In the production process of meltblown non-woven fabrics, because the parameter ratio of temperature, air pressure, mold, speed and other aspects are involved, continuous running-in and debugging are required to achieve the best results. The following is the experience summarized in the actual production process for your reference:
1: Tuning process
1. Under the condition of higher temperature and wind pressure, make the cloth softer;
2. Slowly lower the die temperature and the hot air temperature in turn until the cloth just looks a little hard;
3. Record the die temperature and screw temperature at this time;
4. Adjust the wind pressure, the amount of melt extrusion, and the distance of the net to make the cloth softer;
5. Adjust the winding speed to achieve full traction effect;
6. According to the speed of rewinding, the electret usually needs to add two electrets, the static voltage is 40kv-60kv, and the distance between the electret rods is 5-7 cm, and the net rewinding speed is slow plus one static electricity. You can choose to add positive You can also choose to add negative electricity, which can be determined by experiment.
2: Tuning initial parameter setting
1. Screw temperature: set 190 degrees, 230 degrees, 230 degrees, ..., 230 degrees, 270 degrees (the material of 1500 melt index does not exceed 270 degrees, and it can be 260 degrees);
2. Die temperature: 252 degrees, 252 degrees,..., 252 degrees (generally 240 degrees -255 degrees);
3. Quick screen changer, metering pump, die filter screen: 240 degrees;
4. Heating pot temperature: 300 degrees, hot air temperature: 240 degrees;
5. Wind pressure: 0.2-0.5MPa (generally low temperature PP materials, the wind pressure can be selected a little lower, medium and high temperature materials, the melting index of about 1300 materials, the wind pressure can be larger);
6. Retracting distance: 15-19 cm;
7. The size of the tuyere is the same as the distance from the tip of the spinneret to the plane of the wind knife, 1-2mm;
8. The screw speed is moderate or small (the wind pressure is small, the extrusion volume can be small, and the wind pressure is large, the extrusion volume can be larger).
Three: Handling of abnormal conditions
1. If the cloth is still not soft at the recommended relatively high temperature, there may be a problem with temperature sensing or temperature control, so directly continue to increase the temperature until the cloth is in a soft state;
2. If the wind pressure is below 0.2Mpa and the die temperature is near or below 210°C, there will be a phenomenon of flying. The melt finger of the meltblown PP material may be abnormal, or the temperature induction may be abnormal, the wind pressure display is abnormal, or the air duct tuyere size If the angle is abnormal, you need to contact the equipment manufacturer or raw material manufacturer to eliminate the abnormality;
3. It is recommended to use low temperature materials for large equipment, and medium and high temperature materials for small equipment;
4. Generally, when the temperature is very high, the cloth is still not soft, or it starts to become brittle, and then the temperature is further increased, and the cloth starts to become soft. Generally speaking, there is a problem with the equipment itself. It is recommended to contact the equipment manufacturer, or the material is of serious quality problem;
5. The addition of electret masterbatch generally needs to be matched by adjusting appropriate process parameters. Different electret masterbatches have different corresponding process parameters, and can be adjusted to the best state according to this rapid adjustment process. Compare performance again;
6. The greater the amount of electret masterbatch added, the better the electrostatic effect, but the greater the impact on the fabric, it needs to be balanced, and the premise is to make the fabric well.
Four: Application case (temperature setting)
1. Screw temperature: 190 degrees, 230 degrees, 230 degrees,..., 230 degrees, 260 degrees;
2. Die temperature: 240 degrees, 240 degrees, ..., 240 degrees;
3. Quick screen changer, metering pump, die filter: 245 degrees;
4. Heating pot temperature: 300 degrees, hot air temperature: 220 degrees.
Fibers are easily oxidized in the air, especially at relatively high temperatures. Therefore, in general, the temperature of the die and the hot air should be lower, and the temperature of the screw should be higher. At the same time, the filter position and the temperature need to be higher to reduce The frequency of plugging the die.
Five: Explanation about electrostatic attenuation
To improve the efficiency of air filtration of meltblown cloth, it is also necessary to pass electret treatment and add electret master particles to improve its electrostatic adsorption force and more effectively filter the sub-micron particles in the gas carrier.
1. After the meltblown cloth is treated by electret, besides the electret masterbatch can be charged with static electricity, the meltblown PP material can also be charged with static electricity. The static electricity on the electret masterbatch with a small amount of addition has a general contribution to the filtration efficiency. In terms of about 10-20%, and this static electricity is relatively stable, under suitable storage conditions, the attenuation is very slow, and the melt blown PP material can also carry a large amount of static electricity, which can contribute a very large filter efficiency improvement. But the decay is also very fast;
2. The decrease in filtration efficiency is not equivalent to the attenuation of electret masterbatch static electricity, but the static attenuation of melt-blown PP may cause the filtration efficiency to drop quickly;
3. The cloth made under the conditions of relatively high die temperature and hot air temperature looks soft, but its toughness is insufficient. As time goes by, the cloth will become brittle and cause a drop in filter efficiency;
Six: Debugging methods to improve filtration efficiency
1. If you want to make a cloth with stable filtration efficiency, first of all, without adding electret masterbatch and electret treatment, the basic physical filtration efficiency of the melt blown cloth is required to be higher. On this basis, you can Add electret masterbatch without electret treatment to test the difference in filtration efficiency. A good electret masterbatch without electret treatment can still pass the static electricity generated during the winding process, thereby improving the filtration efficiency of the meltblown cloth;
2. Generally speaking, the basic physical filtration efficiency of meltblown cloth needs to reach 60%-80%, and then through the addition of electret masterbatch and electret treatment, a relatively stable filtration efficiency can be achieved.
Here is a recommended nano-level super-dispersed electret masterbatch. ZJN101 is based on high-melt finger meltblown PP material. Through super rheological shearing technology, the electret masterbatch charge enhancer is used as an electret of about 100 nanometers. The morphology is dispersed in the matrix resin.