High-strength corrugated paper box based on waterproof agent and preparation method thereof

Abstract

The application discloses a high-strength corrugated carton based on a waterproof agent and a preparation method thereof, relates to the technical field of corrugated cartons, and the preparation method comprises the following preparation steps: a mercaptan curing agent containing a dopamine structure is added into tetrahydrofuran and stirred uniformly to obtain a curing agent solution; a waterproof agent is added into tetrahydrofuran and stirred uniformly to obtain a waterproof agent solution; a waterproof reinforcing agent is coated on the surface of the corrugated carton; the curing agent solution is coated on the waterproof reinforcing agent layer; finally, the waterproof agent solution is coated on the curing agent solution layer; ultraviolet irradiation curing is carried out for 1-2 hours; room temperature drying is carried out; and the high-strength corrugated carton based on the waterproof agent is obtained.

Description

Technical Field

[0001] This invention relates to the field of corrugated cardboard box technology, specifically a high-strength corrugated cardboard box based on a waterproofing agent and its preparation method. Background Technology

[0002] In modern logistics and transportation, corrugated cardboard boxes are a primary packaging material, widely used for packaging various goods due to their advantages such as light weight, high strength, low cost, and high recyclability. However, in certain special environments, such as humid or rainy transportation and storage conditions, traditional corrugated cardboard boxes are prone to moisture absorption, leading to decreased box strength, and even deformation and damage, affecting the safety and integrity of the goods. Therefore, improving the water resistance and strength of corrugated cardboard boxes in humid environments has become an important issue in the field of packaging material research and development.

[0003] In existing technologies, waterproofing corrugated cardboard boxes primarily involves applying a waterproofing agent to form a waterproof coating on the box surface, thereby improving its water resistance. However, these coatings often suffer from insufficient adhesion. Specifically, the coating exhibits weak bonding between itself and the cardboard substrate, making it prone to peeling or detachment during transportation, folding, or long-term storage. Insufficient adhesion prevents the coating from effectively remaining on the box surface, thus compromising its waterproofing effect and even affecting the overall strength and performance of the box.

[0004] Therefore, a high-strength corrugated cardboard box based on a waterproofing agent and its preparation method are invented. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength corrugated cardboard box based on a waterproofing agent and its preparation method, so as to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a high-strength corrugated cardboard box based on a waterproofing agent includes the following preparation steps: S1: Add lignin to acetone, stir evenly, add palm oil and concentrated sulfuric acid mixture, heat to 70-75℃ under nitrogen atmosphere and react for 2.5-3h, cool to room temperature, wash the product with pentane, vacuum dry for 48h, grind and pulverize, and sieve to obtain lignin derivative. S2: Add the lignin derivative to acetone, stir evenly, add silane coupling agent KH550, stir and react at room temperature for 48h, add dicyclohexylmethane diisocyanate, stir and react at room temperature for 24h, wash the product with pentane, vacuum dry for 48h, grind and pulverize, sieve, and graft lignin derivative. S3: Grafted lignin derivatives and hydroxyl-terminated polydimethylsiloxane are added to a reaction vessel, followed by ditin butyl dilaurate. The mixture is heated to 70-75℃ and reacted for 4-4.5 hours under a nitrogen atmosphere. Then, 1,4-butanediol and N,N-dimethylformamide solution of bis(4-hydroxyphenyl) disulfide are added, and the mixture is kept at this temperature for 4-4.5 hours. Finally, methanol is added, and the mixture is kept at this temperature and stirred for 2-3 hours. The mixture is then vacuum dried for 48 hours to obtain a waterproofing agent. S4: Add a thiol curing agent containing a dopamine structure to tetrahydrofuran and stir until homogeneous to obtain a curing agent solution; add a waterproofing agent to tetrahydrofuran and stir until homogeneous to obtain a waterproofing agent solution; coat the waterproofing reinforcing agent onto the surface of the corrugated cardboard box, then coat the waterproofing reinforcing agent layer with the curing agent solution, and finally coat the waterproofing agent solution layer with the curing agent solution layer. Cure by ultraviolet irradiation for 1-2 hours and dry at room temperature to obtain a high-strength corrugated cardboard box based on the waterproofing agent.

