JP2929730B2 - Method for producing urethane compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a urethane compound starting from a formamide compound or an amine compound and dimethyl carbonate. Urethane compounds are used as intermediate materials for isocyanate production because they can be easily converted to the corresponding isocyanate compounds by thermal decomposition. In particular, an aliphatic diisocyanate compound derived from an aliphatic urethane compound having two carbamate groups in the molecule is useful as a raw material for producing polyurethane or polyurea having excellent yellowing resistance.

[0002]

2. Description of the Related Art Urethane compounds can be produced from nitro compounds, amine compounds, and formamide compounds according to the main starting materials, and various reactions have been proposed. Japanese Patent Application Laid-Open
No. 147253 discloses a reductive carbonylation method in which a nitro compound is reacted with carbon monoxide in the presence of an alcohol. As a method using an amine compound as a main raw material,
59-172451 discloses an carbonylation process in which an amine compound is reacted with carbon monoxide and molecular oxygen or a nitro compound in the presence of an alcohol. These reductive carbonylation and oxidative carbonylation methods use expensive platinum group catalysts such as Pd and Rh, and must be reacted at high temperature and high pressure. There are bulky drawbacks. JP-A-56-169665 discloses a method for reacting an amine compound with a carbamic acid ester or an amine compound with urea and alcohol. This method has the disadvantages that the space-time yield is low due to the low reaction rate, and that high-boiling by-products from carbamic acid esters or urea are large and it is difficult to separate and recover urethane compounds.

As a method using an amine compound as a main raw material, various methods have been further proposed in which an amine compound is reacted with dimethyl carbonate in the presence of a catalyst (JP-B-51-33095, JP-A-57-82361, US Patent 4,395,565). As this catalyst, a Lewis acid catalyst, a lead, titanium or zirconium-based catalyst, an alkali catalyst or the like is used. However, according to the Examples, the reaction rate is generally low, and the yield of the urethane compound is low because an alkylated product is easily generated as a by-product.

As an improved method, Japanese Patent Application Laid-Open No. 64-85956 focuses on a specific amine compound in which an alkylation reaction as a side reaction is unlikely to occur. There has been proposed a method of continuously or intermittently adding.

On the other hand, US Pat. No. 4,661,217 discloses a method of oxidizing a formamide compound in an alcohol solvent on a graphite electrode using NaBr as a supporting electrode, as a method using a formamide compound as a main raw material. However, as a result of studying this method by the present inventors, it was found that although a relatively high yield of the urethane compound was obtained, the electrode was significantly deteriorated, so that it was difficult to carry out the method using an industrial-scale apparatus.

[0006]

SUMMARY OF THE INVENTION The present inventors have previously described a novel method for producing a urethane compound by reacting a formamide compound with dimethyl carbonate in the presence of an alkali catalyst or an amine compound and dimethyl carbonate in the presence of an alkali catalyst and methyl formate. ( Japanese Patent Laid-Open No. 3-200756 ).

The above-mentioned JP-A- 64-85956 and JP-A- Hei 3-20
From the urethane compound obtained by the method of No. 0756, the corresponding isocyanate can be produced by thermal decomposition.
However, in these methods, it is essential that the alkali catalyst be completely removed since the side reaction is remarkably accelerated in the urethane pyrolysis step. Usually, an acid is added to the reaction solution to neutralize and separate the precipitated salt.However, when the excess acid or the neutralized salt has high solubility, the salt itself has a bad influence on thermal decomposition. , Water extraction or water washing,
Furthermore, complicated purification operations such as distillation are required, and it is not always industrially satisfactory.

[0008]

The present inventors have made intensive studies to develop a method for producing a urethane compound which is advantageous as an intermediate material for producing an isocyanate. It has been found that, when the reaction is carried out in a specific temperature range, a urethane compound can be obtained at a high reaction rate and in a high yield without using a catalyst, thereby completing the present invention.

That is, the present invention is a process for producing a urethane compound, which comprises reacting a formamide compound with dimethyl carbonate or an amine compound with a carbonate ester in the presence of methyl formate at a temperature of 100 to 200 ° C. without a catalyst. .

