CS209595B1 - Method of preparation of the amino salts of the 2-mercaptobenzthiazole - Google Patents

Description

The present invention provides a novel process for the preparation of amine salts of 2-mercaptobenzothiazole by extraction of 2-mercaptobenzothiazole from its crude melt with dilute aqueous amine solutions.

The amine salts of 2-mercaptobenzothiazole are an intermediate in the preparation of N-substituted beozthiazole-2-sulfenamides. They are formed by the reaction of an amine with 2-mercaptobenzothiazole, respectively. with its water-permeable salts. _

+ε + η HN /

^ R ²

H _? 0 —-—>

NH ^X + Me 2 R ² wherein Me. = H, Na, Ca, n = 1.2 (according to Me binding). 1 2 '

R, R = identical or different, H, a primary, secondary or tertiary, straight-chain or branched C 2 -C 4 alkyl, cycloalkyl or C 5 -C 8 cycloalkyl, or form a six to eight-membered ring optionally containing an oxygen atom, or nitrogen

U.S. Patents 2100,692, 2,214,460 and 2,226,767 protect the preparation of the cyclohexylamine salt of 2-mercaptobenzothiazole from technical 2-mercapobenzothiazole and its use as a vulcanizing agent. More particularly, processes for the preparation of amine salts are disclosed in the pa- tients protecting the preparation of N-substituted benzothiazole-2-sulfenamides, e.g. in US 2,339,002, 2,772,279, 3,144,652, British 413,296, 452,044, 519,617, 655,668,

106 577, 1 389 407, German 615 589, 2 056 762, Japanese 74 110 664, 74 134 674, French 852 118, 950 693, 1 549 002.>

Prior to the known processes for the preparation of the amine salts of 2-mercaptobenzothiazole, only 2-mercaptobenzothiazole can be used, from which pitches and other impurities were by-products of the manufacturing process. A variety of methods are available for the purification of 2-mercaptobenzothiazole on different principles. The most widespread method is to convert 2-mercaptobenzothiazole to water-soluble salts e.g. for sodium salts (U.S. Pat. Nos. 114,693; 2,191,657; 2,807,620; British 642,597; German 855,564; 1,940,364); lij 006, german 1 940 364 /, ammonium / czech. AO 108,884 /.

The process for the preparation of the amine salts of 2-mercaptobenzothiazole according to the invention allows the production of these salts in one step, without the need for auxiliary drugs such as e.g. inorganic salts and acids. The process is a useful melt for a melt from which some components, e.g. by steam steaming (j) and p. pat. 7 8j7 662 /, hydrogen sulphide / MS. AO 197 513; otherwise. In the preparation process, the amount of flakes, the amount of which is practically the same in all processes for the preparation of the 2-mercaptobenzothiazole salts, depends in particular on the melt quality of the 2-mercaptobenzothiazole. The solid amine salt of 2-mercaptobenzothiazole is a more convenient form for transport than an aqueous solution e.g. sodium salt. The process according to the invention is also advantageous from the point of view of further processing, in particular to the corresponding N-substituted benzothiazole-2-sulfenamides because of their very good quality and the considerably less waste water pollution.

The process for the preparation of the amine salts of 2-mercaptobenzothiazole according to the invention is as follows: The crude 2-mercaptothienzthiazole melt is discharged from the reactor or other suitable apparatus to ensure the best possible melt mixing with the present amine, water and, if necessary. organic solvent. The amine is used in an amount of 1.05-5 moles per 1 mole of 2-mercaptobenzothiazole and diluted with a twenty-fold amount of water relative to. the amount of melt. Preferably, a dilute amine solution obtained from the distillation of the mother liquors is used after separation of the product of the after-treatment of the amine salt of 2-mercaptobenzothiazole (e.g. the saturated mother liquor is recycled after separation of the solid amine salt of 2-mercaptobenzothiazole to the sulfenamide, supplemented with fresh amine, optionally with water, or after appropriate treatment. Of the organic solvents, suitable are liquid aliphatic and aromatic hydrocarbons, optionally chlorinated, and sparingly soluble lower aliphatic alcohols in an amount of 0,1 0.1-2 parts per 1 part of the crude melt of 2-mercaptobenzothiazole. Suitable are e.g. gasoline, kerosene, benzene, toluene, xylene, trichlorethylene, perchlorethylene, tetrachlorethylene, chloroform, chlorobenzene, butanol, amyl alcohols and the like. An appropriately elevated temperature of 40 ° C up to the boiling point of the extraction system used is maintained in the mixer and the mixture is transferred to an extraction apparatus in which the amine salt is converted into aqueous. solution. The mixer can be mixed. dosing. all or part of the amine and water and the remainder to the extraction apparatus.

From the solution of pitch after extraction! the solvent regenerates.

