Environmentally friendly mildew-proof and antibacterial corrugated paperboard and preparation method thereof

Abstract

The invention relates to the technical field of paperboard products, and discloses an environment-friendly mildew-proof and antibacterial corrugated paperboard and a preparation method thereof. The quaternary ammonium salt substance of the modified terminal isocyanate polyurethane can attack the cell membrane or cell wall of microorganisms, so that the cell membrane function is affected and irreversible damage is caused to the structure of the microorganism organelles. The chemical element S is contained in the structure and has strong oxidizing and reducing properties, so that the cell membrane of microorganisms can be destroyed, organic matter can be decomposed, and the metabolism and growth environment of molds can be destroyed. The epoxy group and isocyanate group of the modified terminal isocyanate polyurethane can react with the hydroxyl group and carboxyl group on the surface of oxidized cassava starch, and at the same time, the dimethylol urea and oligomers in the urea-formaldehyde resin undergo cross-linking reaction with the hydroxyl group in the starch molecules to form a cross-linked network structure, so that water molecules are prevented from penetrating into the paper, thereby improving the bonding strength and water resistance of the corrugated paperboard.

Description

Technical Field

[0001] The invention relates to the technical field of paperboard products, in particular to an environmentally friendly mildew-proof and antibacterial corrugated paperboard and a preparation method thereof. Background Art

[0002] Corrugated paperboard is a multi-layer adhesive body, which is composed of at least one layer of corrugated core paper interlayer and one layer of paperboard. It occupies a very important position in the packaging field due to its advantages of light weight, low price, full protection function for goods and ability to withstand collisions and falls during transportation. In the prior art, corrugated paperboard is mainly made of fiber raw materials, and water molecule adhesives are mostly used in production. The common problems are: it is easy to become thin during recycling; the unstable performance leads to easy stratification and precipitation during storage and cannot be used continuously, making the produced corrugated paperboard easy to get damp and soften, resulting in a decrease in the bonding strength and edge pressure strength of the paperboard, and easy to absorb moisture and breed bacteria and mold, which seriously affects its normal use. Therefore, the preparation of an antibacterial and mildew-proof corrugated paperboard has become a hot topic in current research.

[0003] In the prior art, the waterproof and antibacterial properties of corrugated paper can be improved by coating the surface of the corrugated paper with a waterproof coating. However, the conventional waterproof coating generally has the disadvantages of poor wear resistance and low scratch resistance. Once the coating surface is worn or scratched, moisture can penetrate into the corrugated paperboard, reducing its hardness and mechanical strength, and accelerating the mildew and decay of the corrugated paperboard. Chinese patent CN112277392B discloses a method for preparing antibacterial and antistatic corrugated paperboard. During the preparation, the corrugated paperboard is coated with an adhesive on both sides of the corrugated paperboard, and then bonded with the inner paper and the face paper to form the corrugated paperboard. The adhesive is made of a mixture of purple sweet potato starch, melamine and polyformaldehyde, and then bonded with the inner paper and the face paper to form the corrugated paperboard. 60 Co r Irradiation with radiation sources enhances its activity, thereby improving the antibacterial and antistatic capabilities of the product. However, radiation has the disadvantage of being environmentally unfriendly. Simply adding antibacterial ingredients to the adhesive is not enough to improve the overall antibacterial properties of corrugated cardboard.

[0004] Patent No. CN111907181B discloses a high-strength and impact-resistant composite corrugated paper and a preparation method thereof, comprising an outer paper layer, an intermediate filling layer, a core paper layer, a wavy core layer and an inner paper layer arranged in sequence from top to bottom, and adjacent layers are bonded by an adhesive. However, while improving the impact resistance and strength of the corrugated paper layer, it is difficult to exert its antibacterial properties in the use environment. For example, in a humid environment, the corrugated paper structure is easily disintegrated and mold occurs, resulting in its high-strength performance being difficult to exert; the present invention aims to synthesize a polyurethane modified with epoxy quaternary ammonium salt, which is added to the face paper, corrugated core base and adhesive of the corrugated board respectively, and can be chemically cross-linked with oxidized cassava starch to form a stable cross-linked network structure, and its quaternary ammonium salt has antibacterial properties, is safe and environmentally friendly, and has strong feasibility. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an environmentally friendly mildew-proof and antibacterial corrugated paperboard and a preparation method thereof, thereby improving the antibacterial and antibacterial properties of the corrugated paperboard and making up for its poor water resistance.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The invention discloses an environment-friendly mildew-proof and antibacterial corrugated paperboard which is made of upper paper, a V-shaped corrugated core base layer and lower paper bonded by an adhesive.

