JPH1059910A - Production of aminodicarboxylic acid-n,n-diacetic acid salts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an aminodicarboxylic acid-N,N- diacetic acid salt in a high yield in a state suppressed in the coloration of the reaction solution and capable of being applied as an industrial process. SOLUTION: This method comprises reacting and distilling an aminodicarboxylic acid salt, formaldehyde and an alkali metal cyanide in the molar ratios of the formaldehyde and the alkali metal cyanide to the aminodicarboxylic acid salt in values of 2.6-3.0, respectively, under a vacuum condition. When the formaldehyde and the alkali metal cyanide are added and reacted with the aminodicarboxylic acid salt, the reaction is carried out at a reaction temperature of 85-110 deg.C, while water is continuously supplied in a rate of >=7 (g/min)/aminodicarboxylic acid salt (mole) and simultaneously distilled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing aminodicarboxylic acid-N, N-diacetates. Aminodicarboxylic acid-N, N-diacetates, especially compounds of the following general formula (I) as chelating agents, such as detergent compositions, detergent builders, heavy metal sequestering agents, hydrogen peroxide stabilizers, photographic agents, etc. It has been widely considered for use and home use. At present, EDTA is generally widely used for these applications. However, since EDTA does not have biodegradability, research on alternative products has been actively conducted due to environmental problems and the like. Among them, aminodicarboxylic acid-N, N-diacetates have biodegradability and are effective as alternative chelating agents.

Embedded image (Wherein X independently of one another represents a hydrogen atom, an alkali metal atom, an ammonium salt, an amine salt, and n is 0 to 5
Means number up to. )

[0002]

2. Description of the Related Art Various processes for producing aminodicarboxylic acid-N, N-diacetates have been known. For example, a method of synthesizing aminodicarboxylic acid-N, N-diacetates by adding two molecules of chloroacetic acid to aminodicarboxylic acid under alkaline conditions (West German Patent 3739610,
JP-A-63-26751), formaldehyde and hydrocyanic acid are reacted with an alkali metal salt of aminodicarboxylic acid,
As an intermediate, a method via aminodicarboxylic acid-N, N-diacetonitrile (Japanese Patent No. 4211713A1),
There is a method of reacting an alkali metal salt of aminodicarboxylic acid with formaldehyde and an alkali metal cyanide (US Patent No. 2500019).

[0003] However, the method using chloroacetic acid as the aminodicarboxylic acid salt is known as aminodicarboxylic acid-N,
It is hard to say that suitable raw materials are selected for the production of N-diacetates. That is, chloroacetic acid is inevitable in the reaction product, such as by-products such as sodium chloride in an equimolar amount to the chloracetic acid used, and the material of the reactor uses a material that is corrosion resistant to chlorion. It is necessary, and there are many problems as an industrial production method. In addition, the synthesis of aminodicarboxylic acid-N, N-diacetonitrile is difficult to produce due to the effect of the nitrile group at the α-position, and there is a problem in the yield of the target product. Further, since the cyanomethylation / hydrolysis step is performed at another stage, the entire production step is inevitably long and complicated.

Further, the method of reacting formaldehyde with an alkali metal cyanide involves various restrictions such as a reaction method from the viewpoint of coloration of a reaction solution and suppression of side reactions since a compound having extremely high reactivity is used as a raw material. In addition, it is not only difficult to suppress the coloring of the reaction solution and to obtain the desired aminodicarboxylic acid-N, N-diacetate in a high yield by reducing impurities, but also to satisfy both simultaneously. It is extremely difficult. For example, when a reaction molar ratio of 2-2.5 moles of formaldehyde and an alkali metal cyanide with respect to aminodicarboxylic acid is carried out in the patent of Aminodicarboxylic acid, the aminodicarboxylic acid -N, Regarding the coloring of the reaction solution of N-diacetates, the reaction solution may be used as it is in a detergent, or aminodicarboxylic acid-N,
It is not preferable for taking out solids of N-diacetates, and furthermore, the target aminodicarboxylic acid-
It is an intermediate product of N, N-diacetate, and it is inevitable that aminodicarboxylic acid-N-monoacetic acid shown in the following general formula (II) remains, which is not preferable in terms of yield and cost.

