Environment-friendly printing process of waterproof corrugated board

Abstract

The invention discloses an environment-friendly printing process of a waterproof corrugated board, and relates to the technical field of corrugated boards. The water-based ink layer is subjected to pre-emulsification and polymerization reaction, double bonds and acrylic monomers are introduced for copolymerization, small molecule migration is avoided through free radical polymerization reaction, the water resistance is remarkably improved, the thermal stability is improved, and the wear resistance and the scratch resistance are enhanced; the environment-friendly glue layer takes renewable corn starch as a main raw material, so that the environmental protection property is greatly improved, the modified waterborne polyurethane not only greatly improves the mechanical strength of the glue film, but also improves the toughness and adhesive force by virtue of a compact nano composite structure which can block water vapor, oxygen and oil stains; meanwhile, organosilicone acrylic resin molecules of the water-based ink layer react with groups in the waterproof adhesive layer to form hydrogen bonds and covalent bonds for bridging, so that the adhesive has extremely high bonding strength, durability and wear resistance, the water resistance is remarkably improved, the environment-friendly requirement is met, and the performance is excellent.

Description

Technical Field

[0001] This invention relates to the field of corrugated cardboard technology, specifically to an environmentally friendly printing process for waterproof corrugated cardboard. Background Technology

[0002] Corrugated cardboard, as a crucial substrate in the modern packaging industry, faces key technological challenges in terms of environmental friendliness, water resistance, and printability, making it a critical area for industrial upgrading. Traditional polyethylene lamination processes suffer from environmental bottlenecks such as non-degradability and difficulty in recycling, while ordinary water-based printing struggles to overcome strength degradation and print quality issues caused by paper fiber moisture absorption. Therefore, developing a waterproof printing process that combines environmental friendliness and high performance has become an urgent industry need. With socio-economic development and rising consumption levels, industries such as food, pharmaceuticals, and cosmetics are placing higher demands on the safety and environmental friendliness of packaging printing. Water-based inks, due to their near-zero emissions of volatile organic compounds (VOCs) and their non-toxic, energy-saving, and environmentally friendly advantages, are gradually becoming an important choice for packaging printing. In recent years, my country has successively introduced a series of regulations related to food and pharmaceutical packaging safety, further promoting the development of the water-based ink printing market, whose application scale continues to expand, indicating a promising future.

[0003] Currently, environmentally friendly printing inks mainly fall into three categories: water-based inks, UV inks, and vegetable oil-based inks. Among them, water-based inks, due to their significant environmental benefits, have been widely used in flexographic and gravure printing processes. These inks use water as the dispersion medium and are composed of binders, pigments, and additives. Although water-based inks have clear advantages, they still face technical bottlenecks such as slow drying speed, insufficient water and alkali resistance, and low gloss, which hinder their further promotion. Therefore, researchers are dedicated to improving their overall performance through material modification and process optimization.

[0004] Inks using water-based polyacrylic resin as a binder perform well in terms of gloss, transparency, adhesion, and weather resistance, but they are lacking in stain resistance, water resistance, and adhesion to non-absorbent substrates. In addition, polyacrylate materials have a slow drying speed and poor anti-sticking properties, and their application range needs to be expanded through composite modification or process innovation.

[0005] Therefore, this invention provides an environmentally friendly printing process for waterproof corrugated cardboard. Based on biomass modification chemistry and polymer synthesis technology, polymer materials with different chemical compositions and properties are compounded in a certain way to improve their performance and construct environmentally friendly waterproof printed corrugated cardboard. This provides a brand-new technical solution for green packaging, and is particularly suitable for packaging fields with extremely high environmental protection requirements, such as food and pharmaceutical, thus promoting the healthy development of my country's water-based ink printing market. Summary of the Invention

[0006] The purpose of this invention is to provide an environmentally friendly printing process for waterproof corrugated cardboard to solve the problems raised in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: An environmentally friendly printing process for waterproof corrugated cardboard, characterized by the following steps: S1: Spray water-based ink evenly onto the surface of the corrugated cardboard, heat to 60-70℃ to form a printing ink layer, and dry to obtain printed corrugated cardboard; S2: Spray environmentally friendly waterproof colloid onto the ink layer of the printed corrugated cardboard, control the temperature at 60-70℃, vacuum dry, then raise the temperature to 85-95℃ and cure for 10-20 minutes to form a waterproof colloid layer, thus obtaining waterproof printed corrugated cardboard.

