WO2002050020A1 - Method for producing isocyanates - Google Patents

Abstract

The invention relates to a method for producing isocyanates, whereby at least one compound containing carbamate groups is converted into an isocyanate at a reaction temperature above the boiling point of an isocyanate thus arising. The reaction occurs at a reaction temperature above the boiling point of the isocyanate thus arising or the mixture of two or more isocyanates in the presence of at least a compound B which deactivates a compound A which is formed by the reaction or a mixture of two or more A compounds of said type. Deactivation is related to the reactivity of compound A or the mixture of two or more A compounds with respect to isocyanate groups.

Description

 Nerfahren for the production of isocyanates

The present invention relates to a ner process for the preparation of isocyanates, in which at least one compound containing carbamate groups is converted to an isocyanate at a reaction temperature above the boiling point of an isocyanate formed.

Isocyanates represent a valuable raw material for the production of a number of monomeric and polymeric products. In particular, the wide range of variation options with regard to the monomer composition in the production of polymers with the participation of polyisocyanates generally permit specific influencing of certain polymer properties. However, due to their fast and selective bond closure under gentle conditions, for example with OH or ΝH groups, the monoisocyanates also represent an increasingly frequently used building block for the functionalization of monomeric or polymeric compounds. In particular, functional groups can also be introduced into molecules due to their Sensitivity to drastic reaction conditions cannot be attached to a molecule by means of reactions requiring such reaction conditions.

Organic compounds, in particular polymers, which carry both a silyl group and a urethane or urea group are used in many branches of industry, for example in coating or adhesive technology. The advantages of such compounds, in particular of such polymers, lie in particular in their ability to develop a binding effect both to hydrophobic and to hydrophilic substrates and to crosslink them with one another in the event of moisture.

Surface coating compositions which contain the abovementioned compounds have improved properties on both hydrophobic and hydrophilic surfaces Liability on. Adhesives that contain such polymers are able, for example, to permanently bond both hydrophilic and hydrophobic substrates, as well as substrates of different polarities.

In order to introduce such silyl groups into polymers, an isocyanate carrying silyl groups is often used due to the sensitivity of the silyl groups to drastic reaction conditions, in particular due to their sensitivity to compounds bearing OH groups. Because of the high reactivity of isocyanate groups with respect to OH groups, such isocyanates permit simple and gentle introduction of silyl groups into molecules which carry a functional group which is reactive toward isocyanate groups.

However, the production of such silyl compounds bearing isocyanate groups is problematic.

US Pat. No. 6,008,396 describes a process for producing an isocyanato-organosilane in which a carbamato-organosilane is converted into an isocyanato-organosilane in an inert liquid medium. In the process described, a silyl carbamate is introduced into an inert reaction medium at a temperature of 200 to 400 ° C. and a pressure of 10 to 200 mbar, the carbamate being decomposed into the isocyanate. Under the prevailing reaction conditions, the isocyanate distills into a receiver. The fact that the introduction of the carbamate into the reaction medium often leads to a strong, difficult to control foam development has a disadvantage in the process described. This results in a low space-time yield due to the associated careful operation or a correspondingly voluminous reaction apparatus. In addition, fractions of inert reaction medium are often found in the distilled product due to the passage of fine droplets.

US Pat. No. 5,886,205 describes a process for the preparation of an isocyanate containing silyl groups, in which a carbamic acid ester containing silyl groups is decomposed at a pH of at most 8 in the presence of a catalyst and is collected via a distillation column. The backward reaction between However, isocyanate and alcohol in the bottom of the distillation and in the lower region of the distillation column require a high level of equipment to obtain the isocyanate. In addition, the space-time yields in the process described are also low.

There was therefore a need for a process for the preparation of isocyanates, in particular for the production of sensitive functional group-bearing isocyanates, which provides improved space-time yields or an improved product quality or both in comparison with the prior art.

The present invention is therefore based on the object of making such a method available.

The task is solved by a method as described in the following text.

The present invention therefore relates to a process for the preparation of isocyanates, in which at least one compound having at least one carbamate group is converted to at least one isocyanate and at least one compound A which has functional groups X which are reactive toward isocyanate groups, the reaction being carried out at a reaction temperature above the boiling point of the isocyanate formed in the presence of at least one compound B which has a higher boiling point than the isocyanate formed and the compound A formed during the reaction or a mixture of two or more such compounds A, with regard to the reactivity of the compound A or the mixture two or more compounds A deactivated towards isocyanate groups.

In the context of the present invention, a “carbamate group” is understood to mean a structural element of the general formula I.

worin der Rest R⁸ für einen linearen oder verzweigten, gesättigten oder ungesättigten Alkylrest mit 1 bis etwa 10 C-Atomen, einen gesättigten oder ungesättigten Cycloalkylrest mit etwa 6 bis etwa 24 C-Atomen, oder einen Arykest mit 6 bis etwa 24 C-Atomen und X für O oder S steht. Der Begriff „Carbamatgruppe" umfaßt daher im Rahmen der vorliegenden Erfindung auch Thiocarbamatgruppen.

wherein the radical R ^{8 is} a linear or branched, saturated or unsaturated alkyl radical with 1 to about 10 C atoms, a saturated or unsaturated cycloalkyl radical with about 6 to about 24 C atoms, or an aryl radical with 6 to about 24 C atoms and X represents O or S. The term “carbamate group” therefore also includes thiocarbamate groups in the context of the present invention.

A compound which can be used in the context of the present invention and has at least one carbamate group can have, for example, only one carbamate group. However, it is also possible according to the invention that such a compound has two or more carbamate groups.

