JPH0812631A - Production of iminodisuccinic acid and its alkali metal salt and a biodegradable chelating agent containing the same - Google Patents

Abstract

PURPOSE:To obtain high-purity (free from D,D-form) iminodisuccinic acid and an alkali metal salt thereof in high yield and in a short reaction time compared to the conventional processes therefor. CONSTITUTION:A tetraalkali metal salt of iminodisuccinic acid is obtained by adding a half ester of maleic acid to aspartic acid or ammonia under an alkaline condition followed by hydrolysis and evaporation to dryness. The second objective iminosuccinic acid is obtained by the above addition reaction followed by hydrolysis and then addition of sulfuric acid (without conducting an evaporation to dryness). In the above processes, use of L-aspartic acid in place of the ordinary aspartic acid produces D,D-form-free iminodisuccinic acid and tetraalkali metal salt thereof. Or, L,L-iminodisuccinic acid is selectively obtained by prior crystallization and/or washing of a mixture of the L,L-form and D,D- form of iminodisuccinic acid or a tetraalkali metal salt thereof. And, the other objective biodegradable chelating agent contains, as active ingredient, the D,D- form-free iminodisuccinic acid and/or an alkali metal salt thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing iminodisuccinic acid and its alkali metal salt from maleic acid half ester and ammonia, or maleic acid half ester and aspartic acid.

The present invention also relates to a method for producing (D, D) -free iminodisuccinic acid and its alkali metal salt from (L) -aspartic acid and maleic acid half ester.

Furthermore, the present invention relates to the use of (D, D) -free iminodisuccinic acid and its alkali metal salts as biodegradable chelating agents. Iminodisuccinic acid and its alkali metal salts are detergent compositions as biodegradable chelating agents, detergent builders, heavy metal sequestering agents,
Widely used as a peroxide stabilizer.

[0004]

2. Description of the Related Art Various methods for producing iminodisuccinic acid have been conventionally known. For example, a method of adding two molecules of maleic acid to one molecule of ammonia (British Patent Specification No. 1306331), a method of adding one molecule of maleic acid to one molecule of aspartic acid (Japanese Patent Laid-Open No. 5-320109), and the like. is there.

The biggest problem with these prior arts is the low reactivity of maleic acid. In the production of iminodisuccinic acid, it is necessary to reflux the reaction mixture for a long time in order to obtain a practical reaction yield. However, such production conditions are accompanied by side reactions such as isomerization of maleic acid to fumaric acid, hydration of maleic acid to malic acid, or decomposition of iminodisuccinic acid to aspartic acid. The isomerization and hydration of maleic acid not only lowers the yield of the desired product, but often causes coloration in the reaction solution. Further, the decomposition of iminodisuccinic acid is due to the reverse Michael addition reaction, which often causes racemization of the target substance.

Another problem with the prior art is that the desired iminodisuccinic acid is obtained as a mixture of stereoisomers. That is, iminodisuccinic acid obtained by the conventional technique of adding two molecules of maleic acid to one molecule of ammonia is (D, L) -body 75%, (D, D) -body 25%, (L, L) -body Obtaining as a 25% mixture of stereoisomers is self-evident from the reaction mechanism. Similarly, in the conventional technique of adding one molecule of maleic acid to one molecule of aspartic acid, the obtained stereoisomeric mixture of iminodisuccinic acid is extremely biodegradable unless (L) -aspartic acid is used as a raw material. Poor (D, D) -Body 2
Contains 5%.

Yet another problem with the prior art is that
Although (D, L) -iminodisuccinic acid and (D, D)-or (L, L) -iminodisuccinic acid have a diastereomer relationship with chemically different properties, their chelating power and No mention is made of the difference in water solubility. That is, it is particularly excellent in terms of biodegradability, water solubility, and chelating power (L, L).
-The possibility of separating and using iminodisuccinic acid and its alkali metal salt has not yet been investigated.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems of the prior art, and an object thereof is to provide an industrially advantageous method for producing iminodisuccinic acid and its alkali metal salts. Specifically, by using ammonia or aspartic acid as a raw material and using a maleic acid half ester having excellent reactivity for the addition reaction, the desired iminodisuccinic acid and its alkali metal salt can be treated with a short reaction time and a high reaction rate. The object is to provide the product in high yield and high purity.

