JPS58144379A - Recovery of 2-mercaptothiazoline compound - Google Patents

Abstract

PURPOSE:To prepare the titled compound useful as an intermediate of agricultural chemicals, pharmaceuticals, etc., economically, by reacting monoethanolamine with carbon disulfide, separating the compound from the reaction mixture, and extracting the solution left after the separation with a specific halogenated hydrocarbon. CONSTITUTION:Monoethanolamine is made to react with carbon disulfide to obtain 2-mercaptothiazoline compound of formula (R<1>-R<4> are H, lower alkyl or hydroxyl-substituted lower alkyl). The waste liquid left after separating the objective compound from the reaction mixture (including the recrystallization filtrate, washing liquid of crystals, etc.) is extracted with a halogenated aliphatic hydrocarbon of formula CmHnZ (m and l are integer of 1-4; n is integer of 0-10; Z is Cl or Br), especially dichloromethane, 1,2-dichloroethane or 1,2-dichloropropane. The objective compound absolutely devoid of inorganic substance can be prepared in high yield and purity by this process.

Description

Detailed Description of the Invention The present invention uses monoethanolamine as a starting material and reacts it with carbon disulfide to produce 2-mercaptothiazolines. The present invention relates to a method for recovering 2-mercaptothiazolines in high yield and purity by further treating waste liquids such as the like.

The following general formula of 2-mercaptothiazolines (in the formula, R'
1R", R3 and R4 represent a hydrogen atom, a lower alkyl group, or a hydroxy group-substituted lower alkyl group, and may be the same or different from each other. It is an industrially important compound.

The method for synthesizing these 2-mercaptothiazolines includes (1) a method of synthesizing monoethanolamine and carbon disulfide using an alkali hydroxide or a transition metal as a catalyst;
, R2, R3 and R4 have the same meanings as above) (2) Method 3 of converting monoethanolamine into a sulfuric ester and reacting it with carbon disulfide in the presence of an alkali hydroxide R1 1 H2N -C-C- 08O3H+ 2NaOH+C82
1 4R2 (In the formula, R1, R2, R3 and R" have the same meanings as above.) (8) After converting monoethanolamine into halogenated ethylamine, this is reacted with carbon disulfide in the presence of alkali hydroxide. Method 3R1 (wherein R1, R2, R3 and R4 have the same meanings as above, and X represents a halogen atom such as fluorine, chlorine or iodine).

In any of these synthesis methods, water is used as a reaction solvent and a crystallization solvent from the viewpoint of dissolving inorganic reactants or catalysts and dissolving ability of 2-mercaptothiazolines. However, during separation of the product from the reaction solution and crystallization treatment, a considerable amount of the product is dissolved under hydraulic pressure as a solvent, resulting in a loss of 2-mercaptothiazolines as a result of this dissolution. Therefore, the industrial disadvantages of conventional synthesis methods were unavoidable.

Furthermore, even if an attempt is made to concentrate the waste liquid for recovery of 2-mercaptothiazolines, the coexisting inorganic substances are also concentrated and mixed with the 2-mercaptothiazolines, resulting in a significant decrease in purity.

Moreover, since the concentration operation requires thermal energy, it is inevitable that the process will be uneconomical.

The present inventors have conducted various studies in order to overcome these problems in the conventional production of 2-mercaptothiazolines, and as a result, they have discovered that waste liquids such as reaction liquids and filtrates from which the desired product has been separated can be used as a It has been found that 2-mercaptothiazolines can be efficiently separated and recovered with high purity by extraction treatment with halogenated hydrocarbons. The present invention has been made based on this knowledge.

That is, in the present invention, when producing 2-mercaptothiazolines by reacting monoethanolamine and carbon disulfide, the solution after separating the 2-mercaptothiazolines is further converted to , m is from 1 to 4, n is from 0 to 1o, and t is from 1 to
Each represents an integer of 4, and 2 represents a chlorine or bromine atom. Further, CmHn may be linear or branched. ) Provides a method for recovering 2-mercaptothiazolines, which is characterized by carrying out an extraction treatment with a halogenated aliphatic hydrocarbon represented by:

The present invention will be explained in more detail below.

