JPH0254819B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing aliphatic isocyanates. More specifically, the present invention relates to a method for producing aliphatic isocyanate in high yield from an aliphatic primary amine, carbon monoxide, and molecular oxygen. [Prior Art] Conventionally, aliphatic isocyanates have been produced by the reaction of aliphatic primary amines with phosgene, but this requires the use of highly toxic phosgene and the use of large amounts of corrosive hydrogen chloride as a by-product. Isocyanates can be produced relatively easily without using phosgene because of the fact that the product may contain hydrolyzable chlorine compounds and it is very difficult to remove this byproduct. A method for manufacturing is desired. On the other hand, it was already known that aliphatic isocyanates can be produced in about 50% yield by reacting aliphatic primary amines with carbon monoxide and stoichiometric amounts of palladium chloride. (EWStern et al., J.
(Org.Chem., Vol. 31, p. 596, 1966) [Problems] However, this method requires more than an equivalent amount of sodium hydrogen phosphate as a dehydrochlorination agent, and palladium chloride is not used as a catalytic reaction. This method was far from being commercially viable due to the fact that the reaction stopped due to reduction to metal palladium, the reaction time was extremely long at 48 to 60 hours, and the yield was low. Also, Special Publication No. 45-650 (and J.Tsuji et al.
A similar reaction was reported in Chem.Commun., p. 828, 1966), but this method also uses stoichiometric amounts of palladium chloride and allyl halide, and is not a catalytic reaction. It could not be carried out industrially because the reaction stopped when a pialyl complex was formed and the yield was very low. Therefore, the present inventors conducted intensive research to find a method for producing aliphatic isocyanate from an aliphatic primary amine in high yield without using phosgene, and as a result, the present invention was completed. [Structure] That is, the present invention provides a method for producing an aliphatic isocyanate from an aliphatic primary amine, comprising: (a) an aromatic hydroxyl compound, molecular oxygen, and a platinum group metal and a compound containing a platinum group element; An aliphatic primary amine is reacted with carbon monoxide in the presence of a catalyst system comprising at least one selected halogen compound and at least one halogen compound to form a carbonylation product comprising an isocyanate compound and a urethane compound. and (b) heating the obtained carbonylation product to 100 to 300°C.
The isocyanate compound and aromatic hydroxyl obtained by carrying out a thermal decomposition step in which the urethane compound in the carbonylation product is decomposed into an isocyanate compound and an aromatic hydroxyl compound by treatment at a temperature of This is a method for producing aliphatic isocyanate, which is characterized by recovering the compound and the compound separately. The carbonylation process of the present invention is characterized by the co-production of an isocyanate compound and a urethane compound, and although the mechanism of production of this carbonylation product is unknown, the result of the reaction is, for example, an aromatic hydroxyl compound. When using ArOH as , it is expressed by the following general formula. R(NH ₂ ) _o +n・CO+1/2n・O ₂ +(my+nz)・
ArOH →x・R(NCO) _o +y・R(NHCOOAr) _n (NCO) _o
-n +z・R(NHCOOAr) _o +n・H ₂ O (where, R is an n-valent aliphatic group, Ar is an aromatic group, m and n are integers of 1 or more, x, y, z
is 0 or a positive number, x+y+z=1, x≠
0 shall be satisfied. ) Furthermore, in the thermal decomposition process of the present invention, the urethane compound in the carbonylation product is decomposed into an isocyanate compound and an aromatic hydroxyl compound, and this urethane compound is a mixture of aliphatic isocyanates and aromatic hydroxyl compounds. It is characterized by its decomposition occurring more easily than compounds in which alcohol is added to aliphatic isocyanate. This thermal decomposition reaction is expressed, for example, by the following general formula. y・R(NHCOOAr) _n (NCO) _on +z・R(NHCO
OAr) _o → (y+z)・R(NCO) _o +(my+nz)・Ar
OH The platinum group metals and platinum group element-containing compounds used in the carbonylation step of the method of the present invention contain at least one component selected from platinum group elements such as palladium, rhodium, platinum, ruthenium, iridium, and osmium. There is no particular restriction as long as these elements are included, and these elements may be in a metallic state or may be components forming a compound. In addition, these catalyst components include, for example, activated carbon, graphite, silica, alumina, silica-alumina, silica-titania, titania,
