CN116814712A - Method for producing amine monomer by degrading polyurethane through chemical biological method - Google Patents

Abstract

The invention discloses a method for combining chemical and biological methods to degrade polyurethane to produce amine monomers, which includes the following steps: (1) Under the action of a catalyst, polyurethane and an alcoholysis agent perform an alcoholysis reaction to obtain an alcoholysis product; (2) ) in a buffer solution, the obtained alcoholysis product is enzymatically hydrolyzed by an esterase to obtain amine monomers; the esterase includes esterase Aes72. The present invention degrades polyurethane through a combination of chemical and biological methods, thereby reducing energy consumption and realizing the preparation of TDA/MDA monomers. The monomers generated after enzymatic hydrolysis can be re-synthesized into isocyanate, realizing recycling of raw materials.

Description

A method of combining chemical and biological methods to degrade polyurethane to produce amine monomers

Technical field

The invention belongs to the field of biochemical engineering and relates to a method for degrading aromatic polyurethane to produce amine monomers using a combination of chemical and biological methods.

Background technique

Polyurethane (PU) plastic is one of the five largest plastics produced and consumed in the world, and its product applications involve many fields such as textiles, construction, building materials, automobiles, and national defense. According to statistics, global plastic production reached 368 million tons in 2019, of which PU plastic production accounted for 6%-7% of the total production, becoming the second largest polyester plastic in the world. my country's production alone in 2020 reached 14.7 million tons. Consumption is about 11.75 million tons. At present, the methods for processing PU waste plastics mainly include landfill, incineration, mechanical recycling, and physical and chemical reprocessing. However, these traditional methods have disadvantages that are difficult to solve. Compared with other plastics, PU waste plastic has a smaller density, and centralized landfilling will occupy a large amount of land, resulting in a waste of land resources. Although incineration is simple and does not occupy land, it will increase carbon emissions, and the harmful gases produced by incineration will cause air pollution. Mechanical recycling has become an important means of utilizing waste plastic resources. However, the recycled PU fragments can only be used as fillers for toys, pillows, etc. or as a base in subsequent processes (secondary mechanical recycling and raw material recycling), and they cannot be used twice. The scope is limited. In comparison, the use of biological means to achieve biodegradation of PU waste is regarded as an environmentally friendly and mild reaction condition waste plastic treatment method, and can achieve high-value reuse of waste plastic resources.

However, due to the currently discovered degrading bacteria or enzymes that have problems such as low efficiency, poor environmental adaptability, and weak compatibility with industrial environments in the actual degradation process of PU plastics, PU biodegradation and high-value reuse are still far away from industrial needs. A larger gap. Multidisciplinary interdisciplinary implementation of rational disposal and resource utilization of waste plastics. Due to the special structure and properties of plastic polymers, it is difficult to achieve efficient utilization of waste plastics using biodegradation as the only means. Through the integration of chemistry, materials science, biochemical engineering, microbiology and other disciplines, establishing a technical system from plastic pre-treatment to application pilot to engineering scale-up is an effective method to realize the reuse of waste plastic resources and solve the environmental pollution and resource waste of waste plastics. .

Among the current PU raw material recycling, chemical recycling is the most widely studied. Chemical recycling can use hydrolysis, acidolysis, ammonolysis, alcoholysis and other processes to achieve a certain degree of recycling of PU plastics. Historically, glycolysis has received the most attention on an industrial scale, although other commercial technologies have recently emerged targeting primarily the polyol fraction. Current glycolysis technologies are dedicated to the separation of polyols and diphenylamines for the optimization of PU plastics. yield, especially for polyols. Compared with the recovery of polyols, the recovery of diphenylamine requires reaction under conditions such as high temperature, high pressure, and precious metal catalysts, and it is difficult to fully convert diphenylamine monomer.

Contents of the invention

Purpose of the invention: The technical problem to be solved by this invention is to provide a method for degrading polyurethane to produce phenylenediamine monomers by combining chemical and biological methods in view of the shortcomings of the existing technology.