In the method of the present invention, the produced 2-mercaptothiazolines are separated from the reaction solution by IC such as filtration or centrifugation.
-Recovers mercaptothiazolines. Of course, this waste liquid may also contain recrystallization filtrate, crystal washing liquid, etc.

The waste liquid discharged during the synthesis of 2-mercaptothiazolines is usually 0.5 to 2-mercaptothiazolines.
5.0 wt% and K Na2S, Na5H1Na2
It contains alkali salts such as SO4, NaCt, transition metals, etc. in the range of 10 to 55% by weight, but according to the method of the present invention, the concentration traps of 2-mercaptothiazolines and inorganic substances are not limited, and dissolved It is possible to recover only the 2-mercaptothiazolifs with high purity and high yield.

Examples of the halogenated aliphatic hydrocarbon represented by the general formula (2) used in the present invention include 1-chlorobutane, 1
-Bromobutane, monochlorobutane, monobromomethane, dichloromethane, dibromomethane, monochloroethane, monobromoethane, 1,2-dichloroethane, ■, 2
-dibromoethane, 1.1-dichloroethane, 1.2-
Dichloropropane, 1,2-dibromopropane, trichloromethane, tribromomethane, 1,1.1-)IJchloroethane%11112-trichloroethane, 1,1.
1.2-tetrachloroethane, 1.1.2-).

Lichloropropane, 1,2.3-trichloropropane,
Tetrachloromethane, 1.1-dichloroethene, 1.2
-dichloroethene, 1,1.2-)lichloroethene,
1.1.2.2-f trough o O etheno, 3-chloropropene-1, etc. Among them, 2-mercaptothiazolines generally have a high solubility, and dichloromethane, which is relatively inexpensive, 1.2 -dichloroethane and 1,2-dichloropropane are preferred.

If the number of carbon atoms is 5 or more (such as dichloropentane), the solubility of 2-mercaptothiazolines is low and it is not practical. Furthermore, aromatic hydrocarbons such as chlorobenzene and chlorotoluene, and aromatic hydrocarbons such as benzene, toluene and xylene have low solubility and are therefore unsuitable as processing solvents.

The amount of solvent used may vary depending on the solvent used, the type of target 2-mercaptothiazoline, treatment temperature, number of treatment operations, amount of inorganic salt, etc., but it is usually 200 parts per 100 parts of 2-mercaptothiazoline dissolved in the waste liquid. Part to 5
000 parts, preferably 500 to 3000 parts. In this case, it is of course preferable to use a necessary and sufficient amount to dissolve the 2-mercaptothiazoliph.

Although the method of the present invention can be applied to the 2-mercaptothiazoline waste liquid of the conventional synthesis method, it is not limited to this waste liquid, and can be applied to any waste liquid that contains inorganic substances together with 2-mercaptothiazoline. It can also be applied to things.

Further, the waste liquid may contain unreacted substances, by-products, and the like.

The method of the present invention includes 2-mercaptothiazolines represented by the general formula (I), such as 2-mercaptothiazoline,
4-Methyl-2-mercaptothiazoline, 4,4-dimethyl-2-mercaptothiazoline, 4.4-bis(hydroxymethyl)-2-mercaptothiazoline, 5.5-
Dimethyl-2-mercaptothiacyly/5-ethyl-2
-Mercaptothiazoline, 4.5-dimethyl-2-mercaptothiazoline, 4.4.5-trimethyl-2-mercaptothiazoline, 4.4.5.5-tetramethyl-
2-mercaptothiazoline, 4.5-bis(hydroxymethyl)=2-mercaptothiazoline, 4-propyl-
It can be applied to 2-mercaptothiazoline, 4-ethyl-2-mercaptothiazoline, 5-propyl-2-mercaptothiazoline, and 5-methyl-2-mercaptothiazoline, but also in the production of other 2-mercaptothiazolines. Of course it can be applied.

