JPS60172957A - Production of diphenylmethane dicarbamate - Google Patents

Abstract

PURPOSE:To produce the titled compound useful as a raw material of polyurethane elastomer, spandex, coating agent of artifitial leather, etc. in high yield, by reacting an N-phenylcarbamate with a methylenation agent under specific condition. CONSTITUTION:An N-phenylcarbamate is made to react with a methylenation agent in an aqueous solution of an inorganic acid (e.g. 20-70wt% aqueous solution of sulfuric acid) or a mixture of an aqueous solution of an inorganic acid and an organic solvent at 40-150 deg.C. The amount of the N-phenylcarbamate is >=2mol per 1mol equivalent of the emthylene group of the methylenation agent. The reaction product is separated into the aqueous solution of inorganic acid and the organic phase comprising the reaction mixture, which is heat-treated at 40-200 deg.C in the presence of N-phenylcarbamate and a crystalline aluminosilicate or a crystalline silicate to obtain the objective compound. The atomic ratio of silicon to aluminum in the aluminosilicate is >=10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for condensing N-phenylcarbamates, more specifically, a method for condensing N-phenylcarbamates through a methylene group by reacting the N-phenylcarbamates with a methylene component. The present invention relates to an industrially advantageous method for obtaining diphenylmethane dicarbamates with high selectivity.

Diphenylmethane dicarbamates can be prepared using diphenylmethane diinocyana (MDI) without the use of phosgene.
) is a material useful as a precursor for the production of i. In particular, 4,4'-diphenylmethane diisocyaner) (1,->so-called pure MD
I) is polyurethane elastomer, spandex,
Demand has been rapidly increasing in recent years as a raw material for coating materials for artificial leather. Therefore, it is desired to develop an industrially advantageous method for producing diphenylmethane dicarbamates that can be used as raw materials.

Conventionally, the method for producing diphenylmethane dicarbamates has been, for example, by reacting N-phenyl carbamate with a condensing agent such as formaldehyde, paraformaldehyde, methylal, or trioxane in the presence of an acid such as a mineral acid or an organic sulfonic acid. There are known ways to do this.

In this case, large amounts of strong acids are used. Raise the reaction temperature.

When the reaction is carried out under relatively severe conditions such as increasing the reaction time, in addition to the target diphenylmethanedicarbamate, for example, compounds of the general formula (wherein R is an alkyl group, an aromatic group, or an alicyclic group, 2 represents an integer of 1 or more.) It is known that the polynuclear polymethylene polyphenyl carbamate represented by the following formula is produced in large quantities.

Furthermore, when such a strong liquid acid is used, separation from the reaction mixture and recovery operations for reuse are complicated and costly, making it difficult to implement industrially. It is clear that there are various problems.

Therefore, as a method to eliminate such drawbacks in terms of acid recovery, a method using an acid aqueous solution having a concentration of 10% or more (% JP-A-55-81850, JP-A-55-81851) has been proposed. has been done. By the way, when these methods were studied, it was found that when using an acid aqueous solution having an a degree of 50 degrees or less, as in the example, separation from organic substances can be relatively easily performed by layer separation. In a system where a large amount of water exists, it is difficult to complete the reaction, and a considerable amount of compounds having a methylene amino bond (-CI(, -N<)) in which the methylene group is bonded to the nitrogen atom of the carbamate group. Therefore, in order to complete the reaction, it became clear that it was necessary to increase the a degree of the acid and reduce the amount of water, for example, to use an acid aqueous solution with a concentration of 80% or more. If this is done, problems arise, such as hydrolysis of the raw materials and products, and (b) that a large amount of the raw materials and products dissolve in the concentrated acid aqueous solution, making it difficult to separate them.

In any case, N
- A method for carrying out a condensation reaction of phenyl carbamates, as a method for obtaining a product for the production of isocyanates,
This cannot necessarily be said to be industrially satisfactory.

That is, in the above method, it is not possible to separate the remaining binuclear, trinuclear or higher compound having a methylene amino bond from the condensation reaction mixture containing diphenylmethane dicarbamates, polymethylene polyphenyl carbamates, etc. If the condensation reaction mixture containing these methylene amino bond-containing compounds is thermally decomposed, these compounds will either not give incyanates or may be mixed with incyanates formed from carbamates such as diphenylmethane dicarbamates. It has been revealed that various side reactions occur and the yield of the desired incyanate is reduced. Furthermore, these by-products are difficult to separate from the product inocyanates, especially polymethylene polyphenylisocyanates, so they are always included in products called polymeric isocyanates. It has also become clear that this has an adverse effect on the physical properties of the product.

Therefore, it is necessary to carry out the condensation reaction so that the compound having a methylene amino bond, which causes this problem, is not present in the condensation reaction mixture as much as possible.

One method is to prepare these compounds under substantially anhydrous conditions in the presence of a protic or Lewis acid having a strength of at least 75% sulfuric acid.
A rearrangement reaction method has been proposed in which the methylene group bonded to the nitrogen atom is bonded to the benzene term by performing the reaction at a temperature of c (Japanese Patent Application Laid-Open No. 54-59264).

