PROCEDURE FOR THE PRODUCTION OF N-METHYLCABAMATES

Description

TITLE INV. DES. PROCEDURE FOR THE PRODUCTION OF N-METHYL ARBAMATES RIVETTI FRANCO / MIZIA FRA NC0 , GARO NE GUIDO / ROMANO UGO „ 22 OCT. Wì Rome, there..................................... Register A Profocollo η 1945 3 TO / MINISTRY OF INDUSTRY, COMMERCE AND ARTICLES Provincial Office of Industry, Commerce and Crafts of Milan COPY OF THE MINUTES OF FILING FOR INDUSTRIAL INVENTION PATENT In the year 1995, on the EIGHTH day of the month of FETIBRAIO, lA.pi.Ua_ ENICHEM SINTESI SpA ikSkgiW of Italian nationality IT? in PALERMO, Via Ruggero Settimo, 55 ** through the agent: Eng. Gerolamo FUSINA and with domicile for legal purposes in Milan) - San Donato Milanese at ENIRICERCHE SpA - Patents Licenses and Documentation has presented to me, the undersigned: - Stamped application for the granting of a PATENT FOR an industrial invention having as TITLE. PROCEDURE FOR THE PRODUCTION OF N-METHYLCABAMATES Inventors designated: Franco RIVETTI, Franco MIZIA, Guido GARONE, Ugo ROMANO Priority of the patent application in; accompanied by: - Description in duplicate of 27 pages of writing. - Drawings, plates no. 1 in duplo. - Letter of appointment - Ettsbcetazix3«exHiBixcQB«KXHdxAtóBxddx(KXsciaK2K. (with reservation) - AtJKxkz3azx0H®XK8KB>dsxs®osiBRe. Declaration pursuant to art. 4 of Ministerial Decree 3.4.81 (with reservation - Act of designation of the inventor. - Proof of payment on postal account no. 00663004 in the name of the Tax and Concession Registry Office to) Rome of L. 292,000.= Revenue stamp of L. 3,000, issued by the Milan Post Office on 8 / 2 / 85 n. 756 found in the present document, which is not in the original. This stamp is issued on the same date by the same owner. The application, descriptions and drawings listed above have been signed by the applicant and countersigned by me and stamped with the office seal. THE DEPOSITORS^ ..rLUT / Jo.....L..Ù.vsAj......................... For a certified copy of the original «It is specified that for the application and attachments the stamp duty was paid in accordance with circular no. 163 / Θ3 of the UCB, subject to any additions that will be requested by the same at the time of the concession.» THE ROGANT OFFICIAL idiu > ·.,· p. the Director (Senito Boschetto) THE HEAD OF THE L'(.7 / / / BMNEJJ .......................... z' V is ' k , 1· : c ' ί ( , / To the MINISTRY OF INDUSTRY AND COMMERCE IREI CENTRAL OFFICE PREviT'l.l PEL ] IWEEZION3 , MODELS E PALCHI li O fu A 'La : ·;··. < ; ci ι ' ; EE1CHEM SIATESI SpA of Italian nationality with registered office in PALERMO, Via Ruggero Selti. mo, through the undersigned agent Ing., Gerolamo , PUH IΗ A and with elective domicile in San Donato Milanese (Lino), pronao EHililCEKCiìE SpA - i'i veI I i , Licenses and Documentation, requests the granting of a certificate of industrial invention patent and having for ti Ioi o : ' PROCEDURE FOR THE PRODUCTION OF PI N-tET'J LCARPAMMATI THE JPen'ifna qua .i inventori isj qnor i : Tronco LI VETI], Franco THE I ; 111ΖIA , Cui dc GAK 0 K1!, Il / -o L 0 E, Λ H 0 . Please attach the following documents to this form: !) description of the invention in duplicate of n, ET each one cries; 2) certificate of payment for the axis and concessions of Lit. 292,0W-- null c / c n. 006GG004 dated . '3) ti, 1 marca dt; stamp from Ri I . 3.000.®85 010453 I 9 4 5 3 A / ' 85 T1985 Z) Letter of appointment; (with reservation) E) The elimination of the arasi one pursuant to art. Z of the Legislative Decree 6} I draw 1 table in duplo; 7) Form fri ecs i p.nazi one inventors; April 1981 (with reservation) Description of the industrial invention entitled: PROCEDURE FOR THE PRODUCTION OF N-METHYLCARBAMMATES by: ENICHEM SINTESI SpA Inventors: Franco RIVETTI, Franco MIZIA, Guido GARONE and Ugo ROMAN. FE3.1985 9 45 3 A / 85 SUMMARY Procedure for the production of N-methylcarbamates: OR / C = 0 (I) \ NH CH (where RO- is the radical of a substituted phenol or a naphthol), where: - in a first reaction stage, methylamine and diphenylcarbonate are made to interact with each other, operating in the liquid phase and continuously, to form phenol and phenyl N-methylurethane; - in a second reaction stage, the phenyl N-methylurethane in the reaction mixture from the first stage is thermally and continuously decomposed to give a gaseous stream containing methyl isocyanate, from which the various constituents of methyl isocyanate are condensed; - in a third stage the methyl isocyanate stream, coming from the second stage, after possible 2. condensation, is continuously fed and placed in contact with a solution, in an inert organic solvent, of a substituted phenol or a naphthol, containing a basic catalyst, to form N-methylcarbamate (I); - finally N-mc1carbamate (I) is recovered from the reaction mixture from the third stage. DESCRIPTION The present invention relates to an