Nanometer modified starch glue for corrugated carton and preparation method thereof

Abstract

The application discloses a kind of nano-modified starch glue for corrugated box and its preparation method.The starch glue includes carrier glue and main body glue with mass ratio of 1:4~5, the carrier glue includes starch 10 parts, water 50~60 parts, sodium hydroxide 0.8~1.2 parts, modified PAE resin 0.8~1.5 parts;Main body glue includes starch 10 parts, water 30~40 parts, oxidant 0.1~0.3 parts;The preparation method of the modified PAE resin is: with molar ratio of 1.2~1.4:1:0.2~0.3 binary acid, polyethylene polyamine and amino acrylate monomer as raw material, alkenyl-containing polyamide polyamine is prepared by polycondensation;Alkenyl-containing polyamide polyamine and hydrogen-containing silane, epoxy chloropropane are sequentially reacted to obtain modified PAE resin.The scheme of the application effectively solves the current corrugated paper starch glue strong hygroscopicity, the defect of easy hydrolysis and opening glue.

Description

TECHNICAL FIELD

[0001] The application relates to the field of technology, and particularly relates to a nano-modified starch glue for corrugated paper boxes and a preparation method thereof. BACKGROUND

[0002] As a container widely used in the fields of logistics transportation and commodity packaging, the mechanical property of a corrugated paper box mainly depends on the structure of corrugated paperboard. The corrugated paperboard is usually composed of corrugated core paper for buffering and supporting and boxboard paper (face paper) covering the two sides of the corrugated core paper, and the firm bonding between the materials is the key to the overall structure. In the manufacturing process, starch adhesive is the first choice for bonding the corrugated core paper peak and the boxboard paper due to its wide source, low cost and environmental friendliness. The adhesive needs to be coated on the corrugated core paper peak during use, and the starch is gelatinized under high-temperature compression after preheating, so as to realize the bonding and compounding of paper.

[0003] At present, the starch glue preparation process based on the carrier-main body two-component framework is generally used in the industry. The carrier glue part is usually a small proportion of starch paste strongly gelatinized by sodium hydroxide, which presents a high-viscosity, semi-transparent gelatinous state; the main body glue is a large proportion of starch suspension treated by an oxidizing agent, which has good fluidity after degradation and can adapt to the industrialized continuous coating production of the corrugated paper production line. When used, the carrier glue prepared in advance is introduced into the main body glue under stirring, the strong alkalinity of the carrier glue and the gelatinized molecules are used to initiate the gelatinization of the main body starch, and finally a uniform and stable adhesive is formed. Although the process is mature and widely used, due to the fact that the starch molecule chain is rich in a large number of hydrophilic hydroxyl groups, the prepared corrugated paperboard is easily softened by moisture absorption in a high-humidity environment or when it is wet, which causes the adhesive to open and delaminate, thereby seriously affecting the stacking strength and service life of the paper box. SUMMARY

[0004] In order to solve the problem that the current corrugated paper starch glue has strong moisture absorption and is easy to open and delaminate, the application provides a nano-modified starch glue for corrugated paper boxes and a preparation method thereof.

[0005] In a first aspect, the application provides a nano-modified starch glue for corrugated cartons, comprising carrier glue and main body glue in a mass ratio of 1:4-5, wherein the carrier glue comprises, in parts by mass, starch 10, water 50-60, sodium hydroxide 0.8-1.2, and modified PAE resin 0.8-1.5; the main body glue comprises starch 10, water 30-40, and oxidant 0.1-0.3; the modified PAE resin is prepared by using binary acid, polyethylene polyamine, and amino acrylate monomer as raw materials in a molar ratio of 1.2-1.4:1:0.2-0.3 to prepare alkenyl-containing polyamide polyamine through polycondensation, and then the alkenyl-containing polyamide polyamine is sequentially reacted with hydrogen-containing silane and epichlorohydrin to obtain the modified PAE resin; the molar ratio of the alkenyl-containing polyamide polyamine to epichlorohydrin is 1:0.6-0.9, and the molar ratio of the amino acrylate monomer to hydrogen-containing silane is 1:1.1-1.3.

[0006] In any of the above technical solutions, the polyethylene polyamine is selected from any one or more of diethylene triamine, triethylene tetramine, and tetraethylene pentamine; preferably, the polyethylene polyamine is diethylene triamine.

[0007] In any of the above technical solutions, the amino acrylate monomer is 2-aminoethyl methacrylate.

[0008] In any of the above technical solutions, the 2-aminoethyl methacrylate is usually in the form of more stable 2-aminoethyl methacrylate hydrochloride; in the actual reaction, after the 2-aminoethyl methacrylate hydrochloride is added, sodium hydroxide (aqueous solution) in an equal molar amount of the hydrochloride is slowly added dropwise under stirring for neutralization to release the amino activity.

[0009] In any of the above technical solutions, the hydrogen-containing silane is selected from any one or more of trimethoxysilane, triethoxysilane, methyldimethoxysilane, methyldiethoxysilane, and ethyldimethoxysilane.