[0008] The adhesive comprises the following components in parts by weight: 50-65 parts of oxidized cassava starch, 12-20 parts of urea-formaldehyde resin, 2-10 parts of modified terminal isocyanate-based polyurethane and 0.5-2 parts of montmorillonite.

[0009] The preparation method of the modified terminal isocyanate polyurethane is as follows: add isophorone isocyanate and tetrahydrofuran to a flask equipped with a condenser, stir evenly, add polyethylene glycol and dibutyltin dilaurate, react at a temperature of 65-75°C and a rotation speed of 250-350r / min for 3-8h, add a structural formula The diepoxy quaternary ammonium salt diol is reacted at 70-80°C for 2-5h, cooled, triethylamine is added for neutralization, and after reduced pressure concentration, distilled water is added, and high-speed stirring is carried out at 1200-1500r / min for 1-3h to obtain a modified terminal isocyanate polyurethane.

[0010] Preferably, the ratio of isophorone isocyanate, polyethylene glycol, dibutyltin dilaurate, and diepoxide quaternary ammonium salt diol is 1 mol: (0.4-0.48) mol: (0.0015-0.0025) mol: (0.1-0.15) mol.

[0011] Preferably, the preparation method of the V-shaped corrugated core base layer is: 20-40 parts by weight of waste paper, 10-15 parts of sawdust, 3-6 parts of cyclodextrin, 10-20 parts of cassava starch, 5-8 parts of boron carbide fiber, 0.2-0.5 parts of carboxymethyl cellulose and 120-150 parts of deionized water are stirred and ground into a pulp liquid, and then 1-5 parts of modified terminal isocyanate polyurethane, 1-2 parts of polyvinyl alcohol and 8-12 parts of oxidized cassava starch are added, mixed evenly, placed in a paper machine for dehydration and molding, and then subjected to papermaking and curling treatments, and corrugated by the corrugating roller of a single-facer to obtain a V-shaped corrugated core base layer.

[0012] Preferably, the preparation method of the upper and lower paper is: 100 parts by weight of lemon eucalyptus powder, 20-30 parts of oxidized cassava starch, 30-50 parts of waste paper pulp, 5-25 parts of modified terminal isocyanate polyurethane and 6-9 parts of diatomaceous earth are mixed evenly, heated to 150-170° C., stirred for 20-40 minutes, then 0.3-0.5 parts of sodium dodecyl sulfate are added and stirred for 10-15 minutes, dehydrated and formed, and subjected to papermaking and curling treatment to obtain the upper and lower paper.

[0013] Preferably, the preparation method of the diepoxy quaternary ammonium salt diol is:

[0014] Step (1), under nitrogen atmosphere, add acryloyl chloride and 1,4-dioxane to a reaction flask, stir evenly, add N'-[2-(dimethylamino)ethyl]-N,N-dimethylethylenediamine and potassium carbonate, react at room temperature for 12-24h, add deionized water and dichloromethane for extraction, concentrate the organic phase, and dry to obtain N,N-bis[2-(dimethylamino)ethyl]acrylamide. The preparation reaction formula is as follows:

[0015]

[0016] Step (2), under nitrogen atmosphere, add 1-thioglycerol and ethanol to the reaction flask, stir evenly, add triethylamine and N, N-bis [2- (dimethylamino) ethyl] acrylamide, react at 30-50 ° C for 8-16 hours, concentrate under reduced pressure, wash with deionized water, and dry to obtain N, N-bis [2- (dimethylamino) ethyl] thiodiol. The preparation reaction formula is as follows:

[0017]

[0018] Step (3), under nitrogen atmosphere, add N, N-bis [2- (dimethylamino) ethyl] thiodiol and acetone to a reaction flask, stir evenly, add epibromopropane, react at 65-80 ° C for 24-48h, distill under reduced pressure, and recrystallize from ethanol to obtain a diepoxy quaternary ammonium salt diol. The preparation reaction formula is as follows:

[0019]

[0020] Preferably, in step (1), the ratio of acryloyl chloride, N'-[2-(dimethylamino)ethyl]-N,N-dimethylethylenediamine, and potassium carbonate is 1 mol:(1.05-1.2) mol:(1.5-2.1) mol.

[0021] Preferably, in step (2), the ratio of 1-thioglycerol, triethylamine, and N,N-bis[2-(dimethylamino)ethyl]acrylamide is 1 mol:(2.4-3) mol:(1.1-1.25) mol.

[0022] Preferably, in step (3), the ratio of N,N-bis[2-(dimethylamino)ethyl]thiodiol to epibromopropane is 1 mol:(1.1-1.3) mol.

[0023] Preferably, the preparation method is: coating the prepared adhesive on the surface of the upper paper and the lower paper respectively, pressing and bonding the upper and lower papers to the V-shaped corrugated core base layer in turn, standing and drying at room temperature, to obtain an environmentally friendly mildew-proof and antibacterial corrugated paperboard.

