The Competence in Dust Less Blends
As there are a wide range of additives used in the polyolefin industry in general, it is impossible to encounter all kinds of physical forms and properties. For example, the melting points of additives range from liquids to a low melting point solids to medium melting products and eventually to non-melting additives. Some of these physical forms can be difficult to handle and feed simply because of their melting points, or because of their powdery, dusty nature.
In the case of low melting point materials, there are many problems associated with using the powder or even the granular form. These problems include compaction during storage and transport, fusion/clumping if too high temperatures are encountered during storage and transport, sticking problems if any heat is generated during its handling (e. g. additive pre-mixing), sticking and feeding problems due to poorly insulated feed hoppers and even to the necessity of melting such additives to facilitate handling and dosing. When such products are used as part of an DLB composition, the above mentioned problems are significantly minimized due to a much reduced surface area/volume ratio, better flow characteristics and the presence of other, higher melting point, additives. This leads to increased confidence in the storage stability and 'usability' of such low melting additives.
If liquid products are added to the polymer then it is quite feasible that these could form part of an DLB, although there is clearly a maximum concentration limit. In such a situation, the requirement for separate handling, heating and feeding systems for liquids (or very low melting) products can be avoided. This woult result in lower capital investment, less manpower to operate the system and reduced energy costs.
Because of the precise and homogeneous level of each component in a DLB, the amount of additive analysis needed from a quality control perspective can be reduced. This is because the ratio of additives is constant (within the errors of the analytical instruments) hence it is only necessary to check the level of one component, the easiest one, and the level of the others is automatically known.
Depending upon exactly how additives are handle from the raw material storage to the additive feeder, one strong benefit of the accurate, homogenous nature of DLB's can be realized. In many polyolefin plants additives are manually transported to a pre-mixing unit of some kind, then the correct numer ob bags/drums of each additive are introduced into the mixer. There is a real potential for human error in this kind of operation as, for example, the additives, all of which can be overcome if they can be introduced as part of an DLB package. Today, many non-melting additives are successfully used as part of a 'fully formulated' DLB by polyolefin producers.