12 Detailed Methods to Reduce the Resistance of Melt-Blown Fabric Summarized by Senior Technicians

Maintaining the working efficiency of melt-blowing machines and minimizing the resistance of melt-blown fabric have become new issues that melt-blown fabric factories need to address currently. For example, for a 25g/m² melt-blowing fabric, it is ideal to control the single-layer resistance below 60Pa and the double-layer resistance below 120Pa at a flow rate of 85L/min; and control the single-layer resistance between 60-70Pa and the double-layer resistance below 150Pa at a flow rate of 95L/min.

However, achieving a balance between maintaining efficiency and reducing resistance is a significant test of the skill level of machine adjustment technicians. The following are 12 practical tips shared by an experienced machine adjustment technician, which factory owners of melt-blown fabric plants can refer to as appropriate.

1.Reduce the rotation speed of the main machine and decrease the output of the metering pump

To control the reduction of metering, you need to record data carefully and conduct debugging patiently. Suppose your melt-blowing machine has a width of 1600mm, and it is generally slit into 9 rolls with a width of 175mm each (for customers who use other widths, the calculation method can be deduced similarly).

For instance, for a melt-blown fabric with a basis weight of 25g/m², it is essential to keep the basis weight of your sample (a 100cm² sample, approximately a circular piece of fabric with a diameter of 11.3cm, as shown in the figure above) between 0.25g and 0.28g. Assume the melt-blown fabric we intend to produce has a sample basis weight within this range, and use a basis weight tester to measure the weight of a single sample. Record the data, mark the 9 rolls from 1 to 9, and then place all the samples from rolls 1 to 9 on the basis weight tester to get the total weight.

Take an example: Suppose Roll 1 weighs 0.27g, Roll 2 weighs 0.28g, Roll 3 weighs 0.27g, Roll 4 weighs 0.29g, Roll 5 weighs 0.26g, Roll 6 weighs 0.26g, Roll 7 weighs 0.28g, Roll 8 weighs 0.25g, and Roll 9 weighs 0.25g. Place all these original samples on the basis weight tester, calculate the total weight, and divide by 9. The average weight we get here is 0.268g. If the average weight calculated by dividing the total weight by 9 falls between 0.25g and 0.28g, it indicates that your metering weight is correct. Later, when adjusting the basis weight of each roll, take Roll 4 mentioned above as an example—it has a basis weight of 0.29g, which exceeds the required range. Adjust each roll individually, and remember this rule: increase the temperature for rolls with low basis weight, and decrease the temperature for rolls with high basis weight.

2.The completion of the above steps is to control your output. Since the weight of each roll varies, the test values will also differ—this step is to guide you to make adjustments within a controllable range. Increasing the fabric efficiency often means a higher basis weight, but this will also lead to increased resistance.

3.Increase the hot air flow rate and boost the hot air pressure.

4.The above factors basically help you control the fabric to achieve high filtration efficiency; next, we will tackle the most critical issue of resistance reduction.

5.Increase the DCD (Die-to-Collector Distance). For example, if your current DCD is 16cm, adjust it to 16.5cm, and so on. Record the data and make fine adjustments accordingly.

6.When the DCD changes, the air suction volume at the bottom of the mesh belt also needs to be adjusted—because polypropylene fibers are entangled into a web relying on their own heat. The shorter the DCD (closer distance), the higher the heat, so the air suction volume at the bottom of the mesh belt should be increased; the longer the DCD (farther distance), the air suction volume should be decreased.

Once the DCD is adjusted, control the air suction volume at the bottom of the mesh belt and make slight adjustments—avoid large-scale reductions. Record the data whenever an adjustment is made, and gradually optimize until reaching the best state. When the resistance decreases, the melt-blowing efficiency may drop; therefore, it is necessary to balance efficiency maintenance and resistance reduction within a controllable range.

7.Reduce the speed of the conveyor belt and the winding speed within a controllable range.

8.Control the hot air temperature to a level where no fiber fly (fluffing) occurs. If the DCD is shortened (distance becomes closer), the hot air temperature should be lowered.

9.The main factors affecting resistance are DCD and the basis weight of the fabric—focus on detailed adjustments in these two aspects. When the DCD changes, the relevant data also needs to be adjusted. If the efficiency decreases, increase the air flow rate and air temperature, and reduce the rotation speed of the main machine, and so on. The above content has covered these points in detail.

10.If the resistance decreases but the efficiency becomes low, you can increase the air flow rate and air pressure while reducing the rotation speed of the main machine. Keep the temperature of each zone of the die at a level that maintains the required basis weight. If the basis weight is insufficient, increase the temperature slightly (adjust the temperature of each zone moderately) to maintain the basis weight within the adjustable range.

11.There is no need to elaborate on electrostatic charging—basically, just ensure no sparking occurs.

12.Pay attention to replacing the filter screen every 2 hours; a filter screen used for an extended period will also affect the resistance.