The Competence in Dust Less Blends
There are quite a number of benefits associated directly with the fact that a No Dust Blend is a composition of several additives in one pellet, all of which contribute towards reduced costs. Examples of this are typically less storage requirements than either powder or master-batch products, logistical benefist due to buying one single product rather than several smaller volume ones, reduced administration and purchasing efforts and having a single contact supplier in the case of any problems which may arise.
There is an enormous scope to really contribute towards reduced operation costs (hence productivity) by simplifying the process of handling and feeding powder or granular additives from the moment they enter a plant until the moment they leave the plant as part of a polymer formulation.
Basically the additives are transported in some way from the raw materials warehouse to the plant. At this point they are introduced into a mixer and mixed together with polypropylene from the reactor to produce something ling a 50 % 'masterfluff' concentration. The mixers used vary from very low shear long mixing times, to higher shear shorter mixing times. Clearly, with higher shear mixers, low melting point additives could prove a problem to handle.
The 'masterfluff' is then fed into a separate hopper, where it can either be further fed into a final 'compound' hopper together with the polypropylene, or it is used to feed directly into the extruder. Furthermore, it is standard for polymer plants handling additives in this way, to have two or more of these mixing units per production train.
If DLB's are used then the whole necessity for handling and transporting powders, as well as the requirements to produce a masterfluff, disappears. It is immediately obvious that powders/dusty products are no longer handled and that only one additive hat to be transported from the warehouse to the plant. Secondly, the whole loading of the mixer, the pre-mixing step and subsequent handling of the masterfluff is eliminated. Both of these elements will significantly contribute to a minimization of the risk of polymer quality problems arising from human error.
The benefits of making the conversion from masterfluff to DLB are that less capital investment is necessary (if it is a new plant), less maintenance of equipment is required, lower energy costs and the potential to reduce manpower. Further to these immediate benefits there are a couple of less apparent ones, for example, when making masterfluff the composition of the additives is never completely homogeneous. Also when transporting masterfluff from the mixer to the hoppers and eventually the extruder, there will be changes in composition simply due to particle size and specific gravity differences between different additives and also the polymer.