A regenerated high-strength corrugated paper, a preparation method thereof and a corrugated paperboard for shoe boxes

Abstract

This application discloses a recycled high-strength corrugated base paper, its preparation method, and corrugated cardboard for shoe boxes. The preparation of the corrugated base paper includes: enzymatically modifying and beating waste paper pulp, then adding cationic starch, polyamide epichlorohydrin wet strength agent, carboxylated cellulose nanocrystals, and alkyl ketene dimers to obtain corrugated paper base pulp; forming the corrugated paper base pulp, and then pressing, dehydrating, and drying it to obtain shaped paper; applying reinforcing sizing agents to the surface of the shaped paper, drying, and calendering to obtain corrugated base paper; the reinforcing sizing agents include: 80-90 parts of film-forming reinforcing agent, 3-5 parts of carboxylated reduced graphene oxide dispersion, 1-2 parts of carbodiimide crosslinking agent, 1-5 parts of borate ester coupling agent, and 5-8 parts of polydimethylsiloxane; the film-forming reinforcing agents include styrene-acrylic emulsion and carboxylated styrene-butadiene emulsion. The corrugated base paper obtained thereby has high strength and excellent moisture resistance, and is suitable for making corrugated cardboard for shoe boxes.

Description

Technical Field

[0001] This application relates to the field of corrugated cardboard for shoe boxes, and in particular to a recycled high-strength corrugated base paper, its preparation method, and corrugated cardboard for shoe boxes. Background Technology

[0002] Corrugated cardboard, a crucial material in the packaging industry, boasts advantages such as low cost, light weight, high strength, excellent cushioning performance, and convenient storage and handling. Its composite structure, formed by bonding multiple layers of paper sheets with a corrugated core, withstands both longitudinal pressure and excellent lateral impact resistance, effectively protecting contents from external mechanical damage. Furthermore, corrugated cardboard can be manufactured from recycled waste paper and can be recycled again after use, forming a "waste paper-cardboard-waste paper" recycling model, aligning with the green development concept of resource conservation and environmental protection. In the packaging field, its applications are widespread, covering multiple categories including electronics, daily necessities, and food, especially playing a vital role in shoe box packaging—its lightweight characteristics reduce transportation costs, its cushioning performance reduces shoe deformation during transportation, and its environmentally friendly attributes meet consumers' demand for sustainable packaging, making it the preferred material for many footwear brands' packaging solutions.

[0003] Despite the numerous advantages of corrugated cardboard in shoe box applications, several technological bottlenecks remain. During storage and handling, some corrugated cardboard shoe boxes are prone to breakage due to insufficient strength, especially when stacked in high layers or subjected to bumpy transport. Localized pressure can lead to structural failure of the cardboard, affecting packaging integrity. Furthermore, corrugated cardboard has insufficient moisture resistance and is highly sensitive to moisture. When exposed to rain or high humidity, the paper fibers absorb water and swell, causing the cardboard to soften, its strength to drop sharply, and even breakage. This not only shortens the packaging's lifespan but can also damage the shoes inside due to packaging failure. Summary of the Invention

[0004] To address the shortcomings of corrugated cardboard in shoe box applications in terms of strength and moisture resistance, this paper provides a recycled high-strength corrugated base paper, its preparation method, and corrugated cardboard for shoe boxes.

[0005] The first inventive objective of this invention is achieved through the following technical solution: A method for preparing recycled high-strength corrugated base paper includes the following steps: S1: Waste paper pulp is enzymatically modified and pulped, and then cationic starch, polyamide epichlorohydrin wet strength agent, carboxylated cellulose nanocrystals and alkyl ketene dimer are added and mixed to obtain corrugated paper pulp. S2: The corrugated paper pulp is formed into shape, and then pressed, dehydrated, and dried to obtain shaped paper; S3: Apply reinforcing sizing agent to the surface of the shaped paper, and obtain corrugated base paper after drying and calendering; The reinforcing compound comprises the following components in parts by weight: 80-90 parts of film-forming enhancer 3-5 parts of carboxylated reduced graphene oxide dispersion 1-2 parts of carbodiimide crosslinking agent, 1-5 parts of borate ester coupling agent 5-8 parts of polydimethylsiloxane; Film-forming enhancers include styrene-acrylic emulsions and carboxylated styrene-butadiene emulsions.

