JPS6365066B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for condensing N-phenylcarbamate esters via a methylene bond. More specifically, the present invention provides N
- This invention relates to a method for obtaining a bis form with high selectivity when phenyl carbamate is reacted with a methylenating agent to condense it.

This methylene-bis-(4-phenylcarbamate ester) is used as a precursor of 4,4'-diphenylmethane diisoanate (so-called pure MDI) ester) and the general formula (In the formula, R represents an alkyl group, an aromatic group, or an alicyclic group, and n represents an integer of 1 to 4).
It is a useful substance as a precursor of MDI. These isocyanates are extremely important industrially as raw materials for polyurethane, and are especially important for PURE MDI.
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 polymethylene polyphenylcarbamate esters containing a large amount of methylene-bis-(4-phenylcarbamate ester), which can be used as a raw material. There is.

Conventionally, methods for producing methylene-bis-(4-phenylcarbamate) using N-phenylcarbamate as a starting material include:
A method of reacting in an aqueous medium using formalin, paraformaldehyde, trioxane, etc. as a condensing agent and a normal liquid mineral acid such as hydrochloric acid, sulfuric acid, or phosphoric acid as a catalyst, or a method of reacting in an organic solvent with an organic sulfonic acid as a catalyst. There are known methods of
JP-A-55-81851, JP-A-55-105658, JP-A-55-115862, JP-A-55-129260
Publication No. 160012, Japanese Patent Publication No. 160012, Japanese Patent Publication No. 1983-160012
Publication No. 167273, Japanese Patent Application Publication No. 1982-26861, Japanese Patent Application Publication No. 1987-26861
JP 56-51443, JP 56-57758, JP 56-57759, JP 56-57760, JP 56-57761, JP 56-68656 ,
(Japanese Patent Application Laid-Open No. 56-65864).

However, these methods produce large amounts of side reaction products in addition to the target substance methylene-bis-(4-phenylcarbamate ester).
It has drawbacks such as low yield of the target product and time-consuming isolation of the target product, and is not industrially satisfactory. For example, in the reaction in an aqueous solution using water as a medium, an N-(alkoxycarbonyl)phenylaminomethylphenyl compound formed by a reaction at the nitrogen of the N-phenylcarbamate ester and this compound N-benzyl compounds such as dimers and trimers of are produced in considerable amounts. In addition, in the condensation reaction in an organic solvent medium using an organic sulfonic acid as a catalyst, a considerable amount of polymethylene polyphenyl carbamate containing three or more benzene rings is produced as a by-product. The selectivity of things is not that high.

In addition, the liquid acid catalyst used in these conventional methods is not easy to separate and recover, and the treatment of the waste acid is also troublesome as it involves pollution problems.In particular, the equipment is highly corroded, so the reaction equipment is made of poor material. It is extremely disadvantageous industrially because it is subject to severe restrictions.

Therefore, the present inventors conducted intensive research on a method for condensing N-phenylcarbamate ester with a methylene bond, and found that a solid superacid is effective as a catalyst, and used dialkoxymethane as a methylenating agent. The method was first applied for (Japanese Patent Application No. 145526/1983, Japanese Patent Application No. 145526/1983)
As a result of further research, the authors discovered that a new solid superacid can be used as an effective catalyst for this reaction, leading to the present invention.

That is, the present invention provides a method for converting N-phenylcarbamate ester into methylene in the presence of a solid superacid consisting of a combination of at least one metal oxide selected from zirconium oxide, iron oxide, and titanium oxide and sulfate ions. This is a condensation method for N-phenylcarbamate ester, which is characterized by reacting with a curing agent.

The solid super strong acid used as a catalyst in the present invention is a composite of at least one metal oxide selected from zirconium oxide, iron oxide, and titanium oxide and sulfate ions, and is stronger than 100% sulfuric acid. It has acid strength.

Such a solid super strong acid can be easily produced by, for example, bringing a metal hydroxide into contact with sulfate ions and then calcining the metal hydroxide. It has been revealed by Arata et al. that the complex of metal oxide and sulfate ion produced in this manner exhibits superacidity. (Kamen, Vol. 19, p. 75, 1981) Of course, it may be manufactured by other methods.

As the sulfate ion source, sulfuric acid, metal salts of sulfuric acid, quaternary ammonium salts, etc. are used.
Particularly preferred is dilute sulfuric acid.

