Moisture-proof and flame-retardant corrugated paperboard and preparation process thereof

Abstract

The application discloses a kind of damp-proof flame-retardant corrugated paperboard and preparation process thereof, belong to paperboard technical field, to solve the technical problems that damp-proof performance, flame-retardant performance and flat pressure strength of corrugated paperboard in prior art need to be further improved, specifically including first plant fiber and waste carton are mixed, and after infiltration, deinking agent is crushed, then with functional inorganic filler, phosphoric acid modified piperazine and preservative are mixed and stirred, are sent into paper machine and are beaten, are formed, are dehydrated, are dried, and are pressed into B type wave-shaped corrugated, after cooling roll shaping, adhesive is evenly coated on the peak tip of corrugated core by roll coater, face paper is pasted on both sides of corrugated core, drying is obtained, and corrugated paperboard is obtained.The application is by the synergistic effect between modified calcium carbonate, modified silicon dioxide, modified aluminum oxide, phosphoric acid modified piperazine and polyurethane emulsion, further improve the damp-proof performance, flame-retardant performance and flat pressure strength of corrugated paperboard.

Description

Technical Field

[0001] This invention relates to the field of paperboard technology, specifically to a moisture-proof and flame-retardant corrugated paperboard and its preparation process. Background Technology

[0002] Corrugated cardboard, with its advantages of being lightweight, low-cost, and recyclable, is widely used in various fields such as logistics packaging, warehousing and transportation, and commodity turnover. Market demand continues to grow. With the expansion of application scenarios, especially in scenarios such as storage in humid environments, long-distance cold chain transportation, and packaging of flammable and explosive materials, higher requirements are placed on the moisture-proof, flame-retardant properties and structural strength of corrugated cardboard.

[0003] However, current corrugated cardboard has performance shortcomings, and further improvements are needed in the synergistic optimization of moisture resistance, flame retardancy, and mechanical strength:

[0004] In terms of moisture resistance, the plant fibers and ordinary inorganic fillers of traditional corrugated cardboard have strong hydrophilicity on their surfaces, and there are gaps between the components, making it easy for moisture to penetrate and causing the cardboard to absorb moisture, deform, and lose strength. In terms of flame retardancy, single-type flame retardants are often used, such as adding only inorganic flame retardant fillers or organic flame retardants. The former has low flame retardant efficiency, while the latter is volatile and may affect the mechanical properties of the cardboard. At the same time, the flame retardant has poor compatibility with fillers and fibers, and uneven dispersion, resulting in unstable flame retardant effect and difficulty in achieving synergistic flame retardancy of the gas phase and condensed phase, leading to a long afterflame time. In terms of structural strength, the surface of ordinary inorganic fillers lacks effective modification, and the interfacial bonding force with plant fibers and adhesives is weak, which easily forms defects inside, resulting in insufficient flat crush strength of corrugated cardboard, which cannot meet the needs of heavy-duty packaging or long-distance transportation. Moreover, adhesives mostly rely on traditional starch-based systems, which have poor bonding network stability and are difficult to firmly integrate the components, further affecting the overall mechanical properties.

[0005] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a moisture-proof and flame-retardant corrugated cardboard and its preparation process, in order to solve the technical problem that the moisture-proof performance, flame-retardant performance and flat crush strength of corrugated cardboard in the prior art need to be further improved.

[0007] The objective of this invention can be achieved through the following technical solution: a preparation process for moisture-proof and flame-retardant corrugated cardboard, comprising the following steps:

[0008] S1. Mix plant fibers and waste cardboard boxes, soak them in deionized water, and then crush them in a pulverizer. Next, add deinking agent, stir and sieve to obtain raw pulp.

[0009] S2. After mixing and stirring the pulp, functional inorganic filler, phosphate-modified piperazine and preservative, the mixture is fed into the paper machine, beaten, formed on the copper wire mesh, dewatered by the press rolls, dried in the drying oven, and then fed into the corrugated forming machine to be pressed into B-type corrugated board. After being shaped by the cooling rolls, the corrugated core is obtained.

[0010] S3. Apply the adhesive evenly to the tip of the corrugated core using a roller coater, attach the face paper to both sides of the corrugated core, put it into a composite press for initial bonding, and then put it into a hot air circulating drying oven for drying to obtain corrugated cardboard.

[0011] Further, in step S1, the ratio of plant fiber, waste cardboard box, deionized water, and deinking agent is 30g:70g:400mL:0.3g; in step S2, the functional inorganic filler is composed of modified calcium carbonate, modified silica, and modified alumina in a ratio of 6-8g:2.5-3.5g:2g; the ratio of pulp, functional inorganic filler, phosphate-modified piperazine, and preservative is 100mL:10-13g:8-9g:0.3g, and the freeness is 35-40ºSR.

[0012] Further, in step S2, the preparation method of the modified calcium carbonate is as follows: nano-calcium carbonate is added to a reaction vessel containing anhydrous ethanol, ultrasonically dispersed at 20-30℃ for 20-30 min, and then 2,3-dihydroxysuccinic acid solution is added dropwise. After the addition is complete, the mixture is stirred at 30-40℃ for 4-5 h, followed by post-treatment to obtain modified calcium carbonate. The 2,3-dihydroxysuccinic acid solution is obtained by dissolving 0.3 g of 2,3-dihydroxysuccinic acid in 30 mL of anhydrous ethanol, and then adjusting the pH of the solution to 7 by adding sodium hydroxide solution. The ratio of nano-calcium carbonate, anhydrous ethanol, and 2,3-dihydroxysuccinic acid solution is 1.5-2 g: 50-60 mL: 30 mL. The post-treatment operation includes: after the reaction is completed, filtration is performed, the product is washed 2-3 times with anhydrous ethanol, then transferred to a vacuum drying oven, dried at 45℃ for 12 h, ground, and passed through a 200-mesh sieve to obtain modified calcium carbonate.

[0013] Reaction mechanism:

[0014] 2,3-Dihydroxysuccinic acid is first neutralized with sodium hydroxide to convert it into sodium tartrate, in which the carboxyl group in the molecule is transformed into an active sodium carboxylate group. After ultrasonic dispersion in anhydrous ethanol, the aggregated structure of nano-calcium carbonate is destroyed, and the surface Ca... 2+ With fully exposed and uniformly dispersed particles, after the addition of sodium tartrate solution, tartrate ions react with CaO on the surface of the nano-calcium carbonate through bidentate chelation. 2+ A coordination reaction occurs, forming a stable organic-inorganic composite interface layer. After filtration, washing, drying, grinding, and sieving, modified calcium carbonate with tartrate grafts is finally obtained.

