Method for preparing cardboard paper from composite mineral fibers

Abstract

The invention relates to the technical field of papermaking, and discloses a method for preparing cardboard paper by using composite mineral fibers, which comprises the following steps: dispersion and micro-nano treatment of attapulgite, preparation of a chitosan-attapulgite composite material, preparation of composite mineral fibers, paper pulp mixing and papermaking. Through micro-nanocrystallization treatment of attapulgite and coating modification of chitosan, the binding force of the composite mineral fiber and the paper pulp fiber is remarkably enhanced, and the mechanical properties such as tightness, burst index and ring crush index of finished paper are superior to those of standard requirements; besides, by adding the composite mineral fibers, fine fibers in the white water are removed, the fiber retention rate is increased, part of paper pulp fibers can be replaced, use of chemical auxiliary materials is reduced, the production cost is reduced, the production efficiency and the finished paper quality are improved, and the clean papermaking purposes of quality improvement, efficiency improvement and pollution reduction are achieved. Therefore, considerable economic benefits and social benefits are obtained.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, and more specifically to a method for preparing linerboard using composite mineral fibers. Background Technology

[0002] Currently, the proportion of wood pulp used in the papermaking industry continues to rise. Wood pulp fibers are easier to use to produce various high-quality paper products, have high production efficiency, and are easier to control pollution. However, with the rapid development of the papermaking industry and the continuous growth of paper consumption, the demand for papermaking fibers is increasing. Excessive deforestation by the global papermaking industry has led to a depletion of forest resources, ecological degradation, and a global shortage of raw materials for papermaking.

[0003] To address the shortage of fiber raw materials in the paper industry, the main measures taken include vigorously promoting integrated forestry and paper production, expanding waste paper recycling and utilization, and rationally using non-wood fiber raw materials. Among these measures, adding fillers during the papermaking process can improve paper's whiteness, opacity, and printability. Moreover, fillers are cheaper than fibers, which helps save costs; therefore, high-filler paper is a new trend in papermaking development.

[0004] However, high filler content can also cause some problems. The addition of filler can reduce the hydrogen bonding force between fibers, leading to a decrease in paper strength, which can have an adverse effect on the operation of the paper machine, causing filler deposition and some related control problems.

[0005] Based on this, composite mineral fibers, as a novel material, can replace some wood fibers and fillers. Their natural mineral source, low viscosity, and high adsorption properties offer a possibility for solving the aforementioned problems. However, existing technologies lack systematic solutions for key processes such as the dispersion treatment of composite mineral fibers and the enhancement of their bonding force with fibers. This results in unstable application effects in papermaking, making it difficult to achieve the goals of "improving quality, increasing efficiency, reducing pollution, and reducing emissions." Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing linerboard using composite mineral fibers. By micro-nano processing of attapulgite, chitosan coating modification, and compounding with sepiolite, the composite mineral fibers and pulp are efficiently combined, improving paper strength, reducing the amount of additives, reducing waste paper consumption, and achieving clean production.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing linerboard using composite mineral fibers includes the following steps: S1. Add attapulgite to a liquid medium and use mechanical stirring. By controlling the stirring speed and stirring time, the attapulgite particles are dispersed by shear force until the dense crystal bundles become loose rod-shaped crystals, thus obtaining an attapulgite suspension. S2. Chitosan is dissolved in acetic acid solution to obtain chitosan solution; the chitosan solution is mixed with the attapulgite suspension in step S1, and after stirring, ammonia is added to adjust the pH value. The chitosan molecules are solidified on the surface of the attapulgite particles by alkaline precipitation to form a chitosan deposition film, thus obtaining chitosan-attapulgite composite material. S3. Mix sepiolite and chitosan-attapulgite composite material from step S2 according to a preset ratio and stir evenly to obtain composite mineral fiber. S4. Add the composite mineral fibers from step S3 to the paper pulp, mix them evenly, and then form the paper. After drying, the paperboard is obtained.

[0008] Optionally, in step S1, the mechanical stirring speed is 800-1500 r / min, and the stirring time is 30-90 min; the liquid medium is water, and the mass ratio of attapulgite to water is 1:5-1:10.

