A high-strength, oil-resistant, and environmentally friendly corrugated cardboard box and its preparation method

Abstract

This invention relates to the field of corrugated cardboard box technology, and discloses a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box and its preparation method, comprising the following steps: dispersing chitosan and mercapto-castor oil-modified montmorillonite in acetic acid solution to obtain chitosan dispersion and montmorillonite dispersion respectively; mixing chitosan dispersion and montmorillonite dispersion uniformly in proportion to obtain coating A; adding silane coupling agent-modified nano-silica to polylactic acid-based waterborne polyurethane and stirring uniformly to obtain coating B; coating A onto the surface of the corrugated cardboard box and drying at 70-75℃ for 60-90s; coating B onto the surface of coating A and curing under ultraviolet light to obtain a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box.

Description

Technical Field

[0001] This invention relates to the field of corrugated cardboard box technology, specifically to a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box and its preparation method. Background Technology

[0002] Since its invention, plastic has been a controversial topic. While it has brought convenience to people's lives, it has also caused a lot of pollution. The term "white pollution" has gradually gained attention. People tend to prefer paper packaging materials that are highly biodegradable, less polluting, and recyclable. However, paperboard itself has many capillary structures, which makes paper packaging materials less waterproof and oil-resistant. At the same time, the low strength of paper materials limits their application areas.

[0003] Therefore, it is of great significance to invent a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box for use in packaging, transportation, and other fields. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box includes the following steps:

[0007] S1: Add castor oil-modified montmorillonite, catalyst, and stabilizer to toluene, stir evenly, add mercaptopropionic acid at 112-115℃ and react for 5-6 hours, then rotary evaporate to obtain mercaptocast oil-modified montmorillonite.

[0008] S2: Mix polylactic acid diol and diisocyanate evenly, react at 85-90℃ for 1-1.5h, add initiator and catalyst and keep the reaction at 85-90℃ for 3-3.5h, add chain extender and keep the reaction at 85-90℃ for 2-2.5h, cool down to 40-45℃ and add triethylamine and react for 30-45min, add deionized water and emulsify to obtain polylactic acid-based waterborne polyurethane;

[0009] S3: Chitosan and mercapto-castor oil-modified montmorillonite are dispersed separately in acetic acid solution to obtain chitosan dispersion and montmorillonite dispersion; chitosan dispersion and montmorillonite dispersion are mixed evenly in proportion to obtain coating A; silane coupling agent-modified nano-silica is added to polylactic acid-based waterborne polyurethane and stirred evenly to obtain coating B; coating A is applied to the surface of corrugated cardboard box and dried at 70-75℃ for 60-90s; coating B is applied to the surface of coating A and cured with ultraviolet light to obtain high-strength oil-proof and environmentally friendly corrugated cardboard box.

[0010] Furthermore, in the mercapto-castor oil modified montmorillonite, the catalyst is p-toluenesulfonic acid; the stabilizer is hydroquinone.

[0011] Furthermore, in the polylactic acid-based waterborne polyurethane, the polylactic acid diol has a molecular weight of 2000; the diisocyanate is either isoflavone diisocyanate or hexamethyl diisocyanate; the initiator is dimethylolpropionic acid; and the catalyst is dibutyltin dilaurate.

[0012] Furthermore, the concentration of the acetic acid solution is 1 v / v%.

[0013] Furthermore, the method for preparing castor oil-modified montmorillonite includes the following steps:

[0014] Montmorillonite was dispersed in deionized water and preheated to 50-55℃ to obtain solution A; castor oil quaternary ammonium salt was dispersed in deionized water and preheated to 50-55℃ to obtain solution B; solution B was added to solution A and reacted for 7-7.5 h, centrifuged, washed, and dried to obtain castor oil modified montmorillonite.

