A process for the production of a multi-ply corrugated paperboard

Abstract

The present application relates to the field of packaging materials, and discloses a production process of multilayer corrugated paper, which comprises the following steps: S1, preparing an impregnation solution added with modified nano-titanium dioxide; S2, preparing modified polyurethane coating added with modified nano-zirconium dioxide; S3, preparing modified silicate adhesive added with polyvinyl alcohol; S4, immersing corrugated paper core paper, surface paper and bottom paper in the impregnation solution, coating the modified polyurethane coating after drying, curing at high temperature, processing the core paper into UV wave shape through corrugated rollers, coating the modified silicate adhesive on the surface, adhering the surface paper and the bottom paper, bonding after heating and cooling, and obtaining multilayer corrugated paperboard. The present application adds modified nano-titanium dioxide in the impregnation solution, adds modified nano-zirconium dioxide in the polyurethane, and adds polyvinyl alcohol in the adhesive, so that the moisture-proof, mildew-proof, fire-resistant capacity of the corrugated paper is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of packaging materials, in particular to a production process of a multi-layer corrugated paperboard. BACKGROUND

[0002] The corrugated paperboard is a board-shaped object formed by bonding the face paper, the bottom paper and the core paper processed into a wave shape by a corrugated roller, has the advantages of low cost, light weight, easy processing, large strength, excellent printing adaptability, convenient storage and transportation, and is widely used.

[0003] The corrugated paper is prone to moisture absorption, mildew and insect damage due to its main component of paper fiber. The existing corrugated paperboard is usually coated with waterproof material on the surface of the corrugated paper, but the waterproof material has poor waterproof durability, and is prone to water seepage when immersed in water for a long time, and cannot achieve complete waterproof, only slight waterproof on the surface. In addition, the main component of the paper fiber is plant cellulose, which is prone to insect damage, and the plant cellulose is flammable, which poses a fire safety hazard during storage and transportation. SUMMARY

[0004] In order to overcome the above technical problems, the purpose of the present application is to provide a production process of a multi-layer corrugated paperboard, which has the characteristics of moisture-proof, mildew-resistant, insect-resistant and flame-retardant.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] A production process of a multi-layer corrugated paperboard, comprising the following steps:

[0007] (1) Immersing the corrugated paper core paper, face paper and bottom paper in an impregnation liquid;

[0008] (2) After drying, uniformly coating the surface of the core paper, face paper and bottom paper with modified polyurethane paint, curing at 105 DEG C for 1h, and standby;

[0009] (3) Processing the core paper into a UV wave shape through a corrugated roller, and coating a modified silicate adhesive on the surface;

[0010] (4) Adhering the core paper between the face paper and the bottom paper, placing at room temperature for 2h, drying at 110 DEG C for 12h, and obtaining a multi-layer corrugated paperboard after cooling;

[0011] The preparation method of the modified polyurethane paint comprises the following steps:

[0012] S1: adding a nano zirconium dioxide dispersion liquid and a mixed liquid into a reaction kettle, heating to 80 DEG C, stirring for 2h, filtering, washing and drying to obtain modified nano zirconium dioxide;

[0013] S2: mixing polycaprolactone diol and isophorone diisocyanate, adding dibutyl tin dilaurate, stirring at 40℃ for 24h, increasing temperature to 60℃, adding modified nano zirconium dioxide, keeping for 2h, adding acetone for dilution, then adding camphor wood powder and stirring for 1h to obtain modified polyurethane coating.

[0014] As a further scheme of the present application: the adding amount of the mixed solution in S1 is 1mL:1g:10mL.

[0015] As a further scheme of the present application: the adding amount of polycaprolactone diol, isophorone diisocyanate, dibutyl tin dilaurate, modified nano zirconium dioxide, acetone and camphor wood powder is 200g:80-90g:2g:5-10g:100mL:1-2g.