[0015] Further, in step S2, the modified silica is prepared as follows: silica sol is added to anhydrous ethanol and stirred for 10-20 min. Then, hydrochloric acid solution is added dropwise to adjust the pH of the solution to 2-3. Next, silane coupling agent solution is added dropwise. After the addition is complete, the mixture is stirred at 20-30℃ for 12 h. After post-treatment, modified silica is obtained. The ratio of silica sol, anhydrous ethanol, and silane coupling agent solution is 10 g: 10 mL: 2-4 mL. The mass fraction of the hydrochloric acid solution is 3.5%. The silane coupling agent solution is obtained by mixing 4 g tetraethyl orthosilicate, 1.8 g hexadecyltrimethoxysilane, and 10 mL of anhydrous ethanol and stirring for 10-20 min. The post-treatment operation includes: after the reaction is completed, centrifugation is performed, and the product is washed with deionized water 2-3 times to obtain modified silica.

[0016] Reaction mechanism:

[0017] In the weakly acidic environment of silica sol, the four methoxy groups of tetraethyl orthosilicate and the three methoxy groups of hexadecyltrimethoxysilane in the mixed silane solution hydrolyze to generate silanol intermediates containing multiple silanol groups. On the one hand, the silanol intermediates undergo dehydration condensation with a large number of hydroxyl groups exposed on the silica sol surface to form stable Si-O-Si covalent bonds and achieve chemical grafting. On the other hand, the silanol intermediates undergo self-condensation reaction to construct a cross-linked and dense organic-inorganic hybrid coating layer. After separation and washing, modified silica is finally obtained.

[0018] Further, in step S2, the modified alumina is prepared by adding alumina powder and an aqueous ethanol solution to a reaction vessel, ultrasonically dispersing at 20-30°C for 20-30 min, then adding octyltrimethoxysilane, stirring at 20-30°C for 2-3 h, then heating to 80-90°C, stirring for 40-60 min, and post-processing to obtain modified alumina; the ratio of alumina powder, aqueous ethanol solution, and octyltrimethoxysilane is 10 g: 60-80 mL: 0.03-0.06 g, and the mass fraction of the aqueous ethanol solution is 85%; the post-processing operation includes: after the reaction is completed, transferring the product to a vacuum drying oven, drying at 100°C to constant weight, grinding, and passing through a 200-mesh sieve to obtain modified alumina.

[0019] Reaction mechanism:

[0020] After alumina powder is ultrasonically dispersed in an ethanol-water solution, a large number of hydroxyl groups are exposed on the surface. When octyltrimethoxysilane is added, the methoxy groups in the molecule undergo a hydrolysis reaction to generate silanol groups. The silanol groups rapidly undergo a dehydration condensation reaction with the hydroxyl groups on the alumina surface to form stable Si-O-Al covalent bonds, allowing silane molecules to be initially grafted onto the alumina surface. Subsequently, under heating conditions, the remaining silanol groups undergo a self-condensation reaction to form a Si-O-Si cross-linked structure, constructing a dense and uniform organic coating layer on the alumina surface. The exposed octyl hydrophobic groups in the coating layer can reduce the polarity of the alumina surface. After drying, grinding, and sieving, modified alumina is finally obtained.

[0021] Further, in step S2, the preparation method of the phosphoric acid modified piperazine is as follows: piperazine hexahydrate is added to deionized water, and stirred at 40-50℃ until the piperazine hexahydrate is completely dissolved. Then, an aqueous phosphoric acid solution is added, and stirred at 40-50℃ for 5-6 hours. Then, it is transferred to a rotary evaporator and dried at 80-90℃ and -0.08MPa for 3-4 hours. After grinding, it is passed through a 200-mesh sieve to obtain the phosphoric acid modified piperazine. The ratio of the amount of piperazine hexahydrate, deionized water and aqueous phosphoric acid solution is 19-20g:200mL:14-15mL, and the mass fraction of the aqueous phosphoric acid solution is 85%.

[0022] Reaction mechanism:

[0023]

[0024] When piperazine hexahydrate is dissolved in deionized water, the amino group in its molecule exhibits basic activity. The added phosphoric acid aqueous solution provides H⁺, and the two undergo an acid-base neutralization reaction to form a stable piperazine phosphate intermediate. Subsequently, the system is evaporated and dried to remove water and unreacted trace free components. Finally, after cooling, grinding and sieving, polyphosphoric acid-modified phosphate-modified piperazine is obtained.

[0025] Further, in step S3, the adhesive is prepared as follows: corn starch is added to deionized water, stirred at 20-30℃ for 10-20 minutes, heated to 50-60℃, sodium hydroxide is added, the temperature is further raised to 80-90℃, and gelatinized at this temperature for 20-30 minutes. After cooling to room temperature, borax, polyurethane emulsion, and isothiazolinone are added, and the mixture is stirred for another 20-30 minutes. The mixture is then passed through a 100-mesh sieve to obtain the adhesive. The ratio of corn starch, deionized water, sodium hydroxide, borax, polyurethane emulsion, and isothiazolinone is 100g:400-450mL:2-3g:1-1.2g:15-20mL:0.3-0.5g.

[0026] Furthermore, the polyurethane emulsion is prepared by the following steps:

[0027] A1. Add 2,2-dimethylolpropionic acid and tripropylamine to a reaction vessel containing N,N-dimethylformamide, stir at 30-40℃ for 20-30 min, and then process to obtain 2,2-dimethylolpropionic acid ammonium salt.

[0028] Reaction mechanism:

[0029]

[0030] In the polar solvent environment of N,N-dimethylformamide, the solvation of the carboxyl group of 2,2-dimethylolpropionic acid is activated, the polarity of the OH bond in the carboxyl group is enhanced and the bond energy is reduced, making it prone to heterolytic cleavage and releasing protons. In tripropylamine, the nitrogen atom has a lone pair of electrons, which has a strong electron accepting ability. It will combine with the proton released by the carboxyl group in 2,2-dimethylolpropionic acid to form a positively charged tripropanolamine cation, while the carboxyl group that has lost the proton is converted into a negatively charged carboxylate ion. The two are combined through ionic bonds to form 2,2-dimethylolpropionic acid ammonium salt.

