Body paper for aluminum spraying and preparation method thereof

Abstract

The invention discloses base paper for aluminum spraying and a preparation method thereof, and relates to the technical field of base paper. The preparation method comprises the following steps: pulping softwood pulp, then adding deionized water to dilute the softwood pulp until the mass concentration is 0.8%-1%, then adding modified gel particles, modified bentonite and a PAE wet strength agent, adjusting the pH value to 6.5-7.5, stirring for 40-60 minutes, and then adding deionized water to dilute the softwood pulp until the mass concentration is 0.5%-0.7% to obtain mixed paper pulp; and then making the mixed paper pulp into paper sheets, squeezing, drying, coating the surface layer coating on the surface of base material paper, and drying with hot air to obtain the body paper for aluminum spraying. According to the invention, the modified gel particles and the modified bentonite are added, so that the mildew-proof and moisture-proof capabilities of the base paper for aluminum spraying are effectively improved; the introduction of the surface coating further improves the mildew-proof and moisture-proof capabilities. Therefore, the method has a wider application prospect.

Description

Technical Field

[0001] This invention relates to the field of base paper technology, specifically to a base paper for aluminum spraying and its preparation method. Background Technology

[0002] Base paper refers to unprocessed paper that has not undergone coating, printing, lamination, or other subsequent processing. It is a fundamental product of the papermaking industry. Made from plant fibers or other fiber raw materials (such as waste paper pulp) through pulping and papermaking, it possesses specific basis weight, thickness, strength, and surface properties, serving as the substrate for further processing into various finished paper products. Metallized base paper is specifically designed for the "metallized process," referring to base paper on which a thin layer of aluminum metal is deposited onto its surface through processes such as spraying or vacuum plating, forming metallized paper with a metallic luster, high barrier properties, or decorative finish.

[0003] However, in practical applications, the base paper used for aluminum spraying still suffers from high hygroscopicity, making it prone to deformation, aluminum layer peeling, and mold growth when exposed to moisture. Therefore, the moisture resistance and mold resistance of existing base paper for aluminum spraying still need to be improved. Summary of the Invention

[0004] The purpose of this invention is to provide a base paper for aluminum spraying and its preparation method, thereby solving the following technical problems:

[0005] The existing base paper still has the problem of poor moisture resistance and mildew resistance.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing aluminum-sprayed base paper includes the following steps:

[0008] S1: After beating the softwood pulp, dilute it with deionized water to a mass concentration of 0.8%-1%, then add modified gel particles, modified bentonite, PAE wet strength agent and adjust the pH to 6.5-7.5. Stir for 40-60 minutes and then dilute with deionized water to a mass concentration of 0.5%-0.7% to obtain mixed pulp.

[0009] S2: The mixed pulp is formed into paper with a basis weight of 60-100 g / m³ using a fourdrinier paper machine. 2 The paper sheets are then pressed at a pressure of 70-80 kN / m, and then dried at 105-120℃ to a dryness of 50%-70%, followed by pressing at 3-5 g / m³. 2 The coating amount is adjusted so that the surface coating is applied to the surface of the substrate paper, and finally dried with hot air at 100-120℃ for 3-5 minutes to obtain the base paper for aluminum spraying.

[0010] Preferably, the amount of modified gel particles used in S1 is 0.9%-1.5% of the oven-dry weight of softwood pulp;

[0011] The amount of modified bentonite mentioned in S1 is 0.8%-1.2% of the oven-dry weight of the softwood pulp;

[0012] The amount of PAE wet strength agent mentioned in S1 is 0.3%-0.5% of the oven-dry weight of softwood pulp;

[0013] The beating degree after pulping described in S1 is 45-50°SR.

[0014] Preferably, the method for preparing the modified gel particles in S1 is as follows:

[0015] A1: Add tetraethyl orthosilicate, methyltrimethoxysilane, and oxalic acid to anhydrous ethanol and stir at 55-60℃ for 1-2 hours. After cooling to 20-35℃, adjust the pH to 6.0-6.5, stir for 30-50 minutes, and let stand for 40-60 minutes to obtain silica gel.

[0016] A2: Add deionized water to anhydrous ethanol and stir well. Then immerse the silicone gel and age it at 38-40℃ for 20-30 hours to obtain aged gel.

[0017] A3: Add hexamethyldisilazane to anhydrous ethanol and stir for 1-2 hours. Then, immerse the aged gel and react at 55-60℃ for 12-15 hours. After gradient drying, pulverize and pass through a 400-mesh sieve to obtain gel particles.