improved process for the preparation of N-methyl 1-carbamates, with continuous operation. N-methylcarbamates are valuable products, many of which are known to have pesticide activity, such as 2,3dihydro-2,2-dimethylbenzofuran-7-yl N-methylcarbamate (known as CARROFURAN), 1-naphthyl N-methylcarbamate (known as CARBARYL) and 2-isopropoxyphenyl1 N-methylcarbamate (known as PROPOXUR). N-methylcarbamates are obtained, according to the known technique, by reacting methyl isocyanate with a substituted phenol or a naphthol, operating in an inert organic solvent and in the presence of a basic catalyst. For this purpose, see R.J. Kuhr and H.W.D.Orough Carbamate Insecticides; Chemistry, Biochemistry and Toxicology, CRC Press (1977). The main drawback of the preparation processes of N-methylcarbamates lies in the use of a reagent such as methyl isocyanate, which is highly toxic and dangerous in 3. transport and storage phase. Methyl isocyanate is in fact highly volatile (boiling point 38°C) and polymerizes easily, exothermically, to the bulk liquid state. When traces of acids, bases, or metals are present, polymerization can occur explosively. Finally, methyl isocyanate can give rise to violent hydrolytic reactions with water, characterized by the development of pressure (formation of carbon dioxide) and high flammability. From the above it appears desirable to have a process for the production of N-methylcarbamates which does not require the storage of methyl isocyanate and in which the quantity of free methyl isocyanate involved at any one time is small. According to the European Patent Application Publication No. 80.584, alkyl isocyanates are obtained by decomposition of phenyl N-alkyl urethanes in the presence of phenol. According to U.S. Patent 4,097,676, phenyl Nalkyl urethanes are prepared by reacting diphenylcarbonate with alkylamine. In the experimental examples of U.S. Patent 4,097,676 the reaction of diphenylcarbonate with alkylamine is carried out in an inert organic solvent such as benzene and dioxane. 4. It has now been found that the reaction described in the U.S. patent 4,097,676 proceeds favorably until the conversion of the reagents is practically complete, when operating continuously, using the same mixture as the reaction liquid between definilcarbonate and alkylamine. It has also been found that the decomposition reaction of the phenyl N-alkyl urethanes of European patent application publication number 80,584 can be carried out continuously, directly on the mixture resulting from the reaction between diphenyl carbonate and alkylamine. Furthermore, when the decomposition reaction of phenylalkyl urethanes is carried out with only a partial step conversion and therefore with recycling of the unreacted product, the development of 1 1-isocyanate to the kyl isocyanate is constant and regular, so much so as to make possible a continuous or semi-continuous conduction of the subsequent reaction with a substituted phenol or with naphthol. On this basis the present invention relates to the preparation of N-methyl1carbamates: OR C -, 0 (I) NHCH (where RO- is a substituted phenol or naphthol radical) by a process comprising the following sequential steps: ] 0 stage : diphenylcarbonate and methylamine are continuously fed to a first reactor, together with a liquid recycling stream consisting of the reaction mixture discharged from said first reactor and the operation is carried out in liquid phase, with a molar ratio in the feed between methylamine and diphenylcarbonate from 0.8 / 1 to approximately 1 / 1 and at a temperature from 20° to 80°C, to form phenyl N-methylurethane and phonol; 2nd stage: the reaction mixture from the first stage and a recycled liquid stream containing phenyl N-methylurethane are continuously fed to a second reactor and the process is carried out in the boiling liquid phase at a temperature of 180° to 220°C and a pressure of 200 mm Hg to atmospheric pressure to partially decompose the phenyl N-methylurethane into phenol and methyl isocyanate and to develop a gaseous stream containing phenol, methyl isocyanate and unchanged phenyl N-methylurethane, said gaseous stream being subjected to partial condensation to separate a gaseous stream of methyl isocyanate from a liquid stream of phenol and phenyl N-methylurethane, the latter being in turn subjected to treatments for the separation and recycling of phenyl N-methylurethane; 3rd stage: the methyl isocyanate stream coming from the second stage is continuously fed to a third reactor and is brought into contact, possibly after condensation, with a solution of a substituted phenol or 6, a naphthol in an inert organic solvent and operated at a temperature of 0° to 50°C, in the presence of a boric catalyst to form N-methylcarbamate (l); Finally, N-methylcarbamate is recovered from the reaction mixture from the third stage. Stage I In the first stage of the process of the present invention diphenylcarbonate and methylamine are made to interact with each other to give phenyl N-methylurethane and phenol according to 1st equation: OPh NH CH / z 3 C = 0 + CH NH ...........