Recycled monomer, method for producing recycled monomer, and apparatus for producing recycled monomer

Abstract

The purpose of the present invention is to provide a method for producing recycled monomers, such as dicarboxylic acids and diols, with high yield while suppressing the over-reaction of a product obtained by depolymerization while exhibiting the advantages of high-temperature and high-pressure water, and to provide a method for producing the recycled monomers, such as dicarboxylic acids and diols. In a suitable aspect of the method for producing a recycled monomer according to the present invention for achieving the above-mentioned purpose, the polymer is a thermoplastic polyester (A), and when the melting point of the thermoplastic polyester (A) as measured by a differential scanning calorimeter is Mp DEG C, the reaction temperature is X DEG C, the reaction time is Y minutes, and the mass ratio of water to the thermoplastic polyester (A) is Z: 1, the polymer is a thermoplastic polyester (A) having a melting point of Mp DEG C, the reaction temperature is X DEG C, the reaction time is Y minutes, and the mass ratio of water to the thermoplastic polyester (A) is Z: 1. X satisfies the following (I), and the product X * Y * Z of X, Y and Z satisfies the following (II). (I) Mp < = X < 300; and (II) 2000 < = X * Y * Z < = 20000.

Description

Technical Field

[0001] The present invention relates to a polymer chemical recycling technology that combines resource recycling with reducing the amount of greenhouse gas emissions from the earth. Background Art

[0002] In recent years, the concern for global environmental issues has increased, triggered by the issue of marine plastics, and the awareness of the need to build a sustainable society has expanded. Among global environmental issues, global warming is the most representative, and there are resource depletion, water shortage, etc., but most of them are caused by the use of fossil fuels since the industrial revolution and the rapid development of industry, which has led to an increase in resource consumption and global greenhouse gas emissions. Therefore, in order to build a sustainable society, technologies related to the recycling of fossil resources such as plastics and the reduction of global greenhouse gas emissions are becoming increasingly important.

[0003] As a technology for depolymerizing thermoplastic polyesters that are used in large quantities in various fields such as fibers, films, bottles, molded products, and engineering plastics, and restoring them to monomers for recycling, there are known technologies such as the methanol decomposition method in which methanol is reacted in the presence of a catalyst such as zinc acetate to recover methyl ester monomers, and the glycolysis method in which ethylene glycol is reacted in the presence of a catalyst such as sodium carbonate to recover oligomers. Commercial equipment that depolymerizes polyesters using these technologies is already in operation.

[0004] In addition, as a method for depolymerizing thermoplastic polyester without using an organic solvent such as methanol or ethylene glycol, a method is disclosed in which polyester is brought into contact with high-temperature and high-pressure water to recover diols and dicarboxylic acids as raw material monomers (see, for example, Patent Documents 1 to 3). The method of depolymerizing only with water has the following advantages: since no catalyst is required and no organic solvent derived from petroleum is used, it is a green recycling method.

[0005] In the depolymerization using high temperature and high pressure water, methods are disclosed in which a base is added to water to improve the recovery rate of dicarboxylic acid as a raw material monomer (for example, Patent Documents 4 to 7). However, the depolymerization requires a long time or an extremely high depolymerization temperature.

[0006] Furthermore, in order to impart the necessary properties to plastics according to their uses, there are many raw materials composed of multiple polymers, and raw materials composed of a single polymer are limited. In order to recycle raw materials composed of multiple polymers, research has been conducted to regenerate monomers by depolymerizing each polymer after separating them into single polymers before depolymerization. However, it is desired to develop recycling technology for raw materials that are difficult to separate.

[0007] In view of the above background, if a method for simultaneously depolymerizing a plurality of polymers can be established, it would be possible to construct a recycling process for raw materials composed of a plurality of polymers that could not be separated into single polymers so far without requiring a pretreatment step.

[0008] Patent Document 8 describes a depolymerization method of hydrolyzing a material selected from polyester, polyamide, and polycarbonate. However, there is no mention of simultaneously depolymerizing a plurality of polymers.

[0009] Although non-patent document 1 mentions the hydrolysis of PC (polycarbonate) / PBT (polybutylene terephthalate), PC / PET (polyethylene terephthalate), and PBT / PET, the reaction temperature is high and it is difficult to obtain recycled monomers at a high yield.

[0010] On the other hand, as a plastic recycling device, for example, an apparatus is disclosed in which an unsaturated polyester resin molded product and subcritical water are intermittently treated, and the weight ratio of the unsaturated polyester resin molded product to the subcritical water is in the range of 1:6 to 1:9, and the monomer is contacted at a temperature of 180°C to 250°C (see patent document 9).

[0011] Furthermore, an apparatus and method for recovering raw material monomers by contacting waste polyethylene terephthalate (PET) in a molten state with high-temperature and high-pressure water to continuously hydrolyze the PET is disclosed (see Patent Document 10).

[0012] Prior art literature

[0013] Patent Literature

[0014] Patent Document 1: Japanese Patent Application Publication No. 2000-309663

[0015] Patent Document 2: Japanese Patent Application Publication No. 2007-332361

[0016] Patent Document 3: Japanese Patent Application Laid-Open No. 6-72922

[0017] Patent Document 4: Japanese Patent Publication No. 11-502870

[0018] Patent Document 5: Japanese Patent Application Laid-Open No. 8-302061

[0019] Patent Document 6: International Publication No. 2007 / 148353

[0020] Patent Document 7: International Publication No. 2004 / 041917

[0021] Patent Document 8: U.S. Patent No. 4,605,762

[0022] Patent Document 9: Japanese Patent Application Publication No. 2012-106244

[0023] Patent Document 10: Japanese Patent Application Laid-Open No. 9-77905

[0024] Non-patent literature

[0025] Non-patent document 1: Waste Management, 68 (2017) 24-31 Summary of the invention

[0026] Problems to be solved by the invention

[0027] According to the depolymerization method of thermoplastic polyester disclosed in Patent Document 1, ethylene glycol is obtained at high yields of 92% and terephthalic acid is obtained at 96%. However, the disclosed polyester depolymerization method uses very high water with a specific heat capacity of 4.2 kJ / kg·K and a vaporization heat of 2,250 kJ / kg, which is about 6 times the amount of thermoplastic polyester, at a high temperature of 300°C to 350°C, and the reaction is carried out. The energy cost for the depolymerization reaction and the recovery of ethylene glycol from a low-concentration ethylene glycol aqueous solution is high.

[0028] In addition, in Patent Document 2, terephthalic acid is added during the hydrolysis of polyethylene terephthalate, and ethylene glycol and terephthalic acid are obtained at a yield of 100% at 300° C. for 10 minutes. However, when the reaction temperature is changed to 265° C., the yield of ethylene glycol and terephthalic acid decreases to 56%, and the yield decreases further if terephthalic acid is not added. Furthermore, since water is used in an amount of about 9 times that of the thermoplastic polyester, there is a problem of high energy cost.

[0029] On the other hand, the depolymerization method of polyethylene terephthalate disclosed in Patent Document 3 obtains a depolymerized product with a high yield of 90% ethylene glycol and 96% terephthalic acid, although only water is used and the reaction temperature is relatively low at 280°C. However, the depolymerization reaction takes 6 hours, which cannot be said to be efficient. Furthermore, in Patent Document 3, in order to improve the deterioration of color caused by coloring impurities with unsaturated bonds that are difficult to purify and remove, waste PET is subjected to hydrogenation treatment using 1% by weight of palladium / carbon catalyst. In fact, when the present inventors conducted a depolymerization experiment using polyethylene terephthalate as a raw material according to the method described in Patent Document 3, except that the hydrogenation treatment was not performed, under the same conditions and similar conditions, the reaction mixture was colored light orange.

[0030] Based on the above-mentioned prior art, the recycled monomer of the present invention, the method for producing the recycled monomer, and the first and second preferred embodiments of the present invention described later aim to provide a method for producing recycled monomers such as dicarboxylic acids and diols at a high yield while taking advantage of the advantages of high-temperature and high-pressure water and suppressing the overreaction of the product obtained by depolymerization.

[0031] Furthermore, a third preferred embodiment of the present invention described below aims to provide a method for producing recycled monomers, particularly dicarboxylic acids and diols, at a high yield from a raw material composed of a plurality of polymers that has been difficult to chemically recycle.

[0032] On the other hand, as a plastic recycling device, the depolymerization device disclosed in Patent Document 9 has an intermittent reactor. Therefore, when a large amount of processing is performed, the volume of the reactor increases due to the influence of the cycle time of addition and discharge, resulting in an increase in the cost of the device for manufacturing the recycled monomer, and insufficient efficiency cannot be obtained. On the other hand, when the subcritical water amount added to the resin molded product is reduced, the efficiency is improved due to the increase in the processing amount of the resin molded product, but a sufficient recycled monomer yield cannot be obtained.

[0033] In addition, the method and apparatus for hydrolyzing waste PET disclosed in Patent Document 10 are continuous, so the increase in reactor volume as in the batch method can be avoided, and the recycled monomer can be produced more efficiently than in the batch method. On the other hand, as described above, when the amount of high-temperature and high-pressure water added to the waste PET is reduced, a sufficient recycled monomer yield cannot be obtained.

[0034] Therefore, an object of the production apparatus of a recycled monomer of the present invention is to provide an apparatus for producing a recycled monomer which can produce the recycled monomer with high efficiency and high yield using a continuous reactor.

[0035] Means for solving problems

[0036] In order to solve the above-mentioned problems, the present invention has the following configurations.

[0037] 1. A recycled monomer, a recycled monomer produced by contacting a composition comprising a polymer with subcritical water, wherein the recycled monomer is produced from a composition comprising a polymer under the following conditions: when the melting point of the polymer measured by a differential scanning calorimeter is set to Mp°C, the reaction temperature is set to X°C, the reaction time is set to Y minutes, and the mass ratio of water to the polymer is set to Z:1, X satisfies the following (I), and the product X·Y·Z of X, Y and Z satisfies the following (II).

[0038] (I)Mp≤X<300

[0039] (II)2000≤X·Y·Z≤20000

[0040] 2. The recycled monomer according to item 1 above, wherein the polymer is a thermoplastic polyester or a thermoplastic polyamide.

[0041] 3. A recycled polymer obtained by repolymerizing the recycled monomer described in 1 above.

[0042] 4. A clothing fiber, industrial fiber, film, sheet, automobile part, or electric / electronic part produced using the recycled polymer described in 3 above.

[0043] 5. A method for producing a recycled monomer, comprising the step of contacting a composition containing a polymer with subcritical water.

[0044] 6. The method for producing a recycled monomer according to 5 above, wherein the polymer is a thermoplastic polyester (A), and when the melting point of the thermoplastic polyester (A) measured by a differential scanning calorimeter is Mp°C, the reaction temperature is X°C, the reaction time is Y minutes, and the mass ratio of water to the thermoplastic polyester (A) is Z:1, X satisfies the following (I), and the product of X, Y and Z, X·Y·Z, satisfies the following (II).

[0045] (I)Mp≤X<300

[0046] (II)2000≤X·Y·Z≤20000

[0047] 7. The method for producing a recycled monomer according to 6 above, wherein a composition containing a thermoplastic polyester (A) is brought into contact with subcritical water, and the concentration of diol derived from the thermoplastic polyester (A) in the reaction mixture obtained by hydrolyzing the thermoplastic polyester (A) is 4.9% by mass or more.

[0048] 8. The method for producing a recycled monomer according to 6 above, wherein a composition containing a thermoplastic polyester (A) is contacted with subcritical water, and the concentration of the cyclic ether derived from the thermoplastic polyester (A) in the reaction mixture obtained by hydrolyzing the thermoplastic polyester (A) is 3.0% by mass or more.

[0049] 9. The method for producing a recycled monomer according to 6 above, wherein the mass ratio Z of the subcritical water to the thermoplastic polyester (A) is less than 6.

[0050] 10. The method for producing recycled monomers according to 6 above, wherein the thermoplastic polyester (A) contains as a main component at least one selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and copolymers thereof.

[0051] 11. The method for producing a recycled monomer according to 6 above, wherein the thermoplastic polyester (A) is waste containing at least polyester.

[0052] 12. The method for producing a recycled monomer according to 6 above, wherein the recycled monomer is a dicarboxylic acid and / or a diol.

[0053] 13. A method for producing a thermoplastic polyester, using the dicarboxylic acid and / or diol obtained by the production method of 12 above as a raw material.

[0054] 14. A method for producing a thermoplastic polyester product, comprising using the thermoplastic polyester obtained by the production method according to 12 above as a raw material to produce a product containing the thermoplastic polyester such as a fiber, a film or a molded article.

[0055] 15. A method for producing a product comprising a thermoplastic polyester composition, comprising using the thermoplastic polyester composition obtained by the production method according to 12 above as a raw material to produce a fiber, a film or a molded article comprising the thermoplastic polyester composition.

[0056] 16. The method for producing recycled monomers according to 5 above, wherein the polymer is a thermoplastic polyester (A), and 0.01 to 4.0 parts by weight of an alkali metal salt and / or an alkaline earth metal salt is blended with respect to 100 parts by weight of the thermoplastic polyester (A).

[0057] 17. The method for producing a recycled monomer according to 16 above, wherein 100 to 1000 parts by weight of subcritical water is mixed with 100 parts by weight of the thermoplastic polyester (A).

[0058] 18. The method for producing a recycled monomer according to 16 above, wherein the temperature in the step of contacting with subcritical water is 250 to 350°C.

[0059] 19. The method for producing a recycled monomer according to 16 above, wherein the pressure in the step of contacting with subcritical water is 3 to 30 MPa.

[0060] 20. The method for producing a recycled monomer according to 16 above, wherein the alkali metal salt and / or alkaline earth metal salt is a metal hydroxide and / or a metal carbonate.

[0061] 21. The method for producing recycled monomers according to 16 above, wherein the thermoplastic polyester (A) is at least one selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and copolymers thereof.

[0062] 22. The method for producing recycled monomers according to 16 above, wherein the composition comprising the thermoplastic polyester (A) comprises at least one selected from the group consisting of an antioxidant, a heat resisting agent, a weather resisting agent, a releasing agent and a crystal nucleating agent.

[0063] 23. The method for producing recycled monomers according to 16 above, wherein the composition containing the thermoplastic polyester (A) is waste.

[0064] 24. The method for producing a recycled monomer according to 16 above, wherein the recycled monomer is a dicarboxylic acid and / or a diol.

[0065] 25. A method for producing a thermoplastic polyester, using the dicarboxylic acid and / or diol obtained by the production method according to 24 above as a raw material.

[0066] 26. A method for producing a composition containing a thermoplastic polyester, comprising blending at least one selected from an antioxidant, a weathering agent, a release agent and a crystal nucleating agent into the thermoplastic polyester obtained by the production method according to 25 above.

[0067] 27. A method for producing a thermoplastic polyester product, comprising using the thermoplastic polyester obtained by the production method according to 25 above as a raw material to produce a product including a fiber, a film or a molded article comprising the thermoplastic polyester.

[0068] 28. A method for producing a product comprising a thermoplastic polyester composition, wherein the product comprising a thermoplastic polyester composition obtained by the production method according to 26 above is used as a raw material to produce a fiber, a film or a molded article.

[0069] 29. The method for producing a recycled monomer according to 5 above, wherein the polymer composition comprises polymer I and polymer II,

[0070] The polymer I is a thermoplastic polyester (A),

[0071] The polymer II is one polymer selected from the group consisting of a thermoplastic polyester (B) having a melting point different from that of the thermoplastic polyester (A), polycarbonate and polyurethane, or a combination of these polymers,

[0072] The content of the polymer II in the composition (the total content of the thermoplastic polyester (B), the polycarbonate and the polyurethane) is 1 to 100 parts by weight relative to 100 parts by weight of the polymer I.

[0073] The method for producing the recycled monomer comprises the step of simultaneously contacting the polymer I and the polymer II in the composition with subcritical water at 250 to 350°C.

[0074] 30. The method for producing a recycled monomer according to 5 above, wherein the composition comprising a polymer comprises a polymer I and a polymer II,

[0075] The polymer I is a thermoplastic polyester (A),

[0076] The polymer II is one polymer selected from the group consisting of a thermoplastic polyester (B) having a melting point different from that of the thermoplastic polyester (A), polycarbonate and polyurethane, or a combination of these polymers,

[0077] The content of the polymer II in the composition (the total content of the thermoplastic polyester (B), the polycarbonate and the polyurethane) is 1 to 100 parts by weight relative to 100 parts by weight of the polymer I.

[0078] The method for producing the recycled monomer comprises a step of simultaneously hydrolyzing the polymer I and the polymer II in the composition by contacting them with subcritical water at 200 to 350° C. in the presence of a basic component.

[0079] 31. The method for producing a recycled monomer according to 29 or 30 above, wherein the composition containing a polymer comprises a composition containing polymer I and polymer II, and / or a mixture of a composition containing polymer I and a composition containing polymer II.

[0080] 32. The method for producing a recycled monomer according to 29 or 30 above, wherein 100 to 900 parts by weight of water is added based on 100 parts by weight of the polymer component in the composition containing the polymer.

[0081] 33. The method for producing a recycled monomer according to 29 or 30 above, wherein the pressure in the step of contacting with subcritical water is 4.0 MPa to 30 MPa.

[0082] 34. The method for producing a recycled monomer according to 29 above, wherein a basic component is further blended into the composition containing the polymer.

[0083] 35. According to the method for producing recycled monomers as described in 29 or 30 above, the thermoplastic polyester (A) is selected from polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate and copolymers thereof.

[0084] 36. According to the method for producing recycled monomers described in 29 or 30 above, the thermoplastic polyester (B) is at least one selected from polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate and their copolymers, and is a thermoplastic polyester having a melting point different from that of the polyester (A).

[0085] 37. The method for producing a recycled monomer according to 29 or 30 above, wherein the difference in melting points between the thermoplastic polyester (A) and the thermoplastic polyester (B) is 10° C. or more.

[0086] 38. The method for producing a recycled monomer according to 29 or 30 above, wherein the composition containing the polymer is waste.

[0087] 39. The method for producing a recycled monomer according to 29 or 30 above, wherein the recycled monomer is terephthalic acid and / or diol.

[0088] 40. A method for producing a thermoplastic polyester, comprising using the dicarboxylic acid and / or diol obtained by the production method according to 29 or 30 above as a polymerization raw material to produce the thermoplastic polyester.

[0089] 41. A method for producing a thermoplastic polyester product, comprising using the thermoplastic polyester obtained by the production method described in 40 above as a raw material to produce a thermoplastic polyester product of fiber, film or molded article.

[0090] 42. A method for producing a product comprising a thermoplastic polyester composition, wherein the thermoplastic polyester composition obtained by the production method described in 40 above is used as a raw material to produce a fiber, a film or a molded article comprising the thermoplastic polyester composition.

[0091] 43. A manufacturing device for a recycled monomer, comprising a unit (L) for heating and pressurizing a composition containing a polymer and supplying it, a unit (M) for generating and supplying subcritical water, a unit (N) for mixing the composition containing a thermoplastic polymer supplied from the above-mentioned unit (L) with the above-mentioned subcritical water supplied from the above-mentioned unit (M), and a continuous reactor (O) for hydrolyzing the polymer.

[0092] 44. The apparatus for producing a recycled monomer according to 43 above, comprising a device (P) for monitoring the internal temperature of the upstream and downstream parts of the continuous reactor (O), and a temperature adjustment mechanism (Q) for heating and / or cooling the continuous reactor (O),

[0093] The temperature regulating mechanism (Q) is operated based on the device (P) to control the internal temperature of the continuous reactor (O).

[0094] 45. The apparatus for producing a recycled monomer according to 43 above, wherein a plurality of the temperature adjustment mechanisms (Q) are provided.

[0095] Based on the above-mentioned device (P), the plurality of temperature adjustment mechanisms (Q) are operated.

[0096] 46. ​​The apparatus for producing a recycled monomer according to 44 or 45 above, wherein the temperature regulating mechanism (Q) is controlled so that the internal temperature of the downstream portion of the continuous reactor (O) is lower by 10° C. or more than the internal temperature of the upstream portion.

[0097] 47. The apparatus for producing a recycled monomer according to 44 or 45 above, wherein the continuous reactor (O) is a tubular continuous reactor.

[0098] 48. The apparatus for producing a recycled monomer according to 44 or 45 above, wherein the unit (L) is an extruder.

[0099] 49. The apparatus for producing a recycled monomer according to 44 or 45 above, wherein the unit (N) is a static mixer.

[0100] 50. The apparatus for producing a recycled monomer according to 44 or 45 above, wherein the composition containing a polymer is waste of resin molded products.

[0101] 51. The apparatus for producing recycled monomers according to 44 or 45 above, wherein the polymer is thermoplastic polyamide or thermoplastic polyester.

[0102] Effects of the Invention

[0103] The recycled monomer of the present invention, the method for producing the recycled monomer, and the first preferred embodiment of the present invention described later can provide a method with low energy consumption required for depolymerization reaction and distillation purification, because the thermoplastic polyester can be depolymerized with high efficiency even in a short treatment time with only a small amount of water, and a reaction mixture containing diol and dicarboxylic acid at high concentrations can be obtained. Furthermore, the secondary reaction of diol and dicarboxylic acid is suppressed by setting the depolymerization reaction conditions at low temperature and for a short time, and non-colored diol and dicarboxylic acid can be obtained at high yield.

[0104] In addition, in a second preferred embodiment of the present invention described below, a composition containing a thermoplastic polyester is hydrolyzed by adding a specific amount of an alkali metal salt and / or an alkaline earth metal salt, thereby suppressing overreaction of the product and producing dicarboxylic acid and / or diol at a high yield.

