EP-4737509-A1 - DEPOLYMERIZATION METHOD AND DEPOLYMERIZATION APPARATUS

Abstract

A depolymerization method for depolymerizing a synthetic resin into a raw material monomer includes the steps of: setting a target temperature in a flow-type reactor (13e) and a target residence time of the synthetic resin and a solvent having a weight ratio of 1.5 times or more relative to the synthetic resin in the flow-type reactor (13e), such that a yield of the raw material monomer is 70% or more; and supplying the synthetic resin and the solvent to the flow-type reactor (13e), such that a temperature in the flow-type reactor (13e) becomes the target temperature, a residence time of the synthetic resin and the solvent in the flow-type reactor (13e) becomes the target residence time, and a pressure in the flow-type reactor (13e) becomes 10 MPa or more.

Inventors

• HIRAOKA SHOKO
• HIRAWAKI SATOSHI
• MORI KAZUHIRO
• BABA TSUYOSHI
• SUZUKI SHUTA

Assignees

• HONDA MOTOR CO., LTD.

Dates

Publication Date

20260506

Application Date

20230627

Claims (9)

1. A depolymerization method for depolymerizing a synthetic resin into a raw material monomer, comprising the steps of: setting a target temperature in a flow-type reactor and a target residence time of the synthetic resin and a solvent having a weight ratio of 1.5 times or more relative to the synthetic resin in the flow-type reactor, such that a yield of the raw material monomer is 70% or more; and supplying the synthetic resin and the solvent to the flow-type reactor, such that a temperature in the flow-type reactor becomes the target temperature, a residence time of the synthetic resin and the solvent in the flow-type reactor becomes the target residence time, and a pressure in the flow-type reactor becomes 10 MPa or more.
2. The depolymerization method according to claim 1, wherein the synthetic resin is a nylon 6, wherein the raw material monomer is a ε-caprolactam, wherein in the setting, the target temperature and the target residence time are set so as to be within a range defined by the following two equations: τ ≥ 43200 e ∧ − 0.0244 T ; and τ ≤ 31800 e ∧ − 0.0211 T , where T is the target temperature and τ is the target residence time.
3. The depolymerization method according to claim 2, wherein in the setting, the target temperature is set to 350°C.
4. The depolymerization method according to claim 2, wherein in the setting, the target residence time is set to a time within a range of 10 minutes or more and 20 minutes or less.
5. The depolymerization method according to claim 1, wherein in the supplying, the synthetic resin and the solvent are supplied to the flow-type reactor, so that the solvent in the flow-type reactor is maintained in a subcritical state.
6. A depolymerization apparatus configured to depolymerize a synthetic resin into a raw material monomer, comprising: a flow-type reactor; a supply unit configured to supply the synthetic resin and a solvent to the flow-type reactor, such that a temperature in the flow-type reactor becomes a predetermined target temperature, a residence time of the synthetic resin and the solvent having a weight ratio of 1.5 times or more relative to the synthetic resin in the flow-type reactor becomes a predetermined target residence time, and a pressure in the flow-type reactor becomes 10 MPa or more; and a back pressure valve provided downstream of the flow-type reactor and set to a set pressure of 10 MPa or more, wherein the target temperature and the target residence time are set in advance such that a yield of the raw material monomer is 70% or more.
7. The depolymerization apparatus according to claim 6, further comprising: a melting section provided upstream of the flow-type reactor and configured to melt the synthetic resin to extrude the melted synthetic resin into the flow-type reactor.
8. The depolymerization apparatus according to claim 6, further comprising a stirring blade configured to stir the synthetic resin and the solvent supplied to the flow-type reactor by the supply unit.
9. The depolymerization apparatus according to claim 6, further comprising: a screw extruder configured to melt the synthetic resin to extrude the melted synthetic resin into the flow-type reactor and configured to stir the synthetic resin and the solvent extruded into the flow-type reactor.

