Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2001-10-19
2002-10-15
O'Sullivan, Peter (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
Reexamination Certificate
active
06465691
ABSTRACT:
The invention relates to a process for preparing thiuram disulfides comprising reacting a secondary amine with carbon disulfide in the presence of oxygen and a metal catalyst.
Such a process is disclosed in U.S. Pat. Nos. 4,468,526 and 4,459,424. The processes that are described in these prior art documents, however, must be performed in a solvent. Typically, methanol is used and in column 5, lines 36-42, of U.S. Pat. No. 4,459,424 it is mentioned that in most cases, as for example with tetramethyl thiuram disulfide, the end product will immediately precipitate out of the reaction mixture and can be filtered off. Alternatively, the products are isolated by means of distillation or extraction from the solvent used.
An obvious disadvantage of using a solvent is that for a process that is to be carried out on an industrial scale, the need of a solvent and the handling thereof add significantly to the cost of the end product. Also, having to use a solvent is a burden on the environment. In addition, fairly large investments need to be made in equipment for separating the product from the solvent used, for example, a solid-liquid separation unit, a liquid-liquid separator (e.g. a centrifuge) when the thiuram disulfide itself is a liquid at room temperature, and a solvent recovery unit.
Surprisingly, we have found a new process which does not suffer from these drawbacks.
The process according to the present invention is characterized in that it is carried out in the absence of a solvent using a secondary amine of which the corresponding thiuram disulfide is liquid under the reaction conditions.
With the invention process thiuram disulfides having good quality can be prepared in at least the same yield as the product which is prepared in a process which employs a solvent. Furthermore, the process is more economical and can be carried out at lower cost, due to the fact that no solvent handling and no investments in equipment for separating the end product from the solvent are required. Also, the reactor capacity is increased, which results in a higher space-time yield.
A wide variety of secondary amines may be used in the process according to the present invention. The only requirement of this amine is that the corresponding thiuram disulfide must be liquid under the reaction conditions, notably the reaction temperature and pressure, of the invention process. The suitability of a secondary amine can be easily checked by running the reaction as described in any one of the Examples described below. The secondary amine which can be used in accordance with the present invention may have the formula R
1
R
2
NH, wherein R
1
and R
2
are independently selected from linear or branched, saturated or unsaturated C
2
-C
24
alkyl groups, C
3
-C
24
cycloalkyl groups, C
6
-C
24
aryl groups, C
7
-C
24
alkaryl groups, and C
7
-C
24
aralkyl groups. Hence, the thiuram disulfides which result from reacting R
1
R
2
NH under the reaction conditions of the process according to the present invention have the formula: R
1
R
2
NC(S)SSC(S)NR
1
R
2
.
Preferably, R
1
and R
2
are independently selected from linear or branched, saturated or unsaturated C
2
-C
24
alkyl groups.
The process according to the present invention typically is carried out at temperatures in the range of room temperature (i.e. about 20° C.) to 90° C., preferably 45° C. to 75° C., more preferably 50° C. to 70° C. For economic and safety reasons, the reaction ordinarily will not be carried out below room temperature or above 90° C.
The invention process is carried out in the presence of oxygen. Either oxygen gas or a gas containing oxygen, such as air, can be used. The invention process is carried out under pressure. Typically, the process is carried out at oxygen pressures or partial oxygen pressures of at least 0.1×10
5
Pa (i.e. 0.1 bar), preferably 0.5×10
5
to 4×10
5
Pa, more preferably 1.5×10
5
to 3×10
5
Pa. As expected, the reaction rate increases with rising oxygen pressure. Due to the fact that the process is carried out under pressure, the reaction typically is carried out in an autoclave suitably equipped with a pressure indicator and a thermometer and, optionally, a mixing device andlor a distillation unit.
The reaction time depends on the process conditions and may range from a few minutes to a few hours under the preferred reaction temperature and partial oxygen pressure conditions. On the reaction scale which is described in the Examples, the reaction typically is stopped when the oxygen flow falls below 1.0 ml/min.
Either a single secondary amine or a mixture of secondary amines can be used in the invention process. Preferably, R
1
and R
2
are the same. When a single secondary amine is used as reactant, a thiuram disulfide carrying the same substituents on both nitrogen atoms is obtained. In the case of a symmetrically substituted secondary amine being used, a thiuram disulfide with four indentical substituents is obtained. When two different secondary amines are used as reactants, depending on the process conditions such as differences in the basicity of the amines and/or molar ratios, thiuram disulfides with two differently substituted nitrogen atoms are obtained.
Typical examples of aliphatic, cycloaliphatic, aromatic, alkaromatic, and araliphatic secondary amines which can be used in the process of the present invention may be selected from the ones that are listed in column 3, line 35, through column 4, line 36, of U.S. Pat. No. 4,459,424.
Preferred secondary amines are diethylamine, dibutylamine, dioctylamine, ditallowamine, and dicocoamine.
In the invention process, the amount of secondary amine relative to carbon disulfide may be varied. Preferably, about equimolar amounts of the secondary amine and carbon disulfide are used. In order to allow all of the secondary amine to react, it may also be practical to use a slight excess of carbon disulfide, i.e. 2-10 mole %. After completion of the reaction said slight excess of carbon disulfide can easily be removed from the reaction mixture by evaporation.
Typical examples of metal catalysts which can be used in the process of the present invention include the catalysts that are described in column 2, line 50, through column 3, line 26, of U.S. Pat. No. 4,459,424.
Preferred catalysts are those based on manganese or copper. A particularly preferred manganese catalyst is manganese acetate.
The amount of catalyst to be used in the invention process can be small. Typically, an amount of 0.01 to 5 mmoles of catalyst per mole of secondary amine is used. Preferably, an amount of 0.05 to 2.5 mmoles of catalyst per mole of secondary amine is used.
The process of the present invention is optionally carried out in the presence of a co-catalyst, typically a tertiary amine. Suitable tertiary amines include the ones listed in column 3, lines 34-41, of U.S. Pat. No. 4,468,526.
The process may be carried out in various ways as, for example, described in column 5, lines 1-21, of U.S. Pat. No. 4,459,424. It is preferred to perform the reaction by dosing such an amount of carbon disulfide to a mixture of the secondary amine (about 0.5 mole based on 1 mole of secondary amine) and metal catalyst that the corresponding ammonium dithiocarbamate is formed, followed by the introduction of oxygen or an oxygen-containing gas and further dosing of carbon disulfide in such a way that the partial pressure of carbon disulfide is kept as low as possible.
Depending on the secondary amine which has been used as the starting material for preparing the thiuram disulfide in accordance with the process of the instant invention, the product is isolated by cooling the reaction mixture in the case of a thiuram disulfide which is liquid at room temperature or by extruding or pelletizing the reaction mixture in the case of a thiuram disulfide which is solid at room temperature Suitable equipment for extrusion and pelletization of the warm reaction mixture is known to the person skilled in the art.
Typically, the metal catalyst and any co-catalyst which may have been used in
Bloemenkamp Robertus Hermanus Jozef
van Hengstum Antonius Johannes
Flexsys B.V.
Morris Louis A.
O'Sullivan Peter
LandOfFree
Solvent-free process for preparing thiuram disulfides does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Solvent-free process for preparing thiuram disulfides, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solvent-free process for preparing thiuram disulfides will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2941369