[0015] Furthermore, the method for preparing castor oil quaternary ammonium salt includes the following steps:

[0016] Castor oil acid, methanol, and concentrated sulfuric acid were stirred evenly and reacted at 60-65℃ for 4-4.5 h. After washing and rotary evaporation, castor oil methyl ester was obtained. Castor oil methyl ester and N,N-dimethyl-1,3-diaminopropane were stirred evenly and reacted at 130-135℃ for 24 h. After washing, castor oil amide was obtained. Castor oil amide, dichloromethane, and benzyl bromide were stirred evenly and reacted at room temperature for 48 h to obtain castor oil quaternary ammonium salt.

[0017] Furthermore, the concentration of solution A is 5-10 wt%; the concentration of solution B is 10-15 wt%.

[0018] Furthermore, the mass ratio of ricinoleic acid to methanol is 1:(10-12); the mass ratio of ricinoleic acid to concentrated sulfuric acid is 1:(0.015-0.02); the mass ratio of methyl castor oil to N,N-dimethyl-1,3-diaminopropane is 1:(6-8); and the mass ratio of ricinoleamide to benzyl bromide is 1:(1.5-2).

[0019] Furthermore, the mass ratio of castor oil-modified montmorillonite to mercaptopropionic acid is 1:(0.5-0.8).

[0020] Furthermore, the proportions of each component raw material in the polylactic acid-based waterborne polyurethane, by mass parts, are as follows: 35-45 parts polylactic acid diol, 20-25 parts diisocyanate, 2-3 parts initiator, 2-3 parts catalyst, and 5-10 parts chain extender; the chain extender is phenolic hydroxy dibenzyl acetone.

[0021] Furthermore, in coating A, the concentration of chitosan dispersion is 1-3 wt%; the concentration of montmorillonite dispersion is 20 wt%; the mass ratio of chitosan dispersion to montmorillonite dispersion is 100:(1-5); in coating B, the silane coupling agent modified nano-silica is any one or both of 3-mercaptopropyltriethoxysilane modified nano-silica and KH570 modified nano-silica; the mass ratio of silane coupling agent modified nano-silica to polylactic acid-based waterborne polyurethane must be 1:(4.5-5); the coating amount of coating A is 2.8-3.2 g / m³. 2 Coating B has a coating weight of 15-16 g / m². 2 .

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0023] This invention uses ricinoleic acid as the main raw material and reacts it with concentrated sulfuric acid, N,N-dimethyl-1,3-diaminopropane, and benzyl bromide in successive esterification, amidation, and quaternization reactions to prepare a ricinoleic quaternary ammonium salt containing active hydroxyl groups. Then, it undergoes organic modification treatment with montmorillonite to prepare ricinoleic oil-modified montmorillonite containing active hydroxyl groups. Finally, it undergoes esterification with mercaptopropylene to prepare mercapto-ricinoleic oil-modified montmorillonite. Finally, it is blended with chitosan to prepare coating A with oil-repellent properties. By controlling the amount of modified montmorillonite added, on the one hand, the problem of montmorillonite agglomeration on the coating surface leading to reduced coverage of corrugated cardboard boxes and thus reduced oil-repellent properties is avoided; on the other hand, the problem of excessive mercapto-ricinoleic oil groups not reacting completely during the coating's photocuring process, reducing the crosslinking density between coating A and coating B, as well as the coating formed by coating A itself, is avoided, thus preventing a decrease in oil-repellent properties. The addition of thiol-modified montmorillonite, through the click chemical reaction of thiol-olefins, overcomes the oleophilicity of castor oil by forming a complex and tight cross-linked layer between coating A and coating B. The layered structure of montmorillonite, combined with chitosan, can better fill the pores of the fiber network structure on the surface of the cardboard box, enabling a tight bond between coating A and the corrugated cardboard box, and between coating A and coating B, greatly improving the oil resistance and mechanical properties of the corrugated cardboard box.

