JP6020741B1 - Method for producing acrylamide aqueous solution and acrylamide polymer - Google Patents

Abstract

A technique for polymerizing acrylamide in an acrylamide aqueous solution as a technique for obtaining a high-quality acrylamide polymer in a short time, characterized in that the acrylamide aqueous solution contains 25 mg or more of oxazole per 1 kg of acrylamide. Provide a way to do it. The acrylamide aqueous solution may further contain a magnesium compound. Acrylamide is preferably produced by hydrating acrylonitrile in the presence of a biocatalyst.

Description

  The present invention relates to an aqueous acrylamide solution and a method for producing an acrylamide polymer. More specifically, the present invention relates to an acrylamide aqueous solution containing oxazole at a high concentration and a method for producing an acrylamide polymer by a polymerization reaction of acrylamide using the aqueous solution.

  Acrylamide polymers are used in many applications such as polymer flocculants, papermaking agents, soil conditioners, oil recovery agents, drilling mud water thickeners and polymer absorbers. In any of these applications, a high molecular weight acrylamide polymer is desired. Moreover, industrially, in order to improve productivity, it is desired to manufacture an acrylamide polymer in a shorter time.

  As a method for producing an acrylamide polymer in a short time, for example, a method of adding a manganese compound into acrylamide is known (Patent Document 1).

JP 2003-306506 A

  However, manganese sulfate generally used as a manganese compound is not only difficult to handle due to deliquescence, but also has the disadvantage that it causes coloring of the acrylamide polymer and lowers the quality of the acrylamide polymer.

  Accordingly, the main object of the present invention is to provide a technique for obtaining a high-quality acrylamide polymer in a short time.

  As a result of intensive studies, the inventor has found that a high-quality acrylamide polymer can be obtained in a short time without using a manganese compound by containing a predetermined amount of oxazole in an acrylamide aqueous solution. The invention has been completed.

That is, the present invention provides the following [1] to [10].
[1] An aqueous acrylamide solution containing 25 mg or more of oxazole per 1 kg of acrylamide.
[2] The aqueous acrylamide solution of [1] containing 0.2 to 40 mg of magnesium in terms of magnesium metal with respect to 1 kg of acrylamide.
[3] The acrylamide aqueous solution according to [1] or [2], wherein the silicon content relative to 1 kg of acrylamide is 120 mg or less.
[4] The acrylamide aqueous solution according to any one of [1] to [3], wherein the acrylamide concentration is 25 to 60% by mass.
[5] The acrylamide aqueous solution according to any one of [1] to [4], wherein acrylamide is acrylamide formed by hydrating acrylonitrile in the presence of a biocatalyst.
[6] Method for producing acrylamide polymer by polymerizing acrylamide contained in acrylamide aqueous solution to produce acrylamide polymer, using acrylamide aqueous solution containing 25 mg or more oxazole per 1 kg of acrylamide as acrylamide aqueous solution .
[7] The method for producing an acrylamide polymer according to [6], wherein an acrylamide aqueous solution containing 0.2 to 40 mg of magnesium in terms of magnesium metal is used per 1 kg of acrylamide as the acrylamide aqueous solution.
[8] The method for producing an acrylamide polymer according to [6] or [7], wherein an acrylamide aqueous solution having a silicon content of 120 mg or less relative to 1 kg of acrylamide is used as the acrylamide aqueous solution.
[9] The method for producing an acrylamide polymer according to any one of [6] to [8], wherein an acrylamide concentration in the acrylamide aqueous solution is 25 to 60% by mass.
[10] The method for producing an acrylamide polymer according to any one of [6] to [9], wherein acrylamide is produced by hydrating acrylonitrile in the presence of a biocatalyst.

  According to the present invention, a technique for obtaining a high-quality acrylamide polymer in a short time is provided.

  Oxazole is sometimes added as a stabilizer in acrylonitrile, which is a raw material for acrylamide. However, when oxazole is contained in acrylonitrile, there is a problem that acrylonitrile is colored over time and acrylamide obtained by hydrating acrylonitrile is also colored. That is, conventionally, it has been considered that the smaller the content of oxazole, both in acrylamide and in acrylonitrile, which is the raw material, is preferable.

