With its proven static mixing technology, Sulzer offers cost-effective solutions for the in-line upgrading of polymer melts by admixing additives such as dyes, nucleating agents, lubricants, pigments, and stabilizers.
After polymerization, additives can be mixed into the polymer melt prior to pelletization, in order to upgrade the final product.
Sulzer has many years of experience in providing successful upgrading solutions for improved product quality and profitability of customers’ products and processes. Our extensive reference list includes examples of complex applications with regard to differences in viscosity, mixing ratio and homogeneity aspects.
Admixing of additives into high-viscosity products is performed in various hydraulic regimes, ranging from laminar to transitional and turbulent. The polymer additive mixing ratio defines the degree of mixing complexity. The Sulzer polymer upgrading technology is based on our proprietary static mixing equipment.
Plant configuration for admixing masterbatch into a main polymer stream
Admixing of low-viscosity additives in polymer melts
Many additives used in the polymer production industry are of low viscosity and are only partly soluble in the polymer melt. Normally, the homogeneity requirements are very high since the polymer is often pelletized immediately after the static mixer, and already small inhomogeneities may result in strand breaking.
Sulzer's SMX and SMX plus static mixers, together with Sulzer's vast experience in admixing low-viscosity additives into polymer melts, enable even viscosity differences of up to six orders of magnitude (106) to be handled, while achieving still excellent homogeneity at the end of the mixer.
Admixing of masterbatch into polymer melt
A common way to incorporate additives into polymer melt is to use masterbatches, that is, concentrates of additives in a polymer carrier.
In particular, solid additives (for example, pigments, fillers) cannot be admixed directly into a melt stream. In such cases, the masterbatch can be fed into the main polymer stream through a small side extruder.
CFD simulation of a Sulzer static mixer for compounding two polymers of similar viscosity
Blending / compounding of two polymers
When two different polymers have to be mixed together to form a compound, very often dynamic systems such as extruders are used.
Static mixers, however, show equally good results for compounding of different polymers, while having the advantage of low maintenance costs and spare requirements. For most compounding tasks, the required shear forces are not very high. Sulzer static mixers are therefore a true and cost-effective alternative in compounding your polymers.
Flow profile in a SMX static mixer compared to the laminar flow in an empty tube
Dispersing of non / partly soluble additives in polymer melts
Insoluble additives or high concentrations of only partly soluble additives can be perfectly dispersed with Sulzer static mixers.
Normally, these additives have a very low viscosity (for example, water, oils, and gasses). Examples are foaming agents, stripping agents, mineral oil, and stearates. The Sulzer mixer geometry along with Sulzer's special distribution devices have proven their efficiency for these applications with many industrial references.
Our experienced engineers will carefully design the mixer to reach the required shear force, in order to overcome the surface tension of the additive, and to achieve the required droplet size. Static mixers may therefore even be used to create stable emulsions and mini-emulsions for polymerization.
In addition, the elongational shear forces – in a properly designed static mixer – ensure optimum dispersion performance within the shortest possible installation length.
In order to enable stable sheet extrusion or stable pelletization with uniform granules, it is essential that the polymer melt stream is as homogeneous as possible prior to pelletization. This applies to composition, viscosity and temperature. Our SMX and SMX plus static mixers show optimally equalized gradients of viscosity, temperature and color. Even in existing plants, where space is limited, mixers of various geometries can be installed to provide the desired effect.
