Polyester textile waste recycling
A method for recovering natural fibers from a textile comprising polyester and natural fibers. The method comprises the steps of: providing said textile soaked in a mixture comprising a solvent and a catalyst, providing and maintaining a temperature of said mixture comprising said textile within a range of 80-240° C. during depolymerization of polyester in said textile; and recovering natural fibers after said depolymerization, wherein, in said step of providing said textile soaked in said mixture, said catalyst of said mixture comprises calcium oxide.
1. A method for recovering natural fibers from a textile comprising polyester and natural fibers, wherein said method comprises the steps of:
providing said textile soaked in a mixture comprising a solvent and a catalyst;
providing and maintaining a temperature of said mixture comprising said textile within a range of 80-240° C. during depolymerization of polyester in said textile; and
recovering natural fibers after said depolymerization,
wherein, in said step of providing said textile soaked in said mixture, said catalyst of said mixture comprises calcium oxide.
2. The method according to claim 1 , wherein said step of maintaining the temperature of said mixture comprising textile lasts until at least 20% of the polyester in said textile is depolymerized to molecules with a molecular weight lower than 600 g/mol, or at least 50% of the polyester in said textile is depolymerized to molecules with a molecular weight lower than 600 g/mol, or at least 80% of the polyester in said textile is depolymerized to molecules with a molecular weight lower than 600 g/mol.
3. The method according to claim 1 , wherein said natural fibers comprise at least one of cotton fibers, viscose fibers, cellulose fibers, and regenerated cotton fibers, such as lyocell type fibers.
4. The method according to claim 3 , wherein said natural fibers comprise cotton fibers.
5. The method according to claim 1 , wherein said catalyst further comprises an oxide of any periodic table group 2 metal, and/or an oxide of any lanthanide metal.
6. The method according to claim 5 , wherein said catalyst further comprises MgO.
7. The method according to claim 1 , wherein, after said depolymerization of polyester, reaction products of said depolymerization of polyester are separated from the natural fibers, the natural fibers being present in a solid fraction.
8. The method according to claim 1 , wherein the textile comprises at least 10% polyester, or at least 25% polyester, or at least 50% polyester, or at least 75% of polyester.
9. The method according to claim 1 , wherein said temperature is above 80° C., or above 90° C., or above 100° C., or above 110° C., or above 120° C., or above 140° C., or above 160° C., or above 180° C.; and/or wherein said temperature is lower than 200° C., or lower than 180° C., or lower than 160° C., or lower than 140° C., or lower than 120° C., or lower than 100° C.
10. The method according to claim 1 , wherein said temperature is within a range of 80-170° C., or within a range of 100-150° C.
11. The method of claim 1 , wherein, in said step of maintaining said temperature of said mixture comprising said textile, said temperature is maintained for at least 10 min, or at least 20 min, or at least 30 min, or at least 40 min, or at least 50 min, or at least 60 min; and/or wherein said temperature is maintained for at most 300 min, or at most 270 min, or at most 240 min, or at most 200 min, or at most 160 min, or at most 120 min, or at most 90 min, or for at most 60 min.
12. The method according to claim 1 , wherein, in said step of maintaining said temperature of said mixture comprising said textile, said temperature is maintained for 10-300 min, or for 30-240 min, or for 60-120 min.
13. The method according to claim 1 , wherein said solvent comprises an alcohol or a diol.
14. The method according to claim 1 , wherein said textile further comprises additional synthetic fibers.
15. The method according to claim 1 , wherein said polyester comprises aromatic polyester; and wherein reaction products of said depolymerization of polyester includes at least one of dimethyl terephthalate, ethylene glycol, 1,3-propanediol, 1,4-butanediol, ethyl methyl terephthalate, dimers of the aromatic polyester, and trimers of the aromatic polyester.
16. The method according to claim 1 , wherein said catalyst has a general formula CaO-xO-yO, where x is any periodic table group 2 metal and where y is any lanthanide metal.
17. The method according to claim 1 , wherein said depolymerization is performed in an autoclave.
18. The method according to claim 15 , wherein said method further comprises the step of:
recovering said at least one of dimethyl terephthalate, ethylene glycol, 1,3-propanediol, 1,4-butanediol, ethyl methyl terephthalate, dimers of aromatic polyester, and trimers of aromatic polyester.
19. The method according to claim 1 , wherein said method further comprises the step of:
producing new textile from recovered natural fibers.
20. A recovered natural fiber obtainable by depolymerization of polyester in a textile comprising polyester and natural fibers, and recovery of natural fibers after said depolymerization.