[0010] The application uses silicone-modified PAE resin as water-resistant reinforcing agent to significantly improve the water resistance of starch glue, and reduce the moisture absorption and glue opening of the glue layer. PAE resin (polyamide epoxy chloropropane resin) can be electrostatically adsorbed with negatively charged starch molecules or fibers through its strong cationic property, and more importantly, its active group aziridinium can cross-link with the hydroxyl groups on the starch molecular chain during hot pressing to form a stable covalent bond network, thereby effectively blocking the penetration and erosion of water molecules on the starch molecules and improving the water resistance of the glue film. The application further introduces amino acrylate monomers into the synthesis of PAE to participate in polycondensation, introduces unsaturated alkenyl groups into the polyamide polyamine skeleton, and then grafts siloxane groups containing hydrogen silane onto the polymer chain through hydrosilylation. These introduced siloxane groups have good hydrophobicity, and the silicon hydroxyl groups generated after hydrolysis can also undergo condensation reaction with starch hydroxyl groups in the high temperature environment of the hot pressing process to form Si-O-C covalent bonds, further strengthening the hydrophobicity and structural stability of the glue network, thereby more effectively preventing the delamination and strength degradation of corrugated paperboard in a high humidity environment.

[0011] It is worth noting that the amount of amino acrylate monomer needs to be controlled within the above range, which on the one hand ensures that it can effectively introduce sufficient alkenyl groups without affecting the smooth progress of the polycondensation reaction and the stability of the intermediate, and on the other hand also avoids excessive introduction which destroys the regularity of the polyamide polyamine molecule and its subsequent reaction activity with epoxy chloropropane, thereby affecting its water-resistant reinforcing effect. In addition, the cationic property of PAE resin itself can also help to inhibit the agglomeration and sedimentation tendency of the components in the glue due to van der Waals force through electrostatic repulsion, maintaining the storage stability of the glue solution.

[0012] In any of the above technical solutions, the binary acid uses hexanedioic acid and pyridyl binary acid in a molar ratio of 3-4:1, and 0.05-0.15 parts of water-soluble metal salt are added to the main glue.

[0013] In any of the above technical solutions, the water-soluble metal salt is a trivalent iron salt.

[0014] In any of the above technical solutions, the trivalent iron salt is any one or several of FeCl3, Fe(NO3)3, and Fe2(SO4)3.

[0015] In any of the above technical solutions, the pyridyl binary acid is selected from any one or several of 2,3-pyridine dicarboxylic acid, 2,4-pyridine dicarboxylic acid, 2,5-pyridine dicarboxylic acid, 2,6-pyridine dicarboxylic acid, 3,4-pyridine dicarboxylic acid, and 3,5-pyridine dicarboxylic acid.

[0016] It is well known that the initial adhesion of starch glue is poor, and the starch glue is easy to slip during hot pressing, which causes the corrugated peaks and the face / inner paper to be easily misaligned and separated, resulting in the problems of "run corrugation" and "collapse corrugation", and the waste rate increases. The pyridine group is introduced into the molecular chain of the modified PAE resin, and a water-soluble metal salt is added in the main body glue. The pyridine group, as an excellent coordination group, has strong coordination ability with Fe 3+ During the hot pressing of corrugated paperboard, the high temperature and high pressure environment greatly promotes the coordination process, and the pyridine group can quickly and efficiently coordinate with metal ions to form a three-dimensional coordination network of "PAE-metal ion-PAE" and "PAE-metal ion-starch" with metal ions as the crosslinking nodes. The network can greatly and quickly improve the cohesive strength and viscoelasticity of the glue, providing instant holding force for the adhesion of the corrugated core paper and the face paper, effectively resisting the shear slip under pressure, thereby significantly inhibiting the "run corrugation" and "collapse corrugation" phenomena, and reducing the waste rate.

[0017] Moreover, this three-dimensional network structure constructed by coordination bonds also plays a role in enhancing the final dry-state adhesion strength and water resistance. Because the strength of the coordination bond is much higher than that of the hydrogen bond, and it is not easily destroyed by water molecules, the initial adhesion and the final adhesion strength are synergistically improved.

[0018] In any of the above technical solutions, 0.3-0.7 parts of nano-starch is added to the carrier glue.

[0019] The above nano-starch is a starch-based nano-particle material formed by treating natural starch with physical, chemical or biological methods, with a particle size in the range of 1-100 nm and retaining the polysaccharide skeleton of starch.

[0020] The application adds an appropriate amount of nano-starch to the carrier glue. Due to its large specific surface area, nano-starch exposes a large number of hydroxyl groups, which can form more extensive and stronger hydrogen bonding and van der Waals forces with the surface of paper fibers, thereby quickly producing excellent initial adhesion. At the same time, its nano-scale particle characteristics make it easier to penetrate into the micro-pore structure of the paper fibers, producing stronger mechanical interlocking effects. The combined effects of the two effectively improve the initial adhesion of the starch glue, allowing it to fix the relative positions of the corrugated peaks and the face paper at the moment of pressure, further reducing the risk of "run corrugation" and "collapse corrugation".

