Environment-friendly glue for paperboard and preparation process thereof

Abstract

The present application relates to the field of adhesive, in particular to an environment-friendly glue for paperboard and a preparation process thereof, which is used to solve the problem of low bonding strength and poor water resistance of the existing starch adhesive for paperboard, which limits the high-speed development and wide application of the paperboard industry; the environment-friendly glue for paperboard adopts epoxy copolymer modified starch as the main raw material, the starch has good biodegradability, and the formula does not contain harmful chemical substances such as formaldehyde and organic solvents, which will not cause harm to the environment and human health in the use process, and meets the environmental protection requirements; moreover, through reasonable raw material formula and preparation process, the glue has good bonding performance, can meet the demand of paperboard production, and has good water resistance, so that it can maintain stable bonding strength under different environmental conditions, effectively prevent the occurrence of phenomena such as paperboard opening and delamination, and prolong the service life of the paperboard.

Description

Technical Field

[0001] This invention relates to the field of adhesives, specifically to an environmentally friendly adhesive for cardboard and its preparation process. Background Technology

[0002] In the paperboard production process, adhesive is an essential raw material, and its performance directly affects the quality of the paperboard. Traditional paperboard adhesives contain a large amount of organic solvents, such as benzene, toluene, and xylene. These solvents evaporate into the air during use, causing air pollution and harming human health. Furthermore, some adhesives also contain harmful substances such as formaldehyde, which can damage the respiratory and nervous systems with prolonged exposure.

[0003] Therefore, environmentally friendly biomass adhesives have received widespread attention and become a research hotspot. Adhesives based on biomass polymers such as starch, protein, tannin, and lignin have become a research focus. Among them, starch adhesives have become one of the alternatives to traditional adhesives due to their advantages such as the wide availability of starch as a raw material, low cost, renewability, and easy biodegradability. However, due to its own structure and other factors, starch adhesives have low bonding strength and poor water resistance, which cannot meet the requirements for long-term use, affecting the service life and application range of paperboard, and limiting their rapid development and widespread application in the paperboard industry.

[0004] Therefore, developing an environmentally friendly adhesive for cardboard and its preparation process is of great practical significance. Summary of the Invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide an environmentally friendly adhesive for paperboard and its preparation process, which solves the problems of low bonding strength and poor water resistance of existing starch adhesives for paperboard, which limit their rapid development and widespread application in the paperboard industry.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, this application provides an environmentally friendly adhesive for cardboard, comprising the following components in parts by weight: The mixture contains 225-255 parts of epoxy copolymer modified starch, 11-35 parts of polysiloxane crosslinking agent, 75-85 parts of kaolin, 0.5-0.6 parts of ferrous ammonium sulfate, 2-2.2 parts of hydrogen peroxide, 0.5-0.7 parts of sodium sulfite, 0.5-0.7 parts of trisodium phosphate, 30-36 parts of sodium hydroxide, 8-10 parts of borax, and 1600-1800 parts of deionized water. The epoxy copolymer-modified starch is prepared by the following steps: Step A1: Add starch and ethanol solution to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and constant pressure dropping funnel. Purge with nitrogen for protection and stir for 20-30 min at 20-25℃ and 200-300 r / min. Then, add sodium hydroxide solution dropwise while stirring, controlling the dropping rate to 1-3 drops / s, until the pH reaches 8-9. Then, add 2-octenyl succinic anhydride dropwise while stirring. After the addition is complete, raise the temperature to 40-45℃ and continue stirring for 2-3 h. After the reaction is complete, cool the reaction product to room temperature and adjust the pH to 5-6 with hydrochloric acid solution. Then pour it into anhydrous ethanol, let it stand to precipitate, centrifuge, and place the precipitate in a vacuum drying oven at 40-50℃ for 3-5 h to obtain alkenyl grafted starch. Step A2: Add alkenyl grafted starch, glycidyl methacrylate, azobisisobutyronitrile, and deionized water to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Purge with nitrogen for protection and stir at 20-25℃ and 200-300 r / min for 20-30 min. Then raise the temperature to 60-65℃ and continue stirring for 2-3 h. After the reaction is complete, cool the reaction product to room temperature and pour it into anhydrous ethanol. Allow it to stand to precipitate, then centrifuge. Place the precipitate in a vacuum drying oven and dry at 60-70℃ for 1-2 h to obtain epoxy copolymer modified starch.

[0007] In a preferred embodiment of the present invention, the ratio of starch, ethanol solution and 2-octenylsuccinic anhydride used in step A1 is 10g:80-90mL:0.8-3.6g.

[0008] In a preferred embodiment of the present invention, the starch in step A1 is one of corn starch, potato starch, and cassava starch; the volume fraction of the ethanol solution is 20-30%; the molar concentration of the sodium hydroxide solution is 0.1-0.2 mol / L; and the molar concentration of the hydrochloric acid solution is 1-1.2 mol / L.

[0009] In a preferred embodiment of the present invention, the ratio of alkenyl grafted starch, glycidyl methacrylate, azobisisobutyronitrile and deionized water in step A2 is 5g:0.5-2.1mL:0.03-0.05g:80-90mL.

