Process and apparatus for preparing biodegradable polyesters

Abstract

There is described a process for preparing a biodegradable polyester from an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid and a diol where in a first reaction step the aromatic acid is esterified with the diol, and in a second reaction step the aliphatic acid is added to the reaction mixture. Furthermore, there is described an apparatus for carrying out this process.

Claims

1. A process for preparing a biodegradable polyester from an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid and a diol where in a first reaction step the aromatic acid is esterified with the diol, and in a second reaction step the aliphatic acid is added to the reaction mixture, wherein in the second reaction step the aliphatic acid is added together with further diol to the reaction mixture wherein the aliphatic acid is added either in a molten state or as a paste or as an ester of the diol or dissolved in the diol.

2. The process according to claim 1, where the pressure for the second reaction step is equal to or lower than the pressure for the first reaction step.

3. The process according to claim 1, where the temperature for the second reaction step is equal to or lower than the temperature for the first reaction step.

4. The process according to claim 1, wherein the process is a batch process or a continuous process.

5. The process according to claim 1, where the product obtained in the second reaction step enters an additional esterification step operated at lower pressure and equal to or higher temperature than the second reaction step.

6. The process according to claim 1, where the product obtained in the second reaction step enters a first prepolycondensation step operated at lower pressure and equal to or higher temperature than the second reaction step.

7. The process according to claim 6, where the product obtained in the first prepolycondensation step enters a second prepolycondensation step operated at lower pressure and equal to or higher temperature than the first prepolycondensation step.

8. The process according to claim 5, where the product obtained in the additional esterification step enters a polycondensation step operated at lower pressure and equal to or higher temperature than the second reaction step.

9. The process according to claim 8, where in the polycondensation step a reactor providing a high polymer surface and/or an active surface renewal is used.

10. The process according to claim 9, wherein the reactor comprises a disc ring reactor or a disc cage reactor.

Description

(1) The FIGURE shows an apparatus suitable for carrying out the process for preparing the biodegradable polyester.

(2) As shown in the FIGURE, the apparatus 1 for preparing a biodegradable polyester comprises a reaction vessel 2 equipped with a partition wall 3 to divide the reaction vessel 2 in a first reaction zone 12 and a second reaction zone 13 for carrying out the first and the second reaction step, respectively, separately. Furthermore, at the bottom there is provided a drain hole 4 which provides a passage through the partition wall 3 between the two reaction zones 12 and 13. The apparatus 1 is further equipped with a stirrer 5 which is provided in the first reaction zone 12 in which the first reaction step is carried out. Furthermore, there is provided an inlet for aromatic acid 6, and an inlet for the dial 7 to feed these compounds into the first reaction zone 12. Moreover, there is provided an inlet for the aliphatic acid 8, and an inlet for the dial 9 to feed these compounds into the second reaction zone 13. The apparatus 1 is also equipped with an outlet for vapor 10 which is provided at the top of the reaction vessel 2 and an outlet for the esterification product 11, which is provided at the bottom of the reaction vessel 2.

EXAMPLES

(3) Example 1 shows the inventive process using a 10 l-reactor as well for TPA as for adipic acid.

(4) Esterification:

(5) Recipe:

(6) 1385.1 g TPA (Terephthalic acid)

(7) 1051.9 g BD (Butanediol, molar ratio BD to TPA=1.4)

(8) 1.554 g Tyzor TnBT catalyst (Dorf Ketal) to the monomers (60 ppm Ti related to final polymer)

(9) 47.4 g Polyethylene glycol 400 (PEG 400), (13 kg/to)

(10) 2.55 g Pentaerythritol, (0.7 kg/to)

(11) Esterification of TPA

(12) After filling the monomers and the catalyst into the reactor, the reactor has been flushed with nitrogen. The reaction mixture was heated up under continuous stirring. When the product temperature reached 195° C. (start of time measurement), the pressure was reduced within 15 min to 400 mbar (abs) while product temperature increased further to 245° C. The esterification was finished after 120 min.

(13) Preparation of Adipic Acid Solution in BD

(14) Recipe:

(15) 1319.5 g adipic acid

(16) 789.3 g BD (molar ratio BD to adipic acid=0.97; resulting molar ratio of BD to both acids=1.176)

(17) Preparation of Solution

(18) BD was filled in to the preparation vessel and afterwards adipic acid was added. The preparation vessel was rendered inert by nitrogen. The mixture was heated up to 160° C. under slight overpressure and stirred until the TPA esterification was finished. During this time, the adipic acid dissolved in BD.

