JP2002320499A - Method for depolymerizing polyalkylene alkanoate or poly (3-hydroxyalkanoate) into an oligomer mainly composed of a cyclic body, and method for polymerizing said cyclic oligomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To convert a polyalkylene alkanoate and a poly (3-hydroxyalkanoate) into an oligomer having a repolymerizable cyclic as a main component, and an original polymer from the cyclic oligomer To provide a method for producing a low energy consumption and environmentally acceptable method by using an enzyme reaction. SOLUTION: The polymer is prepared in the presence of a hydrolase,
A method for producing an oligomer having a cyclic body as a main component represented by the following structural formula (1) or (2) by depolymerization, and a method for producing the oligomer from the cyclic oligomer in the presence of a hydrolase or A method for producing the polymer synthetically. Embedded image Embedded image In the structural formula (1), A represents an alkylene group having 2 to 8 carbon atoms, and B represents an alkylene group having 2 to 6 carbon atoms. m is 1
Represents an integer of 6. In the structural formula (2), R represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and n represents an integer of 2 to 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the conversion of a polyalkylene alkanoate or poly (3-hydroxyalkanoate) into a repolymerizable cyclic oligomer by an enzyme, and the polyalkylene alkanoate or poly (3 -Hydroxyalkanoate).

[0002]

2. Description of the Related Art In a crisis situation in which the global environment is worsening due to global warming in recent years, a sustainable material utilization system is used from the viewpoint of effective use of limited carbon resources (C resources) and saving of finite energy resources. Is urgently needed. Regarding polymer products, after use, they are reused as they are (including the use of PET bottles as a fiber material), recycled, or discarded. As the recycling method, the Material Recycling Law, the Chemical Recycling Law, the Thermal Recycling Law, etc. are used. The thermal recycling method has its own problems, such as the generation of a large amount of carbon dioxide. From the viewpoint of effective use of carbon resources,
Ultimately, it is ideal to return to raw materials by the chemical recycling method. As the chemical recycling method, recovery of a monomer by a depolymerization reaction and recovery of a raw material monomer by a chemical decomposition reaction are known. However, when depolymerization is carried out by chemical decomposition or thermal decomposition, both ends of the resulting low molecular weight compound are irregular, so that it is impossible to repolymerize it as it is, and furthermore, isomerization reaction, purification, etc. Need to do. Further, for example, when a polyester is hydrolyzed at a high temperature and a high pressure in the presence of NaOH, the obtained carboxylic acid exists as a Na salt and must be neutralized with an acid. Therefore, all of these methods are energy intensive, discharge inorganic salts (NaCl and the like), and have a large environmental load, and are generally not profitable.

[0003] Although deviating from the viewpoint of reuse, so-called biodegradable polymers, which are decomposed by underground bacteria and the like, have attracted attention as polymers having a small environmental load, and various biodegradable polymers have been proposed. . For example, a biodegradable polyester is known as a biodegradable polymer. Typical examples thereof include aliphatic polyesters such as polycaprolactone, polylactic acid, and polycondensation polyesters of diol and succinic acid.

[0004] However, biodegradable polymers such as polycaprolactone have a small environmental impact, but their raw materials are not recovered. Therefore, they do not fall into the category of full-cycle recycling in which carbon resources are effectively used. It is difficult to say that this is a simple polymer decomposition method. Therefore, like biodegradable polymers, it can be decomposed into low molecular compounds without the need for high energy such as petroleum energy, and low molecular compounds can be used effectively. If it can be obtained without consuming high energy, a low-energy-consuming and completely-circulating polymer production / decomposition method can be constructed.

[0005] On the other hand, many research papers have been published since the 1970s on the biodegradability and enzymatic degradability of polycaprolactone, and complete biodegradability in nature has been almost universally recognized. T. Suzuki, Nature
270, 76 (1997) "," Y. Tokiwa, T. Suzuki, K. Tak
eda, Agric. Biol. Chem. 52, 1936 (1998) "
Enzymatic degradation of polycaprolactone is described. In addition, the present inventors have previously found that polycaprolactone is decomposed by an enzyme catalyst into a liquid oligomer (a liquid low-molecular-weight substance), which can be repolymerized by an enzyme, and announced as a new method for recycling polycaprolactone (S ．Matsumura, H. Ebata, K. Toshima, Macromo
l. Rapid. Commun. However, this method is strongly affected by the amount of water and impurities in the process of decomposing polycaprolactone into oligomers, and the properties such as the molecular weight of the generated oligomers are different. Have difficulty. In addition, the polymerization reaction using an oligomer requires a decompression operation, furthermore, it is difficult to control the composition accurately in copolymerization, and there is room for improvement in that the obtained molecular weight distribution is widened.

