JP2001192360A - Method of manufacturing iron s,s-ethylenediamine-n,n'- disuccinic alkali salt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of efficiently producing an iron S,S- ethylenediamine-N,N'-disuccinic alkali salt little in the content of a lactam ring compound. SOLUTION: The high purity iron S,S-ethylenediamine-N,N'-disuccinic alkali salt little in the content of a lactam ring compound is produced by adding S,S-ethylenediamine-N,N'-disuccinic acid to an aqueous solution of an iron compound to form an acid type compound of iron S,S-ethylenediamine-N,N'- disuccinic acid and adding an alkali to the reaction product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alkali metal salt of S, S-ethylenediamine-N, N'-disuccinic acid, and more particularly to a method for producing S, S-ethylenediamine-N, N'- having a low lactam ring compound content. The present invention relates to a method for efficiently producing an iron disuccinate alkali salt. The iron alkali salt obtained according to the present invention is useful, for example, as a photographic chemical, a plant minor component fertilizer, a combustion aid, a polishing accelerator, and the like.

[0002]

2. Description of the Related Art S, S-ethylenediamine-N, N'-disuccinic acid (hereinafter abbreviated as S, S-EDDS) has excellent chelating properties, has good biodegradability and causes environmental pollution. Cleaning agent (Japanese Unexamined Patent Publication
It is expected that the ferric salt will be used as a photographic agent (Japanese Patent Application Laid-Open No. 6-12951 / 1991).
It has also been attempted to use this method. The manufacturing method is, for example, "Neal, JA & Rose, NJ, Inorgan
ic Chemistry ", Vol. 7, No. 11, November 1968, No. 2405
, Page 2412, and the like.

[0003] On the other hand, ordinary amino acids tend to form lactam ring compounds which are intramolecular cyclic amide compounds in the synthesis process ("Daikatsu Kagaku", Vol. 5, p. 296, Showa 37)
It has been confirmed that a lactam ring compound is also produced as a by-product when producing S, S-EDDS belonging to amino acids (published on July 30, 3rd edition, Asakura Shoten) (“Chemical Abstract” record number 107: 103785, 1987).

The lactam ring compound (CAS number: 95175-
15-8, hereinafter referred to as lactam) is inferior in biodegradability and chelate-forming ability. Therefore, a method for suppressing lactam by-products in producing S, S-EDDS and metal salts thereof has been studied. Have been.

It has been confirmed that the lactam is formed by an intramolecular dehydration amidation reaction of S, S-EDDS, and that the reaction rate of the lactam is accelerated by heating in an aqueous solution having a pH of 5 or less. . Above all, when producing an S, S-EDDS iron salt using iron oxide, it is necessary to raise the reaction temperature in order to promote the reaction, so that the amount of lactam by-product inevitably increases.

Therefore, as a means for suppressing the amount of lactam by-produced, a method of using iron oxide having a large specific surface area to increase the reaction rate of the main reaction (JP-A-11-130074)
No. 1) and S, S-E corresponding to the amount consumed in the main reaction.
By adding DDS in portions, unreacted S, S-ED
Method for shortening the retention time of DS in a high temperature state
1-1189579) has also been proposed.

However, since the main reaction in which S, S-EDDS reacts with iron oxide and the cyclization reaction for producing lactam are parallel reactions, there is naturally a limit in reducing the amount of by-product lactam.

On the other hand, a method of using a soluble ferric salt for the production of a ferric aminopolycarboxylic acid salt is known (for example, JP-A-49-82623), and an iron ion and S, S-
Since the chelation reaction with EDDS ions proceeds at a high speed even at room temperature, this method can be said to be an advantageous reaction for suppressing the lactam by-product reaction. For this reason, a method of adding an iron salt to an aqueous solution of an aminocarboxylate is widely used for the production of an iron aminocarboxylate, and a similar reaction method is employed for the production of an S, S-EDDS iron salt. (JP-A-7-2745
Issue publication). However, no attempt has been made to suppress the lactam formation reaction by adjusting the order of addition of the raw materials and the pH during the reaction.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and its object is particularly to produce an S, S-EDDS ferric acid alkaline salt. It is an object of the present invention to provide a method capable of suppressing production of a lactam (ring compound) by a reaction as much as possible and producing a high-purity S, S-EDDS ferric alkali salt having a low lactam content with a high yield. .

[0010]

Means for Solving the Problems The production method of the present invention which can solve the above-mentioned problems is a method for preparing an aqueous solution of an iron compound by adding S, S-
S, S-EDD by adding EDDS or its alkali salt
After generating an acid type compound of S iron, an alkali is added to the compound to form a high-purity S, S-ED with a low lactam content.
The gist lies in producing DS iron alkali salts.

