JP3476226B2 - Purification method of methacrylamide aqueous solution - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying an aqueous methacrylamide solution obtained by a hydration reaction using methacrylonitrile and water as raw materials.

[0002]

BACKGROUND OF THE INVENTION Methacrylamide has been widely used in the fields of fiber modifiers, resin modifiers, paint additives, paper latices, etc. Among them, photosensitive resins, windshields, photographic films, agglomerates. In the field of agents and the like, high quality methacrylamide is desired.

As a method for producing this methacrylamide, an industrially practiced method is to use ammonium sulphate aqueous solution by a plurality of crystallization operations after neutralizing methacrylamide sulphate obtained from acetone cyanohydrin and sulfuric acid with ammonia. From the methacrylamide. In this regard, Japanese Patent Publication No. 44-26094, Japanese Patent Publication No. 45-2566, and Japanese Patent Publication No. 47-35885 are disclosed.

However, since it is difficult to produce high quality methacrylamide by these methods, a method for obtaining high quality methacrylamide is to recrystallize it from an aqueous solution of methacrylamide and purify it. A method of performing crystallization operation after adjusting the hydrogen ion concentration to a range of pH 8 or more is Japanese Patent Publication No. 59-506.
Japanese Patent Publication No. Sho 62-5 discloses a method of performing crystallization operation after treating an aqueous solution of methacrylamide with an anion exchange resin.
It is disclosed in Japanese Patent No. 3508. As described above, the conventional production method requires various treatment operations in addition to the dissolution and crystallization operations for a plurality of times to obtain high-quality methacrylamide.
Therefore, it is a complicated method.

[0005]

However, a simple purification method for improving the quality of an aqueous methacrylamide solution obtained by the hydration reaction of methacrylonitrile and water, which is one of the methods for producing methacrylamide, is disclosed. Not not.
That is, an object of the present invention is to provide a simple purification method for improving the quality of an aqueous methacrylamide solution obtained by a hydration reaction of methacrylonitrile and water.

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventor has found that an aqueous solution of methacrylamide obtained by a hydration reaction using methacrylonitrile and water as raw materials is treated with activated carbon and cation exchange. It was found that the quality of the methacrylamide aqueous solution can be improved by bringing the resin and the anion exchange resin into contact with each other and purifying, and thus the present invention was completed.

That is, the present invention is: methacrylonitrile
And methacrylic acid obtained by hydration using water as a raw material
Activated charcoal and cation exchange resin for purification of aqueous amide solution
Methacrylate purified by contact with oil and anion exchange resin
The present invention relates to a method for purifying an aqueous solution of luamide. Also,
Activated carbon and cation-exchange resin are used for the purification of luriamide.
Oil, anion exchange resinsoFor contacting and refining
It has characteristics.   When purifying methacrylamide
Then cation exchange resin, anion exchange resin, activated carbon
It is also characterized in that it is contacted with and purified.

The present invention will be described in detail below. Briefly, the present invention relates to a simple purification method for improving the quality of an aqueous methacrylamide solution obtained by a hydration reaction of methacrylonitrile and water by contacting it with activated carbon, a cation exchange resin and an anion exchange resin. It is a thing. The high-quality methacrylamide aqueous solution referred to in the present invention means that the content of impurities such as organic substances such as methacrylic acid and inorganic substances such as copper, iron and sulfuric acid is small, and therefore has a high purity, and Hazen which is an index of coloring. It refers to an aqueous methacrylamide solution having features such as a small number (APHA), a low turbidity that is an index of insoluble matter such as a polymer, a high transparency, and a small change with time due to storage.

Further, the present invention does not involve complicated dissolution and crystallization operations, only the operation of bringing the methacrylamide solution into contact with the activated carbon, the cation exchange resin and the anion exchange resin. Therefore, the operation is easy and high. It is a simple method to purify high quality methacrylamide solution. In the present invention, as methacrylonitrile, one produced by ammoxidation reaction of isobutene or tertiary butanol with a catalyst containing molybdenum, bismuth and iron as the main components can be used.