Furthermore, it is preferable to use a metal compound with a low degree of crystallinity or an amorphous metal compound before being treated with sulfate ions.

The solid superacid used as a catalyst in the present invention, which is composed of a combination of at least one metal oxide selected from zirconium oxide, iron oxide, and titanium oxide, and sulfate ions, differs from ordinary solid superstrong acids,
Since it does not contain halogens such as SbF ₅ or AlCl ₃ , there are no problems with preparation or disposal, and sulfate ions are strongly adsorbed on the surfaces of zirconium oxide, iron oxide, and titanium oxide, making it easy to remove with water. Not removed by washing. As described above, the catalyst used in the present invention is very stable in water, so it can be used even if it is not a non-aqueous catalyst. Furthermore, if a decrease in activity is observed, this catalyst can be easily regenerated by performing reheat treatment at a temperature of, for example, 300 to 500°C.

The N-phenylcarbamate ester used in the present invention has the general formula It is a compound represented by, where R represents an alkyl group, an aromatic group, or an alicyclic group, and R' is hydrogen or an alkyl group, a halogen atom, a nitro group, a cyano group, an alkoxy group, an alicyclic group, etc. represents a substituent, these substituents are bonded to the ortho position or meta position with respect to the urethane group, and r represents an integer of 0 to 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.

Such N-phenylcarbamate esters include, for example, R in the above general formula, methyl group, ethyl group, 2,2,2-trichloroethyl group, 2,2,2-trifluoroethyl group, propyl group. Alkyl groups such as (n-, iso-), butyl group (n- and various isomers), pentyl group (n- and various isomers), hexyl group (n- and various isomers), or cyclopentyl group, cyclohexyl an alicyclic group such as a 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, chlorine, bromine,
Examples include N-phenylcarbamate esters having a halogen atom such as iodine, a nitro group, a cyano group, or an alkoxy group having the above-mentioned alkyl group as a constituent component.

Preferred are methyl N-phenylcarbamate, ethyl N-phenylcarbamate, n-propyl N-phenylcarbamate, iso-propyl N-phenylcarbamate, n-butyl N-phenylcarbamate, N-phenylcarbamic acid
sec-butyl, iso-butyl N-phenylcarbamate, tert-butyl N-phenylcarbamate,
Pentyl N-phenylcarbamate, hexyl N-phenylcarbamate, cyclohexyl N-phenylcarbamate, 2,2,2-trichloroethyl N-phenylcarbamate, 2,2,2 N-phenylcarbamate -trifluoroethyl, N
-o or m-tolylmethylcarbamate, N-o
or ethyl m-tolylcarbamate, 2,2,2-trifluoroethyl N-o or m-tolylcarbamate, propyl N-o or m-tolylcarbamate (each isomer), N-o or m-tolyl Butyl carbamate (each isomer), N-o or m-chlorophenylmethylcarbamate, N-o or m
- Ethyl chlorphenylcarbamate, N-o or m-propyl chlorphenylcarbamate (each isomer), N-o or m-butyl chlorphenylcarbamate (each isomer), N-o or m- 2,2,2-trifluoroethyl chlorphenylcarbamate, methyl N-2,6-dimethylphenylcarbamate, ethyl N-2,6-dimethylphenylcarbamate, N-2,6-dimethylphenyl Propyl carbamate (each isomer), N-2,
Butyl 6-dimethylcarbamate (each isomer),
N-2,6-dimethylcarbamic acid 2,2,2-
Trifluoroethyl, methyl N-2,6-dibromphenylcarbamate, ethyl N-2,6-dibromphenylcarbamate, propyl N-2,6-dibromphenylcarbamate (each isomer) ,
N-phenylcarbamate esters such as butyl N-2,6-dibromphenylcarbamate (each isomer), 2,2,2-trifluoroethyl N-2,6-dibromphenylcarbamate is used.

Examples of the methylenating agent used in the present invention include formaldehyde, paraformaldehyde, trioxane, tetraoxane, dialkoxymethane, diacyloxymethane, 1,3-dioxolane, 1,3-dioxane, 1,3-dithiane,
Among these methylenating agents, particularly preferred are formaldehyde, paraformaldehyde, trioxane, and methylenating agents having 1 to 1 carbon atoms.
Dialkoxymethanes having 6 lower alkyl groups, such as dimethoxymethane, diethoxymethane, dipropoxymethane, dipentanoxymethane, dihexyloxymethane, and diacetoxymethane, dipropioxymethane, etc. These include siloxymethane, and these may be used alone or in combination of two or more.