[0024] Preferably, the coating amount of the adhesive is 20-30 g / m 2 .

[0025] By adopting the above technical solution, the beneficial effects of the present invention are:

[0026] The invention firstly reacts acryloyl chloride and N'-[2-(dimethylamino)ethyl]-N,N-dimethylethylenediamine under the action of potassium carbonate to obtain N,N-bis[2-(dimethylamino)ethyl]acrylamide, then reacts with 1-thioglycerol to obtain N,N-bis[2-(dimethylamino)ethyl]thiodiol, then reacts with epibromopropane to obtain diepoxy quaternary ammonium salt diol, then polymerizes with isophorone isocyanate and polyethylene glycol to obtain modified terminal isocyanate polyurethane, and finally adds the modified terminal isocyanate polyurethane to upper and lower paper and V-shaped corrugated core base respectively, and presses and bonds them in sequence to obtain environmentally friendly mildew-proof and antibacterial corrugated paperboard.

[0027] The quaternary ammonium salt substance of the modified terminal isocyanate polyurethane can attack the cell membrane or cell wall of microorganisms, resulting in the influence of cell membrane function, leakage of cell contents, and irreversible damage to the structure of microbial organelles, leading to the death of microorganisms; its structure contains the chemical element S, which has strong oxidizing and reducing properties. During the fumigation process, sulfur dioxide gas is produced, which has strong bactericidal ability, can destroy the cell membrane of microorganisms, decompose organic matter, and destroy the metabolism and growth environment of mold, thereby preventing the occurrence of mildew.

[0028] Even after the corrugated paperboard prepared by the invention is placed under high humidity for 12 hours, its bonding strength is still maintained at a relatively high level, because the epoxy group and the isocyanate group of the modified terminal isocyanate polyurethane can react with the hydroxyl group and the carboxyl group on the surface of the oxidized cassava starch to form a cross-linked network structure, thereby improving the water resistance of the adhesive after curing; at the same time, the dimethylol urea and the oligomer in the urea-formaldehyde resin react with the hydroxyl group in the starch molecule, and the aldehyde group in the starch can react with the hydroxyl group in the resin to form a hemiacetal and acetal structure, thereby forming a cross-linked structure with the participation of starch chains; since the polyurethane, the urea-formaldehyde resin and the oxidized cassava starch react with each other to form a network structure, water molecules are prevented from penetrating into the paper, thereby further improving the bonding strength and water resistance of the corrugated paperboard. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Preparation of oxidized cassava starch: Add 50g of cassava starch into a 250mL beaker, add 0.35g of 0.007mol / L chlorine dioxide solution while stirring, place in an ultrasonic wave with a power of 350W and a temperature of 50°C for reaction for 1h, add 0.1g of 0.2mol / L sodium sulfite, dry and crush to obtain oxidized cassava starch.

[0031] The preparation method of the V-shaped corrugated core base layer is as follows: 20-40 parts by weight of waste paper, 10-15 parts of sawdust, 3-6 parts of cyclodextrin, 10-20 parts of cassava starch, 5-8 parts of boron carbide fiber, 0.2-0.5 parts of carboxymethyl cellulose and 120-150 parts of deionized water are stirred and ground into a pulp liquid, and then 1-5 parts of modified terminal isocyanate polyurethane, 1-2 parts of polyvinyl alcohol and 8-12 parts of oxidized cassava starch are added, mixed evenly, placed in a paper machine for dehydration and forming, and then subjected to papermaking and curling treatments, and corrugated by a corrugated roller of a single-face machine to obtain a V-shaped corrugated core base layer.

[0032] The preparation method of the upper and lower side papers is as follows: 100 parts by weight of lemon eucalyptus powder, 20-30 parts of oxidized cassava starch, 30-50 parts of waste paper pulp, 5-25 parts of modified terminal isocyanate polyurethane and 6-9 parts of diatomaceous earth are mixed evenly, heated to 150-170°C, stirred for 20-40 minutes, then 0.3-0.5 parts of sodium dodecyl sulfate are added and stirred for 10-15 minutes, dehydrated and formed, and subjected to papermaking and curling treatment to obtain the upper and lower side papers.

[0033] Example 1

[0034] (1) Under nitrogen atmosphere, 25 mmol of acryloyl chloride and 100 mL of 1,4-dioxane were added to a reaction flask, and after stirring, 28.2 mmol of N'-[2-(dimethylamino)ethyl]-N,N-dimethylethylenediamine and 45 mmol of potassium carbonate were added, and the mixture was reacted at room temperature for 16 h. Deionized water and dichloromethane were added for extraction, and the organic phase was concentrated and dried to obtain N,N-bis[2-(dimethylamino)ethyl]acrylamide.