The present invention is also excellent in biodegradability (L,
L) or (D, L) -iminodisuccinic acid and an object thereof are to provide an industrially advantageous selective production method of an alkali metal salt thereof. Specifically, using (L) -aspartic acid as a raw material, By using a maleic acid half ester having excellent reactivity in the addition reaction, the target (L, L) or (D, L) -iminodisuccinic acid and its alkali metal salt are added to the (D, D) -form An object of the present invention is to provide a product with no reaction, a short reaction time, a high yield and a high purity.

Further, the present invention provides (L, L) and (D,
L) -A mixture of stereoisomers of iminodisuccinic acid is particularly excellent in biodegradability, chelating power, and water solubility (L, L)-
An object of the present invention is to provide an industrially advantageous separation method of iminodisuccinic acid and its alkali metal salt.

[0011]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that when aspartic acid or ammonia is subjected to an addition reaction under alkaline conditions, it is replaced with maleic acid which has been conventionally used. It was found that by using maleic acid half ester, the desired alkali metal salt of iminodisuccinic acid can be obtained in a high reaction yield, despite the short reaction time. Similarly, when (L) -aspartic acid is subjected to an addition reaction under alkaline conditions, by using maleic acid half ester, the desired (L, L) and (D,
It has been found that a 1: 1 mixture of L) -iminodisuccinic acid alkali metal salts is obtained in high reaction yields. In addition to the extremely low concentration of by-products such as fumaric acid, malic acid and maleic acid in these reaction products, when (L) -aspartic acid is used as a raw material, (D, D) -Since no iminodisuccinic acid has been produced at all, the reaction product is simply evaporated to dryness,
It was found that the tetraalkali metal salts of (L, L) and (D, L) -iminodisuccinic acid were obtained in high yield and high purity.

Furthermore, the present inventors have found that crystals of iminodisuccinic acid can be obtained by appropriately concentrating these reaction products and then adding a mineral acid, and in particular (L)-
When aspartic acid is used as a raw material, after acid precipitation, the (D, L) -form is removed by preferential crystallization, or the (L, L) -form is eluted by washing with water to give (L, L) -form. -We have found that iminodisuccinic acid or its alkali metal salts can be selectively obtained. Moreover, (L, L) and (D, L) -iminodisuccinic acid obtained by these methods,
It was found that and its alkali metal salt are chelating agents having extremely excellent biodegradability. Besides, (L, L)
The present invention has been achieved by finding that iminodisuccinic acid or its alkali metal salt is a particularly excellent chelating agent from the viewpoints of biodegradability, water solubility and chelating power.

That is, the present invention provides a method for producing an alkali metal salt of iminodisuccinic acid, which comprises adding a maleic acid half ester to aspartic acid or ammonia under alkaline conditions, and a maleic acid half ester under alkaline conditions. , Ammonia or aspartic acid, followed by acid precipitation crystallization with a mineral acid, and a method for producing iminodisuccinic acid.

Similarly, the present invention is characterized in that a maleic acid half ester is added to (L) -aspartic acid under alkaline conditions to produce a (D, D) -free alkali metal salt of iminodisuccinic acid. The method is also characterized in that maleic acid half ester is added to (L) -aspartic acid under alkaline conditions, followed by acid precipitation crystallization with a mineral acid to obtain (D, D) -form-free iminodisuccinic acid. It relates to a manufacturing method.

The present invention further relates to (L, L) -form of iminodisuccinic acid or its alkali metal salt and (D,
From the mixture of L) -form by preferential crystallization (D, L)-
A method for obtaining (L, L) -iminodisuccinic acid or an alkali metal salt thereof, which is characterized by selective removal of the body or selective elution of the (L, L) -body by washing, and (D,
D) -The present invention relates to a biodegradable chelate containing at least one kind of iminodisuccinic acid and an alkali metal salt thereof which does not contain a body.

The present invention will be described in detail below. The method of the present invention comprises an addition reaction step in which a maleic acid half ester is allowed to act on aspartic acid or ammonia under alkaline conditions, a hydrolysis reaction step in which an alkali metal hydroxide is added to the reaction product, and further the reaction product. Is completely concentrated to isolate the desired tetraalkali metal iminodisuccinate, which is then evaporated to dryness. Alternatively, an addition reaction step in which a maleic acid half ester is allowed to act on aspartic acid or ammonia under alkaline conditions, a hydrolysis reaction step in which an alkali metal hydroxide is added to the reaction product, and a mineral acid is added to the reaction product. It consists of an acid precipitation crystallization step of adding and isolating iminodisuccinic acid.

