Method for depolymerizing polyester and unsaturated polyester, and method for recovering polyester monomer using the depolymerization
View Patent ↗A method for rapidly depolymerizing a polyester and an unsaturated polyester by irradiating the polyester with microwaves in the presence of an alkylene glycol in which a titanium oxide fine powder having a bulk density of not more than 0.3 g/cm 3 has been dispersed. Another embodiment comprises irradiating a polyester or an unsaturated polyester with microwaves in the presence of a monohydric alcohol or polyhydric alcohol containing an alkali metal and/or an alkaline earth metal. As a result, raw materials of a polyester, an unsaturated polyester or a polyurethane, such as an alkylene glycol and an unsaturated dibasic acid, can be recovered efficiently.
1. A method for depolymerizing a polyester, comprising irradiating a polyester or a molded article containing a polyester with microwaves in the presence of an alkylene glycol in which a titanium oxide fine powder having a bulk density of not more than 0.3 g/cm 3 has been dispersed.
2. The method for depolymerizing a polyester as claimed in claim 1 , wherein the titanium oxide is anatase type titanium oxide.
3. The method for depolymerizing a polyester as claimed in claim 1 , wherein the alkylene glycol is ethylene glycol and/or propylene glycol.
4. The method for depolymerizing a polyester as claimed in claim 1 , wherein the polyester or the molded article containing a polyester is polyethylene terephthalate or a molded article containing polyethylene terephthalate.
5. A method for recovering raw materials of a polyester, an unsaturated polyester or a polyurethane, comprising:
a step of immersing a polyester or a molded article containing a polyester in an alkylene glycol in which a titanium oxide fine powder having a bulk density of not more than 0.3 g/cm 3 has been dispersed, and
a step of forming an alkylene glycol and a bis-β-hydroxyalkyl ester of a saturated dibasic acid by the use of the method for depolymerizing a polyester of claim 1 .
6. The method for recovering raw materials of a polyester, an unsaturated polyester or a polyurethane as claimed in claim 5 , further comprising a step of forming a dimethyl ester of a saturated dibasic acid by transesterification reaction of the bis-β-hydroxyalkyl ester of a saturated basic acid with methanol.
7. The method for recovering raw materials of a polyester, an unsaturated polyester or a polyurethane as claimed in claim 5 , wherein the alkylene glycol formed by the depolymerization reaction is reused as a dispersion medium for the depolymerization reaction.
8. A method for depolymerizing a polyester, comprising irradiating a polyester or a molded article containing a polyester with microwaves in the presence of a monohydric alcohol or polyhydric alcohol containing an alkali metal and/or an alkaline earth metal.
9. The method for depolymerizing a polyester as claimed in claim 8 , wherein the polyester or the molded article containing a polyester is polyethylene terephthalate or a molded article containing polyethylene terephthalate.
10. The method for depolymerizing a polyester as claimed in claim 8 , wherein the alkali metal is one or more alkali metals selected from the group consisting of sodium, potassium and lithium.
11. The method for depolymerizing a polyester as claimed in claim 8 , wherein the monohydric alcohol or polyhydric alcohol containing an alkali metal is one obtained by adding one or more alkali metal compounds selected from the group consisting of hydroxides, carbonates, hydrogencarbonates and phosphates of alkali metals to a monohydric alcohol or a polyhydric alcohol.
12. The method for depolymerizing a polyester as claimed in claim 8 , wherein the monohydric alcohol or the polyhydric alcohol comprises at least one alcohol selected from the group consisting of ethylene glycol, n-propylene glycol, isopropylene glycol, diethylene glycol, polyethylene glycol, triethylene glycol and glycerol, alkyl ether compounds of these alcohols, and benzyl alcohol.
13. A method for recovering raw materials of a polyester, an unsaturated polyester or a polyurethane, comprising:
a step of immersing a polyester or a molded article containing a polyester in a monohydric alcohol or polyhydric alcohol containing an alkali metal and/or an alkaline earth metal, and
a step of depolymerizing the polyester by the depolymerization method of claim 8 to form an alkylene glycol and a dialkali metal salt of a saturated dibasic acid or an ester compound of a saturated dibasic acid.
14. The method for recovering raw materials of a polyester, an unsaturated polyester or a polyurethane as claimed in claim 13 , further comprising a step of neutralizing the dialkali metal salt of a saturated dibasic acid formed by the depolymerization reaction with an acid to form a saturated dibasic acid.
15. The method for recovering raw materials of a polyester, an unsaturated polyester or a polyurethane as claimed in claim 13 , wherein the alkylene glycol formed by the depolymerization reaction is reused by adding it to the solvent for the depolymerization reaction.
16. A method for depolymerizing an unsaturated polyester, comprising irradiating an unsaturated polyester or a molded article containing an unsaturated polyester with microwaves in the presence of a monohydric alcohol or polyhydric alcohol containing an alkali metal and/or an alkaline earth metal.
17. The method for depolymerizing an unsaturated polyester as claimed in claim 16 , wherein the alkali metal is one or more alkali metals selected from the group consisting of sodium, potassium and lithium.
18. The method for depolymerizing an unsaturated polyester as claimed in claim 16 , wherein the monohydric alcohol or polyhydric alcohol containing an alkali metal is one obtained by adding one or more alkali metal compounds selected from the group consisting of hydroxides, carbonates, hydrogencarbonates and phosphates of alkali metals to a monohydric alcohol or a polyhydric alcohol.
19. The method for depolymerizing an unsaturated polyester as claimed in claim 16 , wherein the monohydric alcohol or the polyhydric alcohol comprises at least one alcohol selected from the group consisting of ethylene glycol, n-propylene glycol, isopropylene glycol, diethylene glycol, polyethylene glycol, triethylene glycol and glycerol, alkyl ether compounds of these alcohols, and benzyl alcohol.
20. The method for depolymerizing an unsaturated polyester as claimed in claim 16 , wherein the molded article containing an unsaturated polyester is a molded article containing a fiber-reinforced unsaturated polyester.
21. The method for depolymerizing an unsaturated polyester as claimed in claim 20 , wherein the fiber is a glass fiber.
22. A method for recovering raw materials of a polyester, an unsaturated polyester or a polyurethane, comprising:
a step of immersing an unsaturated polyester or a molded article containing an unsaturated polyester in a monohydric alcohol or polyhydric alcohol containing an alkali metal and/or an alkaline earth metal, and
a step of depolymerizing an unsaturated polyester by the depolymerization method of claim 16 to form an alkylene glycol and an ester compound of an oligomer that is a partial decomposition product of an unsaturated polyester.
23. The method for recovering raw materials of a polyester, an unsaturated polyester or a polyurethane as claimed in claim 22 , wherein the alkylene glycol formed by the depolymerization reaction is reused by adding it to the solvent for the depolymerization reaction.