WO2011145687A1

WO2011145687A1 - Method for stabilizing amide compound having unsaturated bond

Info

Publication number: WO2011145687A1
Application number: PCT/JP2011/061546
Authority: WO
Inventors: 努石田; 新佐藤; 重男渡辺; 輝夫有井
Original assignee: 三井化学株式会社
Priority date: 2010-05-21
Filing date: 2011-05-19
Publication date: 2011-11-24
Also published as: JP5925355B2; JP2015164425A; JPWO2011145687A1; TW201141817A

Abstract

Provided is a method for preserving, in a stable state, an amide compound having an unsaturated bond, which is industrially very important but very easily undergoes polymerization and, therefore, is very hard to handle, without adding a chemical or newly employing a special device or design. Provided is a method for stabilizing an amide compound having an unsaturated bond, which is industrially very important but very easily undergoes polymerization and, therefore, is very hard to handle, comprising controlling the oxygen concentration of a solution containing said amide compound having an unsaturated bond.

Description

Method for stabilizing amide compound having unsaturated bond

The present invention relates to a method for stabilizing an amide compound having an unsaturated bond.

Amide compounds having unsaturated bonds are important industrial raw materials as raw material monomers for various materials, and in particular, (meth) acrylamide is a polymer flocculant, a secondary and tertiary recovery agent for crude oil, and a paper agent. It is an important industrial raw material widely used as a raw material monomer. However, since the amide compound is very easily polymerized, it is a big problem in storage and transportation.

So far, stable storage methods by adding a polymerization inhibitor have been reported (Patent Documents 1 and 2). On the other hand, a physical response method such as continuous stirring has been devised. However, in the former, there is a problem that the quality is affected, for example, the purity of the amide compound having an unsaturated bond is lowered, and in the latter, a dedicated device is required and the equipment cost is increased.

Patent Document 3 discloses that when an acrylamide aqueous solution obtained by reacting acrylonitrile and water in a liquid phase in the presence of a copper-containing catalyst is purified, unreacted acrylonitrile in the reaction solution is substantially free of oxygen. Distilled in the presence, then contacted with oxygen or an oxygen-containing gas to maintain a dissolved oxygen concentration of at least 4 ppm and treated with oxygen, followed by a strongly acidic cation exchange resin and / or a strongly basic anion exchange resin A method for purifying an aqueous acrylamide solution to be treated is disclosed.

However, it is necessary to remove the metallic copper used as a catalyst by an ion exchange resin, and there is a problem that the pH is lowered to 3 to 4 where acrylonitrile is likely to be polymerized.

In Patent Document 4, in a method for directly hydrating acrylamide from acrylonitrile using a microorganism having nitrile hydration ability, when the acrylamide concentration is increased, pigments and trace impurities are extracted from the microorganism into an aqueous solution. Therefore, when purifying an aqueous acrylamide solution using activated carbon, the dissolved oxygen concentration in the water after contact was increased to 0.5 ppm or more by bringing the activated carbon into contact with water in which oxygen was dissolved. Subsequently, a method for purifying an aqueous acrylamide solution in which the activated carbon is brought into contact with the activated carbon is disclosed.

However, in Patent Document 4, there is no description or suggestion about the stage of reaction from acrylonitrile to acrylamide in the microbial method and the stage of storage of acrylamide obtained after purification, which may cause problems in practice.

Japanese Examined Patent Publication No. 39-10109 Japanese Patent No. 2548051 Japanese Examined Patent Publication No. 52-91818 Japanese Patent Publication No. 2-9022

An object of the present invention is to stably store an amide compound having an unsaturated bond without adding a chemical substance or adding a special device or design to an amide compound having an unsaturated bond that is extremely polymerized and difficult to handle. To provide a law.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have an effect of preventing polymerization by containing 1 wt ppm or more of oxygen in an aqueous amide compound solution having a high concentration of unsaturated bonds that are more easily polymerized. In addition, the present inventors have found that the quality of a polymer (polyamide compound) obtained from an amide compound having an unsaturated bond is good, and completed the present invention.

That is, the present invention is as follows.

[1] When producing a reaction liquid containing an amide compound having an unsaturated bond from an aqueous solution containing a nitrile compound using a catalyst containing an enzyme capable of generating an amide compound from a nitrile compound, and / or using the catalyst When the reaction solution containing an amide compound having an unsaturated bond produced from an aqueous solution containing a nitrile compound is stored, the oxygen in the reaction solution is adjusted to 1 ppm by weight or more and a saturated oxygen concentration or less. A method for stabilizing an amide compound having a bond.
[2] The stabilization method according to [1], wherein when the nitrile compound in the reaction solution is less than 1% by weight, oxygen is dissolved in the reaction solution at 1 ppm by weight or more and a saturated oxygen concentration or less. .
[3] The stabilization method according to [1] or [2], wherein when the pH of the reaction solution is 3 or more and less than 7, oxygen is dissolved at 1 ppm by weight or more and a saturated oxygen concentration or less.
[4] The stabilization method according to any one of [1] to [3], wherein the nitrile compound is (meth) acrylonitrile and the amide compound is (meth) acrylamide.
[5] The stabilization method according to any one of [1] to [4], wherein the concentration of the polypeptide contained in the reaction solution is 0.1 to 500 ppm by weight.
[6] The stabilization method according to any one of [1] to [5], wherein the enzyme is nitrile hydratase.
[7] The stabilization method according to [6], wherein the nitrile hydratase is derived from Pseudonocardia.
[8] An amide compound having an unsaturated bond, which is obtained through the stabilization method according to any one of [1] to [7].
[9] A polyamide compound obtained by polymerizing an amide compound having an unsaturated bond obtained through the stabilization method according to any one of [1] to [7].

In this specification, the step of obtaining a reaction solution containing an amide compound having an unsaturated bond from an aqueous solution containing a nitrile compound by a hydration reaction using a catalyst containing an enzyme capable of generating an amide compound from a nitrile compound is referred to as “reaction”. And the step of removing the enzyme and the like by purifying the resulting reaction solution of the amide compound having an unsaturated bond using activated carbon or the like as the “purification step”, and passing through these two steps, the nitrile Obtaining an amide compound having an unsaturated bond from a compound is referred to as “production”.

Further, in the present specification, the “amide compound having an unsaturated bond” is also simply referred to as “amide compound” or “unsaturated amide compound”. A reaction solution containing an amide compound in the middle of a reaction for generating an amide compound from a nitrile compound; a reaction solution containing an amide compound after reaction; a reaction solution containing an amide compound after purification; and an amide compound during and after storage Since any of the reaction liquids contains at least an amide compound, it is also referred to as an “amide compound-containing liquid” or an “amide compound aqueous solution”. “Weight ppm” which is a unit of oxygen concentration may be simply expressed as “ppm”, but unless otherwise specified, all means “ppm by weight”. The terms “amide compound polymer” and “polyamide compound” are used interchangeably.

According to the stabilization method of the present invention, the amide compound having an unsaturated bond is always stable without substantially increasing the impurity content of the amide compound having an unsaturated bond and without adding an expensive facility. Can be manufactured and stored.

Furthermore, the quality of the polyamide compound obtained by polymerizing the amide compound using such a stabilization method is good.

In the method for stabilizing an amide compound having an unsaturated bond according to the present invention, a catalyst containing an enzyme capable of producing an amide compound from a nitrile compound is used to carry out the following steps. Oxygen is made to be 1 ppm by weight or more and saturated oxygen concentration or less.