[0016] As a further scheme of the present application: the preparation method of the impregnating solution comprises the following steps:

[0017] A1: adding N-(β-aminoethyl)-γ-aminopropyl triethoxysilane, propyl triethoxysilane, deionized water and ethanol into a reaction bottle, uniformly mechanically stirring, adjusting pH to 3-4, increasing temperature to 40℃ for 5h, adjusting pH to 7-8, and then removing ethanol under reduced pressure to obtain a silanol solution;

[0018] A2: adding nano titanium dioxide into deionized water and ultrasonically dispersing, then adding propyl triethoxysilane dropwise and reacting at 80℃ for 2h, and then filtering, washing and drying to obtain modified nano titanium dioxide;

[0019] A3: adding the silanol solution and the modified nano titanium dioxide into propyl triethoxysilane, increasing temperature to 40℃, and keeping stirring for 1h to obtain an impregnating solution.

[0020] As a further scheme of the present application: the volume ratio of N-(β-aminoethyl)-γ-aminopropyl triethoxysilane, propyl triethoxysilane, deionized water and ethanol in step A1 is 1:10:30:10.

[0021] As a further scheme of the present application: the adding amount of nano titanium dioxide, deionized water and propyl triethoxysilane in step A2 is 1g:10mL:1mL.

[0022] As a further scheme of the present application: the adding amount of the silanol solution, modified nano titanium dioxide and propyl triethoxysilane in step A3 is 10mL:1g:5mL.

[0023] As a further scheme of the present application: the preparation method of the modified silicate adhesive is as follows:

[0024] Into the mixed solution of potassium silicate and sodium silicate, drop in 10% by mass polyvinyl alcohol solution component one, heat to 60℃ and stir for 1h, add emulsifier ABIL EM180 and stir for 0.5h, add hydroquinone and oxalic acid, heat to 80℃ and stir for 1h, then drop in 10% by mass polyvinyl alcohol solution component two, and stir for 24h to obtain the modified silicate adhesive.

[0025] As a further scheme of the application: the mixed solution of potassium silicate and sodium silicate, 10% by mass polyvinyl alcohol solution component one, emulsifier ABIL EM180, hydroquinone, oxalic acid and 10% by mass polyvinyl alcohol solution component two are added in the amount of 200mL:6mL:1g:4g:6g:42mL; the mixed solution is obtained by mixing potassium silicate, sodium silicate and deionized water in the ratio of 1g:3g:6mL.

[0026] The beneficial effects of the application are:

[0027] The application introduces amino groups by adding N-(β-aminoethyl)-γ-aminopropyl triethoxysilane to modify the preparation of silanol from propyl triethoxysilane, so that when the corrugated paper is compounded with the modified polyurethane coating, the -NH2 in the impregnation solution and the residual -NCO groups in the polyurethane occur crosslinking reaction, increasing the composite strength and compactness, and improving the waterproof ability; since the surface of nano titanium dioxide has more active hydroxyl groups, the propyl triethoxysilane can be grafted to the surface of the modified nano titanium dioxide through the hydroxyl groups, at this time the hydroxyl groups on the surface of the nano titanium dioxide are reduced, and the alkyl groups in the propyl triethoxysilane are arranged outward, improving the hydrophobicity of the nano titanium dioxide, which not only improves the dispersibility of the titanium dioxide, but also improves the water resistance of the corrugated paper, and at the same time, the light-shielding property of the titanium dioxide also improves the flame retardant property of the corrugated paper.

[0028] There are also many active hydroxyl groups on the surface of nano zirconium dioxide, which can be grafted with 2,2-dimethylol propionic acid and 1,2-epoxy propyl phosphonic acid; the nano zirconium dioxide grafted with 2,2-dimethylol propionic acid can be polymerized into the polyurethane molecule through the chain extension reaction of polyurethane, and is not easy to separate from the polyurethane coating, so that the coating has strong mechanical properties; after the 1,2-epoxy propyl phosphonic acid is grafted on the surface of the nano zirconium dioxide, the epoxy propyl groups are arranged outward, improving the hydrophobicity of the surface of the nano zirconium dioxide, which not only improves the dispersibility of the nano zirconium dioxide, but also improves the water resistance of the polyurethane, and at the same time, the nano zirconium dioxide has excellent heat insulation effect due to its low heat transfer coefficient, which enhances the flame retardant ability; as a broad-spectrum antibiotic, the 1,2-epoxy propyl phosphonic acid also makes the coating have anti-mildew effect after being grafted on the surface of the nano zirconium dioxide; the camphor wood powder contains camphor ketone, eucalyptol and other chemicals, and has certain insect repellent ability due to its unique chemical odor, which can prevent the corrugated paper from being damaged by insects.

