JPH0518822B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing diphenylmethane dimethyl carbamate and polymethylene polyphenyl polymethyl carbamate. For more details,
N-phenylcarbamic acid methyl ester and formaldehyde or a substance that generates formaldehyde are reacted in a heterogeneous state in a solvent containing water in the presence of an acid catalyst, and the precipitated high-purity diphenylmethane dimethyl carbamate is separated. Separation of diphenylmethane dimethyl carbamate and polymethylene polyphenyl polymethyl carbamate, comprising reacting the remainder in substantially homogeneous conditions in the presence of an acid catalyst to obtain polymethylene polyphenyl polymethyl carbamate containing diphenylmethane dimethyl carbamate. Regarding manufacturing methods. Diphenylmethane dicarbamate and polymethylene polyphenyl polycarbamate give the corresponding diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate upon thermal decomposition. Diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate are produced in large quantities by phosgenation of diamines and polyamines obtained by condensation of aniline with formaldehyde using mineral acids. . However, this method has several problems, such as the need to use harmful phosgene, the complexity of the phosgenation process, and the need to dispose of hydrochloric acid produced as a by-product in the phosgenation process. In addition, diphenylmethane diisocyanate, which is usually referred to as a dinuclear substance, is used in a wide range of applications such as elastomers, paints, artificial leathers, synthetic leathers, spandex, and adhesives, and its demand has been increasing in recent years. In order to meet these demands and obtain diphenylmethane diisocyanate with high selectivity by the above-mentioned known method, a method of phosgenation is proposed that lowers the reaction rate of aniline and increases the selectivity of diamine. However, in addition to the problem of using phosgene, this method requires recovery of a large amount of aniline, which consumes a lot of energy and is not an economical method. Therefore, there is a strong need for the development of an industrially advantageous manufacturing method that overcomes the problems of the known methods described above. On the other hand, various methods for producing isocyanates without using phosgene have already been proposed.
98240), or by reacting an aromatic nitro compound with carbon monoxide and alcohol in the presence of a catalyst consisting of selenium or sulfur and a base (JP-A-49-62420) to obtain an aromatic carbamate, which is then thermally decomposed. There are methods etc. Further, the phenylcarbamate alkyl ester obtained by the method described above is reacted with formaldehyde, paraformaldehyde, trioxane or a substance that generates formaldehyde to produce diphenylmethane dicarbamate and polymethylene polyphenyl polycarbamate, It has also been proposed to produce the corresponding isocyanates by subsequent thermal decomposition of the diphenylmethane dicarbamate and polymethylene polyphenyl polycarbamate obtained. That is, a method for producing diphenylmethane dicarbamate and polymethylene polyphenyl polycarbamate from an aryl carbamate is disclosed in, for example, US Pat. A method of condensation in an aqueous acid solution is disclosed. However, in this method, in addition to polymethylene polyphenyl polycarbamate, N(-alkoxycarbonyl) having a C-N bond called N-benzyl
It was found that 15 to 50% by weight of phenylaminomethylphenyl compounds and their dimers, trimers, and tetramers were produced as by-products, and these were not converted to isocyanates by thermal decomposition. In order to solve this problem of by-products, a method of rearranging the N-benzyl compound (Japanese Patent Laid-Open No. 54-59264), a method of reaction using an organic sulfonic acid as a catalyst (Japanese Patent Laid-Open No. 55-57550), etc. have been proposed. There is. However, these methods not only have low selectivity for diphenylmethane dicarbamate, but also
The resulting product is a mixture of diphenylmethane dicarbamate and polymethylene polyphenyl polycarbamate. Therefore, in order to separate the dinuclear substance and the polynuclear substance, it is necessary to thermally decompose the carbamate to form isocyanate, which is then separated, which poses the problem of deterioration of the isocyanate due to heating during separation. On the other hand, as a method for increasing the selectivity of diphenylmethane dicarbamate, there is a method characterized in that the reaction is carried out under reaction conditions in which the molar ratio of arylcarbamate to formaldehyde is at least 2.5.