[0035] (2) Under nitrogen atmosphere, 22 mmol of 1-thioglycerol and 145 mL of ethanol were added to a reaction flask. After stirring, 58.3 mmol of triethylamine and 25.2 mmol of N,N-bis[2-(dimethylamino)ethyl]acrylamide were added. The mixture was reacted at 40° C. for 12 h. The mixture was concentrated under reduced pressure, washed with deionized water, and dried to obtain N,N-bis[2-(dimethylamino)ethyl]thiodiol.

[0036] (3) Under nitrogen atmosphere, 18 mmol of N,N-bis[2-(dimethylamino)ethyl]thiodiol and 243 mL of acetone were added to a reaction flask. After stirring, 20.7 mol of epibromopropane was added. The mixture was reacted at 70° C. for 32 h, and then distilled under reduced pressure and recrystallized from ethanol to obtain a diepoxy quaternary ammonium diol.

[0037] (4) Add 100 mmol of isophorone isocyanate and 250 mL of tetrahydrofuran to a flask equipped with a condenser, stir evenly, add 45 mmol of polyethylene glycol and 0.2 mol of dibutyltin dilaurate, react at 70°C and 300 r / min for 5 h, add 10 mmol of diepoxy quaternary ammonium salt diol, react at 75°C for 3 h, cool, add triethylamine for neutralization, concentrate under reduced pressure, add distilled water, and stir at 1300 r / min for 2 h to obtain a modified terminal isocyanate polyurethane.

[0038] (5) 55 g of oxidized cassava starch, 15 g of urea-formaldehyde resin, 2 g of modified terminal isocyanate polyurethane and 1 g of montmorillonite were mixed and stirred evenly, and then coated on the upper and lower paper surfaces respectively, with a coating amount of 22 g / m 2 The upper and lower papers are pressed and bonded to the V-shaped corrugated core base layer in turn, and then dried at room temperature to obtain an environmentally friendly mildew-proof and antibacterial corrugated paperboard.

[0039] Example 2

[0040] (1) Under nitrogen atmosphere, 50 mmol of acryloyl chloride and 150 mL of 1,4-dioxane were added to a reaction flask, and after stirring, 52.5 mmol of N'-[2-(dimethylamino)ethyl]-N,N-dimethylethylenediamine and 75 mmol of potassium carbonate were added. The mixture was reacted at room temperature for 12 h, and deionized water and dichloromethane were added for extraction. The organic phase was concentrated and dried to obtain N,N-bis[2-(dimethylamino)ethyl]acrylamide.

[0041] (2) Under nitrogen atmosphere, 45 mmol of 1-thioglycerol and 225 mL of ethanol were added to a reaction flask. After stirring, 108 mmol of triethylamine and 49.5 mmol of N,N-bis[2-(dimethylamino)ethyl]acrylamide were added. The mixture was reacted at 50° C. for 8 h. The mixture was concentrated under reduced pressure, washed with deionized water, and dried to obtain N,N-bis[2-(dimethylamino)ethyl]thiodiol.

[0042] (3) Under nitrogen atmosphere, 40 mmol of N,N-bis[2-(dimethylamino)ethyl]thiodiol and 480 mL of acetone were added to a reaction flask. After stirring evenly, 44 mol of epibromopropane was added. The mixture was reacted at 80° C. for 24 h, and then distilled under reduced pressure and recrystallized from ethanol to obtain a diepoxy quaternary ammonium diol.

[0043] (4) Add 100 mmol of isophorone isocyanate and 200 mL of tetrahydrofuran to a flask equipped with a condenser, stir evenly, add 40 mmol of polyethylene glycol and 0.15 mol of dibutyltin dilaurate, react at 75°C and 350 r / min for 3 h, add 11 mmol of diepoxy quaternary ammonium salt diol, react at 80°C for 2 h, cool, add triethylamine for neutralization, concentrate under reduced pressure, add distilled water, and stir at 1500 r / min for 1 h to obtain a modified terminal isocyanate polyurethane.

[0044] (5) 50 g of oxidized cassava starch, 12 g of urea-formaldehyde resin, 4 g of modified terminal isocyanate polyurethane and 2 g of montmorillonite were mixed and stirred evenly, and then coated on the upper and lower paper surfaces respectively, with a coating amount of 24 g / m 2 The upper and lower papers are pressed and bonded to the V-shaped corrugated core base layer in turn, and then dried at room temperature to obtain an environmentally friendly mildew-proof and antibacterial corrugated paperboard.