[0018] A4: Add TEMPO to deionized water to oxidize nanocellulose and stir at 55-60℃ for 30-50 min. Then add gel particles and homogenize for 30-50 min, followed by ultrasonic treatment for 20-30 min. Then immerse in liquid nitrogen for 20-30 min, remove and perform gradient drying under vacuum of 5-10 Pa. Finally, pulverize and pass through a 400-mesh sieve to obtain modified gel particles.

[0019] Preferably, the mass ratio of anhydrous ethanol, tetraethyl orthosilicate, methyltrimethoxysilane, and oxalic acid in A1 is 9.2-11:10-12:4-4.8:1.8-2.2;

[0020] The mass ratio of anhydrous ethanol, deionized water, and silicone gel in A2 is 400-440:100-110:25-30.

[0021] Preferably, the mass ratio of anhydrous ethanol, hexamethyldisilazane, and aged gel in A3 is 95-114:5-6:20-24;

[0022] The gradient drying described in A3 involves first drying at 40-45℃ for 5-6 hours, then drying at 55-60℃ for 8-10 hours, and finally drying at 75-80℃ for 4-5 hours.

[0023] The mass ratio of deionized water, TEMPO oxidized nanocellulose, and gel particles described in A4 is 98-117.6: 2-2.4: 0.2-0.25;

[0024] The gradient drying described in A4 involves first holding the temperature at -50 to 40°C for 20 to 30 hours, then raising the temperature to -30 to 20°C and holding it for 10 to 15 hours, then raising the temperature to 0 to 5°C and holding it for 5 to 6 hours, and finally raising the temperature to 20 to 30°C and holding it for 2 to 3 hours.

[0025] Preferably, the modified bentonite described in S1 is prepared as follows:

[0026] B1: Add sodium-based bentonite to deionized water at 55-60℃ and shear at 8000-10000r / min for 20-30min, then perform ultrasonic treatment at 700-800W power and 30-40kHz frequency for 20-30min to obtain bentonite dispersion.

[0027] B2: Add ε-polylysine and dioctadecyldimethylammonium chloride to the bentonite dispersion and stir at 65-70℃ for 4-5 hours. After cooling, centrifuge and wash the precipitate. Then add it to deionized water and finally spray dry it at an inlet air temperature of 120-140℃, an outlet air temperature of 60-80℃, and an atomization pressure of 0.3-0.5MPa to obtain modified bentonite.

[0028] Preferably, the mass ratio of deionized water to sodium-based bentonite in B1 is 150-190:8-10;

[0029] The mass ratio of bentonite dispersion, ε-polylysine, dioctadecyl dimethyl ammonium chloride, and deionized water in B2 is 158-200:1.2-1.5:1.6-2:44-55.

[0030] Preferably, the preparation method of the surface coating in S2 is as follows:

[0031] Add silane coupling agent KH-560 to anhydrous ethanol and stir for 20-40 minutes. Then add deionized water, polyvinyl alcohol, and nano silica and stir at 75-80℃ for 1-2 hours to obtain the surface coating.

[0032] Preferably, the mass ratio of anhydrous ethanol, silane coupling agent KH-560, deionized water, polyvinyl alcohol, and nano silica is 5-6:1-1.2:85-100:10-12:3-3.5.

[0033] The beneficial effects of this invention are:

[0034] This invention provides a base paper for aluminum spraying and its preparation method. The invention effectively improves the moisture resistance and mildew resistance of the base paper through the following method.

[0035] (1) In the preparation process of the modified gel particles of this invention, tetraethyl orthosilicate and methyltrimethoxysilane undergo hydrolysis and condensation to form a silica network framework. The internal pore structure can be controlled by the type of silane and the hydrolysis conditions. The methyl groups introduced by methyltrimethoxysilane can reduce the overall hydrophilicity of the gel and reduce water adsorption. Hexamethyldisilazane reacts with the silanol groups on the surface of the silica gel to form a hydrophobic siloxane layer, which further seals the hydrophilic groups and significantly improves the hydrophobic properties of the gel, thereby enhancing the waterproof and moisture-proof capabilities of the base paper. After hydrophobic modification, the porous network structure of the silica gel has a reduced water content in the pores, which can inhibit the growth of microorganisms. After being crushed, the modified gel particles form nano-sized porous particles, which can increase the surface roughness of the base paper when dispersed in the pulp. During aluminum spraying, the aluminum particles can be embedded in these micropores or protrusions to form a mechanical anchoring effect and prevent the aluminum layer from peeling off. The silanol groups or hydroxyl and carboxyl groups of TEMPO cellulose remaining on the surface of the silicone gel can undergo a condensation reaction with the silane coupling agent KH-560 introduced in the later coating to form chemical bonds. At the same time, the epoxy groups of KH-560 can react with the hydroxyl groups on the surface of the aluminum layer to enhance the interfacial adhesion through chemical bonding.