It may be supported on a carrier such as zirconia, barium sulfate, calcium carbonate, asbestos, bentonite, diatomaceous earth, polymer, ion exchange resin, zeolite, molecular sieve, magnesium silicate, magnesia, or the like. Examples of platinum group elements in the metallic state include metals such as palladium, rhodium, platinum, ruthenium, iridium, and osmium, these metal blacks, and catalyst components containing these metal ions on the above-mentioned carrier, and then hydrogen and Those reduced with formaldehyde, alloys or intermetallic compounds containing these metals, etc. are used. Further, the alloy or intermetallic compound may be one of these platinum group metals, or may be one of these platinum group metals, or may contain other elements such as selenium, tellurium, sulfur, antimony, bismuth,
Copper, silver, gold, zinc, tin, vanadium, iron, cobalt, nickel, mercury, lead, thallium, chromium,
It may also contain molybdenum, tungsten, or the like. On the other hand, compounds containing platinum group elements include inorganic salts such as halides, sulfates, nitrates, phosphates, borates, acetates, oxalates,
Organic acid salts such as formates, cyanides, hydroxides, oxides, sulfides, and metal acid salts containing anions such as nitro groups, cyano groups, halogens, and oxalate ions. Examples include metal complex compounds such as ammonia, amines, phosphines, carbon monoxide, salts or complexes containing chelate ligands, and organometallic compounds having organic ligands or organic groups. Among these catalyst components, those containing palladium or rhodium or both are particularly preferred, such as Pd black, Pd
-C, Pd- _Al2O3 , Pd- _SiO2 , _Pd - _TiO2 , Pd-
Supported palladium catalysts such as ZrO ₂ , Pd-BaSO ₄ , Pd-CaCO ₃ , Pd-asbestos, Pd-zeolite, Pd-molecular sieve; Pd-Pb, Pd-
Se, Pd-Te, Pd-Hg, Pd-Tl, Pd-P, Pd
−Cu, Pd−Ag, Pd−Fe, Pd−Co, Pd−Ni,
Alloys or intermetallic compounds such as Pd-Rh, these alloys or intermetallic compounds supported on the above-mentioned carriers, PdCl ₂ , PdBr ₂ , PdI ₂ , Pd
(NO ₃ ) ₂ , inorganic salts such as PdSO ₄ , Pd
(OCOCH ₃ ) ₂ , organic acid salts such as palladium oxalate, Pd(CN) ₂ , PdO, PdS, M ₂ [PdX ₄ ], M ₂
Palladate salts represented by [PdX ₆ ] (M represents an alkali metal or ammonium ion,
represents a nitro group, a cyano group, or a halogen. )
Palladium ammine complexes such as [Pd(NH ₃ ) ₄ ]X ₂ , [Pd(en) ₂ ]X ₂ (X has the same meaning as above, and en represents ethylenediamine), PdCl ₂
(PhCN) ₂ , PdCl ₂ (PR ₃ ) ₂ , Pd(CO) (PR ₃ ) ₃ , Pd
(PPh ₃ ) ₄ , PdCl(R) (PPh ₃ ) ₂ , Pd(C ₂ H ₄ )
(PPh ₃ ) ₂ , complex compounds or organometallic compounds such as Pd(C ₃ H ₅ ) ₂ (R represents an organic group), Pd(acac) ₂
Complex compounds coordinated with chelate ligands such as
Ph black, supported rhodium catalysts similar to Pd, Rh alloys or intermetallic compounds similar to Pd, and those supported on supports, RhCl ₃ and hydrates, RhBr ₃ and hydrates, RhI ₃ and water Rh ₂ (SO ₄ ) ₃ and inorganic salts such as hydrates, Rh ₂ (OCOCH ₃ ) ₄ , Rh ₂ O ₃ ,
RhO ₂ , M ₃ [RhX ₆ ] and hydrates (M and X have the same meanings as above), [Pd(NH ₃ ) ₅ ]X ₃ , [Rh(en) ₃ ]
Rhodium ammine complexes such as X ₃ , Rh ₄
Rhodium carbonyl clusters such as (CO) ₁₂ , Rh ₆ (CO) ₁₆ , [RhCl(CO ₂ ) ₃ , RhCl ₃ (PR ₃ ) ₃ ,
RhCl (PPh ₃ ) ₃ , RhX (CO) L ₂ (X has the same meaning as above, L is a ligand consisting of an organic phosphorus compound and an organic arsenic compound), RhH (CO) (PPh ₃ ) ₃
Examples include complex compounds such as or organometallic compounds. In the carbonylation step of the present invention, only one type of these platinum group metals or compounds containing platinum group elements may be used, or two or more types may be used as a mixture, and the amount used may be particularly determined. Although there is no limit, it is generally desirable that the component containing the platinum group element is in the range of 0.0001 to 50 mol% based on the primary amine. Further, the halogen compound used in the carbonylation step of the present invention may be either organic or inorganic as long as it is a halogen-containing compound that does not contain a platinum group element, such as a metal halide or an onium halide compound. , a compound capable of producing a halogenated onium compound in a reaction system, a halogen oxoacid or its salt, a halogen-containing complex compound, an organic halide, and the like are preferably used. As the metal halide, halides of alkali metals and alkaline earth metals are particularly preferred. Examples of alkali metal and alkaline earth metal halides include lithium chloride, sodium chloride, potassium chloride, calcium chloride, lithium bromide, sodium bromide, rubidium bromide, cesium bromide, magnesium bromide, strontium bromide, Combining a single metal such as barium bromide, lithium iodide, sodium iodide, potassium iodide, rubidium iodide, cesium iodide, magnesium iodide, calcium iodide, strontium iodide, barium iodide, etc. with a single halogen Compounds, double salts such as sodium magnesium chloride, potassium magnesium bromide, potassium bromine fluoride, potassium iodine chloride, rubidium iodine chloride, cesium iodine chloride, cesium iodine chloride bromide, rubidium iodine chloride bromide, potassium iodine bromide, Examples include polyhalides such as cesium iodine bromide and rubidium iodine bromide. An onium halide compound is a compound containing an element with a lone pair of electrons, in which a proton or other cationic reagent is bonded to these lone pairs, and the element with a lone pair of electrons forms a covalent bond with a valence of 1.
