0.8 parts, and the amount of retention aid added is 0.04-0.12 parts.

[0014] Preferably, in step S1, the wet strength agent is a polyamide epichlorohydrin resin wet strength agent, and the retention aid is cationic polyacrylamide.

[0015] Preferably, in step S2, the mass ratio of β-cyclodextrin to cinnamaldehyde is 8:1-15:1, the embedding temperature is 35-50℃, and the embedding time is 40-90 min.

[0016] Preferably, in step S2, the particle size of the zeolite powder is 800-1500 mesh, and the mass ratio of the zeolite powder to the cinnamaldehyde-β-cyclodextrin inclusion complex is 0.8:1-2.0:1.

[0017] Preferably, in step S3, the antibacterial and preservative coating liquid comprises, by weight, 80-88 parts water, 4-7 parts oxidized starch, 0.6-1.2 parts chitosan, 1.0-2.0 parts polyvinyl alcohol, 0.15-0.40 parts tea polyphenols, 0.15-0.35 parts citric acid, and 2.0-5.0 parts slow-release preservative granules.

[0018] Preferably, in step S5, the amount of antibacterial and preservative coating liquid applied is 8-18 g / m²; in step S6, the drying temperature is 85-115℃, and the moisture content of the conditioned packaging box material is 7%-9%.

[0019] The present invention proposes another technical solution: an antibacterial and fresh-keeping packaging box material, which is prepared by a method for preparing an antibacterial and fresh-keeping packaging box material;

[0020] The antibacterial and fresh-keeping packaging material includes a paper base layer and an antibacterial and fresh-keeping functional layer disposed on one side of the paper base layer;

[0021] The paper base layer is formed by papermaking from a mixture of waste paper pulp and bamboo pulp containing cationic starch, microfibrillated cellulose, wet strength agent and retention aid;

[0022] The antibacterial and preservative functional layer includes oxidized starch, chitosan, polyvinyl alcohol, tea polyphenols, citric acid, and slow-release preservative particles. The slow-release preservative particles include cinnamaldehyde-β-cyclodextrin inclusion complex and zeolite powder compounded with cinnamaldehyde-β-cyclodextrin inclusion complex.

[0023] Preferably, the antibacterial and fresh-keeping packaging box material is die-cut, crimped, folded and glued to form the packaging box, and the antibacterial and fresh-keeping functional layer is located on the inside of the packaging box.

[0024] The technical effects and advantages of this invention are as follows:

[0025] In this invention, waste paper pulp and bamboo pulp biomass fiber pulp are used as the main components. Through pulping modification, papermaking, one-sided coating, and drying, calendering, and humidity conditioning, ordinary biomass fiber materials are transformed into paper-based packaging box materials with antibacterial and freshness-preserving functions. This belongs to the application of biomass conversion materials in the field of functional packaging. At the same time, cationic starch, microfibrillated cellulose, wet strength agents, and retention aids are added to the paper base layer to improve the inter-fiber bonding strength and the strength retention ability in humid environments. This allows the resulting packaging box material to maintain good ring crush strength, burst strength, and adaptability for box processing while possessing antibacterial and freshness-preserving functions.

[0026] Furthermore, this invention first encapsulates cinnamaldehyde with β-cyclodextrin to form a cinnamaldehyde-β-cyclodextrin inclusion complex, then disperses and composites this inclusion complex with zeolite powder to form slow-release preservative particles. These particles are then fixed onto the surface of the paper base layer and within the pores of the surface fibers through a film-forming system formed by oxidized starch, chitosan, and polyvinyl alcohol. This reduces the rapid volatilization and migration of cinnamaldehyde during coating, drying, and storage, improves the retention capacity of the preservative active components in the paper base material, and creates a more stable antibacterial and preservative functional layer on the inside of the packaging box. This extends the antibacterial, antifungal, and preservative effects, and achieves cost-effective preservative packaging with a relatively low amount of functional component added. Attached Figure Description

[0027] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0028] Figure 1 This is a flowchart illustrating the preparation process of the present invention;

[0029] Figure 2 This is a flowchart illustrating the preparation process of the sustained-release preservative granules of the present invention.

[0030] Figure 3 This is a schematic diagram showing the distribution of the antibacterial and preservative functional layer of the present invention in the paper-based substrate;

[0031] Figure 4 This is a comparison chart of cinnamaldehyde retention rates after 14 days of storage in the embodiments and comparative examples of the present invention.

