Process for removal of tetrahydrofuran

Abstract

Provided is a process for the removal of tetrahydrofuran from polyesters or copolyesters comprising 1,4-butylene dicarboxylate repeating units and from compositions comprising the polyesters or copolyesters.

Claims

1. A process for the removal of tetrahydrofuran from a polyester or a copolyester comprising 1,4-butylene dicarboxylate repeating units or from a composition comprising said polyester or copolyester, comprising the steps of: (1) providing a polyester or a copolyester comprising 1,4-butylene dicarboxylate repeating units or a composition comprising said polyester or copolyester by means of a polycondensation reaction and, if a copolyester is formed a coplymerization reaction; (2) contacting a gaseous flow with the polyester or copolyester comprising 1,4-butylene dicarboxylate repeating units or the composition comprising said polyester or copolyester at a temperature in the range between 60 C. and 150 C., at an absolute pressure between 800 mbar and 5 bar; (3) separating the gaseous flow containing the tetrahydrofuran from the polyester or copolyester or from the composition comprising said polyester or copolyester; and (4) recovering the polyester or copolyester or the composition comprising said polyester or copolyester with a residual tetrahydrofuran content of less than 10 ppm; wherein the process for the removal of the tetrahydrofuran is carried out after the polycondensation reaction and, if a copolyester is formed after the coplymerization reaction.

2. The process according to claim 1, in which at the end of step (3) the tetrahydrofuran content is of less than 6 ppm.

3. The process according to claim 1, in which at the end of step (3) the tetrahydrofuran content is of less than 4 ppm.

4. The process according to claim 1, in which at the end of step (3) the tetrahydrofuran content is of 3 ppm or less.

5. The process according to claim 1, in which the gaseous flow is contacted with the polyester, copolyester or composition thereof at a temperature in the range between 70 C. and 145 C.

6. The process according to claim 1, in which the gaseous flow is contacted with the polyester, copolyester or composition thereof at a temperature in the range between 80 C. and 140 C.

7. The process according to claim 1, in which the gaseous flow is contacted with the polyester, copolyester or composition thereof at a temperature in the range between 90 C. and 130 C.

8. The process according to claim 1, in which the gaseous flow is contacted with the polyester, copolyester or composition thereof at an absolute pressure between 900 mbar and 2 bar.

9. The process according to claim 1, in which the gaseous flow is contacted with the polyester, copolyester or composition thereof at an absolute pressure between 1 bar and 1.5 bar.

10. The process according to claim 1, carried out in one or more vertical, horizontal or inclined dryers of rotating drum or fluidised bed, belt drying oven, vessel, fixed, semi-fluid or fluidised bed column type or a diffuser.

11. The process according to claim 1, in which the said polyester or copolyester comprising 1,4-butylene dicarboxylate repeating units or composition thereof is in the form of granules, powders, shavings, particles, lumps, pieces, fragments, flakes, chips of any shape obtained through a comminuting operation, and finished manufactured articles.

12. The process according to claim 1, in which the said gaseous flow comprises air, nitrogen, argon, carbon dioxide, helium and mixtures thereof.

13. The process according to claim 1, in which said gaseous flow consists of air.

14. The process according to claim 1, in which the said polyester or copolyester comprising 1,4-butylene dicarboxylate repeating units is selected from poly(1,4-butylene succinate), poly(1,4-butylene adipate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene 2,5-furandicarboxylate), poly(1,4-butylene terephthalate), and poly(1,4-butylene 2,5-furandicarboxylate).

15. A polyester or copolyester comprising 1,4-butylene dicarboxylate repeating units and a composition thereof, having a residual tetrahydrofuran content of less than 10 ppm, which can be obtained by means of the process according to claim 1.

16. The process according to claim 2, in which the gaseous flow is contacted with the polyester, copolyester or composition thereof at a temperature in the range between 70 C. and 145 C.

17. The process according to claim 3, in which the gaseous flow is contacted with the polyester, copolyester or composition thereof at a temperature in the range between 70 C. and 145 C.

18. The process according to claim 4, in which the gaseous flow is contacted with the polyester, copolyester or composition thereof at a temperature in the range between 70 C. and 145 C.

19. The process according to claim 2, in which the gaseous flow is contacted with the polyester, copolyester or composition thereof at a temperature in the range between 80 C. and 140 C.

20. The process according to claim 3, in which the gaseous flow is contacted with the polyester, copolyester or composition thereof at a temperature in the range between 80 C. and 140 C.

Description

EXAMPLES

(1) THF Analyses

(2) An aliquot of 4-6 g of the sample to be analysed was ground up in a mill with a 500 m sieve (mean particle size of approximately 200 m at the 50th percentile) working in liquid nitrogen.

(3) A suitable quantity of the weighed sample (typically approximately 1 g for samples from which THF had already been removed and 50-100 mg for samples in which THF had not been removed) was placed in a bottle having a head space of 20 ml, the internal standard (5 l of a 0.2% (w/v) solution 2-methyl THF in 2-octanol) was added and the bottle was sealed with a stopper provided with a perforatable PTFE/silicone rubber membrane.

