Production process of special paper for high-grade polished pipe

Abstract

The invention relates to the technical field of waste paper reutilization, and discloses a production process of special paper for a high-grade polished pipe, which comprises the following steps: pulping mixed waste paper; carrying out biological modification treatment on the pulp by adopting compound cellulase; adding a non-reactive salt into the modified slurry to carry out environment presetting so as to adjust the ion concentration; sequentially adding a cationized nanocellulose synergistic enhancer and cationic starch into the wet part; and finally forming and drying to obtain a finished product. According to the method, high-energy-consumption mechanical pulping is replaced by biological modification, fibers are treated under mild conditions, energy consumption is reduced, and fiber damage is avoided; through combination of environment presetting and cationized nano cellulose, effective fixation of hydrophobic stickies in waste paper pulp and synergistic enhancement of physical strength of finished paper are realized. The special paper prepared by the process has the advantages that the cleanliness, interlayer bonding strength and ring crush index are remarkably improved, meanwhile, a wet-end chemical system is simplified, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of waste paper recycling technology, specifically to a production process for high-grade polishing tube paper. Background Technology

[0002] High-grade polishing tube paper, as a type of industrial paper, has strict technical requirements for its physical strength, especially interlayer bond strength and ring crush index. Currently, the main fiber raw material for producing this type of paper comes from recycled waste paper, such as ordinary cardboard boxes and mixed waste paper. These recycled fibers have undergone multiple recycling processes, resulting in shorter fiber length, reduced strength, and the presence of a certain amount of adhesives, inks, and other impurities.

[0003] To produce paper products meeting high-strength requirements using such low-quality raw materials, existing technologies typically employ high-intensity mechanical beating to enhance fiber bonding. This involves prolonged mechanical treatment of the pulp using equipment such as disc mills to increase the fibrillation of the outer fibers, thereby improving paper strength. However, this energy-intensive mechanical treatment, while improving fiber bonding, also causes fiber cutting damage and generates a large number of fine particles. These fine particles significantly deteriorate the pulp's drainage properties, leading to reduced paper machine speed and decreased production efficiency.

[0004] Furthermore, the adhesives present in waste paper raw materials are dispersed into even finer secondary adhesive particles under strong mechanical action. These particles are difficult to remove using conventional screening equipment and easily deposit on key components such as the paper machine wire and felt during production, causing production obstacles such as paper breakage. They also adhere to the paper surface, forming dust spots and reducing the cleanliness of the finished product. To solve these problems, existing processes have to add various chemical additives to the wet end system, such as traditional dry strength agents and adhesive control agents. The addition of multiple chemicals complicates the wet end chemical environment, increases the uncertainty and control difficulty of the production process, and raises production costs. Therefore, how to effectively improve the paper strength of waste paper pulp while controlling the adverse effects of adhesives and other impurities on product quality and production stability with low energy consumption is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a production process for high-grade polished tube paper, which solves the problems of excessive fiber damage, deterioration of pulp filtration performance, and high production energy consumption caused by over-reliance on high-energy-consuming mechanical pulping when producing high-strength paper products from mixed waste paper. It also solves the problems of low product cleanliness, complex wet-end chemical system, and high production cost caused by poor control of adhesives and the addition of various chemicals.

[0006] To achieve the above objectives, the present invention provides a production process for high-grade polishing tube paper, comprising the following steps: S1. Pulping: The waste paper raw materials are crushed and screened to obtain a mixed pulp. The proportion of the waste paper raw materials is 55-60% by weight of mixed waste paper and 40-45% by weight of ordinary cardboard boxes.

[0007] S2. Biomodification: The mixed slurry obtained in step S1 is subjected to bio-enzymatic selective external fibrillation treatment. The freeness of the slurry obtained after bio-enzymatic selective external fibrillation treatment is controlled to be 30-35°SR, thus obtaining biomodified slurry. The conditions for the bio-enzymatic selective external fibrillation treatment are as follows: the concentration of the mixed slurry is adjusted to 4.0-5.0%, a compound cellulase preparation is added, and the treatment is carried out for 1.5-2.5 hours at a pH of 5.0-6.0 and a temperature of 45-55℃. This step generates nanoscale fibrils on the fiber surface, increasing the specific surface area of ​​the fiber.

