Meltblown Nonwoven Line

Overview

A meltblown nonwoven line turns polypropylene pellets into a fabric in one continuous pass, without ever spinning a yarn or weaving a thread. It melts the resin, pushes it through a row of tiny holes, and uses a sheet of hot fast air to draw each soft stream down to a fiber a few microns across. Those fibers cool in flight, land on a moving surface still slightly tacky, and tangle and self-bond into a web. The web is wound into rolls. The whole process is what gives meltblown its defining trait: extremely fine fibers, far finer than spunbond or carded webs, which is why the material is the filtration layer in surgical and respirator masks, in liquid and air filter cartridges, in oil-absorbent pads and in battery separators.

The line here is a single-beam machine built around the Meltblown Die Assembly, with an extruder feeding it, a melt pump metering it, a process air system attenuating the fiber, and a collector and winder turning out the finished roll.

How it works

Pellets fall from the Resin Feeding System into the Single-Screw Extruder, a single screw inside a heated barrel. As the screw turns, the resin is conveyed forward, compressed, and melted by a combination of barrel heat and shear until it leaves the barrel as a uniform melt near 250 °C. From there a Melt Gear Pump takes over the metering. A gear pump displaces a fixed volume per revolution, so output is set by its rpm and is steady regardless of small pressure swings upstream; this is what makes basis weight repeatable. Just ahead of it a Screen Changer holds a Filter Screen Pack that catches gels and grit, because a single contaminated particle can plug a die hole and leave a streak in the web.

The melt then enters the die. The Die Body carries a coat-hanger manifold that spreads the flow evenly across the full width, and the Die Tip / Nosepiece is a knife-edged nosepiece drilled with hundreds of capillary holes, roughly 0.3 mm each, across the working width. Melt extrudes from every hole as a thin stream. On both sides of the tip, the Air Knife Plate plates form a narrow slot that fires a sheet of hot, high-velocity air converging right at the hole exits. That air does the real work of meltblown: it grabs each soft filament and stretches it, thinning it from the hole diameter down to one to five microns before it cools and sets.

The process air system

Because attenuation is done by air, the Process Air System system is as important as the extruder. A high-pressure Process Air Blower supplies a large volume of air, and an inline Process Air Heater brings it up to roughly melt temperature so it stretches the fiber rather than quenching it. Two settings on this air, its temperature and its pressure, are the main levers for fiber diameter. Hotter, faster air makes finer fiber; cooler, slower air makes coarser fiber and a more open web. A Air Pressure Sensor at the die confirms the air is delivering the value the recipe calls for, and a Air Manifold splits the flow evenly to both air knives so the web is uniform from edge to edge.

Collecting and winding the web

The attenuated fibers blow downward onto the Web Collector. A perforated Collector Drum turns under the die, and a Suction Box beneath it pulls air through the holes to pin the fibers as they land and to carry the spent process air away through a Suction Fan. The fibers arrive still warm and slightly tacky, so they fuse at their crossing points and the web is self-bonded; no separate calender or adhesive is needed for a basic meltblown. The gap between die and drum, set by the Die-to-Collector Adjuster, controls how much the fiber cools in flight and therefore how lofty or dense the web is. From the drum the Winder pulls the web at controlled tension, trims and slits it to width, and winds it into rolls.

Materials and properties

The standard polymer is a high-melt-flow fiber-grade polypropylene, chosen because it melts cleanly, draws to fine fiber, and is cheap. The Additive Feeder can blend in masterbatch for colour or for special function. The most important add-on for filter media is an electret charge: many meltblown webs are charged after forming so that, on top of the mechanical sieving the fine fibers already do, electrostatic attraction pulls even smaller particles out of the air. That charge is what lets a thin meltblown layer reach N95 or FFP2 efficiency. Basis weight on this line ranges from light 10 g/m² facing layers up to 100 g/m² filter media, set by the ratio of pump output to collector speed.

Control and operation

The Control & HMI ties the line together. It holds every barrel and die zone to its setpoint through the Zone Temperature Controller modules, coordinates the screw, pump, collector and blower speeds through the Variable Frequency Drive drives, and runs the whole sequence from a saved recipe on the Operator HMI. An operator selects a product, the line heats up, purges, and comes to steady state; from there a single line can run for hours producing the same web. The hot die and the high-velocity air make guarding essential, so the Frame & Guarding carries interlocked panels and emergency stops around the forming zone.