JP2005082710A - Continuous depolymerization method and continuous depolymerization apparatus for polyester, polycarbonate or polylactic acid using supercritical fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a depolymerized product efficiently by continuously depolymerizing polyester, polycarbonate or polylactic acid in a supercritical fluid.
SOLUTION: A supercritical fluid and an organic solvent solution of polyester, polycarbonate, or polylactic acid are continuously passed through a hydrolase packed column, and the polyester, polycarbonate, or polylactic acid is depolymerized by the hydrolase, thereby hydrolyzing the enzyme. A method for continuous depolymerization of polyester, polycarbonate or polylactic acid for separating a depolymerization product from a reaction mixture containing a depolymerization product flowing out from a packed column, and a supercritical fluid generator, a hydrolytic enzyme packed column, a back pressure regulator, Means for separating the depolymerization product from the depolymerization product-containing reaction mixture, means for feeding the supercritical fluid produced by the supercritical fluid generator to the column, and an organic solvent solution of polyester, polycarbonate or polylactic acid The apparatus according to claim 1, further comprising means for feeding the column. A continuous depolymerization apparatus for use in the continuous depolymerization method described.
[Selection] Figure 1

Description

  The present invention relates to a method for continuously depolymerizing polyester, polycarbonate or polylactic acid using a supercritical fluid.

One of the important issues in science and technology in the 21st century is “Building Green Chemistry”. In particular, synthetic polymers are chemically synthesized from 150 million tons of oil and natural gas and other limited fossil resources around the world every year. In order to continue to develop this field in the future, energy-saving type Development of chemical recycling technology is required.
Synthetic polymers are recycled using the Material Recycling Law, Chemical Recycling Law, Thermal Recycling Law, etc., but from the viewpoint of the effective use of carbon resources, it can be finally returned to the raw material by the Chemical Recycling Law. Ideal. This chemical recycling method is known to recover monomers by a chemical depolymerization reaction. However, it is energy intensive and has a large environmental impact and is generally not profitable.

There is an urgent need for energy-saving chemical recycling technology against such energy-intensive chemical recycling technology, and in response to this request, the present inventors proposed a chemical recycling technology using enzyme catalysts. . For example, Patent Document 1 below describes conversion of polycaprolactone to a cyclic dimer by an enzyme catalyst and a repolymerization method of the produced cyclic dimer by an enzyme catalyst. Describes a selective conversion of polytrimethylene carbonate (PTMC) to cyclic trimethylene carbonate (TMC) and a method for enzymatic repolymerization of this cyclic TMC. Further, Patent Document 3 below discloses polyalkylene alkanoates. Alternatively, a method for depolymerizing poly (3-hydroxyalkanoate) into an oligomer mainly composed of a cyclic product and a method for repolymerizing the cyclic oligomer are disclosed. In any of these methods, an oligomer mainly composed of a cyclic product is generated by depolymerization of the polymer with an enzyme, and the oligomer is easily repolymerized with an enzyme (also with a chemical catalyst). Since the polymerization is ring-opening polymerization, there is no elimination component such as water and it is not necessary to take them out of the reaction system. Therefore, the polymerization reaction operation is simple, no exhaust equipment is required, and simultaneous molding is possible. Have advantages.
Further, the present inventor obtained a repolymerizable oligomer mainly composed of a cyclic product by depolymerizing polyester and polycarbonate in a supercritical fluid in the presence of an enzyme catalyst. Further, the repolymerizable oligomer was supercritical. A method of repolymerization in a fluid was proposed (see Patent Document 4 below). This method has advantages that it does not use a normal organic solvent, has a small burden on the environment and the human body, and can easily separate the reaction product from the system.