increases and becomes a cation,
It has a halogen anion as a counter ion. Such onium compounds include ammonium compounds ([R ¹ R ² R ³ R ^{4 N} ]X), phosphonium compounds ([R ¹ R ² R ³ R ^{4 P} ] R ³ R ⁴ As]X), iodonium compounds ([R ¹ R ² I]X), and the like are particularly preferred. Here, R ¹ , R ² , R ³ , and R ⁴ represent hydrogen or a group selected from an aliphatic group, an aromatic group, an alicyclic group, an araliphatic group, and a heterocyclic group, and each is the same. Alternatively, in some cases, it may be a constituent element of a ring containing an element having a lone pair of electrons. Further, X represents a halogen selected from Cl, Br, and I. Of course, it may be a compound having two or more such onium groups in its molecule, or it may be a polymer containing such onium groups in its main chain or side chain. Halogenated onium compounds, which are onium compounds whose anion is a halogen, can be easily synthesized by reacting a hydrogen halide or an organic halide with a corresponding amine or nitrogen-containing compound, phosphine compound, alumine compound, etc. These may be produced outside the reaction system, or may be produced within the reaction system. Of course, it may be produced by other methods, or may be produced within the reaction system by other methods. Among these, particularly preferred are halogenated ammonium compounds and halogenated phosphonium compounds. Halogenated ammonium compounds can be easily obtained by reacting a corresponding nitrogen-containing compound with hydrogen halide, or by reacting a nitrogen-containing compound with an alkyl halide or an aryl halide. Examples include ammonia, amines such as primary amines, secondary amines, and tertiary amines, hydroxylamines, hydrazines, hydrazones, amino acids, oximes, imide esters, amides, and various compounds. There are nitrogen heterocyclic compounds, etc. Examples of quaternary ammonium halides include aliphatic quaternary ammonium halides such as halogenated tetramethylammonium, halogenated tetraethylammonium, halogenated tetrabutylammonium, halogenated trimethylethylammonium, and halogenated diethyldibutylammonium; Alicyclic quaternary ammonium halides such as N,N,N-trimethylcyclohexylammonium, aromatic aliphatic quaternary ammonium halides such as halogenated tetrabenzylammonium, halogenated trimethylbenzylammonium, halogenated N,N, N-trimethylphenylammonium, aromatic quaternary ammonium halides such as halogenated N,N,N-triethylphenylammonium, halogenated N-methylpyridinium, halogenated N-ethylquinolinium, halogenated N, Heterocyclic quaternary ammonium halides such as N-dimethylpiperidinium and halogenated N,N'-dimethylimidazolinium are preferably used. Examples of the halogenated phosphonium compounds include symmetrical tetraalkylphosphonium compounds such as halogenated tetramethylphosphonium, halogenated tetraethylphosphonium, and halogenated tetrabutylphosphonium, and asymmetrical halogenated ethyltrimethylphosphonium and halogenated diethyldimethylphosphonium compounds. Tetraalkylphosphonium compounds, symmetrical tetraarylphosphonium compounds such as halogenated tetraphenylphosphonium, halogenated tetra(p-tolyl)phosphonium, etc., asymmetrical tetraarylphosphonium compounds such as halogenated (α-naphthyl)triphenylphosphonium, etc. halogenated methyltriphenylphosphonium, alkylaryl mixed phosphonium compounds such as halogenated phenyltrimethylphosphonium, and tetraalkylphosphonium compounds such as halogenated tetrabenzylphosphonium. Halogen oxoacids and their salts refer to halogen oxyacids and their salts with positive oxidation numbers of 1, 3, 5, and 7, and specifically include hypochlorous acid, chlorous acid, and chloric acid. , perchloric acid, hypobromite, bromate, perbromate, hypoiodic acid, iodic acid, iodic acid,
Orthoperiodic acid, metaperiodic acid, and salts of these acids. As a salt cation,
Any ions such as ammonium ions and various metal ions may be used, but alkali metal ions and alkaline earth metal ions are particularly preferred. Among these salts, especially bromites such as sodium bromite, bromates such as lithium bromate, sodium bromate, potassium bromate, rubidium bromate, cesium bromate, magnesium bromate, and calcium bromate. , perbromates such as potassium perbromate, sodium hypoiodite, potassium hypoiodite, rubidium hypoiodite, cesium hypoiodite, calcium hypoiodite, barium hypoiodite, etc. Iodites, lithium iodate, sodium iodate,