[0008] S3. Environmental Preset: A non-reactive salt is added to the bio-modified pulp obtained in step S2 to adjust the ion concentration of the pulp system to 0.01-0.05 mol / L, thus obtaining a pulp with a preset environment. The non-reactive salt is sodium sulfate. This step compresses the electric double layer on the surface of the pulp fibers by increasing the ion concentration.

[0009] S4. Wet-end Addition: The pre-set environmental slurry obtained in step S3 is subjected to wet-end chemical addition to obtain a pre-forming slurry. The wet-end chemical addition includes adding a cationic nanocellulose synergistic reinforcing agent to the slurry, with a dry weight addition amount of 8-10 kg / ton of oven-dry slurry. The wet-end chemical addition also includes adding cationic starch before the lining slurry pump, with a dry weight addition amount of 1.5-2.0% of the oven-dry slurry mass.

[0010] Under the synergistic effect of steps S3 and S4, the following occurs: Because the electric double layer of the pulp fibers is compressed, its electrostatic attraction to the subsequently added positively charged cationic cellulose nanoparticles weakens. At this point, the small-sized hydrophobic adhesive particles with concentrated surface charges in the pulp become the preferential targets for adsorption by the cationic cellulose nanoparticles. The cationic cellulose nanoparticles form a hydrophilic coating layer on the surface of these adhesive particles. After coating the adhesive, the cationic cellulose nanoparticles and the nanoscale filaments on the fiber surface treated in step S2 are bonded together through electrostatic interactions and hydrogen bonds, forming a three-dimensional network structure between the fibers.

[0011] S5. Forming and Drying: The pre-forming pulp obtained in step S4 is fed into a paper machine for forming, pressing, and drying to produce high-grade polished tube paper. The forming process uses a three-layer wire paper machine, with a basis weight ratio of 35:35:30 for the top layer, liner layer, and bottom layer. The pressing process includes four pressing zones, with the linear pressures of the four zones set sequentially to 60-80 KN / m, 70-90 KN / m, 260-300 KN / m, and 260-300 KN / m.

[0012] The cationized nanocellulose synergistic reinforcing agent described in this scheme is prepared using microcrystalline cellulose as a raw material and is formulated into an aqueous dispersion with a solid content of 1.0-1.5% (w / w) before use. Its preparation method includes: a. Cationic modification: Microcrystalline cellulose is alkalized in sodium hydroxide solution, followed by the addition of glycidyltrimethylammonium chloride for cationization reaction to obtain cationic cellulose. The molar ratio of glycidyltrimethylammonium chloride to dehydrated glucose units on cellulose is (0.2-0.4):1, the cationization reaction temperature is 60-70℃, and the reaction time is 3.0-5.0 hours.

[0013] b. Nano-sizing treatment: The cationic cellulose obtained in step a is formulated into a slurry with a solid content of 1.0-2.0% (w / w), and then circulated through a high-pressure homogenizer at a pressure of 100-150 MPa for 5-10 times to obtain the cationic nanocellulose synergistic reinforcing agent.

[0014] This invention provides a production process for high-grade polishing tube paper. It has the following beneficial effects: 1. This invention replaces traditional high-intensity mechanical beating with selective external fibrillation treatment using bio-enzymes, precisely controlling the pulp freeness within a lower 30-35°SR range, thus reducing energy consumption in the pulping process. This method selectively acts on the fiber surface under mild conditions to generate nanoscale filaments, avoiding excessive damage to the fiber body caused by high-energy mechanical processing, optimizing fiber morphology, and providing an ideal pulp base for subsequent processes.

[0015] 2. This invention achieves active identification and targeted coating of hydrophobic adhesives in waste paper pulp by setting an ion strength targeting environment before adding core additives in the wet end. The pre-added non-reactive salt compresses the double layer on the fiber surface, allowing the subsequently added cationic nanocellulose to preferentially adsorb and coat the surface of the more charged adhesive particles, transforming them from potential product defects into inert fillers stably bound in the fiber network, thereby improving the cleanliness of the finished paper and the operational stability of the production system.