[0036] (2) In the process of organic modification of sodium-based bentonite in this invention, the long-chain alkyl groups of dioctadecyl dimethyl ammonium chloride can be inserted into the interlayer of bentonite, replacing the original hydrophilic inorganic cations to form a hydrophobic organic layer, significantly reducing the hydrophilicity of bentonite, reducing water adsorption and penetration, thereby improving the waterproof and moisture-proof ability of the base paper; after modification, the interlayer spacing of bentonite is expanded, the interlayer polarity is reduced, water molecules are difficult to enter the interlayer structure, and the water absorption rate is significantly reduced; after dispersion in pulp, the hydrophobic bentonite particles can fill the fiber pores, forming a physical barrier, further hindering the diffusion of water. The bentonite surface carries a negative charge and combines with cationic ε-polylysine through electrostatic interaction to form a stable complex; while ε-polylysine can play a role by destroying the cell membrane of microorganisms and inhibiting nucleic acid synthesis, and has a significant inhibitory effect on mold. After being loaded with modified bentonite, it can slowly release antibacterial components, giving the base paper a long-lasting anti-mold ability.

[0037] (3) The silane coupling agent KH-560 in the surface coating of this invention has an amphiphilic structure. After hydrolysis, it can form a siloxane bond with the hydroxyl groups on the surface of paper fibers. At the same time, its organic groups can enhance the hydrophobicity of the coating, reduce the water penetration path, and thus improve the waterproofness of the paper. In addition, it can crosslink with the hydroxyl groups of polyvinyl alcohol to form a network hydrophobic film, further preventing water from penetrating the substrate. Polyvinyl alcohol is a water-soluble polymer. After drying, it forms a continuous and dense film that physically blocks water penetration. Its intermolecular hydrogen bonding gives the film a certain toughness and sealing properties, which can significantly improve the moisture resistance of the paper. Nano-silica can be embedded in the pores of the polyvinyl alcohol film to form a composite reinforcing structure, reduce film defects, and further improve the waterproof and moisture-proof performance. At the same time, the surface hydroxyl groups of the nanoparticles can react with the silane coupling agent to enhance the internal bonding force of the coating and prevent the film from absorbing water and swelling. The waterproof and moisture-proof performance of the surface coating can reduce the humidity of the paper, destroy the humid environment for mold growth, and thus indirectly inhibit mold reproduction. The epoxy groups of KH-560 can form chemical bonds with the oxides on the surface of the aluminum spray layer, while the other end of the epoxy groups can bond with the paper fibers to form a "molecular bridge", which significantly enhances the interfacial bonding force between the aluminum spray layer and the substrate. The adhesiveness and film-forming properties of polyvinyl alcohol make the coating surface a flexible and highly adhesive substrate. During aluminum spraying, aluminum particles can be embedded into the film surface through mechanical interlocking. The addition of nano-silica can slightly increase the micro-roughness of the coating surface, further enhancing the anchoring effect of the aluminum spray layer and reducing the risk of peeling.

[0038] Therefore, the aluminum-sprayed base paper prepared by this invention has excellent waterproof, moisture-proof and mildew-proof capabilities, as well as a wider range of application prospects. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0040] Unless otherwise specified, the following information pertains to some of the raw materials used in the following embodiments and comparative examples of this invention:

[0041] TEMPO oxidized nanocellulose was purchased from Nanjing Tianlu Nanotechnology Co., Ltd.; sodium bentonite was purchased from Wuhan Jiyesheng Chemical Co., Ltd.; ε-polylysine was purchased from Jiangsu Yihaotian Biotechnology Co., Ltd.; PAE wet strength agent was purchased from Taian Dow Chemical Co., Ltd.; polyvinyl alcohol was purchased from Hubei Jusheng Technology Co., Ltd., product number: JS5033.

[0042] Example 1: A method for preparing a base paper for aluminum spraying is as follows:

[0043] S1: Add 10g tetraethyl orthosilicate, 4g methyltrimethoxysilane, and 1.8g oxalic acid to 9.2g anhydrous ethanol and stir at 55℃ for 1h. After cooling to 20℃, adjust the pH to 6.0 with 25% ammonia water. Then stir at 600r / min for 30min and let stand for 40min to obtain silica gel.

[0044] S2: Add 100g of deionized water to 400g of anhydrous ethanol and stir at 200r / min for 5min. Then immerse 25g of silicone gel and age at 38℃ for 20h to obtain aged gel.