[0029] The silicate adhesive is prepared by using potassium silicate and sodium silicate and adding polyvinyl alcohol, potassium atoms reduce the exchange between ions and water molecules in the adhesive due to the large atomic radius of potassium atoms, and the water resistance is improved, the hydroxyl groups in the polyvinyl alcohol crosslink with the hydroxyl groups in the silicate to form a polymer network, and the water resistance of the adhesive is improved, and the hydroquinone is a free radical trapping agent, and the oxalic acid has a certain reducing property, and the antioxidant capacity of the polyvinyl alcohol is improved, so that the adhesive has long-lasting water resistance, the hydroxyl groups in the adhesive can also react and crosslink with the phosphoric acid groups grafted on the modified nano zirconium dioxide in the polyurethane coating, and the bonding strength is improved, and the batch addition of polyvinyl alcohol and the addition of emulsifier avoid the gelation of the silicate adhesive. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] Embodiment 1

[0032] A prepared impregnating solution has the following preparation method:

[0033] Take N-(β-aminoethyl)-γ-aminopropyl triethoxysilane 1 mL, propyl triethoxysilane 10 mL, deionized water 30 mL, ethanol 10 mL, mix, stir at room temperature for 0.5 h, add hydrochloric acid solution dropwise to adjust the pH value to about 4, then heat to 40℃ and stir for 5 h, add sodium hydroxide solution dropwise to adjust the pH value to about 7, and then remove ethanol under reduced pressure to obtain a silanol solution; 1 g of nano titanium dioxide is added to 10 mL of deionized water and ultrasonically dispersed, 1 mL of propyl triethoxysilane is added, and stirring is carried out at 80℃ for 2 h, then the temperature is lowered to room temperature, filtration is carried out, washing is carried out, and vacuum drying is carried out at 60℃ for 12 h to obtain modified nano titanium dioxide; 50 mL of the silanol solution and 1 g of the modified nano titanium dioxide are added to 25 mL of propyl triethoxysilane, and stirring is carried out at 40℃ for 1 h to obtain an impregnating solution.

[0034] Embodiment 2

[0035] A prepared modified polyurethane coating has the following preparation method:

[0036] 5g of nano-zirconia was added to 50mL of deionized water and ultrasonically dispersed for 0.5h. The temperature was raised to 80℃. 5g of 2,2-dimethylolpropionic acid, 2.5g of 1,2-epoxypropylphosphonic acid, 20mL of ethanol, and 20mL of deionized water were mixed and added dropwise to the nano-zirconia dispersion. The mixture was stirred and reacted for 2h. The mixture was cooled to room temperature, filtered, washed, and vacuum dried at 80℃ for 12h. After grinding, modified nano-zirconia was obtained. 50g of polycaprolactone diol and 20g of isophorone diisocyanate were mixed, and 0.5g of dibutyltin dilaurate was added. The mixture was stirred and reacted at 40℃ for 24h. The temperature was raised to 60℃, and 1.3g of modified nano-zirconia was added for chain extension reaction for 2h. 25mL of acetone was added for dilution, and 0.3g of camphor wood powder was added and stirred for 1h to obtain modified polyurethane coating.