[0007] Furthermore, the coating thickness of the waterproofing enhancer is 20-30 μm, the coating thickness of the curing agent solution is 10-20 μm, and the coating thickness of the waterproofing agent solution is 20-30 μm.

[0008] Furthermore, in the preparation process of the lignin derivative, each 1g of lignin is dissolved in 10mL of acetone, and the mass ratio of the lignin acetone solution to the palm oil-sulfuric acid mixture is 1:(1-2). In the palm oil-sulfuric acid mixture, 0.1mL of concentrated sulfuric acid is added for every 15g of palm oil.

[0009] Furthermore, in the preparation process of the grafted lignin derivative, the molar ratio of silane coupling agent KH550: lignin derivative: dicyclohexylmethane diisocyanate is 1:(5-6):(2-4).

[0010] Furthermore, in the preparation process of the waterproofing agent, the molar ratio of grafted lignin derivative: hydroxyl-terminated polydimethylsiloxane: 1,4-butanediol: bis(4-hydroxyphenyl)disulfide is (15.5-20.5):(3-10):7:3.

[0011] Furthermore, the preparation method of the thiol curing agent containing the dopamine structure includes the following steps: Step (1): Add eugenol and triethylsilane to a reaction vessel, stir evenly, add tris(pentafluorophenyl)borane in two portions, react at room temperature for 12 hours, add dichloromethane to dilute, remove impurities with alkaline alumina, and distill under reduced pressure to obtain grafted eugenol. Step (2): Grafted eugenol, pentaerythritol tetrakis(3-mercaptopropionic acid) and 2,2-dimethoxy-2-phenylacetophenone were added to tetrahydrofuran. The solution was purged with nitrogen for 5-10 min and reacted under ultraviolet light for 1-1.5 h. Impurities were filtered using a 0.2 μm syringe filter and the mixture was distilled under reduced pressure to obtain grafted pentaerythritol tris(3-mercaptopropionic acid). Step (3): Grafted pentaerythritol tris(3-mercaptopropionic acid) ester was added to tetrahydrofuran, hydrochloric acid was added, the mixture was stirred and reacted for 24 h, and then distilled under reduced pressure to obtain a thiol curing agent containing a dopamine structure.

[0012] Furthermore, in the preparation process of the grafted eugenol, the mass ratio of eugenol to triethylsilane is (5.15-5.2):(14.8-15). The tris(pentafluorophenyl)borane is added twice with an interval of 1 hour.

[0013] Furthermore, in the preparation of the grafted pentaerythritol tris(3-mercaptopropionic acid) ester, the mass ratio of grafted eugenol to pentaerythritol tetras(3-mercaptopropionic acid) ester is (3.5-3.6):(4.7-4.8).

[0014] Furthermore, in the preparation process of the thiol curing agent containing the dopamine structure, the amount of hydrochloric acid added is such that the pH of the reaction system is 2.5-2.6 and maintained until the reaction is complete.

[0015] Furthermore, the preparation method of the waterproofing enhancement agent includes the following steps: adding chitosan to a 2% acetic acid solution, heating to 60-62℃ and stirring to dissolve, adding dopamine hydrochloride and laccase, stirring and reacting at room temperature for 24 hours to obtain polydopamine; adding chitosan to a 2% acetic acid solution, heating to 60-62℃ and stirring to dissolve, adding polydopamine and xanthan gum, stirring evenly to obtain the waterproofing enhancement agent; Furthermore, in the preparation of the polydopamine, the mass ratio of chitosan:dopamine hydrochloride:laccase is 60:0.6:2.1; in the preparation of the waterproofing enhancement agent, the mass ratio of chitosan:polydopamine:xanthan gum is 3:50:3.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. To address the current problem of coating adhesion, this invention prepares a polydopamine synthesized via enzymatic action from laccase in the presence of chitosan. Furthermore, a waterproofing reinforcing agent based on a ratio of 3% chitosan, 50% polydopamine, and 3% xanthan gum is used. This agent utilizes the π-π stacking effect between the polydopamine and the dopamine structure in the thiol curing agent to enhance the adhesion between the waterproof coating formed by the waterproofing agent and the surface of the corrugated cardboard box. This effectively improves the adhesion of the coating to the corrugated cardboard box surface. A coating with strong adhesion better resists peeling and detachment, reduces localized wear and damage, and maintains a uniform distribution during friction, reducing excessive localized wear or damage, thus improving the coating's wear resistance.

