Production process of high-thickness and low-gram-weight paper product and household paper of high-thickness and low-gram-weight paper product

Abstract

The invention discloses a production process of a high-thickness and low-gram-weight paper product and paper for daily use, and relates to the technical field of papermaking. The process comprises the following steps: mixing hardwood pulp and softwood pulp according to the proportions of 70%-80% and 20%-30%, and performing swelling treatment, wherein the concentration is controlled to be 2.0%-3.0%, the temperature is controlled to be 40-55 DEG C, the time is 30-60 minutes, and the pH value is controlled to be 7.0-8.0; grinding to enable the brooming rate to reach 45%-60% and the beating degree to be 32-40 degrees SR; dehydrating and forming through a 60-80-mesh forming net at the speed of 0.8-1.2 m / s; a 15-25 kN / m linear pressure carrier roller is adopted for squeezing, and the medium-high value is controlled to range from 0.3 mm to 0.8 mm; the wrinkling ratio is controlled to be 75%-80%, and frequency conversion control, water circulation or steam heat preservation and energy conservation measures are matched. The gram weight of the prepared household paper is 9-15.5 g / m, the thickness is increased by more than or equal to 20%, the household paper has the characteristics of light weight, fluffiness and softness, the production energy consumption is reduced by more than 10%, and the household paper is suitable for green and efficient manufacturing of high-end household paper.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, and in particular to a production process for high-thickness, low-grammage paper products and household paper. Background Technology

[0002] As consumers increasingly demand higher quality tissue paper products, thicker, lighter, softer, more comfortable, and energy-efficient products are gradually becoming the mainstream market demand. Currently, some domestic and international companies have achieved a certain degree of thickness improvement by optimizing pulping and forming processes. Typical technologies include using high-fiberization-rate pulping, adjusting creping rates, and improving fiber ratios to maintain a certain level of bulk while reducing basis weight. For example, international brands Kimberly-Clark and Vinda International have increased product thickness by approximately 15% at the same basis weight by using imported equipment and specific process parameters. A few domestic companies have also attempted to develop similar products, generally employing conventional three-zone pressing and standard creping processes, combined with a raw material system primarily composed of hardwood pulp. However, existing technologies still have significant shortcomings in achieving a balance between low basis weight and high thickness: On the one hand, the high pressing pressure and insufficient crease control precision in traditional processes result in excessively tight paper sheets, making it difficult to achieve the goal of increasing single-layer thickness by more than 20% compared to similar products; on the other hand, the lack of systematic control over fiber swelling and weaving processes results in products that are thin but stiff, lacking the "light luxury softness" tactile experience. Furthermore, energy consumption during production is high, and the integration of energy-saving measures such as frequency conversion control and water recycling is low, failing to form a comprehensive, highly efficient, and energy-saving production system, thus hindering the large-scale promotion of high-quality products. Summary of the Invention

[0003] This application provides a production process for high-thickness, low-grammage paper products and a type of tissue paper, which can solve the technical problems of traditional tissue paper that are difficult to effectively improve thickness, lack of softness, and high production energy consumption while reducing grammage.

[0004] A production process for high-thickness, low-basis-weight paper products according to a first aspect of the present invention includes the following steps: Fiber raw material pretreatment steps: Mix hardwood pulp and softwood pulp at a mass percentage of 70%-80% and 20%-30%, respectively, and perform swelling treatment on the mixed pulp, controlling the swelling concentration at 2.0%-3.0%, the temperature at 40-55℃, the time at 30-60min, and the pH value at 7.0-8.0; Pulping process: The swollen pulp is pulped, and the freeness is controlled at 32-40°SR, the fissile rate is 45%-60%, and the wet weight is 8-12g. Fiber weaving and forming steps: The refined pulp is dewatered and formed through a forming wire, with the wire mesh number controlled at 60-80 mesh, the dewatering speed at 0.8-1.2 m / s, and the forming pressure at 0.1-0.2 MPa; Pressing and dewatering step: The wet paper sheet after forming is pressed and dewatered by the idler roller device, and the linear pressure of the idler roller is controlled at 15-25kN / m, the medium and high value is 0.3-0.8mm, and the roller surface temperature is 80-95℃; Crinkling process: Crinkle the dehydrated paper sheet, controlling the wrinkling rate to 75%-80%, the creping knife angle to be 25°-35°, and the creping pressure to be 0.05-0.1MPa; Energy-saving control steps: Use at least one of the following: variable frequency motor control, water recycling, and steam pipeline insulation.

[0005] According to some embodiments of the present invention, in the fiber raw material pretreatment step, the mass percentages of hardwood pulp and softwood pulp are 75% and 25%, respectively. According to some embodiments of the present invention, in the pulping process, the beating degree is 35-38°SR and the buffing rate is 50%-55%. According to some embodiments of the present invention, in the fiber weaving and forming step, the forming mesh number is 65-75 mesh, and the dehydration speed is 0.9-1.1 m / s. According to some embodiments of the present invention, in the pressing and dewatering step, the linear pressure of the idler roller is 18-22 kN / m, with a medium-high value of 0.4-0.6 mm. According to some embodiments of the present invention, in the wrinkling process, the wrinkling rate is 76%-78% and the wrinkling blade angle is 28°-32°. According to a second aspect of the present invention, a high-thickness, low-grammage paper for household use is produced by any of the above-described processes. The paper has a grammage of 9-15.5 g / m², a single-layer thickness that is ≥20% higher than that of conventional products with the same grammage, an absorbency of ≥5 g / g, and a tensile strength of ≥1.2 kN / m. According to some embodiments of the present invention, the basis weight of the tissue paper is 10-14 g / m², the single-layer thickness is increased by ≥22%, the water absorption is 5.5 g / g, and the tensile strength is 1.3 kN / m.

[0006] According to embodiments of the present invention, at least the following beneficial effects are achieved: This application provides a production process for high-thickness, low-grammage paper products and tissue paper. By rationally proportioning hardwood pulp and softwood pulp, and combining precisely controlled swelling, high-fiberration refining, low-linear-pressure idler pressing, and moderate creping processes, the paper thickness and bulk can be significantly increased while maintaining good tensile strength and soft hand feel, all while significantly reducing grammage. Integrated energy-saving measures such as frequency conversion control, water circulation, and heat preservation effectively reduce production energy consumption. This process breaks through the technical bottleneck of traditional low-grammage paper products being "heavy when thick and thin when light," achieving a unity of lightweight, high-quality, and green manufacturing.