[0045] S3: Add 5g of hexamethyldisilazane to 95g of anhydrous ethanol and stir for 1h. Then, immerse 20g of aged gel and react at 55℃ for 12h. Then, dry at 40℃ for 5h, then at 55℃ for 8h, and finally at 75℃ for 4h. After crushing and passing through a 400-mesh sieve, obtain gel particles.

[0046] S4: Add 2g of TEMPO oxidized nanocellulose to 98g of deionized water and stir at 55℃ for 30min. Then add 0.2g of gel particles and homogenize at 10000r / min for 30min. Then sonicate at 700W and 30kHz for 20min. Then immerse in liquid nitrogen for 20min and remove. Then perform gradient drying under vacuum of 5Pa. Finally, pulverize and pass through a 400-mesh sieve to obtain modified gel particles.

[0047] The gradient drying process involves first holding the temperature at -50℃ for 20 hours, then raising the temperature to -30℃ and holding it for 10 hours, then raising the temperature to 0℃ and holding it for 5 hours, and finally raising the temperature to 20℃ and holding it for 2 hours.

[0048] S5: Add 8g of sodium-based bentonite to 150g of deionized water at 55℃ and shear at 8000r / min for 20min, then perform ultrasonic treatment at 700W power and 30kHz frequency for 20min to obtain bentonite dispersion.

[0049] S6: 1.2g of ε-polylysine and 1.6g of dioctadecyldimethylammonium chloride were added to 158g of bentonite dispersion and stirred at 300r / min for 4h at 65℃ and pH 8.5. After cooling to 20℃, the mixture was centrifuged at 7000r / min for 10min. The supernatant was then discarded and the precipitate was washed three times with a mixture of anhydrous ethanol and deionized water at a volume ratio of 1:1. The precipitate was then added to 44g of deionized water and finally spray-dried at an inlet air temperature of 120℃, an outlet air temperature of 60℃, and an atomization pressure of 0.3MPa to obtain modified bentonite.

[0050] S7: Beat 100g of oven-dry softwood pulp to a freeness of 45°SR, then dilute with deionized water to a mass concentration of 0.8%, then add 0.9g of modified gel particles, 0.8g of modified bentonite, and 0.3g of PAE wet strength agent and adjust the pH to 6.5. Stir at 300r / min for 40min and then dilute with deionized water to a mass concentration of 0.5% to obtain mixed pulp;

[0051] S8: Add 1g of silane coupling agent KH-560 to 5g of anhydrous ethanol and stir for 20min. Then add 85g of deionized water, 10g of polyvinyl alcohol, and 3g of nano silica and stir at 75℃ for 1h to obtain the surface coating.

[0052] S9: The mixed pulp is formed to a basis weight of 60 g / m³ using a long-wire paper machine. 2 The paper sheets are then pressed at a pressure of 70 kN / m, dried at 105°C to a dryness of 50%, and then pressed at 3 g / m³. 2 The coating amount is adjusted so that the surface coating is applied to the surface of the substrate paper, and finally dried with hot air at 100°C for 3 minutes to obtain the base paper for aluminum spraying.

[0053] Example 2: A method for preparing a base paper for aluminum spraying is as follows:

[0054] S1: Add 11g tetraethyl orthosilicate, 4.4g methyltrimethoxysilane, and 2g oxalic acid to 10.1g anhydrous ethanol and stir at 58℃ for 1.5h. After cooling to 30℃, adjust the pH to 6.3 with 27% ammonia water. Then stir at 700r / min for 40min and let stand for 50min to obtain silica gel.

[0055] S2: Add 105g of deionized water to 420g of anhydrous ethanol and stir at 250r / min for 10min. Then, immerse 27.5g of silicone gel in the solution and age it at 39℃ for 25h to obtain aged gel.

[0056] S3: Add 5.5g of hexamethyldisilazane to 103g of anhydrous ethanol and stir for 1.5h. Then, immerse 22g of aged gel and react at 58℃ for 14h. Then, dry at 43℃ for 5.5h, then at 58℃ for 9h, and finally at 78℃ for 4.5h. After crushing and passing through a 400-mesh sieve, obtain gel particles.

[0057] S4: Add 2.2g of TEMPO oxidized nanocellulose to 107.8g of deionized water and stir at 58℃ for 40min. Then add 0.23g of gel particles and homogenize at 13000r / min for 40min. Then sonicate at 750W and 35kHz for 25min. Then immerse in liquid nitrogen for 25min and remove. Then perform gradient drying under vacuum of 8Pa. Finally, pulverize and pass through a 400-mesh sieve to obtain modified gel particles.