[0016] 3. This invention utilizes a single cationic nanocellulose synergistic reinforcing agent, integrating the multiple functions of a dry strength agent, adhesive control agent, and interlayer reinforcing agent. This simplifies the wet-end chemical system and significantly reduces the amount of additives such as starch. The in-situ nanofibers generated on the fiber surface through biomodification synergistically interact with the added cationic nanocellulose, constructing a dense three-dimensional network structure between the fibers through electrostatic attraction and hydrogen bonding. This effectively enhances the bonding force between fibers, thereby improving the interlayer bonding strength of the final paper. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments, comparative examples, and test examples. 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.

[0018] Experimental materials and reagents: Microcrystalline cellulose, CAS No.: 9004-34-6; Sodium hydroxide, CAS No.: 1310-73-2; Hydrochloric acid, CAS No.: 7647-01-0; Anhydrous sodium sulfate, CAS No.: 7757-82-6; Cationic starch, CAS No.: 56780-58-6; Anionic polyacrylamide, CAS No.: 9003-05-8; Fatty alcohol polyoxyethylene ether, CAS No.: 68439-50-9.

[0019] Examples 1-3: Example 1: This embodiment provides a production process for high-grade polishing tube special paper, the specific steps of which are as follows: S1. Pulping: The fiber raw materials are fed into a high-consistency pulper for disintegration, with a ratio of 55% mixed waste paper and 45% ordinary cardboard boxes. The pulp is then screened and deslagging is performed to obtain the mixed pulp.

[0020] S2, Biomodification: The concentration of the mixed slurry obtained in step S1 was adjusted to 4.0%, and a compound cellulase preparation was added at a rate of 0.1% of the oven-dry slurry mass. The pH of the slurry system was adjusted to 5.0 using hydrochloric acid, and the mixture was treated at 45°C for 1.5 hours. After treatment, the freeness of the slurry was measured and controlled to reach 30°SR to obtain the biomodified slurry.

[0021] S3, Environment Preset: Anhydrous sodium sulfate was added to the biomodified slurry obtained in step S2 and stirred to adjust the ion concentration of the slurry system to 0.01 mol / L, thereby obtaining the preset environmental slurry.

[0022] S4, Add to wet area: The pre-set environmental slurry obtained in step S3 is sent into the slurry forming tank. A cationic nanocellulose synergistic reinforcing agent is added to the slurry forming tank at a dry weight addition amount of 8 kg / ton of oven-dry slurry. Cationic starch is added before the lining slurry pump at a dry weight addition amount of 1.5% of the oven-dry slurry mass to obtain the slurry before molding.

[0023] S5. Molding and Drying: The pre-forming pulp obtained in step S4 is fed into a three-layer wire paper machine for forming, controlling the basis weight ratio of the top layer, liner layer, and bottom layer to be 35:35:30. The wet paper sheet passes through four pressing zones sequentially, with the linear pressures of the four pressing zones set to 60KN / m, 70KN / m, 260KN / m, and 260KN / m respectively. After pressing, the wet paper sheet enters the drying section for drying, producing a high-grade polishing tube special paper product, denoted as S1.

[0024] Example 2: This embodiment provides a production process for high-grade polishing tube special paper, the specific steps of which are as follows: S1. Pulping: The fiber raw materials were fed into a high-consistency pulper for disintegration, with a ratio of 57.5% by weight of mixed waste paper and 42.5% by weight of ordinary cardboard boxes. The pulp was then screened and deslagging was carried out in sequence to obtain mixed pulp.

[0025] S2, Biomodification: The concentration of the mixed slurry obtained in step S1 was adjusted to 4.5%, and a compound cellulase preparation was added at a rate of 0.1% of the oven-dry slurry mass. The pH of the slurry system was adjusted to 5.5 using hydrochloric acid, and the mixture was treated at 50°C for 2.0 hours. After the treatment, the freeness of the slurry was measured and controlled to reach 32.5°SR, thus obtaining the biomodified slurry.

[0026] S3, Environment Preset: Anhydrous sodium sulfate was added to the biomodified slurry obtained in step S2 and stirred to adjust the ion concentration of the slurry system to 0.03 mol / L, thereby obtaining the preset environmental slurry.

[0027] S4, Add to wet area: The pre-set environmental slurry obtained in step S3 is fed into the slurry forming tank. A cationic nanocellulose synergistic reinforcing agent is added to the slurry forming tank at a dry weight addition amount of 9 kg / ton of oven-dry slurry. Cationic starch is added before the lining slurry pump at a dry weight addition amount of 1.75% of the oven-dry slurry mass to obtain the slurry before molding.