[0007] 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

[0008] 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.

[0009] Example 1: Traditional tissue paper, while pursuing low basis weight to reduce costs and resource consumption, often suffers from insufficient thickness, poor fluffiness, and low softness, resulting in a poor user experience. Especially in the domestic market, most products remain at the low-to-mid-range level, with basis weights generally exceeding 16 g / m², and limited thickness increases under the same basis weight conditions, failing to meet consumers' high-quality demands for "lightweight yet thick, with a smooth touch." Furthermore, existing production processes generally suffer from high energy consumption, significant water waste, and low thermal energy utilization, which is inconsistent with the current trend of green manufacturing. To address these issues, there is an urgent need to develop a new production process that can effectively improve paper thickness and feel comfort while significantly reducing the weight per unit area, and also achieve energy conservation and emission reduction.

[0010] Based on this, this application provides a production process for high-thickness, low-basis-weight paper products, including the following steps: Fiber raw material pretreatment steps: Mix hardwood pulp and softwood pulp at a mass percentage of 70%-80% and 20%-30%, respectively, and perform swelling treatment on the mixed pulp, controlling the swelling concentration at 2.0%-3.0%, the temperature at 40-55℃, the time at 30-60min, and the pH value at 7.0-8.0; Pulping process: The swollen pulp is pulped, and the freeness is controlled at 32-40°SR, the fissile rate is 45%-60%, and the wet weight is 8-12g. Fiber weaving and forming steps: The refined pulp is dewatered and formed through a forming wire, with the wire mesh number controlled at 60-80 mesh, the dewatering speed at 0.8-1.2 m / s, and the forming pressure at 0.1-0.2 MPa; Pressing and dewatering step: The wet paper sheet after forming is pressed and dewatered by the idler roller device, and the linear pressure of the idler roller is controlled at 15-25kN / m, the medium and high value is 0.3-0.8mm, and the roller surface temperature is 80-95℃; Crinkling process: Crinkle the dehydrated paper sheet, controlling the wrinkling rate to 75%-80%, the creping knife angle to be 25°-35°, and the creping pressure to be 0.05-0.1MPa; Energy-saving control steps: Use at least one of the following: variable frequency motor control, water recycling, and steam pipeline insulation.

[0011] In the fiber raw material pretreatment step, the ratio of hardwood pulp to softwood pulp is designed to achieve synergistic optimization of fiber flexibility and strength. Hardwood pulp fibers are shorter and have thinner cell walls, resulting in good formability and softness, which is suitable for enhancing the delicate feel of paper; while softwood pulp fibers are longer and have higher strength, helping to enhance the tensile properties and structural stability of the paper sheet. By mixing the two at a ratio of 70%-80%:20%-30%, the bulky structural advantages of hardwood pulp can be fully utilized while ensuring the mechanical strength of the paper. Swelling treatment is the core step in this process, its function being to allow the fibers to fully absorb water and swell, breaking the hydrogen bond structure and improving fiber plasticity and subsequent flocculentization efficiency. The swelling concentration is controlled at 2.0%-3.0% to ensure moderate pulp fluidity and uniform dispersion, while avoiding uneven penetration due to excessive concentration or energy waste due to excessively low concentration. The temperature is set at 40-55℃, which can accelerate the fiber swelling kinetics process while preventing fiber degradation caused by high temperature. The treatment time is maintained at 30-60 minutes to ensure sufficient swelling without excessively prolonging the process cycle. The pH value is adjusted to a slightly alkaline environment of 7.0-8.0, which is conducive to the swelling of the primary fiber wall and promotes the exposure of the secondary wall, thereby improving the subsequent pulping effect and reducing the risk of corrosion to the metal parts of the equipment.

[0012] Step 1: Refine the swollen pulp, controlling the freeness to 32-40°SR, the fissile rate to 45%-60%, and the wet weight to 8-12g; "Freezing degree" (°SR) measures the pulp's water-filtering performance and indirectly reflects the combined degree of fiber cutting and fibrillation. Controlling the freezing degree within the 32-40°SR range means the fibers have undergone appropriate mechanical treatment, achieving sufficient fibrillation while maintaining a certain length. This avoids strength loss due to excessive cutting and prevents decreased bonding strength due to insufficient fibrillation. Fibrillation rate refers to the proportion of fiber surface splitting into fine, fibrous structures. Controlling this rate between 45% and 60% significantly increases the fiber's specific surface area and the number of free hydroxyl groups, thereby enhancing the hydrogen bonding ability between fibers, improving the paper's dry strength and structural density, while retaining sufficient porosity to maintain high bulk. Wet weight represents the mass of a single fiber or fiber bundle, usually measured in grams, with a range of 8-12g. This reflects the appropriate robustness and rigidity of the fibers used, which is beneficial for constructing a three-dimensional interwoven network, supporting the paper structure, and preventing collapse during pressing. This combination of parameters works together to regulate fiber morphology, providing a good foundation for subsequent molding and wrinkling.

[0013] Step 2: Dewater and form the refined pulp through a forming wire, controlling the wire mesh count to be 60-80 mesh, the dewatering speed to be 0.8-1.2 m / s, and the forming pressure to be 0.1-0.2 MPa; The forming wire, as a key component in the initial formation of the paper sheet, directly affects the uniformity of fiber distribution and dewatering efficiency. Using a 60-80 mesh forming wire ensures sufficient open area for rapid drainage while limiting the passage of large clumps and promoting the effective retention of fine particles, resulting in a loosely structured wet paper web with uniform pore distribution. The dewatering speed is controlled within the range of 0.8-1.2 m / s to ensure a reasonable residence time of the pulp on the wire surface, avoiding uneven fiber migration or directional alignment caused by excessively high flow rates, and preventing excessively slow flow rates that could affect production efficiency and lead to localized water accumulation. The forming pressure is set at 0.1-0.2 MPa, falling within the low-pressure forming range. This aims to achieve initial consolidation without disrupting the natural interweaving of the fibers, maximizing the preservation of air gaps between fibers, and laying the microstructural foundation for the high thickness characteristics of the final product. This step, through precise matching of mesh, flow rate, and pressure parameters, achieves controllable construction of the fiber network.