[0058] The gradient drying process involves first holding the temperature at -45℃ for 25 hours, then raising the temperature to -25℃ and holding it for 13 hours, then raising the temperature to 3℃ and holding it for 5.5 hours, and finally raising the temperature to 25℃ and holding it for 2.5 hours.

[0059] S5: Add 9g of sodium-based bentonite to 170g of deionized water at 58℃ and shear at 9000r / min for 25min, then perform ultrasonic treatment at 750W power and 35kHz for 25min to obtain bentonite dispersion.

[0060] S6: 1.4 g of ε-polylysine and 1.8 g of dioctadecyl dimethyl ammonium chloride were added to 179 g of bentonite dispersion and stirred at 350 r / min for 4.5 h at 68 °C and pH 8.8. After cooling to 25 °C, the mixture was centrifuged at 7500 r / min for 13 min. The supernatant was then discarded and the precipitate was washed four times with a mixture of anhydrous ethanol and deionized water at a volume ratio of 1:1. The precipitate was then added to 49.5 g of deionized water and finally spray-dried at an inlet air temperature of 130 °C, an outlet air temperature of 70 °C, and an atomization pressure of 0.4 MPa to obtain modified bentonite.

[0061] S7: Beat 100g of oven-dry softwood pulp to a freeness of 48°SR, then dilute with deionized water to a mass concentration of 0.9%, then add 1.2g of modified gel particles, 1g of modified bentonite, and 0.4g of PAE wet strength agent and adjust the pH to 7. Stir at 400r / min for 50min and then further dilute with deionized water to a mass concentration of 0.6% to obtain mixed pulp;

[0062] S8: Add 1.1g of silane coupling agent KH-560 to 5.5g of anhydrous ethanol and stir for 30min. Then add 92.5g of deionized water, 11g of polyvinyl alcohol, and 3.3g of nano silica and stir at 78℃ for 1.5h to obtain the surface coating.

[0063] S9: The mixed pulp is formed to a basis weight of 80 g / m³ using a long-wire paper machine. 2 The paper sheets are then pressed at a pressure of 75 kN / m, dried at 110°C to a dryness of 60%, and then pressed at 4 g / m³.2 The coating amount is adjusted so that the surface coating is applied to the surface of the substrate paper, and finally dried with hot air at 110°C for 4 minutes to obtain the base paper for aluminum spraying.

[0064] Example 3: A method for preparing a base paper for aluminum spraying is as follows:

[0065] S1: Add 12g tetraethyl orthosilicate, 4.8g methyltrimethoxysilane, and 2.2g oxalic acid to 11g anhydrous ethanol and stir at 60℃ for 2h. After cooling to 35℃, adjust the pH to 6.5 with 28% ammonia water. Then stir at 800r / min for 50min and let stand for 60min to obtain silica gel.

[0066] S2: Add 110g of deionized water to 440g of anhydrous ethanol and stir at 300r / min for 15min. Then immerse 30g of silicone gel and age at 40℃ for 30h to obtain aged gel.

[0067] S3: Add 6g of hexamethyldisilazane to 114g of anhydrous ethanol and stir for 2h. Then, immerse 24g of aged gel and react at 60℃ for 15h. Then, dry at 45℃ for 6h, then at 60℃ for 10h, and finally at 80℃ for 5h. After crushing and passing through a 400-mesh sieve, obtain gel particles.

[0068] S4: Add 2.4g of TEMPO oxidized nanocellulose to 117.6g of deionized water and stir at 60℃ for 50min. Then add 0.25g of gel particles and homogenize at 15000r / min for 50min. Then sonicate at 800W and 40kHz for 30min. Then immerse in liquid nitrogen for 30min and remove and perform gradient drying under vacuum of 10Pa. Finally, pulverize and pass through a 400-mesh sieve to obtain modified gel particles.

[0069] The gradient drying process involves first holding the temperature at -40℃ for 30 hours, then raising the temperature to -20℃ and holding it for 15 hours, then raising the temperature to 5℃ and holding it for 6 hours, and finally raising the temperature to 30℃ and holding it for 3 hours.

[0070] S5: Add 10g of sodium-based bentonite to 190g of deionized water at 60℃ and shear at 10000r / min for 30min, then perform ultrasonic treatment at 800W power and 40kHz frequency for 30min to obtain bentonite dispersion.