[0037] Example 3

[0038] The present invention provides a modified polyurethane coating, prepared by the following method:

[0039] 5g of nano-zirconia was added to 50mL of deionized water and ultrasonically dispersed for 0.5h. The temperature was raised to 80℃. 7.5g of 2,2-dimethylolpropionic acid, 3.8g of 1,2-epoxypropylphosphonic acid, 20mL of ethanol, and 20mL of deionized water were mixed and added dropwise to the nano-zirconia dispersion. The mixture was stirred and reacted for 2h. The mixture was cooled to room temperature, filtered, washed, and vacuum dried at 80℃ for 12h. After grinding, modified nano-zirconia was obtained. 50g of polycaprolactone diol and 21g of isophorone diisocyanate were mixed, and 0.5g of dibutyltin dilaurate was added. The mixture was stirred and reacted at 40℃ for 24h. The temperature was raised to 60℃, and 1.9g of modified nano-zirconia was added for chain extension reaction for 2h. 25mL of acetone was added for dilution, and 0.4g of camphor wood powder was added and stirred for 1h to obtain modified polyurethane coating.

[0040] Example 4

[0041] The present invention provides a modified polyurethane coating, prepared by the following method:

[0042] 5g of nano-zirconia was added to 50mL of deionized water and ultrasonically dispersed for 0.5h. The temperature was raised to 80℃. 10g of 2,2-dimethylolpropionic acid, 5g of 1,2-epoxypropylphosphonic acid, 20mL of ethanol, and 20mL of deionized water were mixed and added dropwise to the nano-zirconia dispersion. The mixture was stirred and reacted for 2h. The mixture was cooled to room temperature, filtered, washed, and vacuum dried at 80℃ for 12h. After grinding, modified nano-zirconia was obtained. 50g of polycaprolactone diol and 22g of isophorone diisocyanate were mixed, and 0.5g of dibutyltin dilaurate was added. The mixture was stirred and reacted at 40℃ for 24h. The temperature was raised to 60℃, and 2.5g of modified nano-zirconia was added for chain extension reaction for 2h. 25mL of acetone was added for dilution, and 0.5g of camphor wood powder was added and stirred for 1h to obtain modified polyurethane coating.

[0043] Example 5

[0044] The present invention provides a modified silicate adhesive, prepared by the following method:

[0045] 10g of potassium silicate and 30g of sodium silicate were added to 60mL of water to prepare a mixture. 3mL of 10% polyvinyl alcohol solution was added dropwise to the mixture, the temperature was raised to 60℃ and stirred for 1h. 0.5g of emulsifier ABIL EM180 was added and stirred for 0.5h. 2g of hydroquinone and 3g of oxalic acid were added, the temperature was raised to 80℃ and stirred for 1h. Then 21mL of 10% polyvinyl alcohol solution was added dropwise and stirred for 24h to obtain the modified silicate adhesive.

[0046] Example 6

[0047] The present invention provides a multi-layer corrugated cardboard, the production process of which is as follows:

[0048] The corrugated core paper, face paper, and back paper are immersed in the impregnation solution of Example 1, taken out and dried, and then coated with the modified polyurethane coating of Example 2. The coating is cured at 105°C for 1 hour and set aside. The core paper is processed into a UV waveform by a corrugating roller, and then coated with the modified silicate adhesive of Example 5. The adhesive is then adhered between the face paper and the back paper. The core paper is placed at room temperature for 2 hours and then heated to 110°C for 12 hours to dry. After cooling, multi-layer corrugated cardboard is obtained.

[0049] Example 7

[0050] The present invention provides a multi-layer corrugated cardboard, the production process of which is as follows:

[0051] The corrugated core paper, face paper, and back paper are immersed in the impregnation solution of Example 1, taken out and dried, and then coated with the modified polyurethane coating of Example 3. The coating is cured at 105°C for 1 hour and set aside. The core paper is processed into a UV waveform by a corrugating roller, and then coated with the modified silicate adhesive of Example 5. The adhesive is then adhered between the face paper and the back paper. The core paper is placed at room temperature for 2 hours and then heated to 110°C for 12 hours to dry. After cooling, multi-layer corrugated cardboard is obtained.

[0052] Example 8

[0053] The present invention provides a multi-layer corrugated cardboard, the production process of which is as follows:

[0054] The corrugated core paper, face paper, and back paper are immersed in the impregnation solution in Example 1, taken out and dried, and then coated with the modified polyurethane coating in Example 4. The coating is cured at 105°C for 1 hour and set aside. The core paper is processed into a UV waveform by a corrugating roller, and then coated with the modified silicate adhesive in Example 5. The adhesive is then adhered between the face paper and the back paper. The core paper is placed at room temperature for 2 hours and then heated to 110°C for 12 hours to dry. After cooling, a multi-layer corrugated cardboard is obtained.