[0009] Optionally, in step S2, the concentration of the chitosan solution is 1-3 wt%, the concentration of the acetic acid solution is 1-2 wt%, and the volume ratio of the chitosan solution to the attapulgite suspension is 1:3-1:5.

[0010] Optionally, the concentration of the ammonia water is 5-10 wt%, the adjusted pH value is 7.5-8.5, the stirring speed is 1200-2000 r / min, and the stirring time is 20-40 min.

[0011] Optionally, in step S3, the mass ratio of sepiolite to chitosan-attapulgite composite material is 1:4-1:6.

[0012] Optionally, in step S4, the amount of composite mineral fiber added to the paper pulp is 5-10% of the oven-dry weight of the pulp.

[0013] Optionally, during the papermaking process, the dosage of retention aid is 0.28-0.35 kg / t, and the dosage of defoamer is 0.31-0.45 kg / t.

[0014] Optionally, the linerboard has a density ≥0.75g / cm³, a bursting strength index ≥2.43kPa・m² / g, a ring crush index ≥8.35N・m / g, and an ash content stable at 12.5%±0.5%.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention can improve paper performance. Through the micro-nano treatment of attapulgite and the chitosan coating modification, the bonding force between composite mineral fibers and pulp fibers is significantly enhanced, and the mechanical properties of finished paper, such as density, bursting index, and ring crush index, are better than the standard requirements. (2) The present invention can reduce the amount of additives used. The high retention of composite mineral fibers reduces the consumption of retention aids and defoamers, thereby reducing production costs. (3) This invention can save fiber raw materials, replace some wood fiber with composite mineral fiber, reduce waste paper consumption, and save a significant amount of waste paper per year; it can also reduce the fiber and filler content in white water, reduce the wastewater treatment load, and achieve the clean production goal of "pollution reduction and emission reduction". Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of the method for preparing linerboard using composite mineral fibers in an embodiment of the present invention; Figure 2 This is a schematic diagram of the process for preparing composite mineral fibers in an embodiment of the present invention; Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. These drawings are simplified schematic diagrams, which are only used to illustrate the basic structure of the present invention and therefore only show the components relevant to the present invention.

[0018] like Figure 1 and Figure 2 As shown, a method for preparing linerboard using composite mineral fibers includes the following steps: dispersion and micro / nano treatment of attapulgite, preparation of chitosan-attapulgite composite material, preparation of composite mineral fibers, pulp mixing and papermaking.

[0019] Composite mineral fiber is made by combining various non-metallic minerals through special processing equipment. It possesses strong adsorption, agglomeration, and comprehensive regulatory and strengthening properties, making it a novel material that can partially replace wood fiber and also function as a filler. It can be widely used in packaging paper. This invention utilizes natural minerals based on their content, structure, and other characteristics, and is produced through purification and deep processing. Its main function is to improve suspension and retention. This product has special properties such as low viscosity, small particle size, and high buoyancy, adsorption, and retention. It has a significant effect on improving color absorption and coloring performance, thereby improving product quality and reducing production costs.

[0020] Attapulgite, as the core non-metallic mineral raw material for preparing composite mineral fibers, is a natural mineral. After purification and deep processing, it can be used as the basic component of composite mineral fibers. It has characteristics such as strong adsorption, low viscosity, and small particle size, and can play a role in improving suspension and retention in the papermaking process.

[0021] In this invention, through hydration (dispersion and micro / nano treatment) and modification (chitosan coating) processes, the dense crystalline bundle structure of attapulgite can be transformed into a loose rod-shaped structure, forming a chitosan deposition film on the surface, thereby enhancing its bonding force with paper fibers and fillers. When compounded with sepiolite and added to the pulp, its high adsorption capacity can further improve the bonding force between fibers and fillers, increase filler retention, reduce the amount of retention aids, and lower the fiber content in white water. This makes it one of the key materials for achieving green production of linerboard.

[0022] Specifically, hydration treatment refers to the process of dispersing and micro / nanoizing attapulgite. Using the shear force of mechanical stirring, attapulgite particles are fully dispersed in a liquid medium (such as water) until their originally dense crystalline bundle structure transforms into a loose rod-like crystal structure. This process optimizes the surface microporous structure and dispersibility of attapulgite by controlling parameters such as stirring speed and time, improving its suspension, adsorption, and binding ability with fibers, laying the foundation for subsequent compounding with other materials.

