CN-121986137-A - Method for recovering polyester and method for producing recycled polyester

Abstract

A method for recovering polyester, wherein a structure body which is mainly composed of polyester fibers as a base material and contains polyurethane resin is treated in lower alcohol at a temperature of 125-185 ℃ in the presence of a catalyst of a first transition metal acetate, and the polyurethane resin is removed. Further, it is preferable that the polyurethane resin is a porous polyurethane, the polyurethane resin is a chemically crosslinked polyurethane, and the first transition metal acetate is manganese acetate, zinc acetate or cobalt acetate. And a process for producing a recycled polyester, wherein the polyester obtained by the above process for recovering a polyester is further depolymerized into an aromatic dicarboxylic acid bis (hydroxyalkyl) ester and then repolymerized.

Inventors

• KODA TAKASHI
• YAMAZAKI KENJI
• Xu Zhineihui

Assignees

• 帝人富瑞特株式会社

Dates

Publication Date

20260505

Application Date

20240919

Priority Date

20230929

Claims (8)

1. 1. A method for recovering polyester, characterized in that a structure body which is mainly composed of polyester fibers as a base material and contains polyurethane resin is treated in lower alcohol at a temperature of 125-185 ℃ in the presence of a catalyst of a first transition metal acetate, and the polyurethane resin is removed.
2. 2. The method for recovering polyester according to claim 1, wherein the polyurethane resin is a porous polyurethane.
3. 3. The method for recycling polyester according to claim 1, wherein the polyurethane resin is a chemically crosslinked polyurethane.
4. 4. The method for recovering polyester according to claim 1, wherein the fiber made of the polyester is made of a polyester having alkylene terephthalate or alkylene naphthalate as a main repeating unit.
5. 5. The method for recovering polyester according to claim 1, wherein the lower alcohol is an alcohol selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, 1, 2-propanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, diethylene glycol, ethylene glycol, glycerol, and benzyl alcohol.
6. 6. The method for recovering polyester according to claim 1, wherein the first transition metal acetate is manganese acetate, zinc acetate or cobalt acetate.
7. 7. The method for recovering polyester according to claim 1, wherein after the treatment, the polyester is further washed with water or an organic solvent.
8. 8. A process for producing a recycled polyester, comprising depolymerizing the polyester obtained by the process according to any one of claims 1 to 7 into an aromatic dicarboxylic acid bis (hydroxyalkyl) ester, and then repolymerizing the aromatic dicarboxylic acid bis (hydroxyalkyl) ester.

Description

Method for recovering polyester and method for producing recycled polyester Technical Field The present invention relates to a method for recovering polyester from a structure containing polyurethane resin and mainly composed of polyester fiber as a base material, and a method for producing recycled polyester using the recovered polyester. Background As a structure in which a polyurethane resin is contained in a base material made of a polyester fiber, for example, a sheet-like artificial leather, synthetic leather, printed clothing, clothing such as a brassiere or a shoulder pad using a flexible polyurethane foam, and a wide variety of products such as interior articles have been put into practical use. However, when recycling of these products is attempted after use or the like, the polyester fiber and the polyurethane resin have very different properties, and it is difficult to perform efficient recycling. For example, patent document 1 proposes a method for regenerating a synthetic leather or a regenerated synthetic leather (synthetic leather) which is excellent in abrasion resistance and texture and is mainly composed of a fiber and a polyurethane resin. However, in this invention, it is proposed to replace a usual polyurethane resin as a resin with a polyester-based or polyamide-based thermoplastic resin emulsion to make it easy to regenerate an artificial leather, and not to regenerate an artificial leather or a synthetic leather which has been conventionally used. Patent document 2 discloses a method for classifying and recovering artificial leather having a skin layer. However, although polyurethane resin is used as the resin, a technique of forming a special skin layer which is easily peeled off on the artificial leather has been proposed, and this cannot be said to be a general recycling technique. On the other hand, an invention has been proposed in which a polyester is recovered from a structure containing used polyester fibers and various resins and recycled. However, when the polyester recovered in this manner is used, there is a problem that the recycled polyester polymer is easily colored and is not easily white. Particularly, when chemical regeneration is attempted in which the polyester is depolymerized and repolymerized, the hue of the repolymerized polyester tends to be brown and the quality is poor. As a solution to such a coloring problem, for example, patent document 3 discloses a method of chemically regenerating waste polyethylene terephthalate products. In the first step, as a coloring matter-causing substance removing step, an adsorption treatment of bringing a coloring matter-causing substance into contact with an adsorbent after depolymerizing a polyester, a decomposition treatment of decomposing a coloring matter-causing substance with a decomposer, a reduction treatment of reducing a coloring matter-causing substance with a reducing agent, and the like have been attempted. However, even with such a method, it is difficult to recover the constituent components of the polyester fiber in high purity from the structure containing the polyester fiber and the polyurethane resin. Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2012-201994 Patent document 2 Japanese patent application laid-open No. 2022-67626 Patent document 3 Japanese patent laid-open No. 2008-88096 Disclosure of Invention The present invention provides a method for recovering a polyester component from a structure containing a fiber mainly composed of a polyester and a polyurethane resin, and a method for producing a recycled polyester using the recovered polyester. In order to solve the above problems, the following invention is provided. 1. A method for recovering polyester, characterized in that a structure body which is mainly composed of polyester fibers as a base material and contains polyurethane resin is treated in lower alcohol at a temperature of 125-185 ℃ in the presence of a catalyst of a first transition metal acetate, and the polyurethane resin is removed. 2. The method for recovering a polyester according to the above 1, wherein the polyurethane resin is a porous polyurethane. 3. The method for recovering a polyester according to 1 or 2 above, wherein the polyurethane resin is a chemically crosslinked polyurethane. 4. The method for recovering a polyester according to any one of the above 1 to 3, wherein the fiber made of the polyester is made of a polyester having an alkylene terephthalate or an alkylene naphthalate as a main repeating unit. 5. The method for recovering a polyester according to any one of 1 to 4, wherein the lower alcohol is an alcohol selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, 1, 2-propanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, diethylene glycol, ethylene glycol, glycerol, and benzyl alcohol. 6. The method for recovering a polyester according to any one of 1 t