[0010] In a preferred embodiment of the present invention, the polysiloxane crosslinking agent is prepared by the following steps: Step B1: Add vitamin C, p-toluenesulfonic acid, 3-mercaptopropionic acid, and anhydrous toluene to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Purge with nitrogen for protection and stir the reaction at 20-25℃ and 200-300 r / min for 10-20 min. Then raise the temperature to 90-95℃ and continue stirring for 6-7 h. After the reaction is complete, cool the reaction product to room temperature, then wash it 2-3 times with sodium hydroxide solution and distilled water, then dry it with anhydrous sodium sulfate, then filter it under vacuum, and evaporate the filtrate by rotary evaporation to remove the solvent, to obtain polythiol-grafted vitamin C. Step B2: Add polythiol-grafted vitamins, vinyltriethoxysilane, benzoin dimethyl ether, and anhydrous ethanol to a three-necked flask equipped with a stirrer and thermometer. Stir the reaction at 20-25℃, a stirring rate of 200-300 r / min, and under ultraviolet light at a wavelength of 365 nm for 10-20 min. Then, raise the temperature to 50-55℃ and continue stirring for 3-5 h. After the reaction is completed, cool the reaction product to room temperature and then remove the solvent by rotary evaporation to obtain the polysiloxane crosslinking agent.

[0011] In a preferred embodiment of the present invention, the ratio of vitamin C, p-toluenesulfonic acid, 3-mercaptopropionic acid and anhydrous toluene in step B1 is 10 mmol: 0.08-0.1 g: 50-55 mmol: 60-70 mL.

[0012] In a preferred embodiment of the present invention, the sodium hydroxide solution in step B1 has a mass fraction of 3-5%.

[0013] In a preferred embodiment of the present invention, the ratio of the polythiol-grafted vitamin, vinyltriethoxysilane, benzoin dimethyl ether and anhydrous ethanol in step B2 is 10 mmol: 40 mmol: 0.02-0.04 g: 70-80 mL.

[0014] Secondly, this application provides a process for preparing an environmentally friendly adhesive for cardboard, comprising the following steps: Step 1: Weigh out the following components by weight: 225-255 parts epoxy copolymer modified starch, 11-35 parts polysiloxane crosslinking agent, 75-85 parts kaolin, 0.5-0.6 parts ferrous ammonium sulfate, 2-2.2 parts hydrogen peroxide, 0.5-0.7 parts sodium sulfite, 0.5-0.7 parts trisodium phosphate, 30-36 parts sodium hydroxide, 8-10 parts borax, and 1600-1800 parts deionized water. Set aside. Step 2: Add kaolin and deionized water to a mixer and stir for 20-30 minutes at a temperature of 20-25℃ and a stirring speed of 200-300 r / min. Then add ferrous ammonium sulfate and continue stirring for 5-10 minutes. Next, add epoxy copolymer modified starch and heat to 40-50℃ and continue stirring for 5-10 minutes. Then add hydrogen peroxide, sodium sulfite, and trisodium phosphate and continue stirring for 3-5 minutes. Then add sodium hydroxide and borax and continue stirring for 2-3 hours. Finally, add polysiloxane crosslinking agent and heat to 70-80℃ and continue stirring for 1-3 hours. After the reaction is complete, cool the reaction product to room temperature to obtain environmentally friendly adhesive for cardboard.

[0015] In a preferred embodiment of the present invention, the kaolin has a particle size of 500-600 mesh.

[0016] In a preferred embodiment of the present invention, the hydrogen peroxide has a mass fraction of 28-30%.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses an environmentally friendly adhesive for cardboard and its preparation process. The process involves stirring kaolin and deionized water, followed by the sequential addition of ferrous ammonium sulfate, epoxy copolymer-modified starch, hydrogen peroxide, sodium sulfite, trisodium phosphate, sodium hydroxide, borax, and a polysiloxane crosslinking agent, with continued stirring to obtain the environmentally friendly adhesive for cardboard. This invention uses epoxy copolymer-modified starch as the main raw material. Starch has good biodegradability, and the formula does not contain formaldehyde, organic solvents, or other harmful chemicals. It will not harm the environment or human health during use, meeting environmental protection requirements. Furthermore, through a reasonable raw material formulation and preparation process, the adhesive exhibits excellent bonding performance, meeting the needs of cardboard production. It also possesses good water resistance, maintaining stable bonding strength under different environmental conditions, effectively preventing delamination and extending the service life of the cardboard. Simultaneously, the raw materials for this adhesive are widely available and inexpensive, and the preparation process is simple, easy to operate and control, reducing production costs, improving market competitiveness, and resulting in good economic benefits.

