Recycling solutions are probably the most sought approach to moving from linear to a circular and more sustainable solution. However, polymer modification by additives and how these can be integrated in the catalyst and process development, also offers additional opportunities to be pursued.

The use of additives through the combination of a specific substance(s) and polymers (e.g., polyethylene and polypropylene) helps to enhance or even create new polymer properties. Figure 1 shows how broad the additive role or function spans.

Traditionally the additives are mixed with polymer powder between the reactor and the extruder or added separately to the extruder. In the extruder, shear/mixing at elevated temperatures takes place, targetting homogeneous pelletized products (Figure 2). It is well known that certain additives are poorly dispersed under this process.

Alternative approaches to this conventional additivation have been proposed in the 80s, with the additive being added earlier in the polymerization stage, which is known as in-situ additivation.

The in-situ method should not change the additive function (stabilization, nucleating effect, etc.). The benefit seems to come from the better additive distribution in the polymer matrix and, consequently, less additive is required in comparison to the conventional additivation. In some cases, homogeneous dispersion improves the thermal, mechanical, or optical properties of the polymer, boosting the polymer’s performance.

Norner has explored different in-situ additivation methods, using our bench scale reactors, analytical and mechanical evaluation and small-scale conversion pilots. In-situ stabilization and nucleation have been proven beneficial to the polymer properties, as published in the 2018 edition of Norner News. Graph 1 shows another example of the effect of technology with in-situ additivation for nucleating agents in polypropylene.

At the optimum level, less additive means higher stiffness to the polymer, as was observed in this Norner internal development. Such results require consistent experimental work for the optimization of polymerization conditions and the catalyst–nucleating agent system, as the catalyst is very sensitive to non-typical components in the polymerization medium (Graph 2).

Ideally, a drop-in solution would be a significant benefit, but a careful investigation is required to learn the impacts on the polymerization process when moving to the in-situ technology.

Recently, Norner entered a partnership with the company Xplore, creating an integrated workflow for industrial catalyst and polymer development services. The partnership extends opportunities for accessing high throughput polymerization at Xplore, which enables a fast and reliable screening over a large number of polymerization parameters and levels, which can be relevant for the evaluation of in-situ additivation.

Therefore, opportunities and challenges are present, and Norner can offer a suitable development route, providing a full support package for companies who consider installing in-situ technology.

Opportunities and challenges with In-Situ additivation

Pushing in-situ to the extreme, a more environmentally friendly process with cost savings (less electricity and additives) can be achieved if the plant extruder can be fully omitted.

Process modifications for in-situ required in some technologies.

Mapping and optimization of in-situ additive on catalyst performance and polymerization process.

New areas for development (additive, catalysis, process technologies).

New or improved polymer applications (based on enhanced mechanical and/or optical properties.)

Norner capabilities to support the technology implementations

FTO studies on selected technologies.

Tuning/optimization of catalyst and nucleation systems.

Cost comparisons to clients existing (traditional) nucleation systems.

Design and engineering of modified feed/dosing systems.

Optimized recipes/formulations.

Polymer grade performance testing.

Mapping of benefits for the polymer converter.

For further information please contact:

Cesar Barbosa

Senior Researcher

cesar.barbosa@norner.no

Lars Evensen

Vice President Polymer Industry BU

lars.evensen@norner.no