Method for the continuous production of high-molecular polyester and device for carrying out the method

A method for continuous production of high-molecular weight polyester by esterification of dicarboxylic acids and/or transesterification of dicarboxylic acid esters with diols in the presence of catalysts with formation of a prepolymer and polycondensation thereof into high-molecular weight polyester, wherein

• a1) a paste and/or a suspension of the dicarboxylic acid and of the diol is produced, there being maintained a molar ratio of diol to dicarboxylic acid of 0.8 to 1.8, a temperature of 20 to 90° C. and a pressure between 0.1 to 1.0 bar, or
• a2) the dicarboxylic acid ester is melted and the latter is mixed together with the diol in the molar ratio of diol to dicarboxylic acid ester of 1.2 to 1.8 at a temperature of 145 to 165° C.
• b1) the products from a1) and/or a2) are supplied continuously to a hydrocyclone zone of a tower reactor where esterification and/or transesterification is implemented in the tower reactor continuously, simultaneously and uninterruptedly until and including prepolycondensation, the following conditions being maintained:
• the products from a1) and/or a2) are subjected to a treatment at a temperature of 170 to 270° C. and a pressure of 0.3 to 3 bar, a partial quantity of the catalyst being supplied in this first reaction step and the reaction vapors being removed in situ from the reaction mixture,
• b2) the product of the reaction step b1) is transferred continuously into a heated pressure pipe and maintained at a pressure of 1 to 10 bar and 200 to 280° C., 0.03 to 0.3 mol diol per mol acid being supplied in this reaction step,
• b3) the product of the reaction step b2) is transferred continuously into a further zone, in which automatically reducing pressures in the range of 0.2 to 1 bar and automatically increasing temperatures of 230 to 280° C. are maintained, 0.02 to 0.2 mol diol and a partial quantity of the catalyst being supplied into the further zone,
• b4) the product from reaction step b3) is subjected to a further reaction at 0.01 to 0.1 bar and 240 to 280° C., and
• b5) the reaction products water or respectively methanol, byproducts and excess diol from the reaction steps b1) and b3) to b5) are removed and the diol is directed back again after purification to the individual reaction steps,
• c1) the prepolymer obtained from b4) is continuously polycondensed in a normal polycondensation apparatus at temperatures of 240 to 290° C. and pressures of 0.0002 to 0.003 bar or
• c2) the obtained prepolymer is solidified, processed into pellets and subjected to a subsequent condensation in solid phase at temperatures between 160 and 230° C. under conditioned inert gas.