> C - 0 + PhOH \ 3 2 \ OPh OPh (where Ph is the phenyl radical) The molar ratio in feed between methylamine and diphenylcarbonate can generally vary from 0.8 / 1 to approximately 1 / 1. However, it is very desirable to use a molar ratio of 1 / 1, or at least close to that value. The reaction temperature is conveniently maintained at values ​​in the range from 20° to 80°C. Temperatures lower than 0°C can be used, but this has the disadvantage of a reaction rate that is too slow. Temperatures higher than 80°C on the other hand are undesirable as they favor the occurrence of a secondary reaction which leads to the formation of N,N'-dimethylurea, according to the following equation: . OPh .NHCH / / 3 C 0 4 2CH NH -C - 0 + 3 2 ~ \ 2PhOH \ OPh NHCH 3 (where Ph is the phenyl radical) This reaction occurs significantly especially above about 100°C. The operating pressures can vary from ambient pressure to approximately 5 bar. Generally, the system operates at its autogenous pressure at the chosen temperature. The reaction medium consists of the same reaction mixture which is conveniently recycled to the first stage reactor. In practice, a continuous stream of methylamine and a continuous stream of diphenylcarbonate dissolved in the recycled liquid mixture can be fed to the first stage reactor. Conveniently, in this last stream, the concentration of diphenylcarbonate can vary from 5 to 60% by weight, since in this concentration range, homogeneous liquid streams are obtained, with a low viscosity value for the temperature range at which one operates, which can therefore be handled easily. The first-stage reactor can be a stirred reactor into which the reagents and recycled liquid are continuously fed and from which the reaction mixture is continuously discharged. Alternatively, an elongated reactor can be used, such as a tubular one, with reagents and recycled liquid continuously fed to one end and the reaction mixture discharged to the other. Operating under the conditions described above, the reaction is brought to completion, or substantial completion, in a time of 15 to 30 minutes, in the absence of substances having a catalytic action on the reaction itself. In particular, operating under the conditions previously indicated and with stoichiometric or near-stoichiometric quantities of the reagents, the conversion of the diphenylcarbonate is typically greater than about 98%, with a selectivity for phenyl N-methylurethane typically greater than 99% with respect to the converted diphenylcarbonate, all on a molar basis. The reaction mixture discharged from the first stage reactor is partially recycled, as previously indicated, and the remaining part is continuously sent to the second stage reactor. 2nd Stage In the second stage of the process of the present invention, phenyl N-methylurethane is thermally decomposed into methyl isocyanate and phenol according to the following equation: 9. C = Ο — \ NHCH CH -N = C = 0 4 3 PhOH (where Ph is the phenyl radical). More specifically, according to the process of the present invention, the second-stage reactor is continuously fed with a liquid stream consisting of the reaction products of the first stage and a recycled liquid stream of phenyl N-methylurethane. The process is carried out in a boiling liquid phase, at a temperature of 180° to 2.0°C, at a pressure of 200 mm Hg to atmospheric pressure, in the absence of substances having a catalytic action on the decomposition reaction, to partially decompose (10-90%) the phenyl N-methylurethane into phenol and methyl isocyanate. Under these conditions, a gaseous stream containing methyl isocyanate, phenol, and unchanged phenyl N-methylurethane develops in the second-stage reactor. This stream is cooled, for example to a temperature of around 80-100°C, to separate a gaseous stream of methyl isocyanate from a liquid stream of phenol and phenyl N-methylurethane.The liquid stream thus obtained is subjected to distillation to partially or totally separate the phenol as an overhead product, from a bottoms product formed or containing phenyl N-methylurethane and this bottoms product is recycled to the second stage reactor as. 10. previously indicated. In the preferred embodiment, the second-stage reactor operates at a temperature of about 210°C, at atmospheric or near-atmospheric pressure, with an average residence time (calculated as the ratio of the feed volumetric flow rate to the useful reactor volume) of 0.5 to 3 hours. Furthermore, the reactor is supplied with sufficient heat to generate a weighted evaporate flow rate of 1.5 to 11 times the feed flow rate. Under these conditions, conversions of phenyl-N-methylurethane are achieved by passing