[0023] Modification treatment mainly refers to the surface modification of attapulgite through chitosan coating. Chitosan is dissolved in acetic acid solution and then mixed with an attapulgite suspension at high speed. The pH value is then adjusted with ammonia, and an alkaline precipitation method is used to solidify the chitosan molecules adsorbed on the attapulgite surface, forming a dense chitosan deposition film. This process increases the surface potential and particle size of the attapulgite, enhances its binding force with fibers and fillers, solves the problem of decreased paper strength caused by excessive filler addition, and simultaneously improves filler retention.

[0024] The combination of the two forms a synergistic treatment process of "hydration dispersion-surface modification", which is the core technology link that enables composite mineral fibers to replace part of plant fibers and improve the performance of linerboard.

[0025] The mechanical stirring speed is 800-1500 r / min, and the stirring time is 30-90 min; the liquid medium is water, and the mass ratio of attapulgite to water is 1:5-1:10; the concentration of chitosan solution is 1-3 wt%, and the concentration of acetic acid solution is 1-2 wt%; the volume ratio of chitosan solution to attapulgite suspension is 1:3-1:5; the concentration of ammonia water is 5-10 wt%, and the adjusted pH value is 7.5-8.5; the stirring speed is 1200-2000 r / min, and the stirring time is 20-40 min; the mass ratio of sepiolite to chitosan-attapulgite composite material is 1:4-1:6; the amount of composite mineral fiber added to the paper pulp is 5-10% of the oven-dry weight of the pulp; during the papermaking process, the amount of retention aid is 0.28-0.35 kg / t, and the amount of defoamer is 0.31-0.45 kg / t.

[0026] The properties of the finished paper prepared using this invention are as follows: the density of the linerboard is ≥0.75g / cm³, the bursting index is ≥2.43kPa・m² / g, the ring crush index is ≥8.35N・m / g, and the ash content is stable at 12.5%±0.5%. Example 1

[0027] (1) Dispersion and micro / nano treatment of attapulgite: Attapulgite and water were mixed at a mass ratio of 1:7, and mechanical stirring was carried out at a stirring speed of 1200 r / min for 60 min to obtain an attapulgite suspension (the dense crystal bundles of attapulgite were dispersed into loose rod crystals).

[0028] The mass ratio of attapulgite to water is 1:7: This ensures thorough dispersion of the attapulgite, avoiding uneven dispersion due to excessively high concentration or decreased efficiency in subsequent treatments due to excessively low concentration. The stirring speed is 1200 rpm: This speed provides moderate shear force, dispersing the attapulgite crystal bundles into rod-shaped crystals (1-5 μm in diameter) without causing a surge in energy consumption due to excessively high speed. The stirring time is 60 min: This ensures complete dispersion of the attapulgite particles. Too short a time (e.g., <30 min) results in insufficient dispersion; too long a time (e.g., >90 min) provides no significant improvement in efficiency and only increases energy consumption.

[0029] (2) Preparation of chitosan-attapulgite composite material: Chitosan was dissolved in 1.5wt% acetic acid solution to prepare 2wt% chitosan solution; the chitosan solution was mixed with the aforementioned attapulgite suspension at a volume ratio of 1:4, stirred at 1600r / min for 30min, and 8wt% ammonia was added to adjust the pH value to 8.0 so that the chitosan solidified on the surface of attapulgite to form a deposition film.

[0030] A chitosan solution concentration of 2wt% and an acetic acid concentration of 1.5wt% ensure sufficient dissolution of chitosan while avoiding excessively high acetic acid concentrations that would increase the difficulty of subsequent pH adjustment. A volume ratio of 1:4 results in a moderate amount of chitosan, forming a uniformly thick deposition film (50-200nm). If there is too much chitosan (e.g., volume ratio > 1:3), the film will be too thick, reducing the adsorption capacity of attapulgite; if there is too little (e.g., < 1:5), it will not effectively coat the substrate.

[0031] High-speed stirring at 1600 rpm for 30 minutes: This ensures uniform mixing of the chitosan solution and the attapulgite suspension, allowing chitosan molecules to fully adsorb onto the attapulgite surface. Ammonia concentration 8 wt%, pH=8.0: This gently adjusts the pH, allowing the chitosan to slowly solidify and form a dense deposition film; excessively high pH (e.g., >8.5) will cause rapid precipitation of chitosan, resulting in a loose film.