[0045] Example 3

[0046] (1) Under nitrogen atmosphere, 30 mmol of acryloyl chloride and 180 mL of 1,4-dioxane were added to a reaction flask, and after stirring, 36 mmol of N'-[2-(dimethylamino)ethyl]-N,N-dimethylethylenediamine and 63 mmol of potassium carbonate were added, and the mixture was reacted at room temperature for 24 h. Deionized water and dichloromethane were added for extraction, and the organic phase was concentrated and dried to obtain N,N-bis[2-(dimethylamino)ethyl]acrylamide.

[0047] (2) Under nitrogen atmosphere, 25 mmol of 1-thioglycerol and 250 mL of ethanol were added to a reaction flask. After stirring, 75 mmol of triethylamine and 31.25 mmol of N,N-bis[2-(dimethylamino)ethyl]acrylamide were added. The mixture was reacted at 30° C. for 16 h. The mixture was concentrated under reduced pressure, washed with deionized water, and dried to obtain N,N-bis[2-(dimethylamino)ethyl]thiodiol.

[0048] (3) Under nitrogen atmosphere, 20 mmol of N,N-bis[2-(dimethylamino)ethyl]thiodiol and 300 mL of acetone were added to a reaction flask. After stirring evenly, 36 mol of epibromopropane was added. The mixture was reacted at 65° C. for 48 h, and then distilled under reduced pressure and recrystallized from ethanol to obtain a diepoxy quaternary ammonium diol.

[0049] (4) Add 100 mmol of isophorone isocyanate and 300 mL of tetrahydrofuran to a flask equipped with a condenser, stir evenly, add 48 mmol of polyethylene glycol and 0.25 mol of dibutyltin dilaurate, react at a temperature of 65°C and a rotation speed of 250 r / min for 8 h, add 13 mmol of diepoxy quaternary ammonium salt diol, react at 70°C for 5 h, cool, add triethylamine for neutralization, concentrate under reduced pressure, add distilled water, and stir at a high speed of 1200 r / min for 3 h to obtain a modified terminal isocyanate polyurethane.

[0050] (5) 65 g of oxidized cassava starch, 20 g of urea-formaldehyde resin, 6 g of modified terminal isocyanate polyurethane and 0.5 g of montmorillonite were mixed and stirred evenly, and then coated on the upper and lower paper surfaces respectively, with a coating amount of 26 g / m 2 The upper and lower papers are pressed and bonded to the V-shaped corrugated core base layer in turn, and then dried at room temperature to obtain an environmentally friendly mildew-proof and antibacterial corrugated paperboard.

[0051] Example 4

[0052] (1) Under nitrogen atmosphere, 35 mmol of acryloyl chloride and 145 mL of 1,4-dioxane were added to a reaction flask, and after stirring, 42 mmol of N'-[2-(dimethylamino)ethyl]-N,N-dimethylethylenediamine and 63 mmol of potassium carbonate were added, and the mixture was reacted at room temperature for 18 h. Deionized water and dichloromethane were added for extraction, and the organic phase was concentrated and dried to obtain N,N-bis[2-(dimethylamino)ethyl]acrylamide.

[0053] (2) Under nitrogen atmosphere, 28 mmol of 1-thioglycerol and 260 mL of ethanol were added to a reaction flask. After stirring, 74.2 mmol of triethylamine and 32.2 mmol of N,N-bis[2-(dimethylamino)ethyl]acrylamide were added. The mixture was reacted at 45° C. for 15 h. The mixture was concentrated under reduced pressure, washed with deionized water, and dried to obtain N,N-bis[2-(dimethylamino)ethyl]thiodiol.

[0054] (3) Under nitrogen atmosphere, 20 mmol of N,N-bis[2-(dimethylamino)ethyl]thiodiol and 270 mL of acetone were added to a reaction flask, and after stirring, 24 mol of epibromopropane was added. The mixture was reacted at 75° C. for 32 h, and then distilled under reduced pressure and recrystallized from ethanol to obtain a diepoxy quaternary ammonium diol.

[0055] (4) Add 100 mmol of isophorone isocyanate and 260 mL of tetrahydrofuran to a flask equipped with a condenser, stir evenly, add 45 mmol of polyethylene glycol and 0.25 mol of dibutyltin dilaurate, react at 75°C and 300 r / min for 5 h, add 14 mmol of diepoxy quaternary ammonium salt diol, react at 80°C for 3 h, cool, add triethylamine for neutralization, concentrate under reduced pressure, add distilled water, and stir at 1300 r / min for 3 h to obtain a modified terminal isocyanate polyurethane.