Reaction step: a step in which the amide compound is produced from a nitrile compound by a catalytic reaction in an aqueous solution containing the nitrile compound and the catalyst; and a purification step: a catalyst (activated carbon is used from the reaction solution obtained in the reaction step). A process of removing proteins, polypeptides, etc. derived from a purified enzyme / a crudely purified enzyme, a microorganism containing the enzyme or a culture solution of the microorganism) (the above is collectively referred to as a production process); and / or
Storage step: A step of storing the reaction solution obtained in the manufacturing process.

In the reaction step, the reaction solution during or after the reaction includes an unreacted or residual nitrile compound, the generated amide compound, and a catalyst. On the other hand, the aqueous solution before the reaction (including 0 hours of reaction) contains a nitrile compound and a catalyst.

In addition, the amide compound having an unsaturated bond of the present invention is obtained through the stabilization method of the present invention, and the polyamide compound of the present invention polymerizes the amide compound having an unsaturated bond of the present invention. It is characterized by being obtained.

The nitrile compound applied to the present invention is a substrate of an enzyme (preferably nitrile hydratase) that can generate an amide compound from the nitrile compound, and any nitrile compound that can generate an amide compound having an unsaturated bond described later is used in the present invention. Although not particularly limited, acrylonitrile and methacrylonitrile are preferable. In the present specification, acrylonitrile and methacrylonitrile are collectively referred to as “(meth) acrylonitrile”.

The amide compound having an unsaturated bond applied to the present invention is not particularly limited as long as it is an amide compound having an unsaturated double bond in the molecule. Examples of the amide compound having an unsaturated bond applied to the present invention include acrylamide, methacrylamide, crotonamide, tiglic amide, 2-pentenoic acid amide, 3-pentenoic acid amide, 4-pentenoic acid amide, 2- Monoamide compounds such as hexenoic acid amide, 3-hexenoic acid amide, 5-hexenoic acid amide, fumaric acid diamide, maleic acid diamide, citraconic acid diamide, mesaconic acid diamide, itaconic acid diamide, 2-pentenedioic acid diamide, 3-hexene And diamide compounds such as diacid diamide. Preferably, a monoamide compound is mentioned, More preferably, acrylamide or methacrylamide is mentioned. In the present specification, acrylamide and methacrylamide are collectively referred to as “(meth) acrylamide”. The amide compound-containing liquid having an unsaturated bond applied to the present invention is not particularly limited, but preferably, the amide compound is applied to a product liquid obtained by a hydration reaction of a corresponding nitrile compound. . More preferably, it is particularly preferably applied to an acrylamide-containing liquid obtained by hydration reaction of acrylonitrile or a methacrylamide-containing liquid obtained by hydration reaction of methacrylonitrile.

Although the method for producing an amide compound having an unsaturated bond is not particularly limited, for example, a production method using a microorganism is preferably exemplified. The microorganisms producing nitrile hydratase which are preferably used include Nocardia, Corynebacterium, Bacillus, thermophilic Bacillus, Pseudomonas, Micrococcus. (Micrococcus), Rhodococcus genus represented by Rhodochrous species, Acinetobacter genus, Xanthobacter genus, Streptomyces genus, Rhizobium genus, Klebsiella (Rhizobium genus) Klebsiella, Enterobacter, Erwinia, Aeromonas, Citrobacter, Achromobacter, Agrobacterium or thermophila ) Pseudonocardia genus represented by species, Bacteridiu m) microorganisms belonging to the genus and Brevibacterium. In addition, a transformant in which a nitrile hydratase gene cloned from these microorganisms is highly expressed in an arbitrary host, and one or more of the constituent amino acids of the nitrile hydratase using other DNA by using recombinant DNA technology And a transformant expressing a mutant nitrile hydratase with further improved amide compound resistance, nitrile compound resistance, and temperature resistance by substitution, deletion, deletion or insertion.

In addition, as an arbitrary host mentioned here, Escherichia coli (Escherichia coli) is mentioned as a representative example as described in the examples below, but is not particularly limited to Escherichia coli, and bacillus such as Bacillus subtilis. Other microbial strains such as genera, yeasts and actinomycetes are also included. As an example of such, MT-10822 (this strain was established on February 7, 1996, 1-3-1 Higashi 1-chome, Tsukuba, Ibaraki Prefecture, Institute of Biotechnology, Institute of Industrial Technology, Ministry of International Trade and Industry (currently Tsukuba Ibaraki Prefecture). City East 1-1-1 Tsukuba Center Chuo No. 6 (National Institute of Advanced Industrial Science and Technology, Patent Biological Deposit Center) under the accession number FERM BP-5785, based on the Budapest Treaty on the international approval of the deposit of microorganisms under patent procedures Is deposited).

Among these microorganisms, in terms of having a highly active and highly stable nitrile hydratase, a microorganism belonging to the genus Pseudonocardia and a nitrile hydratase gene cloned from the microorganism can be highly expressed in any host. Among them, a transformant in which a mutant nitrile hydratase is expressed is preferable. In addition, the said transformant is preferable at the point which raises the stability of nitrile hydratase more and the activity per microbial cell is higher.

Also preferred are Rhodococcus rhodochrous J-1, which can highly express nitrile hydratase in microorganisms, and transformants in which the nitrile hydratase gene cloned from the microorganism is highly expressed in any host. The microbial cell producing the nitrile hydratase can be prepared by a general method known in the fields of molecular biology, biotechnology, and genetic engineering.

The recombinant vector according to the present invention contains a gene encoding nitrile hydratase and can be obtained by linking a gene encoding nitrile hydratase to the vector. The vector is not particularly limited. For example, a gene encoding nitrile hydratase in a commercially available expression plasmid represented by pET-21a (+), pKK223-3, pUC19, pBluescriptKS (+), pBR322, etc. Thus, the expression plasmid of nitrile hydratase can be constructed. The host organism to be used for transformation is not limited as long as the recombinant vector is stable and capable of self-propagation and can express foreign DNA traits. For example, E. coli is a good example. The transformant having the ability to produce nitrile hydratase can be obtained by introducing it into Bacillus subtilis, yeast or the like.

A microorganism producing nitrile hydratase as described above may be appropriately cultured and grown by a known method to produce nitrile hydratase. As a medium used in this case, either a synthetic medium or a natural medium can be used as long as it contains a suitable amount of carbon source, nitrogen source, inorganic salts and other nutrients. For example, after inoculating microorganisms in a normal liquid medium such as LB medium or M9 medium, an appropriate culture temperature (generally 20 ° C. to 50 ° C., but in the case of thermophilic bacteria, it may be 50 ° C. or higher). It can be prepared by culturing in the above. Culturing can be performed using a conventional culture method such as shaking culture, aeration and agitation culture, continuous culture, or fed-batch culture in a liquid medium containing the culture components. The culture temperature of the transformant is preferably 15 to 37 ° C. The culture conditions may be appropriately selected depending on the type of culture and the culture method, and are not particularly limited as long as the strain can grow and produce nitrile hydratase.

In the present invention, in order to react the microbial cell producing the above-mentioned nitrile hydratase with the nitrile compound, various treatments such as collection of cells by centrifugation or crushing to produce a crushed cell product are performed. The microbial cells that have been subjected to any of these treatments are collectively referred to as processed microbial cells.

