JP2012072400A - Chemical recycle method for polyesters by diluted amine aqueous solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical recycle method for polyesters, such as polycarbonate resins, performed under milder conditions compared with the conventional method using hot water containing ammonia.SOLUTION: The chemical recycle method is characterized in that a step of depolymerizing polyesters using diluted amine aqueous solution containing amines is included.

Description

  The present invention relates to a method for chemically recycling polyesters with a dilute aqueous amine solution.

  Among polyesters, polycarbonate is a general-purpose engineering plastic with excellent physical properties such as transparency, flame retardancy, and impact resistance. It is used in industrial fields such as electronic and information equipment, medical equipment, building materials, and automobiles, and daily necessities. It is used in a wide range of fields. The amount of production is increasing year by year, but the amount discarded is enormous, and chemical recycling technology that converts waste polycarbonate into raw material with high efficiency is desired from the viewpoint of energy and resource recycling. It is rare.

  So far, the chemical recycling method of polycarbonate has been (1) supercritical water, (2) hydrolysis with subcritical hot water, (3) ethanolysis with supercritical ethanol, (4) ammolysis with supercritical ammonia, (5) alkali and A method based on glycolysis in glycol with addition of a catalyst, (6) hot water containing ammonia (for example, see Non-Patent Document 1), etc. has been proposed.

  Polyethylene terephthalate (PET), which is most produced among polyesters, is a resin that has excellent heat resistance, strength, dyeing properties, and economical properties, such as fibers, films, Chemical recycling technology used in a wide range of fields such as containers. Especially, PET bottles are widely used as beverage containers, and the amount to be discarded is enormous, resulting in high-efficiency conversion from waste polyethylene terephthalate to raw materials. However, it is desired from the viewpoint of energy and resource recycling.

  So far, the chemical recycling method for polyethylene terephthalate has been (7) Glycolysis in glycol with catalyst addition, (8) Methanolysis with subcritical and supercritical methanol, (9) Supercritical water, and (10) Hydrolysis with hot water ( For example, methods using non-patent document 2), (11) hot water containing ammonia (for example, refer to non-patent documents 2 and 3), etc. have been proposed.

R. Arai, et al. , Chem. Eng. Sci. , 65, 36 (2010) O. Sato, et al. , "Chemical Recycling Process of Poly (ethyl terephthalate) in high temperature liquid water," J. Chemical Engineering of Japan, 43, 313-317 (2010) K. Zenda, T .; Funazukuri, "Depolymerization of poly (ethylene terephthalate) in dilute aqua ammonia solution under hydrothermal conditions," J. Chemical Technology & Biotechnology, 83, 1381-1386 (2008)

  However, the polycarbonate chemical recycling methods (1) to (3) above must be carried out in a supercritical or subcritical state under a very high temperature and high pressure environment, and such supercritical or subcritical state can be handled. It is very difficult to scale up a heat-resistant pressure-resistant container to an industrial scale capable of processing a huge amount of waste polycarbonate, and the equipment cost and running cost are very high, making it difficult to profit as a chemical recycling technology was there.

  In the above (4) and (5) chemical recycling methods for polycarbonate, the use of corrosive strong alkalis causes deterioration of equipment corrosion, and further deterioration of quality due to contamination of metal ions eluted by equipment corrosion into the product. There was a problem. Moreover, in order to prevent such corrosion, it is necessary to apply anti-corrosion treatment such as glass lining on the inner surface of the device, which is very expensive and glass lining due to vibration and impact on the device, and scratches during cleaning. The corrosion-resistant treatment part such as the above is damaged, and the alkali erosion from the damaged part easily causes peeling or the like, which causes a problem that it is very difficult to handle. Furthermore, there is a problem of high costs, such as the need to neutralize the alkali used and the cost of treating the generated salt as industrial waste.

  In the polycarbonate chemical recycling method (5) above, it is necessary to use a catalyst, which increases the cost, requires a treatment operation to separate the catalyst from the product, and collects and reuses the catalyst. Equipment is also required. Further, when the catalyst is deteriorated, there is a problem that the cost becomes high, such as replacement work and cost for treating the deteriorated catalyst as industrial waste.

  In the chemical recycling method of polycarbonate described in Non-Patent Document 1 in (6) above, by using ammonia-containing hot water, not by decomposition using hydrolysis reaction but by nucleophilic substitution reaction (nucleophilic substitution method). Since it is a decomposition, it can be decomposed more efficiently than the above methods (1) to (5), but it is 180 ° C in order to obtain a relatively high reaction rate at a relatively high temperature (at least 180 ° C or higher, a high yield). It is necessary to use hot water containing ammonia at a temperature of (° C. or higher) (see Comparative Example 1 and FIG. 2 described later), which is a cause of cost increase, and there is a strong demand for a technology that can be chemically recycled under milder conditions. .

  In the above (7) chemical recycling method for polyethylene terephthalate, (a) a catalyst using a harmful organic metal such as lead acetate as a catalyst, (b) a NaOH as a catalyst. Some use alkali. (A) is harmful, (b) requires alkali neutralization and desalting treatment, both of which require operations such as separation and distillation of the solvent and the produced monomer, and require high separation energy and high cost. There was a problem. In addition, as with the chemical recycling method for polycarbonate, it is necessary to use a catalyst, which increases costs, requires a processing operation to separate the catalyst from the product, and equipment for collecting and reusing the catalyst. Is also required. Further, when the catalyst is deteriorated, there is a problem that the cost becomes high, such as replacement work and cost for treating the deteriorated catalyst as industrial waste. In the case of (b) above, as with the polycarbonate chemical recycling method, the use of corrosive strong alkalis causes deterioration of the equipment, and further deterioration of the quality due to the incorporation of metal ions eluted from the equipment into the product. There were problems such as. Moreover, in order to prevent such corrosion, it is necessary to apply anti-corrosion treatment such as glass lining on the inner surface of the device, which is very expensive and glass lining due to vibration and impact on the device, and scratches during cleaning. The corrosion-resistant treatment part such as the above is damaged, and the alkali erosion from the damaged part easily causes peeling or the like, which causes a problem that it is very difficult to handle. Furthermore, there is a problem of high costs, such as the need to neutralize the alkali used and the cost of treating the generated salt as industrial waste.

  The polyethylene terephthalate chemical recycling method of (8) above requires the use of methanolysis with subcritical and supercritical methanol, the reaction temperature is high, and the product is dimethyl terephthalate instead of ethylene glycol and terephthalic acid. In order to return to the acid, there are problems such as a high number of steps and complicated operations for chemical recycling, such as further reaction required, and high costs. In addition, as in the case of the polycarbonate chemical recycling method, it is necessary to carry out in a very high temperature and high pressure environment such as a subcritical or supercritical state. It was very difficult to scale up to an industrial scale capable of treating the waste polyethylene terephthalate, and the equipment cost and running cost were very high, making it difficult to profit as a chemical recycling technology.

  In the chemical recycling method for polyethylene terephthalate (9) above, it is necessary to use supercritical water, and it is necessary to carry out under the most severe conditions (high temperature and high pressure) in the supercritical state, similar to the chemical recycling method for polycarbonate. In addition, it is very difficult to scale up a heat-resistant pressure-resistant container that can handle such supercritical state to an industrial scale that can process a huge amount of waste polyethylene terephthalate, and the equipment cost and running cost are very high, There was a problem that it was difficult to profit as a chemical recycling technology.

  Polyethylene terephthalate monomers are terephthalic acid and ethylene glycol, but terephthalic acid is relatively stable at high temperatures and in the presence of acid, but ethylene glycol is easily converted into a by-product. As in the method, there was a problem that the yield was low at high temperature or in the presence of an acid.

  In the above-mentioned chemical recycling method for polyethylene terephthalate (10), 573K and 10 minutes are the optimum conditions. If the reaction time is increased, more by-products may be generated. In the experiment (10), a small reactor having an internal volume of 18 mL is used. However, since the reactor is a large reactor in the practical use stage, the residence time of the solution (after the solvent enters the reactor for fluid mixing) Therefore, there is a problem that control is difficult with a short reaction time, leading to an increase in yield of by-products.

  In the chemical recycling method of polyethylene terephthalate of (11) above, by using ammonia-containing hot water, it is not a decomposition using a hydrolysis reaction but a decomposition by a nucleophilic substitution reaction (nucleophilic substitution method). Although it can be decomposed more efficiently than the methods (7) to (10), it is necessary to use ammonia-containing hot water at a relatively high temperature (220 ° C. or higher to obtain a relatively high reaction rate with a high yield). (Refer to Comparative Example 4 and FIG. 17 described later), which is a cost increase factor, and a technology capable of chemical recycling under a milder condition has been strongly demanded.

  Therefore, the present invention aims to provide a chemical recycling method capable of performing polyesters such as polycarbonate resin and polyethylene terephthalate under milder conditions than the conventional chemical recycling method using hot water containing ammonia. To do.

  Therefore, the object of the present invention is to: (1) General formula (1);

(In the formula, R ¹ , R ² and R ³ are each independently a hydrogen atom; or a substituted or unsubstituted hydrocarbon group, provided that at least one of R ¹ , R ² and R ³ Is a substituted or unsubstituted hydrocarbon group.) By a chemical recycling method characterized by having a step of depolymerizing polyesters using a dilute amine aqueous solution containing amines represented by Is achieved.

  The object of the present invention is also achieved by (2) the chemical recycling method according to (1) above, wherein the concentration of the amines is in the range of 0.003 to 26 M with respect to the whole diluted amine aqueous solution. .

  The object of the present invention is also achieved by (3) the chemical recycling method according to the above (1) or (2), wherein the concentration of the amines is in the range of 0.03 to 16 M with respect to the whole diluted amine aqueous solution. Is.

  The object of the present invention is (4) chemical recycling according to any one of the above (1) to (3), wherein the concentration of the amines is in the range of 0.06 to 3.5 M with respect to the whole diluted amine aqueous solution. It can also be achieved by law.

  The object of the present invention is (5) In any one of the above (1) to (4), the content of the polyester is in the range of 0.1 to 50 wt% with respect to the total amount of the diluted amine aqueous solution and the polyester. It can also be achieved by the chemical recycling method described.

  The object of the present invention is also achieved by (6) the chemical recycling method according to any one of (1) to (5) above, wherein the depolymerization reaction temperature is not higher than the melting point of the polyester.

  The object of the present invention is as set forth in any one of (1) to (6), wherein (7) the unsubstituted hydrocarbon group is an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 10 carbon atoms. This can also be achieved by the chemical recycling method.

  The object of the present invention is (8) In any one of the above (1) to (7), the unsubstituted hydrocarbon group is a lower alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 10 carbon atoms. It can also be achieved by the chemical recycling method described.

  The object of the present invention is (9) The chemical recycling method according to any one of the above (1) to (8), wherein the unsubstituted hydrocarbon group is a linear lower alkyl group having 1 to 5 carbon atoms. Can also be achieved.

  The object of the present invention is also achieved by (10) the chemical recycling method according to any one of (1) to (9) above, wherein the substituent of the substituted hydrocarbon group is a hydroxyl group, a thiol group, or a halogen atom. It is what is done.

The object of the present invention is (11) wherein the amine is a linear lower alkyl group having 1 to 5 carbon atoms in which R ¹ in the general formula (1) is unsubstituted, and R ² and R ³ are both This can also be achieved by the chemical recycling method according to any one of the above (1) to (10), which is a primary amine that is a hydrogen atom.

  The object of the present invention is as set forth in any one of (1) to (11) above, wherein the polyester is polycarbonate, polyethylene terephthalate, polyethylene naphthalate, poly-D-lactic acid, or poly-L-lactic acid. It can also be achieved by the Chemical Recycling Law.

  The object of the present invention is also achieved by (13) the chemical recycling method according to any one of the above (1) to (12), wherein the polyester is polycarbonate or polyethylene terephthalate.

  According to the chemical recycling method of the present invention, an aromatic polyester such as polycarbonate resin or polyethylene terephthalate, or a polyester such as polylactic acid is performed under milder conditions than the conventional chemical recycling method using hot water containing ammonia. be able to. Specifically, without adding any catalyst or organic solvent at all, using a very small amount of amines in a dilute aqueous amine solution and a depolymerization reaction (nucleophilic substitution reaction or hydrothermal reaction) at a relatively low temperature, almost completely It is possible to decompose polyester to raw material monomer (for example, polycarbonate from bisphenol A and phosgene to bisphenol A, which is a raw material monomer), and it is an epoch-making that provides almost complete reaction selectivity and relatively high reaction rate. Recycling technology.

It is a graph showing the time-dependent change of each yield of bisphenol A, phenol and residue in the case of the 0.6M methylamine aqueous solution at 120 ° C. in Example 1. Time course of the yield of bisphenol A, the target product, in various 0.6M basic aqueous solutions (methylamine aqueous solution, ethylamine aqueous solution, ammonia aqueous solution, sodium hydroxide aqueous solution) at 120 ° C. in Example 1 and Comparative Examples 1-2 It is a graph drawing showing a change. 6 is a graph showing the change over time in the yield of bisphenol A, which is the target product, depending on the reaction temperature (100 to 140 ° C.) in the case of the 0.6M methylamine aqueous solution of Example 2. It is a graph which shows the Arrhenius plot about the apparent reaction rate constant k calculated | required from Numerical formula (1) based on the experimental result of Example 2. FIG. 6 is a graph showing the change over time in the yield of bisphenol A, which is the target product, according to the difference in methylamine concentration (0.3 to 1.2 M) in the methylamine aqueous solution at 120 ° C. in Example 3. FIG. It is a graph showing the time-dependent change of the decomposition rate of polycarbonate for each concentration (0.3 to 1.2 M) of methylamine in a methylamine aqueous solution at 120 ° C. in Example 3. Note that Y on the vertical axis in FIG. 4B is represented by Y = (BPA yield) / 100, and (1-Y) ^1/3 -1 [−] on the vertical axis is unit time (minutes). ) Represents the dimensionless reaction rate per unit. 6 is a graph showing the concentration dependency of an aqueous methylamine solution on the apparent reaction rate constant at 120 ° C. in Example 3. FIG. In addition, k [min < ^-1 >] of the vertical axis | shaft of FIG. 5 represents an apparent reaction rate constant. Example 4 Structure of butylamine in a 0.6 M aqueous solution of butylamine at 120 ° C., specifically n-butylamine (BuNH ₂ ), sec-butylamine (sec-BuNH ₂ ) to tert-butylamine ( It is a graph showing the change over time of the yield of bisphenol A which is the target product due to the difference in tert-BuNH ₂ ). Primary methylamine (CH ₃ NH ₂ ), secondary dimethylamine ((CH ₃ ) ₂ NH), tertiary trimethylamine (( It is a graph showing the change over time of the yield of bisphenol A which is the target product due to the difference in CH ₃ ) ₃ N). Primary methylamine (CH ₃ NH ₂ ), secondary dimethylamine ((CH ₃ ) ₂ NH), tertiary trimethylamine (( It is a graph showing the change over time of the mass reduction of polycarbonate due to the difference in CH ₃ ) ₃ N). In Example 7, a 0.6M methylamine aqueous solution was used as a diluted amine aqueous solution without addition of NaOH at 120 ° C., and a mixed solution of 0.6M methylamine + 0.6M NaOH aqueous solution was used as a diluted amine aqueous solution with addition of NaOH. 2 is a graph showing the change over time in the yield of bisphenol A (BPA) with respect to the case where it was present. It is drawing which shows the saturated vapor pressure curve of water. It is a graph showing the time-dependent change of the bisphenol A (BPA) yield which is a target object by the difference in the concentration (0.5-3.0M) of monoethanolamine in the monoethanolamine aqueous solution in 130 degreeC of Example 8. . It is a graph which shows the monoethanolamine density | concentration dependence which affects the apparent reaction rate constant in 130 degreeC of Example 8. It is the schematic of the semi-batch type reactor used in Examples 9-12. The yield of terephthalic acid (TPA) and ethylene glycol (EG), which are depolymerization reaction product monomers when the reaction temperature is 200 ° C. and the trimethylamine concentration is 0.6 M, using a semi-batch reactor in Example 9, It is a graph showing the change over time of the integrated yield of TPA + EG. A depolymerization reaction product obtained by using a semi-batch type reactor in Example 10 at a reaction temperature of 200 ° C. and a constant amine concentration of 0.6 M in various amine (methylamine, dimethylamine, trimethylamine, ethylamine) aqueous solutions. It is a graph drawing showing the time-dependent change of the integrated yield of TPA + EG which is a monomer. Using the semi-batch type reactor in Example 11, the trimethylamine concentration of the aqueous trimethylamine solution at each reaction temperature (170 ° C., 180 ° C., 190 ° C., 200 ° C., 210 ° C., 220 ° C., 230 ° C., 240 ° C.) of 0. In the case of 6M, FIG. 16A is a graph showing the change over time in the integrated yield of TPA + EG which is a depolymerization reaction product monomer. Using the semi-batch type reactor in Example 11, the trimethylamine concentration of the aqueous trimethylamine solution at each reaction temperature (170 ° C., 180 ° C., 190 ° C., 200 ° C., 210 ° C., 220 ° C., 230 ° C., 240 ° C.) of 0. In the case of 6M, FIG. 16B is a graph showing the change with time of (1-Y) ^1/3 −1. It is a graph showing the comparison of the reaction rate constant k about the trimethylamine aqueous solution and the ammonia aqueous solution in the density | concentration 0.6M by the Arrhenius plot of Example 11 and Comparative Example 4. FIG. Using a semi-batch type reactor in Example 12, the reaction temperature was 200 ° C., and a depolymerization reaction was produced in the case of trimethylamine aqueous solutions of various concentrations (trimethylamine concentrations 0.3 M, 0.6 M, 0.9 M, 1.2 M). It is a graph showing the change over time of the integrated yield of TPA + EG which is a product monomer.

