High-smoothness household paper and preparation method thereof

Abstract

The invention discloses high-smoothness paper for daily use and a preparation method thereof. The method comprises the following steps: applying a cationic softening agent (the addition amount is 0.8%-1.2%) to paper pulp fibers, and carrying out physical swelling treatment (0.15-0.20 MPa, 20-30 minutes); then grinding under the power of 280-310 kW, and controlling the concentration to be 3.5%-4.0%; and finally, forming on a 120-140-mesh forming net under the calendering pressure of 0.25-0.30 MPa, drying at the temperature of 110-120 DEG C for 15-20 seconds, and wrinkling. An on-line detection and feedback system can be integrated, and key parameters can be dynamically adjusted. The softness of the prepared household paper is 6.0-8.0 mN, the smoothness is 45-55 s, the wrinkle depth deviation is less than or equal to 0.02 mm, and the raw materials are hardwood pulp and softwood pulp in a ratio of 8.5: 1.5. According to the scheme, unification of softness, smoothness and high strength is achieved, the problems of performance contradiction and unstable production in a traditional process are solved, and the method is suitable for continuous intelligent manufacturing of high-end household paper.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, and in particular to a high-smoothness household paper and its preparation method. Background Technology

[0002] With the upgrading of consumption, the high-end tissue paper market is showing a higher demand for softness, smoothness, and delicate texture. Current high-end tissue paper manufacturing generally employs processes such as fiber pretreatment, pulp optimization, and forming control. Some foreign companies achieve high-performance products through refined fiber control and multi-process synergy. For example, Procter & Gamble and Kimberly-Clark utilize advanced fiber swelling, high-power pulping, and precision calendering technologies, combined with online detection systems, to produce products with a softness of less than 7.0 mN and a smoothness of over 50 seconds, achieving stable large-scale production. These processes typically include the addition of chemical additives, high-pressure pulping, and high-precision forming wire combined with calendering to improve fiber fibrillation and paper surface quality.

[0003] However, existing technologies still have significant shortcomings in practical applications: traditional softener treatments often only focus on surface lubrication, lacking synergistic modification of the fiber's internal structure, resulting in a decrease in strength while increasing softness; if the pulping process relies solely on power adjustment without precise control of parameters such as the gap between the pulping discs and the concentration, it is difficult to simultaneously achieve fiber refinement and length maintenance; furthermore, mismatches between drying and wrinkling processes can easily lead to uneven wrinkles, affecting the consistency of the tactile feel. More importantly, most production lines lack real-time feedback mechanisms, making it impossible to dynamically adjust key parameters, resulting in large fluctuations in product quality and making it difficult to consistently meet the comprehensive performance requirements of the high-end market for "softness, smoothness, and delicacy." Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a high-smoothness tissue paper and its preparation method, which can solve the technical problems of existing tissue paper in that it is difficult to achieve a balance between softness, smoothness and wrinkle uniformity, and that it has poor production stability.

[0005] A method for preparing highly smooth tissue paper according to a first aspect of the present invention includes the following steps: Fiber pretreatment steps: The pulp fibers are pretreated by contacting them with a cationic softener, wherein the amount of softener added is 0.8% to 1.2% by weight of oven-dry pulp; and the pulp fibers are subjected to physical swelling treatment under a pressure of 0.15 MPa to 0.20 MPa and a treatment time of 20 min to 30 min. Refining step: The pretreated pulp fibers are refined, with the refining power controlled within the range of 280 kW to 310 kW and the refining concentration within the range of 3.5% to 4.0%. Forming steps: The refined fiber pulp is formed, calendered, dried and creped on a paper machine to obtain high-smooth tissue paper. The forming wire mesh used in the forming step is 120 to 140 mesh, and the calendering roll pressure is 0.25 MPa to 0.30 MPa. According to some embodiments of the present invention, the grinding disc gap is 0.10 mm to 0.15 mm during the grinding step. According to some embodiments of the present invention, in the molding step, the drying temperature is 110°C to 120°C and the drying time is 15s to 20s. According to some embodiments of the present invention, the method further includes an online detection and feedback step: real-time detection of the softness and smoothness of the high-smoothness tissue paper, and feedback adjustment of the amount of softener added, pulping power and / or calendering roller pressure based on the detection results. According to a second aspect of the present invention, a highly smooth household paper is prepared by any of the above-described preparation methods. According to some embodiments of the present invention, the softness of the tissue paper is 6.0 mN to 8.0 mN, and the smoothness is 45 s to 55 s; and the raw material pulp of the tissue paper includes hardwood pulp and softwood pulp, with a weight ratio of hardwood pulp to softwood pulp of 8.5:1.5. According to some embodiments of the present invention, the wrinkle depth deviation of the tissue paper is less than or equal to 0.02 mm. According to an embodiment of the present invention, a high-smoothness tissue paper and its preparation method have at least the following beneficial effects: by introducing a cationic softener and the synergistic effect of low-temperature and low-pressure physical swelling during the fiber pretreatment stage, the surface friction coefficient of the fibers is significantly reduced and their plasticity is improved, thereby improving the softness of the paper; combined with high-power refining (280–310 kW) and a suitable concentration (3.5%–4.0%), the fibers are fully fluffed without being over-cut, enhancing the interweaving ability between fibers and improving smoothness while ensuring strength; furthermore, a fine forming wire (120–140 mesh) and a moderate calendering pressure (0.25–0.30 MPa) are used to achieve uniform fiber distribution and surface densification. This process as a whole solves the problems of difficulty in balancing softness and strength, surface roughness, and uneven wrinkles in traditional methods, ultimately obtaining soft, smooth, and delicate high-quality tissue paper, and can achieve stable and continuous production through a closed-loop feedback system.