Iodates such as potassium iodate, potassium hydrogen iodate, rubidium iodate, cesium iodate, magnesium iodate, calcium iodate, strontium iodate, barium iodate, lithium periodate, sodium metaperiodate, ortho Trisodium dihydrogen periodate, disodium trihydrogen orthoperiodate, potassium metaperiodate, dipotassium trihydrogenorthoperiodate, tripotassium hydrogenperiodate, rubidium periodate, cesium periodate , periodates such as barium periodate are preferably used. The halogen-containing complex compound may be either a cationic or anionic halogen-containing complex compound, such as polyhalogenated halogenated salts such as ammonium dichlorobromate, tetramethylammonium tetrabromoiodate, etc. Potassium iodotellurate, tetraethylammonium tetraiodomercurate, potassium tetraiodobismuthate, sodium tetrabromocuprate, cesium tetrabromoferrate, barium hexaiodostannate,
Metal halides such as potassium tetraiodoleadate and potassium hexabromotellurate, tris(pyridine)chromium tribromide, tris(pyridine)molybdenum tribromide, hexaammine cobalt tribromide, bis(2,2'-pipyridine) Complexes having a ligand such as copper diiodide are used. In addition, organic halides have the general formula R ⁶ (X) _n (wherein R ⁶ is an m-valent organic group, X is a halogen, m
means an integer greater than or equal to 1. ), and when m is 2 or more,
X may be two or more different halogen species. In addition, halogen X is a heteroatom other than carbon,
For example, it may be bonded with nitrogen, phosphorus, oxygen, sulfur, selenium, etc. Furthermore, halogen molecules themselves can also be used. Such halogen compounds may be used alone or in combination of two or more. Such a halogen compound is usually used in an amount of 0.001 to 10,000 times the mole, more preferably 0.1 to 100 times the amount of metal in the platinum group metal or compound containing a platinum group metal element used. be done. Among the halogen-containing compounds used in the method of the present invention, those in which the halogen species is bromine or iodine are preferred, and those containing iodine are particularly preferred. The aromatic hydroxyl compound used in the present invention may be any compound as long as it has a hydroxyl group directly bonded to an aromatic group. For example, phenol; cresol (each isomer), xylenol (each isomer), trimethylphenol (each isomer), tetramethylphenol (each isomer), ethylphenol (each isomer), propylphenol (each isomer) various alkylphenols such as; various alkoxyphenols such as methoxyphenol (each isomer), ethoxyphenol (each isomer); chlorophenol (each isomer), bromophenol (each isomer), dichlorophenol (each isomers), halogenated phenols such as dibromophenol, alkyl- and halogen-substituted phenols such as methylchlorophenol (each isomer), ethylchlorophenol (each isomer), methylbromophenol (each isomer), and ethylbromophenol. type; expression A is a simple bond, or -O-, -S-, _-SO2
-, -CO-, -CH ₂ -, -C(R ₂ )- (R is a lower alkyl group), and the aromatic ring represents a halogen, an alkyl group, an alkoxy group, an ester group, It may be substituted with a substituent such as an amide group or a cyano group. ] various substituted phenols; naphthol (each isomer) and various substituted naphthols; heteroaromatic hydroxyl such as hydroxypyridine (each isomer), hydroxycoumarin (each isomer), hydroxyquinoline (each isomer) Compounds; Aromatic dihydroxy compounds such as hydroquinone, resorcinol, catechol, dihydroxynaphthalene, dihydroxyanthracene and their alkyl-substituted or halogen-substituted dihydroxy compounds; Formula (A is as described above, and the aromatic ring may be substituted with a substituent such as a halogen, an alkyl group, an alkoxy group, an ester group, an amide group, or a cyano group.) Polyhydric phenols such as pyrogallol and phloroglucin are used.Also, a group containing an aromatic hydroxyl group may form the main chain or side chain of the polymer. The aromatic hydroxyl compound may be used alone or in combination of two or more. In the carbonylation step, the aromatic hydroxyl compound has a hydroxyl group per mole of amino group of the primary amine used. It is preferable that the aromatic hydroxyl compound is used in an amount of 1 mol or more.The amount of hydroxyl group used is preferably 5 mol or more, and even more preferably 10 mol or more, per 1 mol of amino group.Amount of aromatic hydroxyl compound If it is less than 1 mole per amino group of the primary amine, a urea compound will be produced as a by-product, which is undesirable.The aliphatic primary amine used in the present invention is