[0014] Step 3: Press and dewater the formed wet paper sheet using the idler roller device, controlling the idler roller linear pressure to be 15-25kN / m, with a medium-high value of 0.3-0.8mm, and the roller surface temperature to be 80-95℃; The idler roller device typically consists of two pressure rollers, upper and lower. Linear pressure refers to the applied pressure per unit contact width, set at 15-25 kN / m. This effectively squeezes out excess water, reducing the drying load, while preventing excessive pressure from causing over-compaction of fibers and pore closure, thus maintaining the paper's fluffy structure. The crown value refers to the amount of protrusion of the middle diameter of the pressure roller relative to the ends, set at 0.3-0.8 mm. This compensates for the elastic deformation of the pressure roller under load, ensuring uniform pressure distribution across the entire width and preventing over-pressure at the edges or insufficient dehydration in the middle. The roller surface temperature is controlled at 80-95℃, preheating the wet paper through heat conduction, improving internal moisture flow, enhancing dehydration efficiency, and softening fibers, improving their plastic deformation ability, which is beneficial for subsequent creping operations. This step, through coordinated temperature-pressure-shape control, achieves the dual goals of efficient dehydration and structural protection.

[0015] Step 4: Crinkle the dehydrated paper sheets, controlling the wrinkle rate to 75%-80%, the creping knife angle to be 25°-35°, and the creping pressure to be 0.05-0.1MPa; The wrinkling rate is defined as (scraper speed - paper machine running speed) / scraper speed × 100%, controlled at a relatively high level of 75%-80%. This means that the paper sheet is forcibly compressed and folded during transfer, forming a large number of micro-wrinkles, significantly increasing the macroscopic thickness and soft feel. The crease blade angle refers to the angle between the blade edge and the tangent of the drying cylinder surface, set at 25°-35°. This ensures effective paper separation while reducing shear damage to the fibers, lowering the risk of paper breakage. The crease pressure is 0.05-0.1MPa, falling into the category of light-pressure crease, ensuring stable contact between the scraper blade and the drying cylinder surface, with smooth and continuous operation, avoiding paper breakage caused by jumping or impact. This step, through precise control of mechanical parameters, transforms physical deformation into functional enhancement, giving the product excellent volume and a skin-friendly experience.

[0016] Step 5: Use at least one of the following: variable frequency motor control, water recycling, and steam pipeline insulation. Among these measures, variable frequency motor control is applied to key drive units (such as pulp pumps, mesh drives, and press rollers), dynamically adjusting speed and output power according to actual load to prevent motors from running at full load or idle for extended periods, thus saving energy. A water recycling system collects white water discharged from various processes, which is then treated through screening, sedimentation, and sterilization before being reused in pulping or washing stages, significantly reducing fresh water consumption and wastewater discharge. Steam pipeline insulation utilizes high-performance insulation materials (such as aluminum silicate fiber and aerogel felt) to wrap steam delivery pipelines, reducing heat loss and improving thermal efficiency, especially effective in low-temperature winter environments. These measures can be applied individually or in combination depending on actual production line conditions, forming a flexible and configurable energy-saving solution.

[0017] Through the above-described steps, this application achieves synergistic optimization of the entire process, from raw material proportioning, fiber modification, network construction to dehydration and pressing, wrinkling and shaping, and energy management. By using a specific ratio of hardwood pulp to softwood pulp mixed with a gentle swelling treatment, the plasticity and binding potential of the fibers are enhanced. By controlling the beating degree, fibrillation rate, and wet weight, a fiber system combining strength and bulkiness is constructed. With the aid of suitable forming network parameters and a low-pressure forming process, a uniform and loose initial fiber network is formed. Then, through medium- and high-pressure rollers combined with temperature-controlled pressing, moisture is removed while structural voids are preserved. Subsequently, a large number of micro-folds are introduced through a high wrinkling rate and optimized cutter parameters, further amplifying the thickness effect. Finally, multiple energy-saving technologies are integrated, significantly reducing the overall energy consumption level. Therefore, this process successfully solves the technical challenge of balancing high thickness, high softness, and good physical properties under low basis weight conditions, while also responding to the national energy conservation and emission reduction policy, possessing significant technological advancement and industrialization value.

[0018] Example 2: Based on the above embodiments, this embodiment further provides: In the fiber raw material pretreatment step, the mass percentages of hardwood pulp and softwood pulp are 75% and 25%, respectively.

[0019] This formulation setting is a further refinement of the original broad formulation range (70%-80% hardwood pulp, 20%-30% softwood pulp). This ratio is selected based on a systematic study of the properties of various fiber combinations, aiming to achieve an optimal balance between softness, bulkiness, and structural strength. The following provides a detailed explanation of this technical feature.

[0020] Hardwood pulp comprises 75% of the paper, providing a rich structure of short fibers. These fibers have a high specific surface area and good swelling capacity, making them easy to fluff and fully combine with water molecules during subsequent pulping and forming processes, thereby enhancing the bulk and softness of the paper. Hardwood pulp mainly comes from fast-growing hardwood species such as eucalyptus and poplar. The fiber length is generally between 0.7 and 1.2 mm, with thin cell walls and good flexibility, which is beneficial for fiber folding and three-dimensional structure construction during creping. When its proportion reaches 75%, it can maximize the "light luxury cotton softness" of the product while ensuring sufficient fiber interlacing density, avoiding the stiffness caused by excessive long fibers.

[0021] The core function of softwood pulp (25%) is to introduce long fibers (typically 2.5–4.0 mm in length) to enhance the overall tensile strength and tensile properties of the fiber network. Softwood pulp, derived from pine or spruce, has robust fibers, thick cell walls, and high crystallinity, providing excellent mechanical support. At low basis weights (9–15.5 g / m²), the number of fibers per unit area in the paper sheet is limited; without sufficient long fiber reinforcement, breakage and shedding are highly likely. Maintaining softwood pulp at 25% effectively compensates for the insufficient strength of hardwood pulp without sacrificing the product's bulkiness and softness due to an excessively high proportion.

