Exxon Chemical Co. of Houston recently claimed two industry firsts because of advances it has made in metallocene catalyst technologies: Exxon said at a Sept. 8 news conference in New York that it is the first company to produce commercial quantities of high-purity, isotactic propylene polymers.
Five days later in Chicago, the company proclaimed itself the first to produce commercial quantities of linear low density polyethylene made with metallocene catalyst technology. The company is designating these new resins generic-ally as mLLDPE.
With both claims, Exxon introduced new lines of products under new trade names.
Further, Exxon said it expects both developments to significantly change the commodity thermoplastics olefins business.
The firm timed the announcements to separate the developments, but keeping them separate almost is impossible because of their common tie - metallocene catalyst technology. Without that technology, neither line of new products would be possible.
Exxon only reluctantly called its development for propylene polymers ``polypropylene.''
That was an effort to put distance between its product, which Exxon says contains less than 0.5 percent atactic polypropylene, and conventional polypropylene, which typically contains 10percent atactic polypropylene.
Atactic polypropylene is a contaminant that negatively affects polymer performance, according to Exxon.
In a telephone interview Sept. 11, Richard Grabham, general manager for Exxon's Polypropylene Americas unit, said the high degree of purity of Exxon's new resins provide improved performance characteristics in a variety of applications.
In some cases, the new propylene polymers will replace existing PP resins, and, in other cases, the new polymers will be counterparts to PP resins, said Grabham.
The metallocene catalysts allow Exxon to make polymers with narrow molecular weight distributions and more uniform compositional distribution, he said.
Those features make the processing of the new resins easier, and allow them to retain strength with finer spun-bonded fibers and at smaller extruded or molded gauges, Grabham said.
Also, he said the metallocene technology allows Exxon to make new random copolymers, including copolymers that combine hexene with propylene backbones. Such products are expected to have better performance characteristics as barriers while being optically clearer and stronger than existing copolymers, which typically have ethylene combined with propylene backbones.
Exxon has produced nearly 2 million pounds of isotactic PP in the first quarter of this year through a full-scale, five-day production run in a reactor at Baytown, Texas.
It targeted the unique resins at the spun-bond segments of markets for nonwoven products.
While the isotactic propylene polymers are directed at nonwovens markets, Greg McPike, worldwide vice president for Exxon's Exxpol Venture, said those products will be the vanguard of a new family of polymers. The Exxpol Venture is Exxon's internal business unit that directs the research into and product commercialization of metallocene catalyst technology.
Exxon will introduce three grades of these propylene polymers under the Achieve trade name by the end of this year.
Exxon is one of the largest producers of conventional PP resins in the world.
Exxon said it accomplished its development in propylene polymers with the help of Hoechst AG of Frankfurt, Germany. Exxon and Hoechst joined forces in June 1994 to develop and license metallocene catalyst technologies for propylene products while independently pursuing the production and marketing of resins made with those catalysts.
In its second announcement Exxon said its mLLDPE resins are large-volume, general-purpose products that offer premium performance and a great degree of flexibility in applications at prices competitive with conventional LLDPE resins.
Gregory L. McPike, vice president of Exxon's Exxpol Venture, said Exxon has the capacity to produce more than 1 billion pounds of mLLDPE resins a year at its Mont Belvieu, Texas, plant, and, with its recently patented supercondensing-mode technology, McPike said he believes Exxon can nearly double that capacity.
The company is marketing its mLLDPE resins them under the Exceed trade name.
Initially, Exxon is targeting its Exceed resins at blown film and cast film applications, such as stretch film, trash bag, can liner, and heavy-duty shipping sacks, and flexible packaging, McPike said.
Films made with the resins have demonstrated a 50 percent increase in puncture resistance and a 40 percent increase in tensile strength, he said. Exxon's customers already have processed more than 30 million pounds of the resins, he noted.
Exxon later expects to pursue applications for monolayer and multilayer films.
While Exxon now is making the mLLDPE resins only at the Texas facility, McPike said it intends to use the technology at other plants around the world.