68656) has been proposed. However, in this method, there are many unreacted substances, and it cannot be said to be an efficient method. In producing diphenylmethane dicarbamate and polymethylene polyphenyl polycarbamate, the present inventors aimed to produce diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate without using phosgene. We conducted intensive studies to increase the selectivity of diphenylmethane dicarbamate and to produce it with high purity. As a result, a limited raw material called phenylcarbamate methyl ester was reacted with formaldehyde, trioxane, paraformaldehyde, and/or a substance that generates formaldehyde in a water-containing solvent in the presence of an acid catalyst in a heterogeneous state. Separate high purity diphenylmethane dimethyl carbamate,
The present invention was completed in which the remainder was reacted in a homogeneous state in the presence of an acid catalyst, optionally with the addition of phenylcarbamate methyl ester. That is, the method of the present invention is a method for separately producing diphenylmethane dimethyl carbamate and polymethylene polyphenyl polymethyl carbamate, which is characterized by comprising the following reaction steps. (1) When N-phenylcarbamic acid methyl ester and formaldehyde or a substance that generates formaldehyde are reacted in a heterogeneous state in a solvent containing water in the presence of an acid catalyst, the diphenylcarbamate precipitates as a solid in the reaction system. Enylmethane dimethyl carbamate is separated, and (2) the remainder is reacted in a substantially homogeneous state in the presence of an acid catalyst after dehydration to obtain diphenylmethane dimethyl carbamate and polymethylene polyphenyl polymethyl carbamate. According to the method of the present invention, since the raw material is phenylcarbamic acid methyl ester, diphenylmethane dimethylcarbamate can be efficiently precipitated by reaction in a heterogeneous reaction system.
Therefore, (1) highly pure diphenylmethane dimethyl carbamate can be isolated, and (2) the selectivity of diphenylmethane dimethyl carbamate can be improved without reducing the reaction rate of phenylcarbamate methyl ester as a raw material. (3) The selectivity of diphenylmethane dimethyl carbamate can be further improved by adding phenylcarbamic acid methyl ester to the second-stage reaction; (4) Diphenylmethane dimethyl carbamate can be precipitated in the first-stage reaction. (5) Since diphenylmethane dimethyl carbamate is separated, the amount of catalyst in the second reaction can be reduced, and the equipment can be made smaller. There are advantages such as being able to adjust the amount of diphenylmethane dimethyl carbamate extracted. The N-phenylcarbamic acid methyl ester used in the method of the present invention has the general formula () (In the formula, R represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group, m is an integer of 1 or 2, and n is 1 or 2.
Examples of such compounds include phenylcarbamic acid methyl ester, toluylcarbamic acid methyl ester, and chlorphenylcarbamic acid methyl ester. The method of the invention also uses formaldehyde or a substance that generates formaldehyde. The substance that generates formaldehyde is paraformaldehyde, trioxane, dimethoxymethane, diethoxydimethane, or the like, and is a substance that generates formaldehyde in the reaction system. Furthermore, acid catalysts used in the method of the present invention include mineral acids such as hydrochloric acid, sulfuric acid, phosphoric acid, and boric acid; organic carboxylic acids such as acetic acid, oxalic acid, and chloroacetic acid; hydrobromic acid, perchloric acid, and methane. Organic sulfonic acids such as sulfonic acid, ethanesulfonic acid, butanesulfonic acid, trifluoromethanesulfonic acid, trichloromethanesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid; further, for example, tin chloride (),
Examples include Lewis acids such as iron chloride, aluminum chloride, antimony pentafluoride, and boron trifluoride. The amounts of the above reaction raw materials and reactants used in the method of the present invention are as follows. The amount of the arylcarbamic acid methyl ester and formaldehyde or the substance that generates formaldehyde to be used is generally in the range of 0.01 to 2 mol, preferably 0.1 to 1 mol, of formaldehyde per 1 mol of phenylcarbamic acid methyl ester. In addition, the amount of acid catalyst used is in the range of 0.01 to 10 moles per mole of arylcarbamate methyl ester, and the concentration of acid is relative to water in the reaction system in (1) below. A range of 10% to 70% is preferred. If it is less than 10%, the reaction will be very slow, and if it exceeds 70%, undesirable side reactions such as hydrolysis will increase. On the other hand, in the homogeneous reaction (2) below,
The amount of acid used must be 1% by weight or more based on the total reaction mixture. The method of the invention is carried out as follows. That is, first (1) N-phenylcarbamic acid methyl ester and formaldehyde or a substance that generates formaldehyde are reacted in a heterogeneous state in a solvent containing water in the presence of an acid catalyst. Diphenylmethane dimethyl carbamate precipitated in the reaction system is separated. (referred to as reaction (1)) Next, (2) the precipitate is separated and the residue is subjected to dehydration treatment, and if necessary, N-phenylcarbamic acid methyl ester is added and reacted in a homogeneous state in the presence of an acid catalyst. In this way, diphenylmethane dimethyl carbamate and polymethylene polyphenyl polycarbamate are obtained. (referred to as reaction (2)) In the reaction (1) in the method of the present invention, water is used as a reaction solvent because the reaction is carried out in a heterogeneous state. By reacting in a heterogeneous system using water as a solvent, the target product, diphenylmethane dimethyl carbamate, will precipitate as a solid during the reaction, so if you want to make it easier to handle, use a solvent other than water that does not interfere with the reaction. It can be used in the form of a mixed solvent with water. Suitable solvents include n-pentane, isopentane, n-hexane, 2-methylpentane, n-heptane, 3,4-dimethylhexane, 2-methylhexane, 3-ethylpentane,
Cyclopentane, cyclohexane, methylcyclohexane, ethylcyclopentane, cyclooctane, chloroform, carbon tetrachloride, dichloromethane, dichloroethane, trichloroethane, tetrachloroethane, benzene, toluene, monochlorobenzene, dichlorobenzene, nitrobenzene,
Examples include nitrotoluene, dibromobenzene, methanol, ethanol, propanol, butanol, diethyl ether, 1,4-dioxane, tetrahydrofuran, acetic acid, furopionic acid, and monochloroacetic acid. The amount of reaction solvent containing water is usually 0.2 parts by weight of N-phenylcarbamic acid methyl ester.
