- A study on highly concentrated lactic acid and the synthesis of lactide from its solution
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Lactic acid is an important platform compound used as raw material for the production of lactide and polylactic acid. However, its concentration and composition distribution are not as simple as those of common compounds. In this work, the mass concentration distribution of highly concentrated lactic acid is determined by back titration. The components of highly concentrated lactic acid, crude lactide, and polymer after the reaction are analyzed by HPLC. Different concentrations of lactic acid solution were prepared for the synthesis of lactide and its content in the product was determined by 1H NMR analysis. We found that lactide is more easily produced from high-concentration lactic acid solution with which the condensed water is easier to release. Hence, the removal of condensed water is crucial to the formation of lactide, although it is not directly formed by esterification of two molecules of lactic acid.
- Liu, Lijuan,Xu, Xiaolong
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p. 856 - 864
(2021/06/16)
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- Chemical Recycling of End-of-Life Poly(lactide) via Zinc-Catalyzed Depolymerization and Polymerization
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The chemical recycling of poly(lactide) was investigated based on depolymerization and polymerization processes. Using methanol as depolymerization reagent and zinc salts as catalyst, poly(lactide) was depolymerized to methyl lactate applying microwave heating. An excellent performance was observed for zinc(II) acetate with turnover frequencies of up to 45000 h?1. In a second step the monomer methyl lactate was converted to (pre)poly(lactide) in the presence of catalytic amounts of zinc salts. Here zinc(II) triflate revealed excellent performance for the polymerization process (yield: 91 %, Mn ~8970 g/mol). Moreover, the (pre)poly(lactide) was depolymerized to lactide, the industrial relevant molecule for accessing high molecular weight poly(lactide), using zinc(II) acetate as catalyst.
- Cheung, Even,Alberti, Christoph,Enthaler, Stephan
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p. 1224 - 1228
(2020/11/03)
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- METHOD FOR SYNTHESIZING LACTIDE BY MEANS OF CATALYSIS OF LACTID ACID
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The present invention relates to a method for the catalytic synthesis of lactide from lactic acid. The method relates to the synthesis of lactide from lactic acid under the catalysis of a zinc oxide nanoparticle aqueous dispersion as a catalyst. The present invention has four technical characteristics: I. the zinc oxide nanoparticle aqueous dispersion catalyst has a sufficient surface area, and the size of nanoparticles is merely 30-40 nm, providing a sufficient contact area between the substrate (lactic acid) and the catalyst; II. the new catalyst has a milder catalytic effect on polymerization, allowing the molecular weight distribution of a prepolymer within a range of 400-1500 g/mol, which is advantageous for depolymerization to proceed; III. the new catalyst is stable, thus avoiding oxidation or carbonization in a high temperature reaction; and IV. the new catalyst has a low toxicity and a small threat to human health.
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Paragraph 0028-0040
(2019/02/24)
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- PROCESS FOR PREPARING A CYCLIC DIESTER OR A CYCLIC DIAMIDE BY REACTING A HYDROXYCARBOXYLIC ACID OR AMIDE WITH AN ACIDIC BEA-TYPE (H-BETA POLYMORPH A) ZEOLITE
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A process for preparing a cyclic diester or a cyclic diamide by reacting a hydroxycarboxylic acid or amide with an acidic BEA (H-beta polymorph A) type zeolite. The process is characterised in that the total amount of acid sites is in the range of from 0.25 to 1.0 mmol/g and the amount of medium acid sites is at least 40% of the total amount of acid sites. The total amount of acid sites and the amount of medium acid sites are determined by NH3-TPD (temperature-programmed desorption of ammonia). Preferably, the process refers to the preparation of lactide from lactic acid. The framework structure of the zeolitic material comprises Si, Al, O, and H.
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Page/Page column 32-33
(2018/10/19)
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- PREPARATION METHOD FOR LACTIDE
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The present invention relates to a method for producing lactide, which comprises the following steps: a first temperature rising and depressurization step for depressurization after raising a temperature of lactic acid up to 160-180anddeg;C; a second temperature rising and depressurization step for adding a reaction catalyst into a product obtained in the first temperature rising and depressurization step, raising the temperature up to 180-210anddeg;C at the rate of 1-10 anddeg;C/min, and depressurizing down to 0.001-1 torr at the rate of 5-20 torr/min; and a lactide extraction step for inserting the product obtained in the second temperature rising and depressurization step into a falling film reactor.COPYRIGHT KIPO 2017
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Paragraph 0043-0047; 0071
(2017/10/20)
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- PREPARATION METHOD FOR LACTIDE
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The present invention refers to, after depressurization step at elevated temperature and elevated temperature until one of lactic acid 160 °C to 180 °C a pressures number 1; number 1 in the range from 1 °C/a pressures obtained resist reaction catalyst at elevated temperature and adding 210 °C temperature up to 180 °C 10 °C/min. after one rate, 20 torr/min. to about 5 torr/rate 0. 001 torr to 1 torr including number 2 to the depressurization step at elevated temperature and a pressures step; and said number 2 in water at elevated temperature and process of 0 °C to 40 °C a pressures obtained contact cleaning step; including a, number of bath method taken to lock are disclosed.
