JP2010215589A - Method of producing carbamate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the load of a work of neutralizing catalytic metal contained in a crude reaction liquid and to reduce the amount of metallic waste discharged in the neutralization work, in producing a carbamate by the reaction of a carbonate and an amine. <P>SOLUTION: There is provided a method of producing a carbamate by the reaction of a carbonate and an amine, wherein a reaction product comprising a metal resulting upon synthesizing a carbamate from a carbonate and an amine in the presence of a basic catalyst comprising the metal is used as a catalyst for the reaction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a carbamic acid ester.

  Carbamate esters (urethanes) are industrially very useful compounds widely used for polyurethane foams, surface coatings, elastomers, paints, adhesives and the like. Carbamates are also useful as raw materials for producing isocyanates without using phosgene.

  The main industrial production method of isocyanate is a reaction between an amine and phosgene (phosgene method), and almost all of the world production is produced by the phosgene method. However, the phosgene method has many problems.

  The first is to use a large amount of phosgene as a raw material. Phosgene is extremely toxic and requires special handling in order to prevent exposure to personnel and special equipment to exclude waste.

  Secondly, in the phosgene method, a large amount of highly corrosive hydrogen chloride is by-produced, so that a process for removing the hydrogen chloride is required, and the produced isocyanate is often hydrolyzable. Chlorine will be contained, and when an isocyanate produced by the phosgene method is used, the weather resistance and heat resistance of the polyurethane product may be adversely affected.

  From such a background, a method for producing an isocyanate without using phosgene is desired. As one of the production methods of isocyanate without using phosgene, a method by thermal decomposition of carbamic acid ester has been proposed. It has long been known that an isocyanate and a hydroxy compound can be obtained by thermal decomposition of a carbamic acid ester (see, for example, Non-Patent Document 1). The basic reaction is exemplified by the following general formula.

(Where:
R represents an x-valent organic residue,
R ′ represents a monovalent organic residue,
x represents an integer of 1 or more. )

  Thus, carbamic acid esters are industrially useful compounds. Various methods have been proposed so far for producing carbamic acid esters.

According to the description of Patent Document 1, an aliphatic diurethane and / or an alicyclic diurethane and / or an aliphatic polyurethane and / or an alicyclic polyurethane is an aliphatic primary diamine and / or an alicyclic primary diamine. And / or an aliphatic primary polyamine and / or an alicyclic primary polyamine in the presence of an O-alkyl carbamate and an alcohol in an amine NH ₂ group: carbamate: alcohol ratio of 1: 0.8. To 10: 0.25 to 50, and the reaction is carried out at 160 ° C. to 300 ° C. in the presence or absence of a catalyst, and ammonia generated as necessary is removed.

  According to the description in Patent Document 2, aryl diurethanes and / or aryl polyurethanes are aromatic primary amines and / or aromatic primary polyamines in the presence or absence of O-alkyl carbamates and catalysts. And the reaction in the presence or absence of urea and alcohol to produce an aryl diurethane and / or aryl polyurethane, and removing the resulting ammonia as needed.

  Other publications include partial ureas and / or diamines with carbonyl-containing compounds such as N-substituted carbamates and / or dialkyl carbonates or mono-substituted ureas or di-substituted ureas or mono-substituted polyureas or di-substituted polyureas. There is a description regarding substitution (see Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 6, and Patent Document 7). Patent Document 8 describes a method for producing an aliphatic O-aryl urethane by reacting a (cyclic) aliphatic polyamine with urea and an aromatic hydroxy compound.

  Patent Document 9 discloses a method for producing a carbamic acid ester from an amine and dimethyl carbonate. In this method, an amine and dimethyl carbonate are reacted in the presence of a Lewis acid catalyst, lead, titanium or zirconium catalyst, an alkali catalyst, or the like.

  As described above, various methods for producing carbamic acid esters have been proposed. As a method of using a basic catalyst, Patent Document 10 discloses that an amine and a carbonate ester contain an alkali metal alcoholate or an alkaline earth metal alcoholate. A method for producing a crude reaction liquid containing a carbamate by reacting under the following conditions is disclosed.