[0017] 2. This invention uses lignin derivatives prepared by reacting lignin with palm oil and hydroxyl-terminated polydimethylsilane as the main waterproofing and abrasion-resistant units, providing excellent waterproofing and abrasion resistance for corrugated boxes. Furthermore, eugenol-modified thiol curing agents are utilized to contain dopamine structures. In addition to eliminating the click chemical curing effect of mercaptoolefins, these agents also act as a bridge between the waterproofing agent and the waterproofing reinforcing agent. The thiol curing agent tightly bonds the waterproofing agent layer and the waterproofing reinforcing agent layer, while the waterproofing reinforcing agent layer tightly bonds the thiol curing agent, the cross-linked curing layer of the waterproofing agent, and the corrugated box substrate. The layers interact and are tightly connected, forming a strong integral structure between the waterproof coating and the surface of the corrugated box, significantly improving the hydrophobicity and abrasion resistance of the waterproof layer. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only 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.

[0019] In the following examples, the chitosan had a molecular weight of 50,000-190,000 Da and a degree of deacetylation of 75-85%; the hydroxyl-terminated polydimethylsilane Mn=2000g / moL with a purity of 92%; the palm oil CAS: 8002-75-3; the high-strength corrugated cardboard raw material, Nine Dragons Corrugated Board, was purchased from Nine Dragons Paper Holdings Limited, E-flute corrugated board; the ultraviolet light intensity was 365nm, 15W; and the remaining raw materials were all commercially available.

[0020] The method for preparing lignin includes the following steps: After washing the empty fruit bunches of oil palm, they were cut into small pieces and dried in a hot air furnace for 72 hours. The dried pieces were then placed in a rotary cooker, and a 20% sodium hydroxide solution was added. The mixture was heated to 170°C for 2 hours to obtain a 1:15 w / v suspension of empty fruit bunches of oil palm. The pulp was filtered to separate the pulp from the black liquor. Soluble lignin in the black liquor was precipitated using 4M sulfuric acid until the pH of the liquid dropped to 5. The lignin was then filtered through filter paper, washed with deionized water, vacuum dried at 70°C for 48 hours, ground, sieved through a 200-mesh sieve, and stored at room temperature away from light to obtain lignin.

[0021] The preparation method of thiol curing agent containing dopamine structure includes the following steps: Step (1): 5.15g eugenol and 14.8g triethylsilane are added to the reaction vessel and stirred evenly. 80mg tris(pentafluorophenyl)borane is added in two portions. The reaction is carried out at room temperature for 12h. Diluted with dichloromethane, impurities are removed by alkaline alumina, and the mixture is distilled under reduced pressure to obtain grafted eugenol. Step (2): 3.5g of grafted eugenol, 4.7g of pentaerythritol tetrakis(3-mercaptopropionic acid) ester and 35.2mg of 2,2-dimethoxy-2-phenylacetophenone were added to tetrahydrofuran. The solution was purged with nitrogen for 5 min and reacted under ultraviolet light for 1 h. Impurities were filtered using a 0.2μm syringe filter and the mixture was distilled under reduced pressure to obtain grafted pentaerythritol tris(3-mercaptopropionic acid) ester. Step (3): Grafted pentaerythritol tris(3-mercaptopropionic acid) ester was added to tetrahydrofuran, hydrochloric acid was added, the mixture was stirred and reacted for 24 h, and then distilled under reduced pressure to obtain a thiol curing agent containing a dopamine structure.