However, if depolymerization and repolymerization in a supercritical liquid are performed in a batch operation, the efficiency is poor and it cannot be said that it is sufficient as a chemical recycling technology for plastics that are consumed in large quantities.
JP 2002-17385 A JP 2002-17384 A JP 2002-320499 A JP 2003-79388 A

  The present invention has been made in view of the above problems, and its purpose is to efficiently depolymerize a polyester, polycarbonate or polylactic acid by continuously depolymerizing it in a supercritical fluid. There is to get.

The object of the present invention is solved by providing the following continuous depolymerization method and continuous depolymerization apparatus.
(1) A supercritical fluid and an organic solvent solution of polyester, polycarbonate, or polylactic acid are continuously passed through a hydrolase packed column, and the polyester, polycarbonate, or polylactic acid is depolymerized by hydrolase, and the hydrolase is packed. A continuous depolymerization method of polyester, polycarbonate or polylactic acid, wherein a depolymerization product is separated from a reaction mixture containing a depolymerization product flowing out from a column.
(2) The method for continuous depolymerization of polyester, polycarbonate or polylactic acid according to (1), wherein the supercritical fluid is supercritical carbon dioxide.
(3) The method for continuous depolymerization of polyester, polycarbonate or polylactic acid as described in (1) or (2) above, wherein the hydrolase is an immobilized enzyme.

(4) Supercritical fluid generator, hydrolase packed column, back pressure regulator, means for separating depolymerized product from depolymerized product-containing reaction mixture, supercritical fluid produced by supercritical fluid generator A continuous depolymerization apparatus for use in the continuous depolymerization method according to the above (1), comprising means for feeding to a column and means for feeding an organic solvent solution of polyester, polycarbonate or polylactic acid to the column.
(5) The continuous depolymerization apparatus according to (4), further comprising means for returning the gasified product from the supercritical fluid released from the back pressure regulator to the supercritical fluid generator.

In the continuous depolymerization method of the present invention, since the raw material polymer is continuously passed through the column packed with the hydrolase, the depolymerization efficiency is dramatically increased as compared with the batch operation. In addition, since the continuous depolymerization method of the present invention uses a supercritical fluid as a solvent, it is more reactive (low temperature reactivity) than a method in which a solution in which a raw material polymer is dissolved only in an organic solvent is continuously passed through an enzyme packed column. And the reaction rate) and the repolymerizable cyclic oligomer production rate are remarkably improved.
The cyclic oligomer obtained by the depolymerization method of the present invention can be easily repolymerized. On the other hand, when depolymerization is carried out by chemical decomposition or thermal decomposition, both ends of the low molecular compound to be produced are irregular, and it is impossible to repolymerize it and to polymerize it. In addition, there is an advantage that there is no desorbed product when the cyclic oligomer is repolymerized.
Furthermore, since the enzyme in the column used in the present invention is stable for a long period (several months) and does not deteriorate, the same column can be used continuously for a long period of time, and a large amount of processing can be performed with high efficiency. .
In particular, by using supercritical carbon dioxide as the supercritical fluid and replacing most of the solvent used for depolymerization with supercritical carbon dioxide, the use of organic solvents harmful to the environment can be greatly reduced (usually polymer) Has a low solubility in organic solvents such as toluene, so it requires a large amount of organic solvent to be dissolved.) Therefore, the cost for regeneration of the solvent can be reduced, and the risk of ignition, explosion and ignition can be reduced. it can. The carbon dioxide used is not dangerous even if released into the atmosphere, and it is easy to recycle.

In the continuous depolymerization method of the present invention, a supercritical fluid and an organic solvent solution of polyester, polycarbonate or polylactic acid are continuously passed through a hydrolase packed column, and the polyester, polycarbonate or polylactic acid is depolymerized by the hydrolase. The depolymerization product is separated from the depolymerization product-containing reaction mixture flowing out from the hydrolase packed column.
Polyesters that can be used in the continuous depolymerization of the present invention include polyesters from polycarboxylic acids and polyols, as well as polyesters or polylactones from hydroxycarboxylic acids or their intramolecular esters (lactones). Examples of polyesters from polycarboxylic acids and polyols include those having a repeating unit represented by the following structural formula (1), such as polybutylene succinate, polybutylene adipate, and poly (butylene succinate-adipate) copolymer. Preferably mentioned.