[0018] In the preparation of environmentally friendly adhesives for cardboard, an epoxy copolymer-modified starch was first prepared. This involved reacting starch with 2-octenyl succinic anhydride, where the anhydride structure on the 2-octenyl succinic anhydride underwent ring-opening and reacted with the hydroxyl groups on the starch to form ester groups. Simultaneously, alkenyl groups were introduced into the starch molecule structure, resulting in alkenyl-grafted starch. Subsequently, the alkenyl-grafted starch reacted with glycidyl methacrylate, and the alkenyl groups and glycidyl methacrylate polymerized, introducing a large number of epoxy groups into the starch molecule structure, thus obtaining epoxy copolymer-modified starch. The presence of numerous epoxy groups in the epoxy copolymer-modified starch molecule structure endows it with excellent adhesive properties. The presence of polymer chains significantly improves the starch's water resistance. Furthermore, kaolin was used to increase the intermolecular gaps in the epoxy copolymer-modified starch, enhancing its density. Hydrogen peroxide oxidation further introduces polar groups into the starch molecule chains, improving the starch's reactivity. Simultaneously, borax and polysiloxane crosslinking agents reacted with the starch molecules to form a three-dimensional network structure, further improving the adhesive and water resistance properties of the epoxy copolymer-modified starch.

[0019] In the process of preparing environmentally friendly adhesives for cardboard, a polysiloxane crosslinking agent was also prepared. This agent utilizes the reaction of vitamin C and 3-mercaptopropionic acid. Vitamin C contains multiple hydroxyl groups that can react with the carboxyl groups on 3-mercaptopropionic acid to form ester groups. Simultaneously, multiple thiol groups are introduced into the vitamin C structure, resulting in a polythiol-grafted vitamin. Then, the polythiol-grafted vitamin reacts with vinyltriethoxysilane. The multiple thiol groups on the polythiol-grafted vitamin undergo click chemistry with the alkenyl groups on vinyltriethoxysilane, thereby introducing a large amount of siloxane and obtaining the polysiloxane crosslinking agent. After hydrolysis, the abundant siloxanes in this polysiloxane crosslinking agent can react with the hydroxyl groups in the epoxy copolymer-modified starch matrix, and simultaneously undergo self-polymerization, thus forming a large number of strong Si-O-Si bond crosslinking structures in the adhesive. This significantly improves the adhesive performance and effectively prevents water molecules from entering, enhancing the adhesive's water resistance. Attached Figure Description

[0020] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0021] Figure 1 This is a schematic diagram showing the test results of the bonding performance and water resistance of the environmentally friendly adhesive for cardboard in Examples 1-3 and Comparative Examples 1-4 of the present invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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.

[0023] Example 1: This embodiment describes a preparation process for an environmentally friendly adhesive for cardboard, including the following steps: Step S1: Add 10g of corn starch and 80mL of 20% ethanol solution to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and constant pressure dropping funnel. Purge with nitrogen for protection and stir for 20min at 20℃ and 200r / min. Then, add 0.1mol / L sodium hydroxide solution dropwise while stirring, controlling the dropping rate to 1 drop / s, until the pH reaches 8. Then, add 0.8g of 2-octenyl succinic anhydride dropwise while stirring. After the addition is complete, raise the temperature to 40℃ and continue stirring for 2h. After the reaction is complete, cool the reaction product to room temperature and adjust the pH to 6 with 1mol / L hydrochloric acid solution. Then pour into anhydrous ethanol, let stand to precipitate, centrifuge, and place the precipitate in a vacuum drying oven and dry at 40℃ for 3h to obtain alkenyl grafted starch. Step S2: Add 5g of alkenyl grafted starch, 0.5mL of glycidyl methacrylate, 0.03g of azobisisobutyronitrile and 80mL of deionized water to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Purge with nitrogen for protection and stir at 20℃ and 200r / min for 20min. Then raise the temperature to 60℃ and continue stirring for 2h. After the reaction is complete, cool the reaction product to room temperature and pour it into anhydrous ethanol. After standing, the precipitate is formed and centrifuged. Place the precipitate in a vacuum drying oven and dry at 60℃ for 1h to obtain epoxy copolymer modified starch. Step S3: Add 10 mmol of vitamin C, 0.08 g of p-toluenesulfonic acid, 50 mmol of 3-mercaptopropionic acid, and 60 mL of anhydrous toluene to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Purge with nitrogen for protection and stir at 20 °C and 200 r / min for 10 min. Then raise the temperature to 90 °C and continue stirring for 6 h. After the reaction is complete, cool the reaction product to room temperature and wash it twice with 3% sodium hydroxide solution and distilled water, respectively. Then dry it with anhydrous sodium sulfate and filter it under vacuum. Remove the solvent by rotary evaporation of the filtrate to obtain polythiol-grafted vitamin C. Step S4: 10 mmol of polythiol-grafted vitamin, 40 mmol of vinyltriethoxysilane, 0.02 g of benzoin dimethyl ether and 70 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer and a thermometer. The mixture was stirred and reacted for 10 min at a temperature of 20 °C, a stirring rate of 200 r / min and a wavelength of 365 nm under ultraviolet light. The temperature was then raised to 50 °C and the mixture was stirred and reacted for another 3 h. After the reaction was completed, the reaction product was cooled to room temperature and the solvent was removed by rotary evaporation to obtain the polysiloxane crosslinking agent. Step S5: Weigh out 225 parts by weight of epoxy copolymer modified starch, 11 parts by weight of polysiloxane crosslinking agent, 75 parts by weight of kaolin, 0.5 parts by weight of ferrous ammonium sulfate, 2 parts by weight of hydrogen peroxide, 0.5 parts by weight of sodium sulfite, 0.5 parts by weight of trisodium phosphate, 30 parts by weight of sodium hydroxide, 8 parts by weight of borax, and 1600 parts by weight of deionized water for later use; wherein, the particle size of the kaolin is 500 mesh; and the mass fraction of the hydrogen peroxide is 28%; Step S6: Add kaolin and deionized water to a mixer and stir for 20 minutes at 20°C and 200 r / min. Then add ferrous ammonium sulfate and continue stirring for 5 minutes. Next, add epoxy copolymer modified starch and heat to 40°C and continue stirring for 5 minutes. Then add hydrogen peroxide, sodium sulfite, and trisodium phosphate and continue stirring for 3 minutes. Then add sodium hydroxide and borax and continue stirring for 2 hours. Finally, add polysiloxane crosslinking agent and heat to 70°C and continue stirring for 1 hour. After the reaction is complete, cool the reaction product to room temperature to obtain environmentally friendly adhesive for cardboard.

