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US 4,797,468 AGranted
Preparation of polylactic acid and copolymers of lactic acids
AssigneeAkzo N.V.
InventorKlaas S. De Vries
Life of this patent
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Abstract
The invention relates to a method for preparing high molecular polylactic acid or copolymers of lactic acids using lactide that is purified by extraction with water.
Claims10
Method for preparing polylactic acid or copolymers of lactic acid by polymerizing the lactide according to formula I:
- ##STR2## comprising forming the lactide according to formula I by polycondensation of L-, D- or D, L-lactic acid followed by decomposition of the low-molecular polylactic acid thus obtained to yield crude lactide I, dissolving the crude lactide I in a liquid organic solvent that is not miscible with water, extracting the solution thus formed with a water solution comprising a basic substance that is sparingly soluble or insoluble in the organic solvent, isolating the lactide I from the organic solvent layer and polymerizing the isolated lactide I to the high-molecular polylactic acid or copolymer thereof.
Method for preparing the lactide formula I:
- ##STR3## comprising the polycondensation of L-, D- or D,L-lactic acid followed by decomposition of the low-molecular polylactic acid thus obtained to yield crude lactide I, dissolving the crude lactide I obtained in an organic solvent that is not miscible with water, extracting the solution thus formed with a water solution comprising a basic substance that is sparingly soluble or insoluble in the organic solvent, and isolating the lactide from the organic solvent layer.
Dependencies are inferred from the claim text.