There are no particular limitations on the form of microorganisms to be crushed as long as they contain microorganisms that produce nitrile hydratase. For example, the culture itself containing the microorganisms, Examples of the collected and collected bacterial bodies, and those obtained by washing the collected bacterial bodies with physiological saline and the like.

The device for crushing the cells is not particularly limited as long as the cells can be crushed. Examples thereof include grinding devices such as an ultrasonic crusher, a French press, a bead shocker, a homogenizer, a dyno mill, and a cool mill. It is done. Among these, a homogenizer is preferable because it can be scaled up at low cost. A homogenizer is a device that adjusts the clearance of a homovalve provided at the outlet of a plunger-type high-pressure pump that feeds liquid with a piston with screws or hydraulic pressure, and has a synergistic effect on the introduced fluid such as shearing, collision, and cavitation. It is a device that generates instantaneously. This homogenizer is commercially available from Sanwa Machinery Co., Ltd. and Izumi Food Machinery Co., Ltd.

The temperature at which the cells are crushed is not particularly limited, but is preferably 0 ° C. or higher and 50 ° C. or lower, more preferably 0 ° C. or higher and 25 ° C. or lower.

The pH at which the cells are disrupted is not particularly limited, but is preferably 4 to 10 and more preferably 6 to 8.

The pressure when crushing the cells using a homogenizer is not particularly limited as long as the cells are crushed, but is preferably 10 MPa or more and 300 MPa or less, more preferably 30 MPa or more and 100 MPa or less.

Surprisingly, the present inventors have revealed for the first time that nitrile hydratase has a polymerization promoting effect on unsaturated amide compounds.

The oxygen concentration of the unsaturated amide compound-containing liquid is not particularly limited as long as it is between 1 ppm by weight and saturated solubility, but more preferably from 1.2 ppm by weight to saturated solubility, and even more preferably from 2 ppm by weight to saturated solubility. From the viewpoint of preventing polymerization. In particular, when the nitrile compound in the unsaturated amide compound-containing liquid is less than 1% by weight, the oxygen concentration of the unsaturated amide compound-containing liquid is preferably within the above range.

In addition, when the pH of the unsaturated amide compound-containing liquid is less than 7, particularly when the pH is 3 or more and less than 7, the polymerization of the unsaturated amide compound is promoted. It is preferably between saturated solubilities, more preferably between 2 ppm by weight and saturated solubilities.

The method for supplying oxygen to the unsaturated amide compound-containing solution is not particularly limited as long as the oxygen concentration of the unsaturated amide compound-containing solution is maintained from 1 ppm by weight to saturated solubility, and may be a known method. For example, a supply method by stirring the unsaturated amide compound-containing liquid in the presence of a gas containing oxygen, a supply method by blowing a gas containing oxygen into the unsaturated amide compound-containing liquid, and the like can be exemplified. In particular, a supply method by stirring is preferable from the viewpoint of supplying oxygen uniformly.

The gas used for supplying oxygen is not particularly limited as long as it contains oxygen, and oxygen, air, and the like are preferably used.

The storage temperature of the unsaturated amide compound is not particularly limited, but is preferably −10 ° C. to 50 ° C., more preferably 10 ° C. to 30 ° C. from the viewpoint of stability.

The polypeptide concentration contained in the unsaturated amide compound-containing solution before the purification step is usually about 10 ppm to 500 ppm, preferably about 10 ppm to 100 ppm.

In addition, when a microorganism containing an enzyme is used as a catalyst, the residual polypeptide concentration contained in the unsaturated amide compound-containing liquid purified by using activated carbon after removing the microorganism with filter paper or the like is preferably about 0.00. It is about 1 ppm to 3 ppm, usually about 0.5 ppm to 1.5 ppm.

As a polypeptide concentration analysis, the method is described in detail in the Examples, but the Bradford method is used.

Next, examples of the present invention will be described in detail, but the present invention is not limited to these examples.

[Example (1-1)]
<Preparation of microbial catalyst containing nitrile hydratase>
In accordance with the method described in Example 1 of Japanese Patent Laid-Open No. 2001-340091, no. Three clonal cells were obtained and similarly cultured by the method of Example 1, that is, the following method, to obtain wet cells containing nitrile hydratase.

100 mL of a medium having the following composition was prepared in a 500 mL Erlenmeyer flask with a baffle and sterilized by autoclaving at 121 ° C. for 20 minutes. After adding ampicillin to this medium so that the final concentration is 50 μg / mL, Three clones were inoculated with ears of white and cultured at 37 ° C./130 rpm for 20 hours. Centrifugation (15000G × 15 minutes) separated only the cells from the culture solution, and then resuspended the cells in 50 mL of physiological saline, and then centrifuged again to obtain wet cells. .

Medium composition Yeast extract 5.0 g / L
Polypeptone 10.0 g / L
NaCl 5.0 g / L
Cobalt chloride hexahydrate 10.0mg / L
Ferric sulfate heptahydrate 40.0mg / L
pH 7.5
In order to obtain a final product having an acrylamide concentration in the aqueous solution of 50% by weight, the reaction was performed under the following conditions.

<Reaction process from acrylonitrile to acrylamide>
(First reaction step using the first reactor)
400 g of water was charged in advance into a 1 L glass flask equipped with a stirrer, which was used as the first reactor. In the first reactor, air was passed through the gas phase portion at a flow rate of 1 L / min.

The wet cells obtained by the above culture method were suspended in pure water.

The suspension was continuously fed at a rate of 11 g / h while stirring in the first reactor. Acrylonitrile was continuously fed at a rate of 32 g / h, and pure water was continuously fed at a rate of 37 g / h. Further, a 0.1 M NaOH aqueous solution was fed so that the reaction pH was 7.5 to 8.5. These feeds were fed from each storage tank in a single line and did not come into contact with other feeds until fed into the reactor.

Furthermore, in order to keep the liquid level of the first reactor constant, the reaction solution is continuously withdrawn from the first reactor at a rate of 80 g / h, and continuously fed to the second reactor. The reaction was allowed to proceed further in the reactor.

The amount of wet cells added was adjusted so that the acrylonitrile conversion rate in the first reactor was 97%.

(Second reaction step using the second reactor)
As the second reactor, a Teflon (registered trademark) tube 20 m having an inner diameter of 5 mm was used.

In the second reaction step, the reaction liquid continuously extracted from the first reactor is continuously fed to the second reactor, and the reaction is further advanced.

The first reactor and the second reactor were both immersed in a water bath having a temperature of 10 to 20 ° C., and the temperature was controlled so that the liquid temperature inside each reactor was 15 ° C.

(HPLC analysis)
On the 30th day from the start of the reaction process, the reaction solution of each reactor was sampled and subjected to HPLC analysis. As a result, the conversion rate to acrylamide at the outlet of the first reactor was 97%, and at the outlet of the first reactor. The concentration of acrylonitrile was 1% by weight, the acrylonitrile concentration at the outlet of the second reactor was below the detection limit (100 ppm by weight or less), and the acrylamide concentration was 53.5% by weight. At this time, the dissolved oxygen concentration in the reaction liquid at the outlet of the first reactor was 8 ppm, and the dissolved oxygen concentration in the reaction liquid at the outlet of the second reactor was 7 ppm.

(Methanol test)
The methanol test is a test in which 90 mL of methanol is added to 10 mL of a reaction solution and the like, and the transmittance at 360 nm is measured. As a result, when the transmittance is 99.9% or more, the presence of an acrylamide polymer is not recognized. .