However, this method requires the use of large amounts of concentrated sulfuric acid and para-toluenesulfonic acid, and requires complicated operations and large costs for separation and recovery.

In addition, a method for obtaining polymethylene polyphenyl carbamate by heating only bis(N-carbalkoxyanilino)methane in the presence of an acid catalyst (JP-A-56
-7749 Publication) has also been proposed, but in this method, a condensation reaction also occurs at the same time as the rearrangement reaction occurs, and in addition to diphenylmethane dicarbamate, trinuclear or more polymethylene polyphenyl carbamate is produced as a by-product. ,
It is not suitable as a method for selectively obtaining diphenylmethane dicarbamate, and furthermore, the reaction rate is slow, resulting in the disadvantage that bis(N-carbalkoxyanilino)methane remains without being completely rearranged.

Furthermore, in the presence of a compound having a methylene amino bond such as bis(N-carbalkoxyanilino)methane, K,
A method for producing diphenylmethane dicarbamate and polymethylenepolyphenyl carbamate by reacting N-phenyl carbamate with formaldehyde or a substance that generates formaldehyde during the reaction in the presence of an acid catalyst (JP 56-12357-A) Publication No. 2) has also been proposed.

However, in this method, it is not possible to reduce the amount of the compound having a methylene amino bond, and a large amount of this compound, on a weight basis, inevitably remains in the condensation product.

The present inventors have conducted extensive research in order to solve these problems and develop a method for producing diphenylmethane dicarbamates that can industrially advantageously produce dinuclear nodiphenylmethane dicarbamates with high selectivity. They discovered that the objective could be achieved by carrying out the reaction in two stages under certain conditions, and filed a patent application (%
Application No. 57-213424, % Application No. 57-215911
As a result of further improvements, they discovered that it is advantageous to use a crystalline aluminosilicate having a specific composition as a solid acid, and based on this knowledge, they completed the present invention.

That is, in producing diphenylmethanedicarbamates by reacting N-phenyl carbamates with a methylenating agent, (4) the methylenating agent is reacted with the methylenating agent in the presence of an inorganic acid aqueous solution or an inorganic acid aqueous solution and an organic solvent. and a first reaction step of reacting it with 92 mol or more of N-phenyl carbamate per 1 molar equivalent of its methylene group in the entire liquid phase, 03)
a separation step of separating the reaction mixture obtained in the first reaction step into an inorganic acid aqueous solution and an organic phase reaction mixture substantially free of the inorganic acid; (C) an organic phase reaction mixture t separated in the separation step; Diphenylmethane dicarbamates characterized by comprising a second reaction step of heat treatment in the presence of N-phenyl carbamates and crystalline aluminosilicate or crystalline silicate having an atomic composition ratio of silicon and aluminum of 10 or more. The present invention provides a method for manufacturing.

One of the objects of the present invention is to produce isocyanates, including diphenylmethane diinocyanate (MDI) and optionally its higher homolog polymethyleneboliphenyl isocyanate (PMPPI), by a thermal decomposition reaction. Condensation products containing diphenylmethane dicarbamates and, in some cases, higher homologs of polymethylene polyphenyl carbamates suitable for We provide all possible manufacturing methods.

Another object of the present invention is to provide a method for producing dinuclear diphenylmethanedicarbamates with high selectivity, and another object is to provide a method for producing dinuclear diphenylmethane dicarbamates with high selectivity. The object is to provide a method that is easy to collect and recycle.

The N-phenyl carbamates used in the method of the present invention are compounds represented by the general formula, where R represents an alkyl group, an aromatic group, or an alicyclic group, R' is hydrogen or an alkyl group, ... Represents a substituent such as a rogene atom, nitro group, cyano group, alkoxy group, alicyclic group, etc., and these substituents are bonded to the ortho or meta position to the urethane group, and r is Represents an integer from ~4. Furthermore, when r is 2 or more, R' may be the same or different substituents. Furthermore, R may have one or more hydrogen atoms substituted with the above-mentioned substituents.

Examples of such N-phenyl carbamates include, for example, in the above general formula (1), R is a methyl group, an ethyl group, a 2,2.2-trichloroethyl group, a 2.2.2-)
Alkyl groups such as lifluoroethyl group, propyl group (n-1iso), butyl group (n- and various isomers), pentyl group (n- and various isomers), hexyl group (n- and various isomers) , or an alicyclic group such as a cyclopentyl group or a cyclohexyl group, or an aromatic group such as a phenyl group or a naphthyl group, and R' is hydrogen, or the above-mentioned alkyl group or alicyclic group, or fluorine, Examples include N-phenyl carbamates which are 2-rogen atoms such as chlorine, bromine, and iodine, or alkoxy groups having a nitro group, a cyano group, or the above-mentioned alkyl group.