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Paragraph 0042-0045
(2017/05/20)
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- METHOD FOR MANUFACTURING LACTIDE
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The invention pertains to a method for producing lactide comprising the steps of - providing a solution of lactic acid in a volatile organic solvent, - subjecting the solution to an evaporation step to remove volatile organic solvent and water, resulting in the formation of a composition comprising lactic acid oligomer, - adding catalyst to the composition comprising lactic acid oligomer, and bringing the mixture to reaction conditions, to form lactide. It has been found that the process according to the invention results in the efficient production of lactide with a high production rate and a good product quality.
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Page/Page column 22; 23
(2016/09/22)
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- Utilizing the catalytic synthesis mode of the method of preparing lactide
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Utilizing the catalytic synthesis mode of the method of preparing lactide to a process for the preparation of lactide. The invention provides an environmental friendly, convenient operation by utilizing catalytic synthesis mode of the method of preparing lactide. Utilizing the catalytic synthesis mode of the method of preparing lactide, characterized in that comprises a lower step. Utilizing the catalytic synthesis mode of the method of preparing lactide, characterized in that comprises a lower step. (1) the D, L-lactic acid heating and dewatering. (2) lactic acid oligosynthetic oligomer. According to the quality than add a certain amount of catalyst, under reduced pressure (13.3KPa) re-under slow heating to 140 °C. (3) adding catalyst latter settles 10 minutes, stirring with water and again heated to 90 degree Celsius to maintain 3 to 5 hours after cooling. (4) low tetramer depolymerises ring. Replace the receiving device, re-started to rise quickly. (5) extraction separation: the resulting solution for 10 minutes later, extraction by adding extracting agent, after extraction to obtain solution, vested.
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Paragraph 0015-0021
(2017/03/22)
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- PREPARATION METHOD FOR LACTIDE
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The lactic acid 160 °C to 180 °C a pressures after depressurization step at elevated temperature and elevated temperature until one number 1; and number 1 in the range from 1 °C/a pressures obtained resist reaction catalyst at elevated temperature and adding 10 °C/min. 180 °C to 210 °C temperature rate until after one, 20 torr/min. to about 5 torr/rate 0. 001 torr to 1 torr a pressures step including number 2 to the depressurization step at elevated temperature and; including a, number of bath method taken to lock are disclosed.
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Paragraph 0041-0052
(2017/06/09)
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- From meso-Lactide to Isotactic Polylactide: Epimerization by B/N Lewis Pairs and Kinetic Resolution by Organic Catalysts
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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 is kinetically polymerized into poly(l-lactide) and optically resolved d-LA, with a high stereoselectivity kL/kD of 53 and an ee of 91% at 50.6% monomer conversion, by newly designed bifunctional chiral catalyst 4 that incorporates three key elements (β-isocupreidine core, thiourea functionality, and chiral BINAM) into a single organic molecule. 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.
- Zhu, Jian-Bo,Chen, Eugene Y.-X.
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supporting information
p. 12506 - 12509
(2015/10/19)
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- Gas phase dehydration of lactic acid to acrylic acid over alkaline-earth phosphates catalysts
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A series of alkaline-earth phosphates were prepared by co-precipitation method using sodium free or sodium containing precursors and evaluated for gas phase dehydration of lactic acid. The catalysts were characterized by BET measurements, X-ray diffraction, chemical analysis, XPS spectroscopy and both NH3 and CO2-TPD. After checking the stability of catalysts under feed, it was shown that selectivity to acrylic acid strongly depended on reaction temperature but not on contact time. At temperature of 380 C, values ranging from 19 to 49% were measured for the different prepared catalysts. The highest value was reached with Ba3(PO4)2 (55% for C3 products) but selectivities rather close were obtained with different other phosphates suggesting kinetic limitation. Acid-base properties measurements revealed that alkaline-earth phosphates exhibited high proportion of acidic and basic sites with same weak strength. Furthermore, correlation between acrylic selectivity of alkaline earth phosphates and the acid-base balance were clearly established for the first time: selectivity was 50% for balance close to 1 and decreased by factor two increasing this parameter to 2. Finally, FTIR spectra of spent catalysts showed alkaline-earth lactates adsorbed over the catalysts which could be reaction intermediates for dehydration of lactic acid.