[0006] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0007] 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.

[0008] Example 1: As consumers' demands for the quality of household paper products continue to rise, the market is setting higher standards for product softness, surface smoothness, and delicate touch. However, existing household paper technologies generally suffer from uneven fiber bonding, rough surfaces, and inconsistent wrinkle depth, resulting in stiff, poorly smooth paper that fails to meet the "soft, smooth, and skin-friendly" user experience requirements of high-end consumers. Especially in traditional production processes, relying solely on high-fiber refining can easily lead to excessive fiber cutting and reduced strength, or improving smoothness through calendering at the expense of softness, creating a technical bottleneck of "strong but not soft, soft but not strong." Furthermore, uneven fiber distribution and insufficient swelling during the forming process further exacerbate the deterioration of the paper's texture. Therefore, how to achieve a synergistic optimization of high softness and high smoothness in household paper while maintaining a certain level of physical strength has become an urgent technical challenge.

[0009] A method for preparing high-smoothness tissue paper includes the following steps: a fiber pretreatment step: pretreating pulp fibers by contacting them with a cationic softener, wherein the softener is added at an amount of 0.8% to 1.2% by weight of oven-dry pulp; and subjecting the pulp fibers to physical swelling treatment under a pressure of 0.15 MPa to 0.20 MPa and a treatment time of 20 min to 30 min; a refining step: refining the pretreated pulp fibers, controlling the refining power to be in the range of 280 kW to 310 kW and the refining concentration to the range of 3.5% to 4.0%; a forming step: forming, calendering, drying, and creping the refined fiber pulp on a paper machine to obtain high-smoothness tissue paper, wherein the forming wire mesh used in the forming step is 120 mesh to 140 mesh, and the calendering roll pressure is 0.25 MPa to 0.30 MPa.

[0010] Step 1: Pre-treat the pulp fibers, which includes contacting the pulp fibers with a cationic softener, wherein the amount of softener added is 0.8% to 1.2% by weight of oven-dry pulp; and subjecting the pulp fibers to physical swelling treatment under a pressure of 0.15 MPa to 0.20 MPa and a treatment time of 20 min to 30 min. Fiber pretreatment is a crucial preliminary step in improving subsequent processing performance and paper quality. This step first involves thoroughly mixing pulp fibers with a cationic softener. Utilizing the electrostatic adsorption between the positively charged groups in the softener molecules and the negatively charged groups on the cellulose surface, a lubricating film is formed on the fiber surface, effectively reducing the coefficient of friction between fibers and enhancing their flexibility and plasticity. Common types of cationic softeners can be selected, such as dialkyldimethyl ammonium chloride (DADMAC), polyquaternary ammonium salts, or ester-based quaternary ammonium salts. The addition amount is controlled between 0.8% and 1.2% of the oven-dry pulp weight to ensure sufficient coverage density for lubrication while avoiding excessive addition that could reduce fiber bonding or cause foaming. An online continuous dripping system can be used for addition, combined with a stirring device to achieve uniform dispersion. The mixing temperature should be controlled at 45–55°C to improve the penetration and adhesion efficiency of the softener on the fiber surface.

[0011] Furthermore, the pretreatment includes physical swelling of the fibers after the softener has been applied. This process is carried out in a closed container under a pressure of 0.15 MPa to 0.20 MPa for 20 to 30 minutes. This low-pressure condition is sufficient to induce water molecules to enter the amorphous regions of the fiber cell walls, initiating fiber swelling without damaging the basic fiber structure. During swelling, the fiber diameter increases, the wall-to-cavity ratio decreases, and the internal hydrogen bond network partially disintegrates, making the fibers softer and easier to spin. Simultaneously, due to the pre-introduction of the softener, its hydrophobic long-chain structure can embed itself within the fiber in the swelling gaps, further inhibiting excessive hydrogen bond rebuilding after drying and preserving more elastic deformation capacity. This physical swelling process can replace traditional high-temperature, high-pressure cooking methods, is energy-saving and environmentally friendly, and is suitable for the retrofitting of conventional production lines.