[0031] A2. Polyethylene terephthalate, polyhexyl adipate, isophorone diisocyanate and catalyst are added to a reactor containing N,N-dimethylacetamide. The reaction is carried out at 80-90℃ under a nitrogen atmosphere for 3-4 hours. The temperature is then lowered to 60-70℃, and 2,2-dimethylolpropionic acid ammonium salt is added and reacted for 1-2 hours. After post-treatment, a polyurethane emulsion is obtained.

[0032] Reaction mechanism:

[0033]

[0034] In the formula:

[0035]

[0036] The hydroxyl groups in polyethylene terephthalate and polyhexyl adipate react with the isocyanate groups in isophorone diisocyanate through an addition reaction to generate a prepolymer with isocyanate-terminated ends. Then, 2,2-dimethylolpropionate ammonium salt is added, and the hydroxyl groups in 2,2-dimethylolpropionate ammonium salt continue to react with the isocyanate groups in the molecule, introducing carboxylate groups into the prepolymer. Finally, deionized water is added and stirred, and the prepolymer containing ionized groups is dispersed in water to finally form a polyurethane emulsion.

[0037] Further, in step A1, the ratio of 2,2-dimethylolpropionic acid, tripropylamine, and N,N-dimethylformamide is 13g:14g:80-90mL. The post-treatment operation includes: after the reaction, transferring the solution to a rotary evaporator and distilling it at 150-160℃ until solid precipitates, then transferring it to a vacuum drying oven and drying it at 40-50℃ for 2-4 hours to obtain 2,2-dimethylolpropionic acid ammonium salt; in step A2, the polyethylene terephthalate, polyethylene adipate, catalyst, and N,N-dimethylacetyl... The ratio of amine to 2,2-dimethylolpropionic acid ammonium salt is 25-35g:100g:0.2-0.4g:74-96mL:7-9g. The amount of isophorone diisocyanate added is 0.55 times the total molar amount of hydroxyl groups in polyethylene terephthalate and polyethylene adipate. The catalyst is dilauryl dibutyltin. The post-treatment operation includes: after the reaction is completed, cooling to 40-50℃, adding deionized water, and stirring at 3000-4000r / min for 20-30min to obtain a polyurethane emulsion.

[0038] The present invention also proposes a preparation process for moisture-proof and flame-retardant corrugated cardboard, which is prepared by the above-mentioned preparation process for moisture-proof and flame-retardant corrugated cardboard.

[0039] The present invention has the following beneficial effects:

[0040] 1. The modified calcium carbonate of this invention has an organic-inorganic composite interface layer on its surface. The modified alumina is modified with octyltrimethoxysilane to introduce hydrophobic groups. The modified silica forms a cross-linked and dense organic-inorganic hybrid coating layer. The three work together to build multiple hydrophobic barriers, effectively reducing the hydrophilicity of the corrugated cardboard surface. The phosphate-modified piperazine interacts with the surface groups of the inorganic filler, further densifying the internal structure of the system. The carboxyl groups and cross-linked structure contained in the polyurethane emulsion can fill the gaps between the pulp fibers and the inorganic filler, reducing the water penetration channels. Each material plays a role from multiple dimensions, including surface hydrophobicity, internal densification, and penetration channel blocking, by synergistic complementarity of its special structure and elemental composition, significantly improving the moisture-proof performance of the corrugated cardboard.

[0041] 2. The phosphate-modified piperazine of this invention contains phosphorus and nitrogen elements and has a polyphosphoric acid structure. At high temperatures, it can promote char formation and release flame-retardant gases, exerting a dual flame-retardant effect in both the gas phase and condensed phase. Modified calcium carbonate, modified silica, and modified alumina are all inorganic rigid fillers that can absorb heat and decompose at high temperatures, forming a continuous inorganic barrier layer that blocks oxygen and heat transfer. The cross-linked structure of the polyurethane emulsion can slow down the spread of combustion. It forms a stable interfacial bond with the inorganic fillers and phosphate-modified piperazine, allowing the flame-retardant components to be uniformly dispersed in the paperboard system. Through the complementarity of phosphorus, nitrogen, and inorganic elements, and the cooperation of the polyphosphoric acid char formation structure, inorganic barrier layer, and cross-linked network structure, the combustion reaction is inhibited and the combustion chain transmission is blocked, greatly enhancing the flame-retardant performance of corrugated paperboard.

[0042] 3. The modified calcium carbonate, modified silica, and modified alumina of this invention all possess stable inorganic rigid structures. As functional fillers, they can provide solid skeletal support for corrugated cardboard, enhancing the system's load-bearing capacity. After organic modification, the compatibility of the three modified inorganic fillers with the virgin pulp fiber and polyurethane emulsion is significantly improved. Through interfacial chemical bonding and physical adsorption, they are tightly bound together, reducing internal defects. The polyurethane emulsion has excellent bonding properties, and its cross-linking structure can construct a stable bonding network, firmly connecting the inorganic fillers, phosphate-modified piperazine, and fibers into a whole. The molecular structure of phosphate-modified piperazine can form a synergistic effect with other components, enhancing the internal forces of the system. Through the synergistic effect of rigid support, strong bonding network, and improved interfacial compatibility, the materials optimize the overall internal structure of the cardboard and significantly improve the flat crush strength of the corrugated cardboard. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0044] In this application, the deinking agent is selected from Shandong Haihua Supply Chain Co., Ltd., CAS No. 10035-04-8, product number 1733058, and item number 20210806;

[0045] In this application, the silica sol is selected from Dongguan Huihe Yongsheng Nanotechnology Co., Ltd., CAS No. HG / T-2521-2008, model SD-5040;

[0046] In this application, the alumina powder is selected from Yongshun Mineral Products Processing Plant in Lingshou County, with a mesh size of 600 mesh and a particle size of 1μm;

[0047] In this application, piperazine hexahydrate was selected from Changzhou Hengda Chemical Co., Ltd., CAS No. 142-63-2, and the active ingredient content was 99%.

[0048] In this application, the borax is selected from Henan Xinzhiyuan Chemical Products Co., Ltd., with CAS number 1303-96-4 and an effective ingredient content of 99%.