[0028] S5. Molding and Drying: The pre-forming pulp obtained in step S4 is fed into a three-layer wire paper machine for forming, controlling the basis weight ratio of the top layer, liner layer, and bottom layer to be 35:35:30. The wet paper sheet passes through four pressing zones sequentially, with the linear pressures of the four pressing zones set to 70KN / m, 80KN / m, 280KN / m, and 280KN / m respectively. After pressing, the wet paper sheet enters the drying section for drying, producing a high-grade polishing tube special paper product, denoted as S2.

[0029] Example 3: This embodiment provides a production process for high-grade polishing tube special paper, the specific steps of which are as follows: S1. Pulping: The fiber raw materials are fed into a high-consistency pulper for disintegration, with a ratio of 60% mixed waste paper and 40% ordinary cardboard boxes. The pulp is then screened and deslagging is performed to obtain the mixed pulp.

[0030] S2, Biomodification: The concentration of the mixed slurry obtained in step S1 was adjusted to 5.0%, and a compound cellulase preparation was added at a rate of 0.1% of the oven-dry slurry mass. The pH of the slurry system was adjusted to 6.0 using hydrochloric acid, and the mixture was treated at 55°C for 2.5 hours. After treatment, the freeness of the slurry was measured and controlled to reach 35°SR to obtain the biomodified slurry.

[0031] S3, Environment Preset: Anhydrous sodium sulfate is added to the biomodified slurry obtained in step S2 and stirred to adjust the ion concentration of the slurry system to 0.05 mol / L, thereby obtaining the preset environmental slurry.

[0032] S4, Add to wet area: The pre-set environmental slurry obtained in step S3 is fed into the slurry forming tank. A cationic nanocellulose synergistic reinforcing agent is added to the slurry forming tank at a dry weight addition amount of 10 kg / ton of oven-dry slurry; cationic starch is added before the lining slurry pump at a dry weight addition amount of 2.0% of the oven-dry slurry mass to obtain the slurry before molding.

[0033] S5. Molding and Drying: The pre-forming pulp obtained in step S4 is fed into a three-layer wire paper machine for forming, controlling the basis weight ratio of the top layer, liner layer, and bottom layer to be 35:35:30. The wet paper sheet passes through four pressing zones sequentially, with the linear pressures of the four pressing zones set to 80KN / m, 90KN / m, 300KN / m, and 300KN / m respectively. After pressing, the wet paper sheet enters the drying section for drying, producing a high-grade polishing tube special paper product, denoted as S3.

[0034] Comparative Examples 1-3: Comparative Example 1: The difference compared to Example 2 is as follows: Step S2 does not employ biological modification treatment. Instead, a disc mill is used to perform high-intensity mechanical beating on the mixed slurry obtained in step S1 until the slurry freeness reaches 48°SR.

[0035] The environment preset for step S3 is omitted.

[0036] In the wet end addition of step S4, instead of adding cationic nanocellulose as a synergistic reinforcing agent, anionic polyacrylamide (3 kg / ton oven-dry pulp) is added as a traditional dry strength agent and fatty alcohol polyoxyethylene ether (1.5 kg / ton oven-dry pulp) as a traditional adhesive control agent; at the same time, the dry weight addition of cationic starch is increased to 2.5% of the oven-dry pulp mass.

[0037] The remaining steps are the same as in Example 2, and the final high-grade polishing tube special paper product is denoted as DS1.

[0038] Comparative Example 2: The difference compared to Example 2 is as follows: The environmental preset in step S3 is omitted, that is, after obtaining the bio-modified slurry in step S2, the ion concentration is not adjusted, and the wet part addition in step S4 is carried out directly.

[0039] The remaining steps are the same as in Example 2. The final high-grade polishing tube paper product is designated as DS2.

[0040] Comparative Example 3: The difference compared to Example 2 is as follows: The environment preset for step S3 is omitted.

[0041] In the wet end addition of step S4, instead of adding cationic nanocellulose as a synergistic reinforcing agent, anionic polyacrylamide (3 kg / ton oven-dried pulp) is added as a traditional dry strength agent; at the same time, the dry weight addition of cationic starch is increased to 2.5% of the oven-dried pulp mass.

[0042] The remaining steps are the same as in Example 2. The final high-grade polishing tube paper product is designated as DS3.