In the context of the present invention, “isocyanates” are understood to mean compounds with at least one NCO group. However, the term also includes compounds with two or more NCO groups. For the purposes of such compounds, the terms “isocyanates” and, Polyisocyanates "used synonymously.

Carbamates which can be used in the process according to the invention have at least one carbamate group. Suitable carbamates can have, for example, two or more carbamate groups, provided that the isocyanates formed from such carbamates are still removed by distillation from the reaction mixture present during the reaction.

The carbamates which can be used according to the invention can in principle be of any nature, that is to say that the carbamate group or the two or more carbamate groups can be covalent with an optionally substituted linear or branched, saturated or unsaturated aliphatic or a saturated or unsaturated cycloaliphatic radical having 2 to about 44 C atoms be connected. Carbamates which are linked to an optionally substituted aromatic or araliphatic radical having 6 to about 44 C atoms can likewise be used in the context of the present invention. In principle, therefore, all customary aliphatic or aromatic mono- or polyisocyanates can be prepared by the process according to the invention, provided the corresponding mono- or polycarbamates are accessible.

In a preferred embodiment of the present invention, however, carbamates are used in the process according to the invention which, in addition to the carbamate group, have at least one further functional group.

Carbamates which are preferred in the context of the present invention for carrying out the process according to the invention have, for example, at least one ether group, thioether group or a silyl group as the functional group.

In the context of the present invention, a “silyl group” is understood to mean a functional group of the general formula U

wherein the radicals R ¹ to R ⁶ each independently represent a linear or branched, saturated or unsaturated hydrocarbon radical having 1 to about 24 carbon atoms, a saturated or unsaturated cycloalkyl radical having 4 to about 24 carbon atoms or an aryl radical having 6 to about 24 carbon atoms, n, m and j each represent an integer from 0 to 3, where m + n + j = 3, a an integer from 0 to 3, b an integer from 0 to 2 and c represents a number from 0 to 8.

In the context of a first embodiment of the present invention, a compound which carries a silyl group according to the general formula π is used as at least one compound bearing carbamate groups. Suitable compounds with at least one carbamate group are in particular compounds of the general formula HI

wherein R ¹ to R ⁶ , a, b, c, n, m and j have the meaning given above, R ⁷ for an optionally substituted alkylene radical having 1 to about 44 C atoms, an optionally substituted cycloalkenyl radical with 6 to about 24 C. -Atoms or an optionally substituted arylene radical having 6 to about 24 carbon atoms and Z represents a carbamate group. Suitable substituents for R ⁷ are, for example, functional groups such as thioether, mercapto, amino, ester, amido, nitro or ether groups or mixtures of two or more thereof.

In the context of a preferred embodiment of the present invention, however, R ⁷ has none of the above-mentioned substituents.

Carbamates such as can be used in the process according to the invention in the context of the present invention can be, for example, by reacting an amine, for example an aminosilane, with a dialkyl or diaryl carbonate or a dialkyl or diaryl pyrocarbonate, or a mixture of two or more thereof, receive. Such a reaction is usually carried out in the presence of a basic catalyst. In principle, however, all other processes known to those skilled in the art are also suitable for the production of carbamates. Suitable is e.g. the implementation of amino compounds, for example aminososilanes, with chloroformic acid esters.

Suitable carbonates for the preparation of the carbamates which can be used in the process according to the invention are, for example, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, diisobutyl carbonate, di-tert-butyl carbonate, diisopentyl carbonate, diisopropyl carbonate, ethyl methyl carbonate, ethyl 2- butoxyethyl carbonate, bis (2-chloroethyl) carbonate, diphenyl carbonate, bis (o, m-chlorophenyl) carbonate, bis (o, p-chlorophenyl) carbonate, bis (dichlorophenyl) carbonate, bis (trichlθφhenyl) carbonate or bis (o-, m -, p-Tolyl) carbonate or mixtures of two or more thereof.

Suitable dialkyl pyrocarbonates are, for example, dimethyl pyrocarbonate, diethyl pyrocarbonate or di-tert-butyl pyrocarbonate.

In the context of the present invention, carbamates, for example carbamatosilanes, are preferably used which have been prepared using dimethyl carbonate, diethyl carbonate or dipropyl carbonate or pyrocarbonate or mixtures of two or more thereof.

The reaction between the aminosilane and the organic carbonate can take place, for example, using stoichiometric amounts of the reactants. However, it is also possible and often preferred to use an excess of organic carbonate from about 0.05 to about 1 mole per mole of aminosilane. Good results can be achieved, for example, with an excess of carbonate of about 0.1 to about 0.4 moles per mole of aminosilane. With higher molecular weight aminosilanes, for example a molecular weight of more than about 200 or more than about 500 or with aminosilanes with a sterically hindered amino group, it may be necessary to use a higher excess of carbonate.

The reaction between amino compound and carbonate is usually catalyzed by a basic catalyst. A strongly basic catalyst is preferably used here. Suitable basic catalysts are, for example, alkali metal alkoxides, as can be obtained by reacting monohydric alcohols with alkali metals. Suitable alkali metals are for example lithium, sodium or potassium, suitable monohydric alcohols are for example methanol, ethanol, propanol or butanol. Suitable strongly basic catalysts are in particular sodium methoxide, sodium ethanolate, sodium propanolate, sodium tert-butoxide, potassium methoxide, potassium ethanolate, potassium propanolate or potassium tert-butoxide and the like. The amount of catalyst during the reaction is about 0.01 to about 2% by weight, based on the carbonate and amine used.