[0008] Furthermore, the preparation process of the environmentally friendly waterproof colloid is as follows: corn starch and deionized water are mixed, a 10% sodium hydroxide solution is added, the pH is adjusted to 9-10, the temperature is raised to 75-85℃ and kept at that temperature for 10-20 minutes, a sodium hypochlorite solution is added, the temperature is raised to 90-100℃ and reacted for 15-30 minutes, a 40% polyvinyl alcohol solution and potassium persulfate are added, the reaction is carried out for 20-30 minutes, the temperature is lowered to 55-60℃, a modified waterborne polyurethane is added, the reaction is carried out for 50-70 minutes, the material is cooled and discharged to obtain the environmentally friendly waterproof colloid; By weight, the raw material composition of the environmentally friendly waterproof colloid is as follows: 40-50 parts corn starch, 2-5 parts sodium hydroxide, 200-250 parts deionized water, 3-7 parts sodium hypochlorite solution, 10-20 parts 40% polyvinyl alcohol solution, 0.3-0.7 parts potassium persulfate, and 15-30 parts modified waterborne polyurethane. Furthermore, the preparation process of the modified waterborne polyurethane is as follows: aminopropyltriethoxysilane, deionized water, and ethanol solvent are mixed, the pH is adjusted to 4-5 with acetic acid, and the mixture is stirred at 40-50℃ for 30-40 min. Nano-SiO2 is added, and the mixture is stirred at 60-80℃ for 4-6 h. After centrifugation, the mixture is washed with ethanol and vacuum dried to obtain modified SiO2. The modified SiO2 and waterborne polyurethane are mixed and stirred for 10-15 min, and the mixture is heated to 40-50℃ and stirred for 20-40 min to obtain the modified waterborne polyurethane. Furthermore, the preparation process of the water-based ink is as follows: water-based acrylic resin binder, deionized water, ethanol, and environmentally friendly water-based pigment are mixed and dispersed for 10-20 minutes, leveling agent is added and stirred for 10-30 minutes, thickener is added, and the mixture is ground for 40-50 minutes, filtered, and packaged to obtain water-based ink; By weight, the raw material composition of the water-based ink is as follows: 40-50 parts water-based acrylic resin binder, 10-20 parts deionized water, 3-8 parts ethanol, 10-20 parts environmentally friendly water-based pigment, 0.2-0.5 parts leveling agent, and 0.5-1.5 parts thickener; Furthermore, the preparation process of the water-based acrylic resin binder is as follows: 1) Mix emulsifier and deionized water, stir at 20-25℃ for 25-35 min, add methyl methacrylate, styrene, butyl acrylate and terminal vinylsiloxane, stir for 20-35 min to obtain pre-emulsion; 2) Mix the buffer and one-third of the pre-emulsion, heat to 65-75℃, stir for 10-15 minutes, add half of the ammonium persulfate mixture, keep warm for 10-20 minutes to form a seed emulsion; 3) Add the remaining pre-emulsion and ammonium persulfate mixture to the seed emulsion, heat to 75-80℃, keep warm for 1-1.5h, cool to 35-40℃, adjust the pH to 7.5-8.5, filter and discharge to obtain water-based acrylic resin binder; The waterborne acrylic resin binder, by weight, comprises: 2-4 parts emulsifier, 90-110 parts deionized water, 25-35 parts methyl methacrylate, 15-25 parts styrene, 40-50 parts butyl acrylate, 2-4 parts vinyl-terminated siloxane, 10-20 parts buffer, and 20-30 parts ammonium persulfate mixture. Furthermore, the buffer is a mixture of deionized water and sodium bicarbonate at a mass ratio of 20:0.2; the ammonium persulfate mixture is a mixture of deionized water and ammonium persulfate at a mass ratio of 20:0.4. The terminal vinylsiloxane is γ-methacryloyloxypropyltrimethoxysilane; the emulsifier is one of sodium dodecyl sulfate, fatty alcohol polyoxyethylene ether, sodium alkyl allyl polyether sulfonate, and alkyl diphenyl ether disulfonate. Furthermore, the emulsifier is a 1:1 mixture of sodium dodecyl sulfate and fatty alcohol polyoxyethylene ether; Furthermore, the leveling agent is one of acrylate polymer, polyether-modified polydimethylsiloxane, and polyester-modified polydimethylsiloxane; the thickener is one of hydroxyethyl cellulose, hydrophobically modified alkali-swellable acrylic emulsion, and bentonite; and the environmentally friendly water-based pigment is one of high-pigment carbon black, phthalocyanine blue, and phthalocyanine green. Furthermore, the thickness of the waterproof colloid layer is 20-40 μm; the thickness of the printing ink layer is 5-10 μm.

[0009] Furthermore, when reusing printed corrugated cardboard, the process for removing the printed markings on the surface of the corrugated cardboard is as follows: spray warm water at a temperature of 50-55℃ onto the printed markings on the surface of the corrugated cardboard. At this time, the ink of the printed markings will flow down from the surface of the corrugated cardboard. Wipe with a damp towel at a temperature of 50-55℃ to remove the printed markings. After wiping, dry the corrugated cardboard in a drying room at a temperature of 40-50℃ before reprinting and reuse.

[0010] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses an environmentally friendly printing process for waterproof corrugated cardboard. The process design is reasonable and the component ratio is appropriate. The core of this process lies in constructing a multifunctional environmentally friendly coating structure: on the one hand, the ink layer presents color and provides necessary wear resistance, scratch resistance and other properties; on the other hand, the waterproof coating can effectively improve the waterproof and moisture-proof performance of the corrugated board, thereby increasing the service life of the product.

