Advances in polyethylene and polypropylene in the 1950s also helped establish these useful plastics as universal materials. Although ICI and DuPont were already producing high-pressure polyethylene for applications such as electric wire insulation, Germany's Karl Ziegler isolated a low-pressure crystalline polyethylene that seemed promising. Ziegler had begun work on ethylene polymerization in the 1930s at the Kaiser Wilhelm Institute for Coal Research in what was to become East Germany after the war, and he carried the work to completion on organometallic catalysis of polyethylene at the Max Planck Institute formed in Mu"lheim in West Germany after the war. Hercules started up the first low-pressure crystalline polyethylene unit in the U.S. in 1957 based on a license from Ziegler's patents; Koppers and Union Carbide soon followed.

Ziegler's was not the only new process for producing polyethylene.
Phillips Petroleum had perfected its own process to make crystalline polyethylene. By the time the Hercules plant was operating, Grace, Celanese, and Allied Chemical were also producing polyethylene using Phillips' process. Ultimately, 15 U.S. companies became polyethylene producers.

Giulio Natta, a chemical engineer working at the Milan Polytechnic Institute, in 1954 discovered another polyolefin- polypropylene-which had a melting point of 170 C. The melting point of Ziegler's polyethylene was 145 C. Financed largely by Italian chemical maker Montecatini, Natta had pursued an extension of Ziegler's catalysis technology allowing the use of propylene instead of ethylene. For their work, Natta and Ziegler shared the 1963 Nobel Prize in Chemistry.

polypropylene was particularly suited for molded objects such as housewares, textile fibers, and film. Whereas 17 U.S. producers eventually made polypropylene, Hercules became the world's first commercial crystalline polypropylene producer in 1957 and for many years was the leading producer.

Rapid growth and the resulting corporate restructuring has affected many of the chemical industry's products and their manufacturers. The disposition of Hercules' original polypropylene unit over the past 40 years is a paradigm for many other chemical businesses and is proof of corporate ingenuity if nothing else.

Hercules started with about 10 million lb of annual polypropylene capacity in 1957. In 1983, Hercules formed a joint venture called
Himont with Italy's Montedison. The venture then had 2.5 billion lb of annual capacity and $750 million in sales. The partners sold a 22% interest in Himont to the public in 1987, and later that year Hercules sold its remaining interest to Montedison. Himont's 1987 sales exceeded $981 million and its annual capacity approached 3 billion lb.

By 1990, Montedison had bought the outstanding public shares of Himont-a company that then had annual sales nearing $2 billion and polypropylene capacity of almost 4 billion lb. Montedison made Himont into another of the many subsidiaries that the byzantine company controlled. In 1995, Montedison merged Himont into a joint venture with Shell Chemical's polypropylene business to form Montell, creating a producer with more than $3 billion in annual sales and more than 7 billion lb of polypropylene capacity. And just last year, Shell worked out an agreement to buy out Montedison for $2 billion. Montell now has nearly 8 billion lb of annual polypropylene capacity and sales approaching $4 billion per year.

Propylene polymerization processes have undergone a number of revolutionary changes since the first processes for the production of crystalline polypropylene (PP) were commercialized in 1957 by Montecatini in Italy and Hercules in the United States. These first processes were based on Natta's discovery in 1954 that a Ziegler catalyst could be used to produce highly isotactic polypropylene. The stereoregular, crystalline polymers produced by this technology had sufficiently attractive economic and property performance that they became significant commercial thermoplastics in a remarkably short period. Consequently, Ziegler and Natta were awarded the Nobel Prize in Chemistry in 1963.

Other technologies invented during the same period, were incapable of achieving commercially viable performance. The tremendous amount of activity in olefin polymerization at this time led to a massive patent interference in the United States, and the award of a U.S. Patent to Phillips for the composition of matter of crystalline polypropylene. Improvements to the basic Ziegler-Natta catalysts made at Solvay increased the activity and stereoregularity of these catalyst systems, extending their commercial application. In most cases, however, supported high yield catalyst systems, invented by Montedison and Mitsui Petrochemical, are used in plants that have been constructed since the early 1980s . The superior performance of these systems allows the use of simplified processes with dramatic reductions in capital and operating costs. This revolution in the economics of polypropylene production spurred an increase in worldwide capacity in the 1980s. Worldwide production of propylene polymers was 14,381,000 t/yr in 1993, an annual increase of 4.7% from 7,147,000 t/yr in 1978.