Any amine having one or more primary amino groups bonded to an aliphatic carbon atom may be used, and may be an alicyclic primary amine or an aromatic aliphatic primary amine. Examples of such aliphatic primary monoamines or polyamines include methylamine, ethylamine, propylamine (each isomer), butylamine (each isomer), pentylamine (each isomer), hexylamine (each isomer), Aliphatic primary monoamines such as dodecylamine (each isomer); ethylenediamine, diaminopropane (each isomer), diaminobutane (each isomer), diaminopentane (each isomer), diaminohexane (each isomer), Aliphatic primary diamines such as diaminodecane (each isomer);
1,2,3-triaminopropane, triaminohexane (each isomer), triaminononane (each isomer), triaminododecane (each isomer), 1,8-
Diamino-4-aminomethyl-octane, 2,6
-diaminocaproic acid 2-aminoethyl ester, 1,3,6-triaminohexane, 1,6,
Aliphatic primary triamines such as 11-triaminoundecane; cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, diaminocyclobutane, diaminocyclohexane (each isomer), 3-aminomethyl-3,5,
Alicyclic primary mono- and polyamines such as 5-trimethylcyclohexylamine, triaminocyclohexane (each isomer); benzylamine, di(aminomethyl)benzene (each isomer), aminomethylpyridine (each isomer), These include aromatic aliphatic primary mono and polyamines such as di(aminomethyl)pyridine (all isomers), aminomethylnaphthalene (all isomers), and di(aminomethyl)naphthalene (all isomers). In addition, in the aliphatic groups, alicyclic groups, and aromatic aliphatic groups that make up the skeletons of these primary amines, some of the hydrogens are halogens, alkyl groups, alkoxy groups, aryl groups, cyano groups, and ester groups. , a sulfone group, or the like, or the skeleton may contain an unsaturated bond, an ether bond, an ester bond, a thioether bond, a sulfone bond, a ketone bond, or the like. In the method of the present invention, it is preferable to use an aromatic hydroxyl compound as a solvent, but other suitable solvents can also be added. Examples of such solvents include aliphatic hydrocarbons such as pentane, hexane, heptane, octane, and decane; alicyclic hydrocarbons such as cyclohexane, tetralin, and decalin; and aromatic solvents such as benzene, toluene, xylene, and mesitylene. Group hydrocarbons; Nitriles such as acetonitrile and benzonitrile;
Sulfones such as sulfolane, methylsulfolane, dimethylsulfolane; tetrahydrofuran,
Examples include ethers such as 1,4-dioxane and 1,2-dimethoxyethane; ketones such as acetone and methyl ethyl ketone; and esters such as ethyl acetate and ethyl benzoate. Furthermore, halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene, trichlorobenzene, fluorobenzene, chlorotoluene, chlornaphthalene, bromnaphthalene; chlorhexane, chlorocyclohexane, trichlorotrifluoroethane, methylene chloride, Halogenated aliphatic hydrocarbons such as carbon chloride or halogenated alicyclic hydrocarbons are also used as solvents. The molecular oxygen used in the carbonylation step of the present invention is pure oxygen or a substance containing oxygen, which may be air, or other gases that do not inhibit the reaction with air or pure oxygen, such as nitrogen, argon, helium, It may be diluted by adding an inert gas such as carbon dioxide. In some cases, it may also contain gases such as hydrogen, carbon monoxide, hydrocarbons, and halogenated hydrocarbons. The carbonylation step of the present invention is usually carried out at a temperature of 80 to 300°C.
Preferably it is carried out at a temperature range of 120 to 250°C. The reaction pressure is 1 to 500Kg/cm ² , preferably 20 to 300Kg/cm 2 .