from approximately to approximately 85% of the feed amount, and a gaseous stream develops in the reactor containing approximately 9 to approximately 22% by weight of unchanged phenyl-N-methylurethane, approximately 63 to approximately 71% by weight of phenol, and approximately 15 to approximately 20% by weight of methyl isocyanate. This gas stream is cooled to a temperature of 80-100°C to separate a condensate consisting of phenol and phenyl N-methylurethane from a gas stream of methyl isocyanate, which is sent to the third stage. Part of the condensate is refluxed to the second-stage reactor (reflux ratio of approximately 0.5 to approximately 10), and the remainder is sent to a distillation column, which operates at a pressure, measured at the head, of the order of 10 mm Hg with an overhead temperature of 77-80°C. 11. and with a bottom temperature of 100-110°C. Under these conditions, a phenol stream separates at the head of the column, which is recovered, and at the bottom a liquid stream containing phenol and phenyl N-methylurethane, in approximately equimolecular proportions, which is recycled. The reactor in which the second stage is carried out is preferably a stirred reactor, surmounted by a partial condenser, preceded or not by some distillation trays or a packing section. Operating under the preferred conditions described above, a complete or practically complete conversion of phenyl N-methylurethane is obtained, with a selectivity for Methyl isocyanate typically greater than 98 mol%. 3rd Stage In the third stage of the process of the present invention Methyl isocyanate, coming as a gaseous stream from the second stage, is reacted, possibly after condensation, with a substituted phenol or a naphthol dissolved in an organic solvent, according to the following equation: OR CH -N - C 3 NHCH is a naphthol. where RO- represents the radical of a substituted phenol or 12. Examples of ROH compounds useful for the purposes of this invention are: phenol substituted with one to three substituent groups, equal to or different from each other, selected from alkyl, oxyalkyl, thioalkyl, aminoalkyl, alkyleneoxyalkyl, alkylenethioalkyl and alkyleneaminoalkyl groups, where the alkyl group, linear or branched, contains from 1 to 5 carbon atoms (preferably from 1 to 3 carbon atoms) and the alkylene contains 1 or 2 carbon atoms (preferably methylene); 1- naphthol; 2- naphthol; 2.3- dihydro-2, 2-dimethyl-benzofuran-2-ol; 2,2-dimeth 1-1,3-benzodi,oxol-4-ol o. 2-(1,3-dioxolan-2-yl)phenol Examples of preferred ROH compounds for the purposes of this invention are: 3,5-xylenol; 3.4- xiPhenol; 2-isopropylphenol; ?-isopropoxy phenol; 2-(ethylthiomethyl)phenol; 2- cresol; 3-isopropyl-5-methylphenol, 4-methylthio-3,5-dimethylenol, Ì3. 4-dimethy1amino-3-methy1phenol ; 1-naphthol ; 2,3-di1dro-2,2-dimethylbenzofuran-2-ol; And 2,2-dimethy1-1,3-benzodi oxol-4-ol According to the process of the present invention The methyl isocyanate, coming from the second stage, after possible condensation, is continuously fed and placed in contact with a solution of the ROH compound in an inert organic solvent, also containing a basic catalyst. Suitable organic solvents for this purpose are aromatic hydrocarbons, such as benzene, toluene, xylene, and cumene; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate, methyl acetate, dimethyl carbonate, and dimethyl carbonate; chlorinated aliphatic hydrocarbons such as chloroform, methylene chloride, carbon tetrachloride, and dichloroethane; and ethers such as diethyl ether and tetrahydrofuran. Generally, the concentration of the compound in its solution in the organic solvent varies from 5 to 60% by weight. Basic substances such as tertiary amines, heterocyclic bases, alkoxides and carbonates of alkali or alkaline earth metals, or organic derivatives of metals such as tin and titanium are used as catalysts for the third-stage reaction. Specific examples of catalysts useful for this purpose are triethylamine, diisopropylethylamine, pyridine, 4-dimethylaminopyridine, N-methylimidazole, and methylated 14. sodium, sodium ethylate, sodium carbonate, dibutyltin dilaurate, dibutyltin diacetate and titanium i.sopropi side. Preferred catalysts are tertiary amines and organic tin compounds. The amount of catalyst used for the third-stage reaction can generally range from 0.001 to 0.1 mole for each mole of the ROH compound. The reaction temperatures are not particularly critical, but preferably one operates in a range of values ​​from 0° to 0°C. Preferably, one operates at atmospheric pressure or in any case without imposed overpressure. In the third stage reaction, we also operate with an equimolecular, or approximately equimolecular, ratio between the ROH compound and the methyl isocyanate, and in particular with ratios from 1 / 1 to 1.1 / 1. The third stage of the process of the present invention can be conducted using