[0024] Example 2: This embodiment describes a preparation process for an environmentally friendly adhesive for cardboard, including the following steps: Step S1: Add 10g of potato starch and 85mL of 25% ethanol solution to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and constant pressure dropping funnel. Purge with nitrogen for protection and stir at 22℃ and 250r / min for 25min. Then, while stirring, add 0.15mol / L sodium hydroxide solution dropwise at a rate of 2 drops / s until the pH reaches 8.5. Then, while stirring, add 2.2g of 2-octenyl succinic anhydride dropwise. After the addition is complete, raise the temperature to 42℃ and continue stirring for 2.5h. After the reaction is complete, cool the reaction product to room temperature and adjust the pH to 5.5 with 1.1mol / L hydrochloric acid solution. Then pour the solution into anhydrous ethanol, let it stand to precipitate, centrifuge, and place the precipitate in a vacuum drying oven at 45℃ for 4h to obtain alkenyl grafted starch. Step S2: Add 5g of alkenyl grafted starch, 1.3mL of glycidyl methacrylate, 0.04g of azobisisobutyronitrile, and 85mL of deionized water to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Purge with nitrogen for protection and stir at 22℃ and 250r / min for 25min. Then raise the temperature to 62℃ and continue stirring for 2.5h. After the reaction is complete, cool the reaction product to room temperature and pour it into anhydrous ethanol. After standing, the precipitate is formed and centrifuged. Place the precipitate in a vacuum drying oven and dry at 65℃ for 1.5h to obtain epoxy copolymer modified starch. Step S3: Add 10 mmol of vitamin C, 0.09 g of p-toluenesulfonic acid, 52 mmol of 3-mercaptopropionic acid, and 65 mL of anhydrous toluene to a three-necked flask equipped with a stirrer, thermometer, and gas delivery tube. Purge with nitrogen for protection and stir at 22 °C and 250 r / min for 15 min. Then raise the temperature to 92 °C and continue stirring for 6.5 h. After the reaction is complete, cool the reaction product to room temperature and wash it twice with 4% sodium hydroxide solution and distilled water, respectively. Then dry it with anhydrous sodium sulfate and filter it under vacuum. Remove the solvent by rotary evaporation of the filtrate to obtain polythiol-grafted vitamin C. Step S4: 10 mmol of polythiol-grafted vitamin, 40 mmol of vinyltriethoxysilane, 0.03 g of benzoin dimethyl ether and 75 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer and a thermometer. The mixture was stirred and reacted for 15 min at a temperature of 22 °C, a stirring rate of 250 r / min and a wavelength of 365 nm under ultraviolet light. The temperature was then raised to 52 °C and the reaction was continued for 4 h. After the reaction was completed, the reaction product was cooled to room temperature and the solvent was removed by rotary evaporation to obtain the polysiloxane crosslinking agent. Step S5: Weigh out 240 parts by weight of epoxy copolymer modified starch, 23 parts by weight of polysiloxane crosslinking agent, 80 parts by weight of kaolin, 0.55 parts by weight of ferrous ammonium sulfate, 2.1 parts by weight of hydrogen peroxide, 0.6 parts by weight of sodium sulfite, 0.6 parts by weight of trisodium phosphate, 33 parts by weight of sodium hydroxide, 9 parts by weight of borax, and 1700 parts by weight of deionized water, and set aside for later use; wherein, the particle size of the kaolin is 550 mesh; and the mass fraction of the hydrogen peroxide is 29%; Step S6: Add kaolin and deionized water to a mixer and stir for 25 minutes at a temperature of 22℃ and a stirring speed of 250r / min. Then add ferrous ammonium sulfate and continue stirring for 8 minutes. Next, add epoxy copolymer modified starch and heat to 45℃ and continue stirring for 8 minutes. Then add hydrogen peroxide, sodium sulfite, and trisodium phosphate and continue stirring for 4 minutes. Then add sodium hydroxide and borax and continue stirring for 2.5 hours. Finally, add polysiloxane crosslinking agent and heat to 75℃ and continue stirring for 2 hours. After the reaction is complete, cool the reaction product to room temperature to obtain environmentally friendly adhesive for cardboard.

