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Journal of the University of Chemical Technology and Metallurgy,
44, 1, 2009, 3-23
THE CHEMICAL RECYCLING OF POLYURETHANES
(REVIEW)
G. Behrendt1, B. W. Naber2
1University of Applied Sciences Wildau,
Bahnhofstrasse 1, D-15745 Wildau, Germany,
E-mail: [email protected] Naber,
Strasse der Jugend 56,
01987- Schwarzheide, Germany
ABSTRACT
Received 15 September 2008
Accepted 09 February 2009
INTRODUCTION
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POLYURETHANES
R N C O R' OH+
RNH
CO
R'
O
HO
R'
NC
O
RO
H
R'
R N C O R' OH+2
RNH
CO
R'
O
R' OH+
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R N C O R' COOH RNH
CO
CR'
OO
+
CR'
O
RNH
+ CO2
R
NH
C
O
R'
O
R" COOH+
N
R
C
O
R"R
NH
C
O
Types of Polyurethanes and their Properties
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Fig. 1. (a) Dependence of the glass transition temperature on
hydroxyl equivalent weight expressed as the molecular weight
between crosslinks in MDI triol systems and (b) on the polyol
functionality at constant hydroxyl number of 430 mg KOH/
g and MDI.
Composition of Selected Types of Polyurethanes
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Reactions of the Urethane Group
RNH
CO
R'
O
+ H2O
R NH2
R'OH+ CO2+
RNH
CO
R'
O
O
CR"
O
C
O
R"
+2+ H
2O
- CO2
N
R
C
O
R"R
NH
C
O
R" COOH R' OH++ H
2O
+ 2- CO2
RNH
CO
R'
O
+ R"2NH
RNH
CN
R"
O
R"
R ' OH+
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RNH
CNH
R
O
R' OH2
R' OHR NH
2 R N C N R2 + + CO
2
Reactions of Polyurethanes
RN
H
CO
R'
O
R N C O R' OH+
RNH
CO
CH
2
C
H2
O
O
R'
R NH2 CH
2
CH
OR'+ + CO
2
RNH
CO
CH C
H2
O
O
R'
CH3
R NH2 C
H
C
H2
OR'CH
2+ + CO2
RNH
CNH
R
O
+ H2O Nc
R NH2+ CO
22
Nc
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RNH
CO
R'
O
+ R"2NH
RNH
CN
R"
O
R"
R' OH+
WAYS TO RECYCLE POLYURETHANES
Thermal methods
Hydrolysis of polyurethanes
RNH
CO
R'
O
+ H2O
R NH2
R' OH+ + CO2
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Alcoholysis of polyurethanes
Glycolysis of polyurethanes
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R NH2
CH2
O
CH2
CHO
CnH
2n+1
+
RNH
CH2
CHCH
2O
OH
CnH
2n+1
Acidolysis of polyurethanes
RNH
CO
R'
O
+ HCl + H2O
R NH2
R' OHHCl + CO2+
RNH
CO
R'
O
CH
CH
COOHHOOC
2 +
RNH
CR
NH
CCH
CH
O
O
Alkaline Cleavage of Polyurethanes
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RNH
CO
R'
O
+ 2 NaOHH
2O
R NH2
R' OH+ + Na2CO3H
2O
Aminolysis of Polyurethanes
Combinations of Reactions
Side Reactions during Solvolysis
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Formation of Aromatic Amines and their Treatment
Alcoholysis with Circulation of Glycols
Alcoholysis using Polyethers or Polyesters
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APPLICATION OF THE CHEMICAL RECYCLING
Rigid Foams
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Polyisocyanurate Foams
Flexible Foams
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Integral Foams
Shoe Soles
Mixed Polymers
Reaction Products
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STRATEGIES TO USE RECYCLING PRODUCTS
Foam to Foam Recycling
Internal Loops
External Loops
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CONCLUSIONS
REFERENCES
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