  Embodiments of the present invention will be described below.

  The chemical recycling method of the present invention is characterized by having a step of depolymerizing polyesters using a diluted amine aqueous solution containing amines. The chemical recycling method of the present invention does not require a catalyst or an additive in addition to a very small amount of amines, and does not use an organic solvent, so that separation and purification of monomers generated by depolymerization of polyesters is also possible. It is a highly efficient chemical recycling method that is easy and consumes less energy. That is, the chemical recycling method of the present invention does not require a catalyst or an additive, does not use an organic solvent, utilizes a very small amount of amines and a depolymerization reaction, and is almost completely polyester at a relatively low temperature. Can be decomposed into raw material monomers, so there is no side reaction or further decomposition reaction (secondary decomposition reaction) of raw material monomers, the recovery rate of raw material monomers is very high, almost complete reaction selectivity and relatively fast reaction rate. Is an epoch-making chemical recycling technology.

  More specifically, the chemical recycling method of the present invention is effective even when the concentration of amines is dilute (especially 6.5 M or less). That is, the reaction mechanism of this method (the chemical recycling method of the present invention) can be considered as follows, taking polycarbonate as an example of polyester. Therefore, since the amines of the reactants return to the amines again, they are not consumed in principle. Therefore, although it depends on the desired reaction rate, it can be said that the content of the polyester may be several times that of the amines as shown in the above range.

PC + amines → BPA (product monomer) + isocyanate (intermediate product) (1)
Isocyanate + water → amines + CO ₂ (2)
If the amine concentration is 100% and there is no water as in the existing chemical recycling method, the above reaction (2) does not occur and the following reaction (3) occurs, so the amine is consumed and reacts immediately. It can be said that the problem that a by-product is produced in a large amount as in the following reaction (3) cannot be solved.

Isocyanate + amines → by-products (3)
As described above, since the amines of the reactants return to the amines again, they are not consumed in principle (in other words, the charged amine is not lost and the reaction rate does not slow down). When the concentration of 100% (= too high), the intermediate isocyanate reacts with the amine, and the reaction is completed as soon as the amine is consumed without being regenerated, and the reaction (3) Thus, it can be said that the problem that by-products are generated in large quantities cannot be solved. Therefore, after removing a large amount of by-products, it was necessary to evaporate or distill the solvent and bisphenol A or the organic solvent. However, in the reaction mechanism of the present invention, the amines of the reactants return to the amines again. (Refer to the above reaction (2)). Since it is not consumed in principle, the concentration of amines can be effectively and sufficiently exhibited even at a dilute concentration. Therefore, it can be said that the concentration is preferably 6.5 M or less. The effect of the aqueous solution is that in the case of polycarbonate (PC), an isocyanate is formed in the intermediate product, but it is hydrolyzed by water and decomposed into CO ₂ and amines (see the above reaction (2)). Furthermore, since the regenerated amines attack the polycarbonate (PC) again (decomposes by the depolymerization reaction), there is an advantage that the reaction rate does not slow down. Further, since bisphenol A, which is a product monomer, is almost insoluble in water, there is an advantage that bisphenol A can be recovered as a precipitate. On the other hand, as in the existing chemical recycling method, in the case of polycarbonate (PC) when the concentration of amines is 100% or amines + organic solvent, the intermediate product isocyanate and amines react to regenerate the amines. There is a problem that the reaction is completed as soon as it is consumed, and a by-product is produced in a large amount as in the above reaction (3). Further, it is necessary to evaporate or distill the solvent and bisphenol A or the organic solvent, and it is necessary to carry out distillation in order to remove a large amount of by-products.

  On the other hand, the chemical recycling method of the present invention is effective even at a dilute concentration of amines as compared with the existing chemical recycling method using 100% amines or amines + organic solvent. There is also an advantage that the amount of the kind used may be small. Furthermore, in the chemical recycling method of the present invention, since organic additives in the polymer (polyesters) are not necessary for the aqueous solution, there is a possibility that they can be recovered as a residue.

  In the chemical recycling method of the present invention, since the reaction temperature is lower than the melting point of the polymer (polyesters) and the reaction temperature is low, the polymer (polyester) sample (actually pulverizing and classifying the waste material to an appropriate size) The polymer powder is not melted and the reaction proceeds with the shape of the sample being excellent. On the other hand, when the reaction temperature is high and the amine concentration is high as in the existing chemical recycling method described above, the Maillard reaction (aminocarbonyl reaction) occurs, which may reduce the monomer yield.

Hereinafter, the chemical recycling method of the present invention will be described for each constituent requirement.
(1) About diluted amine aqueous solution The diluted amine aqueous solution which can be used for the chemical recycling method of this invention contains amines shown by the said General formula (1).

(A) Amines The amines contained in the diluted amine aqueous solution that can be used in the chemical recycling method of the present invention are not particularly limited, but the following general formula (1);

(In the formula, R ¹ , R ² and R ³ are each independently a hydrogen atom; or a substituted or unsubstituted hydrocarbon group, provided that at least one of R ¹ , R ² and R ³ One is a substituted or unsubstituted hydrocarbon group).

In the general formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom; or a substituted or unsubstituted hydrocarbon group. However, at least one of R ¹ , R ² and R ³ is a hydrocarbon group.

The unsubstituted hydrocarbon group is not particularly limited as long as it is a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms. Specifically, a linear, branched or cyclic aliphatic hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms may be mentioned. It is done. Specific examples include linear, branched or cyclic alkyl groups having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, and 6 to 10 carbon atoms. It is not limited. In addition, although a C1-C20 alkanol group is applicable, the said alkanol group shall be contained in the C1-C20 alkyl group substituted by the hydroxyl group. The unsubstituted hydrocarbon group is preferably a linear aliphatic hydrocarbon group having 1 to 10 carbon atoms, more preferably a linear alkyl group having 1 to 5 carbon atoms from the viewpoint of reaction rate. This is because the reaction rate of n-BuNH ₂ > sec-BuNH ₂ > tert is larger when the alkyl group bonded to the amino group (nitrogen atom) is more bulky (for example, butylamine (BuNH ₂ )). the order of -BuNH _2), the reaction rate is due to a tendency to decrease (see FIG. 6). In addition, if the amines are of the same series, the effect is smaller when the number of carbon atoms is smaller (see FIG. 2; however, the effect is small because of the example of carbon numbers 1 and 2, but the number of carbon atoms is larger. The difference in the effect becomes clear as the value increases. It can be said that the effect is larger when the number of carbon atoms is smaller.)

  Specific examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, neopentyl, Examples thereof include, but are not limited to, a cyclopentyl group, an n-hexyl group, a cyclohexyl group, an n-heptyl group, and an n-octyl group.

  Specific examples of the aryl group include phenyl, naphthyl, anthracenyl, 2-tolyl, 3-tolyl, 4-tolyl, 2,3-xylyl, 2,4-xylyl, 2, 5-xylyl group, 2,6-xylyl group, 3,4-xylyl group, 3,5-xylyl group, 2,3,4-trimethylphenyl group, 2,3,5-trimethylphenyl group, 2,3, 6-trimethylphenyl group, 2,4,6-trimethylphenyl group, 3,4,5-trimethylphenyl group, 2,3,4,5-tetramethylphenyl group, 2,3,4,6-tetramethylphenyl Group, 2,3,5,6-tetramethylphenyl group, pentamethylphenyl group, ethylphenyl group, n-propylphenyl group, isopropylphenyl group, n-butylphenyl group, sec-butylphenyl group, ert- butyl phenyl group, n- pentyl phenyl group, neopentyl phenyl group, n- hexylphenyl group, n- octyl phenyl or diphenyl phenyl including without in any way being limited thereto.

  The substituent of the substituted hydrocarbon group is not particularly limited as long as it can achieve the intended purpose without affecting the function and effect of the present invention. For example, a hydroxyl group (hydroxyl group), a thiol group, Examples thereof include, but are not limited to, halogen atoms (for details, refer to specific examples of amines described later).

  The amines contained in the diluted amine aqueous solution may be monoamines or polyamines (diamines, triamines, etc.). The amines may be chain (or chain) amines or cyclic (or cyclic) amines, and may be aliphatic amines or aromatic amines. Furthermore, the amines may be amines having hetero atoms (such as oxygen atoms) other than nitrogen atoms in the molecule (for example, heterocyclic amines). The amines may have a substituent (for example, a functional group such as a hydroxyl group (hydroxyl group), a thiol group, or a halogen atom). The amines may be any of primary amines, secondary amines, and tertiary amines.

  Typical amines contained in the diluted amine aqueous solution include primary to tertiary alkylamines having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, carbon atoms. A cycloalkylamine having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, an arylamine having 6 to 10 carbon atoms, 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms. , More preferably primary to tertiary alkanolamines having 1 to 5 carbon atoms, 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 heterocyclic amines, etc. However, it is not limited to these at all. The amines may be used alone or in combination of two or more. Preferred are primary or tertiary amines from the viewpoint of high reaction rate and suppression of by-products, and more preferred are primary amines having the highest reaction rate with high yield (FIG. 7). , 8). For example, for the production of bisphenol A as a raw material monomer from a polycarbonate which is a kind of polyester, the reaction rate is in the order of primary> tertiary> secondary amine, but the mass reduction rate of the polycarbonate. Is primary≈secondary> tertiary amine. Therefore, regarding the yield of the raw material monomer bisphenol A, in the case of the secondary amine, bisphenol A has reached a peak at about 20%. This is because it is a product (by-product) (see FIGS. 7 and 8).

  Among the amines contained in the diluted amine aqueous solution, specific examples of the aliphatic primary amines include, for example, methylamine, ethylamine, n-propylamine, isopropylamine, 2-methylpropylamine, n-butylamine. , Isobutylamine, sec-butylamine, tert-butylamine, n-pentylamine, isopentylamine, neopentylamine, amylamine, hexylamine, 2-ethylbutylamine, heptylamine, octylamine, nonylamine, decylamine, polyoxyethylene oleylamine, Polyoxyethylene laurelamine, polyoxyethylene stearylamine, methoxypropylamine, dimethylaminopropylamine, dibutylaminopropylamine, ethoxypropylamine, ethylhexyl Examples include ruoxypropylamine, bispropylamine, 2-propenylamine, 2-methyl-2-propenylamine, 2-properoyloxyethylamine, and 2- (2-methylproperoyloxy) ethylamine. It is not limited. Preferably, methylamine, ethylamine, n-propylamine, isopropylamine, 2-methylpropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, n are preferred because the smaller the number of carbons, the greater the effect. -Pentylamine, isopentylamine, neopentylamine, amylamine, hexylamine, 2-ethylbutylamine, heptylamine, octylamine, nonylamine, decylamine and the like, more preferably methylamine, ethylamine, n-propylamine, Examples include n-butylamine, n-pentylamine, amylamine and the like.

  Specific examples of the aliphatic secondary amines include, for example, dimethylamine, ethylmethylamine, diethylamine, di-n-propylamine, diisopropylamine, methylisopropylamine, ethylisopropylamine, di-n-butylamine, diisobutylamine. , Di-sec-butylamine, di-tert-butylamine, methylbutylamine, di-n-pentylamine, di-tert-pentylamine, ethylhexylamine, di (2-propenyl) amine, di (2-methyl-2- Propenyl) amine, 2-propenylamine, 2-methyl-2-propenylamine, 2-properoyloxyethylamine, 2- (2-methylproperoyloxy) ethylamine acrylate), and the like. It is not a thing. Preferably, dimethylamine, ethylmethylamine, diethylamine, di-n-propylamine, diisopropylamine, methylisopropylamine, ethylisopropylamine, di-n-butylamine, diisobutylamine are preferred because the smaller the number of carbons, the greater the effect. , Di-sec-butylamine, di-tert-butylamine, methylbutylamine, di-n-pentylamine, di-tert-pentylamine and the like, more preferably dimethylamine, ethylmethylamine, diethylamine, di-n -Propylamine and the like.

  Specific examples of the aliphatic tertiary amines include, for example, trimethylamine, ethyldimethylamine, diethylmethylamine, triethylamine, ethyldiisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, triisobutyl. Amine, tri-sec-butylamine, tri-tert-butylamine, triamylamine, tri-n-pentylamine, tri-n-hexylamine, cyclohexyldimethylamine, tricyclohexylamine, tri-n-octylamine, triisooctyl Amine, N, N-dimethyl-2-properoyloxyethylamine, N, N-dimethyl-2- (2-methylproperoyloxy) ethylamine, N, N-diethyl-2-properoyloxyethylamine, N, N- Jie Ru-2- (2-methylproperoyloxy) ethylamine, N, N-dimethyl-3-properoyloxypropylamine, N, N-dimethyl-3- (2-methylproperoyloxy) propylamine, N, N -Diethyl-3-properoyloxypropylamine N, N-diethyl-3- (2-methylproperoyloxy) propylamine, N, N-dimethyl-3- (properoylamino) propylamine, N, N-dimethyl -3- (2-methylproperoylamino) propylamine, N, N-diethyl-3- (properoylamino) propylamine, N, N-diethyl-3- (2-methylproperoylamino) propylamine and the like. Although it is mentioned, it is not limited to these at all. Since the effect is larger when the number of carbon atoms is smaller, trimethylamine, ethyldimethylamine, diethylmethylamine, triethylamine, tri-n-propylamine and the like are preferable, and trimethylamine, ethyldimethylamine, diethylmethyl are more preferable. Examples include amines and triethylamine.

  Specific examples of the aromatic primary amines include, for example, benzylamine, methylbenzylamine, ethylbenzylamine, aniline, o, m, p-toluidine, o, m, p-ethylaniline, xylidine, mesidine, o , M, p-chloroaniline, chlorotoluidine, dichloroaniline, trichloroaniline, o, m, p-fluoroaniline, o, m, p-bromoaniline, fluorochloroaniline, o, m, p-aminophenol, o, m, p-aminothiophenol, anisidine, phenetidine, o, m, p-aminobenzoic acid, aminochlorophenol, aminobenzonitrile, cresidine, toluidinesulfonic acid, sulfanilic acid, chlorotoluidinesulfonic acid, aminonaphthalenesulfonic acid, amino Benzotrifluoride, aminoben Nsuruhon acid, p- amino acetanilide, naphthylamine, naphthylamine sulfonic acid, and amino naphthol sulfonic acid, shall by no means be limited to these.

  Specific examples of the aromatic secondary amines include, for example, N-methylaniline, N-ethylaniline, N-ethyltoluidine, dibenzylamine, diphenylamine, di-p-tolylamine, pyrrolidine, and 2,5-dimethylpyrrolidine. 2,5-dimethyl-3-pyrroline, pyrrole, 2,5-dimethylpyrrole, piperidine, 2-methylpiperidine, 2,6-dimethylpiperidine, 3,5-dimethylpiperidine, 2,2,6,6-tetra Examples include, but are not limited to, methylpiperidine, morpholine, hexamethyleneimine, hydroxyphenylglycine, N-methylaminophenol sulfate and the like.

  Specific examples of the aromatic tertiary amines include, for example, N, N-dimethylaniline, N-ethyl-N-hydroxyethyltoluidine, N, N-diethyltoluidine, N-benzyl-N-ethylaniline, N, N-diglycidylaniline, triallylamine, triphenylamine, tribenzylamine, diisopropylethylamine, N-methylmorpholine, tri-p-tolylamine, tropane, quinacridine, 1-methylpyrrole, 1-phenylpyrrole, 1,2,5 -Trimethylpyrrole, 1-methylpiperidine, N-methylpiperidine, imidazole, pyridine, p-chloropyridine, 2-picoline, 3-picoline, 4-N, N-dimethylaminopyridine, 1,7-diazabicyclo- [5, 4,0] -Undec-7-ene, 9-methylcarba Lumpur, 9-but-phenyl carbazole, and the like, shall by no means be limited to these.