[0012] As an optional embodiment, the softener can also be replaced with amphoteric or nonionic surfactants, such as fatty acid polyoxyethylene ether, but the addition amount needs to be adjusted accordingly to 1.0%–1.5%, and the difference in adsorption rate can be compensated by extending the mixing time; the swelling pressure can be adjusted to 0.18±0.02 MPa, and the time is 25±3 min, to adapt to the water absorption characteristics of different raw material pulps (such as bamboo pulp and bagasse pulp).

[0013] Step 2: Refining the pretreated pulp fibers, controlling the refining power within the range of 280 kW to 310 kW and the refining concentration within the range of 3.5% to 4.0%; The refining step aims to promote longitudinal fiber splitting by applying mechanical shearing and compression to the fibers, forming numerous fine, whisker-like structures (i.e., brooming), thereby enhancing the interweaving ability and bonding area between fibers. This embodiment employs a high-power, low-consistency refining mode, setting the refiner's operating power within the range of 280–310 kW, significantly higher than the operating load of conventional refining equipment (typically 180–220 kW), thus providing stronger energy input and promoting deeper fiber brooming. Simultaneously, maintaining a low refining concentration of 3.5%–4.0% helps reduce fiber entanglement, improves beating efficiency per unit energy, and prevents localized overheating leading to fiber degradation.

[0014] The synergistic control of high power and moderate concentration allows the fibers to maintain good integrity even under strong mechanical action, with an average length maintained in the range of 1.2–1.5 mm and a fissile rate of 65%–70%, far exceeding the 40%–50% of traditional processes. This "elongated and fined" fiber morphology improves the density and smoothness of the paper without significantly weakening the tensile strength, thus resolving the contradiction between softness and strength.

[0015] As a variation, when using different types of pulping equipment (such as disc mills and cone mills), the target power range can be achieved by adjusting the rotation speed or feed rate. If the raw material contains a high proportion of short fibers (such as recycled fibers), the pulping power can be appropriately reduced to below 290 kW to avoid excessive cutting.

[0016] Step 3: The refined fiber pulp is formed, calendered, dried and creped on a paper machine to obtain high-smooth tissue paper. The forming wire mesh used in the forming step is 120 to 140 mesh, and the calendering roller pressure is 0.25 MPa to 0.30 MPa. The forming step is a crucial stage that determines the final paper's appearance quality and structural uniformity. After the fiber pulp is distributed in the headbox, it is dewatered on a high-speed forming wire to form a wet paper web. This embodiment uses a 120–140 mesh fine forming wire, which, compared to the conventional 80–100 mesh wire, has smaller mesh size and higher fabric smoothness. This effectively supports fine fibers, reduces settling differences, and makes the fiber distribution more uniform, thus laying the foundation for high smoothness. In addition, the fine wire can also improve the difference between the two sides of the paper and enhance the gloss of the front side.

[0017] After being vacuum-transferred to the press section, the wet paper web enters the calendering unit. The calendering rollers apply a pressure of 0.25–0.30 MPa, which is considered medium to high. This pressure further compacts the paper layer, closes micropores, and eliminates surface unevenness without over-compressing the fibers, significantly improving surface smoothness and gloss. The paper web then enters the drying section, where it is rapidly dried at 110–120°C for 15–20 seconds. Finally, it is creased and peeled by a doctor blade, forming a wrinkled structure with a certain degree of fluffiness and flexibility. The creasing angle and frequency are carefully controlled to ensure fine wrinkles with a depth deviation of ≤0.02mm, avoiding large creases that would affect the feel.

[0018] As an alternative implementation, the forming mesh can be a double-layer composite mesh or a slanted mesh forming machine to further optimize fiber orientation; calendering can be done with a soft calender or a shoe press instead of a traditional hard roller calender, achieving better surface finishing without damaging the fiber structure under the same pressure.

[0019] Through the above-described steps, this application achieves synergistic optimization of the entire process from fiber modification and morphology control to forming and finishing. First, the dual pretreatment of cationic softener and low-temperature, low-pressure physical swelling significantly improves fiber flexibility and plasticity, reducing subsequent processing resistance. Second, high-power refining and precise concentration control enable efficient fiber buffing while maintaining length advantages, enhancing the density and bonding strength of the fiber network. Finally, the combination of a fine forming wire and moderate calendering pressure ensures the uniformity of the paper structure and surface smoothness. These interconnected technical features work together to achieve a harmonious balance between fiber microstructure and macroscopic properties, ultimately producing a tissue paper product that combines high softness (6.0–8.0 mN), high smoothness (45–55 s), and delicate wrinkle characteristics. This effectively overcomes the technical barrier of balancing softness and smoothness in existing technologies, meeting the demands of the high-end market.

[0020] Example 2: Based on the above embodiments, this embodiment further provides: During the grinding process, the gap between the grinding discs is 0.10 mm to 0.15 mm.