When (L) -aspartic acid is used in the addition reaction step, the method of the present invention is a stereoisomerization of (L, L)-and (D, L) -iminodisuccinic acid obtained by the acid precipitation step. It consists of a preferential crystallization removal step in which (D, L) -form crystals are filtered off from the body mixture to selectively obtain (L, L) -iminodisuccinic acid. Alternatively, the stereoisomeric mixture of the (L, L)-and (D, L) -iminodisuccinic acid tetraalkali metal salt obtained by the evaporation to dryness step is washed with water and the (L, L) -iminodisuccinic acid tetraalkali metal salt is washed. It consists of a washing step to selectively obtain salt.

The maleic acid half-ester used as a raw material of the present invention can be selected from half-esters with a low molecular alcohol having about 1 to 5 carbon atoms, but it is easy to prepare, is reactive, and is water-soluble. From the viewpoints of properties and costs, a half ester of methyl, ethyl, propyl, isopropyl, and butyl alcohol is preferable, and a half ester of methyl alcohol is particularly preferable.

The maleic acid half-ester can be prepared by any method, and may be prepared as follows prior to the reaction of the present invention. That is, maleic acid half-ester is 1 part with respect to maleic anhydride.
˜5 times mol, preferably 1.0˜1.5 times mol of low molecular weight alcohol in the vicinity of boiling point of low molecular weight alcohol for 0.1 to 3.2 hours, preferably 0.2˜0. Synthesized by heating under reflux for 7 hours. Usually, maleic acid half ester is quantitatively obtained as a colorless transparent liquid with respect to maleic anhydride by distilling off excess low-molecular alcohol under atmospheric pressure or reduced pressure.

The maleic acid half ester thus obtained may be isolated once or used as it is in the reaction vessel for the next step. It is not always necessary to distill off excess low molecular weight alcohol, but a large amount of residual alcohol may adversely affect the reaction temperature in the next step. The maleic acid half ester can be used by diluting it as a stock solution or its excellent water solubility. Alternatively, it is also an effective means to neutralize with an equimolar amount of alkali metal hydroxide and use it as a maleic acid half ester-alkali metal salt aqueous solution.

As the aspartic acid used in the addition reaction step, D-form, L-form and racemic form can be used.
The L-form is preferably selected from the viewpoint of biodegradability of the product. In the case of obtaining iminodisuccinic acid which does not include (D, D) -form, which is disadvantageous in terms of biodegradability, (L)-is used as a raw material.
It is preferable to select aspartic acid and subject it to an addition reaction with a maleic acid half ester. As the aspartic acid used in the addition reaction step, a commercially available solid having a purity of 70% or more, preferably 85% or more can be used, but an alkali metal salt obtained during the production or an aqueous solution of the alkali metal salt is directly used. It can also be used.

The amount of aspartic acid used in the addition reaction step is 0.6 with respect to the maleic acid half ester.
To 1.4 times mol, preferably 0.8 to 1.2 times mol, particularly preferably 0.9 to 1.1 times mol.

When ammonia is used as a raw material in the addition reaction step, it can be used in various forms such as gas, liquid and aqueous solution, and the amount used is 0.3 to 0.8 times mol based on the maleic acid half ester, Preferably 0.4-0.6
It is appropriately selected within a double molar range.

The alkaline condition in the addition reaction step is achieved by adding an alkali metal hydroxide or an aqueous solution thereof. In addition, aspartic acid alkali metal salt,
Maleic acid half-ester alkali metal salts and aqueous solutions thereof may be used. As the type of alkali metal used, Li, Na or K, preferably K and Na are used. P under alkaline conditions in the addition reaction step
H is selected in the range of 10 to 13, preferably 10.5-12.5. At a pH of 13 or higher, the alkali metal hydroxide is present in a molar amount exceeding the total of the carboxyl groups in the reaction solution, so that hydrolysis of maleic acid half-ester monoalkali metal salt to dimaleic acid dialkali metal salt proceeds. If the by-product ratio of the dialkali metal maleate salt increases, it will lead to a decrease in the overall addition reaction rate.
Excessive alkaline conditions should be avoided.