[0024] This invention uses environmentally friendly polylactic acid glycol as the matrix and phenolic hydroxydibenzyl acetone as a chain extender to prepare polylactic acid-based waterborne polyurethane. Two types of modified nano-silica are then mixed uniformly as reinforcing materials to prepare coating B with high strength. During the crosslinking and curing process, the thiol and olefin groups carried on the surface of the modified nano-silica react with the olefins in the polylactic acid-based waterborne polyurethane chains via click chemistry, and also react with the thiol groups in the modified montmorillonite in coating A. This enhances the crosslinking density of coating B itself and the crosslinking density between coating A and coating B. The phenolic hydroxydibenzyl acetone chain structure in the polylactic acid-based waterborne polyurethane can undergo 1,2-cycloaddition reactions to link the molecular chains together, and also react with the thiol groups in coating A via click chemistry. Ultimately, a tightly bonded crosslinked layer is formed, further improving the strength and oil resistance of corrugated cardboard boxes. Detailed Implementation

[0025] 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.

[0026] In the following examples, the specifications of montmorillonite were as follows: cation exchange capacity 143 mmol / 100g; ricinoleic acid CAS: 141-22-0; N,N-dimethyl-1,3-diaminopropane CAS: 109-55-7; phenolic hydroxydibenzyl acetone CAS: 3654-49-7; polylactic acid diol molecular weight: 2000; nano silica specification: 20nm; and all other raw materials were commercially available.

[0027] The preparation method of 3-mercaptopropyltriethoxysilane-modified nano-silica in the following examples includes the following steps:

[0028] 10g of nano-silica was dispersed in 100g of ethanol solution, the pH was adjusted to 4, 1.5g of 3-mercaptopropyltriethoxysilane was added, and the mixture was reacted at 80℃ for 10h. After filtration, washing, and drying, 3-mercaptopropyltriethoxysilane-modified nano-silica was obtained.

[0029] The preparation method of KH570 modified nano-silica includes the following steps:

[0030] 10g of nano-silica was dispersed in 150mL of toluene solution, and 3.46g of KH570 and 16.6mL of triethylamine were added. The mixture was reacted at 120℃ for 3h, filtered, washed, and dried to obtain KH570 modified nano-silica.

[0031] Example 1: A method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box: S1: 10g ricinoleic acid, 100g methanol, and 0.15g concentrated sulfuric acid were stirred evenly and reacted at 60℃ for 4h. After washing and rotary evaporation, methyl castor oil was obtained. 10g methyl castor oil and 60g N,N-dimethyl-1,3-diaminopropane were stirred evenly and reacted at 130℃ for 24h. After washing, ricinoleamide was obtained. 5g ricinoleamide, 30mL dichloromethane, and 7.5g benzyl bromide were stirred evenly and reacted at room temperature for 48h to obtain quaternary ammonium salt of castor oil.

[0032] S2: Disperse 5g of montmorillonite in 100g of deionized water and preheat to 50℃ to obtain solution A; disperse 10g of castor oil quaternary ammonium salt in 100g of deionized water and preheat to 50℃ to obtain solution B; add solution B to solution A and react for 7 hours, centrifuge, wash, and dry to obtain castor oil modified montmorillonite; add 10g of castor oil modified montmorillonite, 0.25g of p-toluenesulfonic acid, and 0.5g of hydroquinone to 100mL of toluene, stir evenly, add 5g of mercaptopropionic acid at 112℃ and react for 5 hours, then rotary evaporate to obtain mercaptocast oil modified montmorillonite;

[0033] S3: Stir 40g of polylactic acid diol and 20g of hexamethyl diisocyanate evenly, react at 85℃ for 1h, add 2g of dimethylolpropionic acid and 2g of dibutyltin dilaurate and keep the reaction at the temperature for 3h, add 5g of phenolic hydroxy dibenzyl acetone and keep the reaction at the temperature for 2h, cool to 40℃ and add 5g of triethylamine and react for 30-45min, add deionized water and emulsify to obtain polylactic acid-based waterborne polyurethane;

[0034] S4: Disperse 1g of chitosan and 20g of mercaptocast castor oil-modified montmorillonite in 100g of acetic acid solution to obtain chitosan dispersion and montmorillonite dispersion, respectively; mix 100g of chitosan dispersion and 1g of montmorillonite dispersion evenly in proportion to obtain coating A; add 1g of KH570-modified nano-silica and 1g of 3-mercaptopropyltriethoxysilane-modified nano-silica to 10g of polylactic acid-based waterborne polyurethane and stir evenly to obtain coating B; apply coating A to the surface of corrugated cardboard boxes with a coating amount of 2.8g / m². 2 Dry at 70℃ for 60 seconds, then apply coating B onto the surface of coating A, with a coating amount of 15 g / m². 2 UV curing produces high-strength, oil-resistant, and environmentally friendly corrugated cardboard boxes.