[0011] The water-based ink layer consists of two parts: water-based acrylic resin binder synthesis and ink compounding. First, pre-emulsification is used, where emulsifier molecules encapsulate oil-based monomers into tiny micelles, uniformly dispersing them in water. Ammonium persulfate decomposes upon heating, generating sulfate free radicals that initiate the polymerization reaction. Methyl methacrylate provides hardness, gloss, and weather resistance; styrene provides hardness, gloss, and lower cost; butyl acrylate provides flexibility and film-forming properties. γ-methacryloyloxypropyltrimethoxysilane is introduced, copolymerizing it using double bonds with the acrylic monomer double bonds. The unsaturated vinylsiloxane monomer and acrylate monomer are polymerized via free radical polymerization, preventing small molecule migration, significantly improving water resistance and thermal stability. The Si-O-Si network enhances abrasion and scratch resistance. During ink printing and film formation, polyether-modified polydimethylsiloxane improves coating surface flowability, reducing pinholes and orange peel. Hydroxyethyl cellulose acts as a thickener, adjusting system viscosity and improving sagging and storage stability. This enables color printing that is both environmentally friendly and abrasion-resistant.

[0012] The environmentally friendly waterproof colloidal layer combines the low cost and environmental advantages of bio-based materials with the high performance of waterborne polyurethane. Through chemical modification and hydrogen bonding, they are perfectly integrated to form a dense waterproof layer, thereby improving the waterproof performance of corrugated cardboard. Under the combined action of alkali and heat, starch granules begin to swell, and the activity of hydroxyl groups on the starch molecular chains increases. Sodium hypochlorite, acting as an oxidant, oxidizes the hydroxyl groups on the starch molecules into carboxyl and ketone groups, improving the fluidity of the colloid. Potassium persulfate decomposes upon heating to produce sulfate free radicals, increasing the number of active sites. Starch molecules graft and crosslink with polyvinyl alcohol molecules, forming a starch-polyvinyl alcohol interpenetrating network structure, which greatly improves the toughness and film-forming properties of the film. Modified waterborne polyurethane forms a dense hydrogen bond network with the abundant hydroxyl and carboxyl groups on starch and polyvinyl alcohol, improving the bonding force. Rigid silica nanoparticles act as physical crosslinking points, effectively restricting the movement of polyurethane molecular chains, thereby significantly improving the hardness, tensile strength, modulus, and tear resistance of the film. The dense nanocomposite structure not only blocks water vapor but also effectively blocks oxygen and oil stains. Modified silica combines with isocyanate groups in waterborne polyurethane to form an organic-inorganic nanocomposite material, significantly improving the adhesion of the colloid to the cardboard.

[0013] The environmentally friendly adhesive layer uses renewable corn starch as its main raw material, greatly improving its environmental friendliness. The high water resistance of the water-based polyurethane itself, the hydrophobic effect brought by the silane coupling agent, and the cross-linking of carboxyl groups introduced by oxidation, which changes from hydrophilic to hydrophobic, all contribute to improving waterproofness, while also improving toughness and adhesion. At the same time, the carboxyl and hydroxyl groups on the organosilicon acrylic resin molecular chains of the water-based ink layer react with the amino groups in the waterproof adhesive layer to form hydrogen bonds and covalent bonds, providing extremely high bonding strength, durability, and wear resistance. In addition, the silanols between the water-based ink layer and the environmentally friendly adhesive layer collide and condense to form covalent bridges, greatly enhancing interlayer adhesion, preventing delamination, and significantly improving water resistance.

[0014] The corrugated cardboard produced using this printing process exhibits excellent moisture and water resistance, clear ink printing, and good ink adhesion, making it highly practical and providing an excellent technical solution for green packaging. Detailed Implementation

[0015] 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.