[0025] Example 3: This embodiment describes a preparation process for an environmentally friendly adhesive for cardboard, including the following steps: Step S1: Add 10g of cassava starch and 90mL of 30% ethanol solution to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and constant pressure dropping funnel. Purge with nitrogen for protection and stir at 25℃ and 300r / min for 30min. Then, while stirring, add 0.2mol / L sodium hydroxide solution dropwise at a rate of 3 drops / s until the pH reaches 9. Then, while stirring, add 3.6g of 2-octenyl succinic anhydride dropwise. After the addition is complete, raise the temperature to 45℃ and continue stirring for 3h. After the reaction is complete, cool the reaction product to room temperature and adjust the pH to 5 with 1.2mol / L hydrochloric acid solution. Then pour the solution into anhydrous ethanol and let it stand to precipitate. Centrifuge the precipitate and place it in a vacuum drying oven to dry at 50℃ for 5h to obtain alkenyl grafted starch. Step S2: Add 5g of alkenyl grafted starch, 2.1mL of glycidyl methacrylate, 0.05g of azobisisobutyronitrile and 90mL of deionized water to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Purge with nitrogen for protection and stir at 25℃ and 300r / min for 30min. Then raise the temperature to 65℃ and continue stirring for 3h. After the reaction is complete, cool the reaction product to room temperature and pour it into anhydrous ethanol. After standing, the precipitate is formed and centrifuged. Place the precipitate in a vacuum drying oven and dry at 70℃ for 2h to obtain epoxy copolymer modified starch. Step S3: Add 10 mmol of vitamin C, 0.1 g of p-toluenesulfonic acid, 55 mmol of 3-mercaptopropionic acid and 70 mL of anhydrous toluene to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Purge with nitrogen for protection and stir at 25 °C and 300 r / min for 20 min. Then raise the temperature to 95 °C and continue stirring for 7 h. After the reaction is complete, cool the reaction product to room temperature and wash it three times with 5% sodium hydroxide solution and distilled water. Then dry it with anhydrous sodium sulfate and filter it under vacuum. Remove the solvent by rotary evaporation of the filtrate to obtain polythiol-grafted vitamin C. Step S4: 10 mmol of polythiol-grafted vitamin, 40 mmol of vinyltriethoxysilane, 0.04 g of benzoin dimethyl ether and 80 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer and a thermometer. The mixture was stirred and reacted for 20 min at 25 °C, a stirring rate of 300 r / min and a wavelength of 365 nm under ultraviolet light. The mixture was then heated to 55 °C and stirred for another 5 h. After the reaction was completed, the product was cooled to room temperature and the solvent was removed by rotary evaporation to obtain the polysiloxane crosslinking agent. Step S5: Weigh out 255 parts by weight of epoxy copolymer modified starch, 35 parts by weight of polysiloxane crosslinking agent, 85 parts by weight of kaolin, 0.6 parts by weight of ferrous ammonium sulfate, 2.2 parts by weight of hydrogen peroxide, 0.7 parts by weight of sodium sulfite, 0.7 parts by weight of trisodium phosphate, 36 parts by weight of sodium hydroxide, 10 parts by weight of borax, and 1800 parts by weight of deionized water for later use; wherein, the particle size of the kaolin is 600 mesh; and the mass fraction of the hydrogen peroxide is 30%. Step S6: Add kaolin and deionized water to a mixer and stir for 30 minutes at 25°C and 300 r / min. Then add ferrous ammonium sulfate and continue stirring for 10 minutes. Next, add epoxy copolymer modified starch and heat to 50°C and continue stirring for 10 minutes. Then add hydrogen peroxide, sodium sulfite, and trisodium phosphate and continue stirring for 5 minutes. Then add sodium hydroxide and borax and continue stirring for 3 hours. Finally, add polysiloxane crosslinking agent and heat to 80°C and continue stirring for 3 hours. After the reaction is complete, cool the reaction product to room temperature to obtain environmentally friendly adhesive for cardboard.

[0026] Comparative Example 1: This comparative example illustrates the preparation process of an environmentally friendly adhesive for cardboard, including the following steps: Step S1: Weigh out 255 parts by weight of cassava starch, 85 parts by weight of kaolin, 0.6 parts by weight of ferrous ammonium sulfate, 2.2 parts by weight of hydrogen peroxide, 0.7 parts by weight of sodium sulfite, 0.7 parts by weight of trisodium phosphate, 36 parts by weight of sodium hydroxide, 10 parts by weight of borax, and 1800 parts by weight of deionized water for later use; wherein, the particle size of the kaolin is 600 mesh; and the mass fraction of the hydrogen peroxide is 30%. Step S2: Add kaolin and deionized water to a mixer and stir for 30 minutes at 25°C and 300 r / min. Then add ferrous ammonium sulfate and continue stirring for 10 minutes. Next, add cassava starch and heat to 50°C and continue stirring for 10 minutes. Then add hydrogen peroxide, sodium sulfite, and trisodium phosphate and continue stirring for 5 minutes. Then add sodium hydroxide and borax and continue stirring for 3 hours. Finally, heat to 80°C and continue stirring for 3 hours. After the reaction is complete, cool the reaction product to room temperature to obtain environmentally friendly adhesive for cardboard.