In order to solve the above technical problems, the present invention discloses a method for combining chemical and biological methods to degrade polyurethane to produce amine monomers, using alcoholysis to prepare low-weight amino acid methyl esters, and using biological enzymatic methods to treat low-weight amino acid methyl esters under normal temperature and normal pressure conditions. Amino acid methyl ester is degraded to obtain diphenylamine monomers, thereby achieving green preparation and recycling of diphenylamine monomers.

Specifically, the method includes the following steps:

(1) Alcoholysis reaction of polyurethane with an alcoholysis agent under the action of a catalyst to obtain alcoholysis products, including polyether or polyester polyols, amino acid methyl esters, etc.;

(2) In a buffer solution, the obtained alcoholysis product is subjected to an enzymatic hydrolysis reaction with an esterase to obtain diphenylamine monomers; the esterase includes esterase Aes72, that is, the esterase is enzyme ester Aes72, or esterase Aes72 Combination with other esterases with carbamate bond activity.

In step (1), the reaction specifically involves pulverizing the polyurethane and drying it to obtain a block drying material; adding an alcoholysis agent to the reaction system, stirring to raise the temperature, exhausting the air, adding a catalyst, and adding the polyurethane block while stirring. The dried material is subjected to alcoholysis reaction and cooled to obtain an alcoholysis product.

Wherein, the method for exhausting the air is to pass in an inert gas; in some embodiments, nitrogen gas is introduced.

In step (1), inert gas protection is required during the reaction; in some embodiments, nitrogen protection is introduced.

In step (1), the polyurethane includes polyurethane plastic.

In step (1), the polyurethane includes polyester PU, polyether PU, and polyester-polyether mixed PU; the polyester PU includes aromatic polyester PU.

In step (1), the polyurethane includes TDI-based PU and MDI-based PU.

In some embodiments, the polyurethane is TDI-based polyester PU, TDI-based polyether PU, MDI-based polyester PU, or MDI-based polyether PU.

In step (1), the catalyst includes amine compounds, tin compounds, alkali metal salts and alkaline hydroxides.

Among them, the amine compounds include but are not limited to diethylamine and ethanolamine.

Wherein, the tin compounds include but are not limited to dibutyltin dilaurate, butyltin oxide and hydroxybutyltin oxide.

Wherein, the alkali metal salts include but are not limited to potassium acetate, zinc acetate and barium acetate.

Wherein, the alkaline hydroxide includes but is not limited to potassium hydroxide and sodium hydroxide.

Preferably, the catalyst is a tin compound, preferably dibutyltin dilaurate.

In step (1), the usage amount of the catalyst is 0.1-5wt% of the polyurethane, preferably 0.5-3wt%, preferably 1wt%.

In step (1), the alcoholysis agent includes methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol or a mixture thereof, preferably ethanol, ethylene glycol, diethylene glycol, Diethylene glycol is further preferred.

In step (1), the mass ratio of the polyurethane to the alcoholysis agent is 1:1-10, preferably 1:1-6.

In step (1), the reaction temperature is 150-250°C, preferably 180-210°C.

In step (1), the reaction is carried out under stirring.

Wherein, the stirring speed is 50-1000rpm, preferably 200-500rpm.

In step (2), the buffer includes phosphate buffer, Tris·HCl buffer, preferably a phosphate buffer with a pH of 6.5-7.5, Tris·HCl buffer, further preferably phosphate buffer (PB). buffer), 50mM phosphate buffer, pH=7.0.

In step (2), the addition amount of the alcoholysis product is 0.1%-20% v/v, preferably 0.3%-10% v/v, and further preferably 0.5%-1% v/v.

In step (2), the added amount of the esterase is 0.1-10 mg/mL, preferably 0.5-2 mg/mL.

In step (2), the specific enzyme activity of the esterase Aes72 is 67-75U/mg.

In step (2), the temperature of the enzymatic hydrolysis reaction is 25-80°C, preferably 37-60°C.