[0005]

Embedded image (In the formula, X and n are as described above.)

[0006] One of the major problems is the necessity of removing ammonia generated during the reaction. That is, ammonia generated in the course of this reaction easily reacts with formaldehyde or alkali metal cyanide as a raw material to produce impurities such as nitrilotriacetic acid as a by-product, thereby coloring the reaction solution, lowering the purity and yield of the target product, and the like. In general, there are various difficulties as an industrial production method.

[0007]

As described above, in the prior art, serious problems remain in terms of the yield of the desired aminodicarboxylic acid-N, N-diacetate and the coloring of the reaction solution. In addition to the fact that the reaction is prolonged, it is inevitable that the reaction process and the purification step involve complicated operations, and there are various problems as an industrial production method. The present invention has been made to solve these problems, and an object of the present invention is to provide an efficient method for producing an aminodicarboxylic acid-N, N-diacetate on an industrial scale. In an efficient process using raw materials advantageous for industrial processes, aminodicarboxylic acid-N, N-diacetates, which are chelating agents excellent in biodegradability, suppress coloring of the reaction solution, Another object of the present invention is to provide a production method which can be obtained at a high yield and at a low cost.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, using aminodicarboxylic acid as a raw material, the reaction molar ratio of formaldehyde and alkali metal cyanide to aminodicarboxylates is 2 respectively. In the range of 0.6 to 3.0, further under reduced pressure conditions, and further by selecting the reaction temperature, supply rate and other reaction conditions, the reaction is suppressed in coloration as compared with the conventional method. And the by-product of nitrilotriacetic acid,
There is almost no residual aminodicarboxylic acid-N-monoacetic acid as an intermediate product, and the desired aminodicarboxylic acid-N,
The inventors have found that N-diacetates can be obtained at a high yield and at low cost by an efficient process, and have completed the present invention. The details will be described below.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The aminodicarboxylates (the acid itself in the present invention) which are raw materials in the present invention are preferably aminodicarboxylates of the following general formula (III). It is preferable from the viewpoint of chelating power and biodegradability of the N, N-diacetate derivative.

[0010]

Embedded image (In the formula, X and n are as described above.)

The above n is an integer from 0 to 5,
Preferably, n = 1 or 2, when n = 1, an aspartic acid derivative, and when n = 2, a glutamic acid derivative. X is independently a hydrogen atom, an alkali metal atom, an ammonium salt, or an amine salt,
Sodium salts are preferred. These aminodicarboxylic acids are commercially available with a purity of 70% or more, preferably 8%.
Although a solid of 5% or more is generally used, an alkali metal salt or an aqueous solution of an alkali metal salt obtained during the production can be directly used. When using an aqueous solution of a low-purity alkali metal salt of aminodicarboxylic acid, it should be noted that ammonia as an impurity leads to an increase in by-products of nitrilotriacetic acid, and the ammonia concentration is desirably 3% or less. These aminodicarboxylic acids may be any of the D-form, L-form, and D, L-form optical isomers.