[0105] Furthermore, the third preferred embodiment of the present invention described below can provide a method for producing a recycled monomer at a high yield by simultaneously hydrolyzing a raw material composed of a plurality of polymers that have been difficult to chemically recycle. In particular, by having a step of simultaneously hydrolyzing a composition containing a specific amount of a polymer I composed of a thermoplastic polyester (A) and a polymer II composed of at least one selected from a thermoplastic polyester (B) having a melting point different from that of the thermoplastic polyester (A), a polycarbonate, and a polyurethane with subcritical water in a specific temperature range, dicarboxylic acid and / or diol can be produced at a high yield.

[0106] Furthermore, the production apparatus for the recycled monomer of the present invention can produce the recycled monomer with high efficiency and high yield by using a continuous reactor and performing precise control of the reaction temperature of the upstream part and the downstream part of the continuous reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0107] Figure 1This is a schematic diagram showing one embodiment of the production apparatus for recycled monomers of the present invention.

[0108] Figure 2 This is a schematic diagram showing another embodiment of the production apparatus for recycled monomers of the present invention. DETAILED DESCRIPTION

[0109] Hereinafter, the present invention will be described in further detail.

[0110] [1] Recycled monomers, recycled polymers, and various products made from recycled monomers

[0111] The recycled monomer of the present invention is a recycled monomer produced by contacting a composition containing a polymer with subcritical water, wherein the recycled monomer is produced from a composition containing a polymer under the following conditions: when the melting point of the polymer measured by a differential scanning calorimeter is set to Mp°C, the reaction temperature is set to X°C, the reaction time is set to Y minutes, and the mass ratio of water to the polymer is set to Z:1, X satisfies the following (I), and the product X·Y·Z of X, Y and Z satisfies the following (II).

[0112] (I)Mp≤X<300

[0113] (II)2000≤X·Y·Z≤20000.

[0114] As the above-mentioned recycled monomer, it is preferred that the monomer be obtained by depolymerizing a polymer that is produced in large quantities and has a high need for recycling. Specifically, it is preferred that the monomer be a monomer of a thermoplastic polyester or a monomer of a thermoplastic polyamide. As the former monomer, there can be mentioned terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, bis(p-carboxyphenyl)methane, 1,4-anthracene dicarboxylic acid, 1,5-anthracene dicarboxylic acid, 1,8-anthracene dicarboxylic acid, 2,6-anthracene dicarboxylic acid, 9,10-anthracene dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-tetrabutyl ether dicarboxylic acid, Aromatic dicarboxylic acids such as isophthalic acid and 5-sodium sulfonate isophthalic acid, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, dimer acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and their ester-forming derivatives, ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol aliphatic or alicyclic diols having 2 to 20 carbon atoms such as diol, 1,10-decanediol, cyclohexanedimethanol, cyclohexanediol, dimer diol, long chain diols having a molecular weight of 200 to 100,000 such as polyethylene glycol, poly-1,3-propylene glycol, polytetramethylene glycol, 4,4'-dihydroxybiphenyl, hydroquinone, tert-butylhydroquinone, bisphenol A, bisphenol S, bisphenol F, and their ester-forming derivatives.

[0115] Examples of the latter monomer include amino acids such as 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, and p-aminomethylbenzoic acid, lactams such as ε-caprolactam and ω-laurolactam, ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, decanediamine, undecanediamine, dodecanediamine, and tridecanediamine. , aliphatic diamines such as tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecanediamine, octadecanediamine, nonadecanediamine, eicosanediamine, 2-methyl-1,5-diaminopentane, and 2-methyl-1,8-diaminooctane, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, dialkyl esters of these dicarboxylic acids, dichlorides, and the like.

[0116] In the recycled monomer of the present invention, the polymer is preferably a thermoplastic polyester or a thermoplastic polyamide. As the thermoplastic polyester, preferably a homopolymer or a copolymer obtained by polycondensing a dicarboxylic acid or its ester-forming derivative with a diol or its ester-forming derivative, specifically, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polytrimethylene isophthalate, polybutylene isophthalate, polybutylene naphthalate, polypropylene glycol isophthalate / terephthalate can be cited. , Polybutylene isophthalate / terephthalate, Polypropylene terephthalate / naphthalate, Polybutylene terephthalate / naphthalate, Polybutylene terephthalate / decane dicarboxylate, Polypropylene terephthalate / 5-sodium sulfonate isophthalate, Polybutylene terephthalate / 5-sodium sulfonate isophthalate, Polypropylene terephthalate / polyethylene glycol, Polybutylene terephthalate Aromatic polyester resins such as glycol ester / polyethylene glycol, polytrimethylene terephthalate / polybutylene glycol, polybutylene terephthalate / polybutylene glycol, polypropylene terephthalate / isophthalate / polybutylene glycol, polybutylene terephthalate / isophthalate / polybutylene glycol, polybutylene terephthalate / succinate, polypropylene terephthalate / adipate, polybutylene terephthalate / adipate, polypropylene terephthalate / sebacate, polybutylene terephthalate / sebacate, polypropylene terephthalate / isophthalate / adipate, polybutylene terephthalate / isophthalate / succinate, polybutylene terephthalate / isophthalate / adipate, polybutylene terephthalate / isophthalate / sebacate may be a mixture of two or more thereof.

[0117] On the other hand, the thermoplastic polyamide is preferably a homopolymer or copolymer obtained by polycondensing an amino acid, a lactam or a dicarboxylic acid with a diamine, and specifically, polycaprolactam (polyamide 6), polyhexamethylene adipamide (polyamide 66), polybutylene adipamide (polyamide 46), polypentamethylene adipamide (polyamide 56), polybutylene sebacate (polyamide 410), polypentamethylene sebacate (polyamide 510), polyhexamethylene sebacate (polyamide 610), polyhexamethylene dodecanoate (polyamide 612), and copolymers thereof, and a mixture of two or more thereof may be used. From the viewpoint of large production volume and more recycled raw resources being secured, the above polymer is more preferably a thermoplastic polyester.

[0118] The recycled polymer of the present invention is obtained by repolymerizing the recycled monomer of the present invention. By repolymerizing the recycled monomer of the present invention to produce the recycled polymer, it can be used as a plastic material, and can contribute to resource circulation.

[0119] The clothing fiber, industrial fiber, film, sheet, automobile part, or electric / electronic part of the present invention is produced by using the recycled polymer of the present invention. The above-mentioned products have the added value of being environmentally friendly.

[0120] [2] Method for producing recycled monomers

[0121] The method for producing a recycled monomer of the present invention comprises a step of contacting a composition comprising a polymer with subcritical water. The method for producing a recycled monomer of the present invention comprises the following four preferred embodiments. In this specification, the three preferred embodiments of the method for producing a recycled monomer of the present invention are sometimes referred to as "the first preferred embodiment of the present invention", "the second preferred embodiment of the present invention", and "the third preferred embodiment of the present invention", respectively. In addition, the method for producing a recycled monomer described in the item "[3] Apparatus for producing recycled monomers" described later is sometimes referred to as "the fourth preferred embodiment of the present invention".

[0122] [2-1] The first preferred embodiment of the present invention

[0123] A first preferred embodiment is a method for producing a recycled monomer, comprising the step of contacting a composition containing a thermoplastic polyester (A) with subcritical water, wherein, when the melting point of the thermoplastic polyester (A) measured by a differential scanning calorimeter is Mp°C, the reaction temperature is X°C, the reaction time is Y minutes, and the mass ratio of water to the thermoplastic polyester (A) is Z:1, X satisfies the following (I), and the product X·Y·Z of X, Y and Z satisfies the following (II).

[0124] (I)Mp≤X<300

[0125] (II)2000≤X·Y·Z≤20000.

[0126] The thermoplastic polyester (A) can be depolymerized into the diol and / or dicarboxylic acid constituting the thermoplastic polyester (A) by bringing the thermoplastic polyester (A) into contact with subcritical water for hydrolysis.

[0127] The thermoplastic polyester (A) used in the present invention is a homopolymer or copolymer obtained by polycondensation using dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative as main raw materials. Here, the so-called main raw material means that the structural units of dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative in the polymer account for 50 mol% or more, preferably 80 mol% or more, and more preferably 90 mol% or more.

[0128] Examples of the dicarboxylic acids or ester-forming derivatives thereof include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, bis(p-carboxyphenyl)methane, 1,4-anthracenedicarboxylic acid, 1,5-anthracenedicarboxylic acid, 1,8-anthracenedicarboxylic acid, 2,6-anthracenedicarboxylic acid, 9,10-anthracenedicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 5-tetrabutylamine, 1,4-dicarboxylic acid, 1,5-dicarboxylic acid, 1,8-dicarboxylic acid, 2,6-anthracenedicarboxylic acid, 9,10-anthracenedicarboxylic acid, 4,4 Aromatic dicarboxylic acids such as isophthalic acid and 5-sodium sulfonate isophthalic acid, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, and dimer acid, alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, and ester-forming derivatives thereof, etc. Two or more of these may be used.

[0129] The ester-forming derivatives referred to herein are lower alkyl esters, anhydrides, acyl halides, etc. of dicarboxylic acids described above. As lower alkyl esters of dicarboxylic acids, methyl esters, ethyl esters, hydroxyethyl esters, hydroxybutyl esters, etc. are preferably used. As anhydrides of dicarboxylic acids, anhydrides of dicarboxylic acids, anhydrides of dicarboxylic acids and acetic acid, etc. are preferably used. As halides of dicarboxylic acids, acyl chlorides, acyl bromides, acyl iodides, etc. are preferably used.

[0130] Examples of the diol or its ester-forming derivative include aliphatic or alicyclic diols having 2 to 20 carbon atoms such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, cyclohexanedimethanol, cyclohexanediol, and dimer diol, long-chain diols having a molecular weight of 200 to 100,000 such as polyethylene glycol, poly-1,3-propylene glycol, and polytetramethylene glycol, aromatic dihydroxy compounds such as 4,4'-dihydroxybiphenyl, hydroquinone, tert-butylhydroquinone, bisphenol A, bisphenol S, and bisphenol F, and their ester-forming derivatives. Two or more of these may be used.

[0131] Examples of the homopolymer or copolymer having a dicarboxylic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof as structural units include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polytrimethylene isophthalate, polybutylene isophthalate, polybutylene naphthalate, polypropylene isophthalate / terephthalate, polybutylene isophthalate / terephthalate, polypropylene terephthalate / naphthalate, polybutylene terephthalate / naphthalate, polybutylene terephthalate / decane dicarboxylate, polytrimethylene terephthalate / 5-sodium sulfonate isophthalate, polybutylene terephthalate / 5-sodium sulfonate isophthalate, polytrimethylene terephthalate / polyethylene glycol, and polyterephthalate. Aromatic polyester resins such as polybutylene glycol terephthalate / polybutylene glycol, polypropylene terephthalate / polybutylene glycol, polypropylene terephthalate / isophthalate / polybutylene glycol, polybutylene terephthalate / isophthalate / polybutylene glycol, polybutylene terephthalate / succinate, polypropylene terephthalate / adipate, polybutylene terephthalate / adipate, polypropylene terephthalate / sebacate, polybutylene terephthalate / sebacate, polypropylene terephthalate / isophthalate / adipate, polybutylene terephthalate / isophthalate / succinate, polybutylene terephthalate / isophthalate / adipate, polybutylene terephthalate / isophthalate / sebacate.

[0132] Here, " / " represents a copolymer. These homopolymers and copolymers can be used alone or two or more can be mixed and used in any content. Among them, from the perspective of recycling the thermoplastic polyester (A) and promoting the recycling of fossil resources, it is preferred to use a homopolymer or copolymer with a residue of an aromatic dicarboxylic acid or its ester-forming derivative and an aliphatic diol or its ester-forming derivative as the main raw material with a large production and consumption. As an example of the above-mentioned preferred polymer, there can be cited a homopolymer or copolymer obtained by polycondensing at least one selected from terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid and their ester-forming derivatives with at least one selected from ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol or their ester-forming derivatives, wherein it is particularly preferred to use at least one selected from polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and their copolymers.

[0133] The thermoplastic polyester (A) of the present invention may be mixed with a polymerization catalyst, a thermoplastic resin other than the thermoplastic polyester, a dye, various additives, a fibrous filler, a filler other than the fibrous filler, etc., within the range not impairing the purpose of the present invention. The fibrous filler here may be any filler having a fibrous shape. As a filler other than the fibrous filler, any of an organic filler and an inorganic filler may be mentioned, for example, a non-fibrous filler. Two or more of these may be mixed.

[0134] The thermoplastic polyester (A) of the present invention may be waste of a resin molded body containing at least a thermoplastic polyester. Waste of a resin molded body containing a thermoplastic polyester includes thermoplastic polyester products, industrial waste generated in the manufacturing process of thermoplastic polyester products, or waste of thermoplastic polyester products after use. Examples of thermoplastic polyester products include containers such as beverage bottles and seasoning bottles, sheet products such as food trays, blister packages, food partitions, and industrial trays, packaging films, optical functional films, film products such as magnetic tapes and insulating materials, fiber structures for clothing such as used clothes, uniforms, sportswear, and underwear, industrial fiber structures such as curtains, carpets, nets, belts, and sheets, and molded products such as automobile parts, electrical / electronic parts, building components, daily necessities, daily necessities, and sanitary products. Furthermore, product scraps, granular scraps, block scraps, etc. generated in their production processes also become objects of waste. The waste of the resin molded product containing the thermoplastic polyester can be subjected to the depolymerization method of the present invention together with a product composed of other than the thermoplastic polyester (A) within a range not impairing the effects of the present invention.

[0135] The method for depolymerizing a thermoplastic polyester (A) in a first preferred embodiment of the present invention is characterized in that it includes a step of bringing the thermoplastic polyester into contact with subcritical water, wherein when at least the thermoplastic polyester (A) and water are heated and mixed, when the melting point of the thermoplastic polyester is Mp°C, when the reaction temperature is X°C, the reaction time is Y minutes, and the mass ratio of water to the thermoplastic polyester is Z:1, X satisfies (i) Mp≤X<300, and the product X·Y·Z of X, Y and Z satisfies (ii) 2000≤X·Y·Z≤20000.

[0136] The melting point of the thermoplastic polyester (A) in the present invention is the temperature of the endothermic peak that appears when the thermoplastic polyester (A) is cooled from a molten state to 30°C at a cooling rate of 20°C / min and then heated to the melting point + 40°C at a heating rate of 20°C / min in an inert gas atmosphere using a differential scanning calorimeter manufactured by TA Instruments. However, when two or more endothermic peaks are detected, the temperature of the endothermic peak with the largest peak intensity is set as the melting point. There is no particular restriction on the melting point of the thermoplastic polyester, but as a preferred melting point range, it can be exemplified as more than 50°C and less than 300°C. If the melting point exceeds 50°C, the thermoplastic polyester becomes solid at room temperature, so it is excellent in handleability. In addition, by having a melting point of less than 300°C, it can be mixed with water in a molten state in a temperature range where the conversion reaction of the depolymerization product can be suppressed, so the reaction efficiency can be improved, which is preferred.

[0137] The water used here is not particularly limited, and any water such as tap water, ion-exchanged water, distilled water, well water, etc. can be used. However, from the viewpoint of suppressing side reactions caused by the influence of coexisting salts, ion-exchanged water and distilled water are preferably used.

[0138] As water, it is sufficient as long as it is heated to a temperature above the melting point Mp°C of the thermoplastic polyester (A) and below 300°C when reacting it with the thermoplastic polyester (A). If the water is raised to a pressure of 22.1 MPa and a temperature of 374.2°C, it will be in a state that is neither liquid nor gas. This point is called the critical point of water, and hot water in the vicinity of the critical point with a temperature and pressure slightly lower than the critical point is called subcritical water. The water used in the present invention is less than 300°C, which is equivalent to subcritical water. Although the subcritical water is water, it has the characteristics of (i) a low dielectric constant and (ii) a high ion product. The dielectric constant and ion product of subcritical water can be controlled depending on the temperature and the partial pressure of water. As the dielectric constant becomes lower, it becomes an excellent solvent for organic compounds although it is water, and as the ion product becomes higher, the concentrations of hydrogen ions and hydroxide ions become higher, so it has an excellent hydrolysis effect.

[0139] In addition, as the pressure of water, it is preferably exemplified that it is higher than the saturated vapor pressure. As water, it can be in a liquid state or a gaseous state such as water vapor, and both can be used, but as a reaction field, the liquid state is easier to react than the gaseous state, so as the pressure of water, it is preferably higher than the saturated vapor pressure. In addition, as the upper limit of the pressure of water, there is no particular restriction, but it is preferably 30MPa. The upper limit of the pressure of water is more preferably 25MPa, and further preferably 22MPa. By being in such a pressure range, it is preferred that the ion product of the above-mentioned water becomes higher. As a method for making water such a pressure range, a method of pressurizing the inside of a pressure vessel and sealing it can be cited. When the inside of a pressure vessel is pressurized, a method of sealing a gas in addition to water can be cited. As such a gas, air, argon, nitrogen, etc. can be cited. From the viewpoint of suppressing side reactions such as oxidation reactions, nitrogen and argon are preferably used as the sealed gas. In addition, the inside of the pressure vessel can also be pressurized by introducing high-pressure water. In the case of using high-pressure water, it can also be a state where there is no gas in the pressure vessel. The degree of pressurization using gas or high-pressure water is not particularly limited because it is set to a target pressure, but is preferably 0.3 MPa or more.

[0140] Regarding the reaction temperature in the depolymerization method of the thermoplastic polyester resin (A) in the first preferred embodiment of the present invention, when the melting point of the thermoplastic polyester (A) is Mp°C, it is above M°C and less than 300°C. The reaction temperature here refers to the temperature during which the thermoplastic polyester (A) reacts with water for a certain period of time in a temperature-controlled reaction vessel, which can be a constant temperature or a temperature that changes over time. It should be noted that there is no particular restriction on the temperature during the heating process until the reaction temperature is reached and the temperature during the cooling process after the reaction at the reaction temperature as long as it does not exceed the reaction temperature. By setting the reaction temperature to be above the melting point of the thermoplastic polyester, the thermoplastic polyester (A) becomes a molten liquid during the reaction, and when mixed with water, it is dispersed in a droplet shape and the interfacial area is increased, so that the reaction efficiency can be improved. On the other hand, by setting the reaction temperature to be less than 300°C, the hot water solubility of the dicarboxylic acid that catalyzes the conversion reaction (overreaction) of the diol can be adjusted, and the conversion reaction of the diol can be suppressed. From the viewpoint of reducing coloration, the temperature is preferably 290° C. or lower, and from the viewpoint of increasing the yield of the diol, the temperature is particularly preferably 280° C. or lower.

[0141] When the reaction temperature X is in the above preferred range, when the mass ratio of water to the thermoplastic polyester is set to Z:1, Z is preferably less than 6. It is known that diols have high water solubility and are fully mixed with water in the temperature range from room temperature to the temperature range including the reaction temperature X. On the other hand, the water solubility of dicarboxylic acids tends to decrease at room temperature and increase in hot water. For example, terephthalic acid, which is a dicarboxylic acid generated by hydrolysis of polyethylene terephthalate and polybutylene terephthalate, is almost insoluble in water at room temperature (20°C) and is 15 mg / L, but the higher the temperature, the higher the water solubility, and it becomes a 10% by mass terephthalic acid aqueous solution at 250°C and a 44% by mass terephthalic acid aqueous solution at 300°C. By adjusting the hot water solubility of dicarboxylic acids in the temperature range where the reaction temperature X can be preferably used, making Z less than 6, the concentration of dicarboxylic acids relative to diols can be relatively low, and diols and dicarboxylic acids can be obtained in high yields. From the viewpoint of improving the processing efficiency and avoiding the enlargement of the equipment, Z is more preferably 5 or less, and particularly preferably 4 or less.

[0142] The method for depolymerizing the thermoplastic polyester (A) in the first preferred embodiment of the present invention is characterized in that, when the reaction temperature is X°C, the reaction time is Y minutes, and the mass ratio of water to the thermoplastic polyester is Z:1, the product of X, Y and Z, X·Y·Z, is 2000≤X·Y·Z≤20000. The reaction time Y here means the time for mixing the thermoplastic polyester (A) and water in a reaction vessel controlled to the reaction temperature X. The heating time until the reaction temperature X is reached and the cooling time after the reaction at the reaction temperature X are not included in Y. The value of Y is not particularly limited as long as it satisfies the above-mentioned range of the product of X, Y and Z, and can be set corresponding to X and Z. The product of X, Y and Z is preferably 17,500 or less, more preferably 15,000 or less, and particularly preferably 12,500 or less. In addition, the condition that the product of X, Y and Z is preferably 2,200 or more, more preferably 2,400 or more, and particularly preferably 2,600 or more can be exemplified. It should be noted that the reaction can be carried out at multiple temperatures, and the product X·Y·Z in this case is the value obtained by summing the products X·Y·Z at each reaction temperature. The present invention relates to an energy-saving depolymerization method for the purpose of recycling fossil resources and reducing global greenhouse gas emissions. The specific heat capacity of water is 4.3 kJ / kg·K and the heat of vaporization is 2,250 kJ / kg, which are very high compared to other organic solvents. Therefore, it is important to reduce the amount of water used. By making the product of X, Y and Z within these condition ranges, it is possible to achieve both the efficiency of generating dicarboxylic acids and diols and energy saving.

