JPS61268658A - Purification of methacrylamide - Google Patents

Abstract

PURPOSE:To obtain high-quality methacrylamide with simple operation, by recrystallizing methacrylamide containing sulfate radical from an aqueous solution in the presence of hydroxide and/or carbonate of calcium and/or barium. CONSTITUTION:Crude methacrylamide containing sulfate radical as an impurity is produced by heating acetocyanhydrin and sulfuric acid to effect the amidation reaction, and neutralizing the resultant methacrylamide sulfate with ammonia. The crude methacrylamide is dissolved in water in the presence of hydroxide and/or carbonate of calcium and/or barium at 30-60 deg.C, and cooling the solution preferably to 5-15 deg.C to effect the crystallization of the objective compound. USE:Useful as a modifier of resin products such as photo-sensitive resin, wind- shield glass, photographic film, flocculant, etc.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for purifying methacrylamide.More specifically, the present invention relates to a method for purifying methacrylamide.More specifically, the present invention relates to a method for purifying methacrylamide. Method C2 involves purifying methacrylamide obtained by neutralization by a recrystallization method and removing sulfate groups to obtain highly pure methacrylamide.

(Prior art and its problems) Many methods are known for producing methacrylamide, but the cheapest and easiest method is to prepare methacrylamide sulfate obtained from ahitocyanhydrin and sulfuric acid. This method is obtained by summing. However, even if methacrylamide obtained by conventional techniques is recrystallized using an aqueous solvent, sulfate groups remain at 0.1% (1000 ppm).
) is unavoidable, and this is due to fiber modifier 1
Field of paper processing agent C: Can be fully used as a resin modifier in the fields of photosensitive resins, windshields, photographic films, flocculants, etc. (Cannot be used.

This is because many resin products in these fields are required to have a low electrolyte component, so even a small amount of impurities often significantly interfere with the crosslinking and polymerization reactions of the resin being modified. It is from.

However, a purification method for obtaining high quality methacrylamide is disclosed in JP-A-58-109457.

It has been proposed to perform a crystallization operation after treatment with an anion exchange resin. However, this method requires a very large amount of ion exchange resin or a large amount of reagent for its regeneration because the ion exchange resin capacity is small.

In order to improve this, in the invention described above, an aqueous solution of methacrylamide obtained by spray cleaning with water in advance and reducing ammonium sulfate is poured into a column C filled with an ion exchange resin.
Large loss of methacrylamide.

The yield is extremely low at about 40% (based on ahitocyanhydrin).

Furthermore, JP-A-57-120556 describes a method for obtaining high-quality and highly transparent methacrylamide by carrying out a crystallization operation at a pH of 8 or higher in order to improve the transparency. The alkali used for pH adjustment is not particularly limited, and carbonates and hydroxides of alkali metals and alkaline earth metals, ammonia, etc. are used, and it is also stated that aqueous solutions of sodium hydroxide and potassium hydroxide are particularly preferred. However, since these salts are only added in small amounts to sub-adjust the pH, the sulfate radicals contained in the raw material methacrylamide do not adjust the pH (as compared to when purified by double crystallization). Regardless, 0.02
% (200 ppm) of children. It is also written that methacrylamide before purification and crystallized and separated methacrylamide are washed with cold water, but the yield is low due to the loss of methacrylamide that dissolves in the water used. This may cause undesirable problems such as small crystals due to dissolution of the crystals, and the cause of decreased transparency is the formation of methacrylamide dimer during amidation and the generation of polymer products during drying. etc. C: This is largely due to the formation of dimers during amidation, crystallization, and drying steps, and it is important to select conditions that do not cause polymerization.

As described above, the conventional purification methods have various deficiencies as a method for producing surface-quality methacrylamide with simple operations that are industrially advantageous.

(Means to solve the problem) In order to efficiently remove trace amounts of sulfuric acid radicals in methacrylamide (secondly, calcium and/or barium hydroxide and/or carbonate are This is achieved by adding salt.

This method reduces the residual sulfate radicals to substantially less than several tens of ppm, especially (
It is possible to easily reduce C to about 20 ppm or less, and at the same time, the loss of methacrylamide during purification is small, making it industrially advantageous.・Manufacturing (every F is possible.