[0006] By adopting the above technical solution, in step S1, enzyme treatment can selectively modify the fiber surface, increasing its accessibility and reactivity. The subsequent pulping operation further breaks down the fibers, exposing more hydroxyl groups, providing a basis for subsequent chemical bonding. Pulping further breaks down the fibers, increasing the bonding area between fibers. Cationic starch, as a natural cationic polymer, can be adsorbed onto the negatively charged fiber surface through electrostatic interaction and form hydrogen bonds through hydroxyl groups, playing an initial strengthening and retention role. The active groups of polyamide epichlorohydrin wet strength agent can form covalent bonds with the hydroxyl groups of cellulose, forming a water-resistant cross-linked network after paper drying, improving wet strength and overall structural durability. Carboxylated cellulose nanocrystals, as nanoscale cellulose derivatives... Biological materials possess high aspect ratios, high specific surface areas, and abundant carboxyl and hydroxyl functional groups. When dispersed in a pulp system, rigid rod-shaped nanoparticles can uniformly penetrate and adsorb between and onto the surface of micron-sized plant fibers. Their nanoscale size allows them to penetrate deep into the pores between fibers. Through the polar groups on their surface, they form dense hydrogen and ionic bonds with the fiber matrix, effectively enhancing the bonding strength between fibers and filling voids. Their excellent mechanical strength allows them to act as stress transmission units, uniformly distributing external loads and improving the overall stiffness and tensile strength of paper. Alkyl ketene dimers are reactive neutral sizing agents. During paper drying, as moisture evaporates and temperature rises, alkyl ketene dimer particles melt and spread on the fiber surface. Their active lactone rings... The structure undergoes esterification with the hydroxyl groups on the surface of cellulose fibers, forming covalent bonds. Its long-chain alkyl groups align directionally towards the fiber exterior through thermal motion, thus forming a low-surface-energy, highly hydrophobic molecular layer on the fiber surface. This alters the wetting properties of the fiber surface, giving the paper overall water resistance and reducing its moisture absorption rate and capillary water absorption effect. In step S3, the film-forming reinforcing agent is a blend of styrene-acrylic emulsion and carboxylated styrene-butadiene emulsion. The styrene-acrylic emulsion, after film formation, has high hardness and good water resistance, providing rigidity and protection. The carboxylated styrene-butadiene emulsion has excellent flexibility and strong adhesion. The blend of the two can form a continuous, tough, and somewhat elastic polymer film on the paper surface, reinforcing the surface fibers and serving as a carrier matrix for other functional components. Carboxylation also... The original graphene oxide dispersion introduces abundant carboxyl functional groups at the edges of the graphene sheets, ensuring uniform dispersion in water-based adhesives. Furthermore, the carboxyl groups can chemically react with the carbodiimide crosslinking agent in the system, anchoring the graphene sheets to the polymer network via covalent bonds. This enhances the coating's structural density and water resistance, restoring some of the intrinsic high strength and hydrophobicity of graphene. The retained carboxyl groups maintain reactivity and interfacial compatibility, inducing a more ordered arrangement of surrounding polymer molecular chains and strengthening the matrix's rigidity and strength. The carbodiimide crosslinking agent can undergo efficient dehydration condensation reactions with the polymer and carboxyl groups on the graphene oxide, forming amide bonds. This covalent crosslinking network within the coating enhances its water resistance and mechanical stability.The borate ester coupling agent has a molecular structure with a borate ester group at one end that can react with inorganic substances or cellulose hydroxyl groups, and a long-chain organic group compatible with organic polymers at the other end. At the paper-coating interface, the borate ester group can form coordination bonds or reversible covalent bonds with the hydroxyl groups on the surface of cellulose fibers, while the long organic chain intertwines and miscibly dissolves with the polymer matrix in the reinforcing adhesive. This effectively improves the interfacial compatibility and bonding strength between the hydrophobic polymer coating and the hydrophilic paper base, reducing coating peeling or cracking caused by interfacial stress concentration, and ensuring a strong bond between the functional coating and the paper base. Polydimethylsiloxane is a low surface energy organic compound that, after migrating to the coating surface, effectively reduces surface tension, giving the paper excellent smoothness, excellent hydrophobicity, and improved moisture resistance. This composite adhesive system, through multiple cross-linking mechanisms and the superposition of functional components, constructs a functional layer that is both rigid and flexible, strong and durable, and moisture-proof. Combined with the internally reinforcing fiber matrix, the final product possesses both high strength and moisture resistance.

[0007] Optionally, the enzyme preparations used in the enzyme modification treatment include endonuclease and xylanase.

[0008] By adopting the above technical solution, endonuclease can randomly hydrolyze the glycosidic bonds inside the cellulose chain, generating new ends and reducing the degree of polymerization of cellulose, making the fiber structure looser. Xylanase, on the other hand, specifically degrades xylan (the main component of hemicellulose) in the fiber cell wall, which helps to break down the rigid structure of the fiber and promotes the softening and swelling of the fiber. The synergistic effect of the two can more effectively deconstruct and modify the complex fibers in waste paper pulp, especially optimizing the damaged cell wall structure in recycled fibers, increasing the flexibility and specific surface area of ​​the fiber, creating more favorable conditions for the adsorption of subsequent chemical reinforcing agents and the hydrogen bonding between fibers, thereby improving the strength and moisture resistance of the paper.

[0009] Optionally, the enzyme modification treatment temperature is 45-55℃, the pH is 5-6, and the mass ratio of endonuclease to xylanase is (7:3)-(8:2).

