experience share of meltblown cloth making
Overview of melt blown cloth equipment at present, there are many large and small production lines on the market, ranging from 300 to 3200mm wide, and the configuration is also very different. The main core components of melt blown cloth equipment are: extruder, mold, roots blower (or air compressor), electret equipment and other core components, such as screen changer, metering pump and other accessories also need to be equipped:
1. Extruder: according to the product width The extruder is from 50 / 30, 65 / 30, 75 / 30, 90 / 30, 105 / 30, 150 / 30 and other models. The small line is mainly 600mm type. The extruder is 65 / 30 single screw extruder. Generally, this type of Extruder mainly depends on the screw barrel. The barrel should be grooved to increase the feeding effect and plasticizing effect. The large line also needs to be grooved. Screw speed is moderate or slightly lower (small wind pressure, small extrusion amount, large wind pressure, large extrusion amount). Temperature equipment: not too high, small line temperature reference: 160-170 degrees in zone 1, 190-210 degrees in zone 2, 200-225 degrees in zone 3, 205-230 degrees in zone 4, 225-240 degrees in screen changer and metering pump.
2. Mold: the method of mold is also very many, mainly in hanger type, the core is in the selection of air duct, the mold requires uniform discharge. It is recommended to heat the new mould in a high temperature oven before use. In this way, it is not easy to block the mold during the test. Mold temperature 220-250 degrees.
3. Roots blower: at present, roots blower is mostly used, and air compressor can also be selected. The air volume should be ensured. Take 600mm small line as an example: if 22KW roots blower is to provide 0.08-0.1mpa continuously, it is not stable without air compressor, but mainly unstable. The temperature setting of the inlet and outlet is adjusted according to the distribution situation, and the temperature is generally set between 260-270 degrees. Heating pot temperature: 300-330 ℃. 1600mm large line: wind pressure: 0.2-0.5mpa. (generally, for low-temperature PP materials, the wind pressure can be smaller, and for medium and high-temperature PP materials and fusible finger materials around 1300, the wind pressure can be larger.).
4. Electret equipment: the key part of the electret equipment is the rotor, which cannot be broken down at 100000 volts. At present, there are not many electret devices in China. Normal start-up should be over 60000v. The effect of electrostatic adsorption is better.
5. The use of metering pump is more critical. The proportion between screw and metering pump shall be calculated to avoid excessive or insufficient feeding, and uneven backflow and cloth thickness. Melt blown method is a kind of method to produce fiber by blowing polymer melt with high temperature and high speed air flow to get rapid stretching. After the polymer chips are heated and pressurized into a molten state by a screw extruder, they reach the spinneret hole at the front of the nozzle through the melt distribution channel, and then they are refined by two converging high-speed and high-temperature air streams after extrusion. The refined fibers are cooled and solidified on the screen device to form the melt blown nonwovens.
7. According to the receiving speed, the electret can be added with two electrets. The static voltage is above 60kV, and the distance between the electret wire and the cloth surface is 5-7cm, which can be determined by the test.
Adjust the machine to deal with abnormal conditions 1. If the cloth is still not soft at the recommended higher temperature, there may be problems with temperature sensing, or there is a problem with temperature control temperature, directly continue to increase the temperature until the cloth is out of the soft state. 2. If the air pressure is below 0.2MPa and the die head temperature is near or below 210 degrees, there is flying phenomenon. It is possible that the melt finger of melt blown PP material is abnormal, or the temperature induction is abnormal, the air pressure display is abnormal, or the size and angle of the air duct tuyere are abnormal. It is necessary to contact the equipment factory 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 it is added to a very high temperature, the cloth is still not soft or brittle, and then the temperature is further increased, and the cloth starts to soften. Generally speaking, there is a problem with the equipment itself. It is recommended to contact the equipment manufacturer, or there is a serious quality problem with the material. 5. The addition of electret masterbatch generally needs to be matched by adjusting the appropriate process parameters. Different electret masterbatch has different corresponding process parameters, which can be adjusted to the best state according to this rapid adjustment process, and then the performance can be compared. 6. The greater the amount of electret masterbatch is, the better the electrostatic effect is, but the greater the impact on the fabric, the balance needs to be achieved, provided that the fabric is well done. Note on electrostatic attenuation 1. After the melt blown cloth is treated by electret, in addition to the electret masterbatch, the melt blown PP material can also be electrostatic. The contribution of electrostatic on the little amount of electret masterbatch to the filtration efficiency is generally about 10-20%, and the electrostatic is relatively stable. Under the appropriate storage conditions, the attenuation is very slow, and the melt blown PP material can also be electrostatic A large amount of static electricity can contribute to a very large improvement of filtration efficiency, but the attenuation is also very fast. 2. The decrease of filtration efficiency is not the same as the electrostatic attenuation of electret masterbatch, but the electrostatic attenuation of melt blown PP may make the filtration efficiency decrease rapidly. 3. Under the condition of high die temperature and hot air temperature, the cloth looks soft, but its toughness is not enough. With the extension of time, the cloth will become brittle and lead to the decrease of filtration efficiency. 4. If you want to make a cloth with stable filtering effect, you should first add an electret