ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 12, pp. 2016!2021. + Pleiades Publishing, Inc., 2006.
Original Russian Text + A.V. Tokarev, N.V. Sirotinkin, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 12, pp. 2040!2045.
AND POLYMERIC MATERIALS
A Study of Swelling of Polyurethane Wastes
with the Aim of Regeneration
A. V. Tokarev and N. V. Sirotinkin
St. Petersburg State Technological Institute, St. Petersburg, Russia
Received March 10, 2006
Abstract-The optimum time of swelling (required for weakening of the intermolecular interaction) of poly-
urethanes of various compositions in a series of organic plasticizers was determined. The deterioration of
the physicomechanical characteristics with plasticization allows a decrease in the expenses for secondary
recovery of wastes formed in polyurethane production.
In the last decades, polyurethane compositions have
found increased application in all branches of industry.
As predicted, the Russian market of polyurethanes
(PUs) can reach 210 thousand tons in 2007. The pro-
duction of polyurethane materials on an increasingly
large scale requires a search for efficient procedures
for utilization or breakdown of these wastes.
At present, the main procedures for PU reprocess-
ing are mechanical grinding with subsequent use of
the resulting crumb as a filler for various composite
materials, physical or physicomechanical treatment,
and chemical reprocessing.
Mechanical degradation is the most acceptable
procedure for utilization of PU foams, since their de-
gradation requires lower power expenditure in com-
parison with the degradation of monolithic PUs [1, 2].
In addition, grinding of wastes formed in production
of thermoplastic block PUs is very difficult because
of their high elasticity at elevated temperatures: en-
ergy is mostly transformed into heat and only an in-
significant part of energy is expended for degradation.
Physical methods, such as die casting, pressing,
and extrusion, are suitable for reprocessing of ther-
moplastic linear or weakly cross-linked polyurethane
systems [3, 4] and are inapplicable in the case of
thermosetting plastics. Additional use of high tem-
peratures can result in uncontrolled degradation of
cross-linked PU to be recovered, which is reflected
on the quality of the final product.
A huge number of foreign and Russian inventions
are devoted to thermochemical degradation based on
the reaction of PUs with hydroxyl- and amino-con-
taining compounds, which can be regenerated to
the initial components . The drawbacks of this
procedure are the high process temperature and forma-
tion of polyols nonuniform in molecular weight,
which hampers their subsequent use.
One of the successful procedures for utilization of
polyurethane wastes is plasticization, which partly
destroys the structure and makes it possible to obtain
secondary product, e.g., crumb, with high operation
characteristics at minimal power and economic ex-
penses; however, sorption of low-molecular-weight
liquids or their vapor results in a decrease in the ulti-
mate strength and elasticity of swollen PUs. The proc-
edure used for processing of wastes formed in produc-
tion of soles, multicellular PUs of ester nature ,
is based on a similar effect of polar plasticizers of
the dimethylformamide type.
Previously , plasticizers of this type have been
studied as agents promoting thermal degradation.
Granulated wastes were dissolved in boiling DMF in
the presence of amines and organotin compounds
(degradation catalysts) and were added to hydroxy
components. The resulting liquid and paste-like pro-
ducts were used as polyol substitutes (20%) in pro-
duction of PU.
Finely divided polyurethane reclaim was prepared
by dissolution of PU-elastomer foams in DMF at
90oC and subsequent precipitation of the polymer into
methanol  or treatment of wastes preliminary
degraded by heating with a mixture of methylene
chloride (80%) and DMF (20%) .