  Specific examples of aromatic diamines include, for example, o, m, p-phenylenediamine, chloro-p-phenylenediamine, chloro-m-phenylenediamine, fluorophenylenediamine, dichlorophenylenediamine, methylphenylenediamine, and dimethylphenylenediamine. , Phenylenediamines such as chloromethylphenylenediamine, xylylenediamine, toluylenediamine, benzidines such as benzidine, o-tolidine, dianisidine, dichlorobenzidine, diaminodiphenylmethane, diaminodichlorodiphenylmethane, diaminodimethyldiphenylmethane, diaminodiethyldiphenylmethane, etc. Diphenylmethanes, naphthalenediamine, diaminobenzanilide, diaminodiphenyl ether, diaminostilbenz Phosphonic acid, diaminophenol dihydrochloride, leucodiaminoanthraquinone, amino-N, N-diethylaminotoluidine hydrochloride, amino-N-ethyl-N- (β-methanesulfonamidoethyl) -toluidine sulfate hydrate or N, N, N ′, N′-tetramethylethylenediamine and the like can be mentioned, but are not limited thereto.

  Specific examples of the alkanol primary amines include, for example, monomethanolamine, monoethanolamine, monopropanolamine, 3-amino-1-propanol, isopropanolamine, monobutanolamine, monopentanolamine, monoheptanolamine , Monooctanolamine, monononiolamine, monodeciolamine and the like, but are not limited thereto. Preferably, monomethanolamine, monoethanolamine, monopropanolamine, 3-amino-1-propanol, isopropanolamine, monobutanolamine, monopentanolamine and the like are preferable because the effect is higher when the number of carbon atoms is smaller. .

  Specific examples of the alkanol secondary amines include, for example, dimethanolamine, diethanolamine, dipropanolamine, diisopropanolamine, dibutanolamine, dipentanolamine, N-methylaminoethanol, N-ethylaminoethanol, N -Butylethanolamine, N-methylisopropanolamine, 2- (2-aminoethoxy) ethanol, 2-amino-2-methyl-1-propanol, 3-amino-2,2-dimethyl-1-propanol, 2-amino Examples include, but are not limited to, 2-hydroxymethyl-1,3-propanediol, di (diethylene glycol) amine, N- (2-aminoethyl) ethanolamine and the like. Preferably, dimethanolamine, diethanolamine, dipropanolamine, diisopropanolamine, dibutanolamine, dipentanolamine, N-methylaminoethanol, N-ethylaminoethanol, N-butylethanolamine, N-methylisopropanolamine, 2- (2-aminoethoxy) ethanol, 2-amino-2-methyl-1-propanol, 3-amino-2,2-dimethyl-1-propanol, 2-amino-2-hydroxymethyl-1,3-propane Diols and the like are mentioned, and since the effect is larger when the number of carbon atoms is smaller, dimethanolamine, diethanolamine, dipropanolamine, diisopropanolamine, N-methylaminoethanol, N-ethylaminoethanol, N- Chill ethanolamine, N- methyl isopropanolamine, 2-amino-2-methyl-1-propanol, 3-amino-2,2-dimethyl-1-propanol.

  Specific examples of the alkanol tertiary amines include, for example, trimethanolamine, triethanolamine, tripropanolamine, tributanolamine, tripentanolamine, dimethylethanolamine, methyldiethanolamine, ethyldibutanolamine, butyldiethanolamine, Examples include tris (hydroxymethyl) aminomethane, tris (hydroxyethyl) aminomethane, and the like, but are not limited thereto. Since the effect is larger when the number of carbon atoms is smaller, preferably, trimethanolamine, triethanolamine, tripropanolamine, dimethylethanolamine, methyldiethanolamine, ethyldibutanolamine, butyldiethanolamine, and the like are more preferable. Examples include trimethanolamine, triethanolamine, dimethylethanolamine, and methyldiethanolamine.

Specific examples of amines contained in the diluted amine aqueous solution are preferably amines that are easily soluble in water, and can be procured at low cost (for example, amine drainage solution or CO ₂ used as a surfactant or an emulsifier). From the viewpoint of reusing the chemical adsorbent drainage of amines used for absorption), methylamine, ethylamine, n-propylamine, isopropylamine, 2-methylpropylamine, n-butylamine, isobutylamine , Sec-butylamine, tert-butylamine, n-pentylamine, isopentylamine, neopentylamine, amylamine, hexylamine, 2-ethylbutylamine, heptylamine, octylamine, nonylamine, decylamine, monomethanolamine, monoethanolamine, Monopropanol Min, 3-amino-1-propanol, isopropanolamine, mono- butanol amine, mono-pentanol amine. More preferably, methylamine, ethylamine, n-propylamine, isopropylamine, 2-methylpropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, n-pentylamine, isopentylamine, neopentylamine , Amylamine, monomethanolamine, monoethanolamine, monopropanolamine, 3-amino-1-propanol, isopropanolamine, monobutanolamine, monopentanolamine and the like.

(B) Concentration of amines in dilute amine aqueous solution The concentration of the amines of the present invention is 0.003 to 26 M, preferably 0.03 to 16 M, more preferably 0.06 to 6 M, based on the whole diluted amine aqueous solution. .5M, particularly preferably in the range of 0.06 to 3.5M. If the concentration of amines is 0.003 M or more with respect to the whole diluted amine aqueous solution, as described in the reaction mechanism of this method described above, even such diluted amines can sufficiently and effectively exert their effects. It is preferable that it can be exhibited. On the other hand, if the concentration of amines is 26 M or less with respect to the whole diluted amine aqueous solution, as described in the reaction mechanism of this method described above, a side reaction as shown in the equation (3) of the reaction mechanism occurs. The amines can be regenerated by the formula of the reaction (2) without any loss of the charged amine and the reaction rate is not reduced. If the concentration of amines exceeds 26 M with respect to the whole diluted amine aqueous solution and the concentration of amines is too high (close to 100%), the sub-reaction shown in the equation (3) of the reaction mechanism is used. Although it is not desirable because the possibility that a reaction may occur is increased, in this method, even if the concentration of amines is too high, as an effect of forming an aqueous solution, if the water is well dispersed in the solution, the reaction (2 ) Occurs (the amines can be regenerated, the charged amine is not lost, and the reaction rate does not slow down). Further, as described in the reaction mechanism of the present method described above, the concentration of water is better if the reaction (2) of the reaction mechanism is promoted, so that the amines and water are in a molar ratio of 50%, 50%. It can be said that the degree (molar ratio 1: 1) is good. Since the molecular weight of amines is larger than water at mass%, it is not preferable because the possibility of reaction (3) is expected to increase if the amount of water is less than 80 wt% and water up to about 20 wt%. I can say that.

  In particular, in the present invention, as described above, a catalyst is not added at all, and a very small amount of amines and a depolymerization reaction are used to decompose polycarbonate almost completely into bisphenol A and carbon dioxide at a relatively low temperature. However, since it is an epoch-making method capable of obtaining almost complete reaction selectivity and relatively high reaction rate, the concentration of amines is more preferably in a low concentration range of 0.06 to 3.5M. Is desirable. Further, in the present invention, as described above, no catalyst or the like is added, a very small amount of amines and a depolymerization reaction are used, and polyethylene terephthalate (PET) is used as a raw material ethylene glycol (EG) at a relatively low temperature. It breaks down to terephthalic acid (TPA) and is an epoch-making method that provides almost complete reaction selectivity and relatively fast reaction rate. The concentration of amines is more preferably 0.06 to 3.5M. It can be said that it is desirable to carry out in a low concentration range (see Tables 7 and 15). From the above, in the present invention, as described above, the catalyst is not added at all, and a very small amount of amines and a depolymerization reaction are utilized to decompose the polyesters into raw material monomers at a relatively low temperature. It is an epoch-making method capable of obtaining almost complete reaction selectivity and a relatively high reaction rate, and it is desirable that the concentration of amines is preferably in a range of 0.06 to 3.5 M, which is more preferable. I can say that.

(C) About water of diluted amine aqueous solution Water used for the diluted amine aqueous solution is not particularly limited, such as industrial water, tap water (clean water), ion-exchanged water, distilled water, pure water, and ultrapure water. From the viewpoint that the target product can be obtained in a high yield, and from the viewpoint that production of by-products can be significantly suppressed, ion-exchanged water, distilled water, pure water, and ultrapure water are preferable. However, in the present invention, an enormous amount of polyester waste such as PCs discarded after use in a wide range of fields such as industrial fields such as electronic / information equipment, medical equipment, building materials, automobiles, and household goods is handled. Therefore, after collecting such a large amount of polyester waste such as PC, it is possible to completely remove dirt attached to the polyester waste by pretreatment such as washing before being subjected to the chemical recycling method of the present invention. Have difficulty. Therefore, without using expensive water such as pure water or ultrapure water, depolymerization is carried out by the chemical recycling method of the present invention in consideration of contamination of impurities from polyester waste, and then appropriate purification is performed. A high-purity monomer may be recovered using a technique, and it is more preferable to reduce production costs using relatively inexpensive water such as distilled water and ion exchange water used in the examples.

  In addition, water has a role which disperse | distributes a small amount of amines which are reaction raw materials uniformly. Furthermore, it is environmentally friendly and does not dissolve the target monomer (such as bisphenol A) but can be easily separated and recovered (separated by precipitation and filtration). The reaction mechanism of this method (the chemical recycling method of the present invention) can be considered as follows, taking polycarbonate as an example of polyesters.

PC + amines → BPA (product monomer) + isocyanate (intermediate product) (1)
Isocyanate + water → amines + CO ₂ (2)
If the amine concentration is 100% and there is no water as in the existing chemical recycling method, the above reaction (2) does not occur and the following reaction (3) occurs, so the amine is consumed and reacts immediately. It can be said that the problem that a by-product is produced in a large amount as in the following reaction (3) cannot be solved.

Isocyanate + amines → by-products (3)
As described above, the amines of the reactants return to the amines again, so that they are not consumed in principle (in other words, the charged amine is not lost and the reaction rate does not slow down), but the concentration of amines is 100%. In the case where the concentration is too high, the intermediate isocyanate reacts with the amine, and the reaction is completed as soon as the amine is consumed without being regenerated. It can be said that the problem that a large amount of products are generated cannot be solved. Therefore, it was necessary to remove a large amount of by-products and then evaporate or distill the solvent and bisphenol A or the organic solvent. However, in the reaction mechanism of the present invention, the amines of the reactants return to the amines again (see above). Since reaction is not consumed in principle (see Reaction (2)), in this method, water is greatly involved in (contributing to) the effect of slowing the reaction rate due to amine regeneration and the effect of suppressing by-products. I can say that.

(D) Constituents other than water and amines constituting the diluted amine aqueous solution The diluted amine aqueous solution only needs to contain amines having the above-mentioned concentration in water, and the other is within the range not impairing the effects of the present invention. These solvents and additives may be included. In other words, the feature of this method is that no organic solvent is required and only water is required. However, when amines having a large molecular weight are used, it is expected that the solubility of amines in water will decrease and the reaction rate will decrease. obtain. In that case, it can be said that the addition of an amphipathic solvent (which dissolves both water and amine) acetone, ketones such as methyl ethyl ketone, alcohols such as methanol and ethanol, and tetrahydrofuran (THF) is effective. Other DMF (dimethylformamide) and acetonitrile are also amphiphilic solvents, so depending on the conditions, they may decompose themselves, but under mild conditions that do not decompose themselves (the effects of the present invention). It can be used sufficiently in the range not to be damaged.
(2) Polyesters Polyesters that can be used in the present invention include electronic / information equipment, medical equipment, building materials, industrial fields such as the automobile field, and after use in a wide range of fields such as household goods, or Any material that can be recovered as waste, such as mill ends of polyester products discharged from manufacturing processes in a wide range of fields and sheet waste after punching (molding) of polyester products, is particularly limited. is not. That is, polyester is a polycondensate of polycarboxylic acid (dicarboxylic acid) and polyalcohol (diol). Basically, it is made by reacting (dehydrating and condensing) a polyalcohol (alcoholic functional group; a compound having a plurality of —OH groups) and a polycarboxylic acid (carboxylic acid functional group; a compound having a plurality of —COOH groups). To do. Among them, the most produced is polyethylene terephthalate (PET) produced from terephthalic acid and ethylene glycol. If an anhydride is used for the polyvalent carboxylic acid, dehydration does not occur, and an ester exchange reaction is also utilized using an ester (for example, a methyl ester) of the polyvalent carboxylic acid. The classification name has changed depending on the application of the resin. The main ones are (1) terephthalic acid and ethylene glycol (PET), which are used for fibers and PET bottles. In fiber, it is often called with the trade names such as Dacron and Tetron. (2) Used for ships, boats, etc., reinforced with molded products such as buttons, glass fiber, etc. Polyester is incorporated with an unsaturated group and copolymerized with a monomer having a vinyl group such as styrene at the time of molding. It is called unsaturated polyester. (3) Alkyd resin: a polyester resin modified by adding oils and fats and other resins (for example, epoxy resin) to the reaction to adjust (adjust properties). Examples of the dicarboxylic acid component that is a monomer component of the polyester include terephthalic acid (TPA) and 2,6-naphthalenedicarboxylic acid (NDC). Examples of the diol component include ethylene glycol (EG) and 1,3-propane. Examples include diol (PDO), 1,4-butanediol, 1,4-cyclohexanedimethanol (CHDM), and the like. Specific examples of the polyester will be described later. Polyesters that can be used in the present invention preferably have a high production volume and are required to be collected (recycled) (for example, the Automobile Recycling Law, the Home Appliance Recycling Law, the Personal Computer Recycling Law, the Containers and Packaging Recycling Law) Laws, various recycling laws such as the Construction Recycling Law, and applicable products such as the Law for Promotion of Effective Utilization of Resources) and waste materials that can be recovered directly in the manufacturing process are desirable.

  Specific examples of polyesters that can be used in the present invention include polytrimethylene terephthalate, polypentamethylene terephthalate, polyhexamethylene terephthalate, polybutylene terephthalate, polybutylene (terephthalate / isophthalate), polypropylene terephthalate, and polypropylene (terephthalate). / Isophthalate), polyethylene terephthalate, polyethylene (terephthalate / isophthalate), bisphenol A (terephthalate / isophthalate), polypentamethylene naphthalate, polyhexamethylene naphthalate, polybutylene naphthalate, polybutylene (terephthalate / naphthalate) , Polypropylene naphthalate, polypropylene (terephthalate / naphthalate), polyethylene N-naphthalate, polycyclohexanedimethylene terephthalate, polycyclohexane dimethylene (terephthalate / isophthalate), poly (cyclohexanedimethylene / ethylene) terephthalate, poly (cyclohexanedimethylene / ethylene) (terephthalate / isophthalate), polybutylene (terephthalate / isophthalate) Aromatic polyesters such as phthalate) / bisphenol A, polyethylene (terephthalate / isophthalate) / bisphenol A; polybutylene (terephthalate / succinate), polypropylene (terephthalate / succinate), polyethylene (terephthalate / succinate), polybutylene (terephthalate / adipate), Polypropylene (terephthalate / adipate), polyethylene (terephthalate Talate / adipate), polyethylene (terephthalate / sulfoisophthalate / adipate), polyethylene (terephthalate / sulfoisophthalate / succinate), polypropylene (terephthalate / sulfoisophthalate / succinate), polybutylene (terephthalate / sebate), polypropylene (terephthalate / sebate) ), Polyethylene (terephthalate / sebate), polybutylene terephthalate / polyethylene glycol, polypropylene terephthalate / polyethylene glycol, polyethylene terephthalate / polyethylene glycol, polybutylene terephthalate / poly (tetramethylene oxide) glycol, polypropylene terephthalate / poly (tetramethylene oxide) glycol , Poly Butylene (terephthalate / isophthalate) / poly (tetramethylene oxide) glycol, polypropylene (terephthalate / isophthalate) / poly (tetramethylene oxide) glycol, polybutylene terephthalate / poly (propylene oxide / ethylene oxide) glycol, polypropylene terephthalate / poly ( Propylene oxide / ethylene oxide glycol, polybutylene (terephthalate / isophthalate), poly (propylene oxide / ethylene oxide) glycol, polypropylene (terephthalate / isophthalate), poly (propylene oxide / ethylene oxide) glycol, polybutylene (terephthalate / adipate), polypropylene ( Terephthalate / adipate), polybutylene terf Copolymers obtained by copolymerizing polyether such as rate poly-ε-caprolactone or aromatic polyester with aromatic polyester; polyethylene oxalate, polypropylene oxalate, polybutylene oxalate, polyneopentyl glycol oxalate, polyethylene succinate, Aliphatics such as polypropylene succinate, polybutylene succinate, polybutylene adipate, polypropylene adipate, polyethylene adipate, polybutylene (succinate / adipate), polypropylene (succinate / adipate), polyethylene (succinate / adipate), polybutylene succinate carbonate Polyester carbonate, p-oxybenzoic acid / polyethylene terephthalate, p-oxybenzoic acid / 6- Examples thereof include liquid crystalline polyesters such as copolyesters such as oxy-2-naphthoic acid; polycarbonate resins; polylactic acid; fumaric acid ester copolymers. As described above, the polyesters that can be used in the present invention are defined as a general term for polymer compounds containing an ester bond (—CO—O—) in the main chain of a constituent molecule, What is interpreted in a broad sense including polycarbonate resin and polylactic acid.