multiple reactors in parallel, each containing the solution of the ROH compound in the chosen organic solvent as well as the catalyst. In this case, the stream of methyl isocyanate is continuously fed to the first reactor, possibly after liquefaction, until the desired molar ratio between the reactants is reached; then the methyl isocyanate stream is diverted to the 15. second reactor. After the methyl isocyanate feed, the first reactor is maintained under reaction conditions for a time of the order of 0.5-8 hours, in order to complete the reaction and finally N-methylcarbamate is recovered from the reaction mixture. cycle is repeated for the second reactor and so on. According to another embodiment of the present invention, the methyl isocyanate stream from the second stage, optionally liquefied, and a stream consisting of the solution of the ROH compound in the chosen organic solvent and also containing the catalyst, are continuously fed to a third-stage reactor where the general conditions described above are followed, with a residence time that can generally vary from 0.5 to 8 hours. The reaction mixture is continuously discharged from the reactor and subjected to treatments aimed at separating N-methylcarbamate. The third stage is preferably conducted in stirred reactors in the form of a multiple-reactor parallel implementation. In the continuous implementation, a series of continuous reactors in cascade is preferably used, or an elongated tubular reactor to one end of which the reagents are continuously fed. IC. and at the other end the reaction mixture is continuously discharged. Operating under the conditions described above, N-methylcarbamate is typically obtained, with a yield typically greater than 98 mol% of the fed reagents. N-methylcarbamate is separated from the reaction mixture from the third stage by any known technique such as concentration, crystallization, filtration, drying, or a combination of these treatments. In the preferred form, the solvent for the third stage is chosen to favor the precipitation of N-methylcarbamate, thus facilitating its separation from the reaction mixture, which can then be recycled directly after dissolving the ROH compound. If necessary or desired, the separated N-methylcarbamate can be purified, for example by crystallization from an inert solvent, by dissolving it under heat in a suitable solvent, and then precipitating by cooling the solution. Conveniently, the heating temperature of the crude N-methylcarbamate solution should be kept below that which causes degradation of this compound, and will generally be less than 100°C. By the process of the present invention, N-methylcarbamates are prepared by a process in 17. which, at any given time, maintains the amount of free methyl isocyanate at extremely low levels, solving or at least significantly mitigating the problems associated with the use of such a compound. Furthermore, the process of the present invention allows for the simple and economical preparation of N-methylcarbamates, with high yields and selectivity. Furthermore, the continuous process described above offers advantages over discontinuous process, resulting in higher productivity per unit of useful volume of the equipment, greater consistency in the characteristics of the final products, and greater potential for automation of the operations. Finally, the process of the present invention allows for great flexibility as it enables the production of a wide range of N-methylcarbamates. The following experimental examples are illustrative and not limiting for the present invention. Examples ο 1 Referring to figure 1, Rl indicates the first stage reactor, equipped with a stirrer and operating at a temperature of 50°C and a relative pressure of 1 bar. Reactor Rl is continuously fed, via line 1, with a flow of 1.3 kg / hour (42 moles / hour) of methylamine and via line 3 with a liquid flow of 22.5 kg / hour (42 moles / hour). Kg / hour, containing 40% by weight of diphenylcarbonate. 18. current of line 3 is obtained by feeding 9.0 kg / hour (4? moles / hour) of diphenyl carbonate through line 2 and 13.5 Kg / hour of reactor effluent Rl, via line 5. The residence time in the reactor R1 is equal to 0.5 hours and a current of 23.8 kg / hour is discharged via line 4, having the following composition: phenol 38% by weight, phenylN-methyl urethane 61% by weight and diphenylcarbonate 0.8% by weight. This stream is partly (13.5 kg / hour) recycled to the reactor Rl via line 5 and the remaining part (10.3 Kg / hour) constitutes the current of line 6 which is sent to the second stage reactor R-2, together with the current coming from the bottom of the Cl column, via line 12. In particular, the bottom stream of the Cl column has a flow rate of 2.3 kg / hour and the following composition: phenol 39% by weight and phenyl-N-methyl urethane 61% by weight. Therefore, the resulting stream, fed to the reactor R-2 via line 7, has a flow rate of 12.6 kg / hour and the following composition: phenol 38% by weight, phenyl-N-methyl urethane 61% by weight and diphenylcarbonate 0.7% by weight. In the second stage reactor R-2, the temperature is 210°C, at atmospheric pressure and with a residence time of 2 hours. Under these conditions, pyrolysis of phenyl-N-methyl urethane occurs and a gaseous stream is released which is cooled to approximately 100°C with consequent condensation. 