JPH1036329A - Purification of aqueous acrylamide solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly purify an aqueous acrylamide solution by adding an amino acid (salt) to the aqueous acrylamide solution obtained by a catalytically acrylonitrile-hydrating method and subsequently bringing the mixture into contact with an ion exchange resin. SOLUTION: This method for purifying an aqueous acrylamide solution comprises adding an amino acid (salt) such as glycine or alanine, an alkali metal hydroxide and ammonia to the aqueous acrylamide solution obtained by a catalytically acrylonitrile-hydrating method and subsequently bringing the aqueous mixture solution into contact with an ion exchange resin. When the amino acid (salt) is added to the aqueous acrylamide solution, oxygen or an oxygen-containing gas is preferably charged into the aqueous solution. A series of the operations are preferably continuously carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for purifying an aqueous acrylamide solution, and more particularly, to a method for highly purifying an aqueous acrylamide solution by removing impurities from an aqueous acrylamide solution obtained by a catalytic hydration method of acrylonitrile.

[0002]

2. Description of the Related Art Acrylamide is generally used as a metal copper catalyst,
For example, by reacting acrylonitrile with water in the presence of Raney copper or reduced copper, it can be easily obtained in the form of an aqueous solution thereof.

The aqueous acrylamide solution obtained by the above reaction generally contains unreacted acrylonitrile, impurities contained in the raw material acrylonitrile, reaction by-products,
It is usually obtained as containing metal ions such as copper eluted from the catalyst, or if necessary, contamination of the device. Of these, unreacted acrylonitrile can be separated and removed relatively easily by operations such as distillation under reduced pressure.

The above-mentioned acrylamide aqueous solution is generally used when producing an acrylamide polymer having a relatively low molecular weight, for example, a molecular weight of about several hundred thousand, such as used in the field of paper strength enhancers. Is less likely to cause problems.

However, it is very difficult to obtain an acrylamide polymer having a molecular weight of several millions or more than 10 millions, for example, as used in the field of polymer flocculants. In other words, an aqueous solution of acrylamide containing impurities, reaction by-products, or metal ions, etc., is intended to obtain an acrylamide polymer suitable for the above-mentioned applications, if the desired molecular weight is not obtained. In addition, since the polymerization completion time is often fluctuated, the production of the acrylamide polymer is affected. Also, the obtained acrylamide polymer is
Poor solubility in water and poor coagulation ability are not obtained, and high quality products cannot be obtained.

It is said that various impurities such as reducing substances such as 3,3-nitrilotripropionamide by-produced during the catalytic hydration reaction of acrylonitrile affect the polymerization reaction. I have. Further, it is considered that the cause of the deterioration of the water solubility and the decrease of the aggregation ability is a cross-linkable substance such as diacrylimide by-produced during the reaction.

Therefore, these impurities are removed prior to polymerization.
Although it is necessary to remove and purify in advance, as a typical purification method conventionally known, for example, JP-A-52-918
No. 19 discloses a method in which an aqueous acrylamide solution is treated with a strongly acidic cation exchange resin and then further treated with a weakly basic anion exchange resin.

[0008]

However, according to the study of the present inventors, the aqueous solution of acrylamide obtained by the above-mentioned hydration method of acrylonitrile is simply converted into a strong acidic cation exchange resin and a weak base. However, it is still difficult to sufficiently remove the impurities in the aqueous acrylamide solution by the method of treating with an anionic exchange resin.

The present invention provides a method for purifying an aqueous solution of acrylamide obtained by a contact hydration method of acrylonitrile more highly than conventionally known methods. It is an object of the present invention to provide a method for purifying an aqueous acrylamide solution which does not impede the function of bacteria even when the waste liquid produced is treated by, for example, an activated sludge method. It is.

[0010]

Means for Solving the Problems The present inventors have eagerly studied a method of highly removing impurities, reaction by-products, metal ions, and the like contained in an aqueous acrylamide solution obtained by a contact hydration method of acrylonitrile. I have been studying and studying.

As a result, after adding the amino acid or its salt to the aqueous acrylamide solution obtained by the above method,
By contacting this with a cation exchange resin and an anion exchange resin, it was found that the acrylamide aqueous solution could be purified to a very high degree, and it was found that the above-mentioned problems could be solved.

