Method for producing dicarboxylic acid compound and / or diamine compound using polyamide as raw material

Abstract

The present invention relates to a method for producing a dicarboxylic acid compound and / or a diamine compound and optionally a dehydration-condensation product of a dicarboxylic acid compound and a diamine compound (i.e., a dehydration-condensation product of one molecule of the dicarboxylic acid compound and one molecule of the diamine compound, and a dehydration-condensation product of one molecule of one of these compounds and two molecules of the other) using a polyamide as a starting material, the method comprising (i) a first hydrolysis step for hydrolyzing the polyamide in high-temperature water to produce a first hydrolysate and (ii) a second hydrolysis step for subjecting the first hydrolysate to hydrolysis with an enzyme to produce a second hydrolysate, in which the first hydrolysate comprises a water-soluble polyamide capable of being dissolved in water at 20°C and the second hydrolysate comprises a dicarboxylic acid compound and / or a diamine compound and optionally a dehydration-condensation product of a dicarboxylic acid compound and a diamine compound.

Description

[Technical field]

[0001] The present invention relates to a method for producing a dicarboxylic acid compound and / or a diamine compound using polyamide as a raw material. More specifically, the present invention relates to a method for producing a dicarboxylic acid compound and / or a diamine compound, and optionally a dehydration condensation product of a dicarboxylic acid compound and a diamine compound (a dehydration condensation product of one molecule each of a dicarboxylic acid compound and a diamine compound, and a dehydration condensation product of one molecule of one and two molecules of the other) using polyamide as a raw material. [Background technology]

[0002] Polyamides, including nylon 6 and nylon 66, are representative engineering plastics. They have good heat resistance and mechanical properties and are widely used in, for example, textiles, automobile parts, and electrical appliance parts, and are one of the irreplaceable materials in modern society.

[0003] In recent years, various technological developments have been made regarding the recycling of plastics with the aim of resource conservation and carbon neutrality, and polyamides are no exception.

[0004] Recycling can be broadly divided into material recycling, in which molded products are re-pelletized, and chemical recycling, in which monomers are reused through depolymerization. Material recycling is relatively easy, but there are concerns that the quality will not be stable because the polymers contained in the molded products deteriorate and added components remain in the recycled polymer. On the other hand, chemical recycling returns the polymer to the monomer, avoiding deterioration and allowing the desired polymer to be obtained from the highly pure monomer from which unnecessary substances have been removed.

[0005] Depolymerization reaction, which is the basis of chemical recycling, is a method that depends on the bond type of the polymer and the stability of the monomers that make up the polymer. The amide bond that makes up the main chain of polyamide is a bond that is generated by dehydration condensation of amine and carboxylic acid, and the reverse reaction, depolymerization, is carried out by hydrolysis reaction. Examples of hydrolysis reaction methods include reactions under acidic or basic conditions, and reactions using high-temperature water, supercritical water, or steam. Polyamide has high thermal stability and requires high temperature reaction under any reaction conditions, so the stability of the monomer under those reaction conditions has a significant impact on the efficiency of chemical recycling.

[0006] Polyamides are classified into two types based on their constituent monomers: n-nylon (e.g., nylon 6) made from amino acids, and n,m-nylon (e.g., nylon 66) obtained by copolymerization of diamine and dicarboxylic acid monomers.

[0007] When n-nylon is depolymerized by hydrolysis, amino acids are produced. When heated in water, they are usually cyclized to produce lactams through an equilibrium reaction. However, since the lactams themselves are the raw monomers for the polymerization of n-nylon, the monomers can be obtained in high yields.

[0008] On the other hand, n,m-nylons such as nylon 66 generate diamines and dicarboxylic acids by hydrolysis, and these generally undergo cyclization reactions when heated in water. In particular, the linear diamine compounds used in general nylons undergo cyclization reactions easily and irreversibly, making them difficult to recover. For example, hexamethylenediamine is not detected during hydrolysis in high-temperature water because it decomposes (Patent Document 1). In addition, adipic acid also undergoes cyclization reactions, so the yield has only improved to about 25%, which is not yet at a level that can be applied to industrial-scale production.

[0009] In order to suppress the cyclization reaction of diamine compounds and dicarboxylic acid compounds, the reaction must be carried out at low temperatures, which is difficult to achieve with normal organic chemical reactions, but hydrolysis reactions using enzymes have been proposed. For example, a method of hydrolyzing 6,6-nylon using enzymes has been proposed (Non-Patent Document 1). However, polyamides have some crystallized parts due to strong hydrogen bonds between amide bonds, and at low temperatures, the polymer chains and the active sites of the enzymes do not easily interact with each other, so the reaction proceeds very slowly. For example, in the above-mentioned case of hydrolysis of 6,6-nylon (Non-Patent Document 1), the yield of enzymatic hydrolysis of powdered nylon 66 was about 10%, even when soluble oligomers were included. In addition, although the initial reaction rate of the enzyme reaction is fast, the reaction rate thereafter drops significantly. This is presumably because the reaction of the amorphous parts of the polymer surface, which have relatively high reactivity, ends early in the reaction, leaving only the crystalline parts with low reactivity.

[0010] As a method for increasing reactivity, a method of copolymerizing a component that decreases crystallinity has been proposed (Non-Patent Document 1), but this method is not very versatile because it reduces the inherent functionality of the polymer.

[0011] In addition, a method of lowering the molecular weight and increasing the solubility in water before the enzyme reaction has been proposed, specifically, a reaction of decomposing nylon 6 with formic acid before the enzyme reaction (Non-Patent Document 2). However, when n,m-nylon is decomposed with formic acid, a diamine compound reacts with formic acid to form a formic acid amide compound. Even if this formic acid amide compound is hydrolyzed, a dicarboxylic acid compound and a diamine compound can only be obtained as a mixture with formic acid. If formic acid remains, it contributes to the generation of polymer terminals as monocarboxylic acid during polymerization, making it difficult to increase the molecular weight of the polymer. Since even a small amount of remaining formic acid has a large effect, it is necessary to thoroughly remove monocarboxylic acid compounds such as formic acid, but removal is very difficult because it forms a salt with the diamine compound. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2001-302597 A [Non-patent literature]

[0013] [Non-Patent Document 1] Nagai K, Iida K, Shimizu K, Kinugasa R, Izumi M, Kato D, Takeo M, Mochiji K, Negoro S., Appl Microbiol Biotechnol.98(20):8751-61(2014) [Non-Patent Document 2] Negoro S, Kato DI, Ohki T, Yasuhira K, Kawashima Y, Nagai K, Takeo M, Shibata N, Kamiya K, Shigeta Y, Methods Enzymol.648,357-389(2021) Summary of the Invention [Problem to be solved by the invention]

[0014] An object of the present invention is to provide a novel method for producing a diamine compound and / or a dicarboxylic acid compound, which are polymerization raw materials, from a polyamide. [Means for solving the problem]

[0015] The present inventors considered that a hydrolysis reaction using an enzyme at a low temperature is preferable as a method for minimizing the loss of the target product due to side reactions. In order to increase hydrolysis by an enzyme, it is effective to reduce the molecular weight and make the polyamide soluble in water, as shown in the example of PA6 described in Non-Patent Document 1. However, Non-Patent Document 1 does not mention the reduction of the molecular weight of n,m-nylon, and it was very difficult to recover the target product in high purity using the decomposition method used for nylon 6.