[0011] In carrying out this method, while maintaining the pH of the aqueous solution of iron compound at 2 or less and adding S, S-EDDS or an alkali salt thereof to the aqueous solution, the by-product of lactam is obtained. It is preferable because the amount can be suppressed more effectively, and particularly preferable as the iron compound to be used are ferric chloride, ferric sulfate and ferric nitrate, which can be used alone. In addition, two or more kinds can be used in combination as needed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The inventors of the present invention have conducted various studies under the above-mentioned problems, and found that lactamization of S, S-EDDS, which occurs as a side reaction, is caused by (1) an aqueous reaction system. It is easy to proceed when the temperature is increased, (2) pH 2 which is the normal pH range of the synthesis reaction of aminopolycarboxylate iron.
(3) S, once generated,
It was confirmed that the S-EDDS iron salt did not participate in the lactam formation reaction at all. As a result of further research based on these findings, during the progress of the main reaction, S, S-ED
If the concentration of DS is kept low and in a low pH range, side reactions are suppressed, the amount of lactam by-products is reduced, and high purity S, S-ED
The present inventors have found that a DS iron salt can be obtained, and have reached the present invention.

That is, in the present invention, as a first means for realizing the above preferable conditions, S, S
-A method of adding EDDS or an alkali salt thereof is adopted. That is, when this method is employed, the main reaction always proceeds in a state of an excess of iron ions and quickly bonds with the iron ions, so that the unreacted S, S-EDDS is kept close to zero. In addition, if the alkali molar amount of the added S, S-EDDS alkali salt is properly adjusted, the S, S-E
An acid type compound of DDS iron (hereinafter abbreviated as S, S-EDDS ferric acid) can be produced, whereby the pH of the reaction system can always be kept in an acidic range of 2 or less.

[0014] The S, S-EDDS ferric acid once formed does not become lactam any longer even if the pH is increased by adding an alkali, as described above. , S-EDDS iron salt can be produced.

That is, as described above, it is effective to keep the concentration of free S, S-EDDS present in the reaction system low in suppressing lactam by-products.
The present invention employs a reaction procedure in which S, S-EDDS or an alkali salt thereof is added to an aqueous solution containing an iron compound (i.e., iron ions) as described above. , S-EDDS has a low concentration, and the added S, S-EDDS reacts with an iron compound present in an excessive amount in the system sequentially and changes into S, S-EDDS ferric acid.
Therefore, the concentration of free S, S-EDDS present in the reaction system is always kept at a low level, which is coupled with the fact that the reaction system is kept in a low pH range by the production of S, S-EDDS ferric acid. Thus, the lactam by-product reaction is effectively suppressed.

The reaction between iron ions and S, S-EDDS occurs instantaneously. Further, since the formation of the chelate metal salt is an equilibrium reaction, free S, S-ED existing in the main reaction system is present.
Although the amount of DS cannot be completely eliminated, the stability constant of the iron chelate is high, and when the amount of iron ions is excessive, the equilibrium reaction proceeds in the direction of decreasing free S, S-EDDS. Free S, SE present in main reaction system
The DDS will be substantially close to zero. As a result, a lactam by-product reaction caused by the presence of the free S, S-EDDS hardly occurs, and it is possible to obtain an S, S-EDDS iron salt having a small lactam content.

Therefore, in this reaction, a method is employed in which S, S-EDDS is gradually added to the iron salt aqueous solution while stirring it. The addition rate at this time is not particularly limited,
It may be adjusted according to the degree to which the added S, S-EDDS is diffused into the reaction system by stirring, and the cooling conditions for suppressing the exothermic reaction. By the way, if the addition rate is too fast or the whole amount is added all at once, high pH will occur locally in the reaction system.
In addition to the formation of a zone and the formation of iron hydroxide precipitate to cause turbidity, it is heated by the reaction heat until the S, S-EDDS is uniformly dispersed, and the amount of lactam by-product tends to increase. come.

That is, in order to suppress the lactam by-product reaction, the reaction temperature is preferably low, and the reaction is preferably carried out while cooling so as not to exceed 70 ° C., more preferably not to exceed 60 ° C. desirable. The concentration of the reaction system may be adjusted to such an extent that the resulting S, S-EDDS ferric acid slurry can be uniformly stirred and fluidized. If a strong stirrer is used, the concentration can be set higher.

As the iron compound to be used, those having high solubility are advantageous in increasing the concentration of the final product to enhance the productivity, and preferred iron compounds include iron nitrate, iron chloride, and iron sulfate. . These iron compounds can be used as a ferrous salt or a ferric salt.
In applications where a monovalent EDDS iron salt is required, a ferric salt is used, or a ferrous salt is used to produce a divalent EDDS iron salt, and then, for example, air, oxygen, or peroxide or Oxidized using an oxidizing agent such as persulfate and trivalent EDD
What is necessary is just to employ | adopt the method of changing to S iron salt.