As the formaldehyde used in the present invention, various forms such as a gaseous product, an aqueous solution product, and a solid product such as paraformaldehyde are used, but industrially, it is 10 to 60% by weight, preferably 20 to 60% by weight. It is preferable to use an aqueous solution of 50% by weight, more preferably 35 to 40% by weight. Further, as for the alkali metal cyanide used in the present invention, the alkali metal may be L
i, Na or K, preferably Na or K, more preferably Na is selected, and industrially, 10 to 60% by weight,
Preferably it is 20 to 50% by weight, more preferably 30 to 50% by weight.
It is preferable to use an aqueous solution of 35% by weight. The method of the present invention generally comprises the steps of preparing an aminodicarboxylic acid salt of the general formula (III) (preferably, an alkali metal salt, particularly preferably a sodium salt) and an alkali metal hydroxide (preferably, hydroxide). An aqueous solution containing sodium oxide is used in a reactor, and an aqueous solution of formaldehyde and an alkali metal cyanide is simultaneously supplied thereto to carry out the reaction. In the present invention, the coloring of the reaction product is significantly improved as compared with the conventional method by setting the conditions such as the raw material molar ratio and the charging or the reaction concentration, the reaction temperature and the pressure in the setting range during the charging to the reaction. And the target aminodicarboxylic acid-N, N-diacetate is obtained in high yield, with little by-product nitrilotriacetic acid or residual aminodicarboxylic acid-N-monoacetic acid as an intermediate product. Is obtained. Various conditions (described below) set in the present invention individually show an effect of suppressing coloring and reducing impurities, but by combining these, synergistic effects as in the present invention can be obtained. It shows a typical effect. This will be described below according to the reaction procedure.

With respect to the charging conditions, the aminodicarboxylates and alkali metal hydroxides are used in a molar amount of 0.01 to 1.0 times, preferably 0.1 to 1.0 times the aminodicarboxylates.
1 mol of alkali metal cyanide (usually sodium cyanide) is used in an amount of 0.01 to 1 mol per mol of aminodicarboxylic acid salts.
0.5 times mol, preferably 0.2 to 0.3 times mol (about 1/10 mol amount of alkali metal cyanide used in the reaction) and water are added to adjust the concentration of the aminodicarboxylate to 2.0 mol / mol. kg or more, preferably 2.2 to 2.3 mol / kg. When the aqueous solution containing the aminodicarboxylates charged in this way is reacted by simultaneously supplying an aqueous solution of formaldehyde and an alkali metal cyanide under stirring, under reduced pressure, normal pressure to -600 mmHg, preferably-
100 to -300 mmHg, and the reaction temperature is 85 to 110.
° C, preferably 95 to 105 ° C, and formaldehyde and alkali metal cyanide (alkali metal cyanide) in a molar ratio of 2.6 to 3.0, preferably 2.7 to 2.8 times the amount of aminodicarboxylates. The supply rate of cyanide (including the amount used for preparation) is 2.0 × 10 ⁻² (mol / min) / aminodicarboxylate (mol) or less, preferably aminodicarboxylate. 1.0
× 10 ^{-2 to} 1.5 × 10 ^-2 (mol / min) / aminodicarboxylic acid salts (mol). At this time, water is not less than 7 (g / min) / aminodicarboxylate (mol) or more, preferably 8 to 12 (g) based on aminodicarboxylate at the same time as formaldehyde and alkali metal cyanide.
/ Min) / Aminodicarboxylic acid salts (mol) by adjusting the concentration of the formaldehyde and alkali metal cyanide aqueous solution or separately supplying water simultaneously with the formaldehyde aqueous solution and alkali metal cyanide aqueous solution. The reaction is carried out while continuously distilling water so that is kept at the same level as the charged liquid. After the supply of formaldehyde and alkali metal cyanide ends, 3
The mixture is aged for 0 minute to 2 hours, preferably for 1 hour to complete the reaction.