[0022] This 75% / 25% ratio falls within the central range of the original specifications and has been experimentally verified as the optimal solution for overall performance. For example, in multiple rounds of pilot testing on production line #2 at the Sanjiang base, paper products produced using this ratio showed a single-layer thickness ≥22% higher than conventional products of the same basis weight, water absorption exceeding 5.5 g / g, tensile strength stable at 1.3 kN / m, and good crease uniformity with no obvious cracks or paper breaks. In contrast, when the proportion of hardwood pulp is below 70%, the softness decreases significantly; above 80%, the tensile strength is difficult to meet the standard, and the paper breakage rate increases. Similarly, softwood pulp below 20% results in insufficient strength, and above 30% leads to a stiff feel and lower consumer ratings.

[0023] Furthermore, this fixed ratio helps establish stable raw material quality control standards, reduces batch-to-batch fluctuations, and improves the repeatability and process stability of industrial production. Enterprises can monitor the composition of incoming slurry in real time through an online near-infrared detection system and precisely adjust the conveying flow rate in conjunction with an automatic batching device to ensure that the mixed slurry always maintains a 75:25 mass ratio.

[0024] Through the above-described solution, this application achieves, without altering the overall process, the precise control of the basic raw material ratio to enable high-thickness, low-grammage paper products to maintain extremely low areal density while possessing excellent physical properties and a premium user experience. This ratio, as a key parameter, works synergistically with other process steps (such as high-fiberration pulping, optimized idler roller line pressure, and appropriate creping) to support the product positioning of "lightweight + high performance + comfort." This solves the common problem of "thin but not soft, light but brittle" in existing low-grammage paper products, meeting the urgent demand of the mid-to-high-end tissue paper market for high-quality, energy-saving products.

[0025] Example 3: Based on the above embodiments, this embodiment further provides: In the pulping process, the beating degree is 35–38°SR and the flocculentization rate is 50%–55%.

[0026] Freezing degree is a comprehensive indicator reflecting the degree of fiber cutting and fibrillation during the pulping process. It is measured using the Canadian Standard Freeness (CSF) method and converted to °SR (Schopper-Riegler degrees). This parameter directly affects the fiber's specific surface area, swelling capacity, and the bonding strength and bulk of the finished paper. Controlling the freezing degree within the range of 35–38 °SR represents a medium-strength refining level. This avoids the problem of insufficient fiber fibrillation leading to weak hydrogen bonding at low freezing degrees, while also preventing excessive fiber cutting and decreased wet weight caused by high freezing degrees, thus achieving a balance between fiber flexibility and structural integrity. Within this range, the fiber surface is fully fibrillated but not significantly broken, which is conducive to forming a loose and porous fiber network structure, improving the paper's fluffiness and softness. Optionally, under specific production conditions, precise and stable control of the beating degree can be achieved by adjusting the grinding disc gap to 0.15–0.3 mm and controlling the pulp concentration at 2.8%–3.2%.

[0027] Fibrillation rate refers to the proportion of fibers that undergo longitudinal splitting and produce fine, fibrous structures after refining. It is a key indicator for measuring fiber plasticity and paper bonding performance. A fibrillation rate of 50%–55% means that more than half of the fiber surface has formed exposed microfibrils, significantly increasing the contact area between fibers and the density of hydrogen bonds. This change directly enhances the internal bonding strength and tensile strength of the paper sheet. Simultaneously, the more uniform fiber bonding reduces the formation of localized tight zones, helping to maintain a high air gap volume and good bulk and compression resilience. The fibrillation rate can be quantitatively assessed using an optical microscope combined with an image analysis system, or indirectly determined by measuring the trend of the wet weight to freeness ratio. To achieve this fibrillation rate range, a three-pass refining process using a two-disc refiner can be employed, applying an increasing pressure gradient with each pass (e.g., 0.3 MPa for the first pass, 0.4 MPa for the second, and 0.5 MPa for the third), while ensuring that energy consumption per ton of oven-dry pulp is controlled between 180–220 kWh.

[0028] There is a synergistic regulatory relationship between the aforementioned freeness and fissuring rate: moderate freeness intensity (corresponding to 35–38°SR) provides sufficient mechanical force to the fibers to initiate the fissuring process, while a reasonable fiber swelling state (from the preceding swelling treatment) lowers the fiber cuticle breaking energy barrier and promotes fissuring development; conversely, excessively high freeness may increase the fissuring rate, but it is accompanied by increased fiber cutting and a significant decrease in wet weight, which is not conducive to the construction of thick paper structures. Therefore, the two work together to influence the fiber morphology evolution process, and by controlling the rhythm and distribution of refining energy input, surface activity can be maximized without sacrificing fiber length.

[0029] Through the above-described scheme, this application achieves refined control of key process parameters in the pulping process. By limiting the freeness to 35–38°SR and increasing the fissile rate to 50%–55%, it solves the technical problem of insufficient strength or stiff feel that traditional low-grammage paper products often experience during the thinning and weight reduction process. This significantly improves the paper's bulkiness and tactile comfort while ensuring a dry strength of ≥1.2kN / m, meeting the requirements of high-thickness, low-grammage tissue paper for a "light luxury, soft and cottony" experience. This parameter combination has been successfully pilot-scale verified on production line #2 at the Sanjiang Paper Mill, demonstrating good operational stability and parameter fluctuations controlled within the target range, thus possessing industrial replication and promotion value.

[0030] Example 4: Based on the above embodiments, this embodiment further provides: In the fiber weaving and forming process, the mesh size is 65-75, and the dehydration speed is 0.9-1.1 m / s.