[0027] Comparative Example 2: This comparative example illustrates the preparation process of an environmentally friendly adhesive for cardboard, including the following steps: Step S1: Add 10g of cassava starch and 90mL of 30% ethanol solution to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and constant pressure dropping funnel. Purge with nitrogen for protection and stir at 25℃ and 300r / min for 30min. Then, while stirring, add 0.2mol / L sodium hydroxide solution dropwise at a rate of 3 drops / s until the pH reaches 9. Then, while stirring, add 3.6g of 2-octenyl succinic anhydride dropwise. After the addition is complete, raise the temperature to 45℃ and continue stirring for 3h. After the reaction is complete, cool the reaction product to room temperature and adjust the pH to 5 with 1.2mol / L hydrochloric acid solution. Then pour the solution into anhydrous ethanol and let it stand to precipitate. Centrifuge the precipitate and place it in a vacuum drying oven to dry at 50℃ for 5h to obtain alkenyl grafted starch. Step S2: Add 5g of alkenyl grafted starch, 2.1mL of glycidyl methacrylate, 0.05g of azobisisobutyronitrile and 90mL of deionized water to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Purge with nitrogen for protection and stir at 25℃ and 300r / min for 30min. Then raise the temperature to 65℃ and continue stirring for 3h. After the reaction is complete, cool the reaction product to room temperature and pour it into anhydrous ethanol. After standing, the precipitate is formed and centrifuged. Place the precipitate in a vacuum drying oven and dry at 70℃ for 2h to obtain epoxy copolymer modified starch. Step S3: Weigh out 255 parts by weight of epoxy copolymer modified starch, 85 parts by weight of kaolin, 0.6 parts by weight of ferrous ammonium sulfate, 2.2 parts by weight of hydrogen peroxide, 0.7 parts by weight of sodium sulfite, 0.7 parts by weight of trisodium phosphate, 36 parts by weight of sodium hydroxide, 10 parts by weight of borax, and 1800 parts by weight of deionized water for later use; wherein, the particle size of the kaolin is 600 mesh; and the mass fraction of the hydrogen peroxide is 30%. Step S4: Add kaolin and deionized water to a mixer and stir for 30 minutes at 25°C and 300 r / min. Then add ferrous ammonium sulfate and continue stirring for 10 minutes. Next, add epoxy copolymer modified starch and heat to 50°C and continue stirring for 10 minutes. Then add hydrogen peroxide, sodium sulfite, and trisodium phosphate and continue stirring for 5 minutes. Then add sodium hydroxide and borax and continue stirring for 3 hours. Finally, heat to 80°C and continue stirring for 3 hours. After the reaction is complete, cool the reaction product to room temperature to obtain environmentally friendly adhesive for cardboard.

[0028] Comparative Example 3: This comparative example illustrates the preparation process of an environmentally friendly adhesive for cardboard, including the following steps: Step S1: 10 mmol of vitamin C, 0.1 g of p-toluenesulfonic acid, 55 mmol of 3-mercaptopropionic acid and 70 mL of anhydrous toluene were added to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Nitrogen gas was introduced for protection. The mixture was stirred at 25 °C and 300 r / min for 20 min. Then the temperature was raised to 95 °C and the mixture was stirred for 7 h. After the reaction was completed, the reaction product was cooled to room temperature and then washed three times with 5% sodium hydroxide solution and distilled water. The product was then dried with anhydrous sodium sulfate and vacuum filtered. The solvent was removed by rotary evaporation of the filtrate to obtain polythiol-grafted vitamin C. Step S2: 10 mmol of polythiol-grafted vitamin, 40 mmol of vinyltriethoxysilane, 0.04 g of benzoin dimethyl ether and 80 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer and a thermometer. The mixture was stirred and reacted for 20 min at 25 °C, a stirring rate of 300 r / min and a wavelength of 365 nm under ultraviolet light. The mixture was then heated to 55 °C and stirred for another 5 h. After the reaction was completed, the product was cooled to room temperature and the solvent was removed by rotary evaporation to obtain the polysiloxane crosslinking agent. Step S3: Weigh out 255 parts by weight of cassava starch, 35 parts by weight of polysiloxane crosslinking agent, 85 parts by weight of kaolin, 0.6 parts by weight of ferrous ammonium sulfate, 2.2 parts by weight of hydrogen peroxide, 0.7 parts by weight of sodium sulfite, 0.7 parts by weight of trisodium phosphate, 36 parts by weight of sodium hydroxide, 10 parts by weight of borax, and 1800 parts by weight of deionized water for later use; wherein, the particle size of the kaolin is 600 mesh; and the mass fraction of the hydrogen peroxide is 30%. Step S4: Add kaolin and deionized water to a mixer and stir for 30 minutes at 25°C and 300 r / min. Then add ferrous ammonium sulfate and continue stirring for 10 minutes. Next, add cassava starch and heat to 50°C and continue stirring for 10 minutes. Then add hydrogen peroxide, sodium sulfite, and trisodium phosphate and continue stirring for 5 minutes. Then add sodium hydroxide and borax and continue stirring for 3 hours. Finally, add polysiloxane crosslinking agent and heat to 80°C and continue stirring for 3 hours. After the reaction is complete, cool the reaction product to room temperature to obtain environmentally friendly adhesive for cardboard.

