Sustainable polyurethane 2016: Sustainability drives polyurethane innovation

The European polyurethane industry gathered in Amsterdam in October 2016 to find out about the latest trends and developments in polyurethane sustainability. Simon Robinson reports from SusPolyurethane 2016.

In the three years since the previous SusPolyurethane event, the world has moved on. In 2013, the prospect of commercially significant recycling of polyols back into finished flexible polyurethane foam was still remote, but now IKEA specifies a proportion of recycled material in all its flexible mattress foam.

In 2013, there was the real possibility that it would be commercially possible to create polyols from waste carbon dioxide. Both Novomer and Covestro have succeeded in doing just that.

The keynote paper from Richard Northcote, chief sustainability officer of Covestro challenged the audience by asking if we are getting the most out of our resources, or can we improve?

Northcote explained that Covestro and Novomer are both taking a raw material with no or little value, carbon dioxide, and converting it into products with added value, in this case polyols for flexible foam.

Premium please!

“Will we get a premium for our return on investment? Until now, the answer has been no," Northcote said. "But if you are a furniture company that has said that by 2020 all its plastics must be recyclable, and you don't know how to do that, then suppliers will discuss how to extract extra value. This could be in cents, or volume, or some other business model.”

And those business models will start to change, as big brands start to push this. “We will expect to be rewarded for the work we do," he told the meeting.

Northcote confirmed that Covestro’s C1 carbon dioxide technology would be available for licensing. "If we are really going to serve the greater market, we cannot keep this technology to ourselves, we have to license it,” he said. “We are not the world's biggest polyol producer."

He added that the same would be true if the company made a major breakthrough in rigid foam or thermoplastics. “If you don't [license the technology] then you really are not addressing the big issues we face as a global society,” he claimed.

Novomer’s marketing manager Simon Waddington gave details on the types of polyol that can be produced using carbon dioxide, with an emphasis on his firm’s products.

Carbon dioxide-polyols are a new class of materials, he argued, and can be used on their own, or in combination with more conventional polyester- and polyether-based polyols, where they could be used in high-volume applications.

A different slant on CO₂

“The molecular weight distribution is very, very narrow,” Waddington said. “The Novomer process produces a polyol with alternate CO₂ and propylene oxide groups, unless the reaction is modified,” he said. “We have made polyols with functionality of six, but the backbone can be stiff.”

He added that Novomer has made rigid foam using polyols with a functionality of two, and high molecular weight. “Formulators have to throw away a little bit of what they have known before and treat it as a new material,” he said.

There is interest in using CO₂ polyols in polyurethane dispersions, because they give products with good hydrolysis and weathering resistance. “They are also being used in polyurethane hot melts,” Waddington added.

Novomer has trialled the materials in rigid applications at the CEPEDA test centre in Tudela, Spain. Waddington explained that the material has been used successfully in flex-faced and rigid panels up to 100mm thick.

Polyols derived from CO₂ may represent cutting edge technology at the start of a polyurethane foam’s lifecycle, but increasing interest is being shown in polyurethane recycling. Both Rampf and H&S from Germany have developed technology in this area, and are starting to look at opportunities in post-consumer scrap.

Frank Dursten, director of R&D and sustainability at Rampf Holding, explained how the company’s Eco-Solutions division has been recycling polyurethane and polyesters. It is working with an engineering partner, Keil Anlangenbau, to develop tailor-made PET and PU recycling plants.

Recycling

However, Rampf also has a polyols materials business, Dursten said. Its range of three product groups include natural polyols. designated NP, which are based on renewable resources such as rapeseed oil.

The company’s Petol range includes polyols based on PET, which are suitable for use in rigid polyurethane and PIR foam applications. And the Recipol range comprises recovered polyols based on polyurethane.

Rampf has also carried out work on novel polymers based on C19 triglycerides. These can be used in the cast polyurethane sector. It is possible to produce cast polyurethanes that offer translucency and good elastic recovery properties, as well as exceptionally good hydrolysis properties, Dursten told the meeting.

He also outlined some of Rampf’s work using bio-based waste streams such as lignin for integral skin foams. These can be produced with a lignin content of between 30 and 50%, give higher Shore hardness and greater tensile strength than other materials. The company has carried out work in this area with the help of funding from the Federal Ministry of Food and agriculture in Germany.

In 2012, Rampf installed what it claims is the first industrial-scale plant to make polyols from PU flexible foam waste. Dursten explained that it was constructed as part of a project, funded by the German Federal Ministry of Education Research, to develop industrial-scale acidosis for flexible slab stock foams. Rampf has taken part in several collaborative projects to take in-production scrap and convert it into polyols, working with Hennecke, Evonik and Metzler, among others.

Dursten also explained that Rampf has built on its experience with in-process polyurethane scrap, and is now involved in a project to turn bulky waste such as mattresses and furniture foam into high added-value recycled polyol.

The aim of the project, he said, is to synthesise high-quality secondary polyols from post-consumer flexible foam products. It involves an analytical procedure to preselect different foam qualities to ensure consistent product quality of the second piles from batch to batch, and analytical techniques designed to detect toxic substances such as now-banned flame retardants or blowing agents in the post-consumer scrap.

Using post-consumer waste

Lyudmila Skokova from H&S outlined the potential volume of polyurethane raw materials that could be recovered each year from the European mattress and bedding market in her presentation.

Skokova explained that her firm, which installed and in-process polyurethane-to-polyols plant at Dendro’s factory in Poland is, like Rampf, interested in this area. The Polish factory has been up and running for about three years, and is the reference site for H&S’s venture into post-consumer bedding recycling.

At the end of life, there are currently four options for mattresses within the EU, Skokova explained. There are two routes to raw material recovery: mechanical recycling into applications such as carpet underlay and sports mats, or chemical recycling into rigid polyols. The other recycling route, she said, involves energy recovery and thermal recycling. But, Skokova said, 60% of mattresses and upholstered furniture are currently discarded in landfills.

She suggested that a recipe to convert PU foam residues from post-consumer mattresses into usable industrial polyols would consist of about 40% PU foam from post-consumer mattresses, 37%, basic polyol, 13% acids, 6% additives, and 4% catalyst. This will generate around 4% process waste, she said, of which 2% would be water distillate and around 2% evaporation.

The process would take around 12 hours., First, the basic polyol and additives are added to the reactor, which is then heated. Once it is up to temperature, the PU residues are added, the mixture heated further, and when the reaction is complete, the polyol is cooled and discharged.

The recovered polyol can substitute for up to 50% of conventional polyols in rigid polyurethane foam insulation, and higher percentages in other rigid PU foam applications, Skokova told the meeting.

The polyols have a viscosity of between 4500 to 7500 mPa.s They typically have a hydroxyl number of between 240 and 310 mg KOH/g, and an acid number of less than 1.1 mg KOH/g, she said. The polyol is a viscous light brown to dark brown liquid, but the colour of the liquid depends largely on the colour of the foam residues.

The recycled polyols can substitute for aromatic polyester polyols that are used to make insulating polyurethane and PIR foam.

Skokova cited IAL Consultants, who suggested that the global market for aromatic polyester polyols was 584 kT/year in 2012, with an average annual growth of 4.4%. She added that PIR foams produced with between 20 and 50% recoverable polyol have properties that are comparable to, or slightly better than, a formulation made using conventional polyols.