Description

TECHNICAL FIELD The present invention relates to a depolymerization method and a depolymerization apparatus for depolymerizing a synthetic resin into a raw material monomer. BACKGROUND ART As an effort to reduce waste, research and development on recycling of waste has been conducted. As this type of technology, conventionally, a method is known in which nylon 6, which is a synthetic resin (polymer), is depolymerized to ε-caprolactam, which is a raw material monomer (see, for example, Patent Literature 1). In the method described in Patent Literature 1, 15 parts by weight or less of an acidic substance is added to 100 parts by weight of nylon 6 (poly-ε-caprolactam) in waste, heat treatment is performed at 220 to 400°C to lower the solution viscosity, and a non-melted product is separated, then the poly-ε-caprolactam is depolymerized. PRIOR ART DOCUMENTS PATENT LITERATURES Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2001-294571 SUMMARY OF INVENTION PROBLEM TO BE SOLVED BY THE INVENTION However, in the method of adding an acidic substance as described in Patent Literature 1, chemical decomposition takes a long time, and therefore it is difficult to perform depolymerization rapidly. MEANS FOR SOLVING THE PROBLEM An aspect of the present invention is a depolymerization method for depolymerizing a synthetic resin into a raw material monomer, including the steps of: setting a target temperature in a flow-type reactor and a target residence time of the synthetic resin and a solvent having a weight ratio of 1.5 times or more relative to the synthetic resin in the flow-type reactor, such that a yield of the raw material monomer is 70% or more; and supplying the synthetic resin and the solvent to the flow-type reactor, such that a temperature in the flow-type reactor becomes the target temperature, a residence time of the synthetic resin and the solvent in the flow-type reactor becomes the target residence time, and a pressure in the flow-type reactor becomes 10 MPa or more. Another aspect of the present invention is a depolymerization apparatus configured to depolymerize a synthetic resin into a raw material monomer, including: a flow-type reactor; a supply unit configured to supply the synthetic resin and a solvent to the flow-type reactor, such that a temperature in the flow-type reactor becomes a predetermined target temperature, a residence time of the synthetic resin and the solvent having a weight ratio of 1.5 times or more relative to the synthetic resin in the flow-type reactor becomes a predetermined target residence time, and a pressure in the flow-type reactor becomes 10 MPa or more; and a back pressure valve provided downstream of the flow-type reactor and set to a set pressure of 10 MPa or more. The target temperature and the target residence time are set in advance such that a yield of the raw material monomer is 70% or more. EFFECTS OF THE INVENTION According to the present invention, it is possible to rapidly perform depolymerization. BRIEF DESCRIPTION OF DRAWINGS [Fig. 1] A diagram schematically showing an example of an overall configuration of a depolymerization apparatus according to an embodiment of the present invention.[Fig. 2] A diagram for explaining a relationship between a reaction time and a yield when a depolymerization reaction from PA6 to ε-caprolactam was performed using subcritical water.[Fig. 3] A diagram for explaining an appropriate reaction condition when the depolymerization reaction from PA6 to ε-caprolactam is performed using the depolymerization apparatus in Fig. 1. DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to Figs. 1 to 3. In a depolymerization method and a depolymerization apparatus according to the embodiment of the present invention, a synthetic resin (polymer) is depolymerized into a raw material monomer. The synthetic resin is, for example, PA (polyamide) 6 (nylon 6), PA66 (nylon 66), PA12, PA11, PET (polyethylene terephthalate), PBT (polybutylene terephthalate), POM (polyacetal), a urethane resin, or the like. Hereinafter, an example will be described in which PA6, which is a synthetic resin, is depolymerized to ε-caprolactam, which is a raw material monomer. When a synthetic resin such as PA6 is depolymerized into a raw material monomer for the purpose of industrial reuse, it is preferable to rapidly perform depolymerization from an industrial point of view. In this regard, in the present embodiment, the depolymerization method and the depolymerization apparatus are configured as follows such that a depolymerization reaction from the synthetic resin to the raw material monomer can be rapidly performed by using a solvent in a subcritical state. Fig. 1 is a diagram schematically showing an example of an overall configuration of a depolymerization apparatus 10 according to the embodiment of the present invention. As illustrated in Fig. 1, the depolymerization apparatus 10 ma