US1465677A - Process of preparing dithiocarbamic compounds - Google Patents

Description

Patented Aug. 21, 1923.

UNl'TED STATES PATENT orrica- S'IUABT B. HOLONY, OF WELLESLEY HILLS, MASSACHUSETTS, AND ZASUJUBO NIKAIDO, 01 DAY CITY, MICHIGAN, ASSIGNORS TO MICHIGAN CHEMICAL GOM- PANY, A CORPORATION OF MICHIGAN.

PROCESS OF PREPARING DITHIOCARBAMIC COMPOUNDS.

Ho Drawing.

To all whom it may camera:

Be it known thatwe, STUART B. Mono and YASUJUlRO NIKAIDO, citizens of the United States and Japan, respectively, residing at Wellesley Hills, in the county of Norfolk and State of Massachusetts, and Bay City, in the county of Bay and State of Michigan, respectively, have invented new and useful Improvements in Processes of Preparing Dithiocarbamic Compounds, of which the following is a specification.

Our invention relates to the manufacture of dit-hiocarbamic compounds. The object of our invention is theprovision of a proc: ess for the manufacture of dithiocarbamic compounds suitable for use as vulcanization accelerators, in which beet sugar residue is utilized as one of the reacting materials.

A small quantity of beet sugar residue, preferably of 35 B., is placed in a cast iron retort and heated at a temperature ranging from 900 to 1300 F., whereupon vapors of an alkaline nature are produced. As soon as the evolution of the vapors slackens, additional beet sugar residue of the same gravity is introduced into the retort in a small continuous stream, the retort being constantly maintained at the above-mentioned temperature, whereby destructive distillation of the beet sugar residue is effected. The size of the stream of beet sugar residue is controlled by the velocity of the gas reaction. The process of distillation is continued until the desired quantity of beet sugar residue is introduced into the retort and heating is continued until no more gas is produced.

It is quite important that the beet sugar residue be introduced into the retort in controlled continuous streams' in order to avoid the difliculties hereinafter referred to. If a large quantity of the residue is placed in the retort and destructively heated, owing to the presence of a considerable quantity of organic matter, the residue swells, forming a viscous mass which fills the retort and passes along with the vapor into the vapor pipe thereby obstructing the latter and contaminating the vapors. By the introduction of the residue into the retort in a small continuous stream, its viscous nature is destroyed Serial Nb. 491,041.

shortly after it comes into contact with the hot surface of the retort and the swelling subsides quickly. Our experiments have shown that besides the advantages indicated, a much largerquantity of the residue can be distilled by the continuous stream method than by placing a large quantity of the residue in the retort and distilling, assuming in the two cases, the same size retort and period of distillation.

The vapors resulting from the distillation, comprising a mixture of gases and steam, are first passed through a cooling apparatus where they are. cooled to approximately room temperature and then into a receiving vessel containing an acid in order to neutralize the amines and the ammonia which are the chief constituents of the vapors. Either hydrochloric acid or sulfuric acid may be used for this purpose but a commercial B. sulfuric acid is preferred on account of its low cost. The gas bubbles through the acid which absorbs the amines and the ammonia and allows the noncondensable gases such as carbon monoxid and cyanogen to pass into the atmosphere. It is preferred that the quantity of the acid used should be such as to leave the distillate slightly acid when the distillation is completed. The acidity of the distillate is tested during the distillation from time to time, with litmus paper. As soon as it shows alkalinity, more acid is added. It is desired that the distillate be kept slightly acid at the end of the distillation so that the amines will not be lost during the concentration of the distillate, the amines and ammonia being very volatile when not combined with the acid. The distillate is a mixture of two immiscible liquids, tar, and a solution comprising principally the amine sulfates and the sulfates of ammonia. The tar being lighter than the solution remains on top and may be separated therefrom by drawing the solution from the bottom of the receiving vessel.

The distillate obtained is concentrated in a vacuum evaporator at about a 24-inch vacuum and at a temperature of 142 F., until most of the ammonium sulphate crystallizes out. An analysis of the concentrated distillate obtained in one of the operations showed the following result:

Most of the ammonium sulfate crystallizes out while the sulfates of the amines remain in a. liquid state. The ammonium sulfate is separated from the mother-liquor by ariy suitable method such as centrifuging. t

is not essential that the ammonium sulfate be separated from the mother liquor before the distillate is treated with a decomposing agent to liberate the amines, but it is desir- ,able if the ammonium sulfate is to be recovered as a by-product.