Further, in the case where a method of adding an alkali metal hydroxide and / or ammonia in addition to adding an amino acid or a salt thereof and then contacting it with an ion-exchange resin is employed, it is even more preferable that an aqueous acrylamide solution is purified. The inventors have also found that the present invention can be performed, and have completed the present invention.

That is, the present invention provides an aqueous solution of acrylamide obtained by a contact hydration method of acrylonitrile,
Disclosed is a method for purifying an aqueous acrylamide solution, which comprises adding an amino acid or a salt thereof and then contacting the acrylamide aqueous solution with an ion-exchange resin, and further includes adding an alkali metal hydroxide in addition to the addition of the amino acid or a salt thereof. Can be obtained by the method described in (1) Contacting with an ion exchange resin after addition, the method described in (2) in addition to the addition of an amino acid or a salt thereof, and also contacting the ion exchange resin after addition of ammonia, and the contact hydration method of acrylonitrile. An aqueous acrylamide solution, a method for purifying an aqueous acrylamide solution comprising adding an amino acid or a salt thereof, an alkali metal hydroxide and ammonia, and then contacting with an ion exchange resin; adding or adding an amino acid or a salt thereof to the aqueous acrylamide solution In this case, oxygen or oxygen-containing gas is contained in the aqueous solution. Wherein the method for purifying an aqueous acrylamide solution according to any of the above-mentioned, adding an amino acid or a salt thereof to the aqueous acrylamide solution, and continuously contacting the aqueous solution with an ion-exchange resin, A method for purifying an aqueous acrylamide solution according to any of the above to any one of, and
The amino acid is glycine or alanine,
It discloses a method for purifying an aqueous acrylamide solution according to any of the above.

When these methods of the present invention are employed, impurities, reaction by-products, metal ions, and the like in the acrylamide aqueous solution can be removed at a very high level. It is also very easy to obtain a high-molecular-weight acrylamide polymer suitable for use. Therefore, it is extremely advantageous not only in the production of an acrylamide polymer, but also in the application thereof.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The type of acrylamide aqueous solution used in the method of the present invention is not particularly limited, and those produced by a wide range of methods can be used. Usually, an aqueous acrylamide solution is synthesized by hydrating acrylonitrile in a liquid phase in the presence of a metallic copper catalyst such as Raney copper or reduced copper. The copper metal catalyst is usually used in a suspension state, and a flow-type or batch-type reaction type is adopted.In the case of producing an acrylamide aqueous solution on a commercial scale, a flow-type stirred tank type reactor is used. It is common to do.

The metallic copper as the catalyst may be one whose main component is copper. For example, a Raney copper catalyst obtained by developing a Raney copper alloy with an aqueous alkali solution, or a copper salt in an aqueous solution of formaldehyde, hydrazine, borohydride or the like. A reduced copper catalyst obtained by reduction with sodium chloride or the like can be used. These metal copper catalysts, in order to suppress the decrease in the activity and by-products during use, not only before use,
It is usual to avoid contact with oxygen or oxygen-containing gases even during use.

In the hydration reaction of acrylonitrile, the charge of acrylonitrile: water is 50:50 by weight in terms of suppressing side reactions and preventing formation of a polymer.
Usually, it is in the range of 5 to 95. The reaction temperature can be usually from 30 to 200 ° C, more preferably from 50 to 150 ° C.
Range. Reaction time is usually in the range of 0.5-20 hours,
More preferably, it is in the range of 1 to 3 hours.

The concentration of the aqueous acrylamide solution obtained by the reaction naturally depends on the reaction conditions, but is usually 50% by weight.
It is as follows. After the reaction, the catalyst is separated by filtration or the like, and the unreacted acrylonitrile is removed by distillation of the reaction solution under reduced pressure.

In the method of the present invention, an amino acid or a salt thereof, or an alkali metal hydroxide and / or ammonia is further added to the acrylamide aqueous solution obtained as described above. There is no particular limitation as long as it does, and a wide range can be used. For example, glycine, alanine, β-alanine, valine, leucine, isoleucine, aspartic acid, glutamic acid, serine, threonine, cystine, methionine, phenylalanine, tyrosine, histidine, tryptophan, proline, lysine, arginine, γ-aminobutyric acid, and the like. These are not limited to one kind, and two or more kinds may be used. In the present invention, among these, it is more preferable to use an α-amino acid, specifically glycine or alanine, which exerts a remarkable chelating ability in the present method.

