FR2521559A1 - PROCESS FOR THE PREPARATION OF DITHIAZOLE DISULFIDE - Google Patents

Abstract

PROCESS FOR THE PRODUCTION OF DITHIAZOLYL- (2,2) DISULPHIDES OF FORMULA: (CF DRAWING IN BOPI) OR R AND R REPRESENT H, HALOGEN, NITRO, H OR A RADICAL ALKYL OR ALCOXY IN C, CYCLOALKYL OR ARYL IN C, THESE RADICALS BEING POSSIBLE SUSBSTITUTE. THE PROCESS INCLUDES THE OXIDATION OF 2-MERCAPTOTHIAZOLES, WITH OXYGEN, IN WATER AS A REACTIONAL MEDIUM AND IN THE PRESENCE OF AMMONIA AS A CATALYST AND POSSIBLY OF HEAVY METALS AS CO-CATALYZERS. THESE COMPOUNDS AND IN PARTICULAR DIBENZOTHIAZOLYL- (2,2) DISULPHIDES ARE USED AS VULCANIZING AGENTS FOR RUBBER.

Description

PROCESS FOR THE PREPARATION OF DITHIAZOLE DISULFIDE

  The invention relates to a method for preparing disul-

  dithiazolyl- (2,2 '), by oxidation of 2-mercapto

  thiazoles using oxygen, in particular dibenzothiazolyl disulphide from 2-mercaptobenzothiazole. Various oxidants have heretofore been used for the technical preparation of dibenzothiazolyl disulfides by oxidation of 2-mercaptobenzothiazoles. Most of the known processes, however, have the drawback of starting from oxidants which, with respect to oxygen, are such as chlorate / nitrite (Fiat Final Report 1018, page 22), nitrite / oxygen (US 1,908,935), nitrite (US 2,119,131 and 3,062,825), chlorine (KirkOthmer, Encyclopedia to Polymer Science and Technology (1970), Vol 12, p 262 and DE-OS 23 09 584), hydroperoxides (DE-OS 23 49 314) and ozone (SU 420 247).

  publications above also show other

  such as the need for large quantities of acids, bases or other auxiliary substances, the formation of large amounts of by-products

  and secondary products, or reaction conditions

  plicated or critical, with the need for careful control (the latter, for example in the case of the use of chlorine

as an oxidant).

  We must also mention an electro-oxidation process

  lytic form of 2-mercaptobenzothiazole to give dibenzo-

  thiazolyl (DE-OS 27 43 629) DE-OS (published German patent application). It has also been attempted to carry out the oxidation of 2-mercaptobenzothiazole to dibenzothiazolyl disulfide with

  oxygen as the sole oxidant.

  According to the method according to US 3,654,297, this is possible.

  ble when using as catalyst a sulphate, a

  disulphonate, a trisulphonate or cobalt-tetrasulphonate

  phthalocyanine or mixtures thereof as a catalyst, and that the oxidation is carried out at temperatures of 50-80 ° C. in an organic solvent containing less than 15% by weight of water (cf.

  also US 575,348; Chem Abstr 88 (1978), 89657 g).

  the preparation and industrial use of this

lyser have problems.

  It is also known from DE-OS 23 55 897 that

  to the oxidation of 2-mercaptobenzothiazoles to dibenzothiazolyl disulfides by the simultaneous use of oxygen or

  a gas containing oxygen and iron chloride, in parti-

  iron (III) chloride in an aliphatic alcohol saturated with 1-10 carbon atoms, at temperatures between 0 and C. However, this catalyst does not lead to a

  reaction if it is used in large quantities

  The main disadvantage of the process lies, however, in the fact that the iron precipitates, during the reaction, in the form of basic salts, and that the disulphide, in the ratio 0.8-1.5 mol per mole of 2-mercaptobenzothiazole. The dibenzothiazolyl obtainable product is strongly contaminated with iron. A product obtained in this way can not, for example, be used as a vulcanizing agent without

an expensive treatment.

