- Catalytic Gas-Phase Production of Lactide from Renewable Alkyl Lactates
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A new route to lactide, which is a key building block of the bioplastic polylactic acid, is proposed involving a continuous catalytic gas-phase transesterification of renewable alkyl lactates in a scalable fixed-bed setup. Supported TiO2/SiO2 catalysts are highly selective to lactide, with only minimal lactide racemization. The solvent-free process allows for easy product separation and recycling of unconverted alkyl lactates and recyclable lactyl intermediates. The catalytic activity of TiO2/SiO2 catalysts was strongly correlated to their optical properties by DR UV/Vis spectroscopy. Catalysts with high band-gap energy of the supported TiO2 phase, indicative of a high surface spreading of isolated Ti centers, show the highest turnover frequency per Ti site.
- De Clercq, Rik,Dusselier, Michiel,Makshina, Ekaterina,Sels, Bert F.
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- A bifunctional monomer derived from lactide for toughening polylactide
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(6S)-3-Methylene-6-methyl-1,4-dioxane-2,5-dione was synthesized from l-lactide and used as the dienophile to prepare spiro[6-methyl-1,4-dioxane-2,5-dione-3,2′-bicyclo[2.2.1]hept[5]ene] via an exoselective and diastereofacial-selective Diels-Alder reaction. Polymerizations of this bifunctional lactide derivative were successfully carried out under ring-opening and ring-opening metathesis polymerization conditions to yield high molecular weight and high Tg polymers. We further demonstrated that by incorporating a small percentage of spiro[6-methyl-1,4-dioxane-2,5-dione-3,2-bicyclo[2.2.1]hept[5]ene] into poly(1,5-cyclooctadiene) and copolymerizing it with dl-lactide, novel polymeric alloys of PLA can be created that have tremendous improvements in toughness over PLA and the corresponding binary blend of PLA and poly(1,5-cyclooctadiene). Copyright
- Jing, Feng,Hillmyer, Marc A.
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- TRANSFORMATIONS OF MESO-LACTIDE
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B/N Lewis pairs have been discovered to catalyze rapid epimerization of meso-lactide (LA) or LA diastereomers quantitatively into rac-LA. The obtained rac-LA can be kinetically polymerized into poly(L-lactide) and optically resolved D-LA, with a high stereoselectivity factor kL/kD of 53 and an ee value of 91% at 50.6% monomer conversion, by a bifunctional chiral catalyst. The epimerization and enantioselective polymerization can be coupled into a one-pot process for transforming meso-LA directly into poly(L-lactide) and D-LA.
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Paragraph 0096
(2018/09/18)
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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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- Method for obtaining lactide
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Processes for producing lactide from lactic acid oligomers are described herein. The processes generally include heating a lactic acid oligomer in the presence of a catalyst at a temperature of between 150° C. and 300° C. under a pressure of less than 0.01 MPa to form a lactide; distilling the lactide; and condensing and recovering the lactide, wherein the catalyst is a metal salt of the phosphite anion PO33? in which the metal is selected from the group consisting of tin, aluminum, zinc, titanium and zirconium.
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Page/Page column 3; 4; 5
(2013/12/03)
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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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- 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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scheme or table
p. 1027 - 1030
(2011/03/20)
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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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- 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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- Method for the productiion of polylactide from a solution of lactic acid or one of the derivatives thereof
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A process for the production of polylactide, the stages of which for the production and purification of lactide, starting from an aqueous solution of lactic acid or of its derivatives, includes evaporation of water with formation of oligomers, depolymerization to give lactide, condensation and then crystallization of the crude lactide product to give purified lactide, aqueous treatment of the residual fractions from the crystallization and polymerization of purified and/or prepurified lactide to give polylactide in an extruder and in the presence of catalysts. An alternative process includes carrying out the aqueous treatment before the crystallization.
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Page/Page column 9
(2010/02/15)
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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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- Continuous process for the manufacture of lactide and lactide polymers
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A process for the continuous production of substantially purified lactide and lactide polymers from lactic acid or an ester of lactic acid including the steps of forming crude polylactic acid, prefereably in the presence of a catalyst means in the case of the ester of lactic acid, to form a condensation reaction by-product and polylactic acid, and depolymerizing the polylactic acid in a lactide reactor to form crude lactide, followed by subsequent purification of the crude lactide in a distillation system. A purified lactide is then polymerized to form lactide polymers.
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- Process for producing lactides and process for purifying crude lactides
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A process for producing a meso-compound-containing lactide, comprising thermally decomposing a hydroxycarboxylic acid oligomer in the presence of a salt of an alkali metal except sodium and in the presence or absence of a metal of the groups 4 to 15 of the periodic table and/or a salt thereof; and a process for purifying a crude lactide comprising recrystallizing a crude lactide using a poor solvent and a good solvent selected from aliphatic tertiary alcohols, ketones and esters are disclosed. The production ratio of a meso-lactide can be controlled by selection of the kind and the amount of a catalyst so as to obtain a lactide having an appropriate optical purity suitable for production of biodegradable polymers. The purification process achieves a high recovery.
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- Meso-lactide, processes for preparing it and polymers and copolymers produced therefrom
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The invention relates to a meso-lactide having a melting point of 52.8° C., processes for its preparation, and its use in the preparation of resorbable polymers and copolymers.
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