JP2003201275A - Method of producing aromatic urethane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing useful aromatic urethanes with high reaction efficiency. <P>SOLUTION: When the reaction between an aromatic amine and an organic carbonic ester is carried out in the presence of a Lewis acid catalyst at 100-230°C, a solvent bearing hydroxy groups in the molecule is used to maintain the concentration of the alcohol formed as a by-product within 0-5 wt.% in the reaction mixture. In an embodiment, 2,4-diaminotoluene, dimethyl carbonate, zinc acetate and toluene are exemplified as an aromatic amine, an organic carbonic ester, a Lewis acid and a solvent respectively. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an aromatic urethane used as an intermediate raw material for an aromatic isocyanate. More specifically, it relates to a method for producing an aromatic urethane in which an organic carbonate and an aromatic amine are reacted in the presence of a solvent having no hydroxyl group in the molecule.

[0002]

2. Description of the Related Art Conventionally, isocyanates have been produced by the reaction of primary amines with phosgene, but this method has drawbacks such as the use of highly toxic phosgene and the byproduct of corrosive hydrogen chloride. Therefore, there is a strong demand for establishment of an industrial process for producing isocyanates that does not use phosgene.

It is known that an aromatic urethane compound is decomposed into an aromatic isocyanate and an alcohol by a thermal decomposition reaction and is a very important substance as a raw material of the aromatic isocyanate. Particularly, industrially important aromatic isocyanates include methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI).
Examples of raw materials for producing these aromatic isocyanates include 4,4′-methylenediphenyldiurethane and 2,4-toluenediurethane.

As a method for producing an aromatic urethane compound,
In the presence of a suitable catalyst, according to the scheme below,
A method of urethanizing an aromatic amine with an organic carbonate is known. R-NH ₂ + (R'O) ₂ CO →
R-NHCOOR '+ R'OH For example, Japanese Patent Publication No. 51-
No. 33095 discloses a method for producing a urethane compound by reacting an organic carbonate with an amine in the presence of a Lewis acid catalyst. However, under these conditions, the yield of the desired urethane compound is about 20%, and the main products are urea compounds and N-alkylated products.

Japanese Unexamined Patent Publication (Kokai) No. 56-188558 discloses a method for producing a mono- or diurethane compound using a zinc or tin compound as a catalyst in the reaction between an organic carbonate and an aromatic mono- or diamine. The yield of the urethane compound by this production method reaches about 92% for the monourethane compound, but is 58% for the diurethane compound important as a raw material of diisocyanate.
%.

Japanese Patent Laid-Open No. 02-290840 discloses that
(A) a first reaction step of producing a mixture containing a urethane compound and a urea compound by reacting an organic carbonate with a monoamine in the presence of zinc acetate while removing alcohol generated during the reaction, and ( b) A method for synthesizing a urethane compound comprising a second reaction step in which the mixture obtained in the first reaction step is mixed again with a carbonic acid ester and further reacted at 160 ° C. for 3 to 6 hours to convert a urea compound into a urethane compound. Is disclosed. By this method, aromatic monourethane can be produced in good yield. However, when a corresponding urethane compound is produced from a diamine or an aromatic polyamine, a large amount of a polyurea compound or the like is formed, and therefore these substances cannot be selectively converted into the corresponding urethane compound.

In JP-A-11-1462, in the reaction of an aromatic amine and an organic carbonate using a Lewis acid catalyst, the alcohol present in the reaction system is compared with the total amount of alcohol produced during the reaction. 10-40 mol%
A method for producing a urethane compound maintained within the range is disclosed.

[0008] Actually, when alcohol is accumulated in the reaction system, the urethane formation reaction rate is reduced, and the yield of the urethane compound is reduced due to side reactions competing with the urethane formation reaction. In the methods described in JP-A-02-290840 and JP-A-11-1462, in the reaction of amine and organic carbonate, the reaction rate of urethane formation is decreased by extracting the by-product alcohol out of the system. Is to suppress.

In the above-mentioned known method, the reaction is carried out in the form of reactive distillation in order to extract the by-product alcohol out of the system. On the other hand, organic carbonates and alcohols are often known to form azeotropes. For example, the azeotropic composition of dimethyl carbonate and methanol at atmospheric pressure is dimethyl carbonate: methanol = 3: 7 (weight ratio). Therefore, in the method of removing alcohol by reactive distillation in this reaction system, the organic carbonate and alcohol are removed by azeotropic composition, which complicates the reactor and separates the azeotrope in reactive distillation and subsequent steps. There is a problem that the energy required for doing so increases.