[0029] Comparative Example 4: This comparative example illustrates the preparation process of an environmentally friendly adhesive for cardboard, including the following steps: Step S1: Add 10g of cassava starch and 90mL of 30% ethanol solution to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and constant pressure dropping funnel. Purge with nitrogen for protection and stir at 25℃ and 300r / min for 30min. Then, while stirring, add 0.2mol / L sodium hydroxide solution dropwise at a rate of 3 drops / s until the pH reaches 9. Then, while stirring, add 3.6g of 2-octenyl succinic anhydride dropwise. After the addition is complete, raise the temperature to 45℃ and continue stirring for 3h. After the reaction is complete, cool the reaction product to room temperature and adjust the pH to 5 with 1.2mol / L hydrochloric acid solution. Then pour the solution into anhydrous ethanol and let it stand to precipitate. Centrifuge the precipitate and place it in a vacuum drying oven to dry at 50℃ for 5h to obtain alkenyl grafted starch. Step S2: Add 5g of alkenyl grafted starch, 2.1mL of glycidyl methacrylate, 0.05g of azobisisobutyronitrile and 90mL of deionized water to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Purge with nitrogen for protection and stir at 25℃ and 300r / min for 30min. Then raise the temperature to 65℃ and continue stirring for 3h. After the reaction is complete, cool the reaction product to room temperature and pour it into anhydrous ethanol. After standing, the precipitate is formed and centrifuged. Place the precipitate in a vacuum drying oven and dry at 70℃ for 2h to obtain epoxy copolymer modified starch. Step S3: Weigh out 255 parts by weight of epoxy copolymer modified starch, 35 parts by weight of vinyltriethoxysilane, 85 parts by weight of kaolin, 0.6 parts by weight of ferrous ammonium sulfate, 2.2 parts by weight of hydrogen peroxide, 0.7 parts by weight of sodium sulfite, 0.7 parts by weight of trisodium phosphate, 36 parts by weight of sodium hydroxide, 10 parts by weight of borax, and 1800 parts by weight of deionized water for later use; wherein, the particle size of the kaolin is 600 mesh; and the mass fraction of the hydrogen peroxide is 30%. Step S4: Add kaolin and deionized water to a mixer and stir for 30 minutes at 25°C and 300 r / min. Then add ferrous ammonium sulfate and continue stirring for 10 minutes. Next, add epoxy copolymer modified starch and heat to 50°C and continue stirring for 10 minutes. Then add hydrogen peroxide, sodium sulfite, and trisodium phosphate and continue stirring for 5 minutes. Then add sodium hydroxide and borax and continue stirring for 3 hours. Finally, add vinyltriethoxysilane and heat to 80°C and continue stirring for 3 hours. After the reaction is complete, cool the reaction product to room temperature to obtain environmentally friendly adhesive for cardboard.

[0030] Performance testing Two birch blocks, each 30mm × 25mm × 10mm in size, were used. One 30mm × 25mm side was coated with adhesive (using the same environmentally friendly adhesive used for cardboard in Examples 1-3 and Comparative Examples 1-4, respectively). The glued sides of the two birch blocks were then bonded together and pressed with a 25kg weight for 24 hours to obtain the test specimen. The shear strength of the test specimen was tested according to GB / T 17517-1998, and the bonding performance was evaluated using the shear strength. The test specimen was then immersed in a 60℃ water bath, and the time for automatic glue separation was observed. The water resistance was evaluated using the automatic glue separation time. The test results are as follows: Figure 1 As shown.

[0031] See Figure 1 As shown, a comparison between Examples 1-3 and Comparative Examples 1-4 reveals that the environmentally friendly adhesive for cardboard of this application possesses excellent bonding and water resistance properties. Specifically, a comparison between Example 3 and Comparative Example 1 shows that using epoxy copolymer-modified starch as the main raw material to replace ordinary starch and adding a polysiloxane crosslinking agent significantly improves the bonding and water resistance properties of the environmentally friendly adhesive for cardboard. A comparison between Example 3 and Comparative Example 2 shows that adding a polysiloxane crosslinking agent significantly improves the bonding and water resistance properties of the environmentally friendly adhesive for cardboard. A comparison between Example 3 and Comparative Example 3 shows that using epoxy copolymer-modified starch as the main raw material to replace ordinary starch significantly improves the bonding and water resistance properties of the environmentally friendly adhesive for cardboard. A comparison between Example 3 and Comparative Example 4 shows that using a polysiloxane crosslinking agent to replace vinyltriethoxysilane significantly improves the bonding and water resistance properties of the environmentally friendly adhesive for cardboard.