In the present invention, the above-mentioned amino acid may be used in the form of a salt thereof. In this case, the salt is not particularly limited, but is preferably an alkali metal salt of the amino acid, such as a sodium salt or a potassium salt. . Furthermore, by adding an amino acid and an alkali metal hydroxide to an aqueous acrylamide solution, an amino acid salt can be generated in the system, and such an embodiment is also included in the scope of the present invention. The amount of the alkali metal hydroxide for converting the amino acid into a salt is preferably in the range of 0.01 to 1.01 mol per mol of the carboxyl group in the amino acid.

In the method of the present invention, by adding an amino acid or a salt thereof to an aqueous acrylamide solution as described above, the aqueous acrylamide solution can be highly purified in a subsequent ion exchange treatment. In a more preferred embodiment, in addition to the addition of the amino acid or a salt thereof, a method of further adding an alkali metal hydroxide and / or ammonia is included. When this method is employed, the method is included. Oxidation of copper and decomposition of a crosslinkable substance such as by-product diacrylimide can be performed more sufficiently and in a shorter time. Examples of the alkali metal hydroxide in this case include sodium hydroxide and potassium hydroxide. The concentrations of these and ammonia during use are not particularly limited, and any one can be used.

In the present invention, the method of adding an amino acid or a salt thereof, an alkali metal hydroxide and / or ammonia to an aqueous acrylamide solution is not particularly limited. For example, it may be added to a gas phase above an aqueous acrylamide solution. Alternatively, a method of adding to a liquid may be used. In this case, the ammonia may be either liquid or gaseous, or may be an aqueous solution,
There is no limitation to the concentration.

In the present invention, an amino acid or a salt thereof,
Further, when an alkali metal hydroxide and / or ammonia is added in addition to this, it is preferable to add the aqueous solution of acrylamide so that the pH of the aqueous acrylamide solution becomes 8 to 14.
Usually, an aqueous solution of acrylamide obtained by the hydration reaction of acrylonitrile contains 10% of copper ions eluted during the reaction.
Although it contains about 200 ppm, it is considered that the added amino acid or its salt partially forms an ionic bond or a coordinate bond with copper ions. Therefore, the added amino acid or salt thereof is 0.01% based on the contained copper ion.
It is preferable to add the compound in a range of from 20 to 20 moles, more preferably from 0.5 to 10 moles.

When an alkali metal hydroxide and / or ammonia is further added in addition to the addition of an amino acid or a salt thereof, the alkali metal hydroxide and / or ammonia reacts with the contained copper ions. It is good to add in the range of 0.01 to 20 times mol, more preferably 0.01 to 10 times mol. In general, when only an amino acid is added in less than 1 molar amount to the contained copper ion, the pH of the solution often exhibits 5 to 8, and a crosslinkable substance such as diacrylimide present in the solution is used. If the amount used exceeds 20 times the molar amount, the ability to decompose diacrylimide etc. will increase, but the contact with the cation exchange resin in the next step will occur. In this case, the load such as adsorption and removal of the added amino acid or its salt is extremely increased, which is not preferable.

In order to carry out the treatment by adding an amino acid or a salt thereof, or an alkali metal hydroxide and / or ammonia to the acrylamide aqueous solution in addition to the amino acid or a salt thereof, any type such as a flow type or a batch type can be used. The method of the present invention is sufficiently capable of continuously treating an aqueous acrylamide solution in addition to a batch method. In order to purify the acrylamide aqueous solution more efficiently and continuously, it is preferable to employ a flow-type stirring tank type.

In addition, in the method of the present invention, when an amino acid or a salt thereof, and additionally an alkali metal hydroxide and / or ammonia are added, the polymerization of acrylamide is prevented and contained during or after the addition. In order to sufficiently oxidize copper ions, it is preferable that an oxygen-containing gas such as oxygen or air is present in the acrylamide aqueous solution. Specifically, before, during or after the addition of the amino acid or a salt thereof,
Preferably, oxygen or an oxygen-containing gas is passed through the aqueous acrylamide solution. The amount required for oxidation using oxygen or air is usually 0.1 to 10 times the volume of the aqueous acrylamide solution to be treated.