  An economically interesting process for

  the catalytic oxidation of 2-mercaptothiazoles with oxy-

  The gene is finally described in DE-OS 29 44 225 According to the latter, a mercaptothiazole is reacted with oxygen or an oxygen-containing gas in the presence of solvents.

  organic and tertiary amines as a catalyst, possibly

  also heavy metals or metal compounds

  as a co-catalyst, preferably at temperatures below

  The dithiazolyl- (2,2 ') disulfides which can be obtained in this way are characterized by a high purity, they can be used without additional purification, for example directly as rubber vulcanizing agent. to the two processes mentioned above, in which a mercaptobenzothiazole is also oxidized with oxygen, this process is characterized in that it uses

  simple and inexpensive catalysts in very small quantities

  these catalysts can be recycled

  with the mother liquor without much decrease in their activity.

  An application for a patent of addition (No. P 31 13 298 7) to the above German application P 29 44 225 9 describes the preparation of dithiazolyl disulfides (2, 2 ') with ammonia at room temperature.

  tertiary amines as a catalyst.

  In all these processes of oxidation of 2-mercaptobenzo

  thiazole to dibenzothiazolyl disulfide with oxygen as the sole oxidant according to US 3,654,297, DE-OS 23 55 897 and DE-OS 29 44 225 (and the application for addition NP 31 13 298 7), are considered necessary as solvents of organic solvents By comparison, water Uit absolute value

unsuitable as a solvent.

  Thus it is, for example according to US 3,654,297, not recommended to use a solvent having more than 15% by weight

  And OS 29 44 225 (see page 16, lines 23 to 27) recom-

  do not leave the percentage of water in the solvent

  exceed 10% by weight Further tests according to the

  transferred from DE-OS 29 44 255 have shown that it does not occur

  Of course, no conversion of 2-mercaptobenzothiazole to dibenzothiazolyl disulfide (2,2 ') with water as a single solvent is carried out. Examples 18, 24 and 28 mentioned in DE-OS 29 44 225 are prepared in instead of the solvents indicated therein, under otherwise identical conditions, no oxidation occurs, as shown in Table 1.

  Finally, there had to be a prejudice against the use of

  the use of water as a solvent in the process according to patent application No. P 31 13 298 7, since it was known that ammonia, as well as primary and secondary amines,

  in aqueous solution, unlike tertiary amines.

  under the effect of oxygen in the presence of metal catalysts

  For example, it was possible to draw from the paragraph "Chemisches Verhalten des Ammonium-Ions und des Ammoniaks in wassriger Lôsung", in #Gmelins Handbuch der anorganischen Chemie ", 8th edition, volume 23, page 12 ssq (the behavior vis-à- screw oxygen in the presence of metals or metal ions is mentioned in detail on page 13, line 21 to page 15, line 4, considering in particular copper), the fact that in solution

  aqueous ammonia is catalytically oxidized to nitrite.

  It therefore existed, in particular for reasons of

  and safety, a need for the availability of a process for the preparation of 2,2'-dithiazolyl disulfides by oxidation of 2-mercaptobenzothiazoles with oxygen, which can be carried out not in organic solvents ,

  but in water, the solvent the lesscher, harmless and non

  pollutant. It was therefore an object of the invention to provide an economical process for the preparation of 2,2'-dithiazolyl disulfides by the oxidation of 2-mercaptothiazoles with the aid of oxygen.

  presence of water as a solvent.

  Surprisingly, it has now been found that under appropriate reaction conditions, even in water as a solvent, the oxidation of 2-mercaptothiazoles to dithiazolyl disulfides (2, 2 ') using oxygen, if using as a catalyst in Table 1 2mercaptobenzothiazole oxidation (MBT) tests

  dibenzothiazolyl disulfide (MBTS).

  Reaction conditions: 60 mmol MBT, 108 mmol triethylamine, reaction temperature 70 C, oxygen pressure 20 bar, reaction time

reaction 6.5 hours.