  Contrary to such common technical knowledge, the present inventors can manufacture a high-quality acrylamide polymer in a short time without using a manganese compound by adding a high concentration of oxazole to an acrylamide aqueous solution. Unexpectedly found.

(1) Acrylamide aqueous solution (1-1) Acrylamide The concentration of acrylamide in the acrylamide aqueous solution is not particularly limited, and is preferably 25 to 60% by mass, more preferably 30 to 55% by mass, and 40 to 55. More preferably, it is mass%.

  By setting the acrylamide concentration to 25% by mass or more, the tank volume used for storage and storage can be reduced, and the transportation cost can be reduced, which is industrially advantageous from an economic viewpoint. In addition, by setting the acrylamide concentration to 60% by mass or less, it is possible to prevent acrylamide crystals from precipitating at around room temperature, eliminating the need for a device for controlling the temperature of the acrylamide aqueous solution. Excellent in properties.

  The pH (25 ° C.) of the acrylamide aqueous solution is not particularly limited as long as it does not affect the quality of acrylamide. The pH is preferably 4 to 10, more preferably 5 to 9, and still more preferably 6 to 8.

  Acrylamide may be acrylamide produced by a known method, but acrylamide produced by hydrating acrylonitrile in the presence of a biocatalyst is preferable because it has few reaction by-products and high purity.

(1-2) Oxazole The acrylamide aqueous solution of the present invention contains 25 mg or more of oxazole with respect to 1 kg of acrylamide. The content of oxazole is preferably 26 to 100 mg, more preferably 28 to 80 mg, and even more preferably 30 to 60 mg per 1 kg of acrylamide.

  By setting the content of oxazole to 25 mg or more per 1 kg of acrylamide, the polymerization time for polymerizing acrylamide to obtain an acrylamide polymer can be shortened (acrylamide can be polymerized in a short time). , Production efficiency can be improved. On the other hand, by setting the content of oxazole in the acrylamide aqueous solution to 100 mg or less with respect to 1 kg of acrylamide, it is possible to suppress an increase in the insoluble content of the acrylamide polymer obtained by polymerizing acrylamide. It is possible to prevent deterioration in quality of coalescence.

  In order to adjust the content of oxazole to the above-mentioned range, an amount of oxazole obtained by subtracting the amount of oxazole contained in the acrylamide aqueous solution to be used from the target oxazole content in the acrylamide aqueous solution to be used. It may be added to. A commercially available oxazole may be used, and oxazoles produced by various methods may be used. Examples of the synthesis method of oxazole include Robinson-Gabriel synthesis, Fischer oxazole synthesis, Bredereck reaction and the like.

  The concentration of oxazole in the acrylamide aqueous solution can be quantified by gas chromatography (for example, using a DV225 (manufactured by Argent Technologies) column).

(1-3) Magnesium The acrylamide aqueous solution may further contain magnesium. When the acrylamide aqueous solution further contains magnesium, the effect of the present invention can be further enhanced.

  In this specification, content of magnesium is shown as magnesium metal conversion. Magnesium metal conversion means the mass of magnesium metal contained in the magnesium compound. Although content of magnesium is not particularly limited, for example, it is preferably 0.2 to 40 mg, more preferably 0.6 to 20 mg, and more preferably 1.0 to 10 mg with respect to 1 kg of acrylamide. Further preferred.

  By including 0.2 mg or more of magnesium with respect to 1 kg of acrylamide, the polymerization time of acrylamide can be further shortened. Moreover, the reason why the magnesium content is 40 mg or less with respect to 1 kg of acrylamide is that it is difficult to obtain a further dramatic improvement in effect.

  Magnesium may be contained as a compound, and its form and type are not limited. For example, magnesium sulfate, magnesium chloride, magnesium phosphate, magnesium acetate and the like can be mentioned. Among these, magnesium sulfate, magnesium chloride and the like are preferable.

  A commercially available magnesium compound may be used, or a magnesium compound synthesized by a known method may be used. When the addition amount to the acrylamide aqueous solution is extremely small, a solution in which a magnesium compound is dissolved or dispersed in advance can be added so that the addition is easy. At this time, water may be used as the diluent, but if it is not preferable to reduce the acrylamide concentration by adding the magnesium compound diluent, the magnesium compound is diluted in an aqueous acrylamide solution of the desired concentration, and this diluted solution is added to the acrylamide. You may add to aqueous solution.