[0032] Figure 5 The above is a comparison chart showing the rate of rotting of strawberries after 7 days of simulated packaging and storage, as well as for both the example and comparative examples. Detailed Implementation

[0033] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0034] To facilitate a clear understanding of the technical solution of this invention, some terms and detection methods involved in this invention are explained below.

[0035] The waste paper pulp referred to in this invention refers to recycled pulp that has undergone sorting, disintegration, purification, and screening, and can be derived from waste corrugated cardboard boxes, waste kraft paper, or waste linerboard. As a major source of fiber, waste paper pulp has the characteristics of low cost, wide availability, and suitability for large-scale production of packaging materials.

[0036] The bamboo pulp referred to in this invention is a plant fiber pulp obtained from bamboo through pulping. Bamboo pulp has high fiber strength, and when combined with waste paper pulp, it helps improve the ring crush strength and folding endurance of the paper base layer, avoiding the decrease in strength of packaging materials caused by using recycled fibers alone.

[0037] The cinnamaldehyde-β-cyclodextrin inclusion complex referred to in this invention refers to the inclusion structure formed after cinnamaldehyde molecules are embedded in the cavity of β-cyclodextrin molecules. Cinnamaldehyde has volatility and antibacterial and preservative effects, but it is easy to volatilize quickly or migrate in a humid environment when directly added to paper base coating. Therefore, this invention first uses β-cyclodextrin to encapsulate cinnamaldehyde in order to reduce the initial volatilization rate of cinnamaldehyde.

[0038] The slow-release preservation granules referred to in this invention are granular or microparticle-like complexes formed by dispersing and compounding cinnamaldehyde-β-cyclodextrin inclusion complex with zeolite powder. Zeolite powder has a porous adsorption structure, which can perform secondary adsorption and physical fixation of cinnamaldehyde-β-cyclodextrin inclusion complex, and play a certain role in humidity regulation and slow release during the use of packaging materials.

[0039] The antibacterial and preservation functional layer referred to in this invention is a functional layer formed on one side of the paper base layer after the antibacterial and preservation coating liquid is applied and dried, and partially enters the surface fiber pores. This functional layer is not an independent plastic film layer, but a paper base coating layer formed by oxidized starch, chitosan and polyvinyl alcohol, which can combine with the paper base layer and undertake antibacterial, mildew-inhibiting, preservation and certain moisture resistance enhancement effects.

[0040] In this invention, the amount of antibacterial and preservative coating liquid applied is calculated based on the dry basis coating amount, i.e., the mass of newly added dry matter per unit area of ​​paper base material after coating and drying; the moisture content of the conditioned packaging box material is determined by the sample mass change method; the ring crush strength, burst strength, Cobb water absorption value, and other indicators are determined using conventional testing methods in the paper and paperboard industry; the antibacterial rate is determined by the plate count method, and the test bacteria are Escherichia coli and Staphylococcus aureus; the cinnamaldehyde retention rate is determined by headspace gas phase detection or equivalent volatile active component residue detection method; the fruit and vegetable preservation effect is achieved by conducting simulated packaging and storage tests on the same batch of strawberries or cherry tomatoes, with weight loss rate, rot rate, and mold appearance time as evaluation indicators.

[0041] This invention provides a method for preparing an antibacterial and preservative packaging box material, the overall process being as follows: Figure 1 As shown, the process includes, in sequence, the preparation of modified pulp, the preparation of slow-release preservative granules, the preparation of antibacterial preservative coating liquid, the paper base layer fabrication, single-sided coating, and post-treatment steps.

[0042] The preparation method of the present invention specifically includes the following steps:

[0043] S1. Preparation of modified pulp: Based on oven-dry weight, take 60-85 parts of waste paper pulp and 15-40 parts of bamboo pulp and mix them. Add water to adjust the pulp concentration to 2.5%-4.5%. Perform pulping treatment in a pulping equipment to control the freeness of the mixed pulp at 32°SR-40°SR. When the freeness is lower than 32°SR, the fiber fibrillation is insufficient and the strength of the paper base layer is not significantly improved. When the freeness is higher than 40°SR, the pulp's water filtration performance deteriorates, papermaking energy consumption increases, and it is easy to cause increased paper shrinkage.

[0044] After pulping, based on 100 parts of the total oven-dry weight of waste paper pulp and bamboo pulp, add 1.8-3.2 parts of cationic starch, 0.2-0.6 parts of microfibrillated cellulose, 0.4-0.8 parts of wet strength agent and 0.04-0.12 parts of retention aid to the mixed pulp, stir evenly, and obtain modified pulp.