It may be in the range of ~20 parts by weight. Reaction temperature is 40-180℃,
Preferably it is 60-140°C. The reaction pressure is not particularly limited, and usually normal pressure may be used. As the reaction progresses, diphenylmethane dimethyl carbamate precipitates as a solid, and after the reaction is completed, it is separated by a conventional method. This (1)
By this reaction, highly pure diphenylmethane dimethyl carbamate can be obtained in high yield. On the other hand, the residue after separating the precipitate undergoes the reaction (2). Since this reaction takes place in a substantially homogeneous state, dehydration treatment is performed to remove the water contained (2).
Subject to reaction. Dehydration treatment is carried out in a conventional manner. Examples include a method of separating the aqueous phase and removing the aqueous phase, a method of distillation, and the like. After dehydration, it may be subjected to reaction (2) as it is, or it may be subjected to post-treatment such as washing with water and concentration before being subjected to reaction (2). If so, it is not particularly limited (hereinafter, the materials used in the reaction (2) are referred to as the reaction raw materials (2)). The solvent used as necessary in the reaction (2) may be at least one type selected from the various organic solvents used in the reaction (1). The amount used is about 0.2 to 20 parts by weight per 1 part by weight of the reaction raw material (2). The reaction (2) is preferably carried out by mixing the reaction raw materials, catalyst, and solvent of (2), and allowing the reaction to occur while removing as much water as possible from the mixture and water produced by the reaction from the system. As a method for removing water from the system, azeotropic dehydration with a solvent is generally preferred. This operation is preferably performed continuously, but may be performed intermittently.
If the reaction is carried out in a heterogeneous system in the presence of a large amount of water, by-products will increase and the yield and selectivity of the active ingredient will decrease. The reaction temperature is 40 to 180°C, preferably 60 to 140°C, as in the reaction (1). The reaction pressure may be normal pressure, but in some cases it may be preferable to use reduced pressure, which is slightly lower than normal pressure, in order to promote distillation of water out of the system. The degree of pressure reduction at that time is usually 100 to 760 mmHg. Although it is possible to carry out the reaction under pressure, there is generally no need for it. Furthermore, in reaction (2), N-phenylcarbamic acid methyl ester can be added as necessary to obtain a product containing a high proportion of diphenylmethane dimethyl carbamate. In addition, in the method of the present invention, the reaction time varies depending on the type of catalyst, amount used, reaction conditions, and reaction method, and is not limited, but in the case of batch reaction, generally,
It is sufficient to carry out the process in 0.1 to 10 hours. Hereinafter, the present invention will be explained in more detail with reference to Examples. The reaction results were analyzed using high performance liquid chromatography. Example 1 100 g of methyl phenyl carbamate 35% formalin in a flask equipped with a thermometer and a stirrer.
28.6g of sulfuric acid, 392.3g of 50% sulfuric acid, and 100g of 1,2-dichloroethane were charged and stirred at 80°C in an oil bath for 4 hours. Precipitation of solid was observed from the early stage of the reaction. After heating for a predetermined time, the reaction solution was filtered, and the resulting solid was washed with water, followed by a small amount of 1,2-dichloroethane, and dried to obtain 59.9 g of a product. When the product was analyzed by liquid chromatography, it was found that diphenylmethane dimethyl carbamate was 57.5
g, 1.5 g of methyl phenyl carbamate, 0.3 g of N-benzyl compound, and 0.6 g of polymethylene polyphenyl polycarbamate having three phenyl groups. This result means that diphenylmethane dimethyl carbamate was obtained in the first stage reaction with a yield of 55% and purity of 96% based on the methyl phenyl carbamate charged. The liquid from which the solid product obtained in the first stage reaction was separated was separated into an aqueous phase and an organic phase, and the organic phase was washed with water and concentrated to obtain 43.5 g of a concentrate from the liquid. 43.5 g of this concentrate, 42.1 g of nitrobenzene, and 5.0 g of anhydrous ferric chloride were placed in a 200 ml flask and reacted at 100° C. for 30 minutes while stirring. After the reaction was completed, the reaction solution was washed with water and analyzed by liquid chromatography, and it was found that 5.3 g of methyl phenyl carbamate, 17.0 g of diphenylmethane dimethyl carbamate, and polymethylene polyphenylene polyphenylene with 3 or more phenyl groups were found. 20.8g of enyl polymethyl carbamate was detected. The combined yield of diphenylmethane dimethyl carbamate in the first and second stages is 71.6% relative to the charged methyl phenyl carbamate, and the yield (selectivity) relative to the consumed methyl phenyl carbamate is 76.8.