[0055] Comparative Example 1

[0056] An impregnation solution, prepared by the following method:

[0057] Take 1 mL of N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, 10 mL of propyltriethoxysilane component one, 30 mL of deionized water, and 10 mL of ethanol, mix them, stir at room temperature for 0.5 h, add hydrochloric acid solution to adjust the pH to about 4, then heat to 40 °C and stir for 5 h, add sodium hydroxide solution to adjust the pH to about 7, remove ethanol under reduced pressure to obtain silanol solution, take 50 mL of silanol solution and add it to 25 mL of propyltriethoxysilane, stir at 40 °C for 1 h to mix evenly to obtain impregnation solution.

[0058] Comparative Example 2

[0059] A polyurethane coating, prepared by the following method:

[0060] Mix 50g of polycaprolactone diol with 21g of isophorone diisocyanate, add 0.5g of dibutyltin dilaurate, stir at 40℃ for 24h, raise the temperature to 60℃, add 0.15g of acrylic acid for chain extension reaction for 2h, add 25mL of acetone to dilute, and then add 0.4g of camphor wood powder and stir for 1h to obtain polyurethane coating.

[0061] Comparative Example 3

[0062] A silicate adhesive, prepared by the following method.

[0063] 10g of potassium silicate and 30g of sodium silicate were added to 60mL of water to prepare a mixture. The mixture was heated to 60℃ and stirred for 1 hour. 0.5g of emulsifier ABIL EM180 was added and stirred for 0.5 hours. 2g of hydroquinone and 3g of oxalic acid were added. The mixture was heated to 80℃ and stirred for 1 hour. The reaction was carried out for 24 hours to obtain a silicate adhesive.

[0064] Comparative Example 4

[0065] A multi-layer corrugated paper, the production process of which is as follows:

[0066] The corrugated core paper, face paper, and back paper are immersed in the impregnation solution of Example 1, taken out and dried, and then coated with the modified polyurethane coating of Comparative Example 2. They are cured at 105°C for 1 hour and set aside. The core paper is processed into a UV waveform by a corrugating roller, and then coated with the modified silicate adhesive of Example 5. It is then adhered between the face paper and the back paper. After being placed at room temperature for 2 hours, the temperature is raised to 110°C and dried for 12 hours. After cooling, multi-layer corrugated cardboard is obtained.

[0067] Comparative Example 5

[0068] A multi-layer corrugated paper, the production process of which is as follows:

[0069] The corrugated core paper, face paper, and back paper are immersed in the impregnation solution of Example 1, taken out and dried, and then coated with the modified polyurethane coating of Example 3. The coating is cured at 105°C for 1 hour and set aside. The core paper is processed into a UV waveform by a corrugating roller, and then coated with the modified silicate adhesive of Comparative Example 3. The adhesive is then adhered between the face paper and the back paper. The core paper is placed at room temperature for 2 hours and then heated to 110°C for 12 hours to dry. After cooling, a multi-layer corrugated cardboard is obtained.

[0070] Comparative Example 6

[0071] A multi-layer corrugated paper, the production process of which is as follows:

[0072] The corrugated core paper, face paper, and back paper are immersed in the impregnation solution of Example 1, taken out and dried, and then coated with the modified polyurethane coating of Comparative Example 2. They are cured at 105°C for 1 hour and set aside. The core paper is processed into a UV waveform by a corrugating roller, and then coated with the modified silicate adhesive of Comparative Example 3. It is then adhered between the face paper and the back paper. After being placed at room temperature for 2 hours, it is heated to 110°C and dried for 12 hours. After cooling, multi-layer corrugated cardboard is obtained.