  The polycarbonate resin is obtained by reacting a dihydric phenol and a carbonate precursor. The polycarbonate resin is produced by using various conventionally known reaction methods such as an interfacial polymerization method, a melt transesterification method, a solid phase transesterification method of a carbonate prepolymer, and a ring-opening polymerization method of a cyclic carbonate compound. Polycarbonate resins can be used.

  Representative examples of the dihydric phenol include, for example, hydroquinone, resorcinol, 4,4′-biphenol, 1,1-bis (4-hydroxyphenyl) ethane, and 2,2-bis (4-hydroxyphenyl) propane. (Commonly called bisphenol A), 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) -1- Phenylethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 2,2-bis (4-hydroxyphenyl) pentane, 4,4 ′-(p-phenylenediisopropylidene) diphenol, 4,4 ′-(m-phenylenediisopropylidene ) Diphenol, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, bis (4-hydroxyphenyl) oxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfoxide, bis ( 4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) ketone, bis (4-hydroxyphenyl) ester, 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane, bis (3,5- Dibromo-4-hydroxyphenyl) sulfone, bis (4-hydroxy-3-methylphenyl) sulfide, 9,9-bis (4-hydroxyphenyl) fluorene and 9,9-bis (4-hydroxy-3-methylphenyl) Fluorene, etc. Not. A preferred dihydric phenol is bis (4-hydroxyphenyl) alkane, and bisphenol A is particularly preferred from the viewpoint of impact resistance. That is, a particularly preferred component A of the present invention is a bisphenol A type polycarbonate resin.

  As the carbonate precursor, carbonyl halide, carbonic acid diester, haloformate or the like is used, and specific examples include phosgene, diphenyl carbonate, dihaloformate of dihydric phenol, etc., but are not limited thereto.

  The polycarbonate resin produced by interfacial polymerization of the above dihydric phenol and carbonate precursor contains a catalyst, a terminal terminator, an antioxidant for preventing the dihydric phenol from being oxidized, if necessary. It may be. The polycarbonate resin that can be used in the present invention includes a branched polycarbonate resin obtained by copolymerizing a trifunctional or higher polyfunctional aromatic compound, an aromatic or aliphatic (including alicyclic) difunctional carboxylic acid. It includes a copolymerized polyester carbonate resin, a copolymerized polycarbonate resin copolymerized with a bifunctional alcohol (including an alicyclic group), and a polyester carbonate resin copolymerized with such a bifunctional carboxylic acid and a bifunctional alcohol. Moreover, the mixture which mixed 2 or more types of polycarbonate resin may be sufficient.

  Examples of the polylactic acid include poly-L-lactic acid (PLLA) obtained by polymerizing only the L isomer, poly-D-lactic acid (PDLA) obtained by polymerizing only the D isomer, and a stereocomplex polylactic acid obtained by mixing PLLA and PDLA ( SC-PLA). Further, it may be a copolymer of poly-D-lactic acid and other copolymer component units. Other units that the copolymer of the poly-D-lactic acid and other copolymer component units may contain include L-lactic acid units and copolymer component units other than lactic acid. It may be a copolymer of poly-L-lactic acid and other copolymer component units. Other units that the copolymer of the poly-L-lactic acid and other copolymer component units may contain include L-lactic acid units and copolymer component units other than lactic acid. As other copolymer components other than lactic acid that may be contained in the copolymer of these poly-L-lactic acid and other copolymer component units and the copolymer of poly-D-lactic acid and other copolymer component units , Ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, pentaerythritol, bisphenol A, polyethylene glycol, polypropylene Glycol compounds such as glycol and polytetramethylene glycol, oxalic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid Dicarboxylic acids such as naphthalenedicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid, glycolic acid, hydroxypropion Hydroxycarboxylic acids such as acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid, and lactones such as caprolactone, valerolactone, propiolactone, undecalactone, 1,5-oxepan-2-one Can be mentioned.

Polyesters that can be used in the present invention are preferably general-purpose engineering plastics having excellent physical properties such as transparency, flame retardancy, and impact resistance, such as electronic / information equipment, medical equipment, building materials, and automobile fields. Polycarbonate (PC) (bisphenol A-type polycarbonate resin from bisphenol A and phosgene) used in a wide range of fields such as industrial fields and daily necessities; sustainable from agricultural products with excellent biodegradability and carbon neutral properties It is a plastic made of various materials and is used as a multi-sheet and house film for agriculture, and as a BB bullet for outdoor use (commonly known as a bio bullet) in the hobby field, as well as textile products, optical disks, packaging films, plastic bags, etc. Poly-D or L-lactic acid (PDL) used in a wide range of fields Or PLLA); a resin that has excellent heat resistance, strength, dyeing properties, and excellent economic efficiency, and is used in a wide range of fields such as fibers, films, and containers. Polyethylene terephthalate (PET) (Aromatic polyester resin from polyethylene glycol (PE) and terephthalic acid (TPA)), which is widely used in PET bottles; has higher gas ultraviolet barrier properties and mechanical strength than PET, and gas (oxygen, Polyethylene naphthalate (PEN), a plastic with excellent physical properties such as low CO ₂ and water vapor permeability, used in industrial fields such as APS photographic film and materials for electronic parts; used as a material for unit baths, etc. Examples of the fumaric acid ester-based copolymers are not limited to these. .

Regarding the degree of polymerization (or weight average molecular weight) of the above-described polyesters, in the present invention, the depolymerization of the polyesters is a surface reaction (approximate in the surface reaction model of FIG. 4B or FIG. 16B = linearly). It is not limited at all because it is not influenced by the degree of polymerization. Therefore, by arranging different types of polyesters (for example, PET, PEN, PC, PLA, etc.), even if different degrees of polymerization (or weight average molecular weight) are mixed, the target waste (preferably constant waste) It can be said that it is desirable to carry out the industrialization after sampling from the granular material pulverized to a particle size) and specifying the optimum depolymerization reaction conditions by preliminary experiments to the extent performed in the laboratory-level examples. In addition, even when multiple types of polyesters (with different degrees of polymerization) are mixed, as in the above, an appropriate number is sampled from granular materials obtained by pulverizing these wastes to a certain particle size. By specifying the optimum depolymerization reaction conditions by preliminary experiments to the extent performed in the examples of the level, it can be carried out industrially.
(3) Other components used for depolymerization of the polyesters of the present invention In addition, in the chemical recycling method of the present invention, no catalyst or the like is added and a very small amount of amines and a depolymerization reaction are used. Since it is possible to decompose the polymer polyesters almost completely into raw material monomers at a relatively low temperature, it is possible to use an extra component such as a conventionally known catalyst, an alcohol solvent, or an alkali such as NaOH. This is undesirable because it impairs the intended effect of the invention. Therefore, as other components that can be used in the present invention, those that do not impair the above-described effects of the present invention can be added in an appropriate amount, and examples thereof include alkaline substances such as NaOH. There are no restrictions. These may be used alone or in combination of two or more. Here, the addition of alkali such as NaOH can enhance the effect. Specifically, for example, in the case of polycarbonate, carbon dioxide (CO ₂ ) is also generated by the depolymerization reaction, and the pH in the reactor decreases as the reaction proceeds. When the pH is lowered, the ionization of the amine proceeds and the reactivity is lowered. This is because the reaction proceeds if alkali such as NaOH is added and the solution is kept basic (see FIG. 9 in Example 7).
(4) About the process of depolymerizing polyesters using diluted amine aqueous solution In the chemical recycling method of this invention, it has the process of depolymerizing polyesters using the diluted amine aqueous solution containing amine mentioned above. It is. The chemical recycling method of the present invention does not require catalysts (alkali metal carbonates or alkaline earth metal carbonates or oxides) or additives in addition to a very small amount of amines, and is also organic. Since no solvents (alcohols, phenols, etc.) are used, it is a highly efficient chemical recycling method that facilitates separation and purification of polymers produced by depolymerization of polyesters and consumes less energy.

(A) Depolymerization Here, depolymerization refers to a reverse reaction of polymerization, and refers to decomposing a polymer (polymer) into a monomer (monomer) by heat, ultraviolet rays or the like. In the present invention, it means that polyesters as polymers are decomposed into monomers at a relatively low temperature by utilizing a very small amount of amines and a depolymerization reaction. When the polymer is a high molecular weight substance, depolymerization includes a decrease in the degree of polymerization of the polymer and partial decomposition.

(B) Depolymerization method The depolymerization method in the chemical recycling method of the present invention may be any of batch type (batch type), semi-batch type, and continuous type. In other words, as in batch (batch), the steps of charging, reaction, and recovery may be performed one by one in order. If industrialization is considered, solid polymer (polyester) is used as in semi-batch. ) Is fixed in the reactor, and a dilute aqueous amine solution containing solvent amines is continuously supplied to the reactor, and the monomer is immediately dissolved in the solvent and removed from the reaction zone. The recovery may be performed all at once, and may be continuously performed until the entire amount of polyester charged into the reactor is reacted and recovered (see FIG. 13), or the input, reaction, and recovery are all performed simultaneously as in a continuous system. You can go without interruption. There are no particular restrictions on the reactor. Even if it is a batch type (batch type), a semi-batch type, or a continuous type, a conventionally known reactor can be appropriately selected or combined, and can be used by improving as necessary. Good.

(C) Form of contact between polyester and dilute aqueous amine solution (especially amines) In the present invention, depolymerization of polyester as a polymer and dilute aqueous amine solution (particularly very little amine in the aqueous solution). The reaction may be performed in any contact form. For example, solid-liquid contact or liquid-liquid contact may be used. In the case of solid-liquid contact, when the solid form of the polyester is relatively large in size, it can be contacted while flowing a dilute aqueous amine solution (particularly, very few amines in the aqueous solution) on the surface of the solid. Good. Alternatively, it is not particularly limited, for example, a solid form of polyester may be added to a dilute aqueous amine solution (particularly, very few amines in the aqueous solution), and the mixture may be stirred and mixed to be fluidized and contacted. In the solid-liquid contact, it is desirable to fluidize a dilute aqueous amine solution (particularly a very small amount of amines in the aqueous solution) to be brought into contact with the solid surface. In the case of liquid-liquid contact, the liquid form of the diluted amine aqueous solution and the liquid form in which the polyesters are dissolved in an appropriate solvent may be stirred and mixed as necessary to come into contact. That is, the method is not particularly limited as long as it is a method capable of proceeding the decomposition (monomerization) of the polymer by depolymerization by contact. From the viewpoint of reducing the environmental burden, solid-liquid contact that does not require such a solvent is preferable to liquid-liquid contact that requires a solvent for dissolving the polyester as a polymer. This is because the method of the present invention (chemical recycling method by depolymerization) is characterized in that it is carried out at a reaction temperature below the melting point of the polymers (polyesters). In addition, in order to observe the reaction due to solid-liquid contact, the reaction was carried out in a pressure cell (reactor with a window), and the shape of the polymer (polyester) solid was observed over time. The size is observed to decrease. It can be seen that this is a reaction at the solid surface. Formula (1) described later is derived from a reaction rate equation in which the reaction proceeds by a surface reaction. Therefore, it can be said that it is not necessary to dissolve the polymer (polyesters) in the solvent (amines in the diluted amine aqueous solution) (= the depolymerization reaction form by liquid-liquid contact is not necessary). The role of the solvent (amines in dilute aqueous amine solution) is to remove the produced monomer (bisphenol A, for example polycarbonate) from the solid surface. Therefore, no matter how large the solid sample (polymer solid) or the amount of solvent (amount of amines in the diluted amine aqueous solution) is small relative to the polymer solid, the reaction rate does not decrease rapidly, and the contact area Is important. In addition, since the reaction by solid-liquid contact can be performed at a reaction temperature below the melting point of the polymer (polyester), the environmental load can be reduced and the energy consumption required for heating the reaction system can be suppressed. In addition to being economical, it is also possible to reduce the amount of CO ₂ generated with the generation of the energy, which is desirable from the viewpoint of preventing global warming, and also from the viewpoint of greatly simplifying the reactor. It can be said that it is an effective method.

(D) Size of solid polyesters (average particle diameter)
In the case of using solid polyesters, the depolymerization of the present invention is a surface reaction on the surface of the solid polyesters (see FIG. 4B and FIG. 16B). That is, at the reaction interface on the solid surface, the polyesters attack the amines in the diluted amine aqueous solution, and polymer decomposition (monomerization) by depolymerization proceeds. Therefore, increasing the surface area of solid polyesters as much as possible leads to an increase in the contact area with the amines = reaction area, which in turn contributes to an increase in the reaction rate. Therefore, the polyesters are in the form of waste. It can be said that it is desirable to use a material that has been pulverized to an appropriate size. In view of the above, the size (average particle diameter) of the polyesters of the solid, preferably the granular material pulverized (more preferably further classified) into a predetermined particle size range is 1 to 50 mm, preferably 1 to 20 mm. Preferably it is the range of 1-10 mm. That is, since the smaller the particle size of polyesters, the more the surface area increases. Therefore, the size (average particle size) of polyesters is preferably 50 mm or less, more preferably 20 mm or less, and more preferably 10 mm or less. It can be said. On the other hand, in general, pulverization requires a lot of energy and increases the environmental load. Therefore, it is not practical to make fine particles, and in general, it is as simple as a resin for polymer molding raw materials. Since what is obtained by simple pulverization is desirable, it can be said that the size (average particle diameter) of the polyesters is desirably 1 mm or more. However, even if it is outside the range of the size (average particle diameter) of the solid polyesters, it should be included in the technical scope of the present invention as long as the effects of the present invention can be effectively exhibited. Needless to say. The size (average particle diameter) of the solid polyesters can be measured and calculated by laser diffraction / scattering particle size distribution measurement, laser diffraction / dynamic light scattering particle size distribution measurement, or the like. Since it is automatically measured and calculated by the analysis software of the measuring device used for the measurement, it is extremely simple. However, in the case where the apparatus cannot be provided, for example, the size of the solid polyester (average particle diameter) is determined using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). You may use the value calculated as an average value of the particle diameter of the particle | grains observed in several to several dozen visual fields (it is desirable to calculate using image analysis software of SEM, TEM, etc. also in this case).

(E) Content of polyester (mixing ratio of polyester and dilute amine aqueous solution)
The mixing ratio of the polyester and dilute aqueous amine solution is not particularly limited as long as it is a ratio capable of generating (recovering) the monomer (preferably in high yield) by decomposing the polymer by depolymerization (monomerization). . As a rough guide, the content (ratio) of the polyester is 0.05 wt% or more, preferably 0.1 wt% or more, more preferably 0.1 wt% or more on the lower limit side with respect to the total amount of the diluted amine aqueous solution and the polyester. It is 5 wt% or more, more preferably 1 wt% or more, and the upper limit side is not particularly limited, and 90 wt% or more is also possible. This is because amines are not consumed even if the reaction proceeds as shown in the reaction mechanism of the present method shown below (see the reactions (1) and (2) in the reaction mechanism). The upper limit is preferably 90 wt% or less, preferably 70 wt% or less, more preferably 50 wt% or less, further preferably 30 wt% or less, particularly preferably 20 wt% or less, and particularly preferably 10 wt% or less. Here, the reaction mechanism of this method (the chemical recycling method of the present invention) can be considered as follows, taking polycarbonate as an example of polyester. Therefore, since the amines of the reactants return to the amines again, they are not consumed in principle. Therefore, although it depends on the desired reaction rate, it can be said that the content of the polyester may be several times that of the amines as shown in the above range.

PC + amines → BPA (product monomer) + isocyanate (intermediate product) (1)
Isocyanate + water → amines + CO ₂ (2)
As in the existing chemical recycling method, if the amines are 100% and there is no water, the above reaction (2) does not occur and the following reaction (3) occurs, so the reaction is completed as soon as the amines are consumed. However, it can be said that the problem that a by-product is produced in a large amount as in the following reaction (3) cannot be solved.