[0031] The forming fabric mesh count of 65-75 mesh refers to the number of pores per unit length of the forming fabric used for paper forming that falls within this range. This parameter directly affects fiber retention rate, dewatering efficiency, and paper uniformity. Structurally, the forming fabric is usually woven from polymer materials such as polyester, possessing a certain degree of air permeability and mechanical strength. When the mesh count is below 65 mesh, the mesh openings are too large, easily causing fine fibers to be lost with the water flow, reducing paper uniformity and strength. Conversely, when the mesh count exceeds 75 mesh, the mesh openings are too dense. While this can improve fiber retention, it significantly increases dewatering resistance, leading to uneven drainage or localized accumulation, thus disrupting the uniformity of the fiber network. Therefore, controlling the mesh count between 65 and 75 mesh ensures effective dewatering while achieving good retention of fibers, especially fine components, resulting in a loosely structured and evenly distributed wet paper web. As an alternative embodiment, the forming mesh can adopt a double-layer fabric structure, with a fine surface layer to improve the smoothness of the paper surface layer and a coarse bottom layer to enhance water permeability, further optimizing the synergistic performance of dewatering and forming.

[0032] The dewatering rate, 0.9–1.1 m / s, refers to the linear velocity at which water is removed from the pulp layer under vacuum suction or gravity. This rate reflects the kinetic characteristics of the dewatering process and directly affects the fiber arrangement in the forming zone. If the dewatering rate is too fast (e.g., greater than 1.1 m / s), strong turbulent disturbances will occur on the wire surface, causing fiber flocculation or orientation disorder, affecting paper uniformity. If the rate is too slow (e.g., less than 0.9 m / s), the fibers in the pulp layer have sufficient time to settle and stratify, resulting in density differences between the upper and lower surfaces, which is also unfavorable for forming a uniform and fluffy structure. By precisely controlling the dewatering rate within the stable intermediate range of 0.9–1.1 m / s, a smooth dewatering gradient can be established, allowing the fibers to naturally align under moderate shear and gradual drainage conditions, forming a three-dimensional and loosely porous initial network structure. As an alternative, the actual dewatering rate can be dynamically controlled by adjusting the negative pressure intensity of the vacuum chamber (e.g., set to 30–60 kPa), adjusting the slurry concentration (e.g., maintaining at 2.0%–3.0%), or optimizing the length of the forming zone, in order to meet the process stability requirements at different machine speeds.

[0033] There is a synergistic relationship between the aforementioned mesh count and dewatering speed: finer mesh (e.g., 70–75 mesh) corresponds to higher dewatering resistance and is best used with a slightly lower dewatering speed (e.g., 0.9–1.0 m / s) to prevent clogging or over-compaction; while relatively sparse mesh (e.g., 65–70 mesh) allows for faster drainage response and can be matched with a dewatering speed of 1.0–1.1 m / s at higher machine speeds, ensuring production efficiency. Both work together in the solid-liquid separation process of the fiber suspension, ensuring that even under high-speed operating conditions, a thick, low basis weight, and consistent wet paper sheet can still be obtained.

[0034] Through the above-mentioned scheme, this application achieves the following: by setting the forming mesh number to 65–75 mesh and controlling the dewatering speed to 0.9–1.1 m / s, a balance is achieved between avoiding fiber loss and preventing over-dewatering, thereby improving the uniformity and fluffiness of the paper. Since the fiber network forms a stable and loose initial structure during the forming stage, it lays the foundation for maintaining high thickness characteristics in subsequent pressing and creping processes. Ultimately, it solves the technical problem in the prior art that low basis weight products are prone to being thin and compact, or thick and uneven, achieving the technical effects of increasing single-layer thickness, improving soft hand feel, and maintaining good physical strength.

[0035] Example 5: Based on the above embodiments, this embodiment further provides: During the pressing and dewatering process, the linear pressure of the idler rollers is 18-22 kN / m, with a medium-high value of 0.4-0.6 mm.

[0036] The linear pressure of the idler rollers refers to the pressure applied per unit length of the wet paper sheet during the pressing process, and its value is controlled within the range of 18–22 kN / m. This parameter range is lower than the conventional high-pressure pressing range, aiming to achieve moderate dehydration while avoiding excessive compression of the fiber network structure. When the linear pressure is too low (<18 kN / m), the dehydration efficiency is insufficient, leading to increased energy consumption in subsequent drying; while when the linear pressure is too high (>22 kN / m), it will significantly compress the porosity of the paper sheet, destroy the three-dimensional fluffy structure between fibers, and reduce the thickness and softness of the product. By stabilizing the linear pressure within this range, the internal void structure of the paper sheet can be preserved to the maximum extent while ensuring effective dehydration, which is beneficial to improving the final product's feel of bulkiness and liquid absorption performance.

[0037] The "mid-high value" refers to the amount of protrusion from the center of the press roll relative to both ends, set at 0.4–0.6 mm. This geometric design compensates for the sag in the center of the roll caused by bending deformation under working loads. If the mid-high value is too small (<0.4 mm), it cannot completely counteract the natural sag trend in the center of the roll, leading to concentrated stress in the edge area, resulting in edge crushing and lower thickness. If the mid-high value is too large (>0.6 mm), the pressure in the center is too high, causing localized compaction and excessive dewatering, affecting thickness uniformity and consistent creping. By precisely controlling the mid-high value within this range, the linear pressure distribution in the entire width direction can be made more uniform, thereby reducing edge-center differences and improving the transverse thickness stability of the paper sheet.

[0038] There is a synergistic matching relationship between the aforementioned idler roller linear pressure and the medium-high value: an appropriate medium-high value can enhance the effectiveness of linear pressure control, ensuring uniform dewatering across the entire width even under lower linear pressure conditions; conversely, a reasonable linear pressure range also provides a suitable working window for the medium-high compensation mechanism, preventing structural defects caused by pressure imbalance. Both work together in the mechanical dewatering process of the wet paper sheet, satisfying the basic requirements for moisture removal while also protecting the paper sheet's microstructure.

[0039] Through the above-described steps, this application achieves precise control of pressure distribution during the pressing and dewatering stage: on the one hand, by controlling the linear pressure of the idler rollers at 18–22 kN / m, damage to the fiber network from high-intensity compression is avoided, maintaining the loose and porous characteristics of the paper sheet; on the other hand, by setting a medium-high value of 0.4–0.6 mm, the uneven pressure caused by roller deflection is effectively compensated, ensuring the consistency of thickness across the entire width. This parameter combination helps improve batch-to-batch stability, reduce edge-to-center performance differences, and thus support the continuous achievement of the goal of high thickness and low basis weight.

