Method for decolorizing polyester and method for depolymerising polyester comprising the same

Patent metadata

Field	Value
Publication number	US-2024052130-A1
Application number	US-202118260791-A
Country	US
Kind code	A1
Filing date	Nov 3, 2021
Priority date	Jan 14, 2021
Publication date	Feb 15, 2024
Grant date	—

Abstract

Provided is a method for decolorizing a polyester, the method including exposing adding a decoloring agent to the polyester and then contacting the polyester with superheated water vapor.

First claim

1 . A method of decolorizing a polyester, comprising
adding a degradation agent including an alkali, an acid, a salt thereof, a mono-alcohol, a polyhydric alcohol, or a mixture thereof to the polyester, and contacting the polyester with superheated water vapor.

2 . The method of decolorizing the polyester of claim 1 , wherein
a temperature of the superheated water vapor is 250° C. to 450° C.

3 . The method of decolorizing the polyester of claim 1 , wherein
the superheated water vapor is applied with an injection pressure of 0.1 bar to 2 bar.

4 . The method of decolorizing the polyester of claim 1 , wherein
the decolorizing is performed for 1 minute to 60 minutes.

5 . The method of decolorizing the polyester of claim 1 , wherein
the alkali includes sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia, or a mixture thereof.

6 . The method of decolorizing the polyester of claim 1 , wherein
the acid includes hydrochloric acid, nitric acid, sulfuric acid, carbonic acid, phosphoric acid, acetic acid, hypochlorous acid (HClO), or a mixture thereof.

7 . The method of decolorizing the polyester of claim 1 , wherein
the salt includes carbonate, hydrogen carbonate, phosphate, sulfate, sulfite, nitrate, silicate, hypochlorate, formate, acetate, citrate, oxalate, or a mixture thereof.

8 . The method of decolorizing the polyester of claim 1 , wherein
the mono-alcohol includes methanol, ethanol, propanol, butanol, or a mixture thereof.

9 . The method of decolorizing the polyester of claim 1 , wherein
the polyhydric alcohol includes ethylene glycol, n-propylene glycol, isopropylene glycol, diethylene glycol, polyethylene glycol, triethylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, glycerine, benzyl alcohol, polypropylene glycol, pentaerythritol, trimethylolpropane, or a mixture thereof.

10 . The method of decolorizing the polyester of claim 1 , wherein
the decoloring agent is added at 0.05 mol to 1.5 mol per 1.0 mol of dibasic acid in the polyester.

11 . A method of depolymerizing a polyester. comprising
adding a decoloring agent including an alkali, an acid, a salt thereof, a mono-alcohol, a polyhydric alcohol, or a mixture thereof to polyester, and then contacting the polyester with superheated water vapor to decolorize the polyester, depolymerizing the decolorized polyester to obtain a depolymerization product including an alkylene glycol and a dibasic salt, performing solid-liquid separation of liquid-phase alkylene glycol and a solid-phase dibasic salt from the depolymerization product, dissolving the solid-phase dibasic salt in water, neutralizing an aqueous solution of the dibasic salt with an acid to precipitate a dibasic acid crystal, and performing solid-liquid separation of the dibasic acid crystal from a precipitation product.

12 . The method of depolymerizing the polyester of claim 11 , wherein
the method of depolymerizing the polyester further includes removing impurities from the aqueous solution of the dibasic salt.

13 . The method of depolymerizing the polyester of claim 11 , wherein
the method of depolymerizing the polyester further includes recrystallizing the dibasic acid crystal.

14 . A composition for polymerizing recycled polyester, comprising a dibasic acid and an alkylene glycol, obtained by the method of depolymerizing the polyester of claim 11 .

15 . A recycled polyester prepared using the composition for polymerizing polyester of claim 14 .

16 . The recycled polyester of claim 15 , wherein
a color of the recycled polyester has an L-value of 60 or higher.

Assignees

• Kolon Inc

Inventors

• Yoon Joonyoung
• Park Hongkwan
• Cho Haelim

Classifications

• C08J11/14 Primary

  by treatment with steam or water · CPC title

• C08G63/183

  Terephthalic acids · CPC title

• C08L67/02

  Polyesters derived from dicarboxylic acids and dihydroxy compounds (C08L67/06 takes precedence) · CPC title

• C08K3/22

  of metals · CPC title

• C08K3/30

  Sulfur-, selenium- or tellurium-containing compounds · CPC title