The present invention is represented by the following general formula. R (NHCO
H) _n + nCO (OCH ₃ ) ₂ = R (NHCOOCH ₃ ) _n + nHCOOCH ₃
The formamide compound used in the present invention can be obtained by various methods, but is preferably produced by reacting a corresponding amine compound with methyl formate as represented by the following general formula. _{R (NH 2) n + nHCOOCH} 3 = R (NHCOH) n + nCH 3 OH

The methyl formate here is advantageous because the methyl formate formed by the formula can be recycled and used. In this reaction, the amine compound and methyl formate are converted into a non-catalytic, room temperature,
It is characterized in that it proceeds quantitatively simply by mixing under normal pressure and the reaction rate is high. Therefore, as another preferable reaction mode, the reaction of the formula and the reaction of the formula can be carried out simultaneously. That is, the corresponding urethane compound can be obtained by reacting the amine compound with dimethyl carbonate in the presence of methyl formate by the in-sute method.

An embodiment of the present invention will be described in more detail. The formamide compound which is a main raw material in the present invention is classified into an aliphatic formamide compound and an aromatic formamide compound. Particularly preferred is an aliphatic formamide compound having two formamide groups. When classified by molecular structure, aliphatic formamide compounds include chain aliphatic formamide compounds, alicyclic formamide compounds, and formamide compounds in which a formamide group is bonded to a saturated carbon and has an aromatic ring in the skeleton. Raw materials corresponding to industrially useful isocyanate compounds include, for example, N, N,-[1,3-phenylenebis (methylene)] bisformamide and 1,4-isomers of the same structure,
N, N- [1,3-cyclohexylbis (methylene)] bisformamide and 1,4-isomer of the same structure, 3-formamidomethyl-3,5,5-trimethyl-1-formamidocyclohexane, 1,6- Hexamethylene diformamide and the like.

On the other hand, when an amine compound is used as a main raw material in another method, an aliphatic amine compound having two amino groups is preferable, and m- and p-xylenediamine, N, N,-[1,3- Cyclohexylbis (methylene)] bisamine and 1,4-isomer, isophoronediamine, 1,6-
Hexane methylene diamine and the like can be used.

From these, an aliphatic urethane compound which is a raw material of an aliphatic diisocyanate compound having a high added value can be obtained. Further, the present invention can also be applied to the production of an aromatic urethane compound that is a raw material of a highly versatile aromatic diisocyanate.

[0015] Dimethyl carbonate as an auxiliary material and methyl formate as an additive are used as they are, or can be purified as necessary. In the present invention, since no metal alcoholate is used for the catalyst, there is an advantage that it is not necessary to strictly control the water content of the raw material.

The amount of dimethyl carbonate used in the present invention is:
Per mole of formamide group of formamide compound
It is in the range of 1 to 20 mol, preferably 1 to 10 mol. Less than 1 mole used leaves unreacted formamide and 2
If the amount is more than 0 mol, the space-time yield is reduced, which is not practical. Similarly, when using an amine compound of another method as a main raw material,
Dimethyl carbonate is used in an amount of 1 to 20 per mole of amino group.
Moles, preferably in the range of 1 to 10 moles. The addition amount of methyl formate is in the range of 0.1 to 5 mol, preferably 0.1 to 1 mol, per 1 mol of the amino group. When the amount is less than 0.1 mol, the reaction promoting effect by addition of methyl formate is small,
On the other hand, if the amount is more than 5 mol, the space-time yield is undesirably reduced.

In the present invention, when the main raw material is solid,
Alternatively, when the generated urethane compound precipitates as a solid, it can be suitably carried out using a solvent. The solvent needs to be inert to each raw material and the urethane compound to be produced. Specific examples include alcohols such as methanol and ethanol, ethers such as tetrahydrofuran and dioxane, hydrocarbons such as benzene and toluene, and sulfolane. Etc. can be used. It is advantageous to use the solvent in the minimum necessary amount, usually in the range of 1 to 10 times the weight of the main raw material.

The reaction temperature is 100-200 ° C., preferably 120-200 ° C.
In the range of ~ 170 ° C. If the temperature is lower than 100 ° C., the reaction rate is low, and if the temperature is higher than 200 ° C., side reactions such as decomposition of dimethyl carbonate and methyl formate are undesirably increased.