The reaction between amine and organic carbonate is slightly exothermic. Typically, amine and organic carbonate are reacted with one another in the presence of the basic catalyst such that the reaction temperature remains within a range of about 10 to about 120 ° C, for example about 20 to about 80 ° C or about 25 to about 60 ° C. The constancy of the temperature within this range can be achieved, for example, by conventional cooling methods such as cold water, ice bath, dry ice bath or by controlling the rate of addition of the reactants. The reaction is usually carried out at ambient pressure under a protective gas atmosphere.

After completion of the reaction, remaining catalyst and excess amine in the reaction mixture are neutralized by adding a neutralizing agent. Suitable neutralizing agents are, for example, inorganic acids such as anhydrous hydrochloric acid, anhydrous phosphoric acid or organic acids such as glacial acetic acid, propionic acid, butyric acid, hexanoic acid, oleic acid, maleic acid, fumaric acid, succinic acid and the like. Weak organic acids such as glacial acetic acid or inorganic acids such as anhydrous phosphoric acids, for example superphosphoric acid or polyphosphoric acid or, if present, their anhydrides are preferably used for the neutralization. The use of anhydrides of the corresponding acids is particularly suitable since both catalyst and excess amine are bound. The reaction product can be separated off using customary methods known to the person skilled in the art. The separation of precipitated salts by filtration, for example over silica gel or a suitable filter paper, and subsequent removal of volatile components by reduced pressure or temperature increase or both, is particularly suitable.

In principle, all compounds which have at least one amino group are suitable for the preparation of carbamates suitable in the context of the present invention. Such compounds are referred to in the context of the present text as synonymous as amines or amino compounds. Amines suitable for the preparation of carbamates suitable for use in the context of the present invention are, for example, monoalkylamines such as ethylamine, propylamine, butylamine, pentylamine, hexylamine and their linear or branched higher homologues with up to about 100 C atoms, the position of the amino group being terminal or can be located anywhere within the alkyl group.

The alkyl group of the monoalkylamines can optionally be substituted. Suitable substituents are, for example, hydroxyl groups, ester groups, carboxylic acid groups, sulfonic acid groups, phosphonic acid groups and the corresponding esters of the acid groups mentioned.

For example, amino compounds which have two or more amino groups are also suitable for producing carbamates which are suitable in the context of the present invention. These compounds include, for example, butylene diamine, hexamethylene diamine, 2,4,4-trimethylhexamethylene diamine, diethylene triamine, 1,12-diaminododecane, diamines derived from dimer fatty acids or triamines derived from trimer fatty acids, or mixtures of two or more of the compounds mentioned.

In a further embodiment of the present invention, amino compounds which have a saturated or unsaturated, optionally substituted cycloalkyl radical having 6 to about 24 C atoms are used for the production of carbamates which can be treated in the process according to the invention. A corresponding cycloalkyl group can have one or more amino groups. Suitable cycloalkyl compounds are, for example, cyclohexylamine, dicyclohexylamine, 1,4-cyclohexyldiamine, 4,4'-dicyclohexylmethane diamine,

Isophoronediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, and hydrogenated toluenediamines such as l-methyl-2,4, -diaminocyclohexane, l-methyl-2,6, -diaminocyclohexane and the like.

In a further embodiment of the present invention, the optionally substituted aryl groups with 6 to about 24 C- Have atoms. Aryl compounds bearing particularly suitable amino groups are, for example, aniline, 1,4-diaminobenzene, aminotoluene, m- or p-phenylenediamine, diaminobiphenyl, p-methoxyaniline, p-chloroaniline, o-, m- or p-toluidine, 2,4-xylidine, 2 , 4-, and 2,6-toluenediamine and corresponding mixtures, 4,4'-diphenylenediamine, methylene bis (aniline), including ^4.4, methylenebis (aniline), 2,4'-methylenebis (aniline), 4,4 ' -Oxybis (aniline), 4,4'-carbonylbis (aniline), 4,4'-sulfonylbis (aniline) or

Naphthyl diamines or mixtures of two or more of the compounds mentioned.

In a preferred embodiment of the present invention, aminosilanes are used in the process according to the invention for the production of the carbamates which can be treated according to the invention.

Suitable aminosilanes are, for example, N- (α-memyldimethoxysilylmeyl) amine, N- (α-trimemoxysilylmeyl) amine, N- (α-dimethylmethoxysilylmyl) amine, N- (α-

Ethyldimethoxysilylmethyl) amine, N- (α-Methyldiethoxysilyknethyl) amine, N- (α-

Triethoxysilyknethyl) amine, N- (α-Emyldiemoxysilylme yl) amine, N- (ß-

Memyldimethoxysilylethyl) amine, N- (ß-trimethoxysilylethyl) amine, N- (ß-

Ethyldimethoxysilylethyl) amine, N- (ß-Memyldiemoxysilylethyl) amine, N- (ß-

Triethoxysilylethyl) amine, N- (ß-ethyldiethoxysilylethyl) amine, N- (γ-methyldimethoxysilylpropyl) amine, N- (γ-trimethoxysilylpropyl) amine, N- (γ-ethyldimethoxysilylpropyl) amine, N- (di- ) amine, N- (γ-triethoxysilylpropyl) amine, N- (γ-ethyldiethoxysilylpropyl) amine, N- (4-memyldimethoxysilylbutyl) amine, N- (4-trimethoxysilylbutyl) amine, N- (4-triethylsilinbutyl) silylbutyl) (4-