On the other hand, a method of polymerizing ε-caprolactone using an enzyme catalyst is also known (see “D. Knani, AL”).
Gutman, D.S. H. Kohn, J .; Polym. Sci., Part A, Polym
Chem. 31, 1221 (1993) "," H. Uyama, S. Kobayash
i, Chem. Lett. 1994, 1149 "," RT MacDonald,
S. K. Pulapura, Y. Y. Svirkin, R .; A. Gross, D.S. L.
Kaplan, G .; Swift, S. Wolk, Macromolecules 28, 73
(1995) "," H. Uyama, K. Takeya, N. Hoshi, S. Ko
bayashi, Macromolecules 28, 7046 (1995) "," GA
R.Nobes, RJ Kazlauskas, RH Marchessault, Macromole
cules 29, 4829 (1996) '', `` LAHenderson, YYSvirki
n, RAGross, D.Kaplan, G.Swift ,, Macro-molecules 29,
7759 (1996) '', `` A. Cordova, T. Iversen, K. Hult, M. Marti
nelle, Polymer39, 6519 (1998) "). Furthermore, enzyme-catalyzed copolymerization of ε-caprolactone and a cyclic trimethylene carbonate monomer is also known (Deng, F .; G.
ross, R. A. Int. J. Biolog. Macromol. 1999, 25, 15
3． This method can be said to be a method of low energy and low environmental load because an enzyme is used. However, the enzyme-catalyzed polymerization method of ε-caprolactone has problems that the polymerization rate is slightly slow and that monomers cannot be obtained by the enzymatic method with low energy and low environmental load.

Under these circumstances, the present inventor has previously made it possible to decompose polycaprolactone and polytrimethylene carbonate into low molecular compounds without requiring high energy, and to make effective use of the low molecular compounds. (Japanese Patent Application Nos. 2000-198866 and 2000).
-198867). In this method, a caprolactone polymer or a trimethylene carbonate polymer is depolymerized in the presence of a hydrolase, and dicaprolactone or a trimethylene carbonate oligomer is obtained by depolymerization. In the presence of
By polymerizing, the original polymer can be obtained. Therefore, this method has made it possible to construct a low energy consumption type and completely circulating type polymer production / decomposition method. It is desired to realize such a completely circulating polymer production / decomposition method for other plastics.

Incidentally, polybutylene succinate (P
Since BS) is obtained from 1,4-butanediol from succinic acid by a petrochemical industrial process, it has been put to practical use together with polylactic acid and polycaprolactone as a typical chemically synthesized biodegradable plastic. . Furthermore, in recent years, new products and applications that are characterized by biodegradability have been developed, and have been marketed by Showa Polymer Co., Ltd. since 1994 under the trade name “Bionole”. PBS has a melting point of about 1
It is an aliphatic polyester having a temperature of 14 ° C and a glass transition temperature of -32 ° C, and is flexible and has the same tensile strength as polyethylene and polypropylene. In addition, polybutylene succinate /
Adipate copolymer (PBS / A) (trade name "Bionole") is also being studied. Research papers on the biodegradability of PBS and PBS / A have been published since the 1970s, and the complete degradability in the natural world is almost universally recognized.

Also, poly (3-hydroxybutyrate)
Poly (3-hydroxyalkanoates) (PHA) such as (PHB) and poly (3-hydroxybutyrate / valerate) (P (HB / V)) are known as aliphatic polyesters synthesized by microorganisms in cells. Since it is produced by fermentation using a saccharide obtained by photosynthesis as a carbon source, its practical use as a recyclable biodegradable plastic in a broad sense is being studied. The meaning of this “circulation type” is that poly (3-hydroxyalkanoate) is decomposed into carbon dioxide and water by biodegradation, and this carbon dioxide becomes saccharide again by photosynthesis. Is biosynthesized. Therefore, a completely circulating use method in which poly (3-hydroxyalkanoate) is reused without being discarded is as follows:
Not at this time.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a polyalkylene alkanoate and a poly (3-hydroxyalkanoate) which are capable of repolymerizing a cyclic compound. And a method for producing an original polymer from the oligomer as a low energy consumption and environmentally acceptable method by using an enzymatic reaction.

