(143c) Semi-Continuous Processing to Improve Safety and Quality

Challenges exist for processing viscous products that are classified as flammable due to high solvent content. This paper will focus on the processing options for mixing a highly filled shear thinning base material with a low viscosity flammable solvent followed by direct filling into final packaging.

This process can be accomplished using a change can batch mixer, but with significant drawbacks. Injecting hazardous and/or flammable materials through a hand held cartridge device into a pressurized vessel, such as a change can mixer, has potential for operator exposure and relies on personal protective equipment for protection. Another drawback is that batch processing results in a large quantity of work in progress (WIP) material with potential for failure of an entire batch leading to high scrap costs. To avoid these problems an alternate process was sought out to allow for in process adjustments to hit quality targets while minimizing scrap and improving safety.

Multiple solutions were considered. Use of a continuous mixing unit such as a twin screw extruder or pin mixer was examined. Although the mixing in these units was sufficient and provided higher processing rates, material properties were not easily adjusted. A semi-continuous option utilizing a series of static mixers fed through volume controlled feed units with direct filling into the final packaging was then explored. Several potential hurdles were overcome through multiple trials demonstrating the ability to use this process scheme to achieve our processing goals.

By using the semi-continuous process scheme it was possible to reduce the WIP material by 70% compared to the batch change can mixer. Quality was improved by the ability for in-process testing and process productivity increased. Potential chemical exposure for operators was reduced through an upgraded design of the feed systems.