The reaction liquid extracted from the first reactor was filtered with filter paper to remove the cells.

As a result of performing a methanol test on the obtained filtrate, it was found that the acrylamide polymer was not present because the transmittance was 99.9% or more.

In Table 1, as a result of the methanol test, the case where an acrylamide polymer is present is indicated as “x”, and the case where no acrylamide polymer is present is indicated as “◯”.

Here, the analysis conditions were as follows.
Acrylamide analysis conditions:
High-performance liquid chromatograph: LC-10A system (manufactured by Shimadzu Corporation)
(UV detector wavelength 250nm, column temperature 40 ° C)
Separation column: SCR-101H (manufactured by Shimadzu Corporation)
Eluent: 0.05% (volume basis)-phosphoric acid aqueous solution acrylonitrile Analysis conditions:
High-performance liquid chromatograph: LC-10A system (manufactured by Shimadzu Corporation)
(UV detector wavelength 200nm, column temperature 40 ° C)
Separation column: Wakosil-II 5C18HG (Wako Pure Chemical Industries)
Eluent: 7% (volume basis)-acetonitrile,
Aqueous solution containing 0.1 mM acetic acid and 0.2 mM sodium acetate at various concentrations The acrylamide concentration was determined as follows. Commercially available acrylamide was dissolved in pure water to prepare an aqueous acrylamide solution having a known concentration, and a calibration curve for acrylamide concentration analysis in HPLC was prepared. Using this, the area value at the time of HPLC analysis of the test solution was converted to acrylamide concentration (absolute calibration curve method). The amount of the reaction solution used for HPLC measurement was 5 μL. In addition, since there was almost no influence of the density of each reaction liquid, the acrylamide density | concentration (weight%) was obtained in this way.

<Purification process of acrylamide>
This reaction was continued for about 4 days after the analysis was performed on day 30. In about 4 days, about 7500 g of reaction liquid was obtained.

To about 7500 g of the obtained reaction solution, 30 g of activated carbon (powdered activated carbon PM-SX made by Kuraray Chemical Co., Ltd.) was added, and 160 g of 0.5 wt% -acrylic acid aqueous solution was added, and then 1M NaOH aqueous solution. The pH was adjusted to 5. This was stirred at 25 ° C. for 24 hours in an environment in which air was aerated at a flow rate of 1 L / min. The dissolved oxygen concentration of the treatment liquid after stirring for 24 hours was 8 ppm.

Thereafter, filtration was performed with filter paper to remove the activated carbon. In order to recover the acrylamide adhering to the activated carbon, the activated carbon was washed with 300 g of pure water, mixed with the previous activated carbon treatment solution, neutralized with a 1M NaOH aqueous solution, and a pH of 7 was obtained to obtain about 7900 g of product. . The final acrylamide concentration in the product after the activated carbon treatment was 50.5% by weight.

Further, when the residual polypeptide concentration was measured using the following analysis method, it was 0.7 ppm.

In Examples and Comparative Examples, the remaining polypeptide concentration after the purification step was in the range of 0.1 ppm to 1.5 ppm. In the present specification, the “polypeptide” is a term including a protein, one or more polypeptides constituting the protein, and a fragment of the polypeptide.

(Polypeptide concentration analysis method)
The product after the purification step was sampled, acrylamide was removed using a dialysis membrane, the color of the polypeptide was developed using a coloring reagent, and the absorbance at 595 nm was measured with a spectrophotometer.

Analysis conditions:
Spectrophotometer: U-2000 (Hitachi)
Dialysis membrane: Spectra / Por CE (Nippon Genetics)
Coloring reagent: DYE reagent (Bio-Rad)
(Methanol test)
A methanol test was performed on the resulting product. That is, 90 mL of methanol was added to 10 mL of the obtained product, and the transmittance at 360 nm was measured. The transmittance was 99.9% or more, and the presence of a polymer was not recognized.

(Manufacture of acrylamide polymer)
Water was added to the acrylamide aqueous solution obtained as described above to obtain an acrylamide aqueous solution having a concentration of 20% by weight. 500 g of this 20 wt% acrylamide aqueous solution was placed in a 1 L polyethylene container, and while maintaining the temperature at 18 ° C., dissolved oxygen in the liquid was removed through nitrogen, and immediately placed in a heat insulating block made of polystyrene foam.

Then 200 × 10 ⁻⁶ mpm (molar ratio to acrylamide) 4,4′-azobis (sodium 4-cyanovalerate), 200 × 10 ⁻⁶ mpm dimethylaminopropionitrile, and 80 × 10 ⁻⁶ mpm Of ammonium persulfate were each dissolved in a small amount of water and quickly poured into a 1 L polyethylene container in this order. Nitrogen gas was previously passed through these reagents, and before and after injection, a small amount of nitrogen gas was also passed through the polyethylene container to prevent oxygen gas from being mixed.

When the reagent was injected, the supply of nitrogen gas was stopped because it was observed that the temperature inside the polyethylene container increased after an induction period of several minutes. When the polyethylene container was held in the heat insulation block for about 100 minutes, the temperature inside the polyethylene container reached about 70 ° C. Therefore, the polyethylene container was taken out of the heat insulation block and immersed in 97 ° C. water for 2 hours to further proceed the polymerization reaction. Thereafter, it was immersed in cold water and cooled to stop the polymerization reaction.

The water-containing acrylamide polymer gel thus obtained was taken out of the polyethylene container, divided into small blocks, and ground with a meat grinder. This ground acrylamide polymer hydrogel was dried with hot air at 100 ° C. for 2 hours, and further pulverized with a high-speed rotary blade pulverizer to obtain a dry powdery acrylamide polymer.

(Water-soluble test of acrylamide polymer)
The water solubility test means that 600 mL of water is put into a 1 L beaker, and 0.6 g of acrylamide polymer is added while stirring at 25 ° C. using a stirring blade of a predetermined shape, and the insoluble matter is filtered off and dried. The content of insoluble matter is determined from the weight.

In Table 1, as a result of the water solubility test, “x” indicates that the insoluble content exceeds 1%, and “○” indicates that the insoluble content is 1% or less. It is written.

The obtained dry powdery acrylamide polymer was passed through a sieve to fractionate a 32-42 mesh polymer. When this fractionated acrylamide polymer was evaluated by a water solubility test, the content of the insoluble matter was 0.3%, indicating a good water solubility.

<Acrylamide preservation process>
Aeration treatment is performed continuously for 10 days at a flow rate of 1 m ³ / h in a constant temperature bath at 20 ° C. for 500 g of the activated carbon treated product (acrylamide concentration 50.6%) obtained in the purification process. And a storage solution was obtained.

After 10 days, the aeration was stopped and the dissolved oxygen concentration was measured and found to be 8 ppm. 90 mL of methanol was added to 10 mL of the obtained storage treatment solution, and the transmittance at 360 nm was measured (methanol test). In either case, the transmittance was 99.9% or more, and the presence of a polymer was not recognized.

(Manufacture of acrylamide polymer)
A dry powdery acrylamide polymer was obtained in the same manner as in the polymer production method for acrylamide obtained after the purification step.

(Water-soluble test of acrylamide polymer)
The obtained dry powdery acrylamide polymer was passed through a sieve to fractionate a 32-42 mesh polymer. When the fractionated acrylamide polymer was evaluated by a water solubility test, the content of the insoluble matter was 0.7%, indicating good water solubility. The obtained results are shown in Table 1.