[0010]

The object of the present invention is to carry out aromatic urethanes with high selectivity and yield by a simple and economical process which can be carried out on an industrial scale and which does not have the drawbacks of the prior art production processes. It is to get at a rate.

[0011]

DISCLOSURE OF THE INVENTION The present inventors have proposed a high yield and high selectivity from an organic carbonate and an amine compound without complicating the reaction apparatus and increasing the amount of energy required. As a result of intensive studies to develop a method for synthesizing a urethane compound, it was found that the purpose can be easily achieved by adding a solvent containing no hydroxyl group in the molecule to the reaction system, and the present invention It came to completion.

That is, the present invention provides an organic carbonate of the formula
(I)-(III) [Chemical 2]

[0013]

[Chemical 2] (In the formula, R is a hydrogen atom, a halogen atom, or a carbon number 1
To 8 alkyl groups, A represents a divalent hydrocarbon group having 1 to 6 carbon atoms, n represents an integer of 0 or 1, and x represents 1
Represents an integer of 6; ), A method for synthesizing an aromatic urethane by reacting with any of the aromatic amines represented by the formula (1) in the presence of an acid catalyst at a temperature of 100 to 230 ° C., characterized by using a solvent containing no hydroxyl group in the molecule. Is a method for synthesizing an aromatic urethane.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of aromatic amines represented by the formulas (I)-(III) include 4,4'-methylenedianiline,
2,4'-methylenedianiline, 2,4-diaminotoluene (TDA) / 2,6-diaminotoluene or a mixture of two isomers, 1,3-diaminobenzene, 2,
There is, but is not limited to, 6-diaminonaphthalene or polymeric methylenedianiline (a mixture of isomers having formula (III), where x = 1, 2, 3 and 4).

Organic carbonates which can be used in the process of the present invention include alkyl, aryl or alkylaryl esters of carbonic acid. The ester group may be an alkyl group containing up to 12 carbon atoms, preferably up to 6 carbon atoms, or an aryl group up to 10 carbon atoms.

Examples of organic carbonates which are particularly suitable for the process according to the invention are cyclic or acyclic carbonates such as ethylene carbonate, propylene carbonate, styrene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate.
These are diisopropyl carbonate, dihexyl carbonate, methylbutyl carbonate, diphenyl carbonate, and methylphenyl carbonate. The organic carbonic acid ester can be produced using a known method.

In the production method of the present invention, it is preferable to use an organic carbonate ester in an equimolar amount or more with respect to the amino group of the aromatic amine.

The solvent suitable for the production method of the present invention must be free of hydroxyl groups. As a specific example,
Aromatic hydrocarbons such as benzene, toluene, xylene,
aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane and cyclohexane, diisopropyl ether,
Ethers such as tetrahydrofuran, ethylene glycol dimethyl ether, dioxane and the like, nitriles such as acetonitrile, propionitrile, benzonitrile and the like can be preferably mentioned, but dimethylformamide, dimethyl sulfoxide, sulfolane and the like can also be used. Further, the organic carbonate used in the reaction may be used in excess as a solvent.

Suitable catalysts for the purposes of the present invention are generally divalent salts of Lewis acids, such as divalent tin and zinc chlorides, or salts of these metals with organic mono- or dicarboxylic acids. Although zinc compounds and the like can be used, it is preferable to use anhydrous zinc acetate or dihydrate.

The amount of the catalyst is 30 to 0.1 mol%, preferably 20 to 0.5 per mol of the aromatic amine (I)-(III).
Mol% is sufficient.

The reaction temperature is in the range of 100 to 230 ° C. More preferably, it is in the range of about 140 to 200 ° C.

The reaction pressure of the present invention is uniquely determined by the solvent species used, the amount of solvent, the starting materials for the reaction, the composition and the reaction temperature.

Although the reaction time varies depending on the operating conditions,
The range is 6 hours.

No special device is required for the reaction between the organic carbonate and the aromatic amine in the method of the present invention, and a conventional stirring tank may be used as the reaction device. Also, the material of the stirring tank may be a general one such as stainless steel.

The process according to the invention can be carried out batchwise, continuously or semicontinuously. During the reaction, it is preferable to add a solvent so that the alcohol concentration in the reaction solution is maintained at 0 to 5 wt%. The solvent may be added to the reaction raw materials all at once, or may be continuously or intermittently supplied during the reaction.

The produced urethane compound can be recovered and further purified by various methods by combining distillation, solvent extraction, washing, crystallization and the like from the reaction product solution. A concrete example is as follows. The urethane compound can be recovered by separating the organic carbonate, the by-product alcohol and the solvent from the reaction product solution under normal pressure or reduced pressure by ordinary evaporation or simple distillation.