- Blanco,Delichere,Millet,Loridant
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p. 185 - 191
(2014/03/21)
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- Reactions of hydrogen peroxide with acetylacetone and 2- acetylcyclopentanone
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A reaction of acetylacetone with equimolar amount of concentrated aqueous H2O2 in both organic solvents (ButOH, AcOH) and water at various temperatures gave the corresponding 3,5-dihydroxy-1,2- dioxolanes with different configuration of stereogenic centers. In the pres-ence of an excess of H2O2, 3,5-dihydroxy-1,2-dioxolanes were converted to a mixture of 5-hydroperoxy-3-hydroxy-1,2-dioxolanes and further to a mixture of dimeric 1,2-dioxolan-3-ylperoxides. All the peroxides formed exist in solutions as equilibrium mixtures with the starting reagents. A prolonged reflux of solutions of 3,5-dihydroxy-1,2-dioxolanes in ButOH in the presence of a large excess of H2O2 led to the skeletal rearrangements of the substrates to a mixture of propionic acid and hydroxyacetone, which underwent further oxidative transfor-mations. Unlike acetylacetone, 2-acetylcyclopentanone reacted with H2O2 in aqueous phase or in solutions in ButOH under thermodynamic or kinetic control with the formation of the corresponding 5-hydroperoxy-3-hydroxy- 1,2-dioxolanes, rather than 3,5-dihydroxy-1,2-di-oxolanes. Thermodynamically controlled process in solution in AcOH gave a mixture of all four possible hydroperoxyhydroxy-1,2-dioxolanes. These cyclic peroxides in solutions in ButOH or AcOH readily converted to a mixture of AcOH, glutaric, α-methyladipic, and α-hydroxy-α-methyladipic acids. An active α-hydroxylation of the substrate was observed upon reflux of a solution of 2-acetylcyclopentanone and H2O2 in AcOH.
- Novikov,Shestak
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p. 2171 - 2190
(2014/11/07)
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- METHOD OF PREPARING LACTIDE FROM LACTATE
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The present invention provides a method of preparing lactide with a high yield from lactate obtained through a fermentation process. In certain embodiments, the invention provides a method of preparing high-purity lactide with a high yield, wherein the method comprises treating lactate with a specific solvent, using a catalyst, and phase-separating the resultant. In accordance with the invention, costs for manufacturing polylactic acid can be considerably reduced.
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Paragraph 0057-0059
(2013/10/22)
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- PROCESS FOR THE MANUFACTURE OF LACTIDE
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Process for the manufacture of lactide comprising heating lactic acid in the presence of at least one hygroscopic salt present in an amount of at least 1 mol per mol of lactic acid.
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Page/Page column 9-10
(2012/01/14)
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- PROCESS FOR MANUFACTURING A CYCLIC DIESTER OF AN A-HYDROXY ACID
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Process for manufacturing a cyclic diester of an α-hydroxy acid comprising the following steps: a substantially anhydrous salt of a divalent metal and of an α-hydroxy acid is mixed with a strong acid, the pKa of which is less than that of the α-hydroxy acid and the salt of which with the divalent metal is hygroscopic; andthe mixture is left to react for a sufficient time in order to obtain the cyclic diester dispersed in the hygroscopic salt.
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Page/Page column 4
(2009/12/28)
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- A PROCESS FOR THE PRODUCTION OF CYCLIC DIESTERS OF ALPHA-HYDROXYACIDS
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Process for the synthesis of a cyclic diester of an alpha-hydroxyacid, comprising the following steps: an alkalino-earth salt of the corresponding alpha-hydroxyacid is mixed with said alpha-hydroxyacid and water; the mixture is treated by evaporation-crystallization, so that a hydrate of the alkalino-earth salt of the linear dimer of the corresponding alpha-hydroxiacid precipitates; the hydrated salt is dehydrated to give the corresponding anhydrous salt; and the anhydrous salt is pyrolyzed, releasing the cyclic diester of the corresponding alpha-hydroxyacid and leaving the alkalino-earth hydroxide as solid residue.
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Page/Page column 9-10
(2009/07/25)
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- METHOD AND APPARATUS FOR PRODUCING POLYHYDROXY CARBOXYLIC ACID
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The object is to provide a method and apparatus for producing a polyhydroxy carboxylic acid according to which an annular diner can be efficiently obtained in the production of polyhydroxy carboxylic acid which is small in distribution breadth of molecular weight in depolymerization and opening ring polymerization steps. There are provided a depolymerization device 11 which depolymerizes hydroxy carboxylic acid or a polycondensate thereof into an annular dimer, a upper distillation column 13 which condenses the annular dimer vaporized in the depolymerization device 11, and lower distillation column 12 which refluxes the annular dimer and is provided between the depolymerization device 11 and the upper distillation column 13, said depolymerization device 11 having a polycondensate feed opening 54 and an annular dimer discharge opening 55 which are provided at a casing 50, a liquid film being formed inside the casing 50 and heated by a heating part.