[0021] The grinding disc gap, referring to the minimum distance between the stationary and moving grinding discs in a high-power disc mill, is a key structural parameter affecting the stress state of the fibers. The size of this gap directly determines the shear strength, friction duration, and degree of fiber compression experienced by the fibers during the refining process. When the grinding disc gap is within the range of 0.10 mm to 0.15 mm, effective fiber processing can be achieved under relatively high refining power (280–310 kW), avoiding both excessive cutting and fiber damage caused by an excessively small gap, and insufficient fibrillation and fiber separation caused by an excessively large gap. Specifically, when the gap is less than 0.10 mm, the fibers are subjected to strong compression and high-frequency shearing as they pass through the grinding zone, easily leading to longitudinal breakage and a decrease in average length to below 1.2 mm, resulting in a significant reduction in paper strength. Conversely, when the gap is greater than 0.15 mm, the fiber stress weakens, cell wall delamination is insufficient, and the fibrillation rate is difficult to reach above 65%, affecting the softness and smoothness of the subsequent paper.

[0022] To achieve precise control of the grinding disc gap, an automatic adjustment system can be employed, using hydraulic or electric actuators to monitor and adjust the relative position between the two grinding discs in real time. For example, in one optional embodiment, a closed-loop control system with a displacement sensor is used. After setting the target gap value, a PLC controller drives a servo motor for fine-tuning, achieving an adjustment accuracy of ±0.01 mm, ensuring stability during operation. Furthermore, the grinding disc surface can be designed with a serrated or spiral groove structure, and the material can be wear-resistant alloy steel or ceramic-coated material to extend service life and maintain gap consistency. In another variation, a multi-stage tandem grinding process can be used. A larger gap (e.g., 0.14–0.15 mm) is set in the first stage for initial loosening, and a smaller gap (e.g., 0.10–0.12 mm) is set in the second stage for fine buffing, thus balancing processing efficiency and fiber quality.

[0023] The aforementioned grinding disc gap parameters, along with the refining power and concentration, work synergistically to form the core control system of the high-power refining process. At a refining concentration of 3.5%–4.0%, the pulp possesses appropriate fluidity and fiber density. Combined with an input power of 280–310 kW and a grinding disc gap of 0.10–0.15 mm, the fibers undergo a sufficient number of effective collisions and frictions per unit time, achieving the ideal morphological evolution of "elongation and fine refining + full flocculentization." Under these conditions, the average fiber length stabilizes in the range of 1.2–1.5 mm, and the flocculentization rate reaches 65%–70%, which is conducive to forming a dense and uniform fiber network structure, improving the surface smoothness of the paper to 45–55 s (measured according to GB / T 456-2002), while maintaining good softness (6.0–8.0 mN, measured according to GB / T 8942-2016).

[0024] Through the above-described solution, this application achieves a significant improvement in the flexibility and printability of the fiber without sacrificing its basic strength. The setting of this grinding disc gap range effectively solves the problems of uneven fiber processing and large quality fluctuations caused by improper parameter matching in traditional pulping processes. It is particularly suitable for the demand for refined control of fiber morphology in high-grade tissue paper, providing a reliable guarantee for the stable production of high-smoothness paper.

[0025] Example 3: Based on the above embodiments, this embodiment further provides: During the molding process, the drying temperature is 110℃ to 120℃, and the drying time is 15 s to 20 s.

[0026] The drying temperature refers to the combined temperature environment of the paper web as it passes through the drying cylinder in the drying section, encompassing both hot air and contact heat transfer. This temperature range is set between 110°C and 120°C to achieve gradient evaporation of moisture while preventing fiber embrittlement or localized scorching due to high temperatures. Within this temperature range, moisture inside the paper can migrate to the surface at a moderate rate, reducing uneven fiber shrinkage and internal stress buildup caused by rapid dehydration. Temperatures that are too low (e.g., below 110°C) will lead to decreased drying efficiency, insufficient moisture removal, and negatively impact subsequent calendering and smoothness formation. Conversely, temperatures that are too high (e.g., above 120°C) may damage the cellulose structure, reduce fiber flexibility, and potentially cause thermal degradation of cationic softeners, weakening their lubricating function and ultimately affecting the soft feel of the finished product.

[0027] Drying time refers to the effective residence time of the paper web in the drying zone, controlled within the range of 15 to 20 seconds. This time period ensures sufficient diffusion and vaporization of moisture from the inside of the wet paper web, while preventing over-drying that would increase paper brittleness. Shorter times (less than 15 seconds) are insufficient for uniform dehydration, easily leading to a "dry surface, wet interior" phenomenon, resulting in uneven wrinkling and increased wrinkle depth deviations. On the other hand, longer times (more than 20 seconds) not only increase energy consumption but may also cause excessive fiber shrinkage and surface tension imbalance, leading to problems such as warping or surface roughness.

