Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1990-09-18
1993-12-28
Ivy, C. Warren
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
549379, C07D31912, C07D31900
Patent
active
052741273
ABSTRACT:
The present invention is directed to a method for making L-lactide from aqueous L-lactic acid. Aqueous lactic acid feed for present purposes comprehends an aqueous mixture of one or more of L.sub.1 A, L.sub.2 A, and L.sub.3 A, optionally with LD being present. L-lactic acid is the preferred feed configuration for making L-lactide, and is to be understood even though the configuration symbol is not used throughout this application. Aqueous lactic acid feed is treated for removal of water therefrom until a degree of polymerization (DP) not substantially above about 2 is reached. The treatment then is ceased to produce a crude LD product. LD then is separated from the crude LD product. A preferred treatment involves heating the feed at elevated temperature to remove water. LD can be separated from the crude LD product by a variety of techniques to produce an LD-depleted product. This LD-depleted product, optionally augmented with additional aqueous lactic acid and/or water then can be readmitted to the process for making additional lactide. This cyclic or recycle process embodiment of the present invention enables very high lactide conversions to be realized.
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Markle Richard A.
Sinclair Richard G.
Smith Russell K.
BioPak Technology, Ltd.
Covington Raymond
Ivy C. Warren
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