[0016] As a result of various studies on the method for reducing the molecular weight of n,m-nylon before enzymatic degradation, the inventors have found that the hydrolysis method in high-temperature water, which was conventionally avoided by causing a decomposition reaction of the product, is optimal. Conventionally, hydrolysis has been studied from the viewpoint of increasing the yield of dicarboxylic acid in high-temperature water. However, as a result of examining the conditions for suppressing the decomposition reaction of the monomer in the high-temperature hydrolysis step and obtaining low molecular weight substances in which enzymatic reactions are likely to occur, it has been found that the final yield can be greatly improved in the production method including the enzymatic reaction, leading to the completion of the present invention.

[0017] That is, the present invention provides the following: [1] A method for producing a dicarboxylic acid compound (2) represented by the following general formula (2) and / or a diamine compound (3) represented by the following general formula (3) from a polyamide (1) represented by the following general formula (1), and optionally, a salt compound (4) represented by the following general formula (4), a polyamide (5) represented by the following general formula (5) and / or a polyamide (6) represented by the following general formula (6), (i) The temperature is over 200°C A first hydrolysis step of hydrolyzing the polyamide (1) in high-temperature water to obtain a first hydrolyzate, and (ii) A second hydrolysis step of subjecting the first hydrolyzate to enzymatic hydrolysis to obtain a second hydrolyzate comprising: wherein the first hydrolyzate comprises a water-soluble polyamide that dissolves in water at 20°C and polyamide that is insoluble in water at 20°C. comprising: the insoluble polyamide has a number average molecular weight of 5000 or less, and the content of the insoluble polyamide in the first hydrolysate is 10 to 95% by weight; a production method, wherein the second hydrolyzate comprises the dicarboxylic acid compound (2) and / or the diamine compound (3), and optionally, the salt compound (4), the polyamide (5) and / or the polyamide (6): [Chemical formula] [In the formula, R 1 is a substituted or unsubstituted aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 10 carbon atoms, R2 is a substituted or unsubstituted aliphatic hydrocarbon group having 2 to 10 carbon atoms.] [ka] [In the formula, R 1 is as defined in general formula (1). [ka] [In the formula, R 2 is as defined in general formula (1). [ka] [In the formula, R 1 and R 2 is as defined in general formula (1). [ka] [In the formula, R 1 and R 2 is as defined in general formula (1). [ka] [In the formula, R 1 and R 2 is as defined in general formula (1). [2] A dicarboxylic acid compound (2) represented by the general formula (2) and a diamine compound (3) represented by the general formula (3) are produced from a polyamide (1) represented by the general formula (1), The production method according to [1], wherein the second hydrolysate contains the dicarboxylic acid compound (2) and the diamine compound (3); [3] The method according to [1] or [2], wherein the temperature of the high-temperature water is lower than the critical temperature of water; [4] The method according to any one of [1] to [3], wherein in the first hydrolysis step, when a concentration of the polyamide (1) represented by the general formula (1) is 10% by weight relative to 100% by weight of the high-temperature water, a pH of the hydrolysis reaction solution at the end of the hydrolysis is 7.0 to 10.0. [5 ]before the first hydrolysate further contains a diamine compound (3) represented by the general formula (3) and a cyclic compound (7) represented by the following general formula (7), The sum of the yields of the diamine compound (3) represented by the general formula (3) and the cyclic compound (7) represented by the following general formula (7) is 20% or less, [1] to [ 4 ] The method for producing the present invention according to any one of the preceding claims, [ka] [In the formula, R 2 is as defined in general formula (1). [ 6 ]R 2 is a substituted or unsubstituted aliphatic hydrocarbon group having 5 to 9 carbon atoms, [1] to [ 5

[0021] 1. The method for producing a semiconductor device according to any one of the preceding claims; [ 7 ]R 1 is an unsubstituted linear aliphatic hydrocarbon group or aromatic hydrocarbon group having 4 to 8 carbon atoms, [1] to [ 6

[0021] 1. The method for producing a semiconductor device according to any one of the preceding claims; [ 8 ]R 2 is an unsubstituted linear aliphatic hydrocarbon group having 6 carbon atoms, [1]~[ 7

[0021] 1. The method for producing a semiconductor device according to any one of the preceding claims; [ 9 ]R 1 is an unsubstituted linear aliphatic hydrocarbon group having 4 carbon atoms, [1]~[ 8 ] The manufacturing method described in any one of the above items. Effect of the Invention

[0018] According to the present invention, it is possible to provide a novel method for producing a dicarboxylic acid compound and / or a diamine compound, which are polymerization raw materials, from a polyamide. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 shows the amino acid sequences of the enzymes and the nucleotide sequences of these enzymes that have been codon-optimized for expression in E. coli. [Diagram 2] FIG. 2 shows the base sequences of the primers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention (hereinafter, simply referred to as "the present embodiment") will be described in detail. In this specification, unless otherwise specified, nucleotide sequences are described in the 5' to 3' direction, and amino acid sequences are described in the N-terminal to C-terminal direction.

[0021] The present invention provides a method for producing a dicarboxylic acid compound (2) represented by the following general formula (2) and / or a diamine compound (3) represented by the following general formula (3), and optionally a salt compound (4) represented by the following general formula (4), a polyamide (5) represented by the following general formula (5) and / or a polyamide (6) represented by the following general formula (6), from a polyamide (1) represented by the following general formula (1), comprising: (i) a first hydrolysis step of hydrolyzing the polyamide (1) in high-temperature water to obtain a first hydrolyzate; and (ii) a second hydrolysis step in which the first hydrolysate is subjected to enzymatic hydrolysis to obtain a second hydrolysate; Including, the first hydrolysate comprises a water-soluble polyamide that dissolves in water at 20°C; the second hydrolysate comprises the dicarboxylic acid compound (2) and / or the diamine compound (3), and optionally the salt compound (4), the polyamide (5) and / or the polyamide (6).