In the structural formula (1), A represents a linear or branched alkylene group having 2 to 8 carbon atoms, and B represents a linear or branched alkylene group having 2 to 6 carbon atoms. Each of A and B may be two or more different (ie, copolymers). Further, 50 mol% or less of the dicarboxylic acid represented by A (COOH) ₂ may be substituted with an aromatic dicarboxylic acid such as terephthalic acid, phthalic acid, isophthalic acid or the like.
Examples of the polyester of the present invention include repeating units other than those represented by the structural formula (1), for example, repeating units represented by the following structural formulas (2) and / or (3) (in the unit, D represents 2 to 2 carbon atoms) 6 linear or branched alkylene groups, alkenylene groups or alkynylene groups) may be contained in an amount of 50 mol% or less.

  The molecular weight (number average molecular weight) of the polyester is not particularly limited, and the terminal group portion of the polyester can be substituted with any substituent determined by a polymer synthesis method.

Moreover, as the polyester or polylactone derived from the hydroxycarboxylic acid, in addition to a polymer of a hydroxycarboxylic acid or lactone having 3 to 20 carbon atoms, a polyester or polylactone having one or more repeating units represented by the following structural formula (4) Is also included.
In the formula, R represents a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms.

The R may be two or more different types (copolymers) selected from a hydrogen atom and an alkyl group having 1 to 12 carbon atoms. When R is a methyl group, it is poly (3-hydroxybutyric acid). When R is a methyl group and a hydrogen atom, it is a 3-hydroxybutyric acid / 3-hydroxypropionic acid copolymer (PHB / PHP), and R is methyl. In the case of a group and an ethyl group, it is a 3-hydroxybutyric acid / 3-hydroxyvaleric acid copolymer (PHB / PHV). These are known as polymers produced by microorganisms. The terminal group portion of the polylactone can be substituted with any substituent determined by a polymer synthesis method.
The polylactone may further have one or more repeating units represented by the following structural formulas (5) to (7) in the molecule.

In the formula, R ₁ represents a linear or branched alkylene group having 1 to 17 carbon atoms, R ₂ represents a linear or branched alkylene group having 2 to 11 carbon atoms, and R ₃ represents a linear or branched alkylene group having 1 to 10 carbon atoms. A branched alkylene group, R ₄ represents a linear or branched alkylene group having 2 to 10 carbon atoms. (In the case where the repeating unit includes one represented by the structural formula (5), it represents a copolymer containing another lactone.)

  The polyester of the present invention includes 1) a repeating unit from a dicarboxylic acid and a polyol (a repeating unit represented by the structural formula (1). Also represented by a structural formula (2) and / or (3). 2) a repeating unit from a hydroxycarboxylic acid (including a repeating unit represented by structural formula (4)), and 3) a repeating unit from a lactone (structural formula (5) to A copolymer containing two or more kinds of repeating units selected from 1) to 3) of (which may contain the repeating unit represented by (7)) is also included.

  The polycarbonate in the present invention includes, but is not limited to, a trimethylene carbonate polymer. The trimethylene carbonate polymer may contain one or more repeating units (structural formulas (5) to (7)) that may be included as repeating units of the polylactone polymer.

  Also, poly (ester-carbonate) which is a copolymer of polyester and polycarbonate as described above can be used for the continuous depolymerization of the present invention.