[0022] The preparation method of the waterproofing enhancement agent includes the following steps: 60g of chitosan is added to a 2% acetic acid solution, heated to 60℃ and stirred to dissolve, 0.6g of dopamine hydrochloride and 2.1g of laccase are added, and the mixture is stirred at room temperature for 24h to obtain polydopamine; 3g of chitosan is added to a 2% acetic acid solution, heated to 60℃ and stirred to dissolve, 50g of polydopamine and 3g of xanthan gum are added, and the mixture is stirred evenly to obtain the waterproofing enhancement agent.

[0023] Example 1: A method for preparing a high-strength corrugated cardboard box based on a waterproofing agent, comprising the following preparation steps: S1: Add 3g of lignin to 30mL of acetone, stir well, add 3g of palm oil and concentrated sulfuric acid mixture, heat to 70℃ and react for 2.5h under nitrogen atmosphere, cool to room temperature, wash the product with pentane, vacuum dry for 48h, grind and pulverize, and sieve to obtain lignin derivative. S2: Add 5 mmol of lignin derivative to acetone, stir well, add 1 mmol of silane coupling agent KH550, stir and react at room temperature for 48 h, add 3 mmol of dicyclohexylmethane diisocyanate, stir and react at room temperature for 24 h, wash the product with pentane, vacuum dry for 48 h, grind and pulverize, sieve, and graft lignin derivative. S3: 15.5 mmol of grafted lignin derivative and 3 mmol of hydroxyl-terminated polydimethylsiloxane were added to a reaction vessel, along with 0.05 mmol of ditin butyl dilaurate. The mixture was heated to 70 °C for 4-4.5 h under a nitrogen atmosphere. Then, 7 mmol of 1,4-butanediol and 3 mmol of N,N-dimethylformamide solution of bis(4-hydroxyphenyl) disulfide were added. The mixture was kept at this temperature for 4 h. Methanol was added, and the mixture was kept at this temperature and stirred for 2 h. The mixture was then dried under vacuum for 48 h to obtain a waterproofing agent. S4: Add a thiol curing agent containing a dopamine structure to tetrahydrofuran and stir until homogeneous to obtain a curing agent solution; add a waterproofing agent to tetrahydrofuran and stir until homogeneous to obtain a waterproofing agent solution; coat the waterproofing reinforcing agent onto the surface of the corrugated cardboard box, then coat the waterproofing reinforcing agent layer with the curing agent solution, and finally coat the waterproofing agent solution layer with the curing agent solution layer. Cure by ultraviolet irradiation for 1 hour and dry at room temperature to obtain a high-strength corrugated cardboard box based on the waterproofing agent.

[0024] The coating thickness of the waterproofing enhancer is 20 μm, the coating thickness of the curing agent solution is 10 μm, and the coating thickness of the waterproofing agent solution is 30 μm.

[0025] Example 2: A method for preparing a high-strength corrugated cardboard box based on a waterproofing agent, comprising the following preparation steps: S3: 20.5 mmol of grafted lignin derivative and 3 mmol of hydroxyl-terminated polydimethylsiloxane were added to a reaction vessel, along with 0.05 mmol of ditin butyl dilaurate. The mixture was heated to 70 °C for 4-4.5 h under a nitrogen atmosphere. Then, 7 mmol of 1,4-butanediol and 3 mmol of N,N-dimethylformamide solution of bis(4-hydroxyphenyl) disulfide were added. The mixture was kept at this temperature for 4 h. Methanol was added, and the mixture was kept at this temperature and stirred for 2 h. The mixture was then dried under vacuum for 48 h to obtain a waterproofing agent. The remaining steps are the same as in Example 1.

[0026] Example 3: A method for preparing a high-strength corrugated cardboard box based on a waterproofing agent, comprising the following preparation steps: S3: 20.5 mmol of grafted lignin derivative and 10 mmol of hydroxyl-terminated polydimethylsiloxane were added to a reaction vessel, along with 0.05 mmol of ditin butyl dilaurate. The mixture was heated to 70 °C for 4-4.5 h under a nitrogen atmosphere. Then, 7 mmol of 1,4-butanediol and 3 mmol of N,N-dimethylformamide solution of bis(4-hydroxyphenyl) disulfide were added, and the mixture was kept at this temperature for 4 h. Finally, methanol was added, and the mixture was kept at this temperature and stirred for 2 h. The mixture was then dried under vacuum for 48 h to obtain the waterproofing agent. The remaining steps are the same as in Example 1.