Diethylmethoxysilylbutyl) amine, N- (4-Emyldime oxysilylbutyl) amine, N- (4-

Methyldiethoxysilylbutyl) amine, N- (4-triethoxysilylbutyl) amine, N- (4-

Diethylethoxysilylbutyl) amine, N- (4-ethyldiethoxysilylbutyl) amine, N- (5-

Methyldimethoxysilylpentyl) amine, N- (5-trimethoxysilylpentyl) amine, N- (5-triethylsilylpentyl) amine, N- (5-ethyldimethoxysilylpentyl) amine, N- (5-methyldiethoxysilylpentyl) amine, N- (5-triethyl) amine, N- (5-triethyl) , N- (5-dimethyl oxysilylpentyl) amine, N- (5-

Ethyldiethoxysilylpentyl) amine, N- (6-Me yld ^ e oxysily exyl) amine, N- (6-

Trimethoxysilylhexyl) amine, N- (6-ethyldimethoxysilylhexyl) amine, N- (6-

Methyldiethoxysilylhexyl) amine, N- (6-triethoxysilylhexyl) amine, N- (6-ethyl- diethoxysilylhexyl) amine, N- [γ-tris (trimethoxysiloxy) silylpropyl] amine, N- [γ-tris (trimethoxysiloxy) silylpropyl] amine, N- (γ-trimethoxysiloxydimethylsilylpropyl) amine, N- (γ-trimemylsilyl) ammylsilylpimylsilylpropyl) - (γ-triethoxysiloxydiemylpropyl) arnine, N- (γ-triethoxysiloxychethoxysilylpropyl) amine, N, N-butyl- (γ-trimemoxysilylpropyl) amine, N, N-butyl (γ-triethoxysilyl- nyl, propyl) amine γ-trimethoxysilylpropyl) amine, N, N-phenyl- (γ-triemoxysilylpropyl) amine, N, N-cyclohexyl- (γ-

Trimethoxysilylpropyl) amine, N, NE yl- (γ-trimemoxysilylpropyl) arnine, diethyl-N- (trimethoxysilylpropyl) aspartate, diethyl-N- (triethoxysilylpropyl) aspartate N, N-ethyl- (γ-dimemoxymethylnilnylpropyl) Ethyl (γ-trimethoxysilylisobutyl) amine, N, N-bis (trimethoxypropyl) amine, N, N-ethyl- (γ-trimethoxysilylisobutyl) amine, N, N-ethyl (α-trimethoxysilynethyl) amine, dibutyl -N- (trimethoxysilylpropyl) aspartate, dibutyl-N- (triethoxysilylpropyl) aspartate, N, N- (ß-ammopropyl) - (γ-trimemoxysilylpropyl) amine, N, N '-di (trimethoxysilylpropyl) ethylenediamine, tetra - (Trimethoxysilylpropyl) ethylenediamine and N, N-emyl- (ß-trimemoxysilylemyl) amine or N- [γ-tris (trimethylsiloxy) silylpropyl] amine or mixtures of two or more thereof.

Carbamatosilanes according to the general formula LTJ can be prepared from the aminosilanes mentioned in accordance with the process described above.

Carbamatosilanes of the general formula UI which are particularly suitable for use in the process according to the invention are, for example, methyl N- (α-methyldimethoxysilylknethyl) carbamate, methyl N- (α-trimethoxysilylknethyl) carbamate, methyl-N- (α-ethyldimethoxysilylmethyl) carbamate, methyl -N- (α-methyldiethoxysilylmethyl) carbamate, methyl-N- (α-triethoxysilylmethyl) carbamate, methyl-N- (ß-methyldimethoxysilylethyl) carbamate, methyl-N- (ß-trimethoxysilylethyl) carbamate, methyl-N - (ß-Diethynethoxysilylethyl) carbamate, methyl-N- (ß-ethyldimethoxysilylethyl) carbamate, methyl-N- (ß-methyl-diethoxysilylethyl) carbamate, methyl-N- (ß-triethoxysilylethyl) carbamate, methyl-N - (ß-ethyldiethoxysilylethyl) carbamate, methyl-N- (γ-methyldimethoxysilyl-propyl) carbamate, methyl-N- (γ-trimethoxysilylpropyl) carbamate, methyl-N- (γ-

Ethyldimethoxysilylpropyl) carbamate, methyl N- (γ-methyldiethoxysilylpropyl) carbamate, methyl N- (γ-triethoxysilylpropyl) carbamate, methyl N- (γ- Ethyl diethoxysilylpropyl) carbamate, methyl N- (4-trimethoxysilylbutyl) carbamate, methyl N- (4-ethyldimethoxysilylbutyl) carbamate, methyl N- (4-methyldiethoxysilylbutyl) carbamate, methyl N- (4-triethutylsilyl), carbamate Methyl-N- (4-ethyldiethoxysilyl-butyl) carbamate, methyl-N- (5-methyldimethoxysilylpentyl) carbamate, methyl-N- (5-trimethoxysilylpentyl) carbamate, methyl-N- (5-ethyldimethoxysilylpentyl) carbamate, methyl -N- (5-methyldiethoxysilylpentyl) carbamate, methyl N- (5-

