WO2023167314A1

WO2023167314A1 - Method for hydrolyzing nylon

Info

Publication number: WO2023167314A1
Application number: PCT/JP2023/008043
Authority: WO
Inventors: 太一郎加藤; 雄樹白石
Original assignee: 国立大学法人鹿児島大学
Priority date: 2022-03-03
Filing date: 2023-03-03
Publication date: 2023-09-07

Abstract

This method for hydrolyzing nylon involves monomerizing nylon using nylon hydrolase, and comprises: a step for dissolving nylon in an organic solvent in which nylon is soluble so as to prepare a nylon solution; a step for preparing a nylon precipitation liquid by adding the nylon solution to a precipitating solvent for precipitating nylon in the form of particles; a step for removing the organic solvent and the precipitating solvent from the nylon precipitation liquid; a step for adding an aqueous solution so as to prepare a nylon dispersion liquid; and a step for adding nylon hydrolase to the nylon dispersion liquid so as to hydrolyze the nylon.

Description

Nylon hydrolysis method

The present invention relates to a method for hydrolyzing nylon.

Nylon, a type of polyamide, is widely used as fibers and plastics due to its toughness, heat resistance, and chemical resistance. Nylon, on the other hand, is incinerated or landfilled after use because it hardly undergoes biodegradation.

In this way, while nylon is a material with high utility value, it is also a material with a high environmental impact. Establishment of a nylon recycling method is desired in order to reduce the environmental load. As a method for recycling nylon, a method of hydrolyzing nylon using a nylon hydrolase to monomerize it has been reported (Non-Patent Document 1).

The method for hydrolyzing nylon in Non-Patent Document 1 cannot be said to have high enzymatic decomposition efficiency, and there is still room for improvement.

The present invention has been made in view of the above matters, and its object is to provide a method for hydrolyzing nylon that can improve the enzymatic decomposition efficiency of nylon.

The method for hydrolyzing nylon according to the first aspect of the present invention comprises:
A method for hydrolyzing nylon by monomerizing nylon using a nylon hydrolase, comprising:
a step of dissolving the nylon in an organic solvent capable of dissolving the nylon to prepare a nylon solution;
a step of adding the nylon solution to a precipitation solvent for precipitating the nylon into particles to prepare a nylon precipitation solution;
removing the organic solvent and the precipitation solvent from the nylon precipitation solution;
adding an aqueous solution to the nylon obtained by removing the organic solvent and the precipitation solvent to prepare a nylon dispersion;
adding the nylon hydrolase to the nylon dispersion to hydrolyze the nylon;
It is characterized by

Here, a step of adding the nylon obtained by removing the organic solvent and the precipitation solvent to a solution containing a decomposable oxidizing agent or acid and heating to reduce the molecular weight of the nylon;
removing the oxidizing agent or the acid from the solution after heating;
The nylon dispersion may be prepared by adding the aqueous solution to the nylon obtained by removing the oxidizing agent or the acid.

As the nylon, nylon 4, nylon 6, nylon 11, nylon 12,

nylon

6,6, nylon 6,10, nylon 6,12,

nylon

4,6, nylon 6T, nylon 6I, nylon M5T, nylon 6i, or , Nylon 6i-11 may be used.

Also, it is preferable to use trifluoroethanol or hexafluoroisopropanol as the organic solvent.

Also, it is preferable to use ethanol or ethylene glycol as the precipitation solvent.

In addition, it is preferable to use a phosphate buffer solution containing glycerol as the aqueous solution.

The method for hydrolyzing nylon according to the second aspect of the present invention comprises:
A method for hydrolyzing nylon by monomerizing nylon using a nylon hydrolase, comprising:
a step of adding the nylon to a solution containing an oxidizing agent or an acid capable of decomposing the nylon and heating to reduce the molecular weight of the nylon;
removing the oxidizing agent or the acid from the heated solution;
adding an aqueous solution to the nylon obtained by removing the oxidizing agent or the acid to prepare a nylon dispersion;
adding a nylon hydrolase to the nylon dispersion to hydrolyze the nylon;
It is characterized by

a step of dissolving the nylon in an organic solvent capable of dissolving the nylon to prepare a nylon solution;
a step of adding the nylon solution to a precipitation solvent for precipitating the nylon into particles to prepare a nylon precipitation solution;
and removing the organic solvent and the precipitation solvent from the nylon precipitation solution,
The nylon obtained by removing the organic solvent and the precipitation solvent may be added to a solution containing the oxidizing agent or the acid and heated to reduce the molecular weight of the nylon.