[Examples (1-2) to (1-4)]
In Example (1-1), the dissolved oxygen concentration in the first reaction step is 8 ppm to 4 ppm (Example (1-2)), 2 ppm (Example (1-3)) or 1.2 ppm (Example (1) -4)), except that acrylamide was produced in the same manner as in Example (1-1) and subjected to various tests. The obtained results are shown in Table 1.

That is, in the reaction step of Example (1-1), the same operation as in Example (1-1) was performed except that the gas vented to the first reactor was a mixture of nitrogen and air instead of air. went. The proportion of air in the mixture was 50%, 25%, and 15%, respectively. At this time, the dissolved oxygen concentration in the reaction solution at the outlet of the first reactor is 4 ppm, 2 ppm, and 1.2 ppm, respectively, and the dissolved oxygen concentration in the reaction solution at the outlet of the second reactor is 3.5 ppm, 1.8 ppm, and 1 ppm, respectively. 0.0 ppm.

The reaction liquid in the first reactor was filtered with filter paper to remove the cells. 90 mL of methanol was added to 10 mL of the obtained filtrate, and the transmittance at 360 nm was measured (methanol test). The transmittance was 99.9% or more in any case, and the presence of a polymer was not recognized.

In the purification step, activated carbon treatment was performed in the same manner as in Example (1-1) to obtain about 7900 g of product. 90 mL of methanol was added to 10 mL of the obtained product, and the transmittance at 360 nm was measured (methanol test). In either case, the transmittance was 99.9% or more, and the presence of a polymer was not recognized.

Furthermore, when the acrylamide polymer produced from the obtained acrylamide aqueous solution was evaluated by a water solubility test, the content of insoluble matter was 0.3%, indicating good water solubility.

In the preservation process, air was continuously applied for 10 days at a flow rate of 1 m ³ / h in a constant temperature bath at 20 ° C. with respect to 500 g of the activated carbon-treated product (acrylamide concentration 50.6%) obtained in the purification process. Aeration treatment was performed to obtain a storage treatment solution. Ten days later, the aeration was stopped and the dissolved oxygen concentration was measured and found to be 8 ppm. 90 mL of methanol was added to 10 mL of the obtained storage treatment solution, and the transmittance at 360 nm was measured (methanol test). In either case, the transmittance was 99.9% or more, and the presence of a polymer was not recognized. In addition, an acrylamide polymer was produced in the same manner as in Example (1-1), and a water solubility test of the obtained acrylamide polymer was performed. In both cases, the insoluble content was 0.7%, It showed good water solubility.

[Examples (2-1) to (2-3)]
In Example (1-1), the dissolved oxygen concentration in the purification step is 8 ppm to 4 ppm (Example (2-1)), 2 ppm (Example (2-2)), or 1 ppm (Example (2-3)). Acrylamide was produced in the same manner as in Example (1-1) except for changing to, and subjected to various tests. The obtained results are shown in Table 1.

That is, in the purification step of Example (1-1), the air flow during the activated carbon treatment at pH 5 was the same as in Example (1-1) except that air and nitrogen were mixed instead of air. The operation was performed. The proportion of air in the mixture was 50%, 25%, and 12%, respectively. As a result, the dissolved oxygen concentration of the treatment liquid after stirring for 24 hours was 4 ppm, 2 ppm, and 1.0 ppm, respectively. 90 mL of methanol was added to 10 mL of the obtained product, and the transmittance at 360 nm was measured (methanol test). In either case, the transmittance was 99.9% or more, and the presence of a polymer was not recognized.

Further, in this purification process, the acrylamide polymer produced from the obtained aqueous acrylamide solution was evaluated by a water solubility test. In all cases, the content of insoluble matter was 0.3%, indicating good water solubility. .

[Example (3-1)]
In Example (1-1), the point at which oxygen was dissolved when the acrylonitrile concentration in the first reaction step reached 0.4% by weight and the amount of wet cells added were the acrylonitrile conversion rate of the first reactor. Acrylamide was produced in the same manner as in Example (1-1) except that the adjustment was made to 99% and subjected to various tests. The obtained results are shown in Table 1.

That is, in the reaction step, a 1 L glass flask equipped with a stirrer was prepared as the first reactor, and a Teflon (registered trademark) tube 20 m having an inner diameter of 5 mm was prepared as the second reactor. The first reactor was charged with 400 g of water in advance. Air was bubbled through the gas phase portion of the first reactor at a flow rate of 1 L / min.

The wet cells obtained by the same method as described in Example (1-1) were suspended in pure water. The suspension was continuously fed at a rate of 16 g / h while stirring in the first reactor. Acrylonitrile was continuously fed at a rate of 32 g / h, and pure water was continuously fed at a rate of 32 g / h. Further, a 0.1 M NaOH aqueous solution was fed so that the reaction pH was 7.5 to 8.5. These feeds were fed from each storage tank in a single line and did not come into contact with other feeds until fed into the reactor. Furthermore, in order to keep the liquid level of the first reactor constant, the reaction solution is continuously withdrawn from the first reactor at a rate of 80 g / h, and continuously fed to the second reactor. The reaction was allowed to proceed further in the reactor. The amount of wet cells added was adjusted so that the conversion rate of acrylonitrile in the first reactor was 99%.

Both the first reactor and the second reactor were immersed in a water bath at a temperature of 10 to 20 ° C., and the temperature was controlled so that the liquid temperature inside each reactor was 15 ° C.

On the 30th day from the start of operation, the reaction solution in each reactor was sampled and subjected to HPLC analysis. As a result, the conversion rate to acrylamide at the first reactor outlet was 99%, and the reaction at the first reactor outlet was The acrylonitrile concentration was 0.4% by weight, the acrylonitrile concentration at the outlet of the second reactor was below the detection limit (100 ppm by weight or less), and the acrylamide concentration was 53.3% by weight. At this time, the dissolved oxygen concentration in the reaction liquid at the outlet of the first reactor was 8 ppm, and the dissolved oxygen concentration in the reaction liquid at the outlet of the second reactor was 7 ppm.

The reaction liquid in the first reactor was filtered with filter paper to remove the cells. 90 mL of methanol was added to 10 mL of the obtained filtrate, and the transmittance at 360 nm was measured. The transmittance was 99.9% or more, and the presence of a polymer was not recognized.

This analysis was continued for about 4 days after the analysis was performed on the 30th day. In about 4 days, about 7500 g of reaction liquid was obtained. In the purification step, 30 g of activated carbon (powdered activated carbon PM-SX manufactured by Kuraray Chemical Co., Ltd.) was added to about 7500 g of the obtained reaction solution, and 160 g of 0.5 wt% -acrylic acid aqueous solution was added. The pH was adjusted to 5 with 1M NaOH aqueous solution. This was stirred at 25 ° C. for 24 hours in an environment in which air was aerated at a flow rate of 1 L / min. The dissolved oxygen concentration of the treatment liquid after stirring for 24 hours was 8 ppm.

Thereafter, filtration was performed with filter paper to remove the activated carbon. Thereafter, in order to recover acrylamide attached to the activated carbon, the activated carbon is washed with 300 g of pure water, mixed with the previous activated carbon treatment solution, neutralized with 1M NaOH aqueous solution, and about 7900 g of product is prepared with a pH of 7. Obtained. The final acrylamide concentration in the product after the activated carbon treatment was 50.4% by weight. 90 mL of methanol was added to 10 mL of the obtained product, and the transmittance at 360 nm was measured. The transmittance was 99.9% or more, and the presence of a polymer was not recognized.