Further processing of the amine salt of 2-mercaptobenzothiazole depends on the extraction conditions! , the type of amine used and the further treatment. The amine salt solution, if necessary, is cooled to the temperature required for further processing and, if necessary, after adjusting the concentration of the amine salt and amine, the solution or suspension thereof is used for further manufacture. In a second treatment, the hot saturated amine salt solution of 2-mercaptobenzothiazole (2-MBT) is cooled to precipitate as an amine salt as a solid which is collected (by sedimentation, filtration or centrifugation) and the mother liquor is returned after treatment amine content and volume to be extracted. The solid portion of the amine salt of 2-mercaptobenzothiazole is suspended either in water or, after drying in an organic solvent, and used, if necessary, for further management. »

Extraction can be carried out by both batch and continuous processes, the amine addition may be special or combined upon prior mixing with water or recirculated solution. Extraction according to the invention yields 95% of the 2-mercaptobenzothiazole present in the crude melt.

Example 1.

200 g of crude 2-mercaptobenzothiazole melt (88.45%, 1.06 mole of 2-mercaptobenzothiazole), 279.6 g morpholine (99.7%, 3.3 mole) and 525 cm @ 3 of water were charged to a flask. The mixture is heated with vigorous stirring to reflux temperature, after 15 minutes the agitator is stopped, after the layers have been separated, the upper aqueous phase is withdrawn and the residue in the flask is extracted equally while still three times with 525 ml of water. 2243 g of an aqueous solution of 2-mercaptobenzothiazole morpholine salt containing 7.57% of 2-MBT are obtained, which represents 95.9% of the extracted 2-mercaptobenzothiazole from the crude melt.

Example .. 2 ... '

100 g of crude 2-mercaptobenzothiazole melt (88.45%, 0.53 mole 2-MBT), 123.4 g 33% diethylamine solution (0.557 mole), (0 g xylene) and 670 g water were charged to the flask.

After heating to reflux and separating the layers, the upper aqueous layer is separated. After cooling to 30 ° C, 878 g of a 2-mercaptobenzothiazole diethylamine salt suspension is obtained, which contains 86.07 g of 2-mercaptobenzothiazole as diethylamine salt. This represents a yield of 97.3% of 2-mercaptobenzothiazole.

Example 3.

150 kg of raw 2-MBT melt (88.7%, 0.806 mol of 2-mercaptobenzothiazole), 70 kg of chlorobenzene are charged from the reactor to the high speed mixer and extracted with 3076.3 kg of cyclohexylamine aqueous solution (essentially returning) mother liquor in which the cyclohexylamine content is adjusted. The extraction is carried out at a temperature of 90 ° C. After extraction! the obtained solution of the cyclohexylamine salt thereof, - from which, after cooling ^to: normal temperature in a solid salt. This was separated by filtration from the mother liquors. Mother liquors, amounting to 2844.3 kg, after adding 91.3 kg of cyclohexylamine (96.31, 0.886kmol) and

140.7 kg of water used for extraction. The hourly yield of the cyclohexylamine salt of 2-mercaptobenzothiazole is 207.2 kg, which corresponds to 96.5% extraction efficiency. The cyclohexylamine salt of 2-mercaptobenzothiazole is obtained in the form of fine pale yellow crystals with a melting point after drying of 152-156 ° C. In this form, it is suitable for the production of sulfenamide. The examples given are merely illustrative of the principle of the novel process for the preparation of the amine salts of 2-mercaptobenzothiazole and do not limit the use of other amines, solvents and combinations in the text.

Claims (3)

OBJECT OF THE INVENTION A process for the preparation of the amine salts of 2-mercaptobenzothiazole of the general formula CSH. HN ^X R ² Wherein R and R are straight or branched, represent a hydrogen atom, a primary, secondary or tertiary, straight or branched alkyl of 2 to 4 carbon atoms, a cycloalkyl or an alkylcycloalkyl of 5 to 8 carbon atoms, or form a six to eight membered ring optionally containing oxygen or nitrogen as another heteroatom, characterized in that the 2-mercaptobenzothiazole is extracted from the crude melt of 2-mercaptobenzothiazole with a dilute aqueous amine of the formula NH where R @ 1 and R @ ² are as hereinbefore defined, at a temperature of from 40 DEG C. to the boiling point of the one-shot system preferably in the presence of an organic solvent, the molar ratio of amine to 2-mercaptobenzothiazole being 1.05 to 5: 1 2 to 20 parts per 1 part of the raw melt and the amount of organic solvent 0.1 to 2 parts by weight per part of the melt of 2-mercaptobenzothiazole. 2. The process of claim 1 wherein the amine is a cyclohexylamine of the formula: EMI2.1 wherein R is hydrogen, methyl, ethyl R ³ is hydrogen, C 5 -C 8 cycloalkyl n is 0 to 2 3. The process of claim 1 wherein the solvent is benzene, gasoline, xylene, toluene, chlorobenzene, butanol.