Greener polyurethanes – what’s next?

The growing interest in sustainable raw materials and recyclables was evident amongst the attendees of the recent SusPolyurethane Conference organised by Crain Communications in Amsterdam.

Biobased/sustainable polyols from a variety of different routes were the focal point of the two-day conference. Whilst there was a clear interest in developments in sectors such as bio-based polyols and biosuccinic acid, there remained a certain element of skepticism amongst the audience as to how far some of the innovations would be taken up by the polyurethane industry in view of the costs involved.  Some delegates noted that demand for renewables and recycling of PU Foam from mattresses, etc. would be driven principally by governmental and industry wide regulations, which put an emphasis on the concept of the circular economy.  However, some processes were claimed by producers to be competitive against conventionally produced raw materials, and some even boasted additional properties. 

In his keynote speech, Richard Northcote, Chief Sustainability Officer at Covestro noted that the company aims to reduce its CO₂ emissions by 50% by 2025, and to halve its energy use per ton of manufactured products by 2030.  One of the company’s most innovative project with this goal in mind is its work on integrating CO₂ into the production chain, using it as a raw material for polyols by means of its much heralded ‘Dream Production’.

The new polyol is targeting the largest segment of the market – flexible foam which makes up around 40% of the total flexible polyol market which was estimated at around 13.3 million tonnes in 2012.  The polyol has been successfully used in the production of mattresses in conjunction with Belgian foam manufacturer Recticel. The viscosity of the foam depends on the functionality and CO₂ content, and polyols can be designed according to end use requirement.  Covestro plans to develop new areas in which CO₂ based materials could be used, and has successfully incorporated polyols with up to 25% CO₂. CO₂ based thermoplastic polyurethane (TPU) fibres are now available for the first time, albeit only on a lab scale, using a melt spinning process which does not involve solvents. Further upscaling is in development.

Covestro’s Richard Northcote as keynote speaker. Source: @CovestroGroup

Two types of natural oil polyol for use in the polyurethane industry were the subject of further presentations.  The first were palm oil based natural polyols produced by PolyGreen Chemicals based in Malaysia, the sole producer of Palm Oil based NOPs with a capacity of 30ktpa.  These polyols are claimed to be cheaper than conventional polyols, and first inroads are being made into the US and European markets, as and when certification has been achieved.  This particular type of polyol is GMO free and produces up to 10 times more oil per unit area than soybean, rapeseed or sunflower, according to PolyGreen.

Another natural polyol highlighted in the conference was Myrinol, a soybean oil modified polyester polyol for flexible foam applications from Myriant.  Myrinol is up to 95% biorenewable and is claimed also to be cost effective.  The molecule comprises three typical polyol chemistries, and all three moieties are present in the same molecule, allowing the company to tailor material to maximise strength of a specific chemistry which would benefit a given application.  An example cited indicated that the polyester portion would be minimised for PU foams exposed to aqueous environments.

A further type of alternative polyol was introduced by Bioamber, using its succinic acid to produced succinate polyols which can be utilised in many PU applications, although PU based adhesives are particularly suited to the polyol’s high crystallinity and high melting point.  The addition of a co-monomer to a SA-BDO polyol offers new options for tailoring adhesive properties according to requirements.  The polyols are already commercially available from major polyol producers, with BioAmber sharing technical data with formulators in order to facilitate product development.

Further polyurethane raw materials highlighted included Rennovia’s bio based adipic acid, 1,6 hexanediol and hexamethylene diamine which is expected to enable the production of a number of PU applications, most notably in the CASE markets.  The company sees its products as competitive drop in replacements for conventional PU raw materials, with identical performance and no need to reformulate.  This would potentially lead to a 100% bio based materials from renewable feedstocks, and Rennovia plans to have pilot samples ready by next year, and commercial supply ready by the middle of 2019.

Reverdia’s Biobased succinic acid, Biosuccinium, can also be used in numerous PU applications such as TPU, Cast Elastomers, Adhesives and PU flex and rigid foam.  In common with other producers, the company stressed the importance of working together with partner companies to develop new products, citing as an example its partnership with Covestro in producing and promoting  bioTPU, and with Xinhuarun in the development of microcellular foam shoe soles.

The second main element to the conference was the potential for developing polyols by means of recycling.  Rampf Eco Solutions has been producing customised polyols from PU flexible foam waste and post consumer PET flakes for 25 years. H&S Anlagentechnik has also developed a sustainable solution for so called  end of life mattresses (which are not bio degradable) by means of chemical recycling of the PU foam component in the mattresses into high quality polyols which can be used in rigid PU foams.  The company claims that the low manufacturing costs of recycled polyols mean that the technology is economically efficient.  In addition, the benefit of decreasing the amount of waste destined for landfill or incineration is clearly attractive.    According to H&S’s figures, there are at least 160kt of PU foam contained in end of life mattresses.  However, it will never be possible to collect the entirety of this tonnage for recycling into polyols.  H&S has been operating a 2400t/a recycling installation in Dendro, Poland for converting PU flexible foam residues into recovered polyol on an industrial scale since 2013.  Recovered polyol can substitute up to 50% of conventional polyol in rigid foam for insulation.

Whilst research has come a long way, there is still much to be done.  According to the industry bodies Europur and PU Europe, there is a significant difference between countries in their management of  end of life  PU foam today.  Overall 55-60% goes to landfill, 40% to waste-to-energy (mainly due to landfill bans in certain countries), 5% to reuse and less than 1% to recycling.  The regulatory drivers for change include extended producer responsibility schemes, the phasing out of landfill, and the increase in gate fees on landfilling and energy recovery.  EU targets stipulate that by 2025, 60% of all municipal waste must be prepared for re-use or recycled.  A strong message came from the polyurethane industry bodies – business as usual is not an option!

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Rachel Uctas
Senior Consultant – Polyurethanes & Intermediates, 1,4-Butanediol & Derivatives


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