[0073] Comparative Example 7

[0074] A multi-layer corrugated paper, the production process of which is as follows:

[0075] The corrugated core paper, face paper, and back paper are immersed in the impregnation solution in Comparative Example 1, taken out and dried, and then coated with the modified polyurethane coating in Example 3. The coating is cured at 105°C for 1 hour and set aside. The core paper is processed into a UV waveform by a corrugating roller, and then coated with the modified silicate adhesive in Example 5. The adhesive is then adhered between the face paper and the back paper. The core paper is placed at room temperature for 2 hours and then heated to 110°C for 12 hours to dry. After cooling, a multi-layer corrugated cardboard is obtained.

[0076] Comparative Example 8

[0077] A multi-layer corrugated paper, the production process of which is as follows:

[0078] The corrugated core paper, face paper, and back paper are immersed in the impregnation solution of Comparative Example 1, taken out and dried, and then coated with the modified polyurethane coating of Comparative Example 2. They are cured at 105°C for 1 hour and set aside. The core paper is processed into a UV waveform by a corrugating roller, and then coated with the modified silicate adhesive of Example 5. It is then adhered between the face paper and the back paper. After being placed at room temperature for 2 hours, it is heated to 110°C and dried for 12 hours. After cooling, multi-layer corrugated cardboard is obtained.

[0079] Comparative Example 9

[0080] A multi-layer corrugated paper, the production process of which is as follows:

[0081] The corrugated core paper, face paper, and back paper are immersed in the impregnation solution of Comparative Example 1, taken out and dried, and then coated with the modified polyurethane coating of Example 3. The coating is cured at 105°C for 1 hour and set aside. The core paper is processed into a UV waveform by a corrugating roller, and then coated with the modified silicate adhesive of Comparative Example 3. The adhesive is then adhered between the face paper and the back paper. The core paper is placed at room temperature for 2 hours and then heated to 110°C for 12 hours to dry. After cooling, a multi-layer corrugated cardboard is obtained.

[0082] Comparative Example 10

[0083] A multi-layer corrugated paper, the production process of which is as follows:

[0084] The corrugated core paper, face paper, and back paper are immersed in the impregnation solution of Comparative Example 1, taken out and dried, and then coated with the modified polyurethane coating of Comparative Example 2. The coating is cured at 105°C for 1 hour and set aside. The core paper is processed into a UV waveform by a corrugating roller, and then coated with the modified silicate adhesive of Comparative Example 3. The adhesive is then adhered between the face paper and the back paper. The core paper is placed at room temperature for 2 hours and then heated to 110°C for 12 hours to dry. After cooling, multi-layer corrugated cardboard is obtained.

[0085] Comparative Example 11

[0086] A multi-layer corrugated paper, the production process of which is as follows:

[0087] After the corrugated core paper is processed into a UV waveform by a corrugating roller, the modified silicate adhesive from Example 5 is coated on the surface and adhered between the face paper and the back paper. After being placed at room temperature for 2 hours, the temperature is raised to 110°C and dried for 12 hours. After cooling, multi-layer corrugated cardboard is obtained.

[0088] Performance testing

[0089] The corrugated paper obtained in Examples 6-8 and Comparative Examples 4-11 were subjected to the following performance tests: The edge crush strength of the corrugated paperboard was tested according to GB / T6546-1998. The corrugated paperboard was placed at 40°C and 90% humidity for 72 hours, then dried at 60°C for 6 hours. The edge crush strength of the dried corrugated paperboard was then tested. The bursting strength was determined according to GB / T6545-1998. Flame retardancy was tested using an oxygen index meter according to the ASTM D2863 oxygen index test standard. The test results are shown in Table 1.

[0090] Table 1: Performance Tests

[0091]

[0092]

[0093] As can be seen from the data in Table 1, the multi-layer corrugated paperboard prepared in Examples 6-8 of the present invention has high mechanical strength and the strength decreases only slightly before and after being exposed to moisture, indicating that the corrugated paperboard has strong hydrophobicity and exhibits excellent moisture resistance. An oxygen index greater than 27% indicates a flame-retardant material. The multi-layer corrugated paperboard prepared in Examples 6-8 and Comparative Example 5 of the present invention has an oxygen index greater than 27% because flame-retardant materials are added to both the impregnation liquid and the coating, thus exhibiting excellent flame-retardant effects.