The magnesium content in the acrylamide aqueous solution can be calculated based on the magnesium concentration obtained by using ion chromatography, for example. More specifically, it can be calculated as follows.
-Column used: TSKgel IC-Cation
Eluent: 5 mM HNO ₃ +0.5 mM histidine Standard solution: Cation mixed standard solution II (Kanto Chemical Co., Inc.) Magnesium concentration: 5 mg / L
Measurement operation: (a) Dilute the sample to 1/10 with deionized water. (B) Add diluted data and cation mixed standard solution II to the column for analysis. (C) The magnesium-derived peak area of the obtained diluted sample is compared with the magnesium-derived peak area contained in the cation mixed standard solution II, and the magnesium concentration in the sample is calculated.

(1-4) Silicon In the acrylamide aqueous solution, the silicon content is preferably 120 mg or less, more preferably 100 mg or less, and even more preferably 80 mg or less with respect to 1 kg of acrylamide. In the acrylamide aqueous solution, a high-viscosity acrylamide polymer can be obtained by setting the silicon content to 120 mg or less relative to 1 kg of acrylamide.

In the present specification, silicon includes silicon alone, silicic acid represented by [SiO _x (OH) _4-2x ] _n (which may be either insoluble silicic acid or soluble silicic acid), silicon dioxide, silicon oxide, and the like. Including silicon contained, the form is not limited.

  The method for measuring the silicon concentration in the acrylamide aqueous solution is not particularly limited, and a known method such as a molybdenum blue method can be used. The molybdenum blue method is as follows. Silicon partially becomes silicic acid in water. Silicic acid reacts with molybdic acid in an acidic solution having a pH of 1.2 to 1.5 to form a yellow silicomolybdic acid complex. When this silicomolybdic acid complex is reduced with a reducing agent such as ascorbic acid, it produces a deep blue color and the concentration can be measured by absorbance.

  The method for reducing silicon is not particularly limited, and one or more purification means selected from a filter, an ion exchange resin, a reverse osmosis membrane, electrodeionization, and activated carbon can be used. Examples of the anion exchange resin include gel type strongly basic anion exchange resin (SA10A, CI type manufactured by Mitsubishi Chemical Corporation), macroporous type (high porous type) strongly basic anion exchange resin (HPA25, CI type manufactured by Mitsubishi Chemical Corporation). ) And the like. These purifications may be performed in combination of one or more, and may be performed once or a plurality of times (twice or more). Moreover, you may use the raw material with a low silicon concentration which does not require such a refinement | purification process.

(1-5) Hydrocyanic acid The aqueous acrylamide solution preferably has a content of cyanic acid of 1.5 mg or less per 1 kg of acrylamide. By setting the content of hydrocyanic acid to 1.5 mg or less with respect to 1 kg of acrylamide, it is possible to prevent the acrylamide polymer obtained by polymerizing acrylamide from being colored and deteriorating in quality.

  Cyanic acid in the acrylamide aqueous solution is brought in as an impurity of acrylonitrile which is the raw material. Generally, acrylonitrile that is commercially available contains 0.1 to 5 mg of hydrocyanic acid with respect to 1 kg of acrylonitrile. Therefore, with respect to 1 kg of acrylamide produced by hydrating acrylonitrile, 0.07 to 3. It will contain 7 mg.

  Therefore, in order to remove or reduce the hydrocyanic acid concentration in the acrylamide aqueous solution, it is preferable to remove or reduce the hydrocyanic acid in the raw material acrylonitrile to 1.5 mg or less with respect to 1 kg of acrylonitrile.

  The method for removing or reducing hydrocyanic acid in acrylonitrile is not particularly limited, and can be performed by a known method. For example, a method using an anion exchange resin, a method for extracting hydrocyanic acid with an alkaline aqueous solution (Japanese Patent Laid-Open No. 2001-288256), a method for adding hydrocyanic acid to acrylonitrile by adding an alkali (Japanese Patent Laid-Open No. 11-123098), etc. Can be mentioned.