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Page/Page column 5-6
(2010/11/29)
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- Process for production of organic acid esters
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A process for producing organic acid esters using continuous countercurrent reactive distillation using acid catalysts in a structured packing in a single column (10) is described. In the reactive distillation an organic acid ester is formed by chemical reaction and can be purified to its final state within the single column. Organic acid esters are produced at relatively low cost, with less waste production, and in a less complicated manner than prior processes. Organic acid ester have uses as solvents, as intermediate chemicals, and in consumer products.
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Page/Page column 11
(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 18-19
(2010/02/12)
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- Synthesis and characterization of a brush-like copolymer of polylactide grafted onto chitosan
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A brush-like poly(DL)-lactide grafted onto chitosan as the backbone was investigated. The graft copolymerization was carried out with triethylaluminum as catalyst in toluene at 70°C. It was found that a greater lactide content in the feeding ratio results in a higher grafting percentage. FTIR spectrometry, 1H NMR, DSC scanning, and wide-angle X-ray scattering, respectively, are used to characterize these branch copolymers. A copolymer has a definite melting point when the molar feeding ratio of lactide to chitosan is more than 10:1, and the ΔH of the copolymers increases with the feed ratio of lactide to chitosan in feeding.
- Liu,Tian,Hu
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p. 845 - 851
(2007/10/03)
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- Process for the preparation of cyclic esters and method for purification of the same
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The present invention provides a process for production of a cyclic ester by depolymerization of an aliphatic polyester. In the process, a mixture containing the aliphatic polyester and a specific polyalkylene glycol ether, which has a boiling point of 230-450° C. and a molecular weight of 150-450, is heated under normal or reduced pressure to a temperature at which depolymerization of the aliphatic polyester takes place. Then, a substantially homogeneous solution phase, consisting of the melt phase of the aliphatic polyester and the liquid phase of the polyalkylene glycol ether, is formed. Heating of the solution phase is continued to form the cyclic ester by depolymerization and distil out the cyclic ester together with the polyalkylene glycol ether, and then the cyclic ester is recovered from the distillate. The present invention also provides a process for purification of a crude cyclic ester by use of the specific polyalkylene glycol ether described above.
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Page/Page column 16
(2010/11/30)
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- Synthesis of New Substituted 2,3-Dihydro-1,4-dioxin-2-ones and 1,4-Dioxan-2-ones
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3-Alkyl-6-methyl-2,3-dihydro-1,4-dioxin-2-ones reacted with acetyl chloride in the presence of zinc(II) chloride to give 5-acetyl-3-alkyl-6-methyl- 2,3-dihydro-l,4-dioxin-2-ones. Oxidation of the latter with hydrogen peroxide in formic acid, followed by treatment with magnesium bromide, afforded 3-alkyl-6-methyl-1,4-dioxane-2,5-diones. Chlorination of 6-hydroxymethyl-1,4- dioxan-2-ones with thionyl chloride and subsequent dehydrochlorination led to formation of 6-methylene-1,4-dioxan-2-ones.
- Akopyan,Khachatryan
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p. 707 - 709
(2007/10/03)
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- Synthesis of new substituted 2,3-dihydro-1,4-dioxin-2-ones and 1,4-dioxan-2-ones
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3-Alkyl-6-methyl-2,3-dihydro-1,4-dioxin-2-ones reacted with acetyl chloride in the presence of zinc(II) chloride to give the corresponding 3-alkyl-5-acetyl-6-methyl-2,3-dihydro-1,4-dioxin-2-ones. Oxidation of the latter with hydrogen peroxide in formic acid, followed by treatment with magnesium bromide, afforded 3-alkyl-6-methyl-1,4-dioxane-2,5-diones. Successive chlorination and dechlorination of 6-hydroxymethy 1-1,4-dioxan-2-ones yielded 6-methylene-1,4-dioxan-2-ones.
- Akopyan,Khachatryan
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p. 1034 - 1036
(2007/10/03)
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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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- Condensation of Glycolic, Lactic and 2-Hydroxybutanoic Acids during Heating and Identification of the Condensation Products by GLS-MS
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Glycolic, lactic and 2-hydroxybutanoic acids are partly converted to various condensation products during heating.This conversion was studied at 100 deg C and 125 deg C by identifying the trimethylsilylated products consisted of both linear (dimers and trimers) and cyclic (dimers) structures.The influence of the condensation on the recovery and purification of the hydroxy acids by distillation is discussed.
- Alen, Raimo,Sjoestroem, Eero
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p. 633 - 636
(2007/10/02)
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