Triethoxy silylpentyl) carbamate, methyl N- (5-ethyldiethoxysilylpentyl) carbamate, methyl N- (6-trimethoxysilylhexyl) carbamate, methyl N- (6-ethyldimethoxysilylhexyl) carbamate, methyl-N- (6-triethoxysilylhexyl carbamate, methyl-N- (6-ethyl-diethoxysilylhexyl) carbamate, methyl-N- [γ-tris (trimethoxysiloxy) silylpropyl] carbamate, ethyl-N- (α-methyldimethoxysilylmethyl) carbamate, ethyl-N- (α-tri - methoxysilylmethyl) carbamate, ethyl-N- (α-methyldiethoxysilyknethyl) carbamate, ethyl-N- (α-triethoxysilylmethyl) carbamate, ethyl-N- (α-ethyldiethoxysilylmethyl) carbamate, ethyl-N- (ß-methyldimethyl) carbamate -N- (ß-trimethoxysilylethyl) carbamate, ethyl-N- (ß-ethyldimethoxysilylethyl) carbamate, ethyl-N- (ß-

Dimethylethoxysilylethyl) carbamate, ethyl-N- (ß-methyldiethoxysilylethyl) carbamate, ethyl-N- (ß-triethoxysilylethyl) carbamate, ethyl-N- (γ-trimethoxysilylpropyl) carbamate, ethyl-N- (γ-ethyldimethoxyl) carbamate N- (γ-methyldiethoxysilylpropyl) carbamate, ethyl N- (γ-triethoxysilylpropyl) carbamate, ethyl N- (γ-ethyldiethoxysilylpropyl) carbamate, ethyl N- (4-methyldimethoxysilylbutyl) carbamate,

Trimethoxysilylbutyl) carbamate, ethyl-N- (4-ethyldimethoxysilylbutyl) carbamate, ethyl-N- (4-methyldiethoxysilylbutyl) carbamate, ethyl-N- (4-triethoxysilylbutyl) carbamate, ethyl-N- (4-ethyl-ethyl-diethyl) N- (5-methyldimethoxysilylpentyl) carbamate, ethyl-N- (5-trimethoxysilylpentyl) carbamate, ethyl-N- (5-ethyldimethoxysilylpentyl) carbamate, ethyl-N- (5-triethoxysilylpentyl) carbamate, ethyl-N- (5 -Ethyldiethoxysilylpentyl) carbamate, ethyl-N- (6-methyldimethoxysilylhexyl) carbamate, ethyl-N- (6-trimethoxysilylhexyl) carbamate, ethyl-N- (6-ethyldimethoxysilylhexyl) carbamate, ethyl-N- (6-methylhexieth ) carbamate, ethyl N- (6-triethoxysilylhexyl) carbamate, ethyl N- [γ- tris (trimethoxysiloxy) silylpropyl] carbamate, methyl N- [γ- tris (trimethoxysiloxy) silylpropyl] carbamate, methyl N- (γ-trimethoxy-siloxydimethylsilylpropyl) carbamate, methyl-N- (γ-trimethylsiloxydimethoxysilyl-propyl) carbamate, methyl-N- [γ-tris (triethoxysiloxy) silylpropyl] -carbamate, methyl-N- (γ- Triethoxysiloxydiethylpropyl) carbamate, methyl-N- (γ-triethoxysiloxydiethoxysilylpropyl) carbamate, methyl-N- [γ-tris (trimethylsiloxy) -silylpropyljcarbamate and methyl-N- [6-tris (triethoxysiloxy) carbamatehexyl. Ethyl-N- [γ-tris (trimethoxysiloxy) silyl-propyl] carbamate, ethyl-N- (γ-trimethoxysiloxydimethylsilyl-propyl) carbamate, ethyl-N- (γ-trimethylsiloxydimethoxysilyl-propyl) carbamate, ethyl-N- [γ- tris (triethoxysiloxy) silylpropyl] carbamate, ethyl-N- (γ-triethoxysiloxydiethylpropyl) carbamate, ethyl-N- (γ-triethoxysiloxy-diethoxysilylpropyl) carbamate, emyl-N- [γ-tris (trimethylsilyl) carbamate) N- [6-tris (triethoxysiloxy) silylhexyl] carbamate.

The reaction according to the process of the invention can be carried out without a catalyst. In the context of a preferred embodiment of the present invention, however, the reaction according to the method according to the invention takes place in the presence of a catalyst. Suitable catalysts are, for example, compounds of the general formula IV

M (OR ⁹ ) x (TV)

where M is a metal selected from the group consisting of aluminum, titanium, magnesium or z conium and R ^{9 is} identical or different linear or branched hydrocarbon radicals having 1 to 8 carbon atoms and x is 2, 3 or 4. Suitable catalysts are, for example, aluminum alkoxides, titanium alkoxides, magnesium alkoxides and zconium alkoxides. For example, aluminum trimethoxide, aluminum triethoxide, aluminum triisopropoxide, aluminum trisec-butoxide, aluminum tri-tert-butoxide, titanium (ιN) methoxide, titanium (rV) ethoxide, titanium (TN) isopropoxide, titanium (IN) butoxide, titanium (IV) are particularly suitable. 2-ethylhexoxide, zkkon (IN) ethoxide, Zkon (TV) propoxide, zirconium (IN) butoxide, zirconium (IN) isopropoxide, Zkon (IV) tert-butoxide, magnesium methoxide, magnesium ethoxide, magnesium butoxide, magnesium propoxide or magnesium phenoxide.

Tin compounds, in particular organotin carboxylates such as dibutyltin dilaurate, are also suitable as catalysts in the process according to the invention, Dibutyltin diacetate, dibutyltin bis (2-ethylhexanoate) or others

Organotin compounds such as dibutyltin oxide, dibutyltin dimethoxide,

Dibutyltin dibromide, dibutyltin dichloride, di-tert-butyltin dichloride,

Dimethyltin dibromide, dimethyltin dichloride, diphenyltin dichloride or tin octoate. Among the catalysts mentioned, dibutyltin dilaurate, dibutyltin oxide and dibutyltin diacetate are preferred.