[0010] By adopting the above technical solution, the temperature range of 45-55℃ is the suitable activity temperature range for most mesophilic enzyme preparations, which can ensure that the enzyme catalytic reaction proceeds with high efficiency. The slightly acidic environment with a pH value of 5-6 matches the optimal pH range of the endocellulase and xylanase used, which can maintain the spatial conformation and active site stability of the enzyme protein, ensuring the controllability and high efficiency of the enzymatic hydrolysis reaction. The endocellulase and xylanase are in a mass ratio of (7:3)-(8:2) to focus on the endocleavage of cellulose, preferentially and moderately cutting the cellulose chain to facilitate fiber fibrillation. At the same time, an appropriate amount of xylanase is added to break the hemicellulose barrier, realizing a better synergistic effect of the two enzymes when acting on complex fiber matrices. While effectively improving fiber properties, it effectively reduces the decrease in pulp yield or strength loss caused by excessive degradation of xylan.

[0011] Optionally, pulp to a freeness of 28-35°SR.

[0012] By adopting the above technical solution, within this range, the fibers are fully split and finely fibrillated, increasing the specific surface area and flexibility of the fibers. In the subsequent papermaking process, more and stronger hydrogen bonds can be formed. At the same time, the excessive shortening of fibers caused by over-beating is reduced, which reduces the problems of increased paper brittleness and decreased tear strength that may be caused by the decrease in average fiber length. This is conducive to maintaining the necessary toughness of paper while obtaining good tensile strength and ring crush strength.

[0013] Optionally, the mass ratio of styrene-acrylic emulsion to carboxylated styrene-butadiene emulsion is (6:4)-(7:3).

[0014] By adopting the above technical solution, the coating in this range has sufficiently high rigidity and wet friction resistance to effectively improve the stiffness and surface strength of the paper. At the same time, an appropriate amount of carboxylated styrene-butadiene emulsion is interspersed therein, which can absorb stress, prevent crack propagation, and give the coating good toughness and adhesion to the paper base. Through the complementary effect of polymers, the mechanical properties and durability are synergistically optimized.

[0015] Optionally, 0.2-0.4 parts of silicone defoamer may be added to the reinforcing compound.

[0016] By adopting the above technical solution, the low surface tension of the silicone defoamer allows it to spread rapidly on the surface of the foam liquid film, causing the liquid film to thin and break locally, thereby effectively eliminating and suppressing foam. This helps to ensure the stability and uniformity of the adhesive system, so as to form a complete, defect-free, uniform functional coating on the paper surface, achieving better surface enhancement and moisture-proof effects.

[0017] Optionally, 0.5-0.8 parts of polyether-modified silicone leveling agent may be added to the reinforcing compound.

[0018] By adopting the above technical solution, polyether-modified silicone leveling agent can effectively reduce the surface tension of the adhesive, improve its wetting and spreading performance on paper base, and reduce leveling defects such as pinholes and orange peel that are easily generated in the adhesive during the drying process after sizing due to surface tension gradient or uneven solvent evaporation. It promotes the formation of a uniform liquid film in the adhesive before curing, and reduces surface tension differences through its migration and interface regulation, resulting in a smooth and flat surface with a more uniform and effective physical barrier effect.

[0019] The second objective of this invention is as follows: The recycled high-strength corrugated base paper prepared by the above preparation method.

[0020] The third inventive objective of this invention is achieved through the following technical solution: A corrugated cardboard for shoe boxes, the corrugated cardboard being made by bonding a corrugated paper core and two linerboards together, the corrugated paper core being located between the two linerboards, and the corrugated paper core being made by rolling the aforementioned corrugated base paper.

[0021] By adopting the above technical solution, the corrugated cardboard produced has high strength and excellent moisture resistance.

[0022] In summary, this application has at least the following beneficial effects: (1) Enzyme treatment and pulping modify the fiber surface, cationic starch electrostatic adsorption and polyamide epichlorohydrin covalent crosslinking, synergistically enhance fiber reactivity and bonding strength, laying the foundation for reinforcement; (2) Carboxylated cellulose nanocrystals, film-forming enhancers and graphene form a dense network through hydrogen bonds and covalent bonds, which enhances fiber bonding and fills gaps, thereby improving paper stiffness and tensile strength. (3) The reinforcing material is superimposed with functional components through multiple cross-linking mechanisms to construct a rigid and flexible, strong, durable and moisture-proof functional layer, which is combined with the internal fiber matrix to achieve high strength and moisture-proof performance. Detailed Implementation