Isocyanate + amines → by-products (3)
As described above, when the content (ratio) of the polyesters is in the above range, the yield of the target product (monomer generated by decomposition), reaction selectivity, reaction rate, lowering of the reaction temperature, and the like are improved. However, since it varies depending on various reaction conditions described below, such as whether the reaction is carried out batchwise (batch type) or continuous, even if it is outside the range of the polyester content, Needless to say, the present invention is included in the technical scope of the present invention as long as the operational effects of the present invention can be effectively exhibited. For example, when used in a polymer alloy state, the reaction rate seems to depend on the polyester content. However, the range of the polyester content is only a rough guide, and many industrially layered products (for example, shampoo refill bags, nylon and polyester (s) layered together), Such products include non-reactive nylon, polyethylene, polypropylene and the like, and there is no particular limitation as long as the raw material monomer can be generated from the polyester by decomposing the polyester by depolymerization. . Rather, it is an effective technique for separating and recovering polyesters and nylon, polyethylene, polypropylene, etc., which do not react very much, in the case of layered molded products (products) that are produced industrially. It can be said that the content of is not limited at all.

(F) Reaction temperature and reaction apparatus The reaction temperature for depolymerizing the polyesters is not particularly limited as long as it is not higher than the melting point of the polyesters. Again, since the reaction temperature at the time of depolymerizing the polyesters is not higher than the melting point of the polyesters, the polyesters (polymer solids) are not dissolved in the solution (diluted amine aqueous solution) and are in solid-liquid contact. Therefore, the polymer (polyesters) and the amount of the amine solution (amount of amines in the diluted amine aqueous solution) can be appropriately changed depending on the properties of the reactor and the processing conditions. According to observation in the pressure cell (reactor with window), not all the monomer produced by the decomposition of polyesters is dissolved in the solution in the reactor, but the viscosity is high and fluid at the bottom of the reactor. Accumulation as a liquid component was observed. Therefore, even if the amount of the amine solution is small, there is no problem, and because of CO ₂ and amines produced by the reaction of the intermediate product (isocyanate) and water, the solution in the reactor is constantly convected even without stirring. Circulation was also observed (in particular, the amines of the reactants returned to the amines again, so that they were not consumed in principle, the charged amines were not lost, and the reaction rate was not slowed down.) For the above, see the reaction (2) equation of the reaction mechanism of the present method described above).

  The reaction temperature for depolymerizing the polyesters is preferably a temperature range in which a monomer can be produced (recovered) in a high yield by decomposing (monomerizing) the polymer (polyesters) by depolymerization. Considering reactivity and productivity, for example, preferably −50 to 400 ° C., more preferably 0 to 300 ° C. For example, when polycarbonate (PC) is used as the polyester, it is more preferably 50 to 400 ° C. It is 200 degreeC, Most preferably, it is 80-160 degreeC, Especially preferably, it is the range of 100-140 degreeC. Moreover, when using polyethylene terephthalate (PET) as polyester, Preferably it is -50-400 degreeC, More preferably, it is 0-350 degreeC, More preferably, it is 50-350 degreeC, Especially preferably, it is 150-300 degreeC, Especially, Preferably it is the range of 170-250 degreeC. When the reaction temperature is −50 ° C. or higher, it is preferable in that the amine solution having a low freezing point is appropriately selected so that the whole diluted amine aqueous solution can be used in a liquid state without solidifying. If the reaction temperature is 400 ° C. or lower, by appropriately selecting polyesters having a high melting point, a depolymerization reaction by solid-liquid contact can be carried out below the melting point of the polyesters, and amines having a high boiling point are appropriately selected. By doing so, the diluted amine aqueous solution can be used in a liquid state without causing a phase change to a gas state, which is preferable in that the thermal decomposition of amines in the diluted amine aqueous solution is also suppressed. In particular, in the present invention, when polycarbonate (PC) is used as the polyester, 180 ° C. or less, in particular, Examples 1-8, in which no depolymerization reaction occurs in the existing chemical recycling method of polycarbonate using hot ammonia water. Even at a relatively low temperature of 100 to 140 ° C. confirmed in step 1, it is possible to almost completely decompose polycarbonate, which is a kind of polyester, into raw material bisphenol A and carbon dioxide without adding any catalyst. The method is extremely excellent in that almost complete reaction selectivity and a relatively high reaction rate can be obtained (see FIG. 3 in Example 2 and FIGS. 1 and 2 in Example 1). When polyethylene terephthalate is used as the polyester, a relatively high reaction rate can be obtained at a high yield even at the same temperature reactivity as compared with the chemical recycling method of polyethylene terephthalate using hot ammonia water. Hereinafter, even at a relatively low temperature of 170 to 240 ° C. confirmed in Examples 9 to 12, polyethylene terephthalate, which is a type of polyester, is almost completely added without adding any catalyst or the like. (TPA) and ethylene glycol (EG) can be decomposed, and are extremely excellent in that almost complete reaction selectivity and relatively fast reaction rate can be obtained (Compare with Examples 9 to 12, especially Example 11). Diluted aqueous amine solution and aqueous ammonia solution at a concentration of 0.6 M according to the Arrhenius plot of Example 4 (ammonia heat ) See Figure 11 a comparison of the reaction rate constant in). However, it is needless to say that even if the reaction temperature is out of the above range, it is included in the technical scope of the present invention as long as the operational effects of the present invention can be effectively exhibited. That is, the appropriate reaction temperature is completely different depending on the type of polymer (polyester) and the functional group attached to the ester, and it is difficult to define it in general. For example, since PEN (polyethylene naphthalate) is excellent in heat resistance, the reaction temperature is higher than that of PET (polyethylene terephthalate), and 200 ° C. or more is required. The reaction temperature is PEN> PET> PC> PLA, and PLA (polylactic acid) of 100 ° C. or less is sufficient. Therefore, it is difficult to unambiguously define the reaction temperature including all polyesters, and the range of the reaction temperature defined above is only a rough guideline (= index for preliminary experiments). It is good to catch. That is, in the present invention, prior to industrialization, it is desirable to design an industrial large-scale plant after conducting preliminary experiments at the lab level and the small-scale plant stage. In this case, it can be said that the above temperature range may be used as a guide when setting the reaction temperature when performing a preliminary experiment at the laboratory level. The point at that time is that the reaction rate does not decrease so much and the lowest possible reaction temperature is ideal. The reason is that the effect of suppressing side reactions (Maillard reaction, isomerization (from optically active D-form, L-form to racemate) for polylactic acid) can be obtained.

  In addition, the temperature increase rate to the said reaction temperature and the temperature decrease rate after reaction are not restrict | limited in particular. In particular, when industrially performing a depolymerization reaction, rapid heating and rapid cooling as performed to specify the reaction time described later are practically difficult, and heating and cooling means provided in the reactor used. What is necessary is just to implement by the temperature increase rate and temperature decrease rate of the range which can be used using.

  As a reaction apparatus used for the chemical recycling method of the present invention, a pressure-resistant cell (pressure-resistant reactor capable of controlling temperature and pressure) as described above as a batch-type (batch-type) reaction apparatus is industrially enlarged. However, even if the pressure cell (pressure and pressure controllable reactor capable of controlling temperature and pressure) is enlarged as a semi-batch type (polymer is fixed, solution is distributed) reaction apparatus, as shown in FIG. Moreover, it is also possible to use an extruder capable of controlling temperature and pressure which is cheaper and easily available as a flow-through (continuous) reactor. Extruders are often used with a large amount of solid polymer (polyesters) and a small amount of solution (diluted amine aqueous solution) (the use of a large amount of solid polymer and a small amount of solution is common for extruders). Therefore, this method is appropriate. As described above, the decomposition product of the depolymerization reaction extruded from the extruder can be easily separated from the solution (diluted amine aqueous solution), so that the decomposition (chemical recycling) by the depolymerization reaction can be carried out continuously. Excellent in terms.

(G) Reaction pressure The reaction pressure when depolymerizing polyesters is within a pressure range in which a monomer can be generated (recovered) (preferably in a high yield) by decomposing the polymer by depolymerization (monomerization). If there is no particular limitation as long as reactivity and productivity are taken into consideration, for example, 0.01 to 300 atm, preferably 0.1 to 100 atm, more preferably 1 to 50 atm, provided that the reaction pressure is within the above range. It goes without saying that even if it is out of the range, it is included in the technical scope of the present invention as long as the operational effects of the present invention can be effectively exhibited. That is, as shown in the experimental observations of Examples 1 to 5 and 9 to 12 which will be described later and the considerations from the experimental results, the reaction pressure hardly influences the depolymerization reaction, and therefore the reaction pressure is not particularly adjusted. It can be said that it is desirable to implement from the viewpoints of economy, operability, and simplification of the apparatus (no need for a pressure control device or the like). More specifically, in a batch (batch) reactor, when there is no pressurization of inert gas, etc., the pressure is the saturated vapor pressure of the solution, so in the case of dilute amine aqueous solution, if the reaction temperature is determined regardless of the liquid volume It is constant. That is, when using a dilute aqueous amine solution, it is considered that it is not significantly different from the vapor pressure of water.

  Also, when gas is pressurized in a batch (batch) reactor, the pressure can be increased as much as the amount of pressurized gas, but at higher pressures, low boiling point amines are distributed more in the gas phase than at low pressure. If the amount of charged amines is constant, high pressure due to gas pressurization is disadvantageous. Therefore, with regard to the reaction pressure in a batch type (batch type) reactor, it is necessary to carry out without any special pressurization operation, economy, operability, simplification of equipment (pressure control device etc. are not required), etc. From the viewpoint of

  Also in the case of a semi-batch type reactor (see FIG. 13), the reaction pressure in Examples 9 to 12 is 10 MPa (≈100 atm), but is higher than the saturated vapor pressure of the aqueous amine solution at 160 to 240 ° C. Keep the pressure on. Since the reaction solvent (dilute amine aqueous solution) is a liquid phase, the density change due to pressure is small, and the influence of the reaction pressure on the monomer yield and reaction rate is considered to be very small.

  On the other hand, in the case of a flow-through (continuous) reaction apparatus, any amount of pressure can be applied by a pump. However, because the reaction temperature is below the critical point (below the melting point of the polyester), the diluted amine aqueous solution is in the liquid phase, and unless the pressure is extremely high, the change in the solution density is small. The effect is considered low. Therefore, with regard to the reaction pressure in a flow-type (continuous) reaction apparatus, it is necessary to carry out without any special pressurization operation, economy, operability and simplification of the apparatus (no pressure control device etc. are required) It can be said that it is desirable from the viewpoint of.

  In any of the batch, semi-batch, and flow (continuous) types, the reaction is considered to proceed even when the reaction solvent (dilute amine aqueous solution) is used as the vapor phase. However, since the product (monomer or the like) is attached to the polymer surface, the reaction proceeds if there is a method or medium for removing the product. However, from the viewpoint of development of a method for removing such products (such as monomers) from the polymer surface and pressure control, it is considered that the reaction solvent (dilute amine aqueous solution) is preferably in the liquid phase.

(H) Reaction time The reaction time for depolymerizing the polyesters is the reaction temperature, the structure and concentration of the amines, whether the diluted amine aqueous solution is flowing (whether the solid polyesters and the liquid diluted amine aqueous solution Since it differs depending on the solid-liquid contact state) and the like, it cannot be uniquely defined, but it can be generally inferred from the amine concentration (see FIG. 4B). That is, the reaction time is not particularly limited as long as a monomer can be produced (recovered) (preferably in a high yield) by decomposition (monomerization) of the polymer by depolymerization. In reality, in consideration of reactivity (inhibition effect on side reaction), productivity, reaction controllability, etc., it is several minutes (about 5 minutes) to 120 minutes, preferably 10 to 30 minutes if the reaction is completed. preferable. In some cases, a fast reaction rate in 1 or 2 minutes may be required, but if the reaction rate is too high, the reaction control is difficult and the possibility of side reactions increases, so the above range is appropriate. It can be said that.

(I) About a suitable combination of reaction temperature and reaction time As a suitable combination of reaction temperature and reaction time when polyesters are depolymerized, a monomer is obtained in a high yield by decomposition (monomerization) of the polymer by depolymerization. May be appropriately selected so that can be generated (recovered). However, the specific combination of reaction temperature and reaction time varies depending on the system used, such as the type and concentration of amines, the type of polyesters, the type and content of functional groups attached to esters, and so specific values are specified. It is difficult to do. That is, in the batch type, the reaction rate is affected by the type of polymer, temperature, time, type of amine, concentration, semi-batch (polymer is fixed, solution is in circulation) type reactor. In the case of flow rate and flow reactors (both polymer and solution flow), the contact time is the main factor. Therefore, while paying attention to the factors affecting the reaction rate described above, we conduct preliminary experiments at the laboratory level, and confirm and determine the appropriate combination of reaction temperature and reaction time as appropriate. It is desirable to finally carry out a large-scale industrial implementation through a level experimental stage in order to efficiently produce the target monomer (decomposition product).

(J) By-product gas treatment In addition to the target monomer produced by decomposing polyesters by a depolymerization reaction, a by-product gas such as carbon dioxide may be generated. In such a case, when a sealed container is used as the reactor, the generated by-product gas is dissolved in the diluted amine aqueous solution without being exhausted outside the reaction system, and the solution is acidified. The monomer yield may be affected. Therefore, it can be said that it is desirable to use a reaction apparatus provided with a pressure exhaust valve or the like that can periodically exhaust such by-product gas. Alternatively, an appropriate amount of alkali as a neutralizing agent may be added to the reaction system in advance. Note that by-product gas such as carbon dioxide causes global warming when released into the atmosphere, and preferably by-product gas such as carbon dioxide is recovered and such by-product gas as carbon dioxide is recovered. It can be said that it is more desirable to recycle (recycle).

For example, in the case of polycarbonate (PC), an intermediate product (isocyanate) is produced, this intermediate product (isocyanate) reacts with water, and carbon dioxide (CO ₂ ) gas and amines are produced as by-products (regeneration). (Refer to the formulas of reactions (1) and (2) of the reaction mechanism of the present method described above). In this way, the amine of the reactant is returned to the amine again, so it is not consumed in principle, and the regenerated amines attack the polycarbonate (PC) again, so that the charged amines are not lost and the reaction rate is increased. This has the advantage of not slowing down. On the other hand, CO ₂ is not preferable because it lowers the pH of the solution (diluted amine aqueous solution), and increases with the progress of the reaction, leading to an increase in pressure in the system. Therefore, as described above, it is more desirable that the CO ₂ gas is discharged out of the system, preferably recovered outside the system, and such CO ₂ gas is also reused (recycled). However, from the direct observation in the pressure cell, the generation of CO ₂ had the effect of promoting the stirring of the solution in the reactor. From this, while monitoring changes in the pH of the solution and the pressure in the system, CO ₂ gas is periodically discharged out of the system when it becomes close to a level that adversely affects the reaction system. It can be said that it is desirable to construct a system (control mechanism) that can enjoy the effect of promoting the stirring of the solution in the reactor by CO ₂ .
(5) Monomer recovery step The present invention includes a step of recovering the monomer obtained by depolymerization of the polyesters after the step (4).

(A) Monomer recovery method In the step (4), there is no particular limitation on the method for recovering the target product (the raw material monomer of the polyester which is a decomposition product) after completion of the depolymerization reaction of the polyester. Those skilled in the art can carry out by isolating and purifying the target product by appropriately referring to or combining known knowledge. For example, when the target product is bisphenol A obtained by decomposing one kind of polyester polycarbonate (PC), bisphenol A can be easily precipitated because it is hardly soluble in a dilute aqueous amine solution and has a large specific gravity. it can. Therefore, it can be easily separated (isolated) using precipitation / filtration or centrifugation. In addition, bisphenol A has a relatively high boiling point, while dilute amine aqueous solutions (such as water and primary alkylamines having a low carbon number) have a relatively low boiling point. Then, the target product may be isolated by performing a distillation operation. Or if it is a situation where analysis is necessary after the fact, what is necessary is just to perform an extraction operation | work suitably using the solvent etc. which are utilized in that case.

(B) About the recovery monomer which is a decomposition product The recovery monomer which is a decomposition product is a target in the chemical recycling method of the present invention. In the chemical recycling method of the present invention, raw material polyesters and dilute aqueous amine solutions (particularly, very few amines) are used. That is, the recovered monomer that is the decomposition product of the present invention is not particularly limited as long as it is produced by decomposing an ester bond in the raw material polyester.

