Patent ID: 7553910

Claim:
Process for preparing a compound of the formula (I) R 1 R 2 N—(C═S)—S—S—(CH 2 ) n —S—S—(C═S)—NR 1 R 2 (I), wherein the R 1 and R 2 radicals are each independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aralkyl, phenyl, substituted phenyl, alkylaryl, and a heterocyclic ring having 4 to 8 carbon atoms including at least one nitrogen atom, and where n is an integer from 2 to 8, comprising the step of reacting a compound of the formula (II) [R 1 R 2 N—(C═S)—S] z Me 1 (II) wherein R 1 and R 2 radicals are each as defined in the formula (I) and z=1 when Me 1 is an alkali metal or ammonium ion and z=2 when Me 1 is an alkaline earth metal ion, with the a compound of the formula (III) Me 2 O 3 SS—(CH 2 ) n —SSO 3 Me 3 (III) wherein Me 2 and Me 3 are the same or different and are each monovalent metal ions or ammonium ions and n is as defined in the formula (I), wherein said step of reacting is performed in the presence of water, a carbonyl containing compound and an organic solvent, in a pH range of 7 to 14 at a reaction temperature of 0° to 90° C., until the compound of the formula (I) reaches a percent yield of at least 80% based on the salts of the formula (III), further wherein the amount of the compound of the formula (II) is 180 to 250 mol % based on the moles of the compound of the formula (III) used, the amount of the carbonyl containing compound is 5 to 600 mol % based on the moles of the compound of the formula (III) used, and the amount of the organic solvent is 2 to 100,000 parts by weight based on 100 parts by weight of the theoretical yield of the compound of the formula (I).