Kg/cm ² , and the reaction time varies depending on the reaction system, catalyst system, and other reaction conditions, but is usually from several minutes to several hours. This carbonylation reaction can be carried out either batchwise or continuously, in which the reaction solution is continuously drawn out while continuously supplying the reaction components. In the thermal decomposition step, which is the second step of the present invention, the urethane compound in the carbonylation product is removed by treating the carbonylation product produced in the carbonylation step at a temperature of 100 to 300°C. It is decomposed into an isocyanate compound and an aromatic hydroxyl compound, each of which is separated and recovered to produce the desired aliphatic isocyanate. The carbonylation product also contains isocyanate compounds, which may be separated prior to carrying out the pyrolysis step, but may also be pyrolyzed as a mixture without separation. Further, in the carbonylation step, the aromatic hydroxyl compound is usually used in excess, so that it exists as a mixture with the carbonylation product after the reaction. The carbonylated product separated from this mixture may be thermally decomposed, or the mixture may be subjected to a thermal decomposition step without being separated, and the resulting isocyanate compound and aromatic hydroxyl compound may be separated. In this thermal decomposition step, in addition to the carbonylation product or a mixture of the carbonylation product and an aromatic hydroxyl compound, it is also possible to carry out using a solvent inert to isocyanate,
This is the preferred method in some cases. Such solvents include aliphatic, cycloaliphatic or aromatic substituted or unsubstituted hydrocarbons or mixtures thereof, and also certain oxygenated compounds such as ethers, ketones and esters. . Preferred solvents include hexane, heptane,
Octane, nonane, decane, n-hexadecane,
Alkanes such as n-octadecane, eicosane, squalane, and alkenes corresponding to these;
Aromatic hydrocarbons and alkyl-substituted aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, cumene, diisopropylbenzene, dibutylbenzene, naphthalene, lower alkyl-substituted naphthalene, dodecylbenzene; chlorobenzene, dichlorobenzene, bromobenzene, Aromatic compounds substituted with nitro groups and halogens such as dibromobenzene, chlornaphthalene, bromnaphthalene, nitrobenzene, nitronaphthalene; diphenyl, substituted diphenyl, diphenylmethane, terphenyl, anthracene, phenanthrene, various isomers of dibenzyltoluene , polycyclic hydrocarbon compounds such as triphenylmethane; alicyclic hydrocarbons such as cyclohexane and ethylcyclohexane; ketones such as methyl ethyl ketone and acetophenone; esters such as dibutyl phthalate, dihexyl phthalate, and dioctyl phthalate; diphenyl Examples include ethers and thioethers such as ether and diphenyl sulfide; sulfoxides such as dimethyl sulfoxide and diphenyl sulfoxide; nitriles such as benzonitrile; and silicone oil. When carrying out a thermal decomposition reaction, the urethane compound is converted into the corresponding isocyanate compound and aromatic hydroxyl compound, but one component is removed from the reaction system to prevent it from recombining and returning to the urethane compound. We have to go. In this case, it is preferable to remove and separate low boiling point components by distillation or the like among these components that are generated as the reaction progresses. In order to promote this separation, it is also a preferred method to introduce an inert gas such as nitrogen, helium, argon, carbon dioxide, methane, ethane, propane, etc., singly or in combination, into the reaction system. Organic solvents with a similar effect include low boiling point organic solvents, such as halogenated hydrocarbons such as dichloromethane, chloroform, and carbon tetrachloride, lower hydrocarbons such as pentane, hexane, heptane, and benzene, and tetrahydrofuran and dioxane. Ethers can also be used. The thermal decomposition reaction can be carried out either batchwise or continuously. The reaction temperature is usually preferably 100 to 300°C, more preferably 120 to 270°C. The reaction temperature is
If it is below 100°C, the reaction is slow or does not occur, which is industrially unfavorable, and if it is above 300°C, side reactions occur and the yield is reduced, which is not desirable. If the urethane compound of the present invention is used, it can be decomposed at a lower temperature than urethane compounds obtained from ordinary alcohols, and the produced isocyanate is suppressed from becoming a polymeric substance due to side reactions at high temperatures. This is also one of the features of the present invention. A thermal decomposition catalyst can also be used for the purpose of lowering the temperature of the thermal decomposition reaction or increasing the reaction rate. Such catalysts include, for example, rare earth elements, antimony, bismuth, and their oxides, sulfides, and salts; elemental boron and boron compounds; copper group, zinc group of the periodic table,
Metals of the aluminum group, carbon group, titanium group, and oxides and sulfides of these metals; carbides and nitrides of the carbon group excluding carbon in the periodic table, titanium group, vanadium group, and chromium group are preferably used. When using a catalyst, the ratio of these catalysts to the urethane compound can be set as desired, but it is preferable to use the catalyst in an amount of usually 0.0001 to 100 times the weight of the urethane compound. The reaction time for thermal decomposition varies depending on the type of urethane, solvent, catalyst, etc. used, reaction temperature, etc., but is usually from several minutes to several tens of hours. Preferably it is several minutes to several hours, and the shorter the better. In addition, the thermal decomposition reaction can be carried out under any pressure, including normal pressure, reduced pressure, and increased pressure, so it depends on the presence or absence of the urethane compound to be decomposed, the presence or absence of aromatic hydroxyl compounds, the presence or absence of a decomposition solvent, and the type of decomposition solvent. The optimum reaction pressure determined by Examples of preferred embodiments of the method of the invention include:
