Papermaking process for improving durability and waterproof performance of paper

Abstract

The invention discloses a papermaking process for improving durability and water resistance of paper, and belongs to the technical field of modern papermaking. A papermaking process capable of improving durability and water resistance of paper comprises the following steps: adding reinforced fibers (polyester fibers), an antioxidant (vitamin C) and a cross-linking agent (glutaraldehyde) in the pulping process, pulping and mixing at a high speed, adding hydrophobic modified silicon dioxide sol and tannic acid, regulating the pH value to 8-10 by sodium hydroxide, and reacting to obtain the paper. After pulping, the procedures of forming, squeezing, drying, glazing, coating, paper cutting and coiling are sequentially performed, and meanwhile, a surfactant (polyvinyl alcohol) is added in the squeezing stage to improve the uniformity of the paper surface. The process remarkably improves the tensile strength, durability and waterproof and moistureproof performance of the paper, prolongs the service life, is suitable for the fields of packaging, printing and the like, and is simple and convenient to operate, economical, practical and wide in application prospect.

Description

Technical Field

[0001] The present invention relates to the field of modern papermaking technology, and more specifically, to a papermaking process for improving the durability and waterproof performance of paper. Background Art

[0002] The development history of papermaking technology is long. From ancient manual papermaking to modern large-scale mechanized production, it has undergone continuous innovation and progress. Although traditional papermaking processes have become increasingly mature in aspects such as fiber separation, pulping, forming, pressing, and drying, there are still significant deficiencies in the durability and waterproof performance of paper. In traditional processes, due to limited fiber bonding force, uneven filler distribution, and poor post-treatment processes, paper is prone to swelling and deformation when exposed to water, affecting its service life and practical performance, especially its application in fields such as packaging, moisture-proofing, and anti-corrosion is restricted.

[0003] Currently, with the continuous progress of industrial technology and the improvement of environmental protection requirements, new papermaking processes have gradually emerged, aiming to improve the durability and waterproof performance of paper. Modern papermaking processes use advanced methods such as high-speed beating, precise pH value regulation, and multi-component synergistic effects. By introducing reinforcing fibers, antioxidants, and cross-linking agents during the pulping process, closer bonding between fibers is achieved, thereby improving the overall strength and durability of the paper. Subsequently, waterproof agents and surfactants are added during the forming and pressing stages. Through the dual physical and chemical effects, the waterproof and moisture-proof performance of the paper is significantly improved, meeting the requirements for high-performance paper in fields such as modern packaging, printing, and special-purpose paper.

[0004] Looking ahead, papermaking processes will develop towards the directions of green environmental protection, high efficiency, energy conservation, and functional diversification. The integration of new materials, new processes, and intelligent control technologies is expected to further improve the performance of paper, while reducing environmental pollution and resource consumption, bringing a broader development prospect for the papermaking industry. Summary of the Invention

[0005] The purpose of the present invention is to provide a papermaking process for improving the durability and waterproof performance of paper, which has excellent durability and waterproof performance, and is low in cost and environmentally friendly.

[0006] A papermaking process for improving the durability and waterproof performance of paper, characterized in that: in the pulping process, reinforcing fibers, antioxidants, and cross-linking agents are added. After being mixed evenly using a high-speed beater, hydrophobic modified silica sol and tannic acid are added, and the pH is adjusted using sodium hydroxide solution, followed by stirring and reacting. After the pulping is completed, it enters the forming stage. After the forming is completed, it enters the pressing stage. A surfactant is added, and after being mixed evenly, it enters the subsequent pressing, drying, glazing and coating, paper cutting and winding stages, and the finished product can be obtained.

[0007] Preferably, the reinforcing fiber is polyester fiber, and the added amount is 5-9%.

[0008] Preferably, the antioxidant is vitamin C, and the added amount is 0.2-1%.

[0009] Preferably, the crosslinking agent is glutaraldehyde, and the added amount is 1-3%.

[0010] Preferably, the preparation method of the hydrophobic modified silica sol: Add 2 g of nano-silica particles into 150 mL of methanol solution, after ultrasonic dispersion for 1-3 h until evenly dispersed, add 3-5 mL of cetyltrimethoxysilane and 1-3 mL of γ-aminopropyltriethoxysilane, stir at room temperature for 1-3 h, then add 1-3 mL of acetic acid and 1-3 mL of deionized water, stir at 50-70 °C for 10-14 h, and the hydrophobic modified silica sol can be obtained. The added amount is 30-50%.

[0011] Preferably, the added amount of tannic acid is 0.01-0.05%.