As a method for producing methacrylamide by a hydration reaction using methacrylonitrile and water as raw materials, there can be mentioned a method of using a copper-based catalyst, an acid such as sulfuric acid or the like as a catalyst, and a copper-based catalyst such as Raney-copper. Is preferred. Although this methacrylonitrile can be used for the reaction as it is, this methacrylonitrile contains acidic substances such as methacrylic acid, acetic acid and hydrocyanic acid as a trace amount of impurities. When a copper-based catalyst is used as a catalyst for the hydration reaction, it causes deterioration of the catalyst. Therefore, the methacrylonitrile is used as an anion exchange resin, an alkali metal oxide or hydroxide or an aqueous solution thereof, an alkaline earth metal. It is preferable to use it in the reaction after removing the acidic substance by bringing it into contact with a basic substance such as an oxide or hydroxide or an aqueous solution thereof.

Further, oxygen is dissolved in methacrylonitrile and water used for the reaction, and this oxygen causes deterioration of the catalyst when the copper-based catalyst is used. Therefore, it is preferable to supply the reaction after the dissolved oxygen in the methacrylonitrile and water is substantially reduced to zero by an operation such as blowing an inert gas such as nitrogen. The concentration of methacrylonitrile used in the reaction is not particularly limited, but from the viewpoint of productivity and efficiency, it is in the range of 5 to 80%, preferably 10 to 50%, more preferably 15 to 40%.

The hydration reaction of methacrylonitonil can be carried out continuously or batchwise by using a suspension bed or a fixed bed. It is preferable to suspend Raney-copper in the tank reactor with a stirrer for the reaction. The amount of the catalyst is 0.05 to 2 kg / L with respect to the volume of the reactor, preferably 0.1.
1-1 kg / L, more preferably 0.2-0.7 kg / L
It is L.

The contact time or residence time between the catalyst and the raw material methacrylonitrile and water is 0.1 to 10 hours, preferably 0.3 to 5 hours, and more preferably 0.5 to 3 hours.
Is the range. When the contact time or the residence time is less than 0.1 Hr, the conversion rate of the reaction is insufficient, and when the contact time or the residence time is more than 10 Hr, the amount of by-products increases, and it is not preferable from the economical efficiency.

The reaction temperature is 50 to 150 ° C., preferably 7
It is in the range of 0 to 140 ° C, more preferably 90 to 130 ° C. If the reaction temperature is lower than 50 ° C., the reaction rate will be reduced, which is not practical, and if the reaction temperature is higher than 150 ° C., the catalyst will be greatly deteriorated and by-products will increase, which is not preferable. Separation of catalyst and reaction liquid is performed by wire mesh, nylon mesh,
It can be carried out by a separation method such as filtration using a sintered metal, sedimentation separation, centrifugation, or a combination of these methods.

By these methods, an aqueous methacrylamide solution can be obtained by a hydration reaction using methacrylonitrile and water as raw materials. However, since the obtained aqueous methacrylamide solution contains unreacted methacrylonitrile,
It is necessary to separate methacrylonitrile from this methacrylamide solution containing methacrylonitrile.
Examples of the method for separating methacrylonitrile from an aqueous methacrylamide solution containing methacrylonitrile include separation by distillation, separation by stripping with an inert gas such as nitrogen or carbon dioxide, or air, etc. Separation by is preferred.

In performing the separation by distillation, the bottom temperature of the distillation column is 30 to 110 ° C., preferably 40 to 90.
C., more preferably in the range of 50-80.degree. When the bottom temperature of the distillation column is lower than 30 ° C., the operating pressure becomes unnecessarily low, which causes a problem that the device becomes large. Further, when the bottom temperature of the distillation column is higher than 110 ° C., methacrylonitrile or methacrycrylamide is polymerized to form a polymer, which is a quality problem.

As the distillation column, there are columns having trays such as bubble trays, perforated plate trays, valve trays, Raschig rings, Lessing rings, Berlu saddles, interlock saddles, terraret packings, poll rings, McMahon packings, Dixon. A tower packed with a packing such as a ring can be used.