[0028] The aforementioned drying temperature and drying time constitute a synergistic parameter system: appropriate heat input combined with a reasonable residence period ensures uniform and stable moisture gradient evaporation across the entire width of the paper. This control strategy helps maintain the bonding stability between fibers, improves the density and surface smoothness of the paper structure, and provides a good foundation for subsequent calendering processes. Furthermore, this temperature and time combination effectively protects the activity of cationic softeners applied to the fiber surface, preventing their decomposition or migration failure at high temperatures, ensuring the final product possesses lasting softness.

[0029] Through the above-described steps, this application achieves precise control of key parameters in the drying process. By employing a drying temperature of 110℃ to 120℃ and a drying time of 15 s to 20 s, it solves the technical problems in existing technologies caused by mismatched drying conditions, such as uneven moisture removal, changes in surface tension, and irregular wrinkles. This results in stable paper moisture content, high surface smoothness, fine wrinkles, and good softness. This drying regime is particularly suitable for the production needs of high-smoothness tissue paper and can be widely adapted to high-speed paper machine systems with speeds exceeding 1500 m / min, significantly improving product quality consistency and process controllability without adding new equipment.

[0030] Example 4: Based on the above embodiments, this embodiment further provides: The method also includes an online detection and feedback step: real-time detection of the softness and smoothness of high-smoothness tissue paper, and feedback adjustment of the amount of softener added, pulping power and / or calendering roller pressure based on the detection results.

[0031] The online detection and feedback process establishes a closed-loop control system for dynamic monitoring and adaptive parameter adjustment of the production process. The system uses non-contact sensors at the paper machine exit to collect real-time data on the physical properties of the paper. Specifically, softness testing employs an electronic softness meter conforming to GB / T 8942-2016. Its measuring probe lightly touches the paper surface with constant pressure, recording the force required to produce a specified deformation per unit area, with the output in mN. Smoothness testing, based on GB / T 456-2002, uses a Buick smoothness meter or equivalent optical scanning equipment to measure the time it takes for air to pass through the gap between the paper and a standard plane, measured in seconds (s). Both types of instruments are capable of continuous online operation, with a sampling frequency of at least once every 30 seconds. Data is transmitted to the central control unit for real-time analysis.

[0032] After the detected data enters the control algorithm module, it is compared with the preset target range (e.g., softness 6.0–8.0 mN, smoothness 45–55 s). When the detected value deviates from the target range, the system automatically triggers the adjustment mechanism. For example, if the smoothness is below the lower limit, it indicates that the fiber interweaving structure is not dense enough or the surface is rough. At this time, a dual-path response can be activated: on the one hand, the pulping power is increased to close to the upper limit of 310kW to enhance the degree of fiber buffing and the level of fine fiberization, thereby improving the paper uniformity and surface smoothness; on the other hand, the pressure of the calendering roller is moderately increased to 0.30 MPa to strengthen the compression effect of the pressing zone and reduce the micro-unevenness of the paper. Conversely, if the softness exceeds the upper limit (i.e., the value is too small, indicating that it is too soft), it may affect the paper stiffness and user experience. In this case, the amount of softener added is appropriately reduced to 0.8% to avoid excessive lubrication leading to a decrease in fiber bonding force. If the softness is too low (the value is too large), the amount of softener added is increased to 1.2% to compensate for the stiffness caused by the increase in the coefficient of friction of the fiber surface. In addition, when fluctuations in raw materials or changes in vehicle speed cause system disturbances, the control logic supports multi-parameter linkage adjustment, such as synchronous fine-tuning of slurry concentration and calendering pressure, to maintain overall process stability.

[0033] The actuators of the aforementioned control system include a programmable logic controller (PLC), a frequency converter, an electric regulating valve, and a servo hydraulic system. The amount of softener added is controlled by a high-precision metering pump, with an adjustment accuracy of ±0.05% and a response time of less than 10 seconds. The adjustment of the refining power relies on the frequency converter control system of the refining machine's main motor, which can quickly respond to commands within a range of ±5 kW. The pressure of the calendering roller is controlled by a hydraulic servo system, with an adjustment accuracy of ±0.02 MPa, ensuring uniform pressure distribution and rapid response. The entire feedback loop consists of four stages: "perception—analysis—decision—execution," forming a complete automated closed-loop circuit.

[0034] Through the above-described steps, this application achieves real-time monitoring and dynamic optimization of key quality characteristics and process parameters in the production of high-smoothness tissue paper. By introducing an online detection and feedback mechanism, it overcomes the problems of lag and untimely adjustment inherent in traditional manual sampling and testing. It effectively addresses interference caused by batch variations in raw materials, fluctuations in environmental temperature and humidity, and changes in equipment status, thus significantly improving product quality consistency and production process stability. This ensures a product qualification rate consistently above 99%, meeting the stringent quality continuity requirements of the high-end market. This technical solution embodies a shift from experience-driven to data-driven manufacturing, providing a feasible path for the intelligent and refined production of high-grade tissue paper.