[0071] S6: Add 1.5g of ε-polylysine and 2g of dioctadecyl dimethyl ammonium chloride to 200g of bentonite dispersion, and stir at 400r / min for 5h at 70℃ and pH 9. After cooling to 35℃, centrifuge at 8000r / min for 15min, discard the supernatant, and wash the precipitate 5 times with a mixture of anhydrous ethanol and deionized water at a volume ratio of 1:1. Then add 55g of deionized water, and finally spray dry at an inlet air temperature of 140℃, an outlet air temperature of 80℃, and an atomization pressure of 0.5MPa to obtain modified bentonite.

[0072] S7: Beat 100g of oven-dry softwood pulp to a freeness of 50°SR, then dilute with deionized water to a mass concentration of 1%, then add 1.5g of modified gel particles, 1.2g of modified bentonite, and 0.5g of PAE wet strength agent and adjust the pH to 7.5. Stir and react at 500r / min for 60min, then further dilute with deionized water to a mass concentration of 0.7% to obtain mixed pulp;

[0073] S8: Add 1.2g of silane coupling agent KH-560 to 6g of anhydrous ethanol and stir for 40min. Then add 100g of deionized water, 12g of polyvinyl alcohol, and 3.5g of nano silica and stir at 80℃ for 2h to obtain the surface coating.

[0074] S9: The mixed pulp is formed into paper with a basis weight of 100g / m³ using a long-wire paper machine. 2 The paper sheets are then pressed at a pressure of 80 kN / m, dried at 120°C to a dryness of 70%, and then pressed at 5 g / m³. 2 The coating amount is adjusted so that the surface coating is applied to the surface of the substrate paper, and finally dried with hot air at 120°C for 5 minutes to obtain the base paper for aluminum spraying.

[0075] Comparative Example 1:

[0076] Compared with Example 1, this comparative example only replaces the "modified gel particles" added in the preparation process of S7 with the "gel particles" prepared in S3. All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, aluminum-coated base paper is obtained.

[0077] Comparative Example 2:

[0078] Compared with Example 1, this comparative example only did not add "modified gel particles" in the preparation process of S7. All other steps and parameters were the same, and will not be repeated here. The final product was aluminum-coated base paper.

[0079] Comparative Example 3:

[0080] Compared with Example 1, this comparative example only did not add "ε-polylysine" in the preparation process of S6. All other steps and parameters were the same, and will not be repeated here. The final product was aluminum-coated base paper.

[0081] Comparative Example 4:

[0082] Compared with Example 1, this comparative example only replaces "modified bentonite" with "sodium-based bentonite" in the preparation process of S7. All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, aluminum-sprayed base paper is obtained.

[0083] Comparative Example 5:

[0084] Compared with Example 1, this comparative example only did not add "modified bentonite" in the preparation process of S7. All other steps and parameters were the same, and will not be repeated here. The final product was aluminum spraying base paper.

[0085] Comparative Example 6:

[0086] Compared with Example 1, this comparative example only did not add "nano-silica" in the preparation process of S8. All other steps and parameters were the same, and will not be repeated here. The final product was aluminum-coated base paper.

[0087] Comparative Example 7: A method for preparing a base paper for aluminum spraying is as follows:

[0088] S1: Add 10g tetraethyl orthosilicate, 4g methyltrimethoxysilane, and 1.8g oxalic acid to 9.2g anhydrous ethanol and stir at 55℃ for 1h. After cooling to 20℃, adjust the pH to 6.0 with 25% ammonia water. Then stir at 600r / min for 30min and let stand for 40min to obtain silica gel.

[0089] S2: Add 100g of deionized water to 400g of anhydrous ethanol and stir at 200r / min for 5min. Then immerse 25g of silicone gel and age at 38℃ for 20h to obtain aged gel.

[0090] S3: Add 5g of hexamethyldisilazane to 95g of anhydrous ethanol and stir for 1h. Then, immerse 20g of aged gel and react at 55℃ for 12h. Then, dry at 40℃ for 5h, then at 55℃ for 8h, and finally at 75℃ for 4h. After crushing and passing through a 400-mesh sieve, obtain gel particles.

[0091] S4: Add 2g of TEMPO oxidized nanocellulose to 98g of deionized water and stir at 55℃ for 30min. Then add 0.2g of gel particles and homogenize at 10000r / min for 30min. Then sonicate at 700W and 30kHz for 20min. Then immerse in liquid nitrogen for 20min and remove. Then perform gradient drying under vacuum of 5Pa. Finally, pulverize and pass through a 400-mesh sieve to obtain modified gel particles.

[0092] The gradient drying process involves first holding the temperature at -50℃ for 20 hours, then raising the temperature to -30℃ and holding it for 10 hours, then raising the temperature to 0℃ and holding it for 5 hours, and finally raising the temperature to 20℃ and holding it for 2 hours.

