EP-4737510-A1 - METHOD FOR RECYCLING POLYESTER-CONTAINING SUBSTANCE

Abstract

[Problem] To provide a method for recycling polyester-containing substances using a new means. [Solution] A method for recycling polyester-containing substances, which includes a step of alcoholysis of polyester-containing substances in the presence of a catalyst and an alcohol in a solvent, and a step of separating the alcoholysis products obtained in the above-mentioned step. Specifically, the method is carried out using a device that has a tank for storing the polyester-containing substances and a tank and/or path for separating polyester alcoholysis products.

Inventors

• Eda, Yasushi
• TAKANOHASHI, YOSHINORI
• NAKAMURA, NATSUMI
• MIZOGUCHI, JUN
• Mukai, Tomoya
• SHIRAI, Yu
• Mitsuyasu, Hayato
• YOSHIDA, NAOKI
• NAKAMURA, TOSHIO
• Tsunekawa, Yoshihide

Assignees

• Rock Paint Co., Ltd.

Dates

Publication Date

20260506

Application Date

20240618

Claims (12)

1. A method for recycling a polyester-containing substance (a), comprising: a step (A) of subjecting the polyester-containing substance (a) to alcoholysis in a solvent (d) in the presence of a catalyst (b) and an alcohol (c); and a step (B) of separating an alcoholysis product obtained in the step (A); wherein a weight ratio of the alcohol (c)/solvent (d) is 1/1 to 1/99, and the alcoholysis proceeds at a temperature of 20°C or higher and lower than 100°C.
2. The recycling method according to Claim 1, wherein the polyester-containing substance (a) is at least one kind selected from the group consisting of four kinds of a polyethylene terephthalate, a polyester-based adhesive for a laminate film, a polyester-based coating film, and a laminate in which a plurality of films are bonded together with an adhesive.
3. The recycling method according to Claim 1, wherein the catalyst (b) is at least one kind selected from the group consisting of an alkali metal alkoxide and a nitrogen-containing organic basic compound.
4. The recycling method according to Claim 1, wherein the catalyst (b) is sodium methoxide and/or 1,5,7-triazabicyclo[4.4.0]dec-5-ene.
5. The recycling method according to Claim 1, wherein the alcohol (c) is a monohydric alcohol having 1 to 8 carbon atoms, and the amount is 2 to 30 parts by weight to the total amount of 100 parts by weight of the polyester-containing substance (a), the catalyst (b), the alcohol (c) and the solvent (d).
6. The recycling method according to Claim 1, wherein the alcohol (c) is methanol.
7. The recycling method according to Claim 1, wherein the solvent (d) does not react with the alcoholysis product in alcoholysis reaction system.
8. The recycling method according to Claim 1, wherein the solvent (d) contains toluene.
9. The recycling method according to Claim 1, wherein the polyester-containing substance (a) is a laminate in which a plurality of films are bonded together with a polyester-based adhesive for a laminate film, and the catalyst (b) is an alkali metal hydroxide.
10. The recycling method according to Claim 9, wherein the catalyst (b) is sodium hydroxide.
11. The recycling method according to any one of Claims 1 to 10, further comprising a step (C) of separating substance other than the alcoholysis product.
12. The recycling method according to Claim 11, wherein a device that is provided with a tank (X) for storing the polyester-containing substance (a) and a tank and/or path (Y) for separating the polyester alcoholysis product is used.

Description

TECHNICAL FIELD The present invention relates to a method for recycling a polyester-containing substance. For completely decomposing a substance into its smallest units and purifying the decomposition products to remove impurities, not only it requires a significant amount of energy but also considerable effort. Here, the term "recycling" in the present invention refers to making the above-mentioned polyester-containing substance into a state where it can be reused as a resource. That is, it is objected to reduce the energy consumption and effort required for recycling, and it is not necessarily intended to decompose and purify the substance into its smallest units through chemical decomposition. However, this does not exclude decomposition and purification that aims to reduce energy consumption and shortening processes, and for such purposes, the alcoholysis products of the above-mentioned polyester-containing substances obtained by the present invention can be used for chemical recycling. The present invention is particularly useful for application to composites containing polyester components, and further, it is useful to use the components of the above-mentioned composites that remain unaffected by alcoholysis for material recycling. BACKGROUND ART Plastic is a material that is inexpensive and excellent in durability. In particular, polyethylene terephthalate (PET) has been widely used in various fields such as fibers, films, bottles, etc., due to its convenience, and it has been rapidly produced and consumed over the past few decades. On the other hand, despite its excellent durability, it is not easily decomposed, leading to the accumulation of plastic waste in landfills worldwide and exposing social issues of damage to the global environment such as marine pollution caused by microplastics, etc. Given this background, it has been desired to develop recycling technologies for plastic waste, including PET. Compared to Europe and the United States, in Japan, a proportion of thermal recycling is higher, which involves utilizing thermal energy generated during incineration, but there remain concerns about global warming due to carbon dioxide emissions. Thus, extensive research has being conducted on chemical recycling of polyester products, that is, by converting and recovering polyester products into monomers through chemical means and reusing these monomers. Patent document 1 discloses a method for producing aromatic divalent carboxylic acid dimethyl and dihydric alcohol, which are monomer components of aromatic polyesters such as PET, by continuous processing with use of supercritical alcohol. However, this method requires high temperatures of 300°C or higher. Patent document 2 discloses a method for producing dimethyl terephthalate by subjecting to a depolymerization reaction of polyester with alkylene glycol, followed by a transesterification with methanol. However, this method requires to remove alkylene glycol at 150°C or higher by distillation. Patent document 3 discloses a method for recycling a multilayer film containing a plastic layer primarily composed of polyester (PET), polypropylene (PP) and polyethylene (PE), and an aluminum layer. In this invention, the aluminum in the multilayer film waste is selectively dissolved to induce layer separation, and the mixture layer of PP and PE, and the PET layer are separated using difference in specific gravity. In addition, to enhance the purity of the PET separated by its difference in specific gravity, the PP and PE contained in the PET layer are extracted by using organic solvents, whereby the main components of the multilayer film are separated into the mixture of PET, PP and PE, and the aluminum component, respectively. However, since the aluminum is dissolved, energy is required for recycling. Patent document 4 discloses a catalyst composition for polyester depolymerization comprising a base catalyst, a monohydric alcohol, and a carbonate diester or tetraalkoxysilane as a glycol scavenger, as well as a polyester depolymerization method using said catalyst composition. However, since ethylene glycol which is a constitutional component of PET is stably captured, the ethylene carbonate to be produced must be decomposed into ethylene glycol in order to reuse it again as a PET raw material. Patent document 5 discloses a process for converting polyethylene terephthalate or poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) into terephthalic acid esters by depolymerization. In a series of the process, a step of contacting the polyester with a solvent for swelling the polyester, an alcohol-based solvent, and a sub-stoichiometric amount of an alkoxide. In particular, in the examples, as the solvent for swelling the polyester, dichloromethane or dimethyl sulfoxide is used, methanol is used as the alcohol-based solvent, and sodium methoxide is used as the alkoxide in a sub-stoichiometric amount, and polyethylene terephthalate is converted into