Title of Invention

"METHOD FOR THE PREPARATION OF CARBAMATES"

Abstract

The present invention relates to a method for the preparation of carbamates by reaction of amines selected from the group consisting of toluenediarnines, diaminodiphenylmethanes or polyminopolyphenylmethanes or mixtures thereof with organic carbonates of the kind such as herein described in the presence of a metal based catalyst comprising an alkanoate having from 1 to 1 5 carbons atoms or a metal selected from the group consisting of Ti, Zr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Pb, Bi and Cd, wherein the reaction is carried out under such conditions that a precipitate containing said metal is formed, at a temperature between 100 and 250°C and at a pressure of not more than 20 bar in the presence of an inert aromatic solvent, and wherein the precipitate containing the metal is subsequently separated from the reaction mixture.

Full Text

DESCRIPTION The present invention relates to a method for the preparation of carbamates by reaction of amines with organic carbonates. It is known to react amines with organic carbonates in order to obtain carbamates. 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. 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. In DE-A 3.202.690 a method for preparing aromatic urethanes is described by reacting aromatic amines and alkylcarbonates in the presence of an alcoholate of an alkali metal or an alkaline earth metal. 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. None of the above documents discloses the conversion of the catalyst into a compound which forms a precipitate under the reaction conditions applied. An improved method has now been found for the preparation of carbamates by reaction of amines with organic carbonates. The invention thus concerns a method for the preparation of carbamates by reaction of amines with organic carbonates in the presence of a metal based catalyst wherein the reaction is carried out under such conditions that a precipitate containing said metal is formed during or after the reaction. The method allows easy recovery of the spent catalyst, i.e. the metal containing compound, thus improving the economics and environmental impact of the process. The precipitation can be brought about in any suitable manner. Preferably, the catalyst is converted into an insoluble metal carbonate by reaction with the organic carbonate present in the reaction mixture. However, depending on the type of catalyst and reactants used, and the reaction conditions applied, at least a part of the catalyst may still remain unconverted in the reaction mixture after the reaction has taken place. Preferably, a suitable Bronstedt acid or a salt thereof will then be added in order to form a precipitate containing the metal. h suitable Bronstedt acid or metal salt thereof may be any inorganic or organic acid or salt which reacts with the catalyst to form a precipitate containing the metal of the catalyst (for example HCI). Its choice thus largely depends on the type of catalyst used. In a preferred method at least 90% by weight of the catalyst is eventually converted into a metal containing precipitate. Furthermore, the invention concerns the above method in which the precipitate containing the metal is subsequently separated from the reaction mixture. The precipitate may be removed continuously during or after the termination of the reaction by any suitable method. A preferred separation method is filtration. 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-chlorophenylamine, 2-fluorophenyl amine, 3,4-dichlorophenylamine, aniline, benzylamine, tolylamine, diisopropyl phenylamine, 2,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2'-diaminodiphenylmethane and higher homologs (polyaminopolyphenylmethanes), 2,4-toluenediamine, 2,6-toluenediamine, m-phenylenediamine, 1,4-butylenediamine, 1,6-hexylenediamine, 1,5-naphthylenediamine, 1,4-cyclohexylenediamine, isophoronediamine, 2,2,4-trimethylhexamethylenediamine and mixtures thereof. Preferred are aromatic di- or polyamines like toluenediamines, diaminodiphenylmethanes or polyaminopolyphenylmethanes or any mixtures thereof Suitable organic carbonates include cyclic or alicyclic carbonates such as, for example, ethylene carbonate, propylene carbonate, styrene carbonate, diphenyl carbonate, methyl phenyl carbonate,dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dihexyl carbonate, methyl ethyl carbonate, methyl butyl carbonate and the like. Any metal based catalyst capable of forming a metal compound which is present as a precipitate during or after completion of the reaction may be used. Organic or inorganic salts which may be used include, for example, acetates, chlorides, nitrates, sulfonates, propionates, isopropanoates, butanoates, 2-ethylhexanoates, n-octoates, isononanoates, benzoates, chlorobenzoates, naphthenat.es, stearates, itaconates, pivalates, phenolates, acetylacetonates, alkoxides, C16/C18-alkenylsuccinoates (ASA), C12-alkenylsuccinoates (DSA) and the like. Preferred are alkanoates having from 1 to 15 carbons atoms. 