Also, it is preferable to use a hydrogen peroxide solution as the oxidizing agent.

Also, it is preferable to use formic acid as the acid.

It is also preferable to heat the nylon to 75 to 120°C to reduce the molecular weight of the nylon.

A phosphate buffer solution containing glycerol is preferably used as the aqueous solution.

It is also preferable to remove the oxidizing agent or acid by freeze-drying.

According to the present invention, it is possible to provide a method for hydrolyzing nylon that can improve the enzymatic decomposition efficiency of nylon.

1 is a process chart showing a method for hydrolyzing nylon according to Embodiment 1. FIG. It is process drawing which shows the hydrolysis method of nylon which concerns on another form. FIG. 4 is a process chart showing a method for hydrolyzing nylon according to Embodiment 2. FIG. It is process drawing which shows the hydrolysis method of nylon which concerns on another form. 4 is a photograph showing the TLC analysis results of Experiment 1. FIG. 1 is a graph showing measurement results of free amino concentration by TNBS method in Experiment 1. FIG. 2 is a photograph showing the TLC analysis results when nylon 6 was hydrolyzed as it was in Experiment 2. FIG. 2 is a graph showing the measurement results of free amino concentration by TNBS method when nylon 6 is hydrolyzed as it is in Experiment 2. FIG. 10 is a photograph showing the results of TLC analysis when the nylon dispersion was hydrolyzed in Experiment 2. FIG. 10 is a graph showing the measurement results of the free amino concentration by the TNBS method when the nylon dispersion was hydrolyzed in Experiment 2. FIG. 4 is a graph showing the measurement results of free amino concentration by the TNBS method in Experiment 3. FIG. 10 is a graph showing the measurement results of the free amino concentration by the TNBS method in the case of hydrolyzing a nylon dispersion prepared by treating with nylon 6 and formic acid at 120° C. in Experiment 4. FIG. FIG. 10 is a graph showing the measurement results of the free amino concentration by the TNBS method when a nylon dispersion prepared by treating

nylon

6,6 and formic acid at 100° C. in Experiment 4 is hydrolyzed. 10 is a graph showing the measurement results of the free amino concentration by the TNBS method when a nylon dispersion prepared by treating nylon 6 and hydrogen peroxide water at 100° C. in Experiment 4 is hydrolyzed. 10 is a graph showing measurement results of free amino concentration by TNBS method when nylon 6i-11 (50%) and nylon dispersion prepared by treatment with formic acid at 100° C. in Experiment 4 were hydrolyzed.

<Embodiment 1>
The method for hydrolyzing nylon according to Embodiment 1 is a method for hydrolyzing nylon in which nylon is monomerized using a nylon hydrolase, and as shown in FIG. It comprises a preparation step, a solvent removal step, a nylon dispersion preparation step, and a hydrolysis step.

(Nylon solution preparation process)
In the nylon solution preparing step, a nylon solution is prepared by dissolving nylon in an organic solvent capable of dissolving nylon. By allowing nylon to intervene in an organic solvent, the hydrogen bonds of nylon are cut and each molecule becomes dispersed in the organic solvent. In addition, dissolution of nylon can be performed at room temperature. The nylon used for preparing the solution may be pulverized into pellets.

Nylons used include nylon 4, nylon 6, nylon 11, nylon 12,

nylon

6,6, nylon 6,10, nylon 6,12,

nylon

4,6, nylon 6T, nylon 6I, nylon M5T nylon 6i, nylon 6i- 11 are mentioned. Nylon is preferably finely crushed before use so that it can be easily dissolved in a short time.

In addition, the organic solvent to be used should be capable of dissolving nylon, and examples thereof include trifluoroethanol and hexafluoroisopropanol.

(Nylon precipitate preparation process)
In the nylon deposit preparation step, a nylon deposit is obtained by adding a nylon solution to a solvent for depositing dissolved nylon.