[0027] Comparative Example 1: A method for preparing a high-strength corrugated cardboard box based on a waterproofing agent, comprising the following preparation steps: S1: Add 22g of palm oil to a reaction vessel, heat to 100℃ and stir for 1h under a nitrogen atmosphere, cool to 60℃, add 13.4g of diethanolamine and 0.28mL of sodium methoxide, react for 4h, add the product to dichloromethane, wash with saturated sodium chloride aqueous solution, dry the organic phase with magnesium sulfate, evaporate the solvent, and obtain the dihydroxypalm oil derivative. S2: 7 mmol of grafted lignin derivative and 3 mmol of hydroxyl-terminated polydimethylsiloxane were added to a reaction vessel, along with 20 mmol of dicyclohexylmethane diisocyanate and 0.05 mmol of ditin butyl dilaurate. The mixture was heated to 70 °C and reacted for 4-4.5 h under a nitrogen atmosphere. Then, 7 mmol of 1,4-butanediol and 3 mmol of N,N-dimethylformamide solution of bis(4-hydroxyphenyl)disulfide were added, and the mixture was kept at this temperature for 4 h. Finally, methanol was added, and the mixture was kept at this temperature and stirred for 2 h. The mixture was then dried under vacuum for 48 h to obtain the waterproofing agent. S3: Add a thiol curing agent containing a dopamine structure to tetrahydrofuran and stir until homogeneous to obtain a curing agent solution; add a waterproofing agent to tetrahydrofuran and stir until homogeneous to obtain a waterproofing agent solution; coat the waterproofing reinforcing agent onto the surface of the corrugated cardboard box, then coat the waterproofing reinforcing agent layer with the curing agent solution, and finally coat the waterproofing agent solution layer with the curing agent solution layer. Cure by ultraviolet irradiation for 1 hour and dry at room temperature to obtain a high-strength corrugated cardboard box based on the waterproofing agent.

[0028] The coating thickness of the waterproofing enhancer is 20 μm, the coating thickness of the curing agent solution is 10 μm, and the coating thickness of the waterproofing agent solution is 30 μm.

[0029] Comparative Example 2: A method for preparing a high-strength corrugated cardboard box based on a waterproofing agent, comprising the following preparation steps: S1: Add 3g of lignin to 30mL of acetone, stir well, add 3g of palm oil and concentrated sulfuric acid mixture, heat to 70℃ and react for 2.5h under nitrogen atmosphere, cool to room temperature, wash the product with pentane, vacuum dry for 48h, grind and pulverize, and sieve to obtain lignin derivative. S2: Add 5 mmol of lignin derivative to acetone, stir well, add 1 mmol of silane coupling agent KH550, stir and react at room temperature for 48 h, add 3 mmol of dicyclohexylmethane diisocyanate, stir and react at room temperature for 24 h, wash the product with pentane, vacuum dry for 48 h, grind and pulverize, sieve, and graft lignin derivative. S3: 15.5 mmol of grafted lignin derivative and 3 mmol of hydroxyl-terminated polydimethylsiloxane were added to a reaction vessel, along with 0.05 mmol of ditin butyl dilaurate. The mixture was heated to 70 °C for 4-4.5 h under a nitrogen atmosphere. Then, 7 mmol of 1,4-butanediol and 3 mmol of N,N-dimethylformamide solution of bis(4-hydroxyphenyl) disulfide were added. The mixture was kept at this temperature for 4 h. Methanol was added, and the mixture was kept at this temperature and stirred for 2 h. The mixture was then dried under vacuum for 48 h to obtain a waterproofing agent. S4: Add a thiol curing agent containing a dopamine structure to tetrahydrofuran and stir until homogeneous to obtain a curing agent solution; add a waterproofing agent to tetrahydrofuran and stir until homogeneous to obtain a waterproofing agent solution; coat the curing agent solution onto the waterproofing reinforcing agent layer, then coat the waterproofing agent solution onto the curing agent solution layer; cure under ultraviolet light for 1 hour and dry at room temperature to obtain a high-strength corrugated cardboard box based on the waterproofing agent.

