Historical Controversy - Isotactic Polypropylene with Cr-Based Catalyst

3 Historical Controversy - Isotactic Polypropylene with Cr-Based Catalyst 

In order to clarify the historical events pertaining to the initial discovery of crystalline polypropylene, it is important to understand the original research of Hogan and Banks at Phillips Petroleum. The olefin polymerization research carried out by Hogan and Banks was initiated in late 1951, which was two years earlier than the developments of Ziegler and Natta [10]. As part of their research program at Philips Petroleum, Hogan and Banks examined the polymerization of numerous 1-olefins and mixtures of various 1 -olefins with their Cr-based catalyst. 

Consequently, the Phillips Petroleum scientists isolated crystalline polypropylene between October 9,1951 and April 16,1952. Although, initially, the United States Patent and Trademark Office awarded the composition of matter patent for isotactic polypropylene (prepared with a Ti-based catalyst composition) to Montecatini on February 6, 1973 (U.S. Patent 3,715,344), the Federal District Court of Delaware reversed the United States Patent and Trademark Office decision on January 11, 1980, and awarded the composition of matter patent to Phillips Petroleum based on the earlier research carried out by Hogan and Banks (See Chapter 3 of this book for additional details on the historical origins of polyethylene and polypropylene.) 

However, this historical record should not diminish the important contributions made by Natta and coworkers. The Cr-based isotactic polypropylene was produced in low yields and was not an attractive method for the commercial manufacture of isotactic polypropylene. But examination of the research records by the court clearly showed that the PhiUips scientists were the first group to prepare isotactic polypropylene, and correctly awarded the composition of matter patent to the proper owners. 

The research by Natta s group demonstrated that significantly higher yields of isotactic polypropylene could be produced with modified Ti-based catalysts, so that the commercial development of this new type of polymer could take place. Hence, the Phillips scientists were able to show that their research produced the first samples of isotactic polypropylene, while the Natta group research resulted in the rapid commercialization of isotactic polypropylene. 

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