[0022] [ka] [In the formula, R 1 is a substituted or unsubstituted aliphatic or aromatic hydrocarbon group having 1 to 10 carbon atoms, R 2 is a substituted or unsubstituted aliphatic hydrocarbon group having 2 to 10 carbon atoms.]

[0023] [ka] [In the formula, R 1 is as defined in general formula (1).

[0024] [ka] [In the formula, R 2 is as defined in general formula (1).

[0025] [ka] [In the formula, R 1 and R 2 is as defined in general formula (1).

[0026] [ka] [In the formula, R 1 and R 2 is as defined in general formula (1).

[0027] [ka] [In the formula, R 1 and R 2 is as defined in general formula (1).

[0028] In this specification, the polyamide (1) represented by the above general formula (1) may be simply referred to as "polyamide (1)". The dicarboxylic acid compound (2) represented by the above general formula (2) may be simply referred to as "dicarboxylic acid compound (2)" or "compound (2)". The diamine compound (3) represented by the above general formula (3) may be simply referred to as "diamine compound (3)" or "compound (3)". The salt compound (4) represented by the above general formula (4) may be simply referred to as "salt compound (4)" or "compound (4)". The polyamide (5) represented by the above general formula (5) may be simply referred to as "polyamide (5)". The polyamide (6) represented by the above general formula (6) may be simply referred to as "polyamide (6)". The cyclic compound (7) represented by the below-mentioned general formula (7) may be simply referred to as "cyclic compound (7)" or "compound (7)".

[0029] In a preferred embodiment, a dicarboxylic acid compound (2) represented by general formula (2) and a diamine compound (3) represented by general formula (3) are produced from a polyamide (1) represented by general formula (1), and the second hydrolyzate contains the dicarboxylic acid compound (2) and the diamine compound (3). In one preferred embodiment, in addition to the dicarboxylic acid compound (2) and the diamine compound (3), a salt compound (4) represented by general formula (4), a polyamide (5) represented by general formula (5), and / or a polyamide (6) represented by general formula (6) are also produced, and the second hydrolyzate may contain, in addition to the dicarboxylic acid compound (2) and the diamine compound (3), the salt compound (4), the polyamide (5), and / or the polyamide (6).

[0030] <Polyamide (1)> Polyamide (1) is an n,m-nylon, such as, but not limited to, nylon 66, nylon 610, nylon 6T, nylon 6I, nylon 9T and nylon M5T.

[0031] The method for synthesizing polyamide (1) is not particularly limited. Polyamide (1) is synthesized by mixing compound (2), an ester compound of compound (2) and an alcohol, or an acid halide of compound (2), or a mixture thereof, with compound (3), and subjecting the resulting mixture to a condensation reaction involving dehydration, dealcoholization, or dehalogenation ions, or a combination thereof.

[0032] <Dicarboxylic acid compound (2) (compound (2))> Compound (2) is R 1 and two carboxyl groups. In compound (2), R 1 is the R of polyamide (1) 1 Same as above.

[0033] <Diamine compound (3) (compound (3))> Compound (3) is R 2 and two amino groups. In compound (3), R 2 is the R of polyamide (1) 2 Same as above.

[0034] <Salt compound (4) (compound (4))> Compound (4) is a salt (dehydration condensate) of one molecule of dicarboxylic acid compound (2) and one molecule of diamine compound (3), and has a carboxyl group at one end and an amino group at the other end. 1 , R 2 is the R of polyamide (1) 1 , R 2 Same as above.

[0035] <Polyamide (5)> Polyamide (5) is a dehydration condensation product of one molecule of dicarboxylic acid compound (2) and two molecules of diamine compound (3), and has amino groups at both ends. 1 , R 2 is the R of polyamide (1) 1 , R 2 Same as above.

[0036] <Polyamide (6)> Polyamide (6) is a dehydration condensation product of two molecules of dicarboxylic acid compound (2) and one molecule of diamine compound (3), and has carboxyl groups at both ends. 1 , R 2 is the R of polyamide (1) 1 , R 2 Same as above.

[0037] In the general formulas (1) to (6), R 1 R is a substituted or unsubstituted aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 10 carbon atoms. Here, the aliphatic hydrocarbon group includes chain aliphatic hydrocarbon groups and cyclic aliphatic hydrocarbon groups. The chain aliphatic hydrocarbon group includes linear aliphatic hydrocarbon groups and branched aliphatic hydrocarbon groups. 1 When is a substituted aliphatic or aromatic hydrocarbon group, examples of the substituents include methyl, ethyl, n-propyl and isopropyl groups.

[0038] R 1 is preferably an unsubstituted aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 10 carbon atoms, more preferably an unsubstituted linear aliphatic hydrocarbon group or aromatic hydrocarbon group having 4 to 8 carbon atoms, even more preferably an unsubstituted linear aliphatic hydrocarbon group having 4 to 8 carbon atoms, and most preferably an unsubstituted linear aliphatic hydrocarbon group having 4 carbon atoms.

[0039] In the general formulas (1) to (6), R 2 is a substituted or unsubstituted aliphatic hydrocarbon group having 2 to 10 carbon atoms. Here, the aliphatic hydrocarbon group includes R 1 Similarly to the above for R, R includes chain aliphatic hydrocarbon groups and cyclic aliphatic hydrocarbon groups, and the chain aliphatic hydrocarbon groups include linear aliphatic hydrocarbon groups and branched aliphatic hydrocarbon groups. 2 When is a substituted aliphatic hydrocarbon group, examples of the substituents include methyl, ethyl, n-propyl and isopropyl groups.

[0040] R2 is preferably a substituted or unsubstituted aliphatic hydrocarbon group having 5 to 9 carbon atoms, more preferably an unsubstituted aliphatic hydrocarbon group having 5 to 9 carbon atoms, even more preferably an unsubstituted straight-chain aliphatic hydrocarbon group having 6 to 9 carbon atoms, and most preferably an unsubstituted straight-chain aliphatic hydrocarbon group having 6 carbon atoms.

[0041] Polyamide (1), dicarboxylic acid compound (2), diamine compound (3), and R 1 and R 2 The correspondence between the above and the above is exemplified as follows, but is not limited to these.

[0042] [Table 1]

[0043] <Step (i): First Hydrolysis Step> In this step, polyamide (1) is hydrolyzed in high-temperature water to obtain a first hydrolyzate. In this step, the polyamide (1) is hydrolyzed to reduce its molecular weight, loosening the fixation of the oligomer via hydrogen bonds to produce a water-soluble polyamide that dissolves in water. Thus, the first hydrolyzate contains a water-soluble polyamide. Here, the term "water-soluble polyamide" refers to a polyamide that is produced by reducing the molecular weight of polyamide (1) and dissolves in water at 20°C. The water-soluble polyamide may contain a salt compound (4), a polyamide (5) and / or a polyamide (6). The hydrolysis in step (i) is also referred to herein as "hot water hydrolysis."