[0016] Example 1: An environmentally friendly printing process for waterproof corrugated cardboard, comprising the following steps: S1: Spray water-based ink evenly onto the surface of the corrugated cardboard, heat to 60°C to form a printing ink layer, and dry to obtain printed corrugated cardboard; S2: Spray environmentally friendly waterproof colloid onto the ink layer of the printed corrugated cardboard, control the temperature at 65℃, vacuum dry, then raise the temperature to 90℃ and cure for 20 minutes to form a waterproof colloid layer, thus obtaining waterproof printed corrugated cardboard. The preparation process of the environmentally friendly waterproof colloid is as follows: corn starch and deionized water are mixed, 10% sodium hydroxide solution is added, the pH is adjusted to 10, the temperature is raised to 85°C and kept at that temperature for 10 min, sodium hypochlorite solution is added, the temperature is raised to 95°C and reacted for 15 min, 40% polyvinyl alcohol solution and potassium persulfate are added, the reaction is carried out for 20 min, the temperature is lowered to 55°C, modified waterborne polyurethane is added, the reaction is carried out for 70 min, the material is cooled and discharged to obtain the environmentally friendly waterproof colloid; The environmentally friendly waterproof colloid, by weight, consists of the following raw materials: 40 parts corn starch, 4 parts sodium hydroxide, 200 parts deionized water, 5 parts sodium hypochlorite solution, 15 parts 40% polyvinyl alcohol solution, 0.4 parts potassium persulfate, and 30 parts modified waterborne polyurethane. The preparation process of the modified waterborne polyurethane is as follows: 1g of aminopropyltriethoxysilane, 20mL of deionized water, and 80mL of ethanol solvent are mixed, the pH is adjusted to 4.5 with acetic acid, and the mixture is stirred at 50℃ for 35min. 5g of nano-SiO2 is added, and the mixture is stirred at 70℃ for 5h. After centrifugation, the mixture is washed with ethanol and vacuum dried to obtain modified SiO2. 5g of modified SiO2 and 100g of waterborne polyurethane are mixed and stirred for 15min, heated to 50℃, and stirred for 25min to obtain the modified waterborne polyurethane. The preparation process of the water-based ink is as follows: water-based acrylic resin binder, deionized water, ethanol, and phthalocyanine green pigment are mixed and dispersed for 15 minutes. Polyether-modified polydimethylsiloxane is added and stirred for 20 minutes. Hydroxyethyl cellulose is added and ground for 45 minutes. The mixture is then filtered and packaged to obtain the water-based ink. The raw material composition of the water-based ink is as follows: 50 parts water-based acrylic resin binder, 10 parts deionized water, 5 parts ethanol, 12 parts phthalocyanine green pigment, 0.5 parts polyether-modified polydimethylsiloxane, and 1.0 part hydroxyethyl cellulose. The preparation process of the water-based acrylic resin binder is as follows: 1) Mix emulsifier and deionized water, stir at 25°C for 25 min, add methyl methacrylate, styrene, butyl acrylate, and γ-methacryloyloxypropyltrimethoxysilane, and stir for 35 min to obtain a pre-emulsion. 2) Mix the buffer and one-third of the pre-emulsion, heat to 75°C, stir for 10 minutes, add half of the ammonium persulfate mixture, keep warm for 20 minutes to form a seed emulsion; 3) Add the remaining pre-emulsion and ammonium persulfate mixture to the seed emulsion, heat to 80℃, keep warm for 1.5h, cool to 40℃, adjust the pH to 8, filter and discharge to obtain water-based acrylic resin binder; The waterborne acrylic resin binder, by weight, comprises: 3 parts emulsifier, 90 parts deionized water, 30 parts methyl methacrylate, 20 parts styrene, 50 parts butyl acrylate, 4 parts γ-methacryloyloxypropyltrimethoxysilane, 15 parts buffer, and 25 parts ammonium persulfate mixture. The buffer is a mixture of deionized water and sodium bicarbonate at a mass ratio of 20:0.2; the ammonium persulfate mixture is a mixture of deionized water and ammonium persulfate at a mass ratio of 20:0.4; and the emulsifier is a mixture of sodium dodecyl sulfate and fatty alcohol polyoxyethylene ether at a mass ratio of 1:1. The thickness of the waterproof colloid layer is 30 μm; the thickness of the printing ink layer is 3 μm.