39. Partial and obtaining a liquid phase having the following composition: phenol 86.2% by weight and phenyl N-methylurethane 13.8% by weight. This liquid phase is partially refluxed to the second stage reactor R-2 (reflux ratio 10) and the remaining part constitutes the stream of line 9 which is sent, with a flow rate of 10.1 Kg / hour at the distillation column Cl. The Cl distillation column operates at a measured overhead pressure of 10 mm Hg, an overhead temperature of 75°C, and a bottom temperature of 108°C. Under these conditions, phenol separates at the head of the Cl column in a quantity of 7.8 kg / h, and at the bottom of the column, an approximately equimolecular stream of phenol from phenyl-N-methyl urethane (39% by weight and 61% by weight, respectively) separates and is recycled to the pyrolysis reactor R-2, via line 12, at a flow rate of 2.3 kg / h. From the bottom of the pyrolysis reactor R-2 a purge is carried out periodically, via line 10, to eliminate the residual diphenylcarbonate and the high boiling by-products which are formed in very small quantities (less than 0.03 Kg / hour). The methyl isocyanate formed in the pyrolysis in the second stage reactor R-2 does not liquefy at the temperature at which partial condensation of the pyrolysis products is carried out and is discharged via line 8, 20. with a flow rate of 2.35 kg / hour. This current is liquefied in the El exchanger and sent to the R-3a reactor into which the following have previously been loaded: - 2,3-dihydro-2,2-dimethy1-7-benzofuranol: 28.6 Kg - toluene: 86 kg - triethylamine: 0.18 kg (catalyst) The methyl isocyanate stream is fed to the reactor R-3a for 4 hours operating at 15°C and pressure atmospheric. After this period of time the methyl anate stream is diverted into reactor R-3b, operating in parallel with reactor R-3a and containing the same initial charge as the latter. After the methyl isocyanate has been fed into reactor R-3a, the contents of the reactor are stirred at the above-mentioned temperature for a further 2 hours. The contents of reactor R-3a are then discharged via line 13 and subjected to filtration to separate the precipitated 2,3-dihydro-2,2-dimethylbenzofuran-7-1N-methylcarbamate, which is washed with toluene and dried at 80°C at 10 mm Hg. The mother liquors containing excess 2,3-dihydro-2,2-dimethylbenzofuranol, 2,3-di,hydro-2,2-dimethylbenzofuran-7-yl N-methylcarbamate from skim oil (1-2% by weight) and the catalyst can be recovered completely (or after a small purge) for the preparation of the feed solution for the third stage reactors. . A total of 36.0 kg of 2,3-dihydro-2,2dimethylbenzofuran-7-yl N-methylcarbamate (CARBOFURAN) are thus obtained with a yield of 1 kg of useful product for each kg of diphenylcarbonate (96.8% molar). The cycle is repeated with the R-3b reactor, obtaining results completely similar to those of the R-3a reactor. Example ? We proceed in a similar way to example 1, loading into the third stage reactors: - 1-naphthol: 25.1 kg - toluene: 75 kg - triethylamine: 0.18 kg (catalyst) In one cycle, 32.5 kg of 1-naphthyl N-methylcarbamate (CARBARYL) are obtained with a yield of 96% by moles with respect to the diphenylcarbonate. Example 3 We operate similarly to example 1 by loading into the third stage reactors - 2-isopropoxyphenol: 26.5 Kg - toluene; 80 kg - triethylamine: 0.18 kg (catalyst) In one cycle, 34 kg of 2-isopropoxyphenyl N-methylcarbamate (PROPOXUR) are obtained with a 97% molar yield on the diphenylcarbonate. Example 4 Operating similarly to example 1 and loading into the reactors: the following compounds are of the third stage: - 4-dimethylamino-3-methylphenol, - 3,5-xylenol, - 3,4-xylenol, - 2,2-dimethyl 1-1,3-benzodioxol-4-ol, ' 4-methylthio-3,5-dimethyl 1-phenol, - 3-isopropyl-S-methylphenol, • 2-cresol, - ?-isopropylphenol, and - ?(ethyl thiomethyl) phenol The following carbamates can be obtained respectively: - 4-dimeli 1ammίηο-3-methyl 1-phenyl N-methylcarbamate (AMINOCARB), - 3,5-xylyl N-methyl1carbamate (XMMC), - 3,4-xylyl N-methylcarbamate (MPMC), - 2,2-dimethyl-1,3-benzodioxol-4-yl N-methylcarbamate (BENDIOCARB), - 4-methylthio-3,5-xylyl N-methylcarbamate (METHIOCARB), - 3-isopropy1-5-methyl N-methylcarbamate (PROMECARB), - 2-tolyl N-methylcarbamate (MTMC), - 2-isopropylpheni1 N-methylcarbamate (ISOPROCARB), e - 2 (ethyl thiomethyl) phenyl N-methylcarbamate (ETHIOFENCARB) .