[0044] In addition to the water-soluble polyamide, the first hydrolyzate further contains a polyamide that is produced by lowering the molecular weight of polyamide (1) and is insoluble in water at 20°C. In this specification, a polyamide that is insoluble in water at 20°C is also referred to as a "water-insoluble polyamide". The number average molecular weight of the water-insoluble polyamide in the first hydrolyzate is not particularly limited, but is, for example, 10000 or less, preferably 7000 or less, more preferably 5000 or less, even more preferably 4000 or less, and even more preferably 3000 or less. If the molecular weight of the water-insoluble polyamide is high and the water solubility is low, it is difficult to undergo hydrolysis reaction by enzymes, but by reducing the average molecular weight, the reactivity with enzymes in the subsequent second hydrolysis step is improved.

[0045] The content of the water-insoluble polyamide in the first hydrolysate is not particularly limited, and may be 1 to 95% by weight, 10 to 90% by weight, or 50 to 85% by weight. In particular, when the content of the water-insoluble polyamide is 10% by weight or more, the number average molecular weight of the water-soluble polyamide is lower than that of the raw material polyamide, and the subsequent second hydrolysis tends to proceed more smoothly.

[0046] The method for measuring the molecular weight of the water-insoluble polyamide is not particularly limited, but can be, for example, measured by GPC, specifically, the method described in the Examples below.

[0047] The first hydrolysate may further contain, in addition to the water-soluble polyamide and the water-insoluble polyamide, compound (2), compound (3), compound (7) which is a decomposition product of compound (3) described below, and compound (8) which is a decomposition product of compound (2) described below.

[0048] In this specification, "high temperature water" means water having a temperature of 200° C. or higher. High temperature water includes subcritical water and supercritical water. The water during the reaction is in a liquid or supercritical state.

[0049] Supercritical water refers to water in a supercritical state. The supercritical state of water is a state beyond the critical temperature (374 °C) and critical pressure (22.1 MPa) of water. Also, the critical point is included in the supercritical state in this specification.

[0050] Subcritical water is water in a subcritical state. The subcritical state of water is a state where the temperature is below the critical temperature of water and the pressure is equal to or higher than the saturated water vapor pressure. Therefore, the reaction pressure in step (i) is equal to or higher than the saturated water vapor pressure when the reaction temperature is below the critical temperature of water, and equal to or higher than the critical pressure when the reaction temperature is at or above the critical temperature of water.

[0051] The reaction temperature in step (i) is the temperature of high-temperature water and is not particularly limited, but it is preferably 200 °C or higher and 400 °C or lower, more preferably 230 °C or higher and 350 °C or lower, and even more preferably 230 °C or higher and 300 °C or lower. If the reaction temperature is too low, the hydrolysis reaction of polyamide tends to be slow. If the reaction temperature exceeds 400 °C, the decomposition reaction significantly progresses, and the monomer yield tends to decrease.

[0052] In a preferred embodiment, the high-temperature water in step (i) is subcritical water. That is, in this embodiment, the temperature of the high-temperature water in step (i) is below the critical temperature of water. In this case, the reaction pressure may be equal to or higher than the saturated water vapor pressure at each reaction temperature. The upper limit of the reaction pressure is not particularly limited, but the reaction pressure is preferably equal to or lower than the saturated water vapor pressure + 20 MPa, more preferably equal to or lower than the saturated water vapor pressure + 15 MPa, even more preferably equal to or lower than the saturated water vapor pressure + 5 MPa, and most preferably the saturated water vapor pressure. From the perspective of selecting a device for promoting the reaction, it is preferable that the reaction pressure is not too high compared to the saturated water vapor pressure. The reaction pressure may be set to the saturated water vapor pressure by heating in a sealed state, or may be pressurized by injecting an inert gas with the container sealed. Pressurization with an inert gas may be performed before or after heating.

[0053] When the reaction temperature in step (i) is equal to or higher than the critical temperature of water, the reaction pressure may be equal to or higher than the critical pressure. The upper limit of the reaction pressure is not particularly limited, but the reaction pressure is preferably equal to or lower than the critical pressure + 15 MPa, more preferably equal to or lower than the critical pressure + 5 MPa, and particularly preferably equal to the critical pressure. From the viewpoint of selecting an apparatus for proceeding with the reaction, it is preferable that the reaction pressure is not too high compared to the critical pressure. When the temperature of the high-temperature water in step (i) is equal to or higher than the critical temperature, the corrosiveness of the water increases significantly, which may lead to contamination with metals from the equipment and deterioration of the equipment due to corrosion.

[0054] Although there is no particular limitation on the stirring during the reaction, stirring is preferred, as stirring renews the surface of the polyamide solid, the reaction proceeds uniformly, and the reaction rate is improved.

[0055] The shape of the reactor is not particularly limited, and any shape such as a tank type or a circulation type may be used.

[0056] The reaction time is not particularly limited, but is preferably 5 to 300 minutes, more preferably 5 to 100 minutes, and even more preferably 5 to 30 minutes. The reaction time is measured from when the desired reaction conditions are reached until heating is stopped. If the reaction time is too short, there are many high molecular weight components that cannot react with the enzyme, and if the reaction time is too long, the decomposition reaction proceeds and the yield drops significantly.

[0057] The concentration of polyamide in water (high-temperature water) is not particularly limited, but is preferably 1 to 50% by weight, more preferably 5 to 40% by weight, and most preferably 7 to 30% by weight. If the concentration is too low, recovery becomes very difficult, and if the concentration is too high, the fluidity of the reaction liquid is low, making it difficult to cause a uniform reaction.

[0058] In order to improve the reaction efficiency of the first hydrolysis step in high-temperature water, the polyamide (1) can be subjected to a pretreatment.

[0059] For example, in order to carry out the reaction in the first hydrolysis step uniformly, it can be microparticulated. The method of microparticulation is not particularly limited, but examples include a method of dissolving polyamide (1) in a solvent and then using recrystallization, reprecipitation, spray drying, etc., and a microparticulation method by pulverization such as freeze pulverization. The method of dissolving once and then microparticulating is preferred, since it can be uniformly microparticulated regardless of the shape of polyamide (1) used as a raw material.

[0060] In order to improve the reactivity after the start of the reaction, polyamide (1) can be sufficiently permeated with water in advance. The permeation method is not particularly limited, and examples thereof include a method of immersing polyamide (1) in water and heating it, a method of exposing polyamide (1) to a humid atmosphere, and a method of dissolving polyamide (1) in a solvent, adding water, and then precipitating polyamide (1).