[0011]

The object of the present invention is attained by providing the following method for producing an oligomer having a cyclic component as a main component, and a method for producing a polymer from the cyclic oligomer. (1) A method for producing an oligomer having a cyclic body represented by the following structural formula (1) as a main component by depolymerizing a polyalkylene alkanoate in the presence of a hydrolase.

[0012]

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In the formula, 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. m represents an integer of 1 to 6. (2) The method for producing an oligomer having a cyclic body as a main component according to the above (1), wherein the hydrolase is lipase.

(3) A method for producing an oligomer having a cyclic compound represented by the following structural formula (2) as a main component by depolymerizing poly (3-hydroxyalkanoate) in the presence of a hydrolase. .

[0015]

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In the formula, R is a hydrogen atom or a group having 1 to 1 carbon atoms.
2 represents a linear or branched alkyl group;
Represents an integer of 10. (4) The method for producing an oligomer having a cyclic body as a main component according to the above (3), wherein the hydrolase is lipase. (5) A polyalkylene alkanoate or poly (3-hydroxy) polymerized in the presence of a hydrolase, wherein an oligomer having a cyclic body represented by the formula (1) or (2) as a main component is polymerized. Alkanoate). (6) A polyalkylene alkanoate or poly (3-hydroxyalkanoate), which is obtained by polymerizing an oligomer having a cyclic body represented by the formula (1) or (2) as a main component in the presence of a polymerization catalyst. ) Manufacturing method.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention provides a method for depolymerizing a polyalkylene alkanoate or poly (3-hydroxyalkanoate) in the presence of a hydrolase to form an oligomer having a cyclic body as a main component (hereinafter, simply referred to as a “cyclic oligomer”). And a method for producing a polyalkylene alkanoate or poly (3-hydroxyalkanoate) from the cyclic oligomer. The depolymerization is carried out by using a hydrolase. In addition to using a hydrolase to produce a polymer using a cyclic oligomer as a raw material, it is chemically synthesized, that is, in the presence of a catalyst (eg, a polyester polymerization catalyst). It is possible to manufacture. When depolymerization is carried out by chemical decomposition or thermal decomposition, both ends of the resulting low-molecular compound are irregular, and it is impossible to repolymerize the low-molecular compound to produce a polymer. By the legal method, a cyclic oligomer which can be easily repolymerized is produced, and this cyclic oligomer is easily polymerized in the presence of a hydrolase or chemically synthesized to form a polymer. On the other hand, in the case of chemically synthesizing a polyester from a dicarboxylic acid and a diol, and producing a polyester from a hydroxycarboxylic acid, high temperature, high pressure or reduced pressure, a chemical catalyst, and the like are necessary. Compared to the case where the oligomer as the main component is used, the production method consumes more energy.

[Depolymerization of polyalkylene alkanoate] First, a method for obtaining a cyclic oligomer by depolymerizing polyalkylene alkanoate with a hydrolase will be described. The polyalkylene alkanoate used for the depolymerization is a polyester made from a dicarboxylic acid having 4 to 10 carbon atoms and a diol having 2 to 6 carbon atoms, and is a polymer having a repeating unit represented by the following structural formula (3). . Two or more dicarboxylic acids and diols may be used.

[0020]

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In the structural formula (3), 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. . A
And B may each be two or more different. For example, A = (CH ₂ ) ₂ and B = (C
In the case of H ₂ ) ₄ , it is a polybutylene succinate. Dicarboxylic acids and diols (A and B) are each 2
Two or more different copolymers may be used. Further, as the polyalkylene alkanoate of the present invention,
A repeating unit other than that represented by the structural formula (3), for example, a repeating unit as shown below (where D is a linear or branched alkylene group, alkenylene group or alkynylene group having 2 to 6 carbon atoms) ) May be contained in an amount of 50 mol% or less.