Also suitable as catalysts are Nerbindungen which have at least one of the metals selected from the group consisting of antimony, iron, cobalt, nickel, copper, chromium, manganese, molybdenum, tungsten or lead. The oxides, halides, carboxylates, phosphates or organometallic compounds of the metals mentioned are particularly suitable. For example, iron acetate, iron benzoate, iron naphthenates are particularly suitable; Iron acetylacetonates, manganese acetate, manganese naphthenate and manganese acetylacetonate.

The amount of catalyst used in the process according to the invention is in a range from 0 to about 0.8% by weight, for example about 0.01 to about 0.5% by weight, in particular about 0.05 up to about 0.2% by weight, based on the total amount of carbamate.

In the context of the process according to the invention, the conversion of a carbamate or a mixture of two or more carbamates gives rise to at least one compound A which has functional groups HX which are reactive toward isocyanate groups.

The formation of such a connection lies in the elimination of the residue R ^! X based on the general formula I from the carbamate group. If a compound with at least one carbamate group used in the context of the present process is a thiocarbamate, X stands for S in the present case. If a compound with at least one carbamate group used in the context of the present process is a carbamate , X stands for O in the present case. In a preferred embodiment of the present invention, compounds having carbamate groups of the general formula I are used, where X stands for O. Compounds formed in the process according to the invention with a functional group HX have the disadvantage that they can react with an isocyanate group formed within the scope of the present invention in the sense of a back reaction with the formation of a carbamate. A carbamate formed in the course of such a reverse reaction can indeed be split back into a compound A and an isocyanate if the reaction is carried out appropriately, but such a further split reduces the efficiency of the process and considerably reduces the space-time yield of isocyanate.

It is therefore provided in the context of the process according to the invention that the reaction according to the invention is carried out at a reaction temperature above the boiling point of the isocyanate formed or the mixture of two or more isocyanates in the presence of at least one compound B which has a higher boiling point than the isocyanate formed and the Compound A formed during the reaction or a mixture of two or more such compounds A is deactivated with regard to the reactivity of compound A or the mixture of two or more compounds A with isocyanate groups.

In the context of the present invention, for example, only one compound B can be used in the reaction mixture. However, it is also possible to use a mixture of two or more compounds B.

It is preferred in the context of the present invention if the at least one compound B is used in such an amount that at least 1.1 times the amount of compounds A which are formed at most during the reaction can be deactivated. The maximum amount of compounds A formed during the reaction can be determined in a simple manner within the scope of the present invention by making the assumption that each mole of carbamate groups present in the reaction mixture releases a maximum of one mole of compound A. In the context of a further preferred embodiment of the present invention, the compound B is used in such an amount that at least twice the amount of compounds A which are formed at most during the reaction can be deactivated.

The presence of a compound B in the process according to the invention leads to a deactivation of the compound A formed in the process according to the invention with functional groups HX. As a result, compound A is at least temporarily withdrawn from the reaction mixture, so that it is no longer available for a reverse reaction.

In the context of the present invention, the carbamates to be treated according to the invention are preferably selected such that a preferably monofunctional alcohol having 1 to about 8 carbon atoms, in particular 1 to 3 carbon atoms, is formed as compound A.

In the context of the present invention, it is sufficient if at least some of the resulting compounds A are deactivated permanently or at least temporarily by a suitable compound B, since this already leads to an improvement in the space-time yield.

Deactivation of a compound A or a mixture of two or more compounds A by a compound B or a mixture of two or more such compounds can be carried out physically or chemically in the context of the present invention.

A suitable method for physical deactivation consists, for example, in adding a compound to the reaction mixture which, owing to adsorption of molecules of compound A, deactivates it for a further reaction with an isocyanate formed in the process according to the invention.

A suitable class of compounds of compounds B, with the aid of which such deactivation can take place, are, for example, the zeolites. Zeolites have cavities different polarity, in which polar molecules of compound A can be reversibly incorporated and thus removed from the reaction mixture. The deactivation of the zeolites can be supported, for example, by carrying out the implementation according to the invention in an environment which is essentially non-polar. In particular, the adsorption of a polar compound A in a polar zeolite can be supported, for example, by a non-polar environment.

If a compound B is used in the context of the present invention which physically deactivates the compound A, the amount of compound B is preferably selected such that at room temperature at least twice, for example at least 3, 4 or 5 times the amount of compounds A which are formed at most during the reaction can be deactivated.

In addition to physical deactivation, the method according to the invention can be carried out with a compound B or a mixture of two or more such compounds B which cause chemical deactivation. In the case of chemical deactivation, the functional group HX is bound in a covalent bond in such a way that the compound A is at least temporarily no longer available for a reaction with an isocyanate group formed in the course of the process according to the invention.

Compounds B which are suitable for the chemical deactivation of a compound A in the process according to the invention are therefore compounds which have one or more functional groups Y which form a covalent bond with a functional group HX of a compound A.

Suitable functional groups Y in the context of the present invention are in principle all functional groups which can form a covalent bond with the functional groups HX of the compound A under the reaction conditions. In the context of a preferred embodiment of the present invention, a compound is therefore used as compound B which, as functional group Y, has an NCO group, an epoxy group, a carboxylic acid group, an anhydride group or a carboxylic acid chloride group or a mixture of two or more thereof. In a further embodiment of the present invention, at least one compound selected from the group consisting of isocyanates, epoxides, carboxylic acids or carboxylic acid anhydrides and carboxylic acid chlorides is therefore used as compound B.

