Melt blown processing of conventional and metallocene propylene polymers

Melt blowing is a process to produce fine fibered webs. Polypropylene is the major polymer used in this process. Metallocene polypropylene manufactured using the single site catalyst technology is the recent addition to the polypropylene family. Although this new polymer promises enhanced properties, there are questions unanswered about its processability in melt blowing. This research was an effort to understand the complex process of melt blowing of metallocene polypropylene by comparing it with conventional zeigler-natta catalyst propylene polymers.

The experiment was carried out in two phases. In the first phase, high melt flow rate (>1000) resins of conventional and metallocene polypropylenes were melt blown. The webs were then characterized for their structural and mechanical properties. Based on these results, medium range melt flow rate (<900) conventional and metallocene polypropylenes were melt blown and characterized in the second phase. A detailed statistical analysis was carried out on the results to understand and optimize the process conditions for melt blowing of different melt flow rate conventional and metallocene polypropylenes.

The study showed that processing of metallocene polypropylene could be carried out successfully on conventional melt blowing equipment. The results showed that metallocene polypropylene performed better than the conventional polypropylene especially in the high melt flow rate range. Metallocene polypropylene exhibits a broader processing window and can be processed at lower processing temperatures and air flow rates. This understanding can lead to savings in energy and in processing of polypropylene melt blown webs with better properties.