[0061] A catalyst may be mixed in advance so that the reaction starts uniformly at the start of the reaction. The catalyst to be mixed in advance is not particularly limited, but examples thereof include acidic compounds, basic compounds, and inorganic salts. Considering the separability from the obtained compounds (2) and (3), etc., and the use as a polymerization raw material, inorganic salts are preferred as the catalyst to be mixed in advance.

[0062] The method of mixing the catalyst is not particularly limited, and examples thereof include a method of immersing polyamide (1) in a solvent in which the catalyst to be mixed is dissolved, a method of melt-kneading the catalyst to be mixed with polyamide (1), and a method of dissolving the catalyst to be mixed with polyamide (1) in a solvent, mixing them, and then precipitating polyamide (1).

[0063] In one embodiment, the first hydrolysate further includes a monomer and a decomposition product thereof. Specifically, the first hydrolysate further includes a compound (3) and a cyclic compound (7) (diamine cyclization product) represented by the following general formula (7). Compound (7) is a compound generated by decomposition of compound (3). Here, the decomposition is specifically due to a cyclization reaction of compound (3). [ka] [In the formula, R 2 is as defined in general formula (1).

[0064] Examples of compound (7) include hexamethyleneimine, nonamethyleneimine, and 4-methylazepane. When compound (3) is hexamethylenediamine, compound (7) is hexamethyleneimine.

[0065] The amount of the monomer and its decomposition product after the first hydrolysis step is not particularly limited, but from the viewpoint of improving the reaction yield of the target products, compounds (2) and (3), after the hydrolysis step by enzyme, i.e., the reaction yield of the target product by the subsequent second hydrolysis step, it is preferable that the sum of the yields of compounds (3) and (7) in the first hydrolyzate is 20% or less. Moreover, the sum of the yields is more preferably 0.1 to 20%, more preferably 0.5 to 15%, and even more preferably 0.8 to 12%. Since compound (7) is generated by the decomposition of compound (3), if the sum of the yields of compounds (3) and (7) is too high, it means that the hydrolysis reaction has progressed, but the decomposition reaction has also progressed, and the yield after the hydrolysis step using the enzyme may be low. Moreover, if the sum of the yields is too low, the polymer is not reduced in molecular weight, and the hydrolysis reaction by the enzyme does not proceed easily.

[0066] The first hydrolysate may further contain compound (8) (dicarboxylic acid cyclization product) which is a decomposition product of compound (2). Specifically, compound (8) which is a decomposition product of compound (2) is produced by a cyclization reaction of compound (2). For example, when compound (2) is adipic acid, compound (8) which is a decomposition product of compound (2) is cyclopentanone.

[0067] The amount of the monomer and its decomposition product after the first hydrolysis step is not particularly limited, but from the viewpoint of improving the reaction yield of the target products, compounds (2) and (3), after the hydrolysis step by enzyme, i.e., the reaction yield of the target product by the subsequent second hydrolysis step, the sum of the yields of compounds (2) and (8) in the first hydrolyzate may be 0.1 to 40%, may be 0.5 to 20%, or may be 0.8 to 10%. Since compound (8) is generated by the decomposition of compound (2), if the sum of the yields of compounds (2) and (8) is too high, it means that the hydrolysis reaction has progressed, but the decomposition reaction has also progressed, and the yield after the hydrolysis step using the enzyme may be low. In addition, if the sum of the yields is too low, the molecular weight of the polymer has not progressed, and the hydrolysis reaction by the enzyme is difficult to proceed. In addition, the amount of the monomer and its decomposition product after the first hydrolysis step is not particularly limited, but from the viewpoint of improving the reaction yield of the target products, compounds (2) and (3), after the hydrolysis step by enzyme, i.e., the reaction yield of the target product by the subsequent second hydrolysis step, the sum of the yields of compounds (7) and (8) in the first hydrolyzate may be 0 to 80%, may be 0.1 to 60%, or may be 0.5 to 20%. Since compounds (7) and (8) are generated by the decomposition of compounds (3) and (2), respectively, if the sum of the yields of compounds (7) and (8) is too high, it means that the hydrolysis reaction has progressed, but the decomposition reaction has also progressed, and the yield after the hydrolysis step using the enzyme may be low. In addition, if the sum of the yields is too low, the molecular weight of the polymer has not progressed, and the hydrolysis reaction by the enzyme is difficult to proceed.

[0068] When compound (7), which is a decomposition product of compound (3), and compound (8), which is a decomposition product of compound (2), are produced in the first hydrolysis step, the pH of the hydrolysis solution changes. Therefore, the progress of the reaction can be confirmed by measuring the pH of the hydrolysis reaction solution. There are no particular limitations on the pH of the hydrolysis reaction solution at the end of the first hydrolysis step, but if the reaction is started with a concentration of polyamide (1) (concentration of charged polyamide (1)) of 10% by weight relative to 100% by weight of water (high-temperature water), it is preferable to stop the reaction at pH 7.0 to 10.0, more preferably at pH 8.0 to 10.0, and even more preferably at pH 9.0 to 9.5. If the pH is 10.0 or less, the enzyme can be prevented from being inactivated, so the subsequent second hydrolysis tends to proceed well. When the concentration of the charged polyamide (1) is other than 10% by weight, the progress of the reaction can be similarly confirmed and adjusted by concentrating or diluting a pH measurement sample taken from the reaction solution at a concentration ratio or dilution ratio such that the concentration of the charged polyamide (1) is 10% by weight, and measuring the pH. The concentration method and the pH measurement method are not particularly limited, and general methods can be used, specifically, the methods described in the Examples below.

[0069] After completion of the reaction, the solution may be subjected to post-treatment as required, and the method used for the post-treatment is not particularly limited.

[0070] The pH after the first hydrolysis reaction may be adjusted by adding acidic or basic compounds and / or pH fluctuations may be suppressed with a buffer until the pH is in a suitable range for carrying out the subsequent, second enzymatic hydrolysis step.

[0071] In addition, the concentrations of polyamide (1), compound (2), compound (3), and the water-soluble polyamide (which may contain salt compound (4), polyamide (5) and / or (6)) may be concentrated or diluted with water, if necessary, to a level appropriate for carrying out the subsequent second hydrolysis step.

[0072] The solid component (water-insoluble polyamide) precipitated in the first hydrolysis step may be subjected to solid-liquid separation or directly to the second hydrolysis step. When solid-liquid separation is performed, the reaction is completed quickly because only the soluble component is hydrolyzed by the enzyme. On the other hand, when separation is not performed, the hydrolysis of the low molecular weight solid polymer by the enzyme also proceeds, resulting in a high yield of compound (2) and compound (3).