Specifically, the nylon solution is dropped little by little into the precipitation solvent. Since nylon is basically insoluble in solvents other than the organic solvents mentioned above, when it is added dropwise to the precipitation solvent, the dissolved nylon aggregates and precipitates in the form of fine particles. As a result, a nylon precipitate liquid in which the nylon precipitated in the form of fine particles is dispersed is obtained.

The precipitation solvent is not limited as long as it can precipitate nylon in the form of particles, and examples include methanol, ethanol, and ethylene glycol, with ethanol and ethylene glycol being preferred.

(Solvent removal step)
In the solvent removal step, the organic solvent and the precipitation solvent are removed from the nylon precipitation solution. Any method can be used as long as the organic solvent and the precipitation solvent can be separated and removed. For example, the nylon precipitation solution is centrifuged and the supernatant is removed to remove the organic solvent and the precipitation solvent. In this case, the precipitated nylon is recovered as a precipitate.

Further, in the solvent removal step, it is preferable to add an aqueous solution to this, perform centrifugation, and remove the supernatant several times for washing. By performing this washing operation multiple times, the organic solvent and the precipitation solvent can be sufficiently separated and removed.

(Nylon dispersion liquid preparation process)
By separating the organic solvent and the precipitation solvent and adding an aqueous solution to the removed nylon, a nylon dispersion liquid in which nylon is dispersed can be obtained. As the above aqueous solution, it is preferable to use a phosphate buffer to which glycerol has been added. By using a phosphate buffer to which glycerol has been added, the pH can be kept constant in the hydrolysis step described below, and the activity of the nylon hydrolase can be maintained. The pH of the phosphate buffer to which glycerol is added is 7.2-7.4, preferably 7.3, and the content of glycerol is 5-15% by weight, preferably 9-11% by weight.

(Hydrolysis step)
In the hydrolysis step, a nylon hydrolase is added to the nylon dispersion to hydrolyze the nylon. Nylon hydrolase cleaves the polymer chain of nylon, decomposing it into oligomers, dimers, and monomers.

As a nylon hydrolase, a combination of both an endo-type nylonase that cleaves the polymer chain from the intermediate site of the repeating unit of the nylon molecule and an exo-type nylonase that cleaves the polymer chain from the end of the repeating unit. Good to use. Efficient nylon monomerization can be achieved by using both. When the endo-type nylon-degrading enzyme and the exo-type nylon-degrading enzyme are used in combination, the compounding ratio may be arbitrary, for example, 1:9 to 9:1. Hydrolysis should be carried out for 2 hours or more, preferably 24 hours or more.

In Embodiment 1, the efficiency of the enzymatic hydrolysis reaction of nylon is increased by preparing a nylon dispersion liquid in which nylon is dissolved and precipitated in fine particles, and then allowing the nylon hydrolase to act. The improved enzymatic degradation efficiency of nylon enables the recycling of nylon as a monomer.

Furthermore, as shown in FIG. 2, after the above-described nylon solution preparation step, nylon precipitation solution preparation step, and solvent removal step are performed, the below-described low-molecular-weighting step and oxidizing agent or acid removing step are performed, and the oxidizing agent Alternatively, it is preferable to perform the above-described nylon dispersion preparation step and hydrolysis step using nylon after the acid removal step.

(Low molecular weight process)
In the low-molecularization step, the nylon after solvent removal from the above-described nylon precipitation solution is added to a solution containing an oxidizing agent or an acid capable of decomposing nylon, followed by heating. When an oxidizing agent is used, the oxidizing agent becomes a nucleophilic agent, hydrolyzing nylon, and reducing the molecular weight. The oxidizing agent is not limited as long as it can promote the decomposition of nylon, and examples thereof include hydrogen peroxide water and hypohalites such as sodium hypochlorite. Also, when an acid is used, the acid acts as a catalyst to hydrolyze the nylon and reduce the molecular weight. Examples of acids include organic acids such as formic acid, acetic acid, propionic acid, butyric acid, oxalic acid and citric acid, and inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and boric acid. Also, the heating temperature is preferably 75 to 120.degree. Further, the heating time is sufficient as long as the nylon is sufficiently decomposed, and is 96 hours or longer, preferably 168 hours or longer, more preferably 336 hours or longer, depending on the type of nylon and the oxidizing agent.