[0035] Example 5: With the deepening trend of consumption upgrading, the market has placed higher demands on tissue paper products, especially in terms of softness, smoothness, and delicate touch. However, most existing tissue paper products still suffer from problems such as rough surface, uneven fiber bonding, and stiff feel, failing to meet the high-end consumer demand for a "silky smooth and weightless" user experience. While some imported high-end products possess superior performance, their core technologies are protected by patent barriers, making it difficult for domestic companies to directly replicate them. Furthermore, traditional production processes lack precise control over fiber structure, resulting in disordered fiber arrangement and significant surface undulations at the microscopic level, affecting overall smoothness and softness. Therefore, the market urgently needs a technological approach that can stably produce high-quality tissue paper with both high smoothness and good softness.

[0036] This application makes the following: A highly smooth household paper, prepared by any one of claims 1 to 4.

[0037] Based on the above embodiments, this embodiment further provides: This high-smoothness tissue paper is a product obtained through a synergistically optimized manufacturing process, the core of which lies in the overall innovation of the manufacturing process rather than the adjustment of a single parameter. Specifically, the formation of this tissue paper relies on the integration of multi-stage technologies throughout the entire process, from fiber pretreatment to final forming. This includes sufficient contact between fibers and cationic softeners, physical swelling treatment under specific pressure and time conditions, high-power refining to optimize fiber morphology, and the completion of paper sheet forming, calendering, and creping under precise control. The entire process chain achieves microscopic reconstruction of the paper structure through systematic regulation of fiber plasticity, dispersibility, fissuring degree, and forming uniformity, thereby endowing the final product with excellent comprehensive performance.

[0038] The preparation of high-smoothness tissue paper begins with the pretreatment of pulp fibers. In this process, a cationic softener is used to modify the fiber surface. This softener adheres firmly to the fiber surface through electrostatic adsorption, reducing the coefficient of friction between fibers and improving their slippage ability. The amount of softener added is controlled between 0.8% and 1.2% of the oven-dry pulp weight, ensuring sufficient coverage density for lubrication while avoiding excessive addition that could reduce fiber bonding or cause roller sticking. Simultaneously, the fibers undergo a low-temperature, low-pressure physical swelling process, maintained at 0.15 MPa to 0.20 MPa for 20 to 30 minutes. This allows water to fully penetrate the fiber cell walls, inducing lateral fiber expansion and significantly improving its flexibility and deformability, creating favorable conditions for efficient flocculing in subsequent pulping processes.

[0039] The process then proceeds to the refining stage. Through precise control of the refining machine's operating parameters, particularly stabilizing the refining power within the range of 280 kW to 310 kW and maintaining the refining concentration between 3.5% and 4.0%, the fibers undergo moderate refinement and fibrillation under high-intensity shear force. The average length is controlled within the range of 1.2 mm to 1.5 mm, and the fibrillation rate reaches over 65%. This stage not only extends the effective surface area of ​​the fibers and enhances their interweaving ability but also retains sufficient strength support, preventing paper strength degradation due to excessive cutting.

[0040] In the paper forming stage, the optimized fiber pulp is fed onto a high-speed paper machine with a width of 3.4 m and a speed of 1500 m / min for forming. A forming wire with a mesh size of 120 to 140 mesh is used to improve the uniformity of fiber distribution and reduce flocculation. Calendering rollers apply pressure of 0.25 MPa to 0.30 MPa to make the wet paper web surface denser and smoother. The drying temperature is set between 110°C and 120°C, with a drying time of 15 to 20 seconds to ensure gradient evaporation of moisture without causing severe shrinkage or deformation. Finally, a creping doctor blade performs controlled peeling on the surface of the drying cylinder, forming a fine and evenly distributed wrinkle structure, further improving the softness of the paper.

[0041] It is worth noting that the quality advantage of this tissue paper does not stem from the improvement of a single process, but rather from the synergistic effect of multiple processes: fiber pretreatment enhances the processing adaptability of the fibers themselves, high-power pulping achieves an ideal fiber morphology, and the refined control of the forming system ensures the stability and consistency of the paper structure. Each step forms a progressively reinforcing relationship, with the concept of "fiber weaving optimization" permeating the entire process from raw material preparation to final product output, ultimately reflected in the macroscopic properties of the finished paper.

[0042] Through the above technical solution, this application achieves a highly smooth tissue paper with consistent internal structure and batch stability. By employing a collaborative process encompassing softener treatment, physical swelling, high-power refining, and precision molding, the technical challenge of balancing softness and smoothness in traditional products is solved. The resulting tissue paper exhibits tightly bonded fibers, a smooth surface, and a soft touch, with minimal performance fluctuations between different batches, making it suitable for large-scale continuous production. This product is particularly suitable for personal care scenarios where sensory experience is crucial, such as facial cleansing and baby wiping, effectively improving user satisfaction and providing strong support for enterprises to build differentiated competitive barriers.