[0035] Example 2: A method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box: S1: 10g ricinoleic acid, 100g methanol, and 0.15g concentrated sulfuric acid were stirred evenly and reacted at 60℃ for 4h. After washing and rotary evaporation, methyl castor oil was obtained. 10g methyl castor oil and 60g N,N-dimethyl-1,3-diaminopropane were stirred evenly and reacted at 130℃ for 24h. After washing, ricinoleamide was obtained. 5g ricinoleamide, 30mL dichloromethane, and 7.5g benzyl bromide were stirred evenly and reacted at room temperature for 48h to obtain quaternary ammonium salt of castor oil.

[0036] S2: Disperse 8g of montmorillonite in 100g of deionized water and preheat to 50℃ to obtain solution A; disperse 13g of castor oil quaternary ammonium salt in 100g of deionized water and preheat to 50℃ to obtain solution B; add solution B to solution A and react for 7 hours, centrifuge, wash, and dry to obtain castor oil modified montmorillonite; add 10g of castor oil modified montmorillonite, 0.25g of p-toluenesulfonic acid, and 0.5g of hydroquinone to 100mL of toluene, stir evenly, add 5g of mercaptopropionic acid at 112℃ and react for 5 hours, then rotary evaporate to obtain mercaptocast oil modified montmorillonite;

[0037] S3: Stir 40g of polylactic acid diol and 20g of hexamethyl diisocyanate evenly, react at 85℃ for 1h, add 2.5g of dimethylolpropionic acid and 2.5g of dibutyltin dilaurate and keep warm for 3h, add 8g of phenolic hydroxy dibenzyl acetone and keep warm for 2h, cool to 40℃ and add 5g of triethylamine and react for 30-45min, add deionized water and emulsify to obtain polylactic acid-based waterborne polyurethane;

[0038] S4: Disperse 2g of chitosan and 20g of mercaptocast castor oil-modified montmorillonite in 100g of acetic acid solution to obtain chitosan dispersion and montmorillonite dispersion, respectively; mix 100g of chitosan dispersion and 3g of montmorillonite dispersion evenly in proportion to obtain coating A; add 1g of KH570-modified nano-silica and 1g of 3-mercaptopropyltriethoxysilane-modified nano-silica to 10g of polylactic acid-based waterborne polyurethane and stir evenly to obtain coating B; apply coating A to the surface of corrugated cardboard boxes with a coating amount of 3g / m². 2 Dry at 70℃ for 75 seconds, then apply coating B onto the surface of coating A with a coating weight of 15 g / m². 2 UV curing produces high-strength, oil-resistant, and environmentally friendly corrugated cardboard boxes.

[0039] Example 3: A method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box: S1: 10g ricinoleic acid, 100g methanol, and 0.15g concentrated sulfuric acid were stirred evenly and reacted at 60℃ for 4h. After washing and rotary evaporation, methyl castor oil was obtained. 10g methyl castor oil and 60g N,N-dimethyl-1,3-diaminopropane were stirred evenly and reacted at 130℃ for 24h. After washing, ricinoleamide was obtained. 5g ricinoleamide, 30mL dichloromethane, and 7.5g benzyl bromide were stirred evenly and reacted at room temperature for 48h to obtain quaternary ammonium salt of castor oil.

