Patent ID: 8614280

Claim:
A process for the continuous production of a biodegradable polyester based on aliphatic or aliphatic and aromatic dicarboxylic acids and on aliphatic dihydroxy compounds, where a mixture composed of the aliphatic dihydroxy compounds, of the aliphatic and aromatic dicarboxylic acids, and, optionally, of further comonomers (component C) is mixed, without addition of a catalyst, to give a paste, or, as an alternative, the liquid esters of the dicarboxylic acids are fed into the system, as also are the dihydroxy compound and, optionally, further comonomers, without addition of any catalyst, where i) in a first stage, this mixture, together with the entire amount or with a portion of the catalyst, is continuously esterified or, respectively, transesterified; ii) in a second stage, the transesterification or, respectively, esterification product obtained in i) is continuously precondensed to an intrinsic viscosity of from 20 to 70 cm 3 /g to DIN 53728; iii) in a third stage, the product obtainable from ii) is continuously polycondensed to an intrinsic viscosity of from 60 to 170 cm 3 /g to DIN 53728, and iv) in a fourth stage, the product obtainable from iii) is reacted continuously with a chain extender D in a polyaddition reaction to an intrinsic viscosity of from 150 to 320 cm 3 /g to DIN 53728; where stage ii) is carried out in a tower reactor, and the product stream is conducted concurrently by way of a falling-film cascade, and the reaction vapors are removed in situ from the reaction mixture.