[0045] Among them, cationic starch is used to enhance the bonding force between fibers; microfibrillated cellulose is used to fill the fine gaps between fibers and enhance the bonding between the paper base layer and the subsequent coating layer; the wet strength agent is preferably a polyamide epichlorohydrin resin wet strength agent, which is used to improve the strength retention of the packaging box material in a humid environment; the retention aid is preferably cationic polyacrylamide, which is used to improve the retention stability of fine fibers, microfibrillated cellulose and functional components.

[0046] S2. Preparation of sustained-release preservative granules: such as... Figure 2 As shown, the slow-release preservative particles of the present invention are obtained by sequentially encapsulating cinnamaldehyde with β-cyclodextrin, forming a cinnamaldehyde-β-cyclodextrin inclusion complex, and dispersing and compounding with zeolite powder. Through this process, cinnamaldehyde is not directly exposed to the coating liquid system, but is first encapsulated by β-cyclodextrin to form an inclusion complex, and then subjected to secondary adsorption and dispersion fixation by the porous structure of zeolite powder, thereby obtaining slow-release preservative particles suitable for addition to antibacterial preservative coating liquid. β-cyclodextrin is added to water and stirred and dispersed at 35-50°C to obtain a β-cyclodextrin aqueous dispersion. Subsequently, cinnamaldehyde is added dropwise to the β-cyclodextrin aqueous dispersion, controlling the mass ratio of β-cyclodextrin to cinnamaldehyde to be 8:1-15:1, and stirring is continued at 35-50°C for 40-90 min to encapsulate cinnamaldehyde with β-cyclodextrin, resulting in a cinnamaldehyde-β-cyclodextrin inclusion complex dispersion.

[0047] When the mass ratio of β-cyclodextrin to cinnamaldehyde is less than 8:1, the cinnamaldehyde is not fully encapsulated, resulting in significant volatilization loss during the coating and drying stage. When the mass ratio is greater than 15:1, the amount of β-cyclodextrin used is too high. Although the encapsulation ability is enhanced, the content of effective preservative active components per unit mass of material is reduced, and the cost and coating solids content burden increase.

[0048] Add 800-1500 mesh zeolite powder to a dispersion of cinnamaldehyde-β-cyclodextrin inclusion complex, making the mass ratio of zeolite powder to cinnamaldehyde-β-cyclodextrin inclusion complex 0.8:1-2.0:1. Continue stirring and dispersing for 30-60 minutes to allow the cinnamaldehyde-β-cyclodextrin inclusion complex to adsorb or adhere to the pores and surface of the zeolite powder particles. Then, dry at a low temperature of 40-55℃ until the moisture content is 8%-12%, lightly pulverize and sieve to obtain slow-release preservative granules.

[0049] When the particle size of zeolite powder is too coarse, the surface of the coating layer is prone to a grainy feel and it affects the printing and folding of paperboard; when the particle size of zeolite powder is too fine, the dispersion difficulty increases and it is easy to agglomerate. Therefore, the present invention controls the particle size of zeolite powder to 800-1500 mesh, so as to balance dispersibility, adsorption and coating smoothness.

[0050] S3. Preparation of antibacterial and preservative coating solution: Add 80-88 parts of water to the mixing tank by weight, heat to 75-90℃, add 4-7 parts of oxidized starch and stir to gelatinize; after the oxidized starch is evenly dispersed, add 1.0-2.0 parts of polyvinyl alcohol and continue stirring until a uniform film-forming solution is formed; slowly add 0.6-1.2 parts of chitosan to the film-forming solution to make the chitosan evenly dispersed in the system first, and then add 0.15-0.35 parts of citric acid to further swell or dissolve the chitosan, while adjusting the film-forming stability of the coating solution system.

[0051] After the system temperature drops to 45-60℃, add 0.15-0.40 parts of tea polyphenols and stir evenly. Then add 2.0-5.0 parts of the slow-release preservation granules obtained in step S2 and stir at low speed for 15-30 minutes to obtain the antibacterial preservation coating solution.

[0052] Among them, oxidized starch serves as a low-cost film-forming agent, reducing the overall formulation cost; chitosan has auxiliary antibacterial and film-forming effects; polyvinyl alcohol is used to improve coating toughness and adhesion stability; tea polyphenols provide antioxidant and auxiliary antibacterial effects; citric acid improves the water resistance stability of the coating and facilitates the dispersion or swelling of chitosan in the coating solution; and slow-release preservative particles provide continuously released volatile preservative active components.