According to the method of the present invention, the captothiazolines in the 2-mercaptothiazoline waste solution, which conventionally could not be avoided, do not contain any inorganic substances. It is suitable for application to.

Next, the present invention will be explained in more detail based on examples.

In the following examples, 2-mercaptothiazolines were analyzed by the method of quantifying -8H groups using iodine.

Further, the amount of inorganic salts in the crystals was determined by atomic absorption spectrometry from the burning residue obtained by treating the sample at 600 to 700°C, and the amount of organic by-products was determined by liquid chromatography and gas chromatography.

Example 1 Monoethanolamine 30.5g, sodium hydroxide 6
0g and 76g of carbon disulfide were reacted to produce 2-mercapto-2-thiazoline, which was filtered.
A filtrate of the following composition was produced.

Filtrate component Filtrate composition Pure equivalent 2-mercapto-thiazoline 5.72gNa 5.18gNa
OH equivalent Na content: 42.44% This filtrate: 90.6
Add 110 g of dichloromethane to 3 g, keep at 30°C, shake well, and extract. Furthermore, dichloromethane 5 is added to the extraction residue.
0 g was added and the above procedure was repeated, and the extracted layer was placed in an eggplant flask and the solvent was removed using an evaporator. The amount of 2-mercapto-2-thiazoline crystals recovered was 5.16 g.
The purity was 99.9%, the amount of inorganic matter was 0, and the recovery rate was 99.5%.

Example 2 Aminoethyl sulfate 71g 1 Sodium hydroxide 4
0 g and 38 g of carbon disulfide were reacted to produce 2-mercapto-2-thiazoline, which was filtered out. The weight of each component in 422.17 g of the mixed filtrate, which was a mixture of the filtrate and the appropriate crystal washing solution, was as follows.

2-Mercapto-2-thiazoline 3.88
gNa2SO462,39g Other by-products and unreacted substances 1.75g Water
354.15g of this filtrate 4
Put 22.17 g into a separatory funnel, add 110 g of 1,2-dichloroethane, shake thoroughly at room temperature, transfer the extracted layer to an eggplant flask, and then add 50 g of 1,2-dichloroethane to the extraction residue for washing. The extracted layer was transferred to the above-mentioned eggplant flask, and then the extraction solvent was removed using an evaporator.

Thus crystals of 2-mercapto-2-thiazoline 3.8
I got g. The purity was 99.9%, the inorganic content was 0%, and the recovery rate of 2-mercapto-2-thiazoline was 98.0%.

Example 3 The composition of the recrystallized filtrate of 2-mercapto-2-thiazoline synthesized from chloroethylamine hydrochloride was as follows.

2-mercapto-2~thiacyri/3,4 gNaC64
, 1g Unreacted substances and by-products 0.4g water
120.4 g of this filtrate was collected in the same manner as in Example 2. However, 1.2-
Dichloroethane was initially added to i o o g, 50 g for washing.
g was used. After removing 1,2-dichloroethane, 3.36 g of 2-mercapto-2-thiazoline crystals were obtained. The purity was 99.9%, the amount of inorganic substances was 0%, and the recovery rate was 98.7%.

Claims (1)

[Claims] In producing 2-mercaptothiazolines by reacting monoethanolamine and carbon disulfide, the solution after separating the 2-mercaptothiazolines is further mixed with the general formula % formula % (in the formula, m is from 1 to 4, n is from 0 to 10, and t is from 1 to
Each represents an integer of 4, and Z represents a chlorine or bromine atom. 1. A method for recovering 2-mercaptothiazolines, which comprises extraction treatment with a rogogenated aliphatic hydrocarbon represented by