  The concentration of hydrocyanic acid in the acrylamide aqueous solution can be measured by a capillary gas chromatograph (for example, DV225 (manufactured by Argent Technologies)) equipped with an NPD detector (for example, Argent Technologies). Further, the concentration of hydrocyanic acid can also be calculated from the molecular weight ratio of acrylonitrile and acrylamide by measuring the hydrocyanic acid concentration in the raw material acrylonitrile. Further, as a method for measuring the concentration of hydrocyanic acid, a method (ASTM 1178-87) in which acrylonitrile is extracted into an alkaline aqueous solution and then titrated with an aqueous silver nitrate solution is also included.

(2) Preparation of acrylamide aqueous solution As the acrylamide aqueous solution, a commercially available one may be used, or one prepared by various methods may be used. Examples of the method for producing acrylamide include a sulfuric acid hydration method, a copper catalyst method, a microbial method using a biocatalyst, or an enzyme method.

  The acrylamide aqueous solution may be prepared using acrylamide produced by any of the production methods. However, since acrylamide with a high degree of reaction by-products can be obtained, acrylonitrile is hydrated in the presence of a biocatalyst. It is preferred to use the acrylamide produced.

  In the present specification, the biocatalyst includes animal cells, plant cells, cell organelles, microbial cells (live cells or dead) containing an enzyme that catalyzes a target reaction, or processed products thereof. Processed products include crude enzymes or purified enzymes extracted from cells, cell organelles or fungus bodies, animal cells, plant cells, cell organelles, fungus bodies (live or dead) or enzymes themselves. And those immobilized by a crosslinking method, a carrier binding method or the like.

  Examples of animal cells include monkey cells COS-7, Vero, CHO cells, mouse L cells, rat GH3, and human FL cells. Examples of plant cells include tobacco BY-2 cells.

  Examples of the fungus body include, for example, Nocardia, Corynebacterium, Bacillus, Pseudomonas, Micrococcus, Rhodococcus, and Rhodococcus ) Genus, Xanthobacter genus, Streptomyces genus, Rhizobium genus, Klebsiella genus, Enterobacter genus, Erwiniaon genus, Erwiniaon genus Citrobacter genus, a Romobakuta (Achromobacter) genus, Agrobacterium (Agrobacterium) genus or microorganisms belonging to the shoe de Nocardia (Pseudonocardia) genus, and the like. Among these, it is more preferable to use microorganisms belonging to the genus Rhodococcus and Pseudonocardia.

  These animal cells, plant cells, organelles, or fungus bodies include not only wild-type cells but also those in which genes are modified.

  The inclusion method, which is one of the immobilization methods, is a method in which bacterial cells or enzymes are wrapped in a fine lattice of a polymer gel or covered with a semipermeable membrane. The crosslinking method is a method in which an enzyme is crosslinked with a reagent having two or more functional groups (polyfunctional crosslinking agent). The carrier binding method is a method of binding an enzyme to a water-insoluble carrier. Examples of the immobilization carrier used for immobilization include glass beads, silica gel, polyurethane, polyacrylamide, polyvinyl alcohol, carrageenan, alginic acid, agar, and gelatin.

  Examples of the enzyme include nitrile hydratase produced by the microorganism and the like. A method for producing acrylamide by hydrating acrylonitrile in the presence of a biocatalyst is not particularly limited, and acrylonitrile and an enzyme may be contacted in an environment of water or an aqueous solution. For example, acrylamide can be produced by the method described in WO2009 / 113654.

  The aqueous acrylamide solution may contain a biocatalyst or may have a biocatalyst removed. When the biocatalyst is contained in the acrylamide aqueous solution, the biocatalyst is preferably contained in an amount of 1 to 14000 mg by dry weight with respect to 1 kg of the acrylamide aqueous solution. When the aqueous acrylamide solution contains this amount of biocatalyst, the effect of preventing polymerization of acrylamide is enhanced when the aqueous acrylamide solution is stored or stored.

  When producing an acrylamide polymer, if it is not preferable that the biocatalyst is present in the acrylamide aqueous solution, the biocatalyst may be separated from the acrylamide aqueous solution. Examples of the method for separating the biocatalyst from the acrylamide aqueous solution include centrifugation, membrane filtration, cake filtration, coagulation separation, and activated carbon treatment.