[0073] <Step (ii): Second Hydrolysis Step> In this step, the first hydrolysate is subjected to hydrolysis with an enzyme to obtain a second hydrolysate. Specifically, the polyamide (1) that has been reduced in molecular weight in step (i) is subjected to a hydrolysis reaction with an enzyme to obtain a dicarboxylic acid compound (2) and / or a diamine compound (3), and optionally, a salt compound (4), a polyamide (5) and / or a polyamide (6). Thus, the second hydrolysate contains the dicarboxylic acid compound (2) and / or the diamine compound (3), and optionally, a salt compound (4), a polyamide (5) and / or a polyamide (6).

[0074] More specifically, the second hydrolysate includes a water-soluble polyamide (such as salt compound (4), polyamide (5) and / or (6)), a water-insoluble polyamide, a dicarboxylic acid compound (2), a diamine compound (3), a compound (7) which is a decomposition product of the diamine compound (3), and / or a compound (8) which is a decomposition product of the compound (2).

[0075] The enzymes that can be used for hydrolysis of polyamide in this step are not particularly limited as long as they have hydrolytic activity, and examples thereof include NylA (EC 3.5.2.12), a cyclic dimer degrading enzyme of 6-aminocaproic acid, NylB (EC 3.5.1.46), an exo-type oligomer degrading enzyme, and NylC (EC 3.5.1.117), an endo-type oligomer degrading enzyme. Specific examples of typical enzymes include, but are not limited to, NylA, NylB, and NylC from Arthrobacter sp.KI72; NylA and NylB from Pseudomonas sp.NK8; NylB and NylC from Agromyces sp.KY5R; and NylA, NylB, and NylC from Kocuria sp.KY2.

[0076] In this step, a single enzyme may be used, or multiple enzymes may be used in combination.

[0077] The amino acid sequence of the above enzyme that can be used in the present invention may have all mutations that can occur in nature and / or mutations and modifications that have been artificially introduced, for example, mutations such as deletion, substitution, insertion and addition, so long as it has enzyme activity. For example, the amino acid sequence of the above enzyme may include one or more, preferably 1 to 20, more preferably 1 to 10, even more preferably 1 to 7, particularly preferably 1 to 5, and even more preferably 1 to 3 amino acid deletions, substitutions, insertions and / or additions.

[0078] Methods for producing enzymes include, for example, a method for producing the enzyme using an organism that naturally produces the enzyme, and a method for producing the enzyme in a host cell by genetic recombination, but are not limited to these as long as the method can produce an active enzyme. Hosts for heterologous expression include, for example, bacteria such as Escherichia coli, Corynebacterium sp., Bacillus subtilis, Brevibacillus sp., and Rhodococcus sp., fungi such as Saccharomyces cerevisiae, Schizosaccharomyces cerevisiae, Pichia yeast, and Aspergillus oryzae, and eukaryotic cells such as insect cells, animal cells, and plant cells, but are not limited to these.

[0079] The form of the enzyme used in the reaction is not particularly limited. The enzyme produced by a biological technique may be used as it is, as cells or extracellular (such as culture medium) containing the enzyme, or may be used after separation, purification, concentration, or other treatment from cells or extracellular (such as culture medium). A known method can be used for the treatment, and for example, methods such as addition of lysozyme and a surfactant, ultrasonic treatment, cell disruption using a French press or the like, washing, centrifugation, various types of chromatography, various types of membrane separation, salting out, solvent precipitation, dialysis, and electrophoresis can be appropriately selected or combined. Alternatively, from the viewpoint of reusing the enzyme, the enzyme may be immobilized by an entrapment method, a crosslinking method, or a carrier binding method. Examples of immobilization carriers for immobilization include, but are not limited to, glass beads, silica gel, polyurethane, polyacrylamide, polyvinyl alcohol, carrageenan, alginic acid, and the like.

[0080] The temperature of the enzyme reaction in the second hydrolysis step is not particularly limited, but is, for example, 10 to 90°C, preferably 20 to 80°C. If the reaction temperature is too low, the reaction rate is low, and if the reaction temperature is too high, the enzyme is likely to be deactivated. The reaction pH may be adjusted by adding an acidic or basic compound, and / or the pH fluctuation may be suppressed by using a buffer solution. The pH is preferably 2.0 to 10.0, more preferably 3.0 to 8.5. The reaction time varies depending on the amount of enzyme used, but is preferably 20 minutes to 200 hours, more preferably 6 to 80 hours, in consideration of industrial use. However, the present invention is not limited to the above-mentioned reaction conditions and reaction form, and the reaction conditions and reaction form may be appropriately selected.

[0081] The method for recovering the target product, compound (2) and / or compound (3), and the optional target products, salt compound (4), polyamide (5) and / or polyamide (6), is not particularly limited, and may be recovered all together or each separately. For example, compound (2) and compound (3) may be recovered as their salts (in the form of salt compound (4)).

[0082] Methods for recovering them separately include methods for separating and recovering them by crystallization or distillation, which utilize the differences in solubility and boiling point of each compound. For example, an acidic compound is added to the reaction solution to lower the pH to precipitate compound (2) and polyamide (6), and the precipitated compound (2) and polyamide (6) are separated and crystallized to separate and recover them. Alternatively, a basic compound can be added to the mother liquor after separation of compound (2) and polyamide (6) to raise the pH, and then compound (3) and polyamide (5) can be recovered by distillation. Examples of the method for recovering the salt compound (4) and the method for recovering the compound (2) and the compound (3) as their salt, i.e., the above-mentioned separation and recovery method, include a method in which the reaction solution is first concentrated to dryness, reprecipitated, and recrystallized. From the viewpoint of removing impurities, recrystallization is preferred. Examples of the recrystallization method include a method of concentrating the reaction solution, a method of cooling the reaction solution, a method of adding a poor solvent for the salt to the reaction solution, etc. From the viewpoints of improving the yield and reducing the amount of remaining impurities, the recrystallization method is preferred.

[0083] Other examples of the separation and recovery method include sieving based on molecular weight, such as ultrafiltration and nanofiltration.

[0084] The target products, compound (2) and / or compound (3), obtained by the production method of the present invention, and any target products, salt compound (4), polyamide (5) and / or polyamide (6), may be reused in the form of a mixture thereof as a polymerization raw material for polyamide, or only a mixture of compound (2) and / or compound (3) and their salt, salt compound (4), may be reused as a polymerization raw material for polyamide, or only compound (2) and / or compound (3) may be reused as a polymerization raw material for polyamide.