Prior to the addition reaction step, the aspartic acid or ammonia, the maleic acid half ester, and the alkali metal salt to achieve alkaline conditions are mixed in water. One of the advantages of the process of the present invention using maleic acid half-esters over the prior art is the wide range of possible combinations of mixing sequences and processes. That is, in the prior art, a step of previously hydrating maleic anhydride to maleic acid in an aqueous solution was necessary. However, if aspartic acid or ammonia is mixed before the hydration is sufficiently performed, an amino group However, there was a drawback that the amidation with respect to (1) proceeded preferentially. On the other hand, according to the method of the present invention using a maleic acid half ester, there is no fear that side reaction amidation will proceed under any conditions. A further advantage is that maleic acid and maleic anhydride are solids that are inconvenient to handle, while maleic acid half-esters are nonvolatile liquids that are highly water-soluble and fluid.

The temperature in the addition reaction step is 80 to 15
It may be carried out at 0 ° C, preferably in the range of 100 to 120 ° C. The reaction is usually carried out under normal pressure, but it is also an effective means to carry out the reaction under pressure in an autoclave. The pressure reaction is advantageous especially when ammonia is used as a raw material.

The reaction time in the addition reaction step is 0.5
-24 hours, preferably 1-8 hours, more preferably 2-5 hours. One of the most significant improvements in the method of the present invention over the prior art is that the addition reaction is completed within a surprisingly short time. The reason why the reactivity of maleic acid half-ester monoalkali metal salt is increased as compared to dimaleic acid dialkali metal salt is that the addition of amino group as a nucleophile is reduced because the electron density on the conjugated double bond decreases. It is presumed that it is easier to receive. on the other hand,
The addition reaction was examined in the same manner for a diester such as dimethyl maleate, but the diester was poor in water solubility and the reaction did not proceed at all. That is, it is concluded that the maleic acid half ester used in the present invention is a raw material having both high electrophilicity and high water solubility and excellent reactivity.

In the hydrolysis step, 0.9 to 1.3 times mol, preferably 1.0 to 1.05 times mol of metal hydroxide or its aqueous solution is used with respect to the maleic acid half ester used in the addition reaction step. By adding to the reaction solution, a low molecular weight alcohol having an equimolar amount to the maleic acid half ester used in the addition reaction step is released, and a tetraalkali metal salt of iminodisuccinic acid is produced in the reaction solution.

The temperature in the hydrolysis step is 80 to 15
Performed at 0 ° C, preferably in the range of 100-120 ° C,
The reaction time is 0.1 to 3.0 hours, preferably 0.5 to
It is good to carry out within 1.5 hours. Treatment of the reaction solution at a higher temperature than necessary for a long period of time should be avoided because it leads to decomposition and racemization of the target product by reverse Michael addition.

In the method of the present invention, the reaction solution after the hydrolysis step is always colorless and transparent, and usually almost no impurities are detected. This is in sharp contrast to the fact that in the prior art crude reaction solutions are often colored and contain impurities such as fumaric acid, maleic acid, malic acid and aspartic acid.

Further important points in the method of the present invention are:
In the addition reaction step, the tetraalkali metal salt of iminodisuccinic acid obtained when the hydrolysis step is reached by using (L) -aspartic acid and maleic acid half ester as raw materials is (D, L) -form and (L, It is a 1: 1 mixture of L) -form and no (D, D) -form is detected.
This is in sharp contrast to the fact that, even when (L) -aspartic acid and maleic acid are used as raw materials in the prior art, the (D, D) -form is by-produced by racemization. That is, the production of the tetraalkali metal salt of iminodisuccinic acid which does not contain the (D, D) -form can be realized only by the combination of (L) -aspartic acid and the maleic acid half ester in the method of the present invention.

The method for producing a tetraalkali metal salt of iminodisuccinic acid containing no (D, D) -form in the method of the present invention is extremely significant from the viewpoint of supplying a chelating agent having excellent biodegradability. . This is because the (D, D) -form having an unnatural three-dimensional structure at two positions in the molecule is (L,
This is because biodegradability is extremely poor as compared with the (L) -form and the (D, L) -form, and thus they accumulate in the environment. That is, the incorporation of the (D, D) -form in the manufacturing process seriously affects the biodegradability of the chelating agent.

The evaporation-drying step is accomplished by distilling off the water content of the reaction solution obtained by the hydrolysis step to evaporate it to dryness, or by semi-concentrating the reaction solution as it is and then subjecting it to spray drying. However, in any case, the tetraalkali metal salt of iminodisuccinic acid can be obtained as pure white crystals with high purity and high yield. Also, no isomerization or decomposition of the target substance was observed in the evaporation and drying process.