[0093] S5: Add 8g of sodium-based bentonite to 150g of deionized water at 55℃ and shear at 8000r / min for 20min, then perform ultrasonic treatment at 700W power and 30kHz frequency for 20min to obtain bentonite dispersion.

[0094] S6: 1.2g of ε-polylysine and 1.6g of dioctadecyldimethylammonium chloride were added to 158g of bentonite dispersion and stirred at 300r / min for 4h at 65℃ and pH 8.5. After cooling to 20℃, the mixture was centrifuged at 7000r / min for 10min. The supernatant was then discarded and the precipitate was washed three times with a mixture of anhydrous ethanol and deionized water at a volume ratio of 1:1. The precipitate was then added to 44g of deionized water and finally spray-dried at an inlet air temperature of 120℃, an outlet air temperature of 60℃, and an atomization pressure of 0.3MPa to obtain modified bentonite.

[0095] S7: Beat 100g of oven-dry softwood pulp to a freeness of 45°SR, then dilute with deionized water to a mass concentration of 0.8%, then add 0.9g of modified gel particles, 0.8g of modified bentonite, and 0.3g of PAE wet strength agent and adjust the pH to 6.5. Stir at 300r / min for 40min and then dilute with deionized water to a mass concentration of 0.5% to obtain mixed pulp;

[0096] S8: The mixed pulp is formed into a basis weight of 60g / m³ using a long-wire paper machine. 2 The paper sheets are then pressed at a pressure of 70 kN / m, dried at 105°C to a dryness of 50%, and finally dried with hot air at 100°C for 3 minutes to obtain aluminum-sprayed base paper.

[0097] Performance testing:

[0098] Measurement of water contact angle:

[0099] Referring to GB / T 32088-2015 "Determination of wettability of paper and paperboard surfaces (contact angle method)", the static water contact angle (°) of the aluminum-sprayed base paper prepared in Examples 1-3 and Comparative Examples 1-7 of this invention was determined, and the test results are shown in Table 1.

[0100] Determination of water absorption rate:

[0101] Referring to GB / T 1540-2002 "Determination of water absorption of paper and paperboard (Cobb method)", the water absorption rate (g·m³) of the aluminum-coated base paper prepared in Examples 1-3 and Comparative Examples 1-7 of this invention was determined. -2 ·min -1 The test results are shown in Table 1.

[0102] Adhesion determination:

[0103] Referring to GB / T 9286-2021 "Cross-cut test of paint and varnish film", the adhesion (grade) of aluminum film after aluminum spraying on the surface of aluminum-coated base paper prepared in Examples 1-3 and Comparative Examples 1-7 was determined. The test results are shown in Table 1.

[0104] Moisture resistance test:

[0105] Referring to GB / T 9286-2021 "Cross-cut test of paint and varnish film", the adhesion (grade) of the aluminum-coated base paper prepared in Examples 1-3 and Comparative Examples 1-7 of this invention after aluminum coating was performed and stored at 25°C and 95% relative humidity for 30 days was determined to reflect the moisture resistance of the aluminum-coated base paper of this invention. The test results are shown in Table 1.

[0106] Determination of anti-mildew properties:

[0107] Referring to GB / T 24330-2009 "Determination of Anti-mildew Properties of Paper and Paperboard", the surface area ratio (%) of the aluminum-coated base paper prepared in Examples 1-3 and Comparative Examples 1-7 of this invention after being placed in a culture medium containing Aspergillus niger (ATCC 16404) at 28°C and 95% relative humidity for 28 days was determined to reflect the anti-mildew properties of the aluminum-coated base paper of this invention. The test results are shown in Table 1.

[0108] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-7

[0109]

[0110] Data Analysis:

[0111] As can be seen from Table 1, the aluminum-sprayed base paper prepared in the embodiments of the present invention has excellent water resistance, moisture resistance, and mildew resistance.

[0112] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for preparing aluminum-sprayed base paper, characterized in that, Includes the following steps: S1: After beating the softwood pulp, dilute it with deionized water to a mass concentration of 0.8%-1%, then add modified gel particles, modified bentonite, PAE wet strength agent and adjust the pH to 6.5-7.

5. Stir for 40-60 minutes and then dilute with deionized water to a mass concentration of 0.5%-0.7% to obtain mixed pulp. S2: The mixed pulp is made into paper sheets, pressed and dried to a dryness of 50%-70%, and then a surface coating is applied to the surface of the base paper. After hot air drying, aluminum-coated base paper is obtained.

