Hydroentanglement process of spunbond nonwovens
Published Time:
2020-03-13
Hydroentanglement Process Principle
Hydroentanglement (jet-laid) technology for consolidating spun-bonded webs is a newly developed process. Its principle involves high-pressure water jets, generated by a water pump with a pressure of up to 40 MPa, which are sprayed through water needle plate nozzles with a diameter ≤0.15 mm. This forms a water needle curtain distributed across the full width of the web. The high-speed water needles impact the un-consolidated web, penetrating it and reflecting after passing through, causing the fibers to intertwine and form a non-woven fabric with a fixed shape and certain strength. The high-pressure water flow, after passing through the web, enters a filtration system for treatment and recycling. After drying the consolidated web, the hydroentangled fabric product is obtained.
Characteristics of Spun-bonded Hydroentangled Nonwovens
Compared with thermally bonded spun-bonded fabrics, hydroentangled spun-bonded nonwovens have the characteristics of undamaged fiber webs; soft, fluffy hand feel; good breathability; and high strength. This is because after hydroentanglement of continuous filament webs, the consolidation points are formed by fiber bending and entanglement, keeping the fibers continuous and the fiber web undamaged. In contrast, in thermally bonded webs, the consolidation points are formed by partial plasticization of the fibers and the web, resulting in an impermeable sheet-like structure. Because the fibers are undamaged in hydroentangled fabrics, their breaking strength and tear strength are higher than those of thermally bonded spun-bonded fabrics. Since the hydroentangled web is not subjected to the pressing of hot rollers, hydroentangled fabrics have a 30-50% greater thickness than thermally bonded spun-bonded fabrics of the same specifications, resulting in a softer, more breathable hand feel.
Production Process of Spun-bonded Webs Using Hydroentanglement
When using hydroentanglement to consolidate spun-bonded webs, the pre-web forming process and equipment are the same as those of spun-bonded webs consolidated using thermal bonding, except that the hydroentanglement system and drying system replace the thermal bonding machine. The general production process for hydroentangling single-component spun-bonded webs is as follows:
Raw material supply → Screw extruder → Melt filtration → Spinning pump → Spinning box → Melt spinning and web forming → Pre-wetting → Front-side hydroentanglement → Back-side hydroentanglement → Vacuum dewatering → Pre-drying → Finishing → Heating, drying, and shaping → Online inspection → Slitting, winding → Packaging → Product
Basic Components of the Hydroentanglement System
The hydroentanglement system is a relatively complex system, mainly including a high-pressure water pump, a hydroentanglement machine, a water treatment system, and a drying system.
The high-pressure water pump is generally a three-plunger type high-pressure pump used to generate high-pressure water.
The hydroentanglement machine is the core equipment of the hydroentanglement process, used to consolidate the web into fabric. According to its working method, it is mainly divided into drum type (roller type) and flat-net type.
Since the hydroentanglement production line requires a large amount of process water during operation, the water treatment system recovers, purifies, and recycles the process water.
The drying system includes mechanical dewatering and heat drying. Mechanical dewatering generally uses negative pressure suction to remove most of the unbound water from the product with high water content that has just come out of the hydroentanglement system. Heat drying usually uses a hot air penetration dryer to remove the moisture from the web. Since drying consumes a large amount of heat, the energy consumption of hydroentangled fabrics is also high, and the production cost is higher than that of thermally bonded spun-bonded fabrics, but the product quality is superior.
When using hydroentanglement for web consolidation, the plane layout, elevation layout, energy supply, factory area, investment scale, production cost, and operation management of the spun-bond production line are significantly different from those of ordinary thermally bonded spun-bond lines.
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