[0040] Example 6: Based on the above embodiments, this embodiment further provides: In the wrinkling process, the wrinkling rate is 76%-78%, and the wrinkling blade angle is 28°-32°.

[0041] Crinkling rate refers to the longitudinal compression ratio that occurs when the paper sheet is peeled from the surface of the drying cylinder under the action of the doctor blade; that is, the percentage of the length difference of the paper sheet before and after wrinkling to the length before wrinkling. Controlling the wrinkling rate within the range of 76%-78% falls within the optimized convergence range of high wrinkling rates. This preserves the fiber relaxation space required for high bulkiness while avoiding fiber structure breakage and significant strength reduction caused by excessive wrinkling. This parameter range has been verified through multiple rounds of pilot testing, achieving a single-layer thickness increase of ≥20% compared to conventional products while ensuring a tensile strength ≥1.2 kN / m. It is particularly suitable for the production of low basis weight paper products with a basis weight of 9–15.5 g / m². As an optional embodiment, the wrinkling rate can be set to 77% to further balance thickness and strength performance; it can also be adjusted to 76.5% or 77.5% depending on the final product application, both of which maintain good structural integrity and sensory experience.

[0042] The creping blade angle refers to the angle between the creping blade edge and the tangent of the drying cylinder, which directly affects the direction of shearing force and the fiber peeling method. Setting the creping blade angle to 28°-32°, which is in the middle to higher range of the traditional creping blade angle range (usually 20°–40°), is conducive to forming a smooth and continuous shearing action, reducing sudden tearing and local stress concentration. This angle setting makes the force of the doctor blade on the paper sheet closer to a pure shearing mode, reducing the probability of fiber breakage, thereby improving creping uniformity and surface smoothness. Experiments show that when the creping blade angle is 30°, the micro-fold distribution on the paper surface is the most uniform, and the softness score can reach 9.2 points (out of 10), which is in line with the product positioning of "light luxury cotton softness". As an alternative, a dynamic angle control strategy can be adopted with the support of an automatic adjustment device, such as temporarily adjusting the angle to the 29°–31° range during roll changing to adapt to tension fluctuations and ensure creping stability.

[0043] There is a synergistic effect between the two technical parameters mentioned above: under high crease rates, if the crease knife angle is too small (e.g., <25°), it is easy to cause severe impact peeling, exacerbating fiber damage; while if the angle is too large (e.g., >35°), it may lead to insufficient slippage, affecting crease efficiency. This embodiment achieves a balance between high bulk structure and good paper integrity by limiting the crease rate to 76%-78% and matching the knife angle to 28°-32°. In addition, this combination of parameters works in conjunction with upstream processes such as pulping fissure rate (45%-60%) and idler roller linear pressure (15-25 kN / m) to jointly support the thick and soft product characteristics.

[0044] Through the above solution, this application achieves the technical effect of effectively improving the volume and thickness of paper and the tactile quality without sacrificing mechanical properties, and solves the technical contradiction that existing low grammage paper products are generally "thick and hard, soft and weak", thus meeting the demand of the mid-to-high-end tissue paper market for both lightness and fluffiness and strength.

[0045] Example 7: A high-thickness, low-grammage paper for household use is provided, which is produced by the production process of a high-thickness, low-grammage paper as described in any of the preceding claims. The grammage of the household paper is 9-15.5 g / m², the single-layer thickness is ≥20% higher than that of conventional products with the same grammage, the water absorption is ≥5 g / g, and the tensile strength is ≥1.2 kN / m.

[0046] Through the above technical solution, this application realizes a household paper product that still possesses excellent physical properties and sensory experience under extremely low unit area mass conditions. The fiber network structure formed through a specific process path significantly improves volume, softness, and strength while ensuring lightweight design, solving the common problems of "thinness, brittleness, and weakness" in traditional low-grammage paper products, and meeting consumers' dual demands for a "light luxury softness" touch and high functionality.

[0047] The tissue paper is produced using the high-thickness, low-basis-weight paper production process described in any one of claims 1 to 6, meaning that its manufacturing process employs a systematic and synergistic process including fiber raw material pretreatment, pulping, fiber weaving and forming, pressing and dewatering, creping, and energy-saving control. This process system, through precise control of key aspects such as the rational ratio of hardwood pulp and softwood pulp, optimization of swelling conditions, high-brooming-rate pulping, low-linear-press forming, and moderate creping rate control, constructs a loose, porous, and fully fiber-bonded three-dimensional network structure. This structure reduces the amount of fiber used per unit area to lower the basis weight, while retaining a large amount of microporous space to improve overall bulkiness and thickness, and maintaining sufficient hydrogen bond area to ensure mechanical strength.

[0048] A basis weight of 9-15.5 g / m² refers to the weight range of the finished paper sheet per square meter. This basis weight range covers the main application areas of high-end facial tissues, handkerchiefs, and premium toilet paper, achieving significant weight reduction compared to mainstream products on the market with 16-20 g / m², aligning with resource conservation and green consumption trends. For example, under the same usage area, the product of this application can reduce virgin fiber consumption by approximately 30%-40%, demonstrating good environmental benefits. As a variant embodiment, the basis weight can also be set to 10-14 g / m², further focusing on the ultra-lightweight high-end niche market and enhancing product premium capabilities.

[0049] The single-layer thickness is ≥20% higher than that of conventional products of the same basis weight, meaning that under the same basis weight (e.g., both are 12g / m²), the single-layer physical thickness of the product in this application is at least 20% higher than the industry average. This indicator directly reflects the fluffiness and air retention capacity of the fiber structure, and is the core basis for users' perception of "thickness". The thickness improvement is mainly due to the combined effect of the following factors: First, high fibrillation rate pulping ensures sufficient fiber fibrillation, forming more fine fiber filamentous structures and increasing the support points between fibers; second, the use of a lower dewatering speed and moderate forming pressure in the forming stage avoids excessive compaction and facilitates three-dimensional fiber interweaving; third, the control of the roller linear pressure at an appropriate level during the pressing process, combined with the design of medium and high rollers, prevents excessive local compression; fourth, the wrinkling rate is controlled within the range of 75%–80%, which can produce the necessary wrinkles to increase the apparent volume without causing structural loosening and breakage due to excessive wrinkling. As an alternative approach, the uniformity of thickness distribution can be fine-tuned by adjusting the angle of the wrinkling blade to 28°–32° or by adjusting the wrinkling pressure to 0.06–0.09 MPa.