In step (2), the enzymatic hydrolysis reaction time is 5-72h, preferably 10-36h.

In step (2), the enzymatic hydrolysis reaction is carried out in a shaker, and the rotation speed of the shaker is 50-1000 rpm, preferably 200 rpm.

In step (2), after the enzymatic hydrolysis reaction is completed, the reaction solution is filtered with a filter membrane to obtain diphenylamine monomers; preferably, the filter membrane is a 0.22 μm filter membrane.

In step (2), the diphenylamine monomers include 2,4-diaminotoluene 2,4-TDA, 2,6-diaminotoluene 2,6-TDA, and 4,4-diaminodiphenylmethane. 4,4-MDA and 2,4-diaminodiphenylmethane 2,4-MDA.

The present invention degrades polyurethane through a combination of chemical and biological methods, thereby reducing energy consumption and realizing the preparation of TDA/MDA monomers. The monomers generated after enzymatic hydrolysis can be re-synthesized into isocyanate, realizing recycling of raw materials.

Beneficial effects: Compared with the existing technology, the present invention has the following advantages:

The present invention combines chemical alcoholysis and enzymatic hydrolysis to obtain alcoholysis products containing polyols and carbamates through alcoholysis reactions. The obtained polyols can be recycled through subsequent purification. At the same time, the present invention uses enzyme Aes72 to Completely depolymerize the oligomers with urethane bonds produced by alcoholysis to produce diamine monomers (MDA/TDA), reducing side reactions, being green and environmentally friendly, realizing harmless recycling of plastics, and effectively solving the existing technology problems The preparation of diamine monomers from medium carbamates requires a high temperature and high pressure environment, which results in high energy consumption.

Description of the drawings

The above and/or other advantages of the present invention will become more clear when the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Figure 1 shows the LC-MS analysis results of the urethane product components after alcoholysis of TDI-based polyether PU.

Figure 2 shows the HPLC analysis of the product changes before and after enzymatic hydrolysis of TDI-based polyether PU alcoholysis product.

Figure 3 shows the production of enzymatic hydrolysis products of four aromatic polyurethane plastics (TDI-based polyether PU, TDI-based polyester PU, MDI-based polyether PU, MDI-based polyester PU); The concentration is the total concentration of 2,4-TDA and 2,6-TDA in the undiluted reaction solution, and the concentration of MDA is the concentration of 4,4-MDA in the undiluted reaction solution.

Figure 4 shows the FITR characterization of PU plastics in different application scenarios.

Figure 5 shows the HPLC determination of TDA/MDA generated by PU plastics in different application scenarios through a combination of chemical and biological methods.

Figure 6 shows the TDA and MDA concentration standard curves.

Detailed ways

The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described can be obtained from commercial sources unless otherwise specified.

The TDI-based polyether polyurethane and TDI-based polyester polyurethane described in the following examples were purchased from Nantong Dagong Co., Ltd.; the MDI-based polyether polyurethane and MDI-based polyester polyurethane were purchased from Soprema, France. MA) company.

The esterase used in the enzymatic hydrolysis of the alcoholysis product of the present invention is Aes72; among them, the p-NPB used by Aes72 is used to measure the enzyme activity. The enzyme activity is defined as: at 37°C, the hydrolysis of p-NPB per minute to produce 1 μmol of p-nitrophenol is defined as One unit of protease activity.

Among them, the protease activity formula is: protease activity = A/(B*C), where A is the amount of p-nitrophenol produced (μmol)), B is the reaction time (min), and C is the amount of enzyme added to the reaction. (mL).

Among them, specific enzyme activity = protease activity (U/mL)/protein concentration (mg/mL).

The specific enzyme activity of Aes72 was 67U/mg.