Claims

1. CLAIMS 1. Process for the preparation of N-methylcarbamates: / C - fJ \ OR (D NHCH (where RO- is a radical of a substituted phenol or of a naphthol), by reaction of diphenylcarbonate with methylamine to give phenyl N-methylurethane, thermal decomposition of phenyl N-methylurethane to give methyl isocyanate and reaction of methyl isocyanate with a substituted phenol or a naphthol to give N-methylcarbamate (I), characterised in that: - in a first stage, diphenylcarbonate and methylamine are continuously fed to a first reactor, together with a recycle liquid stream consisting of the reaction mixture discharged from said first reactor and the operation is in liquid phase, with a molar ratio in the feed between methylamine and diphenylcarbonate from 0.8 / 1 to approximately 1 / 1 and at a temperature from 20° to 80°C to form phenyl-Nmethylurethane and phenol; - in a second stage, they are continuously fed to a second reactor,the reaction mixture from the first stage is a recycle liquid stream containing phenyl N-methylurethane and is operated in the boiling liquid phase, at a temperature of 180° to 220°C and at a pressure of 200 mm Hg to pressure ?4. atmospheric to partially decompose the phenyl N-methylurethane into phenol and methyl isocyanate and develop a gaseous stream containing phenol, methyl isocyanate and unchanged phenyl N-methylurethane, said gaseous stream being subjected to partial condensation to separate a gaseous stream of methyl isocyanate from a liquid stream of phenol and phenyl N-methylurethane, the latter being in turn subjected to treatments for the separation and recycling of phenyl N-methylurethane, - in a third stage, the stream of methyl isocyanate coming from the second stage is continuously fed to a third reactor and is brought into contact, possibly after condensation,with a solution of a substituted phenol or naphthol in an inert organic solvent and operating at a temperature of 0° to 50°C, in the presence of a basic catalyst, to form N-methylcarbamate (I). - N-methylcarbamate is recovered from the reaction mixture from the third stage.