[0022]

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The molecular weight (number average molecular weight) of the polyalkylene alkanoate is not particularly limited. The terminal group of the polyalkylene alkanoate can be substituted with any substituent determined by a polymer synthesis method. By depolymerizing the polyalkylene alkanoate as described above using a hydrolase, a cyclic oligomer represented by the following structural formula (1) is obtained.

[0024]

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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. . m
Represents an integer of 1 to 6. A and B may each be two or more different.

In the depolymerization of the polyalkylene alkanoate of the present invention, the polyalkylene alkanoate is dissolved in a suitable solvent, a hydrolytic enzyme is added thereto to prepare a depolymerization solution, and the solution is maintained at an appropriate temperature. The depolymerization reaction is preferably carried out for an appropriate time while stirring, preferably. The polyalkylene alkanoate depolymerizes to the cyclic oligomer represented by the structural formula (1) regardless of the molecular weight of the first polyalkylene alkanoate.
In the depolymerization reaction of the present invention, for example, a cyclic oligomer can be obtained in a yield of 70% or more by treating a polyalkylene alkanoate with an enzyme.

The enzyme used in the depolymerization of the present invention is not particularly limited as long as it is a hydrolase that acts on an ester bond. The enzyme may or may not be immobilized, but immobilization is convenient from the viewpoint of recovery of the cyclic oligomer and reuse of the enzyme. As a hydrolase, lipase is preferable due to its availability and the thermostability of the enzyme. Among them, Candida antarctica
A lipase derived from (hereinafter sometimes referred to as “CA lipase”) is preferred. As the lipase, for example, “Novozym 435 (trade name)” of Novozyme Japan Ltd., which is an immobilized enzyme derived from Candida antarctica, can be mentioned. The amount of the enzyme (including the immobilized enzyme) to be added in the depolymerization of the present invention is at least 1% by mass of the enzyme per polymer, and preferably at least 10% by mass. If the amount is less than 1% by mass, the reaction rate is remarkably reduced, so the above-mentioned amount is appropriate. In addition, the reaction rate increases when the amount of the enzyme added is increased, but it is not practical to use a large amount, so that at most about 500% by mass is appropriate.

As the solvent, acetonitrile, 1,4
-Any solvent can be used without limitation as long as it dissolves the polyalkylene alkanoate such as dioxane and tetrahydrofuran and does not deactivate the enzyme. Water and alcohol are not preferred because they cause enzymatic degradation of the resulting cyclic oligomer.

The lower the concentration of the polyalkylene alkanoate in the solvent, the higher the yield of cyclic oligomers tends to be. When the concentration is high, linear oligomers are easily formed. For example, in the case of a solution containing 10 g of polybutylene succinate with respect to 1 L of acetonitrile, a small amount of dimer, tetramer and tetramer is mainly produced, but 60 g
When the density is increased to / L, the linear one becomes the main.

Generally, the concentration of the polyalkylene alkanoate contained in the depolymerization reaction solution is 1 to 300 g /
L, especially 5 to 50 g / L, is appropriate. When the concentration is lower than 1 g / L, the yield itself is not particularly low, but the concentration is low, so that it is difficult to sufficiently secure the amount of the obtained cyclic oligomer, and when it exceeds 300 g / L, the conversion rate to the cyclic oligomer decreases. Therefore, the above range is preferable.

Further, although water is not suitable as a solvent, it is preferable to add a small amount of water to the depolymerization system since the activity of the hydrolase cannot be maintained if no water is present in the depolymerization system. . If the enzyme itself retains water, there is no need to add water. Water for maintaining the activity of the enzyme is about 1 to 10% by mass based on the polyalkylene alkanoate in the reaction system. Depolymerization temperature is 25-9
0 ° C, preferably 50 to 80 ° C. When the temperature is lower than 25 ° C., the depolymerization rate is low, and when the temperature is higher than 90 ° C., the enzyme is easily deactivated, so the above range is appropriate. Further, the reaction time of the depolymerization is desirably about 5 to 48 hours. If the time is shorter than 5 hours, the charge-polymerization polymerization does not proceed, while if it is carried out for 48 hours or more, the depolymerization does not proceed any longer and it is economically disadvantageous, so the above range is appropriate.