In the washing step, the tetraalkali metal salt of iminodisuccinic acid obtained by the evaporation to dryness step is washed with an appropriate amount of water on a suction filtration device, or the tetraalkali metal salt of iminodisuccinic acid is added in an appropriate amount. It is achieved by partially dissolving it in water and filtering off the supernatant and the residue. The amount of water used in the washing step is 50 to 950% by weight, preferably 200 to 500% by weight, based on the tetraalkali metal salt of iminodisuccinic acid, and the water temperature is 0.
It is appropriately carried out in the range of -100 ° C, preferably 10-70 ° C.

What is surprising in the method of the present invention is that the production ratio of (D, L) -form to (L, L) -form, which is originally 1: 1 in the filtrate recovered in the washing step, becomes (L, L) -the body is much more predominant, and this fact is (L, L)
It means that the water-solubility of the -form is far superior to that of the (D, L) -form. By concentrating the filtrate obtained in the washing step, it is possible to selectively obtain the tetraalkali metal salt of (L, L) -iminodisuccinic acid.

However, even when the (D, L) -form is not completely separated, an aqueous solution of an isomer mixture in which the composition ratio of the (L, L) -form is 55% or more, preferably 60% or more. When compared with the conventional aqueous solution of 1: 1 isomer mixture having the same concentration, is clearly transparent and does not show any sign of slurrying or discoloration even after standing for several months. Very easy to handle.

According to the test results using the sample selectively obtained by the method of the present invention, the tetra-alkali metal salt of (L, L) -iminodisuccinic acid has any of biodegradability, water solubility and chelating ability. It is a particularly excellent chelating agent from the viewpoint. This means that in the case of the (D, L) -form, the two succinic acid units protrude forward and backward with respect to the molecular plane, whereas in the case of the (L, L) -form, the two succinic acid units are It is suggested that this is due to the protrusion in the same direction with respect to the molecular plane. That is, the (L, L) -form is considered to be capable of pentadentate coordination with respect to water molecules and cations without difficulty in terms of molecular structure.

Even when (±) -aspartic acid or ammonia is used in the addition reaction step, the racemic mixture of the (D, L) -form or the (L, L)-(D, D) -form is used in the washing process. It is possible to selectively acquire each of these.

Examples of the mineral acid used in the acid precipitation crystallization step include hydrochloric acid, nitric acid and sulfuric acid, and sulfuric acid is particularly preferably used. Sulfuric acid is selected from industrially available ones having a purity of 60 to 98%, and the reaction solution obtained by the hydrolysis step is adjusted to pH 1.0 to 3.0, preferably pH 1.5 to 2.5. The required amount for is used. The temperature at the time of dropping sulfuric acid is preferably 10 to 100 ° C., preferably 40 to 80 ° C., and the dropping time is 0.5 to 6 hours, preferably 1 to 5 hours.

The iminodisuccinic acid which is a target substance is aged after aging the reaction product after addition of sulfuric acid at 0 to 50 ° C., preferably 10 to 40 ° C. for 0 to 72 hours, preferably 1 to 5 hours,
It is obtained by collecting the precipitated crystals by suction filtration. When (L) -aspartic acid is used in the addition reaction step, the obtained crystals are (D, I) of iminodisuccinic acid.
It is composed of a mixture of L) -form and (L, L) -form. Almost no by-products are present.

What is surprising in the method of the present invention is that the production ratio of the (D, L) -form and the (L, L) -form after the hydrolysis step is 1: 1 by the acid precipitation crystallization step. In the resulting crystals, the (D, L) -form is much more predominant. This means that the (D, L) -form having excellent crystallinity is preferentially recovered, whereas the (L, L) -form having excellent water solubility is eluted in the filtrate.

In the acid precipitation crystallization step, not only the desired (D, L) -form and (L, L) -form of iminodisuccinic acid are obtained as crystals of an equal mixture but also after the acid precipitation. Using the principle of preferential crystallization from the reaction solution, (D,
The ratio of the (L) -form and the (L, L) -form in the filtrate can be increased. Thus, by performing the acid precipitation crystallization step as the preferential crystallization removal step, sodium sulfate and the (D, L) -form are removed, and (L, L) -iminodisuccinic acid is selectively obtained. Is possible.