[0040] S2: Disperse 10g of montmorillonite in 100g of deionized water and preheat to 50℃ to obtain solution A; disperse 15g of castor oil quaternary ammonium salt in 100g of deionized water and preheat to 50℃ to obtain solution B; add solution B to solution A and react for 7 hours, centrifuge, wash, and dry to obtain castor oil modified montmorillonite; add 10g of castor oil modified montmorillonite, 0.25g of p-toluenesulfonic acid, and 0.5g of hydroquinone to 100mL of toluene, stir evenly, add 5g of mercaptopropionic acid at 112℃ and react for 5 hours, then rotary evaporate to obtain mercaptocast oil modified montmorillonite;

[0041] S3: Stir 40g of polylactic acid diol and 20g of hexamethyl diisocyanate evenly, react at 85℃ for 1h, add 3g of dimethylolpropionic acid and 3g of dibutyltin dilaurate and keep the reaction at the temperature for 3h, add 10g of phenolic hydroxy dibenzyl acetone and keep the reaction at the temperature for 2h, cool to 40℃ and add 5g of triethylamine and react for 30-45min, add deionized water and emulsify to obtain polylactic acid-based waterborne polyurethane;

[0042] S4: Disperse 3g of chitosan and 20g of mercaptocast castor oil-modified montmorillonite in 100g of acetic acid solution to obtain chitosan dispersion and montmorillonite dispersion, respectively; mix 100g of chitosan dispersion and 5g of montmorillonite dispersion evenly in a certain proportion to obtain coating A; add 1g of KH570-modified nano-silica and 1g of 3-mercaptopropyltriethoxysilane-modified nano-silica to 10g of polylactic acid-based waterborne polyurethane and stir evenly to obtain coating B; apply coating A to the surface of corrugated cardboard boxes with a coating amount of 3.2g / m². 2 Dry at 70℃ for 90 seconds, then apply coating B onto the surface of coating A with a coating weight of 16 g / m². 2 UV curing produces high-strength, oil-resistant, and environmentally friendly corrugated cardboard boxes.

[0043] Comparative Example 1: A method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box: S1: 10g ricinoleic acid, 100g methanol, and 0.15g concentrated sulfuric acid were stirred evenly and reacted at 60℃ for 4h. After washing and rotary evaporation, methyl castor oil was obtained. 10g methyl castor oil and 60g N,N-dimethyl-1,3-diaminopropane were stirred evenly and reacted at 130℃ for 24h. After washing, ricinoleamide was obtained. 5g ricinoleamide, 30mL dichloromethane, and 7.5g benzyl bromide were stirred evenly and reacted at room temperature for 48h to obtain quaternary ammonium salt of castor oil.

[0044] S2: Disperse 5g of montmorillonite in 100g of deionized water and preheat to 50℃ to obtain solution A; disperse 10g of castor oil quaternary ammonium salt in 100g of deionized water and preheat to 50℃ to obtain solution B; add solution B to solution A and react for 7 hours, centrifuge, wash, and dry to obtain castor oil modified montmorillonite; add 10g of castor oil modified montmorillonite, 0.25g of p-toluenesulfonic acid, and 0.5g of hydroquinone to 100mL of toluene, stir evenly, add 5g of mercaptopropionic acid at 112℃ and react for 5 hours, then rotary evaporate to obtain mercaptocast oil modified montmorillonite;

[0045] S3: Stir 40g of polylactic acid diol and 20g of hexamethyl diisocyanate evenly, react at 85℃ for 1h, add 2g of dimethylolpropionic acid and 2g of dibutyltin dilaurate and keep the reaction at the temperature for 3h, add 5g of phenolic hydroxy dibenzyl acetone and keep the reaction at the temperature for 2h, cool to 40℃ and add 5g of triethylamine and react for 30-45min, add deionized water and emulsify to obtain polylactic acid-based waterborne polyurethane;

[0046] S4: Disperse 1g of chitosan and 20g of mercaptocast castor oil-modified montmorillonite in 100g of acetic acid solution to obtain chitosan dispersion and montmorillonite dispersion, respectively; mix 100g of chitosan dispersion and 10g of montmorillonite dispersion evenly in a certain proportion to obtain coating A; add 1g of KH570-modified nano-silica and 1g of 3-mercaptopropyltriethoxysilane-modified nano-silica to 10g of polylactic acid-based waterborne polyurethane and stir evenly to obtain coating B; apply coating A to the surface of corrugated cardboard boxes with a coating amount of 2.8g / m². 2 Dry at 70℃ for 60 seconds, then apply coating B onto the surface of coating A, with a coating amount of 15 g / m². 2 UV curing produces high-strength, oil-resistant, and environmentally friendly corrugated cardboard boxes.