Among these, preferred are methyl N-phenylcarbamate, N-phenylcalci(ethyl mate,
-Phenylcarbamiyen-7'' lovir, N-phenylcarbamate 1so-furovir, N-phenylcarbamate pentyl, N-phenylcarbamate #5ee-butyl, N-phenylcarbamate 1so-butyl, N-
Phenylcalci (tert-phthyl mate, pentyl N-phenylcarbamate, hexyl N-phenylcarbamate, cyclohexyl N-phenylcarbamate, N
-2,2,2-trichloroethyl phenylcarbamate, N-phenylcarbamate M2,2,2-trifluoroethyl, N-0 or m-)lylcarno(methyl mate, N-o or m-)lylcarbamate Ethyl, 2,2,2-trifluoroethyl N-o or m-)lylcarbamate, No- or m-propyl tolylcarbamate (each isomer), No- or m-butylcarbamate (each isomer), N-0 or methyl m-chlorophenylcarbamate, N-0 or ethyl m-chlorophenylcarbamate, N-0 or tdm-chlorphenylcalci (propyl mate (each isomer), N-o Also F
im-methyl chlorphenylcarbamate (each isomer)
, N-o or m~chlorphenylcar/(2゜2.2-1 trifluoroethyl mate, methyl N-2,6-dimethylphenylcarbamate, N-2,6-dimethylphenylcarbamine Ethyl acid, propyl N-2,6-dimethylphenylcarpamate (each isomer), butyl N-2,6-dimethylcarbamate (each isomer), N-2,6-
2,2.2-)lifluoroethyl dimethylcarbamate, N-2,6-dipromphenylcarpami7rllmef
Ethyl N-2,6-dibromphenylcarbamate, Propyl N-2,6-dibromphenylcarbamate (each isomer), Butyl N-2,6-dibromphenylcarbamate (each isomer) , N-phenyl carbamates such as 2,2,2-trifluoroethyl/bromphenylcarbamate are used.

Examples of the methylenating agent used in the present invention include formaldehyde, paraformaldehyde, trioxane, tetraoxane, dialkoxymethane, cyasyloxymethane, 1,3-dioxolane, 1,5-dioxane, 1,
Examples include 5-dithiane, 1,3-oxathiane, hexamethylenetetramine, etc. Among these methylenating agents, preferred are formaldehyde, paraformaldehyde, trioxane, and dithiane having a lower alkyl group having 1 to 6 carbon atoms. Alkoxymethanes, such as dimethoxymethane, jetoxymethane, diacetoxymethane,
These include dipentoxymethane, dihexyloxymethane, diacetoxymethane, and siasiloxymethane containing a lower carboxyl group such as diacetoxymethane, and these may be used alone or in combination of two or more. Among these methylenating agents, an aqueous formaldehyde solution is most preferred. One of the features of the present invention is that diphenylmethane dicarbamates tl- can be produced with high selectivity using the cheapest methylenating agent as one raw material.

Step (4) in the method of the present invention uses an inorganic acid aqueous solution as a catalyst and a preferable temperature range of 40 to 150°C.
This is a step in which phenyl carbamates are reacted with a methylenating agent in the entire liquid phase, and examples of inorganic acids used in this step include hydrochloric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, heteropolyacid, and boric acid. Among these, sulfuric acid is particularly suitable.

Further, the concentration of the inorganic acid in the inorganic acid aqueous solution is preferably 2
The range is 0 to 70% by weight, more preferably 50 to 60% by weight. If this concentration exceeds 70% by weight, hydrolysis of the raw materials and products tends to occur, and in addition, the raw materials and products tend to be easily dissolved in the inorganic acid aqueous solution, making it difficult to separate them. On the other hand, if it is less than 20% by weight, the reaction rate becomes slow and is not practical.

The ratio of N-phenyl carbamates and methylenating agent used in this step (4) is preferably 2 moles or more of N-phenyl carbamates per 1 molar equivalent of methylene group in the methylenator. is 2.2~1
The amount is preferably 0 mol, more preferably 2.5 to 6 mol.

The proportion of the inorganic acid aqueous solution used is in the range of 0.1 to 20 molar equivalents, preferably in the range of 0.5 to 10 molar equivalents, per 1 mole of N-phenyl carbamate.

Furthermore, in this step, the reaction can be carried out in a suspension state using water as a medium, or it can also be carried out in a suspension state using water and an organic solvent as a medium.

The organic solvent preferably has a boiling point of 500 C or less at normal pressure and a mutual solubility with water of 10% or less at normal temperature. Mutual solubility is 1
If an organic solvent of 0% or less is used, after the reaction in step (5) is completed, in the next step (B), the separation between the organic phase containing the diphenylmethane dicarbamate product and the aqueous phase containing the inorganic acid will be reduced. 75X is advantageous because it can be easily carried out by a method such as layer separation, and if the boiling point at normal pressure is 600C or less, separation of the solvent from the organic phase reaction mixture can be easily carried out by a method such as distillation. This is advantageous because it can be easily carried out.