The concentration of iminodisuccinic acid in the acid precipitation liquid in the preferential crystallization removing step is selected from the range of 5 to 85% by weight, preferably 20 to 65% by weight as the acid equivalent concentration of the stereoisomer mixture. The aging temperature and aging time in the preferential crystallization removal step are the same as those in the acid precipitation crystallization step.

Fractionation of the (L, L) -form and the (D, L) -form of iminodisuccinic acid was once isolated by the preferential crystallization removal step and the evaporation-drying step (L, L) and. Also achieved by a washing step in which a stereoisomeric mixture of (D, L) -form tetraalkali metal salt is washed with water to selectively elute and obtain the (L, L) -form tetraalkali metal salt. To be done.

The amount of water in the washing step is 1 to 1 with respect to the stereoisomer mixture of the tetraalkali metal iminodisuccinate.
It is preferable to use 100 times by weight, preferably 2 to 20 times by weight. It is used for washing on a filtration device such as a Buchner funnel, or used in a reaction tank and once partially dissolved as a suspension and then filtered. Good. The aging temperature and aging time in the washing step are the same as those in the acid precipitation crystallization step.

In the preferential crystallization removal step and the washing step, (D,
Partial removal of the L) -form is an effective means for preventing slurrying and coloring of the iminodisuccinic acid and its tetraalkali metal salt aqueous solution and improving the storage stability of the aqueous solution.

Even when (±) -aspartic acid or ammonia is used in the addition reaction step, the (D, L) -form or (L, L) and (D, L) -forms in the preferential crystallization removal step or the washing step. It is possible to selectively obtain each of the racemic mixtures consisting of D) -form. In this case, the racemate surpasses the (D, L) -form in water solubility and chelating power, but is not suitable for use as a biodegradable chelating agent.

According to the test results using the sample selectively obtained by the method of the present invention, (L, L) -iminodisuccinic acid is a chelating agent which is particularly excellent in terms of biodegradability, water solubility and chelating ability. It became clear that there is.

[0049]

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

Example 1 A reactor equipped with a stirrer, a thermometer, a dropping funnel and a distillation apparatus was charged with 100 g (1.02 mol) of maleic anhydride, and 55
After melting at 65 ℃ to 65 ℃, anhydrous methanol 32.6g
(1.02 mol) was added dropwise over 30 minutes. Stirring was continued for another 30 minutes while maintaining the temperature at 65 ° C. 35% by weight of maleic acid monomethyl ester thus obtained (L) -disodium aspartate aqueous solution 389 g (1.02 mol),
Subsequently, 90.7 g (1.02 g) of 45% by weight aqueous sodium hydroxide solution was added.
Mol) was added. The reaction solution was stirred under reflux at 105 ° C for 4 hours, and then again 45% by weight aqueous sodium hydroxide solution 9
0.7 g (1.02 mol) was added, and stirring was continued under reflux for 0.5 hours. The slurry obtained by distilling off the water from the reaction solution for another 0.5 hour was dried and powdered at 120 ° C by a spray drying method to obtain 361 g of tetrasodium iminodisuccinic acid salt (crude yield 105%) as pure white crystals. It was As a result of HPLC analysis using a chiral column, this iminodisuccinic acid tetrasodium salt was a stereoisomer mixture consisting of (L, L) -form 50% and (D, L) -form 50%, and (D, D ) -No body by-product was observed. A detailed component analysis of this tetrasodium iminodisuccinate is shown in Table 1.

Examples 2 to 4 The same operation as in Example 1 was carried out except that the addition reaction time was changed to the conditions shown in Table 1. The results are shown in Table 1.

Example 5 The same operation as in Example 4 was carried out except that the raw material was changed to (D) -aspartic acid. The results are shown in Table 1.