[0012] Preferably, the pH is adjusted with the sodium hydroxide solution and stirred for reaction, that is, the pH is adjusted to 8-10 with 1 mol / L sodium hydroxide solution and stirred at room temperature for 20-28 h.

[0013] Preferably, the surfactant is polyvinyl alcohol, and the added amount is 0.4-2%. Compared with the prior art, the advantages of the present invention are as follows: (1) In the present invention, adding reinforcing fiber (polyester fiber) during the pulping process can significantly improve the bonding force between fibers, and improve the tensile, tear and compressive properties of the paper; the crosslinking agent (glutaraldehyde) reacts with the functional groups in the fiber to form a three-dimensional network structure, enhancing the overall structural stability; the high-speed beater fully mixes each component to ensure the uniform dispersion of the reinforcing fiber and the virgin fiber, and improves the mechanical properties of the finished paper.

[0014] (2) In the present invention, under acidic conditions, cetyltrimethoxysilane and γ-aminopropyltriethoxysilane hydrolyze to form active hydrophilic silanols, and then dehydrate and condense with the silanol groups on the surface of nano-silica to obtain hydrophobic silica sol. Then, under the condition of controlling pH, multiple phenolic hydroxyl groups on tannic acid are used as crosslinking building units, and the paper fibers react with the hydrophobic SiO2 sol in the form of chemical bonds, and then react with the paper fibers through hydrogen bonds and chemical bonds to form a strong superhydrophobic surface, forming a hydrophobic barrier on the paper surface and between fibers to reduce water penetration; adding polyvinyl alcohol as a surfactant in the post-pressing stage further improves the surface wettability of the paper, ensures uniform coating, and effectively prevents moisture absorption and water invasion.

[0015] (3) In the present invention, the introduction of an antioxidant (vitamin C) can inhibit fiber degradation caused by oxidation during the pulping process, delay the aging of paper, and maintain long-term stability. (4) In the present invention, the technological processes at each stage are reasonably connected. The processes of pulping, forming, pressing, drying, glazing and coating, and paper cutting and winding are all effectively controlled to ensure the stable quality of the paper. Uniform mixing and precise pH regulation enable sufficient and uniform reactions, reducing the possibility of local defects in subsequent processes, thereby realizing the continuous production of high-grade and functional papers. Specific Embodiments

[0016] Example 1: A papermaking process for improving the durability and waterproof performance of paper. Add 2 g of nano-silica particles to 150 mL of methanol solution. After ultrasonic dispersion for 1 h until evenly dispersed, add 3 mL of cetyltrimethoxysilane and 1 mL of γ-aminopropyltriethoxysilane. After stirring at room temperature for 1 h, add 1 mL of acetic acid and 1 mL of deionized water, and stir at 50 °C for 10 h to obtain a hydrophobic modified silica sol. During the pulping process, add 5% of reinforcing fibers (polyester fibers), 0.2% of antioxidant (vitamin C), and 1% of crosslinking agent (glutaraldehyde). After mixing evenly using a high-speed beater, add 30% of the hydrophobic modified silica sol and 0.01% of tannic acid. Use 1 mol / L sodium hydroxide solution to adjust the pH to 8, and stir at room temperature for 20 h. After the pulping is completed, enter the forming stage. After the forming is completed, enter the pressing stage. Add 0.4% of surfactant (polyvinyl alcohol), mix evenly, and then enter the subsequent pressing, drying, glazing and coating, and paper cutting and winding stages to obtain the finished product.

[0017] Example 2: A papermaking process for improving the durability and waterproof performance of paper. Add 2 g of nano-silica particles to 150 mL of methanol solution. After ultrasonic dispersion for 1.5 h until evenly dispersed, add 3.5 mL of cetyltrimethoxysilane and 1.5 mL of γ-aminopropyltriethoxysilane. After stirring at room temperature for 1.5 h, add 1.5 mL of acetic acid and 1.5 mL of deionized water, and stir at 55 °C for 11 h to obtain a hydrophobic modified silica sol. During the pulping process, add 6% of reinforcing fibers (polyester fibers), 0.4% of antioxidant (vitamin C), and 1.5% of crosslinking agent (glutaraldehyde). After mixing evenly using a high-speed beater, add 35% of the hydrophobic modified silica sol and 0.02% of tannic acid. Use 1 mol / L sodium hydroxide solution to adjust the pH to 8.5, and stir at room temperature for 22 h. After the pulping is completed, enter the forming stage. After the forming is completed, enter the pressing stage. Add 0.8% of surfactant (polyvinyl alcohol), mix evenly, and then enter the subsequent pressing, drying, glazing and coating, and paper cutting and winding stages to obtain the finished product.