Although the method of the present invention can be carried out without a solvent, it can also be carried out with a suitable solvent if necessary. Such solvents include, for example, pentane, hexane, heptane, octane, nonane, decane, n-
Aliphatic or alicyclic hydrocarbons such as hexadecane, cyclopentane, and cyclohexane, halogenated hydrocarbons such as chloroform, methylene chloride, carbon tetrachloride, dichloroethane, trichloroethane, and tetrachloroethane, methanol, ethanol, propanol, butanol Alcohols such as benzene, toluene, xylene, ethylbenzene, monochlorobenzene, dichlorobenzene,
Bromnaphthalene, nitrobenzene, o- or m
Aromatic compounds such as - or p-nitrotoluene, ethers such as diethyl ether, 1,4-dioxane, and tetrahydrofuran, esters such as methyl acetate, ethyl acetate, and methyl formate;
Sulfolanes such as sulfolane, 3-methylsulfolane, and 2,4-dimethylsulfolane, carboxylic acids such as acetic acid, propionic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, and trifluoroacetic acid, methanesulfonic acid, trichloromethanesulfonic acid, and trifluoroacetic acid. Examples include sulfonic acids such as lomethanesulfonic acid and water.

In carrying out the method of the present invention, the molar ratio of the methylenating agent to the N-phenylcarbamate ester is not particularly limited;
It is preferably used in a range of 10 moles, more preferably in a range of 0.05 to 5 moles. If the amount of methylenating agent used is too small, the residual rate of unreacted N-phenylcarbamate ester will increase, while if it is too large, a polymethylene polyphenylcarbamate ester having three or more phenyl groups will be formed. The percentage increases.

There is no particular restriction on the amount of catalyst used, but when conducting a batch reaction, the amount of sulfate ion in the solid super strong acid is 10 ^-5 to 10 molar equivalents per 1 mole of N-phenylcarbamate ester. It is preferable to use such an amount. When performing a flow reaction,
The flow rate of the N-phenylcarbamate ester is approximately 0.01 to 1000 mol/hr per catalyst.

The reaction of the present invention is carried out at 250°C or lower, preferably at 10-200°C.
It is carried out at a temperature of 80 °C, but a more preferred temperature is 80 °C.
~180℃ range.

Furthermore, although the method of the present invention is usually carried out under normal pressure or increased pressure, it can also be carried out under reduced pressure if necessary.

The reaction time varies depending on other reaction conditions such as reaction temperature, type and amount of catalyst, presence and amount of solvent, raw material composition, reaction method, etc., but is usually from several minutes to several hours.

Further, the reaction method of the present invention is not particularly limited, and includes a method in which a solid superacid catalyst is suspended in the reaction mixture, a method in which the reaction is performed in a fixed bed, and the like. Further, it may be carried out batchwise or continuously.

Since the solid super strong acid catalyst of the present invention is solid compared to ordinary liquid acid catalysts such as hydrochloric acid and sulfuric acid, it is less likely to corrode equipment, is easy to separate and recover from reaction liquid components, and is easy to carry out continuous reactions, and can be disposed of. It has extremely industrial advantages such as not emitting acid aqueous solution.

Furthermore, when the catalyst of the present invention is used as a reaction catalyst between N-phenylcarbamate and a methylenating agent, methylene-bis-(4-
phenylcarbamate) can be obtained.

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

The solid superacid used as the catalyst was prepared by the method of Arata et al. (Surface, Vol. 19, pp. 75-82, 1981), and the reaction product was analyzed using high performance liquid chromatography.

Example 1 ZrOCl ₂ was hydrolyzed with 28% ammonia water, and the precipitate formed was thoroughly washed with deionized water.
Zr(OH) ₄ was obtained by drying at 100°C for 24 hours. After crushing this hydroxide, place 2 g of it on a piece of paper folded into four, and pour 30 ml of 1N sulfuric acid aqueous solution into it.
Leave it alone. After air drying, the solid superacid having sulfate ions (expressed as SO ^2- ₄ /ZrO ₂ ) was obtained by firing in air at 650° C. for 3 hours.