[0021] In any of the above technical solutions, the preparation method of the modified PAE resin is as follows:

[0022] Mixing polyethylene polyamine with dibasic acid, under nitrogen protection, polycondensation reaction at 130-150 DEG C; after 2-4 hours, the reaction temperature is reduced to 80-90 DEG C, drop in amino acrylate monomer, after drop completion, keep reaction for 1-2 hours, after reaction is finished, the obtained product is alkenyl-containing polyamide polyamine;

[0023] Dilute the alkenyl-containing polyamide polyamine in solvent, then add platinum catalyst, stir under nitrogen protection, add hydrogen-containing silane, control temperature at 70-85 DEG C, reaction for 3-5 hours, after reaction is finished, the obtained product is organosilicon-modified polyamide polyamine;

[0024] Dilute the organosilicon-modified polyamide polyamine with water, place in ice water bath, stir and drop in epichlorohydrin; after drop completion, the reaction temperature is increased to 60-70 DEG C, keep reaction for 2-3 hours, then adjust pH to 4-5, the obtained product is modified PAE resin.

[0025] In any of the above technical solutions, the mass of the platinum catalyst is 10-30 ppm of the total mass of the alkenyl-containing polyamide polyamine and the hydrogen-containing silane.

[0026] In a second aspect, the application provides a nano-modified starch glue for corrugated cartons, comprising:

[0027] According to the raw material ratio of the nano-modified starch glue of any of the first aspect, mix carrier glue starch with water, stir to form emulsion, drop in sodium hydroxide solution, stir for 15-25 minutes to obtain gelatinized starch, add water-resistant reinforcing agent, stir to obtain carrier glue.

[0028] Mix main body glue starch with water, stir to obtain main body glue, add oxidizing agent, keep temperature at 30-50 DEG C, continuously stir for 1-2 hours to obtain main body glue.

[0029] Under stirring, add carrier glue to main body glue, continuously stir for 20-30 minutes to gelatinize the main body glue, to obtain finished glue.

[0030] In any of the above technical solutions, the oxidizing agent is hydrogen peroxide.

[0031] In the above main body glue, according to actual use needs, antifungal agent, defoaming agent, antibacterial agent, filler and other auxiliary agents can be added.

[0032] In summary, the application has the following beneficial effects:

[0033] The nano-modified starch adhesive for corrugated boxes provided by the application uses organosilicon modified PAE resin as a water-resistant reinforcing agent, introduces pyridine coordination groups into the PAE molecules, adds water-soluble metal salts and nano starch to the system, and constructs a synergistic reinforcing system. The system not only significantly improves the final water resistance and durability of the adhesive through covalent crosslinking and the introduction of hydrophobic groups, but also effectively solves the problems of "running corrugation" and "collapsing corrugation" that easily occur in high-speed production due to insufficient initial adhesion, while taking into account the storage stability of the adhesive solution, and obtains a high-performance nano-modified starch adhesive for corrugated boxes with excellent comprehensive performance and suitable for industrial production. DETAILED DESCRIPTION

[0034] Preparation Example

[0035] Preparation Example 1, a modified PAE resin, was prepared according to the following steps:

[0036] A four-necked flask equipped with a stirrer, a thermometer, a water separator and a nitrogen inlet tube was protected by nitrogen. 5.0 mol (515.0 g) of diethylenetriamine was added. The stirring was started, and 4.68 mol (684.5 g) of adipic acid, 1.56 mol (260.7 g) of 2,6-pyridinedicarboxylic acid and 46 g of p-toluenesulfonic acid (catalyst) were added in sequence. The temperature was gradually increased to 140±2℃, and the polycondensation reaction was carried out at this temperature for 3 h, and the generated water was separated. Then the system was cooled to 85℃, and 1.25 mol of 2-aminoethyl methacrylate hydrochloride was slowly added dropwise. After the addition was completed, sodium hydroxide aqueous solution (1.25 mol of NaOH dissolved in 1 L of water) was slowly added dropwise under stirring for neutralization. After the neutralization was completed, the reaction was continued at 85℃ for 1.5 h. After the reaction was completed, the alkenyl-containing polyamide polyamine was obtained.

[0037] All the alkenyl-containing polyamide polyamines described above were transferred to a reaction kettle, and 500 g of isopropyl alcohol was added for dilution. Isopropyl alcohol solution of chloroplatinic acid (platinum content was 20 ppm of the total mass of the reactants) was added, and the mixture was stirred uniformly under nitrogen protection. Then 1.5 mol (198.5 g) of trimethoxysilane was slowly added dropwise. The reaction temperature was controlled at 80±2℃, and the reaction was stopped after 4 h. The solvent isopropyl alcohol and low-boiling substances were removed by reduced pressure distillation, and the organosilicon modified polyamide polyamine was obtained.

[0038] The above silicone-modified polyamide polyamine is added to a suitable amount of deionized water and diluted to a solid content of 40%. The solution is transferred to a reaction flask equipped with an ice-water bath and a dropping funnel, and stirring is started, and the temperature is lowered to below 5°C. Epoxy chloropropane 4.25 mol (393.2 g) is slowly added dropwise. The dropping speed is controlled to maintain the reaction temperature below 50°C. After the addition is completed, the temperature is slowly raised to 65°C, and the reaction is maintained at this temperature for 2.5 h. After the reaction is completed, the temperature is cooled to room temperature, deionized water is added to adjust the solid content to 25%, and dilute hydrochloric acid is added to adjust the pH value to 4.5, to obtain the modified PAE resin (calculated according to the solid content when used).

