At present, the most basic requirements for melt-blown cloth on the market are 90%, 95% or 99% of the filtering effect, as well as flexibility and strength, which are the most basic requirements. However, at present, many melt-blown cloth manufacturers are unable to meet these basic requirements, changing raw materials and imported moulds, and paying a lot of money to adjust the master of the machine, adjust the temperature, change the distance between the air knife and the spinneret, or add some electret masterbatch, and so on. The cloth that can be produced still has a lot of problems, either hardening overnight, flexibility, strength are gone, and with the addition of masterbatch, the filtering effect has not been improved at all, and some customers are anxious to cry, saying that they have done electrostatic electret treatment, and the same day it reached 95 kilowatts. The next day all electrostatic ions were gone, and the filtering effect became 80 + again!
Process requirements of melt blown cloth
The mood is understandable, but must not rush to seek medical treatment, must find out the problem point, as for the addition of softener, POE and other auxiliaries, there is still overnight no toughness, very brittle, this is caused by the secondary crystallization of modified polypropylene, for many reasons, most melt blown cloth are single-row spinneret, such as some position hole blockage, temperature is not enough, insufficient silking, abnormal process, uneven melt pressure will appear non-uniform gram weight. Softness and hardness are different. And the base material is not good, this can only be improved by changing the material or adding a toughening agent!
The air needed in the melt-blown cloth process is clean, and the equipment providing the gas source is the most economical and stable melt-blown gas source equipment. Many small production lines use air compressors, even if it is an "oil-free" air compressor, because of its special internal lubrication structure, there will be a small amount of oil mist ejected with the air flow, resulting in a peculiar smell in the melt blown cloth, reducing the filtration efficiency, and various tests are not up to standard. If the fan pressure is generally below 98Kpa, generally 60-80Kpa is enough, if the air compressor is used, the pressure is generally 5-8 kg, and when the melt blown cloth production line reaches the best state, the measured pressure of the die is 60-70KPA. Obviously, the air compressor pressure is too high, there is no need to pursue too high pressure, the best production line should be equipped with different air volume fans or air compressors, the air compressor pressure is higher than the fan pressure, but the air volume is far less than the fan. Therefore, the efficiency is much lower.
Increasing the hot air flow rate, increasing the hot air temperature and increasing the temperature of the die (die tip) can make the fiber finer, the winding nodes increase, the force of the fiber is uniform, and the strength increases, but it will decrease when it increases to a certain extent. Properly reducing the hot air flow rate or temperature, lowering the working temperature of the die (die tip) and lowering the ambient temperature (spinning environment temperature) can make the node slip path larger, the handle harder, the fiber thicker, the porosity increased, and the resistance low. The filtration efficiency is greatly reduced.
In addition, talk about the problem of electrostatic electret treatment, the masterbatch ratio is 2% to 3%, after drying, stir well, but also pay attention to the air humidity, the choice of high-voltage electrostatic generator must be a negative charge reaction, many friends in order to be cheap, buy low-power 120kv electrostatic electret generator, the real power is only 30~50kv, this electrostatic adsorption is very weak, about 2 days, static electricity is lost, the filtering effect is back to the origin.
After a simple replacement of fans, electrostatic electret treatment and other processes, not to ensure that the melt blown cloth up to 90, 95, but through this process can improve a certain amount of space on the basis of the original. For example, you are 40 before electrostatic electret treatment, 75 after electrostatic electret treatment, or 80 before treatment, 90 + or 95 + after treatment. If you want to achieve more than 95% of the best state index, every detail in the process can not be ignored. The whole process is not complex, an excellent combination of process parameters can greatly improve the physical indicators of the product, which needs to be explored on its own.
The above is the introduction of how to produce high-quality melt-blown cloth, if you want to know more about melt-blown nonwovens, please feel free to contact us.
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Post time: Jun-17-2022