[Poly (3-hydroxyalkanoate)]
Next, the depolymerization of poly (3-hydroxyalkanoate) will be described. Poly (3-hydroxyalkanoate) is a polymer having a polymerized unit represented by the following structural formula (4), wherein R is a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms. Represents

[0033]

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R is a hydrogen atom and a carbon atom having 1 to 12 carbon atoms.
And two or more different types (copolymers) selected from the above alkyl groups. When R is a methyl group, poly (3-
Hydroxybutyric acid), and when R is a methyl group and a hydrogen atom, it is a 3-hydroxybutyric acid / 3-hydroxypropionic acid copolymer (PHB / PHP), and when R is a methyl group and an ethyl group, it is 3-hydroxybutyric acid / It is a 3-hydroxyvaleric acid copolymer (PHB / PHV). These are known as polymers produced by microorganisms. The terminal group of the poly (3-hydroxyalkanoate) can be substituted with any substituent determined by a polymer synthesis method.

By depolymerizing poly (3-hydroxyalkanoate), a cyclic oligomer represented by the following structural formula (2) is obtained. In the structural formula (2), R represents a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms, and n represents an integer of 2 to 10. R may be two or more different members selected from a hydrogen atom and an alkyl group having 1 to 12 carbon atoms.

[0036]

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The depolymerization of poly (3-hydroxyalkanoate) can be carried out in the same manner as the above-mentioned depolymerization of polyalkylene alkanoate. The hydrolase used is
This is the same as in the case of depolymerization of polyalkylene alkanoate. The amount of enzyme (including immobilized enzyme) used is poly (3
-Hydroxyalkanoate), at least 1% by weight, preferably at least 50% by weight. If the amount is less than 1% by mass, the reaction rate is remarkably reduced, so that the above-mentioned amount is appropriate. In addition, the reaction rate increases when the amount of the enzyme added is increased, but it is not practical even if the amount is too large, so that at most about 400% by mass is appropriate. As the solvent, any solvent can be used without limitation as long as it dissolves the polyalkylene alkanoate and does not deactivate the enzyme, such as dichloroethane, acetonitrile, 1,4-dioxane, tetrahydrofuran, and toluene. Water and alcohol are not preferred because they cause enzymatic degradation of the resulting cyclic oligomer of structural formula (2). The reaction temperature is
30-80 ° C, preferably 50-75 ° C, reaction time is 5
About 72 hours is appropriate.

Generally, the concentration of poly (3-hydroxyalkanoate) contained in the depolymerization reaction solution is 10 to
200 g / L, especially 20 to 100 g / L, is suitable. If the concentration is lower than 10 g / L, the decomposition rate becomes slow, making it difficult to secure a sufficient amount of the cyclic oligomer.
If it exceeds 00 g / L, the solubility of the raw material polymer is reduced, so the above range is preferable. In addition, if the water content of the depolymerization system is too large, the solubility of the polymer is reduced, resulting in a decrease in yield.Also, if the water content is too small, the activity of the enzyme is reduced. About 2 to 10% by mass is appropriate. By the depolymerization of the poly (3-hydroxyalkanoate), a cyclic oligomer can be obtained in a yield of 30% or more. Unreacted poly (3-hydroxyalkanoate) is recovered and decomposed in the same manner by repeatedly performing a depolymerization reaction again, whereby a cyclic oligomer can be obtained in a similar yield.

[Polymerization of Cyclic Oligomer] The polymerization of the cyclic oligomer represented by the structural formulas (1) and (2) of the present invention is carried out by dissolving the cyclic oligomer in a suitable solvent, adding a hydrolase thereto, and adding a polymerization solution. Is prepared, and the polymerization is carried out for a suitable time while maintaining the solution at an appropriate temperature, preferably with stirring. Since the enzymatic reaction in which a cyclic oligomer is formed by depolymerization of a polyalkylene alkanoate or poly (3-hydroxyalkanoate) is a reversible reaction, the cyclic oligomer can be polymerized with a hydrolase, for example, lipase. The hydrolase may or may not be immobilized. As a lipase used for the polymerization of cyclic oligomers, CA lipase (Candida antarctica lipas)
e), PPL (porcine pancreatic lipase), Candid
a cylindracea lipase, Lipase PS, Lipozyme IM
And the like can be used without limitation, but in particular Candida an
A lipase derived from tarctica (CA lipase) is preferably used. By using CA lipase, it became possible to polymerize the cyclic oligomer at an extremely high monomer conversion rate. As lipase, for example, Candid
Novozym 435 (trade name) of Novozymes Japan, which is an immobilized enzyme derived from a antarctica.