This catalyst and ethyl N-phenylcarbamate
16.5g, dimethoxymethane 1.9g, sulfolane 30
ml was placed in a 50 ml stirring autoclave and reacted at 120°C for 1 hour. The analysis results of the reaction solution showed that the reaction rate of ethyl N-phenylcarbamate was 48%, and the selectivity of methylene-bis-(ethyl 4-phenylcarbamate) was 79%. The selectivity of 2,4'-methylene-di-(phenylcarbamate ethyl) was 12%, and the remainder was trinuclear or higher polymethylene polyphenylcarbamate ethyl.

When the same reaction was repeated using the catalyst separated from the reaction solution by filtration, the reaction rate of ethyl N-phenylcarbamate was 49%, indicating that methylene-bis-(ethyl 4-phenylcarbamate) was selected. The selectivity for 2,4'-methylene-di-(ethyl phenylcarbamate) was 14%, and the selectivity for polymethylene polyphenyl ethyl carbamate was 9%, giving almost similar results. It was done.

Example 2 Fe(OH) ₃ obtained by hydrolyzing Fe(NO ₃ ) ₃ with 28% aqueous ammonia was washed with water and then dried at 100° C. for 24 hours. Place 2 g of this Fe(OH) ₃ on a piece of paper folded into four and pour in 30 ml of 0.5N sulfuric acid aqueous solution. After drying, the powder was pulverized and calcined in air at 500°C for 3 hours to obtain a solid superacid containing sulfate ions (expressed as SO ^2- ₄ /Fe ₂ O ₃ ).

This catalyst and methyl N-phenylcarbamate
When the same reaction as in Example 1 was carried out using 15.1 g of N, 1 g of trioxane, and 30 ml of sulfolane,
-The reaction rate of methyl phenylcarbamate is 45%
The selectivity for methylene-bis-(4-phenylmethylcarbamate) was 75%, and the selectivity for polymethylene polyphenylmethylcarbamate was 13%.

Example 3 Obtained by dissolving titanium isopropoxide in dilute nitric acid and hydrolyzing it with aqueous ammonia.
After washing H ₄ TiO ₄ with water, it was dried at 100°C. this
Place 2g of H ₄ TiO ₄ on a piece of paper and pour in 30ml of 1N sulfuric acid.
After drying, it was pulverized and calcined in air at 500°C for 3 hours to obtain a solid super strong acid containing sulfate ions (expressed as SO ^2- ₄ /TiO ₂ ).

This catalyst and ethyl N-phenylcarbamate
Put 16.5g and 4.2g of diethoxymethane into a sealed tube.
The reaction was carried out by shaking at 150°C for 1 hour. As a result of analyzing the reaction solution, the reaction rate of ethyl N-phenylcarbamate was 76%, and the reaction rate of ethyl N-phenylcarbamate was 76%.
- ethyl phenylcarbamate) selectivity is 70%
The selectivity of ethyl polymethylene polyphenyl carbamate was 16%.

Example 4 10g of the same catalyst as in Example 1 with an inner diameter of 12mm and a length of 20cm
was packed into a stainless steel column. A nitrobenzene solution containing 15% by weight of ethyl N-phenylcarbamate and 1% by weight of trioxane was injected from the bottom of the column at 20ml/hr. Keep this column at 130℃,
After reaching a steady state, analysis of the produced liquid revealed that N
-The reaction rate of ethyl phenyl carbamate is 51%, the selectivity of methylene-bis-(4-phenyl ethyl carbamate) is 82%, the selectivity of polymethylene polyphenyl ethyl carbamate is 10%, 2,
The selectivity of 4'-methylene-di-(ethyl phenylcarbamate) was 8%.

Example 5 A reaction was carried out in an autoclave at 110°C for 1 hour in the same manner as in Example 1 using 2 g of the same catalyst as in Example 1, 8.7 g of butyl N-phenylcarbamate, 1 g of 40% formaldehyde aqueous solution, and 40 ml of acetic acid. However, the reaction rate of butyl N-phenylcarbamate is 40
%, butyl methylene-bis-(4-phenylcarbamate) was produced with a selectivity of 68%.The selectivity of butyl polymethylene polyphenylcarbamate was 20%.

Claims (1)

[Claims] 1. In the presence of a solid superacid consisting of a combination of at least one metal oxide selected from zirconium oxide, iron oxide, and titanium oxide and sulfate ions,
A condensation method for N-phenylcarbamate, which comprises reacting N-phenylcarbamate with a methylenating agent.