[0049] In this application, the polyethylene terephthalate is selected from Dongguan Kaiwan Engineering Plastic Raw Materials Co., Ltd., brand petg, grade VX301;

[0050] In this application, the polyhexyl adipate is selected from Greenlink (Jining) Chemical Technology Co., Ltd., CAS No. 25212-06-0, Item No. AL637395555861.

[0051] Example 1

[0052] This embodiment provides a preparation process for moisture-proof and flame-retardant corrugated cardboard, including the following steps:

[0053] S1. Preparation of modified calcium carbonate

[0054] Weigh out 3g of 2,3-dihydroxysuccinic acid and dissolve it in 300mL of anhydrous ethanol. Then adjust the pH of the solution to 7 by adding sodium hydroxide solution dropwise to obtain a 2,3-dihydroxysuccinic acid solution.

[0055] Weigh 15g of nano-calcium carbonate and add it to a 500mL reaction vessel containing anhydrous ethanol. Disperse the mixture by ultrasonication at 20℃ for 20min. Then, add 300mL of 2,3-dihydroxysuccinic acid solution dropwise. After the addition is complete, stir at 30℃ for 4h. After the reaction is complete, filter the mixture and wash the product twice with anhydrous ethanol. Then, transfer the product to a vacuum drying oven and dry it at 45℃ for 12h. Grind the product and pass it through a 200-mesh sieve to obtain modified calcium carbonate.

[0056] S2, Preparation of modified silica

[0057] Weigh out 40g of tetraethyl orthosilicate, 18g of hexadecyltrimethoxysilane and 100mL of anhydrous ethanol and mix for 10min to obtain a silane coupling agent solution.

[0058] Weigh 100g of silica sol and add it to 100mL of anhydrous ethanol. Stir for 10min. Then, add 3.5wt% hydrochloric acid solution to adjust the pH of the solution to 2. Next, add 20mL of silane coupling agent solution. After the addition is complete, stir at 20℃ for 12h. After the reaction is complete, centrifuge and wash the product twice with deionized water to obtain modified dioxide.

[0059] S3, Preparation of modified alumina

[0060] Weigh 100g of alumina powder and 600mL of 85wt% ethanol aqueous solution and add them to the reaction vessel. Disperse the mixture ultrasonically at 20℃ for 20min. Then add 0.3g of octyltrimethoxysilane and stir at 20℃ for 2h. Then raise the temperature to 80℃ and stir for 40min. After the reaction is complete, transfer the product to a vacuum drying oven and dry it at 100℃ to constant weight. Grind the product and pass it through a 200-mesh sieve to obtain modified alumina.

[0061] S4. Preparation of phosphoric acid-modified piperazine

[0062] Weigh 190g of piperazine hexahydrate and add it to 2L of deionized water. Stir at 40℃ until the piperazine hexahydrate is completely dissolved. Then add 140mL of 85wt% phosphoric acid aqueous solution and stir at 40℃ for 5h. Then transfer it to a rotary evaporator and dry at 80℃ and -0.08MPa for 3h. Grind and pass through a 200-mesh sieve to obtain phosphoric acid modified piperazine.

[0063] S5. Preparation of polyurethane emulsion

[0064] Weigh 130g of 2,2-dimethylolpropionic acid and 140g of tripropylamine and add them to a reaction vessel containing 800mL of N,N-dimethylformamide. Stir at 30℃ for 20min. After the reaction is complete, transfer the solution to a rotary evaporator and distill at 150℃ until solid precipitates. Transfer the solution to a vacuum drying oven and dry at 40℃ for 2h to obtain 2,2-dimethylolpropionic acid ammonium salt.

[0065] Weigh out 250g of polyethylene terephthalate, 1kg of hexanediol adipate, and add isophorone diisocyanate (calculated as 0.55 times the total molar amount of hydroxyl groups in polyethylene terephthalate and hexanediol adipate) and 2g of dilauryl dibutyltin catalyst into a reactor containing 740mL of N,N-dimethylacetamide. After reacting at 80℃ under a nitrogen atmosphere for 3h, cool down to 60℃, add 70g of 2,2-dimethylolpropionic acid ammonium salt and react for 1h. After the reaction is complete, cool down to 40℃, add deionized water, and stir at 3000r / min for 20min to obtain a polyurethane emulsion.

[0066] S6. Preparation of adhesive

[0067] Weigh 100g of corn starch and add it to 400mL of deionized water. Stir at 20℃ for 10min, raise the temperature to 50℃, add 2g of sodium hydroxide, continue to raise the temperature to 80℃, keep warm and gelatinize for 20min, cool to room temperature, then add 1g of borax, 15mL of polyurethane emulsion and 0.3g of isothiazolinone, continue to stir for 20min, and pass through a 100-mesh sieve to obtain the adhesive.

[0068] S7. Preparation of raw pulp

[0069] Weigh out 30kg of plant fiber and 70kg of waste cardboard boxes, mix them, soak them in 400L of deionized water for 2 hours, then put them into a pulverizer to crush them. Next, add 300g of deinking agent, stir at 40℃ for 20 minutes, and pass through a 200-mesh sieve to obtain raw pulp.

[0070] S8. Preparation of corrugated core

[0071] Weigh out 6 kg of modified calcium carbonate, 2.5 kg of modified silicon dioxide and 2 kg of modified alumina and mix them evenly to obtain a functional inorganic filler;

[0072] Weigh out 100L of raw pulp, 10g of functional inorganic filler, 8kg of phosphate-modified piperazine, and 300g of preservative. Mix and stir for 30 minutes, then feed it into a paper machine. Control the beating degree to 35ºSR. Form the pulp on a copper wire mesh, dewater it through the press rolls, and then enter the drying oven. Dry it at 110℃ for 3 minutes, and then feed it into a corrugated forming machine. Press it into a B-type corrugated shape through a 150℃ corrugated roll at 0.3MPa. Finally, shape it through a cooling roll to obtain the corrugated core.

[0073] S9. Preparing corrugated cardboard

[0074] The adhesive is evenly applied to the tips of the corrugated core using a roller coater. The facing paper is then bonded to both sides of the corrugated core. The core is then fed into a laminating press and held for 30 seconds for initial bonding. Finally, it is sent to a hot air circulating drying oven and dried at 120°C for 3 minutes to obtain corrugated cardboard.