The molar ratio of S, S-EDDS to the iron compound is
Usually, it is desirable to use S, S-EDDS in the range of 99 to 101 mol% with respect to the iron compound, although it varies depending on the allowable lactam content. By the way, if the amount of iron compound used is too large, S, S-EDDS in the final step
When the pH is increased by adding an alkali to form an iron alkali salt, precipitation of iron hydroxide is likely to occur, which is not preferable. On the other hand, when the amount of S, S-EDDS is excessive,
When an S, S-EDDS iron alkali salt is produced by increasing the amount of S, S-S-EDDS, excess S, S-EDDS causes a lactam by-product reaction, and the product purity decreases.

S, S-ED added to aqueous solution of iron compound
DS or an alkali salt thereof can be used in any form such as powder, aqueous solution or slurry.
When the method of adding the crystal of S as it is is adopted, if the addition rate is high, it may be difficult to disperse uniformly in a mamako state, and on the other hand, the method of dispersing in water and adding in a slurry form may be a uniform dispersion. Is advantageous, but has fluid S, S
-A large amount of water is required to obtain the EDDS slurry,
The tendency for the concentration of the reaction system to be low cannot be denied.

On the other hand, if the method of adding S, S-EDDS in the form of an aqueous solution or slurry of an alkali salt is adopted, the concentration at the time of addition can be increased, and
The amount of alkali necessary for neutralizing the slurry of S, S-EDDS ferric acid after the reaction is also reduced, which is preferable because the concentration of the final product can be increased.

The amount of alkali used when converting S, S-EDDS into an alkali salt is 3 to S, S-EDDS.
It is desirable to keep it to less than mol. By the way, with an alkali amount of 3 mol or less, all of the S, S-EDDS iron produced is kept in the acid type, and the pH of the reaction solution can be maintained in a low pH range which is preferable for suppressing lactam production. On the other hand, if an excessive amount of alkali is used in excess of 3 mol, the pH of the reaction system increases due to the excessive amount of alkali, the amount of lactam by-produced increases, and the amount of precipitated iron hydroxide increases. In addition, the purity of the final product decreases and the turbidity of the aqueous liquid becomes remarkable.

A predetermined amount of S, S-EDD is added to an aqueous solution of an iron compound.
The reaction solution after the addition of S or the alkali salt thereof is in a slurry state due to the precipitation of the generated water-insoluble S, S-EDDS ferric acid. After the addition of S, S-EDDS or the alkali salt thereof is completed, It is desirable that stirring be continued for 30 minutes or more, preferably 1 hour or more to complete the ferric acid formation reaction and to dissolve a small amount of iron hydroxide that may be formed in the dispersion process.

By filtering the thus obtained S, S-EDDS ferric acid slurry, high purity S, S-EDDS ferric acid having a small lactam content can be obtained as a solid. In addition, as in photographic applications, when it is not necessary to separate inorganic salts by-produced in the reaction step (for example, when ammonium is used as an alkali, ammonium chloride, ammonium sulfate, ammonium nitrate, etc.), the generated S,
An alkali is added to and dissolved in the S-EDDS iron acid slurry, and can be used as it is as an aqueous solution of S, S-EDDS iron alkali salt. The amount of alkali used at this time may be an amount necessary for raising the pH of the S, S-EDDS ferric acid-containing solution to a desired pH to form an alkali salt.

[0026]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and may be appropriately modified within a range that can conform to the purpose of the preceding and the following. Modifications may be made and all of them are included in the technical scope of the present invention.

Example 1 408 g of water was placed in a reaction vessel equipped with a stirrer and a thermometer.
Then, an aqueous solution of ferric nitrate in which 408 g (purity: 99.0% by mass, 1.00 mol) of ferric nitrate nonahydrate was dissolved was added. In another reaction vessel, S, S-EDDS: 342.3 g
(Purity 85.3% by mass, 1.00 mol) in water: 380 g
And ammonia water: dissolved in 204 g (ammonia content 25.0% by mass, 3.00 mol) and 3% of S, S-EDDS
An aqueous ammonium salt solution (the temperature of the solution is 40 ° C.) is obtained.