Among them, the preparation method of Aes72 is as follows: inoculate the Aes72 protein expression strain into LB medium, add 50 μg/mL kanamycin, and culture it at 37°C for 12-16 hours. Add the inoculum amount to liquid LB medium and culture at 37°C. When the concentration of the cultured bacterial solution reaches an OD ₆₀₀ of 0.6-0.8, take it out, add 0.1mM IPTG and culture on a shaking table at 18°C for 24 hours; centrifuge at 8000rpm for 10 minutes to obtain the cells and then use ultrasound After disrupting the cells with a disrupter, centrifuge at 8000 rpm for 10 minutes to take the supernatant to obtain Aes72 protein.

The phosphate buffer (PB buffer) used in the embodiment of the present invention is 50mM phosphate buffer, pH=7.0.

In the HPLC analysis of alcoholysis products and enzymatic hydrolysis products in the embodiments of the present invention, HPLC uses 1260InfinityⅡ high performance liquid chromatography (Agilent Technologies). The specific detection method is:

Liquid chromatography column: Agilent 5HC-C18(2)150×4.6mm;

Detection wavelength: 240nm;

Column temperature: 30℃;

Flow rate: 1mL/min;

Injection volume: 10μL;

The mobile phases were water and acetonitrile respectively;

Gradient elution: 0-5min, the volume fraction of water is 90%, the volume fraction of acetonitrile is 10%; 5-14min, the volume fraction of water is changed from 90% to 35%, and the volume fraction of acetonitrile is changed from 10% to 65%.

Preparation of MDA standard music (including 4,4-MDA): Weigh 19.8mg MDA and dissolve it in 10mL ethanol to prepare a 10mM mother solution. Dilute them into standards of 2.5mM, 1mM, 0.5mM, 0.25mM, 0.125mM, and 0.06125mM respectively. The peak areas corresponding to different concentrations were analyzed by HPLC, and an MDA concentration calibration curve was prepared. The calibration curve is shown in Figure 6.

Preparation of TDA standard song (including 2,4-TDA and 2,6-TDA): Weigh 12.2mg TDA and dissolve it in 10mL ethanol to prepare a 10mM stock solution. Dilute them into standards of 10mM, 5mM, 2mM, 1mM, 0.5mM, 0.25mM, 0.125mM, and 0.06125mM respectively. The peak areas corresponding to different concentrations were analyzed by HPLC, and a TDA concentration calibration curve was prepared. The calibration curve is shown in Figure 6.

MDA content determination: Substitute the peak areas measured by HPLC in the four groups of experiments into the standard curve to calculate the corresponding MDA concentration.

TDA content determination: Substitute the peak areas measured by HPLC in the four groups of experiments into the standard curve to calculate the corresponding TDA concentration.

In the following examples, air was removed by passing inert gas before adding the catalyst.

The alcoholysis reaction described in the following examples was carried out under the protection of inert gas.

The blank control group described in the following examples means that compared with the experimental group, no enzyme is added.

Example 1: Degrading TDI-based polyether PU to produce TDA monomer

Weigh 40g of diethylene glycol, add it to a four-necked flask, preheat to 200°C, add 1% w/w dibutyltin dilaurate, and slowly add 40g of crushed TDI-based polyether PU under stirring at 300rpm until it is completely After dissolution, incubate at 200°C for 2 hours, cool to room temperature, the reaction is completed, and the alcoholysis product is obtained. The LC-MS results of the carbamate component distribution are shown in Figure 1. It can be seen that low molecular carbamate molecules are produced after chemical alcoholysis. compound.

The above-mentioned alcoholysis products were enzymatically hydrolyzed in a phosphate buffer system, and an experimental group and a blank control group were set up in the experiment. The reaction system is 6 mL, pH 7.0, the amount of enzyme Aes72 added is 0.1 mg/mL, and the amount of alcoholysis product added is 600 μL. Then place the above two sets of reaction solutions in a shaker at 37°C or 50°C at 200 rpm for 48 hours. After that, the reaction solution is appropriately diluted and filtered through a 0.22 μm filter. The processed samples are analyzed by HPLC. The results are shown in Figure 2 (37°C). and shown in Figure 3.