The concentrated mother-liquor preferably freed from most of the ammonium sulfate is introduced into a steam-jacketed still, and a decomposing agent, for example, an alkaline earth or an alkali compound added, whereupon amine gases are liberated. Caustic soda or causticpotash may be used for the liberation of the amines but as lime is just as eflicient and costs less it is preferred. It is quite important that the lime be finel ground, so that approximately seventyve per cent thereof will pass through 80 mesh. It is further desirable that the lime contain at least 85% available calcium oxid. Lime of a poor quality and not of the proper fineness will cause a reduced yield, as it is not active enough to cause a complete liberation of the amines. The amount of the lime added should be approximately 50% of the weight of the liquor treated. Very little heat is needed for the liberation of the amine gases, and the necessary amount is usually supplied by the action of the lime on the amine sulfates and moisture contained in the liquor. Steam is used for heating the still only toward the end of the distillation in order to complete the action of the lime on the amine sulfates. It is also quite important that the concentrated distillate be of the correct consistency. If it is thick, the lime will not thoroughly mix therewith and some of the amines will remain unacted upon. If it is too thin, water vapor will pass along with the amine gases diluting the atter, which is undesirable. Experience has shown that a distillate having a gravity between 36 and 40 Be. is desirable.

The retort-tar .contains a considerable proportion of amines and these may be recovered by allowing the tar to stand for a period suflic-ient to enable it to separate from the associated water and thereafter distilling with powdered lime, preferably in an amount equal to 40% of the weight of the tar.

The amine gases produced are conducted into carbon bisulfid undiluted with any associating medium contained in a vessel provided with a water-cooled jacket whereupon amino ammonium salts of (1) monomethyl dithiocarbamic acid, (2) dimethyl dithiocarbamic acid and (3) methyl ester of dimethyl dithiocarbamic acid are formed. The reaction may be represented by the following equations:

' NHCHs 1. znmcnwcsi cs\sNHaCHa /N(CH3)Q SNH1(CHa)2 monoi scH,

Ex eriments have shown that it is decided y more advantageous to form the amino-ammonium salts of dithiocarbamic acid by passing the amine gases into carbon bisulfid than into an alcoholic solution of carbon bisulfid. The disadvantages resulting from passing an alcoholic solution of the amines into carbon bisulfid are practically the same as those resulting from passing a solution of the amines into an alcoholic solution of carbon bisulfid. The advantages connected with the use of straight carbon bisulfid are as follows:

1. It is easier to separate the amino-ammonium salts of dithiocarbamic acid, as the latter are practically insoluble in straight carbon bisulfid, whereas in a mixture of carbon bisulfid and alcohol they are soluble to a considerable extent.

2. The formation of ammonium sulphocyanate which forms by the action of ammonia on carbon bisulfid in the presence of alcohol is prevented to a large extent. It is quite desirable to reduce the formation of ammonium sulphocyanate to a minimum.

3. With the elimination of alcohol the production-cost is considerably reduced.

It is necessary to provide a Water-cooled jacket for the carbon-bisulfid container in order to efliciently effect the combination of the amines with the carbon bisulfid. The reaction between an absorbing liquid such as carbon-bisulfid. and the amines is an exothermic one and unless the excess of heat is dissipated the absorbing liquid will vaporize causing a considerable loss of this agent. In addition, when the absorbing liquid is hot, the action of amines therewith is not complete, some of the latter escaping without combining with the absorbing medium.

The amino-salts are substantially insoluble in carbon bisulfid and may be separated from the mixture by treating the same with a solvent of the former immiscible with the latter. Alcohol will dissolve the aminosalts but as it mixes with carbon bisulfid and cannot be easily and economically separated therefrom it is not a suitable solvent. Ether and chloroform are subject to the same obections. Water is the most suitable solvent. Vhen the mixture of the aminoammonium salts of dithiocarbamic acid and carbon bisulfid is treated with water the aqueous solution of dithiocarbamic salts forms as a layer upon the heavier bisulfid which may be withdrawn leaving the substantially pure dithiocarbamic salt solution, from which the salt may be recovered by suitable methods. The amino-ammonium salts may also be recovered from the carbon bisulfid by centrifuging.

We claim:

1. The process of producing dithiocar carbon bisulfid to form amino-ammonium salts of dithiocarbamic acid, addin 4 to the mixture of the amino-ammonium dithiocarbamic salts and carbon bisulfid a solvent of the former immiscible with the latter, and recovering the amino-ammonium dithiocarbamic salts.

4. The process of producing dithiocarbamic compounds comprising distilling beet sugar residue, separating the amines from the ammonium compounds, passing the amines into carbon bisulfid to form aminoammonium salts of dithiocarbamic acid and recovering the latter.