(3) Production of acrylamide polymer An acrylamide polymer can be obtained by polymerizing acrylamide in an acrylamide aqueous solution containing the above oxazole or the like. The acrylamide polymer may be obtained by homopolymerizing acrylamide, or may be obtained by copolymerizing at least one unsaturated monomer copolymerizable with acrylamide.

  Examples of unsaturated monomers copolymerizable with acrylamide include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and their salts; acrylamide derivatives, acrylate derivatives, acrylonitrile, methacrylates. Examples include olefins such as nitrile, vinyl acetate, vinyl chloride, vinylidene chloride, ethylene, propylene, and butene; styrene; α-methylstyrene; butadiene; isoprene. These monomers may be used individually by 1 type, and may use 2 or more types together.

  The method for producing the acrylamide polymer is not particularly limited, and can be appropriately selected according to the type of monomer used. Examples include aqueous solution polymerization and emulsion polymerization.

  A radical polymerization initiator can be used as the polymerization initiator. As radical polymerization initiators, peroxides such as potassium persulfate, ammonium persulfate, hydrogen peroxide, benzoyl peroxide; azo free radical initiation such as azobisisobutyronitrile, azobis- (2-amidinopropane) dichloride, etc. Agents: So-called redox catalysts using the above-mentioned peroxides in combination with reducing agents such as sodium bisulfite, triethanolamine, and ferrous ammonium sulfide. The above-mentioned polymerization initiators may be used alone or in combination of two or more.

  The amount of the polymerization initiator (when using a plurality of polymerization initiators, the total amount) can be in the range of 0.001 to 5% by mass, preferably 0, based on the total mass of the monomers. The range is from 0.05 to 1% by mass.

  When a single polymerization initiator is used, the polymerization temperature is preferably in the range of −3 to 120 ° C., more preferably in the range of −3 to 90 ° C. The polymerization temperature does not always need to be maintained at a constant temperature, and can be appropriately changed as the polymerization proceeds. As the polymerization proceeds, heat of polymerization is generated and the reaction temperature tends to increase, so that it can be cooled as necessary.

  The atmosphere during the polymerization is not particularly limited, but from the viewpoint of rapidly proceeding the polymerization, it is preferable to carry out the polymerization in an inert gas atmosphere such as nitrogen gas. The polymerization time is not particularly limited, but can usually be in the range of 1 to 20 hours.

  The pH of the aqueous solution at the time of polymerization is not particularly limited, and it may be adjusted and polymerized as necessary. Examples of pH adjusters that can be used in this case include alkalis such as sodium hydroxide, potassium hydroxide and ammonia; mineral acids such as phosphoric acid, sulfuric acid and hydrochloric acid; organic acids such as formic acid and acetic acid.

  Examples of the present invention will be described in detail below, but the present invention is not limited to these examples. The following “%” indicates mass%.

<Preparation Example 1: Preparation of biocatalyst>
Rhodococcus rhodochros J-1 strain having nitrile hydratase activity (Rhodococcus rhodochrous J-1: FERM BP-1478) (Japanese Patent Publication No. 6-55148) was prepared by using 2% glucose, 1% urea, 0.5% peptone, The cells were aerobically cultured in a medium (pH 7.0) containing 0.3% yeast extract and 0.05% cobalt chloride.

  To 500 g of a cell suspension (20% in terms of dry cell) obtained by washing with 50 mM phosphate buffer (pH 7.0), 20% acrylamide, 2% methylenebisacrylamide and 2-dimethylamino 500 g of a monomer mixed solution containing 2% propylmethacrylamide was added and well suspended.

  To this, 2 g of 5% ammonium persulfate and 2 g of 50% N, N, N ′, N′-tetramethylethylenediamine were added for polymerization and gelation. After cutting this into 0.5-1 mm square cubes, the cells were washed 5 times with 1 L of 0.5% sodium sulfate to obtain immobilized microbial cell particles as an acrylamide production catalyst.

<Preparation Example 2: Preparation of acrylamide aqueous solution>
Four jacketed stirring tanks with an inner volume of 1 L and one jacketed stirring tank with an inner volume of 5 L were connected in series so that the overflowed reaction liquid entered the next tank. It controlled so that the temperature of the reaction liquid in each reaction tank might be 20 degreeC.

  As the raw material water, water obtained by adding a sodium acrylate aqueous solution (pH 7.0) to pure water permeated through a filter membrane (organo PF element 5 μm) so that the acrylic acid concentration becomes 100 ppm was used.