[0032] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0033] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. An environmentally friendly adhesive for cardboard, characterized in that, Includes the following components by weight: The mixture contains 225-255 parts of epoxy copolymer modified starch, 11-35 parts of polysiloxane crosslinking agent, 75-85 parts of kaolin, 0.5-0.6 parts of ferrous ammonium sulfate, 2-2.2 parts of hydrogen peroxide, 0.5-0.7 parts of sodium sulfite, 0.5-0.7 parts of trisodium phosphate, 30-36 parts of sodium hydroxide, 8-10 parts of borax, and 1600-1800 parts of deionized water. The epoxy copolymer-modified starch is prepared by the following steps: Step A1: Stir the starch and ethanol solution to react, then add sodium hydroxide solution to adjust the pH, then add 2-octenyl succinic anhydride and continue stirring to react. After the reaction is complete, cool the reaction product, then adjust the pH with hydrochloric acid solution, then pour it into anhydrous ethanol, then let it stand to precipitate, then centrifuge, and dry the precipitate to obtain alkenyl grafted starch. Step A2: The alkenyl grafted starch, glycidyl methacrylate, azobisisobutyronitrile and deionized water were stirred and reacted. After the reaction was completed, the reaction product was cooled and then poured into anhydrous ethanol. After standing, the precipitate was precipitated, centrifuged, and the precipitate was dried to obtain epoxy copolymer modified starch. The polysiloxane crosslinking agent is prepared by the following steps: Step B1: Vitamin C, p-toluenesulfonic acid, 3-mercaptopropionic acid and anhydrous toluene are stirred and reacted. After the reaction is completed, the reaction product is cooled and then washed with sodium hydroxide solution and distilled water in sequence. After drying, it is filtered under vacuum and the filtrate is evaporated by rotary evaporation to obtain polythiol-grafted vitamin. Step B2: The polythiol-grafted vitamin, vinyltriethoxysilane, benzoin dimethyl ether and anhydrous ethanol are stirred and reacted. After the reaction is completed, the reaction product is cooled and then rotary evaporated to obtain the polysiloxane crosslinking agent.

2. The environmentally friendly adhesive for cardboard according to claim 1, characterized in that, The ratio of starch, ethanol solution and 2-octenylsuccinic anhydride used in step A1 is 10g: 80-90mL: 0.8-3.6g.

3. The environmentally friendly adhesive for cardboard according to claim 1, characterized in that, The starch mentioned in step A1 is one of corn starch, potato starch, and cassava starch; the volume fraction of the ethanol solution is 20-30%; the molar concentration of the sodium hydroxide solution is 0.1-0.2 mol / L; and the molar concentration of the hydrochloric acid solution is 1-1.2 mol / L.

4. The environmentally friendly adhesive for cardboard according to claim 1, characterized in that, The ratio of alkenyl grafted starch, glycidyl methacrylate, azobisisobutyronitrile, and deionized water in step A2 is 5g: 0.5-2.1mL: 0.03-0.05g: 80-90mL.

5. The environmentally friendly adhesive for cardboard according to claim 1, characterized in that, The ratio of vitamin C, p-toluenesulfonic acid, 3-mercaptopropionic acid, and anhydrous toluene in step B1 is 10 mmol: 0.08-0.1 g: 50-55 mmol: 60-70 mL.

6. The environmentally friendly adhesive for cardboard according to claim 1, characterized in that, The sodium hydroxide solution in step B1 has a mass fraction of 3-5%.

7. The environmentally friendly adhesive for cardboard according to claim 1, characterized in that, The ratio of the polythiol-grafted vitamin, vinyltriethoxysilane, benzoin dimethyl ether, and anhydrous ethanol in step B2 is 10 mmol: 40 mmol: 0.02-0.04 g: 70-80 mL.

8. A preparation process for an environmentally friendly adhesive for cardboard as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Weigh out the following components by weight: 225-255 parts epoxy copolymer modified starch, 11-35 parts polysiloxane crosslinking agent, 75-85 parts kaolin, 0.5-0.6 parts ferrous ammonium sulfate, 2-2.2 parts hydrogen peroxide, 0.5-0.7 parts sodium sulfite, 0.5-0.7 parts trisodium phosphate, 30-36 parts sodium hydroxide, 8-10 parts borax, and 1600-1800 parts deionized water. Set aside. Step 2: Add kaolin and deionized water to a mixer and stir for 20-30 minutes at a temperature of 20-25℃ and a stirring speed of 200-300 r / min. Then add ferrous ammonium sulfate and continue stirring for 5-10 minutes. Next, add epoxy copolymer modified starch and heat to 40-50℃ and continue stirring for 5-10 minutes. Then add hydrogen peroxide, sodium sulfite, and trisodium phosphate and continue stirring for 3-5 minutes. Then add sodium hydroxide and borax and continue stirring for 2-3 hours. Finally, add polysiloxane crosslinking agent and heat to 70-80℃ and continue stirring for 1-3 hours. After the reaction is complete, cool the reaction product to room temperature to obtain environmentally friendly adhesive for cardboard.

9. The preparation process of an environmentally friendly adhesive for cardboard according to claim 8, characterized in that, The kaolin has a particle size of 500-600 mesh; the hydrogen peroxide has a mass fraction of 28-30%.

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