Under thermal decomposition reaction conditions, a carbonylation step is carried out using an aromatic hydroxyl compound having a boiling point difference of at least 10°C with respect to the isocyanate compound generated, and the isocyanate compound generated in the thermal decomposition step is One example is a method in which low-boiling point products of the isocyanate compounds and aromatic hydroxyl compounds are taken out into the gas phase at the same time as decomposition and separated from high-boiling point products. In a more preferred embodiment of this method, the isocyanate compound is separated by distillation at the same time as the thermal decomposition reaction using an aromatic hydroxyl compound having a boiling point 10°C or more higher than that of the isocyanate compound to be produced. It is. In this method, the aromatic hydroxyl compound, which is a high boiling point compound, is reused in the carbonylation process after the completion of the decomposition process, either as is or after some purification. There is also no need to separate aromatic hydroxyl compounds. Furthermore, there are no limitations on the appearance of the reactor used in the thermal decomposition process or the decomposition method. A method in which low-boiling decomposition products are taken out in gaseous form from the top of the reactor, and high-boiling decomposition products are taken out and collected separately from the bottom of the reactor. A tank-type reactor is used to convert the low-boiling decomposition products into the gas phase. A method of decomposing while taking out and recovering, a method of combining these methods, etc. are preferably used. Further, if necessary, a distillation column and/or a partial condenser may be provided above these thermal decomposition reactors. The method of the present invention comprises an aliphatic monoisocyanate,
This method is suitable for producing aliphatic diisocyanates and aliphatic polyisocyanates, and is also suitable for producing hexamethylene diisocyanate, which is used in large quantities industrially. Next, the present invention will be explained in more detail with reference to Examples. [Example] Example 1 In a stirred autoclave with an internal volume of 200 ml, 12.5 mmol of hexamethylene diamine and 47 mmol of phenol were added.
After adding 0.5 mg of palladium black and 1 mmol of sodium iodide and replacing the inside of the system with carbon monoxide, carbon monoxide was 75 kg/cm ² and then air was 35 kg/cm ²
was added to make the total pressure 110Kg/cm ² . 170 while stirring
After carrying out the carbonylation reaction at ℃ for 1 hour, the entire amount of palladium black was separated and recovered by filtering the reaction mixture. Analysis of the reaction mixture showed that the reaction rate of hexamethylene diamine was 100%, the yield of hexamethylene diisocyanate was 73%, and the monoisocyanate monourethane 1-isocyanate-
It was found that 6-phenoxycarbamoyl-hexane was produced at a yield of 14%, and 1,6-diphenoxycarbamoyl-hexane, which is a diurethane, was produced at a yield of 7%. In addition, when sodium iodide was not used, this carbonylation reaction hardly proceeded. Next, the reaction mixture obtained in the carbonylation step is placed in a simple distillation apparatus consisting of a three-necked flask equipped with a thermometer, a nitrogen inlet extending below the liquid level, and a Liebig condenser, and the reaction mixture obtained in the carbonylation step is placed in the outer bath of the flask. 200
It was heated to 0.degree. C. and nitrogen was introduced at 30/h. Water and most of the phenols produced by the carbonylation reaction were distilled off at temperatures up to 185°C. On this occasion,
Thermal decomposition reaction was also progressing at the same time, but the temperature of the outer bath was raised to 210°C and held for 10 minutes, and the phenol produced by the decomposition was almost completely distilled off. Almost 100% of phenol was recovered. By distilling the obtained residue under reduced pressure, 126-127
1.95 g of hexamethylene diisocyanate (yield 98.2% based on hexamethylene diamine) was obtained by distillation at ℃/10 mmHg. Example 2 A carbonylation reaction was carried out in the same manner as in Example 1 except that 54 g of para-cresol was used instead of phenol. As a result, the reaction rate of hexamethylene diamine was 100%, and the yield of hexamethylene diisocyanate was 100%. 62%, 1-isocyanate-6-(p
It was found that -methylphenoxy)carbamoyl-hexane was produced in a yield of 3%, and di-(p-methylphenoxy)carbamoyl-hexane was produced in a yield of 30%. The reaction mixture from which palladium black had been removed by filtration was subjected to distillation of para-cresol at the same time as the thermal decomposition reaction, using the same method as in Example 1 while maintaining the temperature of the outer bath of the flask at 210°C. After recovering almost the entire amount of para-cresol, the residue was distilled under reduced pressure to obtain 1.93 g of hexamethylene diisocyanate (yield 91.9% based on hexamethylene diamine) distilled at 126-127°C/10 mmHg. Obtained. Example 3 Parachlorophenol 55 instead of phenol
g, Example 1 except that 1 mmol of tetramethylammonium iodide was used instead of sodium iodide.