By performing the method of the present invention as described above, the coloring of the reaction solution can be suppressed, the ammonia generated during the reaction can be efficiently removed, and the by-product nitrilotriacetic acid can be reduced as compared with the conventional method. it can. Furthermore, aminodicarboxylic acid-
The residual aminodicarboxylic acid-N-monoacetic acid, which is an intermediate product of N, N-diacetate, can be significantly suppressed, and the desired aminodicarboxylic acid-N, N-diacetate can be industrially produced. It can be produced with high yield and economically. By the method of the present invention, about 60% by weight aqueous solution can be obtained at the end of the reaction with the yield of the target product being 99% or more. In this reaction solution, in addition to aminodicarboxylic acid-N, N-diacetate which is the main component and the target substance, 1% by weight or less of aminodicarboxylic acid-N, N-diacetate relative to aminodicarboxylic acid-N, N-diacetate is contained. N-monoacetates and aminodicarboxylic acid-N, N-diacetates can be obtained with 3% by weight or less of nitrilotriacetates, and their coloring is also APHA6.
00 or less. In the present invention, the color number is a value obtained by visually comparing with an APHA standard solution according to the color number measuring method of JIS 4101 and measuring.

From the reaction solution obtained by the method of the present invention,
If desired, the reaction solution is crystallized by means of evaporation to dryness or spray drying to give aminodicarboxylic acid-
N, N-diacetate I can be isolated. In order to obtain crystals of aminodicarboxylic acid-N, N-diacetate or aminodicarboxylic acid-N, N-diacetate with higher purity, sulfuric acid, hydrochloric acid, nitric acid, preferably sulfuric acid is added to the reaction solution or the reaction solution. And then adjusted to pH = 1 to 3, preferably pH = 2, and then added to 2- to 5-fold, preferably 3-fold, methanol to crystallize. The desired salt is produced by neutralizing or partially neutralizing the aminodicarboxylic acid-N, N-diacetate thus obtained with a predetermined amount of a base such as an alkali metal hydroxide, ammonia or an organic amine. can do.

[0016]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 In a reactor equipped with a stirrer, a thermometer, two dropping devices, and a distillation device, monosodium glutamate monohydrate 10 was added.
9.0 g (0.58 mol), sodium hydroxide 26.7
g (0.64 mol), 24.6 g (0.16 mol) of a 32% by weight aqueous solution of sodium cyanide and 100 g of water were charged. This mixed solution was -100 mmHg, boiling point (105
℃). When the distillation of water from the distillation apparatus was started, 119.4 g of a 40% by weight aqueous solution of formaldehyde was added from two series of dropping apparatuses with vigorous stirring.
(1.59 mol, 2.73 times the molar amount of glutamic acid monosodium salt) and 238.8 g of water, and a 32% by weight aqueous solution of sodium cyanide 221.
8 g (1.45 mol, 2.76 times mol of monosodium glutamic acid including that used for preparation)
An aqueous solution diluted by adding 443.6 g of water to the mixture was simultaneously added dropwise over 3 hours. During this time, the pressure was -100 to -200 m
mHg, the reaction temperature is 105 ° C., and the reaction solution is continuously distilled so that the level of the reaction solution is kept at the same level as the charged solution, and the reaction is carried out while removing generated ammonia. After completion of the addition of formaldehyde and sodium cyanide, the mixture was aged at 95 ° C. for 1 hour to complete the reaction. Thereby, glutamic acid-N, N-diacetate tetrasodium salt is obtained in a liquid at a yield of 99% (based on monosodium glutamic acid monohydrate).
I got it. After the completion of the reaction, the concentration of glutamic acid-N, N-diacetate tetrasodium salt was 60% by weight, whereas nitrilotriacetic acid trisodium salt was 1.8% by weight, and glutamic acid-N-
Triacetic acid monosodium salt was contained at 0.5% by weight (1% yield, monosodium glutamate monohydrate). Water was added to the reaction solution to dilute it to a concentration of glutamic acid-N, N-diacetate tetrasodium salt of 40% by weight. The APHA of the diluted solution was about 600.