[0030] The coating thickness of the waterproofing enhancer is 20 μm, the coating thickness of the curing agent solution is 10 μm, and the coating thickness of the waterproofing agent solution is 30 μm.

[0031] Comparative Example 3: A method for preparing a high-strength corrugated cardboard box based on a waterproofing agent, comprising the following preparation steps: S1: Add 3g of lignin to 30mL of acetone, stir well, add 3g of palm oil and concentrated sulfuric acid mixture, heat to 70℃ and react for 2.5h under nitrogen atmosphere, cool to room temperature, wash the product with pentane, vacuum dry for 48h, grind and pulverize, and sieve to obtain lignin derivative. S2: Add 5 mmol of lignin derivative to acetone, stir well, add 1 mmol of silane coupling agent KH550, stir and react at room temperature for 48 h, add 3 mmol of dicyclohexylmethane diisocyanate, stir and react at room temperature for 24 h, wash the product with pentane, vacuum dry for 48 h, grind and pulverize, sieve, and graft lignin derivative. S3: 15.5 mmol of grafted lignin derivative and 3 mmol of hydroxyl-terminated polydimethylsiloxane were added to a reaction vessel, along with 0.05 mmol of ditin butyl dilaurate. The mixture was heated to 70 °C for 4-4.5 h under a nitrogen atmosphere. Then, 7 mmol of 1,4-butanediol and 3 mmol of N,N-dimethylformamide solution of bis(4-hydroxyphenyl) disulfide were added. The mixture was kept at this temperature for 4 h. Methanol was added, and the mixture was kept at this temperature and stirred for 2 h. The mixture was then dried under vacuum for 48 h to obtain a waterproofing agent. S4: Add pentaerythritol tetrakis(3-mercaptobutyric acid) to tetrahydrofuran and stir until homogeneous to obtain a curing agent solution; add a waterproofing agent to tetrahydrofuran and stir until homogeneous to obtain a waterproofing agent solution; coat the waterproofing reinforcing agent onto the surface of the corrugated cardboard box, then coat the waterproofing reinforcing agent layer with the curing agent solution, and finally coat the waterproofing agent solution layer with the curing agent solution layer. Cure by ultraviolet irradiation for 1 hour and dry at room temperature to obtain a high-strength corrugated cardboard box based on the waterproofing agent.

[0032] The coating thickness of the waterproofing enhancer is 20 μm, the coating thickness of the curing agent solution is 10 μm, and the coating thickness of the waterproofing agent solution is 30 μm.

[0033] Comparative Example 4: A method for preparing a high-strength corrugated cardboard box based on a waterproofing agent, comprising the following preparation steps: S1: Add 3g of lignin to 30mL of acetone, stir well, add 3g of palm oil and concentrated sulfuric acid mixture, heat to 70℃ and react for 2.5h under nitrogen atmosphere, cool to room temperature, wash the product with pentane, vacuum dry for 48h, grind and pulverize, and sieve to obtain lignin derivative. S2: Add 5 mmol of lignin derivative to acetone, stir well, add 1 mmol of silane coupling agent KH550, stir and react at room temperature for 48 h, add 3 mmol of dicyclohexylmethane diisocyanate, stir and react at room temperature for 24 h, wash the product with pentane, vacuum dry for 48 h, grind and pulverize, sieve, and graft lignin derivative. S3: 10.5 mmol of grafted lignin derivative and 3 mmol of hydroxyl-terminated polydimethylsiloxane were added to a reaction vessel, along with 0.05 mmol of ditin butyl dilaurate. The mixture was heated to 70 °C for 4-4.5 h under a nitrogen atmosphere. Then, 7 mmol of 1,4-butanediol and 3 mmol of N,N-dimethylformamide solution of bis(4-hydroxyphenyl) disulfide were added. The mixture was kept at this temperature for 4 h. Methanol was added, and the mixture was kept at this temperature and stirred for 2 h. The mixture was then dried under vacuum for 48 h to obtain a waterproofing agent. S4: Add a thiol curing agent containing a dopamine structure to tetrahydrofuran and stir until homogeneous to obtain a curing agent solution; add a waterproofing agent to tetrahydrofuran and stir until homogeneous to obtain a waterproofing agent solution; coat the waterproofing reinforcing agent onto the surface of the corrugated cardboard box, then coat the waterproofing reinforcing agent layer with the curing agent solution, and finally coat the waterproofing agent solution layer with the curing agent solution layer. Cure by ultraviolet irradiation for 1 hour and dry at room temperature to obtain a high-strength corrugated cardboard box based on the waterproofing agent.