Preferred organic solvents are aromatic compounds having an electron-withdrawing substituent or a halogen atom, and examples of the electron-withdrawing substituent include a nitro group, a cyan group, an alkoxycarbonyl group, and a sulfonate group. , trifluoromethyl group, trichloromethyl group, etc. Under the reaction conditions in step (4) of the present invention, an aromatic compound having at least one type selected from the above substituents and a halogen atom is substantially resistant to the electrophilic substitution reaction of the methylene group. In addition, it has a high solubility in N-phenyl carbamates as a raw material and diphenylmethane dicarbamates as a product, and therefore is preferably used in the present invention.

Among such organic solvents, aromatic compounds having a nitro group or a nitrogen atom or both are particularly preferred, such as nitrobenzene, nitrotoluene (each isomer), nitrobenzene, Lower alkyl group-substituted nitrobenzenes such as xylene (each isomer), nitromesitylene, nitroethylbenzene (each isomer), rhodane-substituted nitrobenzenes such as chloronitrobenzene (each isomer), bromonitrobenzene (each isomer), chlorobenzene, dichlorobenzene (each isomer), trichlorobenzene (each isomer), bromobenzene, dibromobenzene (each isomer), tribromobenzene (each isomer), chlorobenzenes, chloronaphthalene (each isomer), dichloronaphthalene (each isomer), bromonaphthalene (each isomer), chlorotoluene (11k each), dichlorotoluene (each isomer), ethylchlorobenzene (each isomer) body).

Examples include θ-lower alkyl group-substituted and rhodanated benzenes such as chloroxylene (each J44 layer), furomotoluene (each isomer), and chromoxylene (each isomer).

The reaction temperature in step (4) of the present invention is 40 to 150C
It is preferably in the range of 60 to 120C. The reaction time varies depending on the type, amount, and concentration of the inorganic acid aqueous solution used, the reaction temperature, the presence or absence of an organic solvent, and the reaction method. Therefore, a range of several minutes to several hours is usually used. Further, the reaction may be carried out batchwise or continuously.

In the subsequent step (B), the reaction mixture thus obtained is separated into an inorganic acid aqueous solution and an organic phase reaction mixture that does not substantially contain the inorganic acid, and the inorganic acid aqueous solution is passed through the step and left as it is. Alternatively, it is preferable that the concentration be adjusted to a predetermined concentration as necessary, and then recycled to the confinement process and reused.

Although the separation method in this step (B) may be as described above, the present invention is characterized in that it can be carried out by a simple method of phase separation under these conditions.

This phase separation can usually be carried out by the following two methods. That is, one method is to perform phase separation by cooling the reaction mixture to a temperature near or below room temperature without using an organic solvent; in this case, the organic phase reaction mixture becomes a solid phase. Therefore, separation from the inorganic acid aqueous solution phase can be easily carried out by means such as filtration.

Another method is to perform phase separation by using an organic solvent or by keeping the reaction mixture at a temperature of 50-60°C. Since it becomes a two-layer liquid phase, it can be easily phase-separated.The shoulder mechanical reaction mixture that has been phase-separated in this way may contain a small amount of inorganic acid, and in this case, washing with water etc. It is preferable to remove the inorganic acid by .If this inorganic acid is contained in the condensation reaction product, side reactions and equipment corrosion may occur during the thermal decomposition step necessary to produce incyanate, which is undesirable. .

In addition, the concentration of the inorganic acid in the inorganic acid aqueous solution separated in this step (B) is determined by the fact that when formaldehydes are used as the methylenating agent, water is produced by the reaction, and when an aqueous solution of formaldehyde is used. In this case, the amount of water has increased by that amount, so the initial concentration is usually thinner.

It is preferable to circulate and reuse the inorganic acid aqueous solution, so if you want to carry out the reaction under certain conditions, it is necessary to concentrate it to a predetermined concentration before circulation. be. This concentration can be carried out extremely easily since the concentration of the inorganic acid aqueous solution used in the present invention is relatively low, preferably 20 to 70% by weight, particularly preferably 30 to 60% by weight. Of course, as long as the concentration of the inorganic acid in the separated aqueous inorganic acid solution is within the range used in the present invention, it can be recycled and reused as it is without being concentrated.

In the next second reaction step, it is preferable to carry out the reaction in a state with as little water content as possible from the viewpoint of reaction rate.
Therefore, it is desirable to remove as much water as possible from the organic reaction mixture separated in step (B). As a method for removing this moisture, for example, an azeotropic agent can be added and the moisture can be distilled off by azeotropic distillation, or when an organic solvent is used in the condensation process, this solvent't
When partially or completely distilling off, water can also be distilled off at the same time.

In addition, in the step (C), it is preferable to carry out the reaction in a state in which almost no methylenating agent is present. Therefore, methylene If the methylenating agent remains, it is preferable to remove the methylenating agent at the same time when the water is distilled off. However, since most formaldehyde or methylenating agents that can generate all formaldehyde in the reaction system are water-soluble, the methylenating agent is essentially contained in the organic phase reaction mixture separated in step (B). is extremely rare.