[0027]

EXAMPLES Examples of the present invention will be described below.
The present invention is not limited to the embodiments.

Comparative Example 1 (when no solvent is used) In a 100 ml autoclave, 16.7 mmol of 2,4-toluenediamine (hereinafter referred to as 2,4-TDA), 167 mmol of dimethyl carbonate, 1.7 m of zinc acetate dihydrate.
Mol was charged and reacted at 180 ° C. for 4 hours.
After the reaction, the reaction liquid was analyzed by gas chromatography, and as a result, the concentration of by-product methanol in the reaction liquid was 12.6 wt.
%Met. As a result of analyzing the reaction solution by high performance liquid chromatography, 9.9 mmol of 2,4-toluenedimethylurethane was produced, which was 2,4-TDA.
The yield is 59.3% based on.

Comparative Example 2 (when a solvent containing a hydroxyl group was used) The reaction was carried out in the same manner as in Comparative Example 1 except that 22.7 g of methanol was added as a solvent. At the end of the reaction, the concentration of methanol in the reaction solution was 43.2 wt%. The reaction liquid contains 2,4-toluenedimethylurethane 0.6 mm
was produced (2,4-TDA standard yield 3.84).
%).

Example 1 The reaction was carried out in the same manner as in Comparative Example 1 except that 22.6 g of toluene was added as a solvent. The by-product methanol concentration in the reaction solution was 2.5 wt%. 2,4 in the reaction solution
-Toluenedimethylurethane 15.1 mmol was produced (2,4-TDA standard yield 90.4%).

Example 2 The reaction was carried out in the same manner as in Comparative Example 1 except that 22.7 g of cyclohexane was added as a solvent. The by-product methanol concentration in the reaction solution was 2.3 wt%. In the reaction solution, 14.7 mmol of 2,4-toluenedimethylurethane was formed (2,4-TDA standard yield: 88.0%).

Example 3 Dimethyl carbonate is used as a solvent. 2,4-TDA 16.7 mmol, dimethyl carbonate 418 mmol, zinc acetate dihydrate 1.7 mmol in a 100 ml autoclave.
Was charged and reacted at 180 ° C. for 4 hours. After the reaction, the reaction liquid was analyzed by gas chromatography. As a result, the concentration of by-product methanol in the reaction liquid was 2.4 wt%. As a result of analyzing the reaction solution by high performance liquid chromatography, 2,4-toluenedimethylurethane 16.4
mmol is produced, which gives a yield of 98.2% based on 2,4-TDA.

Comparative Example 3 The reaction was carried out in the same manner as in Comparative Example 1 except that the catalyst was changed to lead acetate trihydrate. At the end of the reaction, the concentration of methanol in the reaction solution was 14.3 wt%. In the reaction solution,
8.0 mmol of 2,4-toluenedimethylurethane was produced (2,4-TDA standard yield 47.9%).

Example 4 2,4-TDA 16.7 m in a 100 ml autoclave
mol, 167 mmol of dimethyl carbonate and 1.7 mmol of lead acetate trihydrate were charged and reacted at 180 ° C. for 4 hours. After the reaction, the reaction liquid was analyzed by gas chromatography, and as a result, the concentration of by-product methanol in the reaction liquid was 3.
It was 6 wt%. As a result of analyzing the reaction solution by high performance liquid chromatography, 15.5 mmol of 2,4-toluenedimethylurethane was produced, which was 2,4-
The yield is 92.8% based on TDA.

Comparative Example 4 2,4-TDA 16.2 m in a 100 ml autoclave.
Mol, diethyl carbonate 130 mmol, and zinc acetate dihydrate 1.6 mmol were charged and reacted at 180 ° C. for 4 hours. After the reaction, the reaction liquid was analyzed by gas chromatography. As a result, the by-product ethanol concentration in the reaction liquid was 7.1 wt%. As a result of analyzing the reaction solution by high performance liquid chromatography, 9.0 mmol of 2,4-diethylurethane was produced, which was 2,4-TDA.
Based on the above, the yield is 55.5%.

Example 5 The reaction was carried out in the same manner as in Comparative Example 2 except that 22.8 g of toluene was added as an inert solvent. The by-product ethanol concentration in the reaction solution was 3.4 wt%. In the reaction solution, 14.9 mmol of 2,4-toluenediethylurethane was formed (2,4-TDA standard yield 91.4%).