[0043] Test Example 1-3: Test subject: Take the high-grade polishing tube special paper products S1, S2, and S3 prepared in Examples 1-3, and the high-grade polishing tube special paper products DS1, DS2, and DS3 prepared in Comparative Examples 1-3.

[0044] Test method: Test Example 1: Cleanliness Test Sample preparation: The paper samples S1-S3 and DS1-DS3 to be tested were subjected to constant temperature and humidity treatment in an environment with a temperature of 23±1℃ and a relative humidity of 50±2% for 24 hours, in accordance with GB / T10739 standard.

[0045] Testing instrument: PDI-2000 paper cleanliness analyzer.

[0046] Test Procedure: Place the paper sample, which has undergone constant temperature and humidity treatment, on the sample stage of the analyzer and start the test program. The instrument's light source uniformly illuminates the surface of the paper sample, and the built-in image acquisition unit acquires images of the paper sample surface. The image analysis system automatically identifies and calculates the number and total area of ​​dust particles with a diameter greater than 0.02 mm per unit area (1 square meter). Measurements are taken at 5 different locations for each sample, and the arithmetic mean is recorded.

[0047] Test results: The cleanliness test results for each paper sample are recorded in Table 1.

[0048] Table 1: Results of Paper Sample Cleanliness Test

[0049] Results analysis: As shown in Table 1, the test data of Examples S1, S2, and S3 indicate that the number and total area of ​​dust particles in the paper samples are significantly lower than those of Comparative Examples DS1, DS2, and DS3. Comparative Example DS1, which uses high-intensity mechanical beating and traditional wet-end chemicals, has the highest paper cleanliness value, indicating that the hydrophobic adhesives in the waste paper pulp were not effectively fixed. Examples S1-S3, through bio-enzyme modification and the addition of cationic nanocellulose synergistic reinforcing agents in the wet end, show low numbers and areas of dust particles in their paper samples, demonstrating the effectiveness of this technology in controlling dust particles in paper sheets.

[0050] Comparing the data from Example S2 and Comparative Example DS2, in the absence of environmental preconditioning using non-reactive salts (DS2), despite the presence of cationic nanocellulose in the system, the number and area of ​​dust particles on the paper sample were significantly higher than in Example S2. This indicates that by adding non-reactive salts to increase the ion concentration of the system, the double layer on the fiber surface is compressed, reducing the electrostatic adsorption of cationic nanocellulose by the fibers. Consequently, the cationic nanocellulose preferentially adsorbs and coats the surface of the hydrophobic adhesive particles, fixing them within the fiber network.

[0051] Comparing the data from Example S2 and Comparative Example DS3, when a traditional dry strength agent was used instead of a cationic nanocellulose synergistic reinforcing agent (DS3), even though the pulp underwent biomodification treatment, the paper cleanliness value was significantly higher than that of Example S2. This indicates that biomodification treatment itself cannot solve the problem of hydrophobic adhesives; the improvement in paper cleanliness directly stems from the coating and fixation effect of the cationic nanocellulose synergistic reinforcing agent on the hydrophobic adhesives.

[0052] Test Example 2: Interlayer Bond Strength Test Sample preparation: The paper samples S1-S3 and DS1-DS3 to be tested were subjected to constant temperature and humidity treatment in an environment with a temperature of 23±1℃ and a relative humidity of 50±2% for 24 hours, in accordance with GB / T10739 standard.

[0053] Testing instrument: DRK133 interlaminar bond strength tester.

[0054] Test Procedure: Performed according to GB / T26203 standard. Cut a 70mm × 70mm paper sample. Apply double-sided tape to both sides of the paper sample and clamp it between two metal test blocks. Place the assembly under a pressure device and maintain a pressure of 700 kPa for 2 minutes. Install the assembled test piece on the fixture of the testing machine, start the instrument, and apply a Z-axis (perpendicular to the paper plane) impact force to the test piece at an impact velocity of 2.5 m / s until internal delamination occurs in the paper sample. The instrument automatically records and calculates the energy consumed in the delamination failure. Ten samples are taken from each sample and their arithmetic mean is recorded.

[0055] Test results: The interlayer bond strength test results for each paper sample are recorded in Table 2.