The organic reaction mixture treated in this way does not substantially contain a methylenating agent, but contains a compound having a methylene amine bond (-0H, -N\), such as bis(N- Carbalkoxyanilino)methane, (N-carbalkoxyanilinomethyl)phenyl carbamate, etc. are included, and in order to convert these compounds to diphenylmethane dicarbamates, (
C5 step is required.

In the (Q step) of the present invention, it is necessary to treat the organic phase reaction mixture described above in the presence of IN-phenyl carbamates.

Conventionally, as a method for rearrangement and condensation reaction of the above-mentioned compound having a methylene amino bond to diphenylmethane dicarbamates and polymethylene polyphenyl carbamates, concentrated sulfuric acid having a concentration of 75% or more or a strong acid equivalent thereto was used, However, in the method of the present invention, the above-mentioned strong acid Crystalline aluminosilicate 1*, which is a much weaker acid, allows the reaction to proceed quantitatively in a short time even in the presence of crystalline silicate.7) In i,
Diphenylmethane dicarbamates can also be obtained with high selectivity when L is used.

The reaction in step (Q) can be easily illustrated using the case of unsubstituted N-phenyl carbamate as an example, and is expressed by the following formula.

and/or (R" in the formula may be the same as R) and a compound having such a dinuclear methylene amino bond and N-
During the reaction with phenyl carbamates, the original N-phenyl carbamates are regenerated, so some compounds are formed with R instead of R#, but in all cases, the dinuclear diphenylmethane di- It is a carbamate and can be used as a raw material for diphenylmethane incyanate.

Furthermore, even if a trinuclear or more compound having a methylene amino bond exists, for example, as shown in the following formula,
It is similarly converted to diphenylmethane dicarbamates.

or 0 or 0. In this way, even if the amount of N-phenyl carbamates to be reacted with a compound having a methylene amino bond is less than or equal to the amount of methylene amino bond present, as can be seen, for example, in the case of a dinuclear reaction, In addition, since N-phenyl carbamates are produced as a by-product, the desired diphenylmethane dicarbamates can be obtained, but in this case, the reaction rate is low, so it is necessary to coexist all of the N-phenyl carbamates in an equivalent amount or more. This is preferable in order to increase the reaction rate and increase the selectivity to diphenylmethane dicarbamates. Therefore, if the amount of unreacted N-phenyl carbamates contained in the organic phase reaction mixture is insufficient, it is preferable to further add N-phenyl carbamates in this step.

The (0 step) of the present invention is characterized in that crystalline aluminosilicate or crystalline silicate having an atomic composition ratio of silicon and aluminum of 10 or more is used as a catalyst.

Crystalline aluminosilicate is a substance generally called zeolite, and has a rigid three-dimensional structure in which Sin and AIO are cross-bonded via oxygen atoms. The ratio of the sum of aluminum atoms and silicon atoms to oxygen atoms in this is 1:2, and the electron valence of the aluminum-containing tetrahedron is balanced by the inclusion of cations in the crystal. It is maintained.

Such crystalline aluminosilicate may be naturally produced or may be produced by any method. The atomic composition ratio of silicon and aluminum is 1
One of the preferable methods for producing crystalline aluminosilicate having an alumina of 0 or more is a hydrothermal synthesis method in which a silica supply material, an alumina supply material, and an alkali metal ion supply material are heated in the presence of water in the coexistence of an organic compound. It is. As the organic compound, oxygen-containing compounds and oxygen-containing compounds such as amines, tetraalkylammonium salts, amides, alcohols, and carboxylic acids are preferably used. Examples of such synthetic zeolites include 'fcZSM type zeolite developed by Mobil Oil Company (% Publication No. 10064, etc.), and amine kumquat which has three or more amino groups in one molecule as an organic compound. Examples include AZ type zeolite (% Application No. 155395/1983, Japanese Patent Application No. 228285/1983) which has a unique crystal structure and was developed by Asahi Kasei Industries, Ltd. Another method for producing such crystalline aluminosilicate is to use natural or synthetic zeolite gold with an atomic composition ratio of silicon and aluminum of 10 F or less, steam treatment at high temperatures, or reagents such as EDTA. A method in which dealumination is carried out by a method such as chemical treatment with
-124723).

Crystalline silicate is a product obtained by further dealumination treatment from such crystalline aluminosilicate.
Or, it is a material obtained by hydrothermally treating and crystallizing a silica supply material and an alkali metal supply material in the absence of an alumina supply material, and the content of aluminum is very low.
It hardly contains any.

As such crystalline aluminosilicate or crystalline silicate, AZ type zeolite or ZSM type zeolite is particularly preferably used.

These crystalline aluminosilicates or crystalline silicates can be used in the form of powder, whole spherical powder,
It is also possible to use a material formed into a cylindrical shape, a plate shape, or the like.

Although it is not clear why these crystalline aluminosilicates or crystalline silicates with an atomic composition ratio of silicon and aluminum of 10 or more, preferably 20 or more, are particularly effective as catalysts in the second reaction step of the present invention, It is thought that the properties of zeolite as a solid acid, such as its acid strength and acid amount, and its unique crystal structure are advantageous.