When separating methacrylonitrile from a methacrylonitrile aqueous solution containing methacrylonitrile, the concentration of methacrylonitrile in the separated methacrylonitrile aqueous solution is 1,000 ppm or less, preferably 50 ppm.
It is 0 ppm or less, more preferably 100 ppm or less. When the concentration of methacrylonitrile in the methacrylamide solution after separation is greater than 1,000 ppm,
This may cause generation of polymers and deterioration of methacrylamide quality in the refining operation.

The methacrylamide solution obtained by separating the methacrylonitrile thus obtained is contacted with activated carbon, a cation exchange resin and an anion exchange resin for purification to obtain a high quality methacrylamide solution. it can. As the purification method of the present invention, the methacrylamide solution and the activated carbon, the cation exchange resin and the anion exchange resin may be contacted in any order, but the activated carbon, the cation exchange resin and the anion are preferable. It is preferable to contact in the order of the exchange resin, or in the order of the cation exchange resin, the anion exchange resin and the activated carbon, more preferably the activated carbon, the cation exchange resin and the anion exchange resin in this order.

The respective functions of the activated carbon, the cation exchange resin and the anion exchange resin in the present invention are considered as follows. Activated carbon mainly removes impurities such as substances that cause coloring, for example, compounds having an aromatic ring such as hydroquinone and metoquinone, and polymers, and cation exchange resins mainly include cations such as copper ions, iron ions, and ammonium ions. For the removal, the anion exchange resin mainly aims to remove anions such as methacrylic acid and sulfuric acid, but in reality, it is considered that the trace amount of unspecified impurities that affect the quality is also removed.

By contact with these activated carbon, cation exchange resin and anion exchange resin, irrespective of the crystallization operation,
It has not been known until now that a high-quality methacrylamide solution can be obtained by a simple operation of contact.

It has also been found that a high quality methacrylamide solution cannot be obtained unless at least one contact of the methacrylamide solution with the activated carbon, cation exchange resin and anion exchange resin is carried out. As the activated carbon in the present invention, it is possible to use activated carbon that is produced from plants, coal, petroleum, etc. as a raw material and is generally commercially available, but from the viewpoint of preventing contamination of impurities from the activated carbon, use activated carbon made from a plant material. Preferably,
Among them, activated carbon made from coconut shell is good.

Granular or powdered activated carbon can be used as the shape, but granular activated carbon is preferably used from the viewpoint of easy separation and low differential pressure, and the particle size is 1 to 500 mesh, preferably 5 mesh. ~ 100 mesh,
It is more preferable to use activated carbon in the range of 10 to 60 mesh. In addition, it is preferable to use the activated carbon after removing the adsorbed material by a treatment such as boiling, steam blowing, contact with hot water, and the like, and the regeneration treatment after use can be similarly performed.

As the cation exchange resin in the present invention, a commercially available porous type or gel type strong or weakly acidic cation exchange resin can be used, but the porous type is preferable. Strongly or weakly acidic cation exchange resins are preferred. For example, Diaion PK-208
Or Diaion WK-10 (manufactured by Mitsubishi Kasei), Revat SP-112, Revat CNP-80 (manufactured by Bayer), Amberlite IR-120B or Amberlite IRC-50 (Rom and Haas) Etc. These cation exchange resins are preferably used after the exchange group is changed to the H type.

As the anion exchange resin in the present invention, a commercially available porous type or gel type anion exchange resin having strong basicity or weak basicity can be used, but preferably it is porous. Strongly basic or weakly basic anion exchange resins are preferred. For example, Diaion PA
-306 and Diaion WA-30 (manufactured by Mitsubishi Kasei),
Levatit MP-500, Levatit MP-62 (manufactured by Bayer), Amberlite IRA-400 and Amber
Light IRA-958 (made by Rohm and Haas Co.) and the like can be mentioned. It is preferable to use these anion exchange resins after converting the exchange group or the free radical into the OH type.