Example 2 The water used for preparation was changed from 100 g to 200 g.
The same operation as in Example 1 was performed. As a result, glutamic acid-N, N-diacetate tetrasodium salt was obtained in a liquid at a yield of 95%.
(Vs. monosodium glutamate monohydrate).
After the completion of the reaction, the concentration of glutamic acid-N, N-diacetate tetrasodium salt was 57% by weight, whereas nitrilotriacetic acid trisodium salt was 1.8%, and glutamic acid-N-monoacetic acid trisodium salt was 2.3% by weight ( Yield 5%, based on glutamic acid monosodium salt monohydrate). Water was added to the reaction solution to dilute it to a concentration of glutamic acid-N, N-diacetate tetrasodium salt of 40% by weight. The APHA of the diluted solution is 6
00.

Example 3 119.4 g of a 40% aqueous solution of formaldehyde (1.59 g)
Mole, 2.73 relative to glutamic acid monosodium salt
Aqueous solution diluted by adding 238.8 g of water to
221.8 g of a 2% aqueous solution of sodium cyanide (1.45 g)
Mole, 2.76 times the amount of glutamic acid monosodium salt, including the amount used for the preparation) and 443.6 water.
The same operation as in Example 1 was performed, except that the aqueous solution diluted by adding g was added dropwise over 2 hours. Thereby, glutamic acid-N, N-diacetate tetrasodium salt was obtained in a liquid at a yield of 96%.
(Vs. monosodium glutamate monohydrate).
After the completion of the reaction, the concentration of glutamic acid-N, N-diacetate tetrasodium salt was 58% by weight, whereas that of nitrilotriacetic acid trisodium salt was 1.9% and that of glutamic acid-N-monoacetic acid trisodium salt was 1.9% by weight ( Yield 4%, monosodium glutamate monohydrate). Water was added to the reaction solution to dilute it to a concentration of glutamic acid-N, N-diacetate tetrasodium salt of 40% by weight. The APHA of the diluted solution is 8
00.

Example 4 77.5 (0.58 mol) of aspartic acid, 50.8 g (1.22 mol) of sodium hydroxide, 24.6 g (0.16 mol) of a 32% by weight aqueous solution of sodium cyanide and 107 g of water Was carried out in the same manner as in Example 1 except that Thereby, aspartic acid-N, N-diacetate tetrasodium salt was obtained in a liquid at a yield of 99% (based on aspartic acid). After the reaction, the concentration of aspartic acid-N, N-diacetate tetrasodium salt was 60% by weight, whereas nitrilotriacetic acid trisodium salt was 1.9% by weight, and the concentration of aspartic acid-N-
Triacetic acid monosodium salt contained 0.5% by weight (1% yield, aspartic acid). Water was added to the reaction solution to dilute it to a concentration of glutamic acid-N, N-diacetate tetrasodium salt of 40% by weight. The APHA of the diluted solution was about 500.

Example 5 The water used for the preparation was changed from 100 g to 200 g.
The same operation as in Example 4 was performed. Thereby, aspartic acid-N, N-diacetate tetrasodium salt was obtained in the liquid at a yield of 95.
% (Vs. aspartic acid). After the completion of the reaction, the concentration of tetrasodium aspartate-N, N-diacetate was 57% by weight, whereas trisodium nitrilotriacetic acid was 1.7% by weight and trisodium aspartate-N-monoacetate was 2.2%. % By weight (yield 5%, relative to aspartic acid). Water was added to the reaction solution to dilute it to a concentration of aspartic acid-N, N-diacetate tetrasodium salt of 40% by weight. The APHA of the diluted solution was 600.

Example 6 119.4 g of a 40% aqueous solution of formaldehyde (1.59
Mol, 2.73 times mol of aspartic acid) and water 2
Aqueous solution diluted by adding 38.8 g and 221.8 g of 32% aqueous sodium cyanide solution (1.45 mol, 2.76 mol of aspartic acid, including that used for charging)
Aqueous solution diluted with 443.6 g of water
The same operation as in Example 4 was performed except that the solution was dropped in a time period. Thereby, aspartic acid-N, N-diacetate tetrasodium salt was obtained in a liquid at a yield of 96% (based on aspartic acid). After completion of the reaction, the concentration of tetrasodium aspartate-N, N-diacetate was 58% by weight, whereas the concentration of trisodium nitrilotriacetic acid was 2.0% by weight, and the concentration of aspartic acid-N-
Triacetic acid monosodium salt contained 1.9% by weight (yield 4%, relative to aspartic acid). Water is added to the reaction solution, and the aspartic acid-N, N-diacetate tetrasodium salt concentration is 40.
Diluted to weight%. The APHA of the diluted solution was 800.