As the polylactic acid used in the depolymerization method of the present invention, polylactic acid or polylactic acid copolymer used for molded articles such as films and fibers can be used without particular limitation. Examples of the homopolymer include poly (L-lactic acid), poly (DL-lactic acid), syndiotactic poly (DL-lactic acid), atactic poly (DL-lactic acid), and the like.
Examples of the polylactic acid copolymer include polylactic acid as described above, β-propiolactone, β-butyrolactone (β-BL), ε-caprolactone (ε-CL), 11-undecanolide, 12-undecanolide and the like. Medium to macrocyclic lactones, cyclic carbonate monomers such as trimethylene carbonate (TMC) and methyl-substituted trimethylene carbonate and oligomers thereof, cyclic ester oligomers, hydroxy acids such as ricinoleic acid and esters thereof, linear carbonate oligomers, Examples thereof include those obtained by copolymerizing a comonomer that forms a bond that can be copolymerized with lactide and can be acted on by a hydrolase, such as a linear ester oligomer, an ester-carbonate oligomer, and an ether-ester oligomer.

The hydrolase used in the present invention is preferably a lipase due to availability and thermal stability of the enzyme, and among them, a lipase derived from Candida antarctica and a lipase derived from Rhizomucor miehei are preferable. For example, the immobilized enzyme derived from Candida antarctica is “Novozym 435 (trade name)” of Novozymes Japan, and the lipase derived from Rhizomucor miehei is “Lipozyme RM IM” (product) of Novozymes Japan. Name) "and the like. In addition, “Bioprase (trade name)” of Nagase ChemteX Co., Ltd., which is a protease derived from Bacillus subtilis, can be similarly used as a hydrolase.
The immobilized enzyme in the depolymerization of the present invention is used while packed in a column, and the inner diameter and length of the column are appropriately determined in consideration of the flow rate of the reaction mixture flowing in the column.

In the present invention, a supercritical fluid is used as a depolymerization main solvent. Examples of the supercritical fluid used include carbon dioxide and fluoroform (CHF ₃ ). Carbon dioxide is harmless, inexpensive and nonflammable, and its critical point is about 31 ° C. and about 7.4 MPa. Therefore, it easily reaches the critical point and is suitable as a medium used for the depolymerization and polymerization of the present invention. Carbon dioxide is suitable for handling relatively hydrophobic molecules, and fluoroform is suitable for handling relatively hydrophilic molecules.
In the depolymerization of the present invention, an organic solvent such as toluene is used to dissolve the polymer. The amount of the organic solvent used is required to dissolve the raw material polymer. For example, when polyhydroxybutyric acid is dissolved in toluene, the ratio of the supercritical fluid flowing in the column to toluene is about 1: 0.1 to 1: 0.6, preferably 1: 0.2 to 1: 0.4. Degree. When the ratio of toluene is larger than 1: 0.6, it is difficult to obtain effects such as reactivity, reaction rate, and environmental compatibility by using the supercritical fluid as described above, and the ratio of toluene is 1: 0. If the ratio is smaller than 1, the polymer is difficult to dissolve, so the ratio is appropriate.
As the organic solvent, in addition to toluene, those which do not inhibit enzyme activity such as xylene and benzene and dissolve the polymer satisfactorily are used.

  The concentration of the depolymerization polymer contained in the depolymerization reaction solution (mixture of raw material polymer, supercritical fluid and organic solvent) is suitably from 0.1 to 50 g / L, particularly from 1 to 20 g / L. When the concentration is lower than 0.1 g / L, the yield itself is not particularly low, but the concentration is low, so that it is difficult to secure a sufficient amount of the depolymerized product. The above-mentioned range is preferable because the conversion rate to is reduced.

When the supercritical fluid is supercritical carbon dioxide, the temperature is more than the temperature that maintains the supercritical temperature to about 80 ° C., preferably about 40 to 60 ° C. from the viewpoint of enzyme activity, reaction rate, temperature controllability, etc. .
The pressure of supercritical fluid carbon dioxide is about 13 to 15 MPa from the viewpoint of oligomer yield.
The flow rate of the reaction solution in the enzyme packed column may be appropriately determined in consideration of the conversion rate to the oligomer, the molecular weight of the oligomer, the reaction rate and the like. For example, if a stainless steel enzyme packed column with an inner diameter of 7.8 mm and a length of 300 mm packed with 6.8 g of immobilized lipase derived from Candida antarctica (Novozym 435 Novozymes Japan Ltd) is used, the total flow rate in the column (supercritical carbon dioxide) Even when the ratio of 4: 1) was increased from 0.5 mL / min to 1.51 mL / mm, the starting polymer was completely depolymerized and disappeared, but the molecular weight of the oligomers formed gradually increased.