[0143] Furthermore, in order to realize energy conservation during diol recovery and purification, the concentration of diol derived from thermoplastic polyester (A) contained in the reaction mixture is preferably 4.9% by mass or more. The concentration of the above diol is more preferably 6.0% by weight or more, and more preferably 7.0% by weight or more. By making the concentration of diol contained in the reaction mixture the above preferred range, the amount of the reaction mixture to be treated in order to recover 1 kg of diol can be reduced, so the equipment can be miniaturized, and the energy required for heating water during recovery can be further reduced. The concentration of diol derived from thermoplastic polyester (A) contained in the reaction mixture referred to here can be obtained by the absolute standard curve method using a gas chromatograph GC-2010 manufactured by Shimadzu Corporation. It should be noted that the diol referred to here is a diol manufactured by depolymerization of thermoplastic polyester (A), and is not added before and / or after the reaction. As a method for adjusting the concentration of the diol derived from the thermoplastic polyester (A) contained in the reaction mixture to the above preferred range, for example, the mass ratio Z of water to the thermoplastic polyester (A) is adjusted to the above preferred range and the thermoplastic polyester (A) is depolymerized according to the present invention.

[0144] When polybutylene terephthalate is used as the thermoplastic polyester (A), the depolymerization generates butanediol as a raw material and a cyclic ether (tetrahydrofuran) obtained by dehydration reaction of butanediol, and the latter has a larger amount of cyclic ether. When polybutylene terephthalate is used as the thermoplastic polyester (A), the concentration of the cyclic ether derived from the thermoplastic polyester (A) in the reaction mixture is preferably 3.0% by mass or more. More preferably, it is 5.0% by weight or more, and further preferably, it is 6.0 parts by weight or more. By being in the above preferred range, the energy consumption during the recovery and purification of the cyclic ether can be suppressed.

[0145] The formation reaction of diol and dicarboxylic acid by the reaction of thermoplastic polyester and water, the hot water solubility of dicarboxylic acid, and the conversion reaction of diol were studied. As a result, it was found that, for thermoplastic polyesters other than the above-mentioned polybutylene terephthalate, by setting X, the product of X, Y and Z, and Z to the above-mentioned range, the conversion reaction of diol can be suppressed, and the yield of dicarboxylic acid and diol, especially diol, constituting the thermoplastic polyester can be greatly improved.

[0146] By further mixing in an alkaline component, the yield of the generated monomer can be improved. As the alkaline component, hydroxides, carbonates, bicarbonates, or amines of alkali metals such as lithium, sodium, potassium, alkaline earth metals such as calcium, ammonium, etc. can be cited. Particularly preferred is at least one selected from sodium hydroxide, potassium hydroxide, and calcium hydroxide. The mixing amount of the alkaline component is preferably 0.01 parts by weight or more and 50 parts by weight or less relative to 100 parts by weight of the thermoplastic polyester (A). More preferably, it is 20 parts by weight or more, and more preferably, it is 30 parts by weight or more. On the other hand, it is more preferably 45 parts by weight or less, and more preferably, it is 42 parts by weight or less. In the case of mixing in an alkaline component, dicarboxylates are generated by hydrolysis of the thermoplastic polyester. The dicarboxylates can be converted into dicarboxylic acids as raw materials for thermoplastic polyesters by treating them with an acidic aqueous solution.

[0147] In the depolymerization of the thermoplastic polyester in the first preferred embodiment of the present invention, various known reaction modes such as intermittent and continuous methods can be adopted. For example, if it is intermittent, autoclaves, vertical / horizontal reactors, vertical / horizontal reactors with compression mechanisms such as barrels in addition to the stirrer and heating functions, etc. can be cited. If it is continuous, extruders, tubular reactors, tubular reactors with mixing mechanisms such as baffles, pipeline mixers, vertical / horizontal reactors, vertical / horizontal reactors with stirrers, towers, etc. can be cited. In addition, the atmosphere during the manufacture is expected to be a non-oxidizing atmosphere, preferably in an inactive atmosphere such as nitrogen, helium, and argon. From the perspective of economy and ease of operation, it is preferably in a nitrogen atmosphere.

[0148] There is no particular limitation on the recovery method of the diols and dicarboxylic acids generated by the depolymerization method of the thermoplastic polyester in the first preferred embodiment of the present invention, and any method can be used. For example, when the depolymerization reaction is carried out in an intermittent manner, the reaction mixture (C) can be obtained in the form of a diol aqueous solution in which solid dicarboxylic acids are dispersed and / or precipitated by distilling out together with water after the depolymerization reaction is completed. In addition, when the depolymerization reaction is carried out in a continuous manner, the reaction mixture (C) can be obtained in the form of a diol aqueous solution in which solid dicarboxylic acids are dispersed along with the progress of the reaction. The obtained reaction mixture (C) can be separated from the solid dicarboxylic acids by known methods such as solid-liquid separation, and the diols and water can be separated by distillation separation, so that diols and dicarboxylic acids with high purity can be recovered. In addition, if there are water-insoluble components in the reaction mixture, they can also be separated by known methods such as solid-liquid separation under the condition that the dicarboxylic acids are dissolved, and provided for the recovery process of diols and dicarboxylic acids.

[0149] As a method for obtaining a diol with a higher purity, the recovered diol can be combined with a purification method such as a method of rectifying the diol, a method of adding a trace amount of sodium hydroxide and performing reduced pressure distillation, a method of performing an activated carbon treatment, a method of performing an ion exchange treatment, a method of performing a recrystallization, etc. These methods can also efficiently remove impurities that are difficult to separate by distillation separation.

[0150] The depolymerization method of the thermoplastic polyester described in the first preferred embodiment of the present invention can obtain diols and dicarboxylic acids with high purity, so they can be used as polymerization raw materials for thermoplastic polyesters in the same manner as diols and carboxylic acids produced from petroleum-derived raw materials. Thermoplastic polyesters can be produced by subjecting diols and dicarboxylic acids or their ester-forming derivatives to a generally known polycondensation reaction to produce thermoplastic polyesters (recycled polymers).

[0151] In addition, the thermoplastic polyester obtained in this way can be processed into various products such as clothing fibers, industrial fibers, films, sheets, bottles, injection molded products, etc., similarly to thermoplastic polyesters produced from petroleum-derived raw materials. These products are useful as agricultural materials, gardening materials, fishery materials, civil engineering / construction materials, stationery, medical supplies, automobile parts, electrical / electronic parts, or other uses.

[0152] [2-2] Second preferred embodiment of the present invention

[0153] The second preferred embodiment of the present invention is a method for producing a recycled monomer, comprising the step of contacting a composition containing a thermoplastic polyester (A) with subcritical water, and mixing 0.01 to 4.0 parts by weight of an alkali metal salt and / or an alkaline earth metal salt with respect to 100 parts by weight of the thermoplastic polyester (A) in the composition containing the thermoplastic polyester (A). In the composition containing the thermoplastic polyester (A), other components such as additives affect the depolymerization of the thermoplastic polyester (A). In the second preferred embodiment of the present invention, by mixing an alkali metal salt and / or an alkaline earth metal salt, the yield of the recycled monomer obtained by depolymerization can be increased, and by making the mixing amount thereof a trace amount, the increase in the amount of global greenhouse gas emissions derived from the alkali metal salt and / or the alkaline earth metal salt can be suppressed.

[0154] The thermoplastic polyester (A) used in the second preferred embodiment of the present invention is a homopolymer or copolymer obtained by polycondensation using dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative as main raw materials. Here, the so-called main raw material means that the structural units of dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative in the polymer are 50 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more.

[0155] Examples of the dicarboxylic acids or ester-forming derivatives thereof include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, bis(p-carboxyphenyl)methane, 1,4-anthracene dicarboxylic acid, 1,5-anthracene dicarboxylic acid, 1,8-anthracene dicarboxylic acid, 2,6-anthracene dicarboxylic acid, 9,10-anthracene dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-tetrabutyl terephthalate, and 1,4-anthracene dicarboxylic acid. Aromatic dicarboxylic acids such as isophthalic acid and 5-sodium sulfonate isophthalic acid, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, and dimer acid, alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, and ester-forming derivatives thereof, etc.

[0156] The ester-forming derivatives referred to herein are lower alkyl esters, anhydrides, acyl halides, etc. of dicarboxylic acids described above. As lower alkyl esters of dicarboxylic acids, methyl esters, ethyl esters, hydroxyethyl esters, hydroxybutyl esters, etc. are preferably used. As anhydrides of dicarboxylic acids, anhydrides of dicarboxylic acids, anhydrides of dicarboxylic acids and acetic acid, etc. are preferably used. As halides of dicarboxylic acids, acyl chlorides, acyl bromides, acyl iodides, etc. are preferably used.

[0157] Examples of the diols or their ester-forming derivatives include aliphatic or alicyclic diols having 2 to 20 carbon atoms such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, cyclohexanedimethanol, cyclohexanediol, and dimer diol; long-chain diols having a molecular weight of 200 to 100,000 such as polyethylene glycol, poly-1,3-propylene glycol, and polytetramethylene glycol; aromatic dihydroxy compounds such as 4,4′-dihydroxybiphenyl, hydroquinone, tert-butylhydroquinone, bisphenol A, bisphenol S, and bisphenol F; and ester-forming derivatives thereof.

[0158] Examples of the homopolymer or copolymer having a dicarboxylic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof as structural units include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene isophthalate, polytrimethylene isophthalate, polybutylene isophthalate, polyethylene naphthalate, polytrimethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate / terephthalate, poly Propylene glycol isophthalate / terephthalate, polybutylene glycol isophthalate / terephthalate, polyethylene glycol terephthalate / naphthalate, polypropylene glycol terephthalate / naphthalate, polybutylene glycol terephthalate / naphthalate, polybutylene glycol terephthalate / decane dicarboxylate, polyethylene terephthalate / 5-sodium sulfonate isophthalate, polypropylene terephthalate / 5-sodium sulfonate isophthalate, polybutylene terephthalate / 5-sulfonate Sodium isophthalate, polyethylene terephthalate / polyethylene glycol, polypropylene terephthalate / polyethylene glycol, polybutylene terephthalate / polyethylene glycol, polypropylene terephthalate / polybutylene glycol, polybutylene terephthalate / polybutylene glycol, polyethylene terephthalate / isophthalate / polybutylene glycol, polypropylene terephthalate / isophthalate / polybutylene glycol, polybutylene terephthalate / isophthalate Aromatic polyester resins such as polybutylene glycol dicarboxylate / polybutylene glycol, polyethylene terephthalate / succinate, polypropylene terephthalate / / succinate, polybutylene glycol terephthalate / succinate, polyethylene terephthalate / adipate, polypropylene terephthalate / adipate, polybutylene glycol terephthalate / adipate, polyethylene terephthalate / sebacate, polypropylene terephthalate / sebacate, and polybutylene glycol terephthalate / sebacate.

[0159] Here, " / " represents a copolymer. These homopolymers and copolymers can be used alone or two or more can be mixed and used in any content. Among them, from the perspective of recycling thermoplastic polyesters and promoting the recycling of fossil resources, it is preferred to use homopolymers or copolymers with aromatic dicarboxylic acids or their ester-forming derivatives and aliphatic diols or their ester-forming derivatives with high production and consumption as the main raw materials. As examples of the above-mentioned preferred polymers, there can be cited homopolymers or copolymers obtained by polycondensing at least one selected from terephthalic acid, naphthalene dicarboxylic acid and their ester-forming derivatives with at least one selected from ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol or their ester-forming derivatives, wherein the thermoplastic polyester (A) in the composition containing the thermoplastic polyester (A) is particularly preferably selected from polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and at least one of their copolymers.

[0160] Examples of the alkali metal salt include lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, cesium hydrogen carbonate, lithium phosphate, sodium phosphate, potassium phosphate, cesium phosphate, dilithium hydrogen phosphate, dipotassium hydrogen phosphate, dicesium hydrogen phosphate, lithium monohydrogen phosphate, sodium monohydrogen phosphate, potassium monohydrogen phosphate, cesium monohydrogen phosphate, lithium borate, sodium borate, potassium borate, cesium borate, lithium citrate, sodium citrate, potassium citrate, cesium citrate, lithium formate, sodium formate, potassium formate, cesium formate, lithium acetate, sodium acetate, potassium acetate, cesium acetate, lithium oxalate, sodium oxalate, potassium oxalate, cesium oxalate, lithium maleate, potassium maleate, cesium maleate, and the like. Among them, more preferred are lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and cesium hydrogen carbonate.

[0161] Examples of the alkaline earth metal salt include magnesium hydroxide, calcium hydroxide, barium hydroxide, magnesium carbonate, calcium carbonate, barium carbonate, magnesium phosphate, calcium phosphate, barium phosphate, magnesium hydrogen phosphate, calcium hydrogen phosphate, barium hydrogen phosphate, dimagnesium hydrogen phosphate, dicalcium hydrogen phosphate, dibarium hydrogen phosphate, magnesium borate, calcium borate, barium borate, magnesium citrate, calcium citrate, barium citrate, magnesium formate, calcium formate, barium formate, magnesium acetate, calcium acetate, barium acetate, magnesium borate, calcium borate, barium borate, magnesium oxalate, calcium oxalate, barium oxalate, magnesium maleate, calcium maleate, and barium maleate. Among these, magnesium hydroxide, calcium hydroxide, barium hydroxide, magnesium carbonate, calcium carbonate, and barium carbonate are more preferred.

[0162] By mixing 0.01 to 4.0 parts by weight of an alkali metal salt and / or an alkaline earth metal salt with respect to 100 parts by weight of the thermoplastic polyester (A), it is possible to suppress the overreaction of the product caused by depolymerization and obtain the polyester monomer at a high yield. The mixing amount of the alkali metal salt and / or the alkaline earth metal salt is more preferably 0.05 parts by weight or more, and further preferably 0.25 parts by weight or more. On the other hand, it is more preferably 2.5 parts by weight or less, and further preferably 1.0 parts by weight or less.

[0163] In the second preferred embodiment of the present invention, 100 to 1000 parts by weight of water is preferably added to 100 parts by weight of the thermoplastic polyester (A) in the composition containing the thermoplastic polyester (A). By adding 100 to 1000 parts by weight of water, the consumption of energy for heating water can be suppressed, thereby suppressing the environmental load, and the polyester monomer can be obtained at a high yield. The amount of water added is more preferably 150 parts by weight or more, and more preferably 200 parts by weight or more. On the other hand, it is more preferably 800 parts by weight or less, and more preferably 600 parts by weight or less.

[0164] In the second preferred embodiment of the present invention, the temperature of the step (step 1) of depolymerizing the thermoplastic polyester (A) by blending an alkali metal salt and / or an alkaline earth metal salt is preferably 250 to 350° C. By setting the temperature in this range, depolymerization can be promoted and overreaction of the product can be suppressed, thereby obtaining the polyester monomer in high yield. It is more preferably 260° C. or higher, and even more preferably 270° C. or higher. On the other hand, it is more preferably 320° C. or lower, and even more preferably 300° C. or lower.

[0165] In the second preferred embodiment of the present invention, the pressure in the step (step 1) of depolymerizing the thermoplastic polyester (A) by mixing an alkali metal salt and / or an alkaline earth metal salt is preferably 3 to 30 MPa. By setting the pressure in this range, the water ion concentration is increased, so that the thermoplastic polyester (A) may be efficiently depolymerized. It is more preferably 4.5 MPa or more, and even more preferably 6.0 MPa or more. On the other hand, it is more preferably 25 MPa or less, and even more preferably 20 MPa or less.

[0166] In the second preferred embodiment of the present invention, a composition containing a thermoplastic polyester (A) can be used, wherein the thermoplastic polyester (A) is blended with a dye, various additives, a fibrous filler, an organic filler other than the fibrous filler, an inorganic filler, etc. Examples of the additives include antioxidants, weathering agents, release agents, crystal nucleating agents, and the like.

[0167] Examples of the antioxidant include hindered phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants.

[0168] Examples of the phenolic antioxidant include 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butyl-4-ethylphenol, 4,4'-butylenebis(6-tert-butyl-3-methylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol) , octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl) propionate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,1,3-tris(2-methyl-4-hydroxy-5-di-tert-butylphenyl)butane, tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, triethylene glycol-bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]], 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine, 2,2-thio-diethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], N,N'-hexamethylenebis(3,5-di-tert-butyl- 4-hydroxyphenylpropionamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid-diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, tris(3,5-di-tert-butyl-4-hydroxybenzyl)-isocyanurate, 2,4-bis[(octylthio)methyl]-o-cresol, or isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, etc.

[0169] Examples of the phosphorus antioxidant include triphenyl phosphite, triisodecyl phosphite, isodecyl diphenyl phosphite, 2-ethylhexyl diphenyl phosphite, 4,4′-isopropylidene diphenol alkyl (C12 to C15) phosphite, tris(nonylphenyl)phosphite (Adeks STABU 1178), tris(2,4-di-tert-butylphenyl)phosphite, 2,2′-methylenebis(4,6-di-tert-butylphenyl)2-ethylhexylphosphite, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, and 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0170] Examples of the sulfur-based antioxidant include dilauryl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, ditridecyl thiodipropionate, pentaerythritol (3-lauryl thiopropionate), and 2-mercaptobenzimidazole.

[0171] These antioxidants may be used alone, but a synergistic effect may be obtained by combining two or more of them. Therefore, a plurality of them may be used in combination.

[0172] Examples of the weathering agent include ultraviolet absorbers and light stabilizers. Specific examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers represented by 2-hydroxy-4-octyloxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, and 2,2',4,4'-tetrahydroxybenzophenone, and 4,6-bis(1-methyl-1-phenylethyl)-2-(2H-benzotriazol-2-yl)phenol, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-[2'-hydroxy-3',5'-bis(α,α'-dimethylbenzyl)phenyl]benzotriazole, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol, Benzotriazole ultraviolet absorbers represented by condensates of methyl-3-[3-tert-butyl-5-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(5-chloro-2H-benzotriazol-2-yl)-6-tert-butyl-4-methylphenol, 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol, and methyl-3-[3-tert-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]propionate-polyethylene glycol, and triazine ultraviolet absorbers represented by 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine.

[0173] Specific examples of the light stabilizer include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, poly{[6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethylpiperidyl)imino]hexamethylene[(2,2,6,6-tetramethylpiperidyl)imino]}, polymethylpropyl 3-oxy-[4-(2,2,6,6-tetramethyl)piperidyl]siloxane , a mixed ester of 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, a mixed ester of 1,2,3,4-butanetetracarboxylic acid, 2,2,6,6-tetramethyl-4-piperidinol and 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, bis(1-undecyloxy-2,2,6,6-tetramethylpiperidin-4-yl) carbonate, 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate), 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, etc.

[0174] Specific examples of the release agent include fatty acids, fatty acid metal salts, hydroxy fatty acids, fatty acid esters, aliphatic partially saponified esters, paraffin waxes, low molecular weight polyolefins, fatty acid amides, alkylenebisfatty acid amides, aliphatic ketones, and modified silicones.

[0175] Among them, the fatty acid ester-based release agent is composed of a tri- to hexavalent aliphatic alcohol and a fatty acid. Examples of the tri- to hexavalent aliphatic alcohol include glycerol, diglycerol, erythritol, pentaerythritol, sorbitol, triglycerol, dipentaerythritol, and tetraglycerol.

[0176] Examples of fatty acid-based release agents include linear or branched saturated fatty acids having 5 to 30 carbon atoms, such as valeric acid, caproic acid, caprylic acid, nonanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, arachidic acid, behenic acid, and saturated fatty acids. Acid, lignoceric acid, cerotic acid, montanic acid, melissic acid, etc.

[0177] Specific examples of the above-mentioned crystal nucleating agent include inorganic crystal nucleating agents such as synthetic mica, talc (trade name: Hitron, etc.), clay, zeolite, magnesium oxide, calcium sulfide, boron nitride, and neodymium oxide.

[0178] In addition, examples of organic crystal nucleating agents include sodium benzoate, potassium benzoate, lithium benzoate, calcium benzoate, magnesium benzoate, barium benzoate, lithium terephthalate, sodium terephthalate, potassium terephthalate, sodium methyl benzoate, sodium salicylate, potassium salicylate, zinc salicylate, aluminum dibenzoate, potassium dibenzoate, lithium dibenzoate, organic carboxylic acid metal salts such as sodium β-naphthalene dicarboxylate and sodium cyclohexanecarboxylate, organic sulfonates such as sodium p-toluenesulfonate and sodium sulfoisophthalate, sorbitol compounds, metal salts of phenylphosphonates, and metal salts of phosphorus compounds such as sodium-2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate.

[0179] The above-mentioned additive is preferably 0.01 to 3.0 parts by weight relative to 100 parts by weight of the thermoplastic polyester (A) in the composition containing the thermoplastic polyester (A). By being within this range, the effect brought by the additive can be maintained, and the thermal decomposition of the additive in the case of melt-kneading with the thermoplastic polyester (A) can be suppressed. The blending amount of the additive is more preferably 0.05 parts by weight or more, and more preferably 0.1 parts by weight or more. On the other hand, it is more preferably 2.0 parts by weight or less, and more preferably 1.0 parts by weight or less.

[0180] When the composition containing the thermoplastic polyester (A) mixed with the above-mentioned additive is depolymerized, there is a problem that the overreaction of the product is easy to proceed, and the yield of the polyester monomer is reduced. In the second preferred embodiment of the present invention, by mixing an alkali metal salt and / or an alkaline earth metal salt, the overreaction can be suppressed and the polyester monomer can be produced in a high yield.

[0181] In the depolymerization of the composition containing thermoplastic polyester (A) in the second preferred embodiment of the present invention, various known reaction modes such as intermittent and continuous methods can be adopted. For example, if it is intermittent, autoclaves, vertical / horizontal reactors, vertical / horizontal reactors with compression mechanisms such as barrels in addition to stirrers and heating functions, etc. can be cited. If it is continuous, extruders, tubular reactors, tubular reactors with mixing mechanisms such as baffles, pipeline mixers, vertical / horizontal reactors, vertical / horizontal reactors with stirrers, towers, etc. can be cited. In addition, the atmosphere during the production is expected to be a non-oxidizing atmosphere, preferably in an inactive atmosphere such as nitrogen, helium, and argon. From the perspective of economy and ease of operation, it is preferably a nitrogen atmosphere.

