5-7 OCTOBERISFR2011

127

TOLEDO (SPAIN)

PRELIMINARY STUDY OF THE RECYCLING OF POLYURETHANES BY
GLYCOLYSIS TO OBTAIN NEW RECYCLED FOAMS
I. Acillona1, S. Arnaiz1, J.I. Gutiérrez-Ortiz2, R. López-Fonseca2, A. Asueta1 and I. Duque-Ingunza2
1 GAIKER Technological Centre, Parque Tecnológico, Edificio 202, 48170 Zamudio, Spain
2 Chemical Engineering Department, Faculty of Science and Technology, University of the Basque Country - UPV/EHU,P.O. Box 644, E-48080 Bilbao, Spaine-mail: acillonai@gaiker.esAbstract
A preliminary study of the main parameters affecting the reaction and properties of the recovered polyol has been carriedout using reference and waste polyurethane samples. The glycolysis experiments were performed under atmosphericpressure in a glass stirred tank reactor at a constant temperature. Diethylene glycol and diethanolamine were used assolvent and catalyst respectively. Gel permeation chromatography was used to determine the presence of polyol in theproducts and chemical structure of glycolysate products were studied by FTIR. The application of the recovered polyol
was evaluated by foaming tests to study the replacement ratio of the commercial polyol by recycled polyol. Replacement
ratios up to 30% of the commercial polyol by the recycled one have been achieved.

Keywords: Waste Polyurethane, Glycolysis, Feedstock Recycling, Polyol

1. Introduction
Polyurethanes (PU) comprise a major engineering plastic
material family with an annual production capacity world
wide of nearly 12 million tonne (2007) [1]. Despite theirspreading in different applications their recycling rate islow. Polyurethanes constitute a group of polymers withversatile properties and a wide range of commercial
products. Polyurethane foams, are used for manyengineering applications, such as thermal insulation inconstruction, cushions, acoustic and comfort applicationsin automotive and so on.

The glycolysis reactions were carried out underatmospheric pressure in a glass stirred tank reactor at aconstant temperature, 195ºC. When the temperature of
DEG and DEA mixture reached the specified value, thescrap flexible PU foam was fed. The temperature waskept at 195ºC during the feeding. At given intervals,
aliquots were sampled and cooled to room temperature.
The samples were dissolved in tetrahydrofuran (HPLC,from Labscan, Ireland) and then filtered (pore size 0.45μm). GPC was used to study the evolution of the reaction
and FTIR spectroscopy was used to study the chemicalstructures of the glycolysate products [4].

The general purpose of the polyurethane feedstock
recycling is to recover constituent polyol, a valuable raw
material. One of the alternatives for the recycling ofpolyurethane foams includes their chemical treatment byglycolysis to convert the PU back to polyols [2]. In thisstudy, the split-phase glycolysis of flexible polyurethanes,from cushions and comfort applications was investigatedto define the suitable treatment for this flexible PU waste.

3. Results and Discussion

2. Materials and Methods

The study of the polyol content of the glycolysate
products was made by following two different strategies.
In the first set of experiments, the zero time for thereaction was taken when all the foam was fed, 50 g.
Then aliquots were sampled at given intervals andsubsequently analyzed by GPC to study the presence ofthe polyol in the upper layer (Figure 1). Peak I is
assigned to the original polyol in agreement with theGPC profile of the commercial polyol. On the other hand,peaks II and III are related to un-reacted DEG and DEA,respectively.

Industrial samples of flexible PU foam and 4,4’methylene bis-(phenylisocyanate) (MDI) were scrappedwith a diameter ranging from 8-15 mm. The scrap foams
were reacted with diethylene glycol (DEG) as a glycolysis
agent (PS, from Panreac, Spain) and diethanolamine(DEA) (PS, from Panreac, Spain) as a catalyst [3]. The
mass ratio of glycolysis agent (DEA+DEG) to PU foam
was 1.5:1.0 and 1:6 between catalyst and glycol(DEA:DEG) [3].

interiores libro.indd 127

The degradation process of the flexible PU foam resulted
in the yield of two liquid phases. The upper one, whichmainly contains the polyol, was pale yellow while theother, essentially DEA and DEG, was brown.
3.1 Study of the polyol content

26/9/11 13:13:10

128

6th International Symposium on Feedstock Recycling of Polymeric Materials

foam with the 33% of replacement and foam with 50% ofreplacement are shown respectively.