[0017] Example 2: An environmentally friendly printing process for waterproof corrugated cardboard, comprising the following steps: S1: Spray water-based ink evenly onto the surface of the corrugated cardboard, heat to 70°C to form a printing ink layer, and dry to obtain printed corrugated cardboard; S2: Spray environmentally friendly waterproof colloid onto the ink layer of the printed corrugated cardboard, control the temperature at 70℃, vacuum dry, then raise the temperature to 90℃ and cure for 14 minutes to form a waterproof colloid layer, thus obtaining waterproof printed corrugated cardboard. The preparation process of the environmentally friendly waterproof colloid is as follows: corn starch and deionized water are mixed, 10% sodium hydroxide solution is added, the pH is adjusted to 10, the temperature is raised to 82°C and kept at that temperature for 14 min, sodium hypochlorite solution is added, the temperature is raised to 100°C and reacted for 15 min, 40% polyvinyl alcohol solution and potassium persulfate are added, the reaction is carried out for 28 min, the temperature is lowered to 55°C, modified waterborne polyurethane is added, the reaction is carried out for 70 min, the material is cooled and discharged to obtain the environmentally friendly waterproof colloid; The environmentally friendly waterproof colloid, by weight, consists of the following raw materials: 45 parts corn starch, 4 parts sodium hydroxide, 220 parts deionized water, 5 parts sodium hypochlorite solution, 15 parts 40% polyvinyl alcohol solution, 0.7 parts potassium persulfate, and 25 parts modified waterborne polyurethane. The preparation process of the modified waterborne polyurethane is as follows: 1g of aminopropyltriethoxysilane, 20mL of deionized water, and 80mL of ethanol solvent are mixed, the pH is adjusted to 4.5 with acetic acid, and the mixture is stirred at 50℃ for 35min. 5g of nano-SiO2 is added, and the mixture is stirred at 70℃ for 5h. After centrifugation, the mixture is washed with ethanol and vacuum dried to obtain modified SiO2. 5g of modified SiO2 and 100g of waterborne polyurethane are mixed and stirred for 15min, heated to 50℃, and stirred for 25min to obtain the modified waterborne polyurethane. The preparation process of the water-based ink is as follows: water-based acrylic resin binder, deionized water, ethanol, and phthalocyanine green pigment are mixed and dispersed for 15 minutes. Polyether-modified polydimethylsiloxane is added and stirred for 20 minutes. Hydroxyethyl cellulose is added and ground for 45 minutes. The mixture is then filtered and packaged to obtain the water-based ink. The raw material composition of the water-based ink is as follows: 45 parts water-based acrylic resin binder, 15 parts deionized water, 6 parts ethanol, 15 parts phthalocyanine green pigment, 0.5 parts polyether-modified polydimethylsiloxane, and 1.5 parts hydroxyethyl cellulose. The preparation process of the water-based acrylic resin binder is as follows: 1) Mix emulsifier and deionized water, stir at 22°C for 35 min, add methyl methacrylate, styrene, butyl acrylate and γ-methacryloyloxypropyltrimethoxysilane, stir for 35 min to obtain pre-emulsion; 2) Mix the buffer and one-third of the pre-emulsion, heat to 68°C, stir for 15 minutes, add half of the ammonium persulfate mixture, keep warm for 20 minutes to form a seed emulsion; 3) Add the remaining pre-emulsion and ammonium persulfate mixture to the seed emulsion, heat to 80℃, keep warm for 1 hour, cool to 40℃, adjust the pH to 8.5, filter and discharge to obtain water-based acrylic resin binder; The raw material composition of the waterborne acrylic resin binder, by weight, is as follows: 4 parts emulsifier, 100 parts deionized water, 25 parts methyl methacrylate, 25 parts styrene, 50 parts butyl acrylate, 3 parts γ-methacryloyloxypropyltrimethoxysilane, 15 parts buffer, and 25 parts ammonium persulfate mixture. The buffer is a mixture of deionized water and sodium bicarbonate at a mass ratio of 20:0.2; the ammonium persulfate mixture is a mixture of deionized water and ammonium persulfate at a mass ratio of 20:0.4; and the emulsifier is a mixture of sodium dodecyl sulfate and fatty alcohol polyoxyethylene ether at a mass ratio of 1:1. The thickness of the waterproof colloid layer is 30 μm; the thickness of the printing ink layer is 3 μm.

[0018] Example 3: An environmentally friendly printing process for waterproof corrugated cardboard, comprising the following steps: S1: Spray water-based ink evenly onto the surface of the corrugated cardboard, heat to 60°C to form a printing ink layer, and dry to obtain printed corrugated cardboard; S2: Spray environmentally friendly waterproof colloid onto the ink layer of the printed corrugated cardboard, control the temperature at 70℃, vacuum dry, then raise the temperature to 95℃ and cure for 15 minutes to form a waterproof colloid layer, thus obtaining waterproof printed corrugated cardboard. The preparation process of the environmentally friendly waterproof colloid is as follows: corn starch and deionized water are mixed, 10% sodium hydroxide solution is added, the pH is adjusted to 9.5, the temperature is raised to 82℃ and kept at that temperature for 20 min, sodium hypochlorite solution is added, the temperature is raised to 100℃ and reacted for 30 min, 40% polyvinyl alcohol solution and potassium persulfate are added, the reaction is carried out for 30 min, the temperature is lowered to 60℃, modified waterborne polyurethane is added, the reaction is carried out for 70 min, the material is cooled and discharged to obtain the environmentally friendly waterproof colloid; The environmentally friendly waterproof colloid, by weight, consists of the following raw materials: 50 parts corn starch, 5 parts sodium hydroxide, 250 parts deionized water, 7 parts sodium hypochlorite solution, 15 parts 40% polyvinyl alcohol solution, 0.7 parts potassium persulfate, and 20 parts modified waterborne polyurethane. The preparation process of the modified waterborne polyurethane is as follows: 1g of aminopropyltriethoxysilane, 20mL of deionized water, and 80mL of ethanol solvent are mixed, the pH is adjusted to 4.5 with acetic acid, and the mixture is stirred at 50℃ for 35min. 5g of nano-SiO2 is added, and the mixture is stirred at 70℃ for 5h. After centrifugation, the mixture is washed with ethanol and vacuum dried to obtain modified SiO2. 5g of modified SiO2 and 100g of waterborne polyurethane are mixed and stirred for 15min, heated to 50℃, and stirred for 25min to obtain the modified waterborne polyurethane. The preparation process of the water-based ink is as follows: water-based acrylic resin binder, deionized water, ethanol, and phthalocyanine green pigment are mixed and dispersed for 15 minutes. Polyether-modified polydimethylsiloxane is added and stirred for 20 minutes. Hydroxyethyl cellulose is added and ground for 45 minutes. The mixture is then filtered and packaged to obtain the water-based ink. The raw material composition of the water-based ink is as follows: 40 parts water-based acrylic resin binder, 20 parts deionized water, 8 parts ethanol, 20 parts phthalocyanine green pigment, 0.5 parts polyether-modified polydimethylsiloxane, and 1.5 parts hydroxyethyl cellulose. The preparation process of the water-based acrylic resin binder is as follows: 1) Mix emulsifier and deionized water, stir at 25°C for 25 min, add methyl methacrylate, styrene, butyl acrylate, and γ-methacryloyloxypropyltrimethoxysilane, and stir for 35 min to obtain a pre-emulsion. 2) Mix the buffer and one-third of the pre-emulsion, heat to 70°C, stir for 12 minutes, add half of the ammonium persulfate mixture, keep warm for 15 minutes to form a seed emulsion; 3) Add the remaining pre-emulsion and ammonium persulfate mixture to the seed emulsion, heat to 80℃, keep warm for 1.2h, cool to 40℃, adjust the pH to 8.5, filter and discharge to obtain water-based acrylic resin binder; The raw material composition of the waterborne acrylic resin binder, by weight, is as follows: 4 parts emulsifier, 110 parts deionized water, 35 parts methyl methacrylate, 25 parts styrene, 40 parts butyl acrylate, 3 parts γ-methacryloyloxypropyltrimethoxysilane, 15 parts buffer, and 30 parts ammonium persulfate mixture. The buffer is a mixture of deionized water and sodium bicarbonate at a mass ratio of 20:0.2; the ammonium persulfate mixture is a mixture of deionized water and ammonium persulfate at a mass ratio of 20:0.4; and the emulsifier is a mixture of sodium dodecyl sulfate and fatty alcohol polyoxyethylene ether at a mass ratio of 1:1. The thickness of the waterproof colloid layer is 30 μm; the thickness of the printing ink layer is 3 μm.