[0056] Table 2: Test results of interlayer bond strength of paper samples

[0057] Results analysis: As shown in Table 2, the interlayer bond strength of the paper samples obtained in Examples S1, S2, and S3 is significantly higher than that of Comparative Examples DS1, DS2, and DS3. Comparative Example DS1, which uses high-strength mechanical pulping and traditional chemicals, has the lowest interlayer bond strength. The technical solutions used in Examples S1-S3, through the synergistic effect of bio-enzyme modification and cationic nanocellulose, yielded paper sheets with higher interlayer bond strength.

[0058] The effectiveness of this technology stems from the combined effect of pulp treatment and wet-end additives. Bioenzymatic selective external fibrillation generates nanoscale filaments in situ on the fiber surface, increasing the fiber's specific surface area and available binding sites. The subsequently added cationic nanocellulose synergistic reinforcing agent, possessing nanoscale size and high specific surface area, adsorbs onto the biomodified fiber surface via electrostatic attraction. These in-situ generated nanofibers and the added cationic nanocellulose form physical cross-links and hydrogen bond networks between fibers and between layers of the paper sheet, increasing the bonding area and number of bonding points between fibers, thereby enhancing resistance to interlayer separation.

[0059] Comparing the data from Example S2 and Comparative Example DS3, the interlayer bonding strength of the pulp after bio-modification but without the use of cationic nanocellulose synergistic reinforcing agent (DS3) was lower than that of Example S2. This indicates that relying solely on in-situ generated nanofibers is insufficient to achieve the highest reinforcing effect, and the added cationic nanocellulose is necessary for constructing the interfiber bonding network. Comparing the data from Example S2 and Comparative Example DS1, the interlayer bonding strength was the lowest when conventional mechanical pulping was used without bio-modification treatment (DS1). This indicates that the role of bio-modification in optimizing fiber morphology and enhancing bonding potential cannot be replaced by mechanical pulping.

[0060] Test Example 3: Ring Compression Index Test Sample preparation: The paper samples S1-S3 and DS1-DS3 to be tested were subjected to constant temperature and humidity treatment in an environment with a temperature of 23±1℃ and a relative humidity of 50±2% for 24 hours, in accordance with GB / T10739 standard.

[0061] Testing instrument: DRK109 microcomputer ring crush strength tester.

[0062] Test Procedure: Performed according to GB / T2679.8 standard. Cut a 152mm × 12.7mm specimen from each sample after constant temperature and humidity treatment. Place the specimen into the groove of the annular specimen holder of the testing machine, forming a ring. Place the specimen holder containing the specimen in the center of the lower pressure plate of the testing machine. Start the instrument; the upper pressure plate moves downward at a constant speed of 12.5mm / min, applying pressure to the annular specimen until it is crushed. Record the maximum pressure value when the specimen is crushed. Take 10 specimens from each sample for testing, record their arithmetic mean, and calculate the ring crush index.

[0063] Test results: The ring crush index test results for each paper sample are recorded in Table 3.

[0064] Table 3: Results of Ring Crush Index Test on Paper Samples

[0065] Results analysis: As shown in Table 3, the ring crush index values ​​of the paper samples obtained in Examples S1, S2, and S3 are all higher than those of Comparative Examples DS1, DS2, and DS3. Comparative Example DS1, which uses high-strength mechanical beating and conventional wet-end chemicals, has the lowest ring crush index value. The technical solutions used in Examples S1-S3 yielded paper sheets with higher ring crush indices, indicating that these paper sheets have higher crush resistance.

[0066] The effectiveness of this technology stems from a specific combination of pulp treatment and wet-end additives. By selectively exfilarizing the fibers with bio-enzymes, nanoscale filaments are generated in situ on the fiber surface without significantly damaging the fiber's bulk structure. These nanofibers increase the fiber's specific surface area. The subsequent addition of cationic nanocellulose synergistic reinforcing agents works in conjunction with these in-situ generated nanofibers to form a physical cross-linking and hydrogen bond network between the fibers, increasing the number and area of ​​bonding points and resulting in a denser paper sheet structure. This structure enhances the paper sheet's overall resistance to external compressive stress.