5. The process of producing alkyl dithiocarbamic compounds comprising distilling beet sugar residue, collecting the distillation vapors in a. liquid menstruum, adding to the liquid menstruum containing the amines a finely-divided decomposing agent to liberate the amines, treating the latter with carbon bisulfid, adding to the mixture of the amino ammonium dithiocarbamic salts and carbon bisulfid a solvent of the former immiscible with the latter, and recovering the aminoammonium dithiocarbamic salts.

6. The process of producing dithiocarbamic compounds comprising distilling beet sugar residue, collecting the distillation vapors in a liquid menstruum, adding a decomposing agent to the latter to liberate the amines,

. adding to the liquid menstruum containing the amines a finely-divided decomposing agent to liberate the amines, treating the latter with carbon bisulfid, adding to the mixture of the amino-ammonium dithio bisulfid, adding water to the mixture of the amino-ammonium dithiocarbamic salts and carbon bisulfid, and recovering the amino-ammonium dithiocarbamic salts.

10. The process of producing alkyl dithiocarbamic compounds comprising introducing beet sugar residue in continuous streams into a retort while heating the latter to effect destructive distillation of the residue, collecting the distillation vapors in a liquid menstruum, adding to the liquid menstruum' containing the amines a finely-divided decomposing agent to liberate the amines, treating the latter with carbon bisulfid, adding to the mixture of the amino-ammonium dithiocarbamic salts and carbon bisulfid a solvent of the former immiscible with the latter, and recovering the aminoammonium dithiocarbamic salts.

11. The process of producing alkyl dithiocarbamic compounds comprising distilling beet sugar residue, collecting the distillation vapors in a liquid neutralizing menstruum, adding to the liquid menstruum containing the amines finely-divided lime to liberate the amines, treating the latter with carbon bisulfid, adding to the mixture of amino-ammonium dithiocarbamic salts and carbon bisulfid a solvent of the former immiscible with the latter, and recovering the amino-ammonium dithiocarbamic salts.

12. The process of producing alkyl dithiocarbamic compounds comprising subjecting beet sugar residue to destructive distillation, adding a neutralization agent to the vapors resulting therefrom in a quantity sufficient to keep the distillate slightly acid, concentrating the neutralization-product, adding a decomposing agent to the same, distilling the reaction-product to produce amine gases, treating the latter with carbon bisulfid to form amino-ammonium salts of dithiocarbamic acid, and recovering the latter.

13. The process of producing alkyl dithiocarbamic compounds comprising distilling beet sugar residue, collecting the distillation vapors ina liquid neutralizing menstruum, adding to the liquid menstruum containing the amines finely-divided lime to liberate the amines, treating the latter with carbon bisulfid, adding water to the mixture of the amino-ammonium dithiocarbamic salts and carbon bisulfid, and recovering the amino-ammonium dithiocarbamic salts.

14. The process of producing alkyl dithiocarbamic compounds comprising introducing beet sugar residue in continuous streams into a retort while heating the latter to effect destructive distillation of the residue, adding a neutralizing agent to the vapors resulting therefrom in a quantity sufiicient to keep the distillate slightly acid, concentrating the neutralization-product, adding a decomposing agentsto the same, distilling the reaction-product to produce amine gases,

treating the latter with carbon bisulfid tov bamic compounds comprising introducing beet sugar residue in continuous streams into a retort while heating the latter to effect destructive distillation of the residue, passing the distillate into carbon bisulfid to form amino-ammonium salts of dithiocarbamic acid, and recovering the latter.

16. The process of producing alkyl dithiocarbamic compounds comprising introducing beet sugar residue in continuous streams into a retort while heating the latter to' effect destructive distillation of the residue, cooling the vapors resulting therefrom, adding a neutralizing agent to the latter in a quantity sufficient to keep the distillate slightly acid, concentrating the neutralization-product, adding a decomposing-agent to the same, distilling the reaction product to produce amine gases, treating the latter with carbon bisulfid to form amino-ammonium salts of dithiocarbamic acid, and recovering the latter.

17. In the process of producing dithiocarbamic compounds by utilizing beet sugar residues as one of the reacting materials, the step of introducing the residue in continuous streams into the retort while heating the latter to effect destructive distillation of the residue.

In testimony whereof, I have hereunto subscribed my name this 27th day of July,

STUART B. MOLONY. In testimony whereof, I have hereunto subscribed my name this 20th day of July, 1921.

YASUJURO NIKAIDO. v