Polycarbonate may gain increased share of engineering plastics market

15 April 2011 15:47  [Source: ICB]

Radical changes in production methods promise lower costs and emissions, and more efficient feedstock use


PC could gain an even larger share of the engineering plastics market

Since its first introduction to the market as a specialty engineering polymer more than 50 years ago, polycarbonate (PC) has gradually become commoditized, enabling worldwide demand to rise from a few tens of thousands of tonnes annually to a current level of more than 3m tonnes.

This commoditization has recently accelerated, as a growing proportion of aromatic PC production capacity has been based on a less expensive and more environmentally-friendly process, which has driven down capital and energy costs. However PC, which has been selling at €2,500-3,000/tonne ($3,571-4,286/tonne) over the past few years, seems likely to become even less expensive in the longer term as a result of a radical change in its production process. This involves the co-polymerization of carbon dioxide (CO2) and propylene oxide (PO) or other epoxides through catalytic reaction into aliphatic PC.

As a result, PC could gain an even larger share of the global engineering plastics market, currently around 9m tonnes/year. On the other hand, the use of sophisticated catalysts in the CO2 process could also provide opportunities for tapping into a higher end of the market, based on customized aliphatic PC grades.

The CO2 route to PC has already been commercialized on a limited scale in China and is at present being developed in Europe and North America in the expectation that it will ultimately become a major source of the polymer. Almost since PC's first entry into the market, scientists have been seeking a substitute to what is still the predominant process for aromatic PC production because of its relatively high cost, use of hazardous chemicals and large amounts of waste. It comprises the interfacial reaction of phosgene, a highly toxic gas, with bisphenol A (BPA), with the use of methylene chloride as a solvent, which is also regarded as very hazardous.

Over the past 10 years the main alternative to the interfacial technology has been the melt process, in which BPA is reacted with diphenyl carbonate (DPC) in a molten state without the need for a solvent. The main melt technology has been jointly developed byAsahi Kasei of Japan andChi Mei Corp. of Taiwan. They claim it is safer, less wasteful, cleaner and less energy intensive than the interfacial process.

Over the past five years, melt-process plants have accounted for most of the new PC capacity, including a 260,000 tonne/year facility which was due to be opened in March at the new Saudi Kayan petrochemicals complex in Saudi Arabia. Around 80% of melt-process plants are located in Asia and the Middle East. By 2013 the melt technology should account for around 20% of global PC capacity, compared with 12% in 2005, according to figures from UK-headquartered Shell Chemicals.

Shell is endeavouring to strengthen its own position in the PC supply chain, to which it already provides bulk chemicals such as phenol, by offering DPC made through a relatively simple proprietary process comprising the multi-stage reaction of CO2, phenol and either PO or ethylene oxide (EO).

"As PC has transitioned from a [specialty] polymer to more of a commodity, its relevance to Shell Chemicals has increased," says Garo Vaporciyan, principal scientist at Shell Global Solutions.

Although Shell has spent more than 10 years developing its DPC technology, it has still not clinched a supply deal for the chemical.

"We are still considering options for how it could be applied commercially," says a Shell spokesperson. "A number of parties have expressed interest in the technology."

The Shell technology should offer an easy option for PC producers wanting to eliminate phosgene entirely from the PC process, which is an opportunity offered by the melt process. Several PC producers applying the melt technology use phosgene to synthesize DPC, according to Shell.

The consultancyNexant ChemSystems has reported that some PC producers have set up melt-process units adjacent to their interfacial plants to take advantage of the availability of phosgene for making DPC.

One reason for the lower costs of the melt process is its use of CO2 as a starting material. The reliance on CO2 is also a major contributor in the relatively low cost of the direct CO2 route. This technology dates back to research in Japan in the 1960s on the use of catalysts for the copolymerization of CO2 and PO. However, the further development of the concept was held back by the lack of suitable catalysts.

Advances in the development of catalysts over the past decade through the application of new imaging technologies in microscopy and spectrometry has made the process in aliphatic PC production much more viable. China, which has been active in research and development (R&D) into catalysts for CO2-based PCs, has been using rare earths as a source of catalysis in processes that have now been commercialized.

Tianguan Group, Nanyang, Henan province, an agribusiness and biofuels producer that has been designated by the Chinese government as a new energy and high-technology development center, is making biodegradable PC plastics with rare earth catalysts. With around 500,000 tonnes/year of bioethanol capacity, it has plentiful supplies of CO2 as a byproduct.

Germany's Bayer MaterialScience (BMS), which is a global leader in PC production, has started R&D work on the CO2 route through a development alliance with RWE Power AG and RWTH Aachen University, backed by a €4.5m grant from the German government.

It has just started up a pilot plant in Leverkusen, Germany, for the production of polyether polycarbonate polyols (PPP) using CO2 from RWE Power's lignite-fueled plant near Cologne. The power plant's gas emissions scrubbing unit has been fitted with liquefaction equipment for the separation of the CO2. The PPPs will be processed into polyurethanes (PUs) for the production of insulation foams.

Novomer, a start-up in Boston, Massachusetts, US, is probably making most headway in the development of CO2-derived polymers at the moment, through the exploitation of technology in cobalt-based catalysts licensed from Cornell University. The company has been allocated $20m in grants from the US Department of Energy to help finance the scaling-up of a pilot plant with the assistance of Albemarle and Eastman Kodak, with CO2 from bioethanol production being supplied by Praxair.

Novomer's catalyst system enables the reaction of CO2 with PO and EO to produce PC polymers with a broad range of material characteristics from low to high molecular weights, suitable for coatings and adhesives through to packaging. It has an alliance in the development of coatings resins based on PC polyols with the resins business of Netherlands-based DSM, which is a shareholder in Novomer. The Dutch company is already sending out samples to prospective customers.

"We are first targeting the can and coil coating markets, which will enable us to build up quickly economies of scale in the production of the PC resins," says Jan Besamusca, innovation director at DSM Neoresins.

"The benefits of this technology are its sustainability with a low carbon footprint, the low cost and the performance of PC in respect of weather, chemical and UV (ultraviolet) resistance. In the longer term we expect PC, whose current use for resins is negligible, to become a mainstream resins coatings material."

In the development of PCs of high molecular weight for packaging, Novomer is working with both polymer producers and consumer product companies. "In this area we cannot yet reveal the identity of prospective partners but they are big names among polymer manufacturers and in the top five of consumer goods companies," says Peter Shepard, executive vice president, polymers, at Novomer.

"Our technology is particularly interesting to these companies because our PCs, in addition to their performance, have 40-50% of CO2 by weight while the products of competitors have less than 20%."

Novomer also considers itself well positioned to benefit from a surge in demand for CO2-derived PC because of what it believes is a strong intellectual property position. "The key issue with our catalysts is not so much the material but their structure," Shepard says.

"In terms of the types of PC we are able to produce it will be very difficult for an outside company to step into the area without running into intellectual property difficulties.

"In the longer term we are not talking about a market of tens or hundreds of thousands of tonnes of PC but one of millions of tonnes," he adds.

For more on PC, visit our comprehensive Chemical Intelligence database

By: Sean Milmo
+44 20 8652 3214

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