[0039] Preparation Example 2, a modified PAE resin, is prepared according to the following procedure:

[0040] A four-necked flask equipped with a stirrer, thermometer, water separator, and nitrogen inlet tube is purged with nitrogen. Diethylenetriamine 5.0 mol (515.0 g) is added. Stirring is started, and adipic acid 5.0 mol (730.5 g), 3,5-pyridinedicarboxylic acid 1.25 mol (208.5 g), and 42 g of p-toluenesulfonic acid (catalyst) are added in sequence. The temperature is gradually raised to 135 ± 2°C, and the polycondensation reaction is carried out at this temperature for 3.5 h, with water being separated off. Subsequently, the system is cooled to 80°C, and 2-aminoethyl methacrylate hydrochloride 1.0 mol is slowly added dropwise. After the addition is completed, sodium hydroxide aqueous solution (1.0 mol NaOH dissolved in 1 L water) is slowly added dropwise under stirring for neutralization. After the neutralization is completed, the reaction is continued at 80°C for 2 h. After the reaction is completed, the ene-containing polyamide polyamine is obtained.

[0041] The above ene-containing polyamide polyamine is transferred to a reaction kettle, and diluted with 500 g of isopropyl alcohol. Isopropyl alcohol solution of chloroplatinic acid (platinum content 10 ppm of the total mass of the reactants) is added, and stirred uniformly under nitrogen protection. Then, methyldimethoxysilane 1.1 mol (136.5 g) is slowly added dropwise. The reaction temperature is controlled at 75 ± 2°C, and the reaction is stopped after 5 h. The solvent isopropyl alcohol and low-boiling substances are removed by distillation under reduced pressure, to obtain the silicone-modified polyamide polyamine.

[0042] The above silicone-modified polyamide polyamine is added to a suitable amount of deionized water and diluted to a solid content of 40%. The solution is transferred to a reaction flask equipped with an ice-water bath and a dropping funnel, and stirring is started, and the temperature is lowered to below 5°C. Epoxy chloropropane 4.25 mol (393.2 g) is slowly added dropwise. The dropping speed is controlled to maintain the reaction temperature below 50°C. After the addition is completed, the temperature is slowly raised to 65°C, and the reaction is maintained at this temperature for 2.5 h. After the reaction is completed, the temperature is cooled to room temperature, deionized water is added to adjust the solid content to 25%, and dilute hydrochloric acid is added to adjust the pH value to 4.5, to obtain the modified PAE resin (calculated according to the solid content when used).

[0043] Preparation Example 3, a modified PAE resin, was prepared according to the following procedure:

[0044] A four-necked flask equipped with a stirrer, thermometer, water separator and nitrogen inlet tube was purged with nitrogen. Diethylenetriamine 5.0 mol (515.0 g) was added into the flask. The stirring was started and adipic acid 4.5 mol (657.5 g), 2,5-pyridinedicarboxylic acid 1.5 mol (250.5 g) and 55 g of p-toluenesulfonic acid (catalyst) were added in turn. The temperature was gradually raised to 143±2°C and the polycondensation reaction was carried out at this temperature for 3 h, during which time water was removed. Then the system was cooled to 90°C and 2-aminoethyl methacrylate hydrochloride 1.5 mol was added dropwise. After the addition was completed, sodium hydroxide aqueous solution (1.5 mol NaOH dissolved in 1 L water) was added dropwise under stirring for neutralization. After the neutralization was completed, the reaction was continued at 90°C for 1.5 h. After the reaction was completed, an olefin-containing polyamide polyamine was obtained.

[0045] The above olefin-containing polyamide polyamine was transferred into a reaction kettle and diluted with 500 g of isopropyl alcohol. A chloroplatinic acid solution in isopropyl alcohol (platinum content: 30 ppm of the total mass of the reactants) was added and stirred uniformly under nitrogen. Then 1.85 mol (274.0 g) of triethoxysilane was added dropwise slowly. The reaction was stopped after 4.5 h at a temperature of 83±2°C. The solvent isopropyl alcohol and low-boiling substances were removed by distillation under reduced pressure to obtain a silicone-modified polyamide polyamine.

[0046] The above silicone-modified polyamide polyamine was diluted with deionized water to a solid content of 40%. The solution was transferred into a reaction bottle equipped with an ice-water bath and a dropping funnel, and the stirring was started and the temperature was lowered to below 5°C. 4.5 mol (416.3 g) of epichlorohydrin was added dropwise slowly. The dropping speed was controlled so that the reaction temperature was maintained below 50°C. After the addition was completed, the temperature was raised to 70°C slowly and the reaction was continued at this temperature for 3 h. After the reaction was completed, the temperature was lowered to room temperature, deionized water was added to adjust the solid content to 25%, and dilute hydrochloric acid was added to adjust the pH value to 5 to obtain a modified PAE resin (used according to the solid content).

[0047] Preparation Example 4, a modified PAE resin, differed from Preparation Example 1 in that the amount of 2-aminoethyl methacrylate hydrochloride used in the preparation of the olefin-containing polyamide polyamine was 2.0 mol (i.e., an excess amount) and the sodium hydroxide aqueous solution added dropwise contained 2.0 mol of NaOH.