When an amino acid or a salt thereof and an alkali metal hydroxide and / or ammonia are added to an aqueous acrylamide solution for treatment, the temperature is preferably not higher than 60 ° C. which does not deteriorate acrylamide. It is usually carried out with stirring. In addition, the treatment time is not particularly limited, but in an extremely long treatment, a part of acrylamide is hydrolyzed and becomes acrylic acid or the like. The range is 6 hours.

In the method of the present invention, in the above-described treatment, despite the acrylamide aqueous solution being in an alkaline atmosphere, the remaining copper ions do not precipitate as copper hydroxide or the like, and are converted into water-soluble copper complex ions. It is dissolved and can be passed through a cation-exchange resin and an anion-exchange resin as it is in the next step for purification operation, which is industrially very advantageous.

In the present invention, the above-processed
Aqueous solution of amide, then cation exchange resin and anion
The purification treatment is performed by contacting with an exchange resin. Use for this
The cation exchange resin that can be treated as above
Exchange with copper ion in quenched acrylamide aqueous solution
Any possible material can be used, but more
A preferred example is a strongly acidic cation exchange tree.
Amberlite IR-200C and IR-120B (above,
Tokyo Organic Chemical Co., Ltd.), Levatit SP 112, S100
(Above, manufactured by Bayer AG), etc.
Diamond Ion WK10 and DIAION WK20 (Mitsubishi Chemical
Ltd.), Levatit CNP 80 (Bayer)
And those marketed under the trade name. these
Among them, strongly acidic cation exchange resins are very preferably used.
It is. And, as a counter ion, Na ⁺Ion and K⁺I
Ion exchange is not impossible even if it is on, but these are
Low exchange efficiency of copper ions due to selectivity of ion exchange
And that these ions cannot be mixed into the product.
Is usually H⁺Preferably, ions are used.

On the other hand, any anion exchange resin can be used as long as it can be ion-exchanged with an organic acid such as acrylic acid as a reaction by-product. Diaion PA 304, PA 306, PA 404, PA 408
(Diaion WA30 and WK20 (Mitsubishi Chemical Corporation), which are weakly basic anion exchange resins, such as Mitsubishi Chemical Corporation, Levatit MP 500 (Bayer Corporation), and Levatit Examples include those commercially available under the trade name of MP62 (manufactured by Bayer AG). Among these, a weakly basic anion exchange resin is very preferably used. Then, as the counter ions OH ^- preferably used ion. In the case of strongly basic anion exchange resins, when acrylamide is present in an aqueous solution, a part of the acrylamide is hydrolyzed and a small amount of acrylic acid may be by-produced. It is more preferable to use an exchange resin. Since these phenomena are likely to occur in a strongly acidic cation exchange resin as well, the flow order of the acrylamide aqueous solution is as follows after contact with the cation exchange resin.
It is preferable to make contact with an anion exchange resin.

The temperature of the aqueous acrylamide solution when it is brought into contact with these may be lower than the service temperature of the cation exchange resin and the anion exchange resin, and may be a temperature at which acrylamide does not deteriorate, and is usually 60 ° C. or lower. Is preferred.

The contact operation with the ion exchange resin in the method for purifying an aqueous acrylamide solution of the present invention is usually carried out by packing the ion exchange resin into a column or the like and passing the aqueous acrylamide solution through the column. In this case, the flow direction of the acrylamide aqueous solution is preferably a downflow type in which the aqueous solution flows downward from above the packed tower. In addition, the flow velocity is the space velocity (hereinafter referred to as SV).
In general, the concentration may be in the range of ¹ to 50 hr ^-1 , and more preferably in the range of 3 to 10 hr ^-1 .

The method of regenerating the ion exchange resin used for the purification of the aqueous acrylamide solution is usually 3 to 10% by weight if the strongly acidic cation exchange resin is regenerated.
Of hydrochloric acid in an amount of 1 to 10 times the total exchange capacity. On the other hand, a weakly basic anion exchange resin can be regenerated by contacting an aqueous solution of sodium hydroxide of 2 to 8% by weight with an amount of 1 to 6 times the total exchange capacity. In any case, the liquid passing rate at the time of the regeneration operation is preferably performed in the range of ¹ to 40 hr ^-1 by SV, so that the adsorbed cation component such as copper ion and the anion component such as organic acid can be recovered. . Further, these treated ion exchange resins can be sufficiently used repeatedly.