2. Process according to claim 1, characterized in that in the first stage the operation is carried out with a molar ratio of methylamine to diphenylcarbonate equal to or close to 1 / 1 and the diphenylcarbonate is fed in the form of a solution in the recycling stream to the first stage, with a concentration of diphenylcarbonate from 5 to 60% by weight and the operation is carried out with a residence time of 15 to 60 minutes.

3. Process according to claim 1, characterized in that in the second stage the operation is carried out at a temperature of the order of 210°C, at atmospheric pressure, with a residence time of 0.5 to 3 hours, converting from about 6 to about 5% of the phenyl N-methylurethane fed and developing a gaseous stream containing from about 9 to about 22% by weight of unaltered phenyl N-methylurethane and said gaseous stream is cooled to about 80-100°C to separate a gaseous stream of methyl isocyanate from a liquid stream of phenol and phenyl N-methylurethane, the liquid stream being partly refluxed (reflux ratio 0.5-10) and the remaining part being subjected to distillation to separate a phenol stream from a stream containing phenol and phenyl N-methylurethane in approximately equimolecular quantities, the latter stream being recycled to the second stage.

4. Process according to claim 1, characterized in that in the third stage the methyl isocyanate is reacted with a phenol substituted with one to three substituent groups, equal to or different from each other 26, selected from alkyl, oxy-alkyl, thio-alkyl, amino-alkyl, alkyl-oxy-alkyl, alkylene-thioalkyl and alkylene-amino-alkyl groups, where the alkyl group, linear or branched, contains from 1 to 5 carbon atoms and preferably from 1 to 3 carbon atoms and the alkylene contains 1 or 2 carbon atoms and is preferably methylene; 1-naphthol; 2-naphthol; 2,3-di,idro-2,2-dimethyl-benzofuran-2-ol; 2,2-dimethyl1.3-benzodioxol-4-ol; and 2-(1,3-dioxolan-2-yl)phenol.

5. Process according to claim 4, characterized in that the methyl isocyanate is reacted with: 3,5-xylenol; 3,4-xylenol; 2-isopropyphenol; 2-isopropoxyphenol; 2-(ethylthiomethyl)phenol; 2-cresol; 3-isopropyl-b-methylphenol; 4-methylthio-3,5-dimethylphenol; 4-dimethylanimino-3-methylphenol; 1-naphthol; 2,3-dihydro2,2-dimethyl-1-benzofuran-2-ol; or 2,2-dimethyl,3-benzodioxol-4-ol.

6. Process according to claim 1, characterized in that the solvent for the third stage is selected from aromatic hydrocarbons, ketones, esters, ethers and chlorinated aliphatic hydrocarbons.

7. Process according to claim 1, characterized in that the basic catalyst in the third stage is used in quantities from 0.001 to 0.1 moles for each mole of substituted phenol or naphthol 4 » * i .

8. Process according to claim 1, characterized in that the catalyst for the third stage is selected from tertiary amines and organic tin compounds.

9. Process according to claim 1, characterised in that in the third stage the molar ratio between substituted phenol or naphthol and methyl isocyanate is 1.0 / 1 to 1.1 / 1.

10. Process according to claim 1, characterized in that in the third stage a stream of methyl isocyanate is continuously fed to a reactor, among a plurality of reactors in parallel, containing a solution in an inert organic solvent of the substituted phenol or naphthol and the catalyst.

11. Process according to claim 1, characterized in that in the third stage the stream of methyl isocyanate coming from the second stage and a stream consisting of a solution of phenol substituted by naphthol and containing the catalyst in an inert organic solvent are continuously fed and the reaction mixture is continuously withdrawn.

27. . 8 FEB. 1985 The agent Eng. Gerolamo FUSINA 1 9 4 5 3 ΑΖ 85