Furthermore, since these zeolites are non-corrosive solid acids, they are very advantageous in industrial implementation, as the equipment is inexpensive and separation from the reaction mixture is easy. In addition, even if the catalytic activity decreases due to the accumulation of organic deposits during long-term use, these zeolites have excellent commercial temperature heat resistance, so they can be easily regenerated by methods such as calcination or high-temperature steam treatment. be able to.

In the present invention, these crystalline aluminosilicate or crystalline silicates may be used alone or in a mixture of two or more types, and there are no particular restrictions on the lid for use, but When carrying out a batchwise reaction, it is preferable to use a ratio such that the amount of acid is 10@-8 to 10@4 equivalents per 1 equivalent of methyleneamino group of the compound having a methyleneamino bond. When carrying out a flow reaction, the flow rate of the methylene amino group-containing compound is preferably in the range of about 10"8 to 104 equivalents/hr of crystalline aluminosilicate or crystalline silicate 1.

The reaction temperature in the second reaction step of the present invention is 40 to 200
C, preferably in the range of 60 to 180 c. In addition, the reaction time is determined by the type and amount of the crystalline aluminosilicate or crystalline silicate used, the reaction temperature, the amount of the compound having a methylene amino bond, and the coexisting N-
Although it varies depending on the amount of phenylcarpamates, reaction method, etc., it is usually in the range of several minutes to several hours. However, in the process according to the invention less than 1 hour is sufficient in most cases.

The reaction method in the second reaction step may be either a batch method or a continuous method, but preferably a fluidized bed method in which powdered crystalline aluminosilicate or crystalline silicate is fluidized in a reactor, or a molded method of It is a fixed bed type in which a reactor is filled with catalyst.

In the second reaction step of the present invention, regardless of the reaction method described above, since these catalysts are solid, there is no need for complicated separation operations, and simple separation methods such as filtration and sedimentation are not required. Alternatively, the reaction can be carried out by a flow reaction method using a fixed bed without the need for any separation operation.

The reaction in this step can be carried out without a solvent or in the presence of a suitable solvent. Examples of this solvent include pentane, hexane, heptane, octane,
Nonane, decane, n-hexadecane, cyclopenta/,
aliphatic or alicyclic hydrocarbons such as cyclohexane;
Mellogen-free hydrocarbons such as chloroform, methylene chloride, carbon tetrachloride, dichloroethane, trichloroethane, and tetrachloroethane, alcohols such as methanol, ethanol, globanol, butanol, benzene,
Aromatic compounds such as toluene, xylene, ethylbenzene, monochlorobenzene, dichlorobenzene, fromnaphthalene, nitrobenzene, O-, m- or p-nitrotoluene, ethers such as diethyl ether, 1,4-dioxane, tetrahydrofuran, acetic acid Examples include esters such as methyl, ethyl acetate, and methyl formate, and sulfolanes such as sulfolane, 5-methylsulfolane, and 2,4-dimethylsulfolane. Furthermore,
Acetic acid, propionic acid, monochloro 6[, dichloroacetic acid,
Aliphatic carboxylic acids and halogenated aliphatic carboxylic acids such as trichloroacetic acid and trifluoroacetic acid are also used, and acid anhydrides of these carboxylic acids can also be used.

Furthermore, when the entire organic solvent is used in the first reaction step, it is also a preferable method to use this organic solvent as it is as a solvent in the second reaction step.

These solvents can be separated after the second reaction step, if necessary by distillation, or if they can be used as a pyrolysis solvent in the production of incyanate, they can be separated at this stage. There is no need to separate the solvent, and it may be separated from the incyanates produced after the thermal decomposition reaction.

Furthermore, if unreacted N-phenyl carbamates remain, they can be separated, for example, by distillation, if necessary.

The condensation product of N-phenylcarbamates obtained in this way contains dinuclear diphenylmethane dicarbamate aAk as a main component, and trinuclear dimethylene triphenyl carbamate at all or contains a small amount. The selectivity of diphenylmethane dicarbamates is 80% or more.

The method of the present invention is a method suitable for industrial implementation. According to this method, dinuclear diphenylmethane carbamates can be obtained with high selectivity, and N-phenylmethane carbamates obtained by the method of the present invention can be obtained with high selectivity. Condensates of carbamates are excellent precursors for producing diphenylmethane diisocyanate.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited by these Examples.

In addition, the reaction product was analyzed using high performance liquid chromatography.

Example 1 First, crystalline aluminosilicate (AZ-1)i was synthesized by the method disclosed in Japanese Patent Application No. 57-228283.

1.8-diamino-4-aminomethyloctane 1°2,
#L-acid aluminum-CA4(SO4)s ・18H!
O) 0.57, sodium hydroxide 0.52 to water 152
Nitogashi, and silica sol (3o%Sin, )
20 f was added to obtain a homogeneous solution. To this solution, 20 sulfuric acid was added dropwise while stirring to adjust the pH to 12 to obtain a homogeneous gel. This gel was placed in a Teflon test tube and allowed to stand in a stainless steel pressure container at 170°C for 48 hours to effect crystallization.