[0075] Example 2

[0076] This embodiment provides a preparation process for moisture-proof and flame-retardant corrugated cardboard, including the following steps:

[0077] S1. Preparation of modified calcium carbonate

[0078] Weigh out 3g of 2,3-dihydroxysuccinic acid and dissolve it in 300mL of anhydrous ethanol. Then adjust the pH of the solution to 7 by adding sodium hydroxide solution dropwise to obtain a 2,3-dihydroxysuccinic acid solution.

[0079] Weigh 18g of nano-calcium carbonate and add it to a 550mL reaction vessel containing anhydrous ethanol. Disperse the mixture ultrasonically at 25℃ for 25min. Then, add 300mL of 2,3-dihydroxysuccinic acid solution dropwise. After the addition is complete, stir at 35℃ for 4.5h. After the reaction is complete, filter the mixture and wash the product twice with anhydrous ethanol. Then, transfer the product to a vacuum drying oven and dry it at 45℃ for 12h. Grind the product and pass it through a 200-mesh sieve to obtain modified calcium carbonate.

[0080] S2, Preparation of modified silica

[0081] Weigh out 40g of tetraethyl orthosilicate, 18g of hexadecyltrimethoxysilane and 100mL of anhydrous ethanol and mix for 15min to obtain a silane coupling agent solution.

[0082] Weigh 100g of silica sol and add it to 100mL of anhydrous ethanol. Stir for 15min, then add 3.5wt% hydrochloric acid solution to adjust the pH of the solution to 2.5. Next, add 30mL of silane coupling agent solution. After the addition is complete, stir at 25℃ for 12h. After the reaction is complete, centrifuge and wash the product twice with deionized water to obtain modified dioxide.

[0083] S3, Preparation of modified alumina

[0084] Weigh 100g of alumina powder and 700mL of 85wt% ethanol aqueous solution and add them to the reaction vessel. Disperse the mixture ultrasonically at 25℃ for 25min. Then add 0.4g of octyltrimethoxysilane and stir at 25℃ for 2.5h. After stirring at 85℃ for 50min, the temperature is raised to 85℃ and stirred for 50min. After the reaction is complete, transfer the product to a vacuum drying oven and dry it at 100℃ to constant weight. Grind the product and pass it through a 200-mesh sieve to obtain modified alumina.

[0085] S4. Preparation of phosphoric acid-modified piperazine

[0086] Weigh 195g of piperazine hexahydrate and add it to 2L of deionized water. Stir at 45℃ until the piperazine hexahydrate is completely dissolved. Then add 145mL of 85wt% phosphoric acid aqueous solution and stir at 45℃ for 5.5h. Then transfer it to a rotary evaporator and dry at 85℃ and -0.08MPa for 3.5h. Grind and pass through a 200-mesh sieve to obtain phosphoric acid modified piperazine.

[0087] S5. Preparation of polyurethane emulsion

[0088] Weigh 130g of 2,2-dimethylolpropionic acid and 140g of tripropylamine and add them to a reaction vessel containing 850mL of N,N-dimethylformamide. Stir at 35℃ for 25min. After the reaction is complete, transfer the solution to a rotary evaporator and distill at 150℃ until solid precipitates. Transfer the solution to a vacuum drying oven and dry at 45℃ for 3h to obtain 2,2-dimethylolpropionic acid ammonium salt.

[0089] Weigh out 300g of polyethylene terephthalate, 1kg of hexanediol adipate, and add isophorone diisocyanate (calculated as 0.55 times the total molar amount of hydroxyl groups in polyethylene terephthalate and hexanediol adipate) and 3g of dilauryl dibutyltin catalyst into a reactor containing 850mL of N,N-dimethylacetamide. React at 85℃ under a nitrogen atmosphere for 3.5h, then cool to 65℃, add 80g of 2,2-dimethylolpropionic acid ammonium salt and react for 1.5h. After the reaction is complete, cool to 45℃, add deionized water, and stir at 3500r / min for 25min to obtain a polyurethane emulsion.

[0090] S6. Preparation of adhesive

[0091] Weigh 100g of corn starch and add it to 420mL of deionized water. Stir at 25℃ for 15min, raise the temperature to 55℃, add 2.5g of sodium hydroxide, continue to raise the temperature to 85℃, keep warm and gelatinize for 25min, cool to room temperature, then add 1.1g of borax, 18mL of polyurethane emulsion and 0.4g of isothiazolinone, continue to stir for 25min, and pass through a 100-mesh sieve to obtain the adhesive.

[0092] S7. Preparation of raw pulp

[0093] Weigh out 30kg of plant fiber and 70kg of waste cardboard boxes, mix them, soak them in 400L of deionized water for 2.5h, then put them into a pulverizer to crush them. Then add 300g of deinking agent, stir at 45℃ for 25min, and pass through a 200-mesh sieve to obtain raw pulp.

[0094] S8. Preparation of corrugated core

[0095] Weigh out 7 kg of modified calcium carbonate, 3 kg of modified silica and 2 kg of modified alumina and mix them evenly to obtain a functional inorganic filler.

[0096] Weigh out 100L of raw pulp, 11g of functional inorganic filler, 8.5kg of phosphate-modified piperazine, and 300g of preservative. Mix and stir for 35 minutes, then feed it into a paper machine. Control the beating degree to 38ºSR. Form the pulp on a copper wire mesh, dewater it through the press rolls, and then enter the drying oven. Dry it at 115℃ for 4 minutes, and then feed it into a corrugated forming machine. Press it into a B-type corrugated shape through a 155℃ corrugated roll at 0.4MPa. Finally, shape it through a cooling roll to obtain the corrugated core.

[0097] S9. Preparing corrugated cardboard

[0098] The adhesive is evenly applied to the tip of the corrugated core using a roller coater. The facing paper is then bonded to both sides of the corrugated core. The core is then fed into a laminating press and held for 30 seconds for initial bonding. Finally, it is sent to a hot air circulating drying oven and dried at 130°C for 4 minutes to obtain corrugated cardboard.