[0182] There is no particular restriction on the method for recovering the diols and dicarboxylic acids generated by the depolymerization method of the composition containing thermoplastic polyester (A) in the second preferred embodiment of the present invention. For example, when the depolymerization reaction is carried out in an intermittent manner, the reaction mixture can be obtained in the form of a diol aqueous solution in which solid dicarboxylic acids are dispersed and / or precipitated by distilling out together with water after the depolymerization reaction is completed. In addition, when the depolymerization reaction is carried out in a continuous manner, the reaction mixture can be obtained in the form of a diol aqueous solution in which solid dicarboxylic acids are dispersed along with the progress of the reaction. The obtained reaction mixture can separate the solid dicarboxylic acids by known methods such as solid-liquid separation, and separate the diols from water by distillation separation, so that diols and dicarboxylic acids with high purity can be recovered. In addition, if there are water-insoluble components in the reaction mixture, they can also be separated by known methods such as solid-liquid separation under the condition that the dicarboxylic acids are dissolved, and provided for the recovery process of diols and dicarboxylic acids.

[0183] As a method for obtaining a diol with a higher purity, the recovered diol can be combined with a purification method such as a method of rectifying the diol, a method of adding a trace amount of sodium hydroxide and performing reduced pressure distillation, a method of performing an activated carbon treatment, a method of performing an ion exchange treatment, a method of performing a recrystallization, etc. These methods can also efficiently remove impurities that are difficult to separate by distillation separation.

[0184] Examples of methods for obtaining a dicarboxylic acid with a higher purity include a method of dissolving in a solvent in which the dicarboxylic acid is dissolved and then recrystallizing, and a method of esterifying a dicarboxylic acid to convert it into a dialkyl dicarboxylate, purifying it by distillation, and then converting it into a dicarboxylic acid again.

[0185] In the depolymerization method of the composition containing thermoplastic polyester (A) in the second preferred embodiment of the present invention, diols and carboxylic acids produced from petroleum-derived raw materials can be used as polymerization raw materials for thermoplastic polyester (A). Thermoplastic polyester (A) can be produced by polycondensing diols and / or dicarboxylic acids directly or by polycondensing their ester-forming derivatives through a generally known esterification reaction or transesterification reaction. According to the second preferred embodiment of the present invention, the composition containing thermoplastic polyester (A) that is discarded after use can be chemically recycled.

[0186] In addition, the polyester obtained in this way can be processed into various products such as fibers, films, bottles, injection molded products, etc., similarly to the thermoplastic polyester (A) produced from petroleum-derived raw materials, and used. These products are useful as agricultural materials, gardening materials, fishery materials, civil engineering / construction materials, stationery, medical supplies, automobile parts, electrical / electronic parts or other uses.

[0187] [2-3] The third preferred embodiment of the present invention

[0188] The third preferred embodiment of the present invention is a method for producing a recycled monomer, which comprises a step of simultaneously hydrolyzing polymers I and II in a composition comprising polymers I and II by contacting them with subcritical water at 250 to 350° C., wherein polymer I is a thermoplastic polyester (A), polymer II is a polymer selected from a group consisting of a thermoplastic polyester (B) having a melting point different from that of the thermoplastic polyester (A), polycarbonate and polyurethane, or a combination of these polymers, and the content of polymer II in the composition (the total content of the thermoplastic polyester (B), polycarbonate and polyurethane) is 1 to 100 parts by weight relative to 100 parts by weight of polymer I.

[0189] In the method for producing a recycled monomer in the third preferred embodiment of the present invention, the recycled monomer is preferably terephthalic acid and / or diol. When the recycled monomer is terephthalic acid and / or diol, polyester produced in large quantities as a plastic can be recycled, thus making a great contribution to resource circulation.

[0190] The thermoplastic polyester (A) and the thermoplastic polyester (B) used in the third preferred embodiment of the present invention are obtained by polycondensation of dicarboxylic acid or its ester-forming derivative and diol as main raw materials. Here, the so-called main raw material means that the total structural units of dicarboxylic acid, its ester-forming derivative and diol in the polymer are 80 mol% or more. The total of the structural units is more preferably 90 mol% or more, further preferably 95 mol% or more, and most preferably 100 mol%.

[0191] The dicarboxylic acid or its ester-forming derivative is not particularly limited, and examples thereof include terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, diphenyl sulfide-4,4'-dicarboxylic acid, 5-tetrabutyl Aromatic dicarboxylic acids such as isophthalic acid and 5-sodium sulfonate isophthalic acid, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, azelaic acid, undecanedioic acid, and dodecanedioic acid, or ester-forming derivatives thereof.

[0192] The ester-forming derivatives referred to herein are lower alkyl esters, anhydrides, acyl halides, etc. of dicarboxylic acids described above. As lower alkyl esters of dicarboxylic acids, methyl esters, ethyl esters, hydroxyethyl esters, hydroxybutyl esters, etc. are preferably used. As anhydrides of dicarboxylic acids, anhydrides of dicarboxylic acids, anhydrides of dicarboxylic acids and acetic acid, etc. are preferably used. As halides of dicarboxylic acids, acyl chlorides, acyl bromides, acyl iodides, etc. are preferably used.

[0193] As dicarboxylic acids or their ester-forming derivatives, aromatic dicarboxylic acids or their ester-forming derivatives, which are used in large amounts as raw materials for thermoplastic polyesters used for fibers, resins, and films, are preferred. As aromatic dicarboxylic acids or their ester-forming derivatives, terephthalic acid, 2,6-naphthalenedicarboxylic acid, or their dimethyl esters are more preferred.

[0194] Examples of the diol include ethylene glycol, 1,3-propylene glycol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, cyclohexanedimethanol, benzyl alcohol, polyethylene glycol, polypropylene glycol, polybutylene glycol, and bisphenol A-ethylene oxide adduct. Among these, ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol are more preferred because the resulting thermoplastic polyester has high versatility.

[0195] Furthermore, dicarboxylic acids, ester-forming derivatives of dicarboxylic acids, and diols may be used alone or in combination of two or more.

[0196] Examples of the thermoplastic polyester used in the third preferred embodiment of the present invention include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polycyclohexanedimethylene terephthalate, polyethylene isophthalate, polytrimethylene isophthalate, polybutylene isophthalate, polycyclohexanedimethylene isophthalate, polyethylene naphthalate, polytrimethylene naphthalate, polybutylene naphthalate, polycyclohexanedimethylene terephthalate / polyethylene terephthalate. Polyethylene terephthalate / naphthalate, polypropylene terephthalate / naphthalate, polybutylene terephthalate / naphthalate, polyethylene terephthalate / naphthalate, polypropylene terephthalate / naphthalate, polybutylene terephthalate / naphthalate, polyethylene terephthalate / 5-sodium sulfonate isophthalate, polypropylene terephthalate / 5-sodium sulfonate isophthalate, polybutylene terephthalate / 5-sodium sulfonate isophthalate, etc. Here, " / " means a copolymer. Among them, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are preferred. Polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate are more preferred because they are excellent in versatility and can be recovered in large amounts as recycled raw resources.

[0197] In the method for producing recycled monomers in the third preferred embodiment of the present invention, the thermoplastic polyester (A) is preferably selected from polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate and copolymers thereof. These thermoplastic polyesters are produced in large quantities and have a high demand for recycling.

[0198] In the method for producing a recycled monomer in the third preferred embodiment of the present invention, the thermoplastic polyester (B) is preferably at least one selected from polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate and copolymers thereof, and has a melting point different from that of the thermoplastic polyester (A). These thermoplastic polyesters are produced in large quantities and have a high demand for recycling.

[0199] In the method for producing a recycled monomer in the third preferred embodiment of the present invention, it is more preferred that both the thermoplastic polyester (A) and the thermoplastic polyester (B) are at least one selected from polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and copolymers thereof. When both the thermoplastic polyester (A) and the thermoplastic polyester (B) are the above-mentioned thermoplastic polyesters, separation and purification of the recycled monomer after simultaneous depolymerization is facilitated.

[0200] The intrinsic viscosity of the thermoplastic polyester (A) and the thermoplastic polyester (B) used in the third preferred embodiment of the present invention is preferably 0.4 to 2.0 dl / g. Here, the intrinsic viscosity of the thermoplastic polyester (A) and the thermoplastic polyester (B) is a value measured at 25°C using o-chlorophenol as a solvent. When the thermoplastic polyester used in the third preferred embodiment of the present invention is polyethylene terephthalate, the intrinsic viscosity IV is preferably 0.4 to 1.5 dl / g, and more preferably 0.6 to 1.3 dl / g. When the thermoplastic polyester used in the third preferred embodiment of the present invention is polypropylene terephthalate, the intrinsic viscosity is more preferably 0.6 to 2.0 dl / g, and more preferably 0.7 to 1.6 dl / g. When the thermoplastic polyester used in the third preferred embodiment of the present invention is polybutylene terephthalate, the intrinsic viscosity is more preferably 0.6 to 2.0 dl / g, and more preferably 0.8 to 1.8 dl / g.

[0201] In the third preferred embodiment of the present invention, when the composition comprises a thermoplastic polyester (A) and a thermoplastic polyester (B), the thermoplastic polyester with a larger blending amount is defined as the thermoplastic polyester (A). When the blending amounts of the thermoplastic polyester (A) and the thermoplastic polyester (B) are the same, the thermoplastic polyester with a higher melting point is defined as the thermoplastic polyester (A).

[0202] As the polycarbonate used in the third preferred embodiment of the present invention, there can be mentioned a substance obtained by interfacial polymerization of a dihydroxy compound and phosgene, a substance obtained by polymerizing a dihydroxy compound and diphenyl carbonate by a melt transesterification reaction, a substance obtained by polymerizing a carbonate prepolymer by a solid phase transesterification reaction, or a substance obtained by ring-opening polymerization of a cyclic carbonate compound. As the dihydroxy compound used here, there can be mentioned one or more selected from 2,2'-bis(4-hydroxyphenyl)propane (bisphenol A), 4,4'-dihydroxydiphenylalkane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ether, 2,2'-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1'-bis(4-hydroxyphenyl)cyclohexane, and isosorbide (1,4:3,6-dianhydro-D-sorbitol). Among them, 2,2'-bis(4-hydroxyphenyl)propane (bisphenol A) is preferred.

[0203] Furthermore, other dihydroxy compounds other than bisphenol A, such as 4,4'-dihydroxydiphenylalkane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ether, or isosorbide (1,4:3,6-dianhydro-D-sorbitol), may be used together with bisphenol A. The amount of the other dihydroxy compound used is preferably 10 mol% or less relative to the total amount of the dihydroxy compounds.

[0204] The polymerization degree of these polycarbonates is not particularly limited, but from the viewpoint of excellent practical strength and easy hydrolysis, the viscosity average molecular weight (Mv) of the polycarbonate resin is preferably 10,000 to 50,000. It is more preferably 15,000 or more, and further preferably 18,000 or more. On the other hand, it is more preferably 40,000 or less, and further preferably 35,000 or less.

[0205] Here, the viscosity average molecular weight (Mv) refers to the value calculated by using the intrinsic viscosity [η] (unit: dl / g) at a temperature of 20°C using an Ubbelohde viscometer using dichloromethane as a solvent, and further using Schnell's viscosity formula, that is, [η] = 1.23×10-4×(Mv)0.83. Here, the intrinsic viscosity [η] is the value calculated by measuring the specific viscosity [ηsp] at each solution concentration [c] (g / dl) using the following formula.

[0206] [η] = limηsp / c(c→0)

[0207] As the polyurethane used in the 3rd preferred scheme of the present invention, any material can be used as the starting material with polymer diol and diisocyanate, without particular limitation. In addition, it can be a polyurethane urea formed by polymer diol, diisocyanate, and a low molecular weight diamine as a chain extender, a polyurethane amine formed by polymer diol, diisocyanate, and a low molecular weight diol as a chain extender, or a polyurethane urea using a compound having a hydroxyl group and an amino group in the molecule as a chain extender.

[0208] The polymer diol used in the third preferred embodiment of the present invention is preferably at least one selected from polyether diols, polyester diols, and polycarbonate diols. In particular, polyether diols are preferably used from the viewpoint of facilitating separation after hydrolysis.

[0209] As the polyether diol, preferably used are, for example, polyethylene oxide, polyethylene glycol, polyethylene glycol derivatives, polypropylene glycol, polytetramethylene ether glycol (hereinafter, abbreviated as PTMG), modified PTMG which is a copolymer of tetrahydrofuran (hereinafter, abbreviated as THF) and 3-methyltetrahydrofuran, modified PTMG which is a copolymer of THF and 2,3-dimethylTHF, polyols having side chains on both sides disclosed in Japanese Patent No. 2615131, etc., random copolymers in which THF and ethylene oxide and / or propylene oxide are irregularly arranged, etc. These polyether diols may be used alone or in combination of two or more thereof.

[0210] In addition, polyester diols such as butylene adipate, polycaprolactone diol, polyester polyols having side chains disclosed in JP-A-61-26612 and the like, and polycarbonate diols disclosed in JP-B-2-289516 and the like can also be used.

[0211] The above-mentioned polymer diols may be used alone or in combination of two or more thereof.

[0212] The molecular weight of the polymer diol used in the third preferred embodiment of the present invention is preferably 1000 to 8000, and more preferably 1800 to 6000, in terms of maintaining practical strength.

[0213] As the diisocyanate used in the third preferred embodiment of the present invention, there can be mentioned aromatic diisocyanates such as diphenylmethane diisocyanate, toluene diisocyanate, 1,4-diisocyanate benzene, xylylene diisocyanate, 2,6-naphthalene diisocyanate, methylenebis (cyclohexyl isocyanate), isophorone diisocyanate, methylcyclohexane 2,4-diisocyanate, methylcyclohexane 2,6-diisocyanate, cyclohexane 1,4-diisocyanate, hexahydroxylene diisocyanate, hexahydrotoluene diisocyanate, octahydro 1,5-naphthalene diisocyanate and the like. Alicyclic diisocyanates can be effectively used in particular to suppress yellowing of polyurethane yarns. These diisocyanates can be used alone or in combination of two or more.

[0214] In the third preferred embodiment of the present invention, the molecular weight of the polyurethane is preferably in the range of 30000 to 150000 as a number average molecular weight from the viewpoint of maintaining practical strength and facilitating depolymerization. It should be noted that the molecular weight is measured by GPC (gel permeation chromatography) and converted by polystyrene.

[0215] In the third preferred embodiment of the present invention, by simultaneously depolymerizing a polymer I composed of a thermoplastic polyester (A) and a polymer II composed of at least one selected from a thermoplastic polyester (B) having a melting point different from that of the thermoplastic polyester (A), a polycarbonate, and a polyurethane, there is an effect of increasing the yield of the generated dicarboxylic acid compared with depolymerizing only the thermoplastic polyester (A). In order to achieve this effect, it is necessary to contain at least one polymer selected from the thermoplastic polyester (B), a polycarbonate, and a polyurethane in an amount of 1 part by weight or more relative to 100 parts by weight of the thermoplastic polyester (A). It is more preferably 5 parts by weight or more, further preferably 10 parts by weight or more, and most preferably 20 parts by weight or more.

[0216] It is presumed that in the hydrolysis of the polymer, the hydrolysis is promoted by the melting of the polymer or the dissolution of the polymer in water. By heating at least one selected from the group consisting of a thermoplastic polyester (B) having a melting point different from that of the thermoplastic polyester (A), a polycarbonate, and a polyurethane in the presence of water, the polymer with a high melting point is dissolved in the melt or solution of the polymer with a low melting point (the glass transition temperature is defined as the melting point for a polymer that does not show a melting point), the hydrolysis of the polymer with a high melting point is also promoted, and / or the depolymerization of one polymer promotes the depolymerization of another polymer, so it is considered that the yield of the generated monomers is increased by the simultaneous hydrolysis.

[0217] Here, the melting point is the temperature of the endothermic peak that appears when the polymer is cooled from a molten state to 0°C at a cooling rate of 20°C / min in a nitrogen atmosphere and then heated to the melting point + 40°C at a heating rate of 20°C / min using a differential scanning calorimeter (DSC). However, when two or more endothermic peaks are detected, the temperature of the endothermic peak with the largest peak intensity is set as the melting point. In addition, for polymers that do not show a melting point, the temperature of the midpoint of the step-shaped endothermic peak that appears when the polymer is cooled from a molten state to 0°C at a cooling rate of 20°C / min in a nitrogen atmosphere and then heated at a heating rate of 20°C / min is set as the glass transition temperature (melting point in the third preferred embodiment of the present invention). Furthermore, in polyurethane urea, since its melting point is higher than the thermal decomposition temperature of the polymer, it is difficult to accurately measure the melting point by DSC. In this case, a thermogravimetric analyzer (TGA) is used, and the temperature is increased at a heating rate of 20°C / min in a nitrogen atmosphere. In the obtained TGA curve, the intersection of the baseline of the starting weight and the tangent of the maximum slope point of the TGA curve after the weight is reduced by thermal decomposition is defined as the decomposition starting temperature (melting point in the third preferred embodiment of the present invention).

[0218] In the third preferred embodiment of the present invention, the difference between the melting point of the thermoplastic polyester (A) and the melting point of the thermoplastic polyester (B), polycarbonate or polyurethane is preferably 10°C or more, and the difference between the melting points of the thermoplastic polyester (A) and the thermoplastic polyester (B) is more preferably 10°C or more. By combining polymers with a large difference in melting points, the polymer with a high melting point is easily dissolved, and hydrolysis can be promoted. The difference in melting points is more preferably 20°C or more, and more preferably 30°C or more.

[0219] As the polymer used in the third preferred embodiment of the present invention, polymers other than thermoplastic polyester, polycarbonate, and polyurethane may also be included. For example, polyamide, polyolefin, modified polyphenylene ether, polysulfone, polyketone, polyetherimide, polyarylate, polyethersulfone, polyetherketone, polythioetherketone, polyetheretherketone, polyimide, polyamideimide, tetrafluoroethylene, polyphenylene sulfide, etc. may be mentioned. Two or more of them may be included. The polymer other than thermoplastic polyester, polycarbonate and polyurethane is preferably less than 50 parts by weight relative to 100 parts by weight of the polymer component in the composition in the third preferred embodiment of the present invention. More preferably, it is less than 40 parts by weight, and further preferably, it is less than 30 parts by weight.

[0220] In addition, the composition used in the third preferred embodiment of the present invention may contain fillers, nucleating agents, plasticizers, UV resistance agents, release agents, flame retardants, colorants (for example, pigments or dyes), lubricants, antistatic agents, antioxidants and other additives in addition to polymers.

[0221] Examples of the filler include glass fiber, carbon fiber, potassium titanate whisker, zinc oxide whisker, aluminum borate whisker, aramid fiber, aluminum oxide fiber, silicon carbide fiber, ceramic fiber, asbestos fiber, gypsum fiber, metal fiber, glass flake, wollastonite, zeolite, sericite, kaolin, mica, talc, clay, pyrophyllite, bentonite, montmorillonite, hectorite, synthetic mica, asbestos, graphite, aluminosilicate, aluminum oxide, silicon dioxide, magnesium oxide, zirconium oxide, titanium oxide, iron oxide, calcium carbonate, magnesium carbonate, dolomite, calcium sulfate, barium sulfate, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, glass beads, hollow glass beads, ceramic beads, boron nitride, silicon carbide, and wollastonite.

[0222] From the viewpoint of the separability after the hydrolysis carried out by contacting with subcritical water, as fibrous filling material, preferably glass fiber or carbon fiber.The cross-sectional shape of fibrous filling material is not particularly limited, and can be any one of circular or flat fiber.In the 3rd preferred scheme of the present invention, the content of the fibrous filling material in the polymer composition is preferably below 50 % by weight in the composition, more preferably below 40 % by weight, further preferably below 30 % by weight.

[0223] In the third preferred embodiment of the present invention, polymer I and polymer II in the composition are contacted with subcritical water at 250 to 350° C. and hydrolyzed simultaneously. If water is raised to a pressure of 22.1 MPa and a temperature of 374.2° C., it is neither a liquid nor a gas. Water in this state is called supercritical water. In addition, hot water in the vicinity of the critical point of a temperature and pressure slightly lower than the critical point of water is called subcritical water. Although subcritical water is water, it has the characteristics of (i) a low dielectric constant and (ii) a high ion product. The dielectric constant and ion product of subcritical water can be controlled depending on the temperature and the partial pressure of water. By lowering the dielectric constant, it becomes an excellent solvent for organic compounds although it is water. In addition, by increasing the ion product, the concentrations of hydrogen ions and hydroxide ions increase. Therefore, subcritical water has an excellent hydrolysis effect.

[0224] The water used as the raw material of subcritical water is not particularly limited, and any water can be used, such as tap water, deionized water, distilled water, well water, etc. Deionized water and distilled water are preferably used from the viewpoint of suppressing side reactions caused by the influence of coexisting salts.

[0225] The hydrolysis in the third preferred embodiment of the present invention needs to include a step of being performed at 250°C or higher and 350°C or lower. By using this temperature range, the hydrolysis can be promoted, and the overreaction of the product can be suppressed, thereby improving the polyester monomer yield. In the third preferred embodiment of the present invention, the step of hydrolysis at a temperature higher than 350°C is not included. It is preferably 260°C or higher, more preferably 270°C or higher, and further preferably 280°C or higher. On the other hand, it is preferably 320°C or lower, more preferably 310°C or lower, and further preferably 300°C or lower.