[0056] (5) 60 g of oxidized cassava starch, 15 g of urea-formaldehyde resin, 8 g of modified terminal isocyanate polyurethane and 1.5 g of montmorillonite were mixed and stirred evenly, and then coated on the upper and lower paper surfaces respectively, with a coating amount of 28 g / m 2 The upper and lower papers are pressed and bonded to the V-shaped corrugated core base layer in turn, and then dried at room temperature to obtain an environmentally friendly mildew-proof and antibacterial corrugated paperboard.

[0057] Example 5

[0058] (1) Under nitrogen atmosphere, 18 mmol of acryloyl chloride and 85 mL of 1,4-dioxane were added to a reaction flask, and after stirring, 20.5 mmol of N'-[2-(dimethylamino)ethyl]-N,N-dimethylethylenediamine and 30 mmol of potassium carbonate were added, and the mixture was reacted at room temperature for 20 h. Deionized water and dichloromethane were added for extraction, and the organic phase was concentrated and dried to obtain N,N-bis[2-(dimethylamino)ethyl]acrylamide.

[0059] (2) Under nitrogen atmosphere, 15 mmol of 1-thioglycerol and 120 mL of ethanol were added to a reaction flask. After stirring, 39 mmol of triethylamine and 16.8 mmol of N,N-bis[2-(dimethylamino)ethyl]acrylamide were added. The mixture was reacted at 40° C. for 12 h. The mixture was concentrated under reduced pressure, washed with deionized water, and dried to obtain N,N-bis[2-(dimethylamino)ethyl]thiodiol.

[0060] (3) Under nitrogen atmosphere, 10 mmol of N,N-bis[2-(dimethylamino)ethyl]thiodiol and 135 mL of acetone were added to a reaction flask, and after stirring, 12.5 mol of epibromopropane was added. The mixture was reacted at 80° C. for 48 h, and then distilled under reduced pressure and recrystallized from ethanol to obtain a diepoxy quaternary ammonium diol.

[0061] (4) Add 100 mmol of isophorone isocyanate and 300 mL of tetrahydrofuran to a flask equipped with a condenser, stir evenly, add 42 mmol of polyethylene glycol and 0.22 mol of dibutyltin dilaurate, react at 70°C and 320 r / min for 5 h, add 15 mmol of diepoxy quaternary ammonium salt diol, react at 80°C for 5 h, cool, add triethylamine for neutralization, concentrate under reduced pressure, add distilled water, and stir at 1500 r / min for 3 h to obtain a modified terminal isocyanate polyurethane.

[0062] (5) 60 g of oxidized cassava starch, 18 g of urea-formaldehyde resin, 10 g of modified terminal isocyanate polyurethane and 1.5 g of montmorillonite were mixed and stirred evenly, and then coated on the upper and lower paper surfaces respectively, with a coating amount of 26 g / m 2 The upper and lower papers are pressed and bonded to the V-shaped corrugated core base layer in turn, and then dried at room temperature to obtain an environmentally friendly mildew-proof and antibacterial corrugated paperboard.

[0063] Comparative Example 1

[0064] (1) Add 100 mmol of isophorone isocyanate and 250 mL of tetrahydrofuran to a flask equipped with a condenser, stir evenly, add 45 mmol of polyethylene glycol and 0.2 mol of dibutyltin dilaurate, react at 70° C. and 300 r / min for 5 h, add 10 mmol of N,N-bis[2-(dimethylamino)ethyl]thiodiol (prepared in Example 1) and react at 75° C. for 3 h, cool, add triethylamine to neutralize, concentrate under reduced pressure, add distilled water, and stir at 1300 r / min for 2 h to obtain a modified terminal isocyanate polyurethane.

[0065] (2) 55 g of oxidized cassava starch, 15 g of urea-formaldehyde resin, 2 g of modified terminal isocyanate polyurethane and 1 g of montmorillonite were mixed and stirred evenly, and then coated on the upper and lower paper surfaces respectively, with a coating amount of 22 g / m 2 , press and bond the upper and lower papers to the V-shaped corrugated core base layer in turn, and let them stand and dry at room temperature to obtain corrugated paperboard.

[0066] Comparative Example 2

[0067] 55g oxidized cassava starch, 15g urea-formaldehyde resin and 1g montmorillonite were mixed and stirred evenly, and then coated on the upper and lower paper surfaces respectively, with a coating amount of 22g / m 2 , press and bond the upper and lower papers to the V-shaped corrugated core base layer in turn, and let them stand and dry at room temperature to obtain corrugated paperboard.

[0068] Antibacterial performance test:

[0069] (1) Preparation of culture medium: Mix 200 g of potato, 20 g of glucose, 14 g of agar and 1000 mL of water, sterilize at 121°C for 20 min and set aside.

[0070] (2) The test strains were Alternaria, Penicillium, Humus and Gray (provided by the School of Food and Bioprocess Engineering of Tianjin University of Science and Technology). Each colony was inoculated on a plate and cultured for 48 h. The plates were washed with sterile saline and prepared into a 10-well plate containing about 10 7 CFU / mL bacterial suspension for later use.

