Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C319/00—Preparation of thiols, sulfides, hydropolysulfides or polysulfides
  • C07C319/22—Preparation of thiols, sulfides, hydropolysulfides or polysulfides of hydropolysulfides or polysulfides
  • C07C319/24—Preparation of thiols, sulfides, hydropolysulfides or polysulfides of hydropolysulfides or polysulfides by reactions involving the formation of sulfur-to-sulfur bonds

Definitions

• This invention relates to a method of preparing 2,2'-dithiodianiline by reacting an alkali metal salt of o-aminothiodianiline with hydrogen peroxide.
• the 2,2'-dithiodianiline is particularly useful for curing, crosslinking or extending isocyanate-terminated polyurethane prepolymers. It can be prepared by oxidizing the sodium salt of o-aminothiophenol. However, the 2,2'-dithiodianiline must be obtained in high purity form, without the attendant typical oxidation byproducts, for satisfactory use in the preparation of most cured polyurethanes.
• 2,2'-dithiodianiline could be prepared by the steps of (A) oxidizing an aqueous solution of the sodium salt of o-aminothiophenol through the slow addition of hydrogen peroxide to form a water slurry of the water insoluble 2,2'-dithiodianiline, and solution of water soluble byproducts and (B) mixing toluene with the slurry to extract the 2,2'-dithiodianiline in the hydrocarbon phase.
• a method of preparing 2,2'-dithiodianiline through the oxidation of a salt of o-aminothiophenol and recovering the 2,2'-dithiodianiline in a relatively high purity form is provided.
• a method of preparing 2,2'-dithiodianiiine by reacting an alkali metal salt or o-aminothiophenol with hydrogen peroxide is characterized by (A) agitating a mixture of a water solution of the sodium or potassium salt of o-aminothiophenol and an unstable dispersion therein of a liquid hydrocarbon selected from at least one of toluene, benzene, or xylene, (B) oxidizing said salt of o-aminothiophenol by slowly adding a water soluble peroxide to said agitated mixture, (C) discontinuing the agitation of the dispersion to allow the mixture to substantially immediately separate into a lower aqueous phase and upper hydrocarbon phase having a continuous, sharply defined innerface therebetween, (D) drawing off said lower aqueous phase and (E) distilling the remaining hydrocarbon phase to remove said hydrocarbon therefrom and recovering said 2,2'-dithiodianitine as a distilland.
• the method of preparing the 2,2'-dithiodianiline is characterized by (A) forming an agitated, unstable mixture comprised of (1) 100 parts by weight of an aqueous solution comprising 10 to 50 weight percent sodium or potasssium salt of o-aminothiophenol, and correspondingly, 90 to 50 weight percent water and (2) a dispersion therein of 10 to 50 parts by weight hydrocarbon selected from at least one of toluene, benzene or xylene, (B) oxidizing said salt of o-aminothiophenol by adding a water soluble peroxide to said agitated dispersion sufficiently slowly so that only a trace, if any, residual peroxide concentration is maintained in the dispersion, at a temperature in the range of 5°C.
• the utilization of the unstable hydro- carbon/water solution dispers on effects both an effective insulation and clean separation of the 2,2'-dithiodianiline product in a relatively high purity form from the presence of degraded reactants and byproducts right at the point of reaction itself.
• the product is immediately both withdrawn from its reaction medium and insulated therefrom.
• the 2,2'-dithiodianiline is uniquely of sufficiently high purity, without additional purification steps, to be satisfactorily used as a curative for some isocyanate-terminated polyurethane prepolymers although at least one water wash of the product is preferably for optimum results. It should readily be appreciated by those having skill in the polyurethane art that purity of reactants is of high priority in such polyurethane reaction systems.
• the hydrocarbon phase containing the 2,2--dithiodianiline (before the distillation step) with at least one, generally from 1 to 5, preferably 2 to 4, water washes.
• the primary purpose is to remove traces of sodium or potassium hydroxide which can typically adhere to surfaces of the physical reactor system itself and bleed into the product or hydrocarbon phase contained in the reactor.
• agitation In the conduct of the reaction, it is necessary to provide an agitated, unstable aqueous solution/hydrocarbon dispersion.
• the liquid hydrocarbon is chosen so that it is naturally immiscible with the aqueous solution. Therefore, the mixture requires agitation, preferably a very rapid or high degree of agitation, to provide and maintain the dispersion. When the agitation stops, the dispersion disappears within a few minutes, typically in a minute or less, yielding sharply defined aqueous and hydrocarbon phases.
• Such agitation can be provided by conventional means.
• the o-aminothiophenol can conveniently be obtained from the reaction of benzothiazole with sodium hydroxide. Such a reaction is generally exothermic and can be conducted at a temperature in the range of about 130°C. to about 170°C.
• the product of such a reaction is upgraded to remove impurities by first steam stripping to remove volatiles, aniline and benzothiazole, following which water and hydrocarbon are added to adjust the concentration of the sodium salt of o-aminothiophenol in the water to about 3 to about 30 weight percent.
• the mixture can be, if desired, treated with activated carbon to remove trace impurities and filtered.
• the o-aminothiophenol salt, as an aqueous solution in the presence of the hydrocarbon is now ready for oxidation.
• the final oxidation product contained 2,2'-dithiodianiline in high purity form in the dispersed toluene phase while the water phase selectively contained reaction byproducts which included inorganic salt, sodium hydroxide as well as the original water.
• the toluene from the toluene phase was simply removed by flash distillation from the top of the reactor through a condenser into a receiver at a reduced pressure of about 1333 Pa (100 mm Hg) and a pot temperature of about 150°C.
• the remaining molten distilland product was removed from the reactor by pressurizing with about 34474 Pa (5 psig) from the reactor at about 130°C. and packaged in containers in which it solidified when cooled below about 90°C.
• the overall yield was above 90 percent of 2,2'-dithiodianiline of a total amine content (purity of about 98.1 percent).
• the 2,2'-dithiodianiline product was then successfully used as a curative for an isocyanate-terminated polyisocyanate/polymeric polyol polyurethane prepolymer of toluene diisocyanate and polytetremethylene ether glycol.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 1977
  • 1977-08-19 US US05/826,020 patent/US4136118A/en not_active Expired - Lifetime
• 1978
  • 1978-06-16 CA CA305,675A patent/CA1088568A/en not_active Expired
  • 1978-07-26 EP EP78100508A patent/EP0000871B1/en not_active Expired
  • 1978-07-26 DE DE7878100508T patent/DE2860470D1/de not_active Expired
  • 1978-08-01 IT IT50561/78A patent/IT1106616B/it active
  • 1978-08-07 JP JP53096067A patent/JPS6042789B2/ja not_active Expired

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