H&S unveils product-scale polyol recycling plant for flexible foam industrial waste at Dendro Poland with capacity to reduce polyol costs.
Being able to reduce the cost of polyols by 20% could have a significant impact on the economics of the flexible polyurethane foam business. H&S Anlagentechnik has a demonstration plant in operation at a major supplier to IKEA that shows it is possible to do just this.
There are considerable potential advantages to flexible foam producers in recycling at least some of their in-factory waste. The overall material cost could come down, the cost of landfill or waste disposal from production could be lowered, and if production costs fall then margins could rise. Moreover, the technology ensures a sustainable way of raw materials recovery and helps to reduce the carbon footprint.
H&S has been working on chemically recycling flexible foams back into flexible polyols for several years. H&S says it has moved from what it characterises as relatively straightforward processes to convert flexible polyurethane scrap into polyols for rigid PU foams.
The company has now installed a plant-sized flexible-foam to flexible polyol process at Dendro Poland. Urethanes Technology International visited the plant and discussed the pros and cons with H&S and Dendro.
H&S is known for its speciality polyurethane tank farm installations, and won an order for the farm at Dendro, located in Rogozno, about 350km west of Warsaw. Dendro, is partly owned by the IKANO investment vehicle for the family behind IKEA, and produces foam mattresses sold by IKEA in Europe.
Dendro put the recycling operation out to competition after the plant was built. “It was a great opportunity to recycle our production waste,” said Michal Soltysinski, head of foam production at the firm. His firm ordered the plant in July 2012 (Urethanes Technology International October/November 2012 page 16).
There was a process of discovery with H&S to see in the lab if it is possible to recycle production waste viably; to ensure it could produce recycled polyols with the right characteristics for successful foam.
Before visiting Dendro, Urethanes Technology International went to see H&S technical centre in Wildau, southeast Berlin. Lyudmila Skokova, product manager recycling, showed UTI around the H&S lab and explained some of the challenges that had to be overcome to make the process viable commercially.
“The project with Dendro started two-and-a half years ago,” explained Skokova. “It took 18 months to get from research to workable technology, she said. The order for the first commercial scale plant from Dendro came in July 2012. Dendro makes conventional, HR and viscoelastic foam. The current H&S process works for conventional and HR foam with ether and ester polyols. At the moment Dendro is using the technology solely for conventional foam. In future it is planned to recycle also HR foam waste.
Dr. Stanislav Fulev, research chemist and head of laboratory, explained the research process. His team started from conventional glycolysis and aminolysis of flexible foams but yields at around 5% were too low and there are a number of problems with these processes.
Glycolysis cuts the polyurethane chains too short to make flexible polyols. The polyols typically processed by this method could be used only for rigid foams. Additionally, the hydroxyl number of polyols regenerated in this way is also very high at around 400mgKOH/g, whereas flexible foam polyols are typically below 50mg KOH/g, Fulev said.
The polyols generated based on the glycolysis method could be used in rigid foams, says Fulev, but there are issues of logistics and registration under REACH legislation. Additional problems would also arise around logistics costs, since very few flexible foam plants are located adjacent to rigid PU foam production (e.g. insulation panels, spray foam etc.).
H&S examined a second approach: aminolysis, but this produces a two-phase mixture. This mixture has to be separated and one of the phases would be waste that would need to be disposed of. H&S therefore did not find glycolysis and aminolysis were suitable processes.
Finally acidolysis was successfully discovered by H&S, in particular based on the research of Dr. Stanislav Fulev. The process, which is based on a combination of two carboxylic acids and an unspecified non-metallic catalyst, proved to be the breakthrough.
The recipe to recycle flexible foam waste is ca. 42% waste, 44% basic polyol, 14% acids and catalyst. That means it is possible to generate approx. 2 tonnes of polyol out of 1 ton waste.
In the H&S process, fully reacted conventional polyurethane slabstock factory waste is converted into a beige-coloured mixture of polyurethane formulation components suspended in a flexible polyol.
A partly formulated polyol component could be an easily re-used formulation component in like-for-like recycling as it could be added straight back into the production process.
H&S was reticent about explaining the process but said: the reaction occurs at around 200°C and the polyol solution is then cooled to around 60°C. The acid breaks up the polyurethane and is then neutralised in order to enable a proper reactivity of the recovered polyols. The catalyst remains with the polyol and is incorporated into it.
During splitting of polyurethane chains amines coming from TDI or MDI will be released. The H&S method bonds free amines so that recovered polyols do not contain toxic primary aromatic amines.
The polyols produced with the H&S process have “a hydroxyl number the same as the original polyol at around 48 mg KOH/g,” says Fulev. The viscosity of the recovered polyol depends on the amount of filler in the original polymer.
Up to 25% of recycled polyol has been added back into standard flexible foam formulations without any changes in the foam properties, says Fulev. The levels higher than 25% could slightly decrease the compression set in mattresses.
H&S has also recycled polyols repeatedly to see how resilient the process is. Fulev says that his group has put the same batches through the recycling process many times to measure the change in properties that could occur if polyol undergoes repeated recycling in use.
No decline in properties was noticed until polyurethane made with recycled polyol had been recycled 20 times.
In order to simulate production process while scaling up from flask to industrial size 3 pilot reactors 90L, 320L and 700L are installed in H&S technical centre.
The installation at Dendro
Dendro Poland was “built on a greenfield site. Work started in 2008, said Soltysinski, Dendro’s head of PU foam production. “Within six months we had a production hall, and at the end of February 2009 we started up with test production. In May 2009 we were in regular production on the foam plant with a hall for foaming, block storage, mattress production and finished goods. It was a time of progress,” said Soltysinski. Total investment was around Euro 30m.