The effect of the fractionating screen are same, to separate the long fiber, medium fiber, short fiber through the different slot sizes of the screen.
Short fiber which length less than 120μm, it is the small fiber of the recycling process without good fibrillation effect and interlayer bonding force, it is dissociated state. so it can only be used as a filling layer of recycled paper to increase the weight and available rate.The total proportion of about 25 to 35%.
Medium fiber which length more than 120μm, less than 150μm, it is the fiber with specific strength, will be more clean after deep treatment (like hot dispersion system or light & heavy impurities cleaning system), so it can be used as the recycle paper top layer to improve the cleanliness and dyeing effect of the paper surface, also guarantee a certain degree of the bursting strength. The total proportion of about 35%.
Long fiber which length more than 150μm, less than 220μm, it is the fiber with best strength, but there will be more screening impurities remain in it, so it can be used as the bottom layer to increase the strength of the finished paper. The total proportion of about 40%.
Although they are from the same original stock, but by separating the different fibers by fractionating system, distributing them to different layers to achieve the purpose of improving the paper properties. This process is already mature in China, we also summed up a lot of relevant experience.