[0226] Another embodiment of the method for producing a recycled monomer in the third preferred embodiment of the present invention comprises a step of simultaneously hydrolyzing polymers I and II in a composition containing polymers including polymers I and II by contacting them with subcritical water at 200 to 350° C. under a condition in which an alkaline component is mixed, wherein polymer I is a thermoplastic polyester (A), polymer II is a polymer selected from a thermoplastic polyester (B) having a melting point different from that of the thermoplastic polyester (A), a polycarbonate, and a polyurethane, or a combination of these polymers, and the content of polymer II in the composition (the total content of the thermoplastic polyester (B), the polycarbonate, and the polyurethane) is 1 to 100 parts by weight relative to 100 parts by weight of polymer I. In another embodiment of the method for producing a recycled monomer in the third preferred embodiment of the present invention, the temperature of the hydrolysis reaction can be increased to 200 to 350° C. by further mixing an alkaline component. That is, by mixing an alkaline component, hydrolysis can be promoted even at a lower temperature. The temperature of the hydrolysis reaction when mixing an alkaline component is preferably 210° C. or higher, and more preferably 220° C. or higher. On the other hand, the temperature of the hydrolysis reaction when a basic component is added is preferably 300° C. or lower, more preferably 290° C. or lower.

[0227] In the method for producing a recycled monomer in the third preferred embodiment of the present invention, the composition may include a composition containing polymer I and polymer II, and / or a mixture of a composition containing polymer I and a composition containing polymer II. That is, in the third preferred embodiment of the present invention, the composition to be hydrolyzed may be a composition containing a composition containing polymer I and polymer II, a mixture of a composition containing polymer I and a composition containing polymer II, or a composition containing both of them. Here, the so-called "composition containing polymer I and polymer II" refers to, for example, a substance obtained by kneading polymer I and polymer II (including the case where these polymers I and / or polymer II contain any other components) at a temperature above the melting point of any polymer (above the glass transition temperature for a polymer without a melting point). In addition, the so-called "mixture of a composition containing polymer I and a composition containing polymer II" refers to, for example, a substance obtained by mixing a composition (for example, particles) containing polymer I (including the case where it contains any other components) and a composition (for example, particles) containing polymer II (including the case where it contains any other components) in a solid state below the melting points of both polymers (for polymers without a melting point, below the glass transition temperature).

[0228] In addition, in the hydrolysis in the third preferred embodiment of the present invention, it is preferred that 100 parts by weight or more and 900 parts by weight or less of water are mixed relative to 100 parts by weight of the polymer component in the composition. By being in this range, hydrolysis can be promoted and the energy consumption for heating water can be suppressed. The mixing amount of water is more preferably more than 150 parts by weight, and more preferably more than 200 parts by weight. On the other hand, the mixing amount of water is more preferably less than 500 parts by weight, and more preferably less than 350 parts by weight.

[0229] Furthermore, in the third preferred embodiment of the present invention, the pressure in the process of contacting with subcritical water at 250 to 350°C and hydrolyzing simultaneously is preferably above the saturated vapor pressure of water, specifically, preferably 4.0 MPa to 30 MPa. By being in this range, the ion concentration of water can be increased, and hydrolysis can be promoted. It is more preferably 5.0 MPa or more, and more preferably 6.0 MPa or more. On the other hand, it is more preferably 25 MPa or less, and more preferably 22 MPa or less. In order to be in the above pressure range, a method of pressurizing the inside of the pressure vessel can be cited. In order to pressurize the inside of the pressure vessel, a method of sealing a gas in addition to water and a method of introducing high-pressure water can be cited. As such a gas, air, argon, nitrogen, etc. can be cited, but from the viewpoint of suppressing side reactions such as oxidation reactions, inert gases such as nitrogen and argon are preferably used. As the degree of pressurization using gas or high-pressure water, it is not particularly limited because it is set in a manner to become the target pressure, but it is preferably 0.3 MPa or more. In the case of pressurizing with high-pressure water, it is also possible to be in a state where there is no gas inside the pressure vessel.

[0230] In the third preferred embodiment of the present invention, it is preferred that an alkaline component is further mixed in the above-mentioned process. By mixing the alkaline component, the overreaction of the product caused by hydrolysis can be suppressed, and the monomer yield can be improved. As the alkaline component, hydroxides, carbonates, bicarbonates, or amines of alkali metals such as lithium, sodium, potassium, alkaline earth metals such as calcium, ammonium, etc. can be cited. Particularly preferred is at least one selected from sodium hydroxide, potassium hydroxide, and calcium hydroxide. The mixing amount of the alkaline component is preferably 0.01 parts by weight or more and 50 parts by weight or less relative to 100 parts by weight of the polymer component in the composition. More preferably, it is 20 parts by weight or more, and further preferably 30 parts by weight or more. On the other hand, it is more preferably 45 parts by weight or less, and further preferably 40 parts by weight or less. In the case of mixing the alkaline component, dicarboxylates are generated by hydrolysis of the thermoplastic polyester. The dicarboxylates can be converted into dicarboxylic acids as raw materials for thermoplastic polyesters by treating them with an acidic aqueous solution.

[0231] In the hydrolysis of the composition containing polymer in the 3rd preferred scheme of the present invention, various known reaction modes such as intermittent and continuous methods can be adopted. For example, if it is intermittent, autoclaves, vertical / horizontal reactors, vertical / horizontal reactors with compression mechanisms such as barrels, etc., which all have stirrers and heating functions, can be cited. If it is continuous, extruders, tubular reactors, tubular reactors with mixing mechanisms such as baffles, pipeline mixers, vertical / horizontal reactors, vertical / horizontal reactors with stirrers, towers, etc., which all have heating functions can be cited. In addition, the atmosphere in the manufacture is expected to be under a non-oxidizing atmosphere, preferably carried out under an inactive atmosphere such as nitrogen, helium, and argon, and is preferably under a nitrogen atmosphere from the perspective of economy and ease of operation.

[0232] There is no particular limitation on the method for recovering the diol and dicarboxylic acid generated by the hydrolysis of the composition in the third preferred embodiment of the present invention. For example, when terephthalic acid is used as the raw material of the thermoplastic polyester, it can be obtained in the form of a reaction mixture in which solid terephthalic acid is dispersed and / or precipitated in water after the hydrolysis reaction. The solid terephthalic acid can be separated by solid-liquid separation of the obtained reaction mixture. As methods for obtaining terephthalic acid with a higher purity, there can be cited a method of dissolving in a solvent in which terephthalic acid is dissolved and recrystallizing, a method of esterifying terephthalic acid and converting it into a dialkyl terephthalate, distilling and refining it, and then converting it into terephthalic acid again, etc. In addition, when a water-soluble diol is used as the raw material of the thermoplastic polyester, the diol and water can be separated by distilling and separating the aqueous solution after the hydrolysis reaction. As a method for obtaining a diol with a higher purity, the recovered diol can be combined with a purification method such as a method of rectifying the diol, a method of performing reduced pressure distillation by adding a trace amount of sodium hydroxide, a method of performing an activated carbon treatment, a method of performing an ion exchange treatment, a method of performing a recrystallization, etc. These methods can also efficiently remove impurities that are difficult to separate by distillation separation.

[0233] In the third preferred embodiment of the present invention, in addition to the hydrolyzate of thermoplastic polyester, the hydrolyzate of polycarbonate and polyurethane can also be generated. Specifically, by hydrolysis of thermoplastic polyester and polycarbonate, diols, dicarboxylic acids and dihydroxy compounds are generated respectively, and thus can be reused as polymer raw materials. On the other hand, in the hydrolysis of polyurethane, diamines, polymer diols and the like are generated. Regarding diamines, they can be reused as raw materials for polyurethane by converting them into isocyanates. In addition, polymer diols can be reused as raw materials for polyurethane.

[0234] In the method for producing thermoplastic polyester in the third preferred embodiment of the present invention, dicarboxylic acid and / or diol obtained by the method for producing recycled monomers in the third preferred embodiment of the present invention are used as a polymerization raw material to produce thermoplastic polyester. The dicarboxylic acid and / or diol obtained by the method for producing recycled monomers in the third preferred embodiment of the present invention are preferably dicarboxylic acid and / or diol obtained by hydrolysis of thermoplastic polyester (A) and / or thermoplastic polyester (B). For example, thermoplastic polyester can be produced by a first step consisting of an esterification reaction of a dicarboxylic acid and a diol, and a second step of a subsequent polycondensation reaction. In addition, thermoplastic polyester can also be produced by a first step consisting of an ester exchange reaction of a dicarboxylic acid dialkyl ester obtained by chemically converting a dicarboxylic acid and a diol, and a second step of a subsequent polycondensation reaction.

[0235] In the method for producing a recycled monomer in the third preferred embodiment of the present invention, the composition is preferably waste. The used waste is hydrolyzed under specific conditions to regenerate the monomer, and then repolymerized to be reused as a thermoplastic polyester.

[0236] Furthermore, a composition containing thermoplastic polyester can be produced by mixing recycled thermoplastic polyester with dyes, various additives, fibrous fillers, non-fibrous fillers, other polymers, etc. Examples of additives include antioxidants, weathering agents, mold release agents, and crystal nucleating agents.

[0237] The thermoplastic polyester obtained by the method for producing a thermoplastic polyester in the third preferred embodiment of the present invention and the composition containing the thermoplastic polyester can be used to produce various thermoplastic polyester products such as fibers, films, bottles obtained by melt spinning, melt film forming, melt extrusion molding, etc., and molded products obtained by injection molding, blow molding, extrusion molding, etc., and products containing various thermoplastic polyester compositions. These products are useful as agricultural materials, gardening materials, fishery materials, civil engineering / construction materials, industrial films, sheets, stationery, medical supplies, clothing products, automobile parts, electric / electronic parts, or other uses.

[0238] In the method for producing a thermoplastic polyester product in the third preferred embodiment of the present invention, a thermoplastic polyester product of a fiber, a film or a molded article is produced using the thermoplastic polyester obtained by the method for producing a thermoplastic polyester in the third preferred embodiment of the present invention as a raw material. In addition, in the method for producing a product of a composition containing a thermoplastic polyester in the third preferred embodiment of the present invention, a product of a composition containing a thermoplastic polyester obtained by the method for producing a thermoplastic polyester in the third preferred embodiment of the present invention is produced. Examples of the thermoplastic polyester product, the product containing a thermoplastic polyester, and the method for producing the thermoplastic polyester product and the product containing a thermoplastic polyester are as described above.

[0239] [3] Recycled monomer production equipment

[0240] The manufacturing device of the recycling monomer of the present invention comprises a unit (L) for heating and pressurizing a composition containing a thermoplastic polymer and supplying it, a unit (M) for generating and supplying subcritical water, a unit (N) for mixing the composition containing a thermoplastic polymer supplied from the above-mentioned unit (L) and the above-mentioned subcritical water supplied from the above-mentioned unit (M), and a continuous reactor (O) for hydrolyzing the thermoplastic polymer. Hereinafter, each component will be described.

[0241] (1) Compositions containing thermoplastic polymers

[0242] The composition containing thermoplastic polymers in the recycling monomer production device of the present invention is of any type as long as it contains a polymer that can be hydrolyzed. As polymers that can be hydrolyzed, for example, thermoplastic polyamides, thermoplastic polyesters, etc. can be cited. As examples of thermoplastic polyamides, polyamide 6, polyamide 66, etc. can be cited. As examples of thermoplastic polyesters, polyethylene terephthalate, polybutylene terephthalate, etc. can be cited. Thermoplastic polyamides are made into engineering plastics and fiber products and are widely used. In addition, thermoplastic polyesters are made into general-purpose plastics, bottles, and fiber products and are widely used. Therefore, these hydrolyzable polymers are preferred in terms of ease of original resource recovery and ease of hydrolysis.

[0243] In the recycling monomer production apparatus of the present invention, the composition containing the thermoplastic polymer may be waste of resin molded products.

[0244] When the thermoplastic polymer is a thermoplastic polyamide, the waste of resin molded bodies containing thermoplastic polyamide includes polyamide products, industrial waste generated in the process of manufacturing polyamide products, or waste after the use of polyamide products. As polyamide products, for example, fiber structures for clothing such as old clothes, uniforms, sportswear and underwear, curtains, carpets, ropes, nets, belts, sheets, industrial fiber structures such as airbags, automobile parts, molded parts for residential building materials, electrical and electronic molded parts, aircraft parts, industrial machinery parts, film products, extrusion molded products, in-situ polymerization molded products, RIM molded products, etc. Furthermore, product scraps, granular scraps, block scraps, and cuttings during cutting processing generated in these production processes are also waste objects.

[0245] When the thermoplastic polymer is a thermoplastic polyester, wastes of resin molded bodies containing thermoplastic polyesters include thermoplastic polyester products, industrial wastes generated in the process of manufacturing thermoplastic polyester products, or wastes after the use of thermoplastic polyester products. Examples of thermoplastic polyester products include, for example, containers such as beverage bottles and seasoning bottles, sheet products such as food trays, blister packages, food partitions, and industrial trays, packaging films, optical functional films, film products such as magnetic tapes and insulating materials, fiber structures for clothing such as used clothes, uniforms, sportswear, and underwear, industrial fiber structures such as curtains, carpets, nets, belts, and sheets, and molded products such as automobile parts, electrical / electronic parts, building components, daily necessities, daily necessities, and sanitary products. Furthermore, product scraps, granular scraps, block scraps, etc. generated in their production processes also become objects of waste.

[0246] The composition containing the thermoplastic polymer in the recycling monomer production device of the present invention may contain a fibrous filler. The fibrous filler here can be any filler having a fibrous shape. Specifically, glass fiber, polyacrylonitrile (PAN)-based, asphalt-based carbon fiber, stainless steel fiber, aluminum fiber, brass fiber and other metal fibers, polyester fiber, aromatic polyamide fiber and other organic fibers, gypsum fiber, ceramic fiber, asbestos fiber, zirconium oxide fiber, aluminum oxide fiber, silica fiber, titanium oxide fiber, silicon carbide fiber, rock wool, potassium titanate whisker, silicon nitride whisker, wollastonite, aluminum silicate and other fibrous, whisker-like fillers, glass fiber, carbon fiber, aromatic polyamide fiber, polyester fiber and the like coated with one or more metals selected from nickel, copper, cobalt, silver, aluminum, iron and their alloys. It can contain two or more of them. The content of the fibrous filler is preferably 1 to 200 parts by mass relative to 100 parts by mass of the thermoplastic polymer considered to be the main component.

[0247] In the composition containing the thermoplastic polymer in the recycling monomer production device of the present invention, fillers other than fibrous fillers, various additives, etc. may be further contained within the scope that does not impair the purpose of the invention of the recycling monomer production device of the present invention. As fillers other than fibrous fillers, that is, non-fibrous fillers, any of organic fillers and inorganic fillers may be used, and two or more of them may be contained. As non-fibrous fillers, for example, non-swelling silicates such as talc, wollastonite, zeolite, sericite, mica, kaolin, clay, pyrophyllite, bentonite, asbestos, aluminum silicate, calcium silicate, swelling mica such as Li-type fluorinated mica, Na-type fluorinated mica, Na-type tetrasilicon fluorinated mica, Li-type tetrasilicon fluorinated mica, silicon oxide, magnesium oxide, aluminum oxide, silicon dioxide, diatomaceous earth, zirconium oxide, titanium oxide, iron oxide, zinc oxide, calcium oxide, tin oxide, antimony oxide, etc., metal oxides, carbon Metal carbonates such as calcium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, dolomite, and hydrotalcite, metal sulfates such as calcium sulfate and barium sulfate, metal hydroxides such as magnesium hydroxide, calcium hydroxide, aluminum hydroxide, and basic magnesium carbonate, montmorillonite, beidellite, nontronite, saponite, hectorite, and sauconite, montmorillonite-based clay minerals such as vermiculite, halloysite, hydrosellarite, hydrosellarite, zirconium phosphate, and titanium phosphate, various clay minerals such as glass beads, glass flakes, ceramic beads, boron nitride, aluminum nitride, silicon carbide, calcium phosphate, carbon black, and graphite. The exchangeable cations present between the layers of the above-mentioned swellable layered silicate can be replaced by organic Ion exchange. As an organic Ions include, for example, ammonium ions, Ions, sulfonium ions, etc.

[0248] Specific examples of various additives include antioxidants, heat stabilizers (hindered phenols, hydroquinones, phosphites and their substitutions, copper halides, iodine compounds, etc.), weathering agents (resorcinols, salicylates, benzotriazoles, benzophenones, hindered amines, etc.), mold release agents and lubricants (aliphatic alcohols, aliphatic amides, aliphatic bisamides, diureas, polyethylene waxes, etc.), pigments (cadmium sulfide, phthalocyanine, carbon black, etc.), dyes (nigrosine, aniline black, etc.), plasticizers (octyl p-hydroxybenzoate, N-butylbenzene, etc.), sulfonamide, etc.), antistatic agents (alkyl sulfate type anionic antistatic agents, quaternary ammonium salt type cationic antistatic agents, nonionic antistatic agents such as polyoxyethylene sorbitan monostearate, betaine type amphoteric antistatic agents, etc.), flame retardants (melamine cyanurate, magnesium hydroxide, aluminum hydroxide and other hydroxides, ammonium polyphosphate, melamine polyphosphate, phosphite metal salts and other phosphorus flame retardants, brominated polystyrene, brominated polyphenylene ether, brominated polycarbonate, brominated epoxy resin or a combination of these brominated flame retardants and antimony trioxide, etc.). When these additives are contained, the content is preferably 10 parts by mass or less, more preferably 1 part by mass or less, when the thermoplastic polymer component considered as the main component is 100 parts by mass.

[0249] (2) A unit (L) for heating and pressurizing a composition containing a thermoplastic polymer and supplying the composition

[0250] The manufacturing device of the recycling monomer in the recycling monomer manufacturing device of the present invention has a unit (L) (sometimes referred to as "unit (L)" in the present invention) for heating and pressurizing a composition containing a thermoplastic polymer and supplying it. As the unit (L), for example, a device for heating and melting by an electric heater and pressurizing by a gear pump, a device for simultaneously heating and pressurizing by an extruder, a device combining an extruder with a gear pump, and a device for further heating the thermoplastic polymer discharged from the extruder by an electric heater, etc. can be cited. Among them, it is preferred that the unit (L) is a device using an extruder. By using the unit (L) as a device using an extruder, the pressure of extruding the thermoplastic polymer is easily stabilized.

[0251] The temperature at which the composition containing the thermoplastic polymer is heated is preferably a temperature at which the composition containing the thermoplastic polymer melts. By heating the composition containing the thermoplastic polymer to a temperature at which the composition containing the thermoplastic polymer melts, the contact area with subcritical water can be increased, and the reaction can proceed rapidly.

[0252] (3) Unit for generating and supplying subcritical water (M)

[0253] The manufacturing device of the recycling monomer of the present invention has a unit (M) for generating and supplying subcritical water (sometimes referred to as "unit (M)" in the recycling monomer manufacturing device of the present invention). If water is raised to a pressure of 22.1MPa and a temperature of 374.2°C, it shows a state that is neither liquid nor gas. Water in this state is called supercritical water. In addition, hot water in the vicinity of the critical point with a temperature and pressure slightly lower than the critical point of water is called subcritical water. Although subcritical water is water, it has the characteristics of (i) low dielectric constant and (ii) high ion product. The dielectric constant and ion product of subcritical water can be controlled depending on temperature and partial pressure of water. By lowering the dielectric constant, although it is water, it becomes an excellent solvent for organic compounds. In addition, by increasing the ion product, the concentrations of hydrogen ions and hydroxide ions become higher. Therefore, subcritical water has an excellent hydrolysis effect.

[0254] The water used as the raw material of subcritical water is not particularly limited, and any water can be used, such as tap water, deionized water, distilled water, well water, etc. Deionized water and distilled water are preferably used from the viewpoint of suppressing side reactions caused by the influence of coexisting salts.

[0255] As the unit (M), for example, there can be cited a device that pressurizes water into a high-pressure device using a diaphragm pump, a mohno pump, a gear pump, a plunger pump, etc., and then heats it to a specified temperature using a heat exchanger, an electric heater, a heating furnace, etc., but devices not shown here may also be used.

[0256] The subcritical water in the recycling monomer production device of the present invention is preferably heated to a temperature above the melting point of the composition containing the thermoplastic polymer. By heating the subcritical water to a temperature above the melting point of the composition containing the thermoplastic polymer, the composition containing the thermoplastic polymer is dispersed in a droplet shape, and the interfacial area is increased, so that the reaction efficiency can be improved. Since the temperature of the reaction system rises and falls by the heat absorption and release of the hydrolysis reaction after the subcritical water is in contact with the composition containing the thermoplastic polymer, it is preferred to control the temperature of the subcritical water according to the composition containing the thermoplastic polymer used. If the temperature of the reaction system becomes low, the hydrolysis reaction becomes insufficient, and if the temperature of the reaction system becomes high, the overreaction is easy to proceed, so both lead to a decrease in the yield of the recycled monomer. If the degree of heat absorption and release during the hydrolysis reaction is considered, the supply temperature of the subcritical water is preferably less than ±20°C relative to the temperature in the inlet of the continuous reactor (O), more preferably less than ±10°C, and further preferably less than ±5°C.

[0257] About the supply pressure of subcritical water, because in continuous reactor (O), subcritical water is preferably maintained as liquid, therefore can preferably exemplify the pressure of the saturated vapor pressure of water under the maximum temperature higher than subcritical water.As the vapor pressure of water, for example, be 6.4MPa in the case of 280 ℃, be 8.6MPa in the case of 300 ℃, be 11.3MPa in the case of 320 ℃, be 16.5MPa in the case of 350 ℃, therefore in order to be maintained as liquid, need to apply the pressure above it.