Example 6 A reactor equipped with a stirrer, a thermometer, a dropping funnel and a distillation apparatus was charged with 100 g (1.02 mol) of maleic anhydride and 100 g of anhydrous methanol, and the mixture was refluxed for 30 minutes with stirring, and then an excess amount of methanol was added. Distilled off. After diluting the thus-obtained monomethyl maleate maleate with 200 g of water, 45
90.7 g (1.02 mol) of a weight% sodium hydroxide aqueous solution
Then, 389 g (1.02 mol) of 35% by weight aqueous solution of (L) -disodium aspartate was added. The reaction mixture was stirred under reflux at 105 ° C for 4 hours, and then 90.7 g (1.02 mol) of 45% by weight aqueous sodium hydroxide solution was added again, and the mixture was refluxed under reflux.
Stirring was continued for 5 hours. The slurry obtained by distilling off the water from the reaction solution for another 0.5 hour was dried and powdered at 120 ° C by a spray drying method, and 361 g of tetrasodium salt of iminodisuccinic acid (crude yield 105%) was obtained as pure white crystals. Obtained. As a result of HPLC analysis using a chiral column, this tetrasodium salt of iminodisuccinic acid was (L, L)-
It was a stereoisomer mixture consisting of 50% body and 50% (D, L) -body, and no by-product of (D, D) -body was observed. Table 1 shows a detailed component analysis of the tetrasodium salt of iminodisuccinic acid.

Examples 7 to 8 The same operation as in Example 6 was performed except that the addition reaction time was changed to the conditions shown in Table 1. The results are shown in Table 1.

Comparative Example 1 49.0 g (0.5 mol) of maleic anhydride was dissolved in 105 g of water to be converted into maleic acid. To this (L) -aspartic acid 66.
After adding 6 g (0.5 mol), 48% by weight aqueous sodium hydroxide solution was added while cooling the solution. This reaction solution was stirred under reflux for 20 hours to carry out a reaction. The tetrasodium salt of iminodisuccinic acid in the obtained reaction solution was analyzed by HPLC using a chiral column, and 41% of (L, L) -form and (D,
In addition to L) -body 50%, by-products of (D, D) -body 9% were observed. A detailed compositional analysis of this tetrasodium salt of iminodisuccinic acid is presented.
Shown in 1.

Comparative Examples 2 to 3 The same operation as in Comparative Example 1 was performed except that the addition reaction time was changed to the conditions shown in Table 1. The results are shown in Table 1.

Comparative Example 4 The same operation as in Comparative Example 1 was carried out except that the raw material was changed to (D) -aspartic acid. The results are shown in Table 1.

[0058]

[Table 1]

However, the abbreviations and analytical conditions in Table 1 are as follows. (Abbreviation) IDSA: iminodisuccinate Asp: aspartic acid Fa: fumaric acid (Analysis conditions) Component analysis ratio: 207 nm using Inertsil ODS-2 column
Detected at IDSA stereoisomer composition ratio: detected at 254 nm using MCL GEL CRSIOW column

Example 9 (L, L) -body 50% and (D, L) -obtained by the same method as in Example 1
337 g (10 mol) of a stereoisomeric mixture of iminodisuccinic acid tetrasodium salt consisting of 50% body was suspended in 150 g of water.
After stirring at ℃ for 1 hour, it was filtered. The colorless and transparent filtrate obtained as the water-soluble fraction was suitable for use as a builder and the like without any sign of discoloration or slurry formation even after standing for 3 months. The filtrate was concentrated and then evaporated to dryness at 120 ° C.
Stereoisomeric mixture of tetrasodium iminodisuccinate consisting of (L, L) -form 57% and (D, L) -form 43% 286 g (8.5 mol,
A recovery rate of 85%) was obtained. On the other hand, when the residue obtained as a sparingly soluble fraction was evaporated to dryness at 120 ° C, (L, L) -form was 7% and (D,
51 g (1.5 mol, recovery 15%) of a stereoisomeric mixture of tetrasodium iminodisuccinate consisting of L) -form 93% was obtained.

Examples 10 to 15 The same operations as in Example 9 were carried out except that the mass and temperature of water used were changed as shown in Table 2. Table 2 shows the results.

[0062]

[Table 2]

Example 16 After the hydrolysis reaction solution obtained in Example 1 was allowed to cool to 50 ° C.,
225 g (2.25 mol) of 98% sulfuric acid was added at a dropping rate of 5.0 g / min. During this period, the temperature of the reaction solution rose to 80 ° C. When this reaction solution was allowed to cool at 20 ° C. for 8 hours, crystals were precipitated and separated by filtration. Wet crystals obtained as a slightly soluble fraction were stored at 105 ° C.
After evaporation to dryness at 508 g, 508 g of crystals consisting of a mixture of stereoisomers of iminodisuccinic acid and sodium sulfate were obtained. On the other hand, the colorless transparent filtrate obtained as the water-soluble fraction was concentrated and then evaporated to dryness at 105 ° C. to give 265 g of a crystal consisting of a stereoisomer mixture of iminodisuccinic acid and sodium sulfate.
I got The composition of each category is shown in Table 3.