[0053] This invention does not use high-cost materials or materials with controversial applicability in food packaging, such as nano-silver, antimicrobial peptides, and metal-organic frameworks. The main components are pulp, starch, water, chitosan, polyvinyl alcohol, β-cyclodextrin, and zeolite powder, making it suitable for large-scale production and cost control of packaging box materials.

[0054] S4. Paper base layer fabrication: The modified pulp obtained in step S1 is fed into the papermaking system, and after being formed on the wire, pressed and pre-dried, a paper base layer is formed. The basis weight of the paper base layer can be controlled at 120-250 g / m². For single-layer linerboard materials, the paper base layer can be directly used as the base paper for packaging boxes. For the face paper or linerboard of corrugated cardboard, the paper base layer can be used as the inner side paper of packaging boxes.

[0055] S5. Antibacterial and Fresh-keeping Coating: Apply the antibacterial and fresh-keeping coating liquid obtained in step S3 to the paper base layer to form the surface of the inner side of the packaging box; the coating method can be roller coating, doctor blade coating, metering rod coating or surface sizing; the dry coating amount of the antibacterial and fresh-keeping coating liquid is controlled at 8-18 g / m².

[0056] During the coating process, the antibacterial and preservative coating liquid forms a continuous or nearly continuous antibacterial and preservative functional layer on the surface of the paper base layer. Simultaneously, some film-forming components and slow-release preservative particles enter the pores of the paper base layer fibers. Figure 3 As shown, the antibacterial and preservation functional layer is formed on one side of the paper base layer, and the slow-release preservation particles are distributed in the antibacterial and preservation functional layer, forming a penetration area on the surface of the paper base layer. This penetration area can improve the bonding stability between the antibacterial and preservation functional layer and the paper base layer, making it less likely for the slow-release preservation particles to concentrate on the cardboard surface or fall off, which is beneficial for the preservation active components to continue to play a role inside the packaging box. Thus, cinnamaldehyde is not simply attached to the cardboard surface, but is distributed on the surface of the paper base material and in the surface fiber pores after being embedded by β-cyclodextrin, adsorbed by zeolite powder, and fixed by oxidized starch / chitosan / polyvinyl alcohol film formation.

[0057] S6. Drying, calendering and moisture conditioning: Dry the coated paper base layer at 85-115℃ to form an antibacterial and fresh-keeping functional layer and bond it with the paper base layer; then calender to improve the surface smoothness of the material and the bonding stability of the coating; finally, moisture conditioning is performed to control the moisture content of the packaging box material at 7%-9% to obtain antibacterial and fresh-keeping packaging box material.

[0058] The resulting antibacterial and fresh-keeping packaging material can be die-cut, crimped, folded, and glued to form a packaging box. The antibacterial and fresh-keeping functional layer is located on the inside of the packaging box and is in contact with the packaging space, thereby playing an antibacterial, anti-mold, and anti-spoilage role for fruits, vegetables, flowers, fresh food, or baked goods inside the box.

[0059] Table 1 shows the main process parameters and formula settings in the embodiments of the present invention.

[0060] Table 1 Main raw materials and process parameters of the examples

[0061]

[0062] Example 1

[0063] This embodiment provides a method for preparing an antibacterial and preservative packaging box material.

[0064] Based on oven-dry weight, take 75 parts of waste paper pulp and 25 parts of bamboo pulp, add water to adjust the pulp concentration to 3.5%, and beat in a pulper to 36°SR; then, based on a total oven-dry weight of 100 parts of waste paper pulp and bamboo pulp, add 2.5 parts of cationic starch, 0.4 parts of microfibrillated cellulose, 0.6 parts of polyamide epichlorohydrin resin wet strength agent and 0.08 parts of cationic polyacrylamide, and stir evenly to obtain modified pulp.

[0065] β-Cyclodextrin was added to water and dispersed by stirring at 42°C. Cinnamaldehyde was added dropwise at a mass ratio of β-cyclodextrin to cinnamaldehyde of 12:1, and stirring was continued for 60 min to obtain a cinnamaldehyde-β-cyclodextrin inclusion complex dispersion. 1200-mesh zeolite powder was added to the dispersion to make the mass ratio of zeolite powder to cinnamaldehyde-β-cyclodextrin inclusion complex 1.2:1. After stirring for 45 min, the mixture was dried at a low temperature of 45°C, lightly pulverized, and sieved to obtain slow-release preservative granules.