[0258] (4) A unit (N) comprising mixing a composition comprising a thermoplastic polymer with subcritical water

[0259] The manufacturing device of the recycling monomer of the present invention has a unit (N) (in the recycling monomer manufacturing device of the present invention, sometimes referred to as "unit (N)") for mixing the above-mentioned composition containing a thermoplastic polymer supplied from the above-mentioned unit (L) and the above-mentioned subcritical water supplied from the above-mentioned unit (M). As the unit (N), for example, a mixing tank, a flow path with a spiral, a jet mixer, a homogenizer, a static mixer, etc. can be cited. In particular, from the perspective of having no movable part and a small pressure loss, it is preferred that the unit (N) is a static mixer.

[0260] As a feature of the manufacturing device of the recycling monomer of the present invention, it can be cited that the subcritical water that has been pre-pressurized and heated is mixed rapidly with the composition containing the thermoplastic polymer. Due to the manufacturing device of the recycling monomer of the batch reactor that is equipped with the reaction tank that pre-added water and the composition containing the thermoplastic polymer are heated up while making it react, and the manufacturing device of the continuous recycling monomer that pressurizes and heats up the slurry containing the composition of the thermoplastic polymer dispersed in water while making it react, the manufacturing device of the recycling monomer of the present invention can control the temperature when the composition containing the thermoplastic polymer contacts with the subcritical water, so the reaction start temperature can be precisely controlled. As a result, since the excessive decomposition of the monomer can be suppressed, the depolymerization reaction of the thermoplastic polymer can be carried out in a short time, so the monomer yield can be improved. In addition, since the reaction starts instantaneously, the residence time in the continuous reactor (O) can be reduced. As a result, since the volume of the continuous reactor (O) can be reduced, the reduction of the device cost is brought about.

[0261] (5) a continuous reactor (O), a device (P) for monitoring the internal temperature of the upstream and downstream parts of the continuous reactor (O), and a temperature adjustment mechanism (Q) for heating and / or cooling the continuous reactor (O)

[0262] The recycling monomer production apparatus of the present invention preferably comprises a device (P) for monitoring the internal temperature of the upstream and downstream parts of the above-mentioned continuous reactor (O) (sometimes referred to as "device (P)" in the recycling monomer production apparatus of the present invention), and a temperature adjustment mechanism (Q) for heating and / or cooling the above-mentioned continuous reactor (O) (sometimes referred to as "temperature adjustment mechanism (Q)" in the recycling monomer production apparatus of the present invention), and the above-mentioned temperature adjustment mechanism (Q) is operated based on the above-mentioned device (P) to control the internal temperature of the above-mentioned continuous reactor (O).

[0263] The manufacturing device of the recycled monomer of the present invention has a continuous reactor (O) for performing hydrolysis treatment of a thermoplastic polymer. Since the continuous reactor (O) can continuously treat a composition containing a thermoplastic polymer, the time required for addition and discharge in intermittent treatment can be reduced, and the volume of the continuous reactor (O) can be reduced.

[0264] As the continuous reactor (O), for example, a tube type, a tower type, a multi-stage mixing tank type, etc. can be cited. A stirrer can be provided in the continuous reactor (O). The continuous reactor (O) can be configured with multiple containers in multiple stages, or multiple flow paths can be arranged in parallel as in a multi-tube type continuous reactor. Among them, it is preferred that the continuous reactor (O) is a tube type continuous reactor. The tube type continuous reactor has no movable part, is simple, and is easy to control the important reaction temperature in the depolymerization treatment of the composition containing the thermoplastic polymer using subcritical water.

[0265] In one embodiment of the recycling monomer production apparatus of the present invention, it is preferred to have a device (P) for monitoring the internal temperature of the upstream and downstream parts of the continuous reactor (O). Examples of the device for monitoring the internal temperature include thermocouples, platinum resistance thermometers, bimetallic thermometers, radiation thermometers, thermographic imaging, thermistors, and the like. The upstream part of the continuous reactor (O) refers to a position less than 1 / 2 of the upstream side of the total reaction volume of the continuous reactor (O). The upstream part of the continuous reactor (O) is preferably a position less than 1 / 3 of the upstream side of the total reaction volume of the continuous reactor (O), more preferably a position less than 1 / 4 of the upstream side, and further preferably a position less than 1 / 5 of the upstream side. In addition, the downstream part of the continuous reactor (O) refers to a position less than 1 / 2 of the downstream side of the total reaction volume of the continuous reactor. The downstream part of the continuous reactor (O) is preferably a position less than 1 / 3 of the downstream side of the total reaction volume of the continuous reactor, more preferably a position less than 1 / 4 of the downstream side, and further preferably a position less than 1 / 5 of the downstream side. Multiple devices for monitoring the internal temperature may be provided in the reactor. The total reaction volume refers to the total reaction volume from the inlet to the outlet of the continuous reactor (O). In addition, when a plurality of containers are arranged in multiple stages as the continuous reactor (O), the total reaction volume is the total volume of the plurality of containers.

[0266] The temperature of the above-mentioned unit (L) and the above-mentioned unit (M) can be controlled based on the internal temperature of the upstream part of the continuous reactor (O). By controlling the supply device based on the internal temperature of the upstream part of the continuous reactor (O), the temperature of the upstream part of the continuous reactor can be precisely controlled. Therefore, excessive decomposition of monomers caused by excessive temperature increase in the initial stage of the reaction and reduction in the depolymerization reaction rate caused by insufficient temperature increase can be prevented.

[0267] The production apparatus of recycled monomers of the present invention preferably comprises a temperature regulating mechanism (Q) for heating and / or cooling the continuous reactor (O), and the temperature regulating mechanism (Q) is operated based on the apparatus (P) to control the internal temperature of the continuous reactor (O). By controlling the temperature of the continuous reactor based on the internal temperature of the upstream and downstream parts of the continuous reactor (O), the temperature of the continuous reactor (O) can be precisely controlled. Therefore, in particular, excessive decomposition of monomers due to excessive temperature rise in the late stage of the reaction, oligomer formation due to repolymerization, and reduction in the depolymerization reaction rate due to insufficient temperature rise can be prevented.

[0268] In the recycling monomer production device of the present invention, it is preferred that a plurality of the temperature adjustment mechanisms (Q) are provided, and the plurality of the temperature adjustment mechanisms (Q) are operated based on the device (P). By providing a plurality of temperature adjustment mechanisms (Q), it is possible to achieve more detailed temperature control according to the degree of progress of the hydrolysis reaction in the upstream and downstream parts of the continuous reactor (O).

[0269] In the manufacturing device of the recycled monomer of the present invention, it is preferable to control the temperature regulating mechanism (Q) in such a manner that the internal temperature of the downstream portion is lower than the internal temperature of the upstream portion of the continuous reactor (O) by 10°C or more. By adopting such a structure, in the reaction of hydrolyzing the thermoplastic polymer, the temperature at the initial stage of the reaction is made higher than that at the later stage of the reaction, thereby making it easy to promote the hydrolysis of the thermoplastic polymer contained in a large amount in the reaction solution at the initial stage of the reaction. On the other hand, since the reaction solution at the later stage of the reaction contains a large amount of hydrolyzed recycled monomers, it is easy to suppress the repolymerization of the recycled monomers by making the temperature lower than that at the initial stage of the reaction. That is, by adopting such a structure, it is easy to both hydrolyze the thermoplastic polymer with high efficiency and obtain the recycled monomer with high yield. The internal temperature of the downstream portion of the continuous reactor (O) is more preferably lower than the internal temperature of the upstream portion by 20°C or more, and more preferably lower by 30°C or more. The internal temperature of the downstream portion of the continuous reactor (O) is not particularly limited relative to the internal temperature of the upstream portion, but is generally 100° C. or lower, preferably 80° C. or lower, and more preferably 60° C. or lower from the viewpoint of maintaining the reaction rate of the reaction for hydrolyzing the thermoplastic polymer.

[0270] When the composition containing a thermoplastic polymer to be depolymerized is waste, it is usually difficult to keep the quality of the waste constant. Furthermore, if the composition of the waste changes, it becomes an external disturbance, which sometimes affects the temperature in the reactor. In such a case, as described in the present invention, the reaction temperature can be controlled by heating and / or cooling the continuous reactor (O) based on the internal temperature of the continuous reactor (O), so that the reaction temperature can be instantaneously controlled even if an external disturbance such as a change in the composition of the composition containing a thermoplastic polymer occurs.

[0271] The means for heating the continuous reactor (O) is not particularly limited, and examples thereof include a method of installing a jacket or shell on the continuous reactor (O) and heating it with a heat medium such as steam, a method of heating it with an electric heater, etc. The means for cooling the continuous reactor (O) is not particularly limited, and examples thereof include a method of installing a jacket or shell on the continuous reactor (O) and cooling it with a heat medium / cooling medium having a temperature lower than the internal temperature of the continuous reactor (O), a method of cooling it by passing air through the surface of the continuous reactor (O), etc.

[0272] When the continuous reactor (O) is a tubular continuous reactor, the larger the inner diameter of the tubular continuous reactor, the greater the flow rate that can be processed per unit surface area of ​​the tubular continuous reactor, but the heat transfer area is reduced, so it is easy to generate temperature distribution along the axial direction and the radial direction. Therefore, it is important to provide a device for monitoring the internal temperature of the continuous reactor described in the present invention and a temperature control device for heating and / or cooling the continuous reactor (O). The inner diameter of the tubular continuous reactor is preferably 1 cm or more, more preferably 2 cm or more.

[0273] If the mass flow ratio of subcritical water to the thermoplastic polymer component in the composition containing a thermoplastic polymer is set to X:1, X is preferably less than 6. Since the specific heat capacity of water is 4.3 kJ / kg·K and the heat of vaporization is 2250 kJ / kg, which are very high compared to other organic solvents, it is preferred to reduce the amount of water used by making X less than 6 from the viewpoint of energy saving. In addition, by making X less than 6, the temperature change in the continuous reactor (O) caused by the reaction heat of the depolymerization reaction of the composition containing a thermoplastic polymer becomes larger, so it is preferred to increase the importance of temperature control based on the internal temperature of the continuous reactor (O) as described in the present invention. Furthermore, by making X less than 6, the processing amount of the composition containing a thermoplastic polymer per unit volume of the continuous reactor (O) can be increased, thereby also leading to a reduction in the cost of the device. Furthermore, by making X less than 6, the concentration of the recycled monomer in the downstream portion of the continuous reactor (O) increases, thereby promoting the repolymerization of the recycled monomer. As described in the present invention, the importance of temperature control based on the internal temperature of the continuous reactor (O) is increased, which is preferred.

[0274] When the maximum temperature of the indication value of the device (P) for monitoring the internal temperature of the upstream and downstream parts of the continuous reactor (O) for performing hydrolysis is set to Y°C, it is preferably controlled so that the product of X and Y becomes 2000 or less. It should be noted that the so-called maximum temperature Y°C refers to the higher temperature of the maximum temperature of the indication value of the internal temperature of the upstream part and the maximum temperature of the indication value of the internal temperature of the downstream part. The product of X and Y is more preferably a condition of 1600 or less, further preferably a condition of 1300 or less, and particularly preferably a condition of 1200 or less. In addition, there is no particular restriction on the lower limit of the product of X and Y, but it is preferably 300, more preferably 320, and particularly preferably 340. By making the product of X and Y within these condition ranges, it is easy to achieve both depolymerization treatment efficiency and energy saving of the composition containing thermoplastic polymers.

[0275] In addition, when the average residence time of the mixture of the composition containing the thermoplastic polymer and the subcritical water in the continuous reactor (O) is set to Z minutes, it is preferably controlled in a manner that the product of X, Y and Z is less than 60,000. It should be noted that the so-called average residence time is the value obtained by dividing the "volume of the continuous reactor (O)" by the "volume flow rate of the mixture of the composition containing the thermoplastic polymer and the subcritical water". It can be cited that the product of X, Y and Z is more preferably less than 40,000, and more preferably less than 30,000. In addition, there is no particular restriction on the lower limit of the product of X, Y and Z, but it is preferably 5000, more preferably 8000, and particularly preferably 9000. By making the product of X, Y and Z such a preferred condition range, it is easy to have both the depolymerization treatment efficiency and energy saving of the composition containing the thermoplastic polymer.

[0276] (6) Cooler, back pressure valve

[0277] The reaction solution discharged from the continuous reactor (O) is preferably introduced into the device that stops the hydrolysis reaction. As the example of the device that stops the hydrolysis reaction, a cooler, a flash tank etc. can be enumerated. Wherein, the device that preferably stops the hydrolysis reaction is a cooler. As the example of a cooler, known means such as heat exchangers can be enumerated. The reaction solution after leaving the cooler is usually often in a state of high pressure, so it is preferably released by known means such as back pressure valves.

[0278] (7) Monomer purification device

[0279] The reaction solution after the reaction is terminated is preferably purified. Examples of the purification method include known methods such as distillation and crystallization.

[0280] The purified monomer is preferably repolymerized and reused as a composition containing a thermoplastic polymer. As a method for repolymerization, a known polymerization method can be used.

[0281] (8) Method for producing recycled monomer (fourth preferred embodiment of the present invention)

[0282] The 4th preferred scheme of the present invention is to have the composition that comprises thermoplastic polymer and contact with subcritical water, the manufacture method of the recycling monomer of the operation of above-mentioned thermoplastic polymer hydrolysis.About the definition, illustration, suitable scheme of the composition that comprises thermoplastic polymer and subcritical water, as mentioned above.In addition, about the reaction conditions of the operation that is hydrolyzed, that is, suitable mixing ratio, temperature, pressure etc., as mentioned above.

[0283] In a fourth preferred embodiment of the present invention, the thermoplastic polymer is preferably a thermoplastic polyester or a thermoplastic polyamide. When the thermoplastic polymer is a thermoplastic polyester or a thermoplastic polyamide, it is easy to recover the monomers before polymerization by hydrolysis.

[0284] In the step of hydrolyzing the thermoplastic polymer in the fourth preferred embodiment of the present invention, the reaction temperature in the later stage of the hydrolysis reaction is preferably 10°C or more lower than the reaction temperature in the initial stage of the hydrolysis reaction. By making the temperature in the initial stage of the hydrolysis reaction higher than that in the later stage of the hydrolysis reaction, the hydrolysis of the thermoplastic polymer contained in a large amount in the reaction solution in the initial stage of the reaction is easily promoted. On the other hand, since the reaction solution in the later stage of the reaction contains a large amount of hydrolyzed recycled monomers, the repolymerization of the recycled monomers can be easily suppressed by making the temperature lower than that in the initial stage of the reaction. That is, it is easy to hydrolyze the thermoplastic polymer with high efficiency and obtain the recycled monomers in high yield. The reaction temperature in the later stage of the hydrolysis reaction is more preferably 20°C or more lower than the reaction temperature in the initial stage of the hydrolysis reaction, and further preferably 30°C or more lower. In addition, the reaction temperature in the later stage of the hydrolysis reaction is not particularly limited relative to the reaction temperature in the initial stage of the hydrolysis reaction, but from the viewpoint of maintaining the reaction speed of the reaction to hydrolyze the thermoplastic polymer, it is usually 100°C or less, preferably 80°C or less, and more preferably 60°C or less.

[0285] Example

[0286] Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.

[0287] The following raw materials were used in the first to fourth preferred embodiments of the present invention and in the examples of the production apparatus for a recycled monomer.

[0288] [Raw materials used in the description of the first preferred embodiment]

[0289] Thermoplastic polyester (A-1): Commercially available polyethylene terephthalate resin pellets, melting point 254°C

[0290] Thermoplastic polyester (A-2): washed and dried PET bottle flakes, melting point 255°C

[0291] Thermoplastic polyester (A-3): Commercially available polybutylene terephthalate resin pellets, melting point 224°C

[0292] Here, the melting point is the temperature of an endothermic peak that appears when each resin molded body is cooled from a molten state to 30° C. at a cooling rate of 20° C. / min and then heated to the melting point + 40° C. at a heating rate of 20° C. / min in a nitrogen atmosphere using a differential scanning calorimeter. However, when two or more endothermic peaks are detected, the temperature of the endothermic peak with the largest peak intensity is set as the melting point.

[0293] [Raw materials used in the description of the second preferred embodiment]

[0294] PET: Polyethylene terephthalate resin manufactured by Toray Industries, Inc. (intrinsic viscosity 0.62 dl / g)

[0295] PBT1: polybutylene terephthalate resin manufactured by Toray Industries, Inc. (intrinsic viscosity: 0.85 dl / g)

[0296] PBT2: A polyester resin composition obtained by blending pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010 [trade name] manufactured by BASF) (0.5 parts by weight) with PBT1 (100 parts by weight), and melt-kneading the mixture at 250° C.

[0297] PBT3: A polyester resin composition obtained by mixing 2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol] (Adeks LA-31G) (0.5 parts by weight) with PBT1 (100 parts by weight), and melt-kneading the mixture at 250° C.

[0298] PBT4: A polyester resin composition obtained by mixing 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (Adekstab PEP-36) (0.5 parts by weight) with PBT1 (100 parts by weight), and melt-kneading the mixture at 250°C.

[0299] PBT5: A polyester resin composition obtained by blending PBT1 (100 parts by weight) with BASF's Irganox 1010 [trade name] (0.5 parts by weight), Adeskastab LA-31G (0.5 parts by weight), and Adeskastab PEP-36 (0.5 parts by weight), and melt-kneading the mixture at 250°C.

[0300] [Raw materials used in the description of the third preferred embodiment]

[0301] Polyethylene terephthalate [PET] (manufactured by Toray Industries, Inc., intrinsic viscosity 0.62 dl / g, melting point 254°C)

[0302] Polybutylene terephthalate [PBT] (manufactured by Toray Industries, Inc., intrinsic viscosity 0.85 dl / g, melting point 224°C)

[0303] Polycarbonate [PC] ("TAFLON" (registered trademark) A2200 manufactured by Idemitsu Kosan Co., Ltd., viscosity average molecular weight 22,000, no melting point, glass transition temperature 150°C)

[0304] Polyurethane [PU] (polyurethane urea having a molecular weight of 1800 and formed from PTMG, diphenylmethane diisocyanate, ethylenediamine and diethylamine as a terminal blocking agent, with a thermal decomposition starting temperature of 277° C.).

[0305] [Apparatus for producing recycled monomer, and raw materials used in the description of the fourth preferred embodiment]

[0306] Polyethylene terephthalate (PET-A)]

[0307] Commercially available polyethylene terephthalate resin pellets (PET-A): melting point 254°C

[0308] Polyethylene terephthalate resin waste (PET-B): washed and dried PET bottle flakes, melting point 255°C.

[0309] Here, the melting point is the temperature of an endothermic peak that appears when the thermoplastic polyester is cooled from a molten state to 30° C. at a cooling rate of 20° C. / min and then heated to the melting point + 40° C. at a heating rate of 20° C. / min in a nitrogen atmosphere using a differential scanning calorimeter. However, when two or more endothermic peaks are detected, the temperature of the endothermic peak with the largest peak intensity is set as the melting point.

[0310] Evaluation Method

[0311] [Diol Yield (GC)]

[0312] The calculation of the diol yield (GC) in the present invention is carried out by gas chromatography measurement. The measurement conditions are described below.

[0313] Device: GC-2010 manufactured by Shimadzu Corporation

[0314] Column: DB-5 made by Agilent Co., Ltd. 0.32mm×30m (0.25μm)

[0315] Carrier gas: Helium

[0316] Detector: Flame ionization detector (FID)

[0317] Sample: About 1.2 g of the reaction mixture was measured and diluted with about 5 g of methanol, and the components insoluble in methanol were separated and removed by filtration to prepare a gas chromatography measurement sample.

[0318] Quantification of diols: The amount of diols was quantified by the absolute standard curve method.

[0319] [Yield of dicarboxylic acid (HPLC)]

[0320] The calculation of the dicarboxylic acid yield (HPLC) of the present invention is carried out by high performance liquid chromatography measurement. The measurement conditions are described below.

[0321] Device: LC-10Avp series manufactured by Shimadzu Corporation

[0322] Column: Mightysil RP-18GP150-4.6

[0323] Detector: Photodiode array detector (UV = 254nm)

[0324] Flow rate: 1mL / min

[0325] Column temperature: 40°C

[0326] Mobile phase: 0.1% acetic acid in water / acetonitrile

[0327] Sample: About 0.1 g of the reaction mixture was measured and diluted with about 10 g of dimethylformamide, and the components insoluble in dimethylformamide were separated and removed by filtration to prepare a high performance liquid chromatography measurement sample.

[0328] Quantification of dicarboxylic acid: The amount of dicarboxylic acid was quantified by the absolute standard curve method (however, in Examples 9, 12 to 25, 35, 36, and Comparative Examples 8 to 10, although disodium terephthalate or diammonium terephthalate was produced, it was converted into terephthalic acid by the acid contained in the mobile phase).

[0329] [Examples and Comparative Examples of the First Preferred Embodiment]

[0330] [Example 1]

[0331] In a SUS316L autoclave equipped with a stirrer, 20.0 g of the thermoplastic polyester (A-1) and 60.0 g of deionized water were placed in a mass ratio (Z:1) of water to the thermoplastic polyester of 3:1.

[0332] The reaction vessel was purged with nitrogen, sealed under nitrogen pressure of 0.5 MPa, and then stirred at 200 rpm while maintaining at 260°C for 15 minutes to react. During the reaction, the pressure in the system was 4.5 MPa. After the reaction was completed, the reaction mixture was cooled to room temperature and recovered. The reaction temperature X°C was 260°C, and the residence time at the reaction temperature of 260°C was 15 minutes, so the product of X, Y, and Z was 11,700.

[0333] The diol yield calculated by gas chromatography of the recovered reaction mixture was 95%, the dicarboxylic acid yield calculated by high performance liquid chromatography was 83%, and the diol concentration in the reaction mixture was 7.63% by mass. The reaction mixture was white.