%. Example 2 100 g of methyl phenyl carbamate, 28.6 g of 35% formalin, 392.3 g of 50% sulfuric acid and 1,2-
100 g of dichloroethane was charged and reacted in the same manner as in Example 1 to obtain 62.1 g of precipitated solid. When analyzed by liquid chromatography, 1.4 g of methyl phenyl carbamate, 59.4 g of diphenylmethane dimethyl carbamate, and 0.7 g of polymethylene polyphenyl polymethyl carbamate having three phenyl groups were detected. The liquid from which the precipitated solid was removed was separated into an aqueous layer and an organic layer by liquid separation, and the organic layer was washed with water and concentrated to obtain 55.5 g of a concentrate. 55.5 g of this concentrate and 24 g of methyl phenyl carbamate,
24 g of anhydrous ferric chloride and 48 g of benzene were placed in a 200 ml flask and reacted at 80° C. for 2 hours. After the reaction was completed, the reaction solution was washed with water and concentrated to obtain 66.2 g of product. When analyzed by liquid chromatography,
As raw materials, 23.4 g of methyl phenyl carbamate, 28.4 g of diphenylmethane dimethyl carbamate, and 14.2 g of polymethylene polyphenyl polymethyl carbamate having 3 or more phenyl groups were obtained. This result shows that the yield of diphenylmethane dimethyl carbamate in the first and second stages is 68.1% based on the total amount of methyl phenyl carbamate.
This means that the yield (selectivity) based on the consumed methyl phenyl carbamate is 85.1%. Comparative Example 1 100 g of ethyl phenyl carbamate, 26 g of 35% formalin, 356.2 g of 50% sulfuric acid, and 100 g of 1,2-dichloroethane were placed in one flask and reacted at 80° C. for 4 hours with stirring. No solid precipitation was observed. After the reaction was completed, the reaction solution was separated, washed and extracted with water, and the organic layer was concentrated to obtain 104.3 g of a product. 104.3 g of this product and 11.1 g of anhydrous ferric chloride
g and 100 g of nitrobenzene were placed in a 500 ml flask and reacted at 100°C for 0.5 hour. After the reaction was completed, the reaction solution was washed with water, extracted, and analyzed by liquid chromatography. The yield of diphenylmethane diethyl carbamate based on the charged ethyl phenyl carbamate was 48.9%, and the yield relative to the consumed ethyl phenyl carbamate ( selection rate) was 54.3%,
Furthermore, the yield of polymethylene polyphenyl polyethyl carbamate having 3 or more phenyl groups is 41.1
%, the selectivity rate was 45.7%. Comparative Example 2 18.1 g of methyl phenyl carbamate, 40 g of benzene, 6.48 g of ferric chloride hexahydrate, and 1.8 g of paraformaldehyde were added to a 100 ml round bottom flask equipped with a thermometer, stirrer, and reflux condenser with separator. The reaction was carried out at 80°C for 5 hours while draining boiling water from the system. No solid precipitation was observed during the reaction. The reaction results were that the yield of diphenylmethane dimethyl carbamate was 40.0%, the selectivity was 51.2%, and the number of phenyl groups was 3.
The yield of polymethylene polyphenyl polymethyl carbamate was 37.7% and the selectivity was 48.2%. Examples 3 to 7 Table 1 shows the results of performing the first-stage heterogeneous reaction according to Example 1 by changing the solvent and catalyst.

[Table] Examples 8 to 12 Experiments were conducted in the same manner as in Example 1 in which the precipitated solid was separated, but with different catalysts and solvents. Table 2 shows the results.
Shown below.

【table】

【table】

Claims (1)

[Claims] 1 N-phenylcarbamic acid methyl ester and formaldehyde or a substance that generates formaldehyde are reacted in a heterogeneous state in a solvent containing water in the presence of an acid catalyst, and the precipitated diphenylmethane dimethyl carbamate is separated, A method for separating and producing diphenylmethane dimethyl carbamate and polymethylene polyphenyl polymethyl carbamate, which comprises then reacting the remainder in a substantially homogeneous state in the presence of an acid catalyst.