| abstract |
The invention relates to a method for the continuous production of a biodegradable polyester on the basis of aliphatic or aliphatic and aromatic dicarboxylic acids and aliphatic dihydroxy compounds. According to said method, a mixture of the aliphatic dihydroxy compounds, the aliphatic and aromatic dicarboxylic acids and optionally other comonomers (component C) is mixed to give a paste, without adding a catalyst, or alternatively, the liquid esters of the dicarboxylic acids and the dihydroxy compound and optionally other comonomers are fed to the mixture, without adding a catalyst, i) the mixture being continuously esterified or transesterified with the total amount or a partial amount of the catalyst in a first step; ii) the transesterification or esterification product obtained according to i) being continuously precondensed in a second step, optionally with the remaining amount of the catalyst, up to a viscosity number of 20 to 70 cm3/g (DIN 53728); iii) the product obtainable according to ii) being polycondensated in a third step up to a viscosity number of 60 to 170 cm3/g (DIN 53728) and iv) the product obtainable according to iii) being reacted in a polyaddition reaction with a chain extender D in a fourth step up to a viscosity number of 150 to 320 cm3/g (DIN 53728). The invention further relates to biodegradable polyesters that are for the first time obtainable by this method. |