[0334] [Examples 2 to 7, Comparative Examples 1 to 5]

[0335] Thermoplastic polyester (A-1) was used as a raw material, and depolymerization was carried out in the same manner as in Example 1, with changes in the amount of water relative to the thermoplastic polyester, reaction temperature, and reaction time. The reaction conditions, diol yield, dicarboxylic acid yield, and color tone of the reaction mixture are shown in Tables 1 and 2.

[0336] [Example 8]

[0337] Depolymerization was carried out in the same manner as in Example 1 except that the thermoplastic polyester (A-2) was used as the raw material. Table 1 shows the diol yield, the dicarboxylic acid yield, and the color tone of the reaction mixture.

[0338] [Example 9]

[0339] Depolymerization was carried out in the same manner as in Example 1 except that sodium hydroxide was further added. Table 1 shows the diol yield, the dicarboxylic acid yield, and the color tone of the reaction mixture.

[0340] [Example 10]

[0341] Depolymerization was carried out in the same manner as in Example 2 except that the thermoplastic polyester (A-3) was used as the raw material. Table 1 shows the diol yield, cyclic ether yield, dicarboxylic acid yield, and color tone of the reaction mixture.

[0342] [Table 1]

[0343]

[0344] [Table 2]

[0345] Table 2

[0346]

[0347] As can be seen from Examples 1 to 8, by setting X to be equal to or higher than the melting point of the thermoplastic polyester (A-1) and the thermoplastic polyester waste (A-2) and lower than 300°C, and setting the product of X, Y and Z to be equal to or higher than 2,000 and equal to or lower than 20,000, the energy required for depolymerization of the thermoplastic polyester can be greatly suppressed, and diol and dicarboxylic acid can be obtained at a high yield, thereby obtaining a non-colored reaction mixture in which the concentration of diol is further increased.

[0348] Comparative Example 1, in which the reaction was carried out at 240°C, which is lower than the melting point of 254°C of the thermoplastic polyester (A-1), showed a significantly lower yield of diol and dicarboxylic acid, which was less than half, compared with Example 1, which was carried out under the same conditions except for the reaction temperature. This is considered to be because the depolymerization reaction was limited to the surface of the solid thermoplastic polyester (A-1), and the reaction became insufficient. Although X and Z were within the preferred range, Comparative Example 3, in which the product of X, Y and Z was less than 2,000 due to the short reaction time, also did not react sufficiently, and the yield of diol and dicarboxylic acid was lower than that of Example 1. In this way, when at least one of X and the product of X, Y and Z does not satisfy the preferred range, the thermoplastic polyester and / or oligomer remains, and the amount discarded as residue increases, which is not preferred.

[0349] In Comparative Example 2, in which the reaction was carried out at 300°C, although a large amount of energy was required by heating water having a large specific heat capacity, the glycol yield was also lower than that of Example 1, and the reaction mixture contained a large amount of over-reactants such as coloring impurities. In Comparative Example 4, in which the product of X, Y, and Z exceeded 20,000, although X and Z were within the preferred range, a decrease in glycol yield and coloring of the reaction mixture were observed due to the long heating period, similar to Comparative Example 2. Thus, when at least one of X and the product of X, Y, and Z exceeded the preferred range, the generated glycol (for example, acetaldehyde, diethylene glycol, coloring impurities, etc. in the case of ethylene glycol) was changed into over-reactants, so the yield was reduced. In particular, acetaldehyde, which is one of the over-reactants, cannot be removed only by removing the heavy components by distillation, and additional treatment such as hydrogenation is required, which complicates the equipment in the recovery process and requires more energy for treatment. Therefore, it is desirable to carry out the depolymerization reaction under conditions that suppress over-reaction.

[0350] In Comparative Example 5, in which the amount of water relative to the thermoplastic polyester (A-1) exceeded the preferred range, the yield was lower than that of Example 1. When the amount of water relative to the thermoplastic polyester exceeds the preferred range, the energy required for heating water having a large specific heat capacity during the depolymerization reaction increases, and the equipment used for the depolymerization reaction becomes larger, which is not preferable.

[0351] Comparison between Example 1 and Example 9 shows that, when the reaction temperature is 260° C., the yield is improved by adding a basic component.

[0352] According to Example 10, also in the case of polybutylene terephthalate as the thermoplastic polyester, terephthalic acid can be obtained at a high yield.

[0353] [Reference Example 1]

[0354] After 123 parts by mass of bis(hydroxyethyl)terephthalate previously produced by transesterification of dimethyl terephthalate (produced by Kanto Chemical Co., Ltd.) and ethylene glycol (produced by Nippon Shokubai Co., Ltd.) was added, the mixture was kept at a temperature of 250°C and a pressure of 1.2×10 5 To the esterification reactor of Pa, 100 parts by mass of high-purity terephthalic acid (Mitsui Chemicals) and 45 parts by mass of ethylene glycol (Nippon Shokubai) were sequentially supplied over 4 hours. After the supply was completed, the esterification reaction was further continued for 1 hour to obtain an esterification reaction product.

[0355] 100 parts by mass of the obtained esterification reaction product were weighed and added to a polycondensation reactor, melted and stirred at a temperature of 250°C, and tetraisopropyl titanium was added in a manner of 15 ppm in terms of titanium atoms relative to the theoretical yield of polyester obtained after polycondensation. The reaction system was slowly heated from 250°C to 285°C while stirring at 30 rpm, and the pressure was reduced to 40 Pa. The time until the final temperature and final pressure were reached was set to 60 minutes. At the moment when the specified stirring torque was reached, the reaction system was purged with nitrogen and returned to normal pressure, the polycondensation reaction was stopped, and the strips were discharged into cold water, and immediately cut to obtain polymer pellets.

[0356] [Example 11]

[0357] The reaction mixture obtained in the same manner as in Example 1 was cooled to room temperature, and the precipitated regenerated terephthalic acid was separated by filtration. On the other hand, water was removed from the filtrate after the regenerated terephthalic acid was separated by filtration under reduced pressure, and then distilled to obtain regenerated ethylene glycol. Polyethylene terephthalate containing 55% by mass of the regenerated monomer was produced in the same manner as in Reference Example 1 except that the regenerated ethylene glycol and regenerated terephthalic acid obtained in this manner were used as esterification reaction raw materials. The melting point of the regenerated polyethylene terephthalate was 256°C, and the color tone was also the same as that of the polyethylene terephthalate obtained in Reference Example 1.

[0358] [Comparative Example 6]

[0359] Regenerated polyethylene terephthalate was produced in the same manner as in Reference Example 1 except that the regenerated terephthalic acid and regenerated ethylene glycol obtained in the same manner as in Comparative Example 2 were used. The obtained regenerated polyethylene terephthalate had a melting point of 256° C. and was light orange.

[0360] Therefore, according to Example 9 and Comparative Example 6, since the depolymerization reaction according to the present invention can obtain non-colored high-purity diol and dicarboxylic acid, it is possible to produce a thermoplastic polyester equivalent to that when commercially available diol and dicarboxylic acid are used as raw materials.

[0361] [Examples and Comparative Examples of the Second Preferred Embodiment]

[0362] [Example 12]

[0363] In a SUS316L autoclave equipped with a stirrer, 20.0 g of polyethylene terephthalate resin (PET), 40.0 g of deionized water, and 0.01 g of sodium hydroxide (manufactured by Fuji Film and Koshun Pharmaceutical) were added. The nitrogen in the reaction vessel was replaced, and the mixture was stirred at 200 rpm at 300 ° C for 15 minutes under nitrogen pressure of 0.5 MPa in a sealed state. During the reaction, the pressure in the system was 8.0 MPa. After the reaction, the reaction was cooled to room temperature and the reactants were recovered. After filtering the reactants, the solid matter was dried and solidified using a vacuum pump (80 ° C). 16.2 g of terephthalic acid (yield 94%) and 0.1 g of benzoic acid (yield 0.8%) were obtained. The results are shown in Table 3.

[0364] [Examples 13, 14, Comparative Examples 7, 8]

[0365] The polyethylene terephthalate resin was depolymerized in exactly the same manner as in Example 12 except that the amount of sodium hydroxide added was changed.

[0366] [Table 3]

[0367]

[0368] Comparison between Examples 12 to 14 and Comparative Examples 7 and 8 shows that by adding a specific amount of sodium hydroxide, PET is depolymerized, thereby suppressing the production of benzoic acid (overreactant of terephthalic acid) and obtaining terephthalic acid at a high yield.

[0369] [Comparative Example 9]

[0370] In a SUS316L autoclave equipped with a stirrer, 20.0 g of polyethylene terephthalate resin (PET), 40.0 g of deionized water, and 0.36 mL of 28% ammonia water (manufactured by Fuji Film and Koshun Pharmaceutical) were added. The nitrogen in the reaction vessel was replaced, and the mixture was stirred at 200 rpm at 300 ° C for 15 minutes under nitrogen pressure of 0.5 MPa in a sealed state. During the reaction, the pressure in the system was 8.0 MPa. After the reaction, the reaction product was cooled to room temperature and the reactant was recovered. After filtering the reactant, the solid material was dried and solidified using a vacuum pump (80 ° C). 10.7 g of terephthalic acid (yield 62%) and 2.3 g of benzoic acid (yield 18%) were obtained. On the other hand, the filtrate was subjected to GC analysis, and the yield of ethylene glycol was 78%. The results are shown in Table 4 together with the results of Example 2.

[0371] [Comparative Example 10]

[0372] In a SUS316L autoclave equipped with a stirrer, 20.0 g of polyethylene terephthalate resin (PET), 40.0 g of deionized water, and 10.0 g of sodium hydroxide were added. The nitrogen in the reaction vessel was replaced, and the mixture was stirred at 200 rpm at 300 ° C for 15 minutes under nitrogen pressure of 0.5 MPa in a closed state. During the reaction, the pressure in the system was 8.0 MPa. After the reaction, the reaction was cooled to room temperature and the reactant was recovered. After filtering the reactant, the solid material was dried and solidified using a vacuum pump (80 ° C). 15.6 g of terephthalic acid (yield 90%) and 0.11 g of benzoic acid (yield 0.9%) were obtained. On the other hand, the filtrate was subjected to GC analysis, and the yield of ethylene glycol was 52%. The results are shown in Table 4.

[0373] [Table 4]

[0374] Table 4

[0375]

[0376] It can be seen from Example 13 and Comparative Example 9 that the yield of benzoic acid in the formulation with sodium hydroxide added is lower than that in the formulation with ammonia added, and the yields of terephthalic acid and ethylene glycol are higher. In addition, it can be seen from Example 13 and Comparative Example 10 that when the amount of sodium hydroxide added is large, the yields of terephthalic acid and ethylene glycol are low.

[0377] [Example 15]

[0378] In a SUS316L autoclave equipped with a stirrer, 20.0 g of polybutylene terephthalate resin (PBT1), 60.0 g of deionized water, and 0.1 g of sodium hydroxide were added. The nitrogen in the reaction vessel was replaced, and the mixture was stirred at 200 rpm at 280 ° C for 15 minutes under nitrogen pressure of 0.5 MPa in a closed state. During the reaction, the pressure in the system was 6.3 MPa. After the reaction, it was cooled to room temperature and the reactant was recovered. After filtering the reactant, the solid material was dried and solidified using a vacuum pump (80 ° C). 16.9 g of terephthalic acid (yield 98%) and 0.03 g of benzoic acid (yield 0.2%) were obtained. The results are shown in Table 5.

[0379] [Examples 16 to 21, Comparative Examples 11 to 15]

[0380] The polybutylene terephthalate resin composition was depolymerized in exactly the same manner as in Example 15 except that the type of the polybutylene terephthalate resin composition and the amount of sodium hydroxide added were changed.

[0381] [Table 5]

[0382]

[0383] From Comparative Example 11 and Comparative Examples 12 to 15, it can be seen that the yield of benzoic acid increases and the yield of terephthalic acid decreases by mixing an antioxidant and a weathering agent into PBT. In addition, from Comparative Examples 12 to 15 and Examples 16 to 21, it can be seen that in PBT mixed with additives, the yield of benzoic acid decreases and the yield of terephthalic acid increases by adding sodium hydroxide.

[0384] [Example 22]

[0385] In a SUS316L autoclave equipped with a stirrer, 20.0 g of a polybutylene terephthalate resin composition (PBT5), 60.0 g of deionized water, and 0.1 g of sodium hydroxide were added. The nitrogen in the reaction vessel was replaced, and the mixture was stirred at 200 rpm at 260°C for 15 minutes under a nitrogen pressure of 0.5 MPa in a sealed state. During the reaction, the pressure in the system was 5.0 MPa. After the reaction, the mixture was cooled to room temperature and the reactants were recovered. After filtering the reactants, the solid matter was dried and solidified using a vacuum pump (80°C). 15.6 g of terephthalic acid (yield 90%) and 0.03 g of benzoic acid (yield 0.2%) were obtained. The results are shown in Table 6 together with the results of Example 20.

[0386] [Example 23]

[0387] The polybutylene terephthalate resin composition was depolymerized in exactly the same manner as in Example 22 except that the temperature was changed.

[0388] [Table 6]

[0389] Table 6

[0390]

[0391] Comparison between Example 22 and Example 20 shows that the yield of terephthalic acid increases by increasing the temperature from 260° C. to 280° C. Comparison between Example 20 and Example 23 shows that the yield of benzoic acid increases and the yield of terephthalic acid decreases by increasing the temperature from 280° C. to 300° C. Therefore, it is known that the yield of terephthalic acid is highest at a temperature of 280° C.

[0392] [Example 24]

[0393] In a SUS316L autoclave equipped with a stirrer, 20.0 g of polybutylene terephthalate resin (PBT5), 40.0 g of deionized water, and 0.1 g of sodium hydroxide were added. The nitrogen in the reaction vessel was replaced, and the mixture was stirred at 200 rpm at 280°C for 15 minutes under nitrogen pressure of 0.5 MPa in a sealed state. During the reaction, the pressure in the system was 6.3 MPa. After the reaction, the mixture was cooled to room temperature and the reactants were recovered. After filtering the reactants, the solid matter was dried and solidified using a vacuum pump (80°C). 14.3 g of terephthalic acid (yield 83%) and 0.01 g of benzoic acid (yield 0.1%) were obtained. The results are shown in Table 7 together with the results of Example 20.

[0394] [Example 25]

[0395] The results are shown in Table 7, except that the compounding amount of the polybutylene terephthalate resin composition and the compounding amount of water were changed, a polybutylene terephthalate resin composition was obtained by the same method as in Example 24.

[0396] [Table 7]

[0397] Table 7

[0398]

[0399] Comparison between Example 24 and Example 20 shows that the yield of terephthalic acid increases by increasing the blending amount of water from 200 parts by weight to 300 parts by weight. Comparison between Example 20 and Example 25 shows that the yield of terephthalic acid decreases by increasing the blending amount of water from 300 parts by weight to 800 parts by weight. Therefore, it is known that the yield of terephthalic acid is highest when the blending amount of water is 300 parts by weight.

[0400] [Examples and Comparative Examples of the Third Preferred Embodiment]

[0401] [Example 26]

[0402] In a SUS316L autoclave equipped with a stirrer, a polyester mixture containing 10.0 g of polyethylene terephthalate and 10.0 g of polybutylene terephthalate and 50.0 g of deionized water were added. The reaction vessel was substituted with nitrogen, and after being sealed under nitrogen pressure of 0.3 MPa, the reaction was carried out while stirring at 200 rpm and maintained at 260 ° C for 15 minutes. During the reaction, the pressure in the system was 4.8 MPa. After the reaction was completed, it was cooled to room temperature and the white precipitated component was recovered by filtration. The terephthalic acid yield calculated by high performance liquid chromatography of the recovered precipitated component is shown in Table 8. The terephthalic acid yield is 90%, and the ethylene glycol yield is 83%.

[0403] [Example 27]

[0404] The polyester mixture was hydrolyzed in the same manner as in Example 26 except that the amount of deionized water was changed to 30.0 g. The results are shown in Table 8. The yield of terephthalic acid was 88%, and the yield of ethylene glycol was 82%.

[0405] [Example 28]

[0406] The polyester mixture was hydrolyzed in the same manner as in Example 26 except that the amount of deionized water was changed to 100 g. The results are shown in Table 8. The yield of terephthalic acid was 95%, and the yield of ethylene glycol was 88%.

[0407] [Example 29]

[0408] Hydrolysis was carried out in the same manner as in Example 26 except that the composition containing the polymer was changed to a polyester mixture containing 19.0 g of polyethylene terephthalate and 1.0 g of polybutylene terephthalate. The results are shown in Table 8. The yield of terephthalic acid was 85%, and the yield of ethylene glycol was 78%.

[0409] [Example 30]

[0410] Hydrolysis was carried out in the same manner as in Example 26 except that the composition containing the polymer was changed to a polyester mixture containing 19.8 g of polyethylene terephthalate and 0.2 g of polybutylene terephthalate. The results are shown in Table 8. The yield of terephthalic acid was 82%, and the yield of ethylene glycol was 76%.

[0411] [Example 31]

[0412] The polyester mixture was hydrolyzed in the same manner as in Example 26 except that the reaction temperature was changed to 290°C. The results are shown in Table 8. The yield of terephthalic acid was 98%, and the yield of ethylene glycol was 90%.

[0413] [Example 32]

[0414] The polyester mixture was hydrolyzed in the same manner as in Example 26 except that the nitrogen pressure was changed to 8.5 MPa. The results are shown in Table 8. The yield of terephthalic acid was 97%, and the yield of ethylene glycol was 90%.

[0415] [Example 33]

[0416] Hydrolysis was carried out in the same manner as in Example 26 except that the composition containing the polymer was changed to a mixture containing 16.0 g of polybutylene terephthalate and 4.0 g of polycarbonate and the reaction temperature was changed to 250° C. The results are shown in Table 8. The yield of terephthalic acid was 85%.

[0417] [Example 34]

[0418] Hydrolysis was carried out in the same manner as in Example 26 except that the composition containing the polymer was changed to a mixture containing 18.0 g of polyethylene terephthalate and 2.0 g of polyurethane urea. The results are shown in Table 8. The yield of terephthalic acid was 84%, and the yield of ethylene glycol was 74%.

[0419] [Example 35]

[0420] Hydrolysis was carried out in the same manner as in Example 34 except that 7.7 g of sodium hydroxide was further added. 100 g of deionized water was added to the obtained hydrolyzate to dissolve all the generated disodium terephthalate. After filtering, hydrochloric acid was added to the aqueous solution to recover the precipitated terephthalic acid. The results are shown in Table 8. The yield of terephthalic acid was 95%, and the yield of ethylene glycol was 93%.

[0421] [Example 36]

[0422] Hydrolysis was carried out in the same manner as in Example 35 except that the reaction temperature was changed to 230°C. The results are shown in Table 8. The yield of terephthalic acid was 92%, and the yield of ethylene glycol was 90%.

[0423] [Comparative Example 16]

[0424] The polyester mixture was hydrolyzed in the same manner as in Example 26 except that the reaction temperature was changed to 240°C. The results are shown in Table 9. The yield of terephthalic acid was 10%, and the yield of ethylene glycol was 8%.

[0425] [Comparative Example 17]

[0426] Hydrolysis was carried out in the same manner as in Example 26 except that the composition containing the polymer was changed to only 20.0 g of polyethylene terephthalate. The results are shown in Table 9. The yield of terephthalic acid was 78%, and the yield of ethylene glycol was 72%.

[0427] [Comparative Example 18]

[0428] Hydrolysis was carried out in the same manner as in Example 26 except that the polymer was changed to only 20.0 g of polyethylene terephthalate and the deionized water was changed to 30 g. The results are shown in Table 9. The yield of terephthalic acid was 73%, and the yield of ethylene glycol was 68%.

[0429] [Comparative Example 19]

[0430] Hydrolysis was carried out in the same manner as in Example 26 except that the polymer was changed to only 20.0 g of polybutylene terephthalate and the reaction temperature was changed to 250° C. The results are shown in Table 9. The yield of terephthalic acid was 75%.

[0431] [Comparative Example 20]

[0432] Hydrolysis was carried out in the same manner as in Example 26 except that the composition containing the polymer was changed to a polyester mixture containing 19.92 g of polyethylene terephthalate and 0.08 g of polybutylene terephthalate. The results are shown in Table 9. The yield of terephthalic acid was 79%, and the yield of ethylene glycol was 72%.

[0433] [Table 8]

[0434]

[0435] [Table 9]

[0436]

[0437] Comparison between Examples 26, 29, and 30 and Comparative Example 17, and comparison between Example 27 and Comparative Example 18, shows that the yield of the recycled monomers is improved by hydrolyzing PET and PBT simultaneously.

[0438] Comparison between Example 33 and Comparative Example 19 shows that the yield of terephthalic acid is improved by hydrolyzing PBT and PC simultaneously.

[0439] Comparison between Examples 26 and 31 and Comparative Example 16 shows that the yield of the recycled monomer is improved by increasing the reaction temperature.

[0440] Comparison between Examples 26 and 28 shows that the yield of the recycled monomers is improved by appropriately increasing the amount of water added during the hydrolysis.

[0441] Comparison between Examples 26 and 32 shows that the yield of the recycled monomers is increased by appropriately increasing the pressure during the hydrolysis.

[0442] Comparison between Comparative Examples 17 and 20 shows that the yield of recycled monomers when a polymer mixture of 100 parts by weight of PET and 0.4 parts by weight of PBT is hydrolyzed simultaneously is substantially the same as when PET alone is hydrolyzed.

[0443] Comparison between Example 34 and Comparative Example 17 shows that the yield of recycled monomers is increased by hydrolyzing PET and PU simultaneously.

[0444] Comparison between Example 34 and Example 35 shows that the recycled monomer can be obtained at a high yield by adding sodium hydroxide for hydrolysis.

[0445] Comparison between Example 35 and Example 36 shows that when a basic component is blended, the recycled monomer can be obtained at a high yield even when the reaction temperature is lowered.