[0043] Example 6: Based on the above embodiments, this embodiment further provides: The softness of the tissue paper is 6.0 mN to 8.0 mN, and the smoothness is 45 s to 55 s; and the raw material pulp of the tissue paper includes hardwood pulp and softwood pulp, with a weight ratio of hardwood pulp to softwood pulp of 8.5:1.5.

[0044] This embodiment achieves a synergistic balance of high smoothness, high softness, and good strength by controlling key performance indicators and raw material ratios in the paper production process. Specifically, the softness of the tissue paper is limited to the range of 6.0 mN to 8.0 mN. This value is measured according to the national standard GB / T8942-2016 "Determination of Paper Softness," reflecting the smoothness of the product when in contact with human skin during use. A lower softness value means better tactile comfort. Controlling the index within the 6.0–8.0 mN range avoids the problems of loose fiber structure and reduced strength caused by excessive softness, and also overcomes the roughness caused by the generally higher softness of traditional products (above 10.0 mN), meeting the consumer demand for "delicate and skin-friendly" tissue paper in high-end tissue paper.

[0045] The smoothness is measured in the range of 45 to 55 seconds. This indicator, determined according to GB / T 456-2002 "Determination of Smoothness of Paper and Paperboard (Beck Method)," represents the time required for air to pass through the paper surface; a longer time indicates a denser and smoother surface. Controlling the smoothness within this range effectively reduces the impact of micro-undulations on the paper surface on tactile sensation, enhancing the smoothness experience. Compared to the industry standard of 25–30 seconds, this embodiment significantly improves surface quality, giving the product surface characteristics approaching those of high-end cosmetic paper or specialty printing paper.

[0046] Furthermore, the raw material pulp for tissue paper consists of hardwood pulp and softwood pulp, mixed in a weight ratio of 8.5:1.5. Hardwood pulp comes from short-fiber woods such as eucalyptus and poplar, with fiber lengths typically between 0.8 and 1.2 mm. It has thin cell walls, good flexibility, and is easy to benign, forming a dense and fine network structure in the paper, which helps improve the smoothness and softness of the paper. Softwood pulp comes from long-fiber tree species such as pine and spruce, with fiber lengths reaching 3.0–4.5 mm. It has high tensile strength and stiffness, effectively enhancing the mechanical properties of the paper sheet in both wet and dry states, preventing problems such as tearing and shedding during use.

[0047] This specific ratio of 8.5:1.5 has been verified through systematic experiments to be the optimal balance between the sensory quality and physical strength of the paper. If the proportion of softwood pulp is too high (e.g., exceeding 2.0), although the strength is improved, the interwoven fibers are coarse and stiff, resulting in decreased softness and a rough feel. If the proportion of hardwood pulp is too high (e.g., exceeding 9.0), the paper is fluffy and soft, but the structure is loose and the tensile strength is insufficient, affecting its practicality. By adopting the 8.5:1.5 ratio, compared with the industry-common 7:3 ratio, the tensile strength of the paper is increased by about 10%, while maintaining a softness of less than 8.0 mN, achieving a technological breakthrough of "strong but not stiff, soft but not weak".

[0048] Furthermore, this raw material combination is well-suited to the fiber pretreatment, high-power refining, and calendering stages in the aforementioned preparation process: cationic softeners preferentially adsorb onto the surface of broadleaf pulp fibers, reducing their surface friction coefficient; high-power refining promotes full fluffing of short fibers, enhancing hydrogen bonding capacity; and the presence of an appropriate amount of long fibers ensures sufficient fiber skeleton support under high-intensity swelling and refining conditions, preventing deterioration of paper uniformity. During the drying and calendering stages, the fiber layers are tightly bonded, further amplifying the surface smoothing effect brought about by the optimized formulation.

[0049] Through the above technical solution, this application achieves a significant improvement in the softness and smoothness of tissue paper without sacrificing physical strength. By employing a specific ratio of hardwood pulp and softwood pulp composite formulation and controlling the softness and smoothness of the final product within the target range, it solves the contradictory problem in existing technologies where unreasonable raw material ratios result in either "softness leading to weakness" or "strength leading to roughness." This achieves the comprehensive performance required for high-grade tissue paper, including a delicate touch, smoothness, wear resistance, and durability, thus meeting the market demand for high-quality paper products in the context of consumption upgrading.

[0050] Example 7: Based on the above embodiments, this embodiment further provides: The wrinkle depth deviation of household paper is less than or equal to 0.02 mm.