[0034] The coating thickness of the waterproofing enhancer is 20 μm, the coating thickness of the curing agent solution is 10 μm, and the coating thickness of the waterproofing agent solution is 30 μm.

[0035] Experiment: Waterproof performance test: Static contact angle test was performed on the surface of the high-strength corrugated cardboard boxes based on waterproofing agent prepared in the above examples and comparative examples; Place 600-grit sandpaper on the surface of the water-resistant corrugated packaging material prepared in the examples and comparative examples, respectively. Then drag the sandpaper 10 times under the pressure of a 400g weight, with each drag distance being 20cm. Finally, retest the static contact angle after dragging.

[0036] The experimental results are shown in Table 1 below.

[0037] Table 1. Experimental data of high-strength corrugated cardboard boxes based on waterproofing agents.

[0038] Conclusion: The corrugated cardboard box prepared by this invention has excellent waterproof and wear-resistant properties.

[0039] Comparative Example 1 used a dihydroxy palm oil derivative instead of a grafted lignin derivative, which resulted in a decrease in water resistance and abrasion resistance.

[0040] Comparative Example 2 did not use a waterproofing enhancer, which resulted in reduced adhesion between coatings and affected wear resistance.

[0041] The curing agent in Comparative Example 3 does not contain a dopamine structure and lacks π-π stacking effect, which reduces the adhesion between coatings and affects wear resistance.

[0042] Comparative Example 4 showed a lower addition of grafted lignin derivatives, resulting in a reduction in cross-linked and cured structures, leading to a decrease in coating density. At the same time, the reduction in lignin and grafted long-chain alkane segments resulted in a decrease in waterproof and wear-resistant properties.

[0043] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a high-strength corrugated cardboard box based on a waterproofing agent, characterized in that: The preparation steps include the following: S1: Add lignin to acetone, stir evenly, add palm oil and concentrated sulfuric acid mixture, heat to 70-75℃ under nitrogen atmosphere and react for 2.5-3 hours, cool to room temperature, wash the product with pentane, vacuum dry, grind and pulverize, and sieve to obtain lignin derivative; S2: Add the lignin derivative to acetone, stir evenly, add silane coupling agent KH550, stir and react at room temperature for 48 hours, add dicyclohexylmethane diisocyanate, stir and react at room temperature, wash the product with pentane, vacuum dry, grind and pulverize, sieve, and graft lignin derivative. S3: Grafted lignin derivatives and hydroxyl-terminated polydimethylsiloxane are added to a reaction vessel, followed by ditin butyl dilaurate. The mixture is heated to 70-75°C and reacted for 4-4.5 hours under a nitrogen atmosphere. Then, 1,4-butanediol and N,N-dimethylformamide solution of bis(4-hydroxyphenyl) disulfide are added, and the mixture is kept at this temperature for 4-4.5 hours. Finally, methanol is added, and the mixture is kept at this temperature and stirred for 2-3 hours. The mixture is then dried under vacuum to obtain a waterproofing agent. S4: Add the thiol curing agent containing the dopamine structure to tetrahydrofuran, stir evenly, and obtain the curing agent solution; Add the waterproofing agent to tetrahydrofuran and stir evenly to obtain a waterproofing agent solution. Apply the waterproofing reinforcing agent to the surface of the corrugated cardboard box, then apply the curing agent solution to the waterproofing reinforcing agent layer, and finally apply the waterproofing agent solution to the curing agent solution layer. Cure by ultraviolet irradiation for 1-2 hours and dry at room temperature to obtain a high-strength corrugated cardboard box based on the waterproofing agent. The preparation method of the thiol curing agent containing the dopamine structure includes the following steps: Step (1): Add eugenol and triethylsilane to a reaction vessel, stir evenly, add tris(pentafluorophenyl)borane in two portions, react at room temperature, add dichloromethane to dilute, remove impurities with alkaline alumina, and distill under reduced pressure to obtain grafted eugenol. Step (2): Grafted eugenol, pentaerythritol tetrakis(3-mercaptopropionic acid) and 2,2-dimethoxy-2-phenylacetophenone were added to tetrahydrofuran. The solution was purged with nitrogen for 5-10 min and reacted under ultraviolet light for 1-1.5 h. Impurities were filtered out and the mixture was distilled under reduced pressure to obtain grafted pentaerythritol tris(3-mercaptopropionic acid). Step (3): Grafted pentaerythritol tris(3-mercaptopropionic acid) ester is added to tetrahydrofuran, hydrochloric acid is added, the mixture is stirred and reacted, and then distilled under reduced pressure to obtain a thiol curing agent containing a dopamine structure.