  Solvent, 120 g Catalyst Conversion rate MBT copper yield,% MBTS,% 0.02 mmol

DE-OS 29 44 225

  Example 18 Isopropanol Acetate 82.7 80.5 Copper-II DE-OS 29 44 225 Toluene Acetate 90.6 88.6 Example 24 Copper-II

O Acetate Water Control Trial -

  copper-II DE-OS 29 44 225 Isopropanol Oleate of 82.0 80.2 Example 28 Copper-II Control Test Copper Oldate Water II

,,,

  The ammonia and optionally a derivative of a heavy metal (see the patent application P 31 13 298 7) In the case of the oxidation of 2-mercaptobenzothiazole, thus obtained with good yields (up to 99%) and a high selectivity (up to> 99%) of dibenzothiazolyl disulfide (2,2 ').

  high purity No secondary reactions were observed.

  which could be expected on the basis of liter-

  (oxidation of ammonia or formation of sulfenamide

  (see DE-OS 23 49 934, page 5, lines 22-24).

  This object has been achieved by a process for preparing dithiazolyl disulfides (2,2 ') of the general formula

R C N N-C-R

he / \ C S S This he WI

R 'C S SC R'

  R and R 'may be the same or different and are each a hydrogen atom, a halogen atom, a nitro group, a

  hydroxyl group or an organic radical, possibly mono-

  or polysubstituted, such as an alkyl or alkoxyl radical with 1 to 6 carbon atoms or a cycloalkyl or aryl radical with 6 to 12 carbon atoms, the substituents, in each case, possibly being a halogen atom, a nitro group, a hydroxyl group or an alkyl or alkoxyl radical of 1 to 5 carbon atoms, or where R and R 'together form the radical R' 'R' '(II)

R '' '

  R 1 'o R ", R"', R "" and R "" 'may be the same or different and each have the same meaning as R and R', by catalytic oxidation of a 2-mercaptothiazole of general formula

R C N

| 'C SH (III)

R 'C S

  R and R 'have the meaning indicated above, using oxygen or an oxygen-containing gas, in a solvent in the presence of a catalyst and optionally a metal cocatalyst heavy, at temperatures between 0-150 C, characterized in that water is used as a solvent and

  ammonia as a catalyst.

  In general, the amount of water is 1.5 to 12 times the weight of 2mercaptothiazole used For economic reasons, it

  avoid larger amounts of water.

  In many cases, it may be advantageous to use water as the reaction medium with additions of water-soluble organic solvents (eg alcohols). The quantity of ammonia can be varied between wide limits; however, ammonia is preferably used in amounts of about 0.5-25% by weight of

reaction mixture.

  The substituents R to R "u 'of general formulas I, II and III are preferably a chlorine or bromine atom, a hydroxyl group, a nitro group or a straight or branched chain alkyl radical containing from 1 to 4 carbon atoms. , such as methyl, ethyl, propyl, isopropyl, butyl or tert-butyl radicals, an alkoxy radical with 1-4 carbon atoms, such as the methoxy, ethoxy, propoxy or butoxy radicals, or a phenyl, tolyl, ethylphenyl or nitrophenyl radical, chlorophenyl, bromophenyl

or naphthyl.

  Dithiazolyl disulfides (2,2 ') are used in

  as vulcanizing agents for rubber.