[0071] (3) Fumigation antibacterial experiment of corrugated cardboard: The prepared corrugated cardboard was cut into discs with a diameter of 90 mm using a proofing machine, sterilized by ultraviolet light, and stored aseptically for later use; 15 mL of melted PDA culture medium was poured into a plate, and 0.1 mL of each experimental bacterial suspension that had been activated and adjusted in concentration was taken with a sterile pipette and added to the PDA culture medium in the plate, and spread evenly; different groups of antibacterial corrugated cardboard discs were placed in the plate, and then cultured in an incubator at 28°C for 12 h, and the antibacterial rate of the corrugated cardboard was calculated.

[0072] Table 1 Antibacterial rate test

[0073]

[0074]

[0075] It can be seen from the test results in the above table that with the increase of the content of modified terminal isocyanate polyurethane in corrugated board and adhesive, the inhibitory effect on common alternating spore enzymes, penicillium, rot enzymes and gray enzymes in fruits and vegetables and other foods is significantly enhanced, wherein in Example 5, each strain is basically completely inhibited. This is because on the one hand, the quaternary ammonium salt substance of the modified terminal isocyanate polyurethane can attack the cell membrane or cell wall of the microorganism, resulting in the cell membrane function being affected, the cell contents leaking out, causing irreversible damage to the structure of the microorganism organelles, and causing the death of the microorganism; on the other hand, the modified terminal isocyanate polyurethane contains the chemical element S, which has strong oxidizing and reducing properties, produces sulfur dioxide gas during the fumigation process, has a strong bactericidal ability, can destroy the cell membrane of the microorganism, decompose organic matter, and destroy the metabolism and growth environment of the mold, thereby preventing the occurrence of mildew.

[0076] Comparative Example 1 does not contain quaternary ammonium salt substances, contains S element, and has certain antibacterial ability; Comparative Example 2 does not contain any antibacterial elements and has no antibacterial property.

[0077] Adhesion strength test: The test was conducted according to GB / T 6548-2011 "Determination of adhesion strength of corrugated cardboard". Before the test, the corrugated cardboard was placed in a constant temperature and humidity test chamber for 12 hours. There are two test environments in the constant temperature and humidity test chamber. The temperature of the two test environments is 35°C, one is 30% humidity, and the other is 80%. The test results are shown in Table 1.

[0078] Table 2 Adhesion strength test

[0079]

[0080]

[0081] From the test results in the above table, it can be seen that with the increase of the content of modified terminal isocyanate polyurethane in corrugated board and adhesive, the bonding strength of corrugated board gradually increases. Even after being placed under high humidity for 12 hours, its bonding strength still remains at a high level. This is because the epoxy group and isocyanate group of the modified terminal isocyanate polyurethane can react with the hydroxyl and carboxyl groups on the surface of oxidized cassava starch to form a cross-linked network structure, thereby improving the water resistance of the adhesive after curing; at the same time, the dimethylol urea and oligomers in the urea-formaldehyde resin react with the hydroxyl groups in the starch molecules, and the aldehyde groups in the starch can react with the hydroxyl groups in the resin to form hemiacetal and acetal structures, thereby forming a cross-linked structure with the participation of starch chains; since the polyurethane, urea-formaldehyde resin and oxidized cassava starch react with each other to form a network structure, water molecules are prevented from penetrating into the paper, thereby improving the bonding strength and water resistance of the corrugated board.

[0082] Corrugated cardboard performance test: Tested in accordance with GB / T 6544-2008 standard.

[0083] Table 3 Corrugated cardboard performance test

[0084] Bursting strength(kPa) Edge compression strength (kN / m) Elastic modulus(GPa) Example 1 2268.54 20.58 7.21 Example 2 2356.16 21.65 7.76 Example 3 2510.68 23.83 8.08 Example 4 2651.15 25.62 8.24 Example 5 2702.43 25.74 8.55 Comparative Example 1 2035.51 20.35 6.36 Comparative Example 2 1920.32 18.36 5.42