U.S. Pat. No. 4,497,963 U.S. Pat. No. 4,290,970 U.S. Pat. No. 4,388,238 US Patent No. 4,430,505 U.S. Pat. No. 4,480,110 U.S. Pat. No. 4,596,678 U.S. Pat. No. 4,596,679 European Patent Application Publication No. 0320235 U.S. Pat. No. 4,395,565 JP-A-6-72982

Berchte der Deutschen Chemischen Gesellshaft, 3, 653, 1870

  When the carbamic acid ester produced by the method disclosed in Patent Document 10 is subsequently used in the production of isocyanate, a side reaction is often caused by the catalyst contained in the crude reaction solution, and is contained in the crude reaction solution. It was necessary to go through a process for deactivating the catalyst, such as neutralizing the catalyst with an ion exchange resin or the like. When neutralizing the catalyst contained in the crude reaction solution with an ion exchange resin, it is necessary to discard the ion exchange resin that has been broken through the neutralization work or to regenerate it by acid washing or the like. . Furthermore, since the metal used as the catalyst is discarded after neutralization, there is a problem that a large amount of metal waste is discharged.

  The present invention reduces the load of neutralization work of the catalytic metal contained in the crude reaction liquid in the production of carbamic acid ester by the reaction of carbonate ester and amine, and discards the metal discharged along with the neutralization work. The purpose is to reduce the amount of objects.

  The present invention relates to a method for producing a carbamate by reacting a carbonate with an amine, and the synthesis of the carbamate from the carbonate and the amine in the presence of a metal-containing basic catalyst as a catalyst for the reaction. Provided is a method for producing a carbamic acid ester using a reaction product containing the metal, which is generated in the process.

  When a carbamic acid ester is synthesized from a carbonate ester and an amine in the presence of a basic catalyst containing a metal, a reaction product containing the metal is obtained in addition to the target carbamic acid ester. In the production of carbamic acid ester by the reaction of carbonic acid ester and amine, it was surprisingly newly found that when the reaction product containing the metal is added to the reaction system, it functions as a catalyst. Since the metal contained in the reaction product containing the metal is derived from the basic catalyst, the metal is reused as a catalyst. Therefore, in the production of the carbamic acid ester, the amount of the basic catalyst to be newly added can be reduced, and the total amount of metals used in the production can be reduced.

  In this invention, it is preferable to isolate | separate the reaction product containing the said metal by filtration.

  Since the reaction product containing the metal is often dispersed as a powder in the reaction mixture, it can be separated by filtration. By separating in this way, the amount of the metal derived from the basic catalyst contained in the reaction solution containing the carbamate can be reduced. That is, the amount of catalytic metal brought into the subsequent neutralization operation is reduced, the load of the neutralization operation can be reduced, and the amount of metal waste discharged with the neutralization operation can be reduced.

In the present invention, the carbonate ester is preferably represented by the following general formula (1).

(In the formula, R ¹ represents an aliphatic group having 1 to 10 carbon atoms.)

In the present invention, it is preferable that the amine is represented by the following general formula (2).

(Wherein R ² is an aliphatic group having 1 to 20 carbon atoms or an aromatic group having 6 to 20 carbon atoms having a valence equal to n. Each group may further contain an oxygen atom, and , N is an integer from 2 to 10.)
And it is more preferable that it is diamine whose n is 2 in the said General formula (2).

  In the present invention, the metal contained in the basic catalyst is preferably an alkali metal or an alkaline earth metal. The basic catalyst is preferably an alkali metal or alkaline earth metal alcoholate.

  By carrying out the method of the present invention, it is possible to reduce the work load for neutralizing the catalyst metal contained in the crude reaction liquid in the production of the carbamate ester by the reaction of the carbonate ester and the amine. In addition, the amount of metal discarded can be reduced.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

Although there is no restriction | limiting in particular about the carbonate ester used in this invention, The carbonate ester represented by the said General formula (1) is used preferably. As R < ¹ > in the said General formula (1), the C1-C10 alkyl group which comprises this group is preferable, for example, a methyl group, an ethyl group, a propyl group (each isomer), a butyl group (each Isomer), pentyl group (each isomer), hexyl group (each isomer), heptyl group (each isomer), octyl group (each isomer), nonyl group (each isomer), decyl group (each isomer) Among them, a carbonate ester in which R ¹ is an alkyl group having 2 to 6 carbon atoms, that is, diethyl carbonate, dipropyl carbonate (each isomer), dibutyl carbonate (each isomer), dipentyl carbonate ( Each isomer) and dihexyl carbonate (each isomer) are preferably used.