[0032] (3) Preparation of composite mineral fibers: Sepiolite and the aforementioned chitosan-attapulgite composite material are mixed at a mass ratio of 1:5 and stirred evenly. The 1:5 ratio allows sepiolite and attapulgite to work synergistically. The fibrous structure of sepiolite enhances the interweaving of the pulp, and the high adsorption of attapulgite improves the retention rate. An imbalance in the ratio (such as >1:4 or <1:6) will lead to a decrease in the synergistic effect.

[0033] (4) Pulp mixing and papermaking: The composite mineral fiber is added to the waste paper pulp at 8% of the oven-dry weight of the pulp, mixed evenly, and then papermade and dried. During the papermaking process, the retention aid dosage is 0.32 kg / t and the defoamer dosage is 0.38 kg / t.

[0034] An addition of 8% composite mineral fiber can balance the strength of the substitute fiber and the paper. Too high an addition (e.g., >10%) will lead to a decrease in strength; too low an addition (e.g., <5%) will result in an insignificant substitution effect. Retention aid 0.32 kg / t, defoamer 0.38 kg / t: Due to the high retention of composite mineral fiber, the dosage of additives is significantly lower than in traditional processes (reduced from 0.35 kg / t and 0.45 kg / t respectively), thus reducing costs.

[0035] Finished paper properties: density 0.78 g / cm³, bursting strength index 2.50 kPa・m² / g, ring crush index 8.50 N・m / g, ash content 12.5%, all of which are better than the national standard. Example 2

[0036] (1) The mass ratio of attapulgite to water is 1:5, the mixing speed is 800 r / min, and the mixing time is 90 min; (2) The chitosan solution concentration is 1wt% (acetic acid concentration is 1wt%), and the volume ratio with the attapulgite suspension is 1:3. Stir at high speed for 1200r / min for 20min, and adjust the pH to 7.5 with 5wt% ammonia water. (3) The mass ratio of sepiolite to chitosan-attapulgite composite material is 1:4; (4) The amount of composite mineral fiber added is 5%, retention aid is 0.28 kg / t, and defoamer is 0.31 kg / t.

[0037] Finished paper properties: density 0.76 g / cm³, bursting strength index 2.45 kPa・m² / g, ring crush index 8.40 N・m / g, ash content 12.3%, meeting the standards. Example 3

[0038] (1) The mass ratio of attapulgite to water is 1:10, the mixing speed is 1500 r / min, and the mixing time is 30 min; (2) The chitosan solution concentration is 3wt% (acetic acid concentration is 2wt%), and the volume ratio with the attapulgite suspension is 1:5. Stir at high speed for 2000r / min for 40min, and adjust the pH to 8.5 with 10wt% ammonia. (3) The mass ratio of sepiolite to chitosan-attapulgite composite material is 1:6; (4) The amount of composite mineral fiber added is 10%, retention aid is 0.35 kg / t, and defoamer is 0.45 kg / t.

[0039] Finished paper properties: density 0.77 g / cm³, bursting strength index 2.48 kPa・m² / g, ring crush index 8.45 N・m / g, ash content 12.7%, meeting the standards.

[0040] Furthermore, the present invention also proposes some comparative embodiments.

[0041] A: Compared with Example 1, the stirring speed in step (1) was 500 r / min (lower than 800 r / min), and the other parameters were the same. Results: The attapulgite crystal bundles were not completely dispersed (some still agglomerated), the bursting index of the finished paper was 2.20 kPa・m² / g (lower than 2.50 in Example 1), and the retention aid consumption was 0.38 kg / t (higher than in Example 1).

[0042] B: Compared with Example 1, the volume ratio of chitosan solution to attapulgite suspension in step (2) was 1:2 (chitosan was in excess), and the other parameters were the same. Results: The chitosan film on the surface of the attapulgite was too thick, the adsorption decreased, the filler retention rate decreased, the fiber content in the white water increased by 15%, and the waste paper consumption increased to 1.08t / t (higher than 1.052t / t in Example 1).

