Verfahren zum Abbau von Polyaethylenterephthalat zu Terephthalsaeuredimethylester

• Main Authors: HAMMERSCHICK,WALTER, HEINZ MEDEM,DR, HANS GRUSCHKE,DR
• Format: Patent
• Language: German
• Published: 07.11.1968
• Subjects: ACYCLIC OR CARBOCYCLIC COMPOUNDS; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F,C08G; CHEMISTRY; COMPOSITIONS BASED THEREON; GENERAL PROCESSES OF COMPOUNDING; METALLURGY; ORGANIC CHEMISTRY; ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; WORKING-UP

Dimethyl terephthalate is obtained by reacting polyethylene terephthalate with 2-8 times its weight of methanol (optionally in presence of catalyst) at 160-240 DEG C. and 20-70 atm. gauge pressure in two stages: -(1) in which partial reaction is effected by stirring in an autoclave for an average residence time of 7-13 minutes and (2) in which the reaction is completed at the same pressure without further application of heat in a large reaction tube, into which the effluent from (1) is passed through an overflow and an immersion tube ending at or near the bottom of the reaction tube, and in which the mixture ascends at a slow enough rate to avoid turbulence and without stirring. The pressure of the solution is then released to 3 atm. gauge, the mixture transferred to a stirring vessel at 100 DEG C. and the pressure released to normal.