Chemical degradation of polyurethanes
3. Degradation of microporous polyurethane elastomer by
diethyl phosphonate and tris(1-methyl-2-chloroethyl) phosphate
K. Troev *, G. Grancharov, R. Tsevi
Institute of Polymers, Bulgarian Academy of Sciences, So®a 1113, Bulgaria
Received 16 February 2000; accepted 27 February 2000
Abstract
Microporous polyurethane elastomer, based on diphenylmethane diisocyanate (MDI) and polyester polyol-Bay¯ex 2003E has
been converted into a liquid by treatment with diethyl phosphonate and tris(1-methyl-2-chloroethyl) phosphate. The structure of
the degraded products has been studied by
1
H,
13
C and
31
P NMR spectroscopy. The degraded products are phosphorus- or phos-
phorus and chlorine-containing oligomers. # 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Microporous polyurethane elastomer; Chemical degradation; Diethyl phosphonate; Tris(1-methyl-2-chloroethyl) phosphate
1. Introduction
Our previous papers [1±5] describe a new method for
chemical degradation of polyurethanes which diers
from the well-known methods of hydrolysis [6], glyco-
lysis [7±9] and aminolysis [10,11].
This paper describes the degradation of microporous
polyurethane elastomer by diethyl phosphonate or
tris(1-methyl-2-chloroethyl) phosphate treatment. The
primary aim of these studies is to develop a novel,
industry-oriented method for converting polyurethane
waste materials and used polyurethanes into reusable
products suitable as raw material in the preparation of
polymers with reduced ¯ammability.
2. Experimental
2.1. Materials
Microporous polyurethane elastomer, based on MDI,
Bayer AG, and polyester polyol-Bay¯ex 2003E, Bayer
AG (adipic acid,1, 4-butane diol, ethylene glycol), was
chosen for degradation. Diethyl phosphonate
(C
2
H
5
O)
2
P(O)H, is commercially available (Fluka), or
can be prepared from phosphorus trichloride and ethanol,
tris(1-methyl-2-chloroethyl) phosphate {ClCH
2
CH(CH
3
)}
3
P(O) is commercially available.
2.2. Instruments
1
H,
13
C and
31
P NMR spectra were recorded on a 500
MHz Bruker instrument, in CDCl
3
. The viscosity was
measured on a Brook®eld LV viscometer. Phosphorus
content was determined on a Specol spectrophotometer,
at 420 nm wavelength.
2.3. Degradation by diethyl phosphonate
Into a three-necked ¯ask equipped with a stirrer,
thermometer and re¯ux condenser 40 g of microporous
polyurethane cut into small pieces 3±5 mm in size and
120 g of diethyl phosphonate were placed. The degra-
dation proceeded at 170
C. Then the temperature was
lowered to 60
C, and the unreacted diethyl phosphonate
was removed under vacuum (0.16±0.18 mm Hg).
Experiments on the chemical degradation of micro-
porous polyurethane were performed with heating for 4,
5, 6 and 8 h. The results from the degradation are pre-
sented in Table 1. The degraded products are soluble in
CHCl
3
,CH
2
Cl
2
, THF, DMF, DMSO.
0141-3910/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0141-3910(00)00086-0
Polymer Degradation and Stability 70 (2000) 43±48
* Corresponding author. Tel.: +359-2-978-2203; fax: +359-2-707-
523.
E-mail address: ktroev@bas.bg (K. Troev).