The depolymerization product obtained by the depolymerization method of the present invention contains a cyclic oligomer as a main component. For example, dicaprolactone is mainly produced from polycaprolactone, and trimethylene carbonate is mainly produced from polytrimethylene carbonate. Further, from the polyester, a cyclic polyester oligomer having a plurality of unit units in the molecule is mainly obtained. Furthermore, cyclic lactic acid oligomers having a plurality of lactic acid units in the molecule are mainly obtained from polylactic acid.
When depolymerization is performed by chemical decomposition or thermal decomposition, both ends of the low molecular weight compound to be produced are irregular and cannot be polymerized by repolymerization. The cyclic oligomer obtained by the method can be easily repolymerized. In addition, when the cyclic oligomer is repolymerized, there is an advantage that there is no desorbed product.
Furthermore, compared with the case where continuous depolymerization is performed using only an organic solvent, the repolymerizable cyclic oligomer production rate is significantly improved.

  The continuous depolymerization apparatus used for the continuous depolymerization method as described above is at least a supercritical fluid generator, a hydrolase packed column, a back pressure regulator, a means for separating the depolymerization product from the depolymerization product-containing reaction mixture, A means for feeding a supercritical fluid produced by the supercritical fluid generator to the column; and a means for feeding an organic solvent solution of a raw material polymer to the column.

  The gasified product from the supercritical fluid released from the back pressure regulator may be recovered or may be released into the atmosphere as it is, but it is preferable to recover and reuse it. When the apparatus is reused, the apparatus is further provided with means for returning the gasified product from the supercritical fluid discharged from the back pressure regulator to the supercritical fluid generator. The means has means for recovering the gasified product from the supercritical fluid discharged from the back pressure regulator and sending it to the supercritical fluid generator.

FIG. 9 shows a conceptual diagram of an example of a continuous depolymerization apparatus using supercritical carbon dioxide as a supercritical fluid.
In FIG. 9, reference numeral 10 denotes a supercritical carbon dioxide generator, and for example, a normal apparatus comprising a carbon dioxide condenser, a pressure pump, and a heat exchanger (not shown) is used. Reference numeral 12 denotes a carbon dioxide supply means (for example, a liquid carbon dioxide cylinder). 20 is a thermostat equipped with a hydrolase packed column 22 inside, and is provided with a heating device and a temperature control device (not shown) so as to keep the column temperature constant. Reference numeral 30 denotes a back pressure regulator (back pressure control device) that controls the pressure of the entire reaction system and separates a mixture of carbon dioxide gas, an organic solvent, and a depolymerization product from the reaction liquid after the completion of the reaction. A commercially available back pressure regulator can be used. Reference numeral 40 denotes a means for separating the organic solvent solution of the depolymerization product into the organic solvent and the depolymerization product, and includes, for example, an evaporator for removing the organic solvent.
The means for feeding the supercritical fluid produced by the supercritical fluid generator to the column has a supercritical carbon dioxide feed pump 14 and a line (tube) L1 for supplying supercritical carbon dioxide. The means for feeding the organic solvent solution of the raw material polymer to the column has a liquid feeding pump 16 for the raw polymer solution and a line (tube) L2 for supplying the organic solvent solution of the raw material polymer.
Further, L3 represents a line (tube) for collecting the carbon dioxide gas released from the back pressure regulator and returning it to the supercritical fluid generator.

  In this embodiment, the carbon dioxide is returned again to the supercritical fluid by the supercritical carbon dioxide generator, but may be released from the back pressure regulator 30 into the air.