2. The method for preparing aluminum-sprayed base paper according to claim 1, characterized in that, The amount of modified gel particles mentioned in S1 is 0.9%-1.5% of the oven-dry weight of softwood pulp; The amount of modified bentonite mentioned in S1 is 0.8%-1.2% of the oven-dry weight of the softwood pulp; The amount of PAE wet strength agent mentioned in S1 is 0.3%-0.5% of the oven-dry weight of softwood pulp; The beating degree after pulping described in S1 is 45-50°SR.

3. The method for preparing aluminum-sprayed base paper according to claim 1, characterized in that, The preparation method of the modified gel particles described in S1 is as follows: A1: Add tetraethyl orthosilicate, methyltrimethoxysilane, and oxalic acid to anhydrous ethanol and stir at 55-60℃ for 1-2 hours. After cooling, adjust the pH to 6.0-6.5 and stir for 30-50 minutes. After standing for 40-60 minutes, a silica gel is obtained. A2: Add deionized water to anhydrous ethanol, then immerse the silicone gel and age it at 38-40℃ for 20-30 hours to obtain aged gel; A3: Add hexamethyldisilazane to anhydrous ethanol and stir for 1-2 hours. Then immerse the aged gel and react at 55-60℃ for 12-15 hours. After gradient drying, crush and sieve to obtain gel particles. A4: Add TEMPO to deionized water to oxidize nanocellulose and stir at 55-60℃ for 30-50 min. Then add gel particles and homogenize for 30-50 min, followed by ultrasonic treatment for 20-30 min. Then immerse in liquid nitrogen for 20-30 min, remove and perform gradient drying, pulverization and sieving to obtain modified gel particles.

4. The method for preparing aluminum-sprayed base paper according to claim 3, characterized in that, The mass ratio of anhydrous ethanol, tetraethyl orthosilicate, methyltrimethoxysilane, and oxalic acid in A1 is 9.2-11:10-12:4-4.8:1.8-2.

2. The mass ratio of anhydrous ethanol, deionized water, and silicone gel in A2 is 400-440:100-110:25-30.

5. The method for preparing aluminum-sprayed base paper according to claim 3, characterized in that, The mass ratio of anhydrous ethanol, hexamethyldisilazane, and aged gel in A3 is 95-114:5-6:20-24; The gradient drying described in A3 involves first drying at 40-45℃ for 5-6 hours, then drying at 55-60℃ for 8-10 hours, and finally drying at 75-80℃ for 4-5 hours. The mass ratio of deionized water, TEMPO oxidized nanocellulose, and gel particles described in A4 is 98-117.6: 2-2.4: 0.2-0.25; The gradient drying described in A4 involves first holding the temperature at -50 to 40°C for 20 to 30 hours, then raising the temperature to -30 to 20°C and holding it for 10 to 15 hours, then raising the temperature to 0 to 5°C and holding it for 5 to 6 hours, and finally raising the temperature to 20 to 30°C and holding it for 2 to 3 hours.

6. The method for preparing aluminum-sprayed base paper according to claim 1, characterized in that, The preparation method of the modified bentonite described in S1 is as follows: B1: Add sodium-based bentonite to deionized water at 55-60℃ and shear for 20-30 min, then sonicate for 20-30 min to obtain bentonite dispersion; B2: Add ε-polylysine and dioctadecyldimethylammonium chloride to the bentonite dispersion and stir at 65-70℃ for 4-5 hours. After cooling, centrifuge, wash the precipitate, add it to deionized water, and spray dry to obtain modified bentonite.

7. The method for preparing aluminum-sprayed base paper according to claim 6, characterized in that, The mass ratio of deionized water to sodium-based bentonite in B1 is 150-190:8-10; The mass ratio of bentonite dispersion, ε-polylysine, dioctadecyl dimethyl ammonium chloride, and deionized water in B2 is 158-200:1.2-1.5:1.6-2:44-55.

8. The method for preparing aluminum-sprayed base paper according to claim 1, characterized in that, The preparation method of the surface coating described in S2 is as follows: Add silane coupling agent KH-560 to anhydrous ethanol and stir for 20-40 minutes. Then add deionized water, polyvinyl alcohol, and nano silica and stir at 75-80℃ for 1-2 hours to obtain the surface coating.

9. The method for preparing aluminum-sprayed base paper according to claim 8, characterized in that, The mass ratio of anhydrous ethanol, silane coupling agent KH-560, deionized water, polyvinyl alcohol, and nano silica is 5-6:1-1.2:85-100:10-12:3-3.

5.

10. A base paper for aluminum spraying, characterized in that, It is prepared by the method described in any one of claims 1-9.

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