Suitable compounds B have, for example, one or more NCO groups. Such compounds react with a functional group HX of a compound A to form a covalent bond and thus at least temporarily remove the compound A from the reaction mixture. Since in the process according to the invention this covalent bond can also be cleaved with renewed release of a compound A, the amount of compounds B which has one or more NCO groups is preferably such that the molar ratio of functional groups Y to the maximum The amount of functional groups HX formed during the reaction is at least 1.1 to 1.

In the context of a preferred embodiment of the present invention, the amount of compounds B is dimensioned such that at least 1.5 times, but preferably at least 2 times, for example at least 3, 4 or 5 times the amount during the Implementation of the resulting connections A can be deactivated.

Suitable compounds with at least one NCO group are, for example, monoisocyanates, such as the linear or branched aliphatic monoisocyanates having 6 to 44 carbon atoms, for example hexyl isocyanate, heptyl isocyanate, octyl isocyanate, nonyl isocyanate, decyl isocyanate, undecyl isocyanate, dodecyl isocyanate, tridecyl isocyanate, quaterdecyl isocyanate, pentadecyl isocyanate, pentadecyl isocyanate, pentadecyl isocyanate , Octadecyl isocyanate and the corresponding higher homologues of this series, as they result from a gradual extension of the carbon chain by one carbon atom each. Aromatic monoisocyanates such as phenyl isocyanate, benzyl isocyanate or biphenyl isocyanate and the like are aromatic monoisocyanates.

Also suitable as compounds with at least one NCO group are compounds from the group of the diisocyanates, for example tekamethylene diisocyanate, Hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, dimer fatty acid diisocyanate, 1,4-diisocyanato-cyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanato-methylcyclohexane (isophorone diisocyanate, IPDi), 4,4'-diisocyanato-dicyclohexylmethane , 4'-Diisocyanato-dicyclohexylpropane-2,2, 1,3- and 1,4-diisocyanatobenzene, 2,4- or 2,6-diisocyanatotoluene (2,4- or 2,6-TDI) or a mixture thereof , 2,2'-, 2,4 or 4,4'-diisocyanatodiphenylmethane (MDI), tetramethylxylylene diisocyanate (TMXDI), p-xylylene diisocyanate, polymeric MDI and mixtures consisting of these compounds.

In a preferred embodiment of the present invention, monoisocyanates are used as the compound B carrying NCO groups.

Compounds B which have at least one epoxy group (epoxides) can likewise be used as compounds B in the context of the present invention. Suitable epoxides in the context of the present invention are, for example, epoxidized, unsaturated fatty acids or the reaction products of aromatic hydroxy compounds with epichlorohydrin, for example the diglyzidyl ether of bisphenol A or epoxidized long-chain olefins having at least about 8 carbon atoms.

Carboxylic acids, their anhydrides or chlorides can also be used as compounds B in the context of the present invention.

Suitable monocarboxylic acids are, for example, the linear or branched, saturated or unsaturated, homologous alkane carboxylic acids with 8 to about 44 carbon atoms, as are known in particular from fat chemistry. Typical examples of such acids are caprylic acid, 2-ethylhexanoic acid, capric acid, lauric acid, isotridecanoic acid, myristic acid, paknitic acid, palmoleic acid, stearic acid, isostearic acid, oleic acid, elaidic acid, pecoselic acid, linoleic acid, linolenic acid, elaeostearic acid, and technical acid, erachic acid, arachene acid, arachene acid Mixtures that occur, for example, in the pressure splitting of natural fats and oils, in the reduction of aldehydes from Roelen's oxosynthesis or in the dimerization of unsaturated fatty acids. Suitable polycarboxylic acids are, for example succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, glutaric acid, glutaric anhydride, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic anhydride, Tekahydrophthalsäureanhydrid, hexahydrophthalic anhydride, TekacMorphthalsäureanhydrid, hydrophthalic Endomethylentefra-, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimer fatty acids or trimer fatty acids or Mixtures of two or more of the polycarboxylic acids mentioned.

The anhydrides (if any) or acid chlorides of the carboxylic acids mentioned are also suitable.

The process according to the invention is preferably carried out at a pH of about 0 to about 12, in particular about 1 to about 7, for example about 2 to about 5.

In a preferred embodiment of the invention, at least one preferably anhydrous inorganic acid, for example HCl, H ₂ SO ₄ , phosphoric acid or partial phosphoric acid ester, is added to the reaction mixture.

The reaction is preferably carried out at a temperature of about 50 to about 300, in particular about 50 to about 250 ° C. Suitable reaction temperatures are in particular in a range from about 80 to about 220 or about 150 to about 190 ° C.

Depending on the temperature and any catalyst or catalyst system used, the reaction time is about 0.1 to about 10 hours. In a preferred embodiment of the present invention, the reaction conditions are chosen so that the reaction time is about 0.5 to about 3 hours.

The process according to the invention can optionally be carried out in an inert solvent or dispersant which does not boil at the reaction temperature. This is particularly recommended when a compound whose melting point is above the reaction temperature is used as compound B. The The boiling temperature of such a solvent or dispersant should be higher than the boiling temperature of the isocyanate formed. Aromatic or aliphatic oils with a boiling point of more than about 150 ° C. are suitable for this purpose. Corresponding oils are described, for example, in EP-B 0 870 769, the corresponding oils disclosing disclosure of which are understood as part of the disclosure of the present text.

