In the process of upgrading the non-woven fabric industry to high-end, low weight wet non-woven fabric has become a key material in medical protection, high-end filtration, precision wiping and other fields due to its advantages of lightness, breathability, and high material utilization. However, when the weight of the product drops below 20 grams per square meter, issues such as uniformity control, strength maintenance, and efficiency balance in the production process become sharply prominent. This article will systematically analyze the process bottlenecks of low weight wet non-woven fabrics, and explore feasible solutions based on the latest technological breakthroughs and enterprise practices.
Multidimensional analysis of process bottlenecks: challenges from micro to macro level
The production of low weight wet non-woven fabric is essentially a technological revolution that pursues balance under extreme conditions. When the fiber usage is reduced by 50%, the product strength often decreases by more than 60%, and the production difficulty increases exponentially. This challenge is reflected in three interrelated dimensions:
1. Microscopic dilemma of fiber dispersion
Low weight products typically rely on ultrafine fibers (diameter<5 μ m) to ensure the necessary specific surface area and pore structure, but the increase in fiber fineness directly leads to a significant increase in surface energy. During the production of ultrafine polyester sea island fibers developed by Henan KeGao Radiation Chemical, it was found that when the fiber diameter was reduced from 10 μ m to 1 μ m, the probability of aggregation in water increased by 300%, and the formed “fiber bundles” would cause defects with a diameter of 0.5-2mm in the finished product. The traditional mechanical stirring and dispersion method has a sharp drop in efficiency in low concentration slurries (concentration<0.5%), and even with the addition of 0.3% polyoxyethylene ether dispersant, the fiber dispersion uniformity is still difficult to control above 85%.
The application of composite fibers intensifies the complexity of dispersion. Dalian Hualun Company observed during the production of two-component ultrafine fiber products that fibers with orange petal structure are more likely to form “clumping” phenomenon at low concentrations, with fiber opening rate fluctuations of up to ± 20%, directly leading to a deviation in product air permeability exceeding 15%. This uneven dispersion manifests as obvious “cloud spots” on the final product, which is completely unacceptable in high-end fields such as medical packaging.
2. Mid scale control of network uniformity
The uniformity of fiber deposition on the forming mesh during wet forming process is the core quality indicator of low weight products. Changzhou Kangjie Special Non woven Fabric found that when the target weight was reduced to below 30 grams, the longitudinal quantitative fluctuation of traditional long web paper machines increased from ± 5% to ± 12%, and the lateral deviation exceeded 15% during the development of 75 grams/square meter reverse osmosis membrane substrates. This fluctuation is due to the reduced probability of fiber overlap in low weight states, and any small flow field disturbance will be amplified.
The design of the slurry box has become a key bottleneck. The accuracy of slurry distribution in ordinary headboxes is difficult to meet the low weight requirements. When the slurry flow rate changes by 0.1m/s, it will result in a 4% deviation in the weight of the finished product. Kangjie Company has developed a “stepped slurry distributor” with independent intellectual property rights through six years of research and development, which controls the unevenness of the flow field within 3% and ultimately achieves precise control of the aperture of 10-15 μ m, breaking the foreign monopoly.
3. Macro equilibrium of dehydration and drying
The structural fragility of low weight substrates poses a dilemma in the dehydration process: increasing pressure can lead to fiber loss and structural damage, while insufficient pressure cannot achieve the necessary dryness. The nano gel spray technology developed by Hainan University has provided a new idea for this dilemma. By constructing hydrophobic mesoporous channels on the surface of the substrate, this technology has improved the water evaporation rate by nearly three times, and can evaporate 3.26 kilograms of water per square meter per hour. This “turbocharged” evaporation mechanism is particularly suitable for low weight products, avoiding structural damage caused by mechanical pressing.
The challenges in the drying process are equally severe. Ultra fine fiber water jet cloth has a larger specific surface area and a drying efficiency 40% lower than ordinary products. The production practice of Dalian Hualun shows that the drying temperature needs to be increased by 10-15 ℃ to achieve the same drying effect, but this may also lead to fiber thermal degradation. A certain enterprise found that when producing medical packaging materials at a rate of 8 grams per square meter, a drying temperature exceeding 130 ℃ would reduce the product’s fracture strength by 20%, and the temperature curve must be precisely controlled.
Technological Matrix for Breakthrough Path: Collaborative Innovation of Materials, Equipment, and Processes
The breakthrough in the production of low weight wet non-woven fabric requires the construction of a three in one technical system of “materials equipment process”, and the resolution of inherent contradictions through multidimensional innovation. The practice of industry-leading enterprises has verified the feasibility of these technological paths.
1. Fiber selection and modification technology
The reasonable selection of ultrafine fibers is the basis for balancing lightness and performance. The polyester sea island fiber used by Henan Kegao can achieve a single fiber fineness of 0.08dtex after water jet splitting, with a specific surface area more than 10 times that of ordinary polyester. The 8 grams per square meter product made of this fiber has a filtration efficiency of up to N95 level, while maintaining good breathability. But the fiber opening rate must be controlled above 60%, otherwise the advantages of ultrafine fibers cannot be fully utilized. This requires precise design of the water jet pressure gradient, usually set at 70-80% of the design value for the first water jet pressure, and gradually increase thereafter.