  For example, when the raw material polyester is polycarbonate, bisphenol A as a target product (recovered monomer as a decomposition product) and carbon dioxide as a by-product (can be easily removed or recovered because it is gasified). can get. As for by-product carbon dioxide, from the viewpoint of prevention of global warming in recent years, reuse (dry ice, supercritical solvent for natural products, etc.) or immobilization of underground storage or seabed storage after liquefaction. Is desirable.

  When the raw material polyester is polyethylene terephthalate (PET), ethylene glycol and terephthalic acid, which are target products (recovered monomers that are decomposition products), are obtained. Desirably, ethylene glycol and terephthalic acid, which are the target products, are recovered by purification and separation from an aqueous amine solution and reused together (for example, recycled polyethylene terephthalate raw material). In this case, a mixed solution of ethylene glycol and terephthalic acid may be used as it is as a raw material for recycled polyethylene terephthalate without separating ethylene glycol and terephthalic acid.

  When the raw material polyester is polylactic acid (PLA), lactic acid as a target product (recovered monomer as a decomposition product) is obtained.

  The recovered monomer is useful in that it can be widely used in various products by being reused (recycled) as a raw material for producing polyesters that are polymers.

  According to the chemical recycling method of the present invention, a desired monomer can be produced very easily with a high yield and with a high reaction selectivity and reaction rate.

  In other words, existing chemical recycling methods use strong acids such as sulfuric acid or strong alkalis such as sodium hydroxide, or are performed under reaction conditions such as supercritical water, subcritical hot water, supercritical ammonia, and supercritical ethanol. In this case, the target monomer bisphenol A, ethylene glycol, lactic acid, or the like is decomposed by strong acid or high temperature, resulting in a very low recovery rate of the target monomer, There was a problem that corrosion became severe. In the chemical recycling method of the present invention, no catalyst or additive is required, no organic solvent is used, a very small amount of amines and a depolymerization reaction (nucleophilic substitution reaction or hydrothermal reaction) are used, Since polyesters can be decomposed almost completely to raw material monomers at low temperatures, there is no side reaction or further decomposition reaction (secondary decomposition reaction) of raw material monomers, so the recovery rate of raw material monomers is very high and almost complete reaction. This is an epoch-making chemical recycling technology that provides selectivity and relatively fast reaction rates. Therefore, secondary decomposition of the target monomer bisphenol A, ethylene glycol, lactic acid or the like does not occur, and corrosion of the apparatus can be suppressed, and the desired monomer can be obtained very easily in a high yield. It can be produced with high reaction selectivity and reaction rate. In the present invention, a very small amount of amines and a depolymerization reaction (aminolysis) are used, but this reaction form is a surface reaction. Therefore, even if the polyesters are not uniformly dissolved, the decomposition reaction proceeds from the surface of the solid polyesters, and the solid polyesters are almost completely decomposed to obtain the target monomer in a high yield. Can do. Accordingly, a treatment operation for uniformly dissolving the solid polyesters in advance is not required, and the reaction is started quickly only by adding granular polyesters, a predetermined amount of water (preferably hot water) and amines. be able to. In addition, as described above, natural convection occurs without agitation and solid-liquid contact is promoted, so that the reaction can be carried out relatively easily in batch (batch), semi-batch, or flow (continuous) systems. Can be performed using a vessel.

(C) Calculation method for yield of recovered monomer that is decomposition product In this specification, when polycarbonate (PC) is used as a raw material polyester, the target product (monomer that is a decomposition product) The yield of bisphenol A (BPA), the yield of phenol produced when the bisphenol A is further decomposed, and the residue after the depolymerization reaction of the raw material polycarbonate (the polycarbonate remaining as an unreacted raw material) The mass reduction rate due to depolymerization of the raw material polycarbonate is calculated by the following formula. In addition, when polyethylene terephthalate is used as the raw material polyester, the yield of ethylene glycol, the yield of terephthalic acid, the residue yield, and the mass reduction rate of the target product (a monomer that is a decomposition product) are as follows: It is calculated by the mathematical formula described in the definition of yield used in Example 6, and in the semi-batch formula, the yield of ethylene glycol and the yield of terephthalic acid are described in the definition of yield used in Examples 9-12. It is calculated by the following formula.

(D) Yield of target product The yield of the target product (recovered monomer as a decomposition product) in the chemical recycling method of the present invention can be arbitrarily adjusted depending on the reaction time, etc., and is 20% or more, 30% or more, It is preferably 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more. Here, the yield of the target product is, for example, the yield of bisphenol A (BPA) that is the target product (monomer that is a decomposition product) when polycarbonate (PC) is used, and polyethylene terephthalate (PET) When used, the yield (integrated yield) of TPA + EG is the sum of the yield of ethylene glycol (EG), which is the target product (monomer that is a decomposition product), and the yield of terephthalic acid (TPA).

(E) Reaction selectivity Since the chemical recycling method of the present invention has almost complete reaction selectivity (see FIG. 1), the reaction selectivity is 90% or more, preferably 95% or more, more preferably 99%. % Or more, particularly preferably 100%. Here, in this specification, the case where polycarbonate is used as the raw material polyester will be described as an example. The reaction selectivity is defined as follows. Here, phenol is a product (an impurity that cannot be recycled as a raw material monomer for a polymer) that is generated when the BPA of the target product (the recovered monomer that is a decomposition product) is further decomposed.

  Reaction selectivity (%) = 100-phenol yield

  Hereinafter, examples and comparative examples will be described. However, the technical scope of the present invention is not limited only to the following examples.

<Example 1: Change over time of yields of target product, phenol and residue>
A small stainless steel batch reactor (hereinafter also simply referred to as a reactor or a reaction tube) having an internal volume of 3.5 mL without a stirrer was used. Samples of polycarbonate (polycarbonate resin obtained using bisphenol A and phosgene; also referred to as PC; also referred to as PC) sample as polyesters having a diameter of 3.0 mm × height of 1.9 mm in the reaction tube at room temperature. 40 M, 0.6 M (1.86 wt%) prepared with a predetermined amount of distilled water and methylamine (CH ₃ NH ₂ ) as a diluted amine aqueous solution (where M is mol / L. The same applies.) 2.0 g of methylamine aqueous solution was added, and the reactor was closed. Immerse the reactor in an oil bath that has been maintained at a preset temperature (120 ° C) at zero time for a predetermined time (5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes to 60 minutes) After the lapse of time, the reactor was taken out and immersed in a water bath to quench the reactor. The reactor was opened, the contents were taken out, and the inside of the reactor was washed with a mixed solution of water and acetonitrile (the mixing ratio of water and acetonitrile was 1: 1 by volume, the same applies hereinafter). The reaction solution and this washing solution were combined, filtered through a glass filter, and the product was analyzed by high performance liquid chromatography. The residual solid was weighed after drying. Various yields were calculated according to the above definitions. The results are shown in Table 1, Table 2, FIG. 1 and FIG.

  The small batch reactors described in Examples 1 to 8 and Comparative Examples 1 to 3 below were used when the reactor was immersed in an oil bath maintained at a constant set temperature. The temperature inside the reactor (= inside the reaction system) can be rapidly heated to the set temperature, the reaction temperature (= set temperature of the oil bath) and the reaction start time (= time when the reactor is immersed) can be accurately specified, When the reactor is taken out and immersed in a water bath after a predetermined period of time, the temperature inside the reactor can be rapidly cooled to a water bath (room temperature), and the reaction stop time (= time of immersion in the water bath) can be accurately specified. is there. In this method, since the reaction temperature is low, the effect of the oil bath is the same as that of the molten salt bath, and an oil bath is used because a higher heating rate and a stable temperature can be obtained than in an electric furnace.

  As shown in Table 1 and FIG. 1, when a 0.6 M methylamine aqueous solution was used, the yield of the monomer bisphenol A (BPA) reached a value close to 100% at 120 ° C. for 40 minutes. Yes.

  Phenol is produced as a secondary decomposition product in various high-temperature treatments at 250 ° C. or higher as in the existing polycarbonate chemical recycling method described above. However, since the reaction temperature is low under the reaction conditions of Example 1, the secondary decomposition product is used. It can be seen that no phenol was produced. It was confirmed that the amount of polycarbonate residue decreased with time, and decreased corresponding to the production of bisphenol A.

<Example 1a: Change over time in yield of target product when the type of amine is changed>
Instead of using 2.0 g of 0.6 M (1.86 wt%) methylamine aqueous solution prepared with a predetermined amount of distilled water and methylamine (CH ₃ NH ₂ ) as the diluted amine aqueous solution of Example 1, dilution was performed. The same method as in Example 1 was used, except that 2.0 g of a 0.6 M (2.70 wt%) ethylamine aqueous solution prepared with a predetermined amount of distilled water and ethylamine (C ₂ H ₅ NH ₂ ) was used as the aqueous amine solution. The yield of the target product was calculated according to the above definition. The results are shown in Table 2 and FIG.

<Comparative Example 1: Change over time in target product yield when NH ₃ is used instead of amines>
Instead of using 2.0 g of a 0.6 M aqueous solution of methylamine prepared with a predetermined amount of distilled water and methylamine (CH ₃ NH ₂ ) in Example 1, a predetermined amount of distilled water and ammonia (NH ₃ ) were used. The yield of the target product was calculated according to the above-described definition by performing the same method as in Example 1 except that 2.0 g of the 0.6 M aqueous ammonia solution prepared in the above was used. The results are shown in Table 2 and FIG.

<Comparative Example 2: Change over time in target product yield when NaOH was used instead of amine>
Instead of using 2.0 g of a 0.6 M aqueous solution of methylamine prepared with a predetermined amount of distilled water and methylamine (CH ₃ NH ₂ ) of Example 1, a predetermined amount of distilled water and sodium hydroxide (NaOH) were used. ) Was used in the same manner as in Example 1 except that 2.0 g of a 0.6 M sodium hydroxide aqueous solution prepared in (1) was used, and the yield of the target product was calculated according to the above definition. The results are shown in Table 2 and FIG.

  “-” In the table indicates that measurement was not performed at that time (hereinafter the same).

As shown in Table 2 and FIG. 2, when a 0.6M methylamine aqueous solution (CH ₃ NH ₂ aq) is used and when a 0.6M ethylamine aqueous solution (C ₂ H ₅ NH ₂ aq) is used, It was confirmed that almost the same reaction rate and BPA yield were obtained. In the case of an aqueous ammonia solution (NH ₃ aq) or an aqueous sodium hydroxide solution (NaOHaq), the yield of bisphenol A (BPA) was 0% at 120 ° C., so it was confirmed that no reaction occurred.

<Example 2: Influence of reaction temperature in the case of 0.6 M methylamine aqueous solution>
A small stainless steel batch reactor having an internal volume of 3.5 mL without a stirrer was used. In the reaction tube at room temperature, 40 mg of a polycarbonate sample of cylindrical particles having a diameter of 3.0 mm and a height of 1.9 mm as polyesters, a predetermined amount of distilled water and methylamine (CH ₃ NH ₂ ) as a dilute amine aqueous solution, and The reactor was closed by adding 2.0 g of a 0.6M methylamine aqueous solution prepared in (1). Immerse the reactor in an oil bath maintained at a preset temperature (100 ° C., 110 ° C., 120 ° C. to 140 ° C.) at zero time, and for a predetermined time (5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, The test was carried out at 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, and 90 minutes, but when the yield of the target product reached almost the theoretical yield, the measurement was carried out for a longer reaction time. After the lapse, the reactor was taken out and immersed in a water bath to cool the reactor rapidly. The reactor was opened, the contents were taken out, and the inside of the reactor was washed with a mixed solution of water and acetonitrile. The reaction solution and this washing solution were combined, filtered through a glass filter, and the product was analyzed by high performance liquid chromatography. The yield of the target product, bisphenol A (BPA), was calculated according to the above definition. The results are shown in Table 3, FIGS. 3A and 3B.

  In Table 3, 100 ° C., 110 ° C., 120 ° C., and 140 ° C. all indicate reaction temperatures.

  Table 3 and FIG. 3A show the change over time in the yield of the target bisphenol A when the reaction temperature is 100 ° C., 110 ° C., 120 ° C., and 140 ° C. in the case of a 0.6 M methylamine aqueous solution. It is. At any reaction temperature, a theoretical yield of almost 100% bisphenol A was obtained, and it was confirmed that the higher the reaction temperature, the faster the reaction rate. It was confirmed that this reaction can be approximated by a surface reaction model (see FIG. 4B based on the result of Example 3. FIG. 4B shows the concentration of methylamine in the aqueous methylamine solution at 120 ° C. in Example 3 (0.3 -1.2M) is a graph showing the change over time in the decomposition rate of polycarbonate. This is because the decomposition rate of polycarbonate is proportional to the 2/3 power of the unreacted amount of polycarbonate. From Table 3 and FIG. 3A, it was confirmed that the polycarbonate can be almost completely converted to the monomer bisphenol A (BPA) within 20 minutes even at a low temperature of about 140 ° C. with a dilute methylamine aqueous solution. Similarly, assuming that the depolymerization reaction occurs on the surface of granular polycarbonate (solid), the surface reaction model shown by the following mathematical formula (1) was applied.

  In the above formula (1), Y is the following formula (2).

Where k is the apparent reaction rate constant and t is the reaction time.

  FIG. 3B is a drawing showing an Arrhenius plot for the apparent reaction rate constant k obtained from the above equation (1) based on the experimental results of Example 2. From FIG. 3B, the Arrhenius plot was approximated by a straight line, and the activation energy was 64.8 kJ / mol. From FIG. 3B and further from FIG. 4B based on the experimental results of Example 4 to be described later, both could be approximated by a surface reaction model (can be approximated by a straight line). It is considered that the assumption (hypothesis) that occurs on the surface of a solid) has been demonstrated through two experiments.

<Example 3: Influence of methylamine concentration at 120 ° C.>
A small stainless steel batch reactor having an internal volume of 3.5 mL without a stirrer was used. In the reaction tube at room temperature, 40 mg of a polycarbonate sample of cylindrical particles having a diameter of 3.0 mm and a height of 1.9 mm as polyesters, a predetermined amount of distilled water and methylamine (CH ₃ NH ₂ ) as a dilute amine aqueous solution, and Methylamine aqueous solution having a predetermined concentration (0.3 M (0.93 wt%), 0.6 M (1.86 wt%), 0.9 M (2.80 wt%), 1.2 M (3.73 wt%)) 2.0 g was charged and the reactor was closed. Immerse the reactor in an oil bath that is maintained at a preset temperature (120 ° C.) at time zero, for a predetermined time (5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 40 minutes, 50 minutes and However, when the yield of the target product reached almost the theoretical yield, no measurement was performed for a longer reaction time.) After the lapse of time, the reactor was taken out and immersed in a water bath. The reactor was quenched. The reactor was opened, the contents were taken out, and the inside of the reactor was washed with a mixed solution of water and acetonitrile. The reaction solution and this washing solution were combined, filtered through a glass filter, and the product was analyzed by high performance liquid chromatography. The residual solid was weighed after drying. Various yields were calculated according to the above definitions. The results are shown in Table 4, FIG. 4A, FIG. 4B and FIG.

  0.3M, 0.6M, 0.9M, and 1.2M in Table 4 indicate the concentration of methylamine in the methylamine aqueous solution.

  Table 4 and FIG. 4A show changes over time in the yield of bisphenol A, which is the target product, due to the difference in methylamine concentration (0.3 to 1.2 M) in the methylamine aqueous solution at a reaction temperature of 120 ° C. It is. At a reaction temperature of 120 ° C., it was confirmed that the polycarbonate was almost completely converted to bisphenol A at any methylamine concentration of 0.3 M to 1.2 M, and that the reaction rate increased as the methylamine concentration increased. .

  In FIG. 5, the apparent reaction rate constant (surface reaction model) at 120 ° C. was proportional to the methylamine concentration. In Example 3, the reaction temperature was 120 ° C., but it was confirmed that the apparent reaction rate constant was proportional to the amine concentration at other reaction temperatures as well.

<Example 4: Comparison of various amines at 120 ° C.>
A small stainless steel batch reactor having an internal volume of 3.5 mL without a stirrer was used. In the reaction tube at room temperature, 40 mg of a polycarbonate sample of cylindrical particles having a diameter of 3.0 mm and a height of 1.9 mm as polyesters, a predetermined amount of distilled water and various butylamines (n-butylamine (BuNH ₂ ), 2.0 g of various 0.6M (4.39 wt%) butylamine aqueous solutions prepared with sec-butylamine (sec-BuNH ₂ ) to tert-butylamine (tert-BuNH ₂ )), and Closed. Immerse the reactor in an oil bath maintained at a preset temperature (120 ° C) at zero time, and after a predetermined time (5 min, 10 min, 15 min, 20 min, 30 min, 40 min and 60) has elapsed, The vessel was removed and immersed in a water bath to quench the reactor. The reactor was opened, the contents were taken out, and the inside of the reactor was washed with a mixed solution of water and acetonitrile. The reaction solution and this washing solution were combined, filtered through a glass filter, and the product was analyzed by high performance liquid chromatography. The residual solid was weighed after drying. Various yields were calculated according to the above definitions. The results are shown in Table 5 and FIG.

