Stress relief and size stabilization — heat setting of dedusting filter material process
Thefinishing process of needle punched nonwoven filter material for bag filtermainly includes singeing, calendering, dipping, heat setting, film covering, etc.
The semi-finished filter material after acupuncture has poor dimensional stability, low density, large breaking elongation and poor heat stability, so it needs to be heat shrinkable. The main purpose ofheat setting of filter materialis to eliminate the residual stress of needle felt and reduce the thermal shrinkage rate. The mechanism of heat setting is as follows: from the microscopic point of view, the forces between some macromolecular chains are destroyed, and the macromolecular chains establish new intermolecular forces at new positions; From the macro point of view, the fiber will be subject to stress relaxation and shrinkage setting (stable shape).
Heat setting is to make the internal and external temperature of the filter material consistent by means of heat transfer. At the same time, the cooling roller is used to make the filter material rapidly cool and set. The cooling roller uses the heat of the filter material to improve its surface finish. The process of heat setting is the process of heat absorption, balance and transfer in the filter material. The heat setting temperature must be above the glass transition temperature of the fiber and below the softening point temperature, which is generally about 30 ℃ higher than its use temperature. It is mainly divided into four processes: heating – heat penetration – molecular adjustment – cooling.
The heat setting link is generally combined with the dip rolling link, which is integrated in the same production line.
SFFILTECH adopts imported high temperature setting line. The tank chain conveying structure makes the cloth surface flat and evenly stressed. The cross air supply mode makes the heat conduction uniform, the temperature precision controlled, and the temperature deviation controlled within 1%. It ensures the dimensional stability of the filter material when it is used under working conditions, to avoid poor blowing effect caused by shrinkage, and even the “lock up” phenomenon, which makes the running resistance high and the operation difficult to replace the cloth bag.