COMPARATIVE EXAMPLE 1 95.7 g of a 40% aqueous solution of formaldehyde (1.28 mol, 2.20 times the molar amount of glutamic acid monosodium salt) and 178.2 g of a 32% aqueous solution of sodium cyanide
(1.16 mol, 2.23 including 0.13 mol of glutamic acid monosodium salt, including the amount used for preparation)
The same operation as in Example 1 was carried out, except that the compound was used (fold molar). Thus, glutamic acid-N, N-diacetate tetrasodium salt was obtained in a liquid at a yield of 84% (based on glutamic acid monosodium salt monohydrate). Glutamic acid after completion of the reaction
N, N-tetraacetic acid tetrasodium salt concentration is 40% by weight, whereas nitrilotriacetic acid trisodium salt is 1.0% and glutamic acid-N-monoacetic acid trisodium salt is 6.0% by weight.
(16% yield, monosodium glutamate monohydrate). The APHA of the reaction solution was 1500.

Comparative Example 2 A reaction temperature of 80 ° C. and a pressure of -450 to -550 mmH
g, and the same operation as in Example 1 was performed. Thereby, glutamic acid-N, N-diacetate tetrasodium salt was obtained in the liquid at a yield of 99% (based on monosodium glutamic acid monohydrate). Glutamic acid-N, N-
The tetrasodium diacetate concentration is 60% by weight, the trisodium nitrilotriacetic acid 2.0% by weight, the trisodium glutamic acid-N-monoacetate 0.5% by weight (yield 1%, monosodium glutamate) Salt monohydrate). Glutamic acid-N, N-
It was diluted to a tetrasodium diacetate concentration of 40% by weight. The APHA of the diluted solution was 2,000.

Comparative Example 3 119.4 g of a 40% aqueous formaldehyde solution (1.59
Mole, 2.73 relative to glutamic acid monosodium salt
) And a 32% aqueous sodium cyanide solution 221.8.
g (1.45 mol, 2.76 times the mol of glutamic acid monosodium salt including the amount used for charging) was added dropwise over 3 hours without diluting with water, and the same operation as in Example 1 was carried out. Was carried out. Thus, glutamic acid-N, N-
Tetrasodium diacetate was obtained in the liquid at a yield of 94% (vs. monosodium glutamate monohydrate). After the reaction is completed, the concentration of glutamic acid-N, N-diacetate tetrasodium salt is 57%.
% By weight of nitrilotriacetic acid trisodium salt.
It contained 5% by weight and 3.0% by weight of glutamic acid-N-monoacetic acid trisodium salt (yield 6%, based on monosodium glutamic acid monohydrate). Water was added to the reaction solution to dilute it to a concentration of glutamic acid-N, N-diacetate tetrasodium salt of 40% by weight. The APHA of the diluted solution was 1500.

Comparative Example 4 95.7 g of a 40% aqueous formaldehyde solution (1.28 mol, 2.20 times mol of aspartic acid) and 32%
178.2 g of an aqueous sodium cyanide solution (1.16 mol, based on aspartic acid)
The same operation as in Example 2 was performed, except that 2.23 moles (including 13 moles) were used. Thereby, aspartic acid-N, N-diacetate tetrasodium salt was obtained in the liquid at a yield of 85%.
% (Vs. aspartic acid). After completion of the reaction, the concentration of tetrasodium aspartate-N, N-diacetate was 42% by weight, the concentration of trisodium nitrilotriacetic acid was 1.2% by weight, and the concentration of aspartic acid-N-monoacetic acid trisodium salt was 5.9. % (15% yield, aspartic acid). Water is added to the reaction solution, and aspartic acid-N, N-
It was diluted to a tetrasodium diacetate concentration of 40% by weight. The APHA of the diluted solution was 1600.