[0066] Take 84 parts by weight of water, heat to 85℃, add 5.5 parts of oxidized starch and stir to gelatinize, then add 1.5 parts of polyvinyl alcohol and stir to dissolve, then add 0.9 parts of chitosan and disperse it evenly, then add 0.25 parts of citric acid to further swell and disperse the chitosan; after cooling the system to 55℃, add 0.25 parts of tea polyphenols and stir evenly, then add 3.5 parts of slow-release preservative granules and stir at low speed for 20 minutes to obtain the antibacterial preservative coating solution.

[0067] Modified pulp was formed into a paper base layer with a basis weight of 180 g / m². After pressing and pre-drying, an antibacterial and fresh-keeping coating liquid was applied to one side of the paper base layer, with the dry basis coating amount controlled at 12 g / m². After coating, it was dried at 100°C, followed by calendering and moisture conditioning to bring the material moisture content to 8.0%, thus obtaining an antibacterial and fresh-keeping packaging box material.

[0068] Example 2

[0069] The difference between this embodiment and Embodiment 1 is that the waste paper pulp is 70 parts, the bamboo pulp is 30 parts, the beating degree of the mixed pulp is 38°SR; the amount of cationic starch added is 2.8 parts, the amount of microfibrillated cellulose added is 0.5 parts, the amount of wet strength agent added is 0.8 parts, and the amount of retention aid added is 0.10 parts.

[0070] The mass ratio of β-cyclodextrin to cinnamaldehyde was 10:1, the embedding temperature was 45℃, and the embedding time was 70 min; the zeolite powder was 1000 mesh, and the mass ratio of zeolite powder to the cinnamaldehyde-β-cyclodextrin inclusion complex was 1.8:1.

[0071] The antibacterial and preservative coating solution comprises, by weight: 82 parts water, 6.5 parts oxidized starch, 1.1 parts chitosan, 1.8 parts polyvinyl alcohol, 0.35 parts tea polyphenols, 0.30 parts citric acid, and 4.5 parts slow-release preservative granules; the dry coating amount is 16 g / m², the drying temperature is 105℃, and the moisture content after conditioning is 7.8%.

[0072] In this embodiment, the amount of zeolite powder and slow-release preservation granules is relatively high, which is suitable for packaging scenarios of humid fruits and vegetables with high requirements for mold inhibition and slow-release preservation.

[0073] Example 3

[0074] The difference between this embodiment and Embodiment 1 is that the waste paper pulp is 85 parts, the bamboo pulp is 15 parts, the beating degree of the mixed pulp is 34°SR; the amount of cationic starch added is 2.0 parts, the amount of microfibrillated cellulose added is 0.25 parts, the amount of wet strength agent added is 0.5 parts, and the amount of retention aid added is 0.05 parts.

[0075] The mass ratio of β-cyclodextrin to cinnamaldehyde was 15:1, the embedding temperature was 40℃, and the embedding time was 50 min; the zeolite powder was 1500 mesh, and the mass ratio of zeolite powder to cinnamaldehyde-β-cyclodextrin inclusion complex was 0.9:1.

[0076] The antibacterial and preservative coating solution comprises, by weight: 87 parts water, 4.5 parts oxidized starch, 0.7 parts chitosan, 1.1 parts polyvinyl alcohol, 0.18 parts tea polyphenols, 0.18 parts citric acid, and 2.4 parts slow-release preservative granules; the dry coating amount is 9 g / m², the drying temperature is 95℃, and the moisture content after conditioning is 8.5%.

[0077] This embodiment reduces the amount of functional coatings and active preservatives used, making it suitable for cost-sensitive packaging materials.

[0078] Example 4

[0079] The difference between this embodiment and Embodiment 1 is that the waste paper pulp is 60 parts, the bamboo pulp is 40 parts, the beating degree of the mixed pulp is 39°SR; the amount of cationic starch added is 3.2 parts, the amount of microfibrillated cellulose added is 0.6 parts, the amount of wet strength agent added is 0.7 parts, and the amount of retention aid added is 0.12 parts.

[0080] The mass ratio of β-cyclodextrin to cinnamaldehyde was 8:1, the embedding temperature was 50℃, and the embedding time was 80 min; the zeolite powder was 800 mesh, and the mass ratio of zeolite powder to the cinnamaldehyde-β-cyclodextrin inclusion complex was 1.0:1.