  As a method for producing the carbonate ester, a known method can be used. Preferably, a carbonate ester is produced by reacting an organic tin compound having a tin-oxygen-carbon bond with carbon dioxide.

  Although there is no restriction | limiting in particular about the amine used in this Embodiment, The amine represented by the said General formula (2) is used preferably. In the above general formula (2), n is preferably a polyamine having 2 or more, and more preferably a diamine in which n is 2.

  Examples of such polyamines include hexamethylenediamine, 4,4′-methylenebis (cyclohexylamine) (each isomer), cyclohexanediamine (each isomer), 3-aminomethyl-3,5,5-trimethylcyclohexyl. Examples include aliphatic diamines such as amines (each isomer); aromatic diamines such as phenylenediamine (each isomer), toluenediamine (each isomer), and 4,4′-methylenedianiline. Among them, hexamethylenediamine, 4,4′-methylenebis (cyclohexylamine) (each isomer), cyclohexanediamine (each isomer), 3-aminomethyl-3,5,5-trimethylcyclohexylamine (each isomer), etc. Aliphatic diamines are preferably used, among which hexamethylenediamine, 4,4′-methylenebis (cyclohexylamine), and 3-aminomethyl-3,5,5-trimethylcyclohexylamine are more preferably used.

  The amount of water contained in the carbonate ester and the amine is preferably 0.001 ppm to 50 ppm. The present inventors surprisingly found that when the amount of water contained in the carbonate ester and amine exceeds 50 ppm, the production amount of the reaction product containing the metal may decrease, It has been found that the separation efficiency becomes difficult and the efficiency of reuse as a catalyst in the reaction between a carbonate ester and an amine may decrease. Although the clear correlation between the amount of the reaction product containing the metal and the amount of water is unknown, the present inventors have produced the reaction containing the metal by water contained in the carbonate and amine. I guess it is because the product is hydrolyzed. From such a viewpoint, the amount of water contained in the carbonate and amine is preferably 30 ppm or less, more preferably 10 ppm or less.

  On the other hand, the present inventors have surprisingly found that a small amount of water contained in a carbonate ester and an amine has an effect of improving the catalytic activity. Although it is not clear about the mechanism that exerts such an effect, the present inventors have found that a small amount of water present in the reaction system acts on the carbonate ester together with the catalyst to activate the carbonyl carbon of the carbonate ester. I guess it is because of this. From such a viewpoint, the amount of water contained in the carbonate ester and the amine is preferably 0.001 ppm or more, and more preferably 0.003 ppm or more.

The amount of water contained in the carbonate ester and amine can be quantified by a known method, and for example, methods such as Karl Fischer, ¹ H-NMR, and infrared absorption method can be used.

As one embodiment for carrying out the present invention, the following steps (1) to (3) can be included in a method for producing a carbamic acid ester by reacting a carbonate ester with an amine.
Step (1): A step of reacting a carbonate ester and an amine in the presence of a basic catalyst containing a metal to obtain a mixture containing the carbamate ester and the reaction product containing the metal,
Step (2): a step of separating the reaction product containing the metal from the mixture of step (1),
Step (3): A step of recycling the reaction product containing the metal separated in Step (2) as part or all of the basic catalyst in Step (1).

  In the present invention, the step (2) and the step (3) can be repeated after performing the step (1) using the reaction product containing the metal as a catalyst.

As the basic catalyst used in the reaction between the carbonate ester and the amine in the step (1), an alkali metal or alkaline earth metal alcoholate is preferably used. Examples of the alkali metal and alkaline earth metal in the basic catalyst include lithium, sodium, potassium, calcium, and barium. On the other hand, as the alkoxy group of the basic catalyst, an alkoxy group in which an oxygen atom is added to an alkyl group having 1 to 10 carbon atoms is preferably used, and a methoxy group, an ethoxy group, a butoxy group (each isomer), a pentyloxy group. (Each isomer), hexyloxy group (each isomer), heptyloxy group (each isomer), octyloxy group (each isomer), nonyloxy group (each isomer), decyloxy group (each isomer) be able to. Among these, the alkoxy group is preferably an alkoxy group having the same R ¹ group as the carbonic acid ester represented by the general formula (1) and represented by R ¹ O (O represents an oxygen atom).