  The process according to the invention is important, in particular

8 2521559

  for the preparation of dibenzothiazolyl disulfide <2.2 '), the main representative of this class of compounds However, it is equally desirable, and successful, for the preparation of other compounds of this type. dibenzothiazolyl- (2,2 '), 2-mercaptobenzothiazole is used as the starting material. Other excipients which may be used are, for example, other mercaptothiazoles suitable as starting materials for the preparation of other dithiazolyl disulfides. - {2,2 ') of general formula I, the following compounds 2mercaptothiazole 2-mercapto-4-methylthiazole 2-mercapto-4-ethylthiazole 2mercapto 4-n propylthiazole 2-mercapto-4,5-dimethylthiazole 2-mercapto-4 5-Di-n-butylthiazole 2-mercapto-4-phenylthiazole 2-7-mercapto-5-chloro-4-phenylthiazole 2-mercapto-4-p-bromophenylthiazole 2-mercapto-4-nitrophenylthiazole 2-mercapto-4-m-chlorophenylthiazole 2-mercapto-4-methylbenzothiazole 2-mercapto-5-methyl benzothiazole 2-mercapto-4,5-dimethylbenzothiazole 2-mercapto-4-phenylbenzothiazole 2-mercapto-4-methoxybenzothiazole 2-mercapto-6-methoxybenzothiazole 2-mercapto-5,6-dimethoxybenzothiazole 2-mercapto-6-methoxy-4-nitro-fluorothiazole 2-mercapto 6-ethoxybenzothiazole 2-mercapto 4-chlorobenzothiazole 2 mercapto-5-chlorobenzothiazole 2-mercapto-6-chlorobenzothiazole 2mercapto-7-chlorobenzothiazole

9 2521559

  2-Mercapto-5-chloro-6-methoxybenzothiazole 2-mercapto-5-chloro-4-nitrobenzothiazole 2-mercapto-5-chloro-6-nitrobenzothiazole 2-mercapto-4,5-dichlorobenzothiazole 2-mercapto-4,7-dichlorobenzothiazole 2 5-mercapto-5-nitrobenzothiazole 2-mercapto-6-nitrobenzothiazole 2-mercapto-4-phenylbenzothiazole 2-mercapto-naphthothiazole 2-mercapto-6-hydroxybenzothiazole The percentage of 2-mercaptothiazole is up to 40% by weight.

  weight relative to the reaction mixture.

  Ammonia can be used as a catalyst, either alone or together with a heavy metal or a metal compound

heavy.

  Examples of suitable co-catalysts are iron, cobalt, nickel, copper, chromium, zinc, manganese, silver, vanadium, molybdenum and cerium, their oxides, as well as their

  salts or complex organic or inorganic compounds.

  The heavy metal or heavy metal compound is used in amounts of less than 0.1% by weight based on 2-mercaptothiazole. Even traces of these co-catalysts, in particular in the case of copper, still develop a considerable catalytic activity and lead to good yields of dithiazolyl disulphides. It is therefore possible to use extremely small amounts of catalyst and to recycle several times.

the mother liquor.

  As a co-catalyst of the heavy metal type, in particular copper and all the copper compounds, it is possible to envisage all the salts of copper as the copper compound.

  copper, simple or complex, organic, inorganic, mono-

or bivalent.

  Examples of mono-copper salts are

  suitable valents chloride, bromide and copper iodide

2521559

  (I), the addition compounds of these copper (I) halides with carbon monoxide, copper (I) complex salts, such as alkali metal chlorocuprates, ammoniacates

  copper (I) cyanide complexes, for example cyano-

  cuprates, such as potassium tricyanocuprate (I), double salts with copper thiocyanate (I), copper (I) acetate, copper (I) sulphide and complex double sulphides formed from acetate of copper (I), copper (I) sulphide and complex double sulphides formed from

  copper (I) sulphide and alkali metal polysulfides.

  Examples of suitable copper (II) salts are chloride, bromide, sulphide, sulphate, nitrate, nitrite, thiocyanate and copper (II) cyanide.

  copper (II) salts of carboxylic acids, such as acetic acid,

  Copper (II) tate, as well as the complex ammoniacates of copper (II) salts Similarly, metallic copper and oxide

  Copper (I) are very suitable as a co-catalyst.

  Preferably, copper (I) chloride, copper (II) acetate, copper (II) sulphate, copper (II) oleate, copper (II) acetylacetonate, sulphide are used. of

  copper (II) or copper oxide (I).

  Since the heavy metal compound is used in small amounts, it is also possible to use, in addition to the readily soluble heavy metal compounds, heavy metal compounds having very low solubility or which are not soluble.

in water as in traces.