[0034]

EXAMPLES Hereinafter, the method for purifying an aqueous acrylamide solution of the present invention will be described in more detail with reference to examples. In the following, "%" and "ppm" are all by weight.

Production Example 1 A Raney copper catalyst (trade name: CDT-60: manufactured by Kawaken Fine Chemical Co., Ltd.) was placed in a four-necked flask having an inner volume of 1 liter.
g of acrylonitrile, 250 g of acrylonitrile in which nitrogen gas was previously introduced and nitrogen gas was passed through to remove dissolved oxygen.
Then, 250 g of ion-exchanged water was added and reacted at 70 ° C. for 2 hours to produce 81 g of acrylamide. After the catalyst was separated from the reaction solution by filtration with a filter, the catalyst was distilled under reduced pressure and concentrated to obtain a crude acrylamide aqueous solution. The acrylamide concentration of this aqueous solution was 33%, the residual concentration of acrylonitrile was 0.01% or less, and the copper ion concentration was 75 ppm.

Production Example 2 15 g of reduced copper catalyst was placed in a four-necked flask having an inner volume of 1 liter.
Was charged in a nitrogen atmosphere, and 250 g of acrylonitrile and 250 g of ion-exchanged water, to which nitrogen gas had been previously passed to remove dissolved oxygen, were added thereto, and reacted at 80 ° C. for 3 hours.
75 g of acrylamide was produced. After the catalyst was separated from the reaction solution by filtration with a filter, the catalyst was distilled under reduced pressure and concentrated to obtain a crude acrylamide aqueous solution. The acrylamide concentration of this aqueous solution is 31%, and the residual concentration of acrylonitrile is
The copper ion concentration was less than 0.01% and the copper ion concentration was 75 ppm.

Example 1 245 g of the crude acrylamide aqueous solution obtained in Production Example 1 above
Was placed in a 0.5-liter four-necked flask equipped with a stirrer, an oxygen gas inlet tube and a thermometer, and 0.0877 g of 99% glycine and 1.73 ml of 1N NaOH were added thereto. At a flow rate of 2 liters / hr at 20 ° C
For 5 hours. The number of revolutions of the stirrer was 300 rpm, and the solution in this case had a pH of 10 to 13 and was blue-violet. Next, the above solution was placed in a column filled with H-type strongly acidic cation exchange resin of Amberlite IR-200C (trade name; manufactured by Tokyo Organic Chemical Co., Ltd.).
= 3 hr ^-1 , and an operation of removing copper ions, glycine, sodium ions and other cation components was performed. As a result, the copper ion concentration in the solution by the chelate titration method using EDTA was 0.05 ppm or less, and the glycine concentration by the gas chromatography method was 1 ppm or less. Next, this solution was continuously passed through a column packed with an OH-type weakly basic anion exchange resin of Levatit MP-62 (trade name, manufactured by Bayer K.K.), and an anionic component such as acrylic acid was added. Was performed. The presence or absence of polymer formation in the contact operation with the ion exchange resin was confirmed by mixing 45 ml of methanol with 5 ml of the above treated aqueous solution, and no formation of an acrylamide polymer was observed.

Polymerization evaluation test Using the acrylamide aqueous solution obtained by the above treatment,
A polymerization reaction was performed by the following method, and a test for evaluating the obtained polymer was performed. First, pure water was added to 240 g of the acrylamide aqueous solution obtained in Example 1 to reduce the total amount to 9 g.
After 80 g, put into a 2 liter reaction vessel equipped with a nitrogen inlet tube and a thermometer.
The solution was passed for 1 hour at a flow rate of liter / minute to remove dissolved oxygen in the solution. Then, 10 g of an aqueous solution of 0.03% ammonium persulfate and 10 g of an aqueous solution of 0.03% ammonium ferrous sulfate were added thereto.
Was added almost simultaneously. About 1.5 hours after these additions, the reaction temperature peaked at 90 ° C. After leaving for 1 hour from that point, the produced polymer was taken out. After crushing the obtained polymer with a meat chopper, 85 ° C
For 2 hours and pulverized with a pulverizer to obtain a powdery acrylamide polymer. This was sieved and 30 to 60 mesh was sampled and used as a test sample.