(Step of removing oxidizing agent or acid)
In the oxidizing agent or acid removing step, the oxidizing agent or acid used in the molecular weight reduction step is removed. The method for removing the oxidizing agent or acid is not limited as long as the oxidizing agent or acid can be removed, and examples thereof include a removal method using a freeze-drying method.

Then, using nylon from which the oxidizing agent or acid has been removed, the above-described nylon dispersion preparation step and hydrolysis step are performed. After dissolving nylon and precipitating it in the form of fine particles, further improvement in enzymatic decomposition efficiency can be achieved by allowing a nylon hydrolase to act on nylon that has been further reduced in molecular weight.

<Embodiment 2>
The method for hydrolyzing nylon according to Embodiment 2 is a method for hydrolyzing nylon in which nylon is monomerized using a nylon hydrolase, and as shown in FIG. , a nylon dispersion preparation step, and a hydrolysis step. As for the nylon to be hydrolyzed, those mentioned in the first embodiment are used.

(Low molecular weight process)
In the molecular weight reduction step, nylon is added to a solution containing an oxidizing agent or acid capable of decomposing nylon and heated. When an oxidizing agent is used, the oxidizing agent becomes a nucleophilic agent, hydrolyzing nylon, and reducing the molecular weight. The solution containing the oxidizing agent is not limited as long as it can accelerate the decomposition of nylon, and examples thereof include hydrogen peroxide water and hypohalites such as sodium hypochlorite. Also, when an acid is used, the acid acts as a catalyst to hydrolyze the nylon and reduce the molecular weight. Examples of acids include organic acids such as formic acid, acetic acid, propionic acid, butyric acid, oxalic acid and citric acid, and inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and boric acid. Also, the heating temperature is preferably 75 to 120.degree. Further, the heating time is sufficient as long as the nylon is sufficiently decomposed, and is 96 hours or longer, preferably 168 hours or longer, more preferably 336 hours or longer, depending on the type of nylon and the oxidizing agent.

(Nylon dispersion liquid preparation process)
In the nylon dispersion preparation step, an aqueous solution is added to nylon after removal of the oxidizing agent or acid to prepare a nylon dispersion. The amount of water to be added should be such that the nylon is sufficiently dispersed. As the aqueous solution to be added, it is preferable to use the phosphate buffer added with glycerol described in Embodiment 1.

(Hydrolysis step)
In the hydrolysis step, a nylon hydrolase is added to the nylon dispersion to hydrolyze the nylon. Others are the same as those of the first embodiment described above, so the description is omitted.

In Embodiment 2, the efficiency of the enzymatic hydrolysis reaction of nylon is increased by decomposing nylon with an oxidizing agent or acid to reduce the molecular weight and then allowing nylon hydrolase to act. The improved enzymatic degradation efficiency of nylon enables the recycling of nylon as a monomer.

Further, as shown in FIG. 4, after performing the molecular weight reduction step and the oxidizing agent or acid removal step, the nylon solution preparation step, the nylon precipitate preparation step, and the solvent removal step are performed, and the nylon after the solvent removal step may be used to perform the nylon dispersion preparation step and the hydrolysis step. The description of the nylon solution preparation process, the nylon precipitation liquid preparation process, and the solvent removal process is the same as that of the first embodiment, so the description is omitted. Further improvement of enzymatic decomposition efficiency can be achieved by further dissolving the low-molecular-weight nylon and allowing a nylon hydrolase to act on the nylon precipitated in the form of fine particles.

<Experiment 1> Hydrolysis of nylon dispersion prepared by dissolving and precipitating nylon (preparation of nylon dispersion)
(a) Nylon 6 pellets were added to trifluoroethanol and dissolved to prepare a nylon solution (25 mg/mL).
(b) The nylon solution (80 μL) was added dropwise to various nylon deposits (720 μL) to prepare nylon deposits.
(c) After centrifuging the nylon precipitate (15,000 xg, 10 minutes), the supernatant was removed.
(d) 20 mM phosphate buffer (pH 7.3, 500 μL) containing 10% glycerol was added to suspend, centrifuged (15,000×g, 10 minutes), and the supernatant was removed.
(e) The operation of (d) above was repeated three times.
(f) A nylon dispersion was prepared by resuspending in 20 mM phosphate buffer (pH 7.3, 200 μL) containing 10% glycerol.