A dry powdery acrylamide polymer was produced from the obtained aqueous acrylamide solution using the same production method as described above. The acrylamide polymer was passed through a sieve to fractionate a 32-42 mesh polymer. When this fractionated acrylamide polymer was evaluated by a water solubility test, the content of the insoluble matter was 0.5%, indicating good water solubility.

In the preservation process, air was continuously applied for 10 days at a flow rate of 1 m ³ / h in a constant temperature bath at 20 ° C. with respect to 500 g of the activated carbon-treated product (acrylamide concentration 50.6%) obtained in the purification process. Aeration treatment was performed to obtain a storage solution. Ten days later, the aeration was stopped and the dissolved oxygen concentration was measured and found to be 8 ppm. 90 mL of methanol was added to 10 mL of the obtained storage treatment solution, and the transmittance at 360 nm was measured (methanol test). In either case, the transmittance was 99.9% or more, and the presence of a polymer was not recognized. Further, when an acrylamide polymer was produced in the same manner as in Example (1-1) and a water solubility test was performed on the obtained acrylamide polymer, the content of insoluble matter was 0.7%, which was good. It showed water solubility.

[Examples (3-2) to (3-4)]
In each of Examples (1-2) to (1-4), the point at which oxygen was dissolved when the acrylonitrile concentration in the first reaction step reached 0.4% by weight and the amount of wet cells added were Acrylamide was produced in the same manner as in Examples (1-2) to (1-4) except that the acrylonitrile conversion rate in the reactor was adjusted to 99% and subjected to various tests. Examples (3-2) to (3-4)). The obtained results are shown in Table 1.

Alternatively, it can be said that the same operation as in Example (3-1) was performed except that the gas vented to the first reactor in Example (3-1) was a mixed gas of nitrogen and air instead of air. . The proportion of air in the mixture was 50%, 25%, and 15%. At this time, the dissolved oxygen concentration in the reaction liquid at the first reactor outlet is 4 ppm, 2 ppm, and 1.2 ppm, respectively, and the dissolved oxygen concentration in the reaction liquid at the second reactor outlet is 3.5 ppm, 1.8 ppm, and 1.0 ppm. Met.

The reaction liquid in the first reactor was filtered with filter paper to remove the cells. 90 mL of methanol was added to 10 mL of the obtained filtrate, and the transmittance at 360 nm was measured. The transmittance was 99.9% or more in any case, and the presence of a polymer was not recognized.

In the purification step, the activated carbon treatment was performed by the same operation as in Example (3-1) including the aeration conditions to obtain about 7900 g of product. 90 mL of methanol was added to 10 mL of the obtained product, and the transmittance at 360 nm was measured. In either case, the transmittance was 99.9% or more, and the presence of a polymer was not recognized.

Moreover, when the acrylamide polymer produced from the obtained acrylamide aqueous solution was evaluated by a water solubility test, the content of the insoluble matter was 0.3%, indicating good water solubility.

[Examples (4-1) to (4-3)]
In Example (3-1), the dissolved oxygen concentration in the purification step is 8 ppm to 4 ppm (Example (4-1)), 2 ppm (Example (4-2)), or 1 ppm (Example (4-3)). Acrylamide was produced in the same manner as in Example (3-1) except that it was changed to. The obtained results are shown in Table 1.

Alternatively, in the purification step of Example (3-1), the same operation as in Example (3-1) was performed except that the air during the activated carbon treatment at pH 5 was a mixed gas of nitrogen and air instead of air. It can be said that it went. The ratio of air in the air-fuel mixture was 50%, 25%, and 12%. The dissolved oxygen concentration of the treatment liquid after stirring for 24 hours was 4 ppm, 2 ppm, and 1.0 ppm, respectively. The dissolved oxygen concentrations of the treatment liquid after stirring for 24 hours were 4 ppm, 2 ppm, and 1 ppm, respectively. 90 mL of methanol was added to 10 mL of the obtained product, and the transmittance at 360 nm was measured. In either case, the transmittance was 99.9% or more, and the presence of a polymer was not recognized.

[Comparative Example 1]
In Example (1-1), acrylamide was produced in the same manner as in Example (1-1) except that the dissolved oxygen concentration in the first reaction step was changed from 8 ppm to less than 1 ppm, and subjected to various tests. The obtained results are shown in Table 1.

That is, in the reaction step of Example (1-1), the same operation as in Example (1-1) was performed except that the gas vented to the first reactor was a mixture of nitrogen and air instead of air. went. The ratio of nitrogen and air was adjusted so that the dissolved oxygen concentration in the reaction liquid at the outlet of the first reactor was less than 1.0 ppm and the dissolved oxygen concentration in the reaction liquid at the outlet of the second reactor was less than 1.0 ppm. This operation was repeated several times.

The reaction liquid in the first reactor and the second reactor was filtered with filter paper to remove the cells. 90 mL of methanol was added to 10 mL of the obtained filtrate, and the transmittance at 360 nm was measured (methanol test). The transmittance of the reaction solution from the first reactor was 99.9% or more, and the presence of a polymer was not recognized. On the other hand, the transmittance of the reaction solution from the second reactor was usually 99.9% or more, but it became 98.5% at a rate of about once every 10 times, and the presence of a polymer was observed. there were.

Further, the activated carbon treatment was performed in the same manner as in Example (1-1) to obtain about 7900 g of product. 90 mL of methanol was added to 10 mL of the obtained product, and the transmittance at 360 nm was measured (methanol test). In the acrylamide solution in which no polymer was observed in the second reactor, the transmittance was 99.9%, and no polymer was observed, but the acrylamide solution in which the polymer was found in the second reactor was activated carbon. In the case of the treatment, the transmittance was 98.0%, and the presence of a polymer was recognized.

In the purification process, the acrylamide polymer produced from the obtained acrylamide aqueous solution was evaluated by a water solubility test. In the acrylamide solution in which no polymer was observed in the second reactor, the content of insoluble matter was 0.3%. However, in the case of the polymer from the acrylamide aqueous solution in the presence of the polymer in the second reactor, the content of the insoluble matter was 5%.

In the preservation process, air was continuously applied for 10 days at a flow rate of 1 m ³ / h in a constant temperature bath at 20 ° C. with respect to 500 g of the activated carbon-treated product (acrylamide concentration 50.6%) obtained in the purification process. Aeration treatment was performed to obtain a storage treatment solution. Ten days later, the aeration was stopped and the dissolved oxygen concentration was measured and found to be 8 ppm. 90 mL of methanol was added to 10 mL of the obtained storage treatment solution, and the transmittance at 360 nm was measured (methanol test). In the acrylamide from the acrylamide aqueous solution when the presence of the polymer was not recognized in the second reactor, the transmittance was 99.9%, and no polymer was observed. On the other hand, the transmittance of the acrylamide from the aqueous acrylamide solution when the presence of the polymer was recognized in the second reactor was 98%, and the presence of the polymer was recognized. Further, when the acrylamide polymer produced from the acrylamide aqueous solution at this time was evaluated by a water solubility test, the content of the insoluble matter was 4%, which caused a problem in quality.