Instead of a corresponding solvent or dispersant, the process according to the invention can also be carried out in such a way that the reaction is carried out in the melt of one of the compounds present in the course of the reaction, in particular in the melt of a compound B or a mixture of two or more compounds B. In a preferred embodiment of the present invention, a compound or a mixture of two or more compounds is therefore used as compound B, the melting point of which lies within the range specified for the reaction temperature.

To carry out the process according to the invention, for example the solvent or dispersant or the compounds B or a mixture of solvent or dispersant and compounds B is initially introduced, optionally kneaded and optionally mixed with a catalyst or a catalyst system composed of two or more different catalysts. If necessary, a corresponding amount of inorganic acid can be added to regulate the pH at this point. The mixture thus obtained is then brought to the reaction temperature and the carbamate to be reacted or a mixture of two or more carbamates is added. The isocyanate formed is preferably collected in a receiver via a corresponding distillation device, for example a Vigreux or sieve plate column. The invention is explained in more detail below by examples.

Examples:

The following examples illustrate the advantages of the method according to the invention. For this purpose, the method according to the invention was compared with procedures known from the prior art. Comparative examples 1 and 2 correspond to the procedures known from the prior art, example 1 represents the method according to the invention.

Apparatus:

All processes were carried out in a distillation apparatus with a 3-necked flask, sieve plate column (10 plates), cooler and receiver (Anschütz-Thiele).

Comparison 1:

Approx. 200 g vacuum pump oil (Alcatel) was weighed into an 11-3 neck flask and knocked at 0.3 mbar / 200 ° C for one hour. The oil was then heated to 295 ° C. at 60 +/- 3 mbar and 237 g of N-methyl- (trimethoxypropysilyl) carbamate (1 mol) were tapped in (about 80 tr. Min). Heavy foaming was observed. Duration of dropping: 3.5 hours

After adding about 10 ml of carbamate, the distillation of the isocyanate began. The top temperature was about 132 ° C, the distillation time about 4 hours. 197.55 g of clear distillate with an NCO content of 16.1% were obtained, which corresponds to a yield of 75.0 theoretical.

Comparison 2:

237 g of N-methyl (trknethoxypropysilyl) carbamate (1 mol) were weighed into a 0.51 3-necked flask and 0.5 g of cobalt naphthenate solution (6% Co) was added with stirring. The mixture was then heated to 180 ° C. under vacuum (40 mbar). The top temperature was 115-125 ° C., the distillation time 3 hours. 179.0 g of clear distillate with an NCO content of 16.6% were obtained, which corresponds to a yield of 71.0% of theory.

Example 1

592 g of melted stearyl isocyanate were weighed into an 11-3 neck flask and 0.25 g of sulfuric acid and 0.25 g of cobalt naphthenate solution (6% Co) were added in succession with stirring. This mixture was then heated to 180 ° C. under vacuum (40 mbar) and 237 g of N-methyl (trimethoxypropylsilyl) carbamate (1 mol) were added within 60 minutes. After adding about 25 ml of the carbamate, the distillation started, the top temperature was about 104 ° C., the distillation time about 2.5 hours. 173.75 g of clear distillate with an NCO content of 20.0% were obtained, which corresponds to a yield of 82.8% of theory.

As the comparison of the processes in Table 1 shows, a purer product is obtained more quickly in a better yield according to the process of the invention.

Comparison of the methods (Table 1):

Table 1

Claims

Patentansprttche 1. A process for the preparation of isocyanates, in which at least one compound having at least one carbamate group is converted into an isocyanate or a mixture of two or more isocyanates and at least one compound A which has functional groups which are reactive toward isocyanate groups, the reaction being carried out at a reaction temperature above the boiling point of the resulting isocyanate or the mixture of two or more isocyanates is carried out in the presence of at least one compound B which has a higher boiling point than the isocyanate formed and the compound A formed in the reaction or a mixture of two or more such compounds A, im With regard to the reactivity of the compound A or the mixture of two or more compounds A towards isocyanate groups deactivated. 2. The method according spoke 1, characterized in that it is carried out in the presence of a catalyst. 3. The method according spoke 1 or 2, characterized in that at least one compound B is used to deactivate the resulting compounds A in the reaction with functional groups reactive towards isocyanate groups, which has at least one functional group Y, which has a covalent bond at the reaction temperature with the functional groups HX of compound A which are reactive toward isocyanate groups. 4. The method according to any one of claims 1 to 3, characterized in that at least one compound selected from the group consisting of isocyanates, epoxides, carboxylic acids or carboxylic acid anhydrides, carboxylic acid chlorides is used as compound B. 5. The method according to any one of claims 1 to 4, characterized in that the reaction temperature is at least 120 ° C. 6. The method according to any one of claims 1 to 5, characterized in that the reaction temperature is 250 ° C or less. 7. The method according to any one of claims 1 to 6, characterized in that the at least one compound B is used in such an amount that at least 1.1 times the amount of at most compounds A formed during the reaction can be deactivated. 8. The method according to any one of claims 1 to 7, characterized in that at least one compound B with at least one functional group Y is used for deactivating compounds A formed during the reaction, the molar ratio of functional groups Y to the maximum amount of at Implementation of the resulting functional groups HX at least 1.1 to 1. 9. The method according to any one of claims 1 to 8, characterized in that at least one silyl carbamate is used as a compound having at least one carbamate group. 10. The method according to any one of claims 1 to 9, characterized in that at least one inorganic acid is added to the reaction mixture.