  Oxygen or an oxygen-containing gas, preferably air, is used as the oxidizing agent. The conversion rate and the reaction rate increase with the pressure or the partial pressure of the oxygen. Oxygen or partial pressure is 0.1-150 bar For economic reasons, oxygen pressures are preferably used.

  or partial pressures of 0.2-10 bar.

  The reaction temperature is 0.degree.-150.degree. C., preferably 20-90.degree. C., and in particular 30.degree.-70.degree.

  lower, the rate of reaction decreases; at temperatures

  tures, the selectivity of the reaction decreases.

  The duration of the reaction is as a rule 0.25-

  6.5 hours under the preferred conditions mentioned above.

  above pressure and temperature, and in the presence of a copper co-catalyst, it is, for a conversion rate

80%, less than one hour.

  The implementation of the process according to the invention is carried out

  in a simple manner, by compressing the oxygen or oxygen-containing gas on the reaction solution, under the indicated conditions of pressure and temperature, or by sending the oxygen or oxygen-containing gas in

  or through the solution composed of water, 2-mercaptothia-

  The reaction product obtained is separated by filtration or centrifugation. The liqueur can be supplemented with fresh 2-mercaptothiazole and recycled. Depending on the starting concentration of the heavy-metal catalyst, after a number of reaction cycles, add

  The process is also suitable for a reaction of

continued.

  In the process according to the invention, good yields (up to 99%) and high selectivities (up to> 99%) are obtained. The dithiazolyl disulfides (2,2 ') obtainable are characterized by a purity They can therefore be used without further purification, for example

  example directly as a vulcanization auxiliary.

  Because of the possibility of sending the liquor-

  mother in recycling, it creates in practice no problem of waste water for the implementation of the process

  Another advantage of the process according to the invention

  In addition to the possibility of having a cheap, safe and non-polluting solvent in the suppression of an operation,

  distinct to remove the reaction water of the solvent.

Example 1

  In a glass autoclave, equipped with a jacket for the circulation of a heating liquid, a thermometer, a manometer and an agitating device, 50 g (0.3 mol) are introduced into the glass autoclave. 2mercaptobenzothiazole (MBT), 12 mg (0.6 moles) of Cu (OAc) 2, H 2 O, 20.4 g (1.2 moles) of ammonia and 320 g of water The mixture is heated at 50 ° C., which forms a clear solution, is stirred vigorously and is

  subjected to an oxygen pressure of 4 bar.

  Oxygen uptake occurs, and a precipitate is formed as a result of the formation of dibenzothiazyl disulfide (MBTS). After one hour, the experiment is terminated, the precipitate is filtered off, washed with water, and dried. ammonia in aqueous solution and with water, and dried under vacuum at 700 ° C. This gives 47.7 g of a product which, according to the analytical results (elemental analysis, IR, 1 H-NMR) and SM) is identical to dibenzothiazyl disulfide and whose purity, determined by chromatographic analysis (PF 178 C)

is 100%.

  The mother liquor, according to gas chromatographic analysis, contains 1.8 g of unreacted MBT. As a result, the conversion rate of MBT is 96.4% and the yield of MBTS is 96.0% of theoretical (selectivity

99.6%).

Example 2

  A solution of 50 g (0.3 mol) of MBT, 2 g (0.6 mole) of ammonia and 3 g of ammonia is dissolved in 160 g of water in the reaction apparatus described in Example 1. mg (0.015 moles) of Cu (O Ac) 2, H 20, and reacted with oxygen as described in Example 1 The oxygen pressure is

  4 bar, the reaction temperature of 50 C.

  After 4.5 hours, dibenzothiazyl disulphide is obtained with a yield of 49.1 g, which corresponds to 98.8% of theory. The conversion rate is

99.4% (selectivity 99.4%).

Example 3

  The procedure is as in Example 1, but without the addition of

  In this case, the degree of conversion of the mercapto

  benzothiazole after 20 hours is 90.8%, MBTS yield 44.9 g, corresponding to 90.3% of the theoretical (

99.5).