The reaction conditions for the reaction between the carbonate ester and the amine vary depending on the types of the carbonate ester and the amine, but the stoichiometric ratio of the carbonate ester to the amino group of the amine ranges from 0.1 to 1000 times. It can be. In order to increase the reaction rate and complete the reaction at an early stage, the carbonate ester is preferably in an excess amount with respect to the amino group of the amine, but preferably 1 to 100 in view of the size of the reactor. The range is twice, more preferably 2 to 30 times. The reaction temperature is usually in the range of 0 ° C. to 300 ° C., and a high temperature is preferable to increase the reaction rate. On the other hand, an undesired reaction may occur at a high temperature, and preferably 20 ° C. to 150 ° C. Range. In order to keep the reaction temperature constant, a known cooling device or heating device may be installed in the reactor. Moreover, although reaction pressure changes with the kind of compound to be used, and reaction temperature, any of pressure reduction, a normal pressure, and pressurization may be sufficient, and it is performed in the range of 20-1x10 < ⁶ > Pa normally.

  There is no restriction | limiting in particular in reaction time (in the case of a continuous method), Usually, 0.001 to 50 hours, Preferably it is 0.01 to 10 hours, More preferably, it is 0.1 to 5 hours. Alternatively, the reaction solution can be collected, and the reaction can be terminated after confirming that a desired amount of carbamic acid ester has been formed, for example, by liquid chromatography.

  In the present embodiment, it is not always necessary to use a reaction solvent, but an appropriate inert solvent such as hexane (each isomer), heptane (each isomer), for example, for the purpose of facilitating the reaction operation, Alkanes such as octane (each isomer), nonane (each isomer), decane (each isomer), etc .; benzene, toluene, xylene (each isomer), ethylbenzene, diisopropylbenzene (each isomer), dibutylbenzene (each Isomers), aromatic hydrocarbons such as naphthalene and alkyl-substituted aromatic hydrocarbons; chlorobenzene, dichlorobenzene (each isomer), bromobenzene, dibromobenzene (each isomer), chloronaphthalene, bromonaphthalene, nitrobenzene, nitro Aromatic compounds substituted by halogen or nitro groups such as naphthalene; diphenyl, substituted Polycyclic hydrocarbon compounds such as phenyl, diphenylmethane, terphenyl, anthracene, and dibenzyltoluene (each isomer); Aliphatic hydrocarbons such as cyclohexane, cyclopentane, cyclooctane, and ethylcyclohexane; Ketones such as methyl ethyl ketone and acetophenone Use of esters such as dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, and benzyl butyl phthalate; ethers such as diphenyl ether and diphenyl sulfide and thioethers; and sulfoxides such as dimethyl sulfoxide and diphenyl sulfoxide as reaction solvents Can do. These solvents can be used alone or as a mixture of two or more. In addition, an excess carbonate ester when used in an excess amount relative to the amino group of the amine is also suitably used as a solvent in the reaction.

  As the reactor, a known tank reactor, a column reactor, a distillation column, and a combination of these reactors can be used. The material of the reactor and the line may be any known material as long as it does not adversely affect the starting materials and reactants, but SUS304, SUS316, SUS316L, etc. are inexpensive and can be preferably used.

The carbamic acid ester obtained by the method shown above is a compound represented by the following general formula (3).

(In the formula, each of R ¹ and R ² is a group defined above, and n is an integer of 2 to 10).