The method of using the apparatus is as follows. First, liquid carbon dioxide or the like is supplied from the carbon dioxide supply means 12 to the supercritical carbon dioxide generator 10 to generate supercritical carbon dioxide, and the liquid feed pump 14 directs it to the column through the line L1. Deliver liquid. On the other hand, the raw material polymer is dissolved in an organic solvent, and this is sent to the column by the liquid feed pump 16 through the line L2. The supercritical carbon dioxide and the raw polymer solution are combined before entering the column, and are mixed to flow into the column. In the thermostat 20, temperature control is already performed in order to maintain the hydrolase packed column 22 at the reaction temperature. A mixture of supercritical carbon dioxide and the raw polymer solution flows into the temperature-controlled column, contacts with a hydrolase packed in the column, and depolymerization is performed. The depolymerization reaction is completed in the reaction solution flowing out from the column, and depolymerized oligomers are generated. The back pressure regulator 30 controls the pressure of the entire reaction system.
Next, the reaction liquid after completion of the reaction enters the back pressure regulator 30 and is separated into two parts, carbon dioxide gas, a mixture of an organic solvent and a depolymerization product. The separated carbon dioxide gas is again introduced into the supercritical carbon dioxide generator through the line L3 and reused. On the other hand, the mixture of the organic solvent and the depolymerization product is separated into the organic solvent and the depolymerization product by means 40 for separating the depolymerization product, and the depolymerization product is recovered.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. The following continuous depolymerization was performed using an apparatus as shown in FIG.
Example 1 [Continuous depolymerization of atactic poly (RS-3-hydroxybutyric acid)]
6.8 g of immobilized lipase derived from Candida antarctica (Novozym 435 Novozymes Japan, Ltd) was packed in a stainless steel column with an inner diameter of 7.8 mm and a length of 300 mm to form a hydrolase-enclosed column, which was placed in a thermostatic chamber. Was controlled at a temperature of 40 ° C. To this enzyme packed column, a 1% toluene solution of atactic poly (RS-3-hydroxybutyric acid) (Mn = 110,000) at a flow rate of 0.1 mL / min, supercritical carbon dioxide at 15 MPa, a flow rate of 0.4 mL / min Passed through. The decomposition product toluene solution and carbon dioxide were separately collected from the back pressure regulator. Toluene was distilled off under reduced pressure from the obtained toluene solution to obtain a depolymerized product.
The molecular structure of the obtained depolymerized product was analyzed by ¹ H NMR analysis, MALDI-TOF MS analysis, and SEC analysis. As a result, it was confirmed by ^l H NMR analysis and MALDI-TOF MS analysis that the oligomer obtained by depolymerization was an almost complete cyclic body centered on the heptamer (see FIGS. 1 and 2). . Further, it was confirmed by SEC analysis that the original polymer portion was completely disappeared and converted into an oligomer having a molecular weight Mn = 500 (see FIG. 3).
Furthermore, hexamers were separated from the produced oligomers by preparative high-performance liquid chromatography using supercritical carbon dioxide as the mobile phase, and structural analysis was performed by ¹ H NMR. As a result, no peak derived from the terminal group (hydroxyl group) was observed within the range indicated by the dotted line in FIG. Further, the MALDI-TOF MS analysis result of the hexamer is shown in FIG. From the results shown in FIGS. 4A and 4B, it was confirmed that the hexamer was a ring.