[0094] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A production process for multi-layer corrugated cardboard, characterized in that, Includes the following steps: (1) Immerse the corrugated paper core, face paper, and back paper in the impregnation solution; (2) After drying, the core paper, face paper and back paper are evenly coated with modified polyurethane coating and cured at 105℃ for 1 hour for later use. (3) After the core paper is processed into a UV waveform by a corrugated roll, a modified silicate adhesive is coated on the surface; (4) Adhere the core paper between the face paper and the back paper, place it at room temperature for 2 hours, heat it to 110°C and dry it for 12 hours, and then cool it to obtain multi-layer corrugated cardboard. The preparation method of modified polyurethane coatings includes the following steps: S1: Add the nano-zirconia dispersion and mixture to the reaction vessel, heat to 80℃, stir and react for 2 hours, filter, wash and dry to obtain modified nano-zirconia; S2: Mix polycaprolactone diol with isophorone diisocyanate, add dibutyltin dilaurate, stir and react at 40°C for 24 hours, raise the temperature to 60°C, add modified nano-zirconia and keep warm for 2 hours, add acetone to dilute, and then add camphor wood powder and stir for 1 hour to obtain modified polyurethane coating. The method for preparing the impregnation solution includes the following steps: A1: N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, propyltriethoxysilane, deionized water and ethanol were added to a reaction flask and mechanically stirred until homogeneous. The pH was adjusted to 3-4, and the temperature was raised to 40℃ for 5 hours. The pH was then adjusted to 7-8, and the ethanol was removed under reduced pressure to obtain a silanol solution. A2: Add nano-titanium dioxide to deionized water and disperse it by ultrasonication. Add propyltriethoxysilane dropwise and react at 80°C for 2 hours. Filter, wash and dry to obtain modified nano-titanium dioxide. A3: Add silanol solution and modified nano-titanium dioxide to propyltriethoxysilane, heat to 40°C, keep warm and stir for 1 hour to obtain impregnation solution; The preparation method of modified silicate adhesive is as follows: Add 10% polyvinyl alcohol solution component one (by mass) to a mixed solution of potassium silicate and sodium silicate, heat to 60°C and stir for 1 hour, add emulsifier ABIL EM180 and stir for 0.5 hours, add hydroquinone and oxalic acid, heat to 80°C and stir for 1 hour, then add 10% polyvinyl alcohol solution component two (by mass) and stir for 24 hours to obtain a modified silicate adhesive.

2. The production process of multi-layer corrugated cardboard according to claim 1, characterized in that, The ratio of nano-zirconia to deionized water in the S1 mixture is 1 mL: 1 g: 10 mL.

3. The production process of multi-layer corrugated cardboard according to claim 1, characterized in that, The addition amounts of polycaprolactone diol, isophorone diisocyanate, dibutyltin dilaurate, modified nano-zirconia, acetone, and camphor wood powder in S2 are 200g, 80-90g, 2g, 5-10g, 100mL, and 1-2g, respectively.

4. The production process of multi-layer corrugated cardboard according to claim 1, characterized in that, In step A1, the volume ratio of N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, propyltriethoxysilane, deionized water, and ethanol is 1:10:30:

10.

5. The production process of multi-layer corrugated cardboard according to claim 1, characterized in that, In step A2, the ratio of nano-titanium dioxide:deionized water:propyltriethoxysilane added is 1g:10mL:1mL.

6. The production process of multi-layer corrugated cardboard according to claim 1, characterized in that, In step A3, the silanol solution consists of modified nano-titanium dioxide and propyltriethoxysilane in a ratio of 10 mL: 1 g: 5 mL.

7. The production process of multi-layer corrugated cardboard according to claim 1, characterized in that, The addition amounts of the mixed solution of potassium silicate and sodium silicate, the 10% polyvinyl alcohol solution (component 1), the emulsifier ABIL EM180, hydroquinone, oxalic acid, and the 10% polyvinyl alcohol solution (component 2) are 200 mL: 6 mL: 1 g: 4 g: 6 g: 42 mL.

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