By polymerizing the cyclic oligomer represented by the structural formula (1) using a hydrolase, a polyalkylene alkanoate having a number average molecular weight of up to about 10,000 can be obtained. The poly (3-hydroxyalkanoate) having a number average molecular weight of up to about 10,000 can be obtained by polymerizing the cyclic oligomer represented by the formula (1). Further, the conversion of the cyclic oligomer can reach 100%. In the polymerization of the cyclic oligomers of the structural formulas (1) and (2) of the present invention, the amount of the enzyme (including the immobilized enzyme) to be added is 0.1 to 50% by mass of the enzyme per cyclic oligomer, preferably 0.1 to 50% by mass. To 10% by mass. If it is less than 0.1% by mass,
The polymerization rate decreases, the monomer conversion rate tends to decrease,
On the other hand, if it exceeds 50% by mass, the molecular weight of the produced polymer tends to be low, so the above range is appropriate.

As a solvent for dissolving the cyclic oligomers of the structural formulas (1) and (2), a solvent that does not deactivate the enzyme, such as acetonitrile, 1,4-dioxane, tetrahydrofuran, isopropyl ether, toluene,
Benzene or the like is used. The amount of water in the reaction system for maintaining the enzyme activity is the same as in the case of the depolymerization of polyalkylene alkanoate or poly (3-hydroxyalkanoate). In addition to the cyclic oligomer of the structural formula (1), copolymerization can also be performed using ε-caprolactone or an oligomer thereof or a cyclic oligomer such as a lactic acid oligomer, and a copolymerized polyester having a unit from these cyclic oligomers is also available. Can be easily obtained. In addition to the cyclic oligomer of the structural formula (2), cyclic lactones such as lactide, ε-caprolactone, β-propiolactone, β-butyrolactone, benzyl β-malolactonate, pentadecanolactone, And cyclic carbonates such as trimethylene carbonate, methyl trimethylene carbonate, and dimethyl trimethylene carbonate. Therefore, a polyester or polyester carbonate having other lactone units and carbonate units in addition to the units of the structural formula (2) can be easily produced.

Since the polymerization of the cyclic oligomers of the structural formulas (1) and (2) is also a reversible reaction, in order to suppress the depolymerization of the produced polymer into the cyclic oligomer, the water content of the polymerization system must be particularly controlled. It is preferable to suppress the temperature and increase the polymerization temperature. In the polymerization reaction, the ratio of the hydrolase to the cyclic oligomer is preferably in the range of 1: 1000 to 1: 2. The temperature of the polymerization can be 30 to 85 ° C, but it is particularly preferable to carry out the polymerization in the range of 40 to 75 ° C. If the temperature is lower than 30 ° C., the reaction rate is reduced. If the temperature is higher than 85 ° C., the enzyme is inactivated. Generally, the polymerization of the cyclic oligomer is preferably higher than the temperature at the time of depolymerization from the polymer. The reaction time is suitably from 0.5 to 48 hours. If less than 0.5 hours, the reaction does not proceed sufficiently,
If the time exceeds 48 hours, the produced polymer may undergo depolymerization, so the above time range is preferable.

[Chemical synthesis of polyalkylene alkanoate or poly (3-hydroxyalkanoate) from cyclic oligomer] For example, under absolute drying conditions,
By adding 0.1% by mass of distanoxane as a catalyst to the cyclic oligomer as a catalyst and performing bulk polymerization at 100 ° C., a corresponding polymer can be obtained.

The method of depolymerizing polyalkylene alkanoate or poly (3-hydroxyalkanoate) with the hydrolase of the present invention may be a simple operation in one pot, or may be carried out under mild or low energy consumption conditions. is there. In addition, the cyclic oligomer obtained by depolymerization is a monomer suitable for enzymatic polymerization, and can be easily polymerized by an enzyme under a simple operation under mild conditions, so that the original polymer can be easily produced. At that time, it is also possible to copolymerize with another monomer. The cyclic oligomer can be polymerized not only by an enzyme but also chemically, that is, in the presence of a polymerization catalyst. Furthermore, since the polymerization of the cyclic oligomer is a ring-opening polymerization, no condensation component such as water is generated, and there is no need to bring them out of the reaction system. Therefore, there is an advantage that the polymerization reaction operation is simple. Furthermore, the hydrolase used to carry out the depolymerization or polymerization has the advantage that it can be recovered and used repeatedly, with substantially no decrease in its activity as an enzyme. Therefore, according to the present invention, it has become possible to construct a complete circulation type polymer utilization system that can reduce the load on the environment with low energy consumption and can completely reuse carbon resources.