[0050] A water absorbency of ≥5 g / g indicates that each gram of dry paper can absorb no less than 5 grams of water, typically determined using the GB / T 1541 standard method. High water absorbency stems from the abundant capillary pore structure within the fiber network and the sufficient number of exposed hydroxyl groups on the fiber surface. Because the swelling treatment is carried out at pH 7.0–8.0 and temperature 40–55℃, the microfibril structure of the fiber cell walls is effectively opened, enhancing hydrophilicity; simultaneously, a moderate beating degree (32–40°SR) increases the specific surface area without excessively cutting the fibers, further promoting water molecule penetration. As an alternative, a small amount of hydrophilic additives (such as polyacrylic acid polymers) can be added to the wet end to increase water absorbency to above 5.5 g / g without significantly affecting softness.

[0051] Tensile strength ≥1.2kN / m refers to the maximum tensile force that the paper sheet can withstand before breaking longitudinally under standard conditions, tested according to GB / T 12914. This strength level ensures the integrity of the product in usage scenarios such as wiping and crumpling, overcoming the problems of easy tearing and shedding of low-basis-weight paper. The achievement of high strength relies on the synergy of multiple process steps: First, hardwood pulp and softwood pulp are mixed in a ratio of 70%–80%:20%–30%, taking into account both the paper uniformity of short fibers and the reinforcing effect of long fibers; second, the wet weight is controlled at 8–12g during pulping, indicating that the fibers are not over-cut and retain sufficient length to form a strong and tough network skeleton; third, the fissuring rate reaches 45%–60%, which significantly increases the contact area between fibers and the density of hydrogen bonding; finally, the pressing and creping parameters are reasonably matched to avoid structural defects caused by excessive compression or stress concentration during creping.

[0052] The combined effect of various process parameters and material selection results in a final product with a "sparse on the outside, dense on the inside, crisscrossing" fiber arrangement at the microscopic level: the surface fibers are highly wrinkled and loosely overlapped, giving it a good softness and visual thickness; while the interior maintains mechanical continuity through appropriate bonding. This structure breaks the traditional perception that "low basis weight necessarily means small thickness and poor strength," achieving a unity of lightweight and high performance.

[0053] Through the above technical solution, this application has achieved the production of tissue paper with high thickness, high absorbency, and sufficient tensile strength within a weight range of 9–15.5 g / m². Due to its single-layer thickness increase of ≥20%, it significantly enhances the user's tactile and visual experience, creating a "light luxury cotton softness" texture similar to fabric; its absorbency of ≥5 g / g meets the requirements for rapid liquid absorption, surpassing most commercially available similar products; and its tensile strength of ≥1.2 kN / m ensures durability in actual use. This product fills the technological gap in high-quality, cost-effective tissue paper in China, is suitable for consumers pursuing a quality lifestyle, and also provides a feasible path for the paper industry to transform and upgrade towards energy conservation, high efficiency, and high added value.

[0054] Example 8: Based on the above embodiments, this embodiment further provides: The basis weight of the tissue paper is 10-14 g / m², the single-layer thickness is increased by ≥22%, the water absorption is 5.5 g / g, and the tensile strength is 1.3 kN / m.

[0055] This embodiment addresses common problems in existing high-thickness, low-basis-weight tissue paper on the market, such as "thick but not soft," "insufficient strength," or "large performance fluctuations," particularly the technical bottlenecks of limited thickness improvement under the same basis weight and the difficulty in balancing absorbency and mechanical strength. It proposes a set of optimized product performance parameters. Currently, most low-basis-weight products in China (9–16 g / m²) often sacrifice bulk and structural integrity in pursuit of lightweighting, resulting in a stiff feel, easy tearing, and slow liquid absorption. While some imported high-end products achieve a certain thickness improvement, they are costly and have not systematically addressed the issue of synergistic optimization between energy consumption and user experience. This embodiment, by limiting a narrower basis weight range and setting higher performance thresholds, achieves a leap in overall product performance while ensuring energy-efficient manufacturing, making it particularly suitable for mid-to-high-end consumer scenarios sensitive to user experience.

[0056] The optimal basis weight for tissue paper, controlled within the range of 10–14 g / m², was determined based on extensive pilot-scale data. This range avoids the difficulties in forming and the risk of strength degradation associated with excessively low basis weights (<10 g / m²), while also mitigating the resource waste and the tendency towards a heavy feel caused by excessively high basis weights (>14 g / m²). In actual production, precise basis weight control can be achieved by adjusting the fiber ratio, forming concentration, and dewatering rate. For example, using a mixture of 75% hardwood pulp and 25% softwood pulp in the fiber raw material pretreatment stage, combined with a freeness of 35–38°SR and a buffing rate of 50%–55%, can effectively improve fiber interlacing ability, thereby maintaining good web uniformity at a lower basis weight. As a variation, some eucalyptus short fibers can be used to replace some hardwood pulp, with a slight increase in wet weight to 10–11 g, to compensate for potential strength loss due to shortened fiber length.

[0057] A single-layer thickness increase of ≥22% refers to a thickness increase of no less than 22% in the single-layer state of the product obtained in this application compared to conventional tissue paper of the same grammage (usually ordinary crepe paper produced by standard creping processes). Achieving this indicator relies on the synergistic effect of multiple processes: including moderately reducing the creping rate (controlled at 76%–78%), optimizing the linear pressure of the idler rollers (18–22 kN / m), and regulating the fiber swelling state (concentration 2.0%–3.0%, temperature 45–50℃). These parameters collectively promote the formation of a looser three-dimensional network structure in the wet paper sheet during pressing and drying. For example, setting the high value of the idler rollers to approximately 0.5 mm during the pressing and dewatering step, combined with heating the roller surface to 85–90℃, can reduce lateral compression while promoting the establishment of moisture evaporation channels. This is beneficial for producing a more uniform and dense small-ripple structure during subsequent creping, thereby significantly increasing the volumetric feel. Furthermore, selecting a forming mesh count of 65–75 mesh also helps to construct an open fiber skeleton, further supporting the thickness increase.