(4) The bottle was conditioned at 125 C. for 30 minutes, after which 100 l of the head space was injected into the GC-MS using a gas syringe.

(5) The GC was provided with a ZB-624 30 m0.32 mm1.0 m type column and quantification was performed by calibration against an internal standard operating in SIM using the m/z ratios=71+72+86.

(6) GC setting: 50 C. (5 isotherm), heating ramp of 6 C./min up to 80 C., then of 20 C./min up to 220 C.

(7) Carrier: He 1.0 ml/min

(8) Injected volume=100 l at 250 C.

Example 1

Removal of THF by Forced Convection from Granules in Movement in an Open Cycle

(9) Removal of THF from an aliphatic-aromatic polybutylene terephthalate-co-butyleneadipate polyester.

(10) Equipment: 1. Piovan model DPM605 dryer (hopper capacity=70 litres); 2. Piovan model S52 pneumatic loader (suction capacity=4 litres);

(11) Gaseous material: air (0.4% relative humidity);

(12) Gaseous flow rate in the hopper=75 m.sup.3/h;

(13) Temperature of the gaseous flow delivered to the hopper: 93 C. (set-up T);

(14) Material: 50 kg of granules of an aliphatic-aromatic polyester containing 48% in moles of 1,4-butylene terephthalate units with an MFR (190 C., 2.16 kg)=5.2 g/10 min (measured before drying at 90 C. for 1 hour.

(15) Initial THF in the material (mean value from 3 samples): 300 ppm.

(16) All the material, 50 kg, was placed in the hopper of the equipment and the devolatilisation process was started up at the set-up T. The gaseous flow comprising air was injected into the bottom of the hopper and distributed over the mass of granules. This mass of granules was uniformly penetrated by the flow of hot air flowing upwards through the hopper and exited to discharge and subsequent knock-down from the top of the hopper. New fresh air was continuously heated to the set-up temperature and injected into the hopper. During the devolatilisation process the pneumatic loader drew 3.3 kg of granules from the bottom of the hopper over 110 seconds and returned them to its top. This operation brought about a quasi-continuous movement of the granules within the hopper, in a downward direction, in countercurrent to the gaseous flow.

(17) The process was carried out for an overall time of 48 hours, after which the final THF content of the granules was determined and found to be 0.5 ppm (mean value from 2 samples).

(18) At the end of the THF removal process, the temperature was reduced to 35 C. and the gaseous flow conditions were maintained for 12 hours.

(19) The devolatilised polyester will be indicated as polyester AARR1 below.

(20) Preparation of a composition comprising the polyester AARR1

(21) The polyester AARR1 was used to manufacture a composition (Composition 1) by feeding 10.1 kg/hour of a polymer premix comprising 36.2% by weight of polyester AARR1, 62.2% of Naturewoks INGEO 3251D polylactic acid, 0.95% of talc and 0.65% of titanium dioxide to an Icma San Giorgio MCM-25HT L/D 25 mm D 52 twin-screw extruder via a gravimetric metering unit with the following operating parameters:

(22) RPM 150

(23) Thermal profile 50-150-20091553 C.

(24) Vacuum degassing: 0.9 bar

(25) 44 mm-hole L/D 1 system.

(26) The head pressure was 10-20 bar, the torque 40-50 bar, the temperature of the melt at the head of the extruder was 155-160 C.

(27) The extrudate so obtained was then cooled in a water bath (23 C.) and surface water was removed with a current of air. Subsequently the rods were cut into small cylinders using a blade cutter.

(28) Composition 1 had a THF content of 11 ppm and an MFR=19 g/10 min.

(29) Removal of THF from Composition 1 Equipment: 1. Piovan model DPM605 dryer (hopper capacity=70 litres); 2. Piovan model S52 pneumatic loader (suction capacity=4 litres);

(30) Gaseous material: air (0.4% relative humidity);

(31) Gaseous flow rate in the hopper=75 m.sup.3/h;

(32) Temperature of the gaseous flow injected into the hopper: 93 C. (set-up T);

(33) Material: 50 kg of the product Composition 1 in the form of granules

(34) Initial THF in the material (mean value from 2 samples): 11 ppm;

(35) All the material, 50 kg, was placed in the hopper of the equipment and the devolatilisation process was started up at the set-up T. The gaseous flow comprising air was injected into the bottom of the hopper and distributed over the mass of granules. This mass of granules was uniformly penetrated by the flow of hot air flowing upwards through the hopper and exited to discharge and subsequent knock-down from the top of the hopper. New fresh air was continuously heated to the set-up temperature and injected into the hopper. During the devolatilisation process the pneumatic loader drew 3.3 kg of granules from the bottom of the hopper over 110 seconds and returned them to its top. This operation brought about a quasi-continuous movement of the granules within the hopper, in a downward direction, in countercurrent to the gaseous flow.