  In the first tank, the raw water, the immobilized bacterial cell particles prepared in Preparation Example 1 and acrylonitrile (manufactured by Mitsubishi Rayon Co., Ltd.) were continuously added at 120 mL / hr, 0.4 g / hr and 40 mL / hr, respectively. . Furthermore, only acrylonitrile was added to the 2nd tank, the 3rd tank, and the 4th tank at 30 mL / hr, 10 mL / hr, and 10 mL / hr, respectively. Nothing was added to the fifth tank, and the reaction liquid with the catalyst flowing in from the fourth tank was stirred.

  Each reaction vessel was stirred so that the catalyst was uniformly dispersed, and the reaction solution and the catalyst were accompanied without distinction even in the overflow portion. In the reaction solution flowing out from the fifth tank, the immobilized cells were removed with a 180 mesh wire net to produce an acrylamide aqueous solution. This reaction was continued for 10 days, and 50% acrylamide aqueous solution was collected from about 5 days after the reaction was stabilized (about 25 L).

  The obtained 50% aqueous acrylamide solution was diluted 4 times with pure water, and the concentration of oxazole in the diluted aqueous acrylamide solution was measured with a gas chromatograph (DV225 (manufactured by Argentent Technologies)). Of 10 mg.

<Example 1>
Reagent oxazole (Sigma-Aldrich) was added to a 50% acrylamide aqueous solution to adjust to contain 30 mg of oxazole per 1 kg of acrylamide.

  When the magnesium concentration in the 50% acrylamide aqueous solution was measured by ion chromatography, it was below the detection limit (less than 0.2 mg with respect to 1 kg of acrylamide).

  The silicon concentration in a 50% acrylamide aqueous solution was measured using a HACH absorptiometer (manufactured by HACH; DR5000) silica measurement kit (manufactured by HACK; silica HR, HACH1087), and the silicon content was determined from the obtained silicon dioxide concentration. When converted, it was 5 mg per 1 kg of acrylamide.

  384 g of acrylamide aqueous solution (192 g of pure acrylamide) was taken, and ion exchange water was added thereto so that the total amount became 790 g. 4 mL of 4% disodium phosphite solution and 1.9 mL of 2% ethylenediaminetetraacetic acid tetrasodium salt solution were added and stirred.

  The aqueous solution was cooled and adjusted to −2 ° C., bubbled with nitrogen gas to remove oxygen in the solution, the temperature was 0 ± 1 ° C., and transferred to a dewar.

  Thereafter, 1.6 mL of 10% 2,2'-azobis (2-amidinopropane) dihydrochloride solution was added, and after 30 seconds, 0.34 mL of 1% perbutyl H69 solution was added.

  Thereafter, 0.17 mL of 1% sodium nithionite solution was added, and after 25 seconds, 0.38 mL of 0.1% ferrous sulfate solution was added. The polymerization proceeded adiabatically and allowed to stand for about 70 minutes after reaching the peak temperature (about 70 ° C.).

〔Evaluation of the physical properties〕
(1) Polymerization time The polymerization behavior is shown by taking the polymerization time [min] on the horizontal axis and the liquid temperature [° C.] on the vertical axis, with 0 minutes at the start of polymerization (when ferrous sulfate solution is added). Recorded. The temperature of the polymerization liquid is 50 ° C. and 60 ° C. are connected by a straight line, and the intersection time between the line obtained by extending the straight line and the line obtained by drawing the maximum liquid temperature at the time of polymerization parallel to the horizontal axis is the polymerization time θ. It was defined as [minutes].

  The polymerization time θ was 15.5 minutes.

(2) Color tone / viscosity The obtained acrylamide polymer hydrogel was divided into small bowls, ground with a crusher of 5 mmφ, and dried with an air dryer set at 60 ° C. for 14 hours. After drying, the mixture was pulverized with a high-speed rotary blade pulverizer having a diameter of 2 mmφ to obtain a dry powdery acrylamide polymer. Further, this was passed through a sieve having an opening of 1 mm to remove a powder of 1 mm or more.

  As a result of visually observing the powder of the acrylamide polymer, it was white and the color tone was good.

