US 12,441,861 B2
Method for improving recovery rate of recycled bis(2-hydroxyethyl) terephthalate
Te-Chao Liao, Taipei (TW); Jung-Jen Chuang, Taipei (TW); Zhang-Jian Huang, Taipei (TW); Yu-Ti Tseng, Taipei (TW); and Cheng-Hsun Chen, Taipei (TW)
Assigned to NAN YA PLASTICS CORPORATION, Taipei (TW)
Filed by NAN YA PLASTICS CORPORATION, Taipei (TW)
Filed on Jul. 25, 2022, as Appl. No. 17/872,287.
Claims priority of application No. 110133987 (TW), filed on Sep. 13, 2021.
Prior Publication US 2023/0081251 A1, Mar. 16, 2023
Int. Cl. C08G 63/00 (2006.01); C08J 11/14 (2006.01); C08J 11/16 (2006.01)
CPC C08J 11/14 (2013.01) [C08J 11/16 (2013.01); C08J 2367/02 (2013.01)] 12 Claims
 
1. A method for improving a recovery rate of recycled bis(2-hydroxyethyl) terephthalate (BHET), comprising:
performing a preparation process which includes: providing a recycled polyester fabric;
performing a de-polymerization process which includes: using a chemical de-polymerization liquid to chemically depolymerize the recycled polyester fabric, so as to form a de-polymerization product mainly containing bis(2-hydroxyethyl) terephthalate (BHET);
performing a separation process which includes: distilling the chemical de-polymerization liquid from the de-polymerization product under an evaporation temperature of between 150° C. and 250° C., so as to separate the BHET from the chemical de-polymerizaiton liquid;
performing a dissolution process which includes: dissolving the BHET in water to form an aqueous phase liquid, and heating the aqueous phase liquid to a dissolution temperature of between 70° C. and 150° C.; wherein a weight ratio of the BHET to the water ranges from 1:3 to 1:20;
performing a crystallization process which includes: a first crystallization procedure and a second crystallization procedure,
wherein the first crystallization procedure includes: cooling the aqueous phase liquid from the dissolution temperature to a first crystallization temperature of between 40° C. and 60° C. at a cooling rate of 5° C./min to 15° C./min, so as to crystallize at least a part of the BHET from the aqueous phase liquid; and
wherein the second crystallization procedure includes: cooling the aqueous phase liquid from the first crystallization temperature to a second crystallization temperature of between 0° C. and 20° C. at a cooling rate of 0.10° C./min to 0.30° C./min, so as to crystallize at least another part of the BHET from the aqueous phase liquid.