[0099] Comparative Example 3

[0100] This embodiment provides a preparation process for moisture-proof and flame-retardant corrugated cardboard, including the following steps:

[0101] S1. Preparation of modified calcium carbonate

[0102] Weigh out 3g of 2,3-dihydroxysuccinic acid and dissolve it in 300mL of anhydrous ethanol. Then adjust the pH of the solution to 7 by adding sodium hydroxide solution dropwise to obtain a 2,3-dihydroxysuccinic acid solution.

[0103] Weigh 20g of nano-calcium carbonate and add it to a 600mL reaction vessel containing anhydrous ethanol. Disperse the mixture ultrasonically at 30℃ for 30min. Then, add 300mL of 2,3-dihydroxysuccinic acid solution dropwise. After the addition is complete, stir at 40℃ for 5h. After the reaction is complete, filter the mixture and wash the product three times with anhydrous ethanol. Then, transfer the product to a vacuum drying oven and dry it at 45℃ for 12h. Grind the product and pass it through a 200-mesh sieve to obtain modified calcium carbonate.

[0104] S2, Preparation of modified silica

[0105] Weigh out 40g of tetraethyl orthosilicate, 18g of hexadecyltrimethoxysilane and 100mL of anhydrous ethanol and mix for 20min to obtain a silane coupling agent solution.

[0106] Weigh 100g of silica sol and add it to 100mL of anhydrous ethanol. Stir for 20min. Then, add 3.5wt% hydrochloric acid solution to adjust the pH of the solution to 3. Next, add 40mL of silane coupling agent solution. After the addition is complete, stir at 30℃ for 12h. After the reaction is complete, centrifuge and wash the product three times with deionized water to obtain modified dioxide.

[0107] S3, Preparation of modified alumina

[0108] Weigh 100g of alumina powder and 800mL of 85wt% ethanol aqueous solution and add them to the reaction vessel. Disperse the mixture ultrasonically at 30℃ for 30min. Then add 0.6g of octyltrimethoxysilane and stir at 30℃ for 3h. Then raise the temperature to 90℃ and stir for 60min. After the reaction is complete, transfer the product to a vacuum drying oven and dry it at 100℃ to constant weight. Grind the product and pass it through a 200-mesh sieve to obtain modified alumina.

[0109] S4. Preparation of phosphoric acid-modified piperazine

[0110] Weigh 200g of piperazine hexahydrate and add it to 2L of deionized water. Stir at 50℃ until the piperazine hexahydrate is completely dissolved. Then add 150mL of 85wt% phosphoric acid aqueous solution and stir at 50℃ for 6h. Then transfer it to a rotary evaporator and dry at 90℃ and -0.08MPa for 4h. Grind and pass through a 200-mesh sieve to obtain phosphoric acid modified piperazine.

[0111] S5. Preparation of polyurethane emulsion

[0112] Weigh 130g of 2,2-dimethylolpropionic acid and 140g of tripropylamine and add them to a reaction vessel containing 900mL of N,N-dimethylformamide. Stir at 40℃ for 30min. After the reaction is complete, transfer the solution to a rotary evaporator and distill at 160℃ until solid precipitates. Transfer the solution to a vacuum drying oven and dry at 50℃ for 4h to obtain 2,2-dimethylolpropionic acid ammonium salt.

[0113] Weigh out 350g of polyethylene terephthalate, 1kg of hexanediol adipate, and add isophorone diisocyanate (calculated as 0.55 times the total molar amount of hydroxyl groups in polyethylene terephthalate and hexanediol adipate) and 4g of dilauryl dibutyltin catalyst into a reactor containing 960mL of N,N-dimethylacetamide. After reacting at 90℃ under a nitrogen atmosphere for 4h, the temperature is lowered to 70℃, and 90g of 2,2-dimethylolpropionic acid ammonium salt is added and reacted for 2h. After the reaction is completed, the temperature is lowered to 50℃, and deionized water is added. The mixture is stirred at 4000r / min for 30min to obtain a polyurethane emulsion.

[0114] S6. Preparation of adhesive

[0115] Weigh 100g of corn starch and add it to 450mL of deionized water. Stir at 30℃ for 20min, raise the temperature to 60℃, add 3g of sodium hydroxide, continue to raise the temperature to 90℃, keep warm and gelatinize for 30min, cool to room temperature, then add 1.2g of borax, 20mL of polyurethane emulsion and 0.5g of isothiazolinone, continue to stir for 30min, and pass through a 100-mesh sieve to obtain the adhesive.

[0116] S7. Preparation of raw pulp

[0117] Weigh out 30kg of plant fiber and 70kg of waste cardboard, mix them, soak them in 400L of deionized water for 3 hours, then put them into a pulverizer to crush them. Next, add 300g of deinking agent, stir at 50℃ for 30 minutes, and pass through a 200-mesh sieve to obtain raw pulp.

[0118] S8. Preparation of corrugated core

[0119] Weigh out 8 kg of modified calcium carbonate, 3.5 kg of modified silica and 2 kg of modified alumina and mix them evenly to obtain a functional inorganic filler.

[0120] Weigh out 100L of raw pulp, 13g of functional inorganic filler, 9kg of phosphate-modified piperazine, and 300g of preservative. Mix and stir for 40 minutes, then feed it into a paper machine. Control the beating degree to 40ºSR. Form the pulp on a copper wire mesh, dewater it through the press rolls, and then enter the drying oven. Dry it at 120℃ for 5 minutes, and then feed it into a corrugated forming machine. Press it into a B-type corrugated shape through a 160℃ corrugated roll at 0.5MPa. Finally, shape it through a cooling roll to obtain the corrugated core.

[0121] S9. Preparing corrugated cardboard

[0122] The adhesive is evenly applied to the tip of the corrugated core using a roller coater. The facing paper is then bonded to both sides of the corrugated core. The core is then fed into a laminating press and held for 30 seconds for initial bonding. Finally, it is sent to a hot air circulating drying oven and dried at 140°C for 5 minutes to obtain corrugated cardboard.

[0123] Comparative Example 1

[0124] The difference between this comparative example and Example 3 is that step S1 is omitted, and the modified calcium carbonate in step S8 is replaced with nano calcium carbonate from step S1.

[0125] Comparative Example 2

[0126] The difference between this comparative example and Example 3 is that step S2 is omitted and modified silica is not added in step S8.

[0127] Comparative Example 3

[0128] The difference between this comparative example and Example 3 is that step S3 is omitted, and the modified alumina in step S8 is replaced with alumina powder from step S3.