[0019] Comparative Example 1: Using Example 1 as the control group, γ-methacryloyloxypropyltrimethoxysilane was not added in the preparation of the waterborne acrylic resin binder, and other processes were normal.

[0020] Comparative Example 2: Using Example 1 as the control group, no modified waterborne polyurethane was added in the preparation of the environmentally friendly waterproof colloid, and other processes were normal.

[0021] Sources of raw materials used (for illustrative purposes only): The raw materials used in this technical solution are all products currently available on the market: Corrugated cardboard: sold by Baoding Zhongshida Packaging Co., Ltd. under product number ZSD-280; Corn starch (9005-25-8, 98%): Hubei Xinmingtai Chemical Co., Ltd.; Sodium hypochlorite (7681-52-9, 99%): Shandong Yukang Chemical Co., Ltd.; Polyvinyl alcohol (99%): sold by Shandong Yukang Chemical Co., Ltd. under product number 25073101; Potassium persulfate (99%): sold by Shanghai Anpu Experimental Technology Co., Ltd. Products sold under product number CFEQ-4-120046-0500: Aminopropyltriethoxysilane (919-30-2, 99%): Hubei Xinkang Pharmaceutical Chemical Co., Ltd.; Nano SiO2 (10nm, 99%): Zhejiang Yamei Nanotechnology Co., Ltd.; Waterborne polyurethane: Products sold by Shanghai Mairui Biochemical Technology Co., Ltd. under product number M90109; γ-methacryloyloxypropyltrimethoxysilane (2530-85-0, 99%): Wuhan Beiguofeng Chemical Co., Ltd.; Phthalocyanine green pigment (1328... -53-6, 98%: Xi'an Qiyue Biotechnology Co., Ltd.; Polyether-modified polydimethylsiloxane (98%): Product sold by Wuhan Shuer Biotechnology Co., Ltd. under product number 633265; Hydroxyethyl cellulose (9004-62-0, 99%): Shenzhen Boshun Chemical Co., Ltd.; Methyl methacrylate (80-62-6, 99%): Shandong Jinyueyuan New Material Co., Ltd.; Styrene (100-42-5, 99.9%): Shandong Yanshuo Chemical Co., Ltd.; Butyl acrylate (1663-39- 4. 98%: Shanghai Bangcheng Chemical Co., Ltd.; Sodium bicarbonate (144-55-8, 99.5%): Langfang Qianyao Technology Co., Ltd.; Ammonium persulfate (7727-54-0, 98.5%): Changzhou Jiaye Chemical Co., Ltd.; Sodium dodecyl sulfate (99%): Hubei Wande Chemical Co., Ltd., sold under product number WD0194; Fatty alcohol polyoxyethylene ether: Guangzhou Xiangmei Chemical Technology Co., Ltd., sold under product number AEO-3; Sodium hydroxide solution, ethanol, ammonia, acetic acid, analytical grade, purchased commercially.