Table _{BuNH 2, sec-BuNH 2,} tert-BuNH 2 in 5 shows both of butylamine in butylamine solution structures (different butylamine isomers).

Table 4 and FIG. 6 show the influence of the butylamine isomer on the time-dependent change in the yield of bisphenol A. Regardless of the structure (isomer) of butylamine, the polycarbonate is almost completely converted to bisphenol A, but the reaction rate greatly depends on the structure of butylamine. The reaction rate was in the order of BuNH ₂ > sec-BuNH ₂ > tert-BuNH ₂ , and it was confirmed that the reaction rate decreased as the alkyl group to which the amino group was bonded was bulky.

<Example 5: Comparison of primary, secondary, and tertiary amines at 120 ° C.>
A small stainless steel batch reactor having an internal volume of 3.5 mL without a stirrer was used. In the reaction tube at room temperature, 40 mg of a polycarbonate sample of cylindrical particles having a diameter of 3.0 mm and a height of 1.9 mm as polyesters, a predetermined amount of distilled water and various methylamines (primary grades) as a dilute aqueous amine solution. 0.6 M (1.86 wt%) prepared with methylamine (CH ₃ NH ₂ ), secondary dimethylamine ((CH ₃ ) ₂ NH) to tertiary trimethylamine ((CH ₃ ) ₃ N)) ), 0.6M (2.70 wt%) secondary amine or 0.6 M (3.55 wt%) tertiary methylamine aqueous solution (2.0 g) was added, and the reactor was closed. . The reactor is immersed in an oil bath that is maintained at a preset temperature (120 ° C) at zero time, and a predetermined time (5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, and 60) has elapsed. Thereafter, the reactor was taken out and immersed in a water bath to quench the reactor. The reactor was opened, the contents were taken out, and the inside of the reactor was washed with a mixed solution of water and acetonitrile. The reaction solution and this washing solution were combined, filtered through a glass filter, and the product was analyzed by high performance liquid chromatography. The residual solid was weighed after drying. Various yields were calculated according to the above definitions. The results are shown in Table 6, FIG. 7 and FIG.

  The primary amine, secondary amine, and tertiary amine in Table 6 indicate primary methylamine, secondary dimethylamine, and tertiary trimethylamine, respectively, in the diluted amine aqueous solution.

  Table 6 and FIG. 7 show a comparison of primary amine, secondary amine, and tertiary amine with respect to time-dependent change in BPA yield at 120 ° C. FIG. 8 shows a comparison of primary amine, secondary amine, and tertiary amine with respect to time-dependent change in the weight loss of polycarbonate at 120 ° C. From Table 6 and FIG. 7, the reaction rate for producing the target bisphenol A (BPA) is in the order of primary amine> tertiary amine> secondary amine, but from Table 6 and FIG. The mass reduction rate of the polycarbonate is in the order of primary amine≈secondary amine> tertiary amine. Therefore, in the case of secondary amine, the yield of bisphenol A (BPA) has reached its peak at about 20%, but this is a product other than bisphenol A when viewed from the mass reduction rate of polycarbonate. It is suggested that

  As described above, although there is a difference in reaction rate, when a relatively low temperature hot water is brought into contact with polycarbonate in the presence of a small amount of amines, the polycarbonate is efficiently depolymerized, and bisphenol A, which is a monomer, and dioxide are almost completely removed. It was found to decompose into carbon. The chemical recycling method of the present invention requires no catalyst or additive in addition to a very small amount of amines, and does not use an organic solvent. Therefore, separation and purification of bisphenol A is easy, and energy consumption is also low. There are few highly efficient chemical recycling methods.

<Example 6: Yield and mass reduction rate of target product (TPA, EG) when using PET instead of PC>
A small stainless steel batch reactor (hereinafter also simply referred to as a reactor or a reaction tube) having an internal volume of 3.5 mL without a stirrer was used. Aromatic polyester resin obtained by using polyethylene terephthalate (ethylene glycol (EG) and terephthalic acid (TPA) in the form of cylindrical particles having a diameter of 3.3 mm and a height of 2.4 mm as polyesters in the reaction tube at room temperature. Also referred to as PET. The same shall apply hereinafter.) 2.0 g of 0.9 M (2.80 wt%) methylamine aqueous solution prepared from 42 mg of sample and a predetermined amount of distilled water and methylamine (CH ₃ NH ₂ ) as a dilute amine aqueous solution. And the reactor was closed. The reactor was immersed in an oil bath maintained at a preset temperature (140 ° C.) at zero time, and after a predetermined time (60 minutes), the reactor was taken out and immersed in a water bath to quench the reactor rapidly. The reactor was opened, the contents were taken out, and the inside of the reactor was washed with a mixed solution of water and acetonitrile. The reaction solution and this washing solution were combined, filtered through a glass filter, and the product was analyzed by high performance liquid chromatography. The residual solid was weighed after drying. Various yields were calculated according to the definitions given below. The results are shown in Table 7.

<Comparative Example 3: Change over time in target product yield when NaOH is used instead of amines>
Instead of using 2.0 g of a 0.9 M aqueous solution of methylamine prepared with a predetermined amount of distilled water and methylamine (CH ₃ NH ₂ ) of Example 6, a predetermined amount of distilled water and sodium hydroxide (NaOH) were used. ) And 0.9M sodium hydroxide aqueous solution prepared in the same manner as in Example 6 except that 2.0 g of an aqueous solution of sodium hydroxide was used, and the TPA yield, EG yield, residue yield, and mass reduction rate were shown below. Calculated according to the definition. The results are shown in Table 7.

From Table 7 above, when 0.9 M aqueous methylamine solution (CH ₃ NH ₂ aq) is used, terephthalic acid (TPA) and ethylene glycol (EG), which are raw material monomers for polyethylene terephthalate (PET), which is the target product, are used. However, it was recovered at almost the same reaction rate and almost the same yield (same molar ratio; because PET decomposes to produce equimolar amounts of terephthalic acid and ethylene glycol). On the other hand, in the case of aqueous sodium hydroxide (NaOHaq), the yield of terephthalic acid (TFA) and ethylene glycol (EG), which are raw material monomers of polyethylene terephthalate (PET), is 0% to almost 0% at 140 ° C. It was confirmed that there was almost no reaction.

<Example 7: Change in yield of BPA over time by NaOH addition and non-addition diluted amine aqueous solution>
(1) A dilute amine aqueous solution not containing NaOH was used as a small batch reactor made of stainless steel (hereinafter also simply referred to as a reactor or a reaction tube) having an internal volume of 3.5 mL without a stirrer. Samples of polycarbonate (polycarbonate resin obtained using bisphenol A and phosgene; also referred to as PC; also referred to as PC) sample as polyesters having a diameter of 3.0 mm × height of 1.9 mm in the reaction tube at room temperature. 160 mg and 2.0 g of a 0.6 M (1.86 wt%) methylamine aqueous solution prepared with a predetermined amount of distilled water and methylamine (CH ₃ NH ₂ ) as a dilute amine aqueous solution were added, and the reactor was closed. After immersing the reactor in an oil bath that has been maintained at a preset temperature (120 ° C) at zero time, and after the predetermined time (10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, and 90 minutes) has elapsed The reactor was removed and immersed in a water bath to quench the reactor. The reactor was opened, the contents were taken out, and the inside of the reactor was washed with a mixed solution of water and acetonitrile. The reaction solution and this washing solution were combined, filtered through a glass filter, and the product was analyzed by high performance liquid chromatography. The residual solid was weighed after drying. The yield of bisphenol A (BPA) was calculated according to the above definition. The results are shown in FIG.

(2) About NaOH-added diluted amine aqueous solution Next, a stainless steel small batch reactor (hereinafter also simply referred to as a reactor or a reaction tube) having an internal volume of 3.5 mL without a stirrer was used. Samples of polycarbonate (polycarbonate resin obtained using bisphenol A and phosgene; also referred to as PC; also referred to as PC) sample as polyesters having a diameter of 3.0 mm × height of 1.9 mm in the reaction tube at room temperature. 160 mg, 1.0 g of a 0.6 M (1.86 wt%) methylamine aqueous solution prepared with a predetermined amount of distilled water and methylamine (CH ₃ NH ₂ ) as a diluted amine aqueous solution, a predetermined amount of distilled water and water 2.0 g of a solution prepared by mixing 1.0 g of a 0.6 M aqueous sodium hydroxide solution prepared with sodium oxide (NaOH) was added, and the reactor was closed. Immerse the reactor in an oil bath that is maintained at a preset temperature (120 ° C) at zero time, and for a predetermined time (10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes and 90 minutes) After the lapse of time, the reactor was taken out and immersed in a water bath to quench the reactor. The reactor was opened, the contents were taken out, and the inside of the reactor was washed with a mixed solution of water and acetonitrile. The reaction solution and this washing solution were combined, filtered through a glass filter, and the product was analyzed by high performance liquid chromatography. The residual solid was weighed after drying. The yield of BPA was calculated according to the above definition. The results are shown in Table 8 below and FIG.

From the results shown in Table 8 and FIG. 9, when a diluted amine aqueous solution added with NaOH is used, there is no effect of addition at the initial stage of reaction (short reaction time) in which CO ₂ is not generated so much. The same BPA yield. That is, at the beginning of the reaction, since CO ₂ has not yet accumulated in the reactor, the BPA yield was the same when using the diluted amine aqueous solution with NaOH and when using the diluted amine aqueous solution without NaOH. However, when the reaction time elapses and CO ₂ accumulates in the reactor, when the diluted amine aqueous solution not added with NaOH is used, the BPA yield reaches a peak, but the diluted amine aqueous solution added with NaOH is used. The case has increased. That is, as the reaction time elapses, the BPA yield reaches its peak when the diluted amine aqueous solution without NaOH is used, but when the diluted amine aqueous solution with NaOH is used, the BPA yield increases as it is. I found out. This is considered to be because the pH drop was suppressed by adding NaOH.

<Consideration of reaction pressure>
According to the observation from the experimental observations and experimental results of Examples 1 to 5 above, the reaction pressure is depolymerized in the liquid phase (even if solid polyesters are used, the reaction on the solid surface). In the liquid phase of the interface (solid-liquid contact interface), it is considered that amines having a lower boiling point as the pressure increases are distributed more in the liquid phase, resulting in an increase in the reaction rate. However, since the concentration of amines is dilute, pressurization with another gas can be considered to increase the pressure (in this case, the concentration of amines in the liquid phase does not increase), but it can be said that there is no effect. In conclusion, the pressure will have little effect on dilute aqueous amine solutions. FIG. 10 is a reference drawing showing a saturated vapor pressure curve of water. As shown in FIG. 10, the pressure at each temperature is the saturated vapor pressure of the aqueous solution at that temperature, but in the presence of a small amount of amines, the amines when the relatively low temperature hot water is brought into contact with the polycarbonate. This is because it can be assumed that the saturated vapor pressure of water at that temperature is not so different even if it is assumed that the diluted amine aqueous solution is pure water.

<Example 8: Concentration dependence of monoethanolamine>
Ethanolamine has many industrial uses such as gas cleaning, and since it can be reused as a reaction solvent for depolymerization of polyester, such as recycled products, in this example, dilute containing amines As the amines in the aqueous amine solution, monoethanolamine, which is an amine having a hydroxyl group, was selected and tested.

A small stainless steel batch reactor having an internal volume of 3.5 mL without a stirrer was used. Into the reaction tube at room temperature, 40 mg of a polycarbonate (PC) sample of cylindrical particles having a diameter of 3.0 mm and a height of 1.9 mm as polyesters, a predetermined amount of distilled water and monoethanolamine (H ₂ as a dilute aqueous amine solution). NCH ₂ CH ₂ OH) and predetermined concentrations (0.3 M (1.8 wt%), 0.5 M (3.0 wt%), 0.8 M (4.7 wt%), 1.0 M (5.8 wt) %), 1.5 M (8.4 wt%), 2.0 M (11 wt%), 3.0 M (15 wt%)) monoethanolamine aqueous solution 2.0 g was added, and the reactor was closed. Immerse the reactor in an oil bath that is maintained at a preset temperature (130 ° C.) at time zero, for a predetermined time (10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, The reaction was carried out at 90 minutes and 100 minutes, but when the yield of the target product reached the theoretical yield, measurement was not carried out for a longer reaction time.) After the passage, the reactor was taken out, The reactor was quenched by immersion in a water bath. The reactor was opened, the contents were taken out, and the inside of the reactor was washed with a mixed solution of water and acetonitrile. The reaction solution and this washing solution were combined, filtered through a glass filter, and the product was analyzed by high performance liquid chromatography. The residual solid was weighed after drying. Various yields were calculated according to the above definitions. The results are shown in Table 9 and FIG.

  0.3M, 0.5M, 0.8M, 1.0M, 1.5M, 2.0M, and 3.0M in Table 9 all indicate the concentration of monoethanolamine in the monoethanolamine aqueous solution.

  FIG. 11 shows the change over time in the yield of bisphenol A (BPA), which is the target product, due to the difference in monoethanolamine concentration (0.5 to 3.0 M) in the monoethanolamine aqueous solution at a reaction temperature of 130 ° C. It is. As shown in Table 9 and FIG. 11, it was confirmed that amines having a hydroxyl group are also effective for the monomerization of PC. It was also confirmed that the reaction rate and the elution start time of the monomer were shortened as the concentration of monoethanolamine was increased. Furthermore, although the reaction was not completed in 100 minutes at a monoethanolamine concentration of 0.5M, it was confirmed that a BPA yield of 90% or more was obtained at a monoethanolamine concentration of 0.8M or more.

  FIG. 12 shows the dependency of the monoethanolamine concentration on the surface reaction rate constant at 130 ° C. Here, the rate constant shown is obtained from the same plot as in FIG. 4B by applying the rate formula based on the surface reaction represented by the above formula (1) to the data shown in Table 9 and FIG. . As shown in FIG. 5, the rate constant is proportional to the amine concentration in FIG. 12, as in the case of amines having no hydroxyl group, but it was confirmed that the rate constant reached a peak at 1 M or more.

<Experiment with PET using semi-batch reactor>
For polyethylene terephthalate (PET), a semi-batch type small reactor (polymer (PET sample) is fixed in the reactor, the solvent is continuously supplied to the reactor, and the product monomer is immediately dissolved in the solvent. Examples of the effectiveness of amines under various conditions are described below using a system configuration removed from

  Examples 1-8 are the results obtained with a small batch reactor. In batch reactors, a sample (polyesters) and a solvent (diluted amine aqueous solution containing amines) are charged and reacted in the reactor, and the reaction product is removed after completion of the reaction. Has the advantage of being able to measure accurately. However, since the product accumulates in the reactor as the reaction proceeds, the accuracy of the obtained reaction rate is lower than that of the semi-batch method when accompanied by mass transfer such as dissolution.

  On the other hand, in a semi-batch reactor, the solid polymer (polyesters) of the sample is fixed in the reactor, and the reaction solvent (diluted amine aqueous solution containing amines) is continuously supplied to the reactor. Since the contact between the polymer and the reaction solvent is good and the product is instantaneously removed from the reaction zone, there is an advantage that an accurate reaction rate can be obtained. In Examples 9-12 shown below, the effectiveness of amine as a reaction solvent is demonstrated by using a semi-batch reactor for PET to demonstrate that the difference in reactors is not. Showing gender. (Example 6 is the result for PET using a batch reactor).

<About the experiment using the semi-batch reactor of Examples 9-12>
The semi-batch type reactor configuration used in the following Examples 9 to 12 is shown in FIG. The semi-batch type reactor 11 is 1/8 inch at both ends of a small reactor (reaction tube; internal volume 3.5 mL) 12 having the same size and shape as the batch reactor used in Examples 1 to 8. A stainless steel pipe (pipe) 13 is connected.

  In the experiment using the semi-batch type reactors of Examples 9 to 12, a small amount of pellet-shaped PET sample was charged into a small-sized reactor 12 at room temperature, and the entire reactor 12 was filled with distilled water. The outlet of the reactor 13 is fixed with a sintered metal plate (not shown) having a pore diameter of 2 μm so that the PET sample does not flow out. The preheating column 14 is immersed in a molten salt bath 15 that is previously maintained at a set temperature. The reactor 12 is immersed in the molten salt bath 15 at time zero, and at the same time, the reaction solvent is supplied from the solvent tank 17 to a predetermined flow rate (mainly a flow rate of 3 mL / min) by a pump (for example, a high-speed liquid chromatograph (HPLC) feed pump). Then, it is supplied to the reactor 12 through the pipe 13 via the preheating column 14.