Acetone, ethyl acetate, ethanol, methanol, water, and ethylene glycol were used as the nylon deposition liquid.

(Hydrolysis of nylon)
An enzyme solution (200 µL) containing a nylon hydrolase was added to the prepared nylon dispersion (200 µL), and the mixture was allowed to stand at 37°C.
Then, samples were taken over time, TLC (Thin-Layer Chromatography) analysis, and free amino group quantification by TNBS (2,4,6-Trinitrobenzenesulfonic Acid) method were performed to evaluate the progress of the reaction. In addition, at the time of sampling, the reaction was stopped by heating at 99° C. for 10 minutes.

The enzyme solution was prepared so that the final concentrations of endo-type nylon hydrolase (hereinafter referred to as GYAQ) and hexo-type nylon hydrolase (hereinafter referred to as DNY) were each 1.0 mg/mL. .

The enzymes GYAQ and DNY used are described below.
- GYAQ: an enzyme with a His-tag added to the N-terminus of EC number 3.5.1.117 - DNY: an enzyme with a His-tag added to the N-terminus of EC number 3.5.1.46

The results of the TLC analysis are shown in Figure 5. Moreover, FIG. 6 shows the measurement results of free amino group concentration by the TNBS method. It can be seen that nylon 6 is decomposed and monomerized over time in all the cases where a nylon deposition solution other than water is used. Among them, the decomposition efficiency was high when ethylene glycol and ethanol were used. When the free amino group concentration was measured 2 hours after the hydrolysis was started, it was almost the same as the amino group concentration after 24 hours.

<Experiment 2> Comparison with hydrolysis of nylon pellets as they are Ethylene glycol was used as the nylon precipitate, and the operations (a) to (f) of Experiment 1 were performed to obtain a nylon 6 dispersion.
An enzyme solution (200 µL) containing a nylon hydrolase was added to the resulting nylon 6 dispersion (200 µL), and the mixture was allowed to stand at 37°C. Then, in the same manner as in Experiment 1, TLC analysis and quantification of free amino groups by the TNBS method were performed. As the enzyme solution, 3 types of GYAQ alone, DNY alone, and a combination of GYAQ and DNY (weight ratio 1:1) were prepared and used (each with a final concentration of 1.0 mg/mL).

Also, for comparison, nylon 6 pellets (5 mg) were directly added to the above three types of enzyme solutions (400 μL). Then, TLC analysis and quantification of free amino groups by the TNBS method were performed in the same manner as described above.

　Figures 7 and 8 show the results of TLC analysis when the nylon 6 dispersion was hydrolyzed and the measurement results of the concentration of free amino groups by the TNBS method. 9 and 10 show the results of TLC analysis when nylon 6 is hydrolyzed as it is and the measurement results of the free amino group concentration by the TNBS method, respectively.

When the nylon 6 dispersion was hydrolyzed, detection by TLC analysis was possible, whereas when nylon 6 was hydrolyzed as it was, it did not reach a level at which detection by TLC analysis was possible.

The estimated free amino group concentration when the used nylon 6 is completely decomposed is 44.2 mM in the case of the nylon 6 dispersion, and 110.5 mM in the case of hydrolyzing the nylon 6 as it is, according to the TNBS method. Table 1 summarizes the decomposition rate of nylon 6 after the reaction for 72 hours calculated based on the analysis. Compared to the hydrolysis of nylon 6 as it is, hydrolysis efficiency of nylon 6 dispersion was about 4 to 7 times higher.

<Experiment 3> Hydrolysis of nylon dispersion prepared by dissolving and precipitating

various nylons Nylon

6, 6, nylon 6, nylon 12, and nylon 4 were used as the nylon, and ethylene glycol was used as the nylon precipitation solution. A nylon dispersion was obtained by carrying out the operations (a) to (f) of Experiment 1.
An enzyme solution (200 µL) containing a nylon hydrolase was added to each nylon dispersion (200 µL) and allowed to stand at 37°C. Then, the free amino groups were quantified by the TNBS method in the same manner as described above. The enzyme solution was prepared so that the final concentration of GYAQ was 1.0 mg/mL.