[0023] raw material The waste paper pulp is white recycled pulp, with 10% unbroken fiber component (10mm (excluding) - 20mm), 0.1% impurity content, D65 brightness of 55%, tensile index of 30 N·m / g, and burst index of 3 kPa·m. 2 / g, tearing index is 8mN·m 2 / g, moisture 50%; Cationic starch was purchased from Shandong Fuyang Biotechnology Co., Ltd. Cellulase, BR grade, enzyme activity 50u / mg, purchased from Shanghai Yuanye Biotechnology Co., Ltd. Xylanase, BR grade, enzyme activity 300,000 U / g, purchased from Shanghai Yuanye Biotechnology Co., Ltd. Polyamide epichlorohydrin wet strength agent, brand name JH-1201, was purchased from Qingzhou Jinhao New Materials Co., Ltd. Carboxylated cellulose nanocrystals, powder, 10-20 nm in diameter and 100-400 nm in length, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. Alkyl ketene dimer, 90 wt% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Styrene-acrylic emulsion, model S-01, solid content 48±2wt%, purchased from Jiangsu Shengda New Material Technology Co., Ltd. Carboxylated styrene-butadiene emulsion, brand name JH-613, solid content 48±2wt%, purchased from Qingzhou Jinhao New Materials Co., Ltd. Carboxylated reduced graphene oxide dispersion, concentration 1 mg / mL, was purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. Carbodiimide crosslinking agent, brand name HyMax®CA, purchased from Shanghai Langyi Functional Materials Co., Ltd.; Boronate coupling agent, purchased from Jingjiang Kanggaote New Material Technology Co., Ltd.; Polydimethylsiloxane, average molecular weight 4200, purchased from Shanghai Yuanye Biotechnology Co., Ltd. The silicone defoamer, model LP-306, was purchased from Hangzhou Jessica Chemical Co., Ltd. Polyether-modified silicone leveling agent, model RH-T1008, was purchased from Ningbo Runhe High-Tech Materials Technology Co., Ltd. Citric acid is available commercially.

[0024] Preparation Example 1 A reinforcing compound is prepared as follows: 55.25 kg of styrene-acrylic emulsion is added to a reaction vessel, stirring is started at 50 rpm, 29.75 kg of carboxylated styrene-butadiene emulsion is added, and after addition, the mixture is stirred for 20 min. The stirring speed is increased to 70 rpm, 4 kg of carboxylated reduced graphene oxide dispersion is added, and the mixture is stirred for 30 min. The temperature is raised to 35°C, 1.5 kg of carbodiimide crosslinking agent is added, and the mixture is stirred for 25 min. Then, 3 kg of borate ester coupling agent and 6 kg of polydimethylsiloxane are added sequentially, the temperature is raised to 50°C, and the mixture is stirred for 20 min. Heating is stopped, and the mixture is allowed to cool naturally to 40°C. Then, 0.6 kg of polyether-modified silicone leveling agent and 0.3 kg of silicone defoamer are added sequentially, and the mixture is stirred for 15 min. The stirring speed is adjusted to 30 rpm, and the mixture is allowed to mature for 1.5 h. Stirring is then stopped to obtain the reinforcing compound.

[0025] Preparation Example 2 A reinforcing compound, which differs from Preparation Example 1 in that: no carboxylated reduced graphene oxide dispersion is added; the rest is the same as Preparation Example 1.

[0026] Preparation Example 3 A reinforcing compound, which differs from Preparation Example 1 in that a borate ester coupling agent is added; the rest is the same as Preparation Example 1.

[0027] Preparation Example 4 A reinforcing compound, which differs from Preparation Example 1 in that: the styrene-acrylic emulsion is 51 kg and the carboxylated styrene-butadiene emulsion is 34 kg; the rest is the same as Preparation Example 1.

[0028] Preparation Example 5 A reinforcing compound differs from Preparation Example 1 in that: the styrene-acrylic emulsion is 59.5 kg and the carboxylated styrene-butadiene emulsion is 25.5 kg; the rest is the same as Preparation Example 1.

[0029] Preparation Example 6 A reinforcing compound differs from Preparation Example 1 in that: the styrene-acrylic emulsion is 42.5 kg and the carboxylated styrene-butadiene emulsion is 42.5 kg; the rest is the same as Preparation Example 1.

[0030] Preparation Example 7 A reinforcing compound differs from Preparation Example 1 in that: the styrene-acrylic emulsion is 68 kg and the carboxylated styrene-butadiene emulsion is 17 kg; the rest is the same as Preparation Example 1.

[0031] Preparation Example 8 A reinforcing compound, which differs from Preparation Example 1 in that: no silicone defoamer is added; the rest is the same as Preparation Example 1.

[0032] Preparation Example 9 A reinforcing compound, which differs from Preparation Example 1 in that: no polyether-modified silicone leveling agent is added; the rest is the same as Preparation Example 1.

[0033] Preparation Example 10 A reinforcing compound differs from Preparation Example 1 in that: 52 kg of styrene-acrylic emulsion, 28 kg of carboxylated styrene-butadiene emulsion, 3 kg of carboxylated reduced graphene oxide dispersion, 1 kg of carbodiimide crosslinking agent, 1 kg of borate ester coupling agent, 5 kg of polydimethylsiloxane, 0.2 kg of silicone defoamer, and 0.8 kg of polyether-modified silicone leveling agent are used; the remaining components are the same as in Preparation Example 1.