2. The method for preparing a high-strength corrugated cardboard box based on a waterproofing agent according to claim 1, characterized in that: In the preparation of lignin derivatives, 1g of lignin is dissolved in 10mL of acetone, and the mass ratio of the lignin acetone solution to the palm oil-sulfuric acid mixture is 1:(1-2). In the palm oil-sulfuric acid mixture, 0.1mL of concentrated sulfuric acid is added for every 15g of palm oil.

3. The method for preparing a high-strength corrugated cardboard box based on a waterproofing agent according to claim 1, characterized in that: In the preparation of grafted lignin derivatives, the molar ratio of silane coupling agent KH550: lignin derivative: dicyclohexylmethane diisocyanate is 1:(5-6):(2-4).

4. The method for preparing a high-strength corrugated cardboard box based on a waterproofing agent according to claim 1, characterized in that: In the preparation of the waterproofing agent, the molar ratio of grafted lignin derivative: hydroxyl-terminated polydimethylsiloxane: 1,4-butanediol: bis(4-hydroxyphenyl)disulfide is (15.5-20.5):(3-10):7:

3.

5. The method for preparing a high-strength corrugated cardboard box based on a waterproofing agent according to claim 1, characterized in that: In the preparation of grafted eugenol, the mass ratio of eugenol to triethylsilane is (5.15-5.2):(14.8-15); the tris(pentafluorophenyl)borane is added twice with an interval of 1 hour.

6. The method for preparing a high-strength corrugated cardboard box based on a waterproofing agent according to claim 1, characterized in that: In the preparation of grafted pentaerythritol tris(3-mercaptopropionic acid) ester, the mass ratio of grafted eugenol to pentaerythritol tetras(3-mercaptopropionic acid) ester is (3.5-3.6):(4.7-4.8).

7. The method for preparing a high-strength corrugated cardboard box based on a waterproofing agent according to claim 1, characterized in that: In the preparation of thiol curing agents containing dopamine structures, hydrochloric acid is added to bring the pH of the reaction system to 2.5-2.6 and maintain this pH until the reaction is complete.

8. The method for preparing a high-strength corrugated cardboard box based on a waterproofing agent according to claim 1, characterized in that: The preparation method of the waterproofing enhancement agent includes the following steps: adding chitosan to a 2% acetic acid solution, heating to 60-62℃ and stirring to dissolve, adding dopamine hydrochloride and laccase, stirring and reacting at room temperature to obtain polydopamine; adding chitosan to a 2% acetic acid solution, heating to 60-62℃ and stirring to dissolve, adding polydopamine and xanthan gum, stirring evenly to obtain the waterproofing enhancement agent; In the preparation of polydopamine, the mass ratio of chitosan:dopamine hydrochloride:laccase is 60:0.6:2.1; in the preparation of waterproofing reinforcing agent, the mass ratio of chitosan:polydopamine:xanthan gum is 3:50:

3.

9. A high-strength corrugated cardboard box based on a waterproofing agent prepared by the method for preparing a high-strength corrugated cardboard box based on a waterproofing agent according to any one of claims 1-8.

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