The obtained product was filtered, washed, and then incubated at 12°C for 3
By drying for hours and further calcining at 500c for 4 hours, AZ-1 zeolite having an atomic composition ratio of silicon to aluminum of about 65 was obtained.

In a 100 ml glass flask, add 50% by weight of sulfur (7
5771, Ethyl N-phenylcarbamate 19156
Add 1.99'c of 7% formaldehyde water bath solution and stir while stirring. After reacting for 2 hours with DC, the reaction mixture was transferred to a separatory funnel, and the organic and aqueous layers were separated and collected separately. After washing the 41st layer with warm water, water was removed using a rotary evaporator. By combining the washing water and the separated water layer and removing a predetermined amount of water with a rotary evaporator, 50*j1% sulfuric acid 7
77 were recovered.

As a result of analyzing the organic layer, the reaction rate of ethyl N-phenylcarbamate was 38.5%, and the composition of the product was 614.4'.
-diethyl diphenylmethanedicarbamate is 50.1
31 ut%, 4 i% of diethyl 2,4'-diphenylmethanedicarbamate, bis-(N-carboethoxyanilino)methane with methylene amino bond and (
Ethyl N-carboethoxyanilinomethyl)phenylcarbamate was 1.9 and 2.4% by weight, respectively, and pentanuclear or higher compounds were 0.9% by weight. Note that formaldehyde was not detected in the organic layer.

Next, add 30% of orthodichlorobenzene to this organic layer. and 32 of the above AZ-1 zeolite and stirred for 15 minutes.
The reaction was carried out at 0C for 30 minutes. After the reaction, AZ-1 zeolite was separated by filtration.

In the reaction mixture thus obtained, no compound having a methylene amino bond was present.

The selectivity of diethyl 4,4'-diphenylmethanedicarbamate in the condensation product was 88.5% and 2.4'
-Diphenylmethane The selectivity of diethyl dicarpamate was 10.4%, and the selectivity of triethyl dimethylenetriphenylcarbamate, which is a trinuclear substance, was 1.1%. The total selectivity of the dinuclear diethyl diphenylmethanedicarbamate was 98.9%.

Note that the JLfcAZ-1 zeolite separated by filtration could be reused as it was and gave similar reaction results.

Example 2 This example is an example of a continuous flow reaction system.

In the first stage reaction process, a complete mixing type device consisting of three overflow type stirred glass reactors with an internal volume of 36 cm is used, and the overflow reaction liquid is sequentially introduced into the lower stage reactor. It is set up like this. Each reactor was maintained at 90C. In the uppermost reactor 1c of this apparatus, a preheated ethyl N-phenylcarbamate solution containing 33% of tr-nido-p-benzene was heated to 90C at 15 g/min.
It was introduced at the speed of the government. At the same time, 55 thiosulfuric acid preheated to 90C was introduced at 18 mt/M into the 57 thiformaldehyde aqueous solution at a total amount of 0.7 d/g. After reaching a steady state, the reaction solution was introduced into a two-layer separator and was continuously separated into a nitrobenzene layer and a sulfuric acid water bath liquid layer. Nitrobenzene solution 190
A trace amount of sulfuric acid was removed by introducing warm water at 90C from the upper part of the multistage extraction column with countercurrent contact, which was maintained at a temperature of 90C, from the bottom. Next, a small amount of water in the nitrobenzene solution was distilled off together with a portion of nitrobenzene under reduced pressure to perform dehydration.

Analysis of the nitrobenzene layer revealed that ethyl N-phenylcarbamate was 67.7% by weight and diethyl 4.4'-diphenylmethanedicarbamate was 75f and 27.5% by weight.
%, 2.3% by weight of diethyl 2.4'-diphenylmethanedicarbamate, bis-
(N-carboethoxyanilino)methane and (N-carboethoxyanilinomethyl)phenylcarbamate ethyl at 0.8 M and 1.2% by weight, respectively, to form trinuclear dimethylene triphenylcarbamate. Triethyl was 0.5ii%.

Next, a second stage reaction was carried out by introducing the nitrobenzene solution 1150c from the bottom of a tubular reactor having an inner diameter of 3 m. This reaction tube was filled with AZ-1 zeolite, which was synthesized by a method similar to that used in Example 1 and had a composition ratio of silicon to aluminum of about 100.

The residence time was set to 30 minutes, and after reaching a steady state, the reaction solution was analyzed, and no compound having a methylene amino bond was present. Nitrobenzene and unreacted ethyl N-phenylcarbamate were separated from the reaction mixture by distillation.

Heavy Jl in the condensation product obtained as distillation residue
The composition is 89.2% diethyl 4.4'-diphenylmethanedicarbamate, 9.3% diethyl 2.4'-diphenylmethanedicarbamate, and 1.5% triethyl dimethylenetriphenylcarbamate. Met.

