Synthesis and Production of Poly lactic Acid

Synthesis and Production of Poly(lactic Acid) Table 2.1 Physical Properties of Lactic Acid... 

HP is chemically a three-carbon, optically inactive, specialty chemical with commercial interest. It is the structural isomer of lactic acid (Kxunar et al., 2013). It can be used as an intermediate for the synthesis of other important chemicals, such as malonic acid, 1,3-propanediol (PDO), acrylonitrile, acrylic acid, and acrylamide. These compounds are used for making adhesives, polymers, fibers, plastic packing, resins, and cleaning agents, as listed in Fig. 6.1.3-HP acts as a starting material for the synthesis and production of poly-3-hydroxy... 

Groot W, van Krieken J, Sliekersl O, de Vos S (2010) Production and purification of lactic acid and lactide. In Poly(lactic acid) synthesis, stmetures properties, processing, and applications, John Wiley Sons, Inc., Hoboken, New Jersey, pp 1-18... 

Similar to the synthesis of poly(lactic acid), the polycondensation of glycolic add is the simplest process available to prepare PGA but it is not the most efficient one because it yidds low-molecular-wdght products. The procediue is as follows glycolic add is heated at atmospheric pressiue and a temperature of about 175-185 C during a time necessary for removing water. Subsequently, the reaction pressure is reduced... 

Polymers derived from renewable resources (biopolymers) are broadly classified according to the method of production (1) Polymers directly extracted/ removed from natural materials (mainly plants) (e.g. polysaccharides such as starch and cellulose and proteins such as casein and wheat gluten), (2) polymers produced by "classical" chemical synthesis from renewable bio-derived monomers [e.g. poly(lactic acid), poly(glycolic acid) and their biopolyesters polymerized from lactic/glycolic acid monomers, which are produced by fermentation of carbohydrate feedstock] and (3) polymers produced by microorganisms or genetically transformed bacteria [e.g. the polyhydroxyalkanoates, mainly poly(hydroxybutyrates) and copolymers of hydroxybutyrate (HB) and hydroxyvalerate (HV)] [4]. 

A. SbdergSrd, M. Stolt, Industrial production of high molecular weight poly(lactic acid), in R. Auras, L.T. Lim, S.E.M. Selke, H. Tsuji (Eds.), Poly(Lactic Acid) Synthesis, Structures, Properties, Processing, and Applications, John Wiley Sons, New York, 2010, pp. 27-41. 

Poly(lactiC acid). Lactic add, CH3CHOHCOOH, occurs naturally in animals and in microorganisms. It can be produced commercially by chemical synthesis, bnt in the United States fermentation is the major route. In bioreactors, microorganisms are fed a carbon source substrate, such as dextrose, with delds of lactic acid greater than 90%. The lactic acid is recovered from the fermentation broth and purified in a multistep process that represents a major part of production costs. Eighty percent of the world s production of lactic acid is from corn sugar. 

The synthetic synthesis of known chiral polymers mostly starts from optically pure monomers obtained form the chiral pool. The optically pure fermentation product L-lactic acid, for example, is the starting material for the synthesis of poly(L-lactide). However, converting a racemic or achiral monomer quantitatively into a homochiral polymer is less straightforward [3]. This is surprising considering the enormous potential of biocatalysis and tandem catalysis that has emerged in the past decades to prepare optically active intermediates [4]. 

Lactic acid is currently produced by fermentation of carbohydrates and is rme of the high potential and versatile biomass-derived platform chemicals, leading to various useful polymer products. PLA is produced by ROP of lactide (derived from lactic acid) and exhibits mechanical properties similar to poly(ethylene terephthal-ate) and polypropylene. Representative examples discussed herein included the synthesis of highly stereo-controlled PLAs, such as isotactic, heterotactic, and syndiotactic PLA materials, rendered by different catalyst/initiator systems. 

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