In the method of the present invention, methacrylamide used as a raw material for recrystallization is prepared using concentrated sulfuric acid of 1 mol (2 to 1.3 to 1.8 mol) of ahitone cyanohydrin at an amidation temperature of 120 to 180°C. It is preferable to use crude methacrylamide obtained by neutralizing methacrylamide sulfate produced under reaction conditions with ammonia in the presence of water.

The crystallization method may basically be a normal crystallization method. That is, the general crystallization process includes heating and dissolving methacrylamide, adding calcium or/and barium hydroxide or/and carbonate (hereinafter referred to as alkali salt) to the methacrylamide aqueous solution, and filtering the undissolved material. It usually consists of crystallization by cooling, centrifugal desorption, water, and drying operations. The dissolution of methacrylamide is carried out in the range of 30 to 60°C, more preferably in the range of 40 to 55°C.
It is preferable to uniformly dissolve in 90 parts. If the melting temperature is too high.

This is because methacrylamide is easily polymerized, and if it is low, the solubility will be low, the amount of crystals obtained will be small, and the efficiency will be reduced.

The methacrylamide contains 3 to 596 ammonium sulfate, and 1 to 3, preferably 1.1 to 2.5 mol, of an alkali salt is added to 1 mol of this ammonium sulfate for reaction.

If the amount of alkali salt added is small, unreacted ammonium sulfate salt will adhere to methacrylamide, making it impossible to remove the sulfate radicals sufficiently. In addition, if the amount is too large, the pH will become high, inhibiting the polymerization stability of methacrylamide and being uneconomical.

The alkali to be added may be one that reacts with the sulfate group to form a salt with low solubility in water, and the reagents that can be advantageously used in industrial C2 are the alkali salts mentioned above. Carbonates of alkali metals, alkaline earth metals, commonly used for neutralization,
Aqueous solutions of ammonium, sodium hydroxide, and potassium hydroxide, which are commonly used for special treatment, are not suitable.

Note that the addition of the alkali salt does not necessarily have to be carried out after the methacrylamide has been dissolved.

It may be added to the raw material methacrylamide or water and then dissolved, as long as it is an insoluble material.

For the purpose of obtaining color-free methacrylamide.

If it is necessary to perform decolorization treatment such as activated carbon treatment, add an alkali salt during this operation.

Addition of alkali salt ζ when removing these decolorizing agents by filtration
; Therefore, the sulfate produced can also be removed at the same time.

Any conventional method may be used to crystallize methacrylamide from a clean aqueous methacrylamide solution from which sulfate groups have been removed, but cooling crystallization is preferred. Since methacrylamide is very easily polymerized, it is preferable to use an indirect cooling method rather than a vacuum adiabatic cooling method because of the presence of oxygen, which is effective in preventing polymerization. The cooling temperature is not particularly limited, but 5 to 15°C is more preferable.

The crystallized methacrylamide is separated into solid methacrylamide and an aqueous solution using a conventional method such as centrifugal dehydration.

The separated methacrylamide crystals have substantially no sulfate attached, and are dried according to a conventional method.
Sulfate-free methacrylamide can be produced.

Washing the separated methacrylamide crystals with a small amount of water removes the attached sulfate and further reduces the amount of residual sulfate. Drying may be carried out by a conventional method. Special C: Although not limited, in order to obtain methacrylamide containing no monopolymer, it is preferable to carry out drying in the presence of oxygen at a low temperature of 40 to 90° C. for a short period of time.

(Example) The pH was adjusted to 3-8I, titrated with the specified barium perchlorate using sulfonashi as an indicator, and the sulfate group (SO4-
). Transparency is JIS
Measurements were made according to the transparency section of the O102 factory wastewater test method, and the sample was methacrylamide 1009 mixed with methanol 4
A solution dissolved at 00 mA is used. A commercially available fluoroscopic needle with a scale up to 50 degrees was used. The purity was determined by determining the double bond value by the bromine addition method, analyzing the methacrylic acid by gas fluorography, and correcting this value.

The color number (APHA) is the value of an aqueous methacrylamide 1096 solution.