(36) The process was carried out over a time of 12 hours preheating+48 hours at the set-up T, at the end of which the final THF content of the granules was determined and found to be 1.8 ppm (mean value from 2 samples).

(37) At the end of the THF removal process the sample was dried at 55 C. for 24 hours maintaining the gaseous flow conditions for 12 hours.

Example 2

Removal of THF by Forced Convection from Granules in Movement in an Open Cycle

(38) Removal of THF from an aliphatic-aromatic polybutylene terephthalate-co-butyleneadipate polyester.

(39) Equipment: 1. Piovan model DPM605 dryer (hopper capacity=70 litres); 2. Piovan model S52 pneumatic loader (suction capacity=4 litres);

(40) Gaseous material: air (0.4% relative humidity);

(41) Gaseous flow rate in the hopper=75 m.sup.3/h;

(42) Temperature of the gaseous flow delivered to the hopper: 93 C. (set-up T);

(43) Material: 50 kg of granules of an aliphatic-aromatic polyester containing 48% in moles of 1,4-butylene terephthalate units with an MFR (190 C., 2.16 kg)=6 g/10 min (measured before drying at 90 C. for 1 hour.

(44) Initial THF in the material (mean value from 3 samples): 9.7 ppm

(45) All the material, 50 kg, was placed in the hopper of the equipment and the devolatilisation process was started up at the set-up T. The gaseous flow comprising air was injected into the bottom of the hopper and distributed over the mass of granules. This mass of granules was uniformly penetrated by the flow of hot air flowing upwards through the hopper and exited to discharge and subsequent knock-down from the top of the hopper. New fresh air was continuously heated to the set-up temperature and injected into the hopper. During the devolatilisation process the pneumatic loader drew 3.3 kg of granules from the bottom of the hopper over 110 seconds and returned them to its top. This operation brought about a quasi-continuous movement of the granules within the hopper, in a downward direction, in countercurrent to the gaseous flow.

(46) The process was carried out for an overall time of 48 hours, after which the final THF content of the granules was determined and found to be 0.6 ppm (mean value from 2 samples).

(47) At the end of the THF removal process, the temperature was reduced to 35 C. and the gaseous flow conditions were maintained for 12 hours.

(48) The devolatilised polyester will be indicated as polyester AARR2 below.

(49) Preparation of a composition comprising the polyester AARR2

(50) The polyester AARR2 was used to manufacture a composition (Composition 2) by feeding 10.1 kg/hour of a polymer premix comprising 36.2% by weight of polyester AARR2, 62.2% of Naturewoks INGEO 3251D polylactic acid, 0.95% of talc and 0.65% of titanium dioxide to an Icma San Giorgio MCM-25HT L/D 25 mm D 52 twin-screw extruder via a gravimetric metering unit with the following operating parameters:

(51) RPM 150

(52) Thermal profile 50-150-20091553 C.

(53) Vacuum degassing: 0.9 bar

(54) 44 mm-hole L/D 1 system.

(55) The head pressure was 10-20 bar, the torque 40-50 bar, the temperature of the melt at the head of the extruder was 155-160 C.

(56) The extrudate so obtained was then cooled in a water bath (23 C.) and surface water was removed with a current of air. Subsequently the rods were cut into small cylinders using a blade cutter.

(57) Composition 2 had a THF content of 15 ppm and an MFR=18.5 g/10 min.

(58) Removal of THF from Composition 2Equipment: 1. Piovan model DPM605 dryer (hopper capacity=70 litres); 2. Piovan model S52 pneumatic loader (suction capacity=4 litres);

(59) Gaseous material: air (0.4% relative humidity);

(60) Gaseous flow rate in the hopper=75 m.sup.3/h;

(61) Temperature of the gaseous flow injected into the hopper: 93 C. (set-up T);

(62) Material: 50 kg of the product Composition 2 in the form of granules (mean dimension of the granules=3.4 mm; bulk density of the granules=0.82 kg/litre);

(63) Initial THF in the material (mean value from 2 samples): 15 ppm;

(64) All the material, 50 kg, was placed in the hopper of the equipment and the devolatilisation process was started up at the set-up T. The gaseous flow comprising air was injected into the bottom of the hopper and distributed over the mass of granules. This mass of granules was uniformly penetrated by the flow of hot air flowing upwards through the hopper and exited to discharge and subsequent knock-down from the top of the hopper. New fresh air was continuously heated to the set-up temperature and injected into the hopper. During the devolatilisation process, the pneumatic loader drew 3.3 kg of granules from the bottom of the hopper over 110 seconds and returned them to its top. This operation brought about a quasi-continuous movement of the granules within the hopper, in a downward direction, in countercurrent to the gaseous flow.

(65) The process was carried out over a time of 12 hours preheating+48 hours at the set-up T, at the end of which the final THF content of the granules was determined and found to be 2.0 ppm (mean value from 2 samples).

(66) At the end of the THF removal process the sample was dried at 55 C. for 24 hours maintaining the gaseous flow conditions for 12 hours.