[0081] The antibacterial and preservative coating solution comprises, by weight: 80 parts water, 7.0 parts oxidized starch, 1.0 part chitosan, 2.0 parts polyvinyl alcohol, 0.30 parts tea polyphenols, 0.35 parts citric acid, and 3.0 parts slow-release preservative granules; the dry coating amount is 13 g / m², the drying temperature is 110℃, and the moisture content after conditioning is 7.5%.

[0082] This embodiment increases the proportion of bamboo pulp, cationic starch, and microfibrillated cellulose to verify the applicability of the invention in high-strength packaging box materials.

[0083] Comparative Example 1

[0084] This comparative example is a control group consisting of ordinary paper-based materials.

[0085] The waste paper pulp, bamboo pulp and modified pulp prepared according to Example 1 are used to form the paper base layer, but no antibacterial and freshness-preserving coating liquid is applied. Only drying, calendering and humidity conditioning are performed to obtain ordinary packaging box paper base material.

[0086] This comparative example illustrates that when no antibacterial preservation layer is provided, the paper-based material, although possessing basic strength, does not exhibit significant antibacterial preservation and slow-release antifungal effects.

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 1 is that cinnamaldehyde-β-cyclodextrin inclusion complex is not prepared, nor is it dispersed and compounded with zeolite powder. Instead, an equal amount of cinnamaldehyde as in Example 1 is directly added to the antibacterial and preservative coating liquid. The remaining paper base formulation, the amount of oxidized starch, chitosan, polyvinyl alcohol, tea polyphenols and citric acid in the coating liquid, as well as the coating, drying and humidity conditioning parameters are the same as in Example 1.

[0089] This comparative example illustrates that when cinnamaldehyde is added directly to the coating solution, although the initial antibacterial effect can be observed, the loss due to volatilization during coating, drying, and storage is significant, resulting in insufficient sustained freshness preservation.

[0090] Comparative Example 3

[0091] The difference between this comparative example and Example 1 is that cinnamaldehyde-β-cyclodextrin inclusion complex was prepared, but zeolite powder was not added for secondary adsorption and recombination. Instead, the cinnamaldehyde-β-cyclodextrin inclusion complex was directly added to the antibacterial and preservative coating liquid. The remaining steps were the same as in Example 1.

[0092] This comparative example illustrates that although β-cyclodextrin encapsulation alone can reduce the volatilization rate of cinnamaldehyde, the sustained-release stability and functional retention under humid conditions are still inferior to those of the embodiments of the present invention due to the lack of porous adsorption of zeolite powder and humidification fixation.

[0093] Test Example 1: Basic Performance Test of Paper-Based Materials

[0094] The packaging box materials obtained in Examples 1-4 and Comparative Examples 1-3 were equilibrated for 24 hours under the same temperature and humidity conditions, and their quantitative properties, ring crush index, bursting strength index, Cobb water absorption value, and wet strength retention rate were tested. The results are shown in Table 2.

[0095] Table 2 Test Results of Basic Properties of Paper-Based Materials

[0096]

[0097] As can be seen from Table 2, the antibacterial and preservation functional layer of the present invention did not lead to a significant decrease in the strength of the paper base material. On the contrary, due to the addition of cationic starch, microfibrillated cellulose, and wet strength agent to the pulp, and the presence of oxidized starch, chitosan, and polyvinyl alcohol in the coating layer, the ring crush index, bursting index, and wet strength retention rate of Examples 1-4 were all higher than those of the ordinary paper base material Comparative Example 1. Compared with Comparative Example 2, Example 1 had a lower Cobb water absorption value and a higher wet strength retention rate under the same cinnamaldehyde addition amount, indicating that the adverse effects of cinnamaldehyde on the stability of the coating after encapsulation, zeolite composite, and film formation fixation were relatively small.

[0098] Test Example 2: Cinnamaldehyde Retention Rate and Antibacterial Effect Test

[0099] The materials obtained in Examples 1-4 and Comparative Examples 2-3 were cut into samples of the same size and placed in a sealed environment at 25°C and 65% relative humidity for 14 days. The relative retention rate of cinnamaldehyde in the samples was measured. At the same time, the antibacterial rate of the samples at the beginning and after 14 days was determined by plate counting method. The results are shown in Table 3.