[0085] As described above, the present invention provides a novel method for producing dicarboxylic acid compounds and / or diamine compounds from polyamides, which are useful as engineering plastics and serve as polymerization raw materials for polyamides. In the production method of the present invention, dicarboxylic acid compounds and / or diamine compounds can be produced from polyamides, particularly m,n-nylon, in high yields by combining hydrolysis in high-temperature water with hydrolysis by enzymes. Here, by combining with an enzyme reaction, decomposition reaction due to cyclization can be suppressed, and the yield is further improved. According to the production method of the present invention, it is not necessary to add an acidic compound (e.g., formic acid) for the purpose of reducing the molecular weight, and therefore the reaction system and the target product during production are not contaminated by the acidic compound or its derivatives, and the target product can be obtained with high purity, and no step of removing the acidic compound is required. EXAMPLES

[0086] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0087] Working Example , reference example The measurement and analysis methods used in the comparative examples are as follows. (1) Liquid chromatograph (LC) Purpose of analysis: Quantitative determination of dicarboxylic acid compound (2) Measuring device: Prominence (manufactured by Shimadzu Corporation) Mobile phase: 8mM methanesulfonic acid Column: Shim-pack Fast-OA(G) + Shim-pack Fast-OA(7.8x100mm) x 2 Column temperature: 35℃ Flow rate: 0.6mL / min Injection volume: 10μL Detector: Differential refractive index detector, UV detector 210 nm

[0088] (2) Gas chromatograph (GC) Purpose of analysis: Quantitative determination of dicarboxylic acid cyclization product (8) Measuring device: GC-2030 Carrier gas: He Column: DB-1 30m x 0.25mm x 1.0um (Agilent Technology) Detector: FID Injection volume: 1.0μL Split ratio: 1:40 Column temperature: 45℃ 5min hold ⇒ Heat up 20℃ / min ⇒ 300℃ 20min hold Injection temperature: 250℃ Detector temperature: 300℃

[0089] (3) Ion chromatograph (IC) Analysis objective: Quantitative determination of diamine (3) and diamine cyclization product (7) Measurement device: Integrion RFIC (Thermo Fisher Scientific Inc.) Mobile phase: 0-0.1 min 9 mM methanesulfonic acid aqueous solution 0.1-10.7min 9→65mM methanesulfonic acid aqueous solution 10.7~12.8min 65mM methanesulfonic acid solution Column: IonPac CG19 (2 x 50 mm) / CS19 (2 x 250 mm) (Thermo Fisher Scientific) Column temperature: 30℃ Flow rate: 0.325mL / min Injection volume: 25μL Detector: Electrical conductivity detector

[0090] (4) Size Exclusion Chromatography (SEC) Analysis purpose: molecular weight measurement Measuring device: TOSOH HLC-8320GPC Mobile phase: HFIP (Na trifluoroacetate-5mmol / L) Column: TSKgel GMHHR-H(S) x 3 (4.6mm I.D. x 15cm) Column temperature: 40℃ Flow rate: 0.175ml / min Injection volume: 10μL Standard sample: PMMA Detector: Differential refractometry

[0091] (5) pH Example 1 4, Reference example 5. The pH of the solutions obtained in Comparative Examples 1 to 3 was measured using a portable pH meter D-51S manufactured by Horiba, Ltd.

[0092] <Construction of plasmid for enzyme expression> KOD Plus Neo (product name, manufactured by Toyobo) was used to amplify the PCR fragments, and E. coli JM109 strain (manufactured by Nippon Gene Co., Ltd.) was used to prepare the plasmids. The artificial gene synthesis service of Eurofins Genomics was used to optimize the base sequence.

[0093] A DNA fragment containing the coding region of the NylB protein (SEQ ID NO: 1) derived from Arthrobacter sp.KI72 and a DNA fragment containing the coding region of the NylC(m) protein (SEQ ID NO: 2), which is a mutant of the NylC protein derived from Arthrobacter sp.KI72, were codon-optimized for expression in E. coli and synthesized using the artificial gene synthesis service of Eurofins Genomics (SEQ ID NO: 3 and 4) (Figure 1). PCR was performed using pRSFDuet-1 (product name, manufactured by Merck) as a template and oligonucleotides of SEQ ID NO: 5 and 6 (Figure 2) as primers to obtain the pRSFDuet-1 fragment. The DNA fragment containing the gene coding region and the pRSFDuet-1 fragment were connected using the In-Fusion HD cloning kit (product name, manufactured by Clontech). The fragment was transformed into E. coli JM109 strain, and a plasmid was extracted from the resulting transformant. The plasmid for expressing NylB was "nylB-pRSFDuet", and the plasmid for expressing NylC(m) was "nylC(m)-pRSFDuet".

[0094] <Preparation of crude enzyme solution> The constructed plasmid was transformed into Escherichia coli BL21 (DE3) strain competent cells (manufactured by Nippon Gene Co., Ltd.), spread onto LB agar medium (tryptone 10 g / L, yeast extract 5 g / L, sodium chloride 5 g / L, agar powder 15 g / L) containing 100 mg / L of kanamycin sulfate, and incubated at 37 ° C. for 24 hours to obtain a single colony of the transformant. One platinum loopful of the transformant was inoculated into 2 mL (14 mL round bottom tube) of LB liquid medium (tryptone 10 g / L, yeast extract 5 g / L, sodium chloride 5 g / L) containing 50 mg / L of kanamycin sulfate, and cultured with shaking at 37 ° C. for 24 hours to obtain a preculture solution. 500 μL of the obtained preculture solution was inoculated into 50 mL (100 mL flask) of LB liquid medium containing 50 mg / L of kanamycin sulfate, and cultured with shaking at 37 ° C. After 3 hours of culture, isopropyl-β-thiogalactosylpyranoside (IPTG) was added to a final concentration of 0.1 mM, and the cells were cultured at 30°C for 24 hours with shaking. 45 mL of the resulting culture solution was centrifuged at 4000×g for 5 minutes, and the supernatant was removed to obtain a pellet. The pellet was washed with 10 mL of 100 mM Tris-HCl buffer (pH 7.5), then centrifuged at 4000×g for 5 minutes, and the supernatant was removed. The pellet was suspended in 2 mL of 100 mM Tris-HCl buffer (pH 7.5), and the cells were disrupted using an ultrasonic disrupter (Digital Sonifier 450, product name, manufactured by Branson). The disrupted solution was centrifuged at 4000×g for 5 minutes, and the resulting supernatant was used as a crude enzyme solution containing NylB or a crude enzyme solution containing NylC(m).