[0047] Comparative Example 2: A method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box: S1: 10g of ricinoleic acid, 100g of methanol, and 0.15g of concentrated sulfuric acid were stirred evenly and reacted at 60℃ for 4h. After washing and rotary evaporation, methyl castor oil was obtained. 10g of methyl castor oil and 60g of N,N-dimethyl-1,3-diaminopropane were stirred evenly and reacted at 130℃ for 24h. After washing, ricinoleamide was obtained. 5g of ricinoleamide, 30mL of dichloromethane, and 7.5g of benzyl bromide were stirred evenly and reacted at room temperature for 48h to obtain quaternary ammonium salt of castor oil.

[0048] S2: Disperse 5g of montmorillonite in 100g of deionized water and preheat to 80℃ to obtain solution A; disperse 10g of castor oil quaternary ammonium salt in 100g of deionized water and preheat to 80℃ to obtain solution B; add solution B to solution A and react for 7 hours, centrifuge, wash, and dry to obtain castor oil modified montmorillonite; add 10g of castor oil modified montmorillonite, 0.25g of p-toluenesulfonic acid, and 0.5g of hydroquinone to 100mL of toluene, stir evenly, add 5g of mercaptopropionic acid at 112℃ and react for 5 hours, then rotary evaporate to obtain mercaptocast oil modified montmorillonite;

[0049] S3: Stir 40g of polylactic acid diol and 20g of hexamethyl diisocyanate evenly, react at 85℃ for 1h, add 2g of dimethylolpropionic acid and 2g of dibutyltin dilaurate and keep the reaction at the temperature for 3h, add 5g of phenolic hydroxy dibenzyl acetone and keep the reaction at the temperature for 2h, cool to 40℃ and add 5g of triethylamine and react for 30-45min, add deionized water and emulsify to obtain polylactic acid-based waterborne polyurethane;

[0050] S4: Disperse 1g of chitosan and 20g of mercaptocast castor oil-modified montmorillonite in 100g of acetic acid solution to obtain chitosan dispersion and montmorillonite dispersion, respectively; mix 100g of chitosan dispersion and 1g of montmorillonite dispersion evenly in proportion to obtain coating A; add 1g of KH570-modified nano-silica and 1g of 3-mercaptopropyltriethoxysilane-modified nano-silica to 10g of polylactic acid-based waterborne polyurethane and stir evenly to obtain coating B; apply coating A to the surface of corrugated cardboard boxes with a coating amount of 2.8g / m². 2 Dry at 70℃ for 60 seconds, then apply coating B onto the surface of coating A, with a coating amount of 15 g / m². 2 UV curing produces high-strength, oil-resistant, and environmentally friendly corrugated cardboard boxes.

[0051] Comparative Example 3: A method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box: S1: 10g ricinoleic acid, 100g methanol, and 0.15g concentrated sulfuric acid were stirred evenly and reacted at 60℃ for 4h. After washing and rotary evaporation, methyl castor oil was obtained. 10g methyl castor oil and 60g N,N-dimethyl-1,3-diaminopropane were stirred evenly and reacted at 130℃ for 24h. After washing, ricinoleamide was obtained. 5g ricinoleamide, 30mL dichloromethane, and 7.5g benzyl bromide were stirred evenly and reacted at room temperature for 48h to obtain quaternary ammonium salt of castor oil.