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. Preferably, 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. A method wherein the precipitate containing the metal is a metal carbonate is preferred. The catalyst is generally used in amounts between 10-3 and 20 mole% based on the amount of amines used. The polyamines and the organic carbonates may be reacted in stoichiometric quantities. The use of an excess of organic carbonates however is preferred. The reaction conditions and reagents are chosen so that as much of the catalyst as possible is converted into a metal compound which is present as a precipitate at the end of the reaction. The method may be carried out at atmospheric or superatmospheric pressures. A pressure of not more than 20 bar is preferred. The 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 3 hours are common, and reaction times of less than 2.5 hours have been achieved without any problem. Generally, the reaction temperature will be between 50 and 300°C. Preferably, the method of the invention is carried out at temperatures between 100 and 250°C. The presence of a solvent is not required, but it may be added without adversely affecting the reaction. 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, trichlorobenzene or 1-chloronaphthalene, alkylated aromatic hydrocarbons like toluene, xylene, ethylbenzene, cumene or tetrahydronaphthalene, other functionalised aromatic hydrocarbons such as anisole, 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, carbontetrachloride, and alkanes with other functional groups like diethylether, acetonitrile, dioxane or mixtures thereof, and the like. Preferred are inert aromatic solvents, particularly solvents comprising monochlorobenzene or ortho-dichlorobenzene. The method 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. During the reaction 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. Accordingly there is provided Method for the preparation of carbamates by reaction of amines selected from the group consisting of toruenediamines, diaminodiphenylmethanes or polyminopolyphenylmethanes or mixtures thereof with organic carbonates of the kind such as herein described in the presence of a metal based catalyst comprising an alkanoate having from 1 to 15 carbons atoms or a metal selected from the group consisting of Ti, Zr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Pb, Bi and Cd, wherein the reaction is carried out under such conditions that a precipitate containing said metal is formed, at a temperature between 100 and 250°C and at a pressure of not more than 20 bar in the presence of an inert aromatic solvent and wherein the precipitate containing the metal is subsequently separated from the reaction mixture. The present invention is illustrated by, but not limited to, the following examples. Examples Example 1 A mixture of 2.0g (8 mmol) polymeric diamino diphenyl methane, 42.8g (0.475 mol) dimethyl carbonate and 0.23g (0.18 mmol active catalyst) of a lead octoate (lead salt of 2-ethyl hexanoic acid) solution in mineral terpentine oil (MTO) (18 wt% Pb) was charged into a 100 ml steel autoclave and purged with nitrogen. The reaction mixture was then heated at 180°C for 2h. After completion of the reaction, the autoclave was cooled to room temperature and 45 mg (84% of the charged catalyst) of spent catalyst (mainly lead carbonate, formed from the catalyst during the reaction) was filtered off. The filtrate was then evaporated to dryness under vacuum to yield a pale yellow solid (3.32g). Conversion of amine was 100% based on the starting material. Selectivity to urethane was found to be 96% based on quantitative IR and 13C NMR. Elemental analysis was satisfactory. Addition of HCI and neutral AI2O3 or montmorillonite K 10 to the carbamate solution in DMC, followed by filtration and evaporation to dryness, reduced the lead content of the carbamate from 2000 ppm to 200 ppm. Example 2 A mixture of 1.2g (9.83 mmol) 2,4-diaminotoluene , 42.8g (0.475 mol) dimethyl carbonate