[0043] C: Compared with Example 1, the composite mineral fibers were prepared using only chitosan-attapulgite composite material (without sepiolite), with all other parameters remaining the same. Results: The paper ring crush index was 7.80 N·m / g (lower than 8.50 in Example 1), and the paper stiffness decreased due to the lack of fibrous support from sepiolite.

[0044] Papermaking process: After screening, grading and purification, waste paper pulp removes impurities and adjusts fiber morphology to obtain purer papermaking pulp that meets the requirements of subsequent production. The papermaking pulp is then mixed with modified mineral fibers to obtain mixed pulp that can be used in subsequent papermaking processes. After forming and pressing, the mixed pulp can be used to obtain finished paper. Subsequently, the ash content, density and other quality of the finished paper are tested.

[0045] White water is generated during the papermaking process. It is wastewater containing fine fibers, fillers (such as composite mineral fibers) and a small amount of chemical additives. It mainly comes from the forming and pressing stages of papermaking. This invention can reduce the fiber content in white water by developing the application process of composite mineral fibers (such as improving their retention), thereby achieving the goals of "reducing pollution, reducing emissions" and saving raw materials.

[0046] In summary, the present invention proposes a method for preparing linerboard using composite mineral fibers. By adding composite mineral fibers, not only can fine fibers be removed from white water and the fiber retention rate be improved, but also some pulp fibers can be replaced, reducing the use of chemical additives, lowering production costs, improving production efficiency and paper quality. This achieves the goal of clean papermaking that improves quality, increases efficiency, and reduces pollution, thereby obtaining considerable economic and social benefits.

[0047] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0048] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0049] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing linerboard using composite mineral fibers, characterized in that, Includes the following steps: S1. Add attapulgite to a liquid medium and use mechanical stirring. By controlling the stirring speed and stirring time, the attapulgite particles are dispersed by shear force until the dense crystal bundles become loose rod-shaped crystals, thus obtaining an attapulgite suspension. S2. Chitosan is dissolved in acetic acid solution to obtain chitosan solution; the chitosan solution is mixed with the attapulgite suspension in step S1, and after stirring, ammonia is added to adjust the pH value. The chitosan molecules are solidified on the surface of the attapulgite particles by alkaline precipitation to form a chitosan deposition film, thus obtaining chitosan-attapulgite composite material. S3. Mix sepiolite and chitosan-attapulgite composite material from step S2 according to a preset ratio and stir evenly to obtain composite mineral fiber. S4. Add the composite mineral fibers from step S3 to the paper pulp, mix them evenly, and then form the paper. After drying, the paperboard is obtained.

2. The method for preparing linerboard using composite mineral fibers according to claim 1, characterized in that, In step S1, the mechanical stirring speed is 800-1500 r / min, and the stirring time is 30-90 min; the liquid medium is water, and the mass ratio of attapulgite to water is 1:5-1:

10.

3. The method for preparing linerboard using composite mineral fibers according to claim 1, characterized in that, In step S2, the concentration of the chitosan solution is 1-3 wt%, the concentration of the acetic acid solution is 1-2 wt%, and the volume ratio of the chitosan solution to the attapulgite suspension is 1:3-1:

5.

4. The method for preparing linerboard using composite mineral fibers according to claim 3, characterized in that, The concentration of the ammonia water is 5-10 wt%, and the adjusted pH value is 7.5-8.5; the stirring speed is 1200-2000 r / min, and the stirring time is 20-40 min.

5. The method for preparing linerboard using composite mineral fibers according to claim 1, characterized in that, In step S3, the mass ratio of sepiolite to chitosan-attapulgite composite material is 1:4-1:

6.

6. The method for preparing linerboard using composite mineral fibers according to claim 1, characterized in that, In step S4, the amount of composite mineral fiber added to the paper pulp is 5-10% of the oven-dry weight of the pulp.

7. The method for preparing linerboard using composite mineral fibers according to claim 6, characterized in that, During the papermaking process, the dosage of retention aid is 0.28-0.35 kg / t, and the dosage of defoamer is 0.31-0.45 kg / t.

8. The method for preparing linerboard using composite mineral fibers according to any one of claims 1-7, characterized in that, The linerboard has a density ≥ 0.75 g / cm³, a bursting strength index ≥ 2.43 kPa・m² / g, a ring crush index ≥ 8.35 N・m / g, and an ash content stable at 12.5% ​​± 0.5%.

Images