The results are shown in Figure 11. Table 2 summarizes the decomposition rate of each nylon after 72 hours of reaction based on analysis by the TNBS method. All nylons were hydrolyzed, and

nylon

6,6 and nylon 6 had higher decomposition efficiency.

<Experiment 4> Hydrolysis of nylon dispersion prepared by reducing the molecular weight (preparation of nylon dispersion)
Pellets (1 g) of nylon 6,

nylon

6,6 and nylon 6i-11 (50%) were each mixed with formic acid (6.8 mL). Incidentally, nylon 6i-11 is a nylon obtained from 1-aminohexyl-2-pyrrolidone-4-carboxylic acid (hereinafter referred to as 6i monomer unit) and 11 aminoundecanoic acid (hereinafter referred to as 11 monomer unit), nylon 6i -11 (50%) was obtained at a compounding ratio of 6i monomer units and 11 monomer units of 50:50. This nylon 6i-11 (50%) was provided by Mr. Yoshiro Kaneko of National University Corporation Kagoshima University.
The mixture was heated at the set temperature for 96 hours while stirring with a stirrer.
After heating, distilled water (25 mL) was added and freeze-dried to remove formic acid.
After removing formic acid, 20 mM phosphate buffer (pH 7.3) containing 10% glycerol was added and resuspended to prepare a nylon dispersion. The final concentration of each nylon was adjusted to 10 mg/mL.
The set temperatures were set to 75° C., 100° C., and 120° C., and the test was performed at each set temperature.

In addition, a nylon dispersion was prepared in the same manner as above, except that 30% hydrogen peroxide water (6.8 mL) was used instead of formic acid.

(Hydrolysis of nylon)
An enzyme solution (200 μL) was added to each nylon dispersion (200 μL) and allowed to stand at 37°C. As in Experiment 1, free amino groups were quantified by the TNBS method. As the enzyme solution, three types (final concentration: 1.0 mg/mL) of GYAQ alone, DNY alone, and GYAQ and DNY in combination (weight ratio 1:1) were prepared and used.

Table 3 shows the decomposition rate of nylon when a nylon dispersion prepared using formic acid is hydrolyzed for 72 hours, and the decomposition rate of nylon when a nylon dispersion prepared using hydrogen peroxide water is hydrolyzed for 72 hours. are summarized in Table 4. In addition, a nylon dispersion prepared by treating nylon 6 with formic acid at 120 ° C.,

nylon

6,6, a nylon dispersion prepared by treating with formic acid at 100 ° C., nylon 6, and hydrogen peroxide solution and nylon 6i-11 (50%), prepared by treatment with formic acid at 100°C. The measurement results of amino group concentrations are shown in FIGS. 12, 13, 14 and 15, respectively. Both nylons are hydrolyzed. Depending on the type of nylon, when formic acid was used, the enzymatic decomposition efficiency was high when treated at 100°C, and when hydrogen peroxide was used, the enzymatic decomposition efficiency was high when treated at 75°C. When the free amino group concentration was measured 2 hours after the hydrolysis was started, it was almost the same as the amino group concentration after 24 hours.

<Experiment 5> Verification of heating time for molecular weight reduction (preparation of nylon dispersion)
A nylon dispersion was prepared in the same manner as in Experiment 4, except that nylon 6 (1 g) and formic acid (6.8 mL) were used, and the heating time at 100° C. was 120 hours and 168 hours.

In addition, a nylon dispersion was prepared in the same manner as in Experiment 4, except that nylon 6,6 (1 g) and formic acid (6.8 mL) were used, and the heating time was set at 100°C for 168 hours.

In addition, nylon 6i-11 (50%) (1 g) and formic acid (6.8 mL) were used, and a nylon dispersion was prepared in the same manner as in Experiment 4 except that the heating time was 168 hours at 100°C.

A nylon dispersion was also prepared in the same manner as in Experiment 4, except that nylon 6 (50 mg) and 30% hydrogen peroxide solution (5 mL) were used, and the heating time was set at 75°C for 192 hours.

In addition, nylon 6i-11 (50%) (1 g) and formic acid (6.8 mL) were used, and a nylon dispersion was prepared in the same manner as in Experiment 4 except that the heating time was 336 hours at 100°C.