In this reaction operation, a formamide compound and dimethyl carbonate, or alternatively, an amine compound, methyl formate and dimethyl carbonate, and a solvent, if necessary, are charged and reacted at a sufficient reaction rate to obtain a urethane compound in good yield. Can be As another example, a method of continuously extracting the generated methyl formate out of the system by a reactive distillation method can also be suitably implemented. The generated urethane compound can be easily separated and recovered and purified from the reaction product liquid by a combination of distillation, solvent extraction, recrystallization and the like. Note that the present invention can be suitably implemented in either a batch system or a continuous system.

[0020]

Industrial Applicability According to the present invention, a urethane compound useful as an intermediate material for producing an isocyanate from a formamide compound or an amine compound and dimethyl carbonate can be produced without a catalyst. The method of the present invention does not use a catalyst such as a metal alcoholate which has a bad effect in the thermal decomposition step of the urethane compound unlike the conventional method, so that a high-grade urethane compound can be easily separated and recovered from the reaction product solution. In addition, since there is no particular need for water management as in the case of using a metal alcoholate catalyst, there is an advantage that a low-grade amine compound or dimethyl carbonate which forms an azeotrope with water can be used, and an industrially superior urethane compound It is a manufacturing method of.

[0021]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by these examples.

Example 1 N, N- [1,3-phenylenebis (methylene)] bisformamide (3 g) and dimethyl carbonate (12 g) were charged into a SUS-316 shaking autoclave having an inner volume of 100 ml, and the inside was replaced with nitrogen. After that, the reaction was carried out at a reaction temperature of 155 ° C. for 3 hours.
After the reaction, the reaction product was analyzed by liquid chromatography and gas chromatography by an internal standard method. As a result, methyl N, N,-[1,3-phenylenebis (methylene)] biscarbamate was recovered based on the formamide compound as the raw material. It was produced at a rate of 94.2%. Further, it was confirmed that methyl formate corresponding to the reacted formamide compound was generated.

Example 2 The same autoclave as in Example 1 was charged with 3 g of N, N,-[1,4-phenylenebis (methylene)] bisformamide, 6 g of dimethyl carbonate and 6 g of methanol. The reaction was performed at a reaction temperature of 155 ° C. for 5 hours. After the reaction, the reaction product solution was analyzed, and as a result, methyl N, N,-[1,4-phenylenebis (methylene)] biscarbamate was formed in a yield of 91.5% based on the starting formamide compound.

Example 3 The same autoclave as in Example 1 was charged with 3 g of N, N,-[1,3-cyclohexylbis (methylene)] bisformamide and 12 g of dimethyl carbonate, and the inside thereof was purged with nitrogen. The reaction was performed at ℃ for 3 hours. After the reaction, the reaction solution was analyzed. As a result, methyl N, N- [1,3-cyclohexylbis (methylene)] biscarbamate was formed in a yield of 95.2% based on the formamide compound as the raw material.

Example 4 The same autoclave as in Example 1 was charged with 3 g of 1,6-hexamethylenediformamide and 13 g of dimethyl carbonate. After the inside of the autoclave was replaced with nitrogen, the mixture was reacted at a reaction temperature of 155 ° C. for 3 hours. After the reaction, the reaction solution was analyzed, and as a result, methyl 1,6-hexamethylenedicarbamate was produced in a yield of 92.3% based on the formamide compound as the raw material.

Example 5 The same autoclave as in Example 1 was charged with 2 g of metaxylenediamine, 12 g of dimethyl carbonate and 2 g of methyl formate, and the inside thereof was purged with nitrogen, followed by a reaction at a reaction temperature of 140 ° C. for 5 hours. After the reaction, the reaction product was analyzed, and as a result, methyl N, N,-[1,3-phenylenebis (methylene)] biscarbamate was obtained in a yield of 9 based on metaxylenediamine.
Generated at 0.8%.

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Claims (2)

(57) [Claims] 1. A process for producing a urethane compound, comprising reacting an amine compound with a carbonate ester in the presence of a formamide compound and dimethyl carbonate or methyl formate at a temperature of 100 to 200 ° C. without a catalyst. 2. The method for producing a urethane compound according to claim 1, wherein the formamide compound is an aliphatic formamide compound and the amine compound is an aliphatic amine compound.