[0446] [Reference Example 2]

[0447] 123 parts by weight of bis(hydroxyethyl)terephthalate produced in advance by transesterification of dimethyl terephthalate (manufactured by Kanto Chemical Co., Ltd.) and ethylene glycol (manufactured by Nippon Shokubai Co., Ltd.) was added. In an esterification reactor maintained at a temperature of 250°C and a pressure of 1.2×105Pa, 100 parts by weight of high-purity terephthalic acid (manufactured by Mitsui Chemicals Co., Ltd.) and 45 parts by weight of ethylene glycol (manufactured by Nippon Shokubai Co., Ltd.) were sequentially supplied over 4 hours. After the supply was completed, an esterification reaction was further carried out over 1 hour to obtain an esterification reaction product.

[0448] 100 parts by weight of the obtained esterification reaction product were weighed and added to the polycondensation reactor, melted and stirred at a temperature of 250°C, and tetraisopropyl titanium was added in a manner converted to 15 ppm of titanium atoms relative to the theoretical yield of polyester obtained after polycondensation. The reaction system was slowly heated from 250°C to 285°C while stirring at 30 rpm, and the pressure was reduced to 40 Pa. The time until the final temperature and final pressure were both set to 60 minutes. At the moment when the specified stirring torque was reached, the reaction system was purged with nitrogen and returned to normal pressure, the polycondensation reaction was stopped, discharged into cold water in strips, and immediately cut to obtain polymer particles. The melting point of the polymer is 254°C.

[0449] [Example 37]

[0450] After the hydrolysis of Example 1, terephthalic acid, monohydroxyethyl terephthalate, and benzoic acid were detected as components precipitated at room temperature. Since monohydroxyethyl terephthalate is a polymerization precursor of polyethylene terephthalate, it can be effectively used as a polymerization raw material. On the other hand, since benzoic acid has the possibility of hindering polymerization as an end-capping agent during polymerization, the precipitated component was washed three times in hot ethanol to remove benzoic acid. By this method, a mixture of terephthalic acid and monohydroxyethyl terephthalate (weight ratio 89:11) was recovered.

[0451] Furthermore, ethylene glycol was recovered by distilling the water-soluble component obtained by the hydrolysis in Example 26.

[0452] 123 parts by weight of bis(hydroxyethyl)terephthalate produced in advance by transesterification of dimethyl terephthalate (manufactured by Kanto Chemical Co., Ltd.) and ethylene glycol (manufactured by Nippon Shokubai Co., Ltd.) was added. In an esterification reactor maintained at a temperature of 250°C and a pressure of 1.2×105 Pa, 102 parts by weight of a mixture of terephthalic acid and monohydroxyethyl terephthalate (recycled monomer) recovered by the above method and 42 parts by weight of ethylene glycol (recycled monomer) were sequentially supplied over 4 hours. After the supply was completed, an esterification reaction was further carried out for 1 hour to obtain an esterification reaction product.

[0453] 100 parts by weight of the obtained esterification reaction product are weighed and added to a polycondensation reactor, melted and stirred at a temperature of 250°C, and tetraisopropyl titanium is added in a manner of 15 ppm in terms of titanium atoms relative to the theoretical yield of polyester obtained after polycondensation. The reaction system is slowly heated from 250°C to 285°C while stirring at 30 rpm, and the pressure is reduced to 40 Pa. The time until the final temperature and final pressure are reached is set to 60 minutes. At the moment when the specified stirring torque is reached, the reaction system is purged with nitrogen to return to normal pressure, the polycondensation reaction is stopped, discharged into cold water in strips, and immediately cut to obtain polymer particles. The melting point of the polymer is 254°C, which is the same as that in Reference Example 2.

[0454] [Apparatus for producing recycled monomer, and examples and comparative examples of the fourth preferred embodiment]

[0455] [Example 38]

[0456] Used Figure 1 A manufacturing device for a recycled monomer as shown. As a unit (L) for heating and pressurizing a composition containing a thermoplastic polymer and supplying it, an extruder 2 is used. As a unit (M) for generating and supplying subcritical water, a high-pressure pump 4 and an electric heater 5 are used. The heating temperature of the extruder 2 and the electric heater 5 is controlled in a manner to become a set temperature using an extruder / electric heater temperature control device 14. As a unit (N) for mixing the above-mentioned composition containing a thermoplastic polymer supplied from the above-mentioned unit (L) with the above-mentioned subcritical water supplied from the above-mentioned unit (M), a static mixer 6 is used. As a continuous reactor (O) for performing hydrolysis connected to the above-mentioned unit (N), a tubular continuous reactor 7 and a tubular continuous reactor 8 that can flow a heat medium by convection in an external jacket are used in series.

[0457] As a composition containing a thermoplastic polymer as a raw material, polyethylene terephthalate (PET-A) is put into a raw material hopper 1, and PET-A is melted and pressurized using an extruder 2. The temperature of PET-A is set to 281°C, the pressure is set to 20MPa, and the supply amount is set to 13.0g / min. Deionized water is accumulated in a water tank 3, pressurized using a high-pressure pump 4, and heated using an electric heater 5 to produce subcritical water. The temperature of the subcritical water is set to 281°C, the pressure is set to 20MPa, and the supply amount is set to 39.0g / min. The mass flow ratio (X:1) of the thermoplastic polymer component in the subcritical water and the composition containing the thermoplastic polymer is 3:1. The heated, melted and pressurized composition containing the thermoplastic polymer is merged with the flow of subcritical water and supplied to a static mixer 6 with 24 elements. The solution discharged from the static mixer 6 was supplied to a tubular continuous reactor 7 having an inner diameter of 2.3 cm and a length of 250 cm, and the solution discharged from the tubular continuous reactor 7 was supplied to a tubular continuous reactor 8 having an inner diameter of 2.3 cm and a length of 250 cm.

[0458] A continuous reactor upstream temperature monitoring device 12 for monitoring the temperature of the upstream portion of the continuous reactor (O) was inserted at a position 5 cm from the inlet of the tubular continuous reactor 7, and a continuous reactor downstream temperature monitoring device 13 for monitoring the temperature of the downstream portion of the continuous reactor (O) was inserted at a position 5 cm from the outlet of the tubular continuous reactor 8. Based on the signal from the continuous reactor upstream temperature monitoring device 12, the flow rate and temperature of the heat medium supplied to the jacket of the tubular continuous reactor 7 were adjusted by the continuous reactor temperature adjustment mechanism 15 of the tubular continuous reactor 7. Based on the signals from the continuous reactor upstream temperature monitoring device 12 and the continuous reactor downstream temperature monitoring device 13, the flow rate and temperature of the heat medium supplied to the jacket of the tubular continuous reactor 8 were adjusted by the continuous reactor temperature adjustment mechanism 16 of the tubular continuous reactor 8. The temperature of the continuous reactor upstream temperature monitoring device 12 was 280° C., and the temperature of the continuous reactor downstream temperature monitoring device 13 was 240° C.

[0459] The average residence time Z of the continuous reactor (O) was 30 minutes. The product of X and Y and the product of X, Y and Z are shown in Table 10.

[0460] The reaction solution discharged from the tubular continuous reactor 8 was cooled to 40° C. by exchanging heat with cooling water in the heat exchanger 9 . Then, the reaction solution was depressurized from 20 MPa to atmospheric pressure by the back pressure valve 10 and stored in the reaction solution tank 11 .

[0461] The reaction solution stored in the reaction solution tank 11 was cooled to room temperature, and suction filtration was performed to recover the solid component (terephthalic acid) and separate it from the solution (ethylene glycol aqueous solution). According to the weight of the solid component and the results of HPLC analysis, the molar yield of terephthalic acid was 98%. On the other hand, according to the weight of the solution and the results of GC analysis, the molar yield of ethylene glycol was 80%.

[0462] [Table 10]

[0463]

[0464] [Example 39]

[0465] The production apparatus for the recycled monomer was operated in the same manner as in Example 38 except for the setting of the temperature of the continuous reactor downstream portion temperature monitoring device 13. The results are shown in Table 10.

[0466] [Example 40]

[0467] The production apparatus for the recycled monomer was operated in the same manner as in Example 38 except for the setting of the temperature of the continuous reactor downstream portion temperature monitoring device 13. The results are shown in Table 10.

[0468] [Example 41]

[0469] Used Figure 2 The manufacturing apparatus for recycled monomers is shown. Figure 2 The device shown is relative to Figure 1 The device shown in the figure is characterized in that the tubular continuous reactor 7 and the continuous reactor temperature adjustment mechanism 15 are one. A continuous reactor upstream temperature monitoring device 12 for monitoring the temperature of the upstream part of the continuous reactor (O) is inserted at a position 5 cm away from the inlet of the tubular continuous reactor 7, and a continuous reactor downstream temperature monitoring device 13 for monitoring the temperature of the downstream part of the continuous reactor (O) is inserted at a position 5 cm away from the outlet of the tubular continuous reactor 7. Figure 2 In the apparatus shown in FIG. 1, the continuous reactor temperature adjustment mechanism 15 was set so that the internal temperature of the upstream and downstream parts of the tubular continuous reactor 7 was maintained at 280° C., and the flow rate and temperature of the heat medium flowing in the tubular continuous reactor 8 were controlled. The other conditions were set as shown in Table 10. Figure 2 The production apparatus of the recycled monomer shown in the figure was operated, and the results are shown in Table 10. By operating at a temperature of 280°C, the hydrolysis reaction proceeded rapidly, so that the treatment could be performed at a shorter residence time than in Example 38. However, in the late stage of the reaction, it was particularly difficult to suppress the repolymerization reaction of terephthalic acid, so it is estimated that the molar yield of terephthalic acid decreased. It should be noted that the molar yield of ethylene glycol was comparable to that of other examples.

[0470] [Example 42]

[0471] Used Figure 2 The manufacturing device of the recycling monomer shown in FIG. Figure 2 In the apparatus shown in FIG. 1, the temperature of the upstream portion of the tubular continuous reactor 7 is maintained at approximately 280° C., and the temperature of the downstream portion of the tubular continuous reactor is set to 240° C. At this time, the flow rate of the heat medium is controlled to decrease so that a temperature gradient is generated in the tubular continuous reactor 8. The other conditions are as shown in Table 10. Figure 2 The production apparatus for the recycled monomer shown was operated, and the results are shown in Table 10. Since there was only one temperature adjustment mechanism, the time for maintaining the maximum temperature was shortened, and therefore it is estimated that the molar yield of terephthalic acid was reduced compared with Example 38.

[0472] [Example 43]

[0473] The production apparatus for the recycled monomer was operated in the same manner as in Example 38 except that the composition containing the thermoplastic polymer was PET-B. The results are shown in Table 10. This shows that the recycled monomer can be produced in the same manner as in Example 38 even when the composition containing the thermoplastic polymer is waste polyethylene terephthalate resin.

[0474] Explanation of symbols

[0475] 1 Raw material hopper

[0476] 2 Extruder

[0477] 3. Water pitcher

[0478] 4 High pressure pump

[0479] 5 Electric heater

[0480] 6 Static mixer

[0481] 7 Tubular Continuous Reactor

[0482] 8 Tubular Continuous Reactor

[0483] 9 Heat exchanger

[0484] 10 Back pressure valve

[0485] 11 Reaction solution tank

[0486] 12 Continuous reactor upstream temperature monitoring device

[0487] 13. Temperature monitoring device for downstream part of continuous reactor

[0488] 14 Extruder / electric heater temperature control device

[0489] 15Continuous reactor temperature adjustment mechanism

[0490] 16. Continuous reactor temperature adjustment mechanism.

Claims

1. A recycled monomer, which is produced by contacting a composition containing a polymer with subcritical water, wherein the recycled monomer is produced from a composition containing a polymer under the following conditions: when the melting point of the polymer measured by a differential scanning calorimeter is Mp°C, the reaction temperature is X°C, the reaction time is Y minutes, and the mass ratio of water to the polymer is Z:1, X satisfies the following (I), and the product of X, Y and Z (X·Y·Z) satisfies the following (II), (I)Mp≤X<300 (II)2000≤X·Y·Z≤20000.

2. The recycled monomer according to claim 1, wherein the polymer is a thermoplastic polyester or a thermoplastic polyamide.

3. A recycled polymer obtained by repolymerizing the recycled monomer according to claim 1.

4. A clothing fiber, industrial fiber, film, sheet, automobile part or electric / electronic part produced by using the recycled polymer according to claim 3.

5. A method for producing a recycled monomer, comprising the step of contacting a composition containing a polymer with subcritical water.

6. The method for producing a recycled monomer according to claim 5, wherein the polymer is a thermoplastic polyester A, and when the melting point of the thermoplastic polyester A measured by a differential scanning calorimeter is Mp°C, the reaction temperature is X°C, the reaction time is Y minutes, and the mass ratio of water to the thermoplastic polyester A is Z:1, X satisfies the following (I), and the product of X, Y and Z (X·Y·Z) satisfies the following (II), (I)Mp≤X<300 (II)2000≤X·Y·Z≤20000. 7 . The method for producing a recycled monomer according to claim 6 , wherein the concentration of the diol derived from the thermoplastic polyester A in the reaction mixture obtained by contacting the composition containing the thermoplastic polyester A with subcritical water to hydrolyze the thermoplastic polyester A is 4.9 mass % or more.

8. The method for producing a recycled monomer according to claim 6, wherein the concentration of the cyclic ether derived from the thermoplastic polyester A in the reaction mixture obtained by contacting the composition containing the thermoplastic polyester A with subcritical water to hydrolyze the thermoplastic polyester A is 3.0 mass % or more. 9 . The method for producing a recycled monomer according to claim 6 , wherein the mass ratio Z of the subcritical water to the thermoplastic polyester A is less than 6.

10. The method for producing recycled monomers according to claim 6, wherein the thermoplastic polyester A contains as a main component at least one selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and copolymers thereof.

11. The method for producing recycled monomers according to claim 6, wherein the thermoplastic polyester A is waste containing at least polyester. 12 . The method for producing a recycled monomer according to claim 6 , wherein the recycled monomer is a dicarboxylic acid and / or a diol.

13. A method for producing a thermoplastic polyester, using the dicarboxylic acid and / or diol obtained by the production method according to claim 12 as a raw material.

14. A method for producing a thermoplastic polyester product, comprising using the thermoplastic polyester obtained by the production method according to claim 12 as a raw material to produce a product containing the thermoplastic polyester such as a fiber, a film or a molded article.

15. A method for producing a product comprising a thermoplastic polyester composition, wherein the product comprising a thermoplastic polyester composition obtained by the production method according to claim 12 is used as a raw material to produce a fiber, a film or a molded article. 16 . The method for producing recycled monomers according to claim 5 , wherein the polymer is a thermoplastic polyester A, and 0.01 to 4.0 parts by weight of an alkali metal salt and / or an alkaline earth metal salt is blended with respect to 100 parts by weight of the thermoplastic polyester A. 17 . The method for producing a recycled monomer according to claim 16 , wherein 100 to 1000 parts by weight of subcritical water is mixed with respect to 100 parts by weight of the thermoplastic polyester A.

18. The method for producing a recycled monomer according to claim 16, wherein the temperature of the step of contacting with subcritical water is 250 to 350°C.

19. The method for producing a recycled monomer according to claim 16, wherein the pressure in the step of contacting with subcritical water is 3 to 30 MPa. 20 . The method for producing a recycled monomer according to claim 16 , wherein the alkali metal salt and / or alkaline earth metal salt is a metal hydroxide and / or a metal carbonate.

21. The method for producing recycled monomers according to claim 16, wherein the thermoplastic polyester A is at least one selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and copolymers thereof. 22 . The method for producing recycled monomers according to claim 16 , wherein the composition comprising the thermoplastic polyester A comprises at least one selected from the group consisting of an antioxidant, a heat resisting agent, a weather resisting agent, a mold release agent, and a crystal nucleating agent.

23. The method for producing recycled monomers according to claim 16, wherein the composition comprising the thermoplastic polyester A is waste.

24. The method for producing a recycled monomer according to claim 16, wherein the recycled monomer is a dicarboxylic acid and / or a diol.

25. A method for producing a thermoplastic polyester, using the dicarboxylic acid and / or diol obtained by the production method according to claim 24 as a raw material.

26. A method for producing a composition containing a thermoplastic polyester, comprising blending at least one selected from the group consisting of an antioxidant, a weathering agent, a release agent and a crystal nucleating agent with the thermoplastic polyester obtained by the production method according to claim 25.

27. A method for producing a thermoplastic polyester product, comprising using the thermoplastic polyester obtained by the production method according to claim 25 as a raw material to produce a product containing the thermoplastic polyester such as a fiber, a film or a molded article.

28. A method for producing a product comprising a thermoplastic polyester composition, wherein the product comprising a thermoplastic polyester composition obtained by the production method according to claim 26 is used as a raw material to produce a fiber, a film or a molded article.

29. The method for producing recycled monomers according to claim 5, wherein the composition comprising polymers comprises polymer I and polymer II, Polymer I is a thermoplastic polyester A, The polymer II is one polymer selected from the group consisting of thermoplastic polyester B having a melting point different from that of the thermoplastic polyester A, polycarbonate and polyurethane, or a combination of these polymers, The content of the polymer II in the composition, that is, the total content of the thermoplastic polyester B, the polycarbonate and the polyurethane, is 1 to 100 parts by weight relative to 100 parts by weight of the polymer I. The method for producing the recycled monomer comprises a step of simultaneously contacting the polymer I and the polymer II in the composition with subcritical water at 250 to 350°C.

30. The method for producing recycled monomers according to claim 5, wherein the composition comprising polymers comprises polymer I and polymer II, Polymer I is a thermoplastic polyester A, The polymer II is one polymer selected from the group consisting of thermoplastic polyester B having a melting point different from that of the thermoplastic polyester A, polycarbonate and polyurethane, or a combination of these polymers, The content of the polymer II in the composition, that is, the total content of the thermoplastic polyester B, the polycarbonate and the polyurethane, is 1 to 100 parts by weight relative to 100 parts by weight of the polymer I. The method for producing a recycled monomer comprises a step of simultaneously hydrolyzing the polymer I and the polymer II in the composition by contacting them with subcritical water at 200 to 350° C. under a condition in which a basic component is mixed.

31. The method for producing recycled monomers according to claim 29 or 30, wherein the composition comprising a polymer comprises a composition comprising polymer I and polymer II, and / or a mixture of a composition comprising polymer I and a composition comprising polymer II.

32. The method for producing a recycled monomer according to claim 29 or 30, wherein 100 to 900 parts by weight of water is added to 100 parts by weight of the polymer component in the composition containing the polymer.

33. The method for producing a recycled monomer according to claim 29 or 30, wherein the pressure in the step of contacting with subcritical water is 4.0 MPa to 30 MPa.

34. The method for producing recycled monomers according to claim 29, further comprising compounding a basic component into the composition containing the polymer.

35. The method for producing recycled monomers according to claim 29 or 30, wherein the thermoplastic polyester A is selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate and copolymers thereof.

36. The method for producing recycled monomers according to claim 29 or 30, wherein the thermoplastic polyester B is at least one selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate and copolymers thereof, and has a melting point different from that of the polyester A.

37. The method for producing recycled monomers according to claim 29 or 30, wherein the difference in melting point between the thermoplastic polyester A and the thermoplastic polyester B is 10°C or more.

38. The method for producing recycled monomers according to claim 29 or 30, wherein the composition containing the polymer is waste.

39. The method for producing a recycled monomer according to claim 29 or 30, wherein the recycled monomer is terephthalic acid and / or diol.

40. A method for producing a thermoplastic polyester, comprising using the dicarboxylic acid and / or diol obtained by the production method according to claim 29 or 30 as a polymerization raw material to produce the thermoplastic polyester.

41. A method for producing a thermoplastic polyester product, comprising using the thermoplastic polyester obtained by the production method according to claim 40 as a raw material to produce a thermoplastic polyester product of fiber, film or molded article.

42. A method for producing a product comprising a thermoplastic polyester composition, comprising using the thermoplastic polyester composition obtained by the production method according to claim 40 as a raw material to produce a fiber, a film or a molded article comprising the thermoplastic polyester composition.

43. A manufacturing device for recycling monomers, comprising a unit L for heating and pressurizing a composition containing a polymer and supplying it, a unit M for generating and supplying subcritical water, a unit N for mixing the composition containing a thermoplastic polymer supplied from the unit L with the subcritical water supplied from the unit M, and a continuous reactor O for hydrolyzing the polymer.

44. The production apparatus of recycled monomers according to claim 43, comprising a device P for monitoring the internal temperature of the upstream and downstream parts of the continuous reactor O, and a temperature adjustment mechanism Q for heating and / or cooling the continuous reactor O, The temperature adjustment mechanism Q is operated based on the device P, and the internal temperature of the continuous reactor O is controlled.

45. The apparatus for producing a recycled monomer according to claim 43, wherein a plurality of the temperature adjustment mechanisms Q are provided. Based on the device P, the plurality of temperature adjustment mechanisms Q are operated. The apparatus for producing a recycled monomer according to claim 44 or 45, wherein the temperature regulating mechanism Q is controlled so that the internal temperature of the downstream portion of the continuous reactor O is lower than the internal temperature of the upstream portion by 10°C or more.

47. The apparatus for producing recycled monomers according to claim 44 or 45, wherein the continuous reactor O is a tubular continuous reactor. The apparatus for producing recycled monomers according to claim 44 or 45, wherein the unit L is an extruder.

49. The apparatus for producing recycled monomers according to claim 44 or 45, wherein the unit N is a static mixer.

50. The apparatus for producing a recycled monomer according to claim 44 or 45, wherein the composition containing a polymer is waste of resin molded products.

51. The apparatus for producing recycled monomers according to claim 44 or 45, wherein the polymer is thermoplastic polyamide or thermoplastic polyester.

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