[0100] Table 3. Cinnamaldehyde retention rate and antibacterial effect

[0101]

[0102] As shown in Table 3, in Comparative Example 2, the initial antibacterial rate of cinnamaldehyde directly added to the coating solution was close to that of the Example, but the antibacterial rate decreased significantly after 14 days, and the cinnamaldehyde retention rate was only 31.8%. In Comparative Example 3, after encapsulation with β-cyclodextrin, the cinnamaldehyde retention rate increased to 55.6% after 14 days, but it was still lower than that of Example 1. In Examples 1-4, the cinnamaldehyde retention rate was maintained at 68.3%-76.8% after 14 days through β-cyclodextrin encapsulation, secondary adsorption of zeolite powder, and film-forming fixation. This shows that the present invention can improve the ability of volatile preservative active components to be retained continuously in paper-based packaging materials.

[0103] Furthermore, the comparison results of cinnamaldehyde retention rates of each treatment group after 14 days of storage in Table 3 are as follows: Figure 4 As shown; by Figure 4 It can be clearly seen that the cinnamaldehyde retention rates of Examples 1-4 are significantly higher than those of Comparative Examples 2 and 3. Among them, Comparative Example 2 has the lowest retention rate because cinnamaldehyde is directly added to the coating solution. Although Comparative Example 3 uses β-cyclodextrin encapsulation, it lacks secondary adsorption by zeolite powder, and its retention rate is still lower than that of the Example group. This result further illustrates that the present invention uses a combination of β-cyclodextrin encapsulation, zeolite powder dispersion and film formation to improve the retention stability of cinnamaldehyde in paper-based packaging box materials.

[0104] Test Example 3: Simulated Packaging and Preservation Test of Fruits and Vegetables

[0105] Strawberries with uniform maturity, no mechanical damage, and similar individual fruit weight were selected as test subjects. Small packaging boxes with corresponding functional layers on the inner side were made from the packaging materials of each group. 300g of strawberries were placed in each box and stored for 7 days at 25℃ and 65% relative humidity. The appearance of mold spots was observed daily, and the weight loss rate and rot rate were measured on the 7th day. The results are shown in Table 4.

[0106] Table 4 Results of strawberry simulated packaging preservation test

[0107]

[0108] As shown in Table 4, the ordinary paper-based material in Comparative Example 1 did not have a significant preservation function; mold appeared on the strawberries early, and the 7-day rot rate was high. Although Comparative Example 2 contained cinnamaldehyde, it was directly added to the coating liquid, resulting in rapid evaporation in the early stages and a decrease in its anti-mold ability in the later stages. The preservation effect of Comparative Example 3 was improved after encapsulation with β-cyclodextrin, but due to the lack of secondary adsorption by zeolite powder and humidity regulation fixation, the sustained effect was still not as good as that of the examples. Examples 1-4 all delayed the appearance of mold and reduced the 7-day weight loss and rot rate, indicating that the packaging box material of the present invention has a good antibacterial preservation effect on perishable fruits and vegetables.

[0109] Furthermore, the comparison results of the rot rate of strawberries in each treatment group after 7 days of simulated packaged storage in Table 4 are as follows: Figure 5 As shown; by Figure 5 It can be seen that the 7-day rot rate of Examples 1-4 is lower than that of Comparative Examples 1-3, indicating that the antibacterial preservation packaging box material prepared by the present invention can reduce strawberry rot in a real simulated packaging environment; combined with Figure 4 As shown in the cinnamaldehyde retention rate results, this invention further improves the post-containment anti-mold and preservation effects of packaging materials by enhancing the sustained retention capacity of volatile preservative active components.

[0110] Test Case 4: Cost and Feasibility Analysis

[0111] To verify the feasibility of this invention, the sources of the main raw materials and the adaptability of the process were analyzed, and the results are shown in Table 5.

[0112] Table 5 Feasibility Description of Raw Materials and Processes

[0113]

[0114] As can be seen from Table 5, this invention does not use high-priced metal antibacterial agents, complex nanocarriers, or special reaction equipment. It mainly achieves its effects through conventional papermaking wet-end addition, paper coating, and drying and calendering processes. Since cinnamaldehyde, tea polyphenols, chitosan, and β-cyclodextrin are all added in low doses, and the coating layer is mainly composed of oxidized starch, water, and ordinary film-forming materials, the cost of the resulting packaging box material is suitable for positioning in mid-to-high-end preservation packaging scenarios such as fruits and vegetables, fresh produce, and baked goods. It will not lose its industrialization feasibility due to excessive functional components.

