Raw material requirements for polypropylene chips
In the process of polypropylene spinning, different grades of raw materials are often used, and their spinnability will be greatly different.
For example, the service cycle of spinneret components, the productivity of broken wires and the uniformity of fibers are different, which is often caused by impurities in the resin.
Impurities in the resin can be divided into inorganic impurities and organic impurities, including inorganic impurities and organic impurities. Inorganic impurities include foreign impurities and impurities in the resin.
The former comes from the impurities brought into the production environment, storage, transportation and use of resin chips; The latter mainly comes from catalysts and various additives, such as color masterbatch, flame retardant masterbatch and so on.
Therefore, during the operation of Yanpeng's non-woven equipment, there are vacuum calciner and ultrasonic cleaning machine to continuously ensure the cleanness of spinneret filter screen. So as to ensure the quality of cloth.
Inorganic impurities contain titanium, aluminum, silicon, iron, sodium, etc. some people believe that sodium is the main component affecting the filtration performance.
Organic impurities may be some branched oligomerization high melting point foreign bodies with high molecular weight (more than 1 million), which is related to the crystal spots, fisheye or gel particles of resin index.
In the melt spinning process, a small part of the impurities with large particle size are filtered by the filter medium. Some impurities with small particle size can remain in the primary fiber through the gap of the filter medium.
PS: the difference between natural resin and synthetic resin.
Natural resin refers to the amorphous organic substances obtained from the secretions of animals and plants in nature, such as rosin, amber, shellac, etc.Synthetic resin refers to the resin product obtained by chemical synthesis of simple organic substances or chemical reaction of some natural products.
Excessive impurity content can easily lead to blockage of filter mesh in the spinning assembly, and melt pressure rises too fast, especially when the ash content is high and the gel particles are large and numerous.
Therefore, the filter screen of the melt filter should be frequently replaced, otherwise it is easy to cause melt pressure fluctuation, melt leakage, breakdown of the filter screen and shortening the service life of components. Therefore, the impurity content in polypropylene chips should be limited to 0.025% to ensure the continuous spinning process.
Because polypropylene does not contain hydrophilic groups in the molecule and the hydrolysis speed is slow, the moisture content of the chip is not high, as long as it does not affect the spinnability and does not produce bubbles in the forming.
However, due to the fast spinning speed of spunbonded process, the moisture content in the slice is required to be lower, generally within 0.05%.
This is also a problem that needs special attention in the non-woven production line.