[0018] Example 3: A papermaking process for improving the durability and waterproof performance of paper. Add 2 g of nano-silica particles to 150 mL of methanol solution. After ultrasonic dispersion for 2 h until evenly dispersed, add 4 mL of cetyltrimethoxysilane and 2 mL of γ-aminopropyltriethoxysilane. After stirring at room temperature for 2 h, add 2 mL of acetic acid and 2 mL of deionized water, and stir at 60 °C for 12 h to obtain a hydrophobic modified silica sol. During the pulping process, add 7% of reinforcing fibers (polyester fibers), 0.6% of antioxidant (vitamin C), and 2% of crosslinking agent (glutaraldehyde). After mixing evenly with a high-speed beater, add 40% of the hydrophobic modified silica sol and 0.03% of tannic acid. Adjust the pH to 9 with 1 mol / L sodium hydroxide solution and stir at room temperature for 24 h. After the pulping is completed, enter the forming stage. After the forming is completed, enter the pressing stage. Add 1.2% of surfactant (polyvinyl alcohol). After mixing evenly, enter the subsequent pressing, drying, glazing and coating, paper cutting and winding stages to obtain the finished product.

[0019] Example 4: A papermaking process for improving the durability and waterproof performance of paper. Add 2 g of nano-silica particles to 150 mL of methanol solution. After ultrasonic dispersion for 2.5 h until evenly dispersed, add 4.5 mL of cetyltrimethoxysilane and 2.5 mL of γ-aminopropyltriethoxysilane. After stirring at room temperature for 2.5 h, add 2.5 mL of acetic acid and 2.5 mL of deionized water, and stir at 65 °C for 13 h to obtain a hydrophobic modified silica sol. During the pulping process, add 8% of reinforcing fibers (polyester fibers), 0.8% of antioxidant (vitamin C), and 2.5% of crosslinking agent (glutaraldehyde). After mixing evenly with a high-speed beater, add 45% of the hydrophobic modified silica sol and 0.04% of tannic acid. Adjust the pH to 9.5 with 1 mol / L sodium hydroxide solution and stir at room temperature for 26 h. After the pulping is completed, enter the forming stage. After the forming is completed, enter the pressing stage. Add 1.6% of surfactant (polyvinyl alcohol). After mixing evenly, enter the subsequent pressing, drying, glazing and coating, paper cutting and winding stages to obtain the finished product.

[0020] Example 5: A papermaking process for improving the durability and waterproof performance of paper. Add 2 g of nano-silica particles to 150 mL of methanol solution, ultrasonic disperse for 3 h until evenly dispersed, then add 5 mL of cetyltrimethoxysilane and 3 mL of γ-aminopropyltriethoxysilane, stir at room temperature for 3 h, add 3 mL of acetic acid and 3 mL of deionized water, stir at 70 °C for 14 h to obtain a hydrophobic modified silica sol. During the pulping process, add 9% of reinforcing fiber (polyester fiber), 1% of antioxidant (vitamin C), and 3% of crosslinking agent (glutaraldehyde), mix evenly using a high-speed beater, then add 50% of the hydrophobic modified silica sol and 0.05% of tannic acid, adjust the pH to 10 using 1 mol / L sodium hydroxide solution, stir at room temperature for 28 h. After pulping is completed, enter the forming stage, and after forming is completed, enter the pressing stage, add 2% of surfactant (polyvinyl alcohol), mix evenly and then enter the subsequent pressing, drying, glazing and coating, paper cutting and winding stages to obtain the finished product.