[0045]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited to these Examples. Example 1 Polybutylene succinate (Mn = 60,000) 30
was dissolved in 3 mL of acetonitrile, and 3 mg of immobilized lipase (Novozym 435) and 15 mg of water were added thereto.
0 μL was added, and the mixture was stirred at 70 ° C. for 24 hours. A small amount of chloroform was added thereto, and the insoluble immobilized lipase was separated by filtration using celite, and the solvent was concentrated under reduced pressure from the filtrate using an evaporator to obtain a butylene succinate oligomer having a cyclic component as a main component in a yield of 80%. Obtained. By GPC and MALDI-TOF MS, 80
% Is a trimer and about 16% is a dimer, a tetramer, and a pentamer.
Some of the remaining amount was linear oligomer. The unreacted polymer was completely converted into a cyclic oligomer by repeating the above depolymerization operation. The obtained cyclic oligomer was analyzed, and the following results were obtained. ¹ H-NMR (300 MHz, CDCl ₃ ): δ = 1.71 (m, 4H, CH ₂ ), 2.63
_{(M, 4H, CH 2 CO} ), 4.11 (m, 4H, OCH 2).

Example 2 Poly (3-hydroxybutyric acid) (Mn = 230,000)
25 mg was dissolved in 0.25 mL of dichloroethane, and immobilized lipase (Novozym 435) 70 m was added thereto.
g, 0.25 mL of toluene and 2 μL of water were added.
Stirring was performed at 0 ° C. for 48 hours. To this was added a small amount of chloroform, the insoluble immobilized lipase was separated by filtration using Celite, and the solvent was concentrated under reduced pressure from the filtrate using an evaporator to obtain a cyclic 3-hydroxybutyric acid oligomer mainly composed of trimers. The unreacted polymer was completely converted into a cyclic oligomer by repeating the above depolymerization operation. The obtained cyclic oligomer was analyzed, and the following results were obtained. ¹ H-NMR (300 MHz, CDCl ₃ ): δ = 1.3 (d, 3H, J = 5.0 Hz, C
_{H 3), 2.6 (m,} 2H, CH 2), 5.3 (m, 1H, CH)

Example 3 A copolymer of 3-hydroxybutyric acid and 3-hydroxyvaleric acid having a number average molecular weight of 230,000 (P3HB /
V) 25 mg (copolymerization molar ratio of about 92/8) was dissolved in 0.25 mL of dichloroethane, and 70 mg of immobilized lipase (Novozym 435) and 0.25 m
L and 2 mL of water were added, and the mixture was stirred at 70 ° C. for 48 hours. A small amount of chloroform was added thereto, and the insoluble immobilized lipase was separated by filtration using Celite, and the filtrate was concentrated under reduced pressure using an evaporator to obtain a cyclic trimer as a main component.
A cooligomer of 3-hydroxybutyric acid and 3-hydroxyvaleric acid was obtained. The molecular structure of the obtained co-oligomer was analyzed by MALDI-TOF MS, and it was confirmed that units of 3-hydroxybutyric acid and 3-hydroxyvaleric acid were included. The 3-hydroxyvaleric acid unit in the cyclic oligomer depends on the content in the original copolymer, and the cyclic trimer, which is a decomposition product of the copolymer of 8% of 3-hydroxyvaleric acid, Mostly 3-
About 8% of the hydroxybutyric acid units formed a cyclic oligomer mixture containing at most one 3-hydroxyvaleric acid unit in the cyclized product.