[Comparative Example 2]
In Example (3-1), the dissolved oxygen concentration in the first reaction step was changed from 8 ppm to less than 1 ppm, and the amount of wet cells added was adjusted so that the acrylonitrile conversion rate in the first reactor was 99%. The acrylamide was purified in the same manner as in Example (3-1) except that the above was performed. This operation was repeated several times. The obtained results are shown in Table 1.

That is, in the reaction step, a 1 L glass flask equipped with a stirrer as a first reactor and a Teflon (registered trademark) tube 20 m with an inner diameter of 5 mm were prepared as a second reactor. The first reactor was charged with 400 g of water in advance. Nitrogen was bubbled through the first reactor at a flow rate of 1 L / min.

The wet cells obtained by the same method as described in Example (1-1) were suspended in pure water. The suspension was continuously fed at a rate of 16 g / h while stirring in the first reactor. Acrylonitrile was continuously fed at a rate of 32 g / h, and pure water was continuously fed at a rate of 32 g / h. Further, a 0.1 M NaOH aqueous solution was fed so that the reaction pH was 7.5 to 8.5. These feeds were fed from each storage tank in a single line and did not come into contact with other feeds until fed into the reactor.

Furthermore, in order to keep the liquid level of the first reactor constant, the reaction solution is continuously withdrawn from the first reactor at a rate of 80 g / h, and continuously fed to the second reactor. The reaction was allowed to proceed further in the reactor. The amount of wet cells added was adjusted so that the conversion rate of acrylonitrile in the first reactor was 99%.

On the 30th day from the start of operation, the reaction solution in each reactor was sampled and subjected to HPLC analysis. As a result, the conversion rate to acrylamide at the first reactor outlet was 99%, and the reaction at the first reactor outlet was The acrylonitrile concentration was 0.4% by weight, the acrylonitrile concentration at the outlet of the second reactor was below the detection limit (100 ppm by weight or less), and the acrylamide concentration was 53.3% by weight. At this time, the dissolved oxygen concentration in the reaction liquid at the first reactor outlet and the second reactor outlet was both less than 1 ppm.

The reaction solution in the first reactor was filtered with filter paper to remove the cells. 90 mL of methanol was added to 10 mL of the obtained filtrate, and the transmittance at 360 nm was measured. Usually, it was 99.9% or more, but it became 98.5% at a rate of about once every 10 times, and the presence of a polymer was sometimes observed.

Thereafter, filtration was performed with filter paper to remove the activated carbon. Thereafter, in order to recover acrylamide attached to the activated carbon, the activated carbon is washed with 300 g of pure water, mixed with the previous activated carbon treatment solution, neutralized with 1M NaOH aqueous solution, and about 7900 g of product is prepared with a pH of 7. Obtained. The final acrylamide concentration in the product after the activated carbon treatment was 50.5% by weight. 90 mL of methanol was added to 10 mL of the obtained product, and the transmittance at 360 nm was measured. The acrylamide from the acrylamide aqueous solution when the presence of the polymer was not recognized in the first reactor had a transmittance of 99.9% or more, but the acrylamide when the presence of the polymer was recognized in the first reactor. In the case of acrylamide from an aqueous solution, the transmittance was 98%, and the presence of a polymer was recognized.

Moreover, when the acrylamide polymer produced from the obtained acrylamide aqueous solution was evaluated by a water solubility test, the acrylamide polymer from the acrylamide aqueous solution when the presence of the polymer was not recognized in the first reactor, The content rate was 0.3%, but in the acrylamide polymer from the acrylamide aqueous solution when the presence of the polymer was recognized in the first reactor, the content rate of the insoluble content was 5%.

[Comparative Example 3]
In Example (3-1), the concentration of dissolved oxygen in the purification step was changed from 8 ppm to less than 1 ppm, and the amount of wet cells added was adjusted so that the acrylonitrile conversion rate in the first reactor was 99%. Except for the above points, acrylamide was purified in the same manner as in Example (3-1). The obtained results are shown in Table 1.

That is, in the reaction step, a 1 L glass flask equipped with a stirrer as a first reactor and a Teflon (registered trademark) tube 20 m with an inner diameter of 5 mm were prepared as a second reactor. The first reactor was charged with 400 g of water in advance. Air was bubbled through the first reactor at a flow rate of 1 L / min.

On the 30th day from the start of operation, the reaction solution in each reactor was sampled and analyzed under the above HPLC conditions. As a result, the conversion rate to acrylamide at the outlet of the first reactor was 99%. The acrylonitrile concentration at the reactor outlet was 0.4% by weight, the acrylonitrile concentration at the outlet of the second reactor was below the detection limit (100 ppm by weight or less), and the acrylamide concentration was 53.3% by weight. At this time, the dissolved oxygen concentration in the reaction liquid at the outlet of the first reactor was 8 ppm, and the dissolved oxygen concentration in the reaction liquid at the outlet of the second reactor was 7 ppm.

This analysis was continued for about 4 days after the analysis was performed on the 30th day. In about 4 days, about 7500 g of reaction liquid was obtained. In the purification step, 30 g of activated carbon (powdered activated carbon PM-SX manufactured by Kuraray Chemical Co., Ltd.) was added to about 7500 g of the obtained reaction solution, and 160 g of 0.5 wt% -acrylic acid aqueous solution was added. The pH was adjusted to 5 with 1M NaOH aqueous solution. When this was stirred for 12 hours at 25 ° C. in an environment in which nitrogen was vented at a flow rate of 1 L / min, formation of a white insoluble polymer was observed, and it was difficult to continue further work. there were. The dissolved oxygen concentration of the treatment liquid after stirring for 12 hours was less than 1 ppm.

[Comparative Example 4]
In Example (3-1), acrylamide was produced in the same manner as in Example (3-1) except that the dissolved oxygen concentration in the storage step was changed from 8 ppm to less than 1 ppm. The obtained results are shown in Table 1.

That is, 10 g of nitrogen at a flow rate of 1 m ³ / h in a constant temperature bath at 20 ° C. was applied to 500 g of the activated carbon-treated product (acrylamide concentration 50.6%) obtained in Example (3-1). Aeration treatment was performed continuously for days to obtain a preservation solution. After 10 days, the aeration was stopped and the dissolved oxygen concentration was measured and found to be less than 1 ppm. 90 mL of methanol was added to 10 mL of the obtained storage treatment solution, and the transmittance at 360 nm was measured. The transmittance was 95%, and the presence of a polymer was recognized.

[Example 5]
In the first reaction step of Example (1-1), instead of adjusting the amount of wet cells added so that the acrylonitrile conversion rate in the first reactor was 97%, the conversion rate was 90%. Acrylamide was produced in the same manner as in Example (1-1) except that adjustment was performed so as to be, and subjected to various tests. The obtained results are shown in Table 1.

That is, as a reaction step of Example 5, a 1 L glass flask equipped with a stirrer as a first reactor and a Teflon (registered trademark) tube 20 m with an inner diameter of 5 mm were prepared as a second reactor. The first reactor was charged with 400 g of water in advance. In the first reactor, air was passed through the gas phase portion at a flow rate of 1 L / min.

The wet cells obtained by the same method as described in Example (1-1) were suspended in pure water. The suspension was continuously fed at a rate of 11 g / h while stirring in the first reactor. Acrylonitrile was continuously fed at a rate of 32 g / h, and pure water was continuously fed at a rate of 37 g / h. Further, a 0.1 M NaOH aqueous solution was fed so that the reaction pH was 7.5 to 8.5. These feeds were fed from each storage tank in a single line and did not come into contact with other feeds until fed into the reactor. Furthermore, in order to keep the liquid level of the first reactor constant, the reaction solution is continuously withdrawn from the first reactor at a rate of 80 g / h, and continuously fed to the second reactor. The reaction was allowed to proceed further in the reactor. The amount of wet cells added was adjusted so that the acrylonitrile conversion rate in the first reactor was 90%.