[0051] This technical solution involves strict control over the uniformity of the microstructure on the surface of high-smoothness tissue paper, aiming to solve the problem of uneven wrinkle distribution in existing high-grade tissue paper, which leads to a rough feel and reduced visual texture during use. Especially in high-end consumer scenarios, users have extremely high requirements for the fineness and consistency of paper. If there are significant fluctuations in wrinkle depth, it will produce an unpleasant experience of "localized hard spots" or "unevenness" in terms of feel, affecting the overall perception of product quality.

[0052] The wrinkle depth deviation refers to the maximum difference between wrinkle depth values ​​measured in different areas of the same sheet of paper. The smaller the value, the more stable the creping process and the more uniform the stress on the fiber network. Limiting this deviation to ≤0.02mm means that the wrinkle depth variation between any two points within the entire paper width does not exceed 20 micrometers, which falls within the range of nanometer-level precision control. This indicator is not achieved through adjustment of a single device, but relies on the coordinated stability of the entire forming and creping system. For example, in the final stage of drying, when the paper sheet is peeled from the drying cylinder and forms fine wrinkles through the action of the creping doctor blade, uneven pressure distribution, inconsistent blade wear, or fluctuations in paper tension can all lead to differences in the degree of local wrinkling. In addition, fluctuations in calender roller pressure and excessively large drying temperature gradients can also cause inconsistent paper shrinkage behavior, thus affecting the consistency of the final wrinkle morphology.

[0053] To achieve this technical effect, a high degree of matching between multiple process steps is required: First, the distribution of fiber pulp on the forming wire must be uniform to avoid stress concentration caused by basis weight fluctuations during subsequent drying; second, the drying curve should transition smoothly to prevent localized excessively rapid dehydration from causing fiber shrinkage imbalance; third, the pressure in the calendering process must be constant and transversely uniform to ensure consistent pressure on the paper surface; finally, the installation angle, contact pressure, and straightness of the creping doctor blade must be precisely controlled and regularly inspected and maintained to prevent systematic deviations caused by mechanical deformation or wear.

[0054] Optionally, under different implementation conditions, the uniformity of wrinkles can be further improved by adjusting the frequency of the wrinkling scraper to the range of 180–200 times / m, combined with optimizing the drying time (15–20 s) and drying temperature (110–120°C). Alternatively, a high-precision servo control system can be used to dynamically adjust the scraper loading mechanism, compensating in real time for pressure drift caused by thermal expansion or load changes, thereby maintaining the repeatability and consistency of the wrinkling action.

[0055] Through the aforementioned technical solution, this application achieves a significant improvement in the spatial consistency of wrinkles on the surface of tissue paper without altering the basic raw material composition or main process flow. This is achieved through precise control of key molding parameters and continuous monitoring of equipment status. Because the wrinkle depth deviation is effectively controlled to an extremely low level, the paper appears smoother and flatter on a macroscopic level, and conveys a soft and uniform feel on a microscopic level, without any obvious local protrusions or collapses. This meets the stringent requirements of the high-end market for "refined" products.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing highly smooth household paper, characterized in that, Includes the following steps: Fiber pretreatment step: Pretreatment of pulp fibers, the pretreatment including contacting the pulp fibers with a cationic softener, wherein the amount of softener added is 0.8% to 1.2% by weight of oven-dry pulp; and physical swelling treatment of the pulp fibers under a pressure of 0.15 MPa to 0.20 MPa and a treatment time of 20 min to 30 min; Refining step: The pretreated pulp fibers are refined, with the refining power controlled within the range of 280 kW to 310 kW and the refining concentration within the range of 3.5% to 4.0%. Forming step: The fiber pulp that has been refined is formed, calendered, dried and creped on a paper machine to obtain high smoothness tissue paper. The forming wire mesh used in the forming step is 120 to 140 mesh, and the calendering roll pressure is 0.25 MPa to 0.30 MPa.

2. The method for preparing a high-smoothness household paper according to claim 1, characterized in that, In the grinding step, the gap between the grinding discs is 0.10 mm to 0.15 mm.

3. The method for preparing a high-smoothness household paper according to claim 1, characterized in that, In the molding step, the drying temperature is 110℃ to 120℃, and the drying time is 15 s to 20 s.

4. The method for preparing a high-smoothness household paper according to claim 1, characterized in that, The method further includes an online detection and feedback step: real-time detection of the softness and smoothness of the high-smoothness tissue paper, and feedback adjustment of the amount of softener added, the pulping power and / or the pressure of the calendering roller based on the detection results.

5. A type of highly smooth household paper, characterized in that, It is prepared by any one of claims 1 to 4.

6. The high-smoothness household paper according to claim 5, characterized in that, The softness of the tissue paper is 6.0 mN to 8.0 mN, and the smoothness is 45 s to 55 s; and the raw material pulp of the tissue paper includes hardwood pulp and softwood pulp, with the weight ratio of hardwood pulp to softwood pulp being 8.5:1.

5.

7. The high-smoothness household paper according to claim 6, characterized in that, The wrinkle depth deviation of the tissue paper is less than or equal to 0.02 mm.