  Examples of such carbamic acid esters include N, N′-hexanediyl-dicarbamic acid-dimethyl ester, N, N′-hexanediyl-dicarbamic acid-diethyl ester, N, N′-hexanediyl-dicarbamic acid— Dibutyl ester (each isomer), N, N′-hexanediyl-dicarbamic acid-dipentyl ester (each isomer), N, N′-hexanediyl-dicarbamic acid-dihexyl ester (each isomer), N, N ′ -Hexanediyl-dicarbamic acid-dioctyl ester (each isomer), dimethyl-4,4'-methylene-dicyclohexyl carbamate, diethyl-4,4'-methylene-dicyclohexyl carbamate, dipropyl-4,4'-methylene-dicyclohexyl carbamate (Each isomer), dibutyl- , 4'-methylene-dicyclohexyl carbamate (each isomer), dipentyl-4,4'-methylene-dicyclohexyl carbamate (each isomer), dihexyl-4,4'-methylene-dicyclohexyl carbamate (each isomer), diheptyl- 4,4′-methylene-dicyclohexyl carbamate (each isomer), dioctyl-4,4′-methylene-dicyclohexyl carbamate (each isomer), 3- (methoxycarbonylamino-methyl) -3,5,5-trimethylcyclohexyl Carbamic acid methyl ester, 3- (ethoxycarbonylamino-methyl) -3,5,5-trimethylcyclohexylcarbamic acid ethyl ester, 3- (propyloxycarbonylamino-methyl) -3,5,5-trimethylcyclohexylcarbamic acid Lopyl ester (each isomer), 3- (butyloxycarbonylamino-methyl) -3,5,5-trimethylcyclohexylcarbamic acid butyl ester (each isomer), 3- (pentyloxycarbonylamino-methyl) -3,5 , 5-Trimethylcyclohexylcarbamic acid pentyl ester (each isomer), 3- (hexyloxycarbonylamino-methyl) -3,5,5-trimethylcyclohexylcarbamic acid hexyl ester (each isomer), 3- (heptyloxycarbonyl) Amino-methyl) -3,5,5-trimethylcyclohexylcarbamic acid heptyl ester (each isomer), 3- (octyloxycarbonylamino-methyl) -3,5,5-trimethylcyclohexylcarbamic acid octyl ester (each isomer) ), Toluene di Carbamic acid-dimethyl ester (each isomer), toluene-dicarbamic acid-diethyl ester (each isomer), toluene-dicarbamic acid-dipropyl ester (each isomer), toluene-dicarbamic acid-dibutyl ester (each isomer) , Toluene-dicarbamic acid-dipentyl ester (each isomer), toluene-dicarbamic acid-dihexyl ester (each isomer), toluene-dicarbamic acid-diheptyl ester (each isomer), toluene-dicarbamic acid-dioctyl ester (each Isomer), N, N ′-(4,4′-methanediyl-diphenyl) -dicarbamic acid-dimethyl ester, N, N ′-(4,4′-methanediyl-diphenyl) -dicarbamic acid-diethyl ester, N, N ′-(4,4′-methanediyl-diphenyl) -di Rubamic acid-dipropyl ester, N, N ′-(4,4′-methanediyl-diphenyl) -dicarbamic acid-dibutyl ester, N, N ′-(4,4′-methanediyl-diphenyl) -dicarbamic acid-dipentyl ester N, N ′-(4,4′-methanediyl-diphenyl) -dicarbamic acid-dihexyl ester, N, N ′-(4,4′-methanediyl-diphenyl) -dicarbamic acid-diheptyl ester, N, N ′ Mention may be made of carbamic acid esters such as-(4,4'-methanediyl-diphenyl) -dicarbamic acid-dioctyl ester.

On the other hand, although the structure of the reaction product containing the metal produced by the above method is not clear, the present inventors have conducted structural analysis by ¹ H-NMR or ICP (inductive inductively coupled plasma emission spectrometry). From the results of quantification of the metal content by), it is presumed that it is a complex of carbamic acid ester and the metal.

  Next, process (2) is demonstrated. The reaction product containing the metal produced in step (1) is often dispersed as a powder in the reaction system, and the reaction system is obtained by a known method such as filtration, membrane separation, decantation, or centrifugation. It can be further separated and recovered. The separation operation is preferably carried out under an inert atmosphere such as nitrogen, helium, argon, neon or the like. By this operation, the amount of metal contained in the reaction solution can be reduced.

  Further, the present inventors have found that the reaction product containing the metal separated and recovered by the above-described method has a catalytic activity in the reaction between the carbonate ester and the amine.

  That is, in step (3), the reaction product containing the metal separated in step (2) can be reused as part or all of the basic catalyst in step (1). The step (3) has an effect of reducing the amount of newly used catalyst in the reaction between the carbonate ester and the amine.