[0058] With an absorbency of 5.5 g / g, this means that each gram of dry paper can absorb at least 5.5 grams of deionized water, far exceeding the industry average (typically 3.0–4.5 g / g). This performance is mainly attributed to the fiber fracturing effect brought about by the high fracturing rate refining process, which exposes a large number of hydrophilic hydroxyl groups on the fiber surface, while simultaneously enriching and connecting the pore structure between fibers. Specifically, this can be achieved by extending the swelling time to 45–50 minutes and maintaining the pH value around 7.5, thereby enhancing the fiber swelling degree and improving its hydrophilic response speed. Alternatively, without affecting softness, a trace amount of hydrophilic additives (such as polyacrylic acid additives, ≤0.3%) can be introduced to further improve initial wetting properties, especially suitable for scenarios requiring rapid liquid absorption.

[0059] The tensile strength is set at 1.3 kN / m, meaning that the maximum force a unit width of paper sample can withstand before tensile fracture is no less than 1.3 kN / m, significantly better than the 0.8–1.0 kN / m level of ordinary low-basis-weight products. This improvement in mechanical properties stems from the increased interfiber bonding area and enhanced hydrogen bond density, which is the result of the synergistic effect of high fibrillation rate and moderate freeness. When the fibrillation rate reaches 50% or more, the fiber outer wall is fully peeled off, the specific surface area increases, and the number of bonding points increases, thus forming stronger internal adhesion during drying. At the same time, a reasonable creping knife angle (e.g., 30°±2°) and pressure (0.07–0.09 MPa) can avoid excessive scraping that could cause fiber breakage, preserving sufficient structural integrity. As an alternative implementation, the interfiber bonding force can also be strengthened by adding a small amount of cationic starch (0.5%–1.0%) to the pulp, which is particularly suitable for ensuring strength stability under high-speed machine operation conditions.

[0060] The parameters are not isolated but rather a result of mutual constraints and synergistic balance. For example, if one excessively pursues high thickness while excessively reducing wrinkling rate or weakening pressing, it may lead to insufficient fiber bonding and a decrease in tensile strength. Conversely, if one overemphasizes strength by increasing beating or linear pressing, it will compress the fiber gaps, weakening the bulkiness and water absorption capacity. Therefore, it is necessary to comprehensively adjust the process window under the constraint of basis weight to achieve the optimal match of various properties.

[0061] Through the above technical solution, this application achieves the goals of significantly improved single-layer thickness, excellent water absorption, and reliable mechanical strength within a weight range of 10–14 g / m². Because it employs a systematically optimized material ratio and process route, it overcomes the technical defects of traditional low-grammage paper products, namely "thinness, weakness, and poor water absorption." Therefore, it can provide a household paper product that combines a lightweight feel with excellent practical performance without increasing raw material consumption, meeting consumers' growing demand for high-quality, high-experience hygiene products. This implementation plan has passed pilot testing on the No. 2 production line at the Sanjiang base and is feasible for stable mass production. It is planned to be launched into the market as one of the first commercially promoted models.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A production process for high-thickness, low-grammage paper products, characterized in that, Includes the following steps: Fiber raw material pretreatment steps: Mix hardwood pulp and softwood pulp at a mass percentage of 70%-80% and 20%-30% respectively, and perform swelling treatment on the mixed pulp, controlling the swelling concentration at 2.0%-3.0%, the temperature at 40-55℃, the time at 30-60min, and the pH value at 7.0-8.0; Refining treatment steps: Refine the swollen pulp, controlling the freeness at 32-40°SR, the fissile rate at 45%-60%, and the wet weight at 8-12g; Fiber weaving and forming steps: The refined pulp is dewatered and formed through a forming wire, with the wire mesh size controlled at 60-80 mesh, the dewatering speed at 0.8-1.2 m / s, and the forming pressure at 0.1-0.2 MPa; Pressing and dewatering steps: The formed wet paper sheet is pressed and dewatered using a roller device, with the roller linear pressure controlled at 15-25 kN / m, the medium-high value at 0.3-0.8 mm, and the roller surface temperature at 80-95℃; Crinkling process: The dewatered paper sheet is creped, with the creping rate controlled at 75%-80%, the creping knife angle at 25°-35°, and the creping pressure at 0.05-0.1 MPa; Energy-saving control steps: At least one of the following is adopted: variable frequency motor control, water recycling, and steam pipeline insulation.

2. The production process for high-thickness, low-basis-weight paper products according to claim 1, characterized in that, In the fiber raw material pretreatment step, the mass percentages of hardwood pulp and softwood pulp are 75% and 25%, respectively.

3. The production process for high-thickness, low-grammage paper products according to claim 1, characterized in that, In the pulping process, the beating degree is 35-38°SR and the buffing rate is 50%-55%.

4. The production process for high-thickness, low-basis-weight paper products according to claim 1, characterized in that, In the fiber weaving and forming step, the mesh size is 65-75 mesh, and the dehydration speed is 0.9-1.1 m / s.

5. The production process for high-thickness, low-basis-weight paper products according to claim 1, characterized in that, In the pressing and dewatering step, the linear pressure of the idler roller is 18-22 kN / m, with a medium-high value of 0.4-0.6 mm.

6. The production process for high-thickness, low-basis-weight paper products according to claim 1, characterized in that, In the wrinkling process, the wrinkling rate is 76%-78%, and the wrinkling blade angle is 28°-32°.

7. A type of high-thickness, low-grammage paper for household use, characterized in that, The paper is produced by the production process of a high-thickness, low-grammage paper as described in any one of claims 1-6. The grammage of the paper is 9-15.5 g / m², the single-layer thickness is ≥20% higher than that of conventional products with the same grammage, the water absorption is ≥5 g / g, and the tensile strength is ≥1.2 kN / m.

8. The high-thickness, low-grammage paper for household use according to claim 7, characterized in that, The basis weight of the tissue paper is 10-14 g / m², the single-layer thickness is increased by ≥22%, the water absorption is 5.5 g / g, and the tensile strength is 1.3 kN / m.