[0052] S2: Disperse 5g of montmorillonite in 100g of deionized water and preheat to 50℃ to obtain solution A; disperse 10g of castor oil quaternary ammonium salt in 100g of deionized water and preheat to 50℃ to obtain solution B; add solution B to solution A and react for 7 hours, centrifuge, wash, and dry to obtain castor oil modified montmorillonite; add 10g of castor oil modified montmorillonite, 0.25g of p-toluenesulfonic acid, and 0.5g of hydroquinone to 100mL of toluene, stir evenly, add 5g of mercaptopropionic acid at 112℃ and react for 5 hours, then rotary evaporate to obtain mercaptocast oil modified montmorillonite;

[0053] S3: Stir 40g of polylactic acid diol and 20g of hexamethyl diisocyanate evenly, react at 85℃ for 1h, add 2g of dimethylolpropionic acid and 2g of dibutyltin dilaurate and keep the reaction at the temperature for 3h, add 5g of 1,4-butanediol and keep the reaction at the temperature for 2h, cool to 40℃ and add 5g of triethylamine and react for 30-45min, add deionized water and emulsify to obtain polylactic acid-based waterborne polyurethane;

[0054] S4: Disperse 1g of chitosan and 20g of mercaptocast castor oil-modified montmorillonite in 100g of acetic acid solution to obtain chitosan dispersion and montmorillonite dispersion, respectively; mix 100g of chitosan dispersion and 1g of montmorillonite dispersion evenly in proportion to obtain coating A; add 1g of KH570-modified nano-silica and 1g of 3-mercaptopropyltriethoxysilane-modified nano-silica to 10g of polylactic acid-based waterborne polyurethane and stir evenly to obtain coating B; apply coating A to the surface of corrugated cardboard boxes with a coating amount of 2.8g / m². 2 Dry at 70℃ for 60 seconds, then apply coating B onto the surface of coating A, with a coating amount of 15 g / m². 2 UV curing produces high-strength, oil-resistant, and environmentally friendly corrugated cardboard boxes.

[0055] Test: Oil resistance performance test: The corrugated boxes prepared in the examples and comparative examples were tested for oil resistance level according to standard TAPPIT 559cm-12; only those with a level greater than 5 can meet the oil resistance requirements.

[0056] Mechanical performance testing: The corrugated paper prepared in the examples and comparative examples was cut into 15×100mm pieces according to GB / T 22898-2008.2 Size, and the tensile strength and elongation at break of the on-duty personnel are measured.

[0057] Table 1 Performance Test Data of Corrugated Cardboard Boxes

[0058] Example 1 8 18.24 2.66 Example 2 9 21.33 2.63 Example 3 9 23.95 2.59 Comparative Example 1 4 13.66 2.12 Comparative Example 2 2 12.76 1.98 Comparative Example 3 5 15.50 2.34

[0059] Conclusion: The corrugated boxes prepared in Examples 1-3 have significant oil-resistant and mechanical properties.

[0060] Compared with Example 1, in Comparative Example 1, the proportion of montmorillonite dispersion in coating A was too large, resulting in a decrease in the oil-resistant performance of the coating. In Comparative Example 2, the reaction temperature between solution A and solution B during the preparation of castor oil-modified montmorillonite was too high, which reduced the interlayer spacing of montmorillonite and the amount of adsorbed intercalated material. This reduced the active hydroxyl groups carried after modification, which was not conducive to subsequent thiol modification and weakened the thiol-olefin reaction. The crosslinking density decreased, and all properties were reduced. In Comparative Example 3, 1,4-butanediol was used as a chain extender to replace phenolic hydroxydibenzyl acetone, which resulted in a decrease in the crosslinking density of the coating during the UV curing process and a decrease in all properties.