  The carbamic acid ester obtained by the method described above is a compound useful for the production of isocyanate, and the isocyanate produced from the carbamic acid ester is suitably used as a raw material for producing polyurethane foam, paints, adhesives and the like. be able to. In addition, the metal-containing reaction product generated in the manufacture of the carbamic acid ester described above is recycled as a catalyst, so that the effect of reducing metal waste is also achieved. Therefore, the present invention is extremely important in industry.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example and a comparative example, this invention is not limited to this Example.

First, details of the analysis method used in this example will be described.
1) Water analysis method Apparatus: Japan, Mitsubishi Chemical Co., Ltd., CA-05 trace moisture meter (1) Quantitative analysis method In a dry nitrogen atmosphere, about 1 g of an analytical sample was taken with a syringe, and the weight of each syringe was measured. . After injecting the analysis sample into the moisture meter, the weight of the syringe was measured again, and the sample injection amount was calculated from the weight measurement values before and after the injection. The water content in the analytical sample was calculated from this value and the quantitative value of water measured with a moisture meter.

2) Liquid chromatography analysis method Apparatus: LC-10AT system manufactured by Shimadzu Corporation, Japan Column: Silica-60 columns manufactured by Tosoh Corporation, Japan Connected in series Developing solvent: Hexane / tetrahydrofuran = 80/20 (volume ratio) Liquid mixture of solvent: 2 mL / min Column temperature: 35 ° C.
Detector: R.I. I. (Refractometer)
(1) Sample for liquid chromatography analysis About 0.1 g of sample was weighed, about 1 g of tetrahydrofuran (made by Wako Pure Chemical Industries, Japan, dehydration) and bisphenol A (Japan, Wako Pure Chemical Industries, Ltd.) as an internal standard substance. A solution obtained by adding about 0.02 g of (manufactured, first grade) and mixing uniformly was used as a sample for liquid chromatography analysis.
(2) Quantitative analysis method Each standard substance was analyzed, and based on the prepared calibration curve, quantitative analysis of the analysis sample solution was performed.

3) Gas chromatography analysis method Apparatus: GC-2010 manufactured by Shimadzu Corporation, Japan
Column: DB-1 manufactured by Agilent Technologies, USA
Length 30m, inner diameter 0.250mm, film thickness 1.00μm
Column temperature: After holding at 50 ° C. for 5 minutes, the temperature is raised to 200 ° C. at a heating rate of 10 ° C./min.
After holding at 200 ° C. for 5 minutes, the temperature is raised to 300 ° C. at a temperature rising rate of 10 ° C./min. Detector: FID
(1) Sample for gas chromatography analysis About 0.05 g of the sample was weighed, about 1 g of toluene (made by Wako Pure Chemical Industries, Japan, dehydration) and diphenyl ether (made by Wako Pure Chemical Industries, Japan) as an internal standard substance. A solution obtained by adding about 0.02 g of special grade) and mixing them uniformly was used as a sample for gas chromatography analysis.
(2) Quantitative analysis method Each standard substance was analyzed, and based on the prepared calibration curve, quantitative analysis of the analysis sample solution was performed.

4) ICP mass spectrometry apparatus: Seiko Electronics Co., Ltd., SPQ-8000
(1) Quantitative analysis method After 0.1 g of sample was incinerated with dilute sulfuric acid, it was dissolved in dilute nitric acid. The amount of sodium element in this sample was quantified with an ICP mass spectrometer.

Example 1
Process (1): Reaction of carbonate ester and amine In a 4 L flask having a capacity of 5 L, 1537 g (7.6 mol) of bis (3-methylbutyl carbonate) and 220.8 g of hexamethylenediamine (manufactured by Aldrich, USA) (1. 9 mol), a stirring bar, a fractionation tower with a reflux condenser connected to the distillate receiver, and a thermometer were attached, and the inside of the flask was replaced with vacuum-nitrogen. About 1 g of the solution in the flask was collected, and the water content was measured with a Karl Fischer-water meter. As a result, about 10 ppm of water was contained. The flask was immersed in an oil bath heated to 80 ° C., and 10 g of sodium methoxide (manufactured by Aldrich, USA, 25% methanol solution) was added with a syringe. After 6 hours, a white precipitate was visually confirmed. When the reaction solution was sampled and analyzed by gas chromatography, hexamethylenediamine was not detected.