[0034] Preparation Example 11 A reinforcing compound differs from Preparation Example 1 in that: 58.2 kg of styrene-acrylic emulsion, 31.5 kg of carboxylated styrene-butadiene emulsion, 5 kg of carboxylated reduced graphene oxide dispersion, 2 kg of carbodiimide crosslinking agent, 5 kg of borate ester coupling agent, 8 kg of polydimethylsiloxane, 0.4 kg of silicone defoamer, and 0.8 kg of polyether-modified silicone leveling agent are used; the remaining components are the same as in Preparation Example 1.

[0035] Example 1 A recycled high-strength corrugated base paper, the preparation method of which is as follows: S1: Add 375g of cellulase and 125g of xylanase to 1t of waste paper pulp with a solid content of 3.5wt%, add citric acid to adjust the pH to 5.5, heat to 50℃, and perform enzyme treatment for 90min. Then heat to 80℃, and after 10min, lower to room temperature (25℃). Put the pulp into a refiner and beat it to a freeness of 30°SR. Then add 7kg of cationic starch, 2.1kg of polyamide epichlorohydrin wet strength agent, 1.05kg of carboxylated cellulose nanocrystals, and 1.4kg of alkyl ketene dimer in sequence. Disperse the pulp using a high-speed disperser at 5000 rpm for 10min to obtain corrugated paper pulp. S2: The corrugated paper pulp is formed using a rotary paper machine with a pulp concentration of 0.3% and a vacuum degree of 0.03MPa. It is then subjected to three press dewatering processes: the first press is 30kN / m, the second press is 60kN / m, and the third press is 90kN / m. The pulp is then dried at 110℃ for 1 min with a moisture content of 8% to obtain the shaped paper. S3: Apply reinforcing adhesive to the surface of the setting paper using a film transfer sizing machine. The temperature of the reinforcing adhesive is 60℃, the temperature of the setting paper is 80℃, and the application rate is 2.0 g / m². 2 Curing is performed at 100℃ for 8 seconds and 110℃ for 15 seconds, followed by soft calendering with a linear pressure of 100kN / m, a temperature of 70℃, and a gloss level of 20° (75° angle) to obtain recycled high-strength corrugated base paper.

[0036] Comparative Example 1 A recycled high-strength corrugated base paper differs from Example 1 in that it does not contain polyamide epichlorohydrin wet strength agent; the rest is the same as Example 1.

[0037] Comparative Example 2 A recycled high-strength corrugated base paper differs from Example 1 in that it does not contain carboxylated cellulose nanocrystals; the rest is the same as Example 1.

[0038] Comparative Example 3 A recycled high-strength corrugated base paper differs from Example 1 in that it does not contain alkyl ketene dimers; the rest is the same as Example 1.

[0039] Comparative Example 4 A recycled high-strength corrugated base paper, which differs from Example 1 in that: the reinforcing material is derived from Preparation Example 2; the rest is the same as Example 1.

[0040] Comparative Example 5 A recycled high-strength corrugated base paper, which differs from Example 1 in that: the reinforcing material is derived from Preparation Example 3; the rest is the same as Example 1.

[0041] Example 2 A recycled high-strength corrugated base paper differs from Example 1 in that xylanase is not added and the amount of cellulase is 500g; the rest is the same as in Example 1.

[0042] Example 3 A recycled high-strength corrugated base paper differs from Example 1 in that: no cellulase is added, and the amount of xylanase is 500g; the rest is the same as in Example 1.

[0043] Example 4 A recycled high-strength corrugated base paper differs from Example 1 in that: the cellulase content is 350g and the xylanase content is 150g; the rest is the same as in Example 1.

[0044] Example 5 A recycled high-strength corrugated base paper differs from Example 1 in that: the cellulase content is 400g and the xylanase content is 100g; the rest is the same as in Example 1.

[0045] Example 6 A recycled high-strength corrugated base paper differs from Example 1 in that: the cellulase content is 300g and the xylanase content is 200g; the rest is the same as in Example 1.

[0046] Example 7 A recycled high-strength corrugated base paper differs from Example 1 in that: the cellulase content is 450g and the xylanase content is 50g; the rest is the same as in Example 1.

[0047] Example 8 A recycled high-strength corrugated base paper differs from Example 1 in that it is pulped to a freeness of 28°SR; the rest is the same as Example 1.

[0048] Example 9 A recycled high-strength corrugated base paper differs from Example 1 in that it is pulped to a freeness of 35°SR; the rest is the same as Example 1.

[0049] Example 10 A recycled high-strength corrugated base paper differs from Example 1 in that it is pulped to a freeness of 25°SR; the rest is the same as Example 1.

[0050] Example 11 A recycled high-strength corrugated base paper differs from Example 1 in that it is pulped to a freeness of 38°SR; the rest is the same as Example 1.