[0021] Performance testing Mechanical property testing Make the paper obtained in Examples 1 - 5 into a rectangular sample of 150 mm × 150 mm, and conduct mechanical property testing on it using an XH-500 type paper tensile tester. First, place the sample in a thermostatic and humidified chamber (temperature 23 ± 1 °C, relative humidity 50 ± 2%) and equilibrate for 24 hours. Then place it along its long side in the fixture, ensure firm clamping and the sample is at the center of the tester. Start the program and conduct tensile testing at a speed of 50 mm / min until the specimen breaks. Refer to the national standard GB / T 450 - 2008. The following table shows the test results: Example 1 Example 2 Example 3 Example 4 Example 5 Tensile strength (N / m) 481 487 492 490 485 Elongation at break (%) 2.7 2.8 3.0 2.9 2.8 Immersion water absorption rate testing Make the paper obtained in Examples 1 - 5 into a rectangular sample of 100 mm × 100 mm, and conduct immersion water absorption rate testing on it using a WS-200 type waterproof performance tester and an XP-600 type precision electronic balance. First, place the sample in a thermostatic and humidified chamber (temperature 23 ± 1 °C, relative humidity 50 ± 2%) and equilibrate for 24 hours. Weigh the initial mass of each specimen using a precision balance, completely immerse the specimen in a water bath at 23 ± 1 °C for 10 minutes, take it out, dry the surface moisture with standard filter paper, and immediately reweigh the mass. Calculate the water absorption rate (water absorption rate = (mass after immersion - initial mass) / initial mass × 100%). Refer to the national standard GB / T 22864 - 2008. The following table shows the test results: Example 1 Example 2 Example 3 Example 4 Example 5 Water absorption rate (%) 12.2 11.9 11.8 12.0 12.5 Hydrostatic pressure testing The papers obtained in Examples 1-5 were made into rectangular samples of 100 mm × 100 mm, and the hydrostatic pressure test was carried out on them using an SP-100 type hydrostatic pressure tester. The samples were first placed in a constant temperature and humidity chamber (temperature 23 ± 1 °C, relative humidity 50 ± 2%) and equilibrated for 24 hours, and then fixed on the SP-100 type hydrostatic pressure tester. The pressure was slowly increased at a rate of 1 kPa / s, and the paper surface was observed. When water penetration first occurred, the water pressure value was recorded. Referring to the national standard GB 23454-2009, the following table shows the test results: Example 1 Example 2 Example 3 Example 4 Example 5 Hydrostatic pressure (KPa) 95 96 98 97 95 Contact angle measurement The papers obtained in Examples 1-5 were made into rectangular samples of 100 mm × 100 mm, and the contact angle measurement was carried out on them using a JC2000 type contact angle measuring instrument. The samples were first placed in a constant temperature and humidity chamber (temperature 23 ± 1 °C, relative humidity 50 ± 2%) and equilibrated for 24 hours. Then, 5 μL of deionized water was dropped on the flat surface of the sample, and the shape of the water droplet was photographed using the contact angle measuring instrument, and the initial contact angle was automatically calculated. Referring to the national standard GB / T 23899-2009, the following table shows the test results: Example 1 Example 2 Example 3 Example 4 Example 5 Contact angle (°) 141 147 150 145 138

Claims

1. A papermaking process for improving the durability and waterproof performance of paper, characterized in that: A papermaking process for improving the durability and waterproof performance of paper. During the pulping process, reinforcing fibers, antioxidants, and crosslinking agents are added. After being mixed evenly using a high-speed beater, hydrophobic modified silica sol and tannic acid are added. The pH is adjusted using a sodium hydroxide solution, and stirring and reaction are carried out. After the pulping is completed, it enters the forming stage. After the forming is completed, it enters the pressing stage. A surfactant is added, and after being mixed evenly, it enters the subsequent pressing, drying, glazing and coating, paper cutting and winding stages, and then the finished product can be obtained.

2. A papermaking process for improving the durability and waterproof performance of paper according to claim 1, characterized in that: The reinforcing fiber is polyester fiber, and the added amount is 5-9%.

3. A papermaking process for improving the durability and waterproof performance of paper according to claim 1, characterized in that: The antioxidant is vitamin C, and the added amount is 0.2-1%.

4. A papermaking process for improving the durability and waterproof performance of paper according to claim 3, characterized in that: The crosslinking agent is glutaraldehyde, and the added amount is 1-3%.

5. A papermaking process for improving the durability and waterproof performance of paper according to claim 1, characterized in that: The preparation method of the hydrophobic modified silica sol: Add 2 g of nano-silica particles to 150 mL of methanol solution. After ultrasonic dispersion for 1-3 h until evenly dispersed, add 3-5 mL of cetyltrimethoxysilane and 1-3 mL of γ-aminopropyltriethoxysilane. After stirring at room temperature for 1-3 h, add 1-3 mL of acetic acid and 1-3 mL of deionized water, and stir at 50-70 °C for 10-14 h to obtain the hydrophobic modified silica sol. The added amount is 30-50%.

6. A papermaking process for improving the durability and waterproof performance of paper according to claim 1, characterized in that: The added amount of the tannic acid is 0.01-0.05%.

7. A papermaking process for improving the durability and waterproof performance of paper according to claim 1, characterized in that: Adjusting the pH using the sodium hydroxide solution and stirring and reacting means adjusting the pH to 8-10 using a 1 mol / L sodium hydroxide solution and stirring at room temperature for 20-28 h.

8. A papermaking process for improving the durability and waterproof performance of paper according to claim 1, characterized in that: The surfactant is polyvinyl alcohol, and the added amount is 0.4-2%.