Examples 4-8

  In these examples, the amount of ammonia is varied.

  In each case, 50 g (0.3 mole) of 2-mercaptobenzothiazole are then reacted in the manner described in Example 1; the reaction conditions, as well as the conversion rates, yields and selectivities obtained are summarized on the

Table 2.

Example 9-13

  In these examples, different heavy-metal catalysts and different concentrations of the heavy metals are used. In each case, 50 g (0.3 mole) of 2-mercaptobenzothiazole is reacted as described in Example 1. under the reaction conditions shown in Table 2 (reaction temperatures 50 C, oxygen pressure 4 bar); the conversion rates, yields and selectivities obtained are,

same, shown in Table 3.

Example 14

  Oxygen (oxygen pressure 4 bar) is oxidized at room temperature in the reaction apparatus described in

  Example 1, a solution of 50 g (0.3 mole) of 2-mercaptobenzoate

  thiazole, and 12 mg of Cu (OAc) 2, H (0.06 10-3 mol) in 360 g of ammonia in aqueous solution (ammonia content: 50 g (2.9 mol)). 6.5 hours of reaction, the rate of

  The conversion of 2-mercaptobenzothiazole is 95.6% and the

  47.3 g of dibenzothiazyl disulphide, which corresponds to

  95.1% of theory (selectivity 99.5%).

Example 15

  In the example below, air is used as the oxygen-containing gas. In the reaction apparatus described in Example 1, a solution of g (0) is dissolved in 160 g of water. , 3 moles) of MBT, 10.2 g (0.6 moles) of ammonia and 6 mg -3 (0.03 moles) of Cu (O Ac) 2, H 20, and is oxidized at 50 C with air (8 bar) After 8 hours, the conversion rate of MBT is 94.3% and the MBTS yield of 46.6 g, which

  corresponds to 93.7% of theory (selectivity 99.4%).

  Table 2 (Examples 4-8) 3 Cu (OAC> 2 Water Te R VpéPressicri Duration and Rate of Selectivity 6 N "(moles) (% C) <1 < React to MBIS (% Reaction) Dmles) (O c) ne (bar)% (% of th) _______________ (h) MBT (%)

  4 2.3 (19.1> 0.02 90 70 2.5 1.5 86.1 83.4 96.9

  2.4 (10.5) 0.04 300 50 4.0 2.5 95.4 94.1 98.6

  6 0.4 (3.1) 0.015 163 50 4.0 6.0 94.9 94.2 99.3

  7 0.1 (0.9) 0.06 168 70 4.0 6.5 94.1 92.6 98.4

8 0.06 170 70 4.0 8.0

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252155 9

Claims (2)

claims   Process for the preparation of dithiazolyl disulfides (2,2 ') of general formula: R-C-N S / N-C-R || S Ci R'C S 'Ri C S S C R'   o R and R 'may be the same or different and represent   each have a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group or an alkyl or alkoxy radical with 1-6 carbon atoms or a cycloalkyl or aryl radical with 6-12 carbon atoms, these radicals which may be mono- or polysubstituted, the substituents being in each case a halogen atom, a nitro group, a hydroxyl group or an alkyl or alkoxy radical with 1-5 carbon atoms; or else R and R 'together form the radical: R' 'R' '' R '' '' R '' '' '   o R ", R" ', R' '' 'and R' '' '' may be the same or different   fers, and each have the same meaning as R and R ', by catalytic oxidation of a 2-mercaptothiazole of general formula: R C N I C SH R R 'C S   R and R 'have the meaning indicated above, using oxygen or an oxygen-containing gas, in a solvent, in the presence of a catalyst and optionally a cocatalyst. 18 25225559   heavy metals, at temperatures of 0 to 150 ° C, characterized in that water is used as a solvent and ammonia catalyst.   Process according to Claim 1, characterized in that the ammonia is used in amounts of 1-25% by weight of weight of the reaction mixture.