[0048] Preparation Example 5, a modified PAE resin, differed from Preparation Example 1 in that the amount of 2-aminoethyl methacrylate hydrochloride used in the preparation of the olefin-containing polyamide polyamine was 0.5 mol (i.e., an insufficient amount) and the sodium hydroxide aqueous solution added dropwise contained 0.5 mol of NaOH.

[0049] Preparation Example 6, a modified PAE resin, differs from Preparation Example 1 in that the alkenyl-containing polyamide polyamine preparation step uses equimolar adipic acid instead of 2,6-pyridinedicarboxylic acid.

[0050] Preparation Example 7, a modified PAE resin, differs from Preparation Example 1 in that the alkenyl-containing polyamide polyamine preparation step uses equimolar monohydrogenosiloxane (RH-H222-10) instead of monohydrogenosilane.

[0051] Preparation Example 8, a PAE resin, is prepared according to the following procedure:

[0052] A four-necked flask equipped with a stirrer, thermometer, water separator and nitrogen inlet tube is purged with nitrogen. Diethylenetriamine 5.0 mol (515.0 g) is added to the flask. The stirrer is started and adipic acid 4.68 mol (684.5 g) and 2,6-pyridinedicarboxylic acid 1.56 mol (260.7 g) are added in sequence. The temperature is gradually raised to 140±2°C and the polycondensation reaction is carried out at this temperature for 3 h, with water being removed from the reaction. A polyamide intermediate is obtained.

[0053] The polyamide intermediate is diluted to a solid content of 40% by adding deionized water. The solution is transferred to a reaction flask equipped with an ice-water bath and a dropping funnel, and the stirring is started. The temperature is lowered to below 5°C. Epichlorohydrin 4.25 mol (393.2 g) is slowly added dropwise. The dropping speed is controlled to maintain the reaction temperature below 50°C. After the addition is completed, the temperature is slowly raised to 65°C and the reaction is carried out at this temperature for 2.5 h. After the reaction is completed, the temperature is lowered to room temperature. Deionized water is added to adjust the solid content to 25%, and dilute hydrochloric acid is added to adjust the pH value to 4.5. A modified PAE resin is obtained (used as calculated on the basis of solid content).

[0054] Example

[0055] Example 1, a nano-modified starch glue for corrugated paper boxes, is prepared according to the following procedure:

[0056] In a reaction kettle with stirrer, add water 5500 g and corn-derived nanosized starch 50 g (D50 particle size of 30-40 nm). Start stirring at a speed of 200 r / min, slowly add corn starch 1000 g, continue stirring for 15 min to form a uniform emulsion. Under stirring, slowly add an aqueous solution of sodium hydroxide 100 g (sodium hydroxide is previously dissolved in 200 g of water) dropwise. After the dropwise addition is completed, increase the stirring speed to 300 r / min, continue stirring at room temperature for 20 min, and observe that the emulsion becomes a semi-transparent viscous gel, i.e. gelatinization is complete. Then add the modified PAE resin prepared in Preparation Example 1 115 g (calculated according to solid content), continue stirring for 10 min until uniform mixing, to obtain a carrier glue.

[0057] In another reaction kettle with stirring and heating device, add water 3500 g and corn starch 1000 g. Start stirring at a speed of 150 r / min, and stir for 30 min to form a uniform suspension. Add ferric chloride hexahydrate (FeCl3·6H2O) 10 g, and stir until completely dissolved. Warm the system to 40±2°C, then add 20 g of 27.5% mass fraction hydrogen peroxide. Maintain the temperature at 40±2°C, and continue stirring for 1.5 h. After the reaction is completed, cool to room temperature to obtain a main body glue.

[0058] Under stirring (200 r / min), slowly add the prepared carrier glue to the main body glue at a mass ratio of 1:4. After the addition is completed, continue stirring for 25 min to fully gelatinize the main body starch, to obtain a uniform finished product of nanosized modified starch glue.

[0059] Example 2, a nanosized modified starch glue for corrugated cartons, is prepared as follows:

[0060] In a reaction kettle with stirrer, add water 5000 g and corn-derived nanosized starch 35 g (D50 particle size of 65-75 nm). Start stirring at a speed of 150 r / min, slowly add corn starch 1000 g, continue stirring for 20 min to form a uniform emulsion. Under stirring, slowly add an aqueous solution of sodium hydroxide 80 g (sodium hydroxide is previously dissolved in 150 g of water) dropwise. After the dropwise addition is completed, increase the stirring speed to 300 r / min, continue stirring at room temperature for 15 min, and observe that the emulsion becomes a semi-transparent viscous gel, i.e. gelatinization is complete. Then add the modified PAE resin prepared in Preparation Example 2 85 g (calculated according to solid content), continue stirring for 15 min until uniform mixing, to obtain a carrier glue.

[0061] In another reaction vessel with stirring and heating device, add water 3000g and corn starch 1000g. Start stirring, speed 150r / min, stirring 30min to form a uniform suspension. Add aluminum chloride hexahydrate (AlCl3·6H2O) 5g, stirring to completely dissolved. The system is heated to 35±2℃, then add 27.5% by mass of hydrogen peroxide 10g. Maintain the temperature at 35±2℃, continue stirring reaction 2h. After the reaction is completed, cool to room temperature, the main body glue is obtained.

