Production Process of Melt-Blown Non-woven Cloth

Understanding the production process of melt-blown non-woven cloth

The production process of melt-blown non-woven cloth generally involves feeding polymer resin chips, melting, extrusion, melting impurity filtration, metering pump accurate metering, spinning into a net, edge cutting, winding, and post-processing. The principle of melt-blown technology is to extrude polymer melt from the spinneret hole of the mold to form a fine melt stream. At the same time, the high-speed and high-temperature airflow on both sides of the spinneret hole blows and stretches the fine melt stream, refining it into long fibers with a fineness of only 1-5 microns. Then, these long fibers are broken into short fibers of about 45mm by the hot airflow. In order to prevent the short fibers from being blown away by hot air, a vacuum suction device (located under the solidification net) is set up to collect the ultra-fine fibers uniformly formed by the high-speed hot air stretching.

The performance of the polymer raw material for melt-blown non-woven cloth includes the rheological properties, ash content, molecular weight distribution, and so on. Among them, the rheological properties of the raw material are a very important index, usually expressed by melt flow rate (MFR). The greater the MFR, the better the melt flowability of the material, and vice versa. The lower the resin molecular weight, the higher the MFR, and the lower the melt viscosity, which is more suitable for the melt-blown process with large stretching difference. For polypropylene, MFR is required to be in the range of 400 to 1800 g/10 min.

Adjustable parameters in the production process of melt-blown non-woven cloth

In the production process of melt-blown non-woven cloth, the adjustable parameters mainly include:

• The extrusion output of the melt, when the temperature remains the same, if the extrusion output increases, the quantitative output of the melt-blown non-woven cloth increases, and the strength relatively increases (reduced after reaching the peak). It is linearly related to the increase of fiber diameter. Over-pressing leads to larger fiber diameter, reduced quantity and strength of roots, reduced bonding sites, resulting in concurrent filaments, so the relative strength of non-woven cloth decreases.

• The temperature of each section of the screw not only affects the spinning process but also affects the appearance, feel, and performance of the melt-blown non-woven cloth. When the temperature is too high, there will be a blocky polymer, more fabric defects, and more fiber fractures, resulting in "flying flowers". Improper temperature setting can cause nozzle blockage, nozzle wear, and equipment damage.

• The temperature of the stretching hot air, the temperature of the stretching hot air is generally expressed by the hot air speed (pressure), which directly affects the fineness of the melt-blown non-woven fiber. Under the same other parameters, as the hot air speed increases, the fiber becomes finer, the nodes between fibers increase, the force is more uniform, the strength increases, and the feel of the non-woven cloth becomes soft and smooth.
  

• The melt temperature, also known as the melt-blown die temperature, is closely related to the flowability of the melt. As the temperature increases, the melt's flowability improves, and the viscosity decreases, making the fibers thinner and more uniform. However, the lower the viscosity, the better. Too low viscosity will cause excessive stretching of the melt-blown non-woven cloth, and the fibers are prone to breakage, forming ultra-short and ultra-fine fibers that cannot be collected in the air.