and 0.098g (0.082 mmol active catalyst) of a lead octoate (mainly lead salt of 2-ethyl hexanoic acid) solution in MTO (18 wt% Pb) was charged into a 100 ml steel autoclave and purged with nitrogen. The reaction mixture was then heated at 180°C for 2h. After completion of the reaction the autoclave was cooled to room temperature and an equal volume of dichloromethane was added to dissolve partly precipitated 2,4-bis(methoxycarbonylamino)toluene. The solid was then filtered off to separate out the spent catalyst (11 mg, i.e. 49% of the charged catalyst). The filtrate thus obtained was evaporated to dryness under vacuum to obtain yellow 2,4-bis(methoxycarbonylamino)toluene solid (2.34 g). Conversion of amine and selectivity to urethane were found to be >98% and 94% respectively from quantitative HPLC technique. Example 3 A mixture of 2.0g (8 mmol) polymeric diamino diphenyl methane, 42.7g (0.47 mol) dimethyl carbonate and 0.12g (0.1 mmol active catalyst) of a lead isononanoate (lead salt of 3,5,5-trimethyl hexanoic acid) solution in MTO was charged into a 100 ml steel autoclave and purged with nitrogen. The reaction mixture was then heated at 180°C for 2h. After completion of the reaction, the autoclave was cooled to room temperature and the spent catalyst (mainly lead carbonate, formed from the catalyst during the reaction) was filtered off (23 mg; 85% of the charged catalyst). The filtrate was then evaporated to dryness under reduced pressure to yield a pale yellow solid (3.18g). Conversion of amine was >98% based on the starting material. Selectivity to urethane was found to be >95% based on quantitative IR and 13C NMR. Example4 A mixture of 2.0g (8 mmol) polymeric diamino diphenyl methane, 42.7g (0.47 mol) dimethyl carbonate and 0.218g (0.2 mmol active catalyst) of a zinc isononanoate (zinc salt of 3,5,5-trimethyl hexanoic acid) solution in MTO (6 wt% Zn) was charged into a 100 ml steel autoclave and purged with nitrogen. The reaction mixture was then heated at 180°Cfor2h. After completion of the reaction, the autoclave was cooled to room temperature and the spent catalyst (zinc carbonate, formed from the catalyst during the reaction) was filtered off (48% of the charged catalyst). The filtrate was then evaporated to dryness under vacuum to yield a pale yellow solid (3.0g). Conversion of amine was 98% based on the starting material. Selectivity to urethane was found to be 89% based on quantitative IR and 13C NMR. Addition of HCI and neutral AI2O3 or montmorillonite K 10 to the carbamate solution in DMC, followed by filtration and evaporation to dryness, reduced the lead content of the carbamate from 2090 ppm to 80 ppm. WE CLAIM; 1. Method for the preparation of carbamates by reaction of amines selected from the group consisting of toluenediamines, diaminodiphenylmethanes or polyminopolyphenylmethanes or mixtures thereof with organic carbonates of the kind such as herein described in the presence of a metal based catalyst comprising an alkanoate having from 1 to 15 carbons atoms or a metal selected from the group consisting of Ti, Zr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Pb, Bi and Cd, wherein the reaction is carried out under such conditions that a precipitate containing said metal is formed, at a temperature between 100 and 250°C and at a pressure of not more than 20 bar in the presence of an inert aromatic solvent and wherein the precipitate containing the metal is subsequently separated from the reaction mixture. 2. Method as claimed in any one of the preceding claims, wherein the precipitate containing the metal is a metal carbonate. 3. Method as claimed in any one of the preceding claims, wherein a Bronstedt acid or a salt thereof is added after the reaction to form a precipitate containing the metal. 4. Method as claimed in claim 3, wherein the precipitate containing the metal is removed by filtration. 5. Method as claimed in any of the preceding claims having a reaction time of less than 2.5 hours. 6. Method for the preparation of carbamates substantially as herein before described with reference to the foregoing examples.

Documents:

1384-del-1998-abstract.pdf

1384-del-1998-claims.pdf

1384-del-1998-correspondence-others.pdf

1384-del-1998-correspondence-po.pdf

1384-del-1998-description (complete).pdf

1384-del-1998-form-1.pdf

1384-del-1998-form-13.pdf

1384-del-1998-form-19.pdf

1384-del-1998-form-2.pdf

1384-del-1998-form-4.pdf

1384-del-1998-gpa.pdf

1384-del-1998-pct-409.pdf

1384-del-1998-pct-416.pdf

1384-del-1998-petition-137.pdf

1384-del-1998-petition-138.pdf