[0061] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box, characterized in that: Includes the following steps: S1: Add castor oil-modified montmorillonite, catalyst, and stabilizer to toluene, stir evenly, add mercaptopropionic acid at 112-115℃ and react for 5-6 hours, then rotary evaporate to obtain mercaptocast oil-modified montmorillonite. S2: Mix polylactic acid diol and diisocyanate evenly, react at 85-90℃ for 1-1.5h, add initiator and catalyst and keep the reaction at 85-90℃ for 3-3.5h, add chain extender and keep the reaction at 85-90℃ for 2-2.5h, cool down to 40-45℃ and add triethylamine and react for 30-45min, add deionized water and emulsify to obtain polylactic acid-based waterborne polyurethane; S3: Chitosan and mercapto-castor oil-modified montmorillonite are dispersed separately in acetic acid solution to obtain chitosan dispersion and montmorillonite dispersion; chitosan dispersion and montmorillonite dispersion are mixed evenly in proportion to obtain coating A; silane coupling agent-modified nano-silica is added to polylactic acid-based waterborne polyurethane and stirred evenly to obtain coating B; coating A is applied to the surface of corrugated cardboard box and dried at 70-75℃ for 60-90s; coating B is applied to the surface of coating A and cured with ultraviolet light to obtain high-strength oil-proof and environmentally friendly corrugated cardboard box.

2. The method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box according to claim 1, characterized in that: The method for preparing castor oil-modified montmorillonite includes the following steps: Montmorillonite was dispersed in deionized water and preheated to 50-55℃ to obtain solution A; castor oil quaternary ammonium salt was dispersed in deionized water and preheated to 50-55℃ to obtain solution B; solution B was added to solution A and reacted for 7-7.5 h, centrifuged, washed, and dried to obtain castor oil modified montmorillonite.

3. The method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box according to claim 2, characterized in that: The method for preparing castor oil quaternary ammonium salt includes the following steps: Castor oil acid, methanol, and concentrated sulfuric acid were stirred evenly and reacted at 60-65℃ for 4-4.5 h. After washing and rotary evaporation, castor oil methyl ester was obtained. Castor oil methyl ester and N,N-dimethyl-1,3-diaminopropane were stirred evenly and reacted at 130-135℃ for 24 h. After washing, castor oil amide was obtained. Castor oil amide, dichloromethane, and benzyl bromide were stirred evenly and reacted at room temperature for 48 h to obtain castor oil quaternary ammonium salt.

4. The method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box according to claim 2, characterized in that: The concentration of solution A is 5-10 wt%; the concentration of solution B is 10-15 wt%.

5. The method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box according to claim 3, characterized in that: The mass ratio of ricinoleic acid to methanol is 1:(10-12); the mass ratio of ricinoleic acid to concentrated sulfuric acid is 1:(0.015-0.02); the mass ratio of methyl castor oil to N,N-dimethyl-1,3-diaminopropane is 1:(6-8); and the mass ratio of ricinoleamide to benzyl bromide is 1:(1.5-2).

6. The method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box according to claim 1, characterized in that: The mass ratio of castor oil-modified montmorillonite to mercaptopropionic acid is 1:(0.5-0.8).

7. The method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box according to claim 1, characterized in that: The proportions of each component raw material in the polylactic acid-based waterborne polyurethane, by mass, are as follows: 35-45 parts polylactic acid diol, 20-25 parts diisocyanate, 2-3 parts initiator, 2-3 parts catalyst, and 5-10 parts chain extender; the chain extender is phenolic hydroxy dibenzyl acetone.

8. The method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box according to claim 1, characterized in that: In coating A, the concentration of chitosan dispersion is 1-3 wt%; the concentration of montmorillonite dispersion is 20 wt%; the mass ratio of chitosan dispersion to montmorillonite dispersion is 100:(1-5); and the coating amount of coating A is 2.8-3.2 g / m². 2 .

9. The method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box according to claim 1, characterized in that: In coating B, the silane coupling agent modified nano-silica is any one or both of 3-mercaptopropyltriethoxysilane modified nano-silica and KH570 modified nano-silica; the mass ratio of silane coupling agent modified nano-silica to polylactic acid-based waterborne polyurethane is 1:(4.5-5); the coating amount of coating B is 15-16 g / m². 2 .

10. A corrugated cardboard box prepared by the method for preparing a high-strength, oil-resistant, and environmentally friendly corrugated cardboard box according to any one of claims 1-9.