  488 g of pure water was weighed into a 500 mL beaker, and 5.10 g of dry powdery acrylamide polymer was added while stirring at a stirring speed of 240 rpm, followed by stirring at room temperature for 4 hours. Viscosity was measured at 25 ° C. using a B-type viscometer. Viscosity is an indicator of the molecular weight of the polymer.

  The viscosity of the acrylamide polymer was 3590 [mPa · S], which was a good value.

<Example 2>
In the same manner as in Example 1, except that magnesium sulfate heptahydrate was added to the 50% aqueous acrylamide solution used in Example 1 so that 0.5 mg of magnesium was contained in 1 kg of acrylamide. Was polymerized.

  When the polymerization time θ was measured in the same manner as in Example 1, it was 5.7 minutes.

  As a result of visual observation of the acrylamide polymer powder in the same manner as in Example 1, it was white and the color tone was good.

  When the viscosity of the acrylamide polymer was measured in the same manner as in Example 1, it was 3625 [mPa · S], which was a good value.

<Comparative Example 1>
The same procedure as in Example 2 was performed except that an acrylamide aqueous solution containing 10 mg of oxazole per 1 kg of acrylamide was used (that is, the acrylamide aqueous solution obtained in Preparation Example 2 was used without adding oxazole). .

  The polymerization time θ was measured in the same manner as in Example 1. As a result, it was 45.6 minutes, and the progress of polymerization was slower than in Examples 1 and 2.

  As a result of visually observing the powder of the acrylamide polymer in the same manner as in Example 1, it was white and there was no problem with the color tone.

  When the viscosity of the acrylamide polymer was measured in the same manner as in Example 1, it was 3570 [mPa · S], which was a value with no problem.

<Comparative example 2>
The same procedure as in Example 2 was performed except that an acrylamide aqueous solution containing 20 mg of oxazole per 1 kg of acrylamide was used. That is, the reagent oxazole (Sigma Aldrich) was added to the 50% acrylamide aqueous solution obtained in Preparation Example 2 so that 20 mg of oxazole was contained per 1 kg of acrylamide.

  The polymerization time θ was measured in the same manner as in Example 1. As a result, it was 36.0 minutes, and the progress of polymerization was slower than in Examples 1 and 2.

  As a result of visually observing the powder of the acrylamide polymer in the same manner as in Example 1, it was white and there was no problem with the color tone.

  When the viscosity of the acrylamide polymer was measured in the same manner as in Example 1, it was 3570 [mPa · S], which was a value with no problem.

  According to the present invention, by containing a predetermined amount of oxazole in the acrylamide aqueous solution, the polymer can be obtained in a shorter time without deteriorating the quality (color tone, molecular weight) of the acrylamide polymer. Therefore, it can be effectively used to improve productivity in industrial production of acrylamide polymers.

Claims (8)

An aqueous acrylamide solution containing 25 to 100 mg of oxazole and 0.2 to 40 mg of magnesium in terms of magnesium metal per 1 kg of acrylamide. The content of silicon to acrylamide 1kg is less than 120 mg, acrylamide aqueous solution of claim 1 Symbol placement. The acrylamide aqueous solution of Claim 1 or 2 whose acrylamide concentration is 25-60 mass%. The acrylamide aqueous solution according to any one of claims 1 to 3 , wherein the acrylamide is acrylamide formed by hydrating acrylonitrile in the presence of a biocatalyst. In the method of producing an acrylamide polymer by polymerizing acrylamide contained in an acrylamide aqueous solution,
A method for producing an acrylamide polymer, wherein an acrylamide aqueous solution containing 25 to 100 mg of oxazole and 0.2 to 40 mg of magnesium in terms of magnesium metal is used as an acrylamide aqueous solution with respect to 1 kg of acrylamide. The method for producing an acrylamide polymer according to claim 5 , wherein an acrylamide aqueous solution having a silicon content of 120 mg or less per 1 kg of acrylamide is used as the acrylamide aqueous solution. The method for producing an acrylamide polymer according to claim 5 or 6 , wherein the acrylamide concentration in the acrylamide aqueous solution is 25 to 60% by mass. The method for producing an acrylamide polymer according to any one of claims 5 to 7 , wherein acrylamide is produced by hydrating acrylonitrile in the presence of a biocatalyst.