While stirring the ferric nitrate aqueous solution, an aqueous solution of a triammonium salt of S, S-EDDS is added dropwise thereto over 1 hour. After completion of the dropwise addition, stirring is further continued for 1 hour to obtain a S, S-EDDS ferric acid slurry (pH 1.4). To this, ammonia water: 68 g (ammonia content 2)
5.0% by mass, 1.00 mol), and added with S, S-EDD.
S ferric acid was dissolved, pH 4.8 S, S-EDDS iron ammonium salt aqueous solution: 1810 g (content 20.0% by mass,
1.00 mol). The lactam content (calculated on the assumption that the molecular weight is 274, the same applies hereinafter) of the aqueous solution was measured by liquid chromatography and found to be 0.4% by mass based on the S, S-EDDS iron ammonium salt content.

Example 2 In a reaction vessel equipped with a stirrer and a thermometer, water: 787 g, ferric nitrate nonahydrate: 408 g (purity: 99.0% by mass,
1.00 mol) is added.
While stirring this aqueous solution, S, S-EDDS: 34
2.3 g (purity: 85.3% by mass, 1.00 mol) was added little by little over 1 hour while keeping the crystals. After the addition, stirring is continued for another hour to obtain a S, S-EDDS ferric acid slurry (pH 0.1). Ammonia water: 272g
(Ammonia content 25.0% by mass, 4.00 mol) to dissolve S, S-EDDS ferric acid,
S-EDDS iron ammonium salt aqueous solution: 1810 g (content: 20.0% by mass, 1.00 mol) was obtained. When the lactam formation ratio of this liquid was measured in the same manner using liquid chromatography, the formation ratio was 0.2 mass in terms of the S, S-EDDS iron ammonium salt content.

Comparative Example 1 An aqueous solution of ferric nitrate was added dropwise to an aqueous solution of S, S-EDDS triammonium salt at the same charge as in Example 1,
-An EDDS iron ammonium salt aqueous solution was obtained. The lactam generation ratio in the aqueous solution was 1.2% by mass (based on S, S-EDD).
S iron ammonium salt content).

Comparative Example 2 In a reaction vessel equipped with a stirrer and a thermometer, 408 g of water: 408 g of ferric nitrate 9-hydrate (purity: 99.0% by mass,
(1.00 mol) was dissolved therein.
In another reaction vessel, S, S-EDDS: 342.3 g (purity: 85.3% by mass, 1.00 mol) was charged with water: 380 g and ammonia water: 272 g (ammonia content: 25.0% by mass, 4.00 mol). ) To obtain an aqueous solution of tetraammonium salt of S, S-EDDS (liquid temperature: 45 ° C.).

While stirring the aqueous solution of tetraammonium salt of S, S-EDDS, the above aqueous solution of ferric nitrate was added to the aqueous solution for 1 hour.
The mixture was added dropwise over a period of time, and after the completion of the addition, stirring was further continued for 1 hour. The amount of the obtained aqueous solution of S, S-EDDS ammonium salt is 1810 g (content: 20.0% by mass, 1.00 mol).
And the pH was 4.7. The lactam generation ratio of this liquid was 2.2% by mass (based on the amount of S, S-EDDS iron ammonium salt).

The production method of Comparative Example 2 is a known method as a general production method of chelated iron alkali salts. Compared with Examples 1 and 2, the production ratio of lactam is clearly higher.

[0034]

The present invention is constituted as described above and comprises reacting an iron compound with S, S-ethylenediamine-N, N'-disuccinic acid or its alkali salt to form S, S-ethylenediamine-N, N The production of lactam ring compounds by side reactions is suppressed as much as possible by devising the reaction procedure and reaction conditions when producing '-iron disuccinate alkali salt, and high purity S, S- with low lactam content is obtained. It has become possible to efficiently produce an ethylenediamine-N, N'-iron disuccinate alkaline salt.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masanori Furukawa 3-3, Hinagahigashi, Yokkaichi-shi, Mie Pref. F-term (reference) 4Y006 AA02 AC47 BB31 BC16 BE10 BE12 BE14 BE62 BE90 BS10 BS70 BU32

Claims (3)

[Claims] 1. An aqueous solution of an iron compound to which S, S-ethylenediamine-N, N'-disuccinic acid or an alkali salt thereof is added to form an acid type compound of S, S-ethylenediamine-N, N'-disuccinate iron. A method for producing an alkali iron salt of S, S-ethylenediamine-N, N'-disuccinate having a low content of a lactam ring compound, which comprises adding an alkali to the resultant product. 2. The solution of S, S-ethylenediamine-N, N ′ while maintaining the pH of the aqueous solution of iron compound at 2 or less.
2. The method according to claim 1, wherein disuccinic acid or an alkali salt thereof is added.
Production method described in 1. 3. An iron compound comprising: ferric chloride, ferric sulfate,
The method according to claim 1 or 2, wherein the method is at least one selected from the group consisting of ferric nitrate.