[0062] Under stirring (200r / min), the prepared carrier glue is slowly added to the main body glue at a mass ratio of 1:5. After adding, continue stirring for 20min to make the main body starch gelatinize fully, and a uniform finished product of nano-modified starch glue is obtained.

[0063] Example 3, a nano-modified starch glue for corrugated cartons, is prepared as follows:

[0064] In a reaction vessel with a stirrer, add water 6000g and corn source nano starch 70g (D50 particle size is 30-40nm). Start stirring, speed 200r / min, slowly add corn starch 1000g, continue stirring 15min to form a uniform emulsion. Under stirring, slowly add a sodium hydroxide 120g dissolved in water solution (sodium hydroxide is previously dissolved in 250g water). After the addition is completed, increase the stirring speed to 300r / min, continue stirring at room temperature for 30min, and it is observed that the emulsion becomes a semi-transparent viscous gel, i.e. gelatinization is completed. Then add the modified PAE resin prepared in Preparation Example 3 50g (calculated according to solid content), continue stirring for 10min until mixed uniformly, and a carrier glue is obtained.

[0065] In another reaction vessel with stirring and heating device, add water 4000g and corn starch 1000g. Start stirring, speed 200r / min, stirring 35min to form a uniform suspension. Add iron chloride hexahydrate (FeCl3·6H2O) 15g, stirring to completely dissolved. The system is heated to 45±2℃, then add 27.5% by mass of hydrogen peroxide 30g. Maintain the temperature at 45±2℃, continue stirring reaction 1.5h. After the reaction is completed, cool to room temperature, the main body glue is obtained.

[0066] Under stirring (200r / min), the prepared carrier glue is slowly added to the main body glue at a mass ratio of 1:4. After adding, continue stirring for 30min to make the main body starch gelatinize fully, and a uniform finished product of nano-modified starch glue is obtained.

[0067] Example 4, a nano-modified starch adhesive for corrugated carton, which is different from Example 1 in that the modified PAE resin prepared in Preparation Example 4 is used to replace the modified PAE resin prepared in Preparation Example 1 in the carrier adhesive in equal mass.

[0068] Example 5, a nano-modified starch adhesive for corrugated carton, which is different from Example 1 in that the modified PAE resin prepared in Preparation Example 5 is used to replace the modified PAE resin prepared in Preparation Example 1 in the carrier adhesive in equal mass.

[0069] Example 6, a nano-modified starch adhesive for corrugated carton, which is different from Example 1 in that the modified PAE resin prepared in Preparation Example 6 is used to replace the modified PAE resin prepared in Preparation Example 1 in the carrier adhesive in equal mass.

[0070] Example 7, a nano-modified starch adhesive for corrugated carton, which is different from Example 1 in that no FeCl3·6H2O is added to the main body adhesive.

[0071] Example 8, a nano-modified starch adhesive for corrugated carton, which is different from Example 6 in that no FeCl3·6H2O is added to the main body adhesive.

[0072] Example 9, a nano-modified starch adhesive for corrugated carton, which is different from Example 1 in that corn starch is used to replace corn source nano starch in the carrier adhesive in equal mass.

[0073] Comparative Example

[0074] Comparative Example 1, a nano-modified starch adhesive for corrugated carton, which is different from Example 1 in that the modified PAE resin prepared in Preparation Example 7 is used to replace the modified PAE resin prepared in Preparation Example 1 in the carrier adhesive in equal mass.

[0075] Comparative Example 2, a nano-modified starch adhesive for corrugated carton, which is different from Example 1 in that the PAE resin prepared in Preparation Example 8 is used to replace the modified PAE resin prepared in Preparation Example 1 in the carrier adhesive in equal mass.

[0076] Performance detection test

[0077] Test 1: water resistance test

[0078] Sample preparation:

[0079] Material preparation: corrugated core paper (in accordance with GB / T 13023-2008 "Corrugated Core (Original) Paper" standard, basis weight 100 g / m 2 ), kraft box board paper (in accordance with GB / T 13024-2016 "Box Paperboard" standard, basis weight 200 g / m 2), and cut into standard sample size (150 mm x 25 mm). The nano-modified starch adhesives were the nano-modified starch adhesives prepared in the examples and comparative examples of the present application.

[0080] Gluing and compounding: the nano-modified starch adhesives were uniformly coated on the wave crest of the corrugated core paper using a wire bar coater, and the coating amount was controlled at 15±1 g / m 2 . Immediately, the corrugated box paper was covered on the coated surface, and a hand roller press was used to press once at a pressure of 0.5 MPa to ensure the initial adhesion.

[0081] Hot pressing and curing: the compounded sample was placed in a flat plate hot press, and hot pressed at 160±2℃ for 2 minutes, with the pressure set at 0.6 MPa to simulate the hot pressing conditions of the corrugated paperboard production line.

[0082] Conditioning treatment: the hot-pressed sample was placed under standard atmospheric conditions (23±1℃, 50±2% relative humidity) for 24 hours to balance the moisture and stress. Ten effective samples were prepared for each test group.