[0085] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. An environmentally friendly mildew-proof and antibacterial corrugated paperboard, characterized in that: The corrugated paperboard is made of upper paper, V-shaped corrugated core base and lower paper bonded by adhesive; The adhesive comprises the following components in parts by weight: 50-65 parts of oxidized cassava starch, 12-23 parts of urea-formaldehyde resin, 2-10 parts of modified terminal isocyanate-based polyurethane and 0.5-2 parts of montmorillonite; The preparation method of the modified terminal isocyanate polyurethane is as follows: add isophorone isocyanate and tetrahydrofuran into a flask equipped with a condenser, stir evenly, add polyethylene glycol and dibutyltin dilaurate, react for 3-8 hours at a temperature of 65-75° C. and a rotation speed of 250-350 r / min, add a structural formula The diepoxy quaternary ammonium salt diol is reacted at 70-80°C for 2-5h, cooled, and triethylamine is added for neutralization. After reduced pressure concentration, distilled water is added, and high-speed stirring is carried out at 1200-1500r / min for 1-3h to obtain a modified terminal isocyanate polyurethane; The ratio of isophorone isocyanate, polyethylene glycol, dibutyltin dilaurate, and diepoxide quaternary ammonium salt diol is 1 mol: (0.4-0.48) mol: (0.0015-0.0025) mol: (0.1-0.15) mol; The preparation method of the diepoxy quaternary ammonium salt diol is: Step (1), under a nitrogen atmosphere, add acryloyl chloride and 1,4-dioxane to a reaction flask, stir evenly, add N'-[2-(dimethylamino)ethyl]-N,N-dimethylethylenediamine and potassium carbonate, react at room temperature for 12-24 hours, add deionized water and dichloromethane for extraction, concentrate the organic phase, and dry to obtain N,N-bis[2-(dimethylamino)ethyl]acrylamide; Step (2), under a nitrogen atmosphere, add 1-thioglycerol and ethanol to a reaction flask, stir evenly, add triethylamine and N,N-bis[2-(dimethylamino)ethyl]acrylamide, react at 30-50° C. for 8-16 h, concentrate under reduced pressure, wash with deionized water, and dry to obtain N,N-bis[2-(dimethylamino)ethyl]thiodiol; Step (3), under a nitrogen atmosphere, add N,N-bis[2-(dimethylamino)ethyl]thiodiol and acetone to a reaction flask, stir evenly, add epibromopropane, react at 65-80° C. for 24-48 hours, distill under reduced pressure, and recrystallize from ethanol to obtain a diepoxy quaternary ammonium diol; In the step (1), the ratio of acryloyl chloride, N'-[2-(dimethylamino)ethyl]-N,N-dimethylethylenediamine, and potassium carbonate is 1 mol: (1.05-1.2) mol: (1.5-2.1) mol; In step (2), the ratio of 1-thioglycerol, triethylamine, and N,N-bis[2-(dimethylamino)ethyl]acrylamide is 1 mol: (2.4-3) mol: (1.1-1.25) mol; In step (3), the ratio of N,N-bis[2-(dimethylamino)ethyl]thiodiol to epibromopropane is 1 mol:(1.1-1.3) mol.

2. The environmentally friendly mildew-proof and antibacterial corrugated paperboard according to claim 1, characterized in that: The preparation method of the V-shaped corrugated core base layer is as follows: 20-40 parts by weight of waste paper, 10-15 parts of sawdust, 3-6 parts of cyclodextrin, 10-20 parts of cassava starch, 5-8 parts of boron carbide fiber, 0.2-0.5 parts of carboxymethyl cellulose and 120-150 parts of deionized water are stirred and ground into a pulp liquid state, and then 1-5 parts by weight of modified terminal isocyanate polyurethane, 1-2 parts of polyvinyl alcohol and 8-12 parts of oxidized cassava starch are added, mixed evenly, placed in a paper machine for dehydration and forming, and then subjected to papermaking and curling treatments, and corrugated by a corrugating roller of a single-face machine to obtain a V-shaped corrugated core base layer.

3. The environmentally friendly mildew-proof and antibacterial corrugated paperboard according to claim 1, characterized in that: The preparation method of the upper paper and the lower paper is as follows: 100 parts by weight of lemon eucalyptus powder, 20-30 parts of oxidized cassava starch, 30-50 parts of waste paper pulp, 5-25 parts of modified terminal isocyanate polyurethane and 6-9 parts of diatomaceous earth are mixed evenly, heated to 150-170° C., stirred for 20-40 minutes, then 0.3-0.5 parts of sodium dodecyl sulfate are added and stirred for 10-15 minutes, dehydrated and formed, and subjected to papermaking and curling treatment to obtain the upper paper and the lower paper.

4. A method for preparing the environmentally friendly mildew-proof and antibacterial corrugated paperboard according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: coating the prepared adhesive on the surface of the upper paper and the lower paper respectively, pressing and bonding the upper paper, the V-shaped corrugated core base and the lower paper in sequence, and drying them at room temperature to obtain an environmentally friendly mildew-proof and antibacterial corrugated paperboard.

5. The method for preparing the environmentally friendly mildew-proof and antibacterial corrugated paperboard according to claim 4, characterized in that: The coating amount of the adhesive is 20-30 g / m 2 .

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