Flakes of ester mixtures and methods for their production

1. A method for producing flakes of an ester mixture comprising bis-(hydroxyethyl)-terephthalate, dimers, trimers, tetramers, pentamers and higher oligomers of ethane-1,2-diol and terephthalate acid, the method comprising the steps of:

a) flash evaporating ethane-1,2-diol from an ester mixture obtained from the glycolysis of PET (polyethylene terephthalate); and

b) producing flakes of the ester mixture of step (a), wherein the flakes are crystalline, free-flowing non-sticky, stable, storable and reusable.

2. The method according to claim 1 , wherein step (b) is conducted by quenching and solidifying the ester mixture of step (a).

3. The method according to claim 2 , wherein the quenching and solidifying is conducted using a rotary drum flaker.

4. The method according to claim 3 , wherein the rotary drum flaker in step (b) has a cooling medium at a temperature in the range from 8° C. to 90° C.

5. The method according to claim 3 , wherein the rotary drum flaker in step (b) has a cooling medium at a temperature in the range from 70° C. to 80° C.

6. A method for producing PET products from an ester mixture comprising bis-(hydroxyethyl)-terephthalate, dimers, trimers, tetramers, pentamers and higher oligomers of ethane-1,2-diol and terephthalate acid, the method comprising the steps of:

a) flash evaporating ethane-1,2-diol from an ester mixture obtained from the glycolysis of PET; and

b) polymerising the ester mixture from step (a) ready to produce PET products.

7. The method according to claim 1 or 6 wherein the free glycol content of the ester mixture after step (a) is less than about 12%.

8. The method according to claim 1 or 6 , wherein the free glycol content of the ester mixture after step (a) is about 2% or less.

9. The method according to claim 1 or 6 , wherein the ester mixture from step (a) has a diethylene glycol (DEG) content of about 2.5% or less.

10. The method according claim 1 or 6 , wherein the ester mixture from step (a) has a melting point at or below about 150° C.

11. The method according to claim 1 or 6 , wherein the flash evaporating is conducted at a temperature at or below 220° C.

12. The method according to claim 1 or 6 , wherein the flash evaporating is conducted at a temperature at in the range from 190° C. to 220° C.

13. The method according to claim 1 or 6 , wherein the flash evaporating is conducted at reduced pressure.

14. The method according to claim 13 , wherein the flash evaporating is conducted at a pressure in the range from 100 to 300 mbar (10 to 30 kPa).

15. The method according to claim 13 , wherein the flash evaporating is conducted at about 200 mbar (20 kPa).

16. Flakes of an ester mixture comprising bis-(hydroxyethyl)-terephthalate, dimers, trimers, tetramers, pentamers and higher oligomers of ethane-1,2-diol and terephthalate acid, wherein the flakes are crystalline, free-flowing non-sticky, stable, storable and reusable.

17. The flakes according to claim 16 , wherein the flakes have a melting point at or below 150° C.

18. The flakes according to claim 16 or 17 , wherein the flakes have a diethylene glycol content of about 2.5% or less.

19. The flakes according to claim 16 or 17 , wherein the flakes comprise about 2.5% or less diethylene glycol, 45 to 55% bis (hydroxyethyl) terephthalate, 25 to 35% dimers, 10 to 15% trimers, 3 to 8% tetramers, 1 to 2% pentamers and the balance comprising higher oligomers.

20. The flakes according to claim 16 or 17 , wherein the ester mixture comprises recycled esters obtained from the glycolysis of PET waste.

21. The method according to claim 1 , wherein the flakes have a melting point at or below 150° C.

22. The method according to claim 1 , wherein the flakes have a diethylene glycol content of about 2.5% or less.

23. The method according to claim 1 , wherein the flakes comprise about 2.5% or less diethylene glycol, 45 to 55% bis (hydroxyethyl) terephthalate, 25 to 35% dimers, 10 to 15% trimers, 3 to 8% tetramers, 1 to 2% pentamers and the balance comprising higher oligomers.

24. The method according to claim 1 or 6 , wherein the ester mixture comprises recycled esters obtained from the glycolysis of PET waste.