Comparative Example 5 2,4-TDA 14.6m in a 100ml autoclave.
mol, di (n-butyl) carbonate 88 mmol, and zinc acetate dihydrate 1.5 mmol were charged, and at 180 ° C., 4
Reacted for hours. After the reaction, the reaction liquid was analyzed by gas chromatography. As a result, the by-product 1-butanol concentration in the reaction liquid was 6.5 wt%. As a result of analyzing the reaction solution by high performance liquid chromatography, 7.5 mmol of 2,4-toluenedi (n-butyl) urethane was produced, which was a yield of 51.4% based on 2,4-TDA. Become.

Example 6 The reaction was carried out in the same manner as in Comparative Example 3 except that 22.9 g of toluene was added as an inert solvent. The by-product 1-butanol concentration in the reaction solution was 4.8 wt%. The reaction solution contained 2,4-toluene di (n-butyl) urethane 12.
9 mmol had been produced (2,4-TDA standard yield 8
8.4%).

Comparative Example 6 4,4'-methylenedianiline (hereinafter referred to as 4,4'-MDA) 14.3 mmo in a 100 ml autoclave.
1, dimethyl carbonate 145 mmol, and zinc acetate dihydrate 1.5 mmol were charged and reacted at 180 ° C. for 4 hours. After the reaction, the reaction liquid was analyzed by gas chromatography and as a result, the concentration of by-product methanol in the reaction liquid was 1
It was 3.5 wt%. As a result of analyzing the reaction solution by high performance liquid chromatography, 9.4 mmol of 4,4′-methylenediphenyldi (methyl) urethane was produced, which was 65.7% of the yield based on 4,4′-MDA. Become a rate.

Example 7 The reaction was carried out in the same manner as in Comparative Example 4 except that 24 g of toluene was added as an inert solvent. The by-product methanol concentration in the reaction solution was 2.8 wt%. 4, in the reaction solution
4'-methylenediphenyldi (methyl) urethane 13.
4 mmol was produced (4,4'-MDA standard yield 93.7%).

[0041]

According to the present invention, it is possible to provide a method for efficiently producing an aromatic urethane compound at a high reaction yield without using any special reaction apparatus.

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Claims (13)

[Claims] 1. An organic carbonate ester of the formula (I)-(III) [Chemical Formula 1] (In the formula, R is a hydrogen atom, a halogen atom, or a carbon number 1
To 8 alkyl groups, A represents a divalent hydrocarbon group having 1 to 6 carbon atoms, n represents an integer of 0 or 1, and x represents 1
Represents an integer of 4; ), In the method for synthesizing an aromatic urethane in which any of the aromatic amines represented by (4) is reacted at a temperature of 100 to 230 ° C. in the presence of an acid catalyst, a solvent containing no hydroxyl group in the molecule is used. Method for synthesizing aromatic urethane. 2. The method according to claim 1, wherein A is a divalent hydrocarbon group having 1 to 4 carbon atoms. 3. R is an alkyl group having 1 to 4 carbon atoms,
The method of claim 1. 4. The method according to claim 1, wherein the concentration of alcohol by-produced in the reaction solution is maintained within the range of 0 to 5 wt% in the reaction solution. 5. The organic carbonate is selected from ethylene carbonate, propylene carbonate, styrene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, diisopropyl carbonate, dihexyl carbonate, methylbutyl carbonate, diphenyl carbonate and methylphenyl carbonate. The method according to claim 1. 6. The method according to claim 5, wherein the organic carbonate is dimethyl carbonate, diethyl carbonate, dibutyl carbonate, diisopropyl carbonate, diphenyl carbonate. 7. The aromatic amine is 4,4′-methylenedianiline, 2,4′-methylenedianiline, 2,4-diaminotoluene / 2,6-diaminotoluene or a mixture of two isomers, 1,3-diaminobenzene, 2,
The method of claim 1 selected from 6-diaminonaphthalene or polymeric methylenedianiline. 8. The method of claim 1, wherein the acid catalyst is selected from Lewis acids or salts of metals of Lewis acids with organic mono- or dicarboxylic acids. 9. The method of claim 8, wherein the Lewis acid is a divalent tin and zinc chloride. 10. The acid catalyst is zinc acetate anhydride or dihydrate, lead acetate anhydride or trihydrate.
The method described in. 11. The amount of catalyst is aromatic amine (I)-(III)
The method according to claim 1, which is 30 to 0.1 mol% per mol. 12. The amount of catalyst is aromatic amine (I)-(III)
The method according to claim 1, which is 20 to 0.5 mol% per mol. 13. The method according to claim 1, wherein the reaction between the organic carbonate and the aromatic amine is carried out at a temperature of 140 to 200 ° C.