[0067] Comparing the data from Example S2 and Comparative Example DS1, when high-intensity mechanical beating was used (DS1), the fibers were cut and excessively swollen, resulting in a lower ring crush index for the paper compared to Example S2, which underwent biomodification. Comparing the data from Example S2 and Comparative Example DS3, when the pulp underwent biomodification but without the use of a cationic nanocellulose synergistic reinforcing agent (DS3), its ring crush index was lower than that of Example S2. This indicates that the added cationic nanocellulose synergistic reinforcing agent is necessary for forming an effective interfiber bonding network, thereby improving the compressive strength of the paper.

Claims

1. A production process for high-grade polishing tube special paper, characterized in that, Includes the following steps: S1. Pulping: The waste paper raw materials are broken down and screened to obtain a mixed pulp; S2, Biomodification: The mixed slurry obtained in step S1 is subjected to bio-enzyme selective external fibrillation treatment, and the freeness of the slurry obtained after bio-enzyme selective external fibrillation treatment is controlled to be 30-35°SR, so as to obtain biomodified slurry. S3, Environmental Preset: Add non-reactive salts to the biomodified slurry obtained in step S2 to adjust the ion concentration of the slurry system to 0.01-0.05 mol / L, and obtain the preset environmental slurry; S4. Wet-end addition: The preset environmental slurry obtained in step S3 is subjected to wet-end chemical addition, which includes adding a cationic nanocellulose synergistic reinforcing agent to the slurry. The dry weight addition amount of the cationic nanocellulose synergistic reinforcing agent is 8-10 kg / ton of oven-dry slurry to obtain the slurry before molding. S5. Forming and Drying: The pre-forming pulp obtained in step S4 is fed into a paper machine for forming, pressing and drying to produce high-grade polishing tube paper.

2. The production process of high-grade polishing tube special paper according to claim 1, characterized in that, The conditions for the selective external fibrillation treatment by bio-enzymes in step S2 are as follows: adjust the concentration of the mixed slurry to 4.0-5.0%, add the compound cellulase preparation, and treat for 1.5-2.5 hours at a pH of 5.0-6.0 and a temperature of 45-55℃.

3. The production process of high-grade polishing tube special paper according to claim 1, characterized in that, The non-reactive salt added in step S3 is sodium sulfate.

4. The production process of high-grade polishing tube special paper according to claim 1, characterized in that, The cationic nanocellulose synergistic reinforcing agent is prepared using microcrystalline cellulose as raw material and is formulated into an aqueous dispersion with a solid content of 1.0-1.5% (w / w) before use.

5. The production process of high-grade polishing tube special paper according to claim 4, characterized in that, The preparation method of the cationic nanocellulose synergistic reinforcing agent includes: a. Cationic modification: Microcrystalline cellulose is alkalized in sodium hydroxide solution, and then glycidyltrimethylammonium chloride is added to carry out a cationization reaction to obtain cationic cellulose; b. Nano-sizing treatment: The cationic cellulose obtained in step a is formulated into a slurry with a solid content of 1.0-2.0% (w / w), and then circulated through a high-pressure homogenizer at a pressure of 100-150 MPa for 5-10 times to obtain the cationic nanocellulose synergistic reinforcing agent.

6. The production process of high-grade polishing tube special paper according to claim 5, characterized in that, In the cationic modification step a, the molar ratio of glycidyltrimethylammonium chloride to dehydrated glucose units on cellulose is (0.2-0.4):1, the cationic reaction temperature is 60-70℃, and the reaction time is 3.0-5.0 hours.

7. The production process of high-grade polishing tube special paper according to claim 1, characterized in that, The addition of wet-end chemicals in step S4 also includes adding cationic starch before the lining slurry pump, wherein the dry weight of the cationic starch added is 1.5-2.0% of the oven-dry slurry mass.

8. The production process of high-grade polishing tube special paper according to claim 1, characterized in that, In step S1, the ratio of waste paper raw materials is 55-60% by weight of mixed waste paper and 40-45% by weight of ordinary cardboard boxes.

9. The production process of high-grade polishing tube special paper according to claim 1, characterized in that, The forming process in step S5 uses a three-layer paper machine, with the quantitative ratio of the top layer, liner layer, and bottom layer being 35:35:

30.

10. The production process of high-grade polishing tube special paper according to claim 1, characterized in that, The pressing process in step S5 includes four pressing zones, with the linear pressures of the four pressing zones set sequentially to 60-80 KN / m, 70-90 KN / m, 260-300 KN / m, and 260-300 KN / m.

Images