Fiber surface modification technology effectively improves dispersibility. A certain enterprise uses plasma treatment to increase the number of hydroxyl groups on the surface of nanocellulose by 25%, significantly improving its dispersion stability in water and increasing the product qualification rate from 65% to 92%. For composite fibers, by adjusting the interfacial tension between the skin and core layers, the agglomeration phenomenon at low concentrations can be reduced, and the stability retention time of the slurry can be extended from 4 hours to 8 hours.
2. Equipment upgrade and intelligent transformation
The precision of molding equipment is a prerequisite for low weight production. Changzhou Kangjie has achieved precise control of fiber morphology through independently developed fiber pulping machines and papermaking integrated machines. The thickness of its reverse osmosis membrane substrate products is controlled between 95-100 microns, with a tolerance of no more than ± 3 microns. The Laifen 5 production line introduced by Xinjiang Kaiwo Technology represents the current highest level. The equipment adopts Industry 4.0 technology and can stably produce ultra-low weight products of 8 grams per square meter, with a quantitative fluctuation of ≤ 2%.
Intelligent monitoring systems are indispensable. In low weight production, the online quantitative monitoring frequency needs to be increased to 2 times per second in order to adjust the parameters of the slurry box in a timely manner. A certain enterprise has introduced a machine vision inspection system that can identify tiny defects of 0.1mm. With the help of an automatic adjustment device, the first-class product rate has increased by 15 percentage points. This closed-loop control of “perception decision execution” is the key to ensuring the stability of low weight products.
3. Process optimization and innovation
The parameter optimization of water jet technology is particularly important for low weight products. Practice has shown that the use of the “low-pressure pre needling+gradual pressurization” water needling strategy can achieve the best results: the first water needling pressure is controlled at 80-100 bar to achieve initial fiber entanglement; Raise the pressure of the 2nd and 3rd channels to 120-150 bar to promote fiber opening and reinforcement. This gradient pressure design improves the longitudinal and transverse strength ratio of the 20 gram/square meter product from 3:1 to 1.5:1.
Innovation in drying technology is equally crucial. The combination of “infrared preheating+hot air penetration” drying method can save 30% energy compared to traditional hot air drying, while avoiding local overheating. When a certain enterprise produces 12 grams/square meter medical wiping cloth, the drying time is shortened from 60 seconds to 40 seconds by precisely controlling the infrared wavelength in the range of 2-5 μ m, and the product shrinkage rate is controlled within 1%.
Extension of Industrial Value and Future Trends
The technological breakthrough of low weight wet non-woven fabric not only solves the production problem, but also reshapes the industrial value chain, bringing innovative opportunities to multiple application fields. This material philosophy of ‘less wins more’ is creating significant economic and social benefits.
In terms of cost control, although the unit process cost of low weight products has increased by 30-50%, the comprehensive benefits brought by the reduction of raw material consumption are more significant. After achieving import substitution, Changzhou Kangjie’s reverse osmosis membrane substrate products not only reduced customer procurement costs by 40%, but also reduced unit energy consumption by 15% through large-scale production (annual production capacity of 25 million square meters). Xinjiang Kaiwo’s 8g/square meter product has reduced raw material costs by 20% in the application of baby diapers, while improving the softness and breathability of the product.
The expansion of application fields presents a diversified trend. In the medical field, 10-15 grams/square meter of ultra-low weight non-woven fabric is used as the lining of surgical gowns, which can maintain bacterial barrier performance and reduce the wearing weight by 30%; In the electronics industry, 8 grams per square meter of ultra-fine fiber wiping cloth can effectively remove pollutants at the 0.1 μ m level; In the field of environmental protection, filter membrane materials made of low weight non-woven fabrics can increase water treatment efficiency by 25% while reducing material consumption.
Future technological breakthroughs will focus on three directions: first, developing “intelligent responsive” low weight products, which can dynamically control functions by introducing temperature or pH sensitive fibers; The second is to promote green production technologies, such as using bio based solvent systems to improve the dispersibility of ultrafine fibers; The third is to develop “structural biomimetic” designs that mimic the hierarchical structure of spider silk, achieving higher strength at a weight of less than 10 grams per square meter.
The breakthrough in the production process of low weight wet non-woven fabric is essentially a microcosm of precision and intelligence in the manufacturing industry. From Changzhou Kangjie’s insistence on over 400 trials in 6 years, to Henan Kegao’s innovation in transforming papermaking equipment for non-woven fabric production, industry practitioners are constantly expanding the boundaries of material applications. With the continuous advancement of technology, low weight wet non-woven fabrics will go further on the path of “lightweight and efficient”, providing key material support for sustainable development and high-end manufacturing.
Dongguan Liansheng Non woven Technology Co., Ltd. was established in May 2020. It is a large-scale non-woven fabric production enterprise integrating research and development, production, and sales. It can produce various colors of PP spunbond non-woven fabrics with a width of less than 3.2 meters from 9 grams to 300 grams.
Post time: Sep-06-2025