In addition, nylon 6i-11 (75%) (1 g) and formic acid (6.8 mL) were used, and a nylon dispersion was prepared in the same manner as in Experiment 4 except that the heating time was 168 hours at 100°C. Incidentally, nylon 6i-11 (75%) was obtained at a compounding ratio of 6i monomer units and 11 monomer units of 25:75. This nylon 6i-11 (75%) was provided by Mr. Yoshiro Kaneko of Kagoshima University.

(Hydrolysis of nylon)
An enzyme solution (200 μL) was added to each nylon dispersion (200 μL) and allowed to stand at 37°C. Then, in the same manner as in Experiment 1, free amino groups were quantified by the TNBS method. As the enzyme solution, three types (final concentration: 1.0 mg/mL) of GYAQ alone, DNY alone, and GYAQ and DNY in combination (weight ratio 1:1) were prepared and used.

The decomposition rate of nylon is summarized in Tables 5 and 6. Enzymatic decomposition efficiency tended to increase with longer heating time.

<Experiment 6> Verification of hydrolysis of a nylon dispersion prepared by further reducing the molecular weight of nylon 6 after dissolution and precipitation Using nylon 6 (1 g) and ethylene glycol as the nylon precipitation solution, Experiment 1 (a)-( After the operation e), formic acid (6.8 mL) was added.
The mixture was heated at 100° C. for 96 hours while stirring with a stirrer.
After heating, distilled water (25 mL) was added and freeze-dried to remove formic acid.
After removing formic acid, 20 mM phosphate buffer (pH 7.3) containing 10% glycerol was added and resuspended to prepare a nylon dispersion.

The enzyme solution (200 μL) was added to the nylon dispersion (200 μL) and allowed to stand at 37°C. Then, in the same manner as in Experiment 1, free amino groups were quantified by the TNBS method to determine the decomposition rate of nylon 6. As the enzyme solution, three types (final concentration: 1.0 mg/mL) of GYAQ alone, DNY alone, and GYAQ and DNY in combination (weight ratio 1:1) were prepared and used.

In addition, the same procedure as above was performed except that ethanol was used instead of ethylene glycol.

In addition, the procedure was carried out in the same manner as above, except that ethanol was used instead of ethylene glycol and the heating time was changed to 168 hours.

In addition, the above procedure was repeated except that 30% hydrogen peroxide solution (5 mL) was used instead of formic acid, the heating temperature was 75°C, and the heating time was 192 hours.

Table 7 summarizes the decomposition rate of nylon 6 72 hours after adding the enzyme solution. It was demonstrated that the degradation rate of nylon can be increased by allowing a nylon hydrolase to act on a nylon dispersion prepared by further reducing the molecular weight of nylon precipitated in the form of fine particles. In particular, a high decomposition rate (88 to 97%) was exhibited when ethanol was used as the nylon depositing solution and heating was performed using formic acid for 168 hours.

<Experiment 7> Verification of hydrolysis of a nylon dispersion prepared by further reducing the molecular weight of

nylon

6,6 after dissolution and precipitation Using nylon 6,6 (1 g) and ethanol as the nylon precipitation solution, )-(e), formic acid (6.8 mL) was added.
The mixture was heated at 100° C. for 168 hours while stirring with a stirrer.
After heating, distilled water (25 mL) was added and freeze-dried to remove formic acid.
After removing formic acid, 20 mM phosphate buffer (pH 7.3) containing 10% glycerol was added and resuspended to prepare a nylon dispersion.

The enzyme solution (200 μL) was added to the nylon dispersion (200 μL) and allowed to stand at 37°C. Then, in the same manner as in Experiment 1, free amino groups were quantified by the TNBS method to determine the decomposition rate of

nylon

6,6. As the enzyme solution, three types (final concentration: 1.0 mg/mL) of GYAQ alone, DNY alone, and GYAQ and DNY in combination (weight ratio 1:1) were prepared and used.

Table 8 shows the decomposition rate of

nylon

6,6 72 hours after adding the enzyme solution. The combination of GYAQ and DNY achieved 100% decomposition rate.