[0051] Example 12 A recycled high-strength corrugated base paper, which differs from Example 1 in that: the reinforcing material is derived from Preparation Example 4; the rest is the same as Example 1.

[0052] Example 13 A recycled high-strength corrugated base paper, which differs from Example 1 in that: the reinforcing material is derived from Preparation Example 5; the rest is the same as Example 1.

[0053] Example 14 A recycled high-strength corrugated base paper, which differs from Example 1 in that: the reinforcing material is derived from Preparation Example 6; the rest is the same as Example 1.

[0054] Example 15 A recycled high-strength corrugated base paper, which differs from Example 1 in that: the reinforcing material is derived from Preparation Example 7; the rest is the same as Example 1.

[0055] Example 16 A recycled high-strength corrugated base paper, which differs from Example 1 in that: the reinforcing material is derived from Preparation Example 8; the rest is the same as Example 1.

[0056] Example 17 A recycled high-strength corrugated base paper, which differs from Example 1 in that: the reinforcing material is derived from Preparation Example 9; the rest is the same as Example 1.

[0057] Example 18 A recycled high-strength corrugated base paper differs from Example 1 in that the reinforcing material is derived from Preparation Example 10; the rest is the same as Example 1.

[0058] Example 19 A recycled high-strength corrugated base paper differs from Example 1 in that the reinforcing material is derived from Preparation Example 11; the rest is the same as Example 1.

[0059] Example 20 A type of corrugated cardboard for shoe boxes consists of two linerboards and a corrugated core, with the corrugated core located between the two linerboards. The linerboard has a basis weight of 200 g / m². 2The preparation method is as follows: Corrugated base paper is rolled into shape using a corrugating machine. The corrugated base paper is derived from Example 1. The corrugating roll temperature is 170℃, and the rolling pressure is 0.4MPa. The resulting corrugated core has a B-type flute shape, a flute height of 3mm, and a flute count of 50 (flute / 300mm). Glue is applied to both sides of the flute tops at a rate of 12g / m². 2 The two cardboard sheets are bonded to both sides of the corrugated paper core, and then pressed together with a pressure roller at a pressure of 0.5 MPa. After drying at 120°C, corrugated cardboard for shoe boxes is obtained.

[0060] The performance of Examples 1-19 and Comparative Examples 1-5 was tested as follows: 1. Strength testing According to GB / T 2679.8-2016 "Determination of ring crush strength of paper and paperboard", the sample width was 12.7 mm and the length was 150 mm. The test speed was 12.5 mm / min. The ring crush index was tested and the test results are shown in Table 1. According to GB / T 6546-2021 "Determination of edge crush strength of corrugated cardboard", the sample size is 25mm×100mm, the test speed is 12.5mm / min, the edge crush index is tested, and the test results are shown in Table 1; According to GB / T 12914-2018 "Determination of Tensile Strength of Paper and Paperboard - Constant Speed ​​Tensile Test", the sample width was 12 mm, the clamping distance was 180 mm, the test speed was 20 mm / min, the tensile index was tested, and the test results are shown in Table 1. According to GB / T 455-2002 "Determination of tear strength of paper and paperboard", the tear index was tested, and the test results are shown in Table 1.

[0061] 2. Moisture-proof performance test According to GB / T 1540-2002 "Determination of water absorption of paper and paperboard (Cobb method)", the sample area is 100 cm². 2 The water absorption of the circular sample was tested with a water absorption time of 60s and a water volume of 100mL. The results are shown in Table 2. According to GB / T 465.2-2008 "Determination of tensile strength of paper and paperboard after immersion in water", the immersion time was 2 hours, and the wet strength retention rate was tested. The test results are shown in Table 2.

[0062] Table 1. Strength test results of Examples 1-19 and Comparative Examples 1-5

[0063] Table 1. Strength test results of Examples 1-19 and Comparative Examples 1-5 (continued)

[0064] Table 2. Test results of moisture-proof performance of Examples 1-19 and Comparative Examples 1-5

[0065] The test results are analyzed based on Tables 1 and 2 as follows: Comparing Example 1 and Comparative Example 1, Example 1 exhibits superior strength and moisture resistance compared to Comparative Example 1. The difference between Example 1 and Comparative Example 1 lies in the addition of polyamide epichlorohydrin resin to the corrugated base paper. The active groups of polyamide epichlorohydrin wet strength agent can form covalent bonds with the hydroxyl groups of cellulose, forming a water-resistant cross-linked network after the paper dries, thus improving wet strength and overall structural durability. Therefore, the addition of polyamide epichlorohydrin resin to the corrugated base paper is necessary.

[0066] Comparing Example 1 and Comparative Example 2, Example 1 exhibits superior strength and moisture resistance compared to Comparative Example 2. The difference between Example 1 and Comparative Example 2 lies in the addition of carboxylated cellulose nanocrystals to the corrugated base paper in Example 1. As a nanoscale cellulose derivative, carboxylated cellulose nanocrystals possess a high aspect ratio, high specific surface area, and abundant polar groups, enabling them to penetrate deep into fiber pores to form hydrogen / ionic bonds, enhancing bonding strength and filling voids, thereby improving paper stiffness and tensile strength. Therefore, the addition of carboxylated cellulose nanocrystals to the corrugated base paper is essential.

[0067] Comparing Example 1 and Comparative Example 3, Example 1 exhibits superior strength and moisture resistance compared to Comparative Example 3. The difference between Example 1 and Comparative Example 3 lies in the addition of alkyl ketene dimers to the corrugated base paper in Example 1. As a reactive sizing agent, the alkyl ketene dimer melts and spreads on the fiber surface during drying. The lactone ring esterifies with the hydroxyl group to form covalent bonds, and the long-chain alkyl groups are oriented to form a hydrophobic layer, imparting water resistance to the paper and reducing the moisture absorption rate. Therefore, the addition of alkyl ketene dimers to the corrugated base paper is necessary.

[0068] Compared with Comparative Example 4, Example 1 showed superior strength and moisture resistance compared to Comparative Example 4. The difference between Example 1 and Comparative Example 4 lies in the addition of carboxylated reduced graphene oxide dispersion to the reinforcing sizing agent used in the corrugated base paper of Example 1. The carboxylated graphene was uniformly dispersed and covalently anchored with the carbodiimide crosslinking agent, constructing an amide bond network, which improved the coating's density, water resistance, and mechanical stability, restored the intrinsic properties of graphene, and enhanced the matrix strength. Therefore, the addition of carboxylated reduced graphene oxide dispersion to the reinforcing sizing agent used in the corrugated base paper is necessary.

[0069] Compared with Comparative Example 5, Example 1 showed superior strength and moisture resistance. The difference between Example 1 and Comparative Example 5 lies in the fact that the reinforcing sizing agent used in the corrugated base paper of Example 1 contained a borate ester coupling agent. The functional groups at both ends of the borate ester coupling agent formed coordination / reversible covalent bonds with the cellulose hydroxyl groups, respectively, and were miscible with the polymer matrix, improving interfacial compatibility and bonding strength, reducing coating peeling and cracking, and ensuring a firm bond between the paper base and the coating. It can be seen that the addition of a borate ester coupling agent to the reinforcing sizing agent used in the corrugated base paper is necessary.

[0070] Comparing Examples 1 and 2-3, Example 1 demonstrates superior strength and moisture resistance compared to Examples 2-3. The difference between Examples 1 and 2-3 lies in the enzyme preparations added to the corrugated base paper in Example 1: endocellulase and xylanase. Endocellulase hydrolyzes cellulose chains, reducing the degree of polymerization, while xylanase degrades hemicellulose, promoting fiber softening. The two work synergistically to optimize the waste paper pulp fiber structure, facilitating chemical adsorption and hydrogen bonding, thereby improving paper strength and moisture resistance. Therefore, adding endocellulase and xylanase to the corrugated base paper is considered superior.

[0071] Comparing Examples 1 and 4-7, Example 1 exhibits superior strength and moisture resistance compared to Examples 4-7, while Examples 4-5 demonstrate superior strength and moisture resistance compared to Examples 6-7. The difference between Examples 1 and 4-7 lies in the following: In Examples 1 and 4-5, the mass ratio of endocellulase to xylanase in the corrugated base paper is (7:3)-(8:2), the enzyme modification treatment temperature is 45-55℃, and the pH is 5-6. Under conditions of 45-55℃ and pH 5-6, the endocellulase and xylanase work synergistically in a (7:3)-(8:2) ratio to optimize fiber fibrillation, break down the hemicellulose barrier, reduce pulp yield loss, and improve fiber properties and paper strength. Therefore, a mass ratio of endocellulase to xylanase in the corrugated base paper of (7:3)-(8:2), an enzyme modification treatment temperature of 45-55℃, and a pH of 5-6 are considered optimal.

[0072] Comparing Examples 1 and 8-11, Example 1 exhibits superior strength and moisture resistance compared to Examples 8-11, while Examples 8-9 demonstrate superior strength and moisture resistance compared to Examples 10-11. The difference between Examples 1 and 8-11 lies in the following: In Examples 1 and 8-9, the corrugated base paper is pulped to a freeness of 28-35°SR. This ratio increases the fiber specific surface area and flexibility, promotes hydrogen bonding, reduces excessive shaving, avoids increased brittleness and decreased tear strength, and maintains the paper's tensile strength, ring crush strength, and necessary toughness. Therefore, a freeness of 28-35°SR for the corrugated base paper is considered superior.