[0022] Performance testing: The waterproof corrugated cardboard prepared in the examples and comparative examples was tested: (1) Adhesion test: The adhesion tester was used according to GB / T 9286-2021 standard. A 1mm×1mm grid was cut on the surface of the printed sample using a six-blade cutter. After removing the debris with a soft brush, 3M 610 tape was tightly adhered to the grid area and quickly peeled off. The operation was repeated 3 times. The ink peeling in the grid area was observed under a magnifying glass and rated. No peeling was grade 0, peeling area less than 5% was grade 1, peeling area less than 15% was grade 2, peeling area less than 35% was grade 3, peeling area less than 65% was grade 4, and peeling area greater than 65% was grade 5.

[0023] (2) Water resistance test: Cut the printed corrugated cardboard sample into 10cm×10cm size, place half of the sample in deionized water, soak at 25℃ for 24h, take it out after soaking, use filter paper to absorb the surface water, compare the changes in ink before and after soaking, and observe the degree of water staining. If the ink does not change color, the water does not stain, and there are no water wetting marks on the surface, the sample is excellent. If there are a small amount of water stains on the surface, but they do not penetrate into the paper base, it is qualified. If there is obvious water seepage, bubbling, water discoloration or ink peeling, it is unqualified.

[0024] (3) Abrasion resistance test: Cut the waterproof corrugated cardboard into circular test pieces with an outer diameter of 100 mm and a central hole diameter of 6.5 mm. After conditioning for 24 h at 23℃ and 50%RH, weigh the initial mass. Use a Taber abrasion tester with a 500 g loading weight and a standard friction rubber wheel to perform 1000 friction tests at a speed of 60 r / min. Weigh the mass, record the data, and calculate the mass loss value.

[0025] The test results are as follows: Table 1

[0026] The analysis results are as follows: This invention provides an environmentally friendly printing process for waterproof corrugated cardboard. By optimizing the composition and process, an environmentally friendly waterproof printed corrugated cardboard is constructed. The examples and comparative examples are analyzed below. Ordinary corrugated cardboard has extremely high water absorption. The waterproof cardboard prepared by this invention has extremely low water absorption due to its dense coating. The water-based ink layer is made of silicone-modified water-based acrylate, which is copolymerized using double bonds and acrylic monomers, avoiding small molecule migration, significantly improving water resistance and thermal stability. The Si-O-Si network enhances abrasion and scratch resistance. The environmentally friendly waterproof colloidal layer combines the low cost and environmental advantages of bio-based materials with the high performance of water-based polyurethane. Through chemical modification and hydrogen bonding, they are perfectly integrated to form a dense waterproof layer, thereby improving the waterproof performance of the corrugated cardboard.

[0027] Using Example 1 as a control group, analysis of Comparative Example 1 shows that without the addition of γ-methacryloyloxypropyltrimethoxysilane during the synthesis of acrylic resin in the water-based ink layer, the performance loss is severe. The strong Si-O-Si covalent bond bridge between the two layers cannot be established, resulting in a sharp drop in interlayer adhesion. The two layers are only bound by weak intermolecular forces and limited hydrogen bonds, making them prone to delamination and peeling. At the same time, the water resistance deteriorates, and water molecules can easily penetrate to the interface defects, leading to interface swelling and failure. The strength of the paperboard decreases after absorbing water, failing to meet the needs of industrial printing.

[0028] Using Example 1 as the control group, the analysis of Comparative Example 2 shows that in the preparation of the environmentally friendly waterproof colloid, the modified waterborne polyurethane first modifies the surface of nano-SiO2 to solve the inherent agglomeration problem of nanoparticles and improve the compatibility between the two. Under acidic conditions, the coupling agent hydrolyzes to generate highly reactive silanol. The silanol undergoes a dehydration condensation reaction with the hydroxyl groups on the surface of nano-SiO2 to form a strong covalent bond. The amino groups are introduced to react with the isocyanate groups and carboxyl groups on the waterborne polyurethane chain to form an organic-inorganic nanocomposite material. The polyurethane molecules provide elasticity and film-forming properties, the SiO2 nanoparticles provide reinforcement, wear resistance and barrier properties, and the silane plays a "bridging" role. If the modified waterborne polyurethane is not added, the entire colloid will revert to the starch-polyvinyl alcohol system with relatively high brittleness and general water resistance, and will not be able to meet the high-performance waterproof requirements.

[0029] 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. An environmentally friendly printing process for waterproof corrugated cardboard, characterized in that, Includes the following steps, S1: Spray water-based ink evenly onto the surface of the corrugated cardboard, heat it to form a printing ink layer, and dry it to obtain printed corrugated cardboard; S2: Spray an environmentally friendly waterproof colloid onto the ink layer of the printed corrugated cardboard, heat it, vacuum dry it, and then heat it again to cure it for 10-20 minutes to form a waterproof colloid layer, thus obtaining waterproof printed corrugated cardboard.