The method of contacting the methacrylamide aqueous solution with the activated carbon, the cation exchange resin and the anion exchange resin may be a continuous method or a batch method, but the continuous method is preferred. In the continuous method, the space velocity (SV) is 1 to 6
The range of 0 Hr ⁻¹ , preferably 3 to 20 Hr ⁻¹ is good, and the linear velocity (LV) is 0.1 to 20 m / Hr, preferably 0.
A range of 5 to 10 m / Hr is preferable.

The contact between the aqueous solution of methacrylamide and the activated carbon, the cation exchange resin and the anion exchange resin has a temperature of 0.
~ 50 ° C, preferably 5-45 ° C, more preferably 1
It is good to carry out in the range of 0 to 40 ° C. When the temperature is lower than 0 ° C., the solubility of methacrylamide is low, resulting in low productivity, and there are problems such as clogging of the device due to precipitation of crystals. On the other hand, if the temperature is higher than 50 ° C, impurities such as methacrylic acid increase due to side reactions such as hydrolysis of methacrylamide, which causes deterioration of quality of methacrylamide.

Further, an aqueous solution of methacrylamide and activated carbon,
At the time of contact with a cation exchange resin and an anion exchange resin, in order to prevent the polymerization of methacrylamide, the aqueous solution of methacrylamide is brought into contact with a gas containing oxygen such as air, and then activated carbon, a cation exchange resin and an anion. It is preferable to contact with an exchange resin. The oxygen concentration in the methacrylamide aqueous solution is 2 ppm or more, preferably 4 ppm or more.

As described above, the method of the present invention is a method capable of obtaining a high-quality methacrylamide aqueous solution by a simple operation of passing a liquid, as compared with the conventional method of performing crystallization operation. It was also confirmed that the methacrylamide prepared by the method of the present invention has the same or higher physical properties as the methacrylamide with high quality and high transparency disclosed in Japanese Patent Publication No. 62-53508.

The analysis of methacrylamide is carried out by the following method. The purity was calculated by determining the double bond value by the bromine titration method, analyzing methacrylamide and methacrylic acid by gas chromatography, and subtracting these values from the double bond value. Hazen number (APHA) is ASTM D-120
9-88, a 10 wt% methacrylamide aqueous solution was treated with potassium hexachloroplatinate (K
₂ PtCl ₆₎ - cobalt chloride (CoCl ₂ · 6H
₂ O) is a value obtained by a colorimetric method using the color of the aqueous solution as standard chromaticity.

Turbidity is JIS K0101-1979
According to the item of 9.2 transmitted light turbidity on page 14 of the industrial water test method, a 10 wt% methacrylamide aqueous solution was measured and expressed as turbidity. The transparency was measured in accordance with JIS K0101-1979 Industrial Water Test Method, page 17, [Reference] Transparency, and was measured for a solution of 10 g of methacrylamide in a proportion of 40 ml of methanol, and was displayed as a transparency. .

This transparency indicates the degree of transparency of the sample, and when seen through from the top of the fluorometer, the black line double character with a width of 0.5 mm on the marker plate placed at the bottom can be clearly identified for the first time. The height of the water layer at that time was measured, and 10 mm was displayed as 1 degree. It should be noted that it is impossible to measure more than 50 degrees because the display of the fluoroscope is only up to 50 cm.
The absorption value of the solution was measured using a photoelectric photometer, and the absorption value (-
The value was obtained by extrapolation from the correlation between logT) and the transparency.

For this measurement, the methacrylamide crystal obtained by performing the crystallization operation of the methacrylamide solution obtained from the third step was used. The inorganic salts were analyzed for sulfate by ion chromatography.

[0034]

The present invention is described in detail below with reference to examples, but these do not limit the scope of the present invention. (Example 1) In order to hydrate methacrylonitrile and synthesize methacrylamide, 300 m made of SUS304
Into an autoclave, 100 g of Raney copper manufactured by Nikko Rica Ltd. was charged, and methacrylonitrile and water, in which nitrogen was blown in advance to remove dissolved oxygen, were respectively 84 g / Hr, 198.
Supply at g / Hr, rotation speed 350 rpm, temperature 110 ° C
It was made to react with. The conversion of methacrylonitrile to methacrylamide was about 50% and the selectivity to methacrylamide was almost 100%. The reaction solution was extracted from the autoclave through a 2 μm sintered metal filter.