Examples 17 to 22 The same operations as in Example 16 were carried out except that the cooling temperature and time were changed to those shown in Table 3. The results are shown in Table 3.

[0065]

[Table 3]

Example 23 The biodegradability test of (L, L) -iminodisuccinic acid tetrasodium salt obtained in Example 15 was carried out under the following conditions according to the OECD test guideline 301 modified MITI test. The results are shown in Table 4. (Test conditions) Test sample concentration: 30 mg / l Activated sludge: Standard activated sludge Activated sludge concentration: 100 mg / l Test temperature: 25 ± 1 ° C Test period: 28 days

Comparative Examples 5-8 Under the same conditions as in Example 23, (D, D)-, (D, L)
A biodegradability test was carried out on the tetrasodium iminodisuccinate and their isomer mixtures. The results are shown in Table 4.

[0068]

[Table 4]

Example 24 The ability of the (L, L) -iminodisuccinic acid tetrasodium salt obtained in Example 15 to trap calcium ions was determined according to J.
Am. Oil. Chem. Soc., 1970, 48, 682 according to the method described in page. The results are shown in Table 5.

Comparative Examples 9 to 12 Under the same conditions as in Example 24, a trapping ability test was also conducted on (D, L) -iminodisuccinic acid tetrasodium salt and an isomer mixture. The results are shown in Table 5.

[0071]

[Table 5]

According to the method of the present invention, a high-purity iminodisuccinic acid and its alkali metal salt can be obtained with a high yield and a short reaction time by using a maleic acid half ester which is easily prepared from maleic anhydride. . The present invention also has the following advantages. (1) Aspartic acid, alkali metal aspartic acid salt, ammonia, and aqueous solutions thereof that are available as industrial raw materials can be used. (2) Since there is almost no impurity by-product through the addition reaction step, the hydrolysis reaction step, the evaporation-drying step, or the acid precipitation crystallization step, it can be carried out as a one-tank reaction without isolating the intermediate. is there. (3) Maleic acid half ester is a non-volatile liquid that is rich in water solubility and fluidity, unlike maleic anhydride and maleic acid used in the prior art, and is extremely advantageous in handling. (4) Since there is no fear of unfavorable side reactions such as amidation reaction, various combinations are possible in the order of mixing with other raw materials in the addition reaction step. (5) Since the addition reaction is completed within a short period of time, highly productive industrial production is possible. (6) Unlike the prior art, the racemization of the target substance does not proceed at all through the process, and therefore, by using (L) -aspartic acid as a raw material, the purpose of not containing the (D, D) -form which is hardly biodegradable The product is obtained, which is extremely advantageous when used as a biodegradable chelating agent. (7) When (L) -aspartic acid is used as a raw material, (D, L)-by preferential crystallization is selected from the mixture of the (L, L) -form and the (D, L) -form of the target product obtained. By eluting the (L, L) -form by removing the body or washing, the (L, L) -form that is particularly excellent in biodegradability, chelating ability, and water solubility can be selectively obtained.

Claims (6)

[Claims] 1. A method for producing an alkali metal salt of iminodisuccinic acid, which comprises adding a maleic acid half ester to aspartic acid or ammonia under alkaline conditions. 2. A method for producing iminodisuccinic acid, which comprises adding a maleic acid half ester to aspartic acid or ammonia under alkaline conditions and then acidifying and crystallizing with a mineral acid. 3. A process for producing an alkali metal salt of iminodisuccinic acid containing no (D, D) -form, which comprises adding a maleic acid half ester to (L) -aspartic acid under alkaline conditions. 4. An iminodisuccinic acid containing no (D, D) -form, characterized in that a maleic acid half ester is added to (L) -aspartic acid under alkaline conditions, and then acid precipitation crystallization is carried out with a mineral acid. Manufacturing method. 5. Removal of the (D, L) -form by preferential crystallization from the mixture of the (L, L) -form and the (D, L) -form of iminodisuccinic acid or its alkali metal salt, or washing with water. Is characterized by the elution of the (L, L) -form by (L, L)
L) -A method for selectively obtaining iminodisuccinic acid or an alkali metal salt thereof. 6. A biodegradable chelating agent containing, as an active ingredient, at least one of iminodisuccinic acid and its alkali metal salt, which does not contain (D, D) -form.