Example 2 [Continuous depolymerization of atactic poly (RS-3-hydroxybutyric acid)]
The same hydrolase packed column as in Example 1 was prepared, and the temperature was adjusted to 40 ° C. in the same manner. A 1% toluene solution of atactic poly (RS-3-hydroxybutyric acid) (Mn = 110,000) was passed at a flow rate of 0.3 mL / min, and supercritical carbon dioxide was passed at 15 MPa and a flow rate of 1.2 mL / min. The decomposition product toluene solution and carbon dioxide were separately collected from the back pressure regulator. Toluene was distilled off under reduced pressure from the obtained toluene solution to obtain a depolymerized product.
The molecular structure of the obtained depolymerized product was analyzed by ¹ H NMR analysis, MALDI-TOF MS analysis and SEC analysis. As a result, according to ¹ H NMR analysis and MALDI-TOF MS analysis, the oligomer obtained by depolymerization was almost completely cyclic. Further, it was confirmed by SEC analysis that the original polymer portion was completely disappeared and converted into an oligomer having a molecular weight Mn = 1,000. The spectrum and the like were the same as in Example 1.

Example 3 [Continuous depolymerization of poly (ε-caprolactone)]
The same hydrolase packed column as in Example 1 was prepared, and the temperature was adjusted to 40 ° C. in the same manner. A 1% toluene solution of poly (ε-caprolactone) (Mn = 110,000) was passed through this at a flow rate of 0.1 mL / min, supercritical carbon dioxide at 15 MPa, and a flow rate of 0.4 mL / min. The decomposition product toluene solution and carbon dioxide were separately collected from the back pressure regulator. Toluene was distilled off under reduced pressure from the obtained toluene solution to obtain a depolymerized product. The molecular structure of the obtained depolymerized product was analyzed by ¹ H NMR analysis, MALDI-TOF MS analysis and SEC analysis. As a result, it was confirmed by ^l H NMR analysis and MALDI-TOF MS analysis that the oligomer obtained by depolymerization was an almost complete cyclic body centering on the dimer. Further, it was confirmed by SEC analysis that the original polymer portion was completely disappeared and converted to an oligomer having a molecular weight Mn = 200 (see FIG. 5).

Example 4 [Continuous depolymerization of poly (butylene adipate)]
The same hydrolase packed column as in Example 1 was prepared, and the temperature was adjusted to 40 ° C. in the same manner. A 1% toluene solution of poly (butylene adipate) (Mn = 18,000) was passed through this at a flow rate of 0.1 mL / min, supercritical carbon dioxide at 15 MPa, and a flow rate of 0.4 mL / min. The decomposition product toluene solution and carbon dioxide were separately collected from the back pressure regulator. Toluene was distilled off under reduced pressure from the obtained toluene solution to obtain a depolymerized product.
The molecular structure of the obtained depolymerized product was analyzed by ¹ H NMR analysis, MALDI-TOF MS analysis and SEC analysis. As a result, it was confirmed by ^l H NMR analysis and MALDI-TOF MS analysis that the oligomer obtained by depolymerization was an almost complete cyclic body centering on the dimer. Further, it was confirmed by SEC analysis that the original polymer portion was completely disappeared and converted to an oligomer having a molecular weight Mn = 500 (see FIG. 6).

Example 5 [Continuous depolymerization of poly (L-lactic acid-ε-caprolactone) copolymer]
The same hydrolase packed column as in Example 1 was prepared, and the temperature was adjusted to 40 ° C. in the same manner. To this, a 1% toluene solution of a poly (L-lactic acid-ε-caprolactone) copolymer (Mn = 80,000, L-lactic acid: ε-caprolactone = 4: 1) at a flow rate of 0.1 mL / min, Critical carbon dioxide was passed at 15 MPa and a flow rate of 0.4 mL / min. The decomposition product toluene solution and carbon dioxide were separately collected from the back pressure regulator. Toluene was distilled off under reduced pressure from the obtained toluene solution to obtain a depolymerized product.
The molecular structure of the obtained depolymerized product was analyzed by ¹ H NMR analysis, MALDI-TOF MS analysis and SEC analysis. As a result, according to ¹ H NMR analysis and MALDI-TOF MS analysis, the oligomer part obtained by depolymerization was almost completely cyclic. Further, it was confirmed by SEC analysis that the original polymer portion was completely disappeared and converted to an oligomer having a molecular weight Mn = 700 (see FIG. 7).