Production of recrystallized raw material Methacryl was immersed in a water bath and amidated at 135°C with 764f of water added to an enameled path equipped with a stirrer at 1.7 (molar ratio) of 5Ic acid/ahitone cyanohydrin. Amide sulfate 1269F at liquid temperature 30℃
Dropped below. Next, the 2596 ammonia aqueous solution was neutralized to pH 7 to 8 over 2 hours under cooling at a liquid temperature of 30° C. or less.

The resulting slurry was centrifuged to obtain 357 g. It contains 2.3% ammonium sulfate.

Example 1 550f of water was put into a 21 flask equipped with a stirrer and heated to 52°C, and 500ml of methacrylamide, a raw material for recrystallization, was added. , and added calcium hydroxide 9.32.

It was dissolved in 30 minutes.

Next, it was quickly filtered under reduced pressure using a tarache using σ paper pre-coated with Celite, and the filtered methacrylamide aqueous solution was left for 30 minutes.

Thereafter, the mixture was cooled to 7°C over 30 minutes to precipitate crystals. The obtained slurry was sufficiently dehydrated by centrifugal dehydration. The obtained crystals were dried at -6.0°C in a water path while blowing air with a rotary evaporator to obtain methacrylamide 351f.

The water content of this methacrylamide is 0.596 and the purity is 9.
9.596 or more, 1 hue (APHA) 25 or less, the transparency of the methanol solution was 50 or more, the sulfate group was 19 ppm, and the pH of the 1095 aqueous solution was 9.1.

Example 2 Methacrylamide was obtained in exactly the same manner as in Example 1 except that the amount of calcium hydroxide added was changed to 7.92.

The water content of this methacrylamide is 0.5 m, and the purity is 99.
．． 5% or more, hue (APHA) 25 or less, transparency 50
The sulfate content was 98 ppm.

Example 3 A completely similar experiment was carried out in Example 1, except that calcium hydroxide was replaced with calcium carbonate (12.6 FC).The water content of this methacrylamide was 0.5 m2, and the purity was 99.596 or higher. 1 hue (APHA) 2 s or less, the transparency was 50 or more, the sulfate radical was 21 ppm, and the pa of the 10% aqueous solution was 9.1.

Example 4 In Example 1, powdered activated carbon 2,
C: Experimented in exactly the same manner except that 5f was added. The water content of this methacrylamide is 0.5%, the purity is over 99.5%,
Hue (APHA) 5 or less, transparency 50 or more, sulfate group 1
At 9 ppm, the pH was 9.1.

Example 5 Same as Example 1 C: An experiment was carried out to obtain a slurry, which was centrifugally dehydrated, and further centrifugally dehydrated while being sprayed with water at 100F to sufficiently dehydrate it. This was dried in the same manner as in Example 1.
I got it. This methacrylamide has a water content of 0.5% and a purity of 99.54 or higher.

Hue (APHA) was 10 or less, transparency was 50 or more, sulfate radical was 10 ppm or less, and pH was 8.8.

Comparative example 1 Without adding calcium hydroxide in Example 1.

Methacrylamide was obtained in the same manner as above.

The water content of this methacrylamide is 0.5%, purity 99
．． 596 or more, 1 hue (APHA) 25 or less, the transparency of the methanol aqueous solution was 50 or more, the sulfate group was 300 ppm, and the DH was 4.2.

Comparative Example 2 Methacrylamide was obtained in the same manner as in Example 5 except that calcium hydroxide was not added. This sulfate root is 155pp
It was m.

Comparative example 3 I:1042 instead of calcium hydroxide in Example 1 % potassium soda aqueous solution was added to adjust the pH to 12.

Methacrylamide was obtained in the same manner except that the water content of this methacrylamide was 0.595. The purity was 99.5* or more, the hue (APHA) was 25 or less, and the transparency was 50 or more, but sulfate groups were present in a large amount at 3:25 ppm.

Claims (1)

[Claims] When recrystallizing and purifying methacrylamide containing sulfate groups as impurities using a water solvent, calcium or
A method for purifying methacrylamide, which comprises performing a crystallization operation by adding barium hydroxide or/and carbonate.