[0073] Comparing Examples 1 and 12-15, Example 1 exhibits superior strength and moisture resistance compared to Examples 12-15, while Examples 12-13 demonstrate superior strength and moisture resistance compared to Examples 14-15. The difference between Examples 1 and 12-15 lies in the mass ratio of styrene-acrylic emulsion to carboxylated styrene-butadiene emulsion in Examples 1 and 12-13 (6:4)-(7:3). Under these conditions, the coating combines high rigidity with resistance to wet friction, enhancing paper stiffness. The carboxylated styrene-butadiene emulsion absorbs stress, prevents cracking, and synergistically optimizes mechanical properties and durability. Therefore, a mass ratio of (6:4)-(7:3) for the styrene-acrylic emulsion to carboxylated styrene-butadiene emulsion in the corrugated base paper is considered optimal.

[0074] Comparing Example 1 and Example 16, Example 1 exhibits superior strength and moisture resistance compared to Example 16. The difference between Example 1 and Example 16 lies in the addition of a silicone defoamer to the reinforcing sizing agent used in the corrugated base paper of Example 1. This silicone defoamer, with its low surface tension, rapidly spreads and breaks up the foam film, effectively defoaming and suppressing foam, ensuring stable and uniform sizing, and contributing to the formation of a uniform coating on the paper surface and enhancing moisture resistance. Therefore, the addition of a silicone defoamer to the reinforcing sizing agent used in the corrugated base paper is superior.

[0075] Comparing Example 1 and Example 17, Example 1 exhibits superior strength and moisture resistance compared to Example 17. The difference between Example 1 and Example 17 lies in the fact that the reinforcing compound used in the corrugated base paper of Example 1 also incorporates a polyether-modified silicone leveling agent. This polyether-modified silicone leveling agent reduces the surface tension of the compound, improves wetting and spreading, reduces pinholes and orange peel defects, forms a uniform liquid film, reduces tension differences, achieves a smooth surface, and enhances the physical barrier effect. Therefore, the addition of a polyether-modified silicone leveling agent to the reinforcing compound used in the corrugated base paper is superior.

[0076] Comparing Example 1 and Examples 18-19, Example 1 has better strength and moisture resistance than Examples 18-19. The difference between Example 1 and Examples 18-19 is that the mass ratio of styrene-acrylic emulsion, carboxylated styrene-butadiene emulsion, carboxylated reduced graphene oxide dispersion, carbodiimide crosslinking agent, borate coupling agent, polydimethylsiloxane, silicone defoamer, and polyether-modified silicone leveling agent in the reinforcing compound used in the corrugated base paper in Example 1 is 55.25:29.75:4:1.5:3:6:0.3:0.6. Therefore, the mass ratio of styrene-acrylic emulsion, carboxylated styrene-butadiene emulsion, carboxylated reduced graphene oxide dispersion, carbodiimide crosslinking agent, borate coupling agent, polydimethylsiloxane, silicone defoamer, and polyether-modified silicone leveling agent in the reinforcing compound used in the corrugated base paper is 55.25:29.75:4:1.5:3:6:0.3:0.6, which is considered superior.

[0077] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of protection claimed in this application.

Claims

1. A method for preparing recycled high-strength corrugated base paper, characterized in that, Includes the following steps: S1: The waste paper pulp is enzymatically modified and beaten to a freeness of 28-35°SR. Then, cationic starch, polyamide epichlorohydrin wet strength agent, carboxylated cellulose nanocrystals, and alkyl ketene dimer are added and mixed to obtain corrugated paper pulp. The enzyme preparations used in the enzyme modification treatment include endoglucanase and xylanase. The enzyme modification treatment temperature is 45-55℃, the pH is 5-6, and the mass ratio of endoglucanase to xylanase is (7:3)-(8:2). S2: The corrugated paper pulp is formed into shape, and then pressed, dehydrated, and dried to obtain shaped paper; S3: Apply reinforcing sizing agent to the surface of the shaped paper, and obtain corrugated base paper after drying and calendering; The reinforcing compound comprises the following components in parts by weight: 80-90 parts of film-forming enhancer 3-5 parts of carboxylated reduced graphene oxide dispersion 1-2 parts of carbodiimide crosslinking agent, 1-5 parts of borate ester coupling agent 5-8 parts of polydimethylsiloxane; The film-forming enhancer includes styrene-acrylic emulsion and carboxylated styrene-butadiene emulsion, with a mass ratio of styrene-acrylic emulsion to carboxylated styrene-butadiene emulsion of (6:4)-(7:3).

2. The method for preparing recycled high-strength corrugated base paper according to claim 1, characterized in that, The reinforcing compound also contains 0.2-0.4 parts of silicone defoamer.

3. The method for preparing recycled high-strength corrugated base paper according to claim 1, characterized in that, The reinforcing compound also contains 0.5-0.8 parts of polyether-modified silicone leveling agent.

4. Recycled high-strength corrugated base paper prepared by the preparation method according to any one of claims 1-3.

5. A corrugated cardboard for shoe boxes, characterized in that, The corrugated cardboard is made by bonding a corrugated paper core and two linerboards together, with the corrugated paper core located between the two linerboards. The corrugated paper core is made by rolling the corrugated base paper as described in claim 4.

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