On the second day from the start of operation, the reaction solution in each reactor was sampled and analyzed under the above HPLC conditions. As a result, the conversion rate to acrylamide at the outlet of the first reactor was 90%, and the second The acrylonitrile concentration at the outlet of the reactor was below the detection limit (100 ppm by weight or less), and the acrylamide concentration was 53.5% by weight. At this time, the dissolved oxygen concentration in the reaction liquid at the outlet of the first reactor was 8 ppm, and the dissolved oxygen concentration in the reaction liquid at the outlet of the second reactor was 7 ppm.

In the purification process, this reaction was analyzed on the second day and continued for about 4 days. In about 4 days, about 7500 g of reaction liquid was obtained. On the other hand, 30 g of activated carbon (Kuraray Chemical Co., Ltd., powdered activated carbon PM-SX) was added, and after adding 0.5 wt% -acrylic acid aqueous solution 160 g, the pH was adjusted to 5 with 1 M NaOH aqueous solution. . This was stirred for 5 hours at 25 ° C. in an environment in which air was aerated at a flow rate of 1 L / min, and then filtered through filter paper to remove activated carbon. The dissolved oxygen concentration of the treatment liquid after stirring for 5 hours was 8 ppm. Thereafter, in order to recover acrylamide attached to the activated carbon, the activated carbon is washed with 300 g of pure water, mixed with the previous activated carbon treatment solution, neutralized with 1M NaOH aqueous solution, and about 7900 g of product is prepared with a pH of 7. Obtained. The final acrylamide concentration in the product after the activated carbon treatment was 50.6% by weight.

90 mL of methanol was added to 10 mL of the obtained acrylamide aqueous solution, and the transmittance at 360 nm was measured. In either case, the transmittance was 99.9% or more, and the presence of a polymer was not recognized.

In the preservation step, 100 g of this acrylamide aqueous solution was subjected to aeration treatment for 30 days in a constant temperature bath at 20 ° C. at a flow rate of 1 m ³ / h. After 30 days, aeration was stopped and the dissolved oxygen concentration was measured, and it was 8 ppm. Even when 90 mL of methanol was added to 10 mL of the obtained treatment solution, it did not become cloudy and the presence of a polymer was not observed. The obtained results are shown in Table 1. Further, when an acrylamide polymer was produced in the same manner as in Example (1-1) and a water solubility test was performed on the obtained acrylamide polymer, the content of insoluble matter was 0.7%, which was good. It showed water solubility.

[Comparative Example 5]
In the storage step of Example 5, the same treatment as in Example 5 was performed except that nitrogen having a purity of 99.9% was used instead of using air to obtain a treatment liquid. The dissolved oxygen concentration of this treatment liquid was 0.08 ppm. When 90 mL of methanol was added to 10 mL of the obtained treatment solution, it became cloudy and the presence of a polymer was observed.

[Example 6]
In Example (1-1), it was carried out except that the oxygen was dissolved when the acrylonitrile concentration in the first reaction step reached 0.8% by weight and the dissolved oxygen concentration was changed from 8 ppm to 1.2 ppm. Acrylamide was produced in the same manner as in Example (1-1). At this time, the dissolved oxygen concentration in the second reaction step was 1.0 ppm. Furthermore, Example 6 was implemented several times.

[Comparative Example 6]
In Example (1-1), except that the oxygen was dissolved when the acrylonitrile concentration in the first reaction step reached 0.8% by weight, and the dissolved oxygen concentration was changed from 8 ppm to less than 1 ppm. Acrylamide was produced in the same manner as (1-1). At this time, the dissolved oxygen concentration in the second reaction step was less than 1.0 ppm. Further, Comparative Example 6 was performed a plurality of times.

In Example 6 and Comparative Example 6, that is, in the first reaction step of Example (1-1), the conversion rate to acrylamide at the outlet of the first reactor was 98%, and at the outlet of the first reactor. The same procedure as in Example (1-1) was performed except that the acrylonitrile concentration in the first reactor was 0.8% by weight and that the gas vented to the first reactor was a mixed gas of nitrogen and air instead of air. went. The proportion of air in the mixture was 15% and 5%, respectively. At this time, the dissolved oxygen concentrations in the reaction solution at the outlet of the first reactor were 1.2 ppm and less than 1.0 ppm, respectively.

Here, the reaction solution in the first reactor was filtered with filter paper to remove the cells. 90 mL of methanol was added to 10 mL of the obtained filtrate, and the transmittance at 360 nm was measured (methanol test). The transmittance was 99.9% or more when the dissolved oxygen concentration was 1.2 ppm (Example 6), and the presence of a polymer was not observed, but the dissolved oxygen concentration was less than 1.0 ppm (comparison). In Example 6), it was usually 99.9% or more, but it became 98.5% at a rate of about once in 10 times, and the presence of a polymer was sometimes observed.

Further, when the acrylamide polymer produced from the acrylamide aqueous solution obtained by operating the second reaction step and the purification step in the same manner as in Example (1-1) was evaluated by a water solubility test, the transmittance was determined by the first reaction. When the dissolved oxygen concentration was 1.2 ppm in the process (Example 6), the content of insoluble matter was 0.3%, indicating good water solubility. On the other hand, when the dissolved oxygen concentration was less than 1.0 ppm in the first reaction step (Comparative Example 6), the content of insoluble matter was 4% at a rate of about once every 10 times, resulting in quality problems. . The obtained results are shown in Table 1.

Claims

When producing a reaction solution containing an amide compound having an unsaturated bond from an aqueous solution containing a nitrile compound using a catalyst containing an enzyme capable of producing an amide compound from a nitrile compound, and / or using the catalyst, a nitrile When storing a reaction liquid containing an amide compound having an unsaturated bond produced from an aqueous solution containing the compound, the oxygen in the reaction liquid is 1 ppm by weight or more and has a saturated oxygen concentration or less. A method for stabilizing an amide compound.
2. The stabilization method according to claim 1, wherein when the nitrile compound in the reaction solution is less than 1 wt%, oxygen is dissolved in the reaction solution at a concentration of 1 wt ppm or more and a saturated oxygen concentration or less.
The stabilization method according to claim 1 or 2, wherein oxygen is dissolved at 1 ppm by weight or more and a saturated oxygen concentration or less when the pH of the reaction solution is 3 or more and less than 7.
The stabilization method according to any one of claims 1 to 3, wherein the nitrile compound is (meth) acrylonitrile and the amide compound is (meth) acrylamide.
The stabilization method according to any one of claims 1 to 4, wherein the concentration of the polypeptide contained in the reaction solution is 0.1 to 500 ppm by weight.
The stabilization method according to any one of claims 1 to 5, wherein the enzyme is nitrile hydratase.
The stabilization method according to claim 6, wherein the nitrile hydratase is derived from the genus Pseudonocardia.
An amide compound having an unsaturated bond, which is obtained through the stabilization method according to any one of claims 1 to 7.
A polyamide compound obtained by polymerizing an amide compound having an unsaturated bond obtained through the stabilization method according to any one of claims 1 to 7.