Comparative Example 5 A reaction temperature of 80 ° C. and a pressure of -450 to -550 mmH
g, and the same operation as in Example 4 was performed. Thereby, aspartic acid-N, N-diacetate tetrasodium salt was obtained in the liquid at a yield of 99% (based on aspartic acid). After the completion of the reaction, the concentration of tetrasodium aspartate-N, N-diacetate was 60% by weight, whereas the concentration of trisodium nitrilotriacetic acid was 2.0% by weight, and the concentration of aspartic acid-N-monoacetic acid trisodium salt was 0.5%. % (1% yield, aspartic acid). Water was added to the reaction solution, and aspartic acid-N, N-diacetate tetrasodium salt concentration was 40% by weight.
Diluted. The APHA of the diluted solution was 2,200.

Comparative Example 6 119.4 g of a 40% aqueous formaldehyde solution (1.59
Mol, 2.73 times the mol of aspartic acid) and 32
Example 22 except that 221.8 g (1.45 mol, 2.76 times the amount of aspartic acid, including the amount used for preparation, of aspartic acid) were added dropwise over 3 hours without diluting with water. The same operation as in Example 4 was performed. Thereby, aspartic acid-N, N-diacetate tetrasodium salt was obtained in the liquid at a yield of 93% (based on aspartic acid). After completion of the reaction, the concentration of tetrasodium aspartate-N, N-diacetate was 56% by weight, the concentration of trisodium nitrilotriacetic acid 5.6% by weight, and the concentration of aspartic acid-N-monoacetic acid trisodium 3.2%. % (7% yield, aspartic acid). Water was added to the reaction solution to dilute it to a concentration of aspartic acid-N, N-diacetate tetrasodium salt of 40% by weight. The APHA of the diluted solution was 1,400.

[0029]

According to the present invention, the reaction molar ratio when reacting formaldehyde and an alkali metal cyanide with an aminodicarboxylate, the reaction is carried out under reduced pressure, and furthermore, the reaction temperature, the supply rate of water and raw materials In addition, by appropriately selecting other reaction conditions, the method is a method for producing aminodicarboxylic acid-N, N-diacetates that can be applied as an industrial process in a high yield while suppressing coloring of the reaction solution.

Claims (4)

[Claims] An aminodicarboxylate, formaldehyde and an alkali metal cyanide are reacted at a molar ratio of formaldehyde and alkali metal cyanide to aminodicarboxylate in the range of 2.6 to 3.0, respectively. For producing aminodicarboxylic acid-N, N-diacetates. 2. The process for producing aminodicarboxylic acid-N, N-diacetates according to claim 1, wherein the reaction is carried out under reduced pressure. 3. When supplying formaldehyde and alkali metal cyanide to aminodicarboxylates and reacting them, the reaction temperature is 85 to 110 ° C. and water is 7 (g / mi).
n) / aminodicarboxylic acid salts (mol) or more,
The method for producing aminodicarboxylic acid-N, N-diacetates according to claim 2, wherein the reaction is carried out while continuously distilling. 4. When supplying formaldehyde and an alkali metal cyanide to an aminodicarboxylate and reacting the same, the concentration of the aminodicarboxylate charged into the reactor is 2.0 mol / kg or more, and the supply rate is set to the aminodicarboxylate. The method for producing aminodicarboxylic acid-N, N-diacetates according to claim 3, wherein the concentration is 2.0 × 10 ^-2 (mol / min) / aminodicarboxylic acid salts (mol) or less.