Example 3 A second reaction step similar to Example 2 was carried out using the nitrobenzene solution obtained in Example 2 after the first reaction step and separation step. In the reaction tube of the second reaction step, silica feed material is added in the coexistence of tetrapropylammonium hydroxide.
Alumina feed material and alkali metal ion supply'l/
It was filled with ZSM-5 zeolite having an atomic composition ratio of silicon to aluminum of about 50, which had been obtained by hydrothermal treatment to obtain J quality, crystallization, washing with water, drying, and heat treatment.

There was no compound having a methylene amino bond in the reaction solution after the second reaction step, and the composition of the condensation product was almost the same as that obtained in Example 2.

Example 4 The same reactor as used in the first reaction step of Example 2 was used.

Into the uppermost reactor of this equipment, which consists of three tanks maintained at 90C, 20 g/ml of a 28% m-orthodichlorobenzene solution containing ethyl N-phenylcarbamate, which had been preheated to 90C, was added.
It was introduced at a rate of 1 ruR. At the same time, 60 thiosulfuric acid is added to 15-thiosulfate at a rate of 37 thiformaldehyde aqueous solution f0.6d/drive.
/I introduced it at the speed of reading.

After reaching a steady state, the reaction solution was introduced into a two-layer separator and was continuously separated into an orthodichlorobenzene layer and an aqueous sulfuric acid solution layer. The orthodichlorobenzene solution was introduced from the top of a countercurrent contact type multi-stage extraction tower maintained at 90C, and the solution was introduced from the bottom at 90C.
Traces of sulfuric acid were removed by flowing hot water at 0c. Next, a small amount of water in the ortho-dichlorobenzene solution was distilled under reduced pressure together with a portion of the ortho-dichlorobenzene to perform dehydration.

As a result of analyzing the orthodichlorobenzene solution, the reaction rate of ethyl N-phenylcarbamate was 4.4 at t152.
'-Diphenylmethanedicarpamate diethyl oyohi 2
+4'-') diethyl phenylmethanedicarbamate was added to (N
- Ethyl phenylcarbamate (poethoxyanilinomethyl) and trinuclear compounds (including methylene amino bond) were produced with selectivities of 18.5 and 9, respectively. Understood.

Next, a second reaction step was carried out by introducing this orthodichlorobenzene bath solution from the lower part of the tubular reactor maintained at 160C. This reaction tube was filled with AZ-1 zeolite having a silicon to aluminum composition ratio of approximately 80. The residence time was set to 40 minutes in total, and after reaching a steady state, the entire reaction solution was analyzed. As a result, there was no compound having a methylene amino bond, and 4,4'-diphenylmethanedicarbamic acid diethyl, 2,4'-diphenylmethane The selectivity of diethyl dicarbamate is 85.3%, respectively.
The selectivity of triethyl dimethylenetriphenylcarbamate, a hexanuclear substance, decreased to 6.8%.

Claims (9)

[Claims] (1) In producing diphenylmethane dicarbamates by reacting N-phenyl carbamates and a methylenating agent, (4) the methylenating agent and its methylene group 1
N-phenyl force of 2 moles or more per molar equivalent A = First reaction step of reacting with bamates in the entire liquid phase, (B) The reaction mixture obtained in the first reaction step is mixed with an inorganic acid aqueous solution and the inorganic acid (C) separating the organic phase reaction mixture separated in the separation step into an organic phase reaction mixture containing substantially no N-phenyl carbamates and an organic phase reaction mixture having an atomic composition ratio of silicon and aluminum of 10 or more; 1. A method for producing diphenylmethane dicarbamates, which comprises a second reaction step of heat treatment in the presence of crystalline aluminosilicate or crystalline silicate. (2) The method according to claim 1, wherein the inorganic acid aqueous solution is a 20-70% by weight sulfuric acid aqueous solution. (3) 1 molar equivalent of methylene group of methylenating agent] 2 to
2. A process according to claim 1, wherein 10 mol of N-phenylcalcium) Jif is used. (4) The method according to claim 1, wherein the first reaction step is carried out in a temperature range of 40 to 150C. (5) The method according to claim 1, wherein the methylenating agent is an aqueous formaldehyde solution. (6) The method according to claim 1, wherein the organic solvent has a boiling point of 300 C or less at normal pressure and a mutual solubility with water of 10 C or less at room temperature. (7) The method according to claim 6, wherein the organic solvent is an aromatic compound having at least one substituent selected from an electron-withdrawing substituent or a hydrogen atom. (8) The method according to claim 1, wherein the second reaction step is carried out at a temperature range of 40 to 200C. (9) The crystalline aluminosilicate is a zeolite produced by hydrothermal synthesis from a silica supply material, an alumina supply material and an alkali metal ion supply material in the coexistence of an organic compound. Method. Q(I) Item 9 of the M section of claim #!F in which the crystalline aluminosilicate is a zeolite hydrothermally synthesized using an amine having three or more 7mino2&!all in one molecule as an organic compound Method described.