Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C263/00—Preparation of derivatives of isocyanic acid
  • C07C263/04—Preparation of derivatives of isocyanic acid from or via carbamates or carbamoyl halides
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C269/00—Preparation of derivatives of carbamic acid, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups
  • C07C269/04—Preparation of derivatives of carbamic acid, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups from amines with formation of carbamate groups

Definitions

• the present invention relates to a method for the preparation of organic carbamates by reaction of amines with organic carbonates.
• US-A 5.347.034 discloses a process for producing poly(O-alkylurethanes) of the diphenylmethane series by reacting the corresponding amines with dialkyl carbonates in the presence of a catalyst, such that the formed poly(O-alkylurethanes) crystallize out in a highly pure form upon cooling.
• the production of the O-ethylcarbamate of TDI is described in EP-A 520.273.
• EP-A 391.473 describes a process for producing carbamates using reduced amounts of catalyst by first reacting an amine with a (cyclo)alkyl carbonate in the presence of a carbamation catalyst to produce a mixture of a carbamate and an urea, further reacting the urea with carbonate to produce the corresponding carbamate, and finally recovering the carbamate from the reaction mixture.
• US-A 4.268.684 discloses a method for the preparation of carbamates by reacting an organic carbonate with an aromatic amine in the presence of certain zinc, tin or cobalt salts which are only active at temperatures of at least 200° C whereas in US-A 4.268.683 zinc or tin salts are used which are soluble in the reaction mixture at the reaction conditions.
• EP-A 48.371 describes the preparation of N,O-disubstituted urethanes by reacting primary amines with dialkylcarbonates in the presence of neutral or basic inorganic or organic lead, titanium zinc or zirconium compounds. 2
• the preparation of aliphatic carbamates using a sodium methoxide catalyst is disclosed in e.g. US-A 5.138.015 and US-A 5.315.034.
• EP-A 752.414 concerns a process for the preparation of aromatic urethanes in the presence of a zinc and/or copper carbonate hydroxide catalyst.
• carbamates are prepared by heating an organic carbonate and an aromatic amine in the presence of aluminum as catalyst and a promoter comprising a combination of iodine and a mercury salt.
• carbamates can advantageously be prepared by reacting specific organic carbonates with amines.
• the invention thus concerns a method for the preparation of carbamates comprising reacting amines with heteroatom-substituted alkyl carbonates.
• the method of the present invention allows for the production of carbamates under mild reaction conditions, i.e. relatively low temperatures and pressures.
• Typical examples of suitable carbonates are bis(2-isopropoxyethyl) carbonate,bis(l ,3-dimethoxy-2-propyl)carbonate,bis(l , 1 ,-dimethoxy-2-ethyl)carbonate,bis (2-methoxy-l-propyl)carbonate,bis(2-methoxy-3-butyl)carbonate,bis(l-ethoxycyclopropy l)carbonate, bis(N,N-dimethylaminoethyl)carbonate, bis(2,2,2-trifluoroethyl)carbonate, bis(2,2,2-trichloroethyl)carbonate,bis(l,l,l,3,3,3-hexafluoroisopropyl)carbonate,bis(nonaf luorotert.butyl)carbonate, bis(fluorophenyl)carbonates, bis (chlorophenyl)carbonates and polysubstituted halogenated phenylcarbon
• Fluorine-containing carbonates such as bis (l,l,l,3,3,3-hexafluoroisopropyl)carbonate,bis (2,2,2-trifluoroethyl)carbonate or bis(nonafluorotert.butyl)carbonate, are preferred.
• Amine compounds which can be used in the present method include aliphatic, cycloaliphatic or aromatic mono-, di- or polyamines.
• Suitable amines according to the process of the invention include, for example, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, hexylamine, cyclopropylamine, cyclobutylamine, cyclohexylamine, laurylamine, stearylamine, phenylamine, 4-chlorophenyl amine, 2- fluorophenyl amine, 3,4-dichlorophenylamine, aniline, benzylamine, tolylamine, diisopropyl phenylamine, 2,4'-diaminodiphenylmethane,4,4'-diaminodiphenylmethane,2,2'-diaminodiphenylmethan e and higher homologs (polyaminopolyphenylmethanes), 2,4-toluenediamine, 2,6-toluen
• aromatic di- or polyamines like toluenediamines, diaminodiphenylmethanes or polyaminopolyphenylmethanes or any mixtures thereof.
• the polyamines and the organic carbonates may be reacted in stoichiometric quantities.
• the method of the present invention may be carried out in the presence of a catalyst.
• a catalyst Preferred are heterogeneous metal based catalysts, such as organic metal salts on an inert carrier support or metal based catalysts which form a metal compound which is present as a precipitate during or after completion of the reaction.
• Organic or inorganic salts which may used include, for example, acetates, chlorides, propionates, isopropanoates, butanoates, 2-ethylhexanoates, n-octoates, isononanoates, benzoates, chlorobenzoates, naphthenates, stearates, itaconates, pivalates, phenolates, acetylacetonates, alkoxides, C 16 /C 18 -alkenylsuccinoates (ASA), C I2 -alkenylsuccinoates (DSA) and the like.
• ASA alkoxides
• DSA C I2 -alkenylsuccinoates
• alkanoates having from 1 to 15 carbons atoms. 4
• Suitable catalysts include, for example, zinc catalysts such as zinc chloride, zinc acetate, zinc propionate, zinc octoate, zinc benzoate, zinc p-chlorobenzoate, zinc naphthenate, zinc stearate, zinc itaconate, zinc pivalate, zinc phenolate, zinc acetylacetonate, zinc methoxide, lead catalysts like lead acetate and lead octoate, and tin catalysts like stannous chloride, stannous octoate, and mixtures thereof.
