“Biodegradable aliphatic-aromatic polyesters obtained from dicarboxylic acids and dialcohols are known in the literature and are commercially available. The presence of the aromatic component in the polyester chain is important to obtain polymers with sufficiently high melting points and with adequate crystallization rates.
Although polyesters of this sort are currently commercially available, the amount of aromatic acid in the chain is typically lower than 49% since the above said threshold, the percentage of biodegradation of the polyesters decreases significantly above said threshold.
It is reported in the literature (Muller et al., Angew. Chem., Int., Ed. (1999), 38, pp. 1438-1441) that copolymers of the polybutylene adipate-co-terephthalate type with a molar fraction of terephthalate of 42 mol %, biodegrade completely to form compost in twelve weeks, whereas products with 51 mol % of molar fraction of terephthalate show a percentage of biodegradation of less than 40%. This different behaviour was attributed to the formation of a higher number of butylene terephthalate sequences with a length greater than or equal to 3, which are less easily biodegradable. If it were possible to maintain suitable biodegradation properties, an increase in the percentage of aromatic acid in the chain would, however, be desirable in so far as it would enable an increase in the melting point of the polyester, an increase in, or at least a maintenance of, important mechanical properties, such as ultimate strength and elastic modulus, and would moreover enable an increase in the crystallization rate of the polyester, thereby improving its industrial processability.
A further drawback of biodegradable aliphatic-aromatic polyesters that are currently commercially available is represented by the fact that the monomers of which they are constituted come from non-renewable sources, thereby maintaining a significant environmental impact associated to the production of such polyesters despite their biodegradability. They have far more energy content than LDPE and HDPE particularly in the presence of adipic acid. On the other hand, the use of monomers of vegetal origin would contribute to the reduction of emission of CO.sub.2 in the atmosphere and to the reduction in the use of monomers derived from non-renewable resources
[Bastioli et al, US Patent 8,193,300 (6/5/2012)]
Bookmark this page to follow future developments!.
Roger D. Corneliussen
Maro Polymer Links
Tel: 610 363 9920
Fax: 610 363 9921
Copyright 2012 by Roger D. Corneliussen.
No part of this transmission is to be duplicated in any manner or forwarded by electronic mail without the express written permission of Roger D. Corneliussen
* Date of latest addition; date of first entry is 6/28/2012.