ERJ staff report (PR)
Manchester, UK – Dow Chemical Co. is to establish a large-scale EPDM plant by 2016, which will employ new process technology developed by the company partly in response to automotive industry demand for expanded rubber sealing.
The project, which was highlighted by Dr Tim Clayfield, global technology leader at Dow Europe GmbH, at the recent IRC RubberCon conference in Manchester, builds on work at Dow to fast-track the selection of advanced ‘post-metallocene’ catalysts for the polymerisation of EPDM.
Post-metallocene catalysts can deliver highly customised polymer properties, particularly by optimising the chain-branching structures on the polymer chain. Unlike previous catalysis technologies, they incorporate high molecular weight macro monomers into the growing chain in a relatively easy-to-control process that keeps branching uniform and minimises any possibility of gelation.
“You can produce long chain branching with constrained geometry or metallocene type catalysts, but the process is not the most efficient,” said Clayfield. “The advantage is that you can make long chain branching much more comfortably.”
A particular target for the R&D project was a market request to produce an EPDM sponge product for the automotive industry, which was not possible with the previous polymerisation capabilities at Dow.
“This is one of the ways we are justifying a new plant,” said Clayfield. “If we didn’t have these increased capabilities it wouldn't make sense to build a new plant. We couldn't make enough long chain branches to do this, so that the polymer was just too linear and not elastic enough.”
The automotive product was required to have a very good integral skin surface for aesthetic reasons and exhibit very good elasticity. A more critical target, however, was to provide a material that processed easily on customer equipment.
“The real battle ground is mixing,” the Dow expert commented. “There is not an awful lot of differentiation with a black seal for customers. The real differentiator is productivity, which mean mixing and production of the seal, and well as consistency, which means lower scrap.”
Leveraging catalyst-screening technology used in the pharma industry, Dow researchers studied thousands of different variations of the molecule so see which catalysts and process conditions delivered the best results in terms of molecular weight, branching and co-monomer incorporation.
“We had to look at the molecules on paper before [taking the technology] to the pilot plant, which is very expensive,” explained Clayfield. “On a computer you can make hundreds in an hour but you do need to understand what the catalyst does. If that works we can then make hundreds of kilos of polymer to take to development partners for product prototyping.”
According to Clayfield, the R&D work yielded an EPDM product that mixed very well in prototyping tests and is expected to perform equally well when it goes out commercially. Because of the narrow molecular weight distribution, the curing was very fast and products had excellent surface quality, shape retention and bubble structure, he added.
“We have gone from a few prototypes to a commercial product quickly and are pleased that we can design products that meet customers’ needs in a very efficient way,” Clayfield concluded. “We will be leveraging this into a very large plant in 2016.”