- Studies on the epimerization of diastereomeric lactides
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The epimerization of chiral lactides was studied in the presence of various homogeneous and heterogeneous bases. Some solvent/base systems were found to promote epimerization at room temperature efficiently. Side reactions such as polymerization were not observed or occurred only slowly. This new protocol offers the opportunity of the transformation of meso-lactide into rac-lactide. Therefore it can reduce the overall manufacturing costs of polylactides, a problem which currently hampers the broad application of those environmentally friendly polymers in a large scale.
- Shuklov, Ivan A.,Jiao, Haijun,Schulze, Joachim,Tietz, Wolfgang,Kühlein, Klaus,B?rner, Armin
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- Method for catalytically synthesizing lactide
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The invention discloses a method for catalytically synthesizing lactide. According to the method, a mixture of stannous lactate and a urea substance is used as a composite catalyst, L-lactic acid (orD-lactic acid) with the lactic acid content of 90% is used as a raw material, and a reduced pressure distillation technology is adopted to synthesize the L-lactide (or D-lactide). Compared with independent use of onecatalyst, by adopting the composite catalyst, the yield can be effectively increased, under the same experimental conditions, the crude yields of lactide synthesized by independently using stannous lactate or urea catalysts are 69%-72% and 23%-30% respectively, and the yield can be increased to 90% or above by using the composite catalyst of the two. Compared with a traditional tincatalyst or zinc catalyst and other composite catalytic components, the composite catalytic reaction system is low in reaction temperature (150-180 DEG C), short in reaction time (0.5-2 h), high in lactide yield (90% or above), capable of saving more energy and increasing the yield and beneficial to industrial production.
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Paragraph 0056-0076; 0081-0084; 0095-0096; 0099-0100
(2021/01/29)
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- Preparing method of lactide stereisomer mixture
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The invention provides a preparing method of a lactide stereisomer mixture, which comprises: taking an alkali metal compound as a catalyst, performing stereoisomerism reaction on a raw material lactide under a condition of 120-250 DEG C to obtain the stereisomer mixture containing D-, L- and meso- lactide, wherein the catalyst is selected from one or more from hydride, boron hydrogen compound, amide, chloride, bromide, monoiodide, sulfide, chlorate, bromate, iodate, chlorite, hypobromite, perchlorate, perbromate, periodate, sulfite, hydrosulphite, nitrate and nitrite of alkali metal. The specific alkali metal compound is taken as the catalyst for lactide isomerization reaction, the inversion of configuration of the lactide can be efficiently realized in an economic and environment-friendly manner, and the stereisomer mixture containing D-, L- and meso- lactide is prepared.
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Paragraph 0035; 0037; 0038; 0039; 0040; 0041; 0043
(2017/01/26)
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- TECHNOLOGICAL METHOD FOR SYNTHESIS OF OPTICALLY PURE L-/D-LACTIDE CATALYZED BY BIOGENIC GUANIDINE
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A technological method for synthesizing optically pure L-/D-lactide by using a biogenic guanidine catalysis method. The method of the present invention comprises: by using biogenic guanidine creatinine (CR) as a catalyst and L-/D-lactic acid (90% of mass content) as a raw material, synthesizing optically pure L-/D-lactide by using a reactive reduced pressure distillation catalysis method. The method of the present invention has advantages that the used catalyst is biogenic guanidine creatinine and free of toxicity, metal, and cytotoxicity; the synthesized lactide is high in optical purity (the specific rotation of the L-lactide [α]25 D=?276??280, and the specific rotation of the D-lactide [α]25 D=280), and does not contain any metal; the amount of the catalyst used in reaction is low, the technological process is simplified (a process for rectifying and purifying a crude lactide product by using a conventional method is avoided); and the technological method is simple and convenient to operate and easy in industrial implementation.
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Paragraph 0040-0042
(2016/03/26)
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- Synthesis of (R)-lactic acid and (2R,5R)-2-tert-Butyl-5-methyl-1,3-dioxolan-4-one
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Abstract A convenient procedure for the synthesis of very expensive (R)-lactic acid from relatively inexpensive (R)-alanine is described. Its subsequent conversion into a chiral dioxolanone can be carried out by using an inexpensive pivalaldehyde-tert-butanol mixture.
- Aitken, R. Alan,Meehan, Anna,Power, Lynn A.
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p. 1557 - 1559
(2015/06/02)
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- Method for the production of a mixture of lactide derivatives
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A mixture of cyclic diesters derived from lactic acid and in cases a mixture of a racemate of dilactide may be produced in several different processes. In some instances, the process can thereby start from the corresponding alpha-hydroxycarboxylic acids, the corresponding cyclic diesters or oligomers of the corresponding alpha-hydroxycarboxylic acids.
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Page/Page column 7
(2012/06/18)
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- METHODS FOR PRODUCING LACTIDE WITH RECYCLE OF MESO-LACTIDE
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An S, S- and R,R-lactide stream suitable for polymerization is prepared by producing a low molecular weight poly(lactic acid), depolymerizing the low molecular weight poly(lactic acid) to form a mixture of S, S-, R,R- and meso- lactide, and separating meso-lactide from this mixture to form an S, S- and R,R- lactide stream. Meso-lactide is recycled into the process, and shifts the mole fractions of the lactides in the lactide mixture that is produced.
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Page/Page column 32-35
(2010/10/03)
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- RECOVERY OF LACTIC ACID VALUES FROM A MESO-LACTIDE STREAM
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Lactic acid equivalents are recovered from a starting lactide stream by catalytically racemizing a portion of the lactide in the stream at a temperature of 18O°C or below. This increases the proportion of two species of lactide (i.e., at least two of S, S-, R,R- or meso-lactide) at the expense of the third species. The racemized mixture so obtained can be separated to recover some or all of one or more of the lactide species from the remaining lactide species, by a process such as melt crystallization or distillation. Impurities in the starting lactide stream usually are retained mostly in the remaining meso-lactide, so a highly purified S, S- and/or R,R-lactide stream can be produced in this manner. Such a purified S, S- and R,R-lactide stream is suitable for polymerization to form a polylactide.
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Page/Page column 23; 24
(2010/10/03)
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- METHOD OF RECOVERING LACTIDE FROM POLYLACTIC ACID OR DERIVATIVE THEREOF
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To provide an efficient method for recovering and producing lactide having high optical purity by depolymerizing a polylactic acid or derivative thereof in order to carry out chemical recycling of the polylactic acid or derivative thereof or of a resin composition comprising same, wherein a mixture of a polylactic acid or derivative thereof and aluminum hydroxide is thermally decomposed at a temperature in a range from at least the melting temperature of the polylactic acid or derivative thereof to no greater than 320°C, thus recovering lactide.
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Page/Page column 8
(2008/06/13)
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- PURIFICATION PROCESS FOR LACTIDE
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The present case relates to a process for the purification of lactide from a crude lactide vapour product stream which process comprises a rectification/condensation step leading to a lactide-enriched condensate.
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Page/Page column 17-18
(2010/02/12)
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