Example 4 The trimer obtained in Example 1 was mainly used, and a small amount of 2,
200 mg of a butylene succinate cyclic oligomer to which a tetramer or pentamer was added was dissolved in 1 mL of toluene, and 60 mg of immobilized lipase (Novozym 435) was added thereto.
It stirred at 24 degreeC for 24 hours, and polymerized. After completion of the reaction, a small amount of chloroform was added, and the insoluble immobilized lipase was separated by filtration using Celite, and the filtrate was concentrated under reduced pressure using an evaporator to obtain a polymer quantitatively. This was dissolved in a small amount of chloroform, added to a large amount of methanol and purified by reprecipitation to obtain polybutylene succinate.
The molecular weight (weight average molecular weight) determined by gel permeation chromatography (GPC) was 9,200. ¹ H-NMR (300 MHz, CDCl ₃ ): δ = 1.71 (m, 4H, CH ₂ ), 2.63
(M, 4H, CH ₂ CO), 3.68 (2H, CH ₂ OH), 4.12 (m, 4H,
OCH ₂ ). ¹³ C-NMR (75 MHz, CDCl ₃ ): δ = 25.0, 25.2, 28.9, 29.0,
62.2, 64.1, 64.5, 172.2 IR (KBr): 1717, 11
67 (C = O), 2948,1474 (CH 2)

Example 5 100 mg of the cyclic oligomer of 3-hydroxybutyric acid mainly containing the trimer obtained in Example 2 and 100 mg of trimethylene carbonate were dissolved in 1 mL of toluene, and 60 mg of immobilized lipase (Novozym 435) was added thereto. Add 7
The mixture was stirred at 0 ° C. for 24 hours to perform polymerization. After completion of the reaction, a small amount of chloroform was added, the insoluble immobilized lipase was separated by filtration using Celite, the filtrate was concentrated under reduced pressure using an evaporator, and almost quantitatively, a copolymer of 3-hydroxybutyric acid and trimethylene carbonate was used. I got The molecular weight (weight average molecular weight) determined by gel permeation chromatography (GPC) was 4,500. The polymer structure of the obtained copolymer was analyzed by MALDI-TOF MS, and it was confirmed that a copolymer unit of 3-hydroxybutyric acid and trimethylene carbonate was included.

[0050]

The method of the present invention for depolymerizing polyalkylene alkanoate or poly (3-hydroxyalkanoate) with a hydrolase may be a simple operation in a single pot, and the reaction conditions are mild and low. It is also energy consumption. In addition, the cyclic oligomer obtained by depolymerization is a monomer suitable for enzymatic polymerization, and can be easily polymerized by an enzyme under a simple operation under mild conditions, so that the original polymer can be easily produced.
At that time, it is also possible to copolymerize with another monomer. The cyclic oligomer can be polymerized not only by an enzyme but also chemically, that is, in the presence of a polymerization catalyst. Furthermore, since the polymerization of the cyclic oligomer is a ring-opening polymerization, no condensation component such as water is generated, and there is no need to bring them out of the reaction system. Therefore, there is an advantage that the polymerization reaction operation is simple. Furthermore, the hydrolase used to carry out the depolymerization or polymerization has the advantage that it can be recovered and used repeatedly, with substantially no decrease in its activity as an enzyme. Therefore, according to the present invention, it has become possible to construct a complete circulation type polymer utilization system that can reduce the load on the environment with low energy consumption and can completely reuse carbon resources.

Claims (6)

[Claims] 1. A method for producing an oligomer having a cyclic structure represented by the following structural formula (1) as a main component by depolymerizing a polyalkylene alkanoate in the presence of a hydrolase. Embedded image In the formula, 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. m represents an integer of 1 to 6. 2. The method according to claim 1, wherein the hydrolase is a lipase. 3. Poly (3-hydroxyalkanoate)
To produce an oligomer having a cyclic body represented by the following structural formula (2) as a main component by depolymerizing the compound in the presence of a hydrolase. Embedded image In the formula, R represents a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms, and n represents an integer of 2 to 10. 4. The method according to claim 3, wherein the hydrolase is a lipase. 5. A polyalkylene alkanoate or poly (3), which is obtained by polymerizing an oligomer having a cyclic body represented by the formula (1) or (2) as a main component in the presence of a hydrolase. -Hydroxyalkanoate)
Manufacturing method. 6. An oligomer having a cyclic body represented by the formula (1) or (2) as a main component is reacted with a polymerization catalyst in the presence of a polymerization catalyst.
A method for producing a polyalkylene alkanoate or poly (3-hydroxyalkanoate), which comprises polymerizing.