[0129] Comparative Example 4

[0130] The difference between this comparative example and Example 3 is that step S4 is omitted and phosphate-modified piperazine is not added in step S8.

[0131] Comparative Example 5

[0132] The difference between this comparative example and Example 3 is that step S5 is omitted and polyurethane emulsion is not added in step S6.

[0133] Performance testing:

[0134] The Cobb value of the corrugated paperboards prepared in Examples 1-3 and Comparative Examples 1-5 was determined according to the standard GB / T 1540-2002 "Determination of water absorption of paper and paperboard (Cobb method)" to represent the moisture-proof performance of the corrugated paperboards.

[0135] The afterflame time of the corrugated paperboards prepared in Examples 1-3 and Comparative Examples 1-5 was determined according to the standard GB / T 14656-2009 "Test Method for Burning Performance of Flame Retardant Paper and Paperboard" to represent the flame retardant performance of the corrugated paperboards.

[0136] The flat crush strength of the corrugated cardboard prepared in Examples 1-3 and Comparative Examples 1-5 was determined according to the standard GB / T 22874-2008 "Determination of Flat Crush Strength of Single-Face and Single-Corrugated Board". The specific test results are shown in Table 1 below:

[0137] Table 1 - Performance Test Data of Samples

[0138]

[0139] Data Analysis:

[0140] Comparative analysis of the data in Table 1 above shows that the corrugated cardboard prepared by this invention has a Koebner value of 19.1 g / m³. 2 The afterflame time is 3 seconds, and the compressive strength is 6.51 kPa.

[0141] Comparative Example 1 omitted the preparation step of modified calcium carbonate, resulting in an incomplete hydrophobic barrier structure in the corrugated cardboard, increased surface hydrophilicity, decreased moisture resistance, and a Koebner value of 22.9 g / m². 2 Meanwhile, it loses the synergistic rigid support effect of modified calcium carbonate and other materials, and the compatibility of unmodified nano-calcium carbonate with virgin fiber and polyurethane emulsion is poor, resulting in more internal defects and a decrease in compressive strength to 4.87 kPa. In addition, it lacks the synergistic effect of modified calcium carbonate in the flame retardant system, which cannot help to construct an effective inorganic barrier layer, and the afterflame time is extended to 9 seconds.

[0142] Comparative Example 2 omitted the addition of modified silica, thus losing the densifying effect of the dense organic-inorganic hybrid coating layer formed by the cross-linked modified silica. Moisture easily penetrated through the internal pores, resulting in poorer moisture resistance; the Cobb value was 23.8 g / m³. 2 Meanwhile, the lack of modified silica as an inorganic rigid filler skeleton support and interface compatibility improvement effect results in insufficient overall internal structure of corrugated cardboard, reduced flat crush strength to 5.43 kPa, and the lack of flame retardant synergy effect of its heat absorption decomposition at high temperature to form inorganic barrier layer, which cannot effectively block oxygen and heat transfer, and the afterflame time is extended to 11 seconds.

[0143] Comparative Example 3 used unmodified alumina powder instead of octyltrimethoxysilane-modified alumina. This resulted in the loss of the hydrophobic effect and interfacial bonding provided by the octyl hydrophobic groups and Si-O-Al covalent bonds on the surface of the modified alumina, leading to increased surface polarity of the corrugated cardboard and decreased moisture resistance. The Koebner value was 20.7 g / m². 2 Meanwhile, the unmodified alumina powder has poor compatibility with other components, weak interfacial bonding, increased internal defects, and reduced compressive strength to 5.10 kPa. In addition, the lack of synergistic effect between modified alumina and other materials in the flame retardant system makes it impossible to help improve the continuity of the inorganic barrier layer, and the afterflame time is extended to 12 seconds.

[0144] Comparative Example 4, without the addition of phosphate-modified piperazine, lost the dual flame-retardant effects of its contained phosphorus, nitrogen elements, and polyphosphoric acid structure, which provided both gas-phase and condensed-phase flammability. It could not effectively promote char formation and release flame-retardant gases, resulting in a difficult-to-interrupt combustion chain reaction and a significantly prolonged afterflame time to 14 seconds. Furthermore, the lack of interaction between phosphate-modified piperazine and the surface groups of the inorganic filler led to insufficient densification of the internal structure, increased moisture penetration channels, and decreased moisture resistance, resulting in a Koebner value of 21.2 g / m³. 2 Although the direct effect of phosphate-modified piperazine on flat crush strength is small, it loses its synergistic reinforcing effect with other components, weakens the internal forces of corrugated cardboard, and slightly reduces flat crush strength.

[0145] Comparative Example 5, without the addition of polyurethane emulsion, lost the filling effect of its carboxyl groups and cross-linked structure on the gaps between the original pulp fibers and inorganic fillers. This increased the moisture penetration channels, leading to a decrease in moisture resistance; the Cobb value was 22.0 g / m³. 2 Furthermore, the lack of a stable bonding network constructed by polyurethane emulsion makes it impossible to firmly connect inorganic fillers, phosphate-modified piperazine, and fibers into a whole. The components are loosely bonded, and the compressive strength is reduced to 5.82 kPa. In addition, the cross-linking structure of polyurethane emulsion lacks the effect of delaying the spread of combustion and cannot help block the transmission of combustion, extending the afterflame time to 8 seconds.

[0146] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A manufacturing process for moisture-proof and flame-retardant corrugated cardboard, characterized in that, Includes the following steps: S1. Mix plant fibers and waste cardboard boxes, soak them in deionized water, and then crush them in a pulverizer. Next, add deinking agent, stir and sieve to obtain raw pulp. S2. After mixing and stirring the pulp, functional inorganic filler, phosphate-modified piperazine and preservative, the mixture is fed into the paper machine, beaten, formed on the copper wire mesh, dewatered by the press rolls, dried in the drying oven, and then fed into the corrugated forming machine to be pressed into B-type corrugated board. After being shaped by the cooling rolls, the corrugated core is obtained. S3. Apply the adhesive evenly to the tip of the corrugated core using a roller coater, attach the face paper to both sides of the corrugated core, put it into a composite press for initial bonding, and then put it into a hot air circulating drying oven for drying to obtain corrugated cardboard. The preparation method of the phosphoric acid modified piperazine is as follows: piperazine hexahydrate is added to deionized water and stirred at 40-50℃ until the piperazine hexahydrate is completely dissolved. Then, an aqueous solution of phosphoric acid is added and stirred at 40-50℃ for 5-6 hours. Then, it is transferred to a rotary evaporator and dried at 80-90℃ and -0.08MPa for 3-4 hours. After grinding, it is passed through a 200-mesh sieve to obtain phosphoric acid modified piperazine. The adhesive is prepared by adding corn starch to deionized water and stirring at 20-30°C for 10-20 minutes. The temperature is then raised to 50-60°C, sodium hydroxide is added, and the temperature is further raised to 80-90°C. The mixture is kept at this temperature for 20-30 minutes to gelatinize. The mixture is then cooled to room temperature, and borax, polyurethane emulsion, and isothiazolinone are added. The mixture is stirred for another 20-30 minutes and then passed through a 100-mesh sieve to obtain the adhesive.