Figure 1. GPC record of upper liquid layer of products
after PU glycolysis with DEG and DEA
In the second set of experiments, aliquots were sampledduring the feeding process. Polyurethane foam was fed
discontinuously in batches of 5 g. Then, when the 5 g of
PU were totally dissolved the aliquots were sampled. The
increasing intensity of the polyol signal during theaddition of PU foam could mean that the dissolution
process can be considered as a reaction process
because the polyol is appearing in the liquid phase
proportionally to polyurethane addition.

Figure 2. Maximum intensity of the Peak I (polyol) during
the feedingIn Figure 2 are shown the FTIR spectra of the startingpolyol used in the synthesis of the polyurethane foams
and the one recovered from the upper phase. The IR
spectral examination confirms the GPC results; thechemical structure of the recovered product is quite
similar to the virgin one.
1515,36
3359,30
2969,64

1454,84

1295,94

2867,121372,88923,62RECOVERED POLYOL PHASE%T

1083,98
3469,73
1736,04
1455,45
2970,30
2871,75

VIRGIN POLYOL
4000,0

3600

3200

2800

2400

1297,01
1345,94

2000

1800
cm-1

1600

1400

835,47926,951013,051372,97

1200

1000

800

650,0Figure 3. Comparison of FTIR spectra of the polyol andrecovered product3.2 Application of the product in the formulation of newPU foams
Foaming assays were made to study the application of
the upper layer obtained in the glycolysis of flexible PU
foam. The foaming formulations were modified replacing
original polyol by the recovered product but otherproducts like foaming agents and catalyst were notadded in this study. In Figure 3 commercial PU foam,interiores libro.indd 128

Figure 3. Foaming assays with partial replacement of thecommercial polyol by recovered polyol 33% (centre) and50% (right)

4. Conclusions
A simplified evaluation of the recycling of polyurethanes
by glycolysis has been attempted in order to understandhow the process must be carried out in order to recover apolyol which could be used for new formulations offlexible polyurethanes.
GPC profiles show that a polyol containing phase isachieved. According to Figure 1, the dissolution processof the PU must be studied to complete the study of thereaction and the kinetic. The replacement of commercial
polyol by recovered products without adding any othersubstances in the foaming process, decreases the qualityof the final product but show potential to foam. Foaming
assay has to be completed with the optimization of theprocess by adding foaming agents, surfactants andcatalyst and a further characterization of the obtainedfoams.

References[1] G. Behrendt, B.W. Naber, The Chemical Recycling of
Polyurethanes (Review), Journal of the University ofChemical Technology and Metallurgy, 44 (2009) 3-23
[2] M.M.A. Nikje, A.B. Garmarudi, Regeneration of Polyol
by Pentaerythitol-assisted Glycolysis of Flexible
Polyurethane Foam Wastes, Iranian Polymer Journal, 19(2010) 287-295[3] C. Molero, A. de Lucas, J.F. Rodriguez, Recovery ofpolyols from flexible polyurethane foam by “Split-phase”
glycolysis with new catalyst, Polymer Degradation andStability, 91 (2006) 894-901[4] C. Molero, A. de Lucas, J.F. Rodríguez, Activities ofoctoate salts as novel catalysts for the transesterificationof flexible polyurethane foams with dyethylene glycol,
Polymer Degradation and Stability, 94 (2009) 533-539

Acknowledgments
I. Acillona acknowledges the financial support receivedby Fundación Centros Tecnológicos Iñaki Goenaga
through the PhD research fellowship 2009-2013 and thematerial support from GAIKER Technology Centre. The
financial support for this work provided by the Spanish
Ministerio de Ciencia e Innovación (CTQ2008-06868C02-01 and CTQ2008-06868-C02-02) is gratefully
acknowledged by the authors.

26/9/11 13:13:10