• zinc catalysts such as zinc chloride, zinc acetate, zinc propionate, zinc octoate, zinc benzoate, zinc p-chlorobenzoate, zinc naphthenate, zinc stearate, zinc itaconate, zinc pivalate, zinc phenolate, zinc acetylacetonate, zinc methoxide, lead catalysts like lead acetate and lead octoate, and tin catalysts like stannous
• the metal in the catalyst is selected from the group consisting of Ti, Zr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Pb, Bi and Cd.
• the heterogeneous metal based catalyst on the carrier may be made by impregnating the catalyst with or precipitating it on the carrier.
• Suitable inert carrier supports include, for example, alumina, silica, TiO 2 , clays, zeolites, resins, graphite and carbon.
• a preferred carrier comprises TiO
• the catalyst is generally used in amounts between 10 "3 and 20 mole% based on the amount of amines used.
• reaction conditions largely depend on the type of reactants used.
• the method may be carried out at atmospheric or superatmospheric pressures.
• the pressure is preferably not more than 20 bar.
• reaction time is dependent on the temperature and on the type and quantity of the carbamate compound, but will normally be between 0.5 and 6 hours. Reaction times of less than 4 hours are common, and reaction times of not more than 3 hours have been achieved without any problem.
• reaction temperature will be between 20 and 300°C.
• method of the invention is carried out at temperatures between 50 and 200°C. 5
• Any solvent or mixture of solvents which is inert to the reactants under the reaction conditions may be employed.
• Suitable solvents which may be employed include, for example, aromatic hydrocarbons such as benzene, halogenated aromatic hydrocarbons such as monochlorobenzene, ortho-dichlorobenzene or 1-chloronaphthalene, alkylated aromatic hydrocarbons like toluene, xylene, ethylbenzene, cumene or tetrahydronaphthalene, other functionalised aromatic hydrocarbons such as anisol, diphenylether, ethoxybenzene, benzonitrile, 2-fluoroanisole, 2,3-dimethylanisole or trifluorotoluene, alkanes such as n-pentane, n-hexane, n-heptane or higher or branched alkanes, cyclic alkanes like cyclopentane, cyclohexane or derivatives thereof, halogenated alkanes like chloroform, dichloromethane, carbontetrach
• the alcohol which is released by the reaction of the carbonate with the amine may also advantageously be used as the solvent.
• the invention relates to the preparation of organic isocyanates by thermolysis of the organic carbamates thus prepared.
• thermolysis may be carried out solvent-free or in the presence of a solvent. If a solvent is present, it may be the same as that used for the production of the carbamates.
• thermolysis reaction conditions such as temperature and pressure, will depend on the type of carbamate and on whether a solvent is present or not. 6 In the solvent-free method the temperature will preferably be between the melting point of the starting carbamate and 350°C.
• the preferred temperature is between 50 and 200° C, and more preferably between 120 and 190°C.
• thermolysis may be carried out at atmospheric pressure, preferably under nitrogen.
• the reaction preferably takes place under reduced pressure.
• the pressure is preferably reduced to between lO ⁇ and 50 mbar.
• the synthesis and optional thermolysis of the organic carbamates can be conducted in any apparatus which can be equipped, if required, with agitation means and heating and/or cooling means to keep the temperature within the desired range.
• the method of the present invention may be conducted batchwise or as a semi-continuous or continuous process.
• One type of continuous operation is in a fluidized bed reactor in which a catalyst is carried into the reactor as a slurry in one or more of the reactants. Still another way of operating continuously is in a moving bed reactor in which the catalyst bed and the reactants pass concurrently or countercurrently to each other.
• a preferred type of continuous operation however is in a fixed bed reactor in which the reactants are passed over the catalyst bed.
• thermolysis alcohols are formed as by-product. These can be removed from the reaction mixture either continuously during or after completion of the reaction by e.g. distillation. 7
• the isocyanates and alcohols thus obtained are generally of high purity and no additional treatment is required to further purify said products. Only the solvent, if present, needs to be removed.
• reaction products formed may be subjected to known purification methods, such as filtration, extraction, recrystallisation or distillation.
• diaminodiphenylmethane Into a suitable flask equipped with a condenser and a thermometer, 0.1 g of diaminodiphenylmethane are dissolved in 1 g of 1,1,1,3,3,3-hexafluoro isopropanol. When the amine is dissolved, 3.5 g of bis(l, 1,1,3,3,3- hexafluoroisopropyl)carbonate is added. This mixture is heated to reflux temperature (76°C) and stirred for 3 hours at this temperature. To the carbamate formed in this way, 5 g of ortho-dichlorobenzene (ODCB) are added. The mixture is heated and addition of monochlorobenzene (MCB) is started.
• ODCB ortho-dichlorobenzene

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• 1999
  • 1999-03-16 WO PCT/EP1999/001693 patent/WO1999047493A1/en not_active Application Discontinuation
  • 1999-03-16 EP EP99915615A patent/EP1093452A1/de not_active Withdrawn
  • 1999-03-17 AU AU34127/99A patent/AU3412799A/en not_active Abandoned

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