2. The preparation process of a moisture-proof and flame-retardant corrugated cardboard according to claim 1, characterized in that, In step S1, the ratio of plant fiber, waste cardboard box, deionized water, and deinking agent is 30g:70g:400mL:0.3g; in step S2, the functional inorganic filler is composed of modified calcium carbonate, modified silica, and modified alumina in a ratio of 6-8g:2.5-3.5g:2g; the ratio of pulp, functional inorganic filler, phosphate-modified piperazine, and preservative is 100mL:10-13g:8-9g:0.3g, and the freeness is 35-40ºSR.

3. The preparation process of a moisture-proof and flame-retardant corrugated cardboard according to claim 2, characterized in that, In step S2, the modified calcium carbonate is prepared by adding nano-calcium carbonate into a reaction vessel containing anhydrous ethanol, ultrasonically dispersing it at 20-30℃ for 20-30 min, then adding 2,3-dihydroxysuccinic acid solution dropwise, stirring at 30-40℃ for 4-5 h after the addition is complete, and then processing it to obtain modified calcium carbonate. The 2,3-dihydroxysuccinic acid solution is obtained by dissolving 0.3g of 2,3-dihydroxysuccinic acid in 30mL of anhydrous ethanol, and then adjusting the pH of the solution to 7 by adding sodium hydroxide solution dropwise; the ratio of the amount of nano-calcium carbonate, anhydrous ethanol and 2,3-dihydroxysuccinic acid solution is 1.5-2g:50-60mL:30mL.

4. The preparation process of a moisture-proof and flame-retardant corrugated cardboard according to claim 2, characterized in that, In step S2, the modified silica is prepared as follows: silica sol is added to anhydrous ethanol and stirred for 10-20 min. Then, hydrochloric acid solution is added dropwise to adjust the pH of the solution to 2-3. Next, silane coupling agent solution is added dropwise. After the addition is complete, the mixture is stirred at 20-30℃ for 12 h. After post-treatment, modified silica is obtained. The ratio of silica sol, anhydrous ethanol and silane coupling agent solution is 10 g: 10 mL: 2-4 mL. The mass fraction of the hydrochloric acid solution is 3.5%. The silane coupling agent solution is obtained by mixing 4 g tetraethyl orthosilicate, 1.8 g hexadecyltrimethoxysilane and 10 mL anhydrous ethanol and stirring for 10-20 min.

5. The preparation process of a moisture-proof and flame-retardant corrugated cardboard according to claim 2, characterized in that, In step S2, the modified alumina is prepared by adding alumina powder and an ethanol aqueous solution into a reaction vessel, ultrasonically dispersing at 20-30℃ for 20-30 min, then adding octyltrimethoxysilane, stirring at 20-30℃ for 2-3 h, then heating to 80-90℃, stirring for 40-60 min, and finally processing to obtain modified alumina. The ratio of alumina powder, ethanol aqueous solution, and octyltrimethoxysilane is 10 g: 60-80 mL: 0.03-0.06 g, and the mass fraction of the ethanol aqueous solution is 85%.

6. The preparation process of a moisture-proof and flame-retardant corrugated cardboard according to claim 1, characterized in that, The ratio of piperazine hexahydrate, deionized water, and phosphoric acid aqueous solution is 19-20g:200mL:14-15mL, and the mass fraction of the phosphoric acid aqueous solution is 85%.

7. The preparation process of a moisture-proof and flame-retardant corrugated cardboard according to claim 1, characterized in that, The ratio of corn starch, deionized water, sodium hydroxide, borax, polyurethane emulsion and isothiazolinone is 100g:400-450mL:2-3g:1-1.2g:15-20mL:0.3-0.5g.

8. The preparation process of a moisture-proof and flame-retardant corrugated cardboard according to claim 7, characterized in that, The polyurethane emulsion is prepared by the following steps: A1. Add 2,2-dimethylolpropionic acid and tripropylamine to a reaction vessel containing N,N-dimethylformamide, stir at 30-40℃ for 20-30 min, and then process to obtain 2,2-dimethylolpropionic acid ammonium salt. A2. Polyethylene terephthalate, polyhexyl adipate, isophorone diisocyanate and catalyst are added to a reactor containing N,N-dimethylacetamide. The reaction is carried out at 80-90℃ under a nitrogen atmosphere for 3-4 hours. The temperature is then lowered to 60-70℃, and 2,2-dimethylolpropionic acid ammonium salt is added and reacted for 1-2 hours. After post-treatment, a polyurethane emulsion is obtained.

9. The preparation process of a moisture-proof and flame-retardant corrugated cardboard according to claim 8, characterized in that, In step A1, the ratio of 2,2-dimethylolpropionic acid, tripropylamine, and N,N-dimethylformamide is 13g:14g:80-90mL; in step A2, the ratio of polyethylene terephthalate, polyhexanediol adipate, catalyst, N,N-dimethylacetamide, and 2,2-dimethylolpropionic acid amine salt is 25-35g:100g:0.2-0.4g:74-96mL:7-9g; the amount of isophorone diisocyanate added is 0.55 times the total molar amount of hydroxyl groups in polyethylene terephthalate and polyhexanediol adipate; and the catalyst is dilauryl dibutyltin.

10. A process for preparing moisture-proof and flame-retardant corrugated cardboard, characterized in that, It is prepared using the preparation process of a moisture-proof and flame-retardant corrugated cardboard as described in any one of claims 1-9.

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