[0083] Test procedure:

[0084] Randomly select 5 samples treated under the initial conditions, and test according to the provisions of GB / T 6548-2011 "Determination of the bonding strength of corrugated paperboard". The sample was installed on the fixture, and the 180° peeling test was carried out at a stretching speed of 100 mm / min, and the maximum peeling force (unit: N / m) was recorded. The average value of 5 samples was calculated as the initial bonding strength (A0). The remaining at least 5 samples were placed in a constant temperature and humidity chamber under the conditions of temperature 23±1℃ and relative humidity 90±2% for continuous treatment for 96 hours to simulate the extreme humid storage environment. After the treatment was completed, the sample was immediately taken out of the constant temperature and humidity chamber, and the bonding strength test was completed within 5 minutes (the test environment conditions were still 23±1℃, 50±2% RH), and the method was the same as the initial bonding strength test. The bonding strength after high humidity treatment (A1) was recorded. The strength retention rate was calculated according to the following formula: moisture resistance strength retention rate (%) = (A1 / A0) x 100%. The result was taken as the average value. The higher the strength retention rate, the better the moisture resistance of the starch adhesive, and the better the resistance to strength degradation caused by humid environment.

[0085] Test 2: production waste rate test

[0086] Sample preparation:

[0087] Simulation of production line setting: a laboratory small-sized corrugated paperboard forming machine was used, and the production line speed was set at 10 m / min (to simulate the medium-low speed production conditions). The corrugated roller temperature was controlled at 160±2℃, and the pressure roller pressure was 0.6±0.1 MPa.

[0088] Adhesive coating: Add nano-modified starch adhesive into the glue tank, adjust the gap between the glue rollers to make the amount of glue stable at 15±1 g / m 2 The adhesive needs to be stirred evenly before use, and the temperature should be maintained at 25±5°C.

[0089] Continuous production: Using corrugated core paper (B corrugated core paper meeting GB / T 13023-2008, basis weight 100 g / m 2 ) and kraft liner paper (basis weight 200 g / m 2 ) as raw materials, corrugated paperboard was continuously produced for 100 meters. After the production was stable, every 1 meter was cut off to obtain a 300 mm x 300 mm sample, and a total of 200 samples were obtained.

[0090] Test steps:

[0091] Each sample was visually and dimensionally inspected. The corrugation height (distance from the valley bottom of the core paper to the peak top) was measured using a digital caliper, and if the corrugation height decreased by more than 10% of the initial height (relative to the standard corrugation height H0=2.7mm for B corrugation), it was defined as "corrugation collapse"; the misalignment distance between the corrugation peak and the adhesive line of the face paper was measured using a steel ruler, and if the misalignment was more than 5mm, it was defined as "corrugation running". The number of samples with "corrugation running" or "corrugation collapse" defects was recorded. The waste rate (%) = (number of defective samples / total number of samples) x 100%.

[0092] Table 1, test results

[0093]

[0094] Analysis of test results:

[0095] Compared with Example 1, Example 4 (excess amino acrylate during PAE preparation) had a slight decrease in wet strength retention rate and an increase in production waste rate, indicating that excessive use of amino acrylate had a negative impact on water resistance and initial adhesion stability. The reason may be that the introduction of excess mono-amino polymeric raw materials destroys the regularity and molecular weight of the polyamide polyamine molecules, affecting the reactivity of epoxy chloropropane, mechanical properties, and stability of the final cross-linked network, thereby reducing the water resistance and cohesive strength of the adhesive layer (easy "corrugation running" and "corrugation collapse").

[0096] Example 5 (less amino acrylate during PAE preparation) performed poorly in wet strength retention rate and production waste rate, indicating that insufficient use of amino acrylate also had a negative impact on water resistance and initial adhesion stability. The reason may be that insufficient alkenyl introduction results in low silicone grafting rate and insufficient hydrophobic groups, thereby weakening the water resistance.

[0097] Example 6 (no pyridine group introduced during PAE preparation), Example 7 (no metal salt added in the main adhesive), and Example 8 (PAE introduced with pyridine group and no metal salt added) all performed poorly in terms of moisture resistance strength retention rate and production waste rate, and the test results were close. This indicates that the pyridine group and the metal ion have a synergistic effect, and the synergistic effect of the two has a significant positive impact on water resistance and initial adhesion. The reason may be that the absence of either the pyridine group or the metal ion cannot form a coordination network, resulting in insufficient initial adhesion, easy occurrence of "runniness" and "collapse", and the absence of the coordination network affects water resistance, resulting in a decrease in adhesion strength after wet treatment. In addition, Example 6 performed well in terms of waste rate, indicating that the absence of the pyridine group and the metal ion can also form a certain coordination network with starch.

[0098] Example 9 (no nano-starch added in the carrier adhesive) had a certain increase in the production waste rate, indicating that nano-starch has an important contribution to initial adhesion. The reason may be that the absence of the high specific surface area and permeability of nano-starch results in insufficient initial adhesion, leading to an increase in the "runniness" phenomenon during production.