As a result of carrying out the carbonylation reaction in the same manner as
The reaction rate of hexamethylene diamine was 100%, and the yield of hexamethylene diisocyanate was 75%.
-Isocyanate-6-(p-chlorophenoxy)
Carbamoyl-hexane with a yield of 15% and di-(p
It was found that -chlorophenoxy)carbamoyl-hexane was produced in a yield of 5%. The reaction mixture, with the palladium black removed by filtration, was placed in a three-necked flask similar to that used in Example 1. However, in this case, the nitrogen inlet was a capillary tube, and the entire system was maintained at 300 mmHg. The temperature of the outer bath of the flask in this decomposition reaction distillation apparatus was maintained at 220°C, and a thermal decomposition reaction was carried out simultaneously with the distillation of parachlorophenol. After recovering almost the entire amount of parachlorophenol, the residue was distilled under reduced pressure to obtain 1.94 g of hexamethylene diisocyanate (yield 92.4% based on hexamethylene diamine) distilled at 126-127°C/10 mmHg. Obtained. Examples 4 to 9 Carbonylation and thermal decomposition reactions were carried out in the same manner as in Example 1, except that various halogen compounds shown in Table 1 were used instead of sodium iodide, and hexamethylene was produced by distillation under reduced pressure. Diisocyanate was obtained. The results are shown in Table 1. Here, HMDI is hexamethylene diisocyanate, HMIU is 1-isocyanate-6-
Phenoxycarbomoyl-hexane, HMDU
represents 1,6-diphenoxycarbamoylhexane. The yield is based on the hexamethylene diamine used.

〔effect〕

It has been revealed that aliphatic isocyanates can be produced in high yield from aliphatic primary amines by the method of the present invention.

Claims (1)

[Scope of Claims] 1. A method for producing an aliphatic isocyanate from an aliphatic primary amine, comprising (a) an aromatic hydroxyl compound, molecular oxygen, and a compound selected from a platinum group metal and a platinum group element-containing compound; The aliphatic primary amine is reacted with carbon monoxide in the presence of a catalyst system comprising at least one isocyanate compound and at least one halogen compound to obtain a carbonylation product consisting of an isocyanate compound and a urethane compound. and (b) the obtained carbonylation product at 100 to 300°C.
The isocyanate compound and aromatic hydroxyl obtained by carrying out a thermal decomposition step in which the urethane compound in the carbonylation product is decomposed into an isocyanate compound and an aromatic hydroxyl compound by treatment at a temperature of 1. A method for producing an aliphatic isocyanate, which comprises recovering the compound and the isocyanate separately. 2 A platinum group metal and a compound containing a platinum group element,
The method according to claim 1, which is palladium, rhodium, palladium compounds and rhodium compounds. 3. The halogen compound contains a halogen molecule, an alkali metal or alkaline earth metal halide, a halogenated onium compound or a compound capable of producing these compounds in a reaction system, a halogen oxoacid or its salt, or a halogen ion. The method according to claim 1, wherein the compound is at least one selected from complex compounds and organic halides. 4. The method according to claim 2, wherein the platinum group metal and the compound containing a platinum group metal element are palladium or a compound containing palladium. 5. The method according to claim 1 or 3, wherein the halogen compound is a bromine molecule, an iodine molecule, or a compound containing bromine or iodine. 6. The method according to claim 5, wherein the compound containing bromine or iodine is an alkali metal or alkaline earth metal bromide or iodide. 7. The method according to claim 1, wherein the halogen compound is an alkali metal iodide. 8. The method according to claim 1, wherein the aliphatic primary amine is a diamine. 9. Claim 8, wherein the diamine is hexamethylene diamine and the aliphatic isocyanate produced is hexamethylene diisocyanate.
The method described in section. 10. The method according to claim 1, wherein an aromatic hydroxyl compound having a boiling point difference of at least 10°C with respect to the isocyanate compound produced under the thermal decomposition reaction conditions is used. 11. The method according to claim 10, which uses an aromatic hydroxyl compound having a boiling point at least 10° C. higher than the isocyanate compound under thermal decomposition reaction conditions.