Step (2): Separation of white precipitate Stainless steel holder with tank equipped with PTFE membrane filter (manufactured by Toyo Roshi Kaisha, Japan, pore size of 0.25 μm) under a nitrogen atmosphere. (Japan, Toyo Seisakusho KST-90), 0.4 MPa of nitrogen was introduced into the tank and filtration was performed. On the filter, 16.5 g of a white solid was obtained, which contained about 5 wt% sodium.
As a result of analyzing the filtrate by liquid chromatography, sodium contained in the filtrate was about 20 ppm.

Step (3): Using 1510 g (7.5 mol) of recycled white bis (3-methylbutyl) carbonate and 210.5 g (1.8 mol) of hexamethylenediamine in the step (2) instead of sodium methoxide The same method as in step (1) was performed except that 15 g of the separated white precipitate was used. Six hours after the start of the reaction, white precipitate was visually confirmed, and when the reaction solution was sampled and subjected to gas chromatography analysis, hexamethylenediamine was not detected. The reaction solution contained 35.3 wt% of N, N′-hexanediyl-bis-carbamic acid bis (3-methylbutyl) ester.

(Comparative Example 1)
Step (1): Reaction of carbonate ester and amine compound 1245 g (6.2 mol) of bis (3-methylbutyl) carbonate and 179 g (1.5 mol) of hexamethylenediamine are placed in a 5 L four-necked flask with an inner solution, and a stirrer is added. A fractionation tower with a reflux condenser connected to the distillation liquid receiver and a thermometer were attached, and the inside of the flask was replaced with vacuum-nitrogen. About 1 g of the solution in the flask was sampled, and the water content was measured with a Karl Fischer moisture meter. As a result, about 120 ppm of water was contained. The flask was immersed in an oil bath heated to 80 ° C., and 10 g of sodium methoxide (25% methanol solution) was added by a syringe to react. After 6 hours, no white precipitate was observed in the reaction solution. When the reaction solution was sampled and analyzed by gas chromatography, hexamethylenediamine was not detected.

  The white precipitate contained in the reaction solution was subjected to a stainless steel holder with a tank (Japan, manufactured by Toyo Seisakusho Co., Ltd.) equipped with a PTFE membrane filter (manufactured by Toyo Roshi Kaisha, Ltd., pore size 0.25 μm) under a nitrogen atmosphere. KST-90), and 0.4 MPa of nitrogen was introduced into the tank for filtration. No solid matter was obtained on the filter.

  As a result of analyzing the filtrate by liquid chromatography, it contained 35.7 wt% of N, N′-hexanediyl-bis-carbamic acid bis (3-methylbutyl) ester. Moreover, the sodium contained in a filtrate was about 700 ppm.

  The method for producing a carbamic acid ester of the present invention has an effect of reducing metal waste because a reaction product containing a metal derived from a basic catalyst produced in the production of a carbamic acid ester is recycled as a catalyst. Play. Therefore, the present invention is extremely important in industry.

Claims (8)

A method for producing a carbamate by reacting a carbonate with an amine, comprising:
As a catalyst for the reaction,
A method for producing a carbamate using a reaction product containing the metal, which is produced when a carbamate is synthesized from a carbonate and an amine in the presence of a basic catalyst containing the metal.   The production method according to claim 1, wherein the metal-containing reaction product is separated from the reaction system by filtration and then used as a catalyst in the production of a carbamate. The production method according to claim 1 or 2, wherein the carbonate ester is represented by the following general formula (1).

(In the formula, R ¹ represents an aliphatic group having 1 to 10 carbon atoms.) The manufacturing method according to any one of claims 1 to 3, wherein the amine is represented by the following general formula (2).

(Wherein R ² is an aliphatic group having 1 to 20 carbon atoms or an aromatic group having 6 to 20 carbon atoms having a valence equal to n. Each group may further contain an oxygen atom, and , N is an integer from 2 to 10.)   The manufacturing method according to claim 4, wherein n is a diamine of 2 among those represented by the general formula (2).   The manufacturing method according to any one of claims 1 to 5, wherein the metal contained in the basic catalyst is an alkali metal or an alkaline earth metal.   The production method according to claim 6, wherein the basic catalyst is an alcoholate of an alkali metal or an alkaline earth metal.   The production method according to any one of claims 1 to 7, wherein the reaction product is a complex of a carbamate and the metal.