2. The environmentally friendly printing process for waterproof corrugated cardboard according to claim 1, characterized in that, The preparation process of the environmentally friendly waterproof colloid is as follows: corn starch and deionized water are mixed, sodium hydroxide solution is added, the pH is adjusted to 9-10, the temperature is raised to 75-85℃ and kept at that temperature for 10-20 minutes, sodium hypochlorite solution is added, the temperature is raised to 90-100℃ and reacted for 15-30 minutes, polyvinyl alcohol solution and potassium persulfate are added, the reaction is carried out for 20-30 minutes, the temperature is lowered to 55-60℃, modified waterborne polyurethane is added, the reaction is carried out for 50-70 minutes, the material is cooled and discharged to obtain the environmentally friendly waterproof colloid.

3. The environmentally friendly printing process for waterproof corrugated cardboard according to claim 2, characterized in that, By weight, the raw material composition of the environmentally friendly waterproof colloid is as follows: 40-50 parts corn starch, 2-5 parts sodium hydroxide, 200-250 parts deionized water, 3-7 parts sodium hypochlorite solution, 10-20 parts polyvinyl alcohol solution, 0.3-0.7 parts potassium persulfate, and 15-30 parts modified waterborne polyurethane.

4. The environmentally friendly printing process for waterproof corrugated cardboard according to claim 2, characterized in that, The preparation process of the modified waterborne polyurethane is as follows: aminopropyltriethoxysilane, deionized water, and ethanol solvent are mixed, the pH is adjusted to 4-5 with acetic acid, and the mixture is stirred at 40-50℃ for 30-40 min. Nano-SiO2 is added, and the mixture is stirred at 60-80℃ for 4-6 h. After centrifugation, the mixture is washed with ethanol and vacuum dried to obtain modified SiO2. The modified SiO2 and waterborne polyurethane are mixed and stirred for 10-15 min, and the mixture is heated to 40-50℃ and stirred for 20-40 min to obtain the modified waterborne polyurethane.

5. The environmentally friendly printing process for waterproof corrugated cardboard according to claim 1, characterized in that, The preparation process of the water-based ink is as follows: water-based acrylic resin binder, deionized water, ethanol and environmentally friendly water-based pigment are mixed and dispersed for 10-20 minutes, leveling agent is added and stirred for 10-30 minutes, thickener is added, and grinding is carried out for 40-50 minutes. After filtration and packaging, water-based ink is obtained.

6. The environmentally friendly printing process for waterproof corrugated cardboard according to claim 5, characterized in that, The preparation process of the water-based acrylic resin binder is as follows: 1) Mix emulsifier and deionized water, stir at 20-25℃ for 25-35 min, add methyl methacrylate, styrene, butyl acrylate and terminal vinylsiloxane, stir for 20-35 min to obtain pre-emulsion; 2) Mix the buffer and one-third of the pre-emulsion, heat to 65-75℃, stir for 10-15 minutes, add half of the ammonium persulfate mixture, keep warm for 10-20 minutes to form a seed emulsion; 3) Add the remaining pre-emulsion and ammonium persulfate mixture to the seed emulsion, heat to 75-80℃, keep warm for 1-1.5h, cool to 35-40℃, adjust the pH to 7.5-8.5, filter and discharge to obtain water-based acrylic resin binder.

7. The environmentally friendly printing process for waterproof corrugated cardboard according to claim 6, characterized in that, By weight, the raw material composition of the waterborne acrylic resin binder is as follows: 2-4 parts emulsifier, 90-110 parts deionized water, 25-35 parts methyl methacrylate, 15-25 parts styrene, 40-50 parts butyl acrylate, 2-4 parts terminal vinylsiloxane, 10-20 parts buffer, and 20-30 parts ammonium persulfate mixture; the buffer is a mixture of deionized water and sodium bicarbonate at a mass ratio of 20:0.2; the ammonium persulfate mixture is a mixture of deionized water and ammonium persulfate at a mass ratio of 20:0.

4.

8. The environmentally friendly printing process for waterproof corrugated cardboard according to claim 5, characterized in that, The water-based ink, by weight, comprises: 40-50 parts water-based acrylic resin binder, 10-20 parts deionized water, 3-8 parts ethanol, 10-20 parts environmentally friendly water-based pigment, 0.2-0.5 parts leveling agent, and 0.5-1.5 parts thickener.

9. The environmentally friendly printing process for waterproof corrugated cardboard according to claim 5, characterized in that, The leveling agent is one of acrylate polymer, polyether-modified polydimethylsiloxane, and polyester-modified polydimethylsiloxane; the thickener is one of hydroxyethyl cellulose, hydrophobically modified alkali-swellable acrylic emulsion, and bentonite; and the environmentally friendly water-based pigment is one of high-pigment carbon black, phthalocyanine blue, and phthalocyanine green.

10. The environmentally friendly printing process for waterproof corrugated cardboard according to claim 1, characterized in that, The thickness of the waterproof colloid layer is 20-40 μm; the thickness of the printing ink layer is 5-10 μm.

Images