[0099] Comparative Example 1 (hydrogen-containing silicone oil instead of hydrogen-containing silane during PAE preparation) performed poorly in terms of initial adhesion strength and waste rate, but performed well in terms of moisture resistance strength retention rate, indicating that hydrogen-containing silane can improve initial adhesion strength compared to hydrogen-containing silicone oil, but is less hydrophobic than hydrogen-containing silicone oil. The reason may be that hydrogen-containing silicone oil has a long silicon-oxygen-silicon segment and large steric hindrance, which can play a stronger hydrophobic barrier role. However, it lacks silicon hydroxyl groups, which cannot effectively react and bond with starch and paper fibers, so it has no positive effect on adhesion strength. In addition, the grafting of silicone oil segments significantly weakens the initial adhesion, which will significantly increase the "runniness" and "collapse" phenomena.

[0100] Comparative Example 2 (no organic silicon modification during PAE preparation) performed the worst in terms of moisture resistance strength retention rate, indicating that organic silicon modification is crucial for water resistance. The reason may be that the absence of organic silicon hydrophobic groups makes the adhesive layer prone to moisture absorption, and it cannot form Si-O-C covalent bonds, resulting in a significant deterioration in water resistance.

[0101] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. Those skilled in the art can make modifications to the present embodiment without creative contribution after reading the present specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A nanomodified starch glue for corrugated carton characterized in that, The carrier glue and the main body glue include 1:4-5 in mass ratio, the carrier glue includes 10 parts of starch, 50-60 parts of water, 0.8-1.2 parts of sodium hydroxide, 0.8-1.5 parts of modified PAE resin and 0.3-0.7 parts of nano starch in mass parts; the main body glue includes 10 parts of starch, 30-40 parts of water and 0.1-0.3 parts of oxidant; the preparation method of the modified PAE resin is that: alkylene-containing polyamide polyamine is prepared by polycondensation with binary acid, polyethylene polyamine and amino acrylate monomer as raw materials in a molar ratio of 1.2-1.4:1:0.2-0.3; the alkylene-containing polyamide polyamine is sequentially reacted with hydrogen-containing silane and epichlorohydrin to obtain the modified PAE resin; the molar ratio of the alkylene-containing polyamide polyamine and the epichlorohydrin is 1:0.6-0.9, and the molar ratio of the amino acrylate monomer and the hydrogen-containing silane is 1:1.1-1.3; the binary acid is adipic acid and pyridyl binary acid in a molar ratio of 3-4:1, and 0.05-0.15 parts of water-soluble metal salt is added in the main body glue; the hydrogen-containing silane is selected from any one or several of trimethoxysilane, triethoxysilane, methyl dimethoxysilane, methyldiethoxysilane and ethyldimethoxysilane.

2. The starch glue according to claim 1, characterized in that, The polyethylene polyamine is selected from any one or several of diethylene triamine, triethylene tetramine and tetraethylene pentamine.

3. The starch glue according to claim 1, characterized in that, The amino acrylate monomer is 2-aminoethyl methacrylate.

4. The starch glue according to claim 1, characterized in that, The water-soluble metal salt is ferric salt.

5. The starch glue according to claim 1, characterized in that, The pyridyl binary acid is selected from any one or several of 2,3-pyridine dicarboxylic acid, 2,4-pyridine dicarboxylic acid, 2,5-pyridine dicarboxylic acid, 2,6-pyridine dicarboxylic acid, 3,4-pyridine dicarboxylic acid and 3,5-pyridine dicarboxylic acid.

6. The starch glue according to claim 1, characterized in that, The preparation method of the modified PAE resin is: The polyethylene polyamine is mixed with the binary acid, and polycondensation reaction is carried out under nitrogen protection at 130-150 DEG C; after 2-4 hours, the reaction temperature is reduced to 80-90 DEG C, the amino acrylate monomer is dropped, after the dropping is completed, the reaction is carried out for 1-2 hours, and then the alkylene-containing polyamide polyamine is obtained; The alkylene-containing polyamide polyamine is diluted in a solvent, a platinum catalyst is added, stirring is carried out under nitrogen protection, the hydrogen-containing silane is added, the temperature is controlled at 70-85 DEG C, the reaction is carried out for 3-5 hours, and then the silicone-modified polyamide polyamine is obtained; The silicone-modified polyamide polyamine is diluted with water, placed in an ice water bath, and the epichlorohydrin is added by stirring dropwise; after the dropping is completed, the reaction temperature is increased to 60-70 DEG C, the reaction is carried out for 2-3 hours, the pH is adjusted to 4-5, and then the modified PAE resin is obtained.

7. A nanomodified starch glue for corrugated carton characterized in that, The raw material ratio of the nano-modified starch glue for the corrugated paper box according to any one of claims 1-6 is: The carrier glue is mixed with starch, nano starch and water, stirring is carried out to form an emulsion, the sodium hydroxide solution is dropped, stirring is carried out for 15-25 minutes, the gelatinized starch is obtained, the modified PAE resin is added, stirring is carried out uniformly, and then the carrier glue is obtained; The main body glue is mixed with starch and water, stirring is carried out uniformly, the water-soluble metal salt is added, the oxidant is added, the temperature is maintained at 30-50 DEG C, and then the main body glue is obtained. The carrier glue is added into the main glue under stirring, and the main glue is pasted for 20-30 min to obtain the finished glue.

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