As can be seen from Figure 2, after 48 hours of enzymatic hydrolysis reaction, all carbamates were enzymatically hydrolyzed to produce TDA monomers, indicating that Aes72 can efficiently enzymatically hydrolyze the alcoholysis products of polyurethane plastics to produce TDA monomers, which are all converted into TDA within 48 hours. As can be seen from Figure 3, the alcoholysis product achieved full conversion of carbamate in 20 hours.

Example 2: Degrading TDI-based polyester PU to produce TDA monomer

Weigh 120g of diethylene glycol, add it to a four-necked flask, preheat to 200°C, add 1% w/w dibutyltin dilaurate, and slowly add 40g of crushed TDI-based polyester PU under stirring at 250rpm until it is completely After dissolving, incubate at 200°C for 2 hours and cool to room temperature. The reaction ends and the alcoholysis product is obtained.

The above-mentioned alcoholysis products were enzymatically hydrolyzed in a phosphate buffer system, and an experimental group and a blank control group were set up in the experiment. The reaction system is 6 mL, pH 7.0, the amount of enzyme Aes72 added is 0.1 mg/mL, and the amount of alcoholysis product added is 300 μL. Then the above two sets of reaction solutions were placed in a 37°C or 50°C shaker at 200 rpm for 48 hours. The reaction solution was appropriately diluted and filtered through a 0.22 μm filter. HPLC analysis was performed on the processed samples. The results are shown in Figure 3.

Example 3: Degrading MDI-based polyether PU to produce MDA monomer

Weigh 240g of diethylene glycol, add it to a four-necked flask, preheat to 200°C, add 1% w/w dibutyltin dilaurate, and slowly add 40g of crushed TDI-based polyester PU under stirring at 300rpm until it is completely After dissolving, incubate at 200°C for 2 hours and cool to room temperature. The reaction ends and the alcoholysis product is obtained.

The above-mentioned alcoholysis products were enzymatically hydrolyzed in a phosphate buffer system, and an experimental group and a blank control group were set up in the experiment. The reaction system is 6 mL, pH 7.0, the amount of enzyme Aes72 added is 1 mg/mL, and the amount of alcoholysis product added is 300 μL. Then, the above two sets of reaction solutions were placed in a shaker at 37°C or 50°C at 200 rpm for 72 hours. The reaction solution was appropriately diluted and filtered through a 0.22 μm filter. HPLC analysis was performed on the processed samples. The results are shown in Figure 3.

Example 4: Degradation of MDI-based polyester PU to produce MDA monomer

Weigh 240g of diethylene glycol, add it to a four-necked flask, preheat to 210°C, add 1% w/w of dibutyltin dilaurate, and slowly add 40g of crushed MDI-based polyester PU under stirring at 270rpm until it is completely After dissolving, incubate at 200°C for 2 hours and cool to room temperature. The reaction ends and the alcoholysis product is obtained.

The above-mentioned alcoholysis products were enzymatically hydrolyzed in a phosphate buffer system, and an experimental group and a blank control group were set up in the experiment. The reaction system is 6 mL, pH 7.0, the amount of enzyme Aes72 added is 1 mg/mL, and the amount of alcoholysis product added is 300 μL. Then, the above two sets of reaction solutions were placed in a shaker at 37°C or 50°C at 200 rpm for 72 hours. The reaction solution was appropriately diluted and filtered through a 0.22 μm filter. HPLC analysis was performed on the processed samples. The results are shown in Figure 3.

In the above Examples 1-4, the urethane in the alcoholysis product can be effectively converted into diamine monomers, and the urethane conversion of TDI-based PU is more efficient.

Example 5: Degrading PU to produce TDA/MDA in different application scenarios

FITR analysis was performed on PUs in different application scenarios, and the results are shown in Figure 4. 3330cm ^-1 NH stretching vibration peak, 1538cm ^-1 amide II band NH deformation vibration absorption peak, 1730cm ^-1 C=O stretching vibration peak, aromatic CO absorption band at 1220cm ^-1 , absorption of COC group near 1073cm ^-1 Spectrum band, from the infrared characteristic peaks of various PUs in Figure 4, we can determine the types of various PUs. Protective covers, dishwashing wipes, car mats, mattresses are polyether PU, insulation tubes, insulation boards, and adhesives are polyether PU. Ester type PU, the pillow core is polyester polyether mixed PU.