(19) Continuation of Esterification

(20) The adipic acid-BD-solution was fed into the esterification reactor within approximately 5 min.

(21) The product temperature, as result of the feed and a reduction of the heating temperature, dropped to 182° C. and increased in the ongoing esterification to 212° C. The condensate yield indicated the targeted end of esterification reaction after a total of 160 min after start of time measurement (40 minutes after adding of adipic acid solution).

(22) Addition of Phosphorus Component

(23) An amount of 1.583 g Triethyl phosphonoacetat (TEPA) (60 ppm P related to final polymer) was added and prepolycondensation was started.

(24) Prepolycondensation

(25) The condensing system was switched from esterification condenser to prepolycondensation cooling traps and the pressure was reduced to 150 mbar within 5 min and further on to 35 mbar within another 5 min. At this target pressure the reaction continued for 10 min. The melt temperature averaged at 236° C.

(26) The overall prepolycondensation time was 20 min.

(27) Addition of Polycondensation Catalyst

(28) An amount of 2.07 g Tyzor TnBT catalyst (Dorf Ketal), (80 ppm Ti related to final polymer) was fed afterward and post-flashed with 10 g BD into reactor.

(29) Polycondensation

(30) The condensing system was switched from prepolycondensation cooling traps to polycondensation cooling traps. The pressure was reduced within 15 min to <1 mbar. The temperature during polycondensation was 240° C. The total polycondensation time was 380 min. After breaking the vacuum with nitrogen, the polymer was discharged by pressure and granulated. The intrinsic viscosity of the final polymer product was 1.580 dl/g.

(31) Example 2 shows the inventive process using a 10 l-reactor as well for TPA as for adipic acid.

(32) Esterification:

(33) Recipe:

(34) 1385.1 g TPA

(35) 1051.9 g BD (molar ratio BD to TPA=1.4)

(36) 1.554 g Tyzor TnBT catalyst (Dorf Ketal) to the monomers (60 ppm Ti related to final polymer)

(37) 47.4 g Polyethylene glycol 400 (PEG 400), (13 kg/to)

(38) 2.55 g Pentaerythritol, (0.7 kg/to)

(39) Esterification of PTA

(40) After filling the monomers and the catalyst into the reactor, the reactor has been flushed with Nitrogen. The reaction mixture was heated up under continuous stirring. When the product temperature reached 195° C. (start of time measurement), the pressure was reduced within 15 min to 400 mbar (abs) while product temperature increased further to 245° C. The esterification was finished after 120 min.

(41) Preparation of Adipic Acid Solution in BD

(42) Recipe:

(43) 1319.5 g adipic acid

(44) 764.9 g BD (molar ratio BD to adipic acid=0.94)

(45) Resulting molar ratio of both acids to BD: 1.161

(46) Preparation of Solution

(47) BD was filled in to the preparation vessel and afterwards adipic acid was added. The preparation vessel was rendered inert by nitrogen. The mixture was heated up to 160° C. under slight overpressure and stirred until the TPA esterification was finished. During this time, the adipic acid dissolved in BD.

(48) Continuation of Esterification

(49) The adipic acid-BD-solution was fed into the esterification reactor within approximately 10 min.

(50) The product temperature, as result of the feed and a reduction of the heating temperature, dropped to 185° C. and increased in the ongoing esterification to 210° C. The condensate yield indicated the targeted end of esterification reaction after a total of 170 min after start of time measurement (50 minutes after adding of adipic acid solution).

(51) Prepolycondensation

(52) The condensing system was switched from esterification condenser to prepolycondensation cooling traps and the pressure was reduced to 150 mbar within 5 min and further on to 35 mbar within another 5 min. At this target pressure the reaction continued for 10 min. The melt temperature averaged at 236° C.

(53) The overall prepolycondensation time was 20 min.

(54) Addition of Polycondensation Catalyst

(55) An amount of 2.07 g Tyzor TnBT catalyst (Dorf Ketal), (80 ppm Ti related to final polymer) was fed afterward and post-flashed with 10 g BD into reactor.

(56) Polycondensation

(57) The condensing system was switched from prepolycondensation cooling traps to polycondensation cooling traps. The pressure was reduced within 15 min to <1 mbar. The temperature during polycondensation was 240° C. The polycondensation time was 350 min. After breaking the vacuum with nitrogen, the polymer was discharged by pressure and granulated. The intrinsic viscosity of the final polymer product was 1.665 dl/g.