In order to separate methacrylonitrile from the obtained methacrylamide solution containing methacrylonitrile, a double column made of glass having an inner diameter of 30 mm and a length of 400 mm was filled with Dickson packing of 3 mmφ made of SUS316. The obtained reaction solution was supplied from the top of the column using a device having a 300 ml round bottom flask attached to the bottom of the column.

When the pressure in the packed tower was set to 130 to 140 mmHg and the round bottom flask at the bottom of the tower was immersed in an oil bath at about 115 ° C. and heated, the liquid temperature at the bottom of the tower was 58 to 61 ° C.
The vapor phase temperature at the top of the column was 42 to 52 ° C. Methacrylonitrile and water were withdrawn from the top of the column with steam and condensed with a condenser. The condensed liquid can be returned to the step of hydration reaction and used. Further, the methacrylamide solution was extracted from the bottom of the column with a pump so that the liquid level at the bottom was constant, and methacrylonitrile in this methacrylamide solution was 10 ppm. This aqueous solution of methacrylamide was placed in a tank and air was blown into it to dissolve oxygen.

In order to purify the methacrylamide solution thus obtained, three glass double tubes having an inner diameter of 15 mm and a length of 550 mm were prepared, and activated carbon was produced by Kuraray Chemical GL (10-32 mesh). 70 ml,
Diaion PK manufactured by Mitsubishi Kasei as a cation exchange resin
70 ml of -208 and 70 ml of Diaion WA-30 manufactured by Mitsubishi Kasei Co., Ltd. as anion exchange resin were filled. In the use, the activated carbon was subjected to a regenerating operation by boiling, the cation exchange resin was changed to an H-type exchange group, and the anion exchange resin was changed to an OH-type exchange group, and then used for purification.

The methacrylamide aqueous solution has a temperature of 30 ° C., 5
Supply with 30 ml / Hr, activated carbon, cation exchange resin,
The anion exchange resin was passed in this order. The space velocity (SV) is 7.6 Hr ⁻¹ and the linear velocity (LV) is 3.0 m / Hr. Finally, a methacrylamide solution of about 22 wt% was obtained, and the analysis results are shown in Table 1 below.

Further, the obtained methacrylamide solution was put in a brown bottle and stored in a dark place, but even after 30 days, the Hazen number of the solution was 5 or less. Further, the same liquid was put into a brown bottle and a 300 Hr heating test was performed at 60 ° C. The turbidity was 0.2, which was the same as the initial value.

(Example 2) Methacrylonitrile and water supplied in Example 1 were 42 g / Hr and 94 g, respectively.
The reaction was changed to / Hr. The conversion of methacrylonitrile to methacrylamide was about 75%, the selectivity to methacrylamide was 99.5%, and the selectivity to methacrylic acid was 0.5%. The obtained reaction liquid was supplied to the step of separating methacrylonitrile of Example 1 to extract unreacted methacrylonitrile from the top of the tower. A methacrylamide solution was extracted from the bottom of the column, and methacrylonitrile in the solution was 3 ppm.

As the purification step of this methacrylamide solution, the cation exchange resin of Example 1 was used as Levatit SP-112 manufactured by Bayer and the anion exchange resin was used as IRA-900 manufactured by Rohm and Haas. The same operation was performed except that the temperature was changed to 40 ° C. Finally about 32 wt%
The following methacrylic acid aqueous solution was obtained and the analysis results are shown in Table 1 below.

The obtained aqueous solution of methacrylamide was put in a brown bottle and stored in a dark place, but the Hazen number of the solution was 5 or less even after 30 days. Further, the same liquid was put in a brown bottle and subjected to a heating test of 300 hr at 60 ° C. The turbidity was 0.4, which was almost the same as the initial value.