[0115] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A method for preparing an antibacterial and preservative packaging box material, characterized in that, Includes the following steps: S1. Based on the oven-dry weight, take 60-85 parts of waste paper pulp and 15-40 parts of bamboo pulp, mix them, and then perform pulping treatment. Add cationic starch, microfibrillated cellulose, wet strength agent and retention aid to the pulped mixture to obtain modified pulp. S2. Cinnamaldehyde is added to a β-cyclodextrin aqueous dispersion for encapsulation treatment to obtain a cinnamaldehyde-β-cyclodextrin inclusion complex. The cinnamaldehyde-β-cyclodextrin inclusion complex is then dispersed and compounded with zeolite powder to obtain slow-release preservative granules. S3. Disperse or dissolve oxidized starch, chitosan and polyvinyl alcohol in water to obtain a film-forming solution. Add tea polyphenols, citric acid and the slow-release preservative particles obtained in step S2 to the film-forming solution to obtain an antibacterial preservative coating solution. S4. The modified pulp obtained in step S1 is made into a paper base layer; S5. Apply the antibacterial and fresh-keeping coating liquid obtained in step S3 to the surface of the paper base layer used to form the inner side of the packaging box, so that the antibacterial and fresh-keeping coating liquid forms an antibacterial and fresh-keeping functional layer on the surface of the paper base layer and partially penetrates into the surface fiber pores of the paper base layer. S6. The paper base layer after step S5 is dried, calendered and conditioned to obtain antibacterial and fresh-keeping packaging box material.

2. The method for preparing an antibacterial and preservative packaging material according to claim 1, characterized in that: In step S1, the beating degree of the mixed slurry is 32°SR-40°SR.

3. The method for preparing an antibacterial and preservative packaging box material according to claim 1, characterized in that: In step S1, based on 100 parts of the total oven-dry mass of waste paper pulp and bamboo pulp, the amount of cationic starch added is 1.8-3.2 parts, the amount of microfibrillated cellulose added is 0.2-0.6 parts, the amount of wet strength agent added is 0.4-0.8 parts, and the amount of retention aid added is 0.04-0.12 parts.

4. The method for preparing an antibacterial and preservative packaging material according to claim 1, characterized in that: In step S1, the wet strength agent is a polyamide epichlorohydrin resin wet strength agent, and the retention aid is cationic polyacrylamide.

5. The method for preparing an antibacterial and preservative packaging box material according to claim 1, characterized in that: In step S2, the mass ratio of β-cyclodextrin to cinnamaldehyde is 8:1-15:1, the embedding temperature is 35-50℃, and the embedding time is 40-90 min.

6. The method for preparing an antibacterial and preservative packaging material according to claim 1, characterized in that: In step S2, the particle size of the zeolite powder is 800-1500 mesh, and the mass ratio of the zeolite powder to the cinnamaldehyde-β-cyclodextrin inclusion complex is 0.8:1-2.0:

1.

7. The method for preparing an antibacterial and preservative packaging box material according to claim 1, characterized in that: In step S3, the antibacterial and preservative coating liquid comprises, by weight: 80-88 parts water, 4-7 parts oxidized starch, 0.6-1.2 parts chitosan, 1.0-2.0 parts polyvinyl alcohol, 0.15-0.40 parts tea polyphenols, 0.15-0.35 parts citric acid, and 2.0-5.0 parts slow-release preservative granules.

8. The method for preparing an antibacterial and preservative packaging box material according to claim 1, characterized in that: In step S5, the amount of antibacterial and preservative coating liquid applied is 8-18 g / m²; in step S6, the drying temperature is 85-115℃, and the moisture content of the conditioned packaging box material is 7%-9%.

9. A packaging box material with antibacterial and food-preserving properties, characterized in that, The antibacterial and preservative packaging box material is prepared by any one of claims 1-8; The antibacterial and fresh-keeping packaging material includes a paper base layer and an antibacterial and fresh-keeping functional layer disposed on one side surface of the paper base layer; The paper base layer is formed by papermaking from a mixture of waste paper pulp and bamboo pulp containing cationic starch, microfibrillated cellulose, wet strength agent and retention aid; The antibacterial and preservative functional layer includes oxidized starch, chitosan, polyvinyl alcohol, tea polyphenols, citric acid, and slow-release preservative particles. The slow-release preservative particles include cinnamaldehyde-β-cyclodextrin inclusion complex and zeolite powder compounded with the cinnamaldehyde-β-cyclodextrin inclusion complex.

10. The antibacterial and preservative packaging box material according to claim 9, characterized in that: The antibacterial and fresh-keeping packaging box material is formed into a packaging box after being die-cut, creasing, folding and gluing, and the antibacterial and fresh-keeping functional layer is located on the inside of the packaging box.

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