Various embodiments and modifications of the present invention are possible without departing from the broad spirit and scope of the present invention. Moreover, the embodiment described above is for explaining the present invention, and does not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims rather than the embodiments. Various modifications made within the scope of the claims and within the meaning of equivalent inventions are considered to be within the scope of the present invention.

This application is based on Japanese Patent Application No. 2022-32566 filed on March 3, 2022 and Japanese Patent Application No. 2022-150274 filed on September 21, 2022. The entire specification, claims, and drawings of Japanese Patent Application No. 2022-32566 and Japanese Patent Application No. 2022-150274 are incorporated herein by reference.

Can be used to recycle nylon into monomer molecules.

Claims

A method for hydrolyzing nylon by monomerizing nylon using a nylon hydrolase, comprising:
a step of dissolving the nylon in an organic solvent capable of dissolving the nylon to prepare a nylon solution;
a step of adding the nylon solution to a precipitation solvent for precipitating the nylon into particles to prepare a nylon precipitation solution;
removing the organic solvent and the precipitation solvent from the nylon precipitation solution;
adding an aqueous solution to the nylon obtained by removing the organic solvent and the precipitation solvent to prepare a nylon dispersion;
adding the nylon hydrolase to the nylon dispersion to hydrolyze the nylon;
A method for hydrolyzing nylon, characterized by:
a step of adding the nylon obtained by removing the organic solvent and the precipitation solvent to a solution containing an oxidizing agent or an acid capable of decomposing and heating to reduce the molecular weight of the nylon;
removing the oxidizing agent or the acid from the solution after heating;
The nylon dispersion is prepared by adding the aqueous solution to the nylon obtained by removing the oxidizing agent or the acid,
The method for hydrolyzing nylon according to claim 1, characterized in that:
As the nylon, nylon 4, nylon 6, nylon 11, nylon 12, nylon 6,6, nylon 6,10, nylon 6,12, nylon 4,6, nylon 6T, nylon 6I, nylon M5T, nylon 6i, or nylon using 6i-11,
The method for hydrolyzing nylon according to claim 1 or 2, characterized in that:
using trifluoroethanol or hexafluoroisopropanol as the organic solvent;
The method for hydrolyzing nylon according to claim 1 or 2, characterized in that:
using ethanol or ethylene glycol as the precipitation solvent;
The method for hydrolyzing nylon according to claim 1 or 2, characterized in that:
Using a phosphate buffer containing glycerol as the aqueous solution,
The method for hydrolyzing nylon according to claim 1 or 2, characterized in that:
A method for hydrolyzing nylon by monomerizing nylon using a nylon hydrolase, comprising:
a step of adding the nylon to a solution containing an oxidizing agent or an acid capable of decomposing the nylon and heating to reduce the molecular weight of the nylon;
removing the oxidizing agent or the acid from the heated solution;
adding an aqueous solution to the nylon obtained by removing the oxidizing agent or the acid to prepare a nylon dispersion;
adding a nylon hydrolase to the nylon dispersion to hydrolyze the nylon;
A method for hydrolyzing nylon, characterized by:
a step of dissolving the nylon in an organic solvent capable of dissolving the nylon to prepare a nylon solution;
a step of adding the nylon solution to a precipitation solvent for precipitating the nylon into particles to prepare a nylon precipitation solution;
and removing the organic solvent and the precipitation solvent from the nylon precipitation solution,
The nylon obtained by removing the organic solvent and the precipitation solvent is added to a solution containing the oxidizing agent or the acid and heated to reduce the molecular weight of the nylon.
The method for hydrolyzing nylon according to claim 7, characterized in that:
using a hydrogen peroxide solution as the oxidizing agent;
The method for hydrolyzing nylon according to claim 7 or 8, characterized in that:
using formic acid as the acid;
The method for hydrolyzing nylon according to claim 7 or 8, characterized in that:
heating to 75 to 120° C. to reduce the molecular weight of the nylon;
The method for hydrolyzing nylon according to claim 7 or 8, characterized in that:
Using a phosphate buffer containing glycerol as the aqueous solution,
The method for hydrolyzing nylon according to claim 7 or 8, characterized in that:
lyophilizing to remove the oxidizing agent or the acid;
The method for hydrolyzing nylon according to claim 7 or 8, characterized in that: