Development of industrial production of high molecular weight poly-L-lactate from renewable resources

Citation
H. Ohara et al., Development of industrial production of high molecular weight poly-L-lactate from renewable resources, NIP KAG KAI, (6), 2001, pp. 323-331
Citations number
10
Language
GIAPPONESE
art.tipo
Article
Categorie Soggetti
Chemistry
Journal title
NIPPON KAGAKU KAISHI
ISSN journal
0369-4577 → ACNP
Issue
6
Year of publication
2001
Pages
323 - 331
Database
ISI
SICI code
0369-4577(200106):6<323:DOIPOH>2.0.ZU;2-H
Abstract
This development is related to the method of the industrial production of h igh molecular weight poly-L-lactate having the applicable properties as com modity plastics by use of sugars which are derived from renewable resources . To realize the effect of drawing orientation of films and fibers, high cr istallinity of the poly-L-lactate is required. In other words, L-lactic aci d preparation having high optical purity must be used as the raw material t o produce such high crystal poly-L-lactate. Further, the price of the raw m aterial should be reasonable one to make the price of such poly-L-lactate r easonable. For this purpose, we have developed a technology to produce L-la ctic acid preparation of which optical purity is 99.0 % by a strain of Baci llus species which has low auxotrophic characteristic. For the industrial p roduction of poly-L-lactate, LL-dilactide was produced from the pre-polymer s of low molecular weight poly-L-lactate through the intramolecular transes terification. In the preparation of the pre-polymers, polycondensation take s place where the linear mono-, di-, and trimer of lactic acid are totally refluxed so that the yield of LL-dilactide can be improved, then the temper ature of the reactor is raised up in three steps, 135, 150, 160 degreesC to prevent the racemization of L-lactic acid. The high purity of LL-dilactide is also required to produce high molecular weight poly-L-lactate. The melt ing crystallization method without a solvent was developed for the purifica tion of LL-dilactide after consideration of lowering the load on the enviro nment. Among various intramolecular transesterification catalysts which we have examined, tin(II) 2-ethylhexanoate showed highest activity and obtaine d high optical purity LL-dilactide. Ring-opening polymerization of LL-dilac tide was continuously took place without a solvent resulting in the product ion of high molecular weight poly-L-lactate of which weight-average molecul ar weight is 180000 to 200000. In addition, the properties of poly-L-lactat e and the behavior of its biodegradation in a compost were revealed in this work.