Weigh 240g of diethylene glycol, add it to a four-necked flask, preheat to 200°C, add 1% w/w dibutyltin dilaurate, and slowly add 40g of crushed commercial PU with stirring at 300 rpm until completely dissolved. , incubate at 200°C for 2 hours, cool to room temperature, the reaction ends, and the alcoholysis product is obtained.

The above-mentioned alcoholysis products were enzymatically hydrolyzed in a phosphate buffer system, and an experimental group and a blank control group were set up in the experiment. The reaction system is 6 mL, pH 7.0, the amount of enzyme Aes72 added is 1 mg/mL, and the amount of alcoholysis product added is 300 μL.

Then, the above two sets of reaction solutions were placed in a shaker at 37°C and 200 rpm to react for 48 hours. The reaction solutions were appropriately diluted and filtered through a 0.22 μm filter. The processed samples were analyzed by HPLC.

The results are shown in Figure 5. All the carbamates in the TDI-based PU alcoholysis product are converted to TDA, and most of the carbamates in the MDI-based PU alcoholysis product are converted into MDA. As can be seen from Figure 5, Aes72 enzyme can effectively act on urethane bonds or ester bonds and release TDA/MDA monomers; it proves that chemical alcoholysis and biological Aes72 enzymatic hydrolysis can effectively prepare TDA/MDA monomers , Promote closed-loop recycling of monomers.

The above-mentioned embodiments only express several implementation modes of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the patent scope of the present invention. It should be noted that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the scope of protection of the patent of the present invention should be determined by the appended claims.

Claims (10)

1. A method for degrading polyurethane to produce amine monomers using a combination of chemical and biological methods, which is characterized in that it includes the following steps: (1) Under the action of a catalyst, polyurethane and alcoholysis agent undergo alcoholysis reaction to obtain alcoholysis products; (2) In a buffer solution, the obtained alcoholysis product is enzymatically hydrolyzed by an esterase to obtain an amine monomer; the esterase includes esterase Aes72. 2. The method according to claim 1, characterized in that, in step (1), the catalyst includes amine compounds, tin compounds, alkali metal salts and alkaline hydroxides; preferably, the amine compounds Including diethylamine and ethanolamine; preferably, the tin compounds include dibutyltin dilaurate, butyltin oxide and hydroxybutyltin oxide; preferably, the alkali metal salts include potassium acetate, zinc acetate and barium acetate ; Preferably, the alkaline hydroxide includes potassium hydroxide and sodium hydroxide. 3. The method according to claim 1, characterized in that in step (1), the polyurethane includes polyurethane plastic. 4. The method according to claim 1, characterized in that, in step (1), the alcoholysis agent includes methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol or a mixture thereof ; Preferably, the mass ratio of the polyurethane to the alcoholysis agent is 1:1-10. 5. The method according to claim 1, characterized in that in step (1), the temperature of the reaction is 150-250°C. 6. The method according to claim 1, characterized in that in step (1), the reaction is carried out under stirring; preferably, the stirring rate is 50-1000 rpm. 7. The method according to claim 1, characterized in that in step (2), the buffer includes phosphate buffer and Tris·HCl buffer. 8. The method according to claim 1, characterized in that in step (2), the addition amount of the alcoholysis product is 0.1%-20% v/v, preferably 0.3%-10% v/v, further Preferably 0.5%-1% v/v. 9. The method according to claim 1, characterized in that, in step (2), the added amount of the esterase is 0.1-10mg/mL; preferably, the specific enzyme activity of the esterase Aes72 is 67-75U /mg. 10. The method according to claim 1, wherein in step (2), the temperature of the enzymatic hydrolysis reaction is 25-80°C; preferably, the time of the enzymatic hydrolysis reaction is 5-72 hours.