Evaluation method of acrylamide polymer: The obtained acrylamide polymer was subjected to a water solubility test,
The molecular weight measurement and the aggregation performance test were performed as follows. Water solubility test: 400 ml of pure water was put into a 500 ml beaker, and 0.4 g of the obtained polymer powder (weight of the pure polymer excluding water) was added thereto while stirring with a screw-type stirring blade at room temperature. After stirring at 400 rpm for 1.5 hours,
The mixture was filtered through a 150-mesh net, and the presence or absence of insoluble components was visually determined. In addition, the result of the determination was shown as follows. ····················································· Measurement of molecular weight; Was added to a concentration of 1N, and the viscosity was measured using an Ubbelohde viscometer, and the viscosity was calculated from the value. Coagulation ability; coagulation ability is sulfuric acid band in kraft pulp wastewater
400 ppm was added, and 1 ppm of polyacrylamide was added at pH 6, and the mixture was coagulated by a conventional method using a jar tester. The size of the floc generated at this time was determined and evaluated. In addition, the result of the determination was shown as follows.・ ・ ・: Floc diameter: 3 to 4 mm △: Floc diameter: 1 to 3 mm ×: Floc diameter: less than 1 mm The results are shown in Table 1.

Example 2 In Example 1, 99% alanine 0.10 was used instead of glycine.
The same operation was performed except that 4 g was added. In this case, the pH of the solution was 10 to 14, the solution exhibited a blue-violet color, and the formation of an acrylamide polymer was not observed at all in the presence or absence of polymer formation in the solution after the contact treatment with the cation and anion exchange resins. I couldn't. A polymerization test similar to that of Example 1 was performed on the obtained acrylamide aqueous solution. Table 1 shows the results.

Example 3 In Example 1, 0.033 g of 99% glycine, 1N-NaO
All operations were the same except that 0.87 ml of H and 0.038 g of 26% aqueous ammonia were added. In this case, the pH of the solution was 10 to 14, the solution exhibited a blue-violet color, and the formation of an acrylamide polymer was not observed at all in the presence or absence of polymer formation in the solution after the contact treatment with the cation and anion exchange resins. I couldn't. A polymerization test similar to that of Example 1 was performed on the obtained acrylamide aqueous solution. Table 1 shows the results.

Example 4 The procedure of Example 1 was repeated, except that the addition of glycine and NaOH was replaced by 0.052 g of 99% alanine, 1.16 ml of 1N NaOH and
The same operation was performed except that 0.038 g of a 26% aqueous ammonia solution was added. The pH of the solution in this case is 10
~ 14, the solution was blue-purple, and no formation of acrylamide polymer was observed at all in the presence or absence of polymer formation in the solution after the operation of contact treatment with the cation and anion exchange resins. A polymerization test similar to that of Example 1 was performed on the obtained acrylamide aqueous solution. Table 1 shows the results.

Example 5 In Example 1, 0.033 g of 99% glycine, 1N-NaO
All operations were the same except that 0.43 ml of H and 0.0756 g of 26% aqueous ammonia were added. In this case, the pH was 9 to 13 and the solution exhibited a blue-violet color, and no formation of an acrylamide polymer was observed at all in the presence or absence of polymer formation in the solution after the contact treatment with the cation and anion exchange resins. . A polymerization test similar to that of Example 1 was performed on the obtained acrylamide aqueous solution. Table 1 shows the results
Shown in

Example 6 Using the crude acrylamide aqueous solution obtained in Preparation Example 2 above, the operation was carried out exactly in the same manner as described in Example 1, and the obtained acrylamide aqueous solution was subjected to the same polymerization test as in Example 1. Was done. Table 1 shows the results.