Example 6 [Continuous Depolymerization of Poly (trimethylene carbonate)]
The same hydrolase packed column as in Example 1 was prepared, and the temperature was adjusted to 40 ° C. in the same manner. To this, a 1% toluene solution of poly (trimethylene carbonate) (Mn = 5,000) was passed at a flow rate of 0.1 mL / min, and supercritical carbon dioxide was passed at 15 MPa and a flow rate of 0.4 mL / min. The decomposition product toluene solution and carbon dioxide were separately collected from the back pressure regulator. Toluene was distilled off under reduced pressure from the obtained toluene solution to obtain a depolymerized product.
The molecular structure of the obtained depolymerized product was analyzed by ¹ H NMR analysis, MALDI-TOF MS analysis and SEC analysis. As a result, by ¹ H NMR analysis and MALDI-TOF MS analysis, the oligomer part obtained by depolymerization was a trimethylene carbonate monomer and a linear oligomer homologue. Moreover, it was confirmed by SEC analysis that the original polymer portion was completely disappeared and converted into an oligomer.

Comparative Example 1
In Example 2, when a supercritical carbon dioxide was not passed through a hydrolase packed column, a toluene solution (10 mg / mL) of atactic poly (RS-3-hydroxybutyric acid) was passed at a flow rate of 0.5 mL / min. It was confirmed that undecomposed atactic poly (RS-3-hydroxybutyric acid) remained in the depolymerized product (see FIG. 8).

2 is a graph showing a MALDI-TOF MS analysis result of a depolymerized product in Example 1. 2 is a graph showing ¹ H NMR analysis results of a depolymerized product in Example 1. FIG. 2 is a graph showing changes in SEC analysis before and after depolymerization in Example 1. FIG. FIG. 4A shows the analysis of the hexamer in Example 1, FIG. 4A shows the result of structural analysis by ¹ H NMR, and FIG. 4B shows the result of MALDI-TOF MS analysis. 4 is a graph showing changes in SEC analysis before and after depolymerization in Example 3. 4 is a graph showing changes in SEC analysis before and after depolymerization in Example 4. 6 is a graph showing changes in SEC analysis before and after the depolymerization in Example 5. 2 is a graph showing SEC analysis after the reaction of Comparative Example 1. It is a conceptual diagram which shows an example of the continuous depolymerization apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Supercritical carbon dioxide production | generation apparatus 20 Thermostatic bath 22 Hydrolytic enzyme packed column 30 Back pressure regulator 40 Means to separate depolymerization products

Claims (5)

  A supercritical fluid and an organic solvent solution of polyester, polycarbonate, or polylactic acid are continuously passed through a hydrolase packed column, and the polyester, polycarbonate, or polylactic acid is depolymerized by the hydrolase and then flows out of the hydrolase packed column. A method for continuously depolymerizing polyester, polycarbonate or polylactic acid, wherein the depolymerized product is separated from the depolymerized product-containing reaction mixture.   The method for continuous depolymerization of polyester, polycarbonate or polylactic acid according to claim 1, wherein the supercritical fluid is supercritical carbon dioxide.   The method for continuous depolymerization of polyester, polycarbonate or polylactic acid according to claim 1 or 2, wherein the hydrolase is an immobilized enzyme.   Supercritical fluid generator, hydrolytic enzyme packed column, back pressure regulator, means for separating the depolymerization product from the reaction mixture containing the depolymerization product, and the supercritical fluid produced by the supercritical fluid generator is sent to the column. The continuous depolymerization apparatus for using for the continuous depolymerization method of Claim 1 provided with the means to liquefy, and the means to send the organic solvent solution of polyester, a polycarbonate, or polylactic acid to the said column.   The continuous depolymerization apparatus according to claim 4, further comprising means for returning a gasified product from the supercritical fluid discharged from the back pressure regulator to the supercritical fluid generator.

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