[0095] [Example 1] 3 g of nylon 6,6 (polycondensate of adipic acid and hexamethylenediamine, number average molecular weight 23000) and 30 g of water were added to a stationary pressure vessel made of Inconel with an inner diameter of 30 mm and a depth of 78 m, and the vessel was sealed. Nitrogen was circulated through the vessel to replace the gas phase components with nitrogen. The vessel was attached to an electric furnace, and heating was started. The internal temperature was raised to 280°C, and pressurization with nitrogen was performed. The final temperature was 280°C and the pressure was 22 MPa. After 30 minutes of reaction in that state, the power to the electric furnace was turned off, and the vessel was removed from the electric furnace and air-cooled. After cooling, the treated solution was taken out into a glass bottle and weighed. The solution taken out was 30.39 g. The analytical results of the extracted solution are summarized in Table 2.

[0096] [Example 2~ 4. Reference example 5~ 8] Hydrolysis of nylon 6,6 was carried out in the same manner as in Example 1, except that the internal temperature and pressure of the vessel were changed as shown in Table 2. The analytical results of the extracted solution are summarized in Table 2.

[0097] In addition, in Examples 1 to 4, Reference example 5 and 8 are in a subcritical state (below the critical temperature of water, above the saturated water vapor pressure). reference Examples 6 and 7 are in a supercritical state (above the critical temperature and pressure of water).

[0098] [Table 2]

[0099] [Example 9] To the high-temperature water treatment solution obtained in Example 1, 34.1 mL of the crude enzyme solution containing NylB, 34.1 mL of the crude enzyme solution containing NylC(m), 15.7 mL of 1 M Tris-HCl buffer (pH 7.5), and 42.8 mL of water were added, and the enzyme reaction was carried out at 40° C. for 48 hours. Analysis of the enzyme reaction solution revealed that it contained 1.26 g (8.6 mmol, yield 65%) of adipic acid and 0.92 g (7.9 mmol, yield 60%) of hexamethylenediamine. 2 N-(CH 2 ) 6 -NH-CO-(CH 2 ) 4 -COOH(Hexamethylenediamine adipate), H 2 N-(CH 2 ) 6 -NH-CO-(CH 2 ) 4 -CO-NH-(CH 2 ) 6 -NH 2 , COOH-(CH 2 ) 4-CO-NH-(CH 2 ) 6 -NH-CO-(CH 2 ) 4 It also contained -COOH. The analytical results of the enzyme reaction solution are summarized in Table 3.

[0100] [Example 10 ~ 12, Reference example 13, 14] Example 10 12, Reference example 13, 14 are respectively Examples 2 to 4, Reference example 5, An enzyme reaction was carried out in the same manner as in Example 9, except that the high-temperature water-treated solution obtained in 6 was used. The analytical results of the enzyme reaction solution are summarized in Table 3.

[0101] [Table 3]

[0102] [Comparative Example 1] 3 g of the same nylon 6,6 used in Example 1 was mixed with 20 mL of 1 M Tris-HCl buffer (pH 7.5), 20 mL of the crude enzyme solution containing NylB, 20 mL of the crude enzyme solution containing NylC(m), and 140 mL of water, and the enzyme reaction was carried out at 40° C. for 48 hours. Analysis of the enzyme reaction solution revealed that neither adipic acid nor hexamethylenediamine was detected. [Industrial Applicability]

[0103] According to the present invention, diamine compounds and dicarboxylic acid compounds which can be used as raw materials for polyamides and the like can be produced with good yield.

Claims

1. A method for producing a dicarboxylic acid compound (2) represented by the following general formula (2) and / or a diamine compound (3) represented by the following general formula (3), and optionally a salt compound (4) represented by the following general formula (4), a polyamide (5) represented by the following general formula (5) and / or a polyamide (6) represented by the following general formula (6), from a polyamide (1) represented by the following general formula (1), (i) a first hydrolysis step in which the polyamide (1) is hydrolyzed in high-temperature water having a temperature of 200° C. or higher to obtain a first hydrolyzate; and (ii) a second hydrolysis step in which the first hydrolysate is subjected to enzymatic hydrolysis to obtain a second hydrolysate; Including, the first hydrolysate contains a water-soluble polyamide that is soluble in water at 20°C and a polyamide that is insoluble in water at 20°C, the insoluble polyamide has a number average molecular weight of 5000 or less, and the content of the insoluble polyamide in the first hydrolysate is 10 to 95% by weight; A method for producing the second hydrolyzate, comprising the steps of: 【Chemistry 1】 [In the formula, R １ is a substituted or unsubstituted aliphatic or aromatic hydrocarbon group having 1 to 10 carbon atoms, R ２ is a substituted or unsubstituted aliphatic hydrocarbon group having 2 to 10 carbon atoms. 【Chemistry 2】 [In the formula, R １ is as defined in general formula (1). 【Chemistry 3】 [In the formula, R ２ is as defined in general formula (1). 【Chemistry 4】 [In the formula, R １ and R ２ is as defined in general formula (1). 【Chemistry 5】 [In the formula, R １ and R ２ is as defined in general formula (1). 【Chemistry 6】 [In the formula, R １ and R ２ is as defined in general formula (1).

2. A dicarboxylic acid compound (2) represented by the general formula (2) and a diamine compound (3) represented by the general formula (3) are produced from a polyamide (1) represented by the general formula (1), The method according to claim 1 , wherein the second hydrolysate comprises the dicarboxylic acid compound (2) and the diamine compound (3).

3. The method according to claim 1 or 2, wherein the temperature of the high-temperature water is below the critical temperature of water.

4. The method according to claim 1 or 2, wherein in the first hydrolysis step, the pH of the hydrolysis reaction solution at the end of hydrolysis is 7.0 to 10.0 when the concentration of the polyamide (1) represented by the general formula (1) relative to 100% by weight of the high-temperature water is 10% by weight.

5. the first hydrolysate further contains a diamine compound (3) represented by the general formula (3) and a cyclic compound (7) represented by the following general formula (7), The method according to claim 1 or 2, wherein the sum of yields of the diamine compound (3) represented by the general formula (3) and the cyclic compound (7) represented by the following general formula (7) is 20% or less: 【Chemistry 7】 [In the formula, R ２ is as defined in general formula (1).

6. R ２ The method according to claim 1 or 2, wherein is a substituted or unsubstituted aliphatic hydrocarbon group having 5 to 9 carbon atoms.

7. R １ The method according to claim 1 or 2, wherein is an unsubstituted linear aliphatic hydrocarbon group or an aromatic hydrocarbon group having 4 to 8 carbon atoms.

8. R ２ The method according to claim 1 or 2, wherein is an unsubstituted linear aliphatic hydrocarbon group having 6 carbon atoms.

9. R １ The method according to claim 1 or 2, wherein is an unsubstituted linear aliphatic hydrocarbon group having 4 carbon atoms.

Images