(Example 3) Methacrylonitrile and water supplied in Example 1 were 60 g / Hr and 90 g, respectively.
/ Hr and the reaction temperature was changed to 120 ° C. for reaction. The conversion of methacrylonitrile to methacrylamide is about 7
At 5%, the selectivity to methacrylamide is 99.0%,
The selectivity of methacrylic acid was 1.0%.

The obtained reaction liquid was supplied to the step of separating methacrylonitrile in Example 1, and the liquid temperature at the bottom of the tower was adjusted to 45 to
Unreacted methacrylonitrile was withdrawn from the top of the tower at 50 ° C. The vapor phase temperature at the top of the column was 32 to 40 ° C. The methacrylamide solution was extracted from the bottom of the column, and methacrylonitrile in the solution was 2 ppm.

For the purification of this methacrylamide aqueous solution, the same operation was carried out as in Example 1 except that the temperature was 47 ° C. and the cation exchange resin, the anion exchange resin and activated carbon were passed in this order. Finally, a methacrylamide solution of about 40 wt% was obtained, and the analysis results are shown in Table 1 below. Further, the obtained methacrylamide solution was put in a brown bottle and stored in a dark place, but even after 30 days, the Hazen number of the solution was 5 or less. Further, the same liquid was put in a brown bottle and a heating test of 300 hr was performed at 60 ° C. The turbidity was 0.6, which was almost the same as the initial value.

Comparative Example 1 The same operation as in Example 1 was carried out except that the methacrylamide solution was not passed through the activated carbon. When the obtained methacrylamide solution was put in a brown bottle and stored in a dark place, the Hazen number of the solution increased to 20 after 30 days, and the Haze number of the solution was 300H at 60 ° C.
In the heating test of r, the Hazen number was increased to 30, and it was found that the quality of the aqueous methacrylamide solution was deteriorated.

Comparative Example 2 The same operation as in Example 1 was carried out except that the methacrylamide aqueous solution was not passed through the cation exchange resin. 20 ppm of copper was contained in the obtained aqueous solution of methacrylamide, and the obtained aqueous solution of methacrylamide was placed in a brown bottle and heated at 60 ° C. for 300 H.
When the heating test of r was performed, the turbidity was 0.2
However, it was found that the quality of the aqueous methacrylamide solution deteriorates.

Comparative Example 3 The same operation as in Example 1 was performed except that the methacrylamide solution was not passed through the anion exchange resin. The obtained methacrylamide solution contained methacrylic acid in an amount of 200 ppm.
When a heating test was performed at 300 ° C for 300 hours, the polymer
Was observed, and it was found that the quality of the methacrylamide solution was deteriorated.

Reference Examples 1 and 2 As analytical values of high quality methacrylamide, the values of Example 1 and Example 6 of JP-B-62-53508 are shown in Table 1 below as Reference Examples 1 and 2, respectively.

[0050]

[Table 1] * Values of 50 and above are extrapolated values.

[0051]

EFFECTS OF THE INVENTION In purifying an aqueous methacrylamide solution obtained by a hydration reaction using methacrylonitrile and water as raw materials, the aqueous methacrylamide solution is brought into contact with activated carbon, a cation exchange resin and an anion exchange resin to enhance the A quality aqueous methacrylamide solution can be produced.

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Claims (3)

(57) [Claims] 1. A method for purifying an aqueous methacrylamide solution obtained by a hydration reaction using methacrylonitrile and water as raw materials, wherein methacrylic acid is brought into contact with activated carbon, a cation exchange resin and an anion exchange resin for purification. Method for purifying aqueous amide solution. 2. The method for purifying an aqueous methacrylamide solution according to claim 1, wherein the methacrylamide is purified by contacting with activated carbon, a cation exchange resin and an anion exchange resin in that order. 3. When purifying methacrylamide, the
Contact with ion-exchange resin, anion-exchange resin , and activated carbon in that order.
2. The meta according to claim 1, wherein the meta is purified.
A method for purifying an aqueous solution of chloramide.