Example 7 245 g of the crude acrylamide aqueous solution obtained in Production Example 1
The stirrer, oxygen gas inlet tube and thermometer equipped inner volume
The mixture was placed in a 0.5-liter four-necked flask, and stirred at 20 ° C. for 1 hour while passing oxygen gas through the liquid at a flow rate of 2 liter / hr. Then the solution was added at 5 l / hr and 99%
0.033 g of glycine, 1.59 ml of 1N-NaOH, and 14.7 g of an aqueous solution containing 0.038 g of 26% aqueous ammonia were continuously mixed at a rate of 0.3 liter / hr.
A column filled with Raschig rings, a column filled with a cation exchange resin (Amberlite IR-200C), and a column filled with an anion exchange resin (Levatit MP-62) are successively passed at SV = 2.7 hr ^-1. did. However, for columns packed with Raschig rings, the residence time of the solution in the column was 3 hours.
It was set to be time. The obtained acrylamide aqueous solution was subjected to the same polymerization test as in Example 1. As a result, the weight average molecular weight of the acrylamide polymer was 11,730,000, and no insoluble component was observed in the water solubility test.

Comparative Example 1 The procedure of Example 1 was repeated, except that glycine and a 1N aqueous solution of NaOH were not added. A polymerization test was similarly performed on the obtained acrylamide aqueous solution. Table 1 shows the results.

Comparative Example 2 The crude acrylamide aqueous solution obtained in Production Example 2 was
As in Comparative Example 1, a purification operation was performed by directly contacting with a cation exchange resin and an anion exchange resin. A polymerization test was similarly performed on the obtained acrylamide aqueous solution, and the results are shown in Table 1.

[0048]

[Table 1]

Reference Example 1 In Example 1, the cation exchange resin after the contact treatment with the acrylamide aqueous solution was regenerated with a 5% hydrochloric acid aqueous solution to neutralize the washing solution to pH = 7, and a diluted solution of this washing solution (glycine) (Containing 57 ppm) was examined for its inhibitory activity using a BOD-treated zooglia. as a result,
No phenomenon in which the function of the bacteria was inhibited by this diluent was observed at all.

[0050]

The aqueous acrylamide solution obtained by the catalytic hydration of acrylonitrile is converted into an amino acid or a salt thereof,
Alternatively, according to the purification method of the present invention by further adding an alkali metal hydroxide and / or ammonia, and then contacting with an ion-exchange resin, the aqueous acrylamide solution can be more highly prepared than conventionally known methods. It is also clear from the results of the examples that the compound can be purified to a high purity. In addition, when the acrylamide aqueous solution purified by the present invention is used, when the acrylamide polymer is used, there is almost no insoluble component in water, and furthermore, 11 million to 1200
It is possible to easily obtain a polymer having a molecular weight of about 10,000. Furthermore, even if the waste liquid produced by the purification operation is treated by the activated sludge method, the method according to the present invention does not give any inhibitory effect on bacteria, and is therefore a very environmentally preferable method. I can say.

(72) Inventor Eiichi Muranaka 1900 Togo, Mitsui Toatsu Chemical, Mobara City, Chiba Prefecture (72) Inventor Minato 1,900 Togo Togo, Mobara City, Chiba Prefecture Mitsui Toatsu Chemical Corporation

Claims (7)

[Claims] 1. A method for purifying an aqueous acrylamide solution, comprising adding an amino acid or a salt thereof to an aqueous solution of acrylamide obtained by a contact hydration method of acrylonitrile, and then contacting it with an ion exchange resin. 2. The method for purifying an aqueous acrylamide solution according to claim 1, wherein, in addition to the addition of the amino acid or its salt, an alkali metal hydroxide is also added, followed by contact with an ion exchange resin. 3. The method for purifying an aqueous acrylamide solution according to claim 1, wherein, in addition to the addition of the amino acid or its salt, ammonia is also added, followed by contact with the ion exchange resin. 4. Purification of an aqueous acrylamide solution, which comprises adding an amino acid or a salt thereof, an alkali metal hydroxide and ammonia to an aqueous acrylamide solution obtained by a contact hydration method of acrylonitrile and then contacting it with an ion exchange resin. Method. 5. The acrylamide according to claim 1, wherein oxygen or an oxygen-containing gas is present in the aqueous solution of acrylamide when an amino acid or a salt thereof is added or added to the aqueous solution. A method for purifying an aqueous solution. 6. The method for purifying an aqueous acrylamide solution according to claim 1, wherein the addition of the amino acid or its salt to the aqueous acrylamide solution and the continuous contact of the aqueous solution with the ion exchange resin are performed. 7. The method for purifying an aqueous acrylamide solution according to claim 1, wherein the amino acid is glycine or alanine.