  In Examples 9 to 12 below, the reaction solvent is continuously supplied to the reactor 12 in order to accurately measure the reaction rate. To advance the monomerization reaction, the reactor 12 is used. It is not necessary to supply the reaction solvent at a constant flow rate, and there is no problem even if it is interrupted or interrupted in the middle, and if it is interrupted, the conditions are the same as in the batch reactor. Further, the solvent supply method is not limited to the supply method using the pump 16, and the reaction solvent may be circulated through the inside and outside of the reaction vessel repeatedly as in reflux, and the solvent supply method to the reactor 12 is also possible. Is not subject to any restrictions.

  In addition, as for the supply amount, since the produced monomer may be removed from the surface of the solid polymer (PET sample), it is not necessary to uniformly dissolve in the solvent throughout the reactor 12. In this method, the amine is hydrolyzed again through the reaction intermediate and returned to the amine, so that if the amount of amine charged is small relative to the amount of polymer, the reaction rate only decreases and the reaction does not stop. Therefore, there is no restriction on the solvent supply rate, supply amount, or concentration.

  The reaction solvent containing the monomer as the product is passed through the reactor 12 through the cooling pipe 18 (for example, a double cooling pipe, and the reaction solvent containing the monomer as the product is passed through the pipe 13 as the inner pipe 18a, and the outer pipe 18b. The reaction is stopped by cooling, flows out from the back pressure valve 19, and is collected in the reaction liquid tank 20 through the pipe 13. A solution (reaction solution) was collected in the reaction solution tank 20 at a fixed time (mainly at intervals of 2 minutes), and the contents were analyzed using liquid chromatography. Moreover, the presence or absence of the oligomer of the product and its molecular weight were measured using gel filtration chromatography.

  In order to keep the inside of the molten salt bath 15 at a predetermined set temperature, for example, as shown in FIG. 13, the molten salt bath 15 is stirred by the thermocouple 22 while the molten salt bath 15 is uniformly stirred by the stirring blade 21. The temperature in 15 is measured. A heating unit (for example, heating) installed in the molten salt bath 15 based on a signal output by calculation in the control unit based on a temperature difference between the measured temperature data input to the control unit (not shown) and a set temperature. A control device configuration is provided that can adjust the temperature in the molten salt bath 15 (= preheating temperature in the preheating column 14) to be a predetermined set temperature by controlling the energization amount (heating amount) to the heater). It has been. However, the configuration of the control device for maintaining the inside of the molten salt bath 15 at a predetermined set temperature is not limited to the one described above, and a conventionally known temperature control device can be appropriately used.

<Definition of yield when using PET samples in Examples 9-12 below>
Yield was based on carbon content. The TPA yield molar standard and the EG yield molar standard in the following yield definitions were used to calculate the TPA yield and EG yield in the case of the PET samples of Example 6 and Comparative Example 3 described above. The definition shall apply.

<Example 9: Change in accumulated monomer yield over time in the case of trimethylamine aqueous solution>
Using the semi-batch type reactor 11 shown in FIG. 13, the reaction temperature (set temperature) is 200 ° C., the trimethylamine concentration in the trimethylamine aqueous solution is 0.6 M, the flow rate of the reaction solvent supplied to the reactor 12 is 3 mL / min, polyesters As an average value of 3.3 mm × 3.2 mm × 2.4 mm (major axis × minor axis × height) axis-perpendicular cross-section of columnar particles of polyethylene terephthalate (also referred to as PET; hereinafter the same) 90 mg sample The above-described experiment was performed using the sample, and the product was analyzed and measured from the collected reaction solution at regular intervals. From the obtained analysis / measurement results, according to the above yield definition, the integrated yield of terephthalic acid (TPA) and ethylene glycol (EG), which are monomers when the reaction temperature (set temperature) is 200 ° C. and the trimethylamine concentration is 0.6M. Further, a change with time in the integrated yield of TPA + EG obtained by adding them together was determined. The results are shown in Table 10 and FIG.

  As shown in Table 10 and FIG. 14, at the reaction temperature (set temperature) of 200 ° C., the monomer started to elute about 10 minutes after the trimethylamine aqueous solution (trimethylamine concentration 0.6 M) as the reaction solvent was supplied. The respective yields in minutes reached an integrated yield of TPA = 78%, an integrated yield of EG = 18%, an integrated yield of total TPA + EG = 96%, and the raw material PET was converted to a monomer almost 100%. I understood it. Moreover, the residence time of the fluid in the reactor 11 used in this example was 30 seconds or less from the reactor 12 inlet to the back pressure valve 19 outlet from the tracer response measurement.

<Example 10: Effect of different types of amine on time-dependent change of TPA + EG accumulated yield in semi-batch reactor>
Using the semi-batch type reactor 11 shown in FIG. 13, the reaction temperature (set temperature) is 200 ° C., the amine concentration of various amine (methylamine, dimethylamine, trimethylamine, ethylamine) aqueous solutions is constant at 0.6 M, and the reactor The flow rate of the reaction solvent supplied to the column is 3 mL / min, the average value of the polyester as 3.3 mm × 3.2 mm × 2.4 mm (long axis × short axis × height) Using 90 mg of the PET sample, the above-described experiment was performed using the various aqueous amine solutions described above, and the products were analyzed and measured from the collected reaction solutions at regular intervals. From the obtained analysis and measurement results, according to the definition of the yield, terephthalic acid (TPA) and ethylene glycol (EG) which are monomers when the reaction temperature (setting temperature) is 200 ° C. and the amine concentration of various amine aqueous solutions is 0.6 M. ) In total, the change in the integrated yield of TPA + EG over time was determined. The results are shown in Table 11 and FIG.

  FIG. 15 shows the effect of the type of amine on the time-dependent change in the TPA + EG cumulative yield by the semi-batch reactor. From FIG. 15, it was confirmed that the monomer elution started almost 10 minutes after supplying the solvent and the reaction was completed in about 50 minutes for any amine. In the case of methylamine, TPA + EG integrated yield = 80%, the lowest yield, dimethylamine, ethylamine, and trimethylamine increase in order, and trimethylamine has the highest monomer yield, almost 100% monomer. The recovery rate was confirmed.

<Example 11: Effect of reaction temperature in trimethylamine 0.6M>
Using the semi-batch type reactor 11 of FIG. 13 described above, trimethylamine at each reaction temperature (set temperature) (170 ° C., 180 ° C., 190 ° C., 200 ° C., 210 ° C., 220 ° C., 230 ° C., 240 ° C.) The trimethylamine concentration of the aqueous solution is 0.6 M, the flow rate of the reaction solvent supplied to the reactor is 3 mL / min, and the average value is 3.3 mm × 3.2 mm × 2.4 mm (major axis × minor axis × height) as polyesters Using 90 mg of a PET sample of columnar particles with an elliptical cross section at right angles, the above experiment was performed at each reaction temperature (set temperature) described above, and analysis and measurement of the product was performed at regular intervals from the collected reaction solution. went. From the obtained analysis and measurement results, according to the above yield definition, (a) terephthalic acid (TPA), which is a monomer when the trimethylamine concentration of the aqueous trimethylamine solution is 0.6 M, at each reaction temperature (170 to 240 ° C.) (B) (1-Y) ^1/3 -1 (where Y is the above-mentioned formula (2)), and (b) (1-Y) ^1/3 -1 in the above formula (1) The time-dependent change of each time was obtained by substituting “integrated yield of TPA + EG” instead of “BPA yield”. The results are shown in Table 12, Table 13, and FIGS. 16A and 16B.

FIG. 16 shows the change with time of the integrated yield of (A) TPA + EG and the change with time of (B) (1-Y) ^1/3 −1 at each temperature at a trimethylamine concentration of 0.6M. About FIG. 16B, if linear relationship is acquired as said Numerical formula (1), reaction rate can be described as surface reaction.

As shown in FIG. 16A, it was confirmed that the reaction rate increased as the temperature increased. The accumulated yield of TPA + EG is about 90% at 190 ° C. or lower, but reaches 95 to 97% at 200 ° C. or higher. The starting time of elution is shortened with increasing temperature. As shown in FIG. 16B, it was confirmed that each plot shows a linear relationship across the reaction rate and can be described as a surface reaction. Here, Y is a reaction rate based on the TPA + EG yield, and (1-Y) ^1/3 −1 = −0.536 and Y = 0.90.

<Comparative Example 4: Arrhenius plot of reaction rate constant when using 0.6 M ammonia aqueous solution instead of 0.6 M concentration trimethylamine aqueous solution>
An experiment was performed in the same manner as in Example 11 except that an aqueous ammonia solution having a concentration of 0.6M was used instead of an aqueous solution of trimethylamine having a concentration of 0.6M, and analysis / measurement of the product from the collected reaction solution was performed at regular intervals. I went there. According to the above yield definition from the obtained analysis / measurement results, (a) terephthalic acid (TPA) which is a monomer in the case of ammonia concentration 0.6M in the aqueous ammonia solution at each reaction temperature (170 to 240 ° C.) (B) (1-Y) ^1/3 -1 (where Y is the above-mentioned formula (2)), and (b) (1-Y) ^1/3 -1 in the above formula (1) The time-dependent change of each time was obtained by substituting “integrated yield of TPA + EG” instead of “BPA yield”. The results are shown in Tables 14 and 15.

  The reaction rate constants for the trimethylamine aqueous solution and the aqueous ammonia solution at a concentration of 0.6 M were determined from the analysis and measurement results obtained for Example 11 and Comparative Example 4, respectively, and are shown in Table 16, and FIG. An Arrhenius plot was performed.

  FIG. 17 shows an Arrhenius plot of reaction rate constants for an aqueous trimethylamine solution and an aqueous ammonia solution at a concentration of 0.6M. From FIG. 17, trimethylamine and ammonia differ in temperature dependency at reaction temperatures of 210 ° C. or lower and 220 ° C. or higher, and the rate constant at 220 ° C. or higher is slightly smaller than that of trimethylamine, but at 210 ° C. or lower, 2.5 times the trimethylamine has a larger rate constant. The slopes are almost equal, and the activation energy values are both about 50 kJ / mol.

  From the above, even when PET (aromatic polyester) is used as the polyester, it contains the amines of the present invention more than the chemical recycling method using ammonia-containing hot water, like other polyesters such as polycarbonate. The chemical recycling method using dilute aqueous amine solution is more efficient for depolymerization under milder conditions, that is, under the milder reaction temperature condition of 210 ° C or lower, where the trimethylamine has a larger rate constant of 2 to 2.5 times. It was confirmed that the reaction could proceed.

  As described above, in the case of ammonia, the reaction rate is significantly lower than that of trimethylamine at 170 to 210 ° C. (1000 / T = 2.257 to 2.070), which is a milder reaction temperature condition. The reaction rate in the case of triethylamine approaches 220 ° C. (1000 / T = 2.028) or higher, which is a high temperature. Therefore, in the case of ammonia, more severe conditions (high temperature of 220 ° C. or higher) are necessary to obtain a reaction rate comparable to that of trimethylamine.

  In addition, in the case of ammonia, the reaction rate can be increased by increasing the ammonia concentration instead of increasing the reaction temperature so as not to be harsh (high temperature). The product amide tends to form, which is not preferable. On the other hand, in the case of trimethylamine, since the yield of terephthalic acid is close to the theoretical yield in all of the examples, it can be said that the amide is hardly produced because the production rate of amide is very low.

<Example 12: Effect of concentration of trimethylamine on time-dependent change in integrated yield of TPA + EG>
Using the above-described semi-batch type reactor 11 shown in FIG. 13, the reaction temperature (set temperature) is 200 ° C., and trimethylamine aqueous solutions (trimethylamine concentrations of 0.3 M, 0.6 M, 0.9 M, and 1.2 M) at various concentrations are used. The flow rate of the reaction solvent supplied to the reactor is 3 mL / min, and the average value of 3.3 mm × 3.2 mm × 2.4 mm (major axis × minor axis × height) as polyesters is an elliptical columnar section. Using the 90 mg PET sample of the above particles, the above-described experiment was performed with each of the above-described trimethylamine aqueous solutions, and products were analyzed and measured at regular intervals from the collected reaction solution. From the obtained analysis and measurement results, terephthalic acid (TPA), which is a monomer in the case of an aqueous trimethylamine solution at various concentrations (trimethylamine concentration 0.3 M to 1.2 M) at a reaction temperature of 200 ° C. And the time-dependent change in the integrated yield of TPA + EG obtained by adding ethylene glycol (EG). The results are shown in Table 17 and FIG.

  FIG. 18 shows the change over time in the integrated yield of TPA + EG when the trimethylamine concentration is changed. From FIG. 18, the integrated yield reaches 90% or higher at any concentration, and the reaction rate increases with increasing trimethylamine concentration at low concentrations. However, the concentration is higher and the speed is almost the same at 0.9M and 1.2M. It was confirmed that the elution start time was hardly influenced by the concentration within this concentration range.

<Discussion>
The following can be considered through the experimental results of the above-described embodiments.

(1) About pressure Although the reaction pressure in Examples 9-12 is 10 MPa, what is necessary is just to keep a pressure more than the saturated vapor pressure of the amine aqueous solution in 170-240 degreeC. Since the reaction solvent is a liquid phase, the density change due to pressure is small, and the influence of the reaction pressure on the monomer yield and reaction rate is considered to be very small. Furthermore, although the efficiency decreases, the reaction is considered to proceed even in the vapor phase. However, since the product (monomer or the like) is attached to the polymer surface, the reaction proceeds if there is a method or medium for removing the product. Based on the above knowledge, it is considered that the reaction solvent is preferably in the liquid phase.

(2) Difference between PC and PET In the chemical recycling method of the present invention, the effect of the amine on the depolymerization reaction of PC and PET is the same, but the effect differs depending on the difference in the monomer produced. PC monomers are bisphenol A and CO ₂ , and in the case of a batch reactor, CO ₂ accumulates in the solution as the reaction proceeds, resulting in a decrease in the pH of the solution and a decrease in the reaction rate. In PET, TPA is an acid among the monomers terephthalic acid (TPA) and ethylene glycol (EG), so that the pH of the solution is further lowered than CO ₂ and the reaction rate is lowered. Therefore, if alkali is added at the beginning or in the middle so as not to lower the pH in the solution, it can be considered that the reaction rate does not decrease from the fact that Example 7 has confirmed the effect of adding alkali to PC.

Claims (13)

General formula (1);
(In the formula, R ¹ , R ² and R ³ are each independently a hydrogen atom; or a substituted or unsubstituted hydrocarbon group, provided that at least one of R ¹ , R ² and R ³ And a substituted or unsubstituted hydrocarbon group.) A chemical recycling method comprising a step of depolymerizing polyesters using a dilute aqueous amine solution containing amines represented by:   The chemical recycling method according to claim 1, wherein the concentration of the amines is in the range of 0.003 to 26 M with respect to the entire diluted amine aqueous solution.   The chemical recycling method according to claim 1 or 2, wherein the concentration of the amines is in the range of 0.03 to 16M with respect to the whole diluted amine aqueous solution.   The chemical recycling method according to any one of claims 1 to 3, wherein the concentration of the amines is in the range of 0.06 to 3.5 M with respect to the entire diluted amine aqueous solution.   The chemical recycling method according to any one of claims 1 to 4, wherein a content of the polyester is in a range of 0.1 to 50 wt% with respect to a total amount of the diluted amine aqueous solution and the polyester.   The chemical recycling method according to any one of claims 1 to 5, wherein a reaction temperature of the depolymerization is not higher than a melting point of the polyesters.   The chemical recycling method according to claim 1, wherein the unsubstituted hydrocarbon group is an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 10 carbon atoms.   The chemical recycling method according to claim 1, wherein the unsubstituted hydrocarbon group is a lower alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 10 carbon atoms.   The chemical recycling method according to claim 1, wherein the unsubstituted hydrocarbon group is a linear lower alkyl group having 1 to 5 carbon atoms.   The chemical recycling method according to any one of claims 1 to 9, wherein a substituent of the substituted hydrocarbon group is a hydroxyl group, a thiol group, or a halogen atom. The amines are primary amines in which R ¹ in the general formula (1) is an unsubstituted straight-chain lower alkyl group having 1 to 5 carbon atoms, and R ² and R ³ are both hydrogen atoms. The chemical recycling method according to any one of claims 1 to 10.   The chemical recycling method according to claim 1, wherein the polyester is polycarbonate, polyethylene terephthalate, polyethylene naphthalate, poly-D-lactic acid, or poly-L-lactic acid.   The chemical recycling method according to claim 1, wherein the polyester is polycarbonate or polyethylene terephthalate.