The PLA synthesis formula - PLA bottles manufacturer to tell you

In general, polylactic acid ( PLA） The preparation of lactic acid as a raw material for synthesis. At present there are several kinds of synthesis methods is relatively mature, direct polycondensation of lactic acid, the other is a first by lactic acid to synthesize lactide, again under the action of catalyst, ring opening polymerization. There is also a kind of solid together legally. 1) Direct polymerization of lactic acid direct polymerization as early as 30 ~ 40 s of the 20th century has begun to study, but because the key technology such as involves the reaction of water removal also can't get very good solve, so its low molecular weight of the product ( Are all below 4000) , low intensity, easy to decompose, not practical. Showa polymer company USES to lactic acid in inert gas heating temperature and slow decompression, slowly make lactic acid dehydration condensation directly, and make the reactants in 220 ~ 260 ℃, 133 pa further polycondensation, get the relative molecular mass polylactic acid in more than 4000. But this method long reaction time, the product in the later will be aging under the high temperature of decomposition, color, and uneven. Japan's mitsui pressure chemical company by solution polymerization polylactic acid (PLA) for direct polymerization of lactic acid. The main characteristics of the direct method is the synthesis of poly (lactic acid does not contain catalyst, so the polycondensation reaction to a certain degree of system will be the equilibrium state, need to heat up pressure to break the balance reaction, reaction conditions are relatively strict. In recent years, through technical innovation and improvement, direct polymerization has made certain progress, should be in the near future as the technology matures, can be used in the industrial production. 2) Ring opening polymerization ring-opening polymerization is the use of the world's more production methods. As early as in the middle of the 20th century, dupont researchers will use ring opening polymerization of high molecular weight polylactic acid are obtained. In recent years, overseas research on synthesis of poly (lactic acid) (PLA) mainly concentrated on the ring opening polymerization of lactide. Germany's Boeheringer Zngelhelm company using this method the polylactic acid series products with brand name appeared on the market; The United States Cargill company with production of polylactic acid by the melt-blown and spun-bonded after processing, developed medical yuan fabric products; And our country to synthetic polymers of poly (lactic acid) (PLA) is only a handful of several such as institute of zhongshan university high polymer. Ring opening polymerization using stannous caprylate as initiator, can reach millions of molecular weight, high mechanical strength, aggregation separation in two steps: the first step is to polylactic acid by dehydration cyclization lactide was; The second step is to lactide by ring opening polymerization with poly lactide; But the ring opening polymerization on the purity, the catalyst in polymerization monomer purity requirements is extremely high, even trace amounts of impurities can also make the PLA molecular weight less than 100000, and polymerization conditions such as temperature, pressure, the variety and dosage of catalyst, reaction time and so on will also greatly affect the PLA's molecular weight, so the synthesis of high molecular weight PLA is a technical difficulty. 3) Solid together this method is to directly polymerization were low molecular weight of resin in vacuum vacuum and temperature on the Tg - Under the conditions of polymerization reaction between Tm, in order to improve the degree of polymerization, increase the molecular weight, thus improve the strength of materials and processing performance. 1. 2. Preparation process we mainly talk about the ring opening polymerization methods, its process is roughly like this: 1) Drawn to crops such as corn shell after crushing, extract starch, and then will be made without the elaboration starch glucose. Now a lot of high technology has overcome the minus the crushing process, raw materials extracted directly from a large number of crops. 2) Fermentation in a way that is similar to produce beer or alcohol fermentation of glucose, and after the glucose fermentation become food similar to add for the human body within the muscle tissue of lactic acid. 3) Intermediate product condensed the lactic acid monomer in a special process, into the middle type product - — Water reducing lactate lactide. 4) After vacuum purification, polymerization of lactide monomer to a do not use solvent dissolving process